JP2954137B2 - Head drive device for electrostatic inkjet printer - Google Patents

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 printer, and more particularly to a head driving device for an electrostatic ink jet printer (hereinafter simply referred to as "head driving device") which controls color material particles in a pigment ink by an electrophoretic phenomenon. “Head drive device”).

[0002]

2. Description of the Related Art A head for an electrostatic ink jet printer (hereinafter, simply referred to as "head") and a conventional head driving device will be described with reference to FIGS. 6, 7, 8 and 9. FIG.

FIG. 6 is a perspective view of a head, FIG. 7 is a sectional view of the head and a block diagram of a conventional head driving device, FIG. 8 is a waveform of a voltage applied to an electrophoretic electrode and an ejection electrode, and FIG. 7 is a waveform of a voltage applied to each ejection electrode for outputting an arbitrary dot diameter in response.

A head 10 having a plurality of ejection electrodes 106
0 is an electrophoresis for concentrating the ink chamber 102 filled with the pigment-based ink 101 as shown in FIG. 6 and the coloring material particles 201 in the pigment-based ink 101 shown in FIG. Electrode 103 and ink ejection port 104
A plurality of discharge electrodes 106 for discharging the color material particles 201 concentrated on the recording medium 105 and causing them to fly onto the recording medium 105, and a counter electrode 107 disposed on the back surface of the recording medium 105 so as to face the discharge electrodes 106. I have. The ink ejection port 104 is formed so that the meniscus 206 of the pigment-based ink 101 having a convex shape shown in FIG.
Each of the ejection electrodes 106 is partitioned by 8. The ink chamber 102 has an ink supply port 109 and an ink discharge port 110.
And are connected to an ink tank (not shown) via a tube (not shown). Thereby, the ink chamber 102
A back pressure is applied to the ink in the ink chamber and the ink chamber 1
02 is forcibly circulated. As shown in FIG. 7, the head driving unit 200 includes an image data control unit 205, a driver control unit 203, and a pulse width generation unit 2
04, a driver 202 and the like.

Next, the operation will be described.

This method utilizes an electrophoretic 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, when a constant voltage V1 shown in FIG. 8 is applied to the electrophoretic electrode 103 and an electric field is applied to the ink chamber 102 filled with the pigment-based ink 101 shown in FIG. It moves at a certain electrophoretic speed to the ink ejection port 104. When the color material particles 201 move to the ink ejection port 104, a meniscus 206 is generated. FIG. 8 shows the discharge electrode 106 for discharging the color material particles 201.
7 is applied and a pulse-like ejection voltage Vej for a time T50 to 100% is applied, the driver 2 shown in FIG.
02 turns on, and the color material particles 201 move and concentrate at the tip of the discharge electrode 106 due to an electrostatic field generated between the discharge electrode 106 and the counter electrode 107. The coloring material particles 201
The electrostatic force overcomes the surface tension, viscous force, etc. of the pigment ink, and becomes fine color material particles 201 as shown in FIG. From the recording medium 1
05. 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.

Conventionally, when a desired dot diameter is ejected according to gradation data, the following method has been used.

In order to generate an arbitrary dot diameter, the correlation between the dot diameter and the pulse width to be applied as shown in FIG. The pulse width to be applied is stored in storage means (not shown). In FIG. 7, the image data control unit 205 to which the image data including the gradation data is transmitted from the higher-level device (not shown) reads the pulse width data corresponding to the gradation from the storage unit and reads the pulse width generation unit. 204,
Further, image data for on / off control of the driver 202 for driving each ejection electrode 106 is stored in the driver control unit 2.
03 respectively. The pulse width generation unit 204 that has received the pulse width data generates a pulse width corresponding to each gradation for the plurality of ejection electrodes 106, and
02 is supplied with the ejection voltage Vej. Driver control unit 20
3 turns on / off the driver 202 corresponding to each of the plurality of ejection electrodes 106 in accordance with the image data, and applies the ejection voltage Vej to the ejection electrodes 106.

