JP7335770B2 - Adhesive film and surface protection film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive film that can be used as a surface protection film and the like.

Removable pressure-sensitive adhesive films are widely used to temporarily fix and protect various members during transportation and processing. For example, optical members such as polarizing plates, flexible printed wiring (FPC) substrates, conductive films in which a thin film such as indium tin oxide (ITO) is formed as a transparent electrode on one side of a transparent base material, and glass substrates, etc. Product defects such as changes in refractive index occur due to dirt and scratches on the surface. Therefore, when transporting optical members, or when assembling or processing products using optical members, adhesive films for surface protection (hereinafter also referred to as “surface protection films”) are attached to the surfaces of optical members to protect the optical members. Prevents dirt from adhering to or scratching the surface. Such a surface protection film is required to be difficult to peel off during transportation and processing of optical members and to be easily peeled off after use.

Attaching the surface protective film to the optical member can prevent the optical member from being stained or scratched. However, if the optical member is contaminated with the adhesive after the surface protective film is peeled off, product defects occur when the optical member is assembled into a product. In addition, if optical components are contaminated with adhesives, when adhesives or hard coating agents are applied to the optical components to produce products, minute coating unevenness tends to occur on the optical components, resulting in defects in brightness and color unevenness. It occurred and the product was defective. Therefore, the surface protection film is also required to cause less contamination on the adherend surface after peeling.

In addition, the manufacturing process of the polarizing plate, the manufacturing process of the FPC substrate, the manufacturing process of the ITO transparent electrode layer, and the manufacturing process of the flat display in which the polarizing plate, the FPC substrate, the conductive film, the glass substrate, etc. are laminated, etc. There are steps in which the film is exposed to high temperatures. Therefore, surface protective films are required to be resistant to peeling during transportation and processing of optical members even after heat treatment, to be easily peeled after use, and to cause little contamination on the adherend surface after peeling. .

Contamination of the surface of an adherend by a removable adhesive film such as a surface protective film includes contamination that can be visually confirmed and contamination that cannot be visually confirmed. Contamination that can be confirmed with the naked eye is derived from a torn adhesive or the like, and is generally referred to as adhesive residue. Contamination that cannot be confirmed visually is derived from oligomers, adhesive decomposition products, etc. that cannot be confirmed visually, and can be confirmed as a change in the water contact angle (change in wettability) on the adherend surface. can.

The adhesive film has an adhesive layer on at least one surface of the base film. As the adhesive, a (meth)acrylic adhesive composed of a (meth)acrylic copolymer and a cross-linking agent is used because it has excellent optical properties and is relatively easy to design. It is For example, Patent Document 1 discloses that a (meth)acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive, and the change in the water contact angle on the surface of the adherend after peeling off the surface protective film is within 30° from the initial stage. It is disclosed that the applicability of adhesives and hard coating agents is improved even after the surface protective film is peeled off (see Patent Document 1 (paragraph 0011)). (Meth)acrylic copolymers used in pressure-sensitive adhesives are generally produced by free radical polymerization, but it is difficult to obtain homogeneity of the copolymer composition, and as a result, oligomers generate a lot.

Patent Document 2 discloses that a pressure-sensitive adhesive film with little adhesive residue can be obtained by using a (meth)acrylic copolymer produced by a living radical polymerization method in a pressure-sensitive adhesive composition (Patent Document 2). (see paragraph 0002)).

JP-A-2002-173650 WO2007/119884

However, in the adhesive film of Patent Document 1, there is no description about the use after heat treatment, and the contamination resistance after heat treatment is not examined. Patent Literature 2 does not describe a method for reducing adhesive residue and change in water contact angle after heat treatment, and an adhesive film with low adhesive strength (0.96 N/24 mm or less, 1 N/25 mm or less).

The present invention has been made in view of the above circumstances, and an adhesive film that is difficult to peel off during use even after heat treatment, is easy to peel after use, and has less contamination on the surface of the adherend when peeled after heat treatment. intended to provide

The pressure-sensitive adhesive film of the present invention, which can solve the above problems, has a base film and a pressure-sensitive adhesive layer formed on at least one surface of the base film, wherein the pressure-sensitive adhesive layer comprises (meta ) is formed from a pressure-sensitive adhesive composition containing an acrylic copolymer (A) and an epoxy-based cross-linking agent (B), the pressure-sensitive adhesive layer has a gel fraction of 70% by mass or more, and the ( A meth)acrylic copolymer (A) comprises a structural unit (a-1) having a cyclic group and a structural unit (a-2) having an acidic group, and the (meth)acrylic copolymer The coalescence (A) is characterized by having a weight average molecular weight of 200,000 to 2,000,000 and a molecular weight distribution (PDI) of less than 3.0.

In the adhesive film of the present invention, the adhesive layer has excellent heat resistance, is difficult to peel off during use even after heat treatment, is easy to peel after use, and is peeled off after heat treatment. Less pollution. The reason why the pressure-sensitive adhesive layer has such excellent heat resistance is that the (meth)acrylic polymer has a structural unit (a-1) having a cyclic group and has a predetermined weight average molecular weight and molecular weight distribution. This is thought to be due to having

Even after heat treatment, the pressure-sensitive adhesive film of the present invention is difficult to peel off during use, is easy to peel off after use, and causes less contamination on the adherend surface when peeled off after heat treatment.

<Adhesive film>
The pressure-sensitive adhesive film of the present invention has a base film and a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition on at least one surface of the base film. The pressure-sensitive adhesive layer is formed on at least one side or at least a portion of the base film. The pressure-sensitive adhesive layer may be a single layer or may have a multilayer structure.

In general, "sheet" is defined in JIS as a flat product that is thin and generally has a small thickness relative to its length and width. A thin, flat product with an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JIS K6900). For example, regarding the thickness, in a narrow sense, a sheet of 100 μm or more is called a sheet, and a thickness of less than 100 μm is sometimes called a film. However, the boundary between a sheet and a film is not clear, and there is no need to distinguish between the two in the present invention. But "sheet" is included.

Each component constituting the pressure-sensitive adhesive film of the present invention will be described below.

(1. Adhesive composition)
The pressure-sensitive adhesive composition contains a (meth)acrylic copolymer (A) (hereinafter sometimes simply referred to as "copolymer (A)") and an epoxy crosslinking agent (B). The copolymer (A) contains a structural unit (a-1) having a cyclic group and a structural unit (a-2) having an acidic group, and has a weight average molecular weight of 200,000 to 2,000,000. The distribution (PDI) is less than 3.0.

The pressure-sensitive adhesive composition is obtained by applying the composition onto a base film and reacting the acidic groups of the copolymer (A) with the epoxy groups of the epoxy-based cross-linking agent (B) to form a pressure-sensitive adhesive. It can form layers.

(1-1. (Meth) acrylic copolymer (A))
The copolymer (A) has a weight average molecular weight of 200,000 to 2,000,000 and a molecular weight distribution (PDI) of less than 3.0, and has a structural unit (a-1) having a cyclic group and a structural unit having an acidic group. A (meth)acrylic copolymer containing (a-2).

The (meth)acrylic copolymer may be any copolymer whose main component (50% by mass or more) is a structural unit derived from a (meth)acrylic monomer, and vinyl monomers other than (meth)acrylic monomers can contain structural units derived from The content of the structural unit derived from the (meth)acrylic monomer in the copolymer (A) is preferably 80% by mass or more, more preferably 90% by mass or more, in the entire copolymer. The copolymer (A) may be composed only of structural units derived from (meth)acrylic monomers.

In the present invention, "(meth)acrylic" means "at least one of acrylic and methacrylic". "(Meth)acrylic monomer" refers to a monomer having a "(meth)acryloyl group" in the molecule. "(Meth)acryloyl" means "at least one of acryloyl and methacryloyl". A "vinyl monomer" refers to a monomer having a radically polymerizable carbon-carbon double bond in the molecule. A “structural unit derived from a (meth)acrylic monomer” refers to a structural unit in which a radically polymerizable carbon-carbon double bond of a (meth)acrylic monomer is polymerized to form a carbon-carbon single bond. A “structural unit derived from a vinyl monomer” refers to a structural unit in which a radically polymerizable carbon-carbon double bond of a vinyl monomer is polymerized to form a carbon-carbon single bond.

The copolymer (A) may be a random copolymer, a block copolymer, or a graft copolymer, preferably a random copolymer.

The weight average molecular weight (Mw) of the copolymer (A) is 200,000 or more, preferably 300,000 or more, and 2,000,000 or less, preferably less than 1,000,000, more preferably less than 800,000, and still more preferably 500,000. is less than If the Mw of the copolymer (A) is less than 200,000, the heat resistance may be reduced due to insufficient cohesion, and the surface of the adherend may be contaminated. Coating workability may deteriorate. A method for measuring the weight average molecular weight (Mw) will be described later.

The molecular weight distribution (PDI) of the copolymer (A) is less than 3.0, preferably less than 2.5, more preferably less than 2.0. The smaller the PDI, the narrower the width of the molecular weight distribution, the more uniform the molecular weight of the copolymer. That is, the lower limit of PDI is 1.0. If the PDI is less than 3.0, the content of substances with a small molecular weight or a substance with a large molecular weight is low compared to the molecular weight of the designed copolymer, and the adherend stains when used in the pressure-sensitive adhesive composition. Less sticky film can be obtained. In the present invention, the molecular weight distribution (PDI) is a value calculated by (weight average molecular weight (Mw)) / (number average molecular weight (Mn)), and methods for measuring Mw and Mn will be described later.

