Achromatic polarizing plate with high-transmissivity and high-degree of polarization

Abstract

This achromatic polarizing plate has a high transmissivity, while expressing an achromatic white color when the absorption axes of the polarizing elements are positioned in parallel, and expressing an achromatic black color when the absorption axes of the polarizing elements are positioned orthogonally to one another. This polarizing element contains at least two specific azo compounds, and the absolute value of the difference between the average transmissivity of 420 nm to 480 nm light and the average transmissivity of 520 nm to 590 nm light is equal to or less than 2.5, and the absolute value of the difference between the average transmissivity of 520 nm to 590 nm light and the average transmissivity of 590 nm to 640 nm light is equal to or less than 2.0.

Claims

1. A polarizing element, comprising an azo compound represented by formula (1) or a salt thereof and an azo compound represented by formula (2) or a salt thereof, wherein the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is equal to or less than 2.5%, and the absolute value of the difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 590 nm to 640 nm is equal to or less than 2.0% , wherein each wavelength transmittance is obtained using two of said polarizing elements in which their absorption axes are positioned in parallel: ##STR00017## wherein A.sub.1 represents a phenyl group or a naphthyl group having a substituent, R.sub.1 to R.sub.4 each independently represent any of a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, X.sub.1 represents an amino group that may have a substituent, and k represents an integer of 0 or 1; and ##STR00018## wherein A.sub.2 and A.sub.3 each independently represent a naphthyl group or a phenyl group having one or more substituents, at least one of the substituents is a sulfo group, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfo group, a carboxy group, a nitro group, an amino group, or a substituted amino group, and R.sub.5 and R.sub.6 each independently represent any of a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group.

2. The polarizing element according to claim 1, wherein, in value a* and value b* obtained according to JIS Z 8729, the absolute values of value a* and value b* when single body transmittances are measured are equal to or less than 1, and the absolute values of value a* and value b* obtained using two of said polarizing elements in which their absorption axes are positioned in parallel are equal to or less than 2.

3. The polarizing element according to claim 1, wherein a single body transmittance of said polarizing element is between 35% and 60%, and in each wavelength transmittance obtained using two of said polarizing elements in which their absorption axes are positioned in parallel, the average transmittance at 520 nm to 590 nm is between 25% and 55%.

4. The polarizing element according to claim 1, wherein the polarizing element comprises at least one azo compound represented by the following formula (3) or a salt thereof and at least one azo compound represented by the following formula (4) or a salt thereof as azo compounds represented by formula (1) or salts thereof: ##STR00019## wherein A.sub.4 represents a phenyl group or a naphthyl group having a substituent, R.sub.7 and R.sub.8 each independently represent any of a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and X.sub.2 represents a phenyl amino group that may have a substituent, or a benzoyl amino group that may have a substituent; and ##STR00020## wherein A.sub.5 represents a phenyl group or a naphthyl group having a substituent, R.sub.9 to R.sub.12 each independently represent any of a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, R.sub.13 and R.sub.14 each independently represent any of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group, except that all of R.sub.9 to R.sub.12 are simultaneously lower alkoxy groups.

5. The polarizing element according to claim 4, wherein X.sub.2 in formula (3) is a phenyl amino group that may have a substituent, and the substituent of the phenyl group is any of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, or an amino group.

6. The polarizing element according to claim 4, wherein at least one of R.sub.13 and R.sub.14 in formula (4) is any of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, or an amino group.

7. The polarizing element according to claim 4, wherein A.sub.4 in formula (3) is a phenyl group having any substituent from among a methyl group, a methoxy group, a sulfo group, an amino group, or a benzoyl group.

8. The polarizing element according to claim 4, wherein As in formula (4) is a phenyl group having any substituent from among a methyl group, a methoxy group, a sulfo group, an amino group, or a benzoyl group.

9. The polarizing element according to claim 4, wherein at least one of R.sub.11and R.sub.12 in formula (4) is a methoxy group.

10. The polarizing element according to claim 4, wherein at least one of R.sub.9 and R.sub.10 in formula (4) is a methoxy group.

