CN115073777A - Polyvinyl alcohol film, method for producing same, and optical film using same - Google Patents
Polyvinyl alcohol film, method for producing same, and optical film using same Download PDFInfo
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- CN115073777A CN115073777A CN202110346899.2A CN202110346899A CN115073777A CN 115073777 A CN115073777 A CN 115073777A CN 202110346899 A CN202110346899 A CN 202110346899A CN 115073777 A CN115073777 A CN 115073777A
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- polyvinyl alcohol
- pva film
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- boric acid
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- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 168
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 167
- 239000010408 film Substances 0.000 title claims abstract description 149
- 239000012788 optical film Substances 0.000 title claims abstract description 26
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 23
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000004327 boric acid Substances 0.000 claims abstract description 44
- 238000002844 melting Methods 0.000 claims abstract description 21
- 230000008018 melting Effects 0.000 claims abstract description 21
- 238000005266 casting Methods 0.000 claims description 39
- 239000000243 solution Substances 0.000 claims description 35
- 229920005989 resin Polymers 0.000 claims description 26
- 239000011347 resin Substances 0.000 claims description 26
- 239000007864 aqueous solution Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 238000000113 differential scanning calorimetry Methods 0.000 claims description 13
- 238000004090 dissolution Methods 0.000 claims description 12
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 10
- 229910052796 boron Inorganic materials 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 9
- 230000008025 crystallization Effects 0.000 claims description 9
- 239000004014 plasticizer Substances 0.000 claims description 9
- 230000010287 polarization Effects 0.000 claims description 5
- 238000006116 polymerization reaction Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 238000011282 treatment Methods 0.000 claims description 4
- 239000012528 membrane Substances 0.000 claims description 2
- 238000004043 dyeing Methods 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 3
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 7
- -1 olefin compounds Chemical class 0.000 description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 4
- 238000010306 acid treatment Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000004321 preservation Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 229920001567 vinyl ester resin Polymers 0.000 description 4
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000000178 monomer Substances 0.000 description 3
- 238000007127 saponification reaction Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 2
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 235000011187 glycerol Nutrition 0.000 description 2
- 239000011630 iodine Substances 0.000 description 2
- 229910052740 iodine Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- JIGUQPWFLRLWPJ-UHFFFAOYSA-N Ethyl acrylate Chemical compound CCOC(=O)C=C JIGUQPWFLRLWPJ-UHFFFAOYSA-N 0.000 description 1
- UWHCKJMYHZGTIT-UHFFFAOYSA-N Tetraethylene glycol, Natural products OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- MEGHWIAOTJPCHQ-UHFFFAOYSA-N ethenyl butanoate Chemical compound CCCC(=O)OC=C MEGHWIAOTJPCHQ-UHFFFAOYSA-N 0.000 description 1
- GFJVXXWOPWLRNU-UHFFFAOYSA-N ethenyl formate Chemical compound C=COC=O GFJVXXWOPWLRNU-UHFFFAOYSA-N 0.000 description 1
- QBDADGJLZNIRFQ-UHFFFAOYSA-N ethenyl octanoate Chemical compound CCCCCCCC(=O)OC=C QBDADGJLZNIRFQ-UHFFFAOYSA-N 0.000 description 1
- BLZSRIYYOIZLJL-UHFFFAOYSA-N ethenyl pentanoate Chemical compound CCCCC(=O)OC=C BLZSRIYYOIZLJL-UHFFFAOYSA-N 0.000 description 1
- UIWXSTHGICQLQT-UHFFFAOYSA-N ethenyl propanoate Chemical compound CCC(=O)OC=C UIWXSTHGICQLQT-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 229920001477 hydrophilic polymer Polymers 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- PNJWIWWMYCMZRO-UHFFFAOYSA-N pent‐4‐en‐2‐one Natural products CC(=O)CC=C PNJWIWWMYCMZRO-UHFFFAOYSA-N 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 229920001290 polyvinyl ester Polymers 0.000 description 1
- LYBIZMNPXTXVMV-UHFFFAOYSA-N propan-2-yl prop-2-enoate Chemical compound CC(C)OC(=O)C=C LYBIZMNPXTXVMV-UHFFFAOYSA-N 0.000 description 1
- PNXMTCDJUBJHQJ-UHFFFAOYSA-N propyl prop-2-enoate Chemical compound CCCOC(=O)C=C PNXMTCDJUBJHQJ-UHFFFAOYSA-N 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
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Classifications
-
- 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
- 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
- C08J7/12—Chemical modification
- C08J7/14—Chemical modification with acids, their salts or anhydrides
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
-
- 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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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Polarising Elements (AREA)
- Moulding By Coating Moulds (AREA)
- Treatments Of Macromolecular Shaped Articles (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
The invention relates to a polyvinyl alcohol film, a manufacturing method thereof and an optical film using the same, wherein the polyvinyl alcohol film has a melting point (Tm) >210 ℃ after being treated by boric acid, the melting point difference Delta Tm of any two positions of the film is less than 3.2 ℃, the polyvinyl alcohol film with the characteristics has uniform color after being stretched and dyed, the problem of uneven dyeing such as color blocks or color spots and the like is avoided, the defect of the optical film manufactured by the polyvinyl alcohol film is improved, and the yield of the optical film is improved.
