JP4798752B2 - Optical adhesive, optical film with adhesive, and image display device - Google Patents

Description

  The present invention relates to an optical pressure-sensitive adhesive and an optical film with a pressure-sensitive adhesive using the same. The optical pressure-sensitive adhesive and the optical film with the pressure-sensitive adhesive are suitably used for image display devices such as liquid crystal display devices, organic EL display devices, and PDPs. Examples of the optical film include a polarizing plate, a retardation plate, an optical compensation film, a brightness enhancement film, and a laminate of these.

  In the liquid crystal display device, it is indispensable to dispose polarizing elements on both sides of the liquid crystal cell because of its image forming method, and generally a polarizing plate is attached. In addition to polarizing plates, various optical elements have been used for liquid crystal panels in order to improve the display quality of displays. For example, a retardation plate for preventing coloring, a viewing angle widening film for improving the viewing angle of a liquid crystal display, and a brightness enhancement film for increasing the contrast of the display are used. These films are collectively called optical films.

  When sticking the optical film on a liquid crystal cell, an adhesive is usually used. In addition, the adhesion between the optical film and the liquid crystal cell, or the optical film is usually in close contact with each other using an adhesive in order to reduce the loss of light. In such a case, the adhesive has an advantage that a drying step is not required to fix the optical film, so the adhesive is an optical film with an adhesive provided as an adhesive layer in advance on one side of the optical film. Is generally used.

  As the pressure-sensitive adhesive used in the optical film with the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is frequently used because of its excellent adhesion and transparency. Further, the acrylic pressure-sensitive adhesive is often crosslinked using an isocyanate-based crosslinking agent, and mainly utilizes a bond with a functional monomer copolymerized with an acrylic polymer.

  A liquid crystal panel in which the optical film is bonded to a liquid crystal cell is mounted and used in a liquid crystal display device. Liquid crystal display devices are used not only in calculators but also in watches, televisions, monitors, and the like. Since liquid crystal display devices are subjected to various conditions such as heating and humidification conditions, high durability that does not impair display quality is required even in such an environment.

  However, when the liquid crystal display device is heated or humidified, display unevenness may occur in the periphery of the liquid crystal panel, resulting in display defects. This display unevenness in the peripheral portion may be particularly noticeable when an optical film in which a viewing angle widening film is laminated on a polarizing plate is used.

In order to improve the display unevenness of the peripheral portion, it has been proposed to use a pressure-sensitive adhesive composition containing a plasticizer or an oligomer component as a pressure-sensitive adhesive used for an optical film with a pressure-sensitive adhesive (Patent Document 1, Patent Document). 2). However, these pressure-sensitive adhesive compositions have a problem in that the appearance itself and the pressure-sensitive adhesive deteriorate due to precipitation of additives such as plasticizers and oligomer components in a long-time heating test.
Japanese Patent Laid-Open No. 9-87593 JP-A-10-279907

  The present invention is an optical pressure-sensitive adhesive made of an acrylic copolymer used for an optical film with a pressure-sensitive adhesive, etc., and an object thereof is to provide an optical pressure-sensitive adhesive that hardly causes display unevenness in a peripheral portion of a display screen. And

  Moreover, this invention aims at providing the optical film with an adhesive using the said optical adhesive. Furthermore, it aims at providing the image display apparatus using the said optical film with an adhesive.

  As a result of intensive studies to solve the above problems, the present inventors have found the following optical pressure-sensitive adhesive and the like, and have completed the present invention.

  That is, the present invention is characterized by containing an acrylic copolymer containing, as monomer units, alkyl (meth) acrylate (a1) and alkyl = α- (hydroxymethyl) acrylate (a2), and a crosslinking agent. The present invention relates to an optical pressure-sensitive adhesive.

  In the optical pressure-sensitive adhesive, the ratio of alkyl = α- (hydroxymethyl) acrylate (a2) is preferably 0.01 to 100 parts by weight with respect to 100 parts by weight of alkyl (meth) acrylate (a1). .

  In the optical pressure-sensitive adhesive, the monomer unit further contains 50 parts by weight or less of the monomer (a3) excluding the (a1) and (a2) with respect to 100 parts by weight of the alkyl (meth) acrylate (a1). can do.

  In the optical pressure-sensitive adhesive, the monomer (a3) is preferably a monomer containing a carboxyl group.

