JP7196535B2 - POLYVINYL ALCOHOL-BASED FILM FOR MANUFACTURING POLARIZING FILM, AND POLARIZING MEMBRANE AND POLARIZING PLATE USING THE SAME - Google Patents

Description

The present invention relates to a polyvinyl alcohol-based film that is a raw film for manufacturing a polarizing film, and more specifically, a polyvinyl alcohol-based film for manufacturing a polarizing film that is excellent in releasability from a cast mold or the like and has excellent film appearance and transparency. The present invention relates to a film, and a polarizing film and a polarizing plate using the polyvinyl alcohol film.

The development of liquid crystal display devices is remarkable, and they are widely used in smartphones, tablets, personal computers, liquid crystal televisions, projectors, vehicle-mounted panels, and so on. A polarizing film is used in such a liquid crystal display device, and as the polarizing film, a polyvinyl alcohol film to which a dichroic dye such as iodine is adsorbed and oriented is mainly used. In recent years, as screens have become higher definition, higher brightness, and larger, there is a need for polarizing films that have a degree of polarization that is even better than conventional products and that have no color unevenness. In addition, it is required that the film should have excellent transparency, be free from scratches and streaks, and have excellent film appearance.

Methods for improving the appearance and transparency of the original film of the polarizing film include, for example, polyvinyl alcohol (A), nonionic surfactant (B), anionic surfactant (C) and carbon number 6 to 30. A polyvinyl alcohol film made of a resin composition containing a specific proportion of an aliphatic monoalcohol (D) has been proposed (see Patent Document 1).

JP 2018-90691 A

However, in the technique disclosed in Patent Document 1, although the streak-like defects of the film are reduced and the smoothness and transparency of the film are secured, the peelability of the film is insufficient. There are problems such as an increase in film thickness deviation due to poor peeling and uneven dyeing.

Therefore, in view of this background, the present invention provides a polyvinyl alcohol-based film that is excellent in releasability from the surface of the cast mold, furthermore, has excellent film appearance without the occurrence of die lines, and is also excellent in film transparency. An object of the present invention is to provide a polyvinyl alcohol-based film for producing a high-quality polarizing film.

However, as a result of extensive research in view of such circumstances, the present inventors have found that in a system in which a nonionic surfactant and an anionic surfactant are used in combination as a surfactant in a polyvinyl alcohol film for producing a polarizing film, an anionic By using a phosphate ester type anionic surfactant instead of a sulfate type anionic surfactant used as a surfactant, not only the appearance and transparency of the film but also the peeling from the cast mold can be improved. The inventors have found that a polyvinyl alcohol-based film for producing a polarizing film having excellent properties can be obtained, and completed the present invention.

That is, the gist of the present invention is a polyvinyl alcohol film for producing a polarizing film containing a polyvinyl alcohol resin (A), a nonionic surfactant (B1) and an anionic surfactant, wherein the anionic surfactant is a phosphate ester type anionic surfactant (B2).

The present invention also provides a polarizing film and a polarizing plate obtained by using such a polyvinyl alcohol film for producing a polarizing film.

The polyvinyl alcohol-based film for producing a polarizing film of the present invention is excellent in releasability from a cast mold, appearance of the film, and transparency in a well-balanced manner. When used as a raw film for film production, the resulting polarizing film is free from color unevenness and streaks and is excellent in quality.

The present invention will be described in detail below.
The polyvinyl alcohol-based film for producing a polarizing film of the present invention comprises a polyvinyl alcohol-based resin (A), a nonionic surfactant (B1), and a phosphate ester-type anionic surfactant (B2) which is an anionic surfactant. It is a polyvinyl alcohol-based film containing, and is produced by forming a polyvinyl alcohol-based resin aqueous solution (film-forming undiluted solution) containing the raw materials (A), (B1), and (B2).

As the polyvinyl alcohol-based resin (A), an unmodified polyvinyl alcohol-based 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 component copolymerizable with vinyl acetate may be used. can. Components copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (eg, ethylene, propylene, n-butene, , isobutene, etc.), vinyl ethers, unsaturated sulfonates, and the like. Modified polyvinyl alcohol-based resins obtained by chemically modifying hydroxyl groups after saponification can also be used.

As the polyvinyl alcohol resin (A), a polyvinyl alcohol resin having a 1,2-diol structure in a side chain can also be used. A polyvinyl alcohol resin having a 1,2-diol structure in the side chain can be produced by, for example, (i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (ii) acetic acid (iii) saponifying and decarboxylating a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane; (iv) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether; and the like.

