Azo Compound Or Salt Thereof, And Dye-Based Polarizing Film And Dye-Based Polarizing Plate Containing Same

Abstract

An azo compound represented by the following formula (1) or a salt thereof, Wherein A.sup.1 represents a naphthyl group which may have a substituent; A.sup.2, A.sup.3, and A.sup.4 each independently represent a phenyl group which may have a substituent or a naphthyl group which may have a substituent; R.sup.1 represents a hydrogen atom, a hydroxy group, a C1-4 alkoxy group, or a substituted or unsubstituted amino group; m represents an integer of 0 to 5; M represents a hydrogen atom or ion, a metal ion, or an ammonium ion; n represents 1 or 2; k represents 0 or 1; and each hydrogen atom on ring a and ring b may be substituted with the substituent R.sup.1 or substituent SO.sub.3M.

##STR00001##

Claims

1. An azo compound represented by the following formula (1) or a salt thereof: ##STR00037## wherein A.sup.1 represents a naphthyl group which may have a substituent; A.sup.2, A.sup.3 and A.sup.4 each independently represent a phenyl group which may have a substituent or a naphthyl group which may have a substituent; R.sup.1 represents a hydrogen atom, a hydroxy group, a C1-4 alkoxy group or a substituted or unsubstituted amino group; m represents an integer of 0 to 5; M represents a hydrogen atom or ion, a metal ion, or an ammonium ion; n represents 1 or 2; k represents 0 or 1; and each hydrogen atom on ring a and ring b may be substituted with the substituent R.sup.1 or substituent SO.sub.3M.

2. The azo compound or a salt thereof according to claim 1, wherein A.sup.1 in the above formula (1) represents a naphthyl group having one or more substituents selected from the group consisting of a hydroxy group, a C1-4 alkoxy group having a sulfo group, and a sulfo group.

3. The azo compound or a salt thereof according to claim 1, wherein A.sup.2, A.sup.3 and A.sup.4 in the above formula (1) are each independently represented by the following formula (2) or formula (3), and at least one of A.sup.2, A.sup.3 and A.sup.4 is represented by the formula (2): ##STR00038## wherein R.sup.2 represents a hydrogen atom, a hydroxy group, a C1-4 aliphatic hydrocarbon group, a C1-4 alkoxy group, a substituted or unsubstituted amino group, or a C1-4 alkoxy group having a sulfo group; m.sup.2 represents an integer of 0 to 6; M represents a hydrogen atom or ion, a metal ion or an ammonium ion; and n.sup.3 represents an integer of 0 to 2, and ##STR00039## wherein R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a C1-4 aliphatic hydrocarbon group, a C1-4 alkoxy group, a C1-4 alkoxy group having a hydroxy group, or a C1-4 alkoxy group having a sulfo group.

4. The azo compound or a salt thereof according to claim 1, wherein A.sup.1 in the above formula (1) is represented by the following formula (4): ##STR00040## wherein n.sup.4 represents 1 or 2.

5. The azo compound or a salt thereof according to claim 1, wherein the above formula (1) is represented by the following formula (5): ##STR00041## wherein A.sup.1, A.sup.2, A.sup.3, A.sup.4, M, n and k are each the same as those in the above formula (1); and each hydrogen atom on ring a and ring b may be substituted with a substituent SO.sub.3M.

6. The azo compound or a salt thereof according to claim 1, wherein the above formula (1) is represented by the following formula (6): ##STR00042## wherein R.sup.5, R.sup.6 and R.sup.7 each independently represent a hydrogen atom, a hydroxy group, a C1-4 alkoxy group or a substituted or unsubstituted amino group; m.sup.3 to m.sup.5 each independently represent an integer of 0 to 5; M represents a hydrogen atom or ion, a metal ion or an ammonium ion; n.sup.5 and n.sup.6 each independently represent 1 or 2; and k.sup.1 represents 0 or 1.

