TWI814994B - Adhesive layer and adhesive sheet - Google Patents

Abstract

The present invention provides an adhesive layer with low sebum swelling and excellent step absorption. The adhesive layer of the present invention is formed of an adhesive containing an acrylic polymer, and the 300% tensile residual stress value is 0.1 to 6 N/cm ² ; the acrylic polymer contains an alkane with a carbon number of 1 to 5 at the ester end. The alkyl (meth)acrylate, the hydroxyl-containing monomer, and the monomer containing a specific alicyclic structure are used as the monomer components constituting the polymer, and relative to the total amount of the monomer components constituting the above-mentioned polymer, The ratio of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the end of the ester is 40 to 82 mass %, the ratio of the hydroxyl-containing monomer is 17 to 35 mass %, and the above-mentioned specific alicyclic ring The ratio of monomers in the structure is 42% by mass or less.

Description

Adhesive layer and adhesive sheet

The invention relates to an adhesive layer and an adhesive sheet. More specifically, the present invention relates to an adhesive layer and an adhesive sheet having the adhesive layer.

In recent years, input devices (touch panel mounted devices) used in combination with image display devices and touch panels have become increasingly popular in portable information terminals such as mobile phones, portable music players, smart phones, and tablets. As a transparent conductive film used for a touch panel, it is widely known that a transparent conductive film (ITO (Indium Tin Oxides, indium tin oxide) film) is laminated on a transparent plastic film base material or glass. The transparent conductive film is passed through The adhesive layer is laminated on other components. As an adhesive layer used for such an optical member, for example, those disclosed in Patent Documents 1 to 3 are known. [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2003-238915 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-342542 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-231723

[Problem to be solved by the invention]

The above-mentioned touch panel is used in a state of frequent contact with bare hands, so it is unavoidable to prevent the sebum from the hands from migrating to the touch panel. The sebum that migrates to the surface of the touch panel slowly migrates to the adhesive layer inside the touch panel, causing the problem that the adhesive layer swells due to sebum. If the adhesive layer swells, adherends may peel off each other or bulge. In addition, the amount of sebum on the hands differs between users, for example, depending on the country or living environment. In recent years, the number of users of touch panel-mounted devices has continued to expand around the world, so various users are required to have less swelling of the adhesive layer caused by sebum.

Furthermore, in recent years, thinning of touch panel mounting devices has been significantly promoted. Therefore, components constituting the touch panel mounting device, such as adhesive layers, are also required to be thinner. However, if the thickness of the adhesive layer becomes thinner, for example, when it is attached to a member having a printed step, the step absorbability tends to decrease.

Therefore, an object of the present invention is to provide an adhesive layer with low sebum swelling and excellent step absorption. Furthermore, another object of the present invention is to provide an adhesive sheet with low sebum swelling and excellent step absorbability. [Technical means to solve problems]

In order to achieve the above object, the present inventors conducted intensive research and found that the sebum swelling degree is low and the step absorbability is excellent through the following adhesive layer; the adhesive layer is composed of an adhesive layer containing an acrylic polymer. The above-mentioned acrylic polymers contain ( ^meth )acrylic acid alkyl groups having an alkyl group with a carbon number of 1 to 5 at the ester end at a specific ratio. Esters, hydroxyl-containing monomers, and monomers containing specific alicyclic structures are used as monomer components that constitute the polymer. The present invention was accomplished based on these knowledge and insights.

That is, the present invention provides an adhesive layer, which is formed of an adhesive containing an acrylic polymer, and has a 300% tensile residual stress value of 0.1 to 6 N/cm ² ; the acrylic polymer contains an ester terminal with a carbon number Alkyl (meth)acrylate of 1 to 5 alkyl groups, hydroxyl-containing monomers, and alicyclic structure-containing monomers are used as monomer components constituting the polymer. The above-mentioned alicyclic structure-containing monomers are selected from: Cyclohexyl (meth)acrylate, the following formula (1) [Chemical 1] The compound represented by the following formula (2) [Chemical 2] The represented compound and the following formula (3) [Chemical 3] One or more of the compounds represented in the group, the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the end of the above-mentioned ester relative to the total amount of the monomer components constituting the above-mentioned polymer The ratio is 40 to 82 mass%, the ratio of the hydroxyl group-containing monomer is 17 to 35 mass%, and the ratio of the alicyclic structure-containing monomer is 42 mass% or less.

The above-mentioned adhesive layer preferably has a storage modulus at 70°C of 7.0×10 ⁴ Pa or less.

The above-mentioned adhesive layer preferably has a gel fraction of 30 to 85% by mass.

The above-mentioned adhesive layer preferably has a b ^* value of 2.0 or less after the following ultraviolet irradiation test. <Ultraviolet irradiation test> Set the adhesive layer to a thickness of 250 μm, and laminate alkali glass on both sides to make a test piece. The wavelength range is 300~400 nm, the illumination is 110 W/m ² , and the black panel set temperature is 83°C. After irradiating the above test piece with ultraviolet light for 240 hours using a xenon arc lamp, the b ^* value of the above adhesive layer was measured.

The acrylic polymer preferably contains a polyfunctional monomer as a monomer component constituting the polymer. The content ratio of the polyfunctional monomer is preferably 3% by mass or less based on the total amount of monomer components constituting the polymer.

The above adhesive layer is preferably used for optical components.

Furthermore, the present invention provides an adhesive sheet including a base material and the adhesive layer formed on at least one side of the base material. [Effects of the invention]

The adhesive layer of the present invention has low sebum swelling and excellent step absorption. Furthermore, the adhesive sheet of the present invention has a low degree of sebum swelling and excellent step absorption.

The adhesive layer of the present invention is formed of an adhesive containing an acrylic polymer. Regarding the acrylic polymer, as a monomer component constituting the polymer, (methyl) having an alkyl group with 1 to 5 carbon atoms at the ester end is Alkyl acrylate, a hydroxyl-containing monomer, and the above-mentioned monomer containing a specific alicyclic structure are constituted (formed) as essential monomer components (monomer components). That is, the adhesive layer of the present invention is an acrylic adhesive layer formed of an adhesive (acrylic adhesive) containing an acrylic polymer. Furthermore, the above-mentioned alicyclic structure-containing monomer is selected from cyclohexyl (meth)acrylate, a compound represented by the following formula (1), a compound represented by the following formula (2), and the following formula ( 3) One or more of the groups represented by the compounds represented. In this specification, "selected from cyclohexyl (meth)acrylate, a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3) "One or more alicyclic structure-containing monomers" in the group of represented compounds are called "specific alicyclic structure-containing monomers". [Chemical 1] [Chemicalization 2] [Chemical 3]

The above-mentioned acrylic polymer is composed of (meth)acrylic acid alkyl ester having an alkyl group with 1 to 5 carbon atoms at the ester end, a hydroxyl-containing monomer, and the above-mentioned monomer containing a specific alicyclic structure as essential monomer components. A polymer composed (formed) of (monomer components). In this specification, "(meth)acrylic acid" means "acrylic acid" and/or "methacrylic acid" (either or both of "acrylic acid" and "methacrylic acid"), and the others are the same. Only one type of the above-mentioned acrylic polymer may be used, or two or more types may be used.

Examples of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the end of the ester include: (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, and third butyl (meth)acrylate. Among these, a (meth)acrylic acid alkyl ester having an alkyl group having 2 to 4 carbon atoms at the ester terminal is preferred. Only one type of (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the end of the ester may be used, or two or more types may be used.

In the adhesive layer of the present invention, a (meth)acrylic acid alkyl ester whose alkyl carbon number constituting the ester is 1 to 5 is used as the (meth)acrylic acid alkyl ester constituting the acrylic polymer, thereby , the carbon number of the alkyl group constituting the ester is small, so the lipophilicity is relatively low, which can inhibit the absorption of sebum into the adhesive layer, resulting in lower sebum swelling. In addition, it can prevent liquid sebum from penetrating from the end portion where it is attached to the adherend, making it difficult for the end portion to bulge. Furthermore, the following b ^* value tends to become low.

The ratio of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the end of the ester is 40 to 82 mass % relative to 100 mass % of the total amount of monomer components constituting the acrylic polymer, which is relatively Preferably, it is 45-75 mass %, More preferably, it is 50-70 mass %. By setting the above-mentioned ratio within the above-mentioned range, the sebum swelling property can be easily reduced, and a structure excellent in step absorption can be formed by balancing it with other monomer components.

