Abstract: A method is described to control the maximum density and the pixel profile of microdots produced by a binary or multilevel electrophotographic device. In various embodiments, from the maximum development potential. The working point of the device is established by imposing a relation between charge level, discharge level and saturation voltage level of the photosensitive element. This allows to achieve consistent output densities, irrespective of the environmental parameters, such as relative humidity and temperature.

Abstract: In classic optical rendering systems, the spot, illuminating a microdot on the photosensitive medium, is designed to overlap with neighboring microdots, typically having an overlap of 1.7 times the pitch of the microdots, for a luminous intensity of 1/e.sup.2 the highest intensity. A "sharp" photosensitive medium, such as a photographic film used in graphical applications, generates a binary circle, obtainable by thresholding. The area of such a circle is too large, which results in higher dot gain.Many systems, such as electrographic systems, do not behave as a "sharp" medium. If intermediate energy levels are used, in order to obtain continuous tone or multiple density levels, thresholding behavior may be avoided by appropriate choice of energy levels. Such a different sensitometry results in specific requirements for the energy distribution for each microdot.

Abstract: A dry developer composition suitable for use in the development of an electrostatic charge pattern is described. This developer composition comprises toner particles the average particle diameter whereof is comprised between 3 and 10 microns, and spacing particles the average diameter whereof is under 40 microns and at least twice the average particle diameter of the toner particles, and is characterized in that the part of spacing particles in the overall amount of spacing particles and toner particles is comprised between 1 and 8% by weight.

Abstract: Electrophotographic method of obtaining lithographic printing plates comprising the following steps: (i) uniformly electrostatically charging a photoconductor element, (ii) image-wise discharging said photoconductor element, (iii) developing the resulting electrostatic charge pattern with dry toner particles of which more than 90% by volume have an equivalent particle size diameter less than 10 microns and more than 50% by volume have an equivalent particle size diameter less than 7 microns, (iv) electrostatically transferring the developed image to a toner receiving plate, said toner receiving plate comprising a plastic film support that is thermostable to a temperature of at least 140.degree. C. and a crosslinked hydrophilic layer thereon, said layer containing infrared absorbing substances in such an amount that the reflection density of said layer in the visible spectrum is between 0.4 and 1.4, and (v) fixing the transferred toner to said toner receiving plate by infrared radiation fusing.

Abstract: The present invention relates to a xeroprinting process, in particular a xeroprinting process comprising the following steps:(a) image-wise exposing to actinic radiation an electrostatic master having a photopolymerizable conductive layer to selectively polymerize and thereby increase resistivity in exposed areas of the layer;(b) forming a latent image of electrostatic charge by charging the master by corona discharge;(c) reversal developing the latent electrostatic image by depositing toner particles in the non-exposed areas of the layer;(d) transferring the toner image to another substrate and subsequent fusing;(e) resetting the process by cleaning and discharging the electrostatic master.According to a preferred embodiment the reversal development is effected by means of a development electrode inducing charges in the photopolymer plate opposite to the initial electrostatic image, and by means of dry electrophotographic toner.

Abstract: An electrostatic latent image developing assembly having a first feed passage for feeding developing material in a first direction, a second feed passage for feeding the developing material in a direction opposite to the first direction. A helical feed screw in the first feed passage, a helical supply screw in the second feed passsage for supplying part of the developing material to a developing sleeve, a connection between both sets of adjacent ends of such feed passages for permitting the developing material to circulate between the passages, wherein the feed screw and supply screw are disposed in parallel relation and the supply screw is provided with buckets around its periphery, the supply screw having a helical blade for advancing developing material in the second feed passage axially thereof while the buckets move the material circumferentially. Preferably, the radius of the helical blade reaches to at least one-half the depth of the buckets.

Abstract: Dry toner development of an electrostatic charge pattern on a recording surface is carried out with a dry toner layer formed on a donor member by electrostatic attraction resulting from a DC voltage applied across a gap between the surface of the donor member 22 and the surface of an upstream electrically conductive member 16 covered with a mixture of triboelectrically charged toner particles and magnetic carrier particles, the latter with adhering toner particles being attracted to the electrically conductive member surface by magnetic force and forming thereon a magnetic brush. The DC voltage in the gap causes selective attraction of the toner particles free of magnetic carrier particles and an AC voltage of lower peak magnitude can be superimposed on the DC voltage to set the particles in the gap in vibration and facilitate transfer across the gap.

Abstract: Electrophoretic process and apparatus for developing an electrostatic charge pattern carried by a dielectric surface by progressively moving that surface through a development station and simultaneously progressively advancing a layer of liquid toner (11) comprised of toner particles dispersed in a carrier liquid, through that station in proximity to said charge-carrying surface, (3), and imposing an electric field bias to cause or promote selective image-wise movement of toner particles through said liquid at said development station and deposition thereof on said charge-carrying surface in a pattern representing said electrostatic charge pattern, wherein said layer of liquid toner contains toner particles in a concentration of from 2 to 25% by weight, and including the step of applying a film of a substantially toner-free non-polar liquid which is miscible with the carrier liquid of said liquid toner and which has a specific conductivity lower than 0.

Abstract: An optoelectric circuit for measuring the different optical densities of an image carrier, a toned test patch in an otherwise untoned imaging area of a photoconductor surface in a xerographic apparatus, wherein a LED (46) irradiates a test area of the surface, a phototransistor (47) receives radiation reflected from the text area, an amplifier (51) amplifies the output signal of the phototransistor, the LED is driven by the amplified output current of the phototransistor, and the current through the LED is used as a measure of the optical density.