CN115032732A - Method and apparatus for manufacturing polarizing film - Google Patents
Method and apparatus for manufacturing polarizing film Download PDFInfo
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- CN115032732A CN115032732A CN202210212228.1A CN202210212228A CN115032732A CN 115032732 A CN115032732 A CN 115032732A CN 202210212228 A CN202210212228 A CN 202210212228A CN 115032732 A CN115032732 A CN 115032732A
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- film
- bath
- treatment
- crosslinking
- ultrasonic
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 61
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 claims abstract description 60
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 54
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 54
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- 150000001639 boron compounds Chemical class 0.000 claims abstract description 21
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- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 3
- 238000005452 bending Methods 0.000 description 3
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- 229910052938 sodium sulfate Inorganic materials 0.000 description 3
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- 239000004593 Epoxy Substances 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
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- 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
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 2
- 235000019345 sodium thiosulphate Nutrition 0.000 description 2
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- DUNKXUFBGCUVQW-UHFFFAOYSA-J zirconium tetrachloride Chemical compound Cl[Zr](Cl)(Cl)Cl DUNKXUFBGCUVQW-UHFFFAOYSA-J 0.000 description 2
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
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- SMEGJBVQLJJKKX-HOTMZDKISA-N [(2R,3S,4S,5R,6R)-5-acetyloxy-3,4,6-trihydroxyoxan-2-yl]methyl acetate Chemical compound CC(=O)OC[C@@H]1[C@H]([C@@H]([C@H]([C@@H](O1)O)OC(=O)C)O)O SMEGJBVQLJJKKX-HOTMZDKISA-N 0.000 description 1
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- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 1
- 150000001241 acetals Chemical class 0.000 description 1
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- 229920003207 poly(ethylene-2,6-naphthalate) Polymers 0.000 description 1
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Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/0074—Production of other optical elements not provided for in B29D11/00009- B29D11/0073
- B29D11/00788—Producing optical films
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
- B01J19/10—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing sonic or ultrasonic vibrations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/20—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of a vibrating fluid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
- B29C61/02—Thermal shrinking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/0009—After-treatment of articles without altering their shape; Apparatus therefor using liquids, e.g. solvents, swelling agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/04—After-treatment of articles without altering their shape; Apparatus therefor by wave energy or particle radiation, e.g. for curing or vulcanising preformed articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00634—Production of filters
- B29D11/00644—Production of filters polarizing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00865—Applying coatings; tinting; colouring
- B29D11/00894—Applying coatings; tinting; colouring colouring or tinting
-
- 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
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
Abstract
The purpose of the present invention is to provide a method and an apparatus for producing a polarizing film, wherein shrinkage due to temperature change is not easily generated despite an increase in the degree of crosslinking. The method for producing a polarizing film from a polyvinyl alcohol resin film comprises an ultrasonic treatment step of immersing the polyvinyl alcohol resin film in an ultrasonic treatment bath in which ultrasonic waves are propagating, the ultrasonic treatment bath containing potassium iodide and a boron compound.
Description
Technical Field
The present invention relates to a method and an apparatus for producing a polarizing film from a polyvinyl alcohol resin film.
Background
Polarizing plates are widely used as polarizing elements in image display devices such as liquid crystal display devices. The polarizing plate is generally a polarizing plate having a structure in which a transparent resin film (e.g., a protective film) is bonded to one or both surfaces of a polarizing film using an adhesive or the like.
The polarizing film is generally produced by subjecting a raw material film containing a polyvinyl alcohol resin to dyeing treatment of immersing in a dyeing bath containing a dichroic dye such as iodine, and then to crosslinking treatment of immersing in a crosslinking bath containing a crosslinking agent such as boric acid, and uniaxially stretching the film at an arbitrary stage. The uniaxial stretching includes dry stretching in which stretching is performed in the air, and wet stretching in which stretching is performed in a liquid such as the above-mentioned dyeing bath or crosslinking bath.
The polarizing film can obtain high optical characteristics by increasing the degree of crosslinking. Although the degree of crosslinking can be increased by increasing the concentration of the crosslinking agent in the crosslinking bath, there is a problem that shrinkage is liable to occur due to a change in temperature.
Jp 59-094706 a (patent document 1) describes that a polarizing film having a small shrinkage ratio and good flatness can be obtained by performing an immobilization treatment by irradiating with far infrared rays having a wavelength of 1 μm or more.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 59-094706
Disclosure of Invention
Problems to be solved by the invention
The purpose of the present invention is to provide a method and an apparatus for producing a polarizing film, wherein shrinkage due to temperature change is not easily generated despite an increase in the degree of crosslinking.
Means for solving the problems
The present invention provides a method and an apparatus for producing a polarizing film described below.
[ 1 ] A method for producing a polarizing film from a polyvinyl alcohol resin film,
the production method comprises an ultrasonic treatment step of immersing the polyvinyl alcohol resin film in an ultrasonic treatment bath in which ultrasonic waves are propagated,
the ultrasonic treatment bath comprises potassium iodide and a boron compound.
The production method according to [ 1 ], wherein the temperature of the ultrasonic treatment bath in the ultrasonic treatment step is 40 ℃ to 50 ℃.
The method for producing a polarizing film according to [ 1 ] or [ 2 ], wherein in the ultrasonic treatment step, the polyvinyl alcohol resin film is conveyed in the ultrasonic treatment bath, and an angle formed between a conveying direction of the polyvinyl alcohol resin film and a propagation direction of the ultrasonic wave in the ultrasonic treatment bath is 0 ° or more and 90 ° or less.
The method for producing a polarizing film according to any one of [ 1 ] to [ 3 ], further comprising a dyeing step of dyeing the polyvinyl alcohol resin film with a dichroic dye,
the ultrasonic treatment step is performed after the dyeing step.
