KR20150090547A - Protective Film for Polarizing Plate - Google Patents

Abstract

The present invention relates to a protective film for a polarizing plate, including a substrate and an adhesive layer disposed on the substrate, wherein a dimension changing rate is respectively 3% or less when being treated for 96 hours at high temperatures of 80°C and under a high humidity and heat condition of 60°C and 90%RH. The protective film for a polarizing plate according to the present invention is not separated in a severe condition so that inspection can be performed without peeling the protective film when appearance of a display is evaluated.

Description

Protective Film for Polarizing Plate {Protective Film for Polarizing Plate}

The present invention relates to a protective film for a polarizer, and more particularly, to a protective film for a high durability polarizer in which adherence of a pressure-sensitive adhesive is reduced under severe conditions, and deformation of a substrate is less likely to occur and lifting does not occur.

BACKGROUND ART An expensive optical film such as a polarizing plate is laminated on a liquid crystal display device (LCD). Such a polarizing plate may be damaged or contaminated during assembly, bonding process, transportation or distribution with a liquid crystal cell. Since the minute damage and defects of the optical film cause defects of the liquid crystal display device, a protective film attached to the surface of the polarizing plate to protect the polarizing plate is used in order to prevent it.

The protective film for a polarizing plate is composed of a substrate and a pressure-sensitive adhesive layer disposed on the substrate. The pressure-sensitive adhesive force of the pressure-sensitive adhesive is lowered due to temperature and humidity changes during transportation or the like, There is a problem that appearance inspection can not be performed when the appearance of the display is evaluated.

On the other hand, Korean Patent Laid-Open Publication No. 2013-0125319 discloses an optical film containing cellulose ester which is excellent in adhesion to a polarizing film and can be directly bonded to a polarizing film. The optical film has excellent roll appearance, Discloses an optical film having a humidity dependency of retardation and a small dimensional change. However, a method for preventing lifting of the protective film for a polarizing plate is not mentioned.

Korea Patent Publication No. 2013-0125319

It is an object of the present invention to provide a protective film for a high durability polarizing plate in which adherence of a pressure-sensitive adhesive is low and deformation of a substrate is not so small under extreme conditions and lifting does not occur.

Another object of the present invention is to provide a polarizing plate in which the protective film for a polarizing plate is laminated.

On the other hand, the present invention provides a polarizing plate protective film comprising a substrate and a pressure-sensitive adhesive layer disposed on the substrate. The protective film has a dimensional strain of 3% or less at a high temperature of 80 캜 and high humidity of 60 캜 and 90% RH for 96 hours, Or less.

The protective film for a polarizing plate according to one embodiment of the present invention is characterized in that the change in adhesive force during treatment for 96 hours at a high temperature of 80 캜 and a high humidity of 60 캜 and 90% RH is 10% or less.

The protective film for a polarizing plate according to one embodiment of the present invention is characterized in that the pressure sensitive adhesive layer comprises (A) a (meth) acrylic acid ester monomer having an alkyl group of C4 to C10, (B) a copolymerizable monomer containing a hydroxyl group, (Meth) acrylate monomers containing at least a carboxyl group-containing copolymerizable monomer, (D) a polyalkylene glycol mono (meth) acrylate monomer, and (E) a nitrogen-containing vinyl monomer or alkoxy group- (F) a trifunctional or higher isocyanate compound, (G) a crosslinking retarder, (H) a crosslinking catalyst, and (I) a polyether-modified siloxane compound Is crosslinked with the pressure-sensitive adhesive composition.

On the other hand, the present invention provides a polarizing plate in which the protective film for a polarizing plate is laminated.

The protective film for a polarizing plate according to the present invention does not cause a decrease in adhesion of the pressure-sensitive adhesive and a dimensional change of the substrate under severe conditions and does not cause lifting. Therefore, the protective film for a polarizing plate according to the present invention enables the inspection to be carried out without peeling the protective film at the time of appearance evaluation of the display.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention is a protective film for a polarizing plate comprising a substrate and a pressure-sensitive adhesive layer disposed on the substrate. The protective film is characterized in that when the film is subjected to high temperature heat treatment at 80 DEG C and high wet heat at 60 DEG C and 90% RH for 96 hours, % Or less.

