KR102496512B1 - Pressure-sensitive adhesive sheet, method for manufacturing a laminate including a pressure-sensitive adhesive layer, a laminate including a pressure-sensitive adhesive layer, an image display device, and a touch panel - Google Patents

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive sheet having excellent level conformability and blister resistance, and having a high level of reliability and excellent adhesive physical properties (adhesion, holding power), moisture-heat resistance, and blister resistance in a well-balanced manner. The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) and a crosslinking agent (B), and an ethylenically unsaturated compound having one ethylenically unsaturated group (C), wherein the functional group-containing acrylic resin (A) has a glass transition temperature of -35°C or higher.

Description

Pressure-sensitive adhesive sheet, method for manufacturing a laminate including a pressure-sensitive adhesive layer, a laminate including a pressure-sensitive adhesive layer, an image display device, and a touch panel

The present invention relates to a pressure-sensitive adhesive sheet, a method for producing a laminate containing a pressure-sensitive adhesive layer, a laminate containing a pressure-sensitive adhesive layer, an image display device, and a touch panel. It relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is excellent in adhesion properties and heat-and-moisture resistance in a well-balanced manner.

In recent years, in various fields, display devices such as liquid crystal displays (LCDs) and input devices such as touch panels used in combination with the display devices are widely used, and in these productions, transparent adhesive sheets for bonding optical members is being used

For example, transparent double-sided adhesive sheets are used for attaching touch panels and various display devices and optical members (protective plates, etc.). (hereinafter, referred to as step followability) is required. Further, when a plastic material such as polycarbonate resin, acrylic resin, or (cyclic) olefin resin is used as a member constituting the touch panel, the adherend (member) and the adhesive layer are damaged by gas or moisture generated from such a member. Foaming and peeling may occur between the lamina, and blister resistance capable of suppressing them is also required.

As a means for imparting level conformability, there is a method of using a soft pressure-sensitive adhesive layer, but in this method, although the level difference conformability is improved by softening the pressure-sensitive adhesive layer, deformation and distortion easily occur, and there is a problem that durability is further deteriorated.

In view of the above problems, as a pressure-sensitive adhesive sheet capable of securing conformity to steps and preventing deformation and distortion of the film, for example, in Patent Document 1, crosslinking of an acrylic resin using a thermal crosslinkable crosslinking agent and an ethylenically unsaturated monomer A pressure-sensitive adhesive sheet of a type that uses curing by irradiation with active energy rays in combination, wherein the pressure-sensitive adhesive composition containing a base polymer, a monomer having at least one polymerizable unsaturated group, a crosslinking agent that reacts with the base polymer by heat, a polymerization initiator, and a solvent is heated. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive semi-cured by

In addition, as a means for imparting blister resistance, a method of increasing the cohesive force of the adhesive layer by using a polymer containing an acid-based or nitrogen-based monomer as a polymerization component in the adhesive layer, A heating method and the like are proposed.

Patent document 1 WO 2013/061938 A

However, in recent years, as described above, it is required to follow various steps according to changes in the structure of adherends (members), and since the use environment is also diverse, there is still a need for adhesives depending on adherends, use environments, uses, etc. Improvements are required. The PSA sheet disclosed in Patent Literature 1 also has excellent level conformability, but is not sufficient in terms of blister resistance, and a pressure-sensitive adhesive sheet excellent in level conformability and blister resistance is desired.

Therefore, against this background, an object of the present invention is to provide a pressure-sensitive adhesive sheet having excellent level conformability and blister resistance, as well as well-balanced adhesive physical properties (adhesive force, holding power) and heat-and-moisture resistance, and having a high level of reliability.

Accordingly, the inventors of the present invention have conducted extensive research in view of such circumstances, and as a result, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer in which the acrylic resin is crosslinked with a crosslinking agent has a glass transition temperature higher than that of the acrylic resin normally used as the pressure-sensitive adhesive. By using a high-quality acrylic resin, the obtained adhesive sheet exhibits excellent step followability when attached to a base material with irregularities, and at the same time, even when pasted to a plastic base material, there is no foaming or peeling between the base material and the pressure-sensitive adhesive layer. The present invention was completed by finding that it does not occur, has excellent blister resistance, and is also excellent in adhesive physical properties (adhesion, holding power) and heat and humidity resistance.

That is, the gist of the present invention is the following (1) to (9).

(1) A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) and a crosslinking agent (B) and an ethylenically unsaturated compound having one ethylenically unsaturated group (C), wherein the functional group-containing acrylic resin ( A pressure-sensitive adhesive sheet having a glass transition temperature of -35°C or higher.

(2) The pressure-sensitive adhesive sheet according to (1) above, wherein the functional group-containing acrylic resin (A) is an acrylic resin obtained by polymerizing a monomer component containing a methacrylic acid alkyl ester monomer having 1 to 8 carbon atoms in an alkyl group.

(3) The pressure-sensitive adhesive sheet according to (1) or (2) above, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 300 µm.

(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), which is a double-sided pressure-sensitive adhesive sheet in which release sheets are laminated on both sides of the pressure-sensitive adhesive layer.

(5) Manufacturing a laminate containing a pressure-sensitive adhesive layer by bonding the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet according to any one of (1) to (4) above to an adherend, and subjecting to at least one of active energy ray irradiation and heating method.

(6) The manufacturing method of the laminated body containing the adhesive layer as described in said (5) in which the surface of the said adherend has a level difference of 1-100 micrometers.

(7) A layered product containing an adhesive layer obtained by the method for producing a layered product containing the pressure-sensitive adhesive layer described in (5) or (6) above.

(8) An image display device having a laminate comprising the pressure-sensitive adhesive layer according to (7) above.

(9) A touch panel having a laminate comprising the pressure-sensitive adhesive layer according to (7) above.

The greatest feature of the present invention is that an acrylic resin having a high glass transition temperature, which is difficult to use normally, is used for an adhesive requiring level conformability, and an ethylenically unsaturated compound containing one ethylenically unsaturated group is used as the pressure-sensitive adhesive layer. contain in With this structure, when the PSA sheet of the present invention is bonded to an adherend, it exhibits good level conformability and adhesive strength, and after bonded to an adherend, when cured by active energy rays and/or heat, the adherend and the pressure-sensitive adhesive layer are bonded together. Since it is immobilized very firmly, foaming between the adherend and the adhesive layer can be suppressed.

The pressure-sensitive adhesive sheet of the present invention is an adhesive sheet that is excellent in conformability to steps and also in blister resistance, and is excellent in adhesive physical properties (adhesion, holding power) and moisture-heat resistance in a well-balanced manner, and is also excellent in reworkability, especially for touch panels and image displays. It is useful as an adhesive sheet used for bonding of devices.

Hereinafter, the present invention will be described in detail.

In the present invention, (meth)acryl means acryl or methacryl, (meth)acryloyl means acryloyl or methacryloyl, and (meth)acrylate means acrylate or methacrylate, respectively.

In addition, the acrylic resin is a resin obtained by polymerizing a monomer component containing at least one (meth)acrylic monomer.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature and a crosslinking agent (B), and an ethylenically unsaturated compound (C) having one ethylenically unsaturated group. it is a sheet

<Functional group-containing acrylic resin (A)>

The greatest feature of the pressure-sensitive adhesive sheet of the present invention is that a functional group-containing acrylic resin (A) having a glass transition temperature of -35°C or higher is used. The glass transition temperature of the functional group-containing acrylic resin (A) is preferably -35°C to 30°C, more preferably -35°C to 0°C, particularly preferably -35°C to -10°C, and further -30°C. -10 degreeC is especially preferable. If the glass transition temperature of the functional group-containing acrylic resin (A) is too low, the blister resistance deteriorates and the object of the present invention cannot be achieved. In addition, even when the glass transition temperature is too high, conformability to steps tends to deteriorate.

In order to make the glass transition temperature of the functional group-containing acrylic resin (A) within the above range, the type and blending ratio of the monomer components constituting the functional group-containing acrylic resin (A) can be appropriately adjusted.

In addition, said glass transition temperature is computed by the following Fox formula.

Tg: glass transition temperature (K) of the copolymer

Tga: Glass transition temperature (K) of homopolymer of monomer A

Wa: weight fraction of monomer A

Tgb: glass transition temperature (K) of homopolymer of monomer B

Wb: weight fraction of monomer B

Tgn: glass transition temperature (K) of homopolymer of monomer N

Wn: weight fraction of monomer N (provided, Wa + Wb + ... + Wn = 1).

The functional group-containing acrylic resin (A) contains a functional group that can become a crosslinking point by reacting with a crosslinking agent (B) described later, and as a functional group, for example, a hydroxyl group, a carboxyl group, an amino group, an acetacetyl group, an isocyanate group, glycy A dill machine etc. are mentioned.

Among these, it is preferable to contain a hydroxyl group and a carboxyl group from the viewpoint that a crosslinking reaction can be carried out efficiently, and furthermore, it is preferable to contain a hydroxyl group from the viewpoint that heat-and-moisture resistance can also be improved.

The functional group-containing acrylic resin (A) used in the present invention contains a functional group-containing monomer (a1) as an essential component, a (meth)acrylic acid alkyl ester monomer (a2), and, if necessary, other polymerizable monomers It is obtained by polymerizing the monomer component containing (a3).

