JP2018184609A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film which has antistatic performance, is excellent in a balance in adhesive force at a low peeling speed and a high peeling speed, has a long pot life, and is excellent in durability and reworkability.SOLUTION: An acrylic copolymer is an acrylic copolymer formed by copolymerization of (B) at least one of a copolymerizable monomer containing a hydroxyl group as a monomer group copolymerizable with (A) at least one of a (meth)acrylate monomer having an alkyl group having 4 to 18 carbon atoms, where the adhesive composition contains (C) 0.1-10 pts.wt. of a bi- or higher isocyanate compound as a crosslinking agent, (D) 0.001-0.5 pts.wt. of a crosslinking catalyst of a metal chelate compound, (E) 0.1-200 pts.wt. of a keto-enol tautomeric compound, with respect to 100 pts.wt. of the acrylic copolymer, and a pts.wt. ratio of (E)/(D) is 80-300 as a ratio of (E) to (D).SELECTED DRAWING: None

Description

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

  Copolymers that are alkyl (meth) acrylate as a main component and copolymerized with an acrylic monomer having a hydroxyl group, a carboxyl group, etc. as a functional group, because the adhesive for optical use is excellent in transparency. An acrylic pressure-sensitive adhesive made of is preferably used. Furthermore, what adjusted various physical properties, such as the adhesive force of an adhesive, is needed. In particular, the pressure-sensitive adhesive for the surface protective film is suitable for bonding the surface protective film with an automatic bonding apparatus so that it can be adapted to the production process of factory production. There is a demand for an adhesive having an excellent balance of adhesive strength. Furthermore, in addition to the balance of adhesive strength, an adhesive having a long pot life and excellent durability, reworkability, and antistatic properties is required.

  Such physical properties of the pressure-sensitive adhesive are determined by using an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, or the like 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. Thus, a cross-linking reaction is performed to adjust the adhesive force and cohesive force.

Conventionally, an isocyanate-based crosslinking agent has been widely used as a crosslinking agent for acrylic pressure-sensitive adhesives. Further, in the crosslinking reaction using an isocyanate-based crosslinking agent, a metal chelate is often used as a catalyst for promoting the crosslinking reaction.
In general, dibutyltin dilaurate, which is an organotin compound, has been used as a catalyst for the crosslinking reaction because of its excellent reaction rate of the crosslinking reaction. However, the dibutyltin compound exhibits harmful toxicity. It is avoided to use.
For this reason, there is a need for an inexpensive cross-linking catalyst that is used in combination with an isocyanate-based cross-linking agent and that is an inexpensive alternative to the dibutyl tin compound and that has an excellent reaction rate of the cross-linking reaction. It was.

  Under these circumstances, Patent Document 1 discloses that as a crosslinking catalyst used in combination with an isocyanate-based crosslinking agent, iron chelate is preferable among metal chelates, and tris (acetylacetonate) iron is particularly preferable because of its excellent catalytic activity. Yes.

By the way, the acrylic pressure-sensitive adhesive composition containing a crosslinking catalyst gradually undergoes a crosslinking reaction even when left at room temperature. Therefore, in the industrial production of pressure-sensitive adhesives, in order to stop the crosslinking reaction until the time when the crosslinking reaction is started after blending the raw materials of the pressure-sensitive adhesive composition, a crosslinking catalyst and a reaction retarder are generally used. Are used together.
Regarding the combined use of this cross-linking catalyst and reaction retarder, Patent Document 2 discloses a polyurethane production method comprising a mixture of at least one metal acetylacetonate and acetylacetone, and the metal acetylacetonate and the acetylacetone. It is disclosed to use a reaction urethane mixture containing a catalyst system with 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 amount of metal compound (crosslinking catalyst) added to a 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 addition amount of a crosslinking retarder. Patent Document 1 discloses a method of using a reaction retarder, a method of adding a viscosity increase inhibitor, and a functional group such as a blocked isocyanate as a method of suppressing the rate of increase in viscosity after a crosslinking agent is added to the pressure-sensitive adhesive composition. A method of using a crosslinking agent having a blocked group is mentioned, but there is no specific explanation.

Further, Patent Document 2 discloses a metal having excellent stability and good catalytic activity that does not cause early curing even when a metal acetylacetonate catalyst such as iron or copper that is highly active at low temperatures is used. A polyurethane production method 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 blending ratio is applied to the production process of the acrylic pressure-sensitive adhesive, the crosslinking reaction is temporarily performed. The stop could not be made.

