CN110791980A - Method for producing polarizing film and apparatus for producing polarizing film - Google Patents
Method for producing polarizing film and apparatus for producing polarizing film Download PDFInfo
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- CN110791980A CN110791980A CN201910699347.2A CN201910699347A CN110791980A CN 110791980 A CN110791980 A CN 110791980A CN 201910699347 A CN201910699347 A CN 201910699347A CN 110791980 A CN110791980 A CN 110791980A
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- Prior art keywords
- crosslinking
- treatment liquid
- liquid
- tank
- polarizing film
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Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 83
- 239000007788 liquid Substances 0.000 claims abstract description 428
- 238000011282 treatment Methods 0.000 claims abstract description 400
- 238000004132 cross linking Methods 0.000 claims abstract description 390
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Natural products OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 223
- 229920005989 resin Polymers 0.000 claims abstract description 122
- 239000011347 resin Substances 0.000 claims abstract description 122
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 120
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 120
- 238000004043 dyeing Methods 0.000 claims abstract description 103
- -1 oxalic acid compound Chemical class 0.000 claims abstract description 102
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 97
- XMBWDFGMSWQBCA-UHFFFAOYSA-M iodide Chemical compound [I-] XMBWDFGMSWQBCA-UHFFFAOYSA-M 0.000 claims abstract description 80
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 72
- 238000000034 method Methods 0.000 claims abstract description 28
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052740 iodine Inorganic materials 0.000 claims abstract description 22
- 239000011630 iodine Substances 0.000 claims abstract description 22
- 230000001678 irradiating effect Effects 0.000 claims abstract description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 89
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 claims description 39
- 238000002360 preparation method Methods 0.000 claims description 36
- 150000001639 boron compounds Chemical class 0.000 claims description 6
- 206010042674 Swelling Diseases 0.000 description 26
- 238000004140 cleaning Methods 0.000 description 26
- 230000008961 swelling Effects 0.000 description 26
- 229940039748 oxalate Drugs 0.000 description 25
- 238000001035 drying Methods 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 15
- MUBZPKHOEPUJKR-UHFFFAOYSA-L Oxalate Chemical compound [O-]C(=O)C([O-])=O MUBZPKHOEPUJKR-UHFFFAOYSA-L 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 8
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 8
- 239000004327 boric acid Substances 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- UAYWVJHJZHQCIE-UHFFFAOYSA-L zinc iodide Chemical compound I[Zn]I UAYWVJHJZHQCIE-UHFFFAOYSA-L 0.000 description 8
- 230000003287 optical effect Effects 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 101100165177 Caenorhabditis elegans bath-15 gene Proteins 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000007654 immersion Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 230000010287 polarization Effects 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 229920002689 polyvinyl acetate Polymers 0.000 description 4
- 239000011118 polyvinyl acetate Substances 0.000 description 4
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 4
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 3
- 229910021538 borax Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000001186 cumulative effect Effects 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 150000004694 iodide salts Chemical class 0.000 description 3
- 239000000178 monomer Substances 0.000 description 3
- GEVPUGOOGXGPIO-UHFFFAOYSA-N oxalic acid;dihydrate Chemical compound O.O.OC(=O)C(O)=O GEVPUGOOGXGPIO-UHFFFAOYSA-N 0.000 description 3
- ZDYUUBIMAGBMPY-UHFFFAOYSA-N oxalic acid;hydrate Chemical compound O.OC(=O)C(O)=O ZDYUUBIMAGBMPY-UHFFFAOYSA-N 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 239000004328 sodium tetraborate Substances 0.000 description 3
- 235000010339 sodium tetraborate Nutrition 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 230000032258 transport Effects 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 229910001516 alkali metal iodide Inorganic materials 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 229910001619 alkaline earth metal iodide Inorganic materials 0.000 description 2
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 2
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- BHZRJJOHZFYXTO-UHFFFAOYSA-L potassium sulfite Chemical compound [K+].[K+].[O-]S([O-])=O BHZRJJOHZFYXTO-UHFFFAOYSA-L 0.000 description 2
- 235000019252 potassium sulphite Nutrition 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000011592 zinc chloride Substances 0.000 description 2
- 235000005074 zinc chloride Nutrition 0.000 description 2
- NPRYCHLHHVWLQZ-TURQNECASA-N 2-amino-9-[(2R,3S,4S,5R)-4-fluoro-3-hydroxy-5-(hydroxymethyl)oxolan-2-yl]-7-prop-2-ynylpurin-8-one Chemical compound NC1=NC=C2N(C(N(C2=N1)[C@@H]1O[C@@H]([C@H]([C@H]1O)F)CO)=O)CC#C NPRYCHLHHVWLQZ-TURQNECASA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- IMROMDMJAWUWLK-UHFFFAOYSA-N Ethenol Chemical compound OC=C IMROMDMJAWUWLK-UHFFFAOYSA-N 0.000 description 1
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 description 1
- 102000003939 Membrane transport proteins Human genes 0.000 description 1
- 108090000301 Membrane transport proteins Proteins 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- QYKIQEUNHZKYBP-UHFFFAOYSA-N Vinyl ether Chemical class C=COC=C QYKIQEUNHZKYBP-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000003926 acrylamides Chemical class 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
- QGZKDVFQNNGYKY-UHFFFAOYSA-O ammonium group Chemical group [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical compound [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QXDMQSPYEZFLGF-UHFFFAOYSA-L calcium oxalate Chemical compound [Ca+2].[O-]C(=O)C([O-])=O QXDMQSPYEZFLGF-UHFFFAOYSA-L 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 description 1
- IRXRGVFLQOSHOH-UHFFFAOYSA-L dipotassium;oxalate Chemical compound [K+].[K+].[O-]C(=O)C([O-])=O IRXRGVFLQOSHOH-UHFFFAOYSA-L 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229940015043 glyoxal Drugs 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- UHNWOJJPXCYKCG-UHFFFAOYSA-L magnesium oxalate Chemical compound [Mg+2].[O-]C(=O)C([O-])=O UHNWOJJPXCYKCG-UHFFFAOYSA-L 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000009061 membrane transport Effects 0.000 description 1
- 125000005395 methacrylic acid group Chemical group 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 description 1
- 229940039790 sodium oxalate Drugs 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 1
- 235000019345 sodium thiosulphate Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
- D06P3/00—Special processes of dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form, classified according to the material treated
- D06P3/58—Material containing hydroxyl groups
-
- 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
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/06—Coating with compositions not containing macromolecular substances
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
- D06P1/00—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed
-
- 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
-
- 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
- C08J2329/00—Characterised by the use 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; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Polymers & Plastics (AREA)
- Medicinal Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Polarising Elements (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Abstract
The invention provides a method and an apparatus for manufacturing a polarizing film. Provided are a method for producing a polarizing film and an apparatus for producing a polarizing film, wherein tension increase during transportation of a polyvinyl alcohol resin film can be suppressed. The method for manufacturing a polarizing film includes: a step of treating the polyvinyl alcohol resin film with a dyeing treatment liquid containing iodine; a step of adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiating the liquid to which the oxalic acid compound is added with ultraviolet rays to obtain a first crosslinking treatment liquid; and a step of immersing the polyvinyl alcohol resin film after the step of treating with the dyeing treatment liquid in a crosslinking treatment liquid containing a first crosslinking treatment liquid.
Description
Technical Field
The present invention relates to a method for producing a polarizing film and an apparatus for producing a polarizing film.
Background
As the polarizing film, a polarizing film obtained by adsorbing and orienting a dichroic dye such as iodine to a uniaxially stretched polyvinyl alcohol resin film has been conventionally used. Generally, a polarizing film is manufactured by: a dyeing treatment of dyeing a polyvinyl alcohol resin film with a dichroic dye, a crosslinking treatment of treating with a crosslinking agent, and a film drying treatment are sequentially performed, and a stretching treatment is performed on the polyvinyl alcohol resin film during the production process (for example, patent documents 1 and 2).
In the dyeing treatment step or the crosslinking treatment step in the production of a polarizing film, the polyvinyl alcohol resin film is brought into contact with a treatment liquid to perform each treatment. In such a treatment liquid, it is sometimes required to control the pH value thereof to an appropriate range, and sulfuric acid may be added to the crosslinking liquid, for example (for example, patent document 2).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2016-27386
Patent document 2: japanese Kokai publication No. 2006-509250
Disclosure of Invention
Problems to be solved by the invention
Polarizing films are industrially produced by subjecting a long polyvinyl alcohol resin film to dyeing, crosslinking, stretching, and the like while continuously conveying the film along a film conveying path of a polarizing film production apparatus. It has been found that: when a polarizing film is produced while transporting a polyvinyl alcohol resin film, the tension during transportation increases when sulfuric acid is added to the crosslinking liquid.
