KR102253912B1 - Adhesive composition and adhesive sheet - Google Patents

Abstract

To provide a pressure-sensitive adhesive composition for a pressure-sensitive adhesive sheet capable of suppressing residual pressure-sensitive adhesive after peeling while having low haze, easy lamination, and easy to peel. Polyurethane (A) comprising a polyurethane having a structure derived from a polyoxyalkylene polyol and a polyisocyanate, and having a (meth)acryloyl group at a plurality of terminals, and other than the polyurethane (A) It is a compound, and is a compound other than the polyfunctional monomer (B) having a plurality of (meth)acryloyl groups and the polyurethane (A), and is a compound other than the polyfunctional monomer (B), and is a polyurethane (A) and a polyfunctional monomer ( It is set as the pressure-sensitive adhesive composition characterized in that it contains B) and another monomer (C) which can polymerize, and a photoinitiator (D), and the weight average molecular weight of polyurethane (A) is 30,000-200,000.

Description

Adhesive composition and adhesive sheet

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet, and more particularly, to a pressure-sensitive adhesive composition containing a compound having a (meth)acryloyl group, and a pressure-sensitive adhesive sheet having a cured product of the pressure-sensitive adhesive composition.

This application claims priority based on Japanese Patent Application No. 2017-195411 for which it applied to Japan on October 5, 2017, and uses the content here.

Various optical films are used for optical components such as liquid crystal displays such as smartphones, personal computers, and televisions, and touch panels. On the surface of these optical films, in general, a protective sheet (adhesive sheet) is laminated for the purpose of preventing the occurrence of contamination or scratches in the transport process, the manufacturing process, and the inspection process. This protective sheet is peeled off in post-processes, such as a granulation process. As an adhesive for such a protective sheet, various urethane adhesives have been proposed.

For example, in Patent Document 1, a polyurethane having a polyoxyalkylene polyol as a skeleton and a weight average molecular weight of 10,000 to 300,000 having a (meth)acryloyl group at the terminal, and a (meth)acrylic acid ester having a hydroxy group , A photocurable composition for a transparent adhesive sheet containing another photopolymerizable monomer and a photopolymerization initiator is described.

In addition, in Patent Document 2, polyurethane having a (meth)acryloyl group bonded to the terminal of the polyoxyalkylene chain through a urethane bond, (meth)acrylic acid ester having a hydroxy group, (meth)acrylic acid ester having an aromatic ring, and others. A photocurable composition for a transparent adhesive sheet containing a polymerizable monomer and a photopolymerization initiator is described.

Japanese Patent Publication No. 2014-210895 Japanese Patent Publication No. 2016-20477

In the inspection process, there are cases where it is required to sufficiently discover or be able to detect fine foreign matter or scratches on the product or part while the protective sheet is laminated on the product or part. Therefore, the protective sheet is required to have less fogging, that is, low haze.

In the manufacturing process, lamination and peeling may be repeated for the protective sheet. Therefore, the protective sheet is required to be easily laminated to an adherend (high wettability to an adherend) and easy peeling. In addition, in recent years, with the enlargement of the display screen and the thinning of the panel component, the optical component itself is becoming more fragile. Therefore, it is also required that the protective sheet can be peeled off with a lighter force while having an appropriate adhesiveness (peel strength) (light peeling property). In addition, it is also required that there is no so-called adhesive residue (re-peelability) in which a part of the adhesive layer or the like remains on the product surface (adherence) after peeling of the protective sheet.

However, the compositions described in Patent Literature 1 and Patent Literature 2 are not intended to be used for a protective sheet for peeling in a manufacturing process, and a pressure-sensitive adhesive sheet using these compositions has high peel strength.

Therefore, an object of the present invention is to provide a pressure-sensitive adhesive composition for a pressure-sensitive adhesive sheet capable of suppressing residual pressure-sensitive adhesive after peeling while having low haze, easy lamination, and easy peeling. Further, another object of the present invention is to provide a pressure-sensitive adhesive sheet capable of suppressing residual pressure-sensitive adhesive after peeling while having low haze, easy lamination, and easy peeling.

The configuration of the present invention for solving the above problem is as follows.

[1] Polyurethane (A) having a skeleton having a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, a compound other than polyurethane (A), and having a plurality of (meth)acryloyl groups It is a compound other than the functional monomer (B) and the polyurethane (A), and is a compound other than the polyfunctional monomer (B), and is polymerizable with the polyurethane (A) and the polyfunctional monomer (B), and other monomers (C) and , A photoinitiator (D), the polyurethane (A) contains a polyurethane (a1), and the polyurethane (a1) has a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate. It has a skeleton including, and has a (meth)acryloyl group at a plurality of terminals of the polyurethane (a1),

The pressure-sensitive adhesive composition, characterized in that the weight average molecular weight of the polyurethane (A) is 30,000 to 200,000.

[2] With respect to the total amount of polyurethane (A), polyfunctional monomer (B) and other monomers (C), 30 to 60 mass% of polyurethane (A) and 10 to 20 mass of polyfunctional monomer (B) The pressure-sensitive adhesive composition according to [1], containing 20 to 50% by mass of other monomers (C).

[3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the structure derived from the polyoxyalkylene polyol contained in the polyurethane (A) is a structure derived from a polyoxyalkylene polyol having a number average molecular weight of 500 to 5,000.

[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the skeleton of the polyurethane (A) is a copolymer of polyoxyalkylene glycol and diisocyanate.

[5] The pressure-sensitive adhesive composition according to [4], wherein the skeleton of the polyurethane (A) is a copolymer of a hydrogenated product of polypropylene glycol and diphenylmethane diisocyanate.

[6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the (meth)acryloyl group in the polyurethane (A) is a part of the (meth)acryloyloxy group.

[7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the polyfunctional monomer (B) has three or more (meth)acryloyl groups.

[8] The pressure-sensitive adhesive composition according to [7], wherein the polyfunctional monomer (B) is trimethylolpropane triacrylate.

[9] The pressure-sensitive adhesive composition according to [8], wherein the other monomer (C) has a (meth)acryloyl group.

[10] The pressure-sensitive adhesive composition according to [9], wherein the other monomer (C) contains a (meth)alkyl acrylate.

[11] Polyurethane (A) further includes polyurethane (a2), and the polyurethane (a2) has a skeleton including structures derived from polyoxyalkylene polyols and polyisocyanates, and either terminal The pressure-sensitive adhesive composition according to any one of [1] to [10] having only a (meth)acryloyl group.

