Optical pressure-sensitive adhesive composition, pressure-sensitive adhesive film, pressure-sensitive adhesive sheet, and optical film with pressure-sensitive adhesive layer

Abstract

To provide an adhesive composition for optics capable of forming an adhesive layer having all of step followability to a step of frame printing and the like of an adherend, handling ability when reworking, and excellent humidity and heat durability, an adhesive film using the same, an adhesive sheet, and an optical film with an adhesive layer.SOLUTION: An adhesive composition for optics includes: a copolymer having an acid value of 1.0 or lower obtained by copolymerizing a copolymerizable vinyl monomer having any of an alkyl group, a hydroxyl group, an alkoxy group, and an aromatic group, and at least two or more selected from the group of compounds of nitrogen-containing vinyl monomers; a (meth)acrylate monomer (F) having a (meth)acryloyl group and an allyl ether group in one molecule, and having two or more of ethylenic unsaturated groups; a (meth)acrylate monomer (G) having an alkylene oxide group, and two or more of ethylenic unsaturated groups in one molecule; a heat cross-linking agent (E); and a photo cross-linking agent (H).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical pressure-sensitive adhesive composition, and a pressure-sensitive adhesive film and sheet using the same. More specifically, the present invention relates to an optical pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that has excellent conformability to unevenness in frame printing or the like on an adherend, easy handling during rework (easy peeling from the adherend), and excellent humidity and heat durability, and a pressure-sensitive adhesive film and sheet using the same. Furthermore, a pressure-sensitive adhesive layer crosslinked with a thermal crosslinking agent using the optical pressure-sensitive adhesive composition of the present invention has good conformability to unevenness (concave and convex) of frame printing or the like arranged on the surface of an adherend, and good handleability during rework. Furthermore, a pressure-sensitive adhesive layer crosslinked in two stages, first with the thermal crosslinking agent and then with a photocrosslinking agent, has excellent humidity and heat durability. Furthermore, the optical pressure-sensitive adhesive composition of the present invention, and the pressure-sensitive adhesive film and pressure-sensitive adhesive sheet using the same can be used when bonding optical films to various displays, when bonding optical films together to produce optical film laminates, and when fixing optical and electronic components to be incorporated into various electronic devices. In the present invention, the "humid heat durability" of the adhesive layer means the durability of maintaining transparency without causing significant foaming due to moisture even when the adhesive layer is left in a humid heat environment for a long period of time and then taken out into a room temperature environment (temperature 23°C x 50% RH). [Background technology]

[0002] In recent years, electronic devices that combine a display (image display device) with a touch panel as an input device have become widespread. Examples of displays (image display devices) to which touch panels are applied include liquid crystal displays (LCDs) and electroluminescence displays (inorganic EL, organic EL). Specific examples of electronic devices that use touch panels as input devices include LCD televisions, inorganic EL televisions, organic EL televisions, mobile terminals, mobile phones, electronic paper, e-book readers, and personal computers. In these electronic devices, the pressure-sensitive adhesive layer for bonding the optical members that constitute the touch panel is required to have properties such as step conformability and durability against humidity and heat.

[0003] Various proposals have been made to obtain a pressure-sensitive adhesive layer having step-conforming properties (Patent Documents 1 to 3). Also, a proposal has been made to obtain a pressure-sensitive adhesive layer having step-conforming properties and wet heat durability (Patent Document 4). Patent document 1 describes a double-sided adhesive sheet that has excellent adhesion at the unevenness caused by decorative parts on the surface of a transparent panel or the surface of an image display device when fixing the transparent panel and the image display device, and that can suppress foaming and peeling at the unevenness in a high-temperature environment. Furthermore, Patent Document 2 describes a surface protection film with a decorative printing layer that has fewer air bubbles at the printing edges when forming the adhesive layer due to printing steps, does not generate air bubbles when attached to an adherend, and is less likely to develop depressions even when a load is applied. Furthermore, Patent Document 3 describes a photopolymerizable adhesive for touch panels having a conductive film made of metal or metal oxide, which has excellent moist heat resistance and foaming resistance, thereby preventing whitening and foaming, and which does not produce odor or irritate the skin, and is not corrosive to metals or metal oxides. Furthermore, Patent Document 4 describes an acrylic polymer compound used in a pressure-sensitive adhesive composition for touch panels that has excellent transparency, adhesiveness, durability, corrosion resistance, step-following ability, high dielectric constant, and coatability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-211282 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-221531 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-256552 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-041456 Summary of the Invention [Problem to be solved by the invention]

[0005] The double-sided pressure-sensitive adhesive sheet described in Patent Document 1 satisfies the performance requirements for print step conformance by limiting the storage modulus of the pressure-sensitive adhesive layer to a specific range, resulting in a soft pressure-sensitive adhesive layer. However, if the adhesive strength of the pressure-sensitive adhesive layer is increased, peeling may be difficult when re-attaching an optical element to an adherend, resulting in poor handling during rework (ease of re-attachment). Conversely, if the adhesive layer's handling during rework is increased, the adhesive strength after adhering the optical element to the adherend may be too low, resulting in peeling. Therefore, the double-sided pressure-sensitive adhesive sheet described in Patent Document 1 has the problem of difficulty in both ensuring the handleability of the pressure-sensitive adhesive layer during rework and increasing the adhesive strength after adhering the optical element to the adherend.

[0006] Patent Document 2 also discloses a method for obtaining a surface protective film with a decorative printed layer, in which a decorative printed layer (e.g., a graphic or letter) is formed on one side of a transparent resin film, and a flowable photocurable resin composition containing a photopolymerization initiator is applied to the upper portion of the decorative printed layer and to the upper portion of the decorative printed layer, followed by UV irradiation and photocuring to form a pressure-sensitive adhesive layer. The surface protective film with a decorative printed layer of Patent Document 2 is formed by applying a flowable photocurable resin composition containing a photopolymerization initiator, followed by UV irradiation and photocuring to form a pressure-sensitive adhesive layer. Therefore, it is claimed that the surface protective film can fill printed gaps regardless of the flexibility of the pressure-sensitive adhesive layer after UV curing. However, the pressure-sensitive adhesive layer of the invention of Patent Document 2 is formed by applying a liquid pressure-sensitive adhesive composition, which makes it difficult to form a thick pressure-sensitive adhesive layer. Furthermore, applying a liquid photocurable resin composition to the printed gap to fill the printed gap is problematic in that it is cumbersome to handle.

[0007] Patent Document 3 discloses a photopolymerizable adhesive containing 100 parts by weight of a monomer group (A) (total monomers taken as 100% by weight) or a partial polymer (A') thereof that contains 40 to 92% by weight of (a-1) alkyl (meth)acrylate, 5 to 20% by weight of (a-2) hydroxyl group-containing monomer, and 3 to 25% by weight of (a-3) water-soluble N-substituted acrylamide, and that is substantially free of acid group-containing monomers, with 0.01 to 2 parts by weight of an isocyanate-based crosslinking agent and / or a polyfunctional monomer (B), and 0.1 to 2 parts by weight of a photopolymerization initiator (C). The photopolymerizable adhesive in Patent Document 3 is said to have good step-conforming ability and removability. According to Examples 1 to 6 of Patent Document 3, a photopolymerizable adhesive is applied to a substrate to form a 300 μm thick coating film, a 25 μm thick release-treated PET film is placed on the surface of this coating film so that the release-treated surface abuts it, and photopolymerization is carried out by UV irradiation in a nitrogen gas atmosphere to produce an adhesive sheet. However, since the adhesive strength of the obtained adhesive sheet is in the range of 14 to 25 N / 25 mm, when the adhesive sheet is reattached to an adherend, it is difficult to peel the adhesive sheet from the adherend, resulting in poor handleability during rework.

