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Conducting Organic Coatings on Copier Toner Sensor Windows

IP.com Disclosure Number: IPCOM000085736D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Engler, EM: AUTHOR [+4]

Abstract

In electrophotographic copier systems toner material is utilized to develop latent images. For proper development the concentration of toner is controlled within defined limits. In order to measure and control the toner concentration of a developer mixture, the toner is transported past a viewing window. The window may be of glass or of clear plastic. A toner concentration control system located at that window, for example, as described in U.S. Patent 3,756,192, optically monitors the reflectivity of the developer mixture, and causes additional toner to be added in accordance with the sensed signal.

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Conducting Organic Coatings on Copier Toner Sensor Windows

In electrophotographic copier systems toner material is utilized to develop latent images. For proper development the concentration of toner is controlled within defined limits. In order to measure and control the toner concentration of a developer mixture, the toner is transported past a viewing window. The window may be of glass or of clear plastic. A toner concentration control system located at that window, for example, as described in U.S. Patent 3,756,192, optically monitors the reflectivity of the developer mixture, and causes additional toner to be added in accordance with the sensed signal.

In order to insure accurate measurement of toner concentration, it is necessary that the window remain substantially transparent and translucent. Unfortunately, there is a tendency for toner material to accumulate at the window, usually due to isolated electrostatic charges present on the window. Additionally, where the developing system includes a carrier, such as, metal particles coated with polytetrafluoroethylene (PTFE), there may be a tendency for the PTFE to form an interfering film on the window.

An application of coatings of organic conductors onto copier toner sensor windows is described. Thin films of these organic conductors have been found to dissipate charge buildup on the window. Furthermore, these films have softer or more compliant surfaces than the typical conductors described above and have proven successful in preventing TEFLON* filming.

The organic conductors employed are from the general class of donor-acceptor charge-transfer salts. Two of these organic conductors, tetrathiafulvalenium-tetracyano-p-quinodimethanide (abbr. as TTF-TCNQ) and tetrathiafulvalenium bromide (abbr. as TTFBr), are examples of organic conductors and are used here to demonstrate the use of these materials; however, the results are extendable to a much larger number of charge transfer salts.

Two different modes of preparing these organic conducting coatings are employed. The first method involves simply subliming a suitable organic conductor onto the window. In the case of TTF-TCNQ, smooth, highly conducting, nearly transparent films were obtained in a sublimator at 1-3 torr pressure with the material heated at 130-150 degrees C and the window at room temperature. Suitable films were obtained on heating for periods as little as 0.5 minute, longer times provided thicker films. The second method for coating an organic film onto the sensor window involves first subliming the neutral donor o...