JP6600954B2 - Re-peelable pressure-sensitive adhesive and pressure-sensitive adhesive sheet using the same - Google Patents

Description

  The present invention relates to an adhesive that can be used for members such as plastic and glass.

Display devices such as liquid crystal displays used in various devices such as home and commercial appliances such as electronic calculators, electronic watches, mobile phones, and televisions are becoming larger, especially liquid crystal televisions and plasma televisions. The increase in size is remarkable. In recent years, touch panel type liquid crystal displays such as smartphones and tablets are rapidly spreading, and a large market expansion is expected in the future. On the other hand, liquid crystal displays are also used in in-vehicle devices such as car navigation systems, and are required to have durability that can be used in harsh interior environments such as high-temperature and high-humidity atmospheres.
The liquid crystal display uses polarizing plates and retardation plates having various optical functions, and these are attached to an adherend such as a liquid crystal cell using glass or transparent plastic via an adhesive. Affixed.

  The polarizing plate is generally a laminate having a configuration in which a polyvinyl alcohol film is sandwiched between a triacetyl cellulose film or a cycloolefin film. These films have different mechanical properties and therefore have different dimensional change rates during heating. Therefore, when placed in a high temperature atmosphere, the laminate often warps.

  For example, if a liquid crystal cell member of a polarizing plate / adhesive layer / glass (glass is a surface member of a liquid crystal cell) is left in a high temperature atmosphere, warpage derived from the dimensional change rate between the constituent members of the polarizing plate occurs, There may be a problem that bubbles (foaming) are generated at the bonding interface between the pressure-sensitive adhesive layer and the glass, or that the polarizing plate is lifted off from the glass and peeled off. Further, the stress distribution of the liquid crystal cell member becomes non-uniform due to warpage, and the stress concentrates on the peripheral edge of the liquid crystal cell member. As a result, light leaks from the four corners and the peripheral edge of the liquid crystal cell member. The problem of “light leakage phenomenon” may occur. The above problem also occurs in a high temperature and high humidity atmosphere.

  On the other hand, in the manufacturing process of liquid crystal displays, etc., when a polarizing plate is bonded to an optical component such as a liquid crystal cell, the polarizing plate is attached after a certain period of time has elapsed since the bonding position has shifted. Peeling and reusing an expensive liquid crystal cell is performed. For this reason, the pressure-sensitive adhesive is required to have a property (reworkability) capable of re-peeling the polarizing plate from the liquid crystal cell after a predetermined time has elapsed since sticking.

  In order to solve these problems, Patent Document 1 discloses a technique of adding a plasticizer or the like to the pressure-sensitive adhesive to moderately soften the pressure-sensitive adhesive layer to impart stress relaxation and prevent light leakage. Yes. However, when a plasticizer is added, it causes bleed-out that contaminates the adherend when the polarizing plate is peeled off, and reduces cohesive force. There was a problem that floating and peeling were likely to occur, and the addition of an excessive amount of plasticizer caused whitening of the coating film.

  Patent Document 2 discloses a technique for improving stress relaxation and preventing light leakage by including an acrylic copolymer using an aromatic ring-containing monomer. However, the pressure-sensitive adhesive using the aromatic ring-containing monomer described in Patent Document 2 has a problem that white spots are generated and optical characteristics are inferior in light leakage evaluation.

  On the other hand, in Patent Document 3, in order to impart removability, a high molecular weight acrylic polymer having a weight average molecular weight of 500,000 or more has a high acid value and a low molecular weight having a weight average molecular weight of 0.2 to 100,000. Techniques for blending acrylic polymers are disclosed. However, the pressure-sensitive adhesive described in Patent Document 4 has a problem that the drying conditions of the pressure-sensitive adhesive are limited.

  Furthermore, in patent document 4, the technique which improves stress relaxation property by using together the acrylic polymer with a weight average molecular weight of 700,000 or more which has a carboxyl group, and the acrylic polymer with a weight average molecular weight of 800-50,000. Is disclosed. However, the pressure-sensitive adhesive described in Patent Document 4 has a problem that the cohesive force is significantly reduced.

  Moreover, in patent document 5, by using together the acrylic polymer which has a hydroxyl group, and the acrylic polymer containing the monomer containing the (meth) acrylic acid ester whose glass transition temperature (Tg) is 60 degreeC or more. A technique for obtaining a cohesive force is disclosed. However, although these cohesives have relatively good cohesive strength, there is a problem that white spots occur due to insufficient stress relaxation properties.

  Patent Document 6 discloses a technique for reducing light reflection loss at the interface with an optical member by using an acrylic polymer having a Tg of 0 ° C. or lower and a terpene skeleton in the side chain. ing. However, the pressure-sensitive adhesive using an acrylic polymer having a terpene skeleton has a problem that after being exposed to a high-temperature and high-humidity environment, the compatibility with moisture is poor and the coating film is whitened.

  Moreover, in patent document 7, the technique which obtains high adhesiveness by using together the acrylic copolymer which does not contain a carboxyl group, the acrylic polymer of weight average molecular weight 1000 or more and less than 30000, and hydrogenation type tackifying resin is used. It is disclosed. However, a pressure-sensitive adhesive containing a hydrogenated tackifying resin can obtain high adhesiveness, but has a problem that transparency is remarkably lowered.

Japanese Patent Laid-Open No. 9-87593 JP 2007-169329 A JP 2010-1000071 A JP 2004-069975 A JP 2002-327160 A JP 2008-255314 A JP 2012-149179 A

  The problem to be solved by the present invention is to solve the above-mentioned problems, and when used in an adhesive film, is excellent in releasability, and after being exposed to a high temperature environment or a high temperature and high humidity environment, from an adherend. The pressure-sensitive adhesive that is less likely to float or peel off, has a good light leakage evaluation when used for fixing a polarizing plate, and can maintain high transparency even when exposed to a high-temperature and high-humidity environment, and It aims at providing the adhesive sheet using it.

As a result of intensive studies to solve the above problems, the present inventors have reached the present invention.
That is, the present invention is an adhesive comprising an acrylic polymer (A), a tackifier (B), and a crosslinking agent (C), wherein the acrylic polymer (A) is a carboxyl group-containing monomer. It is a polymer having a weight average molecular weight of 500,000 to 2,000,000 obtained by polymerizing a monomer containing 0.1 to 20% by weight of a monomer, and the tackifier (B) has an acid value of 1 to 200 mgKOH / g, a pressure-sensitive adhesive having a softening point of 75 to 160 ° C., containing a compound having at least one aromatic ring in the molecule, and the crosslinking agent (C) containing a polyisocyanate compound.

