MAGNETIC RECORDING MEDIUM AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To easily detect forgery of magnetic information by setting a magnetic recording part essentially consisting of Mn and Bi to a base material and securely providing the base material with an irreversible object which generates an irreversible reaction at a temperature at which the information is written to the magnetic recording part. SOLUTION: A magnetic recording part 3 essentially consisting of Mn and Bi is set on a plastic base 2. An irreversible object 4 is placed on the magnetic recording part 3, which generates an irreversible reaction at a temperature at which magnetic information is written to the magnetic recording part 3 (not higher than 200 deg.K). The irreversible object 4 is formed as a coated film of synthetic resin particles having self film formation properties and inorganic fine particles with keeping a distortion inside in a process where the synthetic resin particles are melted to form a coat. In reloading to the magnetic recording part 3, when the temperature is lowered to not higher than 200 deg.K, the irreversible object 4 decays by itself and therefore the self decay of the irreversible object 4 can be visually observed.