JP4673344B2 - Method for producing pressure-sensitive adhesive sheet for optical film - Google Patents

Description

  The present invention relates to an adhesive sheet for an optical film and a method for producing the same. Furthermore, it is related with the adhesive optical film using the said adhesive sheet for optical films. Further, the present invention relates to an image display device such as a liquid crystal display device, an organic EL display device, a CRT, or a PDP using the adhesive optical film. 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.

  Liquid crystal panels are used for liquid crystal display devices in watches, mobile phones, PDAs, notebook computers, personal computer monitors, DVD players, TVs, and the like. In recent years, optical panels such as liquid crystal panels have been increasingly demanded for display characteristics such as luminance enhancement, high definition, and low reflection. In addition, the optical film used for the optical panel has a high demand for appearance.

  When the optical film is bonded to the 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, since the adhesive has the merit that a drying step is not required for fixing the optical film, the adhesive is an adhesive optical film provided in advance as an adhesive layer on one side of the optical film. Generally used.

  A liquid crystal display device in which the optical film is bonded to each other using an adhesive, in particular, a notebook computer and a monitor for a personal computer have improved brightness and reduced the reflection on the outermost surface of the panel. When the device is visually recognized, there is a problem that uneven coating of the pressure-sensitive adhesive layer is raised, which may greatly affect the visibility.

For the adhesive layer, it has been proposed to control the coating thickness and surface roughness. For example, it has been proposed to improve the durability in a high temperature, high temperature and high humidity environment by reducing the standard deviation of the thickness variation of the pressure-sensitive adhesive layer provided on the polarizing plate or the like (Patent Document 1). In addition, by forming a pressure-sensitive adhesive layer on a release substrate whose surface roughness is controlled to be small and transferring the pressure-sensitive adhesive layer to a protective film, the pressure-sensitive adhesive having a small surface roughness on the protective film It has been proposed to form an agent layer (Patent Document 2). However, even according to the patent document, the influence on the visibility due to the unevenness of the pressure-sensitive adhesive layer cannot be improved.
JP-A-9-90125 JP 2005-306996 A

  An object of the present invention is to provide a pressure-sensitive adhesive sheet for an optical film and a method for producing the same that can reduce the problem of visibility related to the pressure-sensitive adhesive layer when applied to an image display device such as a liquid crystal display device. .

  Another object of the present invention is to provide an adhesive optical film using the optical film adhesive sheet. Another object of the present invention is to provide an image display device using the adhesive optical film.

As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by the following method for producing an optical film pressure-sensitive adhesive sheet , and have completed the present invention.

That is, this invention is a manufacturing method of the adhesive sheet for optical films which has an adhesive layer on a release sheet,
A step of applying a pressure-sensitive adhesive coating solution on the release sheet,
In the pressure-sensitive adhesive coating liquid, a first drying step at a temperature of 30 to 80 ° C. and a wind speed of 0.5 to 15 m / sec, and a second drying step at a temperature of 90 to 160 ° C. and a wind speed of 0.1 to 25 m / sec. Having a step of forming a pressure-sensitive adhesive layer by applying
It is related with the manufacturing method of the adhesive sheet for optical films characterized by surface roughness (Ra) of the adhesive layer surface on a release sheet being 2-150 nm.

  The present inventors have found that the surface roughness Ra of the adhesive to be bonded to the optical film, particularly the surface roughness Ra in the direction perpendicular to the longitudinal direction (orthogonal direction) greatly affects the visibility. In the pressure-sensitive adhesive sheet for optical films of the present invention, the surface roughness (Ra) of the pressure-sensitive adhesive layer provided on the release sheet is controlled to 2 to 150 nm, and the pressure-sensitive adhesive layer is formed without uneven coating. Yes. In the pressure-sensitive adhesive optical film prepared by bonding the pressure-sensitive adhesive sheet for optical films of the present invention to an optical film, the surface of the pressure-sensitive adhesive layer having the surface roughness is bonded to the optical film. As described above, since the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for optical films is formed without unevenness, the deterioration of the visibility due to the pressure-sensitive adhesive layer is suppressed, and the visibility of the liquid crystal display device, in particular, the visibility in an oblique direction is improved. Can be improved.

