JP2005042101A - Conductive cellulosic film, its preparation process, antireflection film, optical element, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a conductive cellulose-based film prevented from being whitened during the formation of a conductive layer, being high in uniformity and transparency, and being excellent in optical properties, to provide a conductive cellulose-based film, to provide an antireflection film and an optical element using the cellulose-based film, and to provide an image display device equipped with the optical element, etc. <P>SOLUTION: In the method for producing the conductive cellulose-based film which comprises coating a cellulose-based film with a coating liquid containing a binder, ultramicroparticles, and a solvent to form a conductive layer on the cellulose-based film, the coating liquid contains 20 to 40 wt.%, based on the entire solvent, at least one glycol monoalkyl ether-based solvent selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether and 20 to 50 wt.%, based on the entire solvent, ketone-based solvent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a conductive cellulose film. The conductive cellulose film is used for various optical film applications as a hard coat film having a hard coat layer and an antireflection film having an antireflection layer. For example, those applied to optical elements such as polarizing plates can be suitably used in various image display devices such as liquid crystal displays, organic EL display devices, PDPs, and CRTs. Moreover, it can utilize suitably as components, such as a polarizing filter and an antireflection filter, or a member for sticking.

  Liquid crystal panels are securing a firm position as displays through recent research and development. However, in car navigation monitors and video camera monitors that are frequently used under bright illumination, visibility is significantly reduced due to surface reflection. Therefore, it is becoming indispensable to apply an antireflection treatment to the polarizing plate used in the liquid crystal panel, and a polarizing plate subjected to the antireflection treatment is used in most liquid crystal displays that are frequently used outdoors.

  The antireflection treatment is generally a multi-layer stack of a plurality of thin films made of materials having different refractive indexes by a dry method such as a vacuum deposition method, a sputtering method, a CVD method, or a wet method using a die or gravure roll coating. The body is designed to reduce reflection in the visible light region as much as possible. In particular, the wet method is preferably used because the equipment cost is low, a large-area thin film can be continuously produced, and the productivity is excellent. As a method of forming a thin film (film) using a wet method, for example, a method of forming a film by coating a cellulose-based sheet or film with a paint containing an aprotic polar solvent is disclosed (Patent Document). 1).

However, in the conventional wet method, a small amount of water may be mixed in the coating liquid depending on the atmospheric humidity during coating work, when adjusting the coating liquid, and during storage. In that case, in the drying process after applying the coating liquid, the organic solvent volatilizes from the solvent having a lower boiling point, so that the solubility of water in the organic solvent reaches a saturated state and phase separation occurs. Then, there is a problem that hydrophilic ultrafine particles are preferentially moved to the aqueous phase to aggregate and whiten, thereby remarkably damaging optical properties such as transmittance.
JP 2000-11070 A

  The present invention solves the above-mentioned problems, and prevents the whitening phenomenon during the formation of the conductive layer, has a high uniformity and transparency, and has excellent optical properties, and a method for producing the conductive cellulose film. It aims at providing a cellulosic film. Another object of the present invention is to provide an antireflection film using the conductive cellulose film, an optical element, and an image display device equipped with the optical element or the like.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the manufacturing method shown below, and have completed the present invention.

That is, the present invention provides a method for producing a conductive cellulose film in which a coating liquid containing a binder, ultrafine particles and a solvent is coated on a cellulose film to form a conductive layer.
The coating liquid contains at least one glycol monoalkyl ether solvent selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether with respect to the total solvent. The present invention relates to a method for producing a conductive cellulose film, comprising 20 to 40% by weight of a ketone solvent and 20 to 50% by weight of a ketone solvent based on the total solvent.

  In the present invention, the coating solution contains a specific amount of a specific glycol monoalkyl ether solvent and a ketone solvent having an azeotropic property with water. Therefore, in the drying step after coating the coating solution, an organic solvent is used. Phase separation between water and water does not occur, and the ultrafine particles do not move to the water phase and aggregate and whiten. Therefore, the conductive cellulose film excellent in uniformity and transparency can be obtained without impairing optical characteristics such as transmittance.

