KR20200107832A - Adhesive layer and adhesive sheet - Google Patents

Abstract

The present invention relates to an adhesive layer having a low degree of swelling of sebum and high level difference absorbability. The adhesive layer according to the present invention includes an acrylic polymer including, as monomer ingredients forming the polymer, an alkyl (meth)acrylate end-capped with a C1-C5 alkyl group, a hydroxyl group-containing monomer and a monomer containing a specific alicyclic structure, wherein the ratio of the alkyl (meth)acrylate end-capped with a C1-C5 alkyl group is 40-82 wt%, the ratio of the hydroxyl group-containing monomer is 17-35 wt%, and the ratio of the monomer containing a specific alicyclic structure is 42 wt% or less, based on the total weight of the monomers forming the polymer. In addition, the adhesive layer has a 300% residual tension stress value of 0.1-6 N/cm^2.

Description

Adhesive layer and adhesive sheet {ADHESIVE LAYER AND ADHESIVE SHEET}

The present 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, in portable information terminals such as mobile phones, portable music players, smartphones, and tablets, input devices (touch panel mounting devices) using a combination of an image display device and a touch panel have been spreading. As a transparent conductive film used for a touch panel, it is known that a transparent plastic film base material or glass is laminated with a transparent conductive thin film (ITO film), and the transparent conductive film is laminated to another member through an adhesive layer. As the pressure-sensitive adhesive layer used for such an optical member, for example, those disclosed in Patent Documents 1 to 3 are known.

Japanese Patent Publication No. 2003-238915 Japanese Patent Publication No. 2003-342542 Japanese Patent Publication No. 2004-231723

Since the touch panel is used in a state in which the bare hand is always in contact, it is inevitable that the sebum of the hand is transferred to the touch panel. The sebum transferred to the surface of the touch panel was a problem that gradually transferred to the adhesive layer inside the touch panel, and the adhesive layer swelled by the sebum. When the adhesive layer swells, adherends are peeled or lifted. In addition, the amount of sebum in the hand varies depending on the user depending on the country or living environment, for example. In recent years, as users of touch panel mounting devices are expanding all over the world, it is required that swelling of the pressure-sensitive adhesive layer by sebum is small for various users.

Moreover, in recent years, the thickness reduction of a touch panel mounting device has progressed remarkably. For this reason, the members constituting the touch panel mounting device, for example, the pressure-sensitive adhesive layer are also required to be thinner. However, when the thickness of the pressure-sensitive adhesive layer becomes thin, there is a tendency that, for example, the step absorbency when affixed to a member having a printing step is lowered.

Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive layer having a low sebum swelling degree and excellent in step absorption properties. Further, another object of the present invention is to provide a pressure-sensitive adhesive sheet having low sebum swelling degree and excellent in step absorption property.

The present inventors, as a result of earnestly examining in order to achieve the above object, as a monomer component constituting a polymer, an alkyl (meth)acrylate having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl group-containing monomer, and a specific alicyclic structure-containing monomer It was found that the pressure-sensitive adhesive layer formed of an acrylic polymer containing an acrylic polymer each containing in a specific ratio and having a 300% tensile residual stress value of 0.1 to 6 N/cm 2 had a low sebum swelling degree and excellent step absorption property. The present invention was completed based on these findings.

That is, the present invention includes, as a monomer component constituting a polymer, an alkyl (meth)acrylate having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl group-containing monomer, and an alicyclic structure-containing monomer,

The alicyclic structure-containing monomer is cyclohexyl (meth)acrylate, the following formula (1)

Compound represented by the following formula (2)

Compound represented by, and the following formula (3)

It is one or more selected from the group consisting of compounds represented by,

The ratio of the (meth)acrylate alkyl ester having the alkyl group having 1 to 5 carbon atoms at the ester terminal to the total amount of the monomer components constituting the polymer is 40 to 82% by mass, and the ratio of the hydroxyl group-containing monomer is 17 to 35% by mass %, a pressure-sensitive adhesive layer formed of an acrylic polymer in which the proportion of the alicyclic structure-containing monomer is 42% by mass or less, and a pressure-sensitive adhesive layer having a tensile residual stress of 300% of 0.1 to 6 N/cm 2.

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

It is preferable that the said adhesive layer has a gel fraction of 30 to 85 mass %.

It is preferable that the said pressure-sensitive adhesive layer has a b ^* value of 2.0 or less after the following ultraviolet irradiation test.

<ultraviolet irradiation test>

The pressure-sensitive adhesive layer is 250 μm thick, and alkali glass is bonded to both sides to prepare a test piece, and the test piece is used in a xenon arc lamp under the conditions of a wavelength range of 300 to 400 nm, an illuminance of 110 W/m 2 and a black panel set temperature of 83°C. After performing UV irradiation for 240 hours, the b ^* value of the pressure-sensitive adhesive layer is measured.

It is preferable that the said acrylic polymer contains a polyfunctional monomer as a monomer component which comprises a polymer. The content ratio of the polyfunctional monomer is preferably 3% by mass or less with respect to the total amount of the monomer components constituting the polymer.

It is preferable that the said adhesive layer is for an optical member.

Further, the present invention provides a pressure-sensitive adhesive sheet comprising a substrate and the pressure-sensitive adhesive layer formed on at least one side of the substrate.

The pressure-sensitive adhesive layer of the present invention has a low degree of sebum swelling and is excellent in step absorption properties. In addition, the pressure-sensitive adhesive sheet of the present invention has a low sebum swelling degree and is excellent in step absorption properties.

1 is a diagram showing an example of a capacitive touch panel in which the pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet of the present invention is used.

The pressure-sensitive adhesive layer of the present invention, as a monomer component constituting a polymer, comprises an alkyl (meth)acrylate having an alkyl group having 1 to 5 carbon atoms at the ester end, a hydroxyl group-containing monomer, and the specific alicyclic structure-containing monomer as an essential monomer component (monomer component ) Is formed of a pressure-sensitive adhesive containing an acrylic polymer constituted (formed). That is, the pressure-sensitive adhesive layer of the present invention is an acrylic pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic polymer. In addition, the alicyclic structure-containing monomer is from the group consisting of 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) Is 1 or more selected. In the present specification, "1 selected from the group consisting of 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) The above-described alicyclic structure-containing monomer" is sometimes referred to as "specific alicyclic structure-containing monomer".

The acrylic polymer is a polymer composed (formed) of an alkyl (meth)acrylate having an alkyl group having 1 to 5 carbon atoms at the end of the ester, a hydroxyl group-containing monomer, and the specific alicyclic structure-containing monomer as essential monomer components (monomer components). In this specification, "(meth)acrylic" represents "acrylic" and/or "methacryl" (either or both of "acrylic" and "methacryl"), and the same is true for others. As for the said acrylic polymer, only 1 type may be used and 2 or more types may be used.

Examples of the (meth)acrylate alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and n (meth)acrylate. -Butyl, isobutyl (meth)acrylate, s-butyl (meth)acrylate, and t-butyl (meth)acrylate. Among them, an alkyl (meth)acrylate having an alkyl group having 2 to 4 carbon atoms at the ester terminal is preferable. As for the alkyl (meth)acrylates having an alkyl group having 1 to 5 carbon atoms at the ester terminal, only one type may be used or two or more types may be used.

