JP2000015801A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and largely displace a vibration plate of an ink-jet head and to control it variously. SOLUTION: An ink-jet head comprises a liquid room 5 having a nozzle filled with an ink, a vibration plate 3 formed in a part of the liquid room, a first electrode 1 provided in the vibration plate, and a second electrode 2 provided facing to the first electrode with a minute distance. At least one of the first electrode or the second electrode comprises split electrodes 2a, 2b, and 2c divided in a plurality so that the ink can be ejected from the nozzle according to deformation of the vibration plate by electrostatic force by generating potential difference between the first and second electrodes 1 and 2 according to drive of the electrodes each comprising the split electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator for ink jet recording using electrostatic force, for example, an electrostatic actuator usable for a recording head of a copying machine, a facsimile, a printer, a plotter, a micropump, and the like. It is about.

[0002]

2. Description of the Related Art For example, JP-A-5-50601 discloses an ink jet recording method in which a vibration plate is deformed by electrostatic force in a minute gap between the vibration plate and a substrate on which electrodes are formed, and ink droplets are ejected from nozzle holes. An apparatus and a method for manufacturing an ink jet head are disclosed. Also, there is an application (Japanese Patent Application No. 9-364173) entitled "Recording Apparatus" filed by the same applicant.

[0003]

In the on-demand type ink jet recording technology, a piezoelectric body is arranged on a part of a wall of a liquid chamber filled with ink, and the volume of the liquid chamber is increased by applying a voltage to the piezoelectric body. By changing the pressure to increase the pressure and ejecting ink (piezo-on-demand type IJ method), or by providing a heating element that generates heat by energization in the liquid chamber, the pressure in the liquid chamber is increased by bubbles generated by the heating element. A method of discharging ink (bubble jet IJ method) is widely known. In addition, as a method that solves the problems of these methods and achieves further compactness, high density, high-speed printing, high quality printing, long life, and high reliability, ink discharge is generated by changing the volume of the liquid chamber by electrostatic force. (Electrostatic type IJ system) has been newly proposed.

For example, in Japanese Patent Application Laid-Open No. Hei 5-50601, a recess for forming a nozzle, a discharge chamber, an ink flow path and a vibration plate is integrally formed on a middle substrate made of silicon by etching, and an ink supply port is provided. A method has been proposed in which a head is formed by joining a substrate and a substrate provided with electrodes corresponding to recesses of a middle substrate, and ink is ejected by applying a voltage between the diaphragm and the electrodes. In this electrostatic force type IJ, vibration is obtained by an electrostatic force acting on the diaphragm and a restoring force generated by deformation of the diaphragm. The electrostatic force increases in inverse proportion to the square of the gap when the diaphragm is displaced and the gap becomes small, but the restoring force of the diaphragm increases in proportion to the first power of the displacement of the diaphragm. When the diaphragm is greatly displaced by increasing the inter-voltage, (restoring force) <(electrostatic force), and the diaphragm collides with the counter electrode. That is, a large displacement can be generated with a small voltage in a small gap region where (restoring force) <(electrostatic force). Utilizing this fact, the same inventor has already made an invention for realizing an ink jet head capable of efficiently discharging ink at a low voltage.
The present invention realizes efficient IJ driving by devising a voltage waveform applied to an electrode.

According to the present invention, at least one of the opposing electrodes is divided into a plurality of electrodes so that the electrodes can be driven independently to obtain the same effect. In addition, by applying a voltage to each of the divided electrodes by an appropriate method, multi-value recording can be performed, and the reliability can be improved. Problems to be solved by the invention according to the individual claims (objectives)
Are listed.

An object (object) of the first aspect of the present invention is to enable various control of the diaphragm of the IJ and to improve the reliability.

An object (object) to be solved by the invention of claim 2 is to reduce the driving frequency of each electrode and simplify the driving circuit.

An object (object) to be solved by the invention of claim 3 is to enable multi-value recording without changing the voltage value of the drive signal.

A problem (object) to be solved by the invention of claim 4 is to facilitate voltage application to the electrodes.

The object of the present invention is to increase the density of an ink jet head by effectively utilizing a large displacement in a minute gap region where (restoring force) <(electrostatic force). High integration.

An object (object) to be solved by the invention of claim 6 is to improve controllability of the displacement of the diaphragm.

An object (object) to be solved by the invention of claim 7 is to improve controllability of displacement of the diaphragm.

The object (object) to be solved by the invention of claim 8 is to improve the controllability of the displacement of the diaphragm,
The purpose is to simplify the driving circuit.

