A developer for electrostatography containing a positive charge controlling agent comprising fumed silica particles treated with a silane coupling agent or titanate coupling agent and controlled to an appropriate degree of hydrophobicity has a stable and sharp distribution in amount of positive triboelectric charges under a variety of conditions including higher temperature-higher humidity or lower temperature-lower humidity conditions. This developer is useful particularly in an electrophotographic process employing a developer carrying member for charging of the developer.
An improved positively charged developer compositions comprised of toner compositions containing resin particles, pigment particles and modified charge enhancing additives comprised of flow aid compositions having chemically bonded thereto, or chemiadsorbed on the surface thereof amino alcohol derivatives comprising at least one hydroxyl group, and at least one amino substituent selected from the group consisting of primary amines, secondary amines, and tertiary amines; and carrier particles.
The tribo-electro static charge is stabilized by treating the surface of the metallic-oxide fine powders such as a silica powder, using the mixed solution which consists of a specific silane coupling agent containing primary amino group, other silane coupling agent containing amino group and the hydrophobic agent The powder such as silica has the small charge variation with time, and is suitable as the additive of the powder coatings or the electrophotographic toner.
A positively chargeable developer, comprising: positively chargeable toner particles, positively chargeable silicate fine powder having a positive triboelectric chargeability higher than that of the toner and a mean particle size of 3 microns or smaller, and a microdisperser having a triboelectric chargeability lower than that of the toner and a mean particle size which is larger than that of the silicate powder and smaller than that of the toner particles. The microdisperser has a function of disintegrating particularly the positively chargeable silicate fine powder and enhances the attachment thereof to the toner particles, whereby the developing characteristics including the triboelectric chargeability are stabilized from the initial stage of electrophotographic copying operation, and the storage stability is also improved.
By treating metal oxide fine particles having a specific surface area of 5 to 500 m.sup.2 /g with a silane coupling agent and then further treating the fine particles with a reactive group-terminated organopolysiloxane, the organopolysiloxane is stably bonded to the surface of the powder particles, to thereby improve stability of the modifying effect against the elapse of time and durability.
An electrophotographic photoconductor is disclosed, which comprises an electroconductive substrate, a photoconductive layer formed on the electroconductive substrate, and a protective layer formed on the photoconductive layer, the protective layer comprising a binder resin and finely-divided particles of at least one metal oxide with the surface thereof being coated with a coupling agent selected from the group consisting of a titanate-type coupling agent, a fluorine-containing silane coupling agent, and an acetoalkoxyaluminum diisopropylate, dispersed in the binder resin.
