JP6744466B2 - Surface protection film - Google Patents

Description

The present invention relates to an adhesive composition and a surface protective film. More specifically, the surface of a polarizing plate that has antistatic properties, has an excellent balance of adhesive strength at low peeling speeds and high peeling speeds, and has 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.

As a pressure-sensitive adhesive for optical use, since it has excellent transparency, 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 composed of is preferably used. Further, it is required that various physical properties such as the adhesive strength of the adhesive are appropriately adjusted. In particular, the pressure-sensitive adhesive for surface protection film is suitable for laminating the surface protection film with an automatic laminating device so that it can be adapted to the manufacturing process of factory production, at a low peeling speed and a high peeling speed. Therefore, there is a demand for an adhesive having an excellent balance of adhesive strength. Furthermore, 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 reacts with a functional group such as a hydroxyl group or a carboxyl group contained in the acrylic pressure-sensitive adhesive made of a copolymer is used. The cross-linking reaction is performed by adjusting the adhesive force and cohesive force.

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

Among them, Patent Document 1 discloses that as a crosslinking catalyst used in combination with an isocyanate-based crosslinking agent, an iron chelate is preferable among metal chelates, and tris(acetylacetonato)iron is particularly preferable because it has excellent catalytic activity. There is.

By the way, in the acrylic pressure-sensitive adhesive composition containing a crosslinking catalyst, the crosslinking reaction gradually progresses even while being left at room temperature. Therefore, in industrial production of pressure-sensitive adhesives, after mixing the raw materials of the pressure-sensitive adhesive composition, until the time to start the cross-linking reaction, in order to leave the cross-linking reaction stopped, a cross-linking catalyst and a reaction retarder, in general, Are used together.
Regarding the combined use of the crosslinking catalyst and the reaction retarder, Patent Document 2 discloses a method for producing a polyurethane, which comprises a mixture of at least one metal acetylacetonate and acetylacetone, and the metal acetylacetonate and the acetylacetone. It is disclosed to use a reactive urethane mixture containing a catalyst system having a weight ratio of 2:1.

JP, 2011-001440, A JP, 2008-285681, A

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

Further, in Patent Document 2, even if a metal acetylacetonate catalyst such as iron or copper having a very high activity at a low temperature is used, a metal having excellent stability and good catalytic activity, which does not cause early curing. A method for producing polyurethane using a catalyst 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, but even if this mixing ratio is applied to the production process of the acrylic pressure-sensitive adhesive, the crosslinking reaction is temporarily stopped. Couldn't stop.

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

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention contains (B) a hydroxyl group as a monomer group with at least 1 type of (meth)acrylic acid ester monomer whose carbon number of (A) alkyl group is C4-C18. (C) 0.1 to 10 parts by weight of a bifunctional or higher functional isocyanate compound, and (D) a metal chelate compound crosslinking catalyst 0.001 to 0 parts by weight per 100 parts by weight of the copolymer with the copolymerizable monomer. 0.5 parts by weight, (E) keto-enol tautomer compound 0.1-200 parts by weight, and (F) an ionic compound 0.05-5 parts by weight having an melting point of 25-50° C. as an antistatic agent. , (E)/(D) in a weight ratio of 70 to 700 are provided.

In addition, the copolymerizable monomer having a hydroxyl group (B) is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 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, the (C) bifunctional or higher functional isocyanate compound is preferably a compound produced by reacting a diisocyanate compound and a diol compound as an acyclic aliphatic isocyanate compound. The diisocyanate compound is an aliphatic diisocyanate, and is preferably one selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate. The diol compound may be 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl. 2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, polypropylene glycol It is preferably composed of one selected from the above.
Further, as the (C) bifunctional or higher-functional isocyanate compound, as the trifunctional isocyanate compound, an isocyanurate body of a hexamethylene diisocyanate compound, an isocyanurate body of an isophorone diisocyanate compound, an adduct body of a hexamethylene diisocyanate compound, an isophorone diisocyanate compound Adduct, burette of hexamethylene diisocyanate compound, burette of isophorone diisocyanate compound, isocyanurate of tolylene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, tolylene diisocyanate At least one selected from the group of compounds consisting of an adduct of a compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound is preferable.

Further, the crosslinking catalyst in the pressure-sensitive adhesive composition is preferably at least one selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds.

