CN111902751A - Polarizer and polarizing plate - Google Patents

Polarizer and polarizing plate Download PDF

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Publication number
CN111902751A
CN111902751A CN201980021191.0A CN201980021191A CN111902751A CN 111902751 A CN111902751 A CN 111902751A CN 201980021191 A CN201980021191 A CN 201980021191A CN 111902751 A CN111902751 A CN 111902751A
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polarizer
pva
content
boric acid
based resin
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猿桥友斗
泽田浩明
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Nitto Denko Corp
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Nitto Denko Corp
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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
    • 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
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • 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
    • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (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
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • 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
    • 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
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Nonlinear Science (AREA)
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  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Polarising Elements (AREA)

Abstract

The invention provides a polarizer which is thin and has very excellent heat resistance. The polarizer of the present invention is composed of a polyvinyl alcohol resin film containing iodine, wherein the content of free boric acid is 0.4 wt% or less.

Description

Polarizer and polarizing plate
Technical Field
The present invention relates to a polarizer and a polarizing plate.
Background
In a liquid crystal display device, which is a typical image display device, polarizers (substantially polarizing plates including polarizers) are disposed on both sides of a liquid crystal cell in accordance with an image forming method. Polarizers are typically manufactured by dyeing a polyvinyl alcohol (PVA) -based resin film with a dichroic substance such as iodine (for example, patent documents 1 and 2). In recent years, there has been an increasing demand for thinner image display devices. Therefore, further thinning of the polarizer is also required. However, the thinner the polarizer is, the lower the heat resistance is, and there is a problem that the optical characteristics are easily changed in a high temperature environment.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5048120
Patent document 2: japanese patent laid-open publication No. 2013-156391
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the conventional problems, and a main object thereof is to provide a polarizer which is thin and has very excellent heat resistance.
Means for solving the problems
The polarizer of the present invention is composed of a polyvinyl alcohol resin film containing iodine,
the content of free boric acid is 0.4 wt% or less.
In one embodiment, the polarizer has a thickness of 7 μm or less.
In one embodiment, the polarizer has an iodine content of 10 to 25 wt%.
According to another aspect of the present invention, there is provided a polarizing plate. The polarizing plate includes: the polarizer described above, and a protective film laminated on one or both sides of the polarizer.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a polarizer having a thin thickness and extremely excellent heat resistance, which has been expected for a long time but has not been achieved, can be realized by setting the content of free boric acid contained in the polarizer to 0.4% by weight or less.
Detailed Description
Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
A. Polarizer
A-1. overview of polarizers
A polarizer according to an embodiment of the present invention is composed of a polyvinyl alcohol (PVA) -based resin film containing iodine, and has a free boric acid content of 0.4 wt% or less.
The free boric acid content of the polarizer is preferably 0.39 wt% or less, more preferably 0.38 wt% or less. The lower limit of the content of free boric acid is, for example, 0.01% by weight. As described above, one of the features of the present invention is to pay attention not to the content of all boric acid contained in the polarizer but to the content of free boric acid. When the content of free boric acid in the polarizer is in the above range, the polarizer can be excellent in heat resistance and can suppress a change in optical characteristics (for example, monomer transmittance) in a high-temperature environment. The content of free boric acid in the polarizer can be typically determined by the following method using inductively coupled plasma emission spectrometry (ICP-AES). Specifically, a measurement sample was obtained by freezing and pulverizing a polarizer, and the measurement sample was mixed with a mixed solution of 2-ethyl-1, 3-hexanediol/chloroform (volume ratio: 10/90), and the mixture was filtered to obtain a filtrate, and the boron content in the filtrate was quantified by using an ICP emission spectrometer. The obtained boron content was regarded as being derived from all boric acid, the boric acid in the filtrate was regarded as being derived from all free boric acid from the polarizer, and the boron content was converted into the free boric acid content of the polarizer. In one embodiment, the content of free boric acid in the polarizer can be adjusted to be within the above range by performing a drying treatment at a temperature lower than a conventional heating temperature (preferably 50 ℃ or lower) in a drying step in the method for producing a polarizer as described later.