  The present invention has been made in view of the above circumstances, and without using an organic tin compound, has an antistatic performance, and has a low peel rate and a high peel rate, and has a good balance of adhesive strength. Furthermore, it is an object to provide a pressure-sensitive 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-described problems, the present invention includes (A) at least one (meth) acrylic acid ester monomer having an alkyl group with C4 to C18 carbon atoms and (B) a hydroxyl group as a copolymerizable monomer group. (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 100 parts by weight of the copolymer with the copolymerizable monomer. .5 parts by weight, (E) 0.1 to 200 parts by weight of a ketoenol tautomer compound, and (F) 0.05 to 5 parts by weight of an ionic compound having a melting point of 25 to 50 ° C. as an antistatic agent. The pressure-sensitive adhesive composition is characterized in that the weight ratio of (E) / (D) is 70 to 700.

  Further, the copolymerizable monomer (B) containing a hydroxyl group may be 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) It is preferably at least one selected from the group consisting of acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide.

The (C) bifunctional or higher functional isocyanate compound is preferably a compound produced by reacting a diisocyanate compound and a diol compound with an acyclic aliphatic isocyanate compound. The diisocyanate compound is an aliphatic diisocyanate, and is preferably composed of one selected from the 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 compound group consisting of 2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, polypropylene glycol It is preferable that it consists of 1 type selected from the inside.
In addition, 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, hexamethylene diisocyanate compound burette, isophorone diisocyanate compound burette, tolylene diisocyanate compound isocyanurate, xylylene diisocyanate compound isocyanurate, hydrogenated xylylene diisocyanate compound isocyanurate, tolylene diisocyanate Compound adduct, xylylene diisocyanate compound adduct, hydrogenated xylile Selected from a compound group consisting of adducts of a diisocyanate compound is preferably at least one or more.

  Moreover, it is preferable that the crosslinking catalyst in the said adhesive composition is at least 1 or more types selected from the group which consists of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound.

  Further, the antistatic agent (F) is an ionic compound having a melting point of 25 to 50 ° C., contained in an amount of 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 is copolymerized in the copolymer in an amount of 0.1 to 5.0% by weight.

  The copolymer includes, as other copolymerizable monomers, a carboxyl group-containing monomer, a nitrogen-containing vinyl monomer that does not contain a hydroxyl group, and a polyalkylene glycol mono (meth) acrylate monomer, and / or Alternatively, it is preferable to include a polyether siloxane compound or other conventional antioxidants as additives.

  The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has an adhesive strength 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 is 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 voltage of ± 0 to 0.5 kV.

  Moreover, this invention provides the adhesive film formed by forming the adhesive layer formed by bridge | crosslinking the said adhesive composition on the single side | surface or both surfaces of a resin film.

  Further, the present invention is a surface protective film formed by forming a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one side of a resin film, and the surface of the surface protective film is interposed through the pressure-sensitive adhesive layer. Provided is a surface protective film characterized in that there is no contamination transfer on an adherend after tracing with a ballpoint pen.

  Moreover, the surface protection film of this invention can be used as a use of the surface protection film of a polarizing plate.

  Moreover, it is preferable that the surface protection film of this invention is antistatic and antifouling-treated on the surface opposite to the side in which the said adhesive layer of the said resin film was formed.

  According to the present invention, all the performance 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 an organic tin compound, and Excellent antistatic performance was obtained, and it was possible to prevent the occurrence 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.

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

The copolymer may contain at least one or more of a carboxyl group-containing monomer, a nitrogen-containing vinyl monomer that does not contain a hydroxyl group, and a polyalkylene glycol mono (meth) acrylate monomer as other copolymerizable monomers.
The antistatic agent (F) is an ionic compound having a melting point of 25 to 50 ° C., 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 The acryloyl group-containing ionic compound copolymerized in the copolymer by 0.1 to 5.0% by weight.
In addition, the pressure-sensitive adhesive composition of the present invention can contain a polyether siloxane compound and other conventional antioxidants as additives.

(A) As a (meth) acrylic acid ester monomer having a C4-C18 alkyl group, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 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, etc. Can be mentioned.
It is preferable that (A) the alkyl group has (C) C4-C18 (meth) acrylic acid ester monomer in an amount of 50 to 98 parts by weight with respect to 100 parts by weight of the copolymer.

