CN108139528B - Polyvinyl alcohol film for producing polarizing film, polarizing film using same, polarizing plate, and method for producing polyvinyl alcohol film for producing polarizing film - Google Patents
Polyvinyl alcohol film for producing polarizing film, polarizing film using same, polarizing plate, and method for producing polyvinyl alcohol film for producing polarizing film Download PDFInfo
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- CN108139528B CN108139528B CN201680058384.XA CN201680058384A CN108139528B CN 108139528 B CN108139528 B CN 108139528B CN 201680058384 A CN201680058384 A CN 201680058384A CN 108139528 B CN108139528 B CN 108139528B
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- polyvinyl alcohol
- polarizing film
- polarizing
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- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 177
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 171
- 238000004519 manufacturing process Methods 0.000 title claims description 68
- 230000008961 swelling Effects 0.000 claims abstract description 86
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000011347 resin Substances 0.000 claims description 47
- 229920005989 resin Polymers 0.000 claims description 47
- 238000000034 method Methods 0.000 claims description 41
- 238000005266 casting Methods 0.000 claims description 28
- 238000001035 drying Methods 0.000 claims description 26
- 239000007864 aqueous solution Substances 0.000 claims description 25
- 230000008859 change Effects 0.000 claims description 11
- 238000009749 continuous casting Methods 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- 239000010408 film Substances 0.000 description 347
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 27
- 230000010287 polarization Effects 0.000 description 19
- 230000002522 swelling effect Effects 0.000 description 14
- 238000002834 transmittance Methods 0.000 description 12
- 238000010438 heat treatment Methods 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 238000004043 dyeing Methods 0.000 description 9
- 229920000642 polymer Polymers 0.000 description 9
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 8
- -1 etc.) Chemical class 0.000 description 7
- 238000007654 immersion Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 229920001577 copolymer Polymers 0.000 description 6
- 239000004973 liquid crystal related substance Substances 0.000 description 6
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 5
- 239000004327 boric acid Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000007127 saponification reaction Methods 0.000 description 5
- 239000010409 thin film Substances 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 229910052740 iodine Inorganic materials 0.000 description 3
- 239000011630 iodine Substances 0.000 description 3
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- 239000004094 surface-active agent Substances 0.000 description 3
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- 238000012360 testing method Methods 0.000 description 3
- 150000000180 1,2-diols Chemical group 0.000 description 2
- 229920002284 Cellulose triacetate Polymers 0.000 description 2
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 2
- 150000001639 boron compounds Chemical class 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000002148 esters Chemical class 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005187 foaming Methods 0.000 description 2
- 235000011187 glycerol Nutrition 0.000 description 2
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 239000004014 plasticizer Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- MWWXARALRVYLAE-UHFFFAOYSA-N 2-acetyloxybut-3-enyl acetate Chemical compound CC(=O)OCC(C=C)OC(C)=O MWWXARALRVYLAE-UHFFFAOYSA-N 0.000 description 1
- IGDCJKDZZUALAO-UHFFFAOYSA-N 2-prop-2-enoxypropane-1,3-diol Chemical compound OCC(CO)OCC=C IGDCJKDZZUALAO-UHFFFAOYSA-N 0.000 description 1
- BJWMSGRKJIOCNR-UHFFFAOYSA-N 4-ethenyl-1,3-dioxolan-2-one Chemical compound C=CC1COC(=O)O1 BJWMSGRKJIOCNR-UHFFFAOYSA-N 0.000 description 1
- WSSSPWUEQFSQQG-UHFFFAOYSA-N 4-methyl-1-pentene Chemical compound CC(C)CC=C WSSSPWUEQFSQQG-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 208000034628 Celiac artery compression syndrome Diseases 0.000 description 1
- 229920001747 Cellulose diacetate Polymers 0.000 description 1
- 229920000089 Cyclic olefin copolymer Polymers 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- DKNPRRRKHAEUMW-UHFFFAOYSA-N Iodine aqueous Chemical compound [K+].I[I-]I DKNPRRRKHAEUMW-UHFFFAOYSA-N 0.000 description 1
- VQTUBCCKSQIDNK-UHFFFAOYSA-N Isobutene Chemical group CC(C)=C VQTUBCCKSQIDNK-UHFFFAOYSA-N 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000004695 Polyether sulfone Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- QYKIQEUNHZKYBP-UHFFFAOYSA-N Vinyl ether Chemical class C=COC=C QYKIQEUNHZKYBP-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000003093 cationic surfactant Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 230000000911 decarboxylating effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 229940105990 diglycerin Drugs 0.000 description 1
- GPLRAVKSCUXZTP-UHFFFAOYSA-N diglycerol Chemical compound OCC(O)COCC(O)CO GPLRAVKSCUXZTP-UHFFFAOYSA-N 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- JRBPAEWTRLWTQC-UHFFFAOYSA-N dodecylamine Chemical compound CCCCCCCCCCCCN JRBPAEWTRLWTQC-UHFFFAOYSA-N 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000000569 multi-angle light scattering Methods 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 239000002736 nonionic surfactant Substances 0.000 description 1
- 239000012788 optical film Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000003791 organic solvent mixture Substances 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920000412 polyarylene Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 229920006393 polyether sulfone Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 229920001955 polyphenylene ether Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 229920002689 polyvinyl acetate Polymers 0.000 description 1
- 239000011118 polyvinyl acetate Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 150000003871 sulfonates Chemical class 0.000 description 1
- 229920002803 thermoplastic polyurethane Polymers 0.000 description 1
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
- B29C55/08—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique transverse to the direction of feed
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
- C08L29/02—Homopolymers or copolymers of unsaturated alcohols
- C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
-
- 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
- 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
- G02F1/13363—Birefringent elements, e.g. for optical compensation
Landscapes
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Nonlinear Science (AREA)
- Health & Medical Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Mathematical Physics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Polarising Elements (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
A polyvinyl alcohol film for producing a polarizing film, characterized in that it is a polyvinyl alcohol film having a thickness of 5 to 60 [ mu ] m, a width of 2m or more and a length of 2km or more, and when the polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the degree of swelling X (%) in the width direction (TD direction) and the degree of swelling Y (%) in the length direction (MD direction) satisfy the following conditions (1) and (2), (1) 110. ltoreq. Y.ltoreq.140, and (2) 1.01. ltoreq. Y/X.ltoreq.1.2.
Description
Technical Field
The present invention relates to a polyvinyl alcohol film for producing a polarizing film (hereinafter, may be simply referred to as "polyvinyl alcohol film"), particularly a polyvinyl alcohol film which can give a polarizing film having excellent dyeing properties, a high degree of polarization, and little color unevenness, a polarizing film using the polyvinyl alcohol film, a polarizing plate, and a method for producing a polyvinyl alcohol film for producing a polarizing film.
Background
Heretofore, a polyvinyl alcohol film has been used in many applications as a film having excellent transparency, and one of the useful applications thereof is a polarizing film. The polarizing film is used as a basic component of a liquid crystal display, and in recent years, the polarizing film is widely used for devices which require high quality and high reliability.
Among them, a polarizing film having excellent polarizing performance is required in accordance with the increase in brightness, high definition, large area, and thickness of a screen of a liquid crystal television, a multi-functional portable terminal, or the like. Specifically, the degree of polarization is further improved, and color unevenness is solved.
In general, a polyvinyl alcohol film for polarizing film production is produced from an aqueous solution of a polyvinyl alcohol resin by a continuous casting method. Specifically, the polyvinyl alcohol film is produced by casting an aqueous solution of a polyvinyl alcohol resin in a casting mold such as a casting drum or an endless belt to form a film, peeling the film from the casting mold, and drying the film by a hot roll or a suspension dryer (floating dryer) while conveying the film in a flow direction (MD direction) by using a nip roll or the like. In the above-described conveying step, the film formed is stretched in the flow direction (MD direction), and therefore the polyvinyl alcohol polymer is easily oriented in the MD direction.
On the other hand, a polarizing film is generally produced by swelling a polyvinyl alcohol film as a material thereof with water (including warm water), dyeing with a dichroic dye such as iodine, and stretching. In the swelling step, it is necessary to rapidly swell the polyvinyl alcohol film in the thickness direction. Further, in the dyeing step, uniform swelling is required to allow the dye to smoothly enter the film.