The above-mentioned hydroxyl-containing monomer only needs to be a monomer having at least one hydroxyl group (hydroxy) in the molecule (within one molecule) and can be copolymerized with the above-mentioned alkyl (meth)acrylate. Preferred examples include: Monomers with polymerizable functional groups such as meth)acrylyl or vinyl groups and hydroxyl groups with unsaturated double bonds. Only one type of the above-mentioned hydroxyl-containing monomer may be used, or two or more types may be used.

Examples of the hydroxyl-containing monomer include: (meth)acrylic acid 2-hydroxyethyl ester, (meth)acrylic acid 2-hydroxypropyl ester, (meth)acrylic acid 3-hydroxypropyl ester, (meth)acrylic acid 4-hydroxybutyl ester, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, etc. (meth)acrylic acid hydroxyalkyl ester; (meth)acrylic acid (4-hydroxymethylcyclohexyl) methyl ester and other alicyclic structure-containing hydroxyalkyl acrylate and other hydroxyl-containing (meth)acrylic acid ester. Furthermore, examples of the above-mentioned hydroxyl-containing monomer include vinyl alcohol, allyl alcohol, hydroxyethyl (meth)acrylamide, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethyl alcohol. Diol monovinyl ether, etc. Among them, as the above-mentioned hydroxyl-containing monomer, a hydroxyl-containing (meth)acrylate is preferred, a hydroxyalkyl (meth)acrylate is more preferred, and a hydroxyalkyl group having 2 to 6 carbon atoms is even more preferred. As the (meth)acrylate, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are particularly preferred.

The ratio of the hydroxyl-containing monomer is 17 to 35 mass %, preferably 20 to 33 mass %, more preferably 25 to 32 mass %, based on 100 mass % of the total monomer components constituting the acrylic polymer. %. By setting the above-mentioned ratio within the above-mentioned range, it is easy to utilize the balance with other monomer components to reduce the swelling property of sebum, and to form a structure having excellent step absorbability. Furthermore, since it can be used as a polar monomer instead of a nitrogen-containing monomer, it is less likely to cause discoloration (yellowing) caused by ultraviolet rays than when a nitrogen-containing monomer is used.

The above-mentioned monomer containing a specific alicyclic structure is selected from the group consisting of cyclohexyl (meth)acrylate, a compound represented by the above formula (1), a compound represented by the above formula (2), and a compound represented by the above formula (3). One or more species in a group of compounds. By using the above-mentioned monomer containing a specific alicyclic structure as the monomer component used to constitute the acrylic polymer, the swelling property of sebum can be reduced, and the Tg of the acrylic polymer can be easily adjusted by balancing it with other monomer components. It is easy to form a structure with excellent step absorption. Among them, cyclohexyl (meth)acrylate is preferred. Only one type of monomer containing a specific alicyclic structure may be used, or two or more types may be used.

The ratio of the monomers containing the specific alicyclic structure is 42 mass% or less (for example, 1 to 42 mass%), preferably 30 mass%, based on 100 mass% of the total amount of monomer components constituting the acrylic polymer. It is less than 15% by mass (for example, 5-30% by mass), and more preferably 15% by mass or less (for example, 8-15% by mass). By including the above-mentioned specific alicyclic structure-containing monomer at a ratio of 42% by mass or less, the sebum swelling property can be easily reduced by utilizing the balance with other monomer components, and a structure with excellent step absorption can be formed.

In addition to the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester end, the hydroxyl-containing monomer, and the above-mentioned monomer containing a specific alicyclic structure, the acrylic polymer may also contain The monomer component (other copolymerizable monomer) obtained by copolymerizing one or more of these monomer components serves as the monomer component constituting the polymer. Examples of the other copolymerizable monomers include nitrogen atom-containing monomers, alicyclic structure-containing monomers other than the above-mentioned specific alicyclic structure-containing monomers, carboxyl group-containing monomers, and cyclic ether group-containing monomers. Monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, (meth)acrylates with aromatic hydrocarbon groups, vinyl esters, aromatic vinyl compounds, olefins or dienes, vinyl ethers Class, alkoxyalkyl (meth)acrylate, silicon atom-containing monomer, glycol monomer, vinyl chloride, tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate, polysilicon Oxy(meth)acrylate, etc. Among them, (meth)acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl-containing monomer, and the above-mentioned The total ratio of monomers containing a specific alicyclic structure is preferably 70 mass% or more, more preferably 80 mass% or more, further preferably 90 mass% or more, and particularly preferably 95 mass% or more. Only one type of each of the above-mentioned other copolymerizable monomers may be used, or two or more types may be used.

The nitrogen atom-containing monomer is not particularly limited, and examples thereof include cyclic nitrogen-containing monomers, (meth)acrylamides, and the like. The above-mentioned cyclic nitrogen-containing monosystem has polymerizable functional groups with unsaturated double bonds such as (meth)acrylyl or vinyl groups, and has a cyclic nitrogen structure. The above-mentioned cyclic nitrogen structure preferably has a nitrogen atom in the cyclic structure. Examples of the above-mentioned cyclic nitrogen-containing monomer include: N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-pyrrolidone, N-ethylene N-vinyl cyclic amide such as 2-caprolactamide, N-vinyl-1,3-㗁𠯤-2-one, N-vinyl-3,5-𠰌lindione, etc.

Examples of vinyl monomers having the above-mentioned nitrogen-containing heterocycles other than N-vinyl cyclic amide include polymerizable functional groups having unsaturated double bonds such as (meth)acrylyl groups or vinyl groups. And those with nitrogen-containing heterocycles such as 𠰌line ring, piperidine ring, pyrrolidine ring, and piperidine ring. The vinyl monomer having the above-mentioned nitrogen-containing heterocycle is not particularly limited, and examples thereof include: (meth)acrylamide, N-vinyl piperazole, N-vinylpyrrole, N-vinylimidazole, N-vinylpyridine, N-vinylpyridine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinylpyridine, vinylisothiazole, vinylisothiazole, vinylisothiazole, ethylene Chloride, (meth)acrylylpyrrolidine, (meth)acrylylpyrrolidine, (meth)acrylylpiperidine, etc.

The ratio of the nitrogen atom-containing monomer is not particularly limited, but is preferably 10 mass% or less, more preferably 5 mass% or less, based on 100 mass% of the total amount of monomer components constituting the acrylic polymer. Preferably it is 1 mass % or less. If the above-mentioned ratio is 10 mass % or less, discoloration (yellowing) caused by ultraviolet rays is less likely to occur, and the following b ^* value can be further reduced. Moreover, the ratio of the cyclic nitrogen-containing monomer is preferably within the above range.

Examples of the above carboxyl group-containing monomer include: (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, methacrylic acid, (meth)acrylic acid carboxyethyl ester, Carboxypentyl (meth)acrylate, etc. The above-mentioned carboxyl group-containing monomer also includes acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride.

The ratio of the carboxyl group-containing monomer is not particularly limited, but is preferably 10 mass% or less, more preferably 5 mass% or less, and still more preferably 100 mass% or less of the total amount of monomer components constituting the acrylic polymer. Preferably, it is 1 mass % or less. If the above ratio is 10% by mass or less, an adhesive layer that is less likely to cause metal corrosion due to carboxyl groups can be formed.

Examples of the cyclic ether group-containing monomer include a polymerizable functional group having an unsaturated double bond such as a (meth)acryl group or a vinyl group, and a cyclic ether group such as an epoxy group or an oxetanyl group. Like ether base. Examples of the epoxy group-containing monomer include: (glycidylmeth)acrylate, methylglycidyl(meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc. Examples of the oxetanyl-containing monomer include: (meth)acrylic acid 3-oxetanylmethyl ester, (meth)acrylic acid 3-methyl-oxetanylmethyl ester, (meth)acrylic acid 3 -Ethyl-oxetanyl methyl ester, (meth)acrylic acid 3-butyl-oxetanyl methyl ester, (meth)acrylic acid 3-hexyl-oxetanyl methyl ester, etc.

