Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-02-28
2002-11-05
Hallacher, Craig A. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000, C347S060000
Reexamination Certificate
active
06474763
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid-discharge control method and a liquid discharging apparatus. More particularly, the invention relates to a liquid-discharge control method when discharging a liquid using a head according to a liquid discharging method utilizing the generation of a bubble by heat, and to a liquid discharging apparatus. The invention also relates to an ink-discharge control method when performing recording on a recording medium using ink as a liquid, and to an ink-jet recording apparatus.
2. Description of the Related Art
From among conventionally known ink-jet recording methods, a recording method (a bubble-jet recording method) has been widely known in which a bubble is generated by heating ink within one of ink discharging ports and a liquid channel communicating therewith (these two components will be hereinafter termed a “nozzle”) by heating means, such as a heater or the like, and a fine ink droplet is discharged from the ink discharging port onto a recording medium by the function of the bubble, in order to form an image by consecutively discharging ink droplets from corresponding ink discharging ports in the same manner. This method has been applied to printers, copiers and the like.
Recording heads which adopt the bubble-jet recording method are suitable for high-speed recording and high-quality image recording, because it is easy to increase the number of nozzles mounted in the head (provision of multiple nozzles) and to provide high-density nozzles. Particularly, attempts to increase the recording speed of a printer, a copier or the like by providing multiple nozzles or increasing the driving frequency for the recording head are actively being tried. There are also attempts to realize high resolution by reducing the amount of droplets (the amount of discharge) of ink, and thereby to improve the quality of a recorded image to the high-quality level of photography.
In the bubble-jet recording, a recording method has been known in which, when performing recording by discharging ink from a discharging port by a bubble generated by heating the ink, the bubble is caused to communicate with the atmospheric air if the internal pressure of the bubble is negative (U.S. Pat. No. 5,218,376). According to this method, it is possible to prevent the generation of ink mist during ink splash or discharge, so that the recording medium or the inside of the apparatus is not stained with the ink. In addition, since ink between the generated bubble and the discharging port can be substantially entirely discharged and the amount of the discharged ink is determined by the shape of the nozzle and the position of the heater, it is possible to perform stable recording in which the amount of the discharged ink droplet is always constant.
In the conventional bubble-jet recording method, when the duty ratio of an image is high or the ambient temperature is high, the temperature of the recording head is raised, so that the discharging direction may slightly change.
FIGS. 11A through 13F
are schematic diagrams illustrating manners in each of which an ink droplet is discharged from an ink discharging port of a recording head. The recording head adopts a recording method in which a bubble generated during recording is caused to communicate with the atmospheric air.
FIGS. 11A-11C
are enlarged views of a nozzle of the recording head.
In
FIGS. 11A-11C
, there are shown an electrothermal transducer
31
for heating ink, an ink discharging port
32
, an ink supply port
33
, and a discharging-port plate
35
.
FIG. 11A
is a side cross-sectional view of the ink discharging nozzle.
FIG. 11B
is a side cross-sectional view of the ink discharging nozzle shown in
FIG. 11A
as seen from a direction rotated by 90 degrees from the state shown in FIG.
11
A.
FIG. 11C
is a top plan view of the ink discharging nozzle. Line
11
A-
11
A ′ shown in
FIG. 1C
is a line of cutting plane for providing the side cross section shown in FIG.
11
A. Line
11
B-
11
B′ shown in
FIG. 11C
is a line of cutting plane for providing the side cross sectional view shown in FIG.
11
B.
FIGS. 12A-12C
and
12
D-
12
F are diagrams, each illustrating how ink is discharged in the ink discharging state of the present invention in which a bubble generated from the recording head discharges ink by communicating with the atmospheric air in a state of negative pressure, as seen from the direction shown in FIG.
11
A.
FIGS. 12A-12C
illustrate how the ink is discharged when the temperature of the recording head is high.
FIGS. 12D-12F
illustrate how the ink is discharged when the same energy (driving signal) as in the case shown in
FIGS. 12A-12C
is applied to the electrothermal transducer in a state in which the temperature of the recording head is close to the room temperature.
As can be understood from
FIGS. 12A-12F
, the generated bubble is larger when the temperature is high than when the temperature is close to the room temperature, and the direction of ink discharge slightly changes depending on the difference between the temperatures of the recording head. It is considered that this is because the amount of ink slightly remaining in the vicinity of the ink discharging port differs depending on the size of the generated bubble, and a portion where the rear end of the ink leaves the ink discharging port differs depending on the difference in the amount of ink remaining in the vicinity of the ink discharging port.
That is, in
FIG. 12B
, consider the amounts of ink remaining at portions n and m, each surrounded by a circle. When the temperature of the recording head is high and therefore the size of the generated bubble is large, the amount of ink remaining at portion m is small, and as shown in
FIG. 12C
, the direction of the ink droplet discharged from ink remaining at portion n opposite to portion m of the ink discharging port slightly deviates from the center of the ink discharging port (indicated by a broken line in FIG.
12
C). On the other hand, when the temperature of the recording head is low and therefore the size of the generated bubble is small, although a bubble tends to be generated slightly toward the ink supply port, this tendency is small, and, as shown in
FIG. 12F
, ink is discharged substantially rectilinearly along the center line of the ink discharging port.
In the case of the conventional recording head in which a bubble does not communicate with the atmospheric air, when the discharged ink droplet is separated from ink within the nozzle, the influence of the separated ink remaining in the vicinity of the ink discharging port does not cause any particular problem, because the ink returns to the inside of the nozzle. However, in the recording head having the above-described configuration in which a bubble generated by driving the electrothermal transducer is caused to communicate with the atmospheric air, the above-described phenomenon that, when the temperature of the recording head is high, the portion where an ink droplet is separated during ink discharge is in the vicinity of the inner wall of the ink discharging port and the discharging direction deviates, as shown in
FIG. 12B
, is observed.
FIGS. 13A-13C
, and
13
D-
13
F are diagrams, each illustrating how ink is discharged from the same viewpoint as shown in
FIG. 11B
, in order to illustrate the state of ink discharge shown in
FIGS. 12A-12F
in further detail.
As in the case of
FIGS. 12A-12C
,
FIGS. 13A-13C
illustrate how the ink is discharged when the temperature of the recording head is high.
FIGS. 13D-13F
illustrate how the ink is discharged when the same energy (driving signal) as in the case shown in
FIGS. 13A-13C
is applied to the electrothermal transducer in a state in which the temperature of the recording head is close to the room temperature.
As can be understood from
FIGS. 13A-13C
, when the temperature of the recording head is high, the generated bubble is large, and asymmetrical with respect to the center of the ink discharging port. A
Inui Toshiharu
Murakami Shuichi
Okito Kazuhiko
Ono Mitsuhiro
Tachihara Masayoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hallacher Craig A.
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