KR20190073211A - Adhesive composition for polarizing plate, adhesive film for polarizing plate, polarizing plate comprising the same and optical display apparatus comprising the same - Google Patents

Abstract

The present invention relates to an adhesive composition for a polarizing plate, an adhesive film for a polarizing plate formed therefrom, and a polarizing plate and an optical display device comprising the same, wherein the adhesive composition for a polarizing plate comprises: 100 parts by weight of a (meth)acrylic copolymer of a monomer mixture containing a (meth)acrylic monomer having a hydroxyl group; 10 to 15 parts by weight of a cross-linking agent; and a solvent. The adhesive film for a polarizing plate formed therefrom has a dent value of 10 to 20 μm. Therefore, the adhesive film can obtain reliable durability and the adhesive composition for a polarizing plate has a low viscosity change rate.

Description

TECHNICAL FIELD [0001] The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a pressure-sensitive adhesive film for a polarizing plate, a polarizing plate including the same, and an optical display device including the polarizing plate.

The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a pressure-sensitive adhesive film for a polarizing plate, a polarizing plate including the same, and an optical display device containing the same.

The liquid crystal display device includes a liquid crystal panel and a polarizing plate attached to both sides of the liquid crystal panel. The polarizing plate includes a polarizer and a protective film formed on one or both surfaces of the polarizer to protect the polarizer. The polarizing plate is attached to the liquid crystal panel by an adhesive film for a polarizing plate.

The adhesive film for a polarizing plate is coated on a release film to a predetermined thickness and then dried. The release film, the polarizing plate adhesive film, and the release film are laminated and packaged, stored and / or transported. The release film prevents the polarizing plate adhesive film from being contaminated from external foreign matter. However, during packaging, storage, and transportation of the polarizing plate adhesive film, the polarizing plate may come in contact with the solid particles outside, which may result in pressing of the adhesive film by the solid particles. This pressing of the adhesive film is called a dent. Although the release film is formed on the adhesive film, there is a limitation in solving the pressing of the adhesive film. The polarizing plate including the pressure-sensitive adhesive film on which the pressure is applied can make the screen quality poor. On the other hand, the pressure sensitive adhesive film for a polarizing plate is adhered to a polarizing plate, cut and processed. In this process, too, the pressing of the adhesive film by the solid particles may occur. Therefore, there is a demand for a pressure-sensitive adhesive film which can be restored even if the pressure-sensitive adhesive film is not pressed by solid particles or the like. On the other hand, a polarizing plate including an adhesive film can not be left for a long time under high temperature or high temperature and high humidity when applied to an optical display device. In this process, an adhesive film having poor durability may cause bubbling, lifting, or peeling. Therefore, there is a demand for a pressure-sensitive adhesive film which minimizes occurrence of pressing and has excellent durability reliability.

In addition, in order to satisfy such physical properties and to increase the coating speed of the pressure-sensitive adhesive in the production line of the pressure-sensitive adhesive film, When the adhesive resin is an acid free type, the acid-containing monomer is not added. Therefore, in order to satisfy the endurance reliability, the weight average molecular weight should generally be as high as 1.5 million or more. In addition, since the weight-average molecular weight is high, the solvent content of the pressure-sensitive adhesive resin itself can not be reduced, so that the pressure-sensitive adhesive composition also has a low solid content. Accordingly, there is a problem that the volatile organic compound (VOC) generated in the solvent drying step can not be properly treated under high-speed coating.

The background art of the present invention is described in Japanese Laid-Open Patent Application No. 2015-010192.

It is an object of the present invention to provide a pressure-sensitive adhesive film which can suppress the pressing of the pressure-sensitive adhesive film by solid particles during processing, cutting, packaging and storage of the pressure-sensitive adhesive film and / And a pressure-sensitive adhesive composition for a polarizing plate.

Another object of the present invention is to provide a pressure-sensitive adhesive composition for a polarizing plate capable of realizing a pressure-sensitive adhesive film capable of suppressing warping due to shrinkage or the like of a polarizing plate at a high temperature.

Another object of the present invention is to provide a pressure-sensitive adhesive composition for a polarizing plate capable of realizing an adhesive film excellent in endurance reliability and having a low rate of change in viscosity.

The pressure sensitive adhesive composition for a polarizing plate of the present invention comprises 100 parts by weight of a (meth) acrylic copolymer of a monomer mixture containing a (meth) acrylic monomer having a hydroxyl group, 10 parts by weight to 15 parts by weight of a crosslinking agent and a solvent, The adhesive film for a polarizing plate formed of the composition may have a dent value of 10 mu m to 20 mu m.

