JP2002144355A - Method for manufacturing polyvinyl alcohol film and polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyvinyl alcohol film which has a uniform thickness suitable for a polarizing film and is excellent in surface smoothness and the polarizing film having uniform polarization performance made with the use of the polymer film. SOLUTION: When a film-making raw material 4 containing polyvinyl alcohol is discharged on a metal roll 6 into a film, the angle θ1 made by a plane A connecting the central axis 7 of the metal roll 6 and a die discharge part 3 and a plane B connecting the central axis 7 of the metal roll 6 and the apex 8 of the metal roll 6 is set up to be 20 or below, and the distance between the die discharge part 3 and the surface of the metal roll 6 is set up to be 10 mm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl alcohol-based polymer film which is useful as a raw material for producing a polarizing film and has excellent surface smoothness and thickness uniformity, and a vinyl alcohol-based polymer obtained thereby. The present invention relates to a polarizing film produced using a film.

[0002]

2. Description of the Related Art A polarizing plate having a function of transmitting and blocking light is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal having a function of switching light. The field of application of this LCD is from small devices such as calculators and watches in the early stages of development to laptop computers,
There is a demand for a polarizing plate that is widely used in word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, and the like, and has more uniform optical characteristics than ever before.

In general, a polarizing plate is a vinyl alcohol polymer film (hereinafter abbreviated as "PVA film", and a vinyl alcohol polymer as a raw material thereof may be abbreviated as "PVA"). Is uniaxially stretched and dyed, and a protective film such as a cellulose triacetate (TAC) film is bonded to both sides of a polarizing film produced by dyeing.

[0004]

In order to make the polarization performance of the polarizing plate uniform, there are many precautions such as uniform stretching of the PVA film and bonding evenly, but the most important point is PVA used as a material for polarizing films
The purpose is to make the surface of the film smooth and to make the thickness uniform. When the surface smoothness of the PVA film is poor or the thickness is uneven, it is difficult to make the polarizing performance of the obtained polarizing plate uniform.

Accordingly, an object of the present invention is to provide a PVA having a uniform thickness and excellent surface smoothness which is particularly suitable for a polarizing film.
It is an object of the present invention to provide a manufacturing method capable of obtaining a film and a polarizing film having a uniform polarizing performance produced by using a PVA film obtained by the method.

[0006]

Means for Solving the Problems In order to achieve the above object, the production method of the present invention is characterized in that a film-forming raw material containing a vinyl alcohol-based polymer is discharged from a die onto a metal roll to form a film. The angle between the plane connecting the central axis of the metal roll and the die discharge portion and the plane connecting the central axis of the metal roll and the vertex of the metal roll is set to 20 ° or less. Is set to 10 mm or less.

According to the above production method, a PVA film having excellent surface smoothness and good thickness uniformity can be obtained.

At this time, it is preferable that the die is installed such that the lip surface inside the die is inclined at an angle of 10 ° to 60 ° upstream from a plane connecting the central axis of the metal roll and the die discharge portion. According to this, a better PVA film can be obtained.

In the production, it is preferable that the film-forming material is moved in a horizontal direction or a lower direction immediately after the film-forming material is discharged from the die and comes into contact with the metal roll. This also provides a better PVA film.

The above production method is suitably used when producing a PVA film for a polarizing film. Moreover, by using this PVA film, a polarizing film having a uniform polarizing performance can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the P used in the manufacturing method of the present invention.
As an example of an apparatus for manufacturing a VA film, a main part of a melt extrusion film forming machine for melting and extruding wet PVA (which may contain an organic solvent; the same applies hereinafter) is shown. This film forming machine is configured to discharge a fixed amount of molten PVA from the discharge section 3 of the flat die 1.
The (film forming raw material) 4 is extruded onto a metal roll 6 rotating in the rotation direction 2 at a constant speed, and a part of the circumferential surface of the metal roll 6 is passed through to dry the PVA film. After this,
This PVA film passes through a not-shown floating dryer, a metal roll for drying, an inspection machine, and the like, and is wound on a winder.

According to the present invention, when a PVA film is melt-extruded and formed by using the above film forming machine, a plane A connecting the center axis 7 of the metal roll 6 and the die discharge section 3 is formed. The angle θ1 between the shaft 7 and the plane B connecting the apex 8 of the metal roll 6 is set to a range of 20 ° or less, more preferably 10 ° or less, and particularly preferably 5 ° or less. 3 is installed. If the die discharge unit 3 is installed at a position where the angle θ1 between the two planes A and B exceeds 20 °, the thickness uniformity of the obtained PVA film deteriorates.

