Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/00634—Production of filters
  • B29D11/00644—Production of filters polarizing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/0009—After-treatment of articles without altering their shape; Apparatus therefor using liquids, e.g. solvents, swelling agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/0063—After-treatment of articles without altering their shape; Apparatus therefor for changing crystallisation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/0074—Production of other optical elements not provided for in B29D11/00009- B29D11/0073
  • B29D11/00788—Producing optical films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D11/00—Producing optical elements, e.g. lenses or prisms
  • B29D11/00865—Applying coatings; tinting; colouring
  • B29D11/00894—Applying coatings; tinting; colouring colouring or tinting
• • 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
• • 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
  • C08J7/12—Chemical modification
  • C08J7/14—Chemical modification with acids, their salts or anhydrides
• • 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
  • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2029/00—Use of polyvinylalcohols, polyvinylethers, polyvinylaldehydes, polyvinylketones or polyvinylketals or derivatives thereof as moulding material
  • B29K2029/04—PVOH, i.e. polyvinyl alcohol
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
  • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
  • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

• the present invention relates to a method for producing a polarizer.
• a polarizer is used in an image display device such as a liquid crystal display device.
• the polarizer is 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).
• PVA polyvinyl alcohol
• a dichroic substance such as iodine
• a method for efficiently dyeing a resin film there is a method using a high-concentration dyeing bath (for example, an iodine aqueous solution).
• a high-concentration dyeing bath for example, an iodine aqueous solution.
• iodine may be brought into another treatment bath, and the treatment bath may be contaminated with iodine.
• the resin film is dyed with iodine brought into another treatment bath, iodine that does not form a complex and an iodine complex with an insufficient orientation can be formed. Since these iodine and iodine complexes are easily removed from the polarizer, the characteristics (single transmittance and degree of polarization) of the polarizer may be reduced.
• the present invention has been made to solve the above conventional problems, and a main object of the present invention is to provide a method capable of producing a polarizer having excellent humidification durability even at a high degree of crystallinity and a high iodine concentration. To provide.
• the method for producing a polarizer of the present invention is a method for producing a polarizer having an iodine content of 10% by weight to 25% by weight.
• the method for producing a polarizer includes dry stretching a polyvinyl alcohol-based resin film, dyeing the dry-stretched polyvinyl alcohol-based resin film in a dye bath, and treating the stained polyvinyl alcohol-based resin film with ascorbin. Including acid treatment.
• the crystallinity of the polyvinyl alcohol-based resin film after the dry process is 40% or more.
• the dyeing bath is an aqueous iodine solution containing 0.3 parts by weight or more of iodine.
• the dye bath contains an oxidizing agent for iodide and iodide ions.
• the oxidizing agent is at least one selected from the group consisting of ferric sulfate, ferric chloride, and ferric nitrate.
• the iodide and the aqueous solution containing an oxidizing agent for iodine ions contain 0.5 to 10 parts by weight of the oxidizing agent and 100 parts by weight of water, and And the molar ratio of the iodide to the oxidizing agent (iodide / oxidizing agent) is 2/1 to 50/1.
• the ascorbic acid treatment is performed using an ascorbic acid bath. The ascorbic acid concentration in this ascorbic acid bath is 0.005% by weight to 1% by weight.
• the present invention it is possible to provide a polarizer having excellent humidification durability even at a high crystallinity and a high iodine concentration.
• the polyvinyl alcohol (PVA) -based resin film that has been dry-stretched and dyed is subjected to ascorbic acid treatment. Thereby, carry-in of iodine to another treatment bath can be reduced. Therefore, even when a polarizer having a high crystallinity and a high iodine concentration is used, a polarizer excellent in humidification durability can be provided.
• PVA polyvinyl alcohol
• the method for producing a polarizer of the present invention is a method for producing a polarizer having an iodine content of 10% by weight to 25% by weight.
• the polarizer can be manufactured, for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step.
• the production method of the present invention comprises dry stretching a polyvinyl alcohol-based resin film, dyeing the dry-stretched polyvinyl alcohol-based resin film in a dye bath, and converting the dyed polyvinyl alcohol-based resin film into ascorbic acid. Processing.
• a PVA-based resin film that has been dry-stretched and dyed is subjected to ascorbic acid treatment.
