We examine a lifetime estimation method for high-density recordable optical disks. It is based on the Eyring acceleration model and statistical analysis. The statistical distribution of life data for the optical disk assumed a lognormal distribution. The standardized life expectancy of an optical disk is defined as the minimum lifetime of 95% survival probability at 25°C / 50%RH with a 95% confidence level. An acceleration test was conducted under stress conditions of temperature and relative humidity. Results have demonstrated that the statistical distribution of lifetime data using the digital error criterion item can be applied to a lognormal distribution. Thereby, we can estimate a standard life expectancy of high-density recordable optical disks as the minimum lifetime of 95% survival probability at a 95% confidence level.
This study examined a lifetime estimation method for optical disks. It is based on the Eyring acceleration model and statistical analysis. The statistical distribution of life data for the optical disk assumed a lognormal distribution. Analysis of statistical techniques based on the ISO standard is proposed as a life expectancy prediction method for CD-R disks. The standardized life expectancy of an optical disk is defined as the minimum lifetime of 95% survival probability at 25/50%RH with a 95% confidence level. An acceleration test was conducted using a high-density optical disk under stress conditions of temperature and relative humidity. Consequently, we confirmed the capability of this method for estimating life expectancy by considering the stresses of temperature and relative humidity, and providing for a confidence level. The statistical distribution function of optical disk lifetime data must be clarified experimentally to apply this technique to lifetime estimation of optical disks in the future.
In order to attempt the direct laser marking for ROM media like a compact disk for identification, various laser heating was carried out against a thin metallic film in the transparent medium. As heat sources for the processing, a semiconductor laser excitation YAG laser (532 nm wavelength of second harmonic, max 150 mW), semiconductor lasers (780 nm, up to 2 W), and an Ar ion laser (514.5 nm, max 2000 mW), etc. were used. The media under consideration on laser marking is an aluminum thin film reflector layer, which was sandwiched between a polycarbonate (PC) of 1.2 mm and a protection film of 5 μm thickness. The aluminum thin film (Al) is 100 nm in thickness. The obtained laser marking sizes were less than 1 μm and were evaluated using SEM and AFM. The observation samples inside a transparency resin were obtained by tearing off a protection film, and the surfaces of the bared PC and protection film were examined. The surface conditions and cross sections of laser-marking area were observed. It seems that the heated aluminum thin film were melted and a hole arose. Then a cavity was not observed from SEM cross-section observation in the marking area. It became clear that the holes were filled with PC by SEM and AFM observation. These results indicate the possibility of heat localization at the Al-PC interface and also significant heat penetration into the PC substrate itself.
The Initializer which has a mechanism that allows for the rotating of the optical disk and scanning the laser head to radial direction, and Initializing the phase-change optical disk with spiral pattern, has basic problems which are caused by this mechanism. In this mechanism, the ruggedness of the laser diode is transcribed on the recording material of the optical disk. This report about the method of reflecting the laser light by the parallel millers that are installed in both sides of the light beam after collimating lens. The reflected lasers light by the parallel millers are focusing on the recording material of the optical disk with the manner of folding. If the reflected time of the lasers light is only one, it is making the 180 degreed rotated images from un-reflected image. And the multiple times reflected laser light make the image at a slightly moved place. So the folded focus image of laser diode is more uniformed compared with the original one and reduces the quality problem, which is caused by un-uniformity of initializing of Phase-Change Optical Disk.
The method of estimating the reliability of recordable phase change media is examined. The PD disks of 650 MB in total capacity in 12 cm diameter are used as experiment samples. The media are put under the acceleration environment of 80 degree in the temperature 85% in humidity, and change of BER is observed. Two kinds of life (archival and shelf) are tested. As for the disk to be examined, it is necessary to do the acceleration reliability test in a linear area in the destruction limit. Therefore, there is a limit in a possible acceleration coefficient. In the optical disk with long life at present time, it will take extremely long time to presume the final life. In this thesis, the method of estimating the life of a long-lived disk at shorter time is discussed.
The method and the device, which initializes phase change media standardized by formats of such as CD-RW, record type DVD and etc., are discussed. In these media it should be a state of the crystal phase with high reflectivity before recording. It is necessary to change into the crystal phase from amorphous phase in a usual state of as-depot. The method to scan the laser spot beam of the oval shape that could be processed by a more high-speed, slighter control was examined. Because the life of laser and the scanning speed of beam spot are important factors that influenced the processing cost, the life of the laser and the improvement of the process speed are considered. The most much relating to the quality of media of finished products is near field pattern of the laser. Initializer in the mechanism, which can be used in the mass production line, is designed.