In one embodiment of the present invention, the protective film for a polarizing plate is characterized in that the change in adhesive force during treatment for 96 hours at a high temperature of 80 캜 and a high mild heat at 60 캜 and 90% RH is 10% or less.

In one embodiment of the present invention, the pressure-sensitive adhesive layer comprises (A) a (meth) acrylic acid ester monomer having an alkyl group of C4 to C10, (B) a copolymerizable monomer containing a hydroxyl group, (C) (D) a polyalkylene glycol mono (meth) acrylate monomer, and (E) a nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer containing no hydroxyl group A pressure-sensitive adhesive composition comprising (F) an isocyanate compound having three or more functional groups, (G) a crosslinking retarder, (H) a crosslinking catalyst, and (I) a polyether-modified siloxane compound .

(A) Examples of the (meth) acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C10 include butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (Meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl Acrylate, and the like.

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.

(B) the copolymerizable monomer containing the hydroxyl group (B) is preferably contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the (meth) acrylic ester monomer having (A) the alkyl group of C4 to C10.

The total amount of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate among the copolymerizable monomers containing a hydroxyl group (B) By weight or less.

(C) a copolymerizable monomer containing a carboxyl group is at least one member selected from the group consisting of (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, and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.

(C) the copolymerizable monomer containing a carboxyl group is contained in an amount of 0.35 to 1.0 part by weight, more preferably 0.35 to 0.6 part by weight, based on 100 parts by weight of the (meth) acrylic acid ester monomer having (A) .

(D) The polyalkylene glycol mono (meth) acrylic acid ester monomer may be any compound in which one of the hydroxyl groups of the polyalkylene glycol 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.

Examples of the polyalkylene glycol mono (meth) acrylate monomer (D) include polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate and ethoxypolyalkylene glycol (meth) And at least one selected from the group consisting of:

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- (Meth) acrylate, methoxypolyethylene glycol- (meth) acrylate, methoxypolypropylene glycol- (meth) acrylate, methoxypolybutylene glycol- (meth) acrylate, methoxypolyethylene glycol-polypropylene glycol- ) Acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polypropylene glycol-polybutylene (Meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, methoxypolyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate, ethoxypolyethylene glycol- (Meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol-methacrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolyethylene glycol-polypropylene glycol- (Meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate, and the like.

It is preferable that (D) the polyalkylene glycol mono (meth) acrylate monomer is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the (meth) acrylate monomer having (A) the alkyl group of C4 to C10.

(E), examples of the nitrogen-containing vinyl monomer include an amide bond-containing vinyl monomer, an amino group-containing vinyl monomer, and a nitrogen-containing heterocyclic structure-containing vinyl monomer. More specifically, there may be mentioned N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N- vinylpyridine, N-vinylpiperidone, N- vinylpyrimidine, Substituted complexes such as N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- A cyclic nitrogen vinyl compound having a cyclic 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 and an ethylenically unsaturated bond in the ring such as N-cyclohexylmaleimide and N-phenylmaleimide; 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, more preferably a compound containing no hydroxyl group and no carboxyl group. Examples of such monomers include the above-exemplified monomers such as acrylic monomers containing an N, N-dialkyl substituted amino group or an N, N-dialkyl substituted amide group; 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.

(A) a (meth) acrylic acid ester monomer (C) having an alkyl group of C4 to C10, and a (meth) acrylic acid ester monomer Is preferably contained in an amount of 1 to 20 parts by weight with respect to 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.

(F) The isocyanate compound having three or more functional groups may be a polyisocyanate compound having at least three isocyanate (NCO) groups in one molecule, and examples thereof include hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, A biuret-modified or isocyanurate-modified product of a diisocyanate (e.g., a compound having two NCO groups in one molecule) such as xylylene diisocyanate, a tri- or higher-valent polyol such as trimethylolpropane or glycerin (A compound having an OH group) and the like (polyol modified product).

(F) The isocyanate compound having three or more functional groups is a polyisocyanate compound having at least three isocyanate (NCO) groups in one molecule. Particularly, the isocyanurate compound of the hexamethylene diisocyanate compound, the isocyanurate compound of the isophorone diisocyanate compound At least one selected from the group consisting of an adduct 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 and a burette of an isophorone diisocyanate compound .