The stretching step is a step of stretching the dyed film in the flow direction (MD direction) to highly orient the dichroic dye in the film, and the polyvinyl alcohol film as a material is required to have good stretchability in the MD direction in order to improve the polarizing performance of the polarizing film.
In the case of producing a polarizing film, the order of the stretching step and the dyeing step is reversed from that described above. That is, in the case where a polyvinyl alcohol film as a material is swollen with water (including warm water) and then stretched, and is dyed with a dichroic dye such as iodine, in the above case, in order to improve the polarizing performance of a polarizing film, it is also necessary that the polyvinyl alcohol film has good swelling properties in the thickness direction and good stretchability in the MD direction.
Further, in recent years, in order to reduce the thickness of the polarizing film, the polyvinyl alcohol film has also been reduced in thickness. The thin film has a problem of productivity such as breakage due to stretching in the production of a polarizing film.
As a method for improving the swelling property, for example, a method of adding a polyol as a water swelling aid to a polyvinyl alcohol resin has been proposed (for example, see patent document 1). As a method for improving stretchability, for example, a method of specifying the ratio of the speed of a casting drum at the time of film formation to the final film take-up speed (for example, see patent document 2), a method of drying a film by suspending it after film formation by a casting drum (for example, see patent document 3), and a method of controlling the stretching state in the drying step of the film formed (for example, see patent document 4) have been proposed.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2001 and 302867
Patent document 2: japanese patent laid-open No. 2001-315141
Patent document 3: japanese patent laid-open No. 2001-315142
Patent document 4: japanese laid-open patent publication No. 2002-79531
Disclosure of Invention
Problems to be solved by the invention
However, even the technique of the above patent document is insufficient for improving the swelling property and the stretchability in the production of a polarizing film.
Even if the swelling property of the entire polyvinyl alcohol film can be improved by the technique disclosed in patent document 1, the orientation state of the polyvinyl alcohol polymer is not taken into consideration, and it is difficult to effectively improve the stretchability in the flow direction (MD direction) in the production of a polarizing film. On the other hand, the orientation state of the polymer tends to be disordered by the addition of the water-swelling agent, and it tends to be difficult to uniformly stretch the polymer in the flow direction (MD direction).
Patent document 2 specifies the degree of stretching in the MD direction (stretching state) in the production of a polyvinyl alcohol film, but if stretching in the TD direction is not taken into consideration, it is not sufficient to improve the stretchability in the production of a polarizing film. In general, it is difficult to stretch a polyvinyl alcohol film oriented in the MD direction during the production of a polarizing film. That is, when the polyvinyl alcohol polymer oriented in the MD direction is further stretched in the MD direction, it is difficult to forcibly elongate the molecular chain. Conversely, it is relatively easy to stretch the polyvinyl alcohol polymer oriented in the TD direction in the MD direction. However, if the polymer orientation in the TD direction is not uniform, the stretching in the MD direction during the production of the polarizing film cannot be performed uniformly. Patent document 2 also has an example in which the film is not stretched so much in the MD direction (an example in which the film is not stretched) in the production of a polyvinyl alcohol film, but there is a problem in that the polymer orientation in the TD direction cannot be sufficiently uniformized only by the shrinkage stress depending on the poisson's ratio and the shrinkage stress due to dehydration. That is, if the stretching in the TD direction is not performed to some extent or the width direction is not fixed at least, a uniform orientation state of the polymer in the TD direction cannot be obtained, and it is not sufficient to improve the stretchability in the MD direction in the production of the polarizing film. Further, there is no description about orientation in the thickness direction, and swelling property in the production of a polarizing film cannot be controlled.
In the case of the technique disclosed in patent document 3, although the film after film formation can be dried uniformly, the orientation of the polymer cannot be controlled, and the improvement of the swelling property and the stretchability in the production of a polarizing film is insufficient.
In the case of the technique disclosed in patent document 4, although the polyvinyl alcohol film can be made uniform in thickness, the orientation of the polymer cannot be controlled, and the swelling property and stretchability in the production of a polarizing film are not sufficiently improved.
Under such circumstances, the present invention provides a polyvinyl alcohol film for producing a polarizing film, which has excellent swelling properties and stretchability in the production of a polarizing film, can provide a polarizing film having high polarizing performance and little color unevenness, particularly a polyvinyl alcohol film for producing a polarizing film, which does not cause breakage in the production of a thin polarizing film, and further provides a polarizing film comprising the polyvinyl alcohol film for producing a polarizing film, a polarizing plate, and a method for producing a polyvinyl alcohol film for producing a polarizing film.
Means for solving the problems
However, the present inventors have intensively studied in view of the above problems, and as a result, they have found that a polyvinyl alcohol film having a ratio of a degree of swelling X (%) in a width direction (TD direction) to a degree of swelling Y (%) in a flow direction (MD direction) within a specific range is excellent in swelling property and stretchability at the time of producing a polarizing film, and that a polarizing film obtained by using the polyvinyl alcohol film has high polarizing performance and little color unevenness.
That is, a first aspect of the present invention is a polyvinyl alcohol film for producing a polarizing film, which is characterized in that the polyvinyl alcohol film has a thickness of 5 to 60 μm, a width of 2m or more, and a length of 2km or more, and when the polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the swelling degree X (%) in the width direction (TD direction) and the swelling degree Y (%) in the length direction (MD direction) satisfy the following conditions (1) and (2).
(1)110≤Y≤140
(2)1.01≤Y/X≤1.2
In particular, a second aspect of the present invention is a polyvinyl alcohol film for producing a polarizing film, wherein the polyvinyl alcohol film has a degree of swelling Z (%) in the thickness direction satisfying the following condition (3) when immersed in water at 30 ℃ for 15 minutes.
(3)140≤Z≤170
A third aspect of the present invention is a polyvinyl alcohol film for producing a polarizing film, wherein a deviation Δ X (%) of a swelling degree X (%) in a width direction (TD direction), a deviation Δ Y (%) of a swelling degree Y (%) in a length direction (MD direction), and a deviation Δ Z (%) of a swelling degree Z (%) in a thickness direction are within 5%.
A fourth aspect of the present invention is a polyvinyl alcohol-based film for producing a polarizing film, which satisfies the following conditions (4) and (5).
(4) In-plane retardation rxy (nm): 100 to 200nm
(5) An intersection angle theta (DEG) of an orientation axis, namely a slow phase axis, and a width direction, namely a TD direction, is 20 DEG or less
Here, the in-plane retardation rxy (nm) is a value calculated by the following formula (a) in the case where the refractive index in the width direction (TD direction) is nx, the refractive index in the length direction (MD direction) is ny, and the thickness is d (nm) in the polyvinyl alcohol film.
(A)Rxy(nm)＝|nx-ny|×d(nm)
In particular, a fifth aspect of the present invention is a polyvinyl alcohol film for producing a polarizing film, wherein the variation Δ rxy (nm) in the in-plane retardation rxy (nm) in the width direction (TD direction) is 10nm or less.
A sixth aspect of the present invention is a polyvinyl alcohol-based film for producing a polarizing film, wherein a deviation Δ θ (°) of the crossing angle θ (°) is 10 ° or less.
Further, a seventh aspect of the present invention is a polyvinyl alcohol film for producing a polarizing film, wherein the polyvinyl alcohol film has a thickness of 5 to 30 μm.
An eighth aspect of the present invention is a polarizing film using the polyvinyl alcohol-based film for producing a polarizing film.
A ninth aspect of the present invention is directed to a polarizing plate including the polarizing film and a protective film provided on at least one surface of the polarizing film.
A tenth aspect of the present invention is a method for producing a polyvinyl alcohol film for producing a polarizing film, including the steps of: a step of forming a film from an aqueous solution of a polyvinyl alcohol resin by a continuous casting method; a step of continuously drying the cast product while conveying the cast product in a flow direction (MD direction) after the cast product is peeled from the casting mold; and a step of stretching the polyvinyl alcohol film in the width direction (TD direction), wherein when the produced polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the degree of swelling X (%) in the width direction (TD direction) and the degree of swelling Y (%) in the flow direction (MD direction) satisfy the following conditions (1) and (2).
