JP3150099B2 - Electrostatic ink jet recording unit and electrostatic ink jet recording apparatus - 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 recording unit and an electrostatic ink jet recording apparatus, and more particularly, to a coulomb acting on a pigment-based ink containing charged colorant particles by applying an electric field to the colorant particles. The present invention relates to an electrostatic ink jet recording unit and an electrostatic ink jet recording apparatus that perform printing on a recording medium by ejecting ink droplets by force.

[0002]

2. Description of the Related Art A conventional electrostatic ink jet recording unit is shown in FIGS. FIG. 4 is a schematic perspective view of an electrostatic ink jet recording unit utilizing the electrophoretic phenomenon, FIG. 5 is a plan view of the electrostatic ink jet recording unit utilizing the electrophoretic phenomenon, and FIG. It is an applied voltage waveform diagram.

As shown in FIG. 4, an electrostatic ink jet recording unit having a plurality of ejection electrodes 106 has an ink chamber 102 filled with a pigment-based ink 101, and an ink chamber 102 shown in FIG. Electrophoretic electrode 10 for concentrating color material particles 117 shown in FIG.
3, a plurality of ejection electrodes 106 for ejecting the coloring material particles 117 concentrated on the ink ejection ports 104 to fly on the recording medium 105, and the recording medium 10 facing the ejection electrodes 106.
5 and a counter electrode 107 disposed on the back surface of the counter electrode 5. The ink discharge ports 104 are partitioned by the flow path walls 108 so as to form a meniscus 116 of the pigment-based ink 101 having a convex shape shown in FIG. The ink chamber 102 is connected to an ink tank (not shown) by an ink supply port 109 and an ink discharge port 110 via a tube. The ink chamber 102 applies a back pressure to the ink in the ink chamber 102 and the pigment-based ink in the ink chamber 102. 1
01 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, when a voltage of the constant voltage V1 shown in FIG. 6 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, the coloring material particles 117 in the pigment-based ink 101 discharge ink. It moves to the outlet 104 at a certain electrophoresis speed. When the color material particles 117 move to the ink ejection port 104, a meniscus 116 is generated. When a voltage V2 shown in FIG. 6 and a pulse-shaped discharge voltage Vej of time T2 are applied to the discharge electrode 106 for discharging the color material particles 117, the driver 113 shown in FIG.
Is turned on, and the color material particles 117 move and concentrate on the tip of the discharge electrode 106 due to an electrostatic field generated between the discharge electrode 106 and the counter electrode 107. The particles overcome the surface tension, viscous force, etc. of the pigment ink by electrostatic force, and become fine flying particles 111 as shown in FIG. It flies from the tip and adheres onto the recording medium 105. Thereafter, the supply of the coloring material particles 117 is performed, and such an operation is repeated to form an image on the recording medium 105.

[0005]

In the above-described conventional electrostatic ink jet recording unit, when the distance between the ejection electrode and the counter electrode varies, the pulse width is modulated accordingly to form a uniform dot diameter. For this purpose, there is a problem that the pulse width generation unit becomes complicated and large-scale due to an increase in the number of signal lines as the number of ejection electrodes increases.

Further, in the conventional image data transfer by serial transfer, only binary data of "on" or "off" can be sent, so that image data including modulated pulse width data is transferred. I couldn't.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrostatic ink-jet apparatus that discharges ink having a uniform dot diameter by varying a drive pulse applied to each discharge electrode according to a variation in the distance between the discharge electrode and a counter electrode with a simple circuit configuration. It is to provide a recording unit and an electrostatic ink jet recording apparatus.

[0008]

According to the electrostatic ink jet recording unit 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. In the electrostatic ink jet recording unit that performs printing on a recording medium, a plurality of ejection electrodes for ejecting the color material particles from an ink ejection port, and at a position facing the ink ejection port via the recording medium. And a driving pulse width applied to the plurality of ejection electrodes is controlled in accordance with individual distances between the plurality of ejection electrodes and the counter electrode.