(F) The isocyanate compound having three or more functional groups is preferably contained in an amount of 0.4 to 5.0 parts by weight based on 100 parts by weight of the copolymer.

(G) As the crosslinking retarder, β-keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoate, acetyl acetone, 2,4- Dione, and benzoyl acetone. These are keto-enol tautomeric compounds. In the pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, blocking the isocyanate group of the cross-linking agent inhibits excessive viscosity increase or gelation of the pressure-sensitive adhesive composition after compounding the cross- Port life can be extended.

The crosslinking retarder (G) is preferably a keto-enol tautomer compound, and is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate.

(G) The crosslinking retarder is preferably contained in an amount of 1.0 to 5.0 parts by weight based on 100 parts by weight of the copolymer.

(H) crosslinking catalyst may be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent in the case where the polyisocyanate compound is used as the crosslinking agent, and may be an amine compound such as a tertiary amine, , 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 .

Examples of the organotin compounds include dialkyltin oxide, dialkyltin fatty acid salts, and stannous primary fatty acid salts.

(H) The crosslinking catalyst is preferably an organotin compound, and more preferably at least one member selected from the group consisting of dioctyltin oxide and dioctyltin dilaurate.

(H) crosslinking catalyst is preferably contained in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the copolymer. When the amount is less than 0.01 part by weight, the adhesive strength is excessively large and the reworkability and durability are poor. When the amount is more than 0.5 part by weight, the adhesive strength may be too low to cause lifting.

(I) a polyether modified siloxane compound, a siloxane compound having a polyether, a typical siloxane unit [-SiR ¹ ₂ -O-] In addition, the siloxane units having polyether ^{[-SiR 1 (R 2 O (R} 3 O) _n R ⁴⁾ has a -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 ].

The polyether-modified siloxane compound (I) is preferably a polyether-modified siloxane compound having an HLB value of 7 to 12. It is also preferable that 0.01 to 0.5 parts by weight of the polyether-modified siloxane compound (I) is contained relative to 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 parts by weight.

HLB 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) .

(I) The blend of the polyether-modified siloxane compound and the pressure-sensitive adhesive composition can improve the adhesive strength and the reworkability of the pressure-sensitive adhesive.

(Meth) acrylate monomer, a (meth) acrylamide monomer, a dialkyl substituted acrylamide monomer, a surfactant, a curing accelerator, a plasticizer, a filler, a curing retarder, a processing aid , An antioxidant, an antioxidant, and an antistatic agent may be appropriately added. They may be used alone or in combination of two or more.

The antistatic agent includes an ionic compound. The antistatic property may also be imparted by copolymerizing the ionic acrylic monomer with a subject copolymer.

(A) a (meth) acrylic acid ester monomer having an alkyl group of C4 to C10, (B) a copolymerizable monomer containing a hydroxyl group, (C) a carboxyl group , And (D) a polyalkylene glycol mono (meth) acrylic acid ester monomer. The polymerization method of the copolymer 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 is obtained by adding (F) an isocyanate compound having three or more functional groups, (G) a crosslinking retarding agent, (H) a crosslinking catalyst, (I) a polyether-modified siloxane compound, .

The copolymer is preferably an acrylic polymer, and it is preferable that the copolymer contains 50 to 100% by weight of an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid or (meth) acrylamide.

The acid value of the acrylic polymer is preferably 0.01 to 8.0. When it is less than 0.01, sufficient adhesion property is not exhibited and it is difficult to exert the adhesion force with the substrate. When it exceeds 8.0, the possibility of occurrence of the adhesive residue is high.

Here, " acid value " is one of indices showing the content of acid, and is expressed in mg of potassium hydroxide necessary for neutralizing 1 g of a carboxyl group-containing polymer.

The gel fraction of the pressure-sensitive adhesive layer (pressure-sensitive adhesive after crosslinking) to be crosslinked with the pressure-sensitive adhesive composition is preferably 95 to 100%. As described above, the gel fraction is so high that the adhesive force is not excessively exerted in peeling at a low speed and the elution of the unpolymerized monomer or oligomer from the copolymer is reduced to improve the durability in reworkability and high temperature and high humidity, Can be suppressed.

In one embodiment of the present invention, a resin film such as a polyester film may be used as the substrate.

