JPH06134992A - Inkjet recording head - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to inkjet recording used in various printing devices, and it is difficult to use conductive ink of electrostatic attraction type inkjet and that the driving voltage is high. It is an object of the present invention to provide a small and low-priced head that solves the problem and can use safe ink that is compatible with plain paper. A counter electrode 11 is provided so as to face the ink ejection port 10, and an ink layer 19 that independently supplies ink to the plurality of ink ejection ports is provided. An electrode 13 and a heater 14 are provided on the ink layer 19 via a coating film 15. A potential difference is provided between the counter electrode 11 and the common ink chamber 20 such that ink is not ejected, and a potential difference at which ink can be ejected is provided between the counter electrode 11 and the electrode 13. When air bubbles are generated by the heater, the ink is divided and the ink is separated by the electrode 13.
It becomes the potential of and is ejected. With this configuration, it is possible to obtain a low-voltage drive head that enables water-based ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for ejecting minute liquid droplets to draw characters, figures, images and the like.

[0002]

2. Description of the Related Art In recent years, ink jet recording technology has been attracting attention as a small printer which is quiet, has high printing quality, and is inexpensive.

Although various methods have been proposed for the ink jet recording technology, the present invention belongs to the electrostatic suction type ink jet.

A conventional electrostatic suction type ink jet will be described below. FIG. 5 shows a multi-nozzle structure of a conventional electrostatic suction type inkjet.

In FIG. 5, 1-1 to 1-3 are ink ejection ports made of an insulating material, and 2-1 to 2-3 are ejection electrodes 3-1 installed on the back surface of the ink ejection port. From 3
-3 is a pulse circuit for applying a signal voltage to the ejection electrode, 4 is ink, 5 is recording paper, and 6 is a back electrode for sucking ink.

The operation of the ink jet system constructed as above will be described below.

First, a bias voltage in a range in which the ink 4 is not ejected is applied to the ink 4 and the back electrode 6 in the ink nozzle.

Next, when a signal voltage is applied to an appropriate ejection electrode of 2-1 to 2-3, the potential difference between the ink 4 in the ink nozzle to which the signal voltage is applied and the back electrode increases. The ink 4 in the ink nozzles is sucked and reaches the recording paper 5.

[0009]

However, in the above-mentioned conventional configuration, since the ejection is controlled independently for each ink nozzle, the voltage applied between the ejection electrodes may vary depending on the voltage applied state.
Since a potential difference corresponding to a signal voltage may occur between adjacent ejection electrodes, a large current may flow into the ink when conductive ink is used, and destruction due to heat generation may occur.

Therefore, insulating oil-based ink is used as the ink. Compared to water-based inks, oil-based inks have the advantage that they have a higher boiling point and are less prone to clogging, but oil-soluble dyes have few types of dyes and have a low degree of freedom in ink design. However, oily solvents generally have low surface tension, and it is difficult to take measures against odor, flammability, safety, etc. It is difficult to operate to an appropriate combined value, and it is difficult to realize ink compatible with plain paper.

In addition, the electrostatic suction type ink jet requires a drive circuit of several hundreds of V, and the circuit structure becomes large,
It also has a general problem that it is difficult to reduce the price.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide an electrostatic attraction type ink jet which can use a conductive ink and has a low drive signal voltage.

[0013]

To achieve this object, the present invention provides a means for separating and separating ink in an ink flow path for supplying ink to an ink ejection port.

[0014]

According to the present invention, since the ink in the ink flow path is separated by the above-mentioned constitution, even if the conductive water-based ink is used, it is electrically cut off from the other nozzles, so that the short circuit between the electrodes is prevented. It is possible to realize an ink jet recording head that operates well without any generation.

[0015]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of an ink jet recording head according to the first embodiment of the present invention.