11. The polarizing element according to claim 1, wherein the polarizing element further comprises an azo compound represented by the following formula (5) or a salt thereof in addition to the azo compound represented by formula (1) or a salt thereof and the azo compound represented by formula (2) or a salt thereof: ##STR00021## wherein R.sub.15 and R.sub.16 each independently represent any of a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxyl group, and n represents an integer from 1 to 3.

12. The polarizing element according to claim 11, wherein the polarizing element comprises an azo compound represented by formula (3) or a salt thereof and an azo compound represented by formula (4) or a salt thereof as azo compounds represented by formula (1) or salts thereof.

13. The polarizing element according to claim 1, wherein, in each wavelength transmittance obtained using two of said polarizing elements in which their absorption axes are positioned orthogonally, the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is equal to or less than 0.3%, and the absolute value of the difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 600 nm to 640 nm is equal to or less than 0.3%.

14. The polarizing element according to claim 1, wherein the absolute values of value a* and value b* obtained using two of said polarizing elements in which their absorption axes are positioned orthogonally are equal to or less than 2.

15. The polarizing element according to claim 1, wherein A.sub.2 and A.sub.3 in formula (2) are each independently a naphthyl group having two or more sulfo groups.

16. The polarizing element according to claim 1, wherein at least one of R.sub.5 and R.sub.6 in formula (2) is a methyl group.

17. The polarizing element according to claim 1, wherein the substrate is comprised of a polyvinyl alcohol resin film.

18. The polarizing element according to claim 1, wherein the polarizing element has a single body transmittance between 35% and 60%and has a degree of polarization greater than or equal to the value obtained by formula (6):
y=0.0906Ys.sup.2+5.97Ysformula (6) wherein Ys represents a single body transmittance and y represents a degree of polarization.

19. A polarizing plate, made by providing a protection film on at least one surface of the polarizing element according to claim 1.

20. A liquid crystal display, employing the polarizing plate according to claim 19.

21. A liquid crystal display, employing the polarizing element according to claim 1.

Description

EXAMPLES

(1) Hereinafter, the present invention will be explained in greater detail according to the examples but not limited thereto. The transmittance shown in the examples will be evaluated as below.

(2) The transmittance at each wavelength when one polarizing element or one polarizing plate is used was defined as transmittance Ts, the transmittance when two polarizing elements or two polarizing plates were overlapped such that the absorption axes thereof were positioned on the same direction was defined as parallel position transmittance Tp, and the transmittance when two polarizing plates were overlapped such that the absorption axes thereof were positioned orthogonally was defined as orthogonal position transmittance Tc.

(3) Within the wavelength range of 400 to 700 nm, spectral transmittance was obtained for each predetermined wavelength interval d (here, 5 nm) and Ys was calculated in formula (8) below by using the . In the formula, P represents the spectral distribution of standard light (C light source), and y represents the y () color-matching function in a two degree view. Single body transmittance corrected according to visibility Ys was calculated using Ts for , parallel position transmittance corrected according to visibility Yp was calculated using Tp for , and orthogonal position transmittance corrected according to visibility Yc was calculated using Tc for .

(4) $\begin{array}{cc}\mathrm{Ys}=\frac{{}_{400}^{700}P.Math.y.Math..Math.d}{{}_{400}^{700}P.Math.y.Math.d}& \mathrm{Formula}\left(8\right)\end{array}$

(5) Spectral transmittance was obtained using a spectral photometer (U-4100 manufactured by Hitachi Ltd.).

(6) Degree of polarization y was obtained from parallel transmittance Yp and orthogonal transmittance Yc in formula (9).
y={(YpYc)/(Yp+Yc)}.sup.1/2100formula (9)

