WO2017204271A1 - ポリビニルアルコール系フィルム、およびその製造方法、ならびにそのポリビニルアルコール系フィルムを用いた偏光膜 - Google Patents

ポリビニルアルコール系フィルム、およびその製造方法、ならびにそのポリビニルアルコール系フィルムを用いた偏光膜 Download PDF

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WO2017204271A1
WO2017204271A1 PCT/JP2017/019450 JP2017019450W WO2017204271A1 WO 2017204271 A1 WO2017204271 A1 WO 2017204271A1 JP 2017019450 W JP2017019450 W JP 2017019450W WO 2017204271 A1 WO2017204271 A1 WO 2017204271A1
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Prior art keywords
film
polyvinyl alcohol
metal heating
alcohol film
water
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PCT/JP2017/019450
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English (en)
French (fr)
Japanese (ja)
Inventor
学 花島
御手洗　宏志
早川　誠一郎
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日本合成化学工業株式会社
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Application filed by 日本合成化学工業株式会社 filed Critical 日本合成化学工業株式会社
Priority to CN201780031812.4A priority Critical patent/CN109312085B/zh
Priority to JP2017528604A priority patent/JP6834956B2/ja
Priority to KR1020187033812A priority patent/KR102400929B1/ko
Priority to CN202210043975.7A priority patent/CN114437385A/zh
Publication of WO2017204271A1 publication Critical patent/WO2017204271A1/ja

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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
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/24—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor for making articles of indefinite length
    • 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
    • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
    • B29C41/34—Component parts, details or accessories; Auxiliary operations
    • B29C41/46—Heating or cooling
    • 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
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • 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 polyvinyl alcohol-based film that is less likely to elute impurities into water and that does not curl even when immersed in water, in particular, a polyvinyl alcohol-based film that can obtain a polarizing film having high polarization performance with high productivity, and
  • the present invention relates to a production method and a polarizing film using the polyvinyl alcohol film.
  • liquid crystal display devices In recent years, the development of liquid crystal display devices has been remarkable, and they are widely used in smartphones, tablets, personal computers, liquid crystal televisions, projectors, in-vehicle panels, and the like.
  • a liquid crystal display device uses a polarizing film.
  • the polarizing film a film obtained by adsorbing and orienting iodine on a polyvinyl alcohol film is mainly used.
  • the increase in screen definition, brightness, and size there has been a need for polarizing films that are more excellent in polarization performance than conventional products, have no color unevenness, and are wide and long.
  • a polarizing film is a raw material polyvinyl alcohol film that is unwound from a roll and swelled with water (including warm water) while being conveyed in the flow direction (MD direction), and then stained with iodine and iodine. It is manufactured through steps such as stretching for orientation and boric acid crosslinking for fixing the orientation state. The defects that occur during these steps greatly reduce the productivity of the polarizing film. For example, in the swelling process, when impurities are eluted from the polyvinyl alcohol film and the swelling tank is contaminated, the contamination is diffused throughout the subsequent process.
  • impurities include low molecular weight polyvinyl alcohol resins (including oligomers) present in the polyvinyl alcohol film.
  • low molecular weight substances having a molecular weight of 50,000 or less are easily eluted in water, and the degree of polarization.
  • TD direction width direction
  • a polyvinyl alcohol-based film as a raw material is generally produced by dissolving a polyvinyl alcohol-based resin as a raw material in water and using such an aqueous solution (film-forming stock solution) by a continuous casting method.
  • a film formed by discharging and casting an aqueous solution of a polyvinyl alcohol-based resin onto a cast mold such as a cast drum or an endless belt is peeled from the cast mold, and then conveyed in the flow direction (MD direction).
  • MD direction flow direction
  • it is manufactured by drying using a plurality of metal heating rolls.
  • the drying process is an important process for controlling the elution amount of the resin from the polyvinyl alcohol film and the swelling property of the polyvinyl alcohol film. That is, if the drying in the drying process is insufficient, the resin eluted during the production of the polarizing film increases, and at the same time, the polyvinyl alcohol film tends to be broken or wrinkled in the swelling process, and conversely, the drying is excessive. And the swelling speed in the swelling tank tends to decrease. In addition, if there is a difference in characteristics between the front and back surfaces of the film formed in the drying process, the film tends to curl in the swelling process.
  • a polyvinyl alcohol film in which the amount of the polyvinyl alcohol resin eluted into water is reduced has been proposed (for example, see Patent Document 1). Further, a polyvinyl alcohol film having a curl angle of 180 ° or less when immersed in water at 30 ° C. for 5 minutes (see, for example, Patent Document 2), a thickness of 50 ⁇ m or less, and immersed in water at 30 ° C. for 30 seconds. A polyvinyl alcohol film having a curl angle of 200 ° or less has been proposed (see, for example, Patent Document 3). Moreover, the manufacturing method of the polyvinyl alcohol-type film by specific drying conditions is proposed (for example, refer patent document 4).
  • the curl angle is an angle formed by the plane portion of the polyvinyl alcohol film and the tangential direction of the edge portion of the curled portion in the width direction (TD direction) of the polyvinyl alcohol film [FIG. ))].
  • the concentration of the eluate of the polyvinyl alcohol resin is 10 to 50 ppm when a 10 cm ⁇ 10 cm square polyvinyl alcohol film is immersed in 1 liter of water at 50 ° C. for 4 hours.
  • polyvinyl alcohol resin of 1,000 to 5,000 ppm / m 2 is eluted, and in order to produce a polarizing film with high production efficiency according to the recent demand for polarizing films. Further reduction of the elution amount of the polyvinyl alcohol resin is necessary.
