JPWO2015083673A1 - High contrast polarizing element and polarizing plate having uniform transmittance at each wavelength - Google Patents

Abstract

When the polarizing element of the present application is arranged parallel to the absorption axis and arranged orthogonally, it has a substantially constant transmittance at each wavelength transmittance and a high contrast in each case. A polarizing element and a polarizing plate are provided. A polarizing element comprising a base material having a polarizing function, which is composed of a hydrophilic polymer adsorbed with boric acid and stretched, and which contains iodine, in the form of a free acid. (In the formula (1), R1 represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxyl group, or a carboxyl group, and k, m, and n each independently represents 0 or 1, provided that m + n> 1)), and when the substrate is measured alone, the visibility corrected single transmittance Yc is 40.0% to 42.5%, The difference between the visibility corrected single transmittance Ys and the single transmittance Ts460 at 460 nm is within 1.2%, and the difference between the visibility corrected single transmittance Ys and the single transmittance Ts550 at 550 nm is within 1%. Visibility correction single transmittance Ys and 610nm The difference from the body transmittance Ts610 is within 1%, and the visibility-corrected orthogonal transmittance when the two base materials are measured perpendicular to the absorption axis direction is 0.01% or less. A polarizing element, wherein an average value Tc Ave 430 to 480 of orthogonal transmittances of 430 nm to 480 nm when two materials are measured perpendicular to the absorption axis direction is 0.03% or less. [Selection figure] None

Description

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

  In general, the polarizing element is produced by adsorbing and orienting iodine or dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film. A protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used for a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine polarizing plate, while a polarizing plate using a dichroic dye as a dichroic dye is called a dye polarizing plate. Among these, dye-based polarizing plates have high heat resistance, high humidity heat durability, high stability, and are characterized by high color selectivity by blending, while having the same degree of polarization. There is a problem that the transmittance is low compared to the plate, that is, the contrast is low. When conventional polarizing elements are placed parallel to the absorption axis and show white, the transmittance from 380 nm to 480 nm is lower than the transmittance from 500 nm to 600 nm, and the light emission uniformity at each wavelength cannot be maintained. It was. Therefore, for example, when the absorption axes of the polarizing elements are installed in parallel, an attempt has been made to improve each wavelength transmittance so as to have a certain transmittance. However, also in this case, there is a problem in that when installed on an axis orthogonal to the absorption axis, the wavelength of 380 nm to 480 nm, particularly the wavelength of 460 nm is higher than the transmittance near 550 nm where the visibility is high, and the contrast is lowered. there were. Accordingly, there has been a demand for a polarizing element or a polarizing plate that has a high polarization performance, that is, a high contrast, and that can maintain a constant wavelength transmittance in the visible region.

JP 2005-49698 A JP-A-2005-202367

Functional dye application first edition, CMC Publishing, supervised by Masahiro Irie, P98-100

  For example, Patent Document 1 or Patent Document 2 discloses a method of making the transmittance of the polarizing plate constant at each wavelength. Patent Document 1 discloses a technique of a polarizing element having a transmittance of 0.001% to 0.1% at 410 nm in crossed Nicols in a polarizing element having a film thickness of 8 to 18 μm. However, this technique does not improve the wavelength transmittance at the parallel position only by improving the color omission and hue at the 410 nm orthogonal position, and a liquid crystal display device provided with a recent LED light source as a backlight. In this case, there is almost no emission at 410 nm, and blue light emission is mainly emitted from 430 nm to 480 nm with the emission line of 460 nm, so that a contrast of 410 nm is almost unnecessary. Therefore, in order to improve the contrast, it is necessary to improve the contrast at a wavelength of 430 to 480 nm. The prescription of Patent Document 1 does not provide sufficient contrast for use in a display device when using a backlight such as an LED light source, and improving the parallel color. Patent Document 2 discloses a technology of a polarizing element made of a film having a structure in which microregions are dispersed in a matrix formed of a water-soluble resin containing a divalent metal. However, even with this technique, a polarizing element or a polarizing plate in which the transmittance of each wavelength at the parallel position and the orthogonal position is constant has not been obtained.

  The inventor of the present invention has completed the present invention as a result of intensive studies to solve the above problems.

（式（１）中、Ｒ_１は水素原子、ハロゲン原子、低級アルキル基、低級アルコシキシル基、またはカルボキシル基を示し、ｋ、ｍ、ｎは個々に０または１を示す。ただし、ｍ＋ｎ＞１である。）
で表される有機化合物又はその塩を含有し、
該基材を単体で測定した場合の視感度補正単体透過率Ｙｃが４０．０％乃至４２．５％であり、
視感度補正単体透過率Ｙｓと４６０ｎｍの単体透過率Ｔｓ_４６０との差が１．２％以内であり、
視感度補正単体透過率Ｙｓと５５０ｎｍの単体透過率Ｔｓ_５５０との差が１％以内であり、
視感度補正単体透過率Ｙｓと６１０ｎｍの単体透過率Ｔｓ_６１０との差が１％以内であり、
該基材２枚を吸収軸方向に対して直交にして測定した場合の視感度補正直交透過率が０．０１％以下であり、
該基材２枚を吸収軸方向に対して直交にして測定した場合の４３０ｎｍ乃至４８０ｎｍの直交透過率の平均値Ｔｃ Ａｖｅ４３０−４８０が０．０３％以下であることを特徴とする、偏光素子；
（２）前記基材２枚を吸収軸方向に対して平行にして測定した場合の視感度補正平行透過率Ｙｐが３３％乃至３７％の範囲であり、
該基板の平行透過率Ｙｐと、該基材２枚を吸収軸方向に対して平行にして測定した場合の２５５ｎｍの透過率Ｔｐ_２５５とが、下記式（２）：
０．７５×Ｙｐ−１３≦Ｔｐ_２５５≦０．７５×Ｙｐ＋１．０ ・・・式（２）
を満たすことを特徴とする、上記（１）に記載の偏光素子；
（３）前記基材２枚を吸収軸方向に対して平行にして測定した場合の視感度補正平行透過率Ｙｐが３３％乃至３７％の範囲であり、
該平行透過率Ｙｐと、該基材２枚を吸収軸方向に対して直交にして測定した場合の２５５ｎｍの透過率Ｔｃ_２５５とが、下記式（３）：
２．０×１０^−６×Ｙｐ^４．１≦Ｔｃ_２５５≦２．０×１０^−６×Ｙｐ^４．４ ・・・式（３）
を満たすことを特徴とする上記（１）または（２）に記載の偏光素子；
（４）前記基材２枚を吸収軸方向に対して平行にして測定した場合の視感度補正平行透過率Ｙｐが３３％乃至３７％の範囲であり、
該平行透過率Ｙｐと、前記基材２枚を吸収軸方向に対して平行にして測定した場合の４６０ｎｍの平行透過率Ｔｐ_４６０との差が３％以内であることを特徴とする、上記（１）乃至（３）のいずれか一項に記載の偏光素子；
（５）前記基材２枚を吸収軸方向に対して平行にして測定した場合の視感度補正透過率Ｙｐが３３％乃至３７％の範囲にあり、
該平行透過率Ｙｐと、前記基材２枚を吸収軸方向に対して平行にして測定した場合の２９５ｎｍの透過率Ｔｐ_２９５とが、下記式（４）を満たし、
該平行透過率Ｙｐと、前記基材２枚を吸収軸方向に対して平行にして測定した場合の３６０ｎｍの透過率Ｔｐ_３６０とが、下記式（５）を満たすことを特徴とする、上記（１）乃至（４）のいずれか一項に記載の偏光素子；
１．０５×Ｙｐ−２６≦Ｔｐ_２９５≦１．０５×Ｙｐ−１３ ・・・式（４）
１．２５×Ｙｐ−２６．２５≦Ｔｐ_３６０≦１．２５×Ｙｐ−１６．２５ ・・・式（５）
（６）前記基材２枚を吸収軸方向に対して直交にして測定した場合の２９５ｎｍの透過率Ｔｃ_２９５が、式（６）を満たし、且つ、
該基材２枚を吸収軸方向に対して平行にして測定した場合の３６０ｎｍの透過率Ｔｃ_３６０が、式（７）を満たすことを特徴とする、上記（１）乃至（５）のいずれか一項に記載の偏光素子；
２．０×１０^−３０×Ｙｐ^１８．６≦Ｔｃ_２９５≦２．０×１０^−３０×Ｙｐ^１９．４ ・・・式（６）
４．０×１０^−３７×Ｙｐ^{２２．１２}≦Ｔｃ_３６０≦４．０×１０^−３７×Ｙｐ^{２２．６７} ・・・式（７）
（７）前記基材２枚を吸収軸方向に対して直交にして測定した場合の４６０ｎｍの透過率Ｔｃ_４６０が０．０３５％以下であり、かつ、
該基材２枚を吸収軸方向に対して直交にして測定した場合の６１０ｎｍの透過率Ｔｃ_６１０が０．０１％以下であることを特徴とする、上記（１）乃至（６）のいずれか一項に記載の偏光素子；
（８）前記基材が、ポリビニルアルコール系樹脂フィルムからなり、
該ポリビニルアルコール系樹脂フィルムの重合度が３０００乃至７０００であることを特徴とする、上記（１）乃至（７）のいずれか一項に記載の偏光素子；
（９）上記（１）〜（８）のいずれか一項に記載の偏光素子の少なくとも片面に支持体フィルムを設けてなる偏光板；
（１０）上記（１）〜（８）のいずれか一項に記載の偏光素子または上記（９）に記載の偏光板を備える液晶表示装置；
（１１）ホウ酸を吸着し延伸された親水性高分子からなり、且つ、ヨウ素を含有する偏光機能を有する基材を含んだ偏光素子の製造方法であって、
（ｉ）ポリビニルアルコール系樹脂フィルムに、二色性色素を含有させ、二色性色素を含有したフィルムを得る工程と、
（ｉｉ）前記二色性色素を含有したフィルムを延伸して、延伸したフィルムを得る工程と、
（ｉｉｉ）前記延伸したフィルムを、塩化物含有溶液またはヨウ化物含有溶液を用いて後処理に供する工程と、
（ｉｖ）前記後処理の後、フィルムを乾燥させて前記基材を得る工程と
を含み、
前記塩化物含有溶液またはヨウ化物含有溶液の濃度が、０．１〜１５重量％であり、
下記式（１）：

