JP6983959B2 - Surface protective film - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition and a surface protective film. More specifically, the surface of a polarizing plate having antistatic performance, an excellent balance of adhesive strength at a low peeling speed and a high peeling speed, a long pot life, and excellent durability and reworkability. The present invention relates to providing a pressure-sensitive adhesive composition for a protective film, and a surface protective film.

Since the pressure-sensitive adhesive for optical use has excellent transparency, it is a copolymer obtained by copolymerizing an alkyl (meth) acrylate as a main component with an acrylic monomer having a hydroxyl group, a carboxyl group, etc. as a functional group. An acrylic pressure-sensitive adhesive comprising the above is preferably used. Further, it is required that various physical properties such as the adhesive strength of the adhesive are appropriately adjusted. In particular, adhesives for surface protective films have a low peeling speed and a high peeling speed, which are suitable for bonding surface protective films with an automatic bonding device so that they can be adapted to factory-produced manufacturing processes. There is a demand for an adhesive having an excellent balance of adhesive strength. Further, in addition to the balance of adhesive strength, there is a need for an adhesive having a long pot life and excellent durability, reworkability, and antistatic property.

For such various physical properties of the pressure-sensitive adhesive, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, etc. that react with functional groups such as hydroxyl groups and carboxyl groups contained in the acrylic pressure-sensitive adhesive made of a copolymer are used. The cross-linking reaction is carried out to adjust the adhesive force and the cohesive force.

Conventionally, an isocyanate-based cross-linking agent has been generally used as a cross-linking agent for an acrylic pressure-sensitive adhesive. Further, in the cross-linking reaction using an isocyanate-based cross-linking agent, a metal chelate is often used as a catalyst for promoting the cross-linking reaction.
In general, dibutyltin dilaurate, which is an organotin compound, has been used as a catalyst for the cross-linking reaction because the reaction rate of the cross-linking reaction is excellent. However, since the dibutyl-tin compound exhibits harmful toxicity. It is avoided to use.
Therefore, there is a demand for a cross-linking catalyst that is inexpensive and has an excellent reaction rate for the cross-linking reaction as an alternative to the dibutyltin compound used in combination with the isocyanate-based cross-linking agent, but it is difficult to find. rice field.

Under these circumstances, Patent Document 1 discloses that iron chelate is preferable as a cross-linking catalyst used in combination with an isocyanate-based cross-linking agent, and tris (acetylacetonate) iron is particularly preferable because it has excellent catalytic activity. There is.

By the way, the cross-linking reaction of the acrylic pressure-sensitive adhesive composition containing the cross-linking catalyst gradually proceeds even while it is left at room temperature. Therefore, in the industrial production of pressure-sensitive adhesives, a cross-linking catalyst and a reaction retarder are generally used in order to stop the cross-linking reaction until the time when the cross-linking reaction is started after the raw material of the pressure-sensitive adhesive composition is blended. It is used together.
Regarding the combined use of this cross-linking catalyst and the reaction retarder, Patent Document 2 describes a method for producing polyurethane, which comprises a mixture of at least one kind of metal acetylacetonate and acetylacetone, and the metal acetylacetonate and the acetylacetone. It is disclosed to use a reactive urethane mixture containing a catalytic system having a weight ratio of 2: 1.

Japanese Unexamined Patent Publication No. 2011-001440 Japanese Unexamined Patent Publication No. 2008-285681

In the pressure-sensitive adhesive composition described in Patent Document 1, the amount of the metal compound (crosslinking catalyst) added to the copolymer containing (meth) acrylate as a constituent monomer unit and containing a hydroxyl group and a carboxyl group is shown. However, there is no description about the amount of the cross-linking retarder added. Further, Patent Document 1 describes a method of using a reaction retarder, a method of adding a viscosity increase suppressing solvent, a functionality of blocked isocyanate and the like as a method of suppressing the viscosity increase rate after adding a cross-linking agent to the pressure-sensitive adhesive composition. A method of using a cross-linking agent that blocks a group is mentioned, but there is no specific explanation.

Further, in Patent Document 2, a metal having excellent stability and good catalytic activity, which does not cause premature curing even when a metal acetylacetonate catalyst such as iron or copper having very high activity at a low temperature is used. A method for producing a polyurethane using a catalytic system containing acetylacetonate and acetylacetone is disclosed.
However, in the method described in Patent Document 2, the weight ratio of metal acetylacetonate to acetylacetone is 2: 1. However, even if this compounding ratio is applied to the manufacturing process of an acrylic pressure-sensitive adhesive, the crosslinking reaction is temporary. Could not make a stop.

The present invention has been made in view of the above circumstances, has antistatic performance without using an organic tin compound, and has an excellent balance of adhesive strength at a low peeling speed and a high peeling speed. Further, it is an object of the present invention to provide an adhesive composition for a surface protective film of a polarizing plate having a long pot life and excellent durability and reworkability, and a surface protective film.

In order to solve the above problems, the present invention contains (A) at least one kind of (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms and (B) a hydroxyl group as a copolymerizable monomer group. 0.1 to 10 parts by weight of (C) bifunctional or higher functional isocyanate compound and 0.001 to 0 parts by weight of (D) metal chelate compound with respect to 100 parts by weight of the copolymer with the copolymerizable monomer. It consists of .5 parts by weight, (E) 0.1 to 200 parts by weight of the ketoenol copolymer compound, and (F) 0.05 to 5 parts by weight of the ionic compound having a melting point of 25 to 50 ° C. as an antistatic agent. , (E) / (D) are provided with a pressure-sensitive adhesive composition having a weight-by-weight ratio of 70 to 700.

Further, the copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxyethyl (meth). ) At least one selected from the compound group consisting of acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide is preferable.

Further, as the (C) bifunctional or higher functional isocyanate compound, the bifunctional isocyanate compound is preferably an acyclic aliphatic isocyanate compound, which is a compound produced by reacting a diisocyanate compound with a diol compound. The diisocyanate compound is an aliphatic diisocyanate, and preferably consists of one selected from the compound group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of the diol compound include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and 2-ethyl. A group of compounds consisting of -2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol. It is preferably composed of one selected from the above.
Further, as the above-mentioned (C) bifunctional or higher functional isocyanate compound, the trifunctional isocyanate compound includes an isocyanurate form of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct form of a hexamethylene diisocyanate compound, and an isophorone diisocyanate compound. Adduct, hexamethylene diisocyanate compound bullet, isophorone diisocyanate compound bullet, tolylene diisocyanate compound isocyanurate, xylylene diisocyanate compound isocyanurate, hydrogenated xylylene diisocyanate compound isocyanurate, tolylene diisocyanate It is preferably at least one selected from the compound group consisting of the adduct body of the compound, the adduct body of the xylylene diisocyanate compound, and the adduct body of the hydrogenated xylylene diisocyanate compound.