Further, the distance D from the die discharge section 3 to the surface of the metal roll 6 is set to 10 mm or less, more preferably 5 mm or less, and further preferably 3 mm or less. At this time, it is important to keep the interval D uniform over the width direction of the flat die 1 (the direction perpendicular to the paper surface). If the distance D exceeds 10 mm, it is difficult for the film forming raw material 4 to uniformly contact the metal roll 6, and the uniformity of the thickness of the obtained PVA film is deteriorated.

Here, the distance D from the discharge section 3 to the surface of the metal roll 6 is the height from the point 9 where the plane A intersects the roll surface to the die discharge section 3 and is generally referred to as air. It is not the gap E (the linear distance from the die discharge unit 3 to the point 5 where the film forming raw material 4 comes into contact with the metal roll 6).

When the die 1 is installed,
The plane C formed by the lip surface inside the metal roll 6
It is preferable to incline a predetermined angle θ2 to the upstream side (rear side in the resin discharge direction) with respect to the plane A connecting the central axis 7 of the die discharge section 3 to the die discharge section 3. This angle θ2 is 10 ° to 60 °,
More preferably 15 ° to 50 °, most preferably 15 °
° to 40 °. Here, the plane C formed by the lip surface is inclined with respect to the plane A at an angle of less than 10 ° upstream, at an angle of more than 60 ° with respect to the upstream side, or as shown in FIG.
When the die 1 is installed by inclining the plane C formed by the lip surface to the downstream side (front side in the resin discharge direction) as shown by the two-dot chain line, the surface smoothness of the obtained PVA film may be deteriorated. is there.

Further, immediately after the film forming raw material 4 discharged from the die discharge unit 3 comes into contact with the metal roll 6, it is preferable to move the film forming raw material 4 in a horizontal direction or a lower direction. . When the film forming raw material 4 is moved upward, the thickness uniformity of the obtained PVA film may deteriorate.

FIG. 2 shows a main part of a melt extrusion film forming machine similar to FIG. 1 as another example of a PVA film production apparatus used in the production method of the present invention. In this embodiment, the plane C formed by the lip surface is located on the upstream side (the rear side in the resin discharge direction).
The die 1 is installed at an angle to the
Is arranged on a plane B connecting the central axis 7 of the metal roll 6 and the vertex 8, and an angle θ1 formed by the plane B and a plane A connecting the central axis 7 of the metal roll 6 and the die discharge unit 3 is set to 0 °. are doing.

The inner lip surface of the die 1 is preferably made of stainless steel whose surface is plated with nickel, chromium, chromium oxide, zinc, tin or the like. Further, the roughness (smoothness) of the metal surface or plating surface of the lip surface is preferably 1S or less, particularly preferably 0.3S or less. If it exceeds 1S, the thickness uniformity and surface smoothness of the obtained PVA film may deteriorate.

Here, the unit "S" of the surface roughness indicates the degree of unevenness of the surface, and the surface roughness is represented by the maximum height. The maximum height ( _Rmax ) is JIS
In accordance with B0601, the distance between two straight lines contacting the highest peak and the deepest valley parallel to the average line of a portion extracted by the reference length from the cross-sectional curve of the object is defined as a micrometer (μ).
m) It is expressed in units. The surface roughness 1S is as follows:
The maximum height is 1 μm.

The thickness of the PVA film is preferably 20 μm to 150 μm, more preferably 30 μm to 80 μm. When the thickness of the PVA film is less than 20 μm,
When manufacturing a polarizing film, it is easy to cut during uniaxial stretching, while when it exceeds 150 μm, stretching unevenness occurs during the uniaxial stretching, and stains and optical unevenness easily occur in the obtained polarizing film.

The metal roll 6 is heated by steam, a heating medium, hot water, an electric heater or the like. Further, a means such as blowing hot air or cold air onto the PVA film, or suctioning air or steam around the PVA film may be used.

It is preferable that the metal roll 6 has a diameter of 2.5 m or more and has a surface plated with nickel, chromium, chromium oxide, zinc, tin or the like. Further, the roughness of the metal surface or plating surface of the metal roll 6 is preferably 3S or less, and particularly preferably 0.5S or less. 3S roughness
When it exceeds, the thickness uniformity and surface smoothness of the obtained PVA film may deteriorate.

