Patent GB-698040-A (GB)
Title: Improvements relating to materials and processes for photo-lithographic printing
IPC: G03F7/016
Filed: 1949-10-13
Abstract: 698,040. Photo-mechanical printing surfaces. KALLE & CO. AKT.-GES. Oct. 13, 1949 [Oct. 15, 1948], No. 26337/49. Class 98 (ii). A foil having a hydrophilic non-metallic surface is sensitized with a specified diazo compound and is provided upon the sensitized surface with a design to be reproduced, executed manually or mechanically in a water-repellent medium which is compatible with greasy printing ink, whereupon the parts of the foil not covered by the design are either simultaneously desensitized and rendered hydrophilic by coupling with an azo component having a hydrophilic substituent, or are merely rendered hydrophilic by coating with a water-soluble hydrophilic colloid substance, and the foil is subsequently exposed to actinic radiation so that all remaining light-sensitive material is decomposed. The water-repellent design repels the azo component ot the colloid substance, and decomposition by light action of the sensitive material beneath the design converts it to a material which accepts greasy ink in the presence of water, and with the remainder of the foil being hydrophilic, the result is a lithographic printing plate. In examples: (1) a parchment paper sheet is spread with an aqueous solution of the diazo compound of 4-amino-1- [N : (2<SP>1</SP>: 3<SP>1</SP>: 4<SP>1</SP>: 6<SP>1</SP> - tetrachlorobenzyl)] - aminobenzene, dried, provided with a design by means of a printing-machine, coated with an aqueous solution containing dextrine and phosphoric acid and exposed through the back, and can then be used for taking prints on a direct or offset machine. (2) A superficially saponified cellulose acetate foil is sensitized with the zinc chloride double salt of the condensation product of the diazo compound of p-aminodiphenylamine and paraformaldehyde, smeared with aqueous sodium hexa-metaphosphate, dried and exposed through the back. (3) a foil as of example 2 is sensitized with the sulphonate of the diazo compound of that example, dried, printed upon, treated with aqueous gum arabic and exposed through the back. (4) Parchment paper is sensitized with the diazo compound of 4-[N(2: 6-dichlorobenzyl)]- amino-aniline, typed upon, treated with gum arabic and exposed. (5) Superficially saponified cellulose acetate is sensitized with the condensation product from the diazo compound of p-aminodiphenylamine and formaldehyde, a design is formed thereon by printing or by use of a lithographic crayon and the sensitive layer is coated with aqueous dextrine and exposed to light. (6) Paper is sensitized with the sulphonate of the condensation product used in example 5, typed upon, treated with aqueous polyvinylpyrrolidone and exposed. (7) Parchment paper is sensitized as in example (2), covered with writing or with a design by means of a lithographic crayon, treated with an aqueous solution of the coupler 1-(4-sulphophenyl)-3-methyl- 5-pyrazolone to form an azo dyestuff on parts of the paper not protected by the crayon, and exposed to light through the back. (8) A superficially saponified acetyl cellulose foil is sensitized as in example (7), typed upon, coupled and exposed similarly. As well as the materials of the examples, other foils, such as superficially saponified polyvinyl esters, esters applied as varnish coatings to supports such as paper, metal or plastic material and having the varnish surface saponified, or urea resin coated paper; other diazo sensitizers as indicated by a structural formula, and other hydrophilic colloid substances such as cellulose ethers, polyuronic acids, sugar, polyvinyl alcohol, protein substances, polyethylene oxide, pectin, sodium alginate, mesquite gum and guar resin, may be used. Specification 697,521 is referred to.