Abstract: A technique for detecting the toner solids concentration of a liquid toner uses electrostatic sensing and avoids reliance on optical transmission paths, which tend to clog and lead to undertoning or overtoning. The toner solids concentration is instead detected by measuring the residual electric potential of a developed area on an image bearing member. The residual electric potential has been discovered to correlate well with the toner solids concentration.

Abstract: A method and apparatus for eliminating undesirable development of background charge potentials in a multicolor electrostatographic system is disclosed, wherein the application of a developer bias at a given development station is selectively controlled to be substantially equal to or greater than the background image voltage of the image generated by a preceding imaging station such that the voltage differential between toner particles at the development station and the background areas including the previous image areas is substantially zero and the electrostatic forces acting on the toner particles are insufficient to attract the toner particles to the residual image.

Abstract: The present invention resides in a method for transferring images from an image-bearing surface, to a moving web or sheet. The image-bearing surface is advanced in a predetermined direction, and the receptor area of the image-bearing surface is exposed to successive images. The successive images are developed using a liquid toner comprising charged pigmented particles, in a liquid hydrocarbon carrier. A porous web is transported in synchronism with movement of said image-bearing surface into position for transfer of said developed images on said receptor area successively onto said web. In one embodiment, the web is an uncoated, non-conductive porous material. The web is treated with a fluorinated or partially fluorinated hydrocarbon surfactant hold-out material in an amount effective to reduce the penetration rate of the toner carrier into the web so as to ensure that sufficient carrier is available for complete and void-free transfer.

Abstract: A copier wherein charge director is supplied to a liquid developer in response to a conductivity measurement thereof. Toner concentrate deficient in charge director is supplied to the liquid developer in response to an optical transmissivity measurement thereof. Conductivity is measured by a pair of spaced electrodes immersed in the developer and through which a variable alternating current is passed. A variable capacitor neutralizes the inherent capacitance of the electrodes. A phase sensitive detector is provided with a reference voltage having the same phase shift as that caused by capacitive effects. The conductivity measurement is corrected in response to a developer temperature measurement.