The PVA is produced by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester. Further, PVA is converted to an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof,
Modified PVA obtained by graft copolymerization of α-olefins having from 30 to 30 or modified by copolymerizing vinyl esters with unsaturated carboxylic acids or derivatives thereof, unsaturated sulfonic acids or derivatives thereof, α-olefins having 2 to 30 carbon atoms, etc. A modified PVA produced by saponifying a polyvinyl ester, a so-called polyvinyl acetal resin obtained by crosslinking a part of the hydroxyl group of an unmodified or modified PVA with an aldehyde, or the like is used.

Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and the like.

The comonomer used in the modified PVA is copolymerized mainly for the purpose of modification, and is used within a range not to impair the purpose of the present invention. Examples of such comonomers include olefins, acrylic acid and salts or esters thereof, methacrylic acid and salts or esters thereof, acrylamide derivatives, methacrylamide derivatives, N-vinylamides, vinyl ethers, nitriles, and halogens. Vinyl chlorides, allyl compounds,
Maleic acid and its salts or esters, itaconic acid and its salts or esters, vinylsilyl compounds, isopropenyl acetate and the like can be mentioned.

When using modified PVA, the amount of modification is 15
Preferably it is at most 5 mol%, more preferably at most 5 mol%.
As the comonomer, α-olefin is preferable,
Particularly, ethylene is preferred.

The degree of saponification of PVA is preferably at least 95 mol%, particularly preferably at least 99.5 mol%, from the viewpoint of the polarizing performance and durability of the obtained polarizing film. .99 mol% or less is preferable.

The degree of saponification indicates the ratio of units actually saponified to vinyl alcohol units among units that can be converted to vinyl alcohol units by saponification. In addition, the saponification degree of PVA was measured by the method described in JIS.

The degree of polymerization of PVA is preferably 1000 or more from the viewpoint of the polarizing performance and durability of the obtained polarizing film.
In particular, 2500 or more is most preferable. The upper limit of the PVA polymerization degree is preferably 8000 or less, more preferably 6000 or less.

The degree of polymerization (Po) of the PVA is determined according to JIS.
It is measured according to K 6726. That is, after PVA is re-saponified and purified, it can be obtained from the intrinsic viscosity [η] (unit: deciliter / g) measured in water at 30 ° C. by the following formula. Po = ([η] × 10 ³ /8.29)
^{(1 / 0.62)}

The hydrated PVA used for producing the PVA film includes dimethyl sulfoxide, if necessary.
Contains one or more solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and diglycerin It may be. Further, a plasticizer, a surfactant, a dichroic dye and the like may be contained.

In producing a PVA film, it is preferable to add a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. One or more of these are used. be able to. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.

The amount of polyhydric alcohol to be added is PVA
The amount is preferably 1 to 30 parts by weight, particularly preferably 5 to 20 parts by weight, per 100 parts by weight. If the amount is less than 1 part by weight, dyeability and stretchability may decrease,
On the other hand, if it exceeds 30 parts by weight, the PVA film becomes too flexible, and the handleability may decrease.

When producing a PVA film,
It is preferable to add a surfactant. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type such as dodecylbenzenesulfonate are preferable. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene lauryl amino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether Nonionic surfactants such as allyl phenyl ether type are preferred. One or a combination of two or more of these surfactants can be used.

The amount of surfactant added is PVA 10
0.01 parts by weight to 1 part by weight, preferably 0.05 parts by weight to 0.3 parts by weight, based on 0 parts by weight.
When the amount is less than 0.01 part by weight, the effect of improving the stretchability and the dyeability is hardly exhibited, and when the amount is more than 1 part by weight, it is eluted on the surface of the PVA film to cause blocking and the handleability may be reduced.

The volatile matter of the film forming raw material (molten PVA) 4 is 4
0% to 90% by weight is preferred, especially 45% by weight.
~ 85% by weight is most preferred. 90% by weight volatiles
When the ratio is more than 40%, the obtained polarizing film tends to cause color unevenness.
A film may be difficult to obtain.

When producing a PVA film, the film forming raw material 4
The temperature of the metal roll 6 from which is discharged is 50 to 110 ° C.
Is preferably 60 to 105 ° C, more preferably 70 to 100 ° C. If the temperature of the metal roll 6 is lower than 50 ° C., drying of the discharged film forming raw material 4 may be uneven, and if the temperature is higher than 110 ° C.,
Since molten PVA may foam, it may be difficult to obtain a PVA film having excellent thickness uniformity.

