TWI646359B - Polarizing element and polarizing plate having uniform transmission at each wavelength and method for manufacturing polarizing element - Google Patents

Abstract

The polarizing element of the present invention provides an iodine-based polarizing element and a polarizing light having a substantially constant transmittance at each wavelength transmittance when disposed in parallel with the absorption axis and disposed orthogonally to the absorption axis. board.

The present invention relates to a polarizing element which comprises a substrate comprising a hydrophilic polymer which adsorbs boric acid and which has a hydrophilic polymer which is extended and which has iodine, and which has a polarizing function, and the sensibility correction when the substrate is separately measured. The monomer transmittance Ys is 40.0% to 42.5%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is within 1%, and the visual sensitivity corrects the monomer transmittance Ys. The difference from the monomer transmittance Ts ₅₅₀ of 550 nm is within 1%, and the difference between the visual sensitivity correction monomer transmittance Ys and the monomer transmittance Ts ₆₁₀ of 610 nm is within 1%, so that two substrates are made. When the measurement is orthogonal to the absorption axis direction and the measurement is performed, the visual sensitivity correction orthogonal transmittance Yc is 0.01% or less.

Description

Polarizing element having uniform transmittance at each wavelength, polarizing plate, and manufacturing method of polarizing element

The present invention relates to a polarizing element having a uniform transmittance at each wavelength and a polarizing plate.

The polarizing element is generally produced by adsorbing and aligning iodine or a dichroic dye which is a dichroic dye on a polyvinyl alcohol resin film. A protective film containing triacetyl cellulose or the like is bonded to at least one surface of the polarizing element via a pressure-sensitive adhesive layer to form a polarizing plate, and is used in a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, and a polarizing plate using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Among these, the dye-based polarizing plate has characteristics of high heat resistance, high moist heat durability, high stability, and high selectivity of color obtained by blending, but on the other hand, it has the same polarized light. The iodine-based polarizing plate has a lower penetration rate, that is, a lower contrast. If the polarizing element hitherto is arranged in parallel with the absorption axis and white is displayed, the transmittance at 380 nm to 480 nm is lower than the transmittance at 500 nm to 600 nm, and the uniformity of luminescence at each wavelength cannot be maintained. Therefore, for example, when attempting to arrange the absorption axes of the polarizing elements in parallel, it is desirable to improve the transmittance of each wavelength to have a certain transmittance. However, in this case, there is also a problem that when it is disposed on the axis orthogonal to the absorption axis, The transmittance of the wavelength of 380 nm to 480 nm, especially the wavelength of 460 nm, is higher than the transmittance of 550 nm near the higher visual sensitivity, and the contrast is lowered. Therefore, as a polarizing element or a polarizing plate, the industry has sought a polarizing element or a polarizing plate which has high polarization performance, that is, has high contrast and can make the transmittance of each wavelength in the visible light range constant.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-49698

[Patent Document 2] Japanese Patent Laid-Open No. 2005-202367

[Non-Patent Document 1] Application of Functional Pigment First Printed Release, CMC (Shares) Publishing, Into Jiang Zhenghao, P98~100

A method of making the transmittance of the polarizing plate constant at each wavelength is disclosed, for example, in Patent Document 1 or Patent Document 2. Patent Document 1 discloses a technique of a polarizing element having a transmittance of 0.001% to 0.1% in the case of orthogonal polarization of 410 nm in a polarizing element having a film thickness of 8 to 18 μm. However, this technique only improves the fading or hue of the orthogonal bits without improving the wavelength transmittance of the parallel bits. Patent Document 2 discloses a technique of a polarizing element comprising a film having a structure in which a minute region is dispersed in a matrix formed of a water-soluble resin containing a divalent metal. However, this technique also does not obtain a polarizing element or a polarizing plate having a constant transmittance of each of the parallel and orthogonal bits.

The present inventors have diligently studied in order to solve the above problems, and as a result, have completed the present invention.

That is, the present invention relates to the following: "(1) A polarizing element comprising a substrate comprising a hydrophilic polymer which adsorbs boric acid and which is extended and which contains iodine, and which has a polarizing function, and is separately measured. In the case of the substrate, the visual sensitivity correction monomer transmittance Ys is 40.0% to 42.5%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is within 1%. The difference between the visual sensitivity correction monomer transmittance Ys and the 550 nm monomer transmittance Ts ₅₅₀ is within 1%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 610 nm monomer transmittance Ts ₆₁₀ is Within 1%, when the two substrates are orthogonal to the absorption axis direction and measured, the luminosity correction orthogonal transmittance Yc is 0.01% or less; (2) the polarizing element of the above (1), It is characterized in that the viewing sensitivity correction parallel penetration rate Yp is in the range of 33% to 37% when the two substrates are parallel to the absorption axis direction, and the parallel transmittance Yp and the two sheets are made. the difference with respect to the substrate of 460nm when the parallel transmittance Tp and the direction parallel to the absorption axis ₄₆₀ of the case of measuring in 3% (3) The polarizing element according to the above (1) or (2), wherein the photographic sensitivity correction parallel penetration rate Yp is 33 when the two substrates are parallel to each other with respect to the absorption axis direction. % to 37% of the range, so that the parallel transmittance Yp and the substrate 2 with respect to the transmittance Tp of 295nm when the absorption axis direction and parallel to the case of ₂₉₅ measurement satisfies the following formula (1), and the The parallel transmittance Yp and the transmittance Tp ₃₆₀ of 360 nm when the two substrates are parallel to the absorption axis direction and satisfy the following formula (2), 1.05 × Yp-26 ≦ Tp ₂₉₅ ≦ 1.05 ×Yp-13 type (1)

_{1.25 × Yp-26.25 ≦ Tp 360} ≦ 1.25 × Yp-16.25 of Formula (2); (4) above (1) to (3) in any of a polarizing element, wherein: the substrate opposite two sheets of When the absorption axis direction is orthogonal to the measurement, the transmittance ₂₉₅ nm of the substrate Tc ₂₉₅ satisfies the following formula (3), and the two substrates are orthogonal to the absorption axis direction and measured 360 nm. The penetration rate Tc ₃₆₀ satisfies the following formula (4), 2.0 × 10 ^-30 × Yp ^18.6 ≦ Tc ₂₉₅ ≦ 2.0 × 10 ^-30 × Yp ^19.4 (3)

^{4.0 × 10 -37 × Yp 22.12 ≦} Tc 360 ≦ 4.0 × 10 -37 × Yp 22.67 formula (4); (5) (1) to (4) of a polarizing element in, characterized in that: Increases When the two substrates are perpendicular to the absorption axis direction and measured, the transmittance ₄₆₀ nm of the 460 nm is 0.035% or less, and two substrates are orthogonal to the absorption axis direction and measured. when the transmittance of 610nm Tc ₆₁₀ is 0.01% or less; (6) the above (1) to (5) of a polarizing element in, characterized in that: the substrate comprises a polyvinyl alcohol resin film, and The polyvinyl alcohol-based resin film has a degree of polymerization of from 3,000 to 7,000. (7) A polarizing plate which is provided with a support film on at least one side of the polarizing element according to any one of the above (1) to (6) (8) A liquid crystal display device comprising the polarizing element according to any one of (1) to (6) above or the polarizing plate according to (7) above; (9) a method of manufacturing a polarizing element, characterized in that The invention relates to a method for producing a polarizing element comprising a substrate having a polarizing function of adsorbing boric acid and extending a hydrophilic polymer and containing iodine, and comprising: (i) agglomerating a step of obtaining a film containing a dichroic dye by containing a dichroic dye in the enol resin film; (ii) a step of stretching the film containing the dichroic dye to obtain an extended film; (iii) using a step of supplying the above-mentioned stretched film to a post-treatment by a chloride-containing solution or an iodide-containing solution; and (iv) a step of drying the film after the above-mentioned post-treatment to obtain the above-mentioned substrate; and the above-mentioned chloride-containing solution or The concentration of the iodide solution is 0.1 to 15% by weight".

The present invention relates to a polarizing element and a polarizing plate having a certain transmittance at each wavelength, and the polarizing element and the polarizing plate can be used as a display having a high transmittance, a high contrast ratio, and a very high color reproducibility. A polarizing plate, especially a polarizing plate for a liquid crystal display.

<polarized element>

The method for producing the polarizing element of the present invention includes, for example, a step of swelling a hydrophilic polymer film, followed by a dyeing step of containing a dichroic dye, and then performing a water resistance treatment step as necessary, and then It is produced through an extension step, a subsequent post-treatment step, and a final drying step.

The hydrophilic polymer film used for the polarizing element is, for example, a film containing a polyvinyl alcohol resin, an amylose resin, a starch resin, a cellulose resin, or a polyacrylate resin, and is used by casting. Such a film is formed into a film. Among these, a polyvinyl alcohol-based resin (hereinafter sometimes abbreviated as "PVA") film is preferred. In the present invention, a polarizing element comprising a polyvinyl alcohol-based resin film and a dichroic substance such as iodine is preferable. The thickness of the polarizing elements is not particularly limited, and is generally about 5 to 80 μm.

The method for producing the polyvinyl alcohol-based resin is not particularly limited, and it can be produced by a known method. For example, a polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin. Here, examples of the polyvinyl acetate-based resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polyvinyl alcohol-based resin may be further modified, for example, by using an aldehyde. Polyvinyl formal or polyvinyl acetal, and the like. A polyvinyl alcohol-based resin film can be used as a film formed of a polyvinyl alcohol-based resin.

In order to improve the optical characteristics of the present invention, the degree of polymerization of PVA needs to be 3,000 to 10,000. If the degree of polymerization of PVA is less than 3,000, it is difficult to exhibit high polarizing performance. When the degree of polymerization exceeds 7,000, the PVA becomes hard, the film formability or the elongation is lowered, and the productivity is lowered. Therefore, from the viewpoint of industrial properties, it is preferably 10,000 or less.

The degree of polymerization of PVA means the degree of polymerization (viscosity average degree of polymerization) measured in the following manner.

0.28 g of PVA was dissolved in 70 g of distilled water at 95 ° C to prepare a 0.4% aqueous PVA solution, which was cooled to 30 ° C. The sample for polymerization degree measurement was prepared by cooling in a constant temperature water tank of 30 °C. Then, 10 mL of the sample for polymerization degree measurement was dried in an evaporating dish for 20 hours by a dryer at 105 ° C, and the dry weight [α (g)] of the sample for polymerization degree measurement was measured. The concentration C (g/L) of the sample for measuring the degree of polymerization was calculated from the following formula (i).

C=1000×α/10...(i)

Further, the sample for polymerization degree measurement or distilled water was placed in an Oswald viscometer using a 10 mL full pipette, and was stabilized in a constant temperature water bath at 30 ° C for 15 minutes. The number of seconds t ₁ (seconds) of the sample for measurement of the degree of polymerization to be measured and the number of seconds t ₀ (seconds) of the distilled water were measured, and the viscosity average polymerization was calculated according to the following formulas (ii) to (iv). Degree E.

Ηt=t ₁ /t ₀ ( ₁ )

η=2.303×Log(ηt/c)...(iii)

Log(E)=1.613×Log([η]×104/8.29)...(iv)

The degree of saponification of PVA is preferably 99 mol% or more, more preferably 99.5 mol% or more. If the degree of saponification is less than 99 mol%, PVA is easily eluted, and the optical characteristics are not induced in-plane. In the mean, the dyeing property in the dyeing step is lowered, and the cutting in the stretching step is performed, and the productivity is remarkably lowered, which is not preferable.

The PVA used in the present invention can be produced by saponifying a polyvinyl ester-based polymer obtained by polymerizing a vinyl ester. Examples of the vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl neodecanoate, vinyl laurate, vinyl stearate, and vinyl benzoate. One or two or more kinds of these are selected from the above. Among these, vinyl acetate can be preferably used. The polymerization temperature is not particularly limited. When methanol is used as the polymerization solvent, since the boiling point of methanol is around 60 ° C, it is preferably about 60 ° C. The PVA is not limited to the saponified product of the homopolymer of vinyl ester as long as the effect of the present invention is not impaired. For example, graft copolymerization of an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, and an α-olefin having 2 to 30 carbon atoms to PVA may be carried out at a ratio of less than 5 mol%. The modified PVAI vinyl ester is copolymerized with an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, an α-olefin having 2 to 30 carbon atoms, and the like at a ratio of less than 15 mol%. A saponified product of a modified polyvinyl ester, a polyvinyl acetal polymer obtained by crosslinking one of the hydroxyl groups of PVA with an aldehyde such as formalin, butyraldehyde or benzaldehyde.