The functional group-containing monomer (a1) may be a monomer containing a functional group capable of becoming a crosslinking point by reacting with a crosslinking agent (B) described later, for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, and acetacetyl A group-containing monomer, an isocyanate group-containing monomer, a glycidyl group-containing monomer, etc. are mentioned.

Among these, it is preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer from the viewpoint that a crosslinking reaction can be efficiently performed, and it is also preferable to use a hydroxyl group-containing monomer from the viewpoint that heat-and-moisture resistance can also be improved.

Moreover, since it becomes easy to corrode when the adherend is a metal or its oxide, it is preferable not to use a carboxyl group-containing monomer.

As a hydroxyl group-containing monomer, for example,

2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( (meth)acrylic acid hydroxyalkyl esters such as meth)acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, polyethylene glycol (meth)acryl Oxyalkylene modified monomers such as rate, other primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid;

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 the hydroxyl group-containing monomers, from the viewpoint of excellent reactivity with the crosslinking agent, primary hydroxyl group-containing monomers are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred.

Further, as the hydroxyl group-containing monomer used in the present invention, it is preferable to use a monomer containing di(meth)acrylate as an impurity of 0.5% or less, particularly 0.2% or less, and more preferably 0.1% or less. Preferable, specifically, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred.

As the carboxyl group-containing monomer, for example, (meth)acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide-N-glycolic acid, cinnamic acid, etc. are mentioned, and (meth)acrylic acid is used preferably especially.

Examples of the amino group-containing monomer include t-butylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. can

Examples of the acetoacetyl group-containing monomer include 2-(acetacetoxy)ethyl (meth)acrylate and allylacetate.

As an isocyanate group containing monomer, 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, these alkylene oxide adducts, etc. are mentioned, for example.

As a glycidyl group-containing monomer, glycidyl (meth)acrylate, glycidyl (meth)acrylate, etc. are mentioned, for example.

These functional group-containing monomers (a1) may be used alone or in combination of two or more.

The content of the functional group-containing monomer (a1) in the monomer component is preferably 0.01 to 70% by weight, particularly preferably 0.1 to 50% by weight, still more preferably 1 to 35% by weight, and further preferably 10% by weight. -30% by weight. When the content of the functional group-containing monomer (a1) is too small, the cohesive force of the acrylic resin tends to be insufficient and durability performance tends to decrease, and when the content is too large, the viscosity of the acrylic resin tends to increase or the storage stability tends to decrease.

When a hydroxyl group-containing monomer is used as such a functional group-containing monomer (a1), the content of the hydroxyl group-containing monomer is preferably 5 to 50% by weight, particularly 7 to 40% by weight, more preferably 10 to 10% by weight with respect to the total amount of the copolymerization component. It is 35% by weight, preferably 15 to 30% by weight. If the content of the hydroxyl group-containing monomer is too small, adhesive strength or heat-and-moisture resistance tends to decrease, and if too large, the viscosity of the acrylic resin tends to increase, making it difficult to form a good coating film.

Examples of the (meth)acrylic acid alkyl ester monomer (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl ( meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, n-stearyl (meth)acrylate, iso-stearyl (meth)acrylate, behenyl (meth)acrylate, 2-decyl tetradecanyl (meth)acrylate, etc. are mentioned.

These (meth)acrylic acid alkyl ester monomers (a2) may be used alone or in combination of two or more.

In the present invention, from the viewpoint of increasing the cohesive force, a methacrylic acid alkyl ester monomer (a2-1) having 1 to 8 carbon atoms in an alkyl group such as methyl methacrylate, ethyl methacrylate, tert-butyl methacrylate, etc. is used It is preferable, and more preferably, the alkyl group having 4 to 8 carbon atoms from the viewpoint of efficiently increasing the rigidity of the main chain and improving blister resistance, or from the viewpoint of excellent copolymerizability with monomers (polymerization stability). It is preferable to use a methacrylic acid alkyl ester type monomer, especially tert-butyl methacrylate.

From the viewpoint of imparting hydrophobicity to the pressure-sensitive adhesive layer, a (meth)acrylic acid alkyl ester monomer (a2-2) having a glass transition temperature of -20 ° C. or higher and an alkyl group having 8 or more carbon atoms when made into a homopolymer (however, (a2 -1) excluded) is preferred.

As a (meth)acrylic acid alkyl ester-based monomer having a glass transition temperature of -20°C or higher when used as a homopolymer and having an alkyl group of 8 or more carbon atoms, for example, lauryl acrylate (Tg = -3°C; carbon number 12) , cetyl acrylate (Tg = 35 ° C; carbon number 16), n-stearyl acrylate (Tg = 30 ° C; carbon number 18), isostearyl acrylate (Tg = -18 ° C; carbon number 18), behenyl acrylate (Tg = 46 ° C; carbon number 22), 2-decyl tetradecanyl acrylate (Tg = 9 ° C; carbon number 24), 2-ethylhexyl methacrylate (Tg = -10 ° C; carbon number 8), cetyl methacrylate (Tg = 23.5 ° C; carbon number 16), n-stearyl methacrylate (Tg = 38 ° C; carbon number 18), behenyl methacrylate (Tg = 44 ° C; carbon number 22), 2-decyl tetradecanyl methacrylate rate (Tg = 10°C; carbon number 24); and the like.

Among these, 2-ethylhexyl methacrylate and isostearyl acrylate are preferably used from the standpoint of excellent polymerization stability and hydrophobicity.

As the content of the (meth)acrylic acid alkyl ester monomer (a2) in the monomer component, it is preferably 5 to 99% by weight, particularly preferably 20 to 80% by weight, and still more preferably 40 to 70% by weight. am. If the content of the alkyl (meth)acrylate monomer (a2) is too small, the blister resistance and cohesive force tend to decrease, and if the content is too large, the adhesive physical properties when used as an adhesive tend to decrease.

In the case of using the methacrylic acid alkyl ester monomer (a2-1) having 1 to 8 carbon atoms in the alkyl group, the content ratio in the monomer component is preferably 10 to 70% by weight, particularly preferably It is 15 to 60% by weight, more preferably 20 to 50% by weight. When the content ratio is too small, the blister resistance tends to decrease due to a decrease in cohesive force, and when the content ratio is too large, the conformability to level differences tends to deteriorate.

In the case of using an alkyl (meth)acrylic acid alkyl ester monomer (a2-2) having a glass transition temperature of -20 ° C. or higher when used as the above homopolymer and having an alkyl group of 8 or more carbon atoms, in all monomer components The content ratio is preferably 1 to 70% by weight, particularly preferably 5 to 60% by weight, still more preferably 7 to 55% by weight, and particularly preferably 10 to 50% by weight. If the content ratio of the (meth)acrylic acid alkyl ester type monomer (a2-2) is too small, the blister resistance tends to decrease, and if it is too large, the viscosity of the acrylic resin increases, making handling difficult or adhesion when used as an adhesive Physical properties tend to deteriorate.

As other polymerizable monomers (a3), for example,

alicyclic (meth)acrylic acid ester monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate;

Phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, styrene , monomers containing one aromatic ring such as α-methylstyrene; biphenyloxy structure-containing (meth)acrylic acid ester monomers such as biphenyloxyethyl (meth)acrylate;

2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-butoxydiethyleneethylene Glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxy Contains ether chains such as polyethylene glycol (meth) acrylate, octoxy polyethylene glycol polypropylene glycol mono (meth) acrylate, lauroxy polyethylene glycol mono (meth) acrylate, stearoxy polyethylene glycol mono (meth) acrylate, etc. ) Acrylic acid ester monomer;

Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester , allyl alcohol, acryl chloride, methyl vinyl ketone, N-acrylamide methyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, (meth)acryloyl morpholine and the like can be used.

These are used alone or in combination of two or more.

The content of the other polymerizable monomer (a3) in the monomer component is preferably 0 to 40% by weight, particularly preferably 0 to 30% by weight, still more preferably 0 to 25% by weight. If there are too many other polymerizable monomers (a3), there is a tendency for adhesive properties to deteriorate easily.

A functional group-containing acrylic resin (A) can be produced by polymerizing the above monomer components. As the polymerization method of the functional group-containing acrylic resin (A), conventionally known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization can be used, and the polymerization conditions are also subject to conventionally known general polymerization conditions. Although polymerization can be carried out according to the above, solution polymerization is preferable from the viewpoint of being able to safely and stably produce the functional group-containing acrylic resin (A) with an arbitrary monomer composition.

In such solution polymerization, for example, the monomer components (a1) to (a3) and the polymerization initiator may be mixed or added dropwise in an organic solvent and polymerized in a reflux state or at 50 to 98°C for 0.1 to 20 hours.

As the organic solvent used in the polymerization reaction, for example, aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, N-propyl alcohol, isopropyl alcohol, etc. aliphatic alcohols, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and the like. Among these solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are preferred, from the viewpoints of the ease of polymerization reaction, the effect of chain transfer, the ease of drying at the time of pressure-sensitive adhesive coating, and safety, and more preferred Preferably, ethyl acetate, acetone, and methyl ethyl ketone are preferred.

