WO2006095815A1

WO2006095815A1 - Iodine-containing polarizing film, process for producing the same, and polarizer comprising the same

Info

Publication number: WO2006095815A1
Application number: PCT/JP2006/304603
Authority: WO
Inventors: Noriaki Mochizuki; Kenichiro Yoshioka; Kouichi Tanaka; Yoshiaki Matsushita
Original assignee: Nippon Kayaku Kabushiki Kaisha; Polatechno Co., Ltd.
Priority date: 2005-03-10
Filing date: 2006-03-09
Publication date: 2006-09-14
Also published as: HK1116258A1; JPWO2006095815A1; TWI388888B; KR20080005357A; CA2600420A1; JP4789925B2; TW200700780A

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, method for producing the same, and polarizing plate using the same

The present invention relates to an iodine polarizing film, a method for producing the same, and an iodine polarizing plate using the iodine polarizing film.

Background art

In general, a polarizing plate is made by adsorbing and orienting a dichroic dye, iodine or a dichroic dye, onto a polybulal alcohol-based resin film to form a polarizing film, and a tri-layer is formed on one or both sides via an adhesive layer. A protective film such as cetyl cellulose is bonded to form a polarizing plate, which is used for liquid crystal display devices. A polarizing plate made of a polarizing film using iodine as a dichroic dye is called an iodine polarizing plate, whereas a polarizing film using a dichroic dye as a dichroic dye is a dye polarizing plate. Called. Iodine polarizing plates are widely used in general liquid crystal monitors, liquid crystal televisions, mobile phones, PDAs, etc., because they exhibit higher transmittance and higher polarization, that is, higher contrast than dye-based polarizing plates. . However, although iodine-based polarizing plates are superior to dye-based polarizing plates in terms of optical properties, they are inferior to dye-based polarizing plates in terms of optical durability. If left underneath, problems such as increased transmissivity due to decolorization and decreased degree of polarization occurred. Furthermore, in terms of dry heat durability, the degree of polarization decreases when left at high temperatures. There is a need for a polarizing plate that has high transmittance and high degree of polarization, and excellent heat resistance and heat and moisture resistance. As an invention to meet this demand, as described in Patent Document 1 and Patent Document 2, a protective film is disclosed. Patent Document 3 and Patent Document 4 describe improvement of wet heat durability by an improvement method based on the above, and a method of modifying an adhesive that adheres a protective film of triacetyl cellulose. In addition, there is an example in which durability is improved as an iodine-based polarizing plate by treating a polyvinyl alcohol-based resin film rather than improvement of durability by a protective film or an adhesive. As one of them, Patent Documents 5, 6, 7 and 8 describe durability improvement by acid treatment and pH control. For example, in Patent Document 5, a polyester film formed from a boron compound-containing polyvinyl alcohol resin film is used. There is disclosed a polarizing film having improved durability using a stretched polybulb alcohol based resin film immersed in an acidic aqueous solution of a vinyl alcohol based resin film. Patent Document 6 also shows excellent heat and heat resistance in which a film made of poly (bull alcohol) -based resin is oxidized in an oxidation bath containing an oxidizing agent such as hydrogen peroxide containing an alkali metal iodide. A method for producing a polarizing film is disclosed. Patent Document 7 describes the production of an iodine-based polarizing film having improved moisture and heat resistance by treating a polyvinyl alcohol film that has been subjected to uniaxial stretching and iodine adsorption orientation treatment with an aqueous boric acid solution having a pH of 4.5 or less. A method is disclosed. Patent Document 8 discloses a patent for a polarizer (polarizing film) having a pH of 1.0 to 5.0 when dissolved in water.

Patent Document 1: Japanese Patent Laid-Open No. 8-5836

Patent Document 2: JP 2001-272534

Patent Document 3: JP 2004-12578

Patent Document 4: JP-A-9-269413

Patent Document 5: JP-A-6-254958

Patent Document 6: JP-A-7-104126

Patent Document 7: JP 2001-83329

Patent Document 8: JP-A-2005-62458

Disclosure of the invention

Problems to be solved by the invention

[0004] In a method of immersing and stretching a polyvinyl alcohol-based resin film formed from the boron compound-containing polyvinyl alcohol-based resin film described in Patent Document 5, in an acidic aqueous solution, boric acid immersed in stretching, Acidic components such as polybulal alcohol-based resin film are eluted in an aqueous solution containing iodine and potassium iodide (so-called dyeing bath). V. The effect of improving the durability of the resulting polarizing film is sufficient. There was a problem that it could not be obtained. Also in Patent Document 6, since the treatment is performed in an oxidation bath adjusted in pH before stretching, the polyvinyl alcohol-based resin film strength oxidizing agent elutes into the stretching bath during stretching, and the resulting polarizing film has moisture resistance. There was a problem that the effect of improving thermal properties could not be sufficiently obtained. Patent Document 7 describes that an aqueous solution containing boric acid is treated with pH ≤ 4.5 or less. Forces on the plate Treatment of acid with boric acid results in variations in the treatment of films with poor treatment efficiency of polyvinyl alcohol-based rosin film and acidic substances. For example, in the example of Patent Document 7, the change in polarization degree is 1.3 when treated with a boric acid-containing treatment solution at pH = 3.4, and the change in polarization degree is 2.when pH = 2.1. 0. This indicates that this method does not provide stable characteristics even when pH is controlled. This is because the pH is controlled! Show me that! / Furthermore, it is described in the literature that acidic substances are vaporized when the processing temperature (processing solution temperature) in the process is high. Poly Bulle alcohol film in Patent Document 8 becomes the film strength has been stretched, patent for polarizing element, wherein the _P H of the liquid dissolved in water 1. 0 to 5.0 is disclosed. However, although the wet heat durability of the polarizing plate obtained by this method is improved, for example, 90 ° C !, a light source of a liquid crystal display device whose transmittance is drastically reduced in a heat test under a high temperature atmosphere. Depending on the usage environment, the display may gradually become darker. Due to these problems, boron is added to the polybulal alcohol-based resin film containing iodine so that it can be processed efficiently and can be processed at a low temperature as well as at a high temperature in order to stabilize the acid concentration. There is a need for an iodine-based polarizing plate that does not contain an acid !, improves wet heat durability by applying an acidic substance treatment with a solution, and is excellent in dry heat durability.

