JP2010126722A - Light leakage controlling self-adhesive composition and optical film coated with the same for display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light leakage controlling self-adhesive composition reducing contraction stress of a self-adhesive to complement a light leakage phenomenon and minimizing residual stress occurring by a dimensional change difference between a base material of an optical film and the self-adhesive, and to provide an optical film coated with the composition for a display. <P>SOLUTION: The light leakage controlling adhesive composition includes three kinds of acrylic copolymers different in weight-average molecular weight and a crosslinking agent. The acrylic copolymers are reactive copolymers polymerized with (a) 90-99.9 pts.wt. of an alkyl acrylate having 4-12C alkyl groups and (b) 0.1-10 pts.wt. of a vinyl monomer having functional groups crosslinkable with the crosslinking agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light leakage control pressure-sensitive adhesive composition and an optical film for a display device to which the composition is applied, and more particularly, to reduce the shrinkage stress of the pressure-sensitive adhesive to complement the light leakage phenomenon. The present invention relates to a light leakage control pressure-sensitive adhesive composition capable of minimizing a residual stress generated by a dimensional change difference between a base material of the optical film and the pressure-sensitive adhesive, and an optical film for a display device to which the composition is applied.

  Recently, various pressure-sensitive adhesives for optical films that require high functionality and durability reliability have been used. In particular, pressure-sensitive adhesives for bonding polarizing films used in liquid crystal elements and the like to substrates have a more severe use environment. It has become. Under such conditions, a dimensional change occurs in the polarizing film, and foaming, peeling, and light leakage are likely to occur due to the dimensional change, and this phenomenon becomes more noticeable as the size increases. The pressure-sensitive adhesive for bonding the polarizing film to the substrate has been improved so that the pressure-sensitive adhesive layer can withstand use under severe conditions by increasing the molecular weight or increasing the degree of crosslinking. Increasing the molecular weight of the pressure-sensitive adhesive or increasing the degree of cross-linking so that the pressure-sensitive adhesive layer can withstand harsh conditions is to use the pressure-sensitive adhesive to forcibly suppress the dimensional change of the polarizing film. Therefore, it is possible to suppress a certain dimensional change or a dimensional change for a certain period, but the internal stress generated by the dimensional change due to long-term use is less in the peripheral part than in the central part of the polarizing film. Therefore, there is a problem that a light leakage phenomenon occurs in which the peripheral portion of the liquid crystal element becomes brighter than the central portion.

  Patent Document 1 below generally includes (A) an alkyl (meth) acrylic copolymer having a reactive functional group, (B) an alkyl (meth) acrylate (co) polymer having no functional group, and (C ) It is composed of a polyfunctional compound having at least two functional groups obtained by reacting with the reactive functional group, and contains (A) and (B) in a weight ratio of 1: 4 to 4: 1. An invention of a polarizing plate in which a reduced pressure adhesive layer is laminated on at least one surface of a polarizing film is disclosed. However, the invention described in Patent Document 1 cannot express the followability of the pressure-sensitive adhesive layer corresponding to the dimensional stability of the polarizing plate.

  In Patent Document 2 below, a polymer component having a weight average molecular weight of 100,000 or less is contained in 15% by weight or less, and a polymer component having a weight average molecular weight of 1,000,000 or more is contained in 10% by weight or more. A polarizing plate to which an acrylic polymer adhesive layer mainly composed of acrylate or methacrylate having 12 alkyl groups is attached is disclosed. When the content of the low molecular weight polymer is low, the followability of the pressure-reducing adhesive layer with respect to the dimensional change of the polarizing plate is low and the internal stress generated from within a certain range can be resisted. Color unevenness occurs on the surface of the liquid crystal element, for example, stress concentrates on the peripheral part of the polarizing plate and the peripheral part of the liquid crystal element becomes brighter or darker than the central part. On the other hand, if the content of the low molecular weight polymer is high, the followability of the pressure-reducing adhesive layer with respect to the dimensional change of the polarizing plate is high, and the internal stress generated in the long term can be relieved, but the polarizing plate is cut. When this occurs, the flow of the pressure-sensitive adhesive is generated, contaminating the edge of the polarizing plate, and causing many defects. For this reason, it is difficult to form an adhesive layer having followability with respect to the dimensional change of the polarizing plate.

  Moreover, although the following patent document 3 uses the high molecular weight acrylic adhesive, the crosslinking density is adjusted within a specific range, and a technique for improving the high temperature adhesive force and improving the durability is disclosed. Because the high molecular weight resin is used, the crosslink density changes drastically depending on the amount of crosslinker used, making it extremely difficult to adjust the intermolecular crosslink density, making it difficult to uniformly adjust the stress concentration phenomenon between substrates. There are disadvantages.

