TWI362509B - The method for producing a polarizing film, the method for producing a polarizer, and the method for producing optical laminate - Google Patents

Description

1362509 IX. Description of the Invention [Technical Field] The present invention relates to a method for producing a polarizing film having less uneven color, and a method for producing a polarizing plate in which at least one side of the polarizing film is laminated with a protective film, and further A method for producing an optical laminate laminate in which a phase difference film, a brightness enhancement film, a viewing angle improvement film, and a semi-transmissive reflection film are individually or mostly bonded together.

[Prior Art] In the case of a polarizing film, it is conventionally used in a polyvinyl alcohol-based film to adsorb a dichroic dye. In other words, an iodine-based polarizing film in which iodine is a dichroic dye or a dye-based polarizing film in which a dichroic dye is a dichroic dye is known. In the polarizing film, a polarizing plate is usually bonded to a protective film such as triacetyl cellulose at least on one side, preferably on both sides of an aqueous solution of a polyvinyl alcohol resin.

In the method for producing a polarizing film, for example, Patent Document 1 discloses that a polyvinyl alcohol-based film is immersed in water and swelled, and then dyed with the dichroic dye to extend it, and then iodine is fixed to the film to form polyvinyl alcohol. The film is treated with boric acid (that is, water-resistant treatment due to cross-linking), and is subjected to water washing and 'drying method. The swelling is performed by uniformly swelling the film before dyeing, for the purpose of shortening the dyeing time, improving the uneven dyeing, and the like. In this case, from the viewpoint of uneven dyeing, etc., in Patent Document 1, boric acid is contained in the swelling treatment bath. Therefore, in Patent Document 1, the film is immersed and stretched in a bath containing boric acid after dyeing. Further, in Patent Document 2, in order to sufficiently swell the film, a chloride such as lithium chloride or zinc chloride is added to the swelling treatment bath. In the above-mentioned Patent Documents 1 and 2, a plasticizer which is dissolved by a film (

When the swelling treatment bath is discarded, the medicine such as boric acid or chloride is discarded together, and there is a problem in the environmental surface on the economic side. Further, as described in the documents of Patent Documents 1 and 2, the method of adding a drug such as boric acid or chloride to the swelling treatment bath is insufficient in terms of improvement in dyeing unevenness. On the other hand, in the second embodiment of Patent Document 3, it is described that the polyvinyl alcohol-based film is immersed in water and swelled, and then stretched in an extension bath containing boric acid, followed by dyeing. However, the extension magnification of Patent Document 3 is as large as three times or more, and in the second embodiment, it is extended to 5.5 times, so that the improvement of the dye unevenness sentence is not sufficient. Patent Document 4 discloses that in order to reduce uneven dyeing, the polyvinyl alcohol-based film is immersed in a water bath to be swollen, and the film is stretched. However, even in the method of Patent Document 4 which is extended at the same time as swelling, the improvement in uneven dyeing is not sufficient. In Patent Document 5, after immersing in water, it is axially extended in water and then dyed. Although this method can improve color unevenness, it is still insufficient. [Patent Document 1] Japanese Laid-Open Patent Publication No. Hei 06-281816 (Patent Document 3) Japanese Laid-Open Patent Publication No. Hei 6-265 727, and the second embodiment. [Problem to be Solved by the Invention] [Problem to be Solved by the Invention] The object of the present invention is to provide a method for producing a polarizing film having less color unevenness. The manufacturing method and the manufacturing method of the optical layered composition [The means to solve the problem] The present inventors have found that the polyvinyl alcohol-based film is subjected to swelling treatment, dyeing treatment, and sequential treatment of boric acid in order to solve the above problems. In the step of producing a polarizing film, a wet stretching step is provided between the swelling treatment and the dyeing to make the film state uniform, and the concentration of the boric acid aqueous solution is extended to the axis at a predetermined extension magnification, and The present invention has been completed by obtaining a new one of a polarizing film having less uneven color. The method for producing a polarizing film according to the present invention is characterized in that the polyethylene film is subjected to a swelling treatment, a dyeing treatment, and a boric acid treatment in a sequential process, and in the processing steps, at least one step is extended to obtain a polarized light. In the method for producing a film, after the swelling treatment, at least one step of a wet stretching step is provided before the dyeing, and in the stretching step, the film is made to have an amount of 0.01 part by weight with respect to 100 parts by weight of boric acid in an aqueous solution containing 0.01 parts by weight of boric acid. One-axis extension is performed by extending the magnification by less than three times. The temperature of the bath used in the wet stretching step is preferably 10 ° C to 40 ° C. The result of the preparation, the color of the color is in the first-color enol bath in the first-color color in the first step ~ 2.0 times the number of 1362509, and the manufacturing method of the polarizing plate related to the present invention, at least in the aforementioned polarizing film The face is made to conform to the protective film. The protective film may have any function of a retardation film, a brightness enhancement film, a viewing angle improvement film, and a semi-transmissive reflection film. Alternatively, at least one of a phase difference plate, a brightness enhancement film, a viewing angle improvement film, and a semi-transmissive reflection plate is bonded to the polarizing plate in which at least one surface of the protective film is bonded to each other to produce an optical laminate. By. [Effects of the Invention] According to the present invention, the polyvinyl alcohol-based film is more than 1.1 times and less than 3 times in an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid in the aqueous solution containing 100 parts by weight of boric acid before the dyeing treatment. Extending the magnification for one-axis extension 'Before the dyeing treatment, the state of the film can be made uniform, so that no uneven dyeing is feasible', and the effect of obtaining a polarizing film with less uneven color is obtained.

