CN113508316A - Polarizing film, polarizing plate, and method for producing polarizing film - Google Patents
Polarizing film, polarizing plate, and method for producing polarizing film Download PDFInfo
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- CN113508316A CN113508316A CN202080017274.5A CN202080017274A CN113508316A CN 113508316 A CN113508316 A CN 113508316A CN 202080017274 A CN202080017274 A CN 202080017274A CN 113508316 A CN113508316 A CN 113508316A
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- polarizing film
- stretching
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- laminate
- alcohol
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Images
Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
- B29C55/06—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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/023—Optical properties
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
- C08L29/02—Homopolymers or copolymers of unsaturated alcohols
- C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
- G02B1/14—Protective coatings, e.g. hard coatings
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Nonlinear Science (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mathematical Physics (AREA)
- Polarising Elements (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
- Laminated Bodies (AREA)
Abstract
Provided is a polarizing film which is thin and has excellent durability in a high-temperature and high-humidity environment. The polarizing film of the present invention is composed of a polyvinyl alcohol resin film containing iodine, has a thickness of 8 [ mu ] m or less, and contains 5 to 350ppm of an alcohol having a boiling point of less than 100 ℃. In 1 embodiment, the alcohol having a boiling point of less than 100 ℃ is at least 1 selected from the group consisting of methanol, ethanol, n-propanol and isopropanol. The polarizing plate of the present invention comprises: the polarizing film and a protective layer disposed on at least one side of the polarizing film.
Description
Technical Field
The present invention relates to a polarizing film, a polarizing plate, and a method for producing the polarizing film.
Background
In a liquid crystal display device, which is a typical image display device, polarizing films are arranged on both sides of a liquid crystal cell depending on an image forming method. As a method for producing a polarizing film, for example, the following methods are proposed: a polarizing film is obtained on a resin substrate by stretching a laminate having the resin substrate and a polyvinyl alcohol (PVA) -based resin layer, and then performing a dyeing treatment (for example, patent document 1). Since a polarizing film having a small thickness can be obtained by such a method, attention has been paid to a method contributing to thinning of an image display device in recent years. However, a thin polarizing film is required to have further improved durability under a high-temperature and high-humidity environment.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2001-343521
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a polarizing film which is thin and has excellent durability in a high-temperature and high-humidity environment, a polarizing plate, and a method for producing such a polarizing film.
Means for solving the problems
The polarizing film of the present invention is composed of a polyvinyl alcohol resin film containing iodine, has a thickness of 8 [ mu ] m or less, and contains 5 to 350ppm of an alcohol having a boiling point of less than 100 ℃.
In 1 embodiment, the alcohol having a boiling point of less than 100 ℃ is at least 1 selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.
According to another aspect of the present invention, there is provided a polarizing plate. The polarizing plate includes: the polarizing film and a protective layer disposed on at least one side of the polarizing film.
According to still another aspect of the present invention, there is provided a method for producing the polarizing film described above. The method comprises the following steps: forming a polyvinyl alcohol resin layer on one side of a long thermoplastic resin base material to form a laminate; stretching and dyeing the laminate to form a polarizing film from the polyvinyl alcohol resin layer; and introducing an alcohol having a boiling point of less than 100 ℃ into the polarizing film.
In 1 embodiment, the method includes immersing the polarizing film in a treatment liquid containing the alcohol having a boiling point of less than 100 ℃.
In 1 embodiment, the method further comprises introducing the alcohol having a boiling point of less than 100 ℃ into the polarizing film and heating the laminate.
In 1 embodiment, the stretching comprises underwater stretching.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a polarizing film which is thin and has excellent durability in a high-temperature and high-humidity environment can be obtained by introducing an alcohol having a boiling point of less than 100 ℃.
Drawings
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention.
Fig. 2 is a schematic diagram showing an example of the drying shrinkage process using a heating roller.
Detailed Description
Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
A. Polarizing film
The polarizing film according to an embodiment of the present invention is composed of a polyvinyl alcohol (PVA) resin film containing iodine, and has a thickness of 8 μm or less and contains 5 to 350ppm of an alcohol having a boiling point lower than 100 ℃ (hereinafter, may be referred to as a low-boiling-point alcohol). By adding a predetermined amount of such a low-boiling alcohol to the polarizing film, a thin polarizing film having excellent durability under a high-temperature and high-humidity environment can be obtained. For such low boiling point alcohol, as described later in item C with respect to the production method, it is representative that a polarizing film may be introduced between the stretching treatment in water and the drying shrinkage treatment. It is presumed that by introducing such a low boiling point alcohol, the durability under a high temperature and high humidity environment can be improved by the following mechanism: (i) the drying efficiency is improved due to the low boiling point alcohol during the drying shrinkage treatment, and the orientation of PVA is improved; and (ii) the PVA-iodine complex is stabilized by the low boiling point alcohol in the obtained polarizing film, and thus the reduction of the optical characteristics in the wet state can be suppressed. Further, although crystallization of PVA may be insufficient in the production of a thin polarizing film, favorable crystallization of PVA can be achieved by introducing a low-boiling alcohol. As a result, even a thin polarizing film having the same monomer transmittance, a particularly high iodine concentration and insufficient iodine stability as compared with a conventional (thick) polarizer can achieve excellent durability in a high-temperature and high-humidity environment. The content of the low-boiling alcohol in the polarizing film is, for example, 8ppm to 320ppm, preferably 20ppm to 200ppm, more preferably 40ppm to 150ppm, and still more preferably 50ppm to 120 ppm. If the content is too small, the effect of the low-boiling alcohol may not be obtained. If the content is too large, the amount introduced during production increases, and therefore the amount of volatilization into the operating environment increases, which may increase the risk of safety.