In the electrostatic ink jet recording unit according to the present invention, the correlation between the distance between the ejection electrode and the counter electrode and the drive pulse width for making the dot diameter of the color material particles ejected from the ejection electrode uniform. Look to store data
An up table may be provided.

In the electrostatic ink jet recording unit according to the present invention, the optimum drive pulse width corresponding to the actually measured distance between the ejection electrode and the counter electrode is determined by the look-up method.
A head control circuit for reading from the up table and converting the read drive pulse width into the number of pulses may be provided.

In the electrostatic ink jet recording unit according to the present invention, the head control circuit may transfer dummy data one or more times at the end of a recording cycle of the ejection electrodes.

[0012] The electrostatic ink jet recording unit of the present invention may include a serial-parallel conversion circuit that serially receives the drive pulses applied to the plurality of ejection electrodes and converts the drive pulses into parallel.

According to the electrostatic ink jet recording apparatus 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 print on a recording medium. A plurality of ejection electrodes for ejecting the color material particles from an ink ejection port, and a counter electrode disposed at a position facing the ink ejection port via the recording medium. Each of the plurality of ejection electrodes and the counter electrode.
The driving pulse width applied to the plurality of ejection electrodes is controlled according to the distance .

In the electrostatic ink jet recording apparatus of the present invention, the correlation between the distance between the ejection electrode and the counter electrode and the driving pulse width for making the dot diameter of the color material particles ejected from the ejection electrode uniform. A look-up table for storing data may be provided.

[0015] The electrostatic ink jet recording apparatus of the present invention.
A head control circuit for reading the optimum drive pulse width corresponding to the actually measured distance between the ejection electrode and the counter electrode from the look-up table, and converting the read drive pulse width into the number of pulses; May be provided.

In the electrostatic ink jet recording apparatus according to the present invention, the head control circuit may transfer the dummy data one or more times at the end of a recording cycle of the ejection electrodes.

[0017] The electrostatic ink jet recording apparatus of the present invention may include a serial-parallel conversion circuit that serially receives the drive pulses applied to the plurality of ejection electrodes and converts the drive pulses into parallel.

[0018]

Embodiments of the present invention will be described with reference to the drawings.

The electrostatic ink jet recording apparatus is used for a printer, a plotter, a copying machine, a facsimile and the like.
FIG. 1 is a block diagram showing the configuration of the electrostatic ink jet recording apparatus of the present invention. It includes an electrostatic ink jet recording unit 1 and a print control unit 2. The print control unit 2 receives a print command from a host device and sends image data to the electrostatic ink jet recording unit 1.

The electrostatic ink jet recording unit 1 comprises:
The basic configuration is the same as that of FIG. 4 described in the section of the prior art. FIG. 1 mainly describes portions different from the prior art in detail. Referring to FIG. 1, the electrostatic ink jet recording unit 1 includes a head control circuit 11, a head driver IC 12, a head 13, a counter electrode 14, U.
It includes a T (lookup table) 15 and prints on the recording medium 3. In the present embodiment, an electrostatic inkjet recording unit having a head having 40 ejection electrodes will be described as an example.

The head driver IC 12 includes a shift register 22, a logic circuit 23, and a head driver 24.

The ejection electrode of the head 13 and the counter electrode 14
The correlation is calculated by experiment and evaluation to determine how much an applied pulse width can be applied to the variation in the inter-distance to obtain a uniform dot diameter. U. It is stored in T15. Next, the actual distance between the discharge electrode and the counter electrode 14 is measured. If the distance variation as shown in FIG. 1 has a relationship of L1 <L2 <L3, the pulse width corresponding to each distance is set to L. . U. T
15 and the optimum pulse width for each ejection electrode is set to L.P. U. It is stored in T15.

When the image data is transmitted from the print control unit 2, the head control circuit 11 converts the optimum pulse width data obtained previously for each of the ejection electrodes into the number of pulses in the divided recording cycle. Then, the data reading clock is serially transferred to the shift register 22 at the same time.
The shift register 22 converts the serially transmitted head data into parallel data, and transmits image data corresponding to each ejection electrode to the logic circuit 23 from each output port (Data 1 to 40). The logic circuit 23 performs a logic operation between the two control signals (enable signal and head energizing pulse width) sent from the head control circuit 11 and the image data sent from the shift register 22, and performs a head operation corresponding to each ejection electrode. The driver 24 is controlled to be on / off / non-ground floating (high impedance).

