KR20060067404A - Acry adhesive composition for large display device, and optical film with using the same - Google Patents

Abstract

The present invention relates to an acrylic pressure-sensitive adhesive composition for an optical film, and more particularly, including a high molecular weight acrylic copolymer, a medium molecular weight acrylic copolymer, and a crosslinking agent, which is caused by the difference in the dimensions of the substrate and the pressure-sensitive adhesive of the optical film for display. It relates to an acrylic pressure-sensitive adhesive composition that can minimize the residual stress.

Adhesive, Optical Film, Display Device, Residual Stress, End Flow, Workability

Description

ACRY ADHESIVE COMPOSITION FOR LARGE DISPLAY DEVICE, AND OPTICAL FILM WITH USING THE SAME}

1 is a view schematically showing a general liquid crystal display device,

FIG. 2 is an enlarged cross-sectional view illustrating the area A of FIG. 1.

The present invention relates to an acrylic pressure-sensitive adhesive composition for an optical film, and more particularly, including a high molecular weight acrylic copolymer, a medium molecular weight acrylic copolymer, and a crosslinking agent, which is caused by the difference in the dimensions of the substrate and the pressure-sensitive adhesive of the optical film for display. It relates to an acrylic pressure-sensitive adhesive composition that can minimize the residual stress.

Recently, it is also used as an adhesive for optical films that require a variety of high functionality and durability. In particular, the pressure-sensitive adhesive for adhering a polarizing film used for a liquid crystal device or the like to a substrate is becoming more severe in the use environment. Under such conditions, a dimensional change of the polarizing film occurs, and foaming, peeling, and light leakage easily occur due to the dimensional change, and this phenomenon is remarkable as the size increases. The pressure-sensitive adhesive for bonding the polarizing film to the substrate is improved to increase the molecular weight or increase the crosslinking degree so that the pressure-sensitive adhesive layer can withstand the use under harsh conditions, but the pressure-sensitive adhesive layer can withstand the harsh conditions by increasing the molecular weight of the pressure-sensitive adhesive or increasing the crosslinking degree. Since it is possible to forcibly suppress the dimensional change of the polarizing film by using an adhesive, it is possible to suppress the constant dimensional change or the dimensional change of a certain period of time, but the internal stress generated by the dimensional change in accordance with long-term use is the polarizing film The light leakage phenomenon in which the periphery of the liquid crystal device is brighter than the center part is concentrated at the periphery area compared to the center part of the liquid crystal device.

Japanese Patent Application Laid-Open No. 1980-207101 generally describes (A) an alkyl (meth) acrylic copolymer having a reactive functional group, (B) an alkyl (meth) acrylate (co) polymer having no functional group, and (C) the above. A pressure-sensitive adhesive layer containing at least two functional groups obtained by reacting with a reactive functional group and containing (A) and (B) in a weight ratio of 1: 4 to 4: 1 is at least a polarizing film. The invention of the polarizing plate laminated | stacked on one surface is disclosed. However, the invention described in the above document does not show the followability of the pressure-sensitive adhesive layer corresponding to the dimensional stability of the polarizing plate.

Japanese Patent Laid-Open Publication No. 1998-066283 has 1 to 12 carbon atoms containing 15 wt% or less of a polymer component having a weight average molecular weight of 100,000 or less and 10 wt% or more of a polymer component having a weight average molecular weight of 1 million or more. Disclosed is a polarizing plate provided with an acrylic polymer adhesive layer composed mainly of acrylate or methacrylate having an alkyl group. When the content of low molecular weight polymer is low, the traceability of the pressure-sensitive adhesive layer with respect to the dimensional change of the polarizing plate is low, and the internal stress occurring within a certain range can be resisted, but internal stresses that occur repeatedly over a long period of time concentrate on the periphery of the polarizing plate. As a result, color unevenness occurs on the surface of the liquid crystal element such as the periphery of the liquid crystal element becomes brighter or darker than the central portion. On the other hand, if the content of the low molecular weight polymer is high, the pressure-sensitive adhesive layer has high traceability to the dimensional change of the polarizing plate, and the internal stress generated in the long term can be alleviated. However, when cutting the polarizing plate, an adhesive flow occurs to contaminate the end of the polarizing plate. Causes many defects. Therefore, it is difficult to form the adhesive layer which has traceability to the dimensional change of a polarizing plate.

In addition, Japanese Patent Publication No. 1991-12471 discloses a technique for improving durability by adjusting the crosslinking density in a specific range using a high molecular weight acrylic pressure-sensitive adhesive in a specific range, but improving the durability by using a high molecular weight resin. Since the crosslinking density is severely changed depending on the amount of used, it is very difficult to control the crosslinking density between molecules and it is difficult to uniformly control the stress concentration phenomenon between the substrates.

