Adhesive composition and optical film with adhesive layer

Abstract

To provide an adhesive composition capable of forming an adhesive layer excellent in heat-resistant durability.SOLUTION: The adhesive composition contains a (meth)acrylic resin, a crosslinking agent, a silane compound, and an ionic compound. The (meth)acrylic resin contains an alkyl (meth)acrylate whose homopolymer has a glass transition temperature lower than 0°C, an alkyl (meth)acrylate whose homopolymer has a glass transition temperature of 0°C or higher, and a monomer having a polar group as monomer units. The ionic compound contains a cyano group-containing anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition and an optical film with a pressure-sensitive adhesive layer. [Background technology]

[0002] Optical films such as polarizing plates used in image display devices such as liquid crystal displays and organic electroluminescence (organic EL) displays are often used by being attached to other members (for example, image display elements such as liquid crystal cells in liquid crystal display devices) via a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive composition. Patent Document 1 discloses a pressure-sensitive adhesive composition for polarizing plates containing an acrylic resin (A) and an ionic compound (B), wherein the acrylic resin (A) contains a structural moiety derived from methyl methacrylate, and the average number of carbon atoms (α) in the side chain structural moieties of the acrylic resin (A) is 3.3 or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-25417 Summary of the Invention [Problem to be solved by the invention]

[0004] The pressure-sensitive adhesive layer described above may be used in a high-temperature environment. In particular, a pressure-sensitive adhesive layer applicable to an optical film for in-vehicle use, etc., is required to be able to withstand use in a severe high-temperature environment (for example, an environment of 100°C or higher).

[0005] An object of one aspect of the present disclosure is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent heat resistance and durability. [Means for solving the problem]

[0006] The present inventors have found that a pressure-sensitive adhesive layer having excellent heat resistance and durability can be formed by using a pressure-sensitive adhesive composition that uses a specific ionic compound in combination with a specific (meth)acrylic resin.

[0007] In some aspects, the present disclosure provides the following [1] to [5]. [1] A pressure-sensitive adhesive composition comprising a (meth)acrylic resin, a crosslinking agent, a silane compound, and an ionic compound, wherein the (meth)acrylic resin comprises, as monomer units, an alkyl(meth)acrylate having a homopolymer glass transition temperature of less than 0°C, an alkyl(meth)acrylate having a homopolymer glass transition temperature of 0°C or higher, and a monomer having a polar group, and the ionic compound comprises a cyano group-containing anion. [2] The pressure-sensitive adhesive composition according to [1], wherein the cyano group-containing anion is at least one selected from the group consisting of a tricyanomethanide anion, a thiocyanate anion, and a dicyanamide anion. [3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the monomer having a polar group comprises a hydroxy group-containing (meth)acrylate and a carboxy group-containing monomer, the content of the hydroxy group-containing (meth)acrylate is 0.3 mass% or more and 5.5 mass% or less based on the total amount of monomer units contained in the (meth)acrylic resin, and the mass ratio of the content of the carboxy group-containing monomer to the content of the hydroxy group-containing (meth)acrylate is 0.06 or more and 1.0 or less. [4] A pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of [1] to [3]. [5] An optical film with a pressure-sensitive adhesive layer, comprising: an optical film; and the pressure-sensitive adhesive layer according to [4] provided on at least one surface of the optical film. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, there is provided a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent heat resistance and durability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a pressure-sensitive adhesive layer-attached optical film. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another example of a pressure-sensitive adhesive layer-attached optical film. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the following embodiments. In all of the drawings, the scales of the components are appropriately adjusted to make them easier to understand, and the scales of the components shown in the drawings do not necessarily match the scales of the actual components.

[0011] <Adhesive composition> <(Meth)acrylic resin> A pressure-sensitive adhesive composition according to one embodiment includes a (meth)acrylic resin. The (meth)acrylic resin includes, as monomer units, an alkyl(meth)acrylate having a homopolymer glass transition temperature of less than 0°C, an alkyl(meth)acrylate having a homopolymer glass transition temperature of 0°C or higher, and a monomer having a polar group. Because the pressure-sensitive adhesive composition according to one embodiment includes such a (meth)acrylic resin together with an ionic compound described below, a pressure-sensitive adhesive layer including the pressure-sensitive adhesive composition has excellent durability (heat resistance durability) in high-temperature environments (e.g., environments of 100°C or higher).

[0012] In this specification, the glass transition temperature (Tg) of a homopolymer of various monomers such as alkyl (meth)acrylate is measured using a differential scanning calorimeter (DSC) (for example, an EXSTAR DSC6000 manufactured by SII NanoTechnology Inc.) in a nitrogen atmosphere at a temperature rise rate of 10°C / min within a measurement temperature range of, for example, -80 to 150°C.

[0013] The alkyl group in the alkyl(meth)acrylate (hereinafter also referred to as alkyl(meth)acrylate (A1)) having a homopolymer Tg of less than 0°C may be linear or branched. The alkyl(meth)acrylate (A1) may also be an alkyl(meth)acrylate having an alicyclic structure (for example, a cycloalkyl(meth)acrylate). The number of carbon atoms in the alkyl group in the alkyl(meth)acrylate (A1) may be 2 or more, or 3 or more, and may be 12 or less, 10 or less, or 8 or less.

[0014] Examples of the alkyl (meth)acrylate (A1) include alkyl acrylates having an alkyl group carbon number of 2 to 12, such as ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, i-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, i-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, i-nonyl acrylate, n-decyl acrylate, i-decyl acrylate, and n-dodecyl acrylate; and alkyl methacrylates having an alkyl group carbon number of 5 to 12, such as n-pentyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, and n-dodecyl methacrylate.

[0015] These alkyl (meth)acrylates (A1) may be used singly or in combination of two or more. From the viewpoint of further improving the conformability (or flexibility or adhesiveness) to the optical film, the alkyl (meth)acrylate (A1) may include an alkyl acrylate having an alkyl group with 2 to 10 carbon atoms, an alkyl acrylate having an alkyl group with 3 to 8 carbon atoms, or an alkyl acrylate having an alkyl group with 4 to 6 carbon atoms.

[0016] The Tg of the alkyl (meth)acrylate (A1) may be −10° C. or lower, −20° C. or lower, or −30° C. or lower, and may be, for example, −100° C. or higher, −80° C. or higher, or −60° C. or higher.

[0017] The content of the alkyl (meth)acrylate (A1) may be 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 90% by mass or less, 80% by mass or less, or 75% by mass or less, based on the total amount of monomer units contained in the (meth)acrylic resin.

[0018] The alkyl group in the alkyl(meth)acrylate (hereinafter also referred to as alkyl(meth)acrylate (A2)) having a homopolymer Tg of 0°C or higher may be linear or branched. The alkyl(meth)acrylate (A2) may also be an alkyl(meth)acrylate having an alicyclic structure (for example, a cycloalkyl(meth)acrylate). The number of carbon atoms in the alkyl group in the alkyl(meth)acrylate (A2) may be 1 or more, or 2 or more, and may be 12 or less, 10 or less, or 8 or less.

[0019] Examples of the alkyl(meth)acrylate (A2) include alkyl(meth)acrylates having a homopolymer Tg of 0°C or higher and lower than 30°C, and alkyl(meth)acrylates having a homopolymer Tg of 30°C or higher.

[0020] An example of an alkyl(meth)acrylate having a homopolymer Tg of 0° C. or higher and lower than 30° C. is methyl acrylate.

[0021] Examples of alkyl (meth)acrylates having a homopolymer Tg of 30°C or higher include alkyl methacrylates having an alkyl group having 1 to 6 carbon atoms, such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, propyl methacrylate, isopropyl methacrylate, 3,3-dimethylbutyl methacrylate, and 3,3-dimethyl-2-butyl methacrylate, as well as n-stearyl methacrylate, stearyl acrylate, t-butyl acrylate, and isobornyl acrylate.

[0022] When the alkyl(meth)acrylate having a homopolymer Tg of 30°C or higher is an alkyl(meth)acrylate having an alicyclic structure, the alicyclic structure may be a cycloparaffin structure having a carbon number of typically 5 or more (e.g., 5 to 7). Examples of alkyl(meth)acrylates having an alicyclic structure and having a homopolymer Tg of 30°C or higher include isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, cyclododecyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, and 1-adamantyl methacrylate.

