JP6180161B2 - Pressure-sensitive adhesive sheet, method for producing laminate with pressure-sensitive adhesive layer, and use thereof - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet and a method for producing a laminate with a pressure-sensitive adhesive layer, and specifically relates to a pressure-sensitive adhesive sheet having excellent step following ability.

In recent years, display devices such as liquid crystal displays (LCDs) and input devices used in combination with the display devices such as touch panels have come to be widely used in various fields. A transparent adhesive sheet is used for the purpose of pasting together.
For example, a transparent double-sided pressure-sensitive adhesive sheet is used for pasting a touch panel and various display devices and optical members (protection plates, etc.). Some of the touch panels, etc. include members having steps such as printing steps. In such an application, the pressure-sensitive adhesive sheet is required to have a capability of filling a printing step at the same time as a performance of sticking and fixing a member, that is, an excellent step following capability.

  As a means for improving the step following ability, a method of increasing the thickness of the adhesive layer or a method of using a soft adhesive layer can be considered. In the latter method, it is difficult to obtain sufficient followability for large steps.

Focusing on these problems, as an adhesive sheet with improved step following ability, for example, in Patent Document 1, the storage elastic modulus at 23 ° C. is 1.0 × 10 ⁴ Pa or more and less than 1.0 × 10 ⁵ Pa. Yes, even if the pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer having a peeling adhesive strength at 80 ° C. (against polyethylene terephthalate, 180 ° peeling) of 2.5 N / 20 mm or more is a thin film, the step absorbability and durability It is disclosed that it is excellent.

JP 2010-77287 A

  However, in recent years, there are a wide variety of types of members used in optical applications, and there is a need for a higher level of step following capability. The step following capability shown in the example of Patent Document 1 and the like. Has a step following ability of following a step of 8 μm by using a 25 μm pressure-sensitive adhesive layer, which is not sufficient for the recent high required level, and further improvement has been demanded.

  Therefore, in the present invention, under such a background, the pressure-sensitive adhesive sheet exhibits a high level of step following property, and also has a well-balanced adhesive property (adhesive strength, holding power), wet heat resistance, and blister resistance. For the purpose of provision.

  However, as a result of intensive studies in view of such circumstances, the present inventor has, as a result, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer obtained by crosslinking an acrylic resin with a crosslinking agent, and further contains one ethylenically unsaturated group in the pressure-sensitive adhesive layer. By including a specific amount of the ethylenically unsaturated compound to be obtained, the resulting pressure-sensitive adhesive sheet exhibits a high level of step following ability, and is well balanced with respect to pressure-sensitive adhesive properties (adhesive strength, holding power), moisture and heat resistance, and blister resistance. As a result, the present invention has been completed.

That is, the gist of the present invention is that a cross-linked product of a functional group-containing acrylic resin (A) and a cross-linking agent (B), an ethylenically unsaturated compound (C) containing one ethylenically unsaturated group, and an ethylenically unsaturated group. It is an adhesive sheet containing an adhesive layer containing an ethylenically unsaturated compound (D) containing two or more saturated groups, and the functional group-containing acrylic resin (A) contains at least 2-ethylhexyl (meth) acrylate ( A monomer component containing a (meth) acrylic acid ester monomer (a2) is polymerized, and the content of the (meth) acrylic acid ester monomer (a2) in the monomer component is 50 to 99.99 weight. %, The content of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group is 5 to 30% by weight with respect to the whole pressure-sensitive adhesive layer, and two ethylenically unsaturated groups are contained. Contains more than The ethylenically unsaturated compound (D) content is 0.01 to 30 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group. An ethylenically unsaturated compound (C) containing one unsaturated group is a long-chain aliphatic (meth) acrylate (C1-1) or alicyclic (meth) acrylate having an aliphatic group having 10 to 18 carbon atoms. The pressure-sensitive adhesive sheet is characterized by being (C1-2), aromatic (meth) acrylate (C1-3), or an oxyalkylene structure-modified compound (C1-4) of these (meth) acrylates.

  Furthermore, this invention relates to the manufacturing method of the laminated body with an adhesive layer which uses the said adhesive sheet.

  The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet exhibiting a high level of step following property, and is a physical property generally required for a pressure-sensitive adhesive sheet used for laminating a touch panel or an image display device (adhesive strength, holding power) ), Heat and moisture resistance, and blister resistance.

The present invention will be described in detail below, but these show examples of desirable embodiments.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive layer containing a cross-linked product of a functional group-containing acrylic resin (A) and a cross-linking agent (B), and an ethylenically unsaturated compound (C) containing one ethylenically unsaturated group. Is a pressure-sensitive adhesive sheet containing
The components (A) to (C) will be described sequentially.

[Acrylic resin (A)]
The functional group-containing acrylic resin (A) used in the present invention contains the functional group-containing monomer (a1) as an essential component as a monomer component, and a (meth) acrylic acid ester monomer (a2), necessary According to this, other copolymerizable monomer (a3) is further contained as a copolymerization component, and these are polymerized.

  The functional group-containing monomer (a1) may be any monomer containing a functional group that can become a crosslinking point by reacting with the later-described crosslinking agent (B). For example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, amino Examples thereof include a group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, and a glycidyl group-containing monomer. Among these, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferably used in terms of efficient crosslinking reaction.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meta ) Acrylic acid hydroxyalkyl esters such as acrylate, caprolactone-modified 2-hydroxyethyl (meth) acrylate and other caprolactone-modified monomers, diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate and other oxyalkylene-modified monomers, and other 2-acrylic Primary hydroxyl group-containing monomers such as leuoxyethyl-2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) a Relate, secondary hydroxyl group-containing monomers such as 3-chloro-2-hydroxypropyl (meth) acrylate; may be mentioned 2,2-dimethyl-2-hydroxyethyl (meth) tertiary hydroxyl group-containing monomers such as acrylates.

  Among the hydroxyl group-containing monomers, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferable in terms of excellent reactivity with the crosslinking agent.