In addition, Japanese Patent Laid-Open Publication No. 1995-301792 discloses a technique for controlling the deformation cohesion of an adhesive in order to solve the problem of screen unevenness of a liquid crystal display panel caused by stress concentration between an adhesive film and a glass plate in a heat and moisture resistant condition. Depending on the pressure-sensitive adhesive used, there is a problem that it is difficult to maintain a constant deformation cohesion such as a change over time due to the continuous progress of the crosslinking reaction. In particular, when the pressure-sensitive adhesive layer is prepared using a copolymer prepared by introducing a certain amount of reactive functional groups into the non-reactive acrylic main monomer, it is difficult to effectively control the crosslinking structure exhibiting cohesion and adhesion. There is a difficult problem.

In addition, Japanese Patent Application Laid-Open No. 1996-120238 discloses a technique using an alcohol containing an epoxy functional group in order to reduce the effect on the durability of the adhesive property change between the film and the glass plate according to the change in cohesion and adhesion of the pressure-sensitive adhesive over time. As a means for adjusting the cohesive force and adhesive force of the pressure-sensitive adhesive, it is insufficient to provide uniform cohesive force and adhesive force, and it is very difficult to control, resulting in insufficient effectiveness. That is, since the crosslinking agent used for the pressure sensitive adhesive mainly contains 3 or more reactive functional groups, it is difficult to precisely control the molecular structure of the pressure sensitive adhesive due to the complexity of the resulting pressure sensitive adhesive layer crosslinked structure.

The existing method minimizes the shrinkage stress of the pressure-sensitive adhesive by adding oligomers and low molecular weight (co) polymers having no curing functional group to the polymer copolymer. However, this method can reduce the shrinkage stress, but when cutting the polarizing plate, adhesive flow or contamination occurs at the end, which causes a great problem in workability and product application.

In order to solve the problems of the prior art as described above, the present invention is a pressure-sensitive adhesive composition comprising a high molecular weight copolymer and a medium molecular weight copolymer having a small functional group, more preferably using an adhesive having a low glass transition temperature and a low crosslinking degree In order to supplement the light leakage phenomenon by relieving the shrinkage stress, in particular, the conventional method used an unreactive oligomer, in the present invention by using a medium-molecular weight copolymer having a small number of functional groups by reducing the shrinkage without the flow or pressure of the end of the light leakage We want to make up for the phenomenon.

An object of the present invention is to provide an acrylic pressure-sensitive adhesive composition that can minimize the residual stress caused by the difference in the dimensional change of the substrate and the pressure-sensitive adhesive of the optical film.

Still another object of the present invention is to provide an optical film for display device, wherein the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition for display device is provided on one or both surfaces of the optical film for display device.

Still another object of the present invention is to provide a display device including an optical film for display device, wherein the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition for display device is provided on one or both surfaces of the optical film for display device.

The present invention,

(A) 100 parts by weight of a high molecular weight acrylic copolymer having a weight average molecular weight of 2,000,000 to 2,500,000, (B) 20-100 parts by weight of a medium molecular weight acrylic copolymer having a weight average molecular weight of 1,500,000 to 2,000,000, and (C) a crosslinking agent An adhesive composition comprising 0.001 to 5 parts by weight,

The high molecular weight acrylic copolymer (A) and the high molecular weight acrylic copolymer (B) may include (a) 90 to 99.9 parts by weight of an alkyl acrylate having an alkyl group having 4 to 12 carbon atoms, and (b) a functional group capable of crosslinking with the crosslinking agent. It is a copolymer polymerized with 0.1 to 10 parts by weight of a vinyl monomer having a monomer, wherein the content ratio of the vinyl monomer of the high molecular weight acrylic copolymer to the vinyl monomer of the medium molecular weight acrylic copolymer is 1: 0.1 to 0.99. And an acrylic pressure-sensitive adhesive for an optical film.

The present invention also provides an optical film for a display device, wherein the pressure-sensitive adhesive layer made of the acrylic adhesive composition for an optical film is provided on one side or both sides of the optical film for display device.

In addition, the present invention provides a display device comprising an optical film for a display device, the pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition for an optical film is provided on one side or both sides of the optical film for display device.

