| abstract |
An object of the present invention is to provide a polyorganosilsesquioxane which can be cured to form a cured product having high surface hardness and excellent in heat resistance, flexibility, and workability. The present invention relates to a polyorganosilsesquioxane characterized by having a structural unit represented by the following formula (1), a structural unit represented by the following formula (I) and a structural unit represented by the following formula (II) The molar ratio of the structural unit [the structural unit represented by the formula (I)/the structural unit represented by the formula (II)] is 5 or more, and the structural unit represented by the following formula (1) and the following formula (4) The ratio of the indicated structural units to the total amount of siloxane structural units (100 mol %) is 55 to 100 mol %, the number average molecular weight is 1000 to 3000, and the molecular weight dispersion (weight average molecular weight/number average molecular weight) is 1.0 ~3.0. [R 1 SiO 3/2 ](1)[R a SiO 3/2 ](I)[R b SiO(OR c )](II)[R 1 SiO(OR c )](4). |