JPWO2015163224A1 - High durability iodine polarizer - Google Patents

Abstract

[Problem] To provide a polarizing element having greatly improved wet heat durability and good in a dry heat test. A polarizing element comprising a polyvinyl alcohol oriented resin film adsorbed with iodine, having a weight of 10 to 30%. % Boric acid, 10000 to 60000 ppm iodine ions, and 200 to 20000 ppm chlorine ions. [Selection figure] None

Description

The present invention relates to a polarizing element having high heat resistance and high wet heat durability.

There is a demand for a polarizing plate having high transmittance and degree of polarization, high contrast, and excellent durability. As an invention for this demand, as described in Patent Document 1, an improved method of containing chlorine ions in an iodine-based polarizing plate, or a method by changing a method of protecting a polarizing element as in Patent Document 2 It describes that heat resistance and wet heat durability are improved. However, the durability is not yet sufficient, and an improvement in wet heat durability of an inexpensive and simple polarizing plate is desired.

Japanese Patent No. 4355317 Patent 4947699

Issued by UV Technology System General Technology Center, Kiyomi Kato, P259-303

In particular, the method of Patent Document 1 has a problem in that the polarization performance is inferior to that of a conventional polarizing plate, and further improvements in heat resistance and wet heat durability have been eagerly desired. Moreover, in the polarizing plate which provides the layer obtained by the polymerizable resin composition as in the method of claim 2 of the same document, although the durability is certainly improved, there is a problem that the color change after the durability test is large. was there. In addition, if the amount of ions contained in the polarizing element is different, problems such as a decrease in the adhesiveness of a protective film layer that protects the polarizing element, for example, a layer made of a polymerizable resin composition, have occurred. There has been a demand for improvement in adhesion between the subsequent color change and the polarizing element.

As a result of intensive studies to solve the above problems, the present inventor is a polarizing element comprising a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented, and includes 10 to 30 wt% boric acid and 10000 to 60000 ppm iodine. By using a polarizing element characterized by containing ions and chlorine ions of 200 to 20000 ppm, the optical properties are good, the heat resistance is high, and the adhesion with the protective film layer is high. It came to provide the iodine type polarizing plate.

That is, the present invention
“(1) A polarizing element comprising an oriented polyvinyl alcohol-based resin film adsorbed with iodine, containing 10 to 30 wt% boric acid, 10000 to 60000 ppm iodine ions, and 200 to 20000 ppm chlorine ions. A polarizing element,
(2) The polarizing element according to (1), further containing 4000 to 12000 ppm of potassium ions,
(3) The polarizing element according to (1) or (2), further containing 300 to 3000 ppm of lithium ions,
(4) A polarizing plate comprising a polarizing film according to (1) to (3), wherein a protective film is bonded to one side or both sides,
(5) The protective film has at least one layer obtained by curing one or more kinds of polymerizable resin compositions, and the thickness of the layer is 0.1 μm to 10 μm ( 4) the polarizing plate,
(6) The polarizing plate according to (4) or (5), wherein the protective film is a cellulose acetate resin film,
(7) A layer obtained by curing the polymerizable resin composition includes at least one (meth) acrylate compound having at least one hydroxyl group and at least one (meth) acryloyl group in the molecule. The polarizing plate according to (5) or (6), comprising 30 to 99,5 parts by weight in 100 parts by weight of the resin composition,
(8) The polarizing plate according to any one of (5) to (7), wherein a layer obtained by curing the polymerizable resin composition is provided between the cellulose acetate resin film and the polarizing element. ,
(9) A display device using the polarizing element or polarizing plate according to (1) to (8),
(10) The method for producing a polarizing element according to (1)-(3), wherein the polyvinyl alcohol resin film is subjected to a dyeing treatment with iodine and a drawing treatment in a boric acid solution to obtain a drawn film, The method comprising the step of treating the stretched film with an aqueous solution containing an alkali metal and / or alkaline earth metal chloride and an alkali metal and / or alkaline earth metal iodide. ".

The polarizing element of the present invention has good optical properties, high heat resistance, and good adhesion to the protective film layer. Moreover, the iodine type polarizing plate using the polarizing element of this invention shows high durability.

Hereinafter, preferred embodiments of the present invention will be described. The polarizing element of the present invention is one in which iodine is adsorbed on a polyvinyl alcohol resin film and oriented, for example, after or simultaneously with the dyeing treatment of the polyvinyl alcohol resin film with iodine, the stretching treatment, boric acid treatment And is further processed by immersion in an aqueous solution containing a chlorine compound and an iodide compound. Furthermore, durability is further improved by providing a layer obtained by curing the polymerizable resin composition.

As a raw material for the polyvinyl alcohol-based resin film, polyvinyl alcohol or a modified polyvinyl alcohol is usually used, and the degree of polymerization thereof is in the range of about 1000 to 10,000, preferably in the range of 1500 to 6000. A saponified polyvinyl alcohol resin is usually used, and the degree of saponification is usually in the range of about 85 to 100 mol%, preferably 98 to 100 mol%. A polyvinyl alcohol-type resin film is manufactured by forming this polyvinyl alcohol-type resin into a film. Film formation can be performed by a known method. The thickness of the polyvinyl alcohol-based resin film is usually about 10 μm to 150 μm.

After the polyvinyl alcohol-based resin film is swollen, a dyeing treatment with iodine is performed. The dyeing treatment with iodine is performed, for example, by immersing the polyvinyl alcohol resin film described above in a dyeing solution containing boric acid in an aqueous solution containing iodine and potassium iodide. When an aqueous solution is used, the amount of iodine and potassium iodide used in the aqueous solution is 0.01 to 0.3 parts by weight of iodine and 0.01 to 3.0 parts by weight of potassium iodide with respect to 100 parts by weight of water. Degree. The temperature of the dyeing solution is about 20 to 50 ° C. The immersion time is in the range of about 10 to 300 seconds. By the dyeing treatment with iodine, iodine is adsorbed on the polyvinyl alcohol resin film.

