JPH03288803A - Polarizing film and production thereof - Google Patents

Abstract

PURPOSE:To obtain the polarizing film having excellent optical characteristics, such as degree of polarization and transmittance, by using a uniaxially stretched film consisting of a polyvinyl alcohol (PVA) polymer having 45 to 52.5mol% syndiotacticity as a base material. CONSTITUTION:The uniaxially stretched film of the so-called atactic PVA polymer having the syndiotacticity lower than the syndiotacticity of PVA used for conventional polarizing films is used as the base material. The syndiotacticity of the PVA polymer is required to be kept at 45 to 52.5mol%, more preferably 45 to 52.5mol%. The degree of polymn. of the PVA system is required to be made to >=1000, more preferably >=1500 in terms of film strength and working characteristics and is <=30000 in terms of working characteristics, such as film forming and stretching. The polarizing film which is higher in the transmittance and degree of polarization than the polarizing films obtd. from the conventional PVA polymers and has the industrially high value as optical films and various separating films, etc., is obtd. in this way.

Description

[Detailed description of the invention] , to The present invention relates to a polarizing film and a method for manufacturing the same.

More details: The present invention relates to a bifacial optical film with excellent optical properties and a method for producing the same.

B. Prior Art Conventionally, liquid crystal display devices have been used as display devices for small, flexible screens such as watches, calculators, word processors, and mechanical instruments.
The requirements for display quality were not particularly strict. but,
In recent years, liquid crystal display devices have become widely used as displays for televisions, laptop computers, automobiles, aircraft instrument panels, etc., and there are demands for larger size, higher quality display, and improved durability. I'm here.

Therefore, in order to achieve the above-mentioned problems, the polarizing film, which is a component of a liquid crystal display device, needs to be made large in area,
There is a demand for improved optical properties such as a high degree of polarization and high transmittance.

Conventionally, a uniaxially stretched film of polyvinyl alcohol adsorbed with iodine or dichroic dyes has been commonly used as a polarizing film, and this polarizing film has a wide range of polarization degrees because it satisfies the above requirements. On the contrary,
A proposal to use a uniaxially stretched film of highly polymerized polyvinyl alcohol as a film (for example, JP-A-1-1032
04, etc.) and an f-2 polarizing film using polyester uniaxially stretched film as a base material (for example, Japanese Patent Laid-Open No. 58-68
008 etc.) are chewed. However, the present inventors investigated these methods and found that in the former case,
When both the degree of polymerization and the degree of saponification of polyvinyl alcohol become high, it is difficult to uniformly dissolve the polyvinyl alcohol in a solvent, and when dissolved under harsh conditions, the degree of polymerization of polyvinyl alcohol decreases, which results in polarized light having satisfactory performance. It turned out that the film was not available. In the latter case, the drawbacks of polarizing films based on polyvinyl alcohol have been improved to some extent, but the degree of polarization is still insufficient and does not fully meet the above requirements.

Problems to be Solved by the Invention Under these circumstances, the present invention seeks to provide an r-2 polarizing film with excellent optical properties such as a high degree of polarization and a transmission chamber, and a method for producing the same.

As a result of intensive studies aimed at solving the above-mentioned problem, the inventors of the present invention, who are in the process of solving Section D, have found that syndiotacticity is 45 to 525 mol% polyvinyl alcohol (hereinafter, polyvinyl alcohol is abbreviated as PVA). The present invention has been completed based on the discovery that the above object can be achieved by using a uniaxially stretched film made of a uniaxially stretched polymer as a base material.

PVA has traditionally been used as a base material for polarizing films.
The syndiotacticity of is 53.0 mol%.

On the other hand, the polarizing film of the present invention is composed of a PVA-based polymer with a syndiotacticity of 45 to 52.5 mol%, so it has good uniaxial stretchability, and in order to be able to stretch the molecular chain more linearly, iodine It is possible to improve the orientation of dichroic substances such as dyes and dyes, and as a result, it has excellent optical properties.

The present invention will be explained in detail below.

The polarizing film of the present invention can be used as a conventional polarizing film, but has a non-diotactic property compared to PVA.
The present invention is characterized in that it is a uniaxially stretched film base material of a low-attractive PvA u polymer.

In the present invention, it is necessary to adjust the content of the PVA polymer to 45 to 525 mol%,
Preferably it is 48 to 52.0 mol%.

