WO2016208652A1 - Poly(vinyl alcohol)-based film, process for producing poly(vinyl alcohol)-based film, and polarizing film - Google Patents

Poly(vinyl alcohol)-based film, process for producing poly(vinyl alcohol)-based film, and polarizing film Download PDF

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Publication number
WO2016208652A1
WO2016208652A1 PCT/JP2016/068598 JP2016068598W WO2016208652A1 WO 2016208652 A1 WO2016208652 A1 WO 2016208652A1 JP 2016068598 W JP2016068598 W JP 2016068598W WO 2016208652 A1 WO2016208652 A1 WO 2016208652A1
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WO
WIPO (PCT)
Prior art keywords
polyvinyl alcohol
film
alcohol film
water
tension
Prior art date
Application number
PCT/JP2016/068598
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French (fr)
Japanese (ja)
Inventor
裕一 寺本
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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Filing date
Publication date
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 JP2016542783A priority Critical patent/JP6883990B2/en
Priority to CN201680029754.7A priority patent/CN107614578A/en
Priority to KR1020177033815A priority patent/KR102475405B1/en
Publication of WO2016208652A1 publication Critical patent/WO2016208652A1/en

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Classifications

    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/05—Alcohols; Metal alcoholates
    • C08K5/053—Polyhydroxylic alcohols
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
    • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
    • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • 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
    • 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 film. More specifically, a polyvinyl alcohol film for producing a polarizing film excellent in dyeability and stretchability as a raw material of the polarizing film and excellent in polarizing performance, a production method thereof, and the polyvinyl alcohol film
  • the present invention relates to a polarizing film obtained by use.
  • the polarizing film is produced by dyeing and stretching a polyvinyl alcohol film as a raw material with a pigment such as iodine.
  • a pigment such as iodine.
  • a polyvinyl alcohol film is swollen with warm water, dyed with iodine, stretched to arrange iodine molecules, cross-linked with a cross-linking agent such as boric acid to maintain the stretched state, washed, And dried.
  • the steps of water swelling, dyeing, stretching, and boric acid crosslinking may be switched in order or a plurality of steps may be performed simultaneously. What is common is that the polyvinyl alcohol film is continuously unwound from the roll, applied with appropriate tension in the flow direction using a winder or nip roll, and conveyed in the horizontal direction. .
  • Such a polarizing film is used as a basic component of liquid crystal display devices such as portable information terminals and televisions.
  • liquid crystal display devices such as portable information terminals and televisions.
  • polarizing films having high light transmittance and high degree of polarization.
  • liquid crystal televisions have become larger and thinner, conventional products have been demanded.
  • polarizing film that is wider, longer, and thinner.
  • a wide, long and thin polyvinyl alcohol-based film having excellent dyeability and stretchability is required.
  • the dyeability of the polyvinyl alcohol film is low, a sufficient degree of polarization cannot be obtained, and polarization unevenness tends to occur.
  • the stretchability of the polyvinyl alcohol-based film is low, breakage occurs in the manufacturing process of the polarizing film, so that a wide, long and thin polarizing film cannot be manufactured. As a matter of course, continuous production is interrupted by breakage, and the productivity of the polarizing film is greatly reduced.
  • the stretchability is low, the dye is not sufficiently oriented, and thus the degree of polarization tends to decrease or polarization unevenness tends to occur.
  • Patent Documents 1 and 2 In order to improve the dyeability of a polyvinyl alcohol film, a technique for controlling the bath temperature in the swelling process has been proposed (see, for example, Patent Documents 1 and 2). Moreover, a polarizing plate using a polyvinyl alcohol film having a specific range of stretchability has been proposed (see, for example, Patent Document 3).
  • Patent Document 3 defines a stress (tension) when a polyvinyl alcohol film is stretched 4 to 6 times in water.
  • the water temperature is often around 30 ° C., which is a relatively low temperature in processes such as swelling and dyeing, and around 50 ° C., which is a relatively high temperature, in processes such as stretching and boric acid crosslinking.
  • a polyvinyl alcohol film that can be obtained is provided.
  • the present inventors have made a polyvinyl alcohol solution obtained by discharging and casting an aqueous solution of a polyvinyl alcohol resin into a cast mold and continuously drying it.
  • the polyvinyl alcohol film produced by paying attention to the underwater tension at a higher temperature of 50 ° C. is particularly wide so that when the film is stretched in water at different temperatures, the underwater tension is in a specific range. It has been found that a polarizing film having a high degree of polarization and no polarization unevenness can be produced even when it is made thin.
  • the gist of the present invention is that the tension when stretched 6 times in the flow direction of the film (MD direction) in water of thickness D (mm) and 30 ° C. is A (N / mm 2 ) and water in 50 ° C.
  • the following formulas (1) and (2) are satisfied when the tension when stretched 6 times in the film flow direction (MD direction) is B (N / mm 2 ): the film.
  • the present invention also provides a method for producing the polyvinyl alcohol film and a polarizing film obtained using the polyvinyl alcohol film.
  • the polyvinyl alcohol film of the present invention is excellent in dyeability and stretchability, and has a high degree of polarization even in the case of being wide, long and thin, and can obtain a polarizing film free from uneven polarization. Can produce a polarizing film with high productivity.
  • the polyvinyl alcohol film of the present invention has a thickness of D (mm) and a tension of A (N / mm 2 ) and 50 ° C. when stretched 6 times in the film flow direction (MD direction) in 30 ° C. water.
  • a polyvinyl alcohol film satisfying the following formulas (1) and (2) when the tension when stretched 6 times in the film flow direction (MD direction) in water is B (N / mm 2 ).
  • Formula (1 ′) 0.65 ⁇ D ⁇ A ⁇ 1.15
  • Formula (2 ′) 0.25 ⁇ D ⁇ B ⁇ 0.39
  • Particularly preferred is a polyvinyl alcohol film satisfying the following formulas (1 ′′) and (2 ′′).
  • Formula (1 ′′) 0.7 ⁇ D ⁇ A ⁇ 1.1
  • Formula (2 ′′) 0.27 ⁇ D ⁇ B ⁇ 0.38
  • the value of the thickness D of the polyvinyl alcohol film is 0.04 mm or less in terms of thinning the polarizing film. It is preferably 0.03 mm or less from the viewpoint of further thinning the polarizing film, and more preferably from 0.01 to 0.03 mm from the viewpoint of avoiding breakage of the polarizing film.
  • the polyvinyl alcohol film of the present invention preferably satisfies the following formula (3), particularly preferably satisfies the following formula (3 ′), and more preferably satisfies the following formula (3 ′′).
  • Formula (3) 0.2 ⁇ B / A ⁇ 0.5 Formula (3 ′) 0.25 ⁇ B / A ⁇ 0.4 Formula (3 ′′) 0.3 ⁇ B / A ⁇ 0.35
  • the polyvinyl alcohol film of the present invention preferably has a tension A of 15 to 40 N / mm 2 when stretched 6 times in the film flow direction (MD direction) in water at 30 ° C., particularly preferably. Is 18 to 35 N / mm 2 , more preferably 20 to 30 N / mm 2 . If the value of the tension A is too low, the film tends to be deformed in the swelling process or the dyeing process, and if it is too high, sufficient dyeing tends to be difficult in the dyeing process.
  • the polyvinyl alcohol film of the present invention preferably has a tension B value of 3 to 15 N / mm 2 when stretched 6 times in the film flow direction (MD direction) in water at 50 ° C., Particularly preferred is 4 to 12 N / mm 2 , and more preferred is 5 to 10 N / mm 2 . If the value of the tension B is too low, the degree of polarization when the polarizing film is formed tends to decrease, and if it is too high, breakage tends to occur during the production of the polarizing film.
  • the polyvinyl alcohol film of the present invention has an E2 / E1 value of 0 when the storage elastic modulus in water at 30 ° C. is E1 (Pa) and the storage elastic modulus in water at 50 ° C. is E2 (Pa). It is preferably from 25 to 0.30, particularly preferably from 0.26 to 0.29. If the value of E2 / E1 is too low, the polarization degree of the obtained polarizing film tends to decrease, and if it is too high, breakage tends to occur during the production of the polarizing film.
  • the polyvinyl alcohol film of the present invention preferably has a storage elastic modulus E1 in water of 30 ° C. of 9 to 12 MPa from the viewpoint of transportability. Further, the storage elastic modulus E2 in water at 50 ° C. is preferably 2 to 4 MPa from the viewpoint of transportability.
  • a method for producing a polyvinyl alcohol film of the present invention that is, an aqueous solution of a polyvinyl alcohol resin is discharged and cast into a cast mold to form a film, and continuously dried to produce a polyvinyl alcohol film. A method will be described.
  • 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, sufficient optical performance tends to be difficult to obtain when the polyvinyl alcohol-based resin is used as an optical film, and if it is too large, it is difficult to stretch the polyvinyl alcohol-based film during the production of the polarizing film. Tend.
  • 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, there is a tendency that sufficient optical performance cannot be obtained when a polyvinyl alcohol film is used as a polarizing film.
  • 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 polyvinyl alcohol-based film of the present invention is prepared by preparing a polyvinyl alcohol-based resin aqueous solution (film forming stock solution) using the polyvinyl alcohol-based resin, and discharging and casting the aqueous solution into a cast mold. It can manufacture continuously by drying, for example, is manufactured by the following processes.
  • Step (A) A step of preparing a polyvinyl alcohol resin aqueous solution.
  • Step (B) A step of casting an aqueous solution of a polyvinyl alcohol resin into a cast mold to form a film.
  • Step (C) A step of heating and drying the formed film by bringing it into contact with a plurality of metal heating rolls.
  • Process (D) The process of heat-processing the obtained film using a hot air.
  • examples of the cast mold include a cast drum (drum mold roll), an endless belt, and the like.
  • the cast mold is preferably performed from the viewpoint of widening, lengthening, and film thickness uniformity.
  • a case where the cast mold is a cast drum will be described as an example.
  • step (A) will be described.
  • the polyvinyl alcohol-based resin described above is washed with water and dehydrated using a centrifuge to obtain a polyvinyl alcohol-based resin wet cake having a water content of 50% by weight or less. It is preferable. 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-based 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.
  • the latter is preferable from the viewpoint of improving the degree of polarization, and it is more preferable to prepare the solution by pressure dissolution at 120 ° C. or higher.
  • the polyvinyl alcohol-based resin aqueous solution may contain a plasticizer and at least one surfactant of nonionic, anionic, and cationic properties as necessary. It is preferable from the point.
  • plasticizer used in the present invention examples include glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and trimethylolpropane.
  • glycerin is preferable because of its low cost.
  • the blending amount is preferably 5 to 12% by weight, particularly preferably 6 to 11.5% by weight, and more preferably 7 to 11% with respect to the polyvinyl alcohol resin. If the amount is too small, the underwater tension of the polyvinyl alcohol film tends to increase, and if too large, the underwater tension of the polyvinyl alcohol film tends to be insufficient.
  • the surfactant used in the present invention is preferably an anionic surfactant from the viewpoint of compatibility with an aqueous polyvinyl alcohol resin solution.
  • 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 is too low, the drying load increases, so the production capacity tends to decrease. If the resin concentration is too high, the viscosity becomes too high and uniform dissolution tends to be difficult.
  • the polyvinyl alcohol resin aqueous solution is defoamed.
  • Examples of the defoaming method include static defoaming and defoaming by 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 casting method.
  • the resin temperature of the T-type slit die discharge port is preferably 80 to 100 ° C., particularly preferably 85 to 99 ° C. If the resin temperature is too low, the flow tends to be poor, and if it is too high, the resin tends to foam.
  • the viscosity of the aqueous polyvinyl alcohol resin 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 0.2 to 5 m / min, particularly preferably 0.4 to 4 m / min, and more preferably 0.8. 6-3 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.
  • Casting is preferably performed with a cast drum from the viewpoint of widening, lengthening, and film thickness uniformity.
  • a cast drum usually, a surface of stainless steel (SUS) whose main component is iron is subjected to metal plating to prevent damage.
  • SUS stainless steel
  • the metal plating include chrome plating, nickel plating, and zinc plating, and these are used alone or in a laminate of two or more layers. Among these, it is preferable that the outermost surface is chrome plating from the viewpoint of durability of the drum surface.
