WO2013054626A1 - Manufacturing method for polarizing film - Google Patents

Manufacturing method for polarizing film Download PDF

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Publication number
WO2013054626A1
WO2013054626A1 PCT/JP2012/073355 JP2012073355W WO2013054626A1 WO 2013054626 A1 WO2013054626 A1 WO 2013054626A1 JP 2012073355 W JP2012073355 W JP 2012073355W WO 2013054626 A1 WO2013054626 A1 WO 2013054626A1
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Prior art keywords
treatment
film
water
polarizing
polarizing film
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PCT/JP2012/073355
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French (fr)
Japanese (ja)
Inventor
ムニルディン 矢仙
尾込　大介
済木　雄二
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日東電工株式会社
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Application filed by 日東電工株式会社 filed Critical 日東電工株式会社
Priority to KR1020137031992A priority Critical patent/KR101626194B1/en
Priority to CN201280042812.1A priority patent/CN103765259B/en
Publication of WO2013054626A1 publication Critical patent/WO2013054626A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements

Definitions

  • the present invention relates to a method for producing a polarizing film.
  • the present invention also relates to a polarizing plate using the polarizing film.
  • the polarizing film 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.
  • a polarizing film used for a liquid crystal display device or the like an absorption dichroic polarizing film formed by uniaxially stretching a polyvinyl alcohol film dyed with iodine or a dichroic dye has been widely used.
  • the polarizing film is used as a polarizing plate supplemented with strength by sticking a transparent protective film such as saponified triacetyl cellulose on both sides or one side.
  • Patent Document 1 for the purpose of improving polarization performance, a polyvinyl alcohol film is swollen with swelling water, heated and humidified with high humidity and low temperature warm air, and then dyed with a dye solution of a dichroic dye.
  • a method for producing a polarizing film which comprises drawing weakly in a drawing solution and then drawing strongly.
  • the polarizing film obtained by the above production method is not satisfactory in terms of contrast, and there is a problem that light leakage tends to occur in a short wavelength region.
  • An object of the present invention is to provide a method for producing a polarizing film having high contrast and excellent polarization characteristics capable of preventing light leakage in a short wavelength region.
  • the present inventors have found that the object can be achieved by the following polarizing film manufacturing method, and have completed the present invention.
  • the present invention provides a polarizing film manufacturing method in which at least a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, and a washing treatment are performed on a polyvinyl alcohol film.
  • a swelling treatment at least a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, and a washing treatment are performed on a polyvinyl alcohol film.
  • staining process it is related with the manufacturing method of the polarizing film characterized by including a water-soluble antioxidant in a process liquid so that following formula (1) may be satisfy
  • A is the concentration (mol / L) of the water-soluble antioxidant in the treatment bath
  • B is the reducing power of the water-soluble antioxidant that reduces iodine to iodine ions.
  • the iodine complex in the polarizing film absorbs light in the visible light region and exhibits polarization characteristics.
  • As a method for suppressing light leakage of the polarizing film it is conceivable to increase the amount of iodine complex in the polarizing film.
  • the iodine complex increases in the PVA molecule, and there is an excess of iodine that is not complexed. In particular, the light transmittance of the polarizing film tends to decrease.
  • the present inventors adsorbed excessively on the PVA molecules by adding a water-soluble antioxidant so as to satisfy the formula (1) in the treatment liquid in at least one treatment after the crosslinking treatment. It has been found that iodine can be selectively removed. As a result, a high-contrast polarizing film can be obtained. Further, by reduction effect of the water-soluble antioxidant, excessively adsorbed iodine iodide ion in PVA molecule - is reduced to, I 3 (I) - complexes and I 5 - for iodide ion to form a complex is increased, consequently I 3 - complex and I 5 - complex can suppress light leakage in the short wavelength region of the polarizing film increases.
  • a ⁇ B in the above formula (1) is an index indicating the reducing ability to reduce iodine to iodine ion (I ⁇ ).
  • I ⁇ B is an index indicating the reducing ability to reduce iodine to iodine ion (I ⁇ ).
  • a ⁇ B is less than 0.0005, iodine excessively adsorbed on the PVA molecules cannot be sufficiently removed, so that the contrast of the polarizing film cannot be improved.
  • a ⁇ B exceeds 0.03, the iodine complex in the PVA film is broken and the polarization characteristics cannot be secured, and the PVA film is in a decolored state, so that the optical characteristics as a polarization film can be obtained. Disappear.
  • the water-soluble antioxidant is preferably at least one selected from the group consisting of ascorbic acid, sodium erythorbate, thiosulfate, and sulfite.
  • the polarizing film obtained by the above production method has a feature that it has high contrast and light leakage hardly occurs in a short wavelength region.
  • the present invention also relates to a polarizing plate in which a transparent protective film is laminated on at least one surface of the polarizing film.
  • the present invention also relates to an optical film in which at least one of the polarizing film or the polarizing plate is laminated.
  • the present invention relates to an image display device including the optical film.
  • the polarizing film according to the production method of the present invention has a high contrast that achieves both high transmittance and high degree of polarization, and has a feature that light leakage hardly occurs in a short wavelength region.
  • the display contrast of the liquid crystal display device is improved.
  • a polyvinyl alcohol film (hereinafter referred to as “PVA film”), which is a raw material for the polarizing film, can be used without particular limitation.
  • PVA film having a thickness of about 10 to 300 ⁇ m is used. The thickness is preferably 20 to 100 ⁇ m.
  • a polyvinyl alcohol film conventionally used for a polarizer is preferably used.
  • the material for the PVA film include polyvinyl alcohol and derivatives thereof.
  • Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid and alkyl esters thereof, acrylamide and the like. Can be given.
  • the degree of polymerization of polyvinyl alcohol is preferably about 100 to 10,000, and more preferably 1,000 to 10,000. A saponification degree of about 80 to 100 mol% is generally used.
  • PVA films include hydrophilic polymer films such as partially saponified ethylene / vinyl acetate copolymers, polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. can give.
  • additives such as a plasticizer and a surfactant may be added.
  • the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol.
  • the amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the PVA film.
  • the polarizing film of the present invention is produced by subjecting the PVA film to at least swelling treatment, dyeing treatment, crosslinking treatment, stretching treatment and washing treatment.
  • Swelling treatment is performed before dyeing treatment.
  • swelling of the PVA film also has an effect of preventing unevenness such as uneven coloring.
  • the swelling treatment is usually performed by immersing the film in a treatment solution.
  • a treatment liquid water, distilled water, or pure water is usually used. If the main component is water, the treatment liquid may contain a small amount of an iodide compound, a surfactant, an additive such as boric acid, alcohol, and the like. Further, when an iodide compound is contained in the treatment liquid, the concentration of the iodide compound is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.
  • the treatment temperature in the swelling treatment is usually preferably adjusted to about 20 to 45 ° C, more preferably 25 to 40 ° C. If there is swelling unevenness, the portion becomes uneven dyeing in the dyeing process, so that swelling unevenness is not generated.
  • the immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.
  • the swelling treatment may be performed together with the stretching treatment.
  • the film is preferably stretched 1.2 to 4 times the original length, more preferably 1.6 to 3 times.
  • the dyeing treatment is usually performed by immersing the film in a dyeing solution.
  • an iodine solution is generally used.
  • 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.
  • 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, preferably 0.02 to 8% by weight. %.
  • 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.
  • a boron compound is usually used as a crosslinking agent.
  • the crosslinking treatment may be performed together with the stretching treatment.
  • the crosslinking treatment can be performed multiple times.
  • the boron compound include boric acid and borax.
  • the boron compound is generally used in the form of an aqueous solution or a water-organic solvent mixed solution. Usually, an aqueous boric acid solution is used.
  • the boric acid concentration of the boric acid aqueous solution is about 0.1 to 13% by weight, preferably 2 to 13% by weight.
  • the boric acid aqueous solution or the like can contain an iodide compound such as potassium iodide. When the iodide compound is contained in the boric acid aqueous solution, the iodide compound concentration is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.
  • the crosslinking treatment can be performed by immersing the dyed PVA film in a boric acid aqueous solution or the like. In addition, it can be performed by applying or spraying a boric acid aqueous solution or the like to the film.
  • the treatment temperature in the crosslinking treatment is usually 25 ° C. or higher, preferably 30 to 85 ° C., more preferably 30 to 60 ° C.
