CN117897460A

CN117897460A - Adhesive composition, adhesive sheet with release film, laminate for image display device, curved image display device, and adhesive composition for curved optical member

Info

Publication number: CN117897460A
Application number: CN202280059067.5A
Authority: CN
Inventors: 浅野铁也; 野原一树; 岛中辽太
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 2021-09-30
Filing date: 2022-09-29
Publication date: 2024-04-16

Abstract

The present invention relates to useful improvements in adhesive compositions that can be used for multi-stage curing and uses thereof. The adhesive composition contains an acrylic resin (A) and a photoinitiator (B), wherein the acrylic resin (A) is a polymerization product of a copolymerization component (a), and the copolymerization component (a) contains: an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer and an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer, wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 5% by weight or more relative to 100% by weight of the copolymerized component (a); examples of applications of the adhesive composition relate to adhesives, adhesive sheets with release films, laminates for image display devices, curved image display devices, and adhesive compositions for curved optical members.

Description

Adhesive composition, adhesive sheet with release film, laminate for image display device, curved image display device, and adhesive composition for curved optical member

Technical Field

The present invention relates to an adhesive composition, an adhesive sheet with a release film, a laminate for an image display device, a curved image display device, and an adhesive composition for a curved optical member.

The present application claims priority to japanese patent application publication nos. 2021-160337, 2021, 9, 30, and 2021, 9, 30, based on japanese patent application nos. 2021-160337, 2021-160488, 9, 30, applied to the japanese patent application, and the contents of which are hereby incorporated herein by reference.

Background

In recent years, touch panels combining a display and a position input device have been widely used in mobile devices such as televisions, computer monitors, notebook computers, mobile phones, smart phones, and tablet terminals. Among them, capacitive touch panels are widely used.

The touch panel is generally composed of a display formed of organic EL or liquid crystal, a transparent conductive film substrate (ITO substrate), and a protective film (protective glass). A transparent pressure-sensitive adhesive sheet is used for bonding members of these touch panels.

Since the transparent pressure-sensitive adhesive sheet requires bonding members of various shapes, the pressure-sensitive adhesive for the transparent pressure-sensitive adhesive sheet is bonded in a low-crosslinked state before being completely cured. Therefore, in the step until the adhesive layer in the low crosslinked state is completely cured, sufficient adhesive properties are required.

For example, when the adhesive sheet is attached to a member having a complicated shape, poor adhesion due to adhesion of the transparent adhesive sheet to a site other than the target site or the like is likely to occur. Therefore, a transparent adhesive sheet having low tackiness is required.

In addition, in order to fix members of complicated shapes to each other, it is required to suppress peeling of the transparent adhesive sheet from the members in a state where stress is applied. Therefore, a transparent adhesive sheet having high constant load holding force even in a low crosslinked state is also demanded.

In addition, the adhesive layer after complete curing is required to have not only general adhesive properties such as adhesive force but also excellent performance for reliability in bonding to various members such as polarizing plates and glass. For example, in order to obtain excellent durability after complete curing, it is required that the degree of crosslinking is as low as possible until the adhesive is adhered to an adherend. In addition, it is also required to efficiently increase the degree of crosslinking upon complete curing.

Therefore, it is desired that the adhesive layer can be sufficiently adhered to the adherend by adhering the adhesive layer to the adherend in a low crosslinked state. Further, the adhesive sheet is expected to have improved durability because the adhesive sheet is highly crosslinked by being fully cured while being bonded to the adherend in a low crosslinked state.

In general, after a primary curing process is performed by thermal crosslinking or a curing process is performed by irradiation of active energy rays, a full curing process is performed by crosslinking by irradiation of active energy rays. As the pressure-sensitive adhesive sheet using the multi-stage curable pressure-sensitive adhesive, for example, those described in patent documents 1 to 3 are cited.

Patent document 1 discloses: an organic solvent which is easily volatilized under a usual dry condition is also used in the solvent-based adhesive containing the acrylic resin, and an ethylenically unsaturated monomer which is not easily volatilized is compounded in a specific ratio.

Patent document 2 discloses that: in order to form a three-dimensional network structure of the solvent-based acrylic adhesive without using a crosslinking agent, a hydrogen abstraction photoinitiator is used, and light irradiation is performed after the coating and drying process, thereby omitting the curing process.

Further, patent document 3 discloses: by using an acrylic resin having a high glass transition temperature, an adhesive having high level difference following property and high foaming resistance is obtained.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2012-111939

Patent document 2: japanese patent application laid-open No. 2017-210542

Patent document 3: international publication No. 2017/022770

Disclosure of Invention

Problems to be solved by the invention

However, in patent documents 1 to 3, there is no consideration concerning the adhesive properties in a low crosslinked state at the time of primary curing. Therefore, there is a case where the adhesive properties in a low-crosslinking state at the time of one-time curing become insufficient, and there is room for improvement. In particular, in the application of bonding the once cured pressure-sensitive adhesive sheet to an adherend of a complex shape to which strong stress is applied, there are cases where defects such as peeling of the pressure-sensitive adhesive sheet after bonding occur.

A main object of the first aspect of the present invention is to provide an adhesive composition which can be used for multi-stage curing, and which can provide excellent adhesive properties in a low-crosslinking state after one-time curing, and can provide excellent adhesive properties and reliability even after complete curing; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

A main object of the second aspect of the present invention is to provide an adhesive composition which can be used for multi-stage curing, and which can provide excellent adhesive properties in a low-crosslinking state after one-time curing, and can provide excellent adhesive properties and reliability even after complete curing; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

A third aspect of the present invention is to provide an adhesive composition which can be used for multi-stage curing and which can provide an adhesive sheet excellent in adhesion even when adhered to an adherend having a complex shape to which a strong stress is applied; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

Solution for solving the problem

The present inventors have conducted intensive studies to solve the problems of the first aspect, and as a result, have found that: by using an adhesive composition containing an acrylic resin obtained by using a copolymerization component of a specific composition and a specific photoinitiator, excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinking state after primary curing can be achieved, and excellent adhesive properties and reliability after complete curing can be achieved.

The first embodiment of the present invention is an adhesive composition containing an acrylic resin (a) and a photoinitiator (B); the acrylic resin (A) is a polymerization product of the following copolymerization component (a); the glass transition temperature of the acrylic resin (A) based on dynamic viscoelasticity is-10 ℃ or higher; the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2).

The copolymerization component (a) of the first embodiment contains at least: an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer, an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer, and a hydroxyl group-containing monomer (a 3), wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45, and the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 30 to 70% by weight relative to the copolymerized component (a).

The present inventors have conducted intensive studies to solve the problems of the second aspect, and as a result, have found that: by using an adhesive composition containing an acrylic resin obtained by using a copolymerization component of a specific composition and a specific photoinitiator, excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinking state after primary curing can be achieved, and excellent adhesive properties and reliability after complete curing can be achieved.

The second embodiment of the present invention is an adhesive composition containing an acrylic resin (a) and a photoinitiator (B); the acrylic resin (A) is a polymerization product of the following copolymerization component (a); the glass transition temperature of the acrylic resin (A) based on dynamic viscoelasticity is-10 ℃ or higher; the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1).

The copolymerization component (a) according to the second aspect contains at least: an alkyl (meth) acrylate (a 1) having an alkyl group having 12 or less carbon atoms and having a glass transition temperature of a homopolymer of-20 to 120 ℃; a hydroxyalkyl monomer (a 2) containing an alkyl chain, a hydroxyl group and an ethylenically unsaturated group; the content of the alkyl (meth) acrylate (a 1) is 30 wt% or more based on 100 wt% of the copolymerization component (a); the content of the hydroxyalkyl monomer (a 2) is 0.1 wt% or more based on 100 wt% of the copolymerization component (a); the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymerization component (a) is 2.1 or more.

The present inventors have conducted intensive studies to solve the problems of the third aspect, and as a result, have found that: by using an adhesive composition containing an acrylic resin obtained by using a copolymerization component of a specific composition and a specific photoinitiator, an adhesive sheet which can be adhered to an adherend of a complicated shape to which stress is applied at the time of one-time curing without peeling can be obtained, and an adhesive sheet which exhibits excellent durability after complete curing can be obtained.

A third aspect of the present invention is an adhesive composition containing an acrylic resin (a) and a photoinitiator (B); the acrylic resin (A) is a polymerization product of a copolymerization component (a) containing a branched alkyl (meth) acrylate (a 1) having a homopolymer glass transition temperature of-30 ℃ or higher; the glass transition temperature of the acrylic resin (A) based on dynamic viscoelasticity is-10 ℃ or higher; the weight average molecular weight of the acrylic resin (A) is 400,000 or less; the photoinitiator (B) contains an intramolecular hydrogen abstraction photoinitiator (B1) and an intermolecular hydrogen abstraction photoinitiator (B2).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the first aspect of the present invention, an adhesive composition which can be used for multi-stage curing, can provide excellent adhesive properties in a low-crosslinking state after primary curing, and can provide excellent adhesive properties and reliability even after complete curing can be provided; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

According to the second aspect of the present invention, an adhesive composition which can be used for multi-stage curing, can provide excellent adhesive properties in a low-crosslinking state after primary curing, and can provide excellent adhesive properties and reliability even after complete curing can be provided; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

According to the third aspect of the present invention, there is provided an adhesive composition which can be used for multi-stage curing and which can provide an adhesive sheet excellent in adhesion even when adhered to an adherend having a complicated shape to which a strong stress is applied; an adhesive obtained by crosslinking the adhesive composition; and an adhesive sheet having an adhesive layer formed of the aforementioned adhesive.

Detailed Description

The following terms in this specification are shown in their meanings.

"(meth) acrylic" refers to acrylic or methacrylic.

"(meth) acryl" means acryl or methacryl.

"(meth) acrylate" means acrylate or methacrylate.

The "acrylic resin" is a resin obtained by polymerizing a monomer component containing at least 1 (meth) acrylic monomer.

"sheet" is a term that generally includes sheets, films, and tapes.

"homopolymer" refers to a homopolymer of a certain monomer.

The term "to" representing a numerical range means that the numerical values before and after the term "to" are included as the lower limit value and the upper limit value.

First mode

Hereinafter, the first embodiment of the present invention will be described in detail, but these are disclosed as typical examples of the preferred embodiments.

< adhesive composition >

The adhesive composition of the first embodiment contains an acrylic resin (a) and a photoinitiator (B). The adhesive composition of the first embodiment may contain, in addition to the acrylic resin (a) and the photoinitiator (B), a crosslinking agent (C), a silane coupling agent (D), a carbodiimide compound (E), and other optional components as necessary. The respective components will be described in order below.

(acrylic resin (A))

The acrylic resin (a) of the first embodiment is a polymerization product of a specific copolymerization component (a). The copolymerization component (a) is a generic term for monomer components having a polymerizable double bond. The copolymerization component (a) contains no polymerization initiator and no polymerization solvent.

The specific copolymerization component (a) of the first embodiment contains at least: an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer, an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer, and a hydroxyl group-containing monomer (a 3). The copolymerization component (a) of the first embodiment may contain, if necessary, an ethylenically unsaturated monomer (a 4) other than the alkyl acrylate (a 1) having a glass transition temperature of-27 to 50 ℃, the alkyl methacrylate (a 2) having a glass transition temperature of 0 to 120 ℃ when forming a homopolymer, and the hydroxyl group-containing monomer (a 3).

[ alkyl acrylate (a 1) ]

The homopolymer of the alkyl acrylate (a 1) according to the first embodiment has a glass transition temperature (hereinafter referred to as "Tg") of-30 to 50 ℃, preferably-27 to 45 ℃, more preferably-10 to 43 ℃, and even more preferably-5 to 10 ℃. When the Tg is within the range, the effect of the first embodiment of the present invention can be obtained.

The homopolymer of the alkyl acrylate (a 1) is the homopolymer of the alkyl acrylate (a 1). As the Tg of the homopolymer of the alkyl acrylate (a 1), the analytical value of the standard described in Wiley publication, "POLYMER HANDBOOK", etc. can be used.

Examples of the alkyl acrylate (a 1) according to the first embodiment include methyl acrylate (Tg: 8 ℃), ethyl acrylate (Tg: -22 ℃), isobutyl acrylate (Tg: -26 ℃), tert-butyl acrylate (Tg: 41 ℃), and cyclohexyl acrylate (Tg: 15 ℃). Among them, methyl acrylate is preferable from the viewpoint of adhesive properties.

The alkyl acrylate (a 1) may be used alone or in combination of 1 or more than 2.

[ alkyl methacrylate (a 2) ]

The homopolymer of the alkyl methacrylate (a 2) according to the first embodiment has a Tg of-10 to 120 ℃, preferably 0 to 110 ℃, more preferably 20 to 105 ℃, still more preferably 40 to 70 ℃. When the Tg is within the range, the effect of the first embodiment of the present invention can be obtained.

The homopolymer of the alkyl methacrylate (a 2) according to the first embodiment is a homopolymer of the alkyl methacrylate (a 2). As the Tg of the homopolymer of the alkyl methacrylate (a 2), the analytical value of the standard described in Wiley publication, "POLYMER HANDBOOK", etc. can be used.

Examples of the alkyl methacrylate (a 2) of the first embodiment include methyl methacrylate (Tg: 105 ℃), ethyl methacrylate (Tg: 65 ℃), n-butyl methacrylate (Tg: 20 ℃), isobutyl methacrylate (Tg: 48 ℃), cyclohexyl methacrylate (Tg: 66 ℃) and t-butyl methacrylate (Tg: 107 ℃).

The alkyl methacrylate (a 2) may be used alone or in combination of 1 or more than 2.

Among them, methyl methacrylate, ethyl methacrylate, and isobutyl methacrylate are preferable.

[ hydroxyl group-containing monomer (a 3) ]

The hydroxyl group-containing monomer (a 3) of the first embodiment contains 1 or more than 2 hydroxyl groups and an ethylenically unsaturated group. Examples of the hydroxyl group-containing monomer (a 3) include hydroxyl group-containing alkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate;

caprolactone-modified monomers such as 2-hydroxyethyl (meth) acrylate; an oxyalkylene-modified monomer such as polyethylene glycol mono (meth) acrylate or polytetramethylene glycol mono (meth) acrylate;

Primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, N-methylol (meth) acrylamide, and hydroxyethyl acrylamide;

secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-chloro 2-hydroxypropyl (meth) acrylate;

and tertiary hydroxyl group-containing monomers such as 2, 2-dimethyl-2-hydroxyethyl (meth) acrylate.

Among them, alkyl (meth) acrylate containing a primary hydroxyl group is preferable from the viewpoint of being capable of efficiently curing at the time of complete curing, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are particularly preferably used in combination or 4-hydroxybutyl (meth) acrylate alone.

[ ethylenically unsaturated monomer (a 4) ]

In the first embodiment, the copolymerizable component (a) may contain, if necessary, other copolymerizable ethylenically unsaturated monomers (a 4) in addition to the monomers (a 1) to (a 3).

Examples of the other copolymerizable ethylenically unsaturated monomer (a 4) include alkyl (meth) acrylates such as n-butyl acrylate and 2-ethylhexyl (meth) acrylate (excluding alkyl acrylate (a 1) and alkyl methacrylate (a 2));

aromatic ring-containing monomers such as phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, phenoxypolyethylene glycol-polypropylene glycol- (meth) acrylate, o-phenylphenoxyethyl (meth) acrylate, nonylphenoxyethane adduct (meth) acrylate, and the like;

Alicyclic-containing monomers such as cyclohexyloxyalkyl (meth) acrylate, t-butylcyclohexyloxyethyl (meth) acrylate, isobornyl methacrylate, and dicyclopentanyl (meth) acrylate;

ether chain-containing monomers such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol-polypropylene glycol mono (meth) acrylate, lauryloxypolyethylene glycol mono (meth) acrylate, stearyloxypolyethylene glycol mono (meth) acrylate;

acrylic acid dimers such as (meth) acrylic acid, β -carboxyethyl acrylate;

carboxyl group-containing monomers such as crotonic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycollic acid, and cinnamic acid;

amide group-containing monomers such as (meth) acrylamide, N- (N-butoxyalkyl) (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, and N, N-dimethylaminoalkyl (meth) acrylamide;

Benzophenone-containing monomers such as 4- (meth) acryloxybenzophenone;

acrylonitrile, methacrylonitrile, styrene, alpha-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, acryloyl chloride, methyl vinyl ketone, N-acrylamidomethyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethylallyl vinyl ketone, and the like.

The ethylenically unsaturated monomer (a 4) may be used alone or in combination of 1 or more than 2.

As the ethylenically unsaturated monomer having two or more ethylenically unsaturated groups, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, divinylbenzene, and the like may be used in combination.

[ composition of the copolymerization component (a) of the first embodiment ]

In the first embodiment, the content of the alkyl acrylate (a 1) is 5 wt% or more, preferably 5 to 45 wt%, more preferably 10 to 40 wt%, particularly preferably 12 to 35 wt%, and particularly preferably 15 to 30 wt% with respect to the copolymer component (a).

If the content is too small, the adhesive properties in the primary cured state tend to be lowered. If the content is too large, the adhesive properties after complete curing tend to be lowered.

In the first embodiment, the content of the alkyl methacrylate (a 2) is 5 wt% or more, preferably 10 to 60 wt%, more preferably 15 to 55 wt%, and particularly preferably 20 to 45 wt% with respect to the copolymer component (a).

In the copolymerization component (a) of the first embodiment, the content ratio (a 1/a 2) of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 5/95 to 55/45, preferably 15/85 to 50/50, particularly preferably 20/80 to 40/60 in terms of weight ratio.

In the first embodiment, the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is preferably 30 to 70% by weight, more preferably 35 to 65% by weight, and particularly preferably 40 to 60% by weight, based on the copolymer component (a).

When the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is within the above numerical range, the adhesion in the low crosslinking state in the primary cured state is good, and thus it is preferable.

The content of the hydroxyl group-containing monomer (a 3) in the first embodiment is more preferably 5 to 30% by weight, still more preferably 10 to 25% by weight, particularly preferably 15 to 20% by weight. If the content of the hydroxyl group-containing monomer (a 3) is too small, the wet heat resistance after complete curing tends to be low. If the content of the hydroxyl group-containing monomer (a 3) is too large, the adhesive properties after complete curing tend to be lowered.

In the copolymerization component (a) of the first embodiment, the ratio (a1+a2)/(a 3) of the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) to the content of the hydroxyl group-containing monomer (a 3) is preferably 95/5 to 50/50, more preferably 85/15 to 70/30, and particularly preferably 80/20 to 75/25 in terms of weight ratio. When the content ratio (a1+a2)/(a 3) is within the above numerical range, the adhesive properties in the primary cured state are excellent.

When the copolymerization component (a) of the first embodiment contains the ethylenically unsaturated monomer (a 4), the content of the ethylenically unsaturated monomer (a 4) is usually 50% by weight or less, preferably 45% by weight or less, and more preferably 40% by weight or less, relative to 100% by weight of the copolymerization component (a). If the content of the ethylenically unsaturated monomer (a 4) is too large, the adhesive properties tend to be lowered at the time of low crosslinking.

In the first embodiment, the acrylic resin (a) may be said to be a copolymer having a structural unit based on the alkyl acrylate (a 1), a structural unit based on the alkyl methacrylate (a 2), and a structural unit based on the hydroxyl group-containing monomer (a 3). In this case, the acrylic resin (a) may have a structural unit based on the ethylenically unsaturated monomer (a 4) in addition to the structural unit based on the alkyl acrylate (a 1), the structural unit based on the alkyl methacrylate (a 2), and the structural unit based on the hydroxyl group-containing monomer (a 3), if necessary. In this case, the ratio of the structural units based on the respective monomers may be determined according to the composition of the copolymerization component (a), and the same preferable mode is adopted.

