JP2005283758A - Method for manufacturing polarizer, polarizer, polarizing plate, optical film, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizer by subjecting a polyvinyl alcohol film to pre-swelling processing, iodine dyeing processing, stretching processing, etc., the manufacturing method for the polarizer suppressing variation in transmissivity of the obtained polarizer even when stretching is carried out in preliminary swelling processing. <P>SOLUTION: The manufacturing method for the polarizer includes steps of: (1) stretching the polyvinyl alcohol film in an electrolyte solution; (2) dyeing the polyvinyl alcohol film with a dichroic material, and (3) further drawing the polyvinyl alcohol film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention 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.

  A polarizer having a light transmission-shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal material. This LCD is used in a wide range of applications from small devices such as calculators and watches to word processors, personal computers, projectors, navigation systems, televisions, and indoor and outdoor measuring devices. The demand for larger size is becoming stronger with the progress of manufacturing. In addition, since the performance of the constituent elements such as the brightness of the display backlight is greatly improved, the optical homogeneity of the display is increasingly required. For this reason, unevenness on the display, which was inconspicuous with the conventional small display, has become apparent due to the increase in size, and higher quality has been demanded in terms of screen uniformity. In the future development of liquid crystal displays, a more uniform display is required, and as one of the improvement factors, the homogeneity of the basic polarizer is required.

  In general, a polarizer is produced by using a polyvinyl alcohol film as a matrix, dyeing it with iodine-potassium iodide (iodine aqueous solution) or a dichroic dye, and further subjecting it to a stretching treatment. As the stretching means, a wet stretching method or a dry heat stretching method is used. In the wet stretching method of a general polarizer production method, it is usually manufactured by performing a pre-swelling treatment, followed by a dyeing treatment, a stretching treatment, a fixing treatment, and a drying treatment, and if necessary, a heat treatment. .

However, when a pre-swelling treatment is performed in the wet stretching method, the polyvinyl alcohol film swells in the bath due to swelling and the films are folded, so that the conveyance handling becomes very difficult and “wrinkles” are generated. It has been proposed that the pre-swelling treatment is performed in a solution containing a chloride such as lithium chloride for the purpose of improving the durability (see Patent Document 1). It cannot be suppressed.
JP-A-6-281816

  In order to suppress the occurrence of “wrinkles” in the pre-swelling treatment as described above, a slight tension is applied to the handling and handling of the swollen film. However, when the stretching process is performed together with the swelling process, the generation of “wrinkles” can be suppressed, while the transmittance of the obtained polarizer varies depending on the degree of tension. For example, when the film is pulled at a draw ratio of 1.5, there is a portion where the original film cannot be stretched locally at 1.5 times. This variation in stretching affects the dyeing and causes a variation in transmittance. The difference in transmittance appears as “unevenness” on the display as it is. “Mura” is likely to be a factor that hinders the progress of LCD TVs.

  The present invention is a method for producing a polarizer by subjecting a polyvinyl alcohol film to a pre-swelling treatment, an iodine dyeing treatment, a stretching treatment, etc., and the polarizer obtained even when the pre-swelling treatment is performed. An object of the present invention is to provide a method for manufacturing a polarizer that can suppress fluctuations in the transmittance of the polarizer.

  Another 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 a polarizer, and have completed the present invention.

That is, the present invention includes a step (1) of stretching a polyvinyl alcohol film in an aqueous electrolyte solution,
Then, the manufacturing method of the polarizer characterized by including the process (2) dye | staining the said polyvinyl alcohol-type film with a dichroic material, and the process (3) of extending the said polyvinyl alcohol-type film further.

  In the method for producing a polarizer, the electrolyte preferably contains at least one selected from salts and bases composed of a monovalent or divalent cation and a monovalent or divalent anion. is there. The electrolyte preferably contains an inorganic salt composed of alkali metal or alkaline earth metal and halogen. Furthermore, it is preferable that the electrolyte contains at least one of potassium chloride, potassium bromide, and potassium iodide. The electrolyte concentration of the aqueous electrolyte solution is preferably 0.0005 to 5% by weight.

  The manufacturing method of the said polarizer is suitable when the draw ratio in a extending process (1) is 1.1-4.5 times.

  In the manufacturing method of the said polarizer, it is suitable to perform a dyeing process (2) and an extending process (3) simultaneously.

  Moreover, this invention relates to the polarizer obtained by the said manufacturing method. The present invention also relates to a polarizing plate comprising a transparent protective film on at least one surface of the polarizer. The present invention also relates to an optical film, wherein another optical layer is laminated on the polarizer or the polarizing plate. Furthermore, the present invention relates to an image display device using at least one of the polarizer, the polarizing plate or the optical film.

