CN1629660A - Method for producing iodine-based polarizing film, method for producing polarizing plate, and method for producing optical laminate - Google Patents

Abstract

Provided are a method for producing a polarizing film, a polarizing plate, and an optical laminate with less dyeing unevenness, less frequent occurrence of wrinkles, or reduced tension in steps after dyeing. The method for producing a polarizing film of the present invention is a method for producing a polarizing film that is uniaxially stretched before and/or during the process of treating a polyvinyl alcohol-based film in the order of swelling treatment, iodine dyeing treatment, and boric acid treatment, It is characterized in that before the boric acid treatment process, iodine dyeing is carried out in two or more dyeing baths, and uniaxial stretching is carried out in two or more dyeing baths, (1) the stretching ratio in the first dyeing bath is adjusted to The total stretching ratio in the second and subsequent dyeing baths is higher, or (2) the stretching ratio in the final dyeing bath is higher than the total stretching ratio in the preceding dyeing baths, and uniaxially stretched.

Description

Manufacturing method of iodine-based polarizing film, polarizing plate and optical laminate

technical field

The present invention relates to a method for producing an iodine-based polarizing film with less dyeing unevenness and reduced frequency of wrinkling or improved productivity, a method for producing a polarizing plate in which a protective film is laminated on at least one side of the obtained polarizing film, and a phase A manufacturing method of an optical laminate formed by sticking one or more of a differential film, a brightness improving film, a viewing angle improving film and a transflective film.

Background technique

Conventionally, as a polarizing film, a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based film. That is, an iodine-based polarizing film using iodine as a dichroic dye, a dye-based polarizing film using a dichroic dye as a dichroic dye, and the like are known. These polarizing films are usually made into polarizers by affixing a protective film such as triacetyl cellulose to at least one side, preferably both sides thereof, with an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin.

As a method for producing a polarizing film, Patent Document 1 describes a method in which a polyvinyl alcohol-based film is immersed in an aqueous solution of iodine and potassium iodide, treated with boric acid while being stretched, washed with water, and then immersed in iodine. and an aqueous solution of potassium iodide and dried.

Patent Document 2 describes a method for producing a polarizing film as follows: after immersing the stretched film in an aqueous solution containing a dichroic dye, and then dipping it in another aqueous solution containing a dichroic dye, stretching it in an aqueous solution of boric acid, By drying, a polarizing film in which two adsorption alignment layers were provided in the thickness direction was produced.

Patent Document 3 describes a method for producing a polarizing film in which a stretched polyvinyl alcohol-based film is immersed in an aqueous solution of a specific dichroic dye (dye solution A), and then immersed in an aqueous solution of iodine and potassium iodide (dye solution A). Solution B), followed by boric acid treatment and water washing to produce a polarizing film.

In each of these patent documents, the dyeing process is performed twice. However, in Patent Document 1, the dyeing process is performed twice after the boric acid treatment. In this case, not only wrinkles are likely to occur, but also the initial optical properties are poor. In addition, Patent Documents 2 and 3 relate to methods using dichroic organic dyes.

[Patent Document 1] JP-A-9-133809

[Patent Document 2] JP-A-60-66205

[Patent Document 3] JP-A-62-70802

Contents of the invention

The main subject of the present invention is to provide a method for producing an iodine-based polarizing film with less uneven dyeing, a method for producing a polarizing plate, and an optical laminate.

Another object of the present invention is to provide a method for producing an iodine-based polarizing film with less dyeing unevenness, less frequent occurrence of wrinkles, or reduced tension in the process after dyeing, and improved productivity; polarizing plate and optical laminate manufacturing method.

The inventors of the present invention have made intensive studies in order to solve the above-mentioned problems, and as a result, found that by sequentially performing iodine dyeing in two or more stages of dyeing baths before the boric acid treatment process, dyeing unevenness is reduced and uniaxial stretching is performed in the dyeing bath , can reduce the frequency of wrinkling, or can reduce the tension in the process after the dyeing process, and improve productivity, thus completing the present invention.

