CN115427849A - Polarizing film and polarizing film - Google Patents
Polarizing film and polarizing film Download PDFInfo
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- CN115427849A CN115427849A CN202180027099.2A CN202180027099A CN115427849A CN 115427849 A CN115427849 A CN 115427849A CN 202180027099 A CN202180027099 A CN 202180027099A CN 115427849 A CN115427849 A CN 115427849A
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- 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
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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
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- 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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Abstract
The present invention provides a polarizing film formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, wherein the content of iodine in the polarizing film exceeds 10 wt%, and the content of a cationic element derived from an iodide is 3.5 wt% or more. Although the polarizing film contains a large amount of iodine, the polarizing film has an excellent effect of suppressing a decrease in the monomer transmittance due to coloring of the polarizing film in a high-temperature environment.
Description
Technical Field
The present invention relates to a polarizing film and a polarizing film.
Background
Conventionally, as a polarizing film used for various image display devices such as a liquid crystal display device and an organic EL display device, a polyvinyl alcohol-based film (containing a dichroic material such as iodine or a dichroic dye) subjected to dyeing treatment has been used in view of having both high transmittance and high degree of polarization. The polarizing film was produced as follows: the polyvinyl alcohol film is subjected to various treatments such as swelling, dyeing, crosslinking, stretching, and the like in a bath, and then subjected to a cleaning treatment, followed by drying. The polarizing film is generally used in the form of a polarizing film (polarizing plate) in which a protective film such as triacetylcellulose is bonded to one surface or both surfaces thereof with an adhesive.
On the other hand, a polarizing film having a large iodine content is required in accordance with the thinning of the polarizing film (patent document 1). Further, among such thin polarizing films, a polarizing film capable of suppressing the amount of change in the monomer transmittance in a high-temperature environment (105 ℃x30 hours) is also known (patent document 2).
Documents of the prior art
Patent document
Patent document 1: international publication No. 2018/186244
Patent document 2: international publication No. 2019/103002
Disclosure of Invention
Problems to be solved by the invention
However, the thin polarizing films specifically disclosed in patent documents 1 and 2 are not sufficient in suppressing the decrease in the monomer transmittance in a high-temperature environment, and there is room for improvement of the performance.
On the other hand, the present inventors have found that iodine contained in an iodine-based polarizing film promotes the polyalkyleneization in a high-temperature environment. Therefore, in order to suppress the decrease in the monomer transmittance caused by the coloring of the polarizing film in a high-temperature environment, it is effective to reduce the content of iodine in the polarizing film. On the other hand, it is difficult to obtain a polarizing film having a good degree of polarization and a large iodine content.
In view of the above circumstances, an object of the present invention is to provide a polarizing film having a high iodine content, which is excellent in the effect of suppressing a decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment.
Another object of the present invention is to provide a polarizing film using the above polarizing film.
Means for solving the problems
That is, the present invention relates to a polarizing film formed by adsorbing iodine to a polyvinyl alcohol-based film and orienting the film, wherein the polarizing film has an iodine content of more than 10% by weight and a cationic element content derived from an iodide of 3.5% by weight or more.
The present invention also relates to a polarizing film having a transparent protective film or an optically functional film bonded to at least one surface of the polarizing film.
ADVANTAGEOUS EFFECTS OF INVENTION
The details of the mechanism of action of the effect of the polarizing film of the present invention are not clear, but are presumed as follows. However, the present invention is not limited to the explanation of this mechanism of action.
The polarizing film of the present invention is formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, and has an iodine content of more than 10% by weight and a cationic element content derived from an iodide of 3.5% by weight or more. It is presumed that the polarizing film of the present invention can suppress a decrease in monomer transmittance (polyene) caused by coloring of the polarizing film in a high-temperature environment by allowing a large amount of iodide contained to interact with an iodine complex present in the polarizing film. In the present invention, the cationic element derived from iodide is quantified as an index for measuring the iodide content in the polarizing film.
Detailed Description
< polarizing film >
The polarizing film of the present invention is a polarizing film formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, and has an iodine content of more than 10 wt% and a cationic element content derived from an iodide of 3.5 wt% or more.