 The present invention relates to an acrylic pressure-sensitive adhesive composition which can minimize the residual stress caused by the difference in the dimensional change of the substrate and the pressure-sensitive adhesive. The present invention uses a high molecular weight copolymer and a medium molecular weight copolymer prepared by introducing a predetermined amount of a monomer having a reactive functional group into an unreactive acrylic main monomer, and by controlling the content of the monomer having a reactive functional group contained in the copolymer The crosslinked structure exhibiting cohesion and adhesion can be effectively controlled. Therefore, the pressure-sensitive adhesive composition according to the present invention improves the light leakage phenomenon of the display device by reducing the complex birefringence phenomenon generated in each component layer by the shrinkage stress of the polarizing plate mounted on the display device. Moreover, it is an acrylic adhesive composition excellent in general physical properties, such as initial adhesive force, a permanent adhesive force, a holding force, and cutting characteristics.

The conventional method minimizes the shrinkage stress of the pressure-sensitive adhesive by adding an oligomer to the polymer copolymer. However, this method is a good way to reduce the shrinkage stress, the adhesive flow occurs at the end when cutting the polarizer. In the present invention, high molecular weight and high molecular weight (co) polymers are blended to widen the molecular weight distribution, and in order to solve such problems, a medium molecular weight copolymer is used instead of an oligomer which serves as a plasticizer. And by using a minimum curing agent to improve the flow of the polymer chain to reduce the shrinkage stress to improve the light leakage phenomenon. In addition, the glass transition temperature (Tg) is -45 ℃ or less to control the shrinkage stress using the acrylic copolymer and the optimal curing system.

The acrylic pressure sensitive adhesive composition according to the present invention includes (A) 100 parts by weight of a high molecular weight acrylic copolymer, (B) 20 to 100 parts by weight of a medium molecular weight acrylic copolymer, and (C) 0.001 to 5 parts by weight of the crosslinking agent.

When the high molecular weight acrylic copolymer and the medium molecular weight acrylic copolymer are prepared, the monomer is 90 to 99.9% by weight of alkyl (meth) acrylate having 4 to 12 carbon atoms, preferably 95 to 99.9% by weight, and a polyfunctional compound. 0.1 to 10% by weight of the functional group-containing monomer having a reactivity, preferably 0.1 to 5% by weight.

In the high molecular weight copolymer, a vinyl monomer content having a functional group crosslinkable with the crosslinking agent to a vinyl monomer content ratio having a functional group crosslinkable with the crosslinking agent in the medium molecular weight acrylic copolymer is 1: 0.1 to 0.99, acrylic type for optical film It relates to an adhesive.

In order to minimize the light leakage phenomenon by excellent relaxation effect of the internal stress caused by the difference in the dimensional change of the substrate and the pressure-sensitive adhesive constituting the optical film, the acrylic pressure-sensitive adhesive composition for an optical film according to the present invention has a gel fraction of 40 ~ 60% is preferred.

The glass transition temperature (Tg) of the high molecular weight and the medium molecular weight acrylic copolymer is -45 ° C or lower, preferably -60 to -45 ° C. If the glass transition temperature exceeds -45 ℃, the shrinkage stress of the polarizing film does not relieve long term.

The weight average molecular weight of the high molecular weight acrylic copolymer constituting the pressure-sensitive adhesive composition of the present invention is 2 million to 2.5 million, preferably in the range of 2.2 million to 2.5 million. By using the high molecular weight acrylic copolymer in this manner, it is possible to ensure good adhesion between the substrate and the polarizing plate or the retardation plate and the polarizing plate and to prevent foaming or peeling. The weight average molecular weight of the medium molecular weight acrylic copolymer is 1.5 million to 2 million, preferably 1.5 million to 1.8 million. Suitable molecular weight control of the acrylic copolymer can be achieved by appropriately adjusting conditions such as polymerization time, polymerization initiator, polymerization reaction temperature, polymerization solvent. In one embodiment according to the present invention, the preparation of high molecular weight acrylic copolymer is a temperature of 60 ℃ to 63 ℃, polymerization initiator initiator azobisisobutyronitrile (AIBN) 0.1 to 0.18 parts by weight, and the like, the medium molecular weight acrylic copolymer The preparation may be polymerized under conditions such as a temperature of 64 ° C. to 68 ° C. and a polymerization reaction initiator azobisisobutyronitrile (AIBN) 0.19 to 0.25 parts by weight.

The said high molecular weight and the medium molecular weight acrylic copolymer are copolymers of the functional group containing monomer which has alkylacrylate as a main component and is reactive with this acrylic acid ester and a polyfunctional compound (C). Examples of the alkyl acrylate having an alkyl group having 4 to 12 carbon atoms to form the high molecular weight and the medium molecular weight acrylic copolymer include methyl arcrate, ethyl acrylate, propyl acrylate, n-butyl acrylate and iso-butyl acryl. Elate, 2-ethylhexyl acrylate, n-octyl acrylate, iso-octyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate and the like, but is not limited thereto. The alkyl acrylates may be used alone or in combination of two or more thereof.

