Yasunori Kanazawa

Development Of Large Capacity Optical Disk

A high performance DRAW type disk is developed, and the disk is used in Hitachis newly developed file memory system, HITFILE 60. The total capacity of the system is 83 gigabytes, and the mean access time is about 6 seconds, on single disk, the mean access time is 250 msec. The resolution of the picture is about 16x15.4 lines/mm. The disk, which diameter is 300 mm 0, has the storage capacity is 1.3 gigabytes for single sided type (0C-301-1) or 2.6 gigabytes for double sided type (0C-301-2).The track pitch is 1.61μm and 48,000 tracks are engraved spirally. A track is devided into 64 sectors and 512 bites of users data can be recorded in each sector. Low error rate of 10-12, has been confirmed after error correction, with above mentioned file memory system. Long life, more than 10 years in normal room condition, has confirmed by accellerated life test under the condition of 60°C 95 %RH. The disk is consisted of three layers on chemically tempered glass plate with 1.1 mm thickness. The first layer is UV-curable polymer layer, the 2nd is intermediate layer of cellulose nitrate, this ensures precise pits formation on grooves, the 3rd isTe-Se-Pb alloy recording layer. The disk has the air sandwitch structure, in which two disks above mentioned are pasted together with 0.6 mm air gap. The disk is completly protected from dust, finger prints and scratches by newly developed plastic cartridge.

Improved Si piezo-transistors for mechano-electrical transducers

Piezo-transistors with stresses applied to the emitter region by means of small hard styli for application as mechano-electric transducers have been improved. High signal-to-noise ratios were obtained in gold-doped n-p-n Si planar transistors. New designs for emitter electrodes have been devised which make the fabrication of the transducer units easy. Rather large stressing areas (60-µm diameter) which are surrounded by ring-type emitter electrodes with overlay bonding pads are provided in the central part of the emitter region (90-µm diameter). Signal-to-noise ratios are high and independent of the position of the stylus over the stressing area. By using these transistors mechano-electrical transducer units were fabricated with higher stabilities. It was found that noise decreases with increasing stress. Life-test results of the transducer units are also indicated. The stress dependence of transistors were explained by the combined effects of the stress dependence of the emitter efficiency and the stress dependence of the base transport factor. Gold-doping seemed to enhance the stress dependence of the base transport factor due to a very short minority carrier lifetime.