(B) As a copolymerizable monomer containing a hydroxyl group, (B) As a copolymerizable monomer containing a hydroxyl group, 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 (meta It is preferably at least one selected from the group consisting of acrylamide and N-hydroxyethyl (meth) acrylamide.
It is preferable that 0.1 to 10 parts by weight of the copolymerizable monomer containing the hydroxyl group (B) is contained with respect to 100 parts by weight of the copolymer.

  The copolymer may contain at least one or more of a carboxyl group-containing monomer, a nitrogen-containing vinyl monomer not containing a hydroxyl group, and a polyalkylene glycol mono (meth) acrylate 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 preferable that it is at least 1 type selected from the compound group which consists of 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.
When the copolymer includes a carboxyl group-containing monomer as another copolymerizable monomer group, the carboxyl group-containing monomer is added in an amount of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the copolymer. It is preferable to contain by a ratio. The copolymer may not contain the carboxyl group-containing monomer.

The polyalkylene glycol mono (meth) acrylate monomer may be a compound in which one hydroxyl group is esterified as a (meth) acrylate 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 main copolymer. The other hydroxyl group may be OH or may be an alkyl ether such as methyl ether or ethyl ether, or a saturated carboxylic acid ester such as acetate.
Examples of the alkylene group of 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 copolymer includes: 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 included in the molecular structure of the polyalkylene glycol mono (meth) acrylate monomer.

The polyalkylene glycol mono (meth) acrylate 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; methoxypolyethylene glycol- (meth) acrylate, methoxypolypropylene 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; ethoxy polyethylene glycol- (meth) acrylate, ethoxy polypropylene 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 - such as (meth) acrylate.
The polyalkylene glycol mono (meth) acrylate 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) acrylate monomer.

  Examples of the nitrogen-containing vinyl monomer not containing a 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-vinyl pyrrolidone, methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl Cyclic nitrogen vinyl compounds having an N-vinyl substituted heterocyclic structure such as pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-vinyllaurylactam; N- ( (Meth) acryloylmorpholine, N- (meth) acryloylpiperazine, N- (meth) acryloylaziridine, N- (meth) acryloylazetidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylpiperidine, N- (meth) ) Acryloyl azepan, N- (meth) a Cyclic nitrogen vinyl compounds having an N- (meth) acryloyl-substituted heterocyclic structure such as liloyl azocan; heterocyclic rings having nitrogen atoms and ethylenically unsaturated bonds in the ring, such as N-cyclohexylmaleimide and N-phenylmaleimide Cyclic nitrogen vinyl compounds having the formula structure: (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nt-butyl (meth) acrylamide, etc. ) 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) acrylate Dialkyl-substituted (meth) acrylamides such as luamide, N-methyl-N-propyl (meth) acrylamide, N-methyl-N-isopropyl (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 (me ) 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 and N-methyl-N-isopropylaminopropyl (meth) acrylamide; N-vinylformamide, N-vinylacetate N-vinylcarboxylic acid amides such as N-vinyl-N-methylacetamide; N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide (Meth) acrylamides such as N, N-methylenebis (meth) acrylamide; Unsaturated carboxylic acid nitriles such as (meth) acrylonitrile;

  It is preferable that the nitrogen-containing vinyl monomer which does not contain the said hydroxyl group is contained in the ratio of 0-20 weight part with respect to 100 weight part of the said copolymers. The copolymer may not contain a nitrogen-containing vinyl monomer that does not contain the hydroxyl group.

(C) The bifunctional or higher functional isocyanate compound may be at least one selected from polyisocyanate compounds having at least two or more isocyanate (NCO) groups in one molecule. Polyisocyanate compounds are classified into aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, and alicyclic isocyanates, and 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). And aromatic isocyanate compounds such as hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylene diisocyanate (TOID), and tolylene diisocyanate (TDI).
As trifunctional or higher functional isocyanate compounds, trifunctional or higher valences of bifunctional isocyanate compounds (compounds having two NCO groups in one molecule) such as burette modified products and isocyanurate modified products, trimethylolpropane (TMP) and glycerin are used. And adduct bodies (polyol-modified bodies) with polyols (compounds having at least 3 or more OH groups in one molecule).
(C) It is also possible to use only the (C-1) trifunctional isocyanate compound or the (C-2) bifunctional isocyanate compound as the bifunctional or higher functional isocyanate compound. Moreover, it is also possible to use together (C-1) trifunctional isocyanate compound and (C-2) bifunctional isocyanate compound.

