TWI666282B - Adhesive composition, adhesion layer, adhesion sheet and laminated product for touch panel - Google Patents

Abstract

The object of the present invention is to provide an adhesive composition which is capable of forming a low-dielectric-constant adhesive agent that can follow the step difference without sticking or the like during the sticking of an adhesive having a step difference, and has excellent followability and durability. Floor.

The solution of the present invention is an adhesive composition containing (A) a (meth) acrylic copolymer and a (B) cross-linking agent, wherein the above-mentioned copolymer (A) is added to all monomer components. 100% by mass of alkyl methacrylate containing (a1) alkyl group having a carbon number of 10 or more 20 to 39% by mass, (a2) alkyl acrylate having a carbon number of 8 or more alkyl group 30 to 60% by mass, (a3 ) A copolymer obtained by copolymerizing a hydroxyl group-containing monomer at 1 to 20% by mass and (a4) a nitrogen atom-containing monomer at 0 to 5% by mass of a monomer component.

Description

Adhesive composition, adhesive layer, adhesive sheet and laminated body for touch panel

The present invention relates to an adhesive composition with low dielectric constant, excellent followability and durability, an adhesive layer formed from the aforementioned adhesive composition, an adhesive sheet having the aforementioned adhesive layer, and the aforementioned adhesive Laminate for touch panel of agent layer.

In recent years, the use of image display devices such as liquid crystal display devices and input devices such as touch pads used in combination with image display devices has become widespread. In the manufacture of such image display devices or input devices, an adhesive sheet having an adhesive layer is used when bonding the constituent members.

The performance required for a touch panel adhesive sheet includes, for example, a low dielectric constant property to prevent malfunction of the touch panel operation, and a level difference absorptivity that does not generate voids when bonded to a member having a level difference. And high heat resistance, moist heat resistance and moist heat whitening resistance and other high durability.

For example, in a liquid crystal display device, a front transparent plate such as a glass plate is provided through an adhesive layer on the side more visible than the display panel. On the other hand, in order to show a specific frame edge or figure around the screen to improve the design By nature, a printed layer is formed on the peripheral edge portion of the front transparent plate. For example, in a touch panel, a transparent plate such as a glass plate is laminated with an adhesive, and a transparent conductive film having a transparent conductive film such as indium tin oxide (ITO) formed on the surface.

As described above, in a liquid crystal display device, a touch panel, and the like, a configuration including a member having a step difference based on a printed layer, a conductive film, or the like is increasing. Therefore, the adhesive layer used for attaching / fixing the aforementioned member is required to have excellent step-followability without generating voids.

For example, Patent Documents 1 and 2 disclose a pressure-sensitive adhesive having a low-dielectric-constant pressure-sensitive adhesive layer. The pressure-sensitive adhesive includes a monomer component containing a specific alkyl (meth) acrylate. (Meth) acrylic polymer obtained by polymerization.

Furthermore, Patent Document 3 discloses a pressure-sensitive adhesive sheet which aims to provide a pressure-sensitive adhesive sheet excellent in moisturizing and white turbidity resistance and excellent in step absorption. The pressure-sensitive adhesive sheet includes an acrylic system obtained by polymerizing specific monomer components. Polymer adhesive layer.

However, from the viewpoint of providing an excellent adhesive layer having a good balance of low dielectric constant, step absorption, and durability, it is desirable to further improve the performance of the adhesive composition forming the adhesive layer.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2012-246477

[Patent Document 2] Japanese Patent Laid-Open No. 2013-194170

[Patent Document 3] Japanese Patent Laid-Open No. 2013-122035

An object of the present invention is to provide an adhesive composition which can form a low-dielectric-constant adhesive agent that does not generate bubbles when attaching an adhesive having a step difference, and can follow the step difference and has excellent durability and durability. Floor.

The present inventors have carefully studied to solve the above problems. As a result, they found that the above-mentioned problems can be solved by using an adhesive composition having the following specific structure, and completed the present invention.

The present invention is, for example, the following [1] to [10].

[1] An adhesive composition containing (A) a (meth) acrylic copolymer and a (B) cross-linking agent, wherein the copolymer (A) is 100% by mass relative to all monomer components (A1) alkyl methacrylate having 10 or more carbon atoms of 20 to 39% by mass, (a2) alkyl acrylate having 8 or more carbon atoms of 30 to 60% by mass, (a3) containing hydroxyl groups A copolymer obtained by copolymerizing 1 to 20% by mass of a monomer and (a4) a monomer component of 0 to 5% by mass of a monomer containing a nitrogen atom.

[2] The adhesive composition according to the above [1], in the monomer component forming the copolymer (A), the methacrylic acid alkyl ester (a1) and the alkyl acrylate (a2) have the foregoing The alkyl systems are all linear alkyl groups or branched alkyl groups.

[3] The adhesive composition according to the above [1] or [2], in the monomer component forming the copolymer (A), the hydroxyl group-containing monomer (a3) is a hydroxyl group-containing (methyl group) )Acrylate.

[4] The adhesive composition according to any one of the above [1] to [3], wherein an acid group-containing monomer is 100% by mass based on 100% by mass of all monomer components forming the copolymer (A). The amount of the body (a6) used is 0.1% by mass or less.

[5] The adhesive composition according to any one of the above [1] to [4], wherein the weight of the copolymer (A) measured by Gel Permeation Chromatography The average molecular weight (Mw) is 30,000 to 500,000 in terms of polystyrene.

[6] The adhesive composition according to any one of the above [1] to [5], further comprising (C) a silane coupling agent.

[7] The adhesive composition according to any one of the aforementioned [1] to [6], wherein a gelation rate of the adhesive formed from the adhesive composition is 10 to 60% by mass.

[8] An adhesive layer formed from the adhesive composition described in any one of the above [1] to [7].

[9] An adhesive sheet having the adhesive layer as described in [8] above.

[10] A laminated body for a touch panel, comprising a support, an adhesive layer as described in [8] above, and a conductive film made of a metal or a metal oxide formed on the surface of a base material. The substrate of the film is laminated in this order.

According to the present invention, it is possible to provide an adhesive composition capable of forming a low-dielectric-constant property, which does not generate bubbles when attaching an adherent having a step difference, and which can follow the step follow-up and excellent durability.剂 层。 The agent layer.

The adhesive composition, the adhesive layer, the adhesive sheet, and the laminate of the present invention will be described below.

