| US 7,402,375 B2 | ||
| Cyanine dyes | ||
| Chiaki Kasada, Okayama (Japan); Yasushi Aizawa, Okayama (Japan); Toshio Kawata, Okayama (Japan); and Shigeo Yasui, Okayama (Japan) | ||
| Assigned to Kabushiki Kaisha Hayashibara Seibutsu Kagaku Kenkyujo, Okayama (Japan) | ||
| Filed on May 16, 2003, as Appl. No. 10/438,839. | ||
| Application 10/438839 is a division of application No. 09/913730, granted, now 6,683,188, previously published as PCT/JP00/08297, filed on Nov. 24, 2000. | ||
| Claims priority of application No. 1999/358949 (JP), filed on Dec. 17, 1999. | ||
| Prior Publication US 2003/0181727 A1, Sep. 25, 2003 | ||
| Int. Cl. G11B 7/24 (2006.01) | ||
| U.S. Cl. 430—270.2 [430/945; 430/270.18; 428/64.8; 369/284] | 2 Claims |
| 1. A light absorbent composition applied to an optical recording medium substrate having a track pitch of below 0.74 microns
comprising (a) a monomethine cyanine dye of Formula 1 which has an absorption maximum at a wavelength of 450 nm or less when
in a thin layer form; and (b) organic dye compounds other than said monomethine cyanine dye, said organic dye compounds being
sensitive to a laser beam with a wavelength of 775 to 795 nm:
ø1−CH=ø2 Formula 1:
wherein in Formula 1, ø1 is a heterocyclic group represented by Formula 5 and ø2 is a heterocyclic group represented by any
one of Formulae 2, 3, 4, 6, 7 and 8 as resonance structures;
 wherein throughout Formulae 2 to 5, Z represents an optionally substituting mono- or polycyclic aromatic ring or heterocycle
which condenses to a nitrogen atom-containing five-membered heterocycle;
throughout Formulae 2 to 8, R1 represents an aliphatic hydrocarbon group and R2 represent hydrogen atom or the same or different aliphatic hydrocarbon group as in R1, wherein the aliphatic hydrocarbon groups may have a substituent, and in Formulae 2 to 8, X− represents an azo metal complex anion being a member selected from the group consisting of:
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