JP2650584B2 - Inkjet recording head - Google Patents

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 drawing characters, figures, images and the like by discharging fine droplets.

[0002]

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

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

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

In FIG. 5, reference numerals 1-1 to 1-3 denote ink discharge ports formed of an insulating material, and 2-1 to 2-3 denote discharge electrodes provided on the back surface of the ink discharge ports. From 3
Reference numeral -3 denotes a pulse circuit for applying a signal voltage to the discharge electrode, reference numeral 4 denotes ink, reference numeral 5 denotes recording paper, and reference numeral 6 denotes a back electrode for sucking ink.

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

First, a bias voltage in a range where 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. Then, the ink 4 in the ink nozzle is sucked and reaches the recording paper 5.

[0009]

However, in the above-described conventional configuration, since the ejection is controlled independently for each ink nozzle, the voltage between the ejection electrodes depends on the voltage application state.
Since there is a case where a potential difference corresponding to a signal voltage is generated between adjacent ejection electrodes, a large current flows through the ink when conductive ink is used, and there is a case where destruction occurs due to heat generation.

[0010] Therefore, an insulating oil-based ink is used as the ink. Oil-based inks have the advantage of being able to realize inks that have a higher boiling point and are less likely to be clogged than water-based inks, but oil-soluble dyes have fewer types of dyes and have less flexibility in ink design. Oil solvents generally have a low surface tension, and the penetration rate of dots on recording paper changes the value of surface tension. It is difficult to operate the combined appropriate value, and it is difficult to realize an ink compatible with plain paper.

[0011] Further, the electrostatic suction type ink jet requires a drive circuit of several hundred volts, and the circuit configuration becomes large.
There is also a general problem that it is difficult to reduce the price.

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

[0013]

In order to achieve the above object, a main structure of the present invention is to provide an ink which is located at an ink discharge port.
Potential difference between the first electrode facing the ink ejection port
And an electrostatic suction type ink for sucking and discharging the ink.
A jet recording head, wherein
A second electrode provided on the side via a coating film;
Ink for supplying ink to the ink ejection port from the ink chamber
The flow path is separated between the ink ejection port side and the ink chamber side
Separation means that can be separated, and
In the non-ejection state, at least the ink ejection port
No ink is ejected to the located ink.
A relative voltage to an electrode is applied and said second electrode
Has a relative voltage with respect to the first electrode capable of discharging ink.
Pressure is applied, and when ink is ejected, the separation
The ink at the ink discharge port and the ink chamber
Ink on the ink ejection port side.
Ink for bringing the voltage of the ink close to the voltage of the second electrode.
This is a jet recording head. Here, the separation and isolation means is air bubbles
It is preferable that this is a means for generating. In addition, multiple
Separation and isolation means may be provided for each of the discharge ports.
In addition, the suction electrode is arranged in a manner opposite to the ink ejection port.
Install it on the surface of the recording paper opposite to the ink ejection port, or
An opening is provided on the front surface of the discharge port, and provided on the surface of the opening.
Is also good. In addition, the air ejected from the ink ejection port
A configuration for accelerating the discharged ink may be added. Also,
The part that separates and isolates the channel is narrower than the other parts.
May be formed. Also separates and isolates the ink flow path
Portion may have an ink repellent substance,
The periphery of the ink ejection port may also have an ink-repellent substance.
No. It is also preferable that the ink ejection port has a convex shape.
It is suitable and occurs when the separation and isolation means separates the ink.
Ink formed at the ink ejection port by the energy
It is also possible to vibrate the meniscus .

[0014]

According to the present invention, when the ink is ejected,
Means that the ink in the ink flow path is
Separated and separated into the chamber side and the ink ejection port side, the ink ejection port
The voltage of the ink on the side closer to the voltage at which ink can be ejected, and
Ink discharge. In addition, a plurality of ink ejection ports are
Even if a water-based ink is used,
Since it is electrically disconnected from the discharge port, a short circuit between the electrodes
Does not occur.