[Adhesive composition]

The adhesive composition of the present invention is an adhesive composition containing a (meth) acrylic copolymer (A) and a crosslinking agent (B) described below. The composition may further contain at least one selected from the group consisting of a silane coupling agent (C) and an organic solvent (D).

[(Meth) acrylic copolymer (A)]

The (meth) acrylic copolymer (A) contains (a1) an alkyl methacrylate having a carbon number of 10 or more in an amount of 20 to 39% by mass based on 100% by mass of the entire monomer component, and (a2 ) Alkyl acrylate having a carbon number of 8 or more, 30 to 60% by mass, (a3) a hydroxyl-containing monomer 1 to 20% by mass, (a4) a nitrogen atom-containing monomer 0 to 5% by mass, a monomer A copolymer obtained by copolymerizing ingredients.

By using a copolymer obtained by copolymerizing the above-mentioned monomer components in the above-mentioned range, an adhesive layer having excellent balance of low dielectric constant, step-followability, and durability can be formed.

In this specification, the collective term of acrylic acid and methacrylic acid is described as "(meth) acrylic acid". Moreover, the polymer contains a monomer derived from a The constituent units are described as "monomer a unit". The aforementioned (a1) to (a4) are described as "monomer (a1)" to "monomer (a4)", respectively.

The monomer components are described below.

`` Alkyl methacrylate (a1) ''

The alkyl methacrylate (a1) is an alkyl methacrylate having a carbon number of 10 or more. Specifically, it is preferably CH ₂ = C (CH ₃ ) -COOR ¹ . In the formula, R ¹ is a linear or branched alkyl group having 10 or more carbon atoms. Among them, the carbon number of the alkyl group is preferably 10 to 20, and more preferably 10 to 18.

By using such a (meth) acrylic copolymer containing the alkyl methacrylate unit which has a long-chain alkyl group, the adhesive layer which has few directional polarization can be obtained. For example, by using the above (a1), there is a tendency that an adhesive layer having a low relative dielectric constant can be obtained.

Examples of the alkyl methacrylate having 10 or more carbon atoms include methacrylic acid esters such as decyl methacrylate, undecyl methacrylate, lauryl methacrylate, and stearyl methacrylate. Alkyl alkyl esters; branched alkyl methacrylates such as isodecyl methacrylate and isostearyl methacrylate. These may be used individually by 1 type, and may use 2 or more types.

The use amount of the alkyl methacrylate (a1) is 20 to 39% by mass, preferably 25 to 39% by mass, and more preferably 30 to 39% by mass, based on 100% by mass of the monomer component. If the use amount of the alkyl methacrylate (a1) is higher than the aforementioned 39% by mass, problems such as a decrease in the followability of the step of the adhesive layer may occur, and appropriate adhesive properties may not be obtained. If the amount of alkyl methacrylate (a1) used is less than the aforementioned 20% by mass, an adhesive may occur The layer has problems such as reduced durability and low dielectric constant.

"Alkyl acrylate (a2)"

The alkyl acrylate (a2) is an alkyl acrylate having a carbon number of 8 or more. Specifically, it is preferably CH ₂ = CH-COOR ² . In the formula, R ² is a linear or branched alkyl group having 8 or more carbon atoms. Among them, the carbon number of the aforementioned alkyl group is preferably 8 to 18, and more preferably 8 to 12.

When such a (meth) acrylic copolymer containing an alkyl acrylate unit having a long-chain alkyl group is used, the increase in the relative dielectric constant of the adhesive layer can be suppressed, and the affinity for the adhesive can be improved. For example, by using the aforementioned (a2), there is a tendency to obtain an adhesive layer having a low relative dielectric constant.

Examples of the alkyl acrylate having a carbon number of 8 or more include linear acrylates such as octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, lauryl acrylate, and stearyl acrylate. ; Branched alkyl acrylates such as 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and isostearyl acrylate. These may be used individually by 1 type, and may use 2 or more types.

The use amount of the alkyl acrylate (a2) is 30 to 60% by mass, preferably 35 to 60% by mass, and more preferably 40 to 60% by mass, based on 100% by mass of the monomer component. When the use amount of the alkyl acrylate (a2) is more than 60% by mass, problems such as a decrease in the durability of the adhesive layer and a deterioration in low dielectric constant may occur. When the use amount of the alkyl acrylate (a2) is less than 30% by mass, problems such as a decrease in the followability of the step of the adhesive layer may occur.

In the monomer component forming the copolymer (A), methacrylic acid The aforementioned alkyl groups possessed by the alkyl ester (a1) and the alkyl acrylate (a2) are preferably all linear alkyl groups or branched alkyl groups.

That is, it is preferable to use the aforementioned (a1) and (a2) in which the alkyl group is linear, or to use the aforementioned (a1) and (a2) in which the alkyl group is branched. In the former case, the adhesive layer has a low dielectric constant, and tends to obtain an adhesive layer having better affinity and adherence to an adherend. In the latter case, it has a low dielectric constant and tends to obtain an adhesive layer having more excellent durability. In particular, from the point that moist heat whitening can be further suppressed, it is preferable to use the aforementioned (a1) and (a2) in which both alkyl groups are branched.

"Hydroxy-containing monomer (a3)"

Examples of the hydroxyl-containing monomer (a3) include (hydroxy) -containing (meth) acrylates, and specifically, 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate Hydroxyalkyl (meth) acrylate, such as 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate. The carbon number of the hydroxyalkyl group of the hydroxyalkyl (meth) acrylate is usually 2 to 8, preferably 2 to 6.

As the hydroxyl group-containing monomer (a3), from the viewpoint of moisture and heat whitening resistance of the adhesive layer, when using the aforementioned (a1) and (a2) in which the alkyl groups are linear, hydroxyalkyl acrylate is preferred. When using the above-mentioned (a1) and (a2) in which hydroxy-containing acrylates are used, and the alkyl groups are branched, hydroxyacrylate-containing methacrylates such as hydroxyalkyl methacrylate are preferred.

The use amount of the hydroxyl group-containing monomer (a3) is 1 to 20% by mass, and preferably 2 to 15% by mass, based on 100% by mass of the monomer components. Especially when the alkyl groups of the monomers (a1) and (a2) are branched chains, 1 to 10 are preferred. Mass%, more preferably 2 to 5 mass%; when the alkyl groups of the monomers (a1) and (a2) are both linear, it is preferably 2 to 20 mass%, more preferably 5 to 15 mass%. When the amount of the monomer (a3) used is more than 20% by mass, problems such as deterioration of the low dielectric constant of the adhesive layer and reduction in the followability of the step may occur. When the amount of the monomer (a3) used is less than 1% by mass, problems such as failure to effectively form a crosslinked structure, failure to obtain an adhesive layer having an appropriate cohesive force, deterioration in durability, and whitening after wet heat may occur.

`` Nitrogen-containing monomer (a4) ''

Examples of the nitrogen atom-containing monomer (a4) include an amine group-containing monomer, a fluorenamine group-containing monomer, a nitrogen-containing heterocyclic monomer, and a cyano group-containing monomer. A single system containing both a hydroxyl group and a nitrogen atom is classified as a monomer (a4).

Of these, particularly preferred are amine-group-containing monomers and amidine-group-containing monomers. In particular, from the viewpoint of moisture and heat whitening resistance of the adhesive layer, it is preferable to use an amine group-containing monomer when the aforementioned alkyl groups (a1) and (a2) are linear. In the case of (a1) and (a2) which are branched, it is preferable to use a sulfonylamine group-containing monomer.

Examples of the amine group-containing monomer include an amine group-containing (meth) acrylate. Specifically, it is preferably CH ₂ = C (R ³ ) -COO-R ⁴ -NR ⁵ ₂ . In the formula, R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkylene group having 1 to 5 carbon atoms, preferably 1 to 3, and R ^{5 is} independently a hydrogen atom or an alkyl group having 1 to 2 carbon atoms. Specific examples include dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

Specifically, the amine group-containing monomer is preferably CH ₂ = C (R ⁶ ) -CO-NR ⁷ ₂ . In the formula, R ⁶ is a hydrogen atom or a methyl group, and R ^{7 is} each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Specific examples include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N- Hexyl (meth) acrylamide.

Examples of the nitrogen-containing heterocyclic monomer include vinyl pyrrolidone, acrylmorpholine, and ethylene caprolactam. Examples of the cyano-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

However, the copolymer (A) of the present invention is preferably a nitrogen atom-containing monomer (a4) having no cyclic structure.

The amount of the nitrogen atom-containing monomer (a4) used is 0 to 5 mass%, preferably 0.5 to 4 mass%, and more preferably 1 to 3 mass%, based on 100 mass% of the monomer components. When the amount of the nitrogen atom-containing monomer (a4) is more than 5% by mass, problems such as reduction in wet heat whitening resistance of the adhesive layer may occur. When the amount of the nitrogen atom-containing monomer (a4) is more than the aforementioned lower limit value, the cross-linking reactivity of the copolymer (A) and the cross-linking agent (B) will be improved, and an adhesive layer with high cohesive force will be obtained. The tendency.

`` Other Monomers (a5) ''

To form a monomer component of the (meth) acrylic copolymer (A), an alkyl methacrylate (a5-1) having an alkyl group of 1 to 9 carbon atoms (CH ₂ = C (CH ₃ )- COOR ⁸ ; R ⁸ is an alkyl group having 1 to 9 carbons) or an alkyl acrylate (a5-2) having an alkyl group having 1 to 7 carbon atoms (CH ₂ = CH-COOR ⁹ ; R ⁹ is a carbon number 1 to 7 alkyl).

However, the total amount of the alkyl methacrylate (a5-1) and the alkyl acrylate (a5-2) used forms a (meth) acrylic copolymer (A) from the viewpoint of low dielectric constant. 100% by mass of the monomer component is preferred It is 30% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less.

Examples of the alkyl methacrylate (a5-1) and the alkyl acrylate (a5-2) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, ( Isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate Ester, heptyl (meth) acrylate. These may be used individually by 1 type, and may use 2 or more types.

The monomer component forming the (meth) acrylic copolymer (A) can be used in a range that does not impair the physical properties of the (meth) acrylic copolymer (A). For example, an alicyclic group or an aromatic ring may be used. Other (meth) acrylates (a5-3) such as (meth) acrylate, alkoxyalkyl (meth) acrylate, and alkoxypolyalkylene glycol mono (meth) acrylate.

Examples of the (meth) acrylate containing an alicyclic group or an aromatic ring include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate.

Examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, and 2-ethoxyethyl (meth) acrylate Ester, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxy (meth) acrylate Butyl ester.

Examples of the alkoxy polyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, and ethoxy Triethylene glycol mono (meth) acrylate, Ethoxy diethylene glycol mono (meth) acrylate and methoxytriethylene glycol mono (meth) acrylate.

In addition, as long as the physical properties of the (meth) acrylic copolymer (A) are not impaired, for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, and propylstyrene may be used. Alkyl styrenes such as butyl styrene, hexyl styrene, heptyl styrene and octyl styrene; fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodinated styrene, acetophenone Styrene-based monomers such as ethylene and methoxystyrene; copolymerizable monomers (a5-4) such as vinyl acetate.

The total amount of other monomers (a5) to be used is preferably 0 to 40% by mass, more preferably 0 to 25% by mass, based on 100% by mass of the monomer components. However, since it tends to increase the relative dielectric constant, it is preferable not to use alkoxyalkyl (meth) acrylate or alkoxy polyalkylene glycol mono (meth) acrylate as much as possible.

The other monomers (a5) may be used alone or in combination of two or more.

"Acid Group-containing Monomer (a6)"

Examples of the acid group in this specification include a carboxyl group, an acid anhydride group, a phosphate group, and a sulfate group. Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloxyethyl succinate, and ω-carboxy polycaprolactone. Carboxy-containing (meth) acrylates such as ester mono (meth) acrylates; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid. Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride. Examples of the phosphate group-containing monomer include (meth) acrylic monomers having a phosphate group in a side chain, and monomers containing a sulfuric acid group in a side chain. A (meth) acrylic monomer having a sulfate group.

The total amount of the acid group-containing monomer in the monomer component 100% by mass is preferably 0.1% by mass or less, and more preferably 0% by mass. If the total amount of the acid group-containing monomer is within the aforementioned range, the (meth) acrylic copolymer (A) will not corrode even if it directly contacts an electrode / wiring pattern containing a metal or a metal oxide. Therefore, the adhesive composition of the present invention can be suitably used in, for example, touch panel applications. For example, the acid value of the (meth) acrylic copolymer (A) is preferably 0.5 mgKOH / g or less, and more preferably 0.1 mgKOH / g or less.