The weight average molecular weight of the polyvinyl alcohol-based resin (A) is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, further 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 resin (A) is used as an optical film. tends to be The weight average molecular weight of the polyvinyl alcohol-based resin (A) is the weight average molecular weight measured by the GPC-MALS method.

The average degree of saponification of the polyvinyl alcohol-based resin (A) used in the present invention is generally preferably 98 mol% or more, particularly preferably 99 mol% or more, further preferably 99.5 mol% or more, especially Preferably, it is 99.8 mol % or more. If the average degree of saponification is too small, there is a tendency that sufficient optical performance cannot be obtained when the polyvinyl alcohol film is used as a polarizing film.
Here, the average degree of saponification in the present invention is measured according to JIS K6726.

As the polyvinyl alcohol resin (A) used in the present invention, two or more different modified species, modified amount, weight average molecular weight, average saponification degree, etc. may be used in combination.

The polyvinyl alcohol film used in the present invention is prepared by preparing a polyvinyl alcohol resin aqueous solution using the above polyvinyl alcohol resin (A), and discharging and casting the polyvinyl alcohol resin aqueous solution into a rotating cast mold. , It can be produced continuously by forming a film by a casting method and drying, for example, it can be produced by the following steps.
(I) A step of forming a film by a casting method.
(II) A step of heating and drying the formed film and, if necessary, heat-treating it.
(III) A step of slitting both ends of the dried film and winding it on a roll.

Examples of the casting mold include a cast drum (drum-type roll) and an endless belt, but the cast drum is preferable from the viewpoint of widening, lengthening, and excellent uniformity of film thickness.
The case where the casting mold is a cast drum will be described below as an example.

First, the step (I) will be described.

In step (I), first, the polyvinyl alcohol-based resin (A) described above is washed with a solvent such as water and dehydrated using a centrifuge or the like to obtain polyvinyl alcohol having a water content of 50% by weight or less. A system resin wet cake is preferred. If the water content is too high, it tends to be difficult to obtain the desired aqueous solution concentration.
The polyvinyl alcohol-based resin wet cake is dissolved in warm or hot water to prepare a polyvinyl alcohol-based resin aqueous solution.

The method for preparing the polyvinyl alcohol resin aqueous solution is not particularly limited, and for example, it may be prepared using a heated multi-screw extruder, and a dissolving can equipped with a stirring blade that generates a vertical circulation flow, as described above. A polyvinyl alcohol-based resin wet cake can also be added and steam blown into the can to dissolve it and prepare an aqueous solution having a desired concentration.

In addition to the polyvinyl alcohol resin (A), the polyvinyl alcohol resin aqueous solution contains a nonionic surfactant (B1) and a phosphate ester type anionic surfactant (B2) which is an anionic surfactant. is required. In addition, the incorporation of commonly used plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and trimethylolpropane is useful in terms of film-forming properties of polyvinyl alcohol-based films. preferable.

Examples of the nonionic surfactant (B1) include polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene dodecyl ether, Polyoxyethylene tetradecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene octadecyl ether, polyoxyethylene eicosyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, coconut oil reduced alcohol ethylene oxide adduct, beef tallow Polyoxyethylene alkyl ethers such as reduced alcohol ethylene oxide adducts, caproic acid mono- or diethanolamide, caprylic acid mono- or diethanolamide, capric acid mono- or diethanolamide, lauric acid mono- or diethanolamide, palmitic acid mono- or diethanolamide, stearin acid mono- or diethanolamide, oleic acid mono- or diethanolamide, coconut oil fatty acid mono- or diethanolamide, or higher fatty acid alkanolamide such as propanolamide, butanolamide, caproamide, caprylic acid amide instead of these ethanolamides, Capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, higher fatty acid amide such as oleic acid amide, hydroxyethyllaurylamine, polyoxyethylenehexylamine, polyoxyethyleneheptylamine, polyoxyethyleneoctylamine, polyoxy Ethylene nonylamine, polyoxyethylenedecylamine, polyoxyethylenedodecylamine, polyoxyethylenetetradecylamine, polyoxyethylenehexadecylamine, polyoxyethyleneoctadecylamine, polyoxyethyleneoleylamine, polyoxyethylenelaurylamine, polyoxyethylene Polyoxyethylene alkylamines such as eicosylamine, polyoxyethylene caproamide, polyoxyethylene caprylic acid amide, polyoxyethylene capric acid amide, polyoxyethylene lauric acid amide, polyoxyethylene palmitic acid amide, polyoxyethylene stearin Acid amide, polyoxyethylene higher fatty acid amide such as polyoxyethylene oleic acid amide, dimethyl lauryl amine oxides such as diamine oxide, dimethylstearyl oxide and dihydroxyethyllaurylamine oxide; and fluoroalkyl acids such as perfluorooctanoic acid. These may be used alone or in combination of two or more.

