JP2014189716A - Re-releasable tackifier and tacky sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a re-releasable tackifier having a favorable transparency and capable, even after having been placed within a high-temperature or high-temperature/high-humidity environment, of preparing a re-releasable tacky sheet while inhibiting delamination and peeling; and a tacky sheet.SOLUTION: The provided re-releasable tackifier includes: an acrylic polymer obtained by copolymerizing a monomer mixture including, with respect to 100 wt.% of the monomer mixture, 0.3-5 wt.% of a monomer (A) having a structure expressed by the general formula (1) together with a (meth)acrylic acid alkyl ester and another monomer(s); and a curative.

Description

  The present invention relates to a releasable pressure-sensitive adhesive that can be suitably used for producing a display such as a liquid crystal used for a glass substrate.

  Display devices such as liquid crystal displays are used in various devices such as home appliances and commercial appliances such as electronic computers, electronic watches, mobile phones, and televisions. Especially, liquid crystal and plasma televisions are becoming larger. In recent years, it is also used for in-vehicle devices such as car navigation, and is required to withstand harsh environments such as high temperature and high temperature and high humidity. For the display device, polarizing plates and retardation plates having various optical functions are used, and these are attached to a member such as glass via an adhesive.

  The polarizing plate is a laminate having a configuration in which a polyvinyl alcohol film is sandwiched between a triacetyl cellulose film or a cycloolefin film. And since each said film differs in the dimensional change rate in each temperature, when it puts in a high temperature environment, a curvature | sledge will often arise in a laminated body.

  In addition, when a polarizing plate is bonded to an optical component such as a liquid crystal cell in the manufacturing process of a liquid crystal display or the like, the polarizing plate is peeled off after a certain time has elapsed since the bonding position has shifted. In some cases, so-called “reworkability” is required in which expensive liquid crystal cells are reused. Therefore, there is a need for a re-adhesive pressure-sensitive adhesive that can be peeled off from the liquid crystal cell relatively easily even after a long period of time after being bonded via the pressure-sensitive adhesive applied to the polarizing plate. Yes.

  Various pressure-sensitive adhesives have been proposed as pressure-sensitive adhesives that satisfy such requirements. For example, a pressure-sensitive adhesive aiming to achieve both durability and removability of the pressure-sensitive adhesive by using a polyether-modified silicone and a silane coupling agent in combination is disclosed (see Patent Document 1).

JP 2010-159346 A

  However, conventional pressure-sensitive adhesives can be re-peeled immediately after being processed and pasted into a pressure-sensitive adhesive sheet. However, the compatibility between the polyether-modified silicone and the acrylic polymer is poor, so that a long time has passed after pasting. There was a problem that phase separation occurred in the agent layer, resulting in a decrease in transparency and a decrease in removability.

  The present invention provides a releasable pressure-sensitive adhesive having good transparency capable of producing a pressure-sensitive adhesive sheet having removability while suppressing the occurrence of floating and peeling after being placed in a high temperature or high temperature and high humidity environment. Objective.

In the present invention, the monomer (A) having a structure represented by the following general formula (1) is 0.3 to 5% by weight based on the monomer mixture, (meth) acrylic acid alkyl ester, and 100% by weight of the monomer mixture containing other monomers. % Is a re-peelable pressure-sensitive adhesive containing an acrylic polymer obtained by copolymerization of a polymer and a curing agent.

General formula (1)

(Where n is an integer from 1 to 200)

According to the present invention having the above structure, the ester structure of the alkyl ester on the side chain of the copolymer has a high affinity and easily adheres to an adherend such as glass, so that it is placed in a high temperature atmosphere after being attached to the adherend. When peeled, adhesion will be further increased and re-peeling will be difficult. However, in the present invention, the structure represented by the general formula (1) of the copolymer side chain (also referred to as a polydimethylsiloxane structure) has better “familiarity” with the adherend than the ester structure, and therefore floats and peels off. Despite being difficult, re-peelability is unlikely to decrease. Therefore, the effect of excellent removability was obtained after being placed in a high temperature atmosphere. On the other hand, in patent document 1, in order to suppress the adhesion | attachment resulting from the said ester structure, the excellent re-peelability is implement | achieved after putting for a long time after sticking by adding polyether modified silicone. However, since the copolymer and the polyether-modified silicone have low compatibility, they are separated when placed in a high-temperature atmosphere and the transparency is lowered. However, in the present invention, there is no compatibility problem because the polydimethylsiloxane structure is present in the side chain of the copolymer. Therefore, an effect that the transparency is hardly lowered even after being placed in a high temperature atmosphere was obtained.
The effect after being placed in the high-temperature atmosphere listed in the previous stage was the same as that obtained after being placed in a high-temperature and high-humidity atmosphere.

