Patent ID: 6924090

Claim:
A method of recording mutually different identifiers on multiple plate members, each said identifier including a group of character strings having character strings A and B, the character string A including a number z 1 at characters, the character string B including a number z 2 of characters, where z 1 and z 2 are both natural numbers, the method comprising the steps of: (a) preparing a photomask of a first type and at least one photomask of a second type, the photomask of the first type having opaque patterns that define a blank region, on which the character string B should be written, and the character string A, the at least one photomask of the second type having an opaque pattern that defines at least one of the characters of the character string B; (b) forming a photoresist layer on the surface of one of the plate members; (c) selectively exposing the photoresist layer to a radiation by using the photomask of the first type, thereby defining an unexposed region, corresponding to the blank region, and a latent image at the character string A in the photoresist layer; and (d) forming a latent image of the at least one character of the character string B in the unexposed region of the photoresist layer by using the at least one photomask of the second type.