PURPOSE: To form a metal back film on a fluorescent screen so as not to generate blisters by pressing an abrasive sheet on an aluminum thin film so as to make a large number of micro holes for degassing in the thin film with micro abrasive particles on the abrasive sheet.

CONSTITUTION: An abrasive sheet 7 is pressed on an aluminum thin film 3 before heat treating to make a large number of micro holes for degassing in the thin film 3 with micro abrasive particles. The abrasive sheet 7 consists of a large number of micro abrasive particles 9 uniformly coated on a flexible polyester resin film 8 of about 75μm in thickness, and the micro abrasive particles 9 may be green silicon carbide or alundum or the like of 3μm-20μm in mean particle diameter. Thereby the generation of blisters in the metal back film can be prevented without loss of its proper functions.