  In addition, as a hydroxyl-containing monomer used by this invention, it is also preferable to use a thing with the content rate of di (meth) acrylate which is an impurity 0.5% or less, and also 0.2% or less, especially 0 It is preferable to use 1% or less, specifically 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamon. An acid etc. are mentioned, Especially, (meth) acrylic acid is used preferably.

  Examples of the amino group-containing monomer include t-butylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

  Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

  Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, allyl glycidyl (meth) acrylate, and the like.
These functional group-containing monomers (a1) may be used alone or in combination of two or more.

  Examples of the (meth) acrylic acid ester monomer (a2) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meta ) Acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (Meth) acrylate alkyl esters such as (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, iso-stearyl (meth) acrylate; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate Cycloaliphatic (meth) acrylic acid esters such as relations are exemplified. In the case of the above (meth) acrylic acid alkyl ester, the alkyl group preferably has 1 to 20 carbon atoms, particularly preferably 1 to 12, more preferably 1 to 8, and particularly preferably 4 to 8. These can be used alone or in combination of two or more.

Among such (meth) acrylic acid ester monomers (a2), n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials. Is preferably used, and more preferably 2-ethylhexyl acrylate is used in terms of excellent step following ability. In the present invention, it is necessary to use 2-ethylhexyl acrylate.

Other copolymerizable monomers (a3) include, for example, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) ) Monomers containing one aromatic ring such as acrylate, styrene, α-methylstyrene; Biphenyloxy structure-containing (meth) acrylic acid ester monomers such as biphenyloxyethyl (meth) acrylate; (2-methoxyethyl (meth) Acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene group Cole (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol-polypropylene glycol-mono (meta) ) Ether chain-containing (meth) acrylic acid ester monomers such as acrylate, lauroxypolyethylene glycol mono (meth) acrylate, stearoxypolyethylene glycol mono (meth) acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, stearic acid Vinyl, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl Pyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinylketone, (meth) acryloylmorpholine, etc. it can.
These may be used alone or in combination of two or more.

  The content of the functional group-containing monomer (a1) in the monomer component is preferably 0.01 to 70% by weight, particularly preferably 0.1 to 50% by weight, more preferably 1 to 35% by weight, Particularly preferably, the content is 5 to 20% by weight. If the content of the functional group-containing monomer (a1) is too small, the durability tends to be lowered due to insufficient cohesive force. Or the stability of the resin tends to decrease.

Examples of the content in the monomer components of the (meth) acrylic acid ester monomer (a2), 50 and 99.99 wt%, good Mashiku from 50 to 95 wt%, more preferably 60 to 90 wt% If the content of the (meth) acrylic acid ester monomer (a2) is too small, the adhesive strength when used as a pressure-sensitive adhesive tends to be insufficient, and if it is too large, the content of the functional group-containing monomer (a1) The amount tends to decrease and the cohesive force tends to decrease.

  The content of the other copolymerizable monomer (a3) in the monomer component is preferably 0 to 40% by weight, particularly preferably 0 to 30% by weight, more preferably 0 to 25% by weight, When there are too many other copolymerizable monomers (a3), the adhesive properties tend to be lowered.

Thus, by polymerizing the monomer component containing the functional group-containing monomer (a1), preferably a (meth) acrylic acid ester monomer (a2) and, if necessary, another copolymerizable monomer (a3). The functional group-containing acrylic resin (A) of the present invention is produced. In such polymerization, it is possible to produce the functional group-containing acrylic resin with any monomer composition safely and stably by solution polymerization. (A) is preferable at the point which can be manufactured.
In such solution polymerization, for example, the monomer components (a1) to (a3) and the polymerization initiator may be mixed or dropped in an organic solvent, and polymerization may be performed at reflux or at 50 to 98 ° C. for 0.1 to 20 hours. .

  Examples of such polymerization initiators include azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are ordinary radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, and di-t-butyl peroxide. Specific examples include peroxide polymerization initiators such as cumene hydroperoxide.

  The weight average molecular weight of the functional group-containing acrylic resin (A) is usually 100,000 to 5,000,000, preferably 200,000 to 1,000,000, particularly preferably 300,000 to 800,000. When the weight average molecular weight is too small, the durability performance tends to decrease, and when it is too large, the step following ability tends to decrease.

  The dispersity (weight average molecular weight / number average molecular weight) of the functional group-containing acrylic resin (A) is preferably 20 or less, particularly preferably 15 or less, more preferably 10 or less, especially 7 or less. Is preferred. If the degree of dispersion is too high, the durability performance of the pressure-sensitive adhesive layer tends to decrease. The lower limit of the degree of dispersion is usually 1.1 from the viewpoint of production limit.

  The glass transition temperature of the functional group-containing acrylic resin (A) is preferably −90 to 10 ° C., particularly preferably −70 to −20 ° C., more preferably −60 to −50 ° C., and the glass transition temperature is too high. There is a tendency that the step following ability is lowered, and when it is too low, the heat resistance tends to be lowered.

Ｔg：共重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ） Ｗa：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗb：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗn：モノマーＮの重量分率
（Ｗa＋Ｗb＋・・・＋Ｗn＝１） In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in high performance liquid chromatography (The Japan Waters company "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler The particle diameter is measured by using three series of 10 μm), and the same method can be used for the number average molecular weight. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight. The glass transition temperature is calculated from the following Fox equation.

Tg: Glass transition temperature of copolymer (K)
Tga: Glass transition temperature of monomer A homopolymer (K) Wa: Weight fraction of monomer A Tgb: Glass transition temperature of homopolymer of monomer B (K) Wb: Weight fraction of monomer B Tgn: Homogeneity of monomer N Glass transition temperature of polymer (K) Wn: weight fraction of monomer N (Wa + Wb +... + Wn = 1)

  Moreover, as acrylic resin (A) used by this invention, the reactive structural site | part which can react with the other hardening component contained in a part of acrylic resin or acrylic resin composition by active energy ray irradiation. It is preferable to use an acrylic resin having an ethylenically unsaturated group-containing acrylic resin because the pressure-sensitive adhesive layer after irradiation with active energy rays can have a higher elastic modulus.