Example 1

(7) A polyvinyl alcohol film (VF-PS, manufactured by KURAREY CO., LTD.), which has an average degree of polymerization of 2400 and a degree of saponification greater than or equal to 99%, was immersed in warm water at 45 C. for two minutes, the swelling treatment was applied thereto so that a draw ratio thereof became 1.30-fold. For a dyeing step, the swelling-treated film was immersed for four minutes 00 second in a liquid at 45 C. comprising 2000 parts by weight of water, 2.0 parts by weight of anhydrous sodium sulfate, 0.34 parts by weight of the azo compound described in Synthesis Example 1 of International Publication No. WO2012/165223 as an azo compound represented by formula (2), 0.027 parts by weight of the azo compound described in Synthesis Example 1 of JP 2003-215338 A as an azo compound represented by formula (3), 0.040 parts by weight of the azo compound described in Example 1 of JP 2622748 B as an azo compound represented by formula (4), and 0.16 parts by weight of C. I. Direct Orenge 39 as an azo compound represented by formula (5) to allow the film to comprise the azo compounds. The obtained film was immersed for one minute in an aqueous solution at 40 C. comprising a 20 g/l boric acid (manufactured by Societa Chimica Larderello s.p.a.). The obtained film was drawing-treated at 50 C. in an aqueous solution comprising 30.0 g/l boric acid for five minutes, while being drawn 5.0-fold. The obtained film was treated in water at 25 C. for 20 seconds while maintaining the state of tension thereof. The obtained film was drying-treated at 70 C. for nine minutes to obtain a polarizing element of the present invention. A triacetylcellulose film (ZRD-60, manufactured by FUJIFILM Holdings Corporation) that was alkali-treated using a polyvinyl alcohol adhesive was laminated on the obtained polarizing element to obtain a polarizing plate. The obtained polarizing plate maintains the function of the polarizing element of the present invention. The polarizing plate was defined as a measurement sample of Example 1.

Example 2 to Example 4, and Examples 7 to 9

(8) In the dyeing step, polarizing elements were obtained in the same manner as Example 1 with the dying time variously changed, and then polarizing plates of the present invention were made.

Example 5

(9) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the liquid comprising the azo compounds in the dyeing step was changed to a liquid comprising 2000 parts by weight of water, 2.0 parts by weight of anhydrous sodium sulfate, 0.34 parts by weight of the azo compound described in WO2012/165223, Composition Example 1 as an azo compound represented by formula (2), 0.027 parts by weight of the azo compound described in Composition Example 1 of JP 2003-215338 A as an azo compound represented by formula (3), 0.078 parts by weight of the azo compound described in JP 2622748 B, Example 3 as an azo compound represented by formula (4), and 0.145 parts by weight of the azo compound described in Example 1 of WO2007/138980 as an azo compound represented by formula (5).

Example 6

(10) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the liquid comprising the azo compounds in the dyeing step was changed to a liquid comprising 2000 parts by weight of water, 2.0 parts by weight of anhydrous sodium sulfate, 0.34 parts by weight of the azo compound described in Composition Example 1 of WO2012/165223 as an azo compound represented by formula (2), 0.080 parts by weight of the azo compound described in Composition Example 1 of JP 4033443 B as an azo compound represented by formula (3), 0.040 parts by weight of the azo compound described in Example 1 of JP 2622748 B as an azo compound represented by formula (4), and 0.16 parts by weight of C. I. Direct Orenge 39 as an azo compound represented by formula (5).

Example 10

(11) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to C. I. Direct Red 81 (same parts by weight) known as an azo compound similarly expressing red.

Example 11

(12) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to C. I. Direct Red 117 (same parts by weight) known as an azo compound similarly expressing red.

Example 12

(13) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as azo compound represented by formula (3) was changed to the azo compound (same parts by weight) described in JP 3661238 B (IIIa-6), which is an azo compound similarly expressing red.

Example 13

(14) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to the azo compound (same parts by weight) represented by formula (3) of JP 2002-105348 A, which is an azo compound, which has a similar structure to the previous azo compound.

Example 14

(15) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to the azo compound (same parts by weight) represented by formula (6) of W02007-148757, which has a similar structure to the previous azo compound.

Example 15

(16) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to the azo compound (same parts by weight) represented by formula (34) of WO2009-142193, which has a similar structure to the previous azo compound.

Example 16

(17) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (2) was changed to 0.45 parts by weight of the azo compound described in Compound Example 27 of International Publication No. WO2012/165223.

Example 17

(18) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (5) was changed to 0.21 parts by weight of C. I. Direct Yellow 28, which is also a dichroism pigment with its highest absorption wavelength at 400 nm to 500 nm.

