JP2001323077A - Polyvinyl alcohol-based film and polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wide polyvinyl alcohol-based film suitable for polarizing films used in wide-screen liquid crystal displays and having uniform optical performance even with large area. SOLUTION: This polyvinyl alcohol-based film is obtained by a drum film formation method so as to set the thickness unevenness in the transverse direction of the film to be <=12%, film thickness 20-150 μm and film width >=2 m.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide polyvinyl alcohol-based film having uniform optical performance even in a large area and suitable for a polarizing film used for a large-screen liquid crystal display.

[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 has expanded from small devices such as calculators and watches in the early days to laptop computers, word processors, liquid crystal color projectors, in-car navigation systems, liquid crystal televisions, etc., and is expected to be used on large screens. Therefore, there has been a demand for a polarizing plate that is more excellent in uniformity of optical performance such as brightness and sharpness on a large screen than conventional products.

In general, a polarizing plate is formed by uniaxially stretching a polyvinyl alcohol-based film (hereinafter, a polyvinyl alcohol-based polymer may be abbreviated as “PVA film” and a polyvinyl alcohol (based polymer) film may be abbreviated as “PVA film”). And a polarizing film manufactured by dyeing, a support plate such as a cellulose triacetate (TAC) film is attached to both surfaces. There are many precautions such as using a PVA film with a uniform thickness, dyeing a dichroic dye uniformly, and bonding without unevenness for the uniformity of polarization performance. An important factor is how uniform it is.

[0004] As a method for producing a PVA film, for example, a film-forming material (which may contain an organic solvent or the like) containing PVA in a solution or molten state is discharged from a die onto a heated belt or drum and dried. A method of forming a film by performing the method is industrially used.

The method of forming a film by discharging a solution or a molten film-forming material from a die onto a belt and drying the film has a problem in obtaining a uniform film over a width of 2 m or more. Since the application is optical, the required quality of the belt is also technically wide because the belt seam must be uniform and the surface must be 2 m or more and have a specular gloss over several tens m in length. In some cases, there is a problem in manufacturing a long belt. In some cases, traces of belt dirt are transferred to a film-formed film due to resin adhesion during film formation, and a problem occurs in that optical uniformity is lost due to a disorder in a film refractive index of a stained portion.

On the other hand, in drum film formation, a seamless and uniform drum can be industrially produced, but it is not sufficient that the drum is wide, has good thickness unevenness, and has uniform retardation. Therefore, a wide polarizing film and a polyvinyl alcohol-based film, which is a material for the polarizing film, which is wide and excellent in polarization performance and excellent in optical performance uniformity in a large area, have been desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wide P-type film having uniform optical performance even in a large area, suitable for a polarizing film used for a large-screen liquid crystal display.
It is to provide a VA film. The present inventors have conducted intensive studies on this problem and found the present invention.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a film having a thickness variation of 12 mm in the TD direction obtained by drum film formation.
% Or less, and the average thickness of the film is 20 to 150 μm
And a width of the film is 2 m or more, which is achieved by a polyvinyl alcohol-based film.

At this time, when the retardation of the full width in the TD direction of the film was measured, the distance in the TD direction was 1 m.
A polyvinyl alcohol-based film in which the difference (ΔRe) between the maximum value and the minimum value of the retardation at any of the following points is 50 nm or less is preferable.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a polyvinyl alcohol-based polymer constituting a PVA-based film, a vinyl ester-based polymer obtained by polymerizing a vinyl ester-based monomer is saponified, and the vinyl ester unit is converted to a vinyl alcohol unit. Can be used. Examples of the vinyl ester monomers include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Among these, it is preferable to use vinyl acetate.

When copolymerizing a vinyl ester-based monomer, if necessary, a copolymerizable monomer may be used within a range not impairing the effects of the present invention (preferably 15 mol% or less, more preferably 5 mol% or less. ).

Examples of such a monomer copolymerizable with the vinyl ester monomer include olefins having 3 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; acrylic acid and its salts; methyl acrylate , Ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, acrylic acid 2
Acrylates such as ethylhexyl, dodecyl acrylate and octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate;
Methacrylates such as n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate And acrylamide,
Acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and salts thereof, acrylamidopropyldimethylamine and salts thereof, N-methylolacrylamide and derivatives thereof; methacryl Amide, N-
Methacrylamide derivatives such as methyl methacrylamide, N-ethyl methacrylamide, methacrylamidopropanesulfonic acid and salts thereof, methacrylamidopropyldimethylamine and salts thereof, N-methylol methacrylamide and derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n- Vinyl ethers such as propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride, and fluorine. Vinyl halides such as vinyl halide and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; Salts or esters thereof; itaconic acid and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; N-vinylamides such as isopropenyl acetate, N-vinylformamide, N-vinylacetamide and N-vinylpyrrolidone; be able to.