Description
Technical Field
The present invention relates to a polyvinyl alcohol (PVA) film which can be used as an optical film, particularly a polarizing film.
Background
A polyvinyl alcohol (PVA) film is a hydrophilic polymer having properties such as transparency, mechanical strength, water solubility, and excellent processability, and has been widely used for an optical film for a packaging material or an electronic product, particularly a polarizing film.
When the polarizing film is manufactured, the PVA film is placed in boric acid solution for stretching and dyeing, dye molecules enter the PVA film through diffusion to be regularly arranged among the PVA molecules, so that the polarizing film can absorb light components parallel to the arrangement direction of the PVA film and pass the light components in the vertical direction to generate the polarizing film with polarization characteristics.
The good polarizing film has the characteristics of uniform color, less color unevenness, no wrinkles and the like, and can provide better optical properties. In order to improve the optical properties of the polarizing film, the prior art may change the viscosity or saponification degree by changing the structure of the polyvinyl alcohol, or adding functional groups (e.g., cationic groups), etc., so as to improve the optical properties.
Disclosure of Invention
Although the prior art provides methods for improving optical properties of a PVA film when the PVA film is used to form a polarizing film, in the prior art, when the PVA film is used to prepare a large-sized optical film, the phenomena of uneven dyeing, color blocks and color spots, or uneven color during stretching often occur, which increases the difficulty of preparing the optical film.
Therefore, in order to solve the above problems, it is an object of the present invention to provide a polyvinyl alcohol (PVA) film having a melting point (Tm) >210 ℃ measured by a Differential Scanning Calorimetry (DSC) after being treated with 0.2 wt% boric acid, and a difference in melting point (Δ Tm) <3.2 ℃ between any two locations of the PVA film.
In a preferred embodiment, the PVA film treated with the 0.2 wt% aqueous boric acid solution has a crystallization temperature (T) measured by DSC c )<153.5℃。
In a preferred embodiment, the temperature difference of crystallization (Δ T) of the PVA film treated with the 0.2 wt% aqueous solution of boric acid is arbitrarily two locations c )<3.85℃。
In a preferred embodiment, the PVA film has a standard deviation of retardation of <3 nm.
In a preferred embodiment, 0.12g of the PVA film is treated with a 0.2 wt% aqueous solution of boric acid and the aqueous solution has a boron content of 16 to 19ppm after dissolution in water.
Another object of the present invention is to provide an optical film, which is made from the PVA film of the present invention.
In a preferred embodiment, the optical film is a polarizing film.
In a preferred embodiment, the polarizing film has a polarization brightness > 99.8.
Another object of the present invention is to provide a method for producing a PVA film of the present invention, comprising: (a) stirring a polyvinyl alcohol resin at a heating rate of 4-20 ℃/h, keeping the temperature for 2-4 hours after the dissolution temperature is higher than 100 ℃, and reversing the stirring direction at least twice per hour to form a polyvinyl alcohol casting solution; (b) casting the casting solution to a casting drum; and (c) drying to form the PVA film.
In a preferred embodiment, the rotation speed of the casting drum is 3 to 7 m/min.
In a preferred embodiment, the drying of step (c) is carried out with a hot roll or a floating dryer.
In a preferred embodiment, the maximum/minimum air flow received by the membrane along the width direction within the floating dryer is ≦ 3.0.
In a preferred embodiment, the polyvinyl alcohol casting solution further includes a plasticizer, and the plasticizer is 3 to 30 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin.
In a preferred embodiment, the polyvinyl alcohol resin content in the polyvinyl alcohol casting solution is 10 to 60% by weight.
