Browse Prior Art Database

SIMULTANEOUS TWO COLOR XEROGRAPHIC LASER PRINTER

IP.com Disclosure Number: IPCOM000025059D
Original Publication Date: 1983-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 155K

Publishing Venue

Xerox Disclosure Journal

Abstract

There is proposed here a method for achieving simultaneous two color imaging in a laser imaged xerographic printer. The proposed method utilizes a developer system with either two separate developers, or a "mixed" developer, the toners of which respond to positively charged images for one color and to negatively charged images for the other color. For this type of developer system, two oppositely charged images must be produced.

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CEROX DISCLOSURE JOURNAL

SIMULTANEOUS TWO COLOR XERO- GRAPHIC LASER PRINTER
Brian E. Springett

Proposed Classification

us. c1. 355/4 Int. C1. G03g 15/01

FIG I

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SIMULTANEOUS TWO COLOR XEROGRAPHIC LASER PRINTER (Cont'd)

There is proposed here a method for achieving simultaneous two color imaging in a laser imaged xerographic printer. The proposed method utilizes a developer system with either two separate developers, or a "mixed" developer, the toners of which respond to positively charged images for one color and to negatively charged images for the other color. For this type of developer system, two oppositely charged images must be produced.

The proposed method employs the photoreceptor 5 shown in Figure 1 which is either a three or four layer sandwich construction depending on the type laser used in the printer. Photoreceptor 5 consists of a trigonal selenium layer 6 which serves to inject holes and which can be light assisted if necessary. A transport layer 7 serves primarily to produce sufficient voltage for imaging while a generator layer 8, which is a Se:Te alloy (nominally approximately 15 wt.% Te), serves as the source of photodischarge for red (i.e., He:Ne) lasers. An insulating overcoat 10 allows the charging scheme to produce both hole injection and image charges.

For blue lasers (i.e., He:Cd or Argon), generator layer 8 may be omitted.

In operation, photoreceptor 5 is first charged uniformly with a negative charge. This causes an equal and opposite positive charge to arrive at the top of generator layer 8. Then a positive charge is applied which does not neutralize the negative charge, but instead leaves the net surface potential positive. Imaging by the laser is then performed, the normal laser intensity producing a net zero potential while no exposure leaves the surface potential positive. These two charge levels permit single color copying. For a second color, a different laser intensity is used to produce a net negative surface potential.

Switching between laser levels can be accomplished in several ways such as by the interposition of a neutral density filter, aperture switching, power supply switching where diode type lasers are used, modulator switching, etc. Once the variously charged images have been produced, the images are selectively developed by the developer system in accordance with the positive and negative image charges.

The equations below show the charge situation and surface potentials at various stages of the process. The charging system is required to maintain a charge balance. And, if an electron transporting layer can be introduced, the polarity of the first two...