AZO compound and ink containing the compound

1. An ink comprising: a solvent having a relative permittivity of 3 or less, as measured at a frequency of 1 kHz and at 22° C., and having a solubility in water of 20 mg/L or less at 25° C.; and an azo compound, the azo compound being represented by formula (I):

wherein

R 1 , R 2 , D 1 , and A 1 each independently represent an arbitrary substituent,

A 2 represents a substituent of formula (II):

wherein D 2 represents an arbitrary substituent, n represents an integer of 1 to 5, and when n is 2 or larger, two or more D 2 groups present in one molecule may be the same or different,

m represents an integer of 1 to 4, and when m is 2 or larger, two or more D 1 groups present in one molecule may be the same or different, and

X represents a nitrogen atom or an optionally substituted methine group.

2. The ink according to claim 1 , wherein the solvent contains at least one selected from the group consisting of hydrocarbon solvents, silicone oils, and fluorocarbon solvents.

3. The ink according to claim 1 , wherein the product of a molar extinction coefficient ε (L·mol −1 ·cm −1 ) at the absorption-maximum wavelength of an n-decane solution of the azo compound and a saturated concentration C (mol·L −1 ) of the azo compound in n-decane at 5° C., εC, is 1,000 cm −1 or larger.

4. The ink according to claim 1 , which further comprises at least one selected from the group consisting of heterocyclic compounds, cyanovinyl compounds, and anthraquinone compounds.

5. The ink according to claim 4 , wherein the heterocyclic compound is at least one selected from the group consisting of formulae (III) to (V):

wherein

R 101 , R 102 , D 3 , and D 4 each independently represent an arbitrary substituent,

e represents an integer of 1 to 5, and when e is 2 or larger, two or more D 3 groups present in one molecule may be the same or different, and

g represents an integer of 1 to 4, and when g is 2 or larger, two or more D 4 groups present in one molecule may be the same or different;

wherein

R 201 , R 202 , R 203 , R 204 , R 205 , R 206 , R 207 , and R 208 each independently represent an arbitrary substituent and

Z represents a nitrogen atom or an optionally substituted methine group;

wherein

R 301 , R 302 , D 5 , and D 6 each independently represent an arbitrary substituent,

l represents an integer of 1 to 4, and when 1 is 2 or larger, two or more D 5 groups present in one molecule may be the same or different, and

j represents an integer of 1 to 4, and when j is 2 or larger, two or more D 6 groups present in one molecule may be the same or different.

6. The ink according to claim 4 , wherein the cyanovinyl compound is represented by formula (VI):

wherein

R 401 , R 402 , R 403 , R 404 , and D 7 each independently represent an arbitrary substituent and

r represents an integer of 1 to 4, and when r is 2 or larger, two or more D 7 groups present in one molecule may be the same or different.

7. The ink according to claim 4 , wherein the anthraquinone compound is represented by formula (VII):

wherein

D 8 represents an arbitrary substituent and t represents an integer of 1 to 8, and when t is 2 or larger, two or more D 8 groups present in one molecule may be the same or different.

8. A display or optical shutter, comprising the ink according to claim 1 .

9. A display comprising a display part containing the ink according to claim 1 , wherein an image is displayed by controlling voltage application to the display part.

10. The display according to claim 9 , wherein the display part further contains electrophoretic particles or an aqueous medium.

11. The display according to claim 9 , wherein an image is displayed by changing a colored state by means of voltage application.

12. The display according to claim 9 , wherein an image is displayed by an electrowetting system or an electrophoretic system.

13. An electronic paper which comprises the display according to claim 9 .

14. An azo compound represented by formula (IX):

wherein

R 701 and R 702 each independently represent an optionally substituted branched alkyl group having 5 to 20 carbon atoms,

D 11 represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkoxy group having 1 to 20 carbon atoms, an —NHCOR 703 group, or an —NHSO 2 R 708 group,

R 703 and R 708 each independently represent an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, or an optionally substituted heteroaryl group having 2 to 20 carbon atoms,

d represents an integer of 1 to 4, and when d is 2 or larger, two or more D 11 groups present in one molecule may be the same or different,

A 5 represents a hydrogen atom, a halogen atom, a cyano group, an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, an optionally substituted heteroaryl group having 2 to 20 carbon atoms, an optionally substituted alkoxy group having 1 to 20 carbon atoms, or a —COOR 704 group,

R 704 represents an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, or an optionally substituted heteroaryl group having 2 to 20 carbon atoms,

D 10 represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a —COOR 706 group,

b represents an integer of 1

R 706 represents an alkyl group having 1 to 20 carbon atoms,

X 3 represents a nitrogen atom, or a methine group which may have a halogen atom, a cyano group, or a —COOR 707 group as a substituent, and

R 707 represents an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group having 6 to 20 carbon atoms, or an optionally substituted heteroaryl group having 2 to 20 carbon atoms.

15. The azo compound according to claim 14 , wherein R 701 and R 702 each independently represent a branched alkyl group having at least 8 carbon atoms.

16. The azo compound according to claim 14 , wherein D 10 represents an alkyl group having 1 to 6 carbon atoms, which binds at the para-position with respect to the azo group.