Further, it is preferable that the cross-linking catalyst in the pressure-sensitive adhesive composition is at least one selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound.

Further, the (F) antistatic agent is an ionic compound having a melting point of 25 to 50 ° C., which is contained in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer. / Or, it is preferably an acryloyl group-containing ionic compound copolymerized in the copolymer by 0.1 to 5.0% by weight.

The copolymer contains at least one or more of a carboxyl group-containing monomer, a hydroxyl group-free nitrogen-containing vinyl monomer, and a polyalkylene glycol mono (meth) acrylic acid ester monomer as other copolymerizable monomer groups, and / Alternatively, it is preferable to include a polyether siloxane compound or other conventional antioxidant as an additive.

Further, the pressure-sensitive adhesive force of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition at a low-speed peeling speed of 0.3 m / min is 0.05 to 0.1 N / 25 mm, and the high-speed peeling speed is 30 m / min. The adhesive strength is preferably 1.0 N / 25 mm or less.

Further, it is preferable that the surface resistivity of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 9.0 × 10 ^{+ 11} Ω / □ or less, and the peeling band voltage is ± 0 to 0.5 kV.

The present invention also provides a pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition is formed on one side or both sides of the resin film.

Further, the present invention is a surface protective film in which a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition is formed on one side of a resin film, and is placed on the surface protection film via the pressure-sensitive adhesive layer. Provided is a surface protective film characterized by no contamination transfer to the adherend after tracing with a ballpoint pen.

Further, the surface protective film of the present invention can be used as a surface protective film for a polarizing plate.

Further, it is preferable that the surface protective film of the present invention is antistatic and antifouling treated on the surface of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed.

According to the present invention, all the performances required for the pressure-sensitive adhesive layer of the surface protective film, which could not be solved by the prior art, can be satisfied without using the organic tin compound, and moreover, they can be satisfied. Excellent antistatic performance was obtained, and it became possible to prevent the generation of adhesive residue. Specifically, while maintaining excellent antistatic performance, the amount of antistatic agent added can be reduced, and the performance of preventing the generation of adhesive residue can be further improved.

Hereinafter, the present invention will be described based on a preferred embodiment.
The pressure-sensitive adhesive composition of the present invention comprises (A) at least one of (meth) acrylic acid ester monomers having an alkyl group having C4 to C18 carbon atoms and (B) a hydroxyl group as a copolymerizable monomer group. 0.1 to 10 parts by weight of (C) a bifunctional or higher functional isocyanate compound and 0.001 to 0.5 parts by weight of a cross-linking catalyst of (D) a metal chelate compound with respect to 100 parts by weight of a copolymer with a possible monomer. (E) 0.1 to 200 parts by weight of the ketoenol copolymer compound, and (F) 0.05 to 5 parts by weight of the ionic compound having a melting point of 25 to 50 ° C. as an antistatic agent, (E). ) / (D) is characterized in that the weight portion ratio is 70 to 700.

The copolymer may contain at least one or more of a carboxyl group-containing monomer, a hydroxyl group-free nitrogen-containing vinyl monomer, and a polyalkylene glycol mono (meth) acrylic acid ester monomer as other copolymerizable monomer groups.
The (F) antistatic agent is an ionic compound having a melting point of 25 to 50 ° C., which is contained in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer, and / or. , 0.1 to 5.0% by weight copolymerized in the copolymer can be an acryloyl group-containing ionic compound.
In addition, the pressure-sensitive adhesive composition of the present invention may contain a polyether siloxane compound or other conventional antioxidants as additives.

(A) Examples of the (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms include butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and heptyl (meth). ) Acrylate, Octyl (meth) acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Nonyl (meth) acrylate, Isononyl (meth) acrylate, Decyl (meth) acrylate, Isodecyl (meth) acrylate, Undecyl (meth) ) Acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate. , Isomyristyl (meth) acrylate, cetyl (meth) acrylate, isosetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, and the like.
It is preferable that the (A) alkyl group contains a (meth) acrylic acid ester monomer having C4 to C18 in a ratio of 50 to 98 parts by weight with respect to 100 parts by weight of the copolymer.

As the (B) hydroxyl group-containing copolymerizable monomer, (B) the hydroxyl group-containing copolymerizable monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-. Hydroxyalkyl (meth) acrylates such as hydroxybutyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth). Examples thereof include hydroxyl group-containing (meth) acrylamides such as acrylamide.
8-Hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) ) At least one selected from the compound group consisting of acrylamide and N-hydroxyethyl (meth) acrylamide is preferable.
It is preferable that the copolymerizable monomer containing the hydroxyl group (B) is contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the copolymer.

The copolymer may contain at least one or more of a carboxyl group-containing monomer, a hydroxyl group-free nitrogen-containing vinyl monomer, and a polyalkylene glycol mono (meth) acrylic acid ester monomer as other copolymerizable monomer groups.

The carboxyl group-containing monomer is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl. Hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, It is preferably at least one selected from the compound group consisting of 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.
When the copolymer contains a carboxyl group-containing monomer as another copolymerizable monomer group, 0.1 to 1.0 part by weight of the carboxyl group-containing monomer is added to 100 parts by weight of the copolymer. It is preferably contained in a proportion. The copolymer does not have to contain the carboxyl group-containing monomer.

The polyalkylene glycol mono (meth) acrylic acid ester monomer may be a compound in which one hydroxyl group is esterified as a (meth) acrylic acid ester among a plurality of hydroxyl groups of the polyalkylene glycol. Since the (meth) acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the copolymer of the main agent. The other hydroxyl group may be OH as it is, or may be an alkyl ether such as methyl ether or ethyl ether, a saturated carboxylic acid ester such as an acetate ester, or the like.
Examples of the alkylene group contained in the polyalkylene glycol include, but are not limited to, an ethylene group, a propylene group, and a butylene group. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of the polyalkylene glycol copolymer include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol, and the like. It may be a block copolymer or a random copolymer.
It is preferable that the polyalkylene glycol mono (meth) acrylic acid ester monomer has an average number of repetitions of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The "average number of repetitions of alkylene oxide" is the average number of repetitions of the alkylene oxide unit in the portion of the "polyalkylene glycol chain" contained in the molecular structure of the polyalkylene glycol mono (meth) acrylic acid ester monomer.