[Best Mode for Carrying Out the Invention] In the present invention, a polyvinyl alcohol-based resin in which a polyvinyl alcohol-based film is formed can be exemplified as a case where a polyacetate-containing vinegar-based resin is used. In terms of the degree of roadway, it is 85 mol% or more, preferably 9 mol% or more, more preferably 99 mol% to 100 mol%. In the case of the polyvinyl acetate-based resin, in addition to the individual polymer polyvinyl acetate of vinyl acetate, vinyl acetate and other monomer copolymers copolymerizable therewith may be mentioned, for example, an ethylene-vinyl acetate copolymer or the like. In terms of other monomers copolymerizable. For example, 1362509 unsaturated carboxylic acid 'olefins, vinyl ethers, unsaturated sulfonic acids, and the like can be exemplified. The degree of polymerization of the polyvinyl alcohol-based resin is from 1,000 to 10,000, preferably from about 1,500 to 5,000. The polyvinyl alcohol-based resin may be modified, for example, a modified polyvinyl alcohol may be used. Formaldehyde, polyvinyl acetal, polyvinyl butyric acid, and the like. Generally, in the starting material for manufacturing a polarizing film, the thickness is 20; tzm~100//m, preferably 30/zm~80#m of polyethylene glycol is used.

An unstretched film of a resin film. Industrially, practical film widths range from 1 500 mm to 4000 mm. The unstretched film is treated by swelling treatment, dyeing treatment, boric acid treatment, and water washing treatment, and finally dried to obtain a polyvinyl alcohol-based polarizing film having a thickness of, for example, about 5 to 50 μm.

In the swelling step, the foreign matter on the surface of the film is removed, and the plasticizer in the film is removed, which is carried out for the purpose of imparting dyeability to the next step, plasticization of the film, and the like. The treatment conditions can be determined within the range in which the objects are achieved, and the extent to which the extreme dissolution of the substrate film, loss of transparency, etc., is not caused. The unextended raw material roll paper film is impregnated with an aqueous solution of, for example, 10 ° C to 50 ° C, preferably 20 ° C to 40 ° C. The immersion time of the film is from 30 seconds to 300 seconds, more preferably from 60 seconds to 2,400 seconds. In the swelling treatment step, the film is swollen in the width direction, and there is a problem that wrinkles or the like may occur in the film, so an open roll (exPander Γ〇Η), a spiral roll, a crown roll, A known widening device such as a cross guider, a bent bar, a tenter cloth (-9-1362509 tentercrip), etc., removes wrinkles of the film while conveying the film. In order to ensure the stability of the film in the bath, the water flow in the swelling bath is controlled by water jet flow or by using an EP C device (Edge Position Control device: detecting the end of the film to prevent the film from being snaked). it works. In this step, the film is swollen and expanded in the traveling direction of the film, and in order to eliminate the slack of the film in the transport direction, for example, it is preferable to control the speed of the φ roll before and after the control tank. In addition, the swelling treatment bath, in addition to the pure water, is a boric acid (described in JP-A-H01-153-709), chloride (JP-A-06-28 1 8 1 6 ), inorganic acid An aqueous solution to which an inorganic salt, a water-soluble organic solvent, an alcohol or the like is added in a range of from 1% by weight to 00% by weight may also be used. After the swelling treatment is carried out in accordance with the above reasons, the polyvinyl alcohol-based film is wet-stretched. The stretching treatment is carried out for one-axis stretching in an aqueous solution containing 0.01 to 2.0 φ by weight of boric acid in an amount of 0.01 to 2.0 times the stretching magnification of the film with respect to 100 parts by weight of water. In the case where the diffusion magnification of the wet stretching step deviates from the above range, the dye unevenness cannot be lowered, and the optical characteristics of the final polarizing film are not sufficient. Further, the wet stretching step is not carried out in a single bath, and may be carried out continuously in a plurality of steps using a plurality of baths. In this case, the cumulative stretching magnification is 1.1 times or more and less than 3 times. In the extension method, for example, an inter-roll extension method -10- 1362509 in which a film having a difference in rotational speed is provided in a nip roll before and after the immersion bath can be suitably employed, but is not limited thereto, and may be employed. Know the various extension methods.