The purpose of the present invention is to provide a method for producing a polarizing film and an apparatus for producing a polarizing film, which can suppress an increase in tension of a polyvinyl alcohol resin film during transportation.
Means for solving the problems
The present invention provides a method for producing a polarizing film and an apparatus for producing a polarizing film, which are described below.
[ 1] A method for producing a polarizing film, which is a method for producing a polarizing film using a polyvinyl alcohol resin film, comprising:
treating the polyvinyl alcohol resin film with a dyeing treatment liquid containing iodine;
a step of adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiating the liquid to which the oxalic acid compound is added with ultraviolet rays to obtain a first crosslinking treatment liquid; and
and a step of immersing the polyvinyl alcohol resin film after the step of treating with the dyeing treatment liquid in a crosslinking treatment liquid containing the first crosslinking treatment liquid.
The method for producing a polarizing film according to [ 1], wherein the step of obtaining the first crosslinking treatment liquid includes a step of subjecting the liquid containing the crosslinking agent and an iodide salt to an activated carbon treatment.
[ 3 ] the method for producing a polarizing film according to [ 1] or [ 2 ], wherein the dipping step is a step of dipping the polyvinyl alcohol resin film after the step of treating with the dyeing treatment liquid in a crosslinking tank containing the crosslinking treatment liquid,
the step of obtaining the first crosslinking treatment liquid is performed in an external tank located outside the crosslinking tank.
[ 4 ] the method for producing a polarizing film according to [ 3 ], wherein the liquid containing a crosslinking agent and an iodide salt is at least a part of a crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank,
the manufacturing method further includes:
supplying at least a part of the extracted crosslinking liquid to the external tank; and
and a step of supplying the first crosslinking liquid from the external tank to the crosslinking tank.
[ 5 ] the method for producing a polarizing film according to [ 3 ] or [ 4 ], wherein the pH of the crosslinking treatment liquid contained in the crosslinking tank is 2 or more and 4 or less.
[ 6 ] the method for producing a polarizing film according to any one of [ 3 ] to [ 5 ], wherein the concentration of oxalate ions in the crosslinking treatment liquid contained in the crosslinking tank is 0.5% by mass or less with respect to the crosslinking treatment liquid.
[ 7 ] the polarizing film production method according to any one of [ 1] to [ 6 ], wherein the crosslinking agent contains a boron compound,
the iodide salt comprises potassium iodide.
[ 8 ] A polarizing film manufacturing apparatus for manufacturing a polarizing film using a polyvinyl alcohol resin film, comprising:
a dyeing treatment section for treating the polyvinyl alcohol resin film with a dyeing treatment liquid containing iodine;
a first crosslinking treatment liquid preparation unit that adds an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiates the liquid to which the oxalic acid compound is added with ultraviolet light to obtain a first crosslinking treatment liquid; and
and a crosslinking tank for immersing the polyvinyl alcohol resin film treated by the dyeing section in a crosslinking treatment liquid containing the first crosslinking treatment liquid.
The polarizing film production apparatus according to [ 9 ] above, wherein the first crosslinking treatment liquid preparation section further comprises an activated carbon treatment section that performs an activated carbon treatment on the liquid containing the crosslinking agent and the iodide salt.
[ 10 ] the polarizing film production apparatus according to [ 8 ] or [ 9 ], wherein the first crosslinking treatment liquid preparation section is provided outside the crosslinking tank.
[ 11 ] the polarizing film production apparatus according to [ 10 ], wherein the liquid containing the crosslinking agent and the iodide salt is at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank,
the manufacturing apparatus further includes:
a first supply unit configured to supply at least a part of the extracted crosslinking liquid to the first crosslinking liquid preparation unit; and
and a second supply unit configured to supply the first crosslinking liquid from the first crosslinking liquid preparation unit to the crosslinking bath.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a polarizing film can be produced by suppressing an increase in tension of a polyvinyl alcohol resin film during transportation.
Drawings
Fig. 1 is a schematic view showing an example of a method for producing a polarizing film and an apparatus for producing a polarizing film used in the method of the present invention.
Description of the reference numerals
Detailed Description
Hereinafter, preferred embodiments of a method and an apparatus for manufacturing a polarizing film according to the present invention will be described with reference to the drawings. The scope of the present invention is not limited to the embodiments described herein, and various modifications can be made within the scope not impairing the gist of the present invention.
The method and apparatus for producing a polarizing film according to the present embodiment produce a polarizing film using a polyvinyl alcohol resin film (hereinafter, sometimes referred to as a "PVA resin film"). The polarizing film can be continuously produced as a long article from a long PVA-based resin film as a raw material film, for example.
< method for producing polarizing film >
Fig. 1 is a schematic view showing an example of a method for producing a polarizing film according to the present embodiment and an apparatus for producing a polarizing film used in the method. The arrows in fig. 1 indicate the membrane transport direction or the flow direction of the liquid. In the method for producing the polarizing film 25 shown in fig. 1, a long polarizing film 25 can be continuously obtained from a long PVA-based resin film 10. Specifically, the polarizing film 25 can be obtained by continuously winding the PVA-based resin film 10 from the winding-out roll 11, sequentially performing the swelling treatment step in the swelling tank 13, the dyeing treatment step in the dyeing tank 15 (dyeing treatment section) containing the dyeing treatment liquid, the crosslinking treatment step in the crosslinking tank 17 containing the crosslinking treatment liquid, and the cleaning treatment step in the cleaning tank 19, and finally passing the film through the drying furnace 21 to perform the drying treatment. The polarizing film 25 manufactured as a long strip may be sequentially wound around the winding roll 27, or may be subjected to a polarizing plate manufacturing step of adhering a thermoplastic resin film such as a protective film to one surface or both surfaces of the polarizing film 25 without winding.
The method for producing the polarizing film 25 of the present embodiment is a method for producing a polarizing film 25 by using the PVA-based resin film 10, and includes:
a step of treating the PVA based resin film 10 with a dyeing treatment liquid containing iodine;
a step of adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiating the liquid to which the oxalic acid compound is added with ultraviolet rays to obtain a first crosslinking treatment liquid; and
and a step of immersing the PVA-based resin film 10 after the step of treating with the dyeing treatment liquid in a crosslinking treatment liquid containing a first crosslinking treatment liquid.
By the above-described steps, the first crosslinking treatment liquid is obtained as at least a part of the crosslinking treatment liquid used for the crosslinking treatment of the PVA-based resin film 10, and the crosslinking treatment of the PVA-based resin film 10 subjected to the dyeing treatment can be favorably performed by using the crosslinking treatment liquid containing the first crosslinking treatment liquid. Hereinafter, each step will be explained.
(step of treating with dyeing treatment solution)
The step of treating with the dyeing treatment liquid is a dyeing treatment step of treating the PVA-based resin film 10 with a dyeing treatment liquid containing iodine, and is performed for the purpose of adsorbing and orienting iodine to the PVA-based resin film 10 and the like. The PVA-based resin film 10 treated with the dyeing liquid is preferably a film swollen in a swelling tank 13 shown in fig. 1. As a method of performing the treatment with the iodine-containing dyeing liquid, for example, as shown in fig. 1, the PVA-based resin film 10 may be immersed in the dyeing liquid for a predetermined time while being conveyed along the film conveyance path, and then drawn out of the dyeing liquid. The treatment with the dyeing treatment liquid may be performed by applying the dyeing treatment liquid to the PVA-based resin film 10.
(step of obtaining first crosslinking treatment liquid)
The step of obtaining the first crosslinking treatment liquid includes: adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt; and irradiating the liquid to which the oxalic acid compound is added with ultraviolet rays to obtain a first crosslinking treatment liquid. The step of obtaining the first crosslinking treatment liquid is performed to obtain the first crosslinking treatment liquid constituting a part of the crosslinking treatment liquid used for the crosslinking treatment in the crosslinking tank 17. Since the crosslinking treatment liquid used for the crosslinking treatment contains the crosslinking agent and the iodide salt, the addition of the oxalic acid compound, the irradiation of ultraviolet rays, and the like are performed to the liquid containing the crosslinking agent and the iodide salt in the step of obtaining the first crosslinking treatment liquid.