Effects of the invention
According to the present invention, it is possible to provide a method and an apparatus for producing a polarizing film, in which shrinkage due to temperature change is not easily generated although the degree of crosslinking is increased.
Drawings
Fig. 1 is a cross-sectional view schematically showing an example of the polarizing film manufacturing method and the polarizing film manufacturing apparatus used in the polarizing film manufacturing method of the present invention.
Fig. 2 is a cross-sectional view schematically showing another embodiment of the ultrasonic treatment bath.
Fig. 3 is a cross-sectional view schematically showing another mode of the ultrasonic treatment bath.
Description of the reference numerals
10 comprises a raw material film of a polyvinyl alcohol resin, 11 raw material reels, 13 a swelling bath, 15 dyeing baths, 17a crosslinking baths, 17b complementary color baths, 19 cleaning baths, 21 drying furnaces, 23 polarizing films, 30-48, 60, 61 guide rollers, 50-52, 53a, 53b, 54, 55 nip rollers, 71 ultrasonic vibrators.
Detailed Description
< method for producing polarizing film >
In the present invention, the polarizing film is a film obtained by adsorbing a dichroic dye (iodine or dichroic dye) to a uniaxially stretched polyvinyl alcohol resin film and orienting the dichroic dye. The polyvinyl alcohol resin forming the polyvinyl alcohol resin film is generally obtained by saponifying a polyvinyl acetate resin. The saponification degree thereof is usually 85 mol% or more, preferably 90 mol% or more, and more preferably 99 mol% or more. The polyvinyl acetate resin may be, for example, polyvinyl acetate which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other copolymerizable monomer include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.
These polyvinyl alcohol resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like modified with aldehydes may be used.
In the present invention, as a starting material for producing a polarizing film, an unstretched polyvinyl alcohol resin film (raw material film) having a thickness of 65 μm or less (for example, 60 μm or less), preferably 50 μm or less, more preferably 35 μm or less, and still more preferably 30 μm or less is used. Thin polarizing films with increasing market demands can thus be obtained. The width of the raw material film is not particularly limited, and may be, for example, 300 to 6000 mm. The raw material film is prepared, for example, in the form of a roll (raw material roll) of a long unstretched polyvinyl alcohol resin film.
The polarizing film can be continuously produced as a long polarizing film by continuously conveying the long raw material film along the film conveying path of the polarizing film production apparatus while being unwound from the raw material roll, performing a predetermined treatment step of immersing the long raw material film in a treatment liquid (hereinafter, also referred to as a "treatment bath") contained in a treatment tank and then drawing the long raw material film, and then performing a drying step. In the treatment step, as long as the treatment is performed by bringing the treatment liquid into contact with the film, the method is not limited to the method of immersing the film in the treatment bath, and the film may be treated by allowing the treatment liquid to adhere to the surface of the film by spraying, flowing down, dropping, or the like. When the treatment step is performed by immersing the film in the treatment bath, the treatment bath for performing one treatment step is not limited to one, and the film may be sequentially immersed in two or more treatment baths to complete one treatment step.
Examples of the treatment liquid include a swelling liquid, a dyeing liquid, a crosslinking liquid, a color correction liquid, and a cleaning liquid. The treatment steps include a swelling step of swelling the raw material film by bringing a swelling solution into contact with the raw material film, a dyeing step of dyeing the film after the swelling treatment by bringing a dyeing solution into contact with the film after the dyeing treatment, a crosslinking step of crosslinking the film after the crosslinking treatment by bringing a crosslinking solution into contact with the film after the crosslinking treatment, a color compensation step of compensating the color by bringing a color compensation solution into contact with the film after the crosslinking treatment, and a cleaning step of cleaning the film after the color compensation treatment by bringing a cleaning solution into contact with the film. During the series of the treatment steps (i.e., before and after any 1 or more treatment steps and/or during any 1 or more treatment steps), the uniaxial stretching treatment is performed in a wet or dry manner. Other treatment steps may be added as necessary.
In the method for producing a polarizing film of the present invention, an ultrasonic treatment step of immersing the film in an ultrasonic treatment bath in which ultrasonic waves are propagated is performed. An ultrasonic treatment step is performed in an ultrasonic treatment bath containing potassium iodide and a boron compound. By performing the ultrasonic treatment step, the degree of crosslinking can be increased while suppressing shrinkage of the obtained polarizing film due to temperature change. By increasing the degree of crosslinking, a polarizing film having excellent optical characteristics can be obtained. As a polarizing film having excellent optical characteristics, for example, a polarizing film having high single-body transmittance, high polarization degree, and small absolute value of cross-tone b value can be obtained.
According to the method for producing a polarizing film of the present invention, for example, a polarizing film having a shrinkage force of 2.82N/2mm or less and a degree of crosslinking of 5.52 or more, a polarizing film having a shrinkage force of 2.5N/2mm or less and a degree of crosslinking of 6.5 or more, and a polarizing film having a shrinkage force of 2.04N/2mm or less and a degree of crosslinking of 6.65 or more can be obtained. The shrinkage force and the degree of crosslinking described herein are based on values measured by the measurement methods described in examples.
The reason why the degree of crosslinking can be improved while suppressing shrinkage due to a temperature change of the obtained polarizing film by performing the ultrasonic treatment step is presumably because cavitation occurs in the ultrasonic treatment bath by the generation of ultrasonic waves (japanese: キャビテーション), whereby minute vibrations are generated in the ultrasonic treatment bath and the film, and the permeation force of a chemical liquid such as a dyeing solution into the film is improved, and the dyeing property and the degree of crosslinking are improved. The ultrasonic treatment bath is not limited as long as it contains potassium iodide and a boron compound, and may be a crosslinking bath containing a crosslinking liquid when the crosslinking liquid contains potassium iodide and a boron compound, or a color correction bath containing a color correction liquid when the color correction liquid contains potassium iodide and a boron compound. In this case, the ultrasonic treatment step is performed in the crosslinking step, or the ultrasonic treatment step is performed in the complementary color step. The ultrasonic treatment step is not limited to 1 time, and may be performed in a plurality of baths in a plurality of times. Examples of the boron compound contained in the ultrasonic treatment bath include boric acid and borax.