  The present invention also relates to the pressure-sensitive adhesive, comprising 5 to 50 parts by weight of the tackifier (B) with respect to 100 parts by weight of the acrylic polymer (A).

  The present invention also relates to the pressure-sensitive adhesive, wherein the crosslinking agent (C) is contained in an amount exceeding 5 parts by weight and not more than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer (A).

  In the present invention, the tackifier (B) compound having an aromatic ring is at least one selected from the group consisting of an acrylic compound, a rosin compound and a styrene compound. It relates to the agent.

  The present invention also relates to the pressure-sensitive adhesive, wherein the crosslinking agent (C) is an araliphatic polyisocyanate compound.

  Furthermore, the present invention relates to the pressure-sensitive adhesive, further comprising a metal chelate compound (D).

  Moreover, this invention relates to the adhesive sheet provided with a base material and the adhesive layer formed from the said adhesive.

  Moreover, this invention relates to the said adhesive sheet whose base material is an optical member.

  According to the present invention configured as described above, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive is a resin network in which the acrylic polymer (A) or the acrylic copolymer (A) and the cross-linking agent (C) are cross-linked. And tackifier (B) form a sea-island structure. Since the pressure-sensitive adhesive layer does not impair the cohesive force and is excellent in stress relaxation, even when exposed to a high-temperature atmosphere or a high-temperature and high-humidity atmosphere, the pressure-sensitive adhesive layer has an effect that it is unlikely to float and peel off and light leakage hardly occurs. . Further, the pressure-sensitive adhesive layer has high transparency, and has an effect that high transparency can be maintained even when exposed to a high temperature and high humidity environment.

  The pressure-sensitive adhesive sheet is excellent in removability according to the present invention and, after being exposed to a high-temperature environment or a high-temperature and high-humidity environment, for example, glass or plastics are unlikely to float or peel off from the adherend, and does not easily leak light. We were able to provide an adhesive that could be made.

The pressure-sensitive adhesive of the present invention is a pressure-sensitive adhesive comprising an acrylic polymer (A), a tackifier (B), and a crosslinking agent (C), wherein the acrylic polymer (A) is a carboxyl group. It is a polymer having a weight average molecular weight of 500,000 to 2,000,000 obtained by polymerizing a monomer containing 0.1 to 20% by weight of the containing monomer, and the tackifier (B) has an acid value of 1 to The pressure-sensitive adhesive is characterized in that it has a mg of 200 mg KOH / g and a softening point of 75 to 160 ° C., contains a compound having at least one aromatic ring in the molecule, and the crosslinking agent (C) contains a polyisocyanate compound.
The pressure-sensitive adhesive of the present invention is preferably used as a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed by coating and drying. The pressure-sensitive adhesive tape is preferably used for an optical member, particularly for bonding a liquid crystal display member.

  In the present invention, the acrylic polymer (A) is a monomer copolymer containing a monomer containing a carboxyl group. The acrylic polymer (A) can maintain high transparency even when exposed to a high-temperature and high-humidity environment by forming a polymer network through a cross-linking reaction, thereby suppressing floating and peeling, light leakage, and high temperature and high humidity. An effect is obtained. In the present invention, (meth) acrylic acid ester includes acrylic acid ester and methacrylic acid ester.

  Monomers containing a carboxyl group include, for example, (meth) acrylic acid, monohydroxyethyl acrylate ester of phthalate, p-carboxybenzyl acrylate ester, ethylene oxide modified (added mole number: 2 to 18) phthalate acrylic acid Ester, monohydroxypropyl acrylate ester, monohydroxyethyl acrylate succinate, β-carboxyethyl acrylate, 2- (4-benzoyl-3-hydroxyphenoxy) ethyl acrylate, maleic acid, monoethylmaleic acid , Itaconic acid, citraconic acid, fumaric acid and the like. These can be used alone or in combination of two or more.

  The polymer having a carboxyl group is preferably contained in an amount of 0.1 to 20% by weight and more preferably 0.5 to 15% by weight in 100% by weight of the monomer mixture. When the content is 0.1% or more, the cohesive force is further improved. Moreover, it becomes easy to make cohesion force and stress relaxation property compatible because content will be 15 weight% or less.

Monomers that can be used for copolymerization of the acrylic polymer (A) are preferably (meth) acrylic acid alkyl esters and other vinyl monomers.
Examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, (meth) Hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, (meth ) Hexadecyl acrylate, octadecyl (meth) acrylate, and the like. Among these, butyl (meth) acrylate is preferable from the viewpoint that good adhesive performance is easily obtained. These can be used alone or in combination of two or more.

  The (meth) acrylic acid alkyl ester is preferably contained in an amount of 80 to 99.9% by weight, more preferably 85 to 99.5% by weight, based on 100% by weight of the monomer mixture. When the content is 80% by weight or more, the cohesive force is further improved. Moreover, it becomes easy to make cohesion force and stress relaxation property compatible because content will be 99.9 weight% or less.

  The other vinyl monomer includes a monomer containing a hydroxyl group, a monomer containing an amide bond, a monomer containing an epoxy group, a monomer containing an amino group, and a monomer having an alkylene oxide unit. A monomer, vinyl acetate, vinyl crotonate, styrene, acrylonitrile and the like are preferable, but the copolymer is not particularly limited as long as it can be copolymerized.

  Examples of the monomer containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. (Meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate And glycol mono (meth) acrylic acid esters such as polyethylene glycol mono (meth) acrylic acid ester, polypropylene glycol mono (meth) acrylic acid ester, 1,4-cyclohexanedimethanol mono (meth) acrylic acid ester, caprolactone modified ( Meta) Acu Le esters, such as hydroxyethyl acrylamide.

  Examples of the monomer containing an amide bond include (meth) acrylamide, N-methylacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropyl (meta). ) Heterocycles such as (meth) acrylamide compounds such as acrylamide, diacetone acrylamide, N- (hydroxymethyl) acrylamide, N- (butoxymethyl) acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, etc. , N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide and the like.