  • the width of the cast drum is preferably 4 m or more, particularly preferably 5 m or more. If the width of the cast drum is too small, it tends to be difficult to obtain a wide film.
  • the diameter of the cast drum is preferably 2 to 5 m, particularly preferably 2.4 to 4.5 m, and more 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 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, and if it is too fast, drying tends to be insufficient.
  • the surface temperature of the cast drum is preferably 40 to 99 ° C, particularly preferably 60 to 95 ° C. If the surface temperature is too low, drying tends to be poor, and if it is too high, foaming tends to occur.
  • Step (C) is a step of heating and drying the formed film by bringing it into contact with a plurality of metal heating rolls.
  • the drying of the polyvinyl alcohol film formed on the cast drum is performed by bringing the front and back surfaces of the film into contact with a plurality of metal heating rolls alternately.
  • the surface temperature of the metal heating roll is not particularly limited, but is usually 60 to 150 ° C., more preferably 70 to 140 ° C. If the surface temperature is too low, drying tends to be poor, and if the surface temperature is too high, drying tends to be excessive, and appearance defects such as undulation tend to be caused.
  • the temperature of the plurality of metal heating rolls is preferably in the order of the following conditions (a) to (d) from the viewpoint of controlling the underwater tension of the polyvinyl alcohol film.
  • Condition (d) ⁇ 100 ° C In general, the number of metal heating rolls is 10 to 30, and is appropriately set so as to satisfy the above temperature condition.
  • step (D) After drying with a metal heating roll, the obtained film is heat-treated using hot air in the step (D). Next, the step (D) will be described.
  • the heat treatment temperature is preferably 110 to 140 ° C., particularly preferably 115 to 135 ° C., and further preferably 120 to 130 ° C. If the heat treatment temperature is too low, the underwater tension of the polyvinyl alcohol film tends to be insufficient, and if it is too high, the underwater tension of the polyvinyl alcohol film tends to increase. As a method of such heat treatment, a method using a floating dryer is preferable in terms of excellent temperature control.
  • the film that has been heat-treated is slit at both ends and wound into a roll to form a roll-shaped polyvinyl alcohol film.
  • the width of the polyvinyl alcohol film is preferably 4 m or more from the viewpoint of widening the polarizing film, particularly preferably 4.5 m or more from the viewpoint of further widening, and more preferably from the viewpoint of avoiding breakage. 4.5 to 6 m.
  • the length of the polyvinyl alcohol film is preferably 4 km or more from the viewpoint of increasing the area of the polarizing film, particularly preferably 4.5 km or more, more preferably from the viewpoint of transport weight. From 4.5 to 50 km.
  • the above-mentioned polyvinyl alcohol film has a tension of 40 to 80 N / mm 2 when stretched four times in the film flow direction (MD direction) in the atmosphere of 20 ° C. and 65% RH in terms of windability. It is preferred, particularly preferably, a point at 43 ⁇ 75N / mm 2 of stability during storage, and more preferably from 46 ⁇ 70N / mm 2 from the ease of control of the water tension.
  • the above-mentioned polyvinyl alcohol film preferably has an in-plane retardation of 50 nm or less, particularly preferably 40 nm or less, and more preferably 30 nm or less, from the viewpoint of uniformity of tension in water.
  • the polyvinyl alcohol film of the present invention is obtained.
  • the polyvinyl alcohol film of the present invention is excellent in optical performance, is suitably used as an optical polyvinyl alcohol film, and is particularly 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 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 42% 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 color unevenness.
  • the manufacturing method of the polarizing plate of this invention is demonstrated.
  • the polarizing film of the present invention is bonded to one side or both sides of an optically isotropic resin film as a protective film via an adhesive 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 or the like is applied to one side or both sides of the protective film and cured to obtain a polarizing plate.
  • a polarizing film comprising a polyvinyl alcohol film obtained by the production method of the present invention is excellent in in-plane uniformity of polarization performance, and is a portable information terminal, personal computer, TV, projector, signage, electronic desk calculator, electronic timepiece.
  • Word processors electronic paper, game 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 paper, etc.) for use in antireflection layers, optical communication equipment, medical equipment, building materials, toys and the like.
  • In-plane retardation (nm) A test piece having a length (MD direction) of 20 cm ⁇ width (TD direction) of 20 cm was cut out from the obtained polyvinyl alcohol film, and a two-dimensional birefringence evaluation system (manufactured by Photonic Lattice: “PA-110L”) was used. In-plane retardation (nm) was measured.
  • Polarization unevenness From the obtained polarizing film, a test piece having a length of 30 cm and a width of 30 cm was cut out, 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 with a surface illuminance of 14,000 lux (lx), and evaluated according to the following criteria. (Evaluation criteria) ⁇ ⁇ ⁇ ⁇ No color unevenness ⁇ ⁇ ⁇ ⁇ Slight color unevenness ⁇ ⁇ ⁇ ⁇ Color unevenness
  • Example 1 Manufacture of polyvinyl alcohol film
  • 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 rotating at 20 m / min from the T-type slit die discharge port
  • the film was formed by discharging and casting.
  • the obtained film was peeled off from the cast drum, and dried while bringing the front and back surfaces of the film into contact with a total of 20 metal heating rolls alternately.
  • Such metal heating rolls are arranged in the order of 90 ° C., 70 ° C., 110 ° C., and 85 ° C.
  • the obtained polyvinyl alcohol film was unwound from a roll and stretched 1.7 times in the MD direction while being swelled by being immersed in a water bath at a water temperature of 30 ° C. while being conveyed in the horizontal direction.
  • the film was stretched 1.6 times in the MD direction while being immersed and dyed in an aqueous solution of 30 g / L of iodine 0.5 g / L and 30 g / L of potassium iodide, and then boric acid 40 g / L, iodine
  • the sample was uniaxially stretched 2.1 times in the MD direction while being immersed in an aqueous solution (50 ° C.) having a composition of 30 g / L of potassium halide and cross-linking with boric acid.
  • it was washed with an aqueous potassium iodide solution and then dried at 50 ° C. for 2 minutes to obtain a polarizing film having a total draw ratio of 5.7 times. No breakage occurred during the production, and the properties of the obtained polarizing film were as shown in Table 2.
  • Example 2 a polyvinyl alcohol film and a polarizing film were obtained in the same manner as in Example 1 except that heat treatment was performed by blowing hot air at 130 ° C. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
  • Example 3 In Example 1, the rotational speed of the cast drum was changed to 10 m / min, the film thickness was changed to 0.06 mm, and a polyvinyl alcohol film was obtained in the same manner as in Example 1 except that heat treatment was performed by blowing hot air at 120 ° C. A polarizing film was obtained. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
  • Example 4 In Example 1, the polyvinyl alcohol film and the polarizing film were changed in the same manner as in Example 1 except that the rotation speed of the cast drum was changed to 10 m / min to change the film thickness to 0.06 mm and the heat treatment temperature to 110 ° C. Got. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
  • Example 1 the polyvinyl alcohol film and the polarizing film were changed in the same manner as in Example 1 except that the rotation speed of the cast drum was changed to 10 m / min to change the film thickness to 0.06 mm and the heat treatment temperature to 100 ° C. Got. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
  • Example 2 a polyvinyl alcohol film was obtained in the same manner as in Example 1 except that the heat treatment temperature was 150 ° C. Production of a polarizing film was started using the polyvinyl alcohol film, but when a polarizing film having a length of 1 km was produced, breakage occurred during stretching in the boric acid crosslinking step, and the intended polarizing film was not obtained. .
  • Example 3 a polyvinyl alcohol film and a polarizing film were obtained in the same manner as in Example 1 except that all metal heating roll temperatures were set to 80 ° C. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
  • the polyvinyl alcohol-based films of Examples 1 to 4 have a thickness D (mm) and a tension when stretched 6 times in the film flow direction (MD direction) in water at 30 ° C. (A (N / mm 2 )),
  • a (N / mm 2 ) When the tension when stretched 6 times in the film flow direction (MD direction) in water at 50 ° C. is B (N / mm 2 ), the values of D ⁇ A and D ⁇ B are both formulas (1)
  • the polyvinyl alcohol film of Comparative Example 1 has a D ⁇ B value outside the range of the formula (2), while the polyvinyl alcohol films of Comparative Examples 2 and 3 satisfy the conditions (2) and (2).
  • the value of D ⁇ A was outside the range of formula (1), and the value of D ⁇ B was also outside the range of formula (2).
  • the polarizing properties of the polarizing films obtained from the respective polyvinyl alcohol-based films are found to be superior to those of Comparative Examples 1 and 3 in Examples 1 to 4. Further, in Comparative Example 2, the polarizing film is broken by breaking. Was not obtained.
  • the value of E2 / E1 is low. In this case, it was confirmed that the degree of polarization when the polarizing film was formed decreased.
  • a polarizing film comprising a polyvinyl alcohol film obtained by the production method of the present invention is excellent in in-plane uniformity of polarization performance, and is a portable information terminal, personal computer, TV, projector, signage, electronic desk calculator, electronic timepiece.
  • Word processors electronic paper, game 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 paper, etc.) for use in antireflection layers, optical communication equipment, medical equipment, building materials, toys and the like.

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Abstract

Provided is a poly(vinyl alcohol)-based film which is excellent in terms of dyeability and stretchability and which, even when produced as a continuous film having a larger width and a smaller thickness, can give a polarizing film that has a high degree of polarization and no unevenness of polarization. The poly(vinyl alcohol)-based film is characterized in that when the thickness is expressed by D (mm), the tension at the time when the film has been stretched 6 times in the running direction (MD direction) in 30ºC water is expressed by A (N/mm2), and the tension at the time when the film has been stretched 6 times in the running direction (MD direction) in 50ºC water is expressed by B (N/mm2), then the film satisfies the following relationships (1) and (2). Relationship (1) 0.6≤D×A≤1.2 Relationship (2) 0.2≤D×B≤0.4

Description

ポリビニルアルコール系フィルム、ポリビニルアルコール系フィルムの製造方法、及び偏光膜Polyvinyl alcohol film, method for producing polyvinyl alcohol film, and polarizing film
　本発明は、ポリビニルアルコール系フィルムに関する。さらに詳しくは、偏光膜の原反として染色性や延伸性に優れ、偏光性能に優れた偏光膜を高い生産性で製造するためのポリビニルアルコール系フィルム、その製造方法、及び該ポリビニルアルコール系フィルムを用いて得られる偏光膜に関する。 The present invention relates to a polyvinyl alcohol film. More specifically, a polyvinyl alcohol film for producing a polarizing film excellent in dyeability and stretchability as a raw material of the polarizing film and excellent in polarizing performance, a production method thereof, and the polyvinyl alcohol film The present invention relates to a polarizing film obtained by use.
　偏光膜は、原反となるポリビニルアルコール系フィルムを、ヨウ素などの色素を用いて染色、及び延伸して製造される。例えば、ポリビニルアルコール系フィルムを、温水で膨潤させた後、ヨウ素で染色し、ヨウ素分子を配列させるために延伸し、延伸した状態を保持するためにホウ酸などの架橋剤で架橋し、洗浄、及び乾燥して製造される。かかる水膨潤、染色、延伸、ホウ酸架橋の各工程は、順序を入れ替えたり、複数の工程が同時に行われることもある。共通しているのは、ロールからポリビニルアルコール系フィルムを連続的に巻き出して、巻き取り機やニップロールを用いて流れ方向に適度な張力をかけて、水平方向に搬送しながら行われる点である。 The polarizing film is produced by dyeing and stretching a polyvinyl alcohol film as a raw material with a pigment such as iodine. For example, after a polyvinyl alcohol film is swollen with warm water, dyed with iodine, stretched to arrange iodine molecules, cross-linked with a cross-linking agent such as boric acid to maintain the stretched state, washed, And dried. The steps of water swelling, dyeing, stretching, and boric acid crosslinking may be switched in order or a plurality of steps may be performed simultaneously. What is common is that the polyvinyl alcohol film is continuously unwound from the roll, applied with appropriate tension in the flow direction using a winder or nip roll, and conveyed in the horizontal direction. .