  The ethylenically unsaturated group-containing acrylic resin is one in which an acrylic resin having a functional group in the molecule is reacted with an ethylenically unsaturated compound having a functional group that reacts with the functional group in the molecule. Examples of the ethylenically unsaturated compound include the carboxyl group-containing unsaturated monomer, the hydroxyl group-containing unsaturated monomer, the glycidyl group-containing unsaturated monomer, the isocyanate group-containing unsaturated monomer, the amide group-containing unsaturated monomer, and the amino group-containing unsaturated monomer. And sulfonic acid group-containing unsaturated monomers.

  For example, when the functional group in the acrylic resin is a carboxyl group, the glycidyl group-containing unsaturated monomer or the isocyanate group-containing unsaturated monomer is used. When the functional group is a hydroxyl group, the isocyanate group-containing unsaturated monomer is used. In the case of a glycidyl group, a carboxyl group-containing unsaturated monomer or an amide group-containing unsaturated monomer is selected, and when the functional group is an amino group, a glycidyl group-containing unsaturated monomer is selected and used. In the case where the group is a hydroxyl group, the ethylenically unsaturated compound is preferably an isocyanate group-containing unsaturated compound from the viewpoint of excellent reactivity of the functional group.

  In addition, in the present invention, when the adhesive sheet is used for an information label used for bonding to a transparent electrode such as a touch panel or other electronic member, particularly a precision electronic member, or used for fixing an electronic member, the corrosion resistance is low. Since it is calculated | required in this case, it is preferable that the said functional group containing acrylic resin (A) does not contain an acidic group.

[Crosslinking agent (B)]
The crosslinking agent (B) used in the present invention exhibits excellent adhesive force by reacting with a functional group derived from the functional group-containing monomer (a1) which is a constituent monomer of the functional group-containing acrylic resin (A). Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. Among these, an isocyanate-based crosslinking agent is preferably used in terms of improving the adhesion to the substrate and the reactivity with the functional group-containing acrylic resin (A).

  Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof And adducts of a polyol compound such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds.

  Examples of the epoxy crosslinking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. , Trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether and the like.

  Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. '-Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like can be mentioned.

  Examples of the melamine-based crosslinking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexaptoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, and melamine resin. .

  Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

  Examples of the amine-based crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, polyamide, and the like.

  Examples of the metal chelate-based crosslinking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium, and zirconium. Can be mentioned.

  Moreover, these crosslinking agents (B) may be used independently and may use 2 or more types together.

  In general, the content of the crosslinking agent (B) is preferably 0.001 to 10 parts by weight, more preferably 0.02 to 100 parts by weight with respect to 100 parts by weight of the functional group-containing acrylic resin (A). 3 parts by weight, particularly preferably 0.1 to 1 part by weight. When the amount of the crosslinking agent (B) is too small, the cohesive force is insufficient and a tendency that sufficient durability cannot be obtained is observed. When the amount is too large, the flexibility is lowered and the step following property tends to be lowered.

[Ethylenically unsaturated compound containing one ethylenically unsaturated group (C)]
As the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group used in the present invention, a (meth) acrylic ester compound (C1) having one ethylenically unsaturated group (described later ( It is preferable to use an ethylenically unsaturated compound (C2) excluding C2) and a nitrogen atom.

Examples of the (meth) acrylic acid ester compound (C1) having one ethylenically unsaturated group include a long-chain aliphatic (meth) acrylate (C1-1) and an alicyclic (meth) acrylate (C1-2). , Aromatic (meth) acrylate (C1-3), and oxyalkylene structure-modified compounds (C1-4) of these (meth) acrylates.
In the present invention, as the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group, long chain aliphatic (meth) acrylate (C1-1), alicyclic (meth) acrylate (C1-2) ), Aromatic (meth) acrylate (C1-3), or an oxyalkylene structure-modified compound (C1-4) of these (meth) acrylates.

The long chain aliphatic (meth) acrylate (C1-1), long chain aliphatic carbon atoms in the aliphatic group is 10 to 18 (meth) acrylate is used, for example, de Sil (meth) acrylate, isodecyl ( Examples include meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, isomyristyl (meth) acrylate, n-stearyl (meth) acrylate, and isostearyl (meth) acrylate.

  Examples of the alicyclic (meth) acrylate (C1-2) include isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and the like.

  Examples of the aromatic (meth) acrylate (C1-3) include biphenyl (meth) acrylate, naphthalene (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and 3-chloro-2-hydroxypropyl ( And (meth) acrylate.

  As the oxyalkylene structure-modified compound (C1-4) of the above (C1-1) to (C1-3), as the oxyalkylene structure-modified compound of (C1-1), for example, 2-ethylhexyl diethylene glycol (meth) acrylate, Methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, alkyl polyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, alkylene glycol monoalkyl ester (meth) acrylate, alkylene glycol mono (meth) acrylate Examples of the (C1-2) oxyalkylene structure-modified compound include t-butylcyclohexyloxyethyl (meth) acrylate, cyclohexyloxy, and the like. Examples include alkyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentanyloxyethyl (meth) acrylate. Examples of the (C1-3) oxyalkylene (alkyl) structure-modified compound include benzyl (Meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, phenyltriethylene glycol (meth) acrylate, phenyltetraglycol (meth) acrylate, biphenyloxyethyl (meth) acrylate, nonylphenol ethylene oxide modification (repeat 4) (Meth) acrylate, nonylphenol ethylene oxide modified (repeated 8) (meth) acrylate, and the like.

  Among these (meth) acrylic acid ester compounds (C1) having one ethylenically unsaturated group, long chain aliphatic (meth) acrylates (C1-1), (C1-2) and (C1-3) It is preferable to use an oxyalkylene structure-modified compound (C1-4) from the viewpoint that stable adhesive strength can be obtained, and particularly preferred is isomyristyl acrylate, tridecyl acrylate, isostearyl acrylate, phenyldiethylene glycol acrylate, dicyclopentenyloxy. Ethyl acrylate.