Next, the basic operation of the present invention will be described with reference to FIG.

When the head control circuit 11 receives the image data (two gradations) including the pulse width data from the print control unit 2, the head control circuit 11 sets the head data and clock for 40 nozzles simultaneously with the start of the recording cycle T. The data is transmitted to the shift register 22. Prior to this, the head control circuit 11 sets the enable signal to “L” and the head energizing pulse width to “H” from the time of power-on, and sets the output of the head driver 24 to prevent unauthorized ejection from the nozzles. All "L"
(0 V). The head control circuit 11 which 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 23. The logic circuit 23 calculates the logic of the two control signals (enable signal, head energizing pulse width) transmitted from the head control circuit 11 and the parallel head data of 40 nozzles transmitted from the shift register 22, The control signal is transmitted to the driver 24. The head driver 24 supplies and shuts off the ejection voltage Vej to the 40 ejection electrodes provided on the head 13 based on the control signal. Before transmitting new head data in the next cycle, the head control circuit 11 sets all the head drivers 24 to the non-ground floating state by changing the enable signal from “L” to “H”. It is held until the time Tz at which the transmission of the head data of the next cycle ends.

Next, as an example, when the head data is transmitted to the ejection electrode 1 and the ejection electrode 2, what kind of output is performed to each ejection electrode will be described.

The ejection electrode 1 having image data outputs a pulse width of a voltage Vej, Tw to the ejection electrode 1 in synchronization with the head energizing pulse width of the head control circuit 11 (part in the figure). 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 discharge electrode 1 is charged by a capacitive component such as ink in the head on the load side even in the non-ground floating state, the voltage V is also maintained in the data transfer period of the next cycle.
ej is kept as it is (period in the figure). The ejection electrode 1 for which there is no image data in the next cycle is forcibly turned off by the “L” pulse of the head conduction pulse width from the head control circuit 11 (part in the figure). Since the ejection electrode 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 circuit 11 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 ejection electrode 2 is maintained at a voltage of 0 V (periods in the drawing). The ejection voltage Vej is output from the ejection electrode 2 having image data in the next cycle by the “L” pulse of the head energizing pulse width from the head control circuit 11 (part in the drawing). As can be seen from the operation of the ejection electrode 1, in the recording head driving means of the present invention, when there is image data, the ejection voltage Vej is a period (one recording cycle) including the head energizing pulse width Tw and the enable period Tz. Will be output.

By performing the above operation and applying the discharge voltage Vej to the discharge electrode in the head, the color material particles fly,
Printing is performed by attaching to the recording medium 3.

Next, the operation of correcting the variation in the distance between the plurality of ejection electrodes and the counter electrode 14 with a simple circuit configuration which is a feature of the present invention will be described with reference to the applied voltage waveform of FIG. Here, as an example, the distance between the forty ejection electrodes and the counter electrode 14 is L1 <L2 <L3 as shown in FIG.
There is a variation in the relationship, and the operation of discharging a uniform dot diameter from this discharge electrode will be described.

Basically, the printing operation described with reference to FIG. 2 is used. However, in order to generate an arbitrary dot diameter, how much variation in the distance between the ejection electrode and the counter electrode 14 is determined in advance. If the applied pulse width is given, a uniform dot diameter can be obtained, or its correlation needs to be calculated by experiment and evaluation. Next, the distance between each ejection electrode and the counter electrode 14 was measured, and the pulse width required to obtain a uniform dot diameter was calculated from the above-described experimental results. U. It is stored in T15 in advance.
In FIG. 1, a head control circuit 11 converts image data obtained by converting pulse width data of five stages into the number of pulses, one or more dummy data (here, one-time imageless data), and a data reading clock. , To the shift register 22. In other words, the recording period T is divided into 6 times of 5 + 1, and the pulse width data corresponding to each ejection electrode is transmitted. The pulse width data is the pulse width data from the first transfer to the fifth transfer in the six-divided cycle, and the last one data is dummy data, so that the last (1/6) of the print cycle T is used. During the period T1, the power supply to the head is always turned off.

