Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F16/00—Homopolymers and 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
  • C08F16/02—Homopolymers and 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 by an alcohol radical
  • C08F16/04—Acyclic compounds
  • C08F16/06—Polyvinyl alcohol ; Vinyl alcohol
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B13/00—Conditioning or physical treatment of the material to be shaped
  • B29B13/06—Conditioning or physical treatment of the material to be shaped by drying
  • B29B13/065—Conditioning or physical treatment of the material to be shaped by drying of powder or pellets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F6/00—Post-polymerisation treatments
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors

Definitions

• the present invention relates to a polyvinyl alcohol resin for manufacturing a polarizing film. More specifically, the present invention relates to a polyvinyl alcohol resin capable of producing a polyvinyl alcohol film excellent in transparency and dyeability with high productivity, a method for producing the same, a polyvinyl alcohol film using the polyvinyl alcohol resin, and a method thereof. The present invention relates to a manufacturing method and a polarizing film using the polyvinyl alcohol film and having excellent uniformity of polarization degree.
• a polyvinyl alcohol film has been produced by dissolving a polyvinyl alcohol resin in water to prepare an aqueous solution (film forming stock solution), and then forming and drying the film by a solution casting method (cast method). .
• the polyvinyl alcohol film thus obtained is used in many applications as a film excellent in transparency and dyeability, and one of its useful applications is a polarizing film.
• a polarizing film is used as a basic component of a liquid crystal display, and in recent years, its use has been expanded to high-luminance and high-definition equipment.
• a polyvinyl alcohol film that is excellent in transparency and dyeability necessary for producing a polarizing film free from display defects and polarization unevenness can be produced with high productivity.
• resin Provide resin.
• the present inventors have focused on the degree of weight swelling of the polyvinyl alcohol resin used as a raw material for the polyvinyl alcohol film, and a polyvinyl alcohol resin having a specific degree of weight swelling is obtained. Because it can suppress the generation of undissolved substances and aggregates in water, and can prevent the adhesion and blockage of these pipes, it can produce polyvinyl alcohol film with high productivity, and can also suppress the generation of clusters.
• the present inventors have found that a polarizing film free from display defects and uneven polarization can be produced.
• the gist of the present invention is a polyvinyl alcohol-based resin for producing a polarizing film, wherein the weight swelling degree calculated by the following formula (1) is 1.4 to 1.65.
• Degree of swelling of weight (weight when immersed in water at 15 ° C. for 1 hour and then centrifuged at 2,000 G for 1 minute) / (weight when dried at 105 ° C. for 2 hours after centrifugation) (1) )
• the present invention also provides a method for producing the above-mentioned polyvinyl alcohol resin for producing a polarizing film, which comprises a step of drying at 120 to 150 ° C. for 1 to 4 hours, A polyvinyl alcohol film obtained by using a polyvinyl alcohol resin for producing a polarizing film, a method for producing a polyvinyl alcohol film comprising the following steps (A) to (D), a polarizing film comprising the film, A polyvinyl alcohol resin having a weight swelling degree calculated by the above formula (1) of 1.4 to 1.65 is also provided.
• B A step of dewatering the polyvinyl alcohol resin after washing with water by centrifugation.
• C The process of preparing the aqueous solution of polyvinyl alcohol-type resin in a dissolution tank.
• D The process of forming into a film the polyvinyl alcohol-type resin aqueous solution by the casting method.
• the polyvinyl alcohol-based resin for producing a polarizing film of the present invention suppresses the generation of undissolved substances and aggregates in water, and prevents the adhesion to these pipes and the pipe clogging. Can be manufactured. Furthermore, since the generation of clusters can be suppressed, it is suitable for producing a polarizing film free from display defects and uneven polarization.
• the present invention is described in detail below.
• an unmodified polyvinyl alcohol resin that is, a resin produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate is used.
• a resin obtained by saponifying a copolymer of vinyl acetate and a small amount (usually 10 mol% or less, preferably 5 mol% or less) of a copolymerizable component with vinyl acetate may be used. it can.
• components copolymerizable with vinyl acetate include unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), and olefins having 2 to 30 carbon atoms (eg, ethylene, propylene, n-butene). , Isobutene, etc.), vinyl ethers, unsaturated sulfonates and the like.
• the modified polyvinyl alcohol-type resin obtained by chemically modifying the hydroxyl group after saponification can also be used.
• a polyvinyl alcohol resin having a 1,2-diol structure in the side chain can be used as the polyvinyl alcohol resin.
• a polyvinyl alcohol resin having a 1,2-diol structure in the side chain includes, for example, (i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, and (ii) acetic acid.