Examples of the (meth)acrylic acid alkoxyalkyl ester include: (meth)acrylic acid 2-methoxyethyl ester, (meth)acrylic acid 2-ethoxyethyl ester, methoxytriethylenediethylene Alcohol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, (meth)acrylate ) 4-ethoxybutyl acrylate, etc.

Examples of the silicon atom-containing monomer include: 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and 4-vinylbutyltrimethoxysilane. Silane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloxydecyltrimethoxysilane silane, 10-acryloxydecyltrimethoxysilane, 10-methacryloxydecyltriethoxysilane, 10-acryloxydecyltriethoxysilane, etc.

Examples of the sulfonic acid group-containing monomer include sodium vinyl sulfonate and the like. Examples of the (meth)acrylate having an aromatic hydrocarbon group include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. Examples of the vinyl esters include vinyl acetate, vinyl propionate, and the like. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, vinyltoluene, and the like. Examples of the olefins or dienes include ethylene, propylene, butadiene, isoprene, isobutylene, and the like. Examples of the vinyl ethers include vinyl alkyl ethers and the like. Examples of the glycol monomer include polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol. (meth)acrylate, etc.

Furthermore, as the said other copolymerizable monomer, a (meth)acrylic acid alkyl ester having an alkyl group having 6 or more carbon atoms at the ester terminal may also be included. Among them, the ratio of alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms at the end of the ester is not particularly limited, but is preferably 100% by mass of the total amount of monomer components constituting the acrylic polymer. It is 10 mass % or less, more preferably 5 mass % or less, still more preferably 1 mass % or less. If the above ratio is 10% by mass or less, the degree of sebum swelling can be suppressed even further. Moreover, the total ratio of the (meth)acrylic acid alkyl ester which has an alkyl group with 5 or more carbon atoms at an ester terminal, and (meth)acrylic acid methyl ester may be in the said range.

Furthermore, in order to adjust the cohesive force of the adhesive and make the step absorption more excellent, it is preferable to include a polyfunctional monomer as the above-mentioned other copolymerizable monomer. The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as (meth)acryl groups or vinyl groups. Only one type of the above-mentioned polyfunctional monomer may be used, or two or more types may be used.

Examples of the polyfunctional monomer include: hexanediol di(meth)acrylate, dodecanediol di(meth)acrylate, butylene glycol di(meth)acrylate, (poly) Ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate Acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, (meth)acrylate vinyl acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, polyurethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate, etc. Among them, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferred.

The ratio of the polyfunctional monomer is not particularly limited, but is preferably 3% by mass or less (for example, 0.001 to 3% by mass), more preferably 100% by mass of the total monomer components constituting the acrylic polymer. It is 0.5 mass % or less (for example, 0.002-0.5 mass %), More preferably, it is 0.1 mass % or less (for example, 0.005-0.1 mass %). If the above ratio is within the above range, the crosslinking density can be appropriately increased, whereby the tensile residual stress value can be easily appropriately reduced, and a structure with excellent step absorption can be formed.

The content ratio of the acrylic polymer in the adhesive layer of the present invention is not particularly limited. It is preferably 50 mass% or more (for example, 50 to 100 mass%) relative to 100 mass% of the adhesive layer of the present invention. Preferably, it is 80 mass % or more (for example, 80-100 mass %), More preferably, it is 90 mass % or more (for example, 90-100 mass %).

The above-mentioned acrylic polymer is obtained by polymerizing monomer components. The polymerization method is not particularly limited, and examples include a solution polymerization method, an emulsion polymerization method, a block polymerization method, a polymerization method using active energy ray irradiation (active energy ray polymerization method), and the like. Moreover, the obtained acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

During the polymerization of the monomer components, various common solvents can be used. Examples of the solvent include: esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane and methylcyclohexane and other alicyclic hydrocarbons; organic solvents for ketones such as methyl ethyl ketone and methyl isobutyl ketone. Only one type of solvent may be used, or two or more types of solvents may be used.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization of the monomer component are not particularly limited and can be appropriately selected and used. Furthermore, the weight average molecular weight of the acrylic polymer can be controlled according to the usage amounts of the polymerization initiator and chain transfer agent and the reaction conditions, and the usage amounts can be appropriately adjusted according to their types. As a specific example of solution polymerization, the reaction is performed by adding a polymerization initiator under a flow of inert gas such as nitrogen, and is usually carried out under reaction conditions of about 50 to 70° C. for about 5 to 30 hours.

As a polymerization initiator used for polymerization of the monomer component, a thermal polymerization initiator, a photopolymerization initiator (photoinitiator), etc. can be used depending on the type of polymerization reaction. Only one type of polymerization initiator may be used, or two or more types of polymerization initiators may be used.

The thermal polymerization initiator is not particularly limited, and examples thereof include azo polymerization initiators, peroxide polymerization initiators, redox polymerization initiators, and the like.

Examples of the azo polymerization initiator include: 2,2'-azobisisobutyronitrile (hereinafter sometimes referred to as "AIBN"), 2,2'-azobis-2-methylbutyronitrile (hereinafter sometimes referred to as "AMBN"), 2,2'-azobis(2-methylpropionate)dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, azobis Isovaleronitrile, 2,2'-Azobis(2-amidinopropane) dihydrochloride, 2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl) Propane] dihydrochloride, 2,2'-Azobis(2-methylpropionamidine) disulfate, 2,2'-Azobis(N,N'-dimethyleneisobutylamidine) , 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (trade name "VA-057", manufactured by Wako Pure Chemical Industries, Ltd.), etc.

Examples of the peroxide-based polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, tert-butyl peroxymaleate, and di(2-ethylhexyl peroxydicarbonate). ester), di(4-tert-butylcyclohexyl peroxydicarbonate), di-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate , tert-butyl pivalate peroxide, dilauryl peroxide, di-n-octyl peroxide, (2-ethylhexanoic acid) 1,1,3,3-tetramethylbutyl peroxide, peroxide Bis(4-methylbenzoyl), dibenzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-di(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide base, hydrogen peroxide, etc.

Examples of the redox polymerization initiator include a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate, and a combination of a peroxide and a reducing agent.

The usage amount of the thermal polymerization initiator is preferably 1 part by mass or less, more preferably 0.005 to 1 part by mass, and still more preferably 0.02 part by mass relative to 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. ~0.5 parts by mass. If the above usage amount is 0.005 parts by mass or more, the molecular weight of the acrylic polymer will be easily controlled to be smaller, the residual stress of the adhesive layer will become higher, and the step absorption will tend to become better.

Examples of the photopolymerization initiator include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketool-based photopolymerization initiators, and aromatic sulfonyl chloride-based photopolymerization initiators. Initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzil-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator Agent, 9-oxosulfide𠮿 It is a photopolymerization initiator, a phosphine oxide-based photopolymerization initiator, a titanocene-based photopolymerization initiator, etc. Among them, benzoin ether-based photopolymerization initiators and acetophenone-based photopolymerization initiators are preferred.

Examples of the benzoin ether photopolymerization initiator include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-di Phenylethane-1-one, anisole methyl ether, etc. Examples of the acetophenone-based photopolymerization initiator include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 1-hydroxycyclohexyl Phenylketone, 4-phenoxydichloroacetophenone, 4-(tert-butyl)dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy -2-Methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, etc. Examples of the α-ketool photopolymerization initiator include: 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane- 1-Keto etc. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl chloride and the like. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime and the like.

Examples of the benzoin-based photopolymerization initiator include benzoin and the like. Examples of the benzilyl-based photopolymerization initiator include benzoyl and the like. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoyl benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyethylene. Benzophenone etc. Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal and the like. As the above 9-oxosulfide𠮿 It is a photopolymerization initiator, for example: 9-oxosulfide , 2-chloro-9-oxosulfide𠮿 , 2-Methyl-9-oxosulfide𠮿 , 2,4-dimethyl-9-oxosulfide𠮿 ,2,4-Dichloro-9-oxosulfide𠮿 , 2,4-diethyl-9-oxosulfide𠮿 , isopropyl-9-oxosulfide𠮿 , 2,4-diisopropyl-9-oxysulfide𠮿 , dodecyl-9-oxosulfide𠮿 wait.