• Ascorbic acid can reduce iodine which can be carried into other treatment baths. Therefore, iodine ions (I 3 ⁇ ) brought into another processing bath can be reduced to I ⁇ that does not show absorption in the visible region (380 to 780 nm).
• I 3 ⁇ iodine ions brought into another processing bath
• I ⁇ that does not show absorption in the visible region (380 to 780 nm).
• iodine content means the amount of all iodine contained in the polarizer (PVA-based resin film).
• iodine is present in the form of iodine ion (I ⁇ ), iodine molecule (I 2 ), polyiodide ion (I 3 ⁇ , I 5 ⁇ ), and the like, and in the present specification, Iodine content refers to the amount of iodine that encompasses all of these forms.
• the iodine content can be calculated, for example, by a calibration curve method of X-ray fluorescence analysis.
• the polyiodide ion exists in a state where a PVA-iodine complex is formed in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the visible light wavelength range.
• the complex of PVA and triiodide ion (PVA.I 3 ⁇ ) has an absorption peak at about 470 nm, and the complex of PVA and pentaiodide ion (PVA.I 5 ⁇ ) is at about 600 nm.
• PVA.I 3 ⁇ the complex of PVA and pentaiodide ion
• PVA.I 5 ⁇ the complex of PVA and pentaiodide ion
• I ⁇ has an absorption peak near 230 nm and does not substantially contribute to absorption of visible light. Therefore, polyiodide ions present in the form of a complex with PVA can mainly contribute to the absorption performance of the polarizer.
• PVA-based resin film examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer.
• Polyvinyl alcohol is obtained by saponifying polyvinyl acetate.
• the ethylene-vinyl alcohol copolymer is obtained by saponifying the 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 99.99 mol%, more preferably 99.0 mol% to 99.99 mol%. is there.
• the saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer having excellent durability can be obtained.
• the average polymerization degree of the PVA-based resin can be appropriately selected depending on the purpose.
• the average degree of polymerization is usually from 1,000 to 10,000, preferably from 1,200 to 4,500, and more preferably from 1,500 to 4,300.
• the average degree of polymerization can be determined according to JIS @ K-6726-1994.
• the thickness of the PVA-based resin film is not particularly limited, and can be set according to a desired thickness of the polarizer.
• the thickness of the PVA-based resin film is, for example, 0.5 ⁇ m to 200 ⁇ m.
• the dyeing solution used in the present invention can dye a PVA-based resin film very efficiently. Therefore, for example, even if the PVA-based resin film is less than 10 ⁇ m, it can be dyed sufficiently in a short time, and can be imparted with properties that can sufficiently function as a polarizer.
• the PVA-based resin film may be a PVA-based resin layer formed on a substrate.
• the laminate of the substrate and the resin layer can be obtained by, for example, a method of applying the coating solution containing the PVA-based resin to the substrate, a method of laminating a PVA-based resin film on the substrate, or the like.
• the substrate any appropriate resin substrate can be used, and for example, a thermoplastic resin substrate can be used.
• the polarizer can be manufactured, for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step.
• a swelling step for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step.
• a swelling step for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step.
• a swelling step for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step, a crosslinking step, a stretching step, a washing step, and a drying step.
• a drying step for example, by subjecting a PVA-based resin film to a swelling step, a dyeing step,
• the PVA-based resin film is uniaxially stretched 3 to 7 times the original length.
• the PVA-based resin film is subjected to dry stretching. Dry stretching is preferable because stretching can be performed in a wider temperature range.
• the temperature at the time of performing the dry stretching is, for example, 50 ° C to 200 ° C, preferably 80 ° C to 180 ° C, more preferably 90 ° C to 160 ° C.
• the stretching direction may be the longitudinal direction of the film (MD direction) or the width direction of the film (TD direction). Note that the stretching direction may correspond to the absorption axis direction of the obtained polarizer.
• Dry stretching is preferably performed to increase the crystallinity of the PVA-based resin film.
• a PVA-based resin film having a high crystallinity iodine hardly enters between PVAs, and dyeing is not easy.
• the production method of the present invention can prevent iodine contamination of other treatment baths even when a high-concentration dye solution is used. Therefore, a polarizer having a high crystallinity can be easily manufactured.
