TWI635327B - Polarizing element and polarizing plate having uniform transmission at each wavelength and having high contrast - Google Patents

Abstract

The polarizing element of the present invention provides a polarizing element having a substantially constant transmittance at each wavelength transmittance when disposed in parallel with the absorption axis and disposed orthogonally to the absorption axis, and having a high contrast ratio. And polarizing plates.

The present invention relates to a polarizing element which comprises a substrate comprising a hydrophilic polymer which adsorbs boric acid and which is extended and which has a polarizing function, and which contains a formula (1) in the form of a free acid:

(In the formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, or a carboxyl group, and k, m, and n each represent 0 or 1; wherein m+n≧1) The organic compound or a salt thereof, when the substrate is separately measured, has a luminosity corrected unit transmittance Ys of 40.0% to 42.5%, and the visibility correction monomer transmittance Ys and 460 nm of the monomer are worn. The difference between the transmittance Ts ₄₆₀ is less than 1.2%, and the difference between the visibility correction monomer transmittance Ys and the 550 nm monomer transmittance Ts ₅₅₀ is within 1%, and the visibility correction monomer transmittance Ys and the 610 nm monomer are worn. When the difference between the transmittance Ts ₆₁₀ is 1% or less, and the two substrates are orthogonal to the absorption axis direction and measured, the visibility correction orthogonal transmittance is 0.01% or less, and the two substrates are absorbed. When the axial direction is orthogonal and measured, the average value of the orthogonal transmittances of 430 nm to 480 nm Tc Ave 430-480 is 0.03% or less.

Description

High contrast polarizing element and polarizing plate having uniform transmittance at each wavelength

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

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 the transmittance of the wavelength of 380 nm to 480 nm, especially the wavelength of 460 nm is higher than the visibility when disposed on the axis orthogonal to the absorption axis. The penetration rate is higher near 550 nm, 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 Pigments First Printed Release, CMC (Shares)

Published), inspected by 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 410 nm orthogonal bit, and does not improve the transmittance of each wavelength of the parallel bit. Moreover, in the liquid crystal display device in which the LED light source is set as the backlight in recent years, there is almost no 410 nm light emission. The blue luminescence is mainly the luminescence source of 430 nm to 480 nm with 460 nm as the bright line, so that there is almost no comparison of 410 nm. Therefore, in order to improve the contrast, it is necessary to improve the contrast of wavelengths of 430 to 480 nm. The color tone of the parallel position is not improved in the formulation of Patent Document 1, and the contrast cannot be sufficiently obtained when used for a display device when a backlight such as an LED light source is used. 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 free The acid form contains the organic compound represented by the formula (1) or a salt thereof:

(In the formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, or a carboxyl group, and k, m, and n each represent 0 or 1; wherein m+n≧1) is separately determined. In the case of the substrate, the luminosity corrected unit transmittance Ys is 40.0% to 42.5%, and the difference between the visibility correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is 1.2%. The difference between the visibility correction monomer transmittance Ys and the 550 nm monomer transmittance Ts ₅₅₀ is within 1%, and the difference between the visibility correction monomer transmittance Ys and the 610 nm monomer transmittance Ts ₆₁₀ is 1%. In the case where two substrates are perpendicular to the absorption axis direction and measured, the visibility correction orthogonal transmittance is 0.01% or less, and two substrates are orthogonal to the absorption axis direction and measured. The average value of the orthogonal transmittance of 430 nm to 480 nm is 0.02 MPa or less. The polarizing element of the above (1) is characterized in that two of the substrates are parallel to the absorption axis direction. And in the case of performing the measurement, the visibility correction parallel transmittance Yp is in the range of 33% to 37%, and the parallel transmittance Yp of the substrate is 2 The substrate and the time of the 255nm absorption axis direction and parallel to the case of measuring the transmittance Tp ₂₅₅ satisfies the following formula (2): 0.75 × Yp- 13 ≦ Tp 255 ≦ 0.75 × Yp + 1.0 (2); ( (3) The polarizing element according to (1) or (2) above, wherein the visibility correction parallel transmittance Yp is 33% to 37% when two substrates are parallel to the absorption axis direction and measured. In the range of the parallel transmittance Yp and the case where the two substrates are orthogonal to the absorption axis direction and measured, the transmittance ₂₅₅ nm of ₂₅₅ nm satisfies the following formula (3): 2.0 × 10 ^-6 × Yp ^4.1 ≦Tc ₂₅₅ ≦2.0×10 ^-6 ×Yp ^4.4 (3), (4) The polarizing element according to any one of the above (1) to (3), characterized in that: When the absorption axis direction is parallel and the measurement is performed, the visibility correction parallel transmittance Yp is in the range of 33% to 37%, and the parallel transmittance Yp is measured in parallel with the two substrates and the absorption axis direction. the parallel transmittance Tp 460nm when the difference is within 3% of _460; (5) above (1) to (4) of a polarizing element in, characterized in that: the substrate 2 so that the absorption axis Parallel direction In the case of the measurement, the visibility correction transmittance Yp is in the range of 33% to 37%, and the parallel transmittance Yp is a transmittance of 295 nm when the two substrates are parallel to the absorption axis direction and measured. Tp ₂₉₅ satisfies the following formula (4), and 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 (5) , 1.05 × Yp-26 ≦ Tp ₂₉₅ ≦ 1.05 × Yp-13 Formula (4) 1.25 × Yp-26.25 ≦ Tp ₃₆₀ ≦ 1.25 × Yp-16.25 Equation (5); (6) As above (1) to (5) The polarizing element according to any one of the preceding claims, wherein the transmittance of ₂₉₅ nm when the two substrates are orthogonal to the absorption axis direction and the measurement is performed, the transmittance Tc _{295 of 295} nm satisfies the formula (6), and two sheets of the substrate are provided. When the material is parallel to the direction of the absorption axis and is measured, the transmittance Tc ₃₆₀ of 360 nm satisfies the formula (7), 2.0 × 10 ^-30 × Yp ^18.6 ≦ Tc ₂₉₅ ≦ 2.0 × 10 ^-30 × Yp ^19.4 (6)

^{4.0 × 10 -37 × Yp 22.12 ≦} Tc 360 ≦ 4.0 × 10 -37 × Yp 22.67 formula (7); (7) the above (1) to (6) 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. transmittance Tc ₆₁₀ 610nm of 0.01% or less; (8) as described in (1) to (7) of a polarizing element in, characterized in that: the substrate comprises a polyvinyl alcohol resin film, and the poly The vinyl alcohol-based resin film has a degree of polymerization of from 3,000 to 7,000. (9) A polarizing plate obtained by providing a support film on at least one side of the polarizing element according to any one of the above (1) to (8); (10) A liquid crystal display device comprising the polarizing element according to any one of (1) to (8) above or the polarizing plate according to (9) above; (11) a method of manufacturing a polarizing element, characterized in that: The present invention comprises 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) making polyvinyl alcohol a step of obtaining a film containing a dichroic dye in a resin film; (ii) a step of stretching the film containing the dichroic dye to obtain an extended film; (iii) using chlorine a step of treating the above-mentioned stretched film to a post-treatment; and (iv) a step of drying the film after the above-mentioned post-treatment to obtain the substrate; and the above-mentioned chloride-containing solution or iodide-containing compound The concentration of the solution is 0.1 to 15% by weight, and further includes the step of causing the polarizing element to contain the organic compound of the following formula (1):

The present invention relates to a polarizing element and a polarizing plate which have a certain transmittance at each wavelength and have a high contrast, and the polarizing element and the polarizing plate can be used as a high transmittance, a high contrast ratio, and a color reproduction. A polarizing plate for a display having a very high performance, in particular, a polarizing plate for a liquid crystal display. The display using the display becomes a display with high reliability, long-term high contrast, and high color reproducibility.

