JP2005054171A - Process for producing polyvinyl alcohol-based film stained with iodine, process for producing polarizer, polarizer, polarizing plate, optical film, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a polyvinyl alcohol-based film stained with iodine, by which the amount of iodine contained in the film can be conveniently controlled without using a step of immersing the polyvinyl alcohol-based film in an iodine aqueous solution. <P>SOLUTION: The process for producing a polyvinyl alcohol-based film stained with iodine comprises a step (1) of preparing a polyvinyl alcohol-based film containing iodide ions and a step (2) of irradiating the polyvinyl alcohol-based film containing the iodide ions with ultraviolet light or visible light, thereby oxidizing the iodide ions to generate iodine. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an iodine-stained polyvinyl alcohol film. The present invention also relates to a method for producing a polarizer and a polarizer obtained by the production method. The present invention also relates to a polarizing plate, an optical film using the polarizer, and an image display device such as a liquid crystal display device, an organic EL display device, and a PDP using the polarizing plate.

  As a polarizer used in an image display device, particularly a liquid crystal display device, since it has high transmittance and polarization degree, a polyvinyl alcohol film dyed with a dichroic dye such as iodine and further stretched is used. It is used. Moreover, the said polarizer is normally used as a polarizing plate by which the protective film was bonded on the single side | surface or both surfaces. These polarizing plates are also used as optical films in which various optical layers are appropriately laminated. Further, along with demands for improving functions and luminance of image display apparatuses, demands for improving quality and durability of polarizers used therein are increasing.

  As a method for iodine staining of a polyvinyl alcohol film, a method of immersing the polyvinyl alcohol film in an iodine aqueous solution bath is common. However, since iodine is highly sublimable, if the iodine aqueous solution is used as it is, the amount of iodine to be dyed decreases, and absorption in the visible light region, which is indispensable for a polarizer, does not fully develop. As a result, the transmittance of the polarizer is reduced. In order to avoid such a problem, it was necessary to manage the process to keep the iodine concentration of the aqueous iodine solution constant. Further, sublimation of iodine in a large amount from an aqueous iodine bath itself is not preferable in terms of work hygiene. As described above, the conventional manufacturing method is a method that requires meticulous process control.

For the above problem, the iodide ion (I ⁻ ) is contained in the polyvinyl alcohol film, and then immersed in a water bath containing an oxidizing agent (for example, hydrogen peroxide, potassium permanganate). There has been proposed a method of dyeing by oxidizing a part of iodide ions in a film into iodine (I ₂ ) (see Patent Document 1). Further, by immersing the film in an aqueous solution containing a polyvalent metal (for example, a water-soluble salt such as cupric oxide sulfate or iron citrate), the iodide ions in the film are similarly converted into iodine (I ₂ ). A method of dyeing by oxidation has been proposed (see Patent Document 2).

However, in the methods of Patent Document 1 and Patent Document 2, as the oxidation reaction of iodide ions proceeds, the concentration of the oxidizing agent and the polyvalent metal also changes. It was necessary to control the concentration of the immersion bath containing an oxidizing agent and a polyvalent metal.
JP-A-7-104126 JP-A-2-73309

  The present invention is a method for producing an iodine-stained polyvinyl alcohol film, and the amount of iodine contained in the film can be easily controlled without using a step of immersing the polyvinyl alcohol film in an aqueous iodine solution. It aims at providing the manufacturing method which can be performed.

  The present invention also relates to a method for producing a polarizer using the method for producing the iodine-stained polyvinyl alcohol film.

  Furthermore, an object of the present invention is to provide a polarizer obtained by the production method, a polarizing plate using the polarizer, an optical film, and an image display device using the polarizing plate.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following method for producing an iodine-stained polyvinyl alcohol film, and a method for producing a polarizer. The invention has been completed. That is, the present invention is as follows.

1. A preparation step (1) of a polyvinyl alcohol film containing iodide ion, and
Irradiation with ultraviolet light or visible light to the polyvinyl alcohol film containing the iodide ion to oxidize the iodide ion to produce iodine (2), A method for producing a polyvinyl alcohol film.

  2. 2. The iodine dyeing process according to 1 above, wherein the step (1) of preparing the polyvinyl alcohol film containing iodide ions is performed by immersing the polyvinyl alcohol film in an aqueous solution containing an alkali metal iodide. A method for producing a polyvinyl alcohol film.