• dry stretching is performed so that the crystallinity of the PVA-based resin film before being subjected to the dyeing treatment is 40% or more, more preferably 50% or more.
• the crystallinity is, for example, 80% or less.
• a PVA-based resin film having a desired crystallinity can be obtained by setting the stretching temperature and the stretching ratio in any appropriate ranges. Specifically, for example, a PVA-based resin film having a crystallinity of 50% or more is obtained by uniaxially stretching the PVA-based resin film at 90 ° C. to 160 ° C. so that the draw ratio becomes 3 to 6 times. Is obtained.
• the crystallinity of a PVA-based resin film refers to a value calculated by the following method.
• FT-IR Fourier-transform infrared spectrophotometer
• ATR attenuated total reflection
• the calculation of the crystallinity can be performed by the following procedure. The measurement is performed with the measurement polarized light at 0 ° and 90 ° with respect to the stretching direction, and the intensity is calculated at 1141 cm ⁇ 1 and 1440 cm ⁇ 1 of the obtained spectrum according to the following equation.
• the intensity of the intensity of 1141 cm ⁇ 1 is correlated with the amount of the crystal part, and the crystallization index is calculated from the following equation using 1440 cm ⁇ 1 as a reference peak (Equation 2). Further, for the crystallinity, a calibration curve of the crystallization index and the crystallinity is prepared in advance using a known PVA sample, and the crystallinity is calculated from the crystallinity index using the obtained calibration curve (Equation 1). ).
• the dry stretched PVA-based resin film is then subjected to a dyeing treatment.
• the dyeing step is a step of dyeing the PVA-based resin film with a dichroic substance. It is preferably carried out by adsorbing a dichroic substance.
• adsorption method for example, a method of immersing a PVA-based resin film in a staining solution containing a dichroic substance, a method of applying the staining solution to a PVA-based resin film, and spraying the staining solution on the PVA-based resin film And the like.
• a preferred method is to immerse the PVA-based resin film in the dyeing solution. This is because dichroic substances can be satisfactorily adsorbed.
• the dichroic substance examples include iodine and a dichroic dye. Preferably, it is iodine.
• iodine is used as the dichroic substance
• an aqueous iodine solution is preferably used as the staining solution.
• the iodine content of the aqueous iodine solution is preferably 0.04 to 5.0 parts by weight. In one embodiment, the iodine content in the iodine aqueous solution is preferably 0.3 parts by weight or more.
• potassium iodide is preferably used as iodide.
• the content of iodide is preferably 0.3 to 15 parts by weight based on 100 parts by weight of water.
• the temperature of the dyeing solution at the time of dyeing can be set to any appropriate value, for example, 20 ° C to 50 ° C.
• the immersion time is, for example, 1 second to 1 minute.
• the dye bath is a solution containing iodide and an oxidizing agent for iodine ions.
• This oxidizing agent is an ionic compound composed of a cation and an anion.
• iodine ions are oxidized to form polyiodide ions.
• the content of the polyiodide ion contained in the dyeing solution is increased, and the PVA-based resin film can be dyed efficiently.
• the content of polyiodine ions in the staining solution can be increased with a smaller amount of iodine than in the case of preparing a staining solution by adding iodine to water or an aqueous solution containing iodide.
• the iodine content in the staining solution can be adjusted by adding an oxidizing agent for iodine ions to the staining solution. Therefore, the content of the polyiodide ion in the staining solution can be adjusted more easily.
• the content of iodide contained in the dyeing solution is preferably 1 to 40 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of the solvent.
• iodide content is within the above range, sufficient polyiodide ions can be formed in the staining solution.
• iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. And the like.
• it is potassium iodide.
• an ionic compound composed of a cation and an anion is used as an oxidizing agent for iodine ions.
• the anion or cation include cations such as Fe 3+ , Ag + , Ag 2+ , Au + , Au 3+ , Co 3+ , Cu 2+ , Mn 3+ , and Pt 2+ , Br 3 ⁇ , ClO 3 ⁇ , and ClO 2 ⁇ . , ClO ⁇ , Cr 2 O 7 2 ⁇ , NO 3 ⁇ , MnO 4 ⁇ and the like.
• it is a trivalent iron ion (Fe 3+ ).
