KR20170031016A - Surface-protective film for polarizing plate - Google Patents

Abstract

The present invention provides a surface-protective film for a polarizing plate which has excellent adhesion balance in a low peeling speed and a high peeling speed; a capability of satisfying sticking for the polarizing plate despite of its small adhesive capabilities; an excellent durability, reworkability, and performance of preventing static change. The surface-protective film for a polarizing plate comprises: an adhesive layer formed on a resin film by cross-linking an acryl-based polymer; a cross linking agent; and an adhesive composition containing an anti-static agent. The acryl-based polymer comprises: (A) a (meta) acrylic ester monomer having an alkyl carbon number of 4-14; (B) a copolymerizable monomer containing a hydroxyl group; and (C) a copolymer formed by copolymerizing a copolymerizable monomer containing a carboxylic group. The weight of the surface-protective film for the polarizing plate affixed to a polarizing plate is 500 g, and the surface-protective film does not deviate in a shear holding power test for the polarizing plate after being left along for 24 hours at 23C.

Description

SURFACE-PROTECTIVE FILM FOR POLARIZING PLATE

The present invention relates to a surface protective film for a polarizing plate. More particularly, the present invention relates to a surface protective agent for a polarizing plate which has excellent balance of adhesive force at a low speed peeling speed and a high speed peeling speed and has excellent adhesion to a polarizing plate despite small adhesive force and excellent durability, Lt; / RTI >

BACKGROUND ART [0002] Conventionally, in a manufacturing process of an optical member such as a polarizing plate and a retarder, which constitute a liquid crystal display, a surface protective film for temporarily protecting the surface of an optical member is attached. Such a surface protective film is used only for the process of manufacturing the optical member, and is peeled off from the optical member at the time of mounting the optical member on the liquid crystal display. Since the surface protective film for protecting the surface of such an optical member is used only in the manufacturing process, it is sometimes called a process film in general.

As described above, the surface protective film used in the process of manufacturing the optical member is formed by forming a pressure-sensitive adhesive layer on one side of a polyethylene terephthalate (PET) resin film having optical transparency, Is peeled off from the surface of the pressure-sensitive adhesive layer.

In addition, since optical members such as a polarizing plate and a retardation plate are subjected to product inspection accompanied by optical evaluation such as display ability, color, contrast, and foreign substance incorporation of the liquid crystal display panel in a state where the surface protective film is stuck, It is required that the pressure-sensitive adhesive layer should not have bubbles or foreign matter attached thereto.

In recent years, when the surface protective film is peeled off from optical members such as a polarizing plate and a phase difference plate, peeling electrification caused by static electricity generated when the pressure sensitive adhesive layer is peeled off from the adherend affects the failure of the electric control circuit of the liquid crystal display And there is a demand for an excellent antistatic property for the pressure-sensitive adhesive layer.

When the surface protective film is attached to an optical member such as a polarizing plate or a retarder, the surface protective film may be peeled off once for various reasons, and the surface protective film may be reattached again for various reasons. (Reworkability) is required.

In addition, when the surface protective film is finally peeled off from optical members such as a polarizing plate and a phase difference plate, it is required to be able to peel quickly. It is required that the adhesive force is little changed even by the peeling speed so that it can be quickly peeled even by the so-called high-speed peeling.

As described above, in recent years, the required performance of the pressure-sensitive adhesive layer constituting the surface protective film has been improved as follows: (i) a balance of adhesive force at a low speed separation speed and a high speed separation speed; (ii) excellent antistatic performance; Workability and the like are required in terms of ease of use in using the surface protective film.

For example, the following proposal is known for (i) balancing the adhesive force at a low speed peeling speed and a high speed peeling speed.

In the acrylic pressure-sensitive adhesive layer comprising a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound as a main component and crosslinking the same with a crosslinking agent, the pressure- And there is also a problem that the adhesiveness to the adherend increases with time. In order to avoid this, it has been known to use a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group, and to form a pressure-sensitive adhesive layer crosslinked with a crosslinking agent Patent Document 1).

It has also been proposed that a small amount of a copolymer of a (meth) acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound is added to the same copolymer as described above, and a pressure-sensitive adhesive layer is formed by crosslinking the copolymer with a crosslinking agent. However, when they are used for protecting the surface of a plastic plate or the like having a low surface tension due to low surface tension, there arises a problem of peeling phenomenon such as lifting due to heating during processing or storage, There was also a problem that the peelability was poor.

In order to solve these problems, it is preferable that (a) 100 parts by weight of (a) a (meth) acrylic acid alkyl ester having a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms as a main component, And c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms is added to a copolymer of a monomer mixture containing a crosslinking agent in an equivalent amount or more with respect to the carboxyl group of the component b) (Patent Document 2).

In the pressure-sensitive adhesive composition described in Patent Document 2, peeling phenomena such as peeling during processing and storage are not generated, and the peelability of the adhesive strength is not so long, so that the peelability is excellent and long-term storage, It is possible to re-peel off with a small force, do not generate adhesive residue on the adherend at this time, and can peel off with small force even when high-speed peeling is performed.

As for the excellent antistatic performance, (ii) a method for incorporating an antistatic agent into a base film as a method for imparting an antistatic property to a surface protective film is disclosed. Examples of the antistatic agent include (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts and primary to tertiary amino groups, (b) sulfonic acid bases, sulfuric acid ester bases, phosphoric acid An anionic antistatic agent having an anionic group such as an ester base or a phosphonic acid base, (c) a positive antistatic agent such as amino acid or amino sulfate ester, (d) a nonionic antioxidant such as amino alcohol, glycerin or polyethylene glycol (E) a polymer-type antistatic agent obtained by polymerizing an antistatic agent as described above (Patent Document 3).

Further, in recent years, it has been proposed to incorporate such an antistatic agent directly in the pressure-sensitive adhesive layer, either in the base film or not in the surface of the base film.

Regarding (iii) the reworkability, there has been proposed, for example, a pressure-sensitive adhesive composition in which a curing agent of an isocyanate compound and an specific silicate oligomer are incorporated in an acrylic resin in an amount of 0.0001 to 10 parts by weight based on 100 parts by weight of an acrylic resin Document 4).

Patent Document 4 discloses a method for producing a polyester resin composition which comprises an acrylic acid alkyl ester having an alkyl group of about 2 to 12 carbon atoms or a methacrylic acid alkyl ester having an alkyl group of about 4 to 12 as a main monomer component, Containing functional monomer component and a functional group-containing monomer component. The content of the monomer component containing a functional group is preferably 0.001 to 50% by weight, more preferably 0.001 to 25% by weight, still more preferably 0.01 to 25% by weight, . The pressure-sensitive adhesive composition described in Patent Document 4 is said to exhibit reworkability because it exhibits a small change in cohesive force and adhesive force over time under high temperature or high temperature and high humidity, and also exhibits an excellent adhesive force against a curved surface.