Means for solving the problem

As a result of intensive studies to solve the above problems, a polyvinyl alcohol resin film containing iodine, iodide, a crosslinking agent and / or a waterproofing agent is removed from the boric acid after stretching, an inorganic acid or a salt thereof, and Z Alternatively, a solution containing organic acid in an amount of 0.0001 to 5.0% by weight (hereinafter abbreviated as wt%. Unless otherwise specified,% indicates% by weight) (hereinafter also referred to as an acid treatment solution in some cases). The polarizing film obtained by processing in (1) has improved wet heat durability, little change in transmittance, and the processing temperature of acidic substances can be processed at low temperatures as well as high temperatures. Stable treatment can be applied without volatilization of acidic substances, and the pH of the acid treatment solution should be 2-5, more preferably 2.2-5, or in some cases 2.4 ≤ pH <6.0. When it is said that the dry heat durability is also increased, pH≤4 with an acid material with acid. than 5, together with Harogeni 匕物 without applying boric acid By applying the treatment with a solution of 2.4 ≤ pH <6.0 containing an acidic substance, and applying the drying treatment after the acidic substance treatment, the wet heat durability with little variation in optical properties is high and the dryness is reduced. The inventors have newly found that a polarizing plate having excellent thermal durability can be obtained, and have reached the present invention. That is, the present invention

(1) After stretching a polybulal alcohol-based resin film containing iodine, iodide, cross-linking agent and / or water-resistant agent, inorganic acid or its salt excluding boric acid and Z or organic acid is added to 0.0001- 5. Polarizing film obtained by treatment with a solution containing 0 ^% (hereinafter referred to as acid treatment solution)

(2) The polarizing film according to (1), wherein the pH of the acid treatment solution is 2≤11≤5,

(3) Polyvinyl alcohol-based resin film containing iodine, iodide, cross-linking agent and / or waterproofing agent is treated with an acid treatment solution having a pH of 2.4≤pH <6.0 after stretching. The polarizing film according to (1),

(4) A solution containing an inorganic acid or a salt thereof excluding boric acid and a Z or organic acid containing a halide (the polarizing film according to 1,

(5) The polarization fine film according to (1), wherein the inorganic acid or its salt excluding boric acid is one or more of aluminum sulfate, aluminum chloride, aluminum nitrate or sulfuric acid,

(6) The polarizing film according to (1) to (2), wherein the inorganic acid excluding boric acid or a salt thereof is aluminum sulfate,

(7) The organic acid is one or more carboxylic acids and / or a-hydroxy acids, and is obtained by treating with a solution containing the organic acid (1) to (6) Polarization of Finolem,

(8) The organic acid is one or more of citrate, oxalic acid, malic acid, tartaric acid or acetic acid, and is obtained by treating with a solution containing the organic acid. Polarized Finolem,

(9) The polyvinyl alcohol-based resin film after stretching is stretched at a stretching ratio of 3 to 8 times as compared with before stretching, according to any one of (1) to (8). Polarized film, (10) The polarizing film according to (1) or (9), wherein the cross-linking agent and / or water-resistant agent used in the stretching treatment is boric acid,

(11) A polarizing plate provided with a protective layer on one or both sides of the polarizing film according to any one of (1) to (9) above,

(12) A liquid crystal display device comprising the polarizing plate according to claim 11,

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

(14) A polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-resistant agent is treated with an acid treatment solution of 2.4≤pH <6.0 after stretching. A method for producing a polarizing plate, comprising providing a protective layer on one or both sides of the obtained polarizing film,

(15) A polarizing film characterized in that a polybulal 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. Manufacturing method,

(16) After stretching a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water resistance agent, an inorganic acid or a salt thereof excluding boric acid and Z or an organic acid is added. A method for producing a polarizing film, characterized by treatment with a solution containing 0% (hereinafter referred to as an acid treatment solution),

(17) The acid treatment solution also has a group strength consisting of sulfuric acid, hydrochloric acid, nitric acid, aluminum sulfate, aluminum chloride, aluminum nitrate, formic acid, citrate, acetic acid acetic acid, oxalic acid, malic acid and tartaric acid. The method for producing a polarizing film according to (15), which is an aqueous solution containing at least one selected acidic substance,

(18) The method for producing a polarizing film according to (16) or (17), wherein the pH of the acid treatment solution is 2 to 5,

About.

The invention's effect

Since the obtained polarizing film is treated with an acidic substance after stretching, it is acidic to the dyeing bath. Since no substances are brought in and no boric acid is used after stretching, no problems arise due to precipitation of boric acid, so that a polarizing film can be produced industrially stably. In addition, when manufactured under favorable conditions with little change in transmittance and decrease in polarization degree in a humid heat environment, for example, at a temperature of 65 ° C and a relative humidity of 93%, the light is also transmitted in a dry heat environment, for example, at 90 ° C. An excellent polarizing film or polarizing plate with little rate change is obtained. By using such a polarizing film or polarizing plate of the present invention, long-term display stability of a liquid crystal display can be ensured.

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, the present invention will be described in detail.

The method for producing the polyvinyl alcohol-based resin constituting the polarizing film is not particularly limited and can be produced by a known method. As a production method, it can be obtained, for example, by saponifying poly (butyl acetate) -based rosin. Examples of the polyvinyl acetate-based resin include the power of poly (vinyl acetate), which is a homopolymer of butyl acetate, and a copolymer of vinyl acetate and other monomers copolymerizable therewith. The Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, burethers, and unsaturated sulfonic acids. The degree of saponification of the polybulal alcohol-based resin is usually about 85 to about LOO mol%, preferably 95 mol% or more. This polybula alcohol-based resin may be further modified, for example, polybulformal or polyblucacetal modified with aldehydes can be used. The degree of polymerization of polyalcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

[0009] A strong polyvinyl alcohol-based resin film is used as a raw film. The method for forming the polyvinyl alcohol-based resin is not particularly limited and can be formed by a known method. In this case, the polybutyl 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%. The film thickness of the raw film which is also a polybulal alcohol-based resin is not particularly limited, but 5 to 150 m is preferable 10 to: L00 m is particularly preferable. [0010] The polybulal 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 this 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 a water-soluble organic solvent. In the case of shortening the time for producing the polarizing film, the swelling process may be omitted because it swells even during the treatment with iodine and iodide.

[0011] After the swelling step, the polybulualcohol-based resin film is treated with a solution containing iodine and iodide (hereinafter also referred to as a dyeing step). The treatment method is preferably immersed in the solution, but the solution may be treated by coating or coating the polybulal alcohol-based resin film. As a solvent of the solution, for example, water is preferable, but it is not limited. As the iodide, for example, an alkali metal iodide compound such as potassium iodide, ammonium iodide, cobalt iodide or zinc iodide can be used, but is not limited, but usually an alkali metal iodide compound. More preferred is potassium iodide. Iodine concentration is preferably 0.0001-0. 5 wt%, more preferably 0.001-0. 4 wt%. The iodide concentration is preferably from 0.0001 to 8 wt%. The treatment temperature in this step is preferably 5 to 50 ° C, more preferably 5 to 40 ° C, and particularly preferably 10 to 30 ° C. The treatment time depends on the concentration at which iodine and iodide are adsorbed, and can be adjusted appropriately, but it is preferably 1 to 5 minutes, more preferably 30 seconds to 6 minutes. After this treatment, cleaning may be performed before entering the next step. In general, water is used as a solvent for washing. By washing, it is possible to suppress the migration of iodine and iodide into the liquid to be processed next.

[0012] Upon treatment with iodine or iodide, a crosslinking agent and Z or a water resistance-imparting agent may be added to the solution.