In the pressure-sensitive adhesive layer of the present invention, by using an alkyl (meth)acrylate having 1 to 5 carbon atoms of the alkyl group constituting the ester as an alkyl (meth)acrylate for constituting the acrylic polymer, the number of carbon atoms of the alkyl group constituting the ester Because is small, the lipophilicity is relatively low, absorption of sebum into the pressure-sensitive adhesive layer can be suppressed, and as a result, the degree of sebum swelling is lowered. In addition, it is possible to prevent the intrusion of liquid sebum from the end of the bonded body to the adherend, thereby making it difficult to cause lift of the end. In addition, there is a tendency for the b ^* value to be described later to decrease.

The ratio of the (meth)acrylate alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal is 40 to 82% by mass, preferably 45 to 100% by mass of the total amount of the monomer components constituting the acrylic polymer. It is 75 mass %, More preferably, it is 50 to 70 mass %. By setting the ratio within the above range, it becomes easy to make the structure excellent in step absorption property by balance with other monomer components while lowering the sebum swelling property.

The hydroxyl group-containing monomer is a monomer having at least one hydroxyl group (hydroxy group) in the molecule (in one molecule), and any one capable of copolymerizing with the (meth)acrylate alkyl ester may be used, such as a (meth)acryloyl group or a vinyl group. A monomer having a polymerizable functional group having an unsaturated double bond and a hydroxy group is preferably mentioned. As for the said hydroxyl-containing monomer, only 1 type may be used and 2 or more types may be used.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, ( Hydroxyalkyl (meth)acrylates such as 6-hydroxyhexyl meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; (Meth)acrylic acid (meth)acrylic acid ester containing an alicyclic structure such as (meth)acrylic acid (4-hydroxymethylcyclohexyl)methyl, etc., and a hydroxyl group-containing (meth)acrylic acid ester such as hydroxyalkyl (meth)acrylate. In addition, as the hydroxyl group-containing monomer, vinyl alcohol, allyl alcohol, hydroxyethyl (meth)acrylamide, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, etc. Can be lifted. Among them, the hydroxyl group-containing monomer is preferably a hydroxyl group-containing (meth)acrylic acid ester, more preferably hydroxyalkyl (meth)acrylate, and still more preferably (meth)acrylic acid having a hydroxyalkyl group having 2 to 6 carbon atoms. Esters, particularly preferably acrylic acid 2-hydroxyethyl (HEA), acrylic acid 4-hydroxybutyl (4HBA).

The proportion of the hydroxyl group-containing monomer is 17 to 35% by mass, preferably 20 to 33% by mass, more preferably 25 to 32% by mass, based on 100% by mass of the total amount of the monomer components constituting the acrylic polymer. . By setting the ratio within the above range, it becomes easy to make a structure having low sebum swelling property and excellent step absorption property by balance with other monomer components. In addition, since it is possible to use it instead of a nitrogen-containing monomer as a polar monomer, discoloration (yellowing) due to ultraviolet rays is more difficult to occur than when a nitrogen-containing monomer is used.

The specific alicyclic structure-containing monomer is from the group consisting of cyclohexyl (meth)acrylate, a compound represented by the formula (1), a compound represented by the formula (2), and a compound represented by the formula (3). Is 1 or more selected. By using the above-mentioned specific alicyclic structure-containing monomer as a monomer component for constituting the acrylic polymer, it is possible to easily adjust the Tg of the acrylic polymer while lowering the sebum swelling property, and the composition has excellent step absorption property due to the balance with other monomer components. It becomes easy to do. Among them, cyclohexyl (meth)acrylate is preferred. As for the said specific alicyclic structure-containing monomer, only 1 type may be used and 2 or more types may be used.

The ratio of the specific alicyclic structure-containing monomer is 42% by mass or less (eg, 1 to 42% by mass), preferably 30% by mass or less, based on 100% by mass of the total amount of the monomer components constituting the acrylic polymer. (For example, 5 to 30 mass%), More preferably, it is 15 mass% or less (for example, 8 to 15 mass%). By including the above-mentioned specific alicyclic structure-containing monomer in a proportion of 42% by mass or less, it becomes easy to obtain a configuration excellent in step absorption property while reducing sebum swelling property by balance with other monomer components.

The acrylic polymer is a monomer component constituting the polymer, in addition to the (meth)acrylate alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl group-containing monomer, and the specific alicyclic structure-containing monomer, at least one of the monomer components and It may contain a copolymerizable monomer component (another copolymerizable monomer). Examples of the other copolymerizable monomers include nitrogen atom-containing monomers, alicyclic structure-containing monomers other than the specific alicyclic structure-containing monomers, carboxyl group-containing monomers, cyclic ether group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, and aromatic hydrocarbon groups. (Meth)acrylic acid esters, vinyl esters, aromatic vinyl compounds, olefins or dienes, vinyl ethers, alkoxyalkyl (meth)acrylates, silicon atom-containing monomers, glycol-based monomers, vinyl chloride, tetra(meth)acrylates Hydrofurfuryl, fluorine (meth)acrylate, silicone (meth)acrylate, etc. are mentioned. However, the total ratio of the (meth)acrylate alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl group-containing monomer, and the specific alicyclic structure-containing monomer with respect to 100% by mass of the total amount of the monomer components constituting the acrylic polymer is , Preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Each of the above other copolymerizable monomers may be used alone or in combination of two or more.

Although it does not specifically limit as said nitrogen atom containing monomer, A cyclic nitrogen containing monomer, (meth)acrylamides, etc. are mentioned. The cyclic nitrogen-containing monomer has a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and has a cyclic nitrogen structure. It is preferable that the cyclic nitrogen structure has a nitrogen atom in the cyclic structure. Examples of the cyclic nitrogen-containing monomer include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N- And N-vinyl cyclic amides such as vinyl-1,3-oxazin-2-one and N-vinyl-3,5-morpholinedione.

Examples of the vinyl-based monomer having a nitrogen-containing heterocycle other than N-vinyl cyclic amide include a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and What has a nitrogen-containing heterocycle, such as a peridine ring, a pyrrolidine ring, and a piperazine ring, is mentioned. The vinyl-based monomer having a nitrogen-containing heterocycle is not particularly limited, but, for example, (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl Pyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisooxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone , (Meth)acryloylpyrrolidine, (meth)acryloylpiperidine, and the like.

The ratio of the nitrogen atom-containing monomer is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably, based on 100% by mass of the total amount of the monomer components constituting the acrylic polymer. Is 1% by mass or less. If the ratio is 10% by mass or less, discoloration (yellowing) due to ultraviolet rays is less likely to occur, and the b ^* value described later can be made smaller. Further, it is preferable that the ratio of the cyclic nitrogen-containing monomer is within the above range.

Examples of the carboxy group-containing monomer include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like. In addition, the carboxy group-containing monomer includes, for example, an acid anhydride group-containing monomer such as maleic anhydride and itaconic anhydride.

The proportion of the carboxy group-containing monomer is not particularly limited, but is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably, based on 100% by mass of the total amount of the monomer components constituting the acrylic polymer. It is 1 mass% or less. When the ratio is 10% by mass or less, a pressure-sensitive adhesive layer that is less likely to cause metal corrosion due to a carboxyl group can be formed.

Examples of the cyclic ether group-containing monomer include those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and having a cyclic ether group such as an epoxy group or an oxetane group. Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylic. And late glycidyl ether. Examples of the oxetane group-containing monomer include 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, 3-hexyl-oxetanylmethyl (meth)acrylate, etc. are mentioned.