[0023] These alkyl (meth)acrylates (A2) may be used singly or in combination of two or more. The alkyl (meth)acrylate (A2) may include both alkyl (meth)acrylates having a homopolymer Tg of 0° C. or higher and lower than 30° C., and alkyl (meth)acrylates having a homopolymer Tg of 30° C. or higher.

[0024] The alkyl(meth)acrylate having a homopolymer Tg of 0° C. or higher and lower than 30° C. may be, for example, methyl acrylate.

[0025] The alkyl(meth)acrylate having a homopolymer Tg of 30°C or higher may be, for example, at least one selected from the group consisting of alkyl methacrylates having an alkyl group with 1 to 4 carbon atoms and alkyl methacrylates having an alicyclic structure, or may be at least one selected from the group consisting of methyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, and cyclohexyl methacrylate.

[0026] The Tg of the alkyl (meth)acrylate, whose homopolymer has a Tg of 0°C or more and less than 30°C, may be 2°C or more, or 5°C or more, and may be 25°C or less, 20°C or less, or 15°C or less.

[0027] The Tg of an alkyl (meth)acrylate whose homopolymer has a Tg of 30°C or higher may be 50°C or higher, 60°C or higher, 80°C or higher, or 100°C or higher, from the viewpoint of providing a pressure-sensitive adhesive layer with better mechanical strength and heat resistance durability, and may be, for example, 200°C or lower, 150°C or lower, or 120°C or lower.

[0028] The content of alkyl (meth)acrylate having a homopolymer Tg of 0°C or more and less than 30°C may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 50% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less, based on the total amount of monomer units contained in the (meth)acrylic resin.

[0029] From the viewpoint of excellent mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the content of the alkyl (meth)acrylate having a homopolymer Tg of 30°C or higher may be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 5% by mass or more, and may be 30% by mass or less, 20% by mass or less, 15% by mass or less, or 13% by mass or less, based on the total amount of monomer units contained in the (meth)acrylic resin. When the content of the alkyl (meth)acrylate having a homopolymer Tg of 30°C or higher is within the above range, the cohesiveness of the pressure-sensitive adhesive is improved, thereby further improving the mechanical strength of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer also has excellent flexibility and adhesiveness, which is more advantageous from the viewpoint of heat resistance durability.

[0030] The content of the alkyl (meth)acrylate (A2) may be 10% by mass or more, 20% by mass or more, or 25% by mass or more, and may be 50% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total amount of monomer units contained in the (meth)acrylic resin.

[0031] The monomer having a polar group is a monomer copolymerizable with the alkyl(meth)acrylate (A1) and alkyl(meth)acrylate (A2) described above, and has a polar group such as a hydroxy group, a carboxy group, a substituted or unsubstituted amino group, or a heterocyclic group such as an epoxy group. The monomer having a polar group may have, for example, at least one polar group of a hydroxy group or a carboxy group. The monomer having a polar group may include, for example, at least one of a (meth)acrylate having a hydroxy group and a monomer having a carboxy group.

[0032] The monomer having a hydroxy group may be a (meth)acrylate having a hydroxy group (hereinafter also referred to as "hydroxy group-containing (meth)acrylate"). The hydroxy group-containing (meth)acrylate may be, for example, a (meth)acrylate having a hydroxyalkyl group. The number of carbon atoms in the hydroxyalkyl group may be 1 or more, or 2 or more, and may be 12 or less, 10 or less, 8 or less, 5 or less, or 4 or less.

[0033] The (meth)acrylate having a hydroxy group may further contain, in addition to the hydroxy group, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), a cycloalkyl group (e.g., a cyclopentyl group, a cyclohexyl group, etc.), an aryl group (e.g., a phenyl group, and an alkylphenyl group (e.g., a tolyl group, a xylyl group, etc.)), an aralkyl group (e.g., a benzyl group), an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, etc.), a polyoxyalkylene group (e.g., a dioxyethylene group, etc.), a cycloalkoxy group (e.g., The (meth)acrylate may have a substituent such as a cycloalkyloxy group having 5 to 10 carbon atoms such as a cyclohexyloxy group, an aryloxy group (e.g., a phenoxy group), an aralkyloxy group (e.g., a benzyloxy group), an alkylthio group (e.g., an alkylthio group having 1 to 4 carbon atoms such as a methylthio group or an ethylthio group), a cycloalkylthio group (e.g., a cyclohexylthio group), an arylthio group (e.g., a thiophenoxy group), an aralkylthio group (e.g., a benzylthio group), an acyl group (e.g., an acetyl group), a nitro group, or a cyano group. The (meth)acrylate having a hydroxy group may be, for example, a (meth)acrylate having a hydroxy group and one or more selected from the group consisting of a halogen atom, an alkoxy group, and an aryloxy group.

[0034] Examples of hydroxy group-containing (meth)acrylates include 1-hydroxy C1-C8 alkyl (meth)acrylates such as 1-hydroxymethyl (meth)acrylate, 1-hydroxyethyl (meth)acrylate, 1-hydroxyheptyl (meth)acrylate, 1-hydroxybutyl (meth)acrylate, and 1-hydroxypentyl (meth)acrylate; 2-hydroxy C2-C9 alkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxypentyl (meth)acrylate, and 2-hydroxyhexyl (meth)acrylate; 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate; acrylate, 3-hydroxy C3 to C10 alkyl (meth)acrylates such as 3-hydroxypentyl (meth)acrylate, 3-hydroxyhexyl (meth)acrylate, and 3-hydroxyheptyl (meth)acrylate; 4-hydroxy C4 to C11 alkyl (meth)acrylates such as 4-hydroxybutyl (meth)acrylate, 4-hydroxypentyl (meth)acrylate, 4-hydroxyhexyl (meth)acrylate, 4-hydroxyheptyl (meth)acrylate, and 4-hydroxyoctyl (meth)acrylate; 2-chloro-2-hydroxypropyl (meth)acrylate; 3-chloro-2-hydroxypropyl (meth)acrylate; and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

[0035] These hydroxy group-containing (meth)acrylates may be used alone or in combination of two or more. From the viewpoint of providing superior mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the hydroxy group-containing (meth)acrylate may be a hydroxyalkyl (meth)acrylate, and may be at least one selected from the group consisting of 2-hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; and 3-hydroxyalkyl (meth)acrylates such as 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 3-hydroxypentyl (meth)acrylate. From the viewpoint of providing superior mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the hydroxy group-containing (meth)acrylate may include a 2-hydroxyalkyl (meth)acrylate or may include 2-hydroxyethyl (meth)acrylate. 2-Hydroxyethyl (meth)acrylate is advantageous for forming a uniform crosslinked structure, and can therefore further improve the mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer.

[0036] From the viewpoint of achieving superior mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the content of the hydroxy group-containing (meth)acrylate may be 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more, and may 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, based on the total amount of monomer units contained in the (meth)acrylic resin. The content of the hydroxy group-containing (meth)acrylate may be, for example, 0.3% by mass or more and 5.5% by mass or more, 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.

[0037] Examples of monomers having a carboxy group (hereinafter also referred to as "carboxy group-containing monomers") include (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, and carboxyalkyl (meth)acrylates (e.g., carboxyethyl (meth)acrylate and carboxypentyl (meth)acrylate). These carboxy group-containing monomers may be used alone or in combination of two or more. The carboxy group-containing monomer may contain acrylic acid. Acrylic acid promotes the reaction between the hydroxy group-containing (meth)acrylate and the crosslinking agent and can contribute to the formation of a uniform crosslinked structure, thereby further improving the mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer.

[0038] The content of the carboxy group-containing monomer may be 0.01 mass% or more, 0.05 mass% or more, or 0.1 mass% or more, based on the total amount of monomer units contained in the (meth)acrylic resin, from the viewpoint of the mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, and may be 5.5 mass% or less, 3 mass% or less, 2 mass% or less, or 1 mass% or less.

[0039] The mass ratio of the content of the carboxyl group-containing monomer to the content of the hydroxyl group-containing (meth)acrylate (carboxyl group-containing monomer content / hydroxyl group-containing (meth)acrylate content) may be 0.06 or more, 0.08 or more, or 0.1 or more, and may be 1.0 or less, 0.8 or less, or 0.7 or less. When the polar group-containing monomer includes a hydroxyl group-containing (meth)acrylate and a carboxyl group-containing monomer, and the mass ratio of the content of the carboxyl group-containing monomer to the content of the hydroxyl group-containing (meth)acrylate is within the above range, a crosslinked structure is likely to be uniformly formed in the adhesive, and the mechanical strength and heat resistance durability of the adhesive layer tend to be better. The mass ratio of the content of the carboxyl group-containing monomer to the content of the hydroxyl group-containing (meth)acrylate may be, for example, 0.06 or more and 1.0 or less, or 0.1 or more and 0.7 or less.