  As described above, the polyvinyl alcohol film is sensitive to the processing environment because the transmittance of the polarizer obtained varies depending on the draw ratio in the pre-swelling treatment step. Therefore, the present inventors considered the influence of the properties of the polyvinyl alcohol film and the stretching in the swelling treatment on the polyvinyl alcohol film. As a result, in the production method of the present invention, the polyvinyl alcohol film was stretched using an aqueous solution containing an electrolyte as a water bath used for the swelling treatment. The polarizer obtained by such a production method was able to suppress fluctuations in the transmittance of the polarizer obtained even when the draw ratio was different by containing an electrolyte in the swelling treatment bath.

  The polyvinyl alcohol-based film can be obtained by saponifying polyvinyl acetate and the like, then purifying the produced aqueous polyvinyl alcohol-based polymer solution, applying the solution by a casting method or the like, and heating and drying to form a film. The polyvinyl alcohol polymer has many hydroxyl groups in the polymer molecular chain, and the produced polyvinyl alcohol film is considered to be in a semi-crystalline polymer state by hydrogen bonding. Therefore, it is considered that the polyvinyl alcohol film used as the matrix of the polarizer is in a state where gelation by hydrogen bonding precedes from the production method. In particular, it is considered that an industrially obtained polyvinyl alcohol-based film not only has a physically inhomogeneous film thickness, but also contains a lack of homogeneity in the bulk itself.

  Thus, it is considered that the polyvinyl alcohol film made into a semi-crystalline polymer state by hydrogen bonding includes a state variation of interaction due to hydrogen bonding, and some environmental variation (for example, swelling tension is added, etc.) It was considered that the interaction between the polymer chains caused fluctuations, the structure as a matrix changed, and the transmittance of the resulting polarizer was different. In accordance with this consideration, in the present invention, the polyvinyl alcohol film is previously given a degree of freedom in the polymer chain by cleaving or weakening its hydrogen bond, and the influence of other factors in the stretching process in the swelling treatment bath is no longer affected. It is a difficult situation. That is, the polymer chain of the raw polyvinyl alcohol film is weakened in the interaction between the chains by the action of the electrolyte or has an extended polymer chain structure. As a result, the matrix polymer chain due to various factors included in the processing It is considered that the fluctuation of the transmittance could be suppressed even when the stretching process was performed together with the swelling process while suppressing the fluctuation.

  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.

  The degree of polymerization and saponification of polyvinyl alcohol affects various performances. The degree of polymerization is preferably 500 or more from the viewpoint of film strength, and more preferably 1000 or more from the viewpoint of polarization performance. Moreover, it is made into about 20000 or less from the point of resin manufacture of a polymerization degree, and raw film manufacture. The saponification degree of polyvinyl alcohol is preferably 90 mol% or more, more preferably 98 mol% or more from the viewpoint of durability.

  The production method of the polyvinyl alcohol film includes a cast film formation method from a solution, a dry film formation method, a wet film formation method, a dry / wet film formation method, a gel film formation method, and these wet film formation methods, A method based on a combination of a formula film forming method and a gel film forming method can be used. As the polyvinyl alcohol film, a film in which a device is incorporated into film-forming drying heating in order to ensure the water resistance can be used. In this step, practical water resistance can be ensured by adopting the semi-crystalline polymer state.

  The polyvinyl alcohol film may contain additives such as a plasticizer and a surfactant. 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.

  In general, the polyvinyl alcohol film is preferably thin from the viewpoint of optical use, and a film having a thickness of about 10 to 100 μm is used.

  First, the step (1) of stretching the polyvinyl alcohol film in the aqueous electrolyte solution in the production method of the present invention will be described.

  The electrolyte used for the electrolyte aqueous solution is a water-soluble compound that can be ionized and dissociated. Examples of the electrolyte include salts and bases composed of a monovalent or divalent cation and a monovalent or divalent anion. These may be any of organic salts, inorganic salts, organic bases, and inorganic bases, and one kind or two or more kinds can be used.

  The electrolyte is preferably an inorganic salt or an inorganic base. Inorganic salts such as lithium chloride, sodium chloride, potassium chloride, zinc chloride, calcium chloride, magnesium chloride; lithium bromide, sodium bromide, potassium bromide, zinc bromide, calcium bromide, magnesium bromide, etc. Bromides; iodides such as lithium iodide, sodium iodide, potassium iodide, zinc iodide, calcium iodide, magnesium iodide; ammonium chloride and the like. Examples of inorganic bases include hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide.