[12] The pressure-sensitive adhesive composition according to any one of [1] to [10], in which a (meth)acryloyl group is introduced into 90 to 100% of the terminals of the polyurethane molecules contained in the polyurethane (A) on a number basis.

[13] An adhesive sheet in which an adhesive layer containing a cured product of the photocurable adhesive composition according to any one of [1] to [12] is formed on a substrate.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for a pressure-sensitive adhesive sheet capable of suppressing residual pressure-sensitive adhesive after peeling while having low haze, easy lamination, and easy peeling. Further, according to the present invention, it is possible to provide a pressure-sensitive adhesive sheet capable of suppressing residual pressure-sensitive adhesive after peeling while having low haze, easy lamination, and easy peeling.

1 is a plan view showing a method for evaluating the lamination property of an adhesive sheet.
2 is a cross-sectional view taken along AA in FIG. 1.

Hereinafter, an embodiment of the present invention will be described. Here, the (meth)acryloyl group means _{a group represented by the formula CH 2} =CH-CO-, or _{a functional group represented by the formula CH 2} =C(CH ₃ )-CO-, and (meth)acryloyl oxide The term means _{a group represented by the formula CH 2} =CH-CO-O-, or a functional group represented by the _{formula CH 2} =C(CH _{3 )-CO-O-.} In addition, an isocyanato group means a functional group represented by the formula -N=C=O.

<1. Adhesive composition>

The pressure-sensitive adhesive composition according to the present embodiment is a compound other than polyurethane (A) and polyurethane (A) having a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and is a (meth)acrylic It is a polyfunctional monomer (B) having a plurality of royl groups and a monomer other than the polyurethane (A) and other than the polyfunctional monomer (B), and can be polymerized with the polyurethane (A) and the polyfunctional monomer (B), It contains an outer monomer (C) and a photoinitiator (D). The polyurethane (A) contains a polyurethane (a1), and the polyurethane (a1) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and the polyurethane It has a (meth)acryloyl group at a plurality of terminals of (a1). The weight average molecular weight of polyurethane (A) is 30,000-200,000. In addition, the pressure-sensitive adhesive composition according to the present embodiment may contain additives such as fatty acid esters, if necessary. In addition, the pressure-sensitive adhesive composition according to the present embodiment may contain a solvent as necessary. Hereinafter, each component included in the pressure-sensitive adhesive composition will be described. In addition, in the following description, components containing polyurethane (A), polyfunctional monomer (B), and other monomers (C) are sometimes referred to as "components (A) to (C)".

<1-1. Polyurethane (A)>

Polyurethane (A) has a skeleton including a structure derived from a polyoxyalkylene polyol and a polyisocyanate. Polyurethane (A) contains polyurethane (a1). The polyurethane (a1) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and has a (meth)acryloyl group at a plurality of terminals of the polyurethane (a1). Further, it is preferable that the terminal (meth)acryloyl group of the polyurethane is a part of the (meth)acryloyloxy group. Further, the polyurethane (A) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and further includes a polyurethane (a2) having a (meth)acryloyl group at only one terminal. You may include it. Components other than polyurethane (a1) and polyurethane (a2) are not contained in polyurethane (A). Here, the method for adjusting the number of terminal (meth)acryloyl groups of the polyurethane will be described later in the section of the method for producing polyurethane (A).

The polyoxyalkylene polyol preferably has an alkylene chain having 2 to 4 carbon atoms, and examples thereof include polyoxyethylene polyol, polyoxypropylene polyol, and polyoxybutylene polyol. Further, among the polyoxyalkylene polyols, polyoxyalkylenediol is preferably used, and polypropylene glycol is particularly preferably used.

In other words, the polyoxyalkylene polyol may be a copolymer of two or more oxyalkylene polyols. Further, the polyurethane (A) may be a structure in which a structure derived from two or more different polyoxyalkylene polyols is polymerized through a polyisocyanate.

When the number average molecular weight of the polyoxyalkylene polyol is excessively small, the peel strength of the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition may decrease. On the other hand, when the number average molecular weight of the polyoxyalkylene polyol is excessively large, the urethane bonds in the polyurethane are reduced, so that the cohesive strength of the adhesive layer may be lowered. From this viewpoint, the number average molecular weight of the polyoxyalkylene polyol is preferably 500 to 5,000, more preferably 800 to 4,000, and still more preferably 1,000 to 3,000.

Although it does not specifically limit as a polyisocyanate, Diisocyanate is preferable. Examples of diisocyanates include tolylene diisocyanate and hydrogenated products thereof, xylylene diisocyanate and hydrogenated products thereof, diphenylmethane diisocyanate and hydrogenated products thereof, 1,5-naphthylene diisocyanate and hydrogenated products thereof, hexamethylenedi Isocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyldiisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, norbornanediisocyanate And the like.

Among these exemplified compounds, a hydrogenated product of isophorone diisocyanate or diphenylmethane diisocyanate is preferable from the viewpoint of controlling light resistance and reactivity, and a hydrogenated product of diphenylmethane diisocyanate is more preferable from the viewpoint of reactivity. The structure derived from the polyisocyanate contained in the polyurethane (A) may be one containing one type or a structure containing two or more types.

The weight average molecular weight of the polyurethane (A) is 30,000 to 200,000, preferably 50,000 to 150,000, and more preferably 70,000 to 100,000. When the weight average molecular weight of the polyurethane (A) is 30,000 or more, the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition has sufficient flexibility, and therefore the pressure-sensitive adhesive sheet having this pressure-sensitive adhesive layer is easily laminated. In addition, when the weight average molecular weight of the polyurethane (A) is 200,000 or less, handling as an adhesive composition is easy and workability can be improved.

By increasing the content of the polyurethane (A), the cohesive force of the cured product of the pressure-sensitive adhesive composition can be increased, and the intercalation of air bubbles to the adhesion surface (between the adhesive layer and the adherend) due to the pressure-sensitive adhesive layer becoming too flexible can be suppressed. have. By reducing the content of the polyurethane (A), the cohesive force of the cured product of the pressure-sensitive adhesive composition is suppressed, the pressure-sensitive adhesive layer becomes flexible, and the wettability of the pressure-sensitive adhesive layer to the adherend can be improved. From these viewpoints, the content of the polyurethane (A) is preferably 30 to 60% by mass, more preferably 34 to 56% by mass, and more preferably 37 to 53% by mass with respect to the total amount of the components (A) to (C). It is more preferable that it is %. When the content of the polyurethane (A) is 30 to 60% by mass, cohesive strength and peel strength when used as an adhesive sheet are suitable.