The pressure sensitive adhesive film for a polarizing plate of the present invention can be formed from the pressure sensitive adhesive composition for a polarizing plate of the present invention.

The polarizing plate of the present invention may comprise the pressure-sensitive adhesive film for a polarizing plate of the present invention.

The optical display device of the present invention may include the polarizing plate of the present invention.

The present invention provides a polarizing plate capable of suppressing the pressing of the pressure-sensitive adhesive film by solid particles during processing, cutting, packaging and storage of the pressure-sensitive adhesive film and / or realizing a pressure- A pressure-sensitive adhesive composition and a pressure-sensitive adhesive film for a polarizing plate.

The present invention provides a pressure-sensitive adhesive composition for a polarizing plate and a pressure-sensitive adhesive film for a polarizing plate capable of realizing a pressure-sensitive adhesive film capable of suppressing warping due to shrinkage or the like of a polarizing plate at a high temperature.

INDUSTRIAL APPLICABILITY The present invention provides a pressure-sensitive adhesive composition for a polarizing plate capable of realizing a pressure-sensitive adhesive film having excellent endurance reliability and a low rate of change in viscosity.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view showing segments 1 to 9 of a specimen for bending measurement. FIG.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In the present specification, "adhesive film for polarizing plate" and "pressure-sensitive adhesive composition for polarizing plate" may be referred to as "adhesive film" and "pressure-sensitive adhesive composition", respectively.

As used herein, "(meth) acrylic" means acrylic and / or methacrylic.

Hereinafter, a pressure-sensitive adhesive composition for a polarizing plate according to an embodiment of the present invention will be described.

The pressure-sensitive adhesive composition for a polarizing plate of the present example was prepared by mixing 100 parts by weight of a (meth) acrylic copolymer of a monomer mixture containing 1 mol% to 10 mol% of a (meth) acrylic monomer having a hydroxyl group, 10 to 15 parts by weight of a cross- The weight average molecular weight of the (meth) acrylic copolymer is from 800,000 to 1,200,000, and the solid content of the pressure sensitive adhesive composition for a polarizing plate may be from 17% by weight to 25% by weight. In the present specification, the "content of solid content in the pressure-sensitive adhesive composition for a polarizing plate" refers to the weight ratio of the entirety of the components other than the solvent in the pressure-sensitive adhesive composition for a polarizing plate. In one embodiment, "solids content in the pressure-sensitive adhesive composition for a polarizing plate" may refer to a ratio of the total content of the (meth) acrylic copolymer, the crosslinking agent, the silane coupling agent and the additives in the pressure-sensitive adhesive composition for a polarizing plate.

The pressure-sensitive adhesive composition has a content of the (meth) acrylic monomer having a hydroxyl group, a weight average molecular weight, a content of a solid content and a range of a content of a cross-linking agent so that the adhesive composition can be used at a pressure of 50 m / / m to 100 m / m, it is possible to remarkably lower the LEL (lower explosion limit) of the adhesive film drying furnace to 25% or less, and the viscosity change rate 10 % Can be ensured. The "LEL" is a limit value for managing the risk of explosion of the drying oven due to the volatile organic compounds volatilized during drying in the drying oven after application of the pressure sensitive adhesive composition. The LEL is usually controlled to be 25% or less. Further, by ensuring the viscosity change ratio of 10% or less in the following formula 1, the coating uniformity of the pressure-sensitive adhesive composition during continuous production of the pressure-sensitive adhesive film is improved, the pressure difference of the filter is increased during the production of the pressure-sensitive adhesive film and the amount of the pressure- There may be no problem that the uniformity of physical properties of the film for a film is lowered:

<Formula 1>

Viscosity change rate = | V2 - V1 | / V1 x 100

(In the above formula 1, V1 is the viscosity (unit: cps) measured at 25 占 폚 for 40 g of the pressure-sensitive adhesive composition,

V2 is the viscosity (unit: cps) measured at 25 캜 after 40 g of the pressure-sensitive adhesive composition was left at 25 캜 for 48 hours.

