Method of manufacturing a printing plate

The method which comprises the steps of

• (1) producing a halftone dot photograph (A) showing shading with the sizes of halftone dots,
• (2) cutting out a desired portion (B) of the halftone dot photograph produced according to step (1), to thereby produce a cut out photograph (B),
• (3) adhering the cutout desired photograph portion (B) resulting from step (2) to the surface of a transparent film (C),
• (4) printing the front side of the product of step (3) on a positive film to thereby produce a halftone positive film (D),
• (5) printing the reverse side of the product of step (3) on a negative film to produce a silhouette film (E) in which said cut out desired portion appears as deep-black,
• (6) superimposing said halftone positive film (D) resulting from step (4) on a photosensitive resin plate and exposing it to light to produce a photographic resin plate (F) in which the transparent portion of the halftone positive film (D) becomes the raised portion,
• (7) turning over said silhouette film (E) and superposing it on the photosensitive resin plate and exposing it to light to thereby produce a silhouette resin plate (G) in which its transparent portion becomes the raised portion,
• (8) said photosensitive resin plates being produced in such a way that a photosensitive resin is formed on a metal plate to a desired thickness,
• (9) alternately bringing said photographic resin plate (F) and said silhouette resin plate (G) into contact with a continuous foaming resin plate (H) under heated conditions to thereby effect at least partial sealing of those portions of the continuous foaming sheet (H) that do not correspond to said desired portion (B) of the halftone dot photograph and to thereby leave the remaining portion of said continuous foaming resin plate (H) receptive to the permeation of ink.