An object (object) to be solved by the invention of claim 9 is to improve controllability of displacement of the diaphragm.

An object (object) to be solved by the invention of claim 10 is to stabilize the behavior of the diaphragm.

An object (object) to be solved by the invention of claim 11 is to simplify a drive circuit of an ink jet head.

An object (object) of the present invention is to provide a recording apparatus having the ink jet head according to any one of the first to eleventh aspects.

[0018]

According to a first aspect of the present invention, there is provided a liquid chamber having a nozzle filled with ink, a diaphragm formed in a part of the liquid chamber, and a diaphragm provided on the diaphragm. An electrode, and a second electrode provided to face the first electrode at a small distance from the first electrode, to generate a potential difference between the first and second electrodes, and to generate the vibration by electrostatic force. In an ink jet head that discharges ink from the nozzles by deforming a plate, at least one of the first electrode and the second electrode is a divided electrode that is divided into a plurality of pieces with respect to one diaphragm. An inkjet head characterized by the following.

According to a second aspect of the present invention, there is provided the ink jet head according to the first aspect, wherein the respective electrodes constituting the divided electrodes are driven in different phases.

According to a third aspect of the present invention, there is provided the ink jet head according to the first aspect, wherein the respective electrodes constituting the divided electrodes are driven in the same phase.

According to a fourth aspect of the present invention, there is provided an ink jet head according to the third aspect, wherein the electrodes driven in the same phase are short-circuited at portions other than immediately below the diaphragm. is there.

According to a fifth aspect of the present invention, in the ink jet head according to the first aspect, an ejection voltage signal synchronized with ink ejection and a control voltage signal higher in frequency than the ejection voltage signal are input to the separate divided electrodes. An ink jet head is characterized in that:

According to a sixth aspect of the present invention, in the inkjet head according to the fifth aspect, the vibration displacement of the diaphragm is controlled by the frequency of the control voltage signal.

According to a seventh aspect of the present invention, in the ink jet head according to the fifth aspect, the vibration displacement of the diaphragm is controlled by the amplitude of at least one of the ejection voltage signal and the control voltage signal. This is an inkjet head that performs the following.

An eighth aspect of the present invention is the ink jet head according to the fifth aspect, wherein the control voltage signal has a pulse waveform.

A ninth aspect of the present invention is the ink jet head according to the eighth aspect, wherein the pulse of the control voltage signal controls the vibration displacement of the diaphragm by the duty ratio.

According to a tenth aspect of the present invention, there is provided an ink jet head according to the fifth aspect, wherein the rising phases of the discharge voltage signal and the control voltage signal do not coincide with each other.

An eleventh aspect of the present invention is the ink jet head according to the fifth aspect, wherein the ink jet head is driven by switching only the ejection voltage signal.

According to a twelfth aspect of the present invention, there is provided a recording apparatus including the ink jet head according to any one of the first to eleventh aspects.

[0030]

FIG. 1 shows a basic configuration of an electrostatic type IJ. A part of the wall surface constituting the liquid chamber 5 also serves as the diaphragm 3, and the deformation of the diaphragm 3 causes a change in the volume of the liquid chamber,
The ink filled in the liquid chamber is discharged from the nozzle 6. The deformation of the diaphragm 3 is caused by an electrostatic force acting between a first electrode 1 provided on the back surface of the diaphragm 3 and a second electrode 2 provided separately from the first electrode 1. In this case, the first
As the gap between the electrode 1 and the second electrode 2 is reduced and the thickness of the diaphragm 3 is reduced, the diaphragm 3 can be displaced at a lower voltage. When assuming a small, high-resolution IJ printer head, the size of the diaphragm 3 needs to be reduced, but the thickness of the diaphragm 3 is made too thin in order to greatly deflect the small-sized diaphragm. As a result, the rigidity of the vibration plate 3 decreases, and ink cannot be ejected. Therefore, to realize a compact, high-resolution, low-voltage driven IJ head, how to reduce the gap between the electrodes is a major issue. Actually, in order to drive at a voltage of about 100 [V] or less, a minute gap of 2 to 3 [μm] or less must be formed. When a voltage is applied between the electrodes in such a gap, an electrostatic force acts on the diaphragm 3 and the diaphragm 3 bends. When the gap between the electrodes is large to some extent, since a restoring force having a magnitude almost proportional to the amount of deflection is generated in the diaphragm 3, the electrostatic force and the restoring force balance and the displacement of the diaphragm 3 is maintained. However, when the diaphragm 3 is displaced by further applying a voltage, the electrostatic force becomes larger than the restoring force, and a large displacement occurs such that two electrodes collide. This is because the restoring force is almost proportional to the displacement of the diaphragm, while the electrostatic force is proportional to the square of the gap change due to the displacement of the diaphragm. If this large displacement in the critical region where (restoring force) <(electrostatic force) is effectively used, a sufficient amount of ink can be ejected even if the volume of the liquid chamber is small. Therefore, a high-density, high-integration inkjet head can be realized. However, if the electrostatic force that reaches the critical region is applied for a longer time than necessary, the electrodes constituting the gap collide with each other, and depending on the configuration of the electrodes, problems such as peeling of the protective film 7 and short-circuiting may occur.