　かかる偏光膜は、携帯情報端末機やテレビなどの液晶表示装置の基幹構成部品として使用されている。近年、液晶表示の高輝度化や高精細化に伴い、高い光線透過率と高い偏光度を有する偏光膜が要望されており、更に、液晶テレビなどの大画面化や薄型化にともない、従来品より一段と幅広長尺薄型な偏光膜が要望されている。 Such a polarizing film is used as a basic component of liquid crystal display devices such as portable information terminals and televisions. In recent years, with the increase in brightness and definition of liquid crystal displays, there has been a demand for polarizing films having high light transmittance and high degree of polarization. Furthermore, as liquid crystal televisions have become larger and thinner, conventional products have been demanded. There is a need for a polarizing film that is wider, longer, and thinner.
　上述した要望に応えるためには、染色性や延伸性に優れ、かつ幅広長尺薄型のポリビニルアルコール系フィルムが必要である。ポリビニルアルコール系フィルムの染色性が低い場合には、充分な偏光度が得られず、また偏光ムラが発生しやすい傾向にある。ポリビニルアルコール系フィルムの延伸性が低い場合には、偏光膜の製造工程において破断が生じるため、幅広長尺薄型の偏光膜を製造することができない。当然のことながら、破断により連続的な製造は中断し、偏光膜の生産性は大幅に低下する。更に、延伸性が低いと、充分に色素が配向しないために偏光度が低下したり、偏光ムラが発生しやすい傾向にある。かかる染色性や延伸性の向上は、ポリビニルアルコール系フィルムが幅広長尺薄型になるほど困難である。また、いわゆる薄型化を目的とした塗布型偏光板においても、上述した染色や延伸などの工程は必須であり、支持フィルム上では有るが、塗布後のポリビニルアルコール系膜の染色性や延伸性の改良が望まれている、 In order to meet the above-mentioned demand, a wide, long and thin polyvinyl alcohol-based film having excellent dyeability and stretchability is required. When the dyeability of the polyvinyl alcohol film is low, a sufficient degree of polarization cannot be obtained, and polarization unevenness tends to occur. When the stretchability of the polyvinyl alcohol-based film is low, breakage occurs in the manufacturing process of the polarizing film, so that a wide, long and thin polarizing film cannot be manufactured. As a matter of course, continuous production is interrupted by breakage, and the productivity of the polarizing film is greatly reduced. Furthermore, when the stretchability is low, the dye is not sufficiently oriented, and thus the degree of polarization tends to decrease or polarization unevenness tends to occur. Such improvement in dyeability and stretchability is more difficult as the polyvinyl alcohol film becomes wider, longer, and thinner. In addition, in the coating type polarizing plate for the purpose of so-called thinning, the above-described steps such as dyeing and stretching are indispensable and are on the support film. Improvement is desired,
　ポリビニルアルコール系フィルムの染色性を向上するために、膨潤工程の浴温を制御する手法が提案されている（例えば特許文献１、２参照。）。また、延伸性が特定範囲のポリビニルアルコール系フィルムを用いた偏光板が提案されている（例えば特許文献３参照。）。 In order to improve the dyeability of a polyvinyl alcohol film, a technique for controlling the bath temperature in the swelling process has been proposed (see, for example, Patent Documents 1 and 2). Moreover, a polarizing plate using a polyvinyl alcohol film having a specific range of stretchability has been proposed (see, for example, Patent Document 3).
特開２００６－０６５３０９号公報JP 2006-065309 A 特開２０１４－１９７０５０号公報JP 2014-197050 A 特開２００２－２３６２１２号公報Japanese Patent Laid-Open No. 2002-236212
　しかしながら、上記特許文献１及び２に開示の技術では、浴温により膨潤度を制御できても、浴槽中でポリビニルアルコール系フィルムにかかる張力が適切でなければ、一様な膨潤状態は得られず、その後の染色工程において、均一に色素が吸着しないという問題があった。 However, in the techniques disclosed in Patent Documents 1 and 2, even if the degree of swelling can be controlled by the bath temperature, a uniform swelling state cannot be obtained unless the tension applied to the polyvinyl alcohol film in the bath is appropriate. In the subsequent dyeing process, there is a problem that the dye does not adsorb uniformly.
　また、上記特許文献３に開示の技術は、ポリビニルアルコール系フィルムを水中で４～６倍に延伸した時の応力（張力）を規定したものであるが、実際の偏光膜の製造においては、各工程の水温が異なるため、全工程にわたって適した張力を得るには不充分であった。なお、水温は、膨潤や染色などの工程では比較的低温の３０℃付近、延伸やホウ酸架橋などの工程では比較的高温の５０℃付近で行われることが多いものである。 In addition, the technique disclosed in Patent Document 3 defines a stress (tension) when a polyvinyl alcohol film is stretched 4 to 6 times in water. In actual production of a polarizing film, Since the water temperature of the process was different, it was insufficient to obtain a suitable tension throughout the entire process. The water temperature is often around 30 ° C., which is a relatively low temperature in processes such as swelling and dyeing, and around 50 ° C., which is a relatively high temperature, in processes such as stretching and boric acid crosslinking.
　そこで、本発明ではこのような背景下において、染色性や延伸性に優れたポリビニルアルコール系フィルムであり、幅広長尺薄型化した場合においても高い偏光度を有し、偏光ムラのない偏光膜を得ることができるポリビニルアルコール系フィルムを提供する。 Therefore, in the present invention, under such a background, a polyvinyl alcohol film excellent in dyeability and stretchability, and a polarizing film having a high degree of polarization and having no polarization unevenness even when widened, elongated and thinned. A polyvinyl alcohol film that can be obtained is provided.
　しかるに、本発明者等はかかる事情に鑑み鋭意研究を重ねた結果、ポリビニルアルコール系樹脂の水溶液を、キャスト型に吐出及び流延して製膜し、連続的に乾燥して得られるポリビニルアルコール系フィルムについて、異なる温度の水中で延伸した時に、それぞれの水中張力が特定範囲となるように、特に高めの温度の５０℃での水中張力に着目して製造されたポリビニルアルコール系フィルムが、幅広長尺薄型化した場合においても高い偏光度を有し、偏光ムラのない偏光膜を製造できることを見出した。 However, as a result of intensive studies in view of such circumstances, the present inventors have made a polyvinyl alcohol solution obtained by discharging and casting an aqueous solution of a polyvinyl alcohol resin into a cast mold and continuously drying it. The polyvinyl alcohol film produced by paying attention to the underwater tension at a higher temperature of 50 ° C. is particularly wide so that when the film is stretched in water at different temperatures, the underwater tension is in a specific range. It has been found that a polarizing film having a high degree of polarization and no polarization unevenness can be produced even when it is made thin.
　即ち、本発明の要旨は、厚さＤ（ｍｍ）、３０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＡ（Ｎ／ｍｍ２）、５０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＢ（Ｎ／ｍｍ２）とした時に、下式（１）及び（２）を満足することを特徴とするポリビニルアルコール系フィルム。
式（１）０．６≦Ｄ×Ａ≦１．２
式（２）０．２≦Ｄ×Ｂ≦０．４ That is, the gist of the present invention is that the tension when stretched 6 times in the flow direction of the film (MD direction) in water of thickness D (mm) and 30 ° C. is A (N / mm 2 ) and water in 50 ° C. In which the following formulas (1) and (2) are satisfied when the tension when stretched 6 times in the film flow direction (MD direction) is B (N / mm 2 ): the film.
Formula (1) 0.6 <= D * A <= 1.2
Formula (2) 0.2 <= D * B <= 0.4
　また、本発明は、上記ポリビニルアルコール系フィルムの製造方法、上記ポリビニルアルコール系フィルムを用いて得られる偏光膜も提供するものである。 The present invention also provides a method for producing the polyvinyl alcohol film and a polarizing film obtained using the polyvinyl alcohol film.
　本発明のポリビニルアルコール系フィルムは、染色性や延伸性に優れており、また、幅広長尺薄型化した場合においても高い偏光度を有し、偏光ムラのない偏光膜を得ることができ、さらには、高い生産性で偏光膜を製造できるものである。 The polyvinyl alcohol film of the present invention is excellent in dyeability and stretchability, and has a high degree of polarization even in the case of being wide, long and thin, and can obtain a polarizing film free from uneven polarization. Can produce a polarizing film with high productivity.
　以下に、本発明を詳細に説明する。
　本発明のポリビニルアルコール系フィルムは、厚さＤ（ｍｍ）、３０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＡ（Ｎ／ｍｍ２）、５０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＢ（Ｎ／ｍｍ２）とした時に、下式（１）及び（２）を満足するポリビニルアルコール系フィルムであることが必要であり、
式（１）０．６≦Ｄ×Ａ≦１．２
式（２）０．２≦Ｄ×Ｂ≦０．４
　好ましくは、下式（１’）及び（２’）を満足するポリビニルアルコール系フィルムであり、
式（１’）０．６５≦Ｄ×Ａ≦１．１５
式（２’）０．２５≦Ｄ×Ｂ≦０．３９
　特に好ましくは、下式（１’’）及び（２’’）を満足するポリビニルアルコール系フィルムである。
式（１’’）０．７≦Ｄ×Ａ≦１．１
式（２’’）０．２７≦Ｄ×Ｂ≦０．３８ The present invention is described in detail below.
The polyvinyl alcohol film of the present invention has a thickness of D (mm) and a tension of A (N / mm 2 ) and 50 ° C. when stretched 6 times in the film flow direction (MD direction) in 30 ° C. water. A polyvinyl alcohol film satisfying the following formulas (1) and (2) when the tension when stretched 6 times in the film flow direction (MD direction) in water is B (N / mm 2 ). Is necessary,
Formula (1) 0.6 <= D * A <= 1.2
Formula (2) 0.2 <= D * B <= 0.4
Preferably, a polyvinyl alcohol film satisfying the following formulas (1 ′) and (2 ′):
Formula (1 ′) 0.65 ≦ D × A ≦ 1.15
Formula (2 ′) 0.25 ≦ D × B ≦ 0.39
Particularly preferred is a polyvinyl alcohol film satisfying the following formulas (1 ″) and (2 ″).
Formula (1 ″) 0.7 ≦ D × A ≦ 1.1
Formula (2 ″) 0.27 ≦ D × B ≦ 0.38
　上記式（１）～（１’’）に関して、Ｄ×Ａの値が低すぎると膨潤工程や染色工程においてフィルムが変形してしまい好ましくなく、高すぎても染色工程において充分な染色が困難となり好ましくない。
　また、上記式（２）～（２’’）に関して、Ｄ×Ｂの値が低すぎると偏光膜とした際の偏光度が低下し好ましくなく、高すぎると偏光膜製造時に破断が発生しやすく好ましくない。 Regarding the above formulas (1) to (1 ″), if the value of D × A is too low, the film will be deformed in the swelling process or the dyeing process, and if it is too high, sufficient dyeing will be difficult in the dyeing process. It is not preferable.
In addition, regarding the above formulas (2) to (2 ″), if the value of D × B is too low, the degree of polarization when the polarizing film is formed is not preferable, and if it is too high, breakage is likely to occur when the polarizing film is manufactured. It is not preferable.
　上記式（１）～（１’’）及び上記式（２）～（２’’）に関して、ポリビニルアルコール系フィルムの厚さＤの値は、偏光膜の薄型化の点で０．０４ｍｍ以下が好ましく、特に好ましくは偏光膜の更なる薄型化の点で０．０３ｍｍ以下、更に好ましくは偏光膜の破断回避の点で０．０１～０．０３ｍｍである。 Regarding the above formulas (1) to (1 ″) and the above formulas (2) to (2 ″), the value of the thickness D of the polyvinyl alcohol film is 0.04 mm or less in terms of thinning the polarizing film. It is preferably 0.03 mm or less from the viewpoint of further thinning the polarizing film, and more preferably from 0.01 to 0.03 mm from the viewpoint of avoiding breakage of the polarizing film.
　更に、本発明のポリビニルアルコール系フィルムは、下式（３）を満足することが好ましく、特に好ましくは下式（３’）、更に好ましくは下式（３’’）を満足することである。
式（３）０．２≦Ｂ／Ａ≦０．５
式（３’）０．２５≦Ｂ／Ａ≦０．４
式（３’’）０．３≦Ｂ／Ａ≦０．３５ Furthermore, the polyvinyl alcohol film of the present invention preferably satisfies the following formula (3), particularly preferably satisfies the following formula (3 ′), and more preferably satisfies the following formula (3 ″).