(1)110≤Y≤140
(2)1.01≤Y/X≤1.2
Particularly, an eleventh aspect of the present invention is a method for producing a polyvinyl alcohol film for producing a polarizing film, wherein the film is stretched at a stretch ratio of 1.05 to 1.5 times in the width direction (TD direction).
Further, a twelfth aspect of the present invention is a method for producing a polyvinyl alcohol film for producing a polarizing film, wherein the stretching in the width direction (TD direction) is performed at 50 to 150 ℃.
A thirteenth aspect of the present invention is directed to a method for producing a polyvinyl alcohol film for producing a polarizing film, wherein the film before stretching in the width direction (TD direction) has a water content of 0.5 to 15 wt%.
A fourteenth aspect of the present invention is directed to a method for producing a polyvinyl alcohol film for polarizing film production, wherein the polyvinyl alcohol film is stretched once more than 1.3 times in the width direction (TD direction), and then subjected to dimensional shrinkage so that the final stretching ratio in the width direction (TD direction) is 1.05 to 1.5 times.
A fifteenth aspect of the present invention is a method for producing a polyvinyl alcohol film for polarizing film production, wherein the dimensional change rate of the film in the flow direction (MD direction) before and after stretching in the width direction (TD direction) is 0.8 to 1.0.
ADVANTAGEOUS EFFECTS OF INVENTION
The polyvinyl alcohol film for producing a polarizing film of the present invention is excellent in swelling property and stretchability during production of a polarizing film, and can provide a polarizing film which exhibits high polarizing performance and little color unevenness without causing breakage even when a thin polarizing film is produced.
The present invention is based on the technical idea of improving the swellability and stretchability of a polyvinyl alcohol film in the production of a polarizing film by improving the swellability in the flow direction (MD direction).
Detailed Description
The present invention will be described in detail below.
The polyvinyl alcohol film for producing a polarizing film of the present invention has a thickness of 5 to 60 μm, a width of 2m or more, and a length of 2km or more, and has the following characteristics. Specifically, a polyvinyl alcohol film is obtained by forming an aqueous solution of a polyvinyl alcohol resin into a film by a continuous casting method, peeling the formed film from a casting die, continuously drying the film while conveying the film in a flow direction (MD direction), and stretching the film in a width direction (TD direction).
In the polyvinyl alcohol film of the present invention, when the polyvinyl alcohol film produced by the above method is immersed in water at 30 ℃ for 15 minutes, the degree of swelling X (%) in the width direction (TD direction) and the degree of swelling Y (%) in the flow direction (MD direction) satisfy the physical property values of both of the following conditions (1) and (2). This is a feature of the present invention. Even if only one of the physical property values is satisfied, the object of the present invention cannot be achieved.
(1)110≤Y≤140
(2)1.01≤Y/X≤1.2
The conditions (1) and (2) can be achieved by, for example, stretching the film in the width direction (TD direction) of the film to be formed, and the stretching ratio in this case is preferably 1.05 to 1.5 times, more preferably 1.1 to 1.45 times, and particularly preferably 1.2 to 1.4 times. When the stretching ratio in the width direction (TD direction) is too low or too high, it is difficult to control the degree of swelling X (%) in the width direction (TD direction), the degree of swelling Y (%) in the flow direction (MD direction), and the retardation, and the swelling property and the stretchability tend to be reduced during the production of the polarizing film.
The condition (1) is specified by the swelling degree Y (%) in the flow direction (MD direction) and is within the range of the known art. The swelling degree Y (%) is required to be 110% to 140%, preferably 115% to 135%, and more preferably 120% to 130%. When the swelling degree Y (%) is less than the lower limit, the stretchability in the production of the polarizing film is undesirably reduced, and conversely, when the swelling degree Y (%) is more than the upper limit, the polarization degree of the polarizing film is undesirably reduced.
Condition (2) specifies the ratio (Y/X) of the degree of swelling Y (%) in the flow direction (MD direction) to the degree of swelling X (%) in the width direction (TD direction). The present invention is most characterized in that the degree of swelling Y (%) in the flow direction (MD direction) is larger than the degree of swelling X (%) in the width direction (TD direction) within a specific range.
The above ratio of the conventional polyvinyl alcohol film is usually 1 or less. This is because the molecular chains of the polyvinyl alcohol polymer are generally oriented in the flow direction (MD direction) and are less likely to swell in this direction.
The ratio (Y/X) of the degree of swelling Y (%) in the flow direction (MD direction) to the degree of swelling X (%) in the width direction (TD direction) is required to satisfy the condition (2) 1.01. ltoreq. Y/X. ltoreq.1.2, preferably the following condition (2 '), particularly preferably the following condition (2').
(2’)1.03≤Y/X≤1.15
(2”)1.05≤Y/X≤1.1
If Y/X is less than the lower limit, the stretchability in the production of the polarizing film is insufficient, which is not preferable, and if Y/X exceeds the upper limit, the polarization degree of the polarizing film is decreased, which is not preferable.
Further, in the polyvinyl alcohol film of the present invention, when the polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the swelling degree Z (%) in the thickness direction preferably satisfies the following condition (3), more preferably satisfies the following condition (3 '), and particularly preferably satisfies the following condition (3').
(3)140≤Z≤170
(3’)143≤Z≤169
(3”)145≤Z≤168
The swelling degree Z (%) in the present invention is a value calculated from the swelling degree X (%) in the width direction (TD direction), the swelling degree Y (%) in the flow direction (MD direction), the weight of the impregnated film and the weight of the impregnated film after drying according to the following formula.
Swelling degree Z (%) is 1000000 × weight after immersion (g)/weight after drying (g)/X/Y
If the swelling degree Z (%) is too low, the swelling property during the production of the polarizing film tends to be low, and conversely, if too high, the polarization degree of the polarizing film tends to be low.
The degree of swelling Z (%) is greater than the degree of swelling in the width direction (TD direction) and the degree of swelling in the flow direction (MD direction) as seen from the conditions (1), (2) and (3). This is because molecular chains of the polyvinyl alcohol polymer are mainly oriented in the plane direction and easily swell in the thickness direction. By the chemical structure, the polyvinyl alcohol film can be quickly and uniformly swollen in the swelling step in the production of the polarizing film.
Further, in the polyvinyl alcohol film of the invention, it is preferable that the deviation Δ X (%) in the swelling degree X (%) in the width direction (TD direction), the deviation Δ Y (%) in the swelling degree Y (%) in the flow direction (MD direction), and the deviation Δ Z (%) in the swelling degree Z (%) in the thickness direction are within 5%, more preferably within 4%, and particularly preferably within 3%. If the deviation is too large, the polarizing film tends to have color unevenness.
In the present invention, as a method for satisfying the conditions (1), (2) and (3), in addition to the method of stretching the film peeled from the casting die in the width direction (TD direction) as in the present invention, a method of adjusting the drying condition of the polyvinyl alcohol resin aqueous solution, a method of adjusting the chemical structure of the polyvinyl alcohol resin, and the like can be exemplified.
The polyvinyl alcohol film produced by the above method preferably satisfies the physical property values of both of the following conditions (4) and (5).
(4) In-plane retardation rxy (nm): 100 to 200nm
(5) An intersection angle theta (DEG) between the orientation axis (slow axis) and the width direction (TD direction) is 20 DEG or less
Here, the in-plane retardation rxy (nm) is a value calculated by the following formula (a) in the case where the refractive index in the width direction (TD direction) is nx, the refractive index in the flow direction (MD direction) is ny, and the thickness is d (nm) in the polyvinyl alcohol film.
(A)Rxy(nm)＝|nx-ny|×d(nm)
The in-plane retardation Rxy (nm) is more preferably 110 to 180nm, particularly preferably 130 to 170 nm. When the in-plane retardation rxy (nm) is too small, the stretchability in the MD direction tends to be reduced during the production of the polarizing film, and when it is too large, the polarizing film tends to have color unevenness.
The variation Δ rxy (nm) in the in-plane retardation rxy (nm) in the width direction (TD direction) is preferably 10nm or less, more preferably 5nm or less, and particularly preferably 3nm or less. If the deviation Δ Rxy is too large, color unevenness tends to occur in the polarizing film.