That is, the first production method of the iodine-based polarizing film of the present invention is characterized in that before and/or during the step of processing the polyvinyl alcohol-based film in the order of swelling treatment, iodine dyeing treatment and boric acid treatment, uniaxial During stretching, iodine dyeing is performed in two or more stages of dyeing baths before the boric acid treatment process.

The second method for producing an iodine-based polarizing film according to the present invention is characterized in that before the boric acid treatment step, iodine dyeing is performed in two or more dyeing baths, and at the same time, uniaxial stretching is performed in at least one dyeing bath.

The third manufacturing method of the iodine-based polarizing film of the present invention is characterized in that before the boric acid treatment process, iodine dyeing is performed in two or more dyeing baths, and at the same time, uniaxial drawing is performed in two or more dyeing baths. stretching, and perform uniaxial stretching in which the stretching ratio in the first dyeing bath is higher than the total stretching ratio in the dyeing baths after the second stage.

The fourth manufacturing method of the iodine-based polarizing film of the present invention is characterized in that before the boric acid treatment process, iodine dyeing is performed in two or more dyeing baths, and at the same time, uniaxial drawing is performed in two or more dyeing baths. stretching, and perform uniaxial stretching in which the stretching ratio in the final dyeing bath is higher than the total stretching ratio in the preceding dyeing baths.

It is preferable that the plurality of dyeing baths of the above-mentioned two or more stages are configured so that the draw ratio can be individually adjusted. In addition, it is preferable that all dyeing baths contain iodide, and the content of the iodide is adjusted so that the content of the iodide becomes higher in the order of treatment.

The method for producing a polarizing plate of the present invention is characterized in that a protective film is attached to at least one surface of the polarizing film obtained by the above method. This protective film may have the function of any one of a phase difference film, a brightness improvement film, a viewing angle improvement film, and a transflective film. Alternatively, the method for producing an optical laminate is characterized in that at least one selected from a phase difference plate, a brightness improving film, a viewing angle improving film, and a transflector is pasted on a polarizing plate obtained by pasting a protective film on at least one side thereof.

Invention effect

According to the present invention, an iodine-based polarizing film with less dyeing unevenness is obtained by performing iodine dyeing in two or more stages of dyeing baths before the boric acid treatment step. Furthermore, by uniaxially stretching in a dyeing bath, it is possible to reduce the frequency of occurrence of wrinkles, or reduce the tension in the process after the dyeing treatment, thereby improving productivity.

Specifically, especially since the uniaxial stretching is performed in two or more stages of dyeing baths, wherein the stretching ratio in the first dyeing bath is made higher than the total stretching ratio in the dyeing baths after the second stage, especially The shrinkage of the film width during drying (generally referred to as drying neck-in) becomes smaller, so the frequency of occurrence of wrinkles in the drying oven becomes smaller.

In addition, especially since uniaxial stretching is performed in two or more stages of dyeing baths, where the stretching ratio in the last dyeing bath is made higher than the total stretching ratio in the previous dyeing baths, even if the stretching ratio after the boric acid treatment step is reduced, The tension applied to prevent the film from shrinking during the process prevents the film from loosening, improving productivity. In addition, when the tension is low, a large load is not imposed on the bearings of the guide rollers for conveying the film, so the durability of the device is improved, and maintenance management becomes easy.

By using the polarizing plate and optical laminate obtained in the present invention for a liquid crystal display device, a thin and high-quality liquid crystal display can be obtained.

Detailed ways

The present invention will be described in detail below.

As the polyvinyl alcohol-based resin forming the polyvinyl alcohol-based film of the present invention, generally, a resin obtained by saponifying a polyvinyl acetate-based resin can be exemplified. The saponification degree is about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% to 100 mol%. Examples of polyvinyl acetate-based resins include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers that can be copolymerized with it, such as ethylene-vinyl acetate copolymer things etc. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The degree of polymerization of the polyvinyl alcohol-based resin is about 1,000 to 10,000, preferably about 1,500 to 5,000.