[0040] Examples of (meth)acrylates having a substituted or unsubstituted amino group include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. These (meth)acrylates having a substituted or unsubstituted amino group may be used alone or in combination of two or more. From the viewpoint of further improving the releasability of a separate film when laminated on the pressure-sensitive adhesive layer, the (meth)acrylic resin may be substantially free of a monomer having a substituted or unsubstituted amino group as a monomer unit. Note that "the (meth)acrylic resin is substantially free of a monomer having a substituted or unsubstituted amino group" means that the content of (meth)acrylates having a substituted or unsubstituted amino group is less than 1.0 mass% based on the total amount of monomer units contained in the (meth)acrylic resin.

[0041] Examples of (meth)acrylates having a heterocyclic group such as an epoxy group 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 a heterocyclic group may be used alone or in combination of two or more.

[0042] The (meth)acrylic resin may contain other monomers as monomer units, such as substituted alkyl (meth)acrylates, (meth)acrylamide monomers, styrene monomers, vinyl monomers, and monomers having multiple (meth)acryloyl groups in the molecule.

[0043] The substituted alkyl(meth)acrylate is, for example, an alkyl(meth)acrylate in which a substituent (excluding polar groups such as carboxyl groups) is introduced into the alkyl group of the alkyl(meth)acrylate (i.e., the hydrogen atom of the alkyl group is substituted with the substituent). Examples of the substituent include an aryl group (e.g., a phenyl group), an aryloxy group (e.g., a phenoxy group), and an alkoxy group (e.g., a methoxy group, an ethoxy group). Examples of the substituted alkyl acrylate include an alkoxyalkyl acrylate (e.g., 2-methoxyethyl acrylate, ethoxymethyl acrylate), an aryloxyalkyl acrylate (e.g., phenoxyethyl acrylate), an aryloxypolyalkylene glycol monoacrylate, and a polyalkylene glycol monoacrylate. These substituted alkyl(meth)acrylates may be used alone or in combination of two or more.

[0044] Examples of (meth)acrylamide monomers include N-methylol (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. Propyl (meth)acrylamide, N-(3-dimethylaminopropyl) (meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl) (meth)acrylamide, N-[2-(2-oxo-1-imidazolidinyl)ethyl] (meth)acrylamide, 2-(meth)acryloylamino-2-methyl-1-propanesulfonic acid, N-(methoxymethyl) (meth)acrylamide, N-(ethoxymethyl) (meth)acrylamide, N-(propoxymethyl) (meth)acrylamide N-(1-methylethoxymethyl)(meth)acrylamide, N-(1-methylpropoxymethyl)(meth)acrylamide, N-(2-methylpropoxymethyl)(meth)acrylamide (also known as N-(isobutoxymethyl)(meth)acrylamide), N-(butoxymethyl)(meth)acrylamide, N-(1,1-dimethylethoxymethyl)(meth)acrylamide, N-(2-methoxyethyl)(meth)acrylamide, N-(2-ethoxyethyl)(meth)acrylamide Examples of the (meth)acrylamide monomer include N-(2-propoxyethyl)(meth)acrylamide, N-[2-(1-methylethoxy)ethyl](meth)acrylamide, N-[2-(1-methylpropoxy)ethyl](meth)acrylamide, N-[2-(2-methylpropoxy)ethyl](meth)acrylamide (also known as N-(2-isobutoxyethyl)acrylamide), N-(2-butoxyethyl)(meth)acrylamide, and N-[2-(1,1-dimethylethoxy)ethyl](meth)acrylamide. These (meth)acrylamide monomers may be used alone or in combination of two or more.

[0045] Examples of styrene-based monomers include styrene, alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene, halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene, nitrostyrene, acetylstyrene, methoxystyrene, and divinylbenzene. These styrene-based monomers may be used alone or in combination of two or more.

[0046] Examples of vinyl-based monomers include fatty acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl laurate; vinyl halides such as vinyl chloride and vinyl bromide; vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyls such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; and conjugated dienes such as butadiene, isoprene, and chloroprene. These vinyl-based monomers may be used alone or in combination of two or more.

[0047] Examples of monomers having multiple (meth)acryloyl groups in the molecule 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, tripropylene glycol di(meth)acrylate, and other monomers having two (meth)acryloyl groups in the molecule; and trimethylolpropane tri(meth)acrylate, and other monomers having three (meth)acryloyl groups in the molecule. These monomers having multiple (meth)acryloyl groups in the molecule may be used alone or in combination of two or more.

[0048] From the viewpoint of achieving superior mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the weight average molecular weight (Mw) of the (meth)acrylic resin may be 1 million or more, 1.1 million or more, 1.2 million or more, 1.3 million or more, or 1.5 million or more, and may be 3.2 million or less, 3.1 million or less, 3 million or less, 2.9 million or less, 2.5 million or less, or 1.7 million or less. The Mw of the (meth)acrylic resin may be, for example, 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.

[0049] The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth)acrylic resin, may be, for example, 1.5 or more, 2 or more, or 2.5 or more, and may 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 into standard polystyrene.

[0050] From the viewpoint of achieving superior mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer, the Tg of the (meth)acrylic resin may be −45° C. or higher, −40° C. or higher, −38° C. or higher, or −35° C. or higher, and may be −10° C. or lower, −15° C. or lower, −20° C. or lower, or −25° C. or lower. The Tg of the (meth)acrylic resin may be, for example, −45° C. to −10° C., −40° C. to −15° C., or −38° C. to −20° C. The Tg of the (meth)acrylic resin is determined by DSC measurement in a nitrogen atmosphere at a heating rate of 10° C. / min.

[0051] The (meth)acrylic resin (or a mixture thereof when two or more types are combined) may have a viscosity of 20 Pa s or less, or even 0.1 Pa s or more and 7 Pa s or less, at 25°C when dissolved in ethyl acetate to a concentration of 20% by mass. The viscosity can be measured using a Brookfield viscometer.

[0052] The content of the (meth)acrylic resin may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, and may be 99% by mass or less, or 98% by mass or less, based on the total mass of the solid content in the pressure-sensitive adhesive composition.

[0053] The (meth)acrylic resin can be produced by known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. A polymerization initiator may be used in the production of the (meth)acrylic resin. The polymerization initiator is used in an amount of, for example, 0.001 to 5 parts by mass relative to 100 parts by mass of the total of all monomers used in the production of the (meth)acrylic resin. The (meth)acrylic resin may also be produced by a method in which polymerization is promoted by active energy rays such as ultraviolet rays.

[0054] Examples of the polymerization initiator include a thermal polymerization initiator, a photopolymerization initiator, etc. Examples of the thermal polymerization initiator include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-hydroxymethylpropionitrile); lauryl peroxide; Examples of suitable photopolymerization initiators include organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, 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) ketone. Other examples of polymerization initiators include redox initiators that use a peroxide in combination with a reducing agent.

[0055] (Meth)acrylic resins are produced, for example, by solution polymerization. One example of the solution polymerization method involves mixing monomers and an organic solvent to prepare a mixed solution, adding a thermal polymerization initiator to the mixed solution under a nitrogen atmosphere, and stirring the mixture at 40 to 90°C (e.g., 60 to 80°C) for approximately 3 to 10 hours. To control the reaction, the monomers and thermal polymerization initiator may be added continuously or intermittently during polymerization. The monomers and thermal polymerization initiator may be added in a dissolved state in an 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 propyl alcohol and isopropyl alcohol; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0056] <Crosslinking agent> The pressure-sensitive adhesive composition according to one embodiment contains a crosslinking agent. Since the (meth)acrylic resin contains a monomer having a polar group as a monomer unit, the polar group is present in the (meth)acrylic resin. The crosslinking agent can be a compound that reacts with the polar group present in the (meth)acrylic resin to form a crosslink. Examples of crosslinking agents include isocyanate-based compounds, epoxy-based compounds, aziridine-based compounds, and metal chelate-based compounds. Of these, isocyanate-based compounds, epoxy-based compounds, and aziridine-based compounds have at least two functional groups in the molecule that can react with the polar group in the (meth)acrylic resin. These crosslinking agents may be used alone or in combination of two or more.