Usually, a crosslinking agent is used. The cross-linking agent is not particularly limited, but boric acid is usually preferred. The concentration of the crosslinking agent such as boric acid is preferably 0.1 to 5.0%, more preferably 2 to 4% by weight. As the water-proofing agent, those described later can be used. The treatment temperature in this step is preferably 5 to 50 ° C, more preferably 5 to 40 ° C, and particularly preferably 10 to 30 ° C. The treatment time depends on the concentration of iodine and iodide adsorbed, so it can be adjusted appropriately. It is preferable to adjust from 0 seconds to 6 minutes, more preferably from 1 to 5 minutes. After this treatment, cleaning may be performed before entering the next step. In general, water is used as a solvent for washing. By performing washing, it is possible to suppress the transfer of iodine, iodide and boric acid into the liquid to be processed next.

In the present invention, in the case of a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-resistant agent, iodine, iodide, crosslinking agent and / or water-resistant resin is not necessarily used as it is as a PVA film. After the dyeing treatment and the crosslinking agent and Z or water-resistant agent treatment, iodine, iodide, crosslinking agent and Z or water-resistant agent are reacted in the PVA film. Including the case where it is contained in ni! As the PVA film containing iodine, iodide, cross-linking agent and / or water-proofing agent, one containing iodine, iodide and cross-linking agent (preferably boron) is preferable.

Usually, after the dyeing step, a crosslinking agent treatment is performed (also referred to as a crosslinking agent treatment step). The crosslinking agent treatment can be performed by treating the polyvinyl alcohol-based resin film with a solution containing a crosslinking agent. As described above, the dyeing process can be performed in the presence of a crosslinking agent. Usually, it is preferably performed after the dyeing process. In this case, the crosslinking agent treatment is carried out by treating the polybulal alcohol-based resin film (hereinafter also referred to as a dyed PVA film) obtained in the dyeing step with a crosslinking agent-containing solution. The treatment method with the crosslinking agent-containing solution is usually preferably a method in which a PVA film dyed in the solution is immersed, but a method in which the solution is applied or coated on a polybulal alcohol-based resin film may be used. . The immersion can be performed before or after the stretching process described later. When the stretching method is a dry stretching method, it is preferable to perform the crosslinking treatment together with the stretching treatment in the case of a wet stretching method in which it is preferable to perform a crosslinking treatment before stretching. Examples of the cross-linking agent include boron compounds such as boric acid or its salts (for example, alkali metal salts such as borax or ammonium borate), polyvalent aldehydes such as glyoxal or glutaraldehyde, biuret type, Polyisocyanate compounds such as isocyanurate type or block type, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether, or polyamide epichlorohydrin can be used. Boric acid, which is usually preferred for boron compounds, is more preferred. In addition, a water-resistant agent may coexist in the crosslinking agent-containing solution. Yes. Examples of water-resistant additives include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride or magnesium chloride, zinc chloride, etc. Salt-ammonium, salt-magnesium, or salt-zinc is preferred. For example, water, an alcohol solvent, a glycol solvent, glycerin, or a mixed solvent thereof can be used as the solvent for the crosslinking agent treatment, and water is usually preferable. The concentration of the cross-linking agent in the solution containing the cross-linking agent varies depending on the type of the cross-linking agent, etc., and cannot be generally stated, but is usually about 0.1 to about L0 wt / vol% with respect to the solvent, boric acid as an example. It is preferable to treat the solvent at a concentration of 0.1 to 6. Owt / vol%, more preferably 2 to 4 wt / vol%. The treatment temperature is preferably 5 to 60 ° C, more preferably 5 to 40 ° C. The treatment time is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes.

[0014] Next, the dyed PVA film or the dyed and crosslinker-treated PVA film is stretched (preferably uniaxially stretched) to impart polarization (hereinafter also referred to as a uniaxial stretching step). The stretching method may be either a wet stretching method or a dry stretching method. In the case of the dry stretching method, a PVA film treated with a crosslinking agent is usually used. In the case of the wet stretching method, a PVA film treated with a cross-linking agent is usually subjected to the above-mentioned cross-linking treatment! In addition, using a dyed PVA film, a cross-linking agent treatment is performed together with stretching. Preferred.

[0015] The dry stretching method is usually performed by heating and stretching the film in a gas medium. As the 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 the cross-linking agent-treated PVA film at a temperature of room temperature to about 180 ° C. In the case of an inert gas or the like, it can be carried out in the same manner as in the case of air, or in some cases at a higher temperature. The stretching treatment is preferably performed in an atmosphere having a relative humidity of 20 to 95%. Examples of the heat stretching method of the film include a zone-to-roll stretching method, a roll calorie heat stretching method, a pressure stretching method, and an infrared heat stretching method, but the stretching method is not limited. The stretching process may be performed once (one stage), or may be performed twice (two stages) or more. In that case, the draw ratio is preferably 3 to 8 times, more preferably 5 to 7 times. [0016] 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 normal heating. It is preferable to stretch the film while the film is immersed in a solution containing a crosslinking agent and / or a water resistance agent. The draw ratio is preferably 3 to 8 times, more preferably 5 to 7 times. The stretching is preferably performed in the aqueous medium heated to 40 to 60 ° C, more preferably 45 to 55 ° C. Examples of the crosslinking agent include those described above, for example, boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, biuret type, isocyanurate type or block. Examples thereof include polyvalent isocyanate compounds such as molds, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether, and polyamideepoxyhydrin. As the cross-linking agent, boric acid is more preferable than a boron compound. Examples of the water-resistant agent include those described above, such as succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, Examples include magnesium chloride or zinc chloride. The concentration of the cross-linking agent and / or water-resistant agent is preferably, for example, 0.5 to 8 wt%, more preferably 2.0 to 4.0 ^%. The stretching time can be 30 seconds to 20 minutes, but 2 to 5 minutes is preferable. The stretching process may be performed once (one stage), or a multi-stage process of two (two stages) or more may be applied.

In the present invention, the uniaxially stretched PVA film (hereinafter also simply referred to as uniaxially stretched PV A film) is used as an inorganic acid or its salt excluding boric acid and Z or organic acid (hereinafter also simply referred to as acidic substance). ) Is treated with a solution containing 0.0001 to 5.0% by weight (hereinafter also referred to as an acid treatment solution). By this treatment, the wet heat durability of the polarizing film can be improved, and in the preferred embodiment, the dry heat durability can also be improved. In some cases, this treatment is also simply referred to as “treatment with an acidic substance”. For 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).

After the stretching treatment, the cross-linking agent is deposited on the film surface or foreign matter adheres to it. Therefore, the film surface may be cleaned before the treatment with an acidic substance (hereinafter also referred to as a cleaning process). In this cleaning step, cleaning with a solution containing boric acid may be performed, but in some cases, cleaning with a solution containing boric acid may cause foreign matter on the surface after the next step or after drying. In general, washing is preferably carried out with a solution containing no boric acid, preferably water. In addition, in cases where washing with a solution containing boric acid may be performed, foreign matters are not generated on the film surface after washing with a boric acid-containing solution, such as by performing acid treatment after the washing and then drying. This includes the processing steps to The cleaning time can be applied from 1 second to 5 minutes. The number of times of washing is not particularly limited, and may be one time, or two or more times of washing as necessary.