The protein used in the present invention is obtained by converting the hydroxyl proton of PVA into a d,-notyl sulfoxide solution.
' Calculated from the absorption intensity of each 3-unit chain structure measured by H-NMR. The absorption of three hydroxyl group protons is 4.0-4
．． It appears as a chemical shift around 5 ppm, and is assigned to tactical (+), heterotactic (H), and nongeotactic (S) from the low magnetic field side.

It's Tactical (■) Knee C1(-CI(,-CH-CH,-]1-OHOH
O)l Heterotuftic (H): CH-CH, -CH-cH+-CH OHOH Non-geotuftic (S).

OH Some CI (-CH, -CH-CH, -CI (-OHOH) The amount of non-diotactic (S), heterotactic (H)
After expressing each ratio as a percentage from the absorption intensities of ) and Ait Tactical (A), the syndiotacticity amount of the two-chain structure is determined from the following formula (1).

Syndiotacticity - 1k (mol%) = (S) (mol%) + (H)/2 (mol%) ...... (1) P
If the syndiotacticity of the VA polymer is greater than 52.5 mol %, the stretchability of the film will decrease, making it impossible to obtain sufficient polarizing properties. Furthermore, in the case of a PVA-based polymer having a high degree of polymerization and a high degree of saponification, it is difficult to uniformly dissolve the PVA-based polymer in a solvent, which makes it difficult to obtain a uniform polarizing film. Non-geo-toughness - 445. If the film strength is less than 0 mol %, it is difficult to obtain a satisfactory polarizing film.

The degree of polymerization and saponification of the PVA polymer affect the performance of the polarizing film of the present invention.

The degree of polymerization needs to be 1,000 or more from the viewpoint of film strength and processing characteristics, preferably 1,500 or more, more preferably 1,700 or more, and 30,000 or less from the viewpoint of processing characteristics such as film forming and stretching. Here, the degree of polymerization of the PVA-based polymer is determined by the following formula from the intrinsic viscosity measured at 30°C in acetone of polyvinyl acetate obtained by reacetylating the PVA-based polymer, and is expressed as a viscosity average degree of polymerization. .

p=([η]
It is mol% or more, preferably 95 mol% or more, more preferably 98 mol% or more.

The PVA-based polymer containing 45 to 52.5 mol % of syndiotuftin tea according to the present invention cannot be obtained by boiling point polymerization of vinyl acetate monomer in bulk and methanol solution phase, which is a conventional method for producing PVA. The active PVA-based polymers used in the present invention include polyvinyl ester chill-based polymers polymerized in a dipole abrotic solvent and polyvinyl esters polymerized with vinyl esters in which aromatic rings and carbonyl groups can have a coplanar structure. Obtained using a polymer as a raw material.

Examples of such guibor abrotic solvents include dimethyl sulfoxide, sulfolane, carbonate esters, and among others, dimethyl sulfoxide is preferably used. Vinyl esters in which the aromatic ring and the carbonyl group can have the same planar structure include vinyl benzoate, vinyl P-fluorobenzoate, vinyl P-chlorobenzoate, vinyl P-bromobenzoate, vinyl P-methylbenzoate, and P-vinyl chlorobenzoate. −
Examples thereof include P-substituted vinyl benzoates such as vinyl methoxybenzoate, and m-substituted vinyl benzoates such as vinyl m-chlorobenzoate and vinyl m-fluorobenzoate, but polymers of vinyl benzoate are particularly preferred.

C which can be copolymerized with the above hinyl ester monomers
Since it is a copolymer obtained by copolymerizing monomers, it may be used within a range that does not deviate from the spirit of the present invention. Such copolymer units include olefins such as ethylene, propylene, ■-butene, isobutyne, acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic acid. Acrylic acid esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, Methacrylates such as ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodenyl methacrylate, and octadenyl methacrylate. Acid esters, acrylamide, n-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, noacetonoacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidepropyldimethylamine and its salts or its quaternary salts, N- Acrylamide derivatives such as methylol acrylamide and its derivatives, methacrylamide, X
- methylacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid and its salts,
methacrylamide propyldimethylamine and its salts or quaternary salts thereof, methacrylamide derivatives such as N-methylolacrylamide and its derivatives, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i- Vinyl ethers such as butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether, nitriles such as acrylonitrile and methacrylonitrile, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and hnylidene fluoride, acetic acid Examples include allyl, allyl compounds such as allyl chloride, maleic acid and its salts, esters thereof, itacanoic acid and its salts, other esters, vinyltrimethine compounds such as vinyl trimethoxysilane, isopropenyl acetate, and the like.