The (F) antistatic agent is an ionic compound having a melting point of 25 to 50° C., which is contained in 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer, and It is preferable that the acryloyl group-containing ionic compound copolymerized in the copolymer is 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 the other copolymerizable monomer group, and/ Alternatively, it is preferable to include a polyether siloxane compound and other conventional antioxidants as additives.

The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has an adhesive force of 0.05 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min and a high peeling speed of 30 m/min. It is preferable that the adhesive strength at 1.0 N/25 mm or less.

The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition preferably has a surface resistivity of 9.0×10 ⁺¹¹ Ω/□ or less and a peeling electrification voltage of ±0 to 0.5 kV.

Further, the present invention provides a pressure-sensitive adhesive film comprising a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition, on one side or both sides of a resin film.

Further, the present invention is a surface protective film comprising a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition, which is formed on one surface of a resin film, wherein the surface protective film is provided via the pressure-sensitive adhesive layer. Provided is a surface protective film which is free from contamination transfer to an 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, in the surface protective film of the present invention, it is preferable that the surface of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed is antistatic and antifouling treated.

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

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive composition of the present invention is a copolymer containing (B) a hydroxyl group (B) as a copolymerizable monomer group, and (A) at least one (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C18. (C) Bifunctional or higher functional isocyanate compound 0.1 to 10 parts by weight, (D) Metal chelate compound crosslinking catalyst 0.001 to 0.5 parts by weight, relative to 100 parts by weight of a copolymer with a possible monomer. Parts, 0.1 to 200 parts by weight of (E) keto-enol tautomer compound, and (F) 0.05 to 5 parts by weight of ionic compound having a melting point of 25 to 50° C. as an antistatic agent. )/(D) weight part ratio is 70-700.

The copolymer may include 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 the other copolymerizable monomer group.
The (F) antistatic agent is an ionic compound having a melting point of 25 to 50° C., which is contained in 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer, and/or The acryloyl group-containing ionic compound copolymerized in the copolymer may be 0.1 to 5.0% by weight.
Further, the pressure-sensitive adhesive composition of the present invention may contain a polyether siloxane compound and other conventional antioxidants as additives.

Examples of the (A) (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C18 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, isocetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and the like.
It is preferable that the (A) alkyl group (C) has a C4 to C18 (meth)acrylic acid ester monomer in an amount of 50 to 98 parts by weight based on 100 parts by weight of the copolymer.

Examples of the (B) hydroxyl group-containing copolymerizable monomer include (B) hydroxyl group-containing copolymerizable monomer: 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, N-hydroxyethyl (meth) Examples 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 group of compounds consisting of acrylamide and N-hydroxyethyl(meth)acrylamide is preferable.
It is preferable that 0.1 to 10 parts by weight of the (B) hydroxyl group-containing copolymerizable monomer is contained in 100 parts by weight of the copolymer.

The copolymer may include 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 another copolymerizable monomer group.

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 group of compounds consisting of 2-(meth)acryloyloxyethyltetrahydrophthalic 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 preferable to contain it in a ratio. The copolymer may not contain the carboxyl group-containing monomer.

The polyalkylene glycol mono(meth)acrylic acid ester monomer may be a compound in which one of a plurality of hydroxyl groups of polyalkylene glycol is esterified as a (meth)acrylic acid ester. Since the (meth)acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the main component copolymer. The other hydroxyl group may be OH as it is, or may be an alkyl ether such as methyl ether or ethyl ether, or a saturated carboxylic acid ester such as acetic acid ester.
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 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.
The polyalkylene glycol mono(meth)acrylic acid ester monomer preferably has an average number of repeating alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The “average number of repeating alkylene oxides” is the average number of repeating alkylene oxide units in the “polyalkylene glycol chain” portion 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-polypropylene glycol-polybutylene glycol-mono(meth)acrylate; methoxy polyethylene glycol-(meth)acrylate, methoxy polypropylene glycol -(Meth)acrylate, methoxypolybutylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polybutylene glycol-(meth)acrylate, methoxy-polypropylene glycol-polybutylene Glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol-(meth)acrylate; ethoxypolyethylene glycol-(meth)acrylate, ethoxypolypropylene glycol-(meth)acrylate, ethoxypolybutylene glycol-(meth). Acrylate, ethoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polybutylene glycol-(meth)acrylate, ethoxy-polypropylene glycol-polybutylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polypropylene glycol -Polybutylene glycol-(meth)acrylate etc. are mentioned.
The polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably contained in a proportion 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 vinyl monomers containing an amide bond, vinyl monomers containing an amino group, and vinyl monomers containing 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. A cyclic nitrogen vinyl compound having an N-vinyl-substituted heterocyclic structure, such as pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-vinyllaurylolactam; N-( (Meth)acryloylmorpholine, N-(meth)acryloylpiperazine, N-(meth)acryloylaziridine, N-(meth)acryloylazetidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth) ) Acyclic nitrogen vinyl compounds having an N-(meth)acryloyl-substituted heterocyclic structure such as acryloylazepan and N-(meth)acryloylazocan; nitrogen atoms such as N-cyclohexylmaleimide and N-phenylmaleimide; Cyclic nitrogen vinyl compounds having a heterocyclic structure having an ethylenically unsaturated bond in the ring; (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nt-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 (Meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-diethylaminomethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N-ethyl-N-methylaminoethyl (meth ) Acrylate, N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl (meth) A) acrylate, dialkylamino(meth)acrylates such as 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 -(Meth)acrylamides such as methylenebis(meth)acrylamide; unsaturated carboxylic acid nitriles such as (meth)acrylonitrile; and the like.