  According to the present invention, it was possible to provide a releasable pressure-sensitive adhesive having good transparency capable of producing a pressure-sensitive adhesive sheet that can be re-peeled while being prevented from being lifted or peeled after being placed in a high temperature or high temperature and high humidity environment.

一般式（１）
The re-peelable pressure-sensitive adhesive of the present invention comprises 0.3 to 5% by weight of a monomer (A) having a structure represented by the following general formula (1) based on the monomer mixture, (meth) acrylic acid alkyl ester, and other monomers An acrylic polymer obtained by copolymerizing 100% by weight of a monomer mixture containing a curing agent and a curing agent. In this specification, the structure represented by the general formula (1) is referred to as a polydimethylsiloxane structure. The re-peelable pressure-sensitive adhesive of the present invention is preferably used after being processed into a pressure-sensitive adhesive tape. In this specification, tape, film, and sheet are synonymous. The (meth) acrylic acid alkyl ester includes an acrylic acid alkyl ester and a methacrylic acid alkyl ester.

General formula (1)

(Where n is an integer from 1 to 200)

  When a pressure-sensitive adhesive sheet containing a general acrylic polymer is bonded to an adherend, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet progresses to the adherend with the passage of time (adhesion increases). For example, the ester bond of the alkyl ester of the polymer side chain with respect to the adherend to glass or the like has high affinity and is easy to adhere, so that the adhesive force is increased. In particular, when placed in a high temperature atmosphere, the adhesion is further increased, and at the same time, the adhesive force is increased, so that re-peeling from the adherend becomes difficult. On the other hand, the re-peelable pressure-sensitive adhesive of the present invention contains a polydimethylsiloxane structure in the side chain of the acrylic polymer. This polydimethylsiloxane structure has a higher affinity with an adherend such as glass as compared with an ester structure, but does not increase the adhesive strength. Therefore, when the adhesive sheet is attached to the adherend, the polydimethylsiloxane structure of the acrylic polymer is in close contact with the adherend in preference to the alkyl ester, so that the adhesive layer is not covered when placed in a high temperature atmosphere. The present inventors have found an excellent effect that re-peeling can be easily performed in spite of the fact that it does not easily float and peel off from the adherend.

  In the present invention, the monomer (A) having the structure represented by the general formula (1) preferably contains 0.3 to 5% by weight, and 0.5 to 3% by weight in 100% by weight of the monomer mixture used for copolymerization. % Is more preferable. By including 0.3% by weight or more, good removability is easily obtained. Moreover, it becomes easy to copolymerize with another monomer by containing 5 weight% or less.

The monomer (A) having the structure represented by the general formula (1) is, for example, a monomer represented by the following general formula (2),
General formula (2)

(In the formula, R1: an alkylene group having 1 or more carbon atoms, R2: an alkyl group having 1 or more carbon atoms, n is an integer of 1 to 200)
A monomer represented by the following general formula (3),
General formula (3)

(Wherein, R1: an alkylene group having 1 or more carbon atoms, R2: an alkyl group having 1 or more carbon atoms, n is an integer of 1 to 200),
A monomer represented by the following general formula (4):
General formula (4)

(Wherein R1: an alkylene group having 1 or more carbon atoms, R2: an alkylene group having 1 or more carbon atoms, R1 and R2 may have the same structure or different structures, and n is an integer of 1 to 200) ,
A monomer represented by the following general formula (5),
General formula (5)

(Wherein R1: an alkylene group having 1 or more carbon atoms, R2: an alkylene group having 1 or more carbon atoms, R1 and R2 may have the same structure or different structures, and n is an integer of 1 to 200) ,
A monomer represented by the following general formula (6):
General formula (6)

(Wherein R1: an alkylene group having 1 or more carbon atoms, R2: an alkylene group having 1 or more carbon atoms, R1 and R2 may have the same structure or different structures, and n is an integer of 1 to 200) ,

  The monomer (A) having the structure represented by the general formula (1) may be used alone or in combination of two or more. Among these, in general formula (1), the monomer whose repeating unit of n is 10-100 is preferable, and the monomer which is 20-80 is more preferable.