The PVA-based polymer of the present invention is obtained by saponifying a polyvinyl ester-based polymer containing 45.0 to 52.5 mol% of syndiotuftin tea by a known method. reactor.

As the dichroic substance used in the polarizing film of the present invention, in addition to iodine, so-called dichroic dyes may be used alone or in combination. For example, black17 is a typical example.
．． 19.154; brown44.106.195°210, 223: red2.23.28.31.37
．． 39.79.81°240, 242.247; bl
ueL, 15.22.7B, 90.9g.

151.168.202.236.249.270;
violet9.1251, 98: greenl,
85: yellow8.12.44. H, 87;
Examples include orange26.39.106.107. If the amount of the dichroic substance in the film is too small, the polarizing film will not be able to exhibit its optical properties, and if it is too large, it will reduce the optical properties, water resistance, and resistance. Therefore, polyvinyl alcohol is usually used. 0.0 for the system polymer
It is adjusted to a range of 1% by weight to 1% by weight.

The polarizing film of the present invention is an extremely useful polarizing film that has improved optical properties over conventional PVA-based polarizing films. The ideal value of the optical properties of an i-light film is that the degree of polarization is 100% at a transmittance of 50%. However, since the dichroic ratio of dichroic molecules has a finite value and the molecules are not perfectly oriented in the base polymer, conventional polarizing films have a degree of polarization of 99.
In the case of 9%, the transmittance was about 40%. In contrast, the polarizing film of the present invention can obtain sufficient polarizing properties with a dichroic substance at a lower concentration than conventional polarizing films.
A high degree of polarization and high transmittance are achieved. For example, transparency 42
-44%, the degree of polarization is 98-100%, more preferably, when the transmittance is 44-48%, the degree of polarization is 99-1.
00% polarizing film is obtained.

The polarizing film of the present invention can be produced by the following method.

One way is to use Syndio Tufting Tea or 45
This is a method in which a film of 0 to 525 mol% PVA-based polymer is prepared and then subjected to adsorption of a dichroic substance such as iodine or dye and uniaxial stretching, and the order of adsorption of the dichroic substance and stretching operation is : It's optional. Another method is to add a dichroic substance during film production and uniaxially stretch the film, and the polarizing film of the present invention can be produced by either method.

First, Syngeo Tufting Tea is 45.0 to 52.5
The solvent used at this time is dimethylsulfoquine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, propylene glycol, glycerin, ethylenediamine, diethylenetriamine, and Water, etc. may be used alone or in combination. Furthermore, aqueous solutions of moth salts such as lithium chloride and carunium chloride can also be used alone or in combination with the above-mentioned organic solvents. Among these, dimethyl sulfoxide, a mixed solvent of dimethylformamide and water, and glycerin are preferably used. Degree of a of the PVA polymer during film formation: Varies depending on the film formation method, but usually 1 to 50% by weight, preferably 2 to 30% by weight
It is.

One method for incorporating a polarizing element into the polarizing film of the present invention is to prepare a solution in which iodine or dichroic dye is dissolved in a pvA solution. Although the concentration varies depending on the type of polarizing element, it is usually adjusted to a range of 0.01 to 1% by weight based on the PVA polymer. PV in which such a polarizing element is dissolved
The A-based polymer solution is usually prepared at room temperature or at a temperature of 9120°C. In this case, depending on the solvent used,
In order to suppress a decrease in the degree of polymerization due to decomposition of the PVA-based polymer, it is preferable to use a lower adjustment temperature within the above temperature range.

Next, a film is formed from the PVA polymer solution.

