Azo-metal chelate dye and optical recording medium

1. An azo-metal chelate dye comprising an azo dye compound and a metal, wherein the azo-metal chelate dye has a OD 2 /OD 1 value of greater than 1.25, which is measured by the following method:

(1) after adding 20 mg of azo-metal chelate dye into 2 g of an octafluoropentanol (OFP) solvent, supersonic dispersion is performed at temperatures between 50° C. and 65° C. for 60 minutes to obtain a solution A, and the solution A is then cooled to room temperature (25±5° C.) to obtain a solution B;

(2) the solution B is applied onto a polycarbonate substrate by spin coating at a rotating speed of 800 rpm, and the substrate onto which the elution B has been spin coated is then annealed at 80° C. for 5 minutes,

the substrate thus obtained, onto which the solution B has been spin coated, being referred to as a coated substrate A;

(3) the absorption spectrum of the coated substrate A is measured in a range of 400 to 800 nm; and

(4) concerning the absorption peaks seen in a range of 500 to 700 nm in the obtained absorption spectrum, the absorption peak at which the optical density is the greatest and the absorption peak at which the optical density is the second greatest are selected, the optical density at the peak on the long wavelength side is defined as OD 2 and the optical density at the peak on the short wavelength side is defined as OD 1 , and the OD 2 /OD 1 value is calculated,

wherein the azo dye compound is represented by the following formula (1):

(where R 1 represents a hydrogen atom or an ester group represented as CO 2 R 3 , R 3 represents a straight or branched chain alkyl group which may be substituted or a cycloalkyl group which may be substituted, R 2 represents a straight or branched chain alkyl group which may be substituted, at least one of X 1 and X 2 represents an NHSO 2 Y group, Y represents a straight or branched chain alkyl group which is substituted with at least two fluorine atoms, R 4 and R 5 independently represents a hydrogen atom or a straight or branched chain alkyl group which may be substituted, and R 6 , R 7 , R 8 and R 9 independently represents a hydrogen atom or a alkyl group having 1 to 2 carbon atoms).

2. The azo-metal chelate dye according to claim 1 , wherein the metal is at least one selected from the group consisting of Ni, Co, Cu and Pd.

3. The azo-metal chelate dye according to claim 1 , having a maximum absorption at a wavelength of 700 nm or less.

4. The azo-metal chelate dye according to claim 1 , having a maximum absorption at a wavelength of from 650 to 500 nm.

5. The azo-metal chelate dye according to claim 1 , having a OD 2 /OD 1 value of 1.29 or more.

6. An optical recording medium comprising a recording layer on a substrate, on which recording layer recording and/or reading of information is performed by use of applied light, wherein the recording layer contains the azo-metal chelate dye according to claim 1 .

7. The optical recording medium according to claim 6 , wherein the metal is at least one selected from the group consisting of Ni, Co, Cu and Pd.

8. The optical recording medium according to claim 6 , wherein the azo-metal chelate dye exhibits the absorption maximum at wavelengths equal to or shorter than 650 nm with regard to the applied light.

9. The optical recording medium according to claim 6 , wherein the recording of information thereon is capable at a speed approximately 28 m/s or more.

10. The optical recording medium according to claim 6 , wherein the recording of information thereon is capable at 8×-speed.

11. The optical recording medium according to claim 6 , having a maximum absorption at a wavelength of 700 nm or less.

12. The optical recording medium according to claim 6 , having a maximum absorption at a wavelength of from 650 to 500 nm.

13. The optical recording medium according to claim 6 , wherein the azo-metal chelate dye has a OD 2 /OD 1 value of 1.29 or more.

14. The optical recording medium according to claim 6 , wherein the metal is at least Ni.