Adhesive composition and optical film with adhesive layer

Abstract

Provided is an adhesive composition capable of forming an adhesive layer excellent in heat resistance and durability. The adhesive composition contains a (meth)acrylic resin, a crosslinking agent, a silane compound, and an ionic compound, the (meth)acrylic resin contains a (meth)acrylic alkyl ester having a glass transition temperature of less than 0°C of a homopolymer, a (meth)acrylic alkyl ester having a glass transition temperature of 0°C or higher of a homopolymer, and a monomer having a polar group as monomer units, and the ionic compound contains a cyano group-containing anion.

Description

Technical Field

[0001] This application relates to adhesive compositions and optical films with adhesive layers. Background Technology

[0002] Optical films such as polarizers used in image display devices, such as liquid crystal display devices and organic electroluminescent (organic EL) display devices, are mostly used by bonding them to other components (such as image display elements such as liquid crystal cells in liquid crystal display devices) via an adhesive layer containing an adhesive composition. Patent Document 1 discloses an adhesive composition for polarizers, characterized in that it contains an acrylic resin (A) and an ionic compound (B), wherein the acrylic resin (A) contains structural sites derived from methyl methacrylate, and the average number of carbon atoms (α) of the side chain structural sites of the acrylic resin (A) is 3.3 or less.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-25417 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The adhesive layers described above are sometimes used in high-temperature environments. In particular, adhesive layers for optical films that can be applied to automotive applications are required to withstand harsh high-temperature environments (e.g., environments above 100°C).

[0008] One aspect of this application is to provide an adhesive composition capable of forming an adhesive layer with excellent heat resistance and durability.

[0009] Methods for solving problems

[0010] The inventors have discovered that an adhesive layer with excellent heat resistance and durability can be formed by combining a specific ionic compound with a specific (meth)acrylic resin in an adhesive composition.

[0011] This application provides the following [1] to [5] in several aspects.

[0012] [1] An adhesive composition comprising a (meth)acrylic resin, a crosslinking agent, a silane compound and an ionic compound, wherein the (meth)acrylic resin comprises an alkyl methacrylate homopolymer with a glass transition temperature less than 0°C, an alkyl methacrylate homopolymer with a glass transition temperature greater than 0°C, and a monomer having a polar group as monomer units, and the ionic compound comprises a cyano-containing anion.

[0013] [2] According to the adhesive composition described in [1], wherein the cyano-containing anion is selected from at least one of tricyanomethyl alkylate anion, thiocyanate anion, and dicyandiamide anion.

[0014] [3] According to the adhesive composition described in [1] or [2], wherein the monomer having a polar group comprises a hydroxyl-containing (meth)acrylate and a carboxyl-containing monomer, and based on the total amount of monomer units contained in the (meth)acrylate resin, the content of the hydroxyl-containing (meth)acrylate is 0.3% by mass or more and 5.5% by mass or less, and the mass ratio of the content of the carboxyl-containing monomer to the content of the hydroxyl-containing (meth)acrylate is 0.06 or more and 1.0 or less.

[0015] [4] An adhesive layer comprising an adhesive composition described in any one of [1] to [3].

[0016] [5] An optical film with an adhesive layer, comprising an optical film and an adhesive layer described in [4] disposed on at least one surface of the optical film.

[0017] Invention Effects

[0018] According to one aspect of this application, an adhesive composition is provided that is capable of forming an adhesive layer with excellent heat resistance and durability. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view showing an example of an optical film with an adhesive layer.

[0020] Figure 2 This is a schematic cross-sectional view showing another example of an optical film with an adhesive layer. Detailed Implementation

[0021] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings. The present application is not limited to the following embodiments. In all the following drawings, the scale has been appropriately adjusted for ease of understanding of the constituent elements, and the scale of each constituent element shown in the drawings may not be consistent with the actual scale of the constituent elements.

[0022] <Adhesive Composition>

[0023] <(meth)acrylic resins>

[0024] One embodiment of the adhesive composition comprises a (meth)acrylic resin. The (meth)acrylic resin comprises alkyl (meth)acrylic esters of homopolymers with a glass transition temperature less than 0°C, alkyl (meth)acrylic esters of homopolymers with a glass transition temperature of 0°C or higher, and monomers having polar groups as monomer units. Because the adhesive composition of one embodiment simultaneously comprises such a (meth)acrylic resin and the ionic compound described later, the adhesive layer comprising this adhesive composition exhibits excellent durability (heat resistance) under high-temperature environments (e.g., environments above 100°C).

[0025] In this specification, the glass transition temperature (Tg) of homopolymers of various monomers such as (meth)acrylates is measured using a differential scanning calorimeter (DSC) (e.g., "EXSTAR DSC6000 (manufactured by SII Nano Technology Co., Ltd.)") under a nitrogen atmosphere, with the measurement temperature range set to, for example, -80 to 150°C at a heating rate of 10°C / min.

[0026] The alkyl group in the homopolymer of alkyl (meth)acrylate (hereinafter also called alkyl (meth)acrylate (A1) with a Tg less than 0 °C can be linear or branched. Additionally, alkyl (meth)acrylate (A1) can be an alkyl (meth)acrylate with an alicyclic structure (e.g., cycloalkyl (meth)acrylate). The number of carbon atoms in the alkyl group of alkyl (meth)acrylate (A1) can be 2 or more, or 3 or more, or 12 or less, 10 or less, or 8 or less.

[0027] Examples of (meth)acrylate alkyl esters (A1) include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, isohexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, n-dodecyl acrylate, etc., where the alkyl group has 2 to 12 carbon atoms; and alkyl acrylate alkyl esters with 5 to 12 carbon atoms, such as n-pentyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, etc.

[0028] These alkyl (meth)acrylates (A1) can be used alone or in combination of two or more. From the viewpoint of further improving the conformability (or flexibility, adhesion) of optical films, the alkyl (meth)acrylates (A1) can contain alkyl acrylates having 2 to 10 carbon atoms, alkyl acrylates having 3 to 8 carbon atoms, or alkyl acrylates having 4 to 6 carbon atoms.

[0029] The Tg of (meth)acrylate (A1) can be below -10°C, below -20°C, or below -30°C, for example, above -100°C, above -80°C, or above -60°C.

[0030] Based on the total amount of monomer units contained in the (meth)acrylic resin, the content of alkyl (meth)acrylic ester (A1) can be 30% or more by mass, 40% or more by mass, 50% or more by mass, or 60% or more by mass, or less than 90% by mass, less than 80% by mass, or less than 75% by mass.

[0031] The homopolymer has a Tg of 0°C or higher. The alkyl group in the (meth)acrylate (hereinafter also called (meth)acrylate (A2) can be linear or branched. Additionally, (meth)acrylate (A2) can be an alkyl acrylate with an alicyclic structure (e.g., (meth)acrylate cycloalkyl ester). The alkyl group in (meth)acrylate (A2) can have 1 or more carbon atoms, or 12 or less, 10 or less, or 8 or less.

[0032] Examples of (meth)acrylate alkyl esters (A2) include (meth)acrylate alkyl esters with a homopolymer Tg of 0°C or higher and less than 30°C, and (meth)acrylate alkyl esters with a homopolymer Tg of 30°C or higher.

[0033] Examples of (meth)acrylate alkyl esters that are homopolymers with a Tg of 0°C or higher and less than 30°C include methyl acrylate.

[0034] Examples of alkyl methacrylates with a Tg of 30°C or higher as homopolymers include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, propyl methacrylate, isopropyl methacrylate, 3,3-dimethylbutyl methacrylate, 3,3-dimethyl-2-butyl methacrylate, and other alkyl methacrylates having 1 to 6 carbon atoms, as well as stearyl methacrylate, stearyl acrylate, tert-butyl methacrylate, and isobornyl methacrylate.

[0035] When the alkyl methacrylate homopolymer has a Tg of 30°C or higher and is an alkyl methacrylate with an alicyclic structure, the alicyclic structure can be a cycloalkane structure with 5 or more carbon atoms (e.g., 5 to 7). Examples of alkyl methacrylate homopolymers with a Tg of 30°C or higher and an alicyclic structure include isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentyl methacrylate, cyclododecyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, and 1-adamantyl methacrylate.

[0036] These alkyl methacrylates (A2) can be used alone or in combination of two or more. Alkyl methacrylates (A2) can include both alkyl methacrylates with a homopolymer Tg of 0°C or higher and less than 30°C, and alkyl methacrylates with a homopolymer Tg of 30°C or higher.

[0037] The homopolymer has a Tg of alkyl (meth)acrylate above 0°C and below 30°C, for example, methyl acrylate.

[0038] The homopolymer with a Tg of 30°C or higher is an alkyl methacrylate, which may be, for example, at least one of alkyl methacrylates having 1 to 4 carbon atoms and alkyl methacrylates having an alicyclic structure, or at least one of methyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate and cyclohexyl methacrylate.

[0039] The Tg of homopolymers is above 0°C and below 30°C. The Tg of alkyl methacrylates can be above 2°C or above 5°C, or below 25°C, below 20°C, or below 15°C.