FIG. 2 shows the basic configuration of the IJ of the present invention. In FIG. 2, the second electrode 2 is divided into three parts, and although not shown, each has a configuration in which a voltage can be independently applied. Here, an ejection voltage signal whose pulse falls at the timing of ink ejection as shown in FIG. 3 is applied to the center electrode 2b. This ejection voltage signal is set to a voltage slightly smaller than a voltage at which the displacement of the diaphragm 3 reaches a critical region (critical voltage). Therefore, a large displacement does not occur in the diaphragm 3 by driving only the electrode 2b. However, since the ejection voltage signal is close to the critical voltage, when a voltage of a certain magnitude is applied to the electrodes 2a and 2c, the electrostatic force acting on the diaphragm 3 reaches a critical state in which the restoring force of the diaphragm 3 is exceeded. .

When the control voltage signal applied to the electrodes 2a and 2c is a DC voltage, the critical state time is too long and the diaphragm 3 collides with the electrode.
ON-OF by changing the critical state to a high frequency oscillation voltage
F is controlled. By doing so, diaphragm 3 can be vibrated greatly. The maximum vibration displacement of the diaphragm 3 when the ejection voltage signal and the control voltage signal are separately applied to the divided electrodes can be controlled by the amplitude of each voltage signal. Considering both the stabilization of the behavior of the diaphragm 3 and the simplification of the driving circuit, the voltage of the high-frequency control voltage signal is reduced as much as possible, and the vibration displacement of the diaphragm 3 is controlled by the amplitude of the control voltage signal. Is more preferred. When the amplitude of the control voltage signal is sufficiently small, since the influence of the control voltage signal when the ejection voltage signal is OFF on the diaphragm 3 is small, the ejection drive is performed only by switching the ejection voltage signal without switching the control voltage signal. Can be. In the case of this configuration, the behavior of the diaphragm 3 can also be controlled by changing the frequency of the control voltage signal. However, if the frequency of the control voltage signal is too low, ripples occur in the vibration displacement in accordance with the frequency of the control voltage signal. Further, when the control voltage signal has a pulse waveform, the vibration displacement of the diaphragm 3 can be controlled by the pulse duty ratio, and the controllability is improved. Also, when the control voltage signal has a waveform that rises steeply like a pulse wave, if the rising of the discharge voltage signal and the rising of the control voltage signal are in phase, there is a relationship between the transient response of the diaphragm at the time of voltage rising. In addition, the behavior of the diaphragm 3 tends to be unstable. Therefore, it is desirable to apply the control voltage signal with a delay so that the control voltage signal rises after the residual vibration of the diaphragm 3 caused by the rise of the discharge voltage signal is attenuated. As described above, a large displacement can be efficiently and stably generated by such a divided electrode configuration and a driving method, so that a higher density and higher integration of an ink jet head can be achieved.

When two electrodes are driven with the same voltage waveform as shown in FIG. 2, both electrodes can be short-circuited. FIG. 5 shows the electrode portions 2a, 2b, 2c in FIG.
FIG. When the three electrodes are independently driven, the electrode configuration is as shown in FIG.
When the same voltage waveform is applied to 2a and 2c, FIG.
When both electrodes are short-circuited as shown in FIG. 2B, the area and pitch of the voltage supply unit 11 can be increased, which simplifies wiring and mounting. In this case, if two electrodes are short-circuited in a region immediately below the diaphragm 3, the electric field in the gap in the same region becomes non-uniform, which may adversely affect the vibration characteristics. Therefore, as shown in FIG. 5B, it is desirable that the short-circuited portion avoid the area immediately below the diaphragm.

FIG. 6 shows another structure of the IJ of the present invention. FIG. 6 (A) is a longitudinal sectional view, and FIG.
It is XX sectional drawing of (A). The second electrode 2 is shown in FIG.
It is divided into five electrodes as shown in FIG. When the electrode is divided into a large number in this manner, the displacement of the diaphragm 3 varies depending on the number of electrodes to be driven. Therefore, by changing the number of electrodes to be driven and changing the number of electrodes to be driven by using synchronized voltage waveforms of the same shape, the dot diameter can be controlled and the dot diameter can be controlled, so that multi-value recording can be realized.

