JP2001150682A - Electrostatic ink-jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent pigment adhesion and plating in an ink channel of an electrostatic ink-jet recording device. SOLUTION: An electrostatic ink-jet recording device comprising a plurality of recording electrodes 1 formed on an electrode substrate 2 having the insulation property, disposed parallel with each other, an upper head block 4 and a lower head block 3 for providing an ink ejection opening and an ink channel, disposed so as to interpose the recording electrodes 1 therebetween, with the tip end of the recording electrodes 1 projected, a pigment eliminating electrode 6 disposed along the ink channel, and a counter electrode disposed facing the recording electrodes 1, wherein a pigment in an ink is ejected an jumped by an electrostatic force for printing on a recording medium, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus capable of obtaining a stable print density.

[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, word processors, etc., as a technology enabling low cost, high image quality and high speed printing.

[0003] Ink jets use a heating resistor such as an electrothermal conversion element as an energy generating means for flying a color material, use a piezo element such as an electromechanical conversion element, and further use an ink jet. 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 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 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 electrostatic type ink jet recording apparatus will be briefly described.

FIG. 6 is a perspective view showing a conventional electrostatic ink jet recording apparatus.

As shown in FIG. 1, an electrostatic ink jet recording apparatus includes a plurality of recording electrodes 1 formed on an electrode substrate 2.
And a pair of head blocks 3 and 4 which are arranged so as to sandwich the recording electrode 1 and form an ink ejection port 10 from which the tip of the recording electrode 1 projects.

When a recording voltage of several kV is applied between a recording electrode 1 filled with ink and a counter electrode holding a recording medium, as reported in Japanese Patent Application Laid-Open No. 56-4467, When the recording voltage exceeds a certain threshold value, the electrostatic force acting on the ink overcomes the surface tension of the ink, and the ink droplet is ejected from the recording electrode 1 and flies to the counter electrode.

Regarding the structure of the head based on this principle,
For example, U.S. Pat.
No. -4467.

In the configuration of this example, a nozzle hole is not necessarily required for each recording electrode, and the ink ejection port can be formed in 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 because there is no need to provide a nozzle. Therefore, not only a so-called serial type head having a few hundred recording electrodes and scanning 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 is very useful. It is an effective technology.

In this electrostatic ink jet recording apparatus, when a plurality of recording electrodes are provided, it is necessary to prevent charge leakage due to forming a closed loop with adjacent electrodes in order to operate each recording electrode independently of each other. is there. For this purpose, an oily solvent having high electric resistance is usually used as a solvent for the ink. For example, in the example disclosed in JP-A-58-215353, 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 an electrostatic ink jet recording apparatus using a pigment and an oily solvent, there is a problem that a certain proportion of the solvent is ejected together with the pigment in the ejection of ink, so that the print density does not increase. This was because the ratio between the pigment and the magnitude of the electrostatic force applied to the solvent was poor.

On the other hand, as disclosed in JP-A-8-295023 and JP-A-9-193389, the ratio of the force applied to the pigment and the solvent is controlled so that only the pigment is ejected from the ink. As a result, attempts have been made to solve these problems. In these documents,
Although the principle of the ejection is not always clearly explained, the above-mentioned problem is solved because only the pigment dispersed in the solvent is applied with electrostatic force to fly the pigment only, so that the carrier liquid is not contained in the ejected ink, and the above-mentioned problem is solved. Is done.

In order to move the pigment and the solvent independently as described above, the pigment must be dispersed without being dissolved in the solvent. This is because if the pigment is dissolved, it becomes impossible to distinguish between the pigment and the solvent, and it is not possible to selectively discharge only the pigment.

According to JP-A-8-295023,
In fact, by applying a voltage of the same polarity as the charged polarity of the pigment to the recording electrode, only the pigment migrates and aggregates at the tip of the recording electrode by electrostatic repulsion, and an ink droplet containing a large amount of pigment is ejected. ing.

[0017]

However, according to such a technique, although the printing density is increased by the aggregation of the pigment, the pigment is deposited on the electrode or the electrode substrate by the aggregation at an unnecessary timing or the aggregation at an unnecessary place. There has been a problem that the ink is fixed or the recording electrode or the electrode substrate is plated with a pigment, thereby causing an undesirable obstacle in the ink flow path.

