JP7465101B2 - Pressure-sensitive adhesive composition for photocurable optical film, pressure-sensitive adhesive layer for photocurable optical film, optical member, and image display device - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition for photocurable optical films, a pressure-sensitive adhesive layer for photocurable optical films, an optical member, and an image display device.

Currently, liquid crystal display panels (LCD) and organic EL display panels are mainly used as display panels. In general, a laminate in which multiple films are stacked is attached to the surface of a display panel. For example, in an LCD, optical films such as a polarizing plate, a retardation plate, a viewing angle widening film, and a brightness improvement film are stacked on the surface of the liquid crystal panel. The layers that make up the display panel are then attached via adhesive layers formed from various types of adhesives.

Meanwhile, in recent years, irregular processing such as curving the edges, making indentations, and drilling holes has become mainstream for mobile displays, such as those used in smartphones.

Optical film laminates laminated with optical films, pressure-sensitive adhesive layers, or adhesive layers are subjected to the above-mentioned contour processing, but they are required to have processing characteristics that are greater than those required for conventional optical films and optical film laminates. In particular, the pressure-sensitive adhesive layer is required to have good processability so that the pressure-sensitive adhesive does not suffer thermal damage due to friction caused by spindle processing or stress during scraping, and the pressure-sensitive adhesive layer is not peeled off and the edges are not disturbed.

In addition to processability, pressure sensitive adhesives for optical films are also required to have the optical properties and various durability test conditions required for long periods of time without peeling or lifting.

Furthermore, in recent years, the field of optical devices, particularly mobile phones and mobile terminals, has seen a trend toward thinner and lighter devices, which has given rise to new problems. That is, in optical devices equipped with a touch sensor function, particularly the widespread capacitance-type touch function, the position is detected by the change in the capacitance of a capacitor formed between two electrodes facing each other via an insulating film when a conductor such as a finger approaches from the surface protection panel side. However, as components become thinner, the gap between the electrode and the surface of the protection panel becomes narrower, and as the change in capacitance in response to touch becomes larger, a problem arises in that noise is more likely to occur in the detection signal.

In addition, not only are components becoming lighter and thinner, but the gaps between the above components are also becoming narrower, so there is a demand for even thinner filling materials used to integrate components, such as adhesive sheets. For this reason, it has become necessary to make the adhesive sheets used to fill the gap between the electrodes and the surface protection panel lower in dielectric constant in order to absorb changes in touch detection sensitivity that accompany thinner components and the thinning of the components themselves.

As electrodes become lighter and less expensive, the electrode substrate is being replaced from glass to resin film. In the case of electrodes with a conductive thin film pattern formed on only one side, it is necessary to laminate two film electrodes together, or a glass electrode and a film electrode, via an adhesive sheet or the like, and the adhesive layer used in this case is also required to have low dielectric constant properties.

In addition, to impart aesthetic appeal to the cover glass or cover plastic film, a black or white printing process is applied to the side on which the optical adhesive layer is to be placed. Since this printed area requires concealment, a printed ink layer having a certain thickness or more is formed. When bonding the cover glass or cover plastic film to the optical adhesive layer, the optical adhesive layer needs to be bonded to the steps of the printed ink layer without any gaps. For this reason, the optical adhesive layer is required to have the property of following the steps of the printed ink layer (step-following ability).

As pressure-sensitive adhesives (or adhesives), pressure-sensitive adhesive layers, and laminates for optical films, there are techniques proposed in, for example, Patent Documents 1 and 2.

JP 2017-125195 A JP 2015-524011 A

The present invention has been made in consideration of the above circumstances. That is, the object is to provide a means for obtaining an adhesive layer that has good step conformability, durability in harsh environments (high temperature, high humidity, heat shock), excellent haze after a humidity and heat durability test, excellent processability and adhesive strength, and can further have a low dielectric constant.

The present inventors conducted extensive research to solve the above problems. As a result, they discovered that a pressure-sensitive adhesive composition having the following composition solves the above problems, and thus completed the present invention.

That is, the photocurable pressure-sensitive adhesive composition for an optical film according to one embodiment of the present invention comprises a base agent (A) and a chain transfer agent (B), the base agent (A) comprises a (meth)acrylic acid ester copolymer (a), and the (meth)acrylic acid ester copolymer (a) is
(a1): 15% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a linear or branched alkyl group having 1 to 14 carbon atoms;
(a2): 10% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a cyclic alkyl group having 3 to 14 carbon atoms;
(a3): 5% by mass or more and 35% by mass or less of structural units derived from hydroxyl group-containing (meth)acrylic acid ester monomers;
(a4) 5% by mass or more and 35% by mass or less of structural units derived from amide group-containing monomers;
(However, the total amount of the structural units derived from (a1) to (a4) is 100 mass%, and the content of the structural units derived from (a1) is 20 mass% or more and 60 mass% or less with respect to the total amount of the structural units derived from (a1) and the structural units derived from (a2).)
Including,
The content of the chain transfer agent (B) is 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the main agent (A).

The present invention provides a means for obtaining an adhesive layer that has good conformability to uneven surfaces, durability in harsh environments (high temperature, high humidity, heat shock), excellent haze after a humidity and heat durability test, excellent processability and adhesive strength, and can also have a low dielectric constant.

FIG. 2 is a cross-sectional view showing a configuration of a thin polarizing plate.

The following describes an embodiment of the present invention, but the technical scope of the present invention should be determined based on the claims and is not limited to the following form. In this specification, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and a relative humidity of 40% RH to 50% RH. In this specification, "(meth)acrylic" is a general term for acrylic and methacrylic. In this specification, "(co)polymer" is a general term for a homopolymer formed by polymerization of a single monomer and a copolymer formed by polymerization of multiple types of monomers.

<Photocurable pressure-sensitive adhesive composition for optical film>
A photocurable pressure-sensitive adhesive composition for optical films (also simply referred to as "pressure-sensitive adhesive composition") according to one embodiment of the present invention is a photocurable pressure-sensitive adhesive composition for optical films, comprising a base agent (A) and a chain transfer agent (B), wherein the base agent (A) comprises a (meth)acrylic acid ester copolymer (a), and the (meth)acrylic acid ester copolymer (a) is
(a1): 15% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a linear or branched alkyl group having 1 to 14 carbon atoms;
(a2): 10% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a cyclic alkyl group having 3 to 14 carbon atoms;
(a3): 5% by mass or more and 35% by mass or less of structural units derived from hydroxyl group-containing (meth)acrylic acid ester monomers;
(a4) 5% by mass or more and 35% by mass or less of structural units derived from amide group-containing monomers;
(However, the total amount of the structural units derived from (a1) to (a4) is 100 mass%, and the content of the structural units derived from (a1) is 20 mass% or more and 60 mass% or less with respect to the total amount of the structural units derived from (a1) and the structural units derived from (a2).)
Including,
The content of the chain transfer agent (B) in the photocurable pressure-sensitive adhesive composition for use in an optical film is from 0.01 parts by mass to 5 parts by mass with respect to 100 parts by mass of the main agent (A).

[Main ingredient (A)]
The pressure-sensitive adhesive composition according to the present invention contains a base agent (A), and the base agent (A) essentially contains a (meth)acrylic acid ester copolymer (a) (hereinafter also simply referred to as "copolymer (a)").

<(Meth)acrylic acid ester copolymer (a)>
The copolymer (a) contains structural units derived from the following monomers (a1) to (a4).

(a1): Structural units derived from (meth)acrylic acid ester monomers having a linear or branched alkyl group having from 1 to 14 carbon atoms, 15% by mass or more and 55% by mass or less; (a2): Structural units derived from (meth)acrylic acid ester monomers having a cyclic alkyl group having from 3 to 14 carbon atoms, 10% by mass or more and 55% by mass or less; (a3): Structural units derived from (meth)acrylic acid ester monomers having a hydroxy group, 5% by mass or more and 35% by mass or less; (a4) Structural units derived from monomers having an amide group, 5% by mass or more and 35% by mass or less, provided that the total amount of the structural units derived from (a1) to (a4) is 100% by mass, and the content of the structural units derived from (a1) is 20% by mass or more and 60% by mass or less relative to the total amount of the structural units derived from (a1) and the structural units derived from (a2).

These components (a1) to (a4) are monomers that have one (meth)acryloyl group in the molecule. Monomers that have two or more (meth)acryloyl groups in the molecule are classified as crosslinking agents (C) and are different from components (a1) to (a4) and also different from component (a5) described below.

Components (a1) to (a4) are explained below.

((Meth)acrylic acid ester monomer (a1) having a linear or branched alkyl group having 1 to 14 carbon atoms)
The copolymer (a) contains a structural unit derived from a (meth)acrylic acid ester monomer (a1) (hereinafter also referred to as "(a1) component") having a linear or branched alkyl group having 1 to 14 carbon atoms. In the pressure-sensitive adhesive layer and its cured product, the structural unit derived from the (a1) component functions as the basic skeleton of the polymer. The (a1) component can be used alone or in combination of two or more kinds. In addition, the (a1) component may be a commercially available product or a synthetic product.

Component (a1) is typically represented by the following formula (1):

In the above formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 14 carbon atoms.

Examples of linear or branched alkyl groups having 1 to 14 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, 2-methylbutyl, n-hexyl, isohexyl, 3-methylpentyl, ethylbutyl, n-heptyl, 2-methylhexyl, n-octyl, isooctyl, tert-octyl, 2-ethylhexyl, 3-methylheptyl, n-nonyl, isononyl, 1-methyloctyl, ethylheptyl, n-decyl, 1-methylnonyl, n-undecyl, 1,1-dimethylnonyl, n-dodecyl, n-tridecyl, and n-tetradecyl. Of these, from the viewpoint of ensuring adhesion and basic properties, n-butyl groups, 2-ethylhexyl groups, and n-dodecyl groups are preferred.

More specifically, examples of component (a1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate (n-lauryl (meth)acrylate), etc. Among these, from the viewpoint of ensuring adhesive strength and low dielectric properties, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-dodecyl acrylate (n-lauryl acrylate) are preferred.

The content of the structural unit derived from the (a1) component in the copolymer (a) is 15% by mass or more and 55% by mass or less, with the total amount of the (a1) to (a4) components being 100% by mass. If the structural unit derived from the (a1) component is less than 15% by mass, the glass transition temperature of the copolymer (a) increases, and the step-following ability and durability decrease. On the other hand, if it exceeds 55% by mass, the water absorption under humid heat conditions decreases, and the haze after the humid heat durability test deteriorates. The content of the structural unit derived from the (a1) component is preferably 20% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 40% by mass or less.

