JP2001158100A - Electrostatic type ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic type ink-jet recording apparatus which can suppress diffusion of coloring material particles during impression of discharge signals. SOLUTION: The electrostatic type ink-jet recording apparatus has recording electrodes 1, cohesion electrodes 2 and a common electrode 3. Coloring material particles are selectively cohered by an electrostatic force by selectively impressing a potential difference between the recording electrodes 1 and the cohesion electrodes 2. An ink 6 is discharged to fly by impressing a potential to the common electrode 3. Printing to a recording medium 9 is thus carried out. In the constitution, coloring material particles are prevented from diffusing during impression of discharge signals and recording without breaking characters, instable discharging, etc., is enabled even in printing at a high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic ink jet recording apparatus capable of obtaining a stable print density.

[0002]

2. Description of the Related Art Ink jet technology is an inexpensive, high image quality and high speed printing technology, and is widely used in copiers, facsimile machines, printers, word processors and the like as information recording devices for office automation and personal use.

[0003] In the ink jet recording method, as a means for generating energy for flying a coloring material, an electrothermal conversion element such as a heating resistor, an electromechanical conversion element such as a piezo element, and the like are used. Is an electrostatic type which uses electric energy as it is.

[0004] Among them, in the electrostatic type ink jet, the production of the recording head is simpler than other methods, and the area gradation recording can be performed by controlling the electric signal applied to the recording electrode. Further, the amount of current consumed at the time of recording is extremely small, and it can be said that this is a recording technique that is useful in the future as an energy saving device. Furthermore, by using an oil-based pigment ink, printing with excellent water resistance can be performed, and the utility value is particularly high for office automation applications.

Here, the principle of the electrostatic ink jet will be briefly described.

As described in Japanese Patent Application Laid-Open No. 56-4467, when a voltage of several kV is applied between a recording electrode filled with ink and a counter electrode holding a recording medium, the voltage is applied. When the voltage exceeds a certain threshold, the electrostatic force acting on the ink overcomes the surface tension of the ink, and the ink droplet is ejected from the recording electrode to the counter electrode and flies.

A head configuration based on this principle is disclosed in, for example, US Pat. No. 4,271,416 and Japanese Patent Application Laid-Open No. 56-4467. In these configurations, a nozzle hole is not necessarily required for each recording electrode, and the ink discharge port can be a so-called slit type common to a plurality of recording electrodes. A feature of such a configuration is that clogging due to drying of ink is reduced by not providing a nozzle. Therefore, this configuration is applicable not only to a so-called serial type head which has several hundred recording electrodes and scans in the width direction of the recording medium, but also to a so-called line type head having the recording electrodes for the width of the recording medium. Is also very effective.

In this electrostatic ink jet, in the case of a configuration having a plurality of recording electrodes, it is necessary to prevent charge leakage caused by forming a closed loop with an adjacent electrode in order to operate each recording electrode independently. . Therefore, an oily solvent having high electric resistance is usually used as a solvent for the ink. Japanese Patent Application JP-A-58-21535
In the example shown in No. 3, the specific resistance is about 10 ⁸ Ωcm, the surface tension is 18 dyne / cm, the viscosity is 2 to 30 cP, and the specific gravity is 1.0.
g / cm ³ of oil-based ink is used. Oil-based pigments and oil-based dyes can be used as the coloring material, but mainly oil-based pigments are used because of their variety.

However, in the above-described electrostatic ink jet using the pigment and the oily solvent, there is a problem that a certain ratio of the solvent is ejected together with the pigment in ejecting the ink, so that the print density is not increased. This was because the ratio of the magnitude of the electrostatic force applied to the colorant particles and the solvent was poor.