The dynamic viscoelasticity-based glass transition temperature of the acrylic resin (A) of the first embodiment is-10℃or higher, preferably-5 to 20 ℃, more preferably 0 to 15 ℃, and particularly preferably 2 to 13 ℃. If the glass transition temperature of the acrylic resin (a) based on dynamic viscoelasticity is too high, the adhesive strength tends to be lowered with a decrease in the level difference following property and a decrease in the adhesion of the adhesive layer. If the glass transition temperature of the acrylic resin (a) based on dynamic viscoelasticity is too low, the adhesive properties at the time of low crosslinking tend to be lowered.

The glass transition temperature based on dynamic viscoelasticity was determined by the following measurement method.

An acrylic resin solution containing only the acrylic resin (a) of the first embodiment and an organic solvent is prepared by adding an appropriate organic solvent. After the concentration of the acrylic resin solution was adjusted, the film was coated on a release sheet so that the thickness after drying became 50. Mu.m. Thereafter, the resultant is dried by a heat treatment at 90 to 105℃for 5 to 10 minutes, etc., to remove the organic solvent, and then the resultant is adhered to a release sheet, whereby an acrylic resin sheet containing 99% or more of the acrylic resin (A) is produced. Thereafter, a plurality of acrylic resin sheets were laminated to prepare an acrylic resin sheet having a thickness of about 800. Mu.m.

The dynamic viscoelasticity of the produced sheet was measured under the following conditions, and the temperature at which the loss tangent (loss modulus G "/storage modulus G' =tan δ) became maximum was read as the glass transition temperature of the acrylic resin (a) based on the dynamic viscoelasticity.

(conditions for measuring dynamic viscoelasticity)

Measurement device: dynamic viscoelasticity measuring device (trade name: DVA-225, TEA- , manufactured by Imperial corporation)

Deformation mode: shearing

Strain: 0.1%

Measuring temperature: 100-60 DEG C

Measuring frequency: 1Hz

In the first embodiment, the weight average molecular weight of the acrylic resin (a) is preferably 50,000 ～ 500,000, more preferably 100,000 ～ 400,000, and further preferably 150,000 ～ 350,000. When the weight average molecular weight of the acrylic resin (a) is too large, the viscosity tends to be too high, and the coatability and handleability tend to be lowered. If the weight average molecular weight of the acrylic resin (a) is too small, cohesive force tends to be lowered and adhesive properties tend to be lowered.

The weight average molecular weight of the acrylic resin (a) is the weight average molecular weight at the completion of the production. The weight average molecular weight was measured for the acrylic resin (a) which was not heated after production.

The weight average molecular weight of the acrylic resin (a) is a weight average molecular weight converted based on the molecular weight of standard polystyrene. Weight average molecular weight by subjecting 3 columns to high performance liquid chromatography (made by Waters Co., ltd., "Waters2695 (Main body)" and "Waters2414 (Detector)"): shodex GPCKF-806L (exclusion limit molecular weight: 2X 10) ⁷ Separation range: 100 to 2X 10 ⁷ Theoretical stage number: 10000 grade/root, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) were used in series for the determination.

The number average molecular weight can also be measured by the same method. The dispersity was determined using the weight average molecular weight and the number average molecular weight.

The dispersity (weight average molecular weight/number average molecular weight) of the acrylic resin (a) is preferably 15 or less, more preferably 10 or less, further preferably 7 or less, particularly preferably 5 or less. If the dispersibility of the acrylic resin (a) is too high, the durability of the adhesive layer tends to be lowered. In addition, foaming and the like tend to occur easily. If the dispersion degree of the acrylic resin (a) is too low, the handleability tends to be lowered. The lower limit of the dispersity is usually 1.1 from the viewpoint of the limit of manufacture.

[ method for producing acrylic resin (A) ]

In the first embodiment, the acrylic resin (a) can be produced by polymerizing a copolymerization component (a) containing an alkyl acrylate (a 1), an alkyl methacrylate (a 2), and a hydroxyl group-containing monomer (a 3).

The copolymerization component (a) of the first embodiment may further contain an ethylenically unsaturated monomer (a 4) which is an optional polymerization component.

The polymerization method of the acrylic resin (a) includes, for example, conventionally known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Solution polymerization is preferable in view of safety and stability of the reaction and the ability to produce the acrylic resin (a) with an arbitrary monomer composition.

Hereinafter, an example of a preferred method for producing the acrylic resin (a) according to the first aspect is shown.

For example, the copolymerization component (a) of the first embodiment and the polymerization initiator may be mixed or added dropwise to an organic solvent, thereby performing solution polymerization.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene;

aliphatic hydrocarbons such as n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; aliphatic alcohols such as methanol, ethanol, n-propanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aliphatic ethers such as dimethyl ether and diethyl ether; aliphatic halogenated hydrocarbons such as methylene chloride and dichloroethane; cyclic ethers such as tetrahydrofuran, and the like.

Among these organic solvents, esters and ketones are preferable, and ethyl acetate, acetone and methyl ethyl ketone are particularly preferable.

The organic solvent may be used alone or in combination of at least 2 kinds.

As the polymerization initiator used in the polymerization reaction, an azo-based polymerization initiator, a peroxide-based polymerization initiator, or the like, which is a general radical polymerization initiator, can be used.

Examples of the azo-based polymerization initiator include 2,2' -azobis (2-methylbutyronitrile), 2' -azobisisobutyronitrile, (1-phenylethyl) azobis-phenyl methane, 2' -azobis (2, 4-dimethylvaleronitrile), 2' -azobis (2-cyclopropylpropionitrile), and 2,2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile).

Examples of the peroxide-based polymerization initiator include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, t-butyl peroxypivalate, t-hexyl peroxyneodecanoate, diisopropyl peroxycarbonate, and diisobutyryl peroxide.

Among them, azo-based polymerization initiators are preferable, and 2,2 '-azobisisobutyronitrile and 2,2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile) are more preferable.

The polymerization initiator may be used alone or in combination of 1 or more than 2.

The amount of the polymerization initiator to be used is usually 0.001 to 10 parts by weight, preferably 0.1 to 8 parts by weight, more preferably 0.5 to 6 parts by weight, particularly preferably 1 to 4 parts by weight, further preferably 1.5 to 3 parts by weight, and most preferably 2 to 2.5 parts by weight based on 100 parts by weight of the copolymerization component (a). If the amount of the polymerization initiator is too small, the polymerization rate of the acrylic resin (a) tends to decrease, and thus the residual monomer tends to increase. In addition, the weight average molecular weight of the acrylic resin (a) tends to be high. If the amount is too large, gelation of the acrylic resin (a) tends to occur.

The polymerization conditions for the solution polymerization are not particularly limited, and the polymerization may be carried out according to conventionally known polymerization conditions. For example, the copolymerization component (a) and the polymerization initiator may be mixed or added dropwise to an organic solvent to polymerize.

The polymerization temperature in the polymerization reaction is usually 40 to 120℃and preferably 50 to 90℃in view of stable reaction. If the polymerization temperature is too high, the acrylic resin (a) tends to be easily gelled. If the polymerization temperature is too low, the activity of the polymerization initiator decreases, and thus the polymerization rate decreases, and as a result, the residual monomer tends to increase.

The polymerization time in the polymerization reaction is not particularly limited, but is 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more, particularly preferably 5 hours or more after the addition of the final polymerization initiator.

The polymerization reaction is preferably carried out while refluxing the solvent in view of easy heat removal.

(photoinitiator (B))

The photoinitiator (B) of the first embodiment contains an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2).

The photoinitiator (B) of the first embodiment may contain a photoinitiator (B3) other than the intramolecular hydrogen abstraction type photoinitiator (B1) and the intermolecular hydrogen abstraction type photoinitiator (B2) as long as the effect of the invention is not impaired.

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

The intramolecular hydrogen abstraction photoinitiator (b 1) of the first embodiment has a structure capable of generating radicals by abstracting hydrogen of the photoinitiator itself. For example, the intramolecular hydrogen abstraction type photoinitiator (b 1) may have a phenylglyoxylate structure or the like.

Examples of the intramolecular hydrogen abstraction photoinitiator (b 1) include 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl ester of oxy-phenyl-acetic acid, methyl phenylglyoxylate, and the like.

Among these, 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl oxy-phenyl-acetate having a plurality of crosslinking points in the molecule is preferable from the viewpoint of crosslinking efficiency at the time of complete curing.

As commercial products, "Omnirad MBF" manufactured by IGM RESINS B.V., and "Omnirad 754" are mentioned.

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

The intermolecular hydrogen abstraction photoinitiator (b 2) of the first embodiment has a structure capable of generating radicals by abstracting hydrogen from outside the photoinitiator itself. The intermolecular hydrogen abstraction type photoinitiator (b 2) may have a benzophenone structure, for example.

Examples thereof include benzophenone, 4-methyl-benzophenone, 2,4, 6-trimethylbenzophenone, 4-phenylbenzophenone, 3 '-dimethyl-4-methoxybenzophenone, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloxyoxy) ethoxy ] benzophenone, 4- (meth) acryloxy4' -methoxybenzophenone, carboxymethoxybenzophenone-polyethylene glycol 250 diester, methyl 2-benzoylbenzoate, 4- (1, 3-acryl-1, 4,7,10, 13-pentaoxo tridecyl) benzophenone, and the like.

Among these, 2,4, 6-trimethylbenzophenone is preferable in terms of ease of handling because it is a low-viscosity liquid. In addition, in terms of achieving high crosslinking, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloxyethoxy ] benzophenone, 4- (meth) acryloxy4' -methoxybenzophenone, carboxymethoxybenzophenone-polyethylene glycol 250 diester in which a plurality of crosslinking points exist in the molecule are preferable.

Examples of the commercial products include "MBP" manufactured by New water chestnut Co., ltd., "Omnirad BP", "Omnirad 4MBZ", "Esacure TZT" manufactured by IGM RESINS B.V. Co., ltd., "OmnipoliBP".

[ other photoinitiators (b 3) ]

Examples of the other photoinitiator (b 3) according to the first embodiment include acetophenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzildimethylketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone oligomer;

benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and the like;

acyl phosphine oxides such as 2,4, 6-trimethylbenzoyl-diphenyl phosphine oxide and bis (2, 6-dimethoxybenzoyl) -2, 4-trimethyl-amyl phosphine oxide and bis (2, 4, 6-trimethylbenzoyl) -phenyl phosphine oxide.

As the auxiliary agent of the photoinitiator (B) of the first embodiment, triethanolamine, triisopropanolamine, 4 '-dimethylaminobenzophenone (milbetone), 4' -diethylaminobenzophenone, 2-dimethylaminoethyl benzoate, ethyl 4-dimethylaminobenzoate (n-butoxy) ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone, and the like may be used in combination.

The auxiliaries of the photoinitiator (B) may be used alone or in combination of 1 or more than 2.

(crosslinking agent (C))

The adhesive composition of the first embodiment preferably contains a crosslinking agent (C) in addition to the acrylic resin (a) and the photoinitiator (B).

Examples of the crosslinking agent (C) include an active energy ray crosslinking agent (C1) and a thermal crosslinking agent (C2). The active energy ray crosslinking agent (c 1) and the thermal crosslinking agent (c 2) may be used alone or in combination of at least 2.

When the crosslinking agent (C) as the first embodiment contains only the active energy ray crosslinking agent (C1), multistage curing can be achieved only by controlling the active energy ray amount. In the case where the active energy ray crosslinking agent (C1) and the thermal crosslinking agent (C2) are contained as the crosslinking agent (C), multi-stage curing can be also achieved by using a combination of thermal curing and active energy ray curing.

By controlling the crosslinking reaction in this way, the cohesive force of the entire adhesive layer can be adjusted, and stable adhesive properties can be obtained after the primary curing and after the complete curing.

[ active energy ray-crosslinking agent (c 1) ]

The active energy ray crosslinking agent (c 1) of the first embodiment is, for example, a polyfunctional crosslinking agent having 1 molecule containing 2 or more ethylenically unsaturated groups.

Examples thereof include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate, (poly) butanediol mono (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (poly) tetramethylene glycol di (meth) acrylate, (poly) pentamethylene glycol di (meth) acrylate, (poly) hexamethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, EO-modified glycerol tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, polyfunctional urethane (meth) acrylate, and the like.

Among them, (meth) acrylic acid esters containing 2 ethylenically unsaturated groups are preferable, and (poly) ethylene glycol di (meth) acrylic acid esters, (poly) propylene glycol di (meth) acrylic acid esters, (poly) tetramethylene glycol di (meth) acrylic acid esters are particularly preferable from the viewpoint of balance of adhesive properties after curing.

The polyfunctional crosslinking agent may be used alone or in combination of 1 or more than 2.

[ thermal crosslinking agent (c 2) ]

The thermal crosslinking agent (c 2) of the first embodiment can exhibit excellent adhesion by reacting with a functional group of a functional group-containing monomer derived from a constituent monomer of mainly the acrylic resin (a). For example, isocyanate-based crosslinking agent (c 2-1), epoxy-based crosslinking agent (c 2-2), aziridine-based crosslinking agent (c 2-3), melamine-based crosslinking agent (c 2-4), aldehyde-based crosslinking agent (c 2-5), amine-based crosslinking agent (c 2-6), and metal chelate-based crosslinking agent (c 2-7). Among these, the isocyanate-based crosslinking agent (c 2-1) is suitably used in terms of improving the adhesion to the substrate and reactivity with the acrylic resin (a).

The thermal crosslinking agent (c 2) may be used alone or in combination of 1 or more than 2.

Examples of the isocyanate-based crosslinking agent (c 2-1) include toluene diisocyanate-based compounds such as 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate;

a xylylene diisocyanate compound such as 1, 3-xylylene diisocyanate, 1, 4-xylylene diisocyanate, and tetramethylxylylene diisocyanate;

Aromatic isocyanate compounds such as 1, 5-naphthalene diisocyanate and triphenylmethane triisocyanate;

hexamethylene diisocyanate-based compounds such as trimethylhexamethylene diisocyanate, and aliphatic isocyanate-based compounds such as lysine diisocyanate;

alicyclic isocyanate compounds such as isophorone diisocyanate;

adducts of these isocyanate compounds with polyhydric alcohol compounds such as trimethylolpropane;

biuret and isocyanurate bodies of these isocyanate compounds; etc.

Among the isocyanate-based crosslinking agents (c 2-1), aromatic isocyanate-based compounds are preferably used, and toluene diisocyanate-based compounds are particularly preferred, in view of excellent reactivity. In addition, from the viewpoint of suppressing yellowing, an aliphatic isocyanate compound is preferably used, and a hexamethylene diisocyanate compound is particularly preferred.

Examples of the epoxy-based crosslinking agent (c 2-2) include bisphenol a epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycidyl ether, pentaerythritol polyglycidyl erythritol, and diglycidyl ether.

Examples of the aziridine-based crosslinking agent (c 2-3) include tetramethylolmethane-tris- β -aziridinylpropionate, trimethylolpropane-tris- β -aziridinylpropionate, N ' -diphenylmethane-4, 4' -bis (1-aziridinecarboxamide), N ' -hexamethylene-1, 6-bis (1-aziridinecarboxamide), and the like.

Examples of the melamine-based crosslinking agent (c 2-4) include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexabutoxymethyl melamine, hexapentoxymethyl melamine, hexahexoxymethyl melamine, and melamine resins.

Examples of the aldehyde-based crosslinking agent (c 2-5) include glyoxal, malondialdehyde, succinaldehyde, maleic dialdehyde, glutaraldehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine-based crosslinking agent (c 2-6) include hexamethylenediamine, triethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resins, and polyamides.

Examples of the metal chelate crosslinking agent (c 2-7) include acetylacetone and acetoacetate complex compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

(silane coupling agent (D))

From the viewpoint of improving durability, the adhesive composition of the first embodiment preferably further contains a compound other than the acrylic resin (a), the photoinitiator (B), and the crosslinking agent (C) as the silane coupling agent (D).

The silane coupling agent (D) is an organosilicon compound having 1 or more of each of a reactive functional group and an alkoxy group bonded to a silicon atom in its structure. The silane coupling agent (D) includes monomer type and oligomer type.

Examples of the reactive functional group in the silane coupling agent (D) include an epoxy group, a (meth) acryl group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, and an isocyanate group. Among these, epoxy groups and mercapto groups are preferable in view of excellent durability and reworkability.

The content ratio of the reactive functional group in the silane coupling agent (D) is preferably 3,000g/mol or less, more preferably 1,500g/mol or less, and still more preferably 1000g/mol or less. When the reactive functional group is within the above numerical range, the balance of durability and reworkability improves. The lower limit of the content ratio of the reactive functional group in the silane coupling agent (D) is 200g/mol.

The alkoxy group bonded to a silicon atom in the silane coupling agent (D) is preferably an alkoxy group having 1 to 8 carbon atoms from the viewpoints of durability and storage stability. Among them, methoxy and ethoxy are more preferable.

The silane coupling agent (D) may have an organic functional group other than the reactive functional group and the alkoxy group bonded to the silicon atom, for example, an alkyl group, a phenyl group, or the like.

Examples of the silane coupling agent (D) include 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, 3-mercaptopropyl dimethoxymethylsilane, gamma-glycidoxypropyl trimethoxysilane, gamma-glycidoxypropyl triethoxysilane, gamma-glycidoxypropyl methyldiethoxysilane, gamma-glycidoxypropyl methyldimethoxysilane, methyltris (glycidyl) silane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, and beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane. Among them, gamma-glycidoxypropyl trimethoxysilane is preferred from the viewpoint of heat resistance.

The silane coupling agent (D) may be used alone or in combination of 1 or more than 2.

(carbodiimide-based Compound (E))

From the viewpoint of heat resistance, the adhesive composition of the first embodiment preferably further contains a carbodiimide compound (E) as a compound other than the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C), and the silane coupling agent (D).

Examples of the carbodiimide-based compound (E) include mono-carbodiimides such as bis (2, 6-diisopropylphenyl) carbodiimide, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and docosalkylcarbodiimide, polycarbodiimides in which a plurality of carbodiimides are present, and cyclic carbodiimides. Among them, a monocarbodiimide compound is preferable from the viewpoint of heat resistance, and bis (2, 6-diisopropylphenyl) carbodiimide is more preferable.

The carbodiimide compound (E) may be used alone or in combination of 1 or more than 2.

(optional component)

The adhesive composition of the first embodiment may contain an adhesive as an optional other component, if necessary. The adhesive composition of the first embodiment may contain conventionally known additives such as a crosslinking accelerator, an antistatic agent, a tackifier, and a functional pigment.

(composition of adhesive composition)

In the first embodiment, the content of the acrylic resin (a) is preferably 80% by weight or more, more preferably 90 to 99.9% by weight, and still more preferably 92 to 99.9% by weight, based on the entire adhesive composition. When the content of the acrylic resin (a) is within the above numerical range, excellent adhesive properties are easily obtained in a low crosslinked state after primary curing.

In the first embodiment, the content of the photoinitiator (B) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 4.0 parts by weight, and still more preferably 1.0 to 3.0 parts by weight, based on 100 parts by weight of the acrylic resin (a). When the content of the photoinitiator (B) is within the above-mentioned numerical range, sufficient curability can be obtained when the curing is performed completely.

In the first embodiment, the content of the intramolecular hydrogen abstraction type photoinitiator (b 1) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the acrylic resin (a).

If the content of the intramolecular hydrogen abstraction photoinitiator (b 1) is too large, the color tends to be easily changed after the durability against damp heat. If the content of the intramolecular hydrogen abstraction photoinitiator (b 1) is too small, the crosslinking degree will not increase, and the adhesive properties at the time of primary curing and the durability after complete curing will tend to be deteriorated.

In the first embodiment, the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is preferably 0.1 to 3.0 parts by weight, more preferably 0.5 to 2.0 parts by weight, based on 100 parts by weight of the acrylic resin (a).

If the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is too large, the durability tends to be deteriorated due to bleeding. If the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is too small, the crosslinking degree does not increase, and the adhesive properties at the time of primary curing and the durability after complete curing tend to deteriorate.

In the case where the photoinitiator (B) in the first embodiment contains another photoinitiator (B3), the content of the photoinitiator (B3) is preferably 2.0 parts by weight or less, more preferably 1.0 parts by weight or less, based on 100 parts by weight of the acrylic resin (a).

