WO2022158088A1 - Procédé de fabrication de plaque polarisante, procédé de fabrication de dispositif d'affichage d'image et procédé de réglage de la transmittance d'un film polarisant - Google Patents

Procédé de fabrication de plaque polarisante, procédé de fabrication de dispositif d'affichage d'image et procédé de réglage de la transmittance d'un film polarisant Download PDF

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Publication number
WO2022158088A1
WO2022158088A1 PCT/JP2021/041182 JP2021041182W WO2022158088A1 WO 2022158088 A1 WO2022158088 A1 WO 2022158088A1 JP 2021041182 W JP2021041182 W JP 2021041182W WO 2022158088 A1 WO2022158088 A1 WO 2022158088A1
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Prior art keywords
polarizing film
film
based resin
weight
pva
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PCT/JP2021/041182
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English (en)
Japanese (ja)
Inventor
周作 後藤
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日東電工株式会社
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Priority to KR1020237024445A priority Critical patent/KR20230129452A/ko
Priority to CN202180091355.4A priority patent/CN116802529A/zh
Publication of WO2022158088A1 publication Critical patent/WO2022158088A1/fr

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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/02—Details
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/8793—Arrangements for polarized light emission
    • 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

Definitions

  • the present invention relates to a method for manufacturing a polarizing plate, a method for manufacturing an image display device, and a method for adjusting the transmittance of a polarizing film.
  • liquid crystal display devices eg, organic EL display devices and inorganic EL display devices
  • EL electroluminescence
  • a liquid crystal display device has polarizing plates arranged on both sides of a liquid crystal cell due to its image forming method.
  • problems such as external light reflection and background reflection can be prevented by placing a circularly polarizing plate including a ⁇ /4 plate on the viewing side of the organic EL cell (for example, Patent Documents 1 and 2).
  • a polarizing plate usually has a structure in which a protective layer is arranged on at least one side of a polarizing film prepared by dyeing and stretching a polyvinyl alcohol-based resin film. It is attached to an image display cell such as an EL cell.
  • the protective layer is laminated after the protective layer is laminated or is attached to the image display cell. After that, it has been desired to develop a method for adjusting the transmittance of the polarizing film.
  • the present invention has been made to solve the conventional problems described above, and its main purpose is to provide a method for adjusting the transmittance of a polarizing film after it has been produced.
  • the primary polarizing film is dried until the moisture content becomes 15% by weight or less. and contacting the surface of the primary polarizing film with an aqueous solvent to change the transmittance to obtain a secondary polarizing film, in this order.
  • the aqueous solvent is brought into contact with the exposed surface of the primary polarizing film with one surface exposed and the other surface protected.
  • a polyvinyl alcohol-based resin film containing a halide and a polyvinyl alcohol-based resin is placed in the air in a state of a laminate with a long thermoplastic resin substrate. It includes subjecting the laminate to auxiliary stretching treatment, dyeing treatment, stretching treatment in an aqueous boric acid solution, and drying shrinkage treatment in this order. shrinking to 2% or more and drying until the water content of the polyvinyl alcohol resin film becomes 15% by weight or less.
  • the halide is iodide or sodium chloride.
  • the primary polarizing film has a thickness of 12 ⁇ m or less.
  • a polarizing film made of a polyvinyl alcohol resin film containing a dichroic substance and having a moisture content of 15% by weight or less, a protective layer, and an adhesive layer are included in this order.
  • a method for manufacturing an image display device comprising the step of bringing an aqueous solvent into contact with the substrate to change the transmittance, in this order.
  • the image display device is a liquid crystal display device or an organic EL display device.
  • the polarizing film comprises a step of bringing an aqueous solvent into contact with the surface of a polarizing film composed of a polyvinyl alcohol-based resin film containing a dichroic substance and having a moisture content of 15% by weight or less.
  • a method for adjusting the permeability of a membrane is provided.
  • the transmittance of the polarizing film can be changed ex post by bringing an aqueous solvent into contact with the surface of the polarizing film produced by dyeing and stretching the polyvinyl alcohol resin film.
  • the surface of the polarizing film whose appearance has been stabilized by drying until the moisture content becomes a predetermined value or less is brought into contact with an aqueous solvent to change the transmittance. Fine adjustment of the rate is possible.
  • variations in luminance between image display devices can be reduced, and when it is desired to match the appearance of multiple display screens, particularly when displaying images by combining multiple display screens (large public display). , digital signage, etc.).
  • FIG. 4 is a schematic diagram showing an example of drying shrinkage treatment using a heating roll. It is a schematic sectional drawing explaining an example of the polarizing plate which can be produced in the process of producing a polarizing plate. It is a schematic sectional drawing explaining an example of the polarizing plate which can be produced in the process of producing a polarizing plate. It is a schematic sectional drawing explaining an example of the polarizing plate which can be produced in the process of producing a polarizing plate.
  • FIG. 4A is a schematic cross-sectional view of an example of a polarizing plate that can be produced by a process of protecting the exposed surface of a secondary polarizing film; FIG. 4A is a schematic cross-sectional view of an example of a polarizing plate that can be produced by a process of protecting the exposed surface of a secondary polarizing film;
  • the polarizing plate obtained by the polarizing plate manufacturing method according to the embodiment of the present invention includes at least a polarizing film, and preferably includes a polarizing film and a protective layer disposed on one side or both sides thereof.
  • A. Method for producing polarizing plate In the method for producing a polarizing plate according to an embodiment of the present invention, a polyvinyl alcohol (PVA)-based resin film is dyed and stretched in an aqueous boric acid solution (stretched in boric acid solution), followed by A step of drying to a moisture content of 15% by weight or less to obtain a primary polarizing film, and contacting the surface of the primary polarizing film with an aqueous solvent to change the transmittance and form a secondary polarizing film. the step of obtaining in this order.
  • PVA polyvinyl alcohol
  • the surface of the polarizing film (primary polarizing film) once produced is decolorized by bringing an aqueous solvent into contact with the surface, thereby changing the transmittance afterward and adjusting it to a desired value.
  • the polarizing film (primary polarizing film) in a state of being highly oriented and having a stabilized appearance through stretching treatment in boric acid solution and drying treatment to contact with an aqueous solvent, the degree of polarization is excessively lowered and wrinkles are formed. It is possible to suitably adjust the transmittance while avoiding the generation, dissolution, etc. of
  • the transmittance may be changed by contacting only one surface of the primary polarizing film with an aqueous solvent, or by contacting both surfaces with an aqueous solvent to change the transmittance. You may let
  • the exposed surface of the primary polarizing film is brought into contact with an aqueous solvent to reduce the transmittance. change.
