Patent GB-1016581-A (GB)
Title: Dyed image xerography
IPC: G03G15/01
Filed: 1962-08-03
Abstract: 1,016,581. Electro-photographic processes. RANK XEROX Ltd. Aug. 3, 1962 [Aug. 3, 1961], No. 29925/62. Heading G2H. A method of single or multi-colour image reproduction comprises xerographically forming a powder reproduction of an original on a dye receptive surface, fusing the powder to form a pattern which is a resist to aqueous dye solutions, and applying dye to the surface bearing the powder reproduction for absorption of the dye at uncovered points along the surface. In one embodiment, a xerographic plate 10 is charged by corona device 11, Fig. 1 (not shown) and then exposed to an original 15 by light source 13, Fig. 2, which may be an incandescent bulb, a lens 16, a filter 17, and half-tone screen 18. Filter 17 separates out an image corresponding to a given colour, e.g. a red filter blocks all illumination other than read from reading plate 10. The latent image is then developed by cascading developer particles across the plate liquid development by a suspension of developer particles in a liquid, transfer development by a sheet carrying developer particles placed in contact with the latent image, or by powder cloud development as shown in Fig. 3. The plate 10 rests on supports 19 adjacent an opening in a powder cloud chamber 20, while a generator supplies an aerosol of fine particles. A development electrode 22, e.g. a wire screen is placed adjacent the plate. The developer may be a resin toner, e.g., as disclosed in Specification 768,293. The developed image is then transferred to a colour absorbent member 26, Fig. 4, secured to a metal cylinder 27. The member 26 comprises a hydrophilic layer that swells and softens, but does not dissolve upon moistening or soaking, e.g., gelatin, cellulose, and hydrophilic or water swellable plastics. A suitable member in Kodak Dye Transfer Paper Type F Glossy. The cylinder 27 is mounted on guide rails 29 and has a pin 30 cooperating with a stop 32 for positioning the cylinder with respect to plate 10. The cylinder is rolled in contact with plate 10, the cylinder 35 being electrically connected to backing plate 10. Alternatively a potential may be applied between cylinder 27 and backing 25. The transferred image is fixed by vapour in a tank 36, Fig. 5 (not shown), such as trichloro ethylene vapour or by heat. The cylinder 27 carrying the member 26 is mounted above a tank 38, Fig. 6 (not shown) containing a dye solution. If a red filter was used for exposure the dye may be cyan which is absorbed in the areas not coated with the fixed image. The member 26 on the cylinder is then rinsed and the fixed image removed by applying a solvent from a tank 3s Fig. 7 (not shown). The solvent may be trichloroethylene. The member is again rinsed and then dried. The transfer of a second image made with a further colour separation filter, e.g., agreen filter together with the fixing, dyeing and removing the fixed image is then repeated and then further repeated using a blue filter and a yellow dye. An explanation of the colour separation process as applied to the present invention is given with reference to Figs. 8 to 11 (not shown). A colour printing apparatus, Fig. 12, has a series of cylinders 50 carrying sheets of dye transfer paper through the various process steps. Twenty xerographic plates bearing powder images produced by exposure to the same number of colour originals are positioned on plate 52. Corona wire 54 traverses the images and a cylinder 50 is rolled across the plate to transfer the powder images to the individual sheets 51. Hot air jets 55 dry the image bearing surfaces of the sheets 51, the images being fixed by solvent vapour in a chamber 58. Examples of sheets are trichloroethylene, butylacetate, butyl alcohol and perchloroethylene. The fixed image is impervious to aqueous dye solution applied at station 60. The cylinder then passes through rinsing station 61 and is dried by hot air jets 62. A rotary brush 65 supplied with solvent then removes the powder image before passing the cylinder through a rinsing station and drying station 67. The procedure is repeated using plates carrying powder images formed as a result of using red filters during exposure and then plates having powder images formed using blue filters to form multicolour prints. In a modification, a continuous web 71, Fig. 13 (not shown) of dye transfer paper is used. Stations corresponding to those of the previous embodiment are arranged along the length of the web path. In another modification, sheet 26, Fig. 4, is replaced by a sheet suitable for dye transfer work. The developed images of dye resistant particles are transferred and then fixed to separate sheets condensed after dye coating in a multiple dyetransfer process to a single sheet in register to form a multi-colour reproduction. The dye-coating and transfer steps may be repeated a plurality of times.