[0008] Patent Document 4 also discloses an acrylic polymer compound used in a pressure-sensitive adhesive composition for a touch panel, which is obtained by copolymerizing monomer components including (a) a (meth)acrylic acid ester monomer having a hydrocarbon group with 1 to 12 carbon atoms, (b) a hydroxyl group-containing (meth)acrylic acid ester monomer, (c) a monomer containing an amide group, and (d) a vinyl ester monomer, and which has a resin acid value of 0.1 mgKOH / g or less, a weight-average molecular weight of 400,000 to 2,000,000, a Tg of −80 to 0° C., and a dielectric constant of 3 to 6. Regarding the acrylic polymer compounds in Patent Document 4, it is stated that "hydroxyl group-containing acrylic acid ester monomers are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred because they can provide the polymer compound with functional groups that become reaction sites with crosslinking agents, and the crosslinked product obtained by crosslinking imparts appropriate elasticity as an adhesive, increasing cohesive strength, increasing the dielectric constant, and further contributing to improving the moist heat resistance of the adhesive sheet" (paragraph

[0021] of Patent Document 4). Furthermore, with regard to the adhesive sheet of Patent Document 4, it is stated that "A printed layer is often provided on a protective transparent plate to enhance the design and differentiate the product. This printed ink layer, layers such as silver paste used in various circuits, and unevenness that occurs in FPD parts often cause unevenness of about 10 to 30 μm in the base sheet or film, which can lead to the problem of air bubbles forming when the adhesive sheet is attached. This is due to insufficient conformability of the adhesive layer to conform to unevenness. This conformability is closely related to the appropriate Tg and gel fraction in the adhesive properties of the adhesive sheet obtained from the adhesive composition. The gel fraction of the adhesive is preferably about 30 to 70%, and more preferably about 40 to 65%." (Paragraph

[0081] of Patent Document 4). However, among the adhesive sheets of Examples 1 to 12 in Cited Document 4, the adhesive sheets of Examples 1, 2, 5, 6, 8, and 10 had a haze value of more than 4.0% after the moist heat resistance test, despite the adhesive layer being as thin as 50 μm, posing the problem that further improvement in moist heat resistance was required.

[0009] As described above, in the prior art, it has been difficult to obtain an optical pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has good conformability to steps in frame printing, etc. of an adherend, good handleability during rework, and excellent wet heat durability, and an adhesive film or adhesive sheet using the same.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an optical pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that combines step-following ability for steps such as frame printing on an adherend, handleability during rework, and excellent wet heat durability, and a pressure-sensitive adhesive film and pressure-sensitive adhesive sheet using the same. [Means for solving the problem]

[0011] The present inventors have conducted extensive research into the above-mentioned problems, and have found that an optical pressure-sensitive adhesive composition containing an acrylic polymer, a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups, a (meth)acrylate monomer having an alkylene oxide group in one molecule and having two or more ethylenically unsaturated groups in one molecule, a thermal crosslinking agent, and a photocrosslinking agent is crosslinked with the thermal crosslinking agent, and the pressure-sensitive adhesive layer (first stage) before crosslinking with the photocrosslinking agent has excellent step-following ability and handleability during rework, and further that an optical pressure-sensitive adhesive layer (second stage) formed by crosslinking the optical pressure-sensitive adhesive composition in two stages, first with the thermal crosslinking agent and then with the photocrosslinking agent, has excellent humidity and heat durability, thereby completing the present invention. The optical pressure-sensitive adhesive composition according to the present invention is characterized in that it can form pressure-sensitive adhesive layers with different physical properties in two steps by crosslinking the optical pressure-sensitive adhesive composition, which contains an acrylic polymer, a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups, a (meth)acrylate monomer having an alkylene oxide group in one molecule and having two or more ethylenically unsaturated groups, a thermal crosslinking agent, and a photocrosslinking agent, in two steps, namely, by crosslinking with the thermal crosslinking agent and crosslinking with the photocrosslinking agent. That is, the technical idea of ​​the present invention is to provide an optical pressure-sensitive adhesive composition capable of forming pressure-sensitive adhesive layers with different physical properties in two stages, the pressure-sensitive adhesive layers being composed of the first-stage pressure-sensitive adhesive layer, which has good conformability to unevenness in frame printing, etc. of an adherend, and good handleability during rework, and the second-stage pressure-sensitive adhesive layer, which has excellent wet heat durability, and to provide a pressure-sensitive adhesive film and a pressure-sensitive adhesive sheet using the same.

[0012] In order to solve the above-mentioned problems, the present invention provides an optical pressure-sensitive adhesive composition comprising: a copolymer obtained by copolymerizing at least two or more compounds selected from the group consisting of copolymerizable vinyl monomers that do not have a carboxyl group as a functional group and that have any of an alkyl group, a hydroxyl group, an alkoxy group, and an aromatic group, and nitrogen-containing vinyl monomers; (F) a (meth)acrylate monomer that has a (meth)acryloyl group and an allyl ether group in one molecule and has two or more ethylenically unsaturated groups in one molecule; (G) a (meth)acrylate monomer that has an alkylene oxide group and has two or more ethylenically unsaturated groups in one molecule; (E) a thermal crosslinking agent; and (H) a photocrosslinking agent.

[0013] The copolymer is a copolymer of 100 parts by weight of (A) at least one alkyl(meth)acrylate monomer having an alkyl group carbon number of C1 to C18, 2.0 to 10 parts by weight of (B) at least one nitrogen-containing vinyl monomer or at least one alkoxy group-containing alkyl(meth)acrylate monomer, 1.0 to 10 parts by weight of (C) at least one polyalkylene glycol mono(meth)acrylate monomer, and 0.5 to 10 parts by weight of (D) at least one copolymerizable vinyl monomer having a hydroxyl group. It is preferable that the optical pressure-sensitive adhesive composition is a copolymer having a molecular weight of 200,000 to 1,000,000, and contains, relative to 100 parts by weight of (A), 0.01 to 5 parts by weight of (E) the thermal crosslinking agent, 0.1 to 10 parts by weight of (F) the (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups, 0.1 to 10 parts by weight of (G) the (meth)acrylate monomer having an alkylene oxide group in one molecule and having two or more ethylenically unsaturated groups, and 0.01 to 5 parts by weight of (H) the photocrosslinking agent.

[0014] Furthermore, it is preferable that the optical pressure-sensitive adhesive composition is crosslinked in two stages, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, to form a 250 μm thick pressure-sensitive adhesive layer, which has a total light transmittance of 90% or more and a haze value of 1.0% or less.

[0015] Furthermore, it is preferable that a 250 μm thick pressure-sensitive adhesive layer formed by crosslinking the optical pressure-sensitive adhesive composition in two stages, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, is left in an atmosphere of 60°C x 90% RH for 240 hours and then taken out into a room temperature environment (23°C x 50% RH), and the haze value is 4.0% or less.

[0016] Furthermore, the copolymer preferably contains 50 parts by weight or more of alkyl (meth)acrylate having an alkyl group carbon number of C8 to C18 out of a total of 100 parts by weight of at least one (A) alkyl (meth)acrylate monomer having an alkyl group carbon number of C1 to C18.

[0017] Preferably, the copolymer is obtained by copolymerizing (C) a polyalkylene glycol mono(meth)acrylate monomer, the optical pressure-sensitive adhesive composition contains (G) a (meth)acrylate monomer having an alkylene oxide group and two or more ethylenically unsaturated groups in one molecule, and the average number of repeating alkylene oxides in (C) and (G) is 4 to 14.

[0018] The present invention also provides a pressure-sensitive adhesive film comprising a pressure-sensitive adhesive layer formed on one surface of a substrate using the optical pressure-sensitive adhesive composition and crosslinked with the (E) thermal crosslinking agent, or a pressure-sensitive adhesive layer formed in two steps, first crosslinking with the (E) thermal crosslinking agent and then crosslinking with the (H) photocrosslinking agent, laminated thereon, wherein the pressure-sensitive adhesive layer after crosslinking with the (E) thermal crosslinking agent has an adhesive strength to soda glass of 10 N / 25 mm or less, and the pressure-sensitive adhesive layer after crosslinking in two steps, first crosslinking with the (E) thermal crosslinking agent and then crosslinking with the (H) photocrosslinking agent has an adhesive strength to soda glass of 25 N / 25 mm or more.

