JP7807198B2 - Pressure-sensitive adhesive composition - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition, and further to a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and an optical laminate including the pressure-sensitive adhesive layer.

Optical components such as polarizing plates and retardation films are widely used in liquid crystal display devices and organic EL display devices. When used in these display devices, such optical components are laminated to the display panel via an adhesive layer. Until the adhesive layer is laminated to the display panel, its surface is protected by a release film (also called a separator), and the release film is peeled off and removed when the adhesive layer is laminated to the display panel (see, for example, Patent Document 1).

JP 2010-066755 A

When laminating an optical element to a display panel via an adhesive layer, the optical element is first fixed to a support table by suction or adsorption, and a release tape is attached to the release film. The release film is then peeled off and removed by pulling on the release tape. However, when peeling off the release film, the optical element may follow the movement of the release film and become unfixed, resulting in a peeling failure in which the release film cannot be peeled off. This tends to become more pronounced as the polarizing plate becomes thinner.

One possible method for preventing the above-mentioned peeling defects is to firmly fix the optical element to the holding table by increasing the suction and adsorption force of the optical element. However, with this method, as the optical element becomes thinner, suction and adsorption marks may be left on the optical element, causing a poor appearance, and the problem remains unresolved.

Another possible method is to reduce the release strength of the release film. However, simply reducing the release strength can result in problems such as the release film peeling off or shifting from the optical element when cutting or transporting the optical element, and this method does not solve the problem. If the release film is prone to peeling off or shifting from the optical element when cutting the optical element, wrinkles (cut wrinkles) often occur at the cut edges.

The object of the present invention is to solve the above-mentioned problems by providing a pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and optical laminate that can reduce the occurrence of cut wrinkles while maintaining adhesion to an adherend such as a polarizing plate, even when the peel strength of the release film of an optical component is reduced.

The present invention provides the following pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and optical laminate.
[1] A pressure-sensitive adhesive composition comprising a (meth)acrylic resin, a crosslinking agent, a reactive silicone oil, and a non-reactive silicone oil.
[2] The reactive silicone oil includes a reactive silicone oil having an amino group on a side chain of a polysiloxane skeleton,
The pressure-sensitive adhesive composition according to [1], wherein the non-reactive silicone oil comprises a non-reactive silicone oil having an alkyl group on a side chain of a polysiloxane skeleton.
[3] The pressure-sensitive adhesive composition according to [2], wherein the amino group is a group derived from a diamine.
[4] The pressure-sensitive adhesive composition according to [2], wherein the alkyl group is at least one selected from the group consisting of a long-chain alkyl group and a fluoroalkyl group.
[5] The pressure-sensitive adhesive composition according to any one of [1] to [4], further comprising a silane coupling agent.
[6] A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [5].
[7] An optical laminate having an optical member, the pressure-sensitive adhesive layer according to [6], and a release film in this order.

The present invention provides a pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and optical laminate that can reduce the occurrence of cut wrinkles while maintaining adhesion to an adherend such as a polarizing plate, even when the release strength of the release film for an optical component is reduced.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of an optical laminate. FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of a pressure-sensitive adhesive layer-attached polarizing plate.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In all of the drawings, the scale has been adjusted appropriately to make each component easier to understand, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Adhesive composition>
A pressure-sensitive adhesive composition according to one embodiment of the present invention contains a (meth)acrylic resin (A), a crosslinking agent (B), a reactive silicone oil (C), and a non-reactive silicone oil (D).

[1] (Meth)acrylic resin (A)
The (meth)acrylic resin (A) is a polymer (hereinafter also referred to as an acrylic polymer (A)) containing a structural unit derived from a (meth)acrylic monomer having a hydroxyl group, and preferably contains, in addition to this structural unit, a structural unit of formula (I):

It is a polymer containing, as a main component, structural units derived from a (meth)acrylic acid ester represented by the formula: In this specification, "(meth)acrylic" means acrylic and/or methacrylic, and the "(meth)" in "(meth)acrylate", "(meth)acryloyl", etc. has the same meaning.

In formula (I), R ¹¹ represents a hydrogen atom or a methyl group, and R ¹² represents an alkyl group having 1 to 14 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms, or an aralkyl group having 7 to 21 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms. ^{R 12} is preferably an alkyl group having 1 to 14 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms.

(Meth)acrylic acid esters represented by formula (I) include (meth)acrylic acid alkyl esters, and specific examples thereof include (meth)acrylic acid alkyl esters with linear alkyl moieties such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-octyl (meth)acrylate, and lauryl (meth)acrylate; and (meth)acrylic acid alkyl esters with branched alkyl moieties such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate. The number of carbon atoms in the alkyl moiety in the (meth)acrylic acid alkyl esters is preferably 1 to 8, and more preferably 1 to 6.

When R ¹² is an alkyl group substituted with an alkoxy group, i.e., when R ¹² is an alkoxyalkyl group, specific examples of the (meth)acrylic acid ester represented by formula (I) include 2-methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, etc. The number of carbon atoms in the alkyl group in the alkoxyalkyl group is preferably 1 to 8, more preferably 1 to 6. The number of carbon atoms in the alkoxyalkyl group in the alkoxyalkyl group is preferably 1 to 8, more preferably 1 to 4. When ^{R 12} is an aralkyl group having 7 to 21 carbon atoms, specific examples of the (meth)acrylic acid ester represented by formula (I) include benzyl (meth)acrylate, etc. The number of carbon atoms in the aralkyl group is preferably 7 to 11.

The (meth)acrylic acid ester represented by formula (I) may be used alone or in combination of two or more. Among these, the (meth)acrylic acid ester preferably contains a (meth)acrylic acid alkyl ester, more preferably contains an acrylic acid alkyl ester, and even more preferably contains n-butyl acrylate. It is preferable that the (meth)acrylic resin (A) contains 50% by mass or more of structural units derived from n-butyl acrylate among all structural units constituting the resin. Of course, other (meth)acrylic acid esters represented by formula (I) can also be used in combination with n-butyl acrylate.

The content of the (meth)acrylic acid ester-derived structural units represented by formula (I) in all structural units constituting the (meth)acrylic resin (A) is typically 60% by mass or more and less than 100% by mass, preferably 70% by mass or more and 99.9% by mass or less, and more preferably 80% by mass or more and 99.6% by mass or less.

The (meth)acrylic resin (A) contains a structural unit derived from a (meth)acrylic monomer having a hydroxyl group. The inclusion of this structural unit is advantageous in terms of improving the adhesion between the pressure-sensitive adhesive layer and the optical component and the durability of the pressure-sensitive adhesive layer. A suitable example of a (meth)acrylic monomer having a hydroxyl group is a (meth)acrylic acid ester having a hydroxyl group. Specific examples of a (meth)acrylic acid ester having a hydroxyl group include hydroxyl-containing alkyl esters of (meth)acrylic acid, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, and 2- or 3-chloro-2-hydroxypropyl (meth)acrylate; and incomplete esters of polyfunctional alcohols and (meth)acrylic acid, such as diethylene glycol mono(meth)acrylate. The (meth)acrylic monomer having a hydroxyl group may be used alone or in combination of two or more.