Monomers used for the synthesis of the acrylic polymer are preferably (meth) acrylic acid alkyl esters and other monomers.
The (meth) acrylic acid alkyl ester is preferably a monomer having 1 to 20 carbon atoms in the alkyl chain. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, ( (Meth) acrylic acid cyclohexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid isooctyl, (meth) acrylic acid decyl, (meth) acrylic acid dodecyl, (meth) acrylic acid tetradecyl, (meth) acrylic acid hexadecyl, Examples include (meth) acrylate octadecyl. 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 preferably contains 80 to 99.3% by weight in 100% by weight of the monomer mixture used for copolymerization.

The other monomers are preferably reactive functional group-containing monomers, alkoxy (poly) alkylene oxide-containing monomers, and other vinyl monomers.
The reactive functional group-containing monomer is preferably a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide bond-containing monomer, an epoxy group-containing monomer, an amino group-containing monomer, or the like.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, phthalic acid monohydroxyethyl acrylate ester, p-carboxybenzyl acrylate ester, ethylene oxide-modified (EO addition mole number: 2 to 18) phthalic acid acrylate ester, Phthalic acid monohydroxypropyl acrylate, succinic acid monohydroxyethyl acrylate, β-carboxyethyl acrylate, 2- (4-benzoyl-3-hydroxyphenoxy) ethyl acrylate, maleic acid, monoethylmaleic acid, itacon Examples include acid, citraconic acid, and fumaric acid. Among these, (meth) acrylic acid is preferable. These can be used alone or in combination of two or more.

  The carboxyl group-containing monomer preferably includes 0.5 to 10% by weight, more preferably 1 to 5% by weight, in 100% by weight of the monomer mixture used for copolymerization. By containing 0.5% by weight or more, it is easy to adjust the crosslinking density of the pressure-sensitive adhesive, and it becomes easy to suppress the pressure-sensitive adhesive layer from floating and peeling off in a high-temperature environment. Further, when the content is 10% by weight or less, adhesion between the pressure-sensitive adhesive layer and the adherend becomes difficult to be excessive.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, ( (Meth) acrylic acid hydroxyalkyl esters such as (meth) acrylic acid 3-hydroxybutyl, (meth) acrylic acid 4-hydroxybutyl, (meth) acrylic acid 6-hydroxyhexyl, (meth) acrylic acid 8-hydroxyoctyl, Polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, glycol mono (meth) acrylate such as 1,4-cyclohexanedimethanol mono (meth) acrylate, caprolactone modified (meth) A Acrylic acid esters, such as hydroxyethyl acrylamide. Among these, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable. These can be used alone or in combination of two or more.

  The hydroxyl group-containing monomer preferably contains 0.1 to 5% by weight, more preferably 0.2 to 3% by weight, in 100% by weight of the monomer mixture used for copolymerization. By including 0.1% by weight, the adjustment of the crosslinking density of the pressure-sensitive adhesive is facilitated, and the pressure-sensitive adhesive layer can be easily prevented from floating and peeling off in a high-temperature environment. Further, if the content is 5% by weight or less, the risk of excessive crosslinking density is reduced, and floating and peeling are more easily suppressed.

  Examples of the amide bond-containing monomer include (meth) acrylamide, N-methylacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropyl (meth) acrylamide, Compounds containing heterocycles such as (meth) acrylamide compounds such as acetone acrylamide, N- (hydroxymethyl) acrylamide, N- (butoxymethyl) acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine , N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide and the like. These can be used alone or in combination of two or more.

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

  Examples of the amino group-containing monomer include (meth) acrylic acid monomethylaminoethyl, (meth) acrylic acid monoethylaminoethyl, (meth) acrylic acid monomethylaminopropyl, and (meth) acrylic acid monoethylaminopropyl. ) Acrylic acid monoalkylamino ester and the like.

  The amide bond-containing monomer, the epoxy group-containing monomer, and the amino group-containing monomer are preferably included in an amount of 0.01 to 10 parts by weight in 100% by weight of the monomer mixture used for copolymerization.

  Examples of the alkoxy (poly) alkylene oxide-containing monomer include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth) acrylate, and ethoxypolyethylene glycol (meth). Examples include acrylic acid esters, methoxypolypropylene glycol (meth) acrylic acid esters, ethoxypolypropylene glycol (meth) acrylic acid esters, phenoxypolyethylene glycol (meth) acrylic acid esters, and phenoxypolypropylene glycol (meth) acrylic acid esters.