Examples of the (meth)acrylate alkoxyalkyl ester include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and 3-methacrylate (meth)acrylate. Toxoxypropyl, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, and the like are mentioned.

Examples of the silicon atom-containing monomer include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxyde Siltriethoxysilane, 10-acryloyloxydecyl triethoxysilane, etc. are mentioned.

Examples of the sulfonic acid group-containing monomer include sodium vinyl sulfonate. Examples of the (meth)acrylic acid ester having an aromatic hydrocarbon group include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. As said vinyl ester, vinyl acetate, vinyl propionate, etc. are mentioned, for example. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, and vinyl toluene. As said olefins or dienes, ethylene, propylene, butadiene, isoprene, isobutylene, etc. are mentioned, for example. As said vinyl ether, vinyl alkyl ether etc. are mentioned, for example. Examples of the glycol-based monomer include polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.

Further, as the other copolymerizable monomer, an alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms at the ester terminal may be included. However, the proportion of the alkyl (meth)acrylate having an alkyl group having 6 or more carbon atoms at the ester terminal is not particularly limited, but is preferably 10% by mass or less based on 100% by mass of the total amount of the monomer components constituting the acrylic polymer. , More preferably, it is 5 mass% or less, More preferably, it is 1 mass% or less. When the said ratio is 10 mass% or less, the sebum swelling degree can be suppressed lower. Further, the total ratio of the alkyl (meth)acrylate and methyl (meth)acrylate having an alkyl group having 5 or more carbon atoms at the ester terminal may be within the above range.

In addition, in order to adjust the cohesive force of the pressure-sensitive adhesive and make the step absorption property more excellent, it is preferable to contain a polyfunctional monomer as the other copolymerizable monomer. The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group. As for the said polyfunctional monomer, only 1 type may be used and 2 or more types may be used.

As the polyfunctional monomer, for example, hexanedioldi(meth)acrylate, dodecanedioldi(meth)acrylate, butanedioldi(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, dipentaerythritol hexa(meth)acrylate, Trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylic Rate, butyl di (meth) acrylate, hexyl di (meth) acrylate, and the like. Among them, trimethylolpropane tri(meth)acrylate, hexanedioldi(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferable.

Although the proportion of the polyfunctional monomer is not particularly limited, it is preferably 3% by mass or less (for example, 0.001 to 3% by mass) with respect to 100% by mass of the total amount of the monomer components constituting the acrylic polymer. Preferably it is 0.5 mass% or less (for example, 0.002 to 0.5 mass %), More preferably, it is 0.1 mass% or less (for example, 0.005 to 0.1 mass %). When the ratio is within the above range, the crosslinking density can be appropriately increased, whereby the tensile residual stress value is appropriately reduced, and it becomes easy to obtain a configuration having excellent step absorption property.

The content ratio of the acrylic polymer in the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 50% by mass or more (for example, 50 to 100% by mass) with respect to 100% by mass of the pressure-sensitive adhesive layer of the present invention. It is preferably 80% by mass or more (for example, 80 to 100% by mass), and more preferably 90% by mass or more (for example, 90 to 100% by mass).

The acrylic polymer is obtained by polymerizing a monomer component. Although it does not specifically limit as this polymerization method, For example, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a polymerization method by active energy ray irradiation (active energy ray polymerization method), etc. are mentioned. In addition, the obtained acrylic polymer may be any of a random copolymer, a block copolymer, and a graft copolymer.

In the polymerization of the monomer component, various general solvents may 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; Alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; Organic solvents, such as ketones, such as methyl ethyl ketone and methyl isobutyl ketone, are mentioned. Only 1 type may be used for the said solvent, and 2 or more types may be used for it.

The polymerization initiator, chain transfer agent, emulsifier, and the like used for radical polymerization of the monomer component are not particularly limited and may be appropriately selected and used. In addition, the weight average molecular weight of the acrylic polymer can be controlled by the amount of the polymerization initiator and the chain transfer agent used, and the reaction conditions, and the amount of the acrylic polymer is suitably adjusted according to the types of these. As a specific example of solution polymerization, the reaction is carried out under a flow of an inert gas such as nitrogen, adding a polymerization initiator, and usually at about 50 to 70°C and under reaction conditions of about 5 to 30 hours.

As the polymerization initiator used for polymerization of the monomer component, a thermal polymerization initiator, a photoinitiator (photoinitiator), or the like can be used depending on the type of polymerization reaction. Polymerization initiators may be used alone or in combination of two or more.

Although it does not specifically limit as said thermal polymerization initiator, For example, an azo-type polymerization initiator, a peroxide-type polymerization initiator, a redox polymerization initiator, etc. are mentioned.

As the azo-based polymerization initiator, 2,2'-azobisisobutyronitrile (hereinafter sometimes referred to as ``AIBN''), 2,2'-azobis-2-methylbutyronitrile (hereinafter, ``AMBN ''), 2,2'-azobis(2-methylpropionic acid)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'- Azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azo Bis(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. are mentioned.

Examples of the peroxide polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, t-butylpermaleate, di(2-ethylhexyl)peroxydicarbonate, and di(4-t-butylcyclo Hexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroylperoxide Seed, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl Peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, etc. are mentioned.

Examples of the redox polymerization initiator include a combination of a peroxide and a reducing agent such as a combination of a persulfate and sodium hydrogen sulfite, a combination of a peroxide and sodium ascorbate, and the like.

The amount of the thermal polymerization initiator used is preferably 1 part by mass or less, more preferably 0.005 to 1 part by mass, further preferably 0.02 to 0.5 part by mass, based on 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer. It is wealth. When the amount is 0.005 parts by mass or more, it is easy to control the molecular weight of the acrylic polymer to be small, the residual stress of the pressure-sensitive adhesive layer is increased, and the step absorption property tends to be better.

Examples of the photoinitiator include a benzoin ether photoinitiator, an acetophenone photoinitiator, an α-ketol photoinitiator, an aromatic sulfonyl chloride photoinitiator, a photoactive oxime photoinitiator, a benzoin photoinitiator, a benzyl photoinitiator. Initiators, benzophenone-based photoinitiators, ketal-based photoinitiators, thioxanthone-based photoinitiators, acylphosphine oxide-based photoinitiators, titanocene-based photoinitiators, and the like can be mentioned. Among them, a benzoin ether photoinitiator and an acetophenone photoinitiator are preferable.

Examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2- Diphenylethan-1-one, anisole methyl ether, and the like. Examples of the acetophenone-based photoinitiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-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. are mentioned. Examples of the α-ketol-based photoinitiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. I can. Examples of the aromatic sulfonyl chloride-based photoinitiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photoinitiator include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime and the like.

As said benzoin type photoinitiator, benzoin etc. are mentioned, for example. As said benzyl type photoinitiator, benzyl etc. are mentioned, for example. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of the ketal-based photoinitiator include benzyl dimethyl ketal and the like. As the thioxanthone photoinitiator, for example, thioxanthone, 2-chloro thioxanthone, 2-methyl thioxanthone, 2,4-dimethyl thioxanthone, 2,4-dichloro thioxanthone, 2, 4-diethyl thioxanthone, isopropyl thioxanthone, 2,4-diisopropyl thioxanthone, dodecyl thioxanthone, etc. are mentioned.