Next, a stretching process is performed in which the polyvinyl alcohol-based resin film on which iodine is adsorbed is uniaxially stretched at a predetermined magnification. The stretching treatment is preferably performed while immersing the polyvinyl alcohol-based resin film in an aqueous boric acid solution. The amount of boric acid used in the boric acid aqueous solution is preferably 1.0 to 6.0 parts by weight, preferably about 2.0 to 4.0 parts by weight of boric acid with respect to 100 parts by weight of water. The temperature of the boric acid aqueous solution is, for example, about 30 to 60 ° C. As a stretching method, a method using a hot roll or a method of uniaxial stretching between two rolls having different peripheral speeds may be used. The draw ratio is usually about 4.0 to 7.0 times.

The boric acid treatment is performed by immersing the polyvinyl alcohol resin film that has been subjected to the dyeing treatment and the stretching treatment in an aqueous boric acid solution. As the boric acid aqueous solution in the boric acid treatment, a solution in which 3.0 to 7.0 parts by weight, preferably 4.0 to 6.0 parts by weight of boric acid is dissolved in 100 parts by weight of water is used. The temperature of the boric acid aqueous solution is, for example, 40 ° C. or higher, and preferably 50 to 85 ° C. The immersion time is, for example, 10 to 600 seconds, preferably 30 to 300 seconds, at the above temperature.

The polarizing film in this invention contains a boric acid by the extending | stretching process in a boric-acid aqueous solution mentioned above, and a boric-acid process. The boric acid content of the polarizing element is 10 to 30% by weight. More preferably, it is 15 to 25% by weight. By adjusting the boric acid concentration, the immersion time, and the solution temperature in the stretching treatment and boric acid treatment, the boric acid content of the obtained polarizing element is adjusted.

In the present invention, the treatment with an aqueous solution containing chloride and iodide can be suitably carried out by, for example, performing the above-described dyeing treatment, stretching treatment, and boric acid treatment on a polyvinyl alcohol resin film. This treatment is preferably performed by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing chloride and iodide. The preparation concentration of the aqueous solution of chloride and iodide varies depending on the mode of stretching treatment, the concentration of boric acid, and the temperature during treatment with an aqueous solution containing chloride and iodide, but with respect to 100 parts by weight of water. Thus, 0.1 to 8 parts by weight, preferably 1.0 to 5.0 parts by weight, more preferably 1.5 to 3.0 parts by weight of iodide may be used. The aqueous solution containing chloride is 0.1 to 10 parts by weight, preferably 1.0 to 8.0 parts by weight, more preferably 3.0 to 6.0 parts by weight with respect to 100 parts by weight of water. It is good to use what melt | dissolved the part. For example, the temperature of the aqueous solution is 30 to 70 ° C. The immersion time is, for example, 10 to 300 seconds at the temperature.

Chlorine compounds in aqueous chloride solutions include, for example, alkali metal chlorides such as potassium chloride, sodium chloride, lithium chloride, or alkaline earth metal chlorides such as beryllium chloride, magnesium chloride, calcium chloride, or cobalt chloride, for example. And chlorides of metals such as zinc chloride. Among these, the combined use of potassium chloride and lithium chloride is most preferable, and the use of lithium chloride is preferable because more chloride can be contained as compared with the case of using only potassium chloride. Examples of the iodide in the iodide aqueous solution include potassium iodide, sodium iodide, ammonium iodide, cobalt iodide, and zinc iodide. Of these, potassium iodide is most preferred.

As described above, a predetermined amount of chlorine ions and iodine ions can be contained in the polarizing element by performing treatment with an aqueous solution containing chloride and iodide on the polyvinyl alcohol-based resin film. The chloride ion content in the polarizing element is 200 to 20000 ppm, preferably 1000 to 10,000 ppm, more preferably 2000 to 6000 ppm. Furthermore, the iodine ion content in the polarizing element is 10,000 to 60000 ppm, preferably 15000 to 40000 ppm. By including such specific concentrations of chlorine ions and iodine ions, a polarizing element having high durability and a high degree of polarization can be obtained.

The polarizing element of the present invention can further contain 4000 to 12000 ppm of potassium ions in addition to chlorine ions and iodine ions, thereby further improving optical characteristics and durability. In addition, the content balance of chlorine ions, iodine ions, and potassium ions is important, and simply increasing the amount of potassium ions does not improve the durability.

In order to further improve the heat resistance, it is preferable to contain lithium ions in addition to chlorine ions, iodine ions and potassium ions. The content is preferably about 300 to 3000 ppm in the polarizing element. By containing lithium ions, for example, more chlorine ions can be contained in the polarizing element than when treating with potassium chloride alone, and the heat resistance can also be improved.

Typically, after the treatment with a solution containing chloride and iodide, the polarizing element is dried. The drying temperature in the drying process is about 40 to 50 ° C., and the drying time is about 30 to 700 seconds.

The boric acid concentration in the polarizing element can be measured by a known method such as heating the obtained polarizing element in pure water to completely dissolve it, adding a phenolphthalene indicator, and neutralizing titration with an aqueous NaOH solution. it can. Further, the chlorine ion concentration, iodine ion concentration, potassium ion concentration, and lithium ion concentration can be determined by a known method such as ion chromatography or ICP analysis.

The polarizing element of the present invention obtained as described above contains a specific amount of boric acid, chlorine ions, and iodine ions, thereby realizing high durability under high temperature conditions and high temperature and high humidity conditions. A polarizing plate having a degree is obtained.

In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible. For example, in the above embodiment, the stretching process is performed after the dyeing process with iodine, but may be performed before the dyeing process with iodine or during the dyeing process with iodine. Further, the stretching treatment may be performed during the boric acid treatment. Further, for example, dry stretching may be performed in the air. When the stretching treatment is performed during the dyeing treatment with iodine, the stretching treatment is performed during the boric acid treatment, or the dry stretching is performed, the content of boric acid in the obtained polarizing element is 5 to 40% by weight only by the boric acid treatment. It will be adjusted to be in the range. When the stretching treatment is performed simultaneously with the dyeing treatment with iodine or the boric acid treatment, or when dry stretching is performed, the boric acid concentration of the boric acid aqueous solution of the boric acid treatment may be set higher than the range in the above embodiment or the immersion. You may make time longer than the range in the said embodiment.

