JP2002103625A - Electrostatic ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic ink jet recorder in which particles of coloring material adhering to a recording electrode are decreased by preventing the particles of coloring material from being diffused during ink ejection interval. SOLUTION: The electrostatic ink jet recorder comprises slit-like ink ejecting parts 15 for ejecting ink containing charged particles of coloring material, an electrophoretic electrode 3 for concentrating the particles of coloring material in the widthwise direction of the ink ejecting parts 15, a plurality of first recording electrodes 1 arranged, at an interval, in the widthwise direction of the ink ejecting parts 15 and providing ink ejection positions, a plurality of second recording electrodes 2 arranged, at an interval from the first recording electrodes 1, in the widthwise direction of the ink ejecting parts 15 and providing ink ejection positions, counter electrodes 4 disposed oppositely to the first recording electrode 1 and the second recording electrode 2 and ejecting ink therefrom through electrostatic attraction, and means 10 and 11 for controlling the first and second recording electrodes 1 and 2 to aggregate the particles of coloring material alternately.

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, and more particularly to a technique which is effective when applied to prevent color material particles from sticking.

[0002]

2. Description of the Related Art Ink jet technology is widely used in office automation and personal information recording devices, such as copiers, facsimile machines, printers, and word processors, as a printing technology capable of obtaining high quality images at low cost and at high speed.

[0003] Ink-jet recording principles include those using a heating resistor such as an electrothermal conversion element as an energy generating means for flying a color material, those using a piezo element such as an electromechanical conversion element, There is an electrostatic type that uses electric energy as it is.

[0004] Among them, in the electrostatic ink jet, the production of the recording head is simpler than other methods, and
There is an advantage that area gradation recording can be performed by controlling an electric signal applied to the recording electrode. Further, the amount of current consumed at the time of recording is remarkably small, and it can be said that this is a recording technology 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. When a recording voltage of several kV is applied between a recording electrode filled with ink and a counter electrode holding a recording medium, when a recording voltage exceeds a certain threshold, an electrostatic force acting on the ink is generated. The ink droplets are ejected from the recording electrode to the counter electrode, overcoming the surface tension of the ink.

The configuration of an electrostatic ink jet recording apparatus based on this principle is described in, for example, US Pat.
No. 6 discloses a "slit type ink recording apparatus", and Japanese Patent Application Laid-Open No. 56-4467 discloses that "an ink ejection port is formed in a slit shape, and a number of electrodes are arranged on the inner surface of the slit. Ink recording head "which is disclosed. In this technique, a nozzle hole is not necessarily required for each recording electrode, and a so-called slit type common to a plurality of recording electrodes can be used for an ink ejection unit.
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 not only a so-called serial type head which has several hundred recording electrodes and scans in the width direction of the recording medium, but also a so-called line type head having recording electrodes for the width of the recording medium. It is also very effective.

In the case of a configuration having a plurality of recording electrodes,
In order to operate each recording electrode independently, it is necessary to prevent charge leakage due to forming a closed loop with an adjacent electrode. For this purpose, an oily solvent having a high electric resistance is usually used as a solvent for the ink. As a coloring material, an oil-based pigment or an oil-based dye can be used. However, an oil-based pigment is mainly used because of its variety.

However, in a typical electrostatic ink jet recording apparatus, since both the color material particles and the solvent receive an electrostatic force, a relatively large amount of solvent is discharged together with the color material particles, and the print density is reduced. There was a problem that.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. Hei 9-193389 discloses that "ink containing a dielectric carrier liquid having a high electric resistivity as a component is used and dispersed in the carrier liquid. An ink-jet type recording apparatus characterized in that a force is applied only to a solid component charged toner particle to cause the toner to fly is disclosed.

JP-A-8-295023 (hereinafter referred to as "A") discloses that "only toner particles in ink are ejected from an ejection port, and a control electrode controls the amount of toner consumption of a recorded image. By applying an alternating current,
An electrostatic ink jet recording apparatus that stabilizes the amount of discharged toner irrespective of a recorded image and can achieve recording of high print quality without unevenness ”is disclosed.

