KR20050033805A - The method for producing apolarizing film, the method for producing a polarizer, and the method for producing optical laminate - Google Patents

Abstract

A method of producing a polarizing film, a method of producing a polarizer, and a method of producing an optical laminate are provided to reduce color spots by forming uniformly a state of a film before a dyeing treatment. A method for producing a polarizing film includes a swelling treatment, a dyeing treatment, and a boric acid treatment for a polyvinyl alcohol-based film which are sequentially performed within a chamber. The polarizing film is obtained by drawing the polyvinyl alcohol-based film from one of the swelling treatment, the dyeing treatment, and the boric acid treatment for the polyvinyl alcohol-based film. One or more wet-drawing processes are performed before the dyeing treatment after the swelling treatment. The wet-drawing processes are performed in a drawing rate of 1.1 to 3 times within an aqueous solution including boric acid of 0.01 to 2.0 weight percent in water of 100 weight percent.

Description

The manufacturing method of a polarizing film, the manufacturing method of a polarizing plate, and the manufacturing method of an optical laminated body {THE METHOD FOR PRODUCING APOLARIZING FILM, THE METHOD FOR PRODUCING A POLARIZER, AND THE METHOD FOR PRODUCING OPTICAL LAMINATE}

This invention is a manufacturing method of a polarizing film with few color unevenness, the manufacturing method of the polarizing plate which laminated | stacked the protective film on at least one surface of this polarizing film, and also any one of retardation film, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflective film is independent. The present invention relates to a method for producing an optical laminate, which is laminated in a plurality or in a plurality.

As a polarizing film, what adsorbed and oriented the dichroic dye to the polyvinyl alcohol-type film is used conventionally. That is, the iodine type polarizing film which uses iodine as a dichroic dye, the dye type polarizing film which uses a dichroic dye as a dichroic dye, etc. are known. These polarizing films are laminated | stacked at least one protective film, such as triacetyl cellulose, on an at least one surface, Preferably the adhesive which consists of aqueous solution of polyvinyl alcohol-type resin on both surfaces becomes a polarizing plate.

As a method for producing a polarizing film, for example, Patent Document 1 discloses a polyvinyl alcohol-based film swelled in water, followed by swelling, dyeing with the dichroic dye, stretching it, and subsequently, polyvinyl in order to fix iodine to the film. A method of boric acid treatment (that is, water resistance treatment by crosslinking) of an alcohol-based film, washing with water, and then drying is described. Swelling is performed for the purpose of uniformly swelling the film prior to dyeing, shortening the dyeing time, improving the dyeing stain, and the like. Under the present circumstances, boric acid is contained in the swelling processing tank in patent document 1 from a viewpoint of dyeing | staining stains. And in patent document 1, after dyeing, a film is immersed in the process solution containing boric acid, and is extended | stretched.

Moreover, in patent document 2, in order to fully swell a film, chloride, such as lithium chloride and zinc chloride, is added to a swelling processing tank.

In Patent Documents 1 and 2, when there is a problem in the swelling treatment tank due to the accumulation of plasticizers (glycerine, etc.) eluted from the film, chemicals such as boric acid and chlorides are also discarded when the liquid in the swelling treatment tank is discarded. There is a problem in that. In addition, as in the documents of Patent Documents 1 and 2, the method of adding chemicals such as boric acid and chlorides to the swelling treatment tank cannot be said to be sufficient for the improvement of staining.

On the other hand, Example 2 of patent document 3 describes swelling by dipping a polyvinyl alcohol-based film in water, stretching in a drawing bath containing boric acid, and subsequently dyeing. However, since the draw ratio of patent document 3 is three times or more large and it extends by 5.5 times in Example 2, it was not enough for improvement of dyeing | staining stain.

Patent document 4 describes that the polyvinyl alcohol-based film is stretched while swelling by immersing the polyvinyl alcohol-based film in a water tank in order to reduce staining. However, even the method of patent document 4 which extends | stretches simultaneously with swelling was not enough for improvement of dyeing stain.

Patent document 5 describes uniaxially stretching and dyeing in water after immersion in water. In this way, color blotches were improved, but not enough.