The content of the structural units derived from the (a1) component is 20% by mass or more and 60% by mass or less based on the total amount of the structural units derived from (a1) and the structural units derived from (a2). If the content is less than 20% by mass, the adhesive strength decreases and processability deteriorates. On the other hand, if the content exceeds 60% by mass, the pressure-sensitive adhesive layer becomes too soft and processability deteriorates.

((Meth)acrylic acid ester monomer (a2) having a cyclic alkyl group having 3 to 14 carbon atoms)
The copolymer (a) contains a structural unit derived from a (meth)acrylic acid ester monomer (a2) (hereinafter also referred to as "component (a2)") having a cyclic alkyl group having from 3 to 14 carbon atoms. In the pressure-sensitive adhesive layer and its cured product, the structural unit derived from component (a2) plays a role in ensuring adhesive properties, durability, and a low dielectric constant.

Component (a2) can be used alone or in combination of two or more kinds. In addition, component (a2) may be a commercially available product or a synthetic product.

Examples of cyclic alkyl groups having 3 to 14 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 2-cyclopropylethyl, 2-cyclobutylethyl, 2-cyclopentylethyl, cyclohexylmethyl, 2-cyclohexylethyl, cycloheptylmethyl, 2-cyclooctylethyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 2-methylcyclooctyl, 3-(3-methylcyclohexyl)propyl, 2-(4-methylcyclohexyl)ethyl, 2-(4-ethylcyclohexyl)ethyl, 2-(2-methylcyclooctyl)ethyl, decahydronaphthyl, adamantyl, dicyclopentanyl, and isobornyl groups. Among these, the cyclohexyl and isobornyl groups are preferred from the viewpoint of durability and low dielectric properties.

Specific examples of the (a2) component include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate. Among these, isobornyl (meth)acrylate and cyclohexyl (meth)acrylate are preferred from the viewpoint of durability and ensuring low dielectric properties. Isobornyl (meth)acrylate and cyclohexyl (meth)acrylate are more preferred.

The content of the structural unit derived from the (a2) component in the copolymer (a) is 10% by mass or more and 55% by mass or less, with the total amount of the (a1) to (a4) components being 100% by mass. If the content of the structural unit derived from the (a2) component is less than 15% by mass, durability deteriorates. On the other hand, if it exceeds 55% by mass, the glass transition temperature of the copolymer (a) increases, and the step-following ability and durability decrease. The content of the structural unit derived from the (a2) component is preferably 15% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 45% by mass or less.

((Meth)acrylic acid ester monomer (a3) having a hydroxy group)
The copolymer (a) contains a structural unit derived from a (meth)acrylic acid ester monomer (a3) having a hydroxyl group (hereinafter also referred to as "(a3) component"). The structural unit derived from the (meth)acrylic acid ester monomer (a3) having a hydroxyl group has hydrophilicity. Therefore, in the pressure-sensitive adhesive layer and its cured product, the water retention performance of the polymer can be improved and condensation can be prevented. The (a3) component can be used alone or in combination of two or more kinds. In addition, the (a3) component may be a commercially available product or a synthetic product.

Component (a3) is typically represented by the following formula (2):

In formula (2), ^R3 represents a hydrogen atom or a methyl group, and ^R4 represents a divalent organic group.

The divalent organic group is not particularly limited, but from the viewpoint of improving water absorption under moist heat conditions and improving haze after moist heat durability tests, it is preferably an alkylene group having 1 to 10 carbon atoms, and more preferably an alkylene group having 2 to 6 carbon atoms.

Examples of alkylene groups having 1 to 10 carbon atoms include methylene (-CH ₂ -), ethylene (-CH ₂ CH ₂ -), trimethylene (-CH ₂ CH ₂ CH ₂ -), tetramethylene (-CH ₂ CH ₂ CH ₂ CH ₂ -), propylene (-CH(CH ₃ )CH ₂ -), pentamethylene, hexamethylene, heptamethylene, octamethylene, 2-ethylhexamethylene (-CH ₂ CH(CH ₂ CH ₃ )CH ₂ CH ₂ CH ₂ CH ₂ -), nonamethylene, decamethylene, etc. Of these, from the viewpoint of further improving the haze after a wet heat durability test, ethylene and tetramethylene groups are preferred.

Specific examples of component (a3) include 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxymethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 1,4-cyclohexanedimethanol monoacrylate. Among these, 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate are preferred from the viewpoint of further improving the haze after a wet heat durability test.

The content of the structural unit derived from the (a3) component in the copolymer (a) is 5% by mass or more and 35% by mass or less, with the total amount of the (a1) to (a4) components being 100% by mass. If the content derived from the (a3) component is less than 5% by mass, the haze after the wet heat durability test decreases. On the other hand, if it exceeds 35% by mass, the wet heat durability and step conformability decrease. The content of the structural unit derived from the (a3) component is preferably 7% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less.

((Meth)acrylic monomer having an amide group)
The copolymer (a) contains a structural unit derived from an amide group-containing (meth)acrylic monomer (a4) (hereinafter also referred to as "(a4) component"). The structural unit derived from the (a4) component has hydrophilicity. Therefore, in the pressure-sensitive adhesive layer and its cured product, the water retention performance of the polymer can be improved and condensation can be prevented. The (a4) component can be used alone or in combination of two or more kinds. In addition, the (a4) component may be a commercially available product or a synthetic product.

Component (a4) is typically represented by the following formula (3):

In formula (3), ^R5 represents a hydrogen atom or a methyl group, ^R6 represents a divalent organic group or a single bond, ^R7 represents a hydrogen atom or a hydroxyl group, and ^R8 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

The divalent organic group is not particularly limited, but from the viewpoint of further improving the haze after the wet heat durability test, it is preferably an alkylene group having 1 to 10 carbon atoms, and more preferably an alkylene group having 2 to 6 carbon atoms.

Examples of the alkylene group having 1 to 10 carbon atoms include the same groups as those described in formula (2). Among them, an ethylene group is preferred from the viewpoint of further improving the haze after a wet heat durability test.

Examples of the alkyl group having 1 to 10 carbon atoms include the same groups as those described in formula (2). Among them, an ethyl group is preferred from the viewpoint of further improving the haze after a wet heat durability test.

_R7 and _R8 may form a ring together.

Specific examples of (meth)acrylic monomers having an amide group include N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, (meth)acrylamide, N-isopropyl(meth)acrylamide, and N-t-butyl(meth)acrylamide. Among these, N-(meth)acryloylmorpholine and N-hydroxyethyl(meth)acrylamide are preferred from the viewpoints of ensuring durability and further improving haze after a moist heat durability test. These may be used alone or in combination of two or more. In addition, the (a4) component may be a commercially available product or a synthetic product.

The content of the structural unit derived from the (a4) component in the copolymer (a) is 5% by mass or more and 35% by mass or less, with the total amount of the (a1) to (a4) components being 100% by mass. If the content derived from the (a3) component is less than 5% by mass, the haze after the wet heat durability test decreases. On the other hand, if it exceeds 35% by mass, the wet heat durability and step conformability decrease. The content of the structural unit derived from the (a4) component is preferably 7% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less.

((Meth)acrylic acid ester monomer (a5) having one radically polymerizable functional group other than components (a1), (a2), (a3), and (a4))
It is preferable that the copolymer (a) further contains a structural unit derived from a (meth)acrylic acid ester monomer (a5) (hereinafter also referred to as "(a5) component") having one radically polymerizable functional group other than the (a1) to (a4) components. In the pressure-sensitive adhesive layer and its cured product, the structural unit derived from the (a5) component has the effect of lowering the dielectric constant of the polymer. The (a5) component can be used alone or in combination of two or more kinds. In addition, the (a5) component may be a commercially available product or a synthetic product.

Examples of the (a5) component include (meth)acrylic acid ester monomers having an aromatic hydrocarbon group, (meth)acrylic acid ester monomers having a branched alkyl group with 18 to 36 carbon atoms, and (meth)acrylic acid ester monomers having an alkoxyalkyl group or an alkylene oxide group.

A (meth)acrylic acid ester monomer having an aromatic hydrocarbon group is typically represented by the following formula (4):

In formula (4), R ⁹ represents a hydrogen atom or a methyl group, and R ¹⁰ represents an aromatic hydrocarbon group.

The aromatic hydrocarbon group is not particularly limited, but is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms, and examples thereof include groups having a benzene ring such as a phenyl group or a benzylphenyl group, groups having a naphthalene ring, and groups having a biphenyl ring.

Specific examples of (meth)acrylic acid ester monomers having an aromatic hydrocarbon group include benzyl (meth)acrylate, phenyl (meth)acrylate, benzylphenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, p-t-butylphenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, ethylene oxide modified cresol (meth)acrylate, phenol ester (meth)acrylate, phenyl ... Examples of such compounds include those having a benzene ring, such as ethylene oxide modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, and polystyryl (meth)acrylate; those having a naphthalene ring, such as hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate; and those having a biphenyl ring, such as biphenyl (meth)acrylate.

Among these, benzyl (meth)acrylate is preferred from the viewpoint of ensuring durability and low dielectric properties.

Specific examples of (meth)acrylic acid ester monomers having a branched alkyl group with 18 to 36 carbon atoms include isocetyl stearate, isostearyl stearate, and 2-decyltetradecanyl (meth)acrylate.

Examples of (meth)acrylate monomers having an alkoxyalkyl group or an alkylene oxide group include, for example, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate; ethoxy-diethylene glycol (meth)acrylate, ethoxy-triethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, Examples of such acrylates include methoxy-diethylene glycol (meth)acrylate, methoxy-diethylene glycol (meth)acrylate, propoxy-diethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate (2-ethylhexyloxy-diethylene glycol (meth)acrylate), methoxy-polyethylene glycol (meth)acrylate (n=4-10), methoxydipropylene glycol (meth)acrylate, and 2-ethylhexyl-diglycol acrylate.

Among these, isostearyl stearate, 2-decyltetradecanyl (meth)acrylate, and 2-ethylhexyl-diglycol (meth)acrylate are preferred from the viewpoint of ensuring low dielectric properties.

The content of the structural unit derived from component (a5) in copolymer (a) is preferably 8 parts by mass or more and 45 parts by mass or less, and more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the total amount of the structural units derived from components (a1) to (a4). Within this range, the copolymer has excellent adhesion, low dielectric properties, and durability.

[Form of main component (A)]
The base material (A) of the present invention may be in the form of only copolymer (a), or in the form of a so-called polymer syrup containing copolymer (a) and unreacted monomer. However, from the viewpoint of ease of forming the adhesive layer according to the present invention, and of more efficiently achieving the intended effect of the present invention, it is preferable that the base material (A) is in the form of a polymer syrup containing copolymer (a) and unreacted monomer (monomer of the above-mentioned (a1) to (a4) components (and optionally (a5) component)). Hereinafter, a manufacturing method for obtaining the polymer syrup will be described.

