Abstract: A curable composition comprising: component (A), which is an aliphatic organic compound including at least two carbon-carbon double bonds within one molecule, the at least two carbon-carbon double bonds having reactivity with an SiH group; component (B), which is a compound including at least two SiH groups within one molecule; and component (C), which is a hydrosilylation catalyst. The curable composition can be made into an optical material by being previously mixed so as to allow the carbon-carbon double bonds having reactivity with an SiH group to react with some or all of the SiH groups in the composition, thereby causing curing. There is provided a curable composition having a high heat-resistance, a low birefringence, a small coefficient of photoelasticity, a high optical transparency, and toughness; an optical material; a method for producing the same; and a liquid crystal display device incorporating the same.

Abstract: This invention is a method for the production of a cyclic oligosiloxane, which comprises heating a linear or cyclic polysiloxane in the presence of a metal alkoxide, by which the cyclic oligosiloxane can be produced with high yield by a method having industrially high practical value, because it can carry out the reaction under moderate conditions without causing gelation of the reaction system, in comparison with conventional methods using an alkaline or acidic catalyst.

Abstract: When a polysiloxane or siloxane is contacted with a mixture which comprises an orthoester, a compound having an active hydrogen-containing group and an acid catalyst, it is easily decomposed even at room temperature to provide a silicon compound having a lower molecular weight such as an alkoxysilane.

Abstract: A process for preparing an alkoxysilane of the general formula:R.sup.3.sub.b SiH.sub.c (OR.sup.2).sub.4-(b+c)in which R.sup.2 represents a substituted or unsubstituted alkyl group, R.sup.3 represents a monovalent substituted or unsubstituted hydrocarbon group, b is 1, 2 or 3, and c is 0, 1, or 2, having the step of:reacting an alkoxysilane of the general formula:R.sup.1.sub.a Si(OR.sup.2).sub.4-awherein R.sup.1 represents a monovalent substituted or unsubstituted hydrocarbon group, R.sup.2 is the same as defined above, and a is 0, 1, 2 or 3, with a polysiloxane in the presence of a catalyst containing an aluminum alkoxide, a zirconium alkoxide or a zirconium chelate to obtain the alkoxysilane, which process suppresses side reactions to provide the intended compound which is free from halogen compounds in a high yield.