Here, the operation of the recording apparatus described in Japanese Patent Application Laid-Open Publication No. H07-209 will be briefly described below. It is assumed that the coloring material particles are positively charged. When the coloring material particles are negatively charged, the same description can be made by reversing the relationship of the potential.

By applying a negative potential to the counter electrode disposed opposite to the recording electrode via the recording medium and applying a positive potential higher than the recording electrode to the migration electrode, the color material particles are concentrated. After that, printing is performed by applying a potential equal to or higher than that of the migration electrode to the recording electrode to separate and discharge the ink.

Hereinafter, the structure of the head of the electrostatic ink jet recording apparatus described in Japanese Patent Application Laid-Open Publication No. Hei.

FIG. 4 is a sectional view showing the structure of a recording head of a conventional electrostatic ink jet recording apparatus.

In the electrostatic ink jet recording apparatus shown in FIG.
8 are formed, and an ink discharge portion 115 is formed to be open from the ink flow path 108. The ink ejection unit 115 includes a recording electrode 101 for ejecting ink concentrated on the ink ejection unit 115, and a recording electrode 101.
Are provided in the vicinity of the control electrode 102. The head block 118 is provided with a migration electrode 103 for concentrating the ink on the ink ejection unit 115 by an electrophoresis phenomenon. An opposing electrode 104 for generating a potential difference from the recording electrode 101 is disposed at a position opposing the ink discharge unit 115 so as to be located on the back surface of the recording medium 105. Then, the recording electrode 101 and the control electrode 10
AC power supply 116 for applying an AC voltage between them, and DC for applying a potential to the migration electrode 103 and the counter electrode 104.
A power supply 117 is provided.

Next, a driving method of the electrostatic ink jet recording apparatus described in Japanese Patent Application Laid-Open Publication No. Hei.

FIG. 5 is a waveform diagram showing applied voltages in driving a conventional electrostatic ink jet recording apparatus.

First, a negative potential is always applied to the counter electrode 104. Since a potential of 0 V is applied to the recording electrode 101 during printing, a potential difference occurs between the recording electrode 101 and the counter electrode 104. As a result, the color material particles concentrate in the ink flow path 108 toward the recording electrode 101.

Since a positive potential that gives a potential difference between the counter electrode 104 and the recording electrode 101 is applied to the migrating electrode 103, the coloring material particles further disperse the recording material 101.
Concentrate in the direction of.

At the time of printing, a positive pulse voltage is applied to the recording electrode 101, so that the ink in which the color material particles are concentrated flies toward the opposing electrode 104 by electrostatic repulsion.

An AC voltage is constantly applied to the control electrode 102 with a certain bias potential at the center, and the color material particles vibrate between the control electrode 102 and the recording electrode 101.

[0022]

However, the above prior art has the following problems.

That is, in the electrostatic type ink jet recording apparatus described in Japanese Patent Application Laid-Open Publication No. H07-187, during non-printing, concentration of coloring material particles occurs due to a potential difference between the counter electrode, the recording electrode and the migration electrode. A recording voltage is applied to the recording electrode,
Since the potential difference between the counter electrode and the recording electrode is small, the concentration of the coloring material particles is weakened, and the coloring material particles are diffused, so that stable printing is hindered.

Further, in the electrostatic ink jet recording apparatus described in Japanese Patent Application Laid-Open Publication No. H11-207, since only the concentration of the color material particles is performed and the ink is not ejected at the electrode having no print signal or image signal, the color The material particles adhere to the recording electrode and hinder the stable flow of the ink, thereby hindering stable ink ejection.

Accordingly, the present invention provides an electrostatic ink jet recording apparatus capable of preventing color material particles from being diffused during an ink discharge period to enhance the concentration and reducing the adhesion of the color material particles to a recording electrode. The purpose is to provide.