  The glycol monoalkyl ether solvent is preferably 20 to 30% by weight with respect to the total solvent. When the content of the glycol monoalkyl ether solvent is less than 20% by weight based on the total solvent, separation of the organic phase and the aqueous phase occurs in the drying step after coating, and the ultrafine particles move to the aqueous phase. It is not preferable because it aggregates and whitens. On the other hand, when it exceeds 40% by weight with respect to the total solvent, it is not preferable because the adhesion between the cellulose-based film and the conductive layer is lowered or the binder is hardly dissolved.

  The ketone solvent is preferably 20 to 30% by weight based on the total solvent. Since the ketone solvent has a high boiling point, the ratio of the ketone solvent in the solvent increases during drying, and the conductive layer is formed by curing the binder while dissolving a part of the cellulose film. As a result, a conductive layer with good adhesion can be formed. If the ratio of the ketone solvent to the total solvent is less than 20% by weight, the adhesion between the conductive layer and the cellulose film tends to be insufficient. On the other hand, when the ratio of the ketone solvent to the total solvent exceeds 50% by weight, the cellulose film is excessively dissolved, and the conductive layer tends to be whitened.

  In this invention, it is preferable that the said coating liquid contains 10-60 weight% of 1 or more types of alcohol solvent with respect to all the solvents, More preferably, it is 40-60 weight%. The alcohol solvent is preferably used in combination because it has a high ability to dissolve the binder of the conductive layer.

Another aspect of the present invention is a method for producing a conductive cellulose film in which a cellulose-based film is coated with a coating liquid containing a binder, ultrafine particles and a solvent to form a conductive layer.
The said coating liquid is related with the manufacturing method of the electroconductive cellulose film characterized by including 5 to 40weight% of 2 or more types of organic solvent azeotropic with respect to a total solvent. In another aspect of the present invention, the same effect as described above can be obtained by using a specific amount of two or more organic solvents azeotropic with each other in the coating solution.

  The ultrafine particles are preferably metal oxide ultrafine particles. By using metal oxide ultrafine particles as the ultrafine particles having conductivity, a conductive layer having good adhesion and antistatic properties can be provided.

  Moreover, this invention relates to the electroconductive cellulose film obtained by the said manufacturing method. The conductive cellulose film can be used as a hard coat film in which a hard coat layer is formed on a conductive layer. Moreover, the said conductive cellulose film can provide anti-glare property by making the hard-coat layer surface uneven | corrugated shape.

  The conductive cellulose film can be used as an antireflection film in which an antireflection layer is formed directly on the conductive layer or via another layer (hard coat layer).

  The present invention also relates to an optical element in which the conductive cellulose film or the antireflection film is provided on one side or both sides of the optical element. Furthermore, the present invention relates to an image display device equipped with the conductive cellulose film, the antireflection film, or the optical element.

  In the present invention, a cellulose-based film is coated with a coating liquid containing a binder, ultrafine particles and a solvent to form a conductive layer. Hereinafter, preferred embodiments of the present invention will be described.

  Examples of the material for the cellulose film include cellulose polymers such as diacetyl cellulose and triacetyl cellulose. The thickness of the cellulosic film can be appropriately determined, but is generally about 10 to 300 μm from the viewpoints of workability such as strength and handleability and thin layer properties. 20-300 micrometers is especially preferable, and 30-200 micrometers is more preferable. In addition, surface treatments such as saponification treatment, corona discharge treatment, sputtering treatment, low-pressure UV irradiation, and plasma treatment can be applied to the surface of the cellulose-based film.