As such a polymerization initiator, azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are common radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, and cumene Peroxide type polymerization initiators, such as hydroperoxide, etc. are mentioned as a specific example. These can be appropriately selected and used according to the monomer to be used, and are used alone or in combination of two or more.

The weight average molecular weight of the functional group-containing acrylic resin (A) is usually 50,000 to 2,000,000, preferably 200,000 to 1,000,000, and particularly preferably 300,000 to 800,000. When the weight average molecular weight is too small, durability performance tends to decrease, and when it is too large, conformability to steps tends to decrease.

The degree of dispersion (weight average molecular weight/number average molecular weight) of the functional group-containing acrylic resin (A) is preferably 20 or less, particularly preferably 15 or less, more preferably 10 or less, and more preferably 7 or less. When such a degree of dispersion is too high, the durability performance of the pressure-sensitive adhesive layer tends to decrease. In addition, the lower limit of the degree of dispersion is usually 1.1 from the viewpoint of manufacturing limitations.

Incidentally, the weight average molecular weight is the weight average molecular weight by standard polystyrene molecular weight conversion, high-speed liquid chromatography ("Waters 2695 (body)" and "Waters 2414 (detector)" made by Waters, Japan), column: Shodex GPC KF- Three of 806 L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , number of theoretical plates: 10,000 plates/piece, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) It is measured by using a series, and the same method can be used for number average molecular weight. Dispersity can be calculated|required from a weight average molecular weight and a number average molecular weight.

Further, as the functional group-containing acrylic resin (A) used in the present invention, a functional group-containing acrylic resin having an active energy ray reactive structural site, that is, a functional group-containing acrylic resin containing an ethylenically unsaturated group (ethylenically unsaturated group-containing acrylic resin) It is preferable from the viewpoint that the pressure-sensitive adhesive layer after active energy ray irradiation can be made to have a higher modulus of elasticity.

The ethylenically unsaturated group-containing acrylic resin can be obtained by reacting a functional group of the functional group-containing acrylic resin (A) and an ethylenically unsaturated compound having a functional group that reacts with the functional group. As such ethylenically unsaturated compounds, the above-described unsaturated monomers containing a carboxyl group, unsaturated monomers containing a hydroxyl group, unsaturated monomers containing a glycidyl group, unsaturated monomers containing an isocyanate group, unsaturated monomers containing an amide group, unsaturated monomers containing an amino group, and unsaturated monomers containing a sulfonic acid group, etc. can be heard

For example, when the functional group in the acrylic resin is a carboxyl group, the glycidyl group-containing unsaturated monomer or the isocyanate group-containing unsaturated monomer, when the functional group is a hydroxyl group, the isocyanate group-containing unsaturated monomer, when the functional group is a glycidyl group, When the functional group is an amino group, a carboxyl group-containing unsaturated monomer or an amide group-containing unsaturated monomer is selected and used. Especially, when the functional group in the acrylic resin is a hydroxyl group, it is preferable from the viewpoint of excellent reactivity of the functional group that the ethylenically unsaturated compound is an isocyanate group-containing unsaturated compound.

In addition, in the present invention, when the adhesive sheet is used for information label applications in which the adhesive sheet is bonded to transparent electrodes such as for touch panels or other electronic members, particularly precision electronic members, or for fixing electronic members, corrosion resistance is required. In this case, it is preferable that the functional group-containing acrylic resin (A) does not contain an acidic group.

<Crosslinking agent (B)>

The crosslinking agent (B) used in the present invention mainly reacts with the functional group contained in the functional group-containing acrylic resin (A), and exhibits excellent adhesive strength. For example, isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, A melamine-type crosslinking agent, an aldehyde-type crosslinking agent, an amine-type crosslinking agent, a metal chelate-type crosslinking agent, etc. are mentioned. Among these, an isocyanate-type crosslinking agent is suitably used from a viewpoint of improving adhesiveness with a base material or a reactive viewpoint with a functional group-containing acrylic resin (A).

Examples of the isocyanate-based crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, and hexamethylene Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, tetramethylxylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane Triisocyanates and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, biuret and isocyanurate compounds of these polyisocyanate compounds, and the like are exemplified.

Examples of the epoxy crosslinking agent include bisphenol A epichlorohydrin-type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, and glycerin triglycidyl ether. , 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol Polyglycidyl ether etc. are mentioned.

Examples of the aziridine crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, and N,N'-diphenylmethane-4. , 4'-bis(1-aziridine carboxamide), N,N'-hexamethylene 1,6-bis(1-aziridine carboxamide), etc. are mentioned.

As the melamine-based crosslinking agent, for example, hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, melamine resin, etc. can be heard

Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutaldialdehyde, formaldehyde, acetaldehyde, benzaldehyde, and the like.

Examples of the amine crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resin, polyamide and the like. .

Examples of the metal chelate-based crosslinking agent include acetylacetone and acetacetylester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. can

Moreover, these crosslinking agents (B) may be used independently and may use 2 or more types together.

The mixing amount of the crosslinking agent (B) is usually preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, particularly preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the functional group-containing acrylic resin (A). It is wealth. If the amount of the crosslinking agent (B) used is too small, cohesive strength tends to be insufficient and sufficient durability cannot be obtained, and if the amount is too large, the conformability to steps tends to decrease due to a decrease in flexibility.

The reaction temperature at the time of crosslinking the acrylic resin (A) and the crosslinking agent (B) to form a crosslinked product may be room temperature, and may be heated at, for example, 20 to 60°C.

<Ethylenically unsaturated compound (C) containing one ethylenically unsaturated group>

As the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group used in the present invention (hereinafter also referred to as a monofunctional unsaturated compound (C)), a (meth)acrylic acid ester system having one ethylenically unsaturated group Compound (C1) (excluding (C2) described later, hereinafter also referred to as “monofunctional (meth)acrylic acid ester compound (C1)”) or ethylene containing one ethylenically unsaturated group containing a nitrogen atom It is preferable to use a sexually unsaturated compound (C2) (hereinafter also referred to as "nitrogen-containing monofunctional unsaturated compound (C2)").

As the monofunctional (meth)acrylic acid ester compound (C1), long-chain aliphatic (meth)acrylate (C1-1), alicyclic (meth)acrylate (C1-2), aromatic (meth)acrylate (C1-1) 3) and the oxyalkylene structure modification compound (C1-4) of these (meth)acrylates, etc. are mentioned.

As the long-chain aliphatic (meth)acrylate (C1-1), for example, decane (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, iso Tridecyl (meth)acrylate, isomyristyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, 2-decyltetradecanyl (meth)acrylate etc. are mentioned.

As alicyclic (meth)acrylate (C1-2), isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, etc. are mentioned, for example.

As aromatic (meth)acrylate (C1-3), for example, biphenyl (meth)acrylate, naphthalene (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3- Chloro-2-hydroxypropyl (meth)acrylate etc. are mentioned.

Examples of the oxyalkylene structure-modified compound (C1-4) of (C1-1) to (C1-3) include the following.

Examples of the (C1-1) oxyalkylene structure-modified compound include 2-ethylhexyldiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and ethoxydiethylene glycol (meth)acrylate. , alkyl polyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, alkylene glycol monoalkyl ester (meth) acrylate, alkylene glycol mono (meth) acrylate, and the like.

Examples of the (C1-2) oxyalkylene structure-modified compound include t-butylcyclohexyl oxyethyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. rate, dicyclopentanyloxyethyl (meth)acrylate, and the like.

Examples of the (C1-3) oxyalkylene structure-modified compound include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, and phenyltriethylene glycol (meth)acrylate. Acrylate, phenyltetraglycol (meth)acrylate, biphenyloxyethyl (meth)acrylate, nonylphenol ethylene oxide modified (repeat 4) (meth)acrylate, nonylphenol ethylene oxide modified (repeat 8) (meth)acryl A rate etc. are mentioned.

Among these monofunctional (meth)acrylic acid ester compounds (C1), long-chain aliphatic (meth)acrylates (C1-1), alicyclic (meth)acrylates (C1-2), and aromatic (meth)acrylates (C1-1) It is preferable to use the oxyalkylene structure-modifying compound (C1-4) of -3) from the viewpoint of stably obtaining adhesive strength, and particularly preferably, isomyristyl acrylate, isotridecyl acrylate, isoste They are aryl acrylate, phenyldiethylene glycol acrylate, and dicyclopentenyloxyethyl acrylate.

The use of the nitrogen-containing monofunctional unsaturated compound (C2) can improve the adhesive strength of the pressure-sensitive adhesive, and examples include acrylamide, methacrylamide, butoxymethyl acrylamide, hydroxyethyl acrylamide, and dimethylaminopropyl acrylamide. amides, (meth)acrylamide-based unsaturated monomers such as diacetone acrylamide, N-acryloyloxyethylhexahydrophthalimide, acryloylmorpholine, and oxazolidone acrylate; among these, It is preferable to use a (meth)acrylamide type unsaturated monomer from the standpoint of excellent balance in terms of low volatility and adhesive performance, and butoxymethyl acrylamide and diacetone acrylamide are particularly preferable.