  Examples of the monomer containing an epoxy group include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, and 6-methyl (meth) acrylate. Examples include 3,4-epoxycyclohexylmethyl.

  Examples of the monomer containing an amino group include monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, and monoethylaminopropyl (meth) acrylate. And (meth) acrylic acid monoalkylamino esters.

  The monomer having an alkylene oxide unit preferably has units such as ethylene oxide and propylene oxide. Specifically, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, methoxypolypropylene Examples include glycol (meth) acrylic acid ester, ethoxy polypropylene glycol (meth) acrylic acid ester, phenoxypolyethylene glycol (meth) acrylic acid ester, and phenoxypolypropylene glycol (meth) acrylic acid ester.

  Other vinyl monomers can be used alone or in combination of two or more.

  The other vinyl monomer is preferably contained in an amount of 80 to 99.9% by weight in 100% by weight of the monomer mixture, and more preferably 85 to 99.5% by weight. When the content is 80% by weight or more, the cohesive force is further improved. Moreover, it becomes easy to make cohesion force and stress relaxation property compatible because content will be 99.9 weight% or less.

  In the pressure-sensitive adhesive of the present invention, the weight average molecular weight of the acrylic polymer (A) is preferably 500,000 to 2,000,000, more preferably 700,000 to 1,800,000. Since cohesion force etc. improve more because it exists in the range of 500,000-2 million, a float and peeling can be suppressed more and stress relaxation property improves more. Moreover, 2-20 are preferable as for the molecular weight distribution (The molecular weight distribution (Mw / Mn) showing the ratio of a weight average molecular weight (Mw) and a number average molecular weight (Mn)) of an acrylic polymer (A). By being in the said range, it is hard to produce a float and peeling and adhesive force improves and improves. In addition, the said weight average molecular weight and number average molecular weight are the values of polystyrene conversion measured by the gel permeation chromatography (GPC) method. Details of the GPC measurement method are described in the Examples.

  In the present invention, the acrylic polymer (A) can be obtained by radical polymerization of the monomer mixture with a radical polymerization initiator. The radical polymerization may be a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. In the present invention, solution polymerization is preferred. Solvents that can be used in solution polymerization are preferably acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, and the like. The polymerization temperature is preferably a boiling point reaction of 60 to 120 ° C., and the polymerization time is preferably 5 to 12 hours.

The radical polymerization initiator is not particularly limited as long as it is a compound capable of generating radicals at the polymerization temperature, and known compounds such as peroxides and azo compounds can be used.
Examples of the peroxide include di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, 2,5- Dialkyl peroxides such as di (t-butylperoxy) hexyne-3;
peroxyesters such as t-butylperoxybenzoate, t-butylperoxyacetate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane;
Ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide;
2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t- Peroxyketals such as butylperoxy) cyclohexane and n-butyl-4,4-bis (t-butylperoxy) valate;
Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide;
Diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide;
Examples thereof include organic peroxides such as peroxydicarbonates such as bis (t-butylcyclohexyl) peroxydicarbonate, and mixtures thereof.

Examples of the azo compounds include 2,2′-azobisbutyronitriles such as 2,2′-azobisisobutyronitrile (abbreviation: AIBN) and 2,2′-azobis (2-methylbutyronitrile). ;
2,2′-azobisvaleronitriles such as 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile);
2,2′-azobispropionitriles such as 2,2′-azobis (2-hydroxymethylpropionitrile);
1,1′-azobis-1-alkanenitriles such as 1,1′-azobis (cyclohexane-1-carbonitrile) can be used.

  The radical polymerization initiators can be used alone or in combination of two or more.

  The radical polymerization initiator is preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the monomer mixture.

  The tackifier (B) of the present invention is an aromatic compound having at least one aromatic ring in the molecule. When the tackifier (B) forms a pressure-sensitive adhesive layer, an effect of expressing high cohesive force and high adhesive force can be obtained by forming a highly cohesive domain. Moreover, by having at least one aromatic ring in the molecule, compatibility with the acrylic polymer (A) is improved, high transparency can be obtained, and it is exposed to a high temperature and high humidity environment. In some cases, transparency can be maintained.

  Specific examples of the tackifier (B) in the present invention include rosin compounds, styrene compounds, phenol compounds, xylene compounds, terpene compounds, acrylic compounds, and derivatives thereof. Among these, acrylic compounds, rosin compounds, and styrene compounds are preferable, and rosin tackifiers are more preferable.

  As said acrylic compound, what is marketed by brand names, such as VS-1028 and VS-1029 (made by Seiko PMC Co., Ltd.), and the acrylic compound of the following Example can be used conveniently. .

  Examples of the rosin compound include Pine Crystal KE-100, Pine Crystal KE-359, Pine Crystal KE-311, Pine Crystal KE-612, Pine Crystal KE-614, Pine Crystal KR-140, Pencel D-125, Pencel D -135 (made by Arakawa Chemical Co., Ltd.), SylvatacRE100, SylvatacRE100L, SylvatacRE105L (made by ArizonaCHEMICAL), etc. can be used suitably.

  Examples of the styrenic compound include Alastor 700, Alastar 703S (Arakawa Chemical Industries, Ltd.), US-1071, YS-1274 (Seiko PMC Co., Ltd.), SMA 3840, and SMA 17352 (CRAY VALLEY). What is marketed can be used conveniently.

  As the terpene compound, those commercially available under trade names such as TAMANOL 803L and TAMANOL 901 (manufactured by Arakawa Chemical Industries, Ltd.) can be suitably used.

  As said phenol type compound, what is marketed by brand names, such as TD-1090, TD-2640, and TD-3130 (made by DIC), can be used conveniently.

  As said xylene-type compound, what is marketed by brand names, such as Lignol R-70 and Lignol R-140 (made by Lignite Co., Ltd.), can be used conveniently.

  The tackifier (B) of the present invention preferably has an acid value of 1 mgKOH / g to 200 mgKOH / g, more preferably 2 mgKOH / g to 180 mgKOH / g. When it is 1 mgKOH / g or more, the cohesive force is further improved. Moreover, it becomes easy to make cohesion force and stress relaxation property compatible by becoming 200 mgKOH / g or less. When the tackifier (B) has an acid value, high cohesive force and adhesion to a substrate are improved, and high adhesive force can be obtained.