The polarizing plate of the present invention is obtained by bonding a protective film to one side or both sides of the polarizing element of the present invention obtained as described above. Here, the protective film is added for the purpose of improving the water resistance and handling properties of the polarizing element, and an appropriate transparent material can be used for the formation thereof. The protective film is a film having a layer shape that can be protected, and in particular, plastics having excellent transparency, mechanical strength, thermal stability, moisture shielding properties, etc. are preferably used, but by forming a layer equivalent to it An equivalent function may be provided. Examples thereof include polyester resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, and other thermoplastic resins, acrylic resins, urethane resins, Examples include films obtained from thermosetting resins such as acrylic urethane, epoxy and silicone, or ultraviolet curable resins. Among these, polyolefin resins include amorphous polyolefin resins and norbornene or polycyclic norbornene. Examples thereof include resins having a polymerized unit of cyclic polyolefin such as a monomer. A preferred protective film is triacetyl cellulose (TAC) made of cellulose acetate resin. In addition, the transparent protective film used for the protective film is subjected to a treatment for the purpose of hard coat treatment, antireflection treatment, prevention of sticking, diffusion or anti-glare, etc. unless the purpose of the present invention is impaired. Also good.

In such a protective film, at least one layer obtained by curing one or more kinds of polymerizable resin compositions is provided, and the layer has a thickness of 0.1 μm to 10 μm. Sex is further improved dramatically. In particular, when a layer obtained by curing such a polymerizable resin composition is provided on a cellulose acetate resin film, the durability is remarkably improved.

As the polymerizable resin composition, for example, a thermosetting resin composition or an ultraviolet curable resin composition can be used. It is preferably an ultraviolet-polymerizable curable resin that is inexpensive and can be easily processed in a short time. As the resin at that time, a polymerizable resin exemplified in Non-Patent Document 1 and an initiator thereof can be used, and the resin is not limited thereto, and a known resin or an initiator thereof can be used. it can.

In particular, in order to improve durability, the layer in which the polymerizable resin composition is cured has at least one hydroxyl group in the molecule and (meth) acrylate having at least one (meth) acryloyl group. It is preferable that 30 to 99.5 parts by weight of the compound is contained in 100 parts by weight of the polymerizable resin composition. More preferably, it is 50 to 99.5 parts by weight, still more preferably 70 to 99.5 parts by weight, and even more preferably 90 to 99.5 parts by weight. Since the adhesiveness and dimensional change of the polarizing element change depending on the ions contained in the polarizing element, the selection of the resin is important if high durability is aimed at. In particular, it is more preferable to have two or more (meth) acryloyl groups than a (meth) acrylate compound having at least one hydroxyl group in the molecule. Examples of such a resin include pentaerythritol triacrylate. (Nippon Kayaku Kayrad PET-30), dipentaerythritol monohydroxypentaacrylate (Sartomer-399), ECH-modified 1,6-hexanediol diacrylate (Nippon Kayaku Kayrad R-167) Among them, in particular, pentaerythritol triacrylate (Kayarad PET-30 manufactured by Nippon Kayaku Co., Ltd.) and dipentaerythritol monohydroxypentaacrylate (SR-399 manufactured by Sartomer) which are resins having a pentaerythritol skeleton are particularly preferable. Arbitrariness. The durability is improved by mixing such a resin with the polymerizable resin described in Non-Patent Document 1 to prepare a composition and providing it as a layer on the film.

When the resin composition used in the polarizing element of the present invention is a resin composition that can be polymerized by ultraviolet rays, the polymerization reaction can be carried out by using an ultraviolet polymerization initiator. Examples of such an ultraviolet polymerization initiator include 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1 (Irgacure 907 manufactured by Ciba Specialty Chemicals), 1-hydroxycyclohexyl phenyl ketone (Ciba Specialty). Irgacure 184 from Tea Chemicals), 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone (Irgacure 2959 from Ciba Specialty Chemicals), 1- (4-dodecylphenyl) -2- Hydroxy-2-methylpropan-1-one (Merck Darocur 953), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (Merck Darocur 1116), 2-hydroxy-2 -Methyl-1-phenyl Lopan-1-one (Irgacure 1173 manufactured by Ciba Specialty Chemicals), acetophenone compounds such as diethoxyacetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-2 -Benzoin compounds such as phenylacetophenone (Irgacure 651 manufactured by Ciba Specialty Chemicals), benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3, 3 Benzophenone compounds such as' -dimethyl-4-methoxybenzophenone (Nippon Kayaku MBP), thioxanthone, 2-chloro Oxanson (Nippon Kayaku Caya Cure CTX), 2-Methylthioxanthone, 2,4-Dimethylthioxanthone (Kaya Cure RTX), Isopropylthioxanthone, 2,4-Dichlorothioxanthone (Nippon Kayaku Caya Cure CTX) Thioxanthone compounds such as 2,4-diethylthioxanthone (Nippon Kayaku Kayacure DETX), 2,4-diisopropylthioxanthone (Nippon Kayaku Kyakuure DITX), and the like. More preferably, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1 (Irgacure 907 manufactured by Ciba Specialty Chemicals), 1-hydroxycyclohexyl phenyl ketone (Irgacure manufactured by Ciba Specialty Chemicals) 184), 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651 manufactured by Ciba Specialty Chemicals) is preferable. One or more of these photopolymerization initiators can be mixed and used at any blending ratio.

When a benzophenone compound or a thioxanthone compound is used as the ultraviolet polymerization initiator, an auxiliary agent can be used in combination to promote the photopolymerization reaction. Examples of such auxiliaries include triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-methyldiethanolamine, diethylaminoethyl methacrylate, Michler's ketone, 4,4′-diethylaminophenone, 4-dimethylaminobenzoic acid. Examples include amine compounds such as ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, and 4-dimethylaminobenzoic acid isoamyl.

