JPH11295528A - Polarizing film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing film free of intra-surface optical unevenness with a small dimensional change at the time of wet heat and dry heat without adversely affecting operability at the time of film forming and uniaxial stretching. SOLUTION: This polarizing film consists of a polyvinyl alcohol(PVA) resin film contg. dichromatic dyestuffs and block polyisocyanate and is obtd. by uniaxially stretching the film formed by using an aq. PVA resin soln. contg. the dichromatic dyestuffs and the block polyisocyanate and further subjecting the film to heat fixing. The polarizing film is also obtd. by forming the film at a temp. below the dissociation temp. of the block polyisocyanate contained in the resin and subjecting the film to uniaxial stretching, then to heat fixing at a temp. above the dissociation temp. of the block polyisocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing film having excellent durability, and more particularly, to a polarizing film having a small dimensional shrinkage under wet heat and dry heat environments and a small optical unevenness in a plane. It is. The present invention also relates to a method for producing such a polarizing film.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in desktop electronic calculators, electronic timepieces, word processors, instruments for automobiles and machinery, and the demand for polarizing plates has been increasing with these devices. In particular, since instruments are often used under severe conditions, a polarizing plate excellent in durability such as wet heat resistance and heat resistance is required.

In order to improve the heat resistance and wet heat resistance,
Until now, generally, a polyvinyl alcohol-based resin is formed into a film, subjected to a dyeing treatment (immersing the polyvinyl alcohol-based resin film in iodine or a dichroic dye) and a uniaxial stretching, and then treated with an aqueous solution containing boric acid. The way had been done.

For example, JP-A-1-105204 discloses that a polarizing film is produced using a polyvinyl alcohol-based resin having a degree of polymerization of 2500 or more, and is treated with an aqueous boric acid solution after dyeing. Then
It is described that a composition comprising a polyvinyl alcohol-based resin and polyglycerin is formed into a film and uniaxially stretched to form a polarizing film, which is subjected to boric acid treatment at an optional stage,
As a method of including a dichroic substance such as an iodine compound or a dye in a polyvinyl alcohol-based resin film, in addition to the method of impregnating the film, a method of including a dichroic substance in a polyvinyl alcohol-based resin solution during film production is also available. Are listed.

[0005]

However, the method of treating a uniaxially stretched film of a polyvinyl alcohol-based resin with an aqueous solution containing boric acid as in the technique disclosed in the above publication requires an impregnation step, which complicates the production process. thing,
There is a problem that the film may be deformed during the impregnation operation, it is difficult to uniformly impregnate the inside of the film, and a further drying step is required after the impregnation step, and it is difficult to be industrially adopted. Even if a dichroic substance is contained in the polyvinyl alcohol-based resin solution during the production of the film, it is inevitable to perform boric acid treatment as a post-treatment in consideration of the durability of the polarizing film. Furthermore, the above-mentioned technology disclosed in the above-mentioned publications is not yet satisfactory with respect to the durability corresponding to the recent sophistication of the technology, that is, the dimensional stability at the time of wet heat and dry heat, and further improvement is desired.

In the present invention, under such a background,
It does not adversely affect operability during film formation and uniaxial stretching,
Moreover, it is an object of the present invention to provide a polarizing film having small dimensional change and optical property change at the time of wet heat and dry heat and free from in-plane optical unevenness, and a method of manufacturing such a polarizing film. Things.

[0007]

The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, a polarizing film comprising a polyvinyl alcohol-based resin film containing a dichroic dye and a blocked polyisocyanate has been obtained. The present invention has been found to be excellent in dimensional stability in wet heat and dry heat environments, and has an effect of no in-plane optical unevenness. In the present invention, a method for producing a polarizing film, in which a film formed using an aqueous solution of a polyvinyl alcohol-based resin containing a dichroic dye and a blocked polyisocyanate is uniaxially stretched and further heat-fixed, is preferably employed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The polyvinyl alcohol-based resin used in the present invention is not particularly limited. Usually, in addition to polyvinyl alcohol which is a saponified product of a homopolymer of polyvinyl acetate, vinyl acetate and a small amount of a comonomer (α-olefin,
Ethylenically unsaturated carboxylic acid compounds, ethylenically unsaturated sulfonic acid compounds, (meth) acrylonitrile,
"Copolymerized" polyvinyl alcohols which are saponified copolymers with (meth) acrylamide, vinyl esters other than vinyl acetate, vinyl ethers, vinyl chloride, styrene, etc .; these polyvinyl alcohols and "copolymerized" polyvinyl alcohols Further, "post-modified" polyvinyl alcohol which has been post-modified such as acetalization, urethanization, cyanoethylation and the like can also be used. Among the polyvinyl alcohol resins, the degree of saponification is preferably 80 mol% or more, and more preferably 85 mol% or more.