An example of the method for producing a polarizing film of the present invention will be described in detail below with reference to fig. 1. Fig. 1 is a cross-sectional view schematically showing an example of the polarizing film manufacturing method and the polarizing film manufacturing apparatus used in the polarizing film manufacturing method of the present invention. The polarizing film production apparatus shown in fig. 1 is configured such that a raw material (unstretched) film 10 containing a polyvinyl alcohol resin is continuously unwound from a raw material roll 11, conveyed along a film conveying path, passed through a swelling bath (swelling solution contained in a swelling tank) 13, a dyeing bath (dyeing solution contained in a dyeing tank) 15, a crosslinking bath (crosslinking solution contained in a crosslinking tank) 17a, a color correction bath (color correction solution contained in a color correction tank) 17b, and a cleaning bath (cleaning solution contained in a cleaning tank) 19 provided in the film conveying path in this order, and finally passed through a drying furnace 21. The obtained polarizing film 23 can be directly transported to the following polarizing plate production step (step of laminating a protective film on one or both surfaces of the polarizing film 23), for example. The arrows in fig. 1 indicate the direction of conveyance of the film.
In the description of fig. 1, "treatment bath" is a generic term including a swelling bath, a dyeing bath, a crosslinking bath, a color replenishment bath, and a cleaning bath, "treatment solution" is a generic term including a swelling solution, a dyeing solution, a crosslinking solution, a color replenishment solution, and a cleaning solution, "treatment bath" is a generic term including a swelling bath, a dyeing bath, a crosslinking bath, a color replenishment bath, and a cleaning bath. The swelling bath, dyeing bath, crosslinking bath, color-complementing bath, and washing bath each form the swelling section, dyeing section, crosslinking section, color-complementing section, and washing section of the production apparatus of the present invention.
The film transport path of the polarizing film manufacturing apparatus can be constructed by disposing the treatment bath at an appropriate position, and disposing guide rollers 30 to 48, 60, 61 and nip rollers 50 to 55 at appropriate positions, wherein the guide rollers 30 to 48, 60, 61 can support the transported film, or can change the film transport direction, and the nip rollers 50 to 55 can press and nip the transported film, and can apply a driving force due to the rotation of the film, or can change the film transport direction. The guide roll and the nip roll may be disposed before and after each treatment bath and in the treatment bath, whereby the film can be introduced into, immersed in, and pulled out of the treatment bath (see fig. 1). For example, by providing 1 or more guide rolls in each treatment bath and conveying the film along these guide rolls, the film can be immersed in each treatment bath.
In the polarizing film manufacturing apparatus shown in fig. 1, since the nip rollers (nip rollers 50 to 54) are arranged before and after each treatment bath, it is possible to perform the inter-roller stretching in which the longitudinal uniaxial stretching is performed by providing a circumferential speed difference between the nip rollers arranged before and after any 1 or more treatment baths.
In the polarizing film manufacturing apparatus shown in fig. 1, an ultrasonic vibrator is disposed in the complementary color bath 17b, that is, the complementary color bath 17b also serves as an ultrasonic treatment bath, and the ultrasonic treatment step is performed in the complementary color bath 17b together with the complementary color treatment. Hereinafter, each step will be explained.
(swelling step)
The swelling step is performed for the purpose of removing foreign matter on the surface of the raw material film 10, removing a plasticizer in the raw material film 10, imparting dyeability, plasticizing the raw material film 10, and the like. The processing conditions are determined within a range that can achieve the object and does not cause problems such as extreme dissolution and devitrification of the raw material film 10.
Referring to fig. 1, the raw material film 10 is continuously unwound from the raw material roll 11, conveyed along the film conveying path, immersed in the swelling bath 13 for a predetermined time, and then pulled out, thereby performing the swelling step. In the example of fig. 1, the base film 10 is conveyed along the film conveying path formed by the guide rollers 60 and 61 and the nip roller 50 until the base film 10 is immersed in the swelling bath 13 after being wound off. In the swelling treatment, the film is conveyed along a film conveying path formed by the guide rollers 30 to 32 and the nip roller 51.
As the swelling liquid in the swelling bath 13, pure water may be used, and an aqueous solution containing boric acid (JP-A-10-153709), chloride (JP-A-06-281816), an inorganic acid, an inorganic salt, a water-soluble organic solvent, an alcohol, etc. in an amount of about 0.01 to 10 wt% may be used.
The temperature of the swelling bath 13 is, for example, 10 to 50 ℃, preferably 10 to 40 ℃, and more preferably 15 to 30 ℃. The dipping time of the raw material film 10 is preferably 10 to 300 seconds, and more preferably 20 to 200 seconds. When the raw material film 10 is a polyvinyl alcohol resin film stretched in advance in a gas, the temperature of the swelling bath 13 is, for example, 20 to 70 ℃, preferably 30 to 60 ℃. The dipping time of the raw material film 10 is preferably 30 to 300 seconds, and more preferably 60 to 240 seconds.
In the swelling treatment, there is a problem that wrinkles are easily formed in the film due to the raw material film 10 swelling in the width direction. As 1 method for conveying the film while removing the wrinkles, there may be mentioned using a roll having a spreading function such as a spreader roll, a knurl roll, a crown roll, or a guide roll 30, 31, and/or 32, or using another spreading device such as a cloth guide, a bender roll, or a tenter clip. Another method for suppressing the generation of wrinkles is to perform a stretching treatment. For example, the uniaxial stretching treatment may be performed in the swelling bath 13 by utilizing the difference in peripheral speed between the nip roller 50 and the nip roller 51.