Among these, higher fatty acid alkanolamides are particularly preferred, lauric acid mono- or diethanolamide, palmitic acid mono- or diethanolamide, stearic acid mono- or diethanolamide, and oleic acid mono- or diethanolamide are particularly preferred. is lauric acid mono- or diethanolamide, more preferably lauric acid diethanolamide.

As the phosphate ester type anionic surfactant (B2), for example,
Alkyl phosphate salts such as octyl phosphate, lauryl phosphate, myristyl phosphate, coconut fatty acid phosphate salts;
Alkyl phosphate amine salts such as lauryl phosphate triethanolamine salt, oleyl phosphate diethanolamine salt;
Polyoxyethylene lauryl ether phosphate salt, polyoxyethylene isotridecyl ether phosphate salt, polyoxyethylene myristyl phosphate salt, polyoxyethylene cetyl ether phosphate, polyoxyethylene oleyl ether phosphate salt, dipolyoxyethylene oleyl ether phosphate salt , polyoxyethylene alkyl ether phosphate salts such as polyoxyethylene stearyl ether phosphate salts;
Polyoxyethylene alkylphenyl ether phosphate amine salts such as polyoxyethylene allyl phenyl ether phosphate amine salts;
Polyoxyethylene fatty acid amide ether phosphate salts such as polyoxyethylene laurylamide ether phosphate salts;
etc. These may be used alone or in combination of two or more.

Among these, polyoxyethylene alkyl ether phosphate salts are preferred because they provide excellent film transparency and are less likely to cause optical defects.

The number of carbon atoms in the alkyl group of the polyoxyethylene alkyl ether phosphate salt is preferably 8 or more, particularly preferably 10 or more, and still more preferably 11 or more.
If the number of carbon atoms is too small, optical defects tend to occur. The upper limit of the number of carbon atoms is usually 22 or less, preferably 20 or less.

The average repeating number of ethylene oxide units in the polyoxyethylene alkyl ether phosphate salt is preferably 3 or more, particularly preferably 5 or more, and still more preferably 7 or more.
If the average repeating number is too small, the transparency of the film tends to decrease and optical defects tend to occur. The upper limit of the average repetition number is usually 20 or less, preferably 18 or less.

The polyoxyethylene alkyl ether phosphate salt preferably has a surface tension of 37 mN/m or more, particularly preferably 40 mN/m, when measured in a 0.1% aqueous solution at 23°C and 50% RH. m or more, more preferably 42 mN/m or more.
If the surface tension is too small, the transparency of the film tends to be lowered. The upper limit of such surface tension is usually 65 mN/m or less, preferably 60 mN/m or less.

The content of the nonionic surfactant (B1) is preferably 0.001 to 1 part by weight, particularly preferably 0.003 to 0.9 part by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin (A). , more preferably 0.004 to 0.8 parts by weight. If the content is too high, the appearance and transparency of the film will tend to deteriorate, and if it is too low, the effect of suppressing die lines will tend to be difficult to achieve.

The content of the phosphate ester type anionic surfactant (B2) is preferably 0.005 to 1 part by weight, particularly preferably 0.007 to 0, per 100 parts by weight of the polyvinyl alcohol resin (A). 0.5 parts by weight, more preferably 0.01 to 0.2 parts by weight. If the content is too high, the transparency of the film tends to be lowered, and if it is too low, the peelability of the film tends to be lowered.

In addition, the content ratio ((B2)/(B1); weight ratio) of the nonionic surfactant (B1) and the phosphate ester type anionic surfactant (B2) is preferably 0.01≦(B2)/ (B1)≤20, particularly preferably 0.02≤(B2)/(B1)≤17, more preferably 0.03≤(B2)/(B1)≤15.
If the content ratio of the phosphate ester type anionic surfactant (B2) to the nonionic surfactant (B1) is too high, the transparency of the film tends to decrease, and if it is too low, optical defects tend to occur in the film. Tend.

