JP2006058437A - Manufacturing method of polarizing plate, polarizing plate, optical film and picture display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of a polarizing plate in which warpage can be reduced even when a display device is enlarged. <P>SOLUTION: The manufacturing method of the polarizing plate in which a transparent protective film is formed at least on one surface of a polarizer is provided, the manufacturing method is characterized in that the polarizer is an uniaxially oriented film which includes dichroic material and the polarizer is made to run in the direction of an uniaxial orientation and after the transparent protective film is stretched in the width direction, the stretched transparent protective film is stuck together with the polarizer continuously. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a polarizing plate. Moreover, this invention relates to the polarizing plate obtained by the said manufacturing method. The polarizing plate is an optical film obtained by laminating the polarizing plate alone, or a flat panel display such as a liquid crystal display device (hereinafter abbreviated as LCD) or an electroluminescence display device (hereinafter abbreviated as ELD), or an image such as a PDP. A display device can be formed.

  Polarizers are used for flat panel displays. In general, a polarizer obtained by stretching a polyvinyl alcohol film containing a dichroic material such as iodine is used in order to obtain sufficient optical characteristics. Since the polyvinyl alcohol polarizer is produced by stretching, it is likely to shrink and warp. In addition, since the polyvinyl alcohol film is a hydrophilic polymer, it is very easily deformed under humidified conditions. Moreover, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. For this reason, the polarizer is usually used as a polarizing plate in which a transparent protective film such as triacetyl cellulose is bonded to both sides or one side to supplement the strength. The polarizing plate is generally produced by bonding a polarizer and a transparent protective film with an adhesive (Patent Document 1).

In the field of flat panel displays in recent years, particularly LCDs, improvement in screen uniformity and quality has been demanded with higher definition and higher functionality. Moreover, high heat resistance, moist heat resistance, water resistance and the like are also required due to diversification of use environments. In particular, the demand for high contrast and high definition is increasing as the size of the TV field in LCDs increases. The polarizing plate is also required to satisfy the required performance as described above. However, technical development related to enlargement is not limited to simply increasing the size of a small product, and the current situation is that defects unique to large products such as unevenness of each member and warping of panels occur. About a polarizing plate, generation | occurrence | production of the curvature by enlargement is large.
JP 9-318814 A

  An object of this invention is to provide the manufacturing method of the polarizing plate which can reduce curvature even when it enlarges.

  Another object of the present invention is to provide a polarizing plate obtained by the production method. Moreover, it aims at providing image display apparatuses, such as an optical film which laminated | stacked the said polarizing plate, and also the LCD and ELD which used the said polarizing plate and the optical film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the object can be achieved by the following method for producing a polarizing plate, and have completed the present invention. That is, the present invention is as follows.

That is, the present invention is a method for producing a polarizing plate in which a transparent protective film is provided on at least one surface of a polarizer,
The polarizer is a uniaxially stretched film containing a dichroic substance, the polarizer travels in the uniaxially stretched direction,
A transparent protective film is related with the manufacturing method of the polarizing plate characterized by sticking continuously with the said polarizer, after extending | stretching to the width direction.

  In the manufacturing method of the polarizing plate of the said invention, the transparent protective film extended | stretched in the width direction is bonded together with respect to the polarizer which is a uniaxially stretched film. The polarizer is uniaxially stretched in the running direction (flow direction), while the transparent protective film is stretched in the width direction. Therefore, in the polarizing plate obtained by continuously laminating the polarizer and the transparent protective film, the stretching axis of the polarizer and the stretching axis of the transparent protective film are substantially perpendicular to each other. The warpage caused by stretching in the film cancels each other out, and the warpage can be reduced in the obtained polarizing plate. Reduction of the warpage of the polarizing plate by such a manufacturing method is particularly useful in the case of a large-size polarizing plate.

