The above polishing layer is preferably constituted with a polymer material having {HEAD ~ a tensile elastic modulus} at 50° C. after saturation swelling with water at 50° C. of 130 to 800 MPa, a loss tangent at 50° C. of 0.2 or less, and {TAIL ~ a contact angle} with water of 80° or less 
The above polishing layer is preferably constituted with a polymer material having { HEAD ~ a tensile elastic modulus } at 50 ° C. after saturation swelling with water at 50 ° C. of 130 to 800 MPa , a loss tangent at 50 ° C. of 0.2 or less , and { TAIL ~ a contact angle } with water of 80 ° or less
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH