JP2002052707A - Electrostatic ink jet head, its manufacturing method, and imaging apparatus comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic ink jet head in which ink can be controlled accurately by means of a diaphragm. SOLUTION: The electrostatic ink jet head comprises a nozzle for ejecting an ink liquid drop, a liquid chamber 302 of silicon having a channel for filling ink, and a diaphragm 305 of silicon formed at a part of the liquid chamber 302 wherein a pressure wave is generated in the ink filling the liquid chamber 302 by driving the diaphragm 305 through electrostatic attraction to an electrode 307 disposed oppositely to the diaphragm 305 through a constant gap and an ink liquid drop is ejected from the inside of the liquid chamber 302. A thin metal film or a film of metal oxide or metal nitride is formed on the surface of the diaphragm 305 on the liquid chamber 302 side and a linear recess 304 is made in the surface of the diaphragm 305 on the side opposite to the liquid chamber 302.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromachining technique using a micromachining technique,
More specifically, the present invention relates to an electrostatic inkjet head including a microactuator having a membrane formed by applying micromachining technology, a method of manufacturing the electrostatic inkjet head, and an image forming apparatus using the electrostatic inkjet head. .

[0002]

2. Description of the Related Art An electrostatically driven micropump is conventionally known as a microactuator having a membrane formed of silicon. In this micropump, an electrode plate is placed in parallel with a small gap at a position facing the silicon membrane, and the membrane is deformed by electrostatic attraction generated by a voltage applied between the silicon membrane and the electrode plate. The fluid is extruded by utilizing the above. An electrostatic inkjet printer head has been proposed as an application technique of such a micropump. Since the electrostatic ink jet printer head can be manufactured by a wafer process, which is a semiconductor manufacturing technique, it is easy to increase the density and can manufacture a large number of elements with stable characteristics. In addition, the electrostatic ink jet printer head has an advantage that downsizing becomes extremely easy because of its basic structure. For these reasons, JP-A-2-289351, JP-A-5-050601, and JP-A-6-050601
Various types of electrostatic inkjet printer heads are disclosed in, for example, Japanese Patent Application Laid-Open No. 071882. In these electrostatic ink jet heads, electrodes are formed at a position outside the diaphragm, which faces a part of the liquid chamber, with a gap of a fixed distance therebetween. The basic configuration is that the diaphragm is driven by the attractive force and the rigidity of the diaphragm itself to suck and discharge the ink in the liquid chamber.

[0003]

Generally, in an electrostatic ink jet head having a diaphragm made of silicon, the displacement can be increased at the same voltage by increasing the thickness of the diaphragm in order to increase the displacement. . Further, since a diaphragm made of silicon dissolves in ink, a metal thin film, a metal oxide or a metal nitride film may be formed on the surface thereof. At this time, if the ratio of the metal thin film, the metal oxide or the metal nitride film to the thickness of the diaphragm is large, the diaphragm whose outer periphery is fixed becomes a metal thin film, a metal oxide or a metal nitride film. Buckling may occur due to the compressive stress, and the wrinkle-like deformation caused by the buckling causes a problem that accurate control of ink by the diaphragm cannot be performed. An object of the present invention is to solve such a problem. By forming a metal film or a metal oxide or a metal nitride and a linear depression on a vibration plate of an electrostatic ink jet head, the vibration plate is used. An object of the present invention is to provide an electrostatic inkjet head capable of accurately controlling ink, a method of manufacturing the electrostatic inkjet head, and an image forming apparatus using the electrostatic inkjet head.

[0004]

According to a first aspect of the present invention, there is provided an ink jet head comprising a nozzle having a nozzle for discharging ink droplets and a silicon having a flow path for filling the ink. A diaphragm made of silicon is formed in a part of the liquid chamber, and the diaphragm is driven by electrostatic attraction between an electrode provided with a certain gap at a position facing the diaphragm, In an electrostatic inkjet head that generates a pressure wave in the ink filled in the liquid chamber and ejects ink droplets from inside the liquid chamber,
A metal thin film, a film made of metal oxide or metal nitride is formed on the surface of the diaphragm on the liquid chamber side, and a linear depression is formed on a surface of the diaphragm on the side opposite to the liquid chamber. It is characterized by having. According to a second aspect of the present invention, in the electrostatic inkjet head according to the first aspect, the depression is formed on a center line of the membrane. According to a third aspect of the present invention, in the electrostatic inkjet head according to the first aspect, the depression is formed along an outer periphery of the membrane. According to a fourth aspect of the present invention, there is provided the electrostatic inkjet head according to any one of the first to third aspects. The invention according to claim 5 is characterized in that a metal thin film, a metal oxide or a metal nitride film is formed on the vibration plate after forming the vibration plate provided with the linear depression. .