Example 18

(19) The polarizing element and polarizing plate of the present invention were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (5) was changed to 0.30 parts by weight of C. I. Direct Orange 72, which also has its highest absorption wavelength at 400 nm to 500 nm.

Comparative Example 1

(20) SHC-115, which is a neutral gray high transmittance dye polarizing plate manufactured by Polatechno Co., Ltd., was obtained and used as a measurement sample.

Comparative Example 2

(21) SHC-128, which is a neutral gray dye polarizing plate with high contrast manufactured by Polatechno Co., Ltd., was obtained and used as a measurement sample.

Comparative Example 3 to Comparative Example 6

(22) A polarizing plate was obtained in the same manner as Example 1, except that an iodic polarizing plate was created without azo compounds by arbitrarily changing time for immersing the film into a liquid comprising iodine in accordance with the prescription described in Comparative Example 1 of JP 2008-065222 A, and then used as a measurement sample.

Comparative Example 7

(23) SKN-18242P, which is a neutral gray iodic polarizing plate with super high contrast manufactured by Polatechno Co., Ltd., was obtained and used as a measurement sample.

Comparative Example 8

(24) SKN-18241P, which is a neutral gray iodic polarizing plate with super high contrast manufactured by Polatechno Co., Ltd., was obtained and used as a measurement sample.

Comparative Example 9

(25) SKW-18245P, which is an iodic polarizing plate expressing Paper White in the parallel position manufactured by Polatechno Co., Ltd., was obtained and used as a measurement sample.

Comparative Example 10

(26) Polarizing element and polarizing plate were obtained based on Example 1 of JP H11-218611 A, which describes a dye polarizing plate, and then used as measurement samples.

Comparative Example 11

(27) Polarizing element and polarizing plate were obtained based on Example 3 of JP 4162334 B, which describes a dye polarizing plate, and then used as measurement samples.

Comparative Example 12

(28) Polarizing element and polarizing plate were obtained based on Example 1 of JP 4360100 B, which describes a dye polarizing plate, and then used as measurement samples.

Comparative Example 13

(29) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to 0.087 parts by weight of C. I. Direct Red 80, which is an azo compound having a ureido skeleton with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black; and then used as a measurement sample.

Comparative Example 14

(30) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to 0.077 parts by weight of C. I. Direct Red 84, which is an azo compound having a ureido skeleton with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 15

(31) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to 0.055 parts by weight of C. I. Direct Red 7, which is an azo compound having a dianisidine skeleton with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 16

(32) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (3) was changed to 0.047 parts by weight of C. I. Direct Red 45, which is an azo compound having the same color dichroism, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 17

(33) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to 0.07 parts by weight of C. I. Direct Blue 6, which is an azo compound having a dianisidine skeleton with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 18

(34) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to 0.061 parts by weight of C. I. Direct Blue 15, which is an azo dye with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 19

(35) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (4) was changed to 0.052 parts by weight of C. I. Direct Blue 71, which a tris azo dye with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 20

(36) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (2) was changed to 0.40 parts by weight of C. I. Direct Blue 199, which is a direct dye with the same color, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

Comparative Example 21

(37) Polarizing element and polarizing plate were obtained in the same manner as Example 1, except that the azo compound used as an azo compound represented by formula (2) was changed to 0.415 parts by weight of C. I. Direct Blue 218, which a direct dye with the same color and a similar copperization dye, and that the polarizing element and polarizing plate were designed such that they expressed neutral gray as a single body, transmittance in the orthogonal position was more or less fixed, and the color thereof was black, and then used as a measurement sample.

(38) Table 1 shows, regarding the polarizing elements or polarizing plates obtained in Examples 1 to 18 and Comparative Examples 1 to 21, Ys, Yp, and Yc thereof, the average value of transmittance (Tp) at 420 nm to 480 nm (Ave 420 to 480), the average value of transmittance (Tp) at 520 nm to 590 nm (Ave 520 to 590), and the average value of transmittance (Tp) at 600 nm to 640 nm (Ave 600 to 640) when the absorption axes of two of each polarizing element or polarizing plate were positioned in parallel, and the average value of transmittance (Tc) at 420 nm to 480 nm (Ave 420 to 480), the average value of transmittance (Tc) at 520 nm to 590 nm (Ave 520 to 590), and the average value of 600 nm to 640 nm (Ave 600 to 640) when the absorption axes of two of each polarizing element or polarizing plate were positioned orthogonally.