Examples of the above-mentioned phosphine oxide-based photopolymerization initiator include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide and bis(2,6-dimethoxybenzoyl)phenylphosphine oxide. (2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzyl)n-butylphosphine oxide, bis(2,6-dimethoxybenzyl) Formyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzyl)-(1-methylpropan-1-yl)phosphine oxide, (2,6-dimethoxybenzyl)tert-butylphosphine oxide, bis(2,6-dimethoxybenzyl)cyclohexylphosphine oxide, bis(2,6-dimethoxy Bis(2-methoxybenzyl)octylphosphine oxide, bis(2-methoxybenzyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2-methoxybenzyl) -(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6 -Diethoxybenzyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dibutoxybenzyl)-(2-methylpropane-1- base) phosphine oxide, bis(2,4-dimethoxybenzyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzyl) )-(2,4-dipentyloxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzyl)benzylphosphine oxide, bis(2,6-dimethoxybenzyl)phosphine oxide methyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzyl)-2-phenylethylphosphine oxide, bis(2,6-dimethoxybenzoyl) benzylphosphine oxide, bis(2,6-dimethoxybenzyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzyl)-2- Phenylethylphosphine oxide, 2,6-dimethoxybenzylbenzylbutylphosphine oxide, 2,6-dimethoxybenzylbenzyloctylphosphine oxide, bis(2,4 ,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2-methylphenylphosphine oxide , bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethyl phenylphosphine oxide, bis(2,4,6-trimethylbenzyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethyl Benzyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzyldiphenylphosphine oxide, bis(2,6-dimethoxybenzene Formyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzyl)isobutylphosphine oxide, 2,6-dimethoxybenzene Formyl-2,4,6-trimethylbenzoyl n-butylphosphine oxide, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, bis(2,4, 6-Trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane alkane, tris(2-methylbenzoyl)phosphine oxide, etc.

Examples of the titanocene-based photopolymerization initiator include bis(eta ⁵ -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole- 1-yl)-phenyl) titanium, etc.

The usage amount of the above-mentioned photopolymerization initiator is preferably 0.005 to 1 part by mass, more preferably 0.01 to 0.7 parts by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. 0.18～0.5 parts by mass. If the above usage amount is 0.005 parts by mass or more (especially 0.18 parts by mass or more), it is easy to control the molecular weight of the acrylic polymer to be smaller, the residual stress of the adhesive layer becomes higher, and the step absorption becomes further better. tendency.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, thioglycolic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto- 1-Propanol etc. The usage amount of the chain transfer agent is, for example, about 0.1 parts by mass or less relative to 100 parts by mass of the total amount of monomer components constituting the acrylic polymer.

Examples of emulsifiers used in emulsion polymerization include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl benzene sulfonate, polyoxyethylene alkyl ether ammonium sulfate, and polyoxyethylene alkyl phenyl ether sulfate. Anionic emulsifiers such as sodium; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block polymer, etc.

Furthermore, as a reactive emulsifier in which a radically polymerizable functional group such as an acrylic group or an allyl ether group is introduced, for example, commercially available emulsifiers with the trade name "AQUALON HS-10" and the trade name "HS" can be used. -20", trade name "KH-10", trade name "BC-05", trade name "BC-10", trade name "BC-20" (the above are manufactured by Daiichi Industrial Pharmaceutical Co., Ltd.), trade name "ADEKA REASOAP SE10N" (manufactured by ADEKA Co., Ltd.), etc. The reactive emulsifier is preferably incorporated into the polymer chain after polymerization, thereby improving water resistance. The amount of emulsifier used is preferably 5 parts by mass or less, more preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. In terms of polymerization stability or mechanical stability, From a viewpoint, it is more preferably 0.5 to 1 part by mass.

The Tg of the acrylic polymer is preferably -70 to 30°C, more preferably -60 to 20°C, further preferably -50 to 20°C. If Tg is within the above range, the adhesion can be improved. The Tg of the above-mentioned acrylic polymer is a theoretical value calculated based on the Fox formula.

In this specification, regarding the Tg of the homopolymer of various monomer components used in the Fox formula, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc, 1989) are used. Furthermore, for monomers with multiple values described in this document, the highest value is used. In the case where it is not described in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989), the value obtained by the following measurement method is used (refer to Japanese Patent Laid-Open No. 2007-51271 ).

Specifically, 100 parts by mass of the monomer, 0.2 parts by mass of azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as the polymerization solvent were put into a reactor equipped with a thermometer, a stirrer, a nitrogen introduction pipe, and a reflux cooling pipe. Circulate nitrogen gas while stirring for 1 hour. After removing the oxygen in the polymerization system in this way, the temperature was raised to 63°C and the reaction was carried out for 10 hours. Next, it was cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by mass. Next, the homopolymer solution was cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of approximately 2 mm. The test sample was punched into a disk shape with a diameter of 7.9 mm, clamped with parallel plates, and a viscoelasticity testing machine (trade name "ARES", manufactured by Rheometrics) was used to apply shear strain at a frequency of 1 Hz and at a temperature The viscoelasticity was measured in shear mode at a temperature rise rate of 5°C/min in the range of -70 to 150°C, and the peak temperature of tan δ (loss tangent) was taken as the Tg of the homopolymer.

The weight average molecular weight of the acrylic polymer is preferably 400,000 to 2.5 million, more preferably 600,000 to 2.2 million. If the weight average molecular weight is within the above range, the tensile residual stress of the adhesive layer will be reduced, and the step absorption will tend to be further improved. In addition, the said weight average molecular weight means the value measured by gel permeation chromatography (GPC) and calculated in polystyrene conversion.

The adhesive forming the adhesive layer of the present invention is not particularly limited and may also include a cross-linking agent. For example, the acrylic polymer in the acrylic adhesive layer can be cross-linked to control the gel fraction. Only one type of cross-linking agent may be used, or two or more types of cross-linking agents may be used.

The cross-linking agent is not particularly limited, and examples thereof include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, and metal alkane Oxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, amines cross-linking agent, polysiloxane-based cross-linking agent, silane-based cross-linking agent, etc.

The content of the cross-linking agent is not particularly limited, but it is preferably 5 parts by mass or less, more preferably 0.001 to 5 parts by mass, and still more preferably 0.001 to 4 parts by mass, based on 100 parts by mass of the acrylic polymer. Particularly preferably, it is 0.001 to 3 parts by mass.

Examples of the isocyanate-based crosslinking agent (polyfunctional isocyanate compound) include lower grades such as 1,2-ethylidene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate. Aliphatic polyisocyanates; alicyclic polyisocyanates such as cyclopentyl diisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate; 2,4-toluene diisocyanate Isocyanates, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and other aromatic polyisocyanates. Examples of the isocyanate cross-linking agent include: trimethylolpropane/toluene diisocyanate adduct (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane/ Hexamethylene diisocyanate adduct (trade name "Coronate HL", manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane/xylylene diisocyanate adduct (trade name "Takenate D-110N" , manufactured by Mitsui Chemicals Co., Ltd.) and other commercially available products.

When an isocyanate cross-linking agent is used as the cross-linking agent, the content of the cross-linking agent is not particularly limited, but it is preferably 5 parts by mass or less based on 100 parts by mass of the acrylic polymer, and more preferably 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, particularly preferably 0.02 to 3 parts by mass.

Furthermore, in the aqueous dispersion of the modified acrylic polymer produced by emulsion polymerization, an isocyanate cross-linking agent does not need to be used. However, if necessary, in order to easily react with water, a blocked isocyanate can also be used. Department of cross-linking agent.

Examples of the epoxy-based crosslinking agent (polyfunctional epoxy compound) include: N,N,N',N'-tetraglycidyl metaxylylenediamine, diglycidylaniline, 1,3- Bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether Glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether Glycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris(2-hydroxyethyl)triglycidyl isocyanurate, isophthalic acid Examples include phenol diglycidyl ether, bisphenol S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of the epoxy-based crosslinking agent include commercially available products such as the trade name "Tetrad C" (manufactured by MITSUBISHI GAS CHEMICAL Co., Ltd.).

When an epoxy cross-linking agent is used as the cross-linking agent, the content of the cross-linking agent is not particularly limited. It is preferably 5 parts by mass or less based on 100 parts by mass of the acrylic polymer, and more preferably The amount is 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, and particularly preferably 0.02 to 3 parts by mass.