In the case of dividing into many pieces,
As shown in FIG. 7, it is also possible to change the electrodes to be driven sequentially each time ink is ejected. By doing so, the drive frequency of each electrode can be reduced, and the drive circuit can be simplified. Further, when there are a plurality of electrodes for driving one diaphragm as in the example described above, even if some of the electrodes are damaged for some reason, it is possible to continue driving with another electrode. So,
The reliability as a printer is improved. In the above description, only the configuration in which the second electrode is divided is shown, but the same applies to the configuration in which the first electrode is divided.

Hereinafter, more specific embodiments of the present invention will be described.

(Embodiment 1) FIG. 8 shows a first embodiment of the ink jet head according to the present invention. FIG. 8 (A) is a longitudinal sectional view, and FIG. 8 (B) is a transverse sectional view. A first embodiment of the inkjet head according to the present invention will be described with reference to FIG. As the substrate 4, Pyrex glass having a thickness of 1 [mm] was used, and the substrate 4 was etched using a resist pattern in which only a portion where a gap was formed was opened to form a groove-shaped step on the substrate. Next, as shown in FIG. 5 (A), three lines were provided for one groove in the groove as a Ni thin film as a second electrode by a sputtering method. The line width of each electrode is 100 [μm] only for the central electrode 2b and 40 for the other electrodes 2a and 2c.
[Μm]. The thickness of the electrode was about 0.1 [μm], and the distance between the electrodes was 20 [μm]. Second
An SiO ₂ layer as a protective film 7 having a thickness of 0.1 μm was formed on the electrode 2 by a sputtering method. The groove width of the glass was about 240 [μm] and the depth was about 1.1 [μm]. The vibration plate was formed by etching Si (100) using an aqueous KOH solution so that the plate thickness was about 7 [μm]. Next, the position of the electrode on the substrate 4 and the position of the diaphragm 3 were accurately positioned, and the two were joined by anodic bonding to form a gap of about 0.9 [μm]. As the first electrode 1, a metal layer may be coated on the back surface of the diaphragm,
In this embodiment, since the diaphragm 3 is made of semiconductor Si, the diaphragm 3 also serves as the first electrode 1.

With such a configuration, the electrodes 2a and 2c are grounded, and the frequency of 10 [k] is applied to the second electrode 2b as an ejection voltage signal.
[Hz] while applying a rectangular wave voltage. As a result, the vibration displacement increased in proportion to the square of the applied voltage as theoretically. After a displacement of about 0.1 [μm] was observed when the applied voltage was 100 [V], the diaphragm 3 was greatly dented when the voltage of 2 [V] was increased. Thereafter, when the electrode 2b was observed, it was confirmed that the diaphragm 3 was deflected by the initial gap of 0.9 [μm] or more and contacted with the second electrode 2 because the electrode was peeled off at the center.

Next, a DC voltage of 10 [V] was applied to the electrodes 2a and 2c while a rectangular wave voltage having a frequency of 10 [kHz] and an amplitude of 100 [V] was applied to the electrode 2b. as a result,
Again, the diaphragm 3 was greatly dented and came into contact with the second electrode 2.

Next, under the same conditions, the voltage applied to the electrode 2b is applied to the electrodes 2a and 2c at the frequency 10 as the control voltage signal.
When a sine wave voltage of 0 [kHz] and a voltage of 10 [V] was applied, the diaphragm 3 stably vibrated with a displacement of about 0.3 [μm]. By changing the amplitude of the voltage applied to the electrode 2b and the electrodes 2a and 2c, about 0.1 to 0.45 [μm]
The diaphragm 3 could be vibrated in the range of Diaphragm 3
Can be controlled by the ejection voltage signal applied to the electrode 2b, but the control by the control voltage signal having a small amplitude can be more easily performed.

