Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-08-03
2002-12-24
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06497474
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic actuator vibrating by electrostatic force, a method of producing such an electrostatic actuator, an electrostatic micropump including such an electrostatic actuator, an ink jet recording head including such an electrostatic actuator and ejecting an ink droplet by a pressure wave caused by electrostatic force, an ink jet recording apparatus including such an ink jet recording head, a liquid droplet ejecting head, an ink cartridge including such a liquid droplet ejecting head, an ink jet recording apparatus including such a liquid droplet ejecting head, and a method of producing such a liquid droplet ejecting head.
2. Description of the Related Art
Products to which an electrostatic actuator is applied include an electrostatic micropump and a drop-on-demand ink jet recording head.
As methods of driving a micropump for transporting liquid, there have been disclosed a piezoelectric method using piezoelectric effect, a thermal method utilizing liquid expansion caused by heat, and an electrostatic driving method employing electrostatic attraction. Among those methods, the electrostatic driving method have the advantage of low power consumption due to its use of electrostatic force, and a micropump using this method is easy to make fine in size by means of a processing technique using a silicon device processing technique.
However, since such a micropump employs silicon as a material of its components, the silicon may be eluted from the components depending on the nature of the transported liquid of alkalinity or acidity, thus causing damage to the micropump. Therefore, it is commonly practiced to form an anti-corrosive film on a surface of the silicon which surface contacts the liquid. A description will be given below of ink jet recording heads in which this anti-corrosive film is formed.
There have been proposed a variety of methods of driving an ink jet recording head for an ink jet recording apparatus which ink jet recording head uses an electrostatic actuator which performs recording by ejecting an ink droplet through a nozzle hole directly onto a recording medium.
WO98/42513 discloses an ink jet recording head for a print head employed in a drop-on-demand ink jet recording apparatus in which ink jet recording head an anti-corrosive thin film of Ti, a Ti compound, and Al
2
O
3
having resistance to ink is formed on the surface of a diaphragm forming an ink pressure chamber for pressurizing and ejecting ink.
Japanese Laid-Open Patent Application No. 10-291322 discloses a method of producing an ink jet head which method includes the steps of forming a silicon oxide film on the surface of a diaphragm forming an ink pressure chamber for pressurizing and ejecting ink, and thereafter forming in layers ink-resistant films of oxide, nitride, and a metal to close pinholes in the diaphragm.
Such a diaphragm of an electrostatic actuator which diaphragm is formed by a single or a plurality of layers of ink-resistant anti-corrosive thin films of Ti, a Ti compound, Al
2
O
3
, and a silicon oxide suffers a decrease in a yield due to corrosion, a malfunction caused by a deflection of the diaphragm generated by buckling, and a breakage caused by mishandling during the production thereof, thus resulting in an increase in the production costs of the electrostatic actuator.
When such an electrostatic actuator including a diaphragm formed by a single or a plurality of layers of ink-resistant anti-corrosive thin films of Ti, a Ti compound, Al
2
O
3
, and a silicon oxide is applied to an electrostatic micropump, an ink jet recording head, or an ink jet recording apparatus, the internal stress of the anti-corrosive thin films and a film thickness distribution on the diaphragm cause the diaphragm to buckle to have a deflection. The deflection of the diaphragm causes an increase in a driving voltage, which leads to an increase in the costs of a driving circuit and greater variations in the driving voltage, thus causing an increase in power consumption. Further, the deflection of the diaphragm causes differences in an ejection characteristic among bits at a time of ejecting liquid or ink, poor liquid or ink ejection, and certain corrosion depending on a type of liquid or ink.
Such a conventional method of producing, for instance, an electrostatic micropump, an ink jet recording head, or an ink jet recording apparatus separately produces a first silicon substrate of approximately 200 &mgr;&mgr;m in thickness having liquid or ink chambers and diaphragms of a few microns in thickness formed therein and a second silicon substrate having n
+
or p
+
-type impurity diffusion driving electrodes formed therein, and bonds the first and second silicon substrates directly. In this process, the first silicon substrate may be damaged by mishandling, thus reducing a production yield.
Further, an ink jet recording apparatus employed as an image recording apparatus (an imaging apparatus) such as a printer, a facsimile machine, a copying machine, or a plotter includes an ink jet head as a liquid droplet ejecting head including nozzles for ejecting ink droplets, ink channels (also referred to as ejection chambers, pressure chambers, liquid pressure chambers, or liquid chambers) with which the nozzles communicate, and driving means for pressurizing ink in the ink channels. The liquid droplet ejecting heads include, for instance, those for ejecting liquid resist or DNA specimens as liquid droplets, but a description given below will focus mainly on an ink jet head.
As an ink jet head, known is a piezoelectric ink jet head that ejects ink droplets by changing the capacities of ink channels by deforming diaphragms forming wall faces of the ink channels by using piezoelectric elements as energy generation means for generating energy for pressurizing ink in the ink channels. Further, a so-called bubble type ink jet head that ejects ink droplets by means of pressures produced by generating air bubbles by heating ink in ink channels using calorific resistances is also known. Moreover, Japanese Laid-Open Patent Application No. 6-71882 discloses an electrostatic ink jet head that ejects ink droplets by changing the volumes of ink channels by deforming diaphragms forming wall faces of the ink channels by means of electrostatic forces generated between the diaphragms and electrodes that are arranged to oppose each other.
In order for an ink jet recording apparatus to record, particularly, a color image with high quality at a high speed, in terms of achieving high quality, high-density processing using a micromachine technique is employed to produce the ink jet recording apparatus and a material for head components has shifted from a metal or plastic to silicon, glass, or ceramics with the silicon being particularly employed as a material preferable for fine processing.
Further, in terms of colorization, efforts have been made mainly to develop ink and recording media. The development of ink ingredients and components has been promoted to optimize permeability, coloring, and a color mixture prevention characteristic of ink when the ink adheres to a recording medium and to increase long-term preservability of a printed medium and preservability of the ink itself.
In this case, the ink may dissolves the head components depending on a combination of the ink and a material for the head components. Particularly, in the case of forming a channel formation member of silicon, the silicon is dissolved in the ink to be deposited on nozzle parts so that nozzles are clogged or coloring of the ink is deteriorated to degrade quality of image. Further, in the case of a head using diaphragms, if the diaphragms are formed of silicon thin films and silicon is dissolved in the ink, the vibration characteristic of the diaphragms is altered or the diaphragms are prevented from vibrating.
In this case, it often makes it difficult to perform high-density processing or decrease processing accuracy to cope with the above-described problems by cha
Azumi Junichi
Irinoda Mitsugu
Isshiki Kaihei
Satoh Yukito
Cooper & Dunham LLP
Gordon Raquel Yvette
Ricoh & Company, Ltd.
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