In a preferred embodiment, the polyvinyl alcohol resin has a degree of polymerization of 800 to 10000.
Compared with the prior art, the PVA film has uniform color after being dyed, can not generate the problem of nonuniform color such as color blocks or color spots and the like, effectively improves the defect of the PVA for manufacturing the optical film, improves the yield of the manufactured optical film, and can be particularly used for manufacturing large-size polarizing films.
Drawings
FIG. 1 is a schematic diagram of a PVA film cut into three 10cm by 10cm test pieces with areas of left, middle and right.
Detailed Description
The following embodiments should not be construed to unduly limit the invention. Modifications and variations of the embodiments discussed herein can be made by one of ordinary skill in the art without departing from the spirit or scope of the invention, and still fall within the scope of the invention.
The terms "a" and "an" herein mean one or more than one (i.e., at least one) of the grammatical object of the document.
In the invention, the MD is the mechanical Direction (Machine Direction), namely the longitudinal Direction of the PVA film; the TD is Transverse Direction (Transverse Direction), i.e. Transverse Direction of the PVA film.
The method for manufacturing a polyvinyl alcohol (PVA) film according to the present invention includes the steps of: after preparing a polyvinyl alcohol casting solution, the polyvinyl alcohol casting solution is cast into a casting roller and is dried to form a polyvinyl alcohol polymer film.
Specifically, the method for manufacturing the PVA film comprises the following steps: dissolving the polyvinyl alcohol resin in a solution (e.g., water) in a dissolution tank to form the polyvinyl alcohol casting solution; optionally filtering the polyvinyl alcohol casting solution using a filter; subsequently, the polyvinyl alcohol casting solution is cast to a casting drum using a gear pump (gear pump) and a coater (e.g., a T-die coater); and finally, stripping the PVA film formed on the roller, and carrying out a series of heat treatments of hot rollers and/or drying to obtain the PVA film.
The polyvinyl alcohol casting solution is prepared by dissolving polyvinyl alcohol resin in a dissolution tank, wherein the dissolution temperature in the dissolution tank is >100 ℃, preferably >110 ℃, more preferably >120 ℃, specifically, for example, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃ or 140 ℃, and the invention is not limited thereto. The temperature of the dissolution tank is preferably raised at a rate of 4 to 20 ℃ per hour, more preferably 5 to 15 ℃, still more preferably 6 to 9 ℃, and more specifically, for example, 4.0 ℃/hr, 5.0 ℃/hr, 6.0 ℃/hr, 7.0 ℃/hr, 8.0 ℃/hr, 9.0 ℃/hr, 10 ℃/hr, 11 ℃/hr, 12 ℃/hr, 13 ℃/hr, 14 ℃/hr, 15 ℃/hr, 16 ℃/hr, 17 ℃/hr, 18 ℃/hr, 19 ℃/hr or 20 ℃/hr, etc., and if the temperature raising rate is too fast, the polyvinyl alcohol resin is liable to be agglomerated, resulting in incomplete dissolution. After the temperature is raised to the desired dissolution temperature, the polyvinyl alcohol casting solution is continuously stirred for 2 to 4 hours, preferably 3 hours, and the stirring direction is changed at least 2 times, preferably 3 times, every 1 hour, for example, 20 minutes clockwise rotation is changed to 20 minutes counterclockwise rotation. The reverse direction of the stirring process can increase the dissolving effect and avoid cluster (cluster) residue in the polyvinyl alcohol casting solution.
The polyvinyl alcohol casting solution is prepared, and the content of the polyvinyl alcohol resin is 10 to 60 wt%, preferably 15 to 40 wt%, more preferably 20 to 30 wt%, specifically, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 wt%, and the like. If the content of the polyvinyl alcohol resin is insufficient, the viscosity of the polyvinyl alcohol casting solution is too low, and the drying load is too large, resulting in poor film forming efficiency in producing a PVA film. On the contrary, if the content of the polyvinyl alcohol resin is too high, the polyvinyl alcohol resin is not easily dissolved and clusters are easily remained, which causes the deterioration of the phase difference uniformity of the PVA film and affects the dyeing uniformity of the subsequent process.
The polyvinyl alcohol resin is obtained by polymerizing a vinyl ester resin monomer to form a polyvinyl ester resin and then performing saponification reaction; the vinyl ester resin monomer includes vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, or vinyl caprylate, and the present invention is not limited thereto, and vinyl acetate is preferable. Further, olefin compounds or acrylate derivatives, and the vinyl ester resin monomer copolymerization copolymer can also be used; the olefin compound includes ethylene, propylene, butylene, or the like, and the present invention is not limited thereto. The acrylate derivative includes acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, or the like, and the present invention is not limited thereto.