<< Production conditions of (meth) acrylic copolymer (A) >>

The manufacturing conditions of a (meth) acrylic-type copolymer (A) are not specifically limited, For example, it can manufacture by a solution polymerization method. Specifically, a polymerization solvent and a monomer component are charged into a reaction container, and a polymerization initiator is added under an inert gas environment such as nitrogen. The reaction starting temperature is usually set to 40 to 100 ° C, preferably 50 to 80 ° C. The reaction system is usually maintained at a temperature of 50 to 90 ° C, preferably 70 to 90 ° C, and allowed to react for 4 to 20 hours.

The copolymer (A) is obtained, for example, by copolymerizing the above monomer components, and may be a random copolymer or a block copolymer. Among these, a random copolymer is preferable.

Examples of the polymerization solvent used in the solution polymerization include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; cyclopentane and cyclohexane , Cycloheptane, cyclooctane and other alicyclic hydrocarbons; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, di Ethers such as alkane, anisole, phenylethyl ether, diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; ethyl acetate, propyl acetate , Butyl acetate, methyl propionate and other esters; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones; N, N-dimethylformamide , N, N-dimethylacetamidamine, N-methylpyrrolidone and other amines; acetonitrile, benzonitrile and other nitriles; dimethyl fluorene, cyclobutadiene and other fluorenes. These polymerization solvents may be used individually by 1 type, and may use 2 or more types.

Examples of the polymerization initiator used in the solution polymerization include an azo-based initiator and a peroxide-based initiator. Specific examples include azo compounds such as 2,2'-azobisisobutyronitrile, peroxides such as benzamidine peroxide and lauryl peroxide. Among these, azo compounds are particularly preferred. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2'-azo Azobis (2-cyclopropylpropionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 1 , 1'-Azobis (cyclohexane-1-carbonitrile), 2- (Aminomethylamido) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-di Methylvaleronitrile, 2,2'-azobis (2-fluorenylpropane) dihydrochloride, 2,2'-azobis (N, N'-dimethylene isobutylphosphonium), 2 , 2'-Azobis [2-methyl-N- (2-hydroxyethyl) -propanamide], 2,2'-Azobis (isobutylamidamine) dihydrate, 4,4 '-Azobis (4-cyanovaleric acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionic acid) Ester), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propanamide]. These polymerization initiators may be used individually by 1 type, and may use 2 or more types.

Relative to the amount of the (meth) acrylic copolymer (A) The body component is 100 parts by mass, and the polymerization initiator is usually used in an amount of 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass. Moreover, in the said polymerization reaction, you may add a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent suitably.

"Physical properties and content of (meth) acrylic copolymer (A)"

The weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) measured by the colloidal permeation chromatography (GPC) method, in terms of polystyrene, is usually 30,000 to 500,000, preferably 50,000 to 400,000. More preferably, it is 200,000 to 390,000. By using the copolymer (A) having Mw in the aforementioned range and having the above-mentioned monomer units, it is easy to achieve a balance of adhesion, to become an adhesive composition having a viscosity suitable for painting, and to obtain an adhesive having excellent step-following followability. Tendency of the agent layer.

The molecular weight distribution (Mw / Mn) of the (meth) acrylic copolymer (A) measured by the GPC method is usually from 3 to 30 when the alkyl groups of the monomers (a1) and (a2) are branched chains. , Preferably from 5 to 25, more preferably from 8 to 20; when the alkyl groups of the monomers (a1) and (a2) are both straight-chain, preferably from 4 to 20, more preferably from 5 to 10.

The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) can be calculated, for example, from the monomer units constituting the copolymer and the content ratio thereof using the Fox formula. For example, the (meth) acrylic copolymer (A) can be synthesized such that the glass transition temperature (Tg) obtained by the Fox formula is usually -70 to 0 ° C, preferably -60 to -20 ° C. By using the (meth) acrylic copolymer (A) having such a glass transition temperature (Tg), an adhesive composition having excellent adhesiveness at room temperature can be obtained.

Fox formula: 1 / Tg = (W ₁ / Tg ₁ ) + (W ₂ / Tg ₂ ) +… + (W _m / Tg _m ) W ₁ + W ₂ +… + W _m = 1

In the formula, Tg is the glass transition temperature of the (meth) acrylic copolymer (A), Tg ₁ , Tg ₂ , ..., Tg _m is the glass transition temperature of the homopolymer containing each monomer, and W ₁ and W ₂ , ..., W _m are the weight fractions of the aforementioned copolymer (A) derived from the constituent units of each monomer.

The glass transition temperature of the aforementioned Fox formula including a homopolymer of each monomer can be, for example, a value described in Polymer Handbook Forth Edition (Wiley-Interscience 1999).

The content of the (meth) acrylic copolymer (A) in the adhesive composition of the present invention is usually from 60 to 99.99% by mass based on 100% by mass of the solid content of the organic solvent excluding the composition, and more preferably 70 to 99.95 mass%, particularly preferably 80 to 99.90 mass%. When the content of the (meth) acrylic copolymer (A) is within the above range, the performance as an adhesive can be balanced, and the adhesive properties will be excellent.

[Crosslinking agent (B)]

The crosslinking agent (B) is not particularly limited as long as it is a component that can cause a crosslinking reaction with the (meth) acrylic copolymer (A). Examples thereof include an isocyanate compound (B1), a metal chelate compound (B2), and an epoxy compound (B3).

The crosslinking agent (B) may be used alone or in combination of two or more kinds.

In the adhesive composition of the present invention, the total content of the crosslinking agent (B) is preferably from 0.01 to 5 parts by mass, more preferably from 0.05 to 2.5, based on 100 parts by mass of the (meth) acrylic copolymer (A). It is still more preferably 0.1 to 1 part by mass. By containing such a certain amount of crosslinking agent (B), It has an appropriate degree of crosslinking to achieve excellent adhesion, dimensional stability, and durability under high humidity and heat conditions.

<< Isocyanate compound (B1) >>

As the isocyanate compound (B1), an isocyanate compound having two or more isocyanate groups in one molecule is usually used. The (meth) acrylic copolymer (A) is crosslinked by the isocyanate compound (B1) to form a crosslinked body (network polymer).

The number of isocyanate groups of the isocyanate compound (B1) is usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is within the aforementioned range, the point of the crosslinking reaction efficiency of the (meth) acrylic copolymer (A) and the isocyanate compound (B1) and the point of maintaining the flexibility of the adhesive layer are preferred.