  In the manufacturing method of the polarizing plate, the width of the polarizer and the width of the transparent protective film are not particularly limited. However, the polarizer has a width of 1500 mm or more, and the transparent protective film after stretching in the width direction has a width of 1500 mm or more. It is suitable in some cases.

  Conventionally, when an attempt is made to increase the size of the polarizing plate, the problem of warpage accompanying the increase in size is significant, and the width of the transparent protective film is limited. Production was limited to those up to 1328 mm in the film width direction and 784 mm in the flow direction. According to the manufacturing method of the present invention, the problem of warpage is reduced even when the size is increased, and the limitation on the width of the transparent protective film is that the film width is increased by stretching the transparent protective film in the width direction. However, the width can be increased compared to the conventional case, and the maximum effective width of the polarizer is no longer limited to the 60-inch type. Therefore, it is possible to manufacture a large-size polarizing plate while reducing warpage by using a polarizer having an effective width of 68 inches (film width direction 1505 mm × flow direction 889 mm).

  In the manufacturing method of the polarizing plate, the stretch ratio in the width direction of the transparent protective film is not particularly limited and is appropriately determined depending on the material of the transparent protective film and the required transparent protective film width. It is preferably more than 1 time and 2 times or less. When the draw ratio in the width direction exceeds 2 times, the transparency may decrease, which is not preferable. The stretching ratio in the width direction is preferably 1.2 times or more and preferably 1.3 times or less. For example, if it is a transparent protective film having a width of 1475 mm which is conventionally the maximum width, a transparent protective film having a width of 2950 mm can be obtained by stretching twice, and a large-sized polarizing plate can be obtained using this. it can.

  In the manufacturing method of the said polarizing plate, it is preferable that the temperature which extends | stretches a transparent protective film in the width direction is -20 degreeC-Tg-+50 degreeC on the basis of the glass transition temperature (Tg) of a transparent protective film. Within such a temperature range, the transparent protective film can be suitably stretched in the width direction. The stretching temperature is preferably −10 ° C. to Tg to + 40 ° C. based on Tg of the transparent protective film.

  In the manufacturing method of the said polarizing plate, it is preferable that the haze of the transparent protective film after extending | stretching to the width direction is 10% or less from a viewpoint of transparency. Further, the haze of the transparent protective film is preferably 7% or less, more preferably 5% or less. When the stretch ratio of the transparent protective film is increased, the film surface is crazed and the transparency is lowered. Therefore, it is preferable to control the stretch ratio in the width direction so that the haze is 10% or less. In addition, it is preferable that the transparent protective film after extending | stretching to the width direction has a single-piece | unit transmittance | permeability 90% or more, Furthermore, 95% or more.

  In the method for producing the polarizing plate, as the transparent protective film, a cellulose resin film, a norbornene resin film, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) Any one selected from a film containing a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain is preferably used.

  Moreover, this invention relates to the polarizing plate obtained by the said manufacturing method.

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

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

  As the polarizer, a uniaxially stretched film containing a dichroic material is used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And uniaxially stretched by adsorbing the active substance. Further, there may be mentioned those uniaxially stretched with a polyene-based oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. Among these, a polarizer made of a dichroic substance such as a polyvinyl alcohol film and iodine or a dichroic dye is preferable.

  As a polyvinyl alcohol film, a film formed by any method such as a casting method, a casting method or an extrusion method in which a stock solution in which a polyvinyl alcohol resin is dissolved in water or an organic solvent is cast is appropriately used. can do. The degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5000, and more preferably 1400 to 4000.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine or the like and uniaxially stretching can be produced, for example, by the following method.

  In the dyeing process, the polyvinyl alcohol film is immersed in a dyeing bath at about 20 to 70 ° C. to which iodine is added for about 1 to 20 minutes to adsorb iodine. The iodine concentration in the dyeing bath is usually about 0.001 to 1 part by weight per 100 parts by weight of water. In the dyeing 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 about 0.02 to 20 parts by weight. These additives are particularly preferable for increasing the dyeing efficiency. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The polyvinyl alcohol 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 an aqueous solution containing iodine or a dichroic dye. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there.