In the case where the adhesive composition contains the crosslinking agent (C), the content of the crosslinking agent (C) is usually 20 parts by weight or less, more preferably 0.001 to 10 parts by weight, still more preferably 0.1 to 7.5 parts by weight, based on 100 parts by weight of the acrylic resin (a). If the content of the crosslinking agent (C) is too large, the adhesive strength tends to be low. If the content of the crosslinking agent (C) is too small, durability tends to be lowered.

In the case where the adhesive composition contains the active energy ray crosslinking agent (c 1) in the first embodiment, the content of the active energy ray crosslinking agent (c 1) is usually preferably 0.01 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, still more preferably 0.5 to 7.5 parts by weight, relative to 100 parts by weight of the acrylic resin (a).

If the content of the active energy ray crosslinking agent (c 1) is too small, the cohesive force becomes insufficient, and thus sufficient durability tends to be not obtained. If the content of the active energy ray crosslinking agent (c 1) is too large, the adhesive properties tend to be lowered at the time of primary curing.

In the case where the adhesive composition contains the thermal crosslinking agent (c 2), the content of the thermal crosslinking agent (c 2) is usually preferably 0.001 to 5 parts by weight, more preferably 0.02 to 1 part by weight, still more preferably 0.05 to 0.5 part by weight, relative to 100 parts by weight of the acrylic resin (a).

If the content of the thermal crosslinking agent (c 2) is too small, the cohesive force tends to be insufficient, and the adhesive properties tend to be lowered at the time of primary curing. If the content of the thermal crosslinking agent (c 2) is too large, the adhesive force tends to be lowered when the cured product is completely.

In the case where the adhesive composition contains the silane coupling agent (D), the content of the silane coupling agent (D) is preferably 0.001 to 3 parts by weight, more preferably 0.005 to 1 part by weight, still more preferably 0.01 to 0.5 part by weight, particularly preferably 0.015 to 0.3 part by weight, relative to 100 parts by weight of the acrylic resin (a).

If the content of the silane coupling agent (D) is too small, it tends to be difficult to obtain an effect of improving durability. If the content of the silane coupling agent (D) is too large, the adhesive force tends to be lowered due to the influence of bleeding or the like.

In the case where the adhesive composition contains the carbodiimide compound (E), the content of the carbodiimide compound (E) is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, still more preferably 0.2 to 2 parts by weight, and particularly preferably 0.3 to 1 part by weight, relative to 100 parts by weight of the acrylic resin (a).

If the content of the carbodiimide compound (E) is too small, the thermal stability of the acrylic resin (a) tends to be lowered. If the content of the carbodiimide compound (E) is too large, durability tends to be lowered due to the influence of bleeding or the like.

In the case where the adhesive composition contains other adhesives or additives in the first embodiment, the content of the other adhesives or additives is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, based on 100 parts by weight of the acrylic resin (a).

(preparation of adhesive composition)

The adhesive composition of the first embodiment can be obtained by mixing the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C) if necessary, the silane coupling agent (D), the carbodiimide compound (E), and other optional components.

The mixing method is not particularly limited, and various methods such as a method of mixing the components at once, a method of mixing any of the components and mixing the remaining components at once or sequentially may be employed.

(use)

The adhesive composition of the first aspect may be suitably used for an adhesive of a multi-stage curable adhesive sheet cured by a plurality of stages. With the adhesive composition of the first aspect, excellent adhesive properties can be obtained even in a low crosslinked state after one-time curing. Further, it exhibits not only general adhesive properties such as adhesive force after complete curing, but also excellent durability when it is bonded to various kinds and shapes of members such as polarizing plates and glass.

The adhesive composition of the first embodiment has excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinked state after one-time curing, and thus has improved handling properties and reliability. Therefore, the adhesive sheet is suitable for applications such as adhesives and pressure-sensitive adhesive sheets used in touch panels, image display devices, and the like.

< adhesive >

The adhesive according to the first aspect is obtained by crosslinking the adhesive composition according to the first aspect. The adhesive composition of the present invention is crosslinked (cured), whereby the acrylic resin (a) contained in the adhesive composition forms a crosslinked structure in at least one of the intramolecular and intermolecular directions. As a result, the adhesive composition of the present invention is crosslinked to form the adhesive of the first embodiment.

When the acrylic resin (a) has an active energy ray-crosslinkable structural part, a crosslinked structure can be formed by irradiation with active energy rays.

The adhesive of the first embodiment exhibits multi-stage curability in which it can be cured in multiple stages. The adhesive of the first embodiment is in a low crosslinked state by one-time curing before complete curing. The complete curing and the primary curing are not necessarily clearly distinguishable, but can be distinguished by, for example, differences in gel fraction, dynamic viscoelasticity.

The curing means in any of the primary curing step and the complete curing step is not particularly limited, and may be any of heating and irradiation with active energy rays. The primary curing step may be performed a plurality of times, or may be performed in a plurality of stages so as to be in a completely cured state.

The adhesive according to the first aspect is excellent in adhesive properties after primary curing, and therefore is suitable for bonding optical members constituting touch panels, image display devices, and the like.

The adhesive of the first aspect may be said to contain at least the crosslinked product of the acrylic resin (a) of the first aspect. The crosslinked product may be a partially crosslinked product obtained by partially crosslinking at least a part of the acrylic resin (a), or may be a completely crosslinked product obtained by crosslinking the entire acrylic resin (a). The adhesive according to the first aspect may contain both a partially crosslinked product and a completely crosslinked product of the acrylic resin (a).

< adhesive sheet >

The adhesive sheet of the first aspect has an adhesive layer formed of the adhesive of the first aspect. The adhesive layer of the adhesive sheet of the first embodiment may exhibit multi-stage curability by curing in multiple stages.

The adhesive sheet may be produced by providing an adhesive layer formed of the adhesive of the first embodiment on a base sheet. The double-sided adhesive sheet may be formed by providing an adhesive layer on a release sheet.

Further, a double-sided pressure-sensitive adhesive sheet without a base material may be produced by forming a pressure-sensitive adhesive layer on a release sheet instead of a base material sheet, and bonding the release sheet to the pressure-sensitive adhesive layer on the opposite side. An adhesive layer may be further formed on the formed adhesive layer to further form a thick film adhesive layer.

The obtained pressure-sensitive adhesive sheet and double-sided pressure-sensitive adhesive sheet are used by peeling the release sheet from the pressure-sensitive adhesive layer at the time of use.

As a method for producing the pressure-sensitive adhesive sheet according to the first aspect, for example, the following methods (i) and (ii) are mentioned.

(i) A method of forming an adhesive sheet by applying a coating liquid obtained by dissolving the adhesive composition of the first embodiment in a solvent.

(ii) And a method of producing an adhesive sheet by melting the adhesive composition of the first embodiment by heating.

The method of (i) will be described.

When the adhesive sheet is produced by coating a coating liquid obtained by dissolving the adhesive composition of the first aspect in a solvent, the concentration of the coating liquid containing the adhesive composition of the first aspect is adjusted by using an appropriate organic solvent, and the adhesive sheet is directly coated on the substrate sheet. Thereafter, the sheet is dried by, for example, heating at 80 to 105℃for 0.5 to 10 minutes, and then attached to a base sheet or a release sheet. Thereafter, the adhesive composition is crosslinked (cured) by irradiation with active energy rays or curing, whereby an adhesive sheet having an adhesive layer formed of an adhesive can be produced.

As the organic solvent used for the concentration adjustment, an example of an organic solvent used for the polymerization reaction of the acrylic resin (a) can be used. The concentration of the adhesive composition is usually 20 to 60% by weight, preferably 30 to 50% by weight, based on the solid content.

The method of (ii) is described.

When the adhesive composition of the first aspect is melted by heating to form an adhesive sheet, the adhesive layer is formed on one or both sides of the base sheet so as to have a desired thickness by a method of coating one or both sides of the base sheet in a melted state and then cooling the same, a method of extrusion lamination on the base sheet using a T die or the like, or the like. Then, a release sheet is bonded to the adhesive layer as needed, whereby an adhesive sheet can be produced.

Further, an adhesive sheet having an adhesive layer formed by curing (crosslinking) an adhesive composition may be produced by forming an adhesive layer on a base sheet, then performing an active energy ray irradiation treatment as needed, and further curing the adhesive layer.

Further, a double-sided pressure-sensitive adhesive sheet without a base material may be produced by forming a pressure-sensitive adhesive layer on a release sheet and bonding the release sheet to the pressure-sensitive adhesive layer on the opposite side.

Examples of the base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene and polymethylpentene; polyvinyl fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyvinyl fluoride; polyamides such as nylon 6 and nylon 6, 6; vinyl polymers such as polyvinyl chloride, polyvinyl chloride/vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polyvinyl alcohol, vinylon; cellulose resins such as cellulose triacetate and cellophane (cellophane); acrylic resins such as polymethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; a polystyrene; a polycarbonate; polyarylate; a synthetic resin sheet such as polyimide,

Metal foils of aluminum, copper, iron, etc,

High-quality paper, glassine paper and other paper,

Woven and nonwoven fabrics made of glass fibers, natural fibers, synthetic fibers, and the like. These base sheet may be used in the form of a single layer or in the form of a multilayer body formed by stacking 2 or more kinds of base sheets. Among these, a synthetic resin sheet is preferable in terms of weight reduction and the like.

As the release sheet, for example, a release sheet obtained by subjecting various synthetic resin sheets, paper, woven fabric, nonwoven fabric, and the like exemplified as the base sheet to release treatment can be used. As the release sheet, for example, a silicone release sheet is preferably used.

The method of coating the adhesive composition is not particularly limited. For example, methods such as roll coating, die coating, gravure coating, comma coating, slot coating (slot coating), screen printing, and the like are mentioned.

As the active energy ray, rays such as far ultraviolet rays, near ultraviolet rays, and infrared rays can be used; electromagnetic waves other than X-rays and gamma rays; electron beams may also be utilized; a proton line; neutron rays, and the like. Ultraviolet-based curing is preferred in terms of curing speed, ease of acquisition of the irradiation device, price, and the like.

The gel fraction of the adhesive layer of the adhesive sheet before complete curing is preferably 0.1 to 60% by weight, more preferably 1 to 50% by weight, and particularly preferably 5 to 45% by weight, from the viewpoint that the adhesive layer can be easily bonded depending on the shape of the adherend and from the viewpoint that the adhesive layer can hold the adherend after bonding.

The gel fraction of the adhesive layer of the adhesive sheet after complete curing is preferably 50 to 95% by weight, more preferably 55 to 90% by weight, and particularly preferably 60 to 85% by weight, from the viewpoints of durability and adhesive force. If the gel fraction is too low, the cohesive force tends to decrease, and durability tends to decrease. If the gel fraction is too high, the cohesive force tends to be increased, and the adhesive force tends to be lowered.

The gel fraction can be suitably adjusted by the following procedure, for example.

Adjusting the irradiation amount of the active energy ray.

The content of the active energy ray-crosslinkable structural site in the acrylic resin (A) is adjusted.

Adjusting the types and amounts of the photoinitiator (B) and the crosslinking agent (C).

The gel fraction is an index of the degree of crosslinking (degree of curing), and is calculated by the following method, for example. Specifically, an adhesive sheet (a release sheet was not provided) in which an adhesive layer was formed on a polymer sheet (for example, a polyethylene terephthalate (PET) film) as a base material was wrapped with a 200 mesh SUS wire, and the weight percentage of an insoluble adhesive component remaining in the wire when immersed in toluene kept at 23 ℃ for 24 hours was taken as a gel fraction. Wherein the weight of the base material was subtracted from the weight before and after dissolution of toluene.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is usually preferably 50 to 3000. Mu.m, more preferably 75 to 1000. Mu.m, particularly preferably 100 to 350. Mu.m. If the thickness of the adhesive layer is too small, the impact absorbability tends to be lowered. If the thickness of the pressure-sensitive adhesive layer is too large, the thickness of the whole of the pressure-sensitive adhesive layer tends to increase when the pressure-sensitive adhesive layer is bonded to an optical member, for example, and the practical applicability tends to be lowered.

The thickness of the adhesive layer was obtained by subtracting the measured value of the thickness of the constituent member other than the adhesive layer from the measured value of the thickness of the entire laminate including the adhesive layer using "ID-C112B" manufactured by Mitutoyo Corporation.

The adhesive layer of the adhesive sheet according to the first aspect preferably has a haze value of 2% or less, more preferably 0 to 1.5%, and particularly preferably 0 to 1% when the thickness of the adhesive layer is 100 μm. If the haze value is too high, the pressure-sensitive adhesive layer tends to whiten and the transparency tends to decrease.

The HAZE value was measured using a HAZE mat NDH4000 (manufactured by japan electric color industry corporation), and the obtained values of the Diffuse Transmittance (DT) and the Total Transmittance (TT) were calculated by substituting them into the following expression 1. The machine was in accordance with JIS K7361-1.

Haze value (%) = (DT/TT). Times.100. [ formula 1]

In the first aspect, an adhesive layer is laminated on an optical member, whereby an optical member with an adhesive layer can be obtained. For example, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the first aspect, in which the pressure-sensitive adhesive layer is formed on the release sheet, may be attached to the optical member, and then the release sheet may be peeled off to obtain the optical member with the pressure-sensitive adhesive layer. The optical members may be bonded to each other using the double-sided adhesive sheet.

As the optical member, a member constituting a touch panel or an image display device is exemplified. For example, a display (organic EL, liquid crystal), a transparent conductive film substrate (ITO substrate), a protective film (glass), a transparent antenna (film), a transparent wiring, and the like are given.

In the preferred embodiment of the first aspect described above, the following [ A1] to [ A7] are included, but are not limited thereto.

[A1] An adhesive composition comprising an acrylic resin (A) and a photoinitiator (B), wherein the acrylic resin (A) is a polymerization product of a copolymerization component (a) having a dynamic viscoelasticity-based glass transition temperature of-10 ℃ or higher, and the copolymerization component (a) contains at least: the polymerization initiator (B) comprises an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer, an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer, and a hydroxyl group-containing monomer (a 3), wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45, the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 30 to 70% by weight relative to the copolymerization component (a), and the photoinitiator (B) contains an intramolecular hydrogen-abstracting photoinitiator (B1) and an intermolecular hydrogen-abstracting photoinitiator (B2).

[A2] The adhesive composition according to [ A1], which further contains a crosslinking agent (C).

[A3] The adhesive composition according to [ A1] or [ A2], wherein the acrylic resin (A) has a weight average molecular weight of 50,000 ～ 500,000.

[A4] An adhesive agent obtained by crosslinking the adhesive agent composition according to any one of [ A1] to [ A3 ].

[A5] The adhesive according to [ A4], wherein the crosslinking is performed by irradiation of active energy rays.

[A6] An adhesive sheet having an adhesive layer formed of the adhesive of [ A4] or [ A5 ].

[A7] The adhesive sheet according to [ A6], wherein the adhesive layer is multi-stage curable by curing in a plurality of stages.

Second mode

Hereinafter, the second embodiment of the present invention will be described in detail, but these are disclosed as typical examples of the preferred embodiments.

< adhesive composition >

The adhesive composition of the second embodiment contains an acrylic resin (a) and a photoinitiator (B). The adhesive composition of the second embodiment may contain, in addition to the acrylic resin (a) and the photoinitiator (B), a crosslinking agent (C), a silane coupling agent (D), a carbodiimide compound (E), and other optional components, as necessary. The respective components will be described in order below.

(acrylic resin (A))

The acrylic resin (a) of the second embodiment is a polymerization product of a specific copolymerization component (a). The copolymerization component (a) is a generic term for monomer components having a polymerizable double bond. The copolymerization component (a) contains no polymerization initiator and no polymerization solvent.

The specific copolymerization component (a) according to the second aspect contains at least: an alkyl (meth) acrylate (a 1) having an alkyl group having 12 or less carbon atoms and having a glass transition temperature of a homopolymer of-20 to 120 ℃; and a hydroxyalkyl monomer (a 2) containing an alkyl chain, a hydroxyl group and an ethylenically unsaturated group. The copolymerization component (a) of the second embodiment may further contain an ethylenically unsaturated monomer (a 3) other than the alkyl (meth) acrylate (a 1) and the hydroxyalkyl monomer (a 2), if necessary.

[ alkyl (meth) acrylate (a 1) ]

The alkyl (meth) acrylate (a 1) of the second embodiment has an alkyl group having 12 or less carbon atoms. The alkyl group of the alkyl (meth) acrylate (a 1) preferably has a carbon number of 8 or less, more preferably 4 or less. When the carbon number of the alkyl group of the alkyl (meth) acrylate (a 1) is not more than the above-mentioned upper limit, excellent adhesive properties can be easily obtained in a low crosslinked state after one-time curing.

The alkyl (meth) acrylate (a 1) of the second embodiment is a monomer having a homopolymer thereof and a glass transition temperature (hereinafter referred to as "Tg") of-20 to 120 ℃.

The Tg of the homopolymer of the alkyl (meth) acrylate (a 1) according to the second embodiment is preferably 0 to 105℃and more preferably 5 to 70 ℃. Since the Tg of the homopolymer of the alkyl (meth) acrylate (a 1) is within the above-mentioned numerical range, an adhesive sheet excellent in adhesion even when adhered to an adherend having a complicated shape to which a strong stress is applied can be obtained.

The homopolymer of the alkyl (meth) acrylate (a 1) is a homopolymer of the alkyl (meth) acrylate (a 1). As the Tg of the homopolymer of the alkyl (meth) acrylate (a 1), the analytical value of the standard described in Wiley publication, "POLYMER HANDBOOK", etc. can be used.

Examples of the alkyl (meth) acrylate (a 1) according to the second embodiment include methyl acrylate (Tg: 8 ℃), t-butyl acrylate (Tg: 41 ℃), cyclohexyl acrylate (Tg: 15 ℃), isobornyl acrylate (Tg: 97 ℃), methyl methacrylate (Tg: 105 ℃), ethyl methacrylate (Tg: 65 ℃), n-butyl methacrylate (Tg: 20 ℃), isobutyl methacrylate (Tg: 48 ℃), t-butyl methacrylate (Tg: 107 ℃), 2-ethylhexyl methacrylate (Tg: -10 ℃) and cyclohexyl methacrylate (Tg: 66 ℃). Among them, methyl acrylate, methyl methacrylate, ethyl methacrylate, and isobutyl methacrylate are preferable from the viewpoint of adhesive properties.

The alkyl (meth) acrylate (a 1) may be used alone or in combination of 1 or more than 2.

[ hydroxyalkyl monomer (a 2) ]

The hydroxyalkyl monomer (a 2) of the second embodiment contains an alkyl chain, a hydroxyl group and an ethylenically unsaturated group.

The hydroxyalkyl monomer (a 2) of the second embodiment can be represented by the following general formula, for example.

CH ₂ ＝CHR-X-Y-OH

Wherein R is a hydrogen atom or a methyl group, X is an oxygen atom, COO or CONH, and Y is a linear or branched alkyl chain.

The average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymerization component (a) of the second embodiment is 2.1 or more, preferably 2.1 to 8.0, more preferably 2.4 to 6.0, and particularly preferably 2.6 to 4.0. If the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) is too small, the reliability at the time of complete curing tends to be lowered. If the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) is too large, the adhesive properties after one-time curing tend to be lowered.

Here, when the copolymerization component (a) of the second embodiment contains 1 type of hydroxyalkyl monomer (a 2), the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) is the carbon number itself of the alkyl chain of the 1 type of hydroxyalkyl monomer (a 2).

On the other hand, when the copolymerization component (a) of the second embodiment contains 2 or more hydroxyalkyl monomers (a 2), the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) is the weight average value of the carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymerization component (a) of the second embodiment.

For example, the copolymer component (a) of the second embodiment contains w in 100 parts by weight of the copolymer component (a) _s Weight parts of monomers s and w _t When 2 parts by weight of the monomer t are used as the hydroxyalkyl monomer (a 2), the average carbon number n of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymerization component (a) of the second embodiment is determined as follows.

n＝n _s ×w _s /(w _s +w _t )+n _t ×w _t /(w _s +w _t )

Here, n _s The carbon number of the alkyl chain of the monomer s, n _t Carbon number of the alkyl chain of the monomer t.