• the weight average molecular weight of the polyvinyl alcohol-based resin is preferably 100,000 to 200,000, particularly preferably 111 to 180,000, and more preferably 120,000 to 160,000. If the weight average molecular weight is too small, sufficient optical performance tends not to be obtained when the polyvinyl alcohol resin is used as an optical film, and if it is too large, stretching becomes difficult when the film is used as a polarizing film. Tend to be difficult.
• the weight average molecular weight of the polyvinyl alcohol resin in the present invention is a weight average molecular weight measured by a GPC-MALS method.
• the average saponification degree of the polyvinyl alcohol resin is preferably 99.0 mol% or more, particularly preferably 99.3 mol% or more, more preferably 99.5 mol% or more, and particularly preferably 99.7 mol% or more. It is. If the average saponification degree is too low, sufficient optical performance cannot be obtained when a polyvinyl alcohol-based resin is used as an optical film.
• the average saponification degree in the present invention is measured according to JIS K 6726.
• the polyvinyl alcohol resin preferably has a weight average molecular weight of 120,000 or more and an average saponification degree of 99.5 mol% or more.
• the greatest feature of the present invention is that a polyvinyl alcohol resin having a weight swelling degree of 1.4 to 1.65 is used.
• the weight swelling degree in this invention is computed by following formula (1).
• Weight swell degree (weight when immersed in water at 15 ° C. for 1 hour and then centrifuged at 2,000 G for 1 minute) / (weight when dried at 105 ° C. for 2 hours after centrifugation) (1) )
• the weight swelling degree is preferably 1.43 to 1.62, particularly preferably 1.45 to 1.60, and further preferably 1.47 to 1.58.
• the weight swelling degree exceeds the upper limit, the particles of the polyvinyl alcohol-based resin easily aggregate in water or in a state of containing moisture, and the aggregate easily adheres in the pipe, thereby achieving the object of the present invention. Can not. Moreover, it becomes difficult to dissolve in water due to agglomeration, and the clusters tend to remain in the aqueous solution, and the object of the present invention cannot be achieved. On the other hand, even if the degree of weight swelling is less than the lower limit, it becomes difficult to dissolve in water, and the clusters tend to remain in the aqueous solution, and the object of the present invention cannot be achieved.
• Examples of a method for controlling the weight swelling degree include a technique for controlling the molecular weight and the degree of saponification, a technique for drying the polyvinyl alcohol resin under specific conditions, and a technique for controlling the particle diameter by sieving.
• the method of drying polyvinyl alcohol-type resin on specific conditions as mentioned later is preferable.
• a film called a skin layer
• the degree of weight swelling can be controlled.
• the synthesized polyvinyl alcohol resin is subjected to solvent washing, drying, and, if necessary, subsequent processes such as pulverization and sieving to be used for forming a polyvinyl alcohol film.
• the drying process is important for controlling the degree of weight swelling, and in the present invention, the drying process is preferably performed at 120 to 150 ° C. for 1 to 4 hours.
• the drying temperature is particularly preferably 121 to 145 ° C., more preferably 122 to 140 ° C., and particularly preferably 123 to 135 ° C. If the drying temperature is too high, the degree of weight swelling tends to decrease and the polyvinyl alcohol resin tends to yellow. Conversely, if it is too low, drying tends to be insufficient and the degree of weight swelling tends to increase.
• the drying time is particularly preferably 1.3 to 3.7 hours, more preferably 1.5 to 3.5 hours. If the drying time is too long, the degree of weight swelling tends to decrease and the polyvinyl alcohol resin tends to yellow. On the other hand, if it is too short, drying tends to be insufficient and the degree of weight swelling tends to increase.
• Such a drying step may be performed by a known dry drying technique such as a rotary dryer or a stirring drying tank, but as a preferred embodiment of the present invention, performing the wet drying before the dry drying step, It is preferable for forming an appropriate skin layer.
• the wet drying is performed by spraying water vapor while flowing the resin powder in a heated jacket or a vented extruder. In wet drying, it is impossible to completely remove moisture from the resin, but it is possible to reduce the water content of the resin to the order of several percent.
• the polyvinyl alcohol resin for producing a polarizing film of the present invention is obtained.
• the polyvinyl alcohol film is produced by the following steps (A) to (D) using the polyvinyl alcohol resin of the present invention.
• a step of washing the polyvinyl alcohol resin with water (B) A step of dewatering the polyvinyl alcohol resin after washing with water by centrifugation.
• C The process of preparing the aqueous solution of polyvinyl alcohol-type resin in a dissolution tank.
