(19) |
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(11) |
EP 0 769 384 A3 |
(12) |
EUROPEAN PATENT APPLICATION |
(88) |
Date of publication A3: |
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30.07.1997 Bulletin 1997/31 |
(43) |
Date of publication A2: |
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23.04.1997 Bulletin 1997/17 |
(22) |
Date of filing: 09.09.1996 |
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(51) |
International Patent Classification (IPC)6: B41J 2/415 |
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(84) |
Designated Contracting States: |
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DE FR GB |
(30) |
Priority: |
18.10.1995 US 546166
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(71) |
Applicant: Hewlett-Packard Company |
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Palo Alto,
California 94304 (US) |
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(72) |
Inventor: |
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- Lee, Michael H.
San Jose,
California 95120 (US)
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(74) |
Representative: Williams, John Francis et al |
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WILLIAMS, POWELL & ASSOCIATES
34 Tavistock Street London WC2E 7PB London WC2E 7PB (GB) |
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(54) |
Toner ejection printing |
(57) The present invention provides a method and apparatus for toner ejection printing
(TEP) that improves print quality by synchronizing the developer roll (DR) voltage
to the gate electrode voltage with the proper phase relationship, providing tonal
evenness in the print quality and maximising the development time window. It further
provides an improved DR waveform for TEP. The apparatus (100) for toner ejection printing
includes a developer supply (102) for providing electrostatically charged toner particles
(104), a printhead structure (106) including a plurality of apertures (108) confronting
a back electrode (110) disposed in opposite relation with a surface of the printhead
structure (106). Electrical signals applied to the printhead include a voltage applied
to the developer supply (102) and a voltage applied to the gate electrode (126) of
the printhead, where the voltage applied to the developer supply and the gate electrode
are typically synchronized to maximise the development time window and thus maximise
the amount of toner deposited. The phase relationship between the DR voltage and the
gate electrode voltage is defined so that the gate voltage lags the DR voltage by
a predetermined time value. Preferably, the predetermined time delay equal to the
transit time between the developer roll and the printhead of the highest electrostatically
charged toner particle capable of overcoming electrostatic adhesion to the DR for
the voltage condition used, which maximises the amount of toner deposited, a critical
factor with the small time development window of TEP processes.