Among these, from the viewpoints of adhesion between the pressure-sensitive adhesive layer and the optical component and durability of the pressure-sensitive adhesive layer, the (meth)acrylic acid ester having a hydroxyl group is preferably a hydroxyl-containing alkyl ester of (meth)acrylic acid. The number of carbon atoms in the alkyl portion of the hydroxyl-containing alkyl ester of (meth)acrylic acid is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less.

The content of structural units derived from (meth)acrylic monomers having hydroxyl groups is preferably 6% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less, of all structural units constituting the (meth)acrylic resin (A). If the content of structural units derived from (meth)acrylic monomers having hydroxyl groups exceeds 6% by mass, the durability of the pressure-sensitive adhesive layer, particularly heat resistance, tends to be insufficient. On the other hand, the content of structural units derived from (meth)acrylic monomers having hydroxyl groups is usually 0.5% by mass or more, preferably 0.7% by mass or more, and more preferably 1% by mass or more. If the content of structural units derived from (meth)acrylic monomers having hydroxyl groups is less than 0.5% by mass, the adhesion between the pressure-sensitive adhesive layer and the optical component and the durability of the pressure-sensitive adhesive layer tend to be insufficient.

The (meth)acrylic resin (A) may contain structural units derived from a monomer having a polar functional group other than a (meth)acrylic monomer having a hydroxyl group. The monomer having a polar functional group is preferably a (meth)acrylic monomer having a polar functional group. Examples of the polar functional group possessed by the monomer include a carboxyl group (free carboxyl group), an amino group, and a heterocyclic group (e.g., an epoxy group).

Specific examples of monomers having other polar functional groups include (meth)acrylic monomers having a carboxyl group, such as acrylic acid, methacrylic acid, and β-carboxyethyl (meth)acrylate; monomers having a heterocyclic group, such as 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; and monomers having an amino group other than a heterocyclic ring, such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. Monomers having other polar functional groups may be used alone or in combination of two or more.

The combined use of a (meth)acrylic monomer having a hydroxyl group with a monomer having another polar functional group, particularly a (meth)acrylic monomer having a carboxyl group, is advantageous in improving the adhesion between the pressure-sensitive adhesive layer and the optical component and the durability (particularly heat resistance) of the pressure-sensitive adhesive layer.

The lower limit of the content of structural units derived from monomers having other polar functional groups, preferably structural units derived from (meth)acrylic monomers having a carboxyl group, can be 0% by mass or more of all structural units constituting the (meth)acrylic resin (A). As described above, the (meth)acrylic resin (A) preferably contains structural units derived from (meth)acrylic monomers having a carboxyl group, and the content of these structural units is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 2% by mass or more of all structural units constituting the (meth)acrylic resin (A). If the content of structural units derived from monomers having other polar functional groups is less than 0.05% by mass, the effects of use are difficult to achieve. On the other hand, the content of structural units derived from monomers having other polar functional groups, preferably (meth)acrylic monomers having a carboxyl group, is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less of all structural units constituting the (meth)acrylic resin (A). If the content of structural units derived from monomers having other polar functional groups exceeds 5% by mass, the durability of the pressure-sensitive adhesive layer, particularly heat resistance, tends to be insufficient. The structural units derived from all monomers having polar functional groups, including (meth)acrylic monomers having hydroxyl groups, typically account for 1% by mass or more and 10% by mass or less, and preferably 1.1% by mass or more and 8% by mass or less, of all structural units constituting the (meth)acrylic resin (A).

The (meth)acrylic resin (A) may further contain structural units derived from a monomer having one olefinic double bond and at least one aromatic ring in the molecule (excluding those corresponding to the above formula (I) or the above monomer having a polar functional group). A suitable example of such a monomer is a (meth)acrylic monomer having an aromatic ring. Such (meth)acrylic monomers having an aromatic ring include neopentyl glycol benzoate (meth)acrylate, but are particularly preferred.

Preferred are (meth)acrylic acid esters having an aryloxyalkyl group, such as phenoxyethyl group-containing (meth)acrylic acid esters represented by the formula: Monomers having one olefinic double bond and at least one aromatic ring in the molecule, such as phenoxyethyl group-containing (meth)acrylic acid esters, may be used alone or in combination of two or more types.

In formula (II), ^R13 represents a hydrogen atom or a methyl group, q represents an integer of 1 to 8, and ^R14 represents a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group. When ^R14 is an alkyl group, it may have about 1 to 9 carbon atoms; when R14 is an aralkyl group, it may have about 7 to 11 carbon atoms; and when R14 is an aryl group, it may have about 6 to 10 carbon atoms.

Examples of the alkyl group having 1 to 9 carbon atoms constituting R ¹⁴ in formula (II) include methyl, butyl, nonyl, etc., examples of the aralkyl group having 7 to 11 carbon atoms include benzyl, phenethyl, naphthylmethyl, etc., and examples of the aryl group having 6 to 10 carbon atoms include phenyl, tolyl, naphthyl, etc.

Specific examples of the phenoxyethyl group-containing (meth)acrylic acid ester represented by formula (II) include 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, (meth)acrylic acid esters of ethylene oxide-modified nonylphenol, and 2-(o-phenylphenoxy)ethyl (meth)acrylate. Among these, it is preferable that the phenoxyethyl group-containing (meth)acrylic acid ester include 2-phenoxyethyl (meth)acrylate, 2-(o-phenylphenoxy)ethyl (meth)acrylate, and/or 2-(2-phenoxyethoxy)ethyl (meth)acrylate.

The content of structural units derived from a monomer having one olefinic double bond and at least one aromatic ring in the molecule is typically 0% by mass or more and 20% by mass or less (e.g., 6% by mass or more and 12% by mass or less) of all structural units constituting the (meth)acrylic resin (A).

The (meth)acrylic resin (A) may contain structural units derived from monomers other than the (meth)acrylic acid ester represented by formula (I) described above, the monomer having a polar functional group, and the monomer having one olefinic double bond and at least one aromatic ring in the molecule (hereinafter also referred to as "other monomers"). Examples of other monomers include structural units derived from (meth)acrylic acid esters having an alicyclic structure in the molecule, structural units derived from styrene-based monomers, structural units derived from vinyl-based monomers, structural units derived from monomers having multiple (meth)acryloyl groups in the molecule, and structural units derived from (meth)acrylamide compounds. One type of other monomer may be used alone, or two or more types may be used in combination.

The alicyclic structure in a (meth)acrylic acid ester having an alicyclic structure within the molecule is a cycloparaffin structure typically having 5 or more carbon atoms, preferably about 5 to 7. Specific examples of (meth)acrylic acid esters having an alicyclic structure include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclododecyl (meth)acrylate, methylcyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclohexylphenyl (meth)acrylate, and cyclohexyl α-ethoxyacrylate.

Specific 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.

Specific examples of vinyl 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; conjugated diene monomers such as butadiene, isoprene, and chloroprene; acrylonitrile, methacrylonitrile, and the like.

Specific examples of monomers having multiple (meth)acryloyl groups in the molecule include monomers having two (meth)acryloyl groups in the molecule, such as 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; and monomers having three (meth)acryloyl groups in the molecule, such as trimethylolpropane tri(meth)acrylate.