Here, the minimum pulse width must be determined according to the closest location among the distance variations, and with reference to FIG. It is necessary to set the pulse width between the discharge electrodes 39 and 40 and the opposing electrode L3 to the largest pulse width. If experiments and evaluations indicate that a pulse width of L1 = 5 μs, L2 = 15 μs, and L3 = 25 μs is required in order to form a dot diameter of 20 μm, these pulse width data will U. It is stored in T15.

Next, as an overall flow, a description will be given of distance variation correction using the present invention.

As shown in FIG. U. In T15, as the pulse width data corresponding to the variation in the distance, 5 μs for the ejection electrode 1, 5 μs for the ejection electrode 2,.
5 μs,..., 25 μs are stored in the ejection electrode 40, respectively. The head control circuit 11 in FIG. U. The pulse width data stored in T15 is sequentially read, and in the case of the ejection electrode 1, the ejection voltage Vej is set to 5 μs.
In order to apply a pulse having a width of [(1/6) T1] to the discharge electrode, in the pulse width data transfer of each period (1/6) T1 divided into six, "data is present (hereinafter referred to as on)" No data (hereinafter referred to as "off") "off"
After sequentially transmitting “off” and “off”, the dummy data “off” is transmitted. Figure 2 shows the data transfer period of each cycle.
Similarly, the head driver 24 is set to a non-ground floating state by changing the enable signal from “L” to “H”. Prior to this, the head control circuit 11 sets the enable signal to "L" and the head energizing pulse width to "H" from the time of power-on in order to prevent improper ejection from nozzles and the like.
And all outputs of the head driver 24 are set to “L” (0
V). By the above operation, the discharge electrode 1
Is 1 × Tw + 1 × Tz, that is, 5 μs, as shown in FIG.
The ejection voltage Vej is supplied with a pulse width having a time width of [(1/6) T1].

The same operation as that of the discharge electrode 1 is performed, and in the data transfer of each period (1/6) T1 which is divided into six, the discharge electrode 2 is turned on, off, "off" and "off".
By sequentially transmitting “off” and transmitting dummy data “off”, as shown in FIG. 3, 1 × Tw + 1 × Tz, that is, 5 ×
The ejection voltage Vej is supplied with a pulse width having a time width of μs [(1/6) T1].

The output of the discharge electrode 20 is "on", "o" in the data transfer in each period (1/6) T1 divided into six.
n "," on "," off "," off "and dummy data" o
ff ”are sequentially transmitted, and 3 × Tw + 3 × Tz, that is, 15 μs
The discharge voltage Vej is supplied with a pulse width having a time width of [(3/6) T1]. The discharge electrode 40 energizing a pulse width of 25 μs applies “o” to all data during data transfer.
n "and finally the dummy data" off ", the output of the ejection electrode 3 becomes 5 × Tw + as shown in FIG.
The ejection voltage Vej is supplied with a pulse width having a time width of 5 × Tz, that is, 25 μs [(5/6) T1].

Thus, the discharge electrode and the counter electrode 14
When correcting pulse and distance variations, transfer the pulse width data by dividing the recording cycle by m, transfer it at least once at the end of the printing cycle as dummy data, and leave the discharge electrode ungrounded while receiving the pulse width data. By controlling to a floating state, it is possible to modulate the time for supplying the ejection voltage to the ejection electrode and to make the diameter of the ink droplet uniform.

[0037]

As described above, according to the present invention, an optimum drive pulse is given in accordance with the variation in the distance between the discharge electrode and the counter electrode, so that a uniform dot diameter can be discharged and high print quality can be obtained. This has the effect.

Further, since image data and pulse width data to be transmitted to a large number of ejection electrodes are serially transferred by dividing a recording cycle, the number of signal lines can be reduced and printing can be performed with a simple circuit. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electrostatic ink jet recording apparatus of the present invention.

FIG. 2 is a flowchart showing a basic operation of the present invention.