  The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the pressure-sensitive adhesive sheet A for optical films of the present invention, and has a pressure-sensitive adhesive layer 2 on a release sheet 1. The surface roughness (Ra) of the pressure-sensitive adhesive layer surface 2a is 2 to 150 nm. FIG. 2 shows the pressure-sensitive adhesive optical film of the present invention, in which the pressure-sensitive adhesive layer surface 2 a of the pressure-sensitive adhesive layer 2 of the pressure-sensitive adhesive sheet A for optical films is bonded to the optical film 3. When the adhesive optical film is applied to an image display device such as a liquid crystal display device, the release sheet 1 is peeled off and the adhesive layer surface 2b of the adhesive layer 2 (opposite to the adhesive layer surface 2a). Are bonded to various materials.

  In the pressure-sensitive adhesive sheet A for an optical film of the present invention, the surface roughness (Ra) of the pressure-sensitive adhesive layer surface 2a is 2 to 150 nm. The surface roughness (Ra) is preferably 10 to 140 nm, more preferably 20 to 120 nm, and further preferably 30 to 100 nm. When the surface roughness (Ra) exceeds 180 nm, the unevenness of the pressure-sensitive adhesive layer becomes remarkable and adversely affects visibility. On the other hand, when the surface roughness (Ra) is less than 2 nm, the adhesion with the optical film is lowered or the productivity is significantly adversely affected.

  The release sheet has at least a film substrate. Constituent materials of the film substrate include paper, polyolefin resin such as polyethylene and polypropylene, synthetic resin film such as polyester resin such as polyethylene terephthalate and polyethylene naphthalate, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet And appropriate thin leaf bodies such as metal foil and laminates thereof. Among these, the film substrate is preferably a polyethylene resin, a polyolefin resin, or paper. The thickness of the film substrate is usually 10 to 125 μm, preferably 20 to 100 μm, and more preferably 30 to 80 μm.

  The film base of the release sheet can be provided with a release layer and / or an oligomer migration-preventing layer on the side provided with the pressure-sensitive adhesive layer.

  The release layer can be formed of an appropriate release agent such as silicone, long chain alkyl, fluorine, or molybdenum sulfide. The thickness of the release layer can be appropriately set from the viewpoint of the release effect. In general, from the viewpoint of handleability such as flexibility, the thickness is preferably 20 μm or less, more preferably in the range of 0.01 to 10 μm, and in the range of 0.1 to 5 μm. It is particularly preferred. The method for forming the release layer is not particularly limited, and for example, a coating method, a spray method, a spin coating method, an in-line coating method, or the like is used. Further, a vacuum deposition method, a sputtering method, an ion plating method, a spray pyrolysis method, a chemical plating method, an electroplating method, or the like can also be used.

  When providing the said transition prevention layer with a mold release layer, it is preferable to provide between the film base of a mold release layer and a mold release sheet. The migration preventing layer can be formed of an appropriate material for preventing migration of a migration component in a base film (for example, a polyester film) of a release sheet, particularly a low molecular weight oligomer component of polyester. . As a material for forming the migration prevention layer, an inorganic material, an organic material, or a composite material thereof can be used. The thickness of the migration preventing layer can be appropriately set within a range of 0.01 to 20 μm.

  The method for forming the migration preventing layer is not particularly limited, and a method similar to the method for forming the release layer can be employed. In the coating method, spray method, spin coating method, and in-line coating method, ionizing radiation curable resins such as acrylic resins, urethane resins, melamine resins, and epoxy resins, and the above resins include aluminum oxide and silicon dioxide. A mixture of mica and the like can be used. In addition, when using a vacuum deposition method, sputtering method, ion plating method, spray pyrolysis method, chemical plating method or electroplating method, gold, silver, platinum, palladium, copper, aluminum, nickel, chromium, titanium, iron, It is possible to use a metal oxide made of cobalt or tin, an alloy thereof, or another metal compound made of iodide steel.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and various pressure-sensitive adhesives such as rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives can be used. In general, an acrylic pressure-sensitive adhesive having good adhesion to the resin is used.

  The acrylic pressure-sensitive adhesive has an acrylic polymer having a main skeleton of an alkyl (meth) acrylate monomer unit as a base polymer. (Meth) acrylate refers to acrylate and / or methacrylate, and (meth) of the present invention has the same meaning. The alkyl group of the alkyl (meth) acrylate constituting the main skeleton of the acrylic polymer has about 1 to 14 carbon atoms. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate and ethyl (meth). Acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl ( Examples include (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, These may be used alone or in combination. Among these, alkyl (meth) acrylates having 1 to 9 carbon atoms in the alkyl group are preferable.