The bath used in the wet stretching step is an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid based on 100 parts by weight of water. However, by using such an aqueous solution of boric acid, there is an advantage that wrinkles are hard to occur. Further, the temperature of the bath used in the wet stretching step is preferably from 10 ° C to 40 ° C. When the temperature of the bath is lower than 10 °C, it is not necessary to control the large-scale cooling equipment at the temperature. On the contrary, when it exceeds 40 °C, the raw paper roll film is dissolved.

After the extension treatment, the film was dyed. The dyeing step by a usual dichroic dye is carried out for the purpose of adsorption, orientation, and the like of the film by a dichroic dye. The treatment conditions are determined within a range in which such a purpose can be attained, and the extent to which the substrate film is extremely dissolved, and the transparency is not properly caused. In the case of using iodine in the case of dichroic dye, for example, at 10 ° C to 45 ° C, preferably 2 (TC to 35 ° C, and the weight ratio iodine / KI / water = 0.003 to 0.2 / The concentration of 〇·1~1 〇/1 进行 is 30 seconds to 600 seconds, preferably 60 seconds to 3:00 seconds. Other iodides such as zinc iodide may be used instead of potassium iodide. Iodide and potassium iodide may be used. Also, compounds other than iodide may be coexisted with boric acid 'zinc chloride', cobalt chloride, etc. In the case of adding boric acid, the point of containing iodine may be The difference in boric acid treatment is considered to be a dyeing tank when the iodine content is 0.003 parts by weight or more based on 1 part by weight of water. In the case of using a water-soluble dichroic dye as a dichroic dye, for example, at 20 ° C. 80 ° C ' is preferably 30 ° C ~ 70 ° C temperature, and the weight is more than the concentration of dichroic dye / water = 0.001 ~ 0.1 / 100 30 seconds -11 - 1362509 600 seconds, preferably 60 seconds Immersion treatment for ~300 seconds. The aqueous solution of the dichroic dye used may have a dyeing assistant or the like, and may, for example, contain sodium sulfate or the like. Inorganic salts, surfactants, etc. Dichroic dyes can be used alone or in combination with more than two types of dichroic dyes. Also 'with the swelling step, the open roll, spiral light, medium and high rate rolls, Transducer, steel, etc., can also be placed in the dye bath and / or bath inlet and outlet

The boric acid treatment after the dyeing is carried out by impregnating a polyvinyl alcohol-based film dyed with a dichroic dye in an aqueous solution containing about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. In the case where the dichroic dye is iodine, the iodide may be contained in an amount of about 1 to 30 parts by weight. The iodide may, for example, be potassium iodide or zinc iodide. Further, it may coexist with a compound other than the iodide such as zinc chloride, cobalt chloride, cesium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate or the like. This boric acid treatment is carried out by water resistance or hue adjustment (prevention of φ with blue, etc.) due to crosslinking. In the case of water resistance due to crosslinking, a crosslinking agent such as glyoxal or glutaraldehyde may be used in addition to or in addition to boric acid. Further, boric acid treatment for hydration resistance is also known as a water resistance treatment, a crosslinking treatment, and an immobilization treatment. Further, the boric acid treatment for adjusting the hue may be referred to as a color correction process or a dyeing process. This boric acid treatment can be carried out by appropriately changing the concentration of boric acid and iodide and the temperature of the treatment bath depending on the purpose. -12- 1362509 The boric acid treatment for hydration resistance is not particularly distinguished from the boric acid treatment for hue adjustment, and can be carried out under the following conditions.