Examples of the diisocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of the aliphatic diisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, and 3 -An aliphatic diisocyanate having 4 to 30 carbon atoms such as methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated methylphenyl diisocyanate, and hydrogenated diphenylmethane diisocyanate. , Hydrogenated tetramethylphenylene diisocyanate and other alicyclic diisocyanates having 7 to 30 carbon atoms. Examples of the aromatic diisocyanate include For example, carbons such as phenylene diisocyanate, methylenediphenyl diisocyanate, phenylene dimethyl diisocyanate, naphthyl diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, diphenylpropane diisocyanate, etc. Aromatic diisocyanates of number 8 to 30.

Examples of the isocyanate compound having three or more isocyanate groups in one molecule include aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, 4,4 ', 4 "-triphenylmethane triisocyanate.

Examples of the isocyanate compound (B1) include a polymer (for example, a dimer or a trimer, a biuret, and a trimeric isocyanate) and a derivative of the isocyanate compound having an isocyanate group of 2 or 3 or more. (For example, an addition reaction product of a polyol and two or more diisocyanate compounds), a polymer. As the polyol of the derivative, examples of the low molecular weight polyol include trivalent or higher alcohols such as trimethylolpropane, glycerol, and neopentyl alcohol; examples of the high molecular weight polyol include polyether polyol, polyester polyol, Acrylic polyol, polybutadiene polyol, polyisoprene polyol.

Examples of such an isocyanate compound include a terpolymer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a hexamethylene diisocyanate, or a biuret or trimer of methylenephenyl diisocyanate Reaction product of isocyanate, trimethylolpropane and methylenephenyl diisocyanate or methylenephenyl diisocyanate (e.g. 3 molecule addition product of methylenephenyl diisocyanate or methylenephenyl diisocyanate) Trimethylol The reaction product of propylene propane and hexamethylene diisocyanate (such as the 3-molecular adduct of hexamethylene diisocyanate), polyether polyisocyanate, polyester polyisocyanate.

Among the isocyanate compounds (B1), an aliphatic diisocyanate-based crosslinking agent is preferred, and hexamethylene is more preferred from the viewpoint of improving durability (example: foam resistance, moist heat whitening resistance). Diisocyanate-based crosslinking agent. Examples of the aliphatic diisocyanate-based crosslinking agent include aliphatic diisocyanates and polymers thereof. Examples of the hexamethylene diisocyanate-based crosslinking agent include hexamethylene diisocyanate and a biuret or a trimer isocyanate thereof.

An isocyanate compound (B1) may be used individually by 1 type, and may use 2 or more types.

《Metal Chelate Compound (B2)》

Examples of the metal complex compound (B2) include alkoxides, acetone, acetone, and other polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Ethyl acetate and other compounds. Among these, an aluminum compound (M-12AT manufactured by Soken Chemical Co., Ltd.) is particularly preferred. Specific examples include aluminum isopropoxide, aluminum secondary butyrate, aluminum ethylacetoacetate / diisopropanol, aluminum ginsyl ethylacetate, and aluminum acetoacetone aluminum.

The metal chelate compound (B2) may be used singly or in combination of two or more kinds.

《Epoxy Compound (B3)》

The epoxy compound (B3) is generally an epoxy compound having two or more epoxy groups in one molecule. Examples include ethylene glycol diglycidyl ether, Polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N , N ', N'-tetraglycidyl-m-xylylenediamine, N, N, N', N'-tetraglycidylaminophenylmethane, triglycidyl trimeric isocyanate, m-N , N-diglycidyl phenyl glycidyl ether, N, N-diglycidyl toluidine, N, N-diglycidyl aniline.

[Silane coupling agent (C)]

The adhesive composition of the present invention preferably contains a silane coupling agent (C). The silane coupling agent (C) is helpful in terms of improving the durability of the adhesive layer, firmly adhering the adhesive layer to an adherent such as a glass plate, and preventing peeling in a high humidity and heat environment.

Examples of the silane coupling agent (C) include methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane. Alkyl or aromatic silane coupling agents; Keto group-containing silane coupling agents such as 3-acetamidineethyltrimethoxysilane; vinyltrimethoxysilane, vinyltriethoxy Silane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxy Silane coupling agents containing polymerizable unsaturated groups such as methylsilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Triethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl ) Ethyltrimethoxysilane and other silane-containing coupling agents; 3-aminopropyltrimethoxysilane, 3- Aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyl Dimethoxysilane, 3-triethoxysilane-N- (1,3-dimethyl-butylene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, etc. Silane coupling agents containing amine groups; halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane.

The content of the silane coupling agent (C) in the adhesive composition of the present invention is usually 1 part by mass or less, preferably 0.01 to 1 part by mass, more than 100 parts by mass of the (meth) acrylic copolymer (A). It is preferably from 0.05 to 0.5 parts by mass. When the content is within the aforementioned range, there is a tendency to prevent peeling of adherends in a high-humidity environment and exudation of the silane coupling agent (C) in a high-temperature environment.

[Organic solvent (D)]

In order to adjust the coating property of the adhesive composition of the present invention, it is preferable to contain an organic solvent (D). Examples of the organic solvent (D) include the polymerization solvents described in the (meth) acrylic copolymer (A). For example, an adhesive composition can be prepared by mixing a solution containing the copolymer obtained by the above-mentioned copolymerization and a polymerization solvent with a crosslinking agent. The content of the organic solvent in the adhesive composition of the present invention is usually 20 to 90% by mass, and preferably 30 to 70% by mass.

[additive]

The adhesive composition of the present invention may contain, in addition to the above-mentioned components, a member selected from the group consisting of antioxidants, light stabilizers, anti-corrosive agents, tackifiers, plasticizers, and antistatics in a range that does not impair the effects of the present invention. One or more of crosslinking agents, cross-linking accelerators and heavy industrial agents.

[Preparation of adhesive composition]

According to the adhesive composition of the present invention, (meth) acrylic The polymer (A), the cross-linking agent (B), and other components as necessary are mixed and prepared by a conventionally known method. For example, in a solution containing the copolymer and a polymerization solvent obtained when the (meth) acrylic copolymer (A) is synthesized, a cross-linking agent (B) and other components as necessary are blended.

The gelatinization rate of the adhesive formed from the adhesive composition of the present invention is preferably 10 to 60% by mass, more preferably 15 to 50% by mass, and even more preferably 20 to 40% by mass. The said gelatinization rate is a value measured with respect to the adhesive used under the conditions described in an Example, for example.

[Adhesive layer]

The adhesive layer of the present invention is formed of the above-mentioned adhesive composition.

