Patent GB-1165408-A (GB)
Title: Electrophotography
IPC: G03G15/045
Filed: 1966-07-12
Abstract: 1,165,408. Electro-photographic process. CANON CAMERA CO. Inc. July 12, 1966 [Sept. 1, 1965; Oct.28, 1965; Dec.1, 1965; Dec.24, 1965; Feb.23, 1966], No.16850/69. Divided out of 1,165,405. Heading G2H. An electro-photographic process use an electro-photographic member having first and second insulating layers between which a photoconductive layer is located, at least one of the insulating layers being translucent for exposing the member. The process consists in applying to the surfaces of the first and second insulating layers a positive and a negative primary charge respectively whereupon layers of negative and positive charge are formed in the regions of the interfaces between the photo-conductive layer and the first and second insulating layers respectively. Thereafter the member is exposed to an image while simultaneously applying to the surfaces of the first and second insulating layers a negative and a positive secondary charge respectively so that, in the areas of the image in which the photo-conductive layer is activated, the polarity of the charges of the member on the member is reversed, whereas, in other areas of the image, at least some of the charges of the layers formed in the regions of said interfaces remain bound there, thus forming an electrostatic image on the member. Preferably, the member is exposed to uniform radiation while the primary charge is applied. The process also preferably includes the additional step after termination of the image exposure and application of the secondary charge of exposing the member to radiation to activate the photo-conductor layer overall to increase the contrast of the electrostatic image. In one apparatus Fig.9 the electro-photographic member is in the form of a flexible belt 1s. With the double corona charger 7s, 8s positioned as shown the belt is moved through the charger while being uniformly irradiated by a lamp 9s. The charged belt is stopped when it reaches the exposure position under the reflecting optical system 38s. A frame from the film 44s is projected on to the belt whilst simultaneously the coratron 8s, now working at reverse polarity, is scanned across the belt by a drum 14s (movement of the drum triggers a potential reversing switch on the charger). The belt is then moved on in continuous motion pass the source 17s of uniform radiation (the coratron 8s being returned to its original position) and past the magnetic brush developer 44s'. The developed image is transferred to continuous final image media by the pressure applied by roller 22s or by a potential applied to this roller, and the image fixed by heater 27s, 28s. The copy belt is cleaned by rubber scrapers 33s. In the copying apparatus of Fig. 12 and of Fig. 13 (not shown) the electrographic member rests on a grounded transparent conductive support and has its upper insulating layer opaque. An original 12b is illuminated by the lamp 13b of an optical system 18b. By lateral movement of the optical system an image line is scanned and projected on to the copying material B, the opaque surface of which has been previously charged with a given polarity by a corona generated by one section 23 ab of the charger. While the projected image is scanned over the copying material secondary charging, of opposite polarity to the primary charge, is effected by the second section 23bb of the charger. The charger is mounted on rails (22b) and follows the scan of the motor driven optical system because of attraction between magnets 24b, 25b in the two parts. Following uniform illumination of the copying material by an internal lamp (21b) a visual image may be developed (in normal light) on the opaque surface of the material and transferred to a suitable medium where it is fixed to form the final image. Suitable constructions for the electrophotographic member are described and claimed in co-pending Specification 1, 165, 409.