  The alkoxy (poly) alkylene oxide-containing monomer is preferably contained in an amount of 1 to 50 parts by weight, more preferably 1 to 30 parts by weight, in 100% by weight of the monomer mixture used for copolymerization.

  The other vinyl monomer is preferably vinyl acetate, styrene, α-methylstyrene, vinyltoluene or the like, but is not limited to any monomer that can be copolymerized with other monomers.

  The other monomer is preferably contained in an amount of 1 to 50 parts by weight, more preferably 1 to 30 parts by weight, in 100% by weight of the monomer mixture used for copolymerization.

  In the present invention, the acrylic polymer can be obtained by a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization or the like, but solution polymerization is preferred from the viewpoint of control of weight average molecular weight and reaction control. In the case of solution polymerization, polymerization solvents include methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, and isopropanol. Preferably, one type or two or more types can be appropriately selected according to the desired application.

  The solution polymerization can be performed by adding 0.001 to 1 part by weight of a polymerization initiator to 100 parts by weight of the total monomer mixture. Usually, the polymerization reaction can be carried out under a nitrogen stream under reflux conditions of about 50 ° C. to 90 ° C. for 6 hours to 20 hours. Moreover, the weight average molecular weight of an acrylic polymer can be suitably adjusted using a chain transfer agent for a polymerization reaction.

  Examples of the chain transfer agent include n-dodecyl mercaptan, mercaptoisobutyl alcohol, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, glycidyl mercaptan, α- Examples include methylstyrene dimer, carbon tetrachloride, chloroform, hydroquinone and the like. .

  In the present invention, the weight average molecular weight of the acrylic polymer is preferably 700,000 to 2,000,000, more preferably 800,000 to 1,500,000, and further preferably 850,000 to 1,300,000. By making the weight average molecular weight in the range of 700,000 to 2,000,000, it becomes easy to suppress floating and peeling when placed in a high temperature atmosphere. Handling of the releasable pressure-sensitive adhesive becomes easier.

  In the present invention, the weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

  The polymerization initiator is generally an azo compound or an organic peroxide. The polymerization initiators can be used alone or in combination of two or more.

  Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 , 2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis (2- (2-imidazolin-2-yl) Propane) and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  The curing agent contained in the re-peelable pressure-sensitive adhesive of the present invention is preferably an isocyanate compound, an epoxy compound, an ethyleneimine compound, a metal chelate compound, an amine compound, or the like.

  Examples of the isocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate. Adduct bodies, burette bodies or isocyanurate bodies of isocyanate monomers such as polymethylene polyphenyl isocyanate and polyol compounds such as trimethylolpropane, and these polyether monomers and known polyether polyols or polyester polyols, acrylic polyols, polybutadiene polyols, Po Compounds having 3 or more isocyanate groups in the molecule such as adducts with isoprene polyol, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate , Tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate and other isocyanate monomers, hexamethylene diisocyanate allophanate (coronate 2770: manufactured by Nippon Polyurethane Industry Co., Ltd.) Examples include compounds having an isocyanate group. Among these, a trimethylolpropane adduct of tolylene diisocyanate is preferable because the adhesive properties can be easily adjusted. In addition, the number of isocyanate groups is an average number.

  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, diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidylaminophenylmethane and the like can be mentioned.

  Examples of the ethyleneimine compounds include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxite), N, N′-toluene-2,4-bis (1-aziridinecarboxite), bis Isophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxite), 2,2′-bis Hydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, tris-2,4 Examples include 6- (1-aziridinyl) -1,3,5-triazine.

  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. Can be mentioned.

  Examples of the amine compound include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resin, and methylene resin.

The said hardening | curing agent can be used individually or in combination of 2 or more types.
The curing agent is preferably contained in an amount of 0.01 to 30 parts by weight, more preferably 0.02 to 20 parts by weight, with respect to 100 parts by weight of the acrylic polymer. When the content is 0.01 to 30 parts by weight, it becomes easy to balance the cohesive force and adhesive force of the pressure-sensitive adhesive layer.

  The re-peelable pressure-sensitive adhesive of the present invention preferably contains a silane coupling agent. By including the silane coupling agent, the adhesion between the pressure-sensitive adhesive layer and the adherend is further improved, whereby the durability in a high-temperature atmosphere can be further improved.