These polyvinyl alcohol-based resins may also be modified, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may be used. Usually, as a starting material for producing a polarizing film, an unstretched film of a polyvinyl alcohol-based resin film having a thickness of about 20 μm to 100 μm, preferably about 30 μm to 80 μm, is used. The industrially practical film width is about 1500 mm to 4000 mm.

This unstretched film is treated in the order of swelling treatment, iodine dyeing treatment, boric acid treatment, and water washing treatment, and finally dried to obtain a polyvinyl alcohol-based polarizing film with a thickness of, for example, about 5 to 50 μm.

The manufacturing method of the polarizing film of this invention is roughly divided into two types. One method is a method in which a polyvinyl alcohol-based film is uniaxially stretched in air or an inert gas, followed by solution treatment in the order of swelling treatment, iodine dyeing treatment, boric acid treatment, and water washing treatment, and finally drying. The second method is to perform solution treatment on the unstretched polyvinyl alcohol film in the order of swelling treatment, iodine dyeing treatment, boric acid treatment and water washing treatment in the aqueous solution. In the boric acid treatment process and/or the process before it A method in which uniaxial stretching is carried out in a wet process, followed by drying.

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. As the stretching method, known methods can be used, for example, inter-roll stretching in which a difference in linear velocity is applied between two nip rolls that transport the film, the hot roll stretching method described in Japanese Patent No. 2731813, and tenter roll stretching. Machine stretching method, etc. In addition, basically the sequence of steps is as above, but the number of treatment baths, treatment conditions, and the like are not limited.

In addition, of course, it is free to insert steps not described in the above-mentioned steps for other purposes. As an example of such a process, after boric acid treatment, immersion treatment with an iodide aqueous solution not containing boric acid (iodide treatment), or immersion treatment with an aqueous solution not containing boric acid and containing zinc chloride or the like (zinc treatment ) process, etc.

The swelling treatment process is used to remove foreign matter on the surface of the film, remove the plasticizer in the film, impart easy dyeability in the next process, and plasticize the film. The treatment conditions are determined within a range in which these objects can be achieved, and within a range in which adverse events such as extreme dissolution and devitrification of the base film do not occur. To swell a film previously stretched in air, for example, immerse the film in an aqueous solution at about 20°C to 70°C, preferably about 30°C to 60°C. The immersion time of the membrane is 30 to 300 seconds, more preferably about 60 seconds to 240 seconds. To swell a raw (raw) film that has not been stretched from the beginning, it is carried out by immersing the film in an aqueous solution at, for example, about 10°C to 50°C, preferably about 20°C to 40°C. The immersion time of the membrane is 30 to 300 seconds, more preferably about 60 seconds to 240 seconds.

In the swelling treatment process, the film swells in the transverse direction and is prone to problems such as wrinkles on the film, so it is preferable to use expander rolls, spiral rolls, crown rolls, and cross guide rolls. Known expanding devices such as cross guider, bend bar, and tenter crip transport the film while eliminating the wrinkles of the film. In order to stabilize the film transport in the bath, it is also useful to control the water flow in the swelling bath with a water sprinkler, or use an EPC device (Edge Position Control device: a device that detects the end of the film and prevents the film from meandering) at the same time. In this step, since the film also swells and expands in the traveling direction of the film, in order to eliminate the sag of the film in the conveying direction, it is preferable to take measures such as controlling the speed of conveying rollers before and after the treatment tank. In addition, in addition to pure water, the boron treatment bath used can also use boric acid (recorded in JP-A-10-153709 A) and chloride (JP-A-06-281816 A) in the range of 0.01% to 10% by weight. ), aqueous solutions of inorganic acids, inorganic salts, water-soluble organic solvents, alcohols, etc.