Examples of the acylphosphine oxide photopolymerization initiator include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide Seed, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6 -Dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexyl Phosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, bis(2-methoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2-methoxybenzoyl)( 1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1- Methylpropan-1-yl)phosphine oxide, bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropane -1-yl) phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis( 2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide , Bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide Seed, 2,6-dimethoxybenzoylbenzyloctylphosphine 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-diethylphenylphosphine oxide, Bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphos Pinoxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2, 4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide , Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2, 4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide, and the like.

As the titanocene photoinitiator, for example, bis(η ⁵ -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)- Phenyl) titanium, and the like.

The amount of the photopolymerization initiator used is preferably 0.005 to 1 parts by mass, more preferably 0.01 to 0.7 parts by mass, further preferably 0.18 to 0.5 parts by mass, based on 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer. It is wealth. When the amount is 0.005 parts by mass or more (particularly, 0.18 parts by mass or more), it is easy to control the molecular weight of the acrylic polymer to be small, the residual stress of the pressure-sensitive adhesive layer is increased, and the step absorption property tends to be better.

As the chain transfer agent, for example, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, thioglycolic acid 2-ethylhexyl, 2,3-dimercapto-1- Propanol, etc. are mentioned. The amount of the chain transfer agent used is, for example, about 0.1 parts by mass or less with respect to 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer.

Examples of the emulsifier used in the emulsion polymerization include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate and sodium polyoxyethylene alkylphenyl ether sulfate; Nonionic emulsifiers, such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer, etc. are mentioned.

In addition, as a reactive emulsifier, as an emulsifier in which a radically polymerizable functional group such as a propenyl group or an allyl ether group is introduced, for example, a brand name "Aqualon HS-10", a brand name "HS-20", a brand name "KH-10", Brand name ``BC-05'', brand name ``BC-10'', brand name ``BC-20'' (above, Daiichi Kogyo Seyaku Co., Ltd. make), brand name ``Adecaria Soap SE10N'' (made by ADEKA Co., Ltd.), etc. It can be used as a commercial item. Since the reactive emulsifier is introduced into the polymer chain after polymerization, the water resistance is improved, and thus it is preferable. The amount of emulsifier used is preferably 5 parts by mass or less, more preferably 0.3 to 5 parts by mass, further preferably from the viewpoint of polymerization stability or mechanical stability, based on 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer. It is 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, and still more preferably -50 to 20°C. When Tg is within the above range, adhesive strength can be improved. The Tg of the acrylic polymer is a theoretical value calculated based on Fox's formula.

In the present specification, for homopolymer Tg of various monomer components used in Fox's formula, numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc, 1989) are used. In addition, for a monomer for which a plurality of types of values are described in this document, the highest value is adopted. When not described in the ``Polymer Handbook'' (3rd edition, John Wiley & Sons, Inc, 1989), the value obtained by the following measurement method shall be used (Japanese Patent Laid-Open No. 2007-51271). Reference).

Specifically, 100 parts by mass of a monomer, 0.2 parts by mass of azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooling tube, and nitrogen gas was added. Stir for 1 hour while flowing. After removing oxygen in the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, it is cooled to room temperature, and a homopolymer solution having a solid content concentration of 33% by mass is obtained. Subsequently, this homopolymer solution is cast onto a release liner, and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, inserted into a parallel plate, and sheared at a frequency of 1 Hz using a viscoelastic tester (trade name ``ARES'', manufactured by Rheometrics), and temperature range -70 to 150 The viscoelasticity is measured by shear mode at a temperature increase rate of °C and 5 °C/min, and the peak top temperature of tan δ (loss tangent) is taken as 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. When the weight average molecular weight is within the above range, there is a tendency that the tensile residual stress of the pressure-sensitive adhesive layer is lowered and the level difference absorbency becomes more favorable. In addition, the said weight average molecular weight shall be measured by gel permeation/chromatography (GPC), and shall refer to a value calculated by polystyrene conversion.

The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer of the present invention is not particularly limited, but may contain a crosslinking agent. For example, the acrylic polymer in the acrylic pressure-sensitive adhesive layer can be crosslinked and the gel fraction can be controlled. Only 1 type may be used for the said crosslinking agent, and 2 or more types may be used for it.

Although it does not specifically limit as said crosslinking agent, For example, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, a melamine type crosslinking agent, a peroxide type crosslinking agent, a urea type crosslinking agent, a metal alkoxide type crosslinking agent, a metal chelate type crosslinking agent, a metal salt type crosslinking agent, a carbodiimide type Crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, amine crosslinking agents, silicone crosslinking agents, and silane crosslinking agents.

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

Examples of the isocyanate crosslinking agent (polyfunctional isocyanate compound) include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; Alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylene diisocyanate; And aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. In addition, as the isocyanate-based crosslinking agent, for example, trimethylolpropane/tolylenediisocyanate adduct (brand name ``Coronate L'', manufactured by Nippon Polyurethane Kogyo Co., Ltd.), trimethylolpropane/hexamethylenediisocyanate adduct (brand name Commercial products such as ``Coronate HL'', manufactured by Nippon Polyurethane Kogyo Co., Ltd.), trimethylolpropane/xylylene diisocyanate adduct (trade name ``Takenate D-110N'', manufactured by Mitsui Chemical Co., Ltd.) are also listed. have.

The content of the crosslinking agent in the case of using an isocyanate crosslinking agent as the crosslinking agent is not particularly limited, but it is preferably contained 5 parts by mass or less, more preferably 0.01 to 5 parts by mass, based on 100 parts by mass of the acrylic polymer. , More preferably 0.01 to 4 parts by mass, particularly preferably 0.02 to 3 parts by mass.

In addition, in the aqueous dispersion of the modified acrylic polymer produced by emulsion polymerization, an isocyanate-based crosslinking agent may not be used, but if necessary, a blocked isocyanate-based crosslinking agent may be used because it is easily reacted with water.

As the epoxy-based crosslinking agent (polyfunctional epoxy compound), for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, 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, polyethylene glycol Diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polygly Cidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, resorcindi In addition to glycidyl ether and bisphenol-S-diglycidyl ether, epoxy resins having two or more epoxy groups in the molecule may be mentioned. Moreover, as said epoxy-type crosslinking agent, commercial products, such as a brand name "Tetrad C" (made by Mitsubishi Gas Chemical Co., Ltd.), are also mentioned, for example.

The content of the crosslinking agent in the case of using an epoxy crosslinking agent as the crosslinking agent is not particularly limited, but it is preferably 5 parts by mass or less, and more preferably 0.01 to 5 parts by mass based on 100 parts by mass of the acrylic polymer. , More preferably 0.01 to 4 parts by mass, particularly preferably 0.02 to 3 parts by mass.

As the peroxide-based crosslinking agent, it may be appropriately used as long as it generates radically active species by heat and proceeds crosslinking of the acrylic polymer. However, in consideration of workability and stability, a peroxide having a half-life temperature of 80 to 160°C for 1 minute is used. It is preferred, and it is more preferred to use a peroxide of 90 to 140°C.

As the peroxide-based crosslinking agent, for example, di(2-ethylhexyl)peroxydicarbonate (1 minute half-life temperature: 90.6°C), di(4-t-butylcyclohexyl)peroxydicarbonate (1 minute half-life Temperature: 92.1°C), di-sec-butylperoxydicarbonate (1 minute half-life temperature: 92.4°C), t-butylperoxyneodecanoate (1 minute half-life temperature: 103.5°C), t-hexylperoxy Pivalate (1 minute half-life temperature: 109.1°C), t-butylperoxypivalate (1 minute half-life temperature: 110.3°C), dilauroyl peroxide (1 minute half-life temperature: 116.4°C), di-n-octa Noyl peroxide (1 minute half-life temperature: 117.4°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (1 minute half-life temperature: 124.3°C), di(4-methylbenzoyl) Peroxide (1 minute half-life temperature: 128.2°C), dibenzoyl peroxide (1 minute half-life temperature: 130.0°C), t-butylperoxyisobutyrate (1 minute half-life temperature: 136.1°C), 1,1-di(t -Hexylperoxy)cyclohexane (1 minute half-life temperature: 149.2°C), and the like.

