KR101137551B1 - A method for producing a polarizing film, a method for producing a polarizer, and a method for producing an optical laminate - Google Patents

Abstract

An object of the present invention is to provide a method for producing a polarizing film having a good surface state and less staining, a method for producing a polarizing plate using the polarizing film, and a method for producing an optical laminate.

A method of manufacturing a polarizing film which performs uniaxial stretching before and / or during a process of treating a polyvinyl alcohol-based film in the order of swelling treatment, dyeing treatment and boric acid treatment, wherein two or more dyeing baths are applied before the boric acid treatment process. At the same time, the dyeing is carried out in turn, and the last dyeing bath is characterized by containing boric acid.

Description

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

The present invention relates to a method for producing a polarizing film having a good surface state and less staining, a method for producing a polarizing plate using the polarizing film, and a method for producing an optical laminate.

As a polarizing film, what adsorbed and oriented a 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 usually a polarizing plate by adhering a protective film such as triacetyl cellulose on at least one surface thereof, preferably both surfaces thereof, through an adhesive made of an aqueous solution of polyvinyl alcohol-based resin.

As a method for producing a polarizing film, Japanese Patent Application Laid-Open No. 9-133809 discloses a polyvinyl alcohol-based film immersed in an iodine and potassium iodide aqueous solution, followed by boric acid treatment with stretching, washing with water, and then iodine and potassium iodide again. A method of immersion in an aqueous solution and drying is described.

Japanese Unexamined Patent Publication No. 60-66205 discloses a stretched film in an aqueous solution containing dichroic dye, and then another solution in an aqueous solution containing dichroic dye, followed by stretching in an aqueous solution of boric acid, followed by drying in two directions in the thickness direction. The method of manufacturing the polarizing film which provided the adsorption orientation layer is described.

Japanese Patent Application Laid-Open No. 62-70802 discloses that an oriented polyvinyl alcohol-based film is immersed in an aqueous solution of a specific dichroic dye (dye A), and then immersed in an aqueous solution of iodine and potassium iodide (dye B). A method of boric acid treatment, washing with water and producing a polarizing film is described.

In Examples of JP-238-23881A, a polyvinyl alcohol film is immersed and dyed in an aqueous solution containing iodine, potassium iodide, and boric acid, followed by uniaxial stretching, followed by boric acid treatment to produce a polarizing film. It is described.

However, in the methods of Japanese Patent Application Laid-Open No. 9-133809, Japanese Patent Laid-Open No. 60-66205, and Japanese Patent Laid-Open No. 62-70802 in which the dyeing treatment is performed twice, the surface state is bad. There is a problem that the reflection cannot be obtained and the appearance is bad. On the other hand, in the method of the Example of Unexamined-Japanese-Patent No. 3-23881 which dyes by the dye bath containing a boric acid, there exists a problem that there are many dye stains.

The main subject of this invention is providing the manufacturing method of the polarizing film with a good surface state and few staining, the manufacturing method of the polarizing plate using this polarizing film, and the manufacturing method of an optical laminated body.

The present inventors have diligently studied to solve the above problems, and as a result, when iodine dyes are sequentially performed in two or more dyeing baths before the boric acid treatment step, and boric acid is included in the last dyeing bath, the surface state is good. The new fact that a polarizing film with few dyeing stains can be obtained was discovered and the present invention was completed.

That is, the manufacturing method of the polarizing film which concerns on this invention manufactures the polarizing film which carries out uniaxial stretching before and / or before the process of processing a polyvinyl alcohol-type film in order of a swelling process, a dyeing process, and a boric acid process. The method is characterized in that two or more stages of dye baths are installed prior to the boric acid treatment step to perform dyeing in turn, and boric acid is contained in the last dye bath.

The boric acid concentration in the last dye bath is determined as follows. That is, the boric acid content in the last dyeing bath was a part by weight per 100 parts by weight of water, and the total draw ratio from the disc (unstretched film) of the polyvinyl alcohol-based film to the final dyeing bath was b. In this case, it is preferable that a and b are in a relationship that satisfies Equation 1 below.

b <-0.51 × a + 3.77

The boric acid content in the last dyeing bath is usually preferably about 0.05 to 2.0 parts by weight per 100 parts by weight of water. In addition, it is preferable that the temperature of the two or more dyeing baths is about 10 degreeC-40 degreeC.