The degree of polymerization of the polyvinyl alcohol resin is preferably 2400 or more, and more preferably 3000 to 5000. If the polymerization degree is less than 2400, sufficient optical properties cannot be obtained, which is not preferable.

As the dichroic dye, any of yellow, orange, blue, violet, and red can be used without limitation.
Representative dichroic dyes include, for example, C.I. I. Dir
ect blacks 17, 19 and 154, Bro
wn 44, 106, 195, 210 and 223, Re
d 2, 23, 28, 31, 37, 39, 81, 24
0, 242 and 247, Blue 1, 15, 22, 7
8, 90, 98, 151, 168, 202, 236, 2
49 and 270, Violet 9, 12, 51 and 9
8, Green 1 and 85, Yellow 8, 1
2, 44, 86 and 87, Orange 26, 39,
Direct dyes such as C. 106 and 107; I. Disp
erse Blue 214, Red 60, Yel
low 56 and the like. These dichroic dyes may be used in combination of two or more. Further, in the present invention, iodine and a dichroic dye may be used in combination for the purpose of adjusting the hue.

[0011] The content of the dichroic dye is preferably 0.1 to 1.5 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin, and if the content is less than 0.1 part by weight, the polarizing film may be used. In this case, sufficient polarization performance cannot be obtained, and if it exceeds 1.5 parts by weight, uniform film formation becomes difficult, which is not preferable.

The blocked polyisocyanate is a polyisocyanate in which most or all of the free isocyanate groups are blocked by a blocking agent, and has the property that the blocking agent is dissociated by heating to produce free isocyanate.

Here, the polyisocyanate includes ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 2,4,4-
Or aliphatic diisocyanates such as methyl 2,2,4-trimethylhexamethylene diisocyanate and methyl 2,6-diisocyanatocaproate; 3-isocyanatomethyl-
3,5,5-trimethylcyclohexane, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane,
Alicyclic diisocyanates such as methylcyclohexane-2,4- or 2,6-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3- or 1,4-diisocyanatocyclohexane; m- or p-
Phenylene diisocyanate, diphenylmethane-4,
Aromatic diisocyanates such as 4'-diisocyanate, 2,4- or 2,6-tolylene diisocyanate;
Araliphatic diisocyanates such as 3′- or 1,4-bis (isocyanatomethyl) benzene, 1,3- or 1,4-bis (α-isocyanatoisopropyl) benzene;
And the like.

Further, triphenylmethane-4,4,4 ''-
Triisocyanate, 1,3,5-triisocyanatobenzene, 1,3,5-tris (isocyanatomethyl) cyclohexane, 1,3,5-tris (isocyanatomethyl) benzene, 2,6-diisocyanatocapron Acid-2
-Triisocyanates such as isocyanatoethyl can also be used.

Furthermore, polymerized polyisocyanates such as dimer and trimer of diisocyanate, polymethylene polyphenylene polyisocyanate, an excess of the above polyisocyanate and an active hydrogen-containing low molecular weight compound (ethylene glycol, propylene glycol, dipropylene glycol) , Diethylene glycol, triethylene glycol,
2,2,4-trimethyl-1,3-pentanediol,
Neopentyl glycol, hexanediol, cyclohexanedimethanol, cyclohexanediol, hydrogenated bisphenol A, xylylene glycol, glycerin,
Trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, sorbitol, sucrose, castor oil, ethylenediamine, hexamethylenediamine, diethanolamine, triethanolamine, water, ammonia, urea, etc. or active hydrogen-containing high molecular weight compounds (poly Ether polyol, polyester polyol, etc.), or allophanated polyisocyanates, biuretized polyisocyanates, and the like. These polyisocyanates can be used alone or in combination of two or more.