[0019] The present invention also provides an adhesive film comprising an adhesive layer formed on one side of a polyethylene phthalate resin film having a thickness of 188 μm, the adhesive layer being formed by crosslinking the above-mentioned optical adhesive composition with the (E) thermal crosslinking agent, wherein when the adhesive film is bonded to glass having a printing step of a 42 μm thick printing layer via the adhesive layer having a thickness of 100 μm, the adhesive film has good conformability to the printing step and is completely free of bubbles around the printing step.

[0020] The present invention also provides a film for a touch panel, which uses the above-mentioned pressure-sensitive adhesive film.

[0021] The present invention also provides a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by crosslinking the optical pressure-sensitive adhesive composition with the (E) thermal crosslinking agent and laminated between two release-treated release films.

[0022] The present invention also provides an optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the optical pressure-sensitive adhesive composition with the (E) thermal crosslinking agent, or a pressure-sensitive adhesive layer formed by crosslinking in two steps, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, laminated on at least one surface of the optical film. [Effects of the Invention]

[0023] The optical pressure-sensitive adhesive composition according to the present invention contains an acrylic polymer, a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and two or more ethylenically unsaturated groups, a (meth)acrylate monomer having an alkylene oxide group and two or more ethylenically unsaturated groups in one molecule, a thermal crosslinking agent, and a photocrosslinking agent. The (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and two or more ethylenically unsaturated groups forms a cyclic compound when photocrosslinked with the photocrosslinking agent. Therefore, the pressure-sensitive adhesive layer obtained by two-step crosslinking, first with the thermal crosslinking agent and then with the photocrosslinking agent, has excellent humidity and heat durability.

[0024] Furthermore, the pressure-sensitive adhesive film and pressure-sensitive adhesive sheet according to the present invention have a pressure-sensitive adhesive layer formed thereon that is crosslinked using an optical pressure-sensitive adhesive composition containing an acrylic polymer, a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups, a (meth)acrylate monomer having an alkylene oxide group in one molecule and having two or more ethylenically unsaturated groups in one molecule, a thermal crosslinking agent, and a photocrosslinking agent. The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer crosslinked with a thermal crosslinking agent, and is a pressure-sensitive adhesive layer that can be crosslinked in two steps, first with a thermal crosslinking agent and then with a photocrosslinking agent, or a pressure-sensitive adhesive layer that is crosslinked in two steps, first with a thermal crosslinking agent and then with a photocrosslinking agent. Therefore, according to the present invention, it is possible to provide an adhesive film and adhesive sheet that combine the ability to conform to unevenness such as that of frame printing on an adherend, ease of handling during rework, and excellent wet heat durability. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described below based on preferred embodiments.

[0026] The optical pressure-sensitive adhesive composition of the present embodiment is characterized by containing a copolymer obtained by copolymerizing at least two or more compounds selected from the group consisting of copolymerizable vinyl monomers that do not have a carboxyl group as a functional group and have any of an alkyl group, a hydroxyl group, an alkoxy group, and an aromatic group, and nitrogen-containing vinyl monomers; (F) a (meth)acrylate monomer that has a (meth)acryloyl group and an allyl ether group in one molecule and has two or more ethylenically unsaturated groups; (G) a (meth)acrylate monomer that has an alkylene oxide group and has two or more ethylenically unsaturated groups in one molecule; (E) a thermal crosslinking agent; and (H) a photocrosslinking agent.

[0027] In this specification, (meth)acrylate is a general term for acrylate and methacrylate. Furthermore, (meth)acryloyl group is a general term for acryloyl group and methacryloyl group. The copolymer related to the optical pressure-sensitive adhesive composition of this embodiment is, for example, a copolymer obtained by copolymerizing (A) at least one alkyl(meth)acrylate monomer having an alkyl group with a carbon number of C1 to C18, (B) at least one nitrogen-containing vinyl monomer or at least one alkoxy group-containing alkyl(meth)acrylate monomer, (C) at least one polyalkylene glycol mono(meth)acrylate monomer, and (D) at least one copolymerizable vinyl monomer having a hydroxyl group.

[0028] Examples of the (A) alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C18 include at least one of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, etc. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. For specific compounds belonging to linear alkyl (meth)acrylate monomers with a carbon number of 3 or more, when the presence of branches is not specified, n-propyl (meth)acrylate, n-butyl (meth)acrylate, etc. may be simply referred to as propyl (meth)acrylate, butyl (meth)acrylate, etc.

[0029] Among the (A) monomers, examples of the branched alkyl acrylate monomer (monomer having a branched structure alkyl group) include at least one of isopropyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isooctadecyl (meth)acrylate, isomyristyl (meth)acrylate, and isostearyl (meth)acrylate. The branched alkyl group-containing monomer may have a branched structure in which the alkyl group has two or more branches (for example, two or more side chains on the main chain), such as a t-butyl group.

[0030] Among the (A) compounds, examples of the cyclic alkyl acrylate monomer (alicyclic-containing monomer) include at least one of cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, bicycloheptyl (meth)acrylate, bicyclooctyl (meth)acrylate, dimethylbicycloheptyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0031] Of the total 100 parts by weight of the at least one alkyl (meth)acrylate monomer (A) having a carbon number of C1 to C18 in the alkyl group, the proportion of alkyl (meth)acrylate having a carbon number of C8 to C18 in the alkyl group is preferably 50 parts by weight or more. Among alkyl (meth)acrylates having a carbon number of C8 to C18 in the alkyl group, branched alkyl group-containing monomers such as isooctyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred.

[0032] Among the (B) nitrogen-containing vinyl monomers, at least one of vinyl monomers containing an amide bond, vinyl monomers containing an amino group, and vinyl monomers having a nitrogen-containing heterocyclic structure can be mentioned. Nitrogen-containing vinyl monomers preferably contain no hydroxyl groups, and more preferably no hydroxyl or carboxyl groups. Examples of such monomers include the above-mentioned monomers, such as acrylic monomers containing an N,N-dialkyl-substituted amino group or an N,N-dialkyl-substituted amide group; N-vinyl-substituted lactams such as N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinyl-2-piperidone; and N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

[0033] Examples of acrylic monomers containing an N,N-dialkyl substituted amino group include dimethylaminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dimethylaminoisopropyl (meth)acrylate, dimethylaminobutyl (meth)acrylate, diethylaminomethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, N-ethyl-N-methylaminoethyl (meth)acrylate, N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, N-ethyl-N-methyl ... Examples thereof include dialkylamino(meth)acrylates such as butylaminoethyl(meth)acrylate; and (meth)acrylamides containing an N,N-dialkyl-substituted aminoalkyl group, such as dimethylaminopropyl(meth)acrylamide, diethylaminopropyl(meth)acrylamide, dipropylaminopropyl(meth)acrylamide, diisopropylaminopropyl(meth)acrylamide, N-ethyl-N-methylaminopropyl(meth)acrylamide, N-methyl-N-propylaminopropyl(meth)acrylamide, and N-methyl-N-isopropylaminopropyl(meth)acrylamide.

[0034] Examples of acrylic monomers containing an N,N-dialkyl-substituted amide group include dialkyl-substituted (meth)acrylamides such as dimethyl(meth)acrylamide, diethyl(meth)acrylamide, dipropylacrylamide, diisopropyl(meth)acrylamide, dibutyl(meth)acrylamide, N-ethyl-N-methyl(meth)acrylamide, N-methyl-N-propyl(meth)acrylamide, and N-methyl-N-isopropyl(meth)acrylamide.

[0035] Examples of N-vinyl substituted lactams include N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, and N-vinyllaurolactam. Examples of N-vinyl-substituted heterocyclic vinyl compounds include N-vinylpyridine, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, and N-vinylmorpholine. Examples of N-(meth)acryloyl-substituted cyclic amines include N-(meth)acryloylmorpholine, N-(meth)acryloylpiperazine, N-(meth)acryloylaziridine, N-(meth)acryloylazetidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth)acryloylazepane, and N-(meth)acryloylazocane.