The average degree of polymerization of the PVA constituting the PVA film is preferably at least 500 from the viewpoint of film strength, more preferably at least 1,000 from the viewpoint of polarization performance,
It is more preferably at least 000, particularly preferably at least 3,500. On the other hand, the upper limit of the degree of polymerization of PVA is preferably 10,000 or less from the viewpoint of film forming properties. The degree of polymerization (P) of PVA is measured according to JIS K 6726. That is, after PVA is re-saponified and purified, 30
Intrinsic viscosity [η] (unit: dL / g, measured in water at
L is obtained from the following formula using the following formula.

P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

The degree of saponification of the PVA constituting the PVA film is preferably 90 mol% or more, more preferably 95 mol% or more, and more preferably 98 mol%, from the viewpoint of the durability of the polarizing film.
The above is more preferred. On the other hand, from the viewpoint of the dyeability of the film, the content is preferably 99.99 mol% or less. The degree of saponification in the present specification indicates the ratio of units actually saponified to vinyl alcohol units among units that can be converted into vinyl alcohol units by saponification.
In addition, the saponification degree of PVA was measured by the method described in JIS.

In producing the 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, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. One or more of these may be used. it can. Among them, ethylene glycol or glycerin is preferably used from the viewpoint of the effect of improving stretchability. The addition amount of the polyhydric alcohol is preferably 1 to 30 parts by weight, more preferably 3 to 25 parts by weight, and particularly preferably 5 to 20 parts by weight based on 100 parts by weight of PVA. If the amount is less than 1 part by weight, the dyeability and stretchability may decrease, and
When the amount is more than the weight part, the film becomes too flexible, and the handleability may be reduced.

It is preferable to add a surfactant when producing a PVA film. 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 anionic surfactant such as dodecylbenzenesulfonate are preferable.

Examples of the nonionic surfactant include, for example,
Alkyl ether type such as polyoxyethylene oleyl ether; alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether; alkyl ester type such as polyoxyethylene laurate; alkyl amine type such as polyoxyethylene lauryl amino ether; polyoxyethylene Nonionic interfaces such as alkyl amides such as lauric amide, polypropylene glycol ethers such as polyoxyethylene polyoxypropylene ether, alkanolamides such as diethanolamide oleate, and allyl phenyl ethers such as polyoxyalkylene allyl phenyl ether Activators are preferred. One or a combination of two or more of these surfactants can be used.

The amount of the surfactant added is PVA 10
0.01 to 1 part by weight is preferable for 0 part by weight, and 0.1 to 1 part by weight is preferable.
02-0.5 part by weight is more preferable, and 0.05-0.5 part by weight.
3 parts by weight are particularly preferred. If the amount is less than 0.01 part by weight, the effect of improving the stretchability and the dyeing property is difficult to appear, and if the amount is more than 1 part by weight, it is eluted on the film surface and causes blocking, which may lower the handleability.

The volatile matter content of the PVA-containing film-forming raw material used for producing the PVA film is preferably from 50 to 90% by weight, more preferably from 55 to 80% by weight.
If the volatile content is less than 50% by weight, the viscosity becomes high, so that film formation becomes difficult. On the other hand, when the volatile content is greater than 90% by weight, the viscosity is low, and the uniformity of the thickness of the film is likely to be impaired.

As the metal material constituting the drum used in the present invention, for example, nickel, chromium, copper, stainless steel, etc. are preferable, but a metal material which does not easily corrode the drum surface and can obtain a mirror surface glossy drum surface is preferable. . In order to enhance the durability of the drum, the surface of the drum may be plated with a nickel layer, a chromium layer, or a nickel / chromium alloy layer in a single layer or in combination of two or more layers.

The term "drum film forming" as used in the present invention means that a solution or a molten film forming raw material (organic solvent, etc.) is contained on a rotating metal drum (roll) (preferably having a diameter of 1 to 5 m). Supply), drum (roll)
This is a method in which a film is formed by evaporating and drying a volatile component such as water or an organic solvent contained above. Subsequently, the film is peeled off by a peeling roll, and further dried or conditioned to obtain a suitable film.

The average thickness of the PVA film is from 20 to 150.
μm, preferably 40 to 120 μm. When the average thickness is less than 20 μm, stretching breakage occurs in uniaxial stretching when producing a polarizing film. In addition, the average thickness is 150
When the thickness exceeds μm, stretching unevenness occurs in uniaxial stretching when producing a polarizing film. Thickness irregularity referred to in the present invention is defined as a percentage expressed by multiplying the value obtained by dividing the difference between the thickest portion and the thinnest portion in the TD direction (transverse direction: see JIS K6900) of the film by the average thickness and multiplying by 100 to obtain a percentage. It is 12% or less, preferably 8% or less, more preferably 5% or less, particularly preferably 3% or less. When the thickness unevenness exceeds 12%, the optical unevenness of the obtained polarizing film becomes large.

The width of the polyvinyl alcohol film of the present invention is at least 2 m, preferably at least 2.3 m, more preferably at least 2.6 m, even more preferably at least 3 m. It is particularly preferred that it is 5 m or more. When the width is smaller than 2 m, the entire film including the vicinity of the center of the film is easily affected by the bowing phenomenon due to the drum film formation, and a polarizing film having uniform optical performance may not be obtained. If the width exceeds 6m,
Since it may be difficult to stretch uniformly by uniaxial stretching when producing a polarizing film, the film width is preferably 6 m or less, more preferably 5 m or less, and still more preferably 4 m or less.

The retardation of the film is given by the following formula (1)
Indicated by Here, d is the film thickness (nm), Re
Is retardation (nm), and Δn is birefringence.

Re = d × Δn (1)

When the retardation of the full width in the TD direction of the film is measured, the difference (ΔRe) between the maximum value and the minimum value of the retardation at an arbitrary point whose distance in the TD direction is 1 m or less is 50 nm or less. Preferably, 30n
m is more preferable. When ΔRe exceeds 50 nm, when the polarizing film is used, the display may be distorted due to shading of the luminous intensity or occurrence of color spots.

In order to produce a polarizing film from the polyvinyl alcohol film of the present invention, for example, a PVA film may be dyed, uniaxially stretched, fixed and 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, simultaneously with, or after uniaxial stretching. However, PVA tends to increase the crystallinity by uniaxial stretching, and dyeing properties may be reduced. It is preferred to dye in any preceding step or uniaxial stretching step. As a dye used for dyeing, iodine-potassium iodide or Direct bla
ck 17, 19, 154; Direct brown 44, 106, 195, 21
0, 223; Direct red2, 23, 28, 31, 37, 39, 79, 8
1, 240, 242, 247; Direct blue 1, 15, 22, 78, 9
0, 98, 151, 168, 202, 236, 249, 270; Direct
violet 9, 12, 51, 98; Direct green 1, 85; Direct
yellow 8, 12, 44, 86, 87; Direct orange 26, 39, 1
Dichroic dyes such as 06 and 107 can be used. Dyeing can be usually performed by immersing the PVA film in a solution containing the dye, but the processing conditions and processing method are 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 film after absorbing water. . From the point of uniformity of optical performance,
It is most preferable that the stretching apparatus uses a roll stretching method using a speed difference between rolls. However, even if the polyvinyl alcohol film having a width of 2 m or more of the present invention is used in another stretching method, the uniformity of optical performance can be improved. The effect is obtained. The stretching ratio is preferably at least 4 times, particularly preferably at least 5 times. If the stretching ratio is smaller than 4 times, it is difficult to obtain practically sufficient polarization performance and durability performance. Stretching may be performed in one step up to a target stretching magnification, but performing multi-step stretching in two or more steps further reduces the neck-in and is effective in uniformity of optical performance. The stretching temperature is not particularly limited, but when stretching the film in warm water (wet stretching), the stretching temperature is 30 to 90 ° C.
However, in the case of dry drawing, the temperature is preferably from 50 to 180 ° C. The thickness of the stretched film is preferably from 3 to 75 μm, more preferably from 10 to 50 μm.

For the purpose of strengthening the adsorption of the dye to the polyvinyl alcohol film, a fixing treatment is performed.
Usually, boric acid and a boron compound are 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 process (heat treatment) of the polarizing film is 30
It is preferably performed at a temperature of from 150 to 150 ° C, more preferably from 50 to 150 ° C.

The polarizing film of the present invention obtained as described above is usually used as a polarizing plate by laminating a protective film having optical transparency and mechanical strength on both sides or one side thereof. . As the protective film, a cellulose acetate film, an acrylic film, a polyester film or the like is usually used.

[0034]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. The calculation of thickness unevenness and the measurement of the difference in retardation per unit meter in the TD direction described in the present example and comparative example were performed as follows.

Calculation of thickness unevenness The thickness unevenness is measured by measuring the thickness profile of the film in the TD direction at five locations at 1 m intervals in the MD direction using a film thick nest tester KG601A manufactured by Anritsu Corporation. The value obtained by dividing the difference between the portions by the average thickness was multiplied by 100 to obtain a percentage.

