JP2023002058A - Adhesive composition, adhesive layer, and adhesive film - Google Patents

Abstract

To provide an adhesive composition which exhibits excellent optical transparency, high adhesive strength, and foaming resistance even under a high temperature/high humidity environment and a high temperature water immersion environment.SOLUTION: Provided is an adhesive composition, comprising an acrylic polymer (A), a crosslinking agent (B), and an acrylic polymer (C). The acrylic polymer (A) contains a unit derived from an alkyl (meth)acrylate monomer (a1) having a C1-4 alkyl group, a unit derived from a monomer (a2) having a nitrogen atom, and a unit derived from at least one selected from the group consisting of a monomer (a3) having an acidic group and a monomer (a4) having a hydroxyl group. The acrylic polymer (C) contains a unit derived from a (meth)acrylic monomer (c1) having an alicyclic structure and a unit derived from an alkyl (meth)acrylate monomer (c2).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, an adhesive layer, and an adhesive film.

Acrylic pressure-sensitive adhesives have been used in various fields for a long time. In recent years, demand for them is particularly high in IT-related products such as smartphones. These IT-related products are required to have higher performance and functions due to their product characteristics.

As an example of an acrylic adhesive used in IT-related products, there is a demand for a heat-sensitive adhesive that is slightly sticky at room temperature, but exhibits strong stickiness when heated and maintains stickiness even after the heat is removed. As a specific example thereof, for example, a pressure-sensitive adhesive containing an acrylic low-molecular-weight polymer having a weight-average molecular weight of 2,000 to 9,000 has been proposed (see, for example, Patent Document 1). Further, a polymer having a glass transition temperature of less than 0 ° C.; a monomer having a polyorganosiloxane skeleton and a monomer having a glass transition temperature of 40 ° C. or higher are included as monomer units, and the weight average molecular weight is 10,000 or more and less than 100,000. A pressure-sensitive adhesive containing a polymer has been proposed (see, for example, Patent Document 2).

Protective films for IT-related products with display functions such as TVs, personal computers, mobile terminals, OA equipment, car navigation systems, game devices, and electronic notebooks, and members attached to the surface of the display device, must be highly visible in order to provide visibility. Transparency is imperative. In addition, it is required that strong adhesive strength is exhibited immediately after bonding to a housing or a display device, and that the adhesive strength does not decrease even after being subjected to a durable environment. In the past, metal and glass were used for housings and surface panels of display devices, but in recent years, plastic materials such as acrylic and polycarbonate have been used to reduce weight and add design features such as 3D molding. With conventionally known pressure-sensitive adhesives, when exposed to severe durability conditions such as high-temperature and high-humidity environments or immersion in hot water, air bubbles form between the substrate or adherend and the adhesive surface. , resulting in problems such as an inability to maintain optical transparency, a decrease in visibility, and difficulty in maintaining a high adhesive strength due to foaming.

In addition, in automotive exteriors and outdoor advertising materials, it is sometimes used as a substitute for paint or for attaching a film printed on the paint and replacing it after a certain period of time. Also in this application, as mentioned above, it is required to have excellent optical transparency for imparting a high degree of designability, and to maintain adhesive strength regardless of the type of adherend even under a durable environment.

Japanese Patent No. 6618522 JP 2019-123884 A

The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive composition that exhibits excellent optical transparency, high adhesive strength, and foaming resistance even in a high-temperature and high-humidity environment or in a hot water immersion environment. to provide the film.

The pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer (A), a cross-linking agent (B) and an acrylic polymer (C), wherein the acrylic polymer (A) contains an alkyl group having 1 to 4 carbon atoms. from the group consisting of units derived from the alkyl (meth)acrylate monomer (a1) having; units derived from the monomer (a2) having a nitrogen atom; monomer (a3) having an acid group and monomer (a4) having a hydroxyl group The glass transition temperature of the acrylic polymer (A) is −20° C. or lower, and the weight average molecular weight of the acrylic polymer (A) is 100, 000 or more, and the content of units derived from the alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms is 50% by mass or more and 97% by mass in the acrylic polymer (A). %, and the acrylic polymer (C) contains units derived from the alicyclic structure-containing (meth)acrylate monomer (c1); and units derived from the alkyl (meth)acrylate monomer (c2). The acrylic polymer (C) has a glass transition temperature of 50° C. or higher and a weight average molecular weight of less than 100,000.

The pressure-sensitive adhesive composition of the present invention exhibits excellent optical transparency, high adhesive strength, and foaming resistance even in a high-temperature and high-humidity environment or in a hot-water immersion environment. Appropriate use as a protective film for IT-related products with a display function such as devices, car navigation systems, game devices, and electronic notebooks, a paint protection film used for automobile exteriors, a protective film for outdoor advertising materials and indoor/outdoor building materials, etc. can be done.

The pressure-sensitive adhesive composition of the present invention contains an acrylic polymer (A), a cross-linking agent (B) and an acrylic polymer (C).

The acrylic polymer (A) includes units derived from an alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms; units derived from a monomer (a2) having a nitrogen atom; and a unit derived from at least one selected from the group consisting of a monomer (a3) having a group and a monomer (a4) having a hydroxyl group.

