Nitrogen-containing additives for magnetic toners having hydrophobic and hydrophilic moiety

#This invention generally relates to development of images and more specifically to electrophotographic development employing magnetic toner particles which can be applied from a magnetic brush to the electrostatic latent image without using a carrier material as is normally employed in most development systems.

#The use of development systems for magnetic development without employing carrier materials has been suggested for example, in Wilson U.S. Pat. No. 2,846,333 which discloses the use of magnetic brush system to apply toner particles formed of ferrites and resin materials for developing electrostatic latent images. Although this process performs satisfactorily in most environments, the conductivity of the toner resulted in some instances in causing the electrostatic transfer to be somewhat difficult.

#Kotz U.S. Pat. No. 3,909,258 also teaches the development of magnetic systems without carriers and more specifically there is described in this patent an electrostatic development process employing an inductive magnetic brush without carrier. A toner useful in the magnetic development process of the Kotz patent is described in Nelson U.S. Pat. No. 3,639,245 which teaches a dry toner particle having specific electric conductivity. This type of toner is prepared by blending magnetite with the resin and subsequently pulverizing the material to a small particle size. These particles are then mixed with conductive carbon black which is imbedded in the surface of the particle and small particles of SiO.sub.2 are mixed into the toner to improve flowability. One disadvantage of this type of toner although it is sufficient for most purposes, is that it does not transfer consistently from a photoconductive substrate to a plain bond paper thereby resulting in some instances in image quality of lower resolution that is normally expected. More specifically, the poor transfer efficiency results in low image density and causes photoreceptor cleaning problems.

#The following Examples further define, describe and compare methods of preparing toners of the present invention, and of using these toners in electrophotographic systems. Parts and percentages are by weight unless otherwise indicated.

#There was prepared a toner using melt mixing followed by attrition of a formulation of about 70 parts of Mapico Black magnetite (Cities Service Co.), about 27 parts of 65/35 styrene-n-butyl methacrylate and about 3 parts of dimethyl dihydrogenated tallow ammonium chloride. The powder resistivity of this toner is 10.sup.14 ohm-cm at field strengths of 40 volts/cm.

#This toner was used in an induction magnetic development system without a carrier in a Mita Copystar 700D copier using ZnO paper and was found to produce images of good quality with low background. In a separate test this toner was also found to transfer well electrostatically to plain bond paper. The ability of the toner to develop in an inductive magnetic brush system indicates that the toner is conductive at high field strengths and therefore field dependent.