Examples of the functional group-containing monomer having reactivity with the crosslinking agent include a vinyl monomer containing a carboxyl group, a vinyl monomer containing a hydroxy group, a vinyl monomer containing an amino group, a vinyl monomer containing an epoxy group, and an acetoacetyl group. Vinyl monomers and the like. Among these, the monomer containing a carboxyl group and the monomer containing a hydroxy group are preferable.

Examples of the vinyl monomer having a carboxyl group include, but are not limited to, acrylic acid, beta-carboxyethyl acrylate, itaconic acid, crodonic acid, maleic acid, maleic anhydride and butyl maleic acid. Examples of the vinyl monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and chloro-2-hydroxypropyl (Meth) acrylate, diethylene glycol mono (meth) acrylate, and aryl alcohol. Examples of the monomer containing an amino group include aminomethyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate and vinylpyridine. Moreover, the monomer containing an epoxy group, such as glycidyl (meth) acrylate, and the monomer containing an aceto acetyl group, such as acetoacetoxyethyl (meth) acrylate, etc. are mentioned. The said substance can be used individually or in combination of 2 or more types.

The functional group of the multifunctional compound reacts with the functional group having the reactivity of the acrylic copolymer, and may be at least two functional groups, preferably 2 to 4 functional groups in one molecule. As an example of such a polyfunctional compound, an isocyanate type compound, an epoxy type compound, an amine type compound, a metal chelate type compound, an aziridine type compound, etc. are mentioned.

As an example of an isocyanate type compound, triene diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethyl xylene diisocyanate And receptors with polyols such as naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and trimethylolpropane, and the like.

Moreover, as an example of an epoxy type compound, bisphenol A and epichlorhydrin type epoxy resin. Ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycol Cydylaniline, diglycidylamine, N, N, N ', N'-tetraglycidyl-m-xylenediamine and 1,3-bis (N, N'-diglycidylaminemethyl) cyclohexane Etc. can be mentioned.

Examples of the amine compound include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isoformdiamine, amino resins and methylene resins.

Examples of the metal chelate compound include compounds in which polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium are assigned to acetylacetone or ethyl acetoacetate.

Examples of the aziridine-based compound include N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxide) and N, N'-toluene-2,4-bis (1-aziridinecarboxes) Id), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphineoxide, N, N'-hexamethylene-1,6-bis (1-aziri Dicarboxylic acid), trimethylolpropane-tri-beta-aziridinylpropionate, tetramethylolmethane-tri-beta-aziridinylpropionate, and the like.

The polyfunctional compound may be used in an amount of usually 0.001 to 5 parts by weight, preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the high molecular weight acrylic copolymer. By using a polyfunctional compound in such content, a preferable three-dimensional crosslinked structure is formed between the said high molecular weight (meth) acrylic-type copolymer. In addition, these polyfunctional compounds can be used individually or in combination.

Any known method may be employed for producing the high molecular weight acrylic copolymer and the medium molecular weight acrylic copolymer constituting the pressure-sensitive adhesive for polarizing plates of the present invention.

For example, high molecular weight acrylic copolymers. 0.01 to 0.5 parts by weight of a polymerization initiator (azo-based polymerization initiators such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, peroxides such as benzoyl peroxide and acetyl peroxide, diphenyl ketone, and 2 Photopolymerization initiators such as -hydroxy-2-methyl-1-phenyl-propan-1-one and the like), and are synthesized by a method such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, or the like. Synthesized by polymerization. In the case of the solution polymerization method, ethyl acetate, toluene, hexane, acetone, and the like are used as the polymerization solution, and the reaction temperature is 50 to 150 ° C, preferably 50 to 110 ° C, and the reaction time is 2 to 15 hours, preferably 7 To 10 hours.

In addition, the high molecular weight acrylic copolymer is synthesized by a method such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like, preferably high molecular weight acrylic copolymer. 0.01 to 0.1 parts by weight of a polymerization initiator (azo-based polymerization initiators such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, peroxides such as benzoyl peroxide and acetyl peroxide, diphenyl ketone, 2- Photopolymerization initiators such as hydroxy-2-methyl-1-phenyl-propan-1-one and the like), and are synthesized by a method such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and preferably solution polymerization. Are synthesized.