  The binder in the coating solution is not particularly limited, but it is preferable to use alkoxysilane and / or a condensate thereof. The alkoxysilane is thermally cured to form a polysiloxane structure. Specific examples of the alkoxysilane include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, Methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopro Trialkoxysilanes such as rutriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane , Diethyldimethoxysilane, diethyldiethoxysilane and the like. These alkoxysilanes can be used as a partial condensate thereof. Among these, tetraalkoxysilanes or partial condensates thereof are preferable. In particular, tetramethoxysilane, tetraethoxysilane or a partial condensate thereof is preferable.

  The ultrafine particles are not particularly limited as long as they have electrical conductivity, but it is preferable to use metal oxide ultrafine particles. Metal oxide ultrafine particles include antimony oxide, selenium oxide, titanium oxide, tungsten oxide, tin oxide, antimony-doped tin oxide, phosphorus-doped tin oxide, zinc oxide, zinc antimonate, tin-doped indium oxide, etc. Ultrafine particles. As the metal oxide ultrafine particles, a sol whose main component is an oxide of a metal selected from tin, antimony, and indium, such as highly conductive antimony-doped tin oxide, phosphorus-doped tin oxide, zinc antimonate, and tin-doped indium oxide. Particles are preferred. Of these, antimony-doped tin oxide, which has good paint stability and sol reproducibility, is preferred. The metal oxide ultrafine particles are ultrafine particles having an average particle diameter of preferably 80 nm or less, more preferably 60 nm or less. When the average particle diameter exceeds 80 nm, generally haze increases and transparency tends to be inferior. In order to obtain a highly dispersible sol, a dispersion in a dispersion medium such as water, alcohol, ester or hydrocarbon is usually used.

  As the solvent, at least one glycol monoalkyl ether solvent and ketone solvent selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether are used.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopentanone. Of these, cyclohexanone is preferred.

  In the coating solution, one or more of various solvents such as an aromatic solvent, an ester solvent, an alcohol solvent, an amide solvent, a sulfoxide solvent, and an ether solvent are appropriately combined with the solvent. Can be added. Of these solvents, alcohol solvents are preferably used. Examples of the alcohol solvent include methanol, ethanol, n-propyl alcohol, i-propyl alcohol, n-butanol, i-butanol, and t-butanol.

  In another aspect of the present invention, two or more organic solvents azeotropic with each other are used as the solvent. Examples of the organic solvent azeotropic with each other include, for example, a combination of an alcohol such as methanol and ethanol and at least one selected from the group consisting of methyl ethyl ketone, ethyl acrylate, ethyl acetate, benzene, hexane, toluene, and methylene chloride. Can be mentioned. Among these, a combination of alcohol and methyl ethyl ketone is preferable.

  In the coating liquid, an alkoxysilane curing catalyst can be used in addition to the binder, ultrafine particles and solvent. Curing catalysts include organic acid catalysts such as formic acid, acetic acid, propionic acid, p-toluenesulfonic acid and methanesulfonic acid, tin-based catalysts such as dibutyltin laurate and tin octylate, inorganic acid catalysts such as boric acid and phosphoric acid, Examples include alkaline catalysts. Moreover, the various additives used for a conductive layer can be mix | blended with a coating liquid.

  The solid content concentration of the coating liquid is preferably adjusted to about 1 to 10% by weight, more preferably 1 to 3% by weight. The ratio of the binder and the ultrafine particles in the coating liquid is preferably adjusted so that the ratio of the ultrafine particles is about 40 to 95% by weight in the conductive layer formed by the coating liquid.

  After coating the coating liquid on the cellulose film, the solvent is dried and cured to form a conductive layer. When the alkoxysilane and / or the condensate thereof, which is a binder, has ultraviolet curability, it can be cured with ultraviolet light after heat curing. The coating method of the coating liquid is not particularly limited, and various methods such as a dipping method, a gravure coater method, a spin coating method, and a slot die coating method can be adopted. The thickness of the conductive layer is usually 0.01 to 0.5 μm, preferably 0.05 to 0.2 μm.