The thickness of the substrate is preferably 30 to 80 mu m. When the thickness is less than 30 mu m, it is vulnerable to badness of the substrate, and when the thickness is more than 80 mu m, the shrinkage rate changes greatly under severe conditions, and the possibility of flooding is high.

Antistatic treatment with an antifouling treatment with silicone or fluorine type releasing agent, a coating agent, fine silica particles or the like, antistatic treatment with application or incorporation of an antistatic agent, etc. can be performed on the surface of the substrate opposite to the side on which the pressure-

The protective film for a polarizing plate according to an embodiment of the present invention may further include a release film (separator) for protecting the pressure-sensitive adhesive surface.

As the release film, a resin film such as a polyester film can be used. The release film may be subjected to releasing treatment by a silicone-based, fluorine-based releasing agent or the like on the surface to be combined with the adhesive surface of the pressure-

One embodiment of the present invention relates to a polarizing plate in which the protective film for a polarizing plate is laminated.

The structure of the polarizing plate of the present invention is not particularly limited and may have a structure known in the art. For example, it may include a polarizer and a protective film formed on at least one side of the polarizer.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Synthesis Example 1: Preparation of acrylic polymer

Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Thereafter, 100 parts by weight of isobutyl (meth) acrylate, 1 part by weight of 6-hydroxyhexyl (meth) acrylate, 0.5 part by weight of carboxyethyl (meth) acrylate, and 3 parts by weight of polyethylene glycol monoacrylate And 5 parts by weight of N-vinylpyrrolidone were added together with 60 parts by weight of ethyl acetate as a solvent. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65 DEG C for 6 hours to obtain an acrylic copolymer having an acid value of 5.8 and a weight average molecular weight of 500,000.

Synthesis Example 2: Preparation of acrylic polymer

(Meth) acrylate, 5 parts by weight of 6-hydroxyhexyl (meth) acrylate, 3 parts by weight of carboxyethyl (meth) acrylate, 0.5 part by weight of polyethylene glycol monoacrylate, An acrylic copolymer having an acid value of 9.2 and a weight average molecular weight of 400,000 was obtained in the same manner as in Synthesis Example 1, except that 60 parts by weight of ethyl acetate was added as a solvent together with 0.5 part by weight of the monomers.

Preparation Example 1: Preparation of pressure-sensitive adhesive composition

0.1 part by weight of KF-351A (polyether-modified siloxane compound having HLB = 12) and 2 parts by weight of acetylacetone were added to 100 parts by weight of the acrylic copolymer obtained in Synthesis Example 1, followed by stirring, followed by addition of coronate HX , 3 parts by weight of isocyanurate of a diisocyanate compound) and 0.1 part by weight of dioctyltin dilaurate were added and stirred to obtain a pressure-sensitive adhesive composition.

Production Example 2: Preparation of pressure-sensitive adhesive composition

A pressure-sensitive adhesive composition was obtained in the same manner as in Production Example 1, except that 1 part by weight of dioctyltin dilaurate was used.

Preparation Example 3: Preparation of pressure-sensitive adhesive composition

A pressure-sensitive adhesive composition was obtained in the same manner as in Production Example 1, except that the acrylic copolymer obtained in Synthesis Example 2 was used instead of the acrylic copolymer obtained in Synthesis Example 1.

Example 1: Preparation of protective film for polarizing plate

The pressure-sensitive adhesive composition obtained in Preparation Example 1 was coated on a polyethylene terephthalate (PET) film having a thickness of 38 탆 and dried at 90 캜 to prepare a protective film for a polarizing plate.

Example 2: Preparation of protective film for polarizing plate

A protective film for a polarizing plate was produced in the same manner as in Example 1, except that a PET film having a thickness of 50 mu m was used.

Comparative Example 1: Production of protective film for polarizing plate

A protective film for a polarizing plate was produced in the same manner as in Example 1, except that a PET film having a thickness of 100 mu m was used.

Comparative Example 2: Preparation of protective film for polarizing plate

A protective film for a polarizing plate was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition obtained in Production Example 2 was used.

Comparative Example 3: Production of protective film for polarizing plate

A protective film for a polarizing plate was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition obtained in Production Example 3 was used.