The half-life of the peroxide-based crosslinking agent is an index indicating the decomposition rate of the peroxide, and refers to the time until the residual amount of the peroxide becomes half. The decomposition temperature for obtaining the half-life at an arbitrary time and the half-life at an arbitrary temperature are described in the manufacturer's catalog, for example, Nichiyu Corporation's "Organic Peroxide Catalog 9th Edition (May 2003 ）" etc. In addition, as a method of measuring the amount of decomposition of peroxide remaining after the reaction treatment, it can be measured by, for example, HPLC (high-speed liquid chromatography). More specifically, for example, the reaction treatment is performed. After taking out about 0.2 g of the subsequent adhesive, it was immersed in 10 ml of ethyl acetate, extracted with shaking at 25°C at 120 rpm for 3 hours on a shaker, and then left to stand for 3 days at room temperature, then 10 ml of acetonitrile was added and at 25°C. , About 10 μl of the extract obtained by shaking at 120 rpm for 30 minutes and filtering through a membrane filter (0.45 μm) was injected into HPLC for analysis, and the amount of peroxide after the reaction treatment can be obtained.

When a peroxide-based crosslinking agent is used as the crosslinking agent, the content of the crosslinking agent is not particularly limited, but it is preferably contained in an amount of 2 parts by mass or less, and more preferably 0.02 to 2 parts by mass based on 100 parts by mass of the acrylic polymer. , More preferably 0.05 to 1 part by mass.

Further, as the crosslinking agent, an organic crosslinking agent and a polyfunctional metal chelate may be used in combination. The polyfunctional metal chelate is one in which a polyvalent metal is covalently bonded or coordinated with an organic compound. 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, etc. have. An oxygen atom etc. are mentioned as an atom in the organic compound which is covalently bonded or coordinated, and an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound, etc. are mentioned as an organic compound.

The acrylic pressure-sensitive adhesive (the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer of the present invention) may contain an acrylic oligomer from the viewpoint of improving adhesion. It is preferable that the said acrylic oligomer is a polymer with a weight average molecular weight smaller than the said acrylic polymer. The acrylic oligomer functions as a tackifying resin and has an advantage of increasing adhesive strength without increasing the dielectric constant. The pressure-sensitive adhesive having a low blending amount of the acrylic oligomer can reduce the degree of sebum swelling. The amount of the acrylic oligomer used 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 acrylic oligomer preferably has a Tg higher than that of the acrylic polymer, and is, for example, 0 to 200°C, preferably 20 to 150°C, more preferably 40 to 120°C. When Tg is within the above range, adhesion can be improved. In addition, the Tg of the acrylic oligomer is a theoretical value calculated based on Fox's formula, similar to the Tg of the acrylic polymer.

The pressure-sensitive adhesive layer of the present invention may further contain a silane coupling agent. When the silane coupling agent is included, the water resistance at the interface can be improved when the pressure-sensitive adhesive layer of the present invention is applied to a hydrophilic adherend such as glass. Only 1 type may be used for the said silane coupling agent, and 2 or more types may be used for it.

As the silane coupling agent, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4 epoxycyclo Epoxy group-containing silane coupling agents such as hexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N -Amino group-containing silane coupling agents such as phenyl-γ-aminopropyltrimethoxysilane; (Meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; An isocyanate group-containing silane coupling agent, such as 3-isocyanate propyl triethoxysilane, etc. are mentioned. Among them, γ-glycidoxypropyltrimethoxysilane is preferable as the silane coupling agent.

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

The pressure-sensitive adhesive layer of the present invention, if necessary, further includes a crosslinking accelerator, tackifier resin (rosin derivative, polyterpene resin, petroleum resin, oil-soluble phenol, etc.), anti-aging agent, filler (metal powder, organic filler, inorganic filler, etc.) , Additives such as coloring agents (pigments and dyes), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, granular substances, thin substances, etc. It may be contained within a range not impairing the effect of. Each of the above additives may be used alone or in combination of two or more.

The pressure-sensitive adhesive layer of the present invention is formed of the pressure-sensitive adhesive containing the acrylic polymer. The thickness of the pressure-sensitive 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 pressure-sensitive adhesive layer of the present invention can be appropriately set in a preferable range by the method for producing an acrylic polymer used for the pressure-sensitive adhesive. For example, in the case of preparing an acrylic polymer by solution polymerization or the like, the thickness of the pressure-sensitive adhesive layer is preferably 1 to 100 µm, more preferably 2 to 50 µm, further preferably 2 to 40 µm, particularly It is preferably 5 to 35 μm. In the case of producing an acrylic polymer by active energy ray polymerization or the like, the thickness of the pressure-sensitive adhesive layer is preferably 50 to 400 µm, more preferably 75 to 300 µm, and still more preferably 100 to 200 µm.

The pressure-sensitive adhesive layer of the present invention has a 300% tensile residual stress value of 0.1 to 6 N/cm 2, preferably 0.5 to 5.8 N/cm 2, and more preferably 1.0 to 5.6 N/cm 2. Since the 300% tensile residual stress value is 0.1 N/cm 2 or more, it has characteristics such as not causing paste sagging during processing. When the 300% tensile residual stress value is 6 N/cm 2 or less, the step absorption property becomes good. In addition, the 300% tensile residual stress value is obtained by stretching the pressure-sensitive adhesive layer (preferably about 400 μm in thickness) to 300% elongation (deformation) in the length direction of the pressure-sensitive adhesive layer under an environment of 23°C. Is a value obtained by dividing the tensile load by the initial cross-sectional area of the pressure-sensitive adhesive layer (cross-sectional area before tensioning) of the pressure-sensitive adhesive layer after 300 seconds elapsed from the end of the tensile. In addition, the initial elongation of the pressure-sensitive adhesive layer is 100%.

The pressure-sensitive adhesive layer of the present invention preferably has a storage elastic modulus at 70°C of 7.0×10 ⁴ Pa or less, more preferably 6.5×10 ⁴ Pa or less, and still more preferably 6.0×10 ⁴ Pa or less. When the storage modulus is 7.0×10 ⁴ Pa or less, the tensile residual stress value of 300% tends to be lowered, and the step absorption property becomes more favorable. The storage modulus at 70° C. is, for example, 1.0×10 ³ Pa or more, and preferably 1.0×10 ⁴ Pa or more.

The pressure-sensitive adhesive layer of the present invention preferably has a storage modulus of 1.0×10 ⁴ Pa or more at 25°C, more preferably 5.0×10 ⁴ Pa or more, and still more preferably 1.0×10 ⁵ Pa or more. In addition, the storage modulus at 25° C. is, for example, 1.0×10 ⁷ Pa or less, and preferably 1.0×10 ⁶ Pa or less.

The storage modulus at 70°C and the storage modulus at 25°C can be obtained, for example, from dynamic viscoelasticity measurement performed using a dynamic viscoelasticity measuring device (trade name "ARES", manufactured by Rheometrics). In this measurement, the measurement mode is the shear mode, the measurement temperature range is, for example, -70°C to 150°C, the temperature increase rate is, for example, 5°C/min, and the frequency is, for example, 1 Hz. .