  A hard coat layer can be formed on the conductive layer. The resin for forming the hard coat layer is not particularly limited as long as it has excellent hard coat properties (showing a hardness of H or higher in the pencil hardness test of JIS K5400), has sufficient strength, and has excellent light transmittance. Absent. Examples thereof include thermosetting resins, thermoplastic resins, ultraviolet curable resins, electron beam curable resins, two-component mixed resins, and the like. Among these, an ultraviolet curable resin capable of efficiently forming a hard coat layer by a simple processing operation by a curing treatment by ultraviolet irradiation is preferable. Examples of the ultraviolet curable resin include polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins, and include ultraviolet curable monomers, oligomers, polymers, and the like. The UV curable resin preferably used includes, for example, those having an ultraviolet polymerizable functional group, and in particular, those containing an acrylic monomer or oligomer having 2 or more, particularly 3 to 6 functional groups. . Further, an ultraviolet polymerization initiator is blended in the ultraviolet curable resin.

  The transparent resin solution is applied by an appropriate method such as a bar coater such as a wire bar, a micro gravure coater, a die coater, casting, spin coating, or phantom metalling. Examples of the solvent for dissolving the transparent resin include general solvents such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, and ethyl alcohol. The thickness of the hard coat layer is not particularly limited, but is preferably about 1 to 10 μm, particularly 2 to 5 μm.

The hard coat layer can be adjusted to a high refractive index by adding ultrafine particles of a high refractive index metal or metal oxide. Examples of the ultrafine particles having a high refractive index include ultrafine particles of metal oxides such as TiO ₂ , SnO ₂ , ZnO ₂ , ZrO ₂ , aluminum oxide, and zinc oxide. The average particle diameter of such ultrafine particles is usually preferably about 0.1 μm or less. High refractive index ultrafine particles can be dispersed almost uniformly in the hard coat layer.

  The surface of the hard coat layer can have a fine concavo-convex structure to impart antiglare properties. By making the surface of the hard coat layer uneven, antiglare properties due to light diffusion can be imparted. The provision of light diffusibility is also preferable for reducing the reflectance.

  The method for forming the fine concavo-convex structure on the surface is not particularly limited, and an appropriate method can be adopted. For example, the surface of the transparent substrate film 1 used for the formation of the hard coat layer is previously roughened by an appropriate method such as sandblasting, embossing roll, chemical etching, etc. to give a fine uneven structure to the film surface. A method of forming the surface of the material itself forming the hard coat layer into a fine concavo-convex structure by a method or the like can be mentioned. Further, there is a method in which a hard coat layer is separately applied on the hard coat layer, and a fine concavo-convex structure is imparted to the surface of the resin film layer by a transfer method using a mold. Further, a method of imparting a fine concavo-convex structure by dispersing an inorganic or organic spherical or amorphous filler in the hard coat layer can be used. These fine concavo-convex structure forming methods may be formed as a layer in which two or more methods are combined to combine the fine concavo-convex structure surfaces in different states.

  As a method of forming the hard coat layer on the surface of the fine concavo-convex structure, a method of providing a hard coat layer containing an inorganic or organic spherical or amorphous filler in a dispersed manner is preferable from the viewpoint of formability and the like. Examples of inorganic or organic spherical or amorphous fillers include, for example, crosslinked or uncrosslinked organic fine particles composed of various polymers such as PMMA (polymethyl methacrylate), polyurethane, polystyrene, and melamine resin, glass, silica, alumina, and oxidation. Examples thereof include inorganic particles such as calcium, titania, zirconium oxide, and zinc oxide, and conductive inorganic particles such as tin oxide, indium oxide, cadmium oxide, antimony oxide, and a composite thereof. The average particle diameter of the filler (both primary particles and secondary particles) is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. When the fine concavo-convex structure is formed with fine particles, the amount of fine particles used is preferably about 1 to 30 parts by weight with respect to 100 parts by weight of the resin.