The glass transition temperature (Tg) of the copolymer (A) is preferably −80° C. or higher, more preferably −70° C. or higher, still more preferably −50° C. or higher, and particularly preferably −40° C. or higher. , preferably 20° C. or lower, more preferably 0° C. or lower, and still more preferably −10° C. or lower. If the glass transition temperature is −80° C. or higher, the pressure-sensitive adhesive composition will have sufficient cohesive strength, and the heat resistance of the pressure-sensitive adhesive layer will be improved. It becomes high, peeling etc. are suppressed and durability improves.

The glass transition temperature (Tg) of the copolymer (A) is a value calculated by the following FOX formula (formula (1)). In formula (1), Tg represents the glass transition temperature (°C) of the copolymer. Tgi indicates the glass transition temperature (°C) when the vinyl monomer i forms a homopolymer. Wi indicates the mass ratio of vinyl monomer i in all vinyl monomers forming the copolymer, and ΣWi=1. i is a natural number from 1 to n.

Table 1 shows the glass transition temperatures of representative homopolymers.

In the copolymer (A), the content of acidic groups described later is preferably 0.05 mmol/g or more, more preferably 0.1 mmol/g or more, still more preferably 0.2 mmol/g or more, and most preferably It is 0.4 mmol/g or more, preferably 3 mmol/g or less, more preferably 2 mmol/g or less, still more preferably 1 mmol/g or less. If the content of the acidic group is 0.05 mmol/g or more, the cohesive failure of the adhesive is suppressed, and if it is 3 mmol/g or less, the peeling of the film when exposed to high temperature can be suppressed. The acidic group content is the sum of all acidic groups in the copolymer (A), and is the total number of moles of acidic groups per unit g of the copolymer (A).

The copolymer (A) may have a reactive functional group capable of reacting with the reactive group of the epoxy-based cross-linking agent (B) in addition to the acidic group. Examples of the reactive functional group include a hydroxy group in addition to the acidic group. The content of the reactive functional group in the copolymer (A) is preferably 0.05 mmol/g or more, more preferably 0.15 mmol/g or more, still more preferably 0.25 mmol/g or more, and particularly preferably It is 0.45 mmol/g or more, preferably 5 mmol/g or less, more preferably 3.5 mmol/g or less, still more preferably 2.0 mmol/g or less, and particularly preferably 1.0 mmol/g or less. The content of the reactive functional groups is the total sum of all reactive functional groups possessed by the copolymer (A), and is the total number of moles of reactive functional groups per unit g of the copolymer (A). .

(1-1-1. Structural unit (a-1))
The structural unit (a-1) having a cyclic group may be of only one type, or may be of two or more types. By having the structural unit (a-1), when the copolymer (A) and the epoxy-based cross-linking agent (B) are used in the pressure-sensitive adhesive composition, the adherend contamination, In particular, changes in water contact angle and adhesion can be reduced even when exposed to high temperatures. The structural unit (a-1) having a cyclic group preferably does not have an acidic group or a hydroxy group, which will be described later.

Examples of the cyclic group include at least one selected from the group consisting of aromatic groups and alicyclic hydrocarbon groups, preferably aromatic groups.

An aromatic group is a substituent having an aromatic ring structure, and examples thereof include aryl groups, alkylaryl groups, aralkyl groups and aryloxyalkyl groups, preferably the group consisting of aryl groups, aralkyl groups and aryloxyalkyl groups. is at least one selected from The aryl group preferably has 6 to 12 carbon atoms, such as a phenyl group and a naphthyl group. The alkylaryl group preferably has 6 to 12 carbon atoms, such as tolyl and xylyl. The aralkyl group preferably has 6 to 12 carbon atoms, such as a benzyl group and a phenethyl group. The aryloxyalkyl group preferably has 6 to 12 carbon atoms, such as a phenoxymethyl group and a phenoxyethyl group.

The alicyclic hydrocarbon group includes a cyclic alkyl group and a substituent having a polycyclic structure. The cyclic alkyl group includes a cyclic alkyl group (cycloalkyl group) having a monocyclic structure, and may have a chain portion. The cyclic alkyl group having a monocyclic structure preferably has 3 to 12 carbon atoms, such as cyclohexyl group, methylcyclohexyl group, cyclohexylmethyl group and cyclododecyl group. Examples of substituents having a polycyclic structure include cyclic alkyl groups having a bridged ring structure, which may have a chain portion. The cyclic alkyl group having a bridged ring structure preferably has 5 to 12 carbon atoms, and examples thereof include bornyl, isobornyl, adamantyl, norbornyl, dicyclopentanyl and dicyclopentenyl groups.

The cyclic group may be contained in either a structural unit derived from a (meth)acrylic monomer or a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer. The monomer forming the structural unit is a (meth)acrylic monomer having a cyclic group and a vinyl monomer other than the (meth)acrylic monomer having a cyclic group.

Examples of (meth)acrylic monomers having a cyclic group include (meth)acrylates having an aromatic group and (meth)acrylates having an alicyclic hydrocarbon group. Examples of vinyl monomers other than (meth)acrylic monomers having a cyclic group include aromatic vinyl monomers and vinyl monomers having an alicyclic hydrocarbon group. Among these, (meth)acrylates having an aromatic group and (meth)acrylates having an alicyclic hydrocarbon group are preferred, and (meth)acrylates having an aromatic group are preferred.

As the (meth)acrylate having an aromatic group, a (meth)acrylate having an aromatic group having 6 to 12 carbon atoms is preferable. Examples of the (meth)acrylate having an aromatic group include compounds in which an aryl group is directly bonded to a (meth)acryloyloxy group, compounds in which an aralkyl group is directly bonded to a (meth)acryloyloxy group, (meth)acryloyloxy a compound in which an alkylaryl group is directly bonded to a group, a compound in which an aryloxyalkyl group is directly bonded to a (meth)acryloyloxy group, a compound in which a structure having an aromatic ring is bonded to a (meth)acryloyloxy group via an alkylene oxide, and derivatives thereof. Examples of (meth)acrylates having an aromatic group include phenyl (meth)acrylate, tribromophenyl (meth)acrylate, ethylene oxide-modified tribromophenyl (meth)acrylate; benzyl (meth)acrylate; phenoxyethyl (meth)acrylate, Nonylphenoxyethyl (meth)acrylate, 2-(o-phenoxyphenyl)ethyl (meth)acrylate, epichlorohydrin-modified phenoxy (meth)acrylate; phenoxydiethyleneglycol (meth)acrylate, phenoxytetraethyleneglycol (meth)acrylate, phenoxy polyethylene glycol (meth) acrylate, nonylphenoxy diethylene glycol (meth) acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, nonylphenoxy polypropylene glycol acrylate, paracumylphenoxyethylene glycol (meth) acrylate, ethylene oxide-modified phthalic acid (meth) acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalic acid, neopentyl glycol (meth)acrylate benzoate and the like, preferably benzyl (meth)acrylate, phenyl (meth)acrylate and phenoxyethyl (meth)acrylate At least one selected from the group consisting of

Examples of (meth)acrylates having an alicyclic hydrocarbon group include (meth)acrylates having a cyclic alkyl group and (meth)acrylates having a polycyclic structure.

As the (meth)acrylate having a cyclic alkyl group, a (meth)acrylate having a cyclic alkyl group having 6 to 12 carbon atoms is preferable. Examples of the (meth)acrylate having a cyclic alkyl group include compounds in which a cyclic alkyl group is directly bonded to a (meth)acryloyloxy group. Specific examples of (meth)acrylates having a cyclic alkyl group having a monocyclic structure include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, and 3,3,5-trimethylcyclohexyl (meth)acrylate. acrylates, 4-tert-butylcyclohexyl (meth)acrylate, hexahydrophthalyloxyethyl (meth)acrylate, hexahydrophthalyloxypropyl (meth)acrylate and the like.

As the (meth)acrylate having a polycyclic structure, a (meth)acrylate having a polycyclic structure having 6 to 12 carbon atoms is preferable. Examples of the (meth)acrylate having a polycyclic structure include compounds in which a cyclic alkyl group having a bridged ring structure is directly bonded to a (meth)acryloyloxy group. Specific examples of (meth)acrylates having a polycyclic structure include bornyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 2-methyl-2- adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyloxyethyl (meth) Acrylate, dicyclopentenyloxyethyl (meth)acrylate, 2-(meth)acryloyloxy-2-(1-adamantyl)propane, 2-(meth)acryloyloxy-2-(1-adamantyl)butane, 3- (Meth)acryloyloxy-3-(1-adamantyl)pentane, tricyclodecanyl (meth)acrylate and the like.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, 1-vinylnaphthalene, 4-t- butoxystyrene, 4-acetoxystyrene, 4-t-butoxycarbonyloxystyrene, 4-t-butoxycarbonylmethyloxystyrene, 4-ethoxyethoxystyrene, 4-(2-t-butoxycarbonylethyloxy)styrene, etc. .

Examples of vinyl monomers having an alicyclic hydrocarbon group include vinylcyclohexane and vinyladamantane.