The method for producing the copolymer (a) is not particularly limited, and a conventionally known method such as a solution polymerization method using a polymerization initiator, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method, a reversed-phase suspension polymerization method, a thin film polymerization method, or a spray polymerization method can be used. Examples of a method for controlling polymerization include an adiabatic polymerization method, a temperature-controlled polymerization method, and an isothermal polymerization method. The polymerization initiator may be either a thermal polymerization initiator or a photopolymerization initiator. In addition to or in addition to the method of initiating polymerization using a polymerization initiator, a method of initiating polymerization by irradiating with active energy rays such as radiation, electron beams, or ultraviolet rays can also be used. Among these, the bulk polymerization method using a photopolymerization initiator is more preferable because it is easy to adjust the molecular weight and can reduce impurities.

The bulk polymerization method using a photopolymerization initiator is not particularly limited, but for example, the raw material monomers of copolymer (a) and a photopolymerization initiator are added, and the reaction start temperature is set to 20°C to 35°C in a nitrogen atmosphere, and active energy rays are irradiated. When the temperature in the reaction system rises from the reaction start temperature by 5°C to 15°C, the reaction is stopped by introducing air into the reaction system, etc., to obtain copolymer (a). In this case, it is not necessary to react all of the raw material monomers used, and the reaction can be stopped when the desired weight average molecular weight is reached. Since the unreacted raw material monomers (a1) to (a5) serve as a solvent for dissolving copolymer (a), this method can produce a polymer syrup.

Examples of active energy rays used in the bulk polymerization method include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams, and ultraviolet rays are preferably used in terms of controllability, ease of handling, and cost. More preferably, ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. The ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave excitation lamp, a chemical lamp, or a black light. The illuminance of the light source is preferably 1.0 mW/ ^cm2 or more and 50 mW/ ^cm2 or less.

Examples of photopolymerization initiators include acetophenone, 3-methylacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and other acetophenones; benzophenone, 4-chlorobenzophenone, 4,4'-diaminobenzophenone, and other benzoin ethers; benzoin propyl ether, benzoin ethyl ether, and other benzoin ethers; thioxanthones, such as 4-isopropylthioxanthone; 1-hydroxycyclohexyl-phenyl ketone, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, and the like. These photopolymerization initiators can be used alone or in combination of two or more.

The photopolymerization initiator may be a commercially available product. Examples of commercially available products include Omnirad (registered trademark) 184, 819, 907, 651, 1700, 1800, 819, 369, 261, 1173, TPO (all manufactured by IGM Resins B.V.), Ezacure (registered trademark) KIP150, TZT (all manufactured by IGM Resins B.V.), Kayacure (registered trademark) BMS, DMBI (all manufactured by Nippon Kayaku Co., Ltd.), etc.

The amount of photopolymerization initiator used is preferably 0.0005 parts by mass or more and 1 part by mass or less, more preferably 0.002 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of the total amount of raw material monomers.

From the viewpoint of the viscosity of the adhesive composition, the content of copolymer (a) in the polymer syrup is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, based on the total mass of polymer syrup (A).

In the present invention, the composition of copolymer (a) (content of each monomer) and the composition of components (a1) to (a5) may be the same or different. However, in order to improve the properties of the pressure-sensitive adhesive layer and its cured product, it is preferable that the compositions are the same.

In the present invention, the weight average molecular weight (Mw) of the copolymer (a) is preferably 300,000 or more and 3,000,000 or less, and more preferably 500,000 or more and 2,000,000 or less. Within this range, the adhesive layer has excellent coatability when it is formed and excellent durability as an adhesive layer. The weight average molecular weight (Mw) of the copolymer (a) can be measured by the method described in the Examples.

In the present invention, the glass transition temperature (Tg) of copolymer (a) is preferably -40°C or higher and 20°C or lower, and more preferably -20°C or higher and 10°C or lower. Within this range, the durability, step-following ability, and processability are excellent. The glass transition temperature (Tg) of copolymer (a) is calculated using the Fox formula based on the glass transition temperatures of the homopolymers of each monomer used.

[Chain transfer agent (B)]
The chain transfer agent (B) receives radicals from a growing polymer chain to stop the elongation of the growing polymer, and the chain transfer agent (B) that has received the radicals attacks the monomer to restart the polymerization reaction. In the present invention, the chain transfer agent (B) contributes to improving the step-following ability.

Examples of chain transfer agents (B) include primary or secondary monofunctional thiol compounds or polyfunctional thiol compounds, thioglycolic acid compounds, thiocarbonyl compounds, mercaptopropionic acid compounds, etc.

Specific examples of chain transfer agents (B) include β-mercaptopropionic acid, 2-ethylhexyl-3-mercaptopropionate, n-octyl-3-mercaptopropionate, methoxybutyl-3-mercaptopropionate, stearyl-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), 3,3'-thiodipropionic acid, dithiopropionic acid, laurylthiopropionic acid, thioglycolic acid, ammonium thioglycolate, monoethanolamine thioglycolate, and diammonium thioglycolate. Commercially available products include those with the product names BMPA, EHMP, NOMP, MBMP, STMP, TMMP, TEMPIC, PEMP, EGMP-4, DPMP, TDPA, DTDPA, LTPA, ATG, TG-MEA, and DATG (all manufactured by SC Organic Chemical Co., Ltd.). These may be used alone or in combination of two or more.

The amount of the chain transfer agent (B) is 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the main component (A). If the amount of the chain transfer agent (B) is less than 0.01 parts by mass, the molecular weight in the adhesive layer may be nonuniform, and sufficient step-following ability may not be obtained, or it may be difficult to control the curing reaction, and an adhesive layer having sufficient step-following ability may not be obtained stably. If the amount of the chain transfer agent (B) exceeds 5 parts by mass, the molecular weight of the adhesive composition may become too low, and durability may deteriorate. The amount of the chain transfer agent (B) is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0.05 parts by mass or more and 1 part by mass or less, and even more preferably 0.05 parts by mass or more and 0.1 parts by mass or less with respect to 100 parts by mass of the main component (A). If it is within the above range, it is possible to stably obtain an adhesive layer that has sufficient step-following ability and can ensure durability.

[Crosslinking agent (C)]
The pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent (C). The crosslinking agent (C) reacts with the copolymer (a) to form a crosslinked structure. Thus, in the pressure-sensitive adhesive composition, the crosslinking agent (C) can mainly contribute to the adhesiveness (tackiness) and durability.

In the present invention, the crosslinking agent (C) preferably contains at least one selected from the group consisting of an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound, a polyfunctional (meth)acrylic acid ester monomer, and a peroxide. These various crosslinking agents are described below.

[Isocyanate Compound]
In the present invention, specific examples of the isocyanate compound used as the crosslinking agent (C) include dimer acid diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylidene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). Examples of the diisocyanates include aromatic diisocyanates such as allyl isocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanate methyl (NBDI); alicyclic diisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrogenated XDI), and H12-MDI (hydrogenated MDI); carbodiimide-modified diisocyanates of the above diisocyanates; and isocyanurate-modified diisocyanates thereof. Adducts of the above isocyanate compounds with polyol compounds such as trimethylolpropane, polytetramethylene ether glycol (PTMG), and polypropylene glycol (PPG), and biuret and isocyanurate forms of these isocyanate compounds can also be suitably used.

These isocyanate compounds may be commercially available or synthetic.

Commercially available products include, for example, Coronate (registered trademark) L, Coronate (registered trademark) HL, Coronate (registered trademark) HX, Coronate (registered trademark) 2030, Coronate (registered trademark) 2031 (all manufactured by Tosoh Corporation), Takenate (registered trademark) D-102, Takenate (registered trademark) D-110N, Takenate (registered trademark) D-200, Takenate (registered trademark) D-202 (all manufactured by Mitsui Chemicals, Inc.), Duranate (registered trademark) 24A-100, Duranate (registered trademark) TPA-100, Duranate (registered trademark) TKA-100, Duranate (registered trademark) P301-75E, Duranate (registered trademark) E402-90T, Duranate (registered trademark) E405-80T, Duranate (registered trademark) TSE-100, Duranate (registered trademark) D-101, Duranate (registered trademark) ) D-201 (all manufactured by Asahi Kasei Corporation), Sumidur (registered trademark) N-75, N-3200, N-3300 (all manufactured by Sumika Covestro Urethane Co., Ltd.), Sanprene (registered trademark) P-6090 (PTMG/MDI type), Sanprene (registered trademark) P-663L (PTMG/TDI type), Sanprene (registered trademark) P-664 (PTMG/TDI type), Sanprene (registered trademark) P-665 (PT Examples include, but are not limited to, Sanprene (registered trademark) P-667 (PTMG/TDI system), Sanprene (registered trademark) P-868 (PTMG/HMDI system), Sanprene (registered trademark) P-870 (PTMG/HMDI system), Sanprene (registered trademark) C-810 (PPG/TDI system) (all manufactured by Sanyo Chemical Industries, Ltd.), and TAIC (manufactured by Mitsubishi Chemical Corporation).

The isocyanate compound may be used in the form of an unblocked isocyanate compound. It may also be used in the form of a blocked isocyanate compound obtained by reacting with a blocking agent that protects the isocyanate group. Such blocked isocyanate compounds may be commercially available products or synthetic products. Commercially available blocked isocyanate compounds include, for example, Duranate (registered trademark) MF-B60X (blocked 1,6-hexamethylene diisocyanate) and Duranate (registered trademark) MF-K60X (blocked 1,6-hexamethylene diisocyanate) manufactured by Asahi Kasei Corporation, Coronate (registered trademark) AP-M, 2503, 2507, 2513, 2515, and Millionate (registered trademark) MS-50 manufactured by Tosoh Corporation, and Takenate (registered trademark) B-830 (blocked tolylene diisocyanate), B-815N (blocked 4,4'-methylenebis(cyclohexyl isocyanate)), and B-842N (blocked 1,3-bis(isocyanate)) manufactured by Mitsui Chemicals, Inc. Examples of such block urethane-modified polyisocyanates include B-846N (blocked 1,3-bis(isocyanatomethyl)cyclohexane), B-874N (blocked isophorone diisocyanate), B-882N (blocked 1,6-hexamethylene diisocyanate), Burnock (registered trademark) D-500 (blocked tolylene diisocyanate) and D-550 (blocked 1,6-hexamethylene diisocyanate) manufactured by DIC Corporation, and Elastron (registered trademark) BN-P17 (blocked 4,4'-diphenylmethane diisocyanate), BN-04, BN-08, BN-44, and BN-45 (all of which are blocked urethane-modified polyisocyanates) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Of these, Duranate (registered trademark) MF-K60X is preferred.