  • the curl angle 180 ° is a folded state
  • the curl angle 90 ° is a wrinkled state
  • the curl angle 45 ° is a greatly warped state. It is necessary to reduce the curl angle.
  • the disclosed technique of the above-mentioned patent document 4 can reduce the retardation of the polyvinyl alcohol film by setting the contact time between the film and each heat roll to 1 to 6 seconds. In order to reduce the resin elution amount, there is room for improvement in terms of further control of drying conditions.
  • the polyvinyl alcohol film is excellent in controllability and swelling property of the elution amount of the polyvinyl alcohol resin during the production of the polarizing film, and can obtain a polarizing film excellent in polarizing performance.
  • the amount of polyvinyl alcohol resin eluted when immersed in water can be reduced, the polarizing film manufacturing equipment is not contaminated, and it is difficult to curl even when immersed in water.
  • the present inventors have found that a polyvinyl alcohol-based film having a small curl angle measured under specific water immersion conditions with a small elution amount of the polyvinyl alcohol-based resin with respect to water at a specific temperature.
  • the present inventors have found that when a polarizing film is produced using a glass, the above-mentioned problems can be solved and a high-performance polarizing film can be produced with high productivity.
  • the first gist of the present invention is that the elution amount of the polyvinyl alcohol resin when immersed in water at 50 ° C. for 1 minute is 900 ppm / m 2 or less, and the short side direction is measured under the following condition A.
  • the polyvinyl alcohol film has a curl angle of 135 ° or less.
  • a rectangular test piece having a long side of 10 cm and a short side of 5 cm cut out from the polyvinyl alcohol film in an arbitrary direction, and a mass attached to the center of the first edge portion in the long side direction of the test piece A condition in which the entire test body is immersed in water at 30 ° C. for 10 seconds in a state where a test body provided with 5 g of weight is supported and suspended at the center of the second end edge in the long side direction of the test piece. .
  • the second gist of the present invention is that a film forming step of continuously discharging and casting an aqueous solution of a polyvinyl alcohol resin into a cast mold to form a film, and peeling the formed film from the cast mold. Then, the manufacturing method of the polyvinyl alcohol-type film of the said 1st summary provided with the drying process which dries the film formed, Comprising: Drying of the film formed in the said drying process formed the said film It is a manufacturing method of the polyvinyl alcohol-type film characterized by performing by making the front surface and back surface of a film contact a some metal heating roll alternately.
  • the 3rd summary of this invention is a polarizing film in which the polyvinyl-alcohol-type film of the said 1st summary is used.
  • the polyvinyl alcohol film according to the first aspect of the present invention has a small amount of polyvinyl alcohol resin eluted with respect to water at a specific temperature and a small curl angle measured under specific water immersion conditions.
  • the amount of elution of the polyvinyl alcohol resin can be reduced, and the curl angle can be reduced. Therefore, the effect that a polarizing film excellent in polarization performance can be produced with high productivity is exhibited.
  • the swelling process during the production of the polarizing film is further increased. Breakage can hardly occur, and breakage when manufacturing a polarizing film can be further prevented. Therefore, the effect that the polarizing film which is excellent in polarization performance can be manufactured with higher productivity is produced.
  • the curl angle is more It can be made small, and the occurrence of the above-described folds at both ends in the width direction can be further suppressed during the production of the polarizing film. Therefore, the effect that a polarizing film excellent in polarization performance can be produced with higher productivity is exhibited.
  • the elution amount of the polyvinyl alcohol-based resin when immersed in water at 30 ° C. for 2 minutes is 50 ppm / m 2 or less, the elution amount is small. Since it can reduce more, there exists an effect that the polarization performance of the polarizing film to manufacture can be improved.
  • the polarizing film can be increased in area.
  • the method for producing a polyvinyl alcohol film according to the second aspect of the present invention is to dry the formed film by bringing the front and back surfaces of the formed film alternately into contact with a plurality of metal heating rolls.
  • the dried state of the front and back surfaces of the formed film can be controlled appropriately.
  • it is possible to produce the polyvinyl alcohol film according to the first aspect which is excellent in suppressing the elution amount of the polyvinyl alcohol resin and suppressing the curl angle during the production of the polarizing film.
  • the total number of the metal heating rolls used in the drying step is P
  • the surface temperature of the metal heating roll with which the film peeled off from the cast mold contacts nth is Tn (° C.)
  • the nth When the contact time between the metal heating roll and the film is Sn (seconds), the thickness of the manufactured polyvinyl alcohol film is D ( ⁇ m), and n is an integer between 1 and P, Tn ⁇ Sn
  • ⁇ (Tn ⁇ Sn) representing the sum of the above satisfies the following formula (1)
  • the elution amount of the polyvinyl alcohol-based resin during the production of the polarizing film can be further suppressed.
  • the total number of the metal heating rolls used in the drying step is P
  • the surface temperature of the metal heating roll that the film peeled from the cast mold contacts xth is Tx (° C.)
  • the film is The surface temperature of the metal heating roll in contact with the yth is Ty (° C.)
  • the contact time between the xth metal heating roll and the film is Sx (seconds)
  • the yth metal heating roll and the film ⁇ (Tx ⁇ Sx) representing the sum of Tx ⁇ Sx, where Ty is a contact time of Sy (seconds)
  • x is an odd number from 1 to P
  • y is an even number from 2 to P
  • the total number of the metal heating rolls used in the drying step is P
  • the surface temperature of the metal heating roll that the film peeled from the cast mold contacts xth is Tx (° C.)
  • the film is The surface temperature of the metal heating roll in contact with the yth is Ty (° C.)