The content of iodine in the polarizing film is more than 10% by weight from the viewpoint of improving the initial degree of polarization of the polarizing film. The content of iodine in the polarizing film is preferably 12 wt% or more, more preferably 15 wt% or more from the viewpoint of controlling the initial degree of polarization to 99.98 or more, and is preferably 30 wt% or less, more preferably 25 wt% or less from the viewpoint of suppressing the polyalkyleneition.
The polarizing film has a content of a cationic element derived from iodide of 3.5 wt% or more. The content of the cationic element derived from iodide in the polarizing film is preferably 3.8 wt% or more, more preferably 4.0 wt% or more from the viewpoint of enhancing the effect of suppressing the decrease in the monomer transmittance due to the coloring of the polarizing film in a high-temperature environment, and the content of the cationic element derived from iodide is preferably 15 wt% or less, more preferably 10 wt% or less from the viewpoint of the hue of the polarizing film. Examples of the iodide include: 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.
The thickness of the polarizing film is preferably 0.2 μm or more, more preferably 0.5 μm or more from the viewpoint of controlling the initial degree of polarization to 99.98 or more, and is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less from the viewpoint of thinning the polarizing film.
< method for producing polarizing film >
The method for producing a polarizing film includes: the polarizing film is obtained by subjecting a polyvinyl alcohol film (PVA-based film) to at least a dyeing step, a crosslinking step, and a stretching step, optionally followed by a swelling step, a washing step, and a drying step. The content of the iodine and the cationic element derived from an iodide contained in the polarizing film can be controlled by the concentration of the iodide such as iodine and potassium iodide contained in any one of the treatment baths in the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step, the treatment temperature and the treatment time in each treatment bath. In particular, when the washing step is performed after the dyeing step, the crosslinking step, and the stretching step are performed, the washing step can easily adjust the content of iodine and the content of a cationic element derived from an iodide to desired ranges from the viewpoint that components such as iodine and an iodide can be eluted from or adsorbed to the polyvinyl alcohol film, in consideration of the processing conditions in the dyeing step, the crosslinking step, the stretching step, and the like. The respective steps may be performed in any suitable order, and 1 step may be performed a plurality of times as needed.
The concentration of the iodide contained in at least one of the treatment baths is not generally determined because it is affected by the number of treatments, the treatment time, the treatment temperature, and the like of each treatment, and is preferably 10% by weight or more, more preferably 12% by weight or more, and still more preferably 15% by weight or more, from the viewpoint of controlling the content of the cationic element derived from iodide in the polarizing film to 3.5% by weight or more, and is preferably 50% by weight or less, more preferably 40% by weight or less, and still more preferably 30% by weight or less, from the viewpoint of the color of the polarizing film.
The polyvinyl alcohol-based film may be, but is not particularly limited to, a polyvinyl alcohol (PVA) -based film that has light transmittance in the visible light region and is obtained by dispersing and adsorbing a dichroic substance such as iodine or a dichroic dye. Examples of the material of the polyvinyl alcohol film include polyvinyl alcohol and derivatives thereof. Examples of the derivative of the polyvinyl alcohol include: polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; and derivatives modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, alkyl esters thereof, acrylamide, and the like. The polyvinyl alcohol preferably has an average polymerization degree of about 100 to 10000, more preferably about 1000 to 10000, and further preferably about 1500 to 4500. The saponification degree of the polyvinyl alcohol is preferably about 80 to 100 mol%, more preferably about 95 to 99.95 mol%. The average polymerization degree and the saponification degree can be determined according to JIS K6726.
The polyvinyl alcohol film may contain additives such as a plasticizer and a surfactant. Examples of the plasticizer include: and polyhydric alcohols such as glycerin, diglycerin, triglycerol, ethylene glycol, propylene glycol, and polyethylene glycol, and condensates thereof. The amount of the above-mentioned additive is not particularly limited, and is preferably about 20% by weight or less in the polyvinyl alcohol film, for example.
The polyvinyl alcohol film may be a laminate in which a polyvinyl alcohol resin layer (PVA type resin layer) containing a polyvinyl alcohol resin (PVA type resin) is formed on one side of a long thermoplastic resin base material. As a method for producing the laminate, any suitable method can be adopted, and examples thereof include: a method of applying a coating solution containing the PVA-based resin on the surface of the thermoplastic resin substrate and drying the coating solution. The thickness of the thermoplastic resin substrate is preferably about 20 to 300. Mu.m, and more preferably about 50 to 200. Mu.m. The thickness of the PVA based resin layer is preferably about 3 to 40 μm, more preferably about 3 to 20 μm.
