PURPOSE: To shorten an injection molding process for a carrier and to prolong a service life of a metallic mold by providing two or more spiral tracks centering prescribed positions on a master disk.

CONSTITUTION: In an annular area 6 between a peripheral area 3 and a central area 5 of a master disk 1, two or more, four pieces, etc., spiral information tracks 9 are provided, of which the centers 7 are positioned off the center 4. When a carrier is injection-molded from a synthetic plastic material by using a nickel metallic mold made according to this disk 1, four equal carriers are produced at the same time and the carrier injection molding process is substantially reduced to 1/4 compared with a single piece production process, and a service life of the nickel metallic mold is substantially prolonged longer.