  In addition, in formation of a hard-coat layer (anti-glare layer), additives, such as a leveling agent, a thixotropic agent, and an antistatic agent, can be contained. In forming a hard coat layer (antiglare layer), a thixotropic agent (silica, mica, etc. of 0.1 μm or less) can be included to easily form a fine relief structure with protruding particles on the surface of the antiglare layer. it can.

  An antireflection layer can be formed on the conductive layer or the hard coat layer. The method for forming the antireflection layer is not particularly limited, but a wet coating method using a low refractive index material is preferable because it is a simpler method than a vacuum deposition method or the like. Examples of the material for forming the antireflection layer include resin materials such as ultraviolet curable acrylic resins, hybrid materials in which inorganic fine particles such as colloidal silica are dispersed in the resin, tetraethoxysilane, titanium tetraethoxide, and the like. Examples include sol-gel materials using metal alkoxides. Each material uses a fluorine group-containing compound for imparting antifouling properties to the surface. From the viewpoint of scratch resistance, a low refractive index layer material having a high inorganic component content tends to be excellent, and a sol-gel material is particularly preferable. Sol-gel materials can be used after partial condensation.

Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. As perfluoroalkyl alkoxysilane, for example, general formula (1): CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms) , N represents an integer of 0 to 12). Specifically, for example, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecafluorodecyltri Examples thereof include ethoxysilane. Among these, the compound wherein n is 2 to 6 is preferable.

  Further, a sol in which silica, alumina, titania, zirconia, magnesium fluoride, ceria or the like is dispersed in an alcohol solvent may be added to the antireflection layer. In addition, additives such as metal salts and metal compounds can be appropriately blended.

  The refractive index of the antireflection layer is preferably 1.35 to 1.45.

  The method for forming the antireflection layer is not particularly limited, and can be formed by an appropriate method such as a doctor blade method, a gravure roll coater method, or a dipping method.

  The thickness of the antireflection layer is not particularly limited, and is usually about 80 to 150 nm on average. The thickness of the antireflection layer is determined so as to be near the target wavelength depending on the refractive index of the material to be used and the set wavelength of the incident light.

  An optical element can be bonded to the side of the conductive cellulose film on which the conductive layer is not formed. Examples of the optical element include a polarizer. The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films 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 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 produced, for example, by dyeing 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, may be performed while dyeing, or may be dyed 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 polarizer is usually used as a polarizing plate with a transparent protective film provided on one side or both sides. The transparent protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like. As the transparent protective film, the same material as the transparent substrate film exemplified above is used. The transparent protective film may be a transparent protective film made of the same polymer material on the front and back, or may be a transparent protective film made of a different polymer material or the like. Those excellent in transparency, mechanical strength, thermal stability, moisture barrier property and the like are preferably used. Further, the transparent protective film is often preferable as the optical anisotropy such as retardation is small. Triacetyl cellulose is optimal as the polymer for forming the transparent protective film. When the hard coat film is provided on one side or both sides of a polarizer (polarizing plate), the transparent base film of the hard coat film can also serve as a transparent protective film for the polarizer. The thickness of the transparent protective film is not particularly limited, but is generally about 10 to 300 μm.

  An anti-reflection polarizing plate in which a polarizing plate is laminated on a hard coat film may be a laminate of a hard protective film, a transparent protective film, a polarizer, and a transparent protective film, or a hard coat film with a polarizer and a transparent protective film. Those sequentially stacked may also be used.

  In addition, the surface of the transparent protective film on which the polarizer is not adhered may be a hard coat layer, a sticking prevention film or a treatment intended. 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. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer. The hard coat layer, the anti-sticking 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, a hard coat layer, a primer layer, an adhesive layer, an adhesive layer, an antistatic layer, a conductive layer, a gas barrier layer, a water vapor barrier layer, a moisture barrier layer, etc. are inserted between the layers of the polarizing plate, or to the surface of the polarizing plate. You may laminate. Also. In the stage of forming each layer of the polarizing plate, for example, conductive particles or antistatic agents, various fine particles, plasticizers, and the like may be added to the material for forming each layer, mixed, or the like, if necessary.