In the case where the raw material roll paper film is subjected to swelling, dyeing, and boric acid treatment, and boric acid treatment is used for water resistance due to crosslinking, about 3 to 10 parts by weight of boric acid is used with respect to 100 parts by weight of water, and iodide is about 1 The 20 parts by weight of the boric acid treatment bath is usually carried out at a temperature of from 50 ° C to 70 ° C, preferably from 55 ° C to 65 ° C. The immersion time is usually about 30 to 600 seconds, preferably 60 to 420 seconds, more preferably 90 to 300 seconds. Further, the pre-stretched film is dyed, and in the case of boric acid treatment, the temperature of the boric acid treatment bath is usually , from 50 ° C to 85 ° C, preferably from 55 ° C to 80 ° C.

After treatment with boric acid for hydration resistance, boric acid treatment for hue adjustment can also be carried out. For example, when the dichroic dye is iodine, 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 may be used with respect to 100 parts by weight of water, usually at 10 °. C~45. (: The temperature is carried out. The immersion time is usually about 3 to 300 seconds, preferably 10 to 240 seconds. The hue adjustment is performed with boric acid, and compared with the boric acid treatment for hydration, usually, The low boric acid concentration, the high iodide concentration, and the boric acid treatment at a low temperature may be carried out in a plurality of steps, usually in the step of 2 to 5. In this case, the aqueous solution of each of the boric acid treatment tanks is used. The temperature may be the same even if it is the same in the above range, and the boric acid treatment for the hydration resistance may be carried out in the steps of -13 to 1362509 in the boric acid treatment step. The step can also be carried out by stretching the film. The final cumulative extension magnification is about 4.5 to 7.0 times, preferably 5.0 to 6.5 times.

After boric acid treatment, it can be washed with water. For the water washing treatment, for example, a polyvinyl alcohol-based film treated with boric acid may be immersed in water for water hydration and/or color tone adjustment, and sprayed with water as a spray or dipped and sprayed. The water temperature in the water washing treatment is usually about 2 to 40 ° C, and the immersion time is preferably about 2 to 120 seconds. The drying after washing with water is carried out in a drying oven at a temperature of about 40 to 100 ° C for about 60 to 600 seconds. In the present invention, the wet stretching step before the dyeing treatment after the above-mentioned swelling treatment adds a shaft extension, and between the swelling step and the boric acid treatment step, a shaft extension is performed in at least one step. This one-axis extension can be carried out in steps, and can be carried out in steps of 2 or more, preferably in the plural steps. Further, as described above, the cumulative stretching magnification is finally made to be about 4.5 to 7.5 times, preferably 5.0 to 6.5 times. At least one side of the polarizing film thus produced can obtain a polarizing plate which bonds the protective film with an adhesive. The protective film may, for example, be a film of a vinylidene-based cellulose or a vinylidene-based cellulose-like resin, polyethylene terephthalate or polynaphthoic acid. A film formed of a polyester resin such as ethylene terephthalate or a polybutylene terephthalate film, a film formed of a polycarbonate resin, and a film formed of a cycloolefin resin. For the commercially available thermoplastic cycloolefin resin, for example, Topas (registered trademark) sold by Ticona, Germany, -14- 1362509 Arton (registered trademark) sold by JSR, Zee sold by Zeon, Japan 〇nor or Zeonex (both registered trademarks), Apel (registered trademark) sold by Mitsui Chemicals Co., Ltd., etc. The film formed of these cycloolefin-based resins is used as a protective film, and a known method such as solvent casting or melt-pressing method can be suitably used for the film formation. The film-formed cycloolefin-based resin film is also commercially available, for example, "Essina" or "SCA40" sold by Sekisui Chemical Co., Ltd.

The thickness of the protective film is preferably thin, but if it is too thin, the strength is lowered, and the workability is deteriorated. On the other hand, if the thickness is too thick, the transparency is lowered, and the maintenance time is required to be long after lamination. produce. Therefore, the appropriate thickness of the protective film is, for example, about 5 to 200 / / m, preferably 10 to 150 μm, more preferably 20 to 100 / zm.