The step of obtaining the first crosslinking treatment liquid may be performed to reuse the crosslinking treatment liquid used for the crosslinking treatment in the crosslinking tank 17 (hereinafter, may be referred to as "used crosslinking treatment liquid") as a usable crosslinking treatment liquid. In this case, the liquid containing the crosslinking agent and the iodide salt to which the oxalic acid compound is added is a used crosslinking treatment liquid, and the addition of the oxalic acid compound and the ultraviolet irradiation performed in the step of obtaining the first crosslinking treatment liquid can be treatments performed for regenerating the used crosslinking treatment liquid into a crosslinking treatment liquid usable for the crosslinking treatment. In the case of performing the step of obtaining the first crosslinking treatment liquid using the used crosslinking treatment liquid, the liquid containing the crosslinking agent and the iodide salt may be at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank 17, and in this case, the step of obtaining the first crosslinking treatment liquid may be performed in the external tank 31 located outside the crosslinking tank 17 as shown in fig. 1. When the step of obtaining the first crosslinking treatment liquid in the external tank 31 is performed, the method for producing the polarizing film 25 may include a step of supplying at least a part of the crosslinking treatment liquid extracted from the crosslinking tank 17 to the external tank 31, or may include a step of supplying the first crosslinking treatment liquid prepared in the external tank 31 to the crosslinking tank 17.
The step of obtaining the first crosslinking treatment liquid includes the step of adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt as described above. In the step of obtaining the first crosslinking treatment liquid, the pH of the crosslinking treatment liquid including the first crosslinking treatment liquid can be controlled to an appropriate range by adjusting the pH of the liquid containing the crosslinking agent and the iodide salt by adding the oxalic acid compound to the liquid containing the crosslinking agent and the iodide salt. From the viewpoint of improving the optical properties of the obtained polarizing film, it is generally preferable to maintain the pH of the crosslinking treatment liquid at 2 or more and 4 or less, but for example, when an additive such as potassium sulfite is added to the crosslinking treatment liquid, or when activated carbon treatment of the used crosslinking treatment liquid is performed as described below, the pH of the crosslinking treatment liquid tends to increase. Since the oxalic acid compound is an acidic substance, the pH of the liquid containing the crosslinking agent and the iodide salt can be lowered by adding the oxalic acid compound, and the first crosslinking treatment liquid having a pH value suitable for the crosslinking treatment liquid can be prepared.
The oxalic acid compound added to the liquid containing the crosslinking agent and the iodide salt includes oxalic acid anhydrate, oxalic acid hydrate, oxalic acid salt, and the like. As the oxalic acid hydrate, oxalic acid dihydrate is exemplified. Examples of the oxalate include alkali metal salts, alkaline earth metal salts, and ammonium oxalate of oxalic acid, and examples of the alkali metal salts or alkaline earth metal salts of oxalic acid include potassium oxalate, sodium oxalate, lithium oxalate, calcium oxalate, and magnesium oxalate. As the oxalic acid compound, oxalic acid anhydrate or oxalic acid hydrate is preferably used.
The amount of the oxalic acid compound added to the liquid containing the crosslinking agent and the iodide salt may be set so that the pH of the liquid containing the crosslinking agent and the iodide salt reaches a desired pH. As shown in fig. 1, when the step of obtaining the first crosslinking treatment liquid is performed in the external tank 31, the pH of the crosslinking treatment liquid contained in the crosslinking tank 17 is preferably maintained at 2 or more and 4 or less. Therefore, when the first crosslinking treatment liquid in the external tank 31 is supplied to the crosslinking tank 17, the amount of the oxalic acid compound to be added is preferably adjusted so that the pH of the crosslinking treatment liquid in the crosslinking tank 17 is kept within the above range. The pH of the crosslinking treatment liquid contained in the crosslinking tank 17 is more preferably 2.3 or more, and may be 2.5 or more, and is more preferably 3.7 or less, and may be 3.5 or less. When the pH of the crosslinking treatment liquid in the crosslinking tank 17 exceeds 4, the optical performance of the obtained polarizing film 25 tends to be lowered.
The step of obtaining the first crosslinking treatment liquid includes the step of irradiating the liquid containing the crosslinking agent and the iodide salt to which the oxalic acid compound is added with ultraviolet rays as described above. The step of irradiating ultraviolet rays may be performed on a liquid containing at least a liquid to which the oxalic acid compound is added, or may be performed on a liquid in which a liquid containing the crosslinking agent and the iodide salt to which the oxalic acid compound is added and a liquid containing the crosslinking agent and the iodide salt before the oxalic acid compound is added are mixed. The liquid to which the oxalic acid compound is added is irradiated with ultraviolet rays, thereby decomposing oxalate ions caused by the oxalic acid compound and removing the oxalate ions from the liquid as carbon dioxide, whereby the concentration of oxalate ions in the liquid can be reduced.
As described above, since the first crosslinking treatment liquid constitutes at least a part of the crosslinking treatment liquid for impregnating the PVA-based resin membrane 10, when oxalate ions are contained in the first crosslinking treatment liquid, the oxalate ions are also contained in the crosslinking treatment liquid. The inventors of the present invention found that: when oxalate ions are contained in the crosslinking treatment liquid at a high concentration, if the step of immersing the PVA-based resin film in the crosslinking treatment liquid is performed while transporting the PVA-based resin film 10 as shown in fig. 1, the tension of the PVA-based resin film 10 increases in the crosslinking tank 17 and the subsequent steps after the crosslinking tank 17. Presumably: such an increase in tension makes it difficult for the PVA-based resin film 10 to develop a good neck-in (neck-in) in the crosslinking bath 17 and the drying oven 21, and thus causes a decrease in the optical performance of the polarizing film 25 to be obtained. In the present embodiment, the liquid to which the oxalic acid compound is added is irradiated with ultraviolet rays as described above to decompose oxalate ions, thereby reducing the concentration of oxalate ions in the liquid. It can be considered that: this can reduce the amount of oxalate ions in the crosslinking treatment liquid containing the first crosslinking treatment liquid, suppress an increase in the tension of the PVA-based resin film, and favorably produce necking-in of the PVA-based resin film 10, thereby suppressing a decrease in the optical performance of the polarizing film 25.
Examples of the method of irradiating the oxalic acid compound-containing liquid with ultraviolet rays include a method of irradiating at least a part of the crosslinking treatment liquid in the crosslinking tank 17 with ultraviolet rays from an ultraviolet irradiation apparatus, and a method of irradiating the oxalic acid compound-containing liquid containing the crosslinking agent and the iodide salt in the external tank 31 with ultraviolet rays from an ultraviolet irradiation apparatus 34 as shown in fig. 1.
The wavelength of ultraviolet light irradiated to the liquid to which the oxalic acid compound is added is preferably in the range of 250 to 400nm, more preferably in the range of 270 to 380nm, and may be in the range of 280 to 360 nm. With ultraviolet light in the above range, the decomposition of oxalate ions contained in the liquid containing the crosslinking agent and the iodide salt can be promoted, so that the decomposition of oxalate ions proceeds efficiently, and the concentration of oxalate ions in the liquid can be easily reduced.
The irradiation energy and the irradiation time of the ultraviolet ray may be set so that the concentration of oxalate ions in the liquid is within a desired range by decomposition of oxalate ions. For example, the irradiation energy may be 0.1W/L or more and 10W/L or less, 0.2W/L or more, 0.3W/L or more, 5W/L or less, or 1W/L or less, in the case of the energy [ W ] of the liquid containing oxalate ions per 1[ L ]. The irradiation time may be 1 second to 5 hours, 1 minute to 1 hour, 3 hours to 3 hours, or 4 hours. When the step of obtaining the first crosslinking treatment liquid is performed in the external tank 31 as shown in fig. 1, the oxalate ion concentration (including the concentration of oxalic acid) of the crosslinking treatment liquid in the crosslinking tank 17 is preferably 0.5% by mass or less with respect to the crosslinking treatment liquid. The oxalate ion concentration can be measured by the method described in examples. Therefore, when the first crosslinking treatment liquid in the outer tank 31 is supplied to the crosslinking tank 17, it is preferable to adjust the irradiation energy and the irradiation time of the ultraviolet ray so that the concentration of the oxalate ion in the crosslinking treatment liquid in the crosslinking tank 17 is kept within the above-mentioned ranges. The concentration of oxalate ions in the crosslinking treatment liquid contained in the crosslinking tank 17 is more preferably 0.3% by mass or less, still more preferably 0.1% by mass or less, and may be 0% by mass. When the oxalate ion concentration in the crosslinking treatment liquid in the crosslinking tank 17 exceeds 0.5 mass%, the PVA-based resin film tends to be easily increased in tension when the PVA-based resin film is immersed in the crosslinking treatment liquid in the crosslinking tank 17 and subjected to crosslinking treatment, and the optical performance of the obtained polarizing film 25 tends to be easily lowered.