The resin concentration of the polyvinyl alcohol resin aqueous solution thus obtained is preferably 15 to 60% by weight, particularly preferably 17 to 55% by weight, further preferably 20 to 50% by weight. If the resin concentration of such an aqueous solution is too low, the drying load tends to increase, resulting in a decrease in production capacity.

Next, the obtained polyvinyl alcohol-based resin aqueous solution is defoamed. Examples of defoaming methods include static defoaming and defoaming using a multi-screw extruder. The multi-screw extruder is not particularly limited as long as it is a multi-screw extruder with vents, but usually a twin-screw extruder with vents is used.

After defoaming, the polyvinyl alcohol resin aqueous solution is introduced into a T-shaped slit die by a fixed amount, discharged and cast onto a rotating cast drum, and formed into a film by a casting method.

The temperature of the polyvinyl alcohol resin aqueous solution at the exit of the T-shaped slit die is preferably 80 to 100°C, particularly preferably 85 to 98°C.
If the temperature of the polyvinyl alcohol resin aqueous solution is too low, it tends to flow poorly, and if it is too high, it tends to foam.

The viscosity of such a polyvinyl alcohol-based resin aqueous solution is preferably 50 to 200 Pa·s, particularly preferably 70 to 150 Pa·s, when discharged.
If the viscosity of such an aqueous solution is too low, it tends to flow poorly, and if it is too high, it tends to make drooling difficult.

The discharge speed of the polyvinyl alcohol resin aqueous 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 0.4 m/min. 6 to 3 m/min.
If the ejection speed is too slow, productivity tends to decrease, and if it is too fast, drooling tends to be difficult.

The diameter of such casting drums is preferably 2-5 m, particularly preferably 2.4-4.5 m, more preferably 2.8-4 m.
If the diameter is too small, the dry length tends to be insufficient and the speed tends to be difficult to achieve.

The width of such a casting drum is preferably 4 m or more, particularly preferably 4.5 m or more, more preferably 5 m or more, particularly preferably 5 to 6 m.
If the width of the casting drum is too small, productivity tends to decrease.

The rotation speed of such a casting drum is preferably 3-50 m/min, particularly preferably 4-40 m/min, and still more preferably 5-35 m/min.
If the rotation speed is too slow, the productivity tends to decrease, and if it is too fast, the drying tends to be insufficient.

The surface temperature of such a cast drum is preferably 40-99°C, particularly preferably 60-95°C.
If the surface temperature is too low, there is a tendency for poor drying, and if it is too high, there is a tendency for foaming.

Next, the step (II) will be explained. Step (II) is a step of heating and drying the formed film.

Drying of the film formed by the cast drum is carried out by alternately bringing the front and back surfaces of the film into contact with a plurality of hot rolls. The surface temperature of the heat roll is usually 40-150°C, preferably 50-130°C, and particularly preferably 60-110°C. If the surface temperature is too low, the drying tends to be poor.
The hot rolls are, for example, rolls with a diameter of 0.2 to 2 m, the surface of which is hard chromium plated or mirror-finished, and usually 2 to 30 rolls, preferably 10 to 25 rolls are used for drying. preferable.

In the present invention, the film is preferably heat-treated after drying with hot rolls. The heat treatment temperature is preferably 60 to 150°C, particularly preferably 70 to 140°C. If the heat treatment temperature is too low, the water resistance of the polyvinyl alcohol film tends to be insufficient and retardation fluctuation tends to occur. Examples of such a heat treatment method include a method of contacting with a hot roll, a method of using a floating dryer, and the like.

The film that has been dried and, if necessary, heat-treated becomes a product (polyvinyl alcohol-based film for producing a polarizing film of the present invention) through the step (III). Step (III) is a step of slitting both ends of the film and winding it on a roll.

An aqueous polyvinyl alcohol-based resin solution is prepared up to this point, and this aqueous solution is cast onto a rotating cast drum (drum-type roll) to form a film by a casting method and dried to produce a polyvinyl alcohol-based film for manufacturing a polarizing film. However, it is also possible to cast the polyvinyl alcohol resin aqueous solution on a resin film or a metal belt, form a film, and dry it.

The thickness of the polyvinyl alcohol film for producing a polarizing film is preferably 5 to 75 μm, particularly preferably 10 to 60 μm from the viewpoint of thinning the polarizing film, and more preferably from the viewpoint of durability. 15 to 60 μm.

