KR20080005357A - Iodine-containing polarizing film, process for producing the same, and polarizer comprising the same - Google Patents

Abstract

A polarizing film obtained by stretching a polyvinyl alcohol resin film containing iodine, an iodide, and a crosslinking agent and/or water resistance imparter and then treating the film with a solution which contains either an inorganic acid other than boric acid or a salt thereof and/or an organic acid in an amount of 0.0001-5.0 wt.% and which has a pH of desirably 2-5, preferably 2.2-5. The polarizing film is excellent in wet heat durability and is less apt to decrease in polarizing properties in a wet heat durability test. The polarizing film obtained according to the preferred embodiment is excellent also in dry heat durability.

Description

Iodine polarizing film, its manufacturing method and polarizing plate using the same {IODINE-CONTAINING POLARIZING FILM, PROCESS FOR PRODUCING THE SAME, AND POLARIZER COMPRISING THE SAME}

The present invention relates to an iodine polarizing film, a manufacturing method thereof, and an iodine polarizing plate using the iodine polarizing film.

The polarizing plate is generally a polarizing film by adsorbing or aligning iodine or dichroic dye, which is a dichroic dye, to a polyvinyl alcohol-based resin film, and attaching a protective film made of triacetyl cellulose or the like to one or both surfaces thereof through an adhesive layer. It can be used as a polarizing plate and a liquid crystal display device. A polarizing plate composed of a polarizing film using iodine as a dichroic dye is called an iodine polarizing plate, while a polarizing plate composed of a polarizing film using a dichroic dye as a dichroic dye is called a dye polarizing plate. Iodine-based polarizing plates are widely used in general liquid crystal displays, liquid crystal televisions, mobile phones, PDAs, and the like in view of high transmittance and high polarity, that is, high contrast, compared to dye-based polarizing plates. However, the iodine polarizing plate is superior to the dye polarizing plate in terms of optical properties, but is inferior to the dye polarizing plate in terms of optical durability. For example, when the iodine polarizing plate is left under high temperature and high humidity, there is a problem that the transmittance increases due to decolorization and the degree of polarization decreases. Moreover, in dry heat durability, when it is left to stand at high temperature, the fall of polarization degree will generate | occur | produce. A polarizing plate having a high transmittance and a high degree of polarization and excellent in high contrast, heat resistance and moisture and heat resistance is desired. As the invention for this request, as described in Patent Documents 1 and 2, a method of improvement by a protective film It is described that improving wet heat durability by the method of modifying the adhesive agent which adheres the protective film of triacetyl cellulose like patent document 3 and patent document 4 is mentioned. In addition, there is an example in which durability is improved as an iodine polarizing plate by treating a polyvinyl alcohol-based resin film instead of improving durability by a protective film or an adhesive. As one of them, the durability improvement by acid treatment and pH control is described in patent documents 5, 6, 7, and 8. For example, in Patent Literature 5, polarized light in which a polyvinyl alcohol-based resin film formed of a boron compound-containing polyvinyl alcohol-based resin film is immersed in an acidic aqueous solution, and the durability is improved by using a stretched polyvinyl alcohol-based resin stretched film. Disclosed is a film. In addition, Patent Document 6 discloses a method for producing a polarizing film having excellent moisture and heat resistance by oxidizing a film made of polyvinyl alcohol-based resin in an oxidation bath containing an oxidizing agent such as hydrogen peroxide containing an alkali metal iodide. Patent Document 7 discloses a method for producing an iodine-based polarizing film in which a polyvinyl alcohol film subjected to uniaxial stretching and adsorption orientation treatment of iodine is treated with an aqueous boric acid solution having a pH of 4.5 or less. In patent document 8, the patent of the polarizer (polarizing film) whose pH of the liquid at the time of melt | dissolving in water is 1.0-5.0 is disclosed.

Patent Document 1: Japanese Unexamined Patent Publication H08-5836

Patent Document 2: Japanese Patent Application Laid-Open No. 2001-272534

Patent Document 3: Japanese Unexamined Patent Publication 2004-12578

Patent document 4: Unexamined-Japanese-Patent No. H09-269413

Patent document 5: Unexamined-Japanese-Patent No. H06-254958

Patent Document 6: Japanese Laid-Open Patent Publication H07-104126

Patent Document 7: Japanese Unexamined Patent Publication 2001-83329

Patent Document 8: Japanese Unexamined Patent Publication 2005-62458

Challenges the invention seeks to solve

In the method of immersing the polyvinyl alcohol-type resin film formed by the boron compound containing polyvinyl alcohol-type resin film of patent document 5 in acidic aqueous solution, and extending | stretching, in the aqueous solution containing boric acid, iodine, and potassium iodide which are immersed when extending | stretching An acidic component eluted from the polyvinyl alcohol-based resin film in the so-called 'dye bath', and there was a problem that the durability improvement effect of the obtained polarizing film could not be sufficiently obtained. Moreover, in patent document 6, since it is processed in the oxidation bath which adjusted pH before extending | stretching, the effect of improving the moisture-and-moisture resistance of the polarizing film obtained by eluting an oxidizing agent with an extending | stretching bath from a polyvinyl alcohol-type resin film at the time of extending | stretching is acquired sufficiently. There was a problem that I could not. Patent Document 7 discloses that treatment is performed by maintaining an aqueous solution containing boric acid at pH ≦ 4.5 or less. However, when the acid is treated with boric acid, the treatment efficiency of the polyvinyl alcohol-based resin film and an acidic substance is poor. Variation in treatment occurs in the film. For example, when looking at the Example of patent document 7, when it processes with the boric acid containing treatment liquid of pH = 3.4, the polarization degree change will be 1.3, and the polarization degree change at pH = 2.1 is 2.0. From this point of view, this method shows that stable properties cannot be obtained even by pH control, and that even if pH is controlled, the intended durability can not be obtained stably. Moreover, the literature describes that an acidic substance vaporizes when the process temperature (process liquid temperature) in a process is high. In patent document 8, the patent which consists of a film which extended | stretched the polyvinyl alcohol film, and whose pH of the liquid melt | dissolved in water is 1.0-5.0 is disclosed. However, although the wet heat durability of the polarizing plate obtained by this method is improved, for example, in the heat resistance test under a high-temperature atmosphere at 90 ° C., the decrease in transmittance is drastic, depending on the light source and the use environment of the liquid crystal display device. The display may become dark. Due to these problems, the polyvinyl alcohol-based resin film containing iodine does not contain boric acid so that it can be treated efficiently and can be treated at high temperature as well as low temperature in order to stabilize the acid concentration. By applying an acidic substance treatment with a solution which does not have a solution, there has been a demand for an iodine polarizing plate having improved wet heat durability and excellent dry heat durability.