In addition, the pressure-sensitive adhesive composition can prevent the pressing of the pressure-sensitive adhesive film from occurring and suppress warpage by securing the content of the (meth) acrylic monomer having a hydroxyl group, the weight average molecular weight, the solid content and the content of the crosslinking agent, Can be improved. The amount of volatile organic compounds generated is increased in comparison with the low speed coating when the pressure sensitive adhesive composition is applied at a high speed, but the present invention controls the solid content of the pressure sensitive adhesive composition and the weight average molecular weight of the (meth) acrylic copolymer to lower the LEL to 25% And is characterized in that the pressing and bending properties of the adhesive film are improved and the durability reliability is improved.

The (meth) acrylic copolymer may be a copolymer of a monomer mixture containing 1 mol% to 10 mol% of a (meth) acrylic monomer having a hydroxyl group. For example, the (meth) acrylic monomer having a hydroxyl group may be contained in an amount of 3 mol% to 7 mol% in the monomer mixture. Within the above range, the adhesive force of the pressure-sensitive adhesive film can be ensured, the pressing of the pressure-sensitive adhesive film can be suppressed by the reaction with the crosslinking agent, and durability and bubbling can be prevented even at high temperature and / or high temperature and high humidity.

The (meth) acrylic monomer having a hydroxyl group is a (meth) acrylic monomer having a C1 to C20 alkyl group having at least one hydroxyl group, a (meth) acrylic monomer having a C3 to C20 cycloalkyl group having at least one hydroxyl group, (Meth) acryl-based monomers having C6 to C20 aromatic groups. Specifically, the (meth) acrylic monomer having a hydroxyl group is preferably a (meth) acrylic monomer having a C1 to C20 alkyl group having at least one hydroxyl group, and 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (Meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl Acrylate, and these may be included singly or in combination of two or more. For example, the (meth) acrylic monomer having a hydroxyl group may be at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl Butyl (meth) acrylate.

The monomer mixture may further comprise a (meth) acrylic monomer having an alkyl group. The (meth) acrylic monomer having an alkyl group may include a (meth) acrylic acid ester having an unsubstituted C1 to C10 alkyl group. Specific examples of the monomer include acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, (Meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylate, and decyl (meth) acrylate, and these may be included singly or in combination of two or more. For example, the (meth) acrylic monomer having an alkyl group may include at least one of n-butyl (meth) acrylate, t-butyl (meth) acrylate and isobutyl (meth) acrylate.

The (meth) acrylic monomer having an alkyl group may be contained in the monomer mixture in an amount of 90 mol% to 99 mol%, specifically 93 mol% to 97 mol%. Within the above range, the mechanical strength of the pressure-sensitive adhesive film is increased and the durability reliability can be improved.

For example, the (meth) acrylic copolymer may be a copolymer of 1 mol% to 10 mol% of a (meth) acrylic monomer having a hydroxyl group and 90 mol% to 99 mol% of a (meth) acrylic monomer having an alkyl group.

(Meth) acrylic copolymer can be a non-carboxylic acid (meth) acrylic copolymer because it does not contain a (meth) acrylic monomer having a carboxylic acid group in the monomer mixture. Therefore, there is an effect of suppressing metal corrosion upon adhesion of the touch screen panel. The (meth) acrylic copolymer may have an acid value of 5 mg KOH / g or less, for example, 1 mg KOH / g or less. Within this range, it is possible to realize a corrosion inhibiting effect directly or indirectly on the adherend.

(Meth) acrylic copolymer may have a glass transition temperature of -35 캜 to -10 캜, for example, from -35 캜 to -15 캜. Within the above range, the dent of the present invention can be ensured and light leakage and warping can be suppressed.

(Meth) acrylic copolymer may have a polydispersion index (PDI) of 4 or less, for example, 2.5 to 3.5. Within the above range, a copolymer having a high weight average molecular weight may be distributed, and thus the durability reliability may be effective.

The (meth) acrylic copolymer may have a viscosity of 6,000 cps to 8,000 cps at 25 ° C. In the above range, the viscosity can be controlled for high-speed coating, so that the appearance of the coating is good and the viscosity after blending is high, so that there is no problem that the coating appearance is poor due to insufficient wetting during high-speed coating.

The (meth) acrylic copolymer may be prepared by polymerizing a monomer mixture by a conventional polymerization method. The polymerization method may include conventional methods known to those skilled in the art. For example, the (meth) acrylic copolymer can be prepared by adding an initiator to a monomer mixture, followed by conventional copolymerization, such as suspension polymerization, emulsion polymerization, solution polymerization and the like. The polymerization temperature may be 65 占 폚 to 70 占 폚, and the polymerization time may be 6 hours to 8 hours. The initiator may be an azo-based polymerization initiator; And / or peroxides such as benzoyl peroxide or acetyl peroxide, and the like.

