Patent ID: 6838215

Claim:
A method for producing a graytone mask for use in the process for producing a display device having a multiplicity of pixel patterns, said graytone mask having an opaque part, a light-transmission part and a graytone part as a region formed with an opaque pattern having pattern dimensions equal to or smaller than a resolution limit of an exposing apparatus using a mask to reduce an amount of exposure light transmission through the region and having said graytone part included in each pixel pattern, the method for forming the graytone mask comprising the steps of: preparing a transparent substrate of a large-sized substrate of 330 mm or greater on one side with an opaque film thereon; forming a resist film on the opaque film, an on-plane distribution of the resist film thickness being suppressed to ±1% or less in a region where a graytone part is to be formed; patterning the resist film with a pattern data including graytone pattern data; developing the resist film to form a resist pattern; etching the opaque film with use of the resist pattern as a mask; stripping away the resist pattern.