Furthermore, 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 selected from the group of (C-1-1) first aliphatic isocyanate compounds, consisting of a burette of hexamethylene diisocyanate compound and a burette of isophorone diisocyanate compound, and a tolylene diisocyanate compound Isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, tolylene diisocyanate Selected from the group (C-1-2) second aromatic isocyanate compound group consisting of an adduct of a compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound, It is preferable to contain at least one or more. It is preferable to use together the (C-1-1) first aliphatic isocyanate compound group and the (C-1-2) second aromatic isocyanate compound group. In the present invention, as the (C-1) trifunctional isocyanate compound, (C-1-1) at least one selected from the first aliphatic isocyanate compound group, and (C-1-2) ) By using in combination with at least one selected from the group of the second aromatic isocyanate compounds, the balance of the adhesive force in the low-speed peeling region and the high-speed peeling region can be further improved.
The (C-1) trifunctional isocyanate compound may be at least one selected from the group (C-1-1) of the first aliphatic isocyanate compound group, and the (C-1-2). ) Including at least one selected from the group of second aromatic isocyanate compounds, and 0.5 to 5.0 parts by weight in total with respect to 100 parts by weight of the copolymer It is preferable that Also, (C-1-1) at least one selected from the first aliphatic isocyanate compound group and (C-1-2) the second aromatic isocyanate compound group. The mixing ratio with at least one or more selected from (C-1-1) :( C-1-2) is within a range of 10%: 90% to 90%: 10% by weight. Is preferred.

Furthermore, the (C-2) bifunctional isocyanate compound used in the present invention is preferably a compound produced by reacting a diisocyanate compound and a diol compound with an acyclic aliphatic isocyanate compound.
For example, the diisocyanate compound represented by the general formula “O═C═N—X—N═C═O” (where X is a divalent group), the general formula “HO—Y—OH” (where Y is a divalent group). ) Represents a compound represented by the following general formula Z, for example, as a compound produced by reacting a diisocyanate compound with a diol compound.

[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 (an unreacted diisocyanate compound with respect to the diol compound) may be included, 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 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, polypropylene glycol It is preferable that it consists of 1 type or 2 types or more selected.

  The weight ratio (C-1 / C-2) between the (C-1) trifunctional isocyanate compound and the (C-2) bifunctional isocyanate compound is preferably 1 to 90. 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 crosslinking catalyst for the metal chelate compound may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent when a polyisocyanate compound is used as the crosslinking agent. Examples include amine compounds such as tertiary amines, metal chelate compounds, organotin compounds, organolead compounds, and organozinc compounds such as organozinc compounds. In the present invention, a metal chelate compound is used as a crosslinking catalyst.

The metal chelate compound is a compound in which one or more multidentate 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 bonded to the metal atom M. For example, when the 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, the m Ls may be the same ligand or different ligands. When n is 2 or more, the 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.
As the polydentate ligand L, β-ketoester such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone (also known as 2,4-pentanedione), Examples include β-diketones such as 2,4-hexanedione and benzoylacetone. These are ketoenol tautomeric compounds, and the polydentate ligand L may be an enolate (for example, acetylacetonate) in which enol is deprotonated.
As monodentate ligand X, acyloxy such as halogen atom 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 Group, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, alkoxy group such as butoxy group, and the like.

  Specific examples of the metal chelate compound include tris (2,4-pentanedionato) iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris Acetylacetonate, zirconium tetrakisacetylacetonate, tris (2,4-hexanedionate) iron (III), bis (2,4-hexanedionate) zinc, tris (2,4-hexanedionate) titanium, tris (2,4-Hexanedionato) aluminum, tetrakis (2,4-hexanedionato) zirconium and the like can be mentioned.

Examples of the organic tin compound include dialkyl tin oxide, fatty acid salt of dialkyl tin, fatty acid salt of stannous and the like. Conventionally, many dibutyltin compounds have been used. Recently, however, the problem of toxicity of organic tin compounds has been pointed out, and in particular, tributyltin (TBT) contained in dibutyltin compounds is also a concern as an endocrine disrupting substance. From the viewpoint of safety, long-chain alkyl tin compounds such as dioctyl tin compounds are preferred. Specific examples of the organic tin compound include dioctyl tin oxide and dioctyl tin dilaurate. Temporarily, Sn compounds can also be used, but in the future, in view of the demand for the use of safer substances, such as Al, Ti, Fe, etc., which are safer than Sn. 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.
(D) It is preferable that 0.001-0.5 weight part of the crosslinking catalyst of a metal chelate compound is contained with respect to 100 weight part of a copolymer.

