Patent attributes
Provided is a polyorganosilsesquioxane capable of forming, when cured, a cured product that offers high surface hardness and good heat resistance, is highly flexible, and has excellent processability. The present invention relates to a polyorganosilsesquioxane including a constitutional unit represented by Formula (1). The polyorganosilsesquioxane includes a constitutional unit represented by Formula (I) and a constitutional unit represented by Formula (II) in a mole ratio of the constitutional unit represented by Formula (I) to the constitutional unit represented by Formula (II) of 5 or more. The polyorganosilsesquioxane has a total proportion of the constitutional unit represented by Formula (1) and a constitutional unit represented by Formula (4) of 55% to 100% by mole based on the total amount (100% by mole) of all siloxane constitutional units. The polyorganosilsesquioxane has a number-average molecular weight of 1,000 to 3,000 and a molecular-weight dispersity (weight-average molecular weight to number-average molecular weight ratio) of 1.0 to 3.0.[R1SiO3/2] (1)[Chem. 2][RaSiO3/2] (I)[Chem. 3][RbSiO(ORc)] (II)[Chem. 4][R1SiO(ORc)] (4).