[0018] After the stretching treatment, it is preferable that the stretched PVA film is treated with a solution containing a halogenated product together with or separately from the treatment with an acidic substance. This treatment is performed for the purpose of adjusting the hue and improving the polarization characteristics (hereinafter referred to as “halogenated material treatment”). Examples of the treatment method include a method of immersing a stretched PVA film in the solution, a method of applying or coating the solution on the PVA film, and the like, and a method of immersing is more preferable. The halide treatment is preferably performed together with the treatment with an acidic substance. In this case, the PVA film may be treated by the method described above with a solution containing a halide together with an acidic substance. Examples of the halide include alkali metal compounds such as potassium iodide and sodium iodide, iodides such as ammonium iodide, cobalt iodide and zinc iodide, salt potassium and salt iodide. Salts such as sodium and alkali metal compounds or salts such as zinc and zinc are preferred and more preferably water-soluble. Of the iodides and iodides, the iodides are preferred. Among the iodides, alkali metal iodide compounds, more preferably potassium iodide, are preferred. The halide concentration is preferably 0.5 to 15 wt%, more preferably 3 to 8 wt%. The treatment temperature is preferably, for example, 5 to 50 ° C or less, more preferably 20 to 40 ° C. The treatment time is preferably, for example, 1 second to 5 minutes, but is preferably 5 to 30 seconds in view of the stability of the in-plane characteristics of the polarizing film. When the purpose is not to prepare the hue, the step of treating with the solution containing the halide can be omitted.

[0019] After the treatment with an acidic substance and, if necessary, the halogen fluoride treatment, the film is dried (hereinafter also referred to as a drying step). When drying, natural drying is good, but more dry In order to increase the drying efficiency, surface moisture may be removed by compression with a roll, an air knife or a water absorption roll, and / or air drying may be performed. The treatment temperature is preferably 20 to 90 ° C, but preferably 40 to 80 ° C. The treatment time is preferably 30 seconds to 20 minutes, more preferably 2 to 10 minutes.

[0020] In the treatment steps so far, examples of the solvent of the treatment solution include, but are not limited to, a solvent such as water, an alcohol solvent, or a glycol solvent. Also, as a mixed solution of water and alcohol, a mixed solvent of dimethyl sulfoxide and water, etc.

A mixed solvent of water and a water-soluble organic solvent may be used. Most preferred is water.

[0021] The treatment with an acidic substance in the present invention may be carried out at any step after stretching (preferably uniaxial stretching) a polyvinyl alcohol film containing iodine, iodide, a crosslinking agent and Z or a water resistance agent. Go!ヽ. For example, in the washing step after stretching or in the Z and halide treatment step, treatment with an acidic substance is performed together, or after stretching of the film, or after a washing step performed as necessary, it is continued independently with an acidic substance. Any of processing may be performed. Usually, after the stretching for imparting polarization (preferably uniaxial stretching) is completed, it is preferably washed as necessary, and then treated with an acidic substance (sometimes referred to as an acid treatment). Moreover, you may carry out in several processes as needed. More preferred is a method in which the stretched PVA film is immersed in a solution containing an acidic substance and a halide to perform the treatment with the acidic substance and the halide treatment together. If necessary, the treatment with an acidic substance may be carried out with a treatment solution containing a crosslinking agent and / or a water-resistant agent other than boric acid together with the acidic substance. 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. Owt%, preferably 0.0005 to 2 wt%, more preferably 0.001 to Lwt%. It is a, preferably from 01~2. Owt ^_0/0 force 0. by the case! /,. In addition, it is preferable that the pH of the treatment solution is adjusted to 1.0≤pH <6.0. A more preferable pH is a range of 2 or more and less than 6.0, and more preferably about 2.1 to 5. The temperature and time of the acid treatment are not particularly limited as long as the effects of the present invention are achieved. The normal treatment temperature is 5 to less than 60 ° C, preferably about 10 to 40 ° C, and the treatment time is 2 to 300 seconds. The time is preferably 3 to 60 seconds, more preferably about 5 to 40 seconds. In some cases, in the washing step, acid treatment can be performed simultaneously with washing with a solution containing an acidic substance. The treatment temperature is preferably less than 5-60 ° C, more preferably 10-40 ° C. The treatment time is preferably 2 to 300 seconds, more preferably 2 to 60 seconds.

[0023] The halide treatment may be performed alone after the stretching treatment or after the washing treatment, or may be performed together with the acid treatment in the acid treatment step as described above. Halide treatment is a process of treating a stretched film by applying a solution containing a halide to the stretched PVA film (hereinafter also simply referred to as a stretched film). In the process, it is preferably carried out together with the acid treatment. The method of treating the film with the halide-containing solution may be any method as long as the solution is applied to the stretched film surface. Usually, it is preferable to immerse the stretched film in the solution. In the case of carrying out together with the acid treatment step, the film may be treated with a solution containing the halide together with the acidic substance. It is preferable to immerse the stretched film in a solution containing both. The concentration of the halide in the solution containing the halide used for the halide treatment is preferably in the range of 0.5 to 15 wt%. When the halide treatment is carried out together with the acid treatment, a solution containing a halide in the above concentration range and an acidic substance in a range of 0.0001 to 5.0% may be used. The treatment temperature is preferably 20 to 40 ° C, more preferably 5 to less than 60 ° C, for example. A treatment time of 2 seconds to 5 minutes can be applied, but 5 seconds to 1 minute is preferable.

[0024] As the acidic substance, any of inorganic acids and organic acids can be used, and further, salts thereof, in which the aqueous solution exhibits acidity, preferably a salt solution having an aqueous solution strength of less than ¾H6, A salt that is preferably less than pH 5 and having a pH value of 1 or more can also be used. Preferable inorganic acids include acids such as sulfuric acid, hydrochloric acid and nitric acid. Of these, sulfuric acid is more preferred. As the salt, a salt of an inorganic acid is usually used, and the preferred inorganic acid salt, particularly an aluminum salt, is preferred. Examples of such salts include aluminum sulfate, aluminum chloride, and aluminum nitrate. Aluminum sulfate is one of the particularly preferred ones. Salt and zinc used as a water-proofing agent and the like are not included in the acidic substance in the present invention because the aqueous solution does not fall within the above pH range. Examples of organic acids usually include carboxylic acids, and hydroxy or halogeno substitution. A C 1 C 4 saturated fatty acid is preferable, and a water-soluble organic acid having an a-hydroxy acid skeleton is one of them. Specific examples include, for example, formic acid, citrate, chloroacetic acid, acetic acid, oxalic acid, malic acid, and tartaric acid, and acetic acid is preferred, with citrate or acetic acid being preferred. One acidic substance may be used, or two or more acidic substances may be used in combination. Among these acidic substances, aluminum sulfate is one of the particularly preferable ones because of its high effect of improving wet heat durability. In organic acids, citrate, acetic acid, oxalic acid, etc. are generally used as food additives and are preferred from the environmental and safety perspectives and are considered to be acidic substances.

