JP2002046279A - Liquid ejection head and microactuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of cost increase. SOLUTION: First and second glass substrates 1 and 3 are anode bonded through a diaphragm 2 of polysilicon film or amorphous silicon film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a droplet discharge head and a microactuator.

[0002]

2. Description of the Related Art As an ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying machine, a plotter, etc., a nozzle for discharging ink droplets and a liquid chamber (discharge chamber, pressure Room,
It is also called a pressurized liquid chamber, an ink flow path, or the like. ), A diaphragm forming the wall surface of the liquid chamber, and an electrode facing the diaphragm, and the diaphragm is deformed and displaced by electrostatic force to pressurize ink in the liquid chamber and eject ink droplets from the nozzles. Some have an electrostatic inkjet head using an electrostatic microactuator to be mounted.

Here, as the electrostatic type ink jet head, for example, Japanese Patent Application Laid-Open No.
As described in JP-A-293141 or the like, a liquid chamber and a diaphragm forming one wall surface of the liquid chamber are formed by etching on a first substrate (diaphragm substrate) made of a silicon substrate. A second substrate (electrode substrate) having electrodes formed thereon is disposed below the first substrate, and the electrodes are opposed to each other with a predetermined gap between the diaphragms to form an electrostatic microactuator. It is known that a voltage is applied between a vibration plate and an electrode to bend the vibration plate by electrostatic force to change the internal volume of the liquid chamber and eject ink droplets from a nozzle communicating with the liquid chamber.

In the electrostatic ink jet head which deforms the diaphragm by the electrostatic force, the mechanical deformation characteristics of the diaphragm greatly affect the ink ejection characteristics, and therefore, it is necessary to control the thickness of the diaphragm with high accuracy. .

Therefore, as described in Japanese Patent Application Laid-Open Nos. 6-71882 and 53-63880, a silicon substrate is utilized by taking advantage of the low etching rate of a P-type high-concentration impurity layer. It is known that a diaphragm made of a P-type high-concentration impurity layer is formed by forming a P-type high-concentration impurity layer on the substrate and stopping the etching at the P-type high-concentration impurity layer.

In an ink jet head using an electrostatic actuator, the gap accuracy for utilizing electrostatic force is important. For example, to manufacture a high density ink jet head exceeding 150 dpi,
The gap between the diaphragm and the electrode must be 1 μm or less.

Therefore, it is known that a silicon substrate is used as the first substrate on which the diaphragm is provided and the second substrate on which the electrodes are provided, and the silicon substrate is directly joined. In this direct bonding, after the surfaces of the substrates are subjected to a hydrophilic treatment, the two substrates are gently bonded to each other, and the two substrates are bonded at a high temperature of about 500 to 1200 ° C.

Further, as described in JP-A-5-50601 and JP-A-6-71882, the second
Anisotropic etching is performed on a silicon substrate as a substrate to form an electrode groove, and a Pyrex (registered trademark) glass substrate is used as a second substrate and anodically bonded to a silicon substrate as a first substrate. Have been done. This anodic bonding is performed by applying a voltage of several hundred volts between substrates to be bonded in an environment heated to about 300 to 450 ° C.

[0009]

However, in the method of forming a diaphragm made of a high-concentration P-type impurity layer by etching a silicon substrate, the etching rate of the silicon substrate is low and the etching takes time. In addition to the increase in cost, the etching does not completely stop at the high-concentration P-type impurity layer, so that it becomes difficult to form a diaphragm having a more accurate thickness.

In addition, since the direct bonding of the silicon substrate is performed at a high temperature of about 500 to 1200 ° C. as described above, the heating and pressurizing equipment is increased in size and cost is increased, and a nozzle for covering the upper part of the liquid chamber is used. The head may be damaged due to a difference in linear thermal expansion coefficient when, for example, a nozzle substrate formed with the above or a top plate which is a simple lid member is joined. In this respect, the yield is low and the cost is high.