In addition, the width of the polyvinyl alcohol film for producing a polarizing film is preferably 4 m or more, more preferably 4.5 m or more from the viewpoint of increasing the area, and particularly preferably from 4.5 to 6 m from the viewpoint of avoiding breakage. be.

In addition, the length of the polyvinyl alcohol film for polarizing film production is preferably 4 km or more, more preferably 4.5 km or more from the viewpoint of increasing the area, and particularly preferably 4.5 to 50 km from the viewpoint of transportation weight. is.

Next, the polarizing film of the present invention will be explained.

The polarizing film of the present invention is manufactured by unwinding the polyvinyl alcohol-based film for manufacturing a polarizing film from a roll, transporting it in a horizontal direction, and subjecting the film to swelling, dyeing, cross-linking with boric acid, stretching, washing, drying, and the like. .

The swelling step is performed before the dyeing step. By the swelling process, stains on the surface of the polyvinyl alcohol film can be cleaned, and the swelling of the polyvinyl alcohol film also has the effect of preventing uneven dyeing. In the swelling step, water is usually used as the treatment liquid. As long as the main component of the treatment liquid is water, the treatment liquid 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 drawing operation during processing as needed.

The dyeing process is carried out by contacting the film with a liquid containing iodine or a dichroic dye. Usually, an iodine-potassium iodide aqueous solution is used, and the suitable iodine concentration is 0.1 to 2 g/L and the potassium iodide concentration is 1 to 100 g/L. A dyeing time of about 30 to 500 seconds is practical. The temperature of the treatment bath is preferably 5-50°C. The aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the water solvent. Moreover, you may perform drawing operation during processing as needed.

The boric acid cross-linking 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 potassium iodide is preferably present in the liquid from the viewpoint of stabilizing the polarization performance. The treatment temperature is preferably about 30 to 70° C., and the treatment time is preferably about 0.1 to 20 minutes. If necessary, a stretching operation may be performed during the treatment.

In the stretching step, the film is uniaxially stretched 3 to 10 times, preferably 3.5 to 6 times. At this time, the film may be slightly stretched in the direction perpendicular to the stretching direction (stretching to the extent that shrinkage in the width direction is prevented or more). The temperature during stretching is preferably 30 to 170°C. Furthermore, the final draw ratio may be set within the above range, and the drawing operation may be performed not only in one step but also in any range of steps in the manufacturing process.

The washing step is performed by, for example, immersing the polyvinyl alcohol-based film in water or an aqueous solution of iodide such as potassium iodide to remove precipitates generated on the surface of the film. When an aqueous potassium iodide solution is used, the potassium iodide concentration 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. Note that washing with water and washing with an aqueous solution of potassium iodide may be appropriately combined.

The drying process may be performed in the air at 40-80° C. for 1-10 minutes.

Also, the degree of polarization 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 ensured.
In addition, the degree of polarization is generally measured in a state in which two polarizing films are superimposed so that the orientation direction is the same, and the light transmittance (H ₁₁ ) measured at the wavelength λ and the two polarized light It is calculated according to the following formula from the light transmittance (H ₁ ) measured at the wavelength λ in a state in which the films are superimposed so that the orientation directions are perpendicular to each other.
[(H ₁₁ −H ₁ )/(H ₁₁ +H ₁ )] ^1/2

Furthermore, the single transmittance of the polarizing film of the present invention is preferably 42% or more. If the single transmittance is too low, there is a tendency that the liquid crystal display cannot achieve high brightness.
Single transmittance is a value obtained by measuring the light transmittance of a single polarizing film using a spectrophotometer.

Thus, the polarizing film of the present invention is obtained, and the polarizing film of the present invention is suitable for producing a polarizing plate with little polarization unevenness.
The method for producing the polarizing plate of the present invention will be described below.

The polarizing film of the present invention is formed into a polarizing plate by laminating an optically isotropic resin film as a protective film on one side or both sides of the polarizing film via an adhesive. 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 you can get a sheet.

The lamination method is performed by a known method. For example, after uniformly applying a liquid adhesive composition to the polarizing film, the protective film, or both, the two are laminated together under pressure, and heated or activated. This is done by irradiating with energy rays.