• Trivalent iron ions and divalent iron ions can be incorporated into the PVA-based resin film in the dyeing process. These iron ions have a function of dehydrating PVA. Therefore, it is possible to suppress the action of polyiodide ions coming out of the PVA-based resin film in a subsequent step. As a result, the dyeability of the PVA-based resin film can be further improved, which is preferable.
• the oxidizing agent is not particularly limited as long as it is an ionic compound in which a desired electrode reaction occurs in the staining solution, and any appropriate compound can be used.
• compounds containing Fe 3+ as a cation such as ferric sulfate, ferric chloride, and ferric nitrate; compounds containing MnO 4 ⁇ as an anion such as potassium permanganate; Cu 2+ such as copper chloride and copper sulfate; And the like as a cation. Since it contains Fe 3+ , it is preferable to use at least one compound selected from the group consisting of ferric sulfate, ferric chloride, and ferric nitrate.
• the oxidizing agent may be used alone or in combination of two or more.
• the content of the oxidizing agent in the dyeing solution is preferably from 0.1 to 10 parts by weight, more preferably from 0.5 to 10 parts by weight, even more preferably from 0 to 10 parts by weight, based on 100 parts by weight of the solvent. 0.5 to 4 parts by weight.
• the content of the oxidizing agent in the staining solution can be determined according to the content of iodide contained in the staining solution.
• the molar ratio between iodide and the oxidizing agent can be set to any appropriate value, for example, 2/1 to 50/1, and preferably 10/1 to 50/1.
• the oxidizing agent can sufficiently function as an oxidizing agent for iodine ions.
• Iodide and oxidizing agent can be used in any appropriate combination.
• a combination using potassium iodide as an iodide and ferric sulfate as an oxidizing agent is preferable from the viewpoint that a polarizer having excellent properties such as durability can be obtained.
• any appropriate solvent can be used, and usually, water is used.
• the dyeing solution may contain any other appropriate compound in addition to the iodide and the oxidizing agent.
• the staining solution may further include iodine.
• the iodine content in the staining solution is, for example, 1 part by weight or less based on 100 parts by weight of the solvent.
• Ascorbic acid treatment The PVA-based resin film that has been subjected to the dry stretching and the dyeing treatment is then subjected to ascorbic acid treatment.
• the ascorbic acid treatment is performed using an aqueous solution containing ascorbic acid (vitamin C) and / or ascorbate (hereinafter also referred to as ascorbic acid aqueous solution).
• the salt include an alkali metal salt such as a sodium salt and a potassium salt.
• the PVA-based resin film contains iodine. This iodine can contaminate other treatment baths (treatment baths other than the dyeing bath) in the steps after the dyeing step.
• the ascorbic acid treatment is preferably performed before being subjected to the treatment with another treatment bath.
• iodine excessively adsorbed on PVA molecules can be selectively removed.
• iodine contamination of another treatment bath can be prevented.
• iodine excessively adsorbed on the PVA molecules iodine ions - is reduced to, I 3 (I) - complex and I 5 - iodide ion to form a complex may increase.
• I 3 - complex and I 5 - complex is increased, humidification durability can be improved.
• the ascorbic acid treatment can be performed by any appropriate method.
• a method of applying or spraying an aqueous solution containing ascorbic acid and / or ascorbate on a PVA-based resin film a method of dipping the PVA-based resin film in an aqueous solution containing ascorbic acid and / or ascorbate, and the like can be given.
• a method of applying or spraying an aqueous solution containing ascorbic acid and / or ascorbate on a PVA-based resin film a method of dipping the PVA-based resin film in an aqueous solution containing ascorbic acid and / or ascorbate, and the like can be given.
• the ascorbic acid treatment may be performed by preparing a treatment solution containing only ascorbic acid and / or ascorbate, and bringing the treatment solution into contact with a PVA-based resin film.
• Ascorbic acid and / or ascorbate may be added to a treatment bath (for example, a crosslinking bath) to be used, and the treatment bath may be brought into contact with the PVA-based resin film, or both may be brought into contact. .
• the concentration of ascorbic acid and / or ascorbate in the aqueous solution of ascorbic acid can be set to any appropriate range according to the amount of iodine that can be brought into another processing solution.