[0057] The crosslinking agent preferably contains an isocyanate compound. The isocyanate compound is preferably a compound having at least two isocyanate groups (-NCO) in the molecule, and examples thereof include aliphatic isocyanate compounds (e.g., hexamethylene diisocyanate), alicyclic isocyanate compounds (e.g., isophorone diisocyanate), and aromatic isocyanate compounds (e.g., tolylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate). The crosslinking agent may also be an adduct of an isocyanate compound with a polyhydric alcohol compound (for example, an adduct with glycerol, trimethylolpropane, or the like), an isocyanurate, a biuret-type compound, or a derivative of a urethane prepolymer-type isocyanate compound subjected to an addition reaction with a polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol, or the like. These crosslinking agents may be used alone or in combination of two or more.

[0058] An epoxy compound is a compound having at least two epoxy groups in its molecule. Specific examples of the compound include bisphenol A epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane. These epoxy compounds may be used alone or in combination of two or more.

[0059] Aziridine compounds are compounds that have at least two three-membered ring skeletons, each consisting of one nitrogen atom and two carbon atoms, also known as ethyleneimines. Specific examples of these compounds include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1-(2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tris-β-aziridinylpropionate, and tetramethylolmethane-tris-β-aziridinylpropionate.

[0060] Examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetoacetate is coordinated with a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, or zirconium.

[0061] Among these, the crosslinking agent may be, for example, at least one selected from the group consisting of aromatic isocyanate compounds, aliphatic isocyanate compounds, and their adducts with polyhydric alcohol compounds. When the crosslinking agent contains an aromatic isocyanate compound and / or its adduct with polyhydric alcohol compounds, a uniform crosslinked structure is easily formed, and the mechanical strength and heat resistance durability of the pressure-sensitive adhesive layer tend to be easily improved.

[0062] The content of the crosslinking agent may be 0.01 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more, and may be 5 parts by mass or less, 3 parts by mass or less, or 2 parts by mass or less, relative to 100 parts by mass of the solid content of the (meth)acrylic resin (the total amount when two or more types are used).

[0063] <Silane compounds> The pressure-sensitive adhesive composition according to one embodiment includes a silane compound. The silane compound may include, for example, a compound represented by the following formula (1-1): [ka] In the above formula (1-1), R 111 represents an alkyl group having 1 to 5 carbon atoms, and R 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 represents an alkylene group having 1 to 20 carbon atoms, or a group in which at least one -CH2- contained in an alkylene group having 1 to 20 carbon atoms is substituted with -NH- or -O-, and X represents a thiol group (-SH), an amino group (-NH2), an epoxy group, or an alicyclic epoxy group.

[0064] R in formula (1-1) 111 ~R 113 The alkyl groups having 1 to 5 carbon atoms as the alkyl groups may each 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 the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, and a pentyl group such as an n-pentyl group, an i-pentyl group, or a t-pentyl group.

[0065] R in formula (1-1) 112 and R 113 The alkoxy groups having 1 to 5 carbon atoms as the alkoxy groups may each 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 the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an i-butoxy group, a t-butoxy group, and a pentyloxy group such as an n-pentyloxy group, an i-pentyloxy group, or a t-pentyloxy group.

[0066] L in formula (1-1) 1 The alkylene group having 1 to 20 carbon atoms as the alkylene group is, for example, —(CH2) n- (n represents an integer of 1 to 20), where n (the number of carbon atoms in the alkylene group) may be 2 or more, 4 or more, 6 or more, or 8 or more, and may be 18 or less, 15 or less, or 12 or less.

[0067] L in formula (1-1) 1 In the alkylene group having 1 to 20 carbon atoms, in which at least one -CH2- (methylene group) contained therein is substituted with -NH- or -O-, the alkylene group having 1 to 20 carbon atoms (the alkylene group before at least one -CH2- is substituted with -NH- or -O-) is, for example, -(CH2) n - (n represents an integer of 1 to 20), where n (the number of carbon atoms in the alkylene group) may be 2 or more, 4 or more, 6 or more, or 8 or more, and may be 18 or less, 15 or less, or 12 or less.

[0068] The above L 1 In the case where at least one -CH2- contained in the alkylene group having 1 to 20 carbon atoms is substituted with -NH- or -O-, only one methylene group contained in the alkylene group having 1 to 20 carbon atoms may be substituted with -NH- or -O-, or two or more methylene groups contained in the alkylene group having 1 to 20 carbon atoms may each independently be substituted with -NH- or -O-. When two or more methylene groups are substituted, the multiple substituents (-NH- and / or -O-) may be separated from each other by alkylene groups having two or more carbon atoms.

[0069] The epoxy group represented by X in formula (1-1) can be a group represented by the following formula (a1). [ka] In formula (a1), * represents a bond.

[0070] Examples of the alicyclic epoxy group represented by X in formula (1-1) include monovalent groups in which one hydrogen atom has been removed from the structure represented by formula (a2) below. [ka] In formula (a2), n represents an integer of 1 to 5. n may be 1 to 3, or 1 to 2.

[0071] Examples of the silane compound represented by formula (1-1) include 3-glycidoxypropyltrialkoxysilanes such as 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane; 3-glycidoxypropylalkyldialkoxysilanes such as 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropylmethyldimethoxysilane; 8-glycidoxyoctyltrialkoxysilanes such as 8-glycidoxyoctyltrimethoxysilane and 8-glycidoxyoctyltriethoxysilane; and 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0072] The silane compound may include a silane compound other than the compound represented by formula (1-1). Examples of silane compounds other than the compound represented by formula (1-1) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 1,3-bis(3'-trimethoxypropyl)urea, 1,6-bis(trimethoxysilyl)hexane, and 1,8-bis(trimethoxysilyl)octane.

[0073] The silane compound may include a silicone oligomer. Examples of the silicone oligomer include mercaptopropyl group-containing oligomers such as 3-mercaptopropyltrimethoxysilane-tetramethoxysilane oligomer (an oligomer containing 3-mercaptopropyltrimethoxysilane and tetramethoxysilane as monomer units; the same applies to similar expressions below), 3-mercaptopropyltrimethoxysilane-tetraethoxysilane oligomer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane oligomer, and 3-mercaptopropyltriethoxysilane-tetraethoxysilane oligomer; mercaptomethyltrimethoxysilane-tetramethoxysilane oligomer, mercaptomethyltrimethoxysilane-tetraethoxysilane oligomer, mercaptomethyltriethoxysilane-tetramethoxysilane oligomer, and mercaptomethyltriethoxysilane-tetraethoxysilane oligomer. mercaptomethyl group-containing oligomers such as 3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomer, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomer, and 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer; methacryloyloxypropyl group-containing oligomers such as 3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer, and 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane oligomer;3-Acryloyloxypropyltrimethoxysilane-tetramethoxysilane oligomer, 3-Acryloyloxypropyltrimethoxysilane-tetraethoxysilane oligomer, 3-Acryloyloxypropyltriethoxysilane-tetramethoxysilane oligomer, 3-Acryloyloxypropyltriethoxysilane-tetraethoxysilane oligomer, 3-Acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane oligomer, 3-Acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane oligomer, 3-Acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane oligomer, 3-Acryloyloxypropylmethyldimethoxysilane and vinyl group-containing oligomers such as vinyltrimethoxysilane-tetramethoxysilane oligomer, vinyltrimethoxysilane-tetraethoxysilane oligomer, vinyltriethoxysilane-tetramethoxysilane oligomer, vinyltriethoxysilane-tetraethoxysilane oligomer, vinyltriethoxysilane-tetraethoxysilane oligomer, vinylmethyldimethoxysilane-tetramethoxysilane oligomer, vinylmethyldimethoxysilane-tetraethoxysilane oligomer, vinylmethyldiethoxysilane-tetramethoxysilane oligomer, and vinylmethyldiethoxysilane-tetraethoxysilane oligomer.

[0074] The content of the silane compound may be 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, or 0.2 parts by mass or more, relative to 100 parts by mass of the solid content of the (meth)acrylic resin (the total amount when two or more types are used), from the viewpoint of easily improving the adhesion (or adhesiveness) between the pressure-sensitive adhesive layer and a metal layer, a glass substrate, etc., and being advantageous for improving peel resistance, etc., and may be 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, or 2 parts by mass or less, from the viewpoint of easily suppressing bleed-out of the silane compound from the pressure-sensitive adhesive layer.