Typical examples of the low boiling point alcohol include lower monohydric alcohols having 1 to 4 carbon atoms. Specific examples thereof include methanol, ethanol, n-propanol, isopropanol and tert-butanol. The low-boiling alcohols may be used alone or in combination of 2 or more. Methanol, ethanol, n-propanol, and isopropanol are preferred. Since these have low boiling points, the drying efficiency in the drying step described later is improved, which is advantageous for improving the properties of the obtained polarizing film.
The thickness of the polarizing film is 8 μm or less, preferably 7 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less as described above. The lower limit of the thickness of the polarizing film may be 1 μm in 1 embodiment, and may be 2 μm in another embodiment.
The polarizing film preferably exhibits absorption dichroism at an arbitrary wavelength of 380nm to 780 nm. The polarizing film preferably has a monomer transmittance of 42.0% or more, more preferably 42.5% or more, and still more preferably 43.0% or more. On the other hand, the monomer transmittance is preferably 47.0% or less, more preferably 46.0% or less. The polarization degree of the polarizing film is preferably 99.90% or more, more preferably 99.95% or more. On the other hand, the degree of polarization is preferably 99.998% or less. According to the embodiments of the present invention, it is possible to achieve both high monomer transmittance and high polarization degree, and to achieve excellent durability in a high-temperature and high-humidity environment as described above. The monomer transmittance is typically a Y value measured by an ultraviolet-visible spectrophotometer and corrected for visual sensitivity. The single transmittance is a value obtained by converting the refractive index of one surface of the polarizing plate to 1.50 and the refractive index of the other surface to 1.53. The degree of polarization is typically determined by the following equation based on the parallel transmittance Tp and the orthogonal transmittance Tc obtained by measuring with an ultraviolet-visible spectrophotometer and performing a visual sensitivity correction.
Polarization degree (%) { (Tp-Tc)/(Tp + Tc) }1/2×100
The polarization degree of the polarizing film after a 120-hour durability test at a temperature of 60 ℃ and a relative humidity of 95% changes Δ P preferably by-0.70% or more, more preferably by-0.55% or more, and still more preferably by-0.20% or more. The upper limit of Δ P may be 0.0% or more, for example, and Δ P may be 0.10% or less, for example. Δ P is represented by the following formula.
ΔP＝P120-P0
In the above formula, P120Degree of polarization after endurance test, P0The polarization degree before the durability test (the polarization degree explained above). That is, the polarizing film of the embodiment of the present invention has the following features: the reduction in bias light is small in a high-temperature and high-humidity environment, and there are also cases where it increases.
The polarizing film may be produced using a single resin film, or may be produced using a laminate of two or more layers. Specific examples of the polarizing film obtained using the laminate include a polarizing film obtained using a laminate of a resin substrate and a PVA-based resin layer applied to the resin substrate. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced, for example, as follows: coating a PVA-based resin solution on a resin base material and drying the coating to form a PVA-based resin layer on the resin base material, thereby obtaining a laminate of the resin base material and the PVA-based resin layer; the laminate is stretched and dyed to form a polarizing film from the PVA-based resin layer. In the embodiment of the present invention, a low boiling point alcohol is introduced into the polarizing film. This can realize excellent durability under a high-temperature and high-humidity environment as described above. Preferably, a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin is formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, the stretching may further include subjecting the laminate to in-air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution, if necessary. In the present embodiment, the laminate is preferably subjected to a drying shrinkage treatment for shrinking the laminate in the width direction by 2% or more by heating while conveying the laminate in the longitudinal direction. Typically, the manufacturing method of the present embodiment includes: the laminate is subjected to an in-air auxiliary stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even if the PVA is coated on the thermoplastic resin, the crystallinity of the PVA can be improved, and high optical characteristics can be achieved. Further, by simultaneously improving the orientation of the PVA in advance, it is possible to prevent problems such as reduction in orientation and dissolution of the PVA when the PVA is immersed in water in the subsequent dyeing step and stretching step, and to achieve high optical characteristics. Further, when the PVA-based resin layer is immersed in a liquid, disorder of the orientation of the polyvinyl alcohol molecules and reduction of the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical properties of the polarizing film obtained through a treatment step of immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment. Further, the optical properties can be improved by shrinking the laminate in the width direction by the drying shrinkage treatment. The obtained resin substrate/polarizing film laminate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizing film), or the resin substrate may be peeled from the resin substrate/polarizing film laminate and an arbitrary appropriate protective layer suitable for the purpose may be laminated on the peeled surface. Details of the method for producing the polarizing film will be described later in item C.
B. Polarizing plate
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention. The polarizing plate 100 includes: the liquid crystal display device includes a polarizing film 10, a 1 st protective layer 20 disposed on one side of the polarizing film 10, and a 2 nd protective layer 30 disposed on the other side of the polarizing film 10. The polarizing film 10 is the polarizing film of the present invention described in the above item a. One of the 1 st protective layer 20 and the 2 nd protective layer 30 may be omitted. As described above, one of the 1 st protective layer and the 2 nd protective layer may be a resin substrate used for producing the polarizing film.
The 1 st and 2 nd protective layers are formed of any suitable film that can be used as a protective layer for a polarizing film. Specific examples of the material as the main component of the film include cellulose resins such as Triacetylcellulose (TAC), polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, acetate resins, and the like transparent resins. Further, there may be mentioned thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, silicone and the like, ultraviolet-curable resins and the like. Further, for example, a glassy polymer such as a siloxane polymer can be cited. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO01/37007) may be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used, and for example, a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film may be, for example, an extrusion molded product of the resin composition.