[0036] Other nitrogen-containing vinyl monomers include N-vinylcarboxylic acid amides such as N-vinylformamide, N-vinylacetamide, and N-vinyl-N-methylacetamide; (meth)acrylamides such as unsubstituted (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nt-butyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxyethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone acrylamide, and N,N-methylenebis(meth)acrylamide; unsaturated carboxylic acid imides such as N-cyclohexylmaleimide and N-phenylmaleimide; and unsaturated carboxylic acid nitriles such as (meth)acrylonitrile. The nitrogen-containing vinyl monomer preferably does not contain an isocyanate group. Furthermore, the nitrogen-containing vinyl monomer preferably does not contain a quaternary cation structure such as a quaternary ammonium. The nitrogen-containing vinyl monomer may contain a tertiary cation structure in which the N,N-dialkyl-substituted amino group is neutralized to such an extent that it does not become acidic.

[0037] Among the (B) above, examples of the alkoxy group-containing alkyl (meth)acrylate monomer include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-isopropoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 2-propoxypropyl (meth)acrylate, 2-isopropoxypropyl (meth)acrylate, and 2-butoxypropyl. Examples of the alkyl (meth)acrylate monomer include at least one of 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 3-propoxypropyl (meth)acrylate, 3-isopropoxypropyl (meth)acrylate, 3-butoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, 4-propoxybutyl (meth)acrylate, 4-isopropoxybutyl (meth)acrylate, 4-butoxybutyl (meth)acrylate, etc. These alkoxy group-containing alkyl (meth)acrylate monomers have a structure in which the alkyl group atom in the alkyl (meth)acrylate is substituted with an alkoxy group.

[0038] The copolymer is preferably copolymerized with 100 parts by weight of (A) at least one alkyl(meth)acrylate monomer having an alkyl group carbon number of C1 to C18, and 2.0 to 10 parts by weight of (B) at least one nitrogen-containing vinyl monomer or alkoxy-containing alkyl(meth)acrylate monomer, more preferably 2.0 to 9 parts by weight, and particularly preferably 2.5 to 9 parts by weight. One or more types of nitrogen-containing vinyl monomer and one or more types of alkoxy-containing alkyl(meth)acrylate monomer may be used in combination.

[0039] The (C) polyalkylene glycol mono(meth)acrylate monomer is a mono(meth)acrylate monomer having a polyalkylene glycol chain, and is a compound in which one of the hydroxyl groups of the polyalkylene glycol is esterified as a (meth)acrylic acid ester. The (meth)acrylic acid ester group serves as a polymerizable group, so it can be copolymerized into the copolymer. The other hydroxyl group may remain as OH or may be an alkyl ether such as methyl ether or ethyl ether, or a saturated carboxylic acid ester such as acetate ester.

[0040] In (C), examples of the alkylene group contained in the polyalkylene glycol include, but are not limited to, an ethylene group, a propylene group, a butylene group, etc. The polyalkylene glycol may be a polyalkylene glycol having two or more types of alkylene groups in one molecule, such as polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, or polypropylene glycol-polybutylene glycol. In addition, in the above (C), the average repeat number of alkylene oxide constituting the polyalkylene glycol chain is preferably 4 to 14. Here, the "average repeat number of alkylene oxide" refers to the average number of repeats of alkylene oxide units in the "polyalkylene glycol chain" portion.

[0041] The (C) is preferably at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate. More specifically, examples thereof include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, methoxypolybutylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, ethoxypolypropylene glycol (meth)acrylate, and ethoxypolybutylene glycol (meth)acrylate. The copolymer is preferably obtained by copolymerizing at least one or more (C) polyalkylene glycol mono(meth)acrylate monomers in a ratio of 1.0 to 10 parts by weight, more preferably 1.5 to 9 parts by weight, and particularly preferably 2.0 to 9 parts by weight, with 100 parts by weight of at least one or more (A) alkyl (meth)acrylate monomers in a ratio of C1 to C18.

[0042] Examples of the (D) copolymerizable vinyl monomer having a hydroxyl group include at least one of hydroxyl group-containing alkyl (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate, and hydroxyl group-containing (meth)acrylamides such as N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide. The copolymer is preferably obtained by copolymerizing at least one or more copolymerizable vinyl monomers (D) having a hydroxyl group in a ratio of 0.5 to 10 parts by weight, more preferably 0.8 to 9 parts by weight, and particularly preferably 0.8 to 8 parts by weight, per 100 parts by weight of at least one or more alkyl (meth)acrylate monomers (A) having an alkyl group with a carbon number of C1 to C18. When (C) may have a hydroxyl group, it is preferable that (D) does not have a polyalkylene glycol chain.

[0043] The copolymer may be prepared by copolymerizing a copolymerizable vinyl monomer having an aromatic group in addition to at least one of the above (A) to (D). Examples of the copolymerizable vinyl monomer having an aromatic group include at least one of (meth)acrylate monomers having an aromatic group, such as benzyl (meth)acrylate, naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, 2-(1-naphthyloxy)ethyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)hexyl (meth)acrylate, 6-(2-naphthyloxy)hexyl (meth)acrylate, 8-(1-naphthyloxy)octyl (meth)acrylate, and 8-(2-naphthyloxy)octyl (meth)acrylate, and styrene-based monomers, such as styrene and methylstyrene. The (A) to (D) may be copolymerizable vinyl monomers having no aromatic group.

[0044] The polymerization method for the copolymer is not particularly limited, and known polymerization methods such as solution polymerization and emulsion polymerization can be used as appropriate. The copolymer is preferably an acrylic polymer containing 50 to 100% by weight of an acrylic monomer such as a (meth)acrylate monomer. The copolymer preferably has a weight-average molecular weight of 200,000 to 1,000,000. The copolymer is preferably a copolymer that does not contain a copolymerizable vinyl monomer having a carboxyl group. Furthermore, from the perspective of suppressing corrosiveness of easily corroded substrates such as the ITO surface of a transparent conductive film, it is preferable to use a copolymer that does not contain a copolymerizable vinyl monomer having a carboxyl group, thereby making the acid value of the copolymer 1.0 or less.

[0045] The (E) thermal crosslinking agent may include at least one of an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aluminum chelate-based crosslinking agent, and the like. Examples of isocyanate crosslinking agents include bifunctional isocyanates (diisocyanate compounds) such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), and xylylene diisocyanate (XDI), as well as trifunctional or higher polyisocyanate compounds such as their biuret-modified products, isocyanurate-modified products, and adducts. Examples of trifunctional or higher adducts include adducts of diisocyanate compounds with trivalent or higher polyols such as trimethylolpropane and glycerin. Only an isocyanate compound may be used as the (E) thermal crosslinking agent. The copolymer preferably has a hydroxyl group as a functional group capable of reacting with the (E) thermal crosslinking agent, and is particularly preferably obtained by copolymerizing the (D) above. The optical pressure-sensitive adhesive composition preferably contains 0.01 to 5 parts by weight of the thermal crosslinking agent (E) relative to 100 parts by weight of the component (A).

[0046] Examples of (F) include at least one (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule. Since the (meth)acryloyl group and the allyl ether group each have an ethylenically unsaturated group, (F) has two or more ethylenically unsaturated groups. The number of (meth)acryloyl groups in one molecule of (F) is 1 or 2 or more, and the number of allyl ether groups in one molecule of (F) is 1 or 2 or more. The number of (meth)acryloyl groups and the number of allyl ether groups in one molecule of (F) may be different, but are preferably the same.