(Embodiment 2) FIG. 9 shows a second embodiment of the present invention.
It will be described based on. Here, FIG. 9A is a longitudinal sectional view,
FIG. 9B is a cross-sectional view. The thickness of the substrate 4 is 1
Using Pyrex glass of [mm], the substrate 4 was etched using a resist pattern having an opening only at a portion where a gap was to be formed, thereby forming a groove-shaped step on the substrate. Next, three lines of Ni thin films were provided as second electrodes in the grooves by sputtering. The line width of each electrode was 20 [μm] only for the center electrode 2b, and 80 [μm] for the other electrodes 2a and 2c. The thickness of the electrode was about 0.1 [μm], and the distance between the electrodes was 20 [μm]. FIG. 5 (B)
As described above, the electrode 2a and the electrode 2c were short-circuited on the side opposite to the voltage supply unit 11. On the second electrode 2, a thickness of 0.1
An SiO ₂ layer was formed by a sputtering method as a [μm] protective film 7. The groove width of the glass was about 240 [μm] and the depth was about 1.1 [μm]. The diaphragm is made of Si (110)
It was formed by etching using an OH aqueous solution so that the plate thickness was about 5 [μm]. Next, the position of the electrode on the substrate 4 and the position of the diaphragm 3 were accurately positioned, and the two were joined by anodic bonding to form a gap of about 0.9 [μm]. As the first electrode 1, a metal layer may be coated on the back surface of the diaphragm. However, in this embodiment, the diaphragm 3 is also used as the first electrode 1 because the diaphragm 3 is made of semiconductor Si.

With such a configuration, the electrode 2b is grounded, and the electrodes 2a and 2c are supplied with a frequency of 10 [kHz] as a discharge voltage signal.
z], the vibration displacement was measured while applying a rectangular wave voltage. As a result, when the applied voltage is 70 [V], about 0.1
After the displacement of [μm] was observed, when the voltage was increased by about 3 [V], the diaphragm 3 was greatly dented, and the diaphragm 3 was fixed to the second electrode 2.

Next, a voltage under the same condition is applied to the electrodes 2a and 2c, and a frequency of 10 [kHz] is applied to the electrode 2b as a control voltage signal.
z], an amplitude of 5 [V], and a pulse-like voltage having a duty ratio of 20% were applied to measure the vibration displacement. as a result,
The diaphragm 3 vibrated stably at a displacement of about 0.2 [μm]. When the duty ratio of the pulse voltage applied to the electrode 2b was changed from 5% to 95% and the change in vibration displacement was examined, when the duty ratio was 60% or less, about 0.1 to 0.1%.
A stable displacement was obtained between 5 [μm], and when the duty ratio was 65% or more, a phenomenon that the diaphragm was greatly dented appeared. Then, the same evaluation was performed with the pulse voltage set to 4 [V]. As a result, a stable vibration displacement was obtained at a duty ratio of 80% or less. In this embodiment, since a pulse waveform is used for the control voltage signal, the signal generation circuit can be simplified as compared with the sine waveform as in the first embodiment. In addition, because of the pulse voltage, the vibration displacement could be controlled stably even at the duty ratio.
In this embodiment, since the electrodes 2a and 2c are short-circuited as shown in FIG. 5B, the number of signal lines is reduced and the voltage is reduced as compared with the electrode configuration shown in FIG. The electrode width of the supply section 11 and the pitch between the electrodes were large, and power supply was easy. Further, in the present embodiment, the electrodes were short-circuited so as not to be directly below the diaphragm 3, but when the electrodes were short-circuited immediately below the electrodes, the controllability of the diaphragm was slightly deteriorated. This is presumably because the short-circuited portion was disposed immediately below the diaphragm, and the electric field in that portion and other portions became non-uniform. Therefore, it is preferable that the electrodes be short-circuited so as not to be directly under the diaphragm as long as space is allowed.

(Embodiment 3) An actuator having the same configuration as that of Embodiment 2 with the electrode 2b grounded and the electrodes 2a and 2c having a frequency of 10 kHz as a discharge voltage signal and an amplitude of 70 V
When the rectangular waveform voltage was applied, the displacement waveform of the diaphragm 3 was as shown in FIG. Next, an amplitude of 5 [V] as a control voltage signal and a duty ratio of 25% are applied to the electrode 2b.
The pulsed voltage was applied to measure the vibration displacement. As a result, the vibration displacement was about 2.5 times larger than when the electrode 2b was grounded. Then, the influence of the frequency of the control voltage signal applied to the electrode 2b was examined next. When the frequency is small, ripples are conspicuous in the displacement waveform when the maximum deflection occurs (see arrow A in FIG. 11), and the behavior of the diaphragm tends to be unstable. When the frequency was increased, the vibration waveform itself became smooth, but when the frequency was increased too much, the vibration displacement tended to decrease. For this reason, the frequency is actually 50 to 4
A range of 00 [kHz] is desirable.