The dyeing process using iodine is used to make the film absorb iodine and align it. The treatment conditions are determined within a range in which these objects can be achieved, and within a range in which adverse events such as extreme dissolution and devitrification of the base film do not occur. In the present invention, more than two stages of dyeing baths are specially arranged to carry out iodine dyeing sequentially. The dyeing bath is preferably 2 stages to 4 stages.

Dye baths can also contain boric acid. When boric acid is added, it is distinguished from the following boric acid treatment in terms of containing iodine. It contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, and if the temperature is about 40°C or less, it is regarded as a dyeing bath.

The concentration of each dyeing bath is iodine/potassium iodide/water=about 0.003～0.2/about 0.1～10/100 by weight ratio, preferably about 0.003～0.1/about 0.1～3.0/100. The content of iodine may be the same for each dyeing bath, or the content may be decreased or increased in the order of dyeing treatment within the above range.

The potassium iodide concentration of each dyeing bath is preferably adjusted so that it becomes higher in the order of dyeing treatments. If the concentration of potassium iodide is the same in each dyeing bath or becomes lower in the order of treatment, the balance of liquid concentration will be disrupted during long-term operation, and the quality of the polarizing film cannot be maintained stably. That is, since the concentration of potassium iodide in the dyeing bath on the back-stage side becomes higher with the treatment, it is necessary to discard the supplementary liquid water in order to reduce the concentration of potassium iodide in the dyeing bath on the back-stage side. This is economically wasteful, and the environmental load also increases. On the other hand, if the concentration of potassium iodide is adjusted to increase in the order of dyeing treatment from the beginning, even if the concentration of potassium iodide in the dyeing bath on the downstream side becomes high through long-term operation, the balance of liquid concentration can be prevented from being disrupted.

In addition, other iodides such as zinc iodide may be used instead of potassium iodide. In addition, other iodides may be used simultaneously with potassium iodide. In these cases, it is preferable to adjust the concentration of iodide so that the concentration of iodide becomes higher in the order of dyeing treatment. In addition, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, and the like may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in terms of containing iodine. If it contains about 0.003 weight part or more of iodine with respect to 100 weight part of water, it will be regarded as a dyeing tank. Boric acid is particularly preferably added only in the final dyebath. In this way, the surface state of the polarizing film becomes favorable, and unevenness in dyeing decreases. The concentration of boric acid added in the final dyeing bath is about 0.05-2.0 parts by weight per 100 parts by weight of water.

The dyeing treatment in each dyeing bath is, for example, performed at a temperature of about 10°C to 40°C, preferably about 20°C to 35°C, for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds.

In the present invention, when performing uniaxial stretching in a dyeing bath, it is preferable to individually adjust the stretching ratio in each dyeing bath. For this purpose, for example, nip rolls are respectively provided on the inlet side and the outlet side of each dyeing bath, and the rotational speed ratio of both nip rolls can be changed. In addition, tenter rolls, helical rolls, nip rolls, cross guide rolls, bending bars, etc. may be installed in the dyeing bath and/or at the entrance and exit of the bath as long as the draw ratio can be individually adjusted. In addition, after the swelling treatment and before the dyeing treatment, the polyvinyl alcohol-based film can also be subjected to wet stretching treatment. In addition, it can also be uniaxially stretched between each dyeing bath, or it can also be stretched in each dyeing bath. Set water between baths.

The stretching ratio in the case of uniaxial stretching in two or more stages of dyeing baths is not particularly limited, but either of the following two methods is adopted depending on the purpose.

(1) The draw ratio in the first dyeing bath is higher than the total draw ratio in the dyeing baths after the second step. As a result, the drying shrinkage during drying after washing with water becomes smaller, so that the occurrence frequency of wrinkles in the drying oven becomes smaller. Specifically, it is preferable that the draw ratio in the first dyeing bath is in the range of about 1.1 to 3.0 times, and it is about 1.05 to 2.0 times the total draw ratio in the second and subsequent dyeing baths.