The gel fraction of the pressure-sensitive adhesive layer of the present invention is preferably 30 to 85% by mass, more preferably 35 to 80% by mass, and still more preferably 40 to 70% by mass. When the said gel fraction is 30 mass% or more, workability and handling property of an adhesive become favorable. When the gel fraction is 85% by mass or less, the stress at the step is relieved, and the step absorbency becomes more favorable. The gel fraction can be controlled in consideration of the influence of the crosslinking treatment temperature and the crosslinking treatment time, as well as adjusting the amount of the crosslinking agent or the polyfunctional monomer added.

The pressure-sensitive adhesive layer of the present invention preferably has a b ^* value of 2.0 or less, more preferably 1.6 or less, and still more preferably 1.2 or less after the following ultraviolet irradiation test. When the b ^* value is 2.0 or less, the pressure-sensitive adhesive layer is difficult to discolor under an environment exposed to ultraviolet rays. The b ^* values, L ^* a ^* b ^* color system of the b ^* value is, in accordance with JIS Z 8781-4 (2013 years), such as Simple spectroscopic color difference meter (trade name "DOT-3C", as to whether or It can be measured by Keisha Murakami Shikisai Kijutsu Genkyu Corporation).

<ultraviolet irradiation test>

The pressure-sensitive adhesive layer is 250 μm thick, and alkali glass is bonded to both sides to prepare a test piece, and the test piece is used in a xenon arc lamp under the conditions of a wavelength range of 300 to 400 nm, an illuminance of 110 W/m 2 and a black panel set temperature of 83°C. After performing UV irradiation for 240 hours, the b ^* value of the pressure-sensitive adhesive layer is measured.

The pressure-sensitive adhesive layer of the present invention preferably has a haze value of 2% or less, more preferably 1.5% or less, and still more preferably 1% or less when the thickness is 100 µm. When the haze value is 2% or less, transparency required when the pressure-sensitive adhesive layer of the present invention is used for an optical member can be satisfied. The haze value can be measured according to JIS K 7136 using, for example, a haze meter.

In the pressure-sensitive adhesive layer of the present invention, the amount of protrusion of the pressure-sensitive adhesive layer measured by the following sebum swelling test is preferably less than 2 mm, and more preferably less than 1 mm. The lower the protruding amount is, the more preferable it is, and ideally, it is 0 mm.

<Sebum swelling test>

A sample consisting of polyethylene terephthalate (100 μm)/adhesive layer (100 μm)/glass was prepared in a size of 5 cm×10 cm, and this was immersed in an artificial sebum solution in which squalene and oleic acid were mixed at a mass ratio of 1:1, After leaving to stand at 60° C. for 5 days, the sample is taken out from the artificial sebum liquid, and the amount of protruding of the pressure-sensitive adhesive layer from the glass end is measured.

The method for producing the pressure-sensitive adhesive layer of the present invention is not particularly limited, for example, applying (coating) a pressure-sensitive adhesive (adhesive composition) containing the acrylic polymer onto a substrate or a release liner, and drying and curing the obtained pressure-sensitive adhesive composition layer. It may be mentioned that the pressure-sensitive adhesive composition is applied (coated) onto a base material or a release liner, and the obtained pressure-sensitive adhesive composition layer is irradiated with active energy rays to cure it. Moreover, you may heat-dry further as needed.

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

The pressure-sensitive adhesive composition can be produced by a known or common method. For example, a solvent-type pressure-sensitive adhesive composition can be produced by mixing an additive as necessary with a solution containing the acrylic polymer. For example, an active energy ray-curable pressure-sensitive adhesive composition can be produced by mixing an additive, if necessary, with a mixture of monomer components constituting the acrylic polymer or a partial polymer thereof.

In addition, a known coating method may be used for application (coating) of the pressure-sensitive adhesive composition. For example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, a direct coater or the like may be used.

The heat-drying temperature of the solvent-type pressure-sensitive adhesive composition is preferably 40 to 200°C, more preferably 50 to 180°C, and still more preferably 70 to 170°C. The drying time may be suitably and appropriately employed, but is, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

When the pressure-sensitive adhesive layer is formed by irradiation with active energy rays, the acrylic polymer can be prepared from the monomer component and the pressure-sensitive adhesive layer can be formed. The above-mentioned monomer component can be used as a syrup by polymerizing a part of the monomer component in advance in irradiation with active energy rays. For ultraviolet irradiation, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, or the like can be used.

An adhesive sheet can be obtained using the adhesive layer of the present invention. In addition, the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention is sometimes referred to as "the pressure-sensitive adhesive sheet of the present invention".

The pressure-sensitive adhesive sheet of the present invention may be a so-called “inorganic material type” pressure-sensitive adhesive sheet without a substrate (substrate layer), or may be a type pressure-sensitive adhesive sheet having a substrate. In addition, in this specification, the adhesive sheet of the "inorganic material type" may be referred to as a "inorganic material adhesive sheet", and the type of adhesive sheet having a base material may be referred to as a "adhesive sheet with a base material". Examples of the inorganic material pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet made of only the pressure-sensitive adhesive layer of the present invention, or a double-sided pressure-sensitive adhesive sheet made of the pressure-sensitive adhesive layer of the present invention and other pressure-sensitive adhesive layers (adhesive layers other than the pressure-sensitive adhesive layer of the present invention). Can be lifted. In addition, the pressure-sensitive adhesive sheet provided with the substrate is a pressure-sensitive adhesive sheet comprising a substrate and an adhesive layer of the present invention formed on at least one side of the substrate, for example, a single-sided adhesive layer having the adhesive layer of the present invention on one side of the substrate A pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on both sides of the substrate, or a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the invention on one side of the substrate and another pressure-sensitive adhesive layer on the other side. Can be lifted. In addition, the said "substrate (substrate layer)" is a support body, and when using (attaching) the adhesive sheet of this invention to an adherend, it is a part attached to an adherend together with an adhesive layer. The separator (release liner) that is peeled off at the time of use (sticking) of the pressure-sensitive adhesive sheet is not included in the substrate.

Although it does not specifically limit as a base material when the adhesive sheet of this invention is an adhesive sheet provided with a base material, For example, various optical films, such as a plastic film, an antireflection (AR) film, a polarizing plate, and a retardation plate, are mentioned. Further, examples of the substrate include porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, and metal foils. Examples of materials such as the plastic film include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetylcellulose (TAC), poly Sulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, brand name ``Atone'' (cyclic olefin polymer, manufactured by JSR Corporation), brand name ``Zeonoa'' And plastic materials such as cyclic olefin-based polymers such as (cyclic olefin-based polymer and Nippon Xeon Co., Ltd. product). In addition, these plastic materials may be used alone or in combination of two or more.

The thickness of the substrate is not particularly limited, but is preferably 12 to 75 μm, for example. Further, the substrate may have either a single layer or a multilayer. In addition, the surface of the substrate may be appropriately subjected to known and conventional surface treatment such as physical treatment such as corona discharge treatment and plasma treatment, and chemical treatment such as primer treatment.