[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 a first embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an ink discharge port;
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 a bubble, 19 is an ink layer, 20 is a common ink chamber, 21 is an electrode protection film, and 22 is a heater protection film. , 23 is a heating circuit, and 24 is a high voltage circuit.

In this embodiment, the description is based on the configuration of a single nozzle having a single ink discharge port. However, when the ink jet head is a multi-nozzle having a plurality of ink discharge ports, the ink discharge port and the ink The layers are
A plurality of each are provided independently in the vertical direction on the paper surface of FIG.

Here, the ink discharge port 10 is perforated in the insulating nozzle plate 16, and a counter electrode 11 is provided opposite the ink discharge port 10 with the recording paper 12 interposed therebetween.

The electrode 13 is provided on the back surface of the insulating nozzle plate 16 via a thin ink layer 19.

The electrode 13 is provided with an electrode protective film 21. The electrode protective film 21 has a material, dimensions and structure having electrical properties through which an appropriate potential can be applied to the ink. Is selected.

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

The common ink chamber 20 is provided below the ink layer 19 and is an ink chamber for communicating 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 openings.

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

In the electrostatic suction type ink jet, the ink is sucked and discharged by the electrostatic force between the ink in the ink discharge port 10 and the counter electrode 11, but the magnitude of the potential difference is as follows. Whether the ink is ejected is determined by the electric field force and the amount of electric charge acting on the ink at the tip of the ink ejection port.

That is, the potential difference required for ink ejection is
It is determined as needed depending on the shape and dimensions of the shape of the ink discharge port, the position of the counter electrode, etc. In the present embodiment shown in FIG. 1, for example, the discharge of the ink is started at a potential difference of 1.8 kV. First, -1.7 k is applied to the opposite electrode.
V is applied.

When no ink ejection signal is applied, the potential of the electrode 13 is 0 V, and the ink is set at 0 V via 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 heat generating circuit 23 to the heater 14, and the heater 14 generates heat and the ink in the ink layer 19 is applied to the ink. Bubbles 17 are generated.

When the bubble 17 is generated, the high voltage circuit 24 is activated, and the potentials of the electrode 13 and the heater 14 are raised to, for example, +300 V. As a result, the ink in the ink discharge port 10 and the counter electrode 11 becomes a high voltage of 2.0 kV, the ink is sucked and discharged from the ink discharge port 10 to the recording paper 12 side, and recording is performed on the recording paper 12.

At the time of discharging the ink, since the ink in the ink layer 19 and the ink in the common ink chamber 20 are electrically separated by the generation of bubbles 17, the electric field applied by the electrode 13 The force is effectively limited to the area shielded by the bubbles 17, and even if the conductive ink is used, the ink can be suctioned and discharged from the ink discharge port 10.

Even in the case of a multi-nozzle head configuration, the common ink chamber 20 communicating with another ink ejection port by the bubble 17 is electrically insulated from the ink in the ink layer 19, so that the other ink ejection port is not used. There is no electrical influence on the device, and no malfunction or the like occurs.

After the ink ejection is completed, and before a predetermined time before the bubble 17 disappears, the high voltage circuit 24
To stop applying the voltage to the electrode 13 and the heater 14, lower these potentials and return them to the initial state,
When the next ink ejection signal is generated, the above operation is repeated corresponding to the signal, and ink ejection is performed.

As described in detail above, according to the structure of the present invention, since the ink in the ink ejection port can be electrically separated by the generation of bubbles, it is necessary to use conductive water-soluble ink. Can be. Further, the multi-nozzle head has a great effect in that ink can be ejected with a similar configuration.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.

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

In this embodiment, the description will be made on the basis of the configuration of a single nozzle having a single ink discharge port. However, when the ink jet head is a multi-nozzle having a plurality of ink discharge ports, the ink discharge port and A plurality of ink layers are independently provided in a direction perpendicular to the paper surface of FIG.