Hereinafter, a number is assigned to each of the plurality of ejection electrodes 106, and ejection electrode-1, ejection electrode-2,.
It will be expressed as 0. For example, as shown in FIG. 9, as the gradation control for each ejection electrode, a dot of 20 μm for ejection electrode-1, 50 μm for ejection electrode-2, 75 μm for ejection electrode-3,. When it is desired to discharge the diameter, the pulse width generation unit 204 applies a discharge to each discharge electrode.
An ejection voltage having a pulse width of 50 μs, 80 μs, 90 μs, and 100 μs is supplied to the driver 202. Then, the driver 202 is turned on by the driver control unit 203, and an ejection voltage Vej based on the pulse width data is applied to each ejection electrode. Thus, the flying color material particles 201 have a desired dot diameter according to the gradation and adhere to the recording medium 105.

[0010]

In the above-mentioned conventional head driving apparatus, the pulse width generating section for modulating the pulse width given to each discharge electrode based on the pulse width data increases the number of discharge electrodes and the number of gradations. Accordingly, there is a problem that the size becomes complicated and large.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a head driving device which does not become complicated even if the number of discharge electrodes and the number of gradations increase.

[0012]

According to the present invention, there is provided a head driving device which applies an electric field to a pigment-based ink containing charged coloring material particles by a plurality of discharge electrodes, and uses a Coulomb force acting on the coloring material particles to form each of the above-mentioned components. The color material particles are simultaneously ejected from an ejection electrode to perform printing on a recording medium, and the gradation of the printing is controlled by controlling a pulse width of a voltage applied to the ejection electrode. When the time required to eject the color material particles for one dot is defined as one recording cycle, and one recording cycle is divided into a plurality of unit pulses, the gradation data input from a higher-level device is defined as the unit pulse. A head control unit that converts the number of unit pulses for each ejection electrode and outputs the presence / absence of the unit pulse for all the ejection electrodes in the order of the unit pulse, and inputs the presence / absence of the unit pulse from the head control unit. A pulse width generation unit for applying a voltage having a predetermined pulse width to the discharge electrode having the unit pulse.

For example, in the case of increasing the number of ejection electrodes, the conventional technique requires a drastic change in the driver control unit and the pulse width generation unit, and requires two lines of driver wiring and ejection voltage application wiring per ejection electrode. I needed a book.
On the other hand, in the present invention, only one unit pulse is increased for each ejection electrode, and only one ejection voltage application wiring is required. The reason is that, in the present invention, the driver control unit and the pulse width generation unit in the related art are integrated by the above configuration. Also,
In the case of increasing the number of gradations, in the related art, it was necessary to change the circuit configuration itself of the pulse width generation unit.
Since it is only necessary to divide one recording cycle more and increase the number of unit pulses per recording cycle, there is no need to change the circuit configuration.

Further, the pulse width generating unit, inputted from the head controller of the existence of the unit pulse serially,
If you assumed that a voltage of a predetermined pulse width in parallel to the discharge electrode can reduce the number of signal lines by serial communication.

Further, in the head driving device according to the present invention, when the pulse width generation section applies the voltage having the predetermined pulse width, the state in which the voltage is applied is determined by the presence or absence of the next unit pulse. It is held until input. As a result, an uninterrupted long pulse width is obtained.

In addition, the head driving device according to claim 1
The head control unit outputs dummy data indicating that all the ejection electrodes do not have the unit pulse after outputting the presence or absence of the unit pulse of all the ejection electrodes in the order of the unit pulse. Is what you do. With this dummy data, the end of the pulse width in all the ejection electrodes can be obtained.

According to a second aspect of the present invention , in the head driving device, the pulse width generating section sets the ejection electrode to a non-ground floating state so that the state in which the voltage is applied determines whether or not the next unit pulse is present. It is held until input. According to a third aspect of the present invention, in the head driving apparatus according to the second aspect , the pulse width generation unit includes a first switch connected to a supply voltage and a second switch connected to a ground potential. Applying a voltage to the discharge electrode by turning on the first switch and turning off the second switch, turning off the first switch and turning on the second switch, The discharge electrode is grounded, and the first and second switches are both turned off to bring the discharge electrode into a non-ground floating state. This switch is an electronic switch such as a field effect transistor and a bipolar transistor, for example.