In order to further improve the durability of the adhesive, it is preferable that the isocyanate compound is used in the form of an unblocked isocyanate compound.

[Carbodiimide Compound]
In the present invention, the carbodiimide compound used as the crosslinking agent (C) is not particularly limited. As an example, a high molecular weight polycarbodiimide produced by subjecting a diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst is used.

Examples of diisocyanates used in the decarboxylation condensation reaction include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 3,3'-dimethyl-4,4'-diphenylether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate.

In addition, examples of the carbodiimidization catalyst used in the above decarboxylation condensation reaction include phospholene oxides such as 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and 3-phospholene isomers of these.

The high molecular weight polycarbodiimide may be a commercially available product or a synthetic product. Examples of commercially available products include the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Inc. Among them, Carbodilite (registered trademark) V-01, V-03, V-05, V-07, and V-09 are preferred because of their excellent compatibility with organic solvents.

[Oxazoline Compounds]
In the present invention, the oxazoline compound used as the crosslinking agent (C) is not particularly limited.However, it is preferable to use an oxazoline group-containing acrylic/styrene-based polymer that has a main chain made of an acrylic skeleton or a styrene skeleton and has an oxazoline group on the side chain of the main chain.In addition, it is also preferable to use an oxazoline group-containing polymer such as an oxazoline group-containing acrylic polymer that has a main chain made of an acrylic skeleton and has an oxazoline group on the side chain of the main chain.

Examples of oxazoline groups include 2-oxazoline groups, 3-oxazoline groups, and 4-oxazoline groups, with the 2-oxazoline group being preferred.

The oxazoline group-containing polymer may also have a polyoxyalkylene group in addition to the oxazoline group.

Specific examples of oxazoline group-containing polymers include oxazoline group-containing acrylic polymers such as Epocross (registered trademark) WS-300, Epocross (registered trademark) WS-500, and Epocross (registered trademark) WS-700 manufactured by Nippon Shokubai Co., Ltd., and oxazoline group-containing acrylic/styrene polymers such as Epocross (registered trademark) K-1000 series and Epocross (registered trademark) K-2000 series manufactured by Nippon Shokubai Co., Ltd.

[Epoxy Compound]
In the present invention, the epoxy compound used as the crosslinking agent (C) is not particularly limited, and a known epoxy-based crosslinking agent can be appropriately adopted. Commercially available epoxy compounds include liquid epoxy resins such as "TETRAD (registered trademark)-C" and "TETRAD (registered trademark)-X" manufactured by Mitsubishi Gas Chemical Company, Inc., "ADEKA RESIN (registered trademark) EPU series" and "ADEKA RESIN (registered trademark) EPR series" manufactured by ADEKA Corporation, and "Celloxide (registered trademark)" manufactured by Daicel Corporation. These liquid epoxy resins are preferred in that they facilitate the mixing operation when producing a pressure-sensitive adhesive for optical films.

[Polyfunctional (meth)acrylic acid ester monomer]
The polyfunctional (meth)acrylic acid ester monomer used as the crosslinking agent (C) of the present invention is a (meth)acrylic acid ester monomer having a plurality (two or more) of radical polymerizable functional groups. Examples of such monomers include polyfunctional monomers of hydrocarbon or hydrocarbon ether. The polyfunctional monomers of hydrocarbon or hydrocarbon ether are compounds in which the hydroxyl group of a polyhydric alcohol having a main skeleton of a hydrocarbon group or a hydrocarbon ether group having 10 to 100 carbon atoms is (meth)acrylated. The compound is preferable from the viewpoint of improving adhesion by crosslinking. Examples of the hydrocarbon group of the polyhydric alcohol include linear or branched aliphatic hydrocarbon groups, aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and hydrocarbon groups combining these hydrocarbon groups. Examples of the hydrocarbon ether group include those obtained by etherifying the hydrocarbon group. In addition, examples of polyhydric alcohols having a main skeleton of a hydrocarbon ether group include compounds in which an alkylene oxide having 2 to 4 carbon atoms is added to the polyhydric alcohol (addition number 1 to 30). Further examples include polyalkylene glycols (addition number 1 to 30) obtained from alkylene oxides having 2 to 4 carbon atoms.

Specific examples of the above-mentioned hydrocarbon-based bifunctional monomers include di(meth)acrylates of alkylene glycols such as ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; di(meth)acrylates of diol compounds having alicyclic hydrocarbon groups such as cyclohexane dimethanol di(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate (dimethylol-tricyclodecane diacrylate); and di(meth)acrylates of diol compounds having aromatic hydrocarbon groups such as bisphenol A di(meth)acrylate.

Specific examples of the hydrocarbon ether-based bifunctional monomer include, for example, di(meth)acrylates of alkylene glycols and diol compounds added with alkylene oxides, such as alkoxylated hexanediol di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, alkoxylated di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, and alkoxylated bisphenol A di(meth)acrylate. Specific examples of the hydrocarbon ether-based bifunctional monomer include di(meth)acrylates of polyalkylene glycols, such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and dipropylene glycol di(meth)acrylate, and dioxane glycol di(meth)acrylate.

Examples of hydrocarbon or hydrocarbon ether trifunctional or tetrafunctional monomers include tri(meth)acrylates or tetra(meth)acrylates of tri- or tetraol compounds such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, glyceryl tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and trimethylolpropane tetra(meth)acrylate, as well as tri(meth)acrylates or tetra(meth)acrylates of compounds obtained by adding alkylene oxide to the above tri- or tetraol compounds.

In addition, examples of monomers other than the above-mentioned hydrocarbon-based or hydrocarbon ether-based monomers include polyester poly(meth)acrylates having two or more (meth)acryloyl groups at the terminals, epoxy (meth)acrylates, etc.

[Polyfunctional Allyl Monomer]
The polyfunctional allyl monomer used as the crosslinking agent (C) of the present invention is a monomer having at least one allyl group and a plurality (two or more) of radical polymerizable functional groups including the allyl group. Examples of such monomers include allyl (meth)acrylate, diallyl phthalate (DAP), trimethylolpropane diallyl ether, pentaerythritol triallyl ether, triallyl isocyanurate, etc.

[Peroxide]
In the present invention, the peroxide used as the crosslinking agent (C) is not particularly limited, and any known peroxide can be used. In addition, taking into consideration productivity and stability, the peroxide is preferably one having a one-minute half-life temperature of 80° C. or more and 160° C. or less. The one-minute half-life temperature is more preferably 80° C. or more and 140° C. or less. It is even more preferably 80° C. or more and 125° C. or less, and particularly preferably 90° C. or more and 125° C. or less. The "half-life of peroxide" is an index representing the decomposition rate of peroxide, and means the time until the remaining amount of peroxide is reduced to half. The decomposition temperature for obtaining the half-life at a certain time and the half-life time at a certain temperature are described in the manufacturer's catalog, etc. For example, it is described in the 9th edition of the Organic Peroxide Catalog (May 2003) published by NOF Corporation.

Examples of such peroxides include diisopropyl peroxydicarbonate (one-minute half-life temperature 88.3°C; hereafter, the temperatures in parentheses indicate one-minute half-life temperatures), di(2-ethylhexyl) peroxydicarbonate (90.6°C), bis(4-t-butylcyclohexyl) peroxydicarbonate (92.1°C), di-sec-butyl peroxydicarbonate (92.4°C), t-butyl peroxyneodecanoate (103.5°C), t-hexyl peroxypivalate (109.1°C), and t-butyl peroxypivalate (110 .3°C), dilauroyl peroxide (116.4°C), bis-n-octanoyl peroxide (117.4°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3°C), di(4-methylbenzoyl)peroxide (128.2°C), dibenzoyl peroxide (benzoyl peroxide) (130.0°C), a mixture of dibenzoyl peroxide, benzoyl m-methylbenzoyl peroxide and m-toluoyl peroxide (131.1°C), t-butyl peroxybutyrate (136.1°C), etc. are included. Among them, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, and t-butyl peroxyneodecanoate are preferably used. These may be used alone, but it is also preferable to use two or more of them in combination from the viewpoint of adjusting the reactivity. An example of a combination of two or more types is di(4-t-butylcyclohexyl) peroxydicarbonate and dilauroyl peroxide.

The peroxide may be a commercially available product or a synthetic product. Examples of commercially available products include those manufactured by NOF Corporation under the trade names: "Perloyl (registered trademark, the same below) IB" (85.1°C), "Percumyl (registered trademark, the same below) ND" (94.0°C), "Perloyl NPP" (94.0°C), "Perloyl IPP" (88.3°C), "Perloyl SBP" (92.4°C), "Perocta (registered trademark, the same below) ND" (92.4°C), "Perloyl TCP" (92.1°C), and "Perloyl OPP" (9 0.6°C), "Perhexyl (registered trademark, the same below) ND" (100.9°C), "Perbutyl (registered trademark, the same below) ND" (103.5°C), "Perbutyl NHP" (104.6°C), "Perhexyl PV" (109.1°C), "Perbutyl PV" (110.3°C), "Peroyl 355" (112.6°C), "Peroyl L" (116.4°C), "Perocta O" (124.3°C), "Peroyl SA" (131.8°C), "Perhexa (registered trademark, the same below) 25O" (118.8°C), "Perhexyl O" (132.6°C), "Niper (registered trademark, the same below) PMB" (128.2°C), "Perbutyl O" (134.0°C), "Niper BMT" (131.1°C), "Niper BW" (130.0°C), "Niper BMT-K40" (131.1°C), "Niper BMT-M" (131.1°C), "Perhexa MC" (142.1°C), "Per Examples include Hexa TMH (147.1°C), Perhexa HC (149.2°C), Perhexa C (153.8°C), Pertetra (registered trademark, same below) A (153.8°C), Perhexyl I (155.0°C), Perbutyl L (159.4°C), Perbutyl I (158.8°C), Perhexa 25Z (158.2°C), Perbutyl A (159.9°C), and Perhexa 22 (159.9°C).

In the present invention, the crosslinking agent (C) may be used alone or in combination of two or more. When two or more types are combined, two or more types of crosslinking agents of the same type (e.g., two types of isocyanate compounds) may be combined. One or more types of crosslinking agents of different types (e.g., one type of isocyanate compound and one type of peroxide) may be combined.

The content of the crosslinking agent (C) in the pressure-sensitive adhesive for optical films of the present invention is not particularly limited, but is preferably 0.01 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the main agent (A). The content is more preferably 0.02 parts by mass or more and 4 parts by mass or less, and even more preferably 0.03 parts by mass or more and 3 parts by mass or less. It is particularly preferably 0.05 parts by mass or more and 3 parts by mass or less. When the content of the crosslinking agent (C) is within the above range, durability and step-following ability can be ensured.