Generally, if the pressure-sensitive adhesive layer has a soft property, the pressure-sensitive adhesive residue tends to be generated, and the workability tends to decrease. That is, it is difficult to peel off when it is mistakenly bonded, and it is apt to be difficult to reattach. Therefore, it is considered that it is necessary to cross-link a monomer having a functional group such as a carboxyl group to a subject so as to make the pressure-sensitive adhesive layer have a constant hardness, in order to obtain reworkability.

Japanese Patent Application Laid-Open No. 63-225677 Japanese Laid-Open Patent Publication No. 11-256111 Japanese Laid-Open Patent Publication No. 11-070629 Japanese Unexamined Patent Publication No. 8-199130

2. Description of the Related Art Recently, various types of displays such as a liquid crystal display have been rapidly developed. However, with the increase in the size of the liquid crystal display, new problems have arisen in the process of manufacturing members of the liquid crystal display. For example, the following problems arise with respect to the surface protective film for a polarizing plate for protecting the polarizing plate by being attached to the surface of the polarizing plate.

With respect to the desire to easily peel off the surface protective film in the polarizing plate after peeling the surface protective film onto the polarizing plate as the adherend in the manufacturing process of the polarizing plate which is a member of the liquid crystal display in the prior art, The adhesive strength of the pressure-sensitive adhesive layer formed on the pressure-sensitive adhesive layer is reduced to satisfy this demand.

However, if the adhesive force of the pressure-sensitive adhesive layer is made small and the surface protective film is easily peeled off from the adherend, the adhesion of the surface protective film to the polarizing plate is lowered. The surface protective film is peeled off at the end portion of the polarizing plate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has an object of providing a polarizing plate excellent in balance of an adhesive force at a low speed peeling speed and a high speed peeling speed and having good adhesion to a polarizing plate despite small adhesive force, And an object of the present invention is to provide an excellent surface protective film for a polarizing plate.

In order to solve the above problems, the present invention provides a polarizing plate surface protective film comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent on one side of a resin film, (A) at least one or more of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18, (B) at least one copolymerizable monomer containing a hydroxyl group, and (C) (D) at least one or more kinds of polyalkylene glycol mono (meth) acrylate monomers, (E) a nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth) acrylate Wherein the crosslinking agent is a trifunctional isocyanate compound, and the cross-linking agent is a trifunctional isocyanate compound. , Said pressure-sensitive adhesive composition further comprising (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, and having a width of 25 mm and a length of 35 mm bonded to a polarizing plate subjected to AG treatment There is provided a surface protective film for a polarizing plate characterized in that there is no discoloration in a shear holding force test for a polarizing plate which is carried out by applying a load of 500 g to the surface protective film for a polarizing plate and leaving it in an atmosphere at a temperature of 23 캜 for 24 hours.

The present invention also provides a polarizing plate surface protective film comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent on one side of a resin film, wherein the acryl- (Meth) acrylate monomer having a carbon number of C4 to C18, and (B) 2 to 10 parts by weight in total of at least one copolymerizable monomer containing a hydroxyl group, (C) a carboxyl group (D) 3 to 40 parts by weight in total of at least one of polyalkylene glycol mono (meth) acrylic acid ester monomers and (E) at least one member selected from the group consisting of a hydroxyl group And 0.1 to 20 parts by weight of a total of at least one of a nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer not containing Wherein the crosslinking agent is a trifunctional isocyanate compound and the pressure-sensitive adhesive composition comprises 100 parts by weight of a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having (A) the alkyl group of C4 to C18, (F) a polyether-modified siloxane compound having an HLB value of 7 to 12 in an amount of 0.001 to 0.5 parts by weight, and having a width of 25 mm A surface protective film for a polarizing plate was prepared by applying 500 g to a surface protective film for a polarizing plate cut to a length of 35 mm and leaving it in an atmosphere at a temperature of 23 캜 for 24 hours for a polarizing plate to be subjected to a shear holding force test .

The polyalkylene glycol mono (meth) acrylic acid ester monomer (D) is at least one selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, ethoxypolyalkylene glycol , The average number of repeating units of the alkylene oxide constituting the polyalkylene glycol chain is 3 to 14, the content of the diester in the monomer is 0.2% or less, the content of water is 0.1% or less, In addition, it is preferable that the haze value of the solubility in water in a 20% aqueous solution is 2% or less.

(Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and 2-hydroxyethyl (Meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide and N-hydroxyethyl .

(Meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (Meth) acryloyloxyethylmaleic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- Caprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyltetrahydrophthalic acid, and the like.

Wherein the trifunctional isocyanate compound is an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound , A burette of a hexamethylene diisocyanate compound, a burette of an isophorone diisocyanate compound, an isocyanurate of a tolylene diisocyanate compound, an isocyanurate of a xylylene diisocyanate compound, an isocyanurate of a xylenylene diisocyanate compound A cyanurate, an adduct of a tolylene diisocyanate compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound The.

Wherein the antistatic agent (J) is contained in the pressure-sensitive adhesive composition in an amount of 0.01 to 5.0 parts by weight based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of C4- Is an ionic compound which is solid at 25 占 폚 at 25 to 50 占 폚.

It is preferable that the pressure-sensitive adhesive layer has a pressure-sensitive adhesive force of 0.04 to 0.2 N / 25 mm at a low speed peeling speed of 0.3 m / min and a pressure-sensitive adhesive force of 2.0 N / 25 mm or less at a high speed peeling speed of 30 m / min.

It is preferable that the pressure-sensitive adhesive layer has a surface resistivity of 9.0 x 10 + ¹¹ ? /? Or less and a peeling electrification voltage of 占 0 to 0.5 kV.

It is preferable that an antistatic treatment and an antifouling treatment are performed on a surface of one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed.

According to the present invention, it is possible to provide a surface protective film for a polarizing plate which is excellent in balance of adhesive force at a low speed peeling rate and a high peeling rate and which has good adherence to a polarizing plate in spite of a small adhesive force and excellent durability, A film can be provided.

Hereinafter, the present invention will be described based on preferred embodiments.