The film original film can be obtained by forming a film of PVA obtained in the above manner. Examples of the PVA film forming method include a method of melt-extruding aqueous PVA, and a casting film forming method, a wet film forming method (dissolving into a poor solvent), and a gel film forming method (PVA). The aqueous solution is temporarily cooled and gelled, and then the solvent is extracted and removed. The casting film forming method (the PVA aqueous solution is allowed to flow on the substrate and dried), and the combination methods thereof are not limited thereto.

Examples of the solvent used in the film formation include dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, and the like. Ethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, water, etc., but is not limited thereto. One type of the solvent may be used, or two or more types may be used in combination. The amount of the solvent used for film formation is, for example, 50 to 95% by mass, preferably 70 to 95. % by mass, but not limited to these ranges. However, when the amount of the solvent is less than 50% by mass, the viscosity of the film-forming stock solution becomes high, and filtration or defoaming at the time of preparation becomes difficult, and it is difficult to obtain a film original sheet which does not contain foreign matter and which is free from defects. Further, when the volatile fraction exceeds 95% by mass, the viscosity of the film forming solution becomes too low, and the control of the target thickness is difficult, and the influence of surface fluctuation caused by the wind during drying or the drying time becomes long, and production is performed. Reduced sex.

A plasticizer can also be used in the production of the original film. Examples of the plasticizer include glycerin, diglycerin, ethylene glycol, and the like, but are not limited thereto. The amount of the plasticizer to be used is not particularly limited, but is usually in the range of 5 to 15 parts by mass based on 100 parts by mass of the PVA.

Examples of the method for drying the film original film after film formation include, but are not limited to, drying by hot air, contact drying using a hot roll, or drying by an infrared heater. One of these methods may be used alone, or two or more of them may be combined and dried. The drying temperature is also not particularly limited, and is preferably in the range of 50 to 70 °C.

The film original film after drying is preferably subjected to heat treatment in order to control the degree of swelling to a specific range described below. The heat treatment method of the film original film after the film formation is, for example, a method using hot air or a method of bringing the film original sheet into contact with a heat roll, and is not particularly limited as long as it is a method which can be treated by heat. One of these methods may be used alone, or two or more of them may be combined. The heat treatment temperature and time are not particularly limited, but are preferably in the range of 110 to 140 ° C, and more preferably about 1 minute to 10 minutes, but are not particularly limited.

The thickness of the film original film thus obtained is preferably from 20 to 100 μm, more preferably from 20 to 80 μm, still more preferably from 20 to 60 μm. If the thickness is less than 20 μm, cracking of the film is liable to occur. When the thickness exceeds 100 μm, the stress applied to the film during stretching becomes large, and the mechanical load in the stretching step becomes large, and a large-scale apparatus for withstanding the load is required.

The degree of swelling F of the original film is preferably from 180 to 250%, more preferably from 205 to 235%, and still more preferably from 210 to 230%. If the degree of swelling F is less than 180%, the ductility at the time of stretching is small, and the possibility of cracking at a low rate becomes high, and it is difficult to sufficiently extend. Also, if it swells When the degree F exceeds 240%, the swelling becomes excessive, and wrinkles or slacks may occur, which may cause cutting during stretching. In order to control the degree of swelling F, for example, a degree of swelling F which is suitable for the temperature and time at which the film original film after film formation is heat-treated can be used.

The method for measuring the degree of swelling F of the original film is as follows.

The original film was cut into 5 cm × 5 cm, and immersed in 1 liter of distilled water at 30 ° C for 4 hours. The immersed film was taken out from the distilled water, and the water droplets on the surface were absorbed by sandwiching two sheets of filter paper, and then the weight [β(g)] of the film immersed in water was measured. Further, the film which was immersed and absorbed with water droplets was dried by a dryer at 105 ° C for 20 hours, and cooled by a drier for 30 minutes, and then the weight [γ (g)] of the film after drying was measured, and it was calculated from the formula (v). The degree of swelling of the original film of the film F.

Swelling degree F=100×β/γ(%)...Formula (v)

Using the original film produced in the above manner, the polarizing element of the present invention is produced by a method including the steps described below.

(swelling step)

First, the above-mentioned film original sheet is supplied to a swelling step of swelling the film.

In this step, swelling is performed by immersing the polyvinyl alcohol-based resin film in a solution of 20 to 50 ° C for 15 seconds to 10 minutes. The solution at this time is preferably water, and 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 swelling step, it is also preferred to appropriately extend in order to prevent generation of wrinkles or creases, and the stretching ratio is preferably from 1.00 to 1.50 times, more preferably from 1.10 to 1.35 times. In the case where the time for producing the polarizing element is shortened, since the swelling effect can be obtained in the dyeing step of the iodine, the iodide treatment, or the dye, the step can be omitted.

(staining step)

Then, the swollen polyvinyl alcohol-based resin film is subjected to a dyeing step of dyeing with a solution containing a dichroic dye.

The solvent as the solution is preferably water, but is not particularly limited. Examples of the dichroic dye include polyiodide ions obtained by a mixed solution of iodine and iodide, or dichroic dyes of an organic compound. As the iodide, for example, potassium iodide, ammonium iodide, cobalt iodide, zinc iodide or the like can be used, but it is not limited to the iodide exemplified herein. The iodine concentration in the mixed solution of iodine and iodide is 0.0001 to 0.5% by weight, preferably 0.001 to 0.4% by weight. The concentration of the iodide used is preferably 0.0001 to 8 wt%. For example, a dichroic dye such as the dichroic dye described in Non-Patent Document 1 may be used as the dichroic dye of the organic compound, and color correction may be performed within a range not impairing the performance required by the present application. The dye is not limited, and a known dichroic dye can be used. The dye concentration is not particularly limited and is, for example, about 0.006 wt% to 0.3 wt%. When the dyeability is insufficient, it is preferred to add a coloring aid such as sodium tripolyphosphate and/or sodium sulfate (sodium sulfate) for dyeing. Further, the dyeing temperature is 5 ° C to 50 ° C, preferably 5 to 40 ° C, more preferably 10 ° C to 30 ° C. The dyeing time can be appropriately adjusted depending on the transmittance of the polarizing element obtained, etc., and is about 30 seconds to 6 minutes, more preferably 1 minute to 5 minutes. In this step, it is also preferred to appropriately extend in order to prevent generation of wrinkles or creases. The stretching ratio is preferably from 0.90 to 2.00 times, more preferably from 1.00 to 1.30 times.