The step of obtaining the first crosslinking treatment liquid may include a step of subjecting a liquid containing a crosslinking agent and an iodide salt to an activated carbon treatment. The step of performing the activated carbon treatment may be performed on a liquid containing at least a liquid containing the crosslinking agent and the iodide salt, or may be performed on a liquid in which a liquid containing the crosslinking agent and the iodide salt and a liquid to which the oxalic acid compound is added are mixed.
The step of performing the activated carbon treatment is effective when the liquid containing the crosslinking agent and the iodide salt is a used crosslinking treatment liquid, for example, when at least a part of the crosslinking treatment liquid is extracted from the crosslinking treatment liquid in the crosslinking tank 17. This is because: the excess I in the crosslinking treatment liquid can be removed by the treatment with activated carbon3 -. The dyeing treatment liquid in the dyeing tank 15 shown in fig. 1 contains iodine, and generally contains an iodide salt in order to dissolve iodine in water. In addition, since the PVA based resin film 10 having passed through the dyeing bath 15 is immersed in the crosslinking treatment liquid in the crosslinking bath 17, the crosslinking treatment liquid after the crosslinking treatment is removedThe crosslinking agent and the iodide salt contained in the crosslinking treatment liquid contain iodine and iodide salt carried in the PVA-based resin film 10 after passing through the dyeing bath 15. Therefore, when the crosslinking treatment of the PVA-based resin film 10 is repeated, the crosslinking treatment liquid in the crosslinking tank 17 is subjected to iodine entrainment from the dyeing treatment liquid and air oxidation of iodide salt, thereby causing I in the crosslinking treatment liquid3 -The concentration tends to increase. I in the crosslinking treatment liquid3 -The increase in concentration may cause a decrease in optical performance, particularly transmittance, of the polarizing film 25 to be obtained. Therefore, I in the crosslinking treatment liquid can be removed by subjecting the used crosslinking treatment liquid (for example, at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank 17) to an activated carbon treatment3 -To inhibit I in the crosslinking treatment liquid3 -The increase in concentration.
The step of performing the activated carbon treatment may be performed by bringing a liquid containing a crosslinking agent and an iodide salt into contact with activated carbon. Examples of the method of performing the activated carbon treatment include a method of adding activated carbon to the crosslinking tank 17 or the external tank 31 and stirring the mixture, a method of extracting at least a part of the liquid containing the crosslinking agent and the iodide salt in the external tank 31 and bringing the extracted liquid into contact with activated carbon in the activated carbon treatment section 33 as shown in fig. 1, and a method of bringing the extracted liquid into contact with activated carbon in the process of supplying at least a part of the crosslinking treatment liquid from the crosslinking tank 17 to the external tank 31.
The liquid containing the crosslinking agent and the iodide salt subjected to the activated carbon treatment tends to have a high pH. Therefore, it is preferable to add an oxalic acid compound to the liquid containing the crosslinking agent and the iodide salt subjected to the activated carbon treatment to suppress the increase in pH.
When the step of obtaining the first crosslinking treatment liquid is performed in the external tank 31 as shown in fig. 1, the first crosslinking treatment liquid is prepared in the external tank 31. Therefore, the method for producing the polarizing film 25 may further include a step of supplying the obtained first crosslinking treatment liquid from the external tank 31 to the crosslinking tank 17.
(impregnation step)
The impregnation step is a step of impregnating the PVA-based resin film 10 after the step of treating with the dyeing treatment liquid into a crosslinking treatment liquid containing the first crosslinking treatment liquid, and may be a crosslinking treatment step of crosslinking the PVA-based resin film 10. The crosslinking treatment step is performed for the purpose of water resistance by crosslinking, color tone adjustment, and the like. As a method of immersing the PVA-based resin film 10 in the crosslinking treatment liquid, there is a method of immersing the PVA-based resin film in the crosslinking treatment liquid containing the first crosslinking treatment liquid obtained in the step of obtaining the first crosslinking treatment liquid, which is stored in the crosslinking tank 17.
The first crosslinking treatment liquid obtained in the step of obtaining the first crosslinking treatment liquid is adjusted in pH by adding an oxalic acid compound, and decomposition of oxalate ions is promoted by ultraviolet irradiation. Therefore, the polarizing film 25 having excellent optical properties can be obtained by performing the crosslinking treatment of the PVA-based resin film 10 subjected to the dyeing treatment using the crosslinking treatment liquid containing the obtained first crosslinking treatment liquid.
The step of obtaining the first crosslinking treatment liquid in the method for producing the polarizing film 25 of the present embodiment may be performed in the crosslinking tank 17 shown in fig. 1, or may be performed outside the crosslinking tank 17, for example, in the external tank 31, as shown in fig. 1. The step of obtaining the first crosslinking treatment liquid may be performed simultaneously with the dipping step (step of performing crosslinking treatment), or may be performed while circulating the crosslinking treatment liquid and the first crosslinking treatment liquid between the crosslinking tank 17 and the external tank 31. For example, as shown in fig. 1, the crosslinking treatment may be performed by continuously withdrawing the crosslinking treatment liquid in the crosslinking tank 17, preparing the first crosslinking treatment liquid in the external tank 31, supplying the obtained first crosslinking treatment liquid to the crosslinking tank 17, and immersing the PVA-based resin film 10 after the step of treating with the dyeing treatment liquid in the crosslinking tank 17 in the crosslinking treatment liquid containing the first crosslinking treatment liquid. The respective treatments of the activated carbon treatment, the addition of the oxalic acid compound and the ultraviolet irradiation may be performed simultaneously. In this case, in the step of performing the activated carbon treatment, the liquid in which the liquid containing the crosslinking agent and the iodide salt is mixed with the liquid to which the oxalic acid compound is added may be used. In the step of irradiating ultraviolet light, a liquid in which a liquid containing a crosslinking agent and an iodide salt before the oxalic acid compound is added and a liquid to which the oxalic acid compound is added are mixed may be used.
< apparatus for producing polarizing film >
The polarizing film 25 manufacturing apparatus of the present embodiment is an apparatus used in the above-described polarizing film 25 manufacturing method. In the apparatus for producing the polarizing film 25 shown in fig. 1, a long PVA-based resin film 10 is continuously immersed in a swelling treatment liquid in a swelling tank 13, a dyeing treatment liquid in a dyeing tank 15 (dyeing treatment section), a crosslinking treatment liquid in a crosslinking tank 17, and a cleaning treatment liquid in a cleaning tank 19 in this order, and finally passed through a drying furnace 21 to be dried, whereby a long polarizing film 25 can be obtained.
As shown in fig. 1, for example, the polarizing film 25 manufacturing apparatus includes a swelling tank 13, a dyeing tank 15 (dyeing section), a crosslinking tank 17, a cleaning tank 19, and a drying furnace 21 in this order from the upstream side of a film transport path (a path for transporting the PVA-based resin film 10 and the polarizing film 25). The polarizing film 25 manufacturing apparatus further includes a first crosslinking treatment liquid preparation unit 30, and the first crosslinking treatment liquid preparation unit 30 may include an external tank 31, an oxalic acid compound supply unit 32, an activated carbon treatment unit 33, and an ultraviolet irradiation device 34. The manufacturing apparatus may include a first supply unit 35 that supplies the crosslinking treatment liquid in the crosslinking tank 17 to the external tank 31 and a second supply unit 36 that supplies the first crosslinking treatment liquid from the external tank 31 to the crosslinking tank 17, thereby circulating the crosslinking treatment liquid and the first crosslinking treatment liquid between the crosslinking tank 17 and the first crosslinking treatment liquid preparation unit 30. The polarizing film 25 manufacturing apparatus may include a polarizing plate manufacturing unit for manufacturing a polarizing plate by laminating a protective film or the like on one or both sides of the obtained polarizing film 25.
As described above, the polarizing film 25 manufacturing apparatus is a manufacturing apparatus that performs various processes while conveying a long PVA-based resin film 10, and a plurality of rollers that support and guide the film being conveyed are provided on the film conveying path so as to pass through the respective grooves and portions described above. The plurality of rollers include a guide roller that supports one side of the film and does not apply a driving force to the film, and a pinch roller (typically, a driving roller that can apply a driving force to the film) that is configured by 1 pair of rollers that are disposed on both sides of the film and sandwich the film. In the manufacturing apparatus shown in fig. 1, guide rollers 1a to 1k and pinch rollers 2a to 2f are provided on the film transport path. A part of the guide roller and a part of the nip roller may be a suction roller (suction roller) that can be used as a drive roller. The plurality of rollers may be provided at any position of the film conveying path.