The surface protective film for a polarizing plate of the present invention is a surface protective film for a polarizing plate wherein a pressure sensitive adhesive layer formed by crosslinking a pressure sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent is formed on one side of a resin film, (A) at least one or more of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18, (B) at least one copolymerizable monomer containing a hydroxyl group, and (C) a copolymerizable monomer containing a carboxyl group (D) at least one of polyalkylene glycol mono (meth) acrylic acid ester monomers and (E) a nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth) acrylate containing no hydroxyl group Wherein the cross-linking agent is a trifunctional isocyanate compound, and the cross-linking agent is a trifunctional isocyanate compound. , Said pressure-sensitive adhesive composition further comprising (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, and having a width of 25 mm and a length of 35 mm bonded to a polarizing plate subjected to AG treatment Wherein the surface protective film for a polarizing plate is a surface protective film for a polarizing plate characterized in that there is no discoloration in a shear holding force test for a polarizing plate which is carried out by applying a load of 500 g to a surface protective film for a polarizing plate and leaving the film in an atmosphere at a temperature of 23 캜 for 24 hours.

Further, the surface protective film for a polarizing plate of the present invention is a surface protective film for a polarizing plate comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent on one side of a resin film, (A) 100 parts by weight in total of at least one of (A) at least one (meth) acrylic acid ester monomer having an alkyl group having from 4 to 18 carbon atoms, and (B) 2 to 10 parts by weight in total of at least one copolymerizable monomer containing a hydroxyl group And (C) 0.05 to 0.3 parts by weight in total of at least one copolymerizable monomer containing a carboxyl group, and (D) 3 to 40 parts by weight in total of at least one polyalkylene glycol mono (meth) acrylic acid ester monomer (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group, Wherein the crosslinking agent is a trifunctional isocyanate compound, and the pressure-sensitive adhesive composition comprises (A) at least one (meth) acrylate monomer having an alkyl group of C4 to C18 in the alkyl group (F) a polyether modified siloxane compound having an HLB value of 7 to 12 in an amount of 0.001 to 0.5 parts by weight based on 100 parts by weight of the total of , A 500 g load was applied to the above surface protective film for polarizing plate cut to a size of 25 mm wide × 35 mm long and allowed to stand for 24 hours in an atmosphere at a temperature of 23 ° C., Is a surface protective film for a polarizing plate.

Examples of the (meth) acrylic acid ester monomer (A) in which the alkyl group has 4 to 18 carbon atoms include butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (Meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (Meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (Meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate, isomyristyl Cetyl (meth) acrylate Sites, and the like can be mentioned stearyl (meth) acrylate, isostearyl (meth) acrylate.

Examples of the copolymerizable monomer containing a hydroxyl group (B) include a copolymerizable monomer having a hydroxyl group such as 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) (Meth) acrylate such as ethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (Meth) acrylamides containing hydroxyl groups.

(Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy ) Acrylamide, N-hydroxymethyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide.

(A) a total of at least one copolymerizable monomer containing (B) a hydroxyl group, relative to 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of C4 to C18, By weight, more preferably in a proportion of 3.5 to 10 parts by weight, and particularly preferably in a proportion of 4.2 to 10 parts by weight.

(Meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (Meth) acryloyloxyethylmaleic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- Caprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyltetrahydrophthalic acid, and the like.

(A) a total of at least one copolymerizable monomer containing a carboxyl group (C) in an amount of 0.05 to 0.3 wt% based on 100 wt% of the total of at least one (meth) acrylate monomer having an alkyl group having a carbon number of C4 to C18 By weight, more preferably 0.05 to 0.25 parts by weight, and particularly preferably 0.05 to 0.2 parts by weight.

As the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, any of the plurality of hydroxyl groups of the polyalkylene glycol may be a compound in which one hydroxyl group is esterified as a (meth) acrylic acid ester. (Meth) acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the subject polymer. The other hydroxyl group may be the same as OH, 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 of the polyalkylene glycol include an ethylene group, a propylene group, and a butylene group, but are not limited thereto. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol. Examples of the copolymer of polyalkylene glycol include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol. The copolymer may be a block copolymer or a random copolymer.

The (D) 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 units of alkylene oxide" refers to the number of repeating units in the "polyalkylene glycol chain" included in the molecular structure of the polyalkylene glycol mono (meth) acrylate monomer (D) It is the average number.

The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer preferably has a diester content in the monomer of 0.2% or less, a water content of 0.1% or less and a solubility in water of 20% 2% or less.

The "diester content in the monomer" is the content (% by weight) of the polyalkylene glycol di (meth) acrylate ester contained in the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer.

The "water content rate" is the content (% by weight) of water contained in the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer.

The "haze value in the 20% aqueous solution state" is the haze value (%) of the aqueous solution in the state of (D) 20% by weight aqueous solution of the polyalkylene glycol mono (meth) acrylic acid ester monomer. That is, not only has the water-solubility (water solubility) of the polyalkylene glycol mono (meth) acrylic acid ester monomer (D) to 20% aqueous solution, but also the haze value (% Is less).

In the present specification, the haze value of the 20% aqueous solution is a value measured by a haze meter after the aqueous solution is injected into a quartz cell having an optical path length of 10 mm. This index was introduced to select a monomer having high hydrophilicity, which is a degree of hydrophilicity of the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer and which gives a solution without cloudiness even at a high concentration.

Examples of the polyalkylene glycol mono (meth) acrylate monomer (D) include polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, ethoxypolyalkylene glycol (meth) At least one compound selected from the group consisting of compounds of the formula

More specifically, there may be mentioned polyolefin such as polyethylene glycol-mono (meth) acrylate, polypropylene glycol-mono (meth) acrylate, polybutylene glycol- mono (meth) acrylate, polyethylene glycol-polypropylene glycol- Poly (ethylene glycol) -polybutylene glycol-mono (meth) acrylate, polypropylene glycol-polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polypropylene glycol- Rate; Methoxypolyethylene glycol- (meth) acrylate, methoxypolyethylene glycol- (meth) acrylate, methoxypolypropylene glycol- (meth) acrylate, methoxypolybutylene glycol- (meth) acrylate, methoxypolyethylene glycol- (Meth) acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxypolypropylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene Glycol - (meth) acrylate; Acrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolypropylene glycol- (meth) acrylate, ethoxypolybutylene glycol- (Meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polypropylene glycol-polybutylene glycol- Glycol- (meth) acrylate, and the like.

(Meth) acrylic acid ester monomer (D) is 100 parts by weight or more based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of (C4) More preferably 3 to 40 parts by weight, more preferably 3 to 30 parts by weight, particularly preferably 5 to 30 parts by weight.