の有機化合物を含有させる工程を更に含むことを特徴とする、製造方法」
に関する。That is, the present invention
“(1) A polarizing element comprising a base material having a polarizing function, which is composed of a hydrophilic polymer drawn by adsorbing boric acid and containing iodine,
In the form of the free acid, formula (1):

(In Formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxyl group, or a carboxyl group, and k, m, and n each independently represent 0 or 1, provided that m + n> 1. is there.)
Containing an organic compound represented by
When the substrate is measured alone, the visibility corrected single transmittance Yc is 40.0% to 42.5%,
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{460 at 460} nm is within 1.2%,
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{550 at 550} nm is within 1%.
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{610 at 610} nm is within 1%,
Visibility corrected orthogonal transmittance when the two substrates are measured perpendicular to the absorption axis direction is 0.01% or less,
A polarizing element characterized in that an average value Tc Ave 430-480 of orthogonal transmittances of 430 nm to 480 nm when the two substrates are measured perpendicular to the absorption axis direction is 0.03% or less;
(2) Visibility corrected parallel transmittance Yp when the two base materials are measured parallel to the absorption axis direction is in a range of 33% to 37%,
The parallel transmittance Yp of the substrate and the transmittance Tp _{255 of 255} nm when the two base materials are measured parallel to the absorption axis direction are expressed by the following formula (2):
_{0.75 × Yp-13 ≦ Tp 255} ≦ 0.75 × Yp + 1.0 ··· formula (2)
The polarizing element according to the above (1), characterized in that:
(3) The visibility corrected parallel transmittance Yp when the two base materials are measured parallel to the absorption axis direction is in the range of 33% to 37%,
The parallel transmittance Yp and the transmittance Tc _{255 of 255} nm when the two substrates are measured perpendicular to the absorption axis direction are expressed by the following formula (3):
2.0 × 10 ⁻⁶ × Yp ^4.1 ≦ Tc ₂₅₅ ≦ 2.0 × 10 ⁻⁶ × Yp ^4.4 Formula (3)
The polarizing element as described in (1) or (2) above, wherein:
(4) Visibility corrected parallel transmittance Yp when the two base materials are measured parallel to the absorption axis direction is in a range of 33% to 37%,
The difference between the parallel transmittance Yp and the parallel transmittance Tp ₄₆₀ of 460 nm measured when the two base materials are parallel to the absorption axis direction is within 3%, 1) The polarizing element as described in any one of (3);
(5) The visibility correction transmittance Yp when the two base materials are measured parallel to the absorption axis direction is in the range of 33% to 37%,
The parallel transmittance Yp and the transmittance Tp _{295 of 295} nm when the two substrates are measured in parallel with the absorption axis direction satisfy the following formula (4):
The parallel transmittance Yp and the transmittance Tp _{360 of 360} nm when the two substrates are measured in parallel with the absorption axis direction satisfy the following formula (5): 1) The polarizing element as described in any one of (4);
1.05 × Yp−26 ≦ Tp ₂₉₅ ≦ 1.05 × Yp−13 Formula (4)
1.25 × Yp−26.25 ≦ Tp ₃₆₀ ≦ 1.25 × Yp−16.25 Formula (5)
(6) The transmittance Tc _{295 of 295} nm when the two substrates are measured perpendicular to the absorption axis direction satisfies the formula (6), and
Any of the above (1) to (5), wherein a transmittance Tc _{360 of 360} nm when the two substrates are measured parallel to the absorption axis direction satisfies the formula (7) The polarizing element according to one item;
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)
(7) The transmittance Tc _{460 at 460} nm when the two substrates are measured perpendicular to the absorption axis direction is 0.035% or less, and
Any of (1) to (6) above, wherein a transmittance Tc _{610 at 610} nm when the two substrates are measured perpendicular to the absorption axis direction is 0.01% or less. The polarizing element according to one item;
(8) The substrate is made of a polyvinyl alcohol resin film,
The polarizing element according to any one of (1) to (7) above, wherein the degree of polymerization of the polyvinyl alcohol-based resin film is 3000 to 7000;
(9) A polarizing plate comprising a support film on at least one surface of the polarizing element according to any one of (1) to (8) above;
(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 for producing a polarizing element comprising a base material having a polarizing function, which is composed of a hydrophilic polymer that has been adsorbed with boric acid and is stretched, and that contains iodine.
(I) adding a dichroic dye to the polyvinyl alcohol-based resin film and obtaining a film containing the dichroic dye;
(Ii) stretching the film containing the dichroic dye to obtain a stretched film;
(Iii) subjecting the stretched film to a post-treatment using a chloride-containing solution or an iodide-containing solution;
(Iv) after the post-treatment, drying the film to obtain the substrate,
The concentration of the chloride-containing solution or iodide-containing solution is 0.1 to 15% by weight,
Following formula (1):

The method further comprises a step of containing an organic compound of
About.

  The present invention relates to a polarizing element and a polarizing plate having a constant transmittance at each wavelength and having a high contrast. The polarizing element and the polarizing plate have a high transmittance, a high contrast ratio, and It can be used as a polarizing plate for a display having a very high color reproducibility, particularly as a polarizing plate for a liquid crystal display. A display using this is highly reliable, has a long-term high contrast, and has a high color reproducibility.