Examples of the blocking agent include phenol-based blocking agents such as phenol, cresol, p-nonylphenol and hydroxybenzoate; lactam-based blocking agents such as ε-caprolactam and γ-butyrolactam; diethyl malonate, acetoacetic acid Active methylene blocking agents such as methyl and acetylacetone; ethanol,
Alcohol blocking agents such as isopropanol, tert-butanol, lauryl alcohol, ethylene glycol monoethyl ether, benzyl alcohol, glycolic acid, glycolic acid ester, lactic acid, lactic acid ester, diacetone alcohol, ethylene chlorohydrin; butyl mercaptan, octyl Mercaptan, tert-
Mercaptan-based blocking agents such as dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol;
Acid amide blocking agents such as acetanilide, acetate amide, acrylamide, benzamide; succinimide;
Imide blocking agents such as phthalimide; amine blocking agents such as diphenylamine, carbazole, aniline and dibutylamine; imidazole blocking agents such as imidazole and 2-ethylimidazole; urea compounds such as urea, thiourea and ethylenethiourea. Blocking agents; carbamic acid-based blocking agents such as 2-oxazolidone and phenyl N-phenylcarbamate; oxime-based blocking agents such as formamidoxime, acetoaldoxime, acetoxime, methylethylketoxime, diacetylmonooxime, cyclohexanone oxime and benzophenone oxime. Agents; sulfite blocking agents such as sodium bisulfite and potassium bisulfite; and the like. These blocking agents can be used alone or in combination of two or more.

The blocked polyisocyanate can be obtained by reacting a polyisocyanate with a blocking agent in a conventional manner. This reaction can be carried out without a solvent or in a solvent having no active hydrogen. Examples of the solvent having no active hydrogen include, for example, ethyl acetate, butyl acetate, cellosolve acetate, carbitol acetate,
Esters such as dimethyl ester of dibasic acid; ketones such as methyl ethyl ketone, methyl butyl butyl ketone and cyclohexanone; aromatic solvents such as toluene, xylene, Solvesso (trademark) # 100 and Solvesso (trademark) # 150; No. When a sulfite blocking agent is used as the blocking agent, water is often used as a solvent.

More specifically, the blocking agent for the polyisocyanate is a polyisocyanate and the blocking agent in an isocyanate group / blocking agent equivalent ratio of 0.9 to 0.9.
1.1 (preferably 0.95 to 1.0), wherein the polyisocyanate and the blocking agent are reacted in an isocyanate group / blocking agent equivalent ratio of 1.1 to 3.0.
(Preferably 1.2 to 2.0), and then reacting it with an active hydrogen-containing low molecular weight compound or / and an active hydrogen containing high molecular weight compound. And an active hydrogen-containing high molecular weight compound in an equivalent ratio of isocyanate group / blocking agent of 1.5 to 10.0 (preferably 2.0 to 7.0).
After the reaction as in 0), the polyisocyanate is removed if necessary, and then a blocking agent is reacted therewith. However, the method is not limited to these methods. In blocking the polyisocyanate, a conventionally known catalyst such as a tertiary amine or an organometallic compound can be used.

The content of the blocked polyisocyanate is
Although not particularly limited, polyvinyl alcohol resin 10
The amount is preferably from 5 to 30 parts by weight, more preferably from 5 to 25 parts by weight, per 0 parts by weight. When the content is less than 5 parts by weight, the effect of improving the moist heat resistance when formed into a uniaxially stretched film becomes insufficient, and when it exceeds 30 parts by weight, the optical properties when formed into a uniaxially stretched film tend to be impaired, and thus it is preferable. Absent.

Thus, a film is formed using the aqueous solution of a polyvinyl alcohol-based resin containing the dichroic dye and the blocked polyisocyanate, and is subjected to uniaxial stretching to obtain a polarizing film.