The polyalkylene glycol mono (meth) acrylic acid ester monomer is at least one selected from polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. The above is preferable.
More specifically, polyethylene glycol-mono (meth) acrylate, polypropylene glycol-mono (meth) acrylate, polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polypropylene glycol-mono (meth) acrylate, polyethylene glycol-poly. Butylene glycol-mono (meth) acrylate, polypropylene glycol-polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polyethylene glycol-polybutylene glycol-mono (meth) acrylate; methoxypolyethylene glycol- (meth) acrylate, methoxypolyethylene glycol -(Meta) acrylate, methoxypolyethylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene Glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate; ethoxypolyethylene glycol- (meth) acrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolybutylene glycol- (meth) Acrylate, ethoxy-polyethylene glycol-polyethylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol -Polybutylene glycol- (meth) acrylate and the like.
It is preferable that the polyalkylene glycol mono (meth) acrylic acid ester monomer is contained in a ratio of 0 to 50 parts by weight with respect to 100 parts by weight of the copolymer. The copolymer may not contain the polyalkylene glycol mono (meth) acrylic acid ester monomer.

Examples of the nitrogen-containing vinyl monomer containing no hydroxyl group include a vinyl monomer containing an amide bond, a vinyl monomer containing an amino group, and a vinyl monomer having a nitrogen-containing heterocyclic structure. More specifically, N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl. Cyclic nitrogen vinyl compounds having an N-vinyl-substituted heterocyclic structure, such as pyrrol, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolacttam, N-vinyllauryllolactum; N-( Meta) acryloyl morpholine, N- (meth) acryloyl piperazine, N- (meth) acryloyl azilydin, N- (meth) acryloyl azetidin, N- (meth) acryloyl pyrrylidine, N- (meth) acryloyl piperidin, N- (meta). ) Cyclic nitrogen vinyl compounds having a heterocyclic structure of N- (meth) acryloyl substitution such as acryloyl azepan, N- (meth) acryloyl azocan; nitrogen atoms such as N-cyclohexylmaleimide, N-phenylmaleimide and Cyclic nitrogen vinyl compound having a heterocyclic structure having an ethylene-based unsaturated bond in the ring; (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-butyl (meth) Unsubstituted or monoalkyl-substituted (meth) acrylamide such as acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropylacrylamide, N, N-diisopropyl (meth). ) Acrylamide, N, N-dibutyl (meth) acrylamide, N-ethyl-N-methyl (meth) acrylamide, N-methyl-N-propyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide, etc. Dialkyl-substituted (meth) acrylamide; N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminoisopropyl (Meta) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminomethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N-ethyl-N-methylaminoethyl (meth) ) Acrylic, N-methyl-N-propylaminoethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (me D) Dialkylamino (meth) acrylates such as acrylate, N, N-dibutylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate; N, N-dimethylaminopropyl (meth) acrylamide, N, N- Diethylaminopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-diisopropylaminopropyl (meth) acrylamide, N-ethyl-N-methylaminopropyl (meth) acrylamide, N-methyl- N, N-dialkyl-substituted aminopropyl (meth) acrylamides such as N-propylaminopropyl (meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide; N-vinylformamide, N-vinylacetamide, N- N-vinylcarboxylic acid amides such as vinyl-N-methylacetamide; N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, N, N -(Meta) acrylamides such as methylenebis (meth) acrylamide; unsaturated carboxylic acid nitriles such as (meth) acrylonitrile; and the like.

It is preferable that the nitrogen-containing vinyl monomer containing no hydroxyl group is contained in a ratio of 0 to 20 parts by weight with respect to 100 parts by weight of the copolymer. The copolymer does not have to contain the nitrogen-containing vinyl monomer containing no hydroxyl group.

(C) The bifunctional or higher functional isocyanate compound may be at least one or more selected from polyisocyanate compounds having at least two or more isocyanate (NCO) groups in one molecule. The polyisocyanate compound is classified into an aliphatic isocyanate, an aromatic isocyanate, an acyclic isocyanate, an alicyclic isocyanate and the like, but any of them may be used. Specific examples of the polyisocyanate compound include aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI), diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI). , Aromatic isocyanate compounds such as hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylenedi isocyanate (TOID), and tolylene diisocyanate (TDI).
Examples of the trifunctional or higher functional isocyanate compound include a burette-modified form of a bifunctional isocyanate compound (a compound having two NCO groups in one molecule), an isocyanurate-modified form, and trivalent or higher valents such as trimethylolpropane (TMP) and glycerin. Examples thereof include an adduct (modified polyol) with a polyol (a compound having at least 3 or more OH groups in one molecule).
As the (C) bifunctional or higher functional isocyanate compound, it is also possible to use only the (C-1) trifunctional isocyanate compound or only the (C-2) bifunctional isocyanate compound. It is also possible to use the (C-1) trifunctional isocyanate compound and the (C-2) bifunctional isocyanate compound in combination.

Further, as the (C-1) trifunctional isocyanate compound used in the present invention, an isocyanurate form of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct body of a hexamethylene diisocyanate compound, an adduct body of an isophorone diisocyanate compound, and the like. At least one selected from the (C-1-1) first aliphatic isocyanate compound group consisting of a burette of a hexamethylene diisocyanate compound and a burette of an isophorone diisocyanate compound, and a tolylene diisocyanate compound. Isocyanurate form, isocyanurate form of xylylene diisocyanate compound, isocyanurate form of hydrogenated xylylene diisocyanate compound, adduct form of tolylene diisocyanate compound, adduct form of xylylene diisocyanate compound, adduct form of hydrogenated xylylene diisocyanate compound. (C-1-2) It is preferable to contain at least one selected from the group of second aromatic isocyanate compounds. It is preferable to use (C-1-1) the first aliphatic isocyanate compound group and (C-1-2) the second aromatic isocyanate compound group in combination. In the present invention, as the (C-1) trifunctional isocyanate compound, at least one selected from the (C-1-1) first aliphatic isocyanate compound group and (C-1-2). ) By using at least one selected from the second aromatic isocyanate compound group in combination, the balance of adhesive force between the low-speed peeling region and the high-speed peeling region can be further improved.
Further, the (C-1) trifunctional isocyanate compound is at least one selected from the above-mentioned (C-1-1) first aliphatic isocyanate compound group, and the above-mentioned (C-1-2). ) Contains at least one selected from the second aromatic isocyanate compound group, and contains 0.5 to 5.0 parts by weight in total with respect to 100 parts by weight of the copolymer. Is preferable. Further, at least one selected from the (C-1-1) first aliphatic isocyanate compound group and (C-1-2) the second aromatic isocyanate compound group. The mixing ratio with at least one selected from the above is in the range of 10%: 90% to 90%: 10% by weight of (C-1-1) :( C-1-2). Is preferable.