  • the treatment time is usually 10 to 800 seconds, preferably 30 to 500 seconds.
  • the stretching process is usually performed by uniaxial stretching. This stretching process can be performed together with the dyeing process and the crosslinking process.
  • the stretching method either a wet stretching method or a dry stretching method can be adopted, but it is preferable to use a wet stretching method.
  • the wet stretching method for example, stretching is generally performed in a solution in a swelling process or after a dyeing process.
  • the stretching treatment can be performed after the crosslinking treatment or together with the crosslinking treatment.
  • examples of the stretching means include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. The stretching process can be performed in multiple stages.
  • An iodide compound such as potassium iodide can be contained in the treatment liquid used in the wet stretching method.
  • the iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.2 to 5% by weight.
  • the treatment temperature in the wet stretching method is usually 25 ° C. or higher, preferably 30 to 85 ° C., more preferably 50 to 70 ° C.
  • the immersion time is usually about 10 to 800 seconds, preferably about 30 to 500 seconds.
  • the draw ratio can be appropriately set according to the purpose, but the total draw ratio is about 2 to 9 times, preferably 4.5 to 6.8 times, more preferably 5 to 6.5 times.
  • the total stretching ratio refers to a cumulative stretching ratio including stretching in those steps when stretching is involved in a swelling process described later other than the stretching process.
  • the washing process can be performed by washing with water, distilled water, pure water or the like, for example.
  • the water washing treatment is usually performed by immersing the film in a water washing bath.
  • the washing treatment can be performed by immersing in an aqueous solution containing an iodide such as potassium iodide.
  • 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 cleaning liquid in the cleaning treatment is usually 5 to 50 ° C., preferably 10 to 45 ° C., more preferably 15 to 40 ° C.
  • the immersion time is usually 1 to 300 seconds, preferably 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.
  • an insolubilization treatment may be performed.
  • the insolubilization treatment is performed by immersing the PVA film in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA film.
  • the concentration of boric acid is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water.
  • the temperature of the boric acid aqueous solution is preferably 20 to 50 ° C.
  • the insolubilization treatment is usually performed before the swelling treatment or simultaneously with the swelling treatment, before the dyeing treatment, or before the crosslinking treatment.
  • a water-soluble antioxidant is contained in the treatment liquid so as to satisfy the following formula (1).
  • A is the concentration (mol / L) of the water-soluble antioxidant in the treatment bath
  • B is the reducing power of the water-soluble antioxidant that reduces iodine to iodine ions.
  • a ⁇ B is preferably 0.0008 to 0.025, more preferably 0.0015 to 0.02.
  • the calculation method of the reducing power of the water-soluble antioxidant is as described in the examples.
  • water-soluble antioxidant examples include ascorbic acid, erythorbic acid, chlorogenic acid, citric acid, rosmarinic acid, salts thereof, thiosulfate, and sulfite, and these can be used alone. Or two or more of them may be used in combination.
  • the salt examples include alkali metal salts such as sodium salt and potassium salt.
  • ascorbic acid, sodium erythorbate, or thiosulfate is preferably used from the viewpoint of stability in aqueous solution (sustainability of reducing power).
  • the water-soluble antioxidant is contained in at least one of the baths used for at least one treatment after the dyeing treatment, or separately in a treatment liquid containing the water-soluble antioxidant.
  • the swelling treatment is first applied.
  • a water-soluble antioxidant can be contained in a crosslinking process, a stretching process, a cleaning process, or a separate water-soluble antioxidant process.
  • stretching process can be performed by the batch process which performs a some process simultaneously.
  • a water-soluble antioxidant can be contained in the bath used for the batch process.
  • a water-soluble antioxidant can be contained in at least 1 process of the said multistage process.
  • the film may be dried.
  • the drying time and the drying temperature are appropriately set according to the moisture content required for the obtained polarizer (film).
  • the drying temperature is usually controlled in the range of 20 to 150 ° C, preferably 40 to 100 ° C.
  • the polarizing film produced by the above method can be a polarizing plate provided with a transparent protective film on at least one side in accordance with a conventional method.
  • the transparent protective film can be provided as a coating layer made of a polymer or a laminate layer of the film.
  • 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.
  • 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
  • styrene polymers such as styrene copolymers (AS resins), polycarbonate polymers, and the like.
  • 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.
  • a polymer film described in JP-A-2001-343529 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 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.
  • the thickness of the transparent protective film can be appropriately determined, but is generally about 1 to 500 ⁇ m from the viewpoints of workability such as strength and handleability, and thin layer properties. 1 to 300 ⁇ m is particularly preferable, and 5 to 200 ⁇ m is more preferable.
  • a transparent protective film having a direction retardation value of ⁇ 90 nm to +75 nm is preferably used.
  • the thickness direction retardation value (Rth) is more preferably ⁇ 80 nm to +60 nm, and particularly preferably ⁇ 70 nm to +45 nm.
  • a triacetyl cellulose film 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.
  • 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 polarizing film is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.
  • 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 polarizing film and the transparent protective film.
  • the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters.
  • 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 polarizing film using the adhesive.
  • coating of an adhesive agent may be performed to any of a transparent protective film and a polarizing film, and may be performed to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. Bonding of the polarizing film and the transparent protective film can be performed with a roll laminator or the like.
  • the thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 ⁇ m.
  • 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.
  • 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.
  • 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.
  • the polarizing plate or 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.
  • 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.
  • 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.
  • the liquid crystal cell any type such as a TN type, an STN type, or a ⁇ type can be used.
  • the reducing power of the water-soluble antioxidant was measured by the following volumetric titration method. 1 to 2 ml of a 0.5% aqueous starch solution (manufactured by Kishida Chemical Co., Ltd., for titration) was added to a 0.1% aqueous iodine solution (25 ml) and colored black.
  • a water-soluble antioxidant aqueous solution having a molar concentration of 0.01 mol / L was dropped into the colored iodine aqueous solution using a burette, and the titration amount (ml) when the color of the aqueous solution became colorless was determined as reducing power.
  • Example 1 A 75 ⁇ m-thick PVA film (trade name: VF-PS # 7500, manufactured by Kuraray Co., Ltd.) is immersed in pure water (swelling bath) at 30 ° C. for 1 minute to swell, and the draw ratio is 2 relative to the original length The film was stretched in the flow direction so as to be doubled. Thereafter, the PVA film was immersed in an iodine aqueous solution (dye bath) at 30 ° C. containing 0.045% iodine and 0.315% potassium iodide for 30 seconds, and the draw ratio was 3 with respect to the original length while dyeing. The film was stretched in the flow direction so as to be 3 times.
  • the film was stretched in the flow direction so that the stretch ratio was 3.6 times the original length while being immersed in an aqueous solution containing 3% boric acid and 3% potassium iodide for 30 seconds. . Thereafter, the film was immersed in a 60 ° C. aqueous solution (crosslinking bath) containing 4% boric acid, 5% potassium iodide and 0.0000662 mol / L ascorbic acid for 60 seconds, and the draw ratio with respect to the original length was The film was stretched in the flow direction so as to be 6.0 times. Thereafter, the film was immersed in a 30 ° C. aqueous solution (cleaning bath) containing 3% potassium iodide for 10 seconds for cleaning. Finally, the film was drained and dried for 4 minutes in an oven at 60 ° C. while maintaining tension to produce a polarizing film.
  • the spectral transmittance of the polarizing film at a wavelength of 380 to 780 nm was measured using a spectrophotometer with an integrating sphere (trade name: V7100, manufactured by JASCO Corporation).
  • the transmittance for each linearly polarized light was measured with 100% of the completely polarized light obtained through the Grantera-prism polarizing film.
  • the Y value in the C light source 2 ° field of view was calculated from the measured spectral transmittance according to the CIE1931 Yxy color system. These were designated 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 (%).
  • the dichroic ratio was calculated by substituting the single transmittance (Ts (Y)) and the degree of polarization (P) obtained by the above measurement into the following formula.
  • Dichroic ratio log [Ts (Y) /91.6 ⁇ ⁇ 1- (P / 100) ⁇ ] / log [Ts (Y) /91.6 ⁇ ⁇ 1+ (P / 100) ⁇ ]
  • the spectral transmittance of the polarizing film at a wavelength of 410 nm was measured using a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, trade name: V7100). The transmittance for each linearly polarized light was measured with 100% of the completely polarized light obtained through the Grantera-prism polarizing film.