[Patent Document 1] Japanese Patent Application Laid-Open No. 10-153709

[Patent Document 2] Japanese Patent Application Laid-Open No. 06-281816

[Patent Document 3] Japanese Patent Application Laid-Open No. 6-265727, Example 2

[Patent Document 4] Japanese Patent Application Laid-Open No. 2001-141926

[Patent Document 5] Japanese Patent Application Laid-Open No. 4-351640

This invention makes it a subject to provide the manufacturing method of a polarizing film with few color unevenness, the manufacturing method of a polarizing plate, and the manufacturing method of an optical laminated body.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to solve the said subject, As a result, in the process of manufacturing a polarizing film by processing a polyvinyl alcohol-type film in order of a swelling process, a dyeing process, and a boric acid process, swelling process and dyeing In the process, the present invention finds a new fact that a polarizing film with less color unevenness can be obtained when a wet stretching step is provided to uniformize the film state and uniaxially stretched at a predetermined draw ratio in an aqueous solution containing boric acid at a predetermined concentration. To complete.

The method for producing a polarizing film of the present invention is a polarizing film obtained by uniaxially stretching in at least one of these processing steps to obtain a polarizing film while continuously treating a polyalcohol-based film in a swelling treatment, a dyeing treatment, and a boric acid treatment. As a manufacturing method, one or more wet stretching processes are provided before the dyeing treatment after the swelling treatment, and in the stretching process, the film is 1.1 times or more and less than 3 times in an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid based on 100 parts by weight of water. It is characterized by uniaxial stretching at a draw ratio of.

It is preferable that the temperature of the process solution used at the said wet extending process is 10 degreeC-40 degreeC.

Moreover, the manufacturing method of this invention polarizing plate is characterized by laminating | stacking a protective film on at least one surface of the said polarizing film. It is preferable that this protective film is equipped with the function of any one of retardation film, a brightness improving film, a viewing angle improvement film, and a transflective film. Or an optical laminated body can be manufactured by laminating | stacking 1 or more types chosen from a phase difference plate, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflecting plate to the said polarizing plate which laminated | stacked the protective film on at least one surface.

According to the present invention, prior to the dyeing treatment, the polyvinyl alcohol-based film is uniaxially stretched at a draw ratio of at least 1.1 times and less than 3 times in an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid based on 100 parts by weight of water before the dyeing treatment after the swelling treatment. Since the state of a film becomes uniform, there exists an effect that dyeing without a stain is possible and a polarizing film with few color unevenness can be obtained.

As for the polyvinyl alcohol-type resin which forms the polyvinyl alcohol-type film in this invention, what saponified polyvinyl acetate type resin is illustrated normally. As saponification degree, it is 85 mol% or more, Preferably it is 90 mol% or more, More preferably, it is 99 mol%-100 mol%. As polyvinyl acetate type resin, the copolymer of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate, for example, an ethylene vinyl acetate copolymer, etc. are mentioned. As another monomer which can be copolymerized, unsaturated carboxylic acid, olefins, vinyl ether, unsaturated sulfonic acid, etc. are mentioned, for example. As polymerization degree of polyvinyl alcohol-type resin, it is 1000-10000, Preferably it is about 1500-5000.

These polyvinyl alcohol-based resins may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes can also be used. Usually, as a starting material of polarizing film manufacture, the unstretched film of the polyvinyl alcohol-type resin film whose thickness is 20 micrometers-100 micrometers, Preferably 30 micrometers-80 micrometers is used. Industrially, the width of the film is practically 1500 mm to 4000 mm.

The thickness of the polyvinyl alcohol polarizing film obtained by swelling, extending | stretching, dyeing | staining, boric acid treatment, water washing process, and finally drying this unstretched film is about 5-50 micrometers, for example.

The swelling step is performed for the purpose of removing foreign substances on the surface of the film, removing the plasticizer in the film, imparting reverse dyeing property in the next step, plasticizing the film and the like. The treatment conditions are within a range in which these objects can be achieved, and are determined in a range in which problems such as extreme dissolution of the base film, loss of transparency, and the like do not occur. The unstretched raw film is immersed in an aqueous solution of, for example, 10 ° C to 50 ° C, preferably 20 ° C to 40 ° C. Immersion time of a film is 30 second-300 second, More preferably, it is about 60 second-240 second.

In the swelling process, problems such as swelling of the film in the width direction and wrinkles of the film are likely to occur, so that an expander roll, a spiral roll, a crown roll, and a cross guider are used. It is preferable to convey the film while removing wrinkles of the film by a known width-expansion device such as a bend bar, tenter crip, or the like. In order to stabilize the conveyance of the film in the bath, the water flow is controlled by an underwater shower in the swelling tank, or an EPC device (Edge Position Control device: a device which detects the end of the film and prevents meandering of the film) may be used in combination. useful. In this process, since a film swells and expands also in the traveling direction of a film, in order to remove the looseness of the film of a conveyance direction, it is preferable to take means, such as controlling the speed of the conveyance roll before and behind a processing tank. In addition to the pure water, the swelling treatment tank used may include boric acid (described in Japanese Patent Application Laid-open No. Hei 10-153709), chloride (described in Japanese Patent Application Laid-open No. Hei 06-281816), an inorganic acid, an inorganic salt, a water-soluble organic solvent, and alcohols. An aqueous solution added in the range of 0.01% by weight to 10% by weight can also be used, but water is preferred for the reasons described above.

After the swelling treatment, the polyvinyl alcohol-based film is wet stretched. In this extending | stretching process, a film is uniaxially stretched by the draw ratio of 1.1 times or more and less than 3 times in the aqueous solution containing 0,01-2.0 weight part of boric acid with respect to 100 weight part of water. When the draw ratio in this wet drawing process is out of the said range, dyeing unevenness cannot be reduced, or the optical characteristic of a final polarizing film will become insufficient. In addition, the wet stretching step may be performed not only by one treatment solution but also continuously in a plurality of steps using a plurality of treatment solutions, but in such a case, the wet stretching step may be in the range of 1.1 to 3 times the integrated draw ratio.

As a stretching method, although the inter-roll stretching method which draws a difference to the circumferential speed of the nip roll prepared before and behind an immersion bath, and stretches a film is employ | adopted suitably, it is not limited to this, Various conventionally known stretching methods are employable. Do.

Although the treatment solution used in this wet drawing process is an aqueous solution containing 0.01-2.0 weight part of boric acid with respect to 100 weight part of water, there exists also an advantage that wrinkles are hard to produce by using such boric acid aqueous solution. Moreover, it is preferable that the temperature of the process solution used by a wet extending process is 10 degreeC-40 degreeC. If the temperature of the treatment solution is lower than 10 ° C, a large-scale cooling facility is required for temperature control, which is uneconomical. On the contrary, if the temperature exceeds 40 ° C, the raw film may be dissolved.

After the stretching treatment, the membrane is dyed. Usually, the dyeing process by a dichroic dye is performed for the purpose of adsorbing and orienting a dichroic dye to a film. The treatment conditions are within a range in which these objects can be achieved, and are determined in a range in which problems such as extreme dissolution of the base film, loss of transparency, and the like do not occur. In the case of using iodine as a dichroic dye, for example, at a temperature of 10 ° C. to 45 ° C., preferably at 20 ° C. to 35 ° C., at a weight ratio of iodine / KI / water = 0.003 to 0.2 / 0.1 to 10/100 for 30 seconds. 600 seconds, Preferably it is 60 to 300 second immersion process. Instead of potassium iodide, other iodides such as zinc iodide may be used. In addition, you may use another iodide together with potassium iodide. In addition, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it differs from the following boric acid treatment in the point which contains iodine. If it contains 0.003 weight part or more of iodine with respect to 100 weight part of water, it can be considered a dyeing tank.

In the case of using a water-soluble dichroic dye as the dichroic dye, for example, at a temperature of 20 ° C to 80 ° C, preferably 30 ° C to 70 ° C, and at a weight ratio of dichroic dye / water = 0.01 to 0.1 / 100 for 30 seconds 600 seconds, Preferably it is 60 to 300 second immersion process. The aqueous solution of the dichroic dye to be used may have a dyeing assistant etc., For example, may contain inorganic salts, such as sodium sulfate, surfactant, etc. Dichroic dyes may be used alone or in combination of two or more dichroic dyes.

In addition, expander rolls, spiral rolls, crown rolls, cross guiders, bend bars and the like may be installed in the dye bath and / or in the bath entrance as in the swelling step.

Boric acid treatment after dyeing is performed by immersing the polyvinyl alcohol-type film dyed with dichroic dye in the aqueous solution containing about 1-10 weight part of boric acid with respect to 100 weight part of water. When the dichroic dye is iodine, it is preferable to contain about 1 to 30 parts by weight of iodide.

