JP2008102274A - Polarizer, polarizing plate, optical film, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be particularly suitable for a liquid crystal display device for television use, which has excellent durability, high transmittance, high polarization degree, and polarization characteristics that enable achromatic display during black display. To provide a polarizer.
SOLUTION: A polarizer in which a polyvinyl alcohol film is subjected to at least a dyeing process, a stretching process, and a crosslinking process. The polyvinyl alcohol film has 1 to 4 mol% of ethylene units and 0 vinyl ester units. 0.5 to 2 mol%, and an ethylene-vinyl alcohol copolymer having an average polymerization degree of 2000 to 2600 and a saponification degree of 98.0 to 99.5 mol%, Measured with respect to light having a wavelength of 380 nm to 780 nm, the single transmittance is 40 to 44%, the degree of polarization is 99.95% or more, and the orthogonal transmittance measured with light having a wavelength of 440 nm is 0.023% or less. A polarizer characterized by that.
[Selection figure] None

Description

  The present invention relates to a polarizer. The present invention also relates to a polarizing plate using the polarizer. The polarizer and the polarizing plate can be used alone or as an optical film laminated thereon to form an image display device such as a flat panel display such as a liquid crystal display device or an organic EL display device.

  Conventionally, as a polarizer used for a liquid crystal display device or the like, an absorption dichroic polarizer formed by uniaxially stretching a polyvinyl alcohol resin film dyed with iodine or a dichroic dye has been widely used. . Further, the polarizer is used as a polarizing plate having a strength enhanced by bonding a saponified transparent protective film such as triacetyl cellulose to both sides or one side of the polarizer.

  In recent liquid crystal display devices, with the improvement of display performance, polarizers are required to have higher transmittance and higher degree of polarization. In order to meet such demands, for example, it has been proposed to use a polyvinyl alcohol film having a high degree of polymerization having an average degree of polymerization of 2600 or more or a film obtained by stretching an ethylene-modified polyvinyl alcohol film at a high draw ratio (Patent Literature). 1, Patent Document 2). However, since the film described in the above-mentioned patent document has a high average degree of polymerization, it is difficult to form a film and there is a problem of durability, and it cannot be used industrially.

  In addition, liquid crystal display devices for television and the like are required to have an achromatic color display during black display as well as high transmittance and high polarization degree. Furthermore, since it is used for a long time in the lighting environment of a high-intensity backlight, heat resistance is also required. However, in a polarizer made using a conventional polyvinyl alcohol film, only a short wavelength side absorption is obtained when the single transmittance is high. For this reason, in the vicinity of the bright line wavelength of 440 nm in the blue region of the backlight using a widely adopted cold cathode tube, light inevitably leaks, and there is a problem that the black display itself is colored blue.

Japanese Patent Laid-Open No. 6-250019 JP 2003-268127 A

  The present invention is excellent in durability, has a high transmittance, a high degree of polarization, and has a polarization characteristic that enables an achromatic display during black display, and is particularly suitable for a liquid crystal display device for television use. An object is to provide a polarizer.

  The present invention also provides a polarizing plate using the polarizer, an optical film in which the polarizer or the polarizing plate is laminated, and a liquid crystal display device using the polarizer, the polarizing plate, or the optical film. An object of the present invention is to provide an image display device such as the above.

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

That is, the present invention is a polarizer in which at least a dyeing process, a stretching process, and a crosslinking process are performed on the polyvinyl alcohol film,
The polyvinyl alcohol-based film contains 1 to 4 mol% of ethylene units, 0.5 to 2 mol% of vinyl ester units, and
Formed with an ethylene-vinyl alcohol copolymer having an average polymerization degree of 2000 to 2600 and a saponification degree of 98.0 to 99.5 mol%,
The polarizer has a single transmittance of 40 to 44%, a degree of polarization of 99.95% or more, measured with respect to light having a wavelength of 380 nm to 780 nm, and
The present invention relates to a polarizer characterized in that the orthogonal transmittance measured with light having a wavelength of 440 nm is 0.023% or less.

  The polarizer preferably has a degree of polarization of 99.8% or more measured with light having a wavelength of 440 nm.