In the dyeing step, a crosslinking agent and/or a water resistance agent may be added to the solution containing the dichroic dye. As the crosslinking agent, for example, a boron compound such as boric acid, borax or ammonium borate, a polyvalent aldehyde such as glyoxal or glutaraldehyde, a polyisocyanate compound such as a biuret type, an isocyanurate type or a blocked type can be used. A titanium-based compound such as titanyl sulfate or the like may be used, and ethylene glycol glycidyl ether or polyamine-epichlorohydrin may be used. Examples of the water resistance agent include peroxysuccinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride, and the like, and boric acid is preferred. Regarding the added concentration, for example, in the case of adding boric acid, relative to the case containing dichroic dye The solution is 0.1 to 5.0% by weight, preferably 2 to 4% by weight. Further, the polyvinyl alcohol-based resin film containing the dichroic dye may be washed after the dyeing step and before proceeding to the next stretching step as needed. As the solvent to be washed, water is generally used, and an alcohol solvent, a glycol solvent, a mixed solvent of glycerin or the like can be used, and it is not particularly limited. Further, the temperature or time during the cleaning may be appropriately adjusted depending on the transmittance of the target polarizing element or the type of the dichroic dye to be used.

(Water resistance treatment step)

Then, after the dyeing step, a water-resistant treatment step for subjecting the dyed film to a water-resistant treatment as needed is provided.

In this step, the film is treated with a solution containing a crosslinking agent or/and a water resistance agent. Examples of the crosslinking agent or/and the water resistance agent include boron compounds such as boric acid, borax, and ammonium borate, polyvalent aldehydes such as glyoxal and glutaraldehyde, biuret type, isocyanurate type, and closed type. A polyisocyanate-based compound, a titanium-based compound such as titanyl sulfate, ethylene glycol glycidyl ether, polyamidamine epichlorohydrin, peroxysuccinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol Glycidyl ether, glycerol diglycidyl ether, ammonium chloride, magnesium chloride, etc., preferably boric acid. As the solvent in this case, for example, water, an alcohol solvent, a glycol solvent, a mixed solvent of glycerin or the like can be used. The concentration of the crosslinking agent or/and the water resistance agent, for example, in the case of an aqueous solution of boric acid, is preferably from about 0.1% by weight to about 6.0% by weight in the solution, more preferably from 2% by weight to 4% by weight. The treatment temperature in this step is from 5 ° C to 60 ° C, preferably from about 5 to 45 ° C. The treatment time is preferably from about 1 minute to about 5 minutes. In this step, it is also preferable to appropriately extend in order to prevent generation of wrinkles or creases, and the stretching ratio is about 0.95 to 1.5 times.

(extension step)

Further, it is supplied to an extending step of stretching the polyvinyl alcohol-based resin film.

In this step, the film is uniaxially stretched. As the stretching method, either a wet stretching method or a dry stretching method can be used.

Specific examples of the dry stretching method include, but are not limited to, an inter-roller region stretching method, a roll heating stretching method, a pressure stretching method, and an infrared heating stretching method. The temperature at the time of extension should be normal temperature ~ 180 ° C, and the humidity should be about 20 ~ 95% RH. The extension can be carried out in one stage, or can be extended in multiple stages of two stages.

The wet stretching method is a method of stretching in water, a water-soluble organic solvent, or a mixed aqueous solution thereof, and preferably is subjected to an extension treatment while being immersed in the following solution, and the solution is preferably the water or a water-soluble organic solvent. Or a mixed aqueous solution containing a boron compound such as boric acid, borax or ammonium borate; a polyvalent aldehyde such as glyoxal or glutaraldehyde; a polyisocyanate compound such as a biuret type, an isocyanurate type or a blocked type; Titanium compound such as titanium oxysulfate, ethylene glycol glycidyl ether, polyamine amine epichlorohydrin, peroxy succinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin condensate A crosslinking agent such as glyceryl ether, ammonium chloride or magnesium chloride or the like and/or a water resistance agent is more preferably extended in an aqueous boric acid solution. The concentration of the crosslinking agent or/and the water resistance agent is preferably from 0.5 to 8 wt%, preferably from 2.0 to 4.0 wt%. The stretching ratio is preferably from 3 to 8 times, more preferably from about 5 to 7 times. The extension temperature is preferably from 40 to 60 ° C, more preferably from 45 to 55 ° C. The extension time is preferably from 30 seconds to 20 minutes, more preferably from 2 minutes to 5 minutes. The extension processing may be one segment or a plurality of segments extending over two segments.

The foreign matter may be deposited or adhered to the surface of the stretched polyvinyl alcohol-based resin film containing the dichroic dye, and may be washed. As the solvent to be washed, water, an alcohol solvent or the like can be used, but it is not limited thereto. In the cleaning solvent, a crosslinking agent such as boric acid and/or a water resistance agent may be contained in order to improve the durability of the film. The concentration of the crosslinking agent and/or the water resistance agent is not limited and is, for example, 0.1 to 10% by weight.

(post-processing steps)

Next, in order to adjust the hue, improve the polarization characteristics, and improve the durability, a post-treatment process is performed on the film.

In this step, specifically, using a solution containing chloride or iodide A dichroic dye is used and treated by a uniaxially stretched polyvinyl alcohol resin film. Examples of the chloride or the iodide include iodide such as potassium iodide, sodium iodide, ammonium iodide, cobalt iodide, and zinc iodide; and chlorides such as zinc chloride, potassium chloride, and sodium chloride; One or more of them are mixed into a solution for treatment. The concentration of the chloride or iodide in the solution is preferably from 0.1 to 15% by weight, more preferably from 0.15 to 10% by weight. In this step, it is also preferred to appropriately extend the wrinkles or creases, and the stretching ratio is preferably 0.90 to 1.10 times. Further, the treatment temperature is, for example, preferably 5 to 50 ° C or lower, more preferably 20 to 40 ° C. The treatment time is, for example, about 1 second to 5 minutes, preferably 5 seconds to 30 seconds. In this step, the above crosslinking agent and/or water resistance agent may also be added. The added concentration is, for example, 0.5% to 10% by weight.