• the ascorbic acid concentration of the aqueous ascorbic acid solution is preferably 0.005% by weight to 1% by weight, more preferably 0.005% by weight to 0.5% by weight, and further preferably 0.05% by weight to 0% by weight. 0.5% by weight. When the ascorbic acid concentration is less than 0.005% by weight, the effect of the ascorbic acid treatment may not be sufficiently obtained. If the ascorbic acid concentration exceeds 1% by weight, the dyed PVA-based resin film may be decolorized.
• the swelling step is usually performed before the dyeing step.
• the swelling step may be performed with the dyeing step in the same immersion bath.
• the swelling step is performed, for example, by immersing the PVA-based resin film in a swelling bath.
• any appropriate liquid can be used, and for example, water such as distilled water or pure water is used.
• the swelling bath may include any suitable other components other than water.
• Other components include solvents such as alcohols, additives such as surfactants, and iodides. Examples of the iodide include those exemplified above.
• potassium iodide is used.
• the temperature of the swelling bath is, for example, 20 ° C to 45 ° C.
• the immersion time is, for example, 10 seconds to 300 seconds.
• a boron compound is usually used as a crosslinking agent.
• the boron compound include boric acid and borax. Preferably, it is boric acid.
• the boron compound is usually used in the form of an aqueous solution.
• the concentration of boric acid in the aqueous boric acid solution is, for example, 2% by weight to 15% by weight, and preferably 3% by weight to 13% by weight.
• the boric acid aqueous solution may further contain an iodide such as potassium iodide and a zinc compound such as zinc sulfate and zinc chloride.
• the crosslinking step can be performed by any appropriate method.
• a method of immersing a PVA-based resin film in an aqueous solution containing a boron compound a method of applying an aqueous solution containing a boron compound to a PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto a PVA-based resin film are mentioned.
• the temperature of the solution used for crosslinking is, for example, 25 ° C or higher, preferably 30 ° C to 85 ° C, more preferably 40 ° C to 70 ° C.
• the immersion time is, for example, 5 seconds to 800 seconds, preferably 8 seconds to 500 seconds.
• the washing step is performed using water or an aqueous solution containing the above iodide. Typically, this is performed by immersing a PVA-based resin film in an aqueous potassium iodide solution.
• the temperature of the aqueous solution in the washing step is, for example, 5 ° C. to 50 ° C.
• the immersion time is, for example, 1 second to 300 seconds.
• the drying step can be performed by any appropriate method. For example, natural drying, blast drying, drying under reduced pressure, heating drying and the like can be mentioned, and heating drying is preferably used.
• the heating temperature is, for example, 30 ° C. to 100 ° C.
• the drying time is, for example, 10 seconds to 10 minutes.
• the iodine content of the polarizer obtained by the production method of the present invention is 10% by weight to 25% by weight, preferably 15% by weight to 25% by weight. According to the production method of the present invention, a polarizer having excellent humidification durability while having a high crystallinity and a high iodine content can be obtained.
• the thickness of the polarizer obtained by the production method of the present invention is, for example, 0.5 ⁇ m to 80 ⁇ m, and preferably 0.6 ⁇ m to 20 ⁇ m. In one embodiment, the thickness of the polarizer is preferably between 0.8 ⁇ m and 10 ⁇ m. In yet another embodiment, the thickness of the polarizer is preferably no more than 3 ⁇ m. As described above, the dyeing solution used in the present invention can efficiently dye a PVA-based resin film. Therefore, a desired single transmittance can be sufficiently imparted even with a thin polarizer.
• the single transmittance of the polarizer obtained by the production method of the present invention is, for example, 30% or more.
• the theoretical upper limit of the single transmittance is 50%, and the practical upper limit is 46%.
• the single transmittance (Ts) is a Y value obtained by performing a luminosity correction by measuring with a 2-degree visual field (C light source) according to JIS Z8701, and is, for example, a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, (Product name: V7100).
• the degree of polarization of the polarizer is, for example, 99.0% or more.
• Example 1 An amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 ⁇ m) having a water absorption of 0.75% and a Tg of 75 ° C. was used as a thermoplastic resin substrate.
• One surface of the substrate is subjected to a corona treatment, and the corona-treated surface is treated with polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1200, degree of acetoacetyl modification: 4.6).
• a PVA-based resin layer was formed to produce a laminate.
• the obtained laminate was stretched 4.5 times in the air at 140 ° C. in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretching machine (stretching treatment).