When the polarizing plate 100 is applied to an image display device, the thickness of the protective layer (outer protective layer) disposed on the side opposite to the display panel is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and still more preferably 10 μm to 60 μm. When the surface treatment is performed, the thickness of the outer protective layer is a thickness including the thickness of the surface treatment layer.
When the polarizing plate 100 is applied to an image display device, the thickness of the protective layer (inner protective layer) disposed on the display panel side is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and still more preferably 10 μm to 60 μm. In 1 embodiment, the inner protective layer is a retardation layer having any suitable phase difference value. In this case, the in-plane retardation Re (550) of the retardation layer is, for example, 110nm to 150 nm. "Re (550)" is an in-plane retardation measured at 23 ℃ with light having a wavelength of 550nm, represented by the formula: re ═ x-ny) × d. Here, "nx" is a refractive index in a direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), "nz" is a refractive index in the thickness direction, and "d" is the thickness (nm) of the layer (film).
C. Method for producing polarizing film
The method for manufacturing a polarizing film according to 1 embodiment of the present invention includes: coating a PVA resin solution on one side of a long thermoplastic resin base material and drying the PVA resin solution to form a PVA resin layer, thereby forming a laminate; stretching and dyeing the laminate to form a polarizing film from the PVA resin layer; and introducing a low-boiling alcohol into the polarizing film. By introducing a low-boiling alcohol, a polarizing film having excellent durability in a high-temperature and high-humidity environment can be realized. Preferably, the PVA-based resin solution further contains a halide. Preferably, the above-mentioned manufacturing method includes subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order, the drying shrinkage treatment shrinking the laminate by 2% or more in the width direction by heating while conveying the laminate in the longitudinal direction. In this case, the introduction of the low boiling point alcohol may be preferably performed between the stretching treatment in water and the drying shrinkage treatment. The content of the halide in the PVA-based resin solution (as a result, the PVA-based resin layer) is preferably 5 to 20 parts by weight based on 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably carried out using a heated roller, and the temperature of the heated roller is preferably 60 to 120 ℃. The shrinkage in the width direction of the laminate by the drying shrinkage treatment is preferably 2% or more. According to such a production method, the polarizing film described in the above item a can be obtained. In particular, a polarizing film having excellent optical characteristics (typically, monomer transmittance and unit absorbance) can be obtained by producing a laminate having a PVA-based resin layer containing a halide, stretching the laminate in multiple stages including air-assisted stretching and underwater stretching, and heating the stretched laminate with a heating roller.
Preparation of C-1. laminate
As a method for producing a laminate of the thermoplastic resin substrate and the PVA-based resin layer, any appropriate method can be adopted. Preferably, a PVA-based resin layer is formed on the thermoplastic resin substrate by applying a coating solution containing a halide and a PVA-based resin to the surface of the thermoplastic resin substrate and drying the coating solution. As described above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight based on 100 parts by weight of the PVA-based resin.
As a method for applying the coating liquid, any appropriate method can be adopted. Examples of the coating method include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating). The coating and drying temperature of the coating liquid is preferably 50 ℃ or higher.
The thickness of the PVA resin layer is preferably 3 to 40 μm, and more preferably 3 to 20 μm.
Before the PVA-based resin layer is formed, the thermoplastic resin substrate may be subjected to a surface treatment (for example, corona treatment), 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.
C-1-1. thermoplastic resin base Material
As the thermoplastic resin substrate, any suitable thermoplastic resin film can be used. Details of the thermoplastic resin base material are described in, for example, japanese patent laid-open No. 2012-73580. The entire disclosure of this publication is incorporated herein by reference.
C-1-2 coating liquid
The coating liquid contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution obtained by dissolving the halide and the PVA-based resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferable. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. At such a resin concentration, a uniform coating film can be formed 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 based on 100 parts by weight of the PVA-based resin.
Additives may be compounded in the coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the PVA-based resin layer obtained.
As the PVA-based resin, any suitable resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are listed. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K6726-. By using the PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.
The average polymerization degree of the PVA-based resin can be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K6726-.
As the halide, any suitable halide can be used. For example, iodide and sodium chloride are mentioned. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.
The amount of the halide in the coating liquid is preferably 5 to 20 parts by weight based on 100 parts by weight of the PVA-based resin, and more preferably 10 to 15 parts by weight based on 100 parts by weight of the PVA-based resin. If the amount of the halide exceeds 20 parts by weight based on 100 parts by weight of the PVA-based resin, the halide may bleed out, and the polarizing film finally obtained may be opaque.
In general, the orientation of polyvinyl alcohol molecules in a PVA-based resin is increased by stretching the PVA-based resin layer, but when the stretched PVA-based resin layer is immersed in a liquid containing water, the orientation of polyvinyl alcohol molecules may be disordered and the orientation may be decreased. In particular, when a laminate of a thermoplastic resin and a PVA-based resin layer is stretched in boric acid water, the orientation degree tends to be remarkably decreased when the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin. For example, stretching of a PVA film itself in boric acid water is generally performed at 60 ℃, while stretching of a laminate of a-PET (thermoplastic resin substrate) and a PVA-based resin layer is performed at a high temperature of about 70 ℃, and in this case, the orientation of PVA at the initial stage of stretching is reduced at a stage before it rises due to underwater stretching. In contrast, by producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate and stretching the laminate at a high temperature in air (auxiliary stretching) before stretching the laminate in boric acid water, crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, disorder of the orientation of the polyvinyl alcohol molecules and reduction of the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical properties of the polarizing film obtained through a treatment step of immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment.