  The tackifier (B) of the present invention has a softening point of 75 ° C to 160 ° C, preferably 90 ° C to 140 ° C. When the temperature is 90 ° C. or higher, the cohesive force is further improved. Moreover, it becomes easy to make cohesion force and stress relaxation compatible by being 140 degrees C or less. When the tackifier (B) has a high softening point, high cohesive force and adhesion to the substrate can be improved, and light leakage can be suppressed.

  The tackifier (B) is preferably contained in 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, in 100 parts by weight of the acrylic polymer (A). When the content is 5 parts by weight or more, the cohesive force is further improved. When the content is 50 parts by weight or less, it becomes easy to achieve both cohesion and stress relaxation.

  The crosslinking agent (C) of the present invention is a polyisocyanate compound. The crosslinking agent (C) crosslinks with the acrylic polymer (A) to form a resin network, thereby suppressing floating and peeling, light leakage, and when exposed to a high temperature and high humidity environment. The effect of maintaining high transparency can be obtained.

  In the present invention, the crosslinking agent (C) is specifically an isocyanate monomer having two or more isocyanate groups, specifically an aromatic polyisocyanate, an aliphatic polyisocyanate, an araliphatic polyisocyanate, an alicyclic polyisocyanate. Preferred are isocyanate monomers such as isocyanate, and burettes, nurate bodies, and adduct bodies.

  Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', Examples thereof include 4 "-triphenylmethane triisocyanate.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, and 1,3-butylene diisocyanate. , Dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like.

  Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene. 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.

  Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1, Examples include 4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane, and the like. .

  The burette body refers to a self-condensate having a burette bond in which the isocyanate monomer is self-condensed. Specific examples include a burette of hexamethylene diisocyanate.

  The nurate body refers to a trimer of the isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate.

  The adduct body is a bifunctional or higher functional isocyanate compound obtained by reacting the isocyanate monomer with a bifunctional or higher molecular weight active hydrogen-containing compound. For example, a compound obtained by reacting trimethylolpropane and hexamethylene diisocyanate (trimethylolpropane). And a compound obtained by reacting trimethylol propane and xylylene diisocyanate, a compound obtained by reacting trimethylol propane and isophorone diisocyanate, 1,6-hexanediol and hexamethylene diisocyanate. Examples thereof include reacted compounds.

Examples of the bifunctional or higher functional low molecular active hydrogen-containing compound include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, and 3,3′-dimethylol. Heptane, 2-methyl-1,8-octanediol, 3,3′-dimethylolheptane, 2-butyl-2-ethyl-1,3-propanediol, polyoxyethylene glycol (additional number of moles of ethylene oxide of 10 or less ), Polyoxypropylene glycol (additional mole number of propylene oxide of 10 or less), 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonane Diol, neopentyl glycol, butyl ethyl penta Diol, 2-ethyl-1,3-hexanediol, cyclohexanediol, cyclohexanedimethanol, tricyclodecanedimethanol, cyclopentadiene engine methanol, aliphatic or alicyclic diols and dimer diol;
1,3-bis (2-hydroxyethoxy) benzene, 1,2-bis (2-hydroxyethoxy) benzene, 1,4-bis (2-hydroxyethoxy) benzene, 4,4′-methylenediphenol, 4, 4 ′-(2-norbornylidene) diphenol, 4,4′-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4′-isopropylidenephenol, or bisphenols such as bisphenol A and bisphenol F Aromatic diols such as bisphenols obtained by adding alkylene oxide such as ethylene oxide and propylene oxide to
1,1,1-trimethylolpropane, 1,1,1-trimethylolbutane, 1,1,1-trimethylolpentane, 1,1,1-trimethylolhexane, 1,1,1-trimethylolheptane, 1,1,1-trimethyloloctane, 1,1,1-trimethylol nonane, 1,1,1-trimethyloldecane, 1,1,1-trimethylolundecane, 1,1,1-trimethyloldodecane, 1,1,1-trimethylol tridecane, 1,1,1-trimethylol tetradecane, 1,1,1-trimethylol pentadecane, 1,1,1-trimethylol hexadecane, 1,1,1-trimethylol hepta Decane, 1,1,1-trimethylol octadecane, 1,1,1-trimethylol nanodecane, 1,1,1-trimethylol-sec Butane, 1,1,1-trimethylol-tert-pentane, 1,1,1-trimethylol-tert-nonane, 1,1,1-trimethylol-tert-tridecane, 1,1,1-trimethylol- tert-heptadecane, 1,1,1-trimethylol-2-methyl-hexane, 1,1,1-trimethylol-3-methyl-hexane, 1,1,1-trimethylol-2-ethyl-hexane, , 1,1-trimethylol-3-ethyl-hexane, trimethylol branched alkanes such as 1,1,1-trimethylolisoheptadecane, trimethylolbutene, trimethylolheptene, trimethylolpentene, trimethylolhexene, Trimethylol heptene, trimethylol octene, trimethylol decene, trimethylol dode , Trimethylol tridecene, trimethylol pentadecene, trimethylol hexadecene, trimetroleheptadecene, trimethylol octadecene, 1,2,6-butanetriol, 1,2,4-butanetriol, glycerin, etc. Kind;
Tetrafunctional or higher functional polyols such as pentaerythritol, dipentaerythritol, sorbitol, xylitol;
Ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, hexylenediamine, heptylenediamine, octylenediamine, nonylenediamine, diaminodicyclohexylmethane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 1, Aliphatic polyamines such as 3-bis (aminomethyl) cyclohexane, triethylenetetramine, diethylenetriamine, triaminopropane;
Aromatic polyamines such as phenylenediamine, tolylenediamine, diaminodiphenylmethane, diaminodiphenyl ether;
Ethylenedithiol, propylenedithiol, butylenedithiol, pentylenedithiol, hexylenedithiol, heptylenedithiol, octylenedithiol, nonylenedithiol, dimercaptodicyclohexylmethane, 3-mercaptomethyl-3,5,5-trimethylcyclohexylthiol, Examples include polythiols such as 1,3-bis (mercaptomethyl) cyclohexane, 1,4-bis (3-mercaptobutyryloxy) butane, and pentaerythritol tetrakis (3-mercaptobutyrate).