  The nitrogen-containing ethylenically unsaturated compound (C2) can be used to improve the adhesive strength of the pressure-sensitive adhesive. For example, acrylamide, methacrylamide, butoxymethylacrylamide, hydroxyethylacrylamide, dimethylaminopropyl Examples include (meth) acrylamide unsaturated monomers such as acrylamide and diacetone acrylamide, N-acryloyloxyethylhexahydrophthalimide, acryloylmorpholine, and oxazolidone acrylate. Among these, (meth) acrylamide unsaturated monomers are used. It is preferable to use it because it is hardly volatile and has excellent balance in adhesion performance, and is particularly preferably butoxymethylacrylamide.

  Among these, it is preferable to use a long-chain aliphatic acrylate (C1-1) from the viewpoint that an optically transparent pressure-sensitive adhesive layer that is difficult to be colored is obtained.

The weight average molecular weight of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group is preferably 150 to 2,000, particularly preferably 200 to 1,500, and more preferably 250 to 2,000. 500.
If the weight average molecular weight is too large, the pressure-sensitive adhesive properties tend to decrease, and if it is too small, it tends to volatilize in the drying step.

  Further, the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group is present as a polymer in the pressure-sensitive adhesive layer by being cured by active energy rays and / or heat as described later. However, it is preferable to select the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group so that the glass transition temperature (Tg) of the polymer is -80 to 80 ° C.

The glass transition temperature is particularly preferably −60 to 40 ° C., more preferably −30 to 20 ° C., and particularly preferably −10 to 10 ° C. If the glass transition temperature is too high, the adhesive performance tends not to be obtained. If it is too low, the cohesive force tends to decrease.
The glass transition temperature is calculated from the Fox equation described above.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention comprises a crosslinked product of a functional group-containing acrylic resin (A) and a crosslinking agent (B), and an ethylenically unsaturated compound (C) containing one ethylenically unsaturated group (hereinafter referred to as “single” It is a pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer containing a functional unsaturated compound (C) ”.

In the present invention, the content of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group in the pressure-sensitive adhesive layer is 5 to 30 % by weight with respect to the whole pressure-sensitive adhesive layer. It is necessary, preferably 10 to 30 % by weight, particularly preferably 15 to 30 % by weight, and further preferably 20 to 30% by weight.
If the content of the ethylenically unsaturated compound containing one ethylenically unsaturated group is too small, the step following ability is inferior, and if it is too large, the elastic modulus at the time of creating the sheet is too low and the handling property is inferior. It becomes.

  In addition, about content of the said ethylenically unsaturated compound (C) containing one said ethylenically unsaturated group, the ethylenicity in the whole adhesive composition after drying and removing the organic solvent which comprises an adhesive layer It is calculated | required as a content rate of an unsaturated compound (C).

  The pressure-sensitive adhesive layer may be a mixture of the monofunctional unsaturated compound (C) after the functional group-containing acrylic resin (A) and the cross-linking agent (B) are cross-linked. The compound (C) may be blended and the functional group-containing acrylic resin (A) and the crosslinking agent (B) may be crosslinked in the presence of the monofunctional unsaturated compound (C). The functional group-containing acrylic resin (A) and the cross-linking agent (B) are cross-linked in the presence of the monofunctional unsaturated compound (C) in that an adhesive sheet excellent in properties can be easily obtained. preferable.

  When the functional group-containing acrylic resin (A) and the crosslinking agent (B) are crosslinked in the presence of the monofunctional unsaturated compound (C), the functional group-containing acrylic resin (A) and the crosslinking agent (B ), A monofunctional unsaturated compound (C) as an essential component, and, if necessary, an ethylenically unsaturated compound (D) containing two or more ethylenically unsaturated groups described later, a polymerization initiator (E The pressure-sensitive adhesive composition of the present invention is obtained by coating a base material sheet with a pressure-sensitive adhesive composition, drying, and curing as necessary.

  Examples of the base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, boribylene terephthalate, polyethylene terephthalate / isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; Examples include cyclic olefin resins such as Arton (cyclic olefin polymer; manufactured by JSR) and trade name “Zeonoa (cyclic olefin polymer; manufactured by Nippon Zeon)”; polyvinyl fluoride, polyvinylidene fluoride, and polyfluorinated ethylene. Polyfluorinated ethylene resin such as nylon 6, nylon 6, nylon 6 and the like; polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, Vinyl polymers such as livinyl alcohol and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polystyrene; polycarbonate Polyarylate; synthetic resin sheet such as polyimide, metal foil of aluminum, copper and iron, paper such as fine paper and glassine paper, woven fabric and nonwoven fabric made of glass fiber, natural fiber, synthetic fiber and the like. These base material sheets can be used as a single layer body or a multilayer body in which two or more kinds are laminated.

  In addition, as the base sheet, transparent electrode films such as organic conductive curtains such as ITO electrode films and polythiophenes, or the above various base materials with electrode films, polarizing plates, retardation plates, elliptical polarizing plates, optical compensation films An optical member such as a brightness enhancement film, an electromagnetic wave shielding film, a near-infrared absorbing film, or an AR (anti-reflection) film may be used.

  Examples of the method for applying the pressure-sensitive adhesive composition include a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, and a spray coater.

  As the above drying conditions, the drying temperature is usually 50 ° C to 250 ° C, preferably 60 ° C to 120 ° C, and more preferably 65 ° C to 95 ° C. The drying time is usually 10 seconds to 10 minutes.

  As conditions for the curing treatment, the temperature is usually room temperature to 70 ° C., the time is usually 1 day to 30 days, and specifically, for example, 23 ° C. for 1 day to 20 days, preferably 23 ° C. for 3 days. What is necessary is just to carry out on conditions, such as 1 day-7 days at 40 degreeC for 10 days.