The polarizing film 25 manufacturing apparatus of the present embodiment is an apparatus for manufacturing a polarizing film 25 of a polarizing film 25 using a PVA-based resin film 10, and includes:
a dyeing tank 15 (dyeing section) for treating the PVA-based resin film 10 with a dyeing treatment liquid containing iodine;
a first crosslinking treatment liquid preparation unit 30 that adds an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiates the liquid to which the oxalic acid compound is added with ultraviolet light to obtain a first crosslinking treatment liquid; and
and a crosslinking tank 17 for immersing the polyvinyl alcohol resin film treated in the dyeing tank 15 in a crosslinking treatment liquid containing the first crosslinking treatment liquid.
The manufacturing apparatus can be used for the method of manufacturing the polarizing film 25. According to the above-described manufacturing apparatus, the first crosslinking treatment liquid is prepared and becomes at least a part of the crosslinking treatment liquid used for the crosslinking treatment of the PVA-based resin film 10, and the crosslinking treatment of the PVA-based resin film 10 after the dyeing treatment can be favorably performed by using the crosslinking treatment liquid containing the first crosslinking treatment liquid. Hereinafter, each part of the manufacturing apparatus of the polarizing film 25 will be described.
(dyeing tank)
In order to perform the step of treating the PVA-based resin film 10 with the iodine-containing dyeing treatment liquid in the method for producing the polarizing film 25, the dyeing vessel 15 shown in fig. 1 may be used. The dyeing tank 15 contains a dyeing treatment liquid therein, and is used, for example, to immerse the PVA-based resin film 10 swollen by the swelling tank 13 in the dyeing treatment liquid. The PVA-based resin film 10 is subjected to a dyeing process using a dyeing liquid while being supported and conveyed by guide rollers 1d and 1e provided in the dyeing liquid in a dyeing tank 15. The PVA-based resin film 10 treated with the dyeing treatment liquid and drawn out from the dyeing tank 15 is introduced into the crosslinking tank 17 sequentially through the guide roller 1f and the nip roller 2 c.
When the step of treating the PVA-based resin film 10 with the iodine-containing dyeing treatment liquid is performed by applying the dyeing treatment liquid to the PVA-based resin film 10, a coating device such as a sprayer may be used instead of the dyeing bath 15.
(first crosslinking solution preparation section)
In order to perform the step of obtaining the first crosslinking treatment liquid in the method for manufacturing the polarizing film 25, the first crosslinking treatment liquid preparation unit 30 may be used, and the first crosslinking treatment liquid preparation unit 30 may be configured to add an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and to irradiate the liquid to which the oxalic acid compound is added with ultraviolet rays. Thereby, the first crosslinking treatment liquid preparation unit 30 prepares the first crosslinking treatment liquid which is a part of the crosslinking treatment liquid used for the crosslinking treatment in the crosslinking tank 17. The first crosslinking treatment liquid preparation unit 30 may include: an oxalic acid compound supply part for adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and an ultraviolet irradiation device for irradiating the liquid added with the oxalic acid compound with ultraviolet rays. The first crosslinking treatment liquid preparation unit 30 may further include an activated carbon treatment unit 33 for performing activated carbon treatment on a liquid containing a crosslinking agent and an iodide salt.
The first crosslinking treatment liquid preparation unit 30 prepares the first crosslinking treatment liquid as a part of the crosslinking treatment liquid used in the crosslinking tank 17, and therefore may be provided in the crosslinking tank 17 or may be provided outside the crosslinking tank 17. For example, the first crosslinking treatment liquid preparation unit 30 shown in fig. 1 includes: an outer tank 31 which is provided outside the crosslinking tank 17 and contains a liquid containing a crosslinking agent and an iodide salt therein; an oxalic acid compound supply unit 32 for adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt in the external tank 31; and an ultraviolet irradiation device 34 that irradiates ultraviolet rays to the liquid to which the oxalic acid compound is added. The first crosslinking treatment liquid preparation section 30 may be provided with an activated carbon treatment section 33 outside the outer tank 31.
As described above, the liquid containing the crosslinking agent and the iodide salt used in the first crosslinking treatment liquid preparation unit 30 may be a used crosslinking treatment liquid or may be at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank 17. Therefore, for example, in the case where the first crosslinking treatment liquid preparation part 30 is provided outside the crosslinking tank 17 as shown in fig. 1, the polarizing film 25 manufacturing apparatus may include: a first supply unit 35 for supplying the crosslinking liquid in the crosslinking tank 17 to the external tank 31, and a second supply unit 36 for supplying the first crosslinking liquid from the external tank 31 to the crosslinking tank 17. The first supply part 35 and the second supply part 36 may be formed as pipes for connecting the crosslinking tank 17 and the external tank 31, for example. The first supply unit 35 may supply the crosslinking treatment liquid overflowing from the crosslinking tank 17 to the external tank 31 directly or via a pipe or the like, and the second supply unit 36 may supply the first crosslinking treatment liquid overflowing from the external tank 31 to the crosslinking tank 17 directly or via a pipe or the like.
The external tank 31 shown in fig. 1 can contain at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank 17 through the first supply part 35 as a liquid containing a crosslinking agent and an iodide salt. The outer tank 31 may be used to add and mix an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt contained therein, or may be used to irradiate ultraviolet rays to the liquid to which the oxalic acid compound is added by the ultraviolet ray irradiation device 34. The outer tank 31 may be provided with a stirring device such as a stirring blade or a stirrer for stirring the liquid inside.
The oxalic acid compound supply unit 32 shown in fig. 1 can supply an oxalic acid compound to be added to a liquid containing a crosslinking agent and an iodide salt in the external tank 31. This makes it possible to adjust the pH of the liquid containing the crosslinking agent and the iodide salt. The oxalic acid compound supply part 32 may contain an oxalic acid compound in its inside and supply a required amount of the oxalic acid compound into the outer tank 31. The amount of the oxalic acid compound supplied from the oxalic acid compound supply unit 32 may be set in advance so that the pH of the first crosslinking treatment liquid prepared in the first crosslinking treatment liquid preparation unit 30 reaches a pH value (for example, pH 2 or more and 4 or less) required for the crosslinking treatment liquid in the crosslinking tank 17, or may be adjusted based on a pH value measured for the liquid containing the crosslinking agent and the iodide salt in the external tank 31.
The ultraviolet irradiation device 34 shown in fig. 1 may irradiate ultraviolet rays to the liquid to which the oxalic acid compound is added. The ultraviolet irradiation device 34 may be any device as long as it irradiates ultraviolet rays to a liquid containing at least a liquid to which an oxalic acid compound is added, and may be a liquid in which a liquid containing a crosslinking agent and an iodide salt to which an oxalic acid compound is added and a liquid containing a crosslinking agent and an iodide salt before the oxalic acid compound is added are mixed. This can decompose and remove oxalate ions in the liquid to which the oxalic acid compound is added, thereby making it possible to reduce the concentration of oxalate ions in the liquid. The ultraviolet irradiation device 34 may be any device capable of irradiating ultraviolet rays in the range of 250nm to 400nm, for example. When the liquid to which the oxalic acid compound is added in the external tank 31 is irradiated with ultraviolet rays, the ultraviolet irradiation device 34 may be provided outside the external tank 31 as shown in fig. 1, or may be provided inside the external tank 31. Further, an ultraviolet irradiation device may be provided outside or inside the crosslinking tank 17 to perform ultraviolet irradiation.
The activated carbon treatment section 33 shown in fig. 1 performs a treatment of bringing a liquid containing a crosslinking agent and an iodide salt into contact with activated carbon. The activated carbon treatment unit 33 may perform the activated carbon treatment on a liquid containing at least a liquid containing the crosslinking agent and the iodide salt, or may perform the activated carbon treatment on a liquid in which the liquid containing the crosslinking agent and the iodide salt is mixed with a liquid to which the oxalic acid compound is added. The activated carbon treatment section 33 is provided outside the outer tank 31 as shown in fig. 1, for example, and brings at least a part of the liquid containing the crosslinking agent and the iodide salt drawn out from the outer tank 31 into contact with activated carbon. The activated carbon treatment section 33 may be, for example, an activated carbon filter, and in this case, as shown in fig. 1, the liquid containing the crosslinking agent and the iodide salt withdrawn from the external tank 31 may be passed through the activated carbon treatment section 33 to be subjected to activated carbon treatment, and then returned to the external tank 31.