The acrylic polymer may further contain at least one of (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group. Examples of the nitrogen-containing vinyl monomer (E-1) in the component (E) 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, there may be mentioned N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N- vinylpyridine, N-vinylpiperidone, N- vinylpyrimidine, Substituted vinyls such as N-vinylpyrroles, N-vinylpyrroles, N-vinylimidazoles, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- A cyclic nitrogen vinyl compound having a heterocyclic structure; (Meth) acryloyl morpholine, N- (meth) acryloylpiperazine, N- (meth) acryloyl aziridine, N- (meth) acryloyl azetidine, N- (Meta) acryloyl-substituted complexes such as N- (meth) acryloylpiperidine, N- (meth) acryloyl azelane, N- A cyclic nitrogen vinyl compound having a cyclic structure; A cyclic nitrogen vinyl compound having a heterocyclic structure having a nitrogen atom such as N-cyclohexylmaleimide or N-phenylmaleimide and an ethylenically unsaturated bond in the ring; Unsubstituted or monoalkyl-substituted (meth) acrylamides such as N-methyl (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide and Nt-butyl (meth) acrylamide; (Meth) acrylamide, N, N-diethyl (meth) acrylamide, N, (Meth) acrylamide, N-methyl-N-methyl (meth) acrylamide, N-methyl- Substituted (meth) acrylamides; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, (Meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminomethyl (Meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (Meth) acrylate, t-butylaminoethyl (meth) acrylate and the like; N, N-diethylaminopropyl (meth) acrylamide, N, N-dipropylaminopropyl (meth) acrylamide, N, N-diisopropylaminopropyl (Meth) acrylamide, N-methyl-N-isopropylaminopropyl (meth) acrylamide, N-methyl- N, N-dialkyl-substituted aminopropyl (meth) acrylamides such as amides; N-vinylcarboxylic acid amides such as N-vinyl formamide, N-vinylacetamide and N-vinyl-N-methylacetamide; (Meth) acrylamide, N, N-methylenebis (meth) acrylamide, and the like can be used in combination with one or more of N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (Meth) acrylamides; Unsaturated carboxylic acid nitriles such as (meth) acrylonitrile; And the like.

The nitrogen-containing vinyl monomer (E-1) is preferably a compound containing no hydroxyl group, and more preferably a compound containing no hydroxyl group and no carboxyl group. Examples of such monomers include acrylic monomers containing the above-exemplified monomers, for example, N, N-dialkyl substituted amino groups and N, N-dialkyl substituted amide groups; Vinyl-substituted lactams such as N-vinyl-2-pyrrolidone, N-vinylcaprolactam and N-vinyl-2-piperidone; N- (meth) acryloyl-substituted cyclic amines such as N- (meth) acryloylmorpholine and N- (meth) acryloylpyrrolidine are preferred.

(Meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-propoxyethyl (meth) acrylate and the like can be given as examples of the alkyl (meth) (Meth) acrylate, 2-ethoxypropyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2- (Meth) acrylate, 2-propoxypropyl (meth) acrylate, 2-isopropoxypropyl (meth) acrylate, 2-butoxypropyl Propyl (meth) acrylate, 3-butoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, Acrylate, 4-ethoxybutyl (meth) acrylate, 4-propoxybutyl (meth) acrylate, 4-isopropoxybutyl And the like methacrylate, 4-butoxy-butyl (meth) acrylate.

These alkoxy group-containing alkyl (meth) acrylate monomers have a structure in which the atom of the alkyl group in the alkyl (meth) acrylate is substituted with an alkoxy group.

(E) a nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth) acrylate having no hydroxyl group, based on 100 parts by weight of the total of 100 parts by weight of at least one (meth) acrylate monomer having an alkyl group of C4- It is preferable that the total amount of the at least one type of late monomer is in the range of 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight, particularly preferably 0.3 to 8 parts by weight. (E-1) a nitrogen-containing vinyl monomer containing no hydroxyl group and (E-2) an alkyl (meth) acrylate monomer containing an alkoxy group may be used alone or in combination.

The pressure-sensitive adhesive composition according to the present invention may contain (F) a polyether-modified siloxane compound having an HLB value of 7 to 12. A polyether-modified siloxane compound is a siloxane compound having a polyether, in addition to conventional siloxane units [-SiR ¹ ₂ -O-], a polyether siloxane unit having a group ^{[-SiR 1 (R 2 O (R} 3 O) n R ⁴ ) -O-]. (Wherein R ¹ represents one or two or more kinds of alkyl groups or aryl groups, R ² and R ³ represent one or two or more kinds of alkylene groups, and R ⁴ represents one or two or more kinds of alkyl groups or acyl groups . 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 ].

(F) a total of at least one polyether-modified siloxane compound having an HLB value of 7 to 12, based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group having a carbon number of C4 to C18 (A) In an amount of 0.001 to 0.5 parts by weight. More preferably, it is 0.01 to 0.5 parts by weight. The HLB value is a hydrophilic lipophilic balance (hydrophilic lipophilic ratio) defined by, 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 hydrogenated silicon group by a hydrosilylation reaction. Specific examples thereof include dimethylsiloxane · methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane · methyl (polyoxyethylene) siloxane · methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane · methyl (polyoxypropylene) . The HLB value of the polyether-modified siloxane compound can be adjusted by selecting the ratio of the polyether group and the siloxane group. (F) By blending a polyether-modified siloxane compound having an HLB value of 7 to 12 in the pressure-sensitive adhesive composition, the pressure-sensitive adhesive and the pressure-sensitive adhesive can be improved.

The trifunctional isocyanate compound may be at least one kind selected from polyisocyanate compounds having three isocyanate (NCO) groups in one molecule, or at least two kinds thereof. The polyisocyanate compound may be classified into an aliphatic isocyanate, an aromatic isocyanate, a non-glycidic isocyanate, and an alicyclic isocyanate.

Examples of the trifunctional isocyanate compound include a biuret modified or isocyanurate modified product of a bifunctional isocyanate compound (a compound having two NCO groups in one molecule), trimethylol propane (TMP) and a polyol having three or more valences such as glycerin And an adduct (polyol modified product) with a compound having at least three OH groups in the molecule).

Examples of the trifunctional isocyanate compound include an isocyanurate compound of a hexamethylene diisocyanate compound, an isocyanurate compound of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound A burette of a hexamethylene diisocyanate compound, a burette of an isophorone diisocyanate compound, an isocyanurate compound of a tolylene diisocyanate compound, an isocyanurate compound of a xylylene diisocyanate compound, an isocyanurate of a xylylene diisocyanate compound, At least one member selected from the group consisting of an isocyanurate compound, an adduct of a tolylene diisocyanate compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound is preferable .

(A) the total amount of at least one trifunctional isocyanate compound in a proportion of from 0.1 to 10 parts by weight based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group having from 4 to 18 carbon atoms , More preferably 0.1 to 6 parts by weight.

When the polyisocyanate compound is used as the crosslinking agent, the crosslinking catalyst may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the acrylic polymer and the crosslinking agent, and may be an amine compound such as tertiary amine, a metal chelate compound, , An organic lead compound, an organic zinc compound, and the like.