[0040] From the perspective of superior mechanical strength and heat resistance of the adhesive layer, the Tg of homopolymers is above 30°C. The Tg of (meth)acrylates can be above 50°C, above 60°C, above 80°C, or above 100°C, for example, below 200°C, below 150°C, or below 120°C.

[0041] Based on the total amount of monomer units contained in the (meth)acrylic resin, the content of alkyl (meth)acrylic acid esters with a Tg of 0°C or higher and less than 30°C in the homopolymer can be 5% or higher by mass, 10% or higher by mass, or 15% or higher by mass, or less than 50% by mass, less than 40% by mass, less than 35% by mass, less than 30% by mass, less than 25% by mass, or less than 20% by mass.

[0042] From the perspective of excellent mechanical strength and heat resistance durability of the adhesive layer, based on the total amount of monomer units contained in the (meth)acrylic resin, the content of alkyl (meth)acrylic acid esters with a Tg of 30°C or higher in the homopolymer can be 1% or more by mass, 2% or more by mass, 3% or more by mass, or 5% or more by mass, or less than 30% by mass, less than 20% by mass, less than 15% by mass, or less than 13% by mass. If the content of alkyl (meth)acrylic acid esters with a Tg of 30°C or higher in the homopolymer is within the above range, the cohesiveness of the adhesive is improved, thereby further improving the mechanical strength of the adhesive layer, and the flexibility and adhesion of the adhesive layer are also excellent. Therefore, it is more advantageous from the perspective of heat resistance durability.

[0043] Based on the total amount of monomer units contained in the (meth)acrylic resin, the content of alkyl (meth)acrylic ester (A2) can be more than 10% by mass, more than 20% by mass, or more than 25% by mass, or less than 50% by mass, less than 40% by mass, or less than 35% by mass.

[0044] The monomer with a polar group is a monomer capable of copolymerizing with the aforementioned alkyl (meth)acrylate (A1) and alkyl (meth)acrylate (A2), and has polar groups such as hydroxyl, carboxyl, substituted or unsubstituted amino, epoxy, and other heterocyclic groups. For example, the monomer with a polar group may have at least one polar group selected from hydroxyl and carboxyl groups. For example, the monomer with a polar group may comprise at least one of a (meth)acrylate with a hydroxyl group and a monomer with a carboxyl group.

[0045] The monomer containing a hydroxyl group can be a hydroxyl-containing (meth)acrylate (hereinafter also referred to as "hydroxyl-containing (meth)acrylate"). Hydroxyl-containing (meth)acrylates can be, for example, hydroxyl-alkyl (meth)acrylates. The hydroxyl alkyl group can have 1 or more carbon atoms, or 2 or more, or 12 or less, 10 or less, 8 or less, 5 or less, or 4 or less.

[0046] In addition to the hydroxyl group, (meth)acrylates containing hydroxyl groups may also have halogen atoms (e.g., fluorine, chlorine, bromine, and iodine atoms), cycloalkyl groups (e.g., cyclopentyl, cyclohexyl, etc.), aryl groups (e.g., phenyl and alkylphenyl (tolyl, xylyl, etc.)), aralkyl groups (benzyl, etc.), alkoxy groups (e.g., methoxy, ethoxy, etc., with 1 to 4 carbon atoms), polyoxyalkylene groups (e.g., dioxanediene, etc.), cycloalkoxy groups (e.g., cyclohexyloxy, etc., with 5 to 10 carbon atoms), aryloxy groups (e.g., phenoxy, etc.), arylalkoxy groups (e.g., benzyloxy, etc.), alkylthio groups (e.g., methylthio, ethylthio, etc., with 1 to 4 carbon atoms), cycloalkylthio groups (e.g., cyclohexylthio, etc.), arylthio groups (e.g., thiophenoxy, etc.), arylalkylthio groups (e.g., benzylthio, etc.), acyl groups (e.g., acetyl, etc.), nitro groups, cyano groups, and other substituents. (Meth)acrylates having hydroxyl groups can be, for example, (meth)acrylates having hydroxyl groups and one or more selected from halogen atoms, alkoxy groups, and aryloxy groups.

[0047] Examples of hydroxyl-containing (meth)acrylates include 1-hydroxymethyl (meth)acrylate, 1-hydroxyethyl (meth)acrylate, 1-hydroxyheptyl (meth)acrylate, 1-hydroxybutyl (meth)acrylate, 1-hydroxypentyl (meth)acrylate, and other 1-hydroxyC1–C8 alkyl esters of meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxypentyl (meth)acrylate, 2-hydroxyhexyl (meth)acrylate, and other 2-hydroxyC2–C9 alkyl esters of meth)acrylate; 3-hydroxypropyl (meth)acrylate, ... 3-hydroxybutyl acrylate, 3-hydroxypentyl acrylate, 3-hydroxyhexyl acrylate, 3-hydroxyheptyl acrylate, etc. (meth)acrylate 3-hydroxy C3-C10 alkyl esters; 4-hydroxybutyl acrylate, 4-hydroxypentyl acrylate, 4-hydroxyhexyl acrylate, 4-hydroxyheptyl acrylate, 4-hydroxyoctyl acrylate, etc. (meth)acrylate 4-hydroxy C4-C11 alkyl esters; 2-chloro-2-hydroxypropyl acrylate; 3-chloro-2-hydroxypropyl acrylate; 2-hydroxy-3-phenoxypropyl acrylate, etc.

[0048] These hydroxyl-containing (meth)acrylates can be used alone or in combination of two or more. From the viewpoint of superior mechanical strength and heat resistance of the adhesive layer, the hydroxyl-containing (meth)acrylate can be a hydroxyalkyl (meth)acrylate, specifically a 2-hydroxyalkyl (meth)acrylate selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, etc.; and at least one of 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 3-hydroxypentyl (meth)acrylate, etc. From the viewpoint of superior mechanical strength and heat resistance of the adhesive layer, the hydroxyl-containing (meth)acrylate can include a 2-hydroxyalkyl (meth)acrylate, and can include 2-hydroxyethyl (meth)acrylate. 2-hydroxyethyl (meth)acrylate is beneficial for forming a uniform cross-linked structure, thus further improving the mechanical strength and heat resistance of the adhesive layer.

[0049] From the perspective of superior mechanical strength and heat resistance of the adhesive layer, based on the total amount of monomer units contained in the (meth)acrylic resin, the content of hydroxyl-containing (meth)acrylate can be 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more, and can be 10% by mass or less, 8% by mass or less, 5.5% by mass or less, 4% by mass or less, 3% by mass or less, or 2.5% by mass or less. For example, the content of hydroxyl-containing (meth)acrylate can be 0.3% by mass or more and 5.5% by mass or less, 0.5% by mass or more and 3% by mass or less, or 0.5% by mass or more and 2.5% by mass or less.

[0050] Examples of monomers containing carboxyl groups (hereinafter also referred to as "carboxyl-containing monomers") include (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, and carboxyalkyl esters of (meth)acrylic acid (e.g., carboxyethyl ester and carboxypentyl ester). These carboxyl-containing monomers can be used alone or in combination of two or more. Carboxyl-containing monomers may contain acrylic acid. Acrylic acid promotes the reaction of hydroxyl-containing (meth)acrylic acid esters with crosslinking agents, contributing to the formation of a uniform crosslinked structure, thus further improving the mechanical strength and heat resistance of the adhesive layer.

[0051] From the perspective of the mechanical strength and heat resistance of the adhesive layer, based on the total amount of monomer units contained in the (meth)acrylic resin, the content of carboxyl-containing monomers can be 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, or less than 5.5% by mass, less than 3% by mass, less than 2% by mass, or less than 1% by mass.

[0052] The mass ratio of the content of carboxyl-containing monomers to the content of hydroxyl-containing (meth)acrylates (content of carboxyl-containing monomers / content of hydroxyl-containing (meth)acrylates) can be 0.06 or more, 0.08 or more, or 0.1 or more, or 1.0 or less, 0.8 or less, or 0.7 or less. When the monomers with polar groups include both hydroxyl-containing (meth)acrylates and carboxyl-containing monomers, and the mass ratio of the content of carboxyl-containing monomers to the content of hydroxyl-containing (meth)acrylates is within the above-mentioned range, a cross-linked structure is easily formed uniformly in the adhesive, and there is a tendency for the adhesive layer to have superior mechanical strength and heat resistance durability. For example, the mass ratio of the content of carboxyl-containing monomers to the content of hydroxyl-containing (meth)acrylates can be 0.06 or more and 1.0 or less, or 0.1 or more and 0.7 or less.

[0053] Examples of (meth)acrylates having substituted or unsubstituted amino groups include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. These (meth)acrylates having substituted or unsubstituted amino groups can be used alone or in combination of two or more. From the viewpoint of further improving the peelability of the release film when it is laminated onto the adhesive layer, (meth)acrylate resins may substantially be free of monomers having substituted or unsubstituted amino groups as monomer units. It should be noted that "(meth)acrylate resins substantially free of monomers having substituted or unsubstituted amino groups" means that the content of (meth)acrylates having substituted or unsubstituted amino groups is less than 1.0% by mass, based on the total amount of monomer units contained in the (meth)acrylate resin.