The content of the structural unit (a-1) is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, and particularly preferably 100% by mass of the total copolymer (A). It is 20% by mass or more, preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, particularly preferably 50% by mass or less, and most preferably 40% by mass or less. By setting the content of the structural unit (a-1) within the above range, the adhesive is resistant to peeling during use after being exposed to high temperatures, is easy to peel after use, and causes less contamination on the surface of the adherend after peeling. It can be a film.

(1-1-2. Structural unit (a-2))
Structural units (a-2) having an acidic group may be of one kind or may be of two or more kinds. The acidic group is a functional group (reactive functional group) capable of reacting with a reactive group possessed by the epoxy-based cross-linking agent (B) described below. Examples of the acidic group include at least one selected from the group consisting of a carboxy group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group and a phosphine group, preferably a carboxy group. The structural unit (a-2) having an acidic group does not contain the structural unit (a-1) having the cyclic group.

The acidic group may be contained in either a structural unit derived from a (meth)acrylic monomer or a structural unit derived from a vinyl monomer other than the (meth)acrylic monomer. The monomer forming the structural unit (a-2) is a (meth)acrylic monomer having an acidic group and a vinyl monomer other than the (meth)acrylic monomer having an acidic group.

Examples of (meth)acrylic monomers having an acidic group include (meth)acrylic monomers having a carboxy group, (meth)acrylic monomers having a sulfonic acid group, and (meth)acrylic monomers having a phosphoric acid group. Examples of vinyl monomers other than (meth)acrylic monomers having an acidic group include vinyl monomers having a carboxy group. Among these, a (meth)acrylic monomer having a carboxy group is preferred.

Examples of (meth)acrylic monomers having a carboxy group include 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, and other (meth)acrylates having a hydroxyl group, maleic anhydride and succinic anhydride. Monomers reacted with acid anhydrides such as acids, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like can be mentioned. Among these, (meth)acrylic acid is preferred.

Sulfonic acid ethyl (meth)acrylate etc. are mentioned as a (meth)acrylic monomer which has a sulfonic acid group.

(Meth)acrylic monomers having a phosphoric acid group include 2-(phosphonooxy)ethyl (meth)acrylate.

Vinyl monomers having a carboxyl group include crotonic acid, maleic acid, itaconic acid, citraconic acid, cinnamic acid and the like.

The content of the structural unit (a-2) is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1.0% by mass in 100% by mass of the copolymer (A) as a whole. % or more, particularly preferably 2.0 mass % or more, preferably 20 mass % or less, more preferably 15 mass % or less, still more preferably 10 mass % or less, particularly preferably 8 mass % or less, most preferably 6 mass % or less. % by mass or less. If the content of the structural unit (a-2) is 0.3% by mass or more, cohesive failure of the adhesive is suppressed, and if it is 20% by mass or less, peeling of the film when exposed to high temperatures can be suppressed. can.

The mass ratio ((a-1)/(a-2)) between the structural unit (a-1) and the structural unit (a-2) in the copolymer is preferably 0.25 or more, and more Preferably 0.5 or more, more preferably 1.0 or more, particularly preferably 4.0 or more, preferably 200 or less, more preferably 100 or less, still more preferably 50 or less, particularly preferably 20 or less, most preferably is 10 or less. If the mass ratio ((a-1)/(a-2)) is 0.25 or more, there is little contamination of the adherend even after exposure to high temperatures, and peeling can be suppressed. If there is, cohesive failure can be suppressed even after being exposed to high temperatures.

(1-1-3. Structural unit (a-3))
The copolymer (A) may have a structural unit (a-3) other than the structural unit (a-1) and the structural unit (a-2). The structural unit (a-3) is not particularly limited as long as it is formed from a vinyl monomer that can be copolymerized with both the monomers forming the structural unit (a-1) and the structural unit (a-2). Only one type may be used, or two or more types may be used.

Vinyl monomers capable of forming the structural unit (a-3) include (meth)acrylates having a linear alkyl group, (meth)acrylates having a branched alkyl group, and (meth)acrylates having a polyoxyalkylene alkyl ether group. ) acrylate, (meth)acrylate having an alkoxy group, (meth)acrylic monomer having a hydroxy group, (meth)acrylic monomer having an epoxy group, (meth)acrylate having an oxygen-containing heterocyclic group, having a tertiary amino group (Meth)acrylic monomers such as (meth)acrylates and (meth)acrylamides; vinyl monomers having a hydroxy group, vinyl monomers having an epoxy group, vinyl monomers having a heterocycle, vinyl carboxylates, and tertiary amino groups Vinyl monomers other than (meth)acrylic monomers such as vinyl monomers, vinyl monomers having a quaternary ammonium base, vinylamides, α-olefins and dienes can be mentioned. Among these, at least one selected from the group consisting of (meth)acrylates having a linear alkyl group and (meth)acrylates having a branched alkyl group is preferred.

The (meth)acrylate having a straight-chain alkyl group is preferably a (meth)acrylate having a straight-chain alkyl group having 1 to 20 carbon atoms in the straight-chain alkyl group. (Meth)acrylates having a linear alkyl group in which is 1 to 10 are more preferred. Specific examples of (meth)acrylates having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl ( meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, decyl (meth)acrylate, n-lauryl (meth)acrylate, n-stearyl (meth)acrylate and the like.

The (meth)acrylate having a branched-chain alkyl group is preferably a (meth)acrylate having a branched-chain alkyl group having 3 to 20 carbon atoms in the branched-chain alkyl group. (Meth)acrylates with branched alkyl groups in which is 3-10 are preferred. Specific examples of (meth)acrylates having a branched alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate and isooctyl (meth)acrylate. , 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate and the like.

(Meth)acrylates having a polyoxyalkylene alkyl ether group include polyethylene glycol (degree of polymerization = 2 to 10) methyl ether (meth) acrylate, polyethylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth) acrylate, polyethylene Glycol (degree of polymerization = 2 to 10) propyl ether (meth) acrylate having a polyoxyethylene alkyl ether group (meth) acrylate; polypropylene glycol (degree of polymerization = 2 to 10) methyl ether (meth) acrylate, polypropylene glycol ( Degree of polymerization = 2 to 10) (meth)acrylates having a polyoxypropylene alkyl ether group such as ethyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) and propyl ether (meth)acrylate.

(Meth)acrylates having an alkoxy group include methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.

Examples of (meth)acrylic monomers having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6- Hydroxyalkyl (meth)acrylates such as hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate; caprolactone of hydroxyalkyl (meth)acrylates adducts and the like. Among these, hydroxyalkyl (meth)acrylates are preferred, and (meth)acrylates having a hydroxyalkyl group having 1 to 5 carbon atoms are more preferred.

(Meth)acrylic monomers having an epoxy group include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate and the like.

The (meth)acrylate having an oxygen-containing heterocyclic group is preferably a (meth)acrylate having a 4- to 6-membered oxygen-containing heterocyclic group. Specific examples of (meth)acrylates having an oxygen-containing heterocyclic group include tetrahydrofurfuryl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, (2-methyl-2-ethyl- 1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 2-[(2-tetrahydropyranyl)oxy]ethyl (meth)acrylate, 1,3-dioxane- (Meth)acrylate and the like.

(Meth)acrylates having a tertiary amino group include 2-(dimethylamino)ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate and the like.

(Meth)acrylamides include dialkyl (meth)acrylamides such as N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide; cyclic amides such as acryloylmorpholine; alkoxyalkylacrylamides such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide;

Allyl alcohol etc. are mentioned as a vinyl monomer which has a hydroxyl group.
Vinyl monomers having an epoxy group include 2-allyl oxirane, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether and the like.
Examples of heterocyclic vinyl monomers include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, 4-vinylpyridine, N-phenylmaleimide, and N-benzyl. maleimide, N-cyclohexylmaleimide and the like.
Vinyl carboxylate includes vinyl acetate, vinyl pivalate, vinyl benzoate and the like.
Vinyl monomers having a tertiary amino group include N,N-dimethylallylamine and the like.
Vinyl monomers having a quaternary ammonium base include N-methacryloylaminoethyl-N,N,N-dimethylbenzylammonium chloride and the like.
Examples of vinylamides include N-vinylformamide, N-vinylacetamide, 1-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam and the like.
α-olefins include 1-hexene, 1-octene, 1-decene and the like.
Examples of dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, 7-methyl-1,6-octadiene and the like.

The content of the structural unit (a-3) is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, based on 100% by mass of the entire copolymer (A). % by mass or less is preferable, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

Further, as the structural unit (a-3), at least one (meth)acrylate selected from the group consisting of (meth)acrylates having a linear alkyl group and (meth)acrylates having a branched alkyl group. It preferably has a structure derived from acrylate. In this case, structural units derived from at least one (meth)acrylate selected from the group consisting of (meth)acrylates having a linear alkyl group and (meth)acrylates having a branched alkyl group. The content is preferably 10% by mass or more, more preferably 25% by mass or more, still more preferably 40% by mass or more, and preferably 95% by mass or less, more preferably 80% by mass, based on 100% by mass of the entire copolymer. % or less, more preferably 70 mass % or less.

Moreover, the copolymer (A) preferably does not have a structural unit derived from a (meth)acrylate having a polyoxyalkylene alkyl ether group. Therefore, the content of structural units derived from (meth)acrylate having a polyoxyalkylene alkyl ether group is preferably less than 0.1% by mass, more preferably 0.05% by mass, in 100% by mass of the entire copolymer. It is below.