Preferred acidic substances include at least one selected from the group consisting of sulfuric acid, an aluminum salt of an inorganic acid (preferably an aluminum salt of an inorganic acid selected from the group strength of sulfuric acid, hydrochloric acid, or nitric acid), cuenic acid and acetic acid. Acidic substances such as aluminum sulfate or Z and acetic acid are particularly preferred.

[0025] The solution containing an acidic substance may contain a crosslinking agent (desirably, a crosslinking agent other than boric acid) and / or a waterproofing agent at the same time. Examples of cross-linking agents other than boric acid include polyvalent aldehydes such as darioxal or glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type or block type, and titanium compounds such as titanium oxysulfate. Forces that can be used In addition, ethylene glycol glycidyl ether or polyamide-epoxychlorohydrin can be used. Examples of water resistance agents include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, salt and ammonia, salt and salt. Examples thereof include magnesium or zinc salt.

[0026] When treating with a solution containing an acidic substance, the pH of the solution is also an important indicator. The lower the pH, the higher the wet heat durability of the polarizing film. However, if the pH is too low, there is a possibility that the polyvinyl alcohol-based resin is decomposed or polymerized. According to it

In a dry heat test such as a 90 ° C heat test, the transmittance may change by 1% or more. Therefore, when the pH of a solution containing an acidic substance (acid treatment solution) is adjusted to 1.0≤pH <6.0, it is suitable for obtaining a product with high wet heat durability, and is a more preferable range. The range is 2≤pH≤5. When trying to obtain a product with high dry heat durability, the pH should be 2 or more More preferably, the range is 2.2 or more and less than 6.0, more preferably about 2.2 to 5. Further, in some cases, 2.4≤pH <6.0 is more preferred, preferably 2.4≤pH≤5.0, more preferably 2.4≤pH≤4.0.

[0027] Preferably, the polarizing film of the present invention has high wettability and dry heat durability, and a high decrease in transmittance. In the excellent polarizing film of the present invention, the pH of the aqueous solution in which the polarizing film is dissolved is in the range of 5.0 <pH <6.0, and is one index of the excellent polarizing film of the present invention. It becomes. Further, the pH strength of the aqueous solution is more preferably in the range of 5.1 to 5.6. Further, the pH force of the aqueous solution is more preferably LV when the pH is 5.2 <pH <5.6, and most preferably the polarizing film is U, and the pH force of the solution for the polarizing film is 5. 2 <pH <5.4. The pH of the aqueous solution in which the polarizing film of the present invention is dissolved 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 out, placed in a screw bottle (Takara Seisakusho SV-30) containing distilled water lOcc, the lid was closed, and boiling water was added. An aqueous solution in which the polarizing film is dissolved is obtained by immersing in a bath for 2 hours, the aqueous solution is cooled to 25 ° C, and the pH of the aqueous solution is measured using pH Controller PP-01 manufactured by AZONE Corporation. the pH that is, was a _P H of an aqueous solution prepared by dissolving the polarizing film of the present invention. In the aqueous solution, it is not necessary to completely dissolve the polarizing film of the present invention used in the sample as long as the polarizing film is dissolved in the aqueous solution. It may be in a swollen state. However, preferably, the insoluble portion of the sample polarizing film should be less than 20 wt%.

[0028] In this way, the poly (vinyl alcohol) resin film obtained by treating with a solution containing 0.0001 to 5.0% of an acidic substance has a high concentration of acidic substance (low pH). The more the solution is processed, the lower the pH value of the solution in which the obtained polarizing film is dissolved. This is because the concentration of the acidic substance correlates with the pH of the polarizing film, and the pH of the solution in which the polarizing film is dissolved by controlling the acidic substance of the treatment solution, that is, the degree of treatment of the obtained polarizing film. Show that you can control. The concentration of the acidic substance is an important factor for producing a polarizing film. [0029] A preferable method for producing the polarizing film of the present invention is, for example, in an aqueous solution preferably containing a crosslinking agent (preferably boron) in order to impart a polarizing property to a PVA film dyed with iodine and iodide. PVA film that has been stretched 3 to 8 times, preferably 4 to 7 times (preferably uniaxially stretched), or dyed with iodine and iodide and treated with a crosslinking agent (preferably boron treatment) is subjected to dry stretching. The film is stretched 3 to 8 times, preferably 4 to 7 times (preferably uniaxially stretched), and the resulting stretched film is converted into the acid treatment solution, preferably a solution containing the acidic substance and halide. Then, an acid treatment and a halide treatment are performed, and the treated film can be dried to obtain a dried polarizing film of the present invention.

Through the above process, the iodine polarizing film of the present invention obtained by stretching the polybulal alcohol-based resin film is obtained.

[0030] The obtained polarizing film is made into a polarizing plate by providing a transparent protective layer on at least one side or both sides thereof. The transparent protective layer can be provided as a polymer coating layer or a film laminate layer. The transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. Furthermore, those having excellent moisture barrier properties are preferable. Examples of the material used as the transparent protective layer include cellulose acetate resin or film thereof such as triacetyl cellulose or diacetyl cellulose, acrylic resin or film thereof, polychlorinated bull resin or film thereof, polyester resin, and the like. A resin or a film thereof, a polyarylate resin or a film thereof, a cyclic polyolefin resin using a cyclic olefin as a monomer such as norbornene or a film thereof, polyethylene, polypropylene, a polyolefin having a cyclo or norbornene skeleton or a copolymer thereof, Main chain / or side chain force simide and Z or amide resin or polymer or film thereof

. Since polyvinyl alcohol functions as an alignment film for liquid crystal, rubbing treatment may be applied, or treatment with a photo-alignment film may be performed to provide a liquid crystalline resin or a film thereof. The thickness of the protective film is, for example, about 0.5 m to 200 μm. A polarizing plate is produced by providing one or more of the same or different types of resin or film on one side or both sides. [0031] An adhesive layer such as a pressure-sensitive adhesive may be provided on one surface of the obtained polarizing plate, that is, on the surface of the protective layer or film that becomes a non-exposed surface after being bonded to the display device. By providing an adhesive layer, a polarizing plate can be attached to a display device such as a liquid crystal display or an organic electoluminescence.

[0032] This polarizing plate is coated on one surface, that is, on the exposed surface of the protective layer or film, with an antireflection layer, an antiglare layer, a hard coat layer, a viewing angle improvement, and a liquid crystal coating for improving Z or contrast. You may have various well-known functional layers, such as a construction layer. The layer having various functions is preferably applied by a coating method, but a film having the function may be bonded via an adhesive or a pressure-sensitive adhesive. Further, the various functional layers may be known retardation plates that are layers or films for controlling the retardation.