  • the method for producing the polarizing plate of the present embodiment for example, between the step of obtaining the primary polarizing film and the step of obtaining the secondary polarizing film, one surface of the primary polarizing film is exposed and the other surface is protected.
  • a step of making a layer-protected polarizer can be included.
  • Step of obtaining the primary polarizing film the PVA-based resin film is subjected to dyeing treatment and stretching treatment in boric acid solution, and then dried until the moisture content becomes 15% by weight or less.
  • the primary polarizing film may be produced using a single-layer PVA-based resin film, or may be produced using a laminate of two or more layers including a PVA-based resin layer (PVA-based resin film).
  • a primary polarizing film produced using a laminate of two or more layers avoids the occurrence of wrinkles and the like even after contact with an aqueous solvent, and exhibits excellent optical properties (typically, single transmittance and polarization degree) can be suitably maintained.
  • A-1-1 Production of a primary polarizing film using a laminate of two or more layers
  • the production of a primary polarizing film using a laminate of two or more layers is, for example, a PVA-based resin film containing a halide and a PVA-based resin that is formed into a long shape.
  • a laminate with a thermoplastic resin substrate it can be subjected to an auxiliary stretching treatment in air, a dyeing treatment, a stretching treatment in an aqueous boric acid solution, and a drying shrinkage treatment in this order.
  • a laminate of a thermoplastic resin substrate and a PVA-based resin film includes, for example, a PVA-based resin layer (PVA-based resin film) containing a halide and a PVA-based resin on one side of a long thermoplastic resin substrate. is obtained by forming a laminate.
  • the drying shrinkage treatment for example, the laminate of the long thermoplastic resin substrate and the PVA-based resin film is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction, and the PVA-based resin film. It includes drying until the moisture content of the system resin film becomes 15% by weight or less.
  • the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • the drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60°C to 120°C. According to such a manufacturing method, it is possible to obtain a primary polarizing film having a high degree of orientation of the PVA-based resin and excellent optical properties.
  • A-1-1-1 Production of Laminate Any appropriate method can be adopted as a method for producing a laminate of a thermoplastic resin substrate and a PVA-based resin layer.
  • a coating liquid containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin substrate and dried to form a PVA-based resin layer on the thermoplastic resin substrate.
  • the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • any appropriate method can be adopted as the method of applying the coating liquid. Examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.).
  • the coating/drying temperature of the coating liquid is preferably 50° C. or higher.
  • the thickness of the PVA-based resin layer is preferably 3 ⁇ m to 40 ⁇ m, more preferably 3 ⁇ m to 20 ⁇ m.
  • the thermoplastic resin substrate Before forming the PVA-based resin layer, the thermoplastic resin substrate may be surface-treated (for example, corona treatment, etc.), or an easy-adhesion layer may be formed on the thermoplastic resin substrate. By performing such treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved.
  • surface-treated for example, corona treatment, etc.
  • an easy-adhesion layer may be formed on the thermoplastic resin substrate.
  • the thickness of the thermoplastic resin substrate is preferably 20 ⁇ m to 300 ⁇ m, more preferably 50 ⁇ m to 200 ⁇ m. If the thickness is less than 20 ⁇ m, it may be difficult to form the PVA-based resin layer. If it exceeds 300 ⁇ m, for example, in the later-described underwater stretching treatment, it may take a long time for the thermoplastic resin substrate to absorb water, and an excessive load may be required for stretching.
  • the thermoplastic resin substrate preferably has a water absorption of 0.2% or more, more preferably 0.3% or more.
  • Thermoplastic resin substrates can absorb water and be plasticized with the water acting like a plasticizer. As a result, the stretching stress can be greatly reduced, and the film can be stretched at a high draw ratio.
  • the water absorption rate of the thermoplastic resin substrate is preferably 3.0% or less, more preferably 1.0% or less.
  • thermoplastic resin substrate can be adjusted, for example, by introducing a modifying group into the constituent material.
  • the water absorption is a value determined according to JIS K 7209.
  • the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120°C or less.
  • Tg The glass transition temperature of the thermoplastic resin substrate.
  • the temperature is preferably 100° C. or lower, more preferably 90° C. or lower.
  • the glass transition temperature of the thermoplastic resin substrate is preferably 60°C or higher.
  • the PVA-based resin layer can be satisfactorily stretched at a suitable temperature (for example, about 60°C).
  • the glass transition temperature of the thermoplastic resin substrate can be adjusted, for example, by heating using a crystallization material that introduces a modifying group into the constituent material.
  • the glass transition temperature (Tg) is a value determined according to JIS K 7121.
  • thermoplastic resin can be adopted as a constituent material of the thermoplastic resin base material.
  • thermoplastic resins include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. is mentioned. Among these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferred.
  • an amorphous (not crystallized) polyethylene terephthalate resin is preferably used.
  • amorphous (difficult to crystallize) polyethylene terephthalate resin is particularly preferably used.
  • Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acids, and copolymers further containing cyclohexanedimethanol or diethylene glycol as glycols.
  • the thermoplastic resin base material is composed of a polyethylene terephthalate resin having an isophthalic acid unit.
  • a thermoplastic resin substrate is extremely excellent in stretchability and can suppress crystallization during stretching. This is probably because the introduction of the isophthalic acid unit gives the main chain a large bend.
  • a polyethylene terephthalate-based resin has a terephthalic acid unit and an ethylene glycol unit.
  • the isophthalic acid unit content is preferably 0.1 mol % or more, more preferably 1.0 mol % or more, relative to the total of all repeating units. This is because a thermoplastic resin base material having extremely excellent stretchability can be obtained.
  • the isophthalic acid unit content is preferably 20 mol % or less, more preferably 10 mol % or less, relative to the total of all repeating units.
  • the degree of crystallinity can be favorably increased in the drying shrinkage treatment described later.
  • the thermoplastic resin substrate may be stretched in advance (before forming the PVA-based resin layer). In one embodiment, it is stretched in the transverse direction of the elongated thermoplastic resin substrate.
  • the lateral direction is preferably a direction perpendicular to the stretching direction of the laminate described below.
  • perpendicular also includes the case of being substantially perpendicular.
  • substantially orthogonal includes 90° ⁇ 5.0°, preferably 90° ⁇ 3.0°, more preferably 90° ⁇ 1.0°.
  • the stretching temperature of the thermoplastic resin substrate is preferably Tg-10°C to Tg+50°C with respect to the glass transition temperature (Tg).
  • the draw ratio of the thermoplastic resin substrate is preferably 1.5 to 3.0 times.
  • thermoplastic resin base material Any appropriate method can be adopted as a method for stretching the thermoplastic resin base material.
  • the drawing may be fixed end drawing or free end drawing.