[0018]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

In this embodiment, a head having 40 discharge electrodes will be described as an example. FIG. 1 is a circuit diagram of a head driving device of the present embodiment, FIG. 2 is a correlation diagram of a pulse width applied to an ejection electrode and a dot diameter formed by giving the pulse, and FIG. 3 is a logic circuit in the head driving device. Is a truth table.

The head driving device 10 according to the present embodiment includes a pigment-based ink 10 containing charged coloring material particles 201 (FIG. 7).
1 (FIG. 6), an electric field is applied by a plurality of ejection electrodes 106, and the color material particles 201 are simultaneously ejected from each ejection electrode 106 by the Coulomb force acting on the color material particles 201, and onto the recording medium 105 (FIG. 6). Perform printing and discharge electrode 1
It controls the gradation of the print by controlling the pulse width of the voltage applied to the control signal 06, and includes a head control unit 12 and a pulse width generation unit 14. Head control unit 12
Converts the gradation data input from a higher-level device (not shown) into the number of unit pulses for each ejection electrode 106, and outputs the presence or absence of a unit pulse for all ejection electrodes 106 in the order of the unit pulse. Each time the pulse width generation unit 14 inputs the presence or absence of a unit pulse from the head control unit 12, it applies a voltage having a predetermined pulse width to the ejection electrode 106 having the unit pulse. Further, the pulse width generation unit 14 includes a shift register 16, a logic circuit 18, a driver 20, and the like.

When image data including pulse width data (gradation data) is transmitted from the host device, the head control unit 12 converts the pulse width data into the number of pulses (hereinafter referred to as image data) in the divided recording cycle. , "Head data") and a data reading clock are serially transferred to the shift register 16 at the same time. Shift register 1
In step 6, the serially transmitted head data is converted into parallel data, and each output port (data-1 to -40) is converted.
), The image data corresponding to each ejection electrode 106 is transmitted to the logic circuit 18. The logic circuit 18 transmits a drive signal to the driver 20 based on the truth table shown in FIG. As can be seen from the truth table of FIG. 3, the logic circuit 18 includes two control signals (an enable signal and a head energizing pulse width) sent from the head control unit 12 and the shift register 16.
It takes the logic with the image data sent from the printer and controls the on / off / non-ground floating (high impedance) for the driver 20 corresponding to each ejection electrode 106.

FIG. 4 is an applied voltage waveform diagram showing the principle of the head driving method, and FIG. 5 is an applied voltage waveform diagram of the head driving method for printing image data including gradation. The recording cycle T in FIG. 4 is the same as (1/11) T1 in FIG. The basic operation of the present invention for outputting the pulse width data shown in FIG. 5 will be described in more detail with reference to FIG.

In FIG. 1, when image data (two gradations) is received from a host device, the head control unit 12 sets head data and a clock for 40 nozzles at the same time as the start of a recording cycle T, and sets a shift register 16. Send to Prior to this, the head control unit 12 sets the enable signal to “L” and the head energizing pulse width to “H” from the time of turning on the power, and outputs all the outputs of the driver 20 in order to prevent improper ejection from the nozzles. Set to “L” (0 V). The head control unit 12 that has transmitted all the head data transmits an “L” pulse having a time width Tw to the head energization pulse width signal to the logic circuit 18. In the logic circuit 18, two control signals (enable signal, head energizing pulse width) transmitted from the head control unit 12 and the shift register 1
The control signal is transmitted to the driver 20 so as to obtain the logic based on the parallel head data of 40 nozzles transmitted from 6 and output based on the truth table of FIG. The driver 20 supplies and shuts off the ejection voltage Vej to the 40 ejection electrodes 106 provided on the head 100 based on the control signal. Before transmitting new head data in the next cycle, the head control unit 12 sets all the drivers 20 to the non-ground floating state by changing the enable signal from “L” to “H”. The data is held until Tz time when the transmission of the head data of the next cycle ends.