(E) Ketoenol tautomeric compounds include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone, 2,4-hexanedione And β-diketones such as benzoylacetone. In the pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, by blocking the isocyanate group of the cross-linking agent, excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after blending of the cross-linking agent are suppressed. The pot life of the pressure-sensitive adhesive composition can be extended.
(E) It is preferable that 0.1-200 weight part of keto enol tautomer compound is contained with respect to 100 weight part of a copolymer.

  The (E) ketoenol tautomer compound has an effect of suppressing crosslinking, as opposed to the crosslinking catalyst of the (D) metal chelate compound, and therefore the (E) ketoenol tautomer compound with respect to the crosslinking 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 to improve the storage stability, the weight ratio (E) / (D) of the crosslinking catalyst of (E) ketoenol tautomer compound / (D) metal chelate compound 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.

(F) As an antistatic agent, the antistatic agent contained in an adhesive composition and the antistatic agent copolymerized in the said copolymer are mentioned. It is preferable that 0.05-5.0 weight part of (F) antistatic agent is contained with respect to 100 weight part of a copolymer.
(F) The 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 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 an acrylic copolymer.

(F-1) An 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 pyrazolium cation. Nitrogen-containing onium cations such as pyrrolidinium cation and ammonium cation, phosphonium cation and sulfonium cation, and the anion is hexafluorophosphate (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), alkylbenzene sulfone. Acid salt (RC ₆ H ₄ SO ₃ ⁻ ), perchlorate (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), bis (fluorosulfonyl) imide salt (FSI), bis (trifluoromethanesulfonyl) ) Imide salt (TFSI), trifluoromethanesulfonate (T ) Inorganic or compound which is an organic anions such. It is preferably solid at room temperature (for example, 25 ° C.), and a compound having a melting point of 25 to 50 ° C. can be obtained by selecting the chain length of the alkyl group, the position and number of 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 2-6 position may be substituted or unsubstituted), or 1, Quaternary imidazolium cations such as 3-dialkylimidazolium (the carbon atoms at 2, 4, and 5 positions may be substituted or unsubstituted), quaternary ammonium cations such as tetraalkylammonium, and the like. .
(F-1) It is preferable that 0.05-5 weight part of the ionic compound whose melting | fusing point is 25-50 degreeC is contained with respect to 100 weight part of a copolymer.

(F-2) The acryloyl group-containing ionic compound is an ionic compound having a cation and an anion, and the cation is (meth) acryloyloxyalkyltrialkylammonium [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, and the anion is hexafluorophosphate (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), Organic sulfonate (RSO ₃ ⁻ ), perchlorate (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), and F-containing imide salts (R ^F ₂ N ⁻ ) 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. 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 salts [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ].
(F-2) The acryloyl group-containing ionic compound is preferably copolymerized in an amount of 0.1 to 5.0% by weight in the copolymer.

(F) Although it does not specifically limit as a specific example of an antistatic agent, (F-1) As a specific example of an ionic compound whose melting | fusing point is 25-50 degreeC, 1-octyl pyridinium 6 hexafluoride phosphorus Acid salt, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecyl Examples include pyridinium dodecylbenzene sulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, and quaternary ammonium salts of trifluoromethanesulfonic acid. Moreover, as a specific example 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 ^-, 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 ⁻ , where Q = H or CH ₃ ], dimethylaminomethyl methacrylate bis (fluorosulfonyl) imidomethyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ═CH _2. (FSO ₂ ) ₂ N ⁻ , , 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, and in addition to a normal siloxane unit [—SiR ¹ ₂ —O—], a siloxane unit having a polyether group [—SiR ¹ (R ² O having _{^{(R 3 O) n R 4}} ) -O- ]. Here, R ¹ is one or more alkyl groups or aryl groups, R ² and R ³ are one or more alkylene groups, and R ⁴ is one or more alkyl groups or acyl groups. Etc. (terminal group). Examples of the polyether group include polyoxyalkylene groups 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. Moreover, it is preferable that 0.01-1.0 weight part of said polyether modified siloxane compounds are contained with respect to 100 weight part of a copolymer. More preferably, it is 0.1-0.5 weight part.
HLB is a hydrophilic / lipophilic balance (hydrophilic / lipophilic ratio) defined in, for example, JIS K3211 (surfactant term).
The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group to 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 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. When the pressure-sensitive adhesive composition does not contain a polyether-modified siloxane compound, the cost becomes lower.