(2) The draw ratio in the final dyeing bath is made higher than the total draw ratio in the previous dyeing baths. This makes it difficult for the film to sag in the steps following the boric acid treatment step, thereby improving productivity. Specifically, it is preferable that the draw ratio in the final dyeing bath is in the range of about 1.05 to 2.0 times, and it is about 1.1 to 3.0 times the total draw ratio in the previous dyeing bath.

The boric acid treatment is carried out by immersing the iodine-dyed polyvinyl alcohol-based film in an aqueous solution containing about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. Preferably, about 1 to 30 parts by weight of iodide is contained in the boric acid aqueous solution. Potassium iodide, zinc iodide, etc. are mentioned as an iodide. 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 used for water resistance by crosslinking, adjustment of color tone (prevention of bluishness, etc.), and the like. When used for water resistance by crosslinking, a crosslinking agent such as glyoxal or glutaraldehyde may be used in addition to boric acid or together with boric acid as needed.

In addition, the boric acid treatment for water resistance is sometimes called by names such as crosslinking treatment and immobilization treatment. In addition, boric acid treatment may be performed for color tone adjustment. It is sometimes called this kind of boric acid treatment with names such as complementary color treatment and re-dyeing treatment. In addition, in the following description, both the boric-acid treatment for water resistance and the boric-acid treatment for color tone adjustment are simply referred to as boric-acid treatment.

The boric acid treatment is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose. There is no particular difference between the boric acid treatment for water resistance and the boric acid treatment for color tone adjustment, and they were carried out under the following conditions.

In the case of swelling, dyeing, and boric acid treatment of the rough (original reverse) membrane, when the boric acid treatment is aimed at water resistance through crosslinking, use a material containing about 3 to 10 parts by weight of boric acid relative to 100 parts by weight of water. The boric acid treatment bath of -20 parts by weight iodide is generally carried out at a temperature of about 50°C to 70°C, preferably about 55°C to 65°C. The immersion time is usually about 30 to 600 seconds, preferably about 60 to 420 seconds, more preferably 90 to 300 seconds.

In addition, when performing dyeing and boric acid treatment on a prestretched film, the temperature of the boric acid treatment bath is usually about 50°C to 85°C, preferably about 55°C to 80°C.

After boric acid treatment for water resistance, boric acid treatment for color tone adjustment can also 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, usually at a temperature of about 10°C to 45°C. The immersion time is usually about 3 to 300 seconds, preferably about 10 to 240 seconds. The boric acid treatment for color tone adjustment is generally performed at a lower boric acid concentration, higher iodide concentration, and lower temperature than the boric acid treatment for water resistance.

These boric acid treatments can also be performed in a plurality of steps, and are usually performed in 2 to 5 steps in many cases. At this time, the composition and temperature of the aqueous solution of each boric acid treatment tank used may be the same or different within the above-mentioned range. The above-mentioned boric acid treatment for water resistance and boric acid treatment for color tone adjustment may be performed in a plurality of steps.

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

After boric acid treatment, water washing treatment is carried out. The water washing treatment is performed by, for example, immersing the boric-acid-treated polyvinyl alcohol-based film in water, spraying water as a shower, or using both immersion and spray. The water temperature at the time of washing with water is usually about 2 to 40°C, and the immersion time is preferably about 2 to 120 seconds. Drying after water washing is performed at a temperature of about 40 to 100° C. for about 60 to 600 seconds in a drying oven.

In the present invention, it is preferable to control the tension so that the tension of the film becomes substantially constant in each step after the stretching treatment. When the stretching is completed in the dyeing treatment process, tension control is performed in the subsequent boric acid treatment process and water washing treatment process.

A protective film is attached to at least one side of the polarizing film produced in this way with an adhesive to obtain a polarizing plate.