When the copolymer component (a) of the second embodiment contains 3 or more hydroxyalkyl monomers (a 2), the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymer component (a) is also determined by the same calculation formula.

Examples of the hydroxyalkyl monomer (a 2) of the second embodiment include (meth) acrylic acid hydroxyalkyl ester monomers such as (meth) acrylic acid esters containing a primary hydroxyl group, e.g., 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 7-hydroxyheptyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, and (meth) acrylic acid esters containing a secondary or tertiary hydroxyl group, e.g., 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-dimethyl 2-hydroxyethyl (meth) acrylate; hydroxyalkyl (meth) acrylamides such as N- (2-hydroxyethyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide, and N- (6-hydroxyhexyl) (meth) acrylamide;

Hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and 6-hydroxyhexyl vinyl ether.

The hydroxyalkyl monomer (a 2) may be used alone or in combination of 1 or more than 2.

Of these, primary hydroxyl group-containing (meth) acrylates are preferred, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are particularly preferred to be used in combination or 4-hydroxybutyl (meth) acrylate alone.

[ ethylenically unsaturated monomer (a 3) ]

The copolymerization component (a) of the second embodiment may further contain, if necessary, a copolymerizable ethylenically unsaturated monomer (a 3) other than the alkyl (meth) acrylate (a 1) and the hydroxyalkyl monomer (a 2).

Examples of the other copolymerizable ethylenically unsaturated monomer (a 3) include alkyl (meth) acrylates such as n-butyl acrylate and 2-ethylhexyl (meth) acrylate (excluding alkyl (meth) acrylate (a 1));

carboxyl group-containing monomers such as acrylic acid dimers (meth) acrylic acid, β -carboxyethyl acrylate, etc., crotonic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycollic acid, cinnamic acid, etc.;

hydroxyl group-containing monomers other than the hydroxyalkyl monomer (a 2), such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, caprolactone-modified 2-hydroxyethyl (meth) acrylate, and 2-acryloyloxyethyl-2-hydroxyethyl phthalate;

benzophenone-containing monomers such as 4- (meth) acryloxybenzophenone;

The ethylenically unsaturated monomer (a 3) may be used alone or in combination of 1 or more than 2.

[ composition of the copolymerization component (a) of the second embodiment ]

In the second aspect, the content of the alkyl (meth) acrylate (a 1) is 30 wt% or more with respect to 100 wt% of the copolymerization component (a). The content of the alkyl (meth) acrylate (a 1) is preferably 35 to 75% by weight, more preferably 40 to 65% by weight, and still more preferably 45 to 60% by weight. If the content of the alkyl (meth) acrylate (a 1) is too small, the adhesive properties in the primary cured state tend to be lowered. If the content of the alkyl (meth) acrylate (a 1) is too large, the adhesive properties after complete curing tend to be lowered.

In the second embodiment, the content of the hydroxyalkyl monomer (a 2) is 0.1 wt% or more, preferably 0.1 to 30 wt%, more preferably 5 to 30 wt%, and still more preferably 10 to 25 wt% relative to 100 wt% of the copolymer component (a). If the content of the hydroxyalkyl monomer (a 2) is too small, the adhesive properties in the primary cured state tend to be lowered. If the content of the hydroxyalkyl monomer (a 2) is too large, the adhesive properties after complete curing tend to be lowered.

In the copolymerization component (a) of the second embodiment, the content ratio (a 1/a 2) of the alkyl (meth) acrylate (a 1) and the hydroxyalkyl monomer (a 2) is preferably 95/5 to 50/50, more preferably 85/15 to 70/30, and particularly preferably 80/20 to 75/25 in terms of weight ratio. When the content ratio (a 1/a 2) is within the above numerical range, the adhesive properties in the primary cured state are excellent.

When the second embodiment contains the ethylenically unsaturated monomer (a 3), the content of the ethylenically unsaturated monomer (a 3) is usually 50% by weight or less, preferably 40% by weight or less, and more preferably 35% by weight or less, based on 100% by weight of the copolymerized component (a). If the content of the ethylenically unsaturated monomer (a 3) is too large, the adhesive properties tend to be lowered at the time of low crosslinking.

The acrylic resin (a) of the second embodiment may be a copolymer having a structural unit based on the alkyl (meth) acrylate (a 1) and a structural unit based on the hydroxyalkyl monomer (a 2). In this case, the acrylic resin (a) may have a structural unit based on the ethylenically unsaturated monomer (a 3) in addition to the structural unit based on the alkyl (meth) acrylate (a 1) and the structural unit based on the hydroxyalkyl monomer (a 2), if necessary. In this case, the ratio of the structural units based on the respective monomers may be determined according to the composition of the copolymerization component (a), and the same preferable mode is adopted.

The dynamic viscoelasticity-based glass transition temperature of the acrylic resin (A) of the second embodiment is-10℃or higher, preferably-5 to 20 ℃, more preferably 0 to 15 ℃, and particularly preferably 2 to 13 ℃. If the glass transition temperature of the acrylic resin (a) based on dynamic viscoelasticity is too high, the adhesive strength tends to be lowered with a decrease in the level difference following property and a decrease in the adhesion of the adhesive layer. If the glass transition temperature of the acrylic resin (a) based on dynamic viscoelasticity is too low, the adhesive properties at the time of low crosslinking tend to be lowered.

An acrylic resin solution containing only the acrylic resin (a) and an organic solvent is prepared by using an appropriate organic solvent. After the concentration of the acrylic resin solution was adjusted, the film was coated on a release sheet so that the thickness after drying became 50. Mu.m. Thereafter, the resultant is dried by a heat treatment at 90 to 105℃for 5 to 10 minutes, whereby the organic solvent is removed, and then the resultant is attached to a release sheet, whereby an acrylic resin sheet containing 99% or more of an acrylic resin is produced. Thereafter, a plurality of acrylic resin sheets were laminated to prepare an acrylic resin sheet having a thickness of about 800. Mu.m. The dynamic viscoelasticity of the produced sheet was measured under the following conditions, and the temperature at which the loss tangent (loss modulus G "/storage modulus G' =tan δ) became maximum was read as the glass transition temperature of the acrylic resin (a) based on the dynamic viscoelasticity.

(conditions for measuring dynamic viscoelasticity)

Deformation mode: shearing

Strain: 0.1%

Measuring temperature: 100-60 DEG C

Measuring frequency: 1Hz

In the second embodiment, the weight average molecular weight of the acrylic resin (a) is preferably 50,000 ～ 500,000, more preferably 100,000 ～ 400,000, and further preferably 150,000 ～ 350,000. When the weight average molecular weight of the acrylic resin (a) is too large, the viscosity tends to be too high, and the coatability and handleability tend to be lowered. If the weight average molecular weight of the acrylic resin (a) is too small, cohesive force tends to be lowered and adhesive properties tend to be lowered.

[ method for producing acrylic resin (A) ]

In the second embodiment, the acrylic resin (a) can be produced by polymerizing a copolymerization component (a) containing the alkyl (meth) acrylate (a 1) and the hydroxyalkyl monomer (a 2).

The copolymerization component (a) of the second embodiment may further contain an ethylenically unsaturated monomer (a 3) which is an optional polymerization component.

Hereinafter, an example of a preferred method for producing the acrylic resin (a) according to the second aspect is shown.

For example, the copolymerization component (a) of the second embodiment and the polymerization initiator may be mixed or added dropwise to an organic solvent, thereby performing solution polymerization.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; aliphatic alcohols such as methanol, ethanol, n-propanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aliphatic ethers such as dimethyl ether and diethyl ether; aliphatic halogenated hydrocarbons such as methylene chloride and dichloroethane; cyclic ethers such as tetrahydrofuran, and the like.

The organic solvent may be used alone or in combination of at least 2 kinds.

(photoinitiator (B))

The photoinitiator (B) of the second embodiment contains an intramolecular hydrogen abstraction type photoinitiator (B1). The photoinitiator (B) of the second embodiment preferably further contains an intermolecular hydrogen abstraction type photoinitiator (B2).

The photoinitiator (B) of the second embodiment may contain a photoinitiator (B3) other than the intramolecular hydrogen abstraction type photoinitiator (B1) and the intermolecular hydrogen abstraction type photoinitiator (B2) as long as the effect of the invention is not impaired.

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

The intramolecular hydrogen abstraction photoinitiator (b 1) of the second embodiment has a structure capable of generating radicals by abstracting hydrogen of the photoinitiator itself. For example, the intramolecular hydrogen abstraction type photoinitiator (b 1) may have a phenylglyoxylate structure or the like.

Examples of the intramolecular hydrogen abstraction type photoinitiator (b 1) according to the second embodiment include 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl ester, methyl phenylglyoxylate and the like.

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

The intermolecular hydrogen abstraction type photoinitiator (b 2) of the second embodiment has a structure capable of generating radicals by abstracting hydrogen from outside the photoinitiator itself. The intermolecular hydrogen abstraction type photoinitiator (b 2) may have a benzophenone structure, for example.

Examples of the intermolecular hydrogen abstraction type photoinitiator (b 2) according to the second embodiment include benzophenone, 4-methyl-benzophenone, 2,4, 6-trimethylbenzophenone, 4-phenylbenzophenone, 3 '-dimethyl-4-methoxybenzophenone, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloyloxy) ethoxy ] benzophenone, 4- (meth) acryloyloxy-4' -methoxybenzophenone, carboxymethoxybenzophenone-polyethylene glycol 250 diester, methyl 2-benzoylbenzoate, 4- (1, 3-acryl-1, 4,7,10, 13-pentaoxo tridecyl) benzophenone, and the like.

Among these, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloxyethoxy) benzophenone, 4- (meth) acryloxy4' -methoxybenzophenone, and carboxymethoxybenzophenone-polyethylene glycol 250 diester in which a plurality of crosslinking points exist in the molecule are preferable in terms of achieving high crosslinking.

[ other photoinitiators (b 3) ]

Examples of the other photoinitiator (b 3) of the second embodiment include acetophenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzildimethylketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone oligomer;

As the auxiliary agent of the photoinitiator (B) of the second embodiment, triethanolamine, triisopropanolamine, 4 '-dimethylaminobenzophenone (milbetone), 4' -diethylaminobenzophenone, 2-dimethylaminoethyl benzoate, ethyl 4-dimethylaminobenzoate (n-butoxy) ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone, and the like may be used in combination.

(crosslinking agent (C))

The adhesive composition of the second embodiment preferably contains a crosslinking agent (C) in addition to the acrylic resin (a) and the photoinitiator (B).

Examples of the crosslinking agent (C) include an active energy ray crosslinking agent (C1) and a thermal crosslinking agent (C2).

The active energy ray crosslinking agent (c 1) and the thermal crosslinking agent (c 2) may be used alone or in combination of at least 2.

When the crosslinking agent (C) contains only the active energy ray crosslinking agent (C1), multistage curing can be achieved only by controlling the amount of active energy rays. In the case where the active energy ray crosslinking agent (C1) and the thermal crosslinking agent (C2) are contained as the crosslinking agent (C), multi-stage curing can be also achieved by using a combination of thermal curing and active energy ray curing.

[ active energy ray-crosslinking agent (c 1) ]

The active energy ray crosslinking agent (c 1) includes a polyfunctional crosslinking agent having 2 or more ethylenically unsaturated groups in 1 molecule.

[ thermal crosslinking agent (c 2) ]

The thermal crosslinking agent (c 2) can exhibit excellent adhesion by reacting with a functional group of a functional group-containing monomer derived from a constituent monomer mainly of the acrylic resin (a). For example, isocyanate-based crosslinking agent (c 2-1), epoxy-based crosslinking agent (c 2-2), aziridine-based crosslinking agent (c 2-3), melamine-based crosslinking agent (c 2-4), aldehyde-based crosslinking agent (c 2-5), amine-based crosslinking agent (c 2-6), and metal chelate-based crosslinking agent (c 2-7). Among these, the isocyanate-based crosslinking agent (c 2-1) is suitably used in terms of improving the adhesion to the substrate and reactivity with the acrylic resin (a).

alicyclic isocyanate compounds such as isophorone diisocyanate;

biuret and isocyanurate bodies of these isocyanate compounds; etc.

(silane coupling agent (D))

From the viewpoint of improving durability, the adhesive composition of the second embodiment preferably further contains a compound other than the acrylic resin (a), the photoinitiator (B), and the crosslinking agent (C) as the silane coupling agent (D).

(carbodiimide-based Compound (E))

From the viewpoint of heat resistance, the adhesive composition of the second embodiment preferably further contains a carbodiimide compound (E) as a compound other than the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C), and the silane coupling agent (D).

(optional component)

The adhesive composition of the second embodiment may contain an adhesive as an optional other component, if necessary. The adhesive composition of the second embodiment may contain conventionally known additives such as a crosslinking accelerator, an antistatic agent, a tackifier, and a functional pigment.

(composition of adhesive composition)

In the second aspect, the content of the acrylic resin (a) is preferably 80% by weight or more, more preferably 90 to 99.9% by weight, and still more preferably 92 to 99.9% by weight, based on the entire adhesive composition. When the content of the acrylic resin (a) is within the above numerical range, excellent adhesive properties are easily obtained in a low crosslinked state after primary curing.

In the second embodiment, the content of the photoinitiator (B) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 4.0 parts by weight, and still more preferably 1.0 to 3.0 parts by weight, based on 100 parts by weight of the acrylic resin (a). When the content of the photoinitiator (B) is within the above-mentioned numerical range, sufficient curability can be obtained at the time of complete curing.

In the second embodiment, the content of the intramolecular hydrogen abstraction type photoinitiator (b 1) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the acrylic resin (a).

In the case where the photoinitiator (B) in the second embodiment contains the intermolecular hydrogen-abstraction type photoinitiator (B2), the content of the intermolecular hydrogen-abstraction type photoinitiator (B2) is preferably 0.1 to 3.0 parts by weight, more preferably 0.5 to 2.0 parts by weight, relative to 100 parts by weight of the acrylic resin (a).

In the case where the photoinitiator (B) in the second embodiment contains another photoinitiator (B3), the content of the photoinitiator (B3) is preferably 2.0 parts by weight or less, more preferably 1.0 parts by weight or less, based on 100 parts by weight of the acrylic resin (a).

In the case where the adhesive composition contains the active energy ray crosslinking agent (c 1) in the second embodiment, the content of the active energy ray crosslinking agent (c 1) is usually preferably 0.01 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, still more preferably 0.5 to 7.5 parts by weight, relative to 100 parts by weight of the acrylic resin (a).

As the crosslinking agent (C) in the second embodiment, an active energy ray crosslinking agent (C1) and a thermal crosslinking agent (C2) may be used in combination. When the active energy ray crosslinking agent (c 1) and the thermal crosslinking agent (c 2) are used in combination, the content ratio (c 1/c 2) of the active energy ray crosslinking agent (c 1) to the thermal crosslinking agent (c 2) is preferably 100/1 to 100/50 in terms of weight ratio.

In the case where the adhesive composition in the second embodiment contains the silane coupling agent (D), the content of the silane coupling agent (D) is preferably 0.001 to 3 parts by weight, more preferably 0.005 to 1 part by weight, still more preferably 0.01 to 0.5 part by weight, and particularly preferably 0.015 to 0.3 part by weight, relative to 100 parts by weight of the acrylic resin (a).

In the case where the adhesive composition of the second aspect contains other adhesives or additives, the content of the other adhesives or additives is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, based on 100 parts by weight of the acrylic resin (a).

(preparation of adhesive composition)

The adhesive composition of the second embodiment can be obtained by mixing the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C) if necessary, the silane coupling agent (D), the carbodiimide compound (E), and other optional components.

(use)

The adhesive composition of the second aspect may be suitably used for an adhesive of a multi-stage curable adhesive sheet cured by a plurality of stages. With the adhesive composition of the second aspect, excellent adhesive properties can be obtained even in a low crosslinked state after one-time curing. Further, it exhibits not only general adhesive properties such as adhesive force after complete curing, but also excellent durability when it is bonded to various kinds and shapes of members such as polarizing plates and glass.

The adhesive composition of the second embodiment has excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinked state after one-time curing, and thus has improved handling properties and reliability. Therefore, the adhesive sheet is suitable for applications such as adhesives and pressure-sensitive adhesive sheets used in touch panels, image display devices, and the like.

< adhesive >

The adhesive according to the second aspect is obtained by crosslinking the adhesive composition according to the second aspect. The adhesive composition of the second aspect is crosslinked (cured), whereby the acrylic resin (a) contained in the adhesive composition forms a crosslinked structure in at least one of the intramolecular and intermolecular directions. As a result, the adhesive composition of the second embodiment is crosslinked to form the adhesive of the second embodiment.

The adhesive of the second embodiment exhibits multi-stage curability in which it can be cured in multiple stages. The adhesive of the second embodiment is in a low crosslinked state by one-time curing before complete curing. The complete curing and the primary curing are not necessarily clearly distinguishable, but can be distinguished by, for example, differences in gel fraction, dynamic viscoelasticity.

The adhesive according to the second aspect is excellent in adhesive properties after primary curing, and therefore is suitable for bonding optical members constituting touch panels, image display devices, and the like.

The adhesive according to the second aspect may be said to contain at least the crosslinked product of the acrylic resin (a) according to the second aspect. The crosslinked product may be a partially crosslinked product obtained by partially crosslinking at least a part of the acrylic resin (a), or may be a completely crosslinked product obtained by crosslinking the entire acrylic resin (a). The adhesive according to the second aspect may contain both a partially crosslinked product and a completely crosslinked product of the acrylic resin (a).

< adhesive sheet >

The adhesive sheet of the second aspect has an adhesive layer formed of the adhesive of the second aspect. The adhesive layer of the adhesive sheet of the second embodiment may exhibit multi-stage curability by curing in multiple stages.

The adhesive sheet may be produced by providing an adhesive layer formed of the adhesive of the second aspect on a base sheet. The double-sided adhesive sheet may be formed by providing an adhesive layer on a release sheet.

As a method for producing the pressure-sensitive adhesive sheet according to the second aspect, for example, the following methods (i) and (ii) are mentioned.

(i) And a method of forming an adhesive sheet by applying a coating liquid obtained by dissolving the adhesive composition of the second embodiment in a solvent.

(ii) And a method of melting the adhesive composition of the second embodiment by heating to prepare an adhesive sheet.

The method of (i) will be described.

When the adhesive sheet is produced by coating a coating liquid obtained by dissolving the adhesive composition of the second embodiment in a solvent, the concentration of the coating liquid containing the adhesive composition of the second embodiment is adjusted by using an appropriate organic solvent, and the adhesive sheet is directly coated on the substrate sheet. Thereafter, the sheet is dried by, for example, heating at 80 to 105℃for 0.5 to 10 minutes, and then attached to a base sheet or a release sheet. Thereafter, the adhesive composition is crosslinked (cured) by irradiation with active energy rays or curing, whereby an adhesive sheet having an adhesive layer formed of an adhesive can be produced.

The method of (ii) is described.

When the adhesive composition of the second aspect is melted by heating to form an adhesive sheet, the adhesive layer is formed on one or both sides of the base sheet so as to have a desired film thickness, for example, by a method of coating one or both sides of the base sheet in a melted state and then cooling the same, a method of extrusion lamination on the base sheet using a T die or the like, or the like. Then, a release sheet is bonded to the adhesive layer as needed, whereby an adhesive sheet can be produced.

Metal foils of aluminum, copper, iron, etc,

High-quality paper, glassine paper and other paper,

The method of coating the adhesive composition is not particularly limited. Examples thereof include roll coating, die coating, gravure coating, comma coating, slit coating, screen printing, and the like.

Adjusting the irradiation amount of the active energy ray.

The adhesive layer of the adhesive sheet according to the second aspect preferably has a haze value of 2% or less, more preferably 0 to 1.5%, and particularly preferably 0 to 1% when the thickness of the adhesive layer is 100 μm. If the haze value is too high, the pressure-sensitive adhesive layer tends to whiten and the transparency tends to decrease.