  Further, in Patent Document 4 below, in order to solve the problem of non-uniformity of the screen of the liquid crystal display plate caused by stress concentration between the adhesive film and the glass plate under heat and humidity resistance conditions, However, there is a problem that it is difficult to maintain a constant deformation cohesive force, such as a change with time due to the continuous progress of the crosslinking reaction depending on the pressure-sensitive adhesive used. In particular, the content of the crosslinking agent used when producing a pressure-sensitive adhesive layer using a copolymer produced by introducing a certain amount of a reactive functional group into a non-reactive acrylic main monomer is extremely low. For this reason, there is a problem that it is difficult to effectively adjust the cross-linked structure representing the cohesive strength and the adhesive strength.

  In addition, the following Patent Document 5 contains an epoxy functional group in order to reduce the influence of the adhesive property change between the film and the glass plate depending on the cohesive force and adhesive force change of the adhesive on the durability. Although the technology using the alcohol is disclosed, in order to give uniform cohesive force and adhesive force as a means to adjust the cohesive force and adhesive force of the pressure-sensitive adhesive, there is a lack of feasibility and adjustment is not possible. Because it is extremely difficult, its effectiveness is insufficient. That is, since the crosslinking agent used for the pressure-sensitive adhesive mainly contains 3 or more reactive functional groups, it is difficult to accurately control the molecular structure of the pressure-sensitive adhesive due to the complexity of the resulting pressure-sensitive adhesive layer crosslinking structure.

  On the other hand, among the conventional methods, there is a method for minimizing the shrinkage stress of the pressure-sensitive adhesive by adding an oligomer having no curing functional unit and a low molecular weight (co) polymer to the polymer copolymer. However, such a method can reduce the shrinkage stress, but when the polarizing plate is cut, an adhesive flow or contamination is generated at the end, which causes a great problem in workability and product application. .

Japanese Patent Publication No. 1980-207101 Japanese Patent Publication No. 1998-066283 Japanese Patent Publication No. 9911-12471 Japanese Patent Publication No. 1995-301792 Japanese Patent Publication No. 1996-120238

  The present invention has been made to solve the above problems, and the object of the present invention is to provide a reactive high molecular weight copolymer, a reactive medium molecular weight copolymer, and a reactive low molecular weight copolymer. A pressure-sensitive adhesive composition containing coalescence, more preferably a pressure-sensitive adhesive having a low glass transition temperature and a low degree of crosslinking, is used to relieve the shrinkage stress to supplement the light leakage phenomenon. In the present invention, by using a reactive medium molecular weight copolymer and a reactive low molecular weight copolymer double, the shrinkage can be reduced without end flowability or pressing property. By providing a pressure-sensitive adhesive composition for controlling light leakage, which can complement the light leakage phenomenon and the like, and can minimize the residual stress generated by the dimensional change difference between the base material of the optical film and the pressure-sensitive adhesive. is there.

  Still another object of the present invention is to provide an optical film for a display device in which an adhesive layer made of the pressure-sensitive adhesive composition for light leakage control is provided on one or both sides of the optical film for a display device. .

  Still another object of the present invention is to provide a display device including an optical film for a display device in which an adhesive layer made of the adhesive composition for controlling light leakage is provided on one or both sides of the optical film for a display device. There is to do.

  The above and other objects and advantages of the present invention will become more apparent from the following description of preferred embodiments.

  The above purpose is (A) a reactive high molecular weight acrylic copolymer having a weight average molecular weight of 2,000,000 to 2,500,000, and (B) 1,500,000 to 2,000,000. A reactive medium molecular weight acrylic copolymer having a weight average molecular weight, (C) a reactive low molecular weight acrylic copolymer having a weight average molecular weight of 100,000 to 500,000, and (D) a crosslinking agent, The high molecular weight acrylic copolymer, the medium molecular weight acrylic copolymer, and the low molecular weight acrylic copolymer are (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 reactive copolymer polymerized with 0.1 to 10 parts by weight of a vinyl monomer having a functional group capable of crosslinking with the crosslinking agent. It is achieved by.

  Here, 20 to 100 parts by weight of the medium molecular weight acrylic copolymer per 100 parts by weight of the high molecular weight acrylic copolymer, 1 to 50 parts by weight of the low molecular weight acrylic copolymer, and 0.001 of the crosslinking agent. It is -5 weight part, It is characterized by the above-mentioned.

  Preferably, the glass transition temperature of the high molecular weight acrylic copolymer, the medium molecular weight acrylic copolymer, and the low molecular weight acrylic copolymer is in the range of −60 to −40 ° C. .

