-to-plate Material And Performance Of Electrostatic Photography

Computer-to-plate making is a process in which pre-print DTP digital work-flows are output directly into plate. Due to high light-sensitivity, high imaging speed and excellent operating performance, Xerographies has been widely used in Xerox , laser printer ,digital press and digital color proofing . Based on the technology of organic photoconductor and Xerographies . Computer-to-plate making processes are carried out by two kinds of plate in this thesis.One kind of plate, suitable for high-volume offset press, is base-dissoluble. Two series of co-polymer, which are base-dissoluble, St-AA and St-MAA, have been synthesized by different ratios of St to AA and St to MAA. Their structures are identified by IR . Solubilities in basic-aqueous solution, electrostatic charging properties and Xerographic imaging properties are measured as compared with Novelak . A special device for the measuring of film developing ratio is designed and built up on UV-Vis meter to research dynamically resin solubilities..Base-solubility of copolymers of St-AA and St-MAA with molecule ratio of 0.5:1-1.5:1 have faster speeds than that ofNovolak in 0.15N solution of sodium hydroxide. In original developer used for normal pre-sensitive-plate, our copolymers and Novolak are dissolved fast. But in the developing solution, which is diluted with water in ratio of 1:10 (original developer: water in weight), the copolymers of St-AA and St-MAA with molecule ratios of 0.2:1-1.5:1 have good solubility while the Novolak shows no solubility. Compared with St-AA,copolymers of St-MAA show better properties both in base-solubility and in electrostatic charging .When Novolak film doped with ε -CuPc , its xerographic imaging properties is bad ,for example ,low electrostatic charging voltage and slow light decay speed, so it can not meet needs of Xerographic plate-making. The new plate systems of base-dissoluble copolymers are better than that of Novolak, especially in Xerographic imaging properties. But new plate systems exist some shortages, for example, lower than 500V electrostatic charging voltages, not better light decay speed. Ideal new copolymer systems are being developed. Due to lack of xerographic plate-making device, the printabilities of new copolymer plates can not be given.Another xerographic plate, called additive-type system, is prepared by mixing Vylon 200 and sensitized ZnO. The ZnO is made by injecting Y-TiOPc on the surfaces of ZnO particle to enhance spectrum sensibility. The additive-type plate gives excellent xerographic imaging properties (light sensitivity more than 0.1cm2/μJ) when the ratio of ZnO: Vylon 200 is 4: 1 and the concentration of Y-TiOPc is 3wt% to ZnO. This kind of plate insures more than 5000 copies and meets short-run works. The prints have good properties: clear image, enough printing density, high resolution, low cost.