The crosslinking agent may be included in an amount of 10 parts by weight to 15 parts by weight, for example, 10 parts by weight to 12 parts by weight, based on 100 parts by weight of the (meth) acrylic copolymer. Within the above range, the weight average molecular weight of the copolymer of the present invention and the hydroxyl group content of the copolymer can be controlled to suppress the occurrence of cross-linking, and the warpage at high temperatures can be reduced to solve the problem of panel bending.

The crosslinking agent may be an isocyanate crosslinking agent having two or more functional groups, for example, a bifunctional to hexafunctional isocyanate crosslinking agent. Examples of the crosslinking agent include methylene bis (phenyl isocyanate) (MDI) including xylene diisocyanate (XDI) and 4,4'-methylene bis (phenyl isocyanate) including m-xylene diisocyanate and the like, naphthalene diisocyanate , Tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, or an adduct thereof, or an isocyanurate thereof. Examples of the adduct or isocyanurate include trimethylol propane adduct of tolylene diisocyanate, trimethylol propane adduct of hexamethylene diisocyanate, trimethylol propane adduct of isophorone diisocyanate, and adduct of xylene diisocyanate Trimethylol propane adduct, an isocyanurate of tolylene diisocyanate, an isocyanurate of hexamethylene diisocyanate, and an isocyanurate of isophorone diisocyanate. For example, trimethylol propane adduct of xylene diisocyanate, and trimethylol propane adduct of tolylene diisocyanate.

The pressure-sensitive adhesive composition may include a silane coupling agent. The silane coupling agent may comprise conventional silane coupling agents known to those skilled in the art. For example, the silane coupling agent may have an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. ; A polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane and (meth) acryloxypropyltrimethoxysilane; Containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane. ; And 3-chloropropyltrimethoxysilane, and the like, but are not limited thereto. The silane coupling agent may be included in an amount of 0.001 part by weight to 0.1 part by weight, specifically 0.02 part by weight to 0.05 part by weight, based on 100 parts by weight of the (meth) acrylic copolymer. Within the above range, endurance reliability is excellent, and changes in components and physical properties with time can be small.

The pressure-sensitive adhesive composition may include a solvent. The solvent improves the coating property of the pressure-sensitive adhesive composition and can prevent the self-curing reaction of the pressure-sensitive adhesive composition. The solvent may be any conventional solvent known to those skilled in the art. For example, the solvent may include one or more of methyl ethyl ketone, ethyl acetate, and toluene.

The solvent may be contained so that the solids content of the pressure-sensitive adhesive composition is from 17% by weight to 25% by weight, for example, from 18% by weight to 20% by weight. The risk of explosion of the drying furnace is low even when the pressure-sensitive adhesive composition is coated at a high level in the above solid content range, and the pressing effect can be improved by lowering the content of the volatile organic compounds.

The pressure-sensitive adhesive composition may further include at least one of a reworking agent, a curing catalyst, an antistatic agent, and a curing catalyst.

The reworking agent may include a polysiloxane oligomer or a mixture containing it to improve the reworkability of the adhesive film. The reworking agent may be included in an amount of 0.001 to 5 parts by weight, specifically 0.005 to 1 part by weight based on 100 parts by weight of the (meth) acrylic copolymer. In the above range, it is possible to improve the workability without affecting the physical properties of the polarizing plate adhesive film.

The antistatic agent suppresses the generation of static electricity during rework of the pressure-sensitive adhesive film, and may include a conventional antistatic agent. The antistatic agent may be contained in an amount of 0.001 to 5 parts by weight, specifically 0.1 to 3 parts by weight based on 100 parts by weight of the (meth) acrylic copolymer. Within the above range, the antistatic function can be provided without affecting the physical properties of the polarizing plate adhesive film.