  Preferably, the pressure-sensitive adhesive composition has a gel fraction in the range of 40 to 60%.

  Preferably, the vinyl monomer is at least one vinyl monomer selected from the group consisting of a vinyl monomer having a carboxy group and a vinyl monomer having a hydroxy group. Features.

  Preferably, the pressure-sensitive adhesive composition further includes (E) a silane coupling agent selected from the group consisting of vinyl silane, epoxy silane, and methacryl silane.

  Preferably, the alkyl acrylate is any one or more alkyl acrylates selected from the group consisting of n-butyl acrylate, methyl acrylate 2-ethylhexyl acrylate, t-butyl acrylate, n-octyl acrylate and isononyl acrylate. It is characterized by that.

  Preferably, the vinyl monomer having a carboxyl group is any one or more vinyl monomers selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and maleic acid. And

  Preferably, the vinyl monomer having a hydroxy group is 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meta ) Any one or more vinyl monomers selected from the group consisting of acrylates.

  Preferably, the cross-linking agent is any one or more cross-linking agents selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and tolylene diisocyanate adduct of trimethylolpropane. .

  Another object of the present invention is to provide an optical film for a display device, wherein the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for controlling light leakage is provided on one surface or both surfaces of the substrate of the optical film for display device. Is achieved.

  Here, the pressure-sensitive adhesive layer has a dry thickness of 5 to 100 μm.

  Preferably, the optical film for a display device is a polarizing film, a reflective polarizing film, or a retardation film.

  Preferably, the optical film is an elliptically polarizing film in which a polarizing film and a retardation film are laminated using the acrylic pressure-sensitive adhesive composition.

  Another object of the present invention is that the pressure-sensitive adhesive layer made of the light leakage control pressure-sensitive adhesive composition includes an optical film for a display device provided on one surface or both surfaces of a substrate of the optical film for a display device. This is achieved by the display device.

  According to the present invention, the shrinkage stress of the pressure-sensitive adhesive can be relaxed to supplement the light leakage phenomenon, and the residual stress generated by the dimensional change difference between the base material of the optical film and the pressure-sensitive adhesive can be minimized. It has effects such as.

It is the figure which showed the general liquid crystal display device schematically. It is the expanded sectional view which expanded the A area | region of the said FIG.

  Hereinafter, the present invention will be described in detail with reference to the embodiments of the present invention and the drawings. These examples are merely provided to illustrate the present invention more specifically, and the scope of the present invention is not limited by these examples. It is self-evident for what you have.

  The pressure-sensitive adhesive composition for controlling light leakage according to the present invention comprises (A) a reactive high molecular weight acrylic copolymer having a weight average molecular weight of 2,000,000 to 2,500,000, (B) 1,500, A reactive medium molecular weight acrylic copolymer having a weight average molecular weight of 000 to 2,000,000, (C) a reactive low molecular weight acrylic copolymer having a weight average molecular weight of 100,000 to 500,000, and ( D) Although it contains a crosslinking agent, the high molecular weight acrylic copolymer, the medium molecular weight acrylic copolymer, and the low molecular weight acrylic copolymer are (a) an alkyl having an alkyl group having 4 to 12 carbon atoms. It is a reactive copolymer polymerized with 90 to 99.9 parts by weight of an acrylate and 0.1 to 10 parts by weight of a vinyl monomer having a functional group capable of crosslinking with the crosslinking agent. That.

  Preferably, the medium molecular weight acrylic copolymer is 20 to 100 parts by weight per 100 parts by weight of the high molecular weight acrylic copolymer, the low molecular weight acrylic copolymer is 1 to 50 parts by weight, and the crosslinking agent is 0.001. It is -5 weight part, It is characterized by the above-mentioned.

  The pressure-sensitive adhesive composition for controlling light leakage according to the present invention having the above-described configuration can minimize the residual stress generated by the dimensional change difference between the base material and the pressure-sensitive adhesive. The present invention relates to a high molecular weight copolymer, a medium molecular weight copolymer and a low molecular weight copolymer produced by introducing a certain amount of a monomer having a reactive functional group into a non-reactive acrylic main monomer. By using and adjusting the content of the monomer having a reactive functional group contained in the copolymer, it is possible to effectively adjust the cross-linked structure representing cohesive strength and adhesive strength.

  Therefore, the light leakage control pressure-sensitive adhesive composition according to the present invention reduces the composite birefringence phenomenon generated from each constituent layer due to the contraction stress of the polarizing plate mounted on the display device, thereby reducing the light leakage of the display device. The phenomenon can be improved, and it is characterized by excellent physical properties such as initial adhesive strength, permanent adhesive strength, maintenance strength, and cutting characteristics.