Means to solve the problem

As a result of earnestly examining in order to solve the said subject, 0.0001-5.0 inorganic acid or its salt and / or organic acid except boric acid after extending | stretching the polyvinyl alcohol-type resin film containing an iodine, an iodide, a crosslinking agent, and / or a water-resistant agent are carried out. Obtained by treatment with a solution containing% by weight (hereinafter referred to as 'wt%', unless otherwise indicated)% by weight) (hereinafter sometimes referred to as 'acid treatment solution'). The polarizing film has improved wet heat durability, little change in transmittance, and the processing temperature of acidic material can be processed at high temperature as well as at low temperature, so that acidic material can be treated stably without volatilization. . In addition, when the pH of the acid treatment solution is set to 2 to 5, more preferably 2.2 to 5, or in some cases 2.4≤pH <6.0, it is found that dry heat durability is also increased, and acidic together with boric acid By applying the treatment with a solution of 2.4 ≦ pH <6.0 containing an acid with a halide without applying boric acid rather than bringing the pH to 4.5 using the material, and applying a drying treatment after treating the acid, Newly discovered that a polarizing plate with little variation in characteristics, high wet heat durability, and excellent dry heat durability can be obtained, and have completed the present invention.

That is, the present invention,

(1) After stretching a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-repellent agent, a solution containing 0.0001 to 5.0 wt% of an inorganic acid or a salt thereof and / or an organic acid excluding boric acid (hereinafter Polarizing film obtained by treatment with &quot; acid treatment solution &quot;

(2) The polarizing film according to the above (1), wherein the pH of the acid treatment solution is 2≤pH <5,

(3) In the above (1), the polyvinyl alcohol-based resin film containing iodine, iodide, crosslinking agent and / or water-repellent agent is treated with an acid treatment solution having a pH of 2.4 ≦ pH <6.0 after stretching treatment. Obtained polarizing film,

(4) The polarizing film according to the above (1), wherein the halide is contained in a solution containing an inorganic acid or a salt thereof and / or an organic acid except boric acid,

(5) The polarizing film according to the above (1), wherein the inorganic acid or salt thereof except boric acid is any one of aluminum sulfate, aluminum chloride, aluminum nitrate or sulfuric acid, or two or more,

(6) the polarizing film of (1) to (2), wherein the inorganic acid or its salt except boric acid is aluminum sulfate;

(7) The polarizing film in any one of said (1)-(6) whose organic acid is 1 or more types of carboxylic acid and / or (alpha) -hydroxy acid, and is obtained by processing with the solution containing this organic acid,

(8) The polarizing film of (7), wherein the organic acid is any one or more of citric acid, oxalic acid, malic acid, tartaric acid or acetic acid, and is treated with a solution containing the organic acid,

(9) The polarizing film in any one of said (1)-(8) whose said polyvinyl alcohol-type resin film after extending | stretching was extended | stretched 3 to 8 times compared with before extending | stretching in a draw ratio,

(10) The polarizing film according to (1) or (9), wherein the crosslinking agent and / or the water-resistant agent used in the stretching treatment is boric acid,

(11) A polarizing plate in which a protective layer is formed on one or both surfaces of the polarizing film according to any one of the above (1) to (9),

(12) a liquid crystal display device comprising the polarizing plate according to (11) above;

(13) A method for producing a polarizing film, wherein the polyvinyl alcohol-based resin film containing iodine, iodide, crosslinking agent and / or water-repellent agent is treated with an acid treatment solution of 2.4 ≦ pH <6.0 after stretching treatment. ,

(14) A polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-repellent agent was treated with an acid treatment solution of 2.4 ≦ pH <6.0 after stretching treatment and obtained on one side of the polarizing film or Method for producing a polarizing plate, characterized in that to form a protective layer on both sides,

(15) A method for producing a polarizing film, wherein the polyvinyl alcohol-based resin film containing iodine, iodide and a crosslinking agent is treated with an acid treatment solution of 2.2 ≦ pH ≦ 5 after stretching treatment;

(16) A solution containing 0.0001 to 5.0 wt% of an inorganic acid or a salt thereof and / or an organic acid excluding boric acid after stretching of a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-repellent agent (hereinafter Method for producing a polarizing film, characterized in that the treatment with ('acid treatment solution'),

(17) The solution for acid treatment according to (15), wherein the solution for acid treatment is sulfuric acid, hydrochloric acid, nitric acid, aluminum sulfate, aluminum chloride, aluminum nitrate, formic acid, citric acid, chloroacetic acid, acetic acid, oxalic acid, malic acid and tartaric acid. Method for producing a polarizing film which is an aqueous solution containing at least one acidic material selected,

(18) In the above (17), the pH of the solution for acid treatment relates to a method for producing a polarizing film of 2 to 5.

Effects of the Invention

Since the obtained polarizing film is treated with an acidic substance after stretching, there is no intrusion of an acidic substance into the dye bath, and since boric acid is not used after stretching, there is no problem of precipitation due to boric acid. It can be stably produced a polarizing film. In addition, in a humid heat environment, for example, at a temperature of 65 ° C. and a relative humidity of 93%, a change in transmittance and a decrease in polarization degree are small, and when manufactured under favorable conditions, a change in transmittance even in a dry heat environment, for example, at 90 ° C. A few excellent polarizing films or polarizing plates can be obtained. By using such a polarizing film or polarizing plate of this invention, long-term display stability of a liquid crystal display can be ensured.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The manufacturing method of the polyvinyl alcohol-type resin which comprises a polarizing film is not specifically limited, It can manufacture by a well-known method. As a manufacturing method, it can obtain by saponifying polyvinyl acetate type resin, for example. As polyvinyl acetate type resin, the copolymer etc. of vinyl acetate and the other monomer copolymerizable with this besides the polyvinyl acetate which is a homopolymer of vinyl acetate are illustrated. As another monomer copolymerized with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ether, unsaturated sulfonic acid, etc. are mentioned, for example. The saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, Preferably 95 mol% or more is preferable. This polyvinyl alcohol-type resin may further be modified. For example, polyvinyl foam modified with aldehydes, polyvinyl acetal, or the like can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1, 000 to 10,000, preferably about 1, 500 to 5,000.

What formed such a polyvinyl alcohol-type resin film is used as a raw film. The method of film-forming polyvinyl alcohol-type resin is not specifically limited, It can form film by a well-known method. In this case, the polyvinyl alcohol-based resin film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, or the like as a plasticizer. The amount of plasticizer is 5 to 20 wt%, preferably 8 to 15 wt%. Although the film thickness of the raw film comprised from polyvinyl alcohol-type resin is not specifically limited, 5-150 micrometers is preferable and 10-100 micrometers is especially preferable.

The polyvinyl alcohol-based resin film (hereinafter also referred to as "PVA film") is first subjected to a swelling treatment (also referred to as a "swelling step"). The swelling treatment is performed by immersing in a solution at 20 to 50 ° C. for 30 seconds to 10 minutes. The solution at that time is preferably water, but may be a water-soluble organic solvent such as glycerin, ethanol, ethylene glycol, propylene glycol or low molecular weight polyethylene glycol, or a mixed solution of water and water-soluble organic solvent. In the case of shortening the time for producing the polarizing film, the swelling step can be omitted since it swells even during treatment with iodine and iodide.