<1-2. Polyfunctional monomer (B)>

The polyfunctional monomer (B) adjusts the peel strength of the pressure-sensitive adhesive layer (adhesive sheet) using the cured product of the pressure-sensitive adhesive composition. The polyfunctional monomer (B) is other than the polyurethane (A) and has a plurality of (meth)acryloyl groups, but is not particularly limited as long as the number of (meth)acryloyl groups is two or more. However, from the viewpoint of curability, it is preferable that the polyfunctional monomer (B) has three or more (meth)acryloyl groups.

As the polyfunctional monomer (B), it is preferable that it is a polyol poly(meth)acrylate, for example, polyethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylic. Rate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxypivalic acid ester neopentyl glycol di(meth)acrylate, 1,3-bis(hydroxyethyl)-5, 5-Dimethylhydantoindi(meth)acrylate, α,ω-di(meth)acrylbisdiethylene glycol phthalate, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di (Meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, diacryloxyethylphosphate, dipentaerythritol Trihydroxy(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc. are mentioned.

Among these, 1,6-hexanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol trihydroxy in that it is easy to adjust the peel strength of the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition low. (Meth)acrylate and pentaerythritol tetra(meth)acrylate are more preferable, and trimethylolpropane tri(meth)acrylate is more preferable. Moreover, the polyfunctional monomer (B) may contain one type of compound, or may contain two or more types of compounds.

By increasing the content of the polyfunctional monomer (B), the peel strength as an adhesive sheet can be weakened. Further, by reducing the content of the polyfunctional monomer (B), the haze can be lowered as an adhesive sheet. From these viewpoints, the content of the polyfunctional monomer (B) is preferably 10 to 20% by mass, more preferably 11 to 19% by mass, and more preferably 12 to 18% by mass with respect to the total amount of the components (A) to (C). It is more preferable that it is mass %. When the content of the polyfunctional monomer (B) is 10 to 20 parts by mass, a pressure-sensitive adhesive sheet excellent in light peelability is obtained.

<1-3. Other monomers (C)>

Other monomers (C) are compounds other than polyurethane (A) and other than polyfunctional monomer (B), and are not particularly limited as long as they can be polymerized with polyurethane (A) and polyfunctional monomer (B). However, the other monomer (C) is a functional group for polymerization with the polyurethane (A) and the polyfunctional monomer (B), preferably having an ethylenically unsaturated bond capable of radical polymerization, and among them, a vinyl group or (meth) It is more preferable that it is an acryloyl group, and it is still more preferable that it is a (meth)acryloyl group.

Although it does not specifically limit as another monomer (C), Alkyl (meth)acrylate, cyclic alkyl (meth)acrylate, alkoxyalkyl (meth)acrylate, alkoxy (poly)alkylene glycol (meth)acrylate, hydroxy group Containing (meth)acrylate, carboxy group containing (meth)acrylate, fluorinated alkyl (meth)acrylate, dialkylaminoalkyl (meth)acrylate, (meth)acrylamide, epoxy group-containing (meth)acrylate, and the like. have.

Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and tert-butyl (meth) acrylic. Rate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-hexyl (meth)acrylate, isooctyl (meth)acrylate, isostearyl (meth) ) Acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and the like.

As cyclic alkyl (meth)acrylate, for example, cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, norbornanyl (meth)acrylate, dicyclophene Tenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclodecanedimethyloldi (meth)acrylate, etc. Can be mentioned.

Examples of the alkoxyalkyl (meth)acrylate include ethoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and 2-methoxyethoxyethyl (meth)acrylic. Rate, 2-ethoxyethoxyethyl (meth)acrylate, and the like.

Examples of the alkoxy (poly) alkylene glycol (meth) acrylate include methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. have.

Examples of the hydroxy group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 1,3-butanediol. (Meth)acrylate, 1,4-butanediol (meth)acrylate, 1,6-hexanediol (meth)acrylate, 3-methylpentanediol (meth)acrylate, and the like.

Examples of the carboxy group-containing (meth)acrylate include (meth)acrylic acid and β-carboxyethyl (meth)acrylate.

Examples of the fluorinated alkyl (meth)acrylate include octafluoropentyl (meth)acrylate.

Examples of the dialkylaminoalkyl (meth)acrylate include N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate.

As (meth)acrylamide, for example, (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-isopropyl acrylamide, N-hexyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, (meth)acryloylmorpholine, diacetoneacrylamide, etc. are mentioned. .

Examples of the epoxy group-containing (meth)acrylate include glycidyl (meth)acrylate.

In addition, as other monomers (C), other than the above compounds, for example, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinyl chloride Liden, alkyl vinyl ether, vinyl toluene, N-vinylpyridine, N-vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, 4-hydroxy Hydroxymethylcyclohexylmethyl vinyl ether, triethylene glycol monovinyl ether or diethylene glycol monovinyl ether, methyl vinyl ketone, N-acrylamide methyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, and the like.

Among these exemplified compounds, from the viewpoint of compatibility with polyurethane (A), viscosity of the pressure-sensitive adhesive composition, and adjustment of peel strength, alkyl (meth)acrylate is preferable, and 2-ethylhexyl (meth)acrylate, isooctyl ( Meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, and (meth)acryloylmorpholine are more preferable, and 2-ethylhexyl (meth)acrylate is more preferable. In addition, as for the other monomer (C), one type may contain a compound, and may contain two or more types of compounds.

By increasing the content of the other monomer (C), the cohesive strength of the cured product of the pressure-sensitive adhesive composition is weakened, the pressure-sensitive adhesive layer is made flexible, and the wettability to the adherend can be improved. On the other hand, by reducing the content of the other monomer (C), the cohesive force of the cured product of the pressure-sensitive adhesive composition increases, and the sticking of air bubbles to the adhesive surface (between the adhesive layer and the adherend) due to the pressure-sensitive adhesive layer becoming too flexible can be suppressed. I can. From this point of view, the content of other monomers (C) is preferably 20 to 50% by mass, more preferably 23 to 47% by mass, and more preferably 25 to 45 with respect to the total amount of components (A) to (C). It is more preferable that it is mass %. When the content of the other monomer (C) is 20 to 50% by mass, since the cohesive strength of the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition is sufficiently obtained, it is preferable.