The upper limit of the thickness of the polarizer is 7 μm in one embodiment, 3 μm in another embodiment, and 2 μm in yet another embodiment. The lower limit of the thickness is 0.5 μm in one embodiment, 0.6 μm in another embodiment, and 0.8 μm in yet another embodiment. According to the embodiments of the present invention, even if the polarizer is thin, a desired monomer transmittance can be achieved as described later.
The iodine content of the polarizer can be suitably set so as to achieve both sufficient polarization performance and the most preferable monomer transmittance. The iodine content is preferably 10 to 25% by weight, more preferably 15 to 25% by weight. According to the embodiments of the present invention, a polarizer having an extremely high iodine content as described above can realize extremely excellent heat resistance which has been difficult to realize in the past. More particularly, a polarizer with extremely high iodine content can be usedIn the above manner, the change of the optical characteristics in a high-temperature environment is significantly suppressed. The "iodine content" in the present specification means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine is treated with iodide ion (I) in the polarizer-) Polyiodide (I)3 -、I5 -) The iodine content in the present specification means the amount of iodine including all of these forms. The iodine content can be calculated using a standard curve method such as fluorescent X-ray analysis. The polyiodide exists in the polarizer in a state of forming a PVA-iodine complex. By forming such a complex, absorption dichroism can be exhibited in a wavelength range of visible light. Specifically, a complex of PVA and triiodide ion (PVA. I)3 -) Has an absorption peak around 470 nm; complex of PVA and pentaiodide ion (PVA. I)5 -) Has an absorption peak around 600 nm. As a result, the polyiodide can absorb light in a wide range of visible light depending on its form. On the other hand, iodide ion (I)-) There is an absorption peak near 230nm, which is not substantially correlated with the absorption of visible light. Therefore, the polyiodide existing in a complex state with PVA is mainly related to the absorption performance of the polarizer.
The polarizer preferably has a monomer transmittance (Ts) of 30.0 to 43.0%, more preferably 35.0 to 41.0%. The degree of polarization of the polarizer is preferably 99.9% or more, more preferably 99.95% or more, and still more preferably 99.98% or more. By setting the transmittance of the monomer to be low and the polarization degree to be high, the contrast can be improved, and the black display can be displayed more black, so that an image display device having excellent image quality can be realized. The monomer transmittance is a value measured by a spectrophotometer with an integrating sphere. The monomer transmittance is a Y value obtained by measuring and correcting visibility by a 2-degree field of view (C light source) according to JIS Z8701, and is measured, for example, by an integrating-sphere-equipped spectrophotometer (manufactured by JASCO corporation, product name: V7100).
A-2. PVA-based resin film
Examples of the PVA-based resin forming the PVA-based resin film include: polyvinyl alcohol, ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% or more and less than 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 K6726-1994. By using the PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained. When the degree of saponification is too high, there is a fear of gelation.
The average polymerization degree of the PVA-based resin may be appropriately selected depending on the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average polymerization degree can be determined by JIS K6726-1994.
The thickness of the PVA-based resin film is not particularly limited, and may be set according to a desired polarizer thickness. The thickness of the PVA-based resin film is, for example, 10 to 200. mu.m.
In one embodiment, the PVA-based resin film may be a PVA-based resin layer formed on the substrate. The laminate of the substrate and the PVA-based resin layer can be obtained, for example, by a method of applying a coating solution containing the PVA-based resin to the substrate, a method of laminating the PVA-based resin film to the substrate, or the like.
B. Method for manufacturing polarizer
B-1. overview of the method for manufacturing polarizer
The method for producing a polarizer according to an embodiment of the present invention includes at least stretching and dyeing a PVA-based resin film. Typically, the production method includes a step of preparing a PVA-based resin film, a stretching step, a dyeing step, a crosslinking step, a washing step, and a drying step. If necessary, a swelling step may be provided before the stretching step. The steps using the PVA-based resin film may be performed in any suitable order and time. Therefore, the respective steps may be performed in the order described above, or may be performed in an order different from the order described above. The 1 step may be performed as many times as required. The other steps (e.g., the insolubilization step) may be performed at any appropriate time. In the case of a PVA type resin layer having a PVA type resin film formed on a substrate, a laminate of the substrate and the PVA type resin layer may be subjected to the above-mentioned step.