(39) TABLE-US-00001 TABLE 1 Tp Tc Ys Yp Yc Ave 420-480 Ave 520-590 Ave 600-640 Ave 420-480 Ave 520-590 Ave 600-640 Example 1 47.52 37.71 7.480 37.540 37.536 37.901 7.213 7.217 7.375 Example 2 45.18 36.38 4.467 36.293 36.178 36.599 4.253 4.275 4.336 Example 3 39.24 30.57 0.223 30.784 30.626 31.643 0.218 0.263 0.208 Example 4 50.19 39.49 10.890 38.886 39.376 40.424 10.918 10.865 11.134 Example 5 44.87 35.97 4.288 35.992 35.920 36.807 4.334 4.411 4.387 Example 6 46.83 37.02 6.844 37.033 36.840 37.706 6.863 6.978 7.040 Example 7 58.20 46.31 21.439 46.299 46.105 47.050 21.539 21.389 21.399 Example 8 38.52 29.58 0.093 29.515 28.313 30.080 0.080 0.082 0.080 Example 9 37.10 27.52 0.012 27.619 27.315 28.090 0.001 0.001 0.001 Example 10 43.98 34.95 3.744 34.097 34.814 35.510 3.721 3.711 3.699 Example 11 43.65 34.78 3.344 33.817 34.517 35.210 3.307 3.299 3.256 Example 12 43.87 34.74 3.754 33.201 34.482 35.270 3.710 3.770 3.738 Example 13 44.23 35.54 3.590 33.792 35.290 36.110 3.603 3.601 3.621 Example 14 43.91 35.08 3.489 35.072 34.854 35.550 3.499 3.458 3.435 Example 15 43.20 34.10 3.218 33.010 33.910 34.690 3.187 3.199 3.159 Example 16 44.87 35.69 4.586 34.870 35.421 36.201 4.484 4.458 4.445 Example 17 45.01 35.39 5.130 33.752 35.185 35.874 5.109 5.090 5.050 Example 18 44.91 35.25 5.085 33.154 35.012 35.802 5.126 5.102 5.085 Comparative 43.15 35.79 1.450 33.009 30.005 36.250 1.831 1.533 0.834 Example 1 Comparative 39.10 30.58 0.022 26.061 30.891 31.670 0.027 0.022 0.011 Example 2 Comparative 40.66 33.08 0.003 27.371 33.272 34.687 0.001 0.001 0.002 Example 3 Comparative 41.54 34.52 0.005 29.388 34.633 35.978 0.006 0.003 0.003 Example 4 Comparative 42.09 35.44 0.004 29.533 36.617 37.067 0.007 0.003 0.003 Example 5 Comparative 42.94 36.88 0.008 31.768 37.144 38.283 0.011 0.003 0.010 Example 6 Comparative 42.40 35.98 0.004 31.618 36.693 37.315 0.019 0.004 0.001 Example 7 Comparative 40.95 33.54 0.001 28.730 33.682 34.969 0.003 0.001 0.000 Example 8 Comparative 44.87 39.43 0.848 36.329 39.479 39.650 6.129 0.821 0.022 Example 9 Comparative 40.28 31.02 1.432 26.160 30.802 31.254 1.699 1.209 1.182 Example 10 Comparative 41.32 33.15 0.989 23.981 32.915 33.852 0.864 0.753 0.715 Example 11 Comparative 41.31 33.40 0.726 29.084 33.181 35.252 0.606 0.589 0.515 Example 12 Comparative 44.36 30.48 8.879 26.405 30.166 32.985 8.972 8.565 8.123 Example 13 Comparative 44.35 31.39 7.952 26.842 31.407 34.252 7.985 7.681 7.252 Example 14 Comparative 43.55 28.95 8.975 24.216 28.953 32.059 8.925 8.761 8.710 Example 15 Comparative 43.25 31.05 6.357 25.981 30.815 33.895 6.875 6.153 6.105 Example 16 Comparative 43.25 31.90 5.513 27.546 31.651 32.895 5.556 5.299 5.215 Example 17 Comparative 44.56 30.46 9.256 26.584 30.185 31.985 9.251 9.152 9.183 Example 18 Comparative 45.21 32.18 8.697 25.613 31.804 32.859 8.684 8.053 7.654 Example 19 Comparative 44.90 24.63 15.687 22.562 24.235 25.615 14.103 14.985 13.525 Example 20 Comparative 44.18 30.23 8.811 26.352 30.352 31.562 8.662 8.458 8.354 Example 21