C-2 auxiliary stretching treatment in air
In particular, in order to obtain high optical properties, a 2-stage stretching method combining dry stretching (auxiliary stretching) and boric acid underwater stretching is selected. By introducing the auxiliary stretching as in the 2-stage stretching, the thermoplastic resin substrate can be stretched while suppressing crystallization, and the problem of the reduction in stretchability due to excessive crystallization of the thermoplastic resin substrate in the subsequent boric acid underwater stretching can be solved, and the laminate can be stretched at a high ratio. Further, when a PVA-based resin is coated on a thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, the coating temperature needs to be lowered as compared with the case where the PVA-based resin is usually coated on a metal roll, and as a result, there is a problem that crystallization of the PVA-based resin is relatively lowered and sufficient optical characteristics cannot be obtained. In contrast, by introducing the auxiliary stretching, even when the PVA-based resin is applied to the thermoplastic resin, the crystallinity of the PVA-based resin can be improved, and high optical characteristics can be achieved. Further, by simultaneously improving the orientation of the PVA-based resin in advance, when the PVA-based resin is immersed in water in the subsequent dyeing step or stretching step, problems such as reduction in the orientation and dissolution of the PVA-based resin can be prevented, and high optical properties can be achieved.
The stretching method of the in-air auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter) or free-end stretching (for example, a method of uniaxially stretching a laminate by passing the laminate between rolls having different peripheral speeds), and the free-end stretching is actively employed for obtaining high optical characteristics. In 1 embodiment, the in-flight stretching treatment includes a heated roller stretching step of stretching the laminate by a difference in peripheral speed between heated rollers while conveying the laminate in the longitudinal direction thereof. The in-air stretching process typically includes a zone stretching process and a heated roll stretching process. The order of the area stretching step and the heating roller stretching step is not limited, and the area stretching step may be performed first or the heating roller stretching step may be performed first. The zone stretching process may be omitted. In 1 embodiment, the zone stretching step and the heating roller stretching step are performed in this order. In another embodiment, stretching is performed in a tenter stretching machine by holding the film end and extending the distance between the tenters in the flow direction (the extension of the distance between the tenters is the stretching magnification). At this time, the distance of the tenter in the width direction (the direction perpendicular to the flow direction) is set so as to be arbitrarily close to each other. The draw ratio in the flow direction can be preferably set so as to draw closer to the free end. In the case of free end stretching, the shrinkage in the width direction (1/stretching ratio)1/2To calculate.
The in-air auxiliary stretching may be performed in one stage or may be performed in multiple stages. When the stretching is performed in multiple stages, the stretching ratio is the product of the stretching ratios in the respective stages. The stretching direction in the in-air auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.
The stretching ratio of the aerial auxiliary stretching is preferably 2.0 to 3.5 times. The maximum stretching ratio in the combination of the air-assisted stretching and the underwater stretching is preferably 5.0 times or more, more preferably 5.5 times or more, and still more preferably 6.0 times or more, with respect to the original length of the laminate. In the present specification, the "maximum stretching ratio" refers to the stretching ratio immediately before the laminate breaks, and refers to the stretching ratio at which the laminate is separately observed to break, and is a value lower than that by 0.2.
The stretching temperature of the in-air auxiliary stretching may 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 not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably not less than the glass transition temperature (Tg) +10 ℃ of the thermoplastic resin substrate, and particularly preferably not less than Tg +15 ℃. On the other hand, the upper limit of the stretching temperature is preferably 170 ℃. By stretching at such a temperature, rapid progress of crystallization of the PVA-based resin can be suppressed, and defects caused by the crystallization (for example, inhibition of orientation of the PVA-based resin layer due to stretching) can be suppressed.
C-3 insolubilization treatment, dyeing treatment and crosslinking treatment
If necessary, after the in-air auxiliary stretching treatment, the insolubilization treatment is performed before the stretching treatment in water and the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically, iodine). If necessary, a crosslinking treatment is performed after the dyeing treatment and before the stretching treatment in water. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. Details of the insolubilization treatment, the dyeing treatment and the crosslinking treatment are described in, for example, japanese patent laid-open No. 2012-73580 (described above).
C-4 stretching treatment in water
The underwater stretching treatment is performed by immersing the laminate in a stretching bath. The stretching in water can be performed at a temperature lower than the glass transition temperature (typically, about 80 ℃) of the thermoplastic resin substrate or the PVA-based resin layer, and the PVA-based resin layer can be stretched at a high magnification while suppressing crystallization thereof. As a result, a polarizing film having excellent optical characteristics can be produced.
Any suitable method may be used for stretching the laminate. Specifically, the stretching may be performed at a fixed end or at a free end (for example, a method of passing the laminate between rollers having different peripheral speeds to perform uniaxial stretching). Free end stretching is preferably chosen. The stretching of the laminate may be performed in one stage or may be performed in multiple stages. When the stretching is performed in multiple stages, the stretching ratio (maximum stretching ratio) of the laminate described later is the product of the stretching ratios in the respective stages.
The underwater stretching is preferably performed by immersing the laminate in an aqueous boric acid solution (boric acid underwater stretching). By using the aqueous boric acid solution as the stretching bath, rigidity that resists the tension applied during stretching and water resistance that does not dissolve in water can be imparted to the PVA-based resin layer. Specifically, boric acid generates tetrahydroxyborate anions in an aqueous solution and crosslinks with the PVA-based resin through hydrogen bonds. As a result, the PVA-based resin layer can be provided with rigidity and water resistance and can be stretched well, and a polarizing film having excellent optical characteristics can be produced.
The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, and particularly preferably 3 to 5 parts by weight, based on 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher characteristics can be obtained. In addition to boric acid or a borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent may be used.
Preferably, the stretching bath (aqueous boric acid solution) is mixed with an iodide. By adding an iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of the iodide are as described above. The concentration of the iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of water.