  The dyed polyvinyl alcohol film can be cross-linked as necessary. The composition of the aqueous crosslinking solution used for the crosslinking treatment is usually about 1 to 10 parts by weight per 100 parts by weight of water, alone or mixed with a crosslinking agent such as boric acid, borax, glyoxal, and glutaraldehyde. 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 polyvinyl alcohol 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 about 0.05 to 15% by weight. These additives are particularly preferable from the viewpoint of obtaining in-plane uniform characteristics of the polarizer. The temperature of the aqueous solution is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time is not particularly limited, but is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The total draw ratio of the polyvinyl alcohol film is about 3 to 7 times, preferably 5 to 7 times the original length. When the total draw ratio exceeds 7 times, the film is easily broken. Stretching may be carried out after a swelling step or after dyeing with iodine, or may be stretched while dyeing or crosslinking, or may be dyed with iodine after stretching. The stretching method and the number of stretching are not particularly limited, and may be performed only in any one step. Moreover, you may perform several times in the same process. The stretching method may be either wet or dry.

  In addition, the polyvinyl alcohol film subjected to iodine adsorption alignment treatment is further added to an aqueous iodide solution such as potassium iodide having a water temperature of about 10 to 60 ° C., preferably about 30 to 40 ° C. and a concentration of 0.1 to 10% by mass. A step of dipping for 1 minute to 1 minute can be provided. In the iodide aqueous solution, auxiliary agents such as zinc sulfate and zinc chloride may be added. The polyvinyl alcohol film subjected to the iodine adsorption alignment treatment can be provided with a water washing step and a drying step of about 20 to 80 ° C. for about 1 minute to 10 minutes.

  The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm. When the thickness of the polarizer is reduced, the moisture in the polarizer is likely to be volatilized in the drying process for bonding with the transparent protective film during the manufacturing process of the polarizing plate.

  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 and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A transparent protective film having a 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 transparent 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.

  When providing a transparent protective film on both sides of a polarizer, the transparent protective film which consists of the same polymer material may be used by the front and back, and the transparent protective film which consists of a different polymer material etc. may be used.

  As the transparent protective film, a cellulose film made of a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable.

  Further, as the transparent protective film, a norbornene-based resin film having a small photoelastic coefficient and hardly causing a shift or unevenness in a retardation value due to stress is preferable.

  Examples of the norbornene-based resin include, for example, ring-opening (co) polymers of norbornene-based monomers, polymer modified products such as maleic acid addition and cyclopentadiene addition thereof, and resins obtained by hydrogenating these; norbornene-based monomers A resin obtained by addition polymerization of a norbornene monomer and an olefin monomer such as ethylene or α-olefin. The polymerization method and the hydrogenation method can be performed by conventional methods.

  Examples of the norbornene-based monomer include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl. 2-Norbornene, 5-ethylidene-2-norbornene, and the like, polar substituents such as halogens thereof; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, its alkyl and / or alkylidene Substituents and polar group substituents such as halogen such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6- Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-oct Hydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano -1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a -Octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5 8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; 3-pentamer of cyclopentadiene, for example, 4,9: 5,8-dimethano-3a, 4 4a, 5,8,8a, 9,9a-octahydro-1H-benzoin 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene and the like. It is done.

  The norbornene-based resin can be used in combination with other cycloolefins capable of ring-opening polymerization within the range not impairing the object of the present invention. Specific examples of such cycloolefins include compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

  The norbornene-based resin has a number average molecular weight (Mn) of 25,000 to 200,000, preferably 30,000 to 100,000, more preferably measured by a gel permeation chromatograph (GPC) method using a toluene solvent. Is in the range of 40,000 to 80,000. When the number average molecular weight is in the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  When the norbornene-based resin is obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer, a hydrogenation rate of 90% or more is usually used from the viewpoint of heat deterioration resistance, light deterioration resistance, and the like. It is done. Preferably it is 95% or more. More preferably, it is 99% or more.