[0033] In providing a transparent protective layer on the polarizing film, if the protective layer is a film, it is necessary to perform film lamination. In that case, an adhesive is required. As the adhesive, a polybulal alcohol adhesive is used. Examples of the polybulal alcohol-based adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nihon Gosei Co., Ltd.) or exeval RS-2117 (manufactured by Kuraray Co., Ltd.). A cross-linking agent and / or a waterproofing agent may be added to the adhesive. Further, the adhesive may contain an acidic substance at a concentration of 0.0001 to 20 wt%, preferably 0.02 to 5 wt%. As the polybutyl alcohol-based adhesive, an adhesive in which only a maleic anhydride-isobutylene copolymer / and a crosslinking agent are mixed can be used. As maleic anhydride-isobutylene copolymers, for example, Isoban # 18 (Kurarene), Isoban # 04 (Kurarene), Ammonia Modified Isovan # 104 (Kurarene), Ammonia Modified Isoban # 110 (Kurarene), Examples thereof include imidized isoban # 304 (made by Kurarene), imidized isoban # 310 (made by Kuraene). In this case, a water-soluble polyvalent epoxy compound can be used as the crosslinking agent. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtech) and Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.). As other adhesives, urethane-based, acrylic-based, and epoxy-based adhesives are frequently used, and known adhesives can be used, and the adhesive is not limited. Further, as an additive for the adhesive, a zinc compound or a halogen compound can be simultaneously contained at a concentration of about 0.1 to LOwt%. Limited for additives Is not something After the transparent protective layer is bonded with an adhesive, the polarizing plate is obtained by drying or heat treatment at an appropriate temperature.

[0034] The polarizing plate of the present invention thus obtained has little change in transmittance and degree of polarization even when left in a high-temperature and high-humidity atmosphere for a long time. For example, the transmittance decreases under a high-temperature environment at 90 ° C, for example. Therefore, it can maintain stable performance for a long time. The image display device of the present invention can be obtained by using the polarizing plate of the present invention for a liquid crystal display, an electoluminescence display device, a CRT or the like. In particular, in the case of a liquid crystal display, the liquid crystal display of the present invention can be obtained by adhering the polarizing plate of the present invention to both sides of a liquid crystal cell constituting the liquid crystal display with an adhesive together with a retardation film as necessary. The image display device thus obtained, particularly a liquid crystal display, can suppress a decrease in the visibility of the display image due to deterioration of the polarizing plate, and can stably display an image for a long period of time.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The transmittance and the degree of polarization shown in the examples were evaluated as follows.

[0036] When two polarizing plates obtained by laminating protective films on both sides of the polarizing film are stacked so that the absorption axis directions thereof are the same, the transmittance is the parallel transmittance Tp, The transmittance when the polarizing plates were stacked so that their absorption axes were orthogonal was defined as the orthogonal transmittance Tc.

[0037] The transmittance T was calculated by the following equation (1) by determining the spectral transmittance τ λ at predetermined wavelength intervals d λ (here, lOnm) in the wavelength range of 380 to 780 nm. In the equation, Ρ λ represents the spectral distribution of standard light (C light source), and γ λ represents the color matching function of 2 degrees visual field.

[0038]

The spectral transmittance τ λ was measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.]. [0040] The degree of polarization Py was determined by the equation (2) from the parallel transmittance Tp and the orthogonal transmittance Tc.

[0041] Py = {(Tp-Tc) / (Tp + Tc)} l / 2 X 100 (2)

[0042] The pH of the aqueous solution was measured using pH Controller "PP-01" manufactured by AZONE Corporation.

Example 1

[0043] A polybulal alcohol film (product name: VF-XS, manufactured by Kuraray Co., Ltd.) having a saponification degree of 99% or more and an average polymerization degree of 2400 was immersed in warm water at 40 ° C for 2 minutes, and after swelling treatment, 1 Stretched 30 times. Boric acid (made by Societa Chimica Larderello spa) 28.6 g / l, iodine (made by Junsei Chemical Co.) 0.25 g / l, potassium iodide (made by Junsei Chemical Co., Ltd.) 17.7 g / l Biiodide ammonium (manufactured by Junsei Chemical Co., Ltd.) 1. Iodine and iodide were dyed in an aqueous solution containing Og / 1 at 30 ° C for 2 minutes. The film obtained by dyeing was processed for 5 minutes in a 50 ° C. aqueous solution containing 30. Og / 1 of boric acid while uniaxially stretching 5.0 times. In an aqueous solution adjusted to 50 g / l potassium iodide and aluminum sulfate 14-18 hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.02 g / l while maintaining the tension of the film obtained by boric acid treatment The treatment was performed at 30 ° C for 15 seconds. At that time, the pH of the aqueous solution was 4.8. The film obtained by treatment with potassium iodide and acid was dried at 70 ° C for 9 minutes. A film obtained by drying is laminated with a triacetyl cellulose mouth film (trade name: TD-80U, manufactured by Fuji Photo Film Co., Ltd.), which has been processed with an all-strength process, and then laminated with a polybulal alcohol adhesive to obtain a polarizing plate. It was.

[0044] The obtained polarizing plate was cut into 40 mm x 40 mm and bonded to a lmm-thick glass plate via an adhesive (trade name: PTR-3000 manufactured by Nippon Kayaku Co., Ltd.) to obtain a measurement sample. A dry heat test and a wet heat test were applied to the prepared samples.

[0045] The wet heat test was performed in an atmosphere at a temperature of 65 ° C and a relative humidity of 93%, and the transmittance and the degree of polarization before and after leaving for 18 days (432 hours) were measured. A comparison was made between the case of treatment with a solution containing an acidic substance and the case of non-treatment, and it was used as an index for confirming the superior difference in transmittance (decoloration) and decrease in polarization degree.

[0046] The dry heat test was performed in an atmosphere of 90 ° C, and the transmittance was measured before and after standing for 18 days (432 hours). The change in transmittance was an absolute value within 1.0%, but it was within 1.0%. If the transmittance change is 1.0% or more, the color reproducibility of the display device cannot be obtained. This is preferable because of the effects of When the change of the test result in the dry heat test as viewed from the absolute value of the transmittance was within 1.0%, it was judged as “good”, and when it was over 1.0%, it was judged as “bad”.

Example 2

[0047] In Example 1, the loading amount of aluminum sulfate 14-18 hydrate was 0.2 g / l, and the pH was 3.

Samples were prepared in the same manner except for 4. The durability in the dry heat test and the wet heat test were compared. The pH when the polarizing film after the drying treatment was dissolved was 5.3. Example 3

[0048] In Example 1, except that aluminum sulfate 14-18 hydrate was replaced with citrate (anhydrous) (Pure Chemical Co., Ltd.), the addition amount was 0.05 g / l, and the pH was 4.8. Similarly, samples were prepared and the durability in the dry heat test and the wet heat test were compared.

Example 4

[0049] A sample was prepared in the same manner as in Example 3 except that the amount of added citrate was 0.07 g / l and the pH was 4.3, and the durability in the dry heat test and the wet heat test was confirmed. Compared.