  3. 3. The method for producing an iodine-stained polyvinyl alcohol film according to 1 or 2 above, wherein the polyvinyl alcohol film containing iodide ions contains a photooxidation catalyst.

4). Preparation step (1) of a polyvinyl alcohol film containing iodide ion,
Irradiating the polyvinyl alcohol film containing the iodide ion with ultraviolet light or visible light to oxidize the iodide ion to produce iodine (2), and
The manufacturing method of the polarizer characterized by including the extending process (3) of the said polyvinyl alcohol-type film at least.

  5). 5. The polarizer according to 4 above, wherein the preparation step (1) of the polyvinyl alcohol film containing iodide ions is performed by immersing the polyvinyl alcohol film in an aqueous solution containing an alkali metal iodide. Production method.

  6). 6. The method for producing a polarizer according to 4 or 5, wherein the polyvinyl alcohol film containing iodide ion contains a photooxidation catalyst.

  7). The polarizer obtained by the manufacturing method of the polarizer in any one of said 4-6.

  8). 8. A polarizing plate comprising a transparent protective film on at least one side of the polarizer according to 7.

  9. An optical film, wherein another optical layer is laminated on the polarizer described in 7 or the polarizing plate described in 8 above.

  10. 8. An image display device using at least one of the polarizer described in 7 above, the polarizing plate described in 8 above, or the optical film described in 9 above.

  In the method for producing an iodine-stained polyvinyl alcohol film of the present invention, a method of oxidizing iodide ion after the iodide ion is contained in the polyvinyl alcohol film is employed. There is no problem with the process of immersing the alcohol film. Further, the oxidation of iodide ions is performed by irradiation with ultraviolet light or visible light, and the amount of iodine formed in the film can be easily controlled by the amount of light irradiation. In this way, the optical properties of the polarizer can be stably controlled by dyeing the polyvinyl alcohol film with iodine. In addition, process management can be simplified.

  Polyvinyl alcohol or its derivative is used for the material of the polyvinyl alcohol film applied to the production method of the present invention. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. can give. Polyvinyl alcohol having a polymerization degree of about 1000 to 10000 and a saponification degree of about 80 to 100 mol% is generally used.

  The polyvinyl alcohol film may contain an additive such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film. Usually, a film having a thickness of about 30 to 150 μm is used.

  The method for producing iodine-stained polyvinyl alcohol film of the present invention will be described. First, the preparation process (1) of the polyvinyl alcohol film containing iodide ions in the production method will be described.

  As the said preparation process (1), the method (a) which immerses the formed polyvinyl alcohol-type resin film in the aqueous solution containing the iodide of an alkali metal is mention | raise | lifted, for example. Further, there is a method (b) of forming a solution containing an alkali metal iodide in an aqueous solution of a polyvinyl alcohol resin. In this way, iodide ions are contained in the film by alkali metal iodide. Among these methods, the method (a) is preferably employed because the conventional method for producing a polarizer can be used as it is. Examples of the method for forming a polyvinyl alcohol film include a casting method and an extrusion method.

  Examples of the alkali metal iodide include lithium iodide, sodium iodide, potassium iodide and the like. Of these, potassium iodide is preferred.

  In the obtained polyvinyl alcohol film containing iodide ions, the content of iodide ions is appropriately determined according to the target optical properties and the degree of the oxidation step (2), and is not particularly limited. However, it is preferable to contain about 0.05 to 30 parts by weight, and further 0.1 to 20 parts by weight with respect to 100 parts by weight of the raw material polyvinyl alcohol resin.

  In the case of preparing a polyvinyl alcohol film containing iodide ions from an aqueous solution containing a polyvinyl alcohol resin and an alkali metal iodide by the method (b), iodide ions for the polyvinyl alcohol resin are prepared. The ratio of the alkali metal iodide to be blended can be adjusted as appropriate so that the ratio of is within the above range. On the other hand, when the polyvinyl alcohol film formed by the method (a) is immersed in an aqueous solution containing an alkali metal iodide to prepare a polyvinyl alcohol film containing iodide ions, polyvinyl alcohol System film in an aqueous solution having an iodide concentration of about 3 to 30% by weight, more preferably 5 to 25% by weight, usually at a temperature of about 0 to 60 ° C., preferably 10 to 50 ° C., usually about 10 to 1000 seconds. Preferably, it is performed by dipping for 20 to 500 seconds.

The polyvinyl alcohol film containing iodide ions can contain a photo-oxidation catalyst together with iodide ions. Examples of the photooxidation catalyst include TiO ₂ , ZnO, CdS, GaP, SiC, and the like. The fine particles of the photo-oxidation catalyst are preferably smaller because they scatter visible light when the particle size is large. Usually, the particle size is 500 nm or less, preferably 100 nm or less. Usually, it is 5 nm or more.

  These photo-oxidation catalysts produce an oxidizing action when irradiated with light such as visible light and ultraviolet light. By containing these photooxidation catalysts in the film, the oxidation reaction of iodide ions to iodine can be promoted when irradiation with visible light or ultraviolet light is performed in the oxidation step (2). By containing a photo-oxidation catalyst, the reaction of the oxidation step (2) can proceed relatively rapidly even under visible light depending on conditions.

  The content of the photooxidation catalyst is usually 30 parts by weight or less, preferably 0.05 to 20 parts by weight, and more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. Examples of the method of incorporating the photooxidation catalyst in the polyvinyl alcohol film include a method in which fine particles of the photooxidation catalyst are dispersed in advance in an aqueous solution containing a polyvinyl alcohol resin and a film is formed.

  Next, the polyvinyl alcohol film containing the iodide ion is irradiated with ultraviolet light or visible light to oxidize the iodide ion to generate iodine (2). In the oxidation step (2), iodide ions in the film are oxidized to produce iodine. For the oxidation method, either ultraviolet light or visible light can be used, but ultraviolet light is preferred because it is easily oxidized.

  The wavelength of the irradiated ultraviolet rays may be either far ultraviolet rays of 200 nm or less and near ultraviolet rays exceeding 200 nm. When far ultraviolet rays of 200 nm or less are used, it is known that oxygen in the air is oxidized and ozone is generated. By this ozone, iodide ions are easily oxidized to iodine. More convenient than that. As an ultraviolet ray generator used for irradiation, a known irradiation device such as a metal halide lamp or a xenon lamp can be used in addition to a low-pressure mercury lamp, a high-pressure mercury lamp, or an ultrahigh-pressure mercury lamp.

The degree of oxidation, the amount or the like of iodine to be generated from an iodide ion, is adjusted appropriately, typically, illuminance 10 to 10000 mJ / cm ² or so, more preferably between 50 to 5000 mJ / cm ^2. The generation of iodine by oxidation of iodide ions may be part or all of iodide ions. It is desirable that the iodide ion is partially oxidized. Iodine species in polarizers (including iodine complexes that absorb visible light) exist in the form of polyiodine ions such as I ₃ ⁻ and I ₅ ^{−, and} such ions are basically I ₂ and I. ^This is because it is generated from-.

  In the oxidation step (2) of iodide ions by ultraviolet rays and visible rays, the presence of a large amount of water is preferable because the progress of oxidation is good. Therefore, it is preferable that the oxidation step (2) subsequent to the film preparation step (1) is performed in a wet state. In addition, it is preferable to use what formed the polyvinyl alcohol-type film containing an iodide ion into the water content about 0.1 to 50 weight%, Furthermore, about 0.5 to 30 weight%.

  The method for producing a polarizer of the present invention includes at least a stretching step (3) of the polyvinyl alcohol film in addition to the film preparation step (1) and the oxidation step (2).

  The stretching step (3) may be performed at any stage before or after the oxidation step (2), or may be performed together with the oxidation step (2). Usually, it is preferable to perform the stretching step (3) after the oxidation step (2) from the viewpoint that the iodine complex is well oriented and as a result high polarization performance is obtained. In this case, an iodine complex (which has visible dichroism) is formed in the film by stretching the polyvinyl alcohol film in which iodine is generated, and a polarizer is obtained.

  The draw ratio is appropriately determined according to the required performance of the polarizer, but the film is usually stretched in the MD direction (film running direction) about 1 to 20 times, and further about 2 to 10 times. To do so. Stretching can also be performed in multiple stages. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The thickness of the stretched film is preferably about 5 to 40 μm.

  As the stretching means, either wet stretching or dry stretching can be adopted, but dry stretching must be performed at a higher temperature than wet stretching, and in this case, there is a high possibility that iodine sublimation will occur significantly. Is desirable.

  Examples of the dry stretching method include a method described in Japanese Patent Nos. 1524033 and 2731813, a method of stretching while applying a tensile force between rolls installed in or outside a drying oven, a heated roll Any method such as a method of stretching using a tenter stretching machine or the like can be employed. In the stretching means, the unstretched film is usually heated. On the other hand, in the wet stretching method, a stretching drive roll is submerged in a stretching bath, and a tenter stretching method, an inter-roll stretching method, or the like is applied thereto. The unstretched film is preferably stretched linearly between stretching drive rolls, but a guide roll or the like can be used in the middle.

  In addition, in the method for producing a polarizer of the present invention, in addition to the steps described above, the steps similar to those conventionally adopted in the method for producing a polarizer are mainly used to adjust the degree of polarization and hue of the polarizer. These steps can be added at the same stage as in the prior art.

  An example is a swelling process. The swelling step is performed by immersing the unstretched polyvinyl alcohol film in pure water or the like. The temperature of pure water etc. is about 15-45 degreeC normally, Preferably it is 25-35 degreeC. The immersion time is usually in the range of about 50 to 180 seconds, preferably 80 to 150 seconds.

  A heat treatment process is mentioned. By subjecting the polyvinyl alcohol film to heat treatment, the degree of crystallinity of the polyvinyl alcohol resin increases, so that the stress applied to the film during stretching increases and the orientation of the polyvinyl alcohol resin increases. As a result, the polarization performance is improved. Usually, it is about 80 to 180 ° C., preferably 100 to 160 ° C., usually about 50 to 2000 seconds, preferably 100 to 1000 seconds.

  Examples include a crosslinking step in which the polyvinyl alcohol film is immersed in a crosslinking bath containing a boron compound such as boric acid or borax. By the crosslinking step, three-dimensional networking of the polyvinyl alcohol-based resin proceeds and a high stress is applied during stretching, so that the polyvinyl alcohol is well oriented. The boron compound is usually used in the form of an aqueous solution or a water-organic solvent mixed solution. The boric acid concentration of the boric acid aqueous solution or the like is about 2 to 20% by weight, preferably 3 to 15% by weight. An aqueous boric acid solution or the like can contain potassium iodide. The potassium iodide concentration is preferably about 0.01 to 10% by weight, more preferably 0.02 to 8% by weight. A boric acid aqueous solution or the like containing potassium iodide can obtain a lightly colored polarizer, that is, a so-called neutral gray polarizer having a substantially constant absorbance over almost the entire wavelength range of visible light. The treatment temperature of the boric acid aqueous solution or the like is usually 30 ° C. or higher, preferably 50 to 85 ° C. The treatment time is usually about 10 to 800 seconds, preferably about 30 to 500 seconds. In addition, the crosslinking step can be performed by a coating method, a spraying method, or the like. In addition, when employ | adopting a wet extending | stretching method, bridge | crosslinking process can be performed with extending | stretching bath to boric-acid aqueous solution etc. with extending | stretching.

  Moreover, the process of immersing a polyvinyl alcohol-type film in the aqueous solution containing various additives for hue adjustment is mention | raise | lifted. For example, examples of the additive include iodides of alkali metals such as potassium iodide. Thereby, an iodine ion impregnation process is performed. The potassium iodide concentration is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. In the iodine ion impregnation treatment, the temperature of the aqueous solution is usually about 15 to 60 ° C, preferably 25 to 40 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. Examples of the additive include inorganic metal salts.

  Moreover, the water washing process by a pure water etc. can also be performed. The film treated as described above is preferably dried at an appropriate temperature. Drying is performed according to a conventional method.

  The obtained polarizer can be made into the polarizing plate which provided the transparent protective film in the at least single side | surface according to the conventional method. The transparent protective film can be provided as a coating layer made of a polymer or a laminate layer of the film. As the transparent polymer or film material for forming the transparent protective film, an appropriate transparent material can be used, but a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile, Examples thereof include styrene polymers such as styrene copolymers (AS resins), polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

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

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction 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 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.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. On the other hand, a protective film such as triacetylcellulose has a large retardation value Rth in the thickness direction and has a problem of coloring, but contains an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the resin composition to be used, those having a thickness direction retardation value Rth of 30 nm or less can be used, and coloring can be almost eliminated. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  The 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. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  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 particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 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 a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The 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.

  An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. As the adhesive, an adhesive made of an aqueous solution is usually used.

  The polarizing plate of the present invention is produced by bonding the transparent protective film and the polarizer using the adhesive. The adhesive may be applied to either the transparent protective film or the polarizer, or to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. The polarizer and the transparent protective film can be bonded together using a roll laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 μm.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. 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 or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the 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 through a transparent protective film 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 film.

  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. As shown (made by 3M, D-BEF, etc.), the orientation film of the cholesteric liquid crystal polymer and the oriented liquid crystal layer supported on the film substrate (made by Nitto Denko, PCF350, Merck, Transmax, etc.), Any suitable one can be used, such as one that reflects either left-handed or right-handed circularly polarized light and transmits other light.

  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 monochromatic light with 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.

  An example of the anisotropic reflective polarizer used as the brightness enhancement film is a reflective grid polarizer. As a reflective grid polarizer, a metal grid reflective polarizer (see US Pat. No. 6,288,840, etc.) in which metal is finely processed to produce reflected polarized light in the visible light region, metal fine particles are placed in a polymer matrix. And the like (see JP-A-8-184701, etc.). An example of the brightness enhancement film is an anisotropic scattering polarizer. An example of the anisotropic scattering polarizer is DRP manufactured by 3M (see US Pat. No. 5,825,543). Examples of the brightness enhancement film include a polarizing element that can perform polarization conversion in one pass. For example, one using a smectic C * can be cited (see JP 2001-201635 A). An anisotropic diffraction grating can be used as the brightness enhancement film.

  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 the liquid crystal display device and the like can be improved. 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 may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. 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.

  Attaching the adhesive layer to one or both sides of the polarizing plate or the 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. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. 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, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, and 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 polarizing plate or the 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. That is, 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, 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 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 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.

  The present invention will be specifically described below with reference to examples and comparative examples.

Example 1
(Preparation process (1))
Using polyvinyl alcohol (manufactured by Kuraray Co., Ltd., saponification degree 98.5%, average polymerization degree 2400), a film having a thickness of 75 μm was produced by a casting method. This film was immersed in an aqueous solution having a potassium iodide concentration of 15% by weight at 30 ° C. for 2 minutes to contain potassium iodide in the polyvinyl alcohol film. Thereby, the iodide ion contained 5 weight% in the film.

(Oxidation step (2))
When the film was wet, it was irradiated with ultraviolet rays (irradiation amount: 1000 mJ / cm ² ) for 180 seconds with a low-pressure mercury lamp (device name: ozone generator, manufactured by I-Graphics). Discolored.

(Evaluation)
The resulting film was measured for absorbance by a spectrophotometer (Hitachi Instrument machine Service Co. Ltd. U4100), I ₃ ^- peak ion had appeared. This is caused by I ₂ and I ⁻ generated by oxidation of iodide ions. That is, it can be seen from this result that the oxidation progressed. Oxidation was 15% by weight of the included iodide ion.

(Polarizer manufacturing method)
Next, the obtained film was uniaxially stretched 5 times in the same bath while being immersed in an aqueous solution bath having a boric acid concentration of 4% by weight at 50 ° C. Next, the film was immersed in an aqueous solution bath of 30 ° C. and 5% by weight potassium iodide for 10 seconds, wiped off moisture, and then dried at 50 ° C. for 4 minutes to obtain a polarizer having a thickness of 30 μm.

Example 2
(Preparation process (1))
Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., saponification degree 98.5%, average polymerization degree 2400), water-soluble TiO ₂ (average particle diameter 20 nm), glycerin in order of weight ratio at 100: 1: 15, And the aqueous solution adjusted so that content of polyvinyl alcohol might be 15 weight% was prepared. This aqueous solution was formed into a film with a thickness of 75 μm by a casting method. Subsequently, annealing was performed at 130 ° C. for 5 minutes. This film was immersed in an aqueous solution having a potassium iodide concentration of 15% by weight at 30 ° C. for 2 minutes to contain potassium iodide in the polyvinyl alcohol film. Thereby, the iodide ion contained 3 weight% in the film.

(Oxidation step (2))
When the film was wet and irradiated with ultraviolet rays of about 500 mJ / cm ² using a xenon lamp, the film turned from transparent to brown. This discoloration is considered to be a result indicating that the oxidation progressed as in Example 1.

(Polarizer manufacturing method)
Next, the obtained film was uniaxially stretched 5 times in the same bath while being immersed in an aqueous solution bath having a boric acid concentration of 4% by weight at 50 ° C. Next, the film was immersed in an aqueous solution bath of 30 ° C. and 5% by weight potassium iodide for 10 seconds, wiped off moisture, and then dried at 50 ° C. for 4 minutes to obtain a polarizer having a thickness of 30 μm.

