Patent GB-1398258-A (GB)
Title: Electrophotography
IPC: G03G9/12
Filed: 1973-09-24
Abstract: 1398258 Electrographic development EASTMAN KODAK CO 24 Sept 1973 [22 Sept 1972] 44592/73 Heading G2H. A method of developing an electrostatic charge pattern carried on the surface of an electrically insulating hydrophobic substrate to provide a water-soluble dye image comprises, (A) treating the charge pattern with an electrostatic image developer consisting of a dispersion of hydrophobic polymer toner particles in a liquid having a dielectric constant less than three and a resistivity greater than 10<SP>8</SP> ohm-cm, the polymer of the toner particles having as a repeating unit thereof a group derived from an ethylenically unsaturated polymerizable monomer having attached thereto either (1) a sulphonic acid group, carboxylic acid group, the anhydride or partial alkyl ester of such groups or (2) a basic nitrogen containing group; (B) contacting the deposited toner particle pattern with an activating solution of appropriate acidity or basicity to render the toner pattern hydrophilic and (C) contacting the hydrophilic toner pattern with an aqueous dye solution to form a visible, water-soluble, dye image corresponding to the toner pattern. Steps (A) and (B) may be performed together by using a mixture of the activating and the aqueous dye solutions. Many suitable developer compositions, activating solution compositions and dyes are specified. The preparation of some of the copolymers suitable for use in the developer are described in Specification 1396154. In one Example, an electrostatic image on a photo-conductive sheet, corresponding to one colour of three colour separation positives, is developed with a liquid developer comprising finely divided poly(2-methyl-5-vinylpyridine-comethyl methacrylate-co-lauryl methacrylate) particles in an isoparaffinic hydrocarbon solvent. The polymer particle image is electrostatically transferred to a receiving sheet, comprising poly (ethylene terephthalate) bearing a thin electrically conductive hydrophobic surface layer of cellulose nitrate containing cuprous iodide, and is dyed with a combined activating (acidic) and dye solution. In a second Example, the dye images are transferred successively to a single final support sheet, each image being fused on to said sheet before subsequent transfers thereto. In a third Example, three separate photo-conductive sheet matrices carrying developed separation images are dyed with their respective colours and the dyes in the polymer images transferred sequentially and in register to a single paper transfer sheet having a gelatine overcoat containing a basic mordant. Duplicate prints can be made by re-dying the matrices and transferring the dyes to another transfer sheet. In a fourth Example, a developer comprising a mixture of two hydrophobic polymer dispersions each in an isoparaffinic hydrocarbon solvent is used, the polymers being poly(ethyl acrylate-coethyl methacrylate-lauryl methacrylate-co-sulphoethyl methacrylate) and poly(styrene-co-lauryl methacrylate-co-sulphoethyl methacrylate). Activation and dying of the polymer image is effected with a basic aqueous dye solution containing ammonia.