In the case of the solution polymerization method, ethyl acetate, toluene, hexane, acetone and the like are used as the polymerization solution, the reaction temperature is 50 to 150 ° C, preferably 50 to 110 ° C, and the reaction time is 2 to 15 hours, preferably 5 To 10 hours.

The adhesive for polarizing plates of this invention contains a high molecular weight acrylic copolymer, a high molecular weight acrylic copolymer, and a crosslinking agent as mentioned above, and is a weathering stabilizer, a tachyfire, a plasticizer, a softener, a dye, a pigment, and a silane coupler which are normally mix | blended with an adhesive. A ring agent, an inorganic filler, etc. can be mix | blended further.

The silane coupling agent used in the pressure-sensitive adhesive composition of the present invention can effectively promote the adhesion between the glass substrate and the pressure-sensitive adhesive, and in particular, helps to improve adhesion reliability when left for a long time under high temperature and high humidity conditions, and when considering such a function As for the usage-amount, 0.01-0.1 weight part is preferable with respect to 100 weight part of acrylic copolymers. Examples of the silane coupling agent may include, but are not limited to, vinylsilane, epoxy silane, methacrylsilane, and the like.

The present invention also relates to an optical film for a display device, wherein the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition for an optical film described above is provided on one side or both sides of a substrate of the optical film for display device, and a display device provided with the optical film. will be. Examples of the display device include a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display device (PDP), and the like.

1 is a view schematically showing a general liquid crystal display device.

Referring to FIG. 1, the liquid crystal display device 800 includes a liquid crystal display panel 500 including a liquid crystal cell 560 between a pair of transparent panels 520 and 540, and first and second polarized light incident thereto. 2 includes optical films 610 and 630 and a backlight assembly 700 for generating the light and providing the light to the liquid crystal display panel 500. The first optical film 610 is positioned on the liquid crystal display panel 500, and the second optical film 630 is interposed between the liquid crystal display panel 500 and the backlight assembly 700.

The first and second optical films 610 and 630 divide incident light into two orthogonal components, and transmit only one light component among the two light components to make the transmission direction of light constant. . That is, the first and second optical films 610 and 630 absorb light that vibrates in the same direction as the polarization axis of the first and second optical films 610 and 630 among the incident light, and other directions. The light vibrating is transmitted. In this case, the polarization axis of the first optical film 620 and the polarization axis of the second optical film 620 are perpendicular to each other.

FIG. 2 is an enlarged cross-sectional view illustrating an area A of FIG. 1 and is an enlarged cross-sectional view of an optical film used in a conventional STN or CSTN liquid crystal display, and includes a first transparent film between the release film 12 and the protective film 28. A polarizing film 26 composed of a protective film 20, a polarizer 22, and a second transparent protective film 24, and a retardation film 16 is laminated below the polarizing film 26, wherein the retardation film ( 16 is attached by the polarizing film 26, the protective film 12 and the first and second adhesive layers (14, 18).

The thickness of the pressure-sensitive adhesive layer formed, as a dry thickness may be in the range of usually 10 to 100 um, preferably 20 to 50 um.

The optical film may be a polarizing film, a reflective polarizing film, a retardation film, or the like, and preferably, may be an optical film for a display device, which is an elliptical polarizing film in which a polarizing film and a retardation film are laminated using the acrylic pressure-sensitive adhesive composition. .

As a polarizing film used by this invention, a conventionally well-known polarizing film can be used. For example, a film made of polyvinyl alcohol-based resin such as polyvinyl alcohol, polyvinyl formal, polyvinyl acetal and saponified ethylene vinyl acetate copolymer may contain polarizing components such as iodine dye or dichroic dye. As a polarizer obtained by extending | stretching, the multilayer film etc. which laminated | stacked transparent protective films, such as cellulose-type films, such as cellulose acetate, a polycarbonate film, and a polyether sulfone type film, can be used. There is no restriction | limiting in particular in the method of forming an adhesive layer in such a polarizing film, Although the method of apply | coating and drying the said adhesive using a bar coater etc. directly on this polarizing film surface can be employ | adopted, The said adhesive is once peelable base material After apply | coating to a surface and drying, the method of transferring the adhesive layer formed in the surface of this peelable base material to the polarizing film surface, and then aging can be employ | adopted.