As the constituent material of the thermoplastic resin substrate, any suitable thermoplastic resin can be used. Examples of the thermoplastic resin include: ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. Of these, norbornene-based resins and amorphous (non-crystalline) polyethylene terephthalate-based resins are preferable, and amorphous (non-crystalline) polyethylene terephthalate-based resins are preferably used from the viewpoint that the thermoplastic resin substrate is very excellent in stretchability and can be inhibited from crystallizing during stretching. Examples of the amorphous (noncrystalline) polyethylene terephthalate resin include copolymers containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid, and copolymers containing cyclohexanedimethanol and diethylene glycol as diol.
The thermoplastic resin substrate may be subjected to a surface treatment (e.g., corona treatment) before the PVA-based resin layer is formed, 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. The thermoplastic resin substrate may be stretched before the PVA-based resin layer is formed.
The coating liquid is a solution obtained by dissolving a 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, and water is preferred. These solvents may be used alone, or two or more kinds may be used in combination. The concentration of the PVA-based resin in the coating solution is preferably about 3 to 20 parts by weight per 100 parts by weight of the solvent, from the viewpoint of forming a uniform coating film which adheres to the thermoplastic resin substrate.
From the viewpoint of improving the orientation of the polyvinyl alcohol molecules by stretching, a halide may be blended in the coating liquid. As the halide, any suitable halide may be used, and examples thereof include iodide, sodium chloride, and the like. Examples of the iodide include: potassium iodide, sodium iodide, lithium iodide, etc., with potassium iodide being preferred. The concentration of the halide in the coating liquid is preferably about 5 to 20 parts by weight, more preferably about 10 to 15 parts by weight, based on 100 parts by weight of the PVA-based resin.
Further, an additive may be added to the coating liquid. Examples of the additives include: plasticizers such as ethylene glycol and glycerin; and surfactants such as nonionic surfactants.
As a method for applying the coating liquid, any suitable method can be adopted, and examples thereof include: roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and blade coating (comma coating).
In the stretching step, the PVA-based film is typically stretched unidirectionally by a factor of about 3 to 7. The stretching direction may be the longitudinal direction (MD direction) of the film or the width direction (TD direction) of the film. The stretching direction is preferably the TD direction from the viewpoint of being laminated with a transparent protective film or an optical functional film in a roll-to-roll manner. The stretching method may be dry stretching or wet stretching, or a combination thereof. The PVA-based film may be stretched in the crosslinking step, the swelling step, the dyeing step, or the like. The stretching step may be performed in one stage or in multiple stages. In the case of performing in multiple stages, the stretching magnification is the product of the stretching magnifications in each stage. The stretching direction may correspond to the absorption axis direction of the obtained polarizing film.
The swelling step is performed before the dyeing step, if necessary. The swelling step is performed by, for example, immersing the PVA-based membrane in a swelling bath. As the swelling bath, water such as distilled water or pure water is generally used. The swelling bath may contain any suitable other components besides water. Examples of the other components include: solvents such as alcohols, additives such as surfactants, and iodides. The temperature of the swelling bath is, for example, about 20 to 45 ℃. The immersion time is, for example, about 10 to 300 seconds.
The dyeing step is a step of dyeing the PVA-based film with a dichroic substance. Examples of the adsorption method include: a method of immersing a PVA-based membrane in a dyeing solution containing a dichroic substance; a method of applying the staining solution to a PVA film; a method of spraying the dyeing solution onto the PVA-based film is preferably a method of immersing the PVA-based film in the dyeing solution from the viewpoint of good adsorption of the dichroic substance.
Examples of the dichroic substance include: iodine or a dichroic dye, preferably iodine. 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 about 0.04 to 5.0 parts by weight relative to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the aqueous iodine solution, and in this case, the content of the iodide is preferably about 0.3 to 15 parts by weight relative to 100 parts by weight of water. From the viewpoint of obtaining a polarizing film having good optical characteristics, the ratio of the contents of iodine and iodide in the aqueous iodine solution is preferably about 1. The temperature of the dyeing liquid is, for example, 20 to 50 ℃. The immersion time is, for example, 5 seconds to 5 minutes.
In the crosslinking step, a boron compound is generally used as a crosslinking agent. Examples of the boron compound include: boric acid, borax, etc., preferably boric acid. The boron compound is usually used in the form of an aqueous solution. The concentration of the boron compound in the aqueous solution containing the boron compound is, for example, about 0.5 to 15 wt%, preferably about 1 to 10 wt%. In addition, the aqueous solution containing the boron compound may contain an iodide.
Examples of the crosslinking step include: a method of impregnating a PVA-based film in an aqueous solution containing a boron compound; a method of applying an aqueous solution containing a boron compound to a PVA-based film; a method of spraying an aqueous solution containing a boron compound onto the PVA-based film, and a method of immersing in an aqueous solution containing a boron compound is preferable.
In the crosslinking step, the temperature of the aqueous solution containing the boron compound is, for example, 25 ℃ or higher, preferably about 30 to 85 ℃, and more preferably about 40 to 70 ℃. The immersion time is, for example, about 5 to 800 seconds, preferably about 8 to 500 seconds.
The washing step is performed after the crosslinking step as necessary. The washing step is typically performed by immersing the PVA-based membrane in a washing liquid. As a representative example of the cleaning liquid, pure water is given. The cleaning solution may contain iodide. The temperature of the cleaning liquid is, for example, about 5 to 50 ℃. The immersion time is, for example, about 1 to 300 seconds.
In addition, additives such as zinc salt, pH adjuster, pH buffer, and other salts may be contained in each treatment bath in the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step. Examples of the zinc salt include: zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of the pH adjuster include: strong acids such as hydrochloric acid, sulfuric acid and nitric acid, and strong bases such as sodium hydroxide and potassium hydroxide. Examples of the pH buffer include: carboxylic acids such as acetic acid, oxalic acid and citric acid and salts thereof, and inorganic weak acids such as phosphoric acid and carbonic acid and salts thereof. Examples of the other salts include: chlorides such as sodium chloride, potassium chloride and barium chloride, nitrates such as sodium nitrate and potassium nitrate, sulfates such as sodium sulfate and potassium sulfate, and salts of alkali metals and alkaline earth metals.
Examples of the drying step include: natural drying, air-blowing drying, reduced-pressure drying, heat drying, and the like, and heat drying is preferable. When the heat drying is performed, the heating temperature is, for example, 30 to 100 ℃. The drying time is, for example, 20 seconds to 10 minutes.
< polarizing film >
The polarizing film of the present invention is obtained by laminating a film such as a transparent protective film or an optical functional film on at least one surface of the above polarizing film.
The transparent protective film is not particularly limited, and various transparent protective films used for polarizing films can be used. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like can be used. Examples of the thermoplastic resin include: cellulose ester resins such as cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins such as nylon and aromatic polyamide, polyimide resins, polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymers, (meth) acrylic resins, cyclic polyolefin resins having a cyclic or norbornene structure (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may be a cured layer formed of a thermosetting resin or an ultraviolet-curable resin such as a (meth) acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, or a silicone resin. Among these, cellulose ester resins, polycarbonate resins, (meth) acrylic resins, cyclic polyolefin resins, and polyester resins are preferable.
The thickness of the transparent protective film may be suitably determined, and is generally preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and still more preferably about 5 to 100 μm, from the viewpoints of strength, handling properties such as handling properties, and thin layer properties.
The transparent protective film may contain any suitable additive such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, an antistatic agent, a pigment, and a colorant. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.
The optical functional film is not particularly limited, and for example, an optical functional film used in the formation of a liquid crystal display device or the like may be used, such as a 1-layer or 2-layer or more reflection plate, a semi-transmission plate, a retardation plate (including a 1/2, 1/4 or the like wave plate), a viewing angle compensation film, a luminance improvement film such as a linearly polarized light separation film, or the like. Examples of the polarizing film having the optical functional film include: a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a semi-transmissive reflective plate is further laminated on the polarizing film, an elliptical polarizing film or a circular polarizing film in which a retardation plate is further laminated on the polarizing film, a wide-viewing-angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on the polarizing film.
When the films such as the transparent protective film and the optically functional film are laminated on both surfaces of the polarizing film, the films on both surfaces may be the same or different.