Examples of iodide include potassium iodide, zinc iodide, and the like. In addition, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

This boric acid treatment is performed for water resistance by crosslinking, color adjustment (preventing the turning of blue light, etc.). In the case of water resistance by crosslinking, a crosslinking agent, such as glyoxal and glytalaldehyde, can also be used as needed other than boric acid or like boric acid.

Moreover, the boric acid treatment for water resistance may be called by names, such as a water treatment process, a crosslinking process, and an immobilization process. In addition, the boric acid treatment for color adjustment may be referred to by names such as complementary color treatment and color tone treatment.

This boric acid treatment is performed by suitably changing the concentration of boric acid and iodide, and the temperature of a treatment tank according to the objective.

The boric acid treatment for water resistance and the boric acid treatment for color adjustment are not particularly distinguished, but are carried out under the following conditions.

When the disc film is swelled, dyed, or boric acid treated, when boric acid treatment is intended for water resistance by crosslinking, about 3 to 10 parts by weight of boric acid and about 1 to 20 parts by weight of iodide are used based on 100 parts by weight of water. It is normally performed at 50 degreeC-70 degreeC, Preferably it is 55 degreeC-65 degreeC using the boric acid treatment tank containing a weight part. Immersion time is about 30 to 600 second normally, Preferably it is 60 to 420 second, More preferably, it is 90 to 300 second.

After the boric acid treatment for water resistance, the boric acid treatment for color adjustment may be performed. For example, when the dichroic dye is iodine, for this purpose, a boric acid treatment tank containing about 1 to 5 parts by weight of boric acid and about 3 to 30 parts by weight of iodide is usually used for 100 parts by weight of water. It is performed at the temperature of 45 degreeC-45 degreeC. Immersion time is about 3 to 300 second normally, Preferably it is 10 to 240 second.

Boric acid treatment for color adjustment is usually carried out at low boric acid concentration, high iodide concentration, and low temperature, as compared to boric acid treatment for water resistance.

These boric acid treatments may be carried out in a plurality of steps, but are usually carried out in two to five steps. In this case, the aqueous solution composition and temperature of each boric acid treatment tank to be used may be the same within the said range, and may differ. The boric acid treatment for water resistance and the boric acid treatment for color adjustment may be performed in a plurality of steps, respectively.

In the boric acid treatment step, the film may be stretched in the same manner as in the dyeing step. The final integrated draw ratio is about 4.5 to 7.0 times, preferably 5.0 to 6.5 times.

After the boric acid treatment, it is washed with water. For example, water washing treatment is performed by immersing the boric acid-treated polyvinyl alcohol-based film in water, spraying the water as a shower, or using immersion and spraying together for water resistance and / or color adjustment. The temperature of the water in a water washing process is about 2-40 degreeC normally, and it is good that immersion time is about 2 to 120 second. Drying after washing with water is performed in a drying furnace for about 60 to 600 seconds at a temperature of about 40 to 100 ° C.

In the present invention, in addition to the uniaxial stretching in the wet stretching step after the swelling treatment and before the dyeing treatment, uniaxial stretching is performed in at least one step between the swelling step and the boric acid treatment step. Although this uniaxial stretching may be performed by one process and may be performed by two or more processes, it is preferable to carry out by several processes.

As described above, the final integrated draw ratio is about 4.5 to 7.0 times, preferably 5.0 to 6.5 times.

Thus, a polarizing plate can be obtained by laminating | stacking a protective film with the adhesive agent on at least one surface of the produced polarizing film.

Examples of the protective film include films made of acetyl cellulose resins such as triacetyl cellulose and diacetyl cellulose, films made of polyester resins such as polyethylene terephthalate or polyethylene naphthalate, and polybutylene terephthalate, and polycarbonate resins. The film which consists of a film and cycloolefin resin which consists of these are mentioned. Examples of commercially available thermoplastic cycloolefin resins include "Topas" (trademark registration) sold by Ticona, Germany, and Arton (trademark registration) sold by JSR Co., Ltd. "Zeonor" (Zeonor) and "Zeonex" (all trademark registration) sold by Nihon Xeon (Zeon Corporation), "Apel" sold by Mitsui Kagaku Co., Ltd. (Apel (Trademark registration). Although what produced such cycloolefin resin by the film | membrane is made into a protective film, well-known methods, such as a solvent casting method and a melt extrusion method, are used suitably for film manufacture. Cycloolefin resin films produced from membranes are also commercially available, such as "Esshina" and "SCA40" sold by Sekisui Chemical Co., Ltd., for example.