It is known that such an obstacle caused by the fixation or plating of the pigment disturbs the flow of the ink in the ink flow path and hinders stable ink ejection. According to experiments by the inventors, in the case of a head using a slit-type ink ejection port common to all or a large number of recording electrodes, slight turbulence of ink flow causes variation of ink droplets and non-ejection of ink. It is known to be the cause.

Furthermore, in addition to the cause of aggregation, there is also a problem that the pigment sediments due to the use of the dispersed pigment and is fixed on the recording electrode or the electrode substrate on which the recording electrode is formed, and cannot be removed in due course. is there.

Here, such fixation or plating of the pigment occurs not only in the vicinity of the recording electrode but also in any place where the ink exists, even in a place where it is electrically insulated. This is because, even in a part made of a material such as plastic, such as an ink flow path, the plastic itself has a surface potential, and the surface potential causes adsorption of the pigment.

When the pigment is fixed in the ink flow path, if the pigment is close to the ink discharge port, it greatly affects the ink discharge characteristics. Even if there is a certain distance from the ink ejection port, the fixation of the pigment in the ink flow path becomes a serious problem. For example, there is a problem that the ink concentration changes little by little due to the pigment fixation in the ink flow path caused by long-term use. In addition, when using ink-jet technology, an ink circulation mechanism is often provided to ensure ejection stability.However, if the pigment adheres in the ink flow path, the ink flow velocity and the flow direction change. And stable printing cannot be performed.

Generally, maintenance processing is not performed in the ink flow path, so even if the pigment is simply fixed, it cannot be easily removed once it has occurred. In addition, the recording device cannot be used for a long time.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrostatic ink jet recording apparatus capable of preventing fixation and plating of a pigment in an ink flow path.

[0024]

To solve this problem, an electrostatic ink jet recording apparatus according to the present invention comprises a plurality of recording electrodes formed on an insulating electrode substrate and arranged in parallel with each other. And a first head block and a second head block which are arranged so as to sandwich the recording electrode and form an ink discharge port and an ink flow path where the tip of the recording electrode protrudes, and a pigment which is disposed along the ink flow path It has a configuration in which a removing electrode and a counter electrode arranged opposite to the recording electrode are provided, and the pigment in the ink is ejected and fly by electrostatic force to print on the recording medium.

This makes it possible to prevent the pigment from sticking or plating in the ink flow path.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a plurality of recording electrodes formed on an electrode substrate having an insulating property and arranged in parallel with each other are arranged so as to sandwich the recording electrodes. A first head block and a second head block which form an ink discharge port and an ink flow path in which the leading end of the recording electrode protrudes, a pigment removing electrode disposed along the ink flow path, This is an electrostatic ink jet recording device that has a counter electrode arranged in the vertical direction and discharges and flies the pigment in the ink by electrostatic force to print on the recording medium. It has the effect that it becomes possible to prevent.

According to a second aspect of the present invention, there is provided the electrostatic ink jet recording apparatus according to the first aspect, wherein the pigment removing electrode is formed on an insulating layer provided on the recording electrode. This has the effect that it is possible to reliably prevent the pigment from sticking to the recording electrode.

According to a third aspect of the present invention, in the first or second aspect of the present invention, an electrostatic ink jet recording is provided in which a DC voltage having a polarity opposite to the charging polarity of the pigment is applied to the pigment removing electrode. This is an apparatus and has an effect that it is possible to prevent the fixation and plating of the pigment in the ink flow path.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, the pigment removing electrode is provided with A
This is an electrostatic ink jet recording apparatus to which a voltage C is applied, and has an effect that it is possible to vibrate and remove the fixed pigment.

According to a fifth aspect of the present invention, in the first or the second aspect of the present invention, a DC voltage and an AC voltage having polarities opposite to the charging polarity of the pigment are alternately applied to the pigment removing electrode. This is an electrostatic type ink jet recording apparatus, which has the effect of preventing the pigment from sticking beforehand and vibrating and removing the pigment already fixed.

