JPH11183726A - Polarizing film and polarizing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing film and polarizing plate having excellent optical characteristics and workability. SOLUTION: This polarizing film is produced by biaxially stretching a polyvinylalcoholic film in a dry state and then dyeing. In the biaxial stretching process, the product of the stretching rates in the longitudinal direction and in the lateral direction is controlled to 3 to 8. The stretching process is carried out at 100 to 170 deg.C. The polarizing plate using the polarizing film is produced by laminating a urethane resin layer on at least one surface of the polarizing film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing film and a polarizing plate using the same, and more particularly, to a polarizing film having excellent optical properties such as a degree of polarization, transmittance, and two-color ratio, and further having good processability (cutting property, flexibility). Etc.) and a polarizing plate using the same.

[0002]

2. Description of the Related Art Conventionally, electronic desk calculators, electronic watches,
2. Description of the Related Art Liquid crystal display devices are used in word processors, instruments of automobiles and machinery, and the like, and polarizing plates are used in the liquid crystal display devices. As the polarizing plate, a polarizing plate in which a protective layer such as a cellulose-based film, for example, a cellulose triacetate film or the like is laminated on both surfaces of a polarizing film such as a polyvinyl alcohol film to which a polarizing property is imparted by stretching or dyeing treatment is used. Recently, various required performances such as a high degree of polarization and a high transmittance have been demanded for the polarization performance. In order to satisfy such a high degree of polarization or high transmittance, a film made of polyvinyl alcohol having a degree of polymerization of 2,000 to 10,000 is uniaxially stretched in a dry system, and after dyeing, is dried.
A method of immersion treatment with a boric acid-containing aqueous solution at 0 to 85 ° C. (Japanese Patent Application Laid-Open No. 8-240715) has been proposed. Method of performing two-stage stretching during the process (Japanese Patent Laid-Open No. 4-2
No. 15603), a method of performing two-step stretching such that the stretching ratio in the dyeing step or the preceding step and the stretching ratio in the boron compound treatment step have a specific relationship (Japanese Patent Laid-Open No. 7-120618). Suggested.

[0003]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 8-240715, the polarizing film (polarizer) is very easily torn, which causes inconvenience during production. In the disclosed method and the method disclosed in Japanese Patent Application Laid-Open No. Hei 7-120618, in-plane contrast unevenness is not sufficiently eliminated, and there is still room for improvement, and the optical characteristics as described above are excellent. There is a demand for a polarizing film or a polarizing plate having excellent properties.

[0004]

Accordingly, the present inventor has conducted intensive studies in view of the above-mentioned circumstances, and as a result, obtained a polarizing film obtained by biaxially stretching a polyvinyl alcohol-based film in a dry system and then dyeing the resulting film. A polarizing film having a product of the longitudinal stretching ratio and the transverse stretching ratio at the time of the biaxial stretching of 3 to 8 has excellent optical characteristics, and further comprises a polarizing film provided with a urethane resin layer on at least one surface of the polarizing film. The plate was found to be excellent in workability and completed the present invention.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The polyvinyl alcohol-based resin as a raw material of the polarizing film of the present invention is generally produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but in the present invention,
It is not necessarily limited to this, and a component which can be copolymerized with vinyl acetate, such as a small amount of unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins, vinyl ethers, unsaturated sulfonates, etc. May be contained. Further, polyvinyl butyral resin obtained by reacting a polyvinyl alcohol resin with an aldehyde in the presence of an acid, a so-called polyvinyl acetal resin such as a polyvinyl formal resin and other polyvinyl alcohol resin derivatives are also exemplified, but those not limited thereto. Absent. Among these, polyvinyl alcohol (based resin) having a high degree of saponification and a high degree of polymerization is preferred from the viewpoint of good heat resistance. That is, the saponification degree is preferably 95 mol% or more, more preferably 99 mol% or more, and particularly preferably 99.
5 mol% or more, and the (average) degree of polymerization is from 1100 to 5
If the degree of polymerization is less than 1100, it is difficult to obtain sufficient optical performance. The burden is undesirably increased.

[0006] As a method for producing a polarizing film using the polyvinyl alcohol-based resin, a stock solution obtained by dissolving the polyvinyl alcohol-based resin in water or an organic solvent is cast and formed.
After preparing the raw film, the film is subjected to a treatment such as dyeing and stretching, and a method of imparting polarization performance is generally used.
Examples of the solvent used for preparing the stock solution include water, dimethyl sulfoxide (DMSO), N
-Polyhydric alcohols such as methylpyrrolidone, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane; amines such as ethylenediamine and diethylenetriamine; and mixtures thereof are used.

[0007] In the above organic solvent, a small amount, for example, 5 to 30
Water may be contained by weight. The practical concentration of the polyvinyl alcohol-based resin in the stock solution is 5 to 20% by weight. The undiluted solution of a polyvinyl alcohol resin film obtained using the solvent is formed by any method such as a casting method and an extrusion method. The film forming method is a dry / wet film forming method.
That is, the solution is temporarily discharged from the base slit into the air or into an inert atmosphere such as nitrogen, helium, and argon,
It is then led into a coagulation bath to form an unstretched film. Or the film-forming solution discharged from the die is once a roller,
Alternatively, the solvent may be partially dried on a belt conveyor or the like and then introduced into a coagulation bath.

The solvent used for the coagulation bath is miscible with the solvent of the polyvinyl alcohol resin, and includes, for example, alcohols such as methanol, ethanol, propanol and butanol, acetone, benzene and toluene. As a method for obtaining a polyvinyl alcohol-based raw film, a so-called gel film forming method in which a solution of a polyvinyl alcohol-based resin is introduced into a coagulation bath to form a film, or the like, can also be performed.

The film thickness of the raw film is 30 to
The thickness is preferably 100 μm, more preferably 50 to 90 μm, and if it is less than 30 μm, stretching becomes difficult. The polyvinyl alcohol-based raw (unstretched) film obtained as described above is then subjected to dyeing, stretching, treatment with a boron compound, and the like. Is characterized by being dyed after being subjected to biaxial stretching, and characterized in that the product of the stretching ratio in the longitudinal direction and the stretching ratio in the transverse direction during the biaxial stretching is 3-8. Now, such a method will be specifically described.

The stretching in the dry method is not particularly limited, and a method of passing the raw film through a pair of heating rolls for compression and stretching, a heating roll driven while applying backward tension to the raw film. And a method of stretching the film by contacting the film. The temperature (heating roll) at the time of the stretching is preferably 100 to 175 ° C, and more preferably 1 to 175 ° C.
When the temperature is lower than 100 ° C., uniform stretching is difficult. On the other hand, when the temperature is higher than 175 ° C., the dyeability in the subsequent dyeing step is undesirably reduced. In the present invention, the product of the longitudinal stretching ratio and the transverse stretching ratio during such biaxial stretching needs to be 3 to 8 (further 4 to 6 times), and the product of the stretching ratio is 3 times. If it is less than 10, sufficient film strength cannot be obtained, and conversely, the optical properties are reduced by more than 8 times, and the object of the present invention cannot be achieved.

[0011] The dry-stretched polyvinyl alcohol-based film is then dyed, but it is preferable that the film is brought into contact with water in a state where stretching is maintained before dyeing. Thereafter, dyeing is performed by bringing a liquid containing a polarizing element into contact with the film. Usually, an aqueous solution of iodine-potassium iodide is used. The concentration of iodine is 0.1 to 2 g / l, the concentration of potassium iodide is 10 to 50 g / l, and the weight ratio of iodine / potassium iodide is 20 to 100. Is appropriate. The dyeing time is practically about 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 50C. A small amount of an organic solvent compatible with water other than the water solvent may be contained. Arbitrary means such as immersion, coating, spraying and the like can be applied as the contact means.