The nitrogen-containing vinyl monomer containing no hydroxyl group is preferably contained in an amount of 0 to 20 parts by weight with respect to 100 parts by weight of the copolymer. The copolymer may not contain the nitrogen-containing vinyl monomer that does not contain the hydroxyl group.

The (C) bifunctional or higher functional isocyanate compound may be at least one or two or more selected from polyisocyanate compounds having at least two 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), trimethylhexamethylene diisocyanate (TMDI), diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI). Aromatic hydrogenated isocyanate compounds such as hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylene diisocyanate (TOID) and tolylene diisocyanate (TDI).
Examples of the trifunctional or higher isocyanate compound include a bifunctional isocyanate compound (compound having two NCO groups in one molecule), a buret modified product, an isocyanurate modified product, trimethylolpropane (TMP), glycerin, or the like having a valence of 3 or more. And a polyol (a compound having at least 3 or more OH groups in one molecule) of (1).
As the (C) bifunctional or higher isocyanate compound, it is also possible to use only the (C-1) trifunctional isocyanate compound or 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 together.

Further, as the (C-1) trifunctional isocyanate compound used in the present invention, an isocyanurate body of a hexamethylene diisocyanate compound, an isocyanurate body of an isophorone diisocyanate compound, an adduct body of a hexamethylene diisocyanate compound, an adduct body of an isophorone diisocyanate compound, At least one or more 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 body, isocyanurate body of xylylene diisocyanate compound, isocyanurate body of hydrogenated xylylene diisocyanate compound, adduct body of tolylene diisocyanate compound, adduct body of xylylene diisocyanate compound, adduct body of hydrogenated xylylene diisocyanate compound And (C-1-2) at least one selected from the second aromatic isocyanate compound group. It is preferable to use the (C-1-1) first aliphatic isocyanate compound group and the (C-1-2) second aromatic isocyanate compound group in combination. In the present invention, as the (C-1) trifunctional isocyanate compound, at least one or more selected from the group of the (C-1-1) first aliphatic isocyanate compound, and (C-1-2) ) By using in combination with at least one or more selected from the second aromatic isocyanate compound group, it is possible to further improve the balance of the adhesive strength in the low-speed peeling region and the high-speed peeling region.
Further, the (C-1) trifunctional isocyanate compound is at least one or more selected from the (C-1-1) first aliphatic isocyanate compound group, and the (C-1-2) ) At least one or more selected from the second aromatic isocyanate compound group, and 0.5 to 5.0 parts by weight in total with respect to 100 parts by weight of the copolymer. Preferably. In addition, at least one selected from the group of (C-1-1) first aliphatic isocyanate compound, and (C-1-2) of the second aromatic isocyanate compound group. The mixing ratio with at least one or more selected from (C-1-1):(C-1-2) is in the range of 10%:90% to 90%:10% by weight. Is preferred.

Further, the (C-2) bifunctional isocyanate compound used in the present invention is preferably an acyclic aliphatic isocyanate compound which is produced by reacting a diisocyanate compound and a diol compound.
For example, a diisocyanate compound is represented by the 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). When the diol compound is represented by ), examples of the compound produced by reacting the diisocyanate compound and the diol compound include compounds represented by the following general formula Z.