Further, the present invention is an optical film with an adhesive in which an adhesive layer is laminated on at least one surface of the optical film,
The said adhesive layer is related with the optical film with an adhesive characterized by being formed with the said optical adhesive.

  In the optical film with an adhesive, examples of the optical film include a polarizing plate and / or a retardation plate.

  The present invention also relates to an image display device using the optical film with an adhesive.

  In the present invention, as the copolymer component of the acrylic copolymer used for the base polymer of the optical adhesive, in addition to the main component, alkyl (meth) acrylate (a1), alkyl = α- (hydroxymethyl) Acrylate (a2) is used. By such an action of alkyl = α- (hydroxymethyl) acrylate (a2), when the optical pressure-sensitive adhesive is applied to an optical film with a pressure-sensitive adhesive, display unevenness in the peripheral portion of the display screen can be suppressed. In addition, since the optical pressure-sensitive adhesive of the present invention uses the component (a2) as a monomer unit of the base polymer to suppress display unevenness, an additive such as a plasticizer is used in addition to the base polymer. As in the case of the adhesive, the additive itself does not precipitate and the appearance defect or the adhesive does not deteriorate. In particular, the optical pressure-sensitive adhesive of the present invention is suitable for suppressing display unevenness when an optical film having a pressure-sensitive adhesive is obtained by laminating a viewing angle widening film on a polarizing plate.

  The optical pressure-sensitive adhesive of the present invention contains, as a base polymer, an acrylic copolymer containing alkyl (meth) acrylate (a1) and alkyl = α- (hydroxymethyl) acrylate (a2) as monomer units. (Meth) acrylate refers to acrylate and / or methacrylate, and (meth) of the present invention has the same meaning.

  The acrylic copolymer has a unit of alkyl (meth) acrylate (a1) as a main component. The alkyl group of the alkyl (meth) acrylate (a1) has about 1-18 carbon atoms, preferably 1-9 carbon atoms, and the alkyl group may be linear or branched. Specific examples of the alkyl (meth) acrylate include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, and 2-ethylhexyl. (Meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, etc. can be mentioned. These can be used alone or in combination. The average carbon number of these alkyl groups is preferably 4-12.

  The alkyl group of alkyl = α- (hydroxymethyl) acrylate (a2) has about 1 to 18 carbon atoms, preferably 1 to 9 carbon atoms, and the alkyl group may be linear or branched. Specific examples of alkyl = α- (hydroxymethyl) acrylate include methyl = α- (hydroxymethyl) acrylate, ethyl = α- (hydroxymethyl) acrylate, butyl = α- (hydroxymethyl) acrylate, isooctyl = α- ( Hydroxymethyl) acrylate, isononyl = α- (hydroxymethyl) acrylate, lauryl = α- (hydroxymethyl) acrylate, and the like.

  The ratio of alkyl = α- (hydroxymethyl) acrylate (a2) in the acrylic copolymer is used in the range of 0.01 to 100 parts by weight with respect to 100 parts by weight of alkyl (meth) acrylate (a1). preferable. When the component (a2) is less than 0.01 parts by weight, the hydroxy group does not function effectively at the crosslinking reaction point with the crosslinking agent, and the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive of the present invention There is a risk of insufficient crosslinking. On the other hand, when the component (a2) exceeds 100 parts by weight, the glass transition temperature (Tg) of the acrylic copolymer is increased, and flexibility necessary for the pressure-sensitive adhesive may be impaired. From this viewpoint, the proportion of the component (a2) is preferably 0.05 to 30 parts by weight, and more preferably 0.07 to 5 parts by weight with respect to 100 parts by weight of the component (a1).

  The acrylic copolymer may further contain a monomer (a3) component excluding the component (a1) and the component (a2) as a monomer unit.

  Examples of the component (a3) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl. Hydroxyl group-containing monomers other than the component (a2) such as (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; Carboxyl group-containing monomers such as acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid; acid anhydrides such as maleic anhydride and itaconic anhydride Group-containing monomer; caprolactone adduct of acrylic acid; styrene sulfonic acid or allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth ) A sulfonic acid group-containing monomer such as acryloyloxynaphthalene sulfonic acid; and a phosphoric acid group-containing monomer such as 2-hydroxyethylacryloyl phosphate.

  Moreover, a nitrogen-containing vinyl monomer is mention | raise | lifted as said (a3) component. For example, maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; N-acryloylmorpholine; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-hexyl ( (N-substituted) such as (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, and N-methylolpropane (meth) acrylamide ) Amide monomer; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, 3- (3-pyridinyl) propyl ( Meta) Alkylaminoalkyl (meth) acrylate monomers such as relate; alkoxyalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; N- (meth) acryloyloxymethylene succinimide and N- ( Succinimide monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide, N-acryloylmorpholine, and the like are also examples of monomers for modification.

  Further, as the component (a3), vinyl acetate, vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl Vinyl monomers such as morpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene and N-vinylcaprolactam; Nitrile monomers such as acrylonitrile and methacrylonitrile; Epoxy group-containing acrylics such as glycidyl (meth) acrylate Monomer: Polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene Glycol acrylic ester monomers such as lenglycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate, 2-methoxyethyl acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) (Meth) acrylate monomers such as acrylate) can also be used.

  The component (a3) can be arbitrarily used to modify the base polymer. The proportion of the component (a3) is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 20 parts by weight or less with respect to 100 parts by weight of the alkyl (meth) acrylate (a1). When the proportion of the component (a3) exceeds 50 parts by weight, it is not preferable in that the flexibility as an adhesive may be impaired. As the component (a3), it is preferable to use a monomer containing a carboxyl group, particularly acrylic acid, from the viewpoint of good adhesion.

  The average molecular weight of the acrylic copolymer is not particularly limited, but the weight average molecular weight is preferably about 500,000 to 2.5 million. The acrylic copolymer can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide initiators can be used. The reaction temperature is usually about 50 to 80 ° C., and the reaction time is 1 to 8 hours. Among the above production methods, the solution polymerization method is preferred, and ethyl acetate, toluene and the like are generally used as the solvent for the acrylic copolymer. The solution concentration is usually about 20 to 80% by weight. The acrylic copolymer can be obtained as an aqueous emulsion.

  The optical pressure-sensitive adhesive of the present invention contains a crosslinking agent in addition to the acrylic copolymer as a base polymer. The cross-linking agent can improve the adhesion and durability with the optical film, and can maintain the reliability at high temperature and the shape of the pressure-sensitive adhesive itself. As the crosslinking agent, isocyanate, peroxide, epoxy, metal chelate, oxazoline, and the like can be used as appropriate. As the cross-linking agent, a cross-linking agent containing a functional group reactive with a hydroxyl group is preferable, and an isocyanate-based cross-linking agent is particularly preferable.

  An isocyanate type crosslinking agent contains an isocyanate compound. Isocyanate compounds include isocyanate monomers such as tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, and these isocyanates. Adduct isocyanate compounds in which monomers are added with trimethylolpropane, etc .; isocyanurates, burette type compounds, and urethane prepolymers obtained by addition reaction of known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. Examples thereof include polymer type isocyanate.

  The amount of the crosslinking agent used is 10 parts by weight or less, preferably 0.01 to 5 parts by weight, and more preferably 0.02 to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A). When the proportion of the crosslinking agent used exceeds 10 parts by weight, it is not preferable in that crosslinking may proceed excessively and adhesiveness may be lowered.

  Furthermore, in the optical pressure-sensitive adhesive of the present invention, if necessary, a filler, a pigment, a colorant, a filler made of a tackifier, a plasticizer, glass fiber, glass beads, metal powder, other inorganic powders, and the like. An additive, an antioxidant, an ultraviolet absorber, a silane coupling agent, and the like, and various additives can be appropriately used without departing from the object of the present invention. Moreover, it is good also as an adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility.

  The optical film with an adhesive of the present invention is obtained by forming an adhesive layer on at least one surface of the optical film with the optical adhesive. In addition, the said adhesive layer may provide the single side | surface of the optical film, and may have it on both surfaces of the optical film.

  The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a method of applying and drying the pressure-sensitive adhesive solution on the optical film by an appropriate development method such as a casting method or a coating method, a mold release provided with the pressure-sensitive adhesive layer For example, a transfer method using a sheet is used. As a coating method, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, or a spray method can be adopted. After applying the pressure-sensitive adhesive solution, a solvent or water is volatilized in a drying step to obtain a pressure-sensitive adhesive layer having a predetermined thickness.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 40 μm, preferably 5 to 30 μm, particularly preferably 10 to 25 μm. When the thickness is less than 1 μm, the durability is deteriorated. When the thickness is more than 40 μm, floating or peeling due to foaming or the like is likely to occur, resulting in poor appearance. The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a weight layer of a different composition or type. Moreover, when providing in both surfaces, it can also be set as the adhesion layer of a different composition, a kind, and thickness in the front and back of a polarizing plate or an optical film.