Formula (3) 0.2 ≦ B / A ≦ 0.5
Formula (3 ′) 0.25 ≦ B / A ≦ 0.4
Formula (3 ″) 0.3 ≦ B / A ≦ 0.35
　上記式（３）～（３’’）に関して、Ｂ／Ａの値が低すぎると、偏光膜とした際の偏光度が低下する傾向があり、高すぎると偏光膜製造時に破断が発生しやすい傾向がある。　　　　 Regarding the above formulas (3) to (3 ″), if the value of B / A is too low, the degree of polarization tends to decrease when a polarizing film is formed, and if it is too high, breakage tends to occur during the production of the polarizing film. Tend. .
　また、本発明のポリビニルアルコール系フィルムは、３０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力Ａが、１５～４０Ｎ／ｍｍ２であることが好ましく、特に好ましくは１８～３５Ｎ／ｍｍ２、更に好ましくは２０～３０Ｎ／ｍｍ２である。
　かかる張力Ａの値が低すぎると、膨潤工程や染色工程においてフィルムが変形しやすい傾向があり、高すぎると染色工程において充分な染色が困難となる傾向がある。 The polyvinyl alcohol film of the present invention preferably has a tension A of 15 to 40 N / mm 2 when stretched 6 times in the film flow direction (MD direction) in water at 30 ° C., particularly preferably. Is 18 to 35 N / mm 2 , more preferably 20 to 30 N / mm 2 .
If the value of the tension A is too low, the film tends to be deformed in the swelling process or the dyeing process, and if it is too high, sufficient dyeing tends to be difficult in the dyeing process.
　更に、本発明のポリビニルアルコール系フィルムは、５０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力Ｂの値が、３～１５Ｎ／ｍｍ２であることが好ましく、特に好ましくは４～１２Ｎ／ｍｍ２、更に好ましくは５～１０Ｎ／ｍｍ２である。
　かかる張力Ｂの値が低すぎると、偏光膜とした際の偏光度が低下する傾向があり、高すぎると偏光膜製造時に破断が発生しやすい傾向がある。 Furthermore, the polyvinyl alcohol film of the present invention preferably has a tension B value of 3 to 15 N / mm 2 when stretched 6 times in the film flow direction (MD direction) in water at 50 ° C., Particularly preferred is 4 to 12 N / mm 2 , and more preferred is 5 to 10 N / mm 2 .
If the value of the tension B is too low, the degree of polarization when the polarizing film is formed tends to decrease, and if it is too high, breakage tends to occur during the production of the polarizing film.
　そして、本発明のポリビニルアルコール系フィルムは、３０℃の水中における貯蔵弾性率をＥ１（Ｐａ）、５０℃の水中における貯蔵弾性率をＥ２（Ｐａ）とした場合に、Ｅ２／Ｅ１の値が０．２５～０．３０であることが好ましく、特に好ましくは０．２６～０．２９である。
　かかるＥ２／Ｅ１の値が低すぎると得られる偏光膜の偏光度が低下する傾向にあり、高すぎると偏光膜製造時に破断が発生する傾向がある。 The polyvinyl alcohol film of the present invention has an E2 / E1 value of 0 when the storage elastic modulus in water at 30 ° C. is E1 (Pa) and the storage elastic modulus in water at 50 ° C. is E2 (Pa). It is preferably from 25 to 0.30, particularly preferably from 0.26 to 0.29.
If the value of E2 / E1 is too low, the polarization degree of the obtained polarizing film tends to decrease, and if it is too high, breakage tends to occur during the production of the polarizing film.
　更に、本発明のポリビニルアルコール系フィルムは、上記３０℃の水中における貯蔵弾性率Ｅ１が、９～１２ＭＰａであることが搬送性の点で好ましい。
　また、５０℃の水中における貯蔵弾性率Ｅ２が、２～４ＭＰａであることが搬送性の点で好ましい。 Further, the polyvinyl alcohol film of the present invention preferably has a storage elastic modulus E1 in water of 30 ° C. of 9 to 12 MPa from the viewpoint of transportability.
Further, the storage elastic modulus E2 in water at 50 ° C. is preferably 2 to 4 MPa from the viewpoint of transportability.
　以下、本発明のポリビニルアルコール系フィルムの製造方法、即ち、ポリビニルアルコール系樹脂の水溶液を、キャスト型に吐出及び流延して製膜し、連続的に乾燥することによりポリビニルアルコール系フィルムを製造する方法について説明する。 Hereinafter, a method for producing a polyvinyl alcohol film of the present invention, that is, an aqueous solution of a polyvinyl alcohol resin is discharged and cast into a cast mold to form a film, and continuously dried to produce a polyvinyl alcohol film. A method will be described.
　本発明で用いられるポリビニルアルコール系樹脂としては、通常、未変性のポリビニルアルコール系樹脂、即ち、酢酸ビニルを重合して得られるポリ酢酸ビニルをケン化して製造される樹脂が用いられる。必要に応じて、酢酸ビニルと、少量（通常、１０モル％以下、好ましくは５モル％以下）の酢酸ビニルと共重合可能な成分との共重合体をケン化して得られる樹脂を用いることもできる。酢酸ビニルと共重合可能な成分としては、例えば、不飽和カルボン酸（例えば、塩、エステル、アミド、ニトリル等を含む）、炭素数２～３０のオレフィン類（例えば、エチレン、プロピレン、ｎ－ブテン、イソブテン等）、ビニルエーテル類、不飽和スルホン酸塩等が挙げられる。また、ケン化後の水酸基を化学修飾して得られる変性ポリビニルアルコール系樹脂を用いることもできる。 As the polyvinyl alcohol resin used in the present invention, 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. Examples of 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. Moreover, the modified polyvinyl alcohol-type resin obtained by chemically modifying the hydroxyl group after saponification can also be used.
　また、ポリビニルアルコール系樹脂として、側鎖に１，２－ジオール構造を有するポリビニルアルコール系樹脂を用いることもできる。かかる側鎖に１，２－ジオール構造を有するポリビニルアルコール系樹脂は、例えば、（ｉ）酢酸ビニルと３，４－ジアセトキシ－１－ブテンとの共重合体をケン化する方法、（ｉｉ）酢酸ビニルとビニルエチレンカーボネートとの共重合体をケン化及び脱炭酸する方法、（ｉｉｉ）酢酸ビニルと２，２－ジアルキル－４－ビニル－１，３－ジオキソランとの共重合体をケン化及び脱ケタール化する方法、（ｉｖ）酢酸ビニルとグリセリンモノアリルエーテルとの共重合体をケン化する方法、等により得られる。 Also, as the polyvinyl alcohol resin, a polyvinyl alcohol resin having a 1,2-diol structure in the side chain can be used. Such 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. A method of saponifying and decarboxylating a copolymer of vinyl and vinyl ethylene carbonate; and (iii) saponifying and decarboxylating a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane. It is obtained by a method of ketalization, (iv) a method of saponifying a copolymer of vinyl acetate and glycerol monoallyl ether, or the like.
　ポリビニルアルコール系樹脂の重量平均分子量は、１０万～３０万であることが好ましく、特に好ましくは１１万～２８万、更に好ましくは１２万～２６万である。かかる重量平均分子量が小さすぎるととポリビニルアルコール系樹脂を光学フィルムとする場合に充分な光学性能が得られにくい傾向があり、大きすぎるとポリビニルアルコール系フィルムの偏光膜製造時の延伸が困難となる傾向がある。なお、上記ポリビニルアルコール系樹脂の重量平均分子量は、ＧＰＣ－ＭＡＬＳ法により測定される重量平均分子量である。 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, sufficient optical performance tends to be difficult to obtain when the polyvinyl alcohol-based resin is used as an optical film, and if it is too large, it is difficult to stretch the polyvinyl alcohol-based film during the production of the polarizing film. Tend. The weight average molecular weight of the polyvinyl alcohol resin is a weight average molecular weight measured by GPC-MALS method.
　本発明で用いるポリビニルアルコール系樹脂の平均ケン化度は、通常９８モル％以上であることが好ましく、特に好ましくは９９モル％以上、更に好ましくは９９．５モル％以上、殊に好ましくは９９．８モル％以上である。かかる平均ケン化度が小さすぎるとポリビニルアルコール系フィルムを偏光膜とする場合に充分な光学性能が得られない傾向がある。
　ここで、本発明における平均ケン化度は、ＪＩＳ　Ｋ　６７２６に準じて測定されるものである。 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, there is a tendency that sufficient optical performance cannot be obtained when a polyvinyl alcohol film is used as a polarizing film.
Here, the average saponification degree in the present invention is measured according to JIS K 6726.
　本発明に用いるポリビニルアルコール系樹脂として、変性種、変性量、重量平均分子量、平均ケン化度などの異なる２種以上のものを併用してもよい。 As the 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.
　本発明のポリビニルアルコール系フィルムは、上記ポリビニルアルコール系樹脂を用いてポリビニルアルコール系樹脂水溶液（製膜原液）を調製し、この水溶液をキャスト型に吐出及び流延して、キャスト法により製膜、乾燥することで連続的に製造することができ、例えば、以下の工程により製造される。
工程（Ａ）ポリビニルアルコール系樹脂水溶液を調液する工程。
工程（Ｂ）ポリビニルアルコール系樹脂の水溶液をキャスト型に流延して製膜する工程。
工程（Ｃ）製膜されたフィルムを複数の金属加熱ロールと接触させることにより加熱して乾燥する工程。
工程（Ｄ）得られたフィルムを熱風を用いて熱処理する工程。 The polyvinyl alcohol-based film of the present invention is prepared by preparing a polyvinyl alcohol-based resin aqueous solution (film forming stock solution) using the polyvinyl alcohol-based resin, and discharging and casting the aqueous solution into a cast mold. It can manufacture continuously by drying, for example, is manufactured by the following processes.
Step (A) A step of preparing a polyvinyl alcohol resin aqueous solution.
Step (B) A step of casting an aqueous solution of a polyvinyl alcohol resin into a cast mold to form a film.
Step (C) A step of heating and drying the formed film by bringing it into contact with a plurality of metal heating rolls.
Process (D) The process of heat-processing the obtained film using a hot air.
　ここで、上記キャスト型としては、例えばキャストドラム（ドラム型ロール）やエンドレスベルト等があげられるが、幅広化や長尺化、膜厚の均一性に優れる点からキャストドラムで行うことが好ましい。
　以下、キャスト型がキャストドラムの場合を例にとって説明する。 Here, examples of the cast mold include a cast drum (drum mold roll), an endless belt, and the like. However, the cast mold is preferably performed from the viewpoint of widening, lengthening, and film thickness uniformity.
Hereinafter, a case where the cast mold is a cast drum will be described as an example.
　まず、前記工程（Ａ）について説明する。 First, the step (A) will be described.
　工程（Ａ）においては、まず、前述したポリビニルアルコール系樹脂を、水を用いて洗浄し、遠心分離機などを用いて脱水して、含水率５０重量％以下のポリビニルアルコール系樹脂ウェットケーキとすることが好ましい。含水率が大きすぎると、所望する水溶液濃度にすることが難しくなる傾向がある。
　かかるポリビニルアルコール系樹脂ウェットケーキを温水や熱水に溶解して、ポリビニルアルコール系樹脂水溶液を調製する。 In the step (A), first, the polyvinyl alcohol-based resin described above is washed with water and dehydrated using a centrifuge to obtain a polyvinyl alcohol-based resin wet cake having a water content of 50% by weight or less. It is preferable. 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.
　ポリビニルアルコール系樹脂水溶液の調製方法は、特に限定されず、例えば、加熱された多軸押出機を用いて調製してもよく、また、上下循環流発生型撹拌翼を備えた溶解缶に、前述したポリビニルアルコール系樹脂ウェットケーキを投入し、缶中に水蒸気を吹き込んで、溶解及び所望濃度の水溶液を調製することもできる。
　本発明においては、偏光度向上の点で後者が好ましく、１２０℃以上の加圧溶解により調液することがより好ましい。 The method for preparing the polyvinyl alcohol-based resin aqueous solution is not particularly limited. For example, the polyvinyl alcohol-based resin aqueous solution may be prepared by using a heated multi-screw extruder. The polyvinyl alcohol-based 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.
In the present invention, the latter is preferable from the viewpoint of improving the degree of polarization, and it is more preferable to prepare the solution by pressure dissolution at 120 ° C. or higher.
　ポリビニルアルコール系樹脂水溶液には、ポリビニルアルコール系樹脂以外に、必要に応じて、可塑剤や、ノニオン性、アニオン性、及びカチオン性の少なくとも一つの界面活性剤を含有させることが、製膜性の点から好ましい。 In addition to the polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin aqueous solution may contain a plasticizer and at least one surfactant of nonionic, anionic, and cationic properties as necessary. It is preferable from the point.
　本発明で使用される可塑剤としては、例えば、グリセリン、ジグリセリン、トリグリセリン、エチレングリコール、トリエチレングリコール、ポリエチレングリコール、トリメチロールプロパンなどがあげられる。これらの中でも、安価な点でグリセリンが好ましい。 Examples of the plasticizer used in the present invention include glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and trimethylolpropane. Among these, glycerin is preferable because of its low cost.
　グリセリンを使用する場合の配合量は、ポリビニルアルコール系樹脂に対して、５～１２重量％が好ましく、特に好ましくは６～１１．５重量％、更に好ましくは７～１１％である。
　かかる配合量が少なすぎると、ポリビニルアルコール系フィルムの水中張力が増大する傾向があり、多すぎるとポリビニルアルコール系フィルムの水中張力が不足する傾向がある。 When glycerin is used, the blending amount is preferably 5 to 12% by weight, particularly preferably 6 to 11.5% by weight, and more preferably 7 to 11% with respect to the polyvinyl alcohol resin.
If the amount is too small, the underwater tension of the polyvinyl alcohol film tends to increase, and if too large, the underwater tension of the polyvinyl alcohol film tends to be insufficient.
　本発明で使用される界面活性剤としては、ポリビニルアルコール系樹脂水溶液との相溶性の点から、アニオン性界面活性剤が好ましい。 The surfactant used in the present invention is preferably an anionic surfactant from the viewpoint of compatibility with an aqueous polyvinyl alcohol resin solution.
　かくして得られるポリビニルアルコール系樹脂水溶液の樹脂濃度は、１５～６０重量％であることが好ましく、特に好ましくは１７～５５重量％、更に好ましくは２０～５０重量％である。かかる樹脂濃度が低すぎると乾燥負荷が大きくなるため生産能力が低下する傾向があり、高すぎると粘度が高くなりすぎて均一な溶解ができにくくなる傾向がある。 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 is too low, the drying load increases, so the production capacity tends to decrease. If the resin concentration is too high, the viscosity becomes too high and uniform dissolution tends to be difficult.
　かくして、製膜原液であるポリビニルアルコール系樹脂水溶液が得られる。次に、前記工程（Ｂ）について説明する。 Thus, a polyvinyl alcohol-based resin aqueous solution that is a film-forming stock solution is obtained. Next, the step (B) will be described.
　上記ポリビニルアルコール系樹脂水溶液は、脱泡処理される。脱泡方法としては、静置脱泡やベントを有した多軸押出機による脱泡などの方法があげられる。ベントを有した多軸押出機としては、通常はベントを有した２軸押出機が用いられる。 The polyvinyl alcohol resin aqueous solution is defoamed. Examples of the defoaming method include static defoaming and defoaming by a multi-screw extruder having a vent. As the multi-screw extruder having a vent, a twin-screw extruder having a vent is usually used.
　脱泡処理ののち、ポリビニルアルコール系樹脂水溶液は、一定量ずつＴ型スリットダイに導入され、回転するキャストドラム上に吐出及び流延されて、キャスト法により製膜される。 After the defoaming treatment, 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 casting method.
　Ｔ型スリットダイ吐出口の樹脂温度は、８０～１００℃であることが好ましく、特に好ましくは８５～９９℃である。かかる樹脂温度が低すぎると流動不良となる傾向があり、高すぎると発泡する傾向がある。 The resin temperature of the T-type slit die discharge port is preferably 80 to 100 ° C., particularly preferably 85 to 99 ° C. If the resin temperature is too low, the flow tends to be poor, and if it is too high, the resin tends to foam.
　かかるポリビニルアルコール系樹脂水溶液の粘度は、吐出時に５０～２００Ｐａ・ｓであることが好ましく、特に好ましくは７０～１５０Ｐａ・ｓである。
　かかる水溶液の粘度が、低すぎると流動不良となる傾向があり、高すぎると流延が困難となる傾向がある。 The viscosity of the aqueous polyvinyl alcohol resin solution is preferably 50 to 200 Pa · s, particularly preferably 70 to 150 Pa · s, at the time of discharge.
When 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.
　Ｔ型スリットダイからキャストドラムに吐出されるポリビニルアルコール系樹脂水溶液の吐出速度は、０．２～５ｍ／分であることが好ましく、特に好ましくは０．４～４ｍ／分、更に好ましくは０．６～３ｍ／分である。
　かかる吐出速度が遅すぎると生産性が低下する傾向があり、速すぎると流延が困難となる傾向がある。 The discharge speed of the aqueous polyvinyl alcohol resin solution discharged from the T-type slit die onto the cast drum is preferably 0.2 to 5 m / min, particularly preferably 0.4 to 4 m / min, and more preferably 0.8. 6-3 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.
　流延に際しては、幅広化や長尺化、膜厚の均一性などの点からキャストドラムで行うことが好ましい。キャストドラムとしては、通常、鉄を主成分とするステンレス鋼（ＳＵＳ）の表面に、傷つき防止のため金属メッキが施されているものが使用される。金属メッキとしては、例えば、クロムメッキ、ニッケルメッキ、亜鉛メッキなどが挙げられ、これらが単独または２層以上積層化して使用される。これらの中では、ドラム表面の耐久性の点から、最表面がクロムメッキであることが好ましい。 Casting is preferably performed with a cast drum from the viewpoint of widening, lengthening, and film thickness uniformity. As the cast drum, usually, a surface of stainless steel (SUS) whose main component is iron is subjected to metal plating to prevent damage. Examples of the metal plating include chrome plating, nickel plating, and zinc plating, and these are used alone or in a laminate of two or more layers. Among these, it is preferable that the outermost surface is chrome plating from the viewpoint of durability of the drum surface.
　以下に、キャストドラムを用いた場合を例にとって、製膜方法を説明する。
　キャストドラムの幅は、好ましくは４ｍ以上、特に好ましくは５ｍ以上である。キャストドラムの幅が小さすぎると幅広フィルムが得られにくい傾向がある。 Hereinafter, the film forming method will be described with reference to an example in which a cast drum is used.
The width of the cast drum is preferably 4 m or more, particularly preferably 5 m or more. If the width of the cast drum is too small, it tends to be difficult to obtain a wide film.
　かかるキャストドラムの直径は、好ましくは２～５ｍ、特に好ましくは２．４～４．５ｍ、更に好ましくは２．８～４ｍである。
　かかる直径が小さすぎると乾燥長が不足し速度が出にくい傾向があり、大きすぎると輸送性が低下する傾向がある。 The diameter of the cast drum is preferably 2 to 5 m, particularly preferably 2.4 to 4.5 m, and more 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.
　かかるキャストドラムの回転速度は、３～５０ｍ／分であることが好ましく、特に好ましくは４～４０ｍ／分、更に好ましくは５～３５ｍ／分である。回転速度が遅すぎると生産性が低下する傾向があり、速すぎると乾燥が不足する傾向がある。 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, and if it is too fast, drying tends to be insufficient.
　かかるキャストドラムの表面温度は、４０～９９℃であることが好ましく、特に好ましくは６０～９５℃である。表面温度が低すぎると乾燥不良となる傾向があり、高すぎると発泡する傾向がある。 The surface temperature of the cast drum is preferably 40 to 99 ° C, particularly preferably 60 to 95 ° C. If the surface temperature is too low, drying tends to be poor, and if it is too high, foaming tends to occur.
　かくして、製膜が行われる。 Thus, film formation is performed.
　次いで、前記工程（Ｃ）について説明する。工程（Ｃ）は、製膜されたフィルムを複数の金属加熱ロールと接触させることにより加熱して乾燥する工程である。 Next, the step (C) will be described. Step (C) is a step of heating and drying the formed film by bringing it into contact with a plurality of metal heating rolls.
　キャストドラムで製膜されたポリビニルアルコール系フィルムの乾燥は、膜の表面と裏面とを複数の金属加熱ロールに交互に接触させることにより行なわれる。金属加熱ロールの表面温度は特に限定されないが、通常６０～１５０℃、さらには７０～１４０℃であることが好ましい。かかる表面温度が低すぎると乾燥不良となる傾向があり、高すぎると乾燥しすぎることとなり、うねりなどの外観不良を招く傾向がある。 The drying of the polyvinyl alcohol film formed on the cast drum is performed by bringing the front and back surfaces of the film into contact with a plurality of metal heating rolls alternately. The surface temperature of the metal heating roll is not particularly limited, but is usually 60 to 150 ° C., more preferably 70 to 140 ° C. If the surface temperature is too low, drying tends to be poor, and if the surface temperature is too high, drying tends to be excessive, and appearance defects such as undulation tend to be caused.
　本発明においては、ポリビニルアルコール系フィルムの水中張力を制御する点で、複数の金属加熱ロールの温度が、下記条件（ａ）～（ｄ）の順であることが好ましい。
条件（ａ）≧８０℃
条件（ｂ）＜８０℃
条件（ｃ）≧１００℃
条件（ｄ）＜１００℃
　なお、通常金属加熱ロールの本数は１０～３０本であり、適宜上記温度条件を満たすように設定される。 In the present invention, the temperature of the plurality of metal heating rolls is preferably in the order of the following conditions (a) to (d) from the viewpoint of controlling the underwater tension of the polyvinyl alcohol film.
Condition (a) ≧ 80 ° C
Condition (b) <80 ° C
Condition (c) ≧ 100 ° C.
Condition (d) <100 ° C
In general, the number of metal heating rolls is 10 to 30, and is appropriately set so as to satisfy the above temperature condition.
　金属加熱ロールによる乾燥後、得られたフィルムは、工程（Ｄ）において、熱風を用いて熱処理される。次いで、前記工程（Ｄ）について説明する。 After drying with a metal heating roll, the obtained film is heat-treated using hot air in the step (D). Next, the step (D) will be described.
　熱処理の温度は、１１０～１４０℃が好ましく、特に好ましくは１１５～１３５℃、更に好ましくは１２０～１３０℃である。かかる熱処理温度が低すぎると、ポリビニルアルコール系フィルムの水中張力が不足する傾向にあり、高すぎるとポリビニルアルコール系フィルムの水中張力が増大する傾向にある。
　かかる熱処理の方法としては、温度制御に優れる点で、フローティングドライヤーにて行なう方法が好ましい。 The heat treatment temperature is preferably 110 to 140 ° C., particularly preferably 115 to 135 ° C., and further preferably 120 to 130 ° C. If the heat treatment temperature is too low, the underwater tension of the polyvinyl alcohol film tends to be insufficient, and if it is too high, the underwater tension of the polyvinyl alcohol film tends to increase.
As a method of such heat treatment, a method using a floating dryer is preferable in terms of excellent temperature control.
　熱処理が行われたフィルムは、両端をスリットして、ロールに巻き取られてロール状のポリビニルアルコール系フィルムとなる。 The film that has been heat-treated is slit at both ends and wound into a roll to form a roll-shaped polyvinyl alcohol film.
　また、上記ポリビニルアルコール系フィルムの幅は、偏光膜の幅広化の点で４ｍ以上であることが好ましく、特に好ましくは更なる幅広化の点から４．５ｍ以上、更に好ましくは破断回避の点から４．５～６ｍである。 The width of the polyvinyl alcohol film is preferably 4 m or more from the viewpoint of widening the polarizing film, particularly preferably 4.5 m or more from the viewpoint of further widening, and more preferably from the viewpoint of avoiding breakage. 4.5 to 6 m.
