JP6896822B2 - Adhesive layer and adhesive film - Google Patents

Description

The present invention relates to a method for producing an adhesive film used for bonding layers of optical members, an adhesive composition, and an adhesive film. More specifically, although it is a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure as a main component, it has a low dielectric constant, excellent insulation performance, and tracking of printing steps. The present invention relates to a method for producing an adhesive film having properties and excellent shape retention, an adhesive composition, and an adhesive film.
Further, the pressure-sensitive adhesive composition according to the present invention can be used as an electrically insulating material for attaching an electric member, an electronic circuit member, or the like in addition to an optical member. Further, the adhesive film according to the present invention can be used as a film for a touch panel having electrical insulation, a film for electronic paper, and a film for a display.

In recent years, the amount of information communication handled has increased rapidly, as represented by the widespread use of video distribution via optical fiber communication lines and wireless communication lines. Along with this, there is a demand for miniaturization, high frequency, and high speed of electronic and electrical equipment, as well as improvement of safety and reliability. Therefore, it is required to use an electrically insulating material having a low dielectric constant in response to an increase in the frequency of electronic / electrical equipment.

Conventionally, in order to obtain an electrically insulating material having a low dielectric constant, it has been proposed to form a hollow structure in the electrically insulating material (see, for example, Patent Documents 1 to 3).
Patent Document 1 describes an electrically insulating member in which a foam-type pressure-sensitive adhesive layer is laminated on one surface of an electrically insulating material in which a synthetic resin film such as polyethylene terephthalate contains fine cavities.
Further, Patent Document 2 describes an adhesive film using an adhesive containing microspheres (microballoons) such as glass and silica so that the dielectric constant of the insulating material is 2.5 or less. There is.
Further, Patent Document 3 describes an insulating film for electric wires, which is made of an inorganic-containing microporous film in which silica is contained in a polyolefin resin.
Further, it has been proposed to use a liquid crystal polymer having a low dielectric constant as a base material as an adhesive film for insulation having a low dielectric constant (see, for example, Patent Document 4).
Further, in Patent Document 5, in order to obtain a pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 100 kHz, an alkyl (meth) acrylate having an alkyl group having 10 to 18 carbon atoms at the ester terminal is provided in 30 to 99. It has been proposed to form a pressure-sensitive adhesive layer containing a (meth) acrylic polymer obtained by polymerizing a monomer component containing 0.5 to 50% by weight of a 5% by weight and cyclic nitrogen-containing monomer.

Recently, for the purpose of improving the operability of electronic devices, smartphones (multifunctional mobile phones that combine the functions of mobile phones and mobile information terminals), tablets, and touch panels that incorporate capacitive touch panels. On-board laptop computers and the like are rapidly becoming widespread.
However, since the capacitive touch panel is a sensor that senses changes in the electromagnetic field, it is easily affected by noise, and in order to prevent erroneous recognition of the contact position, a low dielectric constant film is formed in the laminated structure. It has been proposed to stack them or to provide a member having a low dielectric constant in the wiring line of the capacitance sensor (see, for example, Patent Documents 6 and 7).
Patent Document 8 will be described later.

Japanese Unexamined Patent Publication No. 11-025757 Japanese Unexamined Patent Publication No. 11-288621 Japanese Unexamined Patent Publication No. 2006-024473 Japanese Unexamined Patent Publication No. 2003-321655 Japanese Unexamined Patent Publication No. 2013-082880 Japanese Unexamined Patent Publication No. 2012-094017 Japanese Unexamined Patent Publication No. 2013-003758 Japanese Unexamined Patent Publication No. 2011-162657

By the way, optical films used for various image display displays such as PDPs, liquid crystal panels, and organic EL panels, or optical adhesive films are required to have high transparency in order to improve visibility. .. However, in the method of mixing silica fine particles in order to form a hollow structure in the synthetic resin or the pressure-sensitive adhesive layer as disclosed in Patent Document 3, the particle size of the silica fine particles is set to the wavelength of red light of visible light. Unless it is set to a certain value of 400 nm (0.4 μm) or less, the total light transmittance is lowered due to light scattering. However, silica fine powder having a particle size of 0.4 μm or less has a problem that it is expensive because it is difficult to produce and cannot be used for producing a general-purpose insulator that needs to be inexpensive.

Another object of the invention described in Patent Document 4 is to provide a cheaper pressure-sensitive adhesive film for electrical / electronic insulation that retains excellent heat resistance, moisture resistance, and dielectric properties. For this reason, the pressure-sensitive adhesive film according to the invention of Patent Document 4 uses a liquid crystal polymer having a low dielectric constant as a base material, but a general silicone pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer. , The dielectric constant of the adhesive film cannot be further reduced to improve the insulating property.
Further, the pressure-sensitive adhesive according to Patent Document 5 has an excellent insulating property having a relative permittivity of 3.5 or less at a frequency of 100 kHz, but the relative permittivity at around 1 MHz, which is the main driving frequency of the current touch panel, is described. It has not been.
Further, in Patent Documents 6 and 7, in order to prevent erroneous recognition of the capacitance type touch panel, a low dielectric constant film is laminated in the laminated structure, and low relative permittivity is provided in the wiring line of the capacitance sensor. Although it is described that a member having a rate is provided, a method for manufacturing a member having a low dielectric constant to be used is not specifically shown.

As described above, in the prior art, a method for producing an adhesive film, an adhesive composition, and an adhesive film, which can be used for bonding optical members and have excellent insulating performance due to a low dielectric constant, are not known. It was.

Further, a black frame of a light-shielding layer formed by screen printing or the like is arranged on the surface of a front glass plate of a general display display, and a thickness is provided between the front glass plate and the black frame of the light-shielding layer. There is a step of several μm to 50 μm. For example, a protective plate of a mobile phone or the like is often provided with a printing frame having a thickness of about 10 μm to several tens of μm in order to improve the design. Further, electrodes for sending an electric current are arranged in the touch panel on the surface of the ITO layer of the touch panel device, and a printing step having a thickness of about several μm to several tens of μm is formed in the wiring portion by this printing. There is. In this way, when various optical films and protective plates are attached to the display using the adhesive film, or when the ITO layer is attached to other films using the adhesive layer, the adherend is used. There are many configurations with steps on the surface.
If there is a step on the surface of the adherend due to a printing layer or the like, the adhesive film cannot follow the step, and the generated floating causes air bubbles to be entrained, resulting in a problem that a gap is created between the adhesive film and the adherend. there were. Various efforts have been made so far to solve this problem. A method for producing an adhesive film, an adhesive composition and an adhesive film that overcome the above requirements and problems are required.
As a method of improving the followability to the printing step, a method of lowering the storage elastic modulus of the pressure-sensitive adhesive layer is known as in the pressure-sensitive adhesive film according to Patent Document 8. However, if the storage elastic modulus of the pressure-sensitive adhesive layer is lowered, the pressure-sensitive adhesive layer is likely to be deformed, and the adherend may not be fixed for a long period of time and the shape of the pressure-sensitive adhesive layer may not be maintained. ..