Functional layers such as a hard coat layer, an antireflection layer, an adhesion prevention layer, a diffusion layer, and an antiglare layer may be provided on the surface of the film not bonded to the polarizing film. The functional layers such as the hard coat layer, the antireflection layer, the adhesion prevention layer, the diffusion layer, and the antiglare layer may be provided as a layer different from the film, in addition to the film itself.
The polarizing film and the film or the polarizing film and the functional layer are usually bonded together via an adhesive layer or an adhesive layer.
As the adhesive for forming the adhesive layer, various adhesives used for a polarizing film can be applied, and examples thereof include: rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, and the like. Among these, acrylic adhesives are preferred.
As a method of forming the above adhesive layer, for example: a method in which the adhesive is applied to a separator or the like subjected to a peeling treatment, dried to form an adhesive layer, and then transferred to a polarizing film or the like; or a method in which the adhesive is applied to a polarizing film or the like and dried to form an adhesive layer. The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably about 2 to 50 μm.
As the adhesive forming the adhesive layer, various adhesives used for a polarizing film can be applied, and examples thereof include: isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, water-based polyesters, and the like. These adhesives are generally used in the form of an adhesive (aqueous adhesive) formed from an aqueous solution, and contain 0.5 to 60% by weight of a solid content.
The aqueous adhesive may contain a crosslinking agent. As the crosslinking agent, a compound having at least 2 functional groups reactive with a component such as a polymer constituting the adhesive in 1 molecule is generally used, and examples thereof include: alkylene diamines; isocyanates; epoxy resin; aldehydes; amino-formaldehydes such as methylolurea and methylolmelamine. The amount of the crosslinking agent in the adhesive is usually about 10 to 60 parts by weight per 100 parts by weight of the components such as the polymer constituting the adhesive.
Examples of the adhesive include active energy ray-curable adhesives such as ultraviolet-curable adhesives and electron beam-curable adhesives other than the above adhesives. Examples of the active energy ray-curable adhesive include (meth) acrylate adhesives. Examples of the curable component in the (meth) acrylate adhesive include: a compound having a (meth) acryloyl group, a compound having a vinyl group. Examples of the compound having a (meth) acryloyl group include: alkyl (meth) acrylates such as C1-20 chain alkyl (meth) acrylates, alicyclic alkyl (meth) acrylates, and polycyclic alkyl (meth) acrylates; a hydroxyl group-containing (meth) acrylate; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate, and the like. The (meth) acrylate-based adhesive may contain a nitrogen-containing monomer such as hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, or (meth) acryloylmorpholine. The (meth) acrylic adhesive may contain tripropylene glycolDiacrylate, 1, 9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane methylal acrylate, bis (meth) acrylic acid
A polyfunctional monomer such as alkylene glycol diacrylate or EO-modified diglycerol tetraacrylate as a crosslinking component. Further, as the cationic polymerization curing adhesive, a compound having an epoxy group or an oxetane group may be used. The compound having an epoxy group is not particularly limited as long as it has at least 2 epoxy groups in the molecule, and various curable epoxy compounds generally known can be used.
The adhesive may contain an appropriate additive as needed. Examples of the additives include: silane coupling agents, coupling agents such as titanium coupling agents, bonding accelerators such as ethylene oxide, ultraviolet absorbers, deterioration prevention agents, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat-resistant stabilizers, hydrolysis-resistant stabilizers and the like.
The adhesive may be applied to either the film side (or the functional layer side) or the polarizing film side, or may be applied to both sides. After the bonding, a drying step is performed to form an adhesive layer formed by coating a dry layer. After the drying step, ultraviolet rays and electron beams may be irradiated as necessary. The thickness of the adhesive layer is not particularly limited, but is preferably about 30 to 5000nm, more preferably about 100 to 1000nm when an aqueous adhesive or the like is used, and is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm when an ultraviolet-curable adhesive, an electron beam-curable adhesive or the like is used.
The transparent protective film and the polarizing film, or the polarizing film and the functional layer may be laminated with a surface modification treatment layer, an easy adhesion layer, a barrier layer, a refractive index adjustment layer, or the like interposed therebetween.
Examples of the surface modification treatment for forming the surface modification layer include: corona treatment, plasma treatment, undercoating treatment, saponification treatment and the like.