The ejection electrode-1 and its surrounding nozzles are referred to as a head-1, the ejection electrode-2 and its surrounding nozzles are referred to as a head-2,..., The ejection electrode-40 and its surrounding nozzles are referred to as a head- Expressed as 40. Next, when the data as shown in FIG. 4 is transmitted to the head-1 and the head-2, how the respective heads output will be described.

The head-1 having image data is synchronized with the head energizing pulse width of the head control unit 12 (part in the figure),
A pulse having a voltage Vej and a time Tw is output to the head 100. At the same time as the start of data transfer in the next cycle (part in the figure), the enable signal is switched from “L” to “H”, thereby setting a non-ground floating state. However, since the head-1 is charged by a capacitive component such as ink in the head 100 on the load side even in the non-ground floating state, the head V-1 holds the voltage Vej also in the data transfer period of the next cycle. It is kept in the state (period in the figure). The head-1 having no image data in the next cycle is forcibly turned off by the "L" pulse of the head energizing pulse width from the head control unit 12 (part in the figure).

Since the head-2 has no image data in the first recording period T, the ejection voltage Vej is not output even if the head energizing pulse width of the head control unit 12 becomes "L" (part in the figure). Therefore, even if the data transfer in the next cycle is started (the middle part of the figure) and the enable signal is switched from “L” to “H” to be set to the non-ground floating state, the charging is not performed in the previous cycle. The head-2 is maintained at a voltage of 0 V (periods in the drawing). In the head-2 in which image data is present in the next cycle, the ejection voltage Vej is output by the “L” pulse of the head energizing pulse width from the head control unit 12 (part in the drawing).

As can be seen from the operation of the head-1,
In the head driving device of the present invention, when image data is present, the ejection voltage Vej is output during a period (one recording cycle) including the head energizing pulse width Tw and the enable period Tz. By performing the above operation and applying the discharge voltage Vej to the discharge electrode 106 in the head 100, the color material particles fly by performing the operation already described in the conventional example, and adhere to the recording medium to perform printing. Will be

Next, the operation of controlling the gradation of a plurality of ejection electrodes with a simple circuit configuration which is a feature of the present invention will be described with reference to FIG.
This will be described using the applied voltage waveform of FIG. Here, as an example, an operation will be described in which different gradation data is transmitted to 40 discharge electrodes, respectively, and a dot diameter is formed in accordance with the data and discharge is performed.

Basically, the printing operation described with reference to FIG. 3 is used. In order to generate an arbitrary dot diameter according to the gradation, the dot diameter and the pulse width to be applied as shown in FIG. And a pulse width to be applied to each ejection electrode is stored in a storage unit (not shown) based on the correlation.

In FIG. 1, the host device (not shown) is 1
The 0-step pulse width data and, in addition, one or more dummy data (here, one-time no-image data) are transferred to the head control unit 12. That is, the recording cycle T1 is set to 10+
The pulse width data corresponding to each of the ejection electrodes 106 is transmitted after being divided into 11 times. The pulse width data is 1
10 from the first time in one divided cycle (unit pulse)
Since the first transfer is pulse width data and the last one is dummy data, the last (1)
/ 11) During the T1 period, the power supply to the head 100 is always turned off.

From the gradation data for each of the ejection electrodes 106, the ejection electrode-1 was 20 μm, the ejection electrode-2 was 50 μm,
If it is desired that the ejection electrode-3 has a dot diameter of 75 μm and the ejection electrode -40 has a dot diameter of 100 μm, the storage means (not shown) uses the correlation diagram of FIG.
80 μs, discharge electrode-3 90 μs, ..., discharge electrode
-40 stores 100 μs. The head control unit 12 in FIG. 1 sequentially reads out these stored pulse width data, and in the case of the ejection electrode-1, the ejection voltage Vej
In order to apply a pulse having a width of 50 μs [(5/11) T1] to the discharge electrode, each period (1/1) divided into 11
1) In the T1 pulse width data transfer, after "data is present (hereinafter referred to as ON)", "ON", "ON", ... and "ON" are transmitted five times in succession, "No data (hereinafter OFF) "Off", "off", ... and "off" are 5
After transmitting the data continuously, dummy data “OFF” is transmitted. In the data transfer period of each cycle, the driver 20 is set to the non-ground floating state by changing the enable signal from “L” to “H” as in FIG. Prior to this, the head control unit 12 sets the enable signal to “L” and the head energizing pulse width to “H” from the time of turning on the power, and sets all the outputs of the driver 20 in order to prevent improper ejection from the nozzles. Set to “L” (0 V). Due to the above operation, the discharge electrode 1 becomes 5 × T as shown in FIG.
The discharge voltage Vej is supplied with a pulse width having a time width of w + 5 × Tz, that is, 50 μs [(5/11) T1].