The drawing temperature (liquid temperature of the drawing bath) is preferably 40 to 85 ℃ and more preferably 60 to 75 ℃. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while dissolution thereof is suppressed. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ℃ or higher from the viewpoint of the relationship with the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ℃, there is a possibility that the thermoplastic resin substrate cannot be satisfactorily stretched even when plasticization of the thermoplastic resin substrate by water is considered. On the other hand, as the temperature of the stretching bath is higher, the solubility of the PVA-based resin layer becomes higher, and there is a fear that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
The stretching ratio by underwater stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretch ratio of the laminate is preferably 5.0 times or more, and more preferably 5.5 times or more, based on the original length of the laminate. By achieving such a high stretching ratio, a polarizing film having very excellent optical properties can be produced. Such a high stretch ratio can be achieved by using an underwater stretching method (boric acid underwater stretching).
C-5 introduction of Low-boiling alcohols
In the embodiment of the present invention, the low boiling point alcohol is introduced after the underwater stretching treatment (and typically before the drying shrinkage treatment described later). The introduction of the low-boiling alcohol may be carried out by any suitable means. For example, the laminate may be immersed in a treatment liquid containing a low boiling point alcohol, or the treatment liquid containing a low boiling point alcohol may be applied to the polarizing film surface of the laminate. Typically, the introduction of the low boiling point alcohol may be performed by impregnation. The impregnation may be carried out by any suitable means. For example, a low boiling point alcohol may be added to a cleaning bath of the cleaning treatment to prepare a bath of the treatment liquid, and a bath of the treatment liquid may be used instead of the cleaning bath, or a bath of the treatment liquid may be separately provided from the cleaning bath. Typically, a low boiling point alcohol may be added to the cleaning bath (cleaning liquid) of the cleaning treatment. The concentration of the low-boiling alcohol in the treatment liquid (cleaning liquid) is preferably 5 to 35 wt%.
C-6 drying shrinkage treatment
The drying shrinkage treatment may be preferably performed after the introduction of the low boiling point alcohol. By performing the drying shrinkage treatment after the introduction of the low-boiling point alcohol, the drying efficiency can be improved, and as a result, the orientation of the PVA can be improved.
The drying and shrinking treatment may be performed by heating the entire region to heat the region, or may be performed by heating the transport roller (using a so-called hot roller) (hot roller drying method). Both are preferably used. By drying with a heating roller, the laminate can be effectively prevented from curling by heating, and a polarizing film having excellent appearance can be produced. Specifically, by drying the laminate in a state of being along the heating roller, the crystallization of the thermoplastic resin substrate can be effectively promoted to increase the crystallinity, and the crystallinity of the thermoplastic resin substrate can be favorably increased even at a low drying temperature. As a result, the thermoplastic resin substrate has increased rigidity, and is able to withstand shrinkage of the PVA-based resin layer due to drying, and curling can be suppressed. Further, since the laminate can be dried while maintaining a flat state by using the heating roller, not only curling but also wrinkles can be suppressed. At this time, the laminate is shrunk in the width direction by the drying shrinkage treatment, whereby the optical properties can be improved. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage in the width direction of the laminate by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.
Fig. 2 is a schematic diagram showing an example of the drying shrinkage treatment. In the drying shrinkage process, the stacked body 200 is dried while being conveyed by the conveying rollers R1 to R6 and the guide rollers G1 to G4 which are heated to a predetermined temperature. In the illustrated example, the conveying rollers R1 to R6 are disposed so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but the conveying rollers R1 to R6 may be disposed so as to continuously heat only one surface (for example, the surface of the thermoplastic resin substrate) of the laminate 200.
The drying condition can be controlled by adjusting the heating temperature of the conveying roller (temperature of the heating roller), the number of heating rollers, the contact time with the heating roller, and the like. The temperature of the heating roller is preferably 60 to 120 ℃, more preferably 65 to 100 ℃, and particularly preferably 70 to 80 ℃. At such a temperature, the appearance of the obtained polarizing film can be satisfactorily maintained. Further, the orientation of the PVA can be improved while maintaining the appearance by the synergistic effect with the effect of the low-boiling alcohol. Further, an optical laminate which can satisfactorily suppress curling by increasing the crystallinity of the thermoplastic resin and has extremely excellent durability can be produced. The temperature of the heating roller may be measured by a contact thermometer. In the example of the figure, 6 conveying rollers are provided, but there is no particular limitation as long as there are a plurality of conveying rollers. The number of the conveying rollers is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 to 300 seconds, more preferably 1 to 20 seconds, and still more preferably 1 to 10 seconds.
The heating roller may be disposed in a heating furnace (e.g., an oven) or may be disposed in a general production line (room temperature environment). Preferably, the heating furnace is provided with an air blowing means. By using drying by the heating roller and hot air drying in combination, a rapid temperature change between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of the hot air drying is preferably 30 to 100 ℃. At such a temperature, the appearance of the polarizing film can be maintained satisfactorily. Further, the orientation of the PVA can be improved while maintaining the appearance by the synergistic effect with the effect of the low-boiling alcohol. The hot air drying time is preferably 1 to 300 seconds. The wind speed of the hot wind is preferably about 10m/s to 30 m/s. The wind speed is the wind speed in the heating furnace and can be measured by a digital wind speed meter of a miniature blade type.
C-7. others
The thermoplastic resin substrate/polarizing film laminate obtained as described above can be used as it is as a polarizing plate (the thermoplastic resin substrate can be used as a protective layer); the laminate may be used as a polarizing plate having a protective layer/polarizing film structure, in which the protective layer is laminated on the surface of the polarizing film of the laminate and then the thermoplastic resin substrate is peeled off; another protective layer may be laminated on the release surface of the thermoplastic resin substrate, and the laminate may be used as a polarizing plate having a protective layer/polarizing film/protective layer structure.