In FIG. 1, 10 is an ink ejection port, and 11
Is a counter electrode, 12 is a recording paper, 13 is an electrode, 14 is a heater, 16 is an insulating nozzle plate, 17 is an air bubble, 19 is an ink layer, 20 is a common ink chamber, 21 is an electrode protective film, 22 is a heater protective film. , 23 are heat generating circuits, and 24 is a high voltage circuit.

In this embodiment, the structure of a single nozzle having a single ink ejection port will be described as a basis, but when the ink jet head is a multi-nozzle having a plurality of ink ejection ports, the ink ejection port and the ink are ejected. The layers are
A plurality of them are independently provided in the direction perpendicular to the plane of FIG.

Here, the ink discharge port 10 is perforated in the insulating nozzle plate 16, and a counter electrode 11 is provided so as to face the ink discharge port 10 and sandwich the recording paper 12.

The electrode 13 is provided on the back surface of the insulating nozzle plate 16 with the thin ink layer 19 interposed therebetween.

The electrode 13 is provided with an electrode protective film 21. The electrode protective film 21 is of a material, size and structure having an electrical property capable of applying an appropriate electric potential to the ink through the electrode protective film 21. Is selected.

A heater 14 is provided below the electrode 13, and the heater 14 is covered with a heater protective film 22 for protecting it.

The common ink chamber 20 is provided below the ink layer 19 and is an ink chamber that communicates ink with a single ink ejection port 10 in the case of a single nozzle, or all inks in the case of a multi-nozzle. It is a common ink chamber for communicating ink to the ejection port.

A heating circuit 23 for generating heat is connected to the heater 14, and a high voltage circuit 24 for applying a high voltage is connected to the electrode 13 and the heater 14.

In the electrostatic suction type ink jet, the electrostatic force between the ink in the ink discharge port 10 and the counter electrode 11 sucks and discharges the ink. Whether the ink is ejected is determined by the electric field force acting on the ink at the tip of the ink ejection port and the amount of electric charge.

That is, the potential difference required for ink ejection is
Although it will be determined at any time depending on the shape and dimensions of the ink discharge port shape, the position of the counter electrode, etc., in the present embodiment shown in FIG. 1, for example, ink discharge is started at a potential difference of 1.8 kV. First, the counter electrode is -1.7k.
Apply V.

When the ink ejection signal is not applied, the potential of the electrode 13 is 0V, and the ink is set to 0V through the electrode protection film 13.

Next, when an ink ejection signal is applied, first, a pulse signal having a predetermined interval and a pulse length is sent from the heating circuit 23 to the heater 14, the heater 14 generates heat, and the ink of the ink layer 19 is formed. Bubbles 17 are generated.

Then, when the bubble 17 is generated, the high voltage circuit 24 operates to raise the potentials of the electrode 13 and the heater 14 to, for example, +300 V, and as a result, the ink in the ink ejection port 10 and the counter electrode. The potential difference with respect to 11 becomes a high voltage of 2.0 kV, ink is sucked and ejected from the ink ejection port 10 to the recording paper 12 side, and recording is performed on the recording paper 12.

At the time of discharging this ink, since the ink in the ink layer 19 and the ink in the common ink chamber 20 are electrically isolated by the generation of the bubble 17, the electric field applied by the electrode 13 is applied. The force is effectively limited to the region shielded by the bubble 17, and even if the conductive ink is used, suction and ejection from the ink ejection port 10 are possible.

Even in the case of a multi-nozzle head structure, the common ink chamber 20 communicating with another ink ejection port due to the bubbles 17 is electrically insulated from the ink in the ink layer 19, so that the other ink ejection port There is no electrical influence on the device and no malfunction occurs.

Then, after the ink ejection is completed, a predetermined time before the bubble 17 disappears, the high voltage circuit 24
The application of voltage to the electrode 13 and the heater 14 is stopped, the potentials of these are dropped, and the initial state is once returned.
When the next ink ejection signal is generated, the above operation is repeated correspondingly to eject ink.

As described above in detail, according to the constitution of the present invention, since the ink in the ink ejection port can be electrically separated by the generation of bubbles, the conductive water-soluble ink is used. You can Furthermore, the multi-nozzle head also has a great effect in that ink can be ejected with the same configuration.