Experimental Example 1:

(1) Appearance evaluation

Protective films for polarizing plates prepared in Examples 1-2 and 1-3 were cut into A4 size, laminated to a glass substrate at a pressure of 0.25 MPa, and autoclaved to prepare specimens.

The initial appearance was evaluated by visual observation after standing for 24 hours under conditions of 23 ° C and 50% RH. At this time, evaluation was performed under conditions of 23 캜 and 50% RH.

The appearance of harsh conditions was evaluated by observing each specimen after standing for 96 hours under the conditions of (1) 80 ° C and (2) 60 ° C and 90% RH. At this time, evaluation was performed under conditions of 23 캜 and 50% RH.

<Evaluation Criteria>

O: No lift

Δ: Creation of corner bubbles

X: Looks excited.

(2) Evaluation of shrinkage rate

The protective film for polarizing plate prepared in Example 1-2 and Comparative Example 1-3 was cut into a size of 25 mm X 100 mm to prepare a specimen.

The measurement environment was stabilized by maintaining the measurement conditions in the chamber for 30 minutes (1) 80 ° C and 2) 60 ° C, 90% RH, And the dimensional strain rate was calculated according to the following equation.

Dimensional strain = Dimensional strain of long side + Dimensional strain of short side

Dimensional strain of long side and short side = (initial length-length after 96 hours) / initial length x 100

In the above equation, the long side means a long side (100 m) in a rectangular protective film specimen, and the short side means a side having a short length (25 mm).

 (3) Adhesion evaluation

The protective film for polarizing plate prepared in Example 1-2 and Comparative Example 1-3 was cut into a size of 25 mm x 100 mm, laminated on a glass substrate at a pressure of 0.25 MPa, and autoclaved to prepare a specimen.

The initial adhesive strength was measured by peeling the pressure-sensitive adhesive layer at a peeling speed of 300 mm / min and a peeling angle of 180 ° using a universal tensile tester (UTM, Instron) after allowing the sample to stand for 24 hours under conditions of 23 ° C and 50% RH. At this time, measurement was carried out under conditions of 23 캜 and 50% RH.

The harsh condition adhesive strength was evaluated as follows. (1) Each of the specimens after standing for 96 hours under the conditions of (1) 80 ° C and (2) 60 ° C and 90% RH was peeled off at a peeling speed of 300 mm / min using a universal tensile tester Was peeled off and measured. At this time, measurement was carried out under conditions of 23 캜 and 50% RH.

The change in adhesion was calculated according to the following formula.

Adhesion Change = (Initial Adhesion-Adhesion after 96 hours) / Initial Adhesion x 100

[Table 1]

As shown in Table 1, it was confirmed that the protective film for a polarizing plate according to the present invention was excellent in durability (heat resistance and heat and humidity resistance), so that dimensional deformation and deterioration of adhesive strength were small.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (9)

And a pressure-sensitive adhesive layer disposed on the substrate. The protective film has a dimensional strain of 3% or less when treated at a high temperature of 80 캜 and high humidity of 60 캜 and 90% RH for 96 hours. The protective film according to any one of claims 1 to 8, wherein a change in adhesive force during treatment at a high temperature of 80 占 폚 and a high wet heat at 60 占 폚 and 90% RH for 96 hours is 10% or less. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive layer comprising (A) a (meth) acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C10, (B) a copolymerizable monomer containing a hydroxyl group, (C) a copolymerizable monomer containing a carboxyl group (D) a polyalkylene glycol mono (meth) acrylate monomer, and (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group Sensitive adhesive composition further comprising (F) a trifunctional or higher isocyanate compound, (G) a crosslinking retarder, (H) a crosslinking catalyst and (I) a polyether-modified siloxane compound, And the protective film is formed. The protective film according to claim 3, wherein the crosslinking catalyst is contained in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the copolymer. The protective film according to claim 3, wherein the acid value of the acrylic polymer is 0.01 to 8.0. The protective film according to claim 1, wherein the substrate is a polyester film. The protective film according to claim 1, wherein the thickness of the substrate is 30 to 80 占 퐉. The protective film according to claim 1, further comprising a release film for protecting the adhesive surface. A polarizing plate laminated with the protective film for a polarizing plate according to any one of claims 1 to 7.