[Silane coupling agent (D)]
The pressure-sensitive adhesive for optical films of the present invention preferably further contains a silane coupling agent (D). In the pressure-sensitive adhesive composition of the present invention, the silane coupling agent (D) can mainly contribute to improving durability and adhesion to glass when the adherend is glass. In this specification, the term "silane coupling agent" refers to a silane compound that does not have a siloxane bond (Si-O-Si bond) and has two or more reactive groups in the molecule.

In the present invention, the silane coupling agent (D) is not particularly limited. Specifically, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxy Examples of the silane include propylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis-(3-[triethoxysilyl]propyl)tetrasulfide, and γ-isocyanatepropyltriethoxysilane. Further examples include silane coupling agents having functional groups such as epoxy groups (glycidoxy groups), amino groups, mercapto groups, and (meth)acryloyl groups, and silane coupling agents containing functional groups that can react with these functional groups. Compounds having hydrolyzable silyl groups obtained by reacting other coupling agents, polyisocyanates, etc., with each functional group in any ratio can also be used.

The silane coupling agent (D) may be a commercially available product or a synthetic product. Commercially available products of the silane coupling agent (D) include, for example, KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, KBM-803, KBE-846, and KBE-9007 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

The above silane coupling agents (D) can be used alone or in combination of two or more.

When the pressure-sensitive adhesive for optical films of the present invention contains a silane coupling agent (D), the content of the silane coupling agent (D) is not particularly limited. However, it is preferably 0.001 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the main component (A). The content is more preferably 0.001 parts by mass or more and 4 parts by mass or less, and even more preferably 0.01 parts by mass or more and 3 parts by mass or less. If the content is 0.001 parts by mass or more, it is preferable from the viewpoint that the effect on durability can be expressed even in harsh environments. On the other hand, if the content is 5 parts by mass or less, it is preferable from the viewpoint that the deterioration of heat foaming caused by low molecular weight compounds is not caused.

[High Softening Point Resin (E)]
The adhesive composition of the present invention preferably further contains a high softening point resin (E) having a softening point of 60° C. or more and 200° C. or less (hereinafter, also simply referred to as "high softening point resin (E)"). This is because adding the high softening point resin (E) can provide an adhesive having a property of being somewhat hard at room temperature and softening (becoming soft) at high temperatures. Adding the high softening point resin (E) to impart such a property is preferable because durability can be ensured.

From the viewpoint of effectively exerting the above-mentioned action and effect, the high softening point resin (E) used in the present invention is preferably a resin having a softening point of 60°C or more and 200°C or less. Therefore, conventionally known resins can be used. Specific examples thereof include petroleum resins such as aliphatic petroleum resins, alicyclic hydrocarbon resins, aromatic petroleum resins, fully hydrogenated aliphatic petroleum resins, fully hydrogenated alicyclic hydrocarbon resins, fully hydrogenated aromatic petroleum resins, partially hydrogenated aliphatic petroleum resins, partially hydrogenated alicyclic hydrocarbon resins, and partially hydrogenated aromatic petroleum resins, aromatic hydrocarbon resins, aliphatic saturated hydrocarbon resins, terpene resins, terpene phenol resins, hydrogenated terpene resins, coumarone-indene resins, rosin resins (also called rosins or rosin derivatives) such as rosin acid, polymerized rosin acid, and rosin ester resins (rosin acid esters), epoxy resins, phenolic resins, oil-soluble phenols (resins), or modified resins thereof. These high softening point resins (E) may be used alone or in combination of two or more. Among these, alicyclic hydrocarbon resins, terpene phenol resins, and terpene resins are more preferred from the viewpoint of good compatibility with copolymer (a). Furthermore, from the viewpoint of very good compatibility with other components of the pressure-sensitive adhesive and easy transparency when applied to an optical film, it is even more preferred that the high-softening point resin (E) is a rosin ester resin.

The high softening point resin (E) may be a synthetic product or a commercially available product.

Examples of commercially available rosin ester resins include Pine Crystal (registered trademark, hereinafter the same) KR-85 (softening point 80-87°C, hereinafter the temperature in parentheses indicates the softening point), Pine Crystal KR-612 (80-90°C), Pine Crystal KR-614 (84-94°C), Pine Crystal KE-100 (95-105°C), Pine Crystal KE-311 (90-100°C), Pine Crystal PE-590 (90-100°C), etc. ), Pine Crystal KE-359 (94-104°C), Pine Crystal KE-604 (124-134°C), Pine Crystal KR-120 (110-130°C), Pine Crystal KR-140 (130-150°C), Pine Crystal KR-614 (84-94°C), Pine Crystal D-6011 (84-99°C), Pine Crystal KR-50M (145-160°C) (all manufactured by Arakawa Chemical Industries Co., Ltd.). These are ultra-light-colored rosins that are ideal for optical applications requiring transparency.

Other examples of commercially available rosin ester resins include Super Ester A-75 (70-80°C), Super Ester A-100 (95-105°C), Super Ester A-115 (108-120°C), Super Ester A-125 (120-130°C), and Tamanol (registered trademark, the same applies below) 460 (182-192°C) (all manufactured by Arakawa Chemical Industries, Ltd.).

Examples of commercially available alicyclic hydrocarbon resins include Alcon (registered trademark, the same applies below) P-90 (85-95°C), Alcon P-100 (95-105°C), Alcon (registered trademark) P-115 (110-120°C), Alcon P-125 (120-130°C), Alcon P-140 (135-145°C), Alcon M-90 (85-95°C), Alcon M-100 (95-105°C), Alcon M-115 (110-120°C), Alcon M-135 (130-140°C) (all manufactured by Arakawa Chemical Industries, Ltd.), etc.

Examples of commercially available terpene phenol resins include, for example, Tamanol 803L (145-160°C), Tamanol 901 (125-135°C) (both manufactured by Arakawa Chemical Industries, Ltd.), YS Polystar (registered trademark, the same applies below) U130 (125-135°C), YS Polystar U115 (110-120°C), YS Polystar T160 (155-165°C), YS Polystar T145 (140-150°C), YS Polystar T130 (125-135°C), and YS Polystar T11. 5 (110-120°C), YS Polystar T100 (95-105°C), YS Polystar T80 (75-85°C), YS Polystar S145 (140-150°C), YS Polystar G150 (145-155°C), YS Polystar G125 (120-130°C), YS Polystar N125 (120-130°C), YS Polystar K125 (120-130°C), YS Polystar TH130 (125-135°C) (all manufactured by Yasuhara Chemical Co., Ltd.).

Examples of commercially available terpene resins include YS Resin (registered trademark, the same applies below) PX1250 (120-130°C), YS Resin PX1150 (110-120°C), YS Resin PX1000 (95-105°C), YS Resin PX800 (75-85°C), YS Resin PX1150N (110-120°C), YS Resin TO125 (120-130°C), YS Resin TO115 (110-120°C), YS Resin TO105 (100-110°C), and YS Resin TO85 (80-90°C) (all manufactured by Yasuhara Chemical Co., Ltd.).

When the high softening point resin (E) is added to the adhesive composition of the present invention, the amount of the high softening point resin (E) added is not particularly limited. However, it is preferably 0.1 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the main component (A). The amount added is more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1 part by mass or more and 20 parts by mass or less. If the content is 0.1 parts by mass or more, it is preferable from the viewpoint of the softening effect being exhibited during durability testing. On the other hand, if the content is 30 parts by mass or less, it is preferable from the viewpoint of being able to suppress deterioration of durability due to low molecular weight substances. In addition, it is preferable from the viewpoint of ensuring durability even in harsh environments, such as being able to effectively suppress a decrease in the flexibility of the adhesive even in a low temperature range of -25°C or less.

The softening point of the high softening point resin (E) is preferably 60°C or higher and 200°C or lower. From the viewpoint of improving step conformability, processability, and adhesion, it is more preferably 70°C or higher and 150°C or lower. The softening point is further preferably 80°C or higher and 140°C or lower, and particularly preferably 85°C or higher and 130°C or lower. In the present invention, the softening point is a value measured by the method described in JIS K6863 (1994).

[Other added ingredients]
The pressure-sensitive adhesive composition of the present invention may contain, as necessary, other known additive components such as a photopolymerization initiator, a solvent, a crosslinking accelerator, an antiaging agent, a filler, a colorant (e.g., a pigment or a dye), an ultraviolet absorber, an antioxidant, a plasticizer, a softener, a surfactant, and an antistatic agent, within a range that does not impair the effects of the present invention.

Photopolymerization initiators are used when forming the adhesive layer. Examples of photopolymerization initiators include α-diketones such as benzoin and diacetyl; benzophenone derivatives such as benzophenone; benzoic acid ester derivatives; acyloin ether derivatives; acetophenone derivatives such as acetophenone; xanthone and thioxanthone derivatives; halogen-containing compounds such as chlorosulfonyl, chloromethyl polynuclear aromatic compounds, chloromethyl heterocyclic compounds, and chloromethyl benzophenones; triazines; fluorenones; haloalkanes; acridines; redox couples of photoreducible dyes and reducing agents; organic sulfur compounds; and peroxides.

Specific examples of photopolymerization initiators include 1-hydroxyphenyl ketone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one, (2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-benzyl-2-(dimethylamino)-4-morpholinobutylphenone, 2-methyl-4'-(methylthio)-2-morpholino-propiophenone, 1,7-(9-acridinyl)heptane, 2,2'-bis(o-chlorophenyl)-4,5 , 4',5'-tetraphenyl-1,2'-biimidazole, 4,4'-dimethylaminobenzophenone, 4,4'-diethylaminobenzophenone, 7-(diethylamino)-4-methyl-2H-1-benzopyran-2-one (7-(diethylamino)-4-methylcoumarin, 4-dimethylaminobenzoic acid ethyl, 2-dimethylaminobenzoic acid ethyl, 4-dimethylaminobenzoic acid (n-butoxy)ethyl, p-dimethylaminobenzoic acid isoamyl ethyl ester, 4-dimethylaminobenzoic acid 2-ethylhexyl, 4,4'-diethylaminobenzophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and the like. Commercially available products include IGM Examples of such compounds include Omnirad (registered trademark) 907, 369, 184, 819, and TPO manufactured by Resins B.V., Nissocure MABP manufactured by Nippon Soda Co., Ltd., EAB manufactured by Hodogaya Chemical Co., Ltd., Kayacure (registered trademark) EPA and DMBI manufactured by Nippon Kayaku Co., Ltd., Quantacure DMB and BEA manufactured by International Bio-Synthetics, Inc., and Esolol 50 manufactured by Van Dyk. These compounds may be used alone or in combination of two or more kinds.

