| 摘要 |
686,466. Developing electrostatic images. BATTELLE DEVELOPMENT CORPORATION. March 2, 1950, No. 5283/50. Class 98 (ii). A developer for electrostatic images comprises a mixture of electroscopic powder and a granular carrier material consisting of particles, each of which includes a core of selected specific gravity and a coating of material which generates triboelectrically a charge on the electroscopic powder when mixed therewith. The coating is preferably adhered to the core by an adhesive. The electroscopic powder may be produced by pulverizing a heat-formed agglomeration of carbon black and a phenol formaldedehyde resin as described and claimed in Specification 679,715. For developing a positive charge image, the carrier material is composed of steel, carborundum, or glass beads coated with a mixture of an alkylated melamine formaldehyde condensation product, a copolymer of vinyl chloride and vinyl acetate and a black nigrosine dye which is bonded to the bead core with a medium viscosity liquid heatreactive phenolic resin and low water content to which hydrochloric acid is added as a polymerization catalyst. For developing a negative charge image, the carrier material is composed of glass beads and coated with mixtures of a phenol-furfural and phenol-formaldehyde thermosetting resin and a phenol-formaldehyde moulding resin with (a) either a thermoplastic resin copolymer of vinylidene chloride and vinyl chloride or a chlorinated butadiene when the bonding resin is the above-mentioned hydrochloric acid catalized liquid phenolic resin, or (b) a co-polymerized vinyl chloride-vinyl acetate resin when the bonding material is a resin adhesive comprising a phenol-formaldehyde moulding resin and hydrochloric acid. Reference has been directed by the Comptroller to Specification 679,715.
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