The respective steps will be described below, but as described above, the respective steps may be performed in any appropriate order and are not limited to the order described.
B-2 stretching step
In the stretching step, the PVA-based resin film is typically stretched 3 to 7 times in one direction. The stretching direction may be a longitudinal direction (MD direction) of the film or a width direction (TD direction) of the film. The stretching method may be dry stretching or wet stretching, or a combination thereof. Further, the PVA-based resin film may be stretched in the crosslinking step, the swelling step, the dyeing step, or the like. The stretching direction may correspond to the absorption axis direction of the polarizer obtained.
B-3 swelling step
The swelling step is usually performed before the dyeing step. The swelling step can be performed by, for example, immersing the PVA-based resin film in a swelling bath. The swelling bath may be water such as distilled water or pure water. The swelling bath may also contain any suitable other ingredients besides water. Examples of the other components include solvents such as alcohols, additives such as surfactants, and iodides. The iodide may be exemplified by: potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Potassium iodide is preferably used. The temperature of the swelling bath is, for example, 20 ℃ to 45 ℃. The immersion time is, for example, 10 seconds to 300 seconds.
B-4 dyeing Process
The dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. Preferably, the adsorption is performed by allowing a dichroic substance to adsorb. Examples of the adsorption method include: a method of immersing the PVA-based resin film in a dyeing liquid containing a dichroic material, a method of applying the dyeing liquid to the PVA-based resin film, and a method of spraying the dyeing liquid onto the PVA-based resin film. A method of immersing the PVA-based resin film in a dyeing solution is preferable. This is because the dichroic substance can be favorably adsorbed.
Examples of the dichroic substance include: iodine, dichroic dyes. Iodine is preferred. When iodine is used as the dichroic material, an aqueous iodine solution is preferably used as the dyeing liquid. The iodine content of the aqueous iodine solution is preferably 0.04 parts by weight to 5.0 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the aqueous iodine solution. Potassium iodide is preferably used as the iodide. The iodide content is preferably 0.3 to 15 parts by weight relative to 100 parts by weight of water.
The liquid temperature of the dyeing liquid during dyeing can be set to any appropriate value, for example, 20 to 50 ℃. When the PVA-based resin film is immersed in the dyeing liquid, the immersion time is, for example, 5 seconds to 5 minutes.
B-5. Cross-linking Process
In the crosslinking step, a boron compound is generally used as a crosslinking agent. Examples of boron compounds include: boric acid, borax, and the like. Boric acid is preferred. In the crosslinking step, the boron compound is usually used in the form of an aqueous solution.
When the aqueous boric acid solution is used, the boric acid concentration of the aqueous boric acid solution is, for example, 1 to 15% by weight, preferably 1 to 10% by weight. The boric acid aqueous solution may further contain an iodide such as potassium iodide, and a zinc compound such as zinc sulfate or zinc chloride.
The crosslinking step may be performed by any suitable method. Examples thereof include: a method of immersing the PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to the PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound to the PVA-based resin film. Preferably in an aqueous solution containing a boron compound.
The temperature of the solution for crosslinking is, for example, 25 ℃ or higher, preferably 30 to 85 ℃, and more preferably 40 to 70 ℃. The immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.
B-6 cleaning Process
The washing step is typically performed after the crosslinking step. The cleaning step is typically performed by immersing the PVA-based resin film in a cleaning liquid. A typical example of the cleaning liquid is pure water. Potassium iodide may also be added to the pure water.
The temperature of the cleaning liquid is, for example, 5 ℃ to 50 ℃. The immersion time is, for example, 1 to 300 seconds.
B-7. drying step
The drying step may be carried out by any suitable method. Examples of the drying method include: natural drying, air-blowing drying, reduced-pressure drying, heating drying, etc. Preferably, heat drying is used. In the case of heat drying, the heating temperature is preferably 50 ℃ or lower, more preferably 45 ℃ or lower, and particularly preferably 40 ℃ or lower, from the viewpoint of shortening the drying time. The lower limit of the heating temperature is not particularly limited, and is a lower limit temperature that can be set in the heating and drying device. For example 30 deg.c. The drying time is, for example, 20 seconds to 10 minutes. In one embodiment, the heat drying is performed in 2 stages or more. In this case, the heating temperature in at least any one stage is preferably within the above range. When the heating temperature is within the above range during the heat drying, a polarizer having very excellent heat resistance can be obtained.
C. Polarizing plate
