JPH10770A - Inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-demand type inkjet recording apparatus with high density and high efficiency by which enough jetting pressure is obtd. even if the area of a diaphragm is small. SOLUTION: Under waiting condition, a control part 11 gives a potential difference to the electric potential V1 of a base electrode 2 and the electric potential V2 of a diaphragm electrode 5 and a diaphragm 4 is deformed to the base electrode 2 side by electrostatic force and it is kept under this condition. The electric potential between V1-V2 is selectively released based on an image signal and at the same time, a potential difference is given to the electric potential V2 of the diaphragm electrode 5 and the electric potential V3 of a nozzle electrode 10. A restoring force to the deformation under the waiting condition is worked on the diaphragm 4 and an electrostatic force based on the electric potential between V2-V3 is worked on an elastically deformable nozzle forming member 7 and the vol. of an ink room 9 is decreased by the diaphragm 4 and the nozzle forming member 7. Jetting pressure is generated thereby to the ink in an ink room 9 and the ink in the ink room 9 is shot as droplets from a nozzle 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an on-demand type ink jet recording apparatus for selectively discharging ink from an ink discharge element according to image information.

[0002]

2. Description of the Related Art Various types of on-demand type ink jet recording apparatuses have been proposed. As one of the methods, there is a method in which a deformation pressure of a diaphragm due to an electrostatic force is applied to ink and the ink is ejected by the force. In this method, for example, as disclosed in JP-A-6-340069, an electrode is formed on an elastically deformable movable plate,
In addition, an opposing electrode is disposed, the movable plate is deformed by electrostatic force between the opposing electrode, and a pressure due to the restoring force acts on the ink to discharge the ink.

However, in the method in which the discharge is performed by the deformation pressure of the diaphragm due to the electrostatic force, the amount of deformation of the diaphragm is small, and a diaphragm area of a certain value or more is required to obtain a sufficient discharge pressure. There is a problem that it is difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a high-density, high-efficiency, on-demand type ink jet that can obtain a sufficient discharge pressure even if the area of the diaphragm is small. It is an object to provide a recording device.

[0005]

According to a first aspect of the present invention, there is provided an ink jet recording apparatus which discharges ink in an ink chamber from a nozzle on demand according to image information, wherein a part of an inner wall of the ink chamber is formed. Elastically deformable diaphragm, and a first diaphragm formed on the diaphragm.
An electrode, a part of the inner wall of the ink chamber facing the diaphragm, the nozzle is formed and a deformable movable part that is elastically deformable, a second electrode provided on the deformable movable part, A third electrode formed opposite to the first electrode and opposite to the second electrode; and a control for controlling potentials of the first electrode, the second electrode, and the third electrode. It is characterized by having means.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the control means includes:
In the standby state, the diaphragm is deformed by the electrostatic force generated between the third electrode and the first electrode. At the time of ink ejection, the electrostatic force between the third electrode and the first electrode is released. By generating an electrostatic force between the first electrode and the second electrode, the diaphragm is deformed in a direction opposite to a standby state, and the deformable portion is deformed into the ink chamber, and a pressure is applied to the ink in the ink chamber. It is characterized in that it is operated to eject ink.

According to a third aspect of the present invention, in the ink jet recording apparatus according to the first aspect, when an area of the first electrode is S1 and an area of the second electrode is S2,
S1> S2.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the first electrode is an individual electrode for each nozzle, and the second electrode and the third electrode are a plurality of electrodes. It is characterized in that it is a common electrode for the nozzle.

According to a fifth aspect of the present invention, in the ink jet recording apparatus according to the first or fourth aspect, the control means sets the magnitude of an electrostatic force between the first electrode and the third electrode to F13. When the magnitude of the electrostatic force between the first electrode and the second electrode is F12, F13> F12 ≧ 0 in the standby state, and 0 ≦ F13 in the discharge state.
<F12 so that the second electrode and the third electrode
The potential of the first electrode is kept constant, and the potential of the first electrode is controlled to eject ink.

[0010]

FIG. 1 is a cross-sectional view of one element showing an embodiment of an ink jet recording apparatus of the present invention. In the figure, 1 is a substrate, 2 is a substrate electrode, 3 is a pressure generating member, 4 is a diaphragm, 5 is a diaphragm electrode, 6 is an ink chamber forming member, 7 is a nozzle forming member, 8 is a nozzle, 9
Denotes an ink chamber, 10 denotes a nozzle electrode, and 11 denotes a control unit.