In addition, for the purpose of thinning the polarizing film, a curable resin such as a urethane resin, an acrylic resin, or a urea resin is applied to one or both sides of the polarizing film instead of the protective film, and cured to form a polarizing plate. You can also

The polarizing film and polarizing plate obtained by using the polyvinyl alcohol-based film for producing a polarizing film of the present invention can be , videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as automobiles and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements (CRT, LCD, organic EL, electronic paper etc.), optical communication equipment, medical equipment, building materials, toys and the like.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In addition, "parts" and "%" in the examples are based on weight.
Each physical property was measured as follows.

<Measurement conditions>

(1) Peelability "Peelability test (X)"
The resulting polyvinyl alcohol-based resin aqueous solution was cast on a glass surface adjusted to a surface temperature of 92° C. using an applicator with a gap of 560 μm, dried for 6 minutes, and then separated from the glass plate at a speed of 25 mm / sec. An alcohol-based film (dry film; thickness 60 μm, width 150 mm) was peeled off. The peel force (g) at this time was measured with a digital force gauge ZTA-DPU (manufactured by IMADA).
(Evaluation criteria)
○ ... less than 250 g × ... 250 g or more "Peelability test (Y)"
During the formation of the polyvinyl alcohol-based film for polarizing film production, the peeling state of the film from the cast drum was visually observed, and the peelability was evaluated according to the following criteria.
(Evaluation criteria)
○: Peeled cleanly over the entire width ×: Part of the film adhered to the cast mold

(2) Transparency The polyvinyl alcohol-based film (dry film) obtained during the peelability test (X) was sprayed with an anticorrosive oil (manufactured by Kure Kogyo Co., Ltd., trade name "KURE 5-56") on both sides, The transparency of the film was evaluated by measuring the internal haze with a haze meter NDH-4000 (manufactured by Nippon Denshoku Co., Ltd.).
(Evaluation criteria)
○: 0.3 or less ×: greater than 0.3

(3) Appearance of polyvinyl alcohol film (die line evaluation)
Using the obtained polyvinyl alcohol-based film for polarizing film-producing film, the film was projected onto a white screen in a dark room, and shadows reflected on the screen were observed to confirm the presence or absence of die lines.
(Evaluation criteria)
○・・・Nothing visible and uniform ×・・・Die line can be confirmed

(4) Appearance of polarizing film [color unevenness]
A test piece with a length of 30 cm and a width of 30 cm is cut out from the center portion and both side ends of the obtained polarizing film in the width direction (10 cm inside from each end of both side ends of the polarizing film), and two pieces in a crossed Nicol state are cut. After sandwiching it at an angle of 45° between polarizing plates (single transmittance 43.5%, polarization degree 99.9%), using a light box with a surface illuminance of 14,000 lx, optically in transmission mode Color unevenness was observed and evaluated according to the following criteria.
(Evaluation criteria)
○: Color unevenness, no streaks △: Slight color unevenness or streaks ×: Color unevenness, streaks

The following surfactants were prepared.
・Nonionic surfactant (B1)
(B1-1) “lauric acid diethanolamide (1:1 type)”
- Phosphate ester type anionic surfactant (B2)
(B2-1) “Potassium polyoxyethylene alkyl ether phosphate”
: The surface tension of a 0.1% polyoxyethylene alkyl ether phosphate potassium aqueous solution in an environment of 23°C and 50% RH is 37 mN/m.
(B2-2) “Potassium polyoxyethylene alkyl ether phosphate”
: The surface tension of a 0.1% polyoxyethylene alkyl ether phosphate potassium aqueous solution under an environment of 23°C and 50% RH is 49 mN/m.
- Non-phosphate anionic surfactant (B2')
(B2'-1) Sodium polyoxyethylene alkyl ether sulfate

<Example 1>
(Preparation of polyvinyl alcohol-based resin aqueous solution)
100 parts of unmodified PVA resin having a weight average molecular weight of 142,000 and an average saponification degree of 99.8 mol% as polyvinyl alcohol resin (A), 12 parts of glycerin as plasticizer, and laurin as nonionic surfactant (B1) 0.03 parts of acid diethanolamide (B1-1), 0.02 parts of polyoxyethylene alkyl ether phosphate potassium (B2-1) as an anionic surfactant (B2), and 380 parts of water are mixed, C., pressurized dissolution, and a uniformly dissolved polyvinyl alcohol resin aqueous solution having a resin concentration of 20% was obtained by adjusting the concentration.
Using the polyvinyl alcohol-based resin aqueous solution obtained above, peelability evaluation (X) and transparency evaluation were performed. The evaluation results are shown in Table 1 below.