In order to improve the adhesion between the adhesive and the polarizing film and/or the protective film, the polarizing film and/or the protective film may be subjected to corona discharge treatment, pyrotechnic treatment, plasma treatment, ultraviolet irradiation, heuristic coating treatment, saponification. Surface treatment such as processing. The protective film may be subjected to an anti-glare treatment, an anti-reflection treatment, a hard coating treatment, an antistatic treatment, a surface treatment such as an antifouling treatment, or the like, which may be carried out singly or in combination. Further, the protective film and/or the protective film surface protective layer may have a UV absorber such as a diphenylketone-based compound benzotriazole-based compound or a phenyl phosphate-based compound or a phthalate compound. Agent. The protective film can be applied to one side of the polarizing film or to both sides. -15- 1362509 Polarized film and protective film means that it can be laminated using an aqueous solvent-based adhesive, an organic solvent-based adhesive, a hot-melt adhesive, and a solvent-free adhesive. Examples of the aqueous solvent-based adhesive include a polyvinyl alcohol-based resin aqueous solution, an aqueous two-liquid urethane-based emulsified adhesive, and the like, and an organic solvent-based adhesive, for example, a two-component urethane-based adhesive. Examples of the binder and the like, and the solvent-free binder are, for example, a one-liquid type urethane-based adhesive. When the adhesive surface of the polarizing film is hydrophilized by saponification or the like, the acetaminocellulose-based film is used as a protective film, and the polyvinyl alcohol-based resin aqueous solution can be suitably used as a binder. In addition to the vinyl alcohol homopolymer obtained by saponifying the polyvinyl acetate of the individual polymer of vinyl acetate as a binder, the vinyl acetate and other monomers copolymerizable therewith The vinyl alcohol-based copolymer obtained by saponifying the copolymer, and a modified polyvinyl alcohol-based polymer obtained by partially densifying the hydroxyl group. Here, the binder can be used as an additive such as a polyvalent aldehyde, a water-soluble epoxy compound, or a melamine-based compound. The bonding method of the bonding polarizing film and the protective film is not particularly limited, and for example, the bonding agent may be uniformly applied on the surface of the polarizing film or the protective film, and the other film may be laminated on the coated surface by a roller or the like. Combination, drying method, etc. Usually, the adhesive is applied at a temperature of 15 to 40 ° C after the preparation, and the bonding temperature is usually in the range of about 15 to 30 ° C. After the lamination, the drying treatment is carried out to remove the solvent such as water contained in the binder, and the drying temperature at this time is usually 30 to 85 ° C, preferably 40 to 80 ° C -16 to 1362509. Thereafter, at a temperature of 15 to 85 ° C, preferably 20 to 50 ° C, more preferably 35 to 45 ° C, it is usually cured for about 1 to 90 days to harden the adhesive. If the maintenance period is too long, the productivity is deteriorated, so during the curing period, it is about 1 to 30 days, preferably 1 to 7 days. Thus, a polarizing plate for bonding the protective film can be obtained on one or both sides of the polarizing film through the adhesive layer.

In the present invention, in the protective film, the function of the phase difference film, the function of the film is enhanced by the brightness, the function of the film is reflected, the function of the semi-transmissive film is used, the function of the film is diffused, and the function of the film is optically compensated. Can have optical functions. In this case, for example, on the surface of the protective film, the lamination of the optical functional film by the retardation film, the brightness enhancement film, the reflection film, the semi-transmissive reflection film, the diffusion film, the optical compensation film, etc., may have such a In addition to the function, the protective film itself can also be assigned such functions. Further, the protective film itself may have a plurality of functions such as a diffusion film having a function of improving the brightness of the film.