<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. In these Among them, 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 containing a polyvinyl alcohol-based resin 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, and for example, polyvinyl formal or polyvinyl acetal modified by an aldehyde may be used. Further, the degree of polymerization of the polyvinyl alcohol-based resin is usually preferably from 1,000 to 10,000, more preferably from 1,500 to 6,000. A polyvinyl alcohol-based resin film can be used as a film formed of a polyvinyl alcohol-based resin.

In order to enhance the optical characteristics of the present invention, the degree of polymerization of the PVA needs to be from 1,000 to 10,000, more preferably 3,000 or more. If the degree of polymerization of PVA is less than 2,000, 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. When the degree of saponification is less than 99 mol%, the PVA is easily eluted, the in-plane unevenness of the optical characteristics is induced, the dyeability in the dyeing step is lowered, and the cutting in the stretching step is caused, and the productivity is remarkably lowered. It is not good.

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, it is also possible to graft copolymerize 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 with PVA 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%. Saponified product of modified polyvinyl ester A polyvinyl acetal polymer obtained by crosslinking an aldehyde such as formin, butyraldehyde or benzaldehyde to a part of a hydroxyl group of PVA.

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 is 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. As a heat treatment method of the film original film after film formation, for example, The method of using hot air or the method of bringing the original film of the film into contact with the heat roller is not particularly limited as long as it is 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. Moreover, when the swelling degree F exceeds 240%, the swelling becomes excessive, wrinkles or slacks occur, and it becomes a cause of cutting at the time of extension. 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, by including the steps described below The polarizing element of the present invention is produced by the method.

(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%. In order to correct the color, for example, a dichroic dye such as the non-patent document 1 described above 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 to 50 ° C, preferably 5 to 40 ° C, more preferably 10 to 30 ° C. dye The color 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. The concentration to be added is, for example, 0.1 to 5.0% by weight, preferably 2% by weight to 4% by weight based on the solution containing the dichroic dye when the boric acid is added. 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, polyamido-epichlorohydrin, peroxysuccinic acid, ammonium persulfate, perchloric acid Calcium, benzoin ethyl ether, ethylene glycol diglycidyl 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-resistant agent, for example, in the case of an aqueous solution of boric acid, is preferably from about 0.1 to 6.0% by weight, more preferably from 2 to 4% by weight, based on the solution. The treatment temperature in this step is 5 to 60 ° C, preferably 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%, more preferably from 2.0 to 4.0 wt%. The stretching ratio is preferably 3 to 8 times, more preferably 5 to 7 times. about. The extension temperature is preferably from 40 ° C 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, a uniaxially stretched polyvinyl alcohol-based resin film containing a dichroic dye is treated with a solution containing a chloride or an iodide. 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 ° C to 50 ° C or less, 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. Also 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 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, arbitrary water resistance treatment step, stretching step, post-treatment step, and drying step. Further, the substrate obtained in this manner contains a polarizing function containing iodine which adsorbs boric acid and is extended, and contains an organic compound represented by the following formula (1) or a salt thereof in the form of a free acid. The visibility correction monomer transmittance Ys is 40.0% to 42.5% when measured separately, and the difference between the visibility correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is 1.2% or less, and the visibility correction monomer is worn. The difference between the transmittance Ys and the monomer transmittance Ts ₅₅₀ of 550 nm is within 1%, and the difference between the visibility correction monomer transmittance Ys and the monomer transmittance Ts ₆₁₀ of 610 nm is within 1%, so that the two sheets are made. The visibility correction orthogonal transmittance Yc obtained by measuring the material perpendicular to the direction of the absorption axis is 0.01% or less, and the two substrates are orthogonal to the absorption axis direction and measured to obtain a positive value of 430 nm to 480 nm. The average value of the cross-penetration rate is adjusted to be 0.03% or less.