  One or more kinds of various monomers can be introduced into the acrylic polymer by copolymerization for the purpose of improving adhesiveness and heat resistance. Specific examples of such a copolymerization monomer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, a nitrogen-containing monomer (including a heterocyclic ring-containing monomer), an aromatic-containing monomer, and the like.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid and methacrylic acid are preferable.

  Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate. Examples thereof include 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate.

  Examples of the nitrogen-containing monomer include maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; N-acryloylmorpholine; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl ( (Meth) acrylamide, N-hexyl (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meta) ) (N-substituted) amide monomers such as acrylamide; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butyl (meth) acrylate Aminoethyl, 3- (3-pyrini (Meth) acrylate alkylaminoalkyl monomers such as (l) propyl (meth) acrylate; (meth) acrylate alkoxyalkyl monomers such as (meth) acrylate methoxyethyl and (meth) acrylate ethoxyethyl; N- ( Succinimide monomers such as (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide, N-acryloylmorpholine, etc. are also intended for modification. Examples of monomers are listed.

  Examples of the aromatic-containing monomer include benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like.

  In addition to the above monomers, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; styrene sulfonic acid and allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid Sulfonic acid group-containing monomers such as (meth) acrylamide propanesulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalene sulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

  Furthermore, 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 morpholine, N-vinyl carboxylic acid amide , Vinyl monomers such as styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; (meth) acrylic Polyethylene glycol acid, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene (meth) acrylate Glycol acrylic ester monomers such as recall; (meth) acrylic acid tetrahydrofurfuryl, fluorine (meth) acrylate, silicone (meth) acrylate and acrylic acid ester monomers such as 2-methoxyethyl acrylate, etc. may also be used.

  Among these, a hydroxyl group-containing monomer is preferably used from the viewpoint of good reactivity with the crosslinking agent. Further, from the viewpoint of adhesiveness and adhesion durability, a carboxyl group-containing monomer such as acrylic acid is preferably used.

  The ratio of the copolymerization monomer in the acrylic polymer is not particularly limited, but is 50% by weight or less in terms of weight ratio. Preferably it is 0.1 to 10 weight%, More preferably, it is 0.5 to 8 weight%, More preferably, it is 1 to 6 weight%.

  The average molecular weight of the acrylic polymer is not particularly limited, but the weight average molecular weight is preferably about 300,000 to 2.5 million. The acrylic polymer 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 preferable, and ethyl acetate, toluene and the like are generally used as the solvent for the acrylic polymer.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the present invention can contain a crosslinking agent in addition to the 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. When the base polymer is an acrylic polymer, an isocyanate, epoxy, peroxide, metal chelate, oxazoline, or the like can be appropriately used as the crosslinking agent. These crosslinking agents can be used alone or in combination of two or more.

  As the isocyanate-based crosslinking agent, an isocyanate compound is used. 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.

  Examples of the epoxy-based crosslinking agent include bisphenol A epichlorohydrin type epoxy resins. Examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, Diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′- Examples include tetraglycidylaminophenyl methane, triglycidyl isocyanurate, m-N, N-diglycidylaminophenyl glycidyl ether, N, N-diglycidyl toluidine, and N, N-diglycidyl aniline.

  Various peroxides are used as the peroxide-based crosslinking agent. Peroxides include di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate , T-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxyisobutyrate, 1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, and the like. Of these, di (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide, which are particularly excellent in crosslinking reaction efficiency, are preferably used.

  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 polymer. 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, the pressure-sensitive adhesive may include a tackifier, a plasticizer, glass fiber, glass beads, metal powder, other inorganic powders, a pigment, a colorant, a filler, an antioxidant, if necessary. Various additives may be used as appropriate, such as an agent, an ultraviolet absorber, a silane coupling agent, and the like 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.

  Among the additives, it is preferable to add a silane coupling agent. Examples of the silane coupling agent include silicon compounds having a double bond such as vinyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ) Silicon compounds having an epoxy structure such as ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyl Amino group-containing silicon compounds such as methyldimethoxysilane; 3-chloropropyltrimethoxysilane; (meth) acryl such as acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane Base Silane coupling agent; and isocyanate group-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane and the like. The silane coupling agent can provide durability, particularly an effect of suppressing peeling in a humidified environment. The amount of the silane coupling agent used is 1 part by weight or less, further 0.01 to 1 part by weight, preferably 0.02 to 0.6 part by weight, based on 100 parts by weight of the base polymer.

