JP6863524B2 - Adhesive composition and surface protective film - Google Patents

Description

The present invention relates to pressure-sensitive adhesive compositions and surface protective films.

A surface protective film is used for the purpose of preventing the surface of various base materials from being soiled or scratched. The surface protective film is attached to, for example, an optical member or the like in the manufacturing process of a display device, and is peeled off from the optical member or the like when the surface protection is no longer necessary.

As the pressure-sensitive adhesive used for such a surface protective film, a urethane polymer having an ester bond and a pressure-sensitive adhesive containing a fatty acid ester and a curing agent are known (see, for example, Patent Document 1). Further, a pressure-sensitive adhesive containing a urethane resin having a hydroxyl group, a curing agent, and an organic acid diester or triester is known (see, for example, Patent Documents 2 and 3). Further, a pressure-sensitive adhesive containing a polyurethane having two or more hydroxyl groups, a cross-linking agent, a carbodiimide compound and an organic solvent is known (see, for example, Patent Document 4). Further, a pressure-sensitive adhesive containing a polyurethane obtained by reacting a polyisocyanate, a polyol, a dioxycarboxylic acid or the like and a polyisocyanate curing agent is known (see, for example, Patent Document 5).

Japanese Patent No. 5861794 Japanese Patent No. 5974311 Japanese Patent No. 5974313 Japanese Patent No. 6032388 Japanese Unexamined Patent Publication No. 2010-180290

However, when the conventionally known adhesives described in Patent Documents 1 to 5 are used for the surface protective film, the surface protective film may become cloudy (white mist) when left in a high temperature and high humidity. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an adhesive composition capable of maintaining the transparency of a surface protective film even under high temperature and high humidity.

The pressure-sensitive adhesive composition of the present invention contains a urethane resin (A) and a curing agent (B), and the urethane resin (A) is a reaction product of a polyol (a1) and a polyisocyanate (a2). (A1) contains a polymer polyol (a1-1) and a polyol (a1-2) having a carboxyl group, and the curing agent (B) contains a curing agent having a functional group capable of reacting with the carboxyl group. It is a waste.

The pressure-sensitive adhesive composition of the present invention can maintain transparency in the obtained surface protective film even after being placed under high temperature and high humidity.

The pressure-sensitive adhesive composition of the present invention contains a urethane resin (A) and a curing agent (B).

The urethane resin (A) is a reaction product of a polyol (a1) and a polyisocyanate (a2).

The polyol (a1) is a compound having two or more hydroxyl groups in one molecule, and includes a polymer polyol (a1-1) and a polyol (a1-2) having a carboxyl group.

The number average molecular weight of the polymer polyol (a1-1) is preferably 500 or more, more preferably 700 or more, still more preferably 900 or more, preferably 10,000 or less, more preferably 5,000 or less, still more preferably. Is 3,000 or less, particularly preferably 1,200 or less.
In the present invention, the number average molecular weight and the weight average molecular weight represent values measured by gel permeation chromatography in terms of polystyrene.

As the polymer polyol (a1-1), one kind or two or more kinds can be used, and examples thereof include a polyether polyol, a polyester polyol, and a polycarbonate polyol.

The polyether polyol is a compound obtained by addition polymerization of an alkylene oxide using one or more compounds having two or more active hydrogen atoms (for example, a molecular weight of 50 or more and less than 500) as an initiator, or the active hydrogen. Examples thereof include a compound obtained by ring-opening polymerization of a cyclic ether using one or more compounds having two or more atoms (for example, a molecular weight of 50 or more and less than 500) as an initiator, if necessary.

As the compound having two or more active hydrogen atoms, one kind or two or more kinds can be used, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, and the like. Examples thereof include 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, bisphenol A, glycerin, trimethylolethane, and trimethylolpropane.

As the alkylene oxide, one kind or two or more kinds can be used, and examples thereof include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin and the like. Examples of the cyclic ether include tetrahydrofuran, alkyl-substituted tetrahydrofuran and the like.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, a polytetramethylene glycol derivative obtained by reacting tetrahydrofuran with alkyl-substituted tetrahydrofuran, and poly obtained by copolymerizing neopentyl glycol and tetrahydrofuran. Tetrahydrofuran glycol derivatives and the like can be used. Among them, as the polyether polyol, polypropylene glycol, polytetramethylene glycol (PTMG), and polytetramethylene glycol derivative (PTXG) are preferable.

The polyether polyol includes at least a polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more. By containing an oxyalkylene unit having 4 or more carbon atoms, it becomes easy to suppress changes in surface characteristics.

The content of the polyether polyol in the polymer polyol (a1-1) is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less. is there.