  Further, the pressure-sensitive adhesive sheet of the present invention may be a base material-less double-sided pressure-sensitive adhesive sheet that is used without a base material sheet at the time of adhering the adherend, for example, a pressure-sensitive adhesive composition on a release sheet. After forming a pressure-sensitive adhesive layer obtained by coating and drying, another pressure-sensitive adhesive layer is bonded to the side of the pressure-sensitive adhesive layer on which the release sheet is not provided, and is cured by curing as necessary. An agent layer can be formed. As for the method of use, after peeling off one release sheet and bonding it to the adherend, the other release sheet may be peeled off and bonded to the adherend.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is usually preferably from 5 to 300 μm, particularly preferably from 10 to 200 μm, more preferably from 15 to 100 μm, particularly preferably from 20 to 60 μm.
If the thickness of the pressure-sensitive adhesive layer is too thin, the step following ability tends to decrease, and if it is too thick, the thickness of the entire optical member tends to increase too much.

  In particular, when a thick adhesive layer is obtained, it is preferably applied with a film thickness of 10 μm or more, particularly preferably 20 μm or more, more preferably 30 μm or more. The film thickness at the time of coating is usually 800 μm.

  In addition, the said film thickness is a value calculated | required by subtracting the measured value of the thickness of structural members other than an adhesive layer from the measured value of the thickness of the whole adhesive sheet using Mitutoyo "ID-C112B".

  The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably 10 to 80%, particularly preferably 20 to 70%, particularly 30 to 60% from the viewpoints of durability and adhesive strength. It is preferable that If the gel fraction is too low, the pressure-sensitive adhesive sheet tends to have marks due to a decrease in cohesive force, or the pressure-sensitive adhesive sheet tends to sag. On the other hand, if the gel fraction is too high, the step following ability tends to decrease due to an increase in cohesive force.

  The gel fraction is a measure of the degree of crosslinking (curing degree), and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (not provided with a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, polyethylene terephthalate film or the like) as a base material is wrapped with a 200-mesh SUS wire mesh, and 23 in toluene. The weight percentage of the insoluble pressure-sensitive adhesive component immersed in the wire mesh at 24 ° C. for 24 hours is defined as the gel fraction. However, the weight of the substrate is subtracted.

The pressure-sensitive adhesive sheet of the present invention thus obtained contains a monofunctional unsaturated compound (C) in addition to the cross-linked product of the functional group-containing acrylic resin (A) and the cross-linking agent (B) in the pressure-sensitive adhesive layer. For this reason, the monofunctional unsaturated compound (C) imparts a plastic effect to the pressure-sensitive adhesive, so that the elastic modulus of the pressure-sensitive adhesive layer is lowered, and therefore excellent followability to the level difference (unevenness) of the adherend. It is possible to demonstrate.
And after bonding an adherend, the monofunctional unsaturated compound (C) contained in an adhesive layer superposes | polymerizes by applying active energy ray irradiation and / or heating to an adhesive layer, and adheres It becomes possible to adhere more firmly to the body.

  As a method for bonding the pressure-sensitive adhesive sheet and the adherend, for example, the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet is bonded to the adherend, and then heated and pressurized with an autoclave or the like (for example, 50 ° C. · 0. 5 MPa × 30 minutes).

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention includes, in addition to the cross-linked product of the functional group-containing acrylic resin (A) and the cross-linking agent (B) and the monofunctional unsaturated compound (C), The entire pressure-sensitive adhesive layer contains an ethylenically unsaturated compound (D) containing two or more ethylenically unsaturated groups (hereinafter sometimes abbreviated as “polyfunctional unsaturated compound (D)”). It is necessary in that the cohesive force can be adjusted , and it is preferable to further contain a polymerization initiator (E) in that the reaction at the time of irradiation with active energy rays and / or heating can be stabilized.

  As the polyfunctional unsaturated compound (D), for example, an ethylenically unsaturated monomer containing two or more ethylenically unsaturated groups in one molecule, for example, a bifunctional monomer, a trifunctional or higher monomer, Urethane (meth) acrylate compounds, epoxy (meth) acrylate compounds, and polyester (meth) acrylate compounds can be used. Among these, it is preferable to use an ethylenically unsaturated monomer and a urethane (meth) acrylate-based compound from the viewpoint of excellent curing rate and ultimate physical properties.

  The bifunctional monomer may be any monomer containing two ethylenically unsaturated groups. For example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene Oxide modified bisphenol A type di (meth) acrylate, propylene oxide modified bisphenol A type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate 1,6-hexanediol ethylene oxide modified di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di ( Meth) acrylate, diglycidyl phthalate di (meth) acrylate, hydroxypivalic acid modified neopentyl glycol di (meth) acrylate, isocyanuric acid ethylene oxide modified diacrylate, 2- (meth) acryloyloxyethyl acid phosphate diester, etc. It is done.

  The tri- or higher functional monomer may be any monomer containing three or more ethylenically unsaturated groups. For example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, Glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ethylene oxide modified dipentaerythritol (Meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, ethylene oxide modified pentaerythritol tri (meth) acrylate, ethylene oxide modified pentaerythritol tetra (meth) acrylate, succinic acid modified pentaerythritol tri (meth) acrylate Etc.

  The urethane (meth) acrylate compound is a (meth) acrylate compound having a urethane bond in the molecule, a (meth) acrylic compound containing a hydroxyl group and a polyvalent isocyanate compound (if necessary, a polyol What is necessary is just to use what is obtained by making it react by a well-known general method, and what is necessary is just to use the thing of 300-4000 normally as the weight average molecular weight.

  The content of the polyfunctional unsaturated compound (D) is preferably 0.01 to 100 parts by weight, particularly preferably 0.1 to 100 parts by weight with respect to 100 parts by weight of the functional group-containing acrylic resin (A). 30 parts by weight, more preferably 1 to 20 parts by weight, particularly preferably 5 to 15 parts by weight. If the content of the polyfunctional unsaturated compound (D) is too large, in the post-curing process, the cohesive force will increase too much, and shrinkage will occur and the adhesive performance will tend to decrease. Tend to be.

In addition, the content of the polyfunctional unsaturated compound (D) needs to be 0.01 to 30 parts by weight, particularly preferably 100 parts by weight of the monofunctional unsaturated compound (C). 1 to 30 parts by weight, more preferably 10 to 30 parts by weight. If the content of the polyfunctional unsaturated compound (D) is too large, in the post-curing process, the cohesive force will increase too much, and shrinkage will occur and the adhesive performance will tend to decrease. Tend to be.