(40) Table 2 shows, regarding the polarizing elements or polarizing plates obtained in Examples 1 to 18 and Comparative Examples 1 to 21, the absolute value of the difference between the average value of transmittance (Tp) at 520 nm to 590 nm (Ave 520 to 590) and the average value of transmittance (Tp) at 420 nm to 480 nm (Ave 420 to 480), as well as the absolute value of the difference between the average value of transmittance (Tp) at 520 nm to 590 nm (Ave 520 to 590) and the average value of transmittance (Tp) at 600 nm to 640 nm (Ave 600 to 640) when the absorption axes of two of each polarizing element or polarizing plate were positioned in parallel, and the absolute value of the difference between the average value of transmittance (Tc) at 520 nm to 590 nm (Ave 520 to 590) and the average value of transmittance (Tc) at 420 nm to 480 nm (Ave 420 to 480), as well as the absolute value of the difference between the average value at 520 nm to 590 nm (Ave 520 to 590) and the average value of transmittance (Tc) at 600 nm to 640 nm (Ave 600 to 640) when the absorption axes of two of each polarizing element or polarizing plate were positioned orthogonally.

(41) TABLE-US-00002 TABLE 2 The absolute value of The absolute value of the difference from the the difference from the average value in Tp at average value in Tc at 520-590 nm in which two 520-590 nm in which two polarizing elements or polarizing elements or polarizing plates are polarizing plates are positioned in parallel positioned orthogonally Ave 420-480 Ave 600-640 Ave 420-480 Ave 600-640 Example 1 0.00 0.36 0.0046 0.1575 Example 2 0.12 0.42 0.0221 0.0607 Example 3 0.16 1.22 0.0452 0.0550 Example 4 0.39 1.05 0.0528 0.2687 Example 5 0.07 0.89 0.0773 0.0244 Example 6 0.19 0.87 0.1145 0.0620 Example 7 0.19 0.94 0.1500 0.0095 Example 8 0.20 0.77 0.0017 0.0017 Example 9 0.30 0.77 0.0000 0.0001 Example 10 0.82 0.70 0.0107 0.0120 Example 11 0.70 0.69 0.0081 0.0424 Example 12 1.28 0.79 0.0593 0.0314 Example 13 1.50 0.82 0.0013 0.0200 Example 14 0.22 0.70 0.0405 0.0231 Example 15 0.90 0.78 0.0120 0.0396 Example 16 0.55 0.78 0.0056 0.0131 Example 17 1.43 0.69 0.0194 0.0400 Example 18 1.86 0.79 0.0238 0.0169 Comparative 3.00 0.25 0.2982 0.6989 Example 1 Comparative 4.83 0.78 0.0046 0.0113 Example 2 Comparative 5.90 1.41 0.0001 0.0015 Example 3 Comparative 5.23 1.35 0.0047 0.0002 Example 4 Comparative 6.08 1.45 0.0043 0.0000 Example 5 Comparative 5.38 1.14 0.0075 0.0071 Example 6 Comparative 5.07 0.62 0.0148 0.0028 Example 7 Comparative 4.95 1.29 0.0023 0.0003 Example 8 Comparative 3.15 0.17 5.3086 0.7988 Example 9 Comparative 4.64 0.45 0.4903 0.0287 Example 10 Comparative 3.93 0.94 0.1111 0.0378 Example 11 Comparative 4.10 2.07 0.0169 0.0738 Example 12 Comparative 3.76 2.82 0.4073 0.4418 Example 13 Comparative 4.56 2.85 0.3040 0.4297 Example 14 Comparative 4.74 3.11 0.1636 0.0511 Example 15 Comparative 4.83 3.08 0.7225 0.0475 Example 16 Comparative 4.11 1.24 0.2575 0.0837 Example 17 Comparative 3.60 1.80 0.0989 0.0306 Example 18 Comparative 6.19 1.06 0.6316 0.3984 Example 19 Comparative 1.67 1.38 0.8825 1.4599 Example 20 Comparative 4.00 1.21 0.1940 0.1040 Example 21