Among these, in the present invention, it is preferable to use a long-chain aliphatic acrylate (C1-1) from the viewpoint of being able to obtain an optically transparent pressure-sensitive adhesive layer that is difficult to color and imparting hydrophobicity to the pressure-sensitive adhesive layer, and particularly preferable. It is iso myristyl acrylate, isotridecyl acrylate, isostearyl acrylate, and 2-decyl tetradecyl acrylate.

As described later, the monofunctional unsaturated compound (C) is cured using at least one of active energy rays and heat, and exists as a polymer in the pressure-sensitive adhesive layer. However, the glass transition temperature of such a polymer is - It is preferable to select a monofunctional unsaturated compound (C) so that it becomes 80-80 degreeC.

As such a glass transition temperature, it is particularly preferably -60 to 40°C, more preferably -55 to 10°C, and particularly preferably -20 to 0°C. When the glass transition temperature is too high, the adhesive performance tends to be difficult to exhibit, and when the glass transition temperature is too low, the cohesive force tends to decrease.

In addition, a glass transition temperature is computed by the above-mentioned formula of Fox.

In addition, the monofunctional unsaturated compound (C) has the effect of softening the pressure-sensitive adhesive and improving the drying property during coating using an organic solvent, and at the time of coating drying (especially during drying when thick film coating), A solvent that is less volatilized than a solvent and easily stays in the pressure-sensitive adhesive layer is used.

The flash point of the monofunctional unsaturated compound (C) is preferably 40°C or higher, particularly preferably 80°C or higher, still more preferably 100°C or higher, and further preferably 140°C or higher. If the flash point is too low, it tends to volatilize in the drying process. In addition, the upper limit of normal flash point is 350 degreeC.

The weight average molecular weight of the monofunctional unsaturated compound (C) is preferably 100 to 2,000, particularly preferably 120 to 1,000, still more preferably 160 to 600, and particularly preferably 200 to 400.

When such a molecular weight is too large, adhesive physical properties tend to decrease, and when it is too small, volatilization tends to occur in the drying step.

<adhesive sheet>

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature and a crosslinking agent (B), and a monofunctional unsaturated compound (C).

In the pressure-sensitive adhesive layer, the content of the monofunctional unsaturated compound (C) is preferably 5 to 70% by weight, particularly preferably 9 to 50% by weight, further preferably 12 to 40% by weight, with respect to the entirety of the pressure-sensitive adhesive layer. is preferably 15 to 30% by weight.

If the content of such a monofunctional unsaturated compound (C) is too small, the level conformability tends to decrease, and if too large, the modulus of elasticity at the time of sheet preparation is too low, handling properties and stability of the coating film tend to decrease.

In addition, the content ratio of the monofunctional unsaturated compound (C) is a value determined as the content ratio of the monofunctional unsaturated compound (C) to the entire pressure-sensitive adhesive composition after drying and removing the organic solvent constituting the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer may contain a monofunctional unsaturated compound (C) after crosslinking the functional group-containing acrylic resin (A) and the crosslinking agent (B). It may be obtained by crosslinking the functional group-containing acrylic resin (A) and the crosslinking agent (B) in the presence of the compound (C), but from the viewpoint of easiness to obtain a pressure-sensitive adhesive sheet having excellent level conformability, the functional group is contained in the presence of the monofunctional unsaturated compound (C). It is preferable to crosslink acrylic resin (A) and crosslinking agent (B).

A functional group-containing acrylic resin (A), a crosslinking agent (B), and a monofunctional unsaturated compound (C) are used to prepare the pressure-sensitive adhesive sheet of the present invention, and the blending amount of the functional group-containing acrylic resin (A) and the monofunctional unsaturated compound (C) ) is preferably 50:50 to 95:5 (weight ratio), particularly preferably 65:35 to 90:9, and more preferably 70:30 to 85:15.

If the blending amount of the monofunctional unsaturated compound (C) with respect to the functional group-containing acrylic resin (A) is too large, the stability of the coating film tends to decrease, and if too small, the level conformability tends to decrease.

The blending amount of the crosslinking agent (B) and the monofunctional unsaturated compound (C) are preferably 0.1:99.9 to 20:80 (weight ratio), particularly 0.3:99.7 to 2:98, and further 0.5:99.5 to 1:99.5. It is preferably 99.0.

When the blending amount of the monofunctional unsaturated compound (C) is too large relative to the blending amount of the crosslinking agent (B), the stability of the coating film tends to decrease, and when the blending amount is too small, level conformability tends to decrease.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention comprises a crosslinked product of a functional group-containing acrylic resin (A) and a crosslinking agent (B) and a monofunctional unsaturated compound (C), as well as an ethylenically unsaturated compound containing two or more ethylenically unsaturated groups. (D) (hereinafter sometimes abbreviated as "polyfunctional unsaturated compound (D)") is preferably contained from the viewpoint of being able to adjust the cohesive force of the entire pressure-sensitive adhesive layer, and further containing a polymerization initiator (E) is an active energy It is preferable from the viewpoint of being able to stabilize the reaction at the time of pre-irradiation and/or heating.

As the polyfunctional unsaturated compound (D), for example, an ethylenically unsaturated monomer containing two or more ethylenically unsaturated groups in one molecule, such as a bifunctional monomer, a trifunctional or higher functional monomer, and a urethane (meth)acrylic acid. A late-based compound, an epoxy (meth)acrylate-based compound, or a polyester (meth)acrylate-based compound may be used. Among these, it is preferable to use an ethylenically unsaturated monomer or a urethane (meth)acrylate-based compound from the standpoint of excellent stability in terms of curing rate and reachable physical properties.

As the bifunctional monomer, any monomer containing two ethylenically unsaturated groups may be used, and examples thereof include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate. , polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, Neo Pentyl glycol di(meth)acrylate, ethylene oxide modified bisphenol A type di(meth)acrylate, propylene oxide modified bisphenol A type di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6 －Hexanediolethylene oxide modified di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol di Glycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxy pivalic acid modified neopentyl glycol di(meth)acrylate, isocyanuric acid ethylene oxide modified diacrylate, 2 -(meth)acryloyloxyethyl acid phosphate diester, etc. are mentioned.

As the trifunctional or higher functional monomer, it may be a monomer containing three or more ethylenically unsaturated groups, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra (meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(metha)acrylate )Acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide-modified tri(meth)acrylate, ethylene oxide-modified dipentane Lythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, Succinic acid modified pentaerythritol tri(meth)acrylate etc. are mentioned.

As the urethane (meth)acrylate-based compound, it is a (meth)acrylate-based compound having a urethane bond in the molecule, and a (meth)acrylic compound containing a hydroxyl group and a polyvalent isocyanate-based compound (if necessary, a polyol-based compound) , those obtained by reacting by a known general method can be used. What is necessary is just to use the thing of 300-4000 normally as a weight average molecular weight of a urethane (meth)acrylate type compound.

The content of the polyfunctional unsaturated compound (D) in the pressure-sensitive adhesive layer is preferably 20 to 0.1% by weight, particularly 10 to 0.2% by weight, furthermore 5 to 0.3% by weight, and further 1 to 0.1% by weight with respect to the entirety of the pressure-sensitive adhesive layer. It is preferably 0.5% by weight.

When the content of such a polyfunctional unsaturated compound (D) is too small, the reliability when cured by active energy ray irradiation tends to decrease, and when it is too large, the cohesive force when cured by active energy ray irradiation increases too much. Curing shrinkage occurs, and adhesive performance tends to deteriorate.

In addition, about the content rate of the said polyfunctional unsaturated compound (D), it is a value calculated|required as the content rate of the polyfunctional unsaturated compound (D) with respect to the whole adhesive composition after drying and removing the organic solvent which comprises an adhesive layer.

Further, the content of the polyfunctional unsaturated compound (D) in the pressure-sensitive adhesive layer is preferably 0.01 to 50 parts by weight, particularly preferably 0.5 to 20 parts by weight, and still more preferably 0.5 to 20 parts by weight based on 100 parts by weight of the monofunctional unsaturated compound (C). is 1 to 5 parts by weight. If the content of the polyfunctional unsaturated compound (D) is too large, the cohesive force increases too much in the post-curing step, resulting in curing shrinkage, which tends to lower the adhesive performance, and if too small, the holding force tends to be insufficient.

Polyfunctional unsaturated compounds ( The blending amount of D) is preferably 0.01 to 50 parts by weight, particularly preferably 0.1 to 30 parts by weight, still more preferably 0.5 to 20 parts by weight, and further preferably 1 to 50 parts by weight, based on 100 parts by weight of the functional group-containing acrylic resin (A). 5 parts by weight is preferred. If the blending amount of the polyfunctional unsaturated compound (D) is too large, the cohesive force increases too much in the post-curing step, resulting in curing shrinkage, which tends to lower adhesive performance, and if too small, the holding power tends to be insufficient.

As the polymerization initiator (E), it is possible to use various polymerization initiators such as, for example, a photopolymerization initiator (e1) and a thermal polymerization initiator (e2). It is preferable from a viewpoint that it becomes possible to harden by active energy ray irradiation, such as an ultraviolet-ray of.

Moreover, it is also preferable to use both together as needed.