[0026]

In order to solve this problem, an electrostatic ink jet recording apparatus according to the present invention comprises: a slit-shaped ink discharge section from which ink containing charged color material particles is discharged; An electrophoretic electrode for concentrating particles in the width direction of the ink ejection unit, a plurality of first recording electrodes arranged at intervals in the width direction of the ink ejection unit to provide an ejection position at which ink is ejected, and an ink ejection unit A plurality of second recording electrodes, which are alternately arranged at intervals with the first recording electrodes in the width direction, and also provide an ejection position at which ink is ejected; a first recording electrode and a second recording electrode; A counter electrode that is disposed opposite to the first recording electrode and the second recording electrode, and that ejects ink by electrostatic attraction from the first recording electrode and the second recording electrode; Recording electrode control means for aggregating the And, ink from the aggregated records electrode material particles are obtained by a configuration in which flies to the counter electrode.

As a result, the color material particles are gathered and diffused at each recording cycle in each printing cycle. Therefore, the color material particles are prevented from being diffused during the ink discharge period, and the concentration is improved. Can be reduced to the recording electrode.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, there is provided a slit-shaped ink discharge section from which ink containing charged color material particles is discharged, and a method in which the color material particles are arranged in the width direction of the ink discharge section. An electrophoretic electrode to be concentrated, a plurality of first recording electrodes arranged at intervals in the width direction of the ink ejection section to provide an ejection position at which ink is ejected, and a first recording electrode in the width direction of the ink ejection section A plurality of second recording electrodes, which are alternately arranged at an interval and also provide an ejection position at which ink is ejected, and are arranged opposite to the first recording electrode and the second recording electrode; A counter electrode for discharging ink from the recording electrode and the second recording electrode by electrostatic attraction;
A recording electrode control means for alternately aggregating the color material particles on the recording electrode and the second recording electrode, wherein the ink jets from the recording electrode on which the color material particles are aggregated to the opposing electrode. In each recording electrode, the coloring material particles gather and diffuse in each printing cycle, so that the coloring material particles are prevented from being diffused during the ink discharge period, and the concentration is improved. This has the effect that it is possible to reduce sticking to the surface.

According to a second aspect of the present invention, in the first aspect, the recording signal voltages applied to the first recording electrode and the second recording electrode are equal to each other. This is an ink jet recording apparatus, and has an effect that the concentration of color material particles at the first recording electrode and the second recording electrode becomes uniform, and these recording electrodes can be operated stably.

According to a third aspect of the present invention, in the first or second aspect, the maximum pulse lengths of the recording signal voltages applied to the first recording electrode and the second recording electrode are equal to each other. It is an electrostatic ink jet recording device that is not only capable of very stable printing with almost no fixation of color material particles to the recording electrode,
This has the effect that no density unevenness occurs for each recording electrode.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a perspective view showing a recording head of an electrostatic ink jet recording apparatus according to an embodiment of the present invention.

The electrostatic ink jet recording apparatus of this embodiment performs printing using an ink containing charged coloring material particles. As shown in FIG. 1, a first recording electrode 1 and a second recording electrode The electrode 2 is formed on a thin electrode substrate 9 having an insulating property such as a polyimide film.

Here, a plurality of the first recording electrodes 1 are provided for giving an ejection position at which ink is ejected, and a plurality of the first recording electrodes 1 are arranged at regular intervals. The second recording electrode 2 also provides an ejection position at which ink is ejected.
Are arranged alternately at intervals. The first recording electrode 1 includes a first recording electrode control driver (recording electrode control means) 10 for intermittently applying a signal voltage to the first recording electrode 1 to aggregate the color material particles; The second recording electrode 2 includes a second recording electrode control driver (recording electrode control means) 11 for intermittently applying a signal voltage to the second recording electrode 2 to aggregate color material particles, Connected. By these first and second recording electrode control drivers 10 and 11, color material particles are alternately aggregated on the first recording electrode 1 and the second recording electrode 2. In the present embodiment, the first recording electrode 1
And the second recording electrode 2 are controlled by different first and second recording electrode control drivers 10 and 11, respectively, but may be controlled by the same recording electrode control driver.

Here, the ink comprises positively or negatively charged coloring material particles and a solvent in which the coloring material particles are dispersed. In addition, since a constant amount of liquid droplets is ejected from the ink by using the electrostatic force, color material particles having a stable charge amount are used. Further, since the solvent is required to have a high electric resistivity, it is preferable to use an insulating solvent such as paraffin, isoparaffin, and silicone oil.

First recording electrode 1 and second recording electrode 2
Above and below, an upper head block (first head block) 6 and a lower head block (second head block) 7 are arranged so as to sandwich them. The pair of head blocks 6 and 7 form an ink discharge section 15 that is a slit-shaped opening through which ink is discharged, and an ink flow path 8 that is a flow path of ink toward the ink discharge section 15. I have. Note that the tips of the first recording electrode 1 and the second recording electrode 2 are
5 and protruded from it.

In the vicinity of the ink discharge section 15 in the ink flow path 8, the migration electrode 3 for concentrating the color material particles over the width direction of the ink discharge section 15 is arranged. The migration electrode 3 is electrically connected to a migration electrode control driver 12 for applying a signal voltage to the migration electrode 3. In the present embodiment, the migrating electrodes 3 are provided on the surface of the upper head block 6 which contacts the ink, but may be provided on the lower head block 7.

A counter electrode 4 is disposed at a position facing the first and second recording electrodes 1 and 2, and the first recording electrode 1 and the first recording electrode 1 are placed on the front surface of the counter electrode 4 by electrostatic attraction. A recording medium 5 on which ink ejected from the second recording electrode 2 toward the counter electrode 4 adheres to perform printing is set.

A counter electrode control driver 13 for applying this signal voltage is electrically connected to the counter electrode 4, and a voltage applied to the counter electrode 4 is provided between the counter electrode 4 and the counter electrode control driver 13. A protection resistor 14 for preventing discharge due to the applied voltage is provided.

Each of the control drivers 10, 11, 12,
13 receives the print signal and applies a voltage to each of the corresponding electrodes 1, 2, 3, and 4.

In such an electrostatic ink jet recording apparatus, the ink in which the color material particles are dispersed is supplied to the ink flow path 8 sandwiched between the upper head block 6 and the lower head block 7.
Is filled.

FIG. 2 is an explanatory diagram showing the wiring path of each control driver of the electrostatic ink jet recording apparatus of FIG.

In FIG. 2, SO1 to SO8 are first recording electrodes, SE1 to SE8 are second recording electrodes, 3 is a migration electrode, 4 is a counter electrode, and 10 is first recording electrodes SO1 to SO8.
, A first recording electrode control driver for applying a signal voltage to each of the first recording electrodes SO1 to DSO8.
, A control driver for applying a signal voltage to the second recording electrodes SE1 to SE8, and DSE1 to DSE8 corresponding to the individual second recording electrodes SE1 to SE8. Control driver, 12
Denotes a migration electrode control driver, 13 denotes a counter electrode control driver, and 14 denotes a protection resistor.

Next, the printing operation of the electrostatic ink jet recording apparatus of the present embodiment configured as described above will be described with reference to the drawings.

FIG. 3 is an explanatory diagram showing signal voltage waveforms of the migration electrode, the first recording electrode, the second recording electrode, and the counter electrode in the electrostatic ink jet recording apparatus of FIG.

In FIG. 3, T1 is the ink concentration period, T
2 is an ink discharge period, and T3 is a standby period. The description is based on the assumption that the coloring material particles are charged to a positive polarity. In the case where color material particles charged to a negative polarity are used, the same description can be made by reversing the positive and negative potential differences.