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 include triethoxysilane, hexamethyldisilazane, and silicone resins having an alkoxysilyl group in the molecule (X-41-1056: manufactured by Shin-Etsu Chemical Co., Ltd., X-41-1810: manufactured by Shin-Etsu Chemical Co., Ltd.).

The silane coupling agents can be used alone or in combination of two or more.
It is preferable that the said silane coupling agent contains 0.01-2 weight part with respect to 100 weight part of acrylic polymers, and 0.05-1 weight part is more preferable.

  The removable pressure-sensitive adhesive of the present invention can also contain a tackifying resin. When the tackifier resin is included, the adhesive strength is further improved.

  Examples of the tackifying resin include rosin derivatives, polyterpene resins, aliphatic petroleum resins, aromatic petroleum resins, and alkylphenol formaldehyde resins (oil-based phenol resins). These can be used alone or in combination of two or more.

  The tackifier resin is preferably 0.1 to 30 parts by weight, and more preferably 1 to 20 parts by weight with respect to 100 parts by weight of the acrylic polymer.

  The re-peelable pressure-sensitive adhesive of the present invention is a resin, curing catalyst, oil, softener, dye, pigment, antioxidant, ultraviolet absorber, weather stabilizer, as optional components, as long as the effects of the present invention are not impaired. You may mix | blend a plasticizer, a filler, anti-aging agent, an antistatic agent, etc.

  The re-peelable pressure-sensitive adhesive of the present invention is suitable as a pressure-sensitive adhesive for optical members, general labels and seals, paints, elastic wall materials, waterproof coating materials, flooring materials, tackifiers, pressure-sensitive adhesives, and laminated structures. Body 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 cured resin, high solid paint, thermosetting elastomer, microcellular, textile processing agent, plasticizer, sound absorbing material, vibration damping material, surfactant, gel coat agent, artificial Marble resin, impact resistance agent for artificial marble, ink resin, film (laminate adhesive, protective film, etc.), combination Las 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 removable pressure-sensitive adhesive of the present invention.
The pressure-sensitive adhesive layer can be formed by applying a re-peelable pressure-sensitive adhesive on a substrate and drying it. Alternatively, it can be formed by applying a releasable pressure-sensitive adhesive on a peelable sheet and drying it, and then bonding the pressure-sensitive adhesive layer and the substrate together. Needless to say, the peelable sheet is bonded to the surface of the pressure-sensitive adhesive layer that does not contact the substrate.

  When applying the re-peelable pressure-sensitive adhesive, for example, hydrocarbon solvents such as toluene, xylene, hexane and heptane; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; dichloromethane The viscosity can also be adjusted by adding halogenated hydrocarbon solvents such as chloroform; ether solvents such as diethyl ether, methoxytoluene and dioxane, and other hydrocarbon solvents.

  The base material is preferably, for example, cellophane, plastic, optical member, rubber, foam, cloth, rubber cloth, resin-impregnated cloth, glass, and wood. The shape of the substrate can be selected from a plate shape and a film shape, but a film that is easy to handle is preferred. The substrate can be used alone or in combination of two or more.

  Examples of the plastic include polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefin, polyolefin such as ethylene-vinyl acetate copolymer, polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polynorbornene, Examples include polyarylate, polyacryl, polyphenylene sulfide, polystyrene, polyamide, polyimide film, and epoxy.

  The method for applying the releasable adhesive is not particularly limited, and may be Meyer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater, etc. 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. As drying conditions, hot air heating of about 60 to 160 ° C. is usually possible depending on the curing agent type, the thickness of the pressure-sensitive adhesive layer, or the solvent type.

  0.1-300 micrometers is preferable and, as for the thickness of an adhesive layer, 1-100 micrometers is more preferable. The adhesive physical property can be adjusted to an appropriate range by being in the range of 0.1 to 300 μm.

  The pressure-sensitive adhesive sheet of the present invention is preferably 2-15 N / 25 mm, more preferably 2-10 N / 25 mm, after being pasted on alkali-free glass and after autoclaving, at 23 ° C. for 1 hour. When the adhesive strength is 2 N / 25 mm or more, floating and peeling are less likely to occur. Moreover, when the adhesive strength is 15 N / 25 mm or less, re-peeling becomes easier.