In the swelling treatment, since the film swells and expands in the film transport direction, when the film is not actively stretched, it is preferable to adopt a method of controlling the speed of the nip rollers 50 and 51 arranged before and after the swelling bath 13, for example, in order to eliminate the slack of the film in the transport direction. For the purpose of stabilizing the transport of the film in the swelling bath 13, it is also useful to Control the water flow in the swelling bath 13 with an underwater shower, or to use an EPC device (Edge Position Control device: a device for detecting the end of the film and preventing the meandering of the film) in combination, or the like.
In the example shown in fig. 1, the film drawn out from the swelling bath 13 is introduced into the dyeing bath 15 after passing through the guide roll 32, the nip roll 51, and the guide roll 33 in this order.
(dyeing step)
The dyeing step is performed for the purpose of adsorbing the dichroic dye to the polyvinyl alcohol resin film after the swelling treatment, and aligning the dichroic dye. The treatment conditions are determined within a range that can achieve the object and does not cause extreme problems such as dissolution and devitrification of the film. Referring to fig. 1, the swollen film is carried along a film carrying path constituted by a nip roller 51, guide rollers 33 to 36, and a nip roller 52, immersed in a dyeing bath 15 (a treatment liquid contained in a dyeing bath) for a predetermined time, and then drawn out, whereby a dyeing step can be performed. In order to improve the dyeability of the dichroic dye, the film to be subjected to the dyeing step is preferably a film subjected to at least some uniaxial stretching treatment, or is preferably subjected to a uniaxial stretching treatment at the time of dyeing instead of the uniaxial stretching treatment before dyeing, or is further subjected to a uniaxial stretching treatment at the time of dyeing in addition to the uniaxial stretching treatment before dyeing.
When iodine is used as the dichroic dye, an aqueous solution having a concentration of iodine/potassium iodide/water of 0.003 to 0.3/0.1 to 10/100 in terms of a mass ratio can be used as the dyeing liquid in the dyeing bath 15. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, and the like may be coexistent. When boric acid is added, the aqueous solution may be regarded as the dyeing bath 15 as long as it contains 0.003 parts by mass or more of iodine per 100 parts by mass of water, unlike the crosslinking treatment described later. The temperature of the dyeing bath 15 during film dipping is usually 10 to 45 ℃, preferably 10 to 40 ℃, more preferably 20 to 35 ℃, and the film dipping time is usually 30 to 600 seconds, preferably 60 to 300 seconds.
When a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a concentration of dichroic dye/water of 0.001 to 0.1/100 by mass ratio can be used as the dyeing liquid in the dyeing bath 15. In the dyeing bath 15, a dyeing assistant and the like may coexist, and for example, inorganic salts such as sodium sulfate and the like, a surfactant and the like may be contained. Only 1 kind of dichroic dye may be used alone, or 2 or more kinds of dichroic dyes may be used in combination. The temperature of the dyeing bath 15 for dipping the film is, for example, 20 to 80 ℃, preferably 30 to 70 ℃, and the dipping time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds.
As described above, in the dyeing step, the uniaxial stretching of the film may be performed in the dyeing bath 15. The uniaxial stretching of the film may be performed by a method such as providing a circumferential speed difference between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 15.
In the dyeing treatment, in order to convey the polyvinyl alcohol-based resin film while removing wrinkles of the film similarly to the swelling treatment, rolls having a spreading function such as spreader rolls, knurl rolls, or crowned rolls may be used as the guide rolls 33, 34, 35, and/or 36, or other spreading devices such as cloth guides, bending rolls, or tenter clips may be used. Another method for suppressing the generation of wrinkles is to perform stretching treatment, as in the swelling treatment.
In the example shown in fig. 1, the film drawn out of the dyeing bath 15 is introduced into the crosslinking bath 17a after passing through the guide roll 36, the nip roll 52, and the guide roll 37 in this order.
(crosslinking step)
The crosslinking step is intended to prevent water resistance by crosslinking. Referring to fig. 1, the dyed film is carried along a film carrying path constituted by a nip roller 52, guide rollers 37 to 40, and a nip roller 53a, immersed in a crosslinking bath 17a (crosslinking liquid contained in a crosslinking tank) for a predetermined time, and then pulled out, thereby performing a crosslinking step.
As the crosslinking liquid, a solution in which a crosslinking agent is dissolved in a solvent can be used. Examples of the crosslinking agent include boron compounds, glyoxal, and glutaraldehyde. Examples of the boron compound include boric acid and borax. These may be used alone or in combination of two or more. As the solvent, for example, water may be used, but an organic solvent having compatibility with water may be further contained. As the crosslinking liquid, for example, an aqueous solution containing 1 to 10 parts by mass of a boron compound such as boric acid, preferably 1.5 to 3 parts by mass of a boron compound such as boric acid, with respect to 100 parts by mass of water, can be used. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking liquid preferably contains boric acid and an iodide, and the amount of the iodide may be, for example, 1 to 30 parts by mass relative to 100 parts by mass of water. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, and the like may be coexistent.
In the crosslinking treatment, the concentrations of boric acid and iodide in the crosslinking liquid and the temperature of the crosslinking bath 17a may be appropriately selected. The crosslinking liquid can be, for example, an aqueous solution of boric acid/potassium iodide/water in a mass ratio of 1 to 10/1 to 30/100. The temperature of the cross-linking bath 17a for dipping the film is usually 50 to 70 ℃, preferably 53 to 65 ℃, and the dipping time of the film is usually 10 to 600 seconds, preferably 20 to 300 seconds, and more preferably 20 to 200 seconds. When the polyvinyl alcohol resin film stretched in advance before the swelling treatment is subjected to the dyeing treatment and the crosslinking treatment in this order, the temperature of the crosslinking bath 17a is usually about 50 to 85 ℃, and preferably 55 to 80 ℃.