[0054] Examples of (meth)acrylates having heterocyclic groups such as epoxy groups include acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran. These (meth)acrylates having heterocyclic groups can be used alone or in combination of two or more.

[0055] (Meth)acrylic resins may contain other monomers as monomer units. Examples of other monomers include alkyl (meth)acrylates with substituents, (meth)acrylamide monomers, styrene monomers, vinyl monomers, and monomers with multiple (meth)acryloyl groups within the molecule.

[0056] Substituent-containing alkyl (meth)acrylates are, for example, alkyl (meth)acrylates in which a substituent (excluding polar groups such as carboxyl groups) is introduced onto the alkyl group of the alkyl group (where the hydrogen atom of the alkyl group is replaced by the substituent). Examples of such substituents include aryl (phenyl, etc.), aryloxy (phenoxy), and alkoxy (e.g., methoxy, ethoxy, etc.). Examples of substituent-containing alkyl acrylates include, for example, alkoxyalkyl acrylates (e.g., 2-methoxyethyl acrylate, ethoxymethyl acrylate, etc.), aryloxyalkyl acrylates (e.g., phenoxyethyl acrylate, etc.), aryloxypolyalkylene glycol monoacrylates, polyalkylene glycol monoacrylates, etc. These substituent-containing alkyl (meth)acrylates can be used alone or in combination of two or more.

[0057] Examples of (meth)acrylamide monomers include N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, N-(5-hydroxypentyl) (meth)acrylamide, N-(6-hydroxyhexyl) (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and N-isopropyl (meth)acrylamide. Amide, N-(3-dimethylaminopropyl) (methyl)acrylamide, N-(1,1-dimethyl-3-oxobutyl) (methyl)acrylamide, N-[2-(2-oxo-1-imidazolyl)ethyl] (methyl)acrylamide, 2-(meth)acryloylamino-2-methyl-1-propanesulfonic acid, N-(methoxymethyl) (methyl)acrylamide, N-(ethoxymethyl) (methyl)acrylamide, N-(propoxymethyl) (methyl)acrylamide, N-(1-methyl) Ethoxymethyl (methyl)acrylamide, N-(1-methylpropoxymethyl)acrylamide, N-(2-methylpropoxymethyl)acrylamide (also known as: N-(isobutoxymethyl)acrylamide), N-(butoxymethyl)acrylamide, N-(1,1-dimethylethoxymethyl)acrylamide, N-(2-methoxyethyl)acrylamide, N-(2-ethoxyethyl)acrylamide, N-(2-propoxyethyl)acrylamide, N-[2-(1-methylethoxy)ethyl] (methyl)acrylamide, N-[2-(1-methylpropoxy)ethyl] (methyl)acrylamide, N-[2-(2-methylpropoxy)ethyl] (methyl)acrylamide (also known as: N-(2-isobutoxyethyl)acrylamide), N-(2-butoxyethyl) (methyl)acrylamide, N-[2-(1,1-dimethylethoxy)ethyl] (methyl)acrylamide, etc. These (meth)acrylamide monomers can be used alone or in combination of two or more.

[0058] Examples of styrene monomers include styrene; alkylstyrene such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halostyrene such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; nitrostyrene; acetylstyrene; methoxystyrene; and divinylbenzene. These styrene monomers can be used individually or in combination of two or more.

[0059] Examples of vinyl monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, and other fatty acid vinyl esters; vinyl chloride, vinyl bromide, and other haloethylenes; vinylidene chloride, and other dihaloethylenes; vinylpyridine, vinylpyrrolidone, vinylcarbazole, and other nitrogen-containing aromatic vinyl compounds; and butadiene, isoprene, chloroprene, and other conjugated dienes. These vinyl monomers can be used individually or in combination of two or more.

[0060] Examples of monomers with multiple (meth)acryloyl groups within their molecules include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate, which have two (meth)acryloyl groups within their molecules; and trimethylolpropane tri(meth)acrylate, which has three (meth)acryloyl groups within its molecules. These monomers with multiple (meth)acryloyl groups within their molecules can be used alone or in combination of two or more.

[0061] From the perspective of superior mechanical strength and heat resistance of the adhesive layer, the weight-average molecular weight (Mw) of (meth)acrylic resins can be above 1 million, above 1.1 million, above 1.2 million, above 1.3 million, or above 1.5 million, or below 3.2 million, below 3.1 million, below 3 million, below 2.9 million, below 2.5 million, or below 1.7 million. For example, the Mw of (meth)acrylic resins can be 1 million to 3.2 million, 1.1 million to 3.1 million, 1.2 million to 3 million, 1.3 million to 2.9 million, 1.5 million to 2.5 million, or 1.5 million to 1.7 million.

[0062] The molecular weight distribution (Mw / Mn) of (meth)acrylic resins, expressed as the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), can be, for example, 1.5 or more, 2 or more, or 2.5 or more, and can be 10 or less, 8 or less, 7 or less, 5 or less, 4 or less, or 3 or less. Mw and Mn can be analyzed by gel permeation chromatography (GPC) and are values ​​converted from standard polystyrene.

[0063] From the perspective of superior mechanical strength and heat resistance of the adhesive layer, the Tg of (meth)acrylic resins can be above -45°C, above -40°C, above -38°C, or above -35°C, and below -10°C, below -15°C, below -20°C, or below -25°C. For example, the Tg of (meth)acrylic resins can be -45°C to -10°C, -40°C to -15°C, or -38°C to -20°C. The Tg of (meth)acrylic resins is determined by DSC measurement under a nitrogen atmosphere at a heating rate of 10°C / min.

[0064] For (meth)acrylic resins (or mixtures thereof when there are two or more), a solution dissolved in ethyl acetate and adjusted to a concentration of 20% by mass exhibits a viscosity of less than 20 Pa·s, and further more than 0.1 Pa·s and less than 7 Pa·s at 25°C. Viscosity can be measured using a Brookfield viscometer.

[0065] Based on the total mass of the solid components in the adhesive composition, the content of (meth)acrylic resin can be 80% or more by mass, 90% or more by mass, or 95% or more by mass, or less than 99% by mass or less than 98% by mass.

[0066] (Meth)acrylic resins can be manufactured using known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. In the manufacture of (meth)acrylic resins, a polymerization initiator can be used. For example, 0.001 to 5 parts by mass of the polymerization initiator are used relative to 100 parts by mass of all monomers used in the manufacture of the (meth)acrylic resin. Alternatively, (meth)acrylic resins can be manufactured, for example, by polymerization using active energy rays such as ultraviolet light.

[0067] Examples of polymerization initiators include thermal polymerization initiators and photopolymerization initiators. Examples of thermal polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-formonitrile), 2,2'-azobis(2,4-dimethylpentanonitrile), 2,2'-azobis(2,4-dimethyl-4-methoxypentanonitrile), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-hydroxymethylpropionitrile); organic peroxides such as lauryl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl percarbonate, dipropyl percarbonate, tert-butyl peroxyneodecanate, tert-butyl peroxynepentanoate, and (3,5,5-trimethylhexanoyl) peroxide; and inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. Examples of photopolymerization initiators include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)one. Other examples of polymerization initiators include redox initiators that combine peroxides and reducing agents.

[0068] (Meth)acrylic resins are manufactured, for example, by solution polymerization. An example of solution polymerization includes the step of mixing monomers and an organic solvent to prepare a mixed solution; and the step of adding a thermal polymerization initiator to the mixed solution under a nitrogen atmosphere and stirring at 40–90°C (e.g., 60–80°C) for approximately 3–10 hours. To control the reaction, the monomers and thermal polymerization initiator can be added continuously or intermittently during polymerization. The monomers and thermal polymerization initiator can be added in a state dissolved in the organic solvent. Examples of organic solvents that can be used include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as propanol and isopropanol; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0069] <Cross-linking agent>

[0070] One embodiment of the adhesive composition includes a crosslinking agent. Since (meth)acrylic resins contain monomers having polar groups as monomer units, polar groups are present in (meth)acrylic resins. The crosslinking agent can be a compound that reacts with these polar groups present in the (meth)acrylic resin to form a crosslink. Examples of crosslinking agents include isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds. Among these, isocyanate compounds, epoxy compounds, and aziridine compounds have at least two functional groups within their molecules capable of reacting with the polar groups in the (meth)acrylic resin. These crosslinking agents can be used alone or in combination of two or more.

