JPH10296980A - Electrostatic ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary the number of driving pulses being applied to a plurality of jet electrodes depending on the gray level by providing a plurality of jet electrodes for concentrating the coloring material particles in ink to a jet port through an electrophoretic electrode and jetting the concentrated coloring material particles thereby receiving the image data a plurality of times. SOLUTION: Upon receiving an image data containing a gray level data from a host control section, a head control section 1 divides the recording period depending on the number of gray levels and transfers an image data, obtained by converting the gray level data into the number of pulses, and a clock for reading data simultaneously to a shift register 2. In order to prevent incorrect jetting from the nozzle, the head control section 1 brings an enable signal to 'L', a head conduction pulse width to 'H' and a driving polarity signal to 'L' upon turn on power and sets all outputs from a head driver 4 at 'L' (0 V). The host control section transfers one or more dummy data to the head control section 1 in addition to an image data of 4 gray level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus in which coloring material particles in a pigment ink are controlled by an electrophoretic phenomenon.

[0002]

2. Description of the Related Art A conventional electrostatic ink jet recording apparatus will be described with reference to FIGS. 5, 6 and 7. FIG. FIG. 5 is a schematic diagram of an ink jet recording apparatus using the electrophoresis phenomenon, FIG. 6 is a plan view of the ink jet recording apparatus using the electrophoresis phenomenon, and FIG. 7 is a waveform diagram of voltage applied to the electrophoresis electrode and the ejection electrode.

[0003] An electrostatic ink jet recording apparatus having a plurality of ejection electrodes, as shown in FIG.
1, an electrophoretic electrode 103 for concentrating the color material particles 201 in the pigment ink 101 shown in FIG. 4 on the ink ejection port 104, and a color concentrated on the ink ejection port 104. Discharge the material particles 201,
Plural ejection electrodes 1 for flying onto recording medium 105
And a counter electrode 107 disposed on the back surface of the recording medium 105 so as to face the ejection electrode 106.

[0006] The ink discharge ports 104 are partitioned by the flow path walls 108 so as to form a meniscus 206 of the pigment-based ink 101 having a convex shape at the tip of each discharge electrode 106 as shown in FIG. The ink chamber 102 has an ink supply port 109 and an ink discharge port 110 connected to an ink tank (not shown) by a tube.
02 and the ink chamber 10
The pigment-based ink 101 in 2 is forcibly circulated.

Next, the operation will be described. This method utilizes an electrophoresis phenomenon in which, when an electric field is applied to a pigment-based ink containing charged coloring material particles, the coloring material particles move in one direction under the electric field. That is, the voltage of the constant voltage V1 shown in FIG.
Ink chamber 1 filled with the pigment-based ink 101 shown in FIG.
When an electric field is applied to 02, the color material particles 201 in the pigment ink 101 move to the ink ejection port 104 at a certain electrophoretic speed. When the color material particles 201 move to the ink ejection port 104, a meniscus 206 is generated.

The discharge electrode 10 for discharging the color material particles 201
When the voltage Vej shown in FIG. 7 and the pulse-shaped ejection voltage Vej of the time T100% are applied to the driver 2, the driver 2 shown in FIG.
02 is turned on, and the coloring material particles 201 are caused to flow by the discharge electrode 106 by an electrostatic field generated between the discharge electrode 106 and the counter electrode 107.
Move to the tip of and concentrate.

The particles overcome the surface tension, viscous force and the like of the pigment ink by electrostatic force, and are discharged as fine color material particles 201 as shown in FIG. 6 at a timing synchronized with the pulsed discharge voltage Vej. It flies from the tip of the electrode 106 and adheres on the recording medium 105. Thereafter, replenishment of the color material particles 201 is performed, and such an operation is repeated to form an image on the recording medium 105.

Here, when printing multi-gradation image data, a pulse-like rising voltage Vej applied to the ejection electrode 106 is used.
Is modulated by the gradation data, the amount of movement of the color material particles 201 to the ink ejection port 104 is limited, and the dot diameter when the color material particles 201 adhere to the recording medium 105 is modulated to perform gradation expression. .

In the schematic circuit diagram shown in FIG. 6, an image data control unit 205 to which image data including gradation data is transmitted from a higher-level control unit (not shown) transmits pulse width data corresponding to the gradation data to a pulse. The width generation unit 204 and the driver 202 for driving each ejection electrode 106 are turned on-of.
Image data for f-control is transmitted to the driver control unit 203.