After the swelling step, the polyvinyl alcohol-based resin film is treated with a solution containing iodine and iodide (hereinafter also referred to as 'dyeing step'). Although the treatment method is preferably immersed in this solution, the solution may be treated by applying or coating the polyvinyl alcohol-based resin film. As a solvent of a solution, water is preferable, for example, but it is not limited. As iodide, alkali iodide compounds, such as potassium iodide, ammonium iodide, cobalt iodide, zinc iodide, etc. can be used, for example, Although it is not limited, Usually, an alkali iodide compound is preferable and potassium iodide is more preferable. The iodine concentration is preferably 0.0001 to 0.5 wt%, more preferably 0.001 to 0.4 wt%. The iodide concentration is preferably 0.0001 to 8 wt%. 5-50 degreeC is preferable, as for the processing temperature in this process, 5-40 are more preferable, and its 10-30 degreeC is especially preferable. Since the treatment time depends on the concentration of iodine and iodide to be adsorbed, the treatment time can be appropriately adjusted. However, the treatment time is preferably adjusted to 30 seconds to 6 minutes, more preferably 1 to 5 minutes. After this treatment, washing may be performed before entering the next step. As the solvent to be washed, water can be generally used. By performing the washing, it is possible to suppress the migration of iodine and iodide in the liquid to be processed next.

In the treatment of iodine and iodide, a crosslinking agent and / or a water resistant agent may be added to the solution. Usually a crosslinking agent is used. Although it does not specifically limit as a crosslinking agent, Usually, boric acid is preferable. 0.1-5.0 wt% is preferable and, as for the density | concentration which adds a crosslinking agent, for example, boric acid, 2-4 wt% is more preferable. The water resistant agent can be used later. 5-50 degreeC is preferable, as for the processing temperature in this process, 5-40 degreeC is more preferable, and 10-30 degreeC is especially preferable. Since the treatment time depends on the concentration of iodine and iodide to be adsorbed, the treatment time can be appropriately adjusted. However, the treatment time is preferably adjusted to 30 seconds to 6 minutes, more preferably 1 to 5 minutes. After this treatment, washing may be performed before entering the next step. As the solvent to be washed, water can be generally used. By performing the washing, it is possible to suppress the migration of iodine, iodide and boric acid in the liquid to be treated next.

In the present invention, in the case of using a polyvinyl alcohol-based resin film containing iodine, iodide, crosslinking agent and / or water repellent, iodide, iodide, crosslinking agent and / or water repellent must be included in the PVA film as it is. The iodine, the iodide, the crosslinking agent, and / or the water repellent are included in the form reacted in the PVA film through the dyeing treatment and the crosslinking agent and / or the water repellent treatment. As the PVA film containing iodine, iodide, crosslinking agent and / or water repellent, it is preferable to include iodine, iodide and crosslinking agent (preferably boron).

Usually, after the said dyeing process, a crosslinking agent process is performed (it is also called a "crosslinking agent process process."). Crosslinking agent treatment can be performed by treating a polyvinyl alcohol-type resin film with the solution containing a crosslinking agent. As described above, the dyeing step may be carried out in the presence of a crosslinking agent, but it is usually preferable to carry out after the dyeing step. In this case, the crosslinking agent treatment is performed by treating the polyvinyl alcohol-based resin film (hereinafter also referred to as 'dyed PVA film') obtained in this dyeing step with a crosslinking agent-containing solution. The method of treating the crosslinking agent-containing solution is usually preferably a method of immersing the dyed PVA film in this solution, but may also be a method of coating or coating the solution on a polyvinyl alcohol-based resin film. This immersion may be performed before the stretching treatment to be described later, or may be performed together with the stretching treatment. In the case of the dry stretching method, crosslinking treatment is preferably performed before stretching, and in the case of the wet stretching method, the stretching treatment is preferably performed together with the stretching treatment. Examples of the crosslinking agent include boric compounds such as boric acid or salts thereof (for example, alkali metal salts such as borax or ammonium borate), polyvalent aldehydes such as glyoxal or glutaaldehyde, biuret type, isocyanurate type or block type. Titanium compounds, such as polyhydric isocyanate type compounds, titanium oxosulfate, ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. can be used. Usually boron compounds are preferred, and boric acid is more preferred. Moreover, you may make water resistant agent coexist in crosslinking agent containing solution. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerine diglycidyl ether, ammonium chloride or magnesium chloride, zinc chloride, and the like. Magnesium chloride, zinc chloride, etc. are preferable. As a solvent in the crosslinking agent treatment, for example, water, an alcohol solvent, a glycol solvent, glycerin or a mixed solvent thereof may be used, and usually water is preferable. The crosslinking agent concentration in the crosslinking agent-containing solution cannot be uniformly determined depending on the type of the crosslinking agent, but is usually about 0.1 to 10 wt / vol% with respect to the solvent and a concentration of 0.1 to 6.0 wt / vol with respect to the solvent. Treatment with% is preferred, with 2 to 4 wt / vol% being more preferred. 5-60 degreeC is preferable and, as for processing temperature, 5-40 degreeC is more preferable. 30 second-6 minutes are preferable, and 1-5 minutes of processing time are more preferable.

Next, the dyed PVA film, or the PVA film treated with the dyeing and crosslinking agent, is stretched (preferably uniaxially stretched) to give polarity (hereinafter also referred to as 'uniaxial stretching process'). The stretching method may be either a wet stretching method or a dry stretching method. In the case of dry stretching, a crosslinking agent treated PVA film is usually used. In the case of the wet stretching method, a crosslinking agent-treated PVA film can be used, but it is preferable to perform crosslinking agent treatment together with stretching using a dyed PVA film which is not usually crosslinked.

Dry stretching is usually carried out by heating stretching the film in a gas medium. As this gas medium, air or an inert gas can be used, but air is usually used for economic reasons. In the case of an air medium, it is preferable to stretch a crosslinking agent-treated PVA film by making the temperature of this medium into about normal temperature-about 180 degreeC. In the case of an inert gas or the like, the same process as in the case of air may also be performed at higher temperatures. Moreover, it is preferable to perform this extending | stretching process in the atmosphere of 20 to 95% of a relative humidity. As the method of heat stretching of the film, for example, an inter-roll zone stretching method, a roll heating stretching method, a rolling stretching method, or an infrared heating stretching method can be considered, but the stretching method is not limited. Although extending | stretching process can be performed once (one step), you may apply two or more steps (multistage) multistage processing. 3 to 8 times are preferable and, as for the draw ratio at that time, 5 to 7 times are more preferable.

The wet stretching method is usually performed by immersing the film in an aqueous medium such as water, a water-soluble organic solvent or a mixed solution of water and the organic solvent, and stretching the film under ordinary heating. It is preferable to extend | stretch in the state which immersed the said film in the solution containing a crosslinking agent and / or a water-resistant agent. The stretching ratio is preferably 3 to 8 times, more preferably 5 to 7 times. It is preferable to perform extending | stretching in the aqueous medium heated at 40-60 degreeC, More preferably, 45-55 degreeC. Examples of the crosslinking agent include those mentioned above, for example, polyhydric isocyanates such as boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaaldehyde, biuret type, isocyanurate type or block type. Titanium compounds, such as a compound and a titanium oxusate, ethylene glycol glycidyl ether, a polyamide epichlorohydrin, etc. are mentioned. As a crosslinking agent, a boron compound is preferable, and boric acid is more preferable. Examples of the water-resistant agent include those mentioned above, for example, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride or chloride chloride. Zinc and the like. 0.5-8 wt% is preferable and, as for the density | concentration of a crosslinking agent and / or a water-resistant agent, 2.0-4.0 wt% is more preferable, for example. Although extending time can apply 30 second-20 minutes, 2 to 5 minutes are preferable. The stretching treatment may be performed once (one layer), or two or more stages of multistage treatment may be applied.