As the above-mentioned peroxide-based cross-linking agent, any one that generates radical active species by heat and cross-links the above-mentioned acrylic polymer can be used appropriately, but in consideration of workability and stability, it is preferably Use peroxide with a half-life temperature of 80 to 160°C in 1 minute, preferably 90 to 140°C.

Examples of the peroxide-based cross-linking agent include bis(2-ethylhexyl peroxydicarbonate) (1-minute half-life temperature: 90.6°C), bis(4-tert-butylcycloperoxydicarbonate) Hexyl ester) (1-minute half-life temperature: 92.1°C), dibutyl peroxydicarbonate (1-minute half-life temperature: 92.4°C), tert-butyl peroxyneodecanoate (1-minute half-life temperature: 103.5°C) , tert-hexyl pivalate peroxide (half-life temperature in 1 minute: 109.1°C), tert-butyl pivalate peroxide (half-life temperature in 1 minute: 110.3°C), dilauric peroxide (half-life temperature in 1 minute: 110.3°C) 116.4℃), di-n-octyl peroxide (half-life temperature in 1 minute: 117.4℃), 1,1,3,3-tetramethylbutyl peroxide (2-ethylhexanoic acid) (half-life temperature in 1 minute: 124.3 ℃), dibenzoyl peroxide (half-life temperature in 1 minute: 128.2℃), dibenzoyl peroxide (half-life temperature in 1 minute: 130.0℃), tert-butyl peroxide isobutyrate (half-life temperature in 1 minute: 136.1°C), 1,1-di(tert-hexyl peroxide) cyclohexane (half-life temperature in 1 minute: 149.2°C), etc.

The half-life of the above-mentioned peroxide cross-linking agent is an index showing the decomposition rate of the peroxide, and refers to the time until the remaining amount of the peroxide becomes half. The decomposition temperature used to obtain the half-life at any time or the half-life time at any temperature is described in the manufacturer's catalog, for example, in the "Organic Peroxide Catalog, 9th Edition (May 2003)" of NOF Co., Ltd. "wait. In addition, as a method for measuring the decomposition amount of peroxide remaining after the reaction treatment, for example, HPLC (High Performance Liquid Chromatography, high-speed liquid chromatography) can be used. More specifically, for example, about 0.2 g of the reaction-treated adhesive can be taken out each time, immersed in 10 ml of ethyl acetate, shaken with a shaker at 25°C and 120 rpm for 3 hours, and then extracted. Let sit at room temperature for 3 days. Next, add 10 ml of acetonitrile, shake at 120 rpm for 30 minutes at 25°C, and inject about 10 μl of the extract obtained by filtering through a membrane filter (0.45 μm) into HPLC for analysis, and set it as the process after reaction treatment. Amount of oxides.

When a peroxide cross-linking agent is used as the cross-linking agent, the content of the cross-linking agent is not particularly limited, but is preferably 2 parts by mass or less based on 100 parts by mass of the acrylic polymer. Preferably, it is 0.02-2 mass parts, More preferably, it is 0.05-1 mass part.

Furthermore, as the cross-linking agent, an organic cross-linking agent or a polyfunctional metal chelate may be used together. Multifunctional metal chelates are those in which multivalent metals and organic compounds are covalently or coordinately bonded. Examples of polyvalent metal atoms include: Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti wait. Examples of atoms in the covalently bonded or coordinately bonded organic compound include oxygen atoms, and examples of the organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, and the like.

From the viewpoint of improving adhesive strength, the acrylic adhesive (the adhesive forming the adhesive layer of the present invention) may contain an acrylic oligomer. The acrylic oligomer is preferably a polymer having a smaller weight average molecular weight than the acrylic polymer. The above-mentioned acrylic oligomer functions as an adhesion-imparting resin and has the advantage of increasing the adhesive force without increasing the dielectric constant. The adhesive containing the acrylic oligomer in a relatively low amount can suppress the swelling degree of sebum to a low level. The usage amount of the acrylic oligomer is, for example, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less based on 100 parts by mass of the acrylic polymer.

The Tg of the acrylic oligomer is preferably higher than the Tg of the acrylic polymer, and is, for example, 0 to 200°C, preferably 20 to 150°C, and more preferably 40 to 120°C. If Tg is within the above range, the adhesive force can be improved. In addition, the Tg of the above-mentioned acrylic oligomer is the same as the Tg of the above-mentioned acrylic polymer, and is a theoretical value calculated based on the Fox formula.

The adhesive layer of the present invention may further contain a silane coupling agent. If it contains a silane coupling agent, when the adhesive layer of the present invention is applied to a hydrophilic adherend such as glass, the water resistance of the interface can be improved. Only one type of the above-mentioned silane coupling agent may be used, or two or more types may be used.

Examples of the silane coupling agent include: 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropylmethyldiethoxy silane coupling agents containing epoxy groups such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl methyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine, N-phenyl-γ- Silane coupling agents containing amine groups such as aminopropyltrimethoxysilane; 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. containing (methyl )Acrylyl-based silane coupling agent; 3-isocyanatopropyltriethoxysilane and other isocyanate-containing silane coupling agents, etc. Among these, γ-glycidoxypropyltrimethoxysilane is preferred as the silane coupling agent.

The content of the silane coupling agent in the adhesive layer of the present invention is not particularly limited. It is preferably 1 part by mass or less, more preferably 0.01 to 1 part by mass, and still more preferably 100 parts by mass of the acrylic polymer. It is 0.02~0.6 parts by mass. If the above content is within the above range, both good re-peelability and durability can be achieved.

The adhesive layer of the present invention may optionally contain cross-linking accelerators, adhesion-imparting resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents within the scope that does not impair the effects of the present invention. Agents, fillers (metal powder, organic fillers, inorganic fillers, etc.), colorants (pigments or dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, seasoning agents Leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, granules, foils and other additives. Only one type of each of the above-mentioned additives may be used, or two or more types may be used.

The adhesive layer of the present invention is formed of the above-mentioned adhesive containing the above-mentioned acrylic polymer. The thickness of the adhesive layer of the present invention is not particularly limited, but is, for example, about 1 to 400 μm. In addition, the thickness of the adhesive layer of the present invention can be appropriately set to a preferred range according to the manufacturing method of the acrylic polymer used for the adhesive. For example, when an acrylic polymer is produced by solution polymerization or the like, the thickness of the adhesive layer is preferably 1 to 100 μm, more preferably 2 to 50 μm, still more preferably 2 to 40 μm, and particularly preferably is 5~35 μm. Furthermore, when an acrylic polymer is produced by active energy ray polymerization or the like, the thickness of the adhesive layer is preferably 50 to 400 μm, more preferably 75 to 300 μm, and still more preferably 100 to 200 μm.

The 300% tensile residual stress value of the adhesive layer of the present invention is 0.1-6 N/cm ² , preferably 0.5-5.8 N/cm ² , and more preferably 1.0-5.6 N/cm ² . By setting the above-mentioned 300% tensile residual stress value to 0.1 N/cm ² or more, it has characteristics such as no paste sag during processing. By setting the above-mentioned 300% tensile residual stress value to 6 N/cm ² or less, step absorption becomes good. Furthermore, the above-mentioned 300% tensile residual stress value (N/cm ² ) is calculated as follows: the adhesive layer (preferably with a thickness of about 400 μm) is placed in the length direction in an environment of 23°C. Stretch to an elongation (strain) of 300% and maintain the elongation. Find the tensile load applied to the adhesive layer 300 seconds after the end of stretching. Divide the tensile load by the initial cross-sectional area of the adhesive layer. (the cross-sectional area before stretching) is obtained. Furthermore, the initial elongation of the adhesive layer is 100%.

The storage modulus of the adhesive layer of the present invention at 70° C. is preferably 7.0×10 ⁴ Pa or less, more preferably 6.5×10 ⁴ Pa or less, further preferably 6.0×10 ⁴ Pa or less. If the above-mentioned storage modulus is 7.0×10 ⁴ Pa or less, the 300% tensile residual stress value tends to become lower, and the step absorption becomes further improved. The storage modulus at 70° C. is, for example, 1.0×10 ³ Pa or more, preferably 1.0×10 ⁴ Pa or more.

The storage modulus of the adhesive layer of the present invention at 25°C is preferably 1.0×10 ⁴ Pa or more, more preferably 5.0×10 ⁴ Pa or more, and further preferably 1.0×10 ⁵ Pa or more. Moreover, the storage modulus at 25°C is, for example, 1.0×10 ⁷ Pa or less, preferably 1.0×10 ⁶ Pa or less.