Examples of film forming methods include casting from the PVA-based polymer and dry film forming by extrusion into air or an inert gas such as nitrogen. Maf2, the PV
Wet film formation is performed by extruding the A-based polymer solution into a poor solvent. It is also possible to perform wet-dry film forming in which the PVA polymer solution is once extruded into air or an inert gas such as nitrogen to form a liquid film, and then introduced into a coagulating liquid to form a film. To explain this wet-dry film formation in more detail, a liquid film of the PVA polymer solution is formed in an atmosphere, and then this liquid film is mixed with decalin, paraffin, etc.
It is also possible to form a film by cooling, solidifying and gelling with a cooling medium such as trichlorethylene or carbon tetrachloride, and then introducing it into a solvent-removal solution to remove the solvent. Furthermore, it is of course possible to introduce the liquid film into a cooling space such as a freezing room, cool it, solidify it, and gel it, and then remove the solvent and form a film. The coagulant is compatible with the solvent of the PVA polymer solution and is a poor solvent for the PVA polymer, such as alcohols such as methanol, ethanol, propatool, acetone, and benzene. , toluene, or a mixed solvent of these and the solvent for the PV A polymer solution, as well as a free salt aqueous solution are used. The liquid film of the PVA polymer solution is usually adjusted at -30 to 120°C, although it varies depending on the solvent of the PVA polymer solution.

The syndiotactic city obtained in this way was 4.
A film made of 5.0 to 52.5 mol% PVA polymer (hereinafter abbreviated as raw film) is subjected to dichroic substance adsorption and uniaxial stretching, or only -axial stretching is performed. Ru. There is no problem whether the suction operation and the stretching operation are performed simultaneously or separately, and the order thereof is arbitrary. In addition, boron compounds such as boric acid and borax are sometimes added to strengthen the adsorption of dichroic substances onto the raw film, but even if this is done at the same time as adsorption and stretching, these It can be carried out at any time before or after the operation.

Adsorption of a dichroic substance onto a raw film is usually carried out by immersing the raw film in a liquid containing the dichroic substance, but there are particular restrictions on the operating conditions, orientation, etc. Two examples: i' Usually, when using iodine, an iodine-potassium iodide aqueous solution is used, and when using a dye, an aqueous dye solution is used.

Stretching is carried out by wet stretching, dry heat stretching, or a combination of the two, and it is preferable to stretch the film in the -axial direction by 3 times or more, preferably 4 times or more. The stretching speed is preferably 10 to 300%/min based on the original length of the raw film. The temperature during stretching varies depending on the stretching conditions, and is usually between 10°C and 260°C. Further, during dry heat stretching, it is preferable to carry out the operation in an inert gas. When adsorption is performed after the stretching operation, the uniaxially stretched film is preferably heat-treated at 160 to 260° C. in air or in an inert gas before adsorption. There is no particular limit to the thickness of the film after stretching, but it is between 5 and 100 mm.
The thickness is preferably 10 to 40 μm, particularly preferably 10 to 40 μm.

The CO film that has been adsorbed and stretched is subjected to a drying process under a fixed length in the air or in a nitrogen stream.

The polarizing film of the present invention obtained in this way can be used alone, and its double-sided matte color is optically transparent on one side, and it has mechanical strength. It can also be used by laminating a protective film f). As the protective film, cellulose acetate film, acrylic film, polyester film, etc. are usually used.

dan-JLL12 Hereinafter, the present invention will be explained in more detail by giving examples.
The present invention is in no way limited by Koot et al.

In addition, "%" and "parts" in the examples refer to "% by weight" and "parts by weight" unless otherwise specified.

The transmittance and polarization degree were measured using a spectrophotometer.
child. Transmittance was measured in accordance with JIS-Z-8701,
The degree of polarization was calculated using the formula below.

Here, T and T are the transmittances measured by stacking two polarizing films on top of each other with their stretching axes parallel and perpendicular to each other. Polarizing films are usually laminated with a protective film and used in two-dimensional form, but in the following Examples and Comparative Examples, the polarizing film alone without a protective film was measured.

Example 1 Vinyl acetate monomer 200 was added to a reaction vessel equipped with a stirrer.
and 290 parts of nomethyl sulfoquine, and the system was sufficiently purged with nitrogen by bubbling nitrogen gas. Separately, a solution was prepared by dissolving 0.028 parts of 2,2'-azobisisobutyronitrile as an initiator in 10 parts of dimethyl sulfoxide, and the solution was purged with nitrogen by bubbling with nitrogen gas.