  • the stretching method may be a dry method or a wet method.
  • the stretching of the thermoplastic resin substrate may be performed in one step or in multiple steps. When performing in multiple stages, the above-mentioned draw ratio is the product of the draw ratios in each step.
  • the coating liquid contains a halide and a PVA-based resin, as described above.
  • the coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent.
  • solvents include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferred.
  • the concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film in close contact with the thermoplastic resin substrate.
  • the content of the halide in the coating liquid is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
  • Additives may be added to the coating liquid.
  • additives include plasticizers and surfactants.
  • plasticizers include polyhydric alcohols such as ethylene glycol and glycerin.
  • Surfactants include, for example, nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the obtained PVA-based resin layer.
  • any appropriate resin can be adopted as the PVA-based resin.
  • Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers.
  • Polyvinyl alcohol is obtained by saponifying polyvinyl acetate.
  • An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer.
  • the degree of saponification of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. .
  • the degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.
  • the average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose.
  • the average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, more preferably 1,500 to 4,300.
  • the average degree of polymerization can be determined according to JIS K 6726-1994.
  • halide any appropriate halide can be adopted as the halide.
  • examples include iodide and sodium chloride.
  • Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.
  • the amount of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA resin, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA resin. Department. If the amount of the halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out and the finally obtained polarizing film may become cloudy.
  • the orientation of the polyvinyl alcohol molecules in the PVA-based resin layer increases. orientation may be disturbed and the orientation may be lowered.
  • the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin substrate.
  • the film is stretched, the tendency of the degree of orientation to decrease is remarkable.
  • the stretching of a single PVA film in boric acid water is generally carried out at 60° C.
  • the stretching of a laminate of A-PET (thermoplastic resin substrate) and a PVA-based resin layer is It is carried out at a high temperature of about 70° C., and in this case, the orientation of PVA at the initial stage of stretching may be lowered before it is increased by stretching in water.
  • the crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after auxiliary stretching can be promoted.
  • the PVA-based resin layer is immersed in a liquid, the disturbance of the orientation of the polyvinyl alcohol molecules and the deterioration of the orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide.
  • This can improve the optical properties of the polarizing film obtained through treatment steps such as dyeing treatment and underwater stretching treatment in which the laminate is immersed in a liquid.
  • A-1-1-2 Aerial Auxiliary Stretching
  • a two-stage stretching method combining dry stretching (auxiliary stretching) and stretching in boric acid solution is selected.
  • auxiliary stretching such as two-step stretching, it is possible to stretch while suppressing crystallization of the thermoplastic resin substrate, and excessive crystallization of the thermoplastic resin substrate in the subsequent stretching in boric acid water. It is possible to solve the problem that stretchability is reduced by stretching, and stretch the laminate at a higher magnification.
  • the stretching method of the in-air auxiliary stretching may be fixed edge stretching (e.g., a method of stretching using a tenter stretching machine) or free edge stretching (e.g., a method of uniaxially stretching the laminate through rolls having different peripheral speeds).
  • free-end drawing may be positively employed in order to obtain high optical properties.
  • the in-air stretching process includes a heating roll stretching step in which the laminate is stretched by a peripheral speed difference between heating rolls while being conveyed in the longitudinal direction.
  • the air drawing process typically includes a zone drawing process and a hot roll drawing process.
  • the order of the zone stretching process and the heating roll stretching process is not limited, and the zone stretching process may be carried out first, or the heating roll stretching process may be carried out first.
  • the zone drawing step may be omitted. In one embodiment, the zone drawing step and the heated roll drawing step are performed in this order.
  • the laminate is stretched by gripping the ends of the laminate and widening the distance between the tenters in the machine direction in a tenter stretching machine (the widening of the distance between the tenters is the stretching ratio). At this time, the distance between the tenters in the width direction (perpendicular to the machine direction) is set to be arbitrarily close.
  • the draw ratio in the machine direction can be set to be closer to the free end draw.
  • the shrinkage ratio in the width direction is calculated by (1/stretching ratio) 1/2 .
  • Aerial auxiliary stretching may be performed in one step or in multiple steps. When it is carried out in multiple stages, the draw ratio is the product of the draw ratios in each step.
  • the stretching direction in the in-air auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.
  • the draw ratio in the in-air auxiliary drawing is preferably 2.0 to 3.5 times.
  • the maximum draw ratio when the auxiliary drawing in the air and the drawing in water are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and still more preferably 6.0 times the original length of the laminate. That's it.
  • the term "maximum draw ratio" refers to the draw ratio immediately before the laminate breaks, and is 0.2 lower than the draw ratio at which the laminate breaks.
  • the stretching temperature for the in-air auxiliary stretching can be set to any appropriate value depending on the material for forming the thermoplastic resin base material, the stretching method, and the like.
  • the stretching temperature is preferably the glass transition temperature (Tg) of the thermoplastic resin substrate or higher, more preferably the glass transition temperature (Tg) of the thermoplastic resin substrate + 10°C or higher, and particularly preferably Tg + 15°C or higher.
  • the upper limit of the stretching temperature is preferably 170°C.
  • the crystallization index of the PVA-based resin after auxiliary stretching in air is preferably 1.3 to 1.8, more preferably 1.4 to 1.7.
  • an insolubilization treatment is performed after the auxiliary stretching treatment in the air and before the stretching treatment in water or the dyeing treatment.
  • the insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution.
  • the insolubilization treatment imparts water resistance to the PVA-based resin layer, and prevents deterioration of the orientation of the PVA when immersed in water.
  • the concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water.
  • the liquid temperature of the insolubilizing bath is preferably 20°C to 50°C.
  • the dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). Specifically, it is carried out by allowing the PVA-based resin layer to adsorb iodine.
  • adsorption method include a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of coating the PVA-based resin layer with the dyeing solution, and a method of applying the dyeing solution to the PVA-based resin layer.
  • a spraying method and the like can be mentioned.
  • a preferred method is to immerse the laminate in a dyeing solution (dyeing bath). This is because iodine can be well adsorbed.
  • the staining solution is preferably an iodine aqueous solution.
  • the amount of iodine compounded is preferably 0.05 to 0.5 parts by weight per 100 parts by weight of water.
  • an iodide to the iodine aqueous solution.
  • iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. etc.
  • potassium iodide is preferred.
  • the amount of iodide compounded is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, per 100 parts by weight of water.
  • the liquid temperature of the dyeing liquid during dyeing is preferably 20° C. to 50° C. in order to suppress dissolution of the PVA-based resin.
  • the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA-based resin layer.
  • the dyeing conditions can be set so that the single transmittance of the finally obtained polarizing film has the desired value.