Examples of the antioxidant include hindered phenol antioxidants, polyphenol compounds, and tocopherol compounds. Of these, tocopherol compounds are preferred. Tocopherol compounds are generally vitamin E and are naturally derived chemicals. For this reason, there are few adverse effects on the human body, the handling safety is high, and the environment is also friendly. Moreover, since it is oil-soluble and is liquid at normal temperature, it is excellent in compatibility with the pressure-sensitive adhesive composition and in 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.
As the tocopherol compound used in the present invention, it is blended and used in the pressure-sensitive adhesive composition (it is not metabolized like in the human body), so the ferrule hydroxyl group of tocopherol is not changed to an ester, etc. A compound having a hydroxyl group is preferred. For example, tocopherol and tocotrienol are mentioned. It is known that tocopherol and tocotrienol have a distinction such as a natural type compound (d-form), a non-natural type compound (1-form), and a racemic form (dl-form) which is an equivalent mixture thereof. ing. Natural type compounds (d-form) and racemates (dl-form) are preferred because some 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, 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 And at least one selected from the group of compounds consisting of -δ-tocotrienol. Two or more tocopherol compounds may be used in combination. What is called “mixed tocopherol” as a food additive is a mixture mainly composed of d-α-tocopherol, d-β-tocopherol, d-γ-tocopherol and d-δ-tocopherol, 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 adhesive composition of this invention contains a tocopherol type compound, it is preferable to contain 0.01-5 weight part of tocopherol type compounds with respect to 100 weight part of a copolymer.

  In addition, copolymerizable (meth) acrylic monomers, (meth) acrylamide monomers, dialkyl-substituted acrylamide monomers, surfactants, curing catalysts, plasticizers, fillers, cure retarders, processing, which contain alkylene oxide as other components Known additives such as auxiliaries, antioxidants and antioxidants can be appropriately blended. 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 includes (A) at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 as a monomer group copolymerizable with ( B) It can be synthesized by copolymerizing 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 main copolymer used in the pressure-sensitive adhesive composition of the present invention is (A) an alkyl group having a carbon number of C4. ~ C18 (meth) acrylic acid ester monomer, (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 copolymerization.
The copolymer may contain at least one or more of a carboxyl group-containing monomer, a nitrogen-containing vinyl monomer that does not contain a hydroxyl group, and a polyalkylene glycol mono (meth) acrylate monomer as other copolymerizable monomer groups. it can.
The pressure-sensitive adhesive composition of the present invention comprises (C) a bifunctional or higher isocyanate compound, (D) a cross-linking catalyst of a metal chelate compound, (E) a ketoenol tautomer compound, and (F) a charge. 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 optional additive as appropriate. In addition, when (F-2) an acryloyl group-containing ionic compound is polymerized in the copolymer of the main agent, (F-1) an antistatic agent for the copolymer (F-1) has a melting point of 25 to 25. An ionic compound at 50 ° C. may be further added or may not be added.

The copolymer is preferably an acrylic polymer, and preferably contains 50 to 100% by weight of an acrylic monomer such as a (meth) acrylic acid ester monomer, (meth) acrylic acid, or (meth) acrylamide.
Moreover, it is preferable that the acid value of the said copolymer is 0.01-8.0. As a result, the contamination property can be improved and the performance of preventing the occurrence of adhesive residue can be improved.
Here, the “acid value” is one of indices indicating the acid content, and is expressed in mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

  The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has an adhesive strength of 0.05 to 0.1 N / 25 mm at a low 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. Thereby, the performance with little change in the adhesive force depending on the peeling speed can be obtained, and it is possible to peel quickly even by high speed peeling. In addition, when the surface protective film is once peeled off for re-sticking, excessive force is not required and it is easy to peel off from the adherend.

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 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 of releasing static electricity generated by electrification at the time of peeling is inferior. Therefore, peeling caused by static electricity generated when the adherend peels off the adhesive layer by sufficiently reducing the surface resistivity. The charged voltage is reduced, and it is possible to suppress the influence on the electric control circuit and the like of the adherend.