Although it is preferable that the thickness of a protective film is thin, when too thin, intensity | strength will fall and it will be inferior to workability, while too thick will cause a problem, such as transparency falling and the curing time required after lamination | stacking becoming long. . Therefore, the suitable thickness of a protective film is about 5-200 micrometers, for example, Preferably it is 10-150 micrometers, More preferably, it is 20-100 micrometers.

In order to improve the adhesiveness between the adhesive agent and the polarizing film and / or the protective film, the polarizing film and / or the protective film is subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment and saponification treatment. You may also do it.

The protective film may be subjected to surface treatments such as anti-glare treatment, anti-reflection treatment, hard coat treatment, antistatic treatment and antifouling treatment alone or in combination. In addition, the protective film and / or protective film surface protective layer may have plasticizers, such as a ultraviolet absorber, such as a benzophenone type compound and a benzotriazole type compound, a phenyl phosphate type compound, and a phthalic acid ester compound.

Such a protective film may be laminated on one side of the polarizing film, or may be laminated on both sides.

A polarizing film and a protective film are laminated | stacked using adhesive agents, such as an aqueous solvent adhesive, an organic solvent adhesive, a hot melt adhesive, and a solvent-free adhesive. Examples of the aqueous solvent adhesive include polyvinyl alcohol-based resin aqueous solution, aqueous two-component urethane emulsion adhesive, and the like, and organic solvent-based adhesive, for example, two-component urethane adhesive and the like, and solvent-free adhesive, for example, one-component urethane adhesive and the like. Can be. When using the acetyl cellulose type film by which the adhesive surface with a polarizing film was hydrophilized by saponification etc. as a protective film, the polyvinyl alcohol-type resin aqueous solution is used suitably as an adhesive agent. In addition to the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, the polyvinyl alcohol-type resin used as an adhesive agent is a vinyl alcohol system obtained by saponifying the copolymer of vinyl acetate and the other monomer copolymerizable with this. Copolymers, and modified polyvinyl alcohol polymers obtained by partially modifying these hydroxyl groups. In such an adhesive, a polyhydric aldehyde, a water-soluble epoxy compound, a melamine-based compound, or the like may be used as an additive.

The method of laminating a polarizing film and a protective film is not specifically limited, For example, an adhesive agent is apply | coated uniformly to the surface of a polarizing film or a protective film, another film is laminated | stacked on an application surface, and it laminates | stacks with a roll etc., The method of drying, etc. are mentioned.

Usually, after preparation, an adhesive agent is apply | coated under the temperature of 15-40 degreeC, and lamination temperature is the range of about 15-30 degreeC normally. After lamination, a drying process is performed to remove a solvent such as water contained in the adhesive, but the drying temperature at this time is usually in the range of 30 to 85 ° C, preferably 40 to 80 ° C. Thereafter, in a temperature environment of 15 to 85 ° C., preferably 20 to 50 ° C., more preferably 35 to 45 ° C., the curing is usually performed for about 1 to 90 days, and the adhesive may be cured. If this curing period is long, productivity will worsen. Therefore, the curing period is about 1 to 30 days, preferably 1 to 7 days.

In this way, the polarizing plate by which the protective film was laminated | stacked on one side or both sides of a polarizing film can be obtained through an adhesive bond layer.

In the present invention, the protective film can be provided with optical functions such as a function as a retardation film, a function as a brightness enhancement film, a function as a reflective film, a function as a semi-transmissive reflective film, a function as a diffusion film, a function as an optical compensation film, and the like. . In this case, for example, by laminating an optically functional film such as a retardation film, a brightness enhancement film, a reflective film, a semi-transmissive reflective film, a diffusion film, an optical compensation film, and the like on the surface of the protective film, the protective film can be provided with such a function. This function can also be imparted to the film itself. Moreover, you may make a protective film itself a some function like the diffusion film which has a function of a brightness improving film.

