TWI841716B

The present invention is: a curable composition containing a component (A) and a component (B), with the content of the component (B) being 1-110 parts by mass relative to 100 parts by mass of the component (A); a cured product obtained by curing this curable composition; and a method for using the curable composition as an adhesive for an optical element fixing material or as a sealing material for an optical element fixing material. This curable composition exhibits good coatability. This cured product has a low refractive index. Component (A): A curable polysilsesquioxane compound which has a repeating unit represented by formula (a-1) and has a mass average molecular weight (Mw) of 4000-20,000. Formula (a-1): R1SiO3/2 (R1 is at least one type of group selected from the group consisting of an unsubstituted alkyl group having 1-10 carbon atoms, a substituted alkyl group having 1-10 carbon atoms, an unsubstituted aryl group having 6-12 carbon atoms and a substituted aryl group having 6-12 carbon atoms.) Comp