  The gel fraction of the pressure-sensitive adhesive layer (cross-linked pressure-sensitive adhesive) obtained by crosslinking the pressure-sensitive adhesive composition of the present invention is preferably 95 to 100%. Because of the high gel fraction, the adhesive force does not become excessive at a low peeling speed, and the elution of unpolymerized monomers or oligomers from the copolymer is reduced, resulting in reworkability and high temperature / high humidity. 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. Moreover, the surface protective film of this invention is a surface protective film formed by forming the adhesive layer formed by bridge | crosslinking the adhesive composition of this invention on the single side | surface of a resin film. In the pressure-sensitive adhesive composition of the present invention, since the components (A) to (F) are blended in a balanced manner, it has excellent antistatic performance, and at a low peeling speed and a high peeling speed, Excellent balance of adhesive strength, and also excellent durability and rework performance (no contamination transfer on the adherend after tracing the surface protection film with a ballpoint pen through the adhesive layer) Become. For this reason, it can be used suitably as a use of the surface protection film of 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 a substrate for a resin film or a release film (separator) that protects the pressure-sensitive adhesive layer.
Also, on the resin film, on the side opposite to the side on which the adhesive layer of the resin film is formed, antifouling treatment with a silicone-based or fluorine-based release agent or coating agent, silica fine particles, etc., application of an antistatic agent Antistatic treatment by kneading or the like can be performed.
Further, the release film is subjected to a release treatment with a silicone-based or fluorine-based release agent or the like on the surface of the pressure-sensitive adhesive layer that is to be combined with the pressure-sensitive adhesive surface.

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

<Manufacture 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. Thereafter, 100 parts by weight of 2-ethylhexyl acrylate and 3.5 parts by weight of 8-hydroxyoctyl acrylate were added to the reactor. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was dropped over 2 hours and reacted at 65 ° C. for 6 hours, and the acrylic copolymer solution used in Example 1 having a weight average molecular weight of 500,000 was used. 1 was obtained. 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]
Acrylic copolymer solution 1 used in Example 1 above, except that the monomer composition is 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 pressure-sensitive 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 0.05 parts by weight of tris (2,4-pentanedionato) iron (III) were added to the mixture and stirred to mix the pressure-sensitive adhesive composition of Example 1. Got. After applying this adhesive composition on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, the solvent is removed by drying at 90 ° C., and the adhesive layer has a thickness of 25 μm A sheet was obtained.
Then, the adhesive sheet was transferred to the opposite side of the antistatic and antifouling surface of the polyethylene terephthalate (PET) film that had been antistatic and antifouling treated on one side. A surface protective film of Example 1 having a laminated structure of “PET film / adhesive layer / release film (silicone resin-coated PET film)” 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 except that the compositions of the additives are as described in (C) to (F) and (J) of Table 2, respectively. And the surface protection film of Comparative Examples 1-3 was obtained.

Tables 1 and 2 are obtained by dividing the integrated table showing the blending ratio of each component into two, and in both cases, the numerical values of parts by weight calculated with the total of group (A) as 100 parts by weight are enclosed in parentheses. It shows with. Further, Table 3 shows values of the ratio (E) / (D). In addition, Table 4 and Table 5 show the names of the abbreviations of each component used in Tables 1 and 2. Coronate (registered trademark) HX, HL and L are trade names of Nippon Polyurethane Industry Co., Ltd., and Takenate (registered trade marks) D-140N, D-127N and D-110N are trade names of Mitsui Chemicals, Inc. Desmodule (registered trademark) N3400 is a trade name of Sumika Bayer Urethane Co., Ltd.
In Table 1, the (F-2) acryloyl group-containing ionic compound copolymerized in the copolymer among the (F) antistatic agent is added separately from the (F) antistatic agent added after the polymerization. It 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, reacted at 120 ° C. for 3 hours, and then under reduced pressure using a thin film evaporator. Unreacted diisocyanate was removed to obtain the desired bifunctional isocyanate compound.

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

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

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

<Peeling voltage>
When the measurement sample obtained above is peeled 180 ° at a tensile speed of 30 m / min, the voltage (charge voltage) generated by charging the polarizing plate is measured with high-precision electrostatic sensors SK-035 and SK-200 (stocks). (Manufactured by Keyence Co., Ltd.), and the maximum value of the measured value was defined as the peeling voltage.

<Reworkability>
After the surface protective film of the measurement sample obtained above was traced with a ballpoint pen (load 500 g, 3 reciprocations), the surface protective film was peeled off from the polarizing plate, the surface of the polarizing plate was observed, and the polarizing plate was contaminated. Confirmed that there was no migration. Evaluation target criteria are “O” when there is no contamination transfer on the polarizing plate, “△” when contamination transfer is confirmed at least partially along the trace traced with the ballpoint pen, and along the trace traced with the ballpoint pen. The case where contamination transfer was confirmed and the release of the adhesive was also confirmed from the adhesive surface was evaluated as “x”.