  The pressure-sensitive adhesive sheet for optical films of the present invention can be obtained by performing a step of coating a pressure-sensitive adhesive coating solution on a release sheet and a step of forming a pressure-sensitive adhesive layer from the pressure-sensitive adhesive coating solution.

  In performing the coating process, an adhesive coating solution is prepared. The adhesive coating solution may be either a solution or a dispersion. In the case of a solution, for example, an aromatic solvent such as toluene or an ester solvent such as ethyl acetate is used as the solvent. The concentration of the pressure-sensitive adhesive coating solution is usually adjusted to about 2 to 80% by weight, preferably 5 to 40% by weight, and more preferably 7.5 to 20% by weight.

  The method of applying the adhesive coating solution onto the release sheet is not particularly limited. For example, die coating methods such as closed edge die and slot die; roll coating methods such as reverse coating and gravure coating, and spin coating. Method, screen coating method, fountain coating method, dipping method, spraying method, etc. can be adopted.

  In the coating process of the pressure-sensitive adhesive coating solution, the dry thickness of the pressure-sensitive adhesive layer to be formed can be appropriately adjusted, but is usually about 1 to 40 μm, preferably 5 to 30 μm, and more preferably 10 ˜25 μm is preferred.

  Next, the pressure-sensitive adhesive coating solution coated on the release sheet is dried to form a pressure-sensitive adhesive layer having a surface roughness (Ra) of 2 to 150 nm. The pressure-sensitive adhesive layer is formed, for example, after the first drying step at a temperature of 30 to 80 ° C. and a wind speed of 0.5 to 15 m / second, and then at a temperature of 90 to 160 ° C. and a wind speed of 0.1 to 25 m / second. 2 It can carry out by giving a drying process.

  By the first drying step, the solvent of the pressure-sensitive adhesive coating liquid is evaporated, and a pressure-sensitive adhesive layer surface having a surface roughness (Ra) of 2 to 150 nm is formed. Next, in the second drying step, the pressure-sensitive adhesive layer having a surface roughness (Ra) formed in the first drying step is cured (solidified) to form a pressure-sensitive adhesive layer.

  The temperature of the first drying step is 30 to 80 ° C, preferably 40 to 70 ° C, and more preferably 40 to 60 ° C. If the temperature is less than 30 ° C., it takes too much time to dry the solvent, which is not preferable in terms of productivity. On the other hand, if the temperature exceeds 80 ° C., drying proceeds too much, and the surface of the pressure-sensitive adhesive layer cannot be controlled to the surface roughness (Ra). The wind speed is 0.5 to 15 m / sec, preferably 0.5 to 10 m / sec, and more preferably 1 to 5 m / sec. When the wind speed is less than 0.5 m / sec, it takes too much time to dry the solvent, which is not preferable in terms of productivity. On the other hand, if the wind speed is higher than 15 m / sec, drying proceeds too much and the surface of the pressure-sensitive adhesive layer cannot be controlled to the surface roughness (Ra). The treatment time in the first drying step is about 10 seconds to 30 minutes, preferably 30 seconds to 20 minutes, more preferably 45 seconds to 10 minutes. The treatment time in the first drying step is controlled so that the surface of the pressure-sensitive adhesive layer has the surface roughness (Ra) in consideration of the relationship between temperature and wind speed.

  It is 90-160 degreeC of the temperature of a 2nd drying process, 130-160 degreeC is preferable and 135-155 degreeC is more preferable. If the temperature is less than 90 ° C., it takes too much time to dry the solvent, which is not preferable in terms of productivity. On the other hand, when the temperature exceeds 160 ° C., the pressure-sensitive adhesive is colored, which is not preferable. The wind speed is 0.1 to 25 m / second, preferably 1 to 23 m / second, and more preferably 5 to 20 m / second. When the wind speed is less than 0.1 m / sec, it takes too much time to dry the solvent, which is not preferable in terms of productivity. On the other hand, if the wind speed is higher than 25 m / sec, the running property of the film is adversely affected. The treatment time in the second drying step is about 10 seconds to 20 minutes, preferably 20 seconds to 10 minutes, more preferably 30 seconds to 3 minutes. The processing time in the second drying step is controlled so as to cure (solidify) the pressure-sensitive adhesive layer in consideration of the relationship between temperature and wind speed.