  As an optical element, in practical use, an optical film in which another optical element (optical layer) is laminated on the polarizing plate can be used. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. 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. In an elliptically polarizing plate, a polarizing plate with optical compensation, etc., a hard coat film is provided on the polarizing plate side.

  If necessary, various properties such as scratch resistance, durability, weather resistance, heat and humidity resistance, heat resistance, moisture resistance, moisture permeability, antistatic properties, conductivity, interlayer adhesion, mechanical strength, Processing for imparting a function or the like, or insertion or lamination of a functional layer can also be performed.

  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 provided on one surface of the polarizing plate via the transparent protective film or the like, if 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.

  The reflection plate can be used as a reflection sheet in which a reflection layer is provided on an appropriate film according to the transparent film instead of the method of directly applying to the transparent protective film of the polarizing plate. 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 described above are obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, norbornene resin, other polyolefins, polyarylate, and polyamide. Examples thereof include a birefringent film, a liquid crystal polymer alignment film, 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 (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 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 emits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is, but from the viewpoint 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.

  Lamination of the hard coat film to the optical element and further lamination of various optical layers to the polarizing plate can be performed by a method of laminating them separately in the manufacturing process of a liquid crystal display device or the like. The laminated one is excellent in quality stability and assembly work, and has the advantage of improving the manufacturing process of a liquid crystal display device and the like. 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.

  An adhesive layer for adhering to other members such as a liquid crystal cell can be provided on at least one surface of the optical element described above. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to an optical element such as a polarizing plate or an optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. There is a method of attaching it directly on the optical element by an appropriate development method such as a casting method or a coating method, or a method of forming an adhesive layer on the separator according to the above and transferring it onto the optical element. can give. The pressure-sensitive adhesive layer can also be provided as an overlapping layer of different compositions or types in each layer. 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 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  In the present invention, each layer such as a polarizer, a transparent protective film, an optical layer, or an adhesive layer that forms the optical element described above may be, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, or a cyanoacrylate. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.

  The optical element provided with the hard coat 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. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical element, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except for the point which uses an element, and it can be based on the past. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which the optical element is arranged 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 optical element according to the present invention can be installed on one side or both sides of the liquid crystal cell. When optical elements 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. 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. In each example, parts and percentages are by weight.

Example 1
5 parts of tetraalkoxysilane (polysiloxane thermosetting component) and 95 parts of ATO ultrafine particles having a particle diameter of 1 to 20 nm were dissolved in a solvent to prepare a coating solution having a solid concentration of 1.5%. A solvent containing 20% cyclohexanone, 5% methyl ethyl ketone, 10% methanol, 45% ethanol, and 20% propylene glycol monomethyl ether was used.

  The above coating solution is applied to a triacetyl cellulose film having a thickness of 80 μm by a gravure coating method, and heat cured for 3 minutes in an environment of 130 ° C. to form a conductive layer of 0.08 μm. A film was created.

Example 2
A hard coat layer was formed on the conductive layer of the conductive cellulose film obtained in Example 1. For the formation of the hard coat layer, 30 parts of an acrylic urethane type ultraviolet curable resin, 70 parts of ZrO ₂ fine particles having an average particle diameter of 1 to 20 nm, and 5 parts of an ultraviolet polymerization initiator (benzophenone series) are added to 30 parts of methyl ethyl ketone and 70 parts of xylene. A coating solution (solid content concentration 40%) dissolved in a solvent consisting of The coating solution is coated with a die coater, heated and dried at 120 ° C. for 3 minutes, then irradiated with 150 mJ / cm ² of ultraviolet light using a high-pressure mercury lamp, cured, and hard coated with a thickness of 2.2 μm. A layer (refractive index 1.71) was formed.