<1-4. Photoinitiator (D)>

Although it does not specifically limit as a photoinitiator (D), A carbonyl photoinitiator, a sulfide photoinitiator, an acylphosphine oxide, a quinone photoinitiator, a sulfochloride photoinitiator, a thioxanthone system Photoinitiators, etc. are mentioned.

As a carbonyl type photoinitiator, for example, benzophenone, benzyl, benzoin, ω-bromoacetophenone, chloroacetone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2- Phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, Benzoin methyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, benzyl methyl ketal, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one , 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, methylbenzoylformate, 2,2-diethoxyacetophenone, 4-N,N'-dimethylacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and the like.

As a sulfide type photoinitiator, diphenyl disulfide, dibenzyl disulfide, tetraethyl thiuram disulfide, tetramethylammonium monosulfide, etc. are mentioned, for example.

Examples of acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide.

Examples of the quinone-based photoinitiator include quinone-based photoinitiators such as benzoquinone and anthraquinone.

As a sulfochloride type photoinitiator, 2-naphthalenesulfonyl chloride etc. are mentioned, for example.

As a thioxanthone type photoinitiator, thioxanthone, 2-chloro thioxanthone, 2-methyl thioxanthone, etc. are mentioned, for example.

Among these exemplified compounds, 1-hydroxycyclohexylphenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferred from the viewpoint of transparency of the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition. Moreover, as for the photoinitiator (D), one type may contain a compound, and may contain two or more types of compounds.

The content of the photoinitiator (D) is preferably 0.2 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, and more preferably 0.5 to 2 parts by mass, based on 100 parts by mass of the total amount of components (A) to (C). It is more preferable. If the content of the photoinitiator (D) is 0.2 parts by mass or more, it is an amount sufficient for photocuring, and if it is 5 parts by mass or less, the peelability of the obtained pressure-sensitive adhesive sheet is also good.

<1-5. Additives>

To the pressure-sensitive adhesive composition, a fatty acid ester may be added, if necessary, in order to improve the lamination property (wetability) and bubble omission property of the obtained pressure-sensitive adhesive sheet (ease of discharging the bubbles intervening during bonding). Examples of fatty acid esters include monobasic acids having 8 to 18 carbon atoms, esters of polybasic acids and branched alcohols having 18 or less carbon atoms, unsaturated fatty acids having 14 to 18 carbon atoms, or esters of branched acids and tetravalent alcohols. I can. As a specific example preferable as a fatty acid ester, isopropyl myristic acid is mentioned. The amount of fatty acid ester added is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and still more preferably 5 to 15 parts by mass per 100 parts by mass of the total amount of components (A) to (C).

In addition, other additives may be added to the pressure-sensitive adhesive composition, if necessary, within a range that does not impair transparency. As additives, for example, plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, light stabilizers such as benzotriazoles, phosphate esters and other flame retardants, surfactants Such antistatic agents, dyes, etc. are mentioned.

<1-6. Solvent>

Since the pressure-sensitive adhesive composition contains a polyfunctional monomer (B) and other monomers (C) as a low molecular weight component, it can be adjusted to a viscosity that can be applied without adding a solvent, but for the purpose of adjusting the viscosity at the time of coating You may add a solvent. The solvent can be appropriately selected depending on other components included in the pressure-sensitive adhesive composition, but an organic solvent is preferable. Although it does not specifically limit as an organic solvent used, Methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol, isopropanol, etc. are mentioned. These organic solvents may be used alone or in combination of two or more. The solvent is preferably removed by applying the pressure-sensitive adhesive composition to a substrate or the like, followed by drying, and then photocuring.

<2. Manufacturing method of pressure-sensitive adhesive composition>

In addition, examples are described here for the synthesis method of the polyurethane (A), but for the polyfunctional monomer (B) and other monomers (C) and other components included in the pressure-sensitive adhesive composition, the type of compound to be used The description of the synthesis method is omitted because it varies according to the circumstances.

<2-1. Synthesis method of polyurethane (A)>

Hereinafter, an example of a preferred method for synthesizing polyurethane (A) contained in the pressure-sensitive adhesive composition of the present embodiment will be described, but the method for synthesizing polyurethane (A) is not limited thereto, It can be changed appropriately according to conditions. In addition, in this example, the reaction of the hydroxy group and the isocyanato group is, in any step, in the presence of an organic solvent inert to the isocyanato group, dibutyltin dilaurate, dibutyltin diethylhexoate, It is carried out using a urethanization catalyst such as dioctyl tin dilaurate. The reaction is preferably carried out continuously at 30 to 100°C for 1 to 5 hours. The amount of the urethanization catalyst used is preferably 50 to 500 ppm by mass based on the total mass of the reactant.

First, polyoxyalkylene polyol and polyisocyanate are added in a ratio in which the amount of isocyanato groups (number-based, hereinafter the same) is greater than the amount of hydroxy groups (number-based, hereinafter the same), and reacted with the isocyanato group at the terminal. To synthesize a polyurethane having. Specific examples of the polyoxyalkylene polyol and polyisocyanate are as exemplified in the section of polyurethane (A).

At this time, it is possible to adjust the molecular weight (degree of polymerization) by adjusting the amount of isocyanato groups to the amount of hydroxy groups. Specifically, the smaller the excess amount of isocyanato group relative to the amount of hydroxy group, the greater the molecular weight of the polyurethane having an isocyanato group, and the greater the excess amount of isocyanato group relative to the amount of hydroxy group, the more isocyanato group having an isocyanato group. The molecular weight of polyurethane becomes small.

Next, a polyurethane having an isocyanato group at the terminal is reacted with a compound having a hydroxy group and a (meth)acryloyl group, and a polyurethane (A) having a (meth)acryloyl group at the end of the molecular chain is synthesized. . Here, it is preferable that the (meth)acryloyl group contained in this compound is a part of the (meth)acryloyloxy group.