Abstract

This manufacturing method for a polarizing film, in which at least a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, and a cleaning treatment are carried out on a polyvinyl alcohol film, is characterized in that during at least one of the treatments subsequent to the crosslinking treatment, a water-soluble antioxidant is added to the treatment liquid so as to satisfy the following formula (1): 0.0005≤A×B≤0.03 (1) (in the formula, A represents the concentration (mol/L) of the water-soluble antioxidant in the treatment bath, and B represents the reductive power of the water-soluble antioxidant in the reduction of iodine to iodine ions). This manufacturing method makes it possible to provide a polarizing film having high contrast and excellent polarizing capabilities for preventing the occurrence of light leakage in the short wavelength region.

Description

偏光フィルムの製造方法Manufacturing method of polarizing film
　本発明は偏光フィルムの製造方法に関する。また本発明は当該偏光フィルムを用いた偏光板に関する。前記偏光フィルム、偏光板はこれ単独で、またはこれを積層した光学フィルムとして液晶表示装置、有機ＥＬ表示装置等のフラットパネルディスプレー等の画像表示装置を形成しうる。 The present invention relates to a method for producing a polarizing film. The present invention also relates to a polarizing plate using the polarizing film. The polarizing film 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.
　従来、液晶表示装置などに用いられる偏光フィルムとしては、ポリビニルアルコール系フィルムを、ヨウ素や二色性染料などで染色し、一軸延伸して形成された吸収二色性偏光フィルムが広く用いられている。また、前記偏光フィルムは、その両側または片側に鹸化処理したトリアセチルセルロースなどの透明保護フィルムを貼り合わせて、強度を補った偏光板として用いられている。 Conventionally, as a polarizing film used for a liquid crystal display device or the like, an absorption dichroic polarizing film formed by uniaxially stretching a polyvinyl alcohol film dyed with iodine or a dichroic dye has been widely used. . Further, the polarizing film is used as a polarizing plate supplemented with strength by sticking a transparent protective film such as saponified triacetyl cellulose on both sides or one side.
　特に近年では、液晶表示装置の大型化、用途の多様性、機能の向上、及び輝度の向上に伴い、液晶表示装置に用いられる偏光板の光学特性の向上が求められており、高透過率かつ高偏光度、すなわち高コントラストの偏光板の開発が求められている。 Particularly in recent years, with the increase in size of liquid crystal display devices, diversity of applications, improvement of functions, and improvement of luminance, improvement of optical properties of polarizing plates used in liquid crystal display devices has been demanded. Development of a polarizing plate having a high degree of polarization, that is, a high contrast is required.
　例えば、特許文献１では、偏光性能を向上させることを目的として、ポリビニルアルコールフィルムを膨潤水により膨潤した後、高湿低温温風により加熱、加湿し、次いで二色性染料の染料液により染色し、延伸液中において弱延伸した後、強延伸することからなる偏光フィルムの製造方法が提案されている。 For example, in Patent Document 1, for the purpose of improving polarization performance, a polyvinyl alcohol film is swollen with swelling water, heated and humidified with high humidity and low temperature warm air, and then dyed with a dye solution of a dichroic dye. There has been proposed a method for producing a polarizing film, which comprises drawing weakly in a drawing solution and then drawing strongly.
　しかし、上記製造方法により得られる偏光フィルムもコントラストに関して満足できるものではなく、また短波長域で光漏れが生じやすいという問題があった。 However, the polarizing film obtained by the above production method is not satisfactory in terms of contrast, and there is a problem that light leakage tends to occur in a short wavelength region.
特開２００７－１９９５０９号公報JP 2007-199509 A
　本発明は、高コントラストであり、かつ短波長域における光漏れの発生を防止し得る偏光特性に優れた偏光フィルムの製造方法を提供することを目的とする。 An object of the present invention is to provide a method for producing a polarizing film having high contrast and excellent polarization characteristics capable of preventing light leakage in a short wavelength region.
　本発明者らは前記課題を解決すべく鋭意検討を重ねた結果、以下に示す偏光フィルムの製造方法により前記目的に達成できることを見出し、本発明を完成するに至った。 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 polarizing film manufacturing method, and have completed the present invention.
　すなわち本発明は、ポリビニルアルコール系フィルムに、膨潤処理、染色処理、架橋処理、延伸処理及び洗浄処理を少なくとも施す偏光フィルムの製造方法において、
　前記染色処理後の少なくとも１つの処理において、処理液中に水溶性酸化防止剤を下記式（１）を満たすように含有させることを特徴とする偏光フィルムの製造方法、に関する。
　０．０００５≦Ａ×Ｂ≦０．０３　　　　（１）
〔上記式中、Ａは処理浴中の水溶性酸化防止剤の濃度（ｍｏｌ／Ｌ）であり、Ｂはヨウ素をヨウ素イオンに還元する水溶性酸化防止剤の還元力である。〕 That is, the present invention provides a polarizing film manufacturing method in which at least a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, and a washing treatment are performed on a polyvinyl alcohol film.
In at least 1 process after the said dyeing | staining process, it is related with the manufacturing method of the polarizing film characterized by including a water-soluble antioxidant in a process liquid so that following formula (1) may be satisfy | filled.
0.0005 ≦ A × B ≦ 0.03 (1)
[In the above formula, A is the concentration (mol / L) of the water-soluble antioxidant in the treatment bath, and B is the reducing power of the water-soluble antioxidant that reduces iodine to iodine ions. ]
　偏光フィルムの光学特性は、ヨウ素とポリビニルアルコール（ＰＶＡ）分子の非晶部とによりＩ３ －錯体とＩ５ －錯体を形成し、当該錯体が形成された領域を延伸して配向させることによって発現する。 The optical properties of the polarizing film, I 3 by the amorphous portion of iodine and polyvinyl alcohol (PVA) molecule - expression by aligning to form a complex, and stretching the complex was formed region - complex and I 5 To do.
　一般的に、偏光フィルム中のヨウ素錯体が可視光領域の光を吸収して偏光特性を示す。偏光フィルムの光漏れを抑制する方法としては、偏光フィルム中のヨウ素錯体の量を増やすことが考えられる。しかし、ヨウ素錯体の量を増やすためにＰＶＡフィルムを高濃度の染色浴で処理すると、ＰＶＡ分子中にヨウ素錯体が増加すると伴に錯体形成していないヨウ素が過剰に存在することになるため、結果的に偏光フィルムの光透過率が低下する傾向にある。 Generally, the iodine complex in the polarizing film absorbs light in the visible light region and exhibits polarization characteristics. As a method for suppressing light leakage of the polarizing film, it is conceivable to increase the amount of iodine complex in the polarizing film. However, when the PVA film is treated with a high concentration dye bath to increase the amount of iodine complex, the iodine complex increases in the PVA molecule, and there is an excess of iodine that is not complexed. In particular, the light transmittance of the polarizing film tends to decrease.
　本発明者らは、上記のとおり、架橋処理後の少なくとも１つの処理において、処理液中に水溶性酸化防止剤を式（１）を満たすように含有させることにより、ＰＶＡ分子に過剰に吸着したヨウ素を選択的に除去することができることを見出した。その結果、高コントラストな偏光フィルムが得られる。また、水溶性酸化防止剤の還元効果によって、ＰＶＡ分子に過剰に吸着したヨウ素がヨウ素イオン（Ｉ－）に還元され、Ｉ３ －錯体及びＩ５ －錯体を形成するヨウ素イオンが増加するため、結果的にＩ３ －錯体及びＩ５ －錯体が増加して偏光フィルムの短波長域での光漏れを抑制することができる。 As described above, the present inventors adsorbed excessively on the PVA molecules by adding a water-soluble antioxidant so as to satisfy the formula (1) in the treatment liquid in at least one treatment after the crosslinking treatment. It has been found that iodine can be selectively removed. As a result, a high-contrast polarizing film can be obtained. Further, by reduction effect of the water-soluble antioxidant, excessively adsorbed iodine iodide ion in PVA molecule - is reduced to, I 3 (I) - complexes and I 5 - for iodide ion to form a complex is increased, consequently I 3 - complex and I 5 - complex can suppress light leakage in the short wavelength region of the polarizing film increases.