Until use, the pressure-sensitive adhesive sheet of the present invention may be provided with a release liner on the surface (adhesive surface) of the pressure-sensitive adhesive layer. In addition, when the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, each of the pressure-sensitive adhesive faces may be protected by two release liners, respectively, and wound in a roll shape by one release liner having both sides as a release surface. It may be protected in a form (wound body). The release liner is used as a protective material for the pressure-sensitive adhesive layer, and is peeled when affixed to an adherend. In addition, when the pressure-sensitive adhesive sheet of the present invention is an inorganic material pressure-sensitive adhesive sheet, the release liner also serves as a support for the pressure-sensitive adhesive layer. In addition, the release liner need not necessarily be provided.

As the release liner, a common release paper or the like can be used, and although it is not particularly limited, for example, a substrate having a release treatment layer, a low-adhesive substrate made of a fluorine polymer, a low-adhesive substrate made of a non-polar polymer, etc. I can. Examples of the substrate having the release treatment layer include a plastic film or paper surface-treated with a release treatment agent such as silicone, long chain alkyl, fluorine, and molybdenum sulfide. Examples of the fluorine-based polymer in the low-adhesion substrate made of the fluorine polymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and tetrafluoroethylene-hexafluoropropylene. Copolymers, chlorofluoroethylene-vinylidene fluoride copolymers, and the like. Moreover, as said non-polar polymer, an olefin resin (for example, polyethylene, polypropylene, etc.) etc. are mentioned, for example. In addition, the release liner can be formed by a known or common method. Also, the thickness of the release liner is not particularly limited.

The pressure-sensitive adhesive sheet of the present invention is not particularly limited, but can be produced according to a known or common production method. For example, when the adhesive sheet of the present invention is an inorganic adhesive sheet, it is obtained by forming the adhesive layer of the present invention on a release liner by the above method. In addition, when the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet with a substrate, it may be obtained by directly forming the pressure-sensitive adhesive layer of the present invention on the surface of the substrate (direct yarn method). After forming, it may be obtained by transferring (bonding) to the substrate to form the pressure-sensitive adhesive layer of the present invention on the substrate (transfer method).

It is preferable that the adhesive layer of this invention and the adhesive sheet of this invention are for optical members used for optical applications. The optical member refers to a member having optical properties (eg, polarization, light refraction, light scattering, light reflectivity, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). Although it does not specifically limit as a board|substrate which comprises the said optical member, For example, a board|substrate which comprises devices (optical devices), such as a display device (image display device), an input device, or a board used for these devices, is mentioned. , For example, a polarizing plate, a wavelength plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light guide plate, a reflective film, an antireflection film, a hard coating film (a film in which a hard coating treatment is applied to at least one side of a plastic film such as a PET film ), transparent conductive film, design film, decorative film, surface protection plate, prism, lens, color filter, transparent substrate (glass sensor, glass display panel (LCD, etc.), glass substrates such as glass plates with transparent electrodes, etc.), or Further, the substrates on which these are laminated (these are collectively referred to as "functional film" in some cases), etc. are mentioned. In addition, these films may have a printing layer, a conductive polymer layer, or the like. In addition, the above-mentioned "plate" and "film" shall each include a form such as a plate, a film, and a sheet, and, for example, a "polarization film" includes a "polarization plate" and a "polarization sheet". It should be done.

The pressure-sensitive adhesive layer of the present invention and the pressure-sensitive adhesive sheet of the present invention are particularly suitably used in an optical application for affixing to a metal thin film or a metal electrode. As the metal thin film, a thin film made of a metal, a metal oxide, or a mixture thereof may be mentioned, although it is not particularly limited, for example, a thin film of indium tin oxide (ITO), ZnO, SnO, and cadmium tin oxide (CTO). I can. The thickness of the metal thin film is not particularly limited, but is about 10 to 200 nm. Usually, a metal thin film such as ITO is provided on a transparent plastic film substrate such as a polyethylene terephthalate film (PET film), and is used as a transparent conductive film. When affixing the pressure-sensitive adhesive sheet of the present invention to a thin metal film, it is preferable to use the pressure-sensitive adhesive layer so that the surface on the side to be affixed to the thin metal film is the pressure-sensitive adhesive surface.

Examples of the metal electrode include an electrode made of a metal, a metal oxide, or a mixture thereof, and is not particularly limited, and examples thereof include ITO, silver, copper, and CNT (carbon nanotube) electrodes.

As an example of the specific use of the adhesive sheet of this invention, the adhesive sheet for touch panels used for the manufacturing use of a touch panel is mentioned. The adhesive sheet for a touch panel is, for example, in manufacturing a capacitive touch panel, a transparent conductive film provided with a metal thin film such as ITO, a polymethyl methacrylate resin (PMMA) plate, a hard coating film, a glass lens, etc. It is used to join. The touch panel is not particularly limited, but is used, for example, in a mobile phone, a tablet computer, and a portable information terminal.

As a more specific example, an example of a capacitive touch panel in which the pressure-sensitive adhesive layer of the present invention or the pressure-sensitive adhesive sheet of the present invention is used is shown in FIG. 1. In FIG. 1, 1 is a capacitive touch panel, 11 is a decorative panel, 12 is an adhesive layer or an adhesive sheet, 13 is an ITO film, and 14 is a hard coating film. It is preferable that the decorative panel 11 is a glass plate or a transparent acrylic plate (PMMA plate). In addition, as for the ITO film 13, it is preferable that an ITO film is provided on a glass plate or a transparent plastic film (especially a PET film). It is preferable that the hard coating film 14 has been subjected to a hard coating treatment on a transparent plastic film such as a PET film. Since the pressure-sensitive adhesive layer of the present invention or the pressure-sensitive adhesive sheet of the present invention is used for the capacitive touch panel 1, the sebum resistance is high, the thickness can be reduced, and it is excellent in step absorption properties such as printing steps, etc. Has excellent stability. Moreover, the appearance and visibility are good.

[Example]

Hereinafter, the present invention is described in more detail with reference to examples, but the present invention is not limited at all by these examples. In addition, unless otherwise noted, "%" indicating content means mass%. In addition, the number of mixing parts (mass parts) are all values in terms of solid content (non-volatile content).

Example 1

Butyl acrylate (BA) 67 parts by mass, 4-hydroxybutyl acrylate (4BHA) 19 parts by mass, cyclohexyl acrylate (CHA) 14 parts by mass, photoinitiator (trade name "Omnirad 184", manufactured by BASF) 0.09 parts by mass And 0.09 parts by mass of a photoinitiator (trade name "Omnirad 651", manufactured by BASF) was put into a four-necked flask to prepare a monomer mixture. Subsequently, the monomer mixture was partially photopolymerized by exposure to ultraviolet rays in a nitrogen atmosphere to obtain a partially polymerized product (acrylic polymer syrup) having a polymerization rate of about 10% by mass.

To the total amount of acrylic polymer syrup obtained, 8 parts by mass of 4-hydroxybutyl acrylate, 9 parts by mass of 2-hydroxyethyl acrylate (HEA), dipentaerythritol pentaacrylate (trade name ``KAYARAD DPHA'', Nippon Kayaku Corporation) Co., Ltd.) 0.02 parts by mass, photoinitiator (trade name "Omnirad 651", BASF company make) 0.3 parts by mass and silane coupling agent (trade name "KBM-403", γ-glycidoxypropyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) After adding 0.35 parts by mass of Gaku Kogyo Co., Ltd.), these were uniformly mixed to prepare a pressure-sensitive adhesive composition.