The present invention has been made in view of the above circumstances, and although it is a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure as a main component, it has a low dielectric constant and is excellent. An object of the present invention is to provide a method for producing an pressure-sensitive adhesive film, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film, which have excellent insulation performance, followability to a printing step, and excellent shape retention.

In order to solve the above problems, the present invention uses an acrylic polymer and a polyalkylene oxide chain as main components, although it is a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure. By containing the vinyl monomer, the photopolymerization initiator, and the cross-linking agent, the adhesive layer has excellent insulation performance due to its low dielectric constant, followability to printing steps, and excellent shape retention. That is the technical idea.
Therefore, the adhesive film according to the present invention is used in the form of an adhesive film after being thermoset and before being crosslinked by irradiation with ultraviolet rays, and after being attached to an adherend having a printing step, light is applied. By irradiating, a finally crosslinked pressure-sensitive adhesive layer can be obtained.
Further, for an adherend having no printing step, it can be used in the form of an adhesive film having an adhesive layer copolymerized and crosslinked by heating and irradiating with light.

Further, in order to solve the above problems, the present invention is a method for manufacturing an adhesive film used for bonding optical members, and the following steps (1) to (3),
Step (1): A step of copolymerizing two or more kinds of (meth) acrylate monomers other than the polyalkylene glycol (meth) acrylate to obtain an acrylic polymer.
Step (2): For a total of 100 g of the acrylic polymer, the total of vinyl monomers having one or more polyalkylene oxide chains selected from the polyalkylene glycol (meth) acrylate compound group is 0. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having the polyalkylene oxide chain, the photopolymerization initiator, and the cross-linking agent at a ratio of 1 to 20 mol.
Step (3): A pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz by applying the pressure-sensitive adhesive composition to one side of a release film prepared in advance and then heating and copolymerizing the pressure-sensitive adhesive composition. And a step of producing an adhesive film having the composition of a release film / the pressure-sensitive adhesive layer / a release film.
To provide a method for producing an adhesive film, which is characterized by passing through the above steps in order.

Further, the present invention is a method for manufacturing an adhesive film used for bonding optical members, and the following steps (1) to (3),
Step (1): A step of copolymerizing two or more kinds of (meth) acrylate monomers other than the polyalkylene glycol (meth) acrylate to obtain an acrylic polymer.
Step (2): For a total of 100 g of the acrylic polymer, the total of vinyl monomers having one or more polyalkylene oxide chains selected from the polyalkylene glycol (meth) acrylate compound group is 0. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having the polyalkylene oxide chain, the photopolymerization initiator, and the cross-linking agent at a ratio of 1 to 20 mol.
Step (3): A pressure-sensitive adhesive layer having a relative dielectric constant of 3.5 or less at a frequency of 1 MHz by applying the pressure-sensitive adhesive composition to one side of a base film prepared in advance and then heating and copolymerizing the pressure-sensitive adhesive composition. And the process of forming an adhesive film,
A method for producing an adhesive film is provided.

Further, it is preferable to irradiate the pressure-sensitive adhesive film with light to crosslink the pressure-sensitive adhesive composition.

The present invention is a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a cross-linking agent. The based polymer is a monomer of two or more kinds of (meth) acrylates selected from the compound group of a copolymerizable vinyl monomer having any group of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, and an aromatic group. It is an acrylic polymer obtained by copolymerization, and is a copolymerizable vinyl monomer having any one or more functional groups of a hydroxyl group and a carboxyl group with respect to 100 parts by weight of the total amount of the acrylic monomers. A total of one or more copolymerizable vinyl monomers (functional group-containing copolymerizable monomers) selected from the above compound group is copolymerized at a ratio of 0.5 to 15 parts by weight, and the acrylic type For a total of 100 g of the polymer, as the vinyl monomer having the polyalkylene oxide chain, ethylene glycol dimethacrylate (1G), triethylene glycol dimethacrylate (3G), polyethylene glycol # 400 dimethacrylate (9G), polyethylene glycol # 400 The total amount of one or more vinyl monomers having a polyalkylene oxide chain composed of diacrylate (A-200) and polyethylene glycol # 600 diacrylate (A-400) is 0.1 to 20 mol. Provided is a pressure-sensitive adhesive layer having a specific dielectric constant of 3.5 or less at a frequency of 1 MHz of the pressure-sensitive adhesive layer.

Further, the two or more kinds of (meth) acrylate monomers are selected from the compound group of copolymerizable vinyl monomers having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group and an aromatic group. It is preferable that it is made.

Further, the present invention is a copolymerization and cross-linking pressure-sensitive adhesive composition constituting a pressure-sensitive pressure-sensitive adhesive layer for bonding optical members, and two types other than polyalkylene glycol (meth) acrylate. One or more polyalkylene oxides selected from the polyalkylene glycol (meth) acrylate compound group with respect to a total of 100 g of the acrylic polymer obtained by copolymerizing the above (meth) acrylate monomers. A pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having the polyalkylene oxide chain, a photopolymerization initiator, and a cross-linking agent at a ratio of 0.1 to 20 mol of the total number of vinyl monomers having chains. A pressure-sensitive adhesive composition obtained by copolymerizing and cross-linking a product is provided.

Further, the polyalkylene glycol (meth) acrylate is used in the following general formula (1).
CH ₂ = C (R ¹ ) -COO- (R ^2- O) _n- R ³ (1)
(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is 1 to 23. It is preferable that it is represented by (indicating an integer of).

Further, the two or more kinds of (meth) acrylate monomers are selected from the compound group of copolymerizable vinyl monomers having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group and an aromatic group. It is preferable that it is made.

Further, it is preferable that the total amount of the alkyl (meth) acrylate compound group is 50 parts by weight or more out of 100 parts by weight of the total amount of all the monomers.

The present invention also provides an adhesive film having a release film / the pressure-sensitive adhesive layer / release film structure in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is formed on one side of the release film. ..

The present invention also provides an adhesive film in which an adhesive layer made of the adhesive composition is formed on one side of a base film.

Further, it is preferable that the relative permittivity of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less.