Examples of the solvent to be used in the treatment steps up to here include water, dimethyl hydrazine, N-methylpyrrolidone, methanol, ethanol, propanol, isopropanol, glycerin, ethylene glycol, and propylene glycol. An alcohol such as diethylene glycol, triethylene glycol, tetraethylene glycol or trimethylolpropane, or an amine such as ethylenediamine or diethylenetriamine, but is not limited thereto. Further, a mixture of one or more of these solvents may be used. The best solvent is water.

(drying step)

The substrate of the polarizing element of the present invention can be obtained by the drying step after the above post-treatment step.

Examples of the drying method include natural drying, compression by a roll, a method of removing surface moisture by an air knife or a water absorbing roll, drying by heating, and the like. The drying temperature in the case of heat drying is preferably 20 to 90 ° C, more preferably 40 to 70 ° C. The drying time is preferably from about 30 seconds to about 20 minutes, more preferably from about 2 minutes to about 10 minutes. In the drying step, it is also preferred to appropriately extend the wrinkles or streaks caused by shrinkage of the polyvinyl alcohol-based resin film accompanying drying, and the stretching ratio is preferably 0.95 to 1.10. Times.

The substrate of the polarizing element can be obtained by the above-described swelling step, dyeing step, any water resistance treatment step, extension step, post-treatment step, and drying step. Further, with respect to the substrate thus obtained, the apparent sensitivity correction monomer transmittance Ys at the time of individual measurement is 40.0% to 42.5%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 460 nm transmittance Ts ₄₆₀ is Within 1%, the difference between the visual sensitivity correction monomer transmittance Ys and the 550 nm transmittance Ts ₅₅₀ is within 1%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 610 nm transmittance Ts ₆₁₀ is 1%. The illuminance correction transmittance Yc obtained by measuring the two substrates perpendicular to the absorption axis direction and measuring them is adjusted to 0.01% or less.

In order to obtain a polarizing element having a substrate having the above characteristics, it is important to treat the film in a post-treatment step using a solution containing a chloride or iodide having an appropriate concentration. In this step, it is necessary to adjust the concentration of the chloride or iodide contained in the solution according to the extension conditions, and the treatment time thereof. It is very important to adjust the concentration and the treatment time in accordance with the state of impregnation of the polarizing element in the polarizing element such as iodine of the polarizing element, iodide such as potassium iodide, and chloride such as potassium chloride. In particular, the concentration is also affected by the extension state of the stretching step, the temperature or humidity of the place where the polarizing element is made, and the like, and therefore requires a fine adjustment. Usually, the concentration of the chloride-containing solution or the iodide-containing solution used in the post-treatment step is 1.0 parts by weight to 150 parts by weight, preferably 1.5 parts by weight to 100 parts by weight, based on 1000 parts by weight of water. Prepared by serving.

Further, it is preferred to carry out the treatment while maintaining the stretching magnification and/or the stretching tension of the film so as not to cause shrinkage or expansion of the film as much as possible. Further, it is preferable to carry out the treatment in a state where the difference between the transport speed of the film-free transport speed and the water flow speed of the post-treatment step is different, and it is more preferable to use the ultrasonic wave in the treatment liquid at this time and sufficiently perform the treatment until reaching The inside of the polarizing element. The post-processing step can be carried out by the above method to obtain the polarizing element of the present application.

As an index for adjusting the production of the polarizing element, the transmittance of the two substrates is parallel to the absorption axis direction, and the visual sensitivity correction parallel transmittance Yp is in the range of 33% to 37%. The difference between the Yp and the transmittance of 460 nm, Tp ₄₆₀ , when the two substrates were measured in parallel with respect to the absorption axis direction was within 3%. In order to set the difference between Yp and Tp ₄₆₀ to 3% or less, it is necessary to adjust the transmittance of 295 nm and the transmittance of 360 nm obtained by measuring two substrates in parallel with respect to the absorption axis direction. It is considered that the transmittance at 295 nm and the transmittance at 360 nm vary depending on the content of polyiodine such as I ₃ ^- or I ₅ ^- in the polarizing element. By adjusting the content of polyiodine such as I ₃ ^- , I ₅ ^- in the polarizing element, the transmittance of 295 nm and 360 nm can be adjusted, and the difference between Yp and Tp ₄₆₀ can be adjusted to within 3%.

In order to manufacture a more favorable polarizing element, it is necessary to adjust such that the two pieces of the substrate are parallel to each other with respect to the absorption axis direction and the visual sensitivity correction transmittance Yp is in the range of 33% to 37%. The transmittance Yp and the transmittance of Tp _{295 of 295} nm when the two substrates are parallel to the absorption axis direction are satisfied, and the above Yp is opposite to the two substrates. The transmittance Tp ₃₆₀ of 360 nm in the case where the absorption axis direction is parallel and measured is satisfying the following formula (2).

1.05×Yp-26≦Tp ₂₉₅ ≦1.05×Yp-13 (1)

1.25×Yp-26.25≦Tp ₃₆₀ ≦1.25×Yp-16.25 (2)

In order to further improve the performance of the polarizing element, in particular, to improve the performance of the polarizing element as 380 nm to 480 nm in the visible light range, it is necessary to improve the alignment of I ₃ ^- , I ₅ ^- and the like of 295 nm and 360 nm, and it is preferable to satisfy the above. In addition, when the two substrates are orthogonal to the absorption axis direction and are measured, the transmittance ₂₉₅ nm of the ₂₉₅ nm satisfies the following formula (3), and 2 The transmittance Tc ₃₆₀ of 360 nm when the substrate is orthogonal to the absorption axis direction and satisfies the following formula (4). Further, in the following formula, Yp ^18.6 , Yp ^19.4 , Yp ^22.12, and Yp ^22.67 represent the multipliers of the parallel transmittance Yp, respectively.

