GB1257231A - - Google Patents

Abstract

1,257,231. Electro-statographic processes. ELECTROPRINT Inc. Feb.25, 1969 [March 1, 1968 (2)], No. 10048/69. Heading G2H. An electrostatic latent image comprising two layers of opposite charge is formed on the insulating layer of a screen comprising apertured insulating and conductive layers 21, 23 and the screen is exposed to a source of ions which are repelled by the field of the charged parts of the screen and pass through the apertures in the unchanged parts to form a charge pattern in image configuration which is used to form a reproduction of the image. The latent image is formed on the screen by charging the surface of the insulating layer while holding the conductive layer at a fixed potential whereby the double layer of charge is produced as shown in Fig.3. This provides better field definition than a single charge layer. Preferably the insulating layer is photo-conductive and suitable screen constructions are described with reference to Figs. 4a, b, c (not shown). In the embodiment of Fig.7, an endless screen 51a comprising a photo-conductive layer 50a and an earthed conductive layer 52a is charged at 53a exposed line-by-line or whole frame at 61a and subjected to a further discharge at 63a, whereby a paper sheet 77a receives an electrostatic latent image which is developed by an electrically biased brush 83a through an electrically biased mesh 87a. The short conveyors 57a, 67a are also electrically biased. In Fig.6 (not shown) imagewise exposure and the second charging step are simultaneous. In Fig. 6a (not shown) imagewise exposure and the first charging step, which utilizes a transparent electrode (106) are simultaneous. In Figs.8, 9 (not shown) the charge sprayed through the endless screen is received by a second endless screen. In Fig.8, further charge is sprayed through this second screen onto a receiver which is then developed. In Fig. 9, charged toner particles are sprayed through the second screen onto a receiver. A radioactive source is mentioned as an alternation to corona discharge devices.