The manufacturing method of the polarizing plate which concerns on this invention is characterized by adhering a protective film to at least one surface of the polarizing film obtained by said method. It is preferable that a protective film has a function of any 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 which concerns on this invention is characterized by sticking at least 1 sort (s) chosen from a retardation film, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflective film to the polarizing plate obtained by said method.

Hereinafter, the present invention will be described in detail.

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 about 85 mol% or more, Preferably it is about 90 mol% or more, More preferably, it is about 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 copolymerizable, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, etc. are mentioned, for example. As polymerization degree of polyvinyl alcohol-type resin, it is 1,000-10,000, Preferably it is about 1,500-5,000.                     

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 about 20 micrometers-100 micrometers, Preferably about 30-80 micrometers is used. Industrially, the width of the film is about 1,500 to 4,000 mm.

The unstretched film is treated in the order of swelling treatment, dyeing treatment, boric acid treatment, and water washing treatment, and finally, the thickness of the polyvinyl alcohol polarizing film obtained by drying is about 5 to 50 µm, for example.

Although the polarizing film of this invention is the polyvinyl alcohol-type uniaxial stretched film which adsorbed and oriented a dichroic dye, as a manufacturing method, there are two manufacturing methods largely divided. One is a method of monoaxially stretching a polyvinyl alcohol-based film in air or an inert gas, followed by solution treatment in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment, and finally drying. The second is a solution treatment of unstretched polyvinyl alcohol-based film with an aqueous solution in the order of swelling treatment, dyeing treatment, boric acid treatment and water washing treatment, and performing uniaxial stretching as wet in the boric acid treatment process and / or the preceding process, Finally, drying is the method.

In either method, uniaxial stretching may be performed in one step or may be performed in two or more steps, but is preferably performed in a plurality of steps. A stretching method can employ | adopt a well-known method, for example, the inter-roll stretching which performs extending | stretching by making a circumferential speed difference between two nip rolls conveying a film, the hot roll stretching method as described in Unexamined-Japanese-Patent No. 2731813, a tenter stretching method Etc. In addition, although the order of a process is basically the same as the above, there is no restriction | limiting in the number of process baths, process conditions, etc.

In addition, of course, it is also free to insert the process which is not described in the said process for a separate purpose. As an example of this step, after boric acid treatment, an immersion treatment (iodide treatment) with an aqueous solution of iodide not containing boric acid or an immersion treatment (zinc treatment) with an aqueous solution containing zinc chloride or the like which does not contain boric acid, etc. Can be mentioned.

The swelling process is performed for the purpose of removing foreign substances on the surface of the film, removing plasticizer in the film, imparting ease of dyeing in the next step, plasticizing the film, and the like. Treatment conditions are determined in the range which can achieve these objectives, and in the range which the problem of extreme dissolution, devitrification, etc. of a base film do not arise. When swelling the film previously stretched in gas, for example, the film is immersed in an aqueous solution of about 20 ° C to 70 ° C, preferably about 30 ° C to 60 ° C. Immersion time of a film is 30 to 300 second, More preferably, it is about 60 to 240 second. In the case of swelling the unstretched raw film from the beginning, the immersion time of the film performed by immersing the film in an aqueous solution of, for example, about 10 ° C to 50 ° C, preferably about 20 ° C to 40 ° C, is 30 to 300 seconds, more preferably. Crab is about 60-240 seconds.

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 cross-linked. It is preferable to convey the film while removing wrinkles of the film by a known widening device such as a guider, a bend bar, a tenter crip, or the like. In order to stabilize the conveyance of the film in the bath, the flow of water in the swelling bath is controlled by an underwater shower, 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 bath used may include boric acid (described in JP-A-10-153709), chloride (described in JP-A-6-281816), an inorganic acid, an inorganic salt, and a water-soluble organic solvent. And aqueous solutions in which alcohols and the like are added in an amount of 0.01% by weight to 10% by weight can also be used.