The addition amount of the ultraviolet polymerization initiator and the auxiliary agent is preferably used within a range in which the polarization performance does not deteriorate, and the amount is based on 100 parts by weight of the (meth) acrylate compound in the polymerizable resin composition. The amount is preferably 0.5 to 12 parts by weight, more preferably about 2 to 10 parts by weight. Further, the auxiliary agent is preferably about 0.5 to 2 times the amount of the ultraviolet polymerization initiator.

When the resin composition used in the polarizing element of the present invention is a thermopolymerizable resin composition, a polymerization initiator, a crosslinking agent, and / or an initiation catalyst can be used. As the type of the crosslinking agent, various known compounds such as isocyanate, boron, and titanate can be used. The addition amount is 0.1 to 20 parts by weight in 100 parts by weight of the polymerizable resin composition, more preferably about 1 to 10 parts by weight in 100 parts by weight of the composition.

As a method for forming a layer of a polymerizable resin composition on a polarizing plate, for example, the composition is directly or diluted with an appropriate solvent, and applied to a protective film or a polyvinyl alcohol film having iodine adsorbed and oriented. . Thereafter, the solvent is removed by heating or the like, and a layer obtained by curing the polymerizable resin composition of the present invention can be obtained by heating or irradiating with ultraviolet rays. The solvent of the solution of the composition used for coating is not particularly limited as long as it is excellent in solubility of the composition and wettability on the substrate during coating and does not cause deterioration in surface properties. Examples of such solvents include aromatic hydrocarbons such as water, toluene and xylene, ethers such as anisole, dioxane and tetrahydrofuran, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-pentanone and 3-pentanone. , Ketones such as 2-hexanone, 3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2,6-dimethyl-4-heptanone, n-butanol, 2-butanol, cyclohexanol, isopropyl alcohol, etc. Alcohols, cellosolves such as methyl cellosolve, methyl cellosolve acetate, ethyl acetate, butyl acetate, methyl lactate, propylene glycol monomethyl ether acetate, propylene glycol ethyl ether acetate, methoxyethyl acetate Esters such as succinate San ethoxyethyl, dimethyl sulfoxide, acetonitrile, N, including but N- dimethylacetamide dimethylformamide without limitation. Toluene, cyclopentanone, and ethyl acetate are preferable. The solvent may be a single solvent or a mixture. The concentration of the composition when dissolving the composition varies depending on the solvent solubility, wettability on the substrate, thickness after coating, etc., but is preferably 5 to 95% by weight, more preferably 10 to 80% by weight. The degree is good.

In addition, when the wettability onto the substrate is poor or the surface property of the formed composition layer is poor when applied onto the substrate, various leveling levels are included in the composition in order to improve them. It is also possible to add an agent. As the type of leveling agent, various compounds such as silicon-based, fluorine-based, polyether-based, acrylic acid copolymer-based and titanate-based compounds can be used. The addition amount is 0.0001 part by weight or more and 10 parts by weight or less in 100 parts by weight of the polymerizable resin composition, more preferably 0.1 part by weight or more and 5 parts by weight or less in 100 parts by weight of the composition. .

After the composition layer formed on the substrate is cured, various cross-linking agents can be added to the composition in order to further improve the adhesion between the cured layer and the protective film. . As the type of the crosslinking agent, various compounds such as isocyanate, boron, and titanate can be used. The addition amount is 0.0001 part by weight or more and 20 parts by weight or less in 100 parts by weight of the polymerizable resin composition, more preferably 0.1 part by weight or more and 10 parts by weight or less in 100 parts by weight of the composition. .

As a method of forming a layer on the polarizing plate of the polymerizable resin composition, a resin layer may be provided by coating on a protective layer or a protective film, or a layer may be formed by a method such as coating directly on a two polyvinyl alcohol resin film. May be provided. Alternatively, it may be applied not only to the protective film or the polyvinyl alcohol-based resin film but also to a method in which the cured layer previously applied to another film is transferred or laminated on the protective film or the polyvinyl alcohol-based resin film. Furthermore, the method of providing a layer at the same time as providing the adhesive layer is also efficient, and the polarizing plate can be most easily prepared when the resin composition to be the adhesive layer is a polymerizable resin composition. The application method is not particularly limited, and examples thereof include a spin coating method, a wire bar coating method, a gravure coating method, a micro gravure coating method, a calendar coating method, a spray coating method, and a meniscus coating method.

It is preferable that the cured layer made of the polymerizable resin composition of the present invention is sufficiently polymerized by heating or ultraviolet irradiation and has as little unreacted content as possible. The amount of the unreacted acrylate compound in 100 parts by weight of the cured resin composition is 0 to 5 parts by weight, more preferably 0 to 3 parts by weight, and still more preferably 0 to 1 part by weight. It is better to make it less than parts by weight. As a method for obtaining such a layer, for example, a method for optimizing the thickness of the layer of the resin composition after coating, a method for optimizing the type and amount of the UV polymerization initiator to be added, sufficient heating or UV irradiation A method of irradiating, a method of changing the atmosphere at the time of ultraviolet irradiation, such as performing in an inert gas such as nitrogen, and the like, can be mentioned. The simple method is the simplest because the method of optimizing the thickness of the resin layer can be optimized only by changing the resin concentration or changing the resin coating amount. The thickness of the layer obtained by curing the polymerizable resin composition is preferably 0.5 μm to 10 μm, more preferably 1 μm to 8 μm, still more preferably 2 μm to 6 μm. If it is thicker than 10 μm, the residual unreacted monomer increases, the wet heat durability is insufficient, and the polarizing plate turns red in the heat resistance test, which is not suitable. On the other hand, a layer thinner than 0.5 μm does not lead to improvement in wet heat durability. The dose of ultraviolet rays, acrylate compounds type, addition amount and the kind of the ultraviolet polymerization initiator differs depending thickness, for example, be about 100 to 1500 mJ / cm ^2.