[0047] In the optical pressure-sensitive adhesive composition according to the present embodiment, the (F) has the function of significantly improving the wet heat durability of the pressure-sensitive adhesive layer. The reason why the inclusion of the (F) in the optical pressure-sensitive adhesive composition significantly improves the wet heat durability of the pressure-sensitive adhesive layer is not clear, but the following may be one of the reasons. The reason for this is presumably that, when (F) is crosslinked with the (H) photocrosslinking agent, the (meth)acryloyl group and the allyl ether group form a cyclic structure. When (F) is crosslinked with the (H) photocrosslinking agent, it becomes a polymer having a cyclic structure formed by the (meth)acryloyl group and the allyl ether group, and / or the cyclic structure crosslinks with the acrylic polymer copolymer, etc., so that in a pressure-sensitive adhesive layer left in a humid and hot environment for a long period of time, moisture from the humid and hot environment is trapped inside this cyclic structure, and even when the pressure-sensitive adhesive layer is subsequently taken out into a room temperature environment (temperature 23°C x 50% RH), free movement of moisture is prevented, thereby suppressing foaming due to aggregation of moisture. For these reasons, it is believed that the pressure-sensitive adhesive layer after two-step crosslinking, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, will have excellent humidity and heat durability. To form a cyclic structure when the (F) is crosslinked with the (H) photocrosslinking agent to form a pressure-sensitive adhesive layer, it is preferable that the pressure-sensitive adhesive layer crosslinked with the (E) thermal crosslinking agent contains the (F), and that the (F) maintains the reactivity of two or more ethylenically unsaturated groups. Therefore, it is preferable that the optical pressure-sensitive adhesive composition does not contain a thermal polymerization initiator when crosslinking with the (E) thermal crosslinking agent.

[0048] Examples of (F) include allyl ether group-containing alkyl (meth)acrylates [CH2=C(R1)COO-R2-OCH2CH=CH2; where R1 is a hydrogen atom or a methyl group, and R2 is a divalent group such as an alkylene group], 2-(allyloxymethyl)acrylic acid alkyl esters [CH2=CHCHOCH2C(=CH2)COOR; where R is an alkyl group], etc. It is particularly preferable that the compound can form a 5- or 6-membered ring, which has a high stability as a cyclic structure. Specific examples of (F) include allyloxyethyl (meth)acrylate, allyloxypropyl (meth)acrylate, methyl 2-(allyloxymethyl)acrylate, ethyl 2-(allyloxymethyl)acrylate, propyl 2-(allyloxymethyl)acrylate, butyl 2-(allyloxymethyl)acrylate, pentyl 2-(allyloxymethyl)acrylate, and hexyl 2-(allyloxymethyl)acrylate. The optical pressure-sensitive adhesive composition preferably contains 0.1 to 10 parts by weight of (F) relative to 100 parts by weight of (A).

[0049] Examples of the (G) include at least one or more types of (meth)acrylate monomers having an alkylene oxide group and two or more ethylenically unsaturated groups in one molecule. Furthermore, (G) may be, for example, a compound in which two or more of the multiple hydroxyl groups contained in alkylene glycol, polyalkylene glycol, etc. are esterified as (meth)acrylic acid esters. In addition, in (G), the average repeat number of alkylene oxide constituting the polyalkylene glycol chain is preferably 4 to 14. Here, the "average repeat number of alkylene oxide" refers to the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion. The average repeat number of alkylene oxide in (G) may be the same as or different from the average repeat number of alkylene oxide in (C).

[0050] In (G), the alkylene oxide group may be at least one of an ethylene oxide group, a propylene oxide group, a butylene oxide group, etc. The alkylene oxide group in (G) may be the same as or different from the alkylene oxide group in (C). Specific examples of (G) include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polybutylene glycol di(meth)acrylate, etc. The optical pressure-sensitive adhesive composition preferably contains 0.1 to 10 parts by weight of (G) relative to 100 parts by weight of (A).

[0051] Examples of the (H) photocrosslinking agent include photoinitiators such as photoradical initiators. In order to form a pressure-sensitive adhesive layer by crosslinking the optical pressure-sensitive adhesive composition with the (E) thermal crosslinking agent and then crosslinking with the (H) photocrosslinking agent, it is preferable that the (H) photocrosslinking agent maintains its reactivity even after crosslinking with the (E) thermal crosslinking agent. Examples of such (H) photocrosslinking agents include acetophenone-based photocrosslinking agents, benzoin-based photocrosslinking agents, benzophenone-based photocrosslinking agents, thioxanthone-based photocrosslinking agents, and acylphosphine oxide-based photocrosslinking agents. The optical pressure-sensitive adhesive composition preferably contains 0.01 to 5 parts by weight of the (H) photocrosslinking agent relative to 100 parts by weight of the (A).

[0052] Examples of acetophenone-based photocrosslinking agents include acetophenone, p-(tert-butyl)1',1',1'-trichloroacetophenone, chloroacetophenone, 2',2'-diethoxyacetophenone, hydroxylacetophenone, 2,2-dimethoxy-2'-phenylacetophenone, 2-aminoacetophenone, dialkylaminoacetophenone, and 2-hydroxy-2-methyl-1-phenyl-propan-1-one. Examples of benzoin-based photocrosslinking agents include benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-2-methylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, benzil dimethyl ketal, and 2,2-dimethoxy-1,2-diphenylethan-1-one. Examples of benzophenone-based photocrosslinking agents include benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, methyl-o-benzoylbenzoate, 4-phenylbenzophenone, hydroxylbenzophenone, hydroxylpropylbenzophenone, acrylbenzophenone, and 4,4'-bis(dimethylamino)benzophenone. Examples of thioxanthone-based photocrosslinking agents include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, diethylthioxanthone, and dimethylthioxanthone. Examples of the acylphosphine oxide photocrosslinking agent include (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Other photocrosslinking agents include α-acyloxime esters, benzyl-(o-ethoxycarbonyl)-α-monoxime, phenylglyoxylic acid esters, 3-ketocoumarin, 2-ethylanthraquinone, camphorquinone, tetramethylthiuram sulfide, azobisisobutyronitrile, benzoyl peroxide, dialkyl peroxide, and tert-butyl peroxypivalate.

[0053] The optical pressure-sensitive adhesive composition may contain, as optional components, known additives such as antioxidants, surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking retarders, curing retarders, processing aids, antioxidants, etc. These additives may be used alone or in combination of two or more.

[0054] The pressure-sensitive adhesive layer of this embodiment can be produced by applying the optical pressure-sensitive adhesive composition to a substrate or a release film, and then crosslinking the optical pressure-sensitive adhesive composition with the (E) thermal crosslinking agent and the (H) photocrosslinking agent. In the pressure-sensitive adhesive layer of this embodiment, the pressure-sensitive adhesive layer (first stage) after crosslinking with the (E) thermal crosslinking agent but before crosslinking with the (H) photocrosslinking agent has excellent step-following ability and handleability during rework. Furthermore, the pressure-sensitive adhesive layer (second stage) crosslinked in two stages, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, has excellent humidity and heat durability. Depending on the application and purpose, the pressure-sensitive adhesive layer of this embodiment may be bonded to an adherend in either the first stage or the second stage. The first-stage pressure-sensitive adhesive layer contains the (H) photocrosslinking agent and can be crosslinked by the (H) photocrosslinking agent. When the first-stage pressure-sensitive adhesive layer is attached to an adherend, the pressure-sensitive adhesive layer may be crosslinked by the (H) photocrosslinking agent while still attached to the adherend. Examples of energy rays to be irradiated when crosslinking with the (H) photocrosslinking agent include ultraviolet rays, electron beams, and in some cases visible light, but ultraviolet rays are preferably used from the viewpoint of simplicity. However, the present invention is not limited to ultraviolet rays. When irradiating with energy rays, the pressure-sensitive adhesive layer may be exposed, but if a release film or adherend laminated on the pressure-sensitive adhesive layer is permeable to energy rays, it is preferable to irradiate the pressure-sensitive adhesive layer with energy rays through the release film or adherend.

[0055] The optical pressure-sensitive adhesive composition of the present embodiment preferably has excellent optical properties when a pressure-sensitive adhesive layer is prepared. The optical pressure-sensitive adhesive composition is preferably transparent. The additives preferably do not impair the transparency of the pressure-sensitive adhesive layer in terms of function, amount, etc. (are non-coloring). Furthermore, the pressure-sensitive adhesive layer (first-stage pressure-sensitive adhesive layer or second-stage pressure-sensitive adhesive layer) prepared from the optical pressure-sensitive adhesive composition is preferably transparent. Specifically, the optical pressure-sensitive adhesive composition is crosslinked in two steps, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, to form a 250 μm thick pressure-sensitive adhesive layer, which preferably has a total light transmittance of 90% or more, and more preferably has a total light transmittance of 91% or more. Furthermore, the optical pressure-sensitive adhesive composition is crosslinked in two steps, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, to form a 250 μm thick pressure-sensitive adhesive layer, which preferably has a haze value of 1.0% or less, more preferably 0.6% or less. Furthermore, when a pressure-sensitive adhesive layer having a thickness of 250 μm is formed by crosslinking the optical pressure-sensitive adhesive composition in two stages, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, and then left in an atmosphere of 60°C temperature and 90% RH for 240 hours and then taken out into a room temperature environment (23°C temperature and 50% RH), the haze value is preferably 4.0% or less, and more preferably 3.5% or less.

[0056] The pressure-sensitive adhesive layer after crosslinking with the (E) thermal crosslinking agent (before crosslinking with the (H) photocrosslinking agent) preferably has an adhesive strength to soda glass of 10 N / 25 mm or less, which can improve the handleability of the pressure-sensitive adhesive layer during rework. Furthermore, the pressure-sensitive adhesive layer crosslinked in two stages, first with the (E) thermal crosslinking agent and then with the (H) photocrosslinking agent, preferably has an adhesive strength to soda glass of 25 N / 25 mm or more. Even when the pressure-sensitive adhesive layer of the first stage is bonded to an adherend and then crosslinked with the (H) photocrosslinking agent, high adhesive strength can be obtained, similar to when the pressure-sensitive adhesive layer of the second stage is bonded to an adherend after preparation. In an adhesive film having an adhesive layer formed on one side of a polyethylene phthalate resin film having a thickness of 188 μm, the adhesive layer being formed by crosslinking the optical adhesive composition with the (E) thermal crosslinking agent, when the adhesive film is bonded to glass having a printing step of a 42 μm thick printing layer via the adhesive layer having a thickness of 100 μm, it is preferable that the adhesive film has good conformability to the printing step and no bubbles are formed around the printing step.

[0057] The adhesive film and adhesive sheet of this embodiment can be produced by forming the adhesive layer on one side of a substrate or a release film. The 2015 edition of JIS Z0109 (Terminology for Adhesive Tapes and Sheets) defines "adhesive sheet" as "a general term for a plate-shaped substrate having an adhesive layer on one or both sides thereof and a release liner attached thereto," and distinguishes it from "adhesive tape," which is defined as "a general term for a substrate having an adhesive layer on one or both sides thereof and wound into a roll." However, the adhesive film and adhesive sheet of this embodiment are not limited thereto. The thickness of the adhesive layer in the adhesive film and adhesive sheet is not particularly limited, but is preferably 10 to 3,000 μm, and more preferably 50 to 2,000 μm.

[0058] As the base film used to form the pressure-sensitive adhesive layer and the release film (separator) that protects the adhesive surface, a resin film such as a polyester film can be used. The substrate film may be subjected to an antifouling treatment using a silicone-based or fluorine-based release agent or coating agent, silica microparticles, or the like, or an antistatic treatment by coating or kneading in an antistatic agent, on the side opposite to the side on which the pressure-sensitive adhesive layer of the resin film is formed. The release film is treated with a release agent, such as a silicone-based or fluorine-based release agent, on the side that faces the adhesive surface of the adhesive layer. By placing the release-treated surfaces of a release film on both sides of a single adhesive layer, a pressure-sensitive adhesive sheet with a "release film / adhesive layer / release film" configuration can be created. In this case, the release films on both sides are peeled off sequentially or simultaneously to expose the adhesive surface, making it possible to bond optical components such as optical films to glass or other substrates. Examples of optical films include polarizing films, retardation films, anti-reflection films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancement films.

[0059] The pressure-sensitive adhesive layer can provide good step-following properties even when bonding glass to glass, such as between a cover glass and a sensor glass, and can therefore be suitably used when bonding the cover glass and sensor glass of a touch panel. Furthermore, when bonding a film member to a glass member, the pressure-sensitive adhesive film obtained by laminating the pressure-sensitive adhesive layer on one side of the film member can also be bonded to a glass member such as a cover glass or a sensor glass. The pressure-sensitive adhesive layer and pressure-sensitive adhesive film are suitable as pressure-sensitive adhesive layers and pressure-sensitive adhesive films for touch panels. Examples of films for touch panels using the pressure-sensitive adhesive film include pressure-sensitive adhesive films for touch panels, as well as various optical films for touch panels, which will be described later.

[0060] The adhesive film and the adhesive sheet can be used to bond various optical films for peripheral components of liquid crystal display devices, mainly polarizing plates, various optical films for touch panels, various optical films for electronic paper, various optical films for organic EL, etc. Furthermore, the optical film may have the pressure-sensitive adhesive layer laminated on at least one surface thereof, to form a pressure-sensitive adhesive layer-attached optical film. Specific examples of such optical films include "optical film / pressure-sensitive adhesive layer / optical film," "optical film / pressure-sensitive adhesive layer / release film," "optical film / pressure-sensitive adhesive layer," "optical film / pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer / optical film," "optical film / pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer / release film," and the like. For example, in the case of an "optical film / adhesive layer / release film" structure having a pressure-sensitive adhesive layer protected by a release film, the release film can be peeled off to expose the pressure-sensitive adhesive layer as in "optical film / adhesive layer," and then the structure can be bonded to another optical film to obtain a structure such as "optical film / adhesive layer / optical film" in which the pressure-sensitive adhesive layer is used to bond the layers together.

[0061] The pressure-sensitive adhesive film and pressure-sensitive adhesive sheet are preferably used for bonding a polarizing plate and a display panel. Examples of display panels include liquid crystal panels and organic EL panels. The pressure-sensitive adhesive film and pressure-sensitive adhesive sheet can be preferably used as the pressure-sensitive adhesive layer of a polarizing plate with a pressure-sensitive adhesive layer. A retardation film having a phase difference of λ / 4 or λ / 2 may be used as a constituent material of the polarizing plate. The pressure-sensitive adhesive layer can be used for bonding a retardation film and a polarizing plate. Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film and pressure-sensitive adhesive sheet has a low dielectric constant, they can be preferably used for bonding optical components between a polarizing plate and a backlight unit in an on-cell type display device in which a touch sensor is provided between a color filter and a polarizing plate. The pressure-sensitive adhesive film and pressure-sensitive adhesive sheet can also be used for fixing optical and electronic components incorporated in various electronic devices. [Example]

[0062] The present invention will be specifically described below with reference to examples.

[0063] <Production of acrylic polymers> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Then, 70 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of ethyl acrylate, 20 parts by weight of isobornyl acrylate, 5 parts by weight of N-vinylpyrrolidone, 4 parts by weight of polypropylene glycol monoacrylate (average alkylene oxide repeat number n = 12), 3.0 parts by weight of 6-hydroxyhexyl acrylate, and 60 parts by weight of solvent (ethyl acetate) were added to the reactor. Then, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was allowed to react at 65°C for 6 hours, yielding the acrylic polymer solution used in Example 1. [Examples 2 to 5 and Comparative Examples 1 to 3] The acrylic polymer solutions used in Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as the acrylic polymer solution used in Example 1 above, except that the monomer compositions were as shown in Groups (A) to (D) in Table 1.