[General formula Z]
O=C=N-X-(NH-CO-O-Y-O-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 in which n is 0 in the general formula Z (a diisocyanate compound not reacted with the 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 The bifunctional acyclic aliphatic isocyanate compound may be a mixture 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, aliphatic divalent group. The aliphatic diisocyanate is preferably one or more selected from the 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, 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, 2-ethyl-2. -Butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, polypropylene glycol It is preferable to be composed of one kind or two or more kinds selected.

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.

The crosslinking catalyst for the metal chelate compound (D) may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent when the polyisocyanate compound is used as the crosslinking agent. Examples thereof include amine compounds such as tertiary amines, metal chelate compounds, organotin compounds, organolead compounds and organometallic compounds such as organozinc compounds. In the present invention, a metal chelate compound is used as the crosslinking 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 ligand X bonded to the metal atom M. For example, when a general formula of a metal chelate compound having one metal atom M is represented by M(L) _m (X) _n , m≧1 and n≧0. When m is 2 or more, m Ls may be the same ligand or 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 and Sn.
Examples of the polydentate ligand L include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate, acetylacetone (also known as 2,4-pentanedione), Examples include β-diketones such as 2,4-hexanedione and benzoylacetone. These are keto-enol tautomeric compounds, and in the polydentate ligand L, an enol deprotonated enolate (eg, acetylacetonate) may be used.
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 alkoxy groups 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-pentanedionato)iron(III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, and aluminum tris. Acetylacetonate, zirconium tetrakisacetylacetonate, tris(2,4-hexanedionate)iron(III), bis(2,4-hexanedionato)zinc, tris(2,4-hexanedionato)titanium, tris Examples include (2,4-hexanedionate)aluminum and tetrakis(2,4-hexanedionate)zirconium.

Examples of the organotin compound include dialkyltin oxide, fatty acid salt of dialkyltin, and fatty acid salt of stannous tin. Conventionally, many dibutyltin compounds have been used, but in recent years, the toxicity problem of organotin compounds has been pointed out, and particularly tributyltin (TBT) contained in dibutyltin compounds has been feared as an endocrine disrupting substance. From the viewpoint of safety, long-chain alkyltin compounds such as dioctyltin compounds are preferable. Specific examples of the organic tin compound include dioctyl tin oxide and dioctyl tin dilaurate. Temporarily, Sn compounds can also be used, but in view of the trend of requiring the use of substances with higher safety in the future, Al, Ti, Fe, etc., which have higher safety than Sn, can be used. 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 crosslinking catalyst of the metal chelate compound (D) is preferably contained in an amount of 0.001 to 0.5 part by weight, based on 100 parts by weight of the copolymer.

Examples of (E) keto-enol tautomer compounds include β-keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate, acetylacetone, and 2,4-hexanedione. , Β-diketones such as benzoylacetone. These are, in a pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, by blocking the isocyanate group of the cross-linking agent, to suppress excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after the incorporation of the cross-linking agent. The pot life of the pressure-sensitive adhesive composition can be extended.
The (E) 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.

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. It is preferable to appropriately set the ratio of the mutant compound. In order to increase the pot life of the pressure-sensitive adhesive composition and improve the storage stability, the weight ratio (E)/(D) of (E) a ketoenol tautomer compound/(D) a metal chelate crosslinking catalyst is used. The higher 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 antistatic agent (F) include an antistatic agent contained in the pressure-sensitive adhesive composition and an antistatic agent copolymerized in the copolymer. The antistatic agent (F) is preferably contained in an amount of 0.05 to 5.0 parts by weight based on 100 parts by weight of the copolymer.
The antistatic agent (F) 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 the antistatic agent (F), (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 copolymerized in the copolymer. Since these (F) antistatic agents have a low melting point and also have a long-chain alkyl group, they are presumed to have 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, a pyrazolium cation. , Pyrrolidinium cations, nitrogen-containing onium cations such as ammonium cations, phosphonium cations, sulfonium cations, and the like, and the anions include hexafluorophosphate (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), and alkylbenzene sulfone. Acid salt (RC ₆ H ₄ SO ₃ ⁻ ), perchlorate salt (ClO ₄ ⁻ ), tetrafluoroborate salt (BF ₄ ⁻ ), bis(fluorosulfonyl)imide salt (FSI), bis(trifluoromethanesulfonyl). ) Compounds which are inorganic or organic anions such as imide salt (TFSI) and trifluoromethanesulfonate (TF). It is preferably solid at room temperature (for example, 25° C.), and one having 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 the substituents and the like. The cation is preferably a quaternary nitrogen-containing onium cation, and a quaternary pyridinium cation such as 1-alkylpyridinium (the carbon atom at the 2 to 6 position may have a substituent or may be unsubstituted), or 1, Examples thereof include quaternary imidazolium cations such as 3-dialkylimidazolium (the carbon atoms at the 2,4,5-position may have a substituent or unsubstituted), quaternary ammonium cations such as tetraalkylammonium, and the like. ..
The ionic compound (F-1) having a melting point of 25 to 50° C. is preferably contained in 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 a Q = H or _CH 3, R = alkyl], etc. (meth) acryloyl group-containing cationic, anion, hexafluorophosphate (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 The compound which is an anion is mentioned. 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. The F-containing imide salt, bis (fluorosulfonyl) imide salt _{[(FSO 2)} 2 N ^-], bis (trifluoromethanesulfonyl) imide salt _{[(CF 3 SO 2) 2 N} - ], bis (pentafluoroethane sulfonyl ) Bissulfonyl imide salts such as imide salt [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ].
The (F-2) acryloyl group-containing ionic compound is preferably copolymerized in the copolymer in an amount of 0.1 to 5.0% by weight.