  The polymer film containing the norbornene-based resin can be obtained by a generally used casting method or melt extrusion method. The norbornene resin forming the polymer film may be used alone or in combination of two or more. When mixing and using resin, the mixing method is not particularly limited. For example, when producing a film by using a casting method, the mixed components may be stirred and mixed together with a solvent at a predetermined ratio and used as a uniform solution. it can. Moreover, when producing a film using a melt extrusion method, both can be melt-mixed and used in a predetermined ratio. In order to improve the smoothness of the obtained retardation film and obtain good optical uniformity, a casting method from a solution is preferably used.

  Examples of the norbornene resin products include ZEONEX and ZEONOR manufactured by Nippon Zeon Co., Ltd., Arton manufactured by JSR Corporation, and TOPAS manufactured by TICONA.

  The transparent protective film includes (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. A film formed by containing is preferable. Such a transparent protective film can also contain other resins even when the thermoplastic resins (A) and (B) are the main components. Such a transparent protective film can suppress the retardation even when stretched.

  The thermoplastic resin (A) has a substituted and / or unsubstituted imide group in the side chain, and the main chain is an arbitrary thermoplastic resin. The main chain may be, for example, a main chain composed only of carbon, or atoms other than carbon may be inserted between carbons. Moreover, you may consist of atoms other than carbon. The main chain is preferably a hydrocarbon or a substituted product thereof. The main chain is obtained, for example, by addition polymerization. Specifically, for example, polyolefin or polyvinyl. The main chain is obtained by condensation polymerization. For example, it can be obtained by an ester bond or an amide bond. The main chain is preferably a polyvinyl skeleton obtained by polymerizing a substituted vinyl monomer.

  Any conventionally known method can be adopted as a method for introducing a substituted and / or unsubstituted imide group into the thermoplastic resin (A). For example, a method of polymerizing a monomer having the imide group, a method of polymerizing various monomers to form a main chain, and then introducing the imide group, a method of grafting the compound having the imide group to a side chain, etc. It is done. As the substituent of the imide group, a conventionally known substituent that can replace the hydrogen of the imide group can be used. For example, an alkyl group etc. are mention | raise | lifted.

  The thermoplastic resin (A) is a binary copolymer having at least one repeating unit derived from at least one olefin and at least one repeating unit having a substituted and / or unsubstituted maleimide structure. Is preferred. The olefin / maleimide copolymer can be synthesized from an olefin and a maleimide compound by a known method. The synthesis method is described in, for example, JP-A-5-59193, JP-A-5-196801, JP-A-6-1336058 and JP-A-9-328523.

  Examples of the olefin include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 2-methyl-1-heptene, 1-isooctene, 2-methyl- Examples thereof include 1-octene, 2-ethyl-1-pentene, 2-ethyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene and the like. Of these, isobutene is preferred. These olefins may be used alone or in combination of two or more.

  As maleimide compounds, maleimide, N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ns-butylmaleimide, Nt-butyl Maleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclopropylmaleimide, N-cyclo Examples thereof include butyl maleimide, N-cyclopentyl maleimide, N-cyclohexyl maleimide, N-cycloheptyl maleimide, N-cyclooctyl maleimide and the like. Of these, N-methylmaleimide is preferred. These maleimide compounds may be used alone or in combination of two or more.

  In the olefin / maleimide copolymer, the content of the repeating unit of the olefin is not particularly limited, but is about 20 to 70 mol%, preferably 40 to 60 mol%, more preferably about the total repeating unit of the thermoplastic resin (A). It is 45 to 55 mol%. The content of repeating units having a maleimide structure is about 30 to 80 mol%, preferably 40 to 60 mol%, and more preferably 45 to 55 mol%.