• the laminate was immersed in a dyeing bath (aqueous solution having an iodine concentration of 1.4% by weight and a potassium iodide concentration of 9.8% by weight) at a liquid temperature of 25 ° C.
• the laminate was immersed in an ascorbic acid bath (an aqueous solution having an ascorbic acid concentration of 0.067% by weight, an iodine concentration of 0.1% by weight, and a potassium iodide concentration of 0.7% by weight) for 25 seconds (ascorbic acid treatment).
• the laminate was immersed in a cleaning bath (pure water) at a liquid temperature of 25 ° C. for 6 seconds (first cleaning treatment).
• 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 ° C. for 16 seconds (crosslinking treatment).
• the laminate was immersed in a cleaning bath (aqueous solution having a potassium iodide concentration of 1% by weight) at a liquid temperature of 25 ° C. for 3 seconds (second cleaning treatment).
• a cleaning bath aqueous solution having a potassium iodide concentration of 1% by weight
• the laminate was dried in an oven at 60 ° C. for 21 seconds to obtain a laminate having a 2.5 ⁇ m-thick PVA-based resin layer (polarizer).
• Example 1 was the same as Example 1 except that an aqueous solution having an iodine concentration of 0.3% by weight and a potassium iodide concentration of 2.1% by weight was used as a dyeing bath, and no ascorbic acid was added to the ascorbic acid bath. Similarly, a laminate having a 2.5 ⁇ m-thick PVA-based resin layer (polarizer) was obtained.
• Example 2 A 5 ⁇ m thick PVA-based resin layer was formed to obtain a laminate, and the laminate was dyed at 30 ° C. (100 parts by weight of water, 24.0 parts by weight of potassium iodide, 2 parts by weight of sulfuric acid An aqueous solution to which 2.8 parts by weight of iron n-hydrate was added, and the same as in Example 1 except that the dye was immersed in an aqueous solution for 6 seconds in a molar ratio of iodide to the oxidizing agent and dyed, and dyed.
• a laminate having a PVA-based resin layer (polarizer) having a thickness of 1.2 ⁇ m was obtained.
• Example 2 Example 2 was repeated except that an aqueous solution having an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight was used as the dyeing bath, and that ascorbic acid was not added to the ascorbic acid bath. Similarly, a laminate having a 1.2 ⁇ m-thick PVA-based resin layer (polarizer) was obtained.
• the fluorescent X-ray intensity was measured using a fluorescent X-ray analyzer (trade name “ZSX-PRIMUS II” manufactured by Rigaku Corporation, measuring diameter: ⁇ 20 mm). (Kcps) was measured.
• the thickness ( ⁇ m) of the polarizer was measured using a spectral film thickness meter (trade name “MCPD-3000” manufactured by Otsuka Electronics Co., Ltd.).
• the iodine content (% by weight) was determined from the obtained fluorescent X-ray intensity and thickness using the following equation.
• FT-IR Fourier transform infrared spectrophotometer
• SPECTRUM2000 attenuated total reflection spectroscopy
• ATR The surface of the PVA resin layer was evaluated by an attended total reflection measurement.
• the crystallinity was calculated according to the following procedure. The measurement was performed in a state where the measurement polarization was set to 0 ° and 90 ° with respect to the stretching direction. Using the intensity of 1141 cm -1 and 1440 cm -1 of the obtained spectrum, calculation was performed according to the following equation.
• the intensity of the intensity of 1141 cm ⁇ 1 is correlated with the amount of the crystal part, and the crystallization index is calculated from the following equation using 1440 cm ⁇ 1 as a reference peak (Equation 2). Further, for the crystallinity, a calibration curve of the crystallization index and the crystallinity is prepared in advance using a known PVA sample, and the crystallinity is calculated from the crystallinity index using the obtained calibration curve (Equation 1). ).
• the polarizers obtained in Examples 1 and 2 had high iodine content and high crystallinity, but were excellent in humidification durability.
• the production method of the present invention can provide a polarizer excellent in humidification durability while having a high iodine content and a high degree of crystallinity.
• the polarizer obtained by the manufacturing method of the present invention can be applied to liquid crystal panels of liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, faxes, watches, microwave ovens, and the like. Can be widely applied.

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