  The present invention also relates to a polarizing plate, wherein a transparent protective film is laminated on at least one surface of the polarizer.

  In the polarizing plate, the transparent protective film is preferably at least one selected from the group consisting of a triacetyl cellulose film, a norbornene film, a cycloolefin film, and an acrylic resin film.

  The present invention also relates to an optical film in which at least one of the polarizer or the polarizing plate is laminated.

  Furthermore, this invention relates to the image display apparatus characterized by using the said polarizer, the said polarizing plate, or the said optical film.

  In the polarizer of the present invention, an ethylene-polyvinyl alcohol copolymer containing 1 to 4 mol% of ethylene units and 0.5 to 2 mol% of vinyl ester units is used as the polyvinyl alcohol film. Such a polyvinyl alcohol-based film has some hydrophobicity by introducing an ethylene unit in the above range and also having a vinyl ester unit in the above range, so that it has durability such as water resistance. Excellent.

  Moreover, the content rate of the said ethylene unit and a vinyl ester unit is introduce | transduced into the said copolymer so that melting | fusing point of an ethylene-polyvinyl alcohol copolymer can be controlled to become 220-230 degreeC. The melting point of the film material can be controlled by the contents of the ethylene units and vinyl ester units. By using the ethylene-polyvinyl alcohol copolymer as a material for a polarizer raw film, the copolymer is easily unraveled and stretched to the extent that the molecular chains of the copolymer are not dissolved in a warm water bath. Thus, it is considered that the dichroic light absorber (for example, iodine complex in the case of an iodine polarizer) is oriented in a higher order in the dyeing process by being stretched in such a state. As a result, it is considered that a polarizer having a high transmittance and a high degree of polarization, in particular, a polarizing property can be obtained.

  The polarizer of the present invention has a single transmittance of 40 to 44% and a degree of polarization of 99.95% or more measured with respect to wavelength light of 380 nm to 780 nm, and has high transmittance and a high degree of polarization. If the single transmittance exceeds 44%, the orthogonal transmittance increases, and light leakage occurs during black display, which is not preferable. The single transmittance is preferably 41.5 to 43.5%, more preferably 42 to 43.2%, and the degree of polarization is 99.95% or more, further 99.97% or more. Is preferred. In addition, it is preferable that the orthogonal transmittance | permeability measured with the spectrophotometer about wavelength light 380nm -780nm is 0.005% or less, Furthermore, 0.003% or less.

  Further, the polarizer of the present invention has an orthogonal transmittance of 0.023% or less measured with light having a wavelength of 440 nm. As described above, in the polarizer of the present invention, since the high-order dichroic light absorber is oriented, the orthogonal transmittance measured with light having a wavelength of 440 nm is low, and even in the vicinity of a wavelength of 440 nm, black light is displayed. Light leakage can be suppressed, and an achromatic color can be displayed during black display. The orthogonal transmittance measured with light having a wavelength of 440 nm is preferably 0.006% or less, more preferably 0.003% or less. In addition, the polarizer of the present invention has a high degree of polarization measured with light having a wavelength of 440 nm, and can satisfy 99.8% or more. The degree of polarization measured with light having a wavelength of 440 nm is preferably 99.85% or more.

  As a material for the polyvinyl alcohol film used for the polarizer of the present invention, an ethylene-vinyl alcohol copolymer containing an ethylene unit and a vinyl ester unit is used.

  The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerization of ethylene and a vinyl ester monomer such as vinyl acetate to make the vinyl ester unit a vinyl alcohol unit.