<Pot life>
The viscosity η ₀ (initial viscosity) of the pressure-sensitive adhesive composition immediately after the additives (C) to (F) and (J) were blended 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 allowed 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. Evaluation target criteria are “◯” when the viscosity after 8 hours is less than 1.25 times the initial viscosity, “△” when the viscosity 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 allowed to stand in an atmosphere of 60 ° C. and 90% RH for 250 hours, then taken out to room temperature, and further allowed to stand for 12 hours. Then, the adhesive strength was measured and clearly compared with the initial adhesive strength. It was confirmed that there was no significant increase. As the evaluation target criteria, a case where the adhesive strength after the test was 1.5 times or less of the initial adhesive strength was evaluated as “◯”, and a case where the adhesive strength exceeded 1.5 times was evaluated as “X”.

Table 8 shows the evaluation results. The surface resistivity was expressed by a system in which “m × 10 ^{+ n} ” is “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 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. 0.0 N / 25 mm or less, surface resistivity is 9.0 × 10 ⁺¹¹ Ω / □ or less, peeling voltage is ± 0 to 0.5 kV, and the surface protection film is covered with an adhesive layer. After tracing with a ballpoint pen, the adherend did not migrate and 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 a good balance of adhesive strength at a low peeling speed, and a high peeling speed, and has a long pot life and excellent durability and reworkability.
Moreover, according to the surface protection film of Examples 1-6, since an organic tin compound is not contained in an adhesive composition, safety | security is high.

The surface protective film of Comparative Example 1 does not contain (C) a bifunctional or higher isocyanate compound that serves as a cross-linking agent. Adhesive strength at a low release rate of 0.3 m / min and a high release rate of 30 m / min Was too large, the surface resistivity and the stripping voltage were high, and the reworkability and durability were poor.
The surface protective film of Comparative Example 2 has a high stripping voltage, a short pot life, and a poor durability because the ratio of the (E) ketoenol tautomer compound to the crosslinking catalyst of the (D) metal chelate compound is small. It was.
Since the ratio of the (E) keto enol tautomer compound to the crosslinking catalyst of the (D) metal chelate compound is small, the pot life of the surface protective film of Comparative Example 3 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 a low adhesion rate at a low peeling speed, and a high peeling speed, and have a long pot life, durability and It was not possible to satisfy all the required performances of excellent reworkability at the same time.

Claims (3)

A surface protective film formed by forming, on one side of a resin film, an adhesive layer formed by crosslinking an adhesive composition containing an acrylic copolymer, (F) an antistatic agent, and (C) a crosslinking agent. There,
The acrylic copolymer can be copolymerized with (A) at least one (meth) acrylic acid ester monomer having an alkyl group with C4 to C18 carbon atoms and (B) a hydroxyl group as a copolymerizable monomer group. An acrylic copolymer copolymerized with at least one kind of monomer,
The pressure-sensitive adhesive composition is 0.1 to 10 parts by weight of a bifunctional or higher functional isocyanate compound as the (C) crosslinking agent with respect to 100 parts by weight of the acrylic copolymer, and (D) a metal chelate compound is crosslinked. Containing 0.001 to 0.5 parts by weight of the catalyst and 0.1 to 200 parts by weight of the (E) ketoenol tautomer compound,
50 parts of isooctyl (meth) acrylate or 2-ethylhexyl (meth) acrylate, out of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having (A) alkyl group having C4 to C18 carbon atoms. It is contained in a proportion of parts by weight or more,
(D) the crosslinking catalyst of the metal chelate compound is at least one selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound,
(E) / (D) The weight part ratio of (E) / (D) is 80-300 as a ratio of said (E) and said (D), The surface protection film characterized by the above-mentioned. 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) with respect to 100 parts by weight of the acrylic copolymer. Containing
The copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate. At least one selected from the group consisting of N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide,
The acrylic copolymer includes, as other copolymerizable monomers, a carboxyl group-containing monomer, a nitrogen-containing vinyl monomer not containing a hydroxyl group, and at least one polyalkylene glycol mono (meth) acrylate monomer; 2. The surface protective film according to claim 1, wherein the pressure-sensitive adhesive composition contains at least one selected from the group consisting of a polyether siloxane compound and an antioxidant.   The surface protective film of Claim 1 or 2 used as a use of the surface protective film of a polarizing plate.