Further, the (C-2) bifunctional isocyanate compound used in the present invention is preferably an acyclic aliphatic isocyanate compound, which is a compound produced by reacting a diisocyanate compound with a diol compound.
For example, a diisocyanate compound has a general formula "O = C = N-X-N = C = O" (where X is a divalent group), and a general formula "HO-Y-OH" (where Y is a divalent group). ), Examples of the compound produced by reacting the diisocyanate compound with the diol compound include the compound represented by the following general formula Z.

[General formula Z]
O = C = N-X- (NH-CO-O-YO-CO-NH-X) _n- N = C = O

Here, n is an integer of 0 or more. When n is 0, the general formula Z represents "O = C = N-X-N = C = O". As the bifunctional acyclic aliphatic isocyanate compound, a compound having n of 0 in the general formula Z (a diisocyanate compound unreacted with a diol compound) may be contained, but a compound in which n is an integer of 1 or more is an essential component. It is preferable to include as. The bifunctional acyclic aliphatic isocyanate compound may be a mixture composed of a plurality of compounds having different n in the general formula Z.

The diisocyanate compound represented by the general formula “O = C = N—X—N = C = O” is an aliphatic diisocyanate. X is preferably an acyclic and aliphatic divalent group. The aliphatic diisocyanate is preferably one or more selected from the compound group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

The diol compound represented by the general formula "HO-Y-OH" is an aliphatic diol. Y is preferably an acyclic and aliphatic divalent group. Examples of the diol compound include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and 2-ethyl-2. -From the compound group consisting of butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol. It is preferably composed of one or more selected species.

The weight ratio (C-1 / C-2) of the (C-1) trifunctional isocyanate compound to the (C-2) bifunctional isocyanate compound is preferably 1 to 90. The amount of the (C) bifunctional or higher isocyanate compound is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the copolymer.

(D) The cross-linking catalyst of the metal chelate compound may be any substance that functions as a catalyst for the reaction (cross-linking reaction) between the copolymer and the cross-linking agent when the polyisocyanate compound is used as the cross-linking agent. Examples thereof include amine compounds such as tertiary amines, metal chelate compounds, organic tin compounds, organic lead compounds, and organic metal compounds such as organic zinc compounds. In the present invention, a metal chelate compound is used as the cross-linking catalyst.

The metal chelate compound is a compound in which one or more polydentate ligands L are bonded to the central metal atom M. The metal chelate compound may or may not have one or more monodentate ligands X attached to the metal atom M. For example, when the general formula of a metal chelate compound having one metal atom M is _{expressed by M (L) m} (X) _n , m ≧ 1 and n ≧ 0. When m is 2 or more, m L may be the same ligand or may be different ligands. When n is 2 or more, n Xs may be the same ligand or different ligands.

Examples of the metal atom M include Fe, Ni, Mn, Cr, V, Ti, Ru, Zn, Al, Zr, Sn and the like.
Examples of the polydentate ligand L include β-ketoesters such as methyl acetoacetic acid, ethyl acetoacetate, octyl acetoacetic acid, oleyl acetoacetic acid, lauryl acetoacetic acid, and stearyl acetoacetic acid, and acetylacetone (also known as 2,4-pentandione). Examples thereof include β-diketones such as 2,4-hexanedione and benzoylacetone. These are keto-enol tautomeric compounds and may be enol-deprotonated enolates (eg, acetylacetonate) in the polydentate ligand L.
Examples of the monodentate ligand X include halogen atoms such as chlorine atom and bromine atom, pentanoyl group, hexanoyl group, 2-ethylhexanoyl group, octanoyl group, nonanoyl group, decanoyl group, dodecanoyl group and octadecanoyl group. Examples thereof include an alkoxy group such as a group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group and a butoxy group.

Specific examples of the metal chelate compound include tris (2,4-pentandionato) iron (III), iron trisacetylacetonate, titaniumtrisacetylacetonate, rutheniumtrisacetylacetonate, zinc bisacetylacetonate, and aluminum tris. Acetylacetonate, zirconite tetrakis acetylacetonate, tris (2,4-hexanedionat) iron (III), bis (2,4-hexanezonato) zinc, tris (2,4-hexanezonato) titanium, tris Examples thereof include (2,4-hexanezonato) aluminum and tetrakis (2,4-hexanezonato) zirconium.

Examples of the organic tin compound include dialkyl tin oxide, a fatty acid salt of dialkyl tin, and a fatty acid salt of first tin. Conventionally, dibutyltin compounds have been widely used, but in recent years, the problem of toxicity of organotin compounds has been pointed out, and in particular, tributyltin (TBT) contained in dibutyltin compounds is also a concern as an endocrine disturbing substance. From the viewpoint of safety, a long-chain alkyl tin compound such as a dioctyl tin compound is preferable. Specific examples of the organic tin compound include dioctyl tin oxide and dioctyl tin dilaurate. Sn compounds can be used provisionally, but in the future, in view of the trend that the use of safer substances is required, Al, Ti, Fe, etc., which are safer than Sn, etc. It is preferable to use a metal chelate compound.
The metal chelate compound in the pressure-sensitive adhesive composition according to the present invention preferably contains at least one selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound.
The cross-linking catalyst of the (D) metal chelate compound is preferably contained in an amount of 0.001 to 0.5 parts by weight based on 100 parts by weight of the copolymer.

(E) Ketoenol tetonic compounds include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetic acid, lauryl acetoacetic acid, and stearyl acetoacetic acid, and acetylacetone and 2,4-hexanedione. , Β-diketone such as benzoylacetone. In a pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, these prevent excessive increase in viscosity and gelation of the pressure-sensitive adhesive composition after blending the cross-linking agent by blocking the isocyanate group contained in the cross-linking agent. , The pot life of the adhesive composition can be extended.
The keto-enol tautomer compound is preferably contained in an amount of 0.1 to 200 parts by weight based on 100 parts by weight of the copolymer.