(1-1-4. Production method of copolymer (A))
The copolymer (A) can be produced by radical polymerization of a monomer composition containing two or more vinyl monomers, and is preferably obtained by living radical polymerization (living radical polymerization method (obtained by polymerization using

In the conventional radical polymerization method (free radical polymerization method), not only the initiation reaction and propagation reaction, but also termination reaction and chain transfer reaction cause deactivation of the propagating end, resulting in a mixture of polymers with various molecular weights and heterogeneous compositions. tend to be easy. In the living radical polymerization method, while maintaining the simplicity and versatility of the conventional radical polymerization method, termination reaction and chain transfer are unlikely to occur, and the growing terminal grows without being hindered by a side reaction that deactivates the growing terminal, so the high molecular weight However, it is easy to precisely control the molecular weight distribution and to produce a polymer with a uniform composition.

Therefore, it is believed that the copolymer produced by the living radical polymerization method has few low-molecular-weight components (oligomers), and has the advantage of producing few transfer contaminants (adhesive residue, etc.) when used in adhesive compositions. be done. Further, the copolymer (A) is produced by a living radical polymerization method so that the structural units ((a-1) to (a-3)) are uniformly polymerized in each polymer molecule, and the copolymer The pressure-sensitive adhesive composition using (A) has the unexpected effect of reducing the change in the water contact angle of the adherend as the weight-average molecular weight of the copolymer (A) decreases.

In the living radical polymerization method, a vinyl monomer forming the structural unit (a-1), a vinyl monomer forming the structural unit (a-2), and optionally a vinyl monomer forming the structural unit (a-3) A random copolymer can be obtained by using a mixture with a monomer (sometimes simply referred to as "vinyl monomer"). A block copolymer can also be obtained by sequentially reacting the vinyl monomers constituting the copolymer (A). For example, in the case of a diblock copolymer, the first block is first produced, and the first block is polymerized with a vinyl monomer constituting the second block; , a method of polymerizing a vinyl monomer constituting the first block into the second block, and the like. In the case of a triblock copolymer, the first block is first produced, the first block is polymerized with the vinyl monomer that constitutes the second block, and the vinyl monomer that constitutes the third block is polymerized. and a method of producing by polymerization.

Living radical polymerization methods include a method using a transition metal catalyst (ATRP method); a method using a sulfur-based reversible chain transfer agent (RAFT method); There is a method such as a method (TERP method). Since the ATRP method uses an amine-based complex, it may not be possible to use it without protecting the acidic group of the vinyl monomer having an acidic group. In the RAFT method, when a variety of monomers are used, it is difficult to obtain a low molecular weight distribution, and problems such as sulfur odor and coloration may occur. Among these methods, it is preferable to use the TERP method from the viewpoint of the diversity of usable monomers, molecular weight control in the high molecular region, uniform composition, or coloring.

The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent. 2004/072126 and methods described in WO 2004/096870.

Specific polymerization methods for the TERP method include the following (a) to (d).
(a) A vinyl monomer is polymerized using an organic tellurium compound represented by general formula (1).
(b) A vinyl monomer is polymerized using a mixture of an organic tellurium compound represented by general formula (1) and an azo polymerization initiator.
(c) A vinyl monomer is polymerized using a mixture of an organic tellurium compound represented by general formula (1) and an organic ditelluride compound represented by general formula (2).
(d) A vinyl monomer is polymerized using a mixture of an organic tellurium compound represented by general formula (1), an azo polymerization initiator, and an organic ditelluride compound represented by general formula (2).

［一般式（１）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基を示す。Ｒ²およびＲ³は、それぞれ独立に、水素原子または炭素数１～８のアルキル基を示す。Ｒ⁴は、炭素数１～８のアルキル基、アリール基、置換アリール基、芳香族ヘテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、アリル基またはプロパルギル基を示す。
一般式（２）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基を示す。］

[In general formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group. R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁴ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group or a propargyl group.
In general formula (2), R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group. ]

The group represented by R ¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group, and specific examples are as follows.
Examples of alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group and heptyl. linear or branched alkyl groups such as radicals, octyl groups, and cyclic alkyl groups such as cyclohexyl groups. A linear or branched alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.
A phenyl group, a naphthyl group, etc. can be mentioned as an aryl group.
A pyridyl group, a furyl group, a thienyl group, etc. can be mentioned as an aromatic heterocyclic group.

The groups represented by R ² and R ³ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and specific examples of each group are as follows.
Examples of alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group and heptyl. linear or branched alkyl groups such as radicals, octyl groups, and cyclic alkyl groups such as cyclohexyl groups. A linear or branched alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.

The group represented by R ⁴ is an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amide group, an oxycarbonyl group, a cyano group, an allyl group or It is a propargyl group, specifically as follows.
Examples of alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group and heptyl. linear or branched alkyl groups such as octyl groups, cyclic alkyl groups such as cyclohexyl groups, and the like. A linear or branched alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.
A phenyl group, a naphthyl group, etc. can be mentioned as an aryl group. A phenyl group is preferred.
Examples of the substituted aryl group include a phenyl group having a substituent, a naphthyl group having a substituent, and the like. Examples of the substituents of the aryl group having the above substituents include halogen atoms, hydroxy groups, alkoxy groups, amino groups, nitro groups, cyano groups, and carbonyl-containing groups represented by —COR ⁴¹ (R ⁴¹ is a carbon 1 to 8 alkyl groups, aryl groups, C 1 to 8 alkoxy groups or aryloxy groups), sulfonyl groups, trifluoromethyl groups and the like. Moreover, it is preferable that one or two of these substituents are substituted.
A pyridyl group, a furyl group, a thienyl group, etc. can be mentioned as an aromatic heterocyclic group.
The alkoxy group is preferably a group in which an alkyl group having 1 to 8 carbon atoms is bonded to an oxygen atom. butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group and the like.
Acyl groups include acetyl, propionyl, and benzoyl groups.
Examples of amide groups include -CONR ⁴²¹ R ⁴²² (R ⁴²¹ and R ⁴²² are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group).
The oxycarbonyl group is preferably a group represented by --COOR ⁴³ (R ⁴³ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group), such as a carboxy group, a methoxycarbonyl group, an ethoxycarbonyl group and a propoxycarbonyl group. group, n-butoxycarbonyl group, sec-butoxycarbonyl group, tert-butoxycarbonyl group, n-pentyloxycarbonyl group, phenoxycarbonyl group and the like. Preferred oxycarbonyl groups include methoxycarbonyl and ethoxycarbonyl groups.
The allyl group includes -CR ⁴⁴¹ R ⁴⁴² -CR ⁴⁴³ =CR ⁴⁴⁴ R ⁴⁴⁵ (R ⁴⁴¹ and R ⁴⁴² are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ⁴⁴³ , R ⁴⁴⁴ and R ⁴⁴⁵ are , each independently a hydrogen atom, an alkyl group or an aryl group having 1 to 8 carbon atoms, and each substituent may be connected in a cyclic structure).
The propargyl group includes —CR ⁴⁵¹ R ⁴⁵² —C≡CR ⁴⁵³ (R ⁴⁵¹ and R ⁴⁵² are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R ⁴⁵³ is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms , an aryl group or a silyl group) and the like.

Specifically, the organic tellurium compound represented by the general formula (1) is (methyltheranylmethyl)benzene, (methyltheranylmethyl)naphthalene, ethyl-2-methyl-2-methyltheranyl-propionate, ethyl-2- methyl-2-n-butyltheranyl-propionate, (2-trimethylsiloxyethyl)-2-methyl-2-methyltheranyl-propionate, (2-hydroxyethyl)-2-methyl-2-methyltheranyl-propionate or (3-trimethylsilylpropargyl )-2-methyl-2-methylteranyl-propionate, etc., organic All tellurium compounds can be exemplified.

Specific examples of the organic ditelluride compound represented by the general formula (2) include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di -n-butyl ditelluride, di-s-butyl ditelluride, di-t-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis-(p-methoxyphenyl) ditelluride, bis-(p-aminophenyl) ditelluride, bis -(p-Nitrophenyl)ditelluride, bis-(p-cyanophenyl)ditelluride, bis-(p-sulfonylphenyl)ditelluride, dinaphthylditelluride, dipyridylditelluride and the like can be exemplified.

As the azo polymerization initiator, any azo polymerization initiator that is commonly used in radical polymerization can be used without any particular limitation. For example, 2,2′-azobis(isobutyronitrile) (AIBN), 2,2′-azobis(2-methylbutyronitrile) (AMBN), 2,2′-azobis(2,4-dimethylvaleronitrile) ) (ADVN), 1,1′-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2′-azobisisobutyrate (MAIB), 4,4′-azobis(4-cyanovaleric acid ) (ACVA), 1,1′-azobis(1-acetoxy-1-phenylethane), 2,2′-azobis(2-methylbutyramide), 2,2′-azobis(4-methoxy-2,4 -dimethylvaleronitrile) (V-70), 2,2′-azobis(2-methylamidinopropane) dihydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane], 2 , 2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2′-azobis(2,4,4-trimethylpentane), 2-cyano-2-propylazoformamide, 2 , 2′-azobis(N-butyl-2-methylpropionamide) or 2,2′-azobis(N-cyclohexyl-2-methylpropionamide).

In the polymerization step, in a vessel purged with an inert gas, the vinyl monomer and the organic tellurium compound of general formula (1) are added for the purpose of accelerating the reaction, controlling the molecular weight and molecular weight distribution, etc. depending on the type of the vinyl monomer. An azo polymerization initiator and/or an organic ditelluride compound of general formula (2) is mixed. At this time, examples of the inert gas include nitrogen, argon, and helium. Argon and nitrogen are preferred.