In the present invention, the uniaxially-stretched PVA film (hereinafter also referred to simply as 'uniaxially-stretched PVA film') refers to an inorganic acid or salt and / or an organic acid (hereinafter simply referred to as an 'acid substance') except for boric acid. It is characterized by treating with a solution containing 0.0001 to 5.0% by weight (hereinafter also referred to as "acid treatment solution"). By this process, the wet heat durability of a polarizing film can be improved, and dry heat durability can also be improved further in a preferable aspect. In the following cases, this treatment is also simply referred to as "treatment with an acidic substance". In the treatment with an acidic substance, it is usually preferable to immerse the stretched PVA film in a solution containing an acidic substance (preferably an aqueous solution, a water-soluble organic solvent solution or a mixed solution of the organic solvent and water).

Since the crosslinking agent may precipitate or the foreign matter adheres to the surface of the film after the stretching treatment, the surface of the film may be washed before the treatment with an acidic substance (hereinafter also referred to as "cleaning process"). In the washing step, washing with a solution containing boric acid may be performed. In some cases, in the washing with a solution containing boric acid, foreign matter may occur on the surface after the next step or drying. In this case, washing with a solution containing no boric acid, preferably water, is preferred. Moreover, when you may wash with the solution containing a boric acid, after the wash, an acid treatment is performed and it is made to dry, for example, so that a foreign material may not generate | occur | produce on a film surface after washing with a boric acid containing solution. This is the case including a treatment step. The cleaning time can be applied from 1 second to 5 minutes. The number of washings is not particularly limited, and may be one time or several washings two or more times as necessary.

After the stretching treatment, it is preferable to treat the stretched PVA film with a solution containing a halide together with or separately from treatment with an acidic substance. This treatment aims at adjusting the color and improving the polarization characteristic (hereinafter also referred to as 'halide treatment'). As a treatment method, the method of immersing a stretched PVA film in the solution, the method of apply | coating or coating this solution on this PVA film, etc. are mentioned, The method of immersion is more preferable. In addition, it is preferable to perform this halide treatment together with the treatment with an acidic substance. In this case, the PVA film may be treated by the above-described method with a solution containing a halide together with an acidic substance. As the halide, for example, alkali metal iodides such as potassium iodide and sodium iodide, iodide such as ammonium iodide, cobalt iodide or zinc iodide, potassium chloride, and chlorides such as alkali chloride metal compounds such as sodium chloride or zinc chloride are preferred. Furthermore, it is preferable that it is water-soluble. In chloride and iodide, iodide is preferable, and in iodide, it is an alkali metal iodide compound, More preferably, potassium iodide. The concentration of the halide is preferably 0.5 to 15 wt%, more preferably 3 to 8 wt%. Moreover, although 5-50 degrees C or less is preferable, for example, processing temperature, 20-40 degreeC is more preferable. The treatment time is preferably, for example, 1 second to 5 minutes, but is preferably 5 to 30 seconds in consideration of the stability of the in-plane characteristics of the polarizing film. When the purpose of color preparation is not aimed at, the process of processing with the solution containing this halide can be skipped.

After treatment with an acidic substance and, if necessary, halide treatment, the film is dried (hereinafter also referred to as a 'drying step'). Although natural drying is good at the time of drying, in order to further improve drying efficiency, the surface may be removed by compression with a roll, an air knife, an absorption roll, or the like, and / or blow drying may be performed. Although it is preferable to process at 20-90 degreeC as processing temperature, It is preferable to process at 40-80 degreeC preferably. The treatment time is preferably 30 seconds to 20 minutes, more preferably 2 to 10 minutes.

Although a solvent, such as water, an alcoholic solvent, or a glycolic solvent, is mentioned as a solvent of the process solution in the process up to here, for example, It is not limited. Moreover, you may use the mixed solvent of water and a water-soluble organic solvent, such as the solution which mixed water and alcohols, the mixed solvent of dimethyl sulfoxide, and water. Most preferably water.

Treatment with an acidic substance in the present invention can be carried out in any process as long as the polyvinyl alcohol-based film containing iodine, iodide, crosslinking agent and / or water-repellent agent is stretched (preferably uniaxially stretched). . For example, in the washing step after the stretching and / or the halide treatment step, the treatment with an acidic substance is performed together, or after the stretching of the film or after the washing step carried out as necessary, then independently Any of these may be performed, for example, by treatment with an acidic substance. Usually, after finishing stretching (preferably uniaxial stretching) for polarization, it is preferable to wash as necessary, and then to perform treatment with an acidic substance (sometimes referred to as 'acid treatment'). . Moreover, you may carry out in several processes as needed. More preferably, the stretched PVA film is immersed in a solution containing an acidic substance and a halide, and a treatment with an acidic substance and a halide treatment are performed together. The treatment with an acidic substance may be carried out with a treatment solution containing a crosslinking agent excluding boric acid and / or a water-repellent agent together with the acidic substance, if necessary. The concentration of the acidic substance in the treatment solution used for the treatment with the acidic substance is usually in the range of about 0.0001 to 5.0 wt%, preferably 0.0005 to 2 wt%, more preferably 0.001 to 1 wt%, Therefore, 0.01-2.0 wt% is more preferable. In addition, the pH of this treatment solution is preferably adjusted to 1.0 ≦ pH <6.0. More preferable pHs are in the range of 2 or more and less than 6.0, More preferably, they are about 2.1-5. The temperature and time of the acid treatment are not particularly limited as long as the effect of the present invention is achieved. Usually, the treatment temperature is less than 5 to 60 ° C, preferably about 10 to 40 ° C, and the treatment time is 2 to 300 seconds, preferably Is 3 to 60 seconds, more preferably about 5 to 40 seconds.

In some cases, in the washing step, the acid treatment may be performed simultaneously with the solution containing the acidic substance. The treatment temperature is preferably less than 5 to 60 ° C, more preferably 10 to 40 ° C. 2 to 300 second is preferable and, as for processing time, 2 to 60 second is more preferable.

The halide treatment may be carried out after the stretching treatment or after the washing treatment. The halide treatment may be carried out alone or as described above, and may be performed together with the acid treatment in the acid treatment step. The halide treatment applies a halide-containing solution to the PVA film (hereinafter simply referred to as a 'stretched film') after the stretching, and in the process of treating the stretched film, usually in an acid treatment process as described above. And acid treatment are preferred. The method of treating this film with the halide containing solution may be any method as long as the solution is applied to the surface of the stretched film. Usually, it is preferable to immerse the stretched film in the solution. When performing together with the acid treatment step, the film may be treated with a solution containing the halide together with the acidic substance. Preferably, the stretched film is immersed in a solution containing both of them. The concentration of the halide in the halide-containing solution used for the halide treatment is preferably in the range of 0.5 to 15 wt%. When the halide treatment is performed together with the acid treatment, a solution containing a halide in the above concentration range and an acidic substance in the range of 0.0001 to 5.0 wt% may be used. The treatment temperature is preferably, for example, less than 5 to 60 ° C, more preferably 20 to 40 ° C. The treatment time may be 2 seconds to 5 minutes, but 5 seconds to 1 minute is preferable.

