Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-10-24
2001-02-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