FIG. 3 is an applied voltage waveform diagram.

FIG. 4 is a perspective view showing a configuration of a conventional electrostatic ink jet recording unit.

FIG. 5 is a basic structural diagram of a conventional electrostatic ink jet recording unit.

FIG. 6 is a waveform diagram of a voltage applied to a discharge electrode and an electrophoresis electrode of a conventional electrostatic ink jet recording unit.

[Explanation of symbols]

 Reference Signs List 1 electrostatic ink jet recording unit 2 print control unit 3 recording medium 11 head control circuit 12 head driver IC 13 head 14 counter electrode 15 L. U. T 22 shift register 23 logic circuit 24 head driver

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Shima 7546 Yasuda, Oji, Kashiwazaki-shi, Niigata Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Yoshihiro Hagiwara 7546, Yasuda, Oji, Kashiwazaki-shi, Niigata (72) Inventor Hitoshi Minemoto 7546 Yasuda, Kashiwazaki City, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. (72) Inventor Toru Yakushiji 7546 Yasuda Oaza, Kashiwazaki City, Niigata Prefecture Niigata Nippon Electric Co., Ltd. (56) Reference Document JP-A-8-183187 (JP, A) JP-A-10-44433 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/06

Claims (10)

(57) [Claims] 1. An electrostatic ink jet recording unit that applies an electric field to a pigment-based ink containing charged coloring material particles and ejects ink droplets by Coulomb force acting on the coloring material particles to perform printing on a recording medium. A plurality of discharge electrodes for discharging the color material particles from ink discharge ports, and a counter electrode disposed at a position facing the ink discharge ports via the recording medium, wherein the plurality of discharge electrodes Wherein the drive pulse width applied to the plurality of ejection electrodes is controlled in accordance with each distance from the counter electrode. 2. A look-up table for storing correlation data between a distance between the discharge electrode and the counter electrode and a drive pulse width for making a dot diameter of the color material particles discharged from the discharge electrode uniform. The electrostatic ink jet recording unit according to claim 1, further comprising: 3. An optimum drive pulse width corresponding to an actually measured distance between the discharge electrode and the counter electrode is read from the look-up table, and the read drive pulse width is converted into a pulse number. 3. The electrostatic ink jet recording unit according to claim 2, further comprising a head control circuit. 4. The electrostatic ink jet recording unit according to claim 1, wherein said head control circuit transfers dummy data at least once at the end of a recording cycle of said discharge electrode. 5. A serial-parallel conversion circuit for serially receiving a drive pulse applied to the plurality of ejection electrodes and converting the pulse into parallel.
5. The electrostatic ink jet recording unit according to 2, 3 or 4. 6. An electrostatic ink jet recording apparatus for applying an electric field to a pigment-based ink containing charged coloring material particles and ejecting ink droplets by Coulomb force acting on the coloring material particles to perform printing on a recording medium. A plurality of discharge electrodes for discharging the color material particles from ink discharge ports, and a counter electrode disposed at a position facing the ink discharge ports via the recording medium, wherein the plurality of discharge electrodes A driving pulse width applied to the plurality of ejection electrodes is controlled in accordance with an individual distance from the counter electrode. 7. A look-up table for storing correlation data between a distance between the discharge electrode and the counter electrode and a drive pulse width for making a dot diameter of the color material particles discharged from the discharge electrode uniform. The electrostatic ink jet recording apparatus according to claim 6, further comprising: 8. An optimum drive pulse width corresponding to an actually measured distance between the discharge electrode and the counter electrode is read from the look-up table, and the read drive pulse width is converted into a pulse number. The electrostatic ink jet recording apparatus according to claim 7, further comprising a head control circuit. 9. The electrostatic ink jet recording apparatus according to claim 6, wherein the head control circuit transfers dummy data at least once at the end of a recording cycle of the ejection electrodes. 10. The static-parallel conversion circuit according to claim 6, further comprising a serial-to-parallel conversion circuit for serially receiving the drive pulses applied to the plurality of ejection electrodes and converting the drive pulses into parallel. Electric inkjet recording device.