Although it does not specifically limit as a compound which has a hydroxy group and a (meth)acryloyl group, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate Hydroxyalkyl (meth)acrylates such as; 1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, 3-methylpentanediol mono(meth)acrylate, etc. And monools having a (meth)acryloyl group derived from various polyols. These may be used alone or in combination of two or more. Among them, 2-hydroxyethyl (meth)acrylate is preferable from the viewpoint of reactivity with an isocyanato group and photocurability.

In addition, in addition to a compound having a hydroxy group and a (meth)acryloyl group, an alkyl alcohol having no (meth)acryloyl group and one hydroxy group is used in combination to react with a polyurethane having an isocyanato group at the terminal. , The amount of the (meth)acryloyl group introduced can be adjusted. Although it does not specifically limit as an alkyl alcohol, A linear, branched, alicyclic alkyl alcohol, etc. are mentioned, These may be used individually, and may be used in combination of 2 or more types. Thereby, a polyurethane having a structure derived from the alkyl alcohol at least at any terminal is produced. In this case, the polyurethane (A) contains a polyurethane having no (meth)acryloyl group at least at any terminal. Therefore, a polyurethane having a (meth)acryloyl group only at one terminal can be included.

Based on the number, it is preferable that a (meth)acryloyl group is introduced into 90 to 100% of the terminal of the polyurethane contained in the polyurethane (A), more preferably 95 to 100%, and even more preferably 100%. Do. When the amount of (meth)acryloyl group introduced is 90% or more based on the number of isocyanato groups, the cohesive strength of the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition is sufficiently obtained. The ratio of the number of terminals to which the (meth)acryloyl group is introduced to the number of terminals of all polyurethane molecular chains can be measured by IR, NMR, or the like.

<2-2. Modification Example of Synthesis Method of Polyurethane (A)>

A modified example of the method for synthesizing polyurethane (A) will be described. In this example, as in the above example, the reaction of the hydroxy group and the isocyanato group is performed in the presence of an inert organic solvent in the isocyanato group in any step, dibutyltin dilaurate and dibutyltin. It is carried out using a urethanization catalyst such as diethylhexoate and dioctyltin dilaurate. The reaction is preferably carried out continuously at 30 to 100°C for 1 to 5 hours. The amount of the urethanization catalyst used is preferably 50 to 500 ppm by mass based on the total mass of the reactant. In this modified example, first, a polyoxyalkylene polyol and a polyisocyanate are reacted at a rate in which the amount of hydroxy groups is greater than the amount of isocyanato groups, thereby synthesizing a polyurethane having a hydroxy group at the terminal.

At this time, as in the above example, it is possible to adjust the molecular weight by adjusting the ratio of the amount of the hydroxy group to the amount of isocyanato groups. Specifically, the smaller the excess amount of the amount of hydroxy groups relative to the amount of isocyanato groups, the larger the molecular weight of the polyurethane having a hydroxy group, and the greater the amount of excess amount of hydroxy groups relative to the amount of isocyanato groups, the smaller the molecular weight of the polyurethane having a hydroxy group. Lose.

Next, a polyurethane having a hydroxy group at the terminal is reacted with a compound having an isocyanato group and a (meth)acryloyl group, and a polyurethane (A) having a (meth)acryloyl group at the end of the molecular chain is synthesized. . Here, it is preferable that the (meth)acryloyl group contained in this compound is a part of the (meth)acryloyloxy group.

Although it does not specifically limit as a compound which has an isocyanato group and a (meth)acryloyl group, 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, 1,1-bis (Acryloyloxymethyl) ethyl isocyanate, etc. are mentioned. In addition, as a commercial item of a compound having an isocyanato group and a (meth)acryloyl group, for example, Showa Denko Corporation's Carens MOI (registered trademark) and Carens AOI (registered trademark) are exemplified. I can. These may be used individually or may be used in combination of 2 or more types. Among them, 2-(meth)acryloyloxyethyl isocyanate is preferable from the viewpoint of reactivity with a hydroxy group and photocurability.

In addition, in addition to a compound having an isocyanato group and a (meth)acryloyl group, an alkyl isocyanate having no (meth)acryloyl group and one isocyanato group is used in combination, and a polyurethane having a hydroxyl group at the terminal By reacting with, the amount of introduced (meth)acryloyl group can be adjusted. Although it does not specifically limit as an alkyl isocyanate, A linear, branched, alicyclic alkyl isocyanate, etc. are mentioned, These may be used individually, and may be used in combination of 2 or more types. Thereby, a polyurethane having a structure derived from the alkyl isocyanate at least at any terminal is produced. In this case, the polyurethane (A) contains a polyurethane having no (meth)acryloyl group at least at any terminal. Therefore, in this case, the polyurethane (A) can also contain a polyurethane having a (meth)acryloyl group only at one terminal.

Based on the number, it is preferable that a (meth)acryloyl group is introduced into 90 to 100% of the terminal of the polyurethane contained in the polyurethane (A), more preferably 95 to 100%, and even more preferably 100%. Do. When the amount of (meth)acryloyl group introduced is 90% or more based on the number of isocyanato groups, the cohesive strength of the pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition is sufficiently obtained.

<2-3. Mixing method of each component contained in the adhesive composition>

By mixing polyurethane (A), polyfunctional monomer (B), other monomers (C), photoinitiator (D), fatty acid ester added as needed, other additives, and organic solvent, the pressure-sensitive adhesive The composition is prepared. The mixing method is not particularly limited, but can be performed using, for example, a stirring device equipped with a stirring blade such as a homodisper or a paddle blade.

Further, all components may be added and mixed at once, or the addition and mixing may be repeated by dividing into multiple times for each component. In other words, if there is a solid component at room temperature, it is dissolved in a solvent or dispersed in a dispersion medium, or by heating and melting it, the component is mixed with high uniformity in the pressure-sensitive adhesive composition. It gets easier.

<3. Adhesive Sheet>

<3-1. Composition of adhesive sheet>

In the pressure-sensitive adhesive sheet according to the present embodiment, a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition is formed on one side of a substrate. The thickness of the adhesive layer is preferably 3 to 100 µm, more preferably 5 to 50 µm, and still more preferably 10 to 30 µm. When the film thickness of the adhesive layer is 3 μm or more, the strength of the adhesive layer is sufficient, and when the film thickness is 100 μm or less, it is easy to control the film thickness of the adhesive layer.