Examples of the protective film include films made of acetylcellulose-based resins such as triacetylcellulose and diacetylcellulose, polyethylene terephthalate or polyethylene naphthalate, polybutylene terephthalate, etc. Films made of polyester-based resins such as glycol esters, films made of polycarbonate-based resins, and films made of cycloolefin-based resins. Commercially available thermoplastic cycloolefin-based resins include, for example, "Topas" (registered trademark) sold by Ticona Corporation of Germany, "A-TON" (registered trademark) sold by Jieiyesua-ru Co., Ltd., and "A-ton" (registered trademark) sold by Japan Zeon Co., Ltd. "Zeonoa" and "Zonenecsus" (both registered trademarks), "Apel" (registered trademark) sold by Mitsui Chemicals Co., Ltd., etc. Such a cycloolefin-based resin is formed into a film, and the obtained film is used as a protective film. When forming a film, a known method such as a solvent casting method or a melt extrusion method can be appropriately used. The cycloolefin-based resin film after film formation is also commercially available, for example, "Escina" and "SCA40" sold by Sekisui Chemical Co., Ltd. are available.

The thickness of the protective film is preferably thin, but if it is too thin, the strength will decrease and the workability will deteriorate. On the other hand, if it is too thick, the transparency will decrease and the curing time required after lamination will become longer. Therefore, an appropriate thickness of the protective film is, for example, about 5 to 200 μm, preferably about 10 to 150 μm, and more preferably about 20 to 100 μm.

In order to improve the adhesion between the adhesive and the polarizing film and/or protective film, corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification can also be performed on the polarizing film and/or protective film. Treatment and other surface treatment.

Surface treatments such as antiglare treatment, antireflection treatment, hard coating treatment, antistatic treatment, and antifouling treatment may be performed on the protective film alone or in combination. In addition, the protective film and/or the surface protective layer of the protective film may contain ultraviolet absorbers such as benzophenone-based compounds and benzotriazole-based compounds, plasticizers such as phenyl phosphate-based compounds, and phthalate compounds. .

This protective film can be pasted on one side of the polarizing film or on both sides.

The polarizing film and the protective film are laminated using an adhesive such as a water solvent adhesive, an organic solvent adhesive, a hot melt adhesive, or a solventless adhesive. Examples of water-solvent-based adhesives include polyvinyl alcohol-based resin aqueous solutions, water-based two-component urethane-based emulsion adhesives, and the like; examples of organic solvent-based adhesives include two-component urethane-based adhesives, etc. ; As the solventless adhesive, for example, a one-pack type urethane adhesive or the like is mentioned. When using an acetylcellulose-based film whose bonding surface with a polarizing film has been hydrophilized by saponification or the like as a protective film, it is preferable to use a polyvinyl alcohol-based resin aqueous solution as a binder. Polyvinyl alcohol-based resins used as binders include polyvinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and polyvinyl alcohols that can be copolymerized with vinyl acetate. Vinyl alcohol-based copolymers obtained by saponifying copolymers formed from other monomers, modified polyvinyl alcohol-based polymers obtained by modifying their hydroxyl groups, and the like. In these adhesives, polyaldehydes, water-soluble epoxy compounds, melamine-based compounds, and the like can also be used as additives.

The method of sticking the polarizing film and the protective film is not particularly limited, and the method of uniformly coating the adhesive on the surface of the polarizing film or the protective film, laminating another film on the coated surface, laminating it with a roller, etc., and drying it wait.

Usually, the adhesive is prepared and applied at a temperature of about 15 to 40°C, and the sticking temperature is usually in the range of about 15 to 30°C. Drying is performed after pasting to remove solvents such as water contained in the adhesive. The drying temperature at this time is usually about 30 to 85°C, preferably about 40 to 80°C. Thereafter, the adhesive may be cured at a temperature of about 15 to 85°C, preferably about 20 to 50°C, more preferably about 35 to 45°C, usually for about 1 to 90 days. When this curing period is long, the productivity will deteriorate, so the curing period is about 1 to 30 days, preferably about 1 to 7 days.

In this way, a polarizer having a protective film bonded to one or both surfaces of a polarizing film via an adhesive layer can be obtained.

