[Patent application number] 20120077420 [Published] 03-29-2012 [Description] 
METHOD OF MANUFACTURING ANNULAR BODY - A method includes: charging a polishing material into a polishing apparatus that polishes a surface of a cylindrical film including a resin; alternately and repeatedly performing a surface-roughening operation of causing the polishing material to collide with the surface of the cylindrical film, thereby roughening the surface, and a cylindrical film replacing operation of replacing the cylindrical film on which roughening of the surface has been completed with another cylindrical film on which roughening of the surface has not been completed; replacing the polishing material by partially discharging the polishing material, and charging a new polishing material so that the percentage of the new polishing material with respect to the total amount of the polishing material after the new polishing material is charged becomes 30% by weight or more; and alternately and repeatedly performing the surface-roughening operation and the cylindrical film replacing operation again.