Optical disk substrate fabricated by the sol-gel method

Pregrooves for optical memory disks have successfully been fabricated in sol-gel derived SiO2 films on glass substrates of 130 mm in diameter, using a newly developed fine-patterning process. The patterning is carried out under vacuum by pressing a stamper against the SiO2 gel film containing poly(ethylene glycol), PEG, and then the gel film is pre-heat treated with being pressed by the stamper. After the gel film becomes hard, the stamper is removed and the glass disk substrate with patterned gel film is finally heat-treated at 350 degrees C to decompose PEG and to be densified, The process time Is shortened to the practical fabrication level by optimizing the pre heat treatment temperature and the amount of PEG added on the basis of the hardening properties of the gel films. The pregroove depth and pitch of the glass disk substrates fabricated show almost constant values at a given radius. The mechanical characteristics of the glass disk substrates satisfy the international standard(ISO/IEC 10089). The noise levels of the fabricated glass disk substrates are also low enough for the practical use. It is noted that the sol-gel pregrooved glass disk substrates have excellent weathering resistance compared with even the conventional glass disk substrates by the photo-polymerizable resin method or by the dry etching method. Considering the fact that optical disk industry is progressing in many ways, several applications of the sol-gel pregrooved glass disk substrates are proposed. The authors believe that increasing demand of high reliability and large storage capacity for various optical memory disks will require the sol-gel pregrooved glass disk substrates.