  As the polymerization initiator (E), for example, various polymerization initiators such as a photopolymerization initiator (e1) and a thermal polymerization initiator (e2) can be used. It is preferable to use e1) in that it can be cured by irradiation with active energy rays such as ultraviolet rays for a very short time.

  When the photopolymerization initiator (e1) is used, the acrylic resin composition is cured by irradiation with active energy rays. When the thermal polymerization initiator (e2) is used, the acrylic resin composition is cured by heating. However, it is also preferable to use both in combination as necessary.

  A known general polymerization initiator may be used as the photopolymerization initiator (e1) and the thermal polymerization initiator (e2).

  About content of the said polymerization initiator (E), about 100 weight part of monofunctional unsaturated compounds (C) (when using a polyfunctional unsaturated compound (D), (C) and (D) The total amount is preferably from 0.01 to 50 parts by weight, particularly preferably from 0.1 to 20 parts by weight, more preferably from 0.3 to 12 parts by weight, particularly preferably from 0. 5 to 3 parts by weight. If the content of the polymerization initiator (E) is too small, the curability tends to be poor and the physical properties tend to become unstable, and if it is too much, no further effect can be obtained.

  In the present invention, when the adhesive layer is irradiated with active energy rays after bonding the adherend, a transparent material is used for at least one of the base sheet and the adherend, and the active energy rays are applied from the transparent surface. Irradiation may be performed.

  In the active energy ray irradiation, far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays and other electromagnetic waves, X rays, γ rays and other electromagnetic waves, as well as electron beams, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous from the standpoint of availability of the device and price. In addition, when performing electron beam irradiation, it can harden | cure even without using the said photoinitiator (e1).

As a light source for the ultraviolet irradiation, a high pressure mercury lamp, an electrodeless lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, or the like is used. For the high-pressure mercury lamp, for example, 5~3000mJ / cm ^2, preferably at the conditions of 50~2000mJ / cm ^2. Moreover, in the case of the said electrodeless lamp, it is 2-2000 mJ / cm < ² >, for example, Preferably it is performed on the conditions of 10-1000 mJ / cm < ² >. The irradiation time varies depending on the type of the light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but may be usually from several seconds to several tens of seconds, and in some cases, may be a fraction of a second. On the other hand, in the case of the electron beam irradiation, for example, an electron beam having an energy in the range of 50 to 1000 Kev is used, and the irradiation amount is preferably 2 to 50 Mrad.

  Moreover, when using a thermal-polymerization initiator (e2) as said polymerization initiator (E), a polymerization reaction is started and advanced by heating. The treatment temperature and treatment time at the time of curing by heating vary depending on the type of the thermal polymerization initiator (e2) to be used, and are usually calculated from the half-life of the initiator, but the treatment temperature is usually The temperature is preferably 70 to 170 ° C., and the treatment time is usually preferably 0.2 to 20 minutes, and particularly preferably 0.5 to 10 minutes.

  Thus, the pressure-sensitive adhesive sheet of the present invention is bonded to an adherend, and irradiated with active energy rays and / or heated to provide a laminate with an adhesive layer ([adherent / adhesive layer / base sheet] or substrate). When a double-sided pressure-sensitive adhesive sheet is used, [adhered body / adhesive layer / adhered body]) can be obtained.

  The adherend is not particularly limited. For example, transparent electrode films such as ITO electrode films and organic conductive curtains such as polythiophene, polarizing plates, retardation plates, elliptically polarizing plates, optical compensation films, Examples of the optical member include a brightness enhancement film, an electromagnetic wave shielding film, a near-infrared absorbing film, and an AR (anti-reflection) film. In particular, it is preferable that the adherend has a step because the effect of the pressure-sensitive adhesive sheet excellent in followability of the present invention is remarkably exhibited, for example, 1 to 100 μm, particularly 3 to 50 μm, and further 5 to 30 μm. Even an adherend having such a step exhibits good followability.

  The adhesive sheet of the present invention is made of glass, ITO transparent electrode sheet, polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA) and other optical sheets, polarizing plate, retardation plate, optical compensation film, and brightness enhancement. This is useful for attaching optical members such as films. Furthermore, it can be suitably used for an image display device such as a touch panel including these optical members.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis.

  First, various acrylic resin (A) solutions were prepared as follows. In addition, regarding the measurement of the weight average molecular weight, dispersion degree, and glass transition temperature of acrylic resin (A), it measured according to the above-mentioned method.

  Regarding the measurement of the solid content concentration, 1 to 2 g of acrylic resin (A) solution was taken on aluminum foil, dried by heating for 45 minutes with a ket (infrared dryer, 185 W, height 5 cm), and the weight change before and after drying. The viscosity was measured according to the JIS K5400 (1990) 4.5.3 rotational viscometer method.

[Production of acrylic resin (A) solution]
[Acrylic resin (A-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 70 parts of 2-ethylhexyl acrylate (a 2 ), 30 parts of 2-hydroxyethyl acrylate (a 1 ) and acetic acid 80 parts of ethyl was charged, and after heating to reflux, 0.1 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator. After reacting for 3 hours at reflux temperature of ethyl acetate, azobisisobutyronitrile (AIBN) 0 .1 part and 20 parts of ethyl acetate were added and reacted for another 4 hours, diluted with ethyl acetate to obtain an acrylic resin (A-1) solution (weight average molecular weight 750,000, dispersity 3.8, glass transition temperature- 56 ° C., solid content 50%, viscosity 15,000 mPa · s (25 ° C.)).