(color complementing Process)
The complementary color process is one of the purposes of color tone adjustment. Referring to fig. 1, the film after the crosslinking step is carried along a film carrying path constituted by a nip roll 53a, guide rolls 41 to 44, and a nip roll 53b, immersed in a complementary color bath 17b (complementary color liquid contained in a complementary color tank) for a predetermined time, and then drawn out, whereby the complementary color step can be performed.
As the color replenishment liquid, a solution in which a crosslinking agent is dissolved in a solvent can be used in the same manner as the crosslinking liquid. Examples of the crosslinking agent include boron compounds, glyoxal, and glutaraldehyde. Examples of the boron compound include boric acid and borax. These may be used alone or in combination of two or more. As the solvent, for example, water may be used, but an organic solvent having compatibility with water may be further contained. As the color correction liquid, for example, an aqueous solution containing 1 to 10 parts by mass of a boron compound such as boric acid, preferably 1.5 to 3 parts by mass of a boron compound such as boric acid, per 100 parts by mass of water can be used. When the dichroic dye used in the dyeing treatment is iodine, the color replenishment liquid preferably contains boric acid and an iodide, and the amount of the iodide may be set to, for example, 1 to 30 parts by mass with respect to 100 parts by mass of water. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, and the like may be coexistent.
In the color correction treatment, the concentrations of boric acid and iodide in the color correction liquid and the temperature of the color correction bath 17b can be appropriately selected. The color-compensating liquid can be, for example, an aqueous solution of boric acid/potassium iodide/water in a mass ratio of 1 to 5/3 to 30/100. The temperature of the complementary color bath 17b for dipping the film is usually 10 to 55 ℃, preferably 40 to 50 ℃, and the dipping time of the film is usually 1 to 300 seconds, preferably 2 to 100 seconds.
The crosslinking treatment and the complementary color treatment may be performed a plurality of times, and are usually performed 2 to 5 times. In this case, the compositions and temperatures of the respective crosslinking baths and the respective complementary color baths used may be the same or different.
The uniaxial stretching treatment may be performed in the crosslinking bath 17a by utilizing the difference in the peripheral speed between the nip roller 52 and the nip roller 53 a. In addition, the uniaxial stretching treatment may be performed in the complementary color bath 17b by the difference in the peripheral speed between the nip roller 53a and the nip roller 53 b.
In the crosslinking treatment and the complementary color treatment, in order to remove wrinkles of the film and convey the polyvinyl alcohol-based resin film at the same time as the swelling treatment, rolls having a spreading function such as spreader rolls, burl rolls, or crown rolls may be used as the guide rolls 38, 39, 40, 41, 42, 43, and/or 44, or other spreading devices such as cloth guides, bending rolls, or tenter clips may be used. Another method for suppressing the generation of wrinkles is to perform stretching treatment, as in the swelling treatment.
In the example shown in fig. 1, the film drawn out from the complementary color bath 17b is introduced into the cleaning bath 19 after passing through the guide roller 44 and the nip roller 53b in this order.
(cleaning Process)
The example shown in fig. 1 includes a cleaning step after the crosslinking step. The washing treatment is performed for the purpose of removing excess chemical agents such as boric acid and iodine adhered to the polyvinyl alcohol resin film. For example, the cleaning step is performed by immersing the crosslinked polyvinyl alcohol resin film in the cleaning bath 19. Instead of the step of immersing the film in the cleaning bath 19, the cleaning step may be performed by spraying the cleaning liquid as a shower liquid to the film, or by using both immersion in the cleaning bath 19 and spraying of the cleaning liquid.
Fig. 1 shows an example of a case where the polyvinyl alcohol resin film is immersed in the cleaning bath 19 and subjected to the cleaning treatment. The temperature of the cleaning bath 19 in the cleaning treatment is usually 2 to 40 ℃, and the immersion time of the film is usually 2 to 120 seconds.
In the washing treatment, for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles, rolls having a spreading function such as spreader rolls, knurl rolls, or crowned rolls may be used as the guide rolls 45, 46, 47, and/or 48, or other spreading devices such as cloth guides, bending rolls, or tenter clips may be used. In the film cleaning process, a stretching process may be performed to suppress the occurrence of wrinkles.
(stretching Process)
As described above, the raw material film 10 is subjected to the uniaxial stretching treatment in a wet or dry manner during the series of treatment steps (i.e., before and after any 1 or more treatment steps and/or during any 1 or more treatment steps). Specific methods of the uniaxial stretching treatment include, for example, inter-roll stretching in which longitudinal uniaxial stretching is performed by providing a circumferential speed difference between 2 nip rolls (for example, 2 nip rolls disposed before and after the treatment bath) in the film-forming conveyance path, hot-roll stretching as described in japanese patent No. 2731813, tenter stretching, and the like, and preferable is inter-roll stretching. The uniaxial stretching step may be performed a plurality of times from the starting film 10 to the polarizing film 23. As described above, the stretching treatment is also advantageous in suppressing the generation of wrinkles in the film.
The final cumulative stretching ratio of the polarizing film 23 based on the raw film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching step may be performed in any treatment step, and in the case where the stretching treatment is performed in 2 or more treatment steps, the stretching treatment may be performed in any treatment step.
(ultrasonic treatment Process)
In the apparatus shown in fig. 1, an ultrasonic treatment step is performed in the complementary color bath 17 b. That is, the complementary color bath 17b also serves as an ultrasonic treatment bath. In the apparatus shown in fig. 1, an ultrasonic transducer 71 is disposed in the complementary color bath (ultrasonic treatment bath) 17b, ultrasonic waves emitted from the ultrasonic transducer 71 are propagated in the complementary color bath 17b, and the ultrasonic transducer 71 irradiates the film immersed in the complementary color bath 17b with ultrasonic waves. In the apparatus shown in fig. 1, an ultrasonic vibrator 71 is disposed on the side surface on the inlet side of the complementary color bath 17b, and the angle formed by the film transport direction (parallel to the bottom surface of the complementary color bath 17 b) and the vibration plane of the ultrasonic vibrator 71 is 90 °, that is, the angle formed by the film transport direction and the propagation direction of the ultrasonic wave emitted from the ultrasonic vibrator 71 is 0 °. The ultrasonic vibrator 71 is connected to an ultrasonic generator, not shown, and is configured to be capable of irradiating ultrasonic waves with output power from the ultrasonic generator.