(Embodiment 2) A second embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an ink jet recording head according to the second embodiment of the present invention. In FIG. 2, 10 is an ink ejection port, 11 is a counter electrode, 12 is a recording paper, 13 is an electrode, 14 is a heater, 15 is a coating film, 16 is an insulating nozzle plate, 17 is a bubble, 18 is a drive circuit, 19 is an ink layer,
20 is a common ink chamber.

Also in this embodiment, the structure of a single nozzle having a single ink ejection port will be described as a basic, but when the ink jet head is a multi nozzle having a plurality of ink ejection ports, the ink ejection port and the ink ejection port are A plurality of ink layers are independently provided in the direction perpendicular to the paper surface of FIG.

Here, the counter electrode 11 has the recording paper 12 sandwiched therebetween, and the ink discharge port 1 is formed in the insulating nozzle plate 16 by punching.
It is provided facing 0.

The electrode 13 is provided on the back surface of the nozzle plate 16 with the thin ink layer 19 interposed therebetween.

The electrode 13 is covered with a coating film 15 having an appropriate resistance and capacitance, and a potential can be applied to the ink in the form of a capacitor or via a large resistance.

A heater 14 is provided below the electrode 13 to heat the ink layer 19 and generate bubbles 17.

The common ink chamber 20 is provided below the ink layer 19 and is an ink chamber which communicates ink with a single ink ejection port 10 in the case of a single nozzle, and all inks in the case of a multi-nozzle. It is a common ink chamber for communicating ink to the ejection port.

In the structure of this embodiment, if ink ejection is started at 1.8 kV, a potential difference of, for example, -2 kV is applied to the counter electrode 11.

Further, 300 V is applied to the common ink chamber 20, and when the potential of the ink ejection port is the same as that of the ink in the common ink chamber, it is set so that the ink is not ejected.

On the other hand, a drive circuit 18 for heating the heater is connected to the electrode 13, which is normally 0V.

At this time, the ink of the ink layer 19 and the electrode 1
There is a potential difference of 300 V between the coating film 15 and
Since only a minute current flows through, stable insulation is achieved.

Next, when a pulse voltage for heating the heater is applied from the drive circuit 18 to the electrode 13, bubbles 17 are generated in the ink layer 19 to block the ink layer 19 and ink near the ink ejection port 10 is removed. It is separated from the ink in the common ink chamber 20.

The separated ink is then applied to the coating film 1
5, the potential of the electrode 13 approaches 0 V, the potential difference between the ink in the ink ejection port 10 and the counter electrode 11 increases,
Ink is ejected by suction.

When the bubble 17 disappears, the initial potential relationship is reproduced and the ink returns to a state where it is not ejected.

As described above in detail, according to the configuration of the present embodiment, the ink in the plurality of ink ejection ports can be separated by the generation of bubbles, so that the conductive water-soluble ink is used. be able to.

Furthermore, it is natural for the electrode 13 to provide a potential relationship that enables the ink in the ink ejection port 10 to be ejected, and the air bubbles 17 are generated as in the first embodiment. The high voltage circuit 24 becomes unnecessary.

That is, in this embodiment, the ink ejection port 1
The ink potential within 0 will be switched by the bubble 17.

In the first embodiment, the multi-nozzle structure was particularly effective, but in the second embodiment, even in the single nozzle structure, high voltage switching is not necessary, so that an effective structure is obtained. Is.

(Third Embodiment) A third embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an ink jet recording head in the third embodiment of the present invention. In FIG. 3, 10 is an ink ejection port, 12 is a recording paper, 13 is an electrode, 14 is a heater, 16 is an insulating nozzle plate, 17 is a bubble, 18 is a drive circuit, 19 is an ink layer, 20 is a common ink chamber, Reference numeral 25 is a suction electrode, and 26 is an opening.