  On the other hand, conventionally, an oligomer was added to the polymer copolymer to minimize the shrinkage stress of the pressure-sensitive adhesive. However, although such a method is a good method for reducing the shrinkage stress, there arises a problem that an adhesive flow is generated at the end when the polarizing plate is cut.

  Therefore, in the present invention, a high molecular weight and a medium high molecular weight (co) polymer 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 that functions as a plasticizer. Coalescence was used. The light leakage phenomenon is improved by improving the flow of the polymer chain and reducing the shrinkage stress by using a minimum curing agent.

  In addition, the glass transition temperature (Tg) of the acrylic copolymer according to the present invention is set to −40 ° C. or lower, and the shrinkage stress is adjusted using the acrylic copolymer and an optimal curing system. The glass transition temperature (Tg) of the high molecular weight, medium molecular weight, and low molecular weight acrylic copolymer is −40 ° C. or lower, and preferably −60 to −40 ° C. This is because when the glass transition temperature exceeds −40 ° C., the contraction stress of the polarizing film cannot be relaxed for a long time.

  In addition, the light leakage control pressure-sensitive adhesive composition according to the present invention is excellent in the relaxation effect of internal stress generated by the dimensional change difference between the base material constituting the optical film and the pressure-sensitive adhesive, thereby minimizing the light leakage phenomenon. Therefore, the gel fraction of the light leakage control pressure-sensitive adhesive composition according to the present invention is preferably 40 to 60%.

  The weight average molecular weight of the high molecular weight acrylic copolymer constituting the pressure-sensitive adhesive composition for controlling light leakage according to the present invention is 2,000,000 to 2,500,000, preferably 2,200,000 to It is in the range of 2,500,000. Thus, by using a high molecular weight acrylic copolymer, favorable adhesiveness can be ensured between a board | substrate and a polarizing plate or a phase difference plate, and a polarizing plate, and foaming or peeling can be prevented. The weight average molecular weight of the medium molecular weight acrylic copolymer is 1,500,000 to 2,000,000, preferably 1,500,000 to 1,800,000. The weight average molecular weight of the low molecular weight acrylic copolymer is 100,000 to 500,000, preferably 200,000 to 350,000. Adjustment of the suitable molecular weight of the acrylic copolymer can be achieved by appropriately adjusting conditions such as a polymerization reaction time, a polymerization reaction initiator, a polymerization reaction temperature, and a polymerization reaction solvent. As an example according to the present invention, a high molecular weight acrylic copolymer was produced at a temperature of 60 to 63 ° C., and azobisisobutyronitrile (AIBN) as a polymerization reaction initiator was 0.1 to 0.18 weight. The production of a medium molecular weight acrylic copolymer can be carried out under conditions such as a temperature of 64 to 68 ° C. and a polymerization reaction initiator azobisisobutyronitrile (AIBN) 0.19 to 0.25 parts by weight. .

  The high molecular weight, medium molecular weight, and low molecular weight acrylic copolymer is mainly composed of an alkyl acrylate, and is a copolymer of a functional group-containing monomer having reactivity with an acrylic ester and a polyfunctional compound. It is a polymer. The alkyl acrylate having a C 4-12 alkyl group that forms the high molecular weight, medium molecular weight, and low molecular weight acrylic copolymer is methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include 2-ethylhexyl acrylate, n-octyl acrylate, iso-octyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, t-butyl acrylate, and isononyl acrylate. Absent. The said alkyl acrylate can be used individually or in combination of 2 or more types.

  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, and a vinyl containing an amino group. Examples thereof include a vinyl monomer, an epoxy group-containing vinyl monomer, and an acetoacetyl group-containing vinyl monomer. In the present invention, a monomer containing a carboxyl group and a monomer containing a hydroxy group are preferred.

  Examples of the vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, beta-carboxyethyl acrylate, itaconic acid, maleic acid, maleic anhydride and butyl maleate, but are not limited thereto. is not. Examples of the vinyl monomer having a hydroxy group include 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, and 2-hydroxypropylene glycol. (Meth) acrylate and the like. 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 epoxy groups, such as glycidyl (meth) acrylate, the monomer containing acetoacetyl groups, such as acetoacetoxyethyl (meth) acrylate, etc. can be mentioned. The said substance can be used individually or in combination of 2 or more types.

  The functional group of the polyfunctional compound reacts with the reactive functional group of the acrylic copolymer, and has at least two, preferably 2 to 4, functional groups in one molecule. sell. Examples of such polyfunctional compounds include isocyanate compounds, epoxy compounds, amine compounds, metal chelate compounds, and aziridine compounds.