  When ethylene and vinyl ester are copolymerized, other monomers may be copolymerized to such an extent that the gist of the present invention is not impaired. Examples of such comonomers include olefins other than ethylene, acrylic acid and salts thereof, acrylic esters, methacrylic acid and salts thereof, methacrylic esters, acrylamide, derivatives thereof, methacrylamide, derivatives thereof, vinyl ethers, Nitriles, vinyl halides, allyl compounds, maleic acid and salts or esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

In the ethylene-vinyl alcohol copolymer, the ethylene unit is controlled to be 1 to 4 mol%, and the vinyl ester unit is controlled to be 0.5 to 2 mol%. In the ethylene-vinyl alcohol copolymer, the ethylene unit content is preferably 1 to 3.5 mol%, more preferably 2 to 3 mol%. Moreover, the content rate of a vinyl ester unit becomes like this. Preferably it is 0.7-1.7 mol%. The ethylene unit and vinyl ester unit content was calculated from the ¹ H-NMR measurement spectrum using values derived from the respective integral curves of the polyvinyl alcohol peak and the polyethylene or polyvinyl ester peak. As the analyzer, NMR (JEOL EX-400): 400 MHz manufactured by JEOL Ltd. was used. Measurement conditions: pulse width 45 °, measurement solvent DMSO-d ₆ , D ₂ O, measurement temperature: 80 ° C., chemical shift standard: TSP-d ₄ , 0.00 ppm.

  By controlling the ethylene unit and the vinyl ester unit within the above ranges, the ethylene-vinyl alcohol copolymer is controlled to have a melting point of about 220 to 230 ° C. When the melting point of the copolymer is less than 220 ° C., the ethylene unit content is high, so that the film can be easily stretched. However, since appropriate stress is not applied during stretching, sufficient optical properties can be obtained. I can't. In addition, the dyeability is poor, and it is difficult to obtain a sufficient absorbance at a wavelength of 440 nm (orthogonal transmittance is not sufficiently small), the black display itself is colored blue, and it is difficult to realize an achromatic color during black display. On the other hand, when the melting point of the copolymer exceeds 230 ° C., the content of ethylene units is too low (or because no ethylene units are introduced), so the same as the conventional polarizer using polyvinyl alcohol as a material. Only a certain level of properties can be obtained, durability is not sufficient, and optical properties are not sufficient. The melting point of the ethylene-vinyl alcohol copolymer is preferably 225 to 230 ° C, more preferably 227 to 229 ° C. In addition, although the melting point of the ethylene-vinyl alcohol copolymer is controlled to about 220 to 230 ° C., even if the melting point is satisfied, the ethylene unit and the vinyl ester unit are not controlled within the above range. The object of the present invention cannot be achieved.

The average degree of polymerization of the ethylene-vinyl alcohol copolymer is preferably 2000-2600. If the average degree of polymerization is less than 2,000, the performance such as optical characteristics (polarization characteristics) and durability may be deteriorated. On the other hand, when the average degree of polymerization exceeds 2600, the dope viscosity at the time of forming a film from the copolymer by casting becomes high, and it is difficult to obtain a uniform film and it takes time to form the film. The average degree of polymerization of the ethylene-vinyl alcohol copolymer is measured according to JIS-K6726. That is, after re-saponifying and purifying an ethylene-vinyl alcohol copolymer, the following formula: degree of polymerization = ([η] × 10) from the intrinsic viscosity [η] (unit: dl / g) measured in water at 30 ° C. ^{3 /} 8.29) ^{(1 / 0.62)} .

  The saponification degree of the ethylene-vinyl alcohol copolymer is 98.0 to 99.5 mol%. The degree of saponification is the degree of saponification in the vinyl alcohol unit of the ethylene-vinyl alcohol copolymer, which also affects the polarization characteristics and durability of the polarizer of the present invention. The degree of saponification represents the proportion of units that are actually saponified to vinyl alcohol units among the units that can be converted to vinyl alcohol units by saponification, and the residue is a vinyl ester unit. The degree of saponification is 98.0 mol% or more, preferably 98.5 mol% or more, more preferably 99.0 mol% or more. If the degree of saponification is less than 98.0 mol%, the polarization characteristics of the polarizer are not sufficient. On the other hand, the saponification degree is 99.5 mol% or less, preferably 99.4 mol% or less, and more preferably 99.3 mol% or less from the viewpoint of optical properties and durability. The saponification degree was measured by the method described in JIS K0070-1992.

  A polarizer is prepared from the ethylene-vinyl alcohol copolymer, and the copolymer 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 it is preferably 20% by weight or less based on the copolymer.