  In the first drying step and the second drying step, as means for controlling the temperature within the above range, for example, an oven, a hot air heater, a heating roll, a far infrared heater, or the like can be used. Moreover, in the said 1st drying process and a 2nd drying process, it can give by a counterflow type as a ventilation means which controls a wind speed to the said range. The distance to the blowing means is about 10 to 100 cm, preferably 10 to 50 cm. The wind speed can be measured by a mini vane type digital anemometer. The wind speed was measured using an anemometer at a position 3 cm above the pressure-sensitive adhesive coating solution coated on the release sheet under the blowing nozzle. As the anemometer, an anemometer MODEL 1560 / SYSTEM6243 manufactured by Nippon Kanomax Co., Ltd. was used.

  The pressure-sensitive adhesive sheet for optical films of the present invention can be used as a pressure-sensitive adhesive optical film by being bonded to an optical film. By the bonding, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for optical films is transferred to the optical film. When the adhesive optical film is used in an image display device, the release sheet is peeled off, and the exposed adhesive layer is attached to a liquid crystal cell or other member. It is particularly suitable for bonding to a display unit such as a liquid crystal cell.

  As an optical film, what is used for formation of image display apparatuses, such as a liquid crystal display device, is used, and 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.

  Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer obtained from a dichroic substance such as a polyvinyl alcohol film and 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, for example, by immersing 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 of boric acid or potassium iodide. 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, or may be performed while dyeing, or may be performed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath. The stretching method is not particularly limited, and any of wet and dry methods can be employed.

  As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. A transparent protective film is bonded to one side of the polarizer by an adhesive layer. On the other side, as a transparent protective film, (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  Moreover, as a transparent protective film, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, (A) thermoplastic resin which has a substituted and / or unsubstituted imide group in a side chain, ( B) Resin compositions containing thermoplastic resins having substituted and / or unsubstituted phenyl and nitrile groups in the side chains. 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. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a transparent 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 layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. The transparent protective film is particularly suitable when the thickness is 5 to 150 μm.

  In addition, when providing a polarizer protective film on both sides of the polarizer, the material of the polarizer protective film may be a transparent protective film made of the same polymer material on the front and back, or a transparent protective film made of a different polymer material or the like. It may be used.

  As the transparent protective film of the present invention, it is preferable to use at least one selected from cellulose resin, polycarbonate resin, cyclic polyolefin resin, and (meth) acrylic resin. The adhesive for electron beam curable polarizing plates of the present invention exhibits suitable adhesion to the various transparent protective films. In particular, the electron beam curable polarizing plate adhesive of the present invention exhibits good adhesion to acrylic resins that have been difficult to satisfy adhesiveness.

  Cellulose resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available cellulose triacetate include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, and “UZ-” manufactured by Fujifilm Corporation. TAC ”,“ KC series ”manufactured by Konica, and the like. In general, these cellulose triacetates have an in-plane retardation (Re) of almost zero, but a thickness direction retardation (Rth) of about ˜60 nm.

  In addition, the cellulose resin film with a small thickness direction phase difference is obtained by processing the said cellulose resin, for example. For example, a base film such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, at 80 to 150 ° C. for about 3 to 10 minutes). ) And then peeling the base film; a solution obtained by dissolving norbornene resin, (meth) acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc. is applied to a general cellulose resin film and dried by heating ( For example, a method of peeling the coated film after 80 to 150 ° C. for about 3 to 10 minutes is mentioned.

  Moreover, as a cellulose resin film with a small thickness direction retardation, the fatty acid cellulose resin film which controlled the fat substitution degree can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8. Preferably, the Rth can be reduced by controlling the acetic acid substitution degree to 1.8 to 2.7. Rth can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, acetyltriethyl citrate to the fatty acid-substituted cellulose resin. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulose resin.

  Specific examples of the cyclic polyolefin resin are preferably norbornene resins. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, trade names “ARTON” manufactured by JSR Corporation, “TOPASS” manufactured by TICONA, and trade names manufactured by Mitsui Chemicals, Inc. “APEL”.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability. From the (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And a high Tg (meth) acrylic resin system obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  As the (meth) acrylic resin having a lactone ring structure, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A. And (meth) acrylic resins having a lactone ring structure, as described in Japanese Patent Publication No. Gazette.

  The (meth) acrylic resin having a lactone ring structure preferably has a ring pseudo structure represented by the following general formula (Formula 1).