[0012] The dyed film is then treated with a boron compound (aqueous solution). As the boron compound, boric acid and borax are practical. The boron compound is in the form of an aqueous solution or a water-organic solvent mixture, and the concentration of the boron compound aqueous solution (or mixture) at this time is 10 to 80.
It is preferably mol / l, and it is practically desirable to coexist a small amount of potassium iodide in the solution. The treatment method is preferably an immersion method, but of course, a coating method and a spraying method can also be performed. The temperature of the boron compound treatment is preferably 30 to 80C, more preferably 40 to 75C. The above boron compound treatment can be performed twice or more. By this treatment, a dyed and stretched polarizing film is obtained, but the total stretching ratio in the uniaxial direction is preferably 3 to 7 times,
More preferably, it is 4 to 7 times. If the total stretching ratio is less than 4 times, it is difficult to obtain satisfactory optical properties, and conversely, 7.
If it exceeds 0 times, the film is likely to be cut during stretching, which is not preferable.

Thus, the polarizing film of the present invention can be obtained. Usually, however, a water washing treatment is performed thereafter, and the water washing is preferably performed at a water temperature of 20 ° C. or lower. Preferably it is 0-10 degreeC. If the water temperature exceeds 20 ° C., it is necessary to extremely reduce the amount of water for washing, which is not preferable because the removal of foreign substances is incomplete. The processing time of the washing process is 1
5 minutes or less, preferably 10 to 120 seconds is appropriate.
After washing with water, if necessary, at 30 to 120 ° C, 0.5 to 1
A drying process is performed for 0 minutes.

The polarizing film of the present invention thus obtained includes conventionally known cellulose acetate-based films (cellulose diacetate film, cellulose triacetate film and the like) having excellent optical transparency and mechanical strength on both sides or one side thereof, An acrylic film, a polyester film, a polyolefin film, a polycarbonate film, a polyetheretherketo film, a protective film such as a polysulfone film can be used as a polarizing plate by pasting together, but in the present invention, It is also useful to provide a urethane resin layer on at least one surface of the obtained polarizing film to form a polarizing plate, and such a polarizing plate will be described.

The urethane resin layer provided on at least one side of the polarizing film of the present invention has a storage elastic modulus at 70 ° C. of 5 × 10 ⁹ dyn / cm ² or more (furthermore, 10 × 10 ⁹ dyn / cm ² or more).
10 ^{9 to} 500 × 10 ⁹ dyn / cm ² , especially 10 × 10 ⁹ dyn / cm ²
１００100 × 10 ⁹ dyn / cm ² ) is preferred, and the storage elastic modulus is 5 × 10 ⁹ dyn / c.
If it is less than m ² , deformation due to heat shrinkage of the polarizing film cannot be controlled, which is not preferable. The storage elastic modulus referred to here is 1
It means the measured value of the real part of the complex elastic modulus measured when a vibration of 0 Hz is given, and specifically, it is measured by a viscoelasticity measuring device (for example, DVE-V4 FT Rheospectra, manufactured by RHEOLOGY) or the like. In the actual measurement, a single layer of a cured urethane resin layer formed on the surface of a peeled PET film or the like was used.
What is necessary is just to measure in an atmosphere of ° C.

In the present invention, it is only necessary that a urethane resin layer satisfying the above storage modulus is formed on at least one side of the polarizing film. A compound (A) having two or more isocyanate groups in the molecule and a compound (B) having active hydrogen that reacts with the isocyanate group in one molecule
And a urethane resin layer formed by applying a urethane prepolymer (C) obtained by reacting the compound (A) with the compound (A) having two or more isocyanate groups in the molecule.
As aliphatic diisocyanates such as ethylene diisocyanate, 1,4-butane diisocyanate, and 1,6-hexane diisocyanate; alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and methylcyclohexane diisocyanate; 6-tolylene diisocyanate, methylene diphenyl diisocyanate,
Aromatic diisocyanates such as diphenylmethane-4,4 diisocyanate and m-xylylene diisocyanate; aromatic triisocyanates such as triphenylmethane triisocyanate;
As the compound (B) having an active hydrogen that reacts with an isocyanate group in the molecule, mono-di- or tri-ethylene-
Or -propylene-glycol, 1,4-butanediol, 2,2-bis- (4-hydroxyhexyl)
Diols such as propane, or triols such as glycerin, hexanetriol, trimethylolpropane, trimethylolethane, and trimethylolbenzene; copolymerization of adipic acid, succinic acid, phthalic acid, terephthalic acid, acrylic acid, and maleic acid Polyester polyol which is a condensation product of a polycarboxylic acid such as a product and the polyol; glyceride ester of castor oil or other hydroxylated fatty acid; polyethylene glycol;
Examples thereof include polyalkylene glycols such as polypropylene glycol.