Means for carrying out the invention

<Polarizing element>
As a method for producing the polarizing element of the present invention, for example, a step of swelling a hydrophilic polymer film, a dyeing step of containing a dichroic dye, a water-resistant treatment step if necessary, then a stretching step Next, a method of producing through a post-treatment step and finally a drying step can be mentioned.

  Examples of the hydrophilic polymer film used for the polarizing element include films made of polyvinyl alcohol resin, amylose resin, starch resin, cellulose resin, polyacrylate resin, and the like. The film formed into a film is used. Among these, a polyvinyl alcohol resin (hereinafter sometimes abbreviated as “PVA”) film is preferable. In the present invention, a polarizing element comprising a polyvinyl alcohol resin film comprising a polyvinyl alcohol resin and a dichroic substance such as iodine is most preferred. The thickness of these polarizing elements is not particularly limited, but is generally about 5 to 80 μm.

  The manufacturing method of the said polyvinyl alcohol-type resin is not specifically limited, It can produce with a well-known method. For example, a polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. Here, examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. Moreover, 1,000-10,000 are preferable normally and the polymerization degree of polyvinyl alcohol-type resin has more preferable 1,500-6,000. What formed the polyvinyl alcohol-type resin into a film is used as a polyvinyl alcohol-type resin film.

  In order to improve the optical characteristics of the present invention, the polymerization degree of PVA needs to be 1000 to 10,000, and more preferably 3000 or more. If the degree of polymerization of PVA is less than 2000, it will be difficult to develop high polarization performance. When the degree of polymerization exceeds 7000, PVA becomes hard, the film forming property and stretchability are lowered, and the productivity is lowered. Therefore, it is preferably 10,000 or less from an industrial viewpoint.

The degree of polymerization of PVA means the degree of polymerization (viscosity average degree of polymerization) measured as follows.
0.28 g of PVA is dissolved at 95 ° C. with 70 g of distilled water to prepare a 0.4% PVA aqueous solution and cooled to 30 ° C. It cools in a 30 degreeC constant temperature water tank, and is set as the sample for a polymerization degree measurement. Next, 10 mL of the polymerization degree measurement sample is dried in an evaporating dish for 20 hours with a dryer at 105 ° C., and the weight [α (g)] after drying of the polymerization degree measurement sample is measured. The concentration C (g / L) of the sample for measuring the degree of polymerization is calculated by the following formula (i).

Further, a sample for measuring the degree of polymerization or distilled water is put into an Ostwald viscometer with a 10 mL whole pipette and stabilized in a constant temperature water bath at 30 ° C. for 15 minutes. The falling seconds t ₁ (seconds) and the falling seconds t ₀ (seconds) of the distilled water measurement sample were measured, and the viscosity average polymerization degree E was calculated from the following formulas (ii) to (iv). To do.

  The saponification degree of PVA is preferably 99 mol% or more, and more preferably 99.5 mol% or more. When the degree of saponification is less than 99 mol%, PVA is likely to elute, causing in-plane unevenness in optical properties, a decrease in dyeability in the dyeing process, and a cutting in the stretching process, thereby significantly reducing productivity. There is fear and it is not preferable.

  The PVA used in the present invention can be produced by saponifying a polyvinyl ester polymer obtained by polymerizing a vinyl ester. Examples of vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and the like. 1 type or 2 types or more are selected. Among these, vinyl acetate is preferably used. Although there is no restriction | limiting in particular in superposition | polymerization temperature, When using methanol as a superposition | polymerization solvent, since the boiling point of methanol is around 60 degreeC, it is preferable that it is around 60 degreeC. PVA is not limited to a saponified vinyl ester homopolymer unless the effects of the present invention are impaired. For example, a modified PVAl vinyl ester obtained by graft copolymerization of PVA with an unsaturated carboxylic acid or derivative thereof, an unsaturated sulfonic acid or derivative thereof, an α-olefin having 2 to 30 carbon atoms or the like in a proportion of less than 5 mol%, and unsaturated Saponified product of modified polyvinyl ester obtained by copolymerizing carboxylic acid or derivative thereof, unsaturated sulfonic acid or derivative thereof, α-olefin having 2 to 30 carbon atoms or the like in a proportion of less than 15 mol%, formalin, butyraldehyde, benzaldehyde, etc. It may be a polyvinyl acetal polymer in which a part of the hydroxyl group of PVA is cross-linked with such aldehydes.

  A film original can be obtained by forming a film of PVA obtained as described above. As a PVA film forming method, in addition to a method of melt-extruding hydrous PVA, a casting film forming method, a wet film forming method (discharging into a poor solvent), a gel film forming method (a PVA aqueous solution was once cooled and gelled). Thereafter, the solvent is extracted and removed), a cast film forming method (a PVA aqueous solution is poured onto the substrate and dried), a method using a combination thereof, and the like are not limited thereto.

  Examples of the solvent used for film formation include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, Examples include, but are not limited to, ethylenediamine, diethylenetriamine, and water. One type of solvent may be used, or two or more types may be mixed and used. The amount of the solvent used for film formation is, for example, 50 to 95% by mass, and 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 and defoaming at the time of preparation become difficult, and it is difficult to obtain a film original that does not contain foreign substances and has no defects It becomes. In addition, if the volatile content exceeds 95% by mass, the viscosity of the film-forming stock solution becomes too low, making it difficult to control the target thickness. Sex is reduced.

  A plasticizer may 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 used is not particularly limited, but usually it is preferably in the range of 5 to 15 parts by mass with respect to 100 parts by mass of PVA.

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

  The original film after drying is preferably subjected to heat treatment in order to control the degree of swelling within a predetermined range described later. Examples of the heat treatment method of the film original after film formation include a method using hot air and a method of bringing the film original into contact with a hot roll, and are not particularly limited as long as the method can be processed by heat. One of these methods may be adopted alone, or two or more may be combined. Although there is no restriction | limiting in particular about the heat processing temperature and time, The inside of the range of 110-140 degreeC is preferable, and the process for about 1 minute thru | or 10 minutes is suitable, However It does not specifically limit.

  The thickness of the original film thus obtained is preferably 20 to 100 μm, more preferably 20 to 80 μm, and still more preferably 20 to 60 μm. When the thickness is less than 20 μm, the film is easily broken. When the thickness exceeds 100 μm, the stress applied to the film at the time of stretching increases, the mechanical load in the stretching process increases, and a large-scale apparatus is required to withstand the load.

  The swelling degree F of the original film is preferably 180 to 250%, more preferably 205 to 235%, and still more preferably 210 to 230%. When the degree of swelling F is less than 180%, the elongation at the time of stretching is small, the possibility of breaking at a low magnification becomes high, and it becomes difficult to perform sufficient stretching. On the other hand, if the degree of swelling F exceeds 240%, the swelling becomes excessive, wrinkles and slack are generated, which causes cutting during stretching. In order to control the degree of swelling F, for example, a suitable degree of swelling F can be achieved depending on the temperature and time when the original film after film formation is heat-treated.

The method for measuring the degree of swelling F of the original film is as follows.
The original film is cut into 5 cm × 5 cm and immersed in 1 liter of distilled water at 30 ° C. for 4 hours. The soaked film is taken out from the distilled water, and after absorbing water droplets on the surface with two filter papers, the weight [β (g)] of the film soaked in water is measured. Further, the film soaked and absorbed with water droplets was dried with a dryer at 105 ° C. for 20 hours, cooled with a desiccator for 30 minutes, and then the weight [γ (g)] of the dried film was measured. The swelling degree F of the original film is calculated by v).

Using the raw film produced as described above, the polarizing element of the present invention is produced by a method including the steps described below.
(Swelling process)
First, the film original fabric described above is subjected to a swelling process for swelling the film.
In the said process, swelling is achieved by immersing a polyvinyl alcohol-type resin film in a 20-50 degreeC solution for 15 second-10 minutes. The solution at that time is preferably water, but may be a water-soluble organic solvent such as glycerin, ethanol, ethylene glycol, propylene glycol, or low molecular weight polyethylene glycol, or a mixed solution of water and a water-soluble organic solvent. In order to prevent the occurrence of wrinkles and folds even in the swelling step, it is preferably stretched appropriately, and the stretching ratio is preferably 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. It is. In the case of shortening the time for producing the polarizing element, the swelling effect can be obtained also in the dyeing process at the time of iodine and iodide treatment, so this process may be omitted.