  • the content ratio of iodine and potassium iodide in the aqueous iodine solution is preferably 1:5 to 1:10.
  • the boric acid contained in the treatment bath is mixed into the dyeing bath.
  • the boric acid concentration in the dyeing bath may change over time, resulting in unstable dyeability.
  • the upper limit of the boric acid concentration in the dyeing bath is preferably 4 parts by weight, more preferably 2 parts by weight with respect to 100 parts by weight of water. adjusted.
  • the lower limit of the boric acid concentration in the dyeing bath is preferably 0.1 parts by weight, more preferably 0.2 parts by weight, and still more preferably 0.5 parts by weight with respect to 100 parts by weight of water. is.
  • the dyeing process is performed using a dyeing bath pre-blended with boric acid. This can reduce the rate of change in boric acid concentration when the boric acid in the treatment bath is mixed into the dyeing bath.
  • the amount of boric acid blended in advance in the dyeing bath (that is, the content of boric acid not derived from the treatment bath) is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of water. , more preferably 0.5 to 1.5 parts by weight.
  • A-1-1-5 A-1-1-5.
  • Crosslinking Treatment If necessary, a crosslinking treatment is applied after the dyeing treatment and before the underwater stretching treatment.
  • the cross-linking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid.
  • the cross-linking treatment imparts water resistance to the PVA-based resin layer, and prevents deterioration of the orientation of the PVA when immersed in high-temperature water in the subsequent underwater stretching.
  • the concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.
  • the amount of iodide compounded is preferably 1 to 5 parts by weight per 100 parts by weight of water. Specific examples of iodides are as described above.
  • the liquid temperature of the cross-linking bath is preferably 20°C to 50°C.
  • thermoplastic resin substrate and the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80° C.), and the PVA-based resin layer undergoes its crystallization. can be stretched at a high magnification while suppressing the As a result, a polarizing film having excellent optical properties can be produced.
  • any appropriate method can be adopted as the method for stretching the laminate. Specifically, fixed-end stretching or free-end stretching (for example, a method of uniaxially stretching a laminate by passing it between rolls having different peripheral speeds) may be used. Free-end drawing is preferably chosen.
  • the laminate may be stretched in one step or in multiple steps. When the stretching is performed in multiple stages, the draw ratio (maximum draw ratio) of the laminate described below is the product of the draw ratios in each step.
  • the stretching in water is typically performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water).
  • an aqueous boric acid solution as the stretching bath, the PVA-based resin layer can be imparted with rigidity to withstand tension applied during stretching and water resistance that does not dissolve in water.
  • boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink with a PVA-based resin through hydrogen bonding.
  • rigidity and water resistance can be imparted to the PVA-based resin layer, which can be satisfactorily stretched, and a primary polarizing film having excellent optical properties can be produced.
  • the boric acid aqueous solution is preferably obtained by dissolving boric acid and/or a borate salt in water as a solvent.
  • the boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and particularly preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. is.
  • an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.
  • an iodide is added to the stretching bath (boric acid aqueous solution).
  • iodide elution of iodine adsorbed on the PVA-based resin layer can be suppressed.
  • Specific examples of iodides are as described above.
  • the concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, per 100 parts by weight of water.
  • the stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such a temperature, the film can be stretched at a high magnification while suppressing dissolution of the PVA-based resin layer.
  • the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40° C., it may not be possible to stretch well even if the plasticization of the thermoplastic resin base material by water is considered.
  • the higher the temperature of the stretching bath the higher the solubility of the PVA-based resin layer, which may make it impossible to obtain excellent optical properties.
  • the immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
  • the draw ratio by underwater drawing is preferably 1.5 times or more, more preferably 3.0 times or more.
  • the total draw ratio of the laminate is preferably 5.0 times or more, more preferably 5.5 times or more, relative to the original length of the laminate.
  • A-1-1-7 Dry shrinkage treatment
  • the laminate of the long thermoplastic resin substrate and the PVA-based resin film is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. and drying until the water content of the PVA-based resin film becomes 15% by weight or less. From the viewpoint of obtaining a stable appearance, it is preferable to dry to a moisture content of 12% by weight or less, more preferably 10% by weight or less, and even more preferably 1% to 5% by weight.
  • the drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably both are used.
  • heating roll heating roll drying method
  • the crystallization of the thermoplastic resin substrate can be efficiently promoted and the crystallinity can be increased by drying the laminate while it is placed along the heating roll. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be increased satisfactorily.
  • the thermoplastic resin base material has increased rigidity and is in a state capable of withstanding shrinkage of the PVA-based resin layer due to drying, thereby suppressing curling.
  • the layered product can be dried while being maintained in a flat state, so that not only curling but also wrinkling can be suppressed.
  • the laminate can be shrunk in the width direction by drying shrinkage treatment, thereby improving the optical properties. This is because the orientation of PVA and PVA/iodine complex can be effectively enhanced.
  • the shrinkage ratio of the laminate in the width direction due to drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.
  • FIG. 1 is a schematic diagram showing an example of drying shrinkage treatment.
  • the laminate 200 is dried while being transported by transport rolls R1 to R6 heated to a predetermined temperature and guide rolls G1 to G4.
  • the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA-based resin layer and the surface of the thermoplastic resin substrate.
  • the transport rolls R1 to R6 may be arranged so as to continuously heat only the plastic resin substrate surface).
  • the drying conditions can be controlled by adjusting the heating temperature of the transport rolls (the temperature of the heating rolls), the number of heating rolls, the contact time with the heating rolls, and so on.
  • the temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C.
  • the degree of crystallinity of the thermoplastic resin can be favorably increased, curling can be favorably suppressed, and an optical laminate having extremely excellent durability can be produced.
  • the temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as the number of transport rolls is plural. Conveying rolls are usually 2 to 40, preferably 4 to 30 in number.
  • the contact time (total contact time) between the laminate and the heating roll is preferably 1 to 300 seconds, more preferably 1 to 20 seconds, still more preferably 1 to 10 seconds.
  • the heating roll may be provided in a heating furnace (for example, an oven), or may be provided in a normal production line (under room temperature environment). Preferably, it is provided in a heating furnace equipped with air blowing means.
  • a heating furnace equipped with air blowing means.
  • the temperature for hot air drying is preferably 30°C to 100°C.
  • the hot air drying time is preferably 1 second to 300 seconds.
  • the wind speed of the hot air is preferably about 10m/s to 30m/s. The wind speed is the wind speed in the heating furnace and can be measured with a mini-vane digital anemometer.
  • A-1-1-8 Other Treatments
  • a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment.
  • the cleaning treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.