In the ink concentration period T 1 of the first recording electrode 1, a bias voltage of V 2 is applied to the second recording electrode 2, a signal voltage of V 1 is applied to the migration electrode 3, and the first recording electrode 1 is applied with a signal voltage V3. Therefore, the potential difference between the first recording electrode 1 and the second recording electrode 2 adjacent to each other is V2−V3. Then, due to this potential difference, the color material particles in the positively charged ink
From the recording electrode 2 to the first recording electrode 1, and the first recording electrode 1 enters a critical state of ink ejection.

At the counter electrode 4 to which the negative bias voltage V4 is applied, a negative pulse voltage V5 is applied during the ink discharge period T2. In the first recording electrode 1, the coloring material particles are concentrated and in a critical state of ink ejection, so that when a negative pulse voltage V 5 is applied to the counter electrode 4, the ink containing the positively charged coloring material particles is applied. Flies from the first recording electrode 1 to the counter electrode 4 under electrostatic attraction.

Similarly, in the ink concentration period T1 in the next printing cycle, a bias voltage of V2 is applied to the first recording electrode 1, a signal voltage of V1 is applied to the migration electrode 3, and the second recording is performed. The signal voltage V3 is applied to the electrode 2. Therefore, the potential difference between the first recording electrode 1 and the second recording electrode 2 adjacent to each other is V2−V3. Then, due to this potential difference, the color material particles in the positively charged ink concentrate from the first recording electrode 1 to the second recording electrode 2, and the second recording electrode 2 enters a critical state of ink ejection.

At the counter electrode 4 to which the negative bias voltage V4 is applied, a negative pulse voltage V5 is applied during the ink discharge period T2. In the second recording electrode 2, the coloring material particles concentrate and are in a critical state of ink ejection. Therefore, when a negative pulse voltage V 5 is applied to the counter electrode 4, the ink containing the positively charged coloring material particles is applied. Flies from the second recording electrode 2 to the counter electrode 4 under electrostatic attraction.

As described above, in the present embodiment, the potential relationship between the first recording electrode 1 and the second recording electrode 2 adjacent to each other is reversed every printing cycle, and The coloring material particles are alternately aggregated with the recording electrodes 2, 2.
Ink is ejected from the first and second recording electrodes 1 and 2 on the side where the color material particles are aggregated.

Therefore, in the first and second recording electrodes 1 and 2, the color material particles gather or diffuse in each printing cycle. For this reason, the color material particles are prevented from being diffused during the ink discharge period and the concentration is enhanced, and the color material particles can be prevented from sticking to the recording electrodes 1 and 2 so that high-speed printing can be performed stably. It is possible to do.

Further, the occurrence of density unevenness in each of the first and second recording electrodes 1 and 2 is suppressed, and printing with high image quality can be performed.

It is preferable that the bias voltage applied to the first recording electrode 1 and the bias voltage applied to the second recording electrode 2 are equal to each other. In this way, the concentration of the coloring material particles on the first recording electrode 1 and the second recording electrode 2 becomes uniform, and both the recording electrodes 1 and 2 can be operated stably.

The signal voltage V3 of the first and second recording electrodes 1 and 2 may or may not be 0V. During the ink concentration period T1, the first recording electrode 1 and the second recording electrode 2 are connected to each other. Any voltage may be used as long as the potential difference is generated and concentration of color material particles sufficient for ink ejection occurs.

In the standby time T3, a bias voltage of V2 is applied to both the first recording electrode 1 and the second recording electrode 2, a voltage of V1 is applied to the migration electrode 3, and a voltage of V4 is applied to the counter electrode 4. Note that the magnitude relationship between the bias voltage V2 of the first and second recording electrodes 1 and 2 and the signal voltage V1 of the migration electrode 3 may be any.

With respect to the signal voltage V1 of the migration electrode 3 and the bias voltage V2 of the first and second recording electrodes 1 and 2, V1
When> V2, the coloring material particles concentrate on the first recording electrode 1 from the migrating electrode 3 and the second recording electrode 2. By setting in this way, the concentration of the color material particles during standby can be increased, so that higher density printing is possible. Further, in this setting, the potential difference between the signal voltage V1 of the migration electrode 3 and the bias voltage V2 of the first and second recording electrodes 1 and 2 with respect to the applied voltage V4 of the counter electrode 4 is suppressed to an appropriate level. In a recording electrode that does not perform ink ejection, ink ejection does not occur even if a signal voltage is applied to the counter electrode 4.