As the photopolymerization initiator (e1) and the thermal polymerization initiator (e2), known general polymerization initiators can be used. Examples of the photopolymerization initiator (e1) include diethoxyacephenone, 2-hydroxy-2-methyl-1-phenyl propan-1-one, benzyldimethyl ketal, and 4-(2-hydroxyethoxy)phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino Acetphenones such as -1-(4-morpholinophenyl)butanone and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoin, benzoin Benzoins such as methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; Benzophenone, o-benzoylmethylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl Sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2- Benzophenones such as (1-oxo-2-propenyloxy)ethyl]benzenemethananium bromide and (4-benzoylbenzyl)trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl Thioxanthones such as -9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4 -acyl phosphone oxides such as trimethyl-pentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; In addition, as for these photoinitiators (e1), only 1 type may be used independently, or 2 or more types may be used together.

In addition, as these preparations, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Mihiraketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate , 4-dimethylaminobenzoate (n-butoxy)ethyl, 4-dimethylaminobenzoate isoamyl, 4-dimethylaminobenzoate-2-ethylhexyl, 2,4-diethylthioxanone, 2,4-diisopropyl It is also possible to use thioxanone etc. together.

Among these, benzyldimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl) ketone, 2-hydroxy- Preference is given to using 2-methyl-1-phenyl propan-1-one.

In addition, as the thermal polymerization initiator (e2), for example, methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methylacetate peroxide, acetylacetate peroxide, 1,1-bis (t -Hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5 -Trimethylcyclohexane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, 1,1-bis(t-butylperoxy)-cyclohexane, 1,1-bis(t-butylperoxy) oxy)cyclododecane, 1,1-bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, p-menthane hydroperoxide, di Isopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α,α'-bis(t- Butylperoxy)diisopropylbenzene, dicumylperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumylperoxide, di-t-butylperoxide, 2, 5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide Oxide, succinic acid peroxide, m-tall oil benzoyl peroxide, benzoyl peroxide, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di -2-ethoxyethylperoxydicarbonate, di-2-ethoxyhexylperoxydicarbonate, di-3-methoxybutylperoxydicarbonate, di-s-butylperoxydicarbonate, di(3-methyl-3-methoxydicarbonate) Toxybutyl) peroxydicarbonate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate , 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxyfivarate, t-butylperoxy Fibarate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5 -bis(2-ethylhexanoylperoxy)hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butyl Peroxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisobutylate, t-butylperoxymalate, t-butylperoxy-3,5,5-tri Methylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropylmonocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-butylperoxyacetate, t-butylperoxy-m -Tolylbenzoate, t-butylperoxybenzoate, bis(t-butylperoxy)isophthalate, 2,5-dimethyl-2,5-bis(m-tolylperoxy)hexane, t-hexylperoxybenzo Eight, 2,5-dimethyl-2,5-bis (benzoyl peroxy) hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3,3',4,4'-tetra (t -organic peroxide initiators such as butyl peroxycarbonyl)benzophenone and 2,3-dimethyl-2,3-diphenyl butane; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1 -[(1-cyano-1-methylethyl)azo]formamide, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutylonitrile) , 2,2'-azobisisobutylonitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methyl-N-phenylpropionamidine)dihydrochloride, 2,2'-azobis[N-(4-chlorophenyl)-2-methylpropionamidine]dihydride Chloride, 2,2'-azobis[N-(4-hydrophenyl)-2-methylpropionamidine] dihydrochloride, 2,2'-azobis[2-methyl-N-(phenylmethyl)propionami Dean] dihydrochloride, 2,2'-azobis[2-methyl-N-(2-propenyl)propionamidine] dihydrochloride, 2,2'-azobis[N-(2-hydroxyethyl )-2-methylpropionamidine]dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazoline 2-yl)propane]dihydrochloride, 2,2'-azobis [2-(2-imidazoline-2-yl)propane]dihydrochloride, 2,2'- Azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(3,4 ,5,6-tetrahydropylimidin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(5-hydroxy-3,4,5,6-tetrahydropylimidine-2 -yl)propane]dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazoline-2-yl]propane}dihydrochloride, 2,2' -azobis[2-(2-imidazoline-2-yl)propane], 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxy Ethyl]propionamide}, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide}, 2,2'-azobis[2-methyl-N -(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropionamide), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'- Azobis (2-methyl propane), dimethyl-2,2-azobis (2-methylpropionate), 4,4'-azobis (4-cyanopentanoic acid), 2,2'-azobis [2 azo initiators such as -(hydroxymethyl)propionitrile; and the like. In addition, as for these thermal polymerization initiators (e2), only 1 type may be used independently, and 2 or more types may be used together.

The content of the polymerization initiator (E) in the pressure-sensitive adhesive layer is based on 100 parts by weight of the monofunctional unsaturated compound (C) (when using the polyfunctional unsaturated compound (D), 100 parts by weight in total of (C) and (D)) It is preferably 0.01 to 50 parts by weight, particularly preferably 0.1 to 20 parts by weight, still more preferably 0.3 to 12 parts by weight, and particularly preferably 0.5 to 5 parts by weight. If the content of the polymerization initiator (E) is too small, curing properties tend to be poor and physical properties become unstable, and if the content is too large, no further effect can be obtained.

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a base sheet, a double-sided pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a release sheet, and a base material-less double-sided adhesion used without a base sheet during bonding to an adherend. Although a sheet etc. are mentioned, the base materialless double-sided adhesive sheet is preferable from a viewpoint of excellent transparency and high adhesiveness with respect to the thickness which constitutes it.

As the method for producing the pressure-sensitive adhesive sheet of the present invention, for example, a functional group-containing acrylic resin (A), a crosslinking agent (B), and a monofunctional unsaturated compound (C) are contained as essential components and, if necessary, two ethylenically unsaturated groups are added. A functional group-containing acrylic resin (A) and a crosslinking agent by coating a pressure-sensitive adhesive composition containing at least one ethylenically unsaturated compound (D) and a polymerization initiator (E) on a base sheet or release sheet, drying, and curing as necessary. A pressure-sensitive adhesive sheet of the present invention having a pressure-sensitive adhesive layer containing a crosslinked product of (B) and a monofunctional unsaturated compound (C) is obtained.

In the case of a base materialless double-sided pressure-sensitive adhesive sheet, for example, after forming an adhesive layer obtained by coating and drying an adhesive composition on a release sheet, another release sheet is bonded to the side without the release sheet of the adhesive layer, It can be manufactured by curing as needed.

Examples of the substrate sheet include polyester-based resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymer; polyolefins such as polyethylene, polypropylene, and polymethylpentene. cyclic olefin resins such as resins and trade names "Aton (cyclic olefin polymer; manufactured by JSR Corporation)" and trade names "Zeonor (cyclic olefin polymer; manufactured by Nippon Zeon Corporation)"; polyvinyl fluoride, poly Polyfluorinated ethylene resins such as vinylidene fluoride and polyethylene fluoride; polyamides such as nylon 6, nylon 6 and 6; polyvinyl chloride, polyvinyl chloride/vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol Vinyl aggregates such as copolymers, polyvinyl alcohol, and vinylon; Cellulose resins such as cellulose triacetate and cellophane; Acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, ethyl polyacrylate, and butyl polyacrylate; Polystyrene; polycarbonate; polyarylate; and synthetic resin sheets such as polyimide, metal foils of aluminum, copper, and iron, paper such as high-quality paper and glassine paper, and woven and nonwoven fabrics made of glass fibers, natural fibers, synthetic fibers, and the like. . These base sheets can be used as a single layer body or as a multilayer body in which two or more types are laminated.

In addition, as the substrate sheet, various substrates including ITO (indium tin acid) electrode films, Cu mesh, Ag mesh, Ag nanofibers, or transparent electrode films such as organic conductive films such as polythiophene, or electrode films, polarizing plates, Optical members such as a retardation plate, an elliptically polarizing plate, an optical compensation film, a luminance enhancement film, an electromagnetic wave shielding film, a near-infrared ray absorbing film, and an AR (anti-reflection) film may also be used.

As the release sheet, various synthetic resin sheets exemplified in the base sheet, paper, fabric, nonwoven fabric, etc., which have been subjected to release treatment, can be used. For example, silicone-based release sheets, olefin-based release sheets, fluorine-based release sheets, and long-chain alkyl and an alkyd-based release sheet.

As a coating method of the pressure-sensitive adhesive composition, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, or the like can be used.

As for the drying conditions, the drying temperature is usually 50°C to 250°C, preferably 60°C to 120°C, and more preferably 65°C to 95°C. Drying time is 10 seconds - 10 minutes normally.

As conditions for the curing treatment, the temperature is usually room temperature to 70°C and the time is usually 1 to 30 days, specifically, for example, 1 to 20 days at 23°C, preferably 3 to 10 days at 23°C. , It can be carried out under conditions such as 1 to 7 days at 40 ° C.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is usually preferably 5 to 300 μm, particularly preferably 10 to 250 μm, still more preferably 25 to 200 μm, and particularly preferably 50 to 175 μm. When the thickness of such an adhesive layer is too thin, the step followability tends to decrease, and when the thickness is too thick, the thickness of the entire optical member tends to increase too much.