[Crosslinking agent (B)]
The following were prepared as a crosslinking agent (B-1).
-55% ethyl acetate solution of tolylene diisocyanate adduct of trimethylolpropane (
(Japan Coronate L-55E)

[Monofunctional unsaturated compound (C)]
The following were prepared as the monofunctional unsaturated compound (C-1).
Isostearyl acrylate (“ISTA” manufactured by Osaka Organic Chemical Industry); flash point 154 ° C .; molecular weight 324

[Polyfunctional unsaturated compound (D)]
The following were prepared as the polyfunctional unsaturated compound (D-1).
・ Trimethylolpropane triacrylate (TMPTA)

[Polymerization initiator (E)]
The following were prepared as a polymerization initiator (E-1).
A 1: 1 mixture of 1-hydroxycyclohexyl phenyl ketone and benzophenone (Ciba Japan, “Irgacure 500”)

[Example 1]
100 parts of the acrylic resin (A-1), 0.5 part of a crosslinking agent (B-1), 30 parts of a monofunctional unsaturated compound (C-1), a polyfunctional unsaturated compound (D-1) 3 parts and 0.3 part of photoinitiator (E-1) were mix | blended, and the adhesive composition solution was prepared.
This pressure-sensitive adhesive composition solution was applied to a polyester release sheet so that the thickness after drying was 50 μm, and dried at 100 ° C. for 5 minutes to form a pressure-sensitive adhesive composition layer. The obtained pressure-sensitive adhesive composition layer was sandwiched between polyester release sheets, and 23 ° C. × 50% R.D. H. The substrate-less double-sided PSA sheet was obtained by aging for 7 days under the above conditions.
The release sheet on one side is peeled off from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet obtained above and pressed against a 100 μm polyethylene terephthalate (PET) film to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 50 μm. It was.

[Examples 2 to 4, Comparative Examples 1 and 2]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the blending ratio of the components (A) to (E) was changed to the blending ratio shown in Table 1.

  First, the gel fraction and adhesive strength (initial adhesive strength) of the adhesive sheet were measured. The results are shown in Table 1.

[Gel fraction]
After cutting the pressure-sensitive adhesive sheet into 40 mm × 40 mm, the release sheet is peeled off, the pressure-sensitive adhesive layer side is bonded to a 50 mm × 100 mm SUS mesh sheet (200 mesh), and then the longitudinal direction of the SUS mesh sheet. After wrapping the sample from the center and wrapping the sample, the gel fraction (%) was measured by the change in weight when immersed in a sealed container containing 250 g of toluene.

[Initial adhesive strength]
About the pressure-sensitive adhesive sheet, it is cut into a width of 25 mm and a length of 100 mm, the release sheet is peeled off, and the pressure-sensitive adhesive layer side is pressed with soda glass at a temperature of 23 ° C. and a relative humidity of 50% with 2 kg rubber rollers in two reciprocations. Affixed and subjected to pressure heat treatment at 50 ° C. and 0.5 MPa × 20 minutes in an autoclave, left in an atmosphere of 23 ° C. and 50% relative humidity for 30 minutes, and 180 ° C. at a normal temperature with a peeling rate of 300 mm / min. The peel strength (N / 25 mm) was measured.

  Next, after sticking the said adhesive sheet with each to-be-adhered body and performing ultraviolet irradiation, it measured about adhesive force (adhesive force after hardening), holding power, level | step difference followability, wet heat resistance, and blister resistance. The results are shown in Table 1.

[Adhesive strength after curing]
About the pressure-sensitive adhesive sheet, it is cut into a width of 25 mm and a length of 100 mm, the release sheet is peeled off, and the pressure-sensitive adhesive layer side is pressed with soda glass at a temperature of 23 ° C. and a relative humidity of 50% with 2 kg rubber rollers in two reciprocations. Affixed and subjected to pressure heating treatment at 50 ° C. and 0.5 MPa × 20 minutes in an autoclave, then peak illuminance: 150 mW / cm ² , integrated exposure: 500 mJ / cm from the PET film side with a high-pressure mercury UV irradiation device. ² (250 mJ / cm ² × 2 pass), 23 ° C. × 50% R.V. H. After being left for 30 minutes under the above conditions, the 180 ° peel strength (N / 25 mm) was measured at room temperature and a peel rate of 300 mm / min.

[Retention force]
The pressure-sensitive adhesive sheet is cut to a size of 25 mm × 25 mm, the release sheet is peeled off, the pressure-sensitive adhesive layer side is attached to a polished SUS plate, and heated under pressure in an autoclave at 50 ° C. and 0.5 MPa × 20 minutes. Processed. Next, UV irradiation is performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm ² and an integrated exposure amount of 500 mJ / cm ² (250 mJ / cm ² × 2 passes), 23 ° C. × 50% R . H. After being allowed to stand for 30 minutes under the above conditions, a load of 1 kg was applied under the conditions of 80 ° C., and the displacement was evaluated according to the measuring method of the holding power of JIS Z 0237. The evaluation criteria are as follows.
(Evaluation)
○ ・ ・ ・ No deviation occurs after 1440 minutes △ ・ ・ ・ Deformation occurs after 1440 minutes × ・ ・ ・ Drops by 1440 minutes

[Step following capability]
On the soda glass, 8 μm PET film, 16 μm PET film, and 25 μm PET film were fixed with cellophane tape to produce glass with a step. The pressure-sensitive adhesive sheet is pressure-applied to the stepped glass with two reciprocations of a 2 kg rubber roller in an atmosphere of 23 ° C. and 50% relative humidity, and subjected to pressure heat treatment at 50 ° C. and 0.5 MPa × 20 minutes in an autoclave. After that, UV irradiation is performed from the PET film side with a high-pressure mercury UV irradiation device with a peak illuminance of 150 mW / cm ² and an integrated exposure amount of 500 mJ / cm ² (250 mJ / cm ² × 2 passes), 23 ° C. × 50%. R. H. After being allowed to stand for 30 minutes under the above conditions, the ability to follow a step was visually evaluated. The evaluation results are as follows.
(Evaluation)
○: Air can not be found in the step.
Δ: A slight amount of air can be seen in the step.
×: Air is entrained in the step and the pressure-sensitive adhesive layer is largely floating.