Moreover, it is preferable that the layer which hardened | cured polymeric resin composition is transparent even if it processes with an alkaline solution. Specifically, one of the indicators is that there is no cloudiness after treatment with an alkaline aqueous solution of pH 11 or more at 40 ° C. for 10 minutes or more. As the standard, even when a UV curable resin composition is applied to polyethylene terephthalate to a thickness of 5 μm and a film provided with a cured layer is treated with an aqueous solution of pH 11 at 40 ° C. for 10 minutes or more, the wavelength is 550 nm. The light transmittance is preferably 85% or more, and preferably 90% or more. On the other hand, more preferably, the layer obtained by curing the polymerizable resin composition is treated with an alkaline aqueous solution so that the layer obtained by curing the polymerizable resin composition becomes hydrophilic. Is preferable. As an index of hydrophilicity at that time, the contact angle when 10 μl of water is dropped is preferably 60 ° or less, more preferably 50 ° or less, and still more preferably 40 ° or less. In the case of bonding to a polarizing element film, it is preferable to use a solution to which neutralization treatment is performed with water or an acidic aqueous solution after treatment with an alkaline aqueous solution and then a drying treatment is applied.

More preferably, the compound having an acryloyl group in the polymerizable resin composition is a compound having two or more acryloyl groups, and after the layer is formed and cured to have a film thickness of 5 μm. The resin layer is preferably a compound having a moisture permeability of not more than 1500 g · m ^{2 in} 24 hours based on JIS-Z0208. More preferably, the moisture permeability is 1100 g / m ² or less in 24 hours, more preferably 900 g / m ² or less in 24 hours, more preferably 800 g / m ² or less in 24 hours. It is preferable.

Such a method of evaluating moisture permeability is obtained by applying a compound having an acryloyl group to semi-bleached kraft paper (obtained from Totsuya Echo Co., Ltd.) with a solid alcohol concentration of 5% polyvinyl alcohol anchored to a thickness of 1 μm. Work. A compound having an acryloyl group was prepared by mixing 10 parts by weight of a resin having an acryloyl group, 5 parts by weight of toluene, and 0.6 parts by weight of 1-hydroxycyclohexyl phenyl ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals). . The composition was applied to the semi-bleached kraft paper to which polyvinyl alcohol was anchor-coated so that the resin solid content after solvent evaporation would be 5 μm thick. By checking the moisture permeability of the paper based on JIS-Z0208, the moisture permeability of the compound having an acryloyl group can be evaluated.

When the moisture permeability is confirmed by this method, the moisture permeability of the resin layer of the compound having an acryloyl group is further clarified. Table 1 shows compounds having an acryloyl group obtained by the method.

この結果から、ジエチレングリコールジアクリレート、ならびにポリエチレングリコール400ジアクリレートなどは本発明においては、耐久性向上としては乏しいことが分かる。

From this result, it can be seen that diethylene glycol diacrylate, polyethylene glycol 400 diacrylate, and the like are poor in terms of durability improvement in the present invention.

In order to further improve the durability, the layer obtained by curing the polymerizable resin composition is composed of a protective film / adhesive layer / polyvinyl alcohol film / adhesive layer / protective film in which iodine is adsorbed and oriented. One or more layers may be provided between any layers or on the surface. Specifically, one or more layers may be provided on the surface of the protective film that does not face the adhesive layer, between the protective film and the adhesive layer, or between the adhesive layer and the polyvinyl alcohol film in which iodine is adsorbed and oriented. say. In order to further improve the wet heat durability, it is effective to provide a layer obtained by curing the polymerizable resin on the surface side that becomes the exposed surface after being bonded to the display device, and in order to further improve the wet heat durability, Polymerization between the protective film / adhesive layer / adhesive orientation of the protective film / adhesive layer on the exposed surface and the protective film and adhesive layer of the polyvinyl alcohol film adsorbed and oriented, or between the adhesive layer and the polyvinyl alcohol film adsorbed and oriented on iodine A layer obtained by curing the conductive resin composition is preferably provided. In order to further enhance the effect of improving wet heat durability, one layer or two or more layers on which the resin composition is cured are provided on both sides via a polyvinyl alcohol film to which a dichroic dye is adsorbed and oriented. Is more preferable. Even if the adhesive layer of the polarizing plate composed of a protective film / adhesive layer / polyvinyl alcohol film / adhesive layer / protective film in which a dichroic dye is adsorbed and oriented is a layer obtained by a resin composition, the heat and heat resistance is similarly applied. The effect which improves property is acquired.

The polarizing plate of the present invention is obtained by providing at least one layer obtained by curing the polymerizable resin composition by the above steps.

The adhesion treatment between the polarizing element of the present invention and the protective film is not particularly limited. For example, an adhesive made of a polymer made of a polyvinyl alcohol resin, an adhesive made of a vinyl alcohol polymer, boric acid, Adhesives composed of water-soluble crosslinking agents of vinyl alcohol polymers such as borax, glutaraldehyde, melamine, and oxalic acid, highly transparent epoxy resins, polyester resins, solvent-based adhesives such as vinyl acetate, or An adhesive resin that can be cured by a polymerization reaction such as an acrylic resin or a urethane resin can be used. In particular, it is preferable to use acetoacetyl-modified polyvinyl alcohol, and it is preferable to use a polyvalent aldehyde as the cross-linking agent.

The polarizing plate of the present invention can also be used as an optical member laminated on an optical layer of another optical material. For example, used to form liquid crystal display devices such as reflectors, transflective plates, retardation plates (including λ plates such as half-wave plates and quarter-wave plates), viewing angle compensation films, and brightness enhancement films. One layer or two or more layers may be used as appropriate optical materials that may be used. Specific examples thereof include a reflective polarizing plate or a transflective polarizing plate obtained by further laminating a reflecting plate or a transflective plate on the polarizing plate of the present invention, and also a polarizing plate of the present invention and a retardation plate. A polarizing plate in which a viewing angle compensation film is laminated on the polarizing plate of the present invention, or a polarizing plate in which a brightness enhancement film is further laminated on the polarizing plate of the present invention. A board etc. are mentioned.