(Dyeing process)
Next, the swollen polyvinyl alcohol resin film is subjected to a dyeing process in which the film is dyed with a solution containing a dichroic dye.
The solvent of the solution is preferably water, but is not particularly limited. Examples of the dichroic dye include polyiodine ions obtained from a mixed solution of iodine and iodide, dichroic dyes of organic compounds, and the like. As the iodide, for example, potassium iodide, ammonium iodide, cobalt iodide, zinc iodide and the like can be used, but the iodide is not limited to the iodide shown here. The iodine concentration in the mixed solution of iodine and iodide is 0.0001 to 0.5 wt%, preferably 0.001 to 0.4 wt%. The concentration of iodide used is preferably 0.0001-8 wt%. In some cases, in order to correct the color, for example, a dichroic dye described in Non-Patent Document 1 is used as the dichroic dye of the organic compound, and color correction is performed within a range that does not impair the performance required by the present application. You can go. The dye is not limited, and a known dichroic dye can be used. The dye concentration is not particularly limited, but for example, it is preferably about 0.006 wt% to 0.3 wt%. When the dyeability is insufficient, it is preferable to add a coloring aid such as sodium tripolyphosphate and / or sodium nitrate (sodium sodium sulfate) for dyeing. Moreover, dyeing | staining temperature is 5-50 degreeC, Preferably it is 5-40 degreeC, More preferably, it is 10-30 degreeC. The dyeing time can be appropriately adjusted according to the transmittance of the polarizing element to be obtained, but is about 30 seconds to 6 minutes, more preferably 1 minute to 5 minutes. Also in this step, it is preferable to stretch appropriately in order to prevent generation of wrinkles and folds. The draw ratio is preferably 0.90 to 2.00 times, more preferably 1.00 to 1.30 times.

  In the dyeing step, a crosslinking agent and / or a water-resistant agent may be added to the solution containing the dichroic dye. Examples of the crosslinking agent include boron compounds such as boric acid, borax and ammonium borate, polyhydric aldehydes such as glyoxal and glutaraldehyde, polyhydric isocyanate compounds such as biuret type, isocyanurate type and block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used. Examples of water-resistant agents include succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride. Acid is good. For example, when boric acid is added, the concentration to be added is 0.1 to 5.0 wt%, preferably 2 wt% to 4 wt% with respect to the solution containing the dichroic dye. Furthermore, you may wash | clean the polyvinyl-alcohol-type resin film containing the dichroic dye after the said dyeing | staining process before entering the next extending process as needed. As a solvent for washing, water is generally used, but an alcohol solvent, a glycol solvent, glycerin or a mixed solvent thereof can be used and is not particularly limited. Further, the temperature and time for washing may be appropriately adjusted according to the transmittance of the target polarizing element and the type of dichroic dye used.

(Water resistance treatment process)
Subsequently, the film dyed after the dyeing step is subjected to a water-resistant treatment step in which water-proofing treatment is performed as necessary.
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 and / or water-resistant agent include boron compounds such as boric acid, borax and ammonium borate, polyvalent aldehydes such as glyoxal and glutaraldehyde, polyisocyanates such as biuret type, isocyanurate type and block type. Compounds, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether, polyamide epichlorohydrin, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin Examples thereof include diglycidyl ether, ammonium chloride, magnesium chloride, and boric acid is preferable. As the solvent at that time, for example, water, alcohol solvent, glycol solvent, glycerin or a mixed solvent thereof can be used. For example, in the case of an aqueous boric acid solution, the concentration of the crosslinking agent or / and the water resistance-imparting agent is preferably about 0.1 to 6.0 wt%, more preferably 2 to 4 wt% in the solution. The processing temperature in this step is about 5 to 60 ° C, preferably about 5 to 45 ° C. The treatment time is preferably about 1 to 5 minutes. Also in this process, in order to prevent generation | occurrence | production of a wrinkle and a folding, it is preferable to extend | stretch moderately and the draw ratio is about 0.95-1.5 times.

(Stretching process)
Furthermore, it uses for the extending process which extends | stretches a polyvinyl alcohol-type resin film.
In this step, the film is uniaxially stretched. As the stretching method, either a wet stretching method or a dry stretching method may be used.

  Specific examples of the dry stretching method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but are not particularly limited. The stretching temperature is preferably from room temperature to 180 ° C., and the humidity is preferably from about 20 to 95% RH. Stretching may be performed in a single stage or may be a multi-stage stretching of two or more stages.

  The wet stretching method is a method of stretching in water, a water-soluble organic solvent, or a mixed aqueous solution thereof. Preferably, the water, the water-soluble organic solvent, or a mixed aqueous solution thereof contains the boric acid, borax. Boron compounds such as ammonium borate, polyhydric aldehydes such as glyoxal and glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type and block type, titanium compounds such as titanium oxysulfate, ethylene glycol glycidyl ether , Polyamide epichlorohydrin, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride, etc. Or / and it is preferred to stretching while immersed in a solution containing a waterproof agent, and more preferably stretching in an aqueous boric acid solution in. The concentration of the crosslinking agent or / and the water resistance-imparting agent is preferably 0.5 to 8 wt%, more preferably 2.0 to 4.0 wt%. The draw ratio is preferably about 3 to 8 times, more preferably about 5 to 7 times. The stretching temperature is preferably 40 ° C to 60 ° C, more preferably 45 to 55 ° C. The stretching time is preferably 30 seconds to 20 minutes, more preferably 2 minutes to 5 minutes. The stretching process may be one stage or multistage stretching of two or more stages.

  The surface of the polyvinyl alcohol-based resin film containing the stretched dichroic dye may be washed because foreign matter may precipitate or foreign matter may adhere to the surface. As a solvent for washing, water, an alcohol-based solvent, or the like can be used, but it is not limited to these. The cleaning solvent may contain a crosslinking agent such as boric acid and / or a waterproofing agent for the purpose of improving the durability of the film. Although the density | concentration of a crosslinking agent and / or a water resistance agent is not limited, For example, it is 0.1-10 wt%.

(Post-processing process)
Next, in order to adjust the hue, improve the polarization characteristics, and improve the durability, a post-treatment process is performed in which the film is post-treated.
In this step, specifically, the uniaxially stretched polyvinyl alcohol-based resin film containing a dichroic dye is treated with a solution containing chloride or iodide. Examples of the chloride or iodide include iodides 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 two or more of them are mixed into the solution for treatment. The concentration of chloride or iodide in the solution is preferably 0.1 to 15 wt%, more preferably 0.15 to 10 wt%. Also in this process, in order to prevent generation | occurrence | production of a wrinkle and a crease | fold, it is preferable to extend | stretch moderately and the draw ratio in that case has preferable 0.90-1.10 times. The treatment temperature is preferably, for example, 5 ° C to 50 ° C or less, more preferably 20 to 40 ° C. The processing time is, for example, about 1 second to 5 minutes, preferably 5 seconds to 30 seconds. In this step, the cross-linking agent and / or water-resistant agent may be added. The concentration to be added is, for example, 0.5 to 10 wt%.

  Examples of the solvent used in the treatment steps so far include, for example, water, dimethylsulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, or Examples of the solvent include alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine, but are not limited thereto. A mixture of one or more of these solvents can also be used. The most preferred solvent is water.