The intersection angle θ (°) between the orientation axis (slow axis) and the width direction (TD direction) is preferably 20 ° or less, more preferably 10 ° or less, and particularly preferably 5 ° or less. When the crossing angle θ (°) is too large, the stretchability in the MD direction tends to decrease during the production of the polarizing film.
The deviation Δ θ (°) of the intersection angle θ (°) in the width direction (TD direction) is preferably 10 ° or less, more preferably 5 ° or less, and particularly preferably 3 ° or less. If the deviation Δ θ (°) is too large, color unevenness tends to occur in the polarizing film.
As a method for controlling the in-plane retardation rxy (nm) and the intersection angle θ (°), in addition to the method of stretching the film peeled from the casting die in the width direction (TD direction) as in the present invention, a method of adjusting the drying condition of the aqueous solution, a method of adjusting the chemical structure of the polyvinyl alcohol resin, and the like can be mentioned.
The process for producing the polyvinyl alcohol film for polarizing film production of the present invention will be described in more detail in the order of steps.
[ film Material ]
First, the polyvinyl alcohol resin and its aqueous solution used in the present invention will be described.
In the present invention, as the polyvinyl alcohol resin constituting the polyvinyl alcohol film, an unmodified polyvinyl alcohol resin, that is, a resin produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate is generally used. If necessary, a resin obtained by saponifying a copolymer of vinyl acetate and a small amount (usually 10 mol% or less, preferably 5 mol% or less) of a component copolymerizable with vinyl acetate may be used. Examples of the component copolymerizable with vinyl acetate include unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (e.g., ethylene, propylene, n-butene, isobutylene, etc.), vinyl ethers, and unsaturated sulfonates. Further, a modified polyvinyl alcohol resin obtained by chemically modifying a saponified hydroxyl group may be used. These may be used alone or in combination of two or more.
Further, as the polyvinyl alcohol resin, a polyvinyl alcohol resin having a 1, 2-diol structure in a side chain may be used. The polyvinyl alcohol resin having a 1, 2-diol structure in the side chain is obtained, for example, by (i) a method of saponifying a copolymer of vinyl acetate and 3, 4-diacetoxy-1-butene, (ii) a method of saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, (iii) a method of saponifying and dehydroketalizing a copolymer of vinyl acetate and 2, 2-dialkyl-4-vinyl-1, 3-dioxolane, and (iv) a method of saponifying a copolymer of vinyl acetate and glycerol monoallyl ether.
The weight average molecular weight of the polyvinyl alcohol resin is preferably 10 to 30 ten thousand, more preferably 11 to 28 ten thousand, and particularly preferably 12 to 26 ten thousand. When the weight average molecular weight is too small, it tends to be difficult to obtain sufficient optical properties when the polyvinyl alcohol resin is formed into an optical film, and when it is too large, stretching when a polarizing film is produced using the polyvinyl alcohol film tends to be difficult. The weight average molecular weight of the polyvinyl alcohol resin is measured by the GPC-MALS method.
The average saponification degree of the polyvinyl alcohol resin used in the present invention is preferably 98 mol% or more, more preferably 99 mol% or more, particularly preferably 99.5 mol% or more, and particularly preferably 99.8 mol% or more. If the average saponification degree is too small, the polyvinyl alcohol-based film tends to fail to provide sufficient optical properties when formed into a polarizing film.
Here, the average saponification degree in the present invention is measured according to JIS K6726.
The polyvinyl alcohol resin used in the present invention may be two or more kinds of polyvinyl alcohol resins different in modification type, modification amount, weight average molecular weight, average saponification degree, and the like.
The aqueous polyvinyl alcohol resin solution preferably contains, in addition to the polyvinyl alcohol resin, a plasticizer generally used, such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, trimethylolpropane, and at least one surfactant selected from nonionic, anionic, and cationic surfactants, as necessary, from the viewpoint of film-forming properties. These may be used alone or in combination of two or more.
The resin concentration of the aqueous polyvinyl alcohol resin solution thus obtained is preferably 15 to 60 wt%, more preferably 17 to 55 wt%, and particularly preferably 20 to 50 wt%. If the resin concentration of the aqueous solution is too low, the drying load tends to increase, and therefore, the productivity tends to decrease, and if it is too high, the viscosity tends to be too high and uniform dissolution tends to be difficult.
Next, the obtained polyvinyl alcohol resin aqueous solution is subjected to a defoaming treatment. Examples of the defoaming method include standing defoaming, defoaming with a multi-screw extruder, and the like. As the multi-screw extruder, a multi-screw extruder having a vent may be used, and a twin-screw extruder having a vent is generally used.
[ film-Forming Process ]
After the defoaming treatment, the polyvinyl alcohol resin aqueous solution was introduced into a T-shaped slit die at a fixed amount, discharged, cast on a rotating casting drum, and formed into a film by a continuous casting method.
The continuous casting method in the present invention refers to a method of forming a film by, for example, discharging an aqueous solution of a polyvinyl alcohol resin from a T-slot die and casting the solution onto a casting die such as a rotating casting drum, an endless belt, or a resin film. The film thus formed can be continuously dried by a hot roll, for example, heat treatment by a suspension dryer, while being conveyed in the flow direction (MD direction) after being peeled off from the casting die.
The resin temperature of the polyvinyl alcohol resin aqueous solution at the T-shaped slot die outlet is preferably 80 to 100 ℃, and particularly preferably 85 to 98 ℃.
When the resin temperature of the aqueous polyvinyl alcohol resin solution is too low, the flow tends to be poor, and when it is too high, the foaming tends to occur.
The viscosity of the aqueous polyvinyl alcohol resin solution is preferably 50 to 200 pas, and particularly preferably 70 to 150 pas, at the time of discharge.
If the viscosity of the aqueous solution is too low, flow tends to be poor, and if it is too high, casting tends to be difficult.
The discharge rate of the polyvinyl alcohol resin aqueous solution discharged from the T-slot die to the casting drum is preferably 0.2 to 5 m/min, more preferably 0.4 to 4 m/min, and particularly preferably 0.6 to 3 m/min.
If the discharge speed is too slow, productivity tends to be lowered, and if it is too fast, casting tends to be difficult.
The diameter of the casting drum is preferably 2 to 5m, more preferably 2.4 to 4.5m, and particularly preferably 2.8 to 4 m.
If the diameter is too small, the drying zone on the casting drum is shortened, and therefore, it tends to be difficult to increase the speed, while if it is too large, the transportability tends to be lowered.
The width of the casting drum is preferably 4m or more, more preferably 4.5m or more, particularly preferably 5m or more, and particularly preferably 5 to 6 m.
If the width of the casting drum is too small, productivity tends to be lowered.
The rotational speed of the casting drum is preferably 3 to 50 m/min, more preferably 4 to 40 m/min, and particularly preferably 5 to 35 m/min.
If the rotation speed is too slow, productivity tends to be lowered, and if it is too fast, drying tends to be insufficient.
The surface temperature of the casting drum is preferably 40 to 99 ℃, and particularly preferably 60 to 95 ℃.
If the surface temperature is too low, drying tends to be poor, and if it is too high, foaming tends to occur.
[ film to be formed ]
The moisture content of the film [ the film before stretching in the width direction (TD direction) ] formed as described above is preferably 0.5 to 15% by weight, more preferably 1 to 13% by weight, and particularly preferably 2 to 12% by weight. When the water content is too low or too high, the orientation of the target polymer, that is, the target degree of swelling and stretchability, tends to be hardly exhibited.
In order to adjust the moisture content, when the moisture content of the film before stretching in the width direction (TD direction) is too high, it is preferable to dry the film before stretching in the width direction (TD direction), and conversely, when the moisture content of the film before stretching in the width direction (TD direction) is too low, it is preferable to perform humidity conditioning before stretching in the width direction (TD direction). More preferably, the conditions of the drying step are adjusted so that the water content is within the above range.
The drying can be carried out by a known method using a heating roller, an infrared heater, or the like, but in the present invention, the drying is preferably carried out using a plurality of heating rollers, more preferably the temperature of the heating rollers is 40 to 150 ℃, and particularly preferably 50 to 120 ℃. In order to adjust the moisture content, the humidity control region may be provided before stretching in the width direction (TD direction).