Examples of the polyester polyol include an esterification reaction product of a low molecular weight polyol and a polycarboxylic acid; a ring-opening polymer of a cyclic ester compound such as ε-caprolactone; and a copolymerized polyester of the esterification reaction product and the ring-opening polymer. Can be used.

Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, and theirs. Examples thereof include anhydrides and esterified products.

Examples of the polycarbonate polyol include a reaction between a carbonic acid ester and / or phosgene and a low molecular weight polyol. As the carbonic acid ester, one kind or two or more kinds can be used, and for example, an aliphatic carbonate such as an alkyl carbonate (for example, methyl carbonate, ethyl carbonate, etc.) and a dialkyl carbonate (for example, dimethyl carbonate, diethyl carbonate, etc.) A carbonate containing an alicyclic structure such as cyclocarbonate (hereinafter, "including an alicyclic structure" may be simply referred to as an "alicyclic"); an aromatic carbonate such as diphenyl carbonate can be mentioned. Among them, aliphatic carbonates and alicyclic carbonates are preferable, aliphatic carbonates are more preferable, and dialkyl carbonates are more preferable.

Examples of the low molecular weight polyol capable of reacting with the carbonate ester and phosgen include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol and tripropylene glycol. , 1,2-Butandiol, 1,3-Butandiol, 1,4-Butandiol, 2,3-Butandiol, 1,5-Pentanediol, 1,5-Hexanediol, 1,6-Hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2 -Methyl-1,3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol , 2-Methyl-1,8-octanediol and other aliphatic polyols; 1,4-cyclohexanedimethanol and other alicyclic polyols; hydroquinone, resorcin; bisphenol A, bisphenol F, 4,4'-biphenol and other aromatics Examples include group polyols.

As the low molecular weight polyol, an aliphatic polyol and an alicyclic polyol are preferable, and an aliphatic polyol is more preferable, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-. 1,5-pentanediol and 1,6-hexanediol are more preferable.

The polycarbonate polyol is an aliphatic polycarbonate polyol which is a reaction product of an aliphatic carbonate and an aliphatic polyol; a reaction product of an aliphatic carbonate and / or an alicyclic carbonate and an aliphatic polyol and / or an alicyclic polyol. A certain alicyclic polycarbonate polyol or the like is preferable.

The content of the polymer polyol (a1-1) in the polyol (a1) is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and preferably 100% by mass or less. is there.

As the polyol (a1-2) having a carboxyl group, one kind or two or more kinds can be used, for example, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-. Hydroxy acids such as dimethylol butyric acid and 2,2-dimethylol valeric acid; and a reaction product of the polyol having a carboxy group and the polycarboxylic acid can be mentioned. As the polyol (a1-2) having a carboxyl group, a hydroxy acid is preferable, and 2,2-dimethylolpropionic acid is more preferable.

The content of the polyol (a1-2) having a carboxyl group is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 with respect to 100 parts by mass of the polymer polyol (a1-1). It is 5 parts by mass or more, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less.

The total content of the polymer polyol (a1-1) and the polyol having a carboxyl group (a1-2) in the polyol (a1) is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably. Is 90% by mass or more, preferably 100% by mass or less.

The polyol (a1) may contain a polyol (a1-3) other than the polymer polyol (a1-1) and the polyol having a carboxyl group (a1-2).

As the polyisocyanate (a2), one type or two or more types can be used, for example, diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylenediisocyanate, trienediisocyanate, naphthalene. Aromatic polyisocyanates such as diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine diisocyanate; isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 4,4' −Dicyclohexylmethane diisocyanate, 2,4- and / or 2,6-methylcyclohexanediisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis (2-isocyanatoethyl) -4-cyclohexylene-1,2-dicarboxylate And 2,5- and / or 2,6-norbornandiisocyanate, diisocyanate dimerate, bicycloheptanetriisocyanate, alicyclic polyisocyanate such as hydrogenated xylylene diisocyanate and the like. Of these, aliphatic polyisocyanates and alicyclic polyisocyanates are preferable.

The molar ratio (isocyanate group / hydroxyl group) of the isocyanate group contained in the polyisocyanate (a2) to the hydroxyl group contained in the polyol (a1) is 0.5 or more, preferably 0.7 or more. It is more preferably 0.8 or more, further preferably 0.85 or more, less than 1, preferably 1 or less, and more preferably 0.95 or less.