The film is formed by a casting method, a water-containing extrusion method, or the like. In this case, the film is formed so as to obtain an optically uniform film having good precision. At this time, in addition to water, polyhydric alcohols such as dimethyl sulfoxide (DMSO), N-methylpyrrolidone, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane; ethylenediamine;
Amines such as diethylenetriamine and mixtures thereof can also be used. The concentration of the aqueous polyvinyl alcohol-based resin solution is preferably 5 to 20% by weight. The thickness of the obtained film is preferably from 30 to 100 μm, more preferably from 40 to 90 μm, and if it is less than 30 μm, stretching is difficult, and if it is more than 100 μm, the accuracy of the film thickness is undesirably reduced.

The obtained film is then subjected to uniaxial stretching. The stretching ratio is suitably about 3 to 6 times. As a uniaxial stretching operation, a method of preheating the film by passing the film between a number of rolls, and then stretching the film to a predetermined magnification with two pairs of stretching rolls, while passing the film between the number of rolls A method of bringing up to a predetermined magnification while performing preheating and stepwise stretching in parallel,
A transverse uniaxial stretching method of stretching in the width direction by a tenter method, a longitudinal uniaxial stretching method of stretching in a length direction (machine direction) by a tenter method, and the like are employed. After completion of the stretching, heat setting is performed.
The heat setting step has the meaning of preventing shrinkage of the uniaxially stretched film and improving wet heat resistance.

The above-mentioned film formation and uniaxial stretching are preferably carried out at a temperature lower than the dissociation temperature of the compounded block polyisocyanate. If the temperature is higher than the dissociation temperature, the film may be cut during the stretching operation, which is not preferable.
Further, the heat setting is preferably performed at a temperature higher than the dissociation temperature of the compounded block polyisocyanate. If the temperature is lower than the dissociation temperature, a sufficient reforming effect cannot be obtained, which is not preferable.

The uniaxially stretched film obtained by the above method may be optionally treated with a boron compound. Boric acid and borax are practical as boron compounds. It is practically desirable that the boron compound is used in the form of an aqueous solution or a mixed solution of water and an organic solvent at a concentration of about 0.5 to 2 mol / l. The treatment method is preferably an immersion method, but of course, a coating method and a spraying method can also be performed. The temperature at the time of the treatment is preferably about 50 to 70 ° C., and the treatment time is preferably about 5 to 20 minutes. If necessary, the stretching operation may be performed during the treatment.

The thus obtained polarizing film comprising a uniaxially stretched film may be used by laminating and adhering an optically isotropic polymer film or sheet as a protective film on one or both sides thereof. As such a protective film,
For example, films or sheets of cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, polystyrene, polyether sulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide and the like can be mentioned.

In order to reduce the thickness of the polarizing film of the present invention, a curable resin such as a urethane resin, an acrylic resin, or a urea resin is applied on one or both sides of the polarizing film instead of the protective film. They can also be stacked.

The polarizing film of the present invention (or a protective film or a curable resin laminated on at least one surface thereof)
In some cases, if necessary, a transparent pressure-sensitive adhesive layer is formed on one surface thereof by a generally known method, and may be put to practical use. Examples of the pressure-sensitive adhesive layer include acrylates such as butyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate and the like and α-monoolefin carboxylic acids such as acrylic acid, maleic acid, itaconic acid and methacrylic acid. Copolymers with acids, crotonic acid, etc. (including those to which vinyl monomers such as acrylonitrile, vinyl acetate, styrene are added)
Is mainly preferable because it does not hinder the polarizing properties of the polarizing film, but is not limited thereto, and any pressure-sensitive adhesive having transparency can be used. , Rubber, and the like.

Further, it is also possible to provide various functional layers on one side (the surface on which the above-mentioned pressure-sensitive adhesive is not provided) of the polarizing plate (on which the above-mentioned pressure-sensitive adhesive is provided). Is, for example, an anti-glare layer, a hard coat layer,
Examples include an anti-reflection layer, a half-reflection layer, a reflection layer, a luminous layer, a diffusion layer, an electroluminescent layer, and the like. Further, a combination of two or more kinds can be used. For example, an anti-glare layer, an anti-reflection layer, and a luminous layer And a reflection layer, a light storage layer and a half reflection layer, a light storage layer and a light diffusion layer, a light storage layer and an electroluminescence layer, and a combination of a half reflection layer and an electroluminescence layer. However, it is not limited to these.