Examples of the alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, ) acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate and the like. These alkyl (meth)acrylate monomers (a1) can be used alone or in combination of two or more. However, n-butyl acrylate is preferably contained because it is easy to balance cohesion and flexibility. The content of -butyl acrylate is more preferably 25% by mass or more, still more preferably 30% by mass or more, in the alkyl (meth)acrylate monomer (a1).

The monomer having a nitrogen atom (a2) is a monomer having a nitrogen atom and a polymerizable double bond in the molecule, and a monomer having an amide bond and a polymerizable double bond in the molecule. For example, a lactam compound having a vinyl group; a (meth)acrylamide monomer; a functional group containing a nitrogen atom (e.g., an amino group, a monosubstituted amino group, a disubstituted amino group, a nitrile group, etc.) (Meth)acrylate compounds having These nitrogen atom-containing monomers (a2) can be used alone or in combination of two or more.

Examples of the lactam compound having a vinyl group include N-vinylpyrrolidone and N-vinylcaprolactam.

The (meth)acrylamide monomer has a nitrogen atom of (meth)acrylamide attached to a hydrogen atom or a hydrocarbon group (preferably an aliphatic hydrocarbon group. However, —CH ₂ — contained in the hydrocarbon is —CO may be substituted with -, and the hydrogen atom contained in the hydrocarbon group may be substituted with a hydroxyl group.) is bonded. In addition, when the nitrogen atom of (meth)acrylamide is substituted with two or more groups (the above hydrocarbon groups), those groups may be bonded to each other to form a ring containing the nitrogen atom.

The number of carbon atoms in the hydrocarbon group (preferably aliphatic hydrocarbon group) substituting the nitrogen atom contained in the amide bond is preferably 1 or more, preferably 10 or less, more preferably 6 or less.

One or more of the (meth)acrylamide monomers may be used. The (meth)acrylamide monomer may be (meth)acrylamide, an N-1-substituted (meth)acrylamide compound, or an N,N-2-substituted (meth)acrylamide compound.

As the (meth)acrylamide compound, one or two or more can be used, and examples include (meth)acrylamide; N-isopropyl(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide , N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-(2-hydroxymethyl)acrylamide, N-(2-hydroxyethyl)acrylamide, etc. Monosubstituted (meth)acrylamide compounds; N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloyl-4- piperidone, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-methylenebis(meth)acrylamide, N,N-dimethylaminopropyl ( Examples include N-2 substituted (meth)acrylamide compounds such as meth)acrylamide.

Among them, the (meth)acrylamide monomer preferably contains a monomer represented by formula (1).

［式（１）中、Ｒ^１は、水素原子又はメチル基を表す。Ｒ^２及びＲ^３は、それぞれ独立に、水素原子又は炭素原子数１～２０の炭化水素基を表し、該炭化水素基に含まれる－ＣＨ_２－は、－ＣＯ－又は－Ｏ－に置き換わっていてもよく、該炭化水素基に含まれる水素原子はヒドロキシル基に置き換わっていてもよく、Ｒ^２及びＲ^３は、互いに結合して、窒素原子を含む環を形成していてもよい。］

[In formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and —CH ₂ — contained in the hydrocarbon group is replaced with —CO— or —O— A hydrogen atom contained in the hydrocarbon group may be replaced with a hydroxyl group, and R ² and R ³ may combine with each other to form a ring containing a nitrogen atom. ]

The hydrocarbon groups represented by R ² and R ³ may be one type or two or more types, for example, linear or branched saturated aliphatic hydrocarbon groups; linear or branched and unsaturated aliphatic hydrocarbon groups. Among them, a linear or branched saturated aliphatic hydrocarbon group is preferable, and a branched saturated aliphatic hydrocarbon group is more preferable. At least one of R ² and R ³ is preferably a hydrogen atom.

The (meth)acrylamide monomer preferably includes a (meth)acrylamide monomer in which both R ² and R ³ are the above hydrocarbon groups. When both R ² and R ³ contain a (meth)acrylamide monomer that is a hydrocarbon group, the content of units derived from the monomer is preferably 0.5 in the acrylic polymer (A). It is 5% by mass or more, more preferably 1% by mass or more, preferably 20% by mass or less, and more preferably 15% by mass or less.

In the monomer (a2) having a nitrogen atom, the content of units derived from the acrylamide monomer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more, The upper limit is 100% by mass.

Examples of (meth)acrylate compounds having a functional group containing a nitrogen atom (e.g., amino group, monosubstituted amino group, disubstituted amino group, nitrile group, etc.) include (meth)acrylonitrile, t-butylaminoethyl (meth) Acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate and the like.

The monomer having an acid group (a3) includes a monomer having an acid group and a polymerizable double bond, preferably a monomer having a carboxyl group, a monomer having a sulfo group, and a monomer having a carboxyl group. is preferred.

As the monomer having a carboxyl group, one or two or more can be used, for example, (meth) acrylic acid; carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, β-carboxyethyl (meth) carboxyalkyl (meth)acrylates such as acrylates; unsaturated carboxylic acids such as itaconic acid, itaconic anhydride, maleic acid, maleic anhydride, fumaric acid and crotonic acid;

The content of the carboxyl group-containing monomer in the acid group-containing monomer (a3) is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more, and the upper limit is 100% by mass. %.