The dyeing treatment step is carried out for the purpose of adsorbing and orienting the dichroic dye on the film. Treatment conditions are determined in the range which can achieve these objectives, and in the range which the problem of extreme dissolution, devitrification, etc. of a base film do not arise. In the present invention, in particular, two or more stages of dyeing baths are provided to sequentially perform dyeing. Dyeing bath is suitable for 2 to 4 stages. At this time, the last dyeing bath contains boric acid. Each dye bath except the last dye bath is preferably free of boric acid. In each dye bath, it is preferable to perform the dyeing treatment while performing uniaxial stretching, but the dyeing treatment may be performed while maintaining the tension state.

When boric acid is added, it differs from the following boric acid treatment in the point which contains a dichroic dye. If it contains about 0.003 weight part or more of dichroic dyes with respect to 100 weight part of water, and temperature is about 40 degreeC or less, it can be considered as a dyeing tank.

In the case of using iodine as a dichroic dye, the concentration of each dyeing bath except the last dyeing bath is in a weight ratio of iodine / potassium iodide / water = about 0.003 to 0.2 / about 0.1 to 10/100, preferably about 0.01 to 0.1 / about 0.1 to 3.0 / 100. The concentration of the last dye bath is iodide / potassium iodide / boric acid / water = about 0.003 to 0.2 / about 0.1 to 10 / about 0.05 to 2.0 / 100, preferably about 0.01 to 0.1 / about 0.1 to 3.0 / about 0.1 to 1.5 / 100. The content of iodine may be the same as that of each dyeing bath, or the content may be reduced or increased in the order of dyeing treatment within the above range.

It is preferable to adjust so that the potassium iodide concentration of each dyeing bath may increase in order of dyeing process. When the concentration of potassium iodide is the same in each dyeing bath or decreases in the order of treatment, the balance of the liquid concentration collapses when it is operated for a long time, so that the quality of the polarizing film cannot be stably maintained.

Instead of potassium iodide, other iodides such as zinc iodide may be used. In addition, you may use another iodide together with potassium iodide. Also in these cases, it is preferable to adjust so that an iodide concentration may increase in order of a dyeing process. In addition, compounds other than iodide, such as zinc chloride and cobalt chloride, may coexist.

Although the boric acid concentration in a last dye bath is as above-mentioned, it is preferable to satisfy following formula (1) between draw ratios, and when this relationship is not satisfied, there exists a possibility that the surface state of a polarizing film may deteriorate.                     

Equation 1

b <-0.51 × a + 3.77

Here, a is boric acid content (weight part) per 100 weight part of water, and b shows the total draw ratio from the disc of a polyvinyl alcohol-type film to the last dyeing bath, respectively.

The dyeing treatment in each dye bath is carried out for example for about 30 to 600 seconds, preferably about 60 to 300 seconds, at a temperature of about 10 ° C to 40 ° C, preferably about 20 ° C to 35 ° C. Here, when the temperature of each dye bath is less than about 10 degreeC, boric acid becomes difficult to melt | dissolve, On the contrary, when exceeding about 40 degreeC, there exists a possibility that the dissolution of polyvinyl alcohol may increase.

In performing uniaxial stretching in each dye bath, it is preferable to adjust a draw ratio independently in each dye bath. For this purpose, for example, it is preferable to provide nip rolls at the inlet side and the outlet side of each dye bath so that the rotational speed ratio of both nip rolls can be changed. In addition, expander rolls, spiral rolls, crown rolls, cross guiders, bend bars and the like can be installed in the dye bath and / or bath entrance and exit to perform uniaxial stretching.

After the swelling treatment, the polyvinyl alcohol-based film may be wet-stretched before the dyeing treatment, or may be uniaxially stretched between at least one of the dyeing baths as necessary, or the washing bath may be used. You may install in at least one between dyeing baths.

When performing uniaxial stretching in each dye bath of two or more stages, although draw ratio is not specifically limited, It is preferable to employ either of the following two forms.

(1) The draw ratio in the first dye bath is made higher than the total draw ratio in the dye bath after the second stage. Thereby, since the dry neck-in at the time of drying after water washing becomes small, the frequency | count of generation | occurrence | production of a wrinkle in a drying furnace becomes small. Specifically, the draw ratio in the first dye bath is in the range of about 1.1 to 3.0 times, and the draw ratio in the first dye bath is about 1.05 to 2.0 times the total draw ratio in the dye bath after the second stage. It is preferable that it is about degree.