  • A-1-2. Production of primary polarizing film using single-layer PVA-based resin film Production of a primary polarizing film using a single-layer PVA-based resin film is self-supporting (that is, does not require support by a substrate).
  • a strip-shaped PVA-based resin film is dyed and stretched in boric acid water (typically, uniaxially stretched by a roll stretching machine), and then the water content is 15% by weight or less, preferably 12% by weight or less, more preferably 10% by weight. This can be done by drying to a weight % or less, more preferably 1 to 5 weight %.
  • the dyeing is performed by, for example, immersing the PVA-based resin film in an iodine aqueous solution.
  • the draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending
  • the primary polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm.
  • the transmittance of the primary polarizing film (single transmittance: Ts) is preferably 41.5% or more, more preferably 42.0% or more, still more preferably 42.5% or more.
  • the transmittance of the primary polarizing film is preferably 46.0% or less, more preferably 45.0% or less.
  • the degree of polarization of the primary polarizing film is preferably 98.0% or more, more preferably 99.0% or more, still more preferably 99.9% or more.
  • the degree of polarization of the primary polarizing film is preferably 99.998% or less.
  • the transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and subjected to visibility correction.
  • the degree of polarization is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured using an ultraviolet-visible spectrophotometer and subjected to visibility correction.
  • Degree of polarization (%) ⁇ (Tp-Tc)/(Tp+Tc) ⁇ 1/2 ⁇ 100
  • the transmittance of a thin polarizing film of 12 ⁇ m or less is typically the polarizing film (surface refractive index: 1.53) and the protective layer (protective film) (refractive index: 1.50 ) is measured using an ultraviolet-visible spectrophotometer.
  • the reflectance at each layer interface may change, resulting in a change in the measured transmittance.
  • the transmittance measurements may be corrected according to the refractive index of the surface of the protective layer that is in contact with the air interface.
  • the transmittance correction value C is expressed by the following formula using the reflectance R 1 (transmission axis reflectance) of polarized light parallel to the transmission axis at the interface between the protective layer and the air layer.
  • C R 1 -R 0
  • R 0 ((1.50 ⁇ 1) 2 /(1.50+1) 2 ) ⁇ (T 1 /100)
  • R 1 ((n 1 ⁇ 1) 2 /(n 1 +1) 2 ) ⁇ (T 1 /100)
  • R 0 is the transmission axis reflectance when a protective layer having a refractive index of 1.50 is used
  • n 1 is the refractive index of the protective layer used
  • T 1 is the transmittance of the polarizing film. is.
  • the correction amount C is approximately 0.2%.
  • the transmittance when using a polarizing film with a surface refractive index of 1.53 and a protective layer with a refractive index of 1.50 It is possible to convert to a rate.
  • the amount of change in the correction value C when the transmittance T1 of the polarizing film is changed by 2 % is 0.03% or less, and the transmittance of the polarizing film is equal to the correction value C has a limited effect on the value of Moreover, when the protective layer has absorption other than surface reflection, appropriate correction can be performed according to the amount of absorption.
  • the thickness of the primary polarizing film is typically 25 ⁇ m or less, preferably 12 ⁇ m or less, more preferably 1 ⁇ m to 8 ⁇ m, even more preferably 1 ⁇ m to 7 ⁇ m, still more preferably 2 ⁇ m to 5 ⁇ m.
  • the thickness is small, there is an advantage that wrinkles are less likely to occur in the polarizing film when it is brought into contact with an aqueous solvent.
  • the moisture content of the primary polarizing film is typically 15% by weight or less, preferably 12% by weight or less, more preferably 10% by weight or less, and still more preferably 1% to 5% by weight. If the moisture content is within the above range, the transmittance can be changed without significantly impairing the appearance when contacted with an aqueous solvent.
  • a polarizing plate having a configuration in which a protective layer and optionally a functional layer are laminated on one side of a primary polarizing film and the other side is an exposed surface is produced.
  • Any appropriate functional layer can be selected as the functional layer depending on the purpose, and specific examples thereof include a retardation layer, an adhesive layer, and the like.
  • the process of manufacturing the said polarizing plate is an arbitrary process. Therefore, depending on the purpose, the laminate having the structure of [thermoplastic resin substrate/primary polarizing film] produced by the method described in Section A-1-1 or the single layer described in Section A-1-2
  • the primary polarizing film prepared using the PVA-based resin film of No. 1 can be directly subjected to the step of obtaining the secondary polarizing film.
  • FIG. 2A to 2C are schematic cross-sectional views explaining an example of a polarizing plate that can be produced in the process of producing a polarizing plate.
  • the polarizing plate 100A shown in FIG. 2A includes a polarizing film (primary polarizing film) 10 and a protective layer 20 disposed on one side thereof, and the polarizing film (primary polarizing film) 10 on the side on which the protective layer 20 is provided. The opposite side is the exposed surface.
  • the polarizing plate 100A is, for example, an adhesive layer or a It can be obtained by laminating a protective layer via an adhesive layer and then peeling off the thermoplastic resin substrate. Alternatively, the polarizing plate 100A can be obtained by laminating a protective layer on one surface of the primary polarizing film produced by the method described in Section A-1-2 via an adhesive layer or a pressure-sensitive adhesive layer. .
  • the polarizing plate 100B shown in FIG. 2B includes a polarizing film (primary polarizing film) 10, a protective layer 20, a retardation layer 30, and an adhesive layer 40 in this order. is provided and the opposite side is an exposed surface.
  • the retardation layer 30 is attached to the protective layer 20 side surface of the polarizing plate 100A via an adhesive layer or a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer 40 is provided on the surface of the retardation layer 30.
  • the retardation layer 30 is provided on the thermoplastic resin substrate side surface of the laminate having the configuration of [thermoplastic resin substrate/primary polarizing film] via an adhesive layer or a pressure-sensitive adhesive layer. It can also be obtained by laminating and then providing the pressure-sensitive adhesive layer 40 on the surface of the retardation layer 30 .
  • the thermoplastic resin substrate functions as the protective layer 20 .
  • the retardation layer 30 in the illustrated example may have a single-layer structure, or may have a laminated structure in which two or more retardation layers are laminated.
  • the polarizing plate 100C shown in FIG. 2C includes a polarizing film (primary polarizing film) 10, a protective layer 20, and an adhesive layer 40 in this order. and the opposite side is the exposed surface.
  • the polarizing plate 100C can be obtained, for example, by providing an adhesive layer 40 on the protective layer 20 side surface of the polarizing plate 100A.
  • the polarizing plate 100C can also be obtained by providing an adhesive layer 40 on the thermoplastic resin substrate side surface of the laminate having the structure [thermoplastic resin substrate/primary polarizing film]. In this case, the thermoplastic resin substrate functions as the protective layer 20 .