In the present invention, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet preferably has a gel fraction of 60 to 95% by weight, more preferably 65 to 90% by weight. When the gel fraction is 60 to 95% by weight, cohesion, lifting and peeling can be achieved at a higher level. In the present invention, the gel fraction is determined by attaching a pressure-sensitive adhesive sheet of a predetermined size to SUS200 mesh (aperture: 0.077 mm, wire diameter: 0.05 mm) and then immersing in ethyl acetate at 50 ° C. It is a numerical value calculated by the following formula (1) after being extracted for 24 hours and then dried at 100 ° C. for 30 minutes.
Formula (1) Gel fraction (% by weight) = (G2 / G1) × 100
G1: Weight of the pressure-sensitive adhesive layer before extraction with ethyl acetate
G2: Weight of the pressure-sensitive adhesive layer after extraction and drying with ethyl acetate

The pressure-sensitive adhesive sheet of the present invention can be used for adherends such as glass, plastic, cardboard, and metal. Since the re-peelable pressure-sensitive adhesive is used, it is difficult to float and peel while being attached to the adherend, and can be easily peeled off when peeled.
As a preferable embodiment of the pressure-sensitive adhesive sheet of the present invention, it is preferable to use an optical member as a base material and a surface protective member for a display or a solar cell.
Examples of the optical member include a polarizing plate, a retardation film, an elliptically polarizing film, an antireflection film, a brightness enhancement film, and a transparent conductive film.

  Moreover, it is preferable to use the adhesive sheet of this invention as a laminated body which uses the optical member for the base material. For example, as a laminated body for liquid crystal cells, a configuration of polarizing plate / adhesive layer / liquid crystal cell glass member can be exemplified. When the laminate is placed in a high temperature environment, the polarizing plate may be warped, but there are problems that bubbles (foaming) occur at the interface between the adhesive layer and the glass, or the polarizing plate floats off the glass and peels off. Was. In addition, the stress distribution of the laminate is uneven due to the warp, and as a result of stress being concentrated at the four corners of the laminate or at the peripheral end, light leaks from the four corners and the peripheral end of the laminate, The so-called “light leakage phenomenon” occurred. However, when the re-peelable pressure-sensitive adhesive of the present invention is used, there is an effect that not only floating and peeling are hardly caused in a high temperature environment and a high temperature and high humidity environment, but also a light leakage phenomenon is hardly caused.

  As another preferred usage mode of the pressure-sensitive adhesive sheet of the present invention, for example, touch panel applications can be mentioned. The laminated body which used the transparent conductive film for the base material can mention the structure of a transparent conductive film / adhesive layer / glass member for a display. When the re-peelable pressure-sensitive adhesive of the present invention is used for the laminate, not only does it hardly float and peel off in a high-temperature environment and a high-temperature and high-humidity environment, but it is easy to re-attach the transparent conductive film in the manufacturing process, and durability. The effect of achieving both removability was obtained.

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

Monomers having the structure represented by the general formula (1) used in the synthesis examples are shown below.
X-22-174DX: Methacrylic group-containing silicone (manufactured by Shin-Etsu Chemical Co., Ltd., monomer represented by general formula (3), n repeating unit = 56)
X-22-2426: Methacrylic group-containing silicone (manufactured by Shin-Etsu Chemical Co., Ltd., monomer represented by general formula (3), repeating unit of n = 151)
X-22-2475: Methacrylic group-containing silicone (manufactured by Shin-Etsu Chemical Co., Ltd., repeating unit = 3 in the monomer represented by the general formula (3))

(Synthesis Example 1)
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, 96.5 parts of butyl acrylate, 3 parts of acrylic acid, X − 22-174DX 0.5 parts, ethyl acetate 90 parts, 2,2′-azobisisobutyronitrile (hereinafter referred to as “AIBN”) 0.02 part is charged, and the air in the reaction vessel is nitrogen gas. Replaced with. Thereafter, while stirring under a nitrogen atmosphere, the reaction solution was reacted at reflux temperature for 2 hours, and 0.02 part of AIBN was further added and reacted for 5 hours. After completion of the reaction, the reaction vessel was cooled and 110 parts of ethyl acetate was added to obtain an acrylic polymer solution having a weight average molecular weight of 1,050,000.

(Synthesis Examples 1-2 to 1-10)
Various raw materials were charged according to the weight ratio in Table 1, and a polymer was synthesized in the same manner as in Synthesis Example 1.

  For the acrylic polymer solutions obtained in Synthesis Examples 1-1 to 1-9, the appearance and weight average molecular weight of the solutions were determined according to the following methods. The results are shown in Table 1. In Synthesis Example 10, a polymer could not be synthesized.