Since the (E) keto-enol tautomer compound has an effect of suppressing cross-linking as opposed to the cross-linking catalyst of the (D) metal chelate compound, the (E) keto-enol tautomer with respect to the cross-linking catalyst of the (D) metal chelate compound. It is preferable to appropriately set the ratio of the mutant compound. In order to prolong the pot life of the pressure-sensitive adhesive composition and improve the storage stability, the weight ratio (E) / (D) of the cross-linking catalyst of (E) keto-enol tautomer compound / (D) metal chelate compound is required. Is preferable. The value of (E) / (D) is preferably in the range of 70 to 700, more preferably 70 to 300, and most preferably 80 to 300.

Examples of the (F) antistatic agent include an antistatic agent contained in the pressure-sensitive adhesive composition and an antistatic agent copolymerized in the copolymer. The (F) antistatic agent is preferably contained in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer.
The (F) antistatic agent is preferably (F-1) an ionic compound having a melting point of 25 to 50 ° C. and / or (F-2) an acryloyl group-containing ionic compound.
In the present invention, as (F) an antistatic agent, (F-1) an ionic compound having a melting point of 25 to 50 ° C. is added to the copolymer, and / or (F-2) an acryloyl group-containing ionic compound is added. Is copolymerized in the copolymer. Since these (F) antistatic agents have a low melting point and have a long-chain alkyl group, it is presumed that they have a high affinity with the acrylic copolymer.

(F-1) The ionic compound having a melting point of 25 to 50 ° C. is an ionic compound having a cation and an anion, and the cation is a pyridinium cation, an imidazolium cation, a pyrimidinium cation, or a pyrazonium cation. , pyrrolidinium cation, and nitrogen-containing onium cations such as ammonium cation, phosphonium cation, sulfonium cation or the like, anions, hexafluorophosphate (PF 6 ^_-), thiocyanate (SCN ^-), an alkylbenzenesulfonic salt ^{_{(RC 6 H 4 SO 3 -}} ), perchlorate (ClO ₄ ^-), tetrafluoroborate (BF ₄ ^-), bis (fluorosulfonyl) imide salt (FSI), bis (trifluoromethanesulfonyl ) Inorganic or organic anion compounds such as imide salt (TFSI), trifluoromethanesulfonate (TF) and the like. It is preferably solid at room temperature (for example, 25 ° C.), and a melting point of 25 to 50 ° C. can be obtained by selecting the chain length of the alkyl group, the position of the substituent, the number of substituents, and the like. The cation is preferably a quaternary nitrogen-containing onium cation, and is a quaternary pyridinium cation such as 1-alkylpyridinium (the carbon atom at the 2nd to 6th positions may have a substituent or may be unsubstituted), or 1, Examples thereof include a quaternary imidazolium cation such as 3-dialkyl imidazolium (the carbon atom at the 2, 4 and 5 positions may have a substituent or not substituted), a quaternary ammonium cation such as tetraalkylammonium and the like. ..
(F-1) The ionic compound having a melting point of 25 to 50 ° C. is preferably contained in an amount of 0.05 to 5 parts by weight with respect to 100 parts by weight of the copolymer.

The (F-2) acryloyl group-containing ionic compound, an ionic compound having a cation and an anion, cation, (meth) acryloyloxy alkyl trialkylammonium ^{_{[R 3 N + -C n H 2n}} -OCOCQ = CH ₂ , where Q = H or CH ₃ , R = alkyl] and other (meth) acryloyl group-containing cations, where the anions are hexafluorinated phosphate (PF ₆ ⁻ ), thiocyanate (SCN ^−). ), organic sulfonate (RSO ₃ ^-), perchlorate (ClO ₄ ^-), tetrafluoroborate _(BF ⁴ -), F-containing imide salt _{^(R F} 2 N ^-) inorganic or organic, such as Examples include compounds that are anions. F-containing imide salt (R F ² _N ^-) as the R ^F of, trifluoromethanesulfonyl group, and perfluoro alkane sulfonyl group or fluorosulfonyl group, such as pentafluoroethane sulfonyl group. Examples of the F-containing imide salt include bis (fluorosulfonyl) imide salt [(FSO ₂ ) ₂ N ⁻ ], bis (trifluoromethanesulfonyl) imide salt [(CF ₃ SO ₂ ) ₂ N ⁻ ], and bis (pentafluoroethanesulfonyl). ) Bissulfonylimide salts such as imide salt [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ] can be mentioned.
The (F-2) acryloyl group-containing ionic compound is preferably copolymerized in an amount of 0.1 to 5.0% by weight in the copolymer.

Specific examples of the (F) antistatic agent are not particularly limited, but specific examples of the (F-1) ionic compound having a melting point of 25 to 50 ° C. are 1-octylpyridinium hexafluoride. Acid, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecyl Examples thereof include pyridinium dodecylbenzene sulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, and quaternary ammonium salt of trifluoromethanesulfonic acid. Further, as a specific example of the (F-2) acryloyl group-containing ionic compound, dimethylaminomethyl (meth) acrylate methyl hexafluorophosphate [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ = CH ₂ · PF ₆ ^-, provided that, Q = H or CH _3], dimethylaminoethyl (meth) acrylate bis (trifluoromethanesulfonyl) imidomethyl salt ^{_{[(CH 3) 3 N + (}} CH 2) 2 OCOCQ = CH 2 · (CF 3 SO 2 ) ₂ N ⁻ , but Q = H or CH ₃ ], dimethylaminomethylmethacrylate bis (fluorosulfonyl) imidemethyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ = CH ₂ · (FSO ₂ ) ₂ N ⁻ , but , Q = H or CH ₃ ] and the like.

The pressure-sensitive adhesive composition of the present invention may contain a polyether siloxane compound or other conventional antioxidants as additives.

The polyether-modified siloxane compound is a siloxane compound having a polyether group, and is a siloxane unit having a polyether group [-SiR ¹ (R ^{2 O-]) in addition to the usual siloxane unit [-SiR 1} _{2 -O-].} It has (R ³ O) _n R ⁴ ) -O-]. Here, R ¹ is one or more kinds of alkyl groups or aryl groups, R ² and R ³ are one or more kinds of alkylene groups, and R ⁴ is one or more kinds of alkyl groups or acyl groups. Etc. (terminal group). Examples of the polyether group include a polyoxyalkylene group such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a polyoxypropylene group [(C ₃ H ₆ O) _n ].
The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 7 to 15. Further, it is preferable that the polyether-modified siloxane compound is contained in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 parts by weight.
The HLB is, for example, a hydrophilic lipophilic balance (hydrophilic lipophilic ratio) defined in JIS K3211 (surfactant term) and the like.
The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group on a polyorganosiloxane backbone having a silicon hydride group by a hydrosilylation reaction. Specifically, dimethylsiloxane / methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane / methyl (polyoxyethylene) siloxane / methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane / methyl (polyoxypropylene) Examples thereof include siloxane polymers.
By blending the polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the pressure-sensitive adhesive strength and rework performance of the pressure-sensitive adhesive can be improved. If the pressure-sensitive adhesive composition does not contain a polyether-modified siloxane compound, the cost will be lower.