The degree of saponification of the polyvinyl alcohol resin is 90% or more, preferably 99% or more, to obtain preferable optical characteristics, specifically, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9%, and the like. The polymerization degree of the polyvinyl alcohol is between 800 and 10000, preferably 2200 to 10000, such as 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, etc., and the polymerization degree is higher than 800, which has better processing characteristics, but the polymerization degree is not favorable for dissolution if higher than 10000.
In the casting solution, a plasticizer may be contained in addition to the polyvinyl alcohol-based resin to improve the film-forming processability, and usable plasticizers include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, or glycerin, etc., and the present invention is not limited thereto, and ethylene glycol and glycerin are preferable. The plasticizer is added in an amount of usually 3 to 30 parts by weight, preferably 7 to 20 parts by weight, more specifically, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 parts by weight, etc., based on 100 parts by weight of the polyvinyl alcohol resin. If the plasticizer content is insufficient, the formed PVA film is likely to be crystallized, which affects the dyeing performance of subsequent processing. Conversely, if the plasticizer content is too high, the mechanical properties of the PVA film are deteriorated.
The equipment used in the method for manufacturing the PVA film comprises a dissolving tank, a filter, a coating machine and a conveying pipeline connected from the dissolving tank to the coating machine, wherein the equipment is preferably coated with a heat preservation device which can be a metal electric heating wire or a jacket internally filled with liquid, such as oil or water, and the equipment is kept in a uniformly heated heat preservation state by heating the liquid in the metal wire or the jacket, particularly the surfaces of the equipment and the pipeline, so that the polyvinyl alcohol in the polyvinyl alcohol casting solution is prevented from forming gel or cluster due to the surface loss temperature of the equipment or the pipeline. In addition, the temperature of the heat preservation can not be too high, otherwise, part of the polyvinyl alcohol casting solution can be dehydrated or gelatinized to form a scorched or black gel, and the surface quality and uniformity of the PVA film after the subsequent coating and film forming are affected. The heat preservation temperature of the polyvinyl alcohol casting solution at the coating forming position is 80-120 ℃, preferably 90-110 ℃, more preferably 90-100 ℃, specifically 80, 85, 90, 95, 100, 105, 110, 115, 120 ℃ and the like.
When the polyvinyl alcohol casting solution is cast onto the casting drum, the rotation speed of the casting drum is about 3 to 7m/min, preferably 4 to 6 m/min. When the drum speed is too low, the casting solution tends to be excessively dried, and the phase difference and the melting point tend to be unevenly distributed. Conversely, when the drum speed is too high, the casting solution is insufficiently dried, and the releasability is reduced. In addition, in a preferred embodiment, the temperature of the roller is set to 85 to 90 ℃, specifically, 85, 86, 88, 87, 88, 89, 90 ℃ and the like, and if the temperature of the roller is too high, the casting solution on the roller is likely to have a foaming phenomenon.
The PVA film preliminarily formed on the casting roller is peeled off from the roller and dried to form the PVA film, and the drying process can be carried out on a hot roller or a floating type dryer. The number of the hot roller and the floating dryer is not particularly limited and may be adjusted as necessary. However, in the preferred embodiment, the dry car (i.e., oven) temperature ratio is 2.0-2.4 max/min; when the compartment temperature ratio is too high, the crystallinity tends to be uneven, and the PVA film may react with boric acid unevenly when used for manufacturing an optical film. In addition, the temperature difference between adjacent compartments is preferably 65 ℃ or less, more preferably 60 ℃ or less, and most preferably 50 ℃, and when the temperature difference between adjacent compartments is too large, the phase difference distribution tends to be uneven. Further, the amount of air flow received by the PVA film formed in the width direction (i.e., perpendicular to the machine direction) in the floating dryer is not particularly limited, but the maximum/minimum air flow ratio must be controlled to be 3.0 or less, specifically, 0, 0.5, 1.0, 1.5, 2.0, 2.5, or 3.0, for example. Because the place with large air quantity is easy to take away the moisture, the drying degree is large, and the air quantity ratio range can control the air quantity contacted with each position of the PVA film to be the same, so as to achieve uniform drying. In addition, when the air flow ratio is too large, the PVA film reacts with boric acid unevenly and has a phase difference unevenly when used for manufacturing an optical film.