(In the formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, or a carboxyl group, and k, m, and n each represent 0 or 1; wherein m+n≧1)

In order to obtain a polarizing element having a substrate having the above characteristics, it is necessary to contain the organic compound of the formula (1). Further, as a method of containing the organic compound, the substrate may be in a solution containing an organic compound in any one of a dyeing step containing a dichroic dye, any of a water resistance treatment step, an extension step, and a post-treatment step. The impregnation treatment is carried out, and it is preferably a method in which the steps of swelling the polyvinyl alcohol-based resin film and dyeing the iodine and the iodine compound are carried out, and the method of providing the step and the dyeing step containing the dichroic dye are preferred. At the same time, the method of containing it, the method of setting the step after the iodine is dyed and before the extension, and the method of simultaneously containing it in the post-treatment step. Furthermore, it is more preferable to provide a method of providing a step in which the polyvinyl alcohol-based resin film is swollen and the step of iodine and iodine compound is dyed.

Specific examples of the dye represented by the formula (1) include C.I. Direct Yellow 28 and C.I. Direct Yellow 29. The concentration of the organic compound of the formula (1) is not particularly limited. For example, it is preferably from 0.05 part by weight to 3 parts by weight based on 1000 parts by weight of water. When the dyeability is insufficient, it is preferred to add sodium tripolyphosphate. And / or coloring aids such as sodium sulfate (sodium sulfate) for dyeing. Further, the dyeing temperature is 5 to 50 ° C, preferably 5 to 40 ° C, more preferably 10 to 30 ° C. The dyeing time can be appropriately adjusted depending on the transmittance of the polarizing element obtained, etc., and is, for example, about 30 seconds to 6 minutes, preferably 1 to 5 minutes.

Next, a more specific example of the dye represented by the formula (1) will be described below in the form of a free acid.

[Compound Example 1]

Further, it is important to treat the uniaxially stretched polyvinyl alcohol-based resin film containing a dichroic dye in a post-treatment step using a solution containing a chloride or an 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 extended by the steps The extension state, the temperature or humidity of the place where the polarizing element is made, etc., require very 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 in portions.

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.

The index for adjustment at the time of manufacture in order to have better performance as a polarizing element is the transmittance at 255 nm of the ultraviolet region. The reason for this is that since the organic compound represented by the formula (1) absorbs at 255 nm, when the compound is contained in the substrate, it is possible to determine whether or not the polarizing element has good performance by 255 nm in the ultraviolet region. The absorption in the ultraviolet region of the iodine or iodine compound is 220 nm, 295 nm, and 360 nm, which is different from the absorption of the organic compound of the formula (1), so that the content of the compound of the formula (1) can be preferably adjusted. In order to impart good polarization characteristics, the content of the compound of the formula (1) is preferably such that the two substrates are parallel to the absorption axis direction and the visibility correction parallel transmittance Yp is in the range of 33% to 37%. The parallel transmittance Yp and the transmittance ₂₅₅ nm of the ₂₅₅ nm when the two substrates are parallel to the absorption axis direction satisfy the following formula (2). More preferably, it satisfies the formula (2B).

0.75×Yp-13≦Tp ₂₅₅ ≦0.75×Yp+1.0 (2)

0.75×Yp-11≦Tp ₂₅₅ ≦0.75×Yp (2B)

In addition, in order to determine the content of the compound of the formula (1), it is preferable to adjust the parallel transmittance Yp when the two substrates are parallel to the absorption axis direction and are measured. In the range of 33% to 37%, and the parallel transmittance Yp and the case where two substrates are orthogonal to the absorption axis direction and measured, the transmittance ₂₅₅ nm of ₂₅₅ nm satisfies the following formula (3). .

2.0×10 ^-6 ×Yp ^4.1 ≦Tc ₂₅₅ ≦2.0×10 ^-6 ×Yp ^4.4 (3)

Further, it is necessary to adjust not only the content of the organic compound represented by the formula (1) but also the content of the iodine and the iodine compound. Specifically, when the two base materials are parallel to the absorption axis direction and measured, the visibility correction parallel transmittance Yp is in the range of 33% to 37%, and the parallel transmittance Yp and the two pieces are required to be made. 460nm when the substrate and the absorption axis direction and parallel to the case of measuring the difference between the transmittance Tp of ₄₆₀ was adjusted to 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 Tp _{295 at 295} nm and the transmittance Tp ₃₆₀ at 360 nm when two substrates are parallel to the direction of the absorption axis and measured. . It is considered that the transmittance TL of ₂₉₅ nm Tp ₂₉₅ and the transmittance Tp ₃₆₀ of 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 at 295 nm and 360 nm can be adjusted, and the difference between Yp and Yp ₄₆₀ can be adjusted to within 3%.