Specific examples of the antistatic agent (F) are not particularly limited, but specific examples of the ionic compound (F-1) having a melting point of 25 to 50° C. include 1-octylpyridinium phosphorus hexafluoride. Acid salt, 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 trifluoromethane sulfonic acid. Specific examples of the (F-2) acryloyl group-containing ionic compound, dimethylaminomethyl (meth) acrylate hexafluorophosphate Methyl salt ^{_{[(CH 3) 3 N + CH}} 2 OCOCQ = CH 2 · PF 6 ⁻ , where Q=H or CH ₃ ], dimethylaminoethyl(meth)acrylate bis(trifluoromethanesulfonyl)imide methyl salt [(CH ₃ ) ₃ N ⁺ (CH ₂ ) ₂ OCOCQ=CH ₂ ·(CF ₃ SO ₂ ) ₂ N ^-, however, Q = H or CH _3], dimethylaminomethyl methacrylate bis (fluorosulfonyl) imidomethyl salt ^{_{[(CH 3) 3 N + CH}} 2 OCOCQ = CH 2 · (FSO 2) 2 N -, provided that , Q=H or CH ₃ ] and the like.

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

The polyether-modified siloxane compound is a siloxane compound having a polyether group, in addition to the normal siloxane units [-SiR ¹ ₂ -O-], siloxane units having polyether groups [-SiR ^{1 (R} 2 O having _{^{(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 polyoxyalkylene groups such as polyoxyethylene group [(C ₂ H ₄ O) _n ] and 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 0.01 to 1.0 part by weight of the polyether-modified siloxane compound is included with respect to 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 parts by weight.
The HLB is a hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) defined in JIS K3211 (surfactant term), for example.
The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group onto a polyorganosiloxane main chain 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 adding the polyether-modified siloxane compound to the pressure-sensitive adhesive composition, the pressure-sensitive adhesive strength and rework performance can be improved. When the pressure-sensitive adhesive composition does not contain the polyether-modified siloxane compound, the cost becomes lower.

Examples of the antioxidant include hindered phenolic antioxidants, polyphenol compounds, and tocopherol compounds. Of these, tocopherol compounds are preferable. The tocopherol compound is generally vitamin E, which is also a naturally occurring chemical substance. For this reason, there is little adverse effect on the human body, safety in handling is high, and the environment is friendly. Further, since it is oil-soluble and liquid at room temperature, it has excellent compatibility with the pressure-sensitive adhesive composition and excellent precipitation resistance. By adding 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.
As the tocopherol compound used in the present invention, since it is used by blending it with an adhesive composition (which is not metabolized as in the human body), the ferrule hydroxyl group of tocopherol has not changed to an ester or the like, and has ferrule properties. A compound having a hydroxyl group is preferable. Examples include tocopherol and tocotrienol. It is known that tocopherol and tocotrienol are distinguished from each other as a natural type compound (d-form), a non-natural type compound (1-form), and a racemic form (dl-form) which is a mixture of these in equal amounts. ing. Natural compounds (d-form) and racemic forms (dl-form) are preferable because some of them are used as food additives.
Specific tocopherol compounds include d-α-tocopherol, dl-α-tocopherol, d-β-tocopherol, dl-β-tocopherol, d-γ-tocopherol, dl-γ-tocopherol, 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-tocotrienol can be mentioned. You may use together 2 or more types of tocopherol type compounds. 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 "tocotrienol". What is called is a mixture based on d-α-tocotrienol, d-β-tocotrienol, d-γ-tocotrienol and d-δ-tocotrienol.
When the pressure-sensitive adhesive composition of the present invention contains a tocopherol compound, it is preferable to contain 0.01 to 5 parts by weight of the tocopherol compound with respect to 100 parts by weight of the copolymer.