[ conveying and stretching Processes ]
Subsequently, the film having the adjusted water content, which has been formed as described above, is continuously or intermittently stretched in the width direction (TD direction) while being conveyed in the flow direction (MD direction).
In the present invention, it is not necessary to stretch the film formed into a film in the flow direction (MD direction) in a particular manner, and it is sufficient to carry the film with a stretching tension to such an extent that the film does not bend. Of course, stretching in the width direction (TD direction) causes a neck-in depending on the poisson's ratio in the flow direction (MD direction), and since syneresis occurs also in the flow direction (MD direction) during drying, the film undergoes a slight dimensional shrinkage in the flow direction (MD direction).
Stretching in the flow direction (MD direction) of the degree of dimensional elongation in the flow direction (MD direction) is rather not preferred. The dimensional change rate in the flow direction (MD direction) before and after stretching in the width direction (TD direction) is preferably 0.8 to 1.0, more preferably 0.9 to 1.0, and particularly preferably 0.95 to 1.0. When the dimensional change rate is too small or too large, variation in the degree of swelling tends to increase, and the orientation of the target polymer, that is, the degree of swelling tends to be hardly expressed.
The film to be formed has a transport speed in the flow direction (MD direction) in a preferable range of 5 to 30 m/min, more preferably 7 to 25 m/min, and particularly preferably 8 to 20 m/min. If the transport speed is too slow, productivity tends to be reduced, and if it is too fast, color unevenness of the polarizing film tends to increase.
The method of simultaneously carrying out the transport in the flow direction (MD direction) and the stretching in the width direction (TD direction) of the film to be formed is not particularly limited, and for example, it is preferable to simultaneously carry out the transport and the stretching by sandwiching both ends in the width direction of the film with a plurality of clips. In the above case, the clips at the respective ends are preferably arranged at a pitch of 200mm or less, more preferably at a pitch of 100mm or less, and particularly preferably at a pitch of 50mm or less.
If the distance between the clips is too large, the stretched film tends to be curved, or the resulting polyvinyl alcohol film tends to have uneven thickness at both ends in the width direction and uneven retardation. The clip is preferably clamped at a position (tip end portion of the clip) that is 100mm or less from both ends in the width direction of the film to be formed. When the clipping position (tip end portion) of the clip is excessively positioned at the center portion in the width direction of the film, the waste film end portion tends to be enlarged and the product width tends to be narrowed.
The specific polyvinyl alcohol-based film of the present invention can be obtained by stretching the film formed as described above in the width direction (TD direction), and the stretching ratio in this case is preferably 1.05 to 1.5 times, more preferably 1.1 to 1.45 times, particularly preferably 1.15 to 1.4 times, and particularly preferably 1.2 to 1.3 times. When the stretching ratio in the width direction (TD direction) is too high or too low, the swelling property and the stretchability tend to be reduced in the production of the polarizing film.
The continuous stretching step in the width direction (TD direction) may be performed in 1 stage (1 time), or may be performed in a plurality of stages (multiple times) so that the total stretching magnification falls within the above-described range of stretching magnification (also referred to as sequential stretching). For example, after the first stage stretching, the sheet may be simply conveyed in a fixed width direction (TD direction), and then the second and subsequent stages of stretching may be performed.
In particular, in the case of a thin film, by performing a simple conveyance step, the stress of the film is relaxed, and breakage can be avoided.
In the case of inserting the conveyance step in which the width is fixed, the fixed width can be made narrower than the width after the first stage of stretching. The film immediately after stretching is likely to shrink due to stress relaxation, and also shrinks with dehydration, so that the constant width can be narrowed to these shrunk widths. However, narrowing to a width equal to or larger than the reduction width is not preferable because the film is bent.
The stretching step is preferably performed after the film drying step, but may be performed separately before or after the film drying step, or may be performed during the film drying step.
In a preferred embodiment of the present invention, the film is stretched once more than 1.3 times in the width direction (TD direction) and then shrunk to a dimension in which the final stretching ratio in the width direction (TD direction) is 1.05 to 1.5 times. In this case, the film can be simply conveyed by stretching the film by more than 1.3 times and then by a constant width with a stretch ratio of 1.05 to 1.5. By the above method, stress relaxation of the thin film is performed, and particularly, in the case of a thin film, breakage can be avoided.
In the present invention, the film to be formed is stretched in the width direction (TD direction) preferably at 50 to 150 ℃, more preferably at 60 to 140 ℃, and particularly preferably at 70 to 130 ℃. When the stretching temperature is too low or too high, the stretchability of the polarizing film during production tends to be reduced. When the sequential stretching or the intermittent stretching is performed, the stretching temperature may be changed at each stretching stage, or a temperature gradient may be provided during the stretching.
In the present invention, the stretching time in stretching the film to be formed in the width direction (TD direction) is preferably 2 to 60 seconds, more preferably 5 to 45 seconds, and particularly preferably 10 to 30 seconds. If the stretching time is too short, the film tends to be easily broken, whereas if the stretching time is too long, the equipment load tends to increase. In the case of performing the sequential stretching, the stretching time may be changed at each stretching stage.
In the present invention, the film to be formed may be stretched in the width direction (TD direction) and then subjected to heat treatment using a suspension dryer or the like. The temperature of the heat treatment is preferably 60 to 200 ℃, more preferably 70 to 150 ℃, and particularly preferably 100 to 140 ℃.
If the heat treatment temperature is too low, the dimensional stability tends to be easily lowered, and conversely, if too high, the stretchability in the production of the polarizing film tends to be lowered.
The heat treatment time is preferably 1 to 60 seconds, and particularly preferably 5 to 30 seconds. If the heat treatment time is too short, the dimensional stability tends to be lowered, and conversely, if it is too long, the swelling property and the stretchability tend to be lowered in the production of the polarizing film.
[ polyvinyl alcohol-based film for polarizing film production ]
The polyvinyl alcohol film for polarizing film production of the present invention is thus obtained, and finally wound into a roll to form a product. The thickness of the polyvinyl alcohol film is preferably 5 to 60 μm from the viewpoint of in-plane retardation, more preferably 5 to 45 μm, particularly preferably 5 to 30 μm from the viewpoint of thinning of the polarizing film, and particularly preferably 10 to 20 μm from the viewpoint of avoiding breakage. The thickness of the polyvinyl alcohol film is adjusted by the resin concentration in the polyvinyl alcohol resin aqueous solution, the discharge amount (discharge speed) to the casting die, the draw ratio, and the like.
The polyvinyl alcohol film has a width of 2m or more, more preferably 3m or more from the viewpoint of increasing the area, and particularly preferably 4 to 6m from the viewpoint of avoiding breakage.
The length of the polyvinyl alcohol film is 2km or more, more preferably 3km or more from the viewpoint of increasing the area, and particularly preferably 3 to 50km from the viewpoint of the transport weight.
The polyvinyl alcohol-based film for producing a polarizing film of the present invention is very useful as a raw film for a polarizing film, and a polarizing film formed from the polyvinyl alcohol-based film and a method for producing a polarizing plate will be described below.
[ method for producing polarizing film ]
The polarizing film of the present invention is produced by feeding the polyvinyl alcohol film from a roll and transferring the film in a horizontal direction, followed by swelling, dyeing, boric acid crosslinking, stretching, washing, drying, and the like.
The swelling step is performed before the dyeing step. The swelling step can wash dirt on the surface of the polyvinyl alcohol film, and also has an effect of preventing uneven dyeing or the like by swelling the polyvinyl alcohol film. In the swelling step, water is generally used as the treatment liquid. When the main component of the treatment liquid is water, a small amount of an iodinated compound, an additive such as a surfactant, alcohol, or the like may be added. The temperature of the swelling bath is usually about 10 to 45 ℃ and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.
In the swelling step, the swelling degree of the polyvinyl alcohol film of the invention is as described above, and when the swelling degree of the film is measured by immersing the film in water at 30 ℃ for 15 minutes, the swelling degree X (%) in the width direction (TD direction) and the swelling degree Y (%) in the flow direction (MD direction) satisfy the physical property values of both of the following conditions (1) and (2).
(1)110≤Y≤140
(2)1.01≤Y/X≤1.2
Further, as described above, the swelling degree Z (%) in the thickness direction preferably satisfies the following condition (3).