^Wherein, R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the general formula (Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, More preferably, it is 10 to 60% by weight, and particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, the heat resistance, solvent resistance, and surface hardness are low. May be insufficient. If the content of the lactone ring structure represented by the general formula (Chemical Formula 1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, molding processability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, and particularly preferably. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, it is not preferable from the viewpoint of molding processability.

  The (meth) acrylic resin having a lactone ring structure preferably has a Tg of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. Since Tg is 115 ° C. or higher, for example, when incorporated into a polarizing plate as a transparent protective film, it has excellent durability. Although the upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  As the transparent protective film, one having a front phase difference of less than 40 nm and a thickness direction retardation of less than 80 nm is usually used. The front phase difference Re is represented by Re = (nx−ny) × d. The thickness direction retardation Rth is represented by Rth = (nx−nz) × d. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny). [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. In addition, it is preferable that a transparent protective film has as little color as possible. A protective film having a thickness direction retardation value 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, the coloring (optical coloring) of the polarizing plate caused by the transparent protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  On the other hand, as the transparent protective film, a phase difference plate having a phase difference with a front phase difference of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a transparent protective film, so that the thickness can be reduced.

  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 20 to 150 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 resin, cyclic polyolefin resin (norbornene resin), or any of these binary, ternary copolymers, graft copolymers Examples thereof include polymers and 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 can be prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment 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 those for the purpose of compensating for various wavelength plates or birefringence of liquid crystal layers and compensation of viewing angle, etc. It may be one in which retardation plates are stacked and optical characteristics such as retardation are controlled.

  The retardation plate has a relationship of nx = ny> nz, nx> ny> nz, nx> ny = nz, nx> nz> ny, nz = nx> ny, nz> nx> ny, nz> nx = ny. What is satisfactory is selected and used according to various applications. Note that ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.

  For example, in a phase difference plate that satisfies nx> ny> nz, a surface plate having a front phase difference of 40 to 100 nm, a thickness direction phase difference of 100 to 320 nm, and an Nz coefficient of 1.8 to 4.5 is used. Is preferred. For example, in a retardation plate (positive A plate) that satisfies nx> ny = nz, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, for a retardation plate (negative A plate) that satisfies nz = nx> ny, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, in a retardation plate satisfying nx> nz> ny, it is preferable to use a retardation plate having a front phase difference of 150 to 300 nm and an Nz coefficient exceeding 0 to 0.7. Further, as described above, for example, nx = ny> nz, nz> nx> ny, or nz> nx = ny can be used.

  The transparent protective film can be appropriately selected according to the applied liquid crystal display device. For example, in the case of VA (including Vertical Alignment, MVA, and PVA), it is desirable that at least one of the polarizing plates (cell side) has a retardation. As specific phase differences, it is desirable that Re = 0 to 240 nm and Rth = 0 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> ny> nz, nx> nz> ny, nx = ny> nz (uniaxial, biaxial, Z-ized, negative C plate) is desirable. When polarizing plates are used above and below the liquid crystal cell, both the upper and lower sides of the liquid crystal cell may have a phase difference, or any one of the upper and lower transparent protective films may have a phase difference.

  For example, in the case of IPS (including In-Plane Switching, FFS), both cases where the transparent protective film on one side of the polarizing plate has a phase difference and does not have a phase difference can be used. For example, when there is no phase difference, it is desirable that the liquid crystal cell has no phase difference both above and below (cell side). When the liquid crystal cell has a phase difference, it is desirable that the liquid crystal cell has a phase difference on both the upper and lower sides. When there is no phase difference, or when the A plate is on the upper side and the positive C plate is on the lower side). When it has a phase difference, it is desirable that Re = −500 to 500 nm and Rth = −500 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> nz> ny, nz> nx = ny, nz> nx> ny (uniaxial, Z-ized, positive C plate, positive A plate) are desirable.

  In addition, the film which has the said phase difference can be separately bonded to the transparent protective film which does not have a phase difference, and the said function can be provided.

  The transparent protective film may be subjected to surface modification treatment in order to improve adhesiveness with the polarizer before applying the adhesive. Specific examples of the treatment include corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, and treatment with a coupling agent.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for 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. In addition, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer (for example, a backlight-side diffusion plate).

  The anti-glare treatment is applied for the purpose of preventing the outside 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 a sandblasting method or an embossing method. 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 blending 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 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  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.