The ultrasonic treatment step is not limited to a method in which the ultrasonic treatment step is performed in a bath containing potassium iodide and a boron compound as shown in fig. 1 together with the color correction step in the color correction bath 17b, and when the crosslinking liquid contains potassium iodide and a boron compound, the ultrasonic treatment step may be performed in a crosslinking bath 17a containing the crosslinking liquid together with the crosslinking step, or may be performed separately from the color correction step and the crosslinking step.
The frequency of the ultrasonic wave irradiated from the ultrasonic vibrator 71 is not particularly limited, and may be, for example, in the range of 10kHz to 300kHz, and preferably in the range of 20kHz to 300 kHz. The output of the ultrasonic generator connected to the ultrasonic vibrator 71 is not particularly limited, and may be, for example, in the range of 0.6kW to 10 kW. The output power of the ultrasonic generator can be appropriately selected depending on the size of the ultrasonic treatment bath, and the like.
The angle formed by the film transport direction and the propagation direction of the ultrasonic wave emitted from the ultrasonic vibrator (parallel to the bottom surface of the complementary color bath 17 b) is not limited to 0 ° as shown in fig. 1, and is preferably 0 ° or more and 90 ° or less. The angle formed by the film transport direction and the vibration plane of the ultrasonic vibrator is not limited to 90 ° as shown in fig. 1, and is preferably 0 ° or more and 90 ° or less.
The position of the ultrasonic transducer in the ultrasonic treatment bath is not limited to the inlet-side surface as shown in fig. 1, and may be a bottom surface or an outlet-side surface. Fig. 2 is a view schematically showing a state in which the ultrasonic transducer 71 in the ultrasonic treatment bath is disposed on the bottom surface. Fig. 3 is a diagram schematically showing a case where the ultrasonic transducer 71 in the ultrasonic treatment bath is disposed on the outlet-side surface. From the viewpoint that the membrane can efficiently receive ultrasonic waves and the area of the membrane receiving ultrasonic waves can be increased, it is preferable to dispose the ultrasonic vibrator on the side surface or the bottom surface on the inlet side in the ultrasonic treatment bath.
The ultrasonic treatment step is not limited to 1 time, and may be performed in a plurality of baths in a plurality of times. Examples of the boron compound contained in the ultrasonic treatment bath include boric acid and borax. The ultrasonic treatment bath may be an aqueous solution containing, for example, 1 to 10 parts by mass of a boron compound per 100 parts by mass of water, and preferably 1.5 to 3 parts by mass of a boron compound.
The concentration and temperature of the ultrasonic treatment bath can be appropriately selected. The ultrasonic treatment bath can be, for example, an aqueous solution of boric acid/potassium iodide/water in a mass ratio of 1 to 5/3 to 30/100. The temperature of the ultrasonic treatment bath in the ultrasonic treatment step is usually 10 to 55 ℃, preferably 40 to 50 ℃, and the immersion time of the film in the ultrasonic treatment bath is usually 1 to 300 seconds, preferably 2 to 100 seconds.
(drying Process)
After the washing step, it is preferable to perform a treatment of drying the polyvinyl alcohol resin film. The drying of the film is not particularly limited, and may be performed using a drying furnace 21 as in the example shown in fig. 1. The drying furnace 21 may be a drying furnace provided with a hot air dryer, for example. The drying temperature is, for example, 30 to 100 ℃ and the drying time is, for example, 30 to 600 seconds. The treatment of drying the polyvinyl alcohol resin film may be performed by using a far infrared heater. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 μm.
The obtained polarizing film may be wound around a winding roll in sequence to be in a roll form, or may be directly supplied to a polarizing plate production step (a step of laminating a protective film or the like on one surface or both surfaces of the polarizing film) without being wound.
(other treatment Process for polyvinyl alcohol resin film)
Processing other than the above-described processing may be added. Examples of the treatment that can be added include an immersion treatment in an aqueous iodide solution containing no boric acid, and an immersion treatment (zinc treatment) in an aqueous solution containing no boric acid and zinc chloride or the like.
< polarizing film >
By producing the polarizing film by the above-described method, a polarizing film having reduced shrinkage due to temperature change and simultaneously satisfying the optical characteristics i) to iii) below can be obtained.
i) A visibility-correcting monomer transmittance (Ty) of 42.0% or more,
ii) a visibility-modifying polarization degree (Py) of 99.980% or more,
iii) the absolute value of the b value of the cross-tone is 0.6 or less.
The visibility-correcting monomer transmittance (Ty), the visibility-correcting polarization degree (Py), and the b value of the cross-tone were measured as described in the example below.
The obtained polarizing film may be wound around a winding roll in sequence to be in a roll form, or may be directly supplied to a polarizing plate production step (a step of laminating a protective film or the like on one surface or both surfaces of the polarizing film) without being wound.
< polarizing plate >
A protective film is bonded to at least one surface of the polarizing film produced as described above via an adhesive, whereby a polarizing plate can be obtained. Examples of the protective film include films containing an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose; films comprising polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; polycarbonate resin films and cycloolefin resin films; an acrylic resin film; a film comprising a linear olefin resin such as a polypropylene resin.