[0075] <Ionic compounds> The pressure-sensitive adhesive composition according to one embodiment includes an ionic compound. The ionic compound includes a cyano group-containing anion. The inclusion of the cyano group-containing anion in the ionic compound contributes to further improvement of the antistatic properties of the pressure-sensitive adhesive composition.

[0076] The cyano group-containing anion may be, for example, an anion represented by the following formula (1): [ka] 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 2 represents an organic linking group, a and b each independently represent an integer of 0 or greater, and c and d each independently represent an integer of 1 or greater. The value of a may be 0, and the value of b may be 0.

[0077] Y in formula (1) is preferably boron, carbon, nitrogen, or sulfur. Z in formula (1) may be an alkyl group, and the alkyl group may have 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group and an ethyl group. Z may be a hydrogen atom, a methyl group, or a trifluoromethyl group.

[0078] L in equation (1) 2 may be, for example, -S-, -O-, -SO2-, or -CO-. 2 may be -SO2- or -CO-.

[0079] a and b each independently represent an integer of 0 or greater, and c and d each independently represent an integer of 1 or greater. However, since the valence of the anion in formula (1) is −1, the values ​​of a and d are determined so as to satisfy the relationship y−1=a+d, where y is the valence of Y.

[0080] Examples of anions represented by formula (1) include C - (CN)3 (tricyanomethanide anion), S -(CN) (thiocyanate anion), N - (CN)2 (dicyanamide anion), N - (-SO2-CN)2, B - (CN)4 (tetracyanoborate anion), etc. The cyano group-containing anion may be at least one selected from the group consisting of tricyanomethanide anion, thiocyanate anion, and dicyanamide anion.

[0081] The ionic compound contains a cation in addition to the cyano-containing anion. The cation may be inorganic or organic. Examples of inorganic cations include the lithium cation [Li + ], sodium cation [Na + ], potassium cation [K + alkali metal cations such as beryllium cations [Be 2+ 〕, magnesium cation (Mg 2+ ], calcium cation [Ca 2+ ], transition metal cations, and rare earth metal cations.

[0082] The cation is preferably an organic cation, more preferably a substituted or unsubstituted imidazolium cation, pyrrolidinium 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. The substituted imidazolium cation may be, for example, a 1,3-alkyl-substituted imidazolium cation (e.g., 1-butyl-3-methylimidazolium cation).

[0083] The organic cation may be, for example, a cation represented by the following formula (2): [ka] In formula (2), R 1 ~R4 each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, or an optionally substituted heterocyclic group; R 1 ~R 4 Two or more selected from the group consisting of may be bonded to each other to form a ring.

[0084] R 1 ~R 4 R are preferably each independently an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an aryl group which may have a substituent, or a heterocyclic group which may have a substituent. 1 ~R 4 As the alkyl group, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an aryl group which may have a substituent, and a heterocyclic group which may have a substituent can be used without any particular limitation.

[0085] R 1 ~R 4 For example, R 1 and R 2 , R 2 and R 3 , R 3 and R 4 , and R 4 and R 1 may each independently be bonded to each other to form a ring together with the nitrogen atom to which they are bonded, and R 1 and R 2 and R 3 , R 2 and R 3 and R 4 , and R 3 and R 4 and R 1 may each independently bond to each other to form a ring together with the nitrogen atom to which they are bonded.

[0086] R 1 ~R 4may each independently be an alkyl group which may have a substituent, or an aryl group which may have a substituent. 1 ~R 4 Three selected from the group consisting of R 1 ~R 4 may form an unsaturated ring structure (including an aromatic ring structure) containing an unsaturated bond together with the N atom to which it is bonded.

[0087] The organic cation may be, for example, a cation represented by the following formula (3): [ka] In formula (3), R 5 ~R 8 each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, or an optionally substituted heterocyclic group; R 5 ~R 8 Two or more selected from the group consisting of may be bonded to each other to form a ring.

[0088] The ionic compound may be solid at room temperature (e.g., 23°C). An ionic compound that is solid at room temperature can maintain antistatic performance for a longer period of time than an ionic compound that is liquid at room temperature.

[0089] The content of the ionic compound may 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 content of the (meth)acrylic resin, from the viewpoint of achieving better antistatic properties, and may 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, from the viewpoint of achieving better moisture and heat resistance of the pressure-sensitive adhesive layer-attached optical film.

[0090] <Other ingredients> The pressure-sensitive adhesive composition may further contain a solvent, a crosslinking catalyst, an ultraviolet absorber, a weather stabilizer, a tackifier, a plasticizer, a softener, a dye, a pigment, an inorganic filler, light-scattering fine particles, a rust inhibitor, a release agent, a resin other than a (meth)acrylic resin, etc. In addition, the pressure-sensitive adhesive composition may contain an ultraviolet-curable compound. When the pressure-sensitive adhesive composition contains an ultraviolet-curable compound, a pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive composition, and then the pressure-sensitive adhesive layer is cured by irradiation with ultraviolet light, thereby making it possible to obtain a harder pressure-sensitive adhesive layer.

[0091] When the pressure-sensitive adhesive composition contains a crosslinking catalyst together with a crosslinking agent, the pressure-sensitive adhesive layer can be prepared with shorter aging time. Furthermore, when the pressure-sensitive adhesive composition contains a crosslinking catalyst, lifting or peeling at the interface between the pressure-sensitive adhesive layer and an adjacent member, as well as foaming of the pressure-sensitive adhesive layer, can be more effectively suppressed, and the reworkability of the pressure-sensitive adhesive layer (the property of easily peeling the pressure-sensitive adhesive layer after adhering it to an adherend) can also be further improved. Examples of crosslinking catalysts include amine-based compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resins, and melamine resins. When an amine-based compound is blended as a crosslinking catalyst in the pressure-sensitive adhesive composition, an isocyanate-based compound is preferred as the crosslinking agent.

[0092] The pressure-sensitive adhesive composition described above can be prepared by mixing the above components. The pressure-sensitive adhesive composition may have a gel fraction of, for example, 50% to 98%, preferably 60% to 95%, or 70% to 90%. The gel fraction can be measured according to the measurement method described in the Examples section below. <Adhesive layer>

[0093] The pressure-sensitive adhesive layer according to one embodiment includes the pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive layer may consist of the pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive layer can be obtained, for example, by a method including dissolving or dispersing each component contained in the pressure-sensitive adhesive composition in a solvent to prepare a solvent-containing pressure-sensitive adhesive composition, and applying the pressure-sensitive adhesive composition onto a substrate film and drying it. The pressure-sensitive adhesive layer has excellent heat resistance and durability.

[0094] The substrate film may be a plastic film. The plastic film may be a release film (separator) whose surface has been subjected to a release treatment. The release film may be, for example, a film made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyacrylate, and the surface on which the pressure-sensitive adhesive layer is to be formed has been subjected to a release treatment such as silicone treatment.

[0095] The pressure-sensitive adhesive layer may also be formed by directly applying the pressure-sensitive adhesive composition to the surface of an optical film (described in detail below). When forming the pressure-sensitive adhesive layer on the surface of the optical film, the bonding surface of the optical film and / or the bonding surface of the pressure-sensitive adhesive layer may be subjected to a surface activation treatment (e.g., plasma treatment, corona treatment, etc.) as needed.

[0096] The thickness of the pressure-sensitive adhesive layer may be, for example, 10 μm or more, 15 μm or more, or 18 μm or more, and may be 50 μm or less, 40 μm or less, or 35 μm or less.

[0097] <Optical film with adhesive layer> A pressure-sensitive adhesive layer-attached optical film according to one embodiment includes an optical film and the pressure-sensitive adhesive layer provided on at least one surface of the optical film.

[0098] Examples of optical films include polarizers; protective films provided to protect the surface of polarizers, etc.; polarizing plates in which a protective film is laminated on one or both sides of a polarizer; retardation films; optical compensation films other than retardation films; films with antiglare function and surface antireflection function, each having an uneven surface; reflective films with a reflective function on the surface; semi-transparent reflective films having both a reflective function and a transmissive function; light diffusion films; and hard coat films.

