| 摘要 |
898,354. Printing processes. MIKROKOP1E G.m.b.H. June 16, 1958 [June 14, 1957; Nov. 15, 1957(2)], No. 19270/58. Class 100(2) [Also in Group XX] ' An electrostatic powder image on a photoconductive surface is transferred to a receiving sheet containing a compound with which. the powder reacts in the presence of moisture to give a coloured image. Thus the powder image may comprise N-pyrrolidino-thiocarbamate or N-piperidino-thiocarbamate and the transfer paper may be coated with ferric ammonium sulphate, the paper being moistened before contacting it with the powder image, or the powder image may comprise iron stearate which reacts with gallic acid in the transfer paper after the latter has been moistened with aqueous alcohol. Alternatively, the powder image may comprise a diazonium compound and the transfer paper may contain phloroglucinol, moistening of the transfer paper being effected with a solution of sodium chloride, sodium acetate and tartaric acid, or one of the reactants may be aniline or a derivative thereof and the other may be an oxidizing agent such as K 2 S 2 O 8 or K 2 Cr 2 O 7 and may include a catalyst such as VCl 5 or CuS0 4 . In Example 11, the powder image is of copper sulphate, lead nitrate or silver nitrate, and the transfer paper is soaked in sodium sulphide solution which is first dried and then moistened before transfer. Reference is also made to the use of an eosin image which will react with alkali in the transfer paper when the latter is moistened with acetone. Specifications 308,653 and 425,235 are referred to.
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