The amount of the photopolymerization initiator is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of copolymer (a). When the amount of the photopolymerization initiator is within the above range, the durability and adhesive strength are excellent.

<Method of producing (preparing) pressure-sensitive adhesive composition>
The pressure-sensitive adhesive composition of the present invention can be prepared by mixing the main component (A), the chain transfer agent (B), and other components as necessary. The mixing order and mixing temperature of each component are not particularly limited and can be appropriately adjusted by a person skilled in the art.

[Photocurable pressure-sensitive adhesive layer for optical film]
According to another embodiment of the present invention, there is provided a photocurable pressure-sensitive adhesive layer for optical films (also simply referred to as "pressure-sensitive adhesive layer") obtained by curing the photocurable pressure-sensitive adhesive composition for optical films. The pressure-sensitive adhesive layer is distinguished from the pressure-sensitive adhesive composition described above in that the reaction rate of the monomer is more than 95 mass %. In addition, the pressure-sensitive adhesive layer is distinguished from the cured product of the pressure-sensitive adhesive layer described below in that it contains a certain amount or more of a polyfunctional compound and has reactivity.

The thickness of the adhesive layer is not particularly limited, but is preferably 20 μm to 1 mm, more preferably 30 μm to 500 μm, and even more preferably 50 μm to 300 μm. If the thickness is 20 μm or more, it becomes easier to follow the printing step (usually about 1 μm to 100 μm). If the thickness is 1 mm or less, it is possible to ensure coatability and uniformity of the thickness of the adhesive layer.

The weight average molecular weight of the adhesive layer is preferably 50,000 to 1,000,000, more preferably 100,000 to 800,000, and even more preferably 200,000 to 750,000. A weight average molecular weight of 50,000 or more is preferred from the viewpoint of improving durability. A weight average molecular weight of 1,000,000 or less is preferred from the viewpoint of improving conformability to unevenness. In this specification, the weight average molecular weight is a value measured by the method described in the Examples below.

[Method of manufacturing pressure-sensitive adhesive layer]
According to another embodiment of the present invention, there is provided a method for producing a pressure-sensitive adhesive layer for a photocurable optical film, the method comprising: a laminating step of applying the pressure-sensitive adhesive composition for a photocurable optical film onto a release-treated surface of a first release sheet to form a coating film, and laminating the second release sheet so that the release-treated surface of the second release sheet is in contact with a surface of the coating film; and an active energy ray irradiation step of irradiating the coating film with active energy rays through at least one of the first release sheet and the second release sheet.

When the pressure-sensitive adhesive composition is used for an optical film, the pressure-sensitive adhesive composition may be applied and cured directly onto the optical film to form a pressure-sensitive adhesive layer. However, it is preferable to apply the pressure-sensitive adhesive composition onto the release-treated surface of a first release sheet (also called a "release film" or "separator") to form a coating film, perform a lamination process in which the release-treated surface of a second release sheet is laminated onto the obtained coating film so that it is in contact with the surface of the coating film, and then perform an active energy ray irradiation process in which active energy rays are irradiated onto the coating film through at least one of the first release sheet and the second release sheet to form a pressure-sensitive adhesive layer by curing the pressure-sensitive adhesive composition. It is then preferable to transfer the obtained pressure-sensitive adhesive layer to various optical films for use.

The release sheet with the adhesive layer can be wound up together during the manufacturing process into a roll. When adhering the adhesive layer to various optical films, liquid crystal panels, etc., the rolled release sheet with the adhesive layer is cut or processed as necessary, and the release sheet is removed before use. The release sheet also serves the role of protecting the adhesive layer until it is put to practical use.

Examples of materials that can be used to make the release sheet include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film; porous materials such as paper, cloth, and nonwoven fabric; and appropriate thin materials such as nets, foam sheets, metal foils, and laminates of these. Plastic films are preferably used because of their excellent surface smoothness.

The thickness of the release sheet is usually 5 μm or more and 200 μm or less, and preferably 5 μm or more and 100 μm or less.

The release sheet is treated with a release agent. Examples of release agents include silicone-based, fluorine-based, long-chain alkyl-based, and fatty acid amide-based release agents, and release agents that use silica powder, etc.

The coating method for coating the adhesive composition on the release sheet is not particularly limited. Examples of coating methods include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater, etc.

The coating film formed on the release sheet is irradiated with active energy rays. The irradiation with active energy rays may be performed only through the first release sheet, only through the second release sheet, or through both the first and second release sheets (i.e., from both sides).

Examples of active energy rays include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams. From the viewpoints of controllability, ease of handling, and cost, it is preferable to use ultraviolet rays as the active energy rays, and more preferably ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. Ultraviolet rays are irradiated using a light source such as a high-pressure mercury lamp, a microwave excitation lamp, a chemical lamp, or a black light. Although ultraviolet rays may be irradiated from only one side of the coating film, it is preferable to irradiate the coating film from both sides from the viewpoint of obtaining an adhesive layer with more stable performance.

The illuminance of the active energy ray (preferably ultraviolet ray) is not particularly limited, but it is preferable to produce the adhesive layer by irradiating ultraviolet rays with a lower illuminance than usual. The illuminance is preferably 0.5 mW/cm ² or more and 50 mW/cm ² or less, more preferably 1.0 mW/cm ² or more and 30 mW/cm ² or less. When the illuminance is 0.5 mW/cm ² or more, the curing reaction can be carried out well. When the illuminance is 50 mW/cm ² or less, the adhesive layer having sufficient step followability of the adhesive layer can be produced more stably.

The cumulative light amount when irradiating with active energy rays (preferably ultraviolet rays) in the production of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 300 mJ/cm ² or more and 2000 mJ/cm ² or less, and more preferably 500 mJ/cm ² or more and 1000 mJ/cm ² or less. When the cumulative light amount is within the above range, the effects of the present invention can be obtained more efficiently.

[Optical components]
The pressure-sensitive adhesive layer is completely cured by further irradiating it with active energy rays after being attached to the optical film. This results in an optical member having a first optical film provided on one side of the cured product of the pressure-sensitive adhesive layer. That is, according to another embodiment of the present invention, an optical member is provided having the cured product of the pressure-sensitive adhesive layer and the first optical film provided on one side of the cured product. It is more preferable that the cured product of the pressure-sensitive adhesive layer further has glass, a polymethyl methacrylate plate, a polycarbonate plate, or a second optical film on the side opposite to the side on which the first optical film is provided.

<Easy-adhesion treated layer (easy-adhesion layer)>
The optical member of the present invention preferably further comprises at least one easy-adhesion treatment layer between the first optical film and the cured product of the pressure-sensitive adhesive layer.

In a more preferred embodiment, the easy-adhesion treatment layer has a first easy-adhesion treatment layer and a second easy-adhesion treatment layer. The optical member has a first optical film, a first easy-adhesion treatment layer, a second easy-adhesion treatment layer, and a cured product of the pressure-sensitive adhesive layer for the optical film laminated in this order. In this manner, a configuration having both the first and second easy-adhesion treatment layers in an optical member is preferred from the viewpoint of being able to more firmly adhere the optical film and the cured product of the pressure-sensitive adhesive layer.

The adhesion enhancing treatment layer may be a layer that treats the surface of a member that comes into contact with the adhesive layer, such as a corona treatment or plasma treatment. Alternatively, a separate member such as a primer layer may be provided on the surface of a member that comes into contact with the adhesive layer.

The material constituting the primer layer preferably has good adhesion to the member in contact with the primer layer and forms a film with excellent cohesive force. For example, various polymers, metal oxide sols, silica sols, etc. are used, and among them, polymers are preferably used. The primer layer may have an antistatic function.

Polymers constituting the primer layer include oxazoline group-containing polymers, polyurethane resins, polyester resins, and polymers containing amino groups in the molecule. Among these, polyurethane resins and oxazoline group-containing polymers are more preferably used.

As the oxazoline group-containing polymer, commercially available products can be used. Examples include, but are not limited to, the EPOCROS (registered trademark) series (e.g., EPOCROS (registered trademark) WS700) manufactured by Nippon Shokubai Co., Ltd. In addition, as for polyurethane resins, polyester resins, and polymers containing amino groups in the molecule, those disclosed in paragraphs "0107" to "0113" of JP 2011-105918 A can be appropriately used.

The thickness of the primer layer is preferably 10 nm or more and 5000 nm or less, and more preferably 50 nm or more and 500 nm or less. If it is within the above range, it is possible to maintain optical properties while exhibiting sufficient strength and adhesion.

The method for forming the primer layer is not particularly limited, and examples include a method in which the raw material for the primer layer (undercoat agent) is applied using a coating method such as a coating method, a dipping method, or a spraying method, and then dried.

[Method of manufacturing optical member]
The optical member can be produced by disposing an optical film on one surface of the pressure-sensitive adhesive layer, and irradiating the pressure-sensitive adhesive layer with active energy rays to completely cure the pressure-sensitive adhesive layer.

That is, a method for producing an optical member according to another embodiment of the present invention includes a step of disposing an optical film on one surface of the pressure-sensitive adhesive layer, and a step of irradiating the pressure-sensitive adhesive layer with active energy rays so that the integrated light amount is 300 mJ/cm ² or more and 5000 mJ/cm ² or less. In an embodiment in which a cover glass, a cover plastic film, or a second optical film is further provided on the other surface of the pressure-sensitive adhesive layer, an optical film may be disposed on one surface of the pressure-sensitive adhesive layer, and a cover glass, a cover plastic film, or a second optical film may be disposed on the other surface, and then the pressure-sensitive adhesive layer may be irradiated with active energy rays so that the integrated light amount is 300 mJ/cm ² or more and 5000 mJ/cm ² or less.

The active energy rays are the same as those used in the method for producing the adhesive layer, and examples thereof include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams. From the viewpoints of controllability, ease of handling, and cost, it is preferable to use ultraviolet rays as the active energy rays, and more preferably ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. The ultraviolet rays are irradiated using a light source such as a high-pressure mercury lamp, a microwave excitation lamp, a chemical lamp, or a black light. The ultraviolet rays may be irradiated from only one side of the coating film, but from the viewpoint of obtaining an adhesive layer with more stable performance, it is preferable to irradiate from both sides of the coating film.

The illuminance of the active energy ray (e.g., ultraviolet ray) is not particularly limited, but is preferably 50 mW/ ^cm2 or more and 500 mW/ ^cm2 or less, more preferably 80 mW/ ^cm2 or more and 300 mW/ ^cm2 or less. When the illuminance is 50 mW/ ^cm2 or more, the curing time can be shortened. When the illuminance is 500 mW/ ^cm2 or less, excessive reaction can be suppressed and step followability can be ensured.