On the other hand, Japanese Patent Application Laid-Open No. Hei 8-2
As disclosed in JP-A-95023 and JP-A-9-193389, by controlling the ratio of the force applied to the coloring material particles and the solvent and discharging only the coloring material particles from the ink,
Attempts have been made to solve these problems. In these examples, the discharge principle is not necessarily clearly explained, but the electrostatic force acts only on the color material particles dispersed in the solvent, and only the color material particles fly, so that the discharge ink contains No solvent is included, and the above-mentioned problem is solved. As described above, in order for the coloring material particles and the solvent to move independently, the coloring material particles need to be dispersed without being dissolved in the solvent. This is because if the coloring material particles are dissolved, the coloring material particles cannot be distinguished from the solvent, and only the coloring material particles cannot be selectively discharged.

According to Japanese Patent Application Laid-Open No. 8-295023, actually, when a voltage having the same polarity as the charging polarity of the color material particles is applied to the recording electrode, a color is applied to the tip of the recording electrode by electrostatic repulsion. Electrophoresis and aggregation of material particles only,
Ink droplets containing many color material particles are ejected.

However, in practice, when the color material particles are agglomerated by such a method, Japanese Patent Application Laid-Open No.
As shown in Japanese Patent Application No. 0-52920, when a signal voltage is applied to the recording electrode, the recording electrode receives a three-dimensional repulsion from the recording electrode due to an electrostatic repulsive force.
The color material particles aggregate near the meniscus that terminates at the scus), but diffuse in the other direction. As a result, the color material particles to be supplied at the next ejection are insufficient, and the concentration of the color material particles at the ink ejection port becomes extremely small, so that the printing density is extremely reduced. There is a risk that ejection will not occur. Such a problem may occur even when the number of recording electrodes is one, but becomes serious in a so-called slit type head having a plurality of recording electrodes and having a common ink ejection port,
Further, the problem becomes more serious as the width of the ink ejection port becomes longer. Therefore, the problem becomes particularly remarkable in a so-called full line head in which the ink ejection port has a length in the width direction of the recording medium. This is because the larger the space in which the color material particles can diffuse, the more likely the diffusion occurs.

In order to solve the above problems, a solution as shown in Japanese Patent Application Laid-Open No. Hei 9-156106 has been devised. According to this method, a potential difference is applied between the recording electrode and the electrode adjacent thereto to aggregate the color material particles in the vicinity of the recording electrode, and an ejection signal is applied to the recording electrode during the aggregation period to cause ejection. Things.

FIG. 5 is a perspective view of an electrostatic ink jet head according to a second embodiment of the present invention. For explanation, a conventional control method will be temporarily described with reference to FIG. 10 and 11 are timing charts showing a control method of a conventional electrostatic ink jet head.

In FIG. 5, the ink jet head comprises:
It comprises a recording electrode 11, an aggregation electrode 12, an upper plate 4 and a lower plate 5, in which ink 6 is contained. Recording electrode 1
In FIG. 1, the electrodes selected for printing are hatched. By setting the potential of the aggregation electrode 12 to be higher than that of the recording electrode 11 to be printed, the positively charged pigment aggregates on the recording electrode 11. Then, ink is ejected from the ink ejection port 8 by electrostatic repulsion by a positive potential pulse signal applied to the recording electrode 11.

In FIG. 10, a signal 301 indicates a signal applied to a recording electrode to be printed. A signal 302 indicates a signal applied to the aggregation electrode. A signal 303 indicates a signal given to the counter electrode. In FIG. 11, a signal 304 indicates a signal supplied to a recording electrode on which no printing is performed.

In FIG. 10, the voltage of the recording electrode (signal 3
01) is Low while the potential of the aggregation electrode (signal 30) is low.
2), the positively charged pigment migrates to the recording electrode and aggregates. Next, when the voltage of the recording electrode becomes Hi,
The pigment agglomerated on the recording electrode to be printed is separated from the recording electrode and discharged by electrostatic repulsion. On the other hand, the Hi signal is not given to the recording electrode that is not printed (signal 30).
No. 3 remains Low), and no ink is ejected.

[0018]

However, even with this method, the potential difference between the recording electrode and the aggregated electrode is reduced during the ON time when the voltage of the recording electrode to be printed is Hi. Or disappear,
During this period, there is a problem that the color material particles are diffused, which hinders an improvement in the recording speed, makes it impossible to eject large dots, and impairs the ejection stability.