Further, as other components, copolymerizable (meth)acrylic monomers containing alkylene oxide, (meth)acrylamide monomers, dialkyl-substituted acrylamide monomers, surfactants, curing catalysts, plasticizers, fillers, curing retarders, 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 component used in the pressure-sensitive adhesive composition of the present invention comprises (A) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18 as a copolymerizable monomer group ( It can be synthesized by copolymerizing B) 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-2) an acryloyl group-containing ionic compound is used as the antistatic agent (F), the copolymer of the main agent used in the pressure-sensitive adhesive composition of the present invention has (A) an alkyl group having a carbon number of C4. To at least one C18 (meth)acrylic acid ester monomer, a copolymerizable monomer (B) having a hydroxyl group as a copolymerizable monomer group, and (F-2) an acryloyl group-containing ionic compound. It can be synthesized by copolymerization.
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 a group of other copolymerizable monomers. it can.
The pressure-sensitive adhesive composition of the present invention comprises: (C) a bifunctional or higher functional isocyanate compound; (D) a metal chelate compound crosslinking catalyst; (E) a ketoenol tautomer compound; It can be prepared by blending (F-1) an ionic compound having a melting point of 25 to 50° C. as an inhibitor, and further optionally adding an optional additive. When the (F-2) acryloyl group-containing ionic compound is polymerized in the copolymer of the main component, (F-1) the melting point of the copolymer (F-1) is 25 to The 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, or (meth)acrylamide.
The acid value of the copolymer is preferably 0.01 to 8.0. As a result, the stain resistance can be improved and the adhesive residue generation preventing performance can be improved.
Here, the "acid value" is one of the indexes showing the content of the acid, and is represented by mg of potassium hydroxide required for neutralizing 1 g of the polymer containing a carboxyl group.

The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has an adhesive force of 0.05 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min and a high 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 force does not change much even with the peeling speed, and it is possible to quickly peel even with high-speed peeling. In addition, since the surface protective film is once peeled off, even if the surface protective film is once peeled off, it does not require an excessive force and can be easily peeled off from the adherend.

The pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition preferably has a surface resistivity of 9.0×10 ⁺¹¹ Ω/□ or less and a peeling electrification voltage of ±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 performance to dissipate static electricity generated by electrification at the time of peeling is inferior, so by making the surface resistivity sufficiently small, peeling that occurs with static electricity generated when the adherend peels off the adhesive layer The electrification voltage is reduced, and it is possible to suppress the influence on the electrical control circuit and the like of the adherend.

The gel fraction of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of the present invention (pressure-sensitive adhesive after crosslinking) is preferably 95 to 100%. Due to such a high gel fraction, the adhesive force does not become excessive at a low peeling speed, the elution of unpolymerized monomer or oligomer from the copolymer is reduced, and reworkability and high temperature/high humidity are reduced. 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 obtained by crosslinking the pressure-sensitive adhesive composition of the present invention on one side or both sides of a resin film. The surface protective film of the present invention is a surface protective film obtained by forming a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present invention on one surface of a resin film. Since the pressure-sensitive adhesive composition of the present invention contains the components (A) to (F) described above in a well-balanced manner, it has excellent antistatic performance, and at low peeling speeds and high peeling speeds, It has an excellent balance of adhesive strength, and also has excellent durability performance and rework performance (there is no transfer of contamination to the adherend after tracing with a ballpoint pen on the surface protective film through the adhesive layer). Become. Therefore, it can be preferably used as a surface protection film for a polarizing plate.

In the pressure-sensitive adhesive film and the surface protective 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) for protecting the pressure-sensitive adhesive layer.
In addition, the resin film is coated with a silicone-based or fluorine-based release agent or coating agent, an antifouling treatment with silica fine particles, or an antistatic agent on the surface opposite to the side on which the adhesive layer of the resin film is formed. An antistatic treatment such as kneading or kneading can be performed.
In addition, the release film is subjected to a release treatment with a silicone-based or fluorine-based release agent on the surface of the release layer which is to be joined with the adhesive surface.