2.0×10 ^-30 ×Yp ^18.6 ≦Tc ₂₉₅ ≦2.0×10 ^-30 ×Yp ^19.4 (3)

4.0×10 ^-37 ×Yp ^22.12 ≦Tc ₃₆₀ ≦4.0×10 ^-37 ×Yp ^22.67 (4)

Furthermore, in recent years, in the LED backlight source, the phosphor is used to make the blue light of 460 nm emit white, so the transmittance at the center of 460 nm is to improve the contrast of the polarizing element. It is more important. In particular, when the transmittance of the polarizing element is high when two substrates are orthogonal to the absorption axis direction at 460 nm, the blue light leaks and the display does not exhibit pure black. Further, at this time, if the transmittance at 610 nm does not have a certain transmittance below the 460 nm, the same black color cannot be exhibited, and the contrast between white and black cannot be achieved. Therefore, the transmittance of the polarizing element is preferably such that the transmittance of 460 nm is 0.035% or less when the two substrates are orthogonal to the absorption axis direction, and the two substrates are opposed to the absorption. When the axial direction is orthogonal and measured, the transmittance at 610 nm is adjusted to 0.01% or less.

Furthermore, the present application can be easily achieved by using a film original film comprising a polyvinyl alcohol-based resin having a polyvinyl alcohol-based resin having a polymerization degree of 3,000 to 10,000 as a substrate of a polarizing element. More preferably, the degree of polymerization of the polyvinyl alcohol-based film is from 3,500 to 6,000, and further preferably from 4,500 to 6,000.

<Polarizing plate>

The polarizing plate of the present invention can be obtained by providing a transparent protective layer on at least one side or both sides of the polarizing element of the present invention obtained through the above steps. Specifically, the transparent protective layer can be provided by coating or laminating a polymer or film forming the protective layer onto the polarizing element of the present invention. As the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferred. Furthermore, it is more preferable that it is excellent in moisture barrier property. Examples of the substance used as the transparent protective layer include cellulose acetate resin such as triacetonitrile cellulose or diacetyl cellulose or a film thereof, acrylic resin or film thereof, polyester resin or film thereof. , polyarylate resin or its film, to lower a cyclic olefin such as a olefin as a monomer, a cyclic polyolefin resin or a film thereof, polyethylene, polypropylene, polyethylene terephthalate, ring system or having a drop The polyolefin of the olefin skeleton or a copolymer thereof, a main chain or a side chain thereof, a resin or a polymer of ruthenium or/or guanamine or a film thereof. Further, since it is known that a polyvinyl alcohol-based resin generally functions as an alignment film, a resin having liquid crystal properties may be provided on the surface of the obtained polarizing element by, for example, rubbing treatment, alignment film coating, alignment treatment, or the like. Or its membrane. The thickness of the protective film is, for example, about 0.5 to 200 μm. When the films are provided on both surfaces of the polarizing element, the same film may be used, or a different film may be used.

In the case where the film as the transparent protective layer is laminated with the polarizing element of the present invention, it is preferred to use an adhesive. Examples of the adhesive include polyvinyl alcohol-based, urethane-based, acrylic-based, and epoxy-based adhesives. Examples of the polyvinyl alcohol-based adhesive include, for example, Gosenol NH-26 (manufactured by Nippon Synthetic Co., Ltd.) and EXCEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), but are not limited thereto. A crosslinking agent and/or a water resistance agent may be added to the adhesive. Further, the inorganic acid or a salt thereof and/or an organic acid may be contained in the adhesive at a concentration of 0.0001% by weight to 20% by weight, preferably 0.02 to 5% by weight. It can be used as an adhesive agent in which a maleic anhydride-isobutylene copolymer is used alone or in combination with a crosslinking agent in a polyvinyl alcohol-based adhesive. Examples of the maleic anhydride-isobutylene copolymer include ISOBAM #18 (manufactured by Kuraray Co., Ltd.), ISOBAM #04 (manufactured by Kuraray Co., Ltd.), ammonia-modified ISOBAM #104 (manufactured by Kuraray Co., Ltd.), and ammonia-modified ISOBAM#. 110 (manufactured by Kuraray Co., Ltd.), yttrium imidized ISOBAM #304 (manufactured by Kuraray Co., Ltd.), yttrium imidized ISOBAM #310 (manufactured by Kuraray Co., Ltd.), and the like. For the crosslinking agent at this time, a water-soluble polyvalent epoxy compound can be used. Examples of the water-soluble polyvalent epoxy compound include DENACOL EX-521 (manufactured by Nagase ChemteX Co., Ltd.), Tetrad C (manufactured by Mitsui Gas Chemical Co., Ltd.), and the like. Further, the buffer or the inorganic acid or a salt thereof and/or an organic acid, a zinc compound, a chloride or an iodide, or the like, more preferably the buffer is contained at a concentration of about 0.01 to 10% by weight based on the amount of the adhesive component. The addition of an inorganic acid or a salt thereof and/or an organic acid as an adhesive can similarly improve durability. The film as a transparent protective layer is bonded to the polarizing element of the present invention by the above-mentioned adhesive, and then dried by heating and further heat-treated.

When the obtained polarizing plate is bonded to a display device such as a liquid crystal display or used in a polarizing filter or a polarizing lens, it may become a non-exposed surface later.

The surface of the protective layer or film is provided with various functional layers for improving the viewing angle and/or improving contrast, and a layer or film having brightness enhancement. It is preferred to use an adhesive when bonding the polarizing plate to the film or display device.

The polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface, that is, the exposed surface of the protective layer or the film. When the layer having various functionalities is produced, it is preferably provided on the other surface by a coating method, and a film having the function may be bonded via an adhesive or an adhesive. Further, the various functional layers may be layers or films that control the phase difference.

According to the method described above, a polarizing element or a polarizing plate having a certain transmittance at each wavelength can be obtained. The polarizing element or the polarizing plate of the present invention thus obtained has high polarizing performance, that is, has high contrast, and can achieve a certain transmittance of each wavelength in the visible light range, and is excellent in durability, so that stable performance can be maintained for a long period of time. .

<Liquid crystal display device>

Further, 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 electroluminescence display device, a CRT (cathode-ray tube) or the like. In particular, the liquid crystal display device can be obtained by bonding the polarizing plate of the present invention to the both sides of the liquid crystal cell constituting the liquid crystal display as needed by using an adhesive.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited thereto.