Examples of the monomer (a4) having a hydroxyl group include monomers having a hydroxyl group and a polymerizable double bond. Examples of the (meth)acrylic monomer having a hydroxyl group include hydroxyalkyl (meth)acrylates, polyalkylene glycol (meth)acrylates, etc., and hydroxyalkyl (meth)acrylates are preferred.

Specific examples of the hydroxyl group-containing monomer (a4) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Hydroxyalkyl (meth)acrylates having 2 to 10 carbon atoms in the alkyl group (alkylene group) such as acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate; polyethylene glycol (meth)acrylate, etc. and polyalkylene glycol (meth)acrylate.

The acrylic polymer (A) may contain units derived from a monomer (a5) other than the monomers (a1) to (a4) described above. Examples of the other monomer (a5) include pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Number of carbon atoms such as acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, etc. Alkyl (meth) acrylate having 5 or more alkyl groups; Cyclic ether-containing (meth) acrylate monomers such as glycidyl (meth) acrylate and tetrahydrofurfuryl (meth) acrylate; Cyclohexyl (meth) acrylate, isobornyl (meth) Alicyclic structure-containing (meth)acrylate monomers such as acrylate; aromatic ring-containing (meth)acrylate monomers such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate Alkylene oxide structure-containing (meth)acrylate monomers such as acrylates, methoxypolyethylene glycol (meth)acrylates;
vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versatate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether; styrene, o- methylstyrene, m-methylstyrene, p-methylstyrene, ethylvinylbenzene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p - Aromatic vinyl monomers such as chlorostyrene and parahydroxystyrene; Among these, (meth)acrylate monomers, vinyl ester monomers, and vinyl ether monomers are preferred, since the balance of various properties such as adhesiveness can be easily adjusted. These other monomers (a5) can be used alone or in combination of two or more.

In the acrylic polymer (A), the content of units derived from the alkyl (meth)acrylate monomer (a1) is 45% by mass or more and less than 97% by mass, preferably 55% by mass or more, more preferably It is 70% by mass or more, preferably 95% by mass or less.

In the acrylic polymer (A), the content of units derived from the nitrogen atom-containing monomer (a2) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and preferably 30% by mass. % or less, more preferably 25 mass % or less.

In the acrylic polymer (A), the content of units derived from the monomer (a3) having an acid group is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and preferably It is 20% by mass or less, more preferably 15% by mass or less, and still more preferably 12% by mass or less.

The content of units derived from the monomer (a4) having a hydroxyl group is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and still more preferably 0 in the acrylic monomer (A). 05% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

The total amount of units derived from the monomer (a3) having an acid group and the monomer (a4) having a hydroxyl group is 0.5% by mass or more, preferably 1% by mass or more, in the acrylic polymer (A), It is more preferably 2% by mass or more, preferably 30% by mass or less, more preferably 22% by mass or less, and still more preferably 17% by mass or less.

Units derived from the alkyl (meth)acrylate monomer (a1), the nitrogen atom-containing monomer (a2), the acid group-containing monomer (a3), and the hydroxyl group-containing monomer (a4) in the acrylic polymer (A) is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and the upper limit is 100% by mass in the acrylic polymer (A).

The content of units derived from the other monomer (a5) in the acrylic polymer (A) is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

The acid value of the acrylic polymer (A) is preferably 5 mgKOH/g or more, and preferably 20 mgKOH/g or more, because the cohesive force and adhesion to the adherend, which are effective when suppressing foaming, are further improved. It is more preferably 200 mgKOH/g or less, and more preferably 100 mgKOH/g or less.

The acid value of the polymer in the present invention is a calculated value calculated from the raw material composition.

The weight average molecular weight of the acrylic polymer (A) is 100,000 or more, preferably 200,000 or more, more preferably 300,000 or more, preferably 2,000,000 or less, more preferably 1 , 800,000 or less, more preferably 1,500,000 or less.

In this specification, the number-average molecular weight and weight-average molecular weight of a polymer represent converted values measured by gel permeation chromatography (GPC) using polystyrene as a standard sample.

The glass transition temperature of the acrylic polymer (A) is -20°C or lower, preferably -60°C or higher, more preferably -50°C or higher, and still more preferably -50°C or higher and -25°C or lower. be.

The glass transition temperature Tga (K) of the acrylic polymer (A) can be calculated based on the following FOX formula.
1/Tga=Σ(Wi/Tgi)

In the FOX formula, Wi represents the content of units derived from each monomer in the acrylic polymer (A), and Tgi (K) is the glass transition of a homopolymer formed only from each monomer. Represents temperature (unit is absolute temperature). Details of the FOX formula are described in Bulletin of the American Physical Society, Series 2, Vol. 1, No. 3, p. 123 (1956). It is Further, for the glass transition temperature (Tgi) of the homopolymer of each monomer, for example, the numerical value described in Coating and Coating (Paint Publisher, 10 (No. 358), 1982) can be adopted. .