Therefore, it is preferable to use anodic bonding as a bonding method when bonding the first substrate and the second substrate or when bonding a third substrate such as a nozzle plate or a top plate to the first substrate and the second substrate. When a first substrate made of a silicon substrate having a diaphragm formed with an impurity diffusion layer and a second substrate made of a Pyrex glass substrate are bonded by anodic bonding, the silicon substrate having the bonded diffusion layer formed thereon is heated at a high temperature. When a voltage is applied, there is a concern that the junction is destroyed, and the bonding strength is not sufficient, and the reliability is reduced.

The present invention has been made in view of the above points, and has as its object to provide a low-cost and highly reliable droplet discharge head and microactuator.

[0013]

In order to solve the above-mentioned problems, a droplet discharge head according to the present invention has a structure in which a diaphragm is made of a polysilicon film or an amorphous silicon film.

Here, it is preferable that the thickness of the polysilicon film or the amorphous silicon film is in the range of 200 to 50,000 °.

A droplet discharge head according to the present invention has a structure in which a first substrate forming a liquid chamber and a second substrate forming an electrode are anodically bonded via a polysilicon film or an amorphous silicon film. It is.

Here, it is preferable that the first substrate and the second substrate are glass substrates. Further, it is preferable that a third substrate made of a glass substrate is anodically bonded to the first substrate via a polysilicon film or an amorphous silicon film.

The microactuator according to the present invention comprises:
A first substrate forming a cavity, a diaphragm forming a wall surface of the cavity, and a second substrate provided with electrodes opposed to the diaphragm, wherein the diaphragm is formed of a polysilicon film or an amorphous silicon film; The configuration is as follows. Here, it is preferable that the first substrate and the second substrate are anodically bonded via a polysilicon film or an amorphous silicon film.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view of the inkjet head according to the first embodiment of the present invention in the longitudinal direction of the diaphragm, and FIG. 2 is an explanatory cross-sectional view of the same head in the lateral direction of the diaphragm.

This ink jet head has a first glass substrate 1 serving as a flow path substrate and a second glass substrate 3 serving as an electrode substrate provided on the lower surface of the first glass substrate 1 via a vibration plate 2.
Nozzles 4 for discharging a plurality of ink droplets (only one is shown for the sake of convenience); a discharge chamber 6 as an ink flow path in which each nozzle 4 communicates via a nozzle communication passage 5;
And a common liquid chamber 8 and the like that communicate with each other via a fluid resistance part 7 also serving as an ink supply path.

The first glass substrate 1 has a groove for forming the nozzle 4 and the nozzle communication path 5, a recess for forming the liquid chamber 6,
A groove forming the fluid resistance portion 7 and a concave portion forming the common liquid chamber 8 are formed. Channels of the first glass substrate 1, such as the nozzle 4 and the groove serving as the nozzle communication path 5, the liquid chamber 6 and the through holes serving as the common liquid chamber 8, and the groove serving as the fluid resistance part 7 are formed by a sandblasting method. I have.

The vibration plate 2 is joined between the first glass substrate 1 and the second glass substrate 3 to form a wall surface (bottom surface) of the liquid chamber 6. The diaphragm 2 is formed of a polysilicon (P-Si) film or an amorphous silicon film. The thickness of the polysilicon (P-Si) film or the amorphous silicon film to be the diaphragm 2 is 200 to 50,000 (0.2 to
5 μm). The thickness of the polysilicon (P-Si) film or the amorphous silicon film is 2
If the angle is less than 00 °, sufficient strength as the diaphragm 2 cannot be obtained, and the joining strength at the time of anodic bonding becomes insufficient. If the angle exceeds 50000 °, it becomes difficult to obtain the displacement characteristics of the diaphragm 2.