(2) The draw ratio in the final dyeing bath is made higher than the total draw ratio in the dyeing bath before. Thereby, a film does not loosen easily in the process after a boric acid treatment process, and the polarizing film with high polarization degree can be obtained. Specifically, the draw ratio in the final dyeing bath is in the range of about 1.05 to 2.0 times, and preferably about 1.1 to 3.0 times the total draw ratio in the dyeing bath before.

Boric acid treatment is performed by immersing the polyvinyl alcohol-type film iodine-dyed in the aqueous solution containing about 1-10 weight part of boric acid with respect to 100 weight part of water. It is preferable to contain about 1-30 weight part of iodide in boric-acid aqueous solution. 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 carried out for color adjustment (preventing bluish, etc.) in addition to water resistance by crosslinking. In the case of water resistance by bridge | crosslinking, crosslinking agents, such as glyoxal and glutalaldehyde, can also be used as needed other than boric acid or with boric acid.

Moreover, the boric acid treatment for water resistance may be called by names, such as a crosslinking process and an immobilization process. In addition, when boric acid treatment is performed for color adjustment, such boric acid treatment may be referred to by names such as complementary color treatment and re-dyeing treatment. In the present invention, both the boric acid treatment for water resistance and the boric acid treatment for color adjustment are simply referred to as boric acid treatment.

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 swelling, dyeing, or boric acid treatment of the raw film, 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 about 1 to about 8 parts by weight of iodide A boric acid treatment bath containing 20 parts by weight is used and is usually carried out at a temperature of about 50 ° C to 70 ° C, preferably about 55 ° C to 65 ° C. Immersion time is about 30 to 600 second normally, Preferably it is about 60 to 420 second, More preferably, it is about 90 to 300 second.

In addition, when dyeing and boric acid treatment of the previously stretched film, the temperature of a boric acid treatment bath is about 50 degreeC-85 degreeC normally, Preferably it is about 55 degreeC-80 degreeC.

After the boric acid treatment for water resistance is performed, a boric acid treatment for color adjustment may be performed. For this purpose, a boric acid treatment bath containing about 1 to 5 parts by weight of boric acid and about 3 to 30 parts by weight of iodide is used with respect to 100 parts by weight of water, and is usually performed at a temperature of about 10 ° C to 45 ° C. Immersion time is about 3 to 300 second normally, Preferably it is about 10 to 240 second. Boric acid treatment for color adjustment is usually carried out at low boric acid concentrations and high iodide concentrations lower temperatures than boric acid treatments for water resistance.

These boric acid treatments may be carried out in a plurality of steps, and are usually carried out in a step of 2 to 5 in many cases. 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 processes, respectively. Also in a boric acid treatment process, you may perform extending | stretching of a film with a dyeing process. The final integrated draw ratio is about 4.5 to 7.0 times, preferably about 5.0 to 6.5 times.

After boric acid treatment, it is washed with water. Water washing treatment is performed by immersing the polyvinyl alcohol-type film which processed boric acid in water, spraying water as a shower, or using dipping and spraying together. The temperature of water in a water washing process is about 2 degreeC-40 degreeC normally, and it is good that immersion time is about 2 to 120 second. Drying after washing is carried out in a drying furnace for about 60 to 600 seconds at a temperature of about 40 ~ 100 ℃.

In the present invention, in each step after the stretching treatment, it is preferable to perform tension control so that the tension of the film is substantially constant, respectively. When extending | stretching is complete | finished in a dyeing process, tension control is performed in the subsequent boric acid treatment process and a water washing process process.

A polarizing plate can be obtained by adhering a protective film to at least one side of the polarizing film manufactured in this way with an adhesive agent.                     