Examples of tertiary amines include trialkylamines, N, N, N ', N'-tetraalkyldiamines, N, N-dialkylaminoalcohols, triethylenediamine, morpholine derivatives and piperazine derivatives .

The metal chelate compound is a compound in which at least one dorsal ligand L is bonded to the central metal atom M. The metal chelate compound may or may not have at least one monocyclic ligand X bonded to the metal atom M. For example, when the chemical formula of a metal chelate compound having one metal atom M is represented by M (L) _m (X) _n , _m? 1, _n ? 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 polycondensate L include β-keto esters such as methyl acetoate, ethyl acetoate, octyl acetoate, oleyl acetoate, lauryl acetoacetate, and stearyl acetoate, acetyl acetone (also called 2,4-pentanedione) , 2,4-hexanedione, and benzoyl acetone. These are keto enol tautomeric compounds, and for the polydentate ligands L, enol may be a deprotonated enolate (for example, acetylacetonate).

Examples of the monocyclic ligand X include acyloxys such as a halogen atom such as a chlorine atom and a bromine atom, a pentanoyl group, a hexanoyl group, a 2-ethylhexanoyl group, an octanoyl group, a nonanoyl group, a decanoyl group, a dodecanoyl 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-pentanedionate) iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris (2,4-hexanedionate) iron (III), bis (2,4-hexanedionate) zinc, tris (2,4-hexanedionate) titanium, Tris (2,4-hexanedionate) aluminum, tetrakis (2,4-hexanedionate) zirconium, and the like.

Examples of the organic tin compound include dialkyltin oxide, dialkyltin fatty acid salt, and stannous acid tin salt.

The crosslinking catalyst is preferably a metal chelate compound or an organotin compound. As the metal chelate compound, an aluminum chelate compound, a titanium chelate compound, an iron chelate compound, and a tin chelate compound are preferable. The organotin compound is preferably at least one selected from the group consisting of dioctyltin oxide and dioctyltin dilaurate.

(A) a total amount of at least one crosslinking catalyst in an amount of 0.001 to 0.5 parts by weight based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group having from 4 to 18 carbon atoms .

Examples of the ketoene tautomer compound include? -Keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, acetylacetone, 2,4- And? -Diketones such as hexanedione, benzoyl acetone, and the like. The ketoene tautomeric compound is a pressure-sensitive adhesive composition comprising a polyisocyanate compound as a cross-linking agent. By blocking the isocyanate group of the cross-linking agent, viscosity increase or gelation, which is excessive in the pressure-sensitive adhesive composition after the compounding of the cross- You can extend your life.

As the ketoene tautomer compound, at least one compound selected from the group consisting of acetylacetone and ethyl acetoacetate is particularly preferable.

(A) at a ratio of at least one kind of the ketoene alcohol tautomer compound in a total amount of 0.1 to 300 parts by weight based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of C4 to C18 , And more preferably 1.0 to 30.0 parts by weight.

It is preferable to appropriately set the ratio of the ketoene aliphatic isomer compound to the crosslinking catalyst in that the ketoene aliphatic isomer compound has an effect of inhibiting the crosslinking in contrast to the crosslinking catalyst. In order to extend the pot life of the pressure-sensitive adhesive composition and improve the storage stability, it is preferable that the weight ratio of the crosslinking catalyst to the keto-enol tautomer compound (keto-enol tautomer compound / crosslinking catalyst) is 70-1000.

(J) The antistatic agent is preferably an ionic compound which is solid at 25 占 폚 with a melting point of 25 to 50 占 폚.

In the present invention, as the antistatic agent (J), an ionic compound which is solid at 25 占 폚 having a melting point of 25 to 50 占 폚 is added into the pressure-sensitive adhesive composition. Since the antistatic agent (J) has a low melting point and also has a long-chain alkyl group, it is presumed that the affinity with the acrylic polymer is high.

(J) As an antistatic agent, an ionic compound contained in the pressure-sensitive adhesive composition and having a melting point of 25 to 50 占 폚 and being solid at 25 占 폚 may be mentioned.

Examples of the ionic compound having a melting point of 25 to 50 占 폚 at 25 占 폚 which is solid are ionic compounds having a cation and an anion such that the cation is a pyridinium cation, (PF ₆ ^- ), thiocyanate salt (SCN ^- ), phosphoric acid salt (SCN ^- ), and the like, Alkylbenzenesulfonate (RC ₆ H ₄ SO ₃ ^- ), perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ^- ), bis (fluorosulfonyl) imide salt (FSI), bis (Trifluoromethanesulfonyl) imide salt (TFSI), and trifluoromethanesulfonic acid salt (TF). It is preferably a solid at ordinary temperature (for example, 25 占 폚), and a melting point of 25 to 50 占 폚 can be obtained depending on the choice of the chain length of the alkyl group, the position and the number of substituent groups. The cation is preferably a quaternary nitrogen atom onium cation, a quaternary pyridinium cation or a quaternary pyridinium cation such as 1-alkyl pyridinium (the carbon atom at 2-6 may have a substituent or may be unsubstituted) , Quaternary imidazolium cation such as 3-dialkylimidazolium (the carbon atom at the 2, 4 and 5 positions may have a substituent or may be substituted), quaternary ammonium cation such as tetraalkylammonium And the like.

(A) a total of at least one kind of ionic compound having a melting point of 25 to 50 占 폚 at 25 占 폚 at a total of 100 parts by weight of at least one kind of (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 In a proportion of 0.01 to 5.0 parts by weight.

(J) Specific examples of the antistatic agent include, but are not limited to, specific examples of ionic compounds having a melting point of 25 to 50 占 폚 at 25 占 폚, for example, 1-octylpyridinium hexafluorophosphate , 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecylpyridinium Dodecylbenzenesulfonic acid salt, 4-methyl-1-octylpyridinium hexafluorophosphate, and the like.

Further, it is also possible to use, as other components, a copolymerizable (meth) acrylic monomer containing an alkylene oxide, (meth) acrylamide monomer, dialkyl substituted acrylamide monomer, surfactant, curing accelerator, plasticizer, filler, Antioxidants, antioxidants, and other known additives may be appropriately added. They may be used alone or in combination of two or more.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present invention comprises (A) at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group having from 4 to 18 carbon atoms and (B) at least one or more kinds of copolymerizable monomers containing a hydroxyl group And (C) at least one copolymerizable monomer containing a carboxyl group. (A) at least one or more of (A) at least one (meth) acrylate monomer having an alkyl group of C4 to C18, (B) at least one copolymerizable monomer containing a hydroxyl group, and (C) (D) at least one of polyalkylene glycol mono (meth) acrylic acid ester monomers, (E) a nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth) acrylate containing no hydroxyl group, (Meth) acrylate monomer may be copolymerized. The polymerization method of the acrylic polymer is not particularly limited, and suitable polymerization methods such as solution polymerization, emulsion polymerization and the like can be used.