  • the contact time between the xth metal heating roll and the film is Sx (seconds)
  • the yth metal heating roll and the film When the contact time is Sy (seconds), the surface temperature of the cast mold is T 0 (° C.), x is an odd number from 1 to P, and y is an even number from 2 to P
  • Tx ⁇ Sx When ⁇ (Tx ⁇ Sx) representing the sum and ⁇ (Ty ⁇ Sy) representing the sum of Ty ⁇ Sy satisfy the following formula (3), the curl angle at the time of manufacturing the polarizing film is further reduced.
  • a film wound body is produced by winding the film dried in the drying step around a core tube in a roll shape, and the film wound body is wrapped with a water vapor barrier film, and an atmosphere of 25 to 30 ° C.
  • a temperature for 5 days or more there is an effect that the occurrence of curling during the production of the polarizing film can be further reduced.
  • the polarizing film according to the third aspect of the present invention has the effect that the polarizing performance is excellent since the polyvinyl alcohol film according to the first aspect is used.
  • the present invention is described in detail below.
  • the dissolution amount of the polyvinyl alcohol resin was 900 ppm / m 2 or less, and the following A
  • the curl angle in the short side direction measured under conditions is 135 ° or less.
  • test piece A rectangular test piece (first test piece) having a long side of 10 cm and a short side of 5 cm cut out from the polyvinyl alcohol film in an arbitrary direction, and a first edge portion in the long side direction of the test piece
  • first test piece A rectangular test piece having a long side of 10 cm and a short side of 5 cm cut out from the polyvinyl alcohol film in an arbitrary direction, and a first edge portion in the long side direction of the test piece
  • the entire test body is 30 ° C. Conditions for immersion in water for 10 seconds.
  • the polyvinyl alcohol-based film in which the elution amount and the curl angle of the polyvinyl alcohol-based resin are reduced is obtained by adopting a specific method for the drying process in the process of manufacturing the polyvinyl alcohol-based film by the continuous casting method. can get. That is, as will be described later, in the drying step, the film formed in a cast mold is alternately brought into contact with a plurality of metal heating rolls to dry the formed film. Thereby, the dry state of the surface and the back surface of the film formed above is appropriately controlled, and the polyvinyl alcohol film produced through the drying process has the above-described elution amount and curl angle of the polyvinyl alcohol resin. Is reduced.
  • the said polyvinyl alcohol-type film is formed in a polarizing film through a swelling process, a dyeing
  • the polyvinyl alcohol-based film has an elution amount of the polyvinyl alcohol-based resin with respect to water at a specific temperature as low as 900 ppm / m 2 or less, and a curl angle measured under specific water immersion conditions is 135 °.
  • the following is a small one. Therefore, at the time of manufacturing the polarizing film, the polarizing film manufacturing equipment is not contaminated, and folding and wrinkles are hardly generated in the swelling process. As a result, the productivity of the polarizing film is high, and the obtained polarizing film is excellent in polarizing performance.
  • Elution amount of the polyvinyl alcohol resin in terms of pollution avoidance of the polarizing film manufacturing facility, is preferably 800 ppm / m 2 or less, particularly preferably not more than 700 ppm / m 2, the elution of such a polyvinyl alcohol resin If the amount is too large, the polarizing film manufacturing equipment is contaminated and the object of the present invention cannot be achieved. Moreover, the lower limit of the elution amount of the polyvinyl alcohol-based resin is usually 1 ppm / m 2 . In general, since the polyvinyl alcohol film is immersed in warm water around 50 ° C. for about 1 minute when manufacturing the polarizing film, the immersion condition of 50 ° C.
  • the elution amount (ppm / m 2 ) in the present invention is obtained by dividing the elution concentration (ppm) by the area (m 2 ) of the test piece actually subjected to the elution test and converted to 1 m 2. .
  • the test piece (second test piece: polyvinyl alcohol film) subjected to the dissolution test is conditioned at 23 ° C. and 50% RH for 24 hours or more.
  • Such humidity conditioning conditions are general environmental conditions applied to various tests of plastic films, and are conditions for adjusting the moisture content in the polyvinyl alcohol film to the equilibrium moisture content in such an environment. is there. Normally, the moisture content in the test piece is adjusted to about 10% by such humidity control.
  • the test piece after humidity conditioning is immediately subjected to the dissolution test. The humidity control before the test is also applied in the elution test at 30 ° C. described later.
  • the polyvinyl alcohol film of the present invention preferably has an elution amount of the polyvinyl alcohol resin of 50 ppm / m 2 or less when immersed in water at 30 ° C. for 2 minutes.
  • the elution amount of the polyvinyl alcohol-based resin is particularly preferably 40 ppm / m 2 or less, more preferably 30 ppm / m 2 or less, from the viewpoint of avoiding contamination of the swelling tank in the production of the polarizing film.
  • the lower limit of the elution amount is usually 1 ppm / m 2 .
  • the immersion condition of 30 ° C. for 2 minutes is used.
  • the method for reducing the amount of elution in the immersion at 30 ° C. for 2 minutes is the same as the method described in the case of immersion at 50 ° C. for 1 minute.
  • the curl angle measured under the condition A is required to be 135 ° or less, particularly preferably 90 ° or less, and more preferably 45 ° or less. If the curl angle is larger than 135 °, the film is likely to be broken or wrinkled during the production of the polarizing film, and the object of the present invention cannot be achieved.
  • the polyvinyl alcohol film of the present invention preferably has a curl angle in the short side direction of 40 ° or less, particularly preferably, when the immersion time of the test specimen is 2 minutes under the condition A. 30 ° or less, more preferably 20 ° or less. If the curl angle is too large, breakage occurs in the swelling process during the production of the polarizing film, and breakage tends to occur during the transportation of the polyvinyl alcohol film.