The urethane resin may be obtained by further reacting a chain extender with a polyol (a1) and a polyisocyanate (a2). Further, the molar ratio (isocyanate group / hydroxyl group) of the isocyanate group contained in the polyisocyanate (a2) and the hydroxyl group contained in the polyol (a1) is reacted at a ratio of 1.0 or more in excess of the isocyanate group. A chain extender may be reacted after obtaining an isocyanate-terminated prepolymer. The molar ratio (isocyanate group / hydroxyl group) of the isocyanate group contained in the polyisocyanate (a2) to the hydroxyl group contained in the polyol (a1) when preparing an isocyanate-terminated prepolymer is 1.0 or more. It is preferably 1.05 or more, more preferably 1.1 or more, preferably less than 3.0, more preferably 2.5 or less, still more preferably 2.0 or less.

As the chain extender, one type or two or more types can be used, and examples thereof include compounds having two or more active hydrogen atoms, polyamines, and the like. Examples of the compound having two or more active hydrogen atoms include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, and 3-methyl-. 1,5-Pentanediol, 1,6-hexanediol, 3,3'-dimethylol heptan, neopentyl glycol, 3,3-bis (hydroxymethyl) heptan, diethylene glycol, dipropylene glycol, polyoxypropylene glycol, Alipid chain extenders such as polyoxybutylene glycol, glycerin, trimethylolpropane; 1,2-cyclobutanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1, 4-Cyclohexanedimethanol, hydroxypropylcyclohexanol, tricyclo [5.2.1.0 ^2,6 ] decan-dimethanol, bicyclo [4.3.0] -nonanediol, dicyclohexanediol, bicyclo [4.3] .0] Nonandimethanol, Spiro [3.4] Octanediol, Butylcyclohexanediol, 1,1'-bicyclohexylidenediol, Cyclohexanetriol, Hydrogenated Bisphenol A, Fats such as 1,3-adamantandiol Examples include cyclic chain extenders, and aliphatic alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol; cyclohexane. An alicyclic glycol such as dimethanol is preferable. Examples of the polyamine include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, and 3,3'-. Didimethyl-4,4'-dicyclohexamethylenediamine, 1,4-cyclohexanediamine, N-hydroxymethylaminoethylamine, N-ethylaminoethylamine, N-methylaminopropylamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, hydrazine, N, N'-dimethylhydrazine, 1,6-hexamethylenebishydrazine, dihydrazide succinate, dihydrazide adipic acid, dihydrazide glutarate, dihydrazide sebacic acid, dihydrazide isophthalate, β-semicarbazide propionate hydrazide, 3-semicarbazide-propyl Examples thereof include polyamine extenders such as carbazic acid ester and semicarbazide-3-semicarbazidomethyl-3,5,5-trimethylcyclohexane.

When the chain extender is contained, the content thereof is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, based on the polyol (a1). It is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less.

The urethane resin (A) may be a reaction product of the polyol (a1), the polyisocyanate (a2), and a chain extender used if necessary, further reacted with a terminal terminator. By using a terminal terminator, the isocyanate group can be inactivated.

The terminal terminator is preferably an alcohol, for example, a monofunctional alcohol such as methanol, ethanol, propanol and butanol; a bifunctional alcohol such as 1,2-propylene glycol and 1,3-butylene glycol; a polyfunctional polyol; an alkanol. Examples thereof include alkanolamine compounds such as amines (eg, ethanolamine, etc.) and alkanolamines (eg, diethanolamine, etc.).

When the terminal terminator is used, the molar ratio of the group having an active hydrogen atom contained in the terminal terminator to the isocyanate group contained in the polyisocyanate (a2) is preferably 1.0 or more, more preferably 1. It is .2 or more, more preferably 1.5 or more, preferably 10.0 or less, more preferably 5.0 or less, still more preferably 3.0 or less.

The acid value of the urethane resin (A) is preferably 5 mgKOH / g or more, more preferably 7 mgKOH / g or more, preferably 50 mgKOH / g or less, more preferably 45 mgKOH / g or less, still more preferably 35 mgKOH / g or less. ..

The number average molecular weight of the urethane resin (A) is preferably 7,000 or more, more preferably 9,000 or more, still more preferably 10,000 or more, preferably 80,000 or less, more preferably 60, It is 000 or less, more preferably 40,000 or less.

The weight average molecular weight of the urethane resin (A) is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more, preferably 100,000 or less, and more preferably 70,000. Below, it is more preferably 50,000 or less.

The molecular weight dispersion of the urethane resin (A) is preferably 1.8 or more, more preferably 2 or more, still more preferably 2.3 or more, preferably 7 or less, and more preferably 5 or less.

In the present specification, the number average molecular weight and the weight average molecular weight can be measured as conversion values using polystyrene as a standard sample by using a gel permeation chromatography method.