For example, by performing the stretching treatment described in Patent No. 2841377, Patent No. 3094113, etc., or the treatment described in Patent No. 3168850, the protective film can be provided with a function as a retardation film. have. In addition, by forming micropores in the above-described protective film in the same manner as described in JP-A-2002-169025 or JP-A-2003-29030, two or more layers of cholesteric liquid crystals having different center wavelengths of selective reflection are also formed. By superimposing a layer, the function as a brightness improving film can be provided. By forming a metal thin film on said protective film by vapor deposition, sputtering, etc., the function as a reflective film or a semi-transmissive reflective film can be provided. By coating the resin solution containing microparticles | fine-particles on said protective film, the function as a diffusion film can be provided. Moreover, the function as an optical compensation film can be provided by coating and orienting liquid crystal compounds, such as a discotic liquid crystalline compound, to the said protective film. Moreover, a suitable adhesive agent is used and brand name; Brightness improvement films, such as DBEF (Three M Co., Ltd. product), brand names; Viewing angle improvement films, such as WV film (made by Fujishashin Film Co., Ltd.), and commercially available optical functional films, such as retardation film, such as Sumikalight (trademark registration) (Sumitomokagaku Kogyo Co., Ltd.) You may laminate directly on a polarizing film.

Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

The following example and a comparative example perform various processes, conveying the long film of polyvinyl alcohol by the continuous conveying apparatus which combined the nip roll and the free roll. Stretching was performed by attaching a circumferential speed difference to the driving nip rolls before and after the treatment tank.

Example 1

Immerse the polyvinyl alcohol film (Kurareviniron VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) of 75 μm thickness in pure water at 30 ° C for about 130 seconds while keeping the film free from tension. And the film was sufficiently swollen. After dehydrating with a nip roll, 1.2 times uniaxial stretching was performed in this tank, immersing for about 120 second in the immersion tank which put the 30 degreeC aqueous solution containing boric acid / water in the ratio of 0.1 / 100 weight ratio. Next, uniaxial stretching was performed while iodine / potassium iodide / water was immersed in an aqueous solution of 0.02 / 1.5 / 100 by weight ratio. Then, uniaxial stretching was performed until the integrated draw ratio from the master became 5.9 times while potassium iodide / boric acid / water was immersed in a 10/5/100 aqueous solution at 60 ° C. for about 180 seconds and water-resistant. Finally, after wash | cleaning for 10 second in 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the iodine type polarizing film. Triacetyl cellulose (hereinafter referred to as TAC) was laminated on both surfaces of this polarizing film to obtain a polarizing plate.

Example 2

Immerse the polyvinyl alcohol film (Kuraleviniron VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) with a thickness of 75 μm in 30 ° C pure water for about 130 seconds while maintaining the tension to prevent the film from loosening. The film was sufficiently swollen. After dehydrating with a nip roll, 2.0 times uniaxial stretching was performed in this tank, while immersing for about 120 second in the immersion tank which put the 30 degreeC aqueous solution containing boric acid / water in the ratio of 0.1 / 100 weight ratio. Next, uniaxial stretching was performed while iodine / potassium iodide / water was immersed in an aqueous solution of 0.02 / 1.5 / 100 by weight ratio. Then, uniaxial stretching was performed until the integrated draw ratio from the disk became 5.9 times while immersing and water-resistant in 60 degreeC for about 180 second in the aqueous solution which is potassium iodide / boric acid / water by weight ratio 10/5/100. Finally, after wash | cleaning for 10 second with 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the iodine type polarizing film. Subsequently, similarly to Example 1, TAC was laminated | stacked and it was set as the polarizing plate.

Comparative Example 1

Immerse the polyvinyl alcohol film (Kuraleviniron VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) with a thickness of 75 μm in 30 ° C pure water for about 130 seconds while maintaining the tension to prevent the film from loosening. The film was sufficiently swollen. After dehydrating with a nip roll, 1.2 times uniaxial stretching was performed in the said tank, immersing in a 30 degreeC pure water tank for about 120 second then ,. Next, uniaxial stretching was performed while iodine / potassium iodide / water was immersed in an aqueous solution of 0.02 / 1.5 / 100 by weight ratio. Subsequently, uniaxial stretching was performed until the integrated draw ratio from the master became 5.9 times while potassium iodide / boric acid / water was immersed in a 10/5/100 aqueous solution at 60 ° C. for about 180 seconds and water-resistant. Finally, after wash | cleaning for 10 second with 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the iodine type polarizing film. Next, TAC was laminated | stacked like Example 1 and it was set as the polarizing plate.