The acrylic polymer (A) comprises the alkyl (meth)acrylate monomer (a1), a nitrogen atom-containing monomer (a2), an acid group-containing monomer (a3), a hydroxyl group-containing monomer (a4), and optionally Other monomers (a5) to be used can be produced by copolymerizing in the presence of a polymerization initiator.

As the polymerization initiator, for example, one or more of thermal polymerization initiators can be used. Peroxide initiators such as benzoyl peroxide and lauroyl peroxide; azobismethylbutyronitrile, azobis and azo initiators such as isobutyl nitrile.

The pressure-sensitive adhesive composition of the present invention contains a cross-linking agent (B). As the cross-linking agent, one or more of them can be used. Cross-linking agents, carbodiimide cross-linking agents, silane cross-linking agents, glycidyl(alkoxy)epoxysilane cross-linking agents and the like can be mentioned.

Among them, isocyanate cross-linking agents, epoxy cross-linking agents, metal chelate cross-linking agents, oxazoline cross-linking agents and carbodiimide cross-linking agents are preferred, isocyanate cross-linking agents, epoxy cross-linking agents and carbodiimide cross-linking agents are more preferred, and epoxy cross-linking agents are particularly preferred.

The content of the epoxy cross-linking agent in the cross-linking agent (B) is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more. , preferably 100% by mass or less.

The acrylic polymer (C) contains units derived from the alicyclic structure-containing (meth)acrylate monomer (c1) and units derived from the alkyl (meth)acrylate monomer (c2).

The alicyclic structure-containing (meth)acrylate monomer (c1) (hereinafter sometimes simply referred to as "(meth)acrylate (c1)") represents an alicyclic structure-containing (meth)acrylate monomer in the molecule. The alicyclic hydrocarbon group may be a monocyclic ring or a bridged ring, and the number of alicyclic hydrocarbon groups contained in the (meth)acrylate (c1) is one. may be two or more.

The alicyclic hydrocarbon group contained in the (meth)acrylate (c1) includes monocyclic alicyclic hydrocarbon groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group; A bridged ring alicyclic hydrocarbon group such as a nyl group is included.

The number of carbon atoms in the alicyclic hydrocarbon group contained in the (meth)acrylate (c1) is 3 or more, preferably 5 or more, preferably 20 or less, more preferably 15 or less, and still more preferably 10. It is below.

As the alicyclic structure-containing (meth)acrylate monomer (c1) contained in the (meth)acrylate (c1), specifically, one or more types can be used. For example, cyclopentyl (meth)acrylate , Monocyclic alicyclic structure-containing (meth)acrylate monomers such as cyclohexyl (meth)acrylate and cycloheptyl (meth)acrylate; Norbornyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate and the like Examples thereof include (meth)acrylate monomers containing an alicyclic structure of bridging rings.

The content of units derived from the (meth)acrylate (c1) is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 35% by mass or more in the acrylic polymer (C). , preferably 95% by mass or less, more preferably 92% by mass or less, and still more preferably 90% by mass or less.

The alkyl (meth)acrylate monomer (c2) (hereinafter sometimes simply referred to as "(meth)acrylate (c2)") represents a (meth)acrylate monomer having an alkyl group.

Examples of alkyl groups contained in the (meth)acrylate (c2) include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group and n-octyl. linear alkyl groups such as groups, n-nonyl, n-decyl, lauryl, and stearyl groups; isopropyl, isobutyl, t-butyl, isopentyl, neopentyl, isohexyl, isoheptyl, isooctyl, branched chain alkyl groups such as 2-ethylhexyl group, isononyl group, isodecyl group and isostearyl group;

The number of carbon atoms in the alkyl group contained in the (meth)acrylate (c2) is preferably 1 or more, preferably 20 or less, more preferably 15 or less, still more preferably 12 or less.

As the (meth)acrylate (c2), one or more can be used, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and n-butyl (meth)acrylate. , isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (Meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate and the like.

The content of units derived from the (meth)acrylate (c2) is preferably 1% by mass or more, more preferably 5% by mass or more, and still more preferably 7% by mass or more in the acrylic polymer (C). , preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

The content ratio ((c1)/(c2)) of units derived from the (meth)acrylate (c1) and units derived from the (meth)acrylate (c2) is preferably 0 on a mass basis. 0.1 or more, more preferably 0.5 or more, still more preferably 0.7 or more, preferably 20 or less, more preferably 15 or less, still more preferably 12 or less.

The acrylic polymer (C) contains units derived from other monomers (c3) in addition to the alicyclic structure-containing (meth)acrylate monomer (c1) and the alkyl (meth)acrylate monomer (c2). good too.

Examples of the other monomer (c3) include monomers having an acid group, monomers having a hydroxyl group, monomers having a nitrogen atom, monomers having a cyclic ether, monomers having an aromatic ring, and monomers having an alkylene oxide structure.

The content of the other monomer (c3) in the acrylic polymer (C) is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 12% by mass or less, and the lower limit is 0% by mass. %.

The glass transition temperature of the acrylic polymer (C) is 50° C. or higher, preferably 55° C. or higher, more preferably 60° C. or higher, and preferably 120° C. or lower, more preferably 110° C. or lower.

The glass transition temperature Tga (K) of the acrylic polymer (C) can be calculated based on the FOX formula in the same manner as for the acrylic polymer (A) described above.