The same operation as that of the discharge electrode-1 is performed, and the discharge electrode
In the data transfer of each period (1/11) T1 divided into 11 by -2, "ON" is transmitted eight times continuously,
By transmitting dummy data “off” after transmitting “off” for two consecutive images, 8 × Tw + 8 as shown in FIG.
× Tz, that is, the discharge voltage Vej is supplied with a pulse width having a time width of 80 μs [(8/11) T1]. The output of the discharge electrode-3 is divided into 11 divided periods (1/11) T1.
In the data transfer, if "ON" is transmitted nine times consecutively, "OFF" is transmitted, and then dummy data "OFF" is transmitted, as shown in FIG. 5, 9 × Tw + 9XTz, that is, 90 μs [(9 / 11) The ejection voltage Vej is applied with a pulse width having a time width of T1]. If the ejection electrode 40 with a pulse width of 100 μs transmits “ON” to all data during data transfer and finally transmits dummy data “OFF”, the output of the ejection electrode 40 is as shown in FIG. 10 × Tw + 10 × Tz, that is, 100 μs [(10
/ 11) The ejection voltage Vej is applied with a pulse width having a time width of T1].

In this way, in order to form a dot diameter corresponding to the gradation data on the discharge electrode and discharge the pulse, the recording cycle is divided into m and the pulse width data is transferred. By controlling the ejection electrode to be in a non-ground floating state while receiving the pulse width data after transferring once or more times, the time for supplying the ejection voltage to the ejection electrode can be modulated and the dot diameter can be varied. .

[0034]

According to the head driving device of the present invention,
If the time required to eject one colorant particle for one dot is defined as one recording cycle, and one of the divided recording cycles is defined as a unit pulse, the gradation data input from the host device is output for each ejection electrode. And a head control unit that outputs the presence / absence of a unit pulse for all ejection electrodes in the order of unit pulses, and each time the presence / absence of a unit pulse is input from the head control unit, the presence / absence of the unit pulse is determined. By providing a pulse width generation unit that applies a voltage having a predetermined pulse width to the ejection electrode, even if the number of ejection electrodes or the number of gradations increases,
This can be dealt with by changing the number of unit pulses applied to each ejection electrode, so that the circuit configuration can be prevented from becoming complicated.

Further, the pulse width generating unit inputs the presence or absence of unit pulse serially from the head control unit, and that applies a voltage of a predetermined pulse width in parallel relative to the ejection electrode
In this case, the number of signal lines can be easily reduced by serial communication.

Further, when the pulse width generating section applies a voltage having a predetermined pulse width, the state in which the voltage is applied is maintained until the presence or absence of the next unit pulse is input, so that the pulse width having a long pulse width is not interrupted. Can be easily obtained.

[0037] Moreover, according to the head driving device according to claim 1 wherein, the head control unit, after outputting the presence or absence of individual pulses of all the ejection electrodes for each order of unit pulse, all the discharge electrode without the unit pulse Since the dummy data is output, the end of the pulse width in all the ejection electrodes can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a head driving device according to the present invention.

FIG. 2 is a graph showing a correlation between a pulse width applied to an ejection electrode and a dot diameter formed by giving the pulse.

FIG. 3 is a table showing a truth table of a logic circuit in the head driving device of FIG. 1;

FIG. 4 is a timing chart showing an applied voltage waveform in the operation of the head driving device of FIG. 1;

FIG. 5 is a timing chart showing an applied voltage waveform in the operation of the head driving device of FIG. 1;

FIG. 6 is an external perspective view showing a head.