(Drying process)
The substrate of the polarizing element of the present invention is obtained by passing through a drying step after the post-treatment step.
Examples of the drying method include natural drying, compression with a roll, a method of removing moisture on the surface with an air knife or a water absorption roll, and drying by heating. As drying temperature in the case of heat drying, 20-90 degreeC is preferable, More preferably, it is 40-70 degreeC. The drying time is preferably about 30 seconds to 20 minutes, and more preferably about 2 to 10 minutes. Also in this drying step, in order to prevent wrinkles and streaks due to shrinkage of the polyvinyl alcohol resin film accompanying drying, it is preferable to stretch appropriately, and the draw ratio at that time is preferably 0.95 to 1.10 times .

The substrate of the polarizing element is obtained through the swelling process, the dyeing process, the optional water resistance treatment process, the stretching process, the post-treatment process, and the drying process. And the base material obtained in this way is a base material which has the polarization function containing the iodine which consists of hydrophilic polymer which adsorb | sucked and extended | stretched boric acid, Comprising: 1) The organic compound represented by 1) or a salt thereof is included, and the visibility corrected single transmittance Ys when measured by itself is 40.0% to 42.5%. The difference between the single transmittance Ts _{460 at 460} nm is within 1.2%, the difference between the single transmittance Ts ₅₅₀ at which the visibility is corrected and the single transmittance Ts _{550 at 550} nm is within 1%, and the visibility is corrected at a single transmittance. The difference between Ys and the single transmittance Ts _{610 of 610} nm is within 1%, and the visibility corrected orthogonal transmittance Yc obtained by measuring the two substrates perpendicular to the absorption axis direction is 0.01. %, And the two base materials are orthogonal to the absorption axis direction. The average value of the cross transmittance of 430nm to 480nm obtained by measuring and is adjusted to 0.03% or less.

（式（１）中、Ｒ_１は水素原子、ハロゲン原子、低級アルキル基、低級アルコシキシル基、またはカルボキシル基を示し、ｋ、ｍ、ｎは個々に０または１を示す。ただし、ｍ＋ｎ＞１である。）

(In Formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxyl group, or a carboxyl group, and k, m, and n each independently represent 0 or 1, provided that m + n> 1. is there.)

In order to obtain a polarizing element provided with a substrate having the above characteristics, it is necessary to contain an organic compound of the formula (1). And as a method of making this organic compound contain, in any process of the dyeing | staining process which contains a dichroic pigment | dye, arbitrary water resistance treatment processes, an extending | stretching process, and a post-processing process, it is the solution which the organic compound contains. The base material may be impregnated and contained, but after the polyvinyl alcohol-based resin film is swollen and further dyed with iodine and iodine compound, a method of adding further steps and containing a dichroic dye The method of making it contain simultaneously with the dyeing | staining process to make, the method of providing a process and making it contain before extending | stretching after dyeing iodine, and the method of making it contain simultaneously in a post-processing process are preferable. Furthermore, a method in which a step is provided before the step of dyeing iodine and iodine compound after swelling the polyvinyl alcohol-based resin film is more preferable.
Specific examples of the dye represented by the formula (1) include C.I. I. Direct Yellow 28, C.I. I. Direct Yellow 29 can be exemplified. The concentration of the organic compound of the formula (1) is not particularly limited, but for example, about 0.05 to 3 parts by weight is preferable with respect to 1000 parts by weight of water, and the dyeability is insufficient. In such a case, it is preferable to add a coloring aid such as sodium tripolyphosphate and / or sodium nitrate (sodium sodium sulfate) for dyeing. Moreover, dyeing | staining temperature is 5-50 degreeC, Preferably it is 5-40 degreeC, More preferably, it is 10-30 degreeC. The dyeing time can be adjusted as appropriate according to the transmittance of the polarizing element to be obtained. For example, the dyeing time is preferably about 30 seconds to 6 minutes, and preferably 1 to 5 minutes.

  Next, more specific examples of the dye represented by the formula (1) are shown below in the form of a free acid.

[Compound Example 1]

[Compound Example 2]

[Compound Example 3]

In addition, it is important to treat a uniaxially stretched polyvinyl alcohol-based resin film containing a dichroic dye with a solution containing chloride or iodide having a suitable concentration in a post-treatment step. In this step, the concentration of the chloride or iodide contained in the solution and the treatment time must be adjusted according to the stretching conditions. It is very important that the concentration and the treatment time are adjusted according to the state of impregnation of the polarizing element with iodine and an iodide such as potassium iodide and a chloride such as potassium chloride. It is. In particular, the concentration is affected by the stretching state in the stretching process, the temperature and humidity of the place where the polarizing element is produced, and therefore requires very delicate fine adjustment. In general, the concentration of the chloride-containing solution or iodide-containing solution used in the post-treatment step is 1.0 to 150 parts by weight, preferably 1.5 to 150 parts by weight of chloride or iodide with respect to 1000 parts by weight of water. It is prepared by adding 100 parts by weight.
Further, it is preferable to carry out the treatment while maintaining the stretch ratio and / or stretch tension so that the film shrinks or expands as little as possible. Furthermore, it is preferable to process in a state where there is no difference in relative speed between the film transport speed and the water flow speed in the post-processing step. It is more preferable to sufficiently treat the inside. The polarizing element of this application can be obtained by performing a post-processing process by the above method.

An index for manufacturing adjustment to have better performance as a polarizing element is the transmittance at 255 nm in the ultraviolet region. This is because the organic compound represented by the formula (1) has absorption at 255 nm, and when the compound is contained in the base material, it is possible to determine whether the polarizing element has good performance by the ultraviolet region of 255 nm. This is because it can be done. Absorption in the ultraviolet region of iodine or iodine compound is absorption at 220 nm, 295 nm, and 360 nm, which is different from the absorption of the organic compound of formula (1), so the content of the compound of formula (1) is suitably adjusted I can do it. In order to give good polarization characteristics, the content of the compound of the formula (1) is such that the visibility-corrected parallel transmittance Yp when the two substrates are measured parallel to the absorption axis direction is 33% to 33%. The range is 37%, and the parallel transmittance Yp and the transmittance Tp _{255 of 255} nm when the two base materials are measured in parallel with the absorption axis direction satisfy the following formula (2). Is preferred. More preferably, the formula (2B) is satisfied.

_{0.75 × Yp-13 ≦ Tp 255} ≦ 0.75 × Yp + 1.0 ··· formula (2)

_{0.75 × Yp-11 ≦ Tp 255} ≦ 0.75 × Yp ··· formula (2B)

Further, in order to have better polarization characteristics, as an index for ascertaining the content of the compound of formula (1), the visibility-corrected parallel transmission in the case of measuring with two substrates parallel to the absorption axis direction is used. The transmittance Yp is in the range of 33% to 37%, the parallel transmittance Yp, and the transmittance at 255 nm when the two base materials are measured perpendicular to the absorption axis direction are Tc ₂₅₅ as follows: It is preferable to satisfy Formula (3).

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

Moreover, it is necessary not only to adjust the content of the organic compound represented by the formula (1) but also to adjust the content of iodine and the iodine compound. Specifically, the visibility corrected parallel transmittance Yp when two substrates are measured in parallel with the absorption axis direction is in the range of 33% to 37%. It is necessary to adjust the difference from the transmittance Tp _{460 of 460} nm when the two materials are measured parallel to the absorption axis direction to within 3%. In order to make the difference between Yp and Tp ₄₆₀ within 3%, the transmittance Tp _{295 at 295} nm and the transmittance Tp ₃₆₀ at ₃₆₀ nm when two substrates are measured parallel to the absorption axis direction are adjusted. There is a need to. The transmittance Tp _{295 at 295} nm and the transmittance Tp _{360 at 360} nm are said to vary due to the content of polyiodine such as I ₃ ⁻ and I ₅ ⁻ in the polarizing element. The transmittance of 295 nm and 360 nm can be adjusted by adjusting the content of polyiodine such as I ₃ ⁻ and I ₅ ⁻ in the polarizing element, and the difference between Yp and Yp ₄₆₀ can be adjusted within 3%. it can.