The weight average molecular weight of the acrylic polymer (C) is less than 100,000, preferably 80,000 or less, more preferably 60,000 or less, preferably 1,000 or more, more preferably 1,500. or more, more preferably 2,500 or more.

The acrylic polymer (C) comprises the alicyclic structure-containing (meth)acrylate monomer (c1), the alkyl (meth)acrylate monomer (c2), and other optionally used monomers (c3) in the presence of a polymerization initiator. It can be produced by copolymerizing below.

As the polymerization initiator, for example, one or more of thermal polymerization initiators can be used. Peroxide initiators such as benzoyl peroxide and lauroyl peroxide; azobismethylbutyronitrile, azobis and azo initiators such as isobutyl nitrile.

In the pressure-sensitive adhesive composition of the present invention, the content of the acrylic polymer (A) is preferably 15% by mass or more, more preferably 20% by mass or more, and still more preferably 25% by mass or more in the nonvolatile matter, Preferably, it is 99% by mass or less.

In this specification, the non-volatile content of the pressure-sensitive adhesive composition represents the portion of the pressure-sensitive adhesive composition excluding the solvent component that is included as necessary.

In the pressure-sensitive adhesive composition of the present invention, the content of the cross-linking agent (B) is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass, relative to 100 parts by mass of the acrylic polymer (A). parts or more, more preferably 0.1 parts by mass or more, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

In the pressure-sensitive adhesive composition of the present invention, the content of the acrylic polymer (C) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass in the nonvolatile matter. or more, preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

In the adhesive composition of the present invention, the content of the acrylic polymer (C) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass, based on 100 parts by mass of the acrylic polymer (A). It is at least 1 part by mass, more preferably at least 1 part by mass, preferably at most 60 parts by mass, more preferably at most 30 parts by mass, still more preferably at most 25 parts by mass.

The pressure-sensitive adhesive composition of the present invention preferably contains a solvent (D). As the solvent (D), one or more can be used, and examples include aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone. ; and aliphatic hydrocarbon solvents such as hexane. Among them, it is preferable to contain an ester solvent.

The content of the ester solvent is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and preferably 100% by mass or less in the solvent (D).

The content of the solvent (D) in the adhesive composition is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and preferably 90% by mass or less. It is preferably 70% by mass or less, more preferably 65% by mass or less.

In the pressure-sensitive adhesive composition of the present invention, in order to maintain low yellowing, it is preferable that the content of the tackifying resin is reduced, and preferably less than 10 parts by mass with respect to 100 parts by mass of the acrylic polymer. , more preferably 8 parts by mass or less, still more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and preferably 0 parts by mass.

The adhesive composition of the present invention contains, as additives, a base (such as aqueous ammonia) and an acid for adjusting the pH; a foaming agent; a plasticizer; a softening agent; Fillers such as beads and metal powders; coloring agents such as pigments and dyes; pH adjusters; film-forming aids; leveling agents; thickeners; You can stay.

An adhesive layer can be formed by coating the adhesive composition on a support and drying it. The support may be a base material such as a release sheet or an adhesive sheet.

As the coating method, a knife coater, a reverse coater, a die coater, a lip die coater, a slot die coater, a gravure coater, a curtain coater, or the like can be used.

The thickness of the adhesive layer is preferably 5 µm or more, more preferably 10 µm or more, still more preferably 15 µm or more, and preferably 150 µm or less, more preferably 100 µm or less, still more preferably 75 µm or less.

The adhesive sheet or adhesive tape of the present invention has the adhesive layer and the substrate. The substrate may be film-shaped, sheet-shaped, tape-shaped, plate-shaped, three-dimensional, or the like. Materials of the substrate include polyester resin, polypropylene resin, polyethylene resin, polyimide resin, and vinyl chloride. Plastics such as resins and urethane resins; rubbers; non-woven fabrics; metal foils; The base material may have a smooth surface, or may have an uneven surface such as a fibrous base material or a foam base material.

The thickness of the substrate is preferably 0.1 μm or more and preferably 1,000 μm or less.

The present invention will be described in more detail below with specific examples. The weight average molecular weight (Mw) of the resin of the present invention is measured under the following GPC measurement conditions.

[GPC measurement conditions]
Measuring device: high-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 Book "TSKgel G2000" (7.8 mm I.D. x 30 cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 4 mg/mL)
Standard sample: A calibration curve was created using the following monodisperse polystyrene.

(monodispersed polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

(Synthesis Example 1: Synthesis of acrylic polymer (A-1))
590 parts by mass of butyl acrylate (hereinafter abbreviated as "BA") and 345 parts by mass of methyl acrylate (hereinafter abbreviated as "MA") were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer. parts by mass, diethylacrylamide (hereinafter abbreviated as "DEAA") 50 parts by mass, acrylic acid (hereinafter abbreviated as "AA") 10 parts by mass, 4-hydroxybutyl acrylate (hereinafter abbreviated as "4HBA" ) and 1000 parts by mass of ethyl acetate were charged, and the temperature was raised to 72°C while stirring and blowing nitrogen. After 1 hour, 10 parts by mass of 2,2′-azobis(2-methylbutyronitrile) solution (0.5% by mass of solids) dissolved in ethyl acetate in advance was added. Then, after holding at 72° C. for 8 hours while stirring, the content was cooled and filtered through a 200-mesh wire mesh to obtain a 50 mass % solution of acrylic polymer (A-1).