Examples of the antioxidant include hindered phenolic antioxidants, polyphenol compounds, tocopherol compounds and the like. Of these, tocopherol compounds are preferable. Tocopherol compounds are generally vitamin E and are also naturally occurring chemicals. For this reason, it has little adverse effect on the human body, is highly safe to handle, and is environmentally friendly. Further, since it is oil-soluble and liquid at room temperature, it is excellent in compatibility with the pressure-sensitive adhesive composition and precipitation resistance. By blending the tocopherol compound as the antioxidant, the storage stability of the pressure-sensitive adhesive is improved, so that the pot life of the pressure-sensitive adhesive composition containing the curing agent is improved.
Since the tocopherol-based compound used in the present invention is used by blending it in a pressure-sensitive adhesive composition (it is not metabolized like in the human body), the ferrule-like hydroxyl group of tocopherol has not changed to an ester or the like, and has ferrule-like properties. A compound having a hydroxyl group is preferable. For example, tocopherols and tocotrienols can be mentioned. It is known that tocopherols and tocotrienols are distinguished from natural compounds (d-form), non-natural compounds (l-form), and racemates (dl-form) which are mixtures of these. ing. Natural compounds (d-form) and racemates (dl-form) are preferable because some of them are used as food additives and the like.
Specific tocopherol compounds include d-α-tocopherol, dl-α-tocopherol, d-β-tocopherol, dl-β-tocopherol, d-γ-tocopherol, dl-γ-tocopherol, and d-δ-tocopherol. , Dl-δ-tocopherol, d-α-tocotrienol, dl-α-tocotrienol, d-β-tocotrienol, dl-β-tocotrienol, d-γ-tocotrienol, dl-γ-tocotrienol, d-δ-tocotrienol, dl At least one selected from the group of compounds consisting of -δ-tocotrienols can be mentioned. Two or more kinds of tocopherol compounds may be used in combination. As a food additive, what is called "mixed tocopherol" is a mixture containing d-α-tocopherol, d-β-tocopherol, d-γ-tocopherol and d-δ-tocopherol as main components, and is referred to as "tocotrienol". What is called is a mixture containing d-α-tocotrienol, d-β-tocotrienol, d-γ-tocotrienol and d-δ-tocotrienol as main components.
When the pressure-sensitive adhesive composition of the present invention contains a tocopherol-based compound, it is preferable to contain 0.01 to 5 parts by weight of the tocopherol-based compound with respect to 100 parts by weight of the copolymer.

Further, as other components, copolymerizable (meth) acrylic monomer containing alkylene oxide, (meth) acrylamide monomer, dialkyl-substituted acrylamide monomer, surfactant, curing catalyst, thermoplastic, filler, curing retarder, processing Known additives such as auxiliaries, antioxidants, and antioxidants can be appropriately added. These may be used alone or in combination of two or more.

The copolymer of the main agent used in the pressure-sensitive adhesive composition of the present invention is (A) as a group of monomers copolymerizable with at least one kind of (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms (A). B) It can be synthesized by copolymerizing with a copolymerizable monomer containing a hydroxyl group. The polymerization method of the copolymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.
When (F) an acryloyl group-containing ionic compound is used as the (F) antistatic agent, the copolymer of the main agent used in the pressure-sensitive adhesive composition of the present invention has (A) an alkyl group having C4 carbon atoms. ~ C18, at least one of the (meth) acrylic acid ester monomers, (B) a copolymerizable monomer containing a hydroxyl group as a copolymerizable monomer group, and (F-2) an acryloyl group-containing ionic compound. It can be synthesized by copolymerizing.
Further, the copolymer may contain at least one or more of a carboxyl group-containing monomer, a hydroxyl group-free nitrogen-containing vinyl monomer, and a polyalkylene glycol mono (meth) acrylic acid ester monomer as other copolymerizable monomer groups. can.
In the pressure-sensitive adhesive composition of the present invention, the above-mentioned copolymer is charged with (C) a bifunctional or higher functional isocyanate compound, (D) a cross-linking catalyst for a metal chelate compound, (E) a ketoenol tautomer compound, and (F) charging. As an inhibitor, it can be prepared by blending (F-1) an ionic compound having a melting point of 25 to 50 ° C., and an appropriate additive. When the (F-2) acryloyl group-containing ionic compound is polymerized in the copolymer of the main agent, the (F-1) melting point is 25 to 25 as the (F) antistatic agent for the copolymer. An ionic compound at 50 ° C. may or may not be further added.

The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid, and (meth) acrylamides.
The acid value of the copolymer is preferably 0.01 to 8.0. As a result, the contamination property can be improved and the performance of preventing the generation of adhesive residue can be improved.
Here, the "acid value" is one of the indexes representing the acid content, and is represented by the number of mg of potassium hydroxide required to neutralize 1 g of the polymer containing a carboxyl group.

The pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition has an adhesive force of 0.05 to 0.1 N / 25 mm at a low-speed peeling speed of 0.3 m / min and a high-speed peeling speed of 30 m / min. The adhesive strength is preferably 1.0 N / 25 mm or less. As a result, it is possible to obtain a performance in which the adhesive strength does not change much depending on the peeling speed, and it is possible to quickly peel even by high-speed peeling. Further, since it is reattached, even when the surface protective film is once peeled off, it does not require an excessive force and can be easily peeled off from the adherend.

It is preferable that the surface resistivity of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 9.0 × 10 ⁺¹¹ Ω / □ or less, and the peeling band voltage is ± 0 to 0.5 kV. In the present invention, "± 0 to 0.5 kV" means 0 to −0.5 kV and 0 to +0.5 kV, that is, −0.5 to +0.5 kV. If the surface resistivity is large, the ability to release the static electricity generated by charging during peeling is inferior. Therefore, by making the surface resistivity sufficiently small, the peeling that occurs due to the static electricity generated when the adherend peels off the adhesive layer. The band resistivity is reduced, and it is possible to suppress the influence on the electric control circuit of the adherend and the like.