[0071] The crosslinking agent preferably comprises an isocyanate compound. As an isocyanate compound, it is preferably a compound having at least two isocyanate groups (-NCO) within the molecule, such as aliphatic isocyanate compounds (e.g., hexamethylene diisocyanate), alicyclic isocyanate compounds (e.g., isophorone diisocyanate), aromatic isocyanate compounds (e.g., toluene diisocyanate, phenylenediamine diisocyanate, hydrogenated phenylenediamine diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, etc.). Alternatively, the crosslinking agent can also be an adduct (addition compound) of isocyanate compounds based on polyol compounds (e.g., adducts based on glycerol, trimethylolpropane, etc.), isocyanurate esters, biuret-type compounds, or isocyanate compounds derived from urethane prepolymers obtained by addition reactions with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. These crosslinking agents can be used alone or in combination of two or more.

[0072] Epoxy compounds are compounds having at least two epoxy groups within their molecules. Specific examples include bisphenol A type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidylm-phenylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane. These epoxy compounds can be used alone or in combination of two or more.

[0073] Aziridine compounds are compounds that have a skeleton of at least two three-membered rings, also known as ethyleneimines, containing one nitrogen atom and two carbon atoms. Specific examples include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), triethylene melamine, isophthaloyl bis-1-(2-methylaziridine), tri-1-aziridineylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridine propionate, and tetramethylolmethane-tri-β-aziridine propionate.

[0074] Examples of metal chelate compounds include compounds formed by coordinating acetylacetone and ethyl acetoacetate with multivalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

[0075] The crosslinking agent may be, for example, at least one selected from aromatic isocyanate compounds, aliphatic isocyanate compounds, and their polyol-based adducts. When the crosslinking agent comprises aromatic isocyanate compounds and / or their polyol-based adducts, there is a tendency to easily form a uniform crosslinked structure, and the mechanical strength and heat resistance of the adhesive layer are easily improved.

[0076] The crosslinking agent content can be 0.01 parts or more, 0.05 parts or more, or 0.1 parts or more, or 5 parts or less, 3 parts or less, or 2 parts or less, relative to 100 parts by weight of solid components of (meth)acrylic resins (the total of two or more when using two or more).

[0077] <Silane Compounds>

[0078] One embodiment of the adhesive composition comprises a silane compound. The silane compound may, for example, comprise a compound represented by the following formula (1-1).

[0079] [Chemical Formula 1]

[0080]

[0081] In the above equation (1-1), R 111 R represents an alkyl group having 1 to 5 carbon atoms. 112 and R 113 Each independently represents an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms, L 1 It represents an alkylene group having 1 to 20 carbon atoms, or an alkylene group having 1 to 20 carbon atoms containing at least one -CH2- group replaced by -NH- or -O-, where X represents a mercapto (-SH), amino (-NH2), epoxy group, or alicyclic epoxy group.

[0082] R in equation (1-1) 111 ~R 113 Each of the alkyl groups having 1 to 5 carbon atoms can independently be an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 3 carbon atoms, or an alkyl group having 1 to 2 carbon atoms. Examples of such alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and pentyl, such as n-pentyl, isopentyl, and tert-pentyl.

[0083] R in equation (1-1) 112 and R 113Each of the alkoxy groups having 1 to 5 carbon atoms can independently be an alkoxy group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 2 carbon atoms. Examples of such alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, and pentoxy groups such as n-pentoxy, isopentoxy, and tert-pentoxy.

[0084] As L in equation (1-1) 1 Alkyl groups having 1 to 20 carbon atoms can be, for example, -(CH2). n - (n represents an integer from 1 to 20.) indicates the group. Here, n (the number of carbon atoms in the alkylene group) can be 2 or more, 4 or more, 6 or more, or 8 or more, or 18 or less, 15 or less, or 12 or less.

[0085] L in equation (1-1) 1 In an alkylene group having 1 to 20 carbon atoms, in which at least one -CH2- (methylene) group is replaced by -NH- or -O-, the alkylene group having 1 to 20 carbon atoms (the alkylene group before at least one -CH2- is replaced by -NH- or -O-) can be, for example, -(CH2). n - (n represents an integer from 1 to 20.) indicates the group. Here, n (the number of carbon atoms in the alkylene group) can be 2 or more, 4 or more, 6 or more, or 8 or more, or 18 or less, 15 or less, or 12 or less.

[0086] In the above L 1 In the case where at least one -CH2- group in an alkylene group having 1 to 20 carbon atoms is replaced by -NH- or -O-, it is permissible for only one methylene group in the alkylene group having 1 to 20 carbon atoms to be replaced by -NH- or -O-, or for two or more methylene groups in the alkylene group having 1 to 20 carbon atoms to be independently replaced by -NH- or -O-. In the case where two or more methylene groups are replaced, the multiple substituents (-NH- and / or -O-) can be separated from each other by an alkylene group having 2 or more carbon atoms.

[0087] The epoxy group of X in formula (1-1) can be the group shown in formula (a1) below.

[0088] [Chemical Formula 2]

[0089]

[0090] In equation (a1), * represents a connecting key.

[0091] An example of an alicyclic epoxy group that is X in formula (1-1) can be given as a monovalent group formed by removing one hydrogen atom from the structure shown in formula (a2) below.

[0092] [Chemical Formula 3]

[0093]

[0094] In equation (a2), n represents an integer from 1 to 5. n can be from 1 to 3 or from 1 to 2.

[0095] Examples of silane compounds represented by formula (1-1) include 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, and other 3-epoxypropoxypropyltrialkoxysilanes; 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, and other 3-epoxypropoxypropylalkyldiethoxysilanes; 8-epoxypropoxyoctyltrimethoxysilane, 8-epoxypropoxyoctyltriethoxysilane, and other 8-epoxypropoxyoctyltrialkoxysilanes; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and other 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilanes.

[0096] Silane compounds may include silane compounds other than those shown in formula (1-1). Examples of silane compounds other than those shown in formula (1-1) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 1,3-bis(3'-trimethoxypropyl)urea, 1,6-bis(trimethoxysilyl)hexane, 1,8-bis(trimethoxysilyl)octane, etc.

[0097] Silane compounds can include organosilicon oligomers. Examples of organosilicon oligomers include 3-mercaptopropyltrimethoxysilane-tetramethoxysilane oligomers (oligomers containing 3-mercaptopropyltrimethoxysilane and tetramethoxysilane as monomer units; the same applies in similar descriptions below.), 3-mercaptopropyltrimethoxysilane-tetraethoxysilane oligomers, 3-mercaptopropyltriethoxysilane-tetramethoxysilane oligomers, 3-mercaptopropyltriethoxysilane-tetraethoxysilane oligomers, and other oligomers containing the mercaptopropyl group; mercaptomethyltrimethoxysilane-tetramethoxysilane oligomers, mercaptomethyltrimethoxysilane-tetraethoxysilane oligomers, and mercaptomethyltriethoxysilane-tetramethoxysilane oligomers. Oligomers containing mercaptomethyl groups, such as mercaptomethyltriethoxysilane-tetraethoxysilane oligomers; 3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomers, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane oligomers, 3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane oligomers, 3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane oligomers, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane oligomers, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomers, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomers, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomers. Oligomers containing methacryloxypropyl groups, such as alkyl oligomers and 3-methacryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers; 3-acryloxypropyltrimethoxysilane-tetramethoxysilane oligomers, 3-acryloxypropyltrimethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropyltriethoxysilane-tetramethoxysilane oligomers, 3-acryloxypropyltriethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetramethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers, 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers. Oligomers containing acryloyloxypropyl groups, such as methoxysilane oligomers and 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomers; and vinyl-containing oligomers, such as vinyltrimethoxysilane-tetramethoxysilane oligomers, vinyltrimethoxysilane-tetraethoxysilane oligomers, vinyltriethoxysilane-tetramethoxysilane oligomers, vinyltriethoxysilane-tetraethoxysilane oligomers, vinylmethyldiethoxysilane-tetramethoxysilane oligomers, vinylmethyldiethoxysilane-tetraethoxysilane oligomers, vinylmethyldiethoxysilane-tetraethoxysilane oligomers, vinylmethyldiethoxysilane-tetraethoxysilane oligomers.

[0098] From the viewpoint of easily improving the adhesion (or bonding) between the adhesive layer and the metal layer, glass substrate, etc., and beneficial to improving peel resistance, the content of silane compound relative to 100 parts by weight of the solid component of (meth)acrylic resin (the total of them when two or more are used) can be 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.2 parts by weight or more. From the viewpoint of easily suppressing the seepage of silane compound from the adhesive layer, it can be 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, or 2 parts by weight or less.

[0099] <Ionic Compounds>

[0100] One embodiment of the adhesive composition comprises an ionic compound. The ionic compound contains a cyano-containing anion. The presence of a cyano-containing anion in the ionic compound contributes to a further improvement in the antistatic properties of the adhesive composition.

[0101] The cyano-containing anion can be, for example, the anion shown in formula (1) below.

[0102] [Chemical Formula 4]

[0103]

[0104] In formula (1), Y represents boron, carbon, nitrogen, sulfur, aluminum, silicon, phosphorus, arsenic, or selenium, Z represents a hydrogen atom or a monovalent organic group, and L represents a hydrogen atom or a monovalent organic group. 2 The symbols represent organic linking groups, where a and b each independently represent integers greater than or equal to 0, and c and d each independently represent integers greater than or equal to 1. The value of a can be 0, and the value of b can be 0.

