Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-08-25
2001-02-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06183065
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an electrostatic ink jet recording device and, more particularly, to an electrostatic ink jet recording device including a recording head for ejecting ink containing electrified toner particles.
(b) Description of the Related Art
A non-impact recording technique has drawn attention due to its small noise during a recording operation. Among other non-impact recording techniques, an electrostatic ink jet recording technique is superior because it can record images directly on a recording sheet at a high speed with a simple mechanism. Various devices have been proposed for implementing the electrostatic ink jet recording technique.
JP-A-4(1996)-80037 proposes an ink jet recording device, as shown in
FIG. 1
, wherein the entire spacing area
34
in which a recording head
31
in the recording device
30
moves in the transverse direction of a recording sheet
35
is divided into three areas including a printing area
32
and a pair of non-printing areas
33
disposed at both sides of the printing area
32
. The recording head
31
has a plurality of ink ejection nozzles aligned in the transverse direction of the recording sheet for ejection of the ink.
FIG. 2
schematically shows the longitudinal section of the nozzle surface of the recording head
31
, wherein the plurality of ink ejection nozzles
41
are aligned, for showing the situation of the individual ink ejection nozzles
41
when the recording head resides in the printing area
32
and the non-printing areas
33
.
In
FIG. 2
, “ON” and “OFF” means application of recording voltages to individual ink ejection nozzles
41
. A low bias voltage is applied to all of the ink ejection nozzles
41
when the recording head
31
resides in the non-printing area
33
, whereas a specified group of ink ejection nozzles
41
are driven with a higher, printing pulse train when the recording head
31
resides in the printing area
32
. In this example, the printing pulse train is not applied to the two when the recording head
31
resides in the printing area
32
.
FIG. 2
shows the shape of ink meniscuses
43
and
42
on the nozzle surface in the printing area
32
and the non-printing area
33
. In the non-printing area
33
, the nozzle surface gets wet with ink due to the application of the small bias voltage to the ink ejection nozzles
41
, thereby a small ink meniscus
42
to be formed between each adjacent two of the ink ejection nozzles
41
. It is stated in the publication that the small ink meniscus
42
provides an excellent ejection of ink droplets
43
, the direction of which is substantially normal to the nozzle surface, when the specified ink ejection nozzles
41
are driven by the printing pulse train.
In the proposed ink jet printing device as mentioned above, although the bias voltage is below a threshold voltage for ejection of ink droplets, the bias voltage applied in the non-printing area sometimes causes an undesirable ink ejection from the ink ejection nozzles depending on the situations of the nozzle surface, that is, a lightly wet state or a heavily wet state of the nozzle surface.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide an electrostatic ink jet recording device which is capable of providing an excellent and stable ejection of ink droplets substantially without causing an undesirable ink ejection.
The present invention provides an electrostatic ink jet recording device comprising: a recording head for moving between a printing area and a non-printing area, the recording head having an ink chamber for receiving therein liquid ink containing electrified toner particles, and a plurality of recording electrodes, disposed in operative relationship with the liquid ink, for ejecting the electrified toner particles when the recording head resides in the printing area; a counter electrode disposed opposite to the recording electrodes; and a control unit for applying a bias signal to all of the recording electrodes and a recording signal to a selected group of the recording electrodes with respect to the counter electrode, the bias signal and the recording signal being implemented by a pulse train and a constant voltage, respectively.
In accordance with the electrostatic ink jet recording device of the present invention, the bias pulse train causes less undesirable ink ejection during application of the bias pulse train in the non-printing area because the mean magnitude of the bias pulse train is lower than a constant bias voltage having a same voltage as the peak voltage of the bias pulse train, thereby achieving an excellent and stable ink ejection from the recording head.
REFERENCES:
patent: 5631679 (1997-05-01), Kagayama
patent: 3-190747 (1991-08-01), None
patent: 4-80037 (1992-03-01), None
Hagiwara Yoshihiro
Minemoto Hitoshi
Mizoguchi Tadashi
Shima Kazuo
Suetsugu Junichi
Barlow John
Gordon Raquel Yvette
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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