(Synthesis Example 2: Synthesis of acrylic polymer (A-2))
250 parts by mass of 2-ethylhexyl acrylate (hereinafter abbreviated as "2EHA"), 509 parts by mass of BA, dimethylacrylamide (hereinafter "DMAA ) 25 parts by mass, 215 parts by mass of AA, 1 part by mass of 2-hydroxyethyl acrylate (hereinafter abbreviated as "HEA"), and 950 parts by mass of ethyl acetate are charged, and stirred while blowing nitrogen. The temperature was raised to 65°C. After 1 hour, 10 parts by mass of 2,2′-azobis(2-methylbutyronitrile) solution (0.5% by mass of solids) dissolved in ethyl acetate in advance was added. Then, after holding at 65 ° C. for 10 hours while stirring, the contents are cooled, 50 parts by mass of ethyl acetate is charged, filtered through a 200 mesh wire mesh, and the acrylic polymer (A-2) is 50% by mass. A solution was obtained.

(Synthesis Example 3: Synthesis of acrylic polymer (A-3))
A 50% by mass solution of acrylic polymer (A-3) was obtained in the same manner as in Synthesis Example 2 except that the monomer composition was changed as shown in Table 1.

(Synthesis Examples 4-6: Synthesis of acrylic polymers (A-4) to (A-6))
50% by mass solutions of acrylic polymers (A-4) to (A-6) were obtained in the same manner as in Synthesis Example 1, except that the monomer composition was changed as shown in Table 1.

(Synthesis Example 7: Synthesis of acrylic polymer (A-7))
350 parts by mass of 2EHA, 482 parts by mass of BA, 385 parts by mass of MA, 100 parts by mass of DEAA, 3 parts by mass of 4HBA, and 900 parts by mass of ethyl acetate were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer. After charging, the temperature was raised to 65° C. while stirring and blowing nitrogen. After 1 hour, 10 parts by mass of 2,2′-azobis(2-methylbutyronitrile) solution (0.5% by mass of solids) dissolved in ethyl acetate in advance was added. After that, after holding at 65 ° C. for 10 hours while stirring, the contents were cooled, and after charging 100 parts by mass of ethyl acetate, it was filtered through a 200 mesh wire mesh, and the acrylic polymer (A-7) was 50% by mass. A solution was obtained.

(Synthesis Examples 8 to 9: Synthesis of acrylic polymers (A-8) to (A-9))
A 50 mass % solution of acrylic polymers (A-8) to (A-9) was obtained in the same manner as in Synthesis Example 1, except that the monomer composition was changed as shown in Table 2.

(Synthesis Example 10: Synthesis of acrylic polymer (A-10))
A 50% by mass solution of acrylic polymer (A-10) was obtained in the same manner as in Synthesis Example 3 except that the monomer composition was changed as shown in Table 2.

(Synthesis Example 11: Synthesis of acrylic polymer (C-1))
A reactor equipped with a stirrer, a thermometer, a dropping funnel, a cooling tube and a nitrogen gas inlet was charged with 75 parts by mass of methyl ethyl ketone (hereinafter abbreviated as "MEK") and heated to 80°C. Next, at the same temperature, 78 parts by mass of cyclohexyl methacrylate (hereinafter abbreviated as "CHMA"), 20 parts by mass of methyl methacrylate (hereinafter abbreviated as "MMA"), and methacrylic acid (hereinafter abbreviated as "MAA") were .) 2 parts by mass, MEK 6.8 parts by mass and tert-butyl peroxy-2-ethylhexanoate (hereinafter abbreviated as “TBPEH”) 5.5 parts by mass. After the completion of the dropping, the mixture was further reacted at the same temperature for 12 hours to obtain a 55% by weight solution of the acrylic polymer (C-1).

(Synthesis Examples 12 to 14: Synthesis of acrylic polymers (C-2) to (C-4))
55% by mass solutions of acrylic polymers (C-2) to (C-4) were obtained in the same manner as in Synthesis Example 11, except that the monomer composition was changed as shown in Table 3.

(Synthesis Example 15: Synthesis of acrylic polymer (C-5))
A reactor equipped with a stirrer, a thermometer, a dropping funnel, a cooling tube and a nitrogen gas inlet was charged with 75 parts by mass of methyl ethyl ketone (hereinafter abbreviated as "MEK") and heated to 80°C. Then, at the same temperature, 10 parts by mass of CHMA, 76 parts by mass of MMA, 4 parts by mass of 2-ethylhexyl methacrylate (hereinafter abbreviated as "2EHMA"), 9 parts by mass of MAA, 1 part by mass of 2EHA, and 6.8 parts by mass of MEK and 3 parts by mass of TBPEH was added dropwise into the reaction vessel over 4 hours, and after the completion of the dropwise addition, the mixture was further reacted at the same temperature for 12 hours to obtain a 55% by mass solution of the acrylic polymer (C-1). Obtained.

