Abstract: The present invention provides an encapsulant for optical semiconductor devices, which is capable of suppressing surface tackiness of a cured product and is also capable of enhancing the heat resistance and thermal cycle characteristics of the cured product. An encapsulant for optical semiconductor devices according to the present invention which includes: a first organopolysiloxane which is represented by formula (1A) or formula (1B) and has an alkenyl group and a methyl group bonded to a silicon atom; a second organopolysiloxane which is represented by formula (51A) or formula (51B) and has a hydrogen atom bonded to a silicon atom and a methyl group bonded to a silicon atom; and a catalyst for hydrosilylation reaction, and the content ratios of methyl groups bonded to silicon atoms in the first and second organopolysiloxanes each are 80 mol % or more.

Abstract: Provided is an encapsulant for optical semiconductor devices, which is capable of enhancing the adhesion between a housing and the encapsulant when an optical semiconductor device is encapsulated in the housing, and which is also capable of enhancing the bonding reliability with respect to humidity. The encapsulant for optical semiconductor devices includes: a first organopolysiloxane having an alkenyl group bonded to a silicon atom and an aryl group bonded to a silicon atom, but not having a hydrogen atom bonded to a silicon atom; a second organopolysiloxane having a hydrogen atom bonded to a silicon atom and an aryl group bonded to a silicon atom; a catalyst for hydrosilylation reaction; and an organic compound having a titanium atom.

Abstract: The present invention provides a sealant for an optical semiconductor device which is less likely to reduce its luminance and is also less likely to change its color even used in an energized state in harsh environments of high temperature and high humidity. The sealant for an optical semiconductor device includes: a first organopolysiloxane not containing a hydrogen atom bound to a silicon atom, but containing an alkenyl group bound to a silicon atom and an aryl group bound to a silicon atom, a second organopolysiloxane containing a hydrogen atom bound to a silicon atom and an aryl group bound to a silicon atom, and a platinum-alkenyl complex. The platinum-alkenyl complex is a reaction product obtained by reacting chloroplatinic acid hexahydrate with not less than 6 equivalent of a bi- or more-functional alkenyl compound.

Abstract: The present invention provides a sealant for an optical semiconductor device which is less likely to reduce its luminance and is also less likely to change its color even used in an energized state in harsh environments of high temperature and high humidity. The sealant for an optical semiconductor device includes: a first organopolysiloxane not containing a hydrogen atom bound to a silicon atom, but containing an alkenyl group bound to a silicon atom and an aryl group bound to a silicon atom, a second organopolysiloxane containing a hydrogen atom bound to a silicon atom and an aryl group bound to a silicon atom, and a platinum-alkenyl complex. The platinum-alkenyl complex is a reaction product obtained by reacting chloroplatinic acid hexahydrate with not less than 6 equivalent of a bi- or more-functional alkenyl compound.

Abstract: The present invention provides a sealant for an optical semiconductor device which has high gas barrier property against corrosive gas, and is less likely to crack or is less likely to peel off even when used in harsh environments.