  In addition, the pressure-sensitive adhesive layer is formed by applying a UV-curable pressure-sensitive adhesive syrup on a release film and irradiating with radiation such as an electron beam or UV to form a pressure-sensitive adhesive layer containing the acrylic copolymer. Can be formed. At this time, since the pressure-sensitive adhesive contains a cross-linking agent, the reliability at high temperature and the shape of the pressure-sensitive adhesive itself can be maintained.

  The pressure-sensitive adhesive layer can be cross-linked by the drying step or the UV irradiation step, and a cross-linking form in which cross-linking is accelerated by aging by heating or standing at room temperature after drying can be selected.

  As a constituent material of the release sheet, paper, polyethylene, polypropylene, polyethylene terephthalate and other synthetic resin films, rubber sheets, paper, cloth, non-woven fabric, nets, foam sheets and metal foils, and appropriate thin leaf bodies such as laminates thereof Etc. In order to improve the peelability from the pressure-sensitive adhesive layer, the surface of the release sheet may be subjected to a low-adhesive release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment as necessary.

  In forming the pressure-sensitive adhesive layer or the like, the optical film can be activated in order to improve interlayer adhesion. Various methods can be used for the activation treatment, and surface treatment such as corona discharge treatment, plasma discharge treatment, glow discharge treatment, low pressure UV treatment, and saponification treatment can be applied, and a coupling agent or the like is formed as an anchor layer. Is possible.

  In addition, in each layer such as an optical film and an adhesive layer of the optical film with an adhesive of the present invention, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc. It may be one having a UV absorbing ability by a method such as a method of treating with a UV absorber.

  An anchor coat layer other than those described above may be provided between the optical film and the pressure-sensitive adhesive layer. The material for forming the anchor coat layer provided between the pressure-sensitive adhesive layer and the optical film of the optical film with pressure-sensitive adhesive of the present invention is not particularly limited, but exhibits good adhesion to both the pressure-sensitive adhesive layer and the optical film. Those that form a film with excellent cohesive strength are desirable. Various polymers, metal oxide sols, silica sols, and the like can be used to exhibit such properties. Of these, polymers are particularly preferably used.

  Examples of the polymers include polyurethane resins, polyester resins, and polymers containing amino groups in the molecule. The polymer may be used in any of a solvent-soluble type, a water-dispersed type, and a water-soluble type. For example, water-soluble polyurethane, water-soluble polyester, water-soluble polyamide, etc. and water-dispersible resins (ethylene-vinyl acetate emulsion, (meth) acrylic emulsion, etc.) can be mentioned. The water-dispersed type is obtained by emulsifying various resins such as polyurethane, polyester and polyamide using an emulsifier, or by introducing an anionic group, a cationic group or a nonionic group of a water-dispersible hydrophilic group into the resin. The self-emulsified product can be used. Moreover, an ionic polymer complex can be used.

  Such polymers preferably have a functional group reactive with the isocyanate compound in the pressure-sensitive adhesive layer. As the polymers, polymers containing an amino group in the molecule are preferable. In particular, those having a primary amino group at the terminal are preferably used, and it has been confirmed that they are firmly adhered by reaction with an isocyanate compound.

  Examples of polymers containing an amino group in the molecule include polymers of amino-containing group-containing monomers such as polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, and dimethylaminoethyl acrylate. Of these, polyethyleneimine is preferred.

  Polyethyleneimine is not particularly limited, and various types can be used. The weight average molecular weight of polyethyleneimine is not particularly limited, but is usually about 1 to 1,000,000. For example, as an example of a commercially available product of polyethyleneimine, Epomin SP series (SP-003, SP006, SP012, SP018, SP103, SP110, SP200, etc.) manufactured by Nippon Shokubai Co., Ltd., Epomin P-1000 and the like can be mentioned. Of these, Epomin P-1000 is preferred.