Haze value (%) = (DT/TT). Times.100. [ formula 1]

In the second aspect, an adhesive layer is laminated on the optical member, whereby an optical member with an adhesive layer can be obtained. For example, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the second aspect, in which the pressure-sensitive adhesive layer is formed on the release sheet, may be attached to an optical member, and then the release sheet may be peeled off to obtain an optical member with the pressure-sensitive adhesive layer. The optical members may be bonded to each other using the double-sided adhesive sheet.

In the preferred embodiment of the second aspect described above, the following [ B1] to [ B8] are included, but are not limited thereto.

[B1] An adhesive composition comprising an acrylic resin (A) which is a polymerization product of a copolymerization component (a) described below, and a photoinitiator (B) which contains an intramolecular hydrogen abstraction type photoinitiator (B1), wherein the glass transition temperature of the acrylic resin (A) based on dynamic viscoelasticity is-10 ℃ or higher.

The copolymerization component (a) contains at least: an alkyl (meth) acrylate (a 1) having an alkyl group having 12 or less carbon atoms and having a glass transition temperature of a homopolymer of-20 to 120 ℃; and a hydroxyalkyl monomer (a 2) containing an alkyl chain, a hydroxyl group and an ethylenically unsaturated group, wherein the content of the alkyl (meth) acrylate (a 1) is 30% by weight or more relative to 100% by weight of the copolymerized component (a), the content of the hydroxyalkyl monomer (a 2) is 0.1% by weight or more relative to 100% by weight of the copolymerized component (a), and the average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymerized component (a) is 2.1 or more.

[B2] The adhesive composition according to [ B1], wherein the photoinitiator (B) further comprises an intermolecular hydrogen abstraction type photoinitiator (B2).

[B3] The adhesive composition according to [ B1] or [ B2], which further contains a crosslinking agent (C).

[B4] The adhesive composition according to any one of [ B1] to [ B3], wherein the weight average molecular weight of the acrylic resin (A) is 50,000 ～ 500,000.

[B5] An adhesive comprising a crosslinked adhesive composition according to any one of [ B1] to [ B4 ].

[B6] The adhesive according to [ B5], wherein the crosslinking is performed by irradiation of active energy rays.

[B7] An adhesive sheet having an adhesive layer formed of the adhesive of [ B5] or [ B6 ].

[B8] The adhesive sheet according to [ B7], wherein the adhesive layer is multi-stage curable by curing in a plurality of stages.

Third mode

Hereinafter, the third embodiment of the present invention will be described in detail, but these are disclosed as typical examples of the preferred embodiments.

< adhesive composition >

The adhesive composition of the third embodiment contains an acrylic resin (a) and a photoinitiator (B). The adhesive composition of the third embodiment may contain a crosslinking agent (C), a silane coupling agent (D), a carbodiimide compound (E), and other optional components in addition to the acrylic resin (a) and the photoinitiator (B). The respective components will be described in order below.

(acrylic resin (A))

The acrylic resin (A) of the third embodiment is a polymerization product of a copolymerization component (a) containing a branched alkyl (meth) acrylate (a 1) having a homopolymer glass transition temperature of-30 ℃ or higher. The copolymerization component (a) is a generic term for monomer components having a polymerizable double bond. The copolymerization component (a) contains no polymerization initiator and no polymerization solvent.

The copolymerization component (a) of the third embodiment may contain, in addition to the branched alkyl (meth) acrylate (a 1), at least 1 or more selected from the group consisting of a hydroxyl group-containing (meth) acrylate (a 2), a (meth) acrylate monomer (a 3) containing an active energy ray-crosslinkable structural part, and an ethylenically unsaturated monomer (a 4), as required.

[ branched alkyl (meth) acrylate (a 1) ]

The branched alkyl (meth) acrylate (a 1) according to the third aspect is a (meth) acrylate containing a branched alkyl group.

The number of carbon atoms of the branched alkyl group of the branched alkyl (meth) acrylate (a 1) is not particularly limited. For example, it is preferably 30 or less, more preferably 20 or less, and further preferably 3 to 10. The lower limit of the number of carbons required to form a branch is typically 3.

The branched alkyl (meth) acrylate (a 1) of the third embodiment is a monomer having a homopolymer of which the glass transition temperature (hereinafter referred to as "Tg") is-30℃or higher.

The Tg of the homopolymer of the branched alkyl (meth) acrylate (a 1) according to the third embodiment is preferably from-30 to 150 ℃, more preferably from-20 to 140 ℃, still more preferably from-15 to 130 ℃, particularly preferably from-10 to 100 ℃. Since the Tg of the homopolymer of the branched alkyl (meth) acrylate (a 1) is within the above-mentioned numerical range, an adhesive sheet excellent in adhesion even when adhered to an adherend having a complicated shape to which a strong stress is applied can be obtained.

The homopolymer of the branched alkyl (meth) acrylate (a 1) according to the third embodiment is a homopolymer of the branched alkyl (meth) acrylate (a 1). As the Tg of the homopolymer of the branched alkyl (meth) acrylate (a 1), the standard analytical values described in Wiley publication, "POLYMER HANDBOOK" and the like can be used.

As the branched alkyl (meth) acrylate (a 1) of the third embodiment, for example, 2-ethylhexyl methacrylate (Tg: -10 ℃ C.), isobutyl methacrylate (Tg: 48 ℃ C.), tert-butyl methacrylate (Tg: 107 ℃ C.), and the like can be mentioned. Among them, 2-ethylhexyl methacrylate and isobutyl methacrylate are preferable from the viewpoint of adhesive properties.

The branched alkyl (meth) acrylate (a 1) may be used alone or in combination of 1 or more than 2.

[ hydroxyl group-containing (meth) acrylate (a 2) ]

The hydroxyl group-containing (meth) acrylate (a 2) of the third embodiment is a (meth) acrylate having a hydroxyl group (excluding the branched alkyl (meth) acrylate (a 1)).

The structural part derived from the polar group-containing monomer is introduced into the acrylic resin (a) by incorporating the hydroxyl group-containing (meth) acrylate (a 2) into the polymerization component constituting the acrylic resin (a).

Examples of the hydroxyl group-containing (meth) acrylate (a 2) according to the third aspect include hydroxyalkyl acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate;

caprolactone-modified monomers such as 2-hydroxyethyl (meth) acrylate;

oxyalkylene modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate;

primary hydroxyl group-containing (meth) acrylates such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, N-hydroxymethyl (meth) acrylamide, and hydroxyethyl acrylamide;

secondary hydroxyl group-containing (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-chloro 2-hydroxypropyl (meth) acrylate;

Hydroxy group-containing (meth) acrylates such as 2, 2-dimethyl-2-hydroxyethyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable.

The hydroxyl group-containing (meth) acrylate (a 2) may be used alone or in combination of 1 or more.

The hydroxyl group-containing (meth) acrylate (a 2) according to the third aspect is preferably one in which the content of di (meth) acrylate that can be contained as an impurity in the hydroxyl group-containing (meth) acrylate (a 2) is small. Specifically, the content of the di (meth) acrylate that can be contained in the hydroxyl group-containing (meth) acrylate (a 2) is preferably 0.5 wt% or less, more preferably 0.2 wt% or less, particularly preferably 0.1 wt% or less, and still more preferably 0 wt%.

The hydroxyl group-containing (meth) acrylate (a 2) of the third embodiment often contains acrylic acid as an impurity, and the content thereof is usually about 0.001 to 0.5% by weight, preferably less, in the hydroxyl group-containing (meth) acrylate (a 2).

[ (meth) acrylate monomer (a 3) containing an active energy ray-crosslinkable structural part ]

The acrylic resin (a) of the third aspect may have an active energy ray-crosslinkable structural part. The active energy ray-crosslinkable structural portion is a structural portion capable of forming a crosslinked structure by reacting with a part of the acrylic resin (a) or other curing component that may be contained in the adhesive composition by irradiation with active energy rays.

In the third embodiment, the active energy ray-crosslinkable structural part is preferably a benzophenone-based crosslinkable structural part in view of high reactivity and excellent improvement in cohesive force.

Therefore, the copolymerization component (a) of the third embodiment preferably further comprises a (meth) acrylate monomer (a 3) containing an active energy ray-crosslinkable structural site (excluding (meth) acrylic branched alkyl ester (a 1) and hydroxyl group-containing (meth) acrylate (a 2)).

The (meth) acrylate monomer (a 3) having an active energy ray-crosslinkable structural part as the third aspect is preferably a (meth) acrylate monomer having a benzophenone-based crosslinkable structural part in that an effective crosslinked structure can be formed by active energy rays such as ultraviolet rays and electron beams. Examples thereof include 4- (meth) acryloxybenzophenone.

The (meth) acrylate monomer (a 3) containing an active energy ray-crosslinkable structural part may be used alone or in combination of 1 or more than 2.

In addition, when introducing an active energy ray-crosslinkable structural part into the acrylic resin (a), in addition to copolymerizing the (meth) acrylate monomer (a 3) containing an active energy ray-crosslinkable structural part, the hydroxyl group may be previously contained in the acrylic resin (a), and an ethylenically unsaturated group-containing isocyanate compound may be reacted with the hydroxyl group to introduce an ethylenically unsaturated group as an active energy ray-crosslinkable structural part.

[ ethylenically unsaturated monomer (a 4) ]

The copolymerization component (a) of the third embodiment may further contain, if necessary, a copolymerizable ethylenically unsaturated monomer (a 4) other than the branched alkyl (meth) acrylate (a 1), the hydroxyl group-containing (meth) acrylate (a 2) and the (meth) acrylate monomer (a 3).

Examples of the other copolymerizable ethylenically unsaturated monomer (a 4) of the third embodiment include alkyl (meth) acrylates such as methyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl acrylate (excluding branched alkyl (meth) acrylate (a 1), hydroxyl group-containing (meth) acrylate (a 2), and (meth) acrylate monomer (a 3));

alicyclic-containing monomers such as cyclohexyloxyalkyl (meth) acrylate, t-butylcyclohexyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate;

The other ethylenically unsaturated monomer (a 4) may be used alone or in combination of 1 or more than 2.

For the purpose of increasing the molecular weight of the acrylic resin (a), a compound having two or more ethylenically unsaturated groups such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, divinylbenzene, and the like may be used in combination.

[ composition of the copolymerization component (a) of the third embodiment ]

In the third aspect, the content of the branched alkyl (meth) acrylate (a 1) is preferably 10% by weight or more, more preferably 10 to 60% by weight, still more preferably 15 to 50% by weight, and particularly preferably 20 to 45% by weight, based on 100% by weight of the copolymer component (a).

If the content of the branched alkyl (meth) acrylate (a 1) is too small, the adhesive properties tend to be lowered at the time of primary curing. If the content of the branched alkyl (meth) acrylate (a 1) is too large, the adhesive properties after complete curing tend to be lowered.

In the third aspect, the content of the hydroxyl group-containing (meth) acrylate (a 2) is preferably 5% by weight or more, more preferably 10 to 40% by weight, still more preferably 12 to 30% by weight, based on 100% by weight of the copolymer component (a). If the content of the hydroxyl group-containing (meth) acrylate (a 2) is too small, the wet heat resistance tends to be low. When the content of the hydroxyl group-containing (meth) acrylate (a 2) is too large, self-crosslinking reaction of the acrylic resin tends to occur, and heat resistance tends to be lowered.

In the third aspect, the content of the (meth) acrylate monomer (a 3) is preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, and still more preferably 0.2 to 1% by weight, relative to 100% by weight of the copolymerized component (a).

If the content of the (meth) acrylate monomer (a 3) is too small, the retention force tends to be low when a crosslinked structure is formed by active energy rays. In addition, when a crosslinked structure is formed in order to produce a processable adhesive sheet, a large amount of active energy rays is required. As a result, a large amount of energy is required for producing the pressure-sensitive adhesive sheet, and efficient production tends to be difficult.

If the content of the (meth) acrylate monomer (a 3) is too large, the cohesive force of the whole system is excessively increased, and the adhesive force tends to be lowered.

In the third embodiment, the content of the other ethylenically unsaturated monomer (a 4) is usually preferably 80% by weight or less, more preferably 70% by weight or less, and still more preferably 60% by weight or less, based on 100% by weight of the copolymerized component (a).

If the content of the other ethylenically unsaturated monomer (a 4) is too large, the adhesive properties at the time of low crosslinking may be lowered.

The acrylic resin (a) of the third embodiment may be a polymer having a structural unit based on the alkyl (meth) acrylate (a 1). In this case, the acrylic resin (a) may have at least 1 or more structural units selected from the group consisting of structural units based on the hydroxyl group-containing (meth) acrylate (a 2), structural units based on the (meth) acrylate monomer (a 3), and structural units based on the ethylenically unsaturated monomer (a 4), in addition to the structural units based on the branched alkyl (meth) acrylate (a 1). In this case, the ratio of the structural units based on the respective monomers may be determined according to the composition of the copolymerization component (a), and the same preferable mode is adopted.

The dynamic viscoelasticity-based glass transition temperature of the acrylic resin (A) of the third embodiment is-10℃or higher, preferably-5 to 20 ℃, more preferably 0 to 15 ℃, still more preferably 2 to 13 ℃. If the glass transition temperature due to dynamic viscoelasticity is too high, the adhesive force tends to be lowered with a decrease in the level difference following property and a decrease in the adhesion of the adhesive layer. If the glass transition temperature due to dynamic viscoelasticity is too low, the adhesive properties tend to be lowered at the time of low crosslinking.

(conditions for measuring dynamic viscoelasticity)

Deformation mode: shearing

Strain: 0.1%

Measuring temperature: 100-60 DEG C

Measuring frequency: 1Hz

In the third embodiment, the weight average molecular weight of the acrylic resin (a) is 400,000 or less, preferably 10,000 ～ 350,000, more preferably 50,000 ～ 300,000, further preferably 100,000 ～ 290,000, and particularly preferably 150,000 ～ 280,000. When the weight average molecular weight of the acrylic resin (a) is too large, the viscosity tends to be too high, and the coatability and handleability tend to be lowered. If the weight average molecular weight of the acrylic resin (a) is too small, cohesive force tends to be lowered and adhesive properties tend to be lowered.

The weight average molecular weight of the acrylic resin (a) is the weight average molecular weight at the time of completion of production, and is the weight average molecular weight of the acrylic resin (a) which is not heated or the like after production.

The weight average molecular weight of the acrylic resin (a) is a weight average molecular weight converted based on the molecular weight of standard polystyrene. By subjecting 3 columns to high performance liquid chromatography (made by Waters Co., ltd., "Waters2695 (Main body)" and "Waters2414 (Detector)"): shodex GPCKF-806L (exclusion limit molecular weight: 2X 10) ⁷ Separation range: 100 to 2X 10 ⁷ Theoretical stage number: 10000 grade/root, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) were used in series for the determination.

[ method for producing acrylic resin (A) ]

In the third aspect, the acrylic resin (a) can be produced by polymerizing a copolymerization component (a) containing a branched alkyl (meth) acrylate (a 1).

The copolymerization component (a) of the third embodiment may further contain a hydroxyalkyl (meth) acrylate (a 2), a (meth) acrylate monomer (a 3), and an ethylenically unsaturated monomer (a 4) as required.

Hereinafter, an example of a preferred method for producing the acrylic resin (a) according to the third aspect is shown.

For example, the copolymerization component (a) of the third embodiment and the polymerization initiator may be mixed or added dropwise to an organic solvent, whereby solution polymerization can be performed.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; aliphatic alcohols such as methanol, ethanol, n-propanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aliphatic ethers such as dimethyl ether and diethyl ether; aliphatic halogenated hydrocarbons such as methylene chloride and dichloroethane; cyclic ethers such as tetrahydrofuran, and the like. Among them, esters and ketones are preferable, and ethyl acetate, acetone and methyl ethyl ketone are particularly preferable.

The organic solvent may be used alone or in combination of at least 2 kinds.

The amount of the polymerization initiator to be used is usually 0.001 to 10 parts by weight, preferably 0.1 to 8 parts by weight, more preferably 0.5 to 6 parts by weight, particularly preferably 1 to 4 parts by weight, further preferably 1.5 to 3 parts by weight, and most preferably 2 to 2.5 parts by weight based on 100 parts by weight of the copolymerization component (a). If the amount of the polymerization initiator is too small, the polymerization rate of the acrylic resin (a) tends to decrease, and thus the residual monomer tends to increase. In addition, the weight average molecular weight of the acrylic resin (a) tends to be high. If the amount of the polymerization initiator is too large, gelation of the acrylic resin (a) tends to occur.

(photoinitiator (B))

The photoinitiator (B) of the third embodiment contains an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2). The photoinitiator (B) of the third embodiment may contain a photoinitiator (B3) other than the intramolecular hydrogen abstraction type photoinitiator (B1) and the intermolecular hydrogen abstraction type photoinitiator (B2) as long as the effect of the invention is not impaired.

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

Examples of the intramolecular hydrogen abstraction photoinitiator (b 1) according to the third aspect include 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl oxy-phenyl-acetate, a mixture of 2- [ 2-hydroxy-ethoxy ] -ethyl oxy-phenyl-acetate, and methyl benzoate.

Among these, a mixture of 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl oxy-phenyl-acetate and 2- [ 2-hydroxy-ethoxy ] -ethyl oxy-phenyl-acetate is preferable from the viewpoint of crosslinking efficiency at the time of complete curing.

Examples of the commercial products include "Omnirad 754" and "Omnirad MBF" manufactured by IGM RESINS b.v. company.

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

Examples of the intermolecular hydrogen abstraction type photoinitiator (b 2) according to the third embodiment include benzophenone, 4-methyl-benzophenone, 2,4, 6-trimethylbenzophenone, 4-phenylbenzophenone, 3 '-dimethyl-4-methoxybenzophenone, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloxyethoxy) benzophenone, 4- (meth) acryloxy4' -methoxybenzophenone, and carboxymethoxybenzophenone-polyethylene glycol 250 diester. Among them, 2,4, 6-trimethylbenzophenone is preferable in view of easy handling in a liquid. In addition, in terms of achieving high crosslinking, 4- (meth) acryloxybenzophenone, 4- [2- ((meth) acryloxyethoxy ] benzophenone, 4- (meth) acryloxy4' -methoxybenzophenone, carboxymethoxybenzophenone-polyethylene glycol 250 diester in which a plurality of crosslinking points exist in the molecule are preferable.

[ other photoinitiators (b 3) ]

The other photoinitiator (b 3) of the third embodiment includes 2- [ 2-oxo-2-phenylacetyloxyethoxy ] ethyl oxyphenyl-acetate, which is an intramolecular cleavage type acetophenone photoinitiator;

acetophenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzil dimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholinyl (4-methylthiophenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinylphenyl) butanone, 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone oligomer;

thioxanthones such as 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2, 4-diethylthioxanthone, 2, 4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2- (3-dimethylamino-2-hydroxy) -3, 4-dimethyl-9H-thioxanthone-9-ketone meso chloride;

As the auxiliary agent of the photoinitiator (B) of the third embodiment, triethanolamine, triisopropanolamine, 4 '-dimethylaminobenzophenone (milbetone), 4' -diethylaminobenzophenone, 2-dimethylaminoethyl benzoate, ethyl 4-dimethylaminobenzoate (n-butoxy) ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone, and the like may be used in combination.

(crosslinking agent (C))

The adhesive composition of the third embodiment preferably contains a crosslinking agent (C) in addition to the acrylic resin (a) and the photoinitiator (B).

When the crosslinking agent (C) contains only the active energy ray crosslinking agent (C1), multistage curing can be achieved only by controlling the amount of active energy rays. In the case where the active energy ray crosslinking agent (C1) and the thermal crosslinking agent (C2) are contained as the crosslinking agent (C), multi-stage curing can be also achieved by using a combination of thermal curing and active energy ray curing. By controlling the crosslinking reaction in this way, the cohesive force of the entire adhesive layer can be adjusted, and stable adhesive properties can be obtained after the primary curing and after the complete curing.

