Sayoko Tanaka

The reliability test of center-aperture-detection-type magnetically induced super-resolution magneto-optical disk

The Center Aperture Detection (CAD) type Magnetically Induced Super-resolution (MSR) Magneto-optical Disk is one of method to overcome the limitation of optical resolution. For a reliability of the disk, it is important to investigate the stability of the magneto-static coupling between a readout layer and a recording layer through readout characteristics. In this paper, we tested the reliability of CAD tMSR magneto-optical disk. We used iD PHOTO disk for the CAD MSR magneto-optical disk. In the disk, the data is recorded on land and groove with a track pit of 0.6 µm and a bit length of 0.235 µm, by a method of laser pumped magnetic field modulation with an optical pickup of NA=0.62, λ=650 nm. The reliability was examined by PI error lines under the test condition of 80 °C-90 %RH. There were no considerable changes in read/write characteristics up to with an aging time of 2000 hour. The lifetime of the disk was estimated more than 7000 hour under the condition. By a method of the Arrhenius plots, we assumed that the lifetime of the disk would be more than 100 years under the condition of room temperature. We also confirmed that there were no significant changes in mechanical characteristics of the disks. These results show the disk using magneto-static coupling has sufficient reliability for consumer use.

Life estimation based on statistics for single-sided Magneto-Optical disks with GdDyFeCo film

We have developed single-sided Magneto-Optical (MO) disks with GdDyFeCo film, which is suitable for magnetic field modulation method at low constant velocities. The reliability of our MO disk with a simple structure (polycarbonate/ SiN/ GdDyFeCo/ SiN/ UV resin) was examined with accelerated tests. After aging more than 10,000 hours at 65°C 85% RH, carrier to noise ratio was scarcely lowered, while the value of Block Error Rate increased because of extra noise which was produced by local defects. From the statistical analysis and Arrhenius plot, the lifetime of 95% of our MO disks were estimated to be more than 50 years at an office environment.