Specific examples of (meth)acrylamide compounds 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-acryloylamino-2-methyl-1-propanesulfonic acid, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)(meth)acrylamide, N-(propoxymethyl)(meth)acrylamide, N-(1 N-(1-methylethoxymethyl)(meth)acrylamide, N-(1-methylpropoxymethyl)(meth)acrylamide, N-(2-methylpropoxymethyl)(meth)acrylamide [alias: N-(isobutoxymethyl)(meth)acrylamide], N-(butoxymethyl)(meth)acrylamide, N-(1,1-dimethylethoxymethyl)(meth)acrylamide, N-(2-methoxyethyl)(meth)acrylamide, N-(2-ethoxyethyl)(meth)acrylamide, N- These include (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)(meth)acrylamide), N-(2-butoxyethyl)(meth)acrylamide, and N-[2-(1,1-dimethylethoxy)ethyl](meth)acrylamide. Of these, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)acrylamide, N-(propoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, and N-(2-methylpropoxymethyl)acrylamide are preferred.

Of all the structural units constituting (meth)acrylic resin (A), structural units derived from other monomers typically account for 0% by mass or more and 20% by mass or less, and preferably 0% by mass or more and 10% by mass or less.

The content of (meth)acrylic resin (A) in the pressure-sensitive adhesive composition is not particularly limited, but may be, for example, 0.01% by mass or more and 90% by mass or less, preferably 0.1% by mass or more and 60% by mass or less, and more preferably 1% by mass or more and 40% by mass or less. The pressure-sensitive adhesive composition may contain two or more (meth)acrylic resins belonging to the (meth)acrylic resin (A) group. The pressure-sensitive adhesive composition may also contain a (meth)acrylic resin different from (meth)acrylic resin (A). An example of the other (meth)acrylic resin is a (meth)acrylic resin having a structural unit derived from a (meth)acrylic acid ester represented by formula (I) and not having a polar functional group. However, the pressure-sensitive adhesive composition preferably contains (meth)acrylic resin (A) as the main component, and the content of (meth)acrylic resin (A) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more (e.g., 100% by mass) of the total content of all (meth)acrylic resins.

The (meth)acrylic resin (A) has a glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) of -20°C or lower, preferably -25°C or lower. The pressure-sensitive adhesive composition of the present invention, which contains a (meth)acrylic resin (A) having a Tg of -20°C or lower, can improve the adhesion between the pressure-sensitive adhesive layer and the optical component and the durability of the pressure-sensitive adhesive layer. From the viewpoint of the durability of the pressure-sensitive adhesive layer, the Tg of the (meth)acrylic resin (A) is typically -55°C or higher, preferably -50°C or higher.

In addition, the pressure-sensitive adhesive composition of the present invention, which contains a (meth)acrylic resin (A) with a Tg of -20°C or less, makes it possible to shorten the curing time for the pressure-sensitive adhesive layer. In other words, while pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) are generally cured to allow the crosslinking reaction to proceed to a degree that ensures appropriate handleability and processability, the pressure-sensitive adhesive composition of the present invention makes it possible to shorten the curing time for the pressure-sensitive adhesive layer required for the crosslinking reaction to proceed sufficiently.

The (meth)acrylic resin (A) preferably has a weight-average molecular weight (Mw) of 500,000 to 2,000,000, and more preferably 600,000 to 1,800,000, as measured by gel permeation chromatography (GPC) in terms of standard polystyrene. An Mw of 500,000 or greater improves adhesion between the pressure-sensitive adhesive layer and the optical component in high-temperature, high-humidity environments, reducing the likelihood of lifting or peeling between the pressure-sensitive adhesive layer and the optical component, and improving the reworkability of the pressure-sensitive adhesive layer. Furthermore, an Mw of 2,000,000 or less facilitates the pressure-sensitive adhesive layer to easily follow dimensional changes in the optical component when the pressure-sensitive adhesive layer is attached to the optical component, thereby improving adhesion between the pressure-sensitive adhesive layer and the optical component and its durability. Furthermore, this followability reduces the difference in brightness between the periphery and center of the liquid crystal cell when the pressure-sensitive adhesive layer-attached optical component is used in a liquid crystal display device, reducing whiteout and color unevenness. The molecular weight distribution, expressed as the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn), is typically around 2 to 10, and preferably 3 to 7.

(Meth)acrylic resin (A) and other (meth)acrylic resins that can be used in combination with the (meth)acrylic resin (A) can be produced by known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. A polymerization initiator is typically used in the production of (meth)acrylic resins. The polymerization initiator is used in an amount of 0.001 to 5 parts by mass per 100 parts by mass of the total of all monomers used in the production of the (meth)acrylic resin. Alternatively, the (meth)acrylic resin may be produced by a method in which polymerization is promoted by active energy rays such as ultraviolet light.

The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator. Examples of photopolymerization initiators include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone. Examples of thermal polymerization initiators 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 peroxides include organic peroxides such as tert-butyl hydroperoxide, benzoyl peroxide, 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. Redox initiators that combine a peroxide with a reducing agent can also be used as polymerization initiators.

Among the methods listed above, solution polymerization is preferred as a method for producing (meth)acrylic resins. One example of solution polymerization involves mixing the monomers and organic solvent to be used, adding a thermal polymerization initiator under a nitrogen atmosphere, and stirring for 3 to 15 hours at approximately 40 to 90°C, preferably 50 to 80°C. To control the reaction, the monomers and thermal polymerization initiator may be added continuously or intermittently during polymerization, or may be added dissolved 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.

[2] Crosslinking agent (B)
The crosslinking agent (B) is a compound that reacts with structural units derived from polar functional group-containing monomers in a base polymer such as the (meth)acrylic resin (A), thereby crosslinking the base polymer. Specific examples include isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds. Among these, it is preferable to use an isocyanate compound as a crosslinking agent, which can further improve the adhesion between the pressure-sensitive adhesive layer and the optical component and the durability of the pressure-sensitive adhesive layer (hereinafter, crosslinking agents that are isocyanate compounds are also referred to as isocyanate crosslinking agents). Isocyanate compounds, epoxy compounds, and aziridine compounds have at least two functional groups in the molecule that can react with polar functional groups in the base polymer. The crosslinking agent (B) may be used alone or in combination of two or more types.

An isocyanate compound is a compound having at least two isocyanato groups (-NCO) in its molecule. Specific examples of isocyanate compounds include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. Adducts formed by reacting these isocyanate compounds with polyols such as glycerol or trimethylolpropane, as well as dimers, trimers, and the like of isocyanate compounds, can also serve as the crosslinking agent (B).

Epoxy compounds are compounds that contain at least two epoxy groups in their molecules. Specific examples of epoxy compounds include bisphenol A epoxy resins, 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.

Aziridine compounds, also known as ethyleneimines, are compounds that contain at least two three-membered ring structures consisting of one nitrogen atom and two carbon atoms within the molecule. Specific examples of aziridine 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.

Specific examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetoacetate is coordinated with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

The crosslinking agent (B) is contained in the pressure-sensitive adhesive composition in an amount of, for example, 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, per 100 parts by mass of the (meth)acrylic resin (A). When the content of crosslinking agent (B) is 0.01 part by mass or more, preferably 0.1 part by mass or more, the durability of the pressure-sensitive adhesive layer tends to be improved.