The curing catalyst is a boron-based compound, e.g., boron trifluoride (boron trifuloride) complexes, in particular boron trifluoride rate (etherate), boron trifluoride tetrahydrofuran complex in a (BF ₃ -THF), Boron trifluoride aniline complex (BF ₃ -Aniline), specifically BF ₃ O (CH ₃ ) ₂ (boron trifluoride dimethyl etherate), BF ₃ O (C ₂ H ₅ ) ₂ (boron trifluoride diethyl etherate); Phosphine-based compounds such as triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, triphenylphosphine / triphenylborate, tetraphenylborate and the like; Secondary amine or tertiary amine compounds, for example alpha-tertiary amine compounds such as triethylamine, benzyldiethylamine or benzyldimethylamine (e.g. KH-30, Kukdo); Imidazole-based compounds such as 2-methylimidazole, 2-phenylimidazole, or 2-phenyl-4-methylimidazole; Sulfonic acid-based compounds such as para-toluenesulfonic acid, benzenedodecylsulfonic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid, methanesulfonic acid, methane disulfonic acid, phenolsulfonic acid and the like. The curing catalyst may be contained in an amount of 0.001 to 5 parts by weight, specifically 0.001 to 1 part by weight based on 100 parts by weight of the (meth) acrylic copolymer. Within this range, there is an effect of shortening the curing rate.

The pressure-sensitive adhesive composition may contain conventional additives. The additive may include an ultraviolet absorber, an antioxidant, a tackifier resin, a plasticizer, and the like. The additive may be included in an amount of 0.001 to 5 parts by weight, specifically 0.01 to 1 part by weight based on 100 parts by weight of the (meth) acrylic copolymer. Within the above range, the additive effect can be obtained without affecting the physical properties of the polarizing plate adhesive film.

The pressure-sensitive adhesive composition may have a viscosity of 1,000 cPs to 4,000 cPs at 25 占 폚. Within the above range, the thickness of the adhesive film can be easily adjusted, there is no unevenness in the adhesive film, and the coated surface can have a uniform effect.

Hereinafter, a pressure-sensitive adhesive film for a polarizing plate according to an embodiment of the present invention will be described.

The pressure sensitive adhesive film for a polarizing plate may be formed from the pressure sensitive adhesive composition for a polarizing plate according to an embodiment of the present invention.

The adhesive film may have a dent value of 10 탆 to 20 탆, for example, 13 탆 to 19 탆. In the above range, it can be recovered even if the pressing does not occur, and can be recovered quickly, so that it can be used for a polarizing plate. When applied to a polarizing plate, warping at high temperature and / or high temperature and high humidity satisfies an average value of 2 mm or less, It can be good.

The adhesive film is optically transparent and can be used in an optical display device. Specifically, the adhesive film may have a light transmittance of 85% or more, more specifically 85% to 95% at a wavelength of 380 nm to 780 nm.

The thickness of the adhesive film may be 100 占 퐉 or less, specifically 5 占 퐉 to 50 占 퐉. In the above range, it can be used in an optical display device.

The adhesive film can be produced by coating the pressure-sensitive adhesive composition for a polarizing plate to a predetermined thickness, drying it, and then aging at a constant temperature and humidity of 25 ° C to 35 ° C and a relative humidity of 30% to 60%.

The solvent in the adhesive film may be present in an amount of 100 ppm or less.

Hereinafter, a polarizing plate and an optical display device according to an embodiment of the present invention will be described.

The polarizing plate of the present invention may include a pressure-sensitive adhesive film for a polarizing plate according to embodiments of the present invention. The polarizing plate of the present invention can be manufactured by adhering a pressure sensitive adhesive film for a polarizing plate according to embodiments of the present invention to one side of a polarizing plate or by coating the pressure sensitive adhesive composition for a polarizing plate on a side of a polarizing plate to a predetermined thickness and then aging.

The optical display device of the present invention may include the pressure-sensitive adhesive film of the present invention or the polarizing plate of the present invention. The optical display device may include, but is not limited to, a liquid crystal display device and an organic light emitting display device. The optical display device of the present invention may also include a flexible device.

The polarizing plate may include a polarizer, an optical film formed on at least one side of the polarizer, and an adhesive film formed on at least one side of the optical film. The polarizer and the optical film are based on conventional contents known to those skilled in the art. The thickness of the polarizing plate may be 25 탆 to 100 탆, specifically 50 탆 to 85 탆. In the above range, it can be used in an optical display device. The polarizing plate may include a polarizer, an optical film formed on at least one side of the polarizer, and an adhesive film formed on the optical film. The optical film may be an optically transparent resin film, and may include a cellulose-based film including triacetyl cellulose and the like, a polyester film including a polyethylene terephthalate and the like, a polycarbonate film, an acrylic film, a cycloolefin polymer film and the like.