Here, the counter electrode 11 is provided between the ink discharge port 1 and the insulating nozzle plate 16 with the recording paper 12 interposed therebetween.
0.

The electrode 13 is provided on the back surface of the nozzle plate 16 via a thin ink layer 19.

The electrode 13 is covered with a coating film 15 having an appropriate resistance and capacitance, so that 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 for communicating 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 openings.

In the structure of the present embodiment, assuming that the discharge of ink is started at 1.8 kV, a potential difference of, for example, -2 kV is applied to the counter electrode 11.

When a voltage of 300 V is applied to the common ink chamber 20 and the potential of the ink discharge port is the same as that of the ink in the common ink chamber, the ink is not discharged.

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

At this time, the ink of the ink layer 19 and the electrode 1
3, a potential difference of 300 V is generated.
Since only a very small current flows through, the insulation is stabilized.

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, blocking the ink layer 19, and the ink near the ink discharge port 10 is discharged. 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, and 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 state returns to a state where ink is not ejected.

As described above in detail, according to the structure of this embodiment, the ink in the plurality of ink discharge ports can be separated from each other by the generation of air bubbles, and therefore, the conductive water-soluble ink is used. be able to.

Further, the provision of the potential relationship so that the ink in the ink ejection port 10 can be ejected is naturally made by the electrode 13 when the bubble 17 is generated, as in the first embodiment. The high voltage circuit 24 becomes unnecessary.

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

Although the first embodiment is particularly effective in a multi-nozzle structure, the second embodiment is effective in that a high-voltage switching is unnecessary even with a single-nozzle structure. It is.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described in detail with reference to the drawings.

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

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

Therefore, the operation is the same as that of the second embodiment. However, in this embodiment, since the suction electrode 25 can be installed near the ink discharge port 10, a large electrostatic force is generated with a smaller potential difference. This is advantageous in that ink suction and discharge can be realized more efficiently.

Embodiment 4 Hereinafter, a fourth embodiment of the present invention will be described in detail with reference to the drawings.

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

That is, in this embodiment, the suction electrode 28 is provided around the air discharge port 29, and in an ink jet recording head utilizing this air flow and electrostatic force, the suction electrode 28 faces the ink discharge port 10. An air discharge port 29 is provided, an air flow 27 is sent from a gap between the air discharge port 29 and the ink discharge port 10, and the air flow 27 always flows from the air discharge port 29.

In the ink jet recording head having such a configuration, the suction electrode 28 can be accurately set in the vicinity of the air discharge port 29, and the ink droplet is accelerated by the air flow 27. Characteristic ink ejection characteristics can be obtained.

In the first to fourth embodiments, the structure in which bubbles are generated by the heater 14 is employed. However, other structures are also possible as long as they can divide the liquid.

For example, a micro valve that mechanically closes the flow path, generation of hydrogen bubbles by a hydrogen storage alloy, and the like can be considered.

In the first to fourth embodiments, it is very important to adopt a structure in which the bubbles 17 in the ink layer 9 can be separated from the liquid by the bubbles 17 without fail.

For example, it is conceivable to adopt a structure in which the bubble generating portion is made narrower than other flow path portions, or the ink liquid is quickly separated by forming the bubble generating portion with an ink-repellent substance.

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 capacity and resistance value determined thereby become appropriate. For the heater protection film 22, a material having good heat resistance is selected.

For example, as these materials, ceramic, glass, SiO ₂ , other resins, and the like are applied.

Further, in the first to fourth embodiments, the shape of the ink discharge port 10 is convex, but in the electrostatic suction type ink jet recording head, this shape reduces the concentration of the electric field. This improves ink discharge at a low voltage.

In an electrostatic suction type ink jet recording head, it is important that the meniscus is always kept in a fixed shape so that the ink around the nozzles does not get wet or dripping. Therefore, it is effective to apply an ink-repellent substance such as Teflon around the nozzle.