This embodiment is basically the same as the second embodiment, but an opening 26 slightly larger than the ink ejection opening 10 is provided on the front surface of the ink ejection opening 10, and the surface of the opening 26 is formed. The difference is that a potential difference is provided between the suction electrode 25 and the ink in the ink ejection port 10 to eject ink droplets by electrostatic force.

Therefore, although the operation is similar to that of the second embodiment, in this embodiment, since the suction electrode 25 can be installed in the vicinity of the ink ejection port 10, a large electrostatic force is generated with a smaller potential difference. Is possible, and there is an advantage that the suction and ejection of ink can be realized more efficiently.

(Embodiment 4) A fourth embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 4 shows an ink jet recording head according to the fourth embodiment of the present invention. In FIG. 4, 10 is an ink ejection port, 12 is a recording paper, 13 is an electrode, 14 is a heater, 15 is a coating film, 16 is an insulating nozzle plate, 17 is a bubble, 18 is a drive circuit, 19 is an ink layer, 20 is a common ink chamber, 27 is an air flow, 28 is a suction electrode, and 29 is an air ejection port.

This embodiment is basically the same as the second embodiment, except that it is an ink jet recording head utilizing an air flow and electrostatic force.

That is, in the present embodiment, the suction electrode 28 is provided around the air discharge port 29, and in the ink jet recording head utilizing this air flow and electrostatic force, it faces the ink discharge port 10. The air discharge port 29 is provided, the air flow 27 is sent through the gap between the air discharge port 29 and the ink discharge port 10, and the air flow 27 is constantly flown from the air discharge port 29.

In the ink jet recording head having such a structure, the suction electrode 28 can be accurately installed in the vicinity of the air discharge port 29, and the ink droplets are accelerated by the air flow 27. Ink ejection characteristics with properties are obtained.

In the first to fourth embodiments, the structure in which the bubbles are generated by the heater 14 is adopted, but any other structure is possible as long as it can divide the liquid.

For example, a microvalve that mechanically closes the flow path, generation of hydrogen bubbles due to a hydrogen storage alloy, and the like can be considered.

Further, in the first to fourth embodiments, it is very important to adopt a structure in which the liquid can be reliably separated by the bubbles 17 at the place where the bubbles 17 are generated in the ink layer 9.

For example, it is conceivable that the bubble generation portion is made narrower than the other flow path portions, or the bubble generation portion is formed of an ink repellent substance, so that the ink liquid is quickly separated.

Further, in the first to fourth embodiments, the material shapes of the coating film 15 and the electrode protection film 21 are selected so that the electric capacitance and resistance value determined by them are appropriate. The heater protection film 22 is made of a material having good heat resistance.

For example, as these materials, ceramics, glass, SiO ₂ and other resins are applied.

Further, in the first to fourth embodiments, the shape of the ink discharge port 10 is convex. However, in the electrostatic suction type ink jet recording head, this shape makes it possible to concentrate the electric field. This improves the quality and enables ink ejection at a low voltage.

Further, in the electrostatic suction type ink jet recording head, it is important to always keep the meniscus in a constant shape so as to prevent the ink around the nozzle from getting wet or dripping. Therefore, it is effective to apply an ink repellent substance such as Teflon around the nozzle.

Further, another ink jet recording system has a construction in which the ejection of ink droplets is stopped by utilizing only the generation and contraction of bubbles, but in the present invention, the bubbles are intended to divide the ink layer. Therefore, bubbles having a smaller expansion energy can be adopted, and a printer head with low power consumption can be realized.

Further, since the amount of stored heat is small, it is advantageous in terms of heat dissipation, which is a factor for realizing high-speed response.

In the present invention, when the bubble 17 is generated and disappears, the meniscus of the ink formed in the ink ejection port 10 moves and vibrates.

However, this vibration has the effect of shouldering the energy for raising the ink meniscus by electrostatic force, and therefore rather makes the present invention more effective, and this vibration is effective. By utilizing it, the potential difference for ejecting ink by about 20 to 30% can be reduced.