  Among the electrolytes, inorganic salts composed of alkali metals or alkaline earth metals and halogens are preferred. Furthermore, potassium chloride, potassium bromide and potassium iodide are preferred. In particular, potassium iodide is preferred.

  Water is used as the solvent for dissolving the electrolyte, but other solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, ethyl acetate, toluene, xylene, etc. A solvent can coexist. These other solvents can be used alone or in combination. The concentration of the electrolyte in the aqueous electrolyte solution is preferably 0.0005 to 5% by weight, more preferably 0.001 to 3% by weight, from the viewpoint of obtaining an effect as an electrolyte. If the electrolyte concentration is too high, the cohesive force of the electrolyte on the matrix polymer chain of the polyvinyl alcohol film becomes dominant, which is undesirable because swelling is hindered.

  In the stretching step (1), the polyvinyl alcohol film is immersed in the electrolyte aqueous solution. In the stretching step (1), the stretching ratio is usually preferably 1.1 to 4.5 times. In general, when a polyvinyl alcohol film is immersed in an aqueous solution, swelling of about 1.1 times is observed. Therefore, the swelling amount of about 1.1 times is stretched by simple conveyance without stretching. In the present invention, the amount of swelling generated by such conveyance is also included in the draw ratio. In order to suppress “wrinkles”, the draw ratio is preferably 1.2 times or more. On the other hand, the draw ratio is preferably 4.5 times or less from the design of the final total draw ratio. In particular, the draw ratio is preferably 1.2 to 3.5 times. The immersion time is preferably about 0.2 to 5 minutes. Moreover, the temperature of electrolyte aqueous solution is about 15-45 degreeC normally, Preferably it is 25-35 degreeC.

  Next, the step (2) of dyeing the polyvinyl alcohol film with a dichroic material and the step (3) of further stretching the polyvinyl alcohol film are performed.

  The dichroic material dyeing step (2) is generally performed by immersing the film subjected to the stretching step (1) in a dyeing solution containing the dichroic material. As the dichroic material, iodine or a dichroic dye is used. Iodine is preferred as the dichroic material.

  When iodine is used as the dichroic material, an aqueous iodine solution is generally used as the dyeing solution. As the iodine aqueous solution, an aqueous solution containing iodine ions with, for example, potassium iodide or the like as iodine and a dissolution aid is used. The iodine concentration is about 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. The potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02 to 8% by weight. It is preferable to use it. In the iodine dyeing treatment, the temperature of the iodine solution is usually about 20 to 50 ° C, preferably 25 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

  Examples of the dichroic dye include azo dyes, perylene dyes, and anthraquinone dyes. These dyes can be used as mixed dyes. These dyes are detailed in, for example, JP-A-54-76171.

  The stretching step (3) may be performed before or after the iodine staining step (2), or may be performed together with the iodine staining step (2). In view of simplicity, it is preferable to perform the stretching step (3) together with the iodine staining step (2).

  The stretching ratio in the stretching step (3) is appropriately determined according to the required performance of the polarizer, but the film is usually about 2 to 6 times in the MD direction (film running direction), The stretching process is performed at about 5 times. Stretching can also be performed in multiple stages. In addition, it is preferable to adjust the total draw ratio which combined the draw ratio of the extending process (1) and the draw ratio of the extending process (3) to about 2.4 to 8 times. The thickness of the stretched film is preferably about 5 to 40 μm.

  In the wet stretching method, the 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, in order to mainly adjust the polarization degree and hue of the polarizer, the same steps as those conventionally employed in the method for producing a polarizer are used. These steps can be added at the same stage as in the prior art.

  An example is a heat treatment step. 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 50-150 degreeC, Preferably it is 100-150 degreeC, Usually, it is about 50-2000 second, Preferably it is performed in 100-1000 second.