In the present invention, the protective film may also have a function as a retardation film, a function as a brightness improving film, a function as a reflection film, a function as a semi-transparent reflection film, a function as a diffusion film, or a function as an optical compensation film. functions and other optical functions. In this case, for example, by laminating an optical functional film such as a retardation film, a brightness improvement film, a reflective film, a semi-transparent reflective film, a diffusion film, and an optical compensation film on the surface of the protective film, it can be provided with such a function. Such a function can be imparted to the protective film itself. In addition, the protective film itself may have a plurality of functions, such as a diffusion film having a function of a brightness improving film.

For example, the stretching treatment described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, etc., or the treatment described in Japanese Patent No. 3168850, etc., can be applied to the protective film to function as a retardation film. In addition, micropores are formed on the above-mentioned protective film by the method described in JP-A-2002-169025 or JP-A-2003-29030, and two or more cholesteric liquid crystal layers having different center wavelengths of selective reflection are superimposed, Thereby, the function as a brightness improvement film can be given. By forming a metal thin film on the above-mentioned protective film by vapor deposition, sputtering, etc., it is possible to impart a function as a reflective film or a transflective film. By coating the above protective film with a resin solution containing fine particles, it is possible to impart a function as a diffusion film. In addition, a function as an optical compensation film can be imparted by coating and aligning a liquid crystal compound such as a discotic liquid crystal compound on the protective film. Alternatively, a brightness-enhancing film such as a product name: DBEF (manufactured by Sun-Em Co., Ltd.), a product name: WV film (manufactured by Fujifilm Co., Ltd.), etc., may be directly attached to the polarizing film using an appropriate adhesive. A commercially available optical functional film such as a viewing angle improving film, a retardation film such as a brand name: Sumika Lait (registered trademark) (Sumitomo Chemical Industries, Ltd.).

The following examples are given to illustrate the present invention more specifically, but the present invention is not limited by these examples.

Example 1

Immerse a polyvinyl alcohol film (Kurarevinylon VF-PS#7500, polymerization degree 2400, saponification degree 99.9 mol% or more) with a thickness of 75 μm in pure water at 30°C for about 130 °C while maintaining a tense state so that the film does not loosen. seconds to fully swell the membrane.

Next, uniaxially stretched to 2.50 times while dipping in a 30° C. aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.02/1.0/100. Further, it was dipped in an aqueous solution at 30° C. at a weight ratio of iodine/potassium iodide/water of 0.025/1.5/100, while being uniaxially stretched to 1.04 times. Thereafter, it was dipped in a 60° C. aqueous solution having a weight ratio of potassium iodide/boric acid/water of 10/5/100 to perform boric acid treatment while uniaxially stretching until the cumulative stretching ratio from the rough film reached 5.9 times. After the boric acid treatment, it was washed in pure water at 10°C for about 10 seconds. After washing with water, it was dried at 60° C. for 2 minutes to obtain an iodine-based polarizing film with a thickness of 28 μm.

Drying shrinkage was determined from the film width (W1) immediately after water washing and the film width (W2) after drying, and it was 13%.

A polyvinyl alcohol-based adhesive was applied to both sides of the polarizing film, and a protective film (triacetyl cellulose film with a saponified surface, "Fujitaku (registered trademark) T80NUL", Fujifilm Co., Ltd.) made, thickness 80 μm), and dried at 60° C. for 5 minutes to obtain a polarizing plate.

When the polarizing plate was observed with the naked eye in a darkroom in a Nicol cross state, almost no dyeing unevenness was observed. In addition, uneven dyeing was confirmed by the degree of light leakage from the polarizing plate.

Example 2

Immerse a polyvinyl alcohol film with a thickness of 75 μm (Kurarevinylon VF-PS#7500, a degree of polymerization of 2400, and a degree of saponification of 99.9 mol% or higher) in pure water at 30°C for about 130°C while maintaining a tensioned state so that the film does not loosen. seconds to fully swell the membrane.