As the protective film, for example, a film made of acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose, a film made of polyester resin such as polyethylene terephthalate or polyethylene naphthalate, polybutylene terephthalate, polycarbonate resin The film which consists of a film and a film which consists of cycloolefin resin is mentioned. Commercially available thermoplastic cycloolefin-based resins include, for example, "Topas" (trademark registered) sold by Tiko Corp. of Germany, (Aton) (trademark registered) sold by JSR Corporation, Nihon Xeon Co., Ltd. Zeonor, Zeeonex (both registered trademarks) sold by Kaisha, and Apel (trademark registered) sold by Mitsui Kagaku Kabushi Kaisha. Although what produced such cycloolefin resin was made into a protective film, well-known methods, such as the solvent casting method and the melt-extrusion method, can be used suitably for film forming. The cycloolefin resin film formed into a film is also marketed, For example, "S thinner", "SCA40", etc. which are sold by Sekisui Kagaku Kogyo Co., Ltd. are mentioned.

It is preferable that the thickness of the protective film is thin, but if it is too thin, the strength decreases and the workability is inferior. On the other hand, if the thickness is too thick, problems such as deterioration of transparency or long curing time required after lamination may occur. . Therefore, the suitable thickness of a protective film is about 5-200 micrometers, for example, Preferably it is about 10-150 micrometers, More preferably, it is about 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 may be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, or the like. May be performed.

The protective film may be subjected to surface treatment such as anti-glare treatment, anti-reflection treatment, hard coat treatment, antistatic treatment, antifouling treatment or the like 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 adhere | attached on one side of a polarizing film, and may be adhere | attached on both surfaces.

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 solventless adhesive. Examples of the water-soluble adhesive include polyvinyl alcohol-based resin aqueous solutions and aqueous two-component urethane emulsion adhesives. Examples of the organic solvent adhesives include two-component urethane adhesives. Examples of the solvent-free adhesives include one-component urethane adhesives. Can be mentioned. When using the acetyl cellulose type film hydrophilized by the saponification process etc. as an adhesive surface with a polarizing film 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 furthermore, modified polyvinyl alcohol polymers in which these hydroxyl groups are partially modified. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine type compound, etc. may be used for this adhesive agent as an additive.

The method of adhering a polarizing film and a protective film is not specifically limited, For example, the method of apply | coating an adhesive uniformly on the surface of a polarizing film or a protective film, laminating | stacking another film on an application surface, adhering with a roll, etc., etc. is mentioned. Can be.

Usually, after preparing an adhesive agent, it apply | coats at the temperature of about 15 degreeC-40 degreeC, and an adhesive temperature is a range of about 15 degreeC-30 degreeC normally. After adhesion, a drying treatment 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 about 30 ° C to 85 ° C, preferably about 40 ° C to 80 ° C. Thereafter, the adhesive may be cured by curing approximately 1 to 90 days in a temperature environment of about 15 ° C to 85 ° C, preferably about 20 ° C to 50 ° C, and more preferably about 35 ° C to 45 ° C. Since the productivity worsens when this curing period is long, the curing period is about 1-30 days, Preferably it is about 1-7 days.

In this way, the polarizing plate with a protective film adhere | attached on one side or both sides of a polarizing film through an adhesive bond layer can be obtained.

In this invention, a protective film can also have 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, etc. . In this case, for example, by laminating an optically functional film such as a retardation film, a brightness enhancement film, a reflection film, a semi-transmissive reflection film, a diffusion film, an optical compensation film, and the like on the surface of the protection film, a protective film can be provided. You can also give this function to 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 Japanese Patent No. 2841377, Japanese Patent No. 3094113, etc., or the treatment described in Japanese Patent No. 3168850, the protective film can be imparted with a function as a retardation film. Can be. In addition, two or more layers of cholester having different center wavelengths of selective reflection by forming fine pores in the above-described protective film by the method described in JP-A-2002-169025 or JP-A-2003-29030. By superimposing a lick liquid crystal 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. The function as a diffusion film can be given by coating the resin solution containing microparticles | fine-particles to the said protective film. 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, using suitable adhesive, brand name: DBEF (luminance improvement film, such as 3M Corporation), brand name: viewing angle improvement films, such as a WV film (made by Fuji Photographic Film Co., Ltd.), brand name: Sumikalight ( Trademark registration) Commercially available optical functional films, such as retardation films, such as Sumitomo Kagaku Kogyo Co., Ltd., may be directly bonded to 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.                     

Example 1

A polyvinyl alcohol film (Kurarevinylone VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) having a thickness of 75 μm was immersed in pure water at 30 ° C. for about 130 seconds while keeping the film from loosening, thereby sufficiently immersing the film. Swelling. (Swelling about 1.2 times).