(Synthesis Examples 16 to 20: Synthesis of acrylic polymers (C-6) to (C-10))
55% by mass solutions of acrylic polymers (C-6) to (C-10) were obtained in the same manner as in Synthesis Example 11, except that the monomer composition was changed as shown in Table 3.

In Tables 1 to 4, each abbreviation represents the following compound.
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate EA: ethyl acrylate MA: methyl acrylate CHA: cyclohexyl acrylate DEAA: N,N-diethylacrylamide DMAA: N,N-dimethylacrylamide NIPAM: N,N-diisopropylacrylamide DAAM: Diacetone acrylamide AA: acrylic acid 4HBA: 4-hydroxybutyl acrylate HEA: 2-hydroxyethyl acrylate IBXA: isobornyl acrylate CHMA: cyclohexyl methacrylate DCP: dicyclopentanyl methacrylate MMA: methyl methacrylate EMA: ethyl methacrylate BMA: n- Butyl methacrylate 2EHMA: 2-ethylhexyl methacrylate MAA: methacrylic acid IBXMA: isobornyl methacrylate HEMA: 2-hydroxyethyl methacrylate

(Example 1: Preparation and evaluation of adhesive composition (1))
10 parts by mass of a 55% by mass solution of the acrylic polymer (C-1) obtained in Synthesis Example 4 with respect to 100 parts by mass of the 50% by mass solution of the acrylic polymer (A-1) obtained in Synthesis Example 1 , An epoxy-based cross-linking agent (Mitsubishi Gas Chemical Co., Ltd. "Tetrad X"; hereinafter abbreviated as "cross-linking agent (B-1)".) 0.05 parts by mass are uniformly stirred and mixed to form an adhesive. A composition (1) was obtained.

[Adhesive film processing method 1]
The pressure-sensitive adhesive composition obtained in the example was applied to the surface of a polyethylene terephthalate film having a thickness of 50 μm (release PET 50) whose surface was subjected to release treatment so that the film thickness after solvent drying was 25 μm. After volatilizing the solvent for 3 minutes in a dryer, a polyethylene terephthalate film (PET50) having a thickness of 50 μm was laminated.

[Adhesive film processing method 2]
The surface of a 50 μm thick polyethylene terephthalate film (release PET50) whose surface was subjected to release treatment was coated with the pressure-sensitive adhesive composition obtained in the example so that the film thickness after solvent drying was 50 μm. After volatilizing the solvent for 3 minutes in a dryer, release PET50 was attached.

[Evaluation 1 of Initial Optical Properties]
A test piece was prepared by attaching the pressure-sensitive adhesive film prepared by the method 2 described above to a glass plate. After peeling off the release PET film of the test piece and configuring it as an adhesive layer and a glass plate, a turbidity meter "NDH5000" (manufactured by Nippon Denshoku Industries Co., Ltd.) is used according to JIS K 7361 1. Haze was measured. The initial haze of glass alone was 0.2.

[Evaluation 2 of initial optical properties]
After the pressure-sensitive adhesive film prepared by method 2 described above was attached to a glass adherend, it was pressure-bonded at a temperature of 50° C. and an atmospheric pressure of 0.5 MPa for 20 minutes to obtain a test piece. After peeling off the release PET film of the test piece and forming an adhesive layer and a glass plate, light source C, field of view 2 °, "spectrophotometer" CM 5000d (manufactured by Konica Minolta Sensing Co., Ltd.) , the initial color number (b*) was measured according to JIS K 7105. The initial color number (b*) of the glass alone was 0.1.

[Evaluation of moist heat resistant optical properties]
After attaching the adhesive film prepared by the above-mentioned method 2 to the glass adherend, it was crimped for 20 minutes at a temperature of 50 ° C. and an atmospheric pressure of 0.5 MPa, and was left to stand for 500 hours in an environment of 85 ° C. and 85% RH. The color number (b*) and haze of the test piece were measured in the same manner as described above.

[Evaluation of foaming resistance]
A test piece was prepared by cutting the pressure-sensitive adhesive film prepared by the above method 1 into a width of 50 mm and a length of 50 mm. A 2 mm thick glass, an acrylic plate, and a polycarbonate plate (PC plate) were used as adherends. After affixing to the adherend, pressure bonding was performed for 20 minutes at a temperature of 50° C. and an atmospheric pressure of 0.5 MPa. After that, it was allowed to stand for a predetermined time in each durability test environment (1) to (3), and the appearance immediately after taking out was evaluated according to the following criteria.
Durability test environment (1) 100°C environment for 2 hours Durability test environment (2) 85°C 85% RH environment for 24 hours Durability test environment (3) 80°C hot water immersion for 2 hours ○: No change before and after the durability test, △: Surface unevenness occurs, ×: Foaming and whitening occur

[Evaluation of initial adhesive strength]
A test piece was prepared by cutting the pressure-sensitive adhesive film prepared by the method 1 described above into a width of 25 mm. A polycarbonate plate or a glass plate was used as an adherend, and was attached to the adherend by a 2 kg roll x 2 reciprocations. Two hours after the application, the 180 degree peel strength was measured in an atmosphere of 23° C. and 50% RH, and taken as adhesive strength (N/25 mm).