In addition, when obtaining a particularly thick pressure-sensitive adhesive layer, it is preferable to apply with a film thickness of 10 μm or more, particularly preferably 50 μm or more, still more preferably 100 μm or more, and the upper limit of such a film thickness is at the time of application The film thickness is usually 800 μm.

In addition, the said film thickness is the value calculated|required by subtracting the measured value of the thickness of constituent members other than the adhesive layer from the measured value of the thickness of the whole adhesive sheet using "ID-C112B" by Mitutoyo Corporation.

The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention (before curing by irradiation with active energy rays and/or heating) is preferably 5 to 60%, and preferably 10 to 50% from the viewpoints of adhesive strength and level conformability. , It is particularly preferable that it is 20 to 45%. If the gel fraction is too low, the pressure-sensitive adhesive sheet tends to be scratched by foreign substances due to a decrease in cohesive force, or the pressure-sensitive adhesive sheet tends to sag. In addition, when the gel fraction is too high, there is a tendency that conformability to steps is lowered due to an increase in cohesive force or adhesion to an adherend is lowered, resulting in deterioration in blister resistance.

The gel fraction of the pressure-sensitive adhesive layer after curing of the pressure-sensitive adhesive sheet of the present invention by active energy ray irradiation and/or heating is preferably 10 to 95%, particularly preferably 20 to 90%, from the viewpoint of durability performance and adhesive strength. , and preferably 30 to 80%. When the gel fraction is too low, the durability of the adhesive layer tends to deteriorate due to a decrease in cohesive force. In addition, when the gel fraction is too high, the adhesion to the interface tends to decrease due to an increase in cohesive force.

The gel fraction is a criterion for the degree of crosslinking (degree of curing), and is calculated, for example, by the following method. That is, an adhesive sheet (without a separator) formed by forming an adhesive layer on a polymer sheet serving as a base material (eg, polyethylene terephthalate film, etc.) is wrapped with a 200 mesh SUS wire mesh, and heated in toluene at 23 ° C × The weight percentage of the insoluble adhesive component remaining in the wire mesh after being immersed for 24 hours is referred to as the gel fraction. However, the weight of the base material is subtracted.

Since the pressure-sensitive adhesive sheet of the present invention obtained in this way contains a monofunctional unsaturated compound (C) in addition to a crosslinked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature and a crosslinking agent (B) in the pressure-sensitive adhesive layer, the monofunctional Since the elastic modulus of the pressure-sensitive adhesive layer is lowered by the unsaturated compound (C) imparting a plasticizing effect to the pressure-sensitive adhesive, excellent conformability to steps (irregularities) of the adherend is exhibited. In addition, when the glass transition temperature of the functional group-containing acrylic resin (A) is higher than usual, the content of the crosslinking agent can be reduced, and therefore, the decrease in adhesion due to thermal crosslinking of the acrylic resin can be suppressed to a minimum.

And, after bonding the adherend, by irradiating the pressure-sensitive adhesive layer with active energy rays and/or heating, the monofunctional unsaturated compound (C) contained in the pressure-sensitive adhesive layer is polymerized, and it is possible to adhere more strongly to the adherend. it will be done

As a bonding method between the PSA sheet and the adherend, for example, bonding the PSA layer surface of the PSA sheet to the adherend, followed by heating and pressurizing with an autoclave or the like (e.g., 50°C/0.5 MPa×30 minutes) can be used.

In the present invention, when the pressure-sensitive adhesive layer is cured by active energy ray irradiation, active energy ray irradiation can be performed from such a transparent surface using a transparent material for at least one of the substrate sheet and the adherend.

In the case of irradiation with the active energy ray, in addition to rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and γ-rays, electron beams, proton rays, neutron rays, etc. can be used, but the curing speed and irradiation device Curing by ultraviolet irradiation is advantageous in terms of availability, price, and the like. In the case of irradiation with electron beams, curing is possible without using the photopolymerization initiator (e1).

A high-pressure mercury-vapor lamp, an electrodeless lamp, an ultra-high-pressure mercury-vapor lamp carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp, or the like is used as a light source for performing the ultraviolet irradiation. In the case of the high-pressure mercury lamp, for example, it is 5 to 3000 mJ/cm 2 , preferably 50 to 2000 mJ/cm 2 . In the case of the electrodeless lamp, for example, 2 to 2000 mJ/cm 2 , preferably 10 to 1000 mJ/cm 2 . The irradiation time varies depending on the type of light source, the distance between the light source and the coated surface, and after coating and other conditions, but usually several seconds to several tens of seconds, and in some cases, a fraction of a second. On the other hand, in the case of the electron beam irradiation, it is preferable to use an electron beam having an energy in the range of 50 to 1000 Kev, for example, with an irradiation amount of 2 to 50 Mrad.

In the case of curing the pressure-sensitive adhesive layer by heat, the polymerization reaction is initiated and advanced by heating using a thermal polymerization initiator (e2) as the polymerization initiator (E). The treatment temperature and treatment time at the time of curing by heating vary depending on the type of thermal polymerization initiator (e2) used, and is usually calculated by the half-life of the initiator, but the treatment temperature is usually preferably 70 to 170 ° C. The treatment time is usually preferably 0.2 to 20 minutes, particularly preferably 0.5 to 10 minutes.

In this way, the pressure-sensitive adhesive sheet of the present invention is bonded to an adherend, and at least one of active energy ray irradiation and heating is performed, and the cured pressure-sensitive adhesive layer of the present invention is laminated on the adherend. A laminate including a pressure-sensitive adhesive layer ( [Adherent/Adhesive layer/Substrate sheet] or [Adherent/Adhesive layer/Adherent]) can be obtained when it is used as a substrate-less double-sided pressure-sensitive adhesive sheet.

The adherend is not particularly limited, but examples include ITO film, Cu mesh, Ag nanofiber, transparent electrode film such as organic conductive film such as polythiophene, polarizing plate, retardation plate, elliptically polarizing plate, and optical compensation film. , optical members such as brightness enhancing films, electromagnetic shielding films, near-infrared absorbing films, and AR (anti-reflection) films. Particularly, an adherend having a step on the surface is preferable because the effect of the adhesive sheet having excellent followability of the present invention is remarkably exhibited, for example, 1 to 100 μm, particularly 3 to 50 μm, and further 5 to 30 μm. Even an adherend having a level difference of , on the surface, exhibits good trackability.

The pressure-sensitive adhesive sheet of the present invention preferably has a storage elastic modulus of the pressure-sensitive adhesive layer of 1.0×10 ³ to 1.0×10 ⁵ at 23° C. and 1 Hz, and a tan δ of 0.5 to 0.7 at 50° C. and 1 Hz.

In addition, it is preferable that the storage elastic modulus of the pressure-sensitive adhesive layer after curing by active energy rays and/or heat is 1.0×10 ⁴ or more at 23° C. and 1 Hz, and that tan δ at 50° C. and 1 Hz is less than 0.5.

The adhesive sheet of the present invention is glass or ITO transparent electrode sheet, optical sheets such as polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polarizing plate, retardation plate, optical compensation film, brightness improvement It is useful for applications attaching optical members such as films. Moreover, it can use suitably with respect to image display apparatuses, such as a touch panel, which included these optical members.

(Example)

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "part" and "%" mean a weight basis.

First, solutions of various functional group-containing acrylic resins (A) were prepared as follows. In addition, about the measurement of the weight average molecular weight, dispersion degree, and glass transition temperature of functional group-containing acrylic resin (A), it measured according to the method mentioned above.

In addition, regarding the measurement of the solid content concentration, take 1 to 2 g of a functional group-containing acrylic resin (A) solution in an aluminum foil, heat dry it with a blanket (infrared dryer, 185 W, height 5 cm) for 45 minutes, and measure the weight change before and after drying. Regarding the measurement of the viscosity, it was measured according to the 4.5.3 rotational viscometer method of JIS K 5400 (1990).

[Production of Functional Group-Containing Acrylic Resin (A) Solution]

[Functional group-containing acrylic resin (A-1)]

In a four-inlet round-bottomed flask equipped with a reflux condenser, stirrer, nitrogen gas inlet and thermometer, 29 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), 2 - 15 parts of ethylhexyl methacrylate (a2-2), 15 parts of isostearyl acrylate (a2-2), 11 parts of tert-butyl methacrylate (a2-1), and 8 parts of acetone, 41 parts of methyl ethyl ketone After adding 5 parts of ethyl acetate and heating to reflux, adding 0.04 part of azobisisobutyronitrile (AIBN) as a polymerization initiator, and reacting at methyl ethyl ketone reflux temperature for 3 hours, followed by 0.02 part of azobisisobutyronitrile (AIBN) , 3 parts of ethyl acetate were added, reacted again for 4 hours, and diluted with ethyl acetate to obtain an acrylic resin solution. 0.03 part of 2-methacryloyloxyethyl isocyanate was added to 100 parts of the obtained acrylic resin solution (resin content), and it was made to react at 50 ° C. for 12 hours, adding 0.13 mol% of ethylenically unsaturated groups to the side chain relative to hydroxyethyl acrylate A solution of one functional group-containing acrylic resin (A-1) (weight average molecular weight: 296,000, dispersion degree: 3.72, glass transition temperature -25.4°C, solid content: 60%, viscosity: 12,000 mPa·s (25°C)) was obtained.