In order to manufacture a better polarizing element, the visibility correction transmittance Yp obtained by measuring the two base materials parallel to the absorption axis direction is in the range of 33% to 37%, The transmittance Yp and the transmittance of ₂₉₅ nm when the two substrates are measured in parallel with the absorption axis direction Tp ₂₉₅ satisfy the following formula (4), and the Yp and the substrate It is necessary to adjust the transmittance Tp _{360 of 360} nm when the two sheets are measured parallel to the absorption axis direction so as to 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 Formula (5)

In order to further improve the performance of the polarizing element, in particular, to improve the performance of 380 nm to 480 nm, which is the visible range of the polarizing element, improve the orientation of polyiodine such as 295 nm and 360 nm of I ₃ ⁻ and I ₅ ⁻ The transmittance Tc _{295 of 295} nm when satisfying the above formulas (4) and (5) and measuring the two base materials perpendicular to the absorption axis direction is as follows: It is more preferable that the transmittance Tc _{360 of 360} nm when the equation (6) is satisfied and the two base materials are measured in parallel with the absorption axis direction satisfies the following equation (7). In the following formula, each of Yp ^18.6 , Yp ^19.4 , Yp ^22.12 and Yp ^22.67 represents a multiplier of the parallel transmittance Yp.

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)

  Furthermore, in recent LED backlight light sources, blue light of 460 nm is emitted in white using a phosphor, so that the transmittance of 430 nm to 480 nm centered on 460 nm improves the contrast of the polarizing element. Is important. In particular, if the transmittance of the polarizing element is high when two 460 nm base materials are measured perpendicularly to the absorption axis direction, blue light leaks and a true black color cannot be expressed as a display. At that time, if the transmittance at 610 nm does not have a certain transmittance or less as compared with 460 nm, true black cannot be expressed, and the contrast between white and black cannot be realized. Therefore, the transmittance of the polarizing element is such that the transmittance at 460 nm is 0.035% or less when two substrates are measured perpendicular to the absorption axis direction, and the two substrates are in the absorption axis direction. It is preferable to prepare such that the transmittance at 610 nm is 0.01% or less when measured perpendicularly.

  Furthermore, for this purpose, the present application can be easily achieved by using a film original made of a polyvinyl alcohol-based resin film having a polymerization degree of 1000 to 10,000 as the base material of the polarizing element. More preferably, the degree of polymerization of the polyvinyl alcohol film is 3500 to 6000, and more preferably 4500 to 6000.

<Polarizing plate>
The polarizing plate of the present invention can be obtained by providing a transparent protective layer on at least one surface or both surfaces of the polarizing element of the present invention obtained through the above steps. Specifically, the transparent protective layer can be provided by applying or laminating a polymer or film forming the protective layer to the polarizing element of the present invention. The transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. Furthermore, the thing which is excellent in moisture barrier property is more preferable. Examples of the material used as the transparent protective layer include cellulose acetate resin such as triacetyl cellulose and diacetyl cellulose or a film thereof, acrylic resin or a film thereof, polyester resin or a film thereof, polyarylate resin or a film thereof, and cyclic such as norbornene. Cyclic polyolefin resin or film thereof containing olefin as a monomer, polyethylene, polypropylene, polyethylene terephthalate, polyolefin having a cyclo or norbornene skeleton or copolymer thereof, main chain or side chain of imide or / and amide resin or polymer or its A film etc. are mentioned. Furthermore, since the polyvinyl alcohol-based resin is generally known to function as an alignment film, the surface of the obtained polarizing element is applied with, for example, a rubbing process, or an alignment film coating and alignment process. A resin having a property or a film thereof may be provided. The thickness of the protective film is, for example, about 0.5 to 200 μm. When these films are provided on both surfaces of the polarizing element, the same film may be used or different films may be used.

  When laminating the film which is the said transparent protective layer with the polarizing element of this invention, it is preferable to use an adhesive agent. Examples of the adhesive include polyvinyl alcohol, urethane, acrylic, and epoxy adhesives. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, GOHSENOL NH-26 (manufactured by Nihon Gosei Co., Ltd.), EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and the like. A cross-linking agent and / or a waterproofing agent may be added to the adhesive. The adhesive may contain an inorganic acid or a salt thereof and / or an organic acid at a concentration of 0.0001 wt% to 20 wt%, and preferably 0.02 wt% to 5 wt%. As the polyvinyl alcohol-based adhesive, an adhesive obtained by mixing maleic anhydride-isobutylene copolymer alone or in combination with a crosslinking agent can be used. As maleic anhydride-isobutylene copolymer, for example, isoban # 18 (manufactured by Kuraray), isoban # 04 (manufactured by Kuraray), ammonia-modified isoban # 104 (manufactured by Kuraray), ammonia-modified isoban # 110 (manufactured by Kuraray) ), Imidized isoban # 304 (manufactured by Kuraray), imidized isoban # 310 (manufactured by Kuraray), and the like. A water-soluble polyvalent epoxy compound can be used as the crosslinking agent at that time. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtech), Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.), and the like. Further, as an additive of the adhesive, the buffer, inorganic acid or salt thereof and / or organic acid, zinc compound, chloride or iodide, etc., more preferably, the buffer, inorganic acid or salt thereof and / or Alternatively, the durability can be similarly improved by containing an organic acid at a concentration of about 0.01 wt% to 10 wt% with respect to the adhesive component. After the film which is a transparent protective layer and the polarizing element of this invention are bonded together with the said adhesive agent, it can adhere | attach by heat-drying and also heat-processing.

  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, for example, the viewing angle is improved on the surface of a protective layer or film that will be an unexposed surface later and / or Various functional layers for improving contrast, and a layer or film having brightness enhancement can also be provided. In order to bond the polarizing plate to these films and display devices, it is preferable to use an adhesive.

  This 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 film. In order to produce a layer having various functions, it is preferable to provide the other surface by a coating method, but a film having the function can be bonded via an adhesive or a pressure-sensitive adhesive. The various functional layers can be a layer or a film for controlling the phase difference.

By the method described above, a polarizing element or polarizing plate having a constant transmittance at each wavelength and having high contrast can be obtained. The polarizing element or polarizing plate of the present invention thus obtained has high polarization performance, that is, high contrast, and can maintain a constant wavelength transmittance in the visible range, and is excellent in durability, and thus stable for a long time. The performance can be maintained.
<Liquid crystal display device>
Furthermore, 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 or the like. In particular, a liquid crystal display device can be obtained by bonding the polarizing plate of the present invention to both sides of a liquid crystal cell constituting a liquid crystal display with an adhesive together with a retardation film as necessary.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these.

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

  Each of the spectral transmittances Ts, Tp and Tc was measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.].

  The visibility corrected single transmittance Ys was calculated from the single transmittance Ts measured at predetermined wavelength intervals dλ (here, 5 nm) in the wavelength region of 400 to 700 nm by the following equation (8). In the equation, Pλ represents a spectral distribution of standard light (C light source), and yλ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).

  The visibility corrected parallel transmittance Yp was calculated by the following equation (9) from the parallel transmittance Tp measured at predetermined wavelength intervals dλ (here, 5 nm) in the wavelength region of 400 to 700 nm. In the equation, Pλ represents a spectral distribution of standard light (C light source), and yλ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).

  Visibility corrected orthogonal transmittance Yc was calculated by the following equation (10) from orthogonal transmittance Tc measured at predetermined wavelength intervals dλ (here, 5 nm) in the wavelength region of 400 to 700 nm. In the equation, Pλ represents a spectral distribution of standard light (C light source), and yλ represents a color matching function based on JIS Z 8729 (C light source 2 ° visual field).

  The degree of polarization Py was obtained by the following equation (11) from the visibility corrected parallel transmittance Yp and the visibility corrected orthogonal transmittance Yc.