[0064] <Production of Pressure-Sensitive Adhesive Composition, Pressure-Sensitive Adhesive Layer, and Pressure-Sensitive Adhesive Sheet> [Example 1] To the acrylic polymer solution of Example 1 produced as described above, 0.5 parts by weight of Coronate HX, 5 parts by weight of methyl 2-(allyloxymethyl)acrylate, 5 parts by weight of polyethylene glycol diacrylate (average repeat number of alkylene oxides n = 4), and 0.5 parts by weight of a photocrosslinker (Omnirad® 184) were added and mixed by stirring to obtain a pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was applied to a release film (1) (a polyethylene terephthalate (PET) film having a substrate thickness of 100 μm and coated with a silicone resin as a release agent layer) so that the thickness of the pressure-sensitive adhesive layer after drying would be a predetermined value, and the solvent was removed by drying at 90°C, and the resulting mixture was then aged for 7 days in an atmosphere of 23°C and 50% RH to form a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition was crosslinked with the thermal crosslinker. Furthermore, a release film (2) having a substrate thickness of 75 μm and including a release agent layer with a release force lighter than that of the release film (1) was laminated to the surface of the pressure-sensitive adhesive layer, thereby obtaining a pressure-sensitive adhesive sheet A of Example 1 (on which a first-stage pressure-sensitive adhesive layer was formed) composed of release film (1) / pressure-sensitive adhesive layer / release film (2). After crosslinking with this thermal crosslinking agent, the pressure-sensitive adhesive layer was further irradiated with ultraviolet (UV) rays to be crosslinked with a photocrosslinking agent. In this way, a pressure-sensitive adhesive sheet B of Example 1 (on which a second-stage pressure-sensitive adhesive layer was formed) was obtained, in which a pressure-sensitive adhesive layer that had been crosslinked in two stages by thermal crosslinking and by photocrosslinking was sandwiched between two release films. [Examples 2 to 5 and Comparative Examples 1 to 3] Adhesive sheets A to B of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained in the same manner as adhesive sheets A to B of Example 1 above, except that the compositions of the additives were changed as shown in groups (E) to (H) in Table 1.

[0065] [Table 1]

[0066] Table 1 shows the numerical values ​​in parts by weight, with the total of Group (A) being 100 parts by weight. Table 2 also shows the compound names of the abbreviations for each component used in Table 1. Coronate (registered trademark) is a trade name of Tosoh Corporation, Duranate (registered trademark) is a trade name of Asahi Kasei Corporation, and Omnirad (registered trademark) is a trade name of IGM. Omnirad 184 is a photocrosslinker whose main component is 1-hydroxycyclohexyl phenyl ketone. Omnirad 651 is a photocrosslinker whose main component is 2,2-dimethoxy-2-phenylacetophenone. Omnirad TPO is a photocrosslinker whose main component is (2,4,6-trimethylbenzoyl)diphenylphosphine oxide.

[0067] [Table 2]

[0068] <Test method and evaluation> The release films (1) and (2) were peeled off from the pressure-sensitive adhesive sheets A and B in Examples 1 to 5 and Comparative Examples 1 to 3, as necessary, to expose the pressure-sensitive adhesive layers, which were then evaluated using the following test and measurement methods. In order to comply with the measurement and test methods described below, the pressure-sensitive adhesive sheets A and B in Examples 1 to 5 and Comparative Examples 1 to 3 were prepared as multiple types of pressure-sensitive adhesive sheets A having different pressure-sensitive adhesive layer thicknesses and multiple types of pressure-sensitive adhesive sheets B having a first-stage pressure-sensitive adhesive layer formed thereon, or multiple types of pressure-sensitive adhesive sheets B having a second-stage pressure-sensitive adhesive layer formed thereon. Pressure-sensitive adhesive sheet A was used when testing the first-stage pressure-sensitive adhesive layer. Pressure-sensitive adhesive sheet B was used when testing the second-stage pressure-sensitive adhesive layer.

[0069] <Method for measuring total light transmittance> Method for measuring light transmittance: The total light transmittance (%) of a 250 μm thick adhesive layer (second-stage adhesive layer) was measured according to JIS K7105, "Testing methods for optical properties of plastics," and this was recorded as "Total light transmittance" in Table 3.

[0070] <Method for measuring haze value> Haze measurement method: According to JIS K7136, "Method for determining haze of plastic transparent materials," the haze value (%) of a 250 μm thick adhesive layer (second-stage adhesive layer) was measured and recorded as "Initial haze value" in Table 3. Furthermore, the sample was left in an atmosphere of 60°C and 90% RH for 240 hours, and then removed to a room temperature environment (23°C, 50% RH). Five minutes after removal, the haze value (%) was measured with both sides of the adhesive layer covered with the release films (1) and (2), and recorded as "Haze value after wet heat" in Table 3.

[0071] <Evaluation of humidity and heat durability> The wet heat durability of the pressure-sensitive adhesive layer formed on the pressure-sensitive adhesive sheet B in Examples 1 to 5 and Comparative Examples 1 to 3 was evaluated using the "haze value after wet heat" measured by the above-mentioned haze measurement method. The criteria for wet heat durability were as follows, and the evaluation results were recorded as "wet heat durability" in Table 3. ○: The "haze value after wet heat" is 4.0% or less. △: "Haze value after wet heat" is more than 4.0% and 6.0% or less. ×: The "haze value after wet heat" exceeds 6.0%.

[0072] <Method for measuring adhesive strength> A 175 μm-thick adhesive layer (first-stage adhesive layer or second-stage adhesive layer) from each of PSA Sheets A and B was transferred to one side of a 50 μm-thick polyester film to obtain the adhesive film sample (adhesive-coated optical film). Each adhesive film was then laminated to the non-tin side of alkali-free glass washed with acetone using a pressure roller. The film was then autoclaved at 50°C and 0.5 MPa for 20 minutes, and then returned to an air atmosphere at 23°C and 50% RH for 1 hour. The peel strength of the adhesive film was then measured using a tensile tester in accordance with JIS Z0237 "Test Method for Adhesive Tapes and Adhesive Sheets." The peel strength was measured at a peel speed of 300 mm / min in a 180° direction, and this was recorded as the adhesive strength (N / 25 mm) of each adhesive layer. In Table 3, the adhesive strength measured using the first-stage adhesive layer is referred to as the "adhesive strength after thermal crosslinking," and the adhesive strength measured using the second-stage adhesive layer is referred to as the "adhesive strength after photocrosslinking."

[0073] <Test method for step-following ability> A 100 μm thick adhesive layer (first-stage adhesive layer) crosslinked with a thermal crosslinking agent from adhesive sheet A was transferred and laminated onto one side of a 188 μm thick polyethylene phthalate resin film to obtain a sample adhesive film. A 1.1 mm thick cover glass having a 42 μm thick printed layer with a printing step was then laminated onto the adhesive layer (first-stage adhesive layer) using a vacuum lamination device under conditions of a pressure of 80 kPa and a vacuum of -100 kPa. Furthermore, after autoclaving at a temperature of 60°C, 6 atmospheres, and 30 minutes, the step conformability was visually confirmed. The visual inspection criteria were as follows, and the evaluation results are listed as "step conformability" in Table 3. ◯: The print step is followed and there is absolutely no foaming around the print step. △: There is a small amount of foaming around the printing step. ×: Bubbles are observed around the printing step.

[0074] Table 3 shows the evaluation results of the pressure-sensitive adhesive sheets A and B of Examples 1 to 5 and the pressure-sensitive adhesive sheets A and B of Comparative Examples 1 to 3.