[ active energy ray-crosslinking agent (c 1) ]

Examples of the active energy ray crosslinking agent (c 1) include a monofunctional crosslinking agent having 1 ethylenically unsaturated group in a molecule and a polyfunctional crosslinking agent having 2 or more ethylenically unsaturated groups in a molecule. Among them, a polyfunctional crosslinking agent is preferable.

Examples of the polyfunctional crosslinking agent include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate, (poly) butanediol mono (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (poly) tetramethylene glycol di (meth) acrylate, (poly) pentamethylene glycol di (meth) acrylate, (poly) hexamethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, EO-modified glycerol tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, isocyanuric acid ethylene oxide-modified tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, urethane (meth) acrylates, and the like.

[ thermal crosslinking agent (c 2) ]

The thermal crosslinking agent (c 2) can exhibit excellent adhesion by reacting with a functional group of a functional group-containing monomer derived from a constituent monomer mainly of the acrylic resin (a). For example, isocyanate-based crosslinking agent (c 2-1), epoxy-based crosslinking agent (c 2-2), aziridine-based crosslinking agent (c 2-3), melamine-based crosslinking agent (c 2-4), aldehyde-based crosslinking agent (c 2-5), amine-based crosslinking agent (c 2-6), and metal chelate-based crosslinking agent (c 2-7).

Among them, the isocyanate-based crosslinking agent (c 2-1) is preferably used in terms of improving the adhesion to the substrate and reactivity with the acrylic resin (a).

alicyclic isocyanate compounds such as isophorone diisocyanate;

biuret and isocyanurate bodies of these isocyanate compounds; etc.

(silane coupling agent (D))

From the viewpoint of improving durability, the adhesive composition of the third embodiment preferably further contains a compound other than the acrylic resin (a), the photoinitiator (B), and the crosslinking agent (C) as the silane coupling agent (D).

Examples of the silane coupling agent (D) include 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, 3-mercaptopropyl dimethoxymethylsilane, gamma-glycidoxypropyl trimethoxysilane, gamma-glycidoxypropyl triethoxysilane, gamma-glycidoxypropyl methyldiethoxysilane, gamma-glycidoxypropyl methyldimethoxysilane, methyltris (glycidyl) silane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, and beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane.

Among them, gamma-glycidoxypropyl trimethoxysilane is preferred from the viewpoint of heat resistance.

(carbodiimide-based Compound (E))

In terms of heat resistance, the adhesive composition of the third embodiment preferably further contains a carbodiimide compound (E) as a compound other than the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C) and the silane coupling agent (D).

Examples of the carbodiimide-based compound (E) include mono-carbodiimides such as bis (2, 6-diisopropylphenyl) carbodiimide, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and docosalkylcarbodiimide, polycarbodiimides in which a plurality of carbodiimides are present, and cyclic carbodiimides.

Among them, a monocarbodiimide compound and further bis (2, 6-diisopropylphenyl) carbodiimide are preferable from the viewpoint of heat resistance.

(optional component)

The adhesive composition of the third embodiment may contain an adhesive as another optional component, if necessary. The adhesive composition according to the third embodiment may contain conventionally known additives such as a crosslinking accelerator, an antistatic agent, a thickener, and a functional dye.

(composition of adhesive composition)

In the third aspect, the content of the acrylic resin (a) is preferably 80% by weight or more, more preferably 90 to 99.9% by weight, and still more preferably 92 to 99.9% by weight, based on the entire pressure-sensitive adhesive composition. When the content of the acrylic resin (a) is within the above numerical range, an adhesive sheet exhibiting excellent adhesive properties in a low-crosslinked state after primary curing can be easily obtained.

In the third embodiment, the content of the photoinitiator (B) is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5.0 parts by weight, and still more preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the acrylic resin (a). When the content of the photoinitiator (B) is within the above-mentioned numerical range, sufficient curability can be obtained at the time of complete curing.

In the third embodiment, the content of the intramolecular hydrogen abstraction type photoinitiator (b 1) is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5.0 parts by weight, relative to 100 parts by weight of the acrylic resin (a). If the content of the intramolecular hydrogen abstraction photoinitiator (b 1) is too large, the adhesive force after complete curing tends to be lowered. If the content of the intramolecular hydrogen abstraction photoinitiator (b 1) is too small, the adhesive properties tend to be deteriorated at a low crosslinking degree.

In the third embodiment, the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5.0 parts by weight, based on 100 parts by weight of the acrylic resin (a). If the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is too large, the adhesive force after complete curing tends to be lowered. If the content of the intermolecular hydrogen abstraction type photoinitiator (b 2) is too small, the adhesive properties tend to be deteriorated at a low crosslinking degree.

In the case where the adhesive composition contains the crosslinking agent (C), the content of the crosslinking agent (C) is usually 20 parts by weight or less, more preferably 0.001 to 15 parts by weight, still more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the acrylic resin (a). If the content of the crosslinking agent (C) is too large, the adhesive strength tends to be low. If the content of the crosslinking agent (C) is too small, the adhesive properties tend to be lowered under high temperature conditions.

In the case where the adhesive composition contains the active energy ray crosslinking agent (c 1) in the third embodiment, the content of the active energy ray crosslinking agent (c 1) is usually preferably 0.01 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, still more preferably 0.5 to 7.5 parts by weight, relative to 100 parts by weight of the acrylic resin (a).

As the crosslinking agent (C) in the third aspect, an active energy ray crosslinking agent (C1) and a thermal crosslinking agent (C2) are preferably used in combination. When the active energy ray crosslinking agent (c 1) and the thermal crosslinking agent (c 2) are used in combination, the content ratio (c 1/c 2) of the active energy ray crosslinking agent (c 1) to the thermal crosslinking agent (c 2) is preferably 100/1 to 100/50 in terms of weight ratio.

In the case where the adhesive composition in the third embodiment contains the silane coupling agent (D), the content of the silane coupling agent (D) is preferably 0.001 to 3 parts by weight, more preferably 0.005 to 1 part by weight, still more preferably 0.01 to 0.5 part by weight, and particularly preferably 0.015 to 0.3 part by weight, relative to 100 parts by weight of the acrylic resin (a).

In the case where the adhesive composition contains another adhesive or an additive in the third embodiment, the content of the other adhesive or the additive is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, based on 100 parts by weight of the acrylic resin (a).

(preparation of adhesive composition)

The adhesive composition of the third embodiment can be obtained by mixing the acrylic resin (a), the photoinitiator (B), the crosslinking agent (C) if necessary, the silane coupling agent (D), the carbodiimide compound (E), and other optional components.

(use)

The adhesive composition of the third aspect can be suitably used for an adhesive of a multi-stage curable adhesive sheet cured in multiple stages. The adhesive composition according to the third aspect can provide an adhesive having low tackiness in a low-crosslinking state after one-time curing and excellent adhesive properties in terms of high constant load holding power. The cured product has not only general adhesive properties such as adhesive force after complete curing, but also excellent durability when bonded to various kinds and shapes of members such as polarizing plates and glass.

The adhesive composition of the third embodiment can continue to adhere to a complex shape to which stress is applied even in a low-crosslinking state after one-time curing, and can be completely cured thereafter. Therefore, the adhesive sheet is suitable for applications such as adhesives and pressure-sensitive adhesive sheets used in touch panels, image display devices, and the like.

< adhesive >

The adhesive according to the third aspect is obtained by crosslinking the adhesive composition according to the third aspect. The adhesive composition of the third aspect is crosslinked (cured), whereby the acrylic resin (a) contained in the adhesive composition forms a crosslinked structure in at least one of the intramolecular and intermolecular directions. As a result, the adhesive composition of the third embodiment is crosslinked to form the adhesive of the third embodiment.

The adhesive according to the third aspect exhibits multi-stage curability in which the adhesive can be cured in a plurality of stages. The adhesive according to the third embodiment is in a low crosslinked state by one-time curing before complete curing. The complete curing and the primary curing are not necessarily clearly distinguishable, but can be distinguished by, for example, differences in gel fraction, dynamic viscoelasticity.

The adhesive according to the third aspect is excellent in adhesive properties after primary curing, and therefore is suitable for bonding optical members constituting touch panels, image display devices, and the like.

The adhesive according to the third aspect may be said to contain at least the crosslinked product of the acrylic resin (a) according to the third aspect. The crosslinked product may be a partially crosslinked product obtained by partially crosslinking at least a part of the acrylic resin (a), or may be a completely crosslinked product obtained by crosslinking the entire acrylic resin (a). The adhesive according to the third aspect may contain both a partially crosslinked product and a completely crosslinked product of the acrylic resin (a).

< adhesive sheet >

The adhesive sheet of the third aspect has an adhesive layer formed of the adhesive of the third aspect. The adhesive layer of the adhesive sheet of the third aspect may exhibit multi-stage curability by curing in multiple stages.

The adhesive sheet may be produced by providing an adhesive layer formed of the adhesive of the third aspect on a base sheet. The double-sided adhesive sheet may be formed by providing an adhesive layer on a release sheet.

As a method for producing the pressure-sensitive adhesive sheet according to the third aspect, for example, the following methods (i) and (ii) are mentioned.

(i) And a method of forming an adhesive sheet by applying a coating liquid obtained by dissolving the adhesive composition of the third embodiment in a solvent.

(ii) And a method of melting the adhesive composition of the third embodiment by heating to prepare an adhesive sheet.

The method of (i) will be described.

When the adhesive sheet is produced by coating a coating liquid obtained by dissolving the adhesive composition of the third aspect in a solvent, the concentration of the coating liquid containing the adhesive composition of the third aspect is adjusted by using an appropriate organic solvent, and the adhesive sheet is directly coated on the substrate sheet. Thereafter, the sheet is dried by, for example, heating at 80 to 105℃for 0.5 to 10 minutes, and then attached to a base sheet or a release sheet. Thereafter, the adhesive composition is crosslinked (cured) by irradiation with active energy rays or curing, whereby an adhesive sheet having an adhesive layer formed of an adhesive can be produced.

The method of (ii) is described.

When the adhesive composition of the third aspect is melted by heating to form an adhesive sheet, the adhesive layer is formed on one or both sides of the base sheet so as to have a desired film thickness by a method of coating one or both sides of the base sheet in a melted state and then cooling the same, a method of extrusion lamination on the base sheet using a T die or the like, or the like. Then, a release sheet is bonded to the adhesive layer as needed, whereby an adhesive sheet can be produced.

Metal foils of aluminum, copper, iron, etc,

High-quality paper, glassine paper and other paper,

Woven and nonwoven fabrics made of glass fibers, natural fibers, synthetic fibers, and the like. These base sheet may be used in the form of a single layer or in the form of a multilayer body formed by stacking 2 or more kinds of base sheets. Among these, a synthetic resin sheet is preferable from the viewpoint of weight reduction and the like.

Adjusting the irradiation amount of the active energy ray.

The gel fraction is an index of the degree of crosslinking (degree of curing), and is calculated by the following method, for example. Specifically, an adhesive sheet (a release sheet is not provided) in which an adhesive layer is formed on a polymer sheet (for example, a polyethylene terephthalate (PET) film) as a base material is wrapped with a 200 mesh SUS wire mesh, and the weight percentage of an insoluble adhesive component remaining in the wire mesh when immersed in toluene kept at 23 ℃ for 24 hours is taken as a gel fraction. Wherein the weight of the base material was subtracted from the weight before and after dissolution of toluene.

The haze value of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the third aspect is preferably 2% or less, more preferably 0 to 1.5%, and particularly preferably 0 to 1% when the thickness of the pressure-sensitive adhesive layer is 100. Mu.m. If the haze value is too high, the pressure-sensitive adhesive layer tends to whiten and the transparency tends to decrease.

Haze value (%) = (DT/TT). Times.100. [ formula 1]

In the third aspect, an adhesive layer is laminated on the optical member, whereby an optical member with an adhesive layer can be obtained. For example, the adhesive layer of the adhesive sheet of the third aspect, in which the adhesive layer is formed on the release sheet, may be attached to the optical member, and then the release sheet may be peeled off, thereby obtaining the optical member with the adhesive layer. The optical members may be bonded to each other using the double-sided adhesive sheet.

In the third embodiment described above, the following [ C1] to [ C6] are included, but are not limited thereto.

[C1] An adhesive composition comprising an acrylic resin (A) and a photoinitiator (B), wherein the acrylic resin (A) is a polymerization product of a copolymerization component (a) comprising a branched alkyl (meth) acrylate (a 1) having a homopolymer glass transition temperature of-30 ℃ or higher, the acrylic resin (A) has a dynamic viscoelasticity-based glass transition temperature of-10 ℃ or higher, the acrylic resin (A) has a weight average molecular weight of 400,000 or less, and the photoinitiator (B) comprises an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2).

[C2] The adhesive composition according to [ C1], which further contains a crosslinking agent (C).

[C3] An adhesive agent obtained by crosslinking the adhesive agent composition of [ C1] or [ C2 ].

[C4] The adhesive according to [ C3], wherein the crosslinking is performed by irradiation of active energy rays.

[C5] An adhesive sheet having an adhesive layer formed of the adhesive of [ C3] or [ C4 ].

[C6] The adhesive sheet according to [ C5], wherein the adhesive layer is multi-stage curable by curing in a plurality of stages.

In a preferred embodiment of the present invention, the following [1] to [26] are included, but are not limited thereto.

[1] An adhesive composition comprising an acrylic resin (A) and a photoinitiator (B), wherein the acrylic resin (A) is a polymerization product of a copolymerization component (a) comprising: an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer, and an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer, wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 5% by weight or more relative to 100% by weight of the copolymerization component (a).

[2] The adhesive composition according to [1], wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 3).

[3] The adhesive composition according to [2], wherein the content of the hydroxyl group-containing monomer (a 3) is 0.1% by weight or more relative to 100% by weight of the copolymerization component (a).

[4] The adhesive composition according to any one of [1] to [3], wherein the acrylic resin (A) has a glass transition temperature of-10 ℃ or higher based on dynamic viscoelasticity.

[5] The adhesive composition according to any one of [1] to [4], wherein the weight average molecular weight of the acrylic resin (A) is 50,000 ～ 500,000.

[6] The adhesive composition according to any one of [1] to [5], wherein the weight average molecular weight of the acrylic resin (A) is 50,000 ～ 400,000.

[7] The adhesive composition according to any one of [1] to [6], wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45.

[8] The adhesive composition according to any one of [1] to [7], wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 30 to 70% by weight based on the copolymerization component (a).

[9] The adhesive composition according to any one of [1] to [8], wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 4), and the hydroxyl group-containing monomer (a 4) contains an alkyl chain, a hydroxyl group and an ethylenically unsaturated group.

[10] The adhesive composition according to any one of [1] to [9], wherein the average carbon number of the alkyl chain of the hydroxyl group-containing monomer (a 3) in the copolymerization component (a) is 2.1 or more.

[11] The adhesive composition according to any one of [1] to [10], wherein any one of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) contains an alkyl group having a branched chain.

[12] The adhesive composition according to any one of [1] to [11], wherein the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1) or an intermolecular hydrogen abstraction type photoinitiator (B2).

[13] The adhesive composition according to any one of [1] to [12], wherein the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2).

[14] The adhesive composition according to any one of [1] to [13], which further contains a crosslinking agent (C).

[15] An adhesive comprising a crosslinked adhesive composition according to any one of [1] to [14 ].

[16] The adhesive according to [15], wherein the crosslinking is performed by irradiation of active energy rays.

[17] An adhesive sheet having an adhesive layer formed of the adhesive of [15] or [16 ].

[18] The adhesive sheet according to [17], wherein the adhesive layer is multi-stage curable by curing in a plurality of stages.

[19] An adhesive sheet with a release film, comprising a laminate structure in which a release film is laminated on at least one side of the adhesive sheet described in [17] or [18 ].

[20] A laminate for an image display device is provided with: the laminated structure of 2 image display device constituent members laminated with the adhesive sheet of [17] or [18], wherein one of the 2 image display device constituent members is a cover glass having a curved surface shape, and the other of the 2 image display device constituent members is at least 1 selected from the group consisting of a touch sensor, an image display panel, a surface protective film, an antireflection film, a color filter, a polarizing film, and a retardation film.

[21] A curved image display device comprising the laminate for an image display device according to [20 ].

[22] An adhesive composition for curved optical members, which comprises an acrylic resin (A) which is the polymerization product of a copolymerization component (a) containing an alkyl acrylate (a 1) and an alkyl methacrylate (a 2).

[23] The adhesive composition for curved optical members according to [22], wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 3).

[24] The adhesive composition for curved optical members according to [22] or [23], wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45.

[25] The adhesive composition for curved optical members according to any one of [22] to [24], wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 10% by weight or more relative to the copolymerization component (a).

[26] The adhesive composition for curved optical members according to any one of [22] to [25], further comprising a photopolymerization initiator.

While specific embodiments have been described above for illustrating the embodiments of the present invention, the embodiments are presented by way of example and do not limit the scope of the present invention. The embodiments described in the present specification and the embodiments thereof can be variously modified within a range that exhibits the effects of the invention, and can be combined with the features disclosed in the description of the other embodiments within a range that can be implemented.

Examples

Examples and comparative examples of the first embodiment

Hereinafter, examples and comparative examples of the first embodiment of the present invention will be specifically described, but the present invention is not limited to the following description. In the examples, "parts" and "%" refer to weight basis. The weight average molecular weight, the glass transition temperature due to dynamic viscoelasticity, the thickness of the adhesive layer, and the haze value (%) of the acrylic resin (a) were measured according to the method described in the first embodiment.

< abbreviation, raw Material >

(alkyl acrylate (a 1))

MA: methyl acrylate (Tg of homopolymer: 8 ℃ C.)

tBA: tert-butyl acrylate (Tg of homopolymer: 41 ℃ C.)

(alkyl methacrylate (a 2))

MMA: methyl methacrylate (Tg of homopolymer: 105 ℃ C.)

EMA: ethyl methacrylate (Tg of homopolymer: 65 ℃ C.)

IBMA: isobutyl methacrylate (Tg of homopolymer: 48 ℃ C.)

(hydroxyl group-containing monomer (a 3))

4HBA: acrylic acid 4-hydroxybutyl ester

HEA: acrylic acid 2-hydroxy ethyl ester

(ethylenically unsaturated monomer (a 4))

2EHA: 2-ethylhexyl acrylate (Tg of homopolymer: -70 ℃ C.)

ADVN:2,2' -azobis (2, 4-dimethylvaleronitrile) (10 hour half life temperature 52 ℃ C.)

(photoinitiator (B))

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

Omnirad 754: products manufactured by IGM Resins b.v.)

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

Esacure TZT: products manufactured by IGM Resins b.v.)

MBP: product made by new water chestnut company

(crosslinking agent (C))

Polypropylene glycol #400 diacrylate (NK ester APG400, product of Xinzhongcun chemical industry Co., ltd.)

(silane coupling agent (D))

KBM403 (product of Xinyue chemical industry Co., ltd.)

< production example A1: production of acrylic resin (A-A 1)

EMA:35 parts of MA:10 parts, 4HBA:5 parts of HEA:10 parts, 2EHA:40 parts of the mixture was mixed to prepare a monomer solution. Into a 2L flask with a condenser was placed ethyl acetate previously mixed as a polymerization solvent: 18 parts (boiling point 77 ℃), methyl ethyl ketone: 18 parts (boiling point 80 ℃ C.), advN as polymerization initiator: after 10% of 100 parts of the monomer solution in 0.01 part was heated under reflux in a flask, ethyl acetate was added dropwise over 3 hours: 10 parts of ADVN:0.18 part, the remaining 90% of the monomer solution. Further, after dropping for 30 minutes, ethyl acetate was dropped for 1 hour: 10 parts with ADVN:0.13 part of the mixture was reacted to obtain a solution of the acrylic resin (A-A 1). The measurement results of the weight average molecular weight (Mw), the dispersity and the glass transition temperature based on dynamic viscoelasticity of the acrylic resin (A-A 1) are shown in Table 1.