The urethane resin (A) can be produced by reacting a polyol (a1) and a polyisocyanate (a2), and further reacting a chain extender and / or a terminal terminator, if necessary. The reaction may be carried out in the presence of an organic solvent, and a urethanization catalyst may be allowed to coexist during the reaction.

As the organic solvent, one kind or two or more kinds can be used, for example, an aromatic hydrocarbon solvent such as toluene; an ester solvent such as ethyl acetate and butyl acetate; acetone, methyl ethyl ketone, cyclohexanone, 3-pentanone and the like. Ketone solvent; ether solvent such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, ethyl carbitol; nitrile solvent such as acetonitrile, propionitrile, isobutyronitrile, valeronitrile; dimethyl Sulfoxide solvent such as sulfoxide; amide solvent such as methylformamide, dimethylacetamide, N-methyl-2-pyrrolidone and the like can be mentioned.

Examples of the urethanization catalyst include nitrogen-containing compounds such as triethylamine, triethylenediamine and N-methylmorpholine, metal salts such as potassium acetate, zinc stearate and tin octylate, dibutyltin laurate, dioctyltin dineodecanate and zirconium tetraacetyl. Organic metal compounds such as acetonate can be used.

The curing agent (B) contains a curing agent (b1) having a functional group capable of reacting with a carboxyl group. Examples of the functional group capable of reacting with the carboxyl group include an epoxy group, a carbodiimide-binding group (-N = C = N-), an aziridinyl group, an oxazolyl group and the like. Examples of the curing agent (b1) having a functional group capable of reacting with the carboxyl group include a compound having two or more functional groups capable of reacting with the carboxyl group. Examples of the curing agent (b1) having a functional group capable of reacting with the carboxyl group include an epoxy curing agent, a carbodiimide curing agent, an aziridine curing agent, an oxazoline curing agent, and the like, and these may be used in combination. Above all, it is preferable to contain at least one of an epoxy curing agent and a carbodiimide curing agent.

As the epoxy curing agent, one kind or two or more kinds can be used, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol. Diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, cyclohexanedimethanol diglycidyl ether, resorcinol diglycidyl ether, phenol (EO) 5 glycidyl ether, bis- (p-hydroxyphenyl) methane Diglycidyl ether, 2,2-bis- (p-hydroxyphenyl) propandiglycidyl ether, tris- (p-hydroxyphenyl) methanepolyglycidyl ether, 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane Diglycidyl ethers of aliphatic, alicyclic or aromatic polyol compounds such as polyglycidyl ethers and lauryl alcohol (EO) 15 glycidyl ethers; glycerin triglycidyl ethers, diglycerol polyglycidyl ethers, polyglycerol polyglycidyl ethers, trimethylolpropane Polyglycidyl ethers of aliphatic, alicyclic or aromatic polyol compounds such as triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether; N, N-diglycidyl Aniline, N, N-diglycidyl toluidine 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylene diamine, N, N, N' , N'-Tetraglycidyl-bis- (p-aminophenyl) methane and other amine compounds polyglycidyl ether; terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, naphthalenedicarboxylic acid diglycidyl ester, trimellitic acid polyglycidyl ester , Adiglycidyl ester of fatty acid or aromatic acid such as diglycidyl ester of adipic acid, diglycidyl ester of sebacic acid or polyglycidyl ester; triglycidyl aminophenol; triglycidyltris (2--hydroxyethyl) isocyanurate, triglycri Sigil isocyanurate; orthocresol type epoxy, phenol novolac type epoxy and the like can be mentioned.

When the epoxy curing agent is used, an epoxy curing catalyst may coexist. Examples of the epoxy curing catalyst include tertiary amine compounds such as imidazole and dimethylaminopyridine; phosphorus compounds such as triphenylphosphine; and boron trifluoride amine complexes such as boron trifluoride and boron trifluoride monoethylamine complexes; Organic acid compounds such as thiodipropionic acid; benzoxazine compounds such as thiodiphenol benzoxazine and sulfonyl benzoxazine; sulfonyl compounds and the like can be mentioned.

As the carbodiimide curing agent, one kind or two or more kinds can be used, and for example, N, N'-di-o-toluyl carbodiimide, N, N'-diphenylcarbodiimide, N, N'-di-2, 6-Dimethylphenylcarbodiimide, N, N'-bis (2,6-diisopropylphenyl) carbodiimide, N, N'-dioctyldecylcarbodiimide, N-triyl-N'-cyclohexylcarbodiimide, N, N'-di-2, 2-Di-tert. -Butylphenylcarbodiimide, N-triyl-N'-phenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di-p-aminophenylcarbodiimide, N, N'-di-p- Hydroxyphenylcarbodiimides, N, N'-di-cyclohexylcarbodiimides, N, N'-di-p-toluyl carbodiimides and the like can be mentioned.