  These polyfunctional low molecular active hydrogen-containing compounds can be used alone or in combination of two or more.

  From the viewpoint of forming a sufficient cross-linked structure, the polyisocyanate compound is preferably a trifunctional isocyanate compound, and more preferably an adduct that is a reaction product of an isocyanate monomer and a trifunctional low molecular active hydrogen-containing compound. Specifically, a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, a nurate of isophorone diisocyanate, and a trimethylolpropane adduct of xylylene diisocyanate are preferred. Furthermore, araliphatic polyisocyanate compounds such as a trimethylolpropane adduct of tolylene diisocyanate and a trimethylolpropane adduct of xylylene diisocyanate are preferred. These polyisocyanate compounds can be used alone or in combination of two or more.

  The crosslinking agent (C) is preferably contained in an amount of more than 5 parts by weight to 30 parts by weight or less, and more than 10 parts by weight to 30 parts by weight or less, in 100 parts by weight of the acrylic polymer (A). More preferably. When the content is 5 parts by weight or more, the cohesive force is further improved. When the content is 50 parts by weight or less, it becomes easy to achieve both cohesion and stress relaxation.

  In the pressure-sensitive adhesive of the present invention, other crosslinking agents can be used in combination as long as the effects of the present invention are not impaired. Specific examples include an epoxy compound, an aziridine compound, an acid anhydride group-containing compound, a carbodiimide compound, an N-methylol group-containing compound, and a metal chelate compound.

  Examples of the epoxy compound 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, diglycidyl aniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N , N, N ′, N′-tetraglycidylaminophenylmethane and the like.

  Examples of the aziridine compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxite), N, N′-toluene-2,4-bis (1-aziridinecarboxite), and bisisophthalo. Yl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxite), 2,2′-bishydroxymethyl Butanol-tris [3- (1-aziridinyl) propionate], trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinylpropionate, tris-2,4,6- (1-aziridinyl) -1,3,5-triazine, 4,4′-bis (ethyleneiminocarbonylamino) diph Nirumetan, and the like.

  Examples of the carbodiimide compound include a high molecular weight polycarbodiimide produced by decarboxylation condensation reaction of a diisocyanate compound in the presence of a carbodiimidization catalyst. Examples of such high molecular weight polycarbodiimides include Nisshinbo's Carbodilite series. Among these, Carbodilite V-01, 03, 05, 07, and 09 are preferable because of excellent compatibility with organic solvents.

  The acid anhydride group-containing compound is a compound having two or more carboxylic acid anhydride groups and is not particularly limited, but includes tetracarboxylic dianhydride, hexacarboxylic dianhydride, hexacarboxylic dianhydride. And a maleic anhydride copolymer resin. In addition, polycarboxylic acid, polycarboxylic acid ester, polycarboxylic acid half ester, and the like that can be converted into an anhydride via a dehydration reaction during the reaction are included in the “acid anhydride group-containing compound” of the present invention.

  Examples of the tetracarboxylic dianhydride include pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, diphenylsulfonetetracarboxylic dianhydride, diphenylsulfidetetracarboxylic Examples thereof include acid dianhydride, butanetetracarboxylic dianhydride, perylenetetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride and the like.

  Examples of the metal chelate compounds include coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, and acetylacetone or ethyl acetoacetate. It is done. Specific examples include aluminum ethyl acetoacetate / diisopropylate, aluminum trisacetylacetonate, aluminum bisethylacetoacetate / monoacetylacetonate, and aluminum alkylacetoacetate / diisopropylate.

  These other crosslinking agents can be used alone or in combination of two or more.

  If the adhesive of this invention is a range which does not impair the effect of this invention, you may use a silane coupling agent together. Since the adhesive force is further improved by using the silane coupling agent, the floating and peeling can be further suppressed.

Examples of the silane coupling agent include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropyltripropoxysilane, and 3- (meth). An alkoxysilane compound having a (meth) acryloxy group such as acryloxypropyltributoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane;
Alkoxysilane compounds having a vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane;
3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl)- 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) Alkoxysilane compounds having an amino group, such as -3-aminopropylmethyldiethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane;
Alkoxysilane compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane;
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltributoxysilane, 3-glycidoxypropylmethyldimethoxysilane, Alkoxysilane compounds having an epoxy group such as 3-glycidoxypropylmethyldiethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane;
Tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane;
3-chloropropyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, styryltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyl Examples thereof include triethoxysilane, hexamethyldisilazane, and a silicone resin having an alkoxysilyl group in the molecule.

  The silane coupling agent is preferably used in an amount of 0.01 to 2 parts by weight, more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the acrylic copolymer (A).

  In the pressure-sensitive adhesive of the present invention, various resins, oils, softeners, dyes, pigments, antioxidants, ultraviolet absorbers, weathering stabilizers, plasticizers, and the like as long as the effects of the present invention are not impaired. You may mix | blend a filler, anti-aging agent, an antistatic agent, etc.

  The pressure-sensitive adhesive of the present invention is suitable as a pressure-sensitive adhesive for optical members, as well as various plastic sheets, general labels and seals, paints, elastic wall materials, waterproof coating materials, flooring materials, tackifiers, pressure-sensitive adhesives, and laminates. Structural adhesives, sealing agents, molding materials, surface modification coating agents, binders (magnetic recording media, ink binders, casting binders, fired brick binders, graft materials, microcapsules, glass fiber sizing, etc.), urethane foam ( (Hard, semi-rigid, soft), urethane RIM, UV / EB curable resin, high solid paint, thermosetting elastomer, microcellular, textile processing agent, plasticizer, sound absorbing material, vibration damping material, surfactant, gel coat agent, Resin for artificial marble, impact modifier for artificial marble, resin for ink, film (laminate adhesive, protective film) Beam, etc.), laminated glass resin, reactive diluent, various molding materials, elastic fiber, artificial leather, as a raw material for synthetic leather, can also very effectively used as various resin additives and a raw material thereof or the like.

  The pressure-sensitive adhesive sheet of the present invention includes a base material and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention. The pressure-sensitive adhesive sheet can be obtained, for example, by forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive to a substrate and drying it. Moreover, an adhesive is applied to the peelable sheet and dried to form an adhesive layer, and the substrate is bonded. In addition, the adhesive layer should just be provided in the at least one surface of the base material. In the present invention, a sheet, a film and a tape are synonymous. Needless to say, the peelable sheet is bonded to the surface of the pressure-sensitive adhesive layer that is not in contact with the base material.