7. A polarizing film, comprising at least one azo compound or a salt thereof according to claim 1.

8. The polarizing film according to claim 7, wherein at least one of wavelengths at which an absorbance ratio Rd (=A.sub.H/A.sub.L) of an absorbance (A.sub.H) on an axis giving the lowest transmittance of polarized light to an absorbance (A.sub.L) on an axis giving the highest transmittance of the polarized light indicates a value of 5 or higher is in 700 to 1,500 nm.

9. The polarizing film according to claim 7, further comprising one or more organic dyes other than the azo compound or the salt thereof.

10. The polarizing film according to claim 7, wherein the polarizing film exhibits neutral gray.

11. The polarizing film according to claim 7, using a film comprising a polyvinyl alcohol resin or a derivative thereof as a base material.

12. A polarizing plate, comprising a transparent protection layer on at least one surface of the polarizing film according to claim 7.

13. A display, comprising a polarizing film according to claim 7.

14. The display according to claim 13, wherein the display is used for vehicular usage or outdoor display usage.

15. A display, comprising a polarizing plate according to claim 12.

Description

EXAMPLES

[0104] Hereinafter, the present invention will be described in more detail by way of Examples, however these are exemplary and do not any more limit the present invention. The units “%” and “parts” in Examples are in terms of mass unless otherwise specified.

Example 1

(Step 1)

[0105] To 500 parts of water, 22.3 parts of 4-amino-1-naphthalenesulfonic acid was added, and dissolved by using a 25% sodium hydroxide; and thereafter, a 35% hydrochloric acid was added to adjust the pH to 0.2. To the obtained liquid, 17.3 parts of a 40% sodium nitrite aqueous solution was added to prepare a diazo liquid. Separately, to 200 parts of water, 22.3 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 122 parts of a wet cake of the monoazo compound represented by formula (28).

##STR00013##

(Step 2)

[0106] To 300 parts of water, 122 parts of the obtained wet cake of the monoazo compound (28) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 13.8 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 33.4 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 17.8 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 129 parts of a wet cake of the disazo compound represented by formula (29).

##STR00014##

(Step 3)

[0107] To 300 parts of water, 129 parts of the obtained wet cake of the disazo compound (29) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 9.7 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 23.3 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 10.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 6.5 to 8.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 28.6 parts of the azo compound represented by formula (7).

##STR00015##

<Production of a Polarizing Film and a Polarizing Plate>

[0108] A polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., VF-PS #7500) having a degree of saponification of 99% or higher and an average degree of polymerization of 2,400 was dipped in warm water at 45° C. to be applied to a swelling treatment, and stretched to a stretch ratio of 1.30 times. The swollen film was dipped for 10 min in a dyeing solution at 45° C. containing 1,500 parts by mass of water, 1.5 parts by mass of anhydrous mirabilite and 0.30 part by mass of the azo compound (7) to cause the film to contain the azo compound. The obtained film was dipped for 1 min in an aqueous solution at 40° C. containing 20 g/l boric acid (manufactured by Societa Chimica Larderello s.p.a). The film after the dipping was subjected for 5 min to a stretch treatment being stretched to 5.0 times in an aqueous solution at 50° C. containing 30.0 g/l of boric acid. The obtained film was dipped for 20 s in water at 25° C. with the stretched state being held to be subjected to a cleaning treatment. The film after the cleaning was dried at 70° C. for 9 min to obtain a polarizing film. An alkali-treated triacetylcellulose film (manufactured by Fujifilm Corp., TD-80) was laminated on the polarizing film by using, as an adhesive agent, a polyvinyl alcohol (manufactured by Japan VAM & Poval Co., Ltd., NH-26) dissolved in 4% in water, to obtain a polarizing plate. The obtained polarizing plate retained the optical performance, particularly the transmittance, the degree of polarization and the like, which the above polarizing film had. The polarizing plate was taken as a measuring sample of Example 1.