FIG. 7 is a sectional view showing a head and a block diagram showing a conventional head driving device.

FIG. 8 is a timing chart showing waveforms of voltages applied to an electrophoretic electrode and an ejection electrode in a conventional head driving device.

FIG. 9 is a timing chart showing a waveform of a voltage applied to each ejection electrode for outputting an arbitrary dot diameter according to gradation data in a conventional head driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Head drive device 12 Head control part 14 Pulse width generation part 16 Shift register 18 Logic circuit 20 Driver 100 Head 106 Ejection electrode 201 Color material particle

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hitoshi Minemoto 7546 Yasuda, Kashiwazaki-shi, Niigata Niigata Nippon Electric Co., Ltd. (72) Inventor Kazuo Shima 7546, Yasuda, Kashiwazaki, Niigata Niigata Nippon Electric In-company (72) Inventor Yoshihiro Hagiwara 7546 Yasuda, Kashiwazaki-shi, Niigata Pref. Niigata Nippon Electric Co., Ltd. (72) Inventor Toru Yakushiji 7546 Yasuda, Oji, Kashiwazaki-shi, Niigata Pref. Document JP-A-9-118014 (JP, A) JP-A-63-151211 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/06 B41J 2/205

Claims (3)

(57) [Claims] 1. A pigment-based ink containing charged coloring material particles.
To the color material particles
The color material particles from each of the discharge electrodes due to the working Coulomb force
All at once to print on the recording medium,
Controlling the pulse width of the voltage applied to the discharge electrode.
Therefore, the electrostatic ink jet, which controls the gradation of the printing,
The time required for ejecting the color material particles for one dot in the
One recording period, this one recording period divided into a plurality
Is the unit pulse, the gradation data input from the host device is
To the unit pulse number of the
Outputs the presence / absence of a unit pulse for each unit pulse order
A head control unit, and the presence or absence of the unit pulse is input from the head control unit
A predetermined pulse with respect to the ejection electrode having the unit pulse.
A pulse width generator for applying a pulse width voltage;With The pulse width generator applies the voltage having the predetermined pulse width.
In this case, the state in which this voltage is applied is
Hold until input of the presence or absence of The head controller controls the unit pattern of all the ejection electrodes.
After outputting the presence / absence of a pulse for each unit pulse order,
That all of the ejection electrodes have no unit pulse
Output dummy data indicating  A head for an electrostatic inkjet printer characterized by the following:
Drive. (2)Pigment-based ink containing charged colorant particles
To the color material particles
The color material particles from each of the discharge electrodes due to the working Coulomb force
All at once to print on the recording medium,
Controlling the pulse width of the voltage applied to the discharge electrode.
Therefore, the electrostatic ink jet, which controls the gradation of the printing,
In a head drive for a printer, The time required to eject the color material particles for one dot is
One recording period, this one recording period divided into a plurality
Is the unit pulse, The gradation data input from the host device is applied to each of the ejection electrodes.
To the unit pulse number of the
Outputs the presence / absence of a unit pulse for each unit pulse order
A head control unit, The presence or absence of the unit pulse is input from the head control unit.
A predetermined pulse with respect to the ejection electrode having the unit pulse.
A pulse width generation unit that applies a voltage having a pulse width, this The pulse width generation unitApply the voltage of the predetermined pulse width
If you doSetting the discharge electrode to a non-ground floating state;
ByTheThe state in which the voltage is applied is indicated by the following unit
Hold until you enter the presence or absence ofCharacterized by Head for electrostatic inkjet printer
Drive. 3. The pulse width generation unit includes a first switch connected to a supply voltage and a second switch connected to a ground potential, and turns on the first switch and the second switch. Applying a voltage to the discharge electrode by turning off a switch, grounding the discharge electrode by turning off the first switch and turning on the second switch, and setting the first and second switches 3. The head drive device for an electrostatic ink jet printer according to claim 2 , wherein the discharge electrodes are brought into a non-ground floating state by turning off both of them.