(Embodiment 4) An actuator having the same configuration as that of Embodiment 1 and having a frequency of 10 as an ejection voltage signal is applied to the electrode 2b.
[KHz] and a rectangular wave voltage having an amplitude of 100 [V] are applied to the electrodes 2a and 2c.
When a pulse voltage of 0 [kHz], a voltage of 5 [V] and a duty ratio of 30% was applied, the diaphragm 3 was moved to about 0.2 [μ].
m]. Next, a nozzle plate or the like was joined to the actuator to form an ink jet head as shown in FIG. The discharge performance of the ink is different between the case where the discharge control is performed only by switching the discharge voltage signal as shown in FIG. 13 and the case where the discharge control is performed by switching both the discharge voltage signal and the control voltage signal as shown in FIG. I checked for any differences. As a result, in each case, good ink ejection performance was exhibited, and there was no difference between the two.
It was confirmed that the switching of the OFF state was sufficient only with the ejection voltage signal. However, when a similar experiment was performed under the condition that the amplitude ratio between the ejection voltage signal and the control voltage signal was small, the ejection of the ink became unstable. Whether it is okay to switch only the ejection voltage signal depends on the amplitude ratio of the voltage, the area ratio of the electrodes, the positions of the electrodes, and the like, but if the switching is only the ejection voltage signal as in the present embodiment, The drive circuit of the inkjet head can be greatly simplified.

Embodiment 5 An actuator having the same configuration as that of Embodiment 2 applies a rectangular wave voltage having a frequency of 10 [kHz] and an amplitude of 70 [V] as an ejection voltage signal to the electrodes 2a and 2c. Frequency 100 as a control voltage signal
[KHz], an amplitude of 10 [V], and a pulse-like voltage with a duty ratio of 20% were applied to measure the vibration displacement.
A vibration displacement of about 0.3 [μm] was obtained. Paying attention to the phase difference between the two voltage signals, first, as shown in FIG. 15, driving was performed so that both pulses rise in the same phase. As a result, as shown in FIG. 11, the vibration displacement waveform has a large amount of overshoot of the displacement of the diaphragm, resulting in a long residual vibration. Next, as shown in FIG. 14, a phase difference was provided between the rise of the ejection voltage signal pulse and the rise of the control voltage signal pulse, and the vibration waveform was measured. As shown in FIG. 16, the response of the displacement of the diaphragm was slightly delayed. (2) Since the electrostatic forces generated by the two voltages do not act simultaneously, a smooth vibration displacement with little overshoot was obtained.
When the liquid chamber was joined to the upper part of the actuator and the ink ejection was evaluated, the meniscus of the ink immediately before ejection was more stable and the ejection was more stable when the phase difference was provided between the rise of the ejection voltage signal and the control voltage signal. It was confirmed that the performance was stable.

(Embodiment 6) FIG. 1 shows a sixth embodiment of the present invention.
7 will be described. Here, FIG. 17A is a longitudinal sectional view, and FIG. 17B is a transverse sectional view. As the substrate 4,
Using Pyrex glass having a thickness of 1 [mm], the substrate 4 is etched using a resist pattern having an opening only at a portion where a gap is to be formed.
A groove-shaped step of 1 [μm] was provided. Next, five lines of Ni thin film were provided as second electrodes in this groove by sputtering.
The line width of each electrode is 40 [μm] and the distance between the electrodes is 15
[Μm]. On the second electrode 2, a thickness of 0.1 [μ]
The SiO ₂ layer as a protective film 7 of m] was formed into a film by sputtering. The diaphragm is formed by etching Si (110) using an aqueous KOH solution, and has a thickness of about 5 μm.
m]. Next, the position of the groove on the substrate 4 and the position of the diaphragm 3 were accurately positioned, and the two were joined by anodic bonding to form a gap of about 0.9 [μm]. As the first electrode 1, a metal layer may be coated on the back surface of the diaphragm. However, also in the present embodiment, since the diaphragm 3 is made of semiconductor Si, the diaphragm 3 also serves as the first electrode 1.

With such a configuration, first, a rectangular wave voltage signal having a voltage of about 100 [V] and a frequency of 10 [kHz] was applied only to the electrode 2c, and the vibration displacement was measured. As a result, a displacement of about 0.1 [μm] was observed. Next, when the same voltage signal as that of the electrode 2c was applied to the electrode 2b and the electrode 2d while the voltage to the electrode 2c was unchanged, the vibration displacement was about 0.1.
It increased to 5 [μm]. Further, the same voltage signal was applied to the electrodes 2a and 2e, and all five electrodes were simultaneously driven. As a result, a displacement of about 0.18 [μm] was obtained.
In this embodiment, since five electrodes are provided for one diaphragm, the displacement can be changed depending on the number of electrodes to be driven. A nozzle plate and the like are stacked on the electrostatic actuator, and a liquid chamber is filled with ink to form an ink jet head as shown in FIG. 18. When the number of electrodes to be driven is changed as described above, the The volume could be changed, and the dot diameter on the recording paper could be changed.