According to the present invention, the pressure-sensitive adhesive composition which overcomes the conventional requirements and problems and contains only an acrylic monomer having a general structure has excellent insulation performance due to a low dielectric constant. , A method for producing an adhesive film having a ability to follow a printing step and an excellent shape retention property, an adhesive composition, and an adhesive film can be provided.

Hereinafter, the present invention will be described based on preferred embodiments.
The method for producing the pressure-sensitive adhesive film of the present invention comprises the following steps (1) to (3).
Step (1): A step of copolymerizing two or more kinds of (meth) acrylate monomers other than the polyalkylene glycol (meth) acrylate to obtain an acrylic polymer.
Step (2): For a total of 100 g of the acrylic polymer, the total of vinyl monomers having one or more polyalkylene oxide chains selected from the polyalkylene glycol (meth) acrylate compound group is 0. A step of preparing a pressure-sensitive adhesive composition containing the acrylic polymer, the vinyl monomer having the polyalkylene oxide chain, the photopolymerization initiator, and the cross-linking agent at a ratio of 1 to 20 mol.
Step (3): The pressure-sensitive adhesive composition is applied to one side of a film prepared in advance and then heated and copolymerized to form a pressure-sensitive adhesive layer having a relative permittivity of 3.5 or less at a frequency of 1 MHz. And the process of making the adhesive film,
It is characterized by going through in order. Here, the film used in the step (3) may be a base film or a release film.

The pressure-sensitive adhesive layer of the present invention is a polyalkylene glycol (meth) based on a total of 100 g of an acrylic polymer obtained by copolymerizing two or more kinds of (meth) acrylate monomers other than the polyalkylene glycol (meth) acrylate. The acrylic polymer and the polyalkylene oxide chain at a ratio of 0.1 to 20 mol in total of vinyl monomers having one or more polyalkylene oxide chains selected from the compound group of meta) acrylate. The pressure-sensitive adhesive composition containing the vinyl monomer having the above, the photopolymerization initiator, and the cross-linking agent is copolymerized and cross-linked.

The polyalkylene glycol (meth) acrylate having a polyalkylene oxide chain used as a raw material for the pressure-sensitive adhesive layer according to the present invention has a function of significantly reducing the relative permittivity. It is not clear why the relative permittivity is significantly reduced when the acrylic polymer contains polyalkylene glycol (meth) acrylate and is further copolymerized and crosslinked, but one of the reasons is as follows. I think it might be.
(1) The pressure-sensitive adhesive layer according to the present invention is obtained by copolymerizing and cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer and a polyalkylene glycol (meth) acrylate. In the copolymer-based copolymer after copolymerization and cross-linking, a large number of polyalkylene oxide chains (hereinafter abbreviated as "whiskers") are elongated as side chains. For this reason, the acrylic copolymer (polymer) is thick due to the effect of "whiskers" that not only extend long in the length direction but also extend long in the width direction orthogonal to the length direction. It has a rugged shape. So to speak, the dumpling-like structure that is difficult to polarize even when a high-frequency charge is applied reduces the relative permittivity.
(2) In addition, a large number of "whiskers" extending as side chains of the acrylic copolymer (polymer) interfere with each other, so that the skeletons of the acrylic copolymer (polymer) approach each other. In the pressure-sensitive adhesive layer obtained by cross-linking the acrylic copolymer, fine voids composed of a large number of air layers are generated to reduce the specific dielectric constant.

The polyalkylene glycol (meth) acrylate selected as the vinyl monomer (monomer B) having a polyalkylene oxide chain includes a repeating structure of a polyalkylene oxide chain such as an ethylene oxide chain, a propylene oxide chain, and a butylene oxide chain. Examples thereof include compounds having one type or two or more types.
The polyalkylene glycol (meth) acrylate represented by the formula (1) has ^one _{(meth) acryloyl group represented by CH 2} = C (R 1) -CO- per molecule, and is monofunctional (meth). ) It is an acrylate. A compound having a (meth) acryloyl group at one end of the alkylene oxide chain, or (meth) at one end of the alkylene oxide chain in which an ethylene oxide chain, a propylene oxide chain, a butylene oxide chain, etc. are randomly or blocked. Any compound having an acryloyl group may be used.

The polyalkylene glycol (meth) acrylate is based on the following general formula (1).
CH ₂ = C (R ¹ ) -COO- (R ^2- O) _n- R ³ (1)
(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, R ³ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is 1 to 23. It is preferable that it is represented by (indicating an integer of).

The polyalkylene glycol (meth) acrylate is preferably a (meth) acrylate monomer having an ethylene oxide chain, a propylene oxide chain, or a butylene oxide chain, and the number of repetitions thereof is 2 to 23.

More preferably, it is a polyalkylene glycol (meth) acrylate having a polyalkylene oxide chain repetition number of 5 to 23. With a polyalkylene glycol (meth) acrylate having a polyalkylene oxide chain repetition number of less than 2, it is difficult to set the relative permittivity at a frequency of 1 MHz to 3.5 or less. Further, in the polyalkylene glycol (meth) acrylate in which the number of repetitions of the polyalkylene oxide chain exceeds 23, the relative permittivity at a frequency of 1 MHz is hardly reduced as compared with the compound having the number of repetitions of 23 or less. ..

Examples of the monomer of polyalkylene glycol (meth) acrylate having a polyethylene oxide chain include methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, and polyethylene glycol (meth) acrylate.
Examples of the monomer of polyalkylene glycol (meth) acrylate having a polypropylene oxide chain include methoxypolypropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate.
Examples of the monomer of the polyalkylene glycol (meth) acrylate having a polybutylene oxide chain include methoxypolybutylene glycol (meth) acrylate, ethoxypolybutylene glycol (meth) acrylate, and polybutylene glycol (meth) acrylate.
Further, examples of the monomer of polyalkylene glycol (meth) acrylate having both a polyethylene oxide chain and a polypropylene oxide chain include polyethylene glycol and polypropylene glycol (meth) acrylate.