The pressure-sensitive adhesive composition of the present invention may further comprise (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, and a trifunctional isocyanate compound as a crosslinking agent and an antistatic agent having a melting point of 25 to 50 DEG C at 25 DEG C , Which is a solid, and further optionally, an optional additive.

In the production of the acrylic polymer, it is preferable to carry out the polymerization reaction under anhydrous conditions such as solution polymerization using an anhydrous organic solvent in order to reduce moisture content in the pressure-sensitive adhesive composition. Particularly, since the polyalkylene glycol mono (meth) acrylic acid ester monomer (D) is highly hydrophilic, it is preferable to use a monomer having a low water content.

In order to avoid an increase in the viscosity of the pressure-sensitive adhesive composition, each monomer used in the preparation of the acrylic polymer of the subject is desirably minimized in the amount of the multifunctional (bifunctional or higher) monomer capable of functioning as a crosslinking agent. Particularly, the polyalkylene glycol mono (meth) acrylic acid ester monomer (D) is preferably a di (ester) monomer because the corresponding diester moiety is a di (meth) acrylic acid ester of a bifunctional monomer.

The acrylic polymer preferably contains an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid or (meth) acryl amide in a proportion of 50 to 100 parts by weight based on 100 parts by weight of the acrylic polymer.

The acid value of the acrylic polymer is preferably 0.01 to 8.0. This makes it possible to improve stain resistance and improve the ability to prevent the occurrence of adhesive residue.

Here, "acid value" is one of the indicators of the content of the acid, and is represented by the number of mg of potassium hydroxide necessary for neutralizing 1 g of the carboxyl group-containing polymer.

The adhesive strength of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition to the polarizing plate was 0.04 to 0.2 N / 25 mm at a low speed peeling rate of 0.3 m / min and 2.0 N / 25 mm Or less. As a result, the adhesive force has little change even by the peeling speed, and it is possible to quickly peel off even by high-speed peeling. Further, even when the surface protective film is once peeled off again for bonding, an excessive force is not required and it is easy to peel off from the adherend.

It is preferable that the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 9.0 x 10 + ¹¹ ? /? Or less and a peeling electrification voltage of 占 0 to 0.5 kV. In the present invention, "± 0 to 0.5 kV" means 0 to 0.5 kV and 0 to +0.5 kV, that is, -0.5 to +0.5 kV. If the surface resistivity is large, the ability to escape the static electricity generated by the charging at the time of peeling is degraded. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage generated by the static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend can be reduced, and it is possible to suppress the influence on the electric control circuit of the adherend or the like.

The gel fraction of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition is preferably 95 to 100%. As described above, the gel fraction is high, the adhesive force is not excessively increased at a low rate of peeling, the elution of the unpolymerized monomer or oligomer from the acrylic polymer is reduced, and the durability at high temperature and high humidity is improved, The contamination of the complex can be suppressed.

By forming a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one side or both sides of the resin film, a pressure-sensitive adhesive film is obtained. The surface protective film for a polarizing plate of the present invention is a surface protective film comprising a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one side of a resin film. The surface protective film for a polarizing plate of the present invention is excellent in durability, reworkability, and antistatic performance despite the fact that there is no discrepancy in the shearing force test when adhered to the polarizing plate and the adhesion to the polarizing plate is small. Therefore, it can be preferably used as a surface protective film of a polarizing plate. Examples of the polarizing plate include glare, plane (general purpose), antiglare (AG), and the like. Examples of the protective film material on the surface of the polarizing plate include a TAC-based film (triacetylcellulose-based compound) and an acrylic film.

As the test conditions of the shear holding force, for example, a load (mass of weight) of 500 g, an environmental temperature of 23 캜, and a holding time of 24 hours can be mentioned. This test condition is preferable as a guide for judging that the adhesion of the surface protective film to the polarizing plate is good. The contact area (dimension) of the surface protective film for the polarizing plate to the polarizing plate, which is the adherend of the shear holding force test, is 25 mm x 35 mm. The details of the test method (apparatus, etc.) may comply with, for example, a holding force test of JIS Z 0237 (adhesive tape / pressure sensitive adhesive sheet test method).

As the resin film serving as the base material of the pressure-sensitive adhesive layer or the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film or the like can be used.

Antistatic treatment with an antifouling treatment with a silicon-based or fluorine-based releasing agent, a coating agent, fine silica particles or the like, coating with an antistatic agent, or the like is applied to the resin film as a base material on the side opposite to the side where the pressure- .

The release film is subjected to releasing treatment by a silicone-based, fluorine-based releasing agent or the like on the side of the pressure-sensitive adhesive layer to be combined with the adhesive surface.

Example

Hereinafter, the present invention will be described in detail by way of examples.

≪ Preparation of acrylic polymer &

[Example 1]

Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube to replace the air in the reactor with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 8.0 parts by weight of 8-hydroxyoctyl acrylate, 0.1 part by weight of acrylic acid, polypropylene glycol monoacrylate (alkylene oxide constituting a polyalkylene glycol chain , 8 parts by weight of an average repeating number n of 12, a diester content of 0.1% in a monomer, a solubility in water of 20% in an aqueous solution of 0.8% and a water content of 0.05%), N-vinylpyrrolidone 1 And 60 parts by weight of a solvent (ethyl acetate) were added. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was reacted at 65 DEG C for 6 hours to obtain an acrylic polymer solution used in Example 1 having a weight average molecular weight of 500,000. A part of the acryl-based polymer was sampled and used as a measurement sample of the acid value described later.

[Examples 2 to 8 and Comparative Examples 1 to 4]

The same procedures as in the acrylic polymer solution used in Example 1 were repeated except that the monomers were used in the same manner as in (A) to (E) of Table 1, To obtain an acrylic polymer solution.

≪ Preparation of pressure-sensitive adhesive composition and surface protective film &

[Example 1]

0.05 part by weight of a polyether-modified siloxane compound (HLB value = 7), 1.0 part by weight of 1-octylpyridinium hexafluorophosphate and 8.5 parts by weight of acetylacetone were added to the acrylic polymer solution of Example 1 thus prepared, , 4.0 parts by weight of Coronate HX (isocyanurate of hexamethylene diisocyanate compound) and 0.1 part by weight of titanium trisacetylacetonate were added and stirred to obtain a pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was coated on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin and dried at 90 ° C to remove the solvent to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 25 μm.