In order to improve contrast, the optical film of the present invention may further include a λ / 4 retardation layer that causes circularly polarized light in addition to the polarizing film. The λ / 4 retardation layer may be a polymer film having birefringence or a liquid crystal coating layer arranged in one direction, and may include both a polymer film and a liquid crystal coating layer. The λ / 4 retardation layer serves to impart a retardation of approximately 1/4 wavelength to each wavelength of the visible region, and preferably has excellent controllability, transparency, and heat resistance of birefringence. The material of the λ / 4 retardation layer is not particularly limited, but when the λ / 4 retardation layer is a polymer film having birefringence, polycarbonate, polycarbonate copolymer, polyethylene, polypropylene ), Polynorbornene, polyvinylchloride, polystyrene, polyacrylonitrile, polyester, polyester, polysulfone, polyallyl A film comprising at least one selected from the group consisting of polyarylate, polyvinylalcohol, polymethacrylic ester, polyacrylic ester, and cellulose ester It is preferable.

In addition, the polymer film constituting the λ / 4 retardation layer is preferably a transparent film stretched at 1.1 to 3 magnification, it may be uniaxial or biaxially stretched.

In the case of the film with a polarizing film or retardation film of this invention, other functional layers, such as a protective layer, a reflection layer, and an glare-proof layer, may be laminated | stacked, for example.

In addition, when the optical film of the present invention is used as an optical filter for a plasma display device, in addition to the polarizing film or a film in which the polarizing film and the retardation film are laminated, a hard coating layer, a Ne light blocking layer, an electromagnetic wave shielding layer, and an antireflection layer It may further include one or more functional layers selected from the group consisting of a near infrared ray blocking layer, an antistatic layer, and an antiglare layer.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the following examples are illustrative only and are not intended to limit the scope of the present invention to the examples.

Examples 1 to 5: Acrylic Copolymer Preparation

In Examples 1 to 5, n-butyl acrylate, acrylic acid, and 4-hydroxybutyl (meth) acrylate as a polymerization monomer, 100 g of ethyl acetate as a solvent, and azobisisobutyronitrile (AIBN) as a polymerization initiator were used. To the reaction vessel in the amount shown in Table 1 below. After replacing the air in the reaction vessel with nitrogen gas, the reaction solution was heated to 63 DEG C while stirring to polymerize during the reaction time shown in Table 1. After the reaction, the mixture was diluted with 100 g of ethyl acetate to obtain a solid acrylic copolymer solution. The solids content of the solution in the polymer was measured after the initial weight of the pressure-sensitive adhesive using a solids tester and blown the solvent at 100 ℃ for 30 minutes and then weighed. The molecular weight of the polymer was measured using gel permeation chromatography (GPC). The glass transition temperature was measured by using a differential scanning calorimeter (DSC), drying the pressure-sensitive adhesive at 100 ° C for 3 hours, taking a sample weight of 4-8mg into an aluminum pan, and increasing the temperature increase rate under nitrogen flow by a differential scanning calorimeter (DSC) at 10 ° C / min. It was found by measuring from -70 ° C to 20 ° C. The physical properties are shown in Table 2 below.

Comparative Examples 1 to 5: Acrylic Copolymer Preparation

In Comparative Examples 1 to 5, n-butyl acrylate, methacrylate, acrylic acid, and 4-hydroxybutyl (meth) acrylate were used as the polymerization monomers in the compounding amounts shown in Table 1, and the polymerization initiator initiator content and reaction time were used. Was carried out substantially in the same manner as in Example except that the polymerization was carried out according to the conditions shown in Table 1.

n-BA MA AA 4-HBA AIBN Response time (hr) Example 1 98 0 One One 0.015 15 Example 2 98 0 One One 0.017 13 Example 3 98 0 One One 0.019 11 Example 4 99 0 One 0 0.020 8 Example 5 99 0 One 0 0.022 7 Comparative Example 1 84 10 5 One 0.015 15 Comparative Example 2 74 20 5 One 0.017 13 Comparative Example 3 64 30 5 One 0.020 9 Comparative Example 4 54 40 5 0 0.022 7 Comparative Example 5 44 50 5 0 0.023 5

In Table 1 above,

n-BA: n-butyl acrylate MA: methyl acrylate

AA: 4-HBA acrylic acid: 4-hydroxybutyl (meth) acrylate

AIBN: azobisisobutyronitrile

Solid content (%) Molecular Weight (Mw) Tg (℃) Example 1 20.2 2.5 million -53 Example 2 19.5 2.12 million -52.5 Example 3 18.3 2 million -50.25 Example 4 16.5 1.7 million 49.5 Example 5 15.5 1.5 million -48 Comparative Example 1 20.4 2.39 million -42 Comparative Example 2 18.5 2.15 million -38 Comparative Example 3 16.5 2 million -35 Comparative Example 4 14 1.8 million -32 Comparative Example 5 13.5 1.5 million -28

Examples 6 to 17: polarizing plate to which the pressure-sensitive adhesive is applied

The polymers obtained in Examples 1 to 5 were mixed at the compounding ratios shown in Table 3 below, and 0.2 g of a solid content of trimethylhexamethylenediamine was added thereto as a crosslinking agent and stirred well to obtain a pressure-sensitive adhesive solution for polarizing plates.