  • a test piece (first test piece: test piece under the condition A) used for the measurement of the curl angle is cut out from the long polyvinyl alcohol film.
  • the cutting direction may be any direction, and is not particularly limited, but is cut out in a direction in which the long side of the test piece coincides with the film length direction (MD direction) and the short side corresponds to the film width direction (TD direction). It is preferable from the viewpoint of further reducing the curl angle and further suppressing the occurrence of the bending during the production of the polarizing film.
  • the manufacturing method of the polyvinyl alcohol-type film of this invention comprises a film-forming step of continuously discharging and casting an aqueous solution of a polyvinyl alcohol-based resin into a cast mold, and forming the film thus formed into the cast mold. And then drying the formed film, and then drying the formed film in the drying step, wherein the film is dried on the surface of the formed film. And the back surface are alternately brought into contact with a plurality of metal heating rolls. And in the manufacturing method of this invention, there exists the biggest characteristic in the setting conditions of the said drying process.
  • an unmodified polyvinyl alcohol resin that is, a resin produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate is usually used. If necessary, 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 resin is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, and more preferably 120,000 to 260,000. If the weight average molecular weight is too small, the degree of polarization of the polarizing film tends to decrease, and if it is too large, stretching during the production of the polarizing film tends to be difficult.
  • the weight average molecular weight of the polyvinyl alcohol resin is a weight average molecular weight measured by GPC-MALS method.
  • the average saponification degree of the polyvinyl alcohol resin used in the present invention is usually preferably 98 mol% or more, particularly preferably 99 mol% or more, further preferably 99.5 mol% or more, and particularly preferably 99.mol%. It is 8 mol% or more. If the average degree of saponification is too small, the degree of polarization of the polarizing film tends to decrease.
  • the average saponification degree in the present invention is measured according to JIS K 6726.
  • polyvinyl alcohol resin used in the present invention two or more kinds having different modified species, modified amount, weight average molecular weight, average saponification degree, etc. may be used in combination.
  • the aqueous solution used as the film-forming stock solution is prepared using the said polyvinyl alcohol-type resin. That is, first, the polyvinyl alcohol resin is preferably washed with water and dehydrated using a centrifuge or the like to obtain a polyvinyl alcohol resin wet cake having a water content of 50% by weight or less. When the water content is too large, it tends to be difficult to obtain a desired aqueous solution concentration. Such polyvinyl alcohol resin wet cake is dissolved in warm water or hot water to prepare a polyvinyl alcohol resin aqueous solution.
  • the method for preparing the polyvinyl alcohol-based resin aqueous solution is not particularly limited.
  • the polyvinyl alcohol-based resin aqueous solution may be prepared by using a heated multi-screw extruder. The polyvinyl alcohol resin wet cake thus prepared is charged, and water vapor is blown into the can to prepare an aqueous solution having a desired concentration and dissolution.
  • polyvinyl alcohol resin aqueous solutions include commonly used plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, trimethylolpropane, and nonionic properties. It is preferable from the viewpoint of the film-forming property of the polyvinyl alcohol film to contain at least one surfactant, anionic and cationic.
  • the resin concentration of the aqueous polyvinyl alcohol resin solution thus obtained is preferably 15 to 60% by weight, particularly preferably 17 to 55% by weight, and further preferably 20 to 50% by weight. If the resin concentration of such an aqueous solution is too low, the drying load increases and the production capacity tends to decrease. If it is too high, the viscosity becomes too high and uniform dissolution tends to be difficult.
  • the obtained polyvinyl alcohol resin aqueous solution is defoamed.
  • the defoaming method include stationary defoaming and defoaming using a multi-screw extruder having a vent.
  • a multi-screw extruder having a vent a twin-screw extruder having a vent is usually used.
  • the polyvinyl alcohol-based resin aqueous solution is introduced into a T-shaped slit die by a certain amount, discharged and cast on a rotating cast drum, and formed into a film by a continuous casting method.
  • the temperature of the polyvinyl alcohol resin aqueous solution at the exit of the T-shaped slit die is preferably 80 to 100 ° C., particularly preferably 85 to 98 ° C. If the temperature of the aqueous polyvinyl alcohol resin solution is too low, it tends to cause poor flow, and if it is too high, it tends to foam.
  • the viscosity of the polyvinyl alcohol-based resin aqueous solution is preferably 50 to 200 Pa ⁇ s, particularly preferably 70 to 150 Pa ⁇ s at the time of discharge.
  • the viscosity of the aqueous solution is too low, the flow tends to be poor, and when it is too high, casting tends to be difficult.
  • the discharge speed of the aqueous polyvinyl alcohol resin solution discharged from the T-type slit die onto the cast drum is preferably 0.1 to 5 m / min, particularly preferably 0.2 to 4 m / min, and more preferably 0.8. 3 to 3 m / min. If the discharge speed is too slow, the productivity tends to decrease, and if it is too fast, casting tends to be difficult.
  • SUS stainless steel
  • the metal plating include chrome plating, nickel plating, galvanization, and the like, and these are used alone or in a laminate of two or more layers.
  • the outermost surface is chrome plating from the viewpoint of durability of the drum surface.
  • the diameter of the cast drum is preferably 2 to 5 m, particularly preferably 2.4 to 4.5 m, and further preferably 2.8 to 4 m. If the diameter is too small, the drying length is insufficient and the speed tends not to be obtained, and if it is too large, the transportability tends to decrease.
  • the width of the cast drum is preferably 4 to 7 m, and particularly preferably 5 to 6 m. If the width of the cast drum is too narrow, the productivity tends to decrease, and if it is too wide, the equipment load tends to increase.