Further, in another ink jet recording system, there is a configuration in which the discharge of ink droplets is stopped by utilizing only the generation and contraction of bubbles. In the present invention, the purpose of the bubbles is to separate the ink layer. Therefore, bubbles with smaller expansion energy can be adopted, and a printer head with low power consumption is realized.

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

In the present invention, when the bubbles 17 are generated and extinguished, the meniscus of the ink formed in the ink discharge port 10 moves and causes vibration.

However, since this vibration has the effect of taking over the energy for raising the ink meniscus by the electrostatic force, it rather makes the present invention more effective. Utilization can reduce the potential difference for ink ejection by about 20 to 30%.

[0074]

As described above, according to the present invention, the ink is separated and separated in the ink flow path for supplying the ink to the ink discharge port.
Separation / separation means is provided.
The ink at the ink discharge port and the ink at the ink chamber side
Can be separated and the voltage of the ink on the ink discharge port side can be discharged.
The electrical properties of the coating to achieve an effective relative voltage
This will ensure that conductive, water-soluble ink will be used.
And high voltage switching is not required. Therefore ,
It is possible to realize an excellent ink jet recording head that is compatible with plain paper and that can use ink with excellent safety, and that is suitable for a low-cost, small-sized printer.

[Brief description of the drawings]

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

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

FIG. 3 is a sectional view of an ink jet recording head according to a third embodiment of the present 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 cross-sectional view of a conventional electrostatic suction type inkjet recording head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ink ejection port 11 Counter electrode 12 Recording paper 13 Electrode 14 Heater 15 Coating 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 (11)

(57) [Claims] 1. An ink cartridge according to claim 1 , further comprising:
Potential difference between the first electrode facing the ink discharge port
And an electrostatic suction type ink jet for sucking and discharging the ink.
An ink jet recording head, wherein the ink jet recording head is
A second electrode provided via a coating film,
Ink flow path for supplying ink to the mouth from the ink chamber
At the ink discharge port side and the ink chamber side.
Separation means capable of separating ink,
In the output state, at least the position
The first electrode on which no ink is ejected
And a voltage is applied to the second electrode
The relative voltage with respect to the first electrode from which ink can be ejected is
Is applied and when the ink is ejected,
The ink at the ink ejection port and the ink chamber side
The ink is separated and separated from the ink,
An ink jet recording head for bringing the voltage of the ink jet recording apparatus closer to the voltage of the second electrode . 2. An ink jet recording head according to claim 1, wherein said separation and separation means is means for generating bubbles. 3. The method according to claim 1 , wherein each of the plurality of ink ejection ports is separated.
3. The ink jet recording head according to claim 1, further comprising an isolation unit . 4. A recording sheet arranged opposite to an ink discharge port.
A suction electrode provided on the surface opposite to the ink ejection port
4. The ink jet recording head according to claim 1, wherein: 5. An ink jet printer according to claim 1 , wherein an opening is provided at a front surface of said ink discharge port.
4. The method according to claim 1, wherein a suction electrode is provided on a surface of the opening.
Or an ink jet recording head as described above. 6. An ink jet apparatus which discharges ink from an ink discharge port using an air flow.
The ink jet recording head according to claim 5, wherein the ink is accelerated . 7. A part which separates and separates the ink flow path from another part.
7. The method according to claim 1, wherein the flow path is narrower than the portion.
An ink jet recording head according to any of the preceding claims. 8. portion separating isolating an ink flow path, Bachii
The ink jet recording head according to any one of claims 1 to 7, further comprising an ink material . 9. An ink discharge port having a convex shape.
9. The inkjet recording head according to any one of 1 to 8 . 10. An ink- repellent material around an ink ejection port .
The inkjet recording head according to any one of claims 1 to 9, which has quality . 11. When the ink is separated and separated by the separation and separation means.
Due to the energy generated, the ink formed at the ink ejection port
11. The method according to claim 1, wherein the meniscus of the ink is vibrated.
An ink jet recording head according to any of the preceding claims.