As the aziridine curing agent, one kind or two or more kinds can be used, for example, 2,2'-bishydroxymethylbutanoltris [3- (1-aziridinyl) propionate], 4,4'-bis (ethylene). Iminocarbonylamino) Diphenylmethane and the like.

As the oxazoline curing agent, one kind or two or more kinds can be used, for example, 2'-methylenebis (2-oxazoline), 2,2'-ethylenebis (2-oxazoline), 2,2'-ethylene. Bis (4-methyl-2-oxazoline), 2,2'-propylene bis (2-oxazoline), 2,2'-tetramethylene bis (2-oxazoline), 2,2'-hexazoline bis (2-oxazoline) ), 2,2'-octamethylenebis (2-oxazoline), 2,2'-p-phenylenebis (2-oxazoline), 2,2'-p-phenylenebis (4,4'-dimethyl-2- Oxazoline), 2,2'-p-phenylenebis (4-methyl-2-oxazoline), 2,2'-p-phenylenebis (4-phenyl-2-oxazoline), 2,2'-m-phenylenebis (2-Oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2 '-M-Phenylenebis (4-phenylenebis-2-oxazoline), 2,2'-o-Phenylenebis (2-oxazoline), 2,2'-o-Phenylenebis (4-methyl-2-oxazoline) , 2,2'-bis (2-oxazoline), 2,2'-bis (4-methyl-2-oxazoline), 2,2'-bis (4-ethyl-2-oxazoline), 2,2'- Oxazoline compounds such as bis (4-phenyl-2-oxazoline); Oxazoline copolymerized with vinyl monomers such as 2-isopropenyl-2-oxazoline and 2-isopropenyl-4,4-dimethyl-2-oxazoline Examples thereof include a copolymer having a z-lone group.

The molar ratio of the carboxyl group in the urethane resin (A) to the group capable of reacting with the carboxyl group contained in the curing agent (B) (carboxyl group / functional group capable of reacting with the carboxyl group) is preferably 1 or more. , More preferably 1.2 or more, still more preferably 1.5 or more, preferably 5 or less, more preferably 4 or less, still more preferably 3 or less.

The content of the curing agent (b1) having a functional group capable of reacting with the carboxyl group in the curing agent (B) is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass. The above is preferably 100% by mass or less.

The curing agent (B) may further contain another curing agent (b2) in addition to the curing agent (b1) having a functional group capable of reacting with the carboxyl group. Examples of the other curing agent (b2) include isocyanate curing agents.

As the isocyanate curing agent, one kind or two or more kinds can be used, for example, tolylene diisocyanate, chlorophenylenedi isocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate. Such as polyisocyanates; these trimethylol propane adducts; these isocyanurates; these bullets and the like. Among these, it is preferable to use a trimethylolpropane adduct of polyisocyanate or an isocyanurate form of polyisocyanate.

When the other curing agent (b2) is contained, the content of the other curing agent (b2) is preferably 100 parts by mass with respect to 100 parts by mass of the curing agent (b1) having a functional group capable of reacting with the carboxyl group. It is 5 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 130 parts by mass or less.

The content of the curing agent (B) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the urethane resin (A). Hereinafter, it is more preferably 7 parts by mass or less.

The total content of the urethane resin (A) and the curing agent (B) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass, based on the solid content of the pressure-sensitive adhesive composition. % Or more, preferably 100% by mass or less.
In the present specification, the solid content of the pressure-sensitive adhesive composition means a portion of the pressure-sensitive adhesive composition excluding the solvent.

The pressure-sensitive adhesive composition may further contain a curing catalyst. Examples of the curing catalyst include the same compounds as those exemplified as the urethanization catalyst and the epoxy curing catalyst. When the curing catalyst is contained, the content thereof is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, and further preferably 0.01 with respect to 100 parts by mass of the urethane resin (A). It is more than parts by mass, preferably 1 part by mass or less, more preferably 0.1 part by mass or less, and further preferably 0.05 part by mass or less.

The pressure-sensitive adhesive composition may further contain a plasticizer. Examples of the plasticizer include aliphatic polycarboxylic acid esters such as adipic acid ester, citric acid ester, sebacic acid ester, azelaic acid ester, and maleic acid ester; terephthalic acid ester, isophthalic acid ester, phthalic acid ester, and trimellitic acid ester. , Aromatic polycarboxylic acid esters such as benzoic acid esters; ether-modified polyesters; epoxy-modified polyesters; polyesters formed from polycarboxylic acids and polyols.