< production examples A2 to A6, comparative production examples A1 and A2>

Acrylic resins (a-A2) to (A-A 6), acrylic resins (a '-A1) and acrylic resins (a' -A2) were produced in the same manner as in production example A1 except that the compositions of the copolymerization components formed from the monomer solutions were as shown in table 1. Table 1 shows the measurement results of the weight average molecular weight (Mw), the dispersity, and the glass transition temperature based on dynamic viscoelasticity of each acrylic resin.

TABLE 1

< example A1>

Omnirad754 was mixed with 100 parts (solid content conversion) of the solution of the acrylic resin (A-A 1): 2.0 parts (solid content conversion), esacure TZT:1.0 parts (solid content conversion), polypropylene glycol #400 diacrylate: 5.0 parts (solid content conversion), KBM403:0.1 part (in terms of solid content) of a resin composition. The resulting adhesive composition was adjusted to a solid content of 45% with ethyl acetate, and applied to a polyester release sheet so that the thickness after drying became about 50. Mu.m, and dried at 100℃for 5 minutes to form an adhesive composition layer.

2 polyester release sheets each having an adhesive composition layer formed thereon were prepared, and two adhesive composition layers were laminated in opposition. The laminated adhesive composition layers were sandwiched between polyester release sheets, and the laminated adhesive composition layers were irradiated with a high-pressure mercury UV irradiation device at peak illuminance: 150mW/cm ² Cumulative exposure: 1000mJ/cm ² (500mJ/cm ² X 2 times), thereby forming an adhesive layer (primary curing), and a substrate-free double-sided adhesive sheet having an adhesive layer thickness of 100 μm was obtained.

Next, the release sheet on one side was peeled off from the adhesive layer of the obtained base-material-free double-sided adhesive sheet, and the exposed adhesive layer side was pressed against an easy-to-bond polyethylene terephthalate (PET) sheet (thickness 125 μm), to obtain an adhesive-layer-attached PET sheet having an adhesive layer thickness of 100 μm.

< examples A2 to A6, comparative examples A1 and A2>

Adhesive compositions of respective examples were prepared in the same manner as in example A1, except that the acrylic resin (a) and the photoinitiator (B) were changed as shown in table 2. Subsequently, a base-material-free double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 100 μm and a PET sheet with a pressure-sensitive adhesive layer were produced in this order in the same manner as in example A1. The composition of the adhesive compositions of each example is shown in table 2.

TABLE 2

< measurement method and evaluation method >

The following shows the methods for measuring and evaluating the adhesive compositions of examples A1 to A6 and comparative examples A1 and A2. The results are shown in tables 3 to 5.

(gel fraction: before complete curing (after one-time curing))

After each of the base-material-free double-sided adhesive sheets was cut into 40mm×40mm, the sheet was left standing at 23 ℃ ×50%rh for 30 minutes, and then one release sheet was peeled off, and the exposed adhesive layer side was bonded to a SUS mesh sheet (200 mesh) of 50mm×100 mm. The remaining release sheet was peeled off, folded back from the central portion with respect to the longitudinal direction of the SUS mesh sheet, and the adhesive layer was wrapped with the SUS mesh sheet. The gel fraction (%) was calculated from the weight change when immersed for 24 hours in a sealed vessel containing 250g of toluene maintained at 23 ℃.

( Constant load holding force (50 ℃): before complete curing (after one-time curing) )

The PET sheets with the adhesive layer of each example were cut into pieces having a width of 25mm by a length of 75mm (width of the adhesive layer portion 25mm by a length of 50 mm+width of the non-adhesive layer portion 25mm by a length of 25 mm), and the release sheet was peeled off. The exposed adhesive layer side was pressed against a stainless steel plate (SUS 304) by a 2kg roller (attachment area: 25 mm. Times.50 mm), and allowed to stand at 50℃for 20 minutes. Thereafter, a 50g weight was hung on the longitudinal end of the non-attached portion (area 25 mm. Times.25 mm), and a 50g load was applied to the plane of the stainless steel plate in a direction of 90 °, and the plate was left to stand for 60 minutes in this state, and the distance of PET sheet detachment was measured. The evaluation criteria are as follows.

A.A.A.the peel distance was less than 10mm.

The peeling distance is 10mm or more and less than 50mm.

The C.PET sheet was completely peeled off and dropped.

(probe tackiness: before complete curing (after one-time curing))

The PET sheets with the adhesive layer of each example were cut into pieces of 12mm width by 12mm length, the release sheet was peeled off, and the probe adhesiveness (unit: N) was measured using a probe adhesiveness TESTER (TESTER SANGYO CO,. LTD. Manufactured by the ULTD. Co., ltd., probe adhesiveness TESTER TE-6001) under conditions of a pressing time of 1 second, an adhesion pressure of 500gf, a pressing speed of 120mm/min, a lifting speed of 600mm/min, and a probe diameter of 5.1mm (diameter). The evaluation criteria are as follows.

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(gel fraction: after complete curing)

The substrate-less double-sided adhesive sheets of each example were irradiated with high-pressure mercury UV with peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was subjected to ultraviolet irradiation, cut into 40mm x 40mm, and left standing at 23℃x 50% RH for 30 minutes. Thereafter, one release sheet was peeled off, and the exposed adhesive layer side was bonded to a 50mm×100mm SUS mesh (200 mesh). The remaining release sheet was peeled off, folded back from the central portion with respect to the longitudinal direction of the SUS mesh sheet, and the adhesive layer was wrapped with the SUS mesh sheet. The gel fraction (%) was calculated from the weight change when immersed for 24 hours in a sealed vessel containing 250g of toluene maintained at 23 ℃.

(180 degree peel Strength (23 ℃ C.) after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 25mm in width by 100mm in length, and the sheets were irradiated with high-pressure mercury UV with peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet light, and then the release sheet was peeled off. The exposed adhesive layer side was pressed against alkali-free glass (EAGLE XG, manufactured by Corning Co., ltd., thickness: 1.1 mm) by passing a 2kg rubber roll 2 times under an atmosphere of 50% RH at 23℃and allowed to stand for 30 minutes under the same atmosphere. Thereafter, 180-degree peel strength (N/25 mm) was measured at room temperature (23 ℃) at a peel speed of 300 mm/min.

(constant load holding force (80 ℃ C.) after complete curing)

The PET sheets with adhesive layers of each example were cut into a size of 25mm in width by 75mm in length (25 mm in width by 50mm in length of the adhesive layer portion+25 mm in width by 25mm in length of the non-adhesive layer portion), and subjected to high-pressure mercury UV irradiation at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times), and then peeling the release sheet. The exposed adhesive layer side was pressed against a stainless steel plate (SUS 304) by a 2kg roller (attachment area: 25 mm. Times.50 mm), and allowed to stand at 80℃for 20 minutes. Thereafter, a 50g weight was hung on the longitudinal end of the non-attached portion (area 25 mm. Times.25 mm), and a 50g load was applied to the plane of the stainless steel plate in a direction of 90 °, and the plate was left to stand for 60 minutes in this state, and the distance of PET sheet detachment was measured. The evaluation criteria are as follows.

A.A.A.the peeling distance was less than 5mm.

The separation distance of B.cndot.is 5mm or more and less than 10mm.

The separation distance is 10mm or more, or the PET sheet is completely separated and falls down.

(holding force (80 ℃ C.) after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 25mm by 50mm, and the sheets were irradiated with high-pressure mercury UV with peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet light, and then the release sheet was peeled off. Stainless steel plate (SUS 304) was left to stand on the exposed adhesive layer side, and a 2kg roller was reciprocated to apply pressure (application area 25 mm. Times.25 mm), and a creep TESTER (test SANGYO CO,. LTD. Holding force TESTER BE-501 with constant humidity tank) was used to measure holding force under an atmosphere of 80℃for 24 hours with a load of 1 kg. The evaluation criteria are as follows.

A.cndot.c. has no offset.

The offset of B.cndot.is less than 1.0mm.

The deviation of C.cndot.is 1.0mm or more, or the PET sheet falls down.

(wet heat resistance test: after complete curing)

The PET sheets with the adhesive layer of each example were cut into 30mm by 50mm sizes, and subjected to a high-pressure mercury UV irradiation apparatus at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet light, and then the release sheet was peeled off. The exposed pressure-sensitive adhesive layer was bonded to alkali-free glass (EAGLE XG, manufactured by Corning Co., ltd., thickness: 1.1 mm). Thereafter, autoclave treatment was performed at 50℃under 0.5MPa for 20 minutes, and the mixture was allowed to stand at 23℃under 50% RH for 30 minutes to prepare a test piece having a layer structure of "alkali-free glass/adhesive layer/PET".

The obtained test piece was used to measure haze values before and after the wet heat resistance test by performing the wet heat resistance test at 60℃under an atmosphere of 90% RH for 7 days (168 hours).

The HAZE value was measured using a HAZE mat NDH4000 (manufactured by japan electric color industry corporation), and the obtained values of the Diffuse Transmittance (DT) and the Total Transmittance (TT) were calculated by substituting them into the following expression 1. Further, the rate of increase (%) in haze value was calculated from the following [ formula 2 ]. The machine was in accordance with JIS K7361-1.

Haze value (%) = (DT/TT). Times.100. [ formula 1]

Haze value difference (%) = haze value after the moist heat resistance test-haze value before the start of the moist heat resistance test ·· · [ formula 2]

The evaluation criteria for the wet heat resistance test are as follows.

A.cndot.A.has a haze value of less than 0.5%.

The difference in haze value of B.cndot.is 0.5% or more and less than 3.0%.

The difference in haze value of C.cndot.C is 3.0% or more.

(probe tack: after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 12mm in width by 12mm in length, and subjected to a high-pressure mercury UV irradiation apparatus at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times), and then peeling the release sheet, and using a probe adhesion TESTER (TESTER SANGYO CO,. LT) D. Manufactured by the probe tack tester TE-6001), the probe tack was measured under conditions of a pressing time of 5 seconds, an attaching pressure of 1000gf, a pressing speed of 120mm/min, a lifting speed of 600mm/min, and a probe diameter of 5.1mm (unit: n). The evaluation criteria are as follows.

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(surface durability: after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 40mm by 120mm, and the release sheets were peeled off. The exposed adhesive layer side was bonded to the TAC film surface polarizing plate on the side of the polarizing plate laminated with TAC films on both sides of the polarizing plate by pressing, to obtain a laminate composed of layers of "PET sheet/adhesive layer/polarizing plate".

Thereafter, the laminate was attached and fixed to an aluminum plate (width 70mm, length 150mm, thickness 0.3 mm) with an adhesive tape so that the PET surface became a surface, and an aluminum plate-fixed sample was produced. Bending the fabricated sample with a mandrel tester to becomeAfter being fixed in this state, autoclave treatment (0.5 mpa×50 ℃ c×20 minutes) was performed, and the high-pressure mercury UV irradiation apparatus was used to irradiate the sample with a peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet rays to prepare a curved surface durability evaluation sample. The sample for evaluating the durability of a curved surface was composed of layers of PET/adhesive layer/polarizing plate/aluminum plate in this order from the outside. There is an aluminum plate at the innermost side.

Using the obtained samples for evaluating the durability of the curved surface, the curved portion and the end portion of the polarizing plate other than the curved portion were observed after exposure at 80 ℃, dry, 7 days, and 60 ℃, 90% RH, and 7 days, respectively, and evaluated according to the following criteria.

(evaluation criterion: bending portion)

No floating, foaming and overflow of the glue were observed.

B.A floating, foaming, or overflow of the glue was observed.

(evaluation criterion: polarizing plate end portion)

A. No floating and bubbling were observed at the ends.

B & ltSum & gt at the end view to very few bubbles.

C. A bubble was observed at a part of the end.

D & gtbubble is generated in the whole end portion.

(evaluation criterion: comprehensive evaluation)

A. Bending portion was evaluated as A and the polarizing plate end portion was evaluated as A.

The evaluation of the b··bend was a and the evaluation of the polarizing plate end was B or C.

The evaluation of C.bending portion was A and the evaluation of the polarizing plate end was D.

The evaluation of D.bending portion was B and the evaluation of the polarizing plate end was any one of A to D.

(durability of polarizing plate: after complete curing)

The substrate-free double-sided adhesive sheets of each example were cut into a size of 60mm×100mm, and one release sheet was peeled off. The exposed adhesive layer side is pressed and adhered to the surface polarizing plate of the TAC film on one side of the polarizing plate laminated with the TAC film on both sides of the polarizing material. Then, the other release sheet was peeled off, and the exposed pressure-sensitive adhesive layer was bonded to alkali-free glass (EAGLE XG, manufactured by Corning Co., ltd., thickness: 1.1 mm), followed by autoclave treatment (50 ℃ C., 0.5MPa, 20 minutes). Thereafter, using a high-pressure mercury UV irradiation device, the peak illuminance was set from the alkali-free glass side: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet rays to prepare a sample for evaluating durability of a polarizing plate.

The durability test was performed by standing the polarizing plate durability evaluation sample in an atmosphere of 23℃and 50% RH for 1 day, and then performing the durability test in an atmosphere of 80℃and an atmosphere of 60℃and 90% RH for 7 days (168 hours), respectively, and the evaluation was performed on the basis of the following criteria.

A. Polarization plate has a floating of less than 1mm at the end.

The floating of the end of the B.polarization plate is less than 1-2 mm.

The floating of the end of the C.polarization plate is more than 2 mm.

TABLE 3

TABLE 4

TABLE 5

The adhesive sheets obtained by using the adhesive compositions of examples A1 to A6 exhibited excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinked state before complete curing (after one-time curing). In addition, the cured product exhibits excellent adhesive properties and durability even after complete curing.

On the other hand, the glass transition temperature of the acrylic resin (A) in comparative examples A1 and A2 was lower than-10 ℃. In comparative example A1, the alkyl methacrylate (a 2) was not contained, and the total content of the alkyl acrylate (A1) and the alkyl methacrylate (a 2) was less than 30% by weight. The weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (A2) in comparative example A2 was 85.7/14.3.

These comparative examples A1 and A2 were inferior to examples A1 to A6 in adhesive properties in a low crosslinked state after one-time curing, adhesive properties after complete curing, and reliability.

Examples and comparative examples of the second embodiment

Hereinafter, examples and comparative examples of the second embodiment of the present invention will be specifically described, but the present invention is not limited to the following description. In the examples, "parts" and "%" refer to weight basis. The weight average molecular weight, the glass transition temperature due to dynamic viscoelasticity, the thickness of the adhesive layer, and the haze value (%) of the acrylic resin (a) were measured according to the method described in the second embodiment.

< abbreviation, raw Material >

((meth) acrylic acid alkyl ester (a 1))

EMA: ethyl methacrylate (Tg of homopolymer: 65 ℃ C.)

MA: methyl acrylate (Tg of homopolymer: 8 ℃ C.)

MMA: methyl methacrylate (Tg of homopolymer: 105 ℃ C.)

(hydroxyalkyl monomer (a 2))

4HBA: acrylic acid 4-hydroxybutyl ester

HEA: acrylic acid 2-hydroxy ethyl ester

(ethylenically unsaturated monomer (a 3))

2EHA: 2-ethylhexyl acrylate (Tg of homopolymer: -70 ℃ C.)

(photoinitiator (B))

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

Omnirad 754: products manufactured by IGM Resins b.v.)

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

OmnipolBP: products manufactured by IGM Resins b.v.)

Esacure TZT: products manufactured by IGM Resins b.v.)

MBP: product made by new water chestnut company

(crosslinking agent (C))

(silane coupling agent (D))

KBM403 (product of Xinyue chemical industry Co., ltd.)

< manufacturing example B1: production of acrylic resin (A-B1)

EMA:35 parts of MA:10 parts, 4HBA:5 parts of HEA:10 parts, 2EHA:40 parts of the mixture was mixed to prepare a monomer solution. Into a 2L flask with a condenser was placed ethyl acetate previously mixed as a polymerization solvent: 18 parts (boiling point 77 ℃), methyl ethyl ketone: 18 parts (boiling point 80 ℃ C.), advN as polymerization initiator: after 10% of 100 parts of the monomer solution in 0.01 part was heated under reflux in a flask, ethyl acetate was added dropwise over 3 hours: 10 parts of ADVN:0.18 part, the remaining 90% of the monomer solution. Further, after dropping for 30 minutes, ethyl acetate was dropped for 1 hour: 10 parts and ADVN:0.13 part of the mixture was reacted to obtain a solution of the acrylic resin (A-B1). The measurement results of the weight average molecular weight (Mw), the dispersity and the glass transition temperature based on dynamic viscoelasticity of the acrylic resin (A-B1) are shown in Table 6.

< production examples B2 to B4, comparative production examples B1 to B4>

Acrylic resins (a-B2) to (a-B4) and acrylic resins (a '-B1) to (a' -B4) were produced in the same manner as in production example B1 except that the compositions of the copolymerization components formed from the monomer solutions were as shown in table 6. Table 6 shows the measurement results of the weight average molecular weight (Mw), the dispersity, and the glass transition temperature based on dynamic viscoelasticity of each acrylic resin.

TABLE 6

< example B1>

Omnirad754 was mixed with 100 parts (solid content conversion) of the solution of the acrylic resin (a-B1): 2.0 parts (solid content conversion), MBP:1.0 parts (solid content conversion), polypropylene glycol #400 diacrylate: 5.0 parts (solid content conversion), KBM403:0.1 part (in terms of solid content) of a resin composition. The resulting adhesive composition was adjusted to a solid content of 45% with ethyl acetate, and applied to a polyester release sheet so that the thickness after drying became about 50. Mu.m, and dried at 100℃for 5 minutes to form an adhesive composition layer.

< examples B2 to B5, comparative examples B1 to B4>

Adhesive compositions of respective examples were prepared in the same manner as in example B1, except that the acrylic resin (a) and the photoinitiator (B) were changed as shown in table 7. Subsequently, a base-material-free double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 100 μm and a PET sheet with a pressure-sensitive adhesive layer were produced in this order in the same manner as in example B1. The composition of the adhesive composition of each example is shown in table 7.

TABLE 7

< measurement method and evaluation method >

The following shows the methods for measuring and evaluating the adhesive compositions of examples B1 to B5 and comparative examples B1 to B4. The results are shown in tables 8 to 10.

(gel fraction: before complete curing (after one-time curing))

The PET sheets with the adhesive layer of each example were cut into pieces having a width of 25mm by a length of 75mm (width of the adhesive layer portion 25mm by a length of 50 mm+width of the non-adhesive layer portion 25mm by a length of 25 mm), and the release sheet was peeled off. The exposed adhesive layer side was pressed against a stainless steel plate (SUS 304) (attaching area 25 mm. Times.50 mm) by a 2kg roller and allowed to stand at 50℃for 20 minutes. Thereafter, a 50g weight was hung on the longitudinal end of the non-attached portion (area 25 mm. Times.25 mm), and a 50g load was applied to the plane of the stainless steel plate in a direction of 90 °, and the plate was left to stand for 60 minutes in this state, and the distance of PET sheet detachment was measured. The evaluation criteria are as follows.

A.A.A.the peel distance was less than 10mm.

The peeling distance is 10mm or more and less than 50mm.

The C.PET sheet was completely peeled off and dropped.

(probe tackiness: before complete curing (after one-time curing))

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(gel fraction: after complete curing)

(180 degree peel Strength (23 ℃ C.) after complete curing)

(constant load holding force (80 ℃ C.) after complete curing)

The PET sheets with adhesive layers of each example were cut into a size of 25mm in width by 75mm in length (25 mm in width by 50mm in length of the adhesive layer portion+25 mm in width by 25mm in length of the non-adhesive layer portion), and subjected to high-pressure mercury UV irradiation at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times), and then peeling the release sheet. The exposed adhesive layer side was pressed against a stainless steel plate (SUS 304) by a 2kg roller (attachment area: 25 mm. Times.50 mm), and allowed to stand at 80℃for 20 minutes. Thereafter, the non-attached portion (surfaceProduct 25mm×25 mm) was suspended at the end in the longitudinal direction with a 50g weight, and a 50g load was applied to the plane of the stainless steel plate in a direction of 90 °, and the sheet was left standing for 60 minutes in this state, and the distance of PET sheet separation was measured. The evaluation criteria are as follows.