In order to manufacture a more favorable polarizing element, adjustment is made in such a manner that the two pieces of the substrate are parallel to the absorption axis direction and are measured to obtain a visibility correction transmittance Yp ranging from 33% to 37%. The transmittance Yp and the transmittance of Tp _{295 of 295} nm when the two substrates are parallel to the direction of the absorption axis and satisfy the following formula (4), and the above Yp and the two substrates and the absorption axis direction The transmittance Tp ₃₆₀ of 360 nm in the case where the measurement is performed in parallel and satisfies the following formula (5).

1.05×Yp-26≦Tp ₂₉₅ ≦1.05×Yp-13 (4)

1.25×Yp-26.25≦Tp ₃₆₀ ≦1.25×Yp-16.25 (5)

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. Further, when the two substrates are perpendicular to the absorption axis direction and measured, the transmittance ₂₉₅ nm of the ₂₉₅ nm satisfies the following formula (6), and two sheets are obtained. When the substrate is parallel to the direction of the absorption axis and is measured, the transmittance Tc ₃₆₀ of 360 nm satisfies the following formula (7). 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 (6)

4.0×10 ^-37 ×Yp ^22.12 ≦Tc ₃₆₀ ≦4.0×10 ^-37 ×Yp ^22.67 (7)

Further, in the LED backlight source of recent years, the 460 nm blue light is emitted white by using a phosphor, and thus the transmittance of 430 nm to 480 nm centered at 460 nm is important for improving the contrast of the polarizing element. In particular, when the two substrates are orthogonal to the absorption axis direction at 460 nm and the transmittance of the polarizing element is high, 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 and the absorption axis direction are obtained. When the measurement is performed orthogonally 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 film having a polymerization degree of from 1,000 to 10,000 as a base material 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% by weight 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. Again, by The buffer or inorganic acid or a salt thereof and/or an organic acid, a zinc compound, a chloride or an iodide, etc., more preferably the above buffer or inorganic, is contained at a concentration of about 0.01% by weight to about 10% by weight based on the adhesive component. The addition of an 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 be provided on the surface of the protective layer or film which is later formed as a non-exposed surface. A functional layer, a layer or film having brightness enhancement that improves the viewing angle and/or improves contrast. 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.

By the method described above, a polarizing element or a polarizing plate having a certain transmittance and a high contrast 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 visibility correction monomer transmittance Ys is calculated from 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 (8). 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 visibility correction parallel transmittance Yp is calculated based on 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 (9). 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 visibility correction 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 (10). 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 visibility corrected orthogonal transmittance Yc based on the visibility and according to the following formula (11).

Py=100×{(Yp-Yc)/(Yp+Yc)} ^1/2 (11)

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 used in an amount of 1000 parts by weight of water, International Publication No. WO2005/015275 0.02 parts by weight of the dye having the structure of the formula (1) and 1.0 part by weight of sodium tripolyphosphate described in Synthesis Example 1 were treated for 1 minute and 30 seconds, and then 1000 parts by weight of water and boric acid (Societa larderello spa company) 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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 and maintaining the stretching ratio, the difference between the conveying speed of the film processing and the relative speed of the water flow speed of the processing step is substantially constant Next, one side of the ultrasonic wave of 20 kHz to 40 kHz was applied while the post-processing step was performed for 20 seconds. 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 of the present application was obtained in the same manner as in Example 1 except for the production of VF-PM.

Example 3

A polarizing element was obtained in the same manner as in Example 2 except that the time of the dyeing treatment was set to 1 minute and 30 seconds.

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.