[0099] The pressure-sensitive adhesive layer-attached optical film may include one or more types of optical films, or may include two or more of the same type of optical films. When the pressure-sensitive adhesive layer-attached optical film includes two or more optical films, an adhesive layer (described later) may be used between the optical films to laminate the two or more optical films. In this case, the adhesive layer may also be part of the optical film. The thickness of the optical film is not particularly limited, but may be, for example, 5 μm or more and 300 μm or less. In this specification, a polarizing plate having a protective film laminated on one or both sides of a polarizer is also referred to as a linear polarizing plate.

[0100] Examples of polarizers include those in which iodine is oriented (e.g., adsorption orientation) in a polyvinyl alcohol-based resin layer (e.g., a uniaxially stretched polyvinyl alcohol film), and those in which a liquid crystal compound and a dichroic dye are oriented.

[0101] 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 polyolefin resins such as linear polyolefin resins (e.g., polyethylene resins, polypropylene resins, etc.) and cyclic 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. In this specification, "(meth)acrylic" means "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 fine particles).

[0102] Examples of linear polyolefin resins include linear olefin homopolymers such as polyethylene resins and polypropylene resins, and copolymers containing two or more types of olefins as monomer units.

[0103] Cyclic polyolefin resin is 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 (typically random copolymers) of cyclic olefins with linear olefins such as ethylene and propylene, graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as the cyclic olefin are preferred.

[0104] The cellulose-based resin is a partially or completely esterified product of cellulose, and examples thereof include acetate, propionate, and butyrate esters of cellulose, as well as mixed esters thereof, etc. Examples of the cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

[0105] The polyester resin is a resin having an ester bond other than the cellulose resin, and may be, for example, a polycondensate of a polycarboxylic acid or a derivative thereof with a polyhydric alcohol. The polycarboxylic acid or a derivative thereof may be a dicarboxylic acid or a derivative thereof, and examples of the polycarboxylic acid or a derivative thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. The polyhydric alcohol may be a diol, and examples of the polyhydric alcohol include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

[0106] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate.

[0107] The polycarbonate resin is made of a polymer in which monomer units are bonded via carbonate groups, and may be a resin called a modified polycarbonate in which the polymer skeleton is modified, or a copolymer polycarbonate.

[0108] The (meth)acrylic resin as the thermoplastic resin constituting the protective film can be a polymer mainly containing (meth)acrylic acid ester as a monomer unit, and is preferably a copolymer obtained by copolymerizing a (meth)acrylic acid ester with a small amount of other comonomer. The (meth)acrylic resin as the thermoplastic resin constituting the protective film may contain, as monomer units, methyl methacrylate and methyl acrylate, or may contain methyl methacrylate, methyl acrylate, and a third monofunctional monomer.

[0109] Examples of the third monofunctional monomer include methacrylic acid esters other than methyl methacrylate, such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate; acrylic acid esters other than methyl acrylate, such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; 2-(hydroxymethyl)methyl acrylate, 2- Examples of the third monofunctional monomer include hydroxyalkyl acrylates such as methyl (1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and butyl 2-(hydroxymethyl)acrylate; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. These third monofunctional monomers may be used singly or in combination of two or more.

[0110] The (meth)acrylic resin as the thermoplastic resin constituting the protective film may further contain a polyfunctional monomer as a monomer unit. Examples of polyfunctional 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, and tetradecaethylene glycol di(meth)acrylate, or ethylene glycol or its oligomers, in which both terminal hydroxyl groups are esterified with acrylic acid or methacrylic acid; propylene glycol or its oligomers, in which both terminal hydroxyl groups are esterified with acrylic acid or methacrylic acid; and dihydric alcohol hydroxyl groups, such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate, in which hydroxyl groups are esterified with acrylic acid or methacrylic acid. Examples of the ester include those obtained by esterifying both terminal hydroxyl groups of bisphenol A, alkylene oxide adducts of bisphenol A, or halogen-substituted products thereof with acrylic acid or methacrylic acid; those obtained by esterifying polyhydric alcohols such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid, and those obtained by ring-opening addition of epoxy groups of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl groups of these; those obtained by ring-opening addition of epoxy groups of glycidyl acrylate or glycidyl methacrylate to dibasic acids such as succinic acid, adipic acid, terephthalic acid, and phthalic acid, and halogen-substituted products thereof, and alkylene oxide adducts thereof; aryl (meth)acrylates; and aromatic divinyl compounds such as divinylbenzene. Among these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferred.

[0111] The (meth)acrylic resin as the thermoplastic resin constituting the protective film may be modified by allowing the functional groups of the copolymer to react with each other. Examples of such reactions include an intrapolymer chain demethanolization condensation reaction between the methyl ester group of methyl acrylate and the hydroxyl group of methyl 2-(hydroxymethyl)acrylate, and an intrapolymer chain dehydration condensation reaction between the carboxyl group of acrylic acid and the hydroxyl group of methyl 2-(hydroxymethyl)acrylate. The (meth)acrylic resin as the thermoplastic resin constituting the protective film may have any of the following structures: a glutarimide derivative, a glutaric anhydride derivative, or a lactone ring.

[0112] The Tg of the (meth)acrylic resin as the thermoplastic resin constituting the protective film is preferably 90 to 160°C, more preferably 110 to 160°C, and even more preferably 120 to 150°C.

[0113] The (meth)acrylic resin as the thermoplastic resin constituting the protective film may contain additives as needed, such as lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance modifiers, surfactants, etc.

[0114] The (meth)acrylic resin used as the thermoplastic resin constituting the protective film may contain acrylic rubber particles as an impact modifier from the viewpoint of film formability and impact resistance of the film. The acrylic rubber particles are particles whose essential component is an acrylic acid ester-based elastic polymer. Examples include those with a single-layer structure essentially consisting of this elastic polymer, and those with a multilayer structure in which this elastic polymer forms one layer. Examples of such elastic polymers include crosslinked elastic copolymers in which alkyl acrylate is the main component and other copolymerizable vinyl monomers and crosslinkable monomers are copolymerized with this. Examples of alkyl acrylates that serve as the main component of elastic polymers include those with alkyl groups having 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Acrylic acids with alkyl groups having 4 or more carbon atoms are particularly preferred. Examples of other vinyl monomers copolymerizable with this alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule. More specifically, examples include methacrylic acid esters such as methyl methacrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile. Examples of crosslinkable monomers include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specific examples include (meth)acrylates of polyhydric alcohols such as ethylene glycol di(meth)acrylate and butanediol di(meth)acrylate, alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylate, and divinylbenzene.

[0115] The protective film may also be a laminate of a film made of an acrylic resin that does not contain rubber particles and a film made of an acrylic resin that does contain rubber particles.

[0116] The retardation film is an optical film exhibiting optical anisotropy. The retardation film may be, for example, a stretched film obtained by stretching (for example, stretching 1.01 to 6 times) a resin film made of a polyvinyl alcohol-based resin, a polyarylate-based resin, a polyimide-based resin, a polyethersulfone-based resin, a polyvinylidene fluoride / polymethyl methacrylate-based resin, a liquid crystal polyester-based resin, a saponified ethylene-vinyl acetate copolymer, or a polyvinyl chloride-based resin, in addition to the resins that can be used for the protective film. Among these, a stretched film obtained by uniaxially or biaxially stretching a polycarbonate-based resin film, a cycloolefin-based resin film, a (meth)acrylic resin film, or a cellulose-based resin film is preferred. Furthermore, in this specification, a zero-retardation film is also included in the retardation film (however, a zero-retardation film can also be used as a protective film). In addition, films known as uniaxial retardation films, wide-viewing-angle retardation films, low-photoelasticity retardation films, etc. can also be used as retardation films.

[0117] The retardation film may be a film having an optically anisotropic layer made of a polymer obtained by polymerizing a polymerizable liquid crystal compound in an aligned state on a substrate. The substrate may be the thermoplastic resin film used for the protective film.

[0118] The retardation film can be, for example, a quarter-wave retardation layer with reverse wavelength dispersion, a positive C plate, a half-wave retardation layer with positive wavelength dispersion, a quarter-wave retardation layer with positive wavelength dispersion, etc. The retardation film may be composed of two or more retardation layers, and may have, for example, a configuration in which a quarter-wave retardation layer with reverse wavelength dispersion and a positive C plate are combined, or a configuration in which a half-wave retardation layer with positive wavelength dispersion and a quarter-wave retardation layer with positive wavelength dispersion are combined, etc.

