PURPOSE: To form halftone markings on the surface of a plastic case by a non-printing process wherein the markings consist of a satin finish surface and a number of grooved pats formed in this satin finish surface and the bottom surface of each grooved part is made glossy and flat.
CONSTITUTION: In the plastic case for video tape and audio tape cassette, etc., its surface 3 is given a satin finish (mat finish) and, in the process of producing the case blank, markings 5 and 7 such as designs, letters, symbols and words are formed on this surface 3. Each of the markings 5 and 7 consists of a number of narrow, long grooves and ridges 9 and 10 arranged close to one another and the bottom surface of each groove 9 is made flat and glossy. The depth(d), width(w) and pitch(p) of the groove 9 are appropriately adjusted to change the gradation of tone of the markings so as to obtain a desired tone of marking. Such markings are formed by a cylindrical metal die having a marking forming part consisting of a satin finish surface an a number of projecting parts projecting from this surface and terminating in the formation of a glossy top face.
UEMURA TOKU
SASAGAWA KOJI