[Evaluation of moist heat resistant adhesive strength]
A test piece was prepared by cutting the pressure-sensitive adhesive film prepared by the above method 1 into a width of 25 mm. A polycarbonate plate or a glass plate was used as an adherend, and was attached to the adherend by a 2 kg roll x 2 reciprocations. After 30 minutes from the application, it was allowed to stand in an environment of 85° C. and 85% RH for 500 hours. After taking it out, it was allowed to cool at room temperature, and the 180° peel strength was measured in an atmosphere of 23°C and 50% RH, and was defined as adhesive strength (N/25 mm).

[Evaluation of hot water resistant adhesive strength]
A test piece was prepared by cutting the pressure-sensitive adhesive film prepared by the above method 1 into a width of 25 mm. A polycarbonate plate or a glass plate was used as an adherend, and was attached to the adherend by a 2 kg roll x 2 reciprocations. Thirty minutes after the application, it was immersed in warm water at 80°C for two hours. After being removed from the hot water, the moisture was wiped off, and the 180° peel strength was measured in an atmosphere of 23°C and 50% RH, and was defined as adhesive strength (N/25mm).

(Examples 2 to 19: Preparation and evaluation of adhesive compositions (2) to (19))
The procedure was the same as in Example 1 except that the acrylic polymer (A-1), cross-linking agent (B-1), and acrylic polymer (C-1) used in Example 1 were changed as shown in Tables 5 to 7. After obtaining pressure-sensitive adhesive compositions (2) to (19), various evaluations were performed.

(Comparative Examples 1 to 4: Preparation and evaluation of adhesive compositions (R1) to (R4))
In the same manner as in Example 1 except that the acrylic polymer (A-1), cross-linking agent (B-1), and acrylic polymer (C-1) used in Example 1 were changed as shown in Table 8, After obtaining the adhesive compositions (R1) to (R4), various evaluations were performed.

In Tables 5 to 8, each abbreviation represents the following compound.
Cross-linking agent (B-1): Tetrad X (epoxy-based cross-linking agent: manufactured by Mitsubishi Gas Chemical Company, Inc.)
Cross-linking agent (B-2): Tetrad C (epoxy-based cross-linking agent: manufactured by Mitsubishi Gas Chemical Company, Inc.)
Cross-linking agent (B-3): Barnock D-750 (isocyanate-based cross-linking agent: manufactured by DIC Corporation)
Cross-linking agent (B-4): Takenate D-110N (isocyanate-based cross-linking agent: manufactured by Mitsui Chemicals, Inc.)
Cross-linking agent (B-5): Barnock DN-980 (isocyanate-based cross-linking agent: manufactured by DIC Corporation)

The pressure-sensitive adhesive films obtained from Examples 1 to 19, which are the pressure-sensitive adhesive compositions of the present invention, are excellent in optical transparency, foaming resistance, and adhesive strength even in a high-temperature, high-humidity environment or in a high-temperature warm water immersion environment. confirmed.

Comparative Example 1, which does not contain the acrylic polymer (C), was inferior in resistance to foaming in a high-temperature and high-humidity environment or in a high-temperature warm water immersion environment.

Comparative Example 2 is an example in which an acrylic polymer containing no nitrogen atom-containing monomer (a2) was used instead of the acrylic polymer (A). there were.

In Comparative Example 3, instead of the acrylic polymer (A), the content of units derived from an alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms was less than 50% by mass. Although it is an example using coalescence, it was inferior in foaming resistance in a high-temperature and high-humidity environment or in a high-temperature warm water immersion environment.

Comparative Example 4 is an example in which an acrylic polymer having a glass transition temperature higher than −20° C. was used instead of the acrylic polymer (A). , the adhesive strength was inferior.

Claims (4)

including an acrylic polymer (A), a cross-linking agent (B) and an acrylic polymer (C),
The acrylic polymer (A) is a unit derived from an alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms; a unit derived from a monomer (a2) having a nitrogen atom; and an acid and a unit derived from at least one selected from the group consisting of a monomer (a3) having a group and a monomer (a4) having a hydroxyl group,
The acrylic polymer (A) has a glass transition temperature of −20° C. or lower,
The acrylic polymer (A) has a weight average molecular weight of 100,000 or more,
The content of units derived from the alkyl (meth)acrylate monomer (a1) having an alkyl group having 1 to 4 carbon atoms is 50% by mass or more and less than 97% by mass in the acrylic polymer (A),
The acrylic polymer (C) contains a unit derived from an alicyclic structure-containing (meth)acrylate monomer (c1); and a unit derived from an alkyl (meth)acrylate monomer (c2),
The acrylic polymer (C) has a glass transition temperature of 50° C. or higher,
A pressure-sensitive adhesive composition, wherein the acrylic polymer (C) has a weight-average molecular weight of less than 100,000. The pressure-sensitive adhesive composition according to claim 1, wherein the content of units derived from the nitrogen atom-containing monomer (a2) is 0.5% by mass or more and less than 30% by mass in the acrylic polymer (A). An adhesive layer formed from the adhesive composition according to claim 1 or 2. An adhesive film having the adhesive layer according to claim 3 .