[3] Reactive silicone oil (C) and non-reactive silicone oil (D)
The pressure-sensitive adhesive composition contains a reactive silicone oil (C) and a non-reactive silicone oil (D). Silicone oil is a compound having a siloxane bond as a backbone, and is also called polysiloxane because of the siloxane bond. The side chains and both terminals are usually alkyl groups, and the pressure-sensitive adhesive composition is usually liquid. By including both the reactive silicone oil (C) and the non-reactive silicone oil (D) in the pressure-sensitive adhesive composition, it is possible to obtain a pressure-sensitive adhesive layer that can maintain adhesion to an adherend such as a polarizing plate and suppress defects during processing or transportation of the optical component, even when the peel strength of the release film on the pressure-sensitive adhesive layer surface of the optical component is reduced.

[Reactive Silicone Oil (C)]
The reactive silicone oil (C) has a structure in which one or more of the side chains, both ends, and one end of the polysiloxane are substituted with reactive organic groups. Part or all of the side chains of the polysiloxane can be substituted with reactive organic groups. Among these, reactive silicone oils in which crosslinkable functional groups have been introduced into the side chains of the polysiloxane skeleton (hereinafter also referred to as side-chain reactive silicone oils) are preferably used. The side chains can be, for example, methyl groups.

Examples of crosslinkable functional groups include amino groups, epoxy groups, mercapto groups, carboxyl groups, isocyanate groups, and methacrylate groups. Among these, amino groups are preferred, with monoamine-derived groups and diamine-derived groups being more preferred, and diamine-derived groups being most preferred. The monoamine-derived group can be, for example, a group represented by the formula: _-RNH2 . The diamine-derived group can be, for example, a group represented by the formula: -RNH- _R'NH2 .

The reactive silicone oil (C) preferably contains a reactive silicone oil having an amino group on the side chain of the polysiloxane skeleton (hereinafter also referred to as a side-chain amino-modified silicone oil), more preferably a reactive silicone oil having a diamine-derived group on the side chain of the polysiloxane skeleton (hereinafter also referred to as a side-chain diamine-modified silicone oil), and even more preferably contains only a side-chain diamine-modified silicone oil. When the reactive silicone oil (C) contains a side-chain diamine-modified silicone oil, the side-chain diamine-modified silicone oil can contribute to preventing the occurrence of cut wrinkles. Because diamine-modified silicone oils tend to have high wettability with release films, the pressure-sensitive adhesive layer is formed to fill in the unevenness of the release film surface. As a result, the adhesion between the pressure-sensitive adhesive layer and the release film is improved, and the adhesion between the pressure-sensitive adhesive layer and the release film is strong enough to withstand the impact (shear stress) during cutting, which is thought to prevent the occurrence of cut wrinkles.

Commercially available examples of such reactive silicone oils (C) include "KF-865," "KF-864," "KF-859," "KF-860," "KF-8004," and "KF-8005" manufactured by Shin-Etsu Chemical Co., Ltd. Only one type of reactive silicone oil may be used, or two or more types may be used in combination.

The functional group equivalent weight of the side-chain amino-modified silicone oil may be, for example, 350 g/mol or more and 60,000 g/mol or less, preferably 1,000 g/mol or more and 20,000 g/mol or less, and more preferably 1,500 g/mol or more and 15,000 g/mol or less.

The reactive silicone oil (C) is contained in the pressure-sensitive adhesive composition in an amount of, for example, 0.001 to 0.5 parts by mass, preferably 0.006 to 0.3 parts by mass, and more preferably 0.009 to 0.1 parts by mass, per 100 parts by mass of the (meth)acrylic resin (A).

[Non-reactive silicone oil (D)]
The non-reactive silicone oil (D) has a structure in which one or more of the side chains, both ends, and one end of the polysiloxane are substituted only with non-reactive organic groups. Part or all of the side chains of the polysiloxane can be substituted with non-reactive organic groups. Among these, non-reactive silicone oils in which non-crosslinkable functional groups have been introduced into the side chains of the polysiloxane skeleton (hereinafter also referred to as side-chain type non-reactive silicone oils) are preferably used. The side chains can be, for example, methyl groups.

Examples of non-crosslinkable functional groups include alkyl groups, polyether groups, and polyester groups. Among these, alkyl groups are preferred. The alkyl group may be at least one type selected from the group consisting of long-chain alkyl groups and fluoroalkyl groups, and is preferably a long-chain alkyl group. The long-chain alkyl group can be, for example, a group represented by the formula: -C _a H _2a+1 (wherein a is an integer of 2 or more). a can be an integer of 9 or less. The fluoroalkyl group can be, for example, a group represented by the formula: -CH ₂ CH ₂ CF ₃ .

The non-reactive silicone oil (D) preferably comprises a non-reactive silicone oil having an alkyl group on the side chain of the polysiloxane skeleton (hereinafter also referred to as a side-chain alkyl-modified silicone oil), more preferably at least one selected from the group consisting of a non-reactive silicone oil having a long-chain alkyl group on the side chain of the polysiloxane skeleton (hereinafter also referred to as a side-chain long-chain alkyl-modified silicone oil) and a non-reactive silicone oil having a fluoroalkyl group on the side chain of the polysiloxane skeleton (hereinafter also referred to as a side-chain fluoroalkyl-modified silicone oil), even more preferably comprising only at least one selected from the group consisting of a side-chain long-chain alkyl-modified silicone oil and a side-chain fluoroalkyl-modified silicone oil, and particularly preferably comprising only a side-chain long-chain alkyl-modified silicone oil. When the non-reactive silicone oil (D) comprises a side-chain long-chain alkyl-modified silicone oil, the side-chain long-chain alkyl-modified silicone oil can effectively reduce the adhesion between the pressure-sensitive adhesive layer and the release film while maintaining the adhesion between the pressure-sensitive adhesive layer and the protective film of the polarizing plate. Long-chain alkyl-modified silicone oil is unlikely to localize near the surface of the protective film of the polarizing plate in the adhesive layer, but is likely to localize near the surface of the release film. Therefore, despite being a release agent, it is thought to be unlikely to deteriorate the adhesion between the protective film of the polarizing plate and the adhesive layer.

Commercially available examples of such non-reactive silicone oils (D) include "KF-4003," "KF-4917," "KF-414," "X-22-821," and "X-22-822" manufactured by Shin-Etsu Chemical Co., Ltd. Only one type of non-reactive silicone oil (D) may be used, or two or more types may be used in combination.

The non-reactive silicone oil (D) is contained in the pressure-sensitive adhesive composition in an amount of, for example, 0.005 to 1 part by mass, preferably 0.05 to 0.5 parts by mass, more preferably 0.07 to 0.5 parts by mass, and even more preferably 0.1 to 0.3 parts by mass, per 100 parts by mass of the (meth)acrylic resin (A).

The content ratio of non-reactive silicone oil (D) per 1 part by mass of reactive silicone oil (C) in the pressure-sensitive adhesive composition is preferably 1 part by mass or more and 40 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, and even more preferably 5 parts by mass or more and 25 parts by mass or less.

[4] Silane coupling agent (E)
The pressure-sensitive adhesive composition may further contain a silane coupling agent (E), which can further enhance the adhesion between the pressure-sensitive adhesive layer and an optical member such as a glass substrate.

Examples of silane coupling agents (E) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, and 3-glycidoxypropylethoxydimethylsilane. Two or more silane coupling agents may be used.

The silane coupling agent (E) may be a silicone oligomer type. Examples of silicone oligomers expressed in the form of (monomer) oligomers include the following:

mercaptopropyl group-containing copolymers such as 3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane copolymer, and 3-mercaptopropyltriethoxysilane-tetraethoxysilane copolymer;
mercaptomethyl group-containing copolymers such as mercaptomethyltrimethoxysilane-tetramethoxysilane copolymer, mercaptomethyltrimethoxysilane-tetraethoxysilane copolymer, mercaptomethyltriethoxysilane-tetramethoxysilane copolymer, and mercaptomethyltriethoxysilane-tetraethoxysilane copolymer;
3-glycidoxypropyl group-containing copolymers such as 3-glycidoxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-glycidoxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-glycidoxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-glycidoxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-glycidoxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-glycidoxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-glycidoxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-glycidoxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
methacryloyloxypropyl group-containing copolymers such as 3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
Acryloyloxypropyl group-containing copolymers such as 3-acryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
vinyl group-containing copolymers such as vinyltrimethoxysilane-tetramethoxysilane copolymer, vinyltrimethoxysilane-tetraethoxysilane copolymer, vinyltriethoxysilane-tetramethoxysilane copolymer, vinyltriethoxysilane-tetraethoxysilane copolymer, vinylmethyldimethoxysilane-tetramethoxysilane copolymer, vinylmethyldimethoxysilane-tetraethoxysilane copolymer, vinylmethyldiethoxysilane-tetramethoxysilane copolymer, and vinylmethyldiethoxysilane-tetraethoxysilane copolymer;
Amino group-containing copolymers such as 3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-aminopropylmethyldiethoxysilane-tetraethoxysilane copolymer.

Many of the silane coupling agents (E) exemplified above are liquid. The content of the silane coupling agent (E) in the pressure-sensitive adhesive composition is typically 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of the (meth)acrylic resin (A). When the content of the silane coupling agent (E) is 0.01 parts by mass or more, the effect of improving the adhesion between the pressure-sensitive adhesive layer and optical components such as glass substrates is likely to be achieved. Furthermore, when the content is 10 parts by mass or less, bleeding out of the silane coupling agent (E) from the pressure-sensitive adhesive layer can be suppressed.

[5] Ionic Compound The pressure-sensitive adhesive composition may further contain an ionic compound as an antistatic agent to impart antistatic properties to the pressure-sensitive adhesive layer. The ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion. Two or more types of ionic compounds may be used.

The content of the ionic compound in the pressure-sensitive adhesive composition may be, for example, 0.2 to 8 parts by mass, preferably 0.2 to 5 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic resin (A). An ionic compound content of 0.2 parts by mass or more is advantageous for improving antistatic performance, while an ionic compound content of 8 parts by mass or less is advantageous for maintaining the durability of the pressure-sensitive adhesive layer.

[6] Other Components The pressure-sensitive adhesive composition may contain additives such as solvents, crosslinking catalysts, weather stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers, light-scattering microparticles, and resins other than the (meth)acrylic resin (A). It is also useful to incorporate an ultraviolet-curable compound into the pressure-sensitive adhesive composition, form a pressure-sensitive adhesive layer, and then cure the layer by ultraviolet light to obtain a harder pressure-sensitive adhesive layer. Conventional solvents can be used, such as ethyl acetate. Examples of crosslinking catalysts include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resins, and melamine resins.

<Adhesive Layer>
A pressure-sensitive adhesive layer according to another embodiment of the present invention comprises the pressure-sensitive adhesive composition according to the present invention, and typically consists of the pressure-sensitive adhesive composition according to the present invention. The pressure-sensitive adhesive layer can be obtained by dissolving or dispersing each component constituting the pressure-sensitive adhesive composition in a solvent to form a solvent-containing pressure-sensitive adhesive composition, which is then applied to a substrate film and dried. The pressure-sensitive adhesive layer of the present invention has excellent adhesion to optical components as described below. Furthermore, despite the pressure-sensitive adhesive layer of the present invention having low peel strength from a release film protecting the pressure-sensitive adhesive layer, defects such as poor peeling during processing or transportation of the optical component are suppressed. When the pressure-sensitive adhesive layer is included in the optical component described below, the pressure-sensitive adhesive layer may include a substrate film.

The substrate film is generally a plastic film, and a typical example is a release film (separator) that has been subjected to a release treatment. The release film can be, for example, a film made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyacrylate, with a release treatment such as silicone treatment applied to the surface on which the adhesive layer is to be formed. The release film is releasable from the adhesive layer. For example, an adhesive composition can be directly applied to the release-treated surface of the release film to form an adhesive layer, and this adhesive layer with release film can then be laminated on an optical component to obtain an optical laminate. Alternatively, an adhesive composition can be directly applied to the surface of an optical component to form an adhesive layer, and if necessary, a release film can be laminated on the outer surface of the adhesive layer to obtain an optical laminate. When providing an adhesive layer on the surface of an optical component, it is preferable to subject the bonding surface of the optical component and/or the bonding surface of the adhesive layer to a surface activation treatment such as plasma treatment or corona treatment, with corona treatment being more preferable.

The thickness of the pressure-sensitive adhesive layer may be, for example, 10 μm or more and 45 μm or less, preferably 10 μm or more and 35 μm or less, and more preferably 10 μm or more and 25 μm or less. A pressure-sensitive adhesive layer thickness within this range is advantageous for the adhesion between the pressure-sensitive adhesive layer and the optical component, and for the durability when the pressure-sensitive adhesive layer is attached to the optical component. For the same reason, the pressure-sensitive adhesive layer preferably has a gel fraction in the range of 30% or more and 85% or less.

<Optical laminate>
An optical laminate according to yet another embodiment of the present invention comprises an optical member, the above-described pressure-sensitive adhesive layer, and a release film, in this order. The optical laminate preferably comprises the above-described pressure-sensitive adhesive layer, an optical member in contact with one side of the pressure-sensitive adhesive layer, and a release film in contact with the other side of the pressure-sensitive adhesive layer. Examples of pressure-sensitive adhesive layer-attached optical members include composite films such as linear polarizers and circular polarizers, and films made of thermoplastic resins such as polyolefin resins (e.g., linear polyolefin resins, polypropylene resins, etc.) and cyclic polyolefin resins (e.g., norbornene resins), cellulose resins (e.g., triacetyl cellulose, diacetyl cellulose), polyester resins, polycarbonate resins, (meth)acrylic resins, polystyrene resins, polyether ether ketone resins, polysulfone resins, and polyimide resins. When the optical member is a polarizing plate, the optical laminate can be a pressure-sensitive adhesive layer-attached polarizing plate.

A linear polarizing plate can include a polarizer and a protective film. The polarizer and protective film may be laminated via a bonding layer such as a pressure-sensitive adhesive layer or an adhesive layer. The polarizer is a film that extracts linearly polarized light from incident natural light. A suitable example is a uniaxially stretched polyvinyl alcohol resin film in which dichroic pigments such as iodine or dichroic dyes are adsorbed and oriented. The thickness of the polarizer is not particularly limited, but is typically 0.5 μm or more and 35 μm or less.

The protective film can be a film made of a light-transmitting (preferably optically transparent) resin, for example, a polyolefin resin such as a linear polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin; a polycarbonate resin; a (meth)acrylic resin; a polystyrene resin; a polyether ether ketone resin; or a thermoplastic resin such as a polysulfone resin.

The polarizing plate can include the linear polarizing plate and a retardation film. For example, a viewing angle compensation film used for optical compensation of a liquid crystal cell (hereinafter referred to as an IPS-mode liquid crystal cell) having a liquid crystal layer containing liquid crystal molecules aligned in a homogeneous alignment in the absence of an electric field can be a retardation film having, in order from the polarizing element side, a first optical compensation layer and a second optical compensation layer. In this case, the surface of the second optical compensation layer can be attached to the liquid crystal cell using an adhesive layer or the like. The absorption axis of the polarizing element and the slow axis of the second optical compensation layer are approximately parallel. From the viewpoint of thinning the polarizing plate, it is preferable that both the first optical compensation layer and the second optical compensation layer are made of a cured product of a polymerizable liquid crystal compound. The first optical compensation layer and the second optical compensation layer can satisfy the following formulas (1) and (2).
nz1 > nx1 = ny1 (1)
nx2 > ny2 ≧ nz2 (2)

Here, the refractive indices in the in-plane slow axis direction of the first optical compensation layer and the second optical compensation layer are nx1 and nx2, the refractive indices in the in-plane fast axis direction of the first optical compensation layer and the second optical compensation layer are ny1 and ny2, and the refractive indices in the thickness direction of the first optical compensation layer and the second optical compensation layer are nz1 and nz2. Each refractive index in the above formula (1) and each refractive index in the above formula (2) are values measured at the same wavelength.

Note that "substantially parallel" does not only mean completely parallel, but also includes being substantially parallel, with the angle generally being within ±2°, preferably within ±1°, and more preferably within ±0.5°. Furthermore, "substantially perpendicular" does not only mean being completely perpendicular, but also includes being substantially perpendicular, with the angle generally being in the range of 90±2°, preferably 90±1°, and more preferably 90±0.5°.

(First Optical Compensation Layer, Second Optical Compensation Layer)
The first optical compensation layer and the second optical compensation layer can be made of a cured product of a polymerizable liquid crystal compound. The first optical compensation layer and the second optical compensation layer may be made of the same material or different materials. Known polymerizable liquid crystal compounds can be used. The wavelength dispersion characteristics of the retardation values of the first optical compensation layer and the second optical compensation layer are not particularly limited, and can be suitably used from normal wavelength dispersion to reverse wavelength dispersion. A particularly preferred embodiment is that both the first optical compensation layer and the second optical compensation layer have reverse wavelength dispersion characteristics.

The wavelength dispersion characteristics of the retardation values of the first optical compensation layer and the second optical compensation layer having reverse wavelength dispersion characteristics means that the following formulas (3) to (6) are satisfied.
Rth1(450)/Rth1(550)≦1.00 (3)
1.00≦Rth1(650)/Rth1(550) (4)
Re2(450)/Re2(550)≦1.00 (5)
1.00≦Re2(650)/Re2(550) (6)

Here, Rth1(λ) = {(nx1 + ny1)/2 - nz1} x d1, Rth2(λ) = {(nx2 + ny2)/2 - nz2} x d2, Re1(λ) = (nx1 - ny1) x d1, Re2(λ) = (nx2 - ny2) x d2, where d1 and d2 represent the thicknesses of the first optical compensation layer and the second optical compensation layer, respectively, and λ represents the measurement wavelength.

Materials for the first optical compensation layer and the second optical compensation layer can be, for example, those described in Japanese Patent No. 5463666, JP 2010-031223, JP 2010-030979, JP 2009-173893, JP 2009-227667, JP 2010-241919, JP 2010-024438, JP 2011-162678, JP 2011-207765, and JP 2010 Suitable materials include the polymerizable liquid crystal compounds described in JP-A-270108, JP-A-2011-246381, JP-A-2012-021068, JP-A-2016-121339, JP-A-2018-087152, JP-A-2017-179367, JP-A-2017-210601, JP-A-2019-151763, JP-A-6700468, and JP-A-2020-074021.

The optical properties of the first optical compensation layer and the second optical compensation layer preferably satisfy the following (7) to (10).
0nm ≦ Re1 (550) ≦ 5nm (7)
-200nm ≦ Rth1 (550) ≦ -20nm (8)
110nm ≦ Re2 (550) ≦ 150nm (9)
35nm ≦ Rth2 (550) ≦ 105nm (10)

It is more preferable that the optical properties of the first optical compensation layer and the second optical compensation layer satisfy the following (7a) to (10a).
0nm ≦ Re1 (550) ≦ 5nm (7a)
-120nm ≦ Rth1 (550) ≦ -50nm (8a)
120nm ≦ Re2 (550) ≦ 140nm (9a)
50nm ≦ Rth2 (550) ≦ 80nm (10a)

The thickness of the first optical compensation layer and the second optical compensation layer is not particularly limited, but can typically be 0.1 μm to 10 μm.

The first optical compensation layer and the second optical compensation layer may be laminated directly to each other, or may be laminated via an adhesive layer. The adhesive may be the same as the adhesive used to bond the polarizing element and protective film described above.

The polarizing plate and retardation film can be bonded using the same adhesive layer as used to bond the polarizing element and protective film described above, but it is preferable to use an active energy ray-curable adhesive. By using the same adhesive as used to bond the polarizing element and protective film described above or an active energy ray-curable adhesive, the optical compensation layer is supported by a relatively hard layer, which prevents deformation and helps prevent scratches and dents during transportation, making this preferable.

If the polarizing plate has a protective film on only one side of the polarizing element, the retardation film can be laminated directly onto the polarizing element. However, if the polarizing plate has protective films on both sides of the polarizing element, it is preferable that the protective film between the polarizing element and the retardation film is an optically isotropic film.

The optically isotropic film is one that satisfies the following formulas (11) and (12).
0nm≦｜Re3(590)｜≦20nm (11)
0nm≦｜Rth3(590)｜≦20nm (12)

Here, if the refractive index of the optically isotropic film in the in-plane slow axis direction is nx3, the refractive index of the in-plane fast axis direction is ny3, and the refractive index in the thickness direction is nz3, then Re3(λ) = (nx3 - ny3) x d3, Rth3(λ) = {(nx3 + ny3)/2 - nz3} x d3, where d3 represents the thickness of the optically isotropic film.

There are no particular restrictions on the materials and manufacturing methods of the optically isotropic film, so long as they satisfy the above-mentioned optical properties. The optically isotropic film may be a single optical film or a laminate of two or more optical films. Preferably, the optically isotropic film is a single film. This is because it reduces the occurrence of birefringence and unevenness caused by shrinkage stress of the polarizing element and heat from the light source, and allows the liquid crystal panel to be made thinner.

The optical film used for the optically isotropic film is preferably one that has excellent transparency, mechanical strength, thermal stability, and moisture-blocking properties, and is less likely to develop optical unevenness due to distortion. Polymer films are preferably used as the above-mentioned film.