When the plasticizer is contained, the content of the plasticizer is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, and preferably 50 parts by mass with respect to 100 parts by mass of the urethane resin (A). It is less than or equal to parts by mass, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less.

The pressure-sensitive adhesive composition may further contain a solvent. Examples of the solvent include compounds similar to the compounds exemplified as the organic solvent. When the organic solvent is contained, the content thereof in the pressure-sensitive adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less. Is. The pressure-sensitive adhesive composition of the present invention has a water content of preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and a lower limit of 0% by mass in the solvent. ..

The pressure-sensitive adhesive composition further includes, as other additives, a silane coupling agent, an antioxidant, a light stabilizer, a rust preventive, a thixo-imparting agent, a sensitizer, a polymerization inhibitor, a leveling agent, and a pressure-imparting agent. It may contain an agent, an antistatic agent, a flame retardant and the like. The content of the other additive is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and the lower limit is 0% by mass in the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, can be formed by applying the pressure-sensitive adhesive composition to a base material, removing a solvent if necessary, and further aging if necessary. .. The thickness of the adhesive layer is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, preferably 200 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less.

Examples of the method for forming a sheet from the pressure-sensitive adhesive composition include a method in which the pressure-sensitive adhesive product is applied onto a plastic base material and dried and cured.

Examples of the plastic base material include polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polyolefin resins such as polyethylene and polypropylene; polyacrylic resin; polyvinyl chloride resin; polypropylene ethylene vinyl alcohol; polyvinyl alcohol resin. A sheet or film obtained by using a polypropylene resin, a polyamide resin, a polyimide resin, or the like can be used. The surface of these plastic base materials may be subjected to a mold release treatment, an antistatic treatment, a corona treatment, or the like. The thickness of these plastic substrates is, for example, in the range of 10 to 200 μm.

Examples of the method of applying the pressure-sensitive adhesive composition to the plastic base material include a coating method using a roll coater, a gravure coater, a reverse coater, a spray coater, an air knife coater, a die coater and the like.

The pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, can suppress changes in the surface characteristics of the base material before and after its peeling, and can be used as a surface protective film, and in particular, a display device or the like. It is useful as a surface protective film for protecting the information display part of electronic devices.

Hereinafter, the present invention will be described in more detail with reference to examples.

(Manufacturing Example 1: Production of Urethane Resin (I))
Polytetramethylene ether glycol (number average molecular weight: 1,010.9, hydroxyl value: 111.0) 477 in a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blowing tube under a nitrogen stream. After adding .62 parts by mass and 0.28 parts by mass of neopentyl glycol and mixing uniformly, add 133.04 parts by mass of isophorone diisocyanate, then 0.1 parts by mass of tin octanoate, and add at 90 ° C. for about 3 hours. By reacting, a urethane prepolymer (a) having an isocyanate group at the molecular terminal was obtained.

Next, the urethane prepolymer (a) obtained by the above method was cooled to 60 ° C., 14.96 parts by mass of 2,2-bis (hydroxymethyl) propionic acid and 268.24 parts by mass of methyl ethyl ketone were added, and then octanoic acid. After adding 0.3 parts by mass of tin and reacting at 75 ° C. for about 5 hours, a methyl ethyl ketone solution (solid content 70% by mass) of the urethane prepolymer (b) having an isocyanate group at the molecular terminal was obtained.

Next, the methyl ethyl ketone solution of the urethane prepolymer (b) obtained by the above method was cooled to 50 ° C., and 2.39 parts by mass of diethanolamine as a terminal terminator was added to confirm that the isocyanate had disappeared, and methyl ethyl ketone 359 was confirmed. .99 parts by mass was added and cooled to room temperature to obtain a methyl ethyl ketone solution (solid content 50% by mass) of urethane resin (I). The acid value of this urethane resin (I) is 10 mgKOH / g, the molecular weight distribution by GPC is 10,389 for the number average molecular weight (Mn), 56,341 for the weight average molecular weight (Mw), and the molecular weight dispersion (Mw / Mn). Was 5.43.