Measurement of difference between maximum value and minimum value of retardation (ΔRe) Automatic birefringence meter KOBRA21S manufactured by Oji Scientific Instruments
Using DH, the retardation of the entire width was measured in the TD direction of the film. The difference between the maximum value and the minimum value of the retardation at an arbitrary point whose distance in the TD direction was 1 m or less was determined as ΔRe.

Example 1 PVA 10 having a saponification degree of 99.9 mol% and a polymerization degree of 2400
A film-forming material having a volatile content of 70% by weight, consisting of 0 parts by weight, 10 parts by weight of glycerin, 0.1 part by weight of lauric acid diethanolamide and water, was subjected to chromium plating at 90 ° C. to a diameter of 3.2.
m of a metal drum to form a film. Further, the film forming raw material on the surface of the metal drum was dried with hot air at 95 ° C. to obtain a PVA film having a width of 3.4 m. When the thickness of the obtained film was measured, the average thickness was 74 μm, and the thickest portion was 7 μm.
The thickness was 5.1 μm, the thinnest portion was 73.0 μm, and the thickness unevenness was 2.83%. ΔRe was 28 nm.
The PVA film was raised in front of a board which was whitened in a dark room, and photographed with a projector. No optical spots or defects were found.

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 kept at 30 ° C.
Pre-swell by immersion in water for 3 minutes, iodine concentration 0.4
It was immersed in an aqueous solution at 40 ° C. for 4 minutes at 40 g / L and potassium iodide concentration of 40 g / L for 4 minutes. Subsequently, in a 50% aqueous solution of 4% boric acid, the film was subjected to roll-type uniaxial stretching 5.0 times. Furthermore, it was immersed in an aqueous solution of potassium iodide 40 g / L and boric acid 40 g / L at 30 ° C. for 5 minutes to perform a fixing treatment.
The film was taken out, dried with hot air at 40 ° C. under a constant length, and further heat-treated at 100 ° C. for 5 minutes. The thickness of the obtained polarizing film is 28 μm, no staining spots are observed on the polarizing film, and the obtained polarizing film is sandwiched between two polarizing plates in a crossed Nicols state at an angle of 45 °.
Even when the transmitted light was visually observed, no optical spots were observed and the transmitted light was good.

Example 2 PVA10 having a degree of saponification of 99.9 mol% and a degree of polymerization of 4000
0 parts by weight, 12 parts by weight of glycerin, 0.1 part by weight of polyoxyethylene lauryl ether, and a volatile content of 7 comprising water
3 wt. Of a film forming raw material was discharged to the same metal drum as in Example 1 to form a film. In addition, 95 parts of the film
It dried with the hot air of ° C, and obtained 3.3 m-wide PVA film. When the thickness of the obtained film was measured, the average thickness was 75 μm, the thickest portion was 75.8 μm, the thinnest portion was 73.8 μm, and the thickness unevenness was 2.67%. ΔRe was 30 nm. The PVA film was raised in front of a board which was whitened in a dark room, and photographed with a projector. No optical spots or defects were found. Further, the same treatment as in Example 1 was carried out except that the stretching ratio was set to 5.5, to obtain a polarizing film having a thickness of 30 μm. No staining spots were observed on this polarizing film, and optical spots were observed even when the obtained polarizing film was sandwiched between two polarizing plates in a crossed Nicols state at an angle of 45 ° and the transmitted light was visually observed. It was good.

Comparative Example 1 The same film forming material as in Example 1 was discharged onto a belt controlled at 90 ° C. in an atmosphere to form a belt. The width of the obtained PVA film was 2.6 m. When the thickness of the obtained film was measured, the average thickness was 73 μm, the thickest portion was 73.9 μm, and the thinnest portion was 72.0 μm.
The thickness unevenness was 2.60%. ΔRe was 11 nm. However, when the PVA film was raised in front of a board that was whitened in a dark room and photographed with a projector, an optical streak was clearly observed at the center of the film, which seemed to be a transfer of a belt seam. The quality of the film was poor and the quality of the polarizing film could not be evaluated.