  The polyethyleneimine may be any one having a polyethylene structure, and examples thereof include an ethyleneimine adduct and / or a polyethyleneimine adduct to a polyacrylic acid ester. The polyacrylic acid ester can be obtained by emulsion polymerization of an alkyl (meth) acrylate and a copolymer monomer thereof constituting the base polymer (acrylic polymer) of the above-described acrylic pressure-sensitive adhesive according to a conventional method. As the copolymerization monomer, a monomer having a functional group such as a carboxyl group for reacting ethyleneimine or the like is used. The proportion of the monomer having a functional group such as a carboxyl group is appropriately adjusted depending on the proportion of ethyleneimine to be reacted. Moreover, as a copolymerization monomer, it is suitable to use a styrene-type monomer as above-mentioned. Moreover, it can also be set as the addition product which grafted polyethyleneimine by making the polyethyleneimine separately synthesize | combined react with the carboxyl group etc. in acrylic ester. For example, as an example of a commercially available product, Polyment NK-380 manufactured by Nippon Shokubai Co., Ltd. can be mentioned.

  Further, an ethyleneimine adduct and / or a polyethyleneimine adduct of an acrylic polymer emulsion can be used. For example, as an example of a commercially available product, POLYMENT SK-1000 manufactured by Nippon Shokubai Co., Ltd. can be mentioned.

  The polyallylamine is not particularly limited, and examples thereof include diallylamine hydrochloride-sulfur dioxide copolymer, diallylmethylamine hydrochloride copolymer, polyallylamine hydrochloride, allylamine compounds such as polyallylamine, and polyalkylenepolyamines such as diethylenetriamine. And a condensate of dicarboxylic acid, an adduct of epihalohydrin, polyvinylamine and the like. Polyallylamine is preferred because it is soluble in water / alcohol. The weight average molecular weight of polyallylamine is not particularly limited, but is preferably about 10,000 to 100,000.

  In forming the anchor coat layer, in addition to the polymer containing an amino group, a compound that reacts with the polymer containing an amino group can be mixed and crosslinked to improve the strength of the anchor coat layer. Examples of the compound that reacts with the polymer containing an amino group include an epoxy compound.

  When providing an anchor coat layer, an adhesive layer is formed after forming an anchor coat layer on the optical film. For example, a solution of an anchor component such as a polyethyleneimine aqueous solution is applied and dried using a coating method such as a coating method, a dipping method, or a spray method to form an anchor coat layer. The thickness of the anchor coat layer is preferably about 10 to 5000 nm, more preferably in the range of 50 to 500 nm. When the thickness of the anchor coat layer is reduced, the anchor coat layer does not have bulk properties, does not exhibit sufficient strength, and sufficient adhesion may not be obtained. Moreover, when too thick, there exists a possibility of causing the fall of an optical characteristic.

  An antistatic agent can also be used in the optical film with an adhesive to impart antistatic properties. The antistatic agent can be contained in each layer, and an antistatic layer can be separately formed. Antistatic agents include ionic surfactant systems; conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline; metal oxide systems such as tin oxide, antimony oxide, and indium oxide. From the viewpoint of appearance, antistatic effect, and stability of the antistatic effect when heated and humidified, a conductive polymer system is preferably used. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used. This is preferable in the case where a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer from the viewpoint of suppressing deterioration of the optical film substrate due to an organic solvent during the coating process.

  As an optical film used for the optical film with an adhesive of this invention, what is used for formation of image display apparatuses, such as a liquid crystal display device, is used, The kind in particular is not restrict | limited. For example, the optical film includes a polarizing plate. A polarizing plate having a transparent protective film on one or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of polarizers include dichroic iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include polyene-based oriented films such as those obtained by adsorbing substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be prepared by, for example, dying polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin film property. In particular, 5 to 200 μm is preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = (nx−nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a direction retardation of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation (Rth) is more preferably -80 nm to +60 nm, and particularly preferably -70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. Also, a thermoplastic saturated norbornene resin that hardly causes a phase difference even when subjected to stress due to a change in the dimensions of the polarizer can be used. The thermoplastic saturated norbornene-based resin has a cycloolefin as a main skeleton and has substantially no carbon-carbon double bond. Examples of the thermoplastic saturated norbornene resin include ZEONEGS, ZEONOR manufactured by Nippon Zeon Co., Ltd., and ARTON manufactured by JSR Co., Ltd.