In the manufacturing apparatus shown in fig. 1, the case where the activated carbon treatment section 33 is provided outside the outer tank 31 is described as an example, but the present invention is not limited to this. For example, the activated carbon treatment may be performed by adding activated carbon to a liquid containing a crosslinking agent and an iodide salt in the outer tank 31 and stirring the mixture. In the case where the liquid containing the crosslinking agent and the iodide salt is a used crosslinking treatment liquid, activated carbon may be added to the crosslinking treatment liquid in the crosslinking tank 17. When the liquid containing the crosslinking agent and the iodide salt is at least a part of the crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank 17, an activated carbon treatment section may be provided in the middle of the pipe constituting the first supply section 35 connecting the crosslinking tank 17 and the external tank 31.
The first crosslinking treatment liquid prepared in the first crosslinking treatment liquid preparation part 30 shown in fig. 1 can be supplied from the external tank 31 to the crosslinking tank 17 through the second supply part 36.
(crosslinking tank)
In the method for producing the polarizing film 25, the crosslinking bath 17 may be used to impregnate the PVA-based resin film 10 after the step of treating with the dyeing treatment liquid into the crosslinking treatment liquid including the first crosslinking treatment liquid. The crosslinking tank 17 contains a crosslinking treatment liquid containing a first crosslinking treatment liquid therein, and is used to immerse the PVA-based resin film 10 dyed in the dyeing tank 15 in the crosslinking treatment liquid. The PVA-based resin film 10 is treated with the crosslinking treatment liquid while being supported and conveyed by guide rollers 1g and 1h provided in the crosslinking treatment liquid in the crosslinking tank 17. The PVA-based resin film 10 treated with the crosslinking treatment liquid and drawn out from the crosslinking tank 17 is introduced into the cleaning tank 19 sequentially through the guide roller li and the nip roller 2 d.
The first crosslinking treatment liquid preparation part 30 in the manufacturing apparatus of the polarizing film 25 of the present embodiment may be provided in the crosslinking tank 17 shown in fig. 1, or may be provided outside the crosslinking tank 17 as shown in fig. 1. The preparation of the first crosslinking liquid in the first crosslinking liquid preparation unit 30 may be performed simultaneously with the crosslinking treatment in the crosslinking tank 17, and when the first crosslinking liquid preparation unit 30 is outside the crosslinking tank 17, the crosslinking liquid and the first crosslinking liquid may be circulated between the crosslinking tank 17 and the first crosslinking liquid preparation unit 30. For example, as shown in fig. 1, the crosslinking treatment can be performed by continuously extracting the crosslinking treatment liquid from the crosslinking tank 17, preparing the first crosslinking treatment liquid in the first crosslinking treatment liquid preparation unit 30, and supplying the obtained first crosslinking treatment liquid to the crosslinking tank 17, and immersing the PVA-based resin film 10 extracted from the dyeing tank 15 in the crosslinking tank 17 in the crosslinking treatment liquid. In the first crosslinking liquid preparation section 30 shown in fig. 1, the oxalic acid compound supply section 32, the activated carbon treatment section 33, and the ultraviolet irradiation device 34 may be operated simultaneously.
Hereinafter, each step constituting the method for producing a polarizing film, each member constituting the apparatus for producing a polarizing film, and the like will be described in detail.
(PVA resin film)
The PVA-based resin film 10 used in the method for producing a polarizing film according to the present embodiment is a film formed using a polyvinyl alcohol-based resin. The polyvinyl alcohol resin is a resin containing 50 mass% or more of a structural unit derived from vinyl alcohol. As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. The saponification degree of the polyvinyl acetate resin can be determined in accordance with jis k 6727(1994), and can be, for example, in the range of 80.0 to 100.0 mol%.
Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group. In the present specification, "(meth) acrylic" means at least 1 selected from acrylic and methacrylic. The same applies to other terms with "(methyl)".
An example of the PVA-based resin film 10 may be an unstretched film obtained by forming a polyvinyl alcohol-based resin film, or a stretched film obtained by stretching the unstretched film. When the PVA-based resin film 10 is a stretched film, the stretched film is preferably uniaxially stretched in the longitudinal direction, and is preferably a dry stretched film. The PVA based resin film 10 is usually stretched at a stretch ratio of 1.1 to 8 times when it is a stretched film.
The thickness of the PVA-based resin film 10 used in the method for producing a polarizing film of the present embodiment is usually 10 to 150 μm, and is preferably 100 μm or less, more preferably 75 μm or less, further preferably 50 μm or less, and may be 30 μm or less, from the viewpoint of making the polarizing film 25 to be thin.
(polarizing film)
The polarizing film 25 obtained by the method for producing a polarizing film according to the present embodiment is a polarizing film in which iodine is adsorbed and oriented to a stretched PVA-based resin film. The thickness of the polarizing film 25 is usually 2 to 40 μm, and is preferably 30 μm or less, and more preferably 20 μm or less, from the viewpoint of making the polarizing film thinner.
In consideration of the balance with the visibility correction polarization degree Py, the visibility correction monomer transmittance Ty of the obtained polarizing film 25 is preferably 40 to 47%, more preferably 41 to 45%. The visibility correction polarization degree Py is preferably 99.9% or more, more preferably 99.95% or more. Ty and Py can be determined by performing visibility correction using an absorptiometer with an integrating sphere using a 2 degree field of view (C light source) of JISZ 8701 for the obtained transmittance and polarization.
(swelling step and swelling tank)
The swelling treatment step is a treatment which is performed as necessary for the purpose of removing foreign matter from the PVA-based resin film 10, removing a plasticizer, imparting dyeability, plasticizing the film, and the like. As shown in fig. 1, the swelling step may be performed by immersing the PVA-based resin film 10 in a swelling tank 13 containing a swelling solution for a predetermined time and then pulling it out.
The swelling treatment liquid contained in the swelling tank 13 may be, for example, water (pure water or the like) or an aqueous solution to which a water-soluble organic solvent such as alcohol is added. The swelling treatment liquid may contain a boron compound such as boric acid or borax, a chloride, an inorganic acid, an inorganic salt, or the like. The temperature of the swelling solution is usually 10 to 70 ℃, preferably 15 to 50 ℃, and more preferably 15 to 35 ℃. The immersion time (residence time in the swelling treatment liquid) of the PVA based resin film 10 is usually 10 to 600 seconds, preferably 15 to 300 seconds. When the PVA based resin film 10 is a stretched film, the temperature of the swelling treatment liquid may be, for example, about 20 to 70 ℃ or 30 to 60 ℃.
The PVA-based resin film 10 may be subjected to a wet stretching treatment (usually, a uniaxial stretching treatment) in the swelling treatment. The draw ratio in this case is usually 1.2 to 3 times, preferably 1.3 to 2.5 times. In the apparatus for producing the polarizing film 25 shown in fig. 1, for example, the uniaxial stretching treatment may be performed in the swelling tank 13 by utilizing the peripheral speed difference between the grip roller 2a and the grip roller 2 b.
In the apparatus for producing the polarizing film 25 shown in fig. 1, the film drawn out from the swelling tank 13 is introduced into the dyeing tank 15 by passing through the guide roller 1c and the nip roller 2b in this order.
(dyeing step and dyeing vessel)
The dyeing step and the dyeing vessel 15 will be described in addition to the above description. As the dyeing treatment liquid used in the dyeing treatment step, an aqueous solution containing iodine and an iodide salt can be used. Examples of the iodide salt include an alkali metal iodide salt, an alkaline earth metal iodide salt, and zinc iodide, and potassium iodide and zinc iodide are preferable, and potassium iodide is more preferable. Potassium iodide and other iodide salts may also be used in combination.
The dyeing treatment liquid may contain a boron compound such as boric acid or borax, or a compound other than iodide salts such as zinc chloride or cobalt chloride. The addition of the boron compound is distinguished from the crosslinking treatment described later in that iodine is contained. For example, if the aqueous solution is a solution containing about 0.003 parts by mass or more of iodine per 100 parts by mass of water, it can be regarded as a dyeing treatment liquid. The iodine content in the dyeing liquid is usually 0.003-1 part by mass per 100 parts by mass of water. The content of iodide salt such as potassium iodide in the dyeing liquid is usually 0.1 to 20 parts by mass per 100 parts by mass of water.