  • the rotational speed of the cast drum is preferably 3 to 50 m / min, particularly preferably 4 to 40 m / min, and further preferably 5 to 35 m / min. If the rotational speed is too slow, the productivity tends to decrease. If the rotational speed is too fast, the peelability when the formed film is peeled from the cast mold tends to decrease.
  • the surface temperature of such a cast drum is preferably 40 to 99 ° C., more preferably 50 to 98 ° C., further preferably 60 to 97 ° C., particularly preferably 70 to 96 ° C., and particularly preferably 80 to 95 ° C. It is.
  • the surface temperature is too low, the peelability when the film obtained by film formation is peeled off from the cast mold tends to be lowered, and when it is too high, the film tends to be foamed.
  • the film forming step is performed, and the formed film is peeled off from the cast drum.
  • FIG. 1 shows a case where seven heat rolls R1 to R7 are used.
  • symbol C shows the T-type slit die, and the code
  • the heat rolls R1 to R7 are not particularly limited as long as they are made of a metal having a heating function, but are preferably rolls having a diameter of 0.2 to 2 m with a hard chrome plating treatment or a mirror finish treatment.
  • the number of rolls is usually 2 to 30, preferably 10 to 25.
  • a roll whose surface temperature is heated to 40 ° C. or higher and whose temperature is adjusted is referred to as a hot roll.
  • this drying step it is one of the major features of the present invention that the front and back surfaces of the film peeled off from the cast drum are alternately brought into contact with a plurality of hot rolls for drying.
  • the dried state of the surface and the back surface of the peeled film is appropriately controlled, and the polyvinyl alcohol film produced through this drying step has an elution amount of the polyvinyl alcohol resin and The curl angle can be reduced.
  • the total number of the heat rolls used in the drying step is P
  • the surface temperature of the heat roll at which the film peeled off from the cast drum contacts nth is Tn (° C.)
  • the nth heat When the contact time of the roll and the film is Sn (seconds), the thickness of the polyvinyl alcohol film to be produced is D ( ⁇ m), and n is an integer of 1 to P, the total of Tn ⁇ Sn is expressed. It is preferable that ⁇ (Tn ⁇ Sn) satisfies the following formula (1). 75 ⁇ ⁇ (Tn ⁇ Sn) / D ⁇ 110 (1)
  • ⁇ (Tn ⁇ Sn) is a value obtained by calculating the value of Tn ⁇ Sn for all the 1st to Pth heat rolls and adding them together.
  • the surface temperature T 1 of the first heat roll 70 ° C.
  • the contact time S 1 between the first heat roll and the film 6 seconds.
  • the contact time between the heat roll and the film means the contact time between any one point in the film plane and each heat roll. Such a contact time can be controlled by changing the outer diameter and arrangement of each heat roll even if the film conveyance speed is constant.
  • the surface temperature Tn of all the hot rolls used is preferably 40 to 150 ° C., particularly preferably 50 to 140 ° C., more preferably 60 to 130 ° C., and particularly preferably 70 to 120 ° C. It is. If the surface temperature of such a heat roll is too low, drying tends to be insufficient, and if the surface temperature Tn of the heat roll is too high, the crystallization of the polyvinyl alcohol-based resin proceeds and the swellability during the production of the polarizing film is uniform. There is a tendency to disappear.
  • the contact time Sn between each hot roll and the film is preferably 1 to 60 seconds, particularly preferably 2 to 30 seconds, more preferably 3 to 20 seconds, and particularly preferably 4 to 10 seconds. If the contact time Sn is too short, drying tends to be insufficient, and if the contact time Sn is too long, the equipment load tends to increase.
  • the total number of the said heat rolls used for the said drying process is P piece
  • the surface temperature of the said heat roll which the film peeled from the said casting mold contacts xth (odd number) is set to Tx (degreeC). )
  • the surface temperature of the heat roll contacting the y-th (even number) film is Ty (° C.)
  • the contact time between the x-th (odd number) heat roll and the film is Sx (seconds)
  • y ⁇ (Tx ⁇ Sx) representing the sum of Tx ⁇ Sx
  • ⁇ (Ty ⁇ Sy) representing the sum of Ty ⁇ Sy
  • Sy (seconds) is the contact time between the second (even number) heat roll and the film.
  • the following formula (2) is satisfied.
  • the surface temperature T 1 of the first heat roll 70 ° C.
  • the contact time S 1 between the first heat roll and the film is 6 seconds.
  • the polyvinyl alcohol film tends to curl in the swelling process during the production of the polarizing film. Conversely, even if ⁇ (Ty ⁇ Sy) is excessively small, the polyvinyl alcohol film tends to curl in the reverse direction. That is, the purpose of the above formula (2) is that the surface of the film formed that is in contact with the cast mold is normally in contact with the even-numbered heat roll. The amount of heat supplied to both sides of the film is made equal to less than the amount of heat received from the heat roll.
  • ⁇ (Tx ⁇ Sx) representing the sum of Tx ⁇ Sx
  • ⁇ (Ty ⁇ Sy) representing the sum of Ty ⁇ Sy.
  • the following formula (3 ′) is satisfied, and further preferably, the following formula (3 ′′) is satisfied.
  • the purpose of the above formula (3) is that the surface that is in contact with the cast mold of the film is in contact with the even-numbered heat roll, so the amount of heat received from the cast mold and the even-numbered heat roll is The purpose is to make the amount of heat supplied from both sides of the film substantially equal to the amount of heat received from the heat roll.
  • the moisture content of the dried film is preferably 10% by weight or less, particularly preferably 1 to 9% by weight, and more preferably 2 to 8% by weight. If the moisture content is too high, the finally obtained polyvinyl alcohol film tends to be poorly dried.
  • the heat-treat method include a method of blowing hot air on both surfaces of the film using a floating dryer, and a method of irradiating near infrared rays on both surfaces of the film using an infrared lamp.
  • a heat treatment temperature is preferably 50 to 150 ° C., particularly preferably 70 to 130 ° C.
  • the heat treatment temperature means the temperature of the hot air when the heat treatment method is a method of blowing hot air with the floating dryer, and the heat treatment method is a method of irradiating near infrared light with the infrared lamp. , That means the near infrared temperature.
  • the heat treatment time is not particularly limited, but when a floating dryer is used, it is preferably 10 to 100 seconds, and particularly preferably 20 to 80 seconds. Note that the heat treatment method does not use a heat roll.
  • Polyvinyl alcohol film The said heat processing is performed after the said drying process as needed, and the polyvinyl alcohol-type film of this invention long in a flow direction (MD direction) is obtained.
  • This polyvinyl alcohol film is produced into a film winding body by slitting both ends in the width direction (TD direction) and winding it around a core tube in a roll shape.
  • a package by packaging the film winding body with a water vapor barrier film, and store the package at an atmospheric temperature of 25 to 30 ° C. for 5 days or more.
  • the storage period is particularly preferably 10 days or more, particularly preferably 15 days or more, and further preferably 15 to 60 days. If the storage period is too short, curling during water immersion tends to occur. On the contrary, if the storage period is too long, the production of the polarizing film tends to be delayed.
  • the storage method is not particularly limited, and examples thereof include a method using a constant temperature and humidity chamber and a roll stocker.
  • the length of the polyvinyl alcohol film of the present invention thus obtained is preferably 5 km or more from the viewpoint of increasing the area of the polarizing film, and particularly preferably 5 to 50 km from the viewpoint of transport weight.
  • the width of the polyvinyl alcohol film of the present invention is preferably 4 m or more from the viewpoint of widening the polarizing film, particularly preferably 5 m or more, and more preferably 5 to 6 m from the viewpoint of avoiding breakage during the production of the polarizing film. It is.
  • the polyvinyl alcohol film of the present invention preferably has a thickness of 10 to 75 ⁇ m, preferably 10 to 60 ⁇ m from the viewpoint of thinning, and particularly preferably 20 from the viewpoint of reducing retardation. From 60 to 60 ⁇ m, more preferably from 30 to 60 ⁇ m from the viewpoint of avoiding breakage.
  • the crossing angle ⁇ between the film orientation axis (slow axis) and the width direction (TD direction) is preferably 45 ° or less.
  • the crossing angle ⁇ exceeds 45 °, there is a tendency to curl in the width direction (TD direction) during swelling.
  • Such a phenomenon is expected to occur because water absorption occurs not in the orientation direction of the polymer but in a gap between the polymers. That is, when the orientation direction of the polymer is the length direction (MD direction), swelling is more likely to occur in the width direction (TD direction) than in the intended length direction (MD direction).
  • the polyvinyl alcohol film of the present invention has a refractive index in the length direction (MD direction) of nx, a refractive index in the width direction (TD direction) of ny, a refractive index in the thickness direction of nz, and a thickness of D ( ⁇ m),
  • the thickness direction retardation Rth (nm) calculated by the following formula (4) is preferably 100 nm or more, particularly preferably 110 nm or more, more preferably 110 to 200 nm. is there. If the phase difference Rth is too small, it tends to curl during swelling. Such a phenomenon is expected because, when the phase difference Rth is small, the alignment of the polymer chain in the thickness direction becomes strong, and smooth swelling in the thickness direction is inhibited.
  • the method for producing a polyvinyl alcohol film has been described by taking as an example the case where a cast drum (drum roll) is used as a cast mold.
  • a cast belt or a resin film is used as a cast mold. It is also possible to manufacture.
  • mold in the drying process of the process which manufactures a polyvinyl-alcohol-type film by the continuous casting method, the surface of the film formed with the cast type
  • mold in the drying process of the process which manufactures a polyvinyl-alcohol-type film by the continuous casting method, the surface of the film formed with the cast type
  • mold Although the back surface is alternately brought into contact with a plurality of metal heating rolls, the method of appropriately controlling the dry state of the surface and the back surface of the film formed is adopted, but other methods may be adopted. .
  • a method for adjusting the molecular weight and saponification degree of a polyvinyl alcohol resin as a raw material a method for improving the purity by washing the polyvinyl alcohol resin, a method for adding a surfactant to an aqueous solution of a polyvinyl alcohol resin, polyvinyl
  • examples thereof include a method for controlling the crystallinity and orientation of the polymer in the step of forming a film using an alcohol-based resin aqueous solution, and a method for controlling the dry state of the formed film.
  • the surface and the back surface of the film formed with the cast mold are alternately used in the drying process in the process of producing the polyvinyl alcohol film by the continuous casting method.
  • the method which controls appropriately the dry state of the surface and back surface of the film formed by making it contact with a some metal heating roll was employ
  • a method for controlling the orientation state of the polymer in the step of forming a film using a polyvinyl alcohol resin aqueous solution, a method for improving the thickness accuracy during film formation, a method for controlling the dry state of the formed film, etc. can give.
  • the polyvinyl alcohol-based film of the present invention is particularly preferably used as a raw material for a polarizing film because the polyvinyl alcohol-based resin is hardly eluted when immersed in water and the curl angle is reduced.
  • the polarizing film of the present invention is produced through steps such as swelling, dyeing, boric acid crosslinking, stretching, washing, and drying by feeding the polyvinyl alcohol film out of the film winding body and transporting it in the horizontal direction.
  • the swelling process is performed before the dyeing process.
  • water is usually used as the treatment liquid.
  • the treatment liquid may contain a small amount of an additive such as an iodide compound, a surfactant, alcohol, and 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.
  • the dyeing step is performed by bringing a liquid containing iodine or a dichroic dye into contact with the polyvinyl alcohol film.
  • a liquid containing iodine or a dichroic dye into contact with the polyvinyl alcohol film.
  • 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.
  • 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 is preferably performed 3 to 10 times, preferably 3.5 to 6 times in a uniaxial direction [flow direction (MD direction)].
  • a slight stretching may also be performed in the direction perpendicular to the stretching direction.
  • the temperature during stretching is preferably 30 to 170 ° C.
  • the stretching ratio may be finally set within the above range, and the stretching operation may be performed not only once but plural times in the polarizing film manufacturing process.
  • the washing step is performed, for example, by immersing the polyvinyl alcohol film in an aqueous iodide solution such as water or potassium iodide, and the deposits generated on the surface of the polyvinyl alcohol film can be removed.
  • an aqueous potassium iodide solution such as water or potassium iodide
  • the potassium iodide concentration is 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 polyvinyl alcohol film is dried 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 99.8% or more, more preferably 99.9% 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 single transmittance of the polarizing film of the present invention is preferably 42% or more, more 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 suitable for producing a polarizing plate having excellent degree of polarization and no color unevenness.
  • the manufacturing method of the polarizing plate using the polarizing film of this invention is demonstrated.
  • the polarizing plate is produced by laminating an optically isotropic resin film as a protective film on one or both sides of the polarizing film of the present invention via an adhesive.
  • the protective film include 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. It is performed by irradiating active energy rays.
  • a polarizing plate can be formed by applying a curable resin such as urethane resin, acrylic resin, urea resin or the like to one or both surfaces of the polarizing film and curing to form a cured layer. If it does in this way, the said hardened layer becomes a substitute of the said protective film, and can attain thinning.
  • a curable resin such as urethane resin, acrylic resin, urea resin or the like
  • Polarizing films and polarizing plates using the polyvinyl alcohol film of the present invention are excellent in polarizing performance, such as portable information terminals, personal computers, televisions, projectors, signage, electronic desk calculators, electronic watches, word processors, electronic paper, games.
  • Machines, videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as automobile and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements (CRT, LCD, organic EL, electronic It is preferably used for an antireflection layer for paper and the like, an optical communication device, a medical device, a building material, a toy and the like.
  • the obtained polyvinyl alcohol film was conditioned at 23 ° C. and 50% RH for 24 hours, and then a 100 mm ⁇ 100 mm (0.01 m 2 ) test piece (second test piece) was cut out and 1 L of ion-exchanged water. was immersed for 1 minute at 50 ° C. to obtain an eluate.
  • the long side of the test piece was the length direction (MD direction) of the film
  • the short side was the width direction (TD direction) of the film.
  • the center of the lower edge of the test piece 1 in the long side direction is the (first) clip ("Kokuyo's" eyeball clip pea "); mouth width 20mm; mass 2 .1g)
  • the wire 2b was wound around the clip 2a.
  • the weight of total weight 5 g was changed to a weight 2, and a test body composed of the test piece 1 and the weight 2 was prepared. Thereafter, the center of the upper edge of the test piece 1 in the long side direction is sandwiched between the (second) clip (same as above) 3a, and the string 3b is tied to the clip 3a (the suspension composed of the clip 3a and the string 3b). The lowering jig 3 was attached to the center of the upper edge of the test piece 1 in the long side direction). Next, the entire test body was immersed in 30 ° C. water 4a in the water tank 4 in a state where the test body with the clip 3a was suspended by the string 3b.
  • the curl angle ⁇ (°) in the short side direction (width direction) at the time when 10 seconds have passed and 2 minutes have passed since the immersion, as shown in FIG. 2 (b), the upper part of the water tank 4 (not shown). To observe visually. In FIG. 2 (b), the above-described heavy stone 2, the hanging jig 3, and the water tank 4 are not shown for easy understanding of the configuration. Further, the curl angle ⁇ is an angle formed by the plane portion of the test piece 1 and the tangential direction of the edge of the curled portion in the short side direction.
  • Example 1> (Preparation of polyvinyl alcohol film) 2,000 kg of polyvinyl alcohol resin having a weight average molecular weight of 142,000 and a saponification degree of 99.8 mol%, 5,000 kg of water, and 220 kg of glycerin as a plasticizer are added, heated to 140 ° C. with stirring and dissolved under pressure. Then, the concentration was adjusted to a resin concentration of 25% by weight to obtain a uniformly dissolved polyvinyl alcohol resin aqueous solution.
  • the polyvinyl alcohol-based resin aqueous solution is supplied to a twin-screw extruder having a vent and defoamed, and then the temperature of the aqueous solution is set to 95 ° C., and the cast drum (surface temperature 92 ° C.) is rotated from the T-type slit die discharge port. ) Were discharged (discharge speed 2.5 m / min) and cast to form a film. The formed film was peeled from the cast drum, and dried while the front surface and the back surface (contact surface with the cast drum) of the film were alternately brought into contact with a total of 15 hot rolls. Drying conditions [see the above formulas (1) to (3)] are as shown in Table 1 below.
  • the said film winding body was wrapped twice with the water vapor
  • As the water vapor barrier film a laminated film of an aluminum vapor-deposited polyester film (a polyethylene terephthalate film vapor-deposited with 50 nm of aluminum, 12 ⁇ m thickness) and a polyethylene film (25 ⁇ m thickness) was used. Next, the package was stored for 15 days in a roll stocker with an ambient temperature of 26 ° C. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below.
  • the obtained polyvinyl alcohol film is unwound from the film winding body and transported in the horizontal direction using a transport roll.