Specific examples of commercially available polyalkylene glycol (meth) acrylates having a polyalkylene oxide chain as available include the following.
For example, the trade names of Shin-Nakamura Chemical Industry Co., Ltd. include NK ester AM30G (methoxypolyethylene glycol acrylate, number of repetitions of polyalkylene oxide chain: n = 3), NK ester M40G (methoxypolyethylene glycol methacrylate, n = 4), and the like. NK ester AM90G (methoxypolyethylene glycol acrylate, n = 9), NK ester M90G (methoxypolyethylene glycol methacrylate, n = 9), NK ester AM130G (methoxypolyethylene glycol acrylate, n = 13), NK ester AM230G (methoxypolyethylene glycol acrylate) , N = 23) and the like.
Examples of trade names of Kyoeisha Chemical Co., Ltd. include light acrylate MTG-A (methoxytriethylene glycol acrylate, n = 3) and light acrylate 130A (methoxypolyethylene glycol acrylate, n = 9).
The trade names of Nichiyu Co., Ltd. include Blemmer AE-200 (polyethylene glycol acrylate, n = 4.5), Blemmer AE-350 (polyethylene glycol acrylate, n = 8), and Blemmer AE-400 (polyethylene glycol acrylate). , N = 10), Blemmer PE-200 (polyethylene glycol methacrylate, n = 4.5), Blemmer PE-350 (polyethylene glycol methacrylate, n = 8), Blemmer AP400 (polyethylene glycol acrylate, n = 6), Blemmer AP550. (Polypropylene glycol acrylate, n = 9), Blemmer PP-500 (polyethylene glycol methacrylate, n = 9), Blemmer PP-800 (polyethylene glycol methacrylate, n = 13), Blemmer PP-1000 (polypropylene glycol methacrylate, n = 16). ), Blemmer AME-400 (methoxypolyethylene glycol acrylate, n = 9), Blemmer PME-200 (methoxypolyethylene glycol methacrylate, n = 4), Blemmer PME-400 (methoxypolyethylene glycol methacrylate, n = 9), Blemmer PME- 1000 (methoxypolyethylene glycol methacrylate, n = 23) and the like can be mentioned.
Moreover, as the trade name of Osaka Organic Chemical Industry Co., Ltd., MPE400A (methoxypolyethylene glycol acrylate, n = about 7), MPE550A (methoxypolyethylene glycol acrylate, n = about 9) and the like can be mentioned.

Further, in the pressure-sensitive adhesive layer according to the present invention, the content ratio of the polyalkylene glycol (meth) acrylate in the total amount of the acrylic monomer of the pressure-sensitive adhesive composition (this is 100 g) is 0.1 to 20 mol. The range is preferred. More preferably, it is 0.1 to 15 mol. When the content ratio of the polyalkylene glycol (meth) acrylate is less than 0.1 mol, the effect of reducing the relative permittivity of the pressure-sensitive adhesive layer is small, and it is difficult to reduce the relative dielectric constant of the pressure-sensitive adhesive layer to 3.5 or less. .. Further, if the content ratio of the polyalkylene glycol (meth) acrylate exceeds 20 mol, the viscosity of the pressure-sensitive adhesive composition becomes too high, and the copolymerization reaction becomes difficult, which is not preferable.
Further, if the content ratio of the polyalkylene glycol (meth) acrylate in the entire acrylic monomer of the pressure-sensitive adhesive composition (this is 100 g) is in the range of 0.1 to 20 mol, it is thermoset. When the storage elastic modulus (unit: Pa) at 30 ° C. of the pressure-sensitive adhesive layer before cross-linking by ultraviolet irradiation is expressed as K1, K1 adheres in the range of ^{2 × 10 4} to 1 × 10 ^{5 Pa.} An agent layer is obtained.
As a result, an adhesive layer and an adhesive film having the ability to follow the printing step and the excellent shape retention can be obtained. If the shape retention of the pressure-sensitive adhesive layer is excellent, the adherends are adhered to each other (or between the base film and the adherend) on both sides of the pressure-sensitive adhesive layer (original position). Relationship) can be retained. Then, the shape of the device manufactured by laminating the pressure-sensitive adhesive layer can be maintained. Further, when K1 exceeds 1 × 10 ⁵ Pa, the adhesive layer is difficult to be deformed at the time of bonding, so that the adhesive layer does not follow the printing step and a gap is generated in the printing step portion.
Further, the pressure-sensitive adhesive layer after being crosslinked by UV irradiation, when the storage elastic modulus at 30 ° C. (unit Pa) expressed as K2, when K2 is 3 × less than 10 5 ^Pa, the pressure-sensitive adhesive layer is deformed The adherend cannot be fixed for a long period of time or the shape of the adhesive layer cannot be maintained.

The acrylic polymer (polymer A) according to the present invention is obtained by copolymerizing two or more kinds of (meth) acrylate monomers (monomers A) other than the polyalkylene glycol (meth) acrylate. The monomer A is preferably selected from the compound group of copolymerizable vinyl monomers having any one of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, an imide group and an aromatic group. The polymer A is preferably a polymer having no polyalkylene oxide chain in the side chain.

Examples of the alkyl (meth) acrylate monomer having an alkyl group having C1 to C14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl. (Meta) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl At least one of (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate and the like. More than seeds can be mentioned. The alkyl group of the alkyl (meth) acrylate monomer may be linear, branched or cyclic.
Further, in the pressure-sensitive adhesive layer according to the present invention, the alkyl (meth) acrylate monomer having an alkyl group having C1 to C14 carbon atoms contained in the pressure-sensitive adhesive composition is 95 based on 100 parts by weight of the total amount of the acrylic monomer. It is preferably 5 to 25 parts by weight.

Other copolymerization monomers include vinyl-based monomers such as vinyl acetate, vinyl propionate, styrene, α-methylstyrene, N-vinylcaprolactam, and N-vinylpyrrolidone; polyethylene glycol (meth) acrylate, and (meth) acrylic acid. Glycol-based acrylic ester monomers such as polypropylene glycol, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2 Acrylic acid ester-based monomers such as −methoxyethyl acrylate; amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, nitrogen-containing monomers such as N-acryloylmorpholin; vinyl ether monomers and the like can also be used.
Among them, in order to adjust the cohesive force of the pressure-sensitive adhesive, a nitrogen-containing monomer such as a vinyl monomer having an amide group having no active hydrogen and a vinyl monomer having an amino group having no active hydrogen is contained, if necessary. can do. Here, "active hydrogen" means a hydrogen atom bonded to an atom other than carbon, for example, oxygen or nitrogen.

Examples of the nitrogen-containing monomer having no active hydrogen include cyclic nitrogen-vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, and (meth) acryloylmorpholin, N-ethyl-N-methyl (meth) acrylamide, and N-methyl-. N-propyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, Dialkyl-substituted (meth) acrylamides such as N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N-ethyl-N-methylaminoethyl (meth) acrylate, N-methyl-N-propylamino Ethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (meth) acrylate, N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylamino Dialkylamino (meth) acrylates such as propyl (meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate , N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl-N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide, N, N-dimethylaminopropyl (Meta) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) Dialkyl Substitution such as acrylamide At least one such as aminoalkyl (meth) acrylamide and the like can be mentioned.