  Examples of the isocyanate compounds include tolylene diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, xylene diisocyanate, water-added xylene diisocyanate, diphenylmethane diisocyanate, water-added diphenylmethane diisocyanate, tetramethylxylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate. , Polymethylene polyphenyl isocyanate, and a container with a polyol such as trimethylolpropane.

  Examples of the epoxy compound include bisphenol A, epichlorohydrin 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, diglycidylaniline, diglycidylamine, N, N, N ′, N′-tetraglycidyl-m-xylenediamine and 1,3-bis (N, N′-diglycidylaminemethyl) cyclohexane And so on.

  Examples of the amine compound include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isoform diamine, amino resin, and methylene resin.

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

  Examples of the aziridine-based compound include N, N′-diphenylmethane-4,4′-bis (1-aziridine carboxylate), N, N′-toluene-2,4-bis (1-aziridine carboxylide). ), Triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxyde) , Trimethylolpropane-tri-beta-aziridinylpropionate and tetramethylolmethane-tri-beta-aziridinylpropionate.

  The polyfunctional compound (crosslinking agent) is usually used in an amount of 0.001 to 5 parts by weight, preferably 0.01 to 3 parts by weight with respect to 100 parts by weight of the high molecular weight acrylic copolymer. Can be done. By using a polyfunctional compound with such a content, a preferable three-dimensional crosslinked structure is formed with the high molecular weight (meth) acrylic copolymer. Moreover, these polyfunctional compounds can be used individually or in combination.

  Any known method may be employed for the production of the high molecular weight acrylic copolymer, medium molecular weight acrylic copolymer and low molecular weight acrylic copolymer constituting the light leakage control pressure-sensitive adhesive composition according to the present invention. Can do.

  For example, a high molecular weight acrylic copolymer is used in an amount of 0.01 to 0.5 parts by weight of a polymerization initiator (azobis such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, etc. with respect to 100 parts by weight of the raw material monomer. System polymerization initiators, peroxides such as benzoyl peroxide, acetyl peroxide, photopolymerization initiators such as diphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, etc.) It is synthesized by a method such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization or the like, preferably by solution polymerization. In the case of the solution polymerization method, ethyl acetate, toluene, hexane, acetone or the like is 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 7 to 10 hours.

  Further, the medium and low molecular weight acrylic copolymers are synthesized by a method such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like, like the high molecular weight acrylic copolymers. Synthesized. 0.01 to 0.1 parts by weight of a polymerization initiator (azo-based polymerization initiators such as azobisisobutyronitrile and azobiscyclohexanecarbonitrile, benzoyl peroxide, peroxide) with respect to 100 parts by weight of the raw material monomer Bulk polymerization, solution polymerization, emulsion polymerization, suspension using peroxides such as acetyl, photopolymerization initiators such as diphenyl ketone and 2-hydroxy-2-methyl-1-phenyl-propan-1-one) It is synthesized by a method such as polymerization, preferably by solution polymerization.

  In the case of the solution polymerization method, ethyl acetate, toluene, hexane, acetone or the like is 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 light leakage control pressure-sensitive adhesive composition according to the present invention includes a high molecular weight acrylic copolymer, a medium high molecular weight acrylic copolymer and a crosslinking agent as described above, and a weathering stabilizer usually blended in the pressure sensitive adhesive. Tackfire, a plasticizer, a softener, a dye, a pigment, a silane coupling agent, an inorganic filler, and the like can be further blended.

  In addition, the (E) silane coupling agent used in the light leakage control pressure-sensitive adhesive composition according to the present invention can effectively enhance the adhesion between the glass substrate and the pressure-sensitive adhesive, and particularly at high temperature and high humidity. When it is allowed to stand for a long time under various conditions, it is useful for improving the adhesion reliability. When considering such a function, the amount used is 0.01 to 0 with respect to 100 parts by weight of the acrylic copolymer. .1 part by weight is preferred. Examples of the silane coupling agent include vinyl silane, epoxy silane, and methacryl silane, but are not limited thereto.

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

  FIG. 1 is a diagram schematically illustrating a general liquid crystal display device.

  As shown in FIG. 1, the liquid crystal display device includes a liquid crystal display panel 500 in which a liquid crystal cell 560 is provided between a pair of transparent panels 520 and 540, first and second optics for polarizing and emitting incident light. Films 640 and 620 and a backlight assembly 700 for generating and providing the incident light to the liquid crystal display panel 500 are provided. The first optical film 640 is positioned on the liquid crystal display panel 500, and the second optical film 620 is interposed between the liquid crystal display panel 500 and the backlight assembly 700.