The urethane prepolymer (C) can be obtained by reacting the compound (A) with the compound (B), and the ratio of the isocyanate group to the active hydrogen (hydroxyl group) is 1.5 / 1. The content is more preferably 2/1 or more, and finally the content of free isocyanate groups in the urethane prepolymer (C) is preferably 3% by weight or more, and more preferably 7 to 30% by weight. Preferably, the free isocyanate group causes a crosslinking reaction via moisture in the polarizing film, moisture in the air, or warm water to form a strong protective film. If the amount of the free isocyanate group is too small, the adhesiveness between the urethane resin layer and the polarizing film tends to decrease, which is not preferable.

Thus, the urethane prepolymer (C) is a solvent which does not inhibit the polarizing property of the polarizing film, for example, ethyl acetate, butyl acetate, cellosolve acetate, methyl glycol acetate, ethylene glycol acetate,
Diluted to a desired viscosity with methoxybutyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylene chloride, toluene, xylene, mineral spirit, cresol, xylenol, furfural, naphtha, etc., to become a urethane prepolymer coating liquid (D), It is coated on at least one side of the polarizing film, and it is preferable to add a catalyst to the coating solution (D). Examples of such a catalyst include triethylamine, triethylenediamine, N, N, N ′, N ′,
N ″ -pentadiethyltriamine, N, N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N, N, N ′, N′-tetramethylpropylenediamine, N, N, N ′, N′-tetramethylhexamethylene Amine catalysts such as diamine, N-ethylmorpholine, N-methylmorpholine, N, N-dimethylethanolamine, N, N-diethylethanolamine, and 1,8-diazabicyclo [5,4,0] undecene-7 (DBU )
And its salts or metal catalysts such as stannas octoate and dibutyltin dilaurate. Triethylamine, DBU, and dibutyltin dilaurate are preferably used, and the amount of the urethane prepolymer (C) 100
Parts to 0.01 to 10 parts, more preferably 0.1 to 10 parts.
~ 5 parts are preferred. If the amount is too small, the curing rate will decrease. Conversely, if the amount is too large, the coating solution will gel, which is not preferable.

In the present invention, it is preferable that the urethane prepolymer coating solution (D) is applied and then dipped in water at 40 to 90 ° C. to form a urethane resin layer.
By such a treatment, a suitable urethane resin layer can be easily obtained. If the temperature is lower than 40 ° C., it is difficult to obtain a sufficient cured film because the curing speed is reduced, and conversely, 90 ° C.
If the temperature exceeds the limit, the polarizing film is deformed during the curing treatment, which is not preferable, and the temperature is preferably 50 to 70 ° C. Such a dipping treatment may be performed using a constant temperature water bath or the like.

In the present invention, in addition to the method for forming the urethane resin layer as described above, after the urethane prepolymer (C) is applied, the urethane prepolymer is applied at a temperature of 40 to 90 ° C. and 50 ° C.
% RH or more is preferable. If the temperature is lower than 40 ° C., the curing (forming) speed is reduced, and it is difficult to obtain a sufficient cured film. If the polarizing film is deformed and the humidity is less than 50% RH, the curing does not proceed sufficiently and a good urethane film cannot be obtained, which is not preferable. The temperature condition is more preferably in the range of 50 to 85 ° C., especially 55 to 85 ° C. -80 ° C is preferable, and a more preferable range of the humidity condition is 70% RH or more. In addition, it is preferable that the curing treatment time is as short as possible from the viewpoint of productivity. If the time is too long, the productivity decreases, which is not preferable. Such a curing treatment may be performed using a device such as a thermo-hygrostat or a humidifier.