  Examples include a crosslinking step in which a polyvinyl alcohol film is immersed in a crosslinking bath containing a boron compound such as boric acid or borax. It is said that polyvinyl alcohol is well oriented because a three-dimensional network of the polyvinyl alcohol-based resin proceeds and a high stress is applied during stretching by the crosslinking step. 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 in the range of 30 to 70 ° 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 or the dye-like polarizer-like film in the aqueous solution containing various additives for hue adjustment etc. 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 aforementioned polymer Examples of the polymer for forming the transparent protective film are also blends of the above. 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 an unsubstituted phenyl and a thermoplastic resin having 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. Bonding of a polarizer and a transparent protective film can be performed with 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 (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. 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 emits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer. However, 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 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, a cholesteric liquid crystal layer having a structure in which two layers or three or more layers are superposed with a combination of those having different reflection wavelengths can obtain a layer that reflects circularly polarized light in a wide wavelength range such as a visible light region. 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.) that finely processes metal to produce reflected polarized light even in the visible light region, and metal fine particles in a polymer matrix. And a stretched one (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 made 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, the one using 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 which can 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 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, transparent protective film, optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylates. 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.

Comparative Example 1
(Test 11): A polyvinyl alcohol film having a thickness of 75 μm obtained from polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 98.5% was immersed in water at 30 ° C. for 3 minutes (substantially 1. in the length direction). Swollen twice). Next, the film was uniaxially stretched 5.4 times while dyeing in an aqueous iodine solution at 30 ° C. containing about 0.03% by weight of iodine-0.17% by weight of potassium iodide. Then, after washing with water and draining, the film was dried at 60 ° C. for 10 minutes in the stretched state to obtain a polarizer. This was designated as a polarizer (11).

  (Test 12): In Test 11, instead of swelling the polyvinyl alcohol film in 30 ° C. water, it was uniaxially stretched 1.5 times while being immersed in 30 ° C. water for 3 minutes, and in an aqueous iodine solution A polarizer was obtained in the same manner as in Test 11 except that the stretching ratio was adjusted so that the total stretching ratio was 5.4. This was designated as a polarizer (12).

  (Test 13): In Test 11, instead of swelling the polyvinyl alcohol film in water at 30 ° C., it was uniaxially stretched twice while being immersed in water at 30 ° C. for 3 minutes, and stretching in an aqueous iodine solution A polarizer was obtained in the same manner as in Test 11 except that the magnification was adjusted to 5.4 times as the total draw ratio. This was designated as a polarizer (13).

  (Test 14): In Test 11, instead of swelling the polyvinyl alcohol film in 30 ° C. water, it was uniaxially stretched 2.5 times while being immersed in 30 ° C. water for 3 minutes, and in an aqueous iodine solution. A polarizer was obtained in the same manner as in Test 11 except that the stretching ratio was adjusted so that the total stretching ratio was 5.4. This was designated as a polarizer (14).

  (Test 15): In Test 11, instead of swelling the polyvinyl alcohol film in water at 30 ° C., it was uniaxially stretched three times while being immersed in water at 30 ° C. for 3 minutes, and stretching in an aqueous iodine solution A polarizer was obtained in the same manner as in Test 11 except that the magnification was adjusted to 5.4 times as the total draw ratio. This was designated as a polarizer (15).

  The optical characteristics (transmittance) of the polarizers (11) to (15) obtained in Comparative Example 1 were measured using a spectrophotometer (U4100 manufactured by Hitachi, Ltd.). The results are shown in FIG. It can be seen from FIG. 1 that the obtained polarizers (11) to (15) have different transmittances, and the transmittance of the obtained polarizer varies depending on the degree of stretching magnification in water. Such variation due to stretching results in stretching non-uniformity in the conveyance of the film in the swollen stretched state, and it is not possible to ensure homogeneity in the subsequent dyeing process, and the transmittance varies, particularly with a large screen. Appears as uneven dyeing.

Comparative Example 2
(Test 21): A 75-μm-thick polyvinyl alcohol film obtained from polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 98.5% in a lot different from test 11 of Comparative Example 1 was used. In the same manner as in Test 11 of Comparative Example 1, the polyvinyl alcohol film was immersed in water at 30 ° C. for 3 minutes (substantially swollen 1.2 times in the length direction), and then about 0.03% by weight The uniaxial stretching was performed 5.4 times while dyeing in an iodine aqueous solution at 30 ° C. containing 0.17 wt% potassium iodide. Then, after washing with water and draining, the film was dried at 60 ° C. for 10 minutes in the stretched state to obtain a polarizer. This was designated as a polarizer (21).

  (Test 22): In Test 21, instead of swelling the polyvinyl alcohol film in water at 30 ° C., it was uniaxially stretched twice while being immersed in water at 30 ° C. for 3 minutes, and stretching in an aqueous iodine solution A polarizer was obtained in the same manner as in Test 21 except that the magnification was adjusted to 5.4 times as the total draw ratio. This was designated as a polarizer (22).