(Embodiment 7) FIG. 1 shows a seventh embodiment of the present invention.
8 will be described. Here, FIG. 18A is a vertical cross-sectional view, and FIG. 18B is a XX cross-sectional view of FIG. 18A. As the substrate 4, Pyrex glass having a thickness of 1 [mm] was used, and the substrate 4 was etched using a resist pattern in which only a portion where a gap was formed was opened.
A groove-shaped step having a depth of 0 [μm] and a depth of 1.1 [μm] was provided. Next, five lines of Ni thin film were provided as second electrodes in this groove by sputtering. The line width of each electrode is 45 [μm] for the electrode 2a and the electrode 2e, and 35 [μm] for the electrode 2b and the electrode 2d.
m], the electrode 2c was set to 60 [μm], and the interval between the electrodes was set to 10 [μm]. On the second electrode 2, a SiO ₂ layer as a protective film 7 having a thickness of 0.1 [μm] was formed by a sputtering method. The diaphragm was formed by etching Si (110) using an aqueous KOH solution so that the plate thickness was about 5 μm. Next, the position of the groove on the substrate 4 and the position of the diaphragm 3 were accurately positioned, and the two were joined by anodic bonding to form a gap of about 0.9 [μm]. As the first electrode 1, a metal layer may be coated on the back surface of the diaphragm. However, also in the present embodiment, since the diaphragm 3 is made of semiconductor Si, the diaphragm 3 also serves as the first electrode 1.
Further, a liquid chamber was provided by laminating and joining nozzle plates and the like.
With such a configuration, as shown in FIG. 19, a voltage was applied to each electrode according to the timing of ink ejection. In this embodiment, the electrodes 2a and 2d, and the electrodes 2b and 2e are each used as one set and are driven simultaneously. Then, ink was ejected by a method of exchanging the group of electrodes that are sequentially driven for each ink ejection. As a result, a good image was printed according to the image data. In the present embodiment, since the method of sequentially driving the assembled electrodes is employed, the frequency for driving each electrode can be reduced, and the circuit is simplified. In addition, even when one of the grouped electrodes fails, driving can be continued with the other grouped electrodes, and the reliability of the recording system is improved.

[0050]

According to the ink jet head of the present invention, since one diaphragm is driven by using the divided electrodes composed of a plurality of electrodes, a large displacement can be generated stably. Therefore, the density of the ink jet head can be increased and the density of the ink jet head can be increased, the diaphragm can be variously controlled, and a highly reliable ink jet head can be realized. Further, even if some of the electrodes are damaged, the drive can be continued by another electrode, so that the reliability of the printer is improved.

According to the second aspect of the present invention, since the electrodes constituting the divided electrodes are driven in different phases, the driving frequency of each electrode can be reduced. The driving circuit can be simplified.

According to the third aspect of the present invention, since the respective electrodes constituting the divided electrodes are driven in the same phase, the displacement generated on the diaphragm according to the number of driven electrodes. Can be varied, the amount of ink to be ejected can be changed, and the dot diameter can be controlled, so that multi-value recording can be performed.

According to the fourth aspect of the present invention, the electrodes to be driven synchronously are short-circuited at portions other than immediately below the diaphragm, so that the electric field in the gap does not become uneven and the voltage supply area pitch is increased. Wiring,
Mounting becomes simpler, and voltage application to the electrodes can be facilitated.

According to the fifth aspect of the present invention, the ejection voltage signal synchronized with the ejection of the ink and the control voltage signal higher in frequency than the ejection voltage signal are input to the separate divided electrodes.
The large displacement in the minute gap region where (restoring force) <(electrostatic force) can be effectively used, and the ink jet head can be made dense and highly integrated.

According to the sixth aspect, since the vibration displacement of the diaphragm is controlled by the frequency of the control voltage signal, the controllability of the displacement amount of the diaphragm can be improved.

According to the seventh aspect of the present invention, since the vibration displacement of the diaphragm is controlled by the amplitude of at least one of the discharge voltage signal and the control voltage signal, the controllability of the displacement amount of the diaphragm can be improved. .

According to the eighth aspect, since the control voltage signal has a pulse waveform, the controllability of the amount of displacement of the diaphragm can be improved and the drive circuit can be simplified.

The vibration displacement of the diaphragm is controlled by the duty ratio of the pulse.
The controllability of the displacement amount of the diaphragm can be improved.