  • a release film is temporarily attached to the surface of the adhesive layer 40 until the polarizing plate is used.
  • the protective layer 20 is formed of any appropriate film that can be used as a protective layer for polarizing films.
  • the retardation layer 30 can be, for example, a thermoplastic resin film or a liquid crystal alignment fixed layer. Any appropriate adhesive can be used as the adhesive that forms the adhesive layer 40, and among them, an acrylic adhesive having an acrylic polymer as a base polymer is preferably used.
  • Such protective layer, retardation layer and pressure-sensitive adhesive layer are well known to those skilled in the art, and thus detailed description thereof will be omitted.
  • Step of Obtaining Secondary Polarizing Film In the step of obtaining the secondary polarizing film, the surface of the primary polarizing film is brought into contact with an aqueous solvent to change the transmittance of the primary polarizing film. Specifically, a secondary polarizing film having a desired transmittance can be obtained by decolorizing the primary polarizing film by bringing it into contact with an aqueous solvent.
  • aqueous solvent can be used as the aqueous solvent as long as it can elute the dichroic substance from the primary polarizing film.
  • the aqueous solvent can be, for example, water or a mixture of water and a water-soluble organic solvent.
  • Preferred examples of the water-soluble organic solvent include lower monoalcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propyl alcohol and isopropyl alcohol, and polyhydric alcohols such as glycerin and ethylene glycol.
  • the content of the water-soluble organic solvent in the aqueous solvent is, for example, 20% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less.
  • the method of contact with the aqueous solvent is not particularly limited, and any suitable method such as immersion, spraying, coating, etc. can be used. Spraying or coating is preferred for partial transmittance adjustment, and immersion is preferred for overall transmittance adjustment.
  • the contact time with the aqueous solvent and the temperature of the aqueous solvent during contact can be appropriately set according to the desired change in transmittance. Increasing the contact time or increasing the temperature of the aqueous solvent tends to increase the amount of change in transmittance.
  • the contact time can be, for example, 10 minutes or less, preferably 1 second to 5 minutes, more preferably 2 seconds to 3 minutes.
  • the temperature of the aqueous solvent can be preferably 20°C to 70°C, more preferably 30°C to 65°C, even more preferably 40°C to 60°C.
  • the polarizing film may be dried after contact with the aqueous solvent.
  • the drying temperature can be, for example, 30°C to 100°C, preferably 30°C to 80°C.
  • the moisture content of the dried polarizing film (secondary polarizing film) is typically 15% by weight or less, preferably 12% by weight or less, more preferably 10% by weight or less, and still more preferably 1% by weight. % to 5% by weight.
  • the secondary polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm.
  • the transmittance of the secondary polarizing film (single transmittance: Ts) can be appropriately adjusted depending on the purpose.
  • the transmittance of the secondary polarizing film is preferably 41.5% or more, more preferably 42% or more, still more preferably 42.5% or more.
  • the transmittance of the secondary polarizing film is, for example, 70% or less, preferably 50% or less, more preferably 46% or less.
  • the secondary polarizing film can have a transmission that is, for example, 0.1% to 1.5% higher than the primary polarizing film.
  • the degree of polarization of the secondary polarizing film is, for example, 90% or more, preferably 92.0% or more, more preferably 94.0% or more, still more preferably 96.0% or more, and still more. It is preferably 99.0% or more, still more preferably 99.5% or more, and preferably 99.998% or less.
  • the above transmittance and degree of polarization are values obtained in the same manner as the transmittance and degree of polarization of the primary polarizing film.
  • the thickness of the secondary polarizing film is typically 25 ⁇ m or less, preferably 12 ⁇ m or less, more preferably 1 ⁇ m to 8 ⁇ m, still more preferably 1 ⁇ m to 7 ⁇ m, still more preferably 2 ⁇ m to 5 ⁇ m.
  • the thickness of the secondary polarizing film can be substantially the same as the primary polarizing film.
  • the method for manufacturing the polarizing plate may further include any appropriate steps as necessary.
  • the step of changing the transmittance by contacting the surface of the secondary polarizing film with an aqueous solvent may be further included.
  • the step of changing the transmittance can be repeated two or more times.
  • any suitable layer (protective layer, retardation layer, adhesive layer, etc.) is laminated on the exposed surface of the finally obtained polarizing film (e.g., secondary polarizing film) to protect the exposed surface.
  • polarizing film e.g., secondary polarizing film
  • the polarizing plate 100D includes a first protective layer 20a, a polarizing film (secondary polarizing film) 10, a second protective layer 20b, a retardation layer 30, and an adhesive layer 40 in this order.
  • the polarizing plate 100D is obtained by, for example, forming a second protective layer 20b, a retardation layer 30 and an adhesive layer 40 in this order on the exposed surface of the polarizing film 10 of the polarizing plate 100A (FIG. 2A) that has undergone the step of obtaining a secondary polarizing film.
  • FIG. 2A a polarizing film 10 of the polarizing plate 100A
  • FIG. 2B the polarizing plate 100B
  • the polarizing plate 100E includes a first protective layer 20a, a polarizing film (secondary polarizing film) 10, a second protective layer 20b, and an adhesive layer 40 in this order.
  • the second protective layer 20b may have a desired retardation and function as a retardation layer (for example, a ⁇ /4 plate), as described later.
  • the polarizing plate 100E can be obtained, for example, by providing the second protective layer 20b and the adhesive layer 40 in this order on the exposed surface of the polarizing film 10 of the polarizing plate 100A (FIG. 2A) that has undergone the process of changing the transmittance. .
  • it can be obtained by bonding the first protective layer 20a to the exposed surface of the polarizing film 10 of the polarizing plate 100C (FIG. 2C) that has undergone the process of changing the transmittance.
  • the adhesive layer 40 is used to bond the polarizing plates 100D and 100E to an image display cell (eg liquid crystal cell, organic EL cell).
  • the first protective layer 20a serves as a protective layer (outer protective layer) arranged on the side opposite to the image display cell when the polarizing plate is applied to the image display device, and serves as the second protective layer.
  • the layer 20b becomes a protective layer (inner protective layer) arranged on the image display cell side.
  • the thickness of the outer protective layer is typically 300 ⁇ m or less, preferably 100 ⁇ m or less, more preferably 5 ⁇ m to 80 ⁇ m, still more preferably 10 ⁇ m to 60 ⁇ m.
  • the thickness of the outer protective layer is the thickness including the thickness of the surface treatment layer.
  • the thickness of the inner protective layer is preferably 5 ⁇ m to 200 ⁇ m, more preferably 10 ⁇ m to 100 ⁇ m, still more preferably 10 ⁇ m to 60 ⁇ m.
