Browse Prior Art Database

Window Protection

IP.com Disclosure Number: IPCOM000086837D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Crossan, SC: AUTHOR [+2]

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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Window Protection

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.

Tone build-up at the window due to electrostatic charge is avoided by, for example, rendering the window conductive and grounding it, without interfering with its transparency. Any means of coating the window to render it conductive is suitable as, for example, by the deposition of a thin coating of vacuum-deposited carbon upon the window. A layer of carbon on the order of about 100 Angstroms will serve to render the window conductive without any substantial interference with its transparency. However, merely rendering the window conductive will not avoid all problems. Where the resistance across thy window is decreased to 10/9/ ohms or less the rate of PTFE film formation increases, resulting in a decrease of window...