[0119] The retardation film and the protective film each have a moisture permeability of 500 g / (m) measured at a temperature of 40°C and a relative humidity of 90% by the cup method specified in JIS Z 0208. 224 hours or less.

[0120] Various optical films for liquid crystal display devices, such as polarizers, protective films, retardation films, light diffusion sheets, and reflective sheets, are usually distributed with a surface protection film attached to their surface (when a pressure-sensitive adhesive layer is present on one side, the surface opposite the pressure-sensitive adhesive layer). A surface protection film is a film used for the purpose of protecting the surface of an object to be protected, such as an optical film, from scratches and dirt. The surface protection film is usually peeled off and removed from the optical film after the optical film is attached to a liquid crystal cell or the like.

[0121] Examples of substrates for surface protection films include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; fluorinated polyolefin resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyethylene fluoride; polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; polyamides such as nylon 6 and nylon 6,6; 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; and others such as polystyrene, polycarbonate, polyarylate, and polyimide.

[0122] The attachment layer may be a pressure-sensitive adhesive layer or an adhesive layer. When the attachment layer is a pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer other than the above-mentioned pressure-sensitive adhesive layers can be used for the attachment layer. When the attachment layer is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing as a main component a resin such as a (meth)acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin. Among these, pressure-sensitive adhesive compositions containing a (meth)acrylic resin as a base polymer are preferred from the viewpoint of excellent transparency, weather resistance, heat resistance, etc. The pressure-sensitive adhesive composition may be of an active energy ray-curable type or a thermosetting type.

[0123] When the attachment layer is a pressure-sensitive adhesive layer, the (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, or an epoxy group, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0124] The adhesive composition used when the attachment layer is an adhesive layer may contain only the base polymer, but usually also contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0125] When the attachment layer is a pressure-sensitive adhesive layer, the thickness of the attachment layer is preferably from 1 μm to 200 μm, more preferably from 2 μm to 100 μm, even more preferably from 2 μm to 80 μm, and particularly preferably from 3 μm to 50 μm.

[0126] When the attachment layer is an adhesive layer, the adhesive layer can be prepared using any appropriate adhesive, such as a water-based adhesive or an active energy ray-curable adhesive.

[0127] The thickness of the adhesive when applied can be set to any appropriate value. For example, it is set so that an adhesive layer having a desired thickness is 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, even more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0128] Examples of the water-based adhesive include an aqueous solution of a polyvinyl alcohol-based resin, and a water-based two-component urethane-based emulsion adhesive.

[0129] The active energy ray curable adhesive is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays, and is preferably an ultraviolet ray curable adhesive.

[0130] The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include epoxy compounds (compounds having one or more epoxy groups in the molecule), oxetane compounds (compounds having one or more oxetane rings in the molecule), and combinations thereof. Examples of the radically polymerizable curable compound include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having radically polymerizable double bonds, and combinations thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may be used in combination. An active energy ray-curable adhesive usually further contains at least one of a cationic polymerization initiator and a radical polymerization initiator for initiating the curing reaction of the curable compound.

[0131] For the purpose of improving adhesion, a surface activation treatment may be applied to the bonding surface of at least one of the bonding layer and the optical film. Examples of the surface activation treatment include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.). These surface activation treatments may be applied alone or in combination of two or more. Corona treatment is preferred as the surface activation treatment. Corona treatment may be applied at a dose of, for example, 1 kJ / m 2 More than 50kJ / m 2 The corona treatment can be carried out at the following power: The time for which the corona treatment is carried out may be, for example, from 1 second to 1 minute.

[0132] In the pressure-sensitive adhesive layer-attached optical film according to one embodiment, it is preferable that the above-mentioned release film is attached to the surface of the pressure-sensitive adhesive layer, and that the surface is temporarily protected until use. The pressure-sensitive adhesive layer-attached optical film can be produced, for example, by a method of applying a pressure-sensitive adhesive composition onto a release film to form a pressure-sensitive adhesive layer, and then laminating a resin film on the pressure-sensitive adhesive layer, or by a method of applying a pressure-sensitive adhesive composition onto a resin film to form a pressure-sensitive adhesive layer, and then laminating a release film on the surface of the pressure-sensitive adhesive layer.

[0133] The pressure-sensitive adhesive layer-attached optical film can be used in displays such as organic electroluminescence (organic EL) displays and liquid crystal displays, and can be used, for example, by being attached to the viewing side of the image display element of the display.

[0134] The laminated structure of the pressure-sensitive adhesive layer-attached optical film is not particularly limited as long as it includes an optical film and a pressure-sensitive adhesive layer provided on at least one surface of the optical film.

[0135] Fig. 1 is a schematic cross-sectional view showing one embodiment of an optical film with a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer-attached optical film 10 shown in Fig. 1 includes a linear polarizer 11 and a pressure-sensitive adhesive layer 12 provided on one surface of the linear polarizer 11. The linear polarizer 11 includes a first protective film 13, an adhesive layer 14, a polarizer 15, an adhesive layer 16, and a second protective film 17, in this order. The pressure-sensitive adhesive layer 12 can be used to attach the film to a liquid crystal cell, which is an image display element of a liquid crystal display device. A separator (release film), not shown, may be provided on the surface of the pressure-sensitive adhesive layer 12 opposite to the linear polarizer 11.

[0136] Fig. 2 is a schematic cross-sectional view showing another embodiment of a pressure-sensitive adhesive layer-attached optical film. The pressure-sensitive adhesive layer-attached optical film 20 shown in Fig. 2 includes, in this order, a pressure-sensitive adhesive layer 21, a retardation film 22, an attachment layer 23, and a linear polarizer 24. The linear polarizer 24 includes, in this order, a first protective film 25, an adhesive layer 26, a polarizer 27, an adhesive layer 28, and a second protective film 29. The pressure-sensitive adhesive layer 21 can be used to attach the pressure-sensitive adhesive layer 21 to a liquid crystal cell, which is an image display element of a liquid crystal display device. A separator (release film), not shown, may be provided on the surface of the pressure-sensitive adhesive layer 21 opposite to the retardation film 22.

[0137] 1 and 2 are merely examples, and the pressure-sensitive adhesive layer-attached optical films may have a laminate structure other than those described above. For example, the pressure-sensitive adhesive layer-attached optical film may further include a hard coat film, a film with antiglare function, a film with surface antireflection function, etc.

[0138] <Display device> The above-mentioned pressure-sensitive adhesive layer-attached optical film can be suitably used in display devices such as organic EL display devices, liquid crystal display devices, inorganic electroluminescence (inorganic EL) display devices, electron emission display devices, etc. One example of the display device includes the above-mentioned pressure-sensitive adhesive layer-attached optical film. [Example]

[0139] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Hereinafter, parts and % representing amounts used or contents are by mass unless otherwise specified.

[0140] <Production Example 1> A reaction vessel equipped with a condenser, nitrogen inlet, thermometer, and stirrer was charged with 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 parts 2-hydroxyethyl acrylate, and 0.3 parts acrylic acid. The temperature of the mixed solution was then raised from room temperature to 60°C while the air in the reaction vessel was replaced with nitrogen gas to ensure an oxygen-free atmosphere. A solution of 0.10 parts 2,2'-azobisisobutyronitrile (polymerization initiator) in 13.7 parts ethyl acetate was then added to the mixed solution. The concentration was maintained for 4 hours after the addition of the polymerization initiator, allowing a (meth)acrylic resin to form in the reaction vessel. Finally, ethyl acetate was added to the reaction vessel to adjust the (meth)acrylic resin concentration to 20% by mass, thereby preparing an ethyl acetate solution of the (meth)acrylic resin of Production Example 1. The monomer composition (mass %) of the (meth)acrylic resin of Production Example 1 is shown in Table 1.

[0141] <Manufacturing Examples 2 and 3> Ethyl acetate solutions of the (meth)acrylic resins of Production Examples 2 and 3 were prepared in the same manner as in Production Example 1, except that the monomer compositions were as shown in Table 1.