  The polarizer of the present invention is prepared by subjecting the ethylene-vinyl alcohol copolymer film to at least a dyeing process, a stretching process, and a crosslinking process. Since the obtained polarizer uses the ethylene-vinyl alcohol copolymer film, the single transmittance measured for wavelength light of 380 nm to 780 nm is 40 to 44%, and the degree of polarization is 99.95% or more. In addition, a material satisfying an orthogonal transmittance of 0.023% or less measured with light having a wavelength of 440 nm is obtained. Moreover, what has a degree of polarization of 99.8% or more measured with light having a wavelength of 440 nm can be obtained.

  The dyeing step is performed by adsorbing and orienting iodine or a dichroic dye on the ethylene-vinyl alcohol copolymer film. The dyeing process can be performed together with the stretching process. Dyeing is generally performed by immersing the film in a dyeing solution. As the staining solution, an iodine solution is generally used. As the iodine aqueous solution used as the iodine solution, an aqueous solution containing iodine ions with, for example, potassium iodide or the like as iodine and a dissolution aid is used. Other aids such as iodides such as lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Can be used. The iodine concentration is about 0.01 to 0.5% by weight, preferably 0.02 to 0.4% by weight, and the potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02 to 8% by weight. % Is preferably used. In iodine staining, 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.

  The ethylene-vinyl alcohol copolymer film may be subjected to a swelling treatment at about 20 to 60 ° C. for about 0.1 to 10 minutes in a water bath or the like before being dyed in the dyeing solution. The ethylene-vinyl alcohol copolymer film can be washed with water to remove dirt and anti-blocking agent on the film surface, and also has the effect of preventing unevenness such as uneven coloring by swelling the film. is there.

  In the stretching process, a uniaxial stretching process is usually performed. The stretching method 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. Stretching can also be performed in multiple stages. In the stretching means, the unstretched film is usually heated. 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 6.8 times, more preferably 3.5 to 6.5 times. desirable.

  The stretching process may be performed at any stage before the dyeing process, during the dyeing process, or after the dyeing process. Stretching can also be performed in a plurality of steps. For example, the stretching can be performed in two or three stages before the dyeing process, during the dyeing process, and after the dyeing process.

  The crosslinking step is performed by immersing the ethylene-vinyl alcohol copolymer film in a crosslinking bath (crosslinking aqueous solution). As the aqueous crosslinking solution, one containing about 1 to 10% by weight of a crosslinking agent such as boric acid, borax, glyoxal or glutaraldehyde is usually used. The concentration of the crosslinking agent is determined in consideration of the balance between the optical properties and the contraction of the polarizing plate caused by the stretching force generated in the ethylene-vinyl alcohol copolymer film.

  In the crosslinking bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of 0.05 to 15% by weight, preferably 0.5 to 8% by weight. These additives are particularly preferable from the viewpoint of obtaining in-plane uniform characteristics of the polarizer. The aqueous crosslinking solution may contain a small amount of an organic solvent compatible with water in addition to the aqueous solvent. The temperature of the aqueous crosslinking solution is generally about 20 to 85 ° C, preferably 40 to 70 ° C. The immersion time in the crosslinking step is usually about 10 to 800 seconds, preferably about 30 to 500 seconds.

  The stage of performing the crosslinking process is after the dyeing process. The crosslinking step is performed during or after the stretching step.

  Moreover, the washing | cleaning process can be provided in the ethylene-vinyl alcohol copolymer film in which each said process was given. The precipitate generated on the surface of the stretched film can be removed by the washing step.

  The washing step can be performed by washing with water, distilled water, pure water or the like, for example. The water washing step is usually performed by immersing a polyvinyl alcohol film in a water washing bath. Moreover, a washing | cleaning process can be performed by immersing in the aqueous solution containing iodides, such as potassium iodide. For example, the aqueous solution preferably has a potassium iodide concentration of about 0.5 to 10% by weight, more preferably 1 to 8% by weight. The temperature of the washing bath in the washing step 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 1 to 300 seconds, preferably about 10 to 240 seconds. The cleaning with the aqueous solution can be performed in combination with water cleaning, and can be performed before or after the water cleaning.