<Appearance of solution>
The appearance of each acrylic polymer solution was visually evaluated.

<Measurement of weight average molecular weight>
The weight average molecular weight was measured using Shimadzu GPC “LC-GPC system”. 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 was determined in terms of polystyrene.
Device name: LC-GPC system “Prominence” manufactured by Shimadzu Corporation
Column: Four Tosoh Co., Ltd. GMHXL and one Tosoh Co., Ltd. HXL-H were connected in series.
Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 ml / min
Column temperature: 40 ° C

Abbreviations in Table 1 are listed below.
BA: butyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate KBE-503: 3-methacryloxypropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)

Example 1
For 100 parts of the polymer in the acrylic polymer solution obtained in Synthesis Example 1, 10 parts of coronate L (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Nippon Polyurethane Co., Ltd.) as a curing agent (in terms of nonvolatile content) , 0.2 parts of KBM-403 (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent (non-volatile equivalent) was added, and ethyl acetate was added as a solvent to reduce the non-volatile content. The pressure-sensitive adhesive was obtained by adjusting to 25%.

  The pressure-sensitive adhesive was applied on the release layer of the release sheet made of polyethylene terephthalate having a thickness of 38 μm and dried to a thickness of 25 μm, and then dried at 100 ° C. for 2 minutes. An adhesive layer was formed. Next, one side of a polarizing plate having a multilayer structure in which both sides of a polyvinyl alcohol (PVA) polarizer are sandwiched between triacetylcellulose-based protective films (hereinafter referred to as “TAC film”) is bonded to this pressure-sensitive adhesive layer. Pressure sensitive adhesive sheet / pressure sensitive adhesive layer / TAC film / PVA / TAC film ”was obtained. Next, the obtained pressure-sensitive adhesive film was aged at a temperature of 35 ° C. and a relative humidity of 55% for 1 week to obtain a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer was covered with a peelable sheet.

(Examples 2-8, Comparative Examples 1-5)
According to the weight ratio in Table 2, a pressure-sensitive adhesive was obtained in the same manner as in Example 1. Further, a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer was coated with a peelable sheet was obtained in the same manner as in Example 1.

  The pressure-sensitive adhesive sheets obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were evaluated by the following methods. The results are shown in Table 2.

(1) Adhesive strength The obtained adhesive sheet was prepared to have a width of 25 mm and a length of 150 mm. The peelable sheet was peeled off from the pressure-sensitive adhesive sheet and attached to non-alkali glass (# 1737, manufactured by Corning) using a laminator. Then, it was made to hold | maintain for 20 minutes within the autoclave of 50 degreeC and 5 atmospheres conditions, and it was made to contact | adhere to a glass plate, and the laminated body of the adhesive sheet and the glass plate was obtained. This laminate was held for 1 hour in an environment of 23 ° C. and a relative humidity of 50%. Then, the 180 degree peel test which peels off at a speed | rate of 300 mm / min in a 180 degree direction using the tensile tester was performed, and adhesive force was measured.

(2) Removability A laminate was prepared under the same conditions as in “(1) Adhesive strength”, treated under the following three conditions, and then allowed to stand at 23 ° C. and 50% relative humidity for 1 hour, followed by a tensile tester. Measures the adhesive strength in a 180 ° peel test that peels off at a speed of 300 mm / min in the direction of 180 ° using the adhesive, visually observes adhesive residue and cloudiness of the adhesive on the glass surface after peeling, and evaluates the following four levels. Evaluation was based on criteria.
a) Evaluation conditions Initial removability: left in an environment of 23 ° C. and 50% relative humidity for 1 hour.
Re-peelability after heating: Leave in an environment of 85 ° C. for 3 hours.
Removability with time: Leave in an environment of 23 ° C. and 50% relative humidity for 30 days.
b) Evaluation Criteria A: “Adhesive strength is 10 N / 25 mm or less, no adhesive residue or cloudiness is observed, and it is good”
○: “Adhesive strength is 15 N / 25 mm or less, no adhesive residue or cloudiness is observed, and there is no practical problem”
Δ: “No glue residue or cloudiness is observed, but the adhesive strength is 15 N / 25 mm or more, which is impractical.”
×: “Adhesive strength is 15 N / 25 mm or more, adhesive residue, cloudiness is observed, and impractical”

