Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-02-16
2001-09-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S040000
Reexamination Certificate
active
06286938
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus in which ink drops are jetted from an electrode of a recording head toward a recording medium, thus recording an image on the recording medium.
As one type of ink jetting operation of an ink jet recording apparatus, which is utilized for directly jetting ink drops from a minute ink jetting unit toward a recording medium for forming dots on the recording medium, there is an electrostatic recording system in which the ink drops are drawn by an electrostatic force. According to the electrostatic recording system, it is possible to control the ink jetting amount by subjecting the voltage applied to the recording electrode to a pulse width modulation. Thus, this system has attracted attention as a system for use in a high definition ink jet printer.
As one example of this type of system, WO-A-9311866 discloses a method in which ink composed of a solvent with a color agent dispersed therein at a low concentration is supplied to a front face of a recording electrode, and the recording electrode is supplied with a voltage to form an electric field, so that the color agent with an electric charge is flocculated, thus densely concentrated ink is jetted from the recording electrode toward the recording medium.
On the other hand, WO-A-9727058 discloses a technology in which ink is supplied to a flow path of L-letter shape, having a square cross-section, the flow path being disposed so that a corner thereof is brought to a position nearest to the recording medium, and an electrode having a linear shape provided in the flow path is supplied with a voltage so as to make the ink fly from the L-letter shaped corner position.
Japanese Patent Laid-open No. 10-52919 and the above-mentioned WO-A-9311866 also disclose a technology in which a color agent flocculated material formed around the tip end portion of the recording electrode during bias voltage application is jetted toward the recording medium by applying thereto a pulse voltage corresponding to image information in a superimposing manner. The technology disclosed in these gazettes does not require use of a jetting device having a nozzle aperture which tends to cause ink clogging. Thus, according to these technologies, it becomes possible to realize an ink jet recording apparatus which has an excellent ink jetting stability.
SUMMARY OF THE INVENTION
The electrostatic recording system disclosed in the above gazettes is a system in which ink is circulated, the recording electrode is supplied with a bias voltage so that ink containing a highly concentrated pigment component is collected at the tip end of the recording electrode, and under this condition, the recording electrode is supplied with a pulse voltage in a superimposing fashion so that the highly concentrated ink is jetted toward the recording medium to form an image thereon. Further, with such an arrangement, the ink jetting unit does not have a small aperture, to thereby prevent clogging of the ink jetting unit.
For this reason, even if a number of recording heads are arrayed in a line, each of the heads will not suffer from the problem of not being able to jet ink at some portions. Thus, it is easy to implement an ink jet recording apparatus having a number of heads arrayed in a line (hereinafter referred to as a line head). It is an advantage of the recording apparatus having a line head arrangement that recording can be accomplished over the entire width of the recording medium at one time, which makes it possible to print at a high speed.
According to the present system, the recording electrode is supplied with a voltage derived from a bias voltage to which a pulse voltage is added in a superimposing fashion, whereby highly concentrated ink is jetted from the ink jetting unit. However, the concentrated ink to be jetted is actually not completely jetted, but a little of the concentrated ink remains at the tip end of the recording electrode upon application of the pulse voltage. If such uncompleted jetting is repeated, the remnant of tip end of the electrode. If ink adheres to the recording electrode at the tip end thereof, then the point at which the electric field is concentrated is deviated, with the result that the direction in which the ink drop flies becomes deviated, causing a distortion of the image formed on the recording medium.
The technology disclosed in the above-introduced gazettes, or WO-A-9311866 and WO-A-9727058, does not consider the problem that ink tends to adhere at the tip end of the electrode. Therefore, it can be said that the disclosed arrangement tends to cause a problem in that the flying direction of the ink drop tends to deviate upon recording, with the result that the picture formed on the recording medium is distorted.
Further, when the technology disclosed in the above-introduced gazettes is applied to a line-type ink jet recording apparatus, an electrical interference (cross-talk) is caused between the adjacent recording electrodes, which also causes a distortion of the picture being formed on the recording medium. For example, when only two neighboring electrodes A
i−1
, A
i
of three sequentially arrayed recording electrodes A
i−1
, A
i
, A
i+1
, are supplied with a pulse voltage, the path of the ink drop jetted from the recording electrode A
i
located in the middle of the ink jet array is distorted toward the jetting electrode A
i+1
, due to the influence of the cross talk between the recording electrodes A
i−1
, A
i+1
on both sides thereof. As a result, a dot is not formed at the desired position on the recording medium, with the result that the picture is distorted similarly to the case caused by the ink adhering problem. Such a problem tends to occur more frequently as the recording electrodes are arrayed on the recording head at a narrower pitch.
However, in order to solve the above problem, even if a member for partitioning the ink is provided between the electrodes, if the recording head has a number of electrodes arrayed at a narrow pitch, the electric field distribution generated around the electrode A will vary depending on whether or not recording is simultaneously carried out at a channel in the vicinity of the channel where the electrode A under recording operation is provided. Conversely, if the recording head is arranged to have a number of recording electrodes arrayed at a wide interval so that variation of the electric field distribution can be suppressed, the recording head cannot provide many dots per unit area on the recording medium, with the result that a new problem occurs in that a picture of high definition cannot be obtained.
The example introduced in WO-A-9311866 has an arrangement having no partitioning member between the electrodes arrayed in a line. Therefore, the electric field distribution in terms of the intensity thereof around the electrode A will vary depending on whether or not a pulse voltage is applied to the recording electrode at a channel in the vicinity of the channel where the electrode A under recording operation is provided. Thus, according to such an arrangement, the paths of the ink drops tend to deviate, leading to a picture distortion problem.
Further, the embodiment disclosed in WO-A-9727058 includes a member for partitioning the ink jetting units from one another. However, there is no point at which the electric field is concentrated within each channel, and hence the jetting point of the ink is uncertain, with the result that the direction in which ink drops fly becomes unstable.
Further, according to the technology disclosed in Japanese Patent Laid-open No. 10-52919, an electrode A
i
neighboring the recording electrode A
i
under ink jetting operation is brought under a floating condition (grounded condition), whereby the electric field distribution concerning the recording electrode A
i
and a symmetric property of the ink meniscus with respect to the recording electrode A
i
are maintained. However, this arrangement suffers from repeated high voltage application a
Fujiwara Shigetaka
Fukano Yoshinobu
Okano Mamoru
Onose Atsushi
Yonekura Seiji
Antonelli Terry Stout & Kraus LLP
Barlow John
Hitachi , Ltd.
Mouttet Blaise
LandOfFree
Ink jet recording head and ink jet recording apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet recording head and ink jet recording apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet recording head and ink jet recording apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2495329