[0005]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a membrane formed on a silicon substrate when manufacturing an electrostatic inkjet head according to an embodiment of the present invention. FIG. 1 shows a membrane 102 formed on a silicon substrate 101 having a plane orientation (1, 0, 0). The membrane shape is a square or a rectangle having one side in the plane orientation (1, 1, 1) direction. Such a membrane can be easily formed by etching silicon by anisotropic etching such as KOH using an oxide film or the like as a mask and stopping the etching at a desired thickness. FIG. 2 shows the form of buckling occurring on the membrane 102 of FIG. Since the metal thin film often has a compressive stress, the membrane 102 buckles when its outer periphery is fixed, causing a wrinkled deformation. FIG. 3 shows an actuator portion of the electrostatic inkjet head according to the embodiment of the present invention. As shown in FIG. 3, a liquid chamber 302 and a common liquid chamber 303 for supplying ink to them are formed in the liquid chamber substrate 301. On the bottom surface of the chamber 302, a diaphragm 305 having a depression 304 on the surface is formed. That is, the diaphragm 3
A depression 304 is formed on the surface of the area 05 opposite to the chamber 302. Electrode substrate 306 bonded below liquid chamber substrate 301
Has an electrode 307 for electrostatically driving the diaphragm 305,
An extension pad 308 from the electrode 307 which is an extension thereof
Are formed. A gap 309 is formed between the electrode 307 and the diaphragm 305.

A method for manufacturing an ink jet head according to an embodiment of the present invention will be described with reference to FIGS. For forming a liquid chamber and a vibration plate, a silicon substrate 402 having a SiN film 401 formed on its surface is prepared (see FIG. 4A). Next, a thermal oxide film 403 is formed on the surface to form an electrode substrate.
The silicon substrate 404 on which was formed was used. Thermal oxide film 4
A recess having a depth of 0.5 μm for forming a gap was formed on buffer 03 by buffer hydrofluoric acid etching using a resist mask. A TiN film 405 is formed as an electrode by sputtering in the concave portion formed in this thermal oxide film by 1500.
A film was formed and patterned to a thickness of パ タ ー ニ ン グ, and a SiO ₂ film 406 was formed to a thickness of 1000 で by a CVD method using the electrode surface as an insulating film (see FIG. 4B). Here, TiN was used as the electrode material, but other materials having low resistance and high temperature resistance, such as poly-S doped with impurities, were used.
i, Pt, Au or the like may be used. Further, although SiO ₂ is used here as the insulating film, SiN, SiOH, or the like may be used. Next, the liquid chamber, the diaphragm substrate and the electrode substrate were joined (see FIG. 4C). Since a gap for electrostatic drive is formed by this joining, joining accuracy, especially the accuracy of the distance between the electrode and the diaphragm is required, so that the two are directly joined without using an adhesive layer here. Direct bonding was used. In this method, the clean surface of the silicon substrate is brought into contact with the clean surface of the silicon substrate on which the thermal oxide film is formed, and the two are joined by heat treatment at a high temperature of 1000 ° C. At this time, the pressure at the time of joining was adjusted so that the pressure in the gap closed after joining was substantially equal to the outside air. Next, the SiN on the liquid chamber substrate was dry-etched with a resist mask to pattern the liquid chamber and the electrode pad portions (see FIG. 4D).

Next, the liquid chamber 407 and the electrode pad portion 408 are formed by anisotropically etching the liquid chamber substrate in a 30% KOH solution, and the etching is stopped by stopping the etching of the silicon substrate except for 5 μm. A plate 409 was formed (see FIG. 5E). In this step, a depression 412 was formed on the surface of the vibration plate 409 on the side opposite to the liquid chamber 407 by the same method as described above. Next, the inner surface of the liquid chamber 407 is subjected to an ink-resistant treatment, and a TiN film 410
Was formed by a sputtering method (see FIG. 5F). Thereafter, the electrode 411 was taken out by dry-etching the TiN and silicon in the pad portion (see FIG. 5G).
Thus, the liquid chamber and the actuator portion of the electrostatic ink jet are completed. FIG. 6 shows an ink jet head completed by bonding a Ni nozzle plate thereon. The liquid chamber substrate 501 is formed with liquid chambers 502 corresponding to the respective nozzles, a common liquid chamber 503 for supplying ink to the nozzles, and a fluid resistor 504 for communicating the two. A diaphragm 505 having a depression 512 formed on the surface is formed on the bottom surface of the liquid chamber 502. The nozzle plate 506 joined on the liquid chamber substrate is provided with a nozzle 507 communicating with the liquid chamber. An electrode 509 for electrostatically driving the diaphragm is provided on an electrode substrate 508 bonded below the liquid chamber substrate.
And extension pad 5 from electrode 509 as an extension
10, and a gap 511 is formed between the electrode 509 and the diaphragm 505. In the ink jet head manufactured in this manner, the lead wire was taken out from the electrode pad by wire bonding, a voltage was individually applied, and the diaphragm was driven at a constant frequency to discharge ink from the nozzle. In the electrostatic ink jet head according to the second and third aspects of the present invention, the diaphragm is formed with a linear thin film or a metal oxide or a metal nitride, and each of the recesses is formed on the center line of the diaphragm. , Formed along the outer periphery of the diaphragm. The arrangement of such depressions can be easily set by changing the pattern of the depressions in the above-described manufacturing method.