Thereafter, the pressure-sensitive adhesive sheet was transferred onto the surface opposite to the antistatic and antifouling treated surface of a polyethylene terephthalate (PET) film having antistatic and antifouling treatment on one side, Sensitive adhesive layer / release film (PET film coated with silicone resin) ".

[Examples 2 to 8 and Comparative Examples 1 to 4]

The surface protective films of Examples 2 to 8 and Comparative Examples 1 to 4 were prepared in the same manner as in the surface protective film of Example 1 except that the composition of the additives was changed as shown in Table 2 (F) to (J) .

In Table 1 and Table 2, the compounding ratio of each component is expressed in parentheses in the numerical value of the weight part obtained by taking the total of the group (A) as 100 parts by weight.

Tables 3 and 4 show the compound names of the weak symbols of the respective components used in Tables 1 and 2. D-140N, D-127N, D-110N and D-120N are trade names of Nippon Polyurethane Industry Co., Ltd., to be. With respect to group (D) in Table 3, the numerical value of "n" is the average number of repeating alkylene oxides constituting the polyalkylene glycol chain. The value of "diester" is the diester content (%) in the monomer. The numerical value of "moisture" is the water content (%). The value of "haze" is the haze value (%) in the state of 20% aqueous solution.

<Test Method and Evaluation>

After the surface protective films of Examples 1 to 8 and Comparative Examples 1 to 4 were aged for 7 days under the atmosphere of 23 ° C and 50% RH, the release film (PET film coated with silicone resin) was peeled off to expose the pressure- Was used as a sample for measuring the gel fraction and the surface resistivity.

The surface protective film on which the pressure-sensitive adhesive layer was exposed was adhered to the surface of the polarizing plate attached to the liquid crystal cell via the pressure-sensitive adhesive layer, allowed to stand for one day, autoclaved at 50 DEG C and 5 atm for 20 minutes, The samples left for 12 hours were used as samples for measuring adhesion, peeling electrification voltage, shearing force (deviation), reworkability and durability. The polarizer of the adherend is a polarizer plate which has been subjected to AG treatment on its surface.

<Gel fraction>

After the completion of the aging, the mass of the pressure-sensitive adhesive layer separated from the sample to be measured before the application to the polarizing plate was precisely measured. The sample was immersed in toluene for 24 hours and then filtered through a wire mesh of 200 mesh. Thereafter, the filtrate was dried at 100 DEG C for 1 hour, and the mass of the residue was accurately measured. From the following equation, the gel fraction of the pressure-sensitive adhesive layer (pressure-sensitive adhesive layer after crosslinking) was calculated.

Gel fraction (%) = Insoluble part mass (g) / Mass of pressure-sensitive adhesive layer (g) × 100

<adhesiveness>

The test specimen obtained in the above manner (a surface protective film having a width of 25 mm and a surface of a polarizing plate subjected to AG treatment on its surface) was stuck to the surface of the polarizer in the direction of 180 DEG at a low rate of peeling (0.3 m / min) Peeled at a speed of 30 m / min, and the peel strength measured was determined as an adhesive force (N / 25 mm).

<Surface resistivity>

After aging, a release film (PET resin film coated with a silicone resin) was peeled off before being adhered to the polarizing plate to expose the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was exposed using a resistivity meter HILESTA UP-HT450 (manufactured by Mitsubishi Chemical Engineering Co., Ltd.) The resistivity (? /?) Was measured.

<Peeling Voltage>

The voltage (voltage) generated by charging the polarizing plate subjected to the AG treatment on the surface when the measurement sample thus obtained was peeled 180 ° at a tensile rate of 30 m / min was measured with a high-precision electrostatic sensor SK-035, SK-200 , And the maximum value of the measured values was taken as the peeling electrification voltage (kV).

&Lt; Shear retentivity against polarizer &gt;

A surface protective film (thickness of the pressure-sensitive adhesive layer: 20 mu m) cut to a size of 25 mm in width x 35 mm in length was applied to a polarizing plate whose surface was subjected to AG treatment, and the surface protective film adhered to the polarizing plate A load of 500 g was applied, and the displacement (mm) of the surface protective film after standing for 24 hours was measured.

<Workability>

The surface protective film of the measurement sample thus obtained was overlaid with a ballpoint pen (load: 500 g, three reciprocations), and then the surface protective film was peeled off from the polarizing plate to observe the surface of the polarizing plate. The evaluation target standard was "◯" when no pollution was observed on the polarizer, "Δ" when the pollution was confirmed to be at least partially along the locus padded with the ballpoint pen, the contamination was confirmed along the locus of the ballpoint pen, Quot ;, and the case where the release of the pressure-sensitive adhesive was confirmed also from &quot; X &quot;.

<durability>

The test sample thus obtained was allowed to stand in an atmosphere at 60 DEG C and 90% RH for 250 hours, taken out at room temperature and left for another 12 hours, and then its adhesive strength was measured to confirm that there was no clear increase compared with the initial adhesive strength. The evaluation target standard was evaluated as &quot;? &Quot; when the adhesion after the test was 1.5 times or less than the initial adhesion, and &quot; x &quot;

Table 5 shows the evaluation results. Here, the surface resistivity is represented by a method of "m × 10 ^{+ n} " being "mE + n" (where m is an arbitrary real number and n is a positive integer).

The deviations shown in Table 5 indicate measured values of the deviation (mm) of the surface protective film in the shear holding force test for the polarizing plate.

The surface protective films of Examples 1 to 8 had an adhesive force of 0.04 to 0.2 N / 25 mm at a low speed peeling rate of 0.3 m / min and an adhesive force of 2.0 N / 25 mm or less, a surface resistivity of 9.0 × 10 + ¹¹ Ω / □ or less, a peeling electrification voltage of ± 0 to 0.5 kV, a load of 500 g and a temperature of 23 ° C. × 24 hours, The surface protection film was covered with a ballpoint pen, and there was no contamination on the adherend, and durability was excellent when the film was allowed to stand in an atmosphere of 60 ° C and 90% RH for 250 hours.

That is, (1) the adhesive force to the polarizing plate is good, (2) durability, (3) reworkability, and (4) antistatic performance are excellent in spite of small adhesive force, .

The surface protective film of Comparative Example 1 is a surface protective film of Comparative Example 1 in which (C) the copolymerizable monomer containing a carboxyl group is excessive, the acrylic polymer does not contain (D) a polyalkylene glycol mono (meth) acrylate monomer, (J) does not contain an antistatic agent, or a low-rate peeling rate of 0.3 m / min and a high-speed peeling rate of 0.3 m / min, because the polyfunctional siloxane compound having an HLB value of 7 to 12 is not contained, The adhesive force at the peeling speed of 30 m / min was too large, the surface resistivity and the peeling electrification voltage were high, and there was a deviation in the shear holding test, and the reworkability and durability were poor.