According to the tenth aspect, since the rising phases of the ejection voltage signal and the control voltage signal do not match, the behavior of the diaphragm can be stabilized.

According to the eleventh aspect, since the driving is performed by switching only the ejection voltage signal, the driving circuit of the ink jet head can be simplified.

According to a twelfth aspect of the present invention, by configuring a recording apparatus including the inkjet head according to any one of the first to eleventh aspects, the effect of the inkjet head can be realized in the recording apparatus. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an electrostatic IJ to which the present invention is applied.

FIG. 2 is a diagram illustrating another basic configuration of the electrostatic IJ of the present invention.

FIG. 3 is a diagram illustrating an ejection voltage signal applied at the timing of ink ejection.

FIG. 4 is a diagram illustrating a control voltage signal of the ink ejection head.

FIG. 5 is a diagram showing an electrode portion viewed from the direction of arrow Y in FIG. 2;

FIG. 6 is a diagram showing another embodiment of the IJ of the present invention.

FIG. 7 is a diagram for explaining a relationship between ink ejection timing and a drive waveform of a drive electrode.

FIG. 8 is a view showing a first embodiment of the ink jet head of the present invention.

FIG. 9 is a view showing a second embodiment of the ink jet head of the present invention.

FIG. 10 is a diagram showing a displacement waveform of a diaphragm in a third embodiment of the present invention.

FIG. 11 is a diagram showing another displacement waveform of the diaphragm in the third embodiment of the present invention.

FIG. 12 is a view showing a fourth embodiment of the ink jet head of the present invention.

FIG. 13 is a diagram showing ejection timings and driving waveforms in a fourth embodiment of the ink jet head of the present invention.

FIG. 14 is a diagram showing other ejection timings and drive waveforms in a fourth embodiment of the inkjet head of the present invention.

FIG. 15 is a diagram showing a fifth embodiment of the ink jet head of the present invention.

FIG. 16 is a diagram showing a displacement waveform of a diaphragm in a fifth embodiment of the ink jet head of the present invention.

FIG. 17 is a view showing a sixth embodiment of the ink jet head of the present invention.

FIG. 18 is a view showing a seventh embodiment of the ink jet head of the present invention.

FIG. 19 is a diagram showing the relationship between the timing of ink ejection and the drive waveform of each electrode in a seventh embodiment of the ink jet head of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st electrode, 2 (2a, 2b, 2c) ... 2nd electrode, 3
... vibrating plate, 4 ... substrate, 5 ... liquid chamber, 6 ... nozzle, 7 (7
a, 7b, 7c, 7d): protective film, 8: fluid resistance, 9:
Ink droplets, 10: ink supply path, 11: voltage supply unit.

Claims (12)

[Claims] A liquid chamber having a nozzle filled with ink; a vibration plate formed in a part of the liquid chamber; a first electrode provided on the vibration plate; A second electrode provided opposite to each other at a minute interval to generate a potential difference between the first and second electrodes, and deform the diaphragm with electrostatic force to discharge ink from the nozzles In the ink jet head, the first
Wherein at least one of the first electrode and the second electrode is a divided electrode having a structure divided into a plurality of pieces. 2. The ink-jet head according to claim 1, wherein the respective electrodes constituting the divided electrodes are driven in different phases. 3. The ink-jet head according to claim 1, wherein the respective electrodes constituting the divided electrodes are driven in the same phase. 4. The ink-jet head according to claim 3, wherein the electrodes driven in phase are short-circuited at portions other than immediately below the diaphragm. 5. The ink jet head according to claim 1, wherein an ejection voltage signal synchronized with the ejection of the ink and a control voltage signal higher in frequency than the ejection voltage signal are input to the separate divided electrodes. Inkjet head. 6. The ink jet head according to claim 5, wherein a vibration displacement of said diaphragm is controlled by a frequency of said control voltage signal. 7. The ink jet head according to claim 5, wherein a vibration displacement of said diaphragm is controlled by an amplitude of at least one of said ejection voltage signal and said control voltage signal. 8. The ink jet head according to claim 5, wherein the control voltage signal has a pulse waveform. 9. The ink jet head according to claim 8, wherein the pulse of the control voltage signal controls a vibration displacement of the diaphragm by a duty ratio. 10. The ink-jet head according to claim 5, wherein the rising phases of the voltage of the ejection voltage signal and the voltage of the control voltage signal do not match. 11. The ink-jet head according to claim 5, wherein the ink-jet head is driven by switching of only the ejection voltage signal. 12. A recording apparatus comprising the inkjet head according to claim 1.