The polarizing plate may have a warp of 0 mm to 2 mm after being left at a high temperature for a long period of time (for example, at 60 to 85 DEG C for 250 to 500 hours). In the above range, the screen quality may be good even if left at a high temperature for a long time.

The liquid crystal display device is not particularly limited, but may include a liquid crystal display device including an IPS liquid crystal.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The specifications of the components used in the following examples and comparative examples are as follows.

(A) (Meth) Acrylic Copolymer: The (meth) acrylic copolymer

(B) Crosslinking agent: xylene diisocyanate adduct of trimethylolpropane (TD-75, Soken, solids content: 75% by weight)

(C) Silane coupling agent: 3-glycidoxypropyltrimethoxysilane (KBM-403, Shin-Etsu Co., solids content: 100% by weight)

Example  One

Ethyl acetate was added to a 1 L reactor equipped with a cooling device to reflux nitrogen gas and facilitate temperature control. 100 parts by weight of a monomer mixture comprising 97 mol% of n-butyl acrylate (BA) and 3 mol% of 4-hydroxybutyl acrylate (4-HBA) was added to the reactor. In order to remove oxygen from the monomer mixture, nitrogen gas was introduced for 30 minutes to replace the reactor, and the internal temperature of the reactor was maintained at 62 ° C. After homogeneously stirring the monomer mixture, 0.07 parts by weight of AIBN (azobisisobutyronitrile) was added as an initiator and reacted for 8 hours. Ethyl acetate was added to prepare a 24 wt% (meth) acrylic copolymer solution.

10.83 parts by weight of the crosslinking agent (B) and 0.03 part by weight of the silane coupling agent (C) based on the solids content were mixed with 100 parts by weight of the solid content of the above-prepared (meth) acrylic copolymer, and ethyl acetate was mixed with the solvent, A pressure-sensitive adhesive composition for a polarizing plate having a solid content was prepared.

Example  2 to Example  7

Except that the content of monomers in the monomer mixture in Example 1 was changed as shown in Table 1 and the content of initiator, reaction time, and the like were controlled so that the weight average molecular weight of the (meth) acrylic copolymer was changed as shown in Table 1 (Meth) acrylic copolymer was prepared.

The crosslinking agent (B) and the silane coupling agent (C) were mixed with each other in an amount of the following Table 1 based on 100 parts by weight of the solid content of the produced (meth) acrylic copolymer (A), and ethyl acetate was mixed with the solvent, Sensitive adhesive composition for a polarizing plate having a solid content of 1 part by weight was prepared.

Comparative Example  1 to Comparative Example  3

Except that the content of monomers in the monomer mixture in Example 1 was changed as shown in Table 1 and the weight average molecular weight of the (meth) acrylic copolymer was changed as shown in Table 1 by controlling the initiator content, reaction time, and the like In the same manner, a (meth) acrylic copolymer was prepared.

(B) a cross-linking agent, and (C) a silane coupling agent were mixed with 100 parts by weight of the prepared (A) (meth) acrylic copolymer on the basis of a solid content, and ethyl acetate was mixed as a solvent, A pressure-sensitive adhesive composition for a polarizing plate having a solid content of Table 1 was prepared.

BA
(mole%) 4-HBA
(mole%) Weight average
Molecular Weight PDI (A)
(Parts by weight) (B)
(Parts by weight) (C)
(Parts by weight) Solids content
(weight%) Example 1 97 3 90 million 3 100 10.83 0.03 18.66 Example 2 97 3 1.1 million 3.2 100 11.68 0.03 19.4 Production Example 3 95 5 90 million 2.7 100 10.83 0.03 18 Example 4 95 5 1.1 million 3.3 100 11.68 0.03 19.4 Example 5 93 7 90 million 3.3 100 10.5 0.03 18.66 Example 6 93 7 1 million 3.4 100 12 0.03 19.4 Example 7 93 7 1.1 million 3.4 100 10.5 0.03 20 Comparative Example 1 97 3 1.2 million 5.2 100 6.18 0.03 15.3 Comparative Example 2 95 5 90 million 2.7 100 6.18 0.03 19.4 Comparative Example 3 97 3 1.5 million 3.1 100 13.3 0.03 15.2

The properties of the pressure-sensitive adhesive composition for a polarizing plate of Examples and Comparative Examples were evaluated in the following Table 2.

(1) LEL (lower explosion limit) (unit:%): Measured in real time on a Testo LEL measuring instrument mounted in each coating drying zone, and the maximum LEL reading was recorded in each drying zone.