The amount of the vinyl monomer used in (a), (b), (c) and (d) may be appropriately adjusted depending on the physical properties of the intended copolymer (A). It is preferable to use 200 mol to 30000 mol of the vinyl monomer per 1 mol of the organotellurium compound of general formula (1).

When the organic tellurium compound of general formula (1) and the azo polymerization initiator (b) are used in combination, 0.01 mol to 10 mol of the azo polymerization initiator is used per 1 mol of the organic tellurium compound of general formula (1). It is preferable to

When the organic tellurium compound of general formula (1) and the organic ditelluride compound of general formula (2) of (c) are used together, the organic tellurium compound of general formula (2) is used per 1 mol of the organic tellurium compound of general formula (1). The amount of the ditelluride compound is preferably 0.01 mol to 100 mol.

When the organic tellurium compound of general formula (1) in (d) above, the organic ditelluride compound of general formula (2), and an azo polymerization initiator are used in combination, generally The amount of the organic ditelluride compound of formula (2) is preferably 0.01 mol to 100 mol, and the amount of the azo polymerization initiator is preferably 0.01 mol to 10 mol per 1 mol of the organic ditelluride compound of general formula (2).

The polymerization reaction can be carried out without a solvent, but may be carried out by using an aprotic or protic solvent generally used in radical polymerization and stirring the mixture. Aprotic solvents that can be used are, for example, anisole, benzene, toluene, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, 2-butanone (methyl ethyl ketone), dioxane, propylene glycol monomethyl ether acetate, chloroform. , carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, propylene glycol monomethyl ether acetate, trifluoromethylbenzene, and the like. Examples of protic solvents include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol and diacetone alcohol.

The amount of the solvent to be used may be adjusted as appropriate. For example, it is preferably 0.01 ml or more, more preferably 0.05 ml or more, still more preferably 0.1 ml or more, and 50 ml or less per 1 g of the vinyl monomer. It is preferably 10 ml or less, more preferably 1 ml or less.

The reaction temperature and reaction time may be appropriately adjusted depending on the molecular weight or molecular weight distribution of the copolymer (A) to be obtained, but the mixture is usually stirred at 0°C to 150°C for 1 minute to 100 hours. The TERP method can obtain high yields and precise molecular weight distributions even at low polymerization temperatures and short polymerization times. At this time, the pressure is usually normal pressure, but may be pressurized or reduced.

After completion of the polymerization reaction, the target copolymer (A) can be separated from the resulting reaction mixture by removing the solvent used and the residual vinyl monomer, etc., by ordinary separation and purification means. Moreover, the reaction mixture may be used as it is in the pressure-sensitive adhesive composition as long as it does not interfere with the physical properties of the pressure-sensitive adhesive composition.

The growing terminal of the copolymer obtained by the polymerization reaction is in the form of —TeR ¹ (wherein R ¹ is the same as above) derived from the tellurium compound, and is deactivated by an operation in air after the completion of the polymerization reaction. However, tellurium atoms may remain. Since a copolymer having a tellurium atom remaining at the end thereof is colored or has poor thermal stability, it is preferable to remove the tellurium atom.

Methods for removing tellurium atoms include radical reduction methods using tributylstannane or thiol compounds; adsorption methods using activated carbon, silica gel, activated alumina, activated clay, molecular sieves, polymer adsorbents, etc.; ion exchange resins, etc. Method of adsorbing metals: Hydrogen peroxide solution or peroxides such as benzoyl peroxide are added, air or oxygen is blown into the system to oxidize and decompose the tellurium atoms at the ends of the copolymer, washing with water or appropriate A liquid-liquid extraction method or solid-liquid extraction method that removes residual tellurium compounds by combining solvents; a purification method in a solution state such as ultrafiltration that extracts and removes only those with a specific molecular weight or less can be used. , or a combination of these methods can be used.

The other end of the copolymer obtained by the polymerization reaction (the end opposite to the growing end) is -CR ² R ³ R ⁴ derived from a tellurium compound (wherein R ² , R ³ and R ⁴ are represented by the formula The same as R ² , R ³ and R ⁴ in (1)).

(1-2 Epoxy Crosslinking Agent (B))
The epoxy-based cross-linking agent (B) refers to a compound having two or more epoxy groups as reactive groups in one molecule. The epoxy-based cross-linking agent (B) may be used alone or in combination of two or more.

Examples of the epoxy-based cross-linking agent (B) include epoxy-based resins composed of bisphenol A and epichlorohydrin, N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, diamineglycidylamine, 1, 3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, Adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether and the like. Among these, compounds having 2 to 6 epoxy groups in the molecule are preferred, and compounds having 3 to 5 epoxy groups are more preferred.

The content of reactive groups in the epoxy-based cross-linking agent (B) is preferably 0.1 mmol/g or more, more preferably 0.5 mmol/g or more, still more preferably 1.0 mmol/g or more, and particularly preferably 3 0 mmol/g or more, preferably 50 mmol/g or less, more preferably 20 mmol/g or less, still more preferably 10 mmol/g or less. If the content of the reactive groups in the epoxy-based cross-linking agent (B) is 0.1 mmol/g or more, the cohesive failure of the adhesive layer is suppressed, and if it is 50 mmol/g or less, the cross-linking density does not become too high, and the adhesive Good strength.

The content of the epoxy-based cross-linking agent (B) in the adhesive composition is preferably 0.01 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the copolymer (A). More preferably 1.0 parts by mass or more, particularly preferably 2.5 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, particularly preferably 8 parts by mass It is below the department. When the content of the epoxy-based cross-linking agent (B) is 0.01 parts by mass or more, the cohesive force of the adhesive layer is good, and when it is 20 parts by mass or less, the cross-linking density does not become too high and the adhesive strength is good. Become.

In the adhesive composition, the molar ratio of the reactive groups of the cross-linking agent (B) to the reactive functional groups of the copolymer (A) (molar amount of reactive groups/molar amount of reactive functional groups) is , preferably 0.005 or more, more preferably 0.4 or more, still more preferably 0.6 or more, particularly preferably 0.8 or more, preferably 2.0 or less, more preferably 1.5 or less , and more preferably 1.0 or less.

(1-3. Other cross-linking agents)
A cross-linking agent other than the epoxy-based cross-linking agent (B) may be blended in the pressure-sensitive adhesive composition, if necessary. Examples of cross-linking agents other than epoxy-based cross-linking agents (B) include isocyanate-based cross-linking agents, aziridine-based cross-linking agents, metal chelate-based cross-linking agents, melamine resin-based cross-linking agents, and urea resin-based cross-linking agents.

When a cross-linking agent other than the epoxy cross-linking agent (B) is blended, the content of the epoxy cross-linking agent (B) in the total cross-linking agent is preferably 80% by mass or more, more preferably 90% by mass or more, and further Preferably, it is 95% by mass or more. The pressure-sensitive adhesive composition preferably contains only the epoxy-based cross-linking agent (B) as a cross-linking agent.

(1-4. Other additives)
In addition to the copolymer (A) and the epoxy-based cross-linking agent (B), other additives may be added to the pressure-sensitive adhesive composition. Other additives include cross-linking retarders, tackifying resins (tackifiers), cross-linking accelerators, plasticizers, softeners, release aids, silane coupling agents, dyes, pigments, dyes, fluorescent brighteners, Antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble quenching agents, fragrances, metal deactivators , nucleating agents, alkylating agents, flame retardants, lubricants, and processing aids. These are appropriately selected and blended for use according to the application and purpose of use of the pressure-sensitive adhesive.

(1-4-1. Crosslinking retarder)
A cross-linking retarder may be added to the pressure-sensitive adhesive composition, if necessary. A cross-linking retarder is a compound capable of suppressing an excessive increase in viscosity of the pressure-sensitive adhesive composition. The type of cross-linking retarder is not particularly limited, but for example, β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, octane-2,4-dione; β-Ketoesters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; alcohols such as benzoylacetone; isopropyl alcohol, etc. can do. The cross-linking retarder may be used alone or in combination of two or more.

The content of the cross-linking retarder that can be blended in the pressure-sensitive adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the copolymer (A). It is more preferably 1.0 parts by mass or more, preferably 50 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 20 parts by mass or less. By adjusting the content of the cross-linking retarder to the above range, after the epoxy-based cross-linking agent (B) is blended into the pressure-sensitive adhesive composition, excessive viscosity increase and gelation of the pressure-sensitive adhesive composition are suppressed, The storage stability (pot life) of the pressure-sensitive adhesive composition can be extended.

(1-5. Method for producing adhesive composition)
The pressure-sensitive adhesive composition can be produced by mixing the copolymer (A), the epoxy-based cross-linking agent (B), and other additives used as necessary. The pressure-sensitive adhesive composition contains a solvent derived from the production of the copolymer (A), or a suitable solvent is added to dilute the pressure-sensitive adhesive composition to a viscosity suitable for forming the pressure-sensitive adhesive layer. It may be a solution containing

Examples of the solvent include aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone. esters such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve; glycol ether solvents such as propylene glycol monomethyl ether; These solvents may be used singly or in combination of two or more.