  The optical characteristics (transmittance) of the polarizers (21) and (22) obtained in Comparative Example 2 were measured using a spectrophotometer (U4100 manufactured by Hitachi, Ltd.). The results are shown in FIG. From FIG. 2, it is recognized that the obtained polarizers (21) and (22) have different transmittances, and the transmittance of the obtained polarizer varies depending on the degree of stretching magnification in water.

Example 1
(Test 31): A polyvinyl alcohol film having a thickness of 75 μm obtained from polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 98.5%, which is the same as that of Test 21 of Comparative Example 2, was used. Comparative Example 2 in Comparative Example 2 except that the polyvinyl alcohol film was immersed in an aqueous solution of 0.1% by weight potassium iodide at 30 ° C. for 3 minutes instead of being swollen in water at 30 ° C. In the same manner as in Example 1, a polarizer was obtained. This was designated as a polarizer (31).

  (Test 32): In Test 31, instead of swelling the polyvinyl alcohol film with a 30 ° C. aqueous potassium iodide solution, it was uniaxially stretched twice while being immersed in a 30 ° C. aqueous potassium iodide solution for 3 minutes, A polarizer was obtained in the same manner as in Test 31 except that the draw ratio in the aqueous iodine solution was adjusted to 5.4 times the total draw ratio. This was designated as a polarizer (32).

  (Test 33): In Test 31, instead of swelling the polyvinyl alcohol film with a 30 ° C. aqueous potassium iodide solution, the film was uniaxially stretched 3 times while immersed in a 30 ° C. aqueous potassium iodide solution for 3 minutes. A polarizer was obtained in the same manner as in Test 31 except that the draw ratio in the aqueous iodine solution was adjusted to 5.4 times the total draw ratio. This was designated as a polarizer (33).

  The optical properties (transmittance) of the polarizers (31) to (33) obtained in Example 1 were measured using a spectrophotometer (U4100 manufactured by Hitachi, Ltd.). The results are shown in FIG. From FIG. 3, when extending | stretching with potassium iodide aqueous solution, a difference is hardly recognized in the transmittance | permeability.

  In addition, the density observation evaluation was visually performed using a wide polarizer according to the following criteria. When the five-level evaluation of Level 5: Very bad, Level 4: Bad, Level 3: Equivalent to conventional level, Level 2: Almost invisible, Level 1: Invisible, Polarizer (11) to Comparative Example 1 (15) The polarizers (21) and (22) of Comparative Example 2 are at level 3, but the polarizers (31) to (33) of Example 1 all show levels 2-1 and It can be seen that the polarizer obtained by the production method of the invention is homogeneously dyed. In the examples and comparative examples, since the amount swollen in the swelling bath was stretched so as not to bend, “wrinkles” did not occur.

5 is a graph showing the transmittance of the polarizer obtained in Comparative Example 1. 10 is a graph showing the transmittance of the polarizer obtained in Comparative Example 2. 3 is a graph showing the transmittance of the polarizer obtained in Example 1. FIG.

Claims (11)

Step (1) of stretching a polyvinyl alcohol film in an aqueous electrolyte solution;
Then, the manufacturing method of the polarizer characterized by including the process (2) dye | staining the said polyvinyl alcohol-type film with a dichroic material, and the process (3) of extending the said polyvinyl alcohol-type film further.   2. The polarizer according to claim 1, wherein the electrolyte contains at least one selected from salts and bases composed of a monovalent or divalent cation and a monovalent or divalent anion. Production method.   The method for producing a polarizer according to claim 1 or 2, wherein the electrolyte contains an inorganic salt composed of an alkali metal or an alkaline earth metal and a halogen.   The method for producing a polarizer according to claim 1, wherein the electrolyte contains at least one of potassium chloride, potassium bromide, and potassium iodide.   The method for producing a polarizer according to claim 1, wherein the electrolyte concentration of the aqueous electrolyte solution is 0.0005 to 5% by weight.   The method for producing a polarizer according to any one of claims 1 to 5, wherein the draw ratio in the drawing step (1) is 1.1 to 4.5 times.   The method for producing a polarizer according to any one of claims 1 to 6, wherein the iodine dyeing step (2) and the stretching step (3) are performed simultaneously.   The polarizer obtained by the manufacturing method in any one of Claims 1-7.   A polarizing plate comprising a transparent protective film on at least one surface of the polarizer according to claim 8.   An optical film, wherein another optical layer is laminated on the polarizer according to claim 8 or the polarizing plate according to claim 9. An image display device using at least one polarizer according to claim 8, a polarizing plate according to claim 9, or an optical film according to claim 10.

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