Examples
The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method of each property is as follows. Unless otherwise specified, "parts" and "%" in examples and comparative examples are based on weight.
(1) Thickness of
The measurement was carried out using an dry film thickness meter (product name "MCPD-3000" manufactured by Otsuka Denshi Co., Ltd.).
(2) Alcohol concentration of polarizing film
The polarizing films obtained in examples and comparative examples were cut into 10cm pieces2The sample was used as a measurement sample. After sealing the measurement sample in a 20mL headspace bottle, the ethanol-containing sample was heated at 175 ℃ and the isopropanol-containing sample at 215 ℃ for 30 minutes by a headspace sampler (HSS), and 1mL of the heated gas phase fraction was injected into a gas chromatograph (product name "6890N" manufactured by Agilent TechNologies) to calculate the alcohol content from the peak area corresponding to each alcohol type by the following calibration curve.
Ethanol standard curve
y＝4.743E+00x+3.105E-02
Standard curve of isopropanol
y＝4.565E+00x+8.922E-03
(3) Transmittance and degree of polarization of monomer
For the polarizing plates (protective film/polarizing film) of examples and comparative examples, the monomer transmittance Ts, parallel transmittance Tp and orthogonal transmittance Tc measured by an ultraviolet-visible spectrophotometer (Otsuka electronic LPF-200) were respectively used as Ts, Tp and Tc of the polarizing film. These Ts, Tp and Tc are Y values measured with a 2-degree field of view (C light source) of JISZ8701 and corrected for visual sensitivity. The refractive index of the protective film was 1.50, and the refractive index of the surface of the polarizing film opposite to the protective film was 1.53. The degree of polarization was determined from Tp and Tc obtained by the following equation.
Polarization degree (%) { (Tp-Tc)/(Tp + Tc) }1/2×100
Subsequently, the polarizing plate was subjected to a durability test at a temperature of 85 ℃ and a relative humidity of 85% for 120 hours. The degree of cross-transmittance polarization P after the durability test was determined in the same manner as described above120. The durability test was performed by putting a test sample in which the polarizing film side of the polarizing plate was bonded to a glass plate via an adhesive layer into a humidifying oven.
(4) Durability to humidification
The polarization degree P before and after the durability test according to the above (3)0And P120Then, Δ P was obtained by the following equation.
ΔP＝P120-P0
Since Δ P is a parameter that varies depending on the individual transmittance, it is necessary to compare the individual transmittances with the same polarizing plate before the test. Therefore, the durability under a high-temperature and high-humidity environment was evaluated based on comparative example 1 as follows.
Very good: in comparison with comparative example 1, Δ P was significantly large (the absolute value in the negative direction was significantly small)
O: in comparison with comparative example 1, Δ P was large (smaller absolute value in negative direction)
And (delta): Δ P was equivalent to that of comparative example 1
X: relative to comparative example 1, Δ P was small (larger absolute value in negative direction)
[ example 1]
As the thermoplastic resin substrate, a long amorphous ethylene terephthalate isophthalate copolymer film (thickness: 100 μm) having a Tg of about 75 ℃ was used. One surface of the resin substrate is subjected to corona treatment.
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (product name "GOHSEFIMER Z410" manufactured by japan synthetic chemical industries) were mixed at a ratio of 9: 1 to 100 parts by weight of the mixed PVA based resin, 13 parts by weight of potassium iodide was added to prepare an aqueous PVA solution (coating solution).
The aqueous PVA solution was applied to the corona-treated surface of the resin substrate and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was subjected to unidirectional stretching of the free end in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ℃ by a factor of 2.4 (in-air auxiliary stretching treatment).
Next, the laminate was cut into pieces of 15cm × 10cm in the auxiliary stretching axis direction, and the short sides of the cut laminate pieces were fixed with a dedicated stretching jig and immersed in an insolubilization bath (an aqueous solution of boric acid obtained by mixing 3 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).
Next, the polarizing film obtained finally was immersed in a dyeing bath (aqueous iodine solution prepared by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the polarizing film obtained finally became 43.0% ± 0.2% (dyeing treatment).
Next, the substrate was immersed in a crosslinking bath (aqueous boric acid solution prepared by adding 3 parts by weight of potassium iodide to 100 parts by weight of water and 5 parts by weight of boric acid) at a liquid temperature of 30 ℃ for 30 seconds (crosslinking treatment).
Thereafter, the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) so that the total stretching ratio became 5.5 times in the longitudinal direction (water stretching treatment) while being immersed in an aqueous boric acid solution (boric acid concentration: 4.0 wt%, potassium iodide: 5.0 wt%) having a liquid temperature of 70 ℃.
Thereafter, the laminate was immersed in a treatment bath (aqueous solution of 3 wt% potassium iodide and 5 wt% ethanol) at a liquid temperature of 20 ℃ for 3 seconds to clean the laminate and introduce ethanol into the PVA-based resin layer (polarizing film) (cleaning treatment and introduction of ethanol).
Thereafter, drying (drying treatment) was performed in an oven maintained at 60 ℃ for 4 minutes.
In this manner, a polarizing film having a thickness of 5.0 μm was formed on the resin substrate. A cycloolefin Film (product name "G-Film" manufactured by ZEON corporation) as a protective layer (protective Film) was laminated on the surface of the polarizing Film with a UV curable adhesive (thickness 1.0 μm), and then the resin substrate was peeled off to obtain a polarizing plate having a protective layer/polarizing Film structure. The concentration of ethanol in the polarizing film of the obtained polarizing plate was 45 ppm.
The monomer transmittance and Δ P of the obtained polarizing plate (substantially, polarizing film) are shown in table 1. The results of the evaluation (4) are shown in table 1.