  The first and second optical films 640 and 620 divide incident light into two types of components that are orthogonal to each other, and transmit only one light component of the two types of light components so that the light transmission direction is constant. Fulfills the function of That is, the first and second optical films 640 and 620 absorb light that oscillates in the same direction as the polarization axis of the first and second optical films 640 and 620 in the incident light. Light that vibrates in directions other than is transmitted. At this time, the polarization axis of the first optical film 640 and the polarization axis of the second optical film 620 are perpendicular to each other.

  FIG. 2 is an enlarged cross-sectional view in which the region A of FIG. 1 is enlarged, and is a cross-sectional view showing an optical film used in a normal STN or CSTN liquid crystal display device. Between the first transparent protective film 20, the polarizer 22 and the second transparent protective film 24, the retardation film 16 is laminated below the polarizing film 26, and at this time, the retardation film 16 is The polarizing film 26, the release film 12, and the first and second adhesive layers 14 and 18 are attached.

  The thickness of the formed pressure-sensitive adhesive layer is usually 5 to 100 μm, preferably 20 to 50 μm in terms of dry thickness.

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

  As the polarizing film used in the present invention, a conventionally known polarizing film can be used. For example, it is obtained by adding a polarizing component such as an iodo dye or a dichroic dye to a film composed of a polyvinyl alcohol resin such as polyvinyl alcohol, polyvinyl formal, polyvinyl acetal and a saponified ethylene vinyl acetate copolymer. A multilayer film in which a transparent protective film such as a cellulose film such as cellulose triacetate, a polycarbonate film, or a polyethersulfone film is laminated can be used for the polarizer. The method for forming the pressure-sensitive adhesive layer on such a polarizing film is not particularly limited, and a method in which the pressure-sensitive adhesive is applied and dried using a bar coater directly on the surface of the polarizing film can be employed. However, after the pressure-sensitive adhesive is once applied to the surface of the peelable substrate and dried, the pressure-sensitive adhesive layer formed on the surface of the peelable substrate is transferred to the surface of the polarizing film, followed by aging. Can be adopted.

  In order to improve the contrast, the optical film according to the present invention may further include a / 4 retardation layer that causes circular polarization in addition to the polarizing film. The / 4 retardation layer may be a polymer film having birefringence or a liquid crystal coating layer arranged in one direction, and may include all of the polymer film and the liquid crystal coating layer. The / 4 retardation layer has a function of imparting a phase difference of approximately ¼ wavelength to each wavelength in the visible region, and preferably has excellent birefringence controllability, transparency, and heat resistance. The material of the / 4 retardation layer is not particularly limited, but when the / 4 retardation layer is a polymer film having birefringence, polycarbonate (poly carbonate), polycarbonate copolymer, polyethylene (polyethylene) is used. ), Polypropylene (polypropylene), polynorbornene (polynorbornene), polyvinyl chloride (polyvinyl chloride), polystyrene (polystyrene), polyacrylonitrile (polyester), polyester (polyester), polyester (polysulfone). polylylate), polyvinyl alcohol (polyvi) ylalcohol), polymethacrylate (polymethacrylic ester), polyacrylic acid ester (polyacrylic ester) and is preferably a film comprising one or more selected from the group consisting of a cellulose ester (cellulose ester).

  Further, the polymer film forming the / 4 retardation layer is preferably a transparent film stretched by 1.1 to 3 times, and may be uniaxially or biaxially stretched.

  In the case of a polarizing film or a film having a retardation film attached thereto according to the present invention, other functional layers such as a protective layer, a reflective layer, and an antiglare layer may be laminated.

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

Examples 1 to 6: Production of acrylic copolymer

  In Examples 1 to 6, n-butyl acrylate, methyl acrylate, acrylic acid and 4-hydroxybutyl (meth) acrylate as polymerization monomers, 100 g of ethyl acetate as a solvent, and azobisisobutyronitrile (as a polymerization initiator) AIBN) was placed in the reaction vessel at the content shown in Table 1 below (unit is “parts by weight”). After the air in the reaction vessel was replaced with nitrogen gas, this reaction solution was heated to 63 ° C. while stirring and polymerized during the reaction time shown in Table 1. After the reaction, it was diluted with 100 g of ethyl acetate to obtain a solid acrylic copolymer solution. The solid content of the solution in the polymer was measured after the initial weight of the pressure-sensitive adhesive was measured using a solid content measuring machine, and then the solvent was blown off at 100 ° C. for 30 minutes. The molecular weight of the polymer was measured using gel permeation chromatography (GPC). The glass transition temperature was determined by measuring from −70 ° C. to 20 ° C. with a differential scanning calorimeter (DSC) under a nitrogen stream at a heating rate of 10 ° C./min. The physical properties are shown in Table 2 below.

