Toshio Ishida

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 (E1/2RED). 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 (E1/2RED> 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.

Lattice-Site Locations of Tin and Antimony Implanted in Gallium Phosphide

The lattice locations of Sn and Sb atoms implanted in GaP single crystals have been studied as a function of implantation temperature by means of ion channeling and ion-induced X-rays. Angular scans through the major axes were performed to distinguish two types of substitutional sites in GaP. For the implantation at 400°C, about 80% of Sn atoms and 100% of Sb atoms were located on Ga- and P-substitutional sites, respectively. Sn and Sb atoms implanted at room temperature were found to be on off-lattice sites even after annealing at 700°C. An implantation annealing stage for lattice location and lattice disorder was observed in the temperature range from 200°C to 250°C.

Blue-violet laser write-once optical disc with spin-coated dye-based recording layer

Jitter of 9.5% with conventional equalizer and 6.1% with limit equalizer have been achieved on a 23.3GB blue-violet laser write-once optical disc with a recording laeyr formed by spin coating with a dye-based solution. Data transfer speed is 36Mbit/s. The disc is composed of a polycarbonate substrate, a reflective layer, a dye-coated recording layer, a bonding layer, and a polycarbonate protective sheet. Cavities formed in the marks during recording result in large changes in refractive index for signal amplitude. Recording and playback was successful even at 2x drive speeds with data transfer of 72Mbit/s.

Improved Thermal Stability of Dye-Based Optical Discs: Effect of Hydrogen Bonding

To improve the stability of dye-based optical discs during long-term storage, we examined the effect of hydrogen bonding in the dye layer with the expectation that the strong networks of hydrogen bonds would suppress the migration of chemical species, thereby preventing changes in the properties of the amorphous dye films. Intermolecular hydrogen bonding was compared in six dyes, which were composed of a combination of an indodicarbocyanine-dye cation and six colorless naphthalenedisulphonate anions with zero to two hydroxyl groups. Accelerated temperature/humidity testing revealed that the introduction of hydroxyl groups on the colorless anions improved the stability of the cyanine-dye-based optical discs. The error rate was very low, particularly when a thermally stable network of hydrogen bonds involving the hydroxyl (–OH) groups was present, as confirmed by variable-temperature IR spectroscopy. This stabilization due to hydrogen bonding affords a new guideline for designing dyes for optical discs.