　上記ポリビニルアルコール系フィルムの長さは、偏光膜の大面積化の点から４ｋｍ以上であることが好ましく、特に好ましくは更なる大面積化の点から４．５ｋｍ以上、更に好ましくは輸送重量の点から４．５～５０ｋｍである。 The length of the polyvinyl alcohol film is preferably 4 km or more from the viewpoint of increasing the area of the polarizing film, particularly preferably 4.5 km or more, more preferably from the viewpoint of transport weight. From 4.5 to 50 km.
　上記ポリビニルアルコール系フィルムは、巻き取り性の点で、２０℃６５％ＲＨの大気中でフィルムの流れ方向（ＭＤ方向）に４倍に延伸した時の張力が、４０～８０Ｎ／ｍｍ２であることが好ましく、特に好ましくは、保管時の安定性の点で４３～７５Ｎ／ｍｍ２、更に好ましくは、水中張力の制御のしやすさから４６～７０Ｎ／ｍｍ２である。 The above-mentioned polyvinyl alcohol film has a tension of 40 to 80 N / mm 2 when stretched four times in the film flow direction (MD direction) in the atmosphere of 20 ° C. and 65% RH in terms of windability. it is preferred, particularly preferably, a point at 43 ~ 75N / mm 2 of stability during storage, and more preferably from 46 ~ 70N / mm 2 from the ease of control of the water tension.
　上記ポリビニルアルコール系フィルムは、水中張力の均一性の点で、面内位相差が５０ｎｍ以下であることが好ましく、特に好ましくは４０ｎｍ以下、更に好ましくは３０ｎｍ以下である。 The above-mentioned polyvinyl alcohol film preferably has an in-plane retardation of 50 nm or less, particularly preferably 40 nm or less, and more preferably 30 nm or less, from the viewpoint of uniformity of tension in water.
　かくして本発明のポリビニルアルコール系フィルムが得られる。 Thus, the polyvinyl alcohol film of the present invention is obtained.
　本発明のポリビニルアルコール系フィルムは光学性能に優れるものであり、光学用のポリビニルアルコール系フィルムとして好適に用いられ、更には偏光膜用の原反として特に好ましく用いられる。 The polyvinyl alcohol film of the present invention is excellent in optical performance, is suitably used as an optical polyvinyl alcohol film, and is particularly preferably used as a raw material for a polarizing film.
　以下、本発明のポリビニルアルコール系フィルムを用いて得られる偏光膜の製造方法について説明する。 Hereinafter, a method for producing a polarizing film obtained using the polyvinyl alcohol film of the present invention will be described.
　本発明の偏光膜は、上記ポリビニルアルコール系フィルムを、ロールから巻き出して水平方向に移送し、膨潤、染色、ホウ酸架橋、延伸、洗浄、乾燥などの工程を経て製造される。 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.
　膨潤工程は、染色工程の前に施される。膨潤工程により、ポリビニルアルコール系フィルム表面の汚れを洗浄することができるほかに、ポリビニルアルコール系フィルムを膨潤させることで染色ムラなどを防止する効果もある。膨潤工程において、処理液としては、通常、水が用いられる。当該処理液は、主成分が水であれば、ヨウ化化合物、界面活性剤等の添加物、アルコール等が少量入っていてもよい。膨潤浴の温度は、通常１０～４５℃程度であり、膨潤浴への浸漬時間は、通常０．１～１０分間程度である。また、必要に応じて処理中に延伸操作を行なってもよい。 The swelling process is performed before the dyeing process. In addition to washing the surface of the polyvinyl alcohol film by the swelling step, there is also an effect of preventing uneven staining by swelling the polyvinyl alcohol film. In the swelling step, water is usually used as the treatment liquid. If the main component is water, 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 | stretching operation during a process as needed.
　染色工程は、フィルムにヨウ素または二色性染料を含有する液体を接触させることによって行なわれる。通常は、ヨウ素－ヨウ化カリウムの水溶液が用いられ、ヨウ素の濃度は０．１～２ｇ／Ｌ、ヨウ化カリウムの濃度は１～１００ｇ／Ｌが適当である。染色時間は３０～５００秒程度が実用的である。処理浴の温度は５～５０℃が好ましい。水溶液には、水溶媒以外に水と相溶性のある有機溶媒を少量含有させてもよい。また、必要に応じて処理中に延伸操作を行なってもよい。 The dyeing step is performed by bringing the film into contact with 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 | stretching operation during a process as needed.
　ホウ酸架橋工程は、ホウ酸やホウ砂などのホウ素化合物を使用して行われる。ホウ素化合物は水溶液または水－有機溶媒混合液の形で濃度１０～１００ｇ／Ｌ程度で用いられ、液中にはヨウ化カリウムを共存させるのが、偏光性能の安定化の点で好ましい。処理時の温度は３０～７０℃程度、処理時間は０．１～２０分程度が好ましく、また必要に応じて処理中に延伸操作を行なってもよい。 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.
　延伸工程は、一軸方向に３～１０倍、好ましくは３．５～６倍延伸することが好ましい。この際、延伸方向の直角方向にも若干の延伸（幅方向の収縮を防止する程度、またはそれ以上の延伸）を行なっても差し支えない。延伸時の温度は、３０～１７０℃が好ましい。さらに、延伸倍率は最終的に前記範囲に設定されればよく、延伸操作は一段階のみならず、製造工程の任意の範囲の段階に実施すればよい。 In the stretching step, it is preferable to stretch 3 to 10 times, preferably 3.5 to 6 times in a uniaxial direction. At this time, a slight stretching (stretching to prevent shrinkage in the width direction or more) may be performed in a direction perpendicular to the stretching direction. The temperature during stretching is preferably 30 to 170 ° C. Furthermore, 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.
　洗浄工程は、例えば、水やヨウ化カリウム等のヨウ化物水溶液にポリビニルアルコール系フィルムを浸漬することにより行われ、フィルムの表面に発生する析出物を除去することができる。ヨウ化カリウム水溶液を用いる場合のヨウ化カリウム濃度は１～８０ｇ／Ｌ程度でよい。洗浄処理時の温度は、通常、５～５０℃、好ましくは１０～４５℃である。処理時間は、通常、１～３００秒間、好ましくは１０～２４０秒間である。なお、水洗浄とヨウ化カリウム水溶液による洗浄は、適宜組み合わせて行ってもよい。 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. When using an aqueous potassium iodide solution, 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. In addition, you may perform combining water washing | cleaning and washing | cleaning by potassium iodide aqueous solution suitably.
　乾燥工程は、大気中で４０～８０℃で１～１０分間行えばよい。 The drying process may be performed in the atmosphere at 40 to 80 ° C. for 1 to 10 minutes.
　また、偏光膜の偏光度は、好ましくは９９．５％以上、より好ましくは９９．８％以上である。偏光度が低すぎると液晶ディスプレイにおけるコントラストを確保することができなくなる傾向がある。
　なお、偏光度は、一般的に２枚の偏光膜を、その配向方向が同一方向になるように重ね合わせた状態で、波長λにおいて測定した光線透過率（Ｈ１１）と、２枚の偏光膜を、配向方向が互いに直交する方向になる様に重ね合わせた状態で、波長λにおいて測定した光線透過率（Ｈ１）より、下式にしたがって算出される。
　　　〔（Ｈ１１－Ｈ１）／（Ｈ１１＋Ｈ１）〕１／２ Further, the polarization degree of the polarizing film 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.
Note that the degree of polarization is generally the light transmittance (H 11 ) measured at the wavelength λ 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 λ 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
　さらに、本発明の偏光膜の単体透過率は、好ましくは４２％以上である。かかる単体透過率が低すぎると液晶ディスプレイの高輝度化を達成できなくなる傾向がある。
　単体透過率は、分光光度計を用いて偏光膜単体の光線透過率を測定して得られる値である。 Further, the single transmittance of the polarizing film of the present invention is preferably 42% 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.
　かくして、本発明の偏光膜が得られるが、本発明の偏光膜は、色ムラの少ない偏光板を製造するのに好適である。
　以下、本発明の偏光板の製造方法について説明する。 Thus, although 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 color unevenness.
Hereinafter, the manufacturing method of the polarizing plate of this invention is demonstrated.
　本発明の偏光膜は、その片面または両面に、接着剤を介して、光学的に等方性な樹脂フィルムを保護フィルムとして貼合されて偏光板となる。保護フィルムとしては、たとえば、セルローストリアセテート、セルロースジアセテート、ポリカーボネート、ポリメチルメタクリレート、シクロオレフィンポリマー、シクロオレフィンコポリマー、ポリスチレン、ポリエーテルスルホン、ポリアリーレンエステル、ポリ－４－メチルペンテン、ポリフェニレンオキサイドなどのフィルムまたはシートがあげられる。 The polarizing film of the present invention is bonded to one side or both sides of an optically isotropic resin film as a protective film via an adhesive to form a polarizing plate. Examples of 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.
　貼合方法は、公知の手法で行われるが、例えば、液状の接着剤組成物を、偏光膜、保護フィルム、あるいはその両方に均一に塗布した後、両者を貼り合わせて圧着し、加熱や活性エネルギー線を照射することで行われる。 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.
　また、偏光膜には、薄膜化を目的として、上記保護フィルムの代わりに、その片面または両面にウレタン系樹脂、アクリル系樹脂、ウレア樹脂などの硬化性樹脂を塗布し、硬化して偏光板とすることもできる。 In addition, for the purpose of thinning the polarizing film, instead of the protective film, a curable resin such as urethane resin, acrylic resin, urea resin or the like is applied to one side or both sides of the protective film and cured to obtain a polarizing plate. You can also
　本発明の製造方法により得られるポリビニルアルコール系フィルムからなる偏光膜は、偏光性能の面内均一性にも優れており、携帯情報端末機、パソコン、テレビ、プロジェクター、サイネージ、電子卓上計算機、電子時計、ワープロ、電子ペーパー、ゲーム機、ビデオ、カメラ、フォトアルバム、温度計、オーディオ、自動車や機械類の計器類などの液晶表示装置、サングラス、防眩メガネ、立体メガネ、ウェアラブルディスプレイ、表示素子（ＣＲＴ、ＬＣＤ、有機ＥＬ、電子ペーパーなど）用反射防止層、光通信機器、医療機器、建築材料、玩具などに好ましく用いられる。 A polarizing film comprising a polyvinyl alcohol film obtained by the production method of the present invention is excellent in in-plane uniformity of polarization performance, and is a portable information terminal, personal computer, TV, projector, signage, electronic desk calculator, electronic timepiece. , Word processors, electronic paper, game 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 paper, etc.) for use in antireflection layers, optical communication equipment, medical equipment, building materials, toys and the like.
　以下、実施例を挙げて本発明を更に具体的に説明するが、本発明はその要旨を超えない限り以下の実施例に限定されるものではない。
　尚、例中「部」、「％」とあるのは、重量基準を意味する。 EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In the examples, “parts” and “%” mean weight basis.
<測定条件>
（１）水中での延伸張力（Ｎ／ｍｍ２）
　得られたポリビニルアルコール系フィルムから、長さ（ＭＤ方向）５０ｍｍ×幅（ＴＤ方向）３５ｍｍ×厚さＤ（ｍｍ）の試験片を切り出し、チャック間距離が２０ｍｍとなるように長さ方向の両端部を幅３５ｍｍのチャックではさんだ後、３０℃及び５０℃の水中で、ＭＤ方向に速度１８ｍｍ／分で６倍に延伸した時の応力（Ｎ）をばねばかりで測定した。かかる応力をフィルムの断面積で除した値を延伸張力（Ｎ／ｍｍ２）とした。 <Measurement conditions>
(1) Stretch tension in water (N / mm 2 )
A test piece of length (MD direction) 50 mm × width (TD direction) 35 mm × thickness D (mm) was cut out from the obtained polyvinyl alcohol film, and both ends in the length direction so that the distance between chucks was 20 mm. After the part was sandwiched with a chuck having a width of 35 mm, the stress (N) when stretched 6 times in the MD direction at a speed of 18 mm / min in water at 30 ° C. and 50 ° C. was measured using only the spring. A value obtained by dividing the stress by the cross-sectional area of the film was defined as a stretching tension (N / mm 2 ).