The nitrogen-containing monomer preferably does not contain active hydrogen, and more preferably does not contain a hydroxyl group or a carboxyl group, in order to distinguish it from the vinyl monomer having a hydroxyl group described later. Examples of such a monomer include the monomers exemplified above, for example, acrylic monomers containing an N, N-dialkyl-substituted amino group or an N, N-dialkyl-substituted amide group; N-vinylpyrrolidone, N-vinylcaprolactam and the like. N-vinyl-substituted lactams; N- (meth) acryloyl-substituted cyclic amines such as N- (meth) acryloylmorpholine are preferred.
Further, in the pressure-sensitive adhesive layer according to the present invention, examples of the vinyl monomer having an amide group contained in the pressure-sensitive adhesive composition include N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth). Acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (Meta) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N-vinylcaprolactam and the like are particularly preferably used.

Further, in the pressure-sensitive adhesive layer according to the present invention, the nitrogen-containing monomer having no active hydrogen contained in the pressure-sensitive adhesive composition can impart necessary adhesive strength and durability to the pressure-sensitive adhesive layer. Therefore, for applications in which the pressure-sensitive adhesive layer is required to have a large adhesive force with an adherend, the content ratio of the nitrogen-containing monomer having no active hydrogen should be adjusted as in the case of the carboxyl group-containing monomer. The adhesive strength can be adjusted by. Further, in applications where it is not preferable to contain a carboxyl group-containing monomer, for example, when the adherend is an ITO transparent conductive film, a nitrogen-containing monomer having no active hydrogen is used instead of the corrosive carboxyl group-containing monomer. You can use to adjust the adhesive strength.

Examples of the hydroxyl group-containing copolymerizable vinyl monomer (hydroxyl group-containing monomer) include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-. Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) At least one or more kinds of hydroxyl group-containing (meth) acrylamides such as acrylamide can be mentioned. In the present invention, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable.
Further, in the pressure-sensitive adhesive layer according to the present invention, the hydroxyl group-containing monomer contained in the pressure-sensitive adhesive composition affects the corrosiveness of the obtained pressure-sensitive adhesive layer to a corrosive adherend such as the ITO surface of a transparent conductive film. It can be used as a copolymerizable monomer for reducing the content of the carboxyl group-containing monomer, which is said to give. Therefore, the hydroxyl group-containing monomer can be useful for improving the adhesive strength of the pressure-sensitive adhesive layer and reducing the corrosiveness.

Examples of the carboxyl group-containing copolymerizable vinyl monomer (carboxyl group-containing monomer) include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 2- (meth) acryloyloxyethyl. Hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloy At least one or more of loxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl tetrahydrophthalic acid and the like can be mentioned. In the present invention, (meth) acrylic acid is preferable.
Further, in the pressure-sensitive adhesive layer according to the present invention, the carboxyl group-containing monomer contained in the pressure-sensitive adhesive composition can impart a necessary cohesive force to the pressure-sensitive adhesive layer. Therefore, for applications in which the pressure-sensitive adhesive layer is required to have a large adhesive strength with an adherend, the adhesive strength can be adjusted by adjusting the content ratio of the carboxyl group-containing monomer.

Further, in the pressure-sensitive adhesive layer according to the present invention, one or more selected from the compound group of copolymerizable vinyl monomers having any one or more functional groups among the hydroxyl group and the carboxyl group. The total amount of the copolymerizable vinyl monomer (functional group-containing copolymerizable monomer) is preferably 0.5 to 15 parts by weight with respect to the total of 100 parts by weight of the acrylic monomer.
The functional group-containing copolymerizable monomer is preferably 0.5% by weight or more from the viewpoint of maintaining the adhesive force and the cohesive force with respect to 100 parts by weight of the total of the acrylic monomer components. On the other hand, if the amount of the functional group-containing copolymerizable monomer becomes too large, the pressure-sensitive adhesive may become hard and the adhesive strength may decrease, and the viscosity of the pressure-sensitive adhesive composition may become too high or gel may occur. Therefore, the functional group-containing copolymerizable monomer is preferably 15% by weight or less based on 100 parts by weight of the total of the acrylic monomer components.

Examples of the copolymerizable vinyl monomer having an amide group include (meth) acrylates having an amide group such as N- [2- (acryloyloxy) ethyl] acetamide, and (meth) acrylamides.

Examples of the copolymerizable vinyl monomer having an imide group include (meth) acrylate having an imide group such as N- [2- (acryloyloxy) ethyl] phthalimide.

Examples of the copolymerizable vinyl monomer having an aromatic group include (meth) acrylate having an aromatic group such as phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth) acrylate, as well as styrene and α-methyl. Examples thereof include non-acrylic vinyl monomers having an aromatic group such as styrene.

The polymerization method of the polymer A is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. The weight average molecular weight of the polymer A is preferably 200,000 to 2,000,000.
The monomer composition of the polymer A may contain 50 to 100 parts by weight of an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid, and (meth) acrylamide with respect to 100 parts by weight of the polymer A. preferable.

In the pressure-sensitive adhesive composition, properties such as required physical property values can be adjusted by adding a cross-linking agent and an appropriate additive to the polymer A and the monomer B. A pressure-sensitive adhesive composition containing polymer A, monomer B, a photopolymerization initiator, and a cross-linking agent was prepared at a ratio of 0.1 to 20 mol of monomer B to a total of 100 g of polymer A. It is preferable to do so. According to the present invention, the monomer B is added to the polymer A, which is a general acrylic pressure-sensitive adhesive, and the monomer B is copolymerized with the polymer A by heating, and further crosslinked by irradiation with ultraviolet rays. In other words, while producing a general adhesive product (using a general-purpose adhesive), the monomer B is added only "when producing an adhesive product that requires low relative permittivity performance" to achieve its effect. be able to. Therefore, it is possible to produce an adhesive product having a low relative permittivity without holding an inventory of "adhesive for an adhesive product having a low dielectric constant", which is advantageous in terms of cost and management. Further, a pressure-sensitive adhesive having a low relative permittivity can be obtained by simply adding the monomer B and the photoinitiator to the pressure-sensitive adhesive that has been used conventionally. Further, the relative permittivity can be controlled by changing the type and amount of the monomer B to be added with respect to the solid content of the pressure-sensitive adhesive. There is a possibility that it will be possible to create a product that matches the desired relative permittivity, rather than simply lowering the relative permittivity.