Example 2

(Step 1)

[0109] To 500 parts of water, 30.3 parts of 7-amino-1,3-naphthalenedisulfonic acid was added, and dissolved by using a 25% sodium hydroxide; and thereafter, a 35% hydrochloric acid was added to adjust the pH to 0.2. To the obtained liquid, 17.3 parts of a 40% sodium nitrite aqueous solution was added to prepare a diazo liquid. Separately, to 200 parts of water, 23.9 parts of 5-amino-1-naphthol-3-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 129 parts of a wet cake of the monoazo compound represented by formula (30).

##STR00016##

(Step 2)

[0110] To 300 parts of water, 129 parts of the obtained wet cake of the monoazo compound (30) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 12.1 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 29.2 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 15.6 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 110 parts of the wet cake of a disazo compound represented by formula (31).

##STR00017##

(Step 3)

[0111] To 300 parts of water, 110 parts of the obtained wet cake of the disazo compound (31) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 7.3 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 17.5 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 10.0 parts of 5-amino-1-naphthol-3-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 72.5 parts of a wet cake of the trisazo compound represented by formula (32).

##STR00018##

(Step 4)

[0112] To 300 parts of water, 72.5 parts of the obtained wet cake of the trisazo compound (32) was added, and stirred and suspended, and stirred at 70 to 75° C. for 3 days with the pH of the suspension liquid being held at 4.0 to 4.5 by using a 35% hydrochloric acid. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 8.7 parts of the azo compound represented by formula (9).

##STR00019##

<Production of a Polarizing Film and a Polarizing Plate>

[0113] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (9) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Example 2.

Example 31

(Step 1)

[0114] To 200 parts of water, 31.9 parts of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid was added, and dissolved by using a 25% sodium hydroxide; thereafter, 19.1 parts of 4-toluenesulfonyl chloride was dropped while keeping the pH at 10.5 to 11.0, and stirred to complete the reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 142 parts of a wet cake of the compound represented by formula (33).

##STR00020##

(Step 2)

[0115] To 300 parts of water, 142 parts of the obtained wet cake of the compound (33) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 15.5 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 37.5 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 20.1 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 148 parts of a wet cake of the monoazo compound represented by formula (34).

##STR00021##

(Step 3)

[0116] To 300 parts of water 148 parts of the obtained wet cake of the monoazo compound (34) was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 10.9 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 26.3 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 14.0 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 138 parts of a wet cake of the disazo compound represented by formula (35).

##STR00022##

(Step 4)

[0117] To 300 parts of water, 138 parts of the obtained wet cake of the disazo compound (35) was added, and stirred and suspended; the pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 7.6 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 18.4 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 150 parts of water, 14.1 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 6.5 to 8.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 74.6 parts of a wet cake of the trisazo compound represented by formula (36).

##STR00023##

(Step 5)

[0118] To 300 parts of water, 74.6 parts of the obtained wet cake of the trisazo compound (36) was added, and stirred and suspended, and stirred at 50 to 55° C. for 2 days with the pH of the suspension liquid being held at 10.0 to 10.5 by using a 25% sodium hydroxide. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 9.0 parts of the azo compound represented by formula (11).

##STR00024##

<Production of a Polarizing Film and a Polarizing Plate>

[0119] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (11) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Example 3.

Example 4

[0120] 8.5 parts of the azo compound represented by the following formula (13) was obtained in the same manner as Example 3, except for using 23.9 parts of I-amino-8-naphthol-4-sulfonic acid in place of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid.

##STR00025##

<Production of a Polarizing Film and a Polarizing Plate>

[0121] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (13) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Example 4.

Example 51

(Step 1)

[0122] To 300 parts of water, 138 parts of the obtained wet cake of the disazo compound (35) obtained in Example 3 was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 7.6 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 18.4 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 150 parts of water, 9.8 parts of 8-aminonaphthalene-2-sulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 4.5 to 6.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 86.3 parts of a wet cake of the trisazo compound represented by formula (37).

##STR00026##

(Step 2)

[0123] To 300 parts of water, 86.3 parts of the obtained wet cake of the trisazo compound (37) was added, and stirred and suspended, and stirred at 55 to 60° C. for 3 days with the pH being held at 10.0 to 10.5 by using a 25% sodium hydroxide. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 5.0 parts of the azo compound represented by formula (14).

