Patent GB-1073480-A (GB)
Title: Facsinmile recorder
IPC: G03G5/022
Filed: 1964-12-16
Abstract: 1,073,480. Television. RANK XEROX Ltd. Dec. 16, 1964 [Dec. 30, 1963], No. 51246/64. Heading H4F. [Also in Division G2] A recording web 32 used in a recorder for converting electrical signals, e.g. video signals, into visible images comprises a conductive layer 56, to which the video signal is applied by way of a conductive idle roller 31, a deformable photoconductive layer 57, a " frostable " thermoplastic layer 58 (see later), a transparent conductive layer 59, which is earthed by a sliding contact brush 62, and a transparent substrate 61. Simultaneously with the application of the video signal across the moving web, the web and in particular the photoconductive layer 57 is horizontally scanned with a constant intensity light source, e.g. from a cathode-ray tube 36 or a light source and a rotating mirror drum, Fig. 3, not shown, so that the charge pattern set up on the surface of the photoconductive layer moves to the interface between the photoconductive layer and the thermoplastic layer and as the light moves on to another portion of the web the layer 57 reverts to its insulating condition trapping the charge at the interface. With the charge pattern thus formed, or before, the web is heated to soften layers 57 and 58, thermoplastic layer 58 being softened sufficiently to bring its viscosity down to the frost threshold point, i.e. sufficiently low so that the force of the trapped charges overcomes the surface tension forces of the softened thermoplastic layer causing it to form wrinkles, making up the desired image, photoconductive layer 57 being sufficiently soft at this raised temperature so that it will conform to the wrinkles. The web is then cooled thereby hardening the frost image so that if all the layers of the web are transparent it may be used as a transparency, layers 57 and 58 having different refractive indices. The speed of the web is synchronized with the vertical scan of the transmitter pickup and the horizontal scan of the cathode-ray tube 36 is synchronized with the horizontal scan of the transmitter pick-up, Fig. 1 (not shown), and thus the charge pattern formed and trapped at the interface of the recording web exactly corresponds with the original of the image transmitted. After use the web may be resoftened so as to erase the image and may be recycled through the whole process. A supporting substrate similar to substrate 61 may be applied to conductive layer 56, the video signal being applied to this layer through a sliding brush contact. In a further embodiment, Fig. 3 (not shown), the web comprises a supporting substrate (63), a conductive layer (64) to which the video signal is applied, a film of viscous conductor (67), a thermoplastic layer (68), a photoconductive insulating layer (69), an earthed transparent conductive layer (71) and a supporting substrate (72). Layer (67) is softenable by the temperature required to reduce the viscosity of the thermoplastic layer (68) to the frost threshold, and thus since the frost imaging takes place at the interface of layers (67) and (68) photoconductive layer (69) need not be deformable. Layers (67) and (68) have different refractive indices. The maximum light output from a cathode-ray tube is inadequate for high-speed scanning with photoconductors generally employed and thus for high-speed scanning a high intensity light source (74) and a rotating hexagonal mirror drum (78) is used, Fig. 3 (not shown). Instead of a frost image a " relief " image may be formed in which deformation only takes place at places of high potential gradient on the softened charge bearing surface as described in Specification 1,043,981. The recording webs may be as described in Specification 1,069,741. Frostable thermoplastic layer 58 may comprise " Staybelite " ester (Trade Mark). Deformable layer (67) may comprise water, alcohol, glycerine, sucrose, acetate, isobutyrate or polyethylene glycols. Photoconductive insulating layer (69) may comprise cadmium sulphide or amorphous selenium.