In order to improve the adhesiveness between the polarizing film and the protective film, the surface of the polarizing film and/or the protective film to be laminated may be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, or the like. Examples of the adhesive used for bonding the polarizing film and the protective film include an active energy ray-curable adhesive such as an ultraviolet-curable adhesive, an aqueous solution of a polyvinyl alcohol resin, an aqueous solution containing a crosslinking agent, and an aqueous adhesive such as a urethane emulsion adhesive. The ultraviolet-curable adhesive may be a mixture of an acrylic compound and a photo radical polymerization initiator, a mixture of an epoxy compound and a photo cation polymerization initiator, or the like. Further, a cationically polymerizable epoxy compound and a radically polymerizable acrylic compound may be used in combination as an initiator, and a photocationic polymerization initiator and a photoradical polymerization initiator may be used in combination as an initiator.
Examples
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
< example 1 >
The polarizing film of example 1 was produced from a polyvinyl alcohol-based resin film using the production apparatus shown in fig. 1 (the arrangement position of the ultrasonic transducer in the complementary color bath was set to the bottom surface as shown in fig. 2, and the arrangement position was different from that in fig. 1 in that 2 crosslinking baths were provided). Specifically, a long polyvinyl alcohol (PVA) raw material film having a thickness of 45 μm (product name "VF-TS # 4500" manufactured by Kuraray, average polymerization degree 2400, and saponification degree 99.9 mol% or more) was continuously conveyed while being wound up from a roll, and immersed in a swelling bath 13 containing pure water at 25 ℃ for a retention time of 1 minute 20 seconds (swelling step).
Thereafter, the film drawn out from the swelling bath 13 was immersed in a dyeing bath 15 containing 1.25mmML of iodine, 1.25 mass% of potassium iodide, and 0.3 mass% of boric acid at 30 ℃ for a retention time of 2 minutes and 30 seconds (dyeing step). In this case, the stretching was performed at a stretching ratio of 2.15 times and 1.56 times in the swelling step and the dyeing step, respectively, so that the cumulative stretching ratio was 3.5 times until the dyeing step was completed. Then, the film drawn out of the dyeing bath 15 was immersed in a first crosslinking bath 1 containing 8 mass% of potassium iodide and 4 mass% of boric acid at 59 ℃ for a residence time of 26 seconds, and stretched at a stretch ratio of 1.4 times while being crosslinked (first crosslinking step). Next, the sheet was immersed in a 2 nd crosslinking bath containing 8 mass% of potassium iodide and 4 mass% of boric acid at 59 ℃ for a residence time of 20 seconds, and stretched at a stretching ratio of 1.19 times while being crosslinked (2 nd crosslinking step).
Then, the resultant was immersed in a color correction bath 17b containing 8 mass% of potassium iodide and 4 mass% of boric acid at 43 ℃ for a retention time of 10 seconds, and stretched 1.00 times (color correction step). In the complementary color step, ultrasonic waves of 20kHz or more are generated from an ultrasonic vibrator 71 disposed on the bottom surface of the complementary color bath 17b (the angle formed by the conveying direction of the polyvinyl alcohol-based resin film and the propagation direction of the ultrasonic waves is 90 °) (ultrasonic treatment step). The stretching was performed so that the total stretching ratio based on the raw material film after the swelling step, dyeing step, 1 st crosslinking step, 2 nd crosslinking step, and color correction step was 5.7 times.
The film drawn out from the complementary color bath 17b was immersed in a cleaning bath 19 containing pure water at 13 ℃ for a retention time of 2 seconds (cleaning step). Thereafter, the film drawn out from the cleaning bath 19 was dried in a drying furnace 21 at a temperature of 100 ℃ for 110 seconds to obtain a polarizing film. The thickness of the obtained polarizing film was 18 μm.
An ultrasonic vibrator 71 using a multi-frequency ultrasonic device (manufactured by korea ultrasonic corporation, having a frequency of 164kHz and an output of 900W) was disposed in the complementary color bath 17 b.
< example 2 >
A polarizing film was produced in the same manner as in example 1, except that the position of the ultrasonic transducer 71 in the complementary color bath 17b was set to the inlet-side surface (the angle formed by the direction of conveyance of the polyvinyl alcohol resin film and the direction of propagation of the ultrasonic wave was 0 °) as shown in fig. 1.
< example 3 >
A polarizing film was produced in the same manner as in example 1, except that the position of the ultrasonic transducer 71 in the complementary color bath 17b was set to the outlet-side surface (the angle formed by the direction of conveyance of the polyvinyl alcohol-based resin film and the direction of propagation of the ultrasonic wave was 180 °) as shown in fig. 3.
< example 4 >
A polarizing film was produced in the same manner as in example 1, except that an ultrasonic vibrator was disposed on the side surface on the outlet side of the 1 st crosslinking bath in the 1 st crosslinking step, instead of the complementary color step, and the ultrasonic treatment step was performed.
< example 5 >
A polarizing film was produced in the same manner as in example 1, except that the ultrasonic treatment step was performed by disposing an ultrasonic vibrator on the side surface of the dyeing bath on the outlet side in the dyeing step, instead of the complementary color step.
< comparative example 1 >
A polarizing film was produced in the same manner as in example 1, except that the ultrasonic wave treatment step was not performed.
[ evaluation of polarizing film ]
(a) Measurement of monomer transmittance, degree of polarization and b-value of cross color tone
The polarizing films obtained in examples and comparative examples were cut out into measurement samples of 4cm × 4 cm. The MD transmittance and TD transmittance in the wavelength range of 380 to 780nm were measured using an integrating sphere spectrophotometer ("V7100" manufactured by JASCO corporation), and the monomer transmittance and degree of polarization at each wavelength were calculated based on the following formulas:
monomer transmittance (%) - (MD + TD)/2
Degree of polarization (%) { (MD-TD)/(MD + TD) } × 100
The "MD transmittance" is a transmittance when the direction of polarized light emitted from the glan thomson prism is parallel to the transmission axis of the polarizing film sample, and is expressed as "MD" in the above formula. The "TD transmittance" is a transmittance obtained when the direction of polarized light emitted from the glan thomson prism is perpendicular to the transmission axis of the polarizing film sample, and is represented by "TD" in the above formula. The transmittance and the degree of polarization of the resulting monomer were measured according to JIS Z8701: 1999 "color expression method-XYZ color system and X 10 Y 10 Z 10 The visibility was corrected in a 2-degree field of view (C light source) of the color system ", and the b value of the visibility correction individual transmittance (Ty), the visibility correction polarization degree (Py), and the cross-tone was obtained. Table 1 shows the calculation results of the visibility-correcting individual transmittance (Ty), the visibility-correcting polarization degree (Py), and the b value of the cross color tone.