According to the invention of claim 6 of the present invention, in the invention of claim 4 or 5, the AC voltage applied to the pigment removing electrode has a bias voltage having a polarity opposite to the charging polarity of the pigment. An electronic inkjet recording device,
This has the effect that the pigment can be more efficiently removed.

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 an exploded perspective view showing an essential part of an electrostatic ink jet recording apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of the electrostatic ink jet recording apparatus of FIG. 1, and FIG. FIG. 4 is an exploded perspective view showing a main part of an electrostatic ink jet recording apparatus according to another embodiment, FIG. 4 is a sectional view of the electrostatic ink jet recording apparatus of FIG. 3, and FIG. FIG. 4 is a waveform chart showing a voltage applied to a pigment removing electrode in the recording apparatus.

As shown in FIG. 1 and FIG.
Are formed on a thin electrode substrate 2 having an insulating property such as a polyimide film, and are arranged in parallel with each other to be electrically independent.

One end of the recording electrode 1 is electrically connected to a driver (not shown), and a recording signal is sent to the recording electrode 1 from the driver. An upper head block (first head block) 4 and a lower head block (second head block) 3 are arranged above and below the recording electrode 1 with the recording electrode 1 interposed therebetween. The blocks 3 and 4 form an ink discharge port 10 which is a slit-shaped opening communicating with the ink flow path 11. Note that the tip of the recording electrode 1 is attached so as to protrude from the ink ejection port 10.

On the insulating layer 5 provided so as to cover the recording electrode 1 and inside the upper head block 4, a pigment removing electrode 6 electrically connected to a power supply (not shown) is provided, for example, by adhesion. Are arranged along. Here, the pigment removing electrode 6 may be disposed over the entire ink flow path 11 or may be disposed partially. However, it is desirable to arrange the ink flow path 11 over as much of the ink flow path 11 as possible, since the ink contact area is covered with the pigment removal electrode.

In the present embodiment, the pigment removing electrode 6 is formed on the insulating layer 5 provided on the recording electrode 1 in order to reliably prevent the pigment from being fixed on the recording electrode 1. The pigment removing electrode 6 may be formed in the same layer as the recording electrode 1 by laying the wiring of 1 at the end of the electrode substrate 2 or alternately arranging the recording electrode 1 and the pigment removing electrode 6. .

As shown in FIG. 2, a counter electrode 8 is disposed at a position facing the recording electrode 1.
A recording medium 9 to which ink ejected from the recording electrode 1 toward the counter electrode 8 adheres is set on the front surface of the recording medium 9.

Here, as shown in FIGS. 3 and 4, in the vicinity of the ink discharge port 10 in the upper head block 4, the aggregation of the pigment in the ink discharge port 10 to which a voltage having the same polarity as the charged polarity of the pigment is applied. A pigment aggregation electrode 7 for increasing the efficiency may be provided. In such a case, a predetermined distance should be provided between the pigment aggregation electrode 7 and the pigment removal electrode 6 so that a discharge is not generated by the voltage applied between the pigment aggregation electrode 7 and the pigment removal electrode 6. desirable.

Since a voltage at which the pigment is repelled is applied to the pigment aggregation electrode 7 as described above, it is not necessary to overlap the pigment removal electrode thereon. On the other hand, since the level of the potential of the recording electrode 1 changes according to the image signal, there is a period in which the pigment is fixed. Therefore, unlike the pigment aggregation electrode 7, it is necessary to arrange the pigment removal electrode 6 on the recording electrode 1.

In the electrostatic ink jet recording apparatus of this embodiment having such a configuration, a DC voltage having a polarity opposite to the charge polarity of the pigment is applied to the pigment removing electrode 6 so that the ink in the ink flow path 11 is formed. It becomes possible to prevent sticking of the pigment and plating.

In this case, if the pigment adheres to the recording electrode 1 side, the ink ejection performance is seriously affected.
To prevent this, the relationship between the potential of the pigment removing electrode 6 on the recording electrode 1 side and the potential of the pigment removing electrode 6 of the upper head block 4 is set to be opposite to the polarity of the charged pigment. For example, if the charge polarity of the pigment is positive, the potential of the pigment removal electrode 6 on the recording electrode 1 side is set higher than the pigment removal electrode 6 of the upper head block 4. The application of the voltage to the pigment removing electrode 6 may be always performed within a range that does not affect the recording signal, or may be applied only during non-printing.