##STR00027##

<Production of a Polarizing Film and a Polarizing Plate>

[0124] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (14) in place of the compound (7) used in production of the polarizing film in Example 1, and applying, in the stretch treatment, a stretch treatment in an aqueous solution at 50° C. containing 15.0 g/l of boric acid and 15.0 g/l of borax for 5 min, and was taken as a measuring sample of Example 5.

Example 6

[0125] 8.5 parts of an azo compound represented by the following formula (15) was obtained in the same manner as Example 3, except for using 13.8 parts of 2,5-dimethoxyaniline in place of 8-aminonaphthalene-2-sulfonic acid in the monoazo synthesis step.

##STR00028##

<Production of a Polarizing Film and a Polarizing Plate>

[0126] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (15) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Example 6.

Example 7

(Step 1)

[0127] To 300 parts of water, 86.3 parts of the obtained wet cake of the trisazo compound (37) obtained in Example 5 was added, and stirred and suspended. The pH of the suspension liquid was adjusted at 9.0 by using a 25% sodium hydroxide; and to the resultant, 7.6 parts of a 40% sodium nitrite aqueous solution was added. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 18.4 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 180 parts of water, 7.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 6.5 to 8.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered to obtain 27.6 parts of a wet cake of the tetrakisazo compound represented by formula (38).

##STR00029##

(Step 2)

[0128] To 200 parts of water, 27.6 parts of the obtained wet cake of the tetrakisazo compound (38) was added, and stirred and suspended, and stirred at 50 to 55° C. for 2 days with the pH of the suspension liquid being held at 10.0 to 10.5 by using a 25% sodium hydroxide. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 3.0 parts of the azo compound represented by formula (27).

##STR00030##

<Production of a Polarizing Film and a Polarizing Plate>

[0129] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (27) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Example 7.

Comparative Example 1

[0130] To 200 parts of water, 14 parts of 4-((4-aminophenyl)diazenyl)benzenesulfonic acid was added, and stirred and suspended. The pH was adjusted at 9.0 by using a 25% sodium hydroxide; and 9.1 parts of a 40% sodium nitrite aqueous solution was added to the resultant. The obtained suspension liquid was dropped in a mixed liquid of 100 parts of water and 20 parts of a 35% hydrochloric acid to prepare a diazo liquid. Separately, to 200 parts of water, 16.0 parts of 1,5-dihydroxynaphthalene was added, and was weakly alkalified with a 25% sodium hydroxide aqueous solution to be dissolved. To the resultant liquid, the previously obtained diazo liquid was dropped while keeping the pH at 6.5 to 8.0 and stirred to complete a coupling reaction. Thereafter, the resultant was salted out with sodium chloride, and thereafter filtered and dried to obtain 10.0 parts of the azo compound represented by formula (39).

##STR00031##

<Production of a Polarizing Film and a Polarizing Plate>

[0131] A polarizing plate was produced in the same manner as Example 1, except for using the above compound (39) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 1.

Comparative Example 2

<Production of a Polarizing Film and a Polarizing Plate>

[0132] A polarizing plate was produced in the same manner as Example 1, except for using the following compound (40) in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 2.

##STR00032##

Comparative Example 3

<Production of a Polarizing Film and a Polarizing Plate>

[0133] A polarizing plate was produced in the same manner as Example 1, except for using the following compound (41) described in Example 2 in JP 2003-64276 A in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 3.

##STR00033##

Comparative Example 4

<Production of a Polarizing Film and a Polarizing Plate>

[0134] A polarizing plate was produced in the same manner as Example 1, except for using the following compound (42) described in Example 2 in JP 60-168743 B in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 4.

##STR00034##

Comparative Example 5

<Production of a Polarizing Film and a Polarizing Plate>

[0135] A polarizing plate was produced in the same manner as Example 1, except for using the following compound (43) described in compound example No. 1 in JP 2001-56412 A in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 5.