As the acidic substance, both inorganic acid and organic acid can be used, and further, in those salts, those in which the aqueous solution shows acidic acid, preferably those in which the aqueous solution of the salt shows a value smaller than pH 6, preferably less than pH 5, Salts showing one or more values can also be used. Preferable inorganic acids include acids such as sulfuric acid, hydrochloric acid or nitric acid. Among these, sulfuric acid is more preferable. As the salt, salts of inorganic acids are usually used, and salts of the above-mentioned preferred inorganic acids, in particular aluminum salts, are preferable. Examples of such salts include aluminum sulfate, aluminum chloride or aluminum nitrate. Aluminum sulfate is particularly preferred but one. Zinc chloride, which is used as a water resistant agent, is not included in the acidic substance in the present invention because the aqueous solution does not fall within the pH range. As an organic acid, carboxylic acids are mentioned normally, C1-C4 saturated fatty acid which may have a hydroxy or halogeno substitution is preferable, and water-soluble organic acid which has a skeleton of (alpha)-hydroxy acid is one of the preferable things. As a specific example, formic acid, citric acid, chloro acetic acid, acetic acid, oxalic acid, malic acid or tartaric acid, etc. are mentioned, citric acid or acetic acid is preferable, and acetic acid is the most preferable. Although acidic substance may be used individually by 1 type, 2 or more types may be mixed and used for it. Among these acidic substances, aluminum sulfate is one of particularly preferable ones because of its high effect of improving wet heat durability. In organic acids, citric acid, acetic acid, oxalic acid and the like are generally used as food additives, and can be said to be preferable acidic substances in terms of environment and safety.

As an acidic substance, at least one acidic substance selected from the group consisting of sulfuric acid, aluminum salt of inorganic acid (preferably aluminum salt of inorganic acid selected from the group consisting of sulfuric acid, hydrochloric acid or nitric acid), citric acid and acetic acid is used. Aluminum sulfate and / or acetic acid are particularly preferred.

The solution containing an acidic substance may simultaneously contain a crosslinking agent (preferably a crosslinking agent other than boric acid) and / or a water resistant agent. As a crosslinking agent other than boric acid, polyhydric aldehydes, such as glyoxal or glutaraldehyde, polyhydric isocyanate type compounds, such as a biuret type, an isocyanurate type, or a block type, titanium-type compounds, such as titanium oxsulfate, etc. can be used, for example. However, in addition, ethylene glycol glycidyl ether or polyamide epichlorohydrin can be used. Examples of the water resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride or zinc chloride.

When treating with a solution containing an acidic substance, the pH of the solution is also a valuable indicator. The lower the pH, the higher the wet heat durability of the polarizing film. However, when pH is too low, there exists a possibility that decomposition | disassembly, polyenization, etc. of a polyvinyl alcohol-type resin may occur. Thereby, the transmittance may change by 1% or more in the dry heat test, for example, a heat test at 90 ° C. When pH of the solution (acid treatment solution) containing an acidic substance is adjusted to 1.0 <= pH <6.0, it is suitable for obtaining the thing with high wet heat durability, More preferable range is 2 <= p <= 5. When trying to obtain a thing with high dry heat durability, pH is 2 or more, More preferably, it is 2.2 or more, The range smaller than 6.0 is preferable, More preferably, it is about 2.2-5. In some cases, 2.4 ≦ pH <6.0 is preferable, more preferably 2.4 ≦ pH ≦ 5.0, and still more preferably 2.4 ≦ pH ≦ 4.0.

The preferred polarizing film of the present invention is high in both wet heat durability and dry heat durability, and also has a small decrease in transmittance. In the polarizing film of this invention which is so excellent, pH of the aqueous solution which melt | dissolved this polarizing film exists in the range of 5.0 <pH <6.0, and this invention becomes one index | index of the polarizing film which is excellent in this invention. Moreover, when pH of this aqueous solution is the range of 5.1-5.6, it is more preferable. Moreover, when the pH of this aqueous solution is 5.2 <pH <5.6, it is more preferable polarizing film in many cases, and in most preferable polarizing film, pH of this solution is 5.2 <pH <5.4. PH of the aqueous solution which melt | dissolved the polarizing film of this invention can be measured as follows.

That is, 0.0380 g of the polarizing film of the present invention obtained after the drying process was cut, put into a screw mouse bottle (Takara Corporation, Screw Mouse Bottle SV-30) containing 10 cc of distilled water, and the lid was closed, and the water was broken. It was immersed in a bath for 2 hours, the aqueous solution which melt | dissolved the polarizing film was obtained, this aqueous solution was cooled to 25 degreeC, the pH of this aqueous solution was measured using pH Controller PP-01 of AZ Corporation, and the obtained pH was observed. PH of the aqueous solution which melt | dissolved the polarizing film of this invention was taken. In this aqueous solution, the polarizing film should just melt | dissolve in aqueous solution, and the polarizing film of this invention used for the sample does not necessarily need to melt | dissolve all, and the polarizing film of the sample may be a semi-dissolved state, or the state fully swelled. . However, preferably, the insoluble portion of the polarizing film of the sample is preferably less than 20wt%.

In this way, the polyvinyl alcohol-based resin film obtained by treating with a solution containing 0.0001 to 5.0 wt% of acidic acid was dissolved in a polarizing film obtained as it was treated with a solution having a high acidic concentration (low pH). PH is low. This is because the concentration of the acidic substance correlates with the pH of the polarizing film, and by controlling the acidic substance of the treating solution, the pH of the solution in which the polarizing film is dissolved, and ultimately, the degree of treatment of the obtained polarizing film can be controlled. Indicates. In order to produce a polarizing film, the concentration of acidic material is an important factor.

A preferred method for producing the polarizing film of the present invention is to make the PVA film dyed with iodine and iodide polarized, for example, preferably 3 to 8 times in an aqueous solution containing a crosslinking agent (preferably boron). Preferably, the PVA film stretched (preferably uniaxially stretched) about 4 to 7 times, or dyed and crosslinked-treated (preferably boron-treated) with iodine and iodide is 3 to 3 by dry stretching. 8 times, preferably about 4 to 7 times stretching (preferably monoaxially stretching), and the resulting stretched film is acid treated with the acid treatment solution, preferably a solution containing the acidic substance and halide. And a halide treatment, wherein the treated film can be dried to obtain a dried polarizing film of the present invention.

By the above process, the iodine type polarizing film of this invention which extended | stretched the polyvinyl alcohol-type resin film is obtained.

The obtained polarizing film is called a polarizing plate by forming a transparent protective layer on at least one surface or both surfaces. The transparent protective layer can be formed as a coating layer made of a polymer or as a laminate layer of a film. As a transparent polymer or film which forms a transparent protective layer, the transparent polymer or film with high mechanical strength and favorable thermal stability is preferable. In addition, it is preferable that the water barrier property is excellent. As a material for use as a transparent protective layer, for example, cellulose acetate resin or film thereof, such as triacetyl cellulose or diacetyl cellulose, acrylic resin or film thereof, polyvinyl chloride resin or film thereof, polyester resin or film thereof, polya Relative resins or films thereof, cyclic polyolefin resins or films thereof containing cyclic olefins such as norbornene, polyethylene, polypropylene, polyolefins having a cyclo-or norbornene backbone or copolymers thereof, main chain / or side chains And resins or polymers of imides and / or amides, and films thereof. Since polyvinyl alcohol functions as an alignment film for liquid crystals, a rubbing treatment may be applied or may be processed with a photo alignment film to form a resin having liquid crystallinity or a film thereof. The thickness of a protective film is about 0.5 micrometer-200 micrometers, for example. A polarizing plate is produced by forming one or more layers of the same kind or different kinds of resin or film in one side or both sides.