Examples of the easy adhesive agent for forming the easy adhesive layer include: the material for forming the resin composition includes various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, silicones, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. The easy-adhesion layer may be provided on the film in advance, and the easy-adhesion layer side of the film may be laminated on the polarizing film with the pressure-sensitive adhesive layer or the adhesive layer interposed therebetween.
The barrier layer is a layer having a function of preventing impurities such as oligomers and ions dissolved from the film from moving (entering) into the polarizing film. The barrier layer may be any layer that has transparency and can prevent impurities from eluting from the film or the like, and examples of materials for forming the barrier layer include: urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, epoxy-based forming materials, and the like.
The refractive index adjustment layer is provided to suppress a decrease in transmittance due to reflection between the film and a layer having a different refractive index such as a polarizing film. Examples of the refractive index adjusting material for forming the refractive index adjusting layer include: the resin composition contains various resins containing silica, acrylic-styrene, melamine, etc., and additives.
The single transmittance of the polarizing film is preferably 30% or more, more preferably 35% or more from the viewpoint of the brightness of the display panel, and is preferably 41% or less, more preferably 40% or less from the viewpoint of controlling the initial degree of polarization to 99.98 or more. The monomer transmittance is a Y value obtained by measuring and correcting visibility with a spectrophotometer with an integrating sphere (for example, product name: V7100, manufactured by japan spectro corporation) in a 2-degree field of view (C light source) according to JIS Z8701.
The polarization degree of the polarizing film is preferably 99.98% or more, and more preferably 99.99% or more.
An adhesive layer for bonding other members may be provided on one or both surfaces of the polarizing film. The adhesive layer is preferably an adhesive layer. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a pressure-sensitive adhesive using a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be suitably selected and used. In particular, a pressure-sensitive adhesive excellent in optical transparency, exhibiting appropriate wettability, cohesiveness and adhesiveness, and excellent in weather resistance, heat resistance and the like, such as a pressure-sensitive adhesive containing an acrylic polymer, can be preferably used.
The adhesive layer may be provided on one or both surfaces of the polarizing film in an appropriate manner. Examples of the pressure-sensitive adhesive layer include: a method of preparing an adhesive solution and directly applying the adhesive solution to the polarizing film by a suitable spreading method such as a casting method and a coating method; or a method of forming an adhesive layer on a separator and transferring the adhesive layer to the polarizing film. The thickness of the pressure-sensitive adhesive layer may be suitably determined depending on the purpose of use, the adhesive strength, and the like, and is generally 1 to 500. Mu.m, preferably 5 to 200. Mu.m, and more preferably 10 to 100. Mu.m. The polarizing film having a pressure-sensitive adhesive layer on at least one surface thereof is also referred to as a pressure-sensitive adhesive layer-attached polarizing film.
The exposed surface of the pressure-sensitive adhesive layer is preferably covered by a temporary adhesive film for the purpose of preventing contamination or the like until the pressure-sensitive adhesive layer is actually used. This can prevent contamination of the pressure-sensitive adhesive layer and the like in a normal handling state. As the separator, for example, a separator obtained by coating an appropriate thin layer body such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, or a laminate thereof with an appropriate release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, if necessary, can be used.
Examples
The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
< example 1 >
< polarizing film and polarizing film production >
As the thermoplastic resin substrate, a film (thickness: 100 μm) of polyethylene terephthalate isophthalate (IPA-copolymerized PET) was used. One surface of the substrate was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl group-modified PVA (polymerization degree 1200, acetoacetyl group modification rate 4.6%, saponification degree 99.0 mol% or more, product name "Gohsefimer Z200" manufactured by japan synthetic chemical industries, ltd.) in a ratio of 9. The obtained laminate was stretched in a gas atmosphere of 4.5 times at 140 ℃ in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretcher (stretching treatment). Next, the laminate was immersed in a dyeing bath (aqueous solution having an iodine concentration of 1.0 wt% and a potassium iodide concentration of 7.0 wt%) at a liquid temperature of 25 ℃ for 12 seconds to be dyed (dyeing treatment). Subsequently, the resultant film was immersed for 21 seconds in a crosslinking bath (boron concentration: 1.0 wt% and potassium iodide concentration: 1.0 wt%) at a liquid temperature of 60 ℃ (crosslinking treatment). Next, the laminate was immersed in a cleaning bath (an aqueous solution having a potassium iodide concentration of 25 wt%) at a liquid temperature of 25 ℃ for 10 seconds (cleaning treatment). Subsequently, the laminate was dried in an oven at 60 ℃ for 21 seconds (drying treatment), and a laminate having a PVA-based resin layer (polarizing film) with a thickness of 1.2 μm was obtained. Next, a linearly polarized light separating film (product name "DBEF" manufactured by 3M) was laminated on the polarizing film side of the laminate having the PVA type resin layer (polarizing film) obtained through an acrylic pressure sensitive adhesive layer having a thickness of 20 μ M, and then the thermoplastic resin substrate was peeled off, and the acrylic pressure sensitive adhesive layer having a thickness of 20 μ M was applied on the peeled surface to prepare a polarizing film having a monomer transmittance of 39.7%.