• D The process of forming into a film the polyvinyl alcohol-type resin aqueous solution by the casting method.
• the polyvinyl alcohol resin described above is washed with water in order to remove the remaining sodium acetate.
• the water used as the cleaning liquid may contain a small amount of auxiliary components such as alcohol and surfactant.
• the polyvinyl alcohol resin in a slurry state is dehydrated with a centrifugal separator to obtain a wet cake having a water content of 50% by weight or less. If the water content is too high, it tends to be difficult to prepare a desired aqueous solution concentration in the step (C).
• the weight swelling degree of the polyvinyl alcohol-based resin is excessively large or excessively small, adhesion or deposition of the resin to the pipe occurs. Such a defect is most likely to occur in a wet cake state. Specifically, it occurs in SUS piping from the centrifuge outlet to the dissolution tank.
• step (C) water, the obtained polyvinyl alcohol-based resin wet cake, and, if necessary, a plasticizer such as glycerin or a surfactant are charged into the dissolving tank, and dissolved by heating and stirring.
• a plasticizer such as glycerin or a surfactant
• Such dissolution is preferably carried out by blowing water vapor in a dissolution tank equipped with a vertical circulation flow generation type stirring blade in view of solubility. In such a case, it is preferable from the viewpoint that uniform stirring can be performed when steam is blown into the dissolution tank and the temperature in the tank reaches 40 to 80 ° C.
• the dissolution temperature is too low, sufficient dissolution of the polyvinyl alcohol-based resin cannot be obtained, and the transparency of the polyvinyl alcohol-based film tends to decrease. If it is too high, the decomposition product of the polyvinyl alcohol-based resin or the surfactant is present. And the hue of the polyvinyl alcohol film tends to decrease.
• the concentration of the aqueous polyvinyl alcohol-based resin solution is preferably 15 to 60% by weight, particularly preferably 18 to 55% by weight, More preferably, it is 20 to 50% by weight. If the resin concentration is too low, the drying load of the film becomes large. Conversely, if the resin concentration is too high, the viscosity becomes too high and film formation tends to be difficult.
• the aqueous polyvinyl alcohol resin solution used in the present invention is obtained, but the obtained aqueous polyvinyl alcohol resin solution is preferably defoamed.
• the defoaming method include stationary defoaming and defoaming with a multi-screw extruder having a vent.
• a twin-screw extruder having a vent is usually used as the multi-screw extruder having the vent.
• step (D) the polyvinyl alcohol-based resin aqueous solution is filtered, and then discharged and fluted from a T-type slit die to a cast mold such as a cast drum or an endless belt to form a film.
• a cast mold such as a cast drum or an endless belt to form a film.
• the polyvinyl alcohol film of the present invention is obtained.
• the polyvinyl alcohol film of the present invention preferably has a thickness of 60 ⁇ m or less, particularly preferably 30 ⁇ m or less. If the thickness is too large, it is difficult to reduce the thickness of the polarizing film.
• the polyvinyl alcohol film of the present invention preferably has a width of 4 m or more from the viewpoint of productivity, and more preferably 4 km or more from the viewpoint of productivity.
• the polyvinyl alcohol film of the present invention preferably has a haze of 0.3% or less, particularly preferably 0.2% or less, and more preferably 0.1% or less. If the haze is too high, the light transmittance of the polarizing film tends to decrease.
• a method for reducing such haze a method for controlling the weight swelling degree of the polyvinyl alcohol resin described above, a method for improving the solubility by adding a surfactant to the polyvinyl alcohol resin aqueous solution, a cast type surface smoothness The technique etc. which improve are mentioned.
• the polyvinyl alcohol film of the present invention has few defects, is excellent in transparency and dyeability, and is preferably used as a raw material for a polarizing film.
• the polarizing film of the present invention is produced through steps such as swelling, dyeing, boric acid crosslinking, stretching, washing, and drying by unwinding the polyvinyl alcohol film from a roll and transferring it in the horizontal direction.
• the swelling process is performed before the dyeing process.
• water is usually used as the treatment liquid.
• the treatment solution may contain a small amount of an iodide compound, an additive such as a surfactant, alcohol, or the like.
• the temperature of the swelling bath is usually about 10 to 45 ° C., and the immersion time in the swelling bath is usually about 0.1 to 10 minutes. Moreover, you may perform extending
• the dyeing step is performed by bringing the film into contact with a liquid containing iodine or a dichroic dye.
• a liquid containing iodine or a dichroic dye usually, an iodine-potassium iodide aqueous solution is used.