(Manufacturing Example 2: Production of Urethane Resin (II))
Polytetramethylene ether glycol (number average molecular weight 1,010.9, hydroxyl value: 111.0) 405. In a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blowing tube, under a nitrogen stream. After adding 26 parts by mass and 2.02 parts by mass of neopentyl glycol and mixing uniformly, 170.79 parts by mass of isophorone diisocyanate was added, then 0.2 parts by mass of tin octanoate was added, and the reaction was carried out at 90 ° C. for about 3 hours. The urethane prepolymer (c) having an isocyanate group at the molecular terminal was obtained.
Next, the urethane prepolymer (c) obtained by the above method was cooled to 60 ° C., 44.65 parts by mass of 2,2-bis (hydroxymethyl) propionic acid and 266.88 parts by mass of methyl ethyl ketone were added, and then octanoic acid. After adding 0.3 parts by mass of tin and reacting at 75 ° C. for about 5 hours, a methyl ethyl ketone solution (solid content 70% by mass) of urethane prepolymer (d) having an isocyanate group at the molecular terminal was obtained.

Next, the methyl ethyl ketone solution of the urethane prepolymer (d) obtained by the above method was cooled to 50 ° C., and 3.07 parts by mass of diethanolamine as a terminal terminator was added to confirm that the isocyanate had disappeared, and the methyl ethyl ketone 352 was confirmed. .47 parts by mass was added and cooled to room temperature to obtain a methyl ethyl ketone solution (solid content 50% by mass) of urethane resin (II). The acid value of this urethane resin (I) is 30 mgKOH / g, the molecular weight distribution by GPC is 10,063 for the number average molecular weight (Mn), 56,728 for the weight average molecular weight (Mw), and the molecular weight dispersion (Mw / Mn). Was 5.64.

(Manufacturing Example 3: Production of Urethane Resin (III))
A polyester diol consisting of 3-methyl-1,5-pentanediol and adipic acid (number average molecular weight 977.44) in a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blowing tube under a nitrogen stream. , Hydroxyl value: 114.8) 322.83 parts by mass and 422.76 parts by mass of ethyl acetate were added and mixed uniformly, then 100.00 parts by mass of hexamethylene diisocyanate was added, and then 0.01 part by mass of dioctyltin dineodecanate was added. Was added and reacted at 75 ° C. for about 3 hours to obtain an ethyl acetate solution (solid content: 50% by mass) of the urethane prepolymer (e) having an isocyanate group at the molecular terminal.

Next, the ethyl acetate solution of the urethane prepolymer (e) obtained by the above method was cooled to 40 ° C., and polyoxyethylene polyoxypropylene triol (“Sannicks GL-3000” manufactured by Sanyo Kasei Co., Ltd.), molar ratio [EO / PO] = 25/75, number average molecular weight; 3,077.1, hydroxyl value: 54.7) 948.55 parts by mass, ethyl acetate 315.25 parts by mass were added, mixed uniformly, and then at 65 ° C. The reaction was carried out for about 6 hours, and when the NCO% became 0.01% or less, the temperature was cooled to 60 ° C., 3.43 parts by mass of methanol as a terminal terminator was added, and it was confirmed that the NCO disappeared, and acetic acid 231.66 parts by mass of ethyl was added and cooled to room temperature to obtain an ethyl acetate solution (solid content 50% by mass) of the urethane resin (III). The acid value of this urethane resin (III) is 0 mgKOH / g, the molecular weight distribution by GPC is 23,434 for the number average molecular weight (Mn), 129,370 for the weight average molecular weight (Mw), and the molecular weight dispersion (Mw / Mn). Was 5.52.

(Example 1)
Immediately before producing a sheet in 100 parts by mass of a methyl ethyl ketone solution (solid content 50% by mass) of the urethane resin (I) obtained in Production Example 1, a nurate product of hexamethylene diisocyanate as an isocyanate curing agent (manufactured by Asahi Kasei Co., Ltd. "Duranate TKA-100", hereinafter abbreviated as "TKA-100") is 1.72 parts by mass, 1% by mass methyl ethyl ketone solution of dioctyltin dineodecaneate as an isocyanate curing catalyst is 2.00 parts by mass, and acetylacetone is 0.50 parts by mass. , 1.52 parts by mass of aliphatic polyglycidyl ether (“CR-5L” manufactured by DIC Co., Ltd., hereinafter abbreviated as “CR-5L”) as an epoxy curing agent, and 0.05 of triphenylphosphine as an epoxy curing catalyst. 29.82 parts by mass of methyl ethyl ketone was blended to obtain the pressure-sensitive adhesive composition (1) (solid content 40% by mass).