A.A.A.the peeling distance was less than 5mm.

The separation distance of B.cndot.is 5mm or more and less than 10mm.

(holding force (80 ℃ C.) after complete curing)

A.cndot.c. has no offset.

The offset of B.cndot.is less than 1.0mm.

The deviation of C.cndot.is 1.0mm or more, or the PET sheet falls down.

(wet heat resistance test: after complete curing)

Haze value (%) = (DT/TT). Times.100. [ formula 1]

The evaluation criteria for the wet heat resistance test are as follows.

A.cndot.A.has a haze value of less than 0.5%.

The difference in haze value of B.cndot.is 0.5% or more and less than 3.0%.

The difference in haze value of C.cndot.C is 3.0% or more.

(probe tack: after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 12mm in width by 12mm in length, and subjected to a high-pressure mercury UV irradiation apparatus at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times), the release sheet was peeled off after ultraviolet irradiation, and the pressure was applied for 5 seconds using a probe tack TESTER (TESTER SANGYO CO,. LTD. Manufactured by Takaku Kogyo Co., ltd., probe tack TESTER TE-6001), at 1000gf/cm ² The probe viscosity (unit: N) was measured under conditions of a press-in speed of 120mm/min, a lift-up speed of 600mm/min and a probe diameter of 5.1mm (diameter). The evaluation criteria are as follows.

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(surface durability: after complete curing)

(evaluation criterion: bending portion)

No floating, foaming and overflow of the glue were observed.

B.A floating, foaming, or overflow of the glue was observed.

(evaluation criterion: polarizing plate end portion)

A. No floating and bubbling were observed at the ends.

B & ltSum & gt at the end view to very few bubbles.

C. A bubble was observed at a part of the end.

D & gtbubble is generated in the whole end portion.

(evaluation criterion: comprehensive evaluation)

(durability of polarizing plate: after complete curing)

The samples for evaluating durability of the polarizing plates were allowed to stand at 23℃under 50% RH for 1 day, and then subjected to durability test at 80℃under 60℃and 90% RH for 7 days (168 hours), respectively, and evaluated on the basis of the following criteria.

A. Polarization plate has a floating of less than 1mm at the end.

The floating of the end of the polarizing plate is 1-less than 2mm.

The floating of the end of the C.polarization plate is more than 2 mm.

TABLE 8

TABLE 9

TABLE 10

The adhesive sheets obtained by using the adhesive compositions of examples B1 to B5 exhibited excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinked state before complete curing (after one-time curing). In addition, the cured product exhibits excellent adhesive properties and durability even after complete curing.

On the other hand, the glass transition temperature of the acrylic resin (A) in comparative examples B1 and B4 was lower than-10 ℃. The average carbon number of the alkyl chain of the hydroxyalkyl monomer (a 2) in the copolymer component (a) in comparative examples B1, B2 and B4 is less than 2.1. In comparative example B3, no intramolecular hydrogen abstraction type photoinitiator was used. These comparative examples B1 to B4 were inferior in adhesive properties in a low crosslinked state after one-time curing and further inferior in durability after complete curing as compared with examples B1 to B5.

Examples and comparative examples of the third embodiment

Hereinafter, examples and comparative examples of the third embodiment of the present invention will be specifically described, but the present invention is not limited to the following description. In the examples, "parts" and "%" refer to weight basis. The method according to the third embodiment is described above with respect to the weight average molecular weight of the acrylic resin (a), the measurement of the glass transition temperature due to dynamic viscoelasticity, the thickness of the adhesive layer, and the haze value (%).

< abbreviation, raw Material >

(acrylic resin (A))

[ branched alkyl (meth) acrylate (a 1) ]

iBMA: isobutyl methacrylate (Tg of homopolymer: 48 ℃ C.)

2EHMA: 2-ethylhexyl methacrylate (Tg of homopolymer: -10 ℃ C.)

[ hydroxyl group-containing (meth) acrylate (a 2) ]

HEA: 2-hydroxyethyl acrylate (Tg of homopolymer: -15 ℃ C.)

[ ethylenically unsaturated monomer (a 4) ]

2EHA: 2-ethylhexyl acrylate (Tg of homopolymer: -70 ℃ C.)

MA: methyl acrylate (Tg of homopolymer: 8 ℃ C.)

MMA: methyl methacrylate (Tg of homopolymer: 105 ℃ C.)

(photoinitiator (B))

[ intramolecular hydrogen-abstraction photoinitiator (b 1) ]

Omnirad 754: products manufactured by IGM Resins b.v.)

[ intermolecular Hydrogen-abstraction photoinitiator (b 2) ]

Esacure TZT: products manufactured by IGM Resins b.v.)

OmnipolBP: products manufactured by IGM Resins b.v.)

MBP: product made by new water chestnut company

(crosslinking agent (C))

(silane coupling agent (D))

KBM403 (product of Xinyue chemical industry Co., ltd.)

< manufacturing example C1: production of acrylic resin (A-C1)

iBMA:25 parts, 2EHA:35 parts of MA:25 parts of HEA:15 parts of a monomer solution was prepared by mixing. Methyl ethyl ketone as a polymerization solvent was placed in a 2L flask with a condenser: 40 parts (boiling point 80 ℃ C.), advN as polymerization initiator: 0.008 parts of 10% of 100 parts of a previously prepared monomer solution was heated under reflux in a flask, and then, ADVN was added dropwise over 3 hours: 0.11 part of ethyl acetate: 10 parts of a 90% mixed solution of the remaining monomer solution. Further, after dropping for 30 minutes, ethyl acetate was dropped for 1 hour: 10 parts and ADVN:0.13 part of the mixture was reacted to obtain a solution of the acrylic resin (A-C1). The measurement results of the weight average molecular weight (Mw), the dispersity and the glass transition temperature based on dynamic viscoelasticity of the acrylic resin (A-C1) are shown in Table 11.

< production examples C2 to C4, comparative production examples C1 and C2>

Acrylic resins (a-C2) to (a-C4), acrylic resins (a '-C1) and acrylic resins (a' -2) were produced in the same manner as in production example C1 except that the compositions of the copolymerization components formed from the monomer solutions were as shown in table 11. Table 11 shows the measurement results of the weight average molecular weight (Mw), the dispersity, and the glass transition temperature based on dynamic viscoelasticity of each acrylic resin.

TABLE 11

< example C1>

Polypropylene glycol #400 diacrylate was mixed with 100 parts (solid content conversion) of the solution of the acrylic resin (a-C1): 5.0 parts (solid content conversion), KBM403:0.1 part (solid content conversion), esacure TZT:1.0 parts (solid content conversion), omnirad 754:2.0 parts (solid content conversion) of a resin composition was obtained. The resulting adhesive composition solution was adjusted to a solid content of 50% with ethyl acetate, and applied to a polyester release sheet so that the thickness after drying became about 50. Mu.m, and dried at 100℃for 5 minutes to form an adhesive composition layer.

2 polyester release sheets each having an adhesive composition layer formed thereon were prepared, and two adhesive composition layers were laminated in opposition. The laminated adhesive composition layers were sandwiched between polyester release sheets, and the laminated adhesive composition layers were irradiated with a high-pressure mercury UV irradiation device at peak illuminance: 150mW/cm ² Cumulative exposure: 1000mJ/cm ² (500mJ/cm ² X 2 times), thereby forming an adhesive layer (primary curing), and a substrate-free double-sided adhesive sheet having an adhesive layer thickness of 100 μm was produced.

Next, the release sheet on one side was peeled off from the adhesive layer of the obtained base-material-free double-sided adhesive sheet, and the exposed adhesive layer side was pressed against an easy-to-bond polyethylene terephthalate (PET) sheet (thickness 125 μm), to prepare an adhesive-layer-attached PET sheet having an adhesive layer thickness of 100 μm.

The release sheet on one side was peeled off from the adhesive layer of the once-cured base-free double-sided adhesive sheet, and the exposed adhesive layer side was pressed against the surface of the TAC film on the side of the polarizing plate having TAC films laminated on both sides of the polarizing plate, to thereby produce a polarizing plate with an adhesive layer having an adhesive layer thickness of 100 μm.

< examples C2 to C6, comparative examples C1 to C4>

Adhesive compositions of respective examples were prepared in the same manner as in example C1, except that the type of the acrylic resin (a) was changed as shown in table 12. Subsequently, a base-material-free double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 100 μm, a pressure-sensitive adhesive-layer-equipped PET sheet, and a pressure-sensitive-layer-equipped polarizing plate were produced in this order in the same manner as in example C1.

TABLE 12

< measurement method and evaluation method >

The following shows the methods for measuring and evaluating the compositions of examples C1 to C6 and comparative examples C1 to C4. The results are shown in tables 13 to 15.

(gel fraction: before complete curing (after one-time curing))

A.A.A.the peel distance was less than 10mm.

The peeling distance is 10mm or more and less than 50mm.

The C.PET sheet was completely peeled off and dropped.

(probe tackiness: before complete curing (after one-time curing))

The PET sheets with the adhesive layer of each example were cut into pieces having a width of 10mm and a length of 10mm, the release sheet was peeled off, and the probe adhesiveness (unit: N) was measured under conditions of a pressing time of 1 second, an adhesion pressure of 1000gf, a pressing speed of 120mm/min, a lifting speed of 600mm/min, and a probe diameter of 5.1mm (diameter) using a probe adhesiveness TESTER (TESTER SANGYO CO,. LTD. Manufactured by the Co., ltd., probe adhesiveness TESTER TE-6001). The evaluation criteria are as follows.

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(gel fraction: after complete curing)

The substrate-free double-sided adhesive sheets of each example were irradiated with high-pressure mercury UV with peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) is subjected to ultraviolet irradiation, and then cut40 mm. Times.40 mm, and allowed to stand at 23℃for 30 minutes under 50% RH. Thereafter, one release sheet was peeled off, and the exposed adhesive layer side was bonded to a 50mm×100mm SUS mesh (200 mesh). The remaining release sheet was peeled off, folded back from the central portion with respect to the longitudinal direction of the SUS mesh sheet, and the adhesive layer was wrapped with the SUS mesh sheet. The gel fraction (%) was calculated from the weight change when immersed for 24 hours in a sealed vessel containing 250g of toluene maintained at 23 ℃.

(180 degree peel Strength (23 ℃ C.) after complete curing)

(constant load holding force (80 ℃ C.) after complete curing)

A.A.A.the peeling distance was less than 5mm.

The separation distance of B.cndot.is 5mm or more and less than 10mm.

The separation distance is 10mm or more, or the PET sheet falls down.

(holding force (80 ℃ C.) after complete curing)

A.cndot.c. has no offset.

The offset of B.cndot.is less than 1.0mm.

The deviation of C.cndot.is 1.0mm or more, or the PET sheet falls down.

(moist Heat resistance: after complete curing)

The HAZE value was measured using a HAZE mat NDH4000 (manufactured by japan electric color industry corporation), and the obtained values of the Diffuse Transmittance (DT) and the Total Transmittance (TT) were calculated by substituting them into the following formula 1. Further, the rate of increase (%) in haze value was calculated from the following formula 2. The machine was in accordance with JIS K7361-1.

Haze value (%) = (DT/TT). Times.100. [ formula 1]

The evaluation criteria are as follows.

A.cndot.A.has a haze value of less than 0.5%.

The difference in haze value of B.cndot.is 0.5% or more and less than 3.0%.

The difference in haze value of C.cndot.C is 3.0% or more.

(probe tack: after complete curing)

The PET sheets with the adhesive layer of each example were cut into a size of 12mm in width by 12mm in length, and subjected to a high-pressure mercury UV irradiation apparatus at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times), the release sheet was peeled off, and the probe tackiness (unit: n). The evaluation criteria are as follows.

A.A.A probe adhesion (unit: N) is less than 5.

The probe viscosity (unit: N) is 5 or more and less than 7.5.

The probe viscosity (unit: N) is 7.5 or more and less than 10.

The probe viscosity (unit: N) is 10 or more.

(durability of polarizing plate: after complete curing)

The polarizing plate with the adhesive layer of each example was cut into a size of 60mm in width by 100mm in length, and the release sheet was peeled off. The exposed adhesive layer side was pressed against alkali-free glass (EAGLE XG, manufactured by Corning Co., ltd. "EAGLE XG", thickness 1.1 mm) by passing a 2kg rubber roll 2 times under an atmosphere of 50% RH at 23℃and then autoclave-treated (0.5 MPa. Times.50 ℃ C. Times.20 minutes), followed by high pressureMercury UV irradiation device, at peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet rays from the alkali-free glass side to prepare a sample for evaluating durability of a polarizing plate.

The obtained samples for evaluating durability of the polarizing plate were exposed to conditions of 80℃Dry and 60℃and 90% RH for 7 days, respectively, and then the ends of the polarizing plate were observed and evaluated according to the following criteria.

A. Polarization plate has a floating of less than 1mm at the end.

The floating of the end of the polarizing plate is 1-less than 2mm.

The floating of the end of the C.polarization plate is more than 2mm.

(surface durability: after complete curing)

The polarizing plate with the adhesive layer of each example was cut into a size of 40mm in width by 120mm in length, and the release sheet was peeled off. The exposed adhesive layer side was pressure-bonded to an easy-to-bond polyethylene terephthalate (PET) sheet (thickness 125 μm) with a rubber roll at 23℃under 50% RH atmosphere. Thereafter, an aluminum plate (width 70mm, length 150mm, thickness 0.3 mm) was attached and fixed with an adhesive tape so that the PET surface became a surface, and an aluminum plate-fixed sample was produced. Bending the fabricated sample with a mandrel tester to becomeAfter being fixed in this state, autoclave treatment (0.5 mpa×50 ℃ c×20 minutes) was performed, and the high-pressure mercury UV irradiation apparatus was used to irradiate the sample with a peak illuminance: 150mW/cm ² Cumulative exposure: 4000mJ/cm ² (1000mJ/cm ² X 4 times) was irradiated with ultraviolet rays to prepare a curved surface durability evaluation sample. The sample for evaluating the durability of a curved surface was composed of layers of PET/adhesive layer/polarizing plate/aluminum plate in this order from the outside. There is an aluminum plate at the innermost side.

Using the obtained samples for evaluating the durability of curved surfaces, after exposure to the conditions of 80 ℃, dry, 7 days, and 60 ℃, 90% RH, 7 days, the bent portions subjected to ultraviolet irradiation and the ends of the polarizing plates other than the bent portions were observed, and evaluation was performed according to the following criteria.

(evaluation criterion: bending portion)

No floating, foaming and overflow of the glue were observed.

B.A floating, foaming, or overflow of the glue was observed.

(evaluation criterion: polarizing plate end portion)

A. No floating and bubbling were observed at the ends.

B & ltSum & gt at the end view to very few bubbles.

C. A bubble was observed at a part of the end.

D & gtbubble is generated in the whole end portion.

(evaluation criterion: comprehensive evaluation)

TABLE 13

TABLE 14

TABLE 15

The adhesive sheets using the adhesive compositions of examples C1 to C6 exhibited excellent adhesive properties such as low tackiness and high constant load holding power even in a low crosslinked state before complete curing (after one-time curing). In addition, the adhesive composition also shows excellent adhesive properties after complete curing.

On the other hand, in comparative examples C1 and C2, only either one of the intramolecular hydrogen abstraction type photoinitiator or the intermolecular hydrogen abstraction type photoinitiator was used. In comparative examples C3 and C4, a branched alkyl (meth) acrylate having a Tg of-30℃or higher was not used as a homopolymer. The adhesive sheets using the adhesive compositions of comparative examples C1 to C4 were inferior in adhesive properties in a low crosslinked state after one-time curing to those of examples C1 to C6.

Industrial applicability

The adhesive obtained by using the adhesive composition of the invention has excellent adhesive physical properties in a low-crosslinking state after primary curing. The adhesive obtained by using the adhesive composition of the present invention is useful, in particular, as an adhesive for bonding optical members constituting a touch panel, an image display device, etc., sealing an organic EL display, etc.

Claims

1. An adhesive composition comprising an acrylic resin (A) and a photoinitiator (B),

the acrylic resin (A) is a polymerization product of the following copolymerization component (a),

the copolymerization component (a) contains: an alkyl acrylate (a 1) having a glass transition temperature of-30 to 50 ℃ when forming a homopolymer and an alkyl methacrylate (a 2) having a glass transition temperature of-10 to 120 ℃ when forming a homopolymer,

the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 5 wt% or more relative to 100 wt% of the copolymerization component (a).

2. The adhesive composition according to claim 1, wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 3).

3. The adhesive composition according to claim 2, wherein the content of the hydroxyl group-containing monomer (a 3) is 0.1% by weight or more relative to 100% by weight of the copolymerized component (a).

4. The adhesive composition according to claim 1, wherein the acrylic resin (a) has a glass transition temperature based on dynamic viscoelasticity of-10 ℃ or higher.

5. The adhesive composition according to claim 1, wherein the acrylic resin (a) has a weight average molecular weight of 50,000 ～ 500,000.

6. The adhesive composition according to claim 1, wherein the acrylic resin (a) has a weight average molecular weight of 50,000 ～ 400,000.

7. The adhesive composition according to claim 1, wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45.

8. The adhesive composition according to claim 1, wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 30 to 70% by weight relative to the copolymerized component (a).

9. The adhesive composition according to claim 1, wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 4), the hydroxyl group-containing monomer (a 4) containing an alkyl chain, a hydroxyl group and an ethylenically unsaturated group.

10. The adhesive composition according to claim 2, wherein the average carbon number of the alkyl chain of the hydroxyl group-containing monomer (a 3) in the copolymerization component (a) is 2.1 or more.

11. The adhesive composition according to claim 1, wherein any one of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) comprises an alkyl group having a branch.

12. The adhesive composition according to claim 1, wherein the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1) or an intermolecular hydrogen abstraction type photoinitiator (B2).

13. The adhesive composition according to claim 1, wherein the photoinitiator (B) contains an intramolecular hydrogen abstraction type photoinitiator (B1) and an intermolecular hydrogen abstraction type photoinitiator (B2).

14. The adhesive composition according to claim 1, further comprising a crosslinking agent (C).

15. An adhesive agent obtained by crosslinking the adhesive agent composition according to any one of claims 1 to 14.

16. The adhesive according to claim 15, wherein the crosslinking is performed by irradiation of active energy rays.

17. An adhesive sheet having an adhesive layer formed of the adhesive according to claim 15 or 16.

18. The adhesive sheet according to claim 17, wherein the adhesive layer is multi-stage curable by curing in a plurality of stages.

19. An adhesive sheet with a release film, comprising a laminate structure in which the release film is laminated on at least one side of the adhesive sheet according to claim 17 or 18.

20. A laminate for an image display device is provided with: a laminated structure comprising 2 image display device constituent members laminated via the adhesive sheet according to claim 17 or 18,

one of the 2 image display device constituent members is a cover glass having a curved shape,

another one of the 2 image display device constituent members is at least 1 or more selected from the group consisting of a touch sensor, an image display panel, a surface protective film, an antireflection film, a color filter, a polarizing film, and a phase difference film.

21. A curved image display device comprising the laminate for an image display device according to claim 20.

22. An adhesive composition for curved optical members, which comprises an acrylic resin (A),

the copolymerization component (a) contains an alkyl acrylate (a 1) and an alkyl methacrylate (a 2).

23. The adhesive composition for curved optical members according to claim 22, wherein the copolymerization component (a) further contains a hydroxyl group-containing monomer (a 3).

24. The adhesive composition for curved optical members according to claim 22 or 23, wherein the weight ratio of the alkyl acrylate (a 1) to the alkyl methacrylate (a 2) is 5/95 to 55/45.

25. The adhesive composition for curved optical members according to claim 22 or 23, wherein the total content of the alkyl acrylate (a 1) and the alkyl methacrylate (a 2) is 10% by weight or more relative to the copolymerized component (a).

26. The adhesive composition for curved optical members according to claim 22 or 23, further comprising a photopolymerization initiator.