  In addition, the ethylene-vinyl alcohol copolymer film subjected to the above steps can be provided with a drying step at about 20 to 80 ° C. for about 1 minute to 10 minutes.

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

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a transparent 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 transparent 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 triacetyl cellulose film, a norbornene-based film, a cycloolefin-based film, and an acrylic resin film are preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. 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 fine 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 by 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 side of the polarizing plate via a transparent protective film or the like, if necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. 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 vacuum evaporation method, an ion plating method, a sputtering method, or a deposition method It can be performed by a method of attaching directly to the surface of the protective film.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. As shown (made by 3M, D-BEF, etc.), the orientation film of the cholesteric liquid crystal polymer and the oriented liquid crystal layer supported on the film substrate (made by Nitto Denko, PCF350, Merck, Transmax, etc.), Any suitable one can be used, such as one that reflects either left-handed or right-handed circularly polarized light and transmits other light.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light with a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Moreover, the polarizing plate may consist of what laminated | stacked the other optical layer. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

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

  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 conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

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

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

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In each example, parts and% are based on weight unless otherwise specified.

(Measuring method of melting point)
The melting point was measured by the following procedure in order to remove the influence of the plasticizer (glycerin) contained in the raw film. A sample of the original film was immersed in distilled water to remove glycerin from the sample, and left to stand at room temperature (23 ° C.) for 3 days to dry naturally. Thereafter, the sample was precisely weighed and crimped as it was in an aluminum open container and subjected to DSC measurement at a temperature rising rate of 5 ° C./min in the temperature range of 0 to 260 ° C., and the endothermic peak temperature was taken as the melting point. The raw film and the resin before producing the raw film showed the same melting point.

Example 1
(Polarizer)
An ethylene-vinyl alcohol copolymer film having an average polymerization degree of 2400, a saponification degree of 99.3 mol%, an ethylene unit content of 2.3 mol%, a vinyl acetate content of 0.7 mol% and a melting point of 227 ° C. (( Kuraray Co., Ltd., VF-PE # 7500, thickness 75 μm) was dyed, crosslinked and stretched between rolls having different speed ratios to obtain a polarizer. Specifically, it is immersed in an iodine aqueous solution (dye bath) at 30 ° C. containing 0.02% iodine concentration and 2% potassium iodide concentration for 60 seconds, and uniaxially up to 3 times the draw ratio in the flow direction while dyeing. Stretched. Next, the film was stretched until the total draw ratio was 6 times while being immersed in a 62 ° C. aqueous solution (stretching bath) containing 5% boric acid and 5% potassium iodide for 40 seconds. Subsequently, it was washed by immersing it in an aqueous solution at 30 ° C. having a potassium iodide concentration of 3% by weight, and then dried at 50 ° C. for 4 minutes to obtain a polarizer.

(Polarizer)
A saponified surface triacetylcellulose film having a saponified surface was bonded to both sides of the polarizer obtained above with a polyvinyl alcohol adhesive, and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate. Got.

Examples 2-6
In Example 1, a polarizer was produced in the same manner as in Example 1 except that the iodine concentration was changed as shown in Table 1 in producing the polarizer. A polarizing plate was produced in the same manner as in Example 1 using the polarizer.

Comparative Example 1
In Example 1, instead of the ethylene-vinyl alcohol copolymer film, a polyvinyl alcohol film (average polymerization degree 2400, saponification degree 99.9 mol%, vinyl acetate content 0.1 mol%, melting point 232 ° C.) A polarizer was produced in the same manner as in Example 1 except that Kuraray Co., Ltd., VF-PS # 7500, thickness 75 μm) was used. A polarizing plate was produced in the same manner as in Example 1 using the polarizer.

Comparative Examples 2-6
In Comparative Example 1, a polarizer was prepared in the same manner as in Comparative Example 1 except that the iodine concentration was changed as shown in Table 1 in preparing the polarizer. A polarizing plate was produced in the same manner as in Example 1 using the polarizer.