After adhesion to one surface of the obtained polarizing plate, that is, the display device, an adhesive layer such as an adhesive may be formed on the surface of the protective layer or film serving as the non-exposed surface. By forming an adhesive layer, a polarizing plate can be adhere | attached on display apparatuses, such as a liquid crystal and organic EL.

This polarizing plate may have various well-known functional layers, such as an anti-reflection layer, an anti-glare layer, a hard coating layer, a liquid crystal coating layer for improving the viewing angle and / or contrast, on one surface, that is, the exposed surface of the protective layer or the film. . Although the coating method is preferable for the layer which has the various functionalities, you may adhere | attach the film which has the function through an adhesive agent or an adhesive. Moreover, various functional layers may be well-known retardation plates which are layers or films which control retardation.

In forming a transparent protective layer in a polarizing film, when the protective layer is a film, it is necessary to perform film laminating. In that case, an adhesive agent is needed. A polyvinyl alcohol adhesive can be used as an adhesive agent. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, goshenol NH-26 (manufactured by Nippon Synthetic Co., Ltd.), Execal RS-2117 (Kuraraysa), and the like. A crosslinking agent and / or a water resistant agent can also be added to an adhesive agent. In addition, the adhesive may contain an acidic substance at a concentration of 0.0001 to 20 wt%, preferably 0.02 to 5 wt%. As the polyvinyl alcohol-based adhesive, an adhesive obtained by mixing only maleic anhydride-isobutylene copolymer and / or a crosslinking agent can be used. As maleic anhydride-isobutylene copolymer, for example, isoban # 18 (Kuraraya), isoban # 04 (Kuraraya), ammonia-modified Isoban # 104 (Kuraraya), ammonia-modified Isoban # 110 (Kura) Lesa), imidized isoban # 304 (Kuraraya), imidated isoban # 310 (Kuraraya), etc. are mentioned. A water-soluble polyvalent epoxy compound can be used for the crosslinking agent at that time. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (Nagase Chemtech Co., Ltd.), Tetorat-C (Mitsuigas Chemical Co., Ltd.) and the like. As other adhesives, many of urethane, acrylic and epoxy are used, and known adhesives can be used, and the adhesive is not limited. Moreover, as an additive of an adhesive agent, zinc compound, a halide, etc. can be simultaneously contained in the density | concentration about 0.1-10 wt%. It does not restrict | limit also about an additive. After affixing a transparent protective layer with an adhesive agent, a polarizing plate is obtained by drying or heat-processing at a suitable temperature.

The polarizing plate of the present invention thus obtained has little change in transmittance and polarization degree even after being left in a high temperature and high humidity atmosphere for a long time, and has a low drop in transmittance under a high temperature environment at 90 ° C., for example, and is excellent in durability. It can maintain stable performance. By using the polarizing plate of the present invention for a liquid crystal display, an EL display device, a CRT, or the like, the image display device of the present invention is obtained. In particular, in the case of a liquid crystal display, the liquid crystal display of this invention is obtained by adhering the polarizing plate of this invention to both sides of the liquid crystal cell which comprises a liquid crystal display with an adhesive with retardation film as needed. The image display device obtained in this way, especially a liquid crystal display, can suppress the fall of the visibility of the display image by deterioration of a polarizing plate, and can display an image stably for a long time.

Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited by these. In addition, evaluation of the transmittance | permeability and polarization degree shown in the Example was performed as follows.

Transmittance when two polarizing plates obtained by adhering a protective film on both sides of the polarizing film are superimposed so that their absorption axis directions are the same, transmissivity when parallel polarization transmittance (Tp) and two polarizing plates are superposed so that their absorption axes are perpendicular to each other Was taken as orthogonal transmittance (Tc).

In the wavelength region of 380-780 nrn, the transmittance | permeability T calculated | required the spectral transmittance ((tau) (lambda)) for every predetermined | prescribed wavelength space | interval (d (lambda) 10 nm here), and was calculated by following formula (1). In the following formula, Pλ represents the spectral distribution of standard light (C light source), and yλ represents a two-degree field of view color function.

식(1)

Formula (1)

Spectral transmittance (?) Was measured using a spectrophotometer ("U-4100" manufactured by Hitachi).

Polarization degree Py was computed by Formula (2) from the parallel-phase transmittance Tp and the quadrature-transmittance Tc.

Py = {(Tp-Tc) / (Tp + Tc)} 1/2 × 100 Equation (2)

The pH of the aqueous solution was measured using AZ Yarn pH Controller "PP-01".

Example 1

The saponification degree was 99% or more, and the polyvinyl alcohol film (Kuraraya brand name: VF-XS) of 2400 degree of average polymerization degree was immersed in warm water of 40 degreeC for 2 minutes, and it extended | stretched by 1.30 times after swelling process. The obtained film contained 28.6 g / l of boric acid (Societa Chimica Larderello spa), 0.25 g / l of iodine (Chosei Chemical Co., Ltd.), 17.7 g / l of potassium iodide (Chosei Chemical Co., Ltd.) and 1.0 g / l of ammonium iodide (Chosei Chemical Co., Ltd.) In an aqueous solution, it was immersed at 30 degreeC for 2 minutes, and the dyeing process with iodine and iodide was performed. The film obtained by the dyeing treatment was uniaxially stretched 5.0 times, and treated for 5 minutes in an aqueous solution at 50 ° C. containing 30.0 g / L boric acid. While maintaining the tension state of the film obtained by boric acid treatment, the treatment was carried out at 30 ° C. for 15 seconds in an aqueous solution adjusted to 50 g / l potassium iodide and 0.02 g / l aluminum sulfate 14-18 hydrate (Wako Pure Chemical Industries, Ltd.). . At that time, the pH of the aqueous solution was 4.8. The film obtained by potassium iodide and acid treatment was dried at 70 degreeC for 9 minutes. The film obtained by the drying treatment was laminated on a triacetyl cellulose film (Fuji Photo Film Co., Ltd. TD-80U) subjected to alkali treatment using a polyvinyl alcohol-based adhesive to obtain a polarizing plate.

The obtained polarizing plate was cut | disconnected to 40 mm x 40 mm, and it adhere | attached with the glass plate of thickness 1mm through the adhesive (Nihon Kayaku Co., brand name: PTR3000), and used as the measurement sample. The produced sample was subjected to a dry heat test and a wet heat test.

The wet heat test measured the transmittance and polarization degree before and after 18 days (432 hours) in an atmosphere of a temperature of 65 ° C. and a relative humidity of 93%. When treating with a solution containing an acidic substance, compared with the case without treatment, it was used as an index for confirming the difference in superiority in the increase (discoloration) of the transmittance and the decrease in polarization.