　上記式（１）の「Ａ×Ｂ」はヨウ素をヨウ素イオン（Ｉ－）に還元する還元能力を示す指標である。Ａ×Ｂが０．０００５未満の場合には、ＰＶＡ分子に過剰に吸着したヨウ素を十分に除去することができないため、偏光フィルムのコントラストを向上させることができない。一方、Ａ×Ｂが０．０３を超える場合には、ＰＶＡフィルム中のヨウ素錯体まで壊れて偏光特性を確保できず、ＰＶＡフィルムが脱色した状態になるため、偏光フィルムとしての光学特性が得られなくなる。 “A × B” in the above formula (1) is an index indicating the reducing ability to reduce iodine to iodine ion (I − ). When A × B is less than 0.0005, iodine excessively adsorbed on the PVA molecules cannot be sufficiently removed, so that the contrast of the polarizing film cannot be improved. On the other hand, when A × B exceeds 0.03, the iodine complex in the PVA film is broken and the polarization characteristics cannot be secured, and the PVA film is in a decolored state, so that the optical characteristics as a polarization film can be obtained. Disappear.
　前記水溶性酸化防止剤は、アスコルビン酸、エリソルビン酸ナトリウム、チオ硫酸塩、及び亜硫酸塩からなる群より選択される少なくとも１種であることが好ましい。 The water-soluble antioxidant is preferably at least one selected from the group consisting of ascorbic acid, sodium erythorbate, thiosulfate, and sulfite.
　前記製造方法により得られる偏光フィルムは、高コントラストであり、かつ短波長域で光漏れが起こり難いという特徴を有する。 The polarizing film obtained by the above production method has a feature that it has high contrast and light leakage hardly occurs in a short wavelength region.
　また、本発明は、前記偏光フィルムの少なくとも一方の面に透明保護フィルムが積層されている偏光板、に関する。 The present invention also relates to a polarizing plate in which a transparent protective film is laminated on at least one surface of the polarizing film.
　また、本発明は、前記偏光フィルム又は前記偏光板が少なくとも１枚積層されている光学フィルム、に関する。 The present invention also relates to an optical film in which at least one of the polarizing film or the polarizing plate is laminated.
　さらに、本発明は、前記光学フィルムを含む画像表示装置、に関する。 Furthermore, the present invention relates to an image display device including the optical film.
　本発明の製造方法により偏光フィルムは、高透過率及び高偏光度を両立した高コントラストなものであり、しかも短波長域で光漏れが生じ難いという特徴を有する。当該偏光フィルムを用いることにより、液晶表示装置の表示コントラストが向上する。 The polarizing film according to the production method of the present invention has a high contrast that achieves both high transmittance and high degree of polarization, and has a feature that light leakage hardly occurs in a short wavelength region. By using the polarizing film, the display contrast of the liquid crystal display device is improved.
　偏光フィルムの原料であるポリビニルアルコール系フィルム（以下、「ＰＶＡフィルム」という）は公知のものを特に制限なく使用できる。通常、ＰＶＡフィルムは厚さ１０～３００μｍ程度のものが用いられる。好ましくは２０～１００μｍである。 A polyvinyl alcohol film (hereinafter referred to as “PVA film”), which is a raw material for the polarizing film, can be used without particular limitation. Usually, a PVA film having a thickness of about 10 to 300 μm is used. The thickness is preferably 20 to 100 μm.
　ＰＶＡフィルムとしては、例えば、従来、偏光子に用いられているポリビニルアルコール系フィルムが好適に用いられる。ＰＶＡフィルムの材料としては、ポリビニルアルコールまたはその誘導体があげられる。ポリビニルアルコールの誘導体としては、ポリビニルホルマール、ポリビニルアセタール等があげられる他、エチレン、プロピレン等のオレフィン、アクリル酸、メタクリル酸、クロトン酸等の不飽和カルボン酸及びそのアルキルエステル、アクリルアミド等で変性したものがあげられる。ポリビニルアルコールの重合度は、１００～１００００程度が好ましく、１０００～１００００がより好ましい。ケン化度は８０～１００モル％程度のものが一般に用いられる。 As the PVA film, for example, a polyvinyl alcohol film conventionally used for a polarizer is preferably used. Examples of the material for the PVA film include polyvinyl alcohol and derivatives thereof. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid and alkyl esters thereof, acrylamide and the like. Can be given. The degree of polymerization of polyvinyl alcohol is preferably about 100 to 10,000, and more preferably 1,000 to 10,000. A saponification degree of about 80 to 100 mol% is generally used.
　上記の他、ＰＶＡフィルムとしては、エチレン・酢酸ビニル共重合体系部分ケン化フィルム等の親水性高分子フィルム、ポリビニルアルコールの脱水処理物やポリ塩化ビニルの脱塩酸処理物等ポリエン系配向フィルム等があげられる。 In addition to the above, PVA films include hydrophilic polymer films such as partially saponified ethylene / vinyl acetate copolymers, polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. can give.
　ＰＶＡフィルム中には、可塑剤、界面活性剤等の添加剤を添加してもよい。可塑剤としては、ポリオールおよびその縮合物等があげられ、たとえばグリセリン、ジグリセリン、トリグリセリン、エチレングリコール、プロピレングリコール、ポリエチレングリコール等があげられる。可塑剤等の使用量は、特に制限されないがＰＶＡフィルム中に２０重量％以下とするのが好適である。 In the PVA film, additives such as a plasticizer and a surfactant may be added. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the PVA film.
　本発明の偏光フィルムは、前記ＰＶＡフィルムに、少なくとも膨潤処理、染色処理、架橋処理、延伸処理及び洗浄処理を施すことにより製造する。 The polarizing film of the present invention is produced by subjecting the PVA film to at least swelling treatment, dyeing treatment, crosslinking treatment, stretching treatment and washing treatment.
　膨潤処理は、染色処理の前に施される。膨潤処理により、ＰＶＡフィルム表面の汚れやブロッキング防止剤を洗浄することができるほかに、ＰＶＡフィルムを膨潤させることで染色のムラなどの不均一を防止する効果もある。 Swelling treatment is performed before dyeing treatment. In addition to washing the surface of the PVA film and the anti-blocking agent by the swelling treatment, swelling of the PVA film also has an effect of preventing unevenness such as uneven coloring.
　膨潤処理は、通常、前記フィルムを処理液に浸漬することにより行われる。処理液としては、通常、水、蒸留水、純水が用いられる。当該処理液は、主成分が水であれば、ヨウ化化合物、界面活性剤、ホウ酸等の添加物、アルコール等が少量入っていてもよい。また、当該処理液にヨウ化化合物を含有させる場合、ヨウ化化合物の濃度は０．１～１０重量％程度であり、好ましくは０．２～５重量％である。 The swelling treatment is usually performed by immersing the film in a treatment solution. As the treatment liquid, water, distilled water, or pure water is usually used. If the main component is water, the treatment liquid may contain a small amount of an iodide compound, a surfactant, an additive such as boric acid, alcohol, and the like. Further, when an iodide compound is contained in the treatment liquid, the concentration of the iodide compound is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.
　膨潤処理における処理温度は、通常２０～４５℃程度に調整するのが好ましく、より好ましくは２５～４０℃である。なお、膨潤ムラがあるとその部分が染色処理において染色のムラになるため膨潤ムラは発生させないようにする。浸漬時間は通常１０～３００秒間程度、好ましくは２０～２４０秒間である。 The treatment temperature in the swelling treatment is usually preferably adjusted to about 20 to 45 ° C, more preferably 25 to 40 ° C. If there is swelling unevenness, the portion becomes uneven dyeing in the dyeing process, so that swelling unevenness is not generated. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.
　膨潤処理は、延伸処理とともに行ってもよい。その場合、フィルムを元長に対して１．２～４倍延伸することが好ましく、より好ましは１．６～３倍である。 The swelling treatment may be performed together with the stretching treatment. In that case, the film is preferably stretched 1.2 to 4 times the original length, more preferably 1.6 to 3 times.