Comparative Example 7
In Example 1, instead of the ethylene-vinyl alcohol copolymer film, the average polymerization degree was 2400, the saponification degree was 99.8 mol%, the ethylene unit content was 2.4 mol%, and the vinyl acetate content was 0.2. A polarizer was prepared in the same manner as in Example 1 except that a polyvinyl alcohol film having a mol% and a melting point of 228 ° C. (manufactured by Kuraray Co., Ltd., EXVAL 151, thickness 75 μm) was used. A polarizing plate was produced in the same manner as in Example 1 using the polarizer.

(Evaluation)
About the polarizing plate obtained by the Example and the comparative example, the following optical characteristic and durability were evaluated. The results are shown in Tables 1 and 2.

<Optical characteristics>
About the single-piece | unit and a parallel and orthogonal state of a polarizing plate, the spectral transmittance in the wavelength light of 380 nm-780 nm is measured using a high-speed spectrophotometer (Murakami Color Research Laboratory make, DOT-3C), and is measured. The Y value in the C light source 2 ° field of view was calculated from the spectral transmittance according to the CIE1931 Yxy color system. These were defined as single transmittance (Ts (Y)), parallel transmittance (Tp (Y)), and orthogonal transmittance (Tc (Y)).

The degree of polarization (P) was calculated by {(parallel transmittance−orthogonal transmittance) / (parallel transmittance + orthogonal transmittance)} ^1/2 × 100 (%).

  Further, the parallel transmittance (Tp (440 nm)) and the orthogonal transmittance (Tc (440 nm)) at a wavelength of 440 nm were measured in the same manner as described above using the spectral transmittance of the light at a wavelength of 440 nm. The degree of polarization (P (440 nm)) was also calculated in the same manner as described above.

<Durability>
In the state which laminated | stacked the polarizing plate through the acrylic adhesive layer on the glass plate of thickness 1.3mm, it is 500 hours at 80 degreeC, and 60 degreeC / 90% R. H. Each was put in an environment of 500 hours, and the polarization degree after the initial test and after the test was measured and calculated in the same manner as described above. The amount of displacement from the initial value was calculated by (initial polarization degree) − (post-test polarization degree).

<Crack acceleration test method>
The polarizing plate was cut into 5 cm × 5 cm to prepare sample pieces. Prepare a container containing pure water at room temperature (25 ° C.), and put the sample piece in the pure water in the container half (2.5 cm) from one side in the stretching direction so that the stretching direction is the vertical direction. Soaked up to that. After leaving in this state for 20 minutes, the sample piece was taken out and it was confirmed whether or not a crack was generated. When the crack did not occur, “◯” was indicated, when the crack occurred, “the number”, and when the crack occurred, “the entire surface” was described.

Claims (6)

A polarizer in which at least a dyeing process, a stretching process, and a crosslinking process are performed on the polyvinyl alcohol film,
The polyvinyl alcohol-based film contains 1 to 4 mol% of ethylene units, 0.5 to 2 mol% of vinyl ester units, and
Formed with an ethylene-vinyl alcohol copolymer having an average polymerization degree of 2000 to 2600 and a saponification degree of 98.0 to 99.5 mol%,
The polarizer has a single transmittance of 40 to 44%, a degree of polarization of 99.95% or more, measured with respect to light having a wavelength of 380 nm to 780 nm, and
A polarizer having an orthogonal transmittance of 0.023% or less measured with light having a wavelength of 440 nm.   The polarizer according to claim 1, wherein the degree of polarization measured with light having a wavelength of 440 nm is 99.8% or more.   A polarizing plate, wherein a transparent protective film is laminated on at least one surface of the polarizer according to claim 1.   The polarizing plate according to claim 3, wherein the transparent protective film is at least one selected from the group consisting of a triacetyl cellulose film, a norbornene film, a cycloolefin film, and an acrylic resin film.   An optical film, wherein at least one polarizer according to claim 1 or 2 or a polarizing plate according to claim 3 or 4 is laminated.   An image display device comprising the polarizer according to claim 1, the polarizing plate according to claim 3, or the optical film according to claim 5.