  When applying the adhesive, a suitable liquid medium, for example, a hydrocarbon solvent such as toluene, xylene, hexane, heptane; an ester solvent such as ethyl acetate or butyl acetate; a ketone solvent such as acetone or methyl ethyl ketone; The viscosity can be adjusted by adding halogenated hydrocarbon solvents such as dichloromethane and chloroform; ether solvents such as diethyl ether, methoxytoluene and dioxane, and other hydrocarbon solvents. The pressure-sensitive adhesive can be heated to reduce the viscosity. However, since water, alcohol, etc. inhibit the crosslinking reaction of an acrylic copolymer (B) and a polyisocyanate compound, it is preferable to avoid use.

  Examples of the substrate include cellophane, plastic, rubber, foam, cloth, rubber cloth, resin-impregnated cloth, glass plate, and wood. The substrate may be plate-shaped or film-shaped. Moreover, the structure which laminated | stacked the base material independently or several base materials is also preferable.

  Examples of the plastic include polyolefin resins such as polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Polycarbonate resin, polynorbornene resin, polyarylate resin (PAR: copolymer resin of bisphenol A and phthalic acid), polyacrylic resin, polyphenylene sulfide resin, polystyrene resin, polyamide resin, polyimide resin, epoxy resin Examples thereof include resins (resins obtained by reacting epoxy group-containing resins with polyamines or carboxylic anhydrides).

  In the present invention, the pressure-sensitive adhesive can be applied by a known method. For example, Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater and the like can be mentioned. There is no restriction | limiting in particular in a drying method, The thing using hot air drying, infrared rays, and the pressure reduction method is mentioned. The drying condition may be hot air heating of about 60 to 160 ° C.

  0.1-300 micrometers is preferable and, as for the thickness of an adhesive layer, 1-100 micrometers is more preferable. When the thickness is less than 0.1 μm, sufficient adhesive strength may not be obtained, and even when the thickness exceeds 300 μm, the performance such as adhesive strength is often not improved.

  The pressure-sensitive adhesive sheet of the present invention has an adhesive strength of 2 N / 25 mm to 10 N / 25 mm after passing for 1 day at 23 ° C. after being bonded to alkali-free glass, and more preferably 3 N / 25 mm to 8 N / 25 mm. . When the adhesive strength is 2 N / 25 mm or more, it becomes easy to obtain sufficient adhesive strength that is unlikely to cause floating and peeling. In addition, when the adhesive strength is 10 N / 25 mm or less, peeling from the adherend becomes easier.

  The pressure-sensitive adhesive sheet of the present invention is preferably 5N / 25mm to 30N / 25mm, and 8N / 25mm to 25N / 25mm after 14 days at 23 ° C after being bonded to alkali-free glass. Is more preferable. When the adhesive strength is 5 N / 25 mm or more, it becomes easy to obtain sufficient adhesive strength that is unlikely to cause floating and peeling. In addition, when the adhesive strength is 20 N / 25 mm or less, peeling from the adherend becomes easier.

  In particular, in a polarizing plate fixing application in which a polarizing plate is fixed to a liquid crystal device, when fixing failure occurs, an operation of frequently removing the polarizing plate once applied and recovering an expensive liquid crystal device is often performed. In order to prevent the liquid crystal device from being contaminated or damaged, it is preferable that the adhesive strength after 1 day at 23 ° C. is 2 N / 25 mm to 10 N / 25 mm after being bonded to non-alkali glass. In addition, in order to improve work efficiency, a liquid crystal device in which a fixing failure has occurred may be stored for a certain period. After collecting for a certain period, when collecting the liquid crystal device, in order not to contaminate or break the liquid crystal device, the adhesive strength after 14 days is 5 N / 25 mm to 30 N / 25 mm after being bonded to non-alkali glass. It is preferable.

  The pressure-sensitive adhesive sheet of the present invention can be suitably used for laminating optical members. That is, it is preferable to use an optical member for the substrate. Specific examples of the optical member include a polarizing plate, a retardation film, an elliptically polarizing film, an antireflection film, and a brightness enhancement film.

  It is also preferable that the pressure-sensitive adhesive sheet of the present invention using an optical member as a base material is attached to a glass member of a liquid crystal cell and used as a liquid crystal cell member. When the optical member is a polarizing plate, even when left in a high-temperature atmosphere and a high-temperature and high-humidity atmosphere, the pressure-sensitive adhesive layer has good stress relaxation properties, so that light leakage due to warping of the polarizing plate can be suppressed.

  The pressure-sensitive adhesive sheet of the present invention can be preferably used for various electronics-related members such as liquid crystal displays, plasma displays, touch panels, and electrode peripheral members, protective films, building materials, glass members such as vehicle window glass, polyolefin, ABS, acrylic, etc. It can also be used for metals such as plastic, cardboard, wood, plywood, stainless steel and aluminum.

  EXAMPLES Next, although an Example of this invention is shown and it demonstrates further in detail, this invention is not limited by these. In the examples, “part” means “part by weight” and “%” means “% by weight”.

<Synthesis Example 1: Acrylic Copolymer (A)>
In a reaction vessel (hereinafter simply referred to as “reaction vessel”) equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 99.9 parts of butyl acrylate, 0.1 part of acrylic acid, 100 parts of ethyl acetate and 0.025 part of 2,2′-azobisisobutyronitrile (hereinafter referred to as AIBN) were charged, and the air in the reaction vessel was replaced with nitrogen gas. Then, it heated to 80 degreeC, stirring under nitrogen atmosphere, and reaction was started. Thereafter, the reaction solution was reacted at reflux temperature for 7 hours. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain a copolymer solution having a nonvolatile content of 30% and a viscosity of 3000 mPa · s. Moreover, when the weight average molecular weight (Mw) of the acrylic copolymer was measured using GPC, the weight average molecular weight was 1,000,000. Let the obtained copolymer be a copolymer (A-1).