##STR00035##

Comparative Example 6

<Production of a Polarizing Film and a Polarizing Plate>

[0136] A polarizing plate was produced in the same manner as Example 1, except for using the following compound (44) described in JP 11-269136 A in place of the compound (7) used in production of the polarizing film in Example 1, and was taken as a measuring sample of Comparative Example 6. However, the following compound (44) not only did not dissolve in water but also was not contained in a polyvinyl alcohol film; that is, the film did not function as a polarizing film.

##STR00036##

(Measurement of the Maximum Absorption Wavelength, the Transmittance and the Degree of Polarization of the Polarizing Plates)

[0137] For the polarizing plates obtained in Examples 1 to 7 and Comparative Examples 1 to 6, the maximum absorption wavelength, the single transmittance (%) at the wavelength and the degree of polarization (%) thereat were measured. In the measurement of the maximum absorption wavelength (nm, λmax) of the polarizing plates and the calculation of the degree of polarization, the parallel transmittance (Ky, %) and the orthogonal transmittance (Kz, %) in the polarized light incidence were measured by using a spectrophotometer (manufactured by Hitachi, Ltd., U-4100). Here, the parallel transmittance (Ky) indicates a transmittance when the absorption axis of an absolute polarizer and the absorption axis of a polarizing plate used in measurement are parallel; and the orthogonal transmittance (Kz) indicates a transmittance when the absorption axis of the absolute polarizer and the absorption axis of the polarizing plate used in measurement are orthogonal. The parallel transmittance and the orthogonal transmittance at each wavelength were measured at intervals of 5 nm in 380 to 1,200 nm. By using each measurement value, the single transmittance at each wavelength was calculated by the following expression (i); the degree of polarization at each wavelength was calculated by the following expression (ii); and there were obtained the degree of polarization at a maximum absorption wavelength in 380 to 1,200 nm, the maximum absorption wavelength (λmax) and the single transmittance thereat. Then, Ky and Kz were converted to absorbances (A.sub.L=log(1/(Ky/100)), A.sub.H=log(1/(Kz/100)), and the dichroic ratio Rd (=A.sub.H/A.sub.L=log(Kz/100)/log(Ky/100)) were calculated therefrom. Further, there were ascertained a wavelength region where the dichroic ratio indicated a value equal to or higher than 5, and a wavelength region where the dichroic ratio indicated a value equal to or higher than 10. The results are shown in Table 1. Here, the measuring sample of Comparative Example 6, since exhibiting no polarizing function, is not described in Table 1.

Transmittance (%)=(Ky+Kz)/2  (i)

Degree of polarization (%)=[(Ky−Kz)/(Ky+Kz)]×100  (ii)

TABLE-US-00001 TABLE 1 Single Degree of Wavelength region Wavelength region λmax Ky at λmax Kz at λmax transmittance polarization Rd having Rd of 5 having Rd of 10 (nm) (%) (%) at λmax (%) at λmax(%) at λmax or higher (nm) or higher (nm) Example 1 690 82.87 0.69 41.78 98.35 26.49 420-970 530-920 Example 2 710 74.50 0.015 37.26 99.96 29.91  480-1100  550-1070 Example 3 830 73.40 0.004 36.70 99.99 33.18  470-1200  530-1100 Example 4 820 69.63 0.02 34.83 99.94 23.53  490-1100  590-1060 Example 5 690 65.90 1.29 33.60 96.16 10.43  520-1100 680-850 Example 6 790 72.70 0.05 36.37 99.87 24.10 560-980 640-940 Example 7 850 76.60 0.00 37.80 99.99 37.23  460-1200  610-1100 Comparative 540 83.38 4.50 43.94 69.75 17.06 380-620 480-590 Example 1 Comparative 590 59.69 15.56 37.72 58.76  3.63 Absent Absent Example 2 Comparative 550 86.85 0.94 43.89 97.86 33.12 380-620 390-600 Example 3 Comparative 610 86.18 1.30 43.74 97.02 29.19 380-690 510-680 Example 4 Comparative 615 87.26 1.10 44.18 97.50 33.06 470-690 510-670 Example 5

[0138] As seen in Table 1, the polarizing plates obtained in Examples 1 to 7 each had a high polarizing performance in the maximum absorption wavelength (λmax), and an absorption anisotropy of 5 or higher in the dichroic ratio (Rd) in the near infrared region, that is, a polarizing function. Further, the polarizing plates each developed a dichroic ratio of 10 or higher even in 850 nm or more, that is, had a degree of polarization high in the broad band.

[0139] By contrast, in Comparative Examples 1 to 5, the bands exhibiting a dichroic ratio of 5 or higher were all limited to the wavelength region of less than 700 nm. It was found that the compounds of Comparative Examples 1 to 3 and 5, though as described in JP 11-269136 A, at least one —OH group is attached to the p-position of a diazenyl group, had almost no polarizing function in 700 nm or more. In particular, in Comparative Example 2, it was found that the polarizing function was remarkably low because there was no wavelength region where the dichroic ratio was 5 or higher. Further, it was found that Comparative Example 1 using a compound similar to the pigment represented by the structural formula (III) in JP 11-269136 A exhibited a λmax of 540 nm; Comparative Example 2 using a compound similar to the pigment represented by the structural formula (X) therein exhibited a λmax of 590 nm; so the both in the polarizing plate state had no maximum absorption wavelength in the near infrared region.

[Production Example of a Neutral Gray Polarizing Plate]

[0140] A polarizing film was produced in the same production method for the polarizing film as Example 1, except for using, as a dyeing solution, an aqueous solution at 45° C. containing 0.2% of the compound (11) obtained in Example 3, 0.07% of C.I. Direct Orange 39, 0.02% of C.I. Direct Red 81 and 0.1% of mirabilite. The obtained polarizing film had a single plate average transmittance in 380 to 1,200 nm of 38% and an average light transmittance at the orthogonal position of 0.02%, and had a high degree of polarization exhibiting a dichroic ratio of 10 or higher over the broad band. Further, the parallel position and the orthogonal position both assumed a hue of neutral gray in the hue in the visible region. On each of both surfaces of the polarizing film, one sheet of triacetylcellulose film (TAC film, manufactured by Fujifilm Corp., brand name: TD-80U) was laminated through an adhesive agent of a polyvinyl alcohol aqueous solution. Then, an AR support (manufactured by NOF Corp., ReaLook 4010) was laminated on one of the TAC films by using a pressure-sensitive adhesive agent to obtain a neutral gray dye polarizing plate with an AR support. The obtained polarizing plate, similarly to the polarizing film, assumed a neutral gray hue and had a high degree of polarization from the visible region to the near infrared region. The obtained polarizing plate exhibited durability over a long time even in a high-temperature and high-humidity state, and was excellent also in the light resistance to long-time exposure.

INDUSTRIAL APPLICABILITY

[0141] The polarizing film and the polarizing plate obtained by using the azo compound represented by formula (1) or a salt thereof was able to have a high degree of polarization in the infrared region or from the visible region to the infrared region. The obtained polarizing plate exhibits durability over a long time even in a high-temperature and high-humidity state, and is excellent also in the light resistance to long-time exposure, and is thus remarkably useful. Accordingly, the polarizing plate obtained by using the azo compound represented by formula (1) or a salt thereof can be applied to sensors, lenses, switching devices, isolators, cameras, indoor and outdoor measuring instruments, and vehicular devices such as driver sensing modules, which all require a high degree of polarization. Further, the polarizing plate can suitably be used for devices sensing infrared light, for example, infrared panels and spacial infrared touch modules, and by being used concurrently with conventional displays, for example, electronic calculators, watches and clocks, laptop computers, word processors, liquid crystal televisions, polarizing lenses, polarizing eyeglasses and car navigations, is enabled to provide modules not only displaying in the visible region but also making use of infrared light.