Example 3 PVA 10 having a saponification degree of 99.9 mol% and a polymerization degree of 1700
A film-forming material consisting of 0 parts by weight, 15 parts by weight of glycerin, 0.1 part by weight of lauric acid diethanolamide and water and having a volatile content of 60% by weight was chrome-plated at 95 ° C. and had a diameter of 2.5 m.
Was discharged to a metal drum to form a film. Further, the film forming material on the surface of the metal drum is dried with hot air of 95 ° C.
A VA film was obtained. When the thickness of the obtained film was measured, the average thickness was 74 μm, and the thickest portion was 76.
The thickness was 3 μm, the thinnest portion was 73.2 μm, and the thickness unevenness was 4.05%. ΔRe was 33 nm. The PVA film was raised in front of a board which was whitened in a dark room, and photographed with a projector. No optical spots or defects were found. Further, the same treatment as in Example 1 was carried out except that the stretching ratio was changed to 4.6, to obtain a polarizing film having a thickness of 34 μm. No stain was observed on this polarizing film, and the obtained polarizing film was placed at 45 ° between two polarizing plates in a crossed Nicols state.
And the transmitted light was visually observed and no optical spots were observed.

Comparative Example 2 The same film-forming raw material as in Example 3 was discharged onto a chrome-plated metal drum having a diameter of 2.0 m at 95 ° C. to form a film. Further, the film forming raw material on the surface of the metal drum was dried with hot air at 95 ° C. to obtain a PVA film having a width of 1.6 m. When the thickness of the obtained film was measured, the average thickness was 75 μm, the thickest portion was 80.8 μm, the thinnest portion was 70.9 μm, and the thickness unevenness was 13.20%. Perhaps because the drying does not progress, the peeling line from some metal drums is not stable,
Poor peeling often occurred. ΔRe was 53 nm. The PVA film was raised in front of a board which was whitened in a dark room, and photographed with a projector. No optical spots or defects were found. The film was treated at a stretching ratio of 4.6 in the same manner as in Example 3 to obtain a polarizing film having a thickness of 35 μm. In the polarizing film, stained spots in which dark portions and light portions coexisted locally were observed, and were poor. Also,
When the obtained polarizing film was sandwiched between two polarizing plates in a crossed Nicols state at an angle of 45 ° and the transmitted light was visually observed, severe optical spots were observed and were poor.

Comparative Example 3 The same film forming raw material as in Example 1 was discharged onto a 3.2 m diameter metal drum plated with chromium at 86 ° C. to form a film. Further, the film forming raw material on the surface of the metal drum was dried with hot air at 88 ° C. to obtain a PVA film having a width of 3.2 m. When the thickness of the obtained film was measured, the average thickness was 185 μm, the thickest part was 188.3 μm, and the thinnest part was 182.6 μm.
m, and the thickness unevenness was 3.08%. Perhaps because the drying did not proceed, the peeling line from the metal drum was partially unstable, and peeling failure often occurred. ΔRe is 67 nm
Met. The PVA film was raised in front of a board which was whitened in a dark room, and photographed with a projector. No optical spots or defects were found. The film was treated at a stretching ratio of 6.1 to obtain a polarizing film having a stretch unevenness and a thickness of 98 μm. In this polarizing film, stained spots in which a dark portion and a light portion coexist were recognized as a whole, and were poor. When the obtained polarizing film was sandwiched between two polarizing plates in a crossed Nicols state at an angle of 45 ° and the transmitted light was visually observed, severe optical spots were observed and were poor. Example 1 above
Table 1 summarizes the data of Comparative Examples 1 to 3 and Comparative Examples 1 to 3.

[0044]

[Table 1]

[0045]

As described in detail above, the P of the present invention
A polarizing film obtained from a VA film has uniform optical performance even in a large area as compared with a conventional polarizing film.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 29:04 C08L 29:04 (72) Inventor Tsutomu Kawai 892 Sakuhi-shi, Saijo-shi, Ehime Pref. (Reference) 2H049 BA02 BA06 BA27 BB03 BB49 BB62 BC03 BC09 BC22 4F071 AA29 AF35 AH16 BA02 BB02 BC01 BC12 4F205 AA19 AC05 AG01 AH73 AR12 GA07 GB02 GC02 GF01 GF24 GN13 GN22 GN24

Claims (4)

[Claims] 1. A film having a thickness unevenness in the TD direction of 12% or less, obtained by drum film formation, having an average film thickness of 20 to 150 μm, and a film width of 2 m.
A polyvinyl alcohol-based film as described above. 2. When the retardation of the full width in the TD direction of the film is measured, the difference (ΔRe) between the maximum value and the minimum value of the retardation at any point whose distance in the TD direction is 1 m or less is 50 nm or less. The polyvinyl alcohol-based film according to claim 1, wherein: 3. The method according to claim 1, which is for a polarizing film.
The polyvinyl alcohol-based film as described in the above. 4. A polarizing film produced from the polyvinyl alcohol-based film for a polarizing film according to claim 3.