An object of the present invention is to provide an electrostatic ink jet recording apparatus which can solve the above-mentioned conventional problems.

[0020]

The electrostatic ink jet recording apparatus of the present invention has the following arrangement.

A first electrode, a second electrode, and a third electrode are provided, and by selectively applying a potential difference between the first electrode and the second electrode, color is generated by electrostatic force. By selectively aggregating the material particles and applying a potential to the third electrode, the ink is ejected and flies to print on the recording medium.

With this configuration, it is possible to solve the conventional problems such as a decrease in recording speed due to diffusion of color material particles during application of an ejection signal, non-ejection of large dots, and unstable ejection.

[0023]

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

(Embodiment 1) FIG. 1 is a perspective view of an electrostatic ink jet head according to Embodiment 1 of the present invention, FIG. 2 is a sectional view thereof, and FIGS. 3 and 4 are views of Embodiment 1 of the present invention. FIG. 3 is a timing chart illustrating a control method of the electrostatic inkjet head.

1 and 2, the ink jet head of the electrostatic ink jet recording apparatus includes a recording electrode 1 (first electrode), an aggregate electrode 2 (second electrode), an upper plate 4 and a lower plate 5. And the ink 6 is contained therein.

A plurality of recording electrodes 1 are formed independently of each other, and a driver (not shown) individually applying a potential.
It is connected to the. In the first embodiment, for example, 30
256 recording electrodes 1 arranged at a recording density of 0 dpi are provided. In accordance with a print data signal sent from a printer driver (not shown) provided in the printer main body, the first driver applies an electric potential to an electrode (called a selection electrode) for ejecting ink among the recording electrodes. Is selectively applied. In FIG. 1, the selection electrodes are hatched. Although not shown, the apparatus is provided with a control unit for controlling the first driver. This control unit also controls a second driver and a third driver described later.

The aggregation electrode 2 is applied with a voltage for causing the pigment to aggregate around the recording electrode 1. When the pigment is positively charged as in the first embodiment, a higher potential is applied to the aggregation electrode 2 than to the recording electrode 1. Further, a plurality of the aggregated electrodes 2 may be provided independently, or may be provided as a common electrode. Also, as means for applying a potential,
A second driver may be provided, or the first driver may be provided between the recording electrode 1 and the aggregated electrode 2 and operated with a potential difference therebetween.

The ink jet recording apparatus according to the first embodiment has a cylindrical common electrode 3 (third electrode) facing the ink jet head as shown in FIG. The common electrode 3 is configured as a platen so that the recording medium 9 extends along the platen. The surface or inside of the common electrode 3 is formed of a conductive material at least in a region along the recording medium 9 so as to function as a third electrode. The common electrode 3 is supplied with a potential by a third driver (not shown). It is also possible to select a flat platen shape.

The rollers 31 and 32 are connected to the common electrode 3.
Is provided upstream of the recording medium 9 in the conveying direction with respect to
The recording medium 9 is transported toward the common electrode 3 with the recording medium 9 interposed therebetween. At least one of the roller 31 and the roller 32 is formed of a conductive material and is grounded. Thereby, the recording medium 9 conveyed is discharged. By this charge elimination, a change in the potential difference between the common electrode 3 and the recording electrode 1 due to the charging of the recording medium 9 can be suppressed, and stable recording characteristics can be realized.

The ink supply port 7 is for supplying ink to a space between the upper plate 4 and the lower plate 5 for storing ink. The ink discharge port 8 supplies ink from the recording electrode 1 and the common electrode 3 by applying a recording voltage between the recording electrode 1 and the common electrode 3.

Here, the distance from the recording electrode 1 to the common electrode 3 is set to about 0.4 mm in the first embodiment, but if it is 0.2 to 3 mm, the recording position shift due to disturbance is prevented. This is preferable because excellent printing quality can be realized while performing the printing. The distance from the recording electrode 1 to the aggregated electrode 2 is
In the first embodiment, the thickness is about 80 μm,
A thickness of 0 μm is preferred because good pigment aggregation can be realized and large pigment dots can be easily formed.