In the present invention, in any of the above forming methods, the solvent in the urethane polymer coating layer is volatilized after the application of the urethane polymer coating liquid (D) and before the formation (curing) treatment. A drying treatment may be performed for the purpose. The drying temperature at this time depends on the type of the solvent, but is 40 to 90 ° C, preferably 50 to 70 ° C.
If the temperature is lower than 40 ° C., it takes a long time to dry. If the temperature is higher than 90 ° C., the polarizing film is undesirably deformed.
Thus, although the polarizing plate of the present invention is obtained, the thickness (after drying) of the formed urethane resin layer is 0.5
It is preferably from 100 to 100 µm, more preferably from 5 to 80 µm, particularly preferably from 10 to 60 µm. The urethane resin layer may be formed on one side of the polarizing film, or may be formed on both sides. As compared with a conventional polarizing plate having a cellulose triacetate-based protective film, a thin polarizing plate having high durability and polarizing properties can be obtained.

The polarizing plate of the present invention may be provided with a transparent pressure-sensitive adhesive layer on its surface, if necessary, by a generally known method, and may be put to practical use. As the pressure-sensitive adhesive layer, 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, methacrylic acid, Especially those mainly composed of copolymers with crotonic acid (including those to which vinyl monomers such as acrylonitrile, vinyl acetate and styrene are added) do not hinder the polarizing properties of the polarizing film, and Preferred, but
The present invention is not limited to this, and any transparent adhesive can be used. For example, a polyvinyl ether-based or rubber-based adhesive may be used.

Further, it is also possible to provide various functional layers on one surface of the polarizing plate (the surface on which the above-mentioned adhesive is not provided). Examples of the functional layers include an anti-glare layer, a hard coat layer, an anti-reflection layer, and the like. Examples include a half-reflection layer, a reflection layer, a luminous layer, an electroluminescence layer, and the like. Further, a combination of two or more kinds can be used. For example, an anti-glare layer and an anti-reflection layer, a luminous layer and a reflection layer, a luminous layer and a half Examples include a combination of a reflection layer, a light storage layer and a light diffusion layer, a light storage layer and an electroluminescence layer, and 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 plate of the present invention, or by providing the above-mentioned various functional layers in various combinations on the polarizing plate, it is possible to obtain an optical laminate having more excellent various functions. It is.

The polarizing film and the polarizing plate of the present invention are excellent in optical properties, further excellent in workability, and can be laminated with various functional layers, so that the functions of various functional layers can be sufficiently exhibited. Liquid crystal display devices such as electronic desk calculators, electronic watches, word processors, instruments for automobiles and machinery, sunglasses, eye-resistant glasses, stereo glasses, reflection-reducing layers for display elements (CRT, LCD, etc.), medical equipment, building materials, It is used for toys and the like, and is particularly useful for liquid crystal display devices such as instruments for automobiles and machinery.

[0026]

Next, the present invention will be described in more detail by way of examples. In the examples, “%” is based on weight unless otherwise specified. Example 1 A polyvinyl alcohol resin having an average polymerization degree of 1700 and a saponification degree of 99.5 mol% was dissolved in water to obtain a 10% solution. The solution was cast on a polyethylene terephthalate film and dried to obtain a raw film (thickness: 70 μm). The film was mounted on a biaxial stretching machine, and was subjected to dry stretching (times of 4) in the longitudinal direction by fixing it in the transverse (width) direction (1x) in an atmosphere at 130 ° C. Next, the obtained stretched film was immersed in a water bath at 20 ° C. for 5 minutes while maintaining the tension (stretching), and then further lowered to 20 ° C. in an aqueous solution comprising 0.2 g / l of iodine and 30 g / l of potassium iodide. After dyeing by dipping for 5 minutes, it is further dipped in a boric acid aqueous solution tank (temperature 55 ° C.) composed of boric acid 60 g / l and potassium iodide 40 g / l for 5 minutes to carry out the treatment of the boron compound. After that, the film was rinsed with pure water at 10 ° C. for 15 seconds, and then dried at 80 ° C. for 2 minutes to obtain a polarizing film of the present invention (single transmittance: 40.55%, degree of polarization: 99.78%, dichroic ratio) 3
3) was obtained.