The adhesive layer formed from the adhesive composition of the present invention has a gelation rate of 10 to 60% by mass, and more preferably 15 to 50% by mass from the viewpoints of cohesive force, adhesive force, and re-peelability. Still more preferably, it is 20 to 40% by mass.

The adhesive layer formed by the adhesive composition of the present invention has a low dielectric constant. The relative dielectric constant at a frequency of 100 Hz is preferably 5.0 or less, more preferably 2.0 to 4.5, and even more preferably 2.0 to 4.0. The adhesive layer having a relative dielectric constant within the aforementioned range can be applied to, for example, a touch panel application.

Since the adhesive layer of the present invention is excellent in flexibility, when the adhesive sheet is attached to the adherend while being heated and / or pressurized (for example, a temperature of 50 to 90 ° C, 2 to 10 atm), The followability of the step difference is improved. For example, when a pressure-sensitive adhesive sheet is attached to a stepped adhesive such as a support on which a print layer is formed or a substrate on which a conductive film is formed, the present invention The adhesive layer of the present invention exhibits excellent step-followability. In addition, since the adhesive layer that once followed the step has sufficient flexibility in a high-temperature environment, even if exposed to a high-temperature environment, the adhesive layer does not easily float / peel off from the step.

The adhesive layer formed from the adhesive composition of the present invention is excellent in durability.

For example, even when the adhesive layer is placed in a high-temperature / high-humidity environment, defects such as foaming at the interface with the adhesive, breakage of the adhesive layer, and floating / peeling of the adhesive are not easily generated.

Moreover, for example, the above-mentioned adhesive layer with a film thickness of 50 μm is the absolute difference in the haze value before and after standing (after the endurance test) after standing for 24 hours (after the endurance test) under an environment of 85 ° C / 85% RH The value is usually 0.5% or less, and more preferably 0.3% or less, and is excellent in whitening resistance. In addition, "%" is a unit of a haze value. Therefore, when the aforementioned adhesive layer is used in an image display device or an input device, the visibility of the image display portion is also excellent.

The detailed measurement conditions of the relative dielectric constant and the haze value are described in Examples.

The adhesive layer of the present invention is, for example, by performing a cross-linking reaction in the above-mentioned adhesive composition, specifically, by crosslinking the (meth) acrylic copolymer (A) with a crosslinking agent (B). And get.

The formation conditions of an adhesive layer are as follows, for example. Although the adhesive composition of the present invention is coated on a support, although it varies depending on the type of the solvent, it is usually 50 to 150 ° C, preferably 60 to 100 ° C. It is usually 1 to 5 minutes, preferably 3 to 5 minutes, followed by drying to remove the solvent and form a coating film. The film thickness of the dry coating film is usually 10 to 300 μm, preferably 20 to 180 μm.

The adhesive layer is preferably formed under the following conditions. After the adhesive composition of the present invention is coated on a support and a cover film is attached to a coating film formed under the above conditions, it is usually 3 days or more, preferably 7 to 10 days. It is usually 5 to 60 ° C, preferably 15 to 40 ° C, usually 20 to 80% RH, and preferably 30 to 70% RH. Crosslinking (network polymer) can be formed with good efficiency by performing crosslinking under the above-mentioned ripening conditions.

The coating method of the adhesive composition can be a well-known method, for example, a spin coating method, a knife coating method, a roll coating method, a bar coating method, a doctor blade coating method, a die coating method, a gravure coating method, or the like can be used. A method of coating / drying in a predetermined thickness.

Examples of the support and the film include polyester films such as polyethylene terephthalate (PET); plastic films such as polyethylene films, polypropylene, and polyolefin films such as ethylene-vinyl acetate copolymers.

[Adhesive sheet]

The adhesive sheet of the present invention has an adhesive layer formed of the adhesive composition. Examples of the adhesive sheet include a double-sided adhesive sheet having only the above-mentioned adhesive layer, a double-sided adhesive sheet having a base material and the above-mentioned adhesive layer formed on both sides of the base material, and the above-mentioned having a base material and one side of the base material. The single-sided adhesive sheet of the adhesive layer, and the adhesive sheet on which the surface of the adhesive layer of the adhesive sheet which is not in contact with the substrate is attached with a peeling treatment film.

Examples of the substrate and the film include polyester films such as polyethylene terephthalate (PET); polyolefin films such as polyethylene, polypropylene, polycarbonate (PC), and ethylene-vinyl acetate copolymers, etc. Plastic film; glass film, etc.

The film thickness of the adhesive layer can be determined, for example, by taking into account the step difference (step difference followability) or transparency of the surface of the adherend. The film thickness of the adhesive layer is usually 10 to 300 μm, preferably 20 to 180 μm. The film thickness of the substrate and the film is not particularly limited, but it is usually 5 to 1000 μm, and preferably 10 to 700 μm.

[Applicable use]

The adhesive composition, the adhesive layer or the adhesive sheet of the present invention can be applied to the manufacture of image display devices such as liquid crystal display devices and electronic paper, and has optical type, ultrasonic type, electrostatic capacity type, resistive film type, etc. Manufacturing applications of input devices such as touchpads. It is especially suitable for the manufacture of an electrostatic capacitance type touch panel.

The adhesive composition, the adhesive layer, or the adhesive sheet of the present invention can be applied to a support and a conductive material having a conductive film (eg, an electrode, a wiring pattern) formed on the surface of a substrate including a metal or a metal oxide. Use of laminated substrates.

Examples of the support include glass plates; transparent plastic films such as polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA). The thickness of the support is usually 25 to 2000 μm.

In order to improve the design of a liquid crystal display device, a touch panel, or the like, the support may include a printing layer on a peripheral edge portion of a surface in contact with the adhesive layer. The thickness of the printed layer is usually 10 to 50 μm. Such as a rectangle.

Examples of the conductive film constituting the base material with a conductive film include films containing metals, metal oxides, or mixtures thereof, and examples include indium tin oxide (ITO), antimony tin oxide (ATO), and tin oxide. Transparent film. The thickness of the conductive film is usually 10 to 200 nm. Examples of the substrate constituting the substrate with a conductive film include transparent plastic films such as a polyethylene terephthalate film. The thickness of the substrate is usually 25 to 1000 μm.

The adhesive layer containing the adhesive composition of the present invention is disposed so as to adhere to the support and the substrate with the conductive film, and the adhesive layer is in direct contact with the conductive film formed on the substrate with the conductive film When the printed layer is formed on the support, it is also in direct contact with the printed layer.