Various optical members using the polarizing plate of the present invention can be preferably used for forming various devices such as a liquid crystal display device. For example, the polarizing plate of the present invention can be used in a liquid crystal display device such as a reflective type, a transmissive type, or a transmissive / reflective type in which a polarizing plate is disposed on one side or both sides of a liquid crystal cell. In this case, the liquid crystal cell forming the liquid crystal display device is arbitrary, such as an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twist nematic type or a super twist nematic type, etc. An appropriate type of liquid crystal cell may be used.

Moreover, when providing a polarizing plate and an optical member in the both sides of a liquid crystal cell, they may be the same and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged in one or more layers at appropriate positions.

When using a polarizing plate as a member of a liquid crystal display device, an adhesive layer for adhering to other members such as a liquid crystal cell may be provided on one side or both sides thereof. For the formation of the adhesive layer, an appropriate adhesive substance or adhesive can be used, and there is no particular limitation. Examples thereof include an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer or a rubber-based polymer as a base polymer.

The polarizing plate of the present invention is used in all liquid crystal display devices such as twisted nematic (TN) M super twisted nematic (STN), thin film transistor (TFT), vertical alignment (VA), and in-plane switching (IPS). can do.

Hereinafter, the present invention will be described more specifically with reference to examples. Although described in more detail, the present invention is not limited thereto. In addition, the transmittance | permeability shown in an Example was performed as follows.

The transmittance of each wavelength when measuring a polarizing element or a polarizing plate with one sheet is defined as transmittance Ts, and two polarizing elements or polarizing plates are stacked so that their absorption axis directions are the same. The transmittance in this case was defined as parallel transmittance Tp, and the transmittance when two polarizing plates were stacked so that their absorption axes were orthogonal to each other was defined as orthogonal transmittance Tc.

Spectral transmittance τλ was determined every predetermined wavelength interval dλ (here, 5 nm) in the wavelength region of 400 to 700 nm, and calculated by the following equation (1). In the formula, Pλ represents a spectral distribution of standard light (C light source), and yλ represents a y (λ) color matching function in a two-degree field of view. The single transmittance Ys corrected to the visibility is Ts to τλ, the parallel transmittance Yp corrected to the visibility is Tp to τλ, and the orthogonal transmittance Yc corrected to the visibility is Tc to τλ. Used to calculate.

Spectral transmittance τλ was measured using a spectrophotometer (“U-4100” manufactured by Hitachi, Ltd.).

The degree of polarization ρy was determined by the equation (2) from the parallel transmittance Yp and the orthogonal transmittance Yc.

Furthermore, in the color system shown by JIS Z8729 (color display method L *, a *, b * display system and L *, u *, v * color system) about the hue of the polarizing plate, a * and b * were measured. The term “orthogonal hue” as used herein means that the measurement was performed in a state where two polarizing plates were overlapped so that their absorption axes were orthogonal to each other. In the L *, a *, and b * color systems, the hues indicate neutral colors as a * and b * are closer to zero.

Example 1
A polyvinyl alcohol film (VF-XS manufactured by Kuraray Co., Ltd.) having a thickness of 75 μm, a polymerization degree of 2400, and a saponification degree of 99% or more is swollen with warm water at 40 ° C., and then an aqueous solution containing iodine, potassium iodide and boric acid. Staining was carried out. The dyed film is stretched 5 times in an aqueous solution at 50 ° C. containing 3% by weight of boric acid, and after stretching, the aqueous solution is 2.5% by weight of potassium iodide and 5.0% by weight of potassium chloride. Soaked. The film soaked with the aqueous potassium iodide solution was dried for 9 minutes in a dryer at 70 ° C. to obtain a polarizing element. The obtained polarizing element was laminated on both sides with a triacetyl cellulose film (TD-80U, manufactured by Fuji Photo Film Co., Ltd., hereinafter abbreviated as TAC) as a protective film to obtain a polarizing plate.

Example 2
In Example 1, the polarizing plate of the present invention was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 1.5% by weight potassium iodide and 5.0% by weight potassium chloride. .

Example 3
In Example 1, the polarizing plate of the present invention was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 2.5% by weight potassium iodide and 3.0% by weight potassium chloride. .

Example 4
In Example 1, the polarizing plate of the present invention was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 2.5% by weight potassium iodide and 1.5% by weight potassium chloride. .

Example 5
In Example 1, the polarizing plate of the present invention was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 5.0% by weight potassium iodide and 5.0% by weight potassium chloride. .

Example 6
In Example 1, the polarizing plate of the present invention was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 5.0% by weight potassium iodide and 8.0% by weight potassium chloride. .

Example 7
In Example 1, the same applies except that the aqueous solution in which the stretched film is immersed is an aqueous solution containing 2.5% by weight of potassium iodide, 5.0% by weight of potassium chloride, and 1.0% by weight of lithium chloride. Thus, a polarizing plate of the present invention was obtained.

Example 8
In Example 1, the same applies except that the aqueous solution in which the stretched film is immersed is an aqueous solution containing 2.5% by weight of potassium iodide, 5.0% by weight of potassium chloride, and 5.0% by weight of lithium chloride. Thus, a polarizing plate of the present invention was obtained.

Example 9
95 parts by weight of pentaerythritol triacrylate (PET-30 manufactured by Nippon Kayaku Co., Ltd.) and 5 parts by weight of Irgacure 184 (manufactured by Ciba Specialty Chemicals) were stirred and mixed to obtain a polymerizable resin composition used in the present invention. This composition was diluted with methyl ethyl ketone (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution having a solid content concentration of 50% by weight. This solution was applied to the TAC surface using a spin coater, and the film thickness after removal of the solvent by heating was 3 μm. After the solvent was dried at 50 ° C. for 2 minutes, it was cured by irradiation with a high-pressure mercury lamp (integrated light amount 400 mJ / cm ² ) in air to obtain a layer in which the polymerizable resin composition of the present invention was cured. The surface of the layer was contacted with an alkaline aqueous solution of pH 11 for 10 minutes, and the contact angle with water on the surface of the layer was reduced from 80 ° to 52.5 °. The layer obtained by curing the polymerizable resin composition is bonded to a composition comprising 8 parts by weight of a polyvinyl alcohol-based resin (Nippon Gosei Co., Ltd. Gohsephimer Z200), 0.8 parts by weight of dialdehyde, and 100 parts by weight of water. The adhesive was used to adhere to the polarizing element used in Example 1, and the structure was a cured TAC / polymerizable resin composition / adhesive layer / polarizing element / adhesive layer / polymerizable resin composition. A polarizing plate to be a layer / TAC was obtained.

