Classifications

• • 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.

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• Physics & Mathematics (AREA)
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• Optics & Photonics (AREA)
• Nonlinear Science (AREA)
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• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Polarising Elements (AREA)
• Liquid Crystal (AREA)

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• 2012
  • 2012-05-09 JP JP2012107678A patent/JP5300160B2/ja not_active Expired - Fee Related
  • 2012-09-12 WO PCT/JP2012/073355 patent/WO2013054626A1/ja active Application Filing
  • 2012-09-12 CN CN201280042812.1A patent/CN103765259B/zh active Active
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