The storage modulus at 70° C. and the storage modulus at 25° C. can be determined, for example, by dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device (trade name “ARES”, manufactured by Rheometric Corporation). In this measurement, the measurement mode is set to shear mode, the measurement temperature range is set to -70°C to 150°C, for example, the temperature rise rate is set to 5°C/min, for example, and the frequency is set to 1 Hz, for example.

The gel fraction of the adhesive layer of the present invention is preferably 30 to 85 mass%, more preferably 35 to 80 mass%, and further preferably 40 to 70 mass%. If the above-mentioned gel fraction is 30% by mass or more, the processability and operability of the adhesive become good. If the above-mentioned gel fraction is 85% by mass, the stress on the step is relaxed, and the step absorption becomes further improved. The above-mentioned gel fraction can be controlled by adjusting the added amount of the cross-linking agent or the polyfunctional monomer and taking into account the influence of the cross-linking treatment temperature or the cross-linking treatment time.

The b ^* value of the adhesive layer of the present invention after the following ultraviolet irradiation test is preferably 2.0 or less, more preferably 1.6 or less, and still more preferably 1.2 or less. If the above b ^* value is 2.0 or less, the adhesive layer will not easily change color when exposed to ultraviolet rays. The above b ^* value is the b ^* value of the L ^* a ^* b ^* colorimetric system, which can be based on JIS Z 8781-4 (2013), for example, by a simple spectrophotometer (trade name "DOT-3C", Murakami Color (manufactured by Institute of Technology Co., Ltd.). <Ultraviolet irradiation test> Set the adhesive layer to a thickness of 250 μm, and laminate alkali glass on both sides to make a test piece. The wavelength range is 300~400 nm, the illumination is 110 W/m ² , and the black panel set temperature is 83°C. After irradiating the above test piece with ultraviolet light for 240 hours using a xenon arc lamp, the b ^* value of the above adhesive layer was measured.

When the thickness of the adhesive layer of the present invention is 100 μm, the haze value is preferably 2% or less, more preferably 1.5% or less, and further preferably 1% or less. If the haze value is 2% or less, the transparency required when the adhesive layer of the present invention is used for an optical member can be satisfied. The haze value can be measured in accordance with JIS K 7136 using a haze meter, for example.

The protrusion amount of the adhesive layer of the present invention measured by the following sebum swelling test is preferably less than 2 mm, more preferably less than 1 mm. The lower the above-mentioned protrusion, the better, and ideally it is 0 mm. ＜Sebum swelling test＞ A sample composed of polyethylene terephthalate (100 μm)/adhesive layer (100 μm)/glass was produced in a size of 5 cm × 10 cm, and then immersed in squalene and oleic acid. Mix the artificial sebum liquid with a mass ratio of 1:1 and place it at 60°C for 5 days. Take out the sample from the artificial sebum liquid and measure the protrusion amount of the adhesive layer from the end of the glass.

The method of making the adhesive layer of the present invention is not particularly limited. For example, the following method can be used: applying (coating) an adhesive (adhesive composition) containing the above-mentioned acrylic polymer to a base material or a release liner. , drying and hardening the obtained adhesive composition layer; or coating (coating) the above-mentioned adhesive composition on the base material or release liner, and irradiating the obtained adhesive composition layer with active energy rays to cure. Moreover, if necessary, you may further heat-dry.

Examples of the active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, or ultraviolet rays, and ultraviolet rays are particularly preferred. In addition, the irradiation energy, irradiation time, irradiation method, etc. of active energy rays are not particularly limited.

The above-mentioned adhesive composition can be produced by known or even conventional methods. For example, a solvent-based adhesive composition can be prepared by optionally mixing additives into a solution containing the above-mentioned acrylic polymer. For example, an active energy ray-curable adhesive composition can be produced by optionally mixing an additive into a mixture of monomer components constituting the acrylic polymer or a partial polymer thereof.

In addition, a known coating method can be used for coating (coating) of the said adhesive composition. For example, gravure roll coaters, reverse roll coaters, contact roll coaters, dip roll coaters, rod coaters, blade coaters, spray coaters, notch wheel coaters, Coating machines such as direct coaters.

The heating and drying temperature of the solvent-based adhesive composition is preferably 40 to 200°C, more preferably 50 to 180°C, and further preferably 70 to 170°C. An appropriate drying time can be suitably used, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, more preferably 10 seconds to 5 minutes.

When the adhesive layer is formed by active energy ray irradiation, the acrylic polymer can be produced from the monomer components and the adhesive layer can be formed. When the above-mentioned monomer components are irradiated with active energy rays, a part thereof may be polymerized in advance to form a slurry. Ultraviolet irradiation can use high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, etc.

An adhesive sheet can be obtained using the adhesive layer of the present invention. Furthermore, the adhesive sheet having the adhesive layer of the present invention is sometimes referred to as the "adhesive sheet of the present invention."

The adhesive sheet of the present invention may be a so-called "base material-free type" adhesive sheet that does not have a base material (base material layer), or may be a base material type adhesive sheet. Furthermore, in this specification, the "substrate-free type" adhesive sheet is sometimes referred to as "substrate-free adhesive sheet", and the adhesive sheet with a substrate type is sometimes referred to as "substrate-attached adhesive sheet". Sheet". Examples of the base-free adhesive sheet include a double-sided adhesive sheet containing only the adhesive layer of the present invention, or a double-sided adhesive sheet containing the adhesive layer of the present invention and other adhesive layers (other than the adhesive layer of the present invention). Adhesive layer) double-sided adhesive sheet, etc. In addition, the adhesive sheet with a base material is an adhesive sheet including a base material and an adhesive layer of the present invention formed on at least one side of the base material. For example, an adhesive sheet having the adhesive layer of the present invention on one side of the base material can be used. A single-sided adhesive sheet with an adhesive layer on both sides of the base material, a double-sided adhesive sheet with an adhesive layer of the present invention on both sides of the base material, or a base material with an adhesive layer of the present invention on one side and the other side Double-sided adhesive sheets with other adhesive layers, etc. Furthermore, the above-mentioned "base material (base material layer)" is a support, which is the part that is attached to the adherend together with the adhesive layer when the adhesive sheet of the present invention is used (attached) to the adherend. . When the adhesive sheet is used (attached), the release film (release liner) that is peeled off is not included in the above-mentioned base material.

When the adhesive sheet of the present invention is an adhesive sheet with a base material, the base material is not particularly limited, and examples include various optical films such as plastic films, anti-reflection (AR) films, polarizing plates, and phase difference plates. membrane. Examples of the base material include porous materials such as paper, cloth, and nonwoven fabrics, meshes, foam sheets, and metal foils. Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, and triacetyl. Cellulose (TAC), polypropylene, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, trade name "ARTON" (cyclic olefin polymerization Plastic materials such as cyclic olefin-based polymers such as "ZEONOR" (cyclic olefin-based polymer, manufactured by JSR Co., Ltd.) and "ZEONOR" (cyclic olefin-based polymer, manufactured by ZEON Co., Ltd.). Furthermore, only one type of plastic material can be used, or two or more types of plastic materials can be used.

The thickness of the above-mentioned base material is not particularly limited, but is preferably 12 to 75 μm, for example. In addition, the above-mentioned base material may have any form of a single layer or a plurality of layers. In addition, the surface of the above-mentioned base material can be appropriately subjected to known and conventional surface treatments such as corona discharge treatment, physical treatment such as plasma treatment, chemical treatment such as primer treatment, and the like.

The adhesive sheet of the present invention can be provided with a release liner on the surface (adhesive surface) of the adhesive layer before use. Furthermore, when the adhesive sheet of the present invention is a double-sided adhesive sheet, each adhesive surface can be protected by two release liners, or a release liner with both sides serving as release surfaces can be used. It is wound into a roll shape (winding body) for protection. The release liner is used as a protective material for the adhesive layer and is peeled off when it is attached to the adherend. Furthermore, when the adhesive sheet of the present invention is a substrate-less adhesive sheet, the release liner also serves as a support for the adhesive layer. Furthermore, the release liner may not necessarily be provided.