Comparative Example 1
In Example 1, the same operation as in Example 1 was performed except that the oxidation step (2) was performed by immersing the film in an aqueous solution of 10% by weight hydrogen peroxide at 25 ° C. for 60 seconds. A polarizer was obtained.

  In both Examples and Comparative Examples, the same operation was performed 10 times in total, and the following optical characteristics were compared for the polarizers obtained in the first and tenth times.

The optical characteristics of the polarizer are obtained by using a spectrophotometer equipped with a Glan-Thompson polarizing prism (U4100 manufactured by Hitachi, Ltd.), and converting the completely polarized light obtained by the Glan-Thompson polarizing prism into the direction of the transmission axis of the polarizer as a sample. transmittance when made incident (vertical direction in stretching axis) and k _1, transmittance when made incident to the absorption axis (stretching axis direction) were each measured for k _2. Table 1 shows measured values of k ₁ and k ₂ at a wavelength of 550 nm.

表１に示すように、比較例１は、１回目で得られた偏光子に比べて１０回目で得られた偏光子は、その透過率が大きく上昇していることが分かる。これは、回数を重ねるごとに浴中の過酸化水素が反応によって消費されるために、浴中の過酸化水素濃度が減少し、その結果、酸化の進行の程度が減少して、ヨウ素の生成量が減少したためである。これに対し、実施例１、２では１０回目で得られた偏光子も、１回目で得られた偏光子とほぼ同じ透過率であった。これは、低圧ＵＶの照射室を一定に保つことで、酸化の進行程度（つまりヨウ素の生成量）をほぼ一定に保つことができ、結果として目的の光学特性を安定して再現できることを示すものである。

As shown in Table 1, it can be seen that in Comparative Example 1, the transmittance of the polarizer obtained at the 10th time is greatly increased as compared with the polarizer obtained at the 1st time. This is because hydrogen peroxide in the bath is consumed by the reaction each time it is repeated, so the concentration of hydrogen peroxide in the bath decreases, resulting in a decrease in the degree of progress of oxidation and the production of iodine. This is because the amount decreased. On the other hand, in Examples 1 and 2, the polarizer obtained at the 10th time also had substantially the same transmittance as the polarizer obtained at the first time. This indicates that by maintaining the low-pressure UV irradiation chamber constant, the degree of progress of oxidation (that is, the amount of iodine produced) can be kept substantially constant, and as a result, the desired optical characteristics can be stably reproduced. It is.

Claims (10)

A preparation step (1) of a polyvinyl alcohol film containing iodide ion, and
Irradiation with ultraviolet light or visible light to the polyvinyl alcohol film containing the iodide ion to oxidize the iodide ion to produce iodine (2), A method for producing a polyvinyl alcohol film.   The iodine staining according to claim 1, wherein the step (1) of preparing a polyvinyl alcohol film containing iodide ions is performed by immersing the polyvinyl alcohol film in an aqueous solution containing an alkali metal iodide. Method for producing a polyvinyl alcohol film.   The method for producing an iodine-stained polyvinyl alcohol film according to claim 1 or 2, wherein the polyvinyl alcohol film containing iodide ions contains a photooxidation catalyst. Preparation step (1) of a polyvinyl alcohol film containing iodide ion,
Irradiating the polyvinyl alcohol film containing the iodide ion with ultraviolet light or visible light to oxidize the iodide ion to produce iodine (2), and
The manufacturing method of the polarizer characterized by including the extending process (3) of the said polyvinyl alcohol-type film at least.   The polarizer according to claim 4, wherein the preparation step (1) of the polyvinyl alcohol film containing iodide ions is performed by immersing the polyvinyl alcohol film in an aqueous solution containing an alkali metal iodide. Manufacturing method.   The method for producing a polarizer according to claim 4 or 5, wherein the polyvinyl alcohol film containing iodide ions contains a photooxidation catalyst.   The polarizer obtained by the manufacturing method of the polarizer in any one of Claims 4-6.   A polarizing plate comprising a transparent protective film on at least one surface of the polarizer according to claim 7.   An optical film, wherein another optical layer is laminated on the polarizer according to claim 7 or the polarizing plate according to claim 8.   An image display device using at least one of the polarizer according to claim 7, the polarizing plate according to claim 8, or the optical film according to claim 9.