Separately, a urethane prepolymer (C) comprising (A) component: 2,4-tolylene diisocyanate (80%), 2,6-tolylene diisocyanate (20%) and (B) component: trimethylolpropane 100 parts of a 75% ethyl acetate solution ("Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate group / hydroxyl group # 3, free isocyanate group content: 13%) was added with 1.5 parts of triethylamine, and a urethane prepolymer coating solution was added. (D)
I got After applying the urethane prepolymer coating solution (D) on both sides of the polarizing film, the coating is dried at 55 ° C. for 3 minutes, treated at 50 ° C. and 90% RH for 10 minutes, and further heated at 60 ° C. in warm water at 10 ° C. After immersion for 30 minutes, a urethane resin layer of 30 μm was formed on both surfaces of the polarizing film to obtain a polarizing plate of the present invention. Further, a urethane resin layer (single layer) was prepared under the same conditions as above, and a viscoelasticity measuring device (manufactured by Rheology, D
(VE-V4 FT Rheospectra), a vibration of 10 Hz was given, and the storage elastic modulus at 70 ° C. was measured to be 35 × 10 ⁹ dyn / cm ² . The following evaluation was performed using the obtained polarizing plate.

(Polarization Characteristics) The single transmittance (%) and the degree of polarization (%) of the obtained polarizing plate were measured using a high-speed multi-wavelength birefringence measuring apparatus (“RETS2000” manufactured by Otsuka Electronics Co., Ltd.). 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. (Adhesion) It was carried out according to a cross-cut test of JIS K 5400. On the surface (urethane resin layer) of the obtained polarizing plate, 100 cells / cm ² were made, and a cellophane tape was stuck from above and sufficiently pressed, and then the cellophane tape was peeled off at a stretch and remained on the polarizing film. The number of squares in the urethane resin layer was examined.

(Durability) The obtained polarizing plate was 150 mm ×
Two pieces punched out in a size of 200 mm so that the light absorption axis is in the 45 ° direction, and 150 mm × 200 mm
2 optical glass plates (1.2 mm thick) each having the size described above were prepared, and two laminate samples were prepared by attaching a polarizing plate to the glass plate via a pressure-sensitive adhesive. The samples are overlapped with each other via liquid paraffin so that their light absorption axes are orthogonal to each other, and the transmittance (%) of the vertical ray (460 nm) is measured using a high-speed multi-wavelength birefringence measuring device (“RETS2000” manufactured by Otsuka Electronics Co., Ltd.). (Initial). The measurement points at this time were two points at the center and the end of the laminate sample, and the end was an average value of two portions 5 mm from the end at the center of the long side of the laminate sample. Further, each of the two laminate samples was subjected to 500 ° C at 70 ° C.
After standing for a period of time, they were superposed in the same manner as described above, and the light transmittance (%) in the vertical direction (460 nm) was measured (after endurance). (Visibility) After the laminate sample left at 70 ° C. for 500 hours, liquid paraffin was placed on both sides of a liquid crystal display device (10.4 inches, TFT type, number of pixels VAG) such that the light absorption axes were perpendicular to each other. A liquid crystal display device was prepared by superimposing the liquid crystal display devices through the above, and the visibility of the liquid crystal display element when the liquid crystal display device was viewed from above, below, left and right was evaluated by a panel of 10 persons as follows. ○ −−− 7 or more judged good visibility × −−− 6 or less judged good visibility