  • the film is immersed in a water bath with a water temperature of 30 ° C. and swollen in 2 minutes (MD direction). ) was stretched 1.7 times.
  • the film is stretched 1.6 times in the flow direction (MD direction) in 0.5 minutes while being immersed and dyed in a 28 ° C. aqueous solution composed of 0.5 g / L of iodine and 30 g / L of potassium iodide.
  • the film was immersed in a 50 ° C.
  • Example 2 A film winding body (size of polyvinyl alcohol film: thickness 60 ⁇ m, width 5 m, length 5 km) was obtained in the same manner as in Example 1 except that the production was performed under the conditions shown in Table 1 below. Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Further, a polarizing film was obtained in the same manner as in Example 1. The properties of the obtained polarizing film are shown in Table 2 below.
  • Example 3 a film wound body (polyvinyl alcohol film) was prepared in the same manner as in Example 1 except that the discharge rate was 2.5 m / min and the production was performed under the conditions shown in Table 1 below. Dimension: thickness 45 ⁇ m, width 5 m, length 5 km). Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Further, a polarizing film was obtained in the same manner as in Example 1. The properties of the obtained polarizing film are shown in Table 2 below.
  • Example 4 the film winding body (polyvinyl alcohol film) was prepared in the same manner as in Example 1 except that the discharge rate was 2.5 m / min and the condition shown in Table 1 below was set to 1.3 m / min. Dimension: thickness 30 ⁇ m, width 5 m, length 5 km). Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Further, a polarizing film was obtained in the same manner as in Example 1. The properties of the obtained polarizing film are shown in Table 2 below.
  • a film winding body (size of polyvinyl alcohol film: thickness 60 ⁇ m, width 5 m, length 5 km) was obtained in the same manner as in Example 1 except that the production was performed under the conditions shown in Table 1 below. Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Further, a polarizing film was obtained in the same manner as in Example 1. The properties of the obtained polarizing film are shown in Table 2 below. In addition, when the chemical
  • Example 2 ⁇ Comparative Example 2> (corresponding to Example 1 of Patent Document 3)
  • the film winding body polyvinyl alcohol type
  • Example 1 the film winding body (polyvinyl alcohol type) was prepared in the same manner as in Example 1 except that the discharge rate was 2.5 m / min and the production was performed under the conditions shown in Table 1 below. Film dimensions: thickness 45 ⁇ m, width 5 m, length 5 km). Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Further, the production of the polarizing film was started in the same manner as in Example 1, but the production was stopped because the film edge was broken in the swelling process. The characteristics of the obtained portion (tip portion) of the polarizing film are shown in Table 2 below.
  • Example 3 the film winding body (polyvinyl alcohol film) was prepared in the same manner as in Example 1 except that the discharge rate was 2.5 m / min and the condition shown in Table 1 below was set to 1.3 m / min. Dimension: thickness 30 ⁇ m, width 5 m, length 5 km). Further, the film winding body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below. Furthermore, an attempt was made to produce a polarizing film in the same manner as in Example 1. However, a fold occurred at the end of the film in the swelling process, and a rupture occurred in the subsequent stretching process, so that the polarizing film was not obtained.
  • Example 4 ⁇ Comparative Example 4>
  • the discharge speed was 2.5 m / min, 2.1 m / min, and the production was performed under the conditions shown in Table 1 below using a total of 18 heat rolls.
  • a film winding body size of polyvinyl alcohol film: thickness 50 ⁇ m, width 5 m, length 5 km
  • the film winding body was stored in the same manner as in Example 1.
  • the characteristics of the polyvinyl alcohol film after storage are shown in Table 1 below.
  • an attempt was made to produce a polarizing film in the same manner as in Example 1. However, a fold occurred at the end of the film in the swelling process, and a rupture occurred in the subsequent stretching process, so that the polarizing film was not obtained.
  • the polyvinyl alcohol film of Examples 1 to 4 has a resin elution amount in water and a curl angle when immersed in water within the specific range of the present application, the polarizing film has excellent productivity and polarization performance and no color unevenness. was gotten.
  • the polyvinyl alcohol film of Comparative Example 1 has a resin elution amount in water outside the specific range of the present application, it can be seen that the obtained polarizing film is inferior in polarization performance and has color unevenness.
  • the polyvinyl alcohol films of Comparative Examples 2 to 4 had a curl angle when immersed in water outside the specific range of the present application, a wide and long polarizing film could not be obtained.
  • Polarizing films and polarizing plates using the polyvinyl alcohol film of the present invention are excellent in polarizing performance, such as portable information terminals, personal computers, televisions, projectors, signage, electronic desk calculators, electronic watches, word processors, electronic paper, games.
  • Machines, videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as automobile and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements (CRT, LCD, organic EL, electronic It is preferably used for an antireflection layer for paper and the like, an optical communication device, a medical device, a building material, a toy and the like.

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CN112041715A (zh) * 2019-02-26 2020-12-04 日东电工株式会社 偏光件的制造方法、偏光薄膜的制造方法、层叠偏光薄膜的制造方法、图像显示面板的制造方法和图像显示装置的制造方法
KR20230160238A (ko) 2021-03-24 2023-11-23 미쯔비시 케미컬 주식회사 폴리비닐알코올계 필름, 및 이의 제조 방법, 및 이를 이용한 편광막, 편광판

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EP3904035A4 (en) * 2018-12-28 2022-09-14 Kuraray Co., Ltd. WATER SOLUBLE FILM, METHOD OF MANUFACTURE THEREOF AND PACKAGING
CN114761200A (zh) * 2019-12-11 2022-07-15 株式会社可乐丽 光学用聚乙烯醇膜的制造方法
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