　染色処理は、通常、前記フィルムを染色溶液に浸漬することにより行われる。染色溶液としてはヨウ素溶液が一般的である。ヨウ素溶液として用いられるヨウ素水溶液は、ヨウ素および溶解助剤として例えばヨウ化カリウム等によりヨウ素イオンを含有させた水溶液などが用いられる。その他、ヨウ化リチウム、ヨウ化ナトリウム、ヨウ化亜鉛、ヨウ化アルミニウム、ヨウ化鉛、ヨウ化銅、ヨウ化バリウム、ヨウ化カルシウム、ヨウ化錫、ヨウ化チタン等のヨウ化物等の助剤を用いることができる。ヨウ素濃度は０．０１～０．５重量％程度、好ましくは０．０２～０．４重量％であり、ヨウ化カリウム濃度は０．０１～１０重量％程度、好ましくは０．０２～８重量％である。ヨウ素染色にあたり、ヨウ素溶液の温度は、通常２０～５０℃程度、好ましくは２５～４０℃である。浸漬時間は通常１０～３００秒間程度、好ましくは２０～２４０秒間である。 The dyeing treatment is usually 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, preferably 0.02 to 8% by weight. %. 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.
　架橋処理においては、通常、架橋剤としてホウ素化合物が用いられる。架橋処理は、延伸処理とともに行ってもよい。架橋処理は複数回行うことができる。ホウ素化合物としては、ホウ酸、ホウ砂等があげられる。ホウ素化合物は、水溶液または水－有機溶媒混合溶液の形態で一般に用いられる。通常は、ホウ酸水溶液が用いられる。ホウ酸水溶液のホウ酸濃度は、０．１～１３重量％程度、好ましくは２～１３重量％である。ホウ酸水溶液等には、ヨウ化カリウム等のヨウ化化合物を含有させることができる。ホウ酸水溶液にヨウ化化合物を含有させる場合、ヨウ化化合物濃度は０．１～１０重量％程度であり、好ましくは０．２～５重量％である。 In the crosslinking treatment, a boron compound is usually used as a crosslinking agent. The crosslinking treatment may be performed together with the stretching treatment. The crosslinking treatment can be performed multiple times. Examples of the boron compound include boric acid and borax. The boron compound is generally used in the form of an aqueous solution or a water-organic solvent mixed solution. Usually, an aqueous boric acid solution is used. The boric acid concentration of the boric acid aqueous solution is about 0.1 to 13% by weight, preferably 2 to 13% by weight. The boric acid aqueous solution or the like can contain an iodide compound such as potassium iodide. When the iodide compound is contained in the boric acid aqueous solution, the iodide compound concentration is about 0.1 to 10% by weight, preferably 0.2 to 5% by weight.
　架橋処理は、染色処理したＰＶＡフィルムをホウ酸水溶液等へ浸漬することにより行うことができる。その他、前記フィルムに、ホウ酸水溶液等を塗布又は噴霧等することにより行うことができる。架橋処理における処理温度は、通常２５℃以上であり、好ましくは３０～８５℃、より好ましくは３０～６０℃である。処理時間は、通常１０～８００秒間であり、好ましくは３０～５００秒間である。 The crosslinking treatment can be performed by immersing the dyed PVA film in a boric acid aqueous solution or the like. In addition, it can be performed by applying or spraying a boric acid aqueous solution or the like to the film. The treatment temperature in the crosslinking treatment is usually 25 ° C. or higher, preferably 30 to 85 ° C., more preferably 30 to 60 ° C. The treatment time is usually 10 to 800 seconds, preferably 30 to 500 seconds.
　延伸処理は、通常、一軸延伸を施すことにより行う。この延伸処理は、染色処理、架橋処理とともに施すことができる。延伸方法は、湿潤式延伸方法と乾式延伸方法のいずれも採用できるが湿潤式延伸方法を用いるのが好ましい。湿潤式延伸方法としては、例えば、膨潤処理において、又は染色処理を施した後、溶液中で延伸を行うことが一般的である。また架橋処理後、あるいは架橋処理とともに延伸処理を行うことができる。一方、乾式延伸の場合は、延伸手段としては、例えば、ロール間延伸方法、加熱ロール延伸方法、圧縮延伸方法等があげられる。延伸処理は多段で行うこともできる。 The stretching process is usually performed by uniaxial stretching. This stretching process can be performed together with the dyeing process and the crosslinking process. As the stretching method, either a wet stretching method or a dry stretching method can be adopted, but it is preferable to use a wet stretching method. As the wet stretching method, for example, stretching is generally performed in a solution in a swelling process or after a dyeing process. Further, the stretching treatment can be performed after the crosslinking treatment or together with the crosslinking treatment. On the other hand, in the case of dry stretching, examples of the stretching means include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. The stretching process can be performed in multiple stages.
　湿潤式延伸方法に用いる処理液にヨウ化カリウム等のヨウ化化合物を含有させることができる。当該処理液にヨウ化化合物を含有させる場合、ヨウ化化合物濃度は０．１～１０重量％程度、さらには０．２～５重量％で用いるのが好ましい。湿潤式延伸方法における処理温度は、通常、２５℃以上、好ましくは３０～８５℃、さらには５０～７０℃の範囲である。浸漬時間は、通常、１０～８００秒間、好ましくは３０～５００秒間程度である。 An iodide compound such as potassium iodide can be contained in the treatment liquid used in the wet stretching method. When the treatment liquid contains an iodide compound, the iodide compound concentration is preferably about 0.1 to 10% by weight, more preferably 0.2 to 5% by weight. The treatment temperature in the wet stretching method is usually 25 ° C. or higher, preferably 30 to 85 ° C., more preferably 50 to 70 ° C. The immersion time is usually about 10 to 800 seconds, preferably about 30 to 500 seconds.
　延伸倍率は目的に応じて適宜に設定できるが、総延伸倍率は２～９倍程度、好ましくは４．５～６．８倍、より好ましくは５～６．５倍である。前記総延伸倍率は、延伸工程以外の、後述の膨潤工程等において延伸を伴う場合には、それらの工程における延伸を含めた累積の延伸倍率をいう。 The draw ratio can be appropriately set according to the purpose, but the total draw ratio is about 2 to 9 times, preferably 4.5 to 6.8 times, more preferably 5 to 6.5 times. The total stretching ratio refers to a cumulative stretching ratio including stretching in those steps when stretching is involved in a swelling process described later other than the stretching process.
　洗浄処理は、例えば、水、蒸留水、純水等の水洗浄により行うことができる。水洗浄処理は、通常、水洗浄浴にフィルムを浸漬することにより行う。また洗浄処理は、ヨウ化カリウム等のヨウ化物を含有する水溶液に浸漬することにより行うことができる。例えば、当該水溶液としては、ヨウ化カリウム濃度０．５～１０重量％程度、さらには１～８重量％とするのが好ましい。洗浄処理における洗浄液の温度は、通常、５～５０℃、好ましくは１０～４５℃、さらに好ましくは１５～４０℃である。浸漬時間は、通常、１～３００秒間、好ましくは１０～２４０秒間である。なお、前記水溶液による洗浄は、水洗浄と組み合わせて行うことができ、水洗浄の前または後において行うことができる。 The washing process can be performed by washing with water, distilled water, pure water or the like, for example. The water washing treatment is usually performed by immersing the film in a water washing bath. The washing treatment can be performed by immersing in an aqueous solution containing an iodide 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 cleaning liquid in the cleaning treatment is usually 5 to 50 ° C., preferably 10 to 45 ° C., more preferably 15 to 40 ° C. The immersion time is usually 1 to 300 seconds, preferably 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.
　上記処理以外に、不溶化処理を施してもよい。不溶化処理は、ホウ酸水溶液にＰＶＡフィルムを浸漬させることにより行う。不溶化処理を施すことにより、ＰＶＡフィルムに耐水性を付与することができる。ホウ酸の濃度は、水１００重量部に対して１～４重量部であることが好ましい。ホウ酸水溶液の温度は２０～５０℃であることが好ましい。不溶化処理は、通常、膨潤処理前又は膨潤処理と同時、染色処理前、あるいは架橋処理前に行われる。 In addition to the above treatment, an insolubilization treatment may be performed. The insolubilization treatment is performed by immersing the PVA film in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA film. The concentration of boric acid is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. The temperature of the boric acid aqueous solution is preferably 20 to 50 ° C. The insolubilization treatment is usually performed before the swelling treatment or simultaneously with the swelling treatment, before the dyeing treatment, or before the crosslinking treatment.