The gel fraction of the pressure-sensitive adhesive layer (the pressure-sensitive adhesive after cross-linking) obtained by cross-linking the pressure-sensitive adhesive composition of the present invention is preferably 95 to 100%. Due to such a high gel content, the adhesive strength does not become excessive at a low peeling speed, the elution of unpolymerized monomers or oligomers from the copolymer is reduced, and the reworkability and high temperature / high humidity are achieved. Durability is improved and contamination of the adherend can be suppressed.

The pressure-sensitive adhesive film of the present invention is formed by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present invention on one or both sides of a resin film. Further, the surface protective film of the present invention is a surface protective film formed by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present invention on one side of a resin film. Since the pressure-sensitive adhesive composition of the present invention contains the above-mentioned components (A) to (F) in a well-balanced manner, it has excellent antistatic performance, and has a low peeling speed and a high peeling speed. It has an excellent balance of adhesive strength, and also has excellent durability and rework performance (no contamination transfer to the adherend after tracing the surface protective film with a ballpoint pen through the adhesive layer). Become. Therefore, it can be suitably used as a surface protective film for a polarizing plate.

In the pressure-sensitive adhesive film and surface protection film according to the present invention, a polyester film or the like can be used as the base material of the resin film or the release film (separator) that protects the pressure-sensitive adhesive layer.
Further, on the resin film, on the surface opposite to the side where the pressure-sensitive adhesive layer of the resin film is formed, a silicone-based or fluorine-based mold release agent or coating agent, antifouling treatment with silica fine particles, etc., and application of an antistatic agent are applied. Antistatic treatment can be applied by kneading or the like.
Further, the release film is subjected to a mold release treatment with a silicone-based or fluorine-based mold release agent or the like on the surface of the pressure-sensitive adhesive layer on the side to be combined with the adhesive surface.

Hereinafter, the present invention will be specifically described with reference to Examples.

<Manufacturing of acrylic copolymer>
[Example 1]
Nitrogen gas was introduced into a reaction device equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, and the air in the reaction device was replaced with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate and 3.5 parts by weight of 8-hydroxyoctyl acrylate were added to the reaction apparatus. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65 ° C. for 6 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 500,000 and used in Example 1. I got 1. A part of the acrylic copolymer was collected and used as a sample for measuring the acid value described later.
[Examples 2 to 6 and Comparative Examples 1 to 3]
The acrylic copolymer solution 1 used in Example 1 above, except that the composition of the monomers is as described in (A), (B), (I) and (F-2) of Table 1, respectively. In the same manner as above, the acrylic copolymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 3 were obtained.

<Manufacturing of adhesive composition and surface protective film>
[Example 1]
To the acrylic copolymer solution 1 of Example 1 produced as described above, 1.5 parts by weight of 1-octylpyridinium hexafluorophosphate and 4.0 parts by weight of acetylacetone were added and stirred, and then Coronate HX. (Isocyanurate of hexamethylene diisocyanate compound) 1.5 parts by weight and Tris (2,4-pentanedionato) iron (III) 0.05 parts by weight are added and mixed by stirring to obtain the pressure-sensitive adhesive composition of Example 1. Got This pressure-sensitive adhesive composition is applied onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, and then dried at 90 ° C. to remove the solvent, and the pressure-sensitive adhesive layer has a thickness of 25 μm. I got a sheet.
After that, the adhesive sheet is transferred to the surface opposite to the antistatic and antifouling treated polyethylene terephthalate (PET) film on one surface, and "antistatic and antifouling treated". A surface protective film of Example 1 having a laminated structure of "PET film / adhesive layer / release film (PET film coated with silicone resin)" was obtained.
[Examples 2 to 6 and Comparative Examples 1 to 3]
Examples 2 to 6 are the same as the surface protective film of Example 1 above, except that the composition of the additive is as described in (C) to (F) and (J) of Table 2, respectively. And the surface protective films of Comparative Examples 1 to 3 were obtained.

Tables 1 and 2 divide the integrated table showing the compounding ratio of each component into two, and in each case, the numerical value of the weight part obtained by assuming that the total of the group (A) is 100 parts by weight is enclosed in parentheses. Indicated by. The values of the ratios (E) / (D) are shown in Table 3. The compound names of the abbreviations of the respective components used in Tables 1 and 2 are shown in Tables 4 and 5. Coronate (registered trademark) HX, HL and L are trade names of Nippon Polyurethane Industry Co., Ltd., and Takenate (registered trademark) D-140N, D-127N, D-110N are trade names of Mitsui Chemicals, Inc. Death Module (registered trademark) N3400 is a trade name of Sumika Bayer Urethane Co., Ltd.
In Table 1, among the (F) antistatic agents, the (F-2) acryloyl group-containing ionic compound copolymerized in the copolymer is different from the (F) antistatic agent added after the polymerization. Described in the column of.

<Synthesis of bifunctional isocyanate compound>
The bifunctional isocyanate compounds of Synthesis Examples 1 and 2 were synthesized by the following method. As shown in Tables 6 and 7, the diisocyanate and the diol compound were mixed at a molar ratio of NCO / OH = 16 and reacted at 120 ° C. for 3 hours, and then under reduced pressure using a thin film evaporator. The unreacted diisocyanate was removed to obtain the desired bifunctional isocyanate compound.

<Test method and evaluation>
The surface protective films of Examples 1 to 6 and Comparative Examples 1 to 3 were aged at 23 ° C. and 50% RH for 7 days, and then the release film (silicone resin coated PET film) was peeled off to adhere. The exposed agent layer was used as a sample for measuring the surface resistance.
Further, the surface protective film on which the pressure-sensitive adhesive layer is exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell via the pressure-sensitive adhesive layer, left for 1 day, and then left at 50 ° C., 5 atm, for 20 minutes. A sample that had been autoclaved and left at room temperature for another 12 hours was used as a sample for measuring adhesive strength, peeling band voltage, reworkability, and durability.

<Adhesive strength>
The measurement sample obtained above (a 25 mm wide surface protective film bonded to the surface of the polarizing plate) was subjected to a low speed peeling speed (0.3 m / min) and a high speed in the 180 ° direction using a tensile tester. The peeling strength was taken as the adhesive strength after peeling at the peeling speed (30 m / min).

