Lithographisches Druckverfahren und hierfuer geeignetes photographisches Material

摘要

1,141,597. Photographic processes and materials. EASTMAN KODAK CO. May 26,1966 [May 28,1965], No. 23529/66. Addition to 978, 744. Headings G2C and G2M. A photo-sensitive material comprises a support coated with a layer containing a silver halide tanning developer and a hardened and unfogged gelatino silver halide emulsion layer containing a benzimidazole or oxacarbocyanine sensitizing dye. The dye may be of the formulae: wherein R, R 1 and R 2 are alkyl or substituted alkyl, R 3 is hydrogen, alkyl with up to 4 carbon atoms or aryl, R 4 and R 5 are hydrogen, halogen, alkyl, alkoxy, hydroxy, amino, alkyl substituted amino, carbomethoxy, carboethoxy, aryl or substituted aryl, Y is sulphur, oxygen, selenium, or -NZ is=C#R6 R7 or=N-R 8 where R 6 - R 8 are alkyl with up to 4 carbon atoms and X- is an anion, and including dyes which are inner salts. The silver halide emulsion may be a direct positive emulsion or be overcoated with a fogged silver halide emulsion. The developer and/or the emulsion layer may be hardened with formaldehyde. The material is imagewise exposed and treated with alkali to produce a planographic printing plate. In the examples, a support is coated with hardened gelatine layer containing a tanning developer and colloidal silver, overcoated with a hardened gelatine silver halide emulsion layer containing a sensitizing dye as specified above and top coated with a fogged gelatino silver halide emulsion. This is imagewise exposed, treated with alkali and fixed with acid to produce a negative planographic plate. Alternatively, the developer layer may contain silver halide and a merocyanine dye and be overcoated with a high-speed silver halide emulsion containing an oxacarbocyanine dye. On exposure and development with a conventional developer, a negative image is produced in the top layer. This material is then further exposed and treated with alkali to produce a tanned positive image in the lower layer so that on removal of the upper layer, a positive lithographic plate is produced. Alternatively, a direct positive emulsion may be used.