The amount of the solvent used may be appropriately adjusted so that the pressure-sensitive adhesive composition has a viscosity suitable for coating, and is not particularly limited. It is preferable to use it so that it will be from mass % to 95 mass %.

(2. Base film)
The base film can be appropriately selected and used according to the application of the adhesive film. For example, from the viewpoint of inspection and management of the optical member by see-through, a transparent base film is preferable. A transparent substrate refers to a substrate that is transparent. Examples of transparent substrate films include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); acrylic resins such as polymethyl methacrylate (PMMA); polycarbonate, triacetyl cellulose (TAC), polystyrene, and polysulfone. , polyether sulfone, polyphenylene sulfone, polyphenylene sulfide, polyether ether ketone, cycloolefin polymer, cycloolefin copolymer, fluoropolymer, polyarylate, polyetherimide, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, Examples include films composed of plastic materials such as ethylene-propylene copolymers. The plastic materials may be used alone or in combination of two or more. Among these, PET is preferable in terms of excellent mechanical strength and dimensional stability. Moreover, polyimide is preferable in terms of excellent heat resistance. That is, the transparent substrate film is preferably a PET film (especially a biaxially stretched PET film) or a polyimide film.

Although the total light transmittance (JIS K7361-1 (1997)) of the transparent base film in the visible light wavelength region is not particularly limited, it is preferably 85% or more. By setting the total light transmittance to 85% or more, the transparency is excellent, so that the optical member can be accurately inspected for defects while the adhesive film is attached.

The thickness of the base film is not particularly limited and is appropriately selected, but is usually preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and preferably 200 μm or less, more preferably 100 μm. 50 μm or less, more preferably 50 μm or less. If the thickness is less than 5 μm, the strength of the base film is insufficient, sufficient protective performance cannot be obtained, and problems such as tearing of the film during peeling occur. On the other hand, if the thickness of the base film is more than 200 μm, the permeability of the base film is deteriorated, and the film itself becomes expensive.

For the purpose of improving adhesion to the layer provided on the surface of the base film, one or both sides of the base film can be subjected to surface treatment by an oxidation method, a roughening method, or the like, if desired. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone/ultraviolet irradiation treatment, and the like. Examples of the roughening method include a sandblasting method and a solvent treatment method. These surface treatment methods are appropriately selected according to the type of substrate film, but generally corona discharge treatment is preferably used from the standpoints of effectiveness and operability. Further, as the base film, one surface or both surfaces of which is subjected to a primer treatment can be used.

(3. Adhesive layer)
The gel fraction of the adhesive layer is 70% by mass or more, preferably 70% by mass to 100% by mass, more preferably 80% by mass to 100% by mass, and still more preferably 90% by mass to 100% by mass. is. If the gel fraction is too low, the adhesive strength tends to increase, and the adherend tends to stain during peeling. The gel fraction can be controlled by the blending amount of the cross-linking agent, the cross-linking treatment temperature, and the cross-linking treatment time in the pressure-sensitive adhesive composition, which will be described later.

The thickness of the pressure-sensitive adhesive layer formed on the substrate film can be appropriately set according to, for example, the adhesive force required for the surface protective film for optical members, the surface roughness of the optical member, and the like. The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm.

(3-1. Method for forming adhesive layer)
The method for forming the pressure-sensitive adhesive layer is not particularly limited, and includes, for example, the following methods (1) and (2).
(1) A method of applying an adhesive composition to one or both sides of a substrate film using various coating devices, removing the solvent by drying, and curing as necessary.
(2) Using various coating devices, apply a pressure-sensitive adhesive composition to the release surface of the release film whose surface has been subjected to release treatment, remove the solvent by drying, and transfer it to one or both sides of the base film. After that, how to cure as necessary.

Examples of the coating apparatus include reverse roll coaters, gravure coaters, forward roll coaters, knife coaters, wire bar coaters, doctor blade coaters, slot die coaters, curtain coaters, and dip coaters.

The drying temperature for removing the solvent by drying is preferably 40°C to 200°C, more preferably 60°C to 180°C. The drying time is preferably 5 seconds to 20 minutes, more preferably 10 seconds to 10 minutes. Drying means include hot air, near-infrared rays, infrared rays, high-frequency waves, and the like. Further, the curing conditions include, for example, 40° C. for 3 to 7 days. By drying and removing the solvent and curing, the cross-linking reaction (the reaction between the acidic group of the copolymer (A) and the epoxy cross-linking agent (B)) is completed, and the pressure-sensitive adhesive layer is formed.

(4. Release film)
The pressure-sensitive adhesive film may have a release film (separator) on the surface of the pressure-sensitive adhesive layer until it is used. A release layer is provided on the opposite side of the adhesive layer laminated surface of the base film without using a separate release film, and the surface of the release layer is wound in a roll so that the exposed surface side of the adhesive layer is in contact. It may be turned or laminated in a stack. The release film is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when the pressure-sensitive adhesive film of the present invention is attached to an adherend.

Examples of the release film include paper such as glassine paper, coated paper, laminated paper, and various plastic films coated with a release agent such as silicone resin. As the plastic film to be used for the release film, the one exemplified as the base film can be appropriately used. Although the thickness of the release film is not particularly limited, it is usually 10 μm to 150 μm.

(5. Application of adhesive film)
Since the pressure-sensitive adhesive film causes less contamination on the surface of the adherend, it can be used as a surface protective film that is peeled off after use. In particular, the adhesive film is difficult to peel off during use after heat treatment, easy to peel after use, and less contamination on the surface of the adherend after peeling. , a conductive film in which a thin film of indium tin oxide (ITO) or the like is formed as a transparent electrode on one surface of a transparent substrate, and a surface protective film for optical members such as a glass substrate.

The pressure-sensitive adhesive film is used by being laminated on the optical member, which is the adherend, such that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film is in contact with the surface of the adherend. The pressure-sensitive adhesive film is preferably used after being laminated with an optical member and then heat-treated at, for example, 100°C to 250°C. The protective film of the present invention protects or reinforces the surface of the optical member in a heat treatment step at, for example, 100° C. to 250° C., can be easily peeled off after the heat treatment step, and prevents contamination of the surface of the optical member after peeling. Less is.

The adhesive film preferably has an adhesive strength to an adherend of 0.01 N/24 mm to 1.0 N/24 mm. In addition, the adhesive film preferably has an adhesive strength to the adherend after heat treatment (200 ° C., 1 hour) of 0.01 N / 24 mm to 2.5 N / 24 mm, and 0.01 N / 24 mm to 1.0 N /24 mm is more preferred. When the adhesive strength is 2.5 N/24 mm or less, deformation of the adherend (for example, optical member) can be suppressed when the adhesive film is peeled from the adherend. Further, if the adhesive strength is 0.01 N/24 mm or more, unintentional peeling from the adherend during use is suppressed.

The adhesive film has a water contact angle (Y1) on the glass surface when the adhesive layer is attached to the glass surface at room temperature (23 ° C.) and then peeled off, and The absolute value (|Y1-Y2|) of the difference from the water contact angle (Y2) of the glass surface is preferably less than 20°, more preferably less than 15°, still more preferably less than 10°. If the absolute value of the difference (|Y1−Y2|) is less than 20°, contamination of the adherend when the adhesive film is used at room temperature is reduced.

The adhesive film has the water contact angle (X1) of the glass surface when the adhesive layer is attached to the glass surface and treated at 200 ° C. for 1 hour, and the glass surface before the adhesive layer is attached. The absolute value (|X1-X2|) of the difference from the water contact angle (X2) (without heat treatment) is preferably less than 20°, more preferably less than 18°, and even more preferably less than 16°. . If the absolute value of the difference (|X1−X2|) is less than 20°, the heat resistance of the adhesive layer is good, and even if the member to which the adhesive film is attached is subjected to heat treatment, the adhesion Contamination on the body is reduced. Therefore, even if the adhesive film is used as a surface protection film, the surface protection tape is peeled off after the completion of various manufacturing processes, and an adhesive or hard coating agent is applied to the peeled surface of the adherend, the appearance of the coating can be improved. becomes good.

The curing type of the hard coating agent is not particularly limited, but includes, for example, ultraviolet (UV) curing type by photochemical reaction; thermosetting type such as room temperature curing type and two-liquid reaction curing type; That is, the hard coating agent is not particularly limited, but includes, for example, generally known UV curable resins, urethane resins, and condensation resins.

Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is by no means limited to the following examples, and can be modified as appropriate without changing the gist of the invention. In addition, the polymerization rate, weight average molecular weight (Mw) and molecular weight distribution (PDI) of the copolymer, the solid content and viscosity of the copolymer solution, the gel fraction of the adhesive layer, and the adhesive strength of the adhesive film before heat treatment, Adhesive strength after heat treatment, film peeling after heat treatment, residue after heat treatment, and water contact angle were evaluated according to the following methods.

Abbreviations have the following meanings.
BTEE: ethyl-2-methyl-2-n-butyltheranyl-propionate AIBN: 2,2'-azobis(isobutyronitrile)
V-70: 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile)
MA: methyl acrylate BA: n-butyl acrylate 2-EHA: 2-ethylhexyl acrylate LA: n-lauryl acrylate BzA: benzyl acrylate CHA: cyclohexyl acrylate PhEA: 2-phenoxyethyl acrylate 4-HBA: 4-hydroxybutyl acrylate AA: Acrylic acid AcOEt: Ethyl acetate IPA: Isopropyl alcohol

[Evaluation method]
(Polymerization rate)
¹ H-NMR was measured (solvent: CDCl ₃ , internal standard: trimethylsilane (TMS)) using a nuclear magnetic resonance (NMR) spectrometer (manufactured by Bruker Biospin, model: AVANCE500 (frequency: 500 MHz)). . With respect to the obtained NMR spectrum, the integration ratio of the peaks of the monomer-derived vinyl group and the polymer-derived ester side chain peak was determined to calculate the polymerization rate of the monomer.

