JP4500194B2 - Manufacturing method of polarizer - Google Patents

Description

  The present invention relates to a method for manufacturing a polarizer. Moreover, this invention relates to the polarizer obtained by the said manufacturing method, the polarizing plate using a polarizer, and an optical film. Further, the present invention relates to an image display device such as a polarizing plate, a liquid crystal display device using an optical film, an organic EL display device, and a PDP.

  Image display devices such as liquid crystal display devices are widely used as components of electronic desk calculators, clocks, personal computers, word processors, televisions, instruments, car navigation systems, car instruments, and the like. Such a liquid crystal display device is usually provided with a polarizing plate for visualizing a change in orientation of the liquid crystal. The polarizing plate has a great influence on the display characteristics of the liquid crystal display device.

  As a polarizing plate, generally, there are laminated protective films such as a triacetyl cellulose film on both surfaces of a polarizer such as a polyvinyl alcohol film in which a dichroic substance such as iodine or an organic dye is adsorbed and oriented. It is used. When the polarizing plate is used for an application that requires high polarization performance, a polarizer containing iodine as a dichroic substance is used as the polarizer.

  In recent years, liquid crystal display devices have been improved in performance, and liquid crystal panels have been required to improve contrast in order to obtain high visibility. That is, it is desired that black is black and white is whiter and brighter, and accordingly, further improvement in the polarization performance of the polarizer is required. Therefore, it is very important for the polarization performance to have a high transmittance while having a high degree of polarization.

  In order to obtain such a polarizing plate, many methods have been proposed so far. For example, a polarizer obtained by uniaxially stretching a film using polyvinyl alcohol having a high degree of polymerization has been proposed (see Patent Document 1 and Patent Document 2). Moreover, a polarizer formed by uniaxially stretching a film using polyvinyl alcohol having a syndiotacticity of 45 mol% or more and less than 50 mol% and a polymerization degree of 1000 to 30000 has been proposed (see Patent Document 3). Moreover, the method of performing two-stage extending | stretching in the process process in the boron compound of a polyvinyl alcohol-type film is proposed (refer patent document 4). In addition, a method has been proposed in which two-stage stretching is performed so that the draw ratio in the dyeing process of the polyvinyl alcohol film or in the previous process and the draw ratio in the boron compound treatment process have a specific relationship (patent) Reference 5). Moreover, in addition to the proposal of two-stage stretching, a method of making the bath temperature of the first bath higher than the bath temperature of the second bath has been proposed (see Patent Document 6).

Among the above methods, the method using polyvinyl alcohol with a high degree of polymerization is most effective for improving the properties. However, in the method using polyvinyl alcohol with a high degree of polymerization or polyvinyl alcohol with biased tacticity, Since the previous solution is unstable at room temperature, and uniform film formation is difficult, it is not practical. Although a method of performing two-stage stretching in a boron compound is also effective, there is a limit in improving the characteristics as compared with a commonly used polarizer.
Japanese Patent No. 2543748 Japanese Patent No. 2631403 Japanese Patent No. 3317494 Japanese Patent No. 2512408 Japanese Patent No. 3392196 JP 2003-240945 A

  An object of this invention is to provide the practical manufacturing method of the iodine type polarizer which consists of a polyvinyl-alcohol-type film which has high polarization degree and high transmittance | permeability.

  Another object of the present invention is to provide a polarizer obtained by the production method, a polarizing plate using the polarizer, and an optical film. Furthermore, it aims at providing the image display apparatus using the said polarizing plate and an optical film.

  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 provides a method for producing a polarizer comprising at least a uniaxial stretching treatment step and an iodine dyeing treatment step for a polyvinyl alcohol film.
The present invention relates to a method for producing a polarizer, comprising a step of irradiating a polyvinyl alcohol film with an electron beam before the iodine dyeing treatment step.

In the production method of the present invention, the electron beam irradiation step is preferably performed in a state where a polyvinyl alcohol film is immersed in water.

In the production method of the present invention, the electron beam irradiation amount is preferably 50 to 500 kGy.