[0075] [Table 3]

[0076] The adhesive sheets B of Examples 1 to 5 according to the present invention had a 250 μm thick adhesive layer after crosslinking in two stages, first with a thermal crosslinking agent and then with a photocrosslinking agent, with a total light transmittance of 90% or more, an "initial haze value" of 1.0% or less, and a "haze value after wet heat" of 4.0% or less. Even when the adhesive layer was left in a wet heat environment for a long period of time and then taken out into a room temperature environment (temperature 23°C x 50% RH), it still had excellent optical properties and was therefore excellent in wet heat durability. Furthermore, the adhesive films produced using the adhesive sheets A and B of Examples 1 to 5 according to the present invention had an adhesive strength to soda glass of 10 N / 25 mm or less after crosslinking with a thermal crosslinking agent, and 25 N / 25 mm or more after two-stage crosslinking with a thermal crosslinking agent followed by crosslinking with a photocrosslinking agent. Therefore, the adhesive layer after crosslinking with a thermal crosslinking agent had excellent handleability (ease of peeling from the adherend) during rework, and the adhesive layer after two-stage crosslinking with a thermal crosslinking agent followed by crosslinking with a photocrosslinking agent had high adhesive strength. Furthermore, when an adhesive film prepared using the adhesive sheets A of Examples 1 to 5 according to the present invention was formed with an adhesive layer (first stage adhesive layer) having a thickness of 100 μm, the results of the step-conforming ability test showed that the film conformed to a printing step having a thickness of 42 μm, with absolutely no foaming around the printing step, and the film also had excellent step-conforming ability. In other words, the adhesive sheets A to B of Examples 1 to 5 according to the present invention, and the adhesive films produced using these, were able to achieve the objective of the present invention of providing an adhesive layer that has good conformability to unevenness in frame printing and other irregularities on the adherend, good handling properties during rework, and excellent wet heat durability.

[0077] On the other hand, the adhesive layers formed on the adhesive sheets A and B of Comparative Example 1 were obtained by crosslinking a copolymer obtained by copolymerizing two or more types of monomers, containing a monomer of group (F) but not a monomer of group (G).The adhesive sheet B of Comparative Example 1 had a low "haze value after moist heat" and high transparency, and therefore excellent moist heat durability.Furthermore, the adhesive film produced using the adhesive sheet A of Comparative Example 1 had high "adhesive strength after thermal crosslinking", poor reworkability, foaming around printed steps, and poor step-following ability. Furthermore, the adhesive layers formed on the adhesive sheets A and B of Comparative Example 2 were prepared by crosslinking a copolymer obtained by copolymerizing two or more types of monomers, without containing a monomer from group (F), but containing a monomer from group (G). However, the adhesive sheet B of Comparative Example 2 had a high "haze value after wet heat" and low transparency, indicating poor wet heat durability. The adhesive film prepared using the adhesive sheet B of Comparative Example 2 also had extremely low "adhesive strength after photo-crosslinking." The adhesive film prepared using the adhesive sheet A of Comparative Example 2 had foaming around printing steps and poor step-following ability. Furthermore, the adhesive layers formed on the adhesive sheets A and B of Comparative Example 3 were obtained by crosslinking a copolymer obtained by copolymerizing two or more types of monomers with monomers from groups (F) and (G). Adhesive sheet B of Comparative Example 3 had a low "haze value after wet heat" and high transparency, and therefore excellent wet heat durability. Furthermore, the adhesive film produced using adhesive sheet B of Comparative Example 3 had slightly low "adhesive strength after photo-crosslinking." Furthermore, the adhesive film produced using adhesive sheet A of Comparative Example 3 had foaming around printing steps and poor step-following ability. Thus, the adhesive sheets A to B of Comparative Examples 1 to 3 and the adhesive films produced using them were unable to achieve the objective of the present invention of providing an adhesive layer that has good conformability to unevenness such as that of frame printing on an adherend, good handling properties during rework, and excellent wet heat durability.

[0078] In the pressure-sensitive adhesive sheets B of Comparative Examples 1 to 3 described above, the pressure-sensitive adhesive sheets B of Comparative Example 1 and Comparative Example 3, in which a copolymer obtained by copolymerizing two or more types of monomers was crosslinked by adding a monomer from Group (F), had a low "haze value after wet heat" and the pressure-sensitive adhesive layer had excellent wet heat durability. However, the pressure-sensitive adhesive sheet B of Comparative Example 2, in which a copolymer obtained by copolymerizing two or more types of monomers was crosslinked without adding a monomer from Group (F), had a high "haze value after wet heat" and the pressure-sensitive adhesive layer had poor wet heat durability. Therefore, it was demonstrated that a useful component for obtaining a pressure-sensitive adhesive layer with excellent wet heat durability in the optical pressure-sensitive adhesive composition according to the present invention is (F) a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups.

Claims

1. An optical pressure-sensitive adhesive composition comprising: a copolymer having an acid value of 1.0 or less, obtained by copolymerizing at least two or more compounds selected from the group consisting of copolymerizable vinyl monomers having any of an alkyl group, a hydroxyl group, an alkoxy group, and an aromatic group, and nitrogen-containing vinyl monomers; (F) a (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule, and having two or more ethylenically unsaturated groups in one molecule; (G) a (meth)acrylate monomer having an alkylene oxide group, and having two or more ethylenically unsaturated groups in one molecule; (E) a thermal crosslinking agent; and a photoinitiator, the copolymer is copolymerized in a ratio of 100 parts by weight of (A) at least one alkyl(meth)acrylate monomer having an alkyl group carbon number of C1 to C18, 2.0 to 10 parts by weight of (B) at least one nitrogen-containing vinyl monomer or alkoxy group-containing alkyl(meth)acrylate monomer, 1.0 to 10 parts by weight of (C) at least one polyalkylene glycol mono(meth)acrylate monomer, and 0.5 to 10 parts by weight of (D) at least one copolymerizable vinyl monomer having a hydroxyl group; the optical pressure-sensitive adhesive composition contains, relative to a total of 100 parts by weight of the at least one alkyl (meth)acrylate monomer (A) having a carbon number of C1 to C18 in the alkyl group, 0.01 to 5 parts by weight of the thermal crosslinking agent (E), 0.1 to 10 parts by weight of the (F) (meth)acrylate monomer having a (meth)acryloyl group and an allyl ether group in one molecule and having two or more ethylenically unsaturated groups, 0.1 to 10 parts by weight of the (G) (meth)acrylate monomer having an alkylene oxide group and having two or more ethylenically unsaturated groups in one molecule, and 0.01 to 5 parts by weight of the photoinitiator; the (E) thermal crosslinking agent is at least one selected from the group consisting of an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and an aluminum chelate-based crosslinking agent, The optical pressure-sensitive adhesive composition, characterized in that the photoinitiator is at least one selected from the group consisting of acetophenone-based photoinitiators, benzoin-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphine oxide-based photoinitiators.

2. 2. The optical pressure-sensitive adhesive composition according to claim 1, wherein the copolymer has a weight-average molecular weight of 200,000 to 1,000,000.

3. 3. The optical pressure-sensitive adhesive composition according to claim 1, wherein the copolymer contains 50 parts by weight or more of an alkyl (meth)acrylate having an alkyl group carbon number of C8 to C18 out of a total of 100 parts by weight of at least one alkyl (meth)acrylate monomer (A) having an alkyl group carbon number of C1 to C18.

4. An optical pressure-sensitive adhesive composition as described in claim 1 or 2, characterized in that the average repeat number of alkylene oxide in the (C) polyalkylene glycol mono(meth)acrylate monomer is 4 to 14, and the average repeat number of alkylene oxide in the (G) (meth)acrylate monomer having an alkylene oxide group and two or more ethylenically unsaturated groups in one molecule is 4 to 14.

5. A pressure-sensitive adhesive film comprising a substrate and a pressure-sensitive adhesive layer formed by crosslinking the optical pressure-sensitive adhesive composition according to claim 1 or 2 with the thermal crosslinking agent (E), or a pressure-sensitive adhesive layer formed by crosslinking in two stages, first with the thermal crosslinking agent (E) and then with the photoinitiator, laminated on one side of the substrate.

6. 3. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by crosslinking the optical pressure-sensitive adhesive composition according to claim 1 with the thermal crosslinking agent (E) and laminated between two release-treated release films.

7. 3. An optical film with a pressure-sensitive adhesive layer, comprising: a pressure-sensitive adhesive layer crosslinked by the (E) thermal crosslinking agent using the optical pressure-sensitive adhesive composition according to claim 1 or 2; or a pressure-sensitive adhesive layer crosslinked in two steps, namely, crosslinking by the (E) thermal crosslinking agent and then crosslinking by the photoinitiator, laminated on at least one surface of an optical film.

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