Since the adhesive layer formed from the adhesive composition of the present invention has excellent step-followability as described above, even if there is a step due to an electrode / wiring pattern or a printed layer, no void is formed. In addition, the adhesive layer is also excellent in low dielectric constant and durability.

In addition, the present invention can be configured such that the adhesive layer does not substantially contain an acid group, so even if the adhesive layer directly contacts a conductive film containing a metal or a metal oxide, the conductive film can be prevented from being corroded and its resistance value can be suppressed. rise. Therefore, in a capacitive touch panel, although the so-called adhesive layer is in direct contact with a conductive film having an electrode / wiring pattern formed with a step, the adhesive layer does not change the characteristics of the conductive film. advantage.

[Example]

Hereinafter, the present invention will be further specifically described based on examples. However, the present invention is not limited to these examples. In the following examples and other descriptions, unless otherwise specified, "part" means "mass part".

[Average molecular weight]

For the (meth) acrylic copolymer, the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of standard polystyrene were determined by the colloidal permeation chromatography (GPC) method under the following conditions.

． Measuring device: HLC-8120GPC (manufactured by Tosoh Co., Ltd.)

． GPC column structure: the following 5 pipe columns (all manufactured by Tosoh Co., Ltd.)

(1) TSK-GEL HXL-H (protection column)

(2) TSK-GEL G7000HXL

(3) TSK-GEL GMHXL

(4) TSK-GEL GMHXL

(5) TSK-GEL G2500HXL

． Sample concentration: 1.0mg / cm ³ (diluted with tetrahydrofuran)

． Mobile phase solvent: tetrahydrofuran

． Flow rate: 1.0cm ³ / min

． Column temperature: 40 ℃

(Example) [Example 1]

In a reaction apparatus equipped with a stirrer, a reflux cooler, a thermometer, and a nitrogen introduction tube, 35 parts of isodecyl methacrylate (IDMA), 60 parts of isostearyl acrylate (ISTA), and 2-hydroxyethyl methacrylate were charged. 4 parts of ester (2HEMA), 1 part of acrylamide (AM) and 70 parts of ethyl acetate solvent, while introducing nitrogen The temperature was raised to 80 ° C. Next, 0.3 parts of azobisisobutyronitrile (AIBN) was added, and the polymerization reaction was performed at 80 ° C. for 8 hours under a nitrogen gas environment. After the reaction was completed, it was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 50% by mass. The weight average molecular weight (Mw) of the obtained (meth) acrylic copolymer was 350,000, and the molecular weight distribution (Mw / Mn) was 12.

The obtained (meth) acrylic copolymer solution (solid content concentration: 50% by mass) and the HDI-based isocyanate compound (24A-) based on 100 parts (solid content) of the (meth) acrylic copolymer contained in the solution 100 "(made by Asahi Kasei Chemicals Co., Ltd.) 0.2 parts, 0.2 parts of silane coupling agent" KBM-403 "(made by Shin-Etsu Silicone Co., Ltd.) and ethyl acetate were mixed to obtain an adhesive composition having a solid content concentration of 40% by mass.

The obtained adhesive composition was dried to a thickness of 50 μm, and applied to a 38 μm-thick PET film having a peeling treatment at a liquid temperature of 25 ° C., and dried at 90 ° C. for 4 minutes to remove the solvent to form a coating film. A PET film having a thickness of 38 μm which was peeled off was further laminated on the side opposite to the surface on which the above-mentioned PET film was adhered, and was cured at 23 ° C./50% RH for 7 days to obtain an adhesive layer having a thickness of 50 μm Adhesive sheet.

[Examples 2 to 25, Comparative Examples 1 to 16]

A (meth) acrylic copolymer solution was obtained in the same manner as in Example 1 except that the monomer components described in Tables 1A and 1B were used. Next, the adhesive composition was obtained in the same manner as in Example 1 except that the components were changed to Tables 1A and 1B, and the thickness was 50 μm. Adhesive sheet of adhesive layer. In Tables 1A and 1B, the amounts of the cross-linking agent and the silane coupling agent are based on 100 parts of the (meth) acrylic copolymer. In addition, in Examples 12 and 22, when the (meth) acrylic copolymer was prepared, the amount of the ethyl acetate solvent was changed from 70 parts to 60 parts.

Monomer composition

Alkyl methacrylate (a1)

． IDMA: isodecyl methacrylate (C10 branched alkyl)

． LMA: lauryl methacrylate (C12 linear alkyl)

． NSTMA: n-stearyl methacrylate (C18 linear alkyl)

Alkyl acrylate (a2)

． ISTA: isostearyl acrylate (C18 branched alkyl)

． 2EHA: 2-ethylhexyl acrylate (C8 branched alkyl)

． IOAA: Isooctyl acrylate (C8 branched alkyl)

． LA: Lauryl acrylate (C12 linear alkyl)

． NOAA: n-octyl acrylate (C8 linear alkyl)

Hydroxyl-containing monomer (a3)

． 2HEMA: 2-hydroxyethyl methacrylate

． 2HEA: 2-hydroxyethyl acrylate

Nitrogen atom-containing monomer (a4)

． AM: Acrylamide

． DM: dimethylaminoethyl methacrylate

Other monomers (a5)

． nBA: n-butyl acrylate

Crosslinker

Hexamethylene diisocyanate (HDI) based isocyanate compound

． duranate "24A-100" (manufactured by Asahi Kasei Chemicals Co., Ltd.)

． duranate "TPA-100" (manufactured by Asahi Kasei Chemicals Co., Ltd.)

Methylenephenyl diisocyanate (TDI) based isocyanate compound

． `` CORONATE L '' (manufactured by Japan Polyurethane Co., Ltd.)

Metal chelate compound

． Aluminum alloy crosslinking agent `` M-12AT '' (manufactured by Soken Chemical Co., Ltd.)

Silane coupling agent

． "KBM-403" (by Shin-Etsu Silicone Co., Ltd.)

． "KBM-603" (by Shin-Etsu Silicone Co., Ltd.)

[Evaluation] [Durability test: foaming / floating, wet heat whitening (haze)]

The PET film subjected to the peeling treatment on one side of the adhesive sheet obtained in Examples and the like was peeled off, and the entire surface of the adhesive layer was bonded to a PET film having a thickness of 100 μm, and cut into a size of 50 mm × 50 mm. Then, peel off the PET film on the other side, and stick the exposed adhesive layer to the glass plate, and then treat it in an autoclave at 50 ° C / 5atm for 20 minutes, then in a gas environment of 23 ° C / 50% RH The test piece was left standing for 1 hour to prepare a test piece.