(Punching property) The obtained polarizing plate was 100 m
It was punched out by a punch (manufactured by Dumbbell Co., Ltd.) so that the light absorption axis was in the direction of 45 ° in a size of mx 100 mm, the end was observed with an optical microscope, and evaluated as follows. ○ −−− Crack length is less than 0.05 mm × −−− Crack length is 0.05 mm or more (flexibility) The light transmission axis of the obtained polarizing plate is defined as a long piece.
According to the bending resistance test of IS K 5400, a mandrel having a diameter of 2 mm was evaluated as follows. ○ −−− No abnormality × −−− Cracking and peeling occurred on the polarizing plate

Example 2 In Example 1, biaxial stretching was performed in an atmosphere at 140 ° C., and the stretching ratio was set to 5 times in length and 1 time in width (product of the ratio was 5).
Further, the treatment conditions after applying and drying the urethane prepolymer coating liquid (D) were the same except that the coating was left at 40 ° C. and 90% RH for 20 minutes and then immersed in 80 ° C. warm water for 10 minutes. Single transmittance 41.04%, degree of polarization 99.79
%, A polarizing film having a two-color ratio of 35 was obtained and evaluated in the same manner. Further, a urethane resin layer (single layer) was prepared under the same conditions as above, and the storage modulus at 70 ° C. was measured in the same manner. As a result, it was 32 × 10 ⁹ dyn / cm ² .

Example 3 In Example 1, the stretching ratio at the time of biaxial stretching was set to 4 times in length and 1.5 times in width (the product of the ratio was 6), and a urethane prepolymer coating solution (D) was further applied and dried. The subsequent processing conditions are 70
C., 90% RH for 10 minutes, and then immersed in warm water at 50.degree. C. for 10 minutes. The same procedure was carried out to obtain a single transmittance of 39.084%, a degree of polarization of 99.62%, and a dichroic ratio of 26. A polarizing film was obtained and evaluated similarly. Further, a urethane resin layer (single layer) was prepared under the same conditions as above, and similarly,
When the storage modulus at 70 ° C. was measured, 32 × 1
It was ⁹ dyn / cm ² .

Example 4 In Example 1, biaxial stretching was performed in an atmosphere at 150 ° C., and the stretching ratio was set to 4 times in length and 2 times in width (the product of the ratio was 8).
Furthermore, urethane prepolymer ("Coronate HL" manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate group / hydroxyl group # 3,
(Free isocyanate group content: 13%) Except that the coating solution (D) was applied and dried after being left at 60 ° C. and 90% RH for 10 minutes and then immersed in 60 ° C. warm water for 10 minutes. In the same manner, a polarizing film having a single transmittance of 36.55%, a degree of polarization of 99.74%, and a dichroic ratio of 22 was obtained, and similarly evaluated. Further, a urethane resin layer (single layer) was prepared under the same conditions as above, and the storage modulus at 70 ° C. was measured in the same manner. As a result, it was 10 × 10 ⁹ dyn / cm ² .

Example 5 In Example 1, biaxial stretching was performed in an atmosphere of 120 ° C., and the stretching ratio was set to 4 times in length and 0.8 times in width (the product of the ratio was 3.2). The solution (D) was applied in the same manner as above except that the solution (D) was applied and dried at 60 ° C. and 90% RH for 10 minutes and then immersed in warm water at 60 ° C. for 10 minutes. 63%, degree of polarization 9
9.82%, a polarizing film having a two-color ratio of 35 was obtained and evaluated in the same manner. Further, a urethane resin layer (single layer) was prepared under the same conditions as above, and the storage modulus at 70 ° C. was measured in the same manner. As a result, it was 35 × 10 ⁹ dyn / cm ² .

Comparative Example 1 A polarizing film (transmittance: 39.86%, degree of polarization: 99.82%) was prepared in the same manner as in Example 1 except that stretching was performed in water at 20 ° C. instead of dry stretching. , Two-color ratio: 3
2) was obtained and evaluated similarly.

Comparative Example 2 In Example 1, the stretching ratio in the longitudinal direction during dry stretching was 4
And a polarizing film (transmittance: 37.times.).
55%, degree of polarization: 99.75%, dichroic ratio: 24) were obtained and evaluated in the same manner.

