Support sheet for photographic printing paper and process for producing the sheet

A process for producing a support sheet for photographic printing paper, comprising the steps of:

• forming at least one inner coating liquid layer comprising, as a principal component, at least one unsaturated organic compound curable by an electron beam irradiation on a surface of a substrate paper sheet comprising, as a principal component, a natural pulp;
• separately forming an outermost cured resin layer on a shaping surface by forming an outermost coating liquid layer comprising, as a principal component, at least one unsaturated organic compound curable by an electron beam irradiation on the shaping surface, and then applying a first electron beam irradiation to the outermost coating liquid layer;
• superimposing the inner coating liquid layer formed on the substrate paper sheet on the outermost cured resin layer and then applying a second electron beam irradiation to the resultant superimposed layer, whereby a front surface composite resin coating layer having a laminate structure comprised of (1) at least one inner cured resin layer adjacent to the substrate paper sheet and (2) an outermost cured resin layer laminated on and bonded to the inner cured resin layer is formed and the resultant outermost cured resin layer has a higher density of crosslinking than that of the resultant inner cured resin layer;
• releasing the resultant laminate composed of the substrate paper sheet and the front surface composite resin coating layer from the shaping surface;
• and
• forming a back surface resin coating layer comprising, as a principal component, a film-forming synthetic resin on the opposite surface of the substrate paper sheet.