[0105] In formula (1), Y is preferably boron, carbon, nitrogen, or sulfur. In formula (1), Z can be an alkyl group, which can have 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Examples of such alkyl groups include methyl and ethyl. Z can be a hydrogen atom, methyl, or trifluoromethyl.

[0106] L in equation (1) 2 For example, it can be -S-, -O-, -SO2-, or -CO-. L 2 It can be -SO2- or -CO-.

[0107] a and b each independently represent integers greater than 0, and c and d each independently represent integers greater than 1. Since the valence of the anion in equation (1) is -1, the values ​​of a and d are determined in such a way that when the atomic valence of Y is set to y, the relationship y-1=a+d is satisfied.

[0108] As an example of the anion shown in equation (1), C can be cited. -(CN)3 (tricyanomethane anion), S - (CN) (thiocyanate anion), N - (CN)₂ (dicyanamide anion), N - (-SO2-CN)2, B - (CN)4 (tetracyanoborate anion), etc. The cyanide-containing anion can be at least one selected from tricyanomethane anion, thiocyanate anion, and dicyandiamide anion.

[0109] Ionic compounds contain cations in addition to anions containing cyanide groups. Cations can be inorganic or organic. An example of an inorganic cation is the lithium cation [Li]. ＋ Sodium cations [Na] ＋ Potassium cations [K] ＋ Alkali metal cations, beryllium cations [Be] 2＋ Magnesium cations (Mg) 2＋ ], calcium cations [Ca 2＋ Alkaline earth metal cations, transition metal cations, rare earth metal cations, etc.

[0110] The cation is preferably an organic cation, more preferably a substituted or unsubstituted imidazolium cation, pyrrolidineium cation, piperidinium cation, pyridinium cation, quaternary ammonium cation, or quaternary phosphonium cation, and even more preferably an imidazolium cation, pyridinium cation, quaternary ammonium cation, or quaternary phosphonium cation. A substituted imidazolium cation may, for example, be a 1,3-alkyl-substituted imidazolium cation (e.g., 1-butyl-3-methylimidazolium cation).

[0111] Organic cations can be, for example, the cations represented by the following formula (2).

[0112] [Chemical Formula 5]

[0113]

[0114] In equation (2), R 1 ~R 4 Each can independently represent a hydrogen atom, an alkyl group that may have substituents, an alkenyl group that may have substituents, an alkynyl group that may have substituents, an aryl group that may have substituents, or a heterocyclic group that may have substituents, selected from R. 1 ~R 4 Two or more of them can bond together to form a ring.

[0115] R 1 ~R 4Each of the following is preferably an alkyl group that may have a substituent, an alkenyl group that may have a substituent, an alkynyl group that may have a substituent, an aryl group that may have a substituent, or a heterocyclic group that may have a substituent. As R 1 ~R 4 It is permissible to use alkyl groups that may have substituents, alkenyl groups that may have substituents, alkynyl groups that may have substituents, aryl groups that may have substituents, and heterocyclic groups that may have substituents without particular restrictions.

[0116] R 1 ~R 4 In, for example, R 1 With R 2 R 2 With R 3 R 3 With R 4 and R 4 With R 1 They can independently bond with each other and form rings with their respective bonded nitrogen atoms, R 1 With R 2 With R 3 R 2 With R 3 With R 4 and R 3 With R 4 With R 1 They can independently bond with each other and form rings together with the nitrogen atoms they are bonded to.

[0117] R 1 ~R 4 Each can independently be an alkyl group that can have substituents, or an aryl group that can have substituents. Additionally, it can be selected from R... 1 ~R 4 The three in can be bonded together with R 1 ~R 4 The bonded N atoms together form an unsaturated ring structure containing unsaturated bonds (including aromatic ring structures).

[0118] Organic cations can be, for example, the cations represented by the following formula (3).

[0119] [Chemical Formula 6]

[0120]

[0121] In equation (3), R 5 ~R 8 Each can independently represent a hydrogen atom, an alkyl group that may have substituents, an alkenyl group that may have substituents, an alkynyl group that may have substituents, an aryl group that may have substituents, or a heterocyclic group that may have substituents, selected from R. 5 ~R8 Two or more of them can bond together to form a ring.

[0122] Ionic compounds can be solid at room temperature (e.g., 23°C). Ionic compounds that are solid at room temperature can maintain their antistatic properties for a longer period of time compared to ionic compounds that are liquid at room temperature.

[0123] From the perspective of superior antistatic properties, the content of ionic compounds can be 0.1 parts by mass or more, 0.2 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more, relative to 100 parts by mass of the solid component of (meth)acrylic resin. From the perspective of superior moisture and heat resistance of optical films with adhesive layers, the content can be 10 parts by mass or less, 8 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less.

[0124] <Other Ingredients>

[0125] The adhesive composition may further include solvents, crosslinking catalysts, ultraviolet absorbers, weather stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers, light-scattering particles, rust inhibitors, release agents, and resins other than (meth)acrylic resins. Furthermore, the adhesive composition may also contain ultraviolet-curing compounds. When the adhesive composition contains ultraviolet-curing compounds, a harder adhesive layer can be produced by curing it with ultraviolet light after forming the adhesive layer using the adhesive composition.

[0126] When the adhesive composition contains both a crosslinking agent and a crosslinking catalyst, the adhesive layer can be prepared with a shorter curing time. Furthermore, when the adhesive composition contains a crosslinking catalyst, buoyancy, peeling, and foaming of the adhesive layer at the interface between the adhesive layer and its adjacent components can be more effectively suppressed, and the reprocessability of the adhesive layer (the property of easily peeling off the adhesive layer after it has been applied to the substrate) can also be improved. Examples of crosslinking catalysts include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, triethylenediamine, polyamino resin, and melamine resin. When an amine compound is incorporated as a crosslinking catalyst in the adhesive composition, isocyanate compounds are suitable as the crosslinking agent.

[0127] The adhesive composition described above can be prepared by mixing the above-described components. The gel fraction of the adhesive composition can be, for example, 50% or more and 98% or less, preferably 60% or more and 95% or less, or 70% or more and 90% or less. The gel fraction can be determined according to the measurement method described in the examples section below.

[0128] <Adhesive layer>

[0129] One embodiment of the adhesive layer comprises the above-described adhesive composition. The adhesive layer may comprise the above-described adhesive composition. The adhesive layer can be obtained, for example, by a method comprising the steps of: dissolving or dispersing the components contained in the above-described adhesive composition in a solvent to prepare a solvent-containing adhesive composition; and applying the adhesive composition onto a substrate film and drying it. The adhesive layer exhibits excellent heat resistance and durability.

[0130] The substrate film can be a plastic film. The plastic film can be a release film (release film) whose surface has undergone a release treatment. For example, the release film can be a film whose adhesive layer containing various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate has undergone a release treatment such as silicone treatment.

[0131] Alternatively, the adhesive layer can be formed by directly coating the adhesive composition onto the surface of the optical film (details to follow). When forming the adhesive layer on the surface of the optical film, surface activation treatments (e.g., plasma treatment, corona treatment, etc.) can be applied to the bonding surfaces of the optical film and / or the adhesive layer as needed.

[0132] The thickness of the adhesive layer can be, for example, 10 μm or more, 15 μm or more, or 18 μm or more, or less than 50 μm, less than 40 μm, or less than 35 μm.

[0133] <Optical film with adhesive layer>

[0134] One embodiment of the optical film with an adhesive layer includes an optical film and the aforementioned adhesive layer disposed on at least one surface of the optical film.

[0135] Examples of optical films include polarizers; protective films provided to protect the surface of polarizers, etc.; polarizing plates with protective films laminated on one or both sides of a polarizer; phase difference films; optical compensation films other than phase difference films; films with anti-glare function and surface anti-reflection function with uneven surface shape; reflective films with reflective function; semi-transparent reflective films with both reflective and transmissive functions; light diffusion films; hard coating films, etc.

[0136] An optical film with an adhesive layer may consist of one or more optical films, or more than two identical optical films. When an optical film with an adhesive layer consists of two or more optical films, an adhesive layer (described later) may be used between the optical films to laminate them; in this case, the adhesive layer may also be part of the optical film. The thickness of the optical film is not particularly limited; for example, it may be 5 μm or more, or 300 μm or less. In this specification, a polarizing plate with a protective film laminated on one or both sides of the polarizer is also referred to as a linear polarizing plate.

[0137] Examples of polarizers include polarizers formed by oriented (e.g., adsorption orientation) of iodine on a polyvinyl alcohol-based resin layer (e.g., uniaxially stretched polyvinyl alcohol film), polarizers formed by oriented liquid crystal compounds and dichroic pigments, etc.