(3)140≤Z≤170
The dyeing step is performed by contacting the film with a liquid containing iodine or a dichroic dye. Usually, an aqueous solution of iodine-potassium iodide is used, and preferably, the concentration of iodine is 0.1 to 2g/L and the concentration of potassium iodide is 1 to 100 g/L. The dyeing time is about 30-500 seconds, which is practical. The temperature of the treatment bath is preferably 5 to 50 ℃. The aqueous solution may contain a small amount of an organic solvent having compatibility with water in addition to the aqueous solvent.
The boric acid crosslinking step is carried out by using a boron compound such as boric acid or borax. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture solution at a concentration of about 10 to 100g/L, and the coexistence of potassium iodide in the liquid is preferable from the viewpoint of stabilization of polarization performance. The temperature at the time of treatment is preferably about 30 to 70 ℃ and the treatment time is preferably about 0.1 to 20 minutes, and the stretching operation may be performed during the treatment as needed.
The stretching step preferably stretches the film in the uniaxial direction by 3 to 10 times, preferably 3.5 to 6 times. In this case, the stretching may be performed in a direction perpendicular to the stretching direction by a small amount (to the extent of preventing the shrinkage in the width direction, or by a larger amount). The temperature during stretching is preferably 40 to 170 ℃. Further, the draw ratio may be finally set within the above range, and the drawing operation may be performed only once or may be performed a plurality of times in the production process.
The washing step is performed by, for example, immersing the polyvinyl alcohol film in an aqueous iodide solution such as water or potassium iodide, and can remove precipitates generated on the surface of the film. The concentration of potassium iodide in the aqueous solution of potassium iodide is about 1-80 g/L. The temperature during the washing treatment is usually 5 to 50 ℃, preferably 10 to 45 ℃. The treatment time is usually 1 to 300 seconds, preferably 10 to 240 seconds. The washing with water and the washing with an aqueous solution of potassium iodide may be performed in an appropriate combination.
The drying step is performed, for example, by drying the film in the air at 40 to 80 ℃ for 1 to 10 minutes.
The polarization degree of the polarizing film obtained in this way is preferably 99.5% or more, and particularly preferably 99.8% or more. If the degree of polarization is too lowThere is a tendency that the contrast ratio in the liquid crystal display is lowered. In general, the degree of polarization was calculated by measuring the transmittance (H) at the wavelength λ of 2 polarizing films stacked in such a manner that the orientation directions thereof were the same direction11) The transmittance (H) was measured at a wavelength λ in a state where 2 polarizing films were stacked so that the orientation directions were orthogonal to each other1) Light transmittance (H)11) And light transmittance (H)1) The degree of polarization is calculated according to the following equation.
Degree of polarization [ (H)11-H1)/(H11+H1)]1/2
Further, the polarizing film of the present invention preferably has a single-sheet transmittance of 44% or more. If the single transmittance is too low, the luminance of the liquid crystal display tends to be increased.
The single-sheet transmittance is a value obtained by measuring the transmittance of a polarizing film single sheet using a spectrophotometer.
Next, a method for producing a polarizing plate of the present invention using the polarizing film of the present invention will be described.
The polarizing film of the present invention is suitable for producing a polarizing plate having little color unevenness and excellent polarizing performance.
[ method for producing polarizing plate ]
The polarizing plate of the present invention is produced by bonding an optically isotropic resin film as a protective film to one or both surfaces of the polarizing film of the present invention via an adhesive. Examples of the protective film include films and sheets of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyether sulfone, polyarylene ester, poly-4-methylpentene, polyphenylene ether, and the like.
The bonding method is performed by a known method, for example, by uniformly applying a liquid adhesive composition to a polarizing film, a protective film, or both, bonding the both to each other under pressure, and heating and irradiating the both with an active energy ray.
In addition, a curable resin such as a urethane resin, an acrylic resin, or a urea resin may be applied to one or both surfaces of the polarizing film and cured to form a cured layer, thereby forming a polarizing plate. In this way, the cured layer can be replaced with the protective film, and thus a thin film can be obtained.
The polarizing film and the polarizing plate using the polyvinyl alcohol film of the invention are excellent in polarizing performance, and are preferably used for liquid crystal display devices such as personal digital assistants, personal computers, televisions, projectors, billboards, desktop calculators, electronic watches, word processors, electronic papers, game machines, video recorders, cameras, photo albums, thermometers, audio equipment, automobiles, mechanical measuring instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, antireflection layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical fiber communication instruments, medical instruments, building materials, toys, and the like.
Examples
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.
In the examples, "parts" means weight basis.
Next, the measurement and evaluation of the properties (degree of swelling, variation in degree of swelling, in-plane retardation, variation in-plane retardation, intersection angle of orientation axis and width direction, dimensional change rate) of the polyvinyl alcohol films and the properties (polarization degree, single-sheet transmittance, color unevenness) of the polarizing films in the following examples and comparative examples were carried out as follows.
< measurement conditions >
[ degree of swelling (%) of polyvinyl alcohol film ]
From the central part and the left and right end parts in the width direction of the obtained polyvinyl alcohol film, 1 sheet of each film having a width of 100mm × a length of 100mm was cut out, and immersed in water at 30 ℃ for 15 minutes to swell. From the dimensions before and after the impregnation, the swelling degree X (%) in the width direction (TD direction) and the swelling degree Y (%) in the flow direction (MD direction) were calculated by the following formulas. The degree of swelling Z (%) in the thickness direction is determined from the width direction of the polyvinyl alcohol film1 piece of each film having a width of 100mm × a length of 100mm was cut out from the center and the left and right ends of the sheet, and the sheet was immersed in water at 30 ℃ for 15 minutes to swell, and then taken out and spread on a filter paper (5A). Further, filter paper (5A) was superposed on the film, and 150 mm. times.150 mm. times.4 mm (4.4. times.10 mm) was placed thereon-2g/mm2) The SUS plate (5) was used for 5 seconds to remove the water adhered to the surface of the film. The film was quickly put into a weighing bottle, and the weight was measured and taken as "weight after dipping". The above operation was carried out at 23 ℃ and 50% RH.
Subsequently, the film was left in a drier at 105 ℃ for 16 hours to remove water from the film, and then the film was taken out, quickly put into a weighing bottle, and measured for weight, which was defined as "weight after drying". Subsequently, the swelling degree Z (%) in the thickness direction was calculated from the following formula.
Swelling degree X (%) (100X width in TD after immersion)/width in TD before immersion (mm)
Swelling degree Y (%). 100X width in MD after immersion (mm)/width in MD before immersion (mm)
Swelling degree Z (%) is 1000000 × weight after immersion (g)/weight after drying (g)/X/Y
[ deviation (%) of swelling degree ]
Among the values of the swelling degree X (%) in the width direction (TD direction) obtained in the above measurement (three points, the central portion and the left and right end portions), the difference between the maximum value and the minimum value is used as the deviation Δ X (%) in the swelling degree in the width direction (TD direction). Similarly, the difference Δ Y (%) in the degree of swelling in the flow direction (MD direction) and the difference Δ Z (%) in the degree of swelling in the thickness direction were obtained.
[ in-plane retardation Rxy (nm), variation in-plane retardation Δ Rxy (nm), intersection angle θ (°) between orientation axis (slow axis) and width direction (TD direction), and variation Δ θ (°) of intersection angle θ ]
From the central part and the left and right end parts (from the film end parts to the inside of 10 cm) in the width direction of the obtained polyvinyl alcohol film, a test piece having a length of 4cm × a width of 4cm was cut, and the in-plane retardation rxy (nm) and the intersection angle θ (°) of the orientation axis (slow axis) and the width direction (TD direction) were measured using a retardation (retardation) measuring device ("KOBRA-WR" manufactured by wako corporation). Further, of the in-plane retardation rxy (nm) at the center portion and both the left and right end portions in the width direction obtained in the above measurement, the difference between the maximum value and the minimum value is used as the deviation Δ rxy (nm) of the in-plane retardation. In addition, the difference between the maximum value and the minimum value among the intersection angles θ (°) of the center portion and the left and right end portions in the width direction obtained in the above measurement is used as the deviation Δ θ (°) of the intersection angle θ (°).
