Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-11-25
2001-01-09
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06172693
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an ink jet recording head and, more particularly, to an ink jet recording head capable of controlling the movement of colored particles in a pigmented ink by an electrophoretic force.
Non-impact recording methods attract a large attention in a-printing technology for their low noise during a recording operation. Among other non-impact recording methods, an ink jet recording method has several advantages of direct and high-speed printing onto a recording medium such as a plain paper. A variety of proposals are presented heretofore for improving the ink jet recording head.
A conventional ink jet recording head, such as described in JP-A-60(1985)-228162, comprises a plurality of ejecting electrodes and a counter electrode disposed behind a recording paper. A driving voltage is applied between a specified ejecting electrode and the counter electrode to generate an electric field, which applies an electrostatic force for ejecting colored particles in a pigmented ink from the ejecting electrode.
FIG. 1
shows a conventional ink jet recording head of the type as described above. The ink jet recording head comprises an ink chamber
301
having an ink jet slit
302
for ejecting therefrom colored particles in pigmented ink
310
, an electrophoretic electrode
303
disposed at a rear wall of the ink chamber
301
for concentrating colored particles in the pigmented ink in the vicinity of the ink jet slit
302
, a plurality of elongate, ejecting electrodes
305
arranged in a row along the ink jet slit
302
for ejecting ink droplets
311
of the colored particles from a specified ejecting electrode
305
, and a counter electrode
309
disposed behind a recording medium or paper
304
for generating an electric field between the specified ejecting electrode
305
and the counter electrode
309
.
Ink jet slit
302
is separated by separating walls
308
into a plurality of short channels each corresponding to one of the ejecting electrodes
305
, thereby forming a meniscus of the pigmented ink
310
at each ejecting electrode
305
. The ink chamber
301
is communicated to an ink reservoir not shown in the drawing by tubes connected to the ink inlet port
306
and an ink outlet port
307
for circulating the pigmented ink
310
by a back pressure applied to the pigmented ink in the ink chamber
301
.
FIG. 2
shows voltage waveforms applied to the electrophoretic electrode and the ejecting electrodes of FIG.
1
. The ink jet recording head utilizes an electrophoretic force by which the charged or electrified colored particles in the pigmented ink are moved in a specified direction.
Specifically, an electric field is generated in the ink chamber
301
, which is filled with the pigmented ink, by applying a constant electrophoretic voltage V
1
, as shown in
FIG. 2
, to the electrophoretic electrode
303
. The colored particles in the pigmented ink are moved by the electric field toward the ink jet slit
302
at a constant electrophoretic mobility and concentrated therein, thereby forming an ink meniscus at the front tip of each ejecting electrode
305
. After the ejecting electrode
305
specified for ink ejection receives a voltage pulse having an amplitude of V
2
and a duration of T
2
, the colored particles are further moved toward and concentrated at the tip of the specified ejecting electrode
305
.
The colored particles overcomes the meniscus force, surface tension and viscosity of the pigmented ink by virtue of the electrostatic force and are ejected from the tip of the specified ejecting electrode
305
, forming minute ink droplets
311
, in accordance with the timing in synchrony with the voltage pulse, to adhere to the recording medium
304
. The operation described above is repeated until a desired image is formed on the recording medium
304
.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink jet recording head capable of preventing the colored particles from being ejected from the tip of an ejecting electrode other than the specified ejecting electrode, thereby obtaining a stable operation of the ink jet recording head and an excellent image quality.
The present invention provides, in one aspect thereof, an ink jet recording head comprising an ink jet recording head comprising a housing defining an ink chamber having an ink jet slit at a front side thereof for ejecting colored particles in pigmented ink, at least one electrophoretic electrode disposed at a rear side of the ink chamber for receiving an electrophoretic voltage for moving the colored particles by an electrophoretic force, a plurality of ejecting electrodes having respective tips arranged in a row along the ink jet slit, each of the ejecting electrodes receiving an ejecting voltage, a counter electrode opposed to the row of tips of the ejecting electrodes and maintained at a potential, and a pair of stirring electrodes disposed at both ends of rows of tips of the ejecting electrodes for receiving a stirring voltage therebetween, the stirring voltage reversing its polarity at least once.
The present invention also provides, in another aspect thereof, an ink jet recording head comprising a housing defining an ink chamber having an ink jet slit at a front side thereof for ejecting colored particles in pigmented ink, a plurality of electrophoretic electrodes arranged at a rear side of the ink chamber, each of the electrophoretic electrodes receiving an electrophoretic voltage for moving the colored particles by an electrophoretic force, a plurality of ejecting electrodes disposed corresponding to the electrophoretic electrodes and having respective tips arranged in a row along the ink jet slit, each of the ejecting electrodes receiving an ejecting voltage, and a counter electrode opposed to the row of tips of ejecting electrodes and maintained at a potential.
In accordance with the ink jet recording head of the present invention, colored particles are prevented from being ejected by an ejecting electrode other than the specified ejecting electrode for obtaining a stable operation of the ink jet recording head and an excellent image quality.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.
REFERENCES:
patent: 0703080 (1996-03-01), None
patent: 405208499 (1993-08-01), None
patent: 406234219 (1994-08-01), None
patent: 8-90825 (1996-04-01), None
patent: 8-207307 (1996-08-01), None
patent: 8-309993 (1996-11-01), None
patent: WO 93/11866 (1993-06-01), None
Hagiwara Yoshihiro
Minemoto Hitoshi
Mizoguchi Tadashi
Shima Kazuo
Suetsugu Junichi
Barlow John
Gordon Raquel Yvette
NEC Corporation
Young & Thompson
LandOfFree
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