[0138] The protective film is not particularly limited, but is preferably a light-transmitting (preferably optically transparent) thermoplastic resin film. Examples of thermoplastic resins constituting the protective film include chain polyolefin resins (e.g., polyethylene resins, polypropylene resins, etc.), cyclic polyolefin resins, and other polyolefin resins; cellulose ester resins; polyester resins; polycarbonate resins; (meth)acrylic resins; vinyl alcohol resins such as polyvinyl alcohol and polyvinyl acetate; polystyrene resins; and mixtures and copolymers thereof. It should be noted that, in this specification, "(meth)acrylic" refers to "at least one of acrylic and methacrylic resins". These resins may contain one or more additives (e.g., lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, antioxidants, light diffusing agents such as particulates).

[0139] Examples of chain polyolefin resins include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers containing two or more olefins as monomer units.

[0140] Cyclic polyolefin resins are a general term for resins polymerized using cyclic olefins as monomer units. Examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (represented by random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or their derivatives, and their hydrides. Among these, norbornene resins that use norbornene monomers such as norbornene or polycyclic norbornene monomers as cyclic olefins are preferred.

[0141] Cellulose-based resins are partially or completely esterified forms of cellulose, such as cellulose acetate, propionate, and butyrate, as well as mixtures thereof. Examples of cellulose-based resins include triacetylcellulose, diacetylcellulose, cellulose acetate-propionate, and cellulose acetate-butyrate.

[0142] Polyester resins are resins other than the aforementioned cellulose resins containing ester bonds, and may include, for example, condensations of polycarboxylic acids or their derivatives with polyols. As polycarboxylic acids or their derivatives, dicarboxylic acids or their derivatives can be used; examples of polycarboxylic acids or their derivatives include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalate. As polyols, glycols can be used; examples of polyols include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanediol.

[0143] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polycyclohexanediol terephthalate, and polycyclohexanediol naphthalate.

[0144] Polycarbonate resins include, for example, polymers in which monomer units are bonded via carbonate groups. Polycarbonate resins can also be resins called modified polycarbonates, copolymer polycarbonates, etc., where the polymer backbone has been modified.

[0145] The (meth)acrylic resin used as the thermoplastic resin constituting the protective film can be a polymer mainly comprising (meth)acrylate as a monomer unit, preferably a copolymer formed by copolymerizing (meth)acrylate with a small amount of other comonomers. The (meth)acrylic resin used as the thermoplastic resin constituting the protective film can contain methyl methacrylate and methyl acrylate as monomer units, or it can contain methyl methacrylate, methyl acrylate and a third monofunctional monomer as monomer units.

[0146] Examples of third-functional monomers include methacrylates other than methyl methacrylates, such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate; acrylates other than methyl acrylates, such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; hydroxyalkyl acrylates, such as methyl 2-(hydroxymethyl)acrylate, methyl 2-(1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and butyl 2-(hydroxymethyl)acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrene compounds such as chlorostyrene and bromostyrene; substituted styrene compounds such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated anhydrides such as maleic anhydride and citrate anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. These third functional monomers can be used alone or in combination of two or more.

[0147] Thermoplastic resins (meth)acrylate resins that constitute the protective film can further include multifunctional monomers as monomer units. Examples of multifunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, tetradecanethylene glycol di(meth)acrylate, etc., which are substances formed by esterifying the terminal hydroxyl groups of ethylene glycol or its oligomers with acrylic acid or methacrylate; substances formed by esterifying the terminal hydroxyl groups of propylene glycol or its oligomers with acrylic acid or methacrylate; substances formed by esterifying the hydroxyl groups of diols such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate with acrylic acid or methacrylate; and substances formed by esterifying the hydroxyl groups of diols such as bisphenol A, bis... Substances formed by esterifying the terminal hydroxyl groups of phenol A alkyl oxide adducts or their halogenated derivatives with acrylic acid or methacrylate; substances formed by esterifying polyols such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylate, and substances formed by ring-opening addition of glycidyl acrylate or glycidyl methacrylate epoxy groups to their terminal hydroxyl groups; dicarboxylic acids such as succinic acid, adipic acid, terephthalic acid, and phthalic acid, and their halogenated derivatives, and substances formed by ring-opening addition of glycidyl acrylate or glycidyl methacrylate epoxy groups to their alkyl oxide adducts; aryl esters of (meth)acrylate; aromatic divinyl compounds such as divinylbenzene, etc. Ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferred.

[0148] The (meth)acrylic resin constituting the thermoplastic resin of the protective film can be a (meth)acrylic resin modified by reacting the functional groups of the copolymer with each other. Examples of such reactions include, for instance, the intramolecular demethanolization condensation reaction of the methyl ester group of methyl acrylate with the hydroxyl group of 2-(hydroxymethyl)acrylate, and the intramolecular dehydration condensation reaction of the carboxyl group of acrylic acid with the hydroxyl group of 2-(hydroxymethyl)acrylate. Furthermore, the (meth)acrylic resin constituting the thermoplastic resin of the protective film can have any of the following structures: glutarimide derivative, glutaric anhydride derivative, or lactone ring.

[0149] The Tg of the (meth)acrylic resin, which is the thermoplastic resin constituting the protective film, is preferably 90–160°C, more preferably 110–160°C, and even more preferably 120–150°C.

[0150] (Meth)acrylic resins, which are thermoplastic resins that form protective films, may contain additives as needed. Examples of additives include lubricants, anti-blocking agents, heat stabilizers, antioxidants, antistatic agents, lightfastness agents, impact modifiers, and surfactants.

[0151] From the viewpoints of membrane formation properties and impact resistance, (meth)acrylic resins, which constitute the thermoplastic resin of the protective film, can contain acrylic rubber particles as impact modifiers. Acrylic rubber particles refer to particles in which an elastic polymer, primarily composed of acrylates, is a necessary component. Examples include particles with a single-layer structure consisting essentially of this elastic polymer, and particles with a multilayer structure in which this elastic polymer is a single layer. Examples of such elastic polymers include crosslinked elastic copolymers formed by copolymerizing alkyl acrylates as the main component with other vinyl monomers and crosslinking monomers that can copolymerize with them. Examples of alkyl acrylates that are the main component of the elastic polymer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and other alkyl acrylates with 1 to 8 carbon atoms, with acrylics having 4 or more carbon atoms being particularly preferred. Other vinyl monomers capable of copolymerizing with this alkyl acrylate include compounds having one polymerizable carbon-carbon double bond within the molecule; more specifically, examples include methacrylates such as methyl methacrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile. As crosslinking monomers, examples include crosslinking compounds having at least two polymerizable carbon-carbon double bonds within the molecule; more specifically, examples include (meth)acrylates of polyols such as ethylene glycol di(meth)acrylate and butanediol di(meth)acrylate, alkenyl esters of (meth)acrylates such as allyl (meth)acrylate, and divinylbenzene.

[0152] A laminate of a film made of acrylic resin without rubber particles and a film made of acrylic resin containing rubber particles can also be used as a protective film.

[0153] A retardation film is an optical film that displays optical anisotropy. A retardation film can be, for example, a stretched film obtained by stretching (e.g., to 1.01 to 6 times) a resin film containing resins used in the aforementioned protective films, or other resins such as polyvinyl alcohol resins, polyarylate resins, polyimide resins, polyethersulfone resins, polyvinylidene fluoride / polymethyl methacrylate resins, liquid crystal polyester resins, ethylene-vinyl acetate copolymer saponification, and polyvinyl chloride resins. Among these, stretched films obtained by uniaxial or biaxial stretching of polycarbonate resin films, cycloolefin resin films, (meth)acrylic acid resin films, or cellulose resin films are preferred. Furthermore, in this specification, zero-retardation films are also included in retardation films (however, zero-retardation films can also be used as protective films). In addition, films referred to as uniaxial retardation films, wide-viewing-angle retardation films, and low photoelasticity coefficient retardation films can also be used as retardation films.

[0154] Phase retardation films can also be films having an optically anisotropic layer on a substrate, consisting of a polymer formed by the oriented polymerization of a polymeric liquid crystal compound. The substrate can be a thermoplastic resin film used in the aforementioned protective films.

[0155] The retardation film can be, for example, a quarter-wavelength retardation layer with inverse wavelength dispersion, a positive C-plate, a half-wavelength retardation layer with positive wavelength dispersion, or a quarter-wavelength retardation layer with positive wavelength dispersion. The retardation film can be composed of two or more retardation layers; for example, it can have a configuration combining a quarter-wavelength retardation layer with inverse wavelength dispersion and a positive C-plate, or a configuration combining a half-wavelength retardation layer with a quarter-wavelength retardation layer with positive wavelength dispersion, etc.

[0156] The phase retardation film and the protective film, respectively, were tested using the cup method specified in JIS Z 0208 under conditions of 40℃ and 90% relative humidity, and the permeability was found to be 500 g / (m²). 2 • 24 hours or less.