Example 10
Stir 55 parts by weight of pentaerythritol triacrylate (Nippon Kayaku Co., Ltd. PET-30), 40 parts by weight of dipentaerythritol hexaacrylate (DPHA manufactured by Nippon Kayaku Co., Ltd.), 5 parts by weight of Irgacure 184 (manufactured by Ciba Specialty Chemicals) By mixing, a polymerizable resin composition used in the present invention was obtained. This composition was diluted with methyl ethyl ketone (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution having a solid content concentration of 50% by weight. This solution was applied to the TAC surface using a spin coater, and the film thickness after removal of the solvent by heating was 3 μm. After the solvent was dried at 50 ° C. for 2 minutes, it was cured by irradiation with a high-pressure mercury lamp (integrated light amount 400 mJ / cm ² ) in air to obtain a layer in which the polymerizable resin composition of the present invention was cured. The surface of the layer was contacted with an alkaline aqueous solution of pH 11 for 10 minutes, and the contact angle with water on the surface of the layer was reduced from 80 ° to 55.1 °. The layer obtained by curing the polymerizable resin composition is bonded to a composition comprising 8 parts by weight of a polyvinyl alcohol-based resin (Nippon Gosei Co., Ltd. Gohsephimer Z200), 0.8 parts by weight of dialdehyde, and 100 parts by weight of water. The adhesive was used to adhere to the polarizing element used in Example 5, and the composition was TAC / polymerized resin composition cured layer / adhesive layer / polarizing element / adhesive layer / polymerizable resin composition cured. A polarizing plate to be a layer / TAC was obtained.

Example 11
70 parts by weight of pentaerythritol triacrylate (Nippon Kayaku Co., Ltd., PET-30), 25 parts by weight of dipentaerythritol monohydroxypentaacrylate (SR-399, manufactured by Sartomer), 5 parts by weight of Irgacure 184 (manufactured by Ciba Specialty Chemicals) Were mixed with stirring to obtain a polymerizable resin composition used in the present invention. This composition was diluted with methyl ethyl ketone (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution having a solid content concentration of 50% by weight. This solution was applied to the TAC surface using a spin coater, and the film thickness after removal of the solvent by heating was 3 μm. After the solvent was dried at 50 ° C. for 2 minutes, it was cured by irradiation with a high-pressure mercury lamp (integrated light amount 400 mJ / cm ² ) in air to obtain a layer in which the polymerizable resin composition of the present invention was cured. The surface of the layer was brought into contact with an alkaline aqueous solution of pH 11 for 10 minutes, and the contact angle with water on the surface of the layer was reduced from 80 ° to 51.7 °. The layer obtained by curing the polymerizable resin composition is bonded to a composition comprising 8 parts by weight of a polyvinyl alcohol-based resin (Nippon Gosei Co., Ltd. Gohsephimer Z200), 0.8 parts by weight of dialdehyde, and 100 parts by weight of water. The adhesive was used to adhere to the polarizing element used in Example 8, and the composition was TAC / polymerized resin composition cured layer / adhesive layer / polarizing element / adhesive layer / polymerizable resin composition cured. A polarizing plate to be a layer / TAC was obtained.

Comparative Example 1
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was changed to an aqueous solution containing 3.0% by weight of potassium chloride.

Comparative Example 2
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was changed to an aqueous solution containing 5.0% by weight of potassium chloride as in Japanese Patent No. 4355317.

Comparative Example 3
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 2.5% by weight of potassium iodide.

Comparative Example 4
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 5.0% by weight of potassium iodide.

Comparative Example 5
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was changed to an aqueous solution containing 3.0% by weight of lithium chloride.

Comparative Example 6
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 3.0% by weight of potassium bromide.

Comparative Example 7
In Example 1, a polarizing plate was prepared in the same manner except that the aqueous solution in which the stretched film was immersed was an aqueous solution containing 10 wt% potassium iodide and 5.0 wt% lithium chloride.

Comparative Example 8
Dipentaerythritol hexaacrylate (DPHA manufactured by Nippon Kayaku Co., Ltd.) 50 parts by weight, 30 parts by weight of pentaerythritol triacrylate (PET-30 manufactured by Nippon Kayaku Co., Ltd.), dicyclopentanyl acrylate (FA-513A manufactured by Hitachi Chemical Co., Ltd.) 20 Part by weight and 5 parts by weight of Irgacure 184 (manufactured by Ciba Specialty Chemicals) were mixed with stirring to obtain a polymerizable resin composition described in Examples 4 and 5 of Patent No. 4947699. This composition was diluted with methyl ethyl ketone (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution having a solid content concentration of 50% by weight. This solution was applied to the TAC surface using a spin coater, and the film thickness after removal of the solvent by heating was 3 μm. After the solvent was dried at 50 ° C. for 2 minutes, it was cured by irradiation with a high-pressure mercury lamp (integrated light amount 400 mJ / cm ² ) in air to obtain a layer in which the polymerizable resin composition of the present invention was cured. The surface of the layer was brought into contact with an alkaline aqueous solution of pH 11 for 10 minutes, and the contact angle with water on the surface of the layer was reduced from 80 ° to 57.2 °. The layer obtained by curing the polymerizable resin composition is bonded to a composition comprising 8 parts by weight of a polyvinyl alcohol-based resin (Nippon Gosei Co., Ltd. Gohsephimer Z200), 0.8 parts by weight of dialdehyde, and 100 parts by weight of water. In Example 1, a polarizing element made of an aqueous solution containing 5.0% by weight of lithium chloride was bonded to the aqueous solution in which the stretched film was immersed in Example 1, and the configuration was a TAC / polymerizable resin composition. A polarizing plate was obtained which was a layer obtained by curing the layer / adhesive layer / polarizing element / adhesive layer / layer obtained by curing the polymerizable resin composition / TAC.