<Surface resistivity>
After aging, before bonding to the polarizing plate, the release film (PET film coated with silicone resin) is peeled off to expose the adhesive layer, and the resistance meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytec) is used. The surface resistance of the pressure-sensitive adhesive layer was measured.

<Peeling band voltage>
High-precision electrostatic sensors SK-035 and SK-200 (stocks) can be used to measure the voltage (band voltage) generated by charging the polarizing plate when the measurement sample obtained above is peeled 180 ° at a tensile speed of 30 m / min. It was measured using (manufactured by the company Keyence), and the maximum value of the measured value was taken as the peeling band voltage.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ball pen (load 500 g, 3 reciprocations), the surface protective film is peeled off from the polarizing plate, the surface of the polarizing plate is observed, and the polarizing plate is contaminated. Confirmed that there was no migration. The evaluation target criteria are "○" when there is no contamination transfer on the polarizing plate, "△" when contamination transfer is confirmed at least in part along the trajectory traced with the ballpoint pen, and along the trajectory traced with the ballpoint pen. When the transfer of contamination was confirmed and the detachment of the adhesive was confirmed from the surface of the adhesive, it was evaluated as "x".

<Pot life>
Immediately after blending the additives (C) to (F) and (J), the viscosity η ₀ (initial viscosity) of the pressure-sensitive adhesive composition was measured, and the pressure-sensitive adhesive composition was further sealed at 23 ° C. for 8 hours. _{The viscosity η 1} (viscosity after 8 hours) of the pressure-sensitive adhesive composition after being left to stand was measured. As an index of pot life, the value of η _{1 when η 0} was 1.0, that is, the ratio of _{η 1} / η _{0 was obtained.} The evaluation target criteria are "○" when the viscosity after 8 hours is less than 1.25 times the initial viscosity, "△" when it is 1.25 times or more and less than 1.50 times, 1.50 times or more or The case where the gel was formed after being left for 8 hours was evaluated as "x".

<Durability>
The measurement sample obtained above was left in an atmosphere of 60 ° C. and 90% RH for 250 hours, then taken out to room temperature, left for another 12 hours, and then the adhesive strength was measured and clearly compared with the initial adhesive strength. It was confirmed that there was no significant increase. The evaluation target criteria were evaluated as "◯" when the adhesive strength after the test was 1.5 times or less of the initial adhesive strength, and "x" when the adhesive strength exceeded 1.5 times.

Table 8 shows the evaluation results. The surface resistivity is expressed by a method in which "m × 10 ^{+ n} " is set to "mE + n" (where m is an arbitrary real number and n is a positive integer).

The surface protective films of Examples 1 to 6 have an adhesive strength of 0.05 to 0.1 N / 25 mm at a low peeling speed of 0.3 m / min and an adhesive strength of 1 at a high peeling speed of 30 m / min. It is 0.0 N / 25 mm or less, the surface resistance is 9.0 × 10 ^{+ 11} Ω / □ or less, the peeling band voltage is ± 0 to 0.5 kV, and it is placed on the surface protective film via the adhesive layer. After tracing with a ball pen, there was no transfer of contamination to the adherend, the pot life was long, and the durability was excellent when left in an atmosphere of 60 ° C. and 90% RH for 250 hours.
That is, it has antistatic performance, has an excellent balance of adhesive force at a low peeling speed and a high peeling speed, has a long pot life, and has excellent durability and reworkability.
Further, according to the surface protective films of Examples 1 to 6, the pressure-sensitive adhesive composition does not contain the organic tin compound, so that the safety is high.

The surface protective film of Comparative Example 1 does not contain (C) a bifunctional or higher functional isocyanate compound as a cross-linking agent, and has an adhesive force at a low peeling speed of 0.3 m / min and a high peeling speed of 30 m / min. Was too large, the surface resistance and the peeling band voltage were high, and the reworkability and durability were inferior.
The surface protective film of Comparative Example 2 has a high peeling zone voltage, a short pot life, and inferior durability, probably because the ratio of the (E) keto-enol tautomer compound to the cross-linking catalyst of the (D) metal chelate compound is small. Was there.
The surface protective film of Comparative Example 3 was coated because the ratio of the (E) keto-enol tautomer compound to the cross-linking catalyst of the (D) metal chelate compound was small, the pot life was too short, and the cross-linking proceeded before the coating. I couldn't do the work.
As described above, the surface protective films of Comparative Examples 1 to 3 are provided with antistatic performance, have an excellent balance of adhesive strength at a low peeling speed and a high peeling speed, and have a long pot life, durability and durability. It was not possible to meet all the required performances, which are excellent in reworkability, at the same time.

Claims (2)

A surface protective film formed by forming a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic copolymer, (F) an antistatic agent, and a cross-linking agent on one side of a resin film.
The acrylic copolymer is based on 100 parts by weight of the acrylic copolymer.
(A) The total of at least one of the (meth) acrylic acid ester monomers having an alkyl group having C4 to C18 carbon atoms is 50 to 98 parts by weight.
(B) The total of at least one copolymerizable monomer containing a hydroxyl group is 0.1 to 10 parts by weight.
(C1) The total of one or more types of carboxyl group-containing monomers is 0.1 to 1 part by weight.
(C2) The total of one or more kinds of nitrogen-containing vinyl monomers containing no hydroxyl group is 0 to 20 parts by weight.
(C3) The total of one or more kinds of polyalkylene glycol mono (meth) acrylic acid ester monomers is 0 to 50 parts by weight.
It is an acrylic copolymer obtained by copolymerizing
The content of the above (A), the above (B), and the above (C1) to (C3) is 100 parts by weight.
The acid value of the acrylic copolymer is 0.01 to 8.0, and the acid value is 0.01 to 8.0.
The pressure-sensitive adhesive composition is crosslinked with 100 parts by weight of the acrylic copolymer by 0.05 to 5 parts by weight of an ionic compound having a melting point of 25 to 50 ° C. as the (F) antistatic agent. As an agent, 0.1 to 10 parts by weight of a bifunctional or higher isocyanate compound, 0.001 parts by weight or more of a cross-linking catalyst of (D) a metal chelate compound and 5/109 parts by weight or less , and (E) a ketoenol homozygous compound. It is contained in a proportion of 0.1 parts by weight or more and 800 / 107.4 parts by weight or less.
A surface protective film having a weight-based ratio of (E) / (D) of 80 to 300 as a ratio of the (E) to the (D). The surface protective film according to claim 1, which is used as a surface protective film for a polarizing plate.