[0157] Optical films used in liquid crystal display devices, such as polarizers, protective films, retardation films, light diffusers, and reflectors, are typically manufactured with a surface protective film attached to their surface (or the side opposite to the adhesive layer if an adhesive layer is present on one side). The surface protective film is used to protect the surface of the optical film, etc., from damage and contamination. Generally, after attaching the optical film to the liquid crystal cell, the surface protective film is peeled off from the optical film.

[0158] Examples of substrates for surface protective films include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; fluorinated polyolefin resins such as polyvinylidene fluoride, polyvinylidene fluoride, and ethylene fluoride; polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; and nylon 6, nylon... Polyamides such as Long 6 and 6; vinyl polymers such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as triacetyl cellulose, diacetyl cellulose, and cellophane; (meth)acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; as well as polystyrene, polycarbonate, polyarylate, and polyimide.

[0159] The bonding layer can be either an adhesive layer or a bonding agent layer. When the bonding layer is an adhesive layer, it can be an adhesive layer other than the aforementioned adhesive layers. In the case of an adhesive layer, the adhesive layer can be composed of an adhesive composition whose main components are resins such as (meth)acrylic resins, rubber resins, urethane resins, ester resins, silicone resins, and polyvinyl ether resins. From the viewpoint of excellent transparency, weather resistance, and heat resistance, an adhesive composition based on a (meth)acrylic resin polymer is suitable. The adhesive composition can be of the active energy radiation curing type or the thermosetting type.

[0160] When the bonding layer is an adhesive layer, the (meth)acrylate resin (base polymer) used as the adhesive composition is, for example, a polymer or copolymer with one or more (meth)acrylate monomers such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize the polar monomer with the base polymer. Examples of polar monomers include (meth)acrylate, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate, which have carboxyl, hydroxyl, amide, amino, or epoxy groups.

[0161] When the bonding layer is an adhesive layer, the adhesive composition used may contain only the aforementioned base polymer, but usually also contains a crosslinking agent. Examples of crosslinking agents include crosslinking agents that are divalent or higher metal ions and form a metal carboxylate salt with a carboxyl group; crosslinking agents that are polyamine compounds and form an amide bond with a carboxyl group; crosslinking agents that are polyepoxide compounds or polyols and form an ester bond with a carboxyl group; and crosslinking agents that are polyisocyanate compounds and form an amide bond with a carboxyl group. Among these, polyisocyanate compounds are preferred.

[0162] When the bonding layer is an adhesive layer, the thickness of the bonding layer is preferably 1 μm or more and 200 μm or less, more preferably 2 μm or more and 100 μm or less, even more preferably 2 μm or more and 80 μm or less, and particularly preferably 3 μm or more and 50 μm or less.

[0163] When the bonding layer is an adhesive layer, the adhesive layer can be made using any suitable adhesive. Water-based adhesives, active energy radiation-cured adhesives, etc., can be used.

[0164] The thickness of the adhesive coating can be set to any suitable value. For example, it can be set in such a way that an adhesive layer with a desired thickness can be obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, further preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0165] Examples of water-based adhesives include aqueous solutions of polyvinyl alcohol resins and water-based two-component urethane emulsion adhesives.

[0166] Active energy ray curing adhesives are adhesives containing curable compounds that are cured by irradiation with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays, with ultraviolet curing adhesives being preferred.

[0167] The aforementioned curable compounds can be cationicly polymerizable or radically polymerizable. Examples of cationicly polymerizable curable compounds include epoxy compounds (compounds having one or more epoxy groups within the molecule), oxetane compounds (compounds having one or more oxetane rings within the molecule), and combinations thereof. Examples of radically polymerizable curable compounds include (meth)acrylic acid compounds (compounds having one or more (meth)acryloyloxy groups within the molecule), other vinyl compounds with radically polymerizable double bonds, and combinations thereof. Cationicly polymerizable and radically polymerizable curable compounds can also be used together. Active energy radiation-curable adhesives typically also contain at least one of a cationic polymerization initiator and a radical polymerization initiator for initiating the curing reaction of the aforementioned curable compounds.

[0168] For purposes such as improving adhesion, surface activation treatment can be applied to the bonding surfaces of at least one of the bonding layer and the optical film. Examples of surface activation treatments include corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), ozone treatment, UV ozone treatment, ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.), and dry treatments. These surface activation treatments can be performed individually or in combination of two or more. Corona treatment is preferred as a surface activation treatment. For example, corona treatment can be performed at an intensity of 1 kJ / m 2 Above and 50kJ / m 2 The following output power is applied. The corona treatment time can be, for example, more than 1 second and less than 1 minute.

[0169] In one embodiment of the optical film with an adhesive layer, it is preferable to attach the release film to the surface of its adhesive layer for temporary adhesive protection until use. The optical film with an adhesive layer and the release film attached can be manufactured, for example, by coating an adhesive composition onto the release film to form an adhesive layer, and further laminating a resin film on the adhesive layer; or by coating an adhesive composition onto a resin film to form an adhesive layer, and attaching the release film to the surface of the adhesive layer.

[0170] Optical films with adhesive layers can be used in display devices such as organic electroluminescent (organic EL) display devices and liquid crystal display devices. For example, they can be attached to the viewing side of the image display element of the display device.

[0171] The laminated structure of an optical film with an adhesive layer is not particularly limited as long as it comprises an optical film and an adhesive layer disposed on at least one side of the optical film.

[0172] Figure 1This is a schematic cross-sectional view showing one embodiment of an optical film with an adhesive layer. Figure 1 The optical film 10 with adhesive layer shown includes a linear polarizer 11 and an adhesive layer 12 disposed on one surface of the linear polarizer 11. The linear polarizer 11 sequentially includes a first protective film 13, an adhesive layer 14, a polarizer 15, an adhesive layer 16, and a second protective film 17. The adhesive layer 12 can be used to adhere to a liquid crystal cell, which is an image display element of a liquid crystal display device. A release film (not shown) can also be disposed on the surface of the adhesive layer 12 opposite to the linear polarizer 11.

[0173] Figure 2 This is a schematic cross-sectional view showing another embodiment of an optical film with an adhesive layer. Figure 2 The optical film 20 with adhesive layer shown comprises, in sequence, an adhesive layer 21, a retardation film 22, an adhesive layer 23, and a linear polarizer 24. The linear polarizer 24 comprises, in sequence, a first protective film 25, an adhesive layer 26, a polarizer 27, an adhesive layer 28, and a second protective film 29. The adhesive layer 21 can be used to adhere to a liquid crystal cell, which is an image display element of a liquid crystal display device. A release film (not shown) can be provided on the surface of the adhesive layer 21 opposite to the retardation film 22.

[0174] Figure 1 and Figure 2 The optical films 10 and 20 with adhesive layers shown are merely examples; optical films with adhesive layers can also have other laminated structures than those described above. For example, optical films with adhesive layers can further have hard coatings, anti-glare films, anti-reflective films, etc.

[0175] <Display Device>

[0176] The aforementioned optical film with an adhesive layer is suitable for use in display devices such as organic EL display devices, liquid crystal display devices, inorganic electroluminescent (inorganic EL) display devices, and electron emission display devices. One example of a display device includes the aforementioned optical film with an adhesive layer.

[0177] Example

[0178] The present invention will be illustrated in more detail below with examples and comparative examples, but the invention is not limited to these examples. Unless otherwise specified, parts and percentages of the amount or content used are indicated on a mass basis.

[0179] <Manufacturing Example 1>

[0180] A mixed solution containing 86.4 parts ethyl acetate, 68.7 parts butyl acrylate, 20.0 parts methyl acrylate, 10.0 parts methyl methacrylate, 1.0 part 2-hydroxyethyl acrylate, and 0.3 parts acrylic acid was added to a reaction vessel equipped with a condenser, a nitrogen inlet, a thermometer, and a stirrer. Next, while purging the air in the reaction vessel with nitrogen to create an oxygen-free atmosphere, the temperature of the mixed solution was raised from room temperature to 60°C. Then, a solution containing 0.10 parts of 2,2'-azobisisobutyronitrile (polymerization initiator) dissolved in 13.7 parts ethyl acetate was added entirely to the mixed solution. After adding the polymerization initiator, this concentration was maintained for 4 hours to generate a (meth)acrylic resin in the reaction vessel. Finally, ethyl acetate was added to the reaction vessel to adjust the concentration of the (meth)acrylic resin to 20% by mass, preparing an ethyl acetate solution of the (meth)acrylic resin of Manufacturing Example 1. The monomer composition (mass %) of the (meth)acrylic resin of Manufacturing Example 1 is shown in Table 1.

[0181] <Manufacturing Examples 2 and 3>

[0182] Except that the monomer composition is as shown in Table 1, ethyl acetate solutions of the (meth)acrylic resins of Examples 2 and 3 were prepared in the same manner as in Example 1.

[0183] [Table 1]

[0184]

[0185] The abbreviations in Table 1 refer to the following monomers.