Examples of the cross-linking agent include burette-modified products of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, isocyanurate-modified products, trimethylolpropane, and trivalent or higher glycerin. At least one or more of polyisocyanate compounds such as adducts with polyols, metal-based chelate compounds, and epoxy compounds can be mentioned. Further, the adhesive may be crosslinked by photocrosslinking such as ultraviolet rays.
When the acrylic copolymer is crosslinked using a cross-linking agent, the acrylic copolymer has a functional group capable of cross-linking with the cross-linking agent (depending on the type of the cross-linking agent, such as a hydroxyl group or a carboxyl group). It is preferable, and it is preferable to contain a monomer having these functional groups in the side chain. Further, it is preferable that the pressure-sensitive adhesive composition contains 0.01 to 5 parts by weight of the cross-linking agent with respect to 100 parts by weight of the total of the acrylic monomers.

Other optional ingredients include silane coupling agents, antioxidants, surfactants, curing accelerators, plasticizers, fillers, cross-linking catalysts, cross-linking retarders, curing retardants, processing aids, anti-aging agents, etc. Known additives can be appropriately blended. These may be used alone or in combination of two or more. In the application of electrical insulation, it is preferable that the pressure-sensitive adhesive does not contain ionic compounds such as alkali metal salts, alkaline earth metal salts and quaternary onium salts, conductors such as metals and carbons, and antistatic agents. ..

The pressure-sensitive adhesive layer of the present invention can be obtained by applying the pressure-sensitive adhesive composition to a base film or a release film and then cross-linking the pressure-sensitive adhesive composition.
When the pressure-sensitive adhesive layer according to the present invention is used as an electrically insulating material having a low dielectric constant corresponding to high frequencies of electronic and electrical equipment, the relative dielectric constant of the pressure-sensitive adhesive layer at a frequency of 1 MHz is 3.5 or less. It is preferably 3.0 or less, and more preferably 3.0 or less.
In the copolymerized and crosslinked pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer for a pressure-sensitive adhesive film, the total amount of alkyl (meth) acrylate compounds is 50 parts by weight or more out of 100 parts by weight of the total amount of all the monomers. Is preferable. By increasing the proportion of alkyl (meth) acrylate with low polarity, the relative permittivity can be further reduced.

The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, and is about 5 to 400 μm. For example, when the adhesive layer for electronic insulation of the present invention is used for the capacitance type touch panel, the relative permittivity ε _r of the adhesive layer and the thickness (adhesive thickness) d of the adhesive layer are as shown in the following formula. As a result, the sensor responsiveness of the capacitive touch panel changes, so it is necessary to control the relative permittivity and adhesive thickness according to the design of the electronic device to be mounted. In recent years, there has been a demand for thinner electronic devices and touch panels, and there is an increasing demand for thinner adhesive layers, which are constituent members. By using the pressure-sensitive adhesive layer of the present invention, the same sensitivity as when the conventional pressure-sensitive adhesive layer is used can be realized with a thin pressure-sensitive adhesive thickness.
Further, when the prevention of malfunction is emphasized, the response speed and sensitivity of the touch panel can be expected to be improved by replacing the conventional pressure-sensitive adhesive layer with the pressure-sensitive adhesive layer of the present invention.

Equation: C = ε _r・ ε ₀・ A / d

C: Capacitance, ε _r : Relative permittivity of the pressure-sensitive adhesive layer, ε ₀ : Dielectric constant in space (vacuum), A: Area, d: Thickness of the pressure-sensitive adhesive layer.

When the pressure-sensitive adhesive layer according to the present invention is used for bonding layers of optical members, it is desirable that the difference in refractive index is as small as possible in order to reduce the reflection of light rays at the interface between the pressure-sensitive adhesive layer and the optical member. .. Therefore, the refractive index of the pressure-sensitive adhesive layer is preferably 1.47 to 1.50.
Further, the adhesive strength of the pressure-sensitive adhesive layer according to the present invention can be adjusted by adjusting the composition of the pressure-sensitive adhesive according to the purpose of bonding to the adherend, but generally 0.1. It is about 20 N / 25 mm.

The pressure-sensitive adhesive film of the present invention can be produced by forming the pressure-sensitive adhesive layer of the present invention on one side of a base material or a release film.
As the base film used for forming the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
On the base film, on the side opposite to the side where the adhesive layer of the resin film is formed, antifouling treatment with silicone-based or fluorine-based mold release agent or coating agent, silica fine particles, etc., application of antistatic agent, etc. Antistatic treatment such as kneading can be applied.

The release film is subjected to a release treatment with a silicone-based or fluorine-based release agent or the like on the surface of the pressure-sensitive adhesive layer that is combined with the adhesive surface.
It is also possible to form a "release film / adhesive layer / release film" by aligning the surfaces of the release film that have been subjected to the release treatment on both sides of one pressure-sensitive adhesive layer. In this case, the release films on both sides are peeled off sequentially or at the same time to expose the adhesive surface, so that the release films can be bonded to an optical member such as an optical film. Optical films include cover glass, ITO glass, ITO film, transparent conductive film made of conductive polymer, transparent conductive film made of nano-silver wire, transparent conductive film made of carbon nanotubes, polarizing film, retardation film, and ultraviolet absorption. Examples include films, optical compensation films, and the like.

The adhesive film of the present invention can be used for bonding a touch panel and a display panel. Examples of the display panel include, but are not limited to, a liquid crystal display device, an organic EL, and the like. Further, it can be used as an electric insulating material for laminating an electric member, an electronic circuit member, or the like.
The adhesive film of the present invention includes various optical films for touch panels, various optical films for peripheral members of liquid crystal display devices mainly for polarizing plates, various optical films for electronic paper, various optical films for organic EL, and the like. It can be used for bonding.
Further, an optical film with an adhesive layer obtained by laminating the adhesive layer on at least one surface of these optical films can be obtained. Specifically, "optical film / adhesive layer / optical film", "optical film / adhesive layer / release film", "optical film / adhesive layer", "optical film / adhesive layer / optical film /""Adhesive film / optical film", "optical film / adhesive layer / optical film / adhesive layer / release film", "release film / adhesive layer / optical film / adhesive layer / release film", etc. The configuration can be mentioned.
For example, when having an adhesive layer protected by a release film such as "optical film / adhesive layer / release film", the release film is peeled off to form "optical film / adhesive layer". By exposing the pressure-sensitive adhesive layer and bonding it with another optical film, a configuration such as "optical film / pressure-sensitive adhesive layer / optical film" in which the pressure-sensitive adhesive layer is used for bonding between layers can be obtained.
The pressure-sensitive adhesive film of the present invention is a pressure-sensitive adhesive layer that is exposed by peeling off the release films on one or both sides of the pressure-sensitive adhesive layer after the pressure-sensitive adhesive layer is heat-cured and before being irradiated with ultraviolet rays. The adhesive layer can be crosslinked and used by affixing it to an adherend (optical member or the like) having a printing step and then irradiating it with ultraviolet rays. This makes it possible to manufacture an optical member with an adhesive layer.