[0010] The pulse width generation unit 204 that has received the pulse width data generates a pulse width corresponding to the respective gradation data for each ejection electrode 106, and supplies the ejection voltage Vej to the driver 202. The driver control unit 203 turns on and off the driver 202 corresponding to each of the ejection electrodes 106 in accordance with the image data, and supplies the ejection electrodes 106 with the ejection voltage Vej.

For example, as shown in FIG.
In the case where the image data is transmitted such that the gradation data of the 4th gradation is 2/4 gradation in the first cycle, the 4/4 gradation in the second cycle and the 1/4 gradation in the third cycle, the pulse width is From the generation unit 204, the time T
An ejection voltage having a pulse width of 50%, time T100%, and time T25% is supplied to the driver 202, and the driver 202 is turned on by the driver control unit 203, and the ejection voltage based on the gradation data is applied to the ejection electrode 106. Vej
Are respectively energized.

As a result, the dot diameter of the flying color material particles 201 is modulated, and dots having different diameters are formed and adhere to the recording medium 105. In addition to such a gradation control method for an electrostatic ink jet recording apparatus, a gradation control method for an ink jet recording apparatus using a piezoelectric element (JP-A-8-290587) is disclosed.

However, this method controls the application time of the drive signal to the piezoelectric element so that the number of ink droplets ejected from the liquid surface of the liquid ink changes according to the gradation level of the image. The present invention differs from the present invention in which the number of pulses applied to the ejection electrode is varied according to the gradation data, in the configuration of the control means. In the invention using the same piezoelectric element (Japanese Patent Application Laid-Open No. HEI 8-174868), the driving voltage generation section is
The gradation control is performed by generating various levels of driving voltages to be applied to the respective piezoelectric elements at predetermined time intervals in accordance with the multi-valued image data. And different.

[0014]

In the above-described conventional electrostatic ink jet recording apparatus, the pulse width generating section for modulating the pulse width given to each ejection electrode based on the gradation data includes:
As the number of ejection electrodes and the number of gradations increase, there is a problem that the size becomes complicated and large.

[0015]

According to a first aspect of the present invention, an electric field is applied to a pigment-based ink containing charged coloring material particles, and ink droplets are ejected by Coulomb force acting on the coloring material particles to thereby form a recording medium. In an electrostatic ink jet recording apparatus that performs printing on the top, an electrophoretic electrode for concentrating color material particles in the pigment-based ink on an ink discharge port by an electrophoretic phenomenon, and the color material concentrated on the ink discharge port A plurality of ejection electrodes for ejecting particles, a counter electrode disposed at a position facing the ink ejection port via the recording medium, and receiving image data a plurality of times within one recording cycle of the image data And a head driving means for varying the number of driving pulses applied to the plurality of ejection electrodes in accordance with the gradation level of the image data. To provide.

The invention according to claim 2 has a serial-parallel conversion circuit for serially receiving image data given to the plurality of ejection electrodes and converting the data into parallel. Provided is an ink jet recording apparatus.

[0017]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, a head having 40 ejection electrodes will be described as an example. FIG. 1 is a schematic circuit diagram of a print head control method using the discharge electrode control means and the print head drive means, and FIG. 2 is a truth table of voltages of respective parts of the print head drive means operated by the circuit of FIG.

Referring to FIG. 1, when image data including gradation data is transmitted from a higher-level control unit (not shown), the head control unit 1 divides a recording cycle according to the number of gradations,
The image data obtained by converting the gradation data into the number of pulses and the data reading clock are serially transferred to the shift register 2 at the same time. The shift register 2 converts the serially transmitted head data into parallel data, and transmits image data corresponding to each ejection electrode to the logic circuit 3 from each output port (Data 1-40).

The logic circuit 3 transmits a drive signal to the head driver 4 based on the truth table shown in FIG. As can be seen from the truth table of FIG. 2, in the logic circuit 3, three types of control signals (enable signal, enable signal,
The logic of the head energizing pulse width signal and the drive polarity signal) and the image data sent from the shift register 2 are calculated,
On-off for the head driver 4 corresponding to each ejection electrode
-Control to give three states of non-ground floating (high impedance).

FIG. 3 is an applied voltage waveform diagram showing the principle of the printhead control method, and FIG. 4 is an applied waveform diagram of the printhead control method during multi-tone printing. The principle of the printhead control method will be described with reference to FIG. The recording cycle T in FIG.
This is the same as (1/5) T1 in FIG. 4, and the basic operation of the present invention for outputting the multi-tone data described in FIG. 4 will be described with reference to FIG.