The substrate 1 is an insulating substrate made of ceramic, glass, or the like, and has a substrate electrode 2 formed on the surface thereof. The pressure generating member 3 is made of, for example, silicon or the like, and has a movable portion corresponding to the nozzle 8. The movable portion is processed to be sufficiently thin by a method such as anisotropic etching to form the diaphragm 4. On the surface of the diaphragm 4, a diaphragm electrode 5 is formed. The substrate 1 and the pressure generating member 3 are bonded so that the diaphragm electrode 5 faces the substrate electrode 2. Here, since the diaphragm is deformed in the ink ejection direction as described later, the substrate electrode 2 and the diaphragm electrode 5 are prevented from contacting each other by the operation of the diaphragm 4.
A space is provided between the diaphragm 4 and the substrate 1. In the example shown in FIG. 1, the diaphragm electrode 5 is formed on the surface of the diaphragm 4 on the substrate electrode 2 side, but may be formed on the ink chamber 9 side.

An ink chamber 9 is formed by one surface of the diaphragm 4, the ink chamber forming member 6, and the nozzle forming member 7. The ink chamber 9 is filled with ink. An ink supply path (not shown) is connected to the ink chamber 9 so that consumed ink is supplied. In addition, as the ink to be used, for example, an insulating ink can be used. The ink chamber forming member 6 may be formed integrally with the pressure generating member 3 or the nozzle forming member 7.

The nozzle forming member 7 is formed with a nozzle 8 for discharging ink. At least the vicinity of the nozzle 8 of the nozzle forming member 7 is configured to be elastically deformable, and a nozzle electrode 10 is formed near the nozzle 8. The nozzle forming member 7 can be realized, for example, by using an elastic material such as rubber, or by forming at least the vicinity of the nozzle 8 sufficiently thin using a ceramic or a metal plate. For example, when silicon is used, the diaphragm 4 is used. In the same manner as described above, it can be formed by a technique such as anisotropic etching. Note that the nozzle electrode 10 is connected to the nozzle forming member 7.
May be formed on the outer surface of the ink chamber 9 or on the inner surface of the ink chamber 9.

The control unit 11 applies a potential V1 to the substrate electrode 2,
A potential V2 is supplied to the diaphragm electrode 5 and a potential V3 is supplied to the nozzle electrode 10, and these potentials are controlled so that ink is ejected.

The basic configuration has been described above. However, as long as the driving principle of the present invention can be realized, for example, each of the above-described electrodes is protected by an insulating film such as silicon oxide to prevent a short circuit between the electrodes. Can be changed.

FIG. 2 is an explanatory diagram showing an example of the relationship between the diaphragm electrode and the nozzle electrode. As one modified example, the diaphragm electrode 5 disposed on the diaphragm 4 and the nozzle electrode 10 formed in the vicinity of the ink discharge nozzle 8 are formed by, for example, as shown in FIG.
2. When the area of the nozzle electrode 10 is S3, S2> S
3 can be configured. FIG. 2 also shows electric lines of force on the outer periphery in front of the electrodes when a voltage is applied to both electrodes. As is clear from FIG. 2, the lines of electric force are denser near the nozzle. That is, a larger electric field gradient is formed toward the nozzle.

In general, the force of an electric field acting on a fluid per unit volume includes a Coulomb force acting on a charge per unit volume, a force acting on a spatial change in dielectric constant, and a force acting on a spatial change in electric field strength. Is the sum of The latter two are, in other words, forces acting on the polarization of the fluid. In other words, the amount of charge generated by polarization is zero when the positive and negative are combined, but when the forces acting on each charge are integrated, a stronger force acts on the polarized charges generated where the electric field is strong. Will be drawn by the strongest person. Therefore, when a large electric field is formed in the vicinity of the nozzle, an ink flow toward the nozzle is generated, and plays a part in the ink ejection force.

When each electrode is configured so that the area of the electrode has the above-described relationship, the ink flow is generated by the electric field gradient in addition to the pressure by the diaphragm 4 and the nozzle forming member 7 at the time of ink ejection, and more efficient. Ink discharge can be realized. If such effects are not expected, it is not necessary to satisfy the above relationship. FIG. 2 shows a case where the electrode is formed in a circular shape, but the shape of the electrode is not limited to this, and may be a rectangle, a polygon, an oval, or the like.
It may be of various shapes.

The configuration shown in FIG. 1 shows one element, but when a plurality of nozzles are provided, such a configuration may be provided for each element. At this time, the substrate electrode 2 and the nozzle electrode 10 can be provided corresponding to each nozzle, but can also be provided commonly to a plurality of nozzles. The control unit 11 controls whether or not to eject ink from each nozzle according to the image information.
When the nozzle electrode 10 is a common electrode for each nozzle, ink ejection can be controlled only by controlling the potential of the diaphragm electrode 5 according to image information, as described later.