  In addition, when providing a protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the sticking prevention treatment is performed for the purpose of preventing adhesion between adjacent layers of other members.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles and organic fine particles (including beads) made of a crosslinked or uncrosslinked polymer are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The anti-glare layer may also serve as a diffusion layer (such as a visual enlargement function) for diffusing the light transmitted through the polarizing plate to enlarge vision.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  In addition, as an optical film, for example, it is used for forming a liquid crystal display device such as a reflection plate, an anti-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), a visual compensation film, and a brightness enhancement film. And an optical layer that may be formed. These can be used alone as an optical film, or can be laminated on the polarizing plate for practical use and used as one layer or two or more layers.

  In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate is further laminated with a reflecting plate or a semi-transmissive reflecting plate, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is further laminated on a polarizing plate, a polarizing plate A wide viewing angle polarizing plate in which a visual compensation film is further laminated on a plate, or a polarizing plate in which a luminance enhancement film is further laminated on a polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. In addition, the transparent protective film may contain fine particles to form a surface fine concavo-convex structure, and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by, for example, applying metal to the surface of the transparent protective layer by an appropriate method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the screen.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device of a type that displays an image using a built-in power source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate can be used to form liquid crystal display devices that can save energy when using a light source such as a backlight in a bright atmosphere and can be used with a built-in power supply even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 0.5 to 150 μm and about 0.5 to 50 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymer, norbornene resin, or binary, ternary copolymers, graft copolymers, Examples include blends. These polymer materials become an oriented product (stretched film) by stretching or the like.

  Examples of the liquid crystal polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. . Specific examples of the main chain type liquid crystal polymer include a nematic alignment polyester liquid crystal polymer, a discotic polymer, and a cholesteric polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment-providing para-substitution through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogenic part composed of a cyclic compound unit. These liquid crystal polymers are prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment treatment surface such as a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or an oblique deposition of silicon oxide. This is done by developing and heat treatment.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for coloring, vision, etc. due to birefringence of various wave plates and liquid crystal layers, and may be two or more types. It may be one in which retardation plates are stacked and optical characteristics such as retardation are controlled.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The visual compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. Examples of such a visual compensation phase difference plate include a phase difference plate, an alignment film such as a liquid crystal polymer, and a film in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film that is uniaxially stretched in the plane direction, whereas a retardation plate used as a visual compensation film is biaxially stretched in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. can give. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for liquid crystal image display or the like is reduced and the image becomes dark. The brightness enhancement film reflects light that has a polarization direction that is absorbed by the polarizer without being incident on the polarizer, and is reflected by the brightness enhancement film, and then inverted through a reflective layer or the like provided behind the brightness enhancement film. The brightness enhancement film transmits only the polarized light in which the polarization direction of the light reflected and inverted between the two is allowed to pass through the polarizer. Since the light is supplied to the polarizer, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the light in the natural light state is directed toward the reflection layer or the like, reflected through the reflection layer or the like, and again passes through the diffusion plate and reenters the brightness enhancement film. In this way, by providing a diffuser plate that returns polarized light to the original natural light between the brightness enhancement film and the reflective layer, the brightness of the display screen is maintained, and at the same time, the brightness of the display screen is reduced and uniform. Can provide a bright screen. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is, but from the point of suppressing absorption loss, the circularly polarized light is converted into linearly polarized light through a retardation plate. It is preferably incident on the polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate at a wide wavelength in the visible light region or the like exhibits, for example, a retardation plate that functions as a quarter-wave plate for light-colored light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method in which a phase difference layer, for example, a phase difference layer that functions as a half-wave plate is superimposed. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, a cholesteric liquid crystal layer having a reflection structure that reflects circularly polarized light in a wide wavelength range such as a visible light range can be obtained by combining two or more layers with different reflection wavelengths to form an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or more optical layers as in the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-described reflective polarizing plate or semi-transmissive polarizing plate and a retardation plate are combined may be used.

  The pressure-sensitive adhesive of the present invention is preferably used for an optical film in which unevenness tends to occur in the peripheral portion, such as a film having a retardation function such as a viewing angle widening film including a discotic liquid crystal layer and a film formed by coating.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and the other optical layer, their optical axes can be set at an appropriate arrangement angle in accordance with the target phase difference characteristic.

  The optical film with an adhesive of the present invention can be preferably used for forming various image display devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical film with an adhesive, and a lighting system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the optical film with an adhesive by invention, and it can apply to the former. As the liquid crystal cell, an arbitrary type such as an arbitrary type such as a TN type, an STN type, or a π type can be used.