For example, the above-mentioned protective film is subjected to the extension treatment described in Japanese Patent No. 2,84, 133, Japanese Patent No. 3,094, 133, and the like, and the processing described in Japanese Patent No. 3168850 or the like can be performed. The function of the phase difference film is given. Further, in the above-mentioned protective film, fine pores are formed by the method described in JP-A-2002-169025 or JP-A-2003-29030, and cholesteric liquid crystal having two or more layers having different center wavelengths of selective reflection is selected. The layers are overlapped to impart the function of improving the brightness film. The protective film is formed by vapor deposition or sputtering to form a metal film, -17-1362509, which can be imparted with a reflective film or a semi-transmissive reflective film. In the above protective film, a resin solution containing fine particles is coated to impart a function of a diffusion film. Further, the liquid crystalline compound such as the protective film disc-type liquid crystal compound is coated and oriented to impart an optical compensation film. In addition, a brightness-enhancing film such as a product name: DBF (manufactured by 3M Co., Ltd.), and a viewing angle improvement film such as a WV film (manufactured by Fuji Photo Film Co., Ltd.), and a product name: Sumikalight φ (registered) A phase difference film such as a trademark (Sumitomo Chemical Industry Co., Ltd.) or the like may be directly bonded to a polarizing film. Hereinafter, the present invention will be specifically described by way of examples, but the invention is not limited to the examples. In the following examples and comparative examples, a longer film of polyvinyl alcohol was used, and a continuous conveying apparatus in which a roll and a free roll were combined was conveyed while performing various treatments. The drive system is extended with a difference in rotational speed before and after the treatment tank. [Embodiment] [Example 1] A polyethoglycol film (Kuraray vinyron VF-PS #7500, polymerization degree 2,400, saponification degree: 99.9 mol% or more) having a thickness of 75 #m was kept at 30 ° C in pure water. The film was immersed for about 130 seconds to prevent the film from slacking and to sufficiently swell the film. After the water is removed by the roll, it is impregnated with an aqueous solution containing a boric acid/water weight ratio of 0.1/100 at a temperature of 30 ° C. -18-1362509

While the tank was immersed for about 120 seconds, one-fold extension of 1.2 times was carried out in this tank. Then, the mixture was immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.02/15/100 while performing one-axis extension. Thereafter, the potassium iodide/boric acid/water was immersed in an aqueous solution of 10/5/100 by weight at 60 ° C for about 180 seconds, and subjected to hydration treatment while performing one-axis extension from the cumulative extension magnification of the raw material roll paper to 5.9 times. Finally, it was washed with pure water of 101: about 10 seconds, and then dried at 60 ° C for 2 minutes to obtain an iodine-based polarizing film. On the both surfaces of the polarizing film, triethylenesulfonyl cellulose (hereinafter referred to as TAC) was bonded to each other to form a polarizing plate. [Example 2] Polyvinyl alcohol film of thickness (Kuraray viny ron V F -

PS#7500, degree of polymerization 2,400, saponification degree: 99.9 mol% or more) Pure water of 30 ° C was immersed for about 130 seconds while being kept under tension, so that the film did not relax and the film was sufficiently swollen. After the water is removed by the roll, the ratio of the boric acid/water ratio of 0.1/100 is added to the ratio of the ratio of the ratio of the boric acid/water ratio of 0.1/100 (the dipping bath of the aqueous solution of TC is immersed for about 120 seconds, and the axis is extended by 2.0 times in the groove). While immersing in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.02/1.5/100, a one-axis extension is carried out, and thereafter, an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 10/5/100 is immersed at 60 ° C for about 180 seconds. At the same time, the water-resistant treatment is carried out for one-axis extension from the cumulative extension magnification of the raw material roll paper to 5.9 times. Finally, it is washed with pure water at 10 ° C for about 10 seconds, and then dried at 60 ° C for 2 minutes to obtain The iodine-based polarizing film was bonded to TAC to form a polarizing plate in the same manner as in Example 1. -19- 1362509 [Comparative Example 1] A polyoxyethylene alcohol film having a thickness of 75 #m (Kuraray vinyron VF-PS #7500, polymerization degree 2,400, The degree of saponification is 99.9 mol% or more. The pure water at 30 ° C is immersed for about 130 seconds while being kept under tension, so that the film does not relax, and the film is sufficiently swollen. After removing the moisture by the roll, then, at 30 ° C The pure water tank is immersed for about 120 seconds while being 1.2 times in the tank. The shaft is extended. Then, the iodine/potassium iodide/water weight ratio of 0.02/1.5/100 is impregnated while the one-axis extension is carried out. Thereafter, the weight ratio of potassium iodide/boric acid/water is 10/5/100 to 60. After immersing in °C for about 180 seconds, the water-resistant treatment was carried out while the cumulative extension of the raw material roll paper was amplified to 5.9 times, and the axial stretching was carried out. Finally, after washing with pure water of 10 ° C for about 10 seconds, at 60 ° After drying at ° C for 2 minutes, an iodine-based polarizing film was obtained. Then, TAC was bonded to the polarizing plate in the same manner as in Example 1.