The evaluation of the transmittance shown in each of the examples was carried out in the following manner.

When the transmittance of each wavelength when measuring one polarizing element or a polarizing plate is the monomer transmittance Ts, the two polarizing elements or the polarizing plates are overlapped in such a manner that the absorption axis directions are the same. The transmittance is set to the parallel transmittance Tp, and the transmittance of each wavelength when the two polarizing plates are overlapped so that the absorption axes thereof are orthogonal to each other is defined as the orthogonal transmittance Tc.

The spectral transmittances Ts, Tp, and Tc were measured using a spectrophotometer ["U-4100" manufactured by Hitachi, Ltd.], respectively.

The sensitometric correction monomer transmittance Ys is calculated based on the monomer transmittance Ts measured at a specific wavelength interval dλ (here, 5 nm) in a wavelength region of 400 to 700 nm, and is calculated according to the following formula (5). . In the formula, Pλ represents the spectral distribution of the standard light (C light source), and yλ represents the color matching function based on JIS Z 8729 (C light source 2° field of view).

The visual sensitivity correction parallel transmittance Yp is calculated from the parallel transmittance Tp measured at a specific wavelength interval dλ (here, 5 nm) in a wavelength region of 400 to 700 nm, and is calculated according to the following formula (6). In the formula, Pλ represents the spectral distribution of the standard light (C light source), and yλ represents the color matching function based on JIS Z 8729 (C light source 2° field of view).

The diopter-corrected orthogonal transmittance Yc is calculated based on the orthogonal transmittance Tc measured at a specific wavelength interval dλ (here, 5 nm) in a wavelength region of 400 to 700 nm, and is calculated according to the following formula (7). . In the formula, Pλ represents the spectral distribution of the standard light (C light source), and yλ represents the color matching function based on JIS Z 8729 (C light source 2° field of view).

The degree of polarization Py is obtained by correcting the parallel transmittance Yp and the opacity correction orthogonal transmittance Yc according to the sensibility and according to the following formula (8).

Py=100×{(Yp-Yc)/(Yp+Yc)} ^1/2 (8)

Example 1

A polyvinyl alcohol-based film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 μm, a polymerization degree of 5,500, and a saponification degree of 99% or more was swollen in warm water of 40 ° C, and then boric acid (Societa Chimica Larderello) was contained in an amount of 1000 parts by weight of water. 28.6 parts by weight, 0.25 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 17.7 parts by weight of potassium iodide (manufactured by Junsei Chemical Co., Ltd.) were immersed at 30 ° C for 2 minutes to carry out dyeing treatment. The dyed film was extended 5 times at 58 ° C in a solution containing 3 wt % of boric acid, and after extension, an aqueous solution containing 3.5 parts by weight of potassium iodide was added to 1000 parts by weight of water to maintain an extension. After the tension is maintained and the stretching ratio is maintained, the ultrasonic wave of 20 to 40 kHz is immersed while being subjected to the post-processing step 20 while the difference between the conveying speed of the film processing and the relative speed of the water flow rate of the processing step is substantially constant. second. The film was immersed in an aqueous solution of potassium iodide for 20 seconds, and then dried by a dryer at 70 ° C for 10 minutes to obtain a polarizing element.

Example 2

A polyvinyl alcohol film (VF-PH manufactured by Kuraray Co., Ltd.) having a thickness of 40 μm, a polymerization degree of 4000, and a saponification degree of 99% or more is used instead of a polyvinyl alcohol film having a thickness of 60 μm, a polymerization degree of 4000, and a saponification degree of 99% or more (Kuraray Co., Ltd.) A polarizing element was obtained in the same manner as in Example 1 except for the manufactured VF-PM.

Example 3

The same as in the second embodiment except that the time of the dyeing treatment was set to 1 minute and 30 seconds. In this way, a polarizing element is obtained.

Example 4

A polarizing element was obtained in the same manner as in Example 1 except that the time of the dyeing treatment was changed to 1 minute and 30 seconds.

Comparative example 1

After the extension, the aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water was stirred at a rate of 60 rpm, and the post-treatment step was carried out for 20 seconds while maintaining the magnification after stretching, and the same was carried out. Example 1 obtained a polarizing element in the same manner.

Comparative example 2

After the extension, the aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water was stirred at a rate of 60 rpm, and the post-treatment step was carried out for 20 seconds while maintaining the magnification after stretching, and the same was carried out. Example 2 obtained a polarizing element in the same manner.

Comparative example 3

After the extension, the aqueous solution prepared by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water was stirred at a rate of 60 rpm, and the post-treatment step was carried out for 20 seconds while maintaining the magnification after stretching, and the same was carried out. Example 3 obtained a polarizing element in the same manner.

Comparative example 4

After the extension, the aqueous solution prepared by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water was stirred at a rate of 60 rpm, and the post-treatment step was carried out for 20 seconds while maintaining the magnification after stretching, and the same was carried out. Example 4 obtained a polarizing element in the same manner.

Comparative Example 5

Immersion of iodine-based polarizing plate SKN-18242P manufactured by Polatechno in methylene chloride In the middle, the polarizing element was taken out and set as a comparative sample.

Comparative Example 6

After the stretching, the polarizing element was obtained in the same manner as in Example 1 except that the film was immersed in water for 20 seconds, and it was set as a comparative sample.

The parameters of the polarizing elements obtained in Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 1. The parameters shown in Table 1 are as follows.

The sensibility correction monomer transmittance Ys, the visual sensitivity correction parallel transmittance Yp, the visual sensitivity correction orthogonal transmittance Yc, the monomer transmittance Ts _{460 of 460} nm, and the two substrates are parallel with respect to the absorption axis direction In the case of the measurement, the parallel transmittance Tp ₄₆₀ of 460 nm and the orthogonal transmittance of Tc ₄₆₀ and 550 nm of ₄₆₀ nm when the two substrates are orthogonal to the absorption axis direction are measured. The transmittance Ts ₅₅₀ , the monomer transmittance Ts ₆₁₀ of 610 nm, the orthogonal transmittance Tc ₆₁₀ of 610 nm when the two substrates are orthogonal to the absorption axis direction, and the two substrates are relatively The parallel transmittance Tp _{295 of 295} nm when the absorption axis direction is parallel and measured, and the orthogonal transmittance Tc _{295 of 295} nm when the two substrates are orthogonal to the absorption axis direction, Orthogonality of 360 nm when the two substrates are measured in parallel with the direction of the absorption axis, and the parallel transmittance Tp ₃₆₀ of 360 nm when the two substrates are orthogonal to the absorption axis direction are measured. Penetration rate Tc ₃₆₀ .