The surface-protective film of Comparative Example 2 is a surface-protective film of Comparative Example 2 in which (C) the copolymerizable monomer containing a carboxyl group is low, (D) the diester content of the polyalkylene glycol mono (meth) acrylic acid ester monomer is large and the water content is high, (F) the HLB value of the polyether-modified siloxane compound is excessive, the adhesion at a low rate of peeling at 0.3 m / min and a high rate of peeling at 30 m / min is too high and the surface resistivity and peeling voltage And there was a discrepancy in the shear retention test and the durability was poor.

The surface protective film of Comparative Example 3 is a surface protective film of Comparative Example 3 in which the acrylic polymer does not contain a copolymerizable monomer containing (B) a hydroxyl group, (C) a copolymerizable monomer containing a carboxyl group is excessive and (D) a polyalkylene glycol mono ) Acrylic ester monomers have a high diester content, a high moisture content and a low solubility in water, the gel fraction is low, the adhesive force at a low speed peeling rate of 0.3 m / min and the high peeling rate of 30 m / min is very large, Even if the resistivity was low, the peeling electrification voltage was high and the reworkability was poor.

In the surface protective film of Comparative Example 4, the HLB value of the (F) polyether-modified siloxane compound was excessive and there was a deviation in the shear holding force test.

Thus, in the surface protective films of Comparative Examples 1 to 4, (1) adhesion to the polarizing plate was good despite the small adhesive force, (2) durability, (3) reworkability, and Can not simultaneously satisfy all of the required performance.

The surface protective film for a polarizing plate according to the present invention has a problem in the prior art that the adhesive force of the pressure sensitive adhesive layer is made small so that the surface protective film is easily peeled off from the adherend, When the size of the polarizing plate is enlarged in comparison with the conventional one due to the large screen of the display, the problem that the surface protective film is peeled off at the end of the polarizing plate is solved, which is great in industrial use value.

Claims (9)

A surface protective film for a polarizing plate, comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent on one surface of a resin film,
The acrylic polymer
(A) at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group having a carbon number of C4 to C18,
(B) at least one copolymerizable monomer containing a hydroxyl group,
(C) at least one copolymerizable monomer containing a carboxyl group,
(D) at least one polyalkylene glycol mono (meth) acrylic acid ester monomer,
(E) a copolymer obtained by copolymerizing at least one of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group,
Wherein the crosslinking agent is a trifunctional isocyanate compound,
Wherein the pressure-sensitive adhesive composition further comprises (F) a polyether-modified siloxane compound having an HLB value of 7 to 12,
Shearing retentivity test for a polarizing plate carried out by placing 500 g of a load on the surface protective film for polarizing plate cut to a size of 25 mm in width x 35 mm in length bonded to a polarizing plate subjected to AG treatment for 24 hours in an atmosphere at a temperature of 23 캜 And the surface protective film for a polarizing plate. A surface protective film for a polarizing plate, comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent and an antistatic agent on one surface of a resin film,
The acrylic polymer
(A) 100 parts by weight in total of at least one of (meth) acrylic acid ester monomers having an alkyl group having C4 to C18 carbon atoms,
(B) 2 to 10 parts by weight in total of at least one copolymerizable monomer containing a hydroxyl group,
(C) 0.05 to 0.3 parts by weight in total of at least one copolymerizable monomer containing a carboxyl group,
(D) a polyalkylene glycol mono (meth) acrylic acid ester monomer, and
(E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group in an amount of 0.1 to 20 parts by weight in total,
Wherein the crosslinking agent is a trifunctional isocyanate compound,
Wherein the pressure-sensitive adhesive composition comprises (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of C4- Wherein the total content of at least one kind is further contained in an amount of 0.001 to 0.5 parts by weight,
Shearing retentivity test for a polarizing plate carried out by placing 500 g of a load on the surface protective film for polarizing plate cut to a size of 25 mm in width x 35 mm in length bonded to a polarizing plate subjected to AG treatment for 24 hours in an atmosphere at a temperature of 23 캜 And the surface protective film for a polarizing plate. 3. The method according to claim 1 or 2,
The polyalkylene glycol mono (meth) acrylic acid ester monomer (D) is at least one selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, ethoxypolyalkylene glycol , The average number of repeating units of the alkylene oxide constituting the polyalkylene glycol chain is 3 to 14, the content of the diester in the monomer is 0.2% or less, the content of water is 0.1% or less, The surface protective film for a polarizing plate according to claim 1, wherein the solubility in water is not more than 2% in a 20% aqueous solution. 3. The method according to claim 1 or 2,
(Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and 2-hydroxyethyl (Meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide and N-hydroxyethyl
(Meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (Meth) acryloyloxyethylmaleic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- Acrylate, caprolactone mono (meth) acrylate, and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid. 3. The method according to claim 1 or 2,
Wherein the trifunctional isocyanate compound is an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound , A burette of a hexamethylene diisocyanate compound, a burette of an isophorone diisocyanate compound, an isocyanurate compound of a tolylene diisocyanate compound, an isocyanurate of a xylylene diisocyanate compound, an isocyanurate of a xylenylene diisocyanate compound A cyanurate compound, an adduct of a tolylene diisocyanate compound, an adduct of a xylylene diisocyanate compound, and an adduct of a hydrogenated xylylene diisocyanate compound. A polarizing plate surface protective film for a. 3. The method according to claim 1 or 2,
Wherein the antistatic agent (J) is contained in the pressure-sensitive adhesive composition in an amount of 0.01 to 5.0 parts by weight based on 100 parts by weight of the total of at least one (meth) acrylate monomer having an alkyl group of C4- Is an ionic compound which is solid at 25 占 폚 at 25 to 50 占 폚. 3. The method according to claim 1 or 2,
Wherein the pressure-sensitive adhesive layer has a pressure-sensitive adhesive force of 0.04 to 0.2 N / 25 mm at a low speed peeling speed of 0.3 m / min and a pressure-sensitive adhesive force of 2.0 N / 25 mm or less at a high speed peeling speed of 30 m / Protective film. 3. The method according to claim 1 or 2,
Wherein the pressure-sensitive adhesive layer has a surface resistivity of 9.0 占 0 + ¹¹ ? /? Or less and a peeling electrification voltage of 占 0 to 0.5 kV. 3. The method according to claim 1 or 2,
Wherein an antistatic treatment and an antifouling treatment are carried out on one surface of the resin film opposite to the surface on which the pressure-sensitive adhesive layer is formed.