The cumulative light amount when irradiating with active energy rays (e.g., ultraviolet rays) is not particularly limited, but is preferably 500 mJ/cm ² or more and 5000 mJ/cm ² or less, and more preferably 1000 mJ/cm ² or more and 3000 mJ/cm ² or less. When the cumulative light amount is within the above range, an optical member having sufficient durability can be produced.

[Image display device]
According to another aspect of the present invention, there is provided an image display device having the above optical member.

Image display devices are not particularly limited, but examples include liquid crystal display devices, organic EL display devices, plasma display panels, micro LED display panels, etc.

The present invention will be explained in detail below with reference to examples, but these examples are not intended to limit the present invention in any way. In the following explanation, all "parts" mean "parts by mass." Furthermore, unless otherwise specified, operations and measurements of physical properties were performed under conditions of room temperature of 23°C and relative humidity of 55% RH.

<Method of measuring physical properties>
(Glass Transition Temperature (Tg))
The glass transition temperature of the copolymer (a) was calculated using the Fox equation based on the glass transition temperature of the homopolymer of each monomer used.

The weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer (a) and the adhesive layer was measured by gel permeation chromatography (GPC). The adhesive layer was similarly measured for soluble matter after dissolving in tetrahydrofuran (THF).

Analytical equipment: Tosoh Corporation, HLC-8120GPC
Column: Tosoh Corporation, G7000HXL+GMHXL+GMHXL
Column size: 7.8 mm diameter x 30 cm each, total 90 cm
Column temperature: 40°C
Flow rate: 0.8 ml/min
Injection volume: 100 μl
Eluent: Tetrahydrofuran Detector: Differential refractometer (RI)
Standard sample: polystyrene.

<Preparation of thin polarizing plate>
A method for producing a thin polarizing plate will be described with reference to FIG.

A 20 μm thick polyvinyl alcohol film was stretched 3 times between rolls with different speed ratios while being dyed in a 0.3% iodine solution at 30°C for 1 minute. It was then stretched to a total stretch ratio of 6 times while being immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes. It was then washed by immersing in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds, and then dried at 50°C for 4 minutes to obtain a 7 μm thick polarizer 4.

A 20 μm-thick polycarbonate film 2 was attached to one side of the polarizer 4, and a 50 μm-thick retardation film 6 (quarter-wave plate, "WRS" manufactured by Teijin Limited) was attached to the opposite side of the polarizer 4 using polyvinyl alcohol adhesives 3 and 5, respectively, to produce a thin polarizing plate 1 with a total thickness of 77 μm.

<Preparation of Acrylic Syrup (AS-1)>
[Production Example 1]
Four UV black lights (FL20SBL, manufactured by Sankyo Electric Co., Ltd.) were placed on each of the four sides of a reaction box that cuts out external ultraviolet rays. A 2-L four-neck flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a cooling tube was placed in the reaction box. 35 parts of 2-ethylhexyl acrylate, 15 parts of isobornyl acrylate, 25 parts of 4-hydroxybutyl acrylate, and 25 parts of acryloylmorpholine were added to the flask, and the flask was heated to 30°C while replacing the air in the flask with nitrogen.

Next, 0.005 parts of 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad (registered trademark) 651; manufactured by IGM Resins B.V.) was added as a photopolymerization initiator while stirring, and mixed uniformly.

To initiate polymerization, ultraviolet light was irradiated using a black light (accumulated light amount: 200 mJ/cm ² ). After the start of the reaction, when the reaction temperature rose by 10° C., air was introduced into the flask using an air pump to stop the reaction, thereby obtaining acrylic syrup (as-1). 100 g of acrylic syrup (as-1) contained 10.5 g of (meth)acrylic acid ester copolymer (a-1) and 89.5 g of unreacted monomer. The glass transition temperature (Tg) and weight average molecular weight (Mw) of the (meth)acrylic acid ester copolymer (a-1) contained in the acrylic syrup (AS-1) are shown in Table 1.

[Production Examples 2 to 19]
Acrylic syrups (as-2) to (as-19) were obtained in the same manner as in Production Example 1, except that the types and ratios of monomers and the amount of photopolymerization initiator in Production Example 1 were changed as shown in Table 1 below. 100 g of acrylic syrups (as-2) to (as-19) contained 10.5 g of (meth)acrylic acid ester copolymers (a-2) to (a-19) and 89.5 g of unreacted monomers, respectively. The glass transition temperatures (Tg) and weight average molecular weights (Mw) of the (meth)acrylic acid ester copolymers (a-2) to (a-19) contained in the acrylic syrups (as-2) to (as-19), respectively, are shown in Table 1 below.

The monomers in Table 1 are as follows. Note that blank spaces in Table 1 indicate that the monomer is not used.

2EHA: 2-ethylhexyl acrylate (homopolymer Tg -68°C, manufactured by Nippon Shokubai Co., Ltd.)
IBXA: Isobornyl acrylate (homopolymer Tg 97°C, manufactured by Osaka Organic Chemical Industry Ltd.)
CHA: cyclohexyl acrylate (homopolymer Tg 15°C, manufactured by Osaka Organic Chemical Industry Ltd.)
4HBA: 4-hydroxybutyl acrylate (homopolymer Tg -32°C, manufactured by Osaka Organic Chemical Industry Ltd.)
ACMO (registered trademark): acryloylmorpholine (homopolymer Tg 145°C, manufactured by KJ Chemicals Co., Ltd.)
BzA: benzyl acrylate (homopolymer Tg 9° C., manufactured by Hitachi Chemical Co., Ltd.)
i-StA: isostearyl acrylate (homopolymer Tg -18°C, manufactured by Osaka Organic Chemical Industry Ltd.)
DTD-A: 2-decyltetradecanyl acrylate (homopolymer Tg -36°C, manufactured by Kyoeisha Chemical Co., Ltd.) EHDG-AT: 2-ethylhexyl-diglycol acrylate (light acrylate EHDG-AT, homopolymer Tg -70°C, manufactured by Kyoeisha Chemical Co., Ltd.).

<Preparation of Pressure-Sensitive Adhesive Composition, Pressure-Sensitive Adhesive Layer, and Pressure-Sensitive Adhesive Layer-Attached Polarizing Plate>
[Example 1]
To 100 parts of the (meth)acrylic acid ester copolymer (a-1) in the acrylic syrup (as-1) obtained in Production Example 1, 0.05 parts of dipentaerythritol hexaacrylate (A-DPH; manufactured by Shin-Nakamura Chemical Co., Ltd.) as a crosslinking agent (C), 0.1 parts of 2-ethylhexyl-3-mercaptopropionate (EHMP; manufactured by SC Organic Chemical Co., Ltd.) as a chain transfer agent, and 0.1 parts of 1-hydroxycyclohexyl-phenyl ketone (Omnirad (registered trademark) 184; manufactured by IGM Resins B.V.) as a photopolymerization initiator were added, mixed, and degassed to obtain a pressure-sensitive adhesive composition.

The obtained adhesive composition was applied to a release-treated surface of a 75 μm-thick polyethylene terephthalate (PET) film, one side of which was treated with a release agent (silicone treatment), to a coating thickness of 150 μm. The release-treated surface of a 75 μm-thick PET film, which had been treated with a release agent, was attached to the coating surface, and the PET films were placed above and below the adhesive composition to seal it in a sandwich shape. A black light was used to irradiate ultraviolet rays of 2.0 mW/ ^cm2 from above and below (accumulated light amount: 400 mJ/ ^cm2 each above and below) to obtain an adhesive layer.

Next, one of the PET films was peeled off to expose the adhesive layer, and the adhesive layer was attached to a thin polarizing plate to produce a polarizing plate with an adhesive layer.

[Examples 2 to 28, Comparative Examples 1 to 9]
In the <Preparation of adhesive composition> of Example 1, except that the type of acrylic syrup and the types and amounts of additives added were changed as shown in Table 2 below, an adhesive composition, an adhesive layer, and an adhesive layer-attached polarizing plate were obtained in the same manner as in Example 1.

The ingredients in Table 2 are as follows. Note that blank spaces in Table 2 indicate that the ingredient is not used.

EDMA: Ethylene glycol dimethacrylate (manufactured by Mitsubishi Chemical Corporation)
DCP-A: Dimethylol-tricyclodecane diacrylate (Light Acrylate DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.)
TMP-A: Trimethylolpropane triacrylate (Light Acrylate TMP-A, manufactured by Kyoeisha Chemical Co., Ltd.)
DAP: Diallyl phthalate (manufactured by Osaka Soda Co., Ltd.)
TAIC: Triallyl isocyanate (manufactured by Mitsubishi Chemical Corporation)
D-110N: Adduct of xylylene diisocyanate (XDI) and trimethylolpropane (Takenate (registered trademark) D-110N, manufactured by Mitsui Chemicals, Inc.)
A201H: Polyhexamethylene diisocyanate (Duranate (registered trademark) A201H, manufactured by Asahi Kasei Corporation)
TCP: bis(4-t-butylcyclohexyl) peroxydicarbonate (Perloyl (registered trademark) TCP, manufactured by NOF Corporation)
KBE-403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
KE-100: Pine Crystal KE-100 (rosin ester resin, manufactured by Arakawa Chemical Industries, Ltd.)
TPO: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (Omnirad (registered trademark) TPO, manufactured by IGM Resins B.V.)
The composition of the adhesive composition is shown in Table 2 below.

<Evaluation of Pressure-Sensitive Adhesive Layer>
(Step-following ability)
The remaining other PET film was peeled off from the polarizing plate with the adhesive layer prepared in the examples and comparative examples to expose the adhesive layer. Then, the adhesive layer was bonded to a polycarbonate plate with a thickness of 0.5 mm and a printing step of 50 μm (laminating roll temperature: 25° C. or 60° C.). Then, the polarizing plate with the adhesive layer was completely attached to the polycarbonate plate by autoclaving at 50° C. and 0.5 MPa for 15 minutes. Then, ultraviolet light (UVA, illuminance: 100 mW/cm ² , accumulated light amount: 2000 mJ/cm ² ) was irradiated from the polycarbonate plate side using a metal halide lamp. The appearance was evaluated visually, and air bubbles between the printing step and the cured product of the adhesive layer were evaluated according to the following criteria.

⊚: No air bubbles at all at the edge. ◯: A few air bubbles at the edge, but no practical problem. △: There are air bubbles at the edge, but no practical problem unless it is for a special purpose. ×: There are a significant number of air bubbles at the edge, and there is a practical problem.