Example 5

[0050] A sample was prepared in the same manner as in Example 3 except that the amount of citrate added was 0.1 lg / l and the pH was 3.8, and the durability in the dry heat test and the wet heat test was confirmed. Compared.

Example 6

[0051] In the same manner as in Example 3, except that the amount of added citrate was 0.3 g / l and the pH was 2.5.

耐久 Durability in dry heat test and wet heat test were compared. The pH when the polarizing film after the drying treatment was dissolved was 5.4.

Example 7

[0052] In the same manner as in Example 3, except that the amount of added citrate was 0.5 g / l and the pH was 2.3.

耐久 Durability in dry heat test and wet heat test were compared. The pH when the polarizing film after the drying treatment was dissolved was 5.3.

Example 8

[0053] In Example 1, except that aluminum sulfate 14-18 hydrate was replaced with acetic acid (manufactured by Junsei Co., Ltd.), the addition amount was 0.04 g / l, and the pH of the solution was 5.1. Sample preparation The durability in the dry heat test and the wet heat test was compared.

Example 9

[0054] A sample was prepared in the same manner as in Example 8 except that the amount of acetic acid added was 0.07 g / l and the pH was 4.0, and the durability in the dry heat test and the wet heat test was compared. .

Example 10

[0055] Samples were prepared in the same manner as in Example 8 except that the amount of acetic acid added was 0.1 lg / l and the pH was 3.8, and the durability in the dry heat test and wet heat test was compared. did.

Example 11

[0056] A sample was prepared in the same manner as in Example 8, except that the amount of acetic acid added was 0.6 g / l and the pH was 3.4. The durability in the dry heat test and the wet heat test were compared. did. _P H when dissolved polarizing film after drying was 5.7.

Example 12

[0057] Samples were prepared in the same manner except that the amount of acetic acid added was 3. Og / l and pH was 2.6 in Example 8. Comparison of durability in dry heat test and wet heat test did. _P H when dissolved polarizing film after drying treatment 5. was 4.

Example 13

[0058] In Example 8, except that the amount of acetic acid added was 5. Og / l and the pH was 2.4, samples were prepared in the same manner. The durability in the dry heat test and wet heat test were compared. did. _P H when dissolved polarizing film after drying treatment 5. 1.

[0059] Comparative Example 1

In Example 1, samples were similarly prepared except that aluminum sulfate 14-18 hydrate was not added, and the durability in the dry heat test and the wet heat test were compared. The pH when the polarizing film after the drying treatment was dissolved was 6.0.

[0060] Tables 1 and 2 show the measurement results of transmittance and polarization degree change in Examples 1 to 13 and Comparative Example 1.

[0061] Table 1 Change in transmittance and degree of polarization before and after wet heat durability test

[table 1]

[0062] Table 2 Changes in transmittance and degree of polarization before and after the dry heat durability test

[Table 2]

[0063] As described above in Examples and Comparative Examples, in a film in which a polyvinyl alcohol-based resin film containing iodine and iodide in the present invention contains a cross-linking agent and a stretching treatment is applied. A polarizing film obtained by treatment with a solution containing an acidic substance other than boric acid in a range of 0.0001 to 5.0% and having a pH of 2.4≤pH <6.0 may be used in a humid heat environment, for example, at a temperature of Polarizing film with no loss of color and little decrease in degree of polarization at 65 ° C and 93% relative humidity Or it becomes a polarizing plate. A polarizing plate having high transmittance, high contrast, and high wet heat durability in a polarizing film for liquid crystal displays can be obtained. Furthermore, it can be seen that the polarizing film obtained by the present invention has a dry heat durability, for example, a transmittance change within 1.0% in a dry heat test at 90 ° C. From the above results, it can be seen that the wet-heat durability of the polarizing plate is improved by the pH of the treatment solution, and the polarizing plate is obtained with little change in transmittance in the dry heat durability. On the other hand, looking at the pH of the treatment solution and the pH when the polarizing film is dissolved, the pH when the polarizing film is dissolved is lower as the treatment is performed with a solution having a higher concentration of acidic substances. Therefore, it can be seen that there is a correlation between the concentration of the acidic substance and the concentration of the polarizing film. The lower the concentration of acidic substances, the closer to 6 the pH is when the polarizing film is dissolved, and the dry heat test, for example, at 90 ° C, the transmittance does not decrease, but the wet heat durability gradually decreases. . When the polarizing film is dissolved, the pH is close to 5, and the higher the value, the higher the heat and heat durability! When the pH is 5 or less, it is transmitted in the dry heat test at 90 ° C. It can be seen that there is a significant decrease in the rate. Based on the above results, a polyvinyl alcohol resin film containing iodine is contained in an acidic substance other than boric acid in a range of 0.0001 to 5.0% and a pH of 2.4≤pH <6.0. It can be seen that the polarizing plate obtained by treating with the above has improved wet heat durability, and has a small change in transmittance in dry heat durability, so that a polarizing plate can be obtained.

[0064] Example A-2

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

[0065] Example A-3

In Example 1, except that the aluminum sulfate 14-18 hydrate was replaced with sulfuric acid (manufactured by Junsei Chemical Co., Ltd.), the addition amount was 0.2 g / l, and the pH was 1.88. The durability in the wet heat test was compared.

[0066] Example A—4

In Example 1, except that the aluminum sulfate 14-18 hydrate was replaced with sulfuric acid (manufactured by Junsei Co., Ltd.), the addition amount was 0.03 g / l, and the pH was 3.4. The durability in the wet heat test was compared.

[0067] Example A—5 In Example 1, except that the aluminum sulfate 14-18 hydrate was replaced with aluminum nitrate (Wako Pure Chemical Industries, Ltd.), the addition amount was 5 g / l, and the pH was 2.91. And the durability in the wet heat test was compared.

[0068] Example A—6

In Example 1, aluminum sulfate 14-18 hydrate was replaced with aluminum chloride hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.), and the addition amount was 5 g / l and the pH was 2.83. Other than the above, the preparation of the sample and the durability in the wet heat test were similarly compared.

[0069] Example A—7

A polybulle alcohol film (trade name: VF-XS, manufactured by KURARENE) having an average degree of polymerization of 2400 was immersed in warm water at 40 ° C for 2 minutes, a swelling treatment was applied, and the draw ratio was 1.30 times. The swollen film is immersed in an aqueous solution containing 0.25 g / l iodine (made by Junsei Chemical Co., Ltd.) and 17.7 g / l potassium iodide (made by Junsei Chemical Co., Ltd.) at 30 ° C. for 2 minutes, so that iodine and iodine Chemical treatment was performed. The dyed film was treated with boric acid (manufactured by Societa Chimica Larderello s.p.a.) at a concentration of 28 g / l, a treatment temperature of 30 ° C. for 5 minutes. The film to which the boric acid treatment was applied was treated in a 50 ° C. aqueous solution containing 30. Og / 1 of boric acid for 5 minutes while being stretched 5.0 times. While maintaining the tension of the film obtained by the treatment with hydrofluoric acid, it was maintained at 30 ° C with an aqueous solution adjusted to 50 g / l potassium iodide and 3.5 g / l potassium citrate (made by Junsei Kagaku). Processed for 2 seconds. The pH of the aqueous solution was 1.51. A film obtained by treating potassium iodide containing citrate was dried at 70 ° C. for 9 minutes. A triacetyl cellulose film (trade name: TD-80U, manufactured by Fuji Photo Film Co., Ltd.) obtained by subjecting the dried film to an alkali treatment was laminated by using a polybutyl alcohol adhesive to obtain a polarizing plate.