By providing the above-mentioned various functional layers on the polarizing film of the present invention, or by providing various kinds of functional layers in combination in the polarizing film, an optical laminate having more excellent various functions can be obtained. It is.

Since the polarizing film of the present invention is made of a polyvinyl alcohol resin film containing a dichroic dye and a blocked polyisocyanate, the polarizing film has excellent durability, small dimensional change during wet heat and dry heat, and in-plane No optical unevenness is exhibited. It is also effective to use the polarizing film of the present invention as a polarizing film without a protective film.

Also, various functional layers can be laminated, and the functions of the various functional layers can be fully exhibited, and liquid crystal display devices such as electronic desktop calculators, electronic watches, word processors, instruments of automobiles and machinery, Sunglasses, eye protection glasses, stereo glasses,
It is used for a reflection reduction layer for a display element (CRT, LCD, etc.), a medical device, a building material, a toy, etc., and is particularly useful for a liquid crystal display device such as an instrument of a car or a machine.

[0032]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified. The degree of polarization (%) was calculated by the following equation. _{[(H 11 -H 1) / (} H 11 + H 1) ] ^1/2 × 100 (%) where, H ₁₁ at the time of superposition of two polarizing plates samples, the orientation direction in the same direction of the polarization plate transmittance measured using a spectrophotometer in a state superimposed so as to be (%), H ₁ at the time of superposition of the two samples, as will the direction in which the orientation direction of the polarizer are perpendicular to each other This is the transmittance (%) measured in the state of being superposed.

Example 1 A polyvinyl alcohol resin having a polymerization degree of 1700 and a saponification degree of 99.8 mol% was dissolved in water, and then blocked polyisocyanate (“Elastron BN-5” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., aqueous And a dissociation temperature of 150 ° C.), and then C.I. I. Direct Violet
9 and a polyvinyl alcohol resin concentration of 18
%, A blocked polyisocyanate concentration of 2%, and a dichroic dye concentration of 0.18%. This aqueous solution was cast on a polyethylene terephthalate film, and then dried at a temperature of 120 ° C. to obtain a raw film having a thickness of 40 μm.

After the raw film was peeled off from the polyethylene terephthalate film, the film was uniaxially stretched by a tenter method and heat-fixed. Preheating condition is 120 ℃ × 3
Min, the stretching temperature was 120 ° C., the stretching ratio was 5 times, and the heat setting conditions were 160 ° C. × 1 minute. The optical characteristics of the obtained polarizing film were as follows: the degree of polarization was 85.6%, and the transmittance was 43.3%.
Met. The polarizing film was evaluated as follows.

(Dimensional stability)
When cut into a size of 8 mm × 77 mm (longitudinal direction is the stretching direction) and left for 125 hours under the condition of 40 ° C. and 90% (during wet heat), and when left in a dryer at 80 ° C. for 125 hours ( Dimensional shrinkage ratio (%)
Was evaluated. The formula for calculating the dimensional shrinkage is as follows. Dimensional shrinkage (%) = (dimension after durability-initial dimension) x 10
0 / initial dimensions

(In-plane optical unevenness) The obtained polarizing film is cut into a size of 150 mm × 200 mm (longitudinal direction is a stretching direction), and the two polarizing films are made into a crossed Nicols state. The apparatus was installed in a photo observation device (produced by Hara Medical Industry Co., Ltd.), and in-plane dyeing unevenness was observed. The evaluation criteria are as follows. ○ ・ ・ ・ No dye unevenness × ・ ・ ・ Dye unevenness

Example 2 In Example 1, a polyvinyl alcohol resin having a polymerization degree of 2600 and a saponification degree of 88 mol% was used, and hexamethylene diisocyanate was blocked with phenol as a blocked polyisocyanate (dissociation temperature 130 ° C.).
° C), and evaluated in the same manner as in Example 1. The optical characteristics of the obtained polarizing film were such that the degree of polarization was 86.3% and the transmittance was 43.6%.