The "treatment with a 0.2 wt% aqueous boric acid solution" according to the present invention is (a) placing about 0.1g of a PVA film in 20g of pure water so that the PVA film is completely immersed below the liquid level of the pure water, and stirring at a stirring speed of 250rpm for 1 hour; (b) taking out the PVA film from the pure water, placing the PVA film in 0.2 wt% boric acid aqueous solution, and standing for 1.0 hour; and (c) taking out the PVA film from the 0.2 wt% boric acid aqueous solution, and placing the PVA film in a closed container to stand and age for 16.0 hours to finish the boric acid treatment. (ii) a In the present invention, a lower boric acid concentration is used, and since a higher boric acid concentration is used, the area of the PVA film which is originally difficult to react is also reactive due to the high boric acid concentration, and therefore, the uniformity of the film is not easy to observe.
The PVA film of the present invention, after boric acid treatment, has a melting point (Tm) >210 ℃ measured with a Differential Scanning Calorimetry (DSC), and the difference in melting point (Δ Tm) between any two places of the PVA film is <3.2 ℃. Specifically, for example, the melting point (Tm) is 211 ℃, 212 ℃, 215 ℃, 220 ℃, 225 ℃ or 230 ℃ or the like, and the present invention is not limited thereto; specific examples of Δ Tm at any two positions of the PVA film include 1 ℃, 1.5 ℃, 2 ℃, 2.5 ℃, 3 ℃ and 3.1 ℃, and the present invention is not limited thereto.
When the PVA film is used for manufacturing an optical film, stretching and dyeing are carried out, for example, a polarizing film containing I is used in the manufacturing process of the polarizing film 3 - 、I 5 - The PVA film is dyed by boric acid aqueous solution of iodide ions, and after boric acid can generate cross-linking effect with an amorphous (amophorus) area of PVA, the iodide ions are fixed to avoid dissolving out the iodide ions. However, after the PVA molecules are crosslinked with boric acid, the crystallinity is reduced, and the melting point is reduced; when the crystallinity is not uniformly distributed, the reaction between the PVA film and boric acid is not uniform, resulting in I 3 - 、I 5 - The iodine ions are not fixed uniformly, which leads to color unevenness. Therefore, the present invention simulates the soaking in boric acid used in the polarizer process by treating the PVA film with boric acid, and the difference between different positions is easily analyzed using a lower boric acid concentration (in this document, 0.2 wt%), and the melting point (Tm) measured by a Differential Scanning Calorimetry (DSC)>Δ Tm of PVA film at 210 ℃ at arbitrary two points<3.2 ℃ the PVA filmThe film has suitable and uniform crystallinity, and when stretched and dyed, a polarizing film having a uniform color can be obtained. The PVA film of the present invention can also be used for producing other stretched and dyed optical films, and is not limited to polarizing films.
Further, the PVA film after boric acid treatment had a crystallization temperature (T) measured by DSC c )<153.5 ℃. Specifically, for example, the crystallization temperature (T) of a PVA film after boric acid treatment c ) 110 deg.C, 115 deg.C, 120 deg.C, 125 deg.C, 130 deg.C, 135 deg.C, 140 deg.C, 150 deg.C or 155 deg.C, etc., and the present invention is not limited thereto.
Further, Δ T of the PVA film treated with boric acid at any two places c <3.85 ℃. Specifically, for example, the boric acid-treated PVA film has Δ T at two arbitrary positions c 0 ℃, 0.5 ℃, 1 ℃, 1.5 ℃, 2 ℃, 2.5 ℃, 3 ℃ or 3.19 ℃ and the like, and the present invention is not limited thereto.
In the invention, the method for DSC measurement comprises the following steps: as shown in FIG. 1, three test pieces of 10cm by 10cm area, left, middle and right, were cut out along the TD direction from one of the MD positions of the PVA film within 40 cm of the end in the TD direction. Then, 0.1g of PVA film was weighed out from each test piece, and the test pieces were placed in a glass bottle, 20g of pure water was added thereto so that the PVA film was completely below the level of the pure water, and a stirring stone was added thereto at a stirring speed of 250rpm and stirred at room temperature for 1.0 hour. Subsequently, pure water in the glass bottle was poured out, 20g of a 0.2 wt% aqueous boric acid solution was added, and after standing for 1.0 hour, the aqueous boric acid solution was poured out to allow the boric acid-treated PVA film to stand still in the bottle closed and ripen for 16.0 hours. Finally, taking out the boric acid-treated PVA film, spreading the boric acid-treated PVA film on an iron disc, drying the boric acid-treated PVA film for 1.0h at 105 ℃, taking out the boric acid-treated PVA film, and analyzing DSC; DSC temperature range of 30-250 deg.C, maintaining the temperature at 30 deg.C and 250 deg.C for 1 min, and recording melting point (T) at the first temperature rise m ) Crystallization temperature (T) at the first temperature reduction c ) Glass transition temperature (T) at the second temperature rise g ). The DSC measuring instrument may be a general purpose DSC instrument, such as DSC: TA Instruments DSC 25.