  Table 2 shows potassium ions, iodine ions, chlorine ions, lithium ions, bromine ions, contained boric acid concentrations, and Ys0 contained in the polarizing plates in Examples 1 to 11 and Comparative Examples 1 to 8, and Ys0 is the initial value before the durability test. The transmittance, ρ0, indicates the initial polarization degree. Each ion of potassium, iodine, chlorine, lithium, and bromine was measured with a DX-320 manufactured by Dionex Corporation after the obtained polarizing element was precisely weighed and dissolved in water.

Next, Table 3 shows the measurement results of the transmittance and change in polarization degree after 1000 hours at 105 ° C. in the dry heat test in Examples 1 to 11 and Comparative Examples 1 to 8. In the table, Ys0 is the initial transmittance, ρ0 is the initial polarization degree, a * -c0 is the initial a * -c value, Ys1000 is the transmittance after 105 ° C. × 1000 hours, ρ1000 is the polarization degree after 105 ° C. × 1000 hours, a * -C1000 indicates a * -c after 105 ° C. × 1000. A higher a * -c value indicates red.

Next, Table 4 shows the measurement results of the wet heat test 65 ° C., the relative humidity 93%, the transmittance after 1000 hours, and the change in polarization degree in Examples 1 to 11 and Comparative Examples 1 to 8. In the table, Ys0 is the initial transmittance, ρ0 is the initial polarization degree, Ys-Wet is the transmittance after 65 ° C. × 93% RH × 1000 hours, ρ-Wet is the transmittance after 65 ° C. × 93% RH × 1000 hours, Δ Ys represents a change in transmittance after 65 ° C. × 93% RH × 1000 hours from the initial stage, and Δρ represents a change in polarization degree after 65 ° C. × 93% RH × 1000 hours from the initial stage. Moreover, the result of having confirmed the adhesiveness of each layer after 65 degreeC x 93% RH x1000 time progress is shown. As a result of adhesion, ◯ indicates that the mutual layers have good adhesion, and X indicates that there is an interlayer to be peeled off.

As is clear from the above Examples and Comparative Examples, the polarizing plate performance of the present invention is high, and for example, it is processed under the same conditions as in Japanese Patent No. 4355317 described in Comparative Example 2 (5.0% by weight of potassium chloride). It can be seen that the polarization performance is higher than that at the time. Further, from the experimental results in Table 2, the polarizing plate of the present application has a very high heat resistance, and a polarizing plate having a very high durability with a low transmittance, a low degree of polarization, and a small color change is obtained. Yes. From Comparative Example 3, Comparative Example 5 and Comparative Example 6, it can be seen that good results are not obtained if each ion is contained. Furthermore, from Table 3, the invention of the present application has high adhesion even after the durability test, and there is no problem in durability. Particularly in Examples 9 to 11, a polarizing plate having very high durability was obtained. As can be seen from comparison with the results of Comparative Example 5 and Comparative Example 8, when the contained ions in the polarizing element changed, It turns out that the adhesiveness of a polarizing element falls and durability also falls.

From the above results, the polarizing element comprising the oriented film of polyvinyl alcohol resin adsorbed with iodine according to the present invention, comprising 10 to 30 wt% boric acid, 10000 to 60000 ppm iodine ions, and 200 to 20000 ppm chlorine ions. A polarizing element characterized in that it has improved wet heat durability, for example, at 65 ° C. and a relative humidity of 93%, and suppressed changes in transmittance, decrease in polarization degree, and decrease in boric acid content. In addition, in a dry heat test, for example, at 105 ° C., it was proved that the polarizing plate can be a polarizing plate with little change in transmittance, little decrease in polarization degree, and little color change. In addition, it was shown that the polarizing plate has greatly improved wet heat durability and is good in a dry heat test. A display device using the polarizing element or polarizing plate of the present invention is a display device having high contrast and high durability.

Claims (10)

A polarizing element comprising a polyvinyl alcohol-based resin oriented film adsorbed with iodine, characterized by containing 10 to 30% by weight boric acid, 10,000 to 60,000 ppm iodine ions, and 200 to 20000 ppm chlorine ions. Polarizing element. The polarizing element according to claim 1, further comprising 4000 to 12000 ppm of potassium ions. The polarizing element according to claim 1, further comprising 300 to 3000 ppm of lithium ions. A polarizing plate comprising a polarizing element according to claim 1 and a protective film bonded to one or both sides. The protective film has at least one layer obtained by curing one or more kinds of polymerizable resin compositions, and the thickness of the layer is 0.1 μm to 10 μm. The polarizing plate as described. The polarizing plate according to claim 4, wherein the protective film is a cellulose acetate resin film. The polymerizable resin composition contains a (meth) acrylate compound in which the layer obtained by curing the polymerizable resin composition has at least one hydroxyl group in the molecule and at least one (meth) acryloyl group. The polarizing plate according to claim 5 or 6, comprising 30 to 99,5 parts by weight in 100 weights. The polarizing plate according to claim 5, wherein a layer obtained by curing the polymerizable resin composition is provided between the cellulose acetate resin film and the polarizing element. A display device using the polarizing element or polarizing plate according to claim 1. The method for producing a polarizing element according to claim 1, wherein a polyvinyl alcohol resin film is subjected to a dyeing treatment with iodine and a stretching treatment in a boric acid solution to obtain a stretched film, and then the stretched film is subjected to alkali treatment. The manufacturing method characterized by including the process of processing with the aqueous solution containing the chloride of a metal and / or alkaline-earth metal, and the iodide of an alkali metal and / or alkaline-earth metal.