As the above-mentioned release liner, conventional release paper can be used without particular limitation. Examples thereof include: a base material having a release treatment layer, a low-adhesion base material containing a fluoropolymer, or a low-adhesion base material containing a non-polar polymer. Adhesive substrates, etc. Examples of the substrate having a release treatment layer include plastic films or papers surface-treated with release treatment agents such as polysiloxane-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide. Examples of the fluorine-based polymer in the low-adhesion base material containing a fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and tetrafluoroethylene-hexafluoroethylene. Propylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc. Examples of the nonpolar polymer include olefin-based resins (for example, polyethylene, polypropylene, etc.). Furthermore, the release liner can be formed by known or even conventional methods. In addition, the thickness of the release liner is not particularly limited.

The adhesive sheet of the present invention is not particularly limited and can be manufactured according to known or even commonly used manufacturing methods. For example, when the adhesive sheet of the present invention is a base-less adhesive sheet, it is obtained by forming the adhesive layer of the present invention on a release liner using the above method. In addition, when the adhesive sheet of the present invention is an adhesive sheet with a base material, it can be obtained by directly forming the adhesive layer of the present invention on the surface of the base material (direct printing method), or it can be obtained by the following method Obtain: After temporarily forming the adhesive layer of the present invention on a release liner, it is transferred (laminated) to the base material, thereby setting the adhesive layer of the present invention on the base material (transfer method).

The adhesive layer of the present invention and the adhesive sheet of the present invention are preferably optical members used for optical purposes. The above-mentioned optical member refers to a member having optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.). The substrate constituting the above-mentioned optical member is not particularly limited. Examples thereof include substrates constituting equipment (optical equipment) such as display devices (image display devices) and input devices, or substrates used in such equipment. Examples thereof include polarized light. plate, wavelength plate, phase difference plate, optical compensation film, brightness enhancement film, light guide plate, reflective film, anti-reflective film, hard coat film (film that has been hard coated on at least one side of a plastic film such as PET film), transparent film Conductive films, design films, decorative films, surface protection sheets, lenses, lenses, color filters, transparent substrates (glass sensors, glass display panels (LCD (Liquid Crystal Display), etc.), etc.), attachments Glass substrates such as glass plates with transparent electrodes, etc.), or substrates on which these are laminated (these are sometimes collectively referred to as "functional films"), etc. Moreover, these films may also have a printing layer, a conductive polymer layer, etc. Furthermore, the above-mentioned "plate" and "film" respectively include plate-like, film-like, sheet-like and other forms. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet".

The adhesive layer of the present invention and the adhesive sheet of the present invention are particularly preferably used for attaching to metal films or metal electrodes in optical applications. Examples of the metal thin film include thin films containing metals, metal oxides, or mixtures thereof, and are not particularly limited. Examples include thin films of indium tin oxide (ITO), ZnO, SnO, and cadmium tin oxide (CTO). The thickness of the metal thin film is not particularly limited, but is approximately 10 to 200 nm. Generally, a metal thin film such as ITO is provided on a transparent plastic film base material such as a polyethylene terephthalate film (PET film) and used as a transparent conductive film. When the adhesive sheet of the present invention is attached to a metal film, it is preferably used in such a manner that the surface on the adhesive layer side becomes the adhesive surface attached to the side of the metal film.

Examples of the metal electrode include electrodes containing metals, metal oxides, or mixtures thereof, and are not particularly limited. Examples include electrodes of ITO, silver, copper, and CNT (Carbon Nanotube, carbon nanotube).

An example of a specific use of the adhesive sheet of the present invention is an adhesive sheet for touch panels used in the manufacture of touch panels. Adhesive sheets for touch panels are used, for example, in the manufacture of electrostatic capacitive touch panels to combine a transparent conductive film provided with a metal film such as ITO, a polymethyl methacrylate resin (PMMA) board, and a hard coat film. , glass lens, etc. The above-mentioned touch panel is not particularly limited, and can be used, for example, in mobile phones, tablet computers, portable information terminals, etc.

As a more specific example, an example of an electrostatic capacitive touch panel using the adhesive layer of the present invention or the adhesive sheet of the present invention is shown in FIG. 1 . In Figure 1, 1 represents an electrostatic capacitive touch panel, 11 represents a decorative panel, 12 represents an adhesive layer or adhesive sheet, 13 represents an ITO film, and 14 represents a hard coating film. The decorative panel 11 is preferably a glass plate or a transparent acrylic resin plate (PMMA plate). In addition, the ITO film 13 is preferably provided with an ITO film on a glass plate or a transparent plastic film (especially a PET film). The hard coat film 14 is preferably a transparent plastic film such as a PET film that has been hard coated. Since the above-mentioned electrostatic capacitive touch panel 1 uses the adhesive layer of the present invention or the adhesive sheet of the present invention, it has high sebum resistance, can make the thickness thinner, and has excellent step absorption such as printing steps, making the operation smooth. Excellent stability. In addition, the appearance and visibility are good. [Example]

The following examples are given to illustrate the present invention in more detail, but the present invention is not limited by these examples in any way. In addition, unless otherwise mentioned, "%" indicating content means mass %. In addition, all compounding parts (mass parts) are values converted from solid content (non-volatile content).

Example 1 67 parts by mass of butyl acrylate (BA), 19 parts by mass of 4-hydroxybutyl acrylate (4BHA), 14 parts by mass of cyclohexyl acrylate (CHA), and a photopolymerization initiator (trade name "Omnirad 184", BASF Corporation (manufactured by BASF) and 0.09 parts by mass of a photopolymerization initiator (trade name "Omnirad 651", manufactured by BASF) were put into a four-necked flask to prepare a monomer mixture. Next, the above-mentioned monomer mixture is exposed to ultraviolet rays in a nitrogen atmosphere to perform partial photopolymerization, thereby obtaining a partial polymer (acrylic polymer slurry) with a polymerization rate of about 10% by mass.

To the total amount of the obtained acrylic polymer slurry were added 8 parts by mass of 4-hydroxybutyl acrylate, 9 parts by mass of 2-hydroxyethyl acrylate (HEA), and dipentaerythritol pentaacrylate (trade name "KAYARAD DPHA", Japaneseized Pharmaceutical Co., Ltd.) 0.02 parts by mass, photopolymerization initiator (trade name "Omnirad 651", manufactured by BASF) 0.3 parts by mass, and silane coupling agent (trade name "KBM-403", γ-glycidoxy propyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) 0.35 parts by mass, and then uniformly mixed them to prepare an adhesive composition.

Next, the adhesive composition prepared above was applied to a polyester film with a thickness of 38 μm (trade name "DIAFOIL MRF", Mitsubishi Chemical Co., Ltd.) to form a coating layer. Next, a 38 μm-thick polyester film (trade name " DIAFOIL MRE", manufactured by Mitsubishi Chemical Co., Ltd.). Thereby, the coating layer of the adhesive composition is shielded from the influence of oxygen. The sheet with the coating layer thus obtained was irradiated with ultraviolet light with an illumination intensity of 5 mW/cm ² (measured using "TOPCON UVR-T1" with maximum sensitivity at about 350 nm) using a chemical lamp (manufactured by Toshiba Corporation). 360 seconds to harden the coating layer and form an adhesive layer to produce an adhesive sheet. The polyester film covering both sides of the adhesive layer functions as a release liner.

Examples 2 to 3, Comparative Examples 1 to 2 An adhesive layer and an adhesive sheet were produced in the same manner as in Example 1, except that the types and amounts of the monomer components used and the photopolymerization initiator were changed as shown in the table. In addition, the chain transfer agent used in Example 3 is a trade name "NOFMER MSD" (manufactured by NOF Co., Ltd.). In addition, the acrylic oligomer used in Comparative Example 2 was prepared as follows.

(Preparation of acrylic oligomer) As monomer components, 60 parts by mass of methyl methacrylate (MMA, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 40 parts by mass of dicyclopentyl methacrylate (DCPMA, manufactured by Hitachi Chemical Industries, Ltd.) were used as chain transfer 30 parts by mass of α-thioglycerol (manufactured by Tokyo Chemical Industry Co., Ltd.) as an agent, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN, manufactured by Kishida Chemical Co., Ltd.) as a polymerization initiator, and 60 parts by mass of ethyl acetate as a polymerization solvent were put into a separable flask, and the mixture was stirred for 1 hour while introducing nitrogen gas. In this way, after removing the oxygen in the polymerization system, the temperature was raised to 70°C and reacted for 2 hours, and then further reacted at 80°C for 8 hours to obtain an oligomer solution with a solid content concentration of 60% by mass. The oligomer solution was heated and dried at a vacuum of 7.5 kPa and 85°C for 1 hour to obtain an oligomer powder with a solid content concentration of 100% by mass.