When the reaction solution reached 60° C., a dimethyl sulfoxide solution containing an initiator dissolved therein was injected to initiate polymerization. 1
When the polymerization rate reached 60% after 90 minutes, the polymerization inhibitor was dissolved, diluted methanol was added, and the mixture was further cooled to stop the polymerization. Thereafter, unreacted vinyl acetate monomer was removed by adding methanol under pressure to obtain a mixed solution of polyvinyl acetate in dimethyl sulfoxide and methanol. Take a part of this solution, make the concentration 1O%, [NaOH]
/ [VAC (mole ratio) = O, L] 0.1 part of the obtained PVA was heated at a temperature of 40°C and stirred occasionally in a solution of 8 parts of acetic anhydride and 2 parts of pyridine at 120°C for 20 hours. The product was then re-acetated and purified by reprecipitation using an acetone-ether and acetone-water system to obtain purified re-acetated polyvinyl acetate. Get it, PVA, da DMS
Dissolved in O, measured ')l-NMR, determined the tuftity of each 3-monocarbon chain structure of the hydroxyl group protons, and calculated the syndiotufty city of the 2-chain structure from this to be 51.3. The viscosity average degree of polymerization determined from [η] measured in acetone at 30° C. of the polyvinyl acetate obtained by reacetylation was 2,200.

After re-saponifying this PVA until the degree of saponification reached 99.9 mol%, dimethyl sulfoxide was sufficiently replaced with nitrogen in the system so that the PVA concentration was 10% by weight, and then heated at 70°C. Dissolved below to obtain a PVA solution.

After casting the solution onto a polyethylene terephthalate film and immersing it in a methanol coagulation bath to form a film,
Introduce it into a methanol extraction bath to desolute dimethyl sulfokide. Next, air dry at room temperature for 15 minutes.
It was uniaxially stretched across 91 degrees at 0°C, and further fixed at 190°C for 3 minutes under constant length in a nitrogen gas atmosphere. The stretched film was immersed in an aqueous solution containing 0.2 g/Q of iodine and 50 g/Q of potassium iodide at 30°C for 2 minutes overnight. Next, boric acid 60g/Q, potassium iodide 30g/
(Dissolve the solution in an aqueous solution and bring it to room temperature. After treatment with boric acid for 5 minutes, dry under hot air at 40°C under a fixed length to obtain a polarizing film with a thickness of 18μ. The amount of iodine in the polarizing film was determined by soaking it in sodium thiosulfate, and it was found to be 0.3% by weight in °, I.The transmittance of the obtained polarizing film was 45.5%, degree is 99
It was 7%.

Comparative Example 1 PVA with polymerization degree of 2400 and saponification degree of 99.9 mol%
A polarizing film was prepared in exactly the same manner as in Example 2, except that syndiotacticity of 53.0 mol % was used. The stretching ratio of the original film (length is 6 times and it is hot).The transmittance of the polarizing film is 422%, and the degree of polarization is 99.
It was 2%.

Practical row 2 The active film was immersed in a mixed aqueous solution of iodine and iodine, and 5.0 g of the dichroic dye Direct Sky Blue 6B (manufactured by Shiku Kasei) was added.
A polarizing film with a thickness of 18 μm was obtained in the same manner as in Example 1, except that it was immersed in a dye solution containing Q melted. wavelength 650
Transmittance at nm is 4343%, degree of polarization is 99.0%
And r2.

Example 3 Using the same PVA as in Example
A aqueous solution was obtained. The aqueous solution was cast onto a polyethylene terephthalate film and air-dried at room temperature to form a film. A stretched polarizing film with a thickness of 18 μm was obtained in the same manner as in Example 1 except for the method for preparing the film described above. The transmittance of the polarizing film is 450%, and the degree of polarization is 9.
It was 9.5%.

Comparison row 2: Exactly the same as Example 3 except that PVA with a degree of polymerization of 2400, a saponification level of 99.9 mol%, and a syndiotactic acidity of 53.0 mol% was used; the thickness was 18 μmu')
A polarizing film was prepared. The stretching ratio of the raw film is 4
Double hot. The transmittance of the polarizing film is 41.9%,
The degree of polarization was 99.1%.

Example 4 Using the same PVA as in Example 1, it was dissolved in a mixed solvent of dimethyl sulfoxide/water-90/10 (weight ratio) under heating at 70°C so that the PVA concentration was 10% by weight. P
A VA solution was obtained. A polarizing film with a thickness of 18 μm was obtained in the same manner as in Example 1 except for the method for preparing the PVA solution described above. The transmittance of the polarizing film is 45.7%, and the degree of polarization is 99.
．． It was 8%.