From the above results, it is found that the polarizing elements of Examples 1 to 4 are polarizing elements having a substantially constant transmittance at each wavelength, and the apparent sensitivity monomer transmittance Ys when measured alone is 40.0% to 42.5%, depending on the result, The difference between the sensitivity correction monomer transmittance Ys and the 460 nm transmittance Ts ₄₆₀ is within 1%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 550 nm transmittance Ts ₅₅₀ is within 1%, and the visual sensitivity is corrected. The difference between the monomer transmittance Ys and the transmittance ₆₁₀ nm of Ts ₆₁₀ is 1% or less, and the sensitivities of the two substrates are orthogonal to the absorption axis direction and measured to obtain a sensitometric correction monomer transmittance Yc. 0.01% or less.

Further, a polarizing plate can be obtained by laminating a polarizing element with a protective layer, and the polarizing elements of Embodiments 1 to 4 can be penetrated at a wavelength of 380 nm to 480 nm and penetrated from 500 nm to 650 nm when disposed in parallel with the absorption axis. The rate is successfully maintained at each wavelength of light uniformity compared to a substantially constant optical characteristic. Further, it is also known that the orthogonal transmittance Yc is 0.01% or less in accordance with the sensibility, and the polarizing elements have a high contrast ratio and can make the transmittance of each wavelength in the visible light range constant.

Therefore, the polarizing elements of Examples 1 to 4 obtained by the above method or the polarizing plates produced by using the polarizing elements can be used for higher transmittance, higher contrast ratio, and color reproduction. A polarizing plate for a display which is very high in appearance, especially a polarizing plate for a liquid crystal display. Further, a display using the same can be expected to be a display which is highly reliable, can maintain a high contrast for a long period of time, and has high color reproducibility.

Claims (9)

A polarizing element comprising: a substrate comprising a substrate having a polarizing function of adsorbing boric acid and extending a hydrophilic polymer and containing iodine, and a sensibility correction sheet when the substrate is measured by a monomer; The body penetration rate Ys is 40.0% to 42.5%, and the difference between the visual sensitivity correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is within 1%, and the visual sensitivity corrects the monomer transmittance Ys and The difference of the monomer transmittance Ts ₅₅₀ of 550 nm is within 1%, and the difference between the visual sensitivity correction monomer transmittance Ys and the monomer transmittance Ts ₆₁₀ of 610 nm is within 1%, so that two substrates are relatively When the absorption axis direction is orthogonal and measured, the visual sensitivity correction orthogonal transmittance Yc is 0.01% or less. The polarizing element of claim 1, wherein the photographic sensitivity-correcting parallel transmittance Yp% is in a range of 33% to 37% when the two substrates are parallel with respect to the absorption axis direction, and the parallel penetration is The difference between the rate Yp and the parallel transmittance Tp ₄₆₀ of 460 nm when the two substrates were measured in parallel with respect to the absorption axis direction was within 3%. The polarizing element according to claim 1 or 2, wherein the photographic sensitivity correction parallel transmittance Yp% is in a range of 33% to 37% when the two substrates are parallel with respect to the absorption axis direction, and the parallel The transmittance Yp and the transmittance Tp _{295 of 295} nm when the two substrates are parallel to the absorption axis direction and satisfy the following formula (1), and the parallel transmittance Yp and the two sheets are made. The transmittance Tp ₃₆₀ of 360 nm when the substrate is parallel to the direction of the absorption axis and satisfies the following formula (2), 1.05 × Yp-26 ≦ Tp ₂₉₅ ≦ 1.05 × Yp-13 Formula (1) 1.25 ×Yp-26.25≦Tp ₃₆₀ ≦1.25×Yp-16.25 Equation (2). The polarizing element of claim 1 or 2, wherein the transmittance of ₂₉₅ nm when the two substrates are orthogonal to the absorption axis direction and is measured satisfies the following formula (3), and two sheets are obtained. The transmittance Tc ₃₆₀ of 360 nm when the substrate is orthogonal to the absorption axis direction satisfies the following formula (4), 2.0 × 10 ^-30 × Yp ^18.6 ≦ Tc ₂₉₅ ≦ 2.0 × 10 ^-30 × Yp ^19.4 Formula (3) 4.0×10 ^-37 ×Yp ^22.12 ≦Tc ₃₆₀ ≦4.0×10 ^-37 ×Yp ^22.67 (4). The polarizing element requested item 1 or 2, in which the substrate 2 with respect to the transmittance of 460nm when the absorption axis direction and the orthogonal case of Tc ₄₆₀ measured 0.035%, and two sheets of the substrate When the measurement is orthogonal to the absorption axis direction and the measurement is performed, the transmittance ₆₁₀ nm of 610 nm is 0.01% or less. The polarizing element according to claim 1 or 2, wherein the substrate comprises a polyvinyl alcohol-based resin film having a degree of polymerization of from 3,000 to 7,000. A polarizing plate obtained by providing a support film on at least one side of a polarizing element according to any one of claims 1 to 6. A liquid crystal display device comprising the polarizing element according to any one of claims 1 to 6 or the polarizing plate of claim 7. A method for producing a polarizing element, comprising: a method for producing a polarizing element comprising a substrate having a polarizing function of adsorbing boric acid and extending a hydrophilic polymer and containing iodine, and comprising: (i) agglomerating a step of obtaining a film containing a dichroic dye by containing a dichroic dye in the vinyl alcohol resin film; (ii) a step of extending the film containing the dichroic dye to obtain an extended film; (iii) supplying the above-mentioned stretched film to a step of treating with a chloride-containing solution or an iodide-containing solution; (iv) a step of drying the film to obtain the above substrate after the post-treatment described above; and the concentration of the chloride-containing solution or the iodide-containing solution is 0.1 to 15% by weight.