Further, the PVA film of the present invention has a standard deviation of retardation of <3 nm. Specifically, for example, the standard deviation of the retardation of the PVA film is 0nm, 0.5nm, 1.0nm, 1.5nm, 2.0nm, 2.5nm, 2.9nm or the like, and the present invention is not limited thereto.
Retardation (Retardation) in the present invention refers to the amount of phase change of incident polarized light when light passes through a film, that is, the amount of phase Retardation in nm; the uniformity of the retardation value, which involves the uniformity of molecular orientation and the uniformity of thickness, has a great influence on the subsequent optical film manufacturing process. As shown in FIG. 1, retardation was measured by cutting three 10cm by 10cm test pieces from the left, middle and right sides along the TD direction at one of the MD positions of the PVA film treated with boric acid within 40 cm of the end in the TD direction, and obtaining the numerical values of retardation and statistical data (maximum value, standard deviation, etc.) of all points in the plane.
Further, 0.12g of the PVA film of the present invention was treated with a 0.2 wt% aqueous solution of boric acid and the boron content of the aqueous solution was 16 to 19ppm after dissolving in water. Specifically, for example, 16ppm, 16.5ppm, 17ppm, 17.5ppm, 18ppm, 18.5ppm, 19ppm or the like, and the present invention is not limited thereto. If the content of boron is lower than the content of boron, the color fixing capability of the PVA film in subsequent dyeing is insufficient and poor; if the content of boron is higher than the above, the degree of crosslinking between boric acid and PVA is too high, which is not preferable because it is disadvantageous in the subsequent stretching process.
In the invention, the method for measuring the boron content comprises the following steps: the boric acid-treated PVA film was taken out, passed through pure water, and then placed in a 30ml glass sampling bottle, and 20g of pure water was added thereto, and after fully dissolved, the boron concentration in the solution was analyzed by ICP-OES.
The optical film of the present invention is completed by using the PVA film of the present invention. The optical film includes a polarizing film, a blue-resistant film, a filter, etc., and the present invention is not limited thereto. Preferably, the optical film is a polarizing film, and the polarizing film has a polarization brightness > 99.8.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Hereinafter, the present invention will be further described in detail with reference to the detailed description and examples. However, it should be understood that these examples are only for helping the easier understanding of the present invention and are not intended to limit the scope of the present invention.
Examples 1 to 4
Manufacturing a PVA film: the PVA films of examples 1 to 4 were produced by using the method for producing a PVA film of the present invention, in which polyvinyl alcohol resins having melting points (Tm) of 233.21 ℃, 233.24 ℃, 233.01 ℃ and 233.08 ℃ were used as main components of a polyvinyl alcohol casting solution, respectively, and the operating conditions of the production method are shown in Table 1.
Comparative examples 1 to 3
Preparing a PVA film: PVA films of comparative examples 1 to 3 were produced by using, as the main component of a polyvinyl alcohol casting solution, polyvinyl alcohol resins having melting points (Tm) of 233.15 ℃ and 233.17 ℃ respectively, under the same conditions as those for the production of the PVA films of the present invention, and the conditions for the production methods are shown in Table 1.
Examples of the experiments
Analysis of the properties of the PVA film: the PVA films of examples 1 to 4 and comparative examples 1 to 3 were measured for the standard deviation of retardation, and after further treatment with a 0.2 wt% aqueous solution of boric acid, their melting points (Tm), melting point differences (. DELTA.Tm), and crystallization temperatures (T.sub. c ) Crystallization temperature difference (. DELTA.T) c ) Boron content, the measurement results are shown in table 2.