  A thermoplastic resin (A) contains the repeating unit of the said olefin and the repeating unit of a maleimide structure, and can be formed only with these units. In addition to the above, repeating units of other vinyl monomers may be contained in a proportion of 50 mol% or less. Other vinyl monomers include acrylic acid monomers such as methyl acrylate and butyl acrylate, methacrylic acid monomers such as methyl methacrylate and cyclohexyl methacrylate, and vinyl ester monomers such as vinyl acetate. And vinyl ether monomers such as methyl vinyl ether, acid anhydrides such as maleic anhydride, and styrene monomers such as styrene, α-methylstyrene, and p-methoxystyrene.

The weight average molecular weight of the thermoplastic resin (A) is not particularly limited, but is about 1 × 10 ^{3 to} 5 × 10 ⁶ . The weight average molecular weight is preferably 1 × 10 ⁴ or more, and more preferably 5 × 10 ⁵ or less. The glass transition temperature of the thermoplastic resin (A) is 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 130 ° C. or higher.

  Moreover, as a thermoplastic resin (A), a glutarimide type thermoplastic resin can be used. Glutarimide resins are described in JP-A-2-153904. The glutarimide-based resin has a glutarimide structural unit and a methyl acrylate or methyl methacrylate structural unit. The other vinyl monomers can also be introduced into the glutarimide resin.

  The thermoplastic resin (B) is a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. The main chain of a thermoplastic resin (B) can illustrate the thing similar to a thermoplastic resin (A).

  Examples of the method of introducing the phenyl group into the thermoplastic resin (B) include a method of polymerizing the monomer having the phenyl group, a method of introducing a phenyl group after polymerizing various monomers to form a main chain, Examples thereof include a method of grafting a compound having a phenyl group onto a side chain. As the substituent of the phenyl group, a conventionally known substituent that can replace hydrogen of the phenyl group can be used. For example, an alkyl group can be mentioned. The method for introducing a nitrile group into the thermoplastic resin (B) can be the same as the method for introducing a phenyl group.

  The thermoplastic resin (B) is a binary or ternary multi-copolymer comprising a repeating unit derived from an unsaturated nitrile compound (nitrile unit) and a repeating unit derived from a styrene compound (styrene unit). It is preferably a coalescence. For example, an acrylonitrile / styrene copolymer can be preferably used.

  The unsaturated nitrile compound includes any compound having a cyano group and a reactive double bond. Examples thereof include α-substituted unsaturated nitriles such as acrylonitrile and methacrylonitrile, and nitrile compounds having an α, β-disubstituted olefinically unsaturated bond such as fumaronitrile.

  Examples of the styrenic compound include any compound having a phenyl group and a reactive double bond. Examples thereof include unsubstituted or substituted styrene compounds such as styrene, vinyl toluene, methoxystyrene, and chlorostyrene, and α-substituted styrene compounds such as α-methylstyrene.

  The content of the nitrile unit in the thermoplastic resin (B) is not particularly limited, but is about 10 to 70% by weight, preferably 20 to 60% by weight, more preferably 20 to 50% by weight based on the total repeating units. is there. 20 to 40 weight% and 20 to 30 weight% are especially preferable. The styrenic unit is about 30 to 90% by weight, preferably 40 to 80% by weight, and more preferably 50 to 80% by weight. 60 to 80 weight% and 70 to 80 weight% are especially preferable.

  A thermoplastic resin (B) contains the said nitrile unit and a styrene-type unit, and can be formed only with these units. In addition to the above, repeating units of other vinyl monomers may be contained in a proportion of 50 mol% or less. Examples of the other vinyl monomers include those exemplified for the thermoplastic resin (A), olefin repeating units, maleimide, substituted maleimide repeating units, and the like. Examples of the thermoplastic resin (B) include AS resin, ABS resin, ASA resin, and the like.