  • the inner protective layer is optically isotropic.
  • “optically isotropic” means that the in-plane retardation Re (550) is 0 nm to 10 nm, and the thickness direction retardation Rth (550) is ⁇ 10 nm to +10 nm.
  • nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow axis direction)
  • ny is the in-plane direction orthogonal to the slow axis (that is, the fast is the refractive index in the axial direction)
  • 'nz' is the refractive index in the thickness direction
  • 'd' is the layer (film) thickness (nm).
  • the inner protective layer is a retardation layer having any suitable retardation value.
  • the in-plane retardation Re(550) of the inner protective layer in this embodiment can be, for example, 110 nm to 150 nm.
  • the angle between the slow axis of the inner protective layer and the slow axis of the absorption axis of the polarizing film is clockwise or counterclockwise, for example, 35° to 55°, preferably 38°. ⁇ 52°, more preferably 40° to 50°, more preferably 42° to 48°, and particularly preferably 44° to 46°, thereby functioning as a circularly polarizing plate can.
  • the retardation layer 30 may be a retardation layer having a desired in-plane retardation and/or thickness direction retardation depending on the purpose.
  • the in-plane retardation Re(550) of the retardation layer can be 110 nm to 150 nm.
  • the angle between the slow axis and the slow axis of the absorption axis of the polarizing film is clockwise or counterclockwise, for example, 35° to 55°, preferably 38°. ⁇ 52°, more preferably 40° to 50°, more preferably 42° to 48°, and particularly preferably 44° to 46°, thereby functioning as a circularly polarizing plate can.
  • a method for manufacturing an image display device includes a polarizing film made of a polyvinyl alcohol resin film containing a dichroic substance and having a moisture content of 15% by weight or less, and a protective layer. and an adhesive layer in this order, laminated on the image display cell via the adhesive layer, and the surface of the polarizing film opposite to the side on which the protective layer is arranged is exposed. and step (II) of bringing an aqueous solvent into contact with the exposed surface of the polarizing film to change the transmittance, in this order.
  • the polarizing plate laminated on the image display cell is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and includes a polarizing film having a moisture content of 15% by weight or less, a protective layer, and an adhesive layer in this order.
  • a polarizing film having a moisture content of 15% by weight or less As long as the surface of the polarizing film on which the protective layer is not arranged can be exposed, it can have any configuration.
  • the polarizing plate may be attached to the image display cell with the exposed surface of the polarizing film protected by a surface protective film, and the polarizing film may be exposed by peeling off the surface protective film before contact with the aqueous solvent. .
  • the polarizing plate laminated on the image display cell may further include a retardation layer.
  • the polarizing plates having the configurations illustrated in FIGS. 2B and 2C can be exemplified. Further, the description of the primary polarizing film, protective layer, retardation layer and adhesive layer described in section A can be applied to the polarizing film, protective layer, retardation layer and adhesive layer contained in the polarizing plate.
  • a liquid crystal display device or an organic EL display device can be preferably exemplified as the image display device manufactured by the above manufacturing method. Therefore, a liquid crystal cell or an organic EL cell can be preferably used as the image display cell.
  • a plurality of image display devices may be combined to display one image as a whole and used as digital signage.
  • Step (II) In the step of changing the transmittance, the exposed surface of the polarizing film is brought into contact with an aqueous solvent to change the transmittance. Specifically, the transmittance of the polarizing film can be changed and adjusted to a desired value by decolorizing the dichroic substance through contact with an aqueous solvent. As for the step of changing the transmittance, the same explanation as in Section A-3 can be applied. From the viewpoint of preventing the image display cell from coming into contact with the aqueous solvent, coating or spraying can be preferably used as the method of contact with the aqueous solvent. For the polarizing film after changing the transmittance, the description of the secondary polarizing film described in Section A-3 can be applied.
  • the method for manufacturing the image display device may further include a step of protecting the exposed surface of the polarizing film after the step of changing the transmittance, if necessary. Protection of the exposed surface of the polarizing film can be carried out by laminating a protective layer, a supporting substrate, or the like on the exposed surface via an adhesive layer such as an adhesive layer or pressure-sensitive adhesive layer.
  • an aqueous solvent is brought into contact with the surface of the polarizing film which is composed of a PVA-based resin film containing a dichroic substance and has a moisture content of 15% by weight or less.
  • a method for adjusting the transmittance of a polarizing film is provided, which includes the step of causing a According to the method for adjusting the transmittance of the polarizing film, the transmittance of the polarizing film can be adjusted (typically increased) to a desired value as a result of decolorization of the polarizing film by contact with the aqueous solvent.
  • the primary polarizing film described in Section A-1 is preferably used. Also, the same description as in Section A-3 can be applied to the contact between the polarizing film and the aqueous solvent.
  • Ts, Tp and Tc of the polarizing film were used as Ts, Tp and Tc of the polarizing film, respectively.
  • Ts, Tp and Tc are Y values measured with a 2-degree field of view (C light source) according to JIS Z8701 and subjected to visibility correction.
  • the refractive index of the protective layer was 1.53, and the refractive index of the surface of the polarizing film opposite to the protective layer was 1.53. From the obtained Tp and Tc, the degree of polarization P was determined by the following formula.
  • Example 1-1 A long roll of a 30 ⁇ m-thick PVA-based resin film (manufactured by Kuraray, product name “PE3000”) was immersed in a water bath at 30° C. and stretched 2.2 times in the conveying direction. , while being immersed in an aqueous solution of 0.3% by weight of potassium at 30° C. and dyed, the film was stretched 3 times with respect to the unstretched film (original length). Next, while immersing this stretched film in an aqueous solution of 3% by weight of boric acid and 3% by weight of potassium iodide at 30° C., the stretched film is further stretched to 3.3 times its original length.
  • a polarizing film (primary polarizing film) having a thickness of 12 ⁇ m was produced.
  • the obtained primary polarizing film had a moisture content of 10% by weight.
  • the single transmittance of the polarizing film was 42.5%.
  • a PVA-based resin aqueous solution manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOSEFIMER (registered trademark) Z-200”, resin concentration: 3% by weight
  • GOSEFIMER registered trademark
  • resin concentration: 3% by weight was applied, and a cycloolefin-based A film (Zeonor, thickness: 25 ⁇ m, manufactured by Nippon Zeon Co., Ltd.) was laminated to obtain a polarizing plate (before treatment) having a structure of [primary polarizing film/protective layer].