Preparing a polarizing film: the PVA films of examples 1 to 4 and comparative examples 1 to 3 were each immersed in water at about 30 ℃ to swell, and then subjected to first uniaxial stretching in the MD direction, the stretched length being 2.0 times the original length of the PVA film. Subsequently, the PVA film after the first stretching was immersed in an aqueous solution of 30 ℃ containing 0.03 mass% of iodine and 3 mass% of potassium iodide, and subjected to second uniaxial stretching to be stretched in the MD direction, the stretched length being 3.3 times the original length of the PVA film. Subsequently, the PVA film after the second stretching was immersed in an aqueous solution of 30 ℃ containing 3 mass% of potassium iodide and 3 mass% of boric acid, and subjected to third uniaxial stretching to be stretched in the MD direction, whereby the stretched length was 3.6 times the original length. Subsequently, the PVA film after the third stretching was immersed in an aqueous solution of 60 ℃ containing 5 mass% of potassium iodide and 4 mass% of boric acid, and was uniaxially stretched for the fourth time in the MD direction to have a length 6.0 times as long as the PVA film after the third stretching. Finally, the PVA film after the fourth stretching was immersed in an aqueous solution containing 3 mass% of potassium iodide for 15 seconds, and then dried at 60 ℃ for 4 minutes to obtain a polarizing film. The polarizing films obtained in examples 1 to 4 and comparative examples 1 to 3 were measured for polarization and color uniformity, and the measurement results are shown in table 2.
The method for measuring the deflection brightness comprises the following steps: two identical polarizing films were stacked in the same orientation direction, and the light transmittance (H) was measured at the wavelength 0 ) The two polarizing films were stacked with the orientation direction perpendicular to each other, and the light transmittance (H) was measured at a wavelength 90 ) The bias is calculated by the following formula: [ (H) 0 -H 90 )/(H 0 +H 90 )] 1/2 。
Color uniformity measurement method: two identical polarizing films were orthogonally superimposed, one surface was irradiated with light using a lamp box with a light emission degree of 14000lx, and color uniformity of the other surface was observed and evaluated according to the following rules: o, no color unevenness, delta, weak color unevenness, and X, obvious color unevenness.
TABLE 1
TABLE 2
(Table 2 continuing)
(O: no color unevenness,. DELTA.: slight color unevenness, X: remarkable color unevenness)
As shown in the table 2 below, the following examples,the melting points (Tm) of the PVA films of examples 1 to 4 were all>210 ℃ and any two Δ Tm' s<The polarizing films obtained by using these resins were excellent in color uniformity (no color unevenness) at 3.2 ℃. In contrast, the PVA films of comparative examples 1 to 3 had melting points (Tm) of more than 210 ℃ or Δ Tm of 3.2 ℃ at any two points, respectively, and the polarizing films using them had poor color uniformity, slight color unevenness, and significant color unevenness, particularly comparative examples 2 and 3, which had crystallization temperatures (T ℃) c ) When the temperature is more than 153.5 ℃, the boron content is not 16 to 19ppm or the standard deviation of the retardation is more than 3nm, the polarizing film has obviously poor color uniformity (obvious color unevenness). Thus, the melting point (Tm) of the PVA film is set forth in the present specification>210 ℃ and any two Δ Tm<3.2 ℃, has color uniformity when being used for preparing the polarizing film, and is not easy to generate the problems of color blocks and color spots.
In conclusion, the PVA film has a melting point (Tm) >210 ℃, any two positions of delta Tm <3.2 ℃, and the color uniformity after stretching and dyeing does not generate the problem of color block, color spot and other color non-uniformity, thereby effectively improving the defect of the PVA film in manufacturing the optical film and improving the yield of the optical film, in particular to a large-size polarizing film.
The present invention has been described in detail, and it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Claims (15)
1. A polyvinyl alcohol (PVA) film, characterized in that it has been treated with a 0.2 wt% aqueous solution of boric acid and then measured for melting point (T.sub.m.) by Differential Scanning Calorimetry (DSC) m )>210 ℃ and the melting point difference (Delta T) of any two positions of the PVA film m )<3.2℃。
2. The PVA film of claim 1, having a D value after treatment with a 0.2 wt% aqueous solution of boric acidCrystallization temperature (T) measured by SC c )<153.5℃。
3. The PVA film of claim 2, wherein the PVA film exhibits a temperature differential between crystallization (Δ T) at any two locations after treatment with a 0.2 wt% aqueous solution of boric acid c )<3.85℃。
4. A PVA film according to any one of claims 1 to 3 characterised by having a retardation with a standard deviation of <3 nm.