(durability)
A sample for evaluating durability was prepared in the same manner as the sample for evaluating the step-following property. The following tests were carried out on the obtained sample, and the appearance was evaluated visually. (1) Treatment at 85° C. for 500 hours (heating test)
(2) Processed for 500 hours in an atmosphere of 60° C. and 95% relative humidity (humidification test)
(3) The test piece was left in an environment of 85° C. for 30 minutes and then left in an environment of −40° C. for 30 minutes, with one cycle consisting of one hour, for a total of 300 cycles (300 hours) (heat shock (HS) test).

- Visual evaluation -
⊚: No air bubbles at all at the edge. ◯: A few air bubbles at the edge, but no practical problem. △: There are air bubbles at the edge, but no practical problem unless it is for a special purpose. ×: There are a significant number of air bubbles at the edge, and there is a practical problem.

(Haze after storage in a humid and hot environment)
One PET film of the pressure-sensitive adhesive layer-attached polarizing plate obtained in the examples and comparative examples was peeled off, and the exposed adhesive surface was roll-pressed onto alkali-free glass (82 mm x 53 mm x 0.5 mm thick). Next, the other PET film was peeled off, and alkali-free glass (82 mm x 53 mm x 0.5 mm thick) was laminated using a roll. After that, the plate was autoclaved (80 ° C, gauge pressure 0.2 MPa, 20 minutes) to finish the lamination, and the adhesive sheet was cured by irradiating ultraviolet light with a wavelength of 365 nm using a metal halide lamp so that the accumulated light amount was 2000 mJ / cm ² , to prepare an evaluation sample.

The obtained evaluation samples were stored for 100 hours in an environment of 65°C and 90% RH, and then stored for 2 hours in an environment of 23°C and 50% RH (room temperature (25°C)). The haze was measured according to JIS K7136 (2000) using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(Processability)
The pressure-sensitive adhesive layer-attached polarizing plates obtained in the Examples and Comparative Examples were cut into 100 pieces with a Thomson blade for curve processing and hole punching using a Thomson punching machine while the PET film was still laminated, and the shape of the edge was observed. The number of sheets with crushed edges, glue overflow, and lifting of the PET film were counted and evaluated according to the following evaluation criteria. ⊚ to ◯ are acceptable.

-Evaluation criteria-
◎: 0 to 9 sheets ○: 10 to 20 sheets ×: 21 sheets or more.

(Dielectric constant)
The (meth)acrylic acid ester copolymer obtained in each of the Examples and Comparative Examples was placed between a polyethylene terephthalate (PET) film having a thickness of 125 μm and a release PET film having a thickness of 50 μm, and a film having a thickness of 150 μm was formed by hot pressing at 100° C. Using the obtained test piece, the relative dielectric constant at a frequency of 100 kHz was measured by the following procedure.

The capacitance C _B of the test piece at a frequency of 100 kHz was measured by connecting an IMPEDANCE ANALYZER 4294A manufactured by AGILENT Corporation to an IMPEDANCE ANALYZER 1451B manufactured by the same company. The capacitance C _C of the PET film having a thickness of 125 μm and the capacitance C _D of the peeled PET film having a thickness of 50 μm were also measured, and the capacitance C _A of the test piece was calculated from the following formula (i).

(1/ _CB )=(1/ _CA )+(1/ _CC )+(1/CD ₎ ...(i)
The relative dielectric constant εr of the test piece was calculated from the following formula (ii), and the value was taken as the relative dielectric constant of the copolymer. The thickness of the test piece was measured with a micrometer.

C _A =ε 0 ×ε r ×π ×(L/2) ² /d (ii)
ε0: Dielectric constant of vacuum = 8.854 × ¹⁰
L: Diameter of measuring electrode = 38 mm
d: thickness of adhesive layer.

<Adhesive strength>
The same evaluation samples as those used in the durability test were newly prepared and cut to a width of 25 mm x length of 100 mm, and then autoclaved at 50°C and 0.5 MPa for 15 minutes to ensure complete adhesion. After that, the samples were left to stand for 1 hour in an atmosphere of 23°C and a relative humidity of 55% RH, and the adhesive strength of the samples was measured.

The adhesive strength was determined by measuring the adhesive strength (N/25 mm) when peeling the evaluation sample using a tensile tester (Orientec Co., Ltd., Tensilon universal material testing machine, STA-1150) at 23°C, relative humidity of 55%, peel angle of 180°, and peel speed of 300 mm/min in accordance with the JIS Z0237 (2009) adhesive tape and adhesive sheet test method.

The evaluation results are shown in Table 3 below.

The results in Table 3 above show that the adhesive composition of the present invention provides an adhesive layer that has good conformability to uneven surfaces, durability in harsh environments (high temperature, high humidity, heat shock), excellent haze after a humidity and heat durability test, excellent processability and adhesive strength, and a low dielectric constant.

1. Thin polarizing plate,
2 Polycarbonate film,
3 polyvinyl alcohol adhesive,
4 polarizer,
5 polyvinyl alcohol adhesive,
6 Phase difference film.

Claims (22)

A photocurable pressure-sensitive adhesive composition for optical films, comprising a base agent (A) , a chain transfer agent (B) , and a crosslinking agent (C) ,
The base material (A) is a polymer syrup containing a (meth)acrylic acid ester copolymer (a) and the following unreacted components (a1) to (a4):
The (meth)acrylic acid ester copolymer (a) is
(a1): 15% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a linear or branched alkyl group having 1 to 14 carbon atoms;
(a2): 10% by mass or more and 55% by mass or less of structural units derived from (meth)acrylic acid ester monomers having a cyclic alkyl group having 3 to 14 carbon atoms;
(a3): 5% by mass or more and 35% by mass or less of structural units derived from hydroxyl group-containing (meth)acrylic acid ester monomers;
(a4): 5% by mass or more and 35% by mass or less of structural units derived from amide group-containing monomers;
(However, the total amount of the structural units derived from (a1) to (a4) is 100 mass%, and the content of the structural units derived from (a1) is 20 mass% or more and 60 mass% or less with respect to the total amount of the structural units derived from (a1) and the structural units derived from (a2).)
Including,
The photocurable pressure-sensitive adhesive composition for optical films, wherein the content of the chain transfer agent (B) is 0.01 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the main agent (A). The photocurable pressure-sensitive adhesive composition for optical films according to claim 1, wherein the (meth)acrylic acid ester copolymer (a) further comprises a structural unit derived from a (meth)acrylic acid ester monomer (a5) having one radically polymerizable functional group other than the (a1), (a2), (a3), and (a4) components. The photocurable pressure-sensitive adhesive composition for optical films according to claim 2, wherein the component (a5) contains a (meth)acrylic acid ester monomer having an aromatic hydrocarbon group. The photocurable pressure-sensitive adhesive composition for optical films according to claim 2 or 3, wherein the component (a5) contains a (meth)acrylic acid ester monomer having a branched alkyl group having 18 to 36 carbon atoms. The photocurable pressure-sensitive adhesive composition for optical films according to any one of claims 2 to 4, wherein the content of the structural unit derived from the component (a5) is 10 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the total amount of the structural units derived from the components (a1) to (a4). The photocurable pressure-sensitive adhesive composition for optical films according to any one of claims 1 to 5, wherein the component (a2) is at least one of isobornyl (meth)acrylate and cyclohexyl (meth)acrylate. The photocurable pressure-sensitive adhesive composition for optical films according to any one of claims 1 to 6, wherein the glass transition temperature of the (meth)acrylic acid ester copolymer (a) is -40°C or higher and lower than 20°C. The pressure-sensitive adhesive for optical films according to any one of claims 1 to 7 , wherein the crosslinking agent (C) is contained in an amount of 0.01 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the main agent (A). The pressure-sensitive adhesive for optical films according to any one of claims 1 to 8, wherein the crosslinking agent (C) is at least one selected from the group consisting of an isocyanate compound, a carbodiimide compound, an oxazoline compound, an epoxy compound , a polyfunctional (meth)acrylic acid ester monomer, and a peroxide. The photocurable pressure-sensitive adhesive composition for optical films according to any one of claims 1 to 9 , further comprising 0.001 to 5 parts by mass of a silane coupling agent (D) relative to 100 parts by mass of the main agent (A). The photocurable pressure-sensitive adhesive composition for use in an optical film according to any one of claims 1 to 10 , further comprising a high softening point resin (E) having a softening point of 60°C or higher and 200°C or lower . The photocurable pressure-sensitive adhesive composition for optical films according to claim 11 , wherein the high softening point resin (E) is a rosin ester resin. A pressure-sensitive adhesive layer for photocurable optical films, which is formed from the pressure-sensitive adhesive composition for photocurable optical films according to any one of claims 1 to 12 . The pressure-sensitive adhesive layer for photocurable optical films according to claim 13 , having a weight average molecular weight of 50,000 or more and 1,000,000 or less. The pressure-sensitive adhesive layer for a photocurable optical film according to claim 13 or 14 , having a thickness of 20 μm or more and 1 mm or less. A cured product of the pressure-sensitive adhesive layer for a photocurable optical film according to any one of claims 13 to 15 ,
A first optical film provided on one surface of the cured product of the pressure-sensitive adhesive layer;
An optical member comprising: The optical member according to claim 16 , further comprising glass, a polymethyl methacrylate plate, a polycarbonate plate, or a second optical film on a surface of the cured product of the pressure-sensitive adhesive layer opposite to the surface on which the first optical film is provided. The optical member according to claim 16 or 17 , further comprising at least one easy-adhesion treatment layer between the first optical film and the cured product of the pressure-sensitive adhesive layer for photocurable optical films. The easy-adhesion treatment layer has a first easy-adhesion treatment layer and a second easy-adhesion treatment layer,
The optical member according to claim 18, wherein the optical member is formed by laminating the first optical film, the first easy-adhesion treatment layer, the second easy-adhesion treatment layer, and the cured product of the pressure-sensitive adhesive layer for the optical film in this order. An image display device using at least one optical member according to any one of claims 17 to 19 . a lamination step of applying the pressure-sensitive adhesive composition for photocurable optical films according to any one of claims 1 to 12 onto a release-treated surface of a first release sheet to form a coating film, and laminating the release-treated surface of a second release sheet so that the release-treated surface of the second release sheet is in contact with the surface of the coating film;
an active energy ray irradiation step of irradiating the coating film with active energy rays through at least one of the first release sheet and the second release sheet;
The method for producing a pressure-sensitive adhesive layer for a photocurable optical film comprising the steps of: The method for producing a pressure-sensitive adhesive layer for a photocurable optical film according to claim 21 , wherein an integrated light amount of the active energy rays is 300 mJ/ ^cm2 or more and 2000 mJ/ ^cm2 or less.