A concave portion 14 for forming a gap and an electrode forming groove is formed in the second glass substrate 3, and an electrode (second electrode) 15 facing the diaphragm 2 is formed on the bottom surface of the concave portion 14. A gap 16 is formed between the vibration plate 2 and the electrode 15, and the vibration plate 2 and the electrode 15 constitute a microactuator. In this microactuator, the liquid chamber 6 is empty.

On the surface of the electrode 15, an insulating film 17 such as a SiO ₂ film is formed. Preferably, the thickness of the insulating film 17 is in the range of 50 to 5000 ° (0.05 to 0.5 μm). If the thickness is less than 0.05 μm, the electrode 15 will not function sufficiently as a protective film, and if it exceeds 0.5 μm, the gap 16 between the diaphragm 2 and the electrode 15 will be too large or will not be effective. The gap (here, the gap between the surfaces of the insulating films 17) is too small.

The electrode 15 may be made of a metal material such as Al, Al alloy, Cr, Ni, Ni-Cr, Pt, Au, Mo, or a high melting point metal such as Ti, TiN, W, or the like. . Then, as shown in FIG. 2, the bottom surface of the concave portion 14 of the second glass substrate 3 is formed as an inclined surface in the short direction of the diaphragm, and the electrode 15 is formed on this bottom surface.
The electrode 15 is arranged in a non-parallel state with respect to the diaphragm 2. The gap 16 formed by the non-parallel diaphragm 2 and the electrode 15 is referred to as a non-parallel gap.

The first glass substrate 1 and the second glass substrate 3 are joined by anodic bonding via a polysilicon film or an amorphous silicon film forming the diaphragm 2. This anodic bonding is performed, for example, in a state where the first glass substrate 1 and the second glass substrate 3 are aligned and overlapped with each other.
The first glass substrate 1 and the second glass substrate 3 are bonded to the polysilicon film or the amorphous silicon film forming the vibration plate 2 by applying a DC voltage to the bonding interface by heating to about 450 ° C.

This bonding is performed, for example, on the first glass substrate 1 / S
In the bonding configuration of the i / second glass substrate 3, Na ₂ SiO ₃ in the glass component is ionized by heating and an electric field, separated into Na ions and SiO ₃ ions, and the Na ions react with Si and oxygen O ₂ , Na ₂ Si between the glass substrate and the Si surface
This is performed by forming O ₃ .

In the ink jet head configured as described above, a driving voltage is applied between the vibration plate 2 and the electrode 15 (one of which is a common electrode and the other is an individual electrode) to generate electrostatic force. When the diaphragm 2 is deformed and displaced, and the internal volume of the ejection chamber 6 changes, ink droplets are ejected from the nozzle 4.

In this ink jet head, the vibration plate 2 is displaced toward the electrode 15 in a state where the vibration plate 2 is not brought into contact with the electrode 15 as a displacement driving method of the vibration plate, and the diaphragm 2 is returned by discharging from this state. Although a non-contact drive system in which ink droplets are ejected by the
The contact drive method in which the ink droplets are ejected by displacing the diaphragm until it comes into contact with the diaphragm 5 and discharging from this state to return the diaphragm 2 can perform more stable ink droplet ejection.

Here, since the electrode 15 is inclined, when a driving voltage is applied, the diaphragm 2 starts to generate displacement from a portion having a short gap length with the electrode 15, and the gap length gradually decreases. Therefore, the diaphragm 2 starts deforming and displacing at an extremely low voltage. That is, the electrostatic actuator operates by balancing the electrostatic force generated between the diaphragm 2 and the electrode 15 and the rigidity of the diaphragm 2, and this electrostatic force is inversely proportional to the square of the distance t between the two electrodes. Therefore, a desired electrostatic force can be obtained at a lower voltage V as the distance t between the electrodes is smaller.

Therefore, since the gap 16 between the diaphragm 2 and the electrode 15 is small on the end side of the diaphragm 2, the displacement of the diaphragm 2 changes by the distance t according to the application of the driving voltage.
Starts from the smaller end. Then, as the displacement of the end of the diaphragm 2 starts, the distance between the diaphragm 2 and the electrode 15 gradually decreases, and a large displacement can be obtained with a small increase in voltage.