<Synthesis Examples 2 to 25>
Various raw materials were charged according to the weight ratios in Table 1, and an acrylic copolymer (A) was synthesized in the same manner as in Synthesis Example 1. The weight average molecular weight of the obtained acrylic copolymer is shown in Table 1.

<Synthesis Examples 26 to 28>
According to the weight ratio of Table 1, various raw materials were charged, and 100 parts by weight of ethyl acetate in Synthesis Example 1 was changed to 50 parts by weight of ethyl acetate and 50 parts by weight of methyl ethyl ketone, and the others were synthesized in the same manner. did. The weight average molecular weight of the obtained acrylic copolymer is shown in Table 1.

<Synthesis Examples 29-30>
Various raw materials were charged according to the weight ratios in Table 1, and 100 parts by weight of ethyl acetate in Synthesis Example 1 was changed to 100 parts by weight of acetone, and an acrylic copolymer (A) was synthesized by the same method. The weight average molecular weight of the obtained acrylic copolymer is shown in Table 1.

<Synthesis Example 31: Acrylic compound as tackifier>
In a reaction vessel (hereinafter simply referred to as “reaction vessel”) equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 20 parts of butyl acrylate, 75 parts of benzyl acrylate, 5 parts of acrylic acid Part, toluene 100 parts, thioglycerol 5 parts, 2,2′-azobisisobutyronitrile (hereinafter referred to as AIBN) 0.5 part, and the air in the reaction vessel was replaced with nitrogen gas. Thereafter, the reaction was started by heating to 110 ° C. with stirring in a nitrogen atmosphere. Thereafter, the reaction solution was reacted at reflux temperature for 7 hours. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain a copolymer solution having a nonvolatile content of 50% and a viscosity of 1000 mPa · s. Moreover, when the weight average molecular weight (Mw) of the acrylic copolymer was measured using GPC, the weight average molecular weight was 1500. Moreover, the acid value of the obtained acrylic copolymer was 40 mg / KOH, and the softening point was 90 degreeC. The obtained copolymer is referred to as “acrylic compound (B-1)”.

<Synthesis Examples 32-37>
Various raw materials were charged according to the weight ratios in Table 2, and an acrylic tackifier was synthesized in the same manner as in Synthesis Example 31. The weight average molecular weight of the obtained acrylic copolymer is shown in Table 2.

<Measurement of weight average molecular weight (Mw)>
The weight average molecular weight (Mw) was measured using GPC “LC-GPC system” manufactured by Shimadzu Corporation. GPC is liquid chromatography in which a substance dissolved in a solvent (THF; tetrahydrofuran) is separated and quantified by the difference in molecular size, and the weight average molecular weight (Mw) is determined in terms of polystyrene.
Device name: LC-GPC system “Prominence” manufactured by Shimadzu Corporation
Column: Tosoh Co., Ltd. 4 GMHXL and Tosoh Co., Ltd. HXL-H 1 were connected.
Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 ml / min
Column temperature: 40 ° C

<Measurement of acid value>
About 1 g of a sample (tackifier) is precisely weighed in a stoppered Erlenmeyer flask and dissolved by adding 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixture. To this was added phenolphthalein test solution as an indicator and titrated with 0.1N alcoholic potassium hydroxide solution. Titration was continued until the solution was light red and held for 30 seconds. The acid value was determined by the formula (1). The acid value was a numerical value of the dry state of the resin (unit: mgKOH / g).

<Measurement of softening point>
It was measured based on the softening point test method (ring and ball method) defined in JISK5902 and JISK2207. The dissolved sample was filled into a ring placed on a flat metal plate and solidified again. Next, a supporter (ring stand) is put in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth becomes 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin so as not to contact each other, and the temperature of glycerin is maintained at 20 ° C. plus or minus 5 ° C. for 15 minutes. . Next, a steel ball is placed on the center of the surface of the sample in the ring, and this is placed in a fixed position on the support. Next, keep the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, set the center of the mercury bulb of the thermometer to the same height as the center of the ring, and increase the heating rate at 5.0 ° C per minute The container was heated with a gas burner. The heated sample gradually softened and flowed down from the ring, and finally the temperature when it contacted the bottom plate was read and this was taken as the softening point.

Example 1
Acrylic copolymer (A-1) in the copolymer solution obtained in Synthesis Example 1, 10 parts by weight of acrylic compound (B-1) as a tackifier, and triisocyanate compound as a polyisocyanate compound as a crosslinking agent. A pressure-sensitive adhesive was obtained by adding 10 parts by weight of an adduct of trimethylolpropane, a diisocyanate, and further adding ethyl acetate to adjust the nonvolatile content to 20%.

  The pressure-sensitive adhesive was applied to a 38 μm-thick polyethylene terephthalate peelable sheet (Therapy MF: manufactured by Toray Film Processing Co., Ltd.) as a base material so that the thickness after drying was 25 μm, at 100 ° C. The pressure-sensitive adhesive layer was formed by drying with hot air for 2 minutes. Next, a polarizing plate (HLC2-5618) having a laminated structure in which both surfaces of a polyvinyl alcohol (PVA) polarizer as an optical member are sandwiched by triacetylcellulose-based films (hereinafter referred to as “TAC films”) as optical members. A polarizing plate adhesive sheet having a structure of “peeling film / adhesive layer / TAC film / PVA / TAC film” is obtained by laminating one side of SANRITZ) and then aging for one week at a temperature of 35 ° C. and a relative humidity of 55%. Obtained.

(Examples 2 to 36 , Comparative Examples 1 to 20)
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 according to the blending ratios in Table 3 and Table 4. Further, a laminate was obtained in the same manner as in Example 1. The tackifiers used are listed in Table 5. The obtained polarizing plate adhesive sheet was evaluated by the following method.
However, Examples 1-8 and 13-36 are reference examples.