The weight average molecular weight of the thermoplastic resin (B) is not particularly limited, but is about 1 × 10 ^{3 to} 5 × 10 ⁶ . It is preferably 1 × 10 ⁴ or more and 5 × 10 ⁵ or less.

  The ratio of the thermoplastic resin (A) and the thermoplastic resin (B) is adjusted according to the retardation required for the protective film. In general, the content of the thermoplastic resin (A) is preferably 50 to 95% by weight, more preferably 60 to 95% by weight, based on the total amount of the resin in the film. More preferably, it is 65 to 90% by weight. The content of the thermoplastic resin (B) is preferably 5 to 50% by weight of the total amount of the resin in the film, more preferably 5 to 40% by weight, and still more preferably 10 to 35% by weight. %. The thermoplastic resin (A) and the thermoplastic resin (B) are mixed by hot-melt kneading them.

  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. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 20 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 the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 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.

  In this invention, the polarizer which is a uniaxially stretched film containing the said dichroic substance, and a transparent protective film are bonded together continuously. The polarizer travels in the uniaxial stretching direction, and the transparent protective film is bonded to the polarizer after stretching in the width direction.

  As described above, the draw ratio in the width direction is more than 1 time and 2 times or less. Examples of the stretching method in the width direction include a method using a curved roll, a method using a crown roll whose central portion is lower than both ends, and a tenter stretching method.

  An adhesive is usually used for bonding the polarizer and the 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. Adhesives include cross-linking agents, silane coupling agents, coupling agents such as titanium coupling agents, various tackifiers, UV absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers and other stabilizers, etc. Can also be blended.

  The surface of the transparent protective film that adheres to the polarizer can be subjected to an easy adhesion treatment. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment, and coating treatment for forming an easy adhesive layer. Among these, the coating process which forms an easily adhesive layer is suitable. For the formation of the easy-adhesive layer, various easy-adhesive materials such as polyol resin, polycarboxylic acid resin, and polyester resin can be used. The thickness of the easy-adhesive layer is usually 10 μm or less, preferably about 0.01 to 10 μm.

  The adhesive may be applied to either the transparent protective film or the polarizer, or to both. The application operation is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed. 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 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 5 μm or less, preferably about 0.1 to 5 μm.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  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. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that 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 light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

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

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  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.

  Attaching the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator in accordance with the above, and this is applied to a polarizing plate or an optical film The method of transferring to is included.

  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. Each physical property was measured by the following method.

  Glass transition temperature (Tg: ° C.): measured by TMA method.

  Haze (%): Measured with a haze meter HM150 manufactured by Murakami Color Research Laboratory.

  Single transmittance (%): Measured with a spectrophotometer U-4100 with an integrating sphere manufactured by Hitachi, Ltd.

Example 1
(Production of polarizer)
A polyvinyl alcohol film having a thickness of 80 μm and a width of 3100 mm (manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 99.9 mol%, length 800 m) is immersed in pure water at 30 ° C. for 60 seconds to swell. At the same time, the film was uniaxially stretched in the length direction (flow direction) to a draw ratio of 2.5 times. Next, the film was immersed in an aqueous solution of 0.05% iodine / potassium iodide (weight ratio = 1/10) at 30 ° C. for 60 seconds and stretched so that the total draw ratio was 2.8 times, and then 40 ° C. In an aqueous solution having a boric acid concentration of 3% by weight and a potassium iodide concentration of 2% by weight, the film was stretched until the total stretching ratio was tripled. Further, the film was stretched in an aqueous solution having a boric acid concentration of 4% by weight and a potassium iodide concentration of 3% by weight until the total stretching ratio reached 6 times. Thereafter, the film was immersed in an aqueous solution at 25 ° C. with a potassium iodide concentration of 5% by weight for 30 seconds without stretching. Next, drying was performed for 1 minute at 40 ° C. while maintaining the tension, and a polarizer having a thickness of 20 μm and a width of 1550 mm was obtained. The polarizer was manufactured continuously.

