Optical recording medium

Claim 2

An optical recording medium comprising a recording layer containing at least one compound selected from the group consisting of azulenium salt compounds represented respectively by Formulae, (II), (III) and (IV) shown below: ##STR10## wherein R 1 to R 12 and R' 1 to R' 7 each represent a hydrogen atom, a halogen atom or a substituent that is a monovalent organic residual group: among combinations of R 1 with R' 1 , R 2 with R' 2 , R 3 with R' 3 , R 4 with R' 4 , R 5 with R' 5 , R 6 with R' 6 and R 7 with R' 7 , at least one combination comprises a combination of different substituents; X.sup.⊕ represents an anion residual group, and Y represents a divalent hydrocarbon group that forms a substituted or unsubstituted ring of 5 members, 6 members or 7 members: and any one combination among combinations of R 1 with R 2 , R 2 with R 3 , R 3 with R 4 , R 4 with R 5 , R 5 with R 6 , R 6 with R 7 , R' 1 with R'.sub. 2, R' 2 with R' 3 , R' 3 with R' 4 , R' 4 with R' 5 , R' 5 with R' 6 and R' 6 with R' 7 may form a substituted or unsubstituted condensed ring.

Claim 3

The optical recording medium of claim 1, wherein among the combinations of R 1 with R' 1 , R 2 with R' 2 , R 3 with R' 3 , R 4 with R' 4 , R 5 with R' 5 , R 6 with R' 6 and R 7 with R' 7 of the substituents for the azulenium salts represented respectively by the above Formulae (II), (III) and (IV), at least one combination comprises a combination of a hydrogen atom with an alkyl group or a hydrogen atom with an alkoxy group.

Claim 4

The optical recording medium of claim 1, wherein any of the substituents of R 1 to R 7 or R' 1 to R' 7 in at least one azulene ring form a heterocyclic ring in the form of R n -R n+1 or R' m -R' m+1 (n and m each is an integer of 1 to 6), and the substituent at the corresponding position in the other azulene ring is a hydrogen atom or an alkyl group.

Claim 5

The optical recording medium of claim 1, wherein at least one compound selected from the group consisting of the azulenium salt compound represented respectively by the above Formulae (II), (III) and (IV) is contained in the recording layer in an amount of from 40 to 100 % by weight.

Claim 6

The optical recording medium of claim 4, wherein at least one compound selected from the group consisting of the azulenium salts represented respectively by the above Formulae (II), (III) and (IV) is contained in the recording layer in an amount of from 50 to 100 % by weight

Claim 7

The optical recording medium of claim 1, wherein said recording layer has a film thickness of from 100 Å to 20 μm.

Claim 8

The optical recording medium of claim 6, wherein said recording layer has a film thickness of from 200 Å to 1 μm.

Claim 9

The optical recording medium of claim 1, which has a subbing layer between said recording layer and a substrate.

Claim 10

The optical recording medium of claim 8, herein said subbing layer has a film thickness of from 50 Å to 100 μm.

Claim 11

The optical recording medium of claim 9, wherein said subbing layer has a film thickness of from 200 Å to 30 μm.

Claim 12

The optical recording medium of claim 1, which has a protective layer on said recording layer.

Claim 13

The optical recording medium of claim 11, wherein said protective layer has a film thickness of 100 Å or more.

Claim 14

The optical recording medium of claim 12, wherein said protective layer has a film thickness of 1,000 Å or more.

Claim 15

The optical recording medium of claim 1, wherein a stabilizer is added in said recording layer.

Claim 16

The optical recording medium of claim 1, wherein said recording layer has absorption to the infrared region.

Claim 17

An optical recording method comprising forming pits and recording information by irradiation of a laser beam on an optical recording medium having a recording layer containing one or more of azulenium salt represented by Formulae (II), (III) or (IV) shown below: wherein R 1 to R 12 and R' 1 to R' 7 each represent a hydrogen atom, a halogen atom or a substituent that is a monovalent organic residual group; among combinations of R 1 with R' 1 , R 2 with R' 2 , R 3 with R' 3 , R 4 with R' 4 , R 5 with R' 5 , R 6 with R' 6 and R 7 with R' 7 , at least one combination comprises a combination of different substituents; X.sup.⊕ represents an anion residual group, and Y represents a divalent hydrocarbon group that forms a substituted or unsubstituted ring of 5 members, 6 members or 7 members; and any one combination among combinations of R 1 with R 2 , R 2 with R 3 , R 3 with R 4 , R 4 with R 5 , R 5 with R 6 , R 6 with R 7 , with R' 1 with R' 2 , R' 2 with R' 3 , R' 3 with R' 4 , R' 4 with R' 5 , R'.sub. 5 with R' 6 and R' 6 with R' 7 may form a substituted or unsubstituted condensed ring.

Claim 18

An optical recording method comprising forming pits and recording information by irradiation of a laser beam on an optical recording medium having a recording layer containing one or more of azulenium salt represented by Formulae (II), (III) or (IV) shown below: wherein R 1 to R 12 and R' 1 to R' 7 each represent a hydrogen atom, a halogen atom or a substituent that is a monovalent organic residual group; among combinations of R 1 with R' 1 , R 2 with R' 2 , R 3 with R' 3 , R 4 with R' 4 , R 5 with R' 5 , R 6 with R' 6 and R 7 with R' 7 , at least one combination comprises a combination of different substituents; X.sup.⊕ represents an anion residual group, and Y represents a divalent hydrocarbon group that forms a substituted or unsubstituted ring of 5 members, 6 members or 7 members; and any one combination among combinations of R 1 with R 2 , R 2 with R 3 , R 3 with R 4 , R 4 with R 5 , R 5 with R 6 , R 6 with R 7 , with R' 1 with R' 2 , R' 2 with R' 3 , R' 3 with R' 4 , R' 4 with R' 5 , R'.sub. 5 with R' 6 and R' 6 with R' 7 may form a substituted or unsubstituted condensed ring.

Claim 19

The optical recording method of claim 16, wherein said laser beam has an oscillation wavelength in the near infrared region or infrared region.