  In the present invention, when producing an iodine polarizer in which a polyvinyl alcohol film is subjected to a uniaxial stretching treatment step and an iodine dyeing treatment step, the polyvinyl alcohol film is irradiated with high energy rays before the iodine dyeing treatment is performed. Thus, the polyvinyl alcohol film is crosslinked. By this crosslinking, it is presumed that the iodine dyeing treatment is effectively performed, and an iodine-based polarizer made of a polyvinyl alcohol film having a high degree of polarization and a high transmittance is obtained.

  By applying an optical film in which such a polarizer or a polarizing plate using the polarizer or a retardation plate, a reflecting plate, a transflective reflecting plate, a visual compensation film, a brightness enhancement film, or the like is laminated to an image display device, characteristics are obtained. Can be improved. In particular, in a liquid crystal display device, the contrast of the liquid crystal panel is improved and the single transmittance is high, so that the luminance with the same amount of power is greatly improved without lowering the contrast. Further, if the luminance is set to the same as before, the power consumption can be suppressed.

  Polyvinyl alcohol or a derivative thereof is used as a material for the polyvinyl alcohol film applied to the polarizer 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.

  The polyvinyl alcohol film (unstretched film) is subjected to at least a uniaxial stretching treatment step and an iodine dyeing treatment step according to a conventional method, but before the iodine dyeing treatment step, the polyvinyl alcohol film is subjected to high energy. Irradiating a line. In this invention, the polyvinyl alcohol-type film is bridge | crosslinked by high energy ray irradiation.

  Although it is known that a plastic film is crosslinked by irradiating with a high energy ray, the irradiation with a high energy ray often causes a crosslinking reaction and a collapse reaction in many cases. For example, it is known that a crosslinking reaction easily occurs in an acrylic polymer, and a disintegration reaction easily occurs in a methacrylic polymer. Examples of the conditions for giving priority to the crosslinking reaction by high energy ray irradiation include a method of irradiation while heating, a method of irradiation in the presence of water, and a method of irradiation in a state where oxygen is hardly supplied. Therefore, in the present invention, it is preferable to perform high energy ray irradiation in a state satisfying at least one of the above conditions so as to give priority to the crosslinking reaction of the polyvinyl alcohol film. In particular, since the polyvinyl alcohol film has high hydrophilicity, it is preferable to irradiate high energy rays in the presence of water. For example, it is preferable to irradiate a high energy ray in a state where a polyvinyl alcohol film is immersed in water. In addition, although the temperature of the water bath which immerses a polyvinyl alcohol-type film is not specifically limited, It is 15-55 degreeC, Furthermore, it is preferable to set it as 20-40 degreeC.

  Examples of the high energy ray used in the high energy ray irradiation step include γ ray, X ray, neutron ray, electron beam and the like. Among these, an electron beam is preferable. When an electron beam is used as the high energy beam, the irradiation amount depends mainly on the thickness of the polyvinyl alcohol film used, but is usually about 50 to 500 kGy, preferably 120 to 380 kGy, more preferably 200 to 300 kGy. is there. If the irradiation amount is too low, the electron beam may be attenuated when passing through the protective film, and film crosslinking may not be sufficient. On the other hand, if the irradiation amount is too large, the film may collapse.

  The iodine staining treatment is performed on the film that has been subjected to the high energy ray irradiation treatment. The iodine dyeing treatment is generally performed by immersing the film in an iodine solution. As the iodine aqueous solution used as the iodine solution, in addition to iodine, an aqueous solution containing iodine ions with potassium iodide or the like is used as a solubilizing agent. 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.

  If necessary, the polyvinyl alcohol film may be immersed in water and washed before the iodine dyeing treatment. The immersion in the water can be performed together with the high energy ray irradiation treatment. By washing the polyvinyl alcohol film with water, it is possible to clean the surface of the polyvinyl alcohol film and anti-blocking agents, and also to prevent unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. There is also.

  The stretching method in the uniaxial stretching treatment is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. Examples of the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. In the dry stretching method, the unstretched film is usually heated. Examples of the stretching means of the wet stretching method include a method of stretching between rolls in an aqueous solution after stretching a film. Stretching can also be performed in multiple stages. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the total stretch ratio is about 2 to 7 times, preferably 3 to 6.5 times, and more preferably 3.5 to 6 times. The thickness of the stretched film is preferably about 5 to 40 μm.

