Provided is a composition for forming a polishing layer of a chemical mechanical polishing pad having polishing characteristics such as a high polishing rate, an excellent planarity of the polished object and less scratches of the polished object.
The above composition for forming a polishing layer of a chemical mechanical polishing pad comprises (A) a polyurethane having a carbon-carbon double bond on a side chain and (B) a cross-linking agent. The polyurethane (A) is preferably a thermoplastic polyurethane (A') obtained by mixing at least the following components (a11) to (a13) and component (a2) in a proportion satisfying the following conditions (1) and (2) and reacting them:
(a11) an oligomer which has one or more hydroxyl groups and one or more carbon-carbon double bonds and which has a number average molecular weight of 500 to 2500, (a12) an oligomer which has two or more hydroxyl groups and either one or both of an ether bond and an ester bond and which has a number average molecular weight of 500 to 2500 and is different from the component (a11), (a13) a monomer having two hydroxyl groups and (a2) a monomer having two isocyanate groups; and (1) a value of M-1/M-OH is 0.85 to 1.10, and (2) a value of M-2/M-OH is 0.45 to 0.80, wherein M-1 is the number of isocyanate groups contained in the component (a2), M-2 is the number of hydroxyl groups contained in the component (a13) and M-OH is the total number of hydroxyl groups contained in the components (a11), (a12) and (a13).