(1) The prepared test piece was left to stand in an environment of 85 ° C / 85% RH for 24 hours, and the occurrence of foaming and floating was visually observed and evaluated on the following basis.

． AA: No foaming or floating was recognized.

． BB: No floating was confirmed, but extremely minute foaming was confirmed.

． CC: Obvious foaming or floating was recognized.

(2) After measuring the haze of the prepared test piece before the endurance test, it was left to stand in an environment of 85 ° C / 85% RH for 24 hours. The test piece was taken out and left at room temperature for 1 hour, and then the haze was measured to determine the difference in haze before and after the endurance test (Δhaze; unit%). Haze measurement, used MH-150 (Murakami Color Technology Research Institute Co., Ltd.).

[Relative permittivity]

The adhesive sheets obtained in the two examples were prepared, and the PET film subjected to the peeling treatment was peeled off from the adhesive sheets, and then the adhesive layers were bonded to each other to prepare an adhesive sheet having a thickness of 100 μm, and the aforementioned adhesive was transferred to a copper foil having a thickness of 100 μm An adhesive layer was further attached to the adhesive layer with a copper foil having a thickness of 100 μm as a measurement sample. A LCR meter 6440B manufactured by Toyo Tecnica was connected to the copper foil, and the relative permittivity (100 Hz) in a 23 ° C / 50% RH gas environment was calculated.

[Gelling rate]

About 0.1 g of the adhesive obtained from the example and the like was taken into a sampling bottle, 30 mL of ethyl acetate was added and shaken for 4 hours, and then the content of the sample bottle was filtered through a 200-mesh stainless steel metal mesh to filter the metal mesh. The residue was dried at 100 ° C for 2 hours to measure the dry weight, and the gelation rate was determined by the following formula. In addition, after curing for 7 days in the aforementioned 23 ° C / 50% RH environment, the adhesive sheet was allowed to stand for 30 days in the 23 ° C / 50% RH environment, and the same adhesive was applied to the adhesive sheet. This method finds the gelation rate.

． Gelation rate (%) = (Weight after drying / Adhesive weight taken) × 100 (%)

[180 ° peeling force (adhesive force)]

The PET film subjected to the peeling treatment on one side of the adhesive sheet obtained in the example and the like was peeled off, and the entire surface of the adhesive layer was bonded to a PET film having a thickness of 100 μm, and cut into 25 mm × 150 mm to prepare a test piece. Then peel off the PET film on the other side and stick the exposed adhesive layer on The glass plate was pressed back and forth three times with a roller weighing 2 kg. After pressing, it was left for 2 hours in a 23 ° C / 50% RH gas environment, and the short side of the test piece was pulled at a peeling speed of 300 mm / min toward 180 °, and the peeling force was taken as the 180 ° peeling force (adhesion force). Moreover, the adhesive force was also calculated | required in the same way as the adhesive sheet which was left to stand for 30 days in 23 degreeC / 50% RH environment after 7 days of aging under the 23 degreeC / 50% RH environment.

[Segment following]

The PET film subjected to the peeling treatment on one side of the adhesive sheet obtained in the example and the like was peeled off, and the entire surface of the adhesive layer was bonded to a PET film having a thickness of 100 μm, and cut into 50 mm × 50 mm to prepare a test piece. Then, a 15 μm or 25 μm PET film cut into a thickness of 15 mm × 15 mm was placed on a glass plate, and the peeled PET film on the other side of the test piece was peeled off, and an adhesive layer was applied to cover the PET on the glass plate. The test piece (50mm × 50mm) was attached to the entire surface of the film (15mm × 15mm). After being treated in an autoclave at 50 ° C / 5atm for 20 minutes, it was left at room temperature for 1 hour, and the appearance of the stepped portion was visually observed. .

"×": Either 15 μm or 25 μm step difference has a noticeable bubble in the step portion.

“15 μm”: Bubbles were recognized at 25 μm steps, but no bubbles were recognized at 15 μm.

"25 µm": No bubble was recognized at any of 15 µm and 25 µm steps.

In addition, when the evaluations of "15μm" and "25μm" are marked with "△", they are indicated in the step, and only a few bubbles are recognized in the step.

The above evaluation results are shown in Tables 2A and 2B.

Claims (9)

An adhesive composition containing (A) a (meth) acrylic copolymer and a (B) cross-linking agent, wherein the copolymer (A) is contained in an amount of 100% by mass based on all monomer components It is obtained by copolymerizing the monomer components of the above: (a1) an alkyl methacrylate having an alkyl group having a carbon number of 10 or more and 20 to 39% by mass; 30 to 60% by mass, (a3) a hydroxyl-containing monomer 1 to 20% by mass, (a4) a nitrogen atom-containing monomer 0 to 5% by mass; the gelation rate of the adhesive formed from the aforementioned adhesive composition It is 10 to 60% by mass. The adhesive composition according to item 1 of the scope of patent application, wherein, among the monomer components forming the copolymer (A), the alkane methacrylate (a1) and the alkane acrylate (a2) have The radicals are all linear alkyl groups or branched alkyl groups. The adhesive composition according to item 1 or item 2 of the scope of the patent application, wherein the monomer component (a3) containing a hydroxyl group in the monomer component forming the copolymer (A) is a (methyl) group containing a hydroxyl group Acrylate. The adhesive composition according to item 1 or item 2 of the scope of application for a patent, wherein the monomer component forming the copolymer (A) further contains an acid group-containing monomer (a6), compared to forming the copolymer. The total monomer component of (A) is 100% by mass, and the amount of the acid group-containing monomer (a6) used is 0.1% by mass or less. The adhesive composition according to item 1 or item 2 of the scope of patent application, wherein the weight average molecular weight (Mw) of the copolymer (A) measured by colloidal permeation chromatography is converted into polystyrene as 30,000 to 500,000. The adhesive composition according to item 1 or item 2 of the scope of patent application, further comprising (C) a silane coupling agent. An adhesive layer is formed by the adhesive composition described in any one of the first to sixth aspects of the patent application. An adhesive sheet is provided with the adhesive layer described in item 7 of the patent application scope. A laminated body for a touch panel comprises a support, an adhesive layer described in item 7 of the patent application, and a conductive film with a conductive film formed of a conductive film made of a metal or a metal oxide on the surface of a substrate. The substrates are laminated in this order.