<Example 2>
An aqueous polyvinyl alcohol resin solution was obtained in the same manner as in Example 1, except that the phosphate ester type anionic surfactant (B2) was changed from (B2-1) to (B2-2). rice field. Using the obtained polyvinyl alcohol-based resin aqueous solution, peelability evaluation (X) and transparency evaluation were performed. The evaluation results are shown in Table 1 below.

<Comparative Example 1>
In Example 1, polyvinyl alcohol-based An aqueous resin solution was obtained. Using the obtained polyvinyl alcohol-based resin aqueous solution, peelability evaluation (X) and transparency evaluation were performed. The evaluation results are shown in Table 1 below.

<Comparative Example 2>
In Example 1, the phosphate ester surfactant (B2-1) was changed to a non-phosphate anionic surfactant (B2'-1), except that the amount was 0.06 parts. , in the same manner as in Example 1, to obtain an aqueous polyvinyl alcohol resin solution. Using the obtained polyvinyl alcohol-based resin aqueous solution, peelability evaluation (X) and transparency evaluation were performed. The evaluation results are shown in Table 1 below.

<Example 3>
(Production of polyvinyl alcohol film)
100 parts of unmodified PVA resin having a weight average molecular weight of 142,000 and an average saponification degree of 99.8 mol% as polyvinyl alcohol resin (A), 12 parts of glycerin as plasticizer, nonionic surfactant (B1) 0.03 parts of lauric acid diethanolamide as an anionic surfactant (B2), 0.02 parts of polyoxyethylene alkyl ether phosphate potassium (B2-1) as an anionic surfactant (B2), and 270 parts of water are mixed and heated to 130 ° C. Dissolution under pressure was performed by heating, and an aqueous polyvinyl alcohol resin solution having a resin concentration of 25% was obtained by adjusting the concentration.
The obtained polyvinyl alcohol resin aqueous solution was adjusted to a temperature of 95° C., and was discharged and cast onto a rotating cast drum (surface chromium plating) from the T-shaped slit die outlet at a discharge speed of 2.5 m/min. A film was formed. At this time, the peelability of the film from the cast drum was evaluated based on the peelability test (Y).
Next, the front and back surfaces of the film are dried while being alternately brought into contact with 15 hot rolls (temperature: 70 to 120°C). Then, both ends were slit and wound on a roll to obtain a polyvinyl alcohol film for manufacturing a polarizing film having a width of 5 m, a thickness of 60 μm and a length of 5000 m. Appearance of the obtained polyvinyl alcohol film for producing a polarizing film was evaluated. The evaluation results are shown in Table 2 below.

(Manufacture of polarizing film)
The polyvinyl alcohol-based film thus obtained is unrolled from a roll, conveyed horizontally using a conveying roll, and first immersed in a water tank at a water temperature of 30° C. to swell while being 1.7 times larger in the machine direction (MD direction). Stretched. Next, it is immersed in an aqueous solution of 0.5 g/L of iodine and 30 g/L of potassium iodide at 30° C. and stretched 1.6 times in the machine direction (MD direction) while being dyed, and then boric acid is 40 g/L. The film was immersed in an aqueous solution (50° C.) having a composition of L and 30 g/L of potassium iodide and uniaxially stretched 2.1 times in the machine direction (MD direction) while cross-linking with boric acid. Finally, the film was washed with an aqueous potassium iodide solution and dried at 50° C. for 2 minutes to obtain a polarizing film with a total draw ratio of 5.8. No breakage occurred during such manufacture. Also, the properties of the obtained polarizing film are shown in Table 2 below.

<Example 4>
Polyvinyl alcohol film for polarizing film production in the same manner as in Example 3 except that the phosphate ester type anionic surfactant (B2) was changed from (B2-1) to (B2-2) in Example 3. were manufactured and evaluated for releasability and film appearance. The evaluation results are shown in Table 2 below.
A polarizing film was produced in the same manner as in Example 3 using the obtained polyvinyl alcohol film. Its properties are shown in Table 2.