[Functional group-containing acrylic resin (A-2)]

In a four-inlet round-bottomed flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 50 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), tert - Put 20 parts of butyl methacrylate (a2-1) and 76 parts of ethyl acetate, start heating under reflux, add 0.04 part of azobisisobutyronitrile (AIBN) as a polymerization initiator, and react at ethyl acetate reflux temperature for 3 hours. 0.02 part of azobisisobutyronitrile (AIBN) and 3 parts of ethyl acetate were added, reacted for another 3 hours, and diluted with ethyl acetate to obtain an acrylic resin solution. 0.03 part of 2-methacryloyloxyethyl isocyanate was added to 100 parts of the obtained acrylic resin solution (resin component), and the reaction was carried out at 50 ° C. for 12 hours, and 0.08 mol% of ethylenically unsaturated groups were added to the side chain relative to hydroxyethyl acrylate. A functional group-containing acrylic resin (A-2) solution (weight average molecular weight 622,000, dispersion degree 4.95, glass transition temperature -32.2°C, solid content 49.1%, viscosity 16,000 mPa·s (25°C)) was obtained.

[Functional group-containing acrylic resin (A'-1)]

In a four-inlet round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 70 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), and 150 parts of ethyl acetate was added, after heating to reflux, 0.04 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and after reacting at ethyl acetate reflux temperature for 3 hours, it was diluted with ethyl acetate to obtain an acrylic resin solution. 0.03 part of 2-methacryloyloxyethyl isocyanate was added to 100 parts of the obtained acrylic resin solution (resin component), and it was made to react at 50 ° C. for 12 hours, and 0.17 mol% of ethylenically unsaturated group was added to the side chain relative to hydroxyethyl acrylate. One functional group-containing acrylic resin (A'-1) solution (weight average molecular weight 69.10,000, dispersion degree 4.99, glass transition temperature -56.1 ° C., solid content 51.7%, viscosity 20,000 mPa·s (25 ° C.)) was obtained.

For the functional group-containing acrylic resins (A-1), (A-2) and (A'-1) prepared as described above, the content of the raw material monomer component and the glass transition temperature when each raw material monomer component was made into a homopolymer , The weight average molecular weight, dispersion degree, and viscosity of the functional group-containing acrylic resin are shown in Table 1 below.

Abbreviations in Table 1 represent the following compounds.

HEA: 2-hydroxyethyl acrylate

2EHA: 2-ethylhexyl acrylate

tBMA: tert-butyl methacrylate

2EHMA: 2-ethylhexyl methacrylate

ISTA: Isostearyl Acrylate

[Crosslinking agent (B)]

As a crosslinking agent (B-1), the following were prepared.

- 55% ethyl acetate solution of tolylene diisocyanate adduct of trimethylolpropane ("Colonate L-55E" manufactured by Nippon Polyurethane Co., Ltd.)

[Monofunctional unsaturated compound (C)]

As the monofunctional unsaturated compound (C), the following were prepared.

- (C1-1 a) isotridecyl acrylate ("FA-113 A" manufactured by Hitachi Chemical Co., Ltd.)

- (C1-1 b) 2-decyl tetradecanyl acrylate (“DTD-A” manufactured by Kyoeisha Kagaku Co., Ltd.)

- (C1-1c) isostearyl acrylate ("ISTA" manufactured by Osaka Yuki Kaguko Co., Ltd.)

[Polyfunctional unsaturated compound (D)]

As the polyfunctional unsaturated compound (D-1), the following were prepared.

・Trimethylolpropane triacrylate (TMPTA)

[Polymerization initiator (E)]

As a polymerization initiator (E-1), the following were prepared.

- 1: 1 mixture of 1-hydroxycyclohexylphenyl ketone and benzophenone ("Irgacua 500" manufactured by Chiba Japan)

<Example 1>

100 parts (resin content) of the above functional group-containing acrylic resin (A-1), 0.2 part of crosslinking agent (B-1), 40 parts of monofunctional unsaturated compound (C-1), and 1 part of polyfunctional unsaturated compound (D-1) , 1 part of photopolymerization initiator (E-1) was blended to prepare an adhesive composition solution.

The pressure-sensitive adhesive composition solution was applied to a polyester release sheet to a thickness of 100 μm after drying, and dried at 90° C. for 5 minutes to form a pressure-sensitive adhesive layer. The obtained pressure-sensitive adhesive layer was sandwiched between a polyester release sheet and aged for 3 days under 40°C conditions to obtain a substrate-less double-sided pressure-sensitive adhesive sheet [I-1].

In addition, the release sheet on one side was peeled off from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet obtained above, and pressed onto a polyethylene terephthalate (PET) sheet having an easy adhesion of 125 μm in thickness, so that the film thickness of the pressure-sensitive adhesive layer was 100 μm. A PET sheet [II-1] containing an adhesive layer was obtained.

In addition, the release sheet on one side is peeled off from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet, and pressed onto a polyethylene terephthalate (PET) sheet having a thickness of 50 μm, so that the film thickness of the pressure-sensitive adhesive layer is 100 μm. A PET sheet [III-1] containing was obtained.

<Example 2, Comparative Examples 1 and 2>

Substrate-less double-sided adhesive sheets [I-2], [I'-1], [I'-2] and a PET sheet containing an adhesive layer [II-2], [II'-1], [II'-2], [III-2], [III'-1], [III' -2] was obtained.

<Example 3>

The film thickness of the pressure-sensitive adhesive layer was changed in the same manner as in Example 1 except that the blending ratio of components (A) to (E) was changed to the blending ratio described in Table 2, and the coating was applied so that the thickness after drying was 160 μm. A 160 µm base materialless double-sided adhesive sheet [I-3] and PET sheets [II-3] and [III-3] containing an adhesive layer were obtained.

Gel fraction of the pressure-sensitive adhesive layer, optical properties and blister resistance of the pressure-sensitive adhesive layer using the base materialless double-sided pressure-sensitive adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] Measured. In addition, using the PET sheets [II-1] to [II to 3], [II'-1], and [II'-2] containing the above-mentioned pressure-sensitive adhesive layer, the adhesive force of the pressure-sensitive adhesive layer was measured to evaluate the level conformability. . Again, using the PET sheets [III-1] to [III-3], [III'-1], and [III'-2] containing the above-mentioned pressure-sensitive adhesive layer, the heat-and-moisture resistance of the pressure-sensitive adhesive layer was evaluated. The results are shown in Table 3 below.

[Gel fraction before UV irradiation]

After cutting the above substrate-less double-sided adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] to 40 mm × 40 mm, respectively, under conditions of 23 ° C × 50% R.H. left for 30 minutes. After that, one release sheet is peeled off, and the adhesive layer side is bonded to a 50 mm × 100 mm SUS mesh sheet (200 mesh), and then the other release sheet is peeled off again, and the central portion with respect to the longitudinal direction of the SUS mesh sheet After wrapping the sample by folding it, the gel fraction (%) was measured from the weight change when immersed in a sealed container containing 250 g of toluene for 24 hours.

[Gel fraction after UV irradiation]

After cutting each of the substrate-less double-sided adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] into 40 mm × 40 mm, peak illumination in a high-pressure mercury UV irradiation device : 150 mW/cm 2 , cumulative exposure amount: 1000 mJ/cm 2 was irradiated with ultraviolet rays (500 mJ/cm 2 × 2 passes), and left for 30 minutes under conditions of 23° C. × 50% R.H. After that, one release sheet is peeled off, the adhesive layer side is bonded to a 50 mm × 100 mm SUS mesh sheet (200 mesh), and then the other release sheet is peeled off, and from the center of the SUS mesh sheet in the longitudinal direction After wrapping the sample by folding, the gel fraction (%) was measured from the weight change when immersed in a sealed container containing 250 g of toluene for 24 hours.

[adhesiveness (initial adhesiveness)]

Each of the PET films [II-1] to [II to 3], [II'-1], and [II'-2] including the pressure-sensitive adhesive layer was cut into a width of 25 mm × length of 100 mm, and the release sheet was peeled off. , The pressure-sensitive adhesive layer side was attached to alkali-free glass in an atmosphere of 23 ° C and 50% relative humidity with a 2kg rubber roller 2 reciprocations, and left for 30 minutes in an atmosphere of 23 ° C and 50% relative humidity, peeling speed 300 mm / min at room temperature 180 degree peel strength (N/25 mm) was measured.

[adhesion (adhesion after curing)]

The PET films [II-1] to [II to 3], [II'-1], and [II'-2] containing the pressure-sensitive adhesive layer are cut into a width of 25 mm × length of 100 mm, respectively, and the release sheet is peeled, The pressure-sensitive adhesive layer side was applied to alkali-free glass under pressure with two reciprocations of a 2-kg rubber roller in an atmosphere of 23°C and 50% relative humidity, and subjected to a pressurized heat treatment at 50°C and 0.5 MPa for 20 minutes in an autoclave. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiator at a peak illuminance of 150 mW/cm 2 and an integrated exposure amount of 1000 mJ/cm 2 (500 mJ/cm 2 × 2 passes) under conditions of 23°C × 50% R.H. After leaving it to stand for 30 minutes, the 180 degree peel strength (N/25 mm) was measured at room temperature at a peel rate of 300 mm/min.