Example 5

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 used in an amount of 1000 parts by weight of water, International Publication No. WO2005/015275 An aqueous solution of 0.02 parts by weight of the dye having the structure of the formula (1) and 1.0 part by weight of sodium tripolyphosphate described in Synthesis Example 1 was treated for 1 minute and 30 seconds, and then 1000 parts by weight of water and boric acid (manufactured by Societa larderello spa). 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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% by weight of boric acid, and after stretching, the tension after stretching was maintained and the stretching ratio was maintained, and the conveying speed of the film was treated and the water flow rate of the treatment step was maintained. The difference in relative speed is substantially constant, and the post-treatment step is carried out for 20 seconds. Thereafter, it was dried by a dryer at 70 ° C for 10 minutes. A polarizing element is obtained.

Comparative example 1

It is not treated with an aqueous solution containing a pigment having the structure of the formula (1) described in Synthesis Example 1 of International Publication No. WO2005/015275, and then containing 1000 parts by weight of water and boric acid (Societa larderello spa company) 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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, and after stretching, one side was 60 rpm. A polarizing element was obtained in the same manner as in Example 1 except that the aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water was subjected to a post-treatment step for 20 seconds while maintaining the magnification after stretching. .

Comparative example 2

It is not treated with an aqueous solution containing a pigment having the structure of the formula (1) described in Synthesis Example 1 of International Publication No. WO2005/015275, and then containing 1000 parts by weight of water and boric acid (Societa larderello spa company) 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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, and after stretching, one side was 60 rpm. A polarizing element was obtained in the same manner as in Example 2 except that the aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water was subjected to a post-treatment step for 20 seconds while maintaining the magnification after stretching. .

Comparative example 3

It is not treated with an aqueous solution containing a pigment having the structure of the formula (1) described in Synthesis Example 1 of International Publication No. WO2005/015275, and then containing 1000 parts by weight of water and boric acid (Societa larderello spa company) 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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, and after stretching, one side was 60 rpm. Speed stirring is carried out by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water. The polarizing element was obtained in the same manner as in Example 3 except that the post-treatment step was carried out for 20 seconds while maintaining the magnification after stretching.

Comparative example 4

It is not treated with an aqueous solution containing a pigment having the structure of the formula (1) described in Synthesis Example 1 of International Publication No. WO2005/015275, and then containing 1000 parts by weight of water and boric acid (Societa larderello spa company) 28.6 parts by weight, 0.14 parts by weight of iodine (manufactured by Junsei Chemical Co., Ltd.), and 10.27 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, and after stretching, one side was 60 rpm. A polarizing element was obtained in the same manner as in Example 4 except that the aqueous solution prepared by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water was subjected to a post-treatment step for 20 seconds while maintaining the magnification after stretching. .

Comparative Example 5

The iodine-based polarizing plate SKN-18242P manufactured by Polatechno Co., Ltd. was immersed in dichloromethane, and a polarizing element was taken out, and it was set as a comparative example.

Comparative Example 6

It is not treated with an aqueous solution containing a pigment having the structure of the formula (1) described in Synthesis Example 1 of International Publication No. WO2005/015275, and then containing 1000 parts by weight of water and boric acid (Societa larderello spa company) 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, and after stretching, the film was immersed in A polarizing element was obtained in the same manner as in Example 5 except that the water was treated for 20 seconds.

Comparative Example 7

The solution is treated with an aqueous solution containing 0.1 parts by weight of the compound of the formula (1) and 1.0 part by weight of sodium tripolyphosphate described in Synthesis Example 1 of International Publication No. WO2005/015275, and is treated for 3 minutes and 00 seconds. A polarizer was produced in the same manner as in the first embodiment. Pieces. The obtained polarizing plate was colored yellow in appearance.

The parameters of the polarizing elements obtained in Examples 1 to 5 and Comparative Examples 1 to 7 are shown in Table 1. The parameters shown in Table 1 are as follows.