Comparative Example 3 In Example 1, the stretching ratio in the transverse (width) direction in dry stretching was set to 2.5 times and the stretching ratio in the longitudinal direction was set to 4 times (the product of the ratio was 10). The same procedure was performed to obtain a polarizing film (transmittance: 15.12%, degree of polarization: 98.48%, dichroic ratio: 5), which was similarly evaluated. Tables 1 to 3 show the evaluation results of the examples and comparative examples.

[0038]

[Table 1] Adhesion of polarization characteristics * Single transmittance (%) Degree of polarization (%) Example 1 40.55 99.78 100/100 {2 41.04 99.79 100/100} 3 39.08 99. 62 100/100 〃 4 36.55 99.74 100/100 〃 5 40.63 99.82 100/100 Comparative example 1 39.86 99.82 50/100 〃 2 37.55 99.75 100/100 〃 3 15.12 98.48 100/100 * The indicated value of adhesion indicates the number of cells / the number of cells in the remaining urethane resin layer.

[0039]

[Table 2] Durability * Initial visibility (%) After durability (%) Example 1 0.07 / 0.07 0.10 / 0.52 〃 2 0.07 / 0.07 0.10 / 0 .57 ○ ３ 3 0.11 / 0.11 0.15 / 0.57 ○ ４ 4 0.07 / 0.07 0.10 / 0.57 ○ 〃 5 0.07 / 0.07 0.10 / 0.52 ○ Comparative Example 1 0.07 / 0.07 0.35 / 2.33 × 〃 2 0.07 / 0.07 0.01 / 0.52 ○ 〃 3 0.79 / 0.79 15 / 2.25 × * The indicated value of durability represents the median / end value.

[0040]

[Table 3]

[0041]

The polarizing film and the polarizing plate of the present invention are excellent in optical properties such as transmittance, degree of polarization and dichroic ratio, and excellent in workability such as punching property and flexibility, and further, various functions. Even if the layers are stacked, their functions can be fully exhibited, and liquid crystal display devices such as electronic desk calculators, electronic watches, word processors, instruments for automobiles and machinery, sunglasses, eye-resistant glasses, stereo glasses, and display elements It is used for a reflection reduction layer for (CRT, LCD, etc.), etc., and is particularly useful for liquid crystal display devices such as instruments for automobiles and machinery.

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁶ Identification symbol FI B29L 11:00 C08L 29:04 (72) Inventor Michiko Yamabe 2-13-1, Muroyama, Ibaraki-shi, Osaka Nippon Gosei Chemical Industry Co., Ltd. Central Research Laboratory

Claims (7)

[Claims] 1. A polarizing film obtained by biaxially stretching a polyvinyl alcohol-based film in a dry manner and then dyeing the product, wherein the product of the longitudinal stretching ratio and the transverse stretching ratio during the biaxial stretching is defined as: A polarizing film having a thickness of 3 to 8. 2. The polarizing film according to claim 1, wherein the temperature at the time of biaxial stretching is 100 to 170 ° C. 3. A polarizing plate comprising the polarizing film according to claim 1 and a urethane resin layer laminated on at least one surface. 4. The polarizing plate according to claim 3, wherein the urethane resin layer has a storage elastic modulus at 70 ° C. of 5 × 10 ⁹ dyn / cm ² or more. 5. A compound (A) in which a urethane resin layer has two or more isocyanate groups in a molecule and a compound (B) having active hydrogen which reacts with an isocyanate group in one molecule
And a urethane prepolymer (C) obtained by reacting the above with a resin.
The polarizing plate of the above. 6. The polarizing plate according to claim 5, wherein the urethane resin layer is formed by applying a urethane prepolymer (C) and then immersing the urethane resin layer in water at 40 to 90 ° C. 7. The urethane resin layer is coated at a temperature of 20 to 90 ° C.
The polarizing plate according to claim 5, wherein the polarizing plate is processed under a condition of not less than% RH.