  The uniaxial stretching treatment may be performed at any stage before the iodine dyeing treatment, during the iodine dyeing treatment, or after the iodine dyeing treatment. Further, the uniaxial stretching treatment can be performed in a plurality of steps, and for example, it can be performed in two or three stages before iodine staining, at the time of iodine staining, and after the iodine staining.

  Further, the high energy ray treatment may be performed at any stage before the uniaxial stretching treatment, during the uniaxial stretching treatment, or after the uniaxial stretching treatment as long as it is before the iodine dyeing treatment. In addition, when high energy ray processing is performed after iodine staining, iodine is decomposed, which is not preferable.

  In the method for producing a polarizer of the present invention, in addition to the above steps, a boric acid treatment step, a metal ion treatment step, an iodine ion treatment step, and the like can be performed.

  The boric acid treatment is performed by immersing a polyvinyl alcohol film in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is about 2 to 15% by weight, preferably 3 to 10% by weight. In the boric acid aqueous solution, potassium ions and iodine ions can be contained by potassium iodide. The potassium iodide concentration in the boric acid aqueous solution is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. A boric acid aqueous solution containing potassium iodide can provide 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.

  In the boric acid treatment, the temperature of the boric acid aqueous solution is, for example, 30 ° C. or higher, preferably 40 to 85 ° C. The immersion time is usually about 1 to 1200 seconds, preferably about 10 to 600 seconds, and more preferably about 20 to 500 seconds. The step of performing the boric acid treatment is after the iodine staining treatment. The boric acid treatment is performed during or after uniaxial stretching. The boric acid treatment may be performed a plurality of times.

  The metal ion treatment is performed by immersing a polyvinyl alcohol film in an aqueous solution containing a metal salt. Various metal ions are contained in the polyvinyl alcohol film by metal ion treatment.

  As metal ions, metal ions of transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron are particularly preferably used in terms of color tone adjustment and durability. Among these metal ions, zinc ions are preferable from the viewpoints of color tone adjustment and heat resistance. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

  A metal salt solution is used for the metal ion treatment. Hereinafter, zinc impregnation treatment will be described as a representative example of the case of using a zinc salt aqueous solution among metal ion treatments.

  The concentration of zinc ions in the zinc salt aqueous solution is about 0.1 to 10% by weight, preferably 0.3 to 7% by weight. The zinc salt solution is preferably an aqueous solution containing potassium ions and iodine ions with potassium iodide or the like because it is easy to impregnate zinc ions. The potassium iodide concentration in the zinc salt solution is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight.

  In the zinc impregnation treatment, the temperature of the zinc salt solution is usually about 15 to 85 ° C, preferably 25 to 70 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. In the zinc impregnation treatment, the zinc content in the polyvinyl alcohol film is adjusted to the above range by adjusting the conditions such as the concentration of the zinc salt solution, the immersion temperature of the polyvinyl alcohol film in the zinc salt solution, and the immersion time. adjust. The stage of the zinc impregnation treatment is not particularly limited, and may be before the iodine dyeing treatment, before the immersion treatment in the boric acid aqueous solution after the iodine dyeing treatment, during the boric acid treatment, or after the boric acid treatment. Further, it may be carried out simultaneously with the iodine dyeing treatment in the presence of a zinc salt in the iodine dyeing solution. Moreover, a uniaxial stretching process can be performed with a zinc impregnation process. Moreover, you may perform a zinc impregnation process in multiple times. The zinc impregnation treatment (metal ion treatment) is after the high energy beam irradiation treatment.

  The treated polyvinyl alcohol film (stretched film) may generate precipitates on the surface and can be subjected to a washing step and a drying step according to a conventional method.

  The washing step can be performed with water, for example. The water washing step is usually performed by immersing a polyvinyl alcohol film in pure water. The water washing temperature is usually in the range of 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably about 20 to 240 seconds.

  In the washing step, iodine ion treatment with potassium iodide or the like can be performed. For the iodine ion treatment, for example, an aqueous solution containing iodine ions with potassium iodide or the like is used. 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. The stage of iodine ion treatment is not particularly limited as long as it is before the drying process. The iodine ion treatment can be performed in combination with water washing, and can be performed before or after water washing.

  In addition to the above, the washing step may contain metal salts such as boric acid and zinc salts.