  • the above polarizing plate (before treatment) was cut into a size of 100 mm ⁇ 100 mm and attached to a glass plate so that the surface on the primary polarizing film side was exposed via an acrylic adhesive layer (thickness 15 ⁇ m) at 55 ° C. of water for 6 minutes. Then, by drying at 50° C. for 5 minutes, a polarizing plate (after treatment) having a configuration of [secondary polarizing film/protective layer] was obtained.
  • Example 1-2 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 1-3 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 1-4 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 2-1 A long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 ⁇ m) having a Tg of about 75° C. was used as the thermoplastic resin substrate, and one side of the resin substrate was subjected to corona treatment.
  • Polyvinyl alcohol degree of polymerization: 4,200, degree of saponification: 99.2 mol%
  • acetoacetyl-modified PVA manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER" were mixed at a ratio of 9:1, and 100 parts by weight of PVA-based resin.
  • aqueous PVA solution (coating solution).
  • the above PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 ⁇ m, thereby producing a laminate.
  • the resulting laminate was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in an oven at 130° C. (in-air auxiliary stretching treatment).
  • the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C.
  • the finally obtained polarizing plate was placed in a dyeing bath (iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 42.3% (dyeing treatment). Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 40°C (an aqueous solution of boric acid obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water).
  • crosslinking treatment After that, while immersing the laminate in an aqueous solution of boric acid (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70° C., the laminate was moved vertically (longitudinally) between rolls with different peripheral speeds. Uniaxial stretching was performed so that the stretching ratio was 5.5 times (underwater stretching treatment). After that, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (washing treatment).
  • a washing bath aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water
  • a polarizing film (primary polarizing film) having a moisture content of 4.5% by weight and a thickness of 5 ⁇ m is formed on the resin substrate, and a cycloolefin film (manufactured by Nippon Zeon Co., Ltd.) is formed on the surface of the primary polarizing film.
  • the above polarizing plate (before treatment) was cut into a size of 100 mm ⁇ 100 mm and attached to a glass plate so that the surface on the primary polarizing film side became an exposed surface via an acrylic pressure-sensitive adhesive layer (thickness 15 ⁇ m). of water for 9 minutes. Then, by drying at 50° C. for 5 minutes, a polarizing plate (after treatment) having a configuration of [secondary polarizing film/protective layer] was obtained.
  • Example 2-2 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 2-3 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 2-4 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 2-5 A polarizing plate having a [secondary polarizing film/protective layer] configuration ( after treatment).
  • Example 3-1 Configuration of [primary polarizing film/protective layer] in the same manner as in Example 2-1 except that the iodine concentration in the dyeing bath was changed and the transmittance of the resulting polarizing film was adjusted to 44.3%. A polarizing plate (before treatment) having was obtained. The obtained primary polarizing film had a moisture content of 4.5% by weight.
  • the above polarizing plate (before treatment) was cut into a size of 100 mm ⁇ 100 mm, and attached to a glass plate so that the surface on the primary polarizing film side became an exposed surface via an acrylic pressure-sensitive adhesive layer (thickness: 15 ⁇ m). °C water for 6 minutes. Then, by drying at 50° C. for 5 minutes, a polarizing plate (after treatment) having a configuration of [secondary polarizing film/protective layer] was obtained.
  • Example 3-2 A polarizing plate having a configuration of [secondary polarizing film/protective layer] in the same manner as in Example 3-1 except that it was immersed in water at 55 ° C. for 3 minutes instead of immersing in water at 50 ° C. for 6 minutes ( after treatment).
  • the transmittance of the polarizing film can be changed after the protective layer is laminated to manufacture the polarizing plate.
  • the method for producing a polarizing plate of the present invention is suitably used in the production of image display devices.

Abstract

La présente invention concerne un procédé de réglage de la transmittance d'un film polarisant après la production de celui-ci. Un procédé de fabrication de plaque polarisante selon la présente invention comprend, dans l'ordre donné, une étape consistant à obtenir un film polarisant primaire en soumettant un film de résine à base d'alcool polyvinylique à un traitement de teinture et à un traitement d'étirage dans une solution aqueuse d'acide borique, puis à sécher le film jusqu'à ce que la teneur en humidité atteigne 15 % en poids ou moins, et une étape consistant à obtenir un film polarisant secondaire en amenant la surface du film polarisant primaire en contact avec un solvant aqueux et en modifiant ainsi la transmittance du film.
PCT/JP2021/041182 2021-01-22 2021-11-09 Procédé de fabrication de plaque polarisante, procédé de fabrication de dispositif d'affichage d'image et procédé de réglage de la transmittance d'un film polarisant WO2022158088A1 (fr)

Priority Applications (2)

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KR1020237024445A KR20230129452A (ko) 2021-01-22 2021-11-09 편광판의 제조 방법, 화상 표시 장치의 제조 방법 및편광막의 투과율의 조정 방법
CN202180091355.4A CN116802529A (zh) 2021-01-22 2021-11-09 偏振片的制造方法、图像显示装置的制造方法及偏振膜的透射率的调整方法

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JP2021-008759 2021-01-22
JP2021008759A JP2022112802A (ja) 2021-01-22 2021-01-22 偏光板の製造方法、画像表示装置の製造方法および偏光膜の透過率の調整方法

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015163401A1 (fr) * 2014-04-25 2015-10-29 日東電工株式会社 Polariseur, plaque de polarisation, et dispositif d'affichage d'images
JP2016027136A (ja) * 2014-06-27 2016-02-18 日東電工株式会社 長尺状の粘着フィルム
WO2019235107A1 (fr) * 2018-06-07 2019-12-12 日東電工株式会社 Film polarisant et plaque polarisante avec couche de retard
WO2020066125A1 (fr) * 2018-09-25 2020-04-02 日東電工株式会社 Plaque de polarisation et procédé de fabrication associé et dispositif d'affichage d'image comprenant la plaque de polarisation

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002311239A (ja) 2001-04-16 2002-10-23 Nitto Denko Corp １／４波長板、円偏光板及び表示装置
JP2002372622A (ja) 2001-06-14 2002-12-26 Nitto Denko Corp 複合位相差板、円偏光板及び液晶表示装置、有機ｅｌ表示装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015163401A1 (fr) * 2014-04-25 2015-10-29 日東電工株式会社 Polariseur, plaque de polarisation, et dispositif d'affichage d'images
JP2016027136A (ja) * 2014-06-27 2016-02-18 日東電工株式会社 長尺状の粘着フィルム
WO2019235107A1 (fr) * 2018-06-07 2019-12-12 日東電工株式会社 Film polarisant et plaque polarisante avec couche de retard
WO2020066125A1 (fr) * 2018-09-25 2020-04-02 日東電工株式会社 Plaque de polarisation et procédé de fabrication associé et dispositif d'affichage d'image comprenant la plaque de polarisation

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