The gel fraction of the cured product of the pressure-sensitive adhesive composition contained in the pressure-sensitive adhesive layer is preferably 85 to 100% by mass, more preferably 90 to 100% by mass, and still more preferably 95 to 100% by mass. Here, the gel fraction is the mass fraction of the extracted insoluble matter with respect to the solvent, and the solvent is selected from the cured product of the pressure-sensitive adhesive composition that can dissolve the non-crosslinked component. Here, an example of a specific measuring method of the gel fraction will be described later in Examples. If the gel fraction of the cured product of the pressure-sensitive adhesive composition is 85 to 100% by mass, a so-called pressure-sensitive adhesive residual, in which a part of the pressure-sensitive adhesive layer or the like remains in the adherend when the pressure-sensitive adhesive sheet is peeled can be suppressed.

Although the material of the base material can be appropriately selected according to the use of the pressure-sensitive adhesive sheet, a resin film is mentioned, for example. When the pressure-sensitive adhesive sheet is used as a protective sheet in, for example, a manufacturing process, and is performed in a state in which the protective sheet is laminated when inspecting the presence or absence of an adherend, that is, a scratch or foreign matter on a product, it is preferable that the substrate is transparent. Examples of the transparent substrate include polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, and cellulose.

The thickness of the substrate can be appropriately selected according to the use of the pressure-sensitive adhesive sheet, and is not particularly limited, but in the case of a resin film, the thickness of the substrate is preferably 5 μm or more, more preferably from the viewpoint of handling properties and strength. It is 10 micrometers or more, More preferably, it is 20 micrometers or more. Further, considering the flexibility of the resin film, the thickness of the substrate is preferably 200 µm or less, more preferably 150 µm or less, and still more preferably 100 µm or less.

In addition, as a base material, what has been subjected to antistatic treatment is preferably used. The antistatic treatment to be performed on the substrate is not particularly limited, but a method of providing an antistatic layer on at least one side of the substrate, a method of mixing an antistatic agent in the substrate, or the like can be used. Further, on the surface of the substrate forming the adhesive layer, if necessary, an adhesion facilitating treatment such as an acid treatment, an alkali treatment, a primer treatment, a corona treatment, a plasma treatment, an ultraviolet treatment, and an ozone treatment may be performed.

In the adhesive sheet, for the purpose of protecting the adhesive layer, it is possible to laminate a separator on the surface of the adhesive layer. As the material of the separator, for example, paper, plastic film, or the like can be used, but a plastic film is suitable because it has excellent surface smoothness. The plastic film used as a separator is not particularly limited as long as it can protect the adhesive layer, and examples thereof include polyethylene, polypropylene, polyethylene terephthalate, and polybutene.

<3-2. Manufacturing method of adhesive sheet>

The manufacturing method of the pressure-sensitive adhesive sheet according to the present embodiment can be obtained, for example, by applying a pressure-sensitive adhesive composition to a substrate, and irradiating the applied pressure-sensitive adhesive composition with ultraviolet rays to light cure.

The method of applying the pressure-sensitive adhesive composition to the substrate is not particularly limited and can be appropriately selected. For example, as a method of applying the pressure-sensitive adhesive composition to the substrate, various coaters such as gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, direct coater, etc. are used. Method, screen printing method, etc. are mentioned.

Further, as a light source for photocuring the pressure-sensitive adhesive composition, a black light, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, and the like can be mentioned. As the irradiation intensity of light, it is sufficient that the pressure-sensitive adhesive composition can be sufficiently cured, and, for example, it is preferably 50 to 3000 mW/cm 2. In other words, if the irradiation intensity of light is weak, it takes time to cure, so that productivity decreases.

<3-3. Use of adhesive sheet and required performance>

In the inspection process, there are cases where it is required to sufficiently discover or be able to detect fine foreign matter or scratches on the product or part while the protective sheet is laminated on the product or part. In addition, the protective sheet covers the surface of a plastic film used as an optical component such as a polarizing plate, a wave plate, a retardation plate, an optical compensation film, a reflective sheet, and a brightness enhancing film used in liquid crystal displays such as smartphones, personal computers, and televisions. In some cases, it is suitably used for protection purposes.

When the pressure-sensitive adhesive sheet according to the present embodiment is used as such a protective sheet, the pressure-sensitive adhesive sheet is required to have little fogging, that is, low haze. In that case, the haze value of the pressure-sensitive adhesive sheet is preferably 2.0% or less, more preferably 1.5% or less, and still more preferably 1.0% or less. A specific measuring method of the haze value of the pressure-sensitive adhesive sheet will be described later in Examples.

In addition, when the pressure-sensitive adhesive sheet according to the present embodiment is used as the protective sheet as described above, the pressure-sensitive adhesive sheet needs a minimum peel strength in order to prevent it from peeling from the product or part during handling such as transportation. On the other hand, in the case of peeling the adhesive sheet from a product or part, it is necessary to lower the peel strength in order to facilitate the peeling operation or not to deform or damage the product or part during peeling. From these viewpoints, the peel strength of the pressure-sensitive adhesive sheet is preferably 1 to 25 gf/25 mm, more preferably 4 to 20 gf/25 mm, and still more preferably 7 to 15 gf/25 mm. A specific measurement method of the peel strength of the pressure-sensitive adhesive sheet will be described later in Examples.

Example

Hereinafter, the present invention will be described in detail by examples. The present invention is not limited at all by the examples shown below. In addition, in the following examples, the weight average molecular weight of the obtained polyurethane (A) is gel, permeation, chromatography (Showa Denko Co., Ltd. Shodex GPC-101, hereinafter referred to as GPC). It is a value in terms of polystyrene measured by. The measurement conditions of GPC are as follows.

Column: Showa Denko Corporation LF-804

Column temperature: 40°C

Sample: 0.2% by mass tetrahydrofuran solution of polyurethane (A)

Flow: 1ml/min

Eluent: tetrahydrofuran

Detector: RI detector (differential refractive index detector)

<Synthesis of polyurethane (A)>

(A-1)

In a reactor equipped with a thermometer, agitator, dropping funnel, and a cooling tube with a drying tube, a hydrogenated product of diphenylmethane diisocyanate (death module W, manufactured by Sumica Covestrourethane) was added to 21 mol (5.51 kg) and a hydroxyl value. 20 mol (40.1 kg) of polypropylene glycol D-2000 (manufactured by Mitsui Chemical Co., Ltd., number average molecular weight 2000) having a hydroxy group of 56 mgKOH/g at the terminal was added thereto. Thereafter, the reactor was heated to 60 DEG C and reacted for 4 hours to obtain a polyurethane having isocyanato groups at both ends.