Example 5 The raw film prepared in Example 1 was treated with 0.2 g/Q of iodine.
, potassium iodide 50g/Q dissolved in an aqueous solution,
It was immersed for 3 minutes at 30°C. Next, boric acid 60g/Q,
In an aqueous solution containing 30 g/ff of potassium iodide, 6
The film was uniaxially stretched, treated with boric acid for 5 minutes, and dried under hot air at 40°C to form a polarizing film with a thickness of 18 μm. The amount of iodine in the polarizing film was determined using sodium thiosulfate at a constant rate of 12.
It was 0.3% by weight. The obtained polarizing film had a transmittance of 44.9% and a degree of polarization of 996%.

Example 6 Same equipment, operation and conditions as Example 1, using 2 as initiator.
, 2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and polymerization was carried out at a polymerization temperature of 40°C.
It was. The syndiotacticity of the obtained PVA was 5.
1. , 0 mol%, saponification degree 99.9 mol%, measured at 30°C in acetone of polyvinyl acetate obtained by reacetylation [
The viscosity average degree of polymerization determined from [η] was 6,200.

This PVA was dissolved in dimethyl sulfoxide for 90 minutes under heating at 70° C. to obtain a PVA solution, after sufficiently purging the system with nitrogen so that the PVA concentration was 9% by weight. A polarizing film having a thickness of 18 μm was obtained from this solution in the same manner as in Example 1. The transmittance of the obtained polarizing film was 47
．． 0%, the degree of polarization is 99.9% and r2.

Example 3 PvA with a degree of polymerization of 6000.1, a degree of sonication of 999 mol%, and a non-diotactic content of 530 mol% was added to real #61VA.
Add pvA! to dimethyl sulfoxide in the same manner as +6. It
An attempt was made to melt the solution under heating at 70°C so that the concentration was 9% by weight, but it took 8 hours to dissolve the solution.A polarizing film with a thickness of 18 um was prepared from the solution in the same manner as in Example 6. A film with uniform staining could not be obtained. Moreover, the stretching ratio was 6 times. The transmittance of the polarizing film is 40.0
%, and the degree of polarization was 99.2%.

Example 7 Using the same equipment and operation as in Example 1, using vinyl P-chlorobenzoate as the monomer, polymerization was carried out at 60°C to a polymerization rate of 58%. After that, methanol was added under reduced pressure. Then, unreacted vinyl P-chlorobenzoate monomer was removed to obtain a methanol solution of polyvinyl P-chlorobenzoate. This solution was saponified and re-saponified to have a saponification degree of 99.9.
Mol% of PVA was obtained. The content of this PVA was 470 mol % of potassium, and the resulting polyvinyl acetate was measured in acetone at 30° C. and the average degree of polymerization was 12,250.

A polarizing film with a thickness of 18 μm was prepared in the same manner as in IPI 1 using PVA No. 2, and the transmittance was 4.
6.0%, and the degree of polarization was 99.8%.

As is clear from the above examples, the polarizing film made from the PVA polymer of the present invention has higher transmittance than the polarizing film made from the conventional PVA polymer. It has a high degree of polarization and excellent optical properties. This means that the syndiotacticity of the PVA polymer is 45.0 to 52.5.
C3 was achieved for the first time by using mol % of an actiic PVA-based polymer.

The reason for this is not clear, but the polarizing film of the present invention has less syndiolinkage than conventional polarizing films.
It is assumed that because it is made of A-based polymer, the stretchability is excellent C3 and the orientation is good.

Taking advantage of the above characteristics, the PVA polymer film obtained in the present invention can be used for various packaging applications, gas barrier materials, optical films such as polarizing film base materials and filter base materials, and various separation membranes. It has extremely high industrial value.

Claims (5)

[Claims] (1) A polarizing film whose base material is a uniaxially stretched film made of a polyvinyl alcohol polymer having a syndiotacticity of 45 to 52.5 mol%. (2) The method for producing a polarizing film according to claim 1, characterized in that the film is formed using a solution of a polyvinyl alcohol polymer, and the obtained film is uniaxially stretched. (3) The method for producing a polarizing film according to claim 2, wherein the solution is an aqueous solution. (4) The method for producing a polarizing film according to claim 2, wherein the solution is an organic solvent solution. (5) The method for producing a polarizing film according to claim 2, wherein the solution is a mixed solution of water and an organic solvent.