In the schematic block diagram of FIG. 1, when the head controller 1 receives image data (two gradations) from a higher-level controller (not shown), it sets head data and a clock for 40 nozzles simultaneously with the start of the recording cycle T. And transmits it to the shift register 2. Prior to this, head control unit 1
In order to prevent unauthorized ejection from the nozzles, the enable signal is set to “L”, the head energizing pulse width is set to “H”, the drive polarity signal is set to “L” from power-on, and all outputs of the head driver 4 are set. Set to “L” (0 V).

The head control unit 1 that has transmitted all the head data transmits to the logic circuit 3 the head energizing pulse width signal Tl.
An "L" pulse having a time width of 1w is transmitted, and the drive polarity signal is set to "H". In the logic circuit 3, the logic of the three control signals (enable signal, head energizing pulse width, drive polarity signal) transmitted from the head control unit 1 and the parallel head data of 40 nozzles transmitted from the shift register 2 are used. Then, a control signal is transmitted to the head driver 4 so as to perform an output based on the truth table of FIG.

The head driver 4 supplies and shuts off the ejection voltage Vej to 40 ejection electrodes (not shown) provided on the head 5 based on the control signal. Before transmitting new head data in the next cycle, the head control unit 1 sets all the head drivers 4 to “L” (0 V) by changing the drive polarity signal from “H” to “L”, This state is maintained until the next cycle of head data has been transmitted. Next, how the respective heads output when data as shown in FIG. 3 is transmitted to the heads 1 and 2 will be described.

The head 1 having image data outputs a signal having a pulse width of Vej, Tw to the head 5 in synchronization with the head energizing pulse width of the head control unit 1 (part in the figure). The output is set to “L” (0 V) at the same time as the start of data transfer in the next cycle (part in the figure) by switching the drive polarity signal from “H” to “L”. In the next cycle, the ejection voltage Vej is not output to the head 1 because there is no image data.

Since the head 2 has no image data in the first recording cycle T, even if the head energizing pulse width of the head control unit 1 becomes "L" (part in the figure), the ejection voltage Vej
Is not output. The head 2 having image data in the next cycle is ejected by the “L” pulse of the head energizing pulse width from the head controller 1 and the change of the drive polarity signal from “L” to “H” (part in the figure). Voltage Vej is output.

As can be seen from the operation of the head 1, the recording head driving means of the present invention outputs the ejection voltage Vej during the head energizing pulse width Tw when image data is present. . By performing the above operation and applying the discharge voltage Vej to the discharge electrode in the head 5, the color material particles fly by performing the operation as already described in the related art, and adhere to the recording medium to print. Done.

FIG. 4 shows an operation of performing multi-tone printing of a plurality of ejection electrodes with a simple circuit configuration, which is a feature of the present invention.
This will be described using the applied voltage waveform of FIG. Here, as an example, an operation in which 40 ejection electrodes output image data including four gradation data is shown.

Basically, the printing operation described with reference to FIG. 3 is based. In the schematic block diagram of FIG. 1, a higher-level control unit (not shown) includes four gradation image data and one or more image data. Dummy data (in this case, one imageless data)
Is transferred to the head control unit 1. In other words, here, the recording cycle T is divided into 5 times of 4 + 1, and the gradation data corresponding to each ejection electrode is transmitted. In the gradation data, since the first to fourth transfers of the five divided periods are image data, and the last data is dummy data, the last (1/5) T1 of the printing period T is used. During the period, the power supply to the head is always turned off.

Therefore, if the head 1 has data of 3/4 gradation, it is necessary to apply a pulse having the width Tw as the discharge voltage Vej to the discharge electrode three times. Therefore, the head control unit 1
Represents each period (l) divided into five as gradation data of the head 1.
/ 5) In data transfer of Tl, “data exists (hereinafter referred to as“ on ”)”, “on”, “on”, and “data does not exist (hereinafter“ o ”)
ff)) and the dummy data “of
f ”.

Prior to this, the head control unit 1 sets the enable signal to "L" and the head energizing pulse width to "L" from the time of power-on, as shown in part A of FIG. H ”and the drive polarity signal to“ L ”, and as can be seen from the truth table of FIG.
Are set to “L” (0 V). During the data transfer period of each cycle, the drive polarity signal is set to “H” as in FIG.
To “L”, the head driver 4 is set to “L” (0 V).