（２）大気中での延伸張力（Ｎ／ｍｍ２）
　得られたポリビニルアルコール系フィルムを２０℃６５％ＲＨの大気中で一日状態調整を行なった後、長さ（ＭＤ方向）１２０ｍｍ×幅（ＴＤ方向）１５ｍｍ×厚さＤ（ｍｍ）の試験片を切り出し、島津製作所社製「精密万能試験機、オートグラフ（ＡＧ－ＩＳ）」を用いて、チャック間距離５０ｍｍとなるように、長さ方向の両端部を幅１５ｍｍのチャックではさんだ後、２０℃６５％ＲＨの大気中で、ＭＤ方向に速度１０００ｍｍ／分で４倍に延伸した時の応力（Ｎ）を測定した。かかる応力をフィルムの断面積で除した値を大気中での延伸張力（Ｎ／ｍｍ２）とした。 (2) Stretch tension in air (N / mm 2 )
The obtained polyvinyl alcohol film was subjected to a daily condition adjustment in an atmosphere of 20 ° C. and 65% RH, and then a test piece of length (MD direction) 120 mm × width (TD direction) 15 mm × thickness D (mm) Using a “Precision Universal Testing Machine, Autograph (AG-IS)” manufactured by Shimadzu Corporation, both ends in the longitudinal direction are sandwiched by chucks with a width of 15 mm so that the distance between chucks is 50 mm. The stress (N) was measured when the film was stretched 4 times in the MD direction at a speed of 1000 mm / min in an atmosphere at 65 ° C. and RH. The value obtained by dividing the stress by the cross-sectional area of the film was taken as the stretching tension (N / mm 2 ) in the atmosphere.
（３）面内位相差（ｎｍ）
　得られたポリビニルアルコール系フィルムから、長さ（ＭＤ方向）２０ｃｍ×幅（ＴＤ方向）２０ｃｍの試験片を切り出し、２次元複屈折評価システム（フォトニックラティス社製：「ＰＡ－１１０Ｌ」）を用いて、面内位相差（ｎｍ）を測定した。 (3) In-plane retardation (nm)
A test piece having a length (MD direction) of 20 cm × width (TD direction) of 20 cm was cut out from the obtained polyvinyl alcohol film, and a two-dimensional birefringence evaluation system (manufactured by Photonic Lattice: “PA-110L”) was used. In-plane retardation (nm) was measured.
（４）偏光度（％）、単体透過率（％）
　得られた偏光膜から、長さ４ｃｍ×幅４ｃｍのサンプルを切り出し、自動偏光フィルム測定装置（日本分光社製：ＶＡＰ７０７０）を用いて、偏光度（％）と単体透過率（％）を測定した。 (4) Degree of polarization (%), single transmittance (%)
A sample having a length of 4 cm and a width of 4 cm was cut out from the obtained polarizing film, and the degree of polarization (%) and the single transmittance (%) were measured using an automatic polarizing film measuring device (manufactured by JASCO Corporation: VAP7070). .
（５）偏光ムラ
　得られた偏光膜から、長さ３０ｃｍ×幅３０ｃｍの試験片を切り出し、クロスニコル状態の２枚の偏光板（単体透過率４３．５％、偏光度９９．９％）の間に４５°の角度で挟んだのちに、表面照度１４，０００ルクス（ｌｘ）のライトボックスを用いて、透過モードで光学的な色ムラを観察し、以下の基準で評価した。
（評価基準）
　　○・・・色ムラなし
　　△・・・かすかに色ムラあり
　　×・・・色ムラあり (5) Polarization unevenness From the obtained polarizing film, a test piece having a length of 30 cm and a width of 30 cm was cut out, 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 with a surface illuminance of 14,000 lux (lx), and evaluated according to the following criteria.
(Evaluation criteria)
○ ・ ・ ・ No color unevenness △ ・ ・ ・ Slight color unevenness × ・ ・ ・ Color unevenness
<実施例１> 
（ポリビニルアルコール系フィルムの製造）
　５，０００Ｌの溶解缶に、重量平均分子量１４２，０００、ケン化度９９．８モル％のポリビニルアルコール系樹脂１，０００ｋｇ、水２，５００ｋｇ、可塑剤としてグリセリン１０５ｋｇ、及び界面活性剤としてドデシルスルホン酸ナトリウム０．２５ｋｇを入れ、撹拌しながら１５０℃まで昇温して加圧溶解を行い、樹脂濃度２５％のポリビニルアルコール系樹脂水溶液を得た。
　次に該ポリビニルアルコール系樹脂水溶液を、ベントを有する２軸押出機に供給して脱泡した後、水溶液温度を９５℃にし、Ｔ型スリットダイ吐出口より、２０ｍ／分で回転するキャストドラムに吐出及び流延して製膜した。得られたフィルムをキャストドラムから剥離し、フィルムの表面と裏面とを合計２０本の金属加熱ロールに交互に接触させながら乾燥を行った。かかる金属加熱ロールは、９０℃、７０℃、１１０℃、８５℃の温度順で配置されている。次いで、フィルム両面から１４０℃の熱風を吹き付けて熱処理を行った後、最後にスリットして巻き取り、ロール状のポリビニルアルコール系フィルムを得た（フィルム厚０．０３ｍｍ、幅５ｍ、長さ５ｋｍ）。得られたポリビニルアルコール系フィルムの特性は表１に示される通りであった。 <Example 1>
(Manufacture of polyvinyl alcohol film)
In a 5,000 L dissolution can, 1,000 kg of polyvinyl alcohol resin having a weight average molecular weight of 142,000 and a saponification degree of 99.8 mol%, 2,500 kg of water, 105 kg of glycerin as a plasticizer, and dodecyl sulfone as a surfactant Sodium 0.25 kg was added, heated to 150 ° C. with stirring, and dissolved under pressure to obtain a polyvinyl alcohol resin aqueous solution with a resin concentration of 25%.
Next, 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 rotating at 20 m / min from the T-type slit die discharge port The film was formed by discharging and casting. The obtained film was peeled off from the cast drum, and dried while bringing the front and back surfaces of the film into contact with a total of 20 metal heating rolls alternately. Such metal heating rolls are arranged in the order of 90 ° C., 70 ° C., 110 ° C., and 85 ° C. Next, after 140 ° C. hot air was blown from both sides of the film for heat treatment, the film was finally slit and wound to obtain a roll-like polyvinyl alcohol film (film thickness 0.03 mm, width 5 m, length 5 km). . The properties of the obtained polyvinyl alcohol film were as shown in Table 1.
（偏光膜の製造）
　得られたポリビニルアルコール系フィルムをロールから巻き出し、水平方向に搬送しながら、水温３０℃の水槽に浸漬して膨潤させながら、ＭＤ方向へ１．７倍に延伸した。次に、ヨウ素０．５ｇ／Ｌ、ヨウ化カリウム３０ｇ／Ｌよりなる３０℃の水溶液中に浸漬して染色しながら、ＭＤ方向へ１．６倍に延伸し、ついでホウ酸４０ｇ／Ｌ、ヨウ化カリウム３０ｇ／Ｌの組成の水溶液（５０℃）に浸漬してホウ酸架橋しながら、ＭＤ方向へ２．１倍に一軸延伸した。最後に、ヨウ化カリウム水溶液で洗浄を行い、その後、５０℃で２分間乾燥して総延伸倍率５．７倍の偏光膜を得た。かかる製造中に破断は起きず、得られた偏光膜の特性は表２に示される通りであった。 (Manufacture of polarizing film)
The obtained polyvinyl alcohol film was unwound from a roll and stretched 1.7 times in the MD direction while being swelled by being immersed in a water bath at a water temperature of 30 ° C. while being conveyed in the horizontal direction. Next, the film was stretched 1.6 times in the MD direction while being immersed and dyed in an aqueous solution of 30 g / L of iodine 0.5 g / L and 30 g / L of potassium iodide, and then boric acid 40 g / L, iodine The sample was uniaxially stretched 2.1 times in the MD direction while being immersed in an aqueous solution (50 ° C.) having a composition of 30 g / L of potassium halide and cross-linking with boric acid. Finally, it was washed with an aqueous potassium iodide solution and then dried at 50 ° C. for 2 minutes to obtain a polarizing film having a total draw ratio of 5.7 times. No breakage occurred during the production, and the properties of the obtained polarizing film were as shown in Table 2.
<実施例２> 
　実施例１において、１３０℃の熱風を吹き付けて熱処理する以外は実施例１と同様にして、ポリビニルアルコール系フィルムと偏光膜を得た。得られた偏光膜について、実施例１と同様の評価を行った。評価結果を表１と表２に示す。 <Example 2>
In Example 1, a polyvinyl alcohol film and a polarizing film were obtained in the same manner as in Example 1 except that heat treatment was performed by blowing hot air at 130 ° C. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
<実施例３> 
　実施例１において、キャストドラムの回転速度を１０ｍ／分に変更してフィルム厚を０．０６ｍｍにし、１２０℃の熱風を吹き付けて熱処理する以外は実施例１と同様にして、ポリビニルアルコール系フィルムと偏光膜を得た。得られた偏光膜について、実施例１と同様の評価を行った。評価結果を表１と表２に示す。 <Example 3>
In Example 1, the rotational speed of the cast drum was changed to 10 m / min, the film thickness was changed to 0.06 mm, and a polyvinyl alcohol film was obtained in the same manner as in Example 1 except that heat treatment was performed by blowing hot air at 120 ° C. A polarizing film was obtained. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
＜実施例４＞
　実施例１において、キャストドラムの回転速度を１０ｍ／分に変更してフィルム厚を０．０６ｍｍにし、熱処理温度を１１０℃とする以外は実施例１と同様にして、ポリビニルアルコール系フィルムと偏光膜を得た。得られた偏光膜について、実施例１と同様の評価を行った。評価結果を表１と表２に示す。 <Example 4>
In Example 1, the polyvinyl alcohol film and the polarizing film were changed in the same manner as in Example 1 except that the rotation speed of the cast drum was changed to 10 m / min to change the film thickness to 0.06 mm and the heat treatment temperature to 110 ° C. Got. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
＜比較例１＞
　実施例１において、キャストドラムの回転速度を１０ｍ／分に変更してフィルム厚を０．０６ｍｍにし、熱処理温度を１００℃とする以外は実施例１と同様にして、ポリビニルアルコール系フィルムと偏光膜を得た。得られた偏光膜について、実施例１と同様の評価を行った。評価結果を表１と表２に示す。 <Comparative Example 1>
In Example 1, the polyvinyl alcohol film and the polarizing film were changed in the same manner as in Example 1 except that the rotation speed of the cast drum was changed to 10 m / min to change the film thickness to 0.06 mm and the heat treatment temperature to 100 ° C. Got. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
＜比較例２＞
　実施例１において、熱処理温度を１５０℃とする以外は実施例１と同様にして、ポリビニルアルコール系フィルムを得た。該ポリビニルアルコール系フィルムを用いて偏光膜の製造を開始したが、長さ１ｋｍの偏光膜を製造したところで、ホウ酸架橋工程の延伸中に破断が生じ、目的とする偏光膜は得られなかった。 <Comparative example 2>
In Example 1, a polyvinyl alcohol film was obtained in the same manner as in Example 1 except that the heat treatment temperature was 150 ° C. Production of a polarizing film was started using the polyvinyl alcohol film, but when a polarizing film having a length of 1 km was produced, breakage occurred during stretching in the boric acid crosslinking step, and the intended polarizing film was not obtained. .