(Example 2)
1.72 parts by mass of "Duranate TKA-100" as an isocyanate curing agent was added to 100 parts by mass of the methyl ethyl ketone solution (solid content 50% by mass) of the urethane resin (II) obtained in Production Example 2 immediately before the sheet was produced. , 2.00 parts by mass of 1% by mass methyl ethyl ketone solution of dioctyltin dineodecanate as an isocyanate curing catalyst, 0.50 parts by mass of acetylacetone, 4.57 parts by mass of "CR-5L" as an epoxy curing agent, and triphenyl as an epoxy curing catalyst. 0.14 parts by mass of phosphine, 2.87 parts by mass of N-methyldiethanolamine, and 34.51 parts by mass of methyl ethyl ketone were blended to obtain a pressure-sensitive adhesive composition (2) (solid content 40% by mass).

(Example 3)
Immediately before producing a sheet in 100 parts by mass of the methyl ethyl ketone solution (solid content 50% by mass) of the urethane resin (II) obtained in Production Example 2, a carbodiimide methyl ethyl ketone solution (carbodilite manufactured by Nisshinbo Chemical Co., Ltd.) was used as a carbodiimide curing agent. "V-09B", solid content 70.26% by mass, hereinafter abbreviated as "V-09B") is blended with 15.91 parts by mass and 37.03 parts by mass of methyl ethyl ketone to form a pressure-sensitive adhesive composition (3) (solid). 40% by mass) was obtained.

(Comparative Example 1)
Immediately before producing the sheet, 5.00 mass of "Duranate TKA-100" was added as an isocyanate curing agent to 100 parts by mass of the ethyl acetate solution (solid content 50% by mass) of the urethane resin (III) obtained in Production Example 3. A 1% by mass ethyl acetate solution of dioctyltin dineodecanate as an isocyanate curing catalyst was mixed with 2.00 parts by mass, 0.50 parts by mass of acetylacetone, and 32.50 parts by mass of ethyl acetate, and the pressure-sensitive adhesive composition (X1) (solid) was added. 40% by mass) was obtained.

[Adhesive sheet processing method]
The obtained pressure-sensitive adhesive composition was applied to the surface of a polyethylene terephthalate film having a thickness of 50 μm so that the film thickness after drying was 65 μm, and dried at 60 ° C. for 3 minutes and further at 120 ° C. for 3 minutes. .. A 38 μm-thick polyethylene terephthalate film whose surface was mold-released was attached thereto and cured at 40 ° C. for 3 days to obtain an adhesive sheet.

[Evaluation method of white fog]
The surface protective film obtained in Examples and Comparative Examples was cut into 50 mm × 70 mm and used as a test piece. A single-sided tape having a thickness of 150 μm was cut into a size of 40 mm × 60 mm, and the inside was further hollowed out by 20 mm × 40 mm to prepare a frame having a thickness of 150 μm and a width of 10 mm. The created frame was attached to a glass plate, and a test piece was attached onto it. At this time, since the thickness of the frame is thicker than the film thickness of the adhesive, air bubbles are contained on both sides of the frame. After sticking, it was allowed to stand in an environment of a temperature of 85 ° C. and a humidity of 85% for 3 days, then taken out in an environment of 23 ° C. and left for 1 hour. The surface protective film was peeled off from the glass plate, and the white mist in the place where the air bubbles were present was evaluated.

Shirakiri was evaluated as follows.
○ ； No white fog △ ； Thin but with white fog × ； With white fog

Examples 1 to 3 are examples of the present invention, and the transparency could be maintained even after being placed under high temperature and high humidity. Comparative Example 1 did not contain a curing agent having a functional group capable of reacting with a carboxyl group, and its transparency decreased (white mist was generated) after being placed under high temperature and high humidity.

Claims (5)

It contains a urethane resin (A) and a curing agent (B), the urethane resin (A) is a reaction product of a polyol (a1) and a polyisocyanate (a2), and the polyol (a1) is a polymer polyol (a1). -1) and a polyol (a1-2) having a carboxyl group, and the curing agent (B) contains 10% or more of the curing agent (b1) having a functional group capable of reacting with the carboxyl group, and isocyanate. It contains a cross-linking agent (b2) , is (b2) 5 parts by mass or more and 130 parts by mass or less with respect to 100 parts by mass of (b1) , and contains a carboxyl group in the urethane resin (A) and a curing agent. the molar ratio of groups capable of reacting with a carboxyl group contained in the (B) (functional group capable of reacting with a carboxyl group / carboxyl group) is pressure-sensitive adhesive composition characterized by Ru 1-5 der. The acid value of the urethane resin (A) is 5 mgKOH / g or more and 50 mg.
The pressure-sensitive adhesive composition according to claim 1, which is KOH / g or less. The pressure-sensitive adhesive composition according to claim 1 or 2 , wherein the content of the curing agent (B) is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the urethane resin (A). A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 3. A surface protective film containing the adhesive sheet according to claim 4.