(Transparent protective film)
A lateral stretching machine (Hirano Giken Kogyo Co., Ltd.) running a triacetyl cellulose film (Fuji Photo Film Co., Ltd., TDY80UL, length 3900 m, Tg: 145 ° C.) having a thickness of 80 μm and a width of 1475 mm in the length direction (flow direction). (Made by Co., Ltd.) was stretched 1.13 times in the width direction at 165 ° C. to obtain a stretched transparent protective film having a thickness of 70 μm and a width of 1600 mm. The stretched transparent protective film was produced continuously. The obtained stretched transparent film had a haze of 3% and a single substance transmittance of 97%.

(Preparation of polarizing plate)
While running the polarizer and the stretched transparent protective film in the length direction (flow direction), a stretched transparent protective film was continuously bonded to both sides of the polarizer with a polyvinyl alcohol adhesive to produce a polarizing plate. .

(Evaluation)
A 68-inch type (1505 mm × 889 mm) could be cut from the obtained polarizing plate. A durability test (80 ° C. × 500 hours and 60 ° C./90% RH × 500 hours) was performed on the polarizing plate applied with an adhesive and bonded to a glass substrate, and the warpage of the polarizing plate was measured. . The warpage was calculated from the average value of four points by placing the polarizing plate used for evaluation on a flat plate, measuring the heights of the four corners with a ruler. The warpage was as small as 1.5 mm, which was a good result.

Comparative Example 1
(Polarizer)
In Example 1, a polarizer having a thickness of 20 μm and a width of 1475 mm was obtained in the same manner as in Example 1 except that a polyvinyl alcohol film having a thickness of 80 μm and a width of 2900 mm was used.

(Transparent protective film)
In Example 1, a triacetyl cellulose film having a thickness of 80 μm and a width of 1475 mm was used as it was without being stretched in the width direction.

(Preparation of polarizing plate)
While running the polarizer and transparent protective film in the length direction (flow direction), a stretched transparent protective film was continuously bonded to both sides of the polarizer with a polyvinyl alcohol adhesive to produce a polarizing plate.

(Evaluation)
From the obtained polarizing plate, a maximum 60-inch type (1328 mm × 784 mm) could only be cut. This polarizing plate was subjected to the same durability test as in Example 1 to measure the warpage of the polarizing plate. The warpage was as large as 5 mm and was bad.

Claims (9)

A method for producing a polarizing plate, wherein a transparent protective film is provided on at least one surface of a polarizer,
The polarizer is a uniaxially stretched film containing a dichroic substance, the polarizer travels in the uniaxially stretched direction,
The method for producing a polarizing plate, wherein the transparent protective film is continuously bonded to the polarizer after being stretched in the width direction. The polarizer has a width of 1500 mm or more,
The method for producing a polarizing plate according to claim 1, wherein the transparent protective film after stretching in the width direction has a width of 1500 mm or more.   3. The method for producing a polarizing plate according to claim 1, wherein the transparent protective film has a stretching ratio in the width direction of more than 1 and not more than 2 times.   The temperature at which the transparent protective film is stretched in the width direction is -20 ° C to Tg to + 50 ° C based on the glass transition temperature (Tg) of the transparent protective film. The manufacturing method of the polarizing plate of description.   The transparent protective film after extending | stretching to the width direction is 10% or less of haze, The manufacturing method of the polarizing plate in any one of Claims 1-4 characterized by the above-mentioned.   The transparent protective film includes a cellulose resin film, a norbornene resin film, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substituted and / or unsubstituted side chain. The method for producing a polarizing plate according to any one of claims 1 to 5, comprising at least one selected from films containing a thermoplastic resin having a phenyl group and a nitrile group.   The polarizing plate obtained by the manufacturing method in any one of Claims 1-6.   8. An optical film, wherein at least one polarizing plate according to claim 7 is laminated.   An image display device comprising the polarizing plate according to claim 7 or the optical film according to claim 8.