(Weight average molecular weight (Mw) and molecular weight distribution (PDI))
It was determined by gel permeation chromatography (GPC) using a high-performance liquid chromatograph (Model HLC-8320GPC manufactured by Tosoh Corporation). Two columns of TSKgel Super Multipore HZ-H (manufactured by Tosoh Corporation) were used, a tetrahydrofuran solution was used as a mobile phase, and a differential refractometer was used as a detector. The measurement conditions were a column temperature of 40° C., a sample concentration of 10 mg/mL, a sample injection amount of 10 μm, and a flow rate of 0.2 mL/min. Using polystyrene (molecular weight 1,090,000, 775,000, 427,000, 289,000, 190,000, 96,400, 37,900, 10,200, 2,630, 440) as a standard A calibration curve (calibration curve) was prepared and the weight average molecular weight (Mw) and number average molecular weight (Mn) were measured. A molecular weight distribution (PDI=Mw/Mn) was calculated from this measured value.

(solid content)
A copolymer solution having a weight of W1 (about 1.0 g) was weighed into an aluminum cup (weight of W0) and dried under reduced pressure at 130° C. for 1 hour. The mass (W2) of the aluminum cup containing the dried copolymer was measured, and the solid content was calculated from the following formula.
Solid content (mass%) = [(W2-W0) / W1] × 100

(viscosity)
Using a Brookfield viscometer (trade name: TVB-15, manufactured by Toki Sangyo Co., Ltd.), the viscosity was measured using an M3 rotor at 25° C. and a rotor speed of 60 rpm.

(Gel fraction)
The pressure-sensitive adhesive composition was applied to a release film, dried at 60°C for 2 minutes, and further dried at 120°C for 3 minutes. Then, after standing at 40° C. for 3 days, the pressure-sensitive adhesive layer formed on the release film was peeled off.
The pressure-sensitive adhesive layer was cut into pieces of about 0.1 g to obtain test pieces (weight W1). This test piece was placed in a stainless steel wire mesh (400 mesh) (weight W0). The stainless steel wire mesh containing the test piece was immersed in ethyl acetate at 60°C for 24 hours, then removed from the ethyl acetate, dried at room temperature for 24 hours, and further dried under reduced pressure at 130°C for 1 hour. . After that, the mass W2 of the stainless steel wire mesh containing the dried test piece was measured, and the gel fraction was calculated from the following formula.
Gel fraction (% by weight) = [(W2-W0) / W1] x 100

(Adhesive strength before heat treatment)
Adhesive strength when the adhesive film is pressed against the adherend (non-alkali glass plate) using a pressure bonding device (roller weight: 2 kg) and peeled off at 180° to the adherend within 1 minute. was measured. A tensile tester was used for the measurement, the test temperature was 23° C., and the peeling speed was 300 mm/min. The adhesive film had a width of 24 mm and a length of 300 mm. After the start of the measurement, the first 25 mm length measurements were ignored, and then the adhesion measurements for 50 mm lengths peeled from the test panel were averaged. "○" when the adhesive strength before heat treatment is 1.0 N / 24 mm or less, "△" when it exceeds 1.0 N / 24 mm and 2.5 N / 24 mm or less, "X" when it exceeds 2.5 N / 24 mm ” was evaluated.

(Adhesive strength after heat treatment)
The pressure-sensitive adhesive film was crimped onto an adherend (non-alkali glass plate) using a crimping device (mass of roller: 2 kg). The glass plate to which this adhesive film was adhered was heat-treated at 200° C. for 1 hour. After allowing the glass plate to cool to room temperature, the adhesive force was measured when the adhesive film was peeled off from the adherend at an angle of 180°. A tensile tester was used for the measurement, the test temperature was 23° C., and the peeling speed was 300 mm/min. The adhesive film had a width of 24 mm and a length of 300 mm. After the start of the measurement, the first 25 mm length measurements were ignored, and then the adhesion measurements for 50 mm lengths peeled from the test panel were averaged. "○" when the adhesive strength after heat treatment is 1.0 N / 24 mm or less, "△" when it exceeds 1.0 N / 24 mm and 2.5 N / 24 mm or less, "X" when it exceeds 2.5 N / 24 mm ” was evaluated.

(Film peeling after heat treatment)
When measuring the post-heat-treatment adhesive strength, whether or not the adhesive film adhered to the heat-treated glass plate was peeled off was visually judged before conducting the peeling test. Those with no film peeling were evaluated as "Good", and those with film peeling were evaluated as "Poor".

(Adhesive residue after heat treatment)
After measuring the adhesive strength after the heat treatment, it was judged visually whether there was any adhesive residue on the adherend. Those with no adhesive residue were evaluated as "Good", and those with adhesive residue were evaluated as "Poor".

(water contact angle)
The water contact angle X1 (°) was measured for the adherend after measuring the adhesive strength before heat treatment and the adhesive strength after heat treatment. In addition, the water contact angle X2 (°) was measured for the non-alkali glass before adhering the adhesive film, and this was used as a blank. The water contact angle was measured using an automatic contact angle meter (Kyowa Interface Science Co., Ltd. DM-500) at a test temperature of 23°C. The measurement result of the water contact angle of the alkali-free glass blank was 40°. Calculate the angle difference (X1-X2) from each measurement value, and evaluate the absolute value of the angle difference (|X1-X2|) as “○” if it is less than 20°, and as “X” if the difference is 20° or more. did.

<Synthesis of copolymer>
(Synthesis example 1)
BA (330.0 g), BzA (150.0 g), AA (20.0 g), V-70 (77.1 mg) and AcOEt (328.8 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (374.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 90.0%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 1 was obtained. The obtained copolymer no. The Mw of 1 was 321,200, the PDI was 1.31, the solids content of the solution was 32.3% by weight, and the viscosity was 2,480 mPa·s.

(Synthesis example 2)
BA (330.0 g), PhEA (150.0 g), AA (20.0 g), V-70 (77.1 mg) and AcOEt (328.8 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (374.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 87.8%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 2 was obtained. The obtained copolymer no. 2 had a Mw of 340,300, a PDI of 1.32, a solids content of the solution of 38.4% by weight, and a viscosity of 8,410 mPa·s.

(Synthesis Example 3)
BA (363.0 g), PhEA (165.0 g), AA (22.0 g), AIBN (26.8 mg) and AcOEt (410.4 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer, After purging with argon, BTEE (122.2 mg) was added and reacted at 60° C. for 24 hours to polymerize. The polymerization rate was 77.1%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 3 was obtained. The obtained copolymer no. 3 had a Mw of 958,000, a PDI of 1.42, a solids content of the solution of 27.1% by weight and a viscosity of 23,490 mPa·s.

(Synthesis Example 4)
BA (330.0 g), CHA (150.0 g), AA (20.0 g), V-70 (77.1 mg) and AcOEt (328.8 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (374.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 85.7%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 4 was obtained. The obtained copolymer no. 4 had a Mw of 318,400, a PDI of 1.24, a solids content of the solution of 36.6% by weight, and a viscosity of 7,520 mPa·s.

(Synthesis Example 5)
BA (522.5 g), AA (27.5 g), V-70 (84.8 mg), and AcOEt (410.4 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer, and after purging with argon, BTEE (329.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 89.5%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 5 was obtained. The obtained copolymer no. The Mw of 5 was 433,600, the PDI was 1.33, the solids content of the solution was 27.4% by weight, and the viscosity was 4,840 mPa·s.

(Synthesis Example 6)
BA (88.0 g), PhEA (40.0 g), AA (5.3 g) and AcOEt (240.2 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer, and after argon substitution, the temperature was raised to 80°C. After warming, AIBN (0.17 g) was added, and after 10 minutes using a dropping funnel, BA (176.0 g), PhEA (80.0 g), AA (10.7 g) and AIBN (0.33 g) were added. , AcOEt (6.0 g) was added dropwise. After completion of dropping, AcOEt (120.0 g) and AIBN (0.5 g) were added, reacted for 120 minutes, and polymerized. The polymerization rate was 99.0%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 6 was obtained. The obtained copolymer no. 6 had a Mw of 519,000, a PDI of 8.87, a solids content of the solution of 32.3% by weight, and a viscosity of 2,960 mPa·s.

(Synthesis Example 7)
BA (475.0 g), 4-HBA (25.0 g), V-70 (57.8 mg), and AcOEt (377.2 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer, and the atmosphere was replaced with argon. , and BTEE (187.4 mg) were added and reacted at 33° C. for 20 hours to polymerize. The polymerization rate was 86.2%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 7 was obtained. The obtained copolymer no. The Mw of 7 was 701,000, the PDI was 1.68, the solids content of the solution was 19.8% by weight, and the viscosity was 2,364 mPa·s.