[ method for measuring iodine content (% by weight) in polarizing film ]
The iodine concentration (% by weight) of the polarizing film was determined by the following equation using a fluorescent X-ray analyzer (product of Shigaku corporation, trade name: ZSX-PRIMUS IV, measurement diameter: 20 mm).
Iodine concentration (wt%) =14.474 × (fluorescent X-ray intensity)/(film thickness) (kcps/μm)
The coefficient for calculating the concentration differs depending on the measuring apparatus, and can be obtained by using an appropriate calibration curve. The results are shown in Table 1.
[ method for measuring the content (% by weight) of the cationic element derived from iodide in the polarizing film ]
About 50mg of the polarizing film was weighed in a teflon container, added with nitric acid and covered tightly, irradiated with microwaves, subjected to pressurized acid decomposition at a maximum temperature of 220 ℃, added with ultrapure water to a constant volume of 25mL, diluted appropriately, and subjected to quantitative analysis of a cationic element by ICP-AES. The results are shown in Table 1.
[ method for measuring degree of polarization ]
The degree of polarization of the polarizing film can be measured using a spectrophotometer (product name "V7100" manufactured by japan optical spectroscopy). As a specific method for measuring the degree of polarization, the parallel transmittance (H0) and the orthogonal transmittance (H90) of the polarizing film can be measured according to the formula: the polarization degree (%) = { (H0-H90)/(H0 + H90) }1/2 × 100. The parallel transmittance (H0) is a transmittance value of a parallel laminated polarizing film produced by laminating 2 identical polarizing films so that absorption axes thereof are parallel to each other. The orthogonal transmittance (H90) is a transmittance value of an orthogonal laminated polarizing film produced by laminating 2 identical polarizing films so that absorption axes thereof are orthogonal to each other. These transmittances are Y values obtained by visibility correction with a 2-degree field of view (C light source) of JlS Z8701-1982. The results are shown in Table 1.
[ evaluation of monomer transmittance in high-temperature Environment ]
The polarizing film obtained above was cut into a size of 5.0 × 4.5cm so that the absorption axis of the polarizing film was parallel to the long side, and a 1.3mm alkali-free glass plate was bonded to the adhesive layer of the polarizing film to prepare a laminate. The obtained laminate was left standing in a hot air oven at a temperature of 105 ℃ for 96 hours, and the monomer transmittance (Δ Ts) before and after charging (heating) was measured. The monomer transmittance was measured using a spectrophotometer (product name "V7100" manufactured by japan spectro-photometry) and evaluated based on the following criteria. The measurement wavelength was 380 to 700nm (5 nm interval), and the results are shown in table 1.
ΔTs(％)＝Ts 96 －Ts 0
Here, ts 0 Is the monomer transmittance, ts, of the laminate before heating 96 The monomer transmittance of the laminate after heating for 96 hours. The Δ Ts (%) is preferably 5. Gtoreq.DELTA.Ts (%). Gtoreq.0, and more preferably 3. Gtoreq.DELTA.Ts (%). Gtoreq.0.