Next, uniaxial stretching was carried out at 1.75 times while iodine / potassium iodide / water was immersed in a 30 ° C. aqueous solution of 0.02 / 1.0 / 100 by weight ratio. Further, while iodine / potassium iodide / boric acid / water was immersed in a 300 ° C. aqueous solution of 0.02 / 1.5 / 0.2 / 100 by weight ratio, uniaxial stretching was performed 1.4 times, and the total draw ratio from the disk was tripled. 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 60/5 aqueous solution of 10/5/100 by weight ratio and water-resistant. After water-resistant treatment, it washed with water 10 degreeC pure water for about 10 second. After washing with water, the mixture was dried at 60 ° C. for 2 minutes to obtain an iodine polarizing film having a thickness of 28 μm. As a result of visual observation of the surface state of this polarizing film, the film surface showed favorable mirror reflection.

Polyvinyl alcohol adhesive is coated on both sides of the polarizing film, and a protective film is applied to both sides of the polarizing film. The triacetyl cellulose film subjected to saponification treatment on the surface, `` FUJITAK (trademark registered) T80UNL '', manufactured by Fuji Photo Film Co., Ltd., thickness 80 µm] was bonded and dried at 60 ° C. for 5 minutes to obtain a polarizing plate. This polarizing plate was visually observed in the dark room in the state of crossed nicols, and the staining was slight. In addition, the staining was confirmed in accordance with the degree of light leakage from the polarizing plate.

Comparative Example 1

A polarizing film was obtained in the same manner as in Example 1 except that boric acid was not added to the dye bath in the second stage. As a result of observing the surface state of this polarizing film visually, the reflected light of a fluorescent lamp did not show specular reflection, but was slightly white and showed a poor appearance.

Comparative Example 2

A polarizing film was obtained in the same manner as in Example 1 except that 0.2 part by weight of boric acid was added to the dye bath of the first stage. As a result of observing this polarizing plate visually in a dark room in an orthogonal nicotine state, staining stains were observed more than in Example 1.

According to the present invention, since dyeing is sequentially performed in two or more stages of dyeing, the staining of the polarizing film can be reduced, and the surface state of the film is deteriorated in the boric acid treatment step by containing boric acid in the last dyeing bath. It can suppress, and there exists an effect that an optical characteristic improves.

Claims (17)

A method of manufacturing a polarizing film in which a polyvinyl alcohol-based film is treated in the order of swelling treatment, dyeing treatment, and boric acid treatment, and uniaxially stretched by wet in the boric acid treatment step and / or the preceding step, before the boric acid treatment step At the same time, dyeing is carried out by installing two or more dye baths, and the last dyeing bath contains 0.05 to 2.0 parts by weight of boric acid per 100 parts by weight of water, and each dyeing bath except the last dyeing bath does not contain boric acid. The manufacturing method of the polarizing film to make. The boron content in the last dyeing bath is a part by weight per 100 parts by weight of water, and the total draw ratio from the disc of the polyvinyl alcohol-based film to the last dyeing bath is b. When a and b are in a relationship satisfying the following formula (1): Equation 1 b <-0.51 × a + 3.77 delete The manufacturing method of the polarizing film of Claim 1 or 2 whose temperature of the said 2 or more-stage dyeing bath is 10-40 degreeC. delete A protective film is adhere | attached 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. delete A protective film is bonded to at least one surface of the polarizing film obtained by the method according to claim 4, characterized in that the method for producing a polarizing plate. delete The manufacturing method of the polarizing plate of Claim 6 with which the said protective film has a function of any one of retardation film, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflective film. delete The manufacturing method of the polarizing plate of Claim 8 in which the said protective film has a function of any one of retardation film, a brightness improving film, a viewing angle improvement film, and a semi-transmissive reflective film. delete The polarizing plate obtained by the method of Claim 6 is adhere | attached 1 or more types chosen from 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 the above-mentioned. delete At least 1 type chosen from retardation film, a brightness improving film, a viewing angle improvement film, and a transflective film is adhere | attached to the polarizing plate obtained by the method of Claim 8, The manufacturing method of the optical laminated body characterized by the above-mentioned. delete