[ rate of change in size ]
Before stretching in the width direction (TD direction), a mark (2 dots) was left with a distance of 1m in the flow direction (MD direction) with a universal ink. After the stretching in the width direction (TD direction), the distance l (m) between the 2 points was measured with a vernier caliper, and the dimensional change rate was calculated from the following equation.
Rate of change of dimension L (m)/1(m)
[ degree of polarization (%), monolithic transmittance (%) ]
From the central part in the width direction of the obtained polarizing film, a test piece of 4cm in length × 4cm in width was cut out, and the polarization degree (%) and the single-sheet transmittance (%) were measured using an automatic polarizing film measuring apparatus (manufactured by japan spectrochemical corporation: VAP 7070).
[ color unevenness ]
A test piece having a length of 30cm × a width of 30cm was cut out from the central portion in the width direction of the obtained polarizing film, and the polarizing film was sandwiched between 2 crossed nicols polarizing plates (single sheet transmittance 43.5% and polarization degree 99.9%) at an angle of 45 °, and then optically color unevenness was observed in a transmission mode using a lamp box with a surface illuminance of 14000lx, and evaluated according to the following criteria.
(evaluation criteria)
O … No color unevenness
Slight color unevenness of Δ …
X … color unevenness
< example 1>
(preparation of polyvinyl alcohol film)
A5000L dissolution tank was charged with 1000kg of a polyvinyl alcohol resin having a weight average molecular weight of 142000 and a degree of saponification of 99.8 mol%, 2500kg of water, 105kg of glycerin as a plasticizer, and 0.25kg of polyoxyethylene lauryl amine as a surfactant, and the mixture was heated to 150 ℃ while stirring to be dissolved under pressure, thereby obtaining an aqueous solution of a polyvinyl alcohol resin having a resin concentration of 25 wt%. Then, the aqueous polyvinyl alcohol resin solution was fed to a twin-screw extruder and defoamed, and then the aqueous solution was cooled to 95 ℃ and discharged (discharge speed 2.5 m/min) from a T-slot die discharge port and cast on a rotating casting drum to form a film. The film of the obtained film was peeled off from the casting drum, and while being conveyed in the flow direction (MD direction), the front and back surfaces of the film were alternately brought into contact with 10 total hot rolls and dried. Thus, a film (width: 2m, thickness: 60 μm) having a water content of 10% by weight was obtained. Then, both left and right ends of the film were nipped at a nip pitch of 45mm, and the film was stretched 1.2 times in the width direction (TD direction) at 120 ℃ by a stretcher while being conveyed at a speed of 8 m/min in the flow direction (MD direction). The dimensional change rate in the flow direction (MD direction) before and after stretching in the width direction (TD direction) was 0.96. Finally, the film was heat-treated at 120 ℃ for 10 seconds to obtain a polyvinyl alcohol film (width: 2.4m, thickness: 50 μm, length: 2 km). The properties of the obtained polyvinyl alcohol film are shown in tables 1 and 2.
(production of polarizing film and polarizing plate)
The obtained polyvinyl alcohol film was taken out from the roll, transferred in the horizontal direction, immersed in a water bath at a water temperature of 30 ℃ to swell, and stretched 1.7 times in the flow direction (MD direction). Then, the film was immersed in an aqueous solution of 0.5g/L iodine and 30g/L potassium iodide at 30 ℃ to dye the film and simultaneously stretch the film by 1.6 times in the flow direction (MD direction), and then immersed in an aqueous solution of 40g/L boric acid and 30g/L potassium iodide (50 ℃) to crosslink the film with boric acid and simultaneously uniaxially stretch the film by 2.1 times in the flow direction (MD direction). Finally, the film was washed with an aqueous potassium iodide solution and dried at 50 ℃ for 2 minutes to obtain a polarizing film having a total draw ratio of 5.8 times. The above production process did not cause breakage, and the properties of the obtained polarizing film are shown in table 2.
A triacetyl cellulose film having a thickness of 40 μm was laminated on both sides of the polarizing film obtained above using an aqueous polyvinyl alcohol solution as an adhesive, and dried at 70 ℃ to obtain a polarizing plate.
< example 2>
A polyvinyl alcohol-based film (width 2.4m, thickness 50 μm, length 2km) was obtained in the same manner as in example 1, except that the film formed in example 1 was stretched 1.4 times in the width direction (TD direction) at 120 ℃ using a stretcher, and then conveyed at a constant width of 2.4m (corresponding to 1.2 times stretching). The dimensional change rate in the flow direction (MD direction) before and after stretching in the width direction (TD direction) was 0.96. The properties of the obtained polyvinyl alcohol film are shown in tables 1 and 2.
Further, a polarizing film and a polarizing plate were obtained in the same manner as in example 1 using the polyvinyl alcohol film. No fracture occurred in the above production. The properties of the obtained polarizing film are shown in table 2.
< example 3>
A polyvinyl alcohol film (width 2.6m, thickness 15 μm, length 2km) was obtained in the same manner as in example 1, except that in example 1, the discharge speed during film formation was 0.8 m/min, and the film having a water content of 5% by weight (width 2m, thickness 20 μm) was stretched 1.4 times in the width direction (TD direction) and then conveyed at a constant width 2.6m (corresponding to 1.3 times stretching). The dimensional change rate in the flow direction (MD direction) before and after stretching in the width direction (TD direction) was 0.98. The properties of the obtained polyvinyl alcohol film are shown in tables 1 and 2.
Further, a polarizing film and a polarizing plate were obtained in the same manner as in example 1 using the polyvinyl alcohol film. Even though the polyvinyl alcohol film of the stock is thin, no breakage occurs in the stretching step in the production of the polarizing film. The properties of the obtained polarizing film are shown in table 3.
< comparative example 1>
A polyvinyl alcohol film (width 2m, thickness 60 μm, length 2km) was obtained in the same manner as in example 1, except that the film formed in example 1 was not stretched in the width direction (TD direction) by a stretching machine. The properties of the obtained polyvinyl alcohol film are shown in tables 1 and 2.
Further, a polarizing film and a polarizing plate were obtained in the same manner as in example 1 using the polyvinyl alcohol film. The properties of the obtained polarizing film are shown in table 3.
< comparative example 2>
A polyvinyl alcohol film (width 2m, thickness 20 μm, length 2km) was obtained in the same manner as in example 3, except that the film formed in example 3 was not stretched in the width direction (TD direction) by a stretching machine. The properties of the obtained polyvinyl alcohol film are shown in tables 1 and 2.
Further, a polarizing film and a polarizing plate were obtained in the same manner as in example 1 using the polyvinyl alcohol film. The properties of the obtained polarizing film are shown in table 3.
[ Table 1]
[ Table 2]
[ Table 3]
As is clear from the results of the above examples and comparative examples, the polarizing films of examples 1 to 3 obtained from the polyvinyl alcohol-based films in which the ratio of the degree of swelling X (%) in the width direction (TD direction) to the degree of swelling Y (%) in the flow direction (MD direction) satisfies the range specified by the above conditions (1) and (2) have a high degree of polarization and no color unevenness. On the other hand, the polarizing films of comparative examples 1 and 2 obtained from the polyvinyl alcohol-based films having a ratio of the degree of swelling X (%) in the width direction (TD direction) to the degree of swelling Y (%) in the flow direction (MD direction) outside the range specified under the above conditions (1) and (2) were inferior in polarization degree and also had uneven color.
It is also found that the polarizing films of examples 1 to 3 obtained from the polyvinyl alcohol-based films in which the in-plane retardation (Rxy) and the intersection angle θ (°) of the orientation axis (slow axis) and the width direction (TD direction) satisfy the ranges specified by the above conditions (4) and (5) have a high degree of polarization and no color unevenness. On the other hand, the polarizing films of comparative examples 1 and 2 obtained from the polyvinyl alcohol-based films in which the in-plane retardation (Rxy) and the intersection angle θ (°) of the orientation axis (slow axis) and the width direction (TD direction) were out of the ranges specified under the above conditions (4) and (5) were inferior in polarization degree and also uneven in color was observed.
The above embodiments are merely illustrative and are not to be construed as limiting the present invention. Variations that are obvious to those skilled in the art are within the scope of the invention.