Comparative Examples 1 to 6: Production of acrylic copolymer

In Comparative Examples 1-6, the compounding quantity which represented n-butyl acrylate, methyl acrylate, acrylic acid, and 4-hydroxybutyl (meth) acrylate as a polymerization monomer in Table 1 (a unit is a "part by weight"). The polymerization was carried out in substantially the same manner as in the above example except that the polymerization reaction initiator content and reaction time were polymerized according to the conditions shown in Table 1.

Here, “n-BA” means “n-butyl acrylate”, “MA” means “methyl acrylate”, “AA” means “acrylic acid”, and “4-HBA” means “4”. “Hydroxybutyl (meth) acrylate” and “AIBN” each represent “azobisisobutyronitrile”.

Examples 7 to 14: Polarizing plates to which an adhesive composition was applied

  The polymers obtained from Examples 1 to 6 were mixed at the blending ratio shown in the following Table 3 (unit is “g”), and the solid content of trimethylhexamethylenediamine as a cross-linking agent was 0. 2 g was added and stirred well to obtain a pressure-sensitive adhesive composition for polarizing plates. The pressure-sensitive adhesive composition for a polarizing plate thus obtained was applied to a polyester release film and then dried. At this time, the coating thickness after drying was adjusted to 25 μm. Next, the pressure-sensitive adhesive composition applied on the release film was transferred onto a 200 μm polarizing film and aged for 7 days under the conditions of a temperature of 23 ° C. and a humidity of 45% to obtain the polarizing plate of the present invention.

The polarizing plate on which the pressure-sensitive adhesive layer is installed is cut into 210 mm × 297 mm so that the absorption axis is 45 ° with respect to the long side of the polarizing plate, and this polarizing plate is 30 ° C. on one side of the glass plate and the pressure is 5 kg / cm ^2. This was maintained for 60 minutes for adhesion.

  The sample thus obtained was allowed to stand for 500 hours under the conditions of 70 ° C. and 97%, and the state of foaming and dropping was observed and evaluated with the naked eye, and the state of uneven color was observed with the naked eye. Evaluation was made, and the distance at which the bonding position shifted on the long side of the polarizing plate was measured with a nonius.

The gel fraction was determined by collecting about 0.1 g of the pressure-sensitive adhesive composition aged on the support at a temperature of 23 ° C. and a humidity of 65% RH in a sample bottle and adding 50 g of ethyl acetate for 24 hours. After stirring, the contents of the corresponding sample bottle are separated by filtering with a 200-mesh stainless steel wire mesh, the residue on the wire mesh is dried at 100 ° C. for 2 hours, and the dry weight is measured. Asked.
[Equation 1]
Gel fraction (%) = (Dry weight / Adhesive composition sampling weight) × 100

  The physical property measurement results are shown in Table 4 below.

Comparative Examples 7 to 14: Polarizing plates to which the pressure-sensitive adhesive composition was applied

Substantially the same as in Examples 7 to 14 except that the polymers obtained from Comparative Examples 1 to 6 were mixed at the blending ratio shown in Table 3 below (unit is “g”). The polarizing plate was manufactured by the same method, the physical property of the polarizing plate was measured, and the obtained physical property values are shown in Table 4.

  In Table 4, “◯” means good (peeling: none, foaming: none, light leakage: none), and “Δ” means good (peeling: slightly, foaming: slightly, light leakage: slightly), “ “X” represents the intensity (peeling: many, foaming: many, light leakage: many).

  According to the experimental results, a pressure-sensitive adhesive composition comprising a reactive high molecular weight copolymer, a reactive medium molecular weight copolymer, and a reactive low molecular weight copolymer, more preferably a low glass transition temperature and a low cross-linking. In the present invention, an unreactive oligomer was used in an attempt to supplement the light leakage phenomenon by relaxing the shrinkage stress using a pressure sensitive adhesive, and in the present invention, a reactive medium molecular weight copolymer and By double use of the reactive low molecular weight copolymer, an attempt is made to compensate for the light leakage phenomenon, etc., by reducing the shrinkage without the flowability and pressing property at the end. In this experiment, by using medium and low molecular weight copolymers with a small number of functional groups, light leakage phenomenon and all other problems can be solved by reducing the shrinkage without end flowability and pressing properties. It turns out that the point can be complemented.