Next, an example of the operation of the ink jet recording apparatus according to the embodiment of the present invention will be described. FIG. 3 and FIG. 4 are explanatory views showing one mode at the time of ink ejection in one embodiment of the ink jet recording apparatus of the present invention. FIG. 1 described above shows a standby state. In the standby state,
The control unit 11 gives a potential difference between the potential V1 of the substrate electrode 2 and the potential V2 of the diaphragm electrode 5. As a result, the diaphragm 4 is deformed in the direction of the substrate electrode 2 and is maintained in this state.

In accordance with the image signal, the potential difference between V1 and V2 is selectively released, and at the same time, a potential difference is applied between the potential V2 of the diaphragm electrode 5 and the potential V3 of the nozzle electrode 10.
Thereby, a restoring force acts on the diaphragm 4 against the deformation in the standby state, and an electrostatic force acts on the elastically deformable nozzle forming member 7 due to the potential difference between V2 and V3. As shown, the diaphragm 4 and the nozzle forming member 7 are deformed, and the volume of the ink chamber 9 is reduced. Thus, a discharge pressure is generated in the ink in the ink chamber 9, and the ink in the ink chamber 9 flies as droplets from the nozzle 8.

FIG. 5 is a timing chart for explaining an example of an operation at the time of driving in the embodiment of the ink jet recording apparatus of the present invention. A potential difference corresponding to the drive voltage is given to the substrate electrode and the nozzle electrode in advance.
In the standby state, the potential of the diaphragm electrode 5 is set equal to the potential of the nozzle electrode 10, and in the ejection state, the potential is switched to a value equal to the potential of the substrate electrode 2.

In the section A in FIG. 5, the ejection is not performed by the image signal. Since the diaphragm electrode potential is always equal to the potential of the nozzle electrode 10 during the section A, the diaphragm 4 keeps being deformed by the electrostatic force between V1 and V2, and no ink is ejected.

The sections B, C, and D in FIG. 5 correspond to the case where ink is ejected in accordance with an image signal. At the beginning of the section, by switching the potential of the diaphragm electrode 5 from the standby state to the potential of the substrate electrode 2, V1-V2
There is no electrostatic force between them, and an electrostatic force between V2 and V3 is generated. As a result, the diaphragm 4 has a restoring force from the initial deformation and the deformation pressure of the nozzle forming member 7 acting on the ink, so that the ink droplets can fly from the nozzle 8. Thereafter, by returning the potential of the diaphragm electrode 5 to the standby state again, the electrostatic force between V2 and V3 disappears, and V1−
An electrostatic force between V2 is generated. Thereby, the diaphragm 4
Is deformed toward the substrate 1 and enters a standby state, and the nozzle forming member 7 is restored by its restoring force. At this time, the shape of the ink chamber 9 returns to the standby state, and the inside of the ink chamber 9 becomes a negative pressure. With this negative pressure, only an appropriate amount of the flying ink liquid is supplied into the ink chamber 9 from an ink supply path (not shown). .

FIG. 6 is a timing chart for explaining another example of the operation at the time of driving in the embodiment of the ink jet recording apparatus of the present invention. Similar to FIG. 5, in the section A in the figure, the image signal is not ejected, and in sections B, C, and D, the ink is ejected according to the image signal. In this example, when the potential of the diaphragm electrode 5 is made equal to the potential of the substrate electrode 2 in the sections B, C, and D to eject ink from the nozzles, the potential of the diaphragm electrode 5 is returned to the standby state potential. The potential changes smoothly with respect to time.

When the diaphragm 4 is returned to the standby state after the ink is ejected, the pressure in the ink chamber 9 is negative as described above. The ink is supplied from an ink supply path (not shown) by the negative pressure. In the nozzle 8, the meniscus of the ink is drawn inside the ink chamber 9 by the negative pressure. This causes the ink meniscus to fluctuate. Fluctuations in the meniscus of the ink affect the amount of ink droplets when the next ink is ejected, and thus affect the image quality.

If the negative pressure is further large, the ink supply may not catch up with the change in the volume of the ink chamber 9 due to the fluid resistance of the ink supply path or the like at the time of ink refill, and air may enter the ink chamber 9. When air bubbles are mixed in the ink chamber 9, the pressure due to the deformation of the diaphragm 4 and the nozzle forming member 7 is absorbed by the change in the volume of the air bubbles, and there is a possibility of causing ink ejection failure.