The polarizer according to the embodiment of the present invention is typically used in a state in which a protective film is laminated on one side or both sides (i.e., as a polarizing plate). In actual use, the polarizing plate has an adhesive layer as the outermost layer. The adhesive layer typically becomes the outermost layer on the image display device side. On the adhesive layer, the separator is temporarily bonded in a peelable state, and the adhesive layer can be protected until the actual use to form a roll.
Any suitable resin film may be used for the protective film. Examples of the material for forming the resin film include: and cellulosic resins such as (meth) acrylic resins, cellulose resins such as cellulose diacetate and cellulose triacetate, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. The term "(meth) acrylic resin" means an acrylic resin and/or a methacrylic resin.
In one embodiment, the (meth) acrylic resin has a glutarimide structure. A (meth) acrylic resin having a glutarimide structure (hereinafter also referred to as a glutarimide resin) is described, for example, in the following documents: japanese patent application laid-open Nos. 2006-309033, 2006-317560, 2006-328329, 2006-328334, 2006-337491, 2006-337492, 2006-337493, 2006-337569, 2007-009182, 2009-161744 and 2010-284840. These descriptions are incorporated herein by reference.
When the polarizer is produced using a laminate of a substrate and a PVA-based resin layer, the polarizer can be used as a protective film without peeling the substrate. Alternatively, the protective film may be attached to the polarizer after the base material is peeled off.
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 characteristic is as follows.
(1) Variation of monomer transmittance Ts
The reflection type polarizers (product name "DBEF" manufactured by 3M) were bonded to the polarizers of the laminates obtained in the examples and comparative examples via an adhesive layer having a thickness of 1.0 μ M. Next, the thermoplastic resin substrate was peeled off, and then an alkali-free glass having a thickness of 1.3mm was bonded to the peeled surface via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, to obtain a test sample. The test specimen was heated at 80 ℃ for 200 hours (heat test). The monomer transmittances of the polarizer before and after the test were measured with a spectrophotometer with an integrating sphere (product name: V7100, manufactured by Nippon spectral Co., Ltd.). Then, the monomer transmittance change amount Ts was obtained from the monomer transmittance Ts0 before heating and the monomer transmittance Ts1 after the heating test using the following formula.
Ts(％)＝Ts1－Ts0
(2) Iodine content
The polarizing plates of the laminates obtained in examples and comparative examples were measured for fluorescent X-ray intensity (kcps) using a fluorescent X-ray analyzer (product name "ZSX-PRIMUS II" manufactured by Rigaku corporation, measurement diameter. phi.: 20 mm). On the other hand, the thickness (. mu.m) of the polarizer was measured using a spectroscopic thickness meter (available under the trade name "MCPD-3000" from Otsuka electronics Co.). From the obtained intensity and thickness of the fluorescent X-ray, the iodine content (% by weight) was determined by the following equation.
(iodine concentration) ═ 20.5 × (fluorescence X-ray intensity)/(film thickness)
The coefficient for calculating the iodine content varies depending on the measurement device, and can be obtained using an appropriate calibration curve.
(3) Content of free boric acid
The polarizers obtained in examples and comparative examples were cut into about 5mm square pieces with scissors, and 50mg of the pieces were filled into a sample container together with a steel ball. Then, the measurement sample was freeze-pulverized using a freeze-pulverization apparatus JFC-300 (manufactured by japan analytical industries, ltd.) under conditions of precooling for 7 minutes and vibrating for 5 minutes using liquid nitrogen as a refrigerant. The pulverized measurement sample was left at room temperature for about 30 minutes. The obtained measurement sample was mixed with 3.5mL of a mixed solution of 2-ethyl-1, 3-hexanediol/chloroform (volume ratio: 10/90), and the mixture was left at room temperature for 24 hours. The resulting mixture was filtered using a 0.45 μm filter. The resulting filtrate was heated on a hot plate to remove chloroform, and the residue was transferred to a Teflon (registered trademark) decomposition vessel, followed by addition of an acid and capping. The decomposition vessel is irradiated with microwaves to perform pressurized acidolysis. After the decomposition, ultrapure water was added to the reaction solution to a constant volume of 25mL, and the analysis was performed under the following quantitative conditions for boric acid.
< conditions for determining boric acid >
Device name: ICP emission spectrometer SPS-3520UV (Hitachi High-Tech Science Co., Ltd.)
Measuring wavelength: b249.848 nm
The obtained boron content was regarded as being derived from boric acid in total, and converted into a boric acid content. The boric acid content was taken as the free boric acid content of the polarizer.
[ example 1]
As the thermoplastic resin substrate, an amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of 75 ℃ was used. One side of the substrate was corona treated and coated with a 9: 1 (polymerization degree 4200, saponification degree 99.2 mol%) and an acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modified degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon synthetic chemical industries, Ltd., trade name "GOHSEFIMER Z200") were added to the aqueous solution, and the resulting solution was dried to form a PVA-based resin layer having a thickness of 11 μm, thereby obtaining a laminate.