  The adhesive layer used for laminating the polarizer and the transparent protective film is not particularly limited as long as it is optically transparent, and is water-based, solvent-based, hot-melt-based, radical curable (electro-curable, ultraviolet curable). Although various forms are used, a water-based adhesive or a radical curable adhesive is preferable.

  Examples of the water-based adhesive include polyvinyl alcohol, gelatin, vinyl latex, polyurethane, isocyanate, polyester, and epoxy. The adhesive may contain various crosslinking agents. The adhesive may contain various crosslinking agents. In addition, a stabilizer such as a catalyst, a coupling agent, various tackifiers, an ultraviolet absorber, an antioxidant, a heat stabilizer, and a hydrolysis stabilizer can be added to the adhesive. In addition, a sol or filler of a metal compound such as alumina or silica can be added to the adhesive. The solid content of the adhesive is generally 0.1 to 20% by weight.

  Moreover, as an optical film used for the pressure-sensitive adhesive optical film of the present invention, in addition to the polarizing plate, the exemplified retardation plate (including wavelength plates such as 1/2 and 1/4) alone is used. Can be used. In addition, it may be used for forming liquid crystal display devices such as a reflection plate, an anti-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), a viewing angle compensation film, and a brightness enhancement film. The thing used as a certain optical layer is mention | raise | lifted. 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 viewing angle compensation film is further laminated on a plate, or a polarizing plate in which a brightness 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. Moreover, the transparent protective film contains fine particles so as to have 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. The transparent 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 transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  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 or the like that displays an image using a built-in light 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 is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source 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. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  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 (reflection type) 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 viewing angle compensation film is a film for widening the viewing angle so that an 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. As such a viewing angle compensation phase difference plate, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially 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 be mentioned. 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.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A 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 the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, 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 diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. 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 directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a 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 in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. 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, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having 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 three or more optical layers like 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-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  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 other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  The pressure-sensitive adhesive optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. In other words, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, STN type, π type, VA type, IPS type, or the like can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film 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 diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. In general, 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. In addition, all the parts and% in each example are based on weight.

Production Example 1
<Preparation of acrylic adhesive>
In a four-necked flask equipped with a nitrogen inlet tube and a condenser tube, 96.5 parts of butyl acrylate, 3 parts of acrylic acid, 0.5 part of 2-hydroxyethyl acrylate, 2,2′-azobisisobutyronitrile After 15 parts and 100 parts by weight of ethyl acetate were added and sufficiently purged with nitrogen, the mixture was reacted at 60 ° C. for 8 hours with stirring under a nitrogen stream to obtain an acrylic polymer solution having a weight average molecular weight of 1,650,000. 0.5 parts of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) is blended with 100 parts of the solid content of the acrylic polymer solution to prepare an adhesive coating solution (solid content of 12%). did.

Production Example 2
<Preparation of acrylic adhesive>
In a four-necked flask equipped with a nitrogen inlet tube and a condenser tube, 99.5 parts of butyl acrylate, 0.5 part of 4-hydroxybutyl acrylate, 0.15 part of 2,2′-azobisisobutyronitrile and ethyl acetate After adding 100 parts by weight and sufficiently purging with nitrogen, the mixture was reacted for 8 hours at 60 ° C. with stirring under a nitrogen stream to obtain an acrylic polymer solution having a weight average molecular weight of 1,650,000. As a crosslinking agent, 0.2 part of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) is blended with respect to 100 parts of the solid content of the acrylic polymer solution, and an adhesive coating solution (solid content of 11. 5%) was prepared.

Production Example 3
<Preparation of acrylic adhesive>
In a four-necked flask equipped with a nitrogen inlet tube and a condenser tube, 90 parts of butyl acrylate, 4 parts of acrylic acid, 5 parts of acryloylmorpholine, 1 part of 4-hydroxyethyl acrylate, 2,2′-azobisisobutyronitrile 0 .15 parts and 100 parts by weight of ethyl acetate were added, and after sufficiently purging with nitrogen, the mixture was reacted at 60 ° C. for 8 hours with stirring under a nitrogen stream to obtain an acrylic polymer solution having a weight average molecular weight of 1,650,000. . As a crosslinking agent, 0.3 part of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L) is added to 100 parts of the solid content of the acrylic polymer solution, and a pressure-sensitive adhesive coating solution (solid content of 11. 5%) was prepared.