[Moisture and heat resistance]
The pressure-sensitive adhesive sheet was cut to 25 mm × 25 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer side was bonded to a slide glass (Corning, Corning 1737), followed by autoclaving (50 ° C., 0. 5 MPa, 20 minutes), UV irradiation is performed at a peak illuminance of 150 mW / cm ² and an integrated exposure amount of 500 mJ / cm ² with a high-pressure mercury UV irradiation device from the PET film side (250 mJ / cm ² × 2 passes). 23 ° C. × 50% R.D. H. The test piece having the configuration of “slide glass / adhesive layer / PET film” was produced by leaving it for 30 minutes under the above conditions.
Using the test piece, a moist heat resistance test for 120 hours was performed in an atmosphere of 80 ° C. and 90% RH, and the haze values before the start of the moist heat resistance test and after the moist heat resistance test were measured and evaluated according to the following criteria.
The haze value is determined by measuring the diffuse transmittance and the total light transmittance using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). Substituted to calculate haze. This machine complies with JIS K7361-1.
Haze value (%) = (diffuse transmittance / total light transmittance) × 100
(Evaluation)
○: The haze value after the moist heat resistance test is less than 3.0, and the rate of increase in the haze value before and after the moist heat resistance test is within 1.2 times.
Δ: The haze value immediately after the moist heat resistance test is less than 3.0, and the rate of increase of the haze value before and after the moist heat resistance test is greater than 1.2 times.
X: Haze value immediately after wet heat resistance test is 3.0 or more

[Blister resistance]
The pressure-sensitive adhesive sheet is cut to 25 mm × 25 mm, the release sheet is peeled off, the pressure-sensitive adhesive layer side is attached to a polycarbonate plate, autoclaved (50 ° C., 0.5 MPa, 20 minutes), and then UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation apparatus at a peak illuminance of 150 mW / cm ² and an integrated exposure amount of 500 mJ / cm ² (250 mJ / cm ² × 2 passes), 23 ° C. × 50% R.D. H. A test piece having a configuration of “polycarbonate plate / acrylic pressure-sensitive adhesive layer / PET film” was produced by allowing the sample to stand for 30 minutes.
Then, it left still for 24 hours in 80 degreeC dry atmosphere, and observed the blister generation | occurrence | production degree before and after still standing visually. The evaluation criteria are as follows.
(Evaluation)
○: No foaming exceeding φ0.5 mm.
Δ: There is foaming exceeding φ0.5 mm, but the foaming area is less than 1/3 of the entire pasting surface.
X: Foaming occurred in 1/3 or more of the entire pasting surface.

※表中（ ）内の数字は重量部を表す。また、――は配合しなかったことを表す

* Numbers in parentheses in the table represent parts by weight. Also, ―― indicates that it was not blended

In the pressure-sensitive adhesive sheet having a 50 μm-thick pressure-sensitive adhesive layer of Examples 1 to 4, excellent followability is exhibited for steps of 8 μm and 16 μm, and constant followability is exhibited even for steps of 25 μm. I understand that. Furthermore, it is excellent in physical properties required when the adhesive sheet is used for laminating optical members such as a touch panel, such as strong adhesive force, wet heat whitening resistance, and blister resistance.
In particular, it can be seen that the pressure-sensitive adhesive sheets of Examples 3 and 4 have extremely good level-step following properties and are extremely excellent in blister resistance.

On the other hand, the pressure-sensitive adhesive sheet of Comparative Example 1 that does not contain the monofunctional unsaturated compound (C) in the pressure-sensitive adhesive layer is inferior in level difference followability and blister resistance compared to the pressure-sensitive adhesive sheet of the example. I understand.
The pressure-sensitive adhesive sheet of Comparative Example 2 that does not contain the crosslinking agent (B) and the monofunctional unsaturated compound (C) in the pressure-sensitive adhesive layer does not cure the pressure-sensitive adhesive layer and has an elastic modulus. Although it is low, the step following ability is excellent to some extent, but it is inferior to the adhesive physical properties such as holding force and adhesive force.

The pressure-sensitive adhesive sheet of the present invention is excellent in step following ability, and further has high adhesive strength, high light transmittance, and hardly generates haze, so that glass, ITO transparent electrode sheet, polyethylene terephthalate (PET) is used. ), Polycarbonate (PC), polymethyl methacrylate (PMMA), and other optical sheets, polarizing plates, retardation plates, optical compensation films, brightness enhancement films, and other optical member application applications. Furthermore, it can be suitably used for a touch panel including these optical members.

Claims (8)

Cross-linked product of functional group-containing acrylic resin (A) and cross-linking agent (B), ethylenically unsaturated compound (C) containing one ethylenically unsaturated group, and containing two or more ethylenically unsaturated groups It is a pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer containing an ethylenically unsaturated compound (D),
The functional group-containing acrylic resin (A) is obtained by polymerizing a monomer component containing a (meth) acrylic acid ester monomer (a2) containing at least 2-ethylhexyl (meth) acrylate. The content of the (meth) acrylic acid ester monomer (a2) is 50 to 99.99% by weight,
The content of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group is 5 to 30% by weight with respect to the entire pressure-sensitive adhesive layer,
The content of the ethylenically unsaturated compound (D) containing two or more ethylenically unsaturated groups is 0.100 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated compound (C) containing one ethylenically unsaturated group. 01 to 30 parts by weight,
An ethylenically unsaturated compound (C) containing one ethylenically unsaturated group is a long chain aliphatic (meth) acrylate (C1-1) having an aliphatic group having 10 to 18 carbon atoms , an alicyclic (meta ) An acrylate (C1-2), an aromatic (meth) acrylate (C1-3), or an oxyalkylene structure-modified compound (C1-4) of these (meth) acrylates.   The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 300 μm.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is cured by active energy rays and / or heat.   A method for producing a laminate with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive sheet according to claim 1 or 2 is bonded to an adherend and irradiated with active energy rays and / or heated.   The method for producing a laminate with an adhesive layer according to claim 4, wherein the adherend is an adherend having a step of 1 to 100 µm.   A laminate with a pressure-sensitive adhesive layer obtained by the method for producing a laminate with a pressure-sensitive adhesive layer according to claim 4 or 5.   An image display device comprising the laminate with an adhesive layer according to claim 6.   A touch panel comprising the laminate with an adhesive layer according to claim 6.