[ example 2]
A polarizing plate was produced in the same manner as in example 1, except that the ethanol concentration in the treatment bath was changed to 20 wt%. The obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in example 1. The results are shown in Table 1.
[ example 3]
A polarizing plate was produced in the same manner as in example 1, except that the ethanol concentration in the treatment bath was changed to 25 wt%. The obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in example 1. The results are shown in Table 1.
[ example 4]
A polarizing plate was produced in the same manner as in example 1, except that the ethanol concentration in the treatment bath was changed to 2 wt%. The obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in example 1. The results are shown in Table 1.
[ example 5]
A polarizing plate was produced in the same manner as in example 4. The obtained polarizing plate was subjected to a durability test at a temperature of 60 ℃ and a relative humidity of 95% for 120 hours to obtain Δ P. The procedure of the durability test is as described in (3) above. The obtained Δ P was evaluated for durability as follows with reference to comparative example 3 (described later). The results are shown in Table 1.
Very good: in comparison with comparative example 3, Δ P was significantly large (the absolute value in the negative direction was significantly small)
O: in comparative example 3, Δ P was large (smaller absolute value in negative direction)
And (delta): Δ P is equivalent to that in comparative example 3
X: relative to comparative example 3, Δ P was small (larger absolute value in negative direction)
[ example 6]
A polarizing plate was produced in the same manner as in example 1. The obtained polarizing plate was subjected to the same evaluation as in example 5. The results are shown in Table 1.
[ example 7]
A polarizing plate was produced in the same manner as in example 2. The obtained polarizing plate was subjected to the same evaluation as in example 5. The results are shown in Table 1.
[ example 8]
A polarizing plate was produced in the same manner as in example 3. The obtained polarizing plate was subjected to the same evaluation as in example 5. The results are shown in Table 1.
[ example 9]
A polarizing plate was produced in the same manner as in example 3, except that the immersion time of the treatment bath was changed to 10 seconds. The obtained polarizing plate was subjected to the same evaluation as in example 5. The results are shown in Table 1.
[ example 10]
A polarizing plate was produced in the same manner as in example 5, except that the concentration of the dyeing bath was adjusted so that the monomer transmittance of the polarizing film became 42.0% ± 0.2%, and the alcohol type of the cleaning treatment bath was isopropyl alcohol and the concentration thereof was 5% by weight. The obtained polarizing plate was subjected to the same durability test as in example 5, and evaluated according to the following criteria. The results are shown in Table 1.
Very good: in comparison with comparative example 4, Δ P was significantly large (the absolute value in the negative direction was significantly small)
O: in comparative example 4, Δ P was large (smaller absolute value in negative direction)
And (delta): Δ P is equivalent to that in comparative example 4
X: relative to comparative example 4, Δ P was small (larger absolute value in negative direction)
[ example 11]
A polarizing plate was produced in the same manner as in example 10, except that the isopropyl alcohol concentration in the treatment bath was changed to 20 wt%. The obtained polarizing plate was subjected to the same evaluation as in example 10. The results are shown in Table 1.
[ example 12]
A polarizing plate was produced in the same manner as in example 10, except that the isopropyl alcohol concentration in the treatment bath was changed to 25 wt%. The obtained polarizing plate was subjected to the same evaluation as in example 10. The results are shown in Table 1.
Comparative example 1
A polarizing plate was produced in the same manner as in example 1, except that no low-boiling alcohol was added to the cleaning bath (cleaning solution). The obtained polarizing plate (or polarizing film) was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 2
A polarizing plate was produced in the same manner as in example 1, except that no low-boiling alcohol was added to the cleaning bath (cleaning solution) and the temperature of the drying oven after the cleaning bath was set to 130 ℃. However, since the film is wrinkled and/or dented with heat shrinkage, a measurement sample that can be evaluated cannot be obtained.
Comparative example 3
A polarizing plate was produced in the same manner as in comparative example 1. The obtained polarizing plate was subjected to the same evaluation as in example 5. The results are shown in Table 1.
Comparative example 4
A polarizing plate was produced in the same manner as in comparative example 1, except that the concentration of the dyeing bath was adjusted so that the monomer transmittance of the polarizing film became 42.0% ± 0.2%. The obtained polarizing plate was subjected to the same evaluation as in example 10. The results are shown in Table 1.
[ Table 1]
Boiling point of ethanol: 78.29 deg.C
Boiling point of isopropyl alcohol: 82.5 deg.C
[ reference example 1]
A long roll of a PVA-based resin film (manufactured by KURARAY co., LTD, product name "PS 4500") having a thickness of 45 μm was uniaxially stretched in the longitudinal direction by a roll stretcher so that the total stretching magnification became 6.0 times, and was subjected to swelling, dyeing, crosslinking, and washing treatments, and finally, drying treatments, thereby producing a polarizing film having a thickness of 17 μm. That is, a thick polarizing film into which no low-boiling alcohol is introduced is produced. A cycloolefin film (product name "ZT 12" manufactured by ZEON corporation) as a protective layer (protective film) and an acrylic resin film were respectively bonded to both sides of the polarizing film with a UV curable adhesive (thickness 1.0 μm), and an adhesive layer was further provided on the surface of the cycloolefin film, thereby obtaining a polarizing plate having a structure of protective layer/polarizing film/protective layer/adhesive layer. Δ P was obtained by the following formula, except that the conditions of the durability test were 65 ℃ temperature, 90% relative humidity and 500 hours of the test time, and the same evaluation as in example 1 was performed. The results are shown in Table 2. The durability of reference example 2 described later was evaluated based on Δ P in this reference example.