　本発明の製造方法においては、前記染色処理後の少なくとも１つの処理において、処理液中に水溶性酸化防止剤を下記式（１）を満たすように含有させる。
　０．０００５≦Ａ×Ｂ≦０．０３　　　　（１）
〔上記式中、Ａは処理浴中の水溶性酸化防止剤の濃度（ｍｏｌ／Ｌ）であり、Ｂはヨウ素をヨウ素イオンに還元する水溶性酸化防止剤の還元力である。〕 In the production method of the present invention, in at least one treatment after the dyeing treatment, a water-soluble antioxidant is contained in the treatment liquid so as to satisfy the following formula (1).
0.0005 ≦ A × B ≦ 0.03 (1)
[In the above formula, A is the concentration (mol / L) of the water-soluble antioxidant in the treatment bath, and B is the reducing power of the water-soluble antioxidant that reduces iodine to iodine ions. ]
　「Ａ×Ｂ」は、０．０００８～０．０２５であることが好ましく、より好ましくは０．００１５～０．０２である。水溶性酸化防止剤の還元力の算出方法は、実施例の記載による。 “A × B” is preferably 0.0008 to 0.025, more preferably 0.0015 to 0.02. The calculation method of the reducing power of the water-soluble antioxidant is as described in the examples.
　前記水溶性酸化防止剤としては、例えば、アスコルビン酸、エリソルビン酸、クロロゲン酸、クエン酸、ロスマリン酸、これらの塩、チオ硫酸塩、及び亜硫酸塩などが挙げられ、これらは１種単独で用いてもよく、２種以上を併用してもよい。塩としては、ナトリウム塩、カリウム塩などのアルカリ金属塩などが挙げられる。特に、水溶液中での安定性（還元力の持続性）の観点から、アスコルビン酸、エリソルビン酸ナトリウム、又はチオ硫酸塩を用いることが好ましい。 Examples of the water-soluble antioxidant include ascorbic acid, erythorbic acid, chlorogenic acid, citric acid, rosmarinic acid, salts thereof, thiosulfate, and sulfite, and these can be used alone. Or two or more of them may be used in combination. Examples of the salt include alkali metal salts such as sodium salt and potassium salt. In particular, ascorbic acid, sodium erythorbate, or thiosulfate is preferably used from the viewpoint of stability in aqueous solution (sustainability of reducing power).
　前記水溶性酸化防止剤は、染色処理後の少なくとも１つの処理に用いられる各浴のいずれか少なくとも１つに含有させることにより、または、別途、前記水溶性酸化防止剤を含有する処理液に含有させる。通常、膨潤処理がまず初めに施される。次いで、例えば、染色処理が施された場合には、架橋処理、延伸処理、さらには洗浄処理において、または別途の水溶性酸化防止剤の処理において、水溶性酸化防止剤を含有させることができる。 The water-soluble antioxidant is contained in at least one of the baths used for at least one treatment after the dyeing treatment, or separately in a treatment liquid containing the water-soluble antioxidant. Let Usually, the swelling treatment is first applied. Next, for example, when a dyeing process is performed, a water-soluble antioxidant can be contained in a crosslinking process, a stretching process, a cleaning process, or a separate water-soluble antioxidant process.
　なお、前記染色処理、架橋処理および延伸処理は、複数の処理を同時に行なう一括処理により行うことができる。複数の処理が同時に行なわれる一括処理が行なわれていた場合には、当該一括処理に用いる浴に、水溶性酸化防止剤を含有させることができる。また、前記染色処理、架橋処理および延伸処理の各処理が多段処理である場合においては、当該多段処理のいずれか少なくとも１つの処理において水溶性酸化防止剤を含有させることができる。 In addition, the said dyeing | staining process, bridge | crosslinking process, and extending | stretching process can be performed by the batch process which performs a some process simultaneously. In the case where a batch process in which a plurality of processes are performed simultaneously is performed, a water-soluble antioxidant can be contained in the bath used for the batch process. Moreover, when each process of the said dyeing | staining process, bridge | crosslinking process, and extending | stretching process is a multistage process, a water-soluble antioxidant can be contained in at least 1 process of the said multistage process.
　その後、前記フィルムに乾燥処理を施してもよい。乾燥処理は、得られる偏光子（フィルム）に必要とされる水分率に応じて、適宜に、乾燥時間と乾燥温度が設定される。乾燥温度は、通常、２０～１５０℃、好ましくは４０～１００℃の範囲で制御される。 Thereafter, the film may be dried. In the drying treatment, the drying time and the drying temperature are appropriately set according to the moisture content required for the obtained polarizer (film). The drying temperature is usually controlled in the range of 20 to 150 ° C, preferably 40 to 100 ° C.
　上記方法で製造された偏光フィルムは、常法に従って、その少なくとも片面に透明保護フィルムを設けた偏光板とすることができる。透明保護フィルムはポリマーによる塗布層として、またはフィルムのラミネート層等として設けることができる。透明保護フィルムを形成する、透明ポリマーまたはフィルム材料としては、適宜な透明材料を用いうるが、透明性や機械的強度、熱安定性や水分遮断性などに優れるものが好ましく用いられる。前記透明保護フィルムを形成する材料としては、例えばポリエチレンテレフタレートやポリエチレンナフタレート等のポリエステル系ポリマー、二酢酸セルロースや三酢酸セルロース等のセルロース系ポリマー、ポリメチルメタクリレート等のアクリル系ポリマー、ポリスチレンやアクリロニトリル・スチレン共重合体（ＡＳ樹脂）等のスチレン系ポリマー、ポリカーボネート系ポリマーなどがあげられる。また、ポリエチレン、ポリプロピレン、シクロ系ないしはノルボルネン構造を有するポリオレフィン、エチレン・プロピレン共重合体の如きポリオレフィン系ポリマー、塩化ビニル系ポリマー、ナイロンや芳香族ポリアミド等のアミド系ポリマー、イミド系ポリマー、スルホン系ポリマー、ポリエーテルスルホン系ポリマー、ポリエーテルエーテルケトン系ポリマー、ポリフェニレンスルフィド系ポリマー、ビニルアルコール系ポリマー、塩化ビニリデン系ポリマー、ビニルブチラール系ポリマー、アリレート系ポリマー、ポリオキシメチレン系ポリマー、エポキシ系ポリマー、あるいは前記ポリマーのブレンド物なども前記透明保護フィルムを形成するポリマーの例としてあげられる。透明保護フィルムは、アクリル系、ウレタン系、アクリルウレタン系、エポキシ系、シリコーン系等の熱硬化型、紫外線硬化型の樹脂の硬化層として形成することもできる。 The polarizing film produced by the above method can be a polarizing plate provided with a transparent protective film on at least one side in accordance with a 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.
　また、特開２００１－３４３５２９号公報（ＷＯ０１／３７００７）に記載のポリマーフィルム、たとえば、（Ａ）側鎖に置換および／または非置換イミド基を有する熱可塑性樹脂と、（Ｂ）側鎖に置換および／または非置換フェニルならびにニトリル基を有する熱可塑性樹脂を含有する樹脂組成物があげられる。具体例としてはイソブチレンとＮ－メチルマレイミドからなる交互共重合体とアクリロニトリル・スチレン共重合体とを含有する樹脂組成物のフィルムがあげられる。フィルムは樹脂組成物の混合押出品などからなるフィルムを用いることができる。これらのフィルムは位相差が小さく、光弾性係数が小さいため偏光板の歪みによるムラなどの不具合を解消することができ、また透湿度が小さいため、加湿耐久性に優れる。 Further, a 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 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.
　透明保護フィルムの厚さは、適宜に決定しうるが、一般には強度や取扱性等の作業性、薄層性などの点より１～５００μｍ程度である。特に１～３００μｍが好ましく、５～２００μｍがより好ましい。 The thickness of the transparent protective film can be appropriately determined, but is generally about 1 to 500 μm from the viewpoints of workability such as strength and handleability, and thin layer properties. 1 to 300 μm is particularly preferable, and 5 to 200 μm is more preferable.