Industrial applicability
The polarizing film and the polarizing plate using the polyvinyl alcohol film of the invention are excellent in polarizing performance, and are preferably used for liquid crystal display devices such as personal digital assistants, personal computers, televisions, projectors, billboards, desktop calculators, electronic watches, word processors, electronic papers, game machines, video recorders, cameras, photo albums, thermometers, audio equipment, automobiles, mechanical measuring instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, antireflection layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical fiber communication instruments, medical instruments, building materials, toys, and the like.
Claims (14)
1. A polyvinyl alcohol film for producing a polarizing film, characterized in that it is a polyvinyl alcohol film having a thickness of 5 to 30 μm, a width of 2m or more and a length of 2km or more, and when the polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the polyvinyl alcohol film has a swelling degree X% in the width direction, that is, TD direction, and a swelling degree Y% in the length direction, that is, MD direction, which satisfy the following conditions (1) and (2),
(1)110≤Y≤140
(2)1.05≤Y/X≤1.2。
2. the polyvinyl alcohol film for the production of a polarizing film according to claim 1, wherein when the polyvinyl alcohol film is immersed in water at 30 ℃ for 15 minutes, the degree of swelling Z% in the thickness direction satisfies the following condition (3),
(3)140≤Z≤170。
3. the polyvinyl alcohol film for the production of a polarizing film according to claim 1 or 2, wherein a deviation Δ X% of a swelling degree X% in a width direction, that is, a TD direction, a deviation Δ Y% of a swelling degree Y% in a length direction, that is, an MD direction, and a deviation Δ Z% of a swelling degree Z% in a thickness direction are within 5%.
4. The polyvinyl alcohol-based film for polarizing film production according to claim 1 or 2, which satisfies the following conditions (4) and (5),
(4) in-plane phase difference Rxy: 100 to 200nm
(5) The crossing angle theta DEG between the orientation axis, i.e. the slow axis, and the width direction, i.e. the TD direction, is 20 DEG or less
Here, the in-plane retardation Rxy is a value calculated by the following formula (A) in the case where the refractive index in the width direction, that is, the TD direction, is nx, the refractive index in the length direction, that is, the MD direction, is ny, and the thickness is d in the polyvinyl alcohol film,
(A) rxy = | nx-ny | xd, where Rxy is in nm and d is in nm.
5. The polyvinyl alcohol film for producing a polarizing film according to claim 4, wherein a deviation Δ Rxy of the in-plane retardation Rxy in a width direction, that is, a TD direction is 10nm or less, Rxy is in nm, and Δ Rxy is in nm.
6. The polyvinyl alcohol film for polarizing film production according to claim 4, wherein a deviation Δ θ ° of the crossing angle θ ° is 10 ° or less.
7. A polarizing film comprising the polyvinyl alcohol-based film for producing a polarizing film according to any one of claims 1 to 6.
8. A polarizing plate comprising the polarizing film according to claim 7 and a protective film provided on at least one surface of the polarizing film.
9. A method for producing a polyvinyl alcohol film for polarizing film production, comprising: a step of forming a film from an aqueous solution of a polyvinyl alcohol resin by a continuous casting method; continuously drying the cast product while conveying the cast product in a flow direction, i.e., in the MD direction, after the cast product is peeled from the casting mold; and a step of stretching the polyvinyl alcohol film in the width direction, that is, in the TD direction, wherein when the polyvinyl alcohol film thus produced is immersed in water at 30 ℃ for 15 minutes, the following conditions (1) and (2) are satisfied in the width direction, that is, the swelling degree X% in the TD direction and the swelling degree Y% in the flow direction, that is, the MD direction,
(1)110≤Y≤140
(2)1.05≤Y/X≤1.2。
10. the method for producing a polyvinyl alcohol film for the production of a polarizing film according to claim 9, wherein the film is stretched at a stretch ratio of 1.05 to 1.5 times in the width direction, that is, in the TD direction.
11. The method for producing a polyvinyl alcohol film for the production of a polarizing film according to claim 9 or 10, wherein the stretching in the width direction, that is, the TD direction is performed at 50 to 150 ℃.
12. The method for producing a polyvinyl alcohol film for the production of a polarizing film according to claim 9 or 10, wherein the water content of the film before stretching in the width direction, that is, the TD direction is 0.5 to 15% by weight.
13. The method for producing a polyvinyl alcohol film for the production of a polarizing film according to claim 9 or 10, wherein after the film is once stretched more than 1.3 times in the width direction, that is, in the TD direction, dimensional shrinkage is performed so that the final stretching ratio in the width direction, that is, in the TD direction is 1.05 to 1.5 times.
14. The method for producing a polyvinyl alcohol film for the production of a polarizing film according to claim 9 or 10, wherein the dimensional change rate in the width direction, that is, the MD direction, which is the flow direction of the film before and after stretching in the TD direction, is 0.8 to 1.0.
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| JP2015-226889 | 2015-11-19 | ||
| PCT/JP2016/081793 WO2017073639A1 (en) | 2015-10-27 | 2016-10-27 | Polyvinyl alcohol film for producing polarizing film, polarizing film and polarizing plate using polyvinyl alcohol film for producing polarizing film, and production method for polyvinyl alcohol film for producing polarizing film |
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| CN101329421A (en) * | 2004-11-16 | 2008-12-24 | 大日本印刷株式会社 | Retardation film and method for producing the same, optical functional film, polarizing film, and display device |
| CN102834235A (en) * | 2010-07-02 | 2012-12-19 | 日本合成化学工业株式会社 | Polyvinyl alcohol-based film, method for manufacturing polyvinyl alcohol-based film, polarized film, and polarizing plate |
| CN104662071A (en) * | 2012-09-26 | 2015-05-27 | 株式会社可乐丽 | Polyvinyl alcohol-based polymer film and manufacturing process therefor |
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| JP4592147B2 (en) | 2000-04-21 | 2010-12-01 | 株式会社クラレ | Polyvinyl alcohol film and polarizing film |
| JP3480920B2 (en) | 2000-05-10 | 2003-12-22 | 株式会社クラレ | Method for producing polyvinyl alcohol film |
| JP3496825B2 (en) | 2000-05-12 | 2004-02-16 | 株式会社クラレ | Method for producing polyvinyl alcohol polymer film |
| JP3473839B2 (en) | 2000-06-28 | 2003-12-08 | 株式会社クラレ | Method for producing polyvinyl alcohol film for polarizing film |
| JP4070186B2 (en) * | 2002-04-26 | 2008-04-02 | 日本合成化学工業株式会社 | Polyvinyl alcohol-based resin film laminate and use thereof |
| JP3701022B2 (en) * | 2002-12-19 | 2005-09-28 | 日東電工株式会社 | Manufacturing method of birefringent optical film, film obtained by the manufacturing method, elliptically polarizing plate using the same, and liquid crystal display device using them |
| JP2007051166A (en) * | 2005-07-19 | 2007-03-01 | Yukari Nose | Method and apparatus for swelling polyvinyl alcohol film and method for producing polarizing film and polarizing plate |
| KR20110006461A (en) * | 2009-07-14 | 2011-01-20 | 동우 화인켐 주식회사 | Method for preparing polarizer |
| JP5624803B2 (en) * | 2010-05-31 | 2014-11-12 | 株式会社クラレ | Polyvinyl alcohol polymer film |
| JP5904725B2 (en) * | 2010-07-21 | 2016-04-20 | 日本合成化学工業株式会社 | Production method of polyvinyl alcohol film, polyvinyl alcohol film, polarizing film and polarizing plate |
| JP5911219B2 (en) * | 2010-08-27 | 2016-04-27 | 日本合成化学工業株式会社 | Production method of polyvinyl alcohol film, polyvinyl alcohol film, polarizing film and polarizing plate |
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| CN101329421A (en) * | 2004-11-16 | 2008-12-24 | 大日本印刷株式会社 | Retardation film and method for producing the same, optical functional film, polarizing film, and display device |
| CN102834235A (en) * | 2010-07-02 | 2012-12-19 | 日本合成化学工业株式会社 | Polyvinyl alcohol-based film, method for manufacturing polyvinyl alcohol-based film, polarized film, and polarizing plate |
| CN104662071A (en) * | 2012-09-26 | 2015-05-27 | 株式会社可乐丽 | Polyvinyl alcohol-based polymer film and manufacturing process therefor |
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