(b) MD force of contraction
From the polarizing films obtained in the examples and comparative examples, measurement samples having a width of 2mm and a length of 30mm with the absorption axis direction (MD, stretching direction) as the long side were cut out. This sample was set in an analyzer (Dynamic mechanical analyzer) manufactured by TA, and held at 80 ℃ for 4 hours while keeping the size constant, and the contraction force (MD contraction force) in the longitudinal direction (absorption axis direction, MD) generated at this time was measured. Table 1 shows the measured values of the shrinkage force.
(c) Degree of crosslinking
The polarizing films obtained in examples and comparative examples were cut out into measurement samples of 10cm × 10cm from the central portion thereof. The degree of crosslinking was measured on this sample using a Nicolet5700(FT-IR) apparatus from Thermo fisher scientific.
VeeMAX III (ATR) from Pike technologies was used as FT-IR chip with a scan count of 16, 4cm -1 The resolution of (2) is performed. In addition, the measured IR data is added2850 to 3000cm- 1 The area (a) of the region is set as a reference peak area (a) (measured value: 3.2), and then 1200 to 1360cm- 1 Divided by the reference peak area (a).
The degree of crosslinking is (1200 to 1360cm- 1 Area of (2)/(reference peak area (a))
The average value was obtained after 3 times of the above-mentioned method for measuring the degree of crosslinking. The average value of the degree of crosslinking is shown in Table 1.
[ TABLE 1 ]
< example 6 >
A polarizing film was produced in the same manner as in example 1, except that the thickness of the polyvinyl alcohol (PVA) raw material film was changed to 60 μm (product name VF-PE #6000 manufactured by Kuraray), the arrangement position of the ultrasonic vibrator was set to the inlet side surface (the angle formed by the conveying direction of the polyvinyl alcohol-based resin film and the propagation direction of the ultrasonic wave was 0 °) as shown in fig. 1, and the frequency of use of the ultrasonic wave was set to 35 kHz. The thickness of the obtained polarizing film was 23 μm.
< example 7 >
A polarizing film was produced in the same manner as in example 1, except that the thickness of the polyvinyl alcohol (PVA) raw material film was changed to 60 μm (trade name VF-PE #6000 manufactured by Kuraray, ltd.), and the arrangement position of the ultrasonic vibrator was set to the inlet side surface as shown in fig. 1 (the angle formed by the conveying direction of the polyvinyl alcohol resin film and the propagation direction of the ultrasonic wave was 0 °). The thickness of the obtained polarizing film was 23 μm.
< example 8 >
A polarizing film was produced in the same manner as in example 1, except that the thickness of the polyvinyl alcohol (PVA) raw material film was changed to 20 μm (product name VF-TS #2000 manufactured by Kuraray, ltd.), the arrangement position of the ultrasonic vibrator was changed to the inlet side surface (the angle formed by the conveying direction of the polyvinyl alcohol resin film and the propagation direction of the ultrasonic wave was 0 °) as shown in fig. 1, and the frequency of use of the ultrasonic wave was changed to 35 kHz. The thickness of the obtained polarizing film was 8 μm.
< example 9 >
A polarizing film was produced in the same manner as in example 1, except that the thickness of the polyvinyl alcohol (PVA) raw material film was changed to 20 μm (product name VF-TS #2000 manufactured by Kuraray, ltd.) and the arrangement position of the ultrasonic vibrator was set to the inlet side surface as shown in fig. 1 (the angle formed between the conveying direction of the polyvinyl alcohol resin film and the propagation direction of the ultrasonic wave was 0 °). The thickness of the obtained polarizing film was 8 μm.
The polarizing films produced in examples 6 to 9 were evaluated in the same manner as described above, and the results thereof are shown in table 2.
[ TABLE 2 ]
Claims (4)
1. A method for producing a polarizing film from a polyvinyl alcohol resin film,
the production method comprises an ultrasonic treatment step of immersing the polyvinyl alcohol resin film in an ultrasonic treatment bath in which ultrasonic waves are propagated,
the ultrasonic treatment bath comprises potassium iodide and a boron compound.
2. The method for manufacturing a polarizing film according to claim 1,
in the ultrasonic treatment step, the temperature of the ultrasonic treatment bath is 40 ℃ or higher and 50 ℃ or lower.
3. The method for manufacturing a polarizing film according to claim 1 or 2,
in the ultrasonic treatment step, the polyvinyl alcohol resin film is conveyed in the ultrasonic treatment bath, and an angle formed between a conveying direction of the polyvinyl alcohol resin film in the ultrasonic treatment bath and a propagation direction of the ultrasonic wave is 0 ° or more and 90 ° or less.
4. The method for producing a polarizing film according to any one of claims 1 to 3,
further comprising a dyeing step of dyeing the polyvinyl alcohol resin film with a dichroic dye,
the ultrasonic treatment step is performed after the dyeing step.
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| JP2022017144A JP2022136978A (en) | 2021-03-08 | 2022-02-07 | Method of manufacturing polarizing film, and manufacturing device |
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| JPS5994706A (en) | 1982-11-22 | 1984-05-31 | Mitsui Toatsu Chem Inc | Manufacture of polarizing film |
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