The absolute value of the photoelastic coefficient of the optical film used in the optically isotropic film is preferably 1.0×10 ⁻¹⁰ m ² /N or less, more preferably 5.0×10 ⁻¹¹ m ² /N or less, even more preferably 1.0×10 ⁻¹¹ m ² /N or less, and particularly preferably 5.0×10 ⁻¹² m ² /N or less. By setting the photoelastic coefficient value within the above range, it is possible to obtain a liquid crystal display device that has excellent optical uniformity, little change in optical properties even in environments such as high temperature and high humidity, and excellent durability. In addition, there is no particular lower limit for the photoelastic coefficient, but it is generally 5.0×10 ⁻¹³ m ² /N or more.

Materials that can be used to form the optically isotropic film include polycarbonate resins, polyvinyl alcohol resins, cellulose resins, polyester resins, polyarylate resins, polyimide resins, cyclic polyolefin resins, polysulfone resins, polyethersulfone resins, polyolefin resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Thermosetting or ultraviolet-curable resins such as urethane, acrylic urethane, epoxy, and silicone resins can also be used. The optically isotropic film may contain one or more suitable additives.

The cellulose-based resin is preferably an ester of cellulose and a fatty acid. Specific examples of such cellulose ester-based resins include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, and dipropionyl cellulose. Of these, triacetyl cellulose is particularly preferred. Many triacetyl cellulose products are commercially available, making them advantageous in terms of availability and cost. Many triacetyl cellulose products have a thickness retardation (Rth) of over 10 nm. However, by using additives that counteract this retardation or adjusting the film-forming method, it is possible to obtain a cellulose-based resin film with low retardation not only in the front direction but also in the thickness direction. Examples of the film formation method include a method in which a substrate film such as polyethylene terephthalate, polypropylene, or stainless steel coated with a solvent such as cyclopentanone or methyl ethyl ketone is laminated to a general cellulose-based film, followed by heat drying (for example, at a temperature of 80°C to 150°C for 3 to 10 minutes), and then peeling off the substrate film; and a method in which a solution of a norbornene resin, (meth)acrylic resin, or the like dissolved in a solvent such as cyclopentanone or methyl ethyl ketone is coated on a general cellulose-based resin film, followed by heat drying (for example, at a temperature of 80°C to 150°C for 3 to 10 minutes), and then peeling off the coated film.

Furthermore, as a cellulose-based resin film with low thickness retardation, a fatty acid cellulose-based resin film with a controlled degree of fatty substitution can be used. Commonly used triacetyl cellulose has a degree of acetic acid substitution of approximately 2.8, but Rth can be reduced by controlling the degree of acetic acid substitution to 1.8 or more and 2.7 or less. Rth can be reduced by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, or acetyltriethyl citrate to the above fatty acid-substituted cellulose-based resin. The amount of plasticizer added is preferably 40 parts by weight or less, more preferably 1 part by weight to 20 parts by weight, and even more preferably 1 part by weight to 15 parts by weight, per 100 parts by weight of the fatty acid cellulose-based resin.

In addition, as optically isotropic films, polymer films containing a resin composition containing a thermoplastic resin having substituted and/or unsubstituted imide groups in the side chains and a thermoplastic resin having substituted and/or unsubstituted phenyl and nitrile groups in the side chains, as described in JP 2001-343529 A (WO 01/37007), etc., and films containing a thermoplastic resin having substituted and/or unsubstituted phenyl and nitrile groups in the side chains, as described in JP 2000-230016 A, JP 2001-151814 A, JP 200 Polymer films containing acrylic resins having a lactone ring structure described in JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, JP-A-2006-171464, etc., JP-A-2004-70290, JP-A-2004-70296, JP-A-2004-163924, JP-A-2004-292812, JP-A-2005-3145 polymer films containing acrylic resins having structural units of unsaturated carboxylic acid alkyl esters and structural units of glutaric anhydride, as described in JP-A-2006-34, JP-A-2006-131898, JP-A-2006-206881, JP-A-2006-265532, JP-A-2006-283013, JP-A-2006-299005, JP-A-2006-335902, etc.; It is also possible to use films containing thermoplastic resins having a glutarimide structure, such as those described in JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492, JP-A-2006-337493, and JP-A-2006-337569. These films have small front retardation and thickness retardation, and also have a small photoelastic coefficient, so they are less likely to cause defects such as unevenness even when the polarizing plate is distorted by heating, etc., and are also preferred in that they have low moisture permeability and therefore excellent humidity durability.

It is also preferable to use cyclic polyolefin resins as optically isotropic films. Specific examples of cyclic polyolefin resins include norbornene resins. Cyclic polyolefin resins are a general term for resins polymerized using cyclic olefins as polymerization units, and examples include the resins described in JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins with α-olefins such as ethylene and propylene, graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrogenated versions of these. Specific examples of cyclic olefins include norbornene monomers.

A variety of cyclic polyolefin resins are commercially available. Specific examples include "ZEONOR" manufactured by Zeon Corporation, "ARTON" manufactured by JSR Corporation, "TOPUS" manufactured by TICONA, and "APEL" manufactured by Mitsui Chemicals, Inc.

A surface protection film may be laminated on the side of the optical laminate opposite the pressure-sensitive adhesive to protect the surface of the optical element from scratches and dirt. The surface protection film is typically peeled off and removed after the optical element is attached to a liquid crystal cell or the like.

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 naphthate, 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 other materials such as polystyrene, polycarbonate, polyarylate, and polyimide. Surface protection films can be formed by providing an adhesive layer on these substrates.

When the optical laminate is a polarizing plate with a pressure-sensitive adhesive layer, a test piece is prepared by cutting the polarizing plate with a pressure-sensitive adhesive layer to a width of 25 mm. The edge of the test piece is pulled at an angle of 180° at a rate of 10,000 mm/min, and the release film is peeled off. The peel force of the pressure-sensitive adhesive layer from the release film (hereinafter also referred to as separator peel force) measured when the test piece is peeled off can be less than 0.10 N.

When the optical laminate is a polarizing plate with a pressure-sensitive adhesive layer, the release film is peeled from the polarizing plate with a pressure-sensitive adhesive layer, and the corona-treated side of the pressure-sensitive adhesive layer and the corona-treated side of the PET film are attached. The test piece is then cut to a width of 25 mm to prepare a test piece. The edges of the test piece are pulled at an angle of 180° at a rate of 300 mm/min, and when the PET film is peeled from the polarizing plate with a pressure-sensitive adhesive layer, the state of the pressure-sensitive adhesive layer (adhesion to substrate) observed on the adhesive residue surface can be cohesive failure.

When the optical laminate is a polarizing plate with a pressure-sensitive adhesive layer, the polarizing plate with a pressure-sensitive adhesive layer is cut with a clicker, and the appearance of the prepared test piece is checked from the separator surface. When wrinkles are observed around the edges, the number of wrinkles counted may be 9 or less, and preferably 0.

Figure 1 shows an example of the layer structure of an optical laminate. The optical laminate 10 shown in Figure 1 has an optical member 11, a pressure-sensitive adhesive layer 12, and a release film 13, in this order.