The adhesive solution for polarizing plates thus obtained was applied to a polyester release film and then dried. At this time, it adjusted so that the coating thickness after drying might be 25um. Next, the adhesive applied on this release film was transferred onto a 200 um polarizing film, and aged for 7 days at a temperature of 23 ° C. and a humidity of 45% to obtain a polarizing plate of the present invention.

By cutting a polarizer The pressure-sensitive adhesive layer provided to a 210 mm x 297 mm so that the 45 ℃ with respect to the polarizer long side absorption axis and held 60 minutes the polarizing plate at one side 30 ℃, and pressure conditions of 5 kg / cm ² on the surface of the glass sheet Adhesion.

The sample thus obtained was left to stand at 70 ° C. and 97% for 500 hours to evaluate the state of foaming and dropping by visual observation. The state of color staining was visually observed and evaluated. The distance from which the position shifted was measured with Nonius (North).

The gel fraction was collected from a sample bottle of about 0.1 g of the pressure-sensitive adhesive aged on a support at a temperature of 23 ° C. and a humidity of 65% RH. 50 g of ethyl acetate was stirred for 24 hours, and then the contents of the sample bottle were stained with 200 mesh. The mesh was filtered through a lance wire mesh, and the residue on the wire mesh was dried at 100 ° C. for 2 hours to measure a dry weight, which was obtained by the following formula [I].

Gel fraction (%) = (dry weight / adhesive extract weight) × 100

Physical property measurement results are shown in Table 4 below.

Comparative Examples 6 to 17: polarizing plate to which the pressure-sensitive adhesive is applied

Except for mixing the polymer obtained in Comparative Examples 1 to 5 in the blending ratio shown in Table 3, a polarizing plate was prepared in substantially the same manner as in Example 1, and the physical properties of the polarizing plate were measured. Indicated.

Ingredient 1 Component 2 Kinds Content (g) Kinds Content (g) Example 6 Example 1 100 Example 4 100 Example 7 Example 1 100 Example 4 50 Example 8 Example 1 100 Example 5 100 Example 9 Example 1 100 Example 5 50 Example 10 Example 2 100 Example 4 100 Example 11 Example 2 100 Example 4 50 Example 12 Example 2 100 Example 5 100 Example 13 Example 2 100 Example 5 50 Example 14 Example 3 100 Example 4 100 Example 15 Example 3 100 Example 4 50 Example 16 Example 3 100 Example 5 100 Example 17 Example 3 100 Example 5 50 Comparative Example 6 Example 1 100 Comparative Example 4 100 Comparative Example 7 Example 1 100 Comparative Example 4 50 Comparative Example 8 Example 1 100 Comparative Example 5 100 Comparative Example 9 Example 1 100 Comparative Example 5 50 Comparative Example 10 Example 2 100 Comparative Example 4 100 Comparative Example 11 Example 2 100 Comparative Example 4 50 Comparative Example 12 Example 2 100 Comparative Example 5 100 Comparative Example 13 Example 2 100 Comparative Example 5 50 Comparative Example 14 Example 3 100 Comparative Example 4 100 Comparative Example 15 Example 3 100 Comparative Example 4 50 Comparative Example 16 Example 3 100 Comparative Example 5 100 Comparative Example 17 Example 3 100 Comparative Example 5 50

Gel fraction (%) Dry heat test 100 ?? x 500 hours Gun * wet heat TEST 70 ?? x 97% x 500 hours exfoliation firing Light fountain exfoliation firing Light fountain Example 6 43 o o o o o o Example 7 47 o o o o o o Example 8 42 o o o o o o Example 9 48 o o o o o o Example 10 40 o o o o o o Example 11 46.5 o o o o o o Example 12 41 o o o o o o Example 13 47 o o o o o o Example 14 42 o o o o o o Example 15 48 o o o o o o Example 16 40 o o o o o o Example 17 49 o o o o o o Comparative Example 6 75 o x o △ x Comparative Example 7 82 △ x x △ x x Comparative Example 8 72 o △ x o △ x Comparative Example 9 80 △ x x △ x x Comparative Example 10 70 o △ x o △ x Comparative Example 11 81 △ x x △ x x Comparative Example 12 72 o △ x o △ x Comparative Example 13 79 △ x x △ x x Comparative Example 14 70 o △ x o △ x Comparative Example 15 78 △ x x △ x x Comparative Example 16 73 o △ x o △ x Comparative Example 17 80 △ x x △ x x

