Recently Hi-Vision broadcasts and networks such as Internet have been rapidly popularized. Further, in view of upcoming HDTV (High Definition Television) broadcasting, there is an increasing demand for large-capacity recording media for easily recording image information at low costs. Though CD-Rs and DVD-Rs capable of high-density recording using visible laser lights (630 to 680 nm) have been established to some extent as large-capacity recording media, the recording capacities thereof are not sufficiently large for future requirements. Thus, development of optical disks, which utilize laser lights with shorter wavelengths to achieve higher recording densities and larger recording capacities as compared with the DVD-Rs, has been progressed. For example, an optical recording disk utilizing a 405-nm blue laser light, called a Blu-ray disc, has been proposed.
In conventional DVD-R type optical disks, azo-metal complex dyes have been advantageously used as dye compounds in recording layers (see, for example, Patent Documents 1, 2, 3, and 4) These azo-metal complex dyes show absorption waveforms corresponding to red laser lights, and thereby are unsuitable for the 405-nm laser light. Thus, azo-metal complex dyes for the optical recording disk utilizing the 405-nm blue laser light has been studied so as to shorten the absorption wavelengths of the azo-metal complex dyes for the DVD-Rs as disclosed in Patent Documents 5 to 9, etc. However, in Patent Documents 5 to 9, though the maximum absorption wavelengths of solutions or films containing the dyes are described, the light fastness and the recording/reproducing properties in optical information recording media are not described in detail, and the actual storability and the actual recording/reproducing properties are not known.
Films of the azo-metal complexes described in Patent Documents 5 to 9 were evaluated with respect to the light fastness and recording/reproducing properties in the optical information recording media utilizing blue laser lights. As a result, all the films are not satisfactory in both the light fastness and the recording/reproducing properties (the recording sensitivity, 2T CNR).    Patent Document 1: Japanese Laid-Open Patent Publication No. 11-310728    Patent Document 2: Japanese Laid-Open Patent Publication No. 11-130970    Patent Document 3: Japanese Laid-Open Patent Publication No. 2002-274040    Patent Document 4: Japanese Laid-Open Patent Publication No. 2000-168237    Patent Document 5: Japanese Laid-Open Patent Publication No. 2001-158862    Patent Document 6: Japanese Laid-Open Patent Publication No. 2006-142789    Patent Document 7: Japanese Laid-Open Patent Publication No. 2006-306070    Patent Document 8: Japanese Laid-Open Patent Publication No. 2005-297406    Patent Document 9: Japanese Laid-Open Patent Publication No. 2005-297407
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