• the iodine concentration is suitably 0.1-2 g / L, and the potassium iodide concentration is 1-100 g / L.
• the dyeing time is practically about 30 to 500 seconds.
• the temperature of the treatment bath is preferably 5 to 50 ° C.
• the aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the aqueous solvent. Moreover, you may perform extending
• the boric acid crosslinking step is performed using a boron compound such as boric acid or borax.
• the boron compound is used in the form of an aqueous solution or a water-organic solvent mixture at a concentration of about 10 to 100 g / L, and it is preferable that potassium iodide coexists in the solution from the viewpoint of stabilizing the polarization performance.
• the temperature during the treatment is preferably about 30 to 70 ° C., and the treatment time is preferably about 0.1 to 20 minutes. If necessary, the stretching operation may be performed during the treatment.
• the stretching step it is preferable to stretch 3 to 10 times, preferably 3.5 to 6 times in a uniaxial direction.
• a slight stretching may be performed in a direction perpendicular to the stretching direction.
• the temperature during stretching is preferably 30 to 170 ° C.
• the draw ratio may be finally set within the above range, and the drawing operation may be performed not only in one stage but also in any stage of the manufacturing process.
• the washing step is performed, for example, by immersing a polyvinyl alcohol film in an aqueous solution of iodide such as water or potassium iodide, thereby removing deposits generated on the surface of the film.
• iodide such as water or potassium iodide
• the concentration of potassium iodide may be about 1 to 80 g / L.
• the temperature during the washing treatment is usually 5 to 50 ° C., preferably 10 to 45 ° C.
• the treatment time is usually 1 to 300 seconds, preferably 10 to 240 seconds.
• the drying process may be performed in the atmosphere at 40 to 80 ° C. for 1 to 10 minutes.
• the polarization degree of the polarizing film of the present invention is preferably 99.5% or more, more preferably 99.8% or more. If the degree of polarization is too low, there is a tendency that the contrast in the liquid crystal display cannot be secured.
• the degree of polarization is generally the light transmittance (H 11 ) measured at the wavelength ⁇ in the state where two polarizing films are overlapped so that their orientation directions are the same direction, and the two polarizing films. It is calculated according to the following equation from the light transmittance (H 1 ) measured at the wavelength ⁇ in a state where the films are superposed so that the orientation directions are orthogonal to each other. [(H 11 ⁇ H 1 ) / (H 11 + H 1 )] 1/2
• the single transmittance of the polarizing film of the present invention is preferably 43% or more. If the single transmittance is too low, it tends to be impossible to achieve high brightness of the liquid crystal display.
• the single transmittance is a value obtained by measuring the light transmittance of a single polarizing film using a spectrophotometer.
• the polarizing film of the present invention is obtained, the polarizing film of the present invention is suitable for producing a polarizing plate with little polarization unevenness.
• the manufacturing method of this polarizing plate is demonstrated.
• the polarizing film is bonded to one or both surfaces of the polarizing film through an adhesive as an optically isotropic resin film as a protective film to form a polarizing plate.
• protective films include films of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyethersulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide, and the like. Or a sheet.
• the bonding method is performed by a known method. For example, after a liquid adhesive composition is uniformly applied to a polarizing film, a protective film, or both, the two are bonded and pressure-bonded, and heated or activated. This is done by irradiating energy rays.
• a curable resin such as urethane resin, acrylic resin, urea resin, etc. is applied on one side or both sides and cured and laminated. You can also.
• the polarizing film and polarizing plate obtained by the present invention are free from display defects and uneven polarization, and have excellent in-plane polarization performance, such as portable information terminals, personal computers, televisions, projectors, signage, electronic desk calculators, electronic Watches, word processors, electronic paper, game consoles, videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as cars and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements ( CRT, LCD, organic EL, electronic paper, etc.) for use in antireflection layers, optical communication equipment, medical equipment, building materials, toys and the like.
• portable information terminals personal computers, televisions, projectors, signage, electronic desk calculators, electronic Watches, word processors, electronic paper, game consoles, videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as cars and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements ( CRT, LCD, organic EL
• Polarization unevenness A test piece having a length of 30 cm and a width of 30 cm was cut out from the obtained polarizing film, and two polarizing plates in a crossed Nicol state (single transmittance 43.5%, polarization degree 99.9%) were obtained. After being sandwiched at an angle of 45 °, optical color unevenness was observed in a transmission mode using a light box having a surface illuminance of 14,000 lx and evaluated according to the following criteria. (Evaluation criteria) ⁇ : No color unevenness. ⁇ ... There is uneven color.
• a test piece having a length of 30 cm and a width of 13 cm was cut out from the obtained polarizing film, visually inspected in an environment of 15000 lx, and the number of display defects (pieces) of 100 ⁇ m or more was measured.
• Example 1 Manufacture of polyvinyl alcohol resin
• peroxyester as an initiator, vinyl acetate was polymerized in methanol to obtain polyvinyl acetate.
• the polyvinyl alcohol-type resin composition was obtained by saponifying using 2% NaOH aqueous solution.
• the obtained polyvinyl alcohol-based resin composition was washed with water and dehydrated with a centrifugal separator to obtain a polyvinyl alcohol-based resin wet cake.
• the obtained wet cake was put into a jacket, wet-dried with steam, and then dried at 125 ° C. for 2 hours using a rotary dryer.
• the weight swelling degree of the obtained polyvinyl alcohol-based resin was 1.58, the weight average molecular weight was 128,000, and the average saponification degree was 99.8 mol%.
• the polyvinyl alcohol-based resin aqueous solution was supplied to a twin-screw extruder having a vent and defoamed, and then the aqueous solution temperature was set to 95 ° C. and cast into a cast drum from a T-type slit die to form a film. . Finally, the obtained film is dried using a metal heating roll, both ends are cut off with a slit, and wound to form a roll-like polyvinyl alcohol film (thickness 30 ⁇ m, width 5 m, length 5 km). Obtained. Table 2 shows the characteristics of the obtained polyvinyl alcohol film.
• Examples 2 to 4 A polyvinyl alcohol resin, a polyvinyl alcohol film, and a polarizing film were obtained in the same manner as in Example 1 except that the drying conditions in the production process of the polyvinyl alcohol resin were the drying conditions shown in Table 1. The respective characteristics are shown in Table 1 and Table 2.
• Example 1 A polyvinyl alcohol resin was obtained in the same manner as in Example 1 except that the drying conditions in the production process of the polyvinyl alcohol resin were the drying conditions shown in Table 1. The obtained polyvinyl alcohol-based resin had reduced water solubility. Furthermore, in the same manner as in Example 1, a polyvinyl alcohol film and a polarizing film were obtained. The respective characteristics are shown in Table 1 and Table 2.
• Example 2 A polyvinyl alcohol resin was obtained in the same manner as in Example 1 except that the drying conditions in the production process of the polyvinyl alcohol resin were the drying conditions shown in Table 1.
• the obtained polyvinyl alcohol-based resin has a large amount of adhesion to pipes during the production of the polyvinyl alcohol-based film, and it has been difficult to continuously produce a polyvinyl alcohol-based film stably. In addition, it is difficult to dissolve evenly because it is likely to become lumps when dissolved with water.
• a polyvinyl alcohol film and a polarizing film were obtained. The respective characteristics are shown in Table 1 and Table 2.
• the polyvinyl alcohol resins of Examples 1 to 4 have a degree of weight swelling within the specific range of the present invention, there is no adhesion to the piping during the production of the polyvinyl alcohol film, and the resulting polyvinyl alcohol film is transparent. It was excellent.
• the polyvinyl alcohol-based resin of Comparative Example 1 having a degree of weight swelling smaller than the specific range of the present invention is poor in transparency of the resulting polyvinyl alcohol-based film due to a decrease in water solubility, and the weight swelling.
• the polyvinyl alcohol resin of Comparative Example 2 having a degree greater than the specific range of the present invention has a large amount of adhesion to the pipe during production and is difficult to be stably produced continuously. Therefore, the polyvinyl alcohol film that is difficult to dissolve uniformly is poor in transparency. It can be seen that the polarizing characteristics and quality of the polarizing films obtained from the respective polyvinyl alcohol films are superior to those of Comparative Examples 1 and 2 in Examples 1 to 4.
• the polyvinyl alcohol-based film obtained from the polyvinyl alcohol-based resin for producing the polarizing film of the present invention is excellent in transparency, and the polarizing film obtained from the polyvinyl alcohol-based film is free from display defects and uneven polarization, and is excellent in quality.
• Personal digital assistants personal computers, TVs, projectors, signage, electronic desk calculators, electronic clocks, word processors, electronic paper, game machines, videos, cameras, photo albums, thermometers, audio, automobile and machinery instruments, etc.
• liquid crystal display devices sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, antireflection reducing layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical communication equipment, medical equipment, building materials, toys, etc. Used.
• display elements CRT, LCD, organic EL, electronic paper, etc.
• optical communication equipment medical equipment, building materials, toys, etc. Used.

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