  Appropriate liquid crystal display devices such as a liquid crystal display device in which an optical film with an adhesive is disposed on one side or both sides of a liquid crystal cell and a backlight or a reflector used in an illumination system can be formed. In that case, the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When optical films are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. The optical film (polarizing plate or the like) of the present invention can also be applied to an organic EL display device. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
(Preparation of adhesive)
In a four-flask with a condenser, stirring blades and thermometer,
95.3 parts by weight of butyl acrylate 4 parts by weight of acrylic acid 0.5 part by weight of ethyl α- (hydroxymethyl) acrylate 0.2 part by weight of benzoyl peroxide is added together with 100 parts by weight of ethyl acetate and reacted at 60 ° C. for 7 hours. A solution of an acrylic copolymer having a solid content of 40% by weight (polymerization rate 80%, molecular weight (Mw = 1.800,000: GPC polystyrene conversion)) was obtained. 1 part by weight of an isocyanate-based cross-linking agent (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) is added to 100 parts by weight of the solid content of this acrylic copolymer solution, and ethyl acetate is further added to obtain a solid content of 30 parts. A weight percent adhesive solution was made.

Example 2
(Preparation of adhesive)
In Example 1, the combination of the monomer and the polymerization initiator was
95.8 parts by weight of 2-ethylhexyl acrylate 4 parts by weight of butyl = α- (hydroxymethyl) acrylate A pressure-sensitive adhesive solution was prepared in the same manner as in Example 1 except that 0.2 parts by weight of azobisisobutyronitrile was used.

Comparative Example 1
(Preparation of adhesive)
In Example 1, a pressure-sensitive adhesive solution was prepared in the same manner as in Example 1 except that 2-hydroxyethyl acrylate was used in place of ethyl = α- (hydroxymethyl) acrylate.

  The pressure-sensitive adhesive solutions obtained in Examples and Comparative Examples were applied to a separator made of a polyester film (thickness: 38 μm) subjected to a release treatment using an applicator, and heat-treated at 155 ° C. for 3 minutes to obtain a solvent. The pressure-sensitive adhesive layer having a thickness of 25 μm after drying was obtained. This pressure-sensitive adhesive layer was laminated on a polarizing plate with a viewing angle widening film (manufactured by Nitto Denko: NWF-LE SEG type) to produce an optical film with a pressure-sensitive adhesive. The polarizing plate with a viewing angle widening film is obtained by laminating a liquid crystal layer as a viewing angle widening film with an adhesive on a polarizing plate, and the pressure-sensitive adhesive layer was provided on the viewing angle widening film side surface.

  The following evaluation was performed about the optical film with an adhesive obtained above. Two optical films with a pressure-sensitive adhesive cut into a 17-inch size at an angle of 135 ° with respect to the absorption axis of the polarizing plate were prepared. This optical film with an adhesive was laminated on the front and back of a glass plate with a laminator so as to be crossed Nicol, and then autoclaved at 50 ° C. and 5 atm for 15 minutes. This was the initial state. Subsequently, the heat processing for 24 hours were performed at 80 degreeC. This was the state after the heat treatment. About the initial state and the state after heat processing, the optical film was set | placed on the backlight and the nonuniformity of the peripheral part was confirmed visually.

In the example and the comparative example, the unevenness in the peripheral portion was “none” in the initial state. On the other hand, in the state after the heat treatment, in the example, the unevenness in the peripheral portion was “none”, but in the comparative example, the unevenness in the peripheral portion was “present”.

Claims (4)

An acrylic copolymer containing alkyl (meth) acrylate (a1) and alkyl = α- (hydroxymethyl) acrylate (a2) as monomer units, and a crosslinking agent, and a liquid crystal display device Adhesive for optical films. The ratio of alkyl = α- (hydroxymethyl) acrylate (a2) is 0.01 to 100 parts by weight with respect to 100 parts by weight of alkyl (meth) acrylate (a1). An adhesive for optical films for liquid crystal display devices . The monomer unit further contains 50 parts by weight or less of the monomer (a3) excluding the component (a1) and the component (a2) with respect to 100 parts by weight of the alkyl (meth) acrylate (a1). The pressure-sensitive adhesive for an optical film for a liquid crystal display device according to claim 1 or 2. The pressure-sensitive adhesive for an optical film for a liquid crystal display device according to claim 3 , wherein the monomer (a3) is a monomer containing a carboxyl group.