The obtained laminate was stretched in a direction orthogonal to the longitudinal direction of the laminate at 140 ℃ in a 4.5-fold gas atmosphere using a tenter stretcher (stretching treatment).
Next, the laminate was immersed in a dyeing bath (aqueous solution having an iodine concentration of 1.4 wt% and a potassium iodide concentration of 9.8 wt%) at a liquid temperature of 25 ℃ for 12 seconds to be dyed (dyeing treatment).
Next, the laminate was immersed in a cleaning bath (pure water) at a liquid temperature of 25 ℃ for 6 seconds (1 st cleaning treatment).
Next, the substrate was immersed in a crosslinking bath (aqueous solution having a boron concentration of 1 wt% and a potassium iodide concentration of 1 wt%) at a liquid temperature of 60 ℃ for 16 seconds (crosslinking treatment).
Next, the laminate was immersed in a cleaning bath (aqueous solution having a potassium iodide concentration of 1 wt%) at a liquid temperature of 25 ℃ for 3 seconds (No. 2 cleaning treatment).
The laminate was then dried in an oven at 25 ℃ for 8 seconds (drying treatment No. 1).
Finally, the laminate was dried in an oven at 25 ℃ for 13 seconds (2 nd drying treatment), to obtain a laminate having a PVA-based resin layer (polarizer) with a thickness of 1.2 μm. The polarizer obtained had an iodine content of 18.5 wt.%, a free boric acid content of 0.32 wt.% and a monomer transmittance of 40.0%.
The obtained laminate was subjected to the evaluation of the above (1). The results are shown in Table 1.
[ example 2]
A laminate having a polarizer was obtained in the same manner as in example 1, except that the laminate was dried in an oven at 30 ℃. The polarizer obtained had an iodine content of 18.8 wt.%, a free boric acid content of 0.32 wt.% and a monomer transmittance of 39.9%. The obtained laminate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
[ example 3]
A laminate having a polarizer was obtained in the same manner as in example 1, except that the laminate was dried in an oven of 40 ℃. The polarizer obtained had an iodine content of 18.6% by weight, a free boric acid content of 0.39% by weight and a monomer transmittance of 39.9%. The obtained laminate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 1
A laminate having a polarizer was obtained in the same manner as in example 3, except that the laminate was dried in an oven at 60 ℃. The polarizer obtained had an iodine content of 19.1% by weight, a free boric acid content of 0.45% by weight and a monomer transmittance of 39.9%. The obtained laminate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 2
A laminate having a polarizer was obtained in the same manner as in comparative example 1, except that the laminate was dried in an oven at 50 ℃ in the first drying treatment 1. The polarizer obtained had an iodine content of 19.2% by weight, a free boric acid content of 0.48% by weight and a monomer transmittance of 39.9%. The obtained laminate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 3
A laminate having a polarizer was obtained in the same manner as in comparative example 1, except that the laminate was dried in an oven at 60 ℃. The polarizer obtained had an iodine content of 19.3% by weight, a free boric acid content of 0.57% by weight and a monomer transmittance of 40.0%. The obtained laminate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
[ Table 1]
Figure BDA0002694447070000101
As is clear from table 1, the polarizers of the examples according to the present invention have a smaller amount of change in the transmittance of the monomer after the heat test and have very excellent heat resistance, as compared with the polarizers of the comparative examples. Specifically, the polarizer of the example has Ts of 0.75% to 0.80%, and when Ts is a value of this degree, no problem of heat resistance occurs in actual use. The polarizers of the examples are thin, and the variation of the single transmittance in a high temperature environment is remarkably suppressed. It is presumed that such an excellent effect is achieved by suppressing the content of free boric acid in the obtained polarizer to a low level and preventing polyene formation in a high-temperature environment. This is an unexpected excellent effect that can solve the newly found problem by actually manufacturing a very thin polarizer (for example, a thickness of 7 μm or less) which has been very difficult to manufacture in the past.
Industrial applicability
The polarizer of the present invention can be widely applied to liquid crystal panels of liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, mobile game machines, car navigations, copiers, printers, facsimile machines, clocks, microwave ovens, and the like.

Claims (4)

1. A polarizer comprising a polyvinyl alcohol resin film containing iodine, wherein,
the content of free boric acid is 0.4 wt% or less.
2. A polarizer according to claim 1,
the iodine content is 10-25 wt%.
3. A polarizer according to claim 1 or 2, having a thickness of 7 μm or less.
4. A polarizing plate, comprising: a polarizer according to any of claims 1 to 3, and a protective film laminated on one or both sides of the polarizer.
CN201980021191.0A 2018-03-30 2019-03-29 Polarizer and polarizing plate Pending CN111902751A (en)

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