Example 1
A polyvinyl alcohol film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 μm, a polymerization degree of 5500, and a saponification degree of 99% or more was swollen with hot water at 40 ° C., and then 1000 parts by weight of water, international publication number WO2005 / 015275 Treated with an aqueous solution containing 0.02 part by weight of the dye having the structure of formula (1) described in Example 1 and 1.0 part by weight of sodium tripolyphosphate for 1 minute 30 seconds, followed by 1000 parts by weight of water and boric acid An aqueous solution containing 28.6 parts by weight (manufactured by Societa ladderero spa), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku), and 10.27 parts by weight of potassium iodide (manufactured by Junsei Chemical). The dyeing process was performed by immersion for 2 minutes at 30 ° C. A dyed film is stretched 5 times at 58 ° C. in a solution containing 3% by weight of boric acid, and after stretching, 3.5 parts by weight of potassium iodide is added to 1000 parts by weight of water. In the iodide-containing aqueous solution, while maintaining the tension after stretching, the stretching ratio is maintained, and the difference in the relative speed between the transport speed at which the film is processed and the speed of the water flow in the processing step is almost constant, and the frequency is 20 kHz to 40 kHz. The film was immersed while applying the ultrasonic wave, and the post-treatment process was performed for 20 seconds. The film soaked with an aqueous potassium iodide solution for 20 seconds was then dried for 10 minutes with a dryer at 70 ° C. to obtain a polarizing element.

Example 2
A polyvinyl alcohol film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 μm, a polymerization degree of 4000, and a saponification degree of 99% or more, and a polyvinyl alcohol film (made by Kuraray Co., Ltd.) having a thickness of 40 μm, a polymerization degree of 4000, and a saponification degree of 99% or more. A polarizing element of the present application was obtained in the same manner as in Example 1 except that (VF-PH) was used.

Example 3
A polarizing element was obtained in the same manner as in Example 2 except that the time for the dyeing treatment was 1 minute 30 seconds.

Example 4
A polarizing element was obtained in the same manner as in Example 1 except that the time for the dyeing treatment was 1 minute 30 seconds.

Example 5
A polyvinyl alcohol film (VF-PM manufactured by Kuraray Co., Ltd.) having a thickness of 60 μm, a polymerization degree of 5500, and a saponification degree of 99% or more was swollen with hot water at 40 ° C., and then 1000 parts by weight of water, international publication number WO2005 / 015275 Treated with an aqueous solution containing 0.02 part by weight of the dye having the structure of formula (1) described in Example 1 and 1.0 part by weight of sodium tripolyphosphate for 1 minute 30 seconds, followed by 1000 parts by weight of water and boric acid In an aqueous solution containing 28.6 parts by weight (manufactured by Societa ladderero spa), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku), and 10.27 parts by weight of potassium iodide (manufactured by Junsei Kagaku). The dyeing process was performed by immersion for 2 minutes at 30 ° C. The dyed film is stretched 5 times at 58 ° C. in a solution containing 3% by weight of boric acid. After stretching, the film is processed while maintaining the tension after stretching and maintaining the stretching ratio. The difference in relative speed between the speed and the speed of the water flow in the treatment process was immersed in a substantially constant state, and the post-treatment process was performed for 20 seconds. Then, it dried for 10 minutes with the 70 degreeC dryer, and obtained the polarizing element.

Comparative Example 1
1000 parts by weight of water, International Publication No. WO2005 / 015275 Without treatment with an aqueous solution containing a dye having the structure of formula (1) described in Synthesis Example 1, 1000 parts by weight of water and boric acid (Societa laddereros 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of P. a.), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku) and 10.27 parts by weight of potassium iodide (manufactured by Junsei Kagaku). The film was stretched and dyed, and after stretching, the stretched ratio was maintained while stirring an aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water at a speed of 60 rpm. A polarizing element was obtained in the same manner as in Example 1 except that the post-treatment step was performed for 20 seconds.

Comparative Example 2
1000 parts by weight of water, International Publication No. WO2005 / 015275 Without treatment with an aqueous solution containing a dye having the structure of formula (1) described in Synthesis Example 1, 1000 parts by weight of water and boric acid (Societa laddereros 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of P. a.), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku) and 10.27 parts by weight of potassium iodide (manufactured by Junsei Kagaku). While being immersed for dyeing, and after stretching, an aqueous solution prepared by adding 35 parts by weight of potassium iodide to 1000 parts by weight of water is stirred at a speed of 60 rpm while maintaining the magnification after stretching. A polarizing element was obtained in the same manner as in Example 2 except that the post-treatment process was performed for 20 seconds.

Comparative Example 3
1000 parts by weight of water, International Publication No. WO2005 / 015275 Without treatment with an aqueous solution containing a dye having the structure of formula (1) described in Synthesis Example 1, 1000 parts by weight of water and boric acid (Societa laddereros 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of P. a.), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku) and 10.27 parts by weight of potassium iodide (manufactured by Junsei Kagaku). The film was stretched and dyed, and after stretching, the ratio after stretching was maintained while stirring an aqueous solution prepared by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water at a speed of 60 rpm. A polarizing element was obtained in the same manner as in Example 3 except that the post-treatment step was performed for 20 seconds.

Comparative Example 4
1000 parts by weight of water, International Publication No. WO2005 / 015275 Without treatment with an aqueous solution containing a dye having the structure of formula (1) described in Synthesis Example 1, 1000 parts by weight of water and boric acid (Societa laddereros 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of P. a.), 0.14 parts by weight of iodine (manufactured by Junsei Kagaku) and 10.27 parts by weight of potassium iodide (manufactured by Junsei Kagaku). The film was stretched and dyed, and after stretching, the ratio after stretching was maintained while stirring an aqueous solution prepared by adding 50 parts by weight of potassium iodide to 1000 parts by weight of water at a speed of 60 rpm. A polarizing element was obtained in the same manner as in Example 4 except that the post-treatment step was performed for 20 seconds.

Comparative Example 5
The iodine polarizing plate SKN-18242P manufactured by Polatechno Co., Ltd. was immersed in dichloromethane, and the polarizing element was extracted as a comparative sample.

Comparative Example 6
1000 parts by weight of water, International Publication No. WO2005 / 015275 Without treatment with an aqueous solution containing a dye having the structure of formula (1) described in Synthesis Example 1, 1000 parts by weight of water and boric acid (Societa laddereros 2) at 30 ° C. with an aqueous solution containing 28.6 parts by weight of iodine (made by Pa.), 0.25 parts by weight of iodine (made by Junsei Chemical), and 17.7 parts by weight of potassium iodide (made by Junsei Chemical). A polarizing element was obtained in the same manner as in Example 5, except that the film was immersed for a minute and dyed, and after stretching, the film was immersed in water and treated for 20 seconds.

Comparative Example 7
1000 minutes by weight of water, International Publication No. WO2005 / 015275 3 minutes 00 seconds in an aqueous solution containing 0.1 parts by weight of the dye having the structure of formula (1) described in Synthesis Example 1 and 1.0 part by weight of sodium tripolyphosphate A polarizing element was produced in the same manner as in Example 1 except that the treatment was performed. The obtained polarizing plate was visually colored yellow.

Table 1 shows parameters of the polarizing elements obtained in Examples 1 to 5 and Comparative Examples 1 to 7. The parameters shown in Table 1 are as follows.
Visibility correction single transmittance Ys,
Visibility correction parallel transmittance Yp,
Visibility correction orthogonal transmittance Yc,
460 nm single transmittance Ts ₄₆₀ ,
460 nm parallel transmittance Tp ₄₆₀ when two substrates are measured parallel to the absorption axis direction,
460 nm orthogonal transmittance Tc ₄₆₀ when two substrates are measured perpendicular to the absorption axis direction,
Single transmittance Ts _{550 of 550} nm,
610 nm single transmittance Ts ₆₁₀ ,
610 nm orthogonal transmittance Tc ₆₁₀ when two substrates are measured perpendicular to the absorption axis direction,
Average value of single transmittances from 430 nm to 480 nm Ts Ave 430-480,
Average value Tp Ave 430-480 of transmittance at a parallel position of 430 nm to 480 nm when two substrates are measured parallel to the absorption axis direction,
Average value Tc Ave 430-480 of the transmittance at the orthogonal position of 430 nm to 480 nm when two substrates are measured perpendicular to the absorption axis direction.