[0008]

As described above, according to the first aspect of the present invention, a nozzle for discharging ink droplets,
A vibrating plate made of silicon is formed in a part of a liquid chamber made of silicon having a flow path for filling ink, and a static gap between an electrode provided with a certain gap at a position facing the vibrating plate. An electrostatic ink jet head that drives the vibration plate by an electric attraction force to generate a pressure wave in the ink filled in the liquid chamber and discharge ink droplets from the inside of the liquid chamber. A metal thin film, a film made of a metal oxide or a metal nitride is formed on the surface on the liquid chamber side, and a linear depression is formed on the surface of the diaphragm opposite to the liquid chamber. Since the dent absorbs buckling caused by the compressive stress of the film when forming the metal thin film, the metal oxide or the metal nitride film, irregular wrinkles are not formed on the diaphragm, and the ink is formed by the diaphragm. Precise control It can be made possible. Claim 2
According to the invention described in (1), in the electrostatic inkjet head according to (1), since the depression is formed on the center line of the membrane, the deformation of the diaphragm is symmetric with respect to the center line. The energy required for the deformation is reduced, and the driving voltage can be reduced. According to the third aspect of the present invention, in the electrostatic ink jet head according to the first aspect, since the depression is formed along the outer periphery of the membrane, the entire surface moves up and down when the moving plate is deformed. As a result, local deflection is reduced and the overall stroke can be increased, so that the drive voltage can be reduced. According to a fourth aspect of the present invention, there is provided an image forming apparatus including the electrostatic inkjet head according to any one of the first to third aspects.
Low-voltage drive, that is, a low-cost power supply can be used,
Further, it is possible to form a high-quality image with no variation in dots. According to the invention of claim 5, after forming a diaphragm provided with a linear depression, an electrostatic ink jet head in which a metal thin film, a metal oxide or a metal nitride film is formed on the diaphragm. Because it is a manufacturing method of
The diaphragm provided with the depressions can be formed with high accuracy, and the distortion due to the internal stress after the formation of the thin film material can be effectively absorbed, so that the diaphragm does not deform.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a membrane formed on a silicon substrate when manufacturing an electrostatic inkjet head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a form of buckling occurring on the membrane 102 of FIG.

FIG. 3 is an explanatory diagram showing an actuator portion of the electrostatic inkjet head according to the embodiment of the present invention.

FIGS. 4A to 4D are explanatory diagrams for explaining a method of manufacturing an electrostatic inkjet head according to the embodiment of the present invention.

FIGS. 5E to 5G are explanatory diagrams for explaining a method of manufacturing the electrostatic inkjet head according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating a completed state of the electrostatic inkjet head according to the embodiment of the present invention.

[Explanation of symbols]

101 silicon substrate, 102 membrane, 201
Metal thin film, 301 liquid chamber substrate, 302 liquid chamber, 303
Common liquid chamber, 304 depression, 305 diaphragm, 306 electrode substrate, 307 electrode, 308 extraction pad, 30
9 gap, 401 SiN film, 402 silicon substrate, 403 thermal oxide film, 404 silicon substrate, 405
TiN film, 406 SiO ₂ film, 407 liquid chamber, 40
8 electrode pad part, 409 diaphragm, 410 TiN
Membrane, 411 electrode, 412 depression, 501 liquid chamber substrate,
502 liquid chamber, 503 common liquid chamber, 504 fluid resistance,
505 diaphragm, 506 nozzle plate, 507 nozzle, 508 electrode substrate, 509 electrode, 510 extraction pad, 511 gap, 512 recess.

Claims (5)

[Claims] A nozzle for discharging ink droplets;
A vibrating plate made of silicon is formed in a part of a liquid chamber made of silicon having a flow path for filling ink, and a static gap between an electrode provided with a certain gap at a position facing the vibrating plate. An electrostatic ink jet head that drives the vibration plate by an electric attraction force to generate a pressure wave in the ink filled in the liquid chamber and discharge ink droplets from the inside of the liquid chamber. A film made of a metal thin film, a metal oxide or a metal nitride is formed on the surface on the liquid chamber side, and a linear depression is formed on a surface of the diaphragm opposite to the liquid chamber. An electrostatic ink jet head characterized by the following. 2. The electrostatic ink jet head according to claim 1, wherein the depression is formed on a center line of the membrane. 3. The electrostatic ink jet head according to claim 1, wherein the depression is formed along the outer periphery of the membrane. 4. An image forming apparatus comprising the electrostatic inkjet head according to claim 1. Description: 5. An electrostatic ink jet apparatus comprising: forming a diaphragm provided with a linear depression, and forming a metal thin film, a metal oxide or a metal nitride film on the diaphragm. Head manufacturing method.