Figure 2 shows an example of the layer structure of a polarizing plate with an adhesive layer. The polarizing plate with an adhesive layer 20 shown in Figure 2 has, in this order, a linear polarizing plate 21, an adhesive layer 22, and a release film 23, and the linear polarizing plate 21 has a protective film 24 and a polarizer 25.

The present invention will be explained in more detail below with reference to examples. In the examples, "%" and "parts" refer to % by mass and parts by mass unless otherwise specified.

[Separator peeling force evaluation]
The polarizing plates with pressure-sensitive adhesive layers obtained in the Examples and Comparative Examples were cut into 25 mm widths to prepare test pieces. The ends of the test pieces were pulled at an angle of 180° at a rate of 10,000 mm/min to peel the separator, and the separator peel strength was measured. The evaluation criteria for separator peel strength are shown below.
A: Less than 0.10N B: 0.10N or more but less than 0.11N C: 0.11N or more

[Evaluation of Adhesion to Substrate]
The release film was peeled off from the polarizing plates with a pressure-sensitive adhesive layer obtained in the Examples and Comparative Examples, and the pressure-sensitive adhesive layer was subjected to a corona treatment. Next, a PET film was prepared, and one side of the PET film was subjected to a corona treatment. The pressure-sensitive adhesive layer and the corona-treated side of the PET film were attached to each other, and cut into a 25 mm width to prepare a test piece. The edge of the test piece was pulled at an angle of 180° at a speed of 300 mm/min, and the PET film was peeled off from the polarizing plate. After peeling, the surface with adhesive residue was observed. The evaluation criteria for substrate adhesion are shown below.
A: Cohesive failure of adhesive B: Some adhesive remains on the polarizing plate side C: No adhesive remains on the polarizing plate side

[Cut wrinkle evaluation]
The polarizing plates with pressure-sensitive adhesive layers obtained in the examples and comparative examples were cut with a clicker to prepare test pieces. The appearance was checked from the separator surface side, and cut wrinkles were observed around the edges, and the number of cut wrinkles that occurred was counted. The criteria for cut wrinkle evaluation are shown below.
A: 0 cut wrinkles B: 1 to 9 cut wrinkles C: 10 or more cut wrinkles

[Preparation of Acrylic Polymer]
A solution obtained by mixing 98.4 parts by mass of n-butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, and 0.6 part by mass of acrylic acid monomers with 81.8 parts by mass of ethyl acetate was charged into a reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer, and a stirrer. The air in the reaction vessel was replaced with nitrogen gas, and the internal temperature was then raised to 60°C. A solution of 0.12 parts of azobisisobutyronitrile dissolved in 10 parts of ethyl acetate was then added. The internal temperature was maintained at 54-56°C until 12 hours had elapsed since the addition of azobisisobutyronitrile, and then ethyl acetate was added to adjust the polymer concentration to 20%, thereby preparing a (meth)acrylic polymer ethyl acetate solution.

The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the resulting acrylic polymer were measured. Mw and Mn were measured using a GPC system with five columns connected in series: four "TSKgel XL" columns manufactured by Tosoh Corporation and one "Shodex GPC KF-802" column manufactured by Showa Denko K.K. and sold by Shoko Tsusho Co., Ltd. The eluent was tetrahydrofuran, and the measurement was performed in standard polystyrene terms under the following conditions: sample concentration 5 mg/mL, sample introduction volume 100 μL, temperature 40°C, flow rate 1 mL/min. The weight-average molecular weight Mw of the acrylic polymer was 1,180,000, and the number-average molecular weight Mn was 54,000.

Example 1
[Preparation of Pressure-Sensitive Adhesive Composition]
This was prepared by blending 100 parts by mass of the solid content of the acrylic polymer prepared as described above with 0.136 parts by mass of an isocyanate crosslinking agent [an ethyl acetate solution of a trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75%), "Coronate L" (trade name), manufactured by Tosoh Corporation], 0.207 parts by mass of a silane coupling agent [obtained from Shin-Etsu Chemical Co., Ltd. under the trade name "KBM-403)], and the components shown in Table 1 below.

[Preparation of Pressure-Sensitive Adhesive Layer-Attached Polarizing Plate]
The solutions of the acrylic pressure-sensitive adhesive compositions obtained in the Examples and Comparative Examples were applied to the release-treated surface of a release film (trade name: MRV38 (V04)) made of a release-treated polyethylene terephthalate film obtained from Mitsubishi Plastics, Inc. The coating was dried at 90°C for 3 minutes to form a pressure-sensitive adhesive layer on the surface of the separator film. After drying, the pressure-sensitive adhesive layer was transferred to the surface of a transparent protective film of a polarizing plate to produce a pressure-sensitive adhesive layer-attached polarizing plate. The resulting pressure-sensitive adhesive layer-attached polarizing plate was aged for 7 days in an environment of 23°C and 50% humidity, after which the separator peel strength, substrate adhesion, and cut wrinkles were evaluated. The results are shown in Table 1.

<Examples 2 to 12 and Comparative Examples 1 to 4>
A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1, except that the components shown in Table 1 were used instead of the components used in preparing the pressure-sensitive adhesive composition in Example 1. The results are shown in Table 1.

Details of the abbreviations in Table 1 are as follows:
[Non-reactive silicone oil]
A1: Side-chain long-chain alkyl-modified silicone oil, product name "KF-4003" obtained from Shin-Etsu Chemical Co., Ltd.
A2: Side-chain long-chain alkyl-modified silicone oil, product name "KF-4917" obtained from Shin-Etsu Chemical Co., Ltd.
[Reactive silicone oil]
B1: Side-chain diamine-modified silicone oil, product name "KF-859" obtained from Shin-Etsu Chemical Co., Ltd.
B2: Side-chain diamine-modified silicone oil, product name "KF-8005" obtained from Shin-Etsu Chemical Co., Ltd.

10, 20 Optical laminate, 11, 21 Optical member, 12, 22 Pressure-sensitive adhesive layer, 13, 23 Release film, 24 Protective film, 25 Polarizer.

Claims (4)

The composition includes a (meth)acrylic resin, a crosslinking agent, a reactive silicone oil, and a non-reactive silicone oil,
The reactive silicone oil is a reactive silicone oil in which a crosslinkable functional group is introduced into a side chain of a polysiloxane skeleton,
the crosslinkable functional group is an amino group, an epoxy group, a mercapto group, a carboxyl group, an isocyanate group, or a methacrylate group;
the content ratio of the non-reactive silicone oil to 1 part by mass of the reactive silicone oil is more than 1 part by mass and 40 parts by mass or less;
The reactive silicone oil includes a reactive silicone oil having an amino group on a side chain of a polysiloxane skeleton,
The non-reactive silicone oil includes a non-reactive silicone oil having an alkyl group on a side chain of a polysiloxane skeleton,
the amino group is a group derived from a diamine,
The pressure-sensitive adhesive composition, wherein the alkyl group is at least one selected from the group consisting of a long-chain alkyl group and a fluoroalkyl group . The pressure-sensitive adhesive composition according to claim 1 , further comprising a silane coupling agent. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 or 2 . An optical laminate comprising an optical member, the pressure-sensitive adhesive layer according to claim 3 , and a release film in this order.