(42) From Table 2, it is found that, according to the polarizing elements comprising azo compounds obtained from Examples 1 to 18, in each wavelength transmittance obtained using two of the polarizing elements or polarizing plates in which their absorption axes are positioned in parallel, the average transmittance at 520 nm to 590 nm is greater than or equal to 25%, the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is equal to or less than 2.5%, and the absolute value of the difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 590 nm to 640 nm is equal to or less than 2.0%. Further, in each wavelength transmittance obtained using two of the polarizing element or polarizing plate in which their absorption axes are positioned orthogonally, the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is equal to or less than 0.3%, and the absolute value of the difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 600 nm to 640 nm is equal to or less than 0.3%.

(43) Table 3 shows, regarding the polarizing elements or polarizing plates obtained in Examples 1 to 18 and Comparative Examples 1 to 21, Ys and y of each polarizing plate, value a* (a*s) and value b* (b*s) of a single body of each polarizing plate described according to light source in a two degree view in JIS Z8729 C, value a* (a*p) and value b* (b*p) obtained using two of each polarizing element or polarizing plate in which their absorption axes were positioned in parallel, and value a* (a*c), value b* (b*c) obtained using two of each polarizing element or polarizing plate in which their absorption axes were positioned orthogonally, all of which were obtained in Examples 1 to 18 and Comparative Examples 1 to 21. In addition, we heard opinions on the colors of the polarizing plates when it indicated white in the parallel position and the colors thereof when it indicated black in the orthogonal position from 10 observers, then we represent the most common opinions regarding the visually obtained colors.