O: Good (Shipped: None, Foamed: None, Light Leaks: Ansam)

(Triangle | delta): Good (Peeling: A little peeling, Foaming: Some occurrence, Light leak: A slight leak)

X: Severe (Skin: Peeling a lot, Foaming: A lot, Light leak: Many leaks)

By the above experiment, the high molecular weight copolymer and the low molecular weight copolymer having a low functional group, the low glass transition temperature, and the adhesive having a low crosslinking degree are used to mitigate the shrinkage stress to compensate for the light leakage phenomenon. In particular, the conventional method used an unreactive oligomer, but in this experiment, by using a medium molecular weight copolymer having a small number of functional groups, it can be seen that the light leakage phenomenon and all other problems can be compensated for by alleviating shrinkage without flowability or crushing at the end. Could.

 The present invention provides an acrylic pressure sensitive adhesive for an optical film comprising a high molecular weight acrylic copolymer, a medium molecular weight acrylic copolymer, and a crosslinking agent, thereby minimizing residual stress caused by the difference in the dimensions of the substrate and the pressure sensitive adhesive of the optical film for display. It can be widely used in optical films and display devices.

Claims (14)

(A) 100 parts by weight of a high molecular weight acrylic copolymer having a weight average molecular weight of 2,000,000 to 2,500,000, (B) 20-100 parts by weight of a medium molecular weight acrylic copolymer having a weight average molecular weight of 1,500,000 to 2,000,000, and (C) a crosslinking agent An adhesive composition comprising 0.001 to 5 parts by weight, The high molecular weight acrylic copolymer (A) and the high molecular weight acrylic copolymer (B) may include (a) 90 to 99.9 parts by weight of an alkyl acrylate having an alkyl group having 4 to 12 carbon atoms, and (b) a functional group capable of crosslinking with the crosslinking agent. It is a copolymer polymerized with 0.1 to 10 parts by weight of a vinyl monomer having a monomer, wherein the content ratio of the vinyl monomer of the high molecular weight acrylic copolymer to the vinyl monomer of the medium molecular weight acrylic copolymer is 1: 0.1 to 0.99. , Acrylic adhesive for optical films. The acrylic pressure sensitive adhesive of claim 1, wherein the glass transition temperature of the acrylic copolymer is -60 to -45 ^o C. The acrylic pressure sensitive adhesive of claim 1, wherein the gel fraction of the pressure sensitive adhesive is 40-60%. The acrylic pressure-sensitive adhesive for optical film according to claim 1, wherein the vinyl monomer having a functional group crosslinkable with the crosslinking agent is at least one vinyl monomer selected from the group consisting of a vinyl monomer having a carboxyl group and a vinyl monomer having a hydroxy group. . The acrylic pressure-sensitive adhesive composition of claim 1, wherein the pressure-sensitive adhesive composition further comprises a (D) silane coupling agent selected from the group consisting of vinylsilane, epoxy silane, and methacrylsilane. The acrylic pressure-sensitive adhesive composition of claim 1, wherein the alkyl acrylate is selected from the group consisting of butyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, n-octyl acrylate, and isononyl acrylate. The acrylic pressure-sensitive adhesive composition of claim 1, wherein the vinyl monomer having a carboxyl group is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and maleic acid. The vinyl monomer having a hydroxyl group according to claim 1 is 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene. Acrylic pressure-sensitive adhesive composition which is selected from the group consisting of glycol (meth) acrylate. The acrylic pressure-sensitive adhesive composition of claim 1, wherein the crosslinking agent is selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and tolylene diisocyanate adducts of trimethylolpropane. The optical film for display apparatus provided with the adhesive layer which consists of an acrylic adhesive composition for optical films of any one of Claims 1-9 on one side or both sides of the base material of a display optical film. The optical film for display device according to claim 10, wherein the pressure-sensitive adhesive layer has a dry thickness of 10 to 100 um. The optical film for display of claim 11, wherein the optical film is a polarizing film, a reflective polarizing film, or a retardation film.  The optical film for display device according to claim 10, wherein the optical film is an elliptical polarizing film in which a polarizing film and a retardation film are laminated using the acrylic pressure-sensitive adhesive composition. A display device comprising the optical film for display device, wherein the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition for optical film according to any one of claims 1 to 9 is provided on one or both surfaces of the substrate of the optical film for display device.

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