(1) Evaluation of heat resistance and wet heat resistance The obtained polarizing plate pressure-sensitive adhesive sheet was prepared to have a width of 160 mm and a length of 120 mm. Next, the peelable sheet was peeled off and adhered to an alkali-free glass plate (1737: manufactured by Corning) using a laminator (VA-770A: Taisei Laminator Co., Ltd.) to obtain a liquid crystal cell member. Then, the said glass plate with which this polarizing plate adhesive sheet was affixed was hold | maintained for 20 minutes in the autoclave of conditions of 50 degreeC and 5 atmospheres, and the measurement sample was obtained by sticking each member closely. The measurement sample was evaluated for heat resistance as resistance evaluation in a high temperature atmosphere. That is, the measurement sample was allowed to stand at 85 ° C. for 500 hours and then visually observed for foaming, floating and peeling. In addition, the heat resistance of the measurement sample was evaluated as an evaluation of resistance in a high-temperature and high-humidity atmosphere. That is, the measurement sample was allowed to stand at 60 ° C. and a relative humidity of 95% for 500 hours and then visually observed for foaming, floating and peeling. Heat resistance and moist heat resistance were evaluated based on the following criteria.
A: “Foaming, floating and peeling are not recognized at all, and it is good”
○: “Bubbling, floating or peeling of 0.5 mm or less is recognized, but there is no practical problem”
X: “There is foaming, floating and peeling all over and cannot be used”

(2) Light Leakage Evaluation Two sheets of the obtained polarizing plate pressure-sensitive adhesive sheet having a width of 160 mm and a length of 120 mm were prepared. Next, the peelable sheet was peeled off, and two polarizing plate adhesive sheets were adhered to both surfaces of the alkali-free glass plate using a laminator so that the absorption axes of the polarizing plates were orthogonal to obtain a liquid crystal cell member. Subsequently, the pressure-bonded product was held in an autoclave at 50 ° C. and 5 atm for 20 minutes, and each member was brought into close contact with each other to obtain a measurement sample. The measurement sample was allowed to stand at 85 ° C. for 500 hours, and then light leakage when light was transmitted through the polarizing plate was visually observed. The light leakage was evaluated based on the following criteria.
A: “No white spots and good”
○: “There is a slight white spot, but there is no practical problem”
×: “There are white spots on the entire surface and cannot be used”

(3) Removability evaluation The obtained polarizing plate pressure-sensitive adhesive sheet was prepared to have a width of 160 mm and a length of 120 mm. Next, the peelable sheet was peeled off and attached to a non-alkali glass plate using a laminator. Then, the measurement sample was obtained by making it hold | maintain for 20 minutes in the autoclave of conditions of 50 degreeC and 5 atmospheres, and closely_contact | adhering each member. After the measurement sample was left at 85 ° C. for 3 hours, a peeling test was performed in which the sample was pulled at a speed of 300 mm / min in the 180 ° direction using a tensile tester in an environment of 23 ° C. and 50% relative humidity. . Subsequently, the cloudiness of the glass surface after peeling was observed visually and evaluated based on the following criteria.
○: “Adhesive residue and cloudiness are not recognized and good”
×: “Adhesive residue, cloudiness is recognized and impractical”

(4) Adhesive strength evaluation The obtained polarizing plate adhesive sheet was prepared for the width | variety of 25 mm and the magnitude | size of length 100mm. Next, the peelable sheet was peeled off and attached to a non-alkali glass plate using a laminator. Then, the measurement sample was obtained by making it hold | maintain for 20 minutes in the autoclave of conditions of 50 degreeC and 5 atmospheres, and closely_contact | adhering each member. The measurement sample was allowed to stand at 23 ° C. for one day, and was then peeled at a peeling speed of 300 mm / min, peeling angle using a tensile tester (“Tensilon” manufactured by Orientec Co., Ltd.) in an environment of 23 ° C. and 50% relative humidity. The adhesive strength was measured under the condition of 180 ° (adhesive strength measurement one day after bonding). Moreover, after leaving the said measurement sample to stand at 23 degreeC for 14 days, adhesive force was measured by the same method (adhesion force measurement after 14 days of bonding).

  From the results of Tables 6 and 7, as shown in Examples 1 to 38, the pressure-sensitive adhesive of the present invention is excellent in durability, stress relaxation, and removability in a high temperature atmosphere and a high temperature and high humidity atmosphere. On the other hand, Comparative Examples 1-20 were not able to satisfy | fill all the said characteristics.

Claims (10)

A pressure-sensitive adhesive comprising an acrylic polymer (A), a tackifier (B), and a crosslinking agent (C), wherein the acrylic polymer (A) contains 0.1 carboxyl group-containing monomer. A polymer having a weight average molecular weight of 500,000 to 2,000,000, which is obtained by polymerizing a monomer containing ˜20% by weight,
Wherein said tackifier (B) is an acid value 5 ~200mgKOH / g, a softening point seventy-five to one hundred sixty ° C., rosin-based compound having at least one aromatic ring in the molecule (provided that the compound having a hydroxyl group and a rosin skeleton Except)
The content of the tackifier (B) with respect to 100 parts by weight of the acrylic polymer (A) is 10 to 30 parts by weight,
The releasable pressure-sensitive adhesive, wherein the crosslinking agent (C) contains a polyisocyanate compound. Acrylic polymer (A) with respect to 100 parts by weight, crosslinking agent (C) is according to claim 1 Symbol placement, characterized by containing 30 parts by weight or less than 5 parts by weight removable pressure sensitive adhesive . The releasable pressure-sensitive adhesive according to claim 1 or 2, wherein the crosslinking agent (C) is an araliphatic polyisocyanate compound. Furthermore, the releasable pressure-sensitive adhesive according to any one of claims 1 to 3 , comprising a metal chelate compound (D). A substrate, formed by a claim 1 comprising 4 is formed from a removable pressure sensitive adhesive according to any adhesive layer the adhesive sheet. The pressure-sensitive adhesive sheet according to claim 5 , wherein the substrate is an optical member. When the alkali-free glass plate and the pressure-sensitive adhesive layer are bonded together, the adhesive strength at the interface between the glass plate and the pressure-sensitive adhesive layer is 2 to 10 N / 25 mm after the lapse of 1 day at 23 ° C. The pressure-sensitive adhesive sheet according to claim 5 or 6 , wherein the pressure-sensitive adhesive sheet is 5 to 30 N / 25 mm after 14 days at C. Polarizing plate and a polarizing plate adhesive sheet comprising a formed by forming a removable pressure sensitive adhesive according to any one of claims 1-4 an adhesive layer. A liquid crystal cell member comprising a glass plate, a pressure-sensitive adhesive layer formed from the removable pressure-sensitive adhesive according to any one of claims 1 to 4, and an optical member. The liquid crystal cell member according to claim 9 , wherein the optical member is a polarizing plate.