< example 2 >
A polarizing film and a polarizing film were produced in the same manner as in example 1, except that in the above-mentioned "production of a polarizing film and a polarizing film", the cleaning bath was changed to a cleaning bath (an aqueous solution having a potassium iodide concentration of 15 wt%). The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
< example 3 >
A polarizing film and a polarizing film were produced in the same manner as in example 1, except that the cleaning bath was changed to the cleaning bath (aqueous solution having a calcium iodide concentration of 25 wt%). The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
< example 4 >
In the above-mentioned < production of polarizing film and polarizing film >, a polarizing film and a polarizing film were produced in the same manner as in example 1, except that a laminate was produced by forming a PVA-based resin layer so that the thickness of the finally obtained polarizing film became 4.8 μm, and the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5 wt% and a potassium iodide concentration of 3.5 wt%). The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
< comparative example 1 >
A polarizing film and a polarizing film were produced in the same manner as in example 1, except that the cleaning bath was changed to the cleaning bath (aqueous solution having a potassium iodide concentration of 4.5 wt.%) in the above-mentioned < production of a polarizing film and a polarizing film. The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
< comparative example 2 >
A polarizing film and a polarizing film were produced in the same manner as in example 1, except that the cleaning bath was changed to the cleaning bath (aqueous solution having a potassium iodide concentration of 10 wt.%) in the above-mentioned "production of a polarizing film and a polarizing film". The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
< comparative example 3 >
In the above-mentioned < production of polarizing film and polarizing film >, a polarizing film and a polarizing film were produced in the same manner as in example 1, except that the PVA-based resin layer was formed so that the thickness of the finally obtained polarizing film became 4.8 μm to produce a laminate, the dyeing bath was changed to the dyeing bath (aqueous solution having an iodine concentration of 0.5 wt% and a potassium iodide concentration of 3.5 wt%), and the cleaning bath was changed to the cleaning bath (aqueous solution having a potassium iodide concentration of 4.5 wt%). The results of the measurement and evaluation of the polarizing film and the polarizing film are shown in table 1.
Claims (5)
1. A polarizing film formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film,
the polarizing film has an iodine content of more than 10 wt% and a cationic element content derived from an iodide of 3.5 wt% or more.
2. The polarizing film according to claim 1, which has a thickness of 10 μm or less.
3. A polarizing film comprising the polarizing film according to claim 1 or 2 and, bonded to at least one side thereof, a transparent protective film or an optically functional film.
4. The polarizing film according to claim 3, having a monomer transmittance of 41% or less.
5. The polarizing film according to claim 3 or 4, which has a degree of polarization of 99.98% or more.
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| JP2020-069683 | 2020-04-08 | ||
| JP2020069683A JP2021165809A (en) | 2020-04-08 | 2020-04-08 | Polarizing film and polarizing film product |
| PCT/JP2021/011116 WO2021205840A1 (en) | 2020-04-08 | 2021-03-18 | Polarizing membrane and polarizing film |
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| JP2003029042A (en) * | 2001-07-19 | 2003-01-29 | Nitto Denko Corp | Polarizer, polarizing plate and liquid crystal display device |
| JP5139935B2 (en) * | 2008-09-22 | 2013-02-06 | 日東電工株式会社 | Iodine polarizing film and method for producing the same |
| JP5522730B2 (en) * | 2010-08-18 | 2014-06-18 | 日東電工株式会社 | Adhesive polarizing plate with retardation layer, optical film, and image display device |
| KR20160091014A (en) * | 2015-01-23 | 2016-08-02 | 스미또모 가가꾸 가부시키가이샤 | Polarizer and preparing method for the same |
| KR101839672B1 (en) * | 2015-02-12 | 2018-03-16 | 스미또모 가가꾸 가부시키가이샤 | Polarizing film and polarizing plate comprising the same |
| JP6735541B2 (en) * | 2015-07-31 | 2020-08-05 | 株式会社クラレ | Polarizing film |
| CN110446955B (en) | 2017-04-03 | 2022-03-08 | 日东电工株式会社 | Polarizer and polarizing plate |
| CN110785685A (en) * | 2017-06-23 | 2020-02-11 | 日东电工株式会社 | Polarizing film, polarizing plate comprising same, and in-vehicle image display device comprising same |
| WO2019103002A1 (en) * | 2017-11-24 | 2019-05-31 | 日東電工株式会社 | Polarizer and polarizing plate |
| KR102309627B1 (en) * | 2017-11-28 | 2021-10-08 | 산진 옵토일렉트로닉스 (쑤저우) 컴퍼니 리미티드 | Optical laminate |
| JP6496862B2 (en) * | 2018-05-01 | 2019-04-10 | 日東電工株式会社 | Manufacturing method of polarizing film |
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