Example 3 The procedure of Example 1 was repeated except that a polyvinyl alcohol resin having a degree of polymerization of 3800 and a saponification degree of 95 mol% was used. In addition, the optical characteristics of the obtained polarizing film were such that the degree of polarization was 94.8% and the transmittance was 40.40%.
6%.

Comparative Example 1 The procedure of Example 1 was repeated, except that only the addition of the blocked polyisocyanate was omitted. The optical characteristics of the obtained polarizing film were such that the degree of polarization was 78.8% and the transmittance was 41.5%.

Comparative Example 2 The procedure of Example 1 was repeated, except that a 0.3% aqueous solution of boric acid was used instead of the blocked polyisocyanate. The optical characteristics of the obtained polarizing film were as follows: the degree of polarization was 85.8%, and the transmittance was 41.2%.
%Met.

Comparative Example 3 A polyvinyl alcohol resin having a polymerization degree of 1700 and a saponification degree of 99.8 mol% was dissolved in water to adjust the concentration to 18%, and the aqueous solution was cast on a polyethylene terephthalate film. It dried at ℃, and obtained the 40-micrometer-thick raw film. The raw film was treated with a dichroic dye (C.I.
I. Direct Violet 9) immersed in an aqueous solution of 0.2 g / l at 30 ° C. for 240 seconds, then immersed in an aqueous solution of boric acid (50 ° C.) (50 ° C.) and uniaxially stretched for 5 minutes. Dry for 2 minutes. The obtained polarizing film was evaluated in the same manner as in Example 1. The optical characteristics of the obtained polarizing film are as follows:
The degree of polarization was 81.2% and the transmittance was 39.9%. Table 1 summarizes the evaluation results of the examples and comparative examples.

[0042]

[Table 1] Note) The term “moist heat” refers to standing at 40 ° C and 90% RH for 125 hours.
The term “dry heating” refers to a state of being left at 80 ° C. for 125 hours.

[0043]

The polarizing film of the present invention is excellent in workability because it forms a polyvinyl alcohol-based resin containing a dichroic dye and a blocked polyisocyanate.
The obtained polarizing film is excellent in dimensional stability under wet heat and dry heat, has a small change in optical characteristics, and has an effect of eliminating optical unevenness in a plane. Furthermore, the polarizing film of the present invention is also useful to be used as a polarizing film without a protective film, and can also laminate various functional layers, fully exhibit the functions of various functional layers, an electronic desk calculator, Used for liquid crystal display devices such as electronic watches, word processors, instruments for automobiles and machinery, sunglasses, eye-protection glasses, stereoscopic glasses, reflection-reducing layers for display elements (CRT, LCD, etc.), medical equipment, building materials, toys, etc. It is especially useful for liquid crystal display devices such as instruments for automobiles and machinery.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G02B 1/04 G02B 1/04 // B29K 29:00 B29L 7:00

Claims (6)

[Claims] 1. A polarizing film comprising a polyvinyl alcohol-based resin film containing a dichroic dye and a blocked polyisocyanate. 2. A method for producing a polarizing film, comprising uniaxially stretching a film formed using a polyvinyl alcohol-based resin aqueous solution containing a dichroic dye and a blocked polyisocyanate, and heat fixing the film. 3. Film-forming and uniaxial stretching at a temperature lower than the dissociation temperature of the contained blocked polyisocyanate, and
The method for producing a polarizing film according to claim 2, wherein the heat setting is performed at a temperature equal to or higher than the dissociation temperature of the blocked polyisocyanate. 4. The polarizing film according to claim 1, wherein the content of the dichroic dye is 0.1 to 1.5 parts by weight based on 100 parts by weight of the polyvinyl alcohol-based resin. Or a method for producing the same. 5. The content of the blocked polyisocyanate is 5 to 100 parts by weight of the polyvinyl alcohol resin.
The polarizing film according to any one of claims 1 to 4, or 30% by weight. 6. The polarizing film according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol-based resin is 2400 or more, or the method for producing the polarizing film.