Next, signals applied to the recording electrode 1, the aggregation electrode 2, and the common electrode 3 will be described.

FIG. 3 shows a signal 101 applied to one of the recording electrodes 1 which is selected to eject ink.
And the signal 102 applied to the aggregation electrode 2 and the common electrode 3
Are applied to the signal 103. FIG. 4 shows a signal 104 applied to a non-selected electrode of the recording electrode 1 which does not eject ink, and a signal 102 applied to the aggregated electrode 2.
3 shows a signal 113 applied to the common electrode 3.

First, before an ink ejection signal comes, as shown at the left end in FIG. 3, the recording electrode 1 is smaller than the aggregated electrode 2 arranged on the end face of the upper plate 4 on the ink ejection port 8 side. The potential is set low. At this time, the positively-charged pigment always migrates to the recording electrode 1 and aggregates, so that the state just before the ejection is maintained. Here, the potential of the recording electrode 1 is
Although the voltage is exemplarily set to 0 V, the aggregation electrode 2 and the common electrode 3
(The potential difference between the signal 102 and the signal 103) may be set in any manner. However, recording electrode 1
By setting the potential difference between the recording electrode 1 and the aggregation electrode 2 to about 10 to 500 V, the pigment can be aggregated on the recording electrode 1 satisfactorily. Further, a DC voltage of a certain negative value (first value), for example, −1000 V, is applied to the common electrode 3 so that the ink meniscus can be maintained in a state immediately before ejection.
Is given. At this time, the potential difference between the aggregation electrode 2 and the common electrode 3 is set to a voltage that does not cause ink to be ejected, and preferably a potential difference of about 1000 V to 2000 V.

Next, when an ink ejection signal comes, a second negative pulse voltage having an absolute value larger than the first value, for example, -1500 V, is applied to the common electrode 3 and the recording electrode 1 is selected. The electrode maintains the same potential, and a signal 104 shown in FIG. 4 is applied to a non-selected electrode of the recording electrode 1. Since the signal 104 is set so that the potential difference from the aggregation electrode 2 is reduced or eliminated, aggregation of the pigment is reduced. Therefore, the pigment is not ejected from the non-selected electrode, whereas the pigment remains aggregated at the selected electrode. Discharged.

The magnitude of the second negative pulse preferably has a potential difference of about 300 V to 800 V with respect to the first value. By being within this range, the pigment can be reliably discharged from the selection electrode, the amount of vibration of the meniscus at the end of the discharge can be suppressed, and the next printing system can be quickly shifted. In addition, it is possible to suppress the leakage of the pigment from the non-selection electrodes.

It should be noted that the trailing edge of the second negative pulse signal applied to the common electrode 3 is, like the signal 113 shown in FIG.
It is preferable to make the change slightly or gently compared to the leading edge. By controlling in this way, the vibration of the ink meniscus due to the sudden fluctuation of the voltage of the common electrode 3 can be suppressed, and the printing speed can be improved by improving the response frequency.

In this embodiment, the potential of the non-selection electrode of the recording electrode 1 is controlled so as to be close to the potential of the aggregation electrode 2.
When a plurality of aggregated electrodes 2 are provided corresponding to the recording electrodes 1, among the individual electrodes of the aggregated electrodes 2, control is performed so that the potential of the aggregated electrode 2 corresponding to the non-selected electrode is closer to the potential of the recording electrode 1. May be.

More specifically, as described above, the signal 101 in FIG. 3 is applied to the selected electrode of the recording electrode 1 selected for printing, and the signal is applied to the non-selected electrode of the recording electrode 1 as described above. 4 is applied to the aggregated electrode 2, the DC voltage of the signal 102 shown in FIGS.
3 or 113 is applied.