＜Evaluation＞ The following evaluations were performed on the adhesive layers and adhesive sheets obtained in Examples and Comparative Examples. The results are shown in Table 1.

(1)Sebum swelling degree A sample composed of polyethylene terephthalate (100 μm)/adhesive layer (100 μm)/glass was produced in a size of 5 cm × 10 cm, and then immersed in squalene and oleic acid. Mix the artificial sebum solution with a mass ratio of 1:1 and place it at 60°C for 5 days. Thereafter, a sample was taken out from the artificial sebum solution, and the protrusion amount of the adhesive layer from the end of the glass was measured. The case where the protrusion amount was less than 2 mm was marked as ○, and the case where the protrusion amount was more than 2 mm was marked as ×.

(2) 300% tensile residual stress value Cut the adhesive sheet obtained in the Example and Comparative Example into a size of 40 mm × 40 mm. After peeling off the isolation film on one side, fold it so that the adhesive surfaces fit together 1 Next, peel off the isolation film on one side again, and attach the adhesive surfaces to each other again to make an adhesive layer sample with a size of about 10 mm × 40 mm and a thickness of about 400 μm. Set the above adhesive layer sample on a tensile testing machine with the distance between the chucks set to 20 mm, and stretch it 60 mm (300%) at a stretching speed of 200 mm/min (the distance between the chucks after stretching is 80 mm) ). The tensile position of 60 mm is fixed and maintained for 300 seconds, and then the stress value is measured, and the "300% tensile residual stress value" is calculated by the following formula. 300% tensile residual stress value (N/cm ² ) = stress value after being fixed for 300 seconds (N)/(4×adhesive sheet thickness (mm)/10)

(3) Printing step absorption Peel off the release film on one side of the adhesive sheet obtained in the Examples and Comparative Examples, attach a 100 μm thick PET film to the exposed surface, peel off the release film on the other side, and attach a printed film with a printing step of about 30 μm. The glass is attached to the exposed surface to create an evaluation sample. After the above-mentioned evaluation samples were processed in an autoclave (50°C, 5 atmospheres, 15 minutes), those where no bubbles were observed near the printing step were marked as ○, and those where bubbles were observed were marked as ×, and the printing step absorption was evaluated. sex.

(4) b ^* value after ultraviolet irradiation test Peel off the release film on one side of the adhesive sheet obtained in the Example and Comparative Example, and overlap the adhesive layer made in the same way so that the thickness becomes 250 μm. The two sides of the agent layer are laminated with alkali glass to make a test piece. Under the conditions of wavelength range 300-400 nm, illumination 110 W/m ² and black panel set temperature 83°C, the above test piece is subjected to ultraviolet rays for 240 hours using a xenon arc lamp. After irradiation, the b ^* value of the above-mentioned adhesive layer was measured. The b ^* value was measured with a simple spectrophotometer (trade name "DOT-3C", manufactured by Murakami Color Technology Research Institute Co., Ltd.).

[Table 1] (Table 1) Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Acrylic polymer slurry Alkyl (meth)acrylates BA 67 67 67 67 - 2EHA - - - - 78 Hydroxyl-containing monomer 4HBA 19 19 19 19 - HEA - - - - 4 Monomers containing alicyclic structures CHA 14 14 14 14 - Monomers containing cyclic nitrogen NVP - - - - 18 Photopolymerization initiator Omnirad 184 0.09 0.09 0.09 0.09 0.035 Omnirad 651 0.09 0.09 0.09 0.09 0.035 Add a single unit multifunctional monomer HDDA - - - - 0.088 DPHA 0.02 0.01 0.02 0.12 - Hydroxyl-containing monomer 4HBA 8 8 8 8 - HEA 9 9 9 9 17.6 Additional starter Photopolymerization initiator Omnirad 651 0.3 0.1 0.1 - - chain transfer agent - - 0.05 - - Silane coupling agent 0.35 0.35 0.35 0.35 0.35 Acrylic oligomer - - - - 11.8 sebum swelling ○ ○ ○ ○ × 300% tensile residual stress [N/cm ² ] 3.2 5.2 3.3 12 13 Printing step absorbency ○ ○ ○ × × b ^* value after ultraviolet irradiation test 0.75 0.8 1 0.7 13.5 Gel fraction [mass %] 52 60 55 86 88 Storage modulus [Pa] 25℃ 1.2×10 ⁵ 1.3×10 ⁵ 1.3×10 ⁵ 1.4×10 ⁵ 1.3×10 ⁵ 70℃ 4.5×10 ⁴ 5.0×10 ⁴ 4.5×10 ⁴ 1.0×10 ⁵ 7.6×10 ⁴

The abbreviations shown in the table are as follows. BA: Butyl acrylate (manufactured by Dong-A Gosei Co., Ltd.) 2EHA: 2-ethylhexyl acrylate (manufactured by Toa Gosei Co., Ltd.) 4HBA: 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) HEA: 2-hydroxyethyl acrylate (manufactured by Toa Gosei Co., Ltd.) CHA: cyclohexyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) NVP: N-vinyl-2-pyrrolidone (manufactured by Nippon Shokubai Co., Ltd.) HDDA: 1,6-hexanediol diacrylate DPHA: dipentaerythritol hexaacrylate

1: Electrostatic capacitive touch panel 11: Decorative panel 12: Adhesive layer or adhesive sheet 13:ITO film 14:Hard coating film

FIG. 1 is a diagram showing an example of an electrostatic capacitive touch panel using the adhesive layer or adhesive sheet of the present invention.

1: Electrostatic capacitive touch panel

11: Decorative panel

12: Adhesive layer or adhesive sheet

13:ITO film

14:Hard coating film

Claims (8)

An adhesive layer formed from an adhesive containing an acrylic polymer and having a tensile residual stress of 300% measured under the conditions of a stretching speed of 200 mm/min, a temperature of 23°C, and 300 seconds after the end of stretching. The value is 0.1~6N/cm ² ; the above-mentioned acrylic polymer includes (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1~5 at the ester end, a hydroxyl-containing monomer, and a monomer containing an alicyclic structure As the monomer component constituting the polymer, the above-mentioned monomer containing an alicyclic structure is selected from cyclohexyl (meth)acrylate and the following formula (1)

The compound represented by the following formula (2)

The represented compound and the following formula (3) [Chemical 3]

One or more of the compounds represented in the group are composed of (meth)acrylic acid alkyl esters having an alkyl group with 1 to 5 carbon atoms at the end of the above-mentioned ester relative to the total amount of monomer components constituting the above-mentioned polymer. The ratio is 40 to 82 mass %, the ratio of the above-mentioned hydroxyl group-containing monomer is 17 to 35 mass %, and the ratio of the above-mentioned alicyclic structure-containing monomer is 42 mass % or less. For example, the adhesive layer of claim 1 has a storage modulus at 70°C of 7.0×10 ⁴ Pa or less. For example, the adhesive layer of claim 1 or 2 has a gel fraction of 30 to 85 mass%. For example, in the adhesive layer of claim 1 or 2, the b ^* value after the following ultraviolet irradiation test is less than 2.0; <ultraviolet irradiation test> set the adhesive layer to a thickness of 250 μm, and laminate alkali glass on both sides to make a test The test piece was irradiated with ultraviolet light for 240 hours by a xenon arc lamp under the conditions of wavelength range 300~400nm, illumination 110W/m ² and black panel set temperature 83°C, and then the b ^* value of the adhesive layer was measured. The adhesive layer of claim 1 or 2, wherein the acrylic polymer contains a multifunctional monomer as a monomer component constituting the polymer. The adhesive layer according to claim 5, wherein the content ratio of the polyfunctional monomer is 3% by mass or less relative to the total amount of monomer components constituting the polymer. The adhesive layer of claim 1 or 2 is used for optical components. An adhesive sheet, which includes a base material and an adhesive layer according to any one of claims 1 to 7 formed on at least one side of the base material.