<Polarizing plate>
A polyvinyl alcohol film having a thickness of 80 μm was stretched 5 times in an aqueous iodine solution and then dried to obtain a polarizer. A transparent protective film (triacetylcellulose film, thickness 80 μm) was bonded to both sides of the polarizer with a polyvinyl alcohol adhesive to obtain a polarizing plate.

Example 1
Obtained in Production Example 1 on the release treatment surface (surface roughness 21 nm) of the release-treated polyester film (release sheet, Mitsubishi Chemical Polyester Co., Ltd., trade name Diafoil MRF # 38, thickness 38 μm) The resulting pressure-sensitive adhesive coating solution is applied by a die coater so that the dry thickness is 25 μm, and then is first dried by sending air at a wind speed of 14 m / sec for 1 minute in an oven at 70 ° C. The process was applied. Subsequently, the 2nd drying process was performed by sending the wind of temperature 155 degreeC, and the wind speed of 15 m / sec for 2 minutes, the adhesive layer was formed, and the adhesive sheet for optical films was obtained.

Examples 2-7, Comparative Examples 1-3
In Example 1, the pressure-sensitive adhesive sheet for optical film was the same as Example 1 except that the type of the adhesive coating solution, the conditions of the first drying step, and the conditions of the second drying step were changed as shown in Table 1. Got.

  The following evaluation was performed about the adhesive sheet for optical films obtained above. The results are shown in Table 1.

<Surface roughness (Ra): surface side>
Another release sheet (polyester film subjected to release treatment, manufactured by Mitsubishi Chemical Polyester Co., Ltd., trade name Diafoil MRF # 38, thickness 38 μm) is bonded to the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet for optical films. It was. Thereafter, the release sheet that had been pasted from the original was peeled off and pasted onto glass (Matsunami Glass, MICROSLIDE GLASS) as a sample. About the said sample, it set | placed so that the release sheet bonded later may become the top, and surface roughness was measured using WYKO NT3300 (non-contact three-dimensional roughness measuring apparatus, Nihon Beco Co., Ltd. product). The measurement was observed in a range of 20 mm × 20 mm, and the surface roughness was calculated at 3 points every 5 mm in the direction perpendicular to the coating direction of the pressure-sensitive adhesive layer. Table 1 shows the measured values (in parentheses) at three points together with the average value of the surface roughness. In addition, surface roughness (Ra) is a value measured according to JISB0601.

<Surface roughness (Ra): release sheet side>
Ra of the pressure-sensitive adhesive layer on the release sheet side is a copy of Ra of the release treatment surface of the release sheet. Therefore, Ra of the pressure-sensitive adhesive layer on the release sheet side is obtained by using the fine shape measuring instrument (three-dimensional surface shape measuring instrument) ET4000 (manufactured by Kosaka Laboratory) to determine the surface roughness of the release treatment surface of the release sheet. It was measured. The measurement was observed in a range of 20 mm × 20 mm and measured in a direction perpendicular to the coating direction of the pressure-sensitive adhesive layer. In addition, surface roughness (Ra) is a value measured according to JISB0601.

<Visibility>
The pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet for optical films was transferred to a polarizing plate to prepare a pressure-sensitive adhesive polarizing plate. After peeling off the release sheet from the pressure-sensitive adhesive polarizing plate, it was attached to a portable panel manufactured by Sharp Corporation, and visually observed from two directions, 45 ° and front, according to the following criteria. It was.
A: There is no problem in visibility.
○: A level where there is no problem although some unevenness is confirmed.
X: There is a problem in visibility.

It is sectional drawing of an example of the adhesive sheet for optical films of this invention. It is sectional drawing of an example of the adhesive optical film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release sheet 2 Adhesive layer 2a Adhesive layer surface whose surface roughness (Ra) is 2-150 nm 3 Optical film

Claims (1)

A method for producing a pressure-sensitive adhesive sheet for an optical film having a pressure-sensitive adhesive layer on a release sheet,
A step of applying a pressure-sensitive adhesive coating solution on the release sheet,
In the pressure-sensitive adhesive coating liquid, a first drying step at a temperature of 30 to 80 ° C. and a wind speed of 0.5 to 15 m / sec, and a second drying step at a temperature of 90 to 160 ° C. and a wind speed of 0.1 to 25 m / sec. Having a step of forming a pressure-sensitive adhesive layer by applying
The manufacturing method of the adhesive sheet for optical films characterized by surface roughness (Ra) of the adhesive layer surface on a release sheet being 2-150 nm.