Further, in this ink jet head, since the diaphragm 2 is formed of a polysilicon film or an amorphous silicon film, the diaphragm 2 having high thickness accuracy can be obtained, and the polysilicon film or the amorphous silicon film is made of glass. Since the first substrate 1 and the second substrate 3 can be bonded to a substrate, a strong anodic bonding can be performed by forming the first substrate 1 and the second substrate 3 from the glass substrate as described above, and the cost can be reduced as compared with the case where a silicon substrate is used. Can be achieved.

Next, an ink jet head according to a second embodiment of the present invention will be described with reference to FIGS. 3 is an explanatory cross-sectional view of the head in the longitudinal direction of the diaphragm, and FIG. 4 is an explanatory cross-sectional view of the head in the lateral direction of the diaphragm. This inkjet head has a first glass substrate 21 which is a flow path substrate on which a flow path such as a liquid chamber is formed and a diaphragm is provided.
And a second glass substrate 2 which is an electrode substrate on which electrodes provided below the first glass substrate 21 via a diaphragm 22 are provided.
3 and a third glass substrate 24 serving as a nozzle plate, nozzles 25 for discharging a plurality of (only one is shown for convenience) ink droplets, a discharge chamber 26 as a liquid chamber to which each nozzle 25 communicates, A common liquid chamber 28 and the like communicating with the discharge chamber 26 via a fluid resistance part 27 also serving as an ink supply path are formed.

The first glass substrate 21 is formed with a through hole (recess) forming the liquid chamber 26, a groove forming the fluid resistance portion 27, and a through hole forming the common liquid chamber 28. A diaphragm 22 made of a polysilicon film or an amorphous silicon film is provided on the bottom surface of the substrate 1. After the diaphragm 22 is formed on the first glass substrate 21, the through-holes serving as the liquid chamber 26 and the common liquid chamber 28 and the grooves serving as the fluid resistance portion 27 are formed on the first glass substrate 21 and then the glass substrate is etched. It is formed by doing.

A concave portion 34 for forming a gap and a groove for forming an electrode is formed in the second glass substrate 22.
An electrode (second electrode) 35 facing the vibration plate 22 is provided on the bottom surface of the concave portion 34, a gap 36 is formed between the vibration plate 22 and the electrode 35, and the microactuator is formed by the vibration plate 22 and the electrode 35. Unit. Then, an insulating film 37 such as a SiO ₂ film is formed on the surface of the electrode 35. The electrode materials and the like are the same as in the first embodiment.

In this embodiment, as shown in FIG. 4, the bottom surface of the concave portion 24 of the second glass substrate 22 is formed in parallel with the vibration plate 22, and the electrode 35 is formed on this bottom surface. The electrode 35 is arranged in parallel with the diaphragm 22. In addition, the diaphragm 22 in the parallel state
The gap 36 formed by the electrodes 35 is referred to as a non-parallel gap.

An ink supply port 29 for supplying ink from outside to the common liquid chamber 28 is formed in the third glass substrate 24.

Also in this embodiment, the first glass substrate 21 and the second glass substrate 23 are joined by anodic bonding via a polysilicon film or an amorphous silicon film forming the diaphragm 22. At the same time, the first glass substrate 21 and the third glass substrate 23
A polysilicon film or an amorphous silicon film 30 is formed on the side surface of the liquid chamber 3 and anodically bonded through the polysilicon film or the amorphous silicon film 30.

Thus, the first glass substrate on which the liquid chamber is provided, the second glass substrate on which the electrodes are provided, and the nozzle plate (when the droplet ejection direction is the same as in the first embodiment, a simple top plate may be used). By bonding the third substrate to the third substrate by anodic bonding via a polysilicon film or an amorphous silicon film, a strong bonding can be performed, and the reliability can be improved. Also in this respect, cost reduction can be achieved.