Comparative Example 2

Immerse the polyvinyl alcohol film (Kuraleviniron VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) with a thickness of 75 μm in 30 ° C pure water for about 130 seconds while maintaining the tension to prevent the film from loosening. The film was sufficiently swollen. After dehydrating with a nip roll, uniaxial stretching was performed, then immersing in the aqueous solution which is 0.02 / 1.5 / 100 by weight ratio. Thereafter, potassium iodide / boric acid / water was immersed in an aqueous solution having a weight ratio of 10/5/100 at 60 ° C. for about 180 seconds, and uniaxially stretched until the accumulated draw ratio from the master became 5.9 times while water-resistant. Finally, after wash | cleaning for 10 second in 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the iodine type polarizing film. Next, TAC was laminated | stacked like Example 1 and it was set as the polarizing plate.

Comparative Example 3

A 75 μm thick polyalcohol film (Kurareviniron VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) was immersed in pure water at 30 ° C. for about 130 seconds while maintaining tension to prevent the membrane from loosening. The membrane was swollen sufficiently. Next, 4.0 times uniaxial stretching was performed in this tank, while 30 degreeC boric acid / water was immersed for about 120 second in the immersion tank process containing the aqueous solution which is 0.1 / 100 by weight ratio. After dehydration with a nip roll, uniaxial stretching was performed while iodine / potassium iodide / water was immersed in an aqueous solution of 0.02 / 1.5 / 100 by weight ratio. Then, it immersed for about 180 second in 60 degreeC aqueous solution whose potassium iodide / boric acid / water in the weight ratio at 10/5 / 1OO, and uniaxially stretched until the integrated draw ratio from the disk became 5.9 times, while making it water-resistant. Finally, after wash | cleaning for 10 second in 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the iodine type polarizing film. Subsequently, similarly to Example 1, TAC was laminated | stacked and it was set as the polarizing plate.

The color unevenness of the polarizing plates obtained in Examples 1 and 2 and Comparative Examples 1-3 was observed in the dark room. That is, after arrange | positioning the obtained polarizing plate in the dark chamber with cross nicol, the color unevenness was observed visually on the 6,000 cd / m <2> Palite. And by visual observation, the magnitude | size of the color unevenness was judged by five steps of 1, 2, 3, 4, 5 by an operation | movement test. Evaluation 1 showed the least stain, and evaluation 5 showed the most stain. The results are shown in Table 1.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Evaluation results One One 2 4 4

From Table 1, in Example 1, 2, it turns out that the color unevenness of a film is reduced by providing a wet extending process between a swelling process and a dyeing process, and extending | stretching a film suitably in boric-acid containing aqueous solution.

According to the present invention, the dyeing treatment is performed by uniaxially stretching the polyvinyl alcohol-based film at a draw ratio of 1.1 times or more and less than 3 times in an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid with respect to 100 parts by weight of water before dyeing treatment. Prior to this, since the state of the film is uniform, dyeing without spots is possible, and there is an effect that a polarizing film with few color spots can be obtained.

Claims (5)

In the method for producing a polarizing film, the polyvinyl alcohol-based film is continuously treated in a bath in the order of swelling treatment, dyeing treatment and boric acid treatment, and further uniaxially stretched in at least one of these treatment steps to obtain a polarizing film. In the stretching step, at least one wet stretching step is provided before the dyeing treatment after the swelling treatment, and in the stretching step, the film is stretched 1.1 times or more and less than 3 times in an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid based on 100 parts by weight of water. It uniaxially stretches by magnification, The manufacturing method of the polarizing film characterized by the above-mentioned. The manufacturing method of the polarizing film of Claim 1 whose temperature of the solution used at the said wet extending process is 10 degreeC-40 degreeC. The protective film is laminated | stacked on at least one surface of the polarizing film obtained by the method of Claim 1 or 2, The manufacturing method of the polarizing plate characterized by the above-mentioned. The manufacturing method of the polarizing plate of Claim 3 with which the said protective film is equipped with the function of any one of retardation film, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflective film. The manufacturing method of the optical laminated body characterized by laminating | stacking 1 or more types chosen from retardation film, a brightness improving film, a viewing angle improvement film, and a transflective reflection film to the polarizing plate obtained by the method of Claim 3.