The optical recording media are in widespread use, generally due to its superior characteristics such as large recording capacities, noncontact recording or reproduction, and the like. In the write-once optical discs such as WORM, CD-R, DVD±R, and the like, recording is carried out by focusing the laser light on a minute area of the recording layer to change properties of the optical recording layer, while reproduction is performed based on a difference in intensities of light reflected from the recorded area and non-recorded area.
Compounds having a strong absorption between 550 nm and 620 nm, especially those having absorption maxima (λmax) between 550 and 620 nm are being used as optical recording materials to form optical recording layers of optical recording media such as DVD-R and the like.
As the optical recording material described above, there are many reports on indolium compounds containing an indole ring, which has a merit that it can correspond to high-speed recording due to its high sensitivity. For example, Patent Document Nos. 1 to 6 report styrylindolium compounds. Also, Patent Document 7 reports a cyanine compound of a low decomposition temperature, which has a benzyl group introduced at the 3-position of the indole ring. It is thought that a compound which decomposes at a low temperature forms a recorded portion (pit) of an optical recording layer easily and is considered to adapt to a high-speed recording medium.
However, these materials have not shown satisfactory performance in terms of light stability and recording characteristics.    Patent Document No. 1: Japanese Patent Laid-Open Publication No. H11-34489    Patent Document No. 2: Japanese Patent Laid-Open Publication No. H11-170695    Patent Document No. 3: Japanese Patent Laid-Open Publication No. 2001-342366    Patent Document No. 4: Japanese Patent Laid-Open Publication No. 2002-206061    Patent Document No. 5: Japanese Patent Laid-Open Publication No. 2003-313447    Patent Document No. 6: Japanese Patent Laid-Open Publication No. 2003-321450    Patent Document No. 7: Japanese Patent Laid-Open Publication No. 2003-231359