The voltage applied to the pigment removing electrode 6 is A
The C voltage may be used. By applying the AC signal, the fixed pigment is vibrated and removed. In addition, DC voltage and A
By alternately applying the C voltage, the fixation of the pigment is prevented beforehand, and the already fixed pigment can be removed by vibrating.

This AC signal is desirably biased with a voltage having a polarity opposite to the polarity of the pigment charged. In FIG.
The signal applied to the pigment removing electrode 6 on the recording electrode 1 side when the charge polarity of the pigment is positive is shown. The upper head block 4 is grounded. The application of such a signal causes a phenomenon opposite to that of the plating, so that the pigment is removed from the fixed portion.

As described above, according to the present embodiment, since the pigment removing electrode 6 to which a predetermined potential is applied is arranged along the ink flow path 11, the pigment Sticking and plating can be prevented beforehand.

[0046]

As described above, according to the present invention, there is obtained an effective effect that it is possible to prevent the fixation and plating of the pigment in the ink flow path.

If the pigment removing electrode is formed on the insulating layer provided on the recording electrode, an effective effect that the pigment fixation on the recording electrode can be reliably prevented can be obtained.

When a DC voltage having a polarity opposite to the charge polarity of the pigment is applied to the pigment removing electrode, an effective effect is obtained in that the fixation and plating of the pigment in the ink flow path can be prevented.

When an AC voltage is applied to the pigment removing electrode, an effective effect is obtained that the fixed pigment can be removed by vibrating.

If a DC voltage and an AC voltage having polarities opposite to the charged polarity of the pigment are alternately applied to the pigment removing electrode, the fixation of the pigment can be prevented, and the already fixed pigment can be removed by vibration. An effective effect is obtained that is possible.

When the AC voltage applied to the pigment removing electrode has a bias voltage having a polarity opposite to the charging polarity of the pigment, an effective effect that the pigment can be more efficiently removed can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a main part of an electrostatic inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electrostatic inkjet recording apparatus of FIG.

FIG. 3 is an exploded perspective view showing a main part of an electrostatic ink jet recording apparatus according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of the electrostatic inkjet recording apparatus of FIG.

FIG. 5 is a waveform chart showing a voltage applied to a pigment removing electrode in the electrostatic ink jet recording apparatus of the present embodiment.

FIG. 6 is a perspective view showing a conventional electrostatic ink jet recording apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording electrode 2 Electrode board 3 Lower head block (2nd head block) 4 Upper head block (1st head block) 5 Insulating layer 6 Pigment removal electrode 8 Counter electrode 9 Recording medium 10 Ink ejection opening 11 Ink flow path

Claims (6)

[Claims] A plurality of recording electrodes formed on an electrode substrate having an insulating property and arranged in parallel with each other; an ink ejection port arranged so as to sandwich the recording electrodes and having a tip end of the recording electrodes protruding; A first head block and a second head block that form an ink flow path, a pigment removal electrode disposed along the ink flow path, and a counter electrode disposed to face the recording electrode; An electrostatic ink jet recording apparatus, wherein the pigment in the ink is ejected and fly by electrostatic force to print on the recording medium. 2. The electrostatic ink jet recording apparatus according to claim 1, wherein said pigment removing electrode is formed on an insulating layer provided on said recording electrode. 3. The electrostatic ink jet recording apparatus according to claim 1, wherein a DC voltage having a polarity opposite to a polarity of charging the pigment is applied to the pigment removing electrode. 4. The electrostatic ink jet recording apparatus according to claim 1, wherein an AC voltage is applied to the pigment removing electrode. 5. The electrostatic ink jet recording according to claim 1, wherein a DC voltage and an AC voltage having polarities opposite to the charged polarity of the pigment are alternately applied to the pigment removing electrode. apparatus. 6. The electrostatic ink jet recording apparatus according to claim 4, wherein the AC voltage applied to the pigment removing electrode has a bias voltage having a polarity opposite to a charging polarity of the pigment.