(3) Floating / peeling evaluation The obtained pressure-sensitive adhesive sheet was prepared to have a width of 160 mm and a length of 120 mm, and the peelable sheet was peeled off and adhered to an alkali-free glass (# 1737, manufactured by Corning) using a laminator. did. Subsequently, the glass plate on which the pressure-sensitive adhesive sheet was affixed was held in an autoclave at 50 ° C. and 5 atm for 20 minutes to adhere to the glass plate to obtain a laminate of the pressure-sensitive adhesive sheet and the glass plate. As evaluation in a high temperature atmosphere, foaming (generation of bubbles), floating and peeling after the laminate was left at 85 ° C. for 500 hours were visually observed. As evaluation in a high-temperature and high-humidity atmosphere, foaming, floating, and peeling after the laminate was allowed to stand for 500 hours at 60 ° C. and 95% relative humidity were visually observed. Evaluation in a high temperature atmosphere and a high temperature and high humidity atmosphere was performed based on the following three-stage evaluation 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”
×: “There is foaming, floating and peeling on the whole surface, which is not practical”

(4) Light leakage The obtained pressure-sensitive adhesive sheet was prepared to have a width of 160 mm and a length of 120 mm, and the peelable sheet was peeled off to remove two pressure-sensitive adhesive sheets on both sides of alkali-free glass (# 1737, Corning). A laminator was used to stick the polarizing plates so that the absorption axes thereof were orthogonal to each other. Subsequently, the glass plate on which the adhesive film was attached was held in an autoclave at 50 ° C. and 5 atm for 20 minutes to adhere to the glass plate to obtain a laminate of the adhesive sheet and the glass plate. After leaving this laminated body for 500 hours at 85 degreeC, the light leakage when light was permeate | transmitted the polarizing plate was observed visually. The light leakage was evaluated based on the following three evaluation criteria.
◎: “No whitening is observed and good”
○: “Slight whitening is recognized, but there is no practical problem”
×: “There is whitening on the entire surface and is not practical”

(5) Transparency The appearance of the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet was visually evaluated. The appearance of the pressure-sensitive adhesive layer was evaluated based on the following three-stage evaluation criteria.
○: “The coating is transparent and good”
×: “The coating film is whitened and cannot be used practically”

Abbreviations in Table 3 are listed below.
Coronate L: Trimethylolpropane adduct of tolylene diisocyanate (manufactured by Nippon Polyurethane)
TETRAD X: N, N, N ′, N′-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company)
KBM-403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
X-22-174DX: Methacrylic group-containing silicone (manufactured by Shin-Etsu Chemical Co., Ltd.)

  As shown in Examples 1 to 8 in Table 2, it can be seen that the pressure-sensitive adhesive of the present invention is excellent in removability, heat resistance, moist heat resistance, light leakage, and transparency. On the other hand, in Comparative Examples 1-5, it turns out that any item is defective and has a practical problem or is unpractical.

  The pressure-sensitive adhesive of the present invention has properties excellent in removability, heat resistance, heat and humidity resistance, light leakage, and transparency required for a pressure-sensitive adhesive for optical members. Especially for polarizing plate bonding applications, the rework required to increase the yield during the production of liquid crystal displays is regarded as important, and the required performance has become increasingly severe with the increase in size and functionality of displays. Therefore, the pressure-sensitive adhesive of the present invention is particularly useful because it has excellent reworkability in addition to heat resistance, heat and humidity resistance, light leakage, and transparency as described above.

Claims (6)

The monomer (A) having the structure represented by the following general formula (1) is copolymerized with 0.3 to 5% by weight based on the monomer mixture, and 100% by weight of the monomer mixture containing (meth) acrylic acid alkyl ester and other monomers. A re-peelable pressure-sensitive adhesive comprising an acrylic polymer formed and a curing agent.
General formula (1)

(Where n is an integer from 1 to 200)   The releasable pressure-sensitive adhesive according to claim 1, wherein n in the general formula (1) is 10 to 100.   The adhesive sheet provided with the base material and the adhesive layer formed from the releasable adhesive of Claim 1 or 2.   The pressure-sensitive adhesive sheet according to claim 3, wherein the pressure-sensitive adhesive layer has a gel fraction of 60 to 95%.   The pressure-sensitive adhesive sheet according to claim 3 or 4, wherein the substrate is an optical member. The pressure-sensitive adhesive sheet according to claim 5, wherein the optical member is a polarizing plate.