The signal voltage V1 of the electrophoresis electrode 3 is not a DC voltage, but includes a pulse period of the applied voltage of the first recording electrode 1, a pulse period of the applied voltage of the counter electrode 4, or a part thereof. A pulse signal having a voltage only for a period of time may be used.

It is desirable that the maximum pulse length of the recording signal voltage applied to the first recording electrode 1 and the second recording electrode 2 be equal to each other. In this way, the coloring material particles hardly adhere to the recording electrodes 1 and 2, so that not only a very stable printing can be performed, but also the density unevenness of each of the first and second recording electrodes 1 and 2. Does not occur at all.

[0060]

As described above, according to the present invention, the coloring material particles are gathered or diffused at each recording period in each printing cycle, so that the coloring material particles are prevented from being diffused during the ink discharge period. As a result, it is possible to obtain an effective effect that it is possible to increase the concentration and to reduce the adhesion of the color material particles to the recording electrode.

As a result, an effective effect that high-speed printing can be performed stably can be obtained.

Further, since the occurrence of density unevenness for each recording electrode is suppressed, an effective effect that high-quality printing can be performed can be obtained.

If the recording signal voltages applied to the first recording electrode and the second recording electrode are made equal to each other, the concentration of the coloring material particles at the first recording electrode and the second recording electrode becomes uniform, An effective effect of stably operating these recording electrodes can be obtained.

If the maximum pulse lengths of the recording signal voltages applied to the first recording electrode and the second recording electrode are made equal to each other, there is almost no fixation of the coloring material particles to the recording electrodes, so that the recording electrodes are very stable. Not only can printing be performed, but also an effective effect that no density unevenness occurs for each recording electrode can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a recording head of an electrostatic ink jet recording apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a wiring path of each control driver of the electrostatic inkjet recording apparatus of FIG.

FIG. 3 is an explanatory diagram showing signal voltage waveforms of a migration electrode, a first recording electrode, a second recording electrode, and a counter electrode in the electrostatic inkjet recording apparatus of FIG.

FIG. 4 is a cross-sectional view illustrating a configuration of a recording head of a conventional electrostatic inkjet recording apparatus.

FIG. 5 is a waveform diagram showing applied voltages in driving a conventional electrostatic ink jet recording apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st recording electrode 2 2nd recording electrode 3 migrating electrode 4 counter electrode 10 1st recording electrode control driver (recording electrode control means) 11 2nd recording electrode control driver (recording electrode control means) 15 ink discharge part

Claims (3)

[Claims] 1. A slit-shaped ink discharge section from which ink containing charged color material particles is discharged, an electrophoretic electrode for concentrating the color material particles in a width direction of the ink discharge section, and a width of the ink discharge section. A plurality of first recording electrodes that are arranged at intervals in a direction and provide an ejection position at which the ink is ejected; and are alternately arranged at an interval from the first recording electrodes in a width direction of the ink ejection unit. A plurality of second recording electrodes that also provide an ejection position at which the ink is ejected; and the first recording electrode and the second recording electrode that are disposed to face the first recording electrode and the second recording electrode. A counter electrode for discharging the ink by electrostatic attraction from the second recording electrode; a recording electrode control means for alternately aggregating the color material particles on the first recording electrode and the second recording electrode; Having the coloring material particles Aggregated the recording electrostatic ink jet recording apparatus the ink from the electrode, characterized in that fly into the counter electrode. 2. An electrostatic ink jet recording apparatus according to claim 1, wherein the recording signal voltages applied to said first recording electrode and said second recording electrode are equal to each other. 3. The electrostatic type according to claim 1, wherein the maximum pulse lengths of the recording signal voltages applied to the first recording electrode and the second recording electrode are equal to each other. Ink jet recording device.