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

<Production of acrylic copolymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube, and the air in the reactor 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 reactor. 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. Got 1. A part of the acrylic copolymer was collected and used as a sample for measuring an acid value described later.
[Examples 2 to 6 and Comparative Examples 1 to 3]
Acrylic copolymer solution 1 used in the above Example 1 except that the composition of each of the monomers was as described in (A), (B), (I) and (F-2) of Table 1. In the same manner as above, acrylic copolymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 3 were obtained.

<Production of adhesive composition and surface protection 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 was used. 1.5 parts by weight of (isocyanurate of hexamethylene diisocyanate compound) and 0.05 parts by weight of tris(2,4-pentanedionato)iron(III) were added and mixed by stirring to obtain the pressure-sensitive adhesive composition of Example 1. Got This adhesive composition is applied on a release film made of a polyethylene resin-coated polyethylene terephthalate (PET) film and then dried at 90° C. to remove the solvent, and the adhesive layer has a thickness of 25 μm. Got the sheet.
After that, an adhesive sheet was transferred to the surface opposite to the antistatic and antifouling surface of the polyethylene terephthalate (PET) film which was antistatic and antifouling processing on one surface, and the "antistatic and antifouling processing was performed. A surface protective film of Example 1 having a laminated constitution 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, in the same manner as the surface protective film of Example 1 described above, except that the compositions of the additives are as described in Table 2 (C) to (F) and (J), respectively. And the surface protection film of Comparative Examples 1-3 was obtained.

Tables 1 and 2 are an integrated table showing the compounding ratio of each component divided into two. In each case, the numerical value of the weight part obtained by taking the total of the (A) group as 100 parts by weight is enclosed in parentheses. Indicate. Table 3 shows the value of the ratio (E)/(D). Further, the compound names of the abbreviations of the 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., Takenate (registered trademark) D-140N, D-127N, and D-110N are trade names of Mitsui Chemicals, Inc. And Desmodur (registered trademark) N3400 is a trade name of Sumika Bayer Urethane Co., Ltd.
In Table 1, among the antistatic agents (F), the (F-2) acryloyl group-containing ionic compound copolymerized in the copolymer is different from the antistatic agent (F) added after the polymerization. It was 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 Table 6 and Table 7, the diisocyanate and the diol compound were mixed in a molar ratio of NCO/OH=16 and reacted at 120° C. for 3 hours, and thereafter, using a thin film evaporator under reduced pressure. Unreacted diisocyanate was removed to obtain the desired bifunctional isocyanate compound.

<Test method and evaluation>
The surface protection films in Examples 1 to 6 and Comparative Examples 1 to 3 were aged under an atmosphere of 23° C. and 50% RH for 7 days, and then the release film (a PET film coated with a silicone resin) was peeled off to give an adhesive property. The exposed surface of the agent layer was used as a surface resistivity measurement sample.
Further, the surface protective film showing the pressure-sensitive adhesive layer was 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 atmospheric pressure for 20 minutes. An autoclave-treated sample, which was left at room temperature for 12 hours, was used as a measurement sample for adhesive strength, peeling electrification voltage, reworkability and durability.

<Adhesive strength>
The measurement sample (having a surface protective film with a width of 25 mm attached to the surface of a polarizing plate) obtained above was used in a 180° direction using a tensile tester at a low peeling speed (0.3 m/min) and a high speed. Was peeled at a peeling speed (30 m/min), and the measured peel strength was taken as the adhesive strength.

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

<Peeling electrification voltage>
The voltage (charge voltage) generated when the polarizing plate was charged when the measurement sample obtained above was peeled by 180° at a pulling speed of 30 m/min was measured using high-precision electrostatic sensors SK-035, SK-200 (stock). (Manufactured by KEYENCE CORPORATION), and the maximum value of the measured values was taken as the peeling electrification voltage.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ballpoint pen (load 500 g, 3 reciprocations), peel the surface protective film from the polarizing plate, observe the surface of the polarizing plate, and contaminate the polarizing plate. I confirmed that there was no migration. The evaluation target criteria are "○" when there is no contamination transfer on the polarizing plate, "△" when at least a part of contamination transfer is confirmed along the trajectory traced by the ballpoint pen, and along the trajectory traced by the ballpoint pen. The case where the transfer of contamination was confirmed and the release of the adhesive from the adhesive surface was also confirmed was evaluated as “x”.