The obtained polarizing plate was cut into 40 mm × 40 mm, and bonded to a 1 mm thick glass plate via an adhesive (trade name: PTR-3000, manufactured by Nippon Kayaku Co., Ltd.) to obtain a measurement sample.

[0070] A wet heat test was applied to the prepared sample. The wet heat test was conducted in an atmosphere at a temperature of 65 ° C. and a relative humidity of 93%, and the single transmittance and the degree of polarization before and after being left for 18 days (432 hours) were measured.

[0071] Example A—8

In Example A-7, the same amount was applied except that the amount of added citrate was 0.05 g / l and the pH was 4.8. Similarly, the preparation of the samples and the durability in the wet heat test were compared.

[0072] Example A—9

In Example A-7, the sample preparation and the durability in the wet heat test were compared in the same manner except that the acetic acid was replaced by acetic acid, the acetic acid addition amount was 0.04 g / l, and the pH was 5.1. .

[0073] Example A—10

In Example A-7, except that citrate was replaced with acetic acid, the amount of acetic acid added was 3. Og / l, and the pH was 2.58. did.

[0074] Comparative Example 1

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

[0075] Comparative Example A-2

In Example A-7, except that kenic acid was not added, the preparation of the sample and the durability in the wet heat test were similarly compared.

[0076] Comparative Example A-3

In Example A-4, the film obtained by dyeing was stretched 5.0 times in 5 minutes while maintaining the pH of a 50 ° C aqueous solution containing 30. Og / 1 of boric acid at 3.4. The sample was prepared in the same manner as above except that the film obtained by boric acid treatment was kept in a tension state of the film obtained by boric acid treatment and was treated at 30 ° C for 15 seconds in an aqueous solution adjusted to 50 g / l of potassium iodide. The durability in the wet heat test was compared.

[0077] Table 1 shows the measurement results of changes in transmittance and polarization degree in Example 1, A-2 to A-10, Comparative Example 1, A-2, and A-3.

[0078] Table A—1

[Table A-1]

As can be seen from the above Examples and Comparative Examples, in the film in which the polyvinyl alcohol resin film containing iodine and iodide in the present invention contains a crosslinking agent and applied with a stretching treatment, other than boric acid. A polarizing film obtained by treatment with a solution containing 0.001 to 5.0% of an acidic substance having a pH of 1-0 ≤ pH <6.0 is used in a humid heat environment, for example, at a temperature of 65 ° C. At a relative humidity of 93%, there is no color loss and the polarizing film or polarizing plate has little decrease in polarization degree. A polarizing plate having high transmittance, high contrast, and high wet heat durability in a polarizing film for liquid crystal displays can be obtained. Further, when Example 4 and Comparative Example 3 are compared, it can be seen that the treatment can be performed more effectively by setting the pH of the halogenated material treatment tank to 1.0≤pH <6.0.

Claims

The scope of the claims

[I] After stretching a polyvinyl alcohol resin film containing iodine, iodide, a crosslinking agent and / or a water resistance agent, an inorganic acid or a salt thereof excluding boric acid and Z or an organic acid is added.

0001-5. A polarizing film obtained by treatment with a solution containing 0 ^% (hereinafter referred to as an acid treatment solution).

[2] The polarizing film according to [1], wherein the pH of the acid treatment solution is 2≤pH≤5.

[3] Iodine, iodide, a polyvinyl alcohol榭fat film containing a crosslinking agent and / or waterproofing agents, after stretching, _P H is 2. 4≤pH <6. acid treatment solution in the process of 0 2. The polarizing film according to claim 1, obtained by:

[4] The polarizing film according to [1], wherein the solution containing an inorganic acid other than boric acid or a salt thereof and Z or an organic acid contains a halide.

[5] The polarizing film according to claim 1, wherein the inorganic acid or its salt excluding boric acid is one or more of aluminum sulfate, aluminum chloride, aluminum nitrate and sulfuric acid. Nolem.

6. The polarizing film according to claim 1 or 2, wherein the inorganic acid excluding boric acid or a salt thereof is aluminum sulfate.

[7] The polarized light according to any one of [1] to [6], wherein the organic acid is at least one carboxylic acid and / or ex-hydroxy acid, which is obtained by treatment with a solution containing the organic acid. the film.

[8] The organic acid according to claim 7, wherein the organic acid is one or more of citrate, oxalic acid, malic acid, tartaric acid or acetic acid, and is obtained by treatment with a solution containing the organic acid. Polarized film.

[9] The polarizing film according to any one of [1] to [8], wherein the polybulal alcohol-based resin film after stretching is stretched at a stretching ratio of 3 to 8 times as compared with before stretching. Mu.

[10] The polarizing film according to [1] or [9], wherein the cross-linking agent and / or waterproofing agent used in the stretching treatment is boric acid.

[II] A protective layer on one or both sides of the polarizing film according to any one of claims 1 to 8. A polarizing plate provided with.

12. A liquid crystal display device comprising the polarizing plate according to claim 11.

[13] A polyvinyl alcohol resin film containing iodine, iodide, a crosslinking agent and / or a water-proofing agent should be treated with an acid treatment solution of 2.4≤pH <6.0 after the stretching treatment. A method for producing a characteristic polarizing film.

[14] A polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water resistance agent is treated with an acid treatment solution of 2.4≤pH <6.0 after stretching. A method for producing a polarizing plate, comprising providing a protective layer on one or both sides of the obtained polarizing film.

[15] A polarizing film characterized in that a polybulal 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. Production method.

[16] After stretching a polyvinyl alcohol-based resin film containing iodine, iodide, a crosslinking agent and / or a water-resistant agent, an inorganic acid or a salt thereof excluding boric acid and Z or an organic acid is added. A method for producing a polarizing film, characterized by treatment with a solution containing 0% (hereinafter referred to as an acid treatment solution).

[17] Acid treatment solution is composed of sulfuric acid, hydrochloric acid, nitric acid, aluminum sulfate, aluminum chloride, aluminum nitrate, formic acid, citrate, acetic acid acetic acid, acetic acid, oxalic acid, malic acid and tartaric acid 16. The method for producing a polarizing film according to claim 15, which is an aqueous solution containing at least one kind of acidic substance.

18. The method for producing a polarizing film according to claim 16, wherein the acid treatment solution has a pH of 2 to 5.