The temperature of the dyeing treatment liquid is usually 10 to 45 ℃, preferably 10 to 40 ℃, and more preferably 20 to 35 ℃. The immersion time (residence time in the dyeing treatment liquid) of the PVA based resin film 10 is usually 20 to 600 seconds, preferably 30 to 300 seconds.
The polarizing film 25 may be produced by using a dyeing bath 15 having 2 or more baths. In this case, the composition and temperature of each dyeing treatment liquid may be the same or different independently from each other.
In order to improve the iodine dyeability, the PVA-based resin film 10 subjected to the dyeing treatment is preferably subjected to at least a certain degree of stretching treatment (usually, uniaxial stretching treatment). The stretching treatment may be performed in place of the stretching treatment before the dyeing treatment or in addition to the stretching treatment before the dyeing treatment while the dyeing treatment is performed. The cumulative stretching magnification until the dyeing treatment (in the case where the stretching step is not performed until the dyeing treatment, the stretching magnification during the dyeing treatment) is usually 1.6 to 4.5 times, and preferably 1.8 to 4 times. In the apparatus for producing the polarizing film 25 shown in fig. 1, for example, the uniaxial stretching treatment can be performed in the dyeing bath 15 by utilizing the circumferential speed difference between the nip roller 2b and the nip roller 2 c.
In the apparatus for producing the polarizing film 25 shown in fig. 1, the film drawn out from the dyeing vessel 15 is introduced into the crosslinking vessel 17 through the guide roll 1f and the nip roll 2c in this order.
(crosslinking step and crosslinking tank)
The dyeing step and the dyeing vessel 15 will be described in addition to the above description. The crosslinking treatment liquid used in the crosslinking treatment step may be a liquid (usually an aqueous solution) containing an iodide salt and a crosslinking agent. Examples of the iodide salt include an alkali metal iodide salt, an alkaline earth metal iodide salt, and zinc iodide, and potassium iodide and zinc iodide are preferable, and potassium iodide is more preferable. Potassium iodide and other iodide salts may also be used in combination. Examples of the crosslinking agent include boric acid, boron compounds such as borax, glyoxal, glutaraldehyde, etc., and boric acid is preferred. More than 2 kinds of crosslinking agents may be used in combination.
The crosslinking treatment liquid may contain a compound other than the iodide salt and the crosslinking agent. Examples of the compound include zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate.
The content of the iodide salt in the crosslinking treatment liquid is usually 0.1 to 20 parts by mass, preferably 5 to 15 parts by mass, per 100 parts by mass of water. The content of the crosslinking agent in the crosslinking treatment liquid is usually 0.1 to 15 parts by mass, preferably 1 to 12 parts by mass, per 100 parts by mass of water. The temperature of the crosslinking treatment liquid is usually 20 to 85 ℃, preferably 30 to 70 ℃. The immersion time (residence time in the crosslinking treatment liquid) of the PVA based resin film 10 is usually 10 to 600 seconds, preferably 20 to 300 seconds.
The polarizing film 25 manufacturing apparatus may include 2 or more crosslinking tanks 17. In this case, the composition and temperature of each crosslinking treatment liquid may be the same or different independently from each other. When a plurality of crosslinking grooves 17 are included, a first crosslinking treatment liquid preparation unit may be provided in each crosslinking groove.
The stretching treatment (usually, uniaxial stretching treatment) may be performed while the crosslinking treatment is performed. In the apparatus for producing the polarizing film 25 shown in fig. 1, for example, uniaxial stretching treatment may be performed in the crosslinking tank 17 by utilizing the peripheral speed difference between the grip roller 2c and the grip roller 2 d.
In the apparatus for producing the polarizing film 25 shown in fig. 1, the film drawn out of the crosslinking tank 17 is introduced into the cleaning tank 19 through the guide roller 1i and the nip roller 2d in this order.
(cleaning treatment Process and cleaning tank)
The cleaning treatment step is a treatment performed for the purpose of removing an excessive chemical agent attached to the PVA-based resin film 10 after the crosslinking treatment step. As shown in fig. 1, the cleaning step may be performed by conveying the PVA-based resin film 10 after the crosslinking step (immersed in the crosslinking tank 17) along a film conveying path, immersing the PVA-based resin film in a cleaning tank 19 containing a cleaning solution for a predetermined time, and then extracting the PVA-based resin film.
The cleaning treatment step may be a treatment of spraying a cleaning treatment liquid, for example, in the form of a shower, on the PVA-based resin film 10 after the crosslinking treatment step, instead of the treatment of immersion in the cleaning tank 19 shown in fig. 1. In the cleaning step, immersion in the cleaning tank 19 and spraying of the cleaning solution may be performed in combination.
The cleaning treatment liquid may be, for example, water (pure water or the like), or an aqueous solution to which a water-soluble organic solvent such as an alcohol is added. The temperature of the cleaning bath is, for example, 2 to 40 ℃.
The stretching treatment (usually uniaxial stretching treatment) may be performed while the cleaning treatment step is performed. In the apparatus for manufacturing the polarizing film 25 shown in fig. 1, for example, the uniaxial stretching treatment can be performed in the cleaning tank 19 by utilizing the peripheral speed difference between the grip roller 2d and the grip roller 2 e.
In the apparatus for manufacturing the polarizing film 25 shown in fig. 1, the film drawn out from the cleaning tank 19 is introduced into the drying furnace 21 through the guide roller 11 and the nip roller 2e in this order.
(stretching step and stretching section)
The stretching treatment may be performed while performing the treatment in at least 1 step among the swelling treatment step, the dyeing treatment step, the crosslinking treatment step, and the washing treatment step. The stretching treatment in these steps is wet stretching, and usually uniaxial stretching. The stretching step is preferably performed in the crosslinking step or 1 or 2 or more stages before the crosslinking step. In order to improve the iodine dyeability and obtain a polarizing film 25 having good polarization characteristics, it is more preferable to subject the PVA-based resin film 10 subjected to the dyeing step to at least a certain degree of stretching treatment.
From the viewpoint of the polarization properties of the obtained polarizing film 25, the stretching ratio in the stretching step is adjusted so that the final cumulative stretching ratio of the polarizing film 25 (in the case where the PVA-based resin film 10 as the raw material film is a stretched film, the cumulative stretching ratio including the stretching) becomes 3 to 8 times.
In order to perform the stretching step, the polarizing film manufacturing apparatus includes a stretching unit for stretching the PVA-based resin film 10. The stretching treatment section preferably performs stretching between rollers, and examples thereof include 2 nip rollers disposed in front of and behind each groove shown in fig. 1.
(drying step and drying furnace)
The drying section is a region that is disposed on the downstream side of the cleaning tank 19 in the manufacturing apparatus shown in fig. 1 on the film transport path of the PVA-based resin film 10 and is used to dry the PVA-based resin film 10 after the cleaning process. In the drying process, the PVA-based resin film 10 after the washing process may be introduced into the drying furnace 21 while being continuously conveyed, and the polarizing film 25 may be obtained by performing the drying process.
The drying furnace 21 is a hot air oven capable of raising the temperature inside the furnace by, for example, supplying hot air. Instead of the drying furnace 21, the drying process may be performed using 1 or 2 or more heating bodies, heaters, or the like having a convex curved surface to which the PVA-based resin film 10 after the wet treatment step is closely adhered. Examples of the heating body include a roller (e.g., a guide roller serving also as a heat roller) having a heat source (e.g., a heat medium such as hot water or an infrared heater) therein and capable of increasing the surface temperature. Examples of the heater include an infrared heater, a halogen heater, and a panel heater. The temperature of the drying treatment (for example, the temperature in the drying furnace 21, the surface temperature of the hot roll, etc.) is usually 30 to 100 ℃, preferably 50 to 90 ℃.
Examples
The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" and "parts" are% by mass and "parts by mass" unless otherwise specified.
[ measurement of oxalate ion concentration ]
The crosslinking treatment liquid was diluted 1000 times with pure water and filtered through a 0.22 μm PTFE filter. The obtained diluted solution was analyzed by ion chromatography, and the oxalic acid concentration was quantified by comparing the area integral value of the obtained spectrum with the area integral value of a spectrum obtained by analysis of an oxalic acid aqueous solution having a known concentration. The analytical device used was 883 Basic IC Plus manufactured by Metrohm, and the column used was Metrosep A Supp 5150/4.0. The mobile phase was used containing NaHCO at a concentration of 1.0mM3And contained at a concentration of 3.2mMHas Na2CO3The aqueous solution of (3) is an aqueous solution in which acetone is added in an amount of 5% by mass.