  In addition, an antireflection film was prepared by providing an antireflection layer on the hard coat layer. For the formation of the antireflection layer, a fluorine-containing polysiloxane-based thermosetting resin was used. This was coated with a gravure coater and heated and cured for 3 minutes in an environment of 120 ° C. to form a 0.1 μm antireflection layer (refractive index: 1.43).

Comparative Example 1
In Example 1, the same procedure as in Example 1 was used except that a solvent containing 20% cyclohexanone, 5% methyl ethyl ketone, 10% methanol, 45% ethanol, and 20% isobutanol was used as the solvent for the coating solution. A layer was formed to produce a conductive cellulose film.

Comparative Example 2
In Example 1, a conductive layer was formed in the same manner as in Example 1 except that a solvent containing 10% methanol, 30% ethanol, and 60% propylene glycol monomethyl ether was used as a solvent for the coating solution. Cellulosic film was prepared.

Comparative Example 3
An antireflection film was produced in the same manner as in Example 2, except that the conductive cellulose film obtained in Comparative Example 1 was used instead of the conductive cellulose film obtained in Example 1.

  The following evaluation was performed about the electroconductive cellulose film or antireflection film obtained by the Example and the comparative example. The results are shown in Table 1.

(Haze value)
According to JIS K7105, the haze value of the conductive cellulose film was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.).

(Adhesion)
After putting 100 cross hatches of 1 mm × 1 mm on the surface of the conductive layer, whether or not to peel from the surface of the conductive layer when peeled twice with a cellophane tape was evaluated according to the following criteria.
○: When the number of peeled is 10 or less.
X: When the number of peeled pieces exceeds 10.

(appearance)
The surface of the antireflection layer was visually observed and evaluated according to the following criteria.
○: No cloudiness is seen.
X: Cloudiness and fogging due to whitening of the conductive layer are observed and uneven.

表１から明らかなように、実施例では密着性に優れており、かつ外観不良のない導電性セルロース系フィルム及び反射防止フィルムが得られていることが認められる。

As is clear from Table 1, it is recognized that in the Examples, conductive cellulose films and antireflection films having excellent adhesion and no poor appearance are obtained.

Claims (10)

In the method for producing a conductive cellulose film in which a coating liquid containing a binder, ultrafine particles and a solvent is coated on a cellulose film to form a conductive layer.
The coating liquid contains at least one glycol monoalkyl ether solvent selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether with respect to the total solvent. And 20 to 40% by weight of a ketone solvent, and 20 to 50% by weight of a ketone solvent based on the total solvent. Furthermore, the said coating liquid contains 10-60 weight% of 1 or more types of alcohol solvent with respect to all the solvents, The manufacturing method of the electroconductive cellulose film of Claim 1 characterized by the above-mentioned. In the method for producing a conductive cellulose film in which a coating liquid containing a binder, ultrafine particles and a solvent is coated on a cellulose film to form a conductive layer.
The said coating liquid contains 2-40 weight% of 2 or more types of organic solvent azeotropically mutually, The manufacturing method of the conductive cellulose film characterized by the above-mentioned. The method for producing a conductive cellulose film according to claim 1, wherein the ultrafine particles are metal oxide ultrafine particles. The electroconductive cellulose film obtained by the manufacturing method in any one of Claims 1-4. A conductive cellulose film, wherein a hard coat layer is formed on the conductive layer of the conductive cellulose film according to claim 5. 7. The conductive cellulose film according to claim 6, wherein the surface of the hard coat layer has an uneven shape. An antireflection film, wherein an antireflection layer is formed directly or via another layer on the conductive layer of the conductive cellulose film according to any one of claims 5 to 7. The optical element by which the electroconductive cellulose film in any one of Claims 5-7, or the antireflection film of Claim 8 is provided in the single side | surface or both surfaces of an optical element. An image display device equipped with the conductive cellulose film according to claim 5, the antireflection film according to claim 8, or the optical element according to claim 9.