The dry heat test measured the transmittance before and after leaving for 18 days (432 hours) in a 90 ℃ atmosphere. The change of transmittance | permeability was good as less than 1.0% as an absolute value, and made into an index the thing within 1.0%. A change of transmittance of 1.0% or more is not preferable in order to cause an effect such as color reproducibility of the display device cannot be obtained. The result of the test in the dry heat test was defined as [good] and 1.0% or more in the absolute value of the transmittance within 1.0%.

Example 2

In Example 1, the sample was produced similarly except the addition amount of the aluminum sulfate 14-18 hydrate being 0.2 g / L and pH 3.4, and the durability in the dry heat test and the wet heat test was compared. PH when the polarizing film after drying process was dissolved was 5.3.

Example 3

In Example 1, the sample was produced similarly except that the aluminum sulfate 14-18 hydrate was changed to citric acid (anhydrous) (Jesei Chemical Co., Ltd.), and the addition amount was 0.05 g / L and the pH was 4.8. And durability in the moist heat test.

Example 4

In Example 3, the sample was produced similarly except that the addition amount of citric acid was 0.07g / L and pH was 4.3, and the durability in the dry heat test and the wet heat test was compared.

Example 5

In Example 3, the sample was produced similarly except the addition amount of citric acid being 0.19 / L, and pH 3.8, and the durability in the dry heat test and the wet heat test was compared.

Example 6

In Example 3, the sample was produced similarly except that the addition amount of citric acid was 0.3g / L and pH was 2.5, and the durability in the dry heat test and the wet heat test was compared. PH when melt | dissolving the polarizing film after a drying process was 5.4.

Example 7

In Example 3, the sample was produced similarly except the addition amount of citric acid being 0.5 g / L and pH 2.3, and the durability in the dry heat test and the wet heat test was compared. PH when the polarizing film after drying process was dissolved was 5.3.

Example 8

In Example 1, the sample was produced similarly except the aluminum sulfate 14-18 hydrate was changed to acetic acid (Jesei Chemical Co., Ltd.), the addition amount was 0.04 g / L, and the pH of the solution was 5.1. The durability in the wet heat test was compared.

Example 9

In Example 8, the sample was produced similarly except the addition amount of acetic acid being 0.07 g / L and pH 4.0, and the durability in the dry heat test and the wet heat test was compared.

Example 10

In Example 8, except that the acetic acid addition amount was 0.11 g / L and pH was 3.8, the sample was produced similarly and the durability in the dry heat test and the wet heat test was compared.

Example 11

In Example 8, the sample was produced similarly except having made the acetic acid addition amount 0.6g / L and pH 3.4, and compared the durability in a dry heat test and a wet heat test. PH when melt | dissolving the polarizing film after a drying process was 5.7.

Example 12

In Example 8, except that the acetic acid addition amount was 3.0 g / L and pH was 2.6, the sample was produced similarly and the durability in a dry heat test and a wet heat test was compared. PH when melt | dissolving the polarizing film after a drying process was 5.4.

Example 13

In Example 8, except that the acetic acid addition amount was 5.0 g / L and pH was 2.4, the sample was produced similarly and the durability in a dry heat test and a wet heat test was compared. PH when melt | dissolving the polarizing film after a drying process was 5.1.

Comparative Example 1

In Example 1, the sample was produced similarly except not adding the aluminum sulfate 14-18 hydrate, and the durability in the dry heat test and the wet heat test was compared. PH when melt | dissolving the polarizing film after a drying process was 6.0.

Table 1 and Table 2 show the measurement results of changes in transmittance and polarization degree in Example 1 to 13 and Comparative Example 1.

As can be seen from the above examples and comparative examples, the polyvinyl alcohol-based resin film containing the iodine and iodide in the present invention contains a crosslinking agent, and in the film to which the stretching treatment is applied, an acidic substance other than boric acid The polarizing film obtained by treating with a solution of 2.4≤pH <6.0 with a pH containing 0.0001 to 5.0wt% was free from color loss in a humid heat environment, for example, at a temperature of 65 DEG C and a relative humidity of 93%. It becomes a polarizing film or polarizing plate with little fall of. A polarizing plate having high transmittance, high contrast and high moist heat durability in a polarizing film for liquid crystal display is obtained. In addition, it can be seen that the polarizing film obtained by the present invention has a change in transmittance within 1.0% of dry heat durability, for example, a dry heat test of 90 ° C. According to the above result, it turns out that the wet heat durability of a polarizing plate improves with the pH of a process solution, and the polarizing plate with little change in the transmittance | permeability in dry heat durability is obtained. On the other hand, when the pH of the treatment solution and the pH of the polarizing film are dissolved, the pH of the polarizing film is lower as the solution is treated with a higher acid concentration. Therefore, it can be seen that the concentration of the acidic substance and the concentration of the polarizing film has a correlation. The lower the acidic substance concentration, the lower the pH at the time of dissolving the polarizing film. The transmittance is not lowered in the dry heat test, for example, at 90 ° C., but the wet heat durability gradually decreases. When the pH of the polarizing film was dissolved, the higher the value of wet heat durability was, the higher the pH value was. However, when the pH was 5 or less, a significant decrease in the transmittance was observed in the dry heat test at 90 ° C. have. As a result, the polarizing plate obtained by treating the polyvinyl alcohol-based resin film containing iodine with a solution of 0.001 to 5.0 wt% of an acidic substance other than boric acid at a solution of 2.4≤pH <6.0 has high wet heat durability. It turns out that the polarizing plate which improves and is small in the transmittance | permeability change in dry heat durability is obtained.

Example A-2

In Example 1, the durability of the sample preparation and the wet heat test were compared similarly except that the addition amount of the aluminum sulfate 14-18 hydrate was 4.5 g / L and the pH was 2.73.

Example A-3

In Example 1, the durability of the sample preparation and the wet heat test were compared in the same manner except that the aluminum sulfate 14-18 hydrate was changed to sulfuric acid (Josesei Chemical Co., Ltd.), and the addition amount was 0.2 g / L and the pH was 1.88. .

Example A-4

In Example 1, the durability of the sample preparation and the wet heat test were compared in the same manner except that the aluminum sulfate 14-18 hydrate was changed to sulfuric acid (Josesei Chemical Co., Ltd.), and the addition amount was 0.03 g / L and the pH was 3.4. .

Example A-5

In Example 1, the durability of the sample production and the wet heat test were similarly changed except that the aluminum sulfate 14-18 hydrate was changed to aluminum nitrate (Wako Pure Chemical Industries, Ltd.), and the addition amount was 5 g / l and the pH was 2.911. Compared.

Example A-6

In Example 1, except that the aluminum sulfate 14-18 hydrate was changed to aluminum chloride hexahydrate (Wako Pure Chemical Industries, Ltd.), and the addition amount was 5 g / L and the pH was 2.83, in the preparation of the sample and the wet heat test in the same manner. The durability of the was compared.