The signal 101 applied to the selection electrode is 0 V,
That is, it is always grounded. On the other hand, a pulse waveform having a frequency of 2 kHz, an ON time of 200 μs, and 500 V is applied to the non-selected electrodes. The signal 102 given to the aggregation electrode 2 is 500
V DC voltage. Therefore, during at least one printing cycle (500 μs in this case), the selection electrode
The pigment is always aggregated, and the pigment is aggregated on the non-selected electrodes during a period (300 μs) other than the ink ejection, but the pigment is diffused during the ink ejection period (200 μs).

Signal 103 or 11 applied to common electrode
For 3, a pulse waveform of -500 V based on a frequency of 2 kHz, an ON time of 200 μs, and a bias voltage of -1000 V is used. When a pulse voltage of the signal 103 or 113 is applied, the electric field from the recording electrode 1 to the common electrode 3 increases, and an ink droplet corresponding to a length of 200 μs is formed. Done. In the case of this example, missing dots and unstable ejection were improved at a recording frequency of 2 kHz as compared with the conventional method. Further, a dot having a diameter of 50 μm in the conventional ON time of 200 μs can be obtained in the same ON time in a dot size of 90 μm.

A feature of the present invention is that, even at the time of ink ejection, the relationship of the potential difference between the recording electrode 1 and the aggregation electrode 2 does not change in the selection electrode, and the aggregation of the coloring material particles is always achieved. It is.

In the above description, the charging polarity of the pigment is positive. However, if the polarity is negative, it goes without saying that the relationship of the potentials may be all reversed.

By using the above control method, a potential gradient is always applied from the aggregation electrode 2 to the recording electrode 1. Since the potential gradient does not change, the signal applied to the recording electrode 1 has been turned ON / OFF conventionally,
There is an effect that the problem that has been spreading during the period can be solved.

The common electrode may have any structure as long as the ink droplet is ejected toward the recording medium. For example, a grid may be provided near the first or second electrode. The aggregation electrode may be provided anywhere, in any number, and in any form as long as the color material particles are concentrated on the recording electrode.

In FIGS. 3 and 4, the signal 103 or 1
Although the ON timing of the signal 13 is synchronized with the ON timing of the signal 104, the ON timing of the signal 104 may be set earlier.

(Embodiment 2) FIG. 5 is a perspective view of an electrostatic ink jet head according to Embodiment 2 of the present invention.

Using an edge type head having an electrode density of 300 dpi and 256 electrodes arranged as shown in FIG. 5, the control as shown in FIGS. 3 and 4 is performed. Of the 256 electrodes, the even-numbered electrodes are fixed to the recording electrodes 11 and the odd-numbered electrodes are fixed to the aggregated electrodes 12, and are arranged adjacent to each other on the same plane. The common electrode is a metal platen (not shown) disposed on the back of the recording paper. With this configuration, printing is performed at a recording density of 150 dpi.

In this case, aggregation of the pigment on the recording electrode 11 is observed. On the contrary, no pigment is seen on the aggregated electrode 12, and the metallic luster of the electrode is observed. When a pulse is applied to the common electrode, ejection of ink droplets is observed only from the selected electrode among the recording electrodes 11, and the ejection response is improved and the dot diameter is reduced. In addition, compared with the conventional method, dot missing and unstable ejection are improved. Further, by disposing the aggregated electrode 12 near the recording electrode 1, there is an effect that a sufficient effect can be obtained even if the potential difference applied to both electrodes is small. Also, since both electrodes can be formed simultaneously on the same plane, a head can be manufactured at low cost.

(Embodiment 3) FIG. 6 is a perspective view of an electrostatic ink jet head according to Embodiment 3 of the present invention.