Next, uniaxially stretched to 1.04 times while dipping in a 30° C. aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.02/1.0/100. Further, it was dipped in a 30° C. aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.025/1.5/100, while performing uniaxial stretching to 2.50 times. Thereafter, it was dipped in a 60° C. aqueous solution having a weight ratio of potassium iodide/boric acid/water of 10/5/100 to perform boric acid treatment while uniaxially stretching until the cumulative stretching ratio from the rough film reached 5.9 times. After the boric acid treatment, it was washed in pure water at 10°C for about 10 seconds. After washing with water, it was dried at 60° C. for 2 minutes to obtain an iodine-based polarizing film with a thickness of 28 μm.

A commercially available differential conduction tensiometer was used to measure the tension in the washing step in which the membrane did not loosen when washed with pure water before drying. As a result, the film did not relax under a tension of 850 N/m width.

Using this iodine-based polarizing film, it carried out similarly to Example 1, and obtained the polarizing plate.

When the polarizing plate was observed with the naked eye in a darkroom in a Nicol cross state, almost no dyeing unevenness was observed.

Comparative example 1

The same 75 μm thick polyvinyl alcohol film as in Example 1 was immersed in pure water at 30° C. for about 130 seconds while maintaining tension so that the film did not sag, to fully swell the film.

Next, it was dipped in a 30° C. aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.025/1.5/100, and uniaxially stretched to 2.60 times to achieve the same length as in Example 1 after stretching. Hereinafter, boric acid treatment, water washing, and drying were carried out in the same manner as in Example 1 to obtain an iodine-based polarizing film with a thickness of 28 μm.

Drying shrinkage was determined from the film width (W1) immediately after washing with water and the film width (W2) after drying, and it was 15%.

In addition, when washing with pure water before drying in the same manner as in Example 2, the tension in the washing step in which the membrane did not sag was measured, and the membrane slackened (about 2%) even at a tension of 1200 N/m.

Using this iodine-based polarizing film, it carried out similarly to Example 1, and obtained the polarizing plate.

When the polarizer was visually observed in a darkroom in the Nicol cross state, some dyeing unevenness could be seen.

Claims (9)

1. the manufacture method of an iodine polarizing film, be handle by swelling processing, iodine staining and the operation of the sequential processes polyvinyl alcohol (PVA) mesentery that boric acid is handled before and/or carry out the manufacture method of the light polarizing film of uniaxial tension in the operation, it is characterized in that, in the dye bath more than 2 sections, carrying out iodine staining before the boric acid treatment process.

2. the manufacture method of iodine polarizing film according to claim 1 is characterized in that, carries out uniaxial tension at least one dye bath.

3. the manufacture method of iodine polarizing film according to claim 1, it is characterized in that, in the dye bath more than 2 sections, carry out uniaxial tension, and carry out the uniaxial tension that stretching ratio in the initial dye bath is higher than the 2nd section total stretching ratio in the later dye bath.

4. the manufacture method of iodine polarizing film according to claim 1 is characterized in that, carries out uniaxial tension in the dye bath more than 2 sections, and carries out the uniaxial tension that stretching ratio in the last dye bath is higher than the total stretching ratio in before this dye bath.

5. according to the manufacture method of claim 3 or 4 described iodine polarizing films, it is characterized in that, in a plurality of dye baths more than 2 sections, adjust stretching ratio respectively separately.

6. according to the manufacture method of wantonly 1 described iodine polarizing film in the claim 1～4, wherein, whole dye baths contain iodide, adjust to make the content of these iodide uprise by the order of handling.

7. the manufacture method of a polaroid is characterized in that, pastes diaphragm in the one side at least of the light polarizing film that obtains by the described method of claim 1～4.

8. the manufacture method of polaroid according to claim 7 is characterized in that, said protection film possesses phase retardation film, brightness and improves in film, visual angle improvement film and the transflective film any one function.

9. the manufacture method of an optical laminates is characterized in that, will be by the described method of claim 7 polaroid that obtains and at least a kind of stickup that is selected from phase retardation film, brightness raising film, visual angle improvement film and transflective film.