  Accordingly, the present invention provides an acrylic pressure-sensitive adhesive for optical films comprising a reactive high molecular weight acrylic copolymer, a medium molecular weight acrylic copolymer, a low molecular weight acrylic copolymer and a crosslinking agent. Since the residual stress generated by the dimensional change difference between the base material of the optical film for display and the pressure-sensitive adhesive can be minimized, it can be widely used for optical films and display devices.

  DESCRIPTION OF SYMBOLS 12 ... Release film, 14 ... 1st adhesion layer, 16 ... Retardation film, 18 ... 2nd adhesion layer, 20 ... 1st transparent protective film, 22 ... Polarizer, 24 ... 2nd transparent protective film, 26 ... Polarization Film, 28 ... protective film, 500 ... liquid crystal display panel, 520, 540 ... a pair of transparent panels, 560 ... liquid crystal cell, 620 ... second optical film, 640 ... first optical film, 700 ... backlight assembly

Claims (15)

An adhesive composition for controlling light leakage,
(A) a reactive high molecular weight acrylic copolymer having a weight average molecular weight of 2,000,000 to 2,500,000, and (B) a weight average molecular weight of 1,500,000 to 2,000,000. Although it contains a reactive medium molecular weight acrylic copolymer, (C) a reactive low molecular weight acrylic copolymer having a weight average molecular weight of 100,000 to 500,000, and (D) a crosslinking agent,
The high molecular weight acrylic copolymer, the medium molecular weight acrylic copolymer, and the low molecular weight acrylic copolymer are (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 reactive copolymer polymerized with 0.1 to 10 parts by weight of a vinyl monomer having a functional group capable of crosslinking with the crosslinking agent. Composition.   20-100 parts by weight of the medium molecular weight acrylic copolymer per 100 parts by weight of the high molecular weight acrylic copolymer, 1-50 parts by weight of the low molecular weight acrylic copolymer, and 0.001-5 parts by weight of the crosslinking agent. The pressure-sensitive adhesive composition for controlling light leakage according to claim 1, wherein the pressure-sensitive adhesive composition is a part.   The glass transition temperature of the high molecular weight acrylic copolymer, the medium molecular weight acrylic copolymer, and the low molecular weight acrylic copolymer is in a range of -60 to -40 ° C. The pressure-sensitive adhesive composition for light leakage control according to 1.   The pressure-sensitive adhesive composition for controlling light leakage according to claim 1, wherein the gel fraction of the pressure-sensitive adhesive composition is in the range of 40 to 60%.   The vinyl monomer is at least one vinyl monomer selected from the group consisting of a vinyl monomer having a carboxy group and a vinyl monomer having a hydroxy group. The pressure-sensitive adhesive composition for controlling light leakage according to claim 1.   2. The light leakage control pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition further comprises (E) a silane coupling agent selected from the group consisting of vinyl silane, epoxy silane, and methacryl silane. object.   The alkyl acrylate is any one or more alkyl acrylates selected from the group consisting of n-butyl acrylate, methyl acrylate 2-ethylhexyl acrylate, t-butyl acrylate, n-octyl acrylate and isononyl acrylate. The pressure-sensitive adhesive composition for controlling light leakage according to claim 1.   The vinyl monomer having a carboxyl group is any one or more vinyl monomers selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and maleic acid, The pressure-sensitive adhesive composition for controlling light leakage according to claim 5.   The vinyl monomer having a hydroxy group is composed of 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate. The pressure-sensitive adhesive composition for controlling light leakage according to claim 5, wherein the pressure-sensitive adhesive composition is any one or more vinyl monomers selected from the group consisting of:   The cross-linking agent is any one or more cross-linking agents selected from the group consisting of tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and tolylene diisocyanate adduct of trimethylolpropane. The pressure-sensitive adhesive composition for light leakage control according to 1.   A pressure-sensitive adhesive layer comprising the light leakage control pressure-sensitive adhesive composition according to any one of claims 1 to 10 is provided on one surface or both surfaces of an optical film for a display device. An optical film for a display device.   The optical film for a display device according to claim 11, wherein the pressure-sensitive adhesive layer has a dry thickness of 5 to 100 μm.   The optical film for a display device according to claim 12, wherein the optical film for the display device is a polarizing film, a reflective polarizing film, or a retardation film.   The optical film for a display device according to claim 12, wherein the optical film is an elliptically polarizing film in which a polarizing film and a retardation film are laminated using the acrylic pressure-sensitive adhesive composition. An optical device for a display device, wherein the adhesive layer comprising the adhesive composition for controlling light leakage according to any one of claims 1 to 10 is provided on one surface or both surfaces of an optical film for a display device. A display device comprising a film.

Images