ΔP＝P500-P0
[ reference example 2]
A polarizing film having a thickness of 5 μm was produced by subjecting a laminate of a PVA-based resin/resin substrate used in example 1 to uniaxial stretching in the longitudinal direction by a roll stretcher so that the total stretching ratio was 2.4 times, swelling, dyeing, crosslinking, washing, and finally drying. That is, a thin polarizing film into which no low-boiling alcohol is introduced is produced. A pressure-sensitive adhesive layer was provided on the surface of the polarizing film in the same manner as in reference example 1 to obtain a polarizing plate having a structure of protective layer/polarizing film/protective layer/pressure-sensitive adhesive layer. The polarizing plate was subjected to the same evaluation as in reference example 1 except that the polarizing plate was used, and the evaluation was performed according to the following criteria. The results are shown in Table 2.
Very good: with respect to reference example 1, Δ P was significantly large (the absolute value in the negative direction was significantly small)
O: with respect to reference example 1, Δ P was large (smaller absolute value in negative direction)
And (delta): Δ P is equivalent to that in reference example 1
X: with respect to reference example 1, Δ P was small (larger absolute value in negative direction)
[ Table 2]
As is clear from table 1, the polarizing plate (polarizing film) of the example of the present invention has excellent durability in a high-temperature and high-humidity environment by containing a predetermined amount of low-boiling-point alcohol. Further, as is clear from table 2, the durability under a high-temperature and high-humidity environment is a problem specific to a thin polarizing film.
Industrial applicability
The polarizing film and the polarizing plate of the present invention are suitably used for a liquid crystal display device.
Description of the reference numerals
10 polarizing film
20 st protective layer
30 nd 2 protective layer
100 polarizing plate
Claims (7)
1. A polarizing film comprising a polyvinyl alcohol resin film containing iodine, said polarizing film having a thickness of 8 [ mu ] m or less and containing 5 to 350ppm of an alcohol having a boiling point of less than 100 ℃.
2. The polarized film according to claim 1, wherein the alcohol having a boiling point lower than 100 ℃ is at least 1 selected from the group consisting of methanol, ethanol, n-propanol and isopropanol.
3. A polarizing plate, comprising: the polarizing film of claim 1 or 2, and a protective layer disposed on at least one side of the polarizing film.
4. The method for producing a polarizing film of claim 1 or 2, comprising:
forming a polyvinyl alcohol resin layer on one side of a long thermoplastic resin base material to form a laminate;
stretching and dyeing the laminate to form a polarizing film from the polyvinyl alcohol resin layer; and
an alcohol having a boiling point of less than 100 ℃ is introduced into the polarizing film.
5. The manufacturing method according to claim 4, comprising immersing the polarizing film in a treatment liquid containing the alcohol having the boiling point lower than 100 ℃.
6. The manufacturing method according to claim 4 or 5, further comprising heating the laminate after introducing the alcohol having a boiling point of less than 100 ℃ to the polarizing film.
7. The production method according to any one of claims 4 to 6, wherein the stretching comprises underwater stretching.
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| JP2019-042996 | 2019-03-08 | ||
| JP2019042996 | 2019-03-08 | ||
| PCT/JP2020/006245 WO2020184082A1 (en) | 2019-03-08 | 2020-02-18 | Polarizing film, polarizing plate, and polarizing film production method |
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| JP2008165200A (en) * | 2006-12-08 | 2008-07-17 | Nitto Denko Corp | Method for manufacturing polarizer, polarizer, polarizing plate, optical film, and image display device |
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| JPS5783360A (en) * | 1980-11-11 | 1982-05-25 | Tipton Mfg Corp | Barrel polishing method |
| JP2001343521A (en) | 2000-05-31 | 2001-12-14 | Sumitomo Chem Co Ltd | Polarizing plate and method for manufacturing the same |
| TWI271556B (en) * | 2005-11-15 | 2007-01-21 | Daxon Technology Inc | Method of making a polarizing sheet |
| JP5568800B2 (en) * | 2010-09-08 | 2014-08-13 | 日東電工株式会社 | Method for producing water-resistant optically anisotropic film and image display device |
| KR20220098344A (en) * | 2019-11-11 | 2022-07-12 | 닛토덴코 가부시키가이샤 | Polarizing film, polarizing plate and image display device |
| JPWO2021095526A1 (en) * | 2019-11-11 | 2021-05-20 |
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2020
- 2020-02-18 WO PCT/JP2020/006245 patent/WO2020184082A1/en active Application Filing
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| JP2008165200A (en) * | 2006-12-08 | 2008-07-17 | Nitto Denko Corp | Method for manufacturing polarizer, polarizer, polarizing plate, optical film, and image display device |
| JP2008197510A (en) * | 2007-02-15 | 2008-08-28 | Nitto Denko Corp | Method for producing polarizer, and image display device |
| JP2008287207A (en) * | 2007-04-16 | 2008-11-27 | Nitto Denko Corp | Polarizing plate, optical film and image display |
| CN102338902A (en) * | 2010-09-03 | 2012-02-01 | 日东电工株式会社 | Polarizing film, optical film laminate comprising polarizing film, and stretched laminate for manufacturing the same |
| CN104635290A (en) * | 2013-11-14 | 2015-05-20 | 日东电工株式会社 | Polarizing film and method for manufacturing polarizing film |
| JP6409142B1 (en) * | 2018-02-13 | 2018-10-17 | 日東電工株式会社 | Polarizing film, polarizing plate, and manufacturing method of polarizing film |
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| JPWO2020184082A1 (en) | 2021-11-25 |
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| TW202039599A (en) | 2020-11-01 |
| WO2020184082A1 (en) | 2020-09-17 |
| KR20210136019A (en) | 2021-11-16 |
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