In order to produce a polarizing film from the PVA film of the present invention, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and if necessary, heat-treated. The order of each step is not particularly limited, and two steps such as dyeing and uniaxial stretching may be performed simultaneously. Further, each step may be repeated a plurality of times.

Dyeing can be carried out before, during or after uniaxial stretching. Dyes used for dyeing include iodine-potassium iodide; direct black 1
7, 19, 154; Direct Brown 44, 10
6, 195, 210, 223; Direct Red 2,
23, 28, 31, 37, 39, 79, 81, 240,
242, 247; Direct Blue 1, 15, 22,
78, 90, 98, 151, 168, 202, 236,
249, 270; Direct Violet 9, 12,
Dichroic dyes such as 51, 98; direct green 1, 85; direct yellow 8, 12, 44, 86, 87; direct orange 26, 39, 106, 107 and the like are used in one kind or in a mixture of two or more kinds. it can.
Usually, the dyeing is generally carried out by immersing the PVA film in a solution containing the dye. However, the processing conditions such as coating on the PVA film or mixing with the PVA film to form a film are used. The processing method is not particularly limited.

The uniaxial stretching can be performed by a wet stretching method or a dry heat stretching method, and can be performed in hot water (which may be in a solution containing the dye or in a fixing bath described later) or in air using a PVA film after water absorption. It can be carried out. The stretching temperature is not particularly limited, but is preferably 30 ° C. to 90 ° C. when the PVA film is stretched in warm water (wet stretching), and 50 ° C. to 180 ° C. when the film is stretched by dry heat. The stretching ratio of uniaxial stretching (in the case of multi-stage uniaxial stretching, the total stretching ratio) is 4 from the viewpoint of the polarizing performance of the obtained polarizing film.
It is preferably at least 5 times, particularly preferably at least 5 times. The upper limit of the stretching ratio is not particularly limited, but is preferably 8 times or less since uniform stretching is easily obtained. The thickness of the stretched film is preferably 3 μm to 75 μm, more preferably 5 μm to 50 μm.

In order to strengthen the adsorption of the dye to the stretched film, a fixing treatment is often performed. Usually, boric acid and / or a boron compound is added to the treatment bath used for the fixing treatment. Further, an iodine compound may be added to the treatment bath as needed.

The drying treatment (heat treatment) of the stretched film is preferably performed at 30 ° C. to 150 ° C., and 50 ° C. to 1 ° C.
More preferably, it is carried out at 50 ° C.

The polarizing film obtained as described above is usually used as a polarizing plate by laminating an optically transparent protective film having mechanical strength on both sides or one side thereof. As the protective film, cellulose triacetate (T
AC) film, cellulose acetate / butyrate (CAB) film, acrylic film, polycarbonate film, polyolefin film, polyester film and the like are used. Examples of the adhesive for bonding include a PVA-based adhesive and a urethane-based adhesive, and a PVA-based adhesive is preferable.

[0044]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 A melt extrusion film forming machine described in FIG. 2 was used. Example 1
Then, the discharge part 3 of the die 1 is disposed directly above the vertex 8 of the metal roll 6, that is, the plane A connecting the central axis 7 of the metal roll 6 and the die discharge part 3, and the central axis 7 of the metal roll 6 The angle θ1 between the plane B connecting the apex 9 of the metal roll 6 and the plane B is 0.
° (A, B = 0 °). The plane C formed by the lip surface inside the die 1 and the metal roll 6
Angle θ between the center axis 7 and the plane A connecting the die discharge unit 3
The entirety of the die 1 is inclined to the upstream side (rear side in the resin discharge direction) so that 2 becomes 20 °. Further, the distance D between the die discharge unit 3 and the surface of the metal roll 6 is set to 3 mm. At this time, the surface roughness of the lip surface inside the die 1 is set to 0.3S. Then, 100 parts by weight of PVA having a degree of saponification of 99.9 mol% and a degree of polymerization of 1750, 12 parts by weight of glycerin, and 130 parts by weight of water were melt-kneaded by an extruder, and heated to 90 ° C. with a surface roughness of 0.3 S. It was extruded into a metal roll 6 having a diameter of 2.5 m. Thereafter, the film was dried with hot air at 90 ° C., and then alternately dried on both sides alternately with 15 heated metal rolls to obtain a 75 μm thick PVA film for a polarizing film. This PVA film has a smooth surface, and the thickness unevenness in the width direction of the film is 1.5 μm.
m and good.