(2) Dent (unit: 占 퐉): The dent was measured using a polyethylene terephthalate (PET) film having a thickness of 38 占 퐉 as a release film. The pressure-sensitive adhesive compositions of Examples and Comparative Examples were applied to a PET release film (RPK-201, Toray Co., Ltd., thickness: 38 탆) and dried at 90 캜 for 4 minutes to produce a pressure-sensitive adhesive film having a thickness of 25 탆. The polyvinyl alcohol film was stretched three times at 60 DEG C, adsorbed iodine, and then stretched 2.5 times in an aqueous boric acid solution at 40 DEG C to prepare a polarizer (thickness: 23 mu m). A triacetyl cellulose (TAC) film (thickness: 80 占 퐉) was adhered to both surfaces of the prepared polarizer using an adhesive to prepare a polarizing plate. The adhesive film prepared above was laminated on one side of a TAC film (thickness: 42 탆) of the polarizing plate in a state in which the release film was adhered, and aged at 35 캜 and 45% for 48 hours. The polarizing plate having the release film and the adhesive film was cut into a width x length (15 mm x 50 mm). The cut polarizing plate was placed on a soda lime glass plate (thickness: 1 mm) so that the release film was directed to the top, and a TAC film (TAC film on which the adhesive film was not adhered) was fixed with an adhesive tape.

The dent was measured at 25 ° C using a TA Instrument (TEXTURE ANALYZER TA.XT PLUS, 5 kg load cell, EKO Instruments). A spherical stainless steel tip (diameter 1 mm) of TA Instrument was placed on the release film of the specimen at a height of 1 mm. The spherical stainless steel tip was pressed at a rate of 0.5 mm / sec for 15 seconds at a load of 40 gf, and then the spherical stainless steel tip was removed from the release film and left for 3 minutes. Then, the release film was removed and the pressing trace formed on the adhesive film was observed with a 3D optical profiler to record the maximum depth of the pressing trace (dent). The dent should be 10 占 퐉 to 20 占 퐉 so that the pressing phenomenon does not occur, the generated pressing can be recovered quickly, the high temperature warpage average value can be satisfied to 2 mm or less, and the durability reliability can be good.

(3) Warpage (unit: mm): The pressure-sensitive adhesive composition of Examples and Comparative Examples was applied to a polyethylene terephthalate release film and dried at 90 DEG C for 4 minutes. The obtained adhesive film had a thickness of 25 mu m. A polarizing plate having a triacetyl cellulose film adhered on both sides of the polarizer was prepared in the same manner as in (2). The adhesive film prepared above was laminated on one side of a triacetyl cellulose film (thickness: 42 탆) of the polarizing plate and aged at 35 캜 and 45% for 48 hours. The polarizing plate having the adhesive film was cut into a rectangular size having a length x width (260 mm x 180 mm, TD of a MD x polarizer of a polarizer), and then a non-alkali glass plate having a length x width x thickness (264 mm x 184 mm x 0.5 mm) Adhered via an adhesive film, and subjected to autoclave treatment at 50 DEG C for 1000 seconds to prepare specimens for bending measurement.

The obtained specimens were left in an oven at 60 ° C. for 250 hours, and the specimens were taken out of the oven and kept at room temperature for 1 hour. Then, as shown in FIG. 1, the specimen was divided into nine sections, and the heights of the glass plates from the bottom were measured for the first to eighth compartments, and the maximum value of the eight measured values was taken. The warpage should satisfy an average value of 0 mm to 2 mm.

(4) Endurance reliability: A polarizing plate to which an adhesive film was adhered was prepared in the same manner as in (2). The polarizing plate thus prepared was cut into a rectangular shape with a size of width x length (150 mm x 90 mm) (TD of the MD x polarizer of the polarizer). Then, the cut polarizing plate was attached to both sides of an alkali-free glass plate (width x length, 110 mm x 90 mm) via an adhesive film, and a pressure of 4 to 5 kg / cm ² was applied to prepare a sample. The specimens were allowed to stand at 85 占 폚 for 500 hours (heat-resistant reliability), or the specimens were left at 60 占 폚 and 95% relative humidity for 500 hours (wet heat resistance reliability)

○: No lift, drag, and bubble formation

Δ: At least one of lifting, dragging, and bubbling is present

X: A lot of lifting, attracting and bubbling occurs.

