| 摘要 |
PURPOSE:To prepare the title material which has an improved light transmittance and is free from crack by hydrolyzing and polycondensing a specific compd. in the presence of a drying-controlling agent to give a gel and subjecting the gel to a supercritical drying. CONSTITUTION:A compd. selected from the group consisting of a difunctional alkoxysilane of formula I (wherein R<1>, R<2>, and R<3> are each 1-5C alkyl or phenyl), a trifunctional alkoxysilane of formula II (wherein R<4> and R<5> are each and a tetrafunctional alkoxysilane of formula III (wherein R<6> is R<1>) (e.g. tetramethoxysilane) is hydrolyzed and polycondensed in the presence of a drying- controlling agent (e.g. dimethylformamide) in a mixture of water and alcohol to give a gel, which is subjected to a supercritical drying to give the title material. |
