Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-06-06
2003-01-21
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06508539
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a liquid-firing head and a manufacturing method thereof, and, an ink-jet recording device and a micro-actuator.
2. Description of the Related Art
In general, an electrostatic ink-jet head, which is one of liquid-firing heads, is used in an ink-jet recording device used as an image recording/forming device of a printer, a facsimile machine, a copier, a plotter and so forth. The electrostatic ink-jet head includes a nozzle firing an ink drop, a liquid chamber (which may also be referred to as an ink flow path, a pressurizing chamber, a firing chamber, a pressure chamber, a pressurizing liquid chamber, or the like) communicating with the nozzle, a vibration plate which is used as a wall of the liquid chamber, and an electrode facing the vibration plate. Then, as a result of a voltage being applied between the vibration plate and electrode, an electrostatic force is generated, which deforms the vibration plate so that the pressure/volume in the liquid chamber is changed. As a result, an ink drop is fired via the nozzle. A part of this ink-jet head including the vibration plate and electrode is called a micro-actuator. The micro-actuator may also be used as a micro-pump or the like.
Japanese Laid-Open Patent Application No. 6-71882discloses such an electrostatic ink-jet head. In this ink-jet head, the vibration plate which is used as a wall of the liquid chamber and the electrode are disposed in parallel with one another. A gap formed thereby is called ‘a parallel gap’.
Further, Japanese Laid-Open Patent Application No. 9-39235 discloses an electrostatic ink-jet head in which a length of a gap formed between the vibration plate and electrode varies stepwise as a result of the electrode being disposed stepwise. Furthermore, Japanese Laid-Open Patent Application No. 9-193375 discloses such an electrostatic ink-jet head that, as a result of the electrode being disposed obliquely with respect to the vibration plate, a sectional shape of the gap formed between the vibration plate and electrode is such that a surface on the vibration plate and a surface on the electrode are not parallel at least at a part thereof (such a gap is called ‘non-parallel gap’).
In such an electrostatic ink-jet head (also in a micro-actuator), it is necessary to form the gap between the vibration plate and electrode at a high accuracy. For this purpose, an oxide film is formed on a silicon substrate, or an insulating substrate such as a Pyrex glass is used, a groove for forming an electrode having a predetermined depth is formed into the oxide film or insulating substrate, and an electrode having a predetermined thickness is formed on a bottom surface of the groove. Thereby, as a result of utilizing the part of the oxide film or insulating substrate other than the groove as a gap spacer for determining the gap between the vibration plate and electrode, it is possible to obtain a predetermined gap length between the vibration plate and electrode.
However, in such an electrostatic ink-jet head in the related art, when the above-mentioned parallel gap is formed, the gap length (the distance between the surface of the vibration plate and the surface of the electrode) may vary, due to variation in depth of the groove for forming the electrode (variation in height of the gap spacer), variation in thickness of the electrode, and also, variation in thickness of a protection insulating film if this film is formed on the surface of the electrode. Also, it is difficult to further reduce the size of the gap.
Further, if the non-parallel gap is formed, especially if the non-parallel gap starting from a position at which the gap length of 0 is formed, a groove having a shape of the non-parallel gap should be formed in a silicon substrate, and an electrode should be formed in the groove. Accordingly, an end of the electrode or an end of a protection insulating film formed on the surface of the electrode may project from or may be lower than the top surface of the silicon substrate (the top surface of the gap spacer). Thereby, unevenness occurs on the surface of the silicon substrate.
In such a case, it may be difficult to bond the thus-formed part with a substrate in which a vibration plate is provided, or, even when the bonding may be achieved, such a large amount of polishing is needed for enabling the bonding that variation in gap length increases.
When variation in gap length thus increases, it may result in variation in firing performance of the resulting ink-jet head such as ink-drop firing volume, ink-drop firing speed and so forth, variation in position at which fired ink reaches, degradation in image quality obtained through printing by using the ink-jet head, and so forth.
SUMMARY OF THE INVENTION
The present invention has been devised in consideration of the above-mentioned problems, and, an object of the present invention is to provide a liquid-firing head in which gap accuracy is improved, a method of manufacturing it, an ink-jet recording device in which image quality of recorded image is improved, and a micro-actuator in which the gap accuracy is improved.
A liquid-firing head according to the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein a groove for forming a gap between the electrode and the vibration plate is formed in the electrode.
Thereby, it is possible to form the gap at a high accuracy, and to improve the ink-drop firing performance.
In this configuration, it is preferable that the electrode comprises a polysilicon layer. Thereby, it is possible to easily form the high-accuracy gap.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein a groove for forming a gap between a protection insulating film, formed on the electrode, and the vibration plate is formed in the protection insulating film.
Thereby, controllability of the gap is improved, and the process yield increases.
In this configuration, the electrode may comprise one of a polysilicon layer, a tungsten silicide layer, a titan silicide layer, and a laminated layer thereof. Thereby, it is possible to easily form the protection insulating film.
Further, the protection insulating film may comprise one of a polysilicon oxide film or a high-temperature oxide film. Thereby, the reliability is improved, and degradation of the electric performance is reduced.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein:
a gap spacer part determining a gap between the vibration plate and the electrode comprises the same layer as that of the electrode; and
a groove for forming the gap between the electrode and the vibration plate is formed in the electrode.
Thereby, the gap accuracy is improved, the liquid-firing performance is improved, a high-accuracy gap can be formed with higher process yield, and, in particular, a high-accuracy non-parallel gap can be easily formed.
In this configuration, by employing a polysilicon layer for the electrode, it is possible to easily form the high-accuracy gap.
A liquid-firing head according to another aspect of the prese
Cooper & Dunham LLP
Gordon Raquel Yvette
Ricoh & Company, Ltd.
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