(44) TABLE-US-00003 TABLE 3 Visual color of polarizing plate Ys py a*-s b*-s a*-p b*-p a*-o b*-o Parallel position Orthogonal position Example 1 47.52 81.87 0.34 0.26 0.29 0.19 0.80 0.99 White Black Example 2 45.18 86.46 0.33 0.16 0.31 0.07 0.89 0.97 White Black Example 3 39.24 99.27 0.31 0.12 0.41 0.11 0.66 0.49 White Black Example 4 50.19 76.34 0.22 0.06 0.18 0.09 0.51 0.20 White Black Example 5 44.87 88.71 0.19 0.06 0.01 1.02 0.21 0.92 White Black Example 6 46.83 82.95 0.17 0.26 0.72 0.21 0.32 0.65 White Black Example 7 58.20 60.59 0.28 0.41 0.08 0.62 0.71 0.72 White Black Example 8 38.52 99.69 0.35 0.34 0.25 0.53 0.41 0.56 White Black Example 9 37.10 99.95 0.17 0.08 0.21 0.62 0.63 0.22 White Black Example 10 43.98 89.80 0.14 0.82 0.56 1.87 0.12 1.65 White Black Example 11 43.65 90.80 0.18 0.66 0.24 1.90 0.56 1.35 White Black Example 12 43.87 89.72 0.20 0.56 0.44 1.62 0.81 1.79 White Black Example 13 44.23 90.36 0.16 0.61 0.31 1.69 0.35 1.21 White Black Example 14 43.91 90.50 0.82 0.37 1.73 1.25 0.33 0.21 White Black Example 15 43.20 90.97 0.23 0.47 1.06 1.48 0.22 0.98 White Black Example 16 44.87 87.88 0.28 0.46 1.52 1.46 0.92 0.92 White Black Example 17 45.01 86.42 0.19 1.13 0.64 1.48 0.14 1.45 White Black Example 18 44.91 86.48 0.34 0.82 0.99 1.87 0.01 1.88 White Black Comparative 43.13 96.03 0.47 1.63 0.47 3.53 2.59 3.84 Yellow Blue-green Example 1 Comparative 39.09 99.93 0.42 3.69 0.56 6.69 0.03 0.08 Yellow Black Example 2 Comparative 40.66 99.99 1.73 4.26 2.91 7.71 0.01 0.01 Yellow-green Black Example 3 Comparative 41.54 99.99 1.43 4.18 2.53 7.62 0.02 0.07 Yellow-green Black Example 4 Comparative 42.09 99.99 1.37 4.15 2.36 7.62 0.02 0.07 Yellow-green Black Example 5 Comparative 42.94 99.99 1.13 3.44 1.99 6.38 0.05 0.10 Yellow-green Black Example 6 Comparative 42.40 99.99 1.37 3.33 2.36 6.17 0.04 0.20 Yellow-green Black Example 7 Comparative 40.95 100.00 0.97 3.56 1.57 6.52 0.01 0.04 Yellow-green Black Example 8 Comparative 44.86 97.87 0.32 2.79 1.00 0.95 19.58 38.73 White Blue-purple Example 9 Comparative 40.28 95.49 0.45 2.13 0.48 6.88 0.69 0.63 Yellow Black Example 10 Comparative 41.32 97.08 0.49 4.65 0.21 7.28 0.55 0.15 Yellow Black Example 11 Comparative 41.31 97.85 0.81 8.36 1.20 11.26 0.36 0.95 Yellow Black Example 12 Comparative 44.36 74.08 4.00 7.07 7.98 8.92 0.10 0.32 Orange Black Example 13 Comparative 44.35 77.18 3.77 6.32 6.25 8.37 0.36 0.34 Orange Black Example 14 Comparative 43.55 72.57 2.99 5.87 5.63 7.36 0.51 0.58 Orange Black Example 15 Comparative 43.25 83.98 3.27 5.31 6.70 6.92 0.63 0.94 Orange Black Example 16 Comparative 44.25 83.98 1.38 6.20 3.06 7.08 0.31 0.67 Yellow-green Black Example 17 Comparative 44.56 73.06 0.97 6.91 2.30 8.19 0.37 0.68 Yellow-green Black Example 18 Comparative 45.21 75.80 2.22 7.57 4.68 9.26 0.69 0.49 Yellow-green Black Example 19 Comparative 44.90 47.10 7.82 2.57 15.69 3.55 1.89 0.21 Yellow-green Black Example 20 Comparative 44.18 74.07 1.91 2.76 4.10 5.96 0.52 0.37 Yellow-green Black Example 21

(45) From the results of Table 3, according to the polarizing elements of the present invention comprising the azo compounds represented by formula (1) and formula (2) or salts thereof, wherein the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is equal to or less than 2.5, and the absolute value of the difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 590 nm to 640 nm is equal to or less than 2.0, it is found that the present polarizing elements can express a high grade paper-like white using the absorption axes of the polarizing elements in parallel while having high transmittance, and express achromatic properties in the parallel position even at a high degree of polarization and high transmittance, with a color phase having a neutral color as a single body. Further, it is found that polarizing elements can be obtained which express a high-grade achromatic black when the absorption axes of the polarizing elements are positioned orthogonally.

(46) Durability Test

(47) When the polarizing plates according to Examples 1 to 18 and Comparative Examples 3 to 9 were applied in the environment at 85 C. with a relative humidity of 85% RH for 240 hours, the degrees of polarization of the polarizing plates in Comparative Examples 3 to 9 were lowered greater than or equal to 10%, b*c is lower than 10, the visual colors thereof were changed to blue, and particularly when the polarizing plates were positioned orthogonally, they strongly express blue. In contrast, the polarizing plates according to Examples 1 to 18 of the present application underwent no change in transmittance and color phase. This revealed that liquid crystal displays using the polarizing elements or polarizing plates of the present invention have high reliability, high contrast over the long term, and high color reproducibility.