　また、透明保護フィルムは、できるだけ色付きがないことが好ましい。したがって、Ｒｔｈ＝（ｎｘ－ｎｚ）・ｄ（ただし、ｎｘはフィルム平面内の遅相軸方向の屈折率、ｎｚはフィルム厚方向の屈折率、ｄはフィルム厚みである）で表されるフィルム厚み方向の位相差値が－９０ｎｍ～＋７５ｎｍである透明保護フィルムが好ましく用いられる。かかる厚み方向の位相差値（Ｒｔｈ）が－９０ｎｍ～＋７５ｎｍのものを使用することにより、保護フィルムに起因する偏光板の着色（光学的な着色）をほぼ解消することができる。厚み方向位相差値（Ｒｔｈ）は、さらに好ましくは－８０ｎｍ～＋６０ｎｍ、特に－７０ｎｍ～＋４５ｎｍが好ましい。 Further, it is preferable that the transparent protective film is as colored 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.
　保護フィルムとしては、偏光特性や耐久性などの点より、トリアセチルセルロースフィルム、ノルボルネン系フィルム、シクロオレフィン系フィルムおよびアクリル樹脂フィルムが好ましい。特にトリアセチルセルロースフィルムが好適である。なお、偏光フィルムの両側に保護フィルムを設ける場合、その表裏で同じポリマー材料からなる保護フィルムを用いてもよく、異なるポリマー材料等からなる保護フィルムを用いてもよい。 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 on both sides of a polarizing film, 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.
　前記透明保護フィルムの偏光フィルムを接着させない面には、ハードコート層や反射防止処理、スティッキング防止や、拡散ないしアンチグレアを目的とした処理を施したものであってもよい。 The surface of the transparent protective film to which the polarizing film is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.
　なお、反射防止層、スティッキング防止層、拡散層やアンチグレア層等は、透明保護フィルムそのものに設けることができるほか、別途光学層として透明保護フィルムとは別体のものとして設けることもできる。 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.
　前記偏光フィルムと透明保護フィルムとの接着処理には、接着剤が用いられる。接着剤としては、イソシアネート系接着剤、ポリビニルアルコール系接着剤、ゼラチン系接着剤、ビニル系ラテックス系、水系ポリエステル等を例示できる。前記接着剤は、通常、水溶液からなる接着剤が用いられる。 An adhesive is used for the adhesion treatment between the polarizing film 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.
　本発明の偏光板は、前記透明保護フィルムと偏光フィルムを、前記接着剤を用いて貼り合わせることにより製造する。接着剤の塗布は、透明保護フィルム、偏光フィルムのいずれに行ってもよく、両者に行ってもよい。貼り合わせ後には、乾燥工程を施し、塗布乾燥層からなる接着層を形成する。偏光フィルムと透明保護フィルムの貼り合わせは、ロールラミネーター等により行うことができる。接着層の厚さは、特に制限されないが、通常０．１～５μｍ程度である。 The polarizing plate of the present invention is produced by bonding the transparent protective film and the polarizing film using the adhesive. Application | coating of an adhesive agent may be performed to any of a transparent protective film and a polarizing film, and may be performed to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. Bonding of the polarizing film and the transparent protective film can be performed with a roll laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 μm.
　本発明の偏光板は、実用に際して他の光学層と積層した光学フィルムとして用いることができる。その光学層については特に限定はないが、例えば反射板や半透過板、位相差板（１／２や１／４等の波長板を含む）、視角補償フィルムなどの液晶表示装置等の形成に用いられることのある光学層を１層または２層以上用いることができる。特に、本発明の偏光板に更に反射板または半透過反射板が積層されてなる反射型偏光板または半透過型偏光板、偏光板に更に位相差板が積層されてなる楕円偏光板または円偏光板、偏光板に更に視角補償フィルムが積層されてなる広視野角偏光板、あるいは偏光板に更に輝度向上フィルムが積層されてなる偏光板が好ましい。 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.
　本発明の偏光板または光学フィルムは液晶表示装置等の各種装置の形成などに好ましく用いることができる。液晶表示装置の形成は、従来に準じて行いうる。すなわち液晶表示装置は一般に、液晶セルと偏光板または光学フィルム、及び必要に応じての照明システム等の構成部品を適宜に組立てて駆動回路を組込むことなどにより形成されるが、本発明においては本発明による偏光板または光学フィルムを用いる点を除いて特に限定はなく、従来に準じうる。液晶セルについても、例えばＴＮ型やＳＴＮ型、π型などの任意なタイプのものを用いうる。 The polarizing plate or 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. In other words, 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.
　以下、本発明の構成と効果を具体的に示す実施例等について説明する。なお、各例中、部および％は特記ない限り重量基準である。 Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. In each example, parts and% are based on weight unless otherwise specified.
　（水溶性酸化防止剤の還元力の測定）
　酸化還元反応により、水溶性酸化防止剤の還元力を下記容量滴定法により測定した。
　濃度０．１％のヨウ素水溶液（２５ｍｌ）に、濃度０．５％のデンプン水溶液（キシダ化学（株）製、滴定用）を１～２ｍｌ加えて黒色に着色させた。モル濃度０．０１ｍｏｌ／Ｌの水溶性酸化防止剤水溶液を、前記着色させたヨウ素水溶液中にビュレットを使用して滴下し、水溶液の色が無色になった時の滴定量（ｍｌ）を還元力Ｂとした。 (Measurement of reducing power of water-soluble antioxidants)
By the oxidation-reduction reaction, the reducing power of the water-soluble antioxidant was measured by the following volumetric titration method.
1 to 2 ml of a 0.5% aqueous starch solution (manufactured by Kishida Chemical Co., Ltd., for titration) was added to a 0.1% aqueous iodine solution (25 ml) and colored black. A water-soluble antioxidant aqueous solution having a molar concentration of 0.01 mol / L was dropped into the colored iodine aqueous solution using a burette, and the titration amount (ml) when the color of the aqueous solution became colorless was determined as reducing power. B.
　実施例１
　厚み７５μｍのＰＶＡフィルム（クラレ社製、商品名：ＶＦ－ＰＳ＃７５００）を、３０℃の純水（膨潤浴）中に１分間浸漬して膨潤させつつ、元長に対して延伸倍率が２．２倍になるように流れ方向に延伸した。その後、ＰＶＡフィルムをヨウ素０．０４５％及びヨウ化カリウム０．３１５％を含む３０℃のヨウ素水溶液（染色浴）中に３０秒間浸漬して、染色しながら、元長に対して延伸倍率が３．３倍になるように流れ方向に延伸した。次に、前記フィルムをホウ酸３％及びヨウ化カリウム３％を含む３０℃の水溶液に３０秒間浸漬しながら、元長に対して延伸倍率が３．６倍になるように流れ方向に延伸した。その後、前記フィルムをホウ酸４％、ヨウ化カリウム５％、及びアスコルビン酸０．００００６６２ｍｏｌ／Ｌを含む６０℃の水溶液（架橋浴）中に６０秒間浸漬しながら、元長に対して延伸倍率が６．０倍になるように流れ方向に延伸した。その後、前記フィルムをヨウ化カリウム３％を含む３０℃の水溶液（洗浄浴）中に１０秒間浸漬して洗浄した。最後に、前記フィルムを水切りし、緊張を保ったまま６０℃のオーブン中で４分間乾燥して偏光フィルムを製造した。 Example 1
A 75 μm-thick PVA film (trade name: VF-PS # 7500, manufactured by Kuraray Co., Ltd.) is immersed in pure water (swelling bath) at 30 ° C. for 1 minute to swell, and the draw ratio is 2 relative to the original length The film was stretched in the flow direction so as to be doubled. Thereafter, the PVA film was immersed in an iodine aqueous solution (dye bath) at 30 ° C. containing 0.045% iodine and 0.315% potassium iodide for 30 seconds, and the draw ratio was 3 with respect to the original length while dyeing. The film was stretched in the flow direction so as to be 3 times. Next, the film was stretched in the flow direction so that the stretch ratio was 3.6 times the original length while being immersed in an aqueous solution containing 3% boric acid and 3% potassium iodide for 30 seconds. . Thereafter, the film was immersed in a 60 ° C. aqueous solution (crosslinking bath) containing 4% boric acid, 5% potassium iodide and 0.0000662 mol / L ascorbic acid for 60 seconds, and the draw ratio with respect to the original length was The film was stretched in the flow direction so as to be 6.0 times. Thereafter, the film was immersed in a 30 ° C. aqueous solution (cleaning bath) containing 3% potassium iodide for 10 seconds for cleaning. Finally, the film was drained and dried for 4 minutes in an oven at 60 ° C. while maintaining tension to produce a polarizing film.