<Pot life>
Immediately after adding the additives (C) to (F) and (J), the viscosity η ₀ (initial viscosity) of the pressure-sensitive adhesive composition is measured, and the pressure-sensitive adhesive composition is sealed at 23° C. for 8 hours. The viscosity η ₁ (viscosity after 8 hours) of the pressure-sensitive adhesive composition after standing was measured. As an index of pot life, a value of η ₁ when η ₀ was set to 1.0, that is, a ratio of η ₁ /η ₀ was obtained. The evaluation target criterion is “◯” when the viscosity after 8 hours is less than 1.25 times the initial viscosity, “Δ” when it is 1.25 times or more and less than 1.50 times, 1.50 times or more, or The case where gelation occurred after standing 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 at room temperature and further left for 12 hours, and then the adhesive strength was measured and revealed by comparison with the initial adhesive strength. It was confirmed that there was no significant increase. The evaluation target criteria were evaluated as "O" when the adhesive strength after the test was 1.5 times or less of the initial adhesive strength, and "X" when it 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 value and n is a positive integer).

The surface protective films of Examples 1 to 6 have an adhesive force of 0.05 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min, and an adhesive force of 1 at a high peeling speed of 30 m/min. 0.0 N/25 mm or less, the surface resistivity is 9.0×10 ⁺¹¹ Ω/□ or less, the peeling electrification voltage is ±0 to 0.5 kV, and the surface protective film is placed on the surface of the adhesive layer via the adhesive layer. After being traced with a ballpoint pen, the adherend did not migrate to the adherend, had a long pot life, and was excellent in durability when left in an atmosphere of 60° C. and 90% RH for 250 hours.
That is, it has antistatic performance, has excellent balance of adhesive strength at low peeling speed and 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, since the pressure-sensitive adhesive composition does not contain an organotin compound, the safety is high.

The surface protective film of Comparative Example 1 does not contain (C) a bifunctional or higher isocyanate compound serving as a cross-linking agent, probably because of a low peeling speed of 0.3 m/min and a high peeling speed of 30 m/min. Was too large, surface resistivity and peeling electrification voltage were high, and reworkability and durability were poor.
The surface protective film of Comparative Example 2 has a high peeling electrification voltage, a short pot life, and poor durability, probably because the ratio of the (E) ketoenol tautomer compound to the crosslinking catalyst of the (D) metal chelate compound is small. Was there.
The surface protection film of Comparative Example 3 had a small proportion of the (E) keto-enol tautomer compound to the crosslinking catalyst of the (D) metal chelate compound, so that the pot life was too short and the crosslinking proceeded before coating. I couldn't work.
As described above, the surface protective films of Comparative Examples 1 to 3 have antistatic performance, have excellent balance of adhesive strength at low peeling speed and high peeling speed, and further have long pot life, durability and It was not possible to satisfy all required performances at the same time, which was excellent in reworkability.

Claims (2)

A surface protective film comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic copolymer, (F) an antistatic agent, and a crosslinking agent, on one side of a resin film,
The acrylic copolymer is 100 parts by weight of the acrylic copolymer,
(A) the total number of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18 of 50 to 98 parts by weight,
(B) 0.1 to 10 parts by weight of the total of at least one kind of copolymerizable monomer containing a hydroxyl group, (C) a carboxyl group-containing monomer as a copolymerizable monomer group, and a nitrogen-containing vinyl containing no hydroxyl group. An acrylic copolymer obtained by copolymerizing a monomer and at least one selected from the group of compounds consisting of polyalkylene glycol mono(meth)acrylic acid ester monomers,
The (A), the (B), and the (C) are contained in a proportion of 100 parts by weight in total.
The pressure-sensitive adhesive composition contains 0.05 to 5 parts by weight of an ionic compound having a melting point of 25 to 50° C. as the antistatic agent (F), based on 100 parts by weight of the acrylic copolymer, and the crosslinking. As an agent, 0.1 to 10 parts by weight of a bifunctional or higher functional isocyanate compound, 0.001 to 0.5 parts by weight of a (D) metal chelate compound crosslinking catalyst, and (E) 0.1 of a ketoenol tautomer compound. ~200 parts by weight,
The crosslinking catalyst of the metal chelate compound (D) is at least one selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound,
The surface protection film is characterized in that a weight part ratio of (E)/(D) as a ratio of (E) to (D) is 80 to 300. The surface protective film according to claim 1, which is used as a surface protective film for a polarizing plate.