[0142] [Table 1]

[0143] The abbreviations in Table 1 represent the following monomers. BA: n-butyl acrylate (homopolymer Tg: -54°C) MA: Methyl acrylate (homopolymer Tg: 10°C) MMA: Methyl methacrylate (homopolymer Tg: 105°C) HEA: 2-hydroxyethyl acrylate AA: acrylic acid

[0144] The Tg of the resulting (meth)acrylic resin was measured as follows. Tg was measured using an EXSTAR DSC6000 differential scanning calorimeter (DSC) manufactured by SII NanoTechnology, Inc., under conditions of a nitrogen atmosphere, a measurement temperature range of -80 to 150°C, and a heating rate of 10°C / min. The Tg of the resulting (meth)acrylic resin was -29°C (Production Example 1), -37.6°C (Production Example 2), and -53.2°C (Production Example 3).

[0145] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the resulting (meth)acrylic resin were measured as follows. Mw and Mn were measured in standard polystyrene equivalent terms using a GPC system with three columns connected in series: one "TSKgel guard column HHR-H(S)" manufactured by Tosoh Corporation and two "TSKgel GMHHR-H" columns. The eluent was tetrahydrofuran, with a sample concentration of 2 mg / mL, a sample introduction volume of 100 μL, a temperature of 40°C, and a flow rate of 1 mL / min. The Mw of the resulting (meth)acrylic resin was 1.62 million (Production Example 1), 1.52 million (Production Example 2), and 1.8 million (Production Example 3), and the molecular weight distribution (Mw / Mn) was 2.7 (Production Example 1), 3.7 (Production Example 2), and 4.6 (Production Example 3).

[0146] <Examples 1 and 2, Comparative Example 1> (1) Preparation of adhesive composition To an ethyl acetate solution of the (meth)acrylic resin obtained in the above Production Example (resin concentration: 20%), the types and amounts (parts by mass) of crosslinker, silane compound, and ionic compound shown in Table 2 were added and mixed relative to 100 parts by mass of the solids content of the solution, and ethyl acetate was further added to give a solids concentration of 14% by mass to prepare a solution of a pressure-sensitive adhesive composition. In Table 2, the amounts (parts by mass) of the (meth)acrylic resin, crosslinker, silane compound, and ionic compound are calculated as solids.

[0147] [Table 2]

[0148] Details of each compounding component indicated by its abbreviation in Table 2 are as follows: [Crosslinking agent] Crosslinking agent: D-103 (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate: solids concentration 75% by mass, manufactured by Mitsui Chemicals, Inc.) [Silane compounds] Silane compound: 8-glycidoxyoctyltrimethoxysilane "KBM-4803", manufactured by Shin-Etsu Chemical Co., Ltd. [Ionic compounds] Ionic Compounds: 1-Butyl-3-methylimidazolium Tricyanomethanide

[0149] (2) Preparation of adhesive layer The solution of each pressure-sensitive adhesive composition prepared in (1) above was applied using an applicator to the release-treated surface of a separate film made of release-treated polyethylene terephthalate film (Diafoil MRV38 (V04) by Mitsubishi Chemical Corporation) so that the thickness after drying would be 25 μm, and the film was dried at 100°C for 1 minute to prepare a pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) with a separate film.

[0150] (3) Measurement of gel fraction of adhesive layer The separation film was peeled off from the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) with separation film prepared in (2), and the resulting pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) was stored for 7 days in an environment at a temperature of 23°C and a relative humidity of 60%. After storage, the gel fraction [gel fraction at 23°C (G23)] of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) was measured. The gel fraction was measured according to the following [a] to [d]. The results are shown in Table 3. [a] An adhesive layer having an area of ​​approximately 8 cm x 8 cm is placed approximately in the center of a metal mesh (whose mass is Wm) made of SUS304 having an area of ​​approximately 10 cm x 10 cm, and the adhesive layer and the metal mesh are bonded together. [b] The bonded product obtained in [a] above is weighed, and its mass is designated as Ws. Next, the metal mesh of the bonded product is folded four times so as to enclose the pressure-sensitive adhesive layer, and the folded metal mesh is stapled to prepare a measurement sample. The measurement sample is weighed, and its mass is designated as Wb. [c] The measurement sample prepared in [b] above is placed in a glass container, 60 mL of ethyl acetate is added to immerse the measurement sample, and the glass container is then stored at room temperature for 3 days. [d] The measurement sample is removed from the glass container, dried at 120°C for 4 hours, and then weighed. The mass is taken as Wa and calculated using the following formula: Gel fraction (mass%) = [{Wa - (Wb - Ws) - Wm} / (Ws - Wm)] × 100 Calculate the gel fraction based on

[0151] (4) Preparation of polarizing plates A 12-μm-thick polarizer was prepared by aligning iodine adsorbed onto a uniaxially stretched polyvinyl alcohol film. A 40-μm-thick protective film made of saponified triacetyl cellulose resin was attached to both sides of the polarizer using a water-based adhesive to produce a polarizing plate.

[0152] (5) Preparation of polarizing plate with adhesive layer The outer surface of one of the protective films of the polarizing plate prepared in (4) above was bonded to the side opposite the separate film (the side facing the adhesive layer) of the adhesive layer with separate film prepared in (2) above using a laminator, and then the resultant was cured for 7 days under conditions of a temperature of 23°C and a relative humidity of 60% to obtain a laminate (laminated optical film) of the separate film and the polarizing plate with adhesive layer.

[0153] (6) Heat resistance and durability evaluation Two laminated optical films prepared in (5) above were prepared. For each laminated optical film, the separate film was peeled off from the polarizing plate with an adhesive layer, and then the two polarizing plates with adhesive layers were attached to both sides of an alkali-free glass substrate ("Eagle XG" manufactured by Corning Incorporated) in a crossed Nicol configuration so that the exposed adhesive layer surface of each polarizing plate with an adhesive layer was in contact with the surface of the alkali-free glass substrate. The obtained test piece (glass substrate with an adhesive layer attached) was heated in an autoclave at a temperature of 50°C and a pressure of 5 kg / cm. 2 (490.3 kPa) for 20 minutes to prepare a sample for evaluation. The following heat resistance durability test was carried out using this sample for evaluation. [Heat resistance durability test] The prepared evaluation sample was kept under dry conditions at a temperature of 110°C for 500 hours.

[0154] After the test, each evaluation sample was visually inspected for lifting or peeling at the interface between the pressure-sensitive adhesive layer and the glass substrate, and for foaming in the pressure-sensitive adhesive layer, and the heat resistance durability was evaluated according to the following evaluation criteria. The results are shown in Table 3. A: Almost no changes in appearance such as lifting, peeling, cracking, or bubbling are observed (the maximum length of the part where lifting, peeling, cracking, or bubbling is observed is less than 1 mm). B: Changes in appearance such as lifting, peeling, cracking, or foaming were observed (the maximum length of the part where lifting, peeling, cracking, or foaming was observed was 1 mm or more and less than 3 mm). C: Significant changes in appearance such as lifting, peeling, cracking, or bubbling were observed (the maximum length of the part where lifting, peeling, cracking, or bubbling was observed was 3 mm or more)

[0155] [Table 3] [Explanation of symbols]

[0156] 10, 20... optical film with adhesive layer, 11, 24... linear polarizing plate, 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... retardation film, 23... bonding layer.

Claims

1. The composition includes a (meth)acrylic resin, a crosslinking agent, a silane compound, and an ionic compound, The (meth)acrylic resin contains, as monomer units, an alkyl(meth)acrylate having a homopolymer glass transition temperature of less than 0°C, an alkyl(meth)acrylate having a homopolymer glass transition temperature of 0°C or higher, and a monomer having a polar group; The pressure-sensitive adhesive composition, wherein the ionic compound contains a cyano group-containing anion.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the cyano group-containing anion is at least one selected from the group consisting of a tricyanomethanide anion, a thiocyanate anion, and a dicyanamide anion.

3. the monomer having a polar group includes a hydroxy group-containing (meth)acrylate and a carboxy group-containing monomer, the content of the hydroxy group-containing (meth)acrylate is 0.3 mass% or more and 5.5 mass% or less based on the total amount of monomer units contained in the (meth)acrylic resin, The pressure-sensitive adhesive composition according to claim 1 or 2, wherein a mass ratio of the content of the carboxy group-containing monomer to the content of the hydroxy group-containing (meth)acrylate is 0.06 or more and 1.0 or less.

4. A pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to claim 1 or 2.

5. An optical film with a pressure-sensitive adhesive layer, comprising: an optical film; and the pressure-sensitive adhesive layer according to claim 4 provided on at least one surface of the optical film.

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