　実施例２～９、比較例１～６
　水溶性酸化防止剤の種類及び濃度、並びに水溶性酸化防止剤を添加する処理浴を表１に示すように変更した以外は実施例１と同様の方法で偏光フィルムを作製した。 Examples 2 to 9, Comparative Examples 1 to 6
A polarizing film was produced in the same manner as in Example 1 except that the type and concentration of the water-soluble antioxidant and the treatment bath to which the water-soluble antioxidant was added were changed as shown in Table 1.
　（評価）
　実施例および比較例で得られた偏光フィルムについて、下記光学特性について評価した。結果を表１に示す。 (Evaluation)
About the polarizing film obtained by the Example and the comparative example, the following optical characteristic was evaluated. The results are shown in Table 1.
　〔単体透過率及び偏光度の測定〕
　３８０～７８０ｎｍの波長光における偏光フィルムの分光透過率を、積分球付き分光光度計（日本分光株式会社製、商品名：Ｖ７１００）を用いて測定した。各直線偏光に対する透過率はグランテラ－プリズム偏光フィルムを通して得られた完全偏光を１００％として測定した。測定された分光透過率よりＣＩＥ１９３１　Ｙｘｙ表色系に従い、Ｃ光源２°視野でのＹ値を算出した。これらを単体透過率（Ｔｓ（Ｙ））、平行透過率（Ｔｐ（Ｙ））、直交透過率（Ｔｃ（Ｙ））とした。 (Measurement of single transmittance and degree of polarization)
The spectral transmittance of the polarizing film at a wavelength of 380 to 780 nm was measured using a spectrophotometer with an integrating sphere (trade name: V7100, manufactured by JASCO Corporation). The transmittance for each linearly polarized light was measured with 100% of the completely polarized light obtained through the Grantera-prism polarizing film. The Y value in the C light source 2 ° field of view was calculated from the measured spectral transmittance according to the CIE1931 Yxy color system. These were designated as single transmittance (Ts (Y)), parallel transmittance (Tp (Y)), and orthogonal transmittance (Tc (Y)).
　偏光度（Ｐ）は、｛（平行透過率－直交透過率）／（平行透過率＋直交透過率）｝1/2×１００（％）、により算出した。 The degree of polarization (P) was calculated by {(parallel transmittance−orthogonal transmittance) / (parallel transmittance + orthogonal transmittance)} 1/2 × 100 (%).
　〔二色比の評価〕
　上記測定で得られた単体透過率（Ｔｓ（Ｙ））と偏光度（Ｐ）の値を下記式に代入して二色比を算出した。 [Evaluation of dichroic ratio]
The dichroic ratio was calculated by substituting the single transmittance (Ts (Y)) and the degree of polarization (P) obtained by the above measurement into the following formula.
　二色比＝ｌｏｇ[Ｔｓ（Ｙ）／９１．６×{１－（Ｐ／１００）}]／ｌｏｇ[Ｔｓ（Ｙ）／９１．６×{１＋（Ｐ／１００）}] Dichroic ratio = log [Ts (Y) /91.6× {1- (P / 100)}] / log [Ts (Y) /91.6× {1+ (P / 100)}]
　〔コントラストの評価〕
　波長４１０ｎｍにおける偏光フィルムの分光透過率を、積分球付き分光光度計（日本分光株式会社製、商品名：Ｖ７１００）を用いて測定した。各直線偏光に対する透過率はグランテラ－プリズム偏光フィルムを通して得られた完全偏光を１００％として測定した。波長４１０ｎｍにおけるコントラスト（Ｃｒ４１０ｎｍ）は、波長４１０ｎｍにおける平行透過率（Ｔｐ４１０ｎｍ）と波長４１０ｎｍにおける直交透過率（Ｔｃ４１０ｎｍ）の値を下記式に代入することにより算出した。なお、これらの透過率は、ＪＩＳ　Ｚ　８７０１の２度視野（Ｃ光源）により、視感度補正を行ったＹ値である。
　Ｃｒ４１０ｎｍ＝Ｔｐ４１０ｎｍ／Ｔｃ４１０ｎｍ [Evaluation of contrast]
The spectral transmittance of the polarizing film at a wavelength of 410 nm was measured using a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, trade name: V7100). The transmittance for each linearly polarized light was measured with 100% of the completely polarized light obtained through the Grantera-prism polarizing film. The contrast (Cr 410 nm ) at a wavelength of 410 nm was calculated by substituting the parallel transmittance (Tp 410 nm ) at a wavelength of 410 nm and the orthogonal transmittance (Tc 410 nm ) at a wavelength of 410 nm into the following equation. Note that these transmittances are Y values obtained by correcting the visibility with a two-degree field of view (C light source) of JIS Z 8701.
Cr 410nm = Tp 410nm / Tc 410nm
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　本発明の偏光フィルム、偏光板はこれ単独で、またはこれを積層した光学フィルムとして液晶表示装置、有機ＥＬ表示装置等のフラットパネルディスプレー等の画像表示装置を形成しうる。 The polarizing film and polarizing plate of the present invention can form an image display device such as a flat panel display such as a liquid crystal display device and an organic EL display device as a single or a laminated optical film.

Claims (8)

  1. 　ポリビニルアルコール系フィルムに、膨潤処理、染色処理、架橋処理、延伸処理及び洗浄処理を少なくとも施す偏光フィルムの製造方法において、
    　前記染色処理後の少なくとも１つの処理において、処理液中に水溶性酸化防止剤を下記式（１）を満たすように含有させることを特徴とする偏光フィルムの製造方法。
    　０．０００５≦Ａ×Ｂ≦０．０３　　　　（１）
    〔上記式中、Ａは処理浴中の水溶性酸化防止剤の濃度（ｍｏｌ／Ｌ）であり、Ｂはヨウ素をヨウ素イオンに還元する水溶性酸化防止剤の還元力である。〕     In the method for producing a polarizing film, the polyvinyl alcohol film is subjected to at least swelling treatment, dyeing treatment, crosslinking treatment, stretching treatment and washing treatment.
    In at least one treatment after the dyeing treatment, a water-soluble antioxidant is contained in the treatment liquid so as to satisfy the following formula (1).
    0.0005 ≦ A × B ≦ 0.03 (1)
    [In the above formula, A is the concentration (mol / L) of the water-soluble antioxidant in the treatment bath, and B is the reducing power of the water-soluble antioxidant that reduces iodine to iodine ions. ]
  2. 　前記水溶性酸化防止剤が、アスコルビン酸、エリソルビン酸ナトリウム、チオ硫酸塩、及び亜硫酸塩からなる群より選択される少なくとも１種である請求項１記載の偏光フィルムの製造方法。 The method for producing a polarizing film according to claim 1, wherein the water-soluble antioxidant is at least one selected from the group consisting of ascorbic acid, sodium erythorbate, thiosulfate, and sulfite.
  3. 　請求項１又は２記載の製造方法により得られる偏光フィルム。 A polarizing film obtained by the production method according to claim 1.
  4. 　請求項３記載の偏光フィルムの少なくとも一方の面に透明保護フィルムが積層されている偏光板。 A polarizing plate in which a transparent protective film is laminated on at least one surface of the polarizing film according to claim 3.
  5. 　請求項３記載の偏光フィルムが少なくとも１枚積層されている光学フィルム。 An optical film in which at least one polarizing film according to claim 3 is laminated.
  6. 　請求項４記載の偏光板が少なくとも１枚積層されている光学フィルム。 An optical film in which at least one polarizing plate according to claim 4 is laminated.
  7. 　請求項５記載の光学フィルムを含む画像表示装置。 An image display device comprising the optical film according to claim 5.
  8. 　請求項６記載の光学フィルムを含む画像表示装置。
          An image display device comprising the optical film according to claim 6.
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KR101992004B1 (en) * 2016-12-21 2019-06-21 삼성에스디아이 주식회사 Polarizer, method for preparing the same, polarizing plate comprising the same and display apparatus comprising the same
KR102263513B1 (en) * 2017-04-03 2021-06-11 닛토덴코 가부시키가이샤 Method for manufacturing a polarizer
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WO2018134231A1 (en) 2017-01-19 2018-07-26 Kaub GmbH & Co. KG Hydraulic drive for a roller reefing device, and a roller reefing device equipped with such a drive

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