As shown in FIG. 6, by smoothly changing the potential of the diaphragm electrode 5 with respect to time, the inside of the ink chamber 9 generated when the diaphragm 4 and the nozzle forming member 7 are returned to the standby state is formed. It is possible to supply the ink while relaxing the negative pressure, suppressing the fluctuation of the ink meniscus, and preventing the air from entering the ink chamber 9.

As shown in the timing charts of FIGS. 5 and 6, by switching one electrode as a signal electrode, two deformation pressures acting on the ink can be controlled simultaneously. Therefore, despite using a plurality of forces as the ink ejection force, a print head can be manufactured at low cost without requiring a complicated circuit.

Here, the diaphragm electrode potential is not necessarily limited to switching between the potential of the substrate electrode 2 and the potential of the nozzle electrode 10. The electrostatic force between the substrate electrode 2 and the diaphragm electrode is represented by F13, and the diaphragm electrode and the nozzle Assuming that the electrostatic force between the electrodes is F12, control may be performed such that F13> F12 ≧ 0 in the standby state and 0 ≦ F13 <F12 in the discharge state,
It can be changed within a range satisfying this condition including its polarity. For example, in the standby state, the diaphragm 4 does not deform,
It is also possible to control so that the diaphragm 4 and the nozzle forming member 7 are deformed so as to attract each other when the ink is ejected. The potential of the diaphragm electrode 5 in FIGS. 5 and 6 is controlled in a plurality of stages, and the initial deformation amount of the diaphragm 4 and the deformation amount of the nozzle forming member 7 are modulated to make the volume change amount of the ink chamber 9 variable. Also, multi-level recording by volume modulation of ink droplets can be realized.

In the above-described example, the ejection of ink is controlled by controlling the potential of the diaphragm electrode. However, the present invention is not limited to this, and any electrode may be controlled as long as the potential relationship between the electrodes enabling operation is maintained. May be. The operation of the present invention can be performed by controlling the potentials of the substrate electrode 2, the nozzle electrode 10, and one or more diaphragm electrodes 5 by the control unit 11.

Further, the above-described configuration can be used in combination with another ink jet recording system. For example,
A fourth electrode is provided on the recording medium side, and a diaphragm electrode 5 is provided.
It can be combined with a method of drawing ink to a recording medium by an electrostatic field between the first electrode and the fourth electrode. In the method of sucking ink by the electrostatic field, there is a problem that the response to the electrostatic force is poor and the printing speed is slow.
By combining with the above-described configuration, the time required for ink to reach the recording medium can be reduced. In addition, in the method in which ink is sucked by an electrostatic field, the amount of ink adhered to a recording medium can be changed depending on the time for applying the electrostatic field, so that high-speed multi-tone printing can be easily realized.

[0033]

As is apparent from the above description, according to the present invention, both the deformation of the diaphragm and the deformation of the deformable movable portion which forms a part of the wall surface of the ink chamber together with the diaphragm cause the ink in the ink chamber to change. To eject ink. In the conventional ink jet recording apparatus using only the deformation of the diaphragm 4 as in the prior art, the area of the diaphragm 4 must be increased in order to realize the change in the volume of the ink chamber necessary for discharging the ink. Has been a major obstacle to the high density of
According to the configuration of the present invention, in addition to the change in the volume of the ink chamber due to the deformation of the diaphragm, the deformation of the deformable portion also acts, so that the amount of change per element substrate area can be increased. Therefore, it is not necessary to increase the area of the diaphragm, which has a great effect on increasing the density.

Also, the diaphragm can be driven at a higher speed because the electrostatic force between the opposite electrodes on both sides thereof, that is, the second and third electrodes is alternately applied and sucked. Further, a nozzle for ejecting ink is formed on the deformable movable portion provided with the second electrode, and the nozzle is formed on one surface forming an ink chamber, so that the axes of the movable direction of the diaphragm and the deformable movable portion and the ink discharge direction are aligned. A consistent and efficient configuration can be easily realized at low cost.

In particular, according to the second aspect of the present invention,
In the standby state, the diaphragm is deformed by the electrostatic force generated between the third electrode and the first electrode by the control means, and when the ink is ejected, the electrostatic force between the third electrode and the first electrode is released. By generating an electrostatic force between the first electrode and the second electrode, the diaphragm is deformed in a direction opposite to the standby state, and the deformable portion is deformed into the ink chamber;
An operation can be performed such that pressure is applied to the ink in the ink chamber to eject the ink. Alternatively, claim 5
The magnitude of the electrostatic force between the first electrode and the third electrode is represented by F13, and the magnitude of the electrostatic force between the first electrode and the second electrode is represented by F12. When
The potentials of the second and third electrodes are kept constant and the potential of the first electrode is controlled so that F13> F12 ≧ 0 in the standby state and 0 ≦ F13 <F12 in the ejection state. The diaphragm and the deformable movable portion can be operated to deform the ink and the ink into the ink chamber and discharge the ink.

