Toshio Tsuno

Weathering resistance of glass plates coated with sol-gel derived 9TiO2·91SiO2 films

Etude de verres de chaux sodee-silice recouverts de films de SiO 2 et de 9 TiO 2 •91 SiO 2

Pregrooving on glass disks by the sol-gel method (Part II): effects of the addition of organic polymers on the formation of glass films in the SiO2-TiO2 system

The effects of the addition of polyethylene glycol(PEG) on the formation of gel-derived glass films in the Si02-TiO2 system were studied, aimed at their application to the optical memory disks. The viscosity of the as-prepared sols increased almost linearly with increasing PEG content. The increase in viscosity of the sols during the storage was retarded with decreasing molecular weight of PEG added and with increasing amount of PEG added. The viscosity increase of the sols during the storage, however, showed a similar temperature dependence, i.e. almost the same apparent activation energy was obtained, in the sols containing different amounts of PEG. These findings indicate that PEG added to the SiO2-TiO2 sols scarcely reacts with the hydrolyzed inorganic species. The hardness of the resultant PEG-containing gel films greatly decreased with increasing PEG content. The gel films containing PEG of the smaller average molecular weight showed the higher hardness and the steeper increase in hardness with increasing the heat-treatment temperature than those containing PEG of the larger average molecular weight. For a high performance in the fine patterning process and densification of the resultant patterned films, PEG of the smaller amount and the smaller molecular weight is favorable, provided the PEG-containing gel films are initially soft enough to emboss fine patterns by pressing a stamper. Incorporated PEG in the Si02-Ti02 gel films decomposed completely at temperatures over 300 °C and had a very slight influence on chemical bondings in the resultant films.

Pregrooving on glass disks by the sol-gel method (Part I): formation and evaluation of pregrooved glass disks

Pregrooved glass disks were prepared by the application of the sol-gel coating technique; the soda-lime-silica glass disks were coated with polyethylene glycol(PEG)-containing Si02-Ti02 gel films, in which fine patterns were formed by pressing a stamper. The refractive index of the pregrooved layer was matched with that of the glass disks by adjusting the TiO2 content. When the weight ratio of PEG with the average molecular weight of 600 to SiO2-TiO oxides was unity, the pitch of the pregrooves formed was unchanged in comparison with that of the stamper used after the heat-treatment at 350°C, while the land height and the land width of the pregrooves were respectively reduced to 6O9 and 85 of those of the stamper after the heat-treatment. The noise level of the glass disks with the pregrooved SiO2-Ti02 layer was lower by 1-2 dB than that of the disks with pure 5i02 layer in the frequency range from 0.5 to 2.0 MHz. The lower noise level of the former can be ascribed to the agreement in the refractive index between the pregrooved layer and the glass disks.

Extremely durable CD-ROM with a novel structure

This paper describes an extremely durable CD-ROM and its reliability. A pit pattern was fabricated through a sol-gel process utilizing a 2P/epoxy work stamper. Excellent stability was guaranteed by a layered structure, such as the SiO2-ZrO2 over coat on a chemical strengthening glass substrate and the Si/SiO2-ZrO2/Cr tri- layered reflector on a sol-gel layer. Accelerated tests were implemented to estimate its lifetime. The CD-ROM lifetime at 30 degree(s)C (DOT) 90% RH was estimated to be more than 300 years. This exceedingly long lifetime was determined on the basis of the following two experimental results. Little degradation was observed in Cl error rate during about 50 days at 120 degree(s)C (DOT) 90% RH. A main degradation mode, which was observed on longer aging, was Cr film peeling-off. It was found that activation energy for Cr peeling-off process was 0.91 eV by an in-situ peeling detection tester, based on the acoustic emission method.