Hereinafter, the present invention will be specifically described with reference to Examples.

[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction pipe, and the air in the reactor was replaced with nitrogen gas. Then, a solvent (ethyl acetate) was added to the reaction apparatus together with 63 g of butyl acrylate, 32 g of methyl acrylate, and 5 g of 2-hydroxyethyl acrylate. Then, azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, heated and reacted to obtain an acrylic polymer solution having a weight average molecular weight of 230,000 and used in Example 1.
0.026 mol of ethylene glycol dimethacrylate (1G), 0.84 g of cross-linking agent A, which is an isocyanate-based cross-linking agent, and alkylphenone-based photopolymerization were started with respect to the acrylic polymer solution of Example 1 produced as described above. 0.03 g of additive D, which is an agent, was added and stirred and mixed to obtain the pressure-sensitive adhesive composition of Example 1. The solvent is removed by applying this pressure-sensitive adhesive composition on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin so that the thickness after drying is 50 μm, and then drying at 90 ° C. did. Then, after aging for 7 days in an atmosphere of 40 ° C. and 50% RH, the pressure-sensitive adhesive composition is thermally cured by heating and copolymerizing, and the release film / pressure-sensitive adhesive layer / release film is formed. An adhesive film of Example 1 having a structure was obtained.
[Examples 2 to 9 and Comparative Examples 1 to 4]
Adhesion of Examples 2 to 9 and Comparative Examples 1 to 4 in the same manner as the above-mentioned adhesive film of Example 1 except that the compositions of the monomer and the additive are as shown in Tables 1, 3 and 4, respectively. I got a film. The “monomer composition” in Tables 1, 3 and 4 is a breakdown of the monomers constituting 100 g of the “acrylic pressure-sensitive adhesive”. The measurement results and test results shown in Tables 1 to 4 will be described later.

Table 5 shows the contents and names of the components used in Tables 1, 3 and 4.

The blending ratio of the acrylic polymer (polymer A) and the vinyl monomer having a polyalkylene oxide chain (monomer B) in the pressure-sensitive adhesive compositions of Examples 1 to 9 was such that the polyalkylene oxide chain was used with respect to 100 g of the acrylic polymer. It has 1.0 to 14.6 mol of vinyl monomer.
The amount of the monomer used for producing 100 g of the acrylic pressure-sensitive adhesive (1) was BA63 g (0.4915 mol), MA32 g (0.3717 mol), and HEA 5 g (0.0430 mol), and the total of these monomers was It is 0.906 mol.
The amount of the monomer used for producing 100 g of the acrylic pressure-sensitive adhesive (2) is 97 g (0.5264 mol) of 2EHA and 3 g (0.0258 mol) of HEA, and the total of these monomers is 0.552 mol.
The amount of the monomer used for producing 100 g of the acrylic pressure-sensitive adhesive (3) is 95 g (0.5155 mol) of 2EHA and 5 g (0.0438 mol) of 4HBA, and the total of these monomers is 0.559 mol.

<Relative permittivity measurement method and measurement results>
The release film (silicone resin coated PET film) is peeled off from the adhesive films of Examples 1 to 9 and Comparative Examples 1 to 4 to expose the adhesive layer, and the adhesive layer is transferred to one side of the PET film. did. This sample was measured for the relative permittivity of the pressure-sensitive adhesive layer using an LCR meter (manufactured by Hewlett-Packard Company, model: 4284A).

Tables 1, 3 and 4 show the measurement results of the relative permittivity.

The pressure-sensitive adhesive films of Examples 1 to 9 had excellent insulating performance due to a low relative permittivity. That is, the adhesive films of Examples 1 to 9 were able to overcome the requirements and problems.
The adhesive films of Comparative Examples 1, 2 and 4 did not have excellent insulating performance due to the low relative permittivity.
The adhesive film of Comparative Example 3 had excellent insulating performance due to its low relative permittivity.

<Test method and test results for followability to printing steps>
A release film (silicone resin coated PET film) from the adhesive film in Example 2, Example 5, and Comparative Example 1 after being thermoset and before being irradiated with ultraviolet rays. Was peeled off and attached to a PET film (thickness 100 μm) under an atmospheric pressure environment. A bonding device (product name SE320) manufactured by Climb Products Co., Ltd. was used for bonding.
The release film (silicone resin coated PET film) on the heavy peeling surface side was peeled off from this sample, and the obtained pressure-sensitive adhesive layer with the PET film was applied to an adherend (thickness of about 10 μm / about 15 μm by screen printing). (PET film with a hard coat treatment on the opposite side to the printing) on which each of the printing steps of the above was formed) was bonded under an atmospheric pressure environment. After bonding, of each sample, visually check the appearance of the part where the adhesive layer is bonded to the printing step of the adherend, and those where bubbles can be confirmed (×) and those that cannot be confirmed (○) ).

Table 2 shows the test results of the adhesive layer's ability to follow the printing step before irradiation with ultraviolet rays.

In Examples 2 and 5, the pressure-sensitive adhesive layer could be bonded without bubbles entering the printing step portion. In Comparative Example 1, air bubbles entered in the printing step portion at the time of bonding. This is because, in Comparative Example 1, the adhesive layer was crosslinked before the irradiation with ultraviolet rays, the resin became hard, and the adhesive layer had the ability to follow the printing step of the adherend before the irradiation with ultraviolet rays. It is thought that this is because it is getting worse.

<Shape retention test method and test results>
A release film (silicone resin coated PET film) on the lightly peeled surface side from the adhesive films of Example 2, Example 5, and Comparative Example 1 after being thermoset and before being irradiated with ultraviolet rays. Was peeled off and affixed to a PET film (thickness 100 μm) under an atmospheric pressure environment to prepare a sample for a shape retention (measurement of displacement) test. A 2 kg hand roller was used for bonding. The release film (silicone resin coated PET film) on the heavy peeling surface side was peeled off from the sample of this shape retention test, and the obtained adhesive layer with the PET film was attached to a glass plate in an atmospheric pressure environment. It fits. After bonding, each sample was irradiated with ultraviolet rays at 1500 mJ / cm ² to crosslink the pressure-sensitive adhesive layer. After that, a weight of 1500 g was hung on one end of the PET film, and a shape retention test was conducted in an environment of 30 ° C. After 12 hours, the amount of displacement of the pressure-sensitive adhesive layer between the adherends (PET film and glass plate) was measured with a microscope.

Table 2 shows the test results of shape retention.