Using an edge type head having an electrode density of 300 dpi and an array of 256 electrodes as shown in FIG. 6, the control as shown in FIGS. 3 and 4 is performed. The recording electrodes 21 are all 256 electrodes, and the aggregated electrodes 22 are arranged above and below the ink ejection ports so as to sandwich each recording electrode 21 in the vertical direction, and the common electrode made of a metallic platen is arranged on the back of the recording paper ( (Not shown), that is, a configuration in which the aggregated electrodes 22 are arranged adjacent to the plane on which the recording electrodes 21 are formed in the vertical direction. In this case, 300 dpi
An image can be formed at a recording density of

By performing printing in such an electrode configuration, dot skipping and unstable ejection are improved as compared with the conventional method. In addition, the aggregation electrode 22 is arranged in the direction perpendicular to the recording electrode 21 so that the recording electrode 21
This has the effect that the electrode array density of the device can be increased as much as possible.

(Embodiment 4) FIG. 7 is a diagram showing control signals for an electrostatic ink jet head according to Embodiment 4 of the present invention.

In the fourth embodiment, the structure of the ink jet head is the same as that of the first to third embodiments.
Any of the above can be applied.

A positive bias voltage V1 is applied to the recording electrodes 1, 11, 21 when the color material particles are not aggregated. During the aggregation of the color material particles, a signal voltage V2 lower than the bias voltage V1 is applied to the electrode (selection electrode) that performs ink ejection among the recording electrodes, and no signal is applied to the electrode that does not perform ink ejection.

On the other hand, since the positive bias voltage V3 is constantly applied to the aggregation electrodes 2, 12, and 22, during the period when the signal voltage V2 is applied to the recording electrode, the color material particles aggregate with the selection electrode. Due to the potential difference from the electrode, it aggregates on the selected electrode,
Create a critical state for ink ejection.

A negative bias voltage V4 is applied to the common electrode 3 except during ink ejection, and a signal voltage V5 lower than the bias voltage V4 is applied during ink ejection.

When a signal voltage V5 is applied to the common electrode in a state where a critical state of ink ejection is created in the selection electrode, ink is ejected by electrostatic attraction.

By using this control method, there is an advantage that a driver IC that outputs a negative pulse signal can be used effectively.

The signal voltage V2 may be a ground voltage,
It may be less. Further, the relationship between the signal voltage V2 and the bias voltage V3 is preferably V2 <V3,
V2 and V3 are required for good aggregation of the colorant particles.
Is preferably 10 V to 500 V.

The magnitude relationship between the bias voltage V1 and the bias voltage V3 may be any. In order to obtain a larger aggregation rate of the color material particles, it is preferable that V1 <V3. Stable printing is required with a relatively small aggregation rate while avoiding excessive aggregation of the color material particles. in case of,
It is more preferable that V3 ≦ V1.

Further, the bias voltage V4 may be a ground voltage. Further, it is preferable that the signal voltage V5 has a potential difference of 300 V to 800 V with respect to the bias voltage V4. By being within this range, sufficient energy can be given to ink ejection, and stable printing can be performed.

(Embodiment 5) FIG. 8 is a diagram showing control signals for an electrostatic ink jet head according to Embodiment 5 of the present invention.

In the fifth embodiment, the structure of the ink jet head is the same as that of the first to third embodiments.
Any of the above can be applied.

A positive bias voltage V6 is constantly applied to the recording electrodes 1, 11, 21.

On the other hand, the bias voltage V7 is always applied to the electrode adjacent to the recording electrode (selection electrode) from which the ink is ejected, among the aggregated electrodes 2, 12, and 22. In addition, a bias voltage V7 is applied to an electrode adjacent to a recording electrode which does not perform ink ejection among the aggregated electrodes, and a signal voltage V8 higher than the bias voltage V7 is applied during ink ejection. Thus, during the period in which the signal voltage V8 is applied, a potential difference is generated between the selected electrode among the recording electrodes and the electrode adjacent to the selected electrode among the aggregated electrodes, and the color material particles are concentrated. Thus, a critical state of ink ejection is formed.

A negative bias voltage V4 is applied to the common electrode 3 except during ink ejection, and a signal voltage V5 lower than the bias voltage V4 is applied during ink ejection.

When a signal voltage is applied to the common electrode in a state where a critical state of ink ejection is created in the selection electrode, ink is ejected by electrostatic attraction.