[ measurement of the tension of the polyvinyl alcohol resin film in the crosslinking tank ]
A small piece of PVA film having a thickness of 60mm and a width of 50mm was stretched 2.2 times while being immersed in the swelling treatment liquid in the swelling bath and the dyeing treatment liquid in the dyeing bath in this order, and further stretched 5.8 times while being immersed in the crosslinking treatment liquid. The tension of the PVA under tension was measured by a load cell attached between clamps holding both ends of the PVA in the direction of tension, and the tension at the time when the 5.8-fold stretching was completed in the crosslinking treatment liquid in the crosslinking tank was recorded.
[ example 1]
Boric acid, potassium iodide, oxalic acid dihydrate and potassium hydroxide were added to pure water so that the boric acid concentration became 3.4%, the potassium iodide concentration became 10.1%, the oxalic acid dihydrate concentration became 1.7% and the potassium hydroxide concentration became 0.9%, to prepare an oxalic acid-containing liquid. The pH of the resulting oxalic acid-containing liquid was 3.9, and the concentration of oxalate ions was 0.9%.
The obtained oxalic acid-containing liquid was irradiated with ultraviolet light having a wavelength of 280nm so that the irradiation energy was 0.2W/L and the irradiation time was 3hr, to obtain an oxalic acid-containing liquid after the light irradiation.
The oxalate ion concentration of the obtained oxalic acid-containing liquid after light irradiation was measured. Further, the oxalic acid-containing liquid after the irradiation with the light was used to measure the tension of the polyvinyl alcohol resin film in the crosslinking tank. The results are shown in table 1.
[ example 2 ]
An oxalic acid-containing liquid after light irradiation was obtained in the same manner as in example 1, except that the light irradiated to the oxalic acid-containing liquid was changed to ultraviolet light having a wavelength of 340 nm. The concentration of oxalate ions and the tension of the polyvinyl alcohol resin film in the crosslinking tank were measured by the same procedure as in example 1 using the obtained oxalic acid-containing liquid after irradiation with light. The results are shown in table 1.
[ reference example 1]
Boric acid and potassium iodide were added to pure water so that the boric acid concentration became 3.5% and the potassium iodide concentration became 10.3%, to prepare a liquid containing no oxalic acid. The pH of the resulting oxalic acid-free liquid was 4.0. The tension of the polyvinyl alcohol resin film in the crosslinking tank was measured by the same procedure as in example 1 using the obtained oxalic acid-free liquid. The results are shown in table 1.
[ comparative example 1]
An oxalic acid-containing liquid was obtained in the same manner as in example 1, but the oxalic acid-containing liquid was not irradiated with light. The concentration of oxalate ions and the tension of the polyvinyl alcohol resin film in the crosslinking tank were measured by the same procedure as in example 1 using the obtained oxalic acid-containing liquid after irradiation with light. The results are shown in table 1.
[ comparative examples 2 to 4 ]
An oxalic acid-containing liquid after light irradiation was obtained in the same manner as in example 1, except that the light irradiated to the oxalic acid-containing liquid was changed to the light shown in table 1. The concentration of oxalate ions and the tension of the polyvinyl alcohol resin film in the crosslinking tank were measured by the same procedure as in example 1 using the obtained oxalic acid-containing liquid after irradiation with light. The results are shown in table 1.
In table 1, the oxalate ion concentration of the oxalic acid-containing liquid in examples 1 and 2 and comparative examples 1 to 4 and the oxalate ion concentration of the liquid containing no oxalic acid in reference example 1 are shown in the column of "oxalate ion concentration before light irradiation" in table 1, the oxalate ion concentration of the oxalic acid-containing liquid after light irradiation is shown in the column of "oxalate ion concentration after light irradiation" in table 1, and the value of the tension of the polyvinyl alcohol-based resin film in the crosslinking tank is shown in the column of "tension".
[ Table 1]
Claims (11)
1. A method for producing a polarizing film, which uses a polyvinyl alcohol resin film to produce a polarizing film, comprising:
a step of treating the polyvinyl alcohol resin film with a dyeing treatment liquid containing iodine;
a step of adding an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiating the liquid to which the oxalic acid compound is added with ultraviolet rays to obtain a first crosslinking treatment liquid; and
and a step of immersing the polyvinyl alcohol resin film after the step of treating with the dyeing treatment liquid in a crosslinking treatment liquid containing the first crosslinking treatment liquid.
2. The method for producing a polarizing film according to claim 1, wherein the step of obtaining the first crosslinking treatment liquid comprises a step of subjecting the liquid containing the crosslinking agent and the iodide salt to an activated carbon treatment.
3. The method for producing a polarizing film according to claim 1 or 2, wherein the step of immersing is a step of immersing the polyvinyl alcohol resin film after the step of treating with the dyeing treatment liquid in a crosslinking tank containing the crosslinking treatment liquid,
the step of obtaining the first crosslinking treatment liquid is performed in an external tank located outside the crosslinking tank.
4. The polarizing film production method according to claim 3, wherein the liquid containing a crosslinking agent and an iodide salt is at least a part of a crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank,
the manufacturing method further includes:
supplying the extracted at least a part of the crosslinking treatment liquid to the external tank; and
and a step of supplying the first crosslinking treatment liquid from the external tank to the crosslinking tank.
5. The method for manufacturing a polarizing film according to claim 3 or 4, wherein the pH of the crosslinking treatment liquid contained in the crosslinking tank is 2 or more and 4 or less.
6. The polarizing film production method according to any one of claims 3 to 5, wherein the concentration of oxalate ions in the crosslinking treatment liquid contained in the crosslinking tank is 0.5 mass% or less with respect to the crosslinking treatment liquid.
7. The polarizing film production method according to any one of claims 1 to 6, wherein the crosslinking agent comprises a boron compound,
the iodide salt comprises potassium iodide.
8. A polarizing film manufacturing apparatus for manufacturing a polarizing film using a polyvinyl alcohol resin film, comprising:
a dyeing treatment section for treating the polyvinyl alcohol resin film with a dyeing treatment liquid containing iodine;
a first crosslinking treatment liquid preparation unit that adds an oxalic acid compound to a liquid containing a crosslinking agent and an iodide salt, and irradiates the liquid to which the oxalic acid compound is added with ultraviolet light to obtain a first crosslinking treatment liquid; and
and a crosslinking tank for immersing the polyvinyl alcohol resin film treated by the dyeing section in a crosslinking treatment liquid containing the first crosslinking treatment liquid.
9. The polarizing film manufacturing apparatus according to claim 8, wherein the first crosslinking treatment liquid preparation unit further comprises an activated carbon treatment unit that performs activated carbon treatment on the liquid containing the crosslinking agent and the iodide salt.
10. The polarizing film manufacturing apparatus according to claim 8 or 9, wherein the first crosslinking treatment liquid preparation part is provided outside the crosslinking tank.
11. The polarizing film production apparatus according to claim 10, wherein the liquid containing a crosslinking agent and an iodide salt is at least a part of a crosslinking treatment liquid extracted from the crosslinking treatment liquid in the crosslinking tank,
the manufacturing apparatus further includes:
a first supply unit configured to supply the extracted at least a part of the crosslinking liquid to the first crosslinking liquid preparation unit; and
and a second supply unit configured to supply the first crosslinking liquid from the first crosslinking liquid preparation unit to the crosslinking tank.
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| JP2009230131A (en) * | 2008-02-29 | 2009-10-08 | Sumitomo Chemical Co Ltd | Method of manufacturing polarization film, polarizing plate, and optical laminated body |
| US20150219797A1 (en) * | 2012-10-22 | 2015-08-06 | Nitto Denko Corporation | Polarizing film and method for producing polarizing film |
| JP2018036545A (en) * | 2016-09-01 | 2018-03-08 | 日本合成化学工業株式会社 | Production method of polarizing film, polarizing film, and polarizing plate |
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| US10114159B2 (en) | 2015-01-27 | 2018-10-30 | Lg Chem, Ltd. | Method for manufacturing polarizer and polarizer manufactured by the same |
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| JP2009230131A (en) * | 2008-02-29 | 2009-10-08 | Sumitomo Chemical Co Ltd | Method of manufacturing polarization film, polarizing plate, and optical laminated body |
| US20150219797A1 (en) * | 2012-10-22 | 2015-08-06 | Nitto Denko Corporation | Polarizing film and method for producing polarizing film |
| JP2018036545A (en) * | 2016-09-01 | 2018-03-08 | 日本合成化学工業株式会社 | Production method of polarizing film, polarizing film, and polarizing plate |
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