(5) Viscosity change rate (unit:%): 40 g of the pressure-sensitive adhesive composition of the examples and comparative examples were filled in a 50 ml vial bottle, and then spun with a spindle number (No. spindle 63, RPM 50) at 25 ° C with a Brookfield LV The viscosity is measured and the measured viscosity is referred to as V1. 40 g of the pressure-sensitive adhesive composition filled in the 50 ml vial bottle was allowed to stand at 25 캜 for 48 hours, and the viscosity was measured in the same manner. The measured viscosity was V2. The rate of change in viscosity was calculated as | V2 - V1 | / V1 x 100.

LEL Dent warp Endurance reliability Viscosity change rate Heat resistance Wet heat Example 1 13.6 16.2 1.52 ○ ○ 4.3 Example 2 14.8 15.3 1.63 ○ ○ 4.4 Example 3 13.2 16.5 1.82 ○ ○ 5.5 Example 4 15 14.6 1.88 ○ ○ 5.6 Example 5 14.4 16.5 1.72 ○ ○ 5.9 Example 6 15.5 13.5 1.9 ○ ○ 8.2 Example 7 16.2 16.7 1.82 ○ ○ 9.3 Comparative Example 1 22.1 23.5 1.9 ○ △ 4.9 Comparative Example 2 15.9 24.8 1.85 ○ △ 5.4 Comparative Example 3 21.9 5.2 2.9 ○ ○ 4.5

As shown in Table 2, the pressure-sensitive adhesive composition for a polarizing plate of the present invention had a low viscosity change rate and a low bending value. Further, the pressure sensitive adhesive composition for a polarizing plate of the present invention has a dent of 10 占 퐉 to 20 占 퐉, thereby suppressing the pressing of the pressure sensitive adhesive film by solid particles during processing, cutting, packaging and storage of the pressure sensitive adhesive film and / Can be recovered at a high speed, and the endurance reliability is excellent.

On the other hand, in Comparative Example 1 and Comparative Example 2, since the dent exceeded 20 占 퐉 and was pressed by a foreign substance, it was visually seen as a white spot or a black spot, so that appearance problems could be caused and damp heat resistance was not good. Further, in Comparative Example 3, the dent was less than 10 mu m and the warp value exceeded 2 mm, and thus the product was not usable.

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.

Claims (12)

A pressure-sensitive adhesive composition for a polarizing plate, comprising 100 parts by weight of a (meth) acrylic copolymer of a monomer mixture comprising a (meth) acrylic monomer having a hydroxyl group, 10 parts by weight to 15 parts by weight of a crosslinking agent,
Wherein the pressure-sensitive adhesive film for a polarizing plate formed from the pressure-sensitive adhesive composition for a polarizing plate has a dent value of 10 占 퐉 to 20 占 퐉.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the solids content of the pressure-sensitive adhesive composition for a polarizing plate is from 17 wt% to 25 wt%.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the pressure sensitive adhesive composition for a polarizing plate has a lower explosion limit (LEL) of 25% or less when coated at a coating speed of 50 m / m or more.
The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic copolymer is a copolymer of 1 mol% to 10 mol% of a (meth) acrylic monomer having a hydroxyl group and 90 mol% to 99 mol% of a (meth) acrylic monomer having an alkyl group Sensitive adhesive composition for a polarizing plate.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer has a weight average molecular weight of 800,000 to 1,200,000 and a polydispersity index of 4 or less.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the crosslinking agent comprises an isocyanate crosslinking agent having two or more functional groups.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the composition further comprises 0.001 part by weight to 0.1 part by weight of a silane coupling agent based on 100 parts by weight of the (meth) acrylic copolymer.
The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the composition has a viscosity change ratio of 10%
<Formula 1>
Viscosity change rate = | V2 - V1 | / V1 x 100
(In the above formula 1, V1 is the viscosity (unit: cps) measured at 25 占 폚 for 40 g of the pressure-sensitive adhesive composition,
V2 is the viscosity (unit: cps) measured at 25 캜 after 40 g of the pressure-sensitive adhesive composition was left at 25 캜 for 48 hours.
A pressure-sensitive adhesive film for a polarizing plate formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 8.
A polarizer comprising the pressure-sensitive adhesive film for a polarizer according to claim 9.
The polarizer according to claim 10, wherein the polarizer has a warpage of 0 mm to 2 mm measured after standing at 60 to 85 ° C for 250 to 500 hours.
An optical display device comprising the polarizing plate of claim 10.

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