[0186] BA: n-Butyl acrylate (homopolymer Tg: -54℃)

[0187] MA: Methyl acrylate (homopolymer Tg: 10℃)

[0188] MMA: Methyl methacrylate (homogeneous polymer Tg: 105℃)

[0189] HEA: 2-Hydroxyethyl acrylate

[0190] AA: Acrylic acid

[0191] The Tg of the obtained (meth)acrylic resin was measured as follows. Tg was measured using a differential scanning calorimeter (DSC) "EXSTAR DSC6000" manufactured by SII Nano Technology Co., Ltd., under a nitrogen atmosphere, at a measurement temperature range of -80 to 150°C and a heating rate of 10°C / min. The Tg values ​​of the obtained (meth)acrylic resin were -29°C (Manufacturing Example 1), -37.6°C (Manufacturing Example 2), and -53.2°C (Manufacturing Example 3).

[0192] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the obtained (meth)acrylic resins were determined as follows. Mw and Mn were determined as follows: In a GPC apparatus, three columns were connected in series: one "TSKgel guardcolumnHHR-H(S)" and two "TSKgel GMHHR-H" columns manufactured by Tosoh Corporation. Tetrahydrofuran was used as the eluent. The results were determined by conversion to standard polystyrene under the following conditions: sample concentration 2 mg / mL, sample introduction volume 100 μL, temperature 40°C, and flow rate 1 mL / min. The obtained (meth)acrylic resins had Mw values ​​of 1.62 million (Manufacturing Example 1), 1.52 million (Manufacturing Example 2), and 1.8 million (Manufacturing Example 3), and molecular weight distributions (Mw / Mn) of 2.7 (Manufacturing Example 1), 3.7 (Manufacturing Example 2), and 4.6 (Manufacturing Example 3).

[0193] <Examples 1-2, Comparative Example 1>

[0194] (1) Preparation of adhesive composition

[0195] In the ethyl acetate solution of the (meth)acrylic resin obtained in the above manufacturing example (resin concentration: 20%), crosslinking agents, silane compounds, and ionic compounds of the types and amounts (parts by mass) shown in Table 2 are added relative to 100 parts by mass of the solid content of the solution and mixed. Ethyl acetate is then added further to achieve a solid content concentration of 14% by mass to prepare a solution of the adhesive composition. In Table 2, the amounts (parts by mass) of the (meth)acrylic resin, crosslinking agent, silane compound, and ionic compound are converted from solid content.

[0196] [Table 2]

[0197]

[0198] The details of each compounding component, which is abbreviated in Table 2, are as follows.

[0199] [Cross-linking agent]

[0200] Crosslinking agent: D-103 (ethyl acetate solution of trimethylolpropane adduct of toluene diisocyanate: solid content 75% by mass, manufactured by Mitsui Chemicals Co., Ltd.)

[0201] [Silane compounds]

[0202] Silane compound: 8-epoxypropoxyoctyltrimethoxysilane "KBM-4803", manufactured by Shin-Etsu Chemical Co., Ltd.

[0203] [Ionic compounds]

[0204] Ionic compound: 1-Butyl-3-methylimidazolium tricyanomethane

[0205] (2) Preparation of adhesive layer

[0206] Using an applicator, the solutions of each adhesive composition prepared in (1) above are applied to the release treatment surface of the release film containing a polyethylene terephthalate film ("Diafoil MRV38 (V04)", manufactured by Mitsubishi Chemical Co., Ltd.) with a dry thickness of 25 μm. The film is dried at 100°C for 1 minute to produce an adhesive layer (adhesive sheet) with a release film.

[0207] (3) Determination of gel fraction of adhesive layer

[0208] The release membrane of the adhesive layer (adhesive sheet) with release membrane prepared in (2) was peeled off, and the resulting adhesive layer (adhesive sheet) was stored for 7 days at a temperature of 23°C and a relative humidity of 60%. For the stored adhesive layer (adhesive sheet), the gel fraction [gel fraction at 23°C (G23)] was measured. The gel fraction was measured according to [a] to [d] below. The results are shown in Table 3.

[0209] [a] Place an adhesive layer of approximately 8 cm × approximately 8 cm in the approximate center of a metal mesh of approximately 10 cm × approximately 10 cm made of SUS304 (with its mass set to Wm), and adhere the adhesive layer to the metal mesh.

[0210] [b] Weigh the composite obtained in [a] above and denote its mass as Ws. Next, fold the metal mesh in the composite four times in a manner that encloses the adhesive layer, fix it with a stapler, prepare a test sample, weigh the test sample, and denote its mass as Wb.

[0211] [c] Place the test sample prepared in [b] above into a glass container, add 60 mL of ethyl acetate to immerse the test sample, and store the glass container at room temperature for 3 days.

[0212] [d] Remove the sample from the glass container, dry it at 120°C for 4 hours, weigh it, and set its mass as Wa. Calculate the gel fraction based on the following formula.

[0213] Gel fraction (mass%) = [{Wa - (Wb - Ws) - Wm} / (Ws - Wm)] × 100

[0214] (4) Fabrication of polarizing plates

[0215] A 12 μm thick polarizer was prepared by uniaxially stretching a polyvinyl alcohol film to oriented iodine adsorption. A 40 μm thick protective film containing triacetyl cellulose resin, which had undergone saponification treatment, was then bonded to both sides of the polarizer using an aqueous adhesive, thereby fabricating a polarizing plate.

[0216] (5) Fabrication of polarizing plates with adhesive layers

[0217] After attaching the outer surface of the protective film of the polarizing plate made in (4) above to the side opposite to the isolation film (the side of the adhesive layer) of the adhesive layer with the isolation film made in (2) above using a laminator, the plate is cured for 7 days at a temperature of 23°C and a relative humidity of 60% to obtain a laminate of the isolation film and the polarizing plate with the adhesive layer (laminated optical film).

[0218] (6) Evaluation of heat resistance and durability

[0219] Prepare two laminated optical films prepared in (5) above. In each laminated optical film, after peeling the release film from the polarizer with adhesive layer, the two polarizers with adhesive layers are bonded to both sides of the alkali-free glass substrate (Eagle XG manufactured by Corning) in an orthogonal Nicol configuration, with the exposed adhesive layer of each polarizer in contact with the surface of the alkali-free glass substrate. The resulting test piece (glass substrate with adhesive-coated polarizers attached) is placed in an autoclave at a temperature of 50°C and a pressure of 5 kg / cm². 2 The sample was prepared by applying pressure at 490.3 kPa for 20 minutes. The following heat resistance and durability tests were conducted using the sample.

[0220] [Heat resistance and durability test]

[0221] The prepared evaluation samples were kept in a dry environment at 110°C for 500 hours.

[0222] For each evaluation sample after the test, visually inspect for any lifting or peeling at the interface between the adhesive layer and the glass substrate, and for any foaming of the adhesive layer. Evaluate the heat resistance and durability according to the following evaluation criteria. The results are shown in Table 3.

[0223] A: Almost no changes in appearance such as lifting, peeling, cracking, or foaming were observed (the maximum length of the observed lifting, peeling, cracking, or foaming parts was less than 1 mm).

[0224] B: Observe appearance changes such as floating, peeling, cracking, foaming (the maximum length of the observed floating, peeling, cracking, or foaming part is more than 1mm and less than 3mm).

[0225] C: Obvious changes in appearance such as floating, peeling, cracking, and foaming are observed (the maximum length of the observed floating, peeling, cracking, or foaming part is more than 3mm).

[0226] [Table 3]

[0227]

[0228] Explanation of reference numerals in the attached figures

[0229] 10, 20… Optical film with adhesive layer, 11, 24… Linear polarizer, 12… Adhesive layer, 13, 25… First protective film, 14, 16, 26, 28… Adhesive layer, 15, 27… Polarizer, 17, 29… Second protective film, 21… Adhesive layer, 22… Phase retardation film, 23… Adhesive layer.

Claims

1. An adhesive composition comprising a (meth)acrylic resin, a crosslinking agent, a silane compound, and an ionic compound, The (meth)acrylic resin comprises alkyl (meth)acrylates with a glass transition temperature of less than 0°C, alkyl (meth)acrylates with a glass transition temperature of more than 0°C, and monomers with polar groups as monomer units. The ionic compound contains a cyanide-containing anion.

2. The adhesive composition according to claim 1, wherein, The cyano-containing anion is selected from at least one of tricyanomethane anion, thiocyanate anion, and dicyandiamide anion.

3. The adhesive composition according to claim 1 or 2, wherein, The monomers having polar groups include hydroxyl-containing (meth)acrylates and carboxyl-containing monomers. Based on the total amount of monomer units contained in the (meth)acrylic resin, the content of the hydroxyl-containing (meth)acrylate is 0.3% by mass or more and 5.5% by mass or less. The mass ratio of the content of the carboxyl-containing monomer to the content of the hydroxyl-containing (meth)acrylate is 0.06 or more and 1.0 or less.

4. An adhesive layer comprising the adhesive composition of claim 1 or 2.

5. An optical film with an adhesive layer, comprising an optical film and an adhesive layer as described in claim 4 disposed on at least one surface of the optical film.

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