The PVA film was pre-swelled, dyed, uniaxially stretched, fixed, dried, and heat treated in this order to produce a polarizing film. That is, the PVA film is
It was immersed in water at 0 ° C. for 5 minutes for pre-swelling, and immersed in an aqueous solution of 35 ° C. having an iodine concentration of 0.4 g / l and a potassium iodide concentration of 40 g / l for 3 minutes. continue,
The film is uniaxially stretched 5.5 times in an aqueous solution of boric acid concentration of 4% at 40 ° C., and is dissolved in a 30 ° C. aqueous solution of potassium iodide concentration of 40 g / l, boric acid concentration of 40 g / l and zinc chloride concentration of 10 g / l. The fixing process was performed by immersion for 5 minutes. Thereafter, the stretched film is taken out, and at a constant length, at 40 ° C.
And then heat-treated at 100 ° C. for 5 minutes.

The thickness of the obtained polarizing film was 22 μm, and there was no color spot. Then, as a result of observing the transmitted light by interposing a 50 cm square of the obtained polarizing film at an angle of 45 ° between two polarizing plates in a crossed Nicols state, no abnormality was found.

Example 2 The melt extrusion film forming machine shown in FIG. 1 was used. Example 2
Then, the angle θ1 between the plane A connecting the central axis 7 of the metal roll 6 and the die discharge section 3 and the plane B connecting the central axis 7 of the metal roll 6 and the vertex 8 of the metal roll 6 is set to 5 °. ing. Also, the die 1 has a lip surface inside the die 1 and a plane A connecting the center axis 7 of the metal roll 6 and the die discharge portion 3 with the plane C formed by the die 1 so that the inclination angle θ2 is 30 °. The whole is tilted upstream. Further, the distance D between the die discharge unit 3 and the surface of the metal roll 6 is set to 2 mm. At this time, the surface roughness of the lip surface inside the die 1 is set to 0.3S. And a degree of saponification of 9
100 parts by weight of PVA having a polymerization degree of 4,000 at 9.9 mol%, 10 parts by weight of glycerin and 110 parts by weight of water were melt-kneaded with an extruder, and heated to 90 ° C. having a surface roughness of 0.3 S and a diameter of 3.5 m. It was extruded on a metal roll 6. After this 90
It dried with the hot air of ° C, and subsequently, it dried with the pin tenter type floating dryer, and obtained the 75-micrometer-thick PVA film for polarizing films. The surface of this PVA film was smooth, and the thickness unevenness in the width direction of the film was as good as 1.5 μm.

The PVA film was pre-swelled, dyed, uniaxially stretched, fixed, dried, and heat-treated in this order to produce a polarizing film. That is, the PVA film is
It was immersed in water at 0 ° C. for 5 minutes for pre-swelling, and immersed in an aqueous solution of 35 ° C. having an iodine concentration of 0.4 g / l and a potassium iodide concentration of 40 g / l for 3 minutes. continue,
The film is uniaxially stretched 5.6 times in an aqueous solution of boric acid at a concentration of 4% at 40 ° C., and placed in a 30 ° C. aqueous solution of a potassium iodide concentration of 40 g / l, a boric acid concentration of 40 g / l, and a zinc chloride concentration of 10 g / l. The fixing process was performed by immersion for 5 minutes. Thereafter, the stretched film is taken out, and at a constant length, at 40 ° C.
And then heat-treated at 100 ° C. for 5 minutes.

The thickness of the obtained polarizing film was 22 μm, and there was no color spot. Then, as a result of observing the transmitted light by interposing a 50 cm square of the obtained polarizing film at an angle of 45 ° between two polarizing plates in a crossed Nicols state, no abnormality was found.

Embodiment 3 In Embodiment 1, the plane C formed by the lip surface inside the die 1, the center axis 7 of the metal roll 6, and the die discharge portion 3
In the same manner as in Example 1 except that the inclination angle θ2 with respect to the plane A connecting
A VA film was obtained. On the surface of this PVA film,
Slight streaks were observed in the film length direction.

