BASE PLATE FOR MAGNETIC DISC

摘要

PURPOSE:To improve remarkably the degree of surface roughness of a film and to conceal the defects on the surface of an alloy base plate by coating a non- magnetic base plate having surface roughness within a limited range and waving pitch of a limited value or below with a polyimide resin in a thickness of a specific range. CONSTITUTION:An aluminum or aluminum alloy base plate of aluminum alone or aluminum-magnesium alloy or the like is used as a non-magnetic base plate and is finished by turning and press annealing to a prescribed waving pitch and surface roughness. The waving pitch is preferably 50mu and the prescribed surface roughness is preferably <=1muRmax. The film thickness of the polyimide resin to be coated on the base plate is preferably 5-50mu, more particularly 10-25mu. The soln. of the polyimide resin is coated on the non-magnetic base plate and is thereafter predried under leveling for about 10min at 150-60 deg.C. The entire part is then heated, dried and calcined at 200-350 deg.C and the intended base plate for a magnetic disc is manufactured.