Further parameters obtained for Examples 1 to 5 and Comparative Examples 1 to 7 are shown in Table 2. The parameters shown in Table 2 are as follows.
Parallel transmittance Tp _{255 of 255} nm obtained by measuring two substrates parallel to the absorption axis direction,
An orthogonal transmittance Tc _{255 of 255} nm obtained by measuring two substrates orthogonally to the absorption axis direction,
₂₉₅ nm parallel transmittance Tp ₂₉₅ obtained by measuring two substrates parallel to the absorption axis direction,
₂₉₅ nm orthogonal transmittance Tc ₂₉₅ obtained by measuring two substrates orthogonal to the absorption axis direction,
A parallel transmittance Tp _{360 of 360} nm obtained by measuring two substrates in parallel with the absorption axis direction;
An orthogonal transmittance Tc _{360 of 360} nm obtained by measuring two substrates perpendicular to the absorption axis direction.

As can be seen from 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 corrected single transmittance Ys when measured alone is 40.0. % To 42.5%, the difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{460 at 460} nm is within 1.2%, and the visibility corrected single transmittance Ys and the single transmittance Ts at 550 nm are within a range of 1.2%. The difference from the ₅₅₀ is within 1%, the difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{610 at 610} nm is within 1%, and the two substrates are orthogonal to the absorption axis direction. The visibility-corrected orthogonal transmittance Yc obtained by measuring in this manner is 0.01% or less, and the orthogonal transmittance of 430 nm to 480 nm obtained by measuring the two base materials perpendicular to the absorption axis direction. Average value Tc Ave 430-480 is 0.0 It can be seen that it is 3% or less.
In addition, a polarizing plate can be obtained by laminating a polarizing element with a protective layer, but when the polarizing elements of Examples 1 to 5 are installed in parallel to the absorption axis, the transmittance of 430 nm to 480 nm is 500 nm to Compared with the transmittance of 650 nm, the optical characteristics were almost constant, and the light emission uniformity at each wavelength could be maintained. Furthermore, since the visibility corrected orthogonal transmittance Yc is 0.01% or less and the average value Tc Ave 430-480 of the orthogonal transmittance of 430 nm to 480 nm is 0.03% or less, It was found that the polarizing element is a polarizing element or a polarizing plate having a high contrast and having a constant wavelength transmittance in the visible range.
Therefore, the polarizing elements of Examples 1 to 5 obtained by the above method or the polarizing plates produced using these polarizing elements have a high transmittance, a high contrast ratio, and a very high color reproducibility. It can be used as a polarizing plate for a liquid crystal display, particularly as a polarizing plate for a liquid crystal display. In addition, a display using this is expected to be a display having high reliability, capable of maintaining high contrast over a long period of time, and having high color reproducibility.

Claims (11)

A polarizing element comprising a base material having a polarizing function comprising a hydrophilic polymer adsorbed with boric acid and stretched, and containing iodine,
In the form of the free acid, formula (1):

(In Formula (1), R ₁ represents a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxyl group, or a carboxyl group, and k, m, and n each independently represent 0 or 1, provided that m + n> 1. is there.)
Containing an organic compound represented by
When the substrate is measured alone, the visibility corrected single transmittance Yc is 40.0% to 42.5%,
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{460 at 460} nm is within 1.2%,
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{550 at 550} nm is within 1%.
The difference between the visibility corrected single transmittance Ys and the single transmittance Ts _{610 at 610} nm is within 1%,
Visibility corrected orthogonal transmittance when the two substrates are measured perpendicular to the absorption axis direction is 0.01% or less,
A polarizing element characterized in that an average value Tc Ave 430-480 of orthogonal transmittances of 430 nm to 480 nm when the two substrates are measured perpendicular to the absorption axis direction is 0.03% or less. Visibility corrected parallel transmittance Yp when the two substrates are measured parallel to the absorption axis direction is in the range of 33% to 37%,
The parallel transmittance Yp of the substrate and the transmittance Tp _{255 of 255} nm when the two base materials are measured parallel to the absorption axis direction are expressed by the following formula (2):
_{0.75 × Yp-13 ≦ Tp 255} ≦ 0.75 × Yp + 1.0 ··· formula (2)
The polarizing element according to claim 1, wherein: Visibility corrected parallel transmittance Yp when the two substrates are measured parallel to the absorption axis direction is in the range of 33% to 37%,
The parallel transmittance Yp and the transmittance Tc _{255 of 255} nm when the two substrates are measured perpendicular to the absorption axis direction are expressed by the following formula (3):
2.0 × 10 ⁻⁶ × Yp ^4.1 ≦ Tc ₂₅₅ ≦ 2.0 × 10 ⁻⁶ × Yp ^4.4 Formula (3)
The polarizing element according to claim 1, wherein: Visibility corrected parallel transmittance Yp when the two substrates are measured parallel to the absorption axis direction is in the range of 33% to 37%,
The difference between the parallel transmittance Yp and the parallel transmittance Tp ₄₆₀ of 460 nm when the two substrates are measured parallel to the absorption axis direction is within 3%. The polarizing element as described in any one of 1 thru | or 3. When the two base materials are measured in parallel with the absorption axis direction, the visibility correction transmittance Yp is in the range of 33% to 37%,
The parallel transmittance Yp and the transmittance Tp _{295 of 295} nm when the two substrates are measured in parallel with the absorption axis direction satisfy the following formula (4):
The parallel transmittance Yp and a transmittance Tp _{360 of 360} nm when the two base materials are measured parallel to the absorption axis direction satisfy the following formula (5): The polarizing element as described in any one of 1 thru | or 4.
1.05 × Yp−26 ≦ Tp ₂₉₅ ≦ 1.05 × Yp−13 Formula (4)
1.25 × Yp−26.25 ≦ Tp ₃₆₀ ≦ 1.25 × Yp−16.25 Formula (5) A transmittance Tc _{295 of 295} nm when the two substrates are measured perpendicular to the absorption axis direction satisfies the formula (6), and
The transmittance Tc _{360 of 360} nm when the two base materials are measured in parallel with the absorption axis direction satisfies the formula (7), according to any one of claims 1 to 5. The polarizing element as described.
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 transmittance Tc _{460 at 460} nm when the two substrates are measured perpendicular to the absorption axis direction is 0.035% or less, and
7. The transmittance Tc _{610 at 610} nm when the two substrates are measured perpendicular to the absorption axis direction is 0.01% or less, according to claim 1. The polarizing element as described. The substrate is made of a polyvinyl alcohol resin film,
The polarizing element according to any one of claims 1 to 7, wherein the degree of polymerization of the polyvinyl alcohol-based resin film is 3000 to 7000.   The polarizing plate which provides a support body film in the at least single side | surface of the polarizing element as described in any one of Claims 1-8.   A liquid crystal display device comprising the polarizing element according to claim 1 or the polarizing plate according to claim 9. A method for producing a polarizing element comprising a base material having a polarizing function comprising a hydrophilic polymer that has been adsorbed with boric acid and stretched, and containing iodine,
(I) adding a dichroic dye to the polyvinyl alcohol-based resin film and obtaining a film containing the dichroic dye;
(Ii) stretching the film containing the dichroic dye to obtain a stretched film;
(Iii) subjecting the stretched film to a post-treatment using a chloride-containing solution or an iodide-containing solution;
(Iv) after the post-treatment, drying the film to obtain the substrate,
The concentration of the chloride-containing solution or iodide-containing solution is 0.1 to 15% by weight,
Following formula (1):

The manufacturing method characterized by further including the process of containing these organic compounds.