Then, a polarizing film was obtained in the same manner as in Example 1. When the transmitted light was observed by sandwiching a 50 cm square of this polarizing film at an angle of 45 ° between two polarizing plates in a crossed Nicols state, a slight streak-like spot was slightly observed, but it could be used for LCD applications. Level.

COMPARATIVE EXAMPLE 1 In Example 1, the plane B connecting the central axis 7 of the metal roll 6 and the vertex 8 of the metal roll 6 and the plane A connecting the central axis 7 of the metal roll 6 and the die discharge unit 3 Make the angle θ1 9
Except that it was set to 0 °, the thickness was 7
A 5 μm PVA film for a polarizing film was obtained. This P
In the VA film, streaks are seen in the film length direction,
The thickness unevenness in the width direction of the film was as large as 8 μm.

Then, a polarizing film was obtained in the same manner as in Example 1. When the transmitted light is observed by sandwiching a 50 cm square of this polarizing film at an angle of 45 ° between two polarizing plates in a crossed Nicols state, streak-like spots and irregular spots are observed and can be used for LCD applications. Did not.

Comparative Example 2 A PVA film for a polarizing film having a thickness of 75 μm was prepared in the same manner as in Example 2 except that the distance D between the die discharge portion 3 and the surface of the metal roll 6 was changed to 20 mm. Obtained. In this PVA film, streaks were observed in the film length direction, and the thickness unevenness in the width direction of the film was as large as 8 μm.

Then, a polarizing film was obtained in the same manner as in Example 2. When the transmitted light is observed by sandwiching a 50 cm square of this polarizing film at an angle of 45 ° between two polarizing plates in a crossed Nicols state, streak-like spots and irregular spots are observed and can be used for LCD applications. Did not.

[0056]

As described above, according to the present invention, it is possible to obtain a PVA film having a uniform thickness and excellent surface smoothness suitable for a polarizing film. Also, this P
A polarizing film having excellent polarizing performance can be obtained using a VA film.

[Brief description of the drawings]

FIG. 1 is a front view showing a main part of an example of a roll film forming machine used in a method for producing a PVA film according to the present invention.

FIG. 2 is a front view showing a main part of another example of the roll film forming machine used in the method for producing a PVA film according to the present invention.

[Explanation of symbols]

1 ... die, 3 ... die discharge part, 4 ... film forming raw material (molten PV
A), 6: metal roll, 7: central axis of metal roll, 8:
The top of the metal roll, 9: the point at which the plane connecting the center axis of the metal roll and the die discharge section intersects the surface of the metal roll, A: the plane connecting the center axis of the metal roll and the die discharge section, B: the center of the metal roll A plane connecting the axis and the vertex of the metal roll, C: a plane formed by the lip surface inside the die, D: an interval from the die discharge portion to the metal roll surface, θ1: a plane connecting the central axis of the metal roll and the die discharge portion and the metal The angle between the center axis of the roll and the plane connecting the vertices of the metal roll.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 29:04 C08L 29:04 F term (Reference) 2H049 BA02 BB43 BC09 4F071 AA29 AF35 BB04 BB06 BC01 BC08 BC17 4F205 AA19 AC05 AG01 AH73 AR07 AR12 GA07 GB02 GC02 GE07 GF01 GF23 GF24 GN29

Claims (5)

[Claims] When a film forming raw material containing a vinyl alcohol-based polymer is discharged from a die onto a metal roll to form a film, a plane connecting a central axis of the metal roll and a die discharge portion, and a center of the metal roll. A vinyl alcohol-based material, wherein the angle between the axis and the plane connecting the vertices of the metal roll is set to 20 ° or less, and the distance between the die discharge portion and the surface of the metal roll is set to 10 mm or less. A method for producing a polymer film. 2. The vinyl according to claim 1, wherein the die is installed such that the lip surface inside the die is inclined at an angle of 10 ° to 60 ° upstream from a plane connecting the central axis of the metal roll and the die discharge portion. A method for producing an alcohol-based polymer film. 3. The film-forming material according to claim 1, wherein the film-forming material is discharged from a die and comes into contact with a metal roll immediately after the film-forming material is contacted with the metal roll. Method for producing a vinyl alcohol polymer film to be transferred to 4. The method for producing a vinyl alcohol-based polymer film according to claim 1, wherein the vinyl alcohol-based polymer film is for a polarizing film. 5. A polarizing film produced using the vinyl alcohol-based polymer film obtained by the production method according to claim 4.