＜比較例３＞
　実施例１において、金属加熱ロール温度を全て８０℃とした以外は実施例１と同様にして、ポリビニルアルコール系フィルムと偏光膜を得た。得られた偏光膜について、実施例１と同様の評価を行った。評価結果を表１と表２に示す。 <Comparative Example 3>
In Example 1, a polyvinyl alcohol film and a polarizing film were obtained in the same manner as in Example 1 except that all metal heating roll temperatures were set to 80 ° C. About the obtained polarizing film, evaluation similar to Example 1 was performed. The evaluation results are shown in Tables 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実施例１～４のポリビニルアルコール系フィルムは、厚さＤ（ｍｍ）、３０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＡ（Ｎ／ｍｍ２）、５０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＢ（Ｎ／ｍｍ２）とした時に、Ｄ×ＡとＤ×Ｂの値がいずれも式（１）及び（２）を満足するものであるのに対し、比較例１のポリビニルアルコール系フィルムはＤ×Ｂの値が式（２）の範囲外であり、比較例２及び３のポリビニルアルコール系フィルムはＤ×Ａの値が式（１）の範囲外であり、かつＤ×Ｂの値も式（２）の範囲外であった。
　そして、各々のポリビニルアルコール系フィルムから得られる偏光膜の偏光特性は、実施例１～４が比較例１及び３よりも優れるものであることがわかり、更に比較例２においては、破断によって偏光膜が得られなかった。 The polyvinyl alcohol-based films of Examples 1 to 4 have a thickness D (mm) and a tension when stretched 6 times in the film flow direction (MD direction) in water at 30 ° C. (A (N / mm 2 )), When the tension when stretched 6 times in the film flow direction (MD direction) in water at 50 ° C. is B (N / mm 2 ), the values of D × A and D × B are both formulas (1) And the polyvinyl alcohol film of Comparative Example 1 has a D × B value outside the range of the formula (2), while the polyvinyl alcohol films of Comparative Examples 2 and 3 satisfy the conditions (2) and (2). The value of D × A was outside the range of formula (1), and the value of D × B was also outside the range of formula (2).
The polarizing properties of the polarizing films obtained from the respective polyvinyl alcohol-based films are found to be superior to those of Comparative Examples 1 and 3 in Examples 1 to 4. Further, in Comparative Example 2, the polarizing film is broken by breaking. Was not obtained.
　更に、実施例３及び４、比較例１で得られたポリビニルアルコール系フィルムについては、下記の方法に従い、貯蔵弾性率Ｅ１，Ｅ２を測定し、Ｅ２／Ｅ１の値を計算した。　　　　 Furthermore, for the polyvinyl alcohol films obtained in Examples 3 and 4 and Comparative Example 1, the storage elastic modulus E1 and E2 were measured according to the following method, and the value of E2 / E1 was calculated. .
（６）貯蔵弾性率（ＭＰａ）
　得られたポリビニルアルコール系フィルムから、長さ（ＭＤ方向）２５ｍｍ×幅（ＴＤ方向）５ｍｍの試験片を切り出し、アイティー計測制御社製ＤＶＡ－２２５を用いて、３０℃と５０℃の水中における貯蔵弾性率を測定した。詳細な試験条件は次の通りである。
周波数：１０Ｈｚ
チャック間距離：１５ｍｍ
荷重：ＭＤ方向に動的歪０．３％、静動比(静的歪と動的歪の比)６
３０℃水浸漬１０分後の貯蔵弾性率Ｅ１（ＭＰａ）と、５０℃水浸漬１０分後の貯蔵弾性率Ｅ２（ＭＰａ）から、Ｅ２／Ｅ１を算出した。なお、水中での貯蔵弾性率算出のための膜厚は水浸漬前の厚さを用いた。 (6) Storage elastic modulus (MPa)
A test piece having a length (MD direction) of 25 mm × width (TD direction) of 5 mm was cut out from the obtained polyvinyl alcohol-based film, and was used in water at 30 ° C. and 50 ° C. using DVA-225 manufactured by IT Measurement & Control Co., Ltd. The storage modulus was measured. Detailed test conditions are as follows.
Frequency: 10Hz
Distance between chucks: 15mm
Load: 0.3% dynamic strain in the MD direction, static to dynamic ratio (ratio of static strain to dynamic strain) 6
E2 / E1 was calculated from the storage elastic modulus E1 (MPa) after 10 minutes of 30 ° C. water immersion and the storage elastic modulus E2 (MPa) after 10 minutes of 50 ° C. water immersion. In addition, the thickness before water immersion was used for the film thickness for the storage elastic modulus calculation in water.
　測定の結果は、実施例３：Ｅ２／Ｅ１＝０．２８、実施例４：Ｅ２／Ｅ１＝０．２７、比較例１：Ｅ２／Ｅ１＝０．２５であり、Ｅ２／Ｅ１の値が低い場合は、偏光膜とした際の偏光度が低下することが確認された。 The measurement results are Example 3: E2 / E1 = 0.28, Example 4: E2 / E1 = 0.27, Comparative Example 1: E2 / E1 = 0.25, and the value of E2 / E1 is low. In this case, it was confirmed that the degree of polarization when the polarizing film was formed decreased.
　上記実施例においては、本発明における具体的な形態について示したが、上記実施例は単なる例示にすぎず、限定的に解釈されるものではない。当業者に明らかな様々な変形は、本発明の範囲内であることが企図されている。 In the above embodiments, specific forms in the present invention have been described. However, the above embodiments are merely examples and are not construed as limiting. Various modifications apparent to those skilled in the art are contemplated to be within the scope of this invention.
　本発明の製造方法により得られるポリビニルアルコール系フィルムからなる偏光膜は、偏光性能の面内均一性にも優れており、携帯情報端末機、パソコン、テレビ、プロジェクター、サイネージ、電子卓上計算機、電子時計、ワープロ、電子ペーパー、ゲーム機、ビデオ、カメラ、フォトアルバム、温度計、オーディオ、自動車や機械類の計器類などの液晶表示装置、サングラス、防眩メガネ、立体メガネ、ウェアラブルディスプレイ、表示素子（ＣＲＴ、ＬＣＤ、有機ＥＬ、電子ペーパーなど）用反射防止層、光通信機器、医療機器、建築材料、玩具などに好ましく用いられる。 A polarizing film comprising a polyvinyl alcohol film obtained by the production method of the present invention is excellent in in-plane uniformity of polarization performance, and is a portable information terminal, personal computer, TV, projector, signage, electronic desk calculator, electronic timepiece. , Word processors, electronic paper, game 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 paper, etc.) for use in antireflection layers, optical communication equipment, medical equipment, building materials, toys and the like.

Claims (13)

  1. 　厚さＤ（ｍｍ）、
    ３０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＡ（Ｎ／ｍｍ２）、
    ５０℃の水中においてフィルムの流れ方向（ＭＤ方向）に６倍に延伸した時の張力をＢ（Ｎ／ｍｍ２）
    とした時に、下式（１）及び（２）を満足することを特徴とするポリビニルアルコール系フィルム。
    式（１）０．６≦Ｄ×Ａ≦１．２
    式（２）０．２≦Ｄ×Ｂ≦０．４     Thickness D (mm),
    A (N / mm 2 ) tension when stretched 6 times in the film flow direction (MD direction) in water at 30 ° C.,
    The tension when stretched 6 times in the film flow direction (MD direction) in water at 50 ° C. is B (N / mm 2 ).
    When satisfied, the following formulas (1) and (2) are satisfied.
    Formula (1) 0.6 <= D * A <= 1.2
    Formula (2) 0.2 <= D * B <= 0.4
  2. 　下式（３）を満足することを特徴とする請求項１記載のポリビニルアルコール系フィルム。
    式（３）０．２≦Ｂ／Ａ≦０．５     The polyvinyl alcohol film according to claim 1, wherein the following formula (3) is satisfied.
    Formula (3) 0.2 ≦ B / A ≦ 0.5
  3. 　３０℃の水中における貯蔵弾性率をＥ１（Ｐａ）、５０℃の水中における貯蔵弾性率をＥ２（Ｐａ）とした場合に、Ｅ２／Ｅ１が０．２５～０．３０であることを特徴とする請求項１または２記載のポリビニルアルコール系フィルム。 When the storage elastic modulus in water at 30 ° C. is E1 (Pa) and the storage elastic modulus in water at 50 ° C. is E2 (Pa), E2 / E1 is 0.25 to 0.30. The polyvinyl alcohol film according to claim 1 or 2.
  4. 　ポリビニルアルコール系フィルムの厚さＤが０．０４ｍｍ以下であることを特徴とする請求項１～３いずれか記載のポリビニルアルコール系フィルム。 The polyvinyl alcohol film according to any one of claims 1 to 3, wherein a thickness D of the polyvinyl alcohol film is 0.04 mm or less.
  5. 　ポリビニルアルコール系フィルムの幅が４ｍ以上、かつ長さが４ｋｍ以上であることを特徴とする請求項１～４いずれか記載のポリビニルアルコール系フィルム。 The polyvinyl alcohol film according to any one of claims 1 to 4, wherein the polyvinyl alcohol film has a width of 4 m or more and a length of 4 km or more.
  6. 　２０℃６５％ＲＨの大気中においてフィルムの流れ方向（ＭＤ方向）に４倍に延伸した時の張力が、４０～８０Ｎ／ｍｍ２であることを特徴とする請求項１～５いずれか記載のポリビニルアルコール系フィルム。 The tension according to any one of claims 1 to 5, wherein the tension when stretched 4 times in the flow direction (MD direction) of the film in the atmosphere of 20 ° C and 65% RH is 40 to 80 N / mm 2 . Polyvinyl alcohol film.
  7. 　面内位相差が５０ｎｍ以下であることを特徴とする請求項１～６いずれか記載のポリビニルアルコール系フィルム。 The polyvinyl alcohol film according to any one of claims 1 to 6, wherein the in-plane retardation is 50 nm or less.
  8. 　請求項１～７いずれか記載のポリビニルアルコール系フィルムを製造する方法であって、下記工程（Ａ）～（Ｄ）を経て製造することを特徴とするポリビニルアルコール系フィルムの製造方法。
    工程（Ａ）ポリビニルアルコール系樹脂水溶液を調液する工程。
    工程（Ｂ）ポリビニルアルコール系樹脂の水溶液をキャスト型に流延して製膜する工程。
    工程（Ｃ）製膜されたフィルムを複数の金属加熱ロールと接触させることにより加熱して乾燥する工程。
    工程（Ｄ）得られたフィルムを熱風を用いて熱処理する工程。     8. A method for producing a polyvinyl alcohol film according to claim 1, wherein the polyvinyl alcohol film is produced through the following steps (A) to (D).
    Step (A) A step of preparing a polyvinyl alcohol resin aqueous solution.
    Step (B) A step of casting an aqueous solution of a polyvinyl alcohol resin into a cast mold to form a film.
    Step (C) A step of heating and drying the formed film by bringing it into contact with a plurality of metal heating rolls.
    Process (D) The process of heat-processing the obtained film using a hot air.
  9. 　工程（Ａ）において、ポリビニルアルコール系樹脂に対して、グリセリンを５～１２重量％配合することを特徴とする請求項８記載のポリビニルアルコール系フィルムの製造方法。 The method for producing a polyvinyl alcohol film according to claim 8, wherein in the step (A), 5 to 12% by weight of glycerin is blended with respect to the polyvinyl alcohol resin.
  10. 　工程（Ｃ）における複数の金属加熱ロールの温度が、下記条件（ａ）～（ｄ）の順であることを特徴とする請求項８または９記載のポリビニルアルコール系フィルムの製造方法。
    条件（ａ）≧８０℃
    条件（ｂ）＜８０℃
    条件（ｃ）≧１００℃
    条件（ｄ）＜１００℃     10. The method for producing a polyvinyl alcohol film according to claim 8, wherein the temperature of the plurality of metal heating rolls in the step (C) is in the order of the following conditions (a) to (d).
    Condition (a) ≧ 80 ° C
    Condition (b) <80 ° C
    Condition (c) ≧ 100 ° C.
    Condition (d) <100 ° C
  11. 　工程（Ｄ）における熱処理温度が、１１０～１４０℃であることを特徴とする請求項８～１０いずれか記載のポリビニルアルコール系フィルムの製造方法。 The method for producing a polyvinyl alcohol film according to any one of claims 8 to 10, wherein the heat treatment temperature in step (D) is 110 to 140 ° C.
  12. 　請求項８～１１いずれか記載の製造方法で製造されることを特徴とするポリビニルアルコール系フィルム。 A polyvinyl alcohol film produced by the production method according to any one of claims 8 to 11.
  13. 請求項１～７、１２いずれか記載のポリビニルアルコール系フィルムからなることを特徴とする偏光膜。 A polarizing film comprising the polyvinyl alcohol film according to any one of claims 1 to 7 and 12.
PCT/JP2016/068598 2015-06-24 2016-06-23 Poly(vinyl alcohol)-based film, process for producing poly(vinyl alcohol)-based film, and polarizing film WO2016208652A1 (en)

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CN201680029754.7A CN107614578A (en) 2015-06-24 2016-06-23 The manufacture method and light polarizing film of polyvinyl alcohol film, polyvinyl alcohol film
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