(Synthesis Example 8)
2-EHA (475.0 g), 4-HBA (25.0 g), V-70 (45.7 mg) and AcOEt (377.2 g) were charged into a flask equipped with an argon gas inlet tube and a stirrer, and argon was added. After substitution, BTEE (111.1 mg) was added and reacted at 33° C. for 20 hours to polymerize. The polymerization rate was 88.5%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 8 was obtained. The obtained copolymer no. 8 had a Mw of 975,000, a PDI of 2.34, a solids content of the solution of 22.3% by weight, and a viscosity of 3,881 mPa·s.

(Synthesis Example 9)
MA (50.0 g), 2-EHA (350.0 g), LA (75.0 g), 4-HBA (25.0 g), V-70 (57 .1 mg) and AcOEt (333.3 g) were charged, and after purging with argon, BTEE (299.9 mg) was added and reacted at 33° C. for 21 hours to polymerize. The polymerization rate was 92.2%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 9 was obtained. The obtained copolymer no. 9 had a Mw of 495,000, a PDI of 1.74, a solids content of the solution of 42.2% by weight, and a viscosity of 8,510 mPa·s.

(Synthesis Example 10)
2-EHA (375.0 g), BzA (100.0 g), 4-HBA (25.0 g), V-70 (37.1 mg), AcOEt (377 .2 g) was charged, and after purging with argon, BTEE (111.1 mg) was added and reacted at 33° C. for 18 hours to polymerize. The polymerization rate was 87.9%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 10 was obtained. The obtained copolymer no. The Mw of 10 was 1,034,000, the PDI was 2.50, the solids content of the solution was 23.4% by weight, and the viscosity was 5,020 mPa·s.

(Synthesis Example 11)
BA (456.0 g), PhEA (120.0 g), AA (24.0 g), V-70 (90.5 mg) and AcOEt (395.5 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (399.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 94.1%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 11 was obtained. The obtained copolymer no. 11 had a Mw of 440,300 and a PDI of 1.39.

(Synthesis Example 12)
BA (276.0 g), PhEA (300.0 g), AA (24.0 g), V-70 (90.5 mg) and AcOEt (395.5 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (399.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 98.2%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 12 was obtained. The obtained copolymer no. The Mw of 12 was 456,500 and the PDI was 1.43.

(Synthesis Example 13)
BA (372.0 g), PhEA (180.0 g), AA (48.0 g), V-70 (90.5 mg) and AcOEt (395.5 g) were placed in a flask equipped with an argon gas inlet tube and a stirrer. After charging and purging with argon, BTEE (399.9 mg) was added and reacted at 33° C. for 24 hours to polymerize. The polymerization rate was 94.2%.

After completion of the reaction, AcOEt was added to the reaction solution to obtain copolymer no. A copolymer solution containing 13 was obtained. The obtained copolymer no. 13 had a Mw of 460,100 and a PDI of 1.40.

A summary of synthesis examples is shown in Table 2. Table 3 shows the composition and physical properties of the copolymer. The content of each structural unit, the amount of hydroxy groups, and the amount of carboxyl groups in the copolymer were calculated from the charging ratio of the vinyl monomers used in the polymerization reaction.

<Production of adhesive composition>
(Adhesive composition No. 1)
Copolymer No. obtained in Synthesis Example 1; 5.69 parts by mass of a cross-linking agent (TETRAD (registered trademark)-C) and 13.3 parts by mass of IPA with respect to 309.6 parts by mass of the solution of 1 (100 parts by mass of the copolymer component, 209.6 parts by mass of AcOEt) Parts by mass and 28.1 parts by mass of AcOEt were added and stirred to obtain PSA composition No. 1. got 1.

(Adhesive composition Nos. 2 to 13)
Except that the formulation was changed as shown in Table 4, pressure-sensitive adhesive composition No. Adhesive composition No. 1 was prepared in the same manner as in No. 1. 2 to 13 were produced. The amount of solvent in Table 4 is the total amount of AcOEt contained in the copolymer solution and AcOEt added during preparation of the pressure-sensitive adhesive composition.

ＴＥＴＲＡＤ（登録商標）－Ｃ：三菱ガス化学社製、１，３－ビス（Ｎ，Ｎ－ジグリシジルアミノエチル）シクロヘキサン（エポキシ基量；１０．１４ｍｍｏｌ／ｇ）
デュラネート（登録商標）ＴＰＡ－１００：旭化成社製、ヘキサメチレンジイソシアネートのイソシアヌレート体（ＮＣＯ％；２３．１質量％）
ネオスタン（登録商標）Ｕ８１０：日東化成社製、ジオクチル錫

TETRAD (registered trademark)-C: manufactured by Mitsubishi Gas Chemical Company, 1,3-bis(N,N-diglycidylaminoethyl)cyclohexane (epoxy group content; 10.14 mmol/g)
Duranate (registered trademark) TPA-100: manufactured by Asahi Kasei Corporation, an isocyanurate form of hexamethylene diisocyanate (NCO%; 23.1% by mass)
Neostan (registered trademark) U810: manufactured by Nitto Kasei Co., Ltd., dioctyl tin

<Production of adhesive film>
(Adhesive film No. 1)
Adhesive composition No. 1 was applied onto a polyimide film (PI) film (thickness: 25 μm, manufactured by Ube Industries, Ltd., “Upilex (registered trademark) 25S”) so that the thickness after drying would be 10 μm. The PI film coated with the adhesive composition was dried at 60° C. for 2 minutes and at 120° C. for 3 minutes. 1 was produced. A release film (thickness: 25 μm, manufactured by Higashiyama Film Co., Ltd., “HY-PS11”) was attached to the resulting pressure-sensitive adhesive layer, and left at 40° C. for 3 days for curing.

(Adhesive film No. 2 to 13)
Adhesive composition No. 1, Adhesive composition No. Adhesive film No. 2 except for changing to 2 to 13. Adhesive film No. 1 was prepared in the same manner as in 1. 2 to 13 were produced.

Table 5 shows the evaluation results of gel fraction, adhesive strength, film peeling after heating, adhesive residue, and water contact angle for the resulting adhesive film.

Adhesive film no. 1 to 4 and 11 to 13, the pressure-sensitive adhesive layer contains a (meth)acrylic copolymer (A) having a predetermined weight average molecular weight, molecular weight distribution and structural unit and an epoxy cross-linking agent (B). It is formed from the agent composition and has a gel fraction of 70% by mass or more. These adhesive film nos. All of 1 to 4 and 11 to 13 had an adhesive strength of 2.5 N/24 mm or less before and after heat treatment, no film peeling due to heat treatment, and contamination of the adherend when peeled after heat treatment was suppressed. .

Adhesive film no. In No. 5, the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a copolymer having no structural unit (a-1). Adhesive film no. 6 is formed from an adhesive composition containing a copolymer with a molecular weight distribution of 8.87. Adhesive film no. In Nos. 7 to 10, the pressure-sensitive adhesive layer was formed from a pressure-sensitive adhesive composition containing a copolymer having no structural unit (a-2) and an isocyanate cross-linking agent. These adhesive film nos. In all of Nos. 5 to 10, contamination of the adherend was not suppressed when peeled off after heat treatment.

The adhesive film of the present invention includes, for example, a polarizing plate, a flexible printed circuit (FPC) substrate, a conductive film in which a thin film such as indium tin oxide (ITO) is formed as a transparent electrode on one surface of a transparent substrate, and a glass substrate. It can be suitably used as a surface protection film for optical members such as.

Claims (8)

Having a base film and an adhesive layer formed on at least one surface of the base film,
The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer (A) and an epoxy-based cross-linking agent (B),
The adhesive layer has a gel fraction of 70% by mass or more,
The (meth)acrylic copolymer (A) comprises a structural unit (a-1) having a cyclic group and a structural unit (a-2) having an acidic group,
The content of the structural unit (a-1) is 5% by mass to 80% by mass in 100% by mass of the entire (meth)acrylic copolymer (A),
The content of the structural unit (a-2) is 2.0% by mass to 20% by mass in the total 100% by mass of the (meth)acrylic copolymer (A),
The mass ratio ((a-1)/(a-2)) between the structural unit (a-1) and the structural unit (a-2) in the (meth)acrylic copolymer (A) is 0.5 to 20, and
An adhesive film, wherein the (meth)acrylic copolymer (A) has a weight average molecular weight of 200,000 to 2,000,000 and a molecular weight distribution (PDI) of less than 3.0. 2. The adhesive film according to claim 1, wherein the cyclic group of the structural unit (a-1) is at least one selected from the group consisting of aromatic groups and alicyclic hydrocarbon groups. 3. The acidic group of the structural unit (a-2) according to claim 1 or 2, wherein the acidic group is at least one selected from the group consisting of a carboxy group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group and a phosphine group. adhesive film. The pressure-sensitive adhesive film according to any one of claims 1 to 3, wherein the (meth)acrylic copolymer (A) is obtained by subjecting a monomer composition to living radical polymerization. When the pressure-sensitive adhesive layer is attached to a glass surface, heat-treated at 200 ° C. for 1 hour, and then peeled off, the initial water contact angle X1 (°) of the glass surface and the water contact angle after peeling the pressure-sensitive adhesive layer X2 (°). The pressure-sensitive adhesive film according to any one of claims 1 to 4 , wherein the absolute value (|X1-X2|) of the difference between is less than 20°. The adhesive film according to any one of claims 1 to 5, which has an adhesive strength of 0.01 N/24 mm to 2.5 N/24 mm. A surface protection film comprising the adhesive film according to any one of claims 1 to 6 . 8. The surface protection film according to claim 7, which is used for optical members.