[Step Difference Followability]

PET films of 25 µm, 38 µm, 50 µm, 70 µm, and 100 µm were fixed on alkali-free glass with cellophane tape, respectively, to produce stepped glass. The PET sheets [II-1] to [II to 3], [II'-1], and [II'-2] containing the above-mentioned pressure-sensitive adhesive layer, respectively, with respect to the glass having the step difference, 23 ° C., 50 relative humidity In an atmosphere of %, pressure was applied with a 2 kg rubber roller 2 reciprocations, and a pressurized heat treatment was performed in an autoclave at 50 ° C. 0.5 MPa × 20 minutes. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm 2 and an integrated exposure amount of 1000 mJ/cm 2 (500 mJ/cm 2 × 2 passes) under conditions of 23°C × 50% R.H. After leaving it to stand for 30 minutes, followability to steps was visually evaluated as follows.

(evaluation)

◎... It was not possible to confirm that air was chewed or lifted at the stepped portion.

○... Some biting of air can be confirmed in a part of the stepped portion, but no lifting can be confirmed.

△... It was confirmed that air was chewed or lifted in a part of the stepped portion.

×... Large lifting was confirmed in the stepped portion.

[Measurement of optical properties of pressure-sensitive adhesive layer]

[Production of samples for optical measurement]

The substrate-less double-sided adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] were cut to 25 mm × 25 mm, respectively, and peak illumination in a high-pressure mercury UV irradiation device: Ultraviolet irradiation was performed at 150 mW/cm 2 and integrated exposure amount: 1000 mJ/cm 2 (500 mJ/cm 2 × 2 passes). After that, the release sheet on one side was peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer side was pasted onto slide glass (Eagle XG, manufactured by Corning Co.), followed by autoclave treatment (50 ° C., 0.5 MPa, 20 minutes), It was left to stand for 30 minutes on conditions of 23 degreeC x 50% R.H. Finally, the other release sheet was peeled off to produce a test piece having a structure of "slide glass/adhesive layer".

Haze value and color difference b* value were measured using the obtained test piece.

[Haze value]

The haze value measured the diffuse transmittance and total light transmittance using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and substituted the values of the obtained diffuse transmittance and total light transmittance into the following formula to calculate the haze. In addition, this machine complies with JIS K 7361-1.

Haze value (%) = (diffuse transmittance (%) / total light transmittance (%)) × 100

[color difference]

The color difference b* value was measured based on JIS K 7105, and the measurement was performed under transmission conditions using a spectrophotometer (SE6000: manufactured by Nippon Denshoku Industries Co., Ltd.). In addition, the measurement of haze, total light transmittance, and color difference b* value in this invention is a value measured by sticking only the adhesive layer to alkali-free glass (total light transmittance = 93, haze = 0.06, b* value = 0.16).

[moisture heat resistance]

The PET films [III-1] to [III-3], [III'-1], and [III'-2] containing the pressure-sensitive adhesive layer are cut to a size of 25 mm x 25 mm, respectively, and the release sheet is peeled off to form the pressure-sensitive adhesive layer. After attaching the side to slide glass (Eagle XG, manufactured by Corning), an autoclave treatment (50°C, 0.5 MPa, 20 minutes) was performed. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at peak illuminance: 150 mW/cm2 and cumulative exposure amount: 1000 mJ/cm2 (500 mJ/cm2×2 passes), conditions of 23°C×50% R.H. It was allowed to stand for 30 minutes under the condition, and a test piece having a configuration of "slide glass/adhesive layer/PET film" was produced.

Using the obtained test piece, a heat-and-moisture resistance test was conducted for 168 hours in an atmosphere of 85°C x 85% R.H., and the haze value was measured before the start of the heat-and-moisture test and after the heat-and-moisture test, and evaluated according to the following criteria.

The haze value was measured in the same manner as in measuring the optical properties of the pressure-sensitive adhesive layer.

(evaluation)

○... The haze value after the heat-and-moisture resistance test is less than 2.0%, and the increase rate of the haze value before and after the heat-and-moisture resistance test is within 1.2 times.

△... Haze value immediately after heat-and-moisture resistance test is less than 2.0%, and the increase rate of haze value before and after heat-and-moisture resistance test is larger than 1.2 times.

×... Haze value immediately after heat-and-moisture resistance test is 2.0% or more.

[Blister Resistance]

The PET films [II-1] to [II-3], [II'-1], and [II'-2] containing the pressure-sensitive adhesive layer are cut to a size of 25 mm x 50 mm, respectively, and the release sheet is peeled off to form the pressure-sensitive adhesive layer. The side was attached to an untreated polycarbonate plate having a thickness of 2 mm and subjected to autoclave treatment (50°C, 0.5 MPa, 20 minutes). Subsequently, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm2 and an integrated exposure amount of 1000 mJ/cm2 (500 mJ/cm2×2 passes), and 30°C under the condition of 23°C×50% R.H. It was left to stand for a while, and a test piece having a configuration of "polycarbonate plate/acrylic pressure-sensitive adhesive layer/PET film" was produced.

After that, it was allowed to stand for 24 hours in an atmosphere of 85° C.×85% R.H., and the degree of blistering before and after standing was visually observed. The evaluation criteria are as follows.

(evaluation)

◎... no foaming

○… Foaming of φ0.5 mm or less was observed, but there was no foam exceeding φ0.5 mm.

△… Foaming exceeding φ0.5 mm occurred in less than 1/3 of the entire attached surface.

×… Foaming exceeding φ0.5 mm occurred in more than 1/3 of the entire attached surface.

From the above results, the PSA sheets of Examples 1 and 2, in which the thickness of the PSA layer is 100 μm, show excellent followability to steps of 25 μm and 38 μm, and the PSA sheets of Example 1 have sufficient followability even for steps of 50 μm. It can be seen that followability is indicated.

In addition, it can be seen that the PSA sheet of Example 3 in which the thickness of the pressure-sensitive adhesive layer is 160 μm shows excellent followability to steps of 25 μm, 38 μm, and 50 μm, and shows sufficient followability to steps of 75 μm. . This shows sufficient followability for a level difference of about 47% of the thickness of the pressure-sensitive adhesive layer, and excellent level difference followability to the same extent as the PSA sheet of Example 1, which exhibits sufficient followability for a level difference of 50% of the thickness of the pressure-sensitive adhesive layer. know what you have

In addition, the PSA sheets of Examples 1 to 3 are excellent in physical properties required when the PSA sheet is used for bonding optical members such as touch panels, such as strong adhesive strength, moisture-heat whitening resistance, and blister resistance. Able to know.

On the other hand, it can be seen that the PSA sheets of Comparative Examples 1 and 2 using the functional group-containing acrylic resin (A) having a glass transition temperature lower than -35°C are inferior in level conformability and blister resistance.

Although this invention was detailed also demonstrated with reference to the specific embodiment, it is clear for those skilled in the art that various changes and correction can be added without deviating from the mind and range of this invention. This application is based on the Japanese Patent Application (Japanese Patent Application No. 2015-153476) filed on August 3, 2015, the contents of which are incorporated herein by reference.

The pressure-sensitive adhesive sheet of the present invention is excellent in level conformability, has high adhesive strength, high light transmittance, and hardly generates haze, from the viewpoints of glass or ITO transparent electrode sheets, polyethylene terephthalate (PET), polycarbonate (PC) ), polymethyl methacrylate (PMMA) and other optical sheets, polarizing plates, retardation plates, optical compensation films, and brightness enhancing films. Moreover, it can use suitably also about the touch panel containing these optical members.

Claims (9)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) and a crosslinking agent (B) and an ethylenically unsaturated compound having one ethylenically unsaturated group (C), wherein the functional group-containing acrylic resin (A) contains a hydroxyl group It is an acrylic resin obtained by polymerizing a monomer component containing a containing monomer and a methacrylic acid alkyl ester monomer having 4 to 8 carbon atoms in an alkyl group, wherein the content of the hydroxyl group-containing monomer is 10 to 40% by weight with respect to the total monomer component ,
A pressure-sensitive adhesive sheet in which the glass transition temperature of the functional group-containing acrylic resin (A) is -35°C or higher. delete The method of claim 1,
A pressure-sensitive adhesive sheet having a thickness of the pressure-sensitive adhesive layer of 5 to 300 μm. The method of claim 1,
A pressure-sensitive adhesive sheet that is a double-sided pressure-sensitive adhesive sheet in which release sheets are laminated on both sides of the pressure-sensitive adhesive layer. A method for producing a laminate comprising a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet according to claim 1 is bonded to an adherend and subjected to at least one of active energy ray irradiation and heating. The method of claim 5,
A method for producing a laminate comprising a pressure-sensitive adhesive layer having a step of 1 to 100 μm on the surface of the adherend. A laminate comprising an adhesive layer obtained by the method for producing a laminate comprising the adhesive layer according to claim 5 or 6. An image display device having a laminate comprising the pressure-sensitive adhesive layer according to claim 7. A touch panel having a laminate comprising the pressure-sensitive adhesive layer according to claim 7.