In each of the above embodiments, the first substrate, the second substrate, and the third substrate are all described as glass substrates, but a metal such as SUS or a silicon substrate may be used. Further, although the present invention has been described using an example in which the present invention is applied to an ink jet head, the present invention can be similarly applied to other electrostatic actuators using a diaphragm and electrodes. Further, in the above embodiment, the nozzles and the like are formed of the third glass substrate, but the nozzles and the like may be formed of other materials. Furthermore, although the inclined region of the electrode has a linear inclination, it may have a curved inclination.

[0040]

As described above, according to the droplet discharge head according to the present invention, since the diaphragm is made of a polysilicon film or an amorphous silicon film, the cost can be reduced and the reliability can be improved. .

Here, by setting the thickness of the polysilicon film or the amorphous silicon film in the range of 200 to 50,000 °, stable diaphragm displacement characteristics and bonding strength can be obtained.

According to the droplet discharge head of the present invention, the first substrate forming the liquid chamber and the second substrate forming the electrodes are anodically bonded via the polysilicon film or the amorphous silicon film. Cost can be reduced and reliability can be improved.

Here, the cost can be reduced by using the first substrate and the second substrate as glass substrates. Also, the first
The cost can be further reduced by anodically bonding a third substrate made of a glass substrate on the substrate via a polysilicon film or an amorphous silicon film.

According to the microactuator of the present invention, the microactuator includes the first substrate that forms the cavity, the diaphragm that forms the wall surface of the cavity, and the second substrate that is provided with electrodes facing the diaphragm. Since the diaphragm is made of a polysilicon film or an amorphous silicon film, the cost can be reduced and the reliability can be improved. Here, the cost can be further reduced by anodically bonding the first substrate and the second substrate via a polysilicon film or an amorphous silicon film.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view in a longitudinal direction of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view of the head in a lateral direction.

FIG. 3 is an explanatory cross-sectional view in a longitudinal direction of the inkjet head according to the first embodiment of the present invention.

FIG. 4 is an explanatory cross-sectional view of the head in a lateral direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st glass substrate, 2 ... diaphragm, 3 ... 2nd glass substrate, 24 ... 3rd glass substrate, 4 ... nozzle, 6 ... discharge chamber,
7: fluid resistance portion, 8: common liquid chamber, 15: electrode, 30: polysilicon film or amorphous silicon film.

Claims (7)

[Claims] A nozzle for discharging a droplet, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
An electrode opposed to the diaphragm, wherein the diaphragm is deformed and displaced by electrostatic force to discharge a liquid from the nozzle, wherein the diaphragm is made of a polysilicon film or an amorphous silicon film. A droplet discharge head characterized in that: 2. The droplet discharge head according to claim 1, wherein the thickness of the polysilicon film or the amorphous silicon film is in a range of 200 to 50,000 °. 3. A nozzle for discharging liquid droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
An electrode opposed to the diaphragm, wherein the diaphragm is deformed and displaced by electrostatic force to discharge a liquid liquid from the nozzle, wherein the first substrate forming the liquid chamber and the electrode are A droplet discharge head, wherein the second substrate to be formed is anodically bonded via a polysilicon film or an amorphous silicon film. 4. The droplet discharge head according to claim 3, wherein the first substrate and the second substrate are glass substrates. 5. The droplet discharge head according to claim 3, wherein a third substrate made of a glass substrate is anodically bonded to the first substrate via a polysilicon film or an amorphous silicon film. Droplet discharge head. 6. A vibrating plate that forms a cavity, a diaphragm that forms a wall surface of the cavity, and a second substrate provided with an electrode facing the diaphragm, wherein the vibrating plate is static. A microactuator for deforming and displacing with electric power, wherein the diaphragm is made of a polysilicon film or an amorphous silicon film. 7. The microactuator according to claim 6, wherein the first substrate and the second substrate are anodically bonded via a polysilicon film or an amorphous silicon film.