[Comparative Example 2] A polyethylene film of a thickness (Kuraray vinyron VF-PS #7500, degree of polymerization 2,400, degree of saponification 99.9 mol% or more) was immersed in a pure water at 30 ° C for about 130 seconds while being kept under tension. The film is not slackened, and the film is sufficiently swollen to remove moisture by the roll, and then, while being immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.02/1.5 /1 00, one-axis extension is performed. Thereafter, the aqueous solution of potassium iodide/boric acid/water in a weight ratio of 10/5/100 was immersed at 60 eC for about 180 seconds, and the water-resistant -20-1362509 treatment was carried out while the cumulative extension magnification of the raw material roll paper was 5.9 times. One axis extends. Finally, it was washed with pure water of 10 ° C for about 10 seconds, and then dried at 60 ° C for 2 minutes to obtain an iodine-based polarizing film. Next, TAC was bonded to the polarizing plate in the same manner as in Example 1. [Comparative Example 3]

The thickness of 75" m polyethylene film (Kuraray vinyron VF. PS#7 500, degree of polymerization 2,400, saponification degree 99.9 mol% or more) was immersed in pure water at 30 ° C for about 130 seconds while maintaining tension. The film is not slackened and the film is sufficiently swollen. Subsequently, the mixture was immersed in an aqueous solution dipping bath containing a boric acid/water ratio of 30 ° C at a weight ratio of 〇·1/100 for about 120 seconds, and a 4.0-fold one-axis extension was carried out in the tank. The water was removed by a roll and then immersed in an aqueous solution of iodine/potassium iodide/water at a weight ratio of 0.02/1.5/100 while performing one-axis extension. Thereafter, the aqueous solution of potassium iodide/boric acid/water in a weight ratio of 10/5/100 was immersed at 60 ° C for about 180 seconds, and subjected to a water resistance treatment while performing one-axis stretching from the cumulative extension magnification of the raw material roll paper to 5.9 times. Finally, it was washed with pure water at 10 ° C for about 10 seconds, and then dried at 6 ° C for 2 minutes to obtain an iodine-based polarizing film. Next, TAC was bonded to the polarizing plate in the same manner as in Example 1. The color unevenness of the polarizing plates obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was observed in a dark room. That is, after the obtained polarizing plate was placed in a dark room with crossed nicol, the color unevenness was visually observed on a backlight of 6000 cd/m2. Next, the size of the color unevenness is determined by visually checking the 5th order -21 - 1362509 segments of 1, 2, 3, 4, and 5. Evaluation 1 indicates that the unevenness is the least, and evaluation 5 indicates that the unevenness is the most. The results are shown in Table 1. [Table 1] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Evaluation Results 1 1 2 4 4

As is apparent from Table 1, in Examples 1, 2, a wet stretching step was provided between the swelling step and the dyeing step, and the film was appropriately stretched in the aqueous solution containing boric acid to reduce the color unevenness of the film.

-twenty two-

Claims (1)

1362509 X. Applying for a patent garden A method for producing a polarizing film, characterized in that 'the polyvinyl alcohol-based film is continuously treated in a bath by swelling treatment, dyeing treatment, boric acid treatment, and at least one dyeing treatment in the treatment steps And a method for producing a polarizing film for obtaining a polarizing film by a step of boric acid treatment, wherein the swelling treatment is performed by immersing the polyvinyl alcohol-based film in water, and at least before the dyeing treatment after the swelling treatment a wet stretching step of 1 step, wherein the stretching step is performed by using an aqueous solution containing 0.01 to 2.0 parts by weight of boric acid relative to 100 parts by weight of water, so that the polyvinyl alcohol-based film is extended by 1.1 times or more and less than 3 times in the aqueous solution. The magnification is extended by one axis, and the cumulative extension magnification until the polarizing film is obtained is in the range of 4.5 to 7.0 times. 2. The method for producing a polarizing film according to claim 1, wherein the temperature of the bath used in the wet stretching step is from 10 ° C to 40 ° C. -twenty three-