5. The PVA film of claim 4, wherein 0.12g of the PVA film has been treated with a 0.2 wt% aqueous solution of boric acid and the aqueous solution has a boron content of 16 to 19ppm after dissolution in water.
6. An optical film obtained from the PVA film according to any one of claims 1 to 7.
7. The optical film of claim 6, which is a polarizing film.
8. The optical film of claim 7, wherein the polarizing film has a polarization brightness > 99.8.
9. A method for producing a PVA film according to any one of claims 1 to 4, characterized by comprising:
(a) stirring a polyvinyl alcohol resin at a heating rate of 4-20 ℃/hour, keeping the temperature for 2-4 hours after the dissolution temperature is higher than 100 ℃, and reversing the stirring direction at least twice per hour to form a polyvinyl alcohol casting solution;
(b) casting the casting solution to a casting drum; and
(c) and drying to form the PVA film.
10. The method of claim 9, wherein the casting drum is rotated at a speed of 3 to 7 m/min.
11. The method of claim 10, wherein the drying of step (c) is by a hot roll or a float dryer.
12. The method of manufacturing of claim 11, wherein the maximum/minimum air flow received by the membrane in the float dryer along the width direction is ≦ 3.0.
13. The manufacturing method according to any one of claims 9 to 12, wherein the polyvinyl alcohol casting solution further includes a plasticizer, and the plasticizer is 3 to 30 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin.
14. The method according to claim 13, wherein the polyvinyl alcohol casting solution contains the polyvinyl alcohol resin in an amount of 10 to 60 wt%.
15. The method according to claim 14, wherein the polyvinyl alcohol resin has a degree of polymerization of 800 to 10000.
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| JP2004160846A (en) * | 2002-11-13 | 2004-06-10 | Nippon Synthetic Chem Ind Co Ltd:The | Method for manufacturing polyvinyl alcohol film and polarizing film using polyvinyl alcohol film |
| JP2006188655A (en) * | 2004-11-02 | 2006-07-20 | Nippon Synthetic Chem Ind Co Ltd:The | Polyvinyl alcohol film and method for producing the same |
| JP2016203623A (en) * | 2015-04-24 | 2016-12-08 | 日本合成化学工業株式会社 | Method for producing polyvinyl alcohol-based film, polyvinyl alcohol-based film, and polarizing film |
| JP2017102436A (en) * | 2015-11-19 | 2017-06-08 | 日本合成化学工業株式会社 | Polyvinyl alcohol-based film, polarizing film using the same, polarizing plate, and manufacturing method for polyvinyl alcohol-based film |
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| JP4755891B2 (en) * | 2004-12-28 | 2011-08-24 | 日本合成化学工業株式会社 | Polyvinyl alcohol film, and polarizing film and polarizing plate using the same |
| JP5036191B2 (en) * | 2005-03-16 | 2012-09-26 | 日本合成化学工業株式会社 | Polyvinyl alcohol film and method for producing the same |
| JP5030418B2 (en) * | 2005-12-02 | 2012-09-19 | 日本合成化学工業株式会社 | Optical polyvinyl alcohol film and polarizing film and polarizing plate using the same |
| CN104395793B (en) * | 2013-06-18 | 2017-05-10 | Lg化学株式会社 | Stretched laminate, preparation method for thin polarizer, thin polarizer prepared by using same and polarizing plate comprising same |
| JP2018135438A (en) * | 2017-02-21 | 2018-08-30 | 日東電工株式会社 | Adhesive composition, adhesive layer, and optical film with adhesive layer |
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| JP2004160846A (en) * | 2002-11-13 | 2004-06-10 | Nippon Synthetic Chem Ind Co Ltd:The | Method for manufacturing polyvinyl alcohol film and polarizing film using polyvinyl alcohol film |
| JP2006188655A (en) * | 2004-11-02 | 2006-07-20 | Nippon Synthetic Chem Ind Co Ltd:The | Polyvinyl alcohol film and method for producing the same |
| JP2016203623A (en) * | 2015-04-24 | 2016-12-08 | 日本合成化学工業株式会社 | Method for producing polyvinyl alcohol-based film, polyvinyl alcohol-based film, and polarizing film |
| JP2017102436A (en) * | 2015-11-19 | 2017-06-08 | 日本合成化学工業株式会社 | Polyvinyl alcohol-based film, polarizing film using the same, polarizing plate, and manufacturing method for polyvinyl alcohol-based film |
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