In the tests of Example 2 and Example 5, a large "displacement amount" of the pressure-sensitive adhesive layer was hardly confirmed. On the other hand, in the test of Comparative Example 1, a "shift amount" of about 6 mm was generated in the pressure-sensitive adhesive layer. Therefore, the adhesive film of Comparative Example 1 cannot sufficiently fix the adherends to each other and maintain the shape of the adhesive layer (positional relationship between the adherends).

<Measurement method and measurement result of storage elastic modulus>
The "storage elastic modulus" means the storage elastic modulus of the pressure-sensitive adhesive layer at 30 ° C. when the viscoelasticity measurement is performed in a temperature rising rate of 2 ° C./min and a solid shear mode of 1 Hz.
In the present specification, in order to distinguish the storage elasticity of the adhesive layer at 30 ° C. before cross-linking by ultraviolet irradiation and after cross-linking by ultraviolet irradiation, the adhesive layer is cross-linked by ultraviolet irradiation and before cross-linking by ultraviolet irradiation. The storage elasticity of the pressure-sensitive adhesive layer after that at 30 ° C. is referred to as K1 and K2, respectively.
In addition, a dynamic viscoelasticity measuring device (product name: Rheogel-E4000) manufactured by UBM was used for measuring the storage elastic modulus.

Table 2 shows the measurement results of the storage elastic modulus. The measured value of the storage elastic modulus was expressed by a method in which "m × 10 ⁿ " was set to "mE + 0n" (where m is an arbitrary real value and n is a positive integer).

According to the above measurement results of the storage elastic modulus, the storage elastic modulus of the pressure-sensitive adhesive layer of Example 2, Example 5, and Comparative Example 1 after being thermoset and before being crosslinked by ultraviolet irradiation at 30 ° C. (K1) was K1 = 6.8 × 10 ⁴ Pa, K1 = 8.2 × 10 ⁴ Pa, and K1 = 1.9 × 10 ⁵ Pa, respectively. Further, according to the test results of the followability to the printing step, the visual evaluation results of the followability to the adherend having the printing step having a step height of 15 μm in Example 2, Example 5 and Comparative Example 1, respectively, are obtained. They were (○), (○), and (×).
From this, it is preferable that ^{K1 is in the range of 1.0 × 10 4 to} 1.0 × 10 ⁵ Pa as the adhesive film having the ability to follow the printing step and the excellent shape retention. More preferably, K1 is in the range of ^{2.0 × 10 4 to} 1.0 × 10 ^{5 Pa.}
Further, K1 when exceeds the 1.0 × 10 5 ^Pa, no follow-up properties to laminated when the adhesive layer is hardly deformed because printing step, bubbles enters a gap occurs in the portion of the printing step.

Further, in the above measurement results of the storage elastic modulus, the storage elastic modulus (K2) at 30 ° C. of the pressure-sensitive adhesive layer after being crosslinked by ultraviolet irradiation of Example 2, Example 5 and Comparative Example 1, respectively. K2 = 5.4 × 10 ⁵ Pa, K2 = 4.3 × 10 ⁵ Pa, and K2 = 2.0 × 10 ⁵ Pa.
Generally, the higher the K2, the more difficult it is for the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film to be deformed, and when the pressure-sensitive adhesive film is used, the adherend can be fixed for a long period of time and the shape of the pressure-sensitive adhesive layer can be maintained. When K2 is less than 3.0 × 10 5 ^Pa, the adhesive layer is susceptible to modification, or fixed over a long period of time the adherend, it is impossible or maintain the shape of the pressure-sensitive adhesive layer.
In Examples 2 and 5, K2 is 3.0 × 10 ⁵ Pa or more (furthermore, K2 is 4 × 10 ⁵ Pa or more), and after cross-linking by irradiation with ultraviolet rays (in actual use), Compared with Comparative Example 1, the pressure-sensitive adhesive layer is less likely to be deformed and has excellent shape retention.
Therefore, K2 is ^{preferably 3.0 × 10 5} Pa or more, and K2 is more preferably 4 × 10 ⁵ Pa or more.

Although the pressure-sensitive adhesive layer according to the present invention uses a pressure-sensitive adhesive composition containing only an acrylic monomer having a general structure, it has excellent insulation performance due to a low dielectric constant. It can be used for bonding members, electrical members, electronic circuit members, and the like. Further, since the adhesive film according to the present invention can be used as a film for a touch panel and a film for a film display for electronic paper, it has great industrial utility value.
Further, since the adhesive film according to the present invention has a low storage elastic modulus of the adhesive layer before being crosslinked by ultraviolet irradiation, air is released even in an adherend having a step at the time of device creation (bonding). It can be pasted together without biting.
Further, the pressure-sensitive adhesive film according to the present invention has excellent shape retention and adhesiveness because the pressure-sensitive adhesive layer has a storage elastic modulus equivalent to that of a general pressure-sensitive adhesive film after being crosslinked by irradiation with ultraviolet rays. It is considered that the problem of deformation of the agent layer is unlikely to occur.

Claims (3)

A pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a vinyl monomer having a polyalkylene oxide chain, a photopolymerization initiator, and a cross-linking agent.
Two or more types of (meth) acrylate monomers selected from the group of copolymerizable vinyl monomers in which the acrylic polymer has any of an alkyl group, a hydroxyl group, a carboxyl group, an amide group, and an aromatic group. Is an acrylic polymer obtained by copolymerizing
One or more selected from the group of copolymerizable vinyl monomers having any one or more functional groups of hydroxyl groups and carboxyl groups with respect to 100 parts by weight of the total amount of acrylic monomers. The total of the copolymerizable vinyl monomers (functional group-containing copolymerizable monomers) of the above is 0.5 to 15 parts by weight.
Ethylene glycol dimethacrylate (1G), triethylene glycol dimethacrylate (3G), polyethylene glycol # 400 dimethacrylate (9G), and polyethylene are used as vinyl monomers having the polyalkylene oxide chain with respect to a total of 100 g of the acrylic polymer. Contains a total of one or more vinyl monomers having a polyalkylene oxide chain composed of glycol # 400 diacrylate (A-200) and polyethylene glycol # 600 diacrylate (A-400) in a ratio of 0.1 to 20 mol. And then
A pressure-sensitive adhesive layer having a relative permittivity of 3.5 or less at a frequency of 1 MHz. A pressure-sensitive adhesive film having the pressure-sensitive adhesive layer according to claim 1 formed on one side of the release-type film and having a release film / the pressure-sensitive adhesive layer / release-type film configuration. An adhesive film having the adhesive layer according to claim 1 formed on one side of a base film.