Example A-7

The polyvinyl alcohol film (Kuraraya, brand name: VF-XS) of average polymerization degree 2400 was immersed in 40 degreeC warm water for 2 minutes, and swelling process was applied and the draw ratio was 1.30 times. The swelled film was immersed at 30 ° C. for 2 minutes by an aqueous solution containing 0.25 g / l of iodine (BKsei Chemical Co., Ltd.) and 17.7 g / L of potassium iodide (BK Seiko Chemical Co., Ltd.) for iodine and iodide treatment. The dyed film was treated with boric acid (Societa chemical Landerello s.p.a) concentration of 28 g / l, treatment temperature of 30 ° C., and 5 minutes treatment. The film to which the boric acid treatment was applied was stretched 5.0 times, and treated for 5 minutes in an aqueous solution at 50 ° C. containing 0.0 g / L of boric acid 3. The process was performed for 15 seconds, maintaining at 30 degreeC in the aqueous solution adjusted to 50 g / l potassium iodide and 3.5 g / l citric acid (Jesei Chemical Co., Ltd.), maintaining the tension state of the film obtained by this boric acid treatment. The pH of the aqueous solution was 1.51. The film obtained by treating potassium iodide containing citric acid was subjected to drying treatment at 70 캜 for 9 minutes. A triacetyl cellulose film (Fuji Photo Film Company, trade name: TD-80U) obtained by alkali treating the film obtained by drying was laminated using a polyvinyl alcohol-based adhesive to obtain a polarizing plate.

The obtained polarizing plate was cut | disconnected to 40 mm x 40 mm, and it bonded to the glass plate of thickness 1mm through the adhesive (Nihon Kayaku Co., brand name: PTR3000), and used as the measurement sample.

The produced sample was subjected to a wet heat test. The wet heat test measured the unitary transmittance and polarization degree before and after leaving for 18 days (432 hours) in an atmosphere having a temperature of 65 ° C. and a relative humidity of 93%.

Example A-8

In Example A-7, the durability of the sample preparation and the wet heat test were compared similarly except that the addition amount of citric acid was 0.05 g / L and pH was 4.8.

Example A-9

Citric acid was changed to acetic acid in Example A-7, and the durability of the preparation of the sample and the wet heat test were compared in the same manner except that the amount of acetic acid added was 0.04 g / L and the pH was 5.1.

Example A-10

In Example A-7, the citric acid was changed to acetic acid, and the durability of the preparation of the sample and the wet heat test were compared in the same manner except that the amount of acetic acid was 3.0 g / L and the pH was 2.58.

Comparative Example 1

In Example 1, the durability of the sample preparation and the wet heat test was compared similarly except not adding the aluminum sulfate 14-18 hydrate.

Comparative Example A-2

In Example A-7, the durability of the sample preparation and the wet heat test was compared similarly except not adding citric acid.

Comparative Example A-3

In Example A-4, the film obtained by dyeing was stretched 5.0 times for 5 minutes while maintaining the pH of an aqueous solution at 50 ° C. containing 30.0 g / L boric acid at 3.4. In the aqueous solution adjusted to 50 g / l of potassium iodide while maintaining the tension state, the durability of the sample was produced and the wet heat test was compared in the same manner except that the treatment was carried out at 30 ° C. for 15 seconds.

In Example 1, A-2, the measurement result of the transmittance | permeability and polarization degree change in A-10, Comparative Examples 1, A-2, and A-3 is shown in Table a.

As can be seen from the above examples and comparative examples, an acidic substance other than boric acid in the film to which the crosslinking agent is contained in the polyvinyl alcohol-based resin film containing the iodine and iodide in the present invention and to which the stretching treatment is applied The polarizing film obtained by treatment with a solution containing 0.0001 to 5.0 wt% of 1.0 ≦ pH <6.0 is free from color loss in a humid heat environment, for example, at a temperature of 65 ° C. and a relative humidity of 93%. It becomes a polarizing film or polarizing plate with little fall. A polarizing plate having high transmittance, high contrast and high moist heat durability in a polarizing film for liquid crystal display can be obtained. Comparing Example 4 and Comparative Example 3, the pH of the halide treatment tank is set to 1.0 ≦ pH <6.0, indicating that the treatment is more effective.

Claims (18)

After stretching a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-repellent agent, a solution containing 0.0001 to 5.0wt% of an inorganic acid or a salt thereof and / or an organic acid excluding boric acid (hereinafter referred to as' acid Polarizing film obtained by treatment with &quot; treatment solution &quot;. The polarizing film of claim 1, wherein the acid treatment solution has a pH of 2 ≦ pH ≦ 5. The polarizing film of Claim 1 obtained by processing the polyvinyl alcohol-type resin film containing an iodine, an iodide, a crosslinking agent, and / or a water-resistant agent, after extending | stretching, by the solution for acid treatment of pH <= pH <6.0. . The polarizing film of claim 1, wherein the halide is contained in a solution containing an inorganic acid or a salt thereof and / or an organic acid except boric acid. The polarizing film of claim 1, wherein the inorganic acid or its salt except boric acid is any one of aluminum sulfate, aluminum chloride, aluminum nitrate, sulfuric acid, or two or more thereof. The polarizing film of claim 1 or 2, wherein the inorganic acid or salt thereof except boric acid is aluminum sulfate. The polarizing film according to any one of claims 1 to 6, wherein the organic acid is at least one carboxylic acid and / or α-hydroxy acid, and is obtained by treating with a solution containing the organic acid. 8. The polarizing film of claim 7, wherein the organic acid is any one or more of citric acid, oxalic acid, malic acid, tartaric acid, or acetic acid, and is obtained by treating with a solution containing the organic acid. The polarizing film of any one of Claims 1-8 in which the said polyvinyl alcohol-type resin film after extending | stretching was extended | stretched 3 to 8 times compared with before extending | stretching in a draw ratio. The polarizing film of Claim 1 or 9 whose crosslinking agent and / or water-resistant agent used for an extending | stretching process are boric acid. The polarizing plate in which the protective layer was formed in one side or both sides of the polarizing film of any one of Claims 1-8. It has a polarizing plate of Claim 11, The liquid crystal display device characterized by the above-mentioned. A polyvinyl alcohol-based resin film containing iodine, iodide, crosslinking agent and / or water repellent is treated with an acid treatment solution of 2.4 ≦ pH <6.0 after stretching treatment. After stretching, the polyvinyl alcohol-based resin film containing iodine, iodide, crosslinking agent and / or water-repellent agent is treated with an acid treatment solution of 2.4 ≦ pH <6.0 and protected on one side or both sides of the obtained polarizing film. A layer is formed, The manufacturing method of the polarizing plate characterized by the above-mentioned. A polyvinyl alcohol-based resin film containing iodine, iodide, and a crosslinking agent is treated with an acid treatment solution of 2.2 ≦ pH ≦ 5 after stretching treatment. After stretching a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-repellent agent, a solution containing 0.0001 to 5.0wt% of an inorganic acid or a salt thereof and / or an organic acid excluding boric acid (hereinafter referred to as' acid A process for producing a polarizing film). 16. The solution of claim 15, wherein the acid treatment solution is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, aluminum sulfate, aluminum chloride, aluminum nitrate, formic acid, citric acid, chloroacetic acid, acetic acid, oxalic acid, malic acid and tartaric acid. Method for producing a polarizing film is an aqueous solution containing an acidic substance of. The method for producing a polarizing film according to claim 16 or 17, wherein the acid treatment solution has a pH of 2 to 5.