<Comparative Example 3>
A polarizing film was produced in the same manner as in Example 3, except that the phosphate ester surfactant (B2-1) was changed to a non-phosphate anionic surfactant (B2'-1) in Example 3. A polyvinyl alcohol-based film for use was produced, and the releasability and film appearance were evaluated. The evaluation results are shown in Table 2 below.
An attempt was made to produce a polarizing film from the obtained polyvinyl alcohol-based film in the same manner as in Example 3, but breakage occurred frequently during stretching. Some of the obtained polarizing films also had color unevenness. Its properties are shown in Table 2.

<Comparative Example 4>
In Example 3, the phosphate ester type surfactant (B2-1) was changed to a non-phosphate type anionic surfactant (B2'-1), except that the blend amount was 0.06 parts. A polyvinyl alcohol film for producing a polarizing film was produced in the same manner as in Example 3, and the releasability and film appearance were evaluated. The evaluation results are shown in Table 2 below.
A polarizing film was produced in the same manner as in Example 3 using the obtained polyvinyl alcohol film. Its properties are shown in Table 2.

<Comparative Example 5>
A polyvinyl alcohol film for producing a polarizing film was produced in the same manner as in Example 3, except that the lauric acid diethanolamide (B1-1) was not blended, and the peelability and film appearance were evaluated. The evaluation results are shown in Table 2 below.
A polarizing film was produced in the same manner as in Example 3 using the obtained polyvinyl alcohol film. Its properties are shown in Table 2.

The polyvinyl alcohol films of Examples 3 and 4 for polarizing film production have no die line, are excellent in transparency, and have excellent film appearance. , a polarizing film of high quality without color unevenness can be obtained. In addition, since the production efficiency of the raw film is improved, the cost merit is also excellent.

On the other hand, the polyvinyl alcohol-based film for producing the polarizing film of Comparative Example 3 had peeling failures, so that breakage occurred frequently during stretching, and some of the obtained polarizing films had color unevenness and were inferior in quality. Met.
The polyvinyl alcohol film of Comparative Example 4 for producing the polarizing film was inferior in transparency, so that the polarizing film obtained from the film had quality deterioration due to uneven light transmittance.
In addition, the polyvinyl alcohol film obtained in Comparative Example 5 had die lines, indicating that the polarizing film obtained from this film had streak defects due to the die lines and was inferior in quality.

The polarizing film and polarizing plate obtained by using the polyvinyl alcohol-based film for producing a polarizing film of the present invention can be , videos, cameras, photo albums, thermometers, audio, liquid crystal display devices such as automobiles and machinery instruments, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, display elements (CRT, LCD, organic EL, electronic paper etc.), optical communication equipment, medical equipment, building materials, toys and the like.

Claims (9)

A polyvinyl alcohol film for producing a polarizing film containing a polyvinyl alcohol resin (A), a nonionic surfactant (B1) and an anionic surfactant, wherein the anionic surfactant is a phosphate ester type anionic interface A polyvinyl alcohol-based film for producing a polarizing film, which is an activator (B2). 2. The polyvinyl alcohol film for producing a polarizing film according to claim 1, wherein the phosphate type anionic surfactant (B2) is a polyoxyethylene alkyl ether phosphate salt. 3. The polyvinyl alcohol film for producing a polarizing film according to claim 2, wherein the alkyl group of the polyoxyethylene alkyl ether phosphate salt has 8 or more carbon atoms. 4. The polyvinyl alcohol film according to claim 2, wherein the polyoxyethylene alkyl ether phosphate salt has an average repeating number of ethylene oxide units of 3 or more. The polyoxyethylene alkyl ether phosphate salt is a polyoxyethylene alkyl ether phosphate salt having a surface tension of 37 mN/m or more as measured in a 0.1% aqueous solution under an environment of 23°C and 50% RH. The polyvinyl alcohol-based film for producing a polarizing film according to any one of claims 2 to 4, characterized by: The content ratio (weight ratio) of the nonionic surfactant (B1) and the phosphate ester type anionic surfactant (B2) is 0.01 ≤ (B2) / (B1) ≤ 20. The polyvinyl alcohol-based film for producing a polarizing film according to any one of claims 1 to 5. The content of the phosphate ester type anionic surfactant (B2) with respect to 100 parts by weight of the polyvinyl alcohol resin (A) is 0.005 to 1 part by weight, according to any one of claims 1 to 6. Polyvinyl alcohol film for manufacturing polarizing films. A polarizing film obtained by using the polyvinyl alcohol film according to any one of claims 1 to 7. A polarizing plate comprising the polarizing film according to claim 8 and a protective film provided on at least one side of the polarizing film.