  A drying process is normally performed by drying at 20-75 degreeC, Preferably it is 25-70 degreeC for about 1 to 5 minutes. A polarizer is obtained by drying. Drying can be carried out under conditions where the deformation of the film and the hue do not change significantly.

  The obtained polarizer can be made into a polarizing plate provided with a transparent protective layer on at least one surface thereof according to a conventional method. The transparent protective layer can be provided as a polymer-coated layer or a film laminate layer. 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−nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the 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, diffusing layer, antiglare layer and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective layer 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. The said adhesive agent is normally used as an adhesive agent which consists of aqueous solution, and contains 0.5 to 60 weight% of solid content normally. The adhesive can contain a crosslinking agent. Further, other additives and catalysts such as acids can be blended. As the adhesive, a polyvinyl alcohol-based adhesive having good adhesiveness with a polyvinyl alcohol-based film is suitable. As a crosslinking agent suitable for the polyvinyl alcohol-based adhesive, boric acid, borax, glutaraldehyde, melamine, oxalic acid and the like can be 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 1 to 500 nm, preferably 10 to 300 nm, and more preferably 20 to 100 nm.

  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 via a transparent protective layer or the like as necessary.

  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 a 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.

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

  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.

  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 ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.

  In the present invention, the polarizer, the transparent protective film, the optical film, etc. that form the polarizing plate described above, and the adhesive layer, for example, each include 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. In general, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In 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. .

  The present invention will be specifically described below with reference to examples and comparative examples. In addition,% in each example is weight%.

Example 1
A 75 μm-thick polyvinyl alcohol film (average polymerization degree 2400, saponification degree 99.9%) was immersed in water at 30 ° C. to make it coexist with water. Next, the film was irradiated with an electron beam of 260 kGy. Thereafter, the film was swelled and uniaxially stretched in water to a draw ratio of 3 times, and then immersed in a dye bath at 30 ° C. containing a potassium iodide concentration of 0.33% and an iodine concentration of 0.048% for dyeing for 50 seconds. Next, after dipping for 20 seconds in a boric acid aqueous solution containing 3% boric acid concentration and 3% potassium iodide concentration at 40 ° C., boric acid aqueous solution having a boric acid concentration of 8% and a potassium iodide concentration of 5% at 65 ° C. The film was stretched up to 6.3 times while immersed in it for 40 seconds. Then, it was immersed in an aqueous solution having a potassium iodide concentration of 1% at 25 ° C. for 20 seconds. Then, it dried at 70 degreeC for 2 minute (s), and obtained the polarizer. A 80 μm thick triacetyl cellulose film having a saponified surface was bonded to both sides of the obtained polarizer with a polyvinyl alcohol adhesive, and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

Comparative Example 1
In Example 1, a polarizer was obtained in the same manner as in Example 1 except that the electron beam was not irradiated. A polarizing plate was obtained in the same manner as in Example 1.

  The optical characteristics (single transmittance, polarization degree) of the obtained polarizing plate were measured by the following methods. The results are shown in Table 1.

(Single transmittance)
This is a Y value measured using a spectrophotometer (DOT-3, manufactured by Murakami Color Research Laboratory) and corrected for visibility by a 2 degree viewing angle (C light source) of JIS Z 8701.

(Cross Nicol polarization degree)
The transmittance (H ₀ ) when two identical polarizing plates are overlapped so that their polarization axes are parallel to each other, and the transmittance (H ₉₀ ) when they are overlapped at right angles are measured for the above-mentioned transmittance. The degree of polarization was determined from the following equation. The transmittance (H ₀ ) in the case of parallel and the transmittance (H ₉₀ ) in the case of orthogonal are Y values obtained by correcting the visibility. Polarization degree (%) = √ (H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ ) × 100.

Claims (3)

For a polyvinyl alcohol film, in a method for producing a polarizer comprising at least a uniaxial stretching treatment step and an iodine staining treatment step,
A method for producing a polarizer, comprising a step of irradiating a polyvinyl alcohol film with an electron beam before the iodine staining treatment step. The method for producing a polarizer according to claim 1, wherein the electron beam irradiation step is performed in a state in which a polyvinyl alcohol film is immersed in water. The method for producing a polarizer according to claim 1 or 2, wherein the irradiation amount of the electron beam is 50 to 500 kGy.