Subsequently, 2 mol (232 g) of 2-hydroxyethyl acrylate was added. Thereafter, the temperature of the four-necked flask was raised to 70 DEG C and reacted for 2 hours to obtain polyurethane (A-1) having an acryloyl group at the terminal. This polyurethane (A-1) is considered to have acryloyl groups at all terminals from the point that it was analyzed by IR and it was confirmed that the peak derived from the isocyanato group had disappeared. The weight average molecular weight of the obtained polyurethane (A-1) was 70,000.

(A-2)

In the same manner as for the synthesis of polyurethane (A-1), except for using 21 mol (4.67 kg) of isophorone diisocyanate (Desmodule I, manufactured by Sumika Covestrourethane) instead of the hydrogenated product of diphenylmethane diisocyanate, Polyurethane (A-2) having acryloyl groups at all terminals was obtained. The weight average molecular weight of the obtained polyurethane (A-2) was 67,000.

(A-3)

8 mol (2.1 kg) of a hydrogenated product of diphenylmethane diisocyanate and 7 mol (14.0 kg) of polypropylene glycol D-2000 (manufactured by Mitsui Chemicals, number average molecular weight 2000) having a hydroxy group having a hydroxyl value of 56 mgKOH/g at the end. Except having changed to ), it carried out similarly to the synthesis method of polyurethane (A-1), and obtained the polyurethane (A-3) which has acryloyl groups at all terminals. The weight average molecular weight of the obtained polyurethane (A-3) was 35,000.

(A-4)

Except having changed the hydrogenated product of diphenylmethane diisocyanate to 4 mol (1.05 kg) and polypropylene glycol D-2000 (manufactured by Mitsui Chemical) having a hydroxyl group of 56 mgKOH/g at the terminal to 3 mol (6.0 kg). In the same manner as in the synthesis method of polyurethane (A-1), polyurethane (A-3) having acryloyl groups at all terminals was obtained. The weight average molecular weight of the obtained polyurethane (A-3) was 12,000.

<Preparation of adhesive composition>

Polyurethane resin (A), polyfunctional monomer (B), other monomers (C), photopolymerization initiator (D), and additives are blended in the composition shown in Tables 1 to 2, and a disper is used at 25°C. And mixed, and the pressure-sensitive adhesive compositions according to Examples 1 to 14 and Comparative Examples 1 to 2 were prepared.

<Production of adhesive sheet>

In the same manner as in Examples 1 to 14 and Comparative Examples 1 to 2, an adhesive sheet having a substrate of an optical PET film on one side was prepared. First, using an applicator, the adjusted pressure-sensitive adhesive composition was applied onto a 50 μm-thick optical PET film (Toyobo Co., Ltd. A4300), and from above the applied pressure-sensitive adhesive composition, a peeling PET film having a thickness of 75 μm (Toyobo Corporation E7006) covered. Next, using an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., UV irradiation device 3kW, high pressure mercury lamp), the sheet covered with the peeling PET film is irradiated with ultraviolet rays from the side of the peeling PET film to light the adhesive composition. Cured. The irradiation distance of ultraviolet rays was 25 cm, the lamp movement speed was 1.0 m/min, and the irradiation amount was 1000 mJ/cm 2. The thickness of the adhesive layer after curing was calculated by measuring the thickness of the adhesive sheet using a dial gauge, and subtracting 50 µm of the thickness of the substrate from this measured value. The measuring surface of the dial gauge was a circular plane having a diameter of 5 mm, and the measuring force was 0.8 N. In both of Examples 1 to 14 and Comparative Examples 1 to 2, it was 20 μm.

<Evaluation of adhesive composition and adhesive sheet>

For the pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets according to Examples 1 to 14 and Comparative Examples 1 to 2, the gel fraction, transparency, peel strength, lamination property (wetability), and residual pressure-sensitive adhesive to the adherend were evaluated by the method described below. I did. The results are shown in Tables 1 to 2.

(Gel fraction)

First, using an applicator, the pressure-sensitive adhesive composition of each of Examples 1 to 14 and Comparative Examples 1 to 2 was prepared with a 50 μm-thick peeling PET film (Higashiyama Film Co., Ltd.) so that the thickness of the pressure-sensitive adhesive layer after curing was 50 μm. It was applied to the first HY-S10). Here, the method of confirming the thickness of the pressure-sensitive adhesive layer is the same as the measurement method in the section of the production of the pressure-sensitive adhesive sheet.

Next, from the top of the pressure-sensitive adhesive composition on the peeled PET film, it was covered with a peeling PET film (E7006 manufactured by Toyobo Co., Ltd.) having a thickness of 75 μm. Next, using an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., a UV irradiation device 3kW, a high pressure mercury lamp), the adhesive composition covered with a peelable PET film on both sides was obtained from the surface on the side of the peeled PET film having a thickness of 75 μm. The pressure-sensitive adhesive composition was photo-cured by irradiation. The irradiation distance of ultraviolet rays was 25 cm, the lamp movement speed was 1.0 m/min, and the irradiation amount was 1000 mJ/cm 2.

The produced sheet was cut out to a size of 100 mm×100 mm, and the peeling PET film on both sides was peeled from the cured product of the pressure-sensitive adhesive composition to obtain a sample for measurement. This sample for measurement was immersed in 50 ml of toluene at 25° C. for 24 hours, dried at 80° C. for 5 hours, and the gel fraction was calculated by the following equation (1) from the mass of the sample for measurement before and after the toluene immersion. . The results are shown in Tables 1 to 2.

Gel fraction (mass%) = [A/B] x 100 (1)

A: Dry mass of the sample for measurement after toluene immersion (mass of toluene is not included)

B: The mass of the sample for measurement before toluene immersion

(Haze value)

The pressure-sensitive adhesive sheets prepared in each of Examples 1 to 14 and Comparative Examples 1 to 2 were cut out to a size of 50 mm×50 mm, and the peeling PET film was peeled off. Thereafter, the entire surface of the exposed pressure-sensitive adhesive layer was laminated on a glass plate, and a rubber roller (diameter: 85 mm, width: 50 mm) having a mass of 2 kg (load 19.6 N) was reciprocated once to prepare a sample for measurement. For this measurement sample, the haze value was measured using a haze meter (NM-150 (manufactured by Murakami Shiki Corporation, Kijutsu Kenkyu Corporation)). The haze value (%) was calculated by dividing the diffuse transmittance by the total light transmittance and multiplying by 100. Here, the measurement was performed in three places with the same sample, and their average value was taken as the haze value.