With the above operation, in the head 1 in which the 3/4 gradation is set, the ejection voltage Vej is energized three times within one recording cycle with a pulse width having a time width of T11 as shown in FIG. You. When the same operation as that of the head 1 is performed and the head 2 is printed at 2/4 gradation, “on” and “o” are used in the data transfer in each period (1/5) T1 divided into five.
n, "off" and "off", and the dummy data "off" is transmitted, the head 2 outputs the ejection voltage Vej with a pulse width having a time width Tw as shown in FIG. Is energized twice.

In the case of 4/4 gradation, the head 3
When "on" is transmitted for all data and dummy data "off" is transmitted at the end of the data transfer, the output of the head 3 is discharged with a pulse width having a time width Tw as shown in FIG. Voltage Vej is energized three times within one recording cycle.

The output of the head 40 is "on" and "of" in the data transfer of each period (1/5) Tl divided into five.
f, "off", "off" and dummy data "off" are sequentially transmitted, and the ejection voltage Vej is energized once in one recording cycle with a pulse width having a time width of Tllw.
吐出 gradation ejection is performed.

As described above, when printing multi-gradation image data, if the image data is, for example, m-gradation image data, the recording cycle is divided into m and the image data is transferred. By controlling the discharge electrode to 0 V during the transfer of the image data at least once and receiving the image data, the number of times of supplying the discharge voltage to the discharge electrode is modulated, and the size of the ink droplet deposited on the recording medium is modulated. It becomes possible.

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0036]

As described above, according to the present invention, image data is received a plurality of times within one recording cycle of the image data, and a plurality of ejection electrodes are provided in accordance with the gradation level of the image data. A head drive unit that varies the number of drive pulses applied to the device enables the number of drive pulses to be applied to each discharge electrode based on the gradation data to be realized with a simple circuit configuration even if the number of discharge electrodes or the number of gradations increases. There is an effect that makes it possible.

Further, since the recording cycle of image data to be transmitted to a large number of ejection electrodes is divided according to the number of gradations and serially transferred, the number of signal lines is reduced and multi-gradation image data is printed. There is an effect that makes it possible.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of a printhead control method using a discharge electrode control unit and a printhead driving unit according to an embodiment of the present invention.

FIG. 2 is a table showing truth values of respective units of a recording head driving unit according to an embodiment of the present invention.

FIG. 3 is an applied voltage waveform diagram of a printhead control method according to an embodiment of the present invention.

FIG. 4 is an applied voltage waveform diagram at the time of multi-tone printing in a printhead control method according to an embodiment of the present invention.

FIG. 5 is a schematic view of an ink jet recording apparatus using an electrophoretic phenomenon according to a conventional technique.

FIG. 6 is a plan view of an ink jet recording apparatus according to a conventional technique.

FIG. 7 is a waveform diagram of a voltage applied to a discharge electrode and an electrophoresis electrode according to a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 head control unit 2 shift register 3 logic circuit 4 head driver 5 head 101 pigment-based ink 102 ink chamber 103 migrating electrode 104 ink discharge port 105 recording medium 106 discharge electrode 107 counter electrode 108 flow path wall 109 ink supply port 110 ink discharge port 201 color material particles 202 driver 203 driver control unit 204 pulse width generation unit 205 image data control unit 206 meniscus

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Tomoya Saeki 7546 Yasuda, Kashiwazaki-shi, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Hitoshi Minemoto 7546 Yasuda, Oaza, Kashiwazaki-shi, Niigata Niigata Nippon Electric (72) Inventor Kazuo Shima 7546 Yasuda, Oji, Kashiwazaki, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Yoshihiro Hagiwara, 7546 Yasuda, Oji, Kashiwazaki, Niigata Niigata Nippon Electric Co., Ltd. 7546 Yasuda, Kashiwazaki, Niigata, Japan

Claims (2)

[Claims] 1. An electrostatic ink jet recording apparatus which applies an electric field to a pigment-based ink containing charged coloring material particles, ejects ink droplets by Coulomb force acting on the coloring material particles, and performs printing on a recording medium. An electrophoresis electrode for concentrating the color material particles in the pigment-based ink on the ink discharge port by an electrophoretic phenomenon; and a plurality of discharge electrodes for discharging the color material particles concentrated on the ink discharge port, A counter electrode disposed at a position facing the ink ejection port via a recording medium; receiving image data a plurality of times within one recording cycle of the image data; A head driving unit for varying the number of driving pulses applied to a plurality of ejection electrodes. 2. The electrostatic ink jet recording apparatus according to claim 1, further comprising a serial / parallel conversion circuit that serially receives image data given to the plurality of ejection electrodes and converts the data into parallel.