A New Type of Light Stabilizer for Dye Layers of Optical Disks: Tetracyanoquinodimethane Derivatives

A new technology to improve the light fastness of cyanine dye layers of a compact disk recordable (CD-R) or a digital video disk recordable (DVD-R) without using any singlet oxygen quenchers was discussed. The light fastness of dicarbocyanine dye layers of a CD-R was improved by doping with tetracyanoquinodimethane (TCNQ) derivatives of various reduction potentials (E 1/2 RED). The optimum potential was found to be around 0 V vs saturated calomel electrode (SCE). Doping with TCNQ derivatives was found to be effective also for the improvement of light fastness of the carbocyanine dye layers which have optical properties suitable for a DVD-R disk. Excessive electron demanding TCNQ derivatives (E 1/2 RED> 0), however, showed rather poor jitter and block-error rate (BLER) after exposure to a xenon lamp as compared to a TCNQ derivative (TCNQ1) with an optimal reduction potential (ca. 0 V vs SCE). Since TCNQ derivatives have no absorption band in a red to near infrared region, the CD-R or the DVD-R having cyanine dye layers doped with TCNQ derivatives exhibit higher reflectivity than those with such singlet oxygen quenchers as diimmonium salts.