(Peel strength)

The adhesive sheets prepared in each of Examples 1 to 14 and Comparative Examples 1 to 2 were cut out to a size of 25 mm×150 mm, and the peeling PET film was peeled off. Thereafter, the entire surface of the exposed pressure-sensitive adhesive layer was laminated on a glass plate, and a rubber roller (diameter: 85 mm, width: 50 mm) having a mass of 2 kg (load 19.6 N) was reciprocated once to prepare a sample for measurement.

The obtained sample for measurement was allowed to stand for 1 hour in an environment at a temperature of 23°C and a relative humidity of 50%. Then, in accordance with JIS K6854-2, a tensile test in the 180° direction was performed at a peel rate of 0.3 m/min and 30 m/min, and the peel strength (g/25 mm) of the protective film with respect to the glass plate was measured.

(Laminate property)

1 is a plan view showing a method for evaluating the lamination property of the pressure-sensitive adhesive sheet 10, and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. The adhesive sheet 10 is cut out to a size of 20 mm×100 mm, and the peeling PET film is peeled off. Next, the adhesive layer 12 is bonded to the glass substrate 30 in the range from one end in the length direction of the adhesive sheet 10 to 15 mm, the adhesive portion is fixed to the glass substrate 30, and shown in FIG. As shown, the other end of the pressure-sensitive adhesive sheet 10 is lifted. As a method of fixing the adhesive portion, as shown in FIG. 1, the upper surface of the adhesive sheet 10 is placed on both sides of the adhesive sheet 10 in the width direction of the adhesive sheet 10 in a range from the one end to 15 mm. The cellophane tape 20 is attached so as to cover the glass substrate 30 on the outside of.

From this state, the other end of the pressure-sensitive adhesive sheet was released, the time until the entire pressure-sensitive adhesive layer adhered to the glass plate by the self-weight of the pressure-sensitive adhesive sheet was measured, and the laminate of the pressure-sensitive adhesive sheet according to Examples 1 to 14 and Comparative Examples 1 to 2 Sex was evaluated based on the following criteria.

(Evaluation criteria for lamination properties)

◎: Less than 5 seconds until close contact

○: 5 seconds or more until close contact, less than 10 seconds

△: 10 seconds or more until close contact, less than 15 seconds

×: 15 seconds or more or no close contact until contact

(Remaining adhesive)

The adhesive sheet was cut out to a size of 50 mm x 50 mm, and the peeling PET film was peeled off. Next, the exposed adhesive surface was laminated on a glass plate, and this was used as a sample. After allowing this sample to stand at 85° C. and 85% relative humidity for 3 days, the pressure-sensitive adhesive sheet was peeled from the glass plate, and the residual pressure-sensitive adhesive on the surface of the glass plate was visually confirmed, and evaluated according to the following criteria.

(Evaluation criteria for residual adhesive)

○: The surface of the glass plate has no change compared to before bonding.

(Triangle|delta): The adhesive residual was confirmed slightly on the surface of a glass plate.

X: Adhesive residual is clearly confirmed on the surface of a glass plate.

<Evaluation results of Examples and Comparative Examples>

According to the above Examples and Comparative Examples, the composition of Comparative Example 1 in which the polyurethane (A-4) having a weight average molecular weight of 12000 was used as the polyurethane (A) was insufficient in lamination property, and the adhesive residual was also observed. In addition, the composition of Comparative Example 2 not containing the polyfunctional monomer (B) had too high peel strength and insufficient lamination properties.

10: adhesive sheet
20: cellophane tape
30: glass substrate
12: adhesive layer
14: description

Claims (13)

Polyurethane (A) having a skeleton comprising a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate,
It is a compound other than polyurethane (A), and is a polyfunctional monomer (B) having a plurality of (meth)acryloyl groups, and
It is a compound other than polyurethane (A), and is a compound other than the polyfunctional monomer (B), and is polymerizable with the polyurethane (A) and the polyfunctional monomer (B),
Including a photoinitiator (D),
The polyurethane (A) contains polyurethane (a1),
The polyurethane (a1) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and has a (meth)acryloyl group at a plurality of terminals of the polyurethane (a1). ,
The weight average molecular weight of the polyurethane (A) is 30,000 to 200,000,
With respect to the total amount of the polyurethane (A), the polyfunctional monomer (B) and other monomers (C), 30 to 60% by mass of the polyurethane (A), 10 to 20% by mass of the polyfunctional monomer (B), The pressure-sensitive adhesive composition comprising 20 to 50% by mass of the outer monomer (C). The pressure-sensitive adhesive composition according to claim 1, wherein the structure derived from a polyoxyalkylene polyol contained in the polyurethane (A) is a structure derived from a polyoxyalkylene polyol having a number average molecular weight of 500 to 5,000. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the skeleton of the polyurethane (A) is a copolymer of polyoxyalkylene glycol and diisocyanate. The pressure-sensitive adhesive composition according to claim 3, wherein the skeleton of the polyurethane (A) is a copolymer of a hydrogenated product of polypropylene glycol and diphenylmethane diisocyanate. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the (meth)acryloyl group in the polyurethane (A) is a part of the (meth)acryloyloxy group. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the polyfunctional monomer (B) has three or more (meth)acryloyl groups. The pressure-sensitive adhesive composition according to claim 6, wherein the polyfunctional monomer (B) is trimethylolpropane triacrylate. The pressure-sensitive adhesive composition according to claim 7, wherein the other monomer (C) has a (meth)acryloyl group. The pressure-sensitive adhesive composition according to claim 8, wherein the other monomer (C) contains a (meth)alkyl acrylate. The polyurethane (A) according to claim 1 or 2, further comprising a polyurethane (a2),
The polyurethane (a2) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and has a (meth)acryloyl group only at any one terminal. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein a (meth)acryloyl group is introduced into 90 to 100% of the ends of the polyurethane molecules contained in the polyurethane (A) on a number basis. An adhesive sheet in which an adhesive layer containing a cured product of the photocurable adhesive composition according to claim 1 or 2 is formed on a substrate. delete

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