By using this control method, there is an advantage that a driver IC that outputs a positive pulse signal can be used effectively. The bias voltage V7 may be a ground voltage or lower.

Further, the relationship between the bias voltage V6 and the bias voltage V7 is preferably V7 <V6. In order to perform good aggregation of the color material particles, 10V to 50V is required.
It is preferable to apply a potential difference of 0 V between V7 and V6.

Further, a signal voltage V8 which is a pulse voltage,
It is preferable that the magnitude relationship of the bias voltage V7 is V7 <V8, but any relationship may be used as long as a potential relationship that causes a potential difference of 10 V to 500 V is obtained.

Further, the bias voltage V4 may be a ground voltage. Further, it is preferable that the signal voltage V5 has a potential difference of 300 V to 800 V with respect to the bias voltage V4. By being within this range, sufficient energy can be given to ink ejection, and stable printing can be performed.

(Embodiment 6) FIG. 9 is a diagram showing control signals for an electrostatic ink jet head according to Embodiment 6 of the present invention.

In the sixth embodiment, the structure of the ink jet head can be any of those in the first to third embodiments.

A positive bias voltage V1 is applied to the recording electrodes 1, 11, 21 in response to non-aggregation of color material particles. During the aggregation of the color material particles, a signal voltage V2 lower than the bias voltage V1 is applied to the electrode (selection electrode) that performs ink ejection among the recording electrodes, and no signal is applied to the electrode that does not perform ink ejection.

On the other hand, since the positive bias voltage V3 is constantly applied to the aggregation electrodes 2, 12, and 22, during the period when the signal voltage V2 is applied to the recording electrode, the color material particles aggregate with the selection electrode. Due to the potential difference from the electrode, it aggregates on the selected electrode,
Create a critical state for ink ejection.

A negative bias voltage V4 is applied to the common electrode 3 except during ink ejection. At the time of ink ejection, a signal voltage V5 lower than the bias voltage V4 after a certain delay time has elapsed from the beginning of the printing cycle. Is applied.

When the signal voltage V5 is applied to the common electrode with a delay time while a critical state of ink ejection is being created at the selection electrode, the color material particles are sufficiently aggregated within the delay time. Since the electrostatic attraction force is applied after this, the ink is quickly ejected, and there is an effect that the printing frequency is improved and the printing stability of minute dots is improved. Here, the delay time is not particularly limited as long as it is within the printing cycle, but is preferably a length from 0 to a period within the aggregation period of the color material particles.

[0079]

According to the present invention, a first electrode, a second electrode, and a third electrode are provided, and by selectively applying a potential difference between the first electrode and the second electrode, the electrostatic force is reduced. By selectively aggregating the color material particles by applying a potential to the third electrode, the ink is ejected, the ink is ejected and printed on the recording medium, so that the space between the first electrode and the second electrode is formed. Since the potential gradient can be made substantially constant, it is possible to suppress problems caused by the fluctuation of the potential gradient, improve the recording speed, discharge large dots, and improve discharge stability.

[Brief description of the drawings]

FIG. 1 is a perspective view of an electrostatic inkjet head according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electrostatic inkjet head according to the first embodiment of the present invention.

FIG. 3 is a timing chart showing a control method of the electrostatic inkjet head according to the first embodiment of the present invention.

FIG. 4 is a timing chart showing a control method of the electrostatic inkjet head according to the first embodiment of the present invention.

FIG. 5 is a perspective view of an electrostatic inkjet head according to Embodiment 2 of the present invention.

FIG. 6 is a perspective view of an electrostatic inkjet head according to Embodiment 3 of the present invention.

FIG. 7 is a diagram showing control signals of an electrostatic inkjet head according to Embodiment 4 of the present invention.

FIG. 8 is a diagram showing control signals for an electrostatic inkjet head according to Embodiment 5 of the present invention.

FIG. 9 is a diagram showing control signals of an electrostatic inkjet head according to Embodiment 6 of the present invention.

FIG. 10 is a timing chart showing a conventional electrostatic inkjet head control method.