[0074]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a conductive water-soluble ink can be used by providing a means for separating and separating ink in the ink flow path for supplying the ink to the ink discharge port. An electrode is provided in the vicinity of the ink discharge port of the ink flow path through a coating film, and when the air bubbles separate and isolate the ink in the ink flow path, the ink near the ink discharge port is changed according to the electrical properties of the coating film. By bringing the ink closer to the potential of the electrode and increasing the electrostatic force to suck and eject the ink, high-voltage switching becomes unnecessary. Therefore, it is possible to realize an excellent inkjet recording head suitable for a low-priced and small-sized printer, which has good compatibility with plain paper and can use ink with excellent safety.

[Brief description of drawings]

FIG. 1 is a sectional view of an ink jet recording head according to a first embodiment of the invention.

FIG. 2 is a sectional view of an ink jet recording head according to a second embodiment of the invention.

FIG. 3 is a sectional view of an ink jet recording head according to a third embodiment of the invention.

FIG. 4 is a sectional view of an ink jet recording head according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a conventional electrostatic suction type inkjet recording head.

[Explanation of symbols]

 10 Ink Discharge Port 11 Counter Electrode 12 Recording Paper 13 Electrode 14 Heater 15 Covering Film 16 Insulating Nozzle Plate 17 Bubble 18 Drive Circuit 19 Ink Layer 20 Common Ink Chamber 21 Electrode Protection Plate 22 Heater Protection Film 23 Heat Generation Circuit 24 High Voltage Circuit 25 Suction electrode 26 Opening 27 Air flow 28 Suction electrode 29 Air outlet

Claims (12)

[Claims] 1. An electrostatic suction type ink jet recording head for sucking and ejecting ink by providing a potential difference between the ink in the ink ejection port and a suction electrode facing the ink ejection port. An ink jet recording head having means for separating and separating ink in an ink flow path to be supplied. 2. The ink jet recording head according to claim 1, wherein the means for separating and separating the ink is a bubble generating means. 3. An electrode is provided in the vicinity of an ink ejection port via a coating film, and means for isolating the ink is provided in an ink flow channel for supplying the ink to the ink ejection port. When the ink in the ink flow channel is separated and isolated. 2. The ink jet recording head according to claim 1, wherein a voltage is applied to the electrodes and ink is sucked and ejected by electrostatic force. 4. A common ink chamber communicating with the ink flow path is provided with an electrode through a coating film in the vicinity of the ink discharge opening, an ink flow path for supplying ink to the ink discharge opening, and means for isolating the ink. Is a voltage at which ink is not ejected and a voltage at which ink can be ejected is applied to the electrodes, and when the ink in the ink ejection port is separated from the ink in the common ink chamber, the ink in the ink ejection port is separated. The ink jet recording head according to claim 1, wherein the ink is sucked and ejected by bringing the ink close to the voltage of the electrode. 5. The ink jet recording head according to claim 1, further comprising means for separating and separating the ink flow paths from the plurality of ink ejection openings. 6. The ink jet recording head according to claim 1, wherein an opening is provided in front of the ink ejection port, a suction electrode is provided on the surface of the opening, and the ink is ejected by a potential difference between the suction electrode and the ink in the ink ejection port. 7. The ink jet recording head according to claim 1, wherein the ink from the ink ejection port is accelerated by using an air flow. 8. The ink jet recording head according to claim 1, wherein the portion that separates and separates the ink flow passage forms a flow passage that is narrower than the other portions. 9. The ink jet recording head according to claim 1, wherein the portion separating and separating the ink flow path has an ink repellent substance. 10. The ink jet recording head according to claim 1, wherein the ink ejection port has a convex shape. 11. The ink jet recording head according to claim 1, wherein the periphery of the ink ejection port has an ink repellent substance. 12. The ink jet recording head according to claim 1, wherein the meniscus of the ink formed at the ink ejection port is vibrated by the energy for separating and isolating the ink flow path.