The visibility correction monomer transmittance Ys, the visibility correction parallel transmittance Yp, the visibility correction orthogonal transmittance Yc, the monomer transmittance Ts _{460 of 460} nm, and the two substrates are parallel to the absorption axis direction and are measured. In the case of the parallel penetration ratio Tp ₄₆₀ of 460 nm, the orthogonal transmittance of Tc ₄₆₀ of 460 nm when the two substrates are orthogonal to the absorption axis direction, and the monomer transmittance Ts _{550 of 550} nm, The average transmittance of Ts _{610 at 610} nm, the average transmittance at ₆₁₀ nm, and the average transmittance at 430 nm to 480 nm when the two substrates are orthogonal to the direction of the absorption axis and measured. Ts Ave 430-480, the average of the transmittance of the parallel position of 430 nm to 480 nm when the two substrates are parallel to the absorption axis direction and measured, Tp Ave 430-480, and the two substrates and the absorption axis direction are positive. The average of the transmittances of the orthogonal positions of 430 nm to 480 nm in the case of the measurement and Tc Ave 430-480.

With respect to Examples 1 to 5 and Comparative Examples 1 to 7, the further parameters obtained are shown in Table 2. The parameters shown in Table 2 are as follows.

The parallel transmittance Tp _{255 of 255} nm obtained by measuring the two substrates in parallel with the absorption axis direction, and the orthogonal transmittance Tc of ₂₅₅ nm obtained by measuring the two substrates in the direction perpendicular to the absorption axis. _255. The parallel penetration rate Tp _{295 of 295} nm obtained by measuring the two substrates in parallel with the absorption axis direction, and the orthogonal penetration of ₂₉₅ nm obtained by measuring the two substrates in the direction perpendicular to the absorption axis direction The ratio Tc ₂₉₅ , the parallel transmittance Tp ₃₆₀ of 360 nm obtained by measuring the two substrates in parallel with the absorption axis direction, and the orthogonality of 360 nm obtained by measuring the two substrates together with the absorption axis direction. Penetration rate Tc ₃₆₀ .

According to the above results, the polarizing elements of Examples 1 to 5 are polarizing elements having a substantially constant transmittance at each wavelength, and the visibility correction monomer transmittance Ys at the time of individual measurement is 40.0% to 42.5%, and the visibility is corrected. The difference between the monomer transmittance Ys and the monomer penetration rate Ts ₄₆₀ of 460 nm is 1.2%, and the difference between the visibility correction monomer transmittance Ys and the monomer penetration rate Ts ₅₅₀ of 550 nm is within 1%, and the visibility correction is performed. The difference between the monomer transmittance Ys and the monomer transmittance Ts ₆₁₀ of 610 nm is within 1%, and the two pieces of the substrate are orthogonal to the absorption axis direction and measured to obtain a visibility-corrected orthogonal transmittance Yc. 0.01% or less, the average value Tc Ave 430-480 of the orthogonal transmittance of 430 nm to 480 nm obtained by measuring the two substrates perpendicular to the absorption axis direction is 0.03% 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 5 are penetrated in parallel with the absorption axis, and have a transmittance of 430 nm to 480 nm and a penetration of 500 nm to 650 nm. The rate is successfully maintained at each wavelength of light uniformity compared to a substantially constant optical characteristic. Further, according to the visibility correction orthogonal transmittance Yc of 0.01% or less and the average value of the orthogonal transmittances of 430 nm to 480 nm Tc Ave 430-480 is 0.03% or less, it is also known that the polarizing elements have a high contrast. Further, the polarizing element or the polarizing plate can be made to have a certain wavelength transmittance in the visible light range.

Therefore, the polarizing elements of Examples 1 to 5 obtained by the above method or the polarizing plate produced using the polarizing elements can be used as a display having a high transmittance, a high contrast ratio, and a very high color reproducibility. A polarizing plate, in particular, 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 (11)

A polarizing element comprising: a substrate comprising a hydrophilic polymer having adsorbed boric acid and extending the hydrophilic polymer and having a polarizing function, and containing the organic compound represented by the formula (1) in the form of a free acid Or its salt: (In the formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, or a carboxyl group, and k, m, and n each represent 0 or 1; wherein m+n≧1) is determined separately In the case of the substrate, the luminosity corrected unit transmittance Ys is 40.0% to 42.5%, and the difference between the visibility correction monomer transmittance Ys and the 460 nm monomer transmittance Ts ₄₆₀ is 1.2. Within %, the difference between the visibility correction monomer transmittance Ys and the 550 nm monomer transmittance Ts ₅₅₀ is within 1%, and the difference between the visibility correction monomer transmittance Ys and the 610 nm monomer transmittance Ts ₆₁₀ is 1 When the two substrates are perpendicular to the absorption axis direction and are measured, the visibility correction orthogonal transmittance is 0.01% or less, and the two substrates are orthogonal to the absorption axis direction and measured. In the case, the average value of the orthogonal transmittances of 430 nm to 480 nm Tc Ave 430-480 is 0.03% or less. The polarizing element of claim 1, wherein the visibility correction parallel transmittance Yp is in the range of 33% to 37% when the two substrates are parallel to the absorption axis direction, and the parallel penetration of the substrate The transmittance Yp and the transmittance ₂₅₅ nm of the ₂₅₅ nm when the two substrates are parallel to the absorption axis direction satisfy the following formula (2): 0.75 × Yp-13 ≦ Tp ₂₅₅ ≦ 0.75 × Yp + 1.0 Formula (2). The polarizing element according to claim 1 or 2, wherein the visibility correction parallel transmittance Yp is in the range of 33% to 37% when the two substrates are parallel to the absorption axis direction, and the parallel transmittance is Yp and the transmittance ₂₅₅ nm of ₂₅₅ nm when the two substrates are orthogonal to the absorption axis direction and satisfy the following formula (3): 2.0 × 10 ^-6 × Yp ^4.1 ≦ Tc ₂₅₅ ≦ 2.0 × 10 ^-6 × Yp ^4.4 (3). The polarizing element according to claim 1 or 2, wherein the visibility correction parallel transmittance Yp is in the range of 33% to 37% when the two substrates are parallel to the absorption axis direction, and the parallel transmittance is Yp is within 3% of the parallel transmittance Tp ₄₆₀ of 460 nm when the two substrates are parallel to the absorption axis direction and measured. The polarizing element of claim 1 or 2, wherein the visibility correction transmittance 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 is The transmittance Tp _{295 of 295} nm when the two substrates are parallel to the direction of the absorption axis and is measured satisfies the following formula (4), and the parallel transmittance Yp and the two substrates are absorbed. When the axial direction is parallel and measured, the transmittance Tp ₃₆₀ of 360 nm satisfies the following formula (5), 1.05 × Yp-26 ≦ Tp ₂₉₅ ≦ 1.05 × Yp-13 (4) 1.25 × Yp-26.25 ≦ Tp ₃₆₀ ≦ 1.25 × Yp-16.25 Equation (5). The polarizing element according to claim 1 or 2, wherein the transmittance of ₂₉₅ nm when the two substrates are orthogonal to the direction of the absorption axis and measured, satisfies the formula (6), and two sheets of the substrate are obtained. The transmittance Tc ₃₆₀ of 360 nm in the case where the direction of the absorption axis is parallel and measured satisfies the formula (7), 2.0 × 10 ^-30 × Yp ^18.6 ≦ Tc ₂₉₅ ≦ 2.0 × 10 ^-30 × Yp ^19.4 (6) 4.0 ×10 ^-37 ×Yp ^22.12 ≦Tc ₃₆₀ ≦4.0×10 ^-37 ×Yp ^22.67 (7). The polarizing element according to claim 1 or 2, wherein the two substrates are orthogonal to the absorption axis direction and measured, and the transmittance ₄₆₀ nm of the 460 nm is 0.035% or less, and two substrates are bonded to each other. When the absorption axis direction is orthogonal and measured, 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 8. A liquid crystal display device comprising the polarizing element according to any one of claims 1 to 8 or the polarizing plate of claim 9. 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 in a vinyl alcohol 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, and further includes the step of causing the polarizing element to contain the organic compound of the following formula (1): (In the formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, or a carboxyl group, and k, m, and n each represent 0 or 1; wherein m + n ≧ 1).