FIG. 11 is a timing chart showing a conventional electrostatic inkjet head control method.

[Explanation of symbols]

 1,11,21 Recording electrode 2,12,22 Aggregated electrode 3 Common electrode 4 Upper plate 5 Lower plate 6 Ink 7 Ink supply port 8 Ink ejection port 9 Recording medium 31,32 Roller

Claims (13)

[Claims] A first electrode, a second electrode, and a third electrode, and selectively applying a potential difference between the first electrode and the second electrode to generate an electrostatic force. An electrostatic ink jet recording apparatus for selectively aggregating color material particles and applying a potential to the third electrode to eject and fly ink to perform printing on a recording medium. 2. The electrostatic ink jet recording apparatus according to claim 1, wherein the second electrode is arranged adjacent to the first electrode on the same plane. 3. The electrostatic ink jet recording apparatus according to claim 1, wherein the second electrode is disposed adjacent to a plane on which the first electrode is formed in a vertical direction. 4. A plurality of first electrodes, a first driver for selectively applying a potential to the first electrodes, a second electrode,
A second driver that applies a potential to the second electrode, a third electrode, a third driver that applies a potential to the third electrode, the first driver, the second driver, and the second driver. A control unit for controlling a third driver, wherein the control unit controls the first driver and the second driver to apply a predetermined potential to the first electrode and the second electrode and select the first electrode and the second electrode. Color material particles aggregated on the first electrode by applying a potential difference, thereby aggregating the color material particles, and controlling the third driver to apply a predetermined potential to the third electrode. An electrostatic ink jet recording apparatus that discharges and flies ink to print on a recording medium. 5. A plurality of first electrodes, a first driver for selectively applying a potential to the first electrodes, a second electrode,
A second driver that applies a potential to the second electrode, a third electrode, a third driver that applies a potential to the third electrode, the first driver, the second driver, and the second driver. A control unit for controlling three drivers, the control unit, as a first potential difference between the potential difference between the selection electrode and the second electrode for discharging the color material particles of the first electrode, While aggregating the color material particles around the selected electrode, the potential difference between the non-selection electrode and the second electrode of the first electrode that does not discharge the color material particles is more than the first potential difference. As a second potential difference that reduces the electrostatic force to be applied, the aggregation of the color material particles around the non-selection electrode is relaxed, and the potential of the third electrode is set to a color higher than the previously applied first potential. The second potential that gives a large electrostatic attraction to the material particles And by the said ejecting colorant particles aggregate to the selective electrode of the first electrode, the electrostatic type ink jet recording apparatus characterized by performing printing on a recording medium by flying. 6. The electrostatic ink jet recording apparatus according to claim 1, wherein a distance between the first electrode and the second electrode is 30 to 500 μm. 7. The method according to claim 1, wherein a distance between the first electrode and the third electrode is 0.2 to 3 mm.
3. The electrostatic ink jet recording apparatus according to item 1. 8. The electrostatic ink jet recording apparatus according to claim 1, wherein the trailing edge of the signal applied to the third electrode is dull or slower than the rising edge. 9. The electrostatic ink jet recording apparatus according to claim 1, wherein a potential difference between the first electrode and the second electrode is 10 to 500 V. 10. The electrostatic ink jet recording apparatus according to claim 1, wherein a discharging member for the recording medium is provided upstream of the third electrode in the recording medium conveyance direction. 11. The method according to claim 1, wherein a positive bias voltage and a negative pulse voltage are applied to the first electrode, and a positive bias voltage is applied to the second electrode. The electrostatic type ink jet recording apparatus as described in the above. 12. The electrostatic type according to claim 1, wherein a positive bias voltage is applied to the first electrode, and a positive pulse voltage is applied to the second electrode. Ink jet recording device. 13. The signal voltage applied to the third electrode is given with a delay time with respect to the signal voltage applied to at least one of the first electrode and the second electrode. 4. The electrostatic ink jet recording apparatus according to any one of claims 1, 2, and 3.