Subsequently, the pressure-sensitive adhesive composition prepared above was peeled off one side with silicone, and the final thickness was 100 μm on the peeling-treated side of a 38 μm-thick polyester film (trade name “Diare Foil MRF”, manufactured by Mitsubishi Chemical Co., Ltd.) It was applied so as to form a coating layer. Next, on the surface of the applied monomer component, a 38 μm-thick polyester film (trade name “Diaafoil MRE”, manufactured by Mitsubishi Chemical Co., Ltd.) was peeled off with silicone on one side. It was covered as possible. Thereby, the coating layer of the pressure-sensitive adhesive composition was blocked from oxygen. Using a chemical light lamp (manufactured by Toshiba Co., Ltd.) on the sheet having the coating layer thus obtained, ultraviolet rays at an illuminance of 5 mW/cm 2 (measured by “Topcon UVR-T1” with maximum sensitivity at about 350 nm) are irradiated for 360 seconds. Then, the coating layer was cured to form an adhesive layer, and an adhesive sheet was produced. The polyester film coated on both sides of the pressure-sensitive adhesive layer functions as a release liner.

Examples 2 to 3, Comparative Examples 1 to 2

A pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet were produced in the same manner as in Example 1, except that the type and amount of the monomer component and the photopolymerization initiator used were changed as shown in the table. In addition, the chain transfer agent used in Example 3 is a brand name "Noffmer MSD" (made by Nichiyu Corporation). In addition, the acrylic oligomer used in Comparative Example 2 was prepared as follows.

(Preparation of acrylic oligomer)

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

<Evaluation>

The following evaluation was performed about the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples. Table 1 shows the results.

(1) Sebum swelling

A sample consisting of polyethylene terephthalate (100 μm)/adhesive layer (100 μm)/glass was prepared in a size of 5 cm×10 cm, and this was immersed in an artificial sebum solution in which squalene and oleic acid were mixed at a mass ratio of 1:1, It was left at 60°C for 5 days. Thereafter, the sample was taken out from the artificial sebum liquid, and the amount of protruding of the pressure-sensitive adhesive layer from the glass end was measured, and the case where the protruding amount was less than 2 mm was set as?

(2) 300% tensile residual stress value

The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut to a size of 40 mm × 40 mm, the separator on one side was peeled off, folded once so that the pressure-sensitive adhesive faces were bonded together, and the separators on one side were peeled again to separate the pressure-sensitive adhesive faces again. By bonding, a sample of a pressure-sensitive adhesive layer having a size of about 10 mm x 40 mm and a thickness of about 400 μm was prepared. The pressure-sensitive adhesive layer sample was set in a tensile testing machine in which the interchuck distance was set to 20 mm, and the sample was pulled by 60 mm (300%) at a tensile speed of 200 mm/min (the interchuck distance after stretching was 80 mm). It held fixed for 300 seconds at the position which was pulled by 60 mm, and measured the stress value after that, and calculated "300% tensile residual stress value" from the following formula.

300% tensile residual stress value (N/㎠) = stress value after holding for 300 seconds (N)/(4×adhesive sheet thickness(mm)/10)

(3) Print step absorption

The separator on one side was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and a PET film having a thickness of 100 μm was bonded to the exposed side, and the separator on the other side was peeled off, and the printing step was about 30 μm on the exposed side. Glass with printing was bonded to prepare an evaluation sample. After the evaluation sample was treated in an autoclave (50° C., 5 atmospheres, 15 minutes), the absence of bubbles in the vicinity of the printing step was designated as ◯, and the appearance of bubbles was designated as x, and the print step absorption property was evaluated.

(4) b ^* value after ultraviolet irradiation test

One separator of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples was peeled off, and the pressure-sensitive adhesive layer prepared in the same manner was overlapped so as to have a thickness of 250 μm, and alkali glass was bonded to both sides of the overlapped pressure-sensitive adhesive layer to prepare a test piece. After the test piece was irradiated with ultraviolet rays for 240 hours with a xenon arc lamp under conditions of a wavelength range of 300 to 400 nm, an illuminance of 110 W/m 2, and a black panel set temperature of 83°C, the b ^* value of the pressure-sensitive adhesive layer was measured. The measurement of the b ^* value was measured with a simple spectroscopic color difference meter (brand name "DOT-3C", manufactured by Shikisai Murakami, Kijutsu Kenkyu Corporation).

The abbreviations shown in the table are as follows.

BA: Butyl acrylate (manufactured by Toa Kose Co., Ltd.)

2EHA: 2-ethylhexyl acrylate (manufactured by Toa Kose Co., Ltd.)

4HBA: 4-hydroxybutyl acrylate (manufactured by Osaka Yuki Chemical Co., Ltd.)

HEA: 2-hydroxyethyl acrylate (manufactured by Toa Kose Co., Ltd.)

CHA: Cyclohexyl acrylate (manufactured by Osaka Yuki Chemical Co., Ltd.)

NVP: N-vinyl-2-pyrrolidone (made by Nippon Shokubai Co., Ltd.)

HDDA: 1,6-hexanediol diacrylate

DPHA: dipentaerythritol hexaacrylate

1: capacitive touch panel
11: decorative panels
12: adhesive layer or adhesive sheet
13: ITO film
14: hard coating film

Claims (8)

As the monomer component constituting the polymer, a (meth)acrylate alkyl ester having an alkyl group having 1 to 5 carbon atoms at the ester terminal, a hydroxyl group-containing monomer, and an alicyclic structure-containing monomer,
The alicyclic structure-containing monomer is cyclohexyl (meth)acrylate, the following formula (1)

Compound represented by the following formula (2)

Compound represented by, and the following formula (3)

It is one or more selected from the group consisting of compounds represented by,
The ratio of the (meth)acrylate alkyl ester having the alkyl group having 1 to 5 carbon atoms at the ester terminal to the total amount of the monomer components constituting the polymer is 40 to 82% by mass, and the ratio of the hydroxyl group-containing monomer is 17 to 35% by mass %, a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive containing an acrylic polymer in which the proportion of the alicyclic structure-containing monomer is 42% by mass or less, and a 300% tensile residual stress value of 0.1 to 6 N/cm 2. The pressure-sensitive adhesive layer according to claim 1, wherein the storage modulus at 70°C is 7.0×10 ⁴ Pa or less. The pressure-sensitive adhesive layer according to claim 1 or 2, wherein the gel fraction is 30 to 85% by mass. The pressure-sensitive adhesive layer according to claim 1 or 2, wherein the b ^* value after the following ultraviolet irradiation test is 2.0 or less.
<ultraviolet irradiation test>
The pressure-sensitive adhesive layer is 250 μm thick, and alkali glass is bonded to both sides to prepare a test piece, and the test piece is used in a xenon arc lamp under the conditions of a wavelength range of 300 to 400 nm, an illuminance of 110 W/m 2 and a black panel set temperature of 83°C. After performing UV irradiation for 240 hours, the b ^* value of the pressure-sensitive adhesive layer is measured. The pressure-sensitive adhesive layer according to claim 1 or 2, wherein the acrylic polymer contains a polyfunctional monomer as a monomer component constituting the polymer. The pressure-sensitive adhesive layer according to claim 5, wherein the content ratio of the polyfunctional monomer is 3% by mass or less with respect to the total amount of the monomer components constituting the polymer. The pressure-sensitive adhesive layer according to claim 1 or 2, which is for an optical member. A pressure-sensitive adhesive sheet comprising a substrate and the pressure-sensitive adhesive layer according to claim 1 or 2 formed on at least one surface of the substrate.

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