When such control is performed, for example, the first electrode is an individual electrode for each nozzle, and the second electrode and the third electrode are a plurality of nozzles. It is possible to perform the discharge operation by controlling the potential of the first electrode as a common electrode for the discharge control, and control the discharge by controlling only the potential of one electrode. Therefore, an inexpensive and small-sized ink jet recording apparatus can be manufactured without requiring a complicated circuit.

Further, according to the third aspect of the present invention,
By making the area of the first electrode larger than the area of the second electrode, a gradient is generated such that the intensity of the electric field formed by the electrode pair becomes larger near the nozzle. Therefore,
An ink flow toward the nozzle is generated and plays a part in the ink ejection force. Thereby, a more compact and highly efficient ink jet recording apparatus can be configured.

As described above, according to the present invention, there is an effect that it is possible to provide a high-efficiency on-demand type ink jet recording apparatus with a simple configuration at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one element showing an embodiment of an ink jet recording apparatus of the present invention.

FIG. 2 is an explanatory diagram of an example of a relationship between a diaphragm electrode and a nozzle electrode.

FIG. 3 is an explanatory diagram showing one mode at the time of ink ejection in an embodiment of the inkjet recording apparatus of the present invention.

FIG. 4 is an explanatory view (continued) illustrating one mode of ink ejection in the embodiment of the inkjet recording apparatus of the present invention.

FIG. 5 is an explanatory diagram showing one mode at the time of ink ejection in one embodiment of the ink jet recording apparatus of the present invention.

FIG. 6 is a timing chart for explaining another example of the operation at the time of driving in the embodiment of the ink jet recording apparatus of the present invention.

DESCRIPTION OF SYMBOLS 1 ... substrate, 2 ... substrate electrode, 3 ... pressure generating member, 4 ... diaphragm, 5 ... diaphragm electrode, 6 ... ink chamber forming member, 7 ... nozzle forming member, 8 ... nozzle, 9 ... ink chamber ,
10 ... nozzle electrode, 11 ... control unit.

Claims (5)

[Claims] 1. An ink jet recording apparatus which discharges ink in an ink chamber from a nozzle on demand in accordance with image information, wherein said diaphragm is an elastically deformable diaphragm forming a part of an inner wall of said ink chamber, and said diaphragm is formed on said diaphragm. A first electrode, a part of the inner wall of the ink chamber facing the diaphragm, a deformable movable part in which the nozzle is formed and is elastically deformable, and a second electrode provided on the deformable movable part And a third electrode formed opposite to the first electrode and opposite to the second electrode; and a potential of the first electrode, the second electrode, and the third electrode. An ink jet recording apparatus comprising a control unit for controlling. 2. The control device according to claim 1, wherein the control unit is configured to control the third control in a standby state.
The diaphragm is deformed by an electrostatic force generated between the first electrode and the first electrode. At the time of ink ejection, the electrostatic force between the third electrode and the first electrode is released, and the first electrode and the third electrode are released. Generating an electrostatic force between the second electrodes, deforming the diaphragm in a direction opposite to a standby state and deforming the deformable portion into the ink chamber,
2. The ink jet recording apparatus according to claim 1, wherein a pressure is applied to the ink in the ink chamber to discharge the ink. 3. The area of the first electrode is defined as S1, and the area of the second electrode is defined as S1.
2. The ink jet recording apparatus according to claim 1, wherein S1> S2, where S2 is the area of the electrode. 4. The method according to claim 1, wherein the first electrode is an individual electrode for each nozzle, and the second electrode and the third electrode are common electrodes for a plurality of nozzles.
3. The ink jet recording apparatus according to claim 1. 5. The control means sets a magnitude of an electrostatic force between the first electrode and the third electrode to F13 and a magnitude of an electrostatic force between the first electrode and the second electrode. When F12 is satisfied, the potentials of the second electrode and the third electrode are kept constant so that F13> F12 ≧ 0 in the standby state and 0 ≦ F13 <F12 in the discharge state, The ink jet recording apparatus according to claim 1, wherein the ink is ejected by controlling the potential of the electrode.