Masaji Ishigaki

Single‐beam overwriting with melt‐erasing process in an InSbTe phase‐change optical disk

Single‐beam overwriting with melt‐erasing process was made in a 5.25‐in.‐diam phase‐change optical disk using an In22Sb37Te41 recording film. In the overwriting between 2 and 3 MHz signals at the linear velocity of 3–11 m/s, a carrier to noise ratio (C/N) more than 46 dB and an erasability less than −35 dB could be obtained. This high erasability was found to be due to the melt‐erasing process. This disk presents highly erasable overwriting and long data retention time supported by an activation energy of 2.3 eV and a temperature of 230 °C for crystallization of the amorphized part.

Melt-Erasing Method Of Single Beam Overwrite For Phase-Change Optical Disk

A new single beam overwrite method for a phase-change optical disk is proposed to obtain both high carrier to noise ratio (CNR) and high overwrite erasing ratio. Contrary to ordinary method is, both writing and erasing process are controlled over the melting point of a phase-change recording film. To realize new overwriting method, we discuss desired thermal characteristics of a disk and crystallization properties of recording film theoretically. Necessary conditions to realize this method are (1) optical disks must have high thermal conductivity to control cooling rate, (2) recording material may have adequate crystallizing tine within dynamic range of disks cooling rate. Examination on this method was carried out by using newly developed In-Sb-Te phase-change optical disk. CNR higher than 50dB and erasing ratio higher than 40dB were obtained.

40 dB OVERWRITE -MODULATION PHASE- CHANGE OPTICAL DISK USING In -Sb -Te ALLOY

A single-beam overwrite was achieved by an In-Sb-Te phase-change optical disk. The carrier to noise (C/N) ratio of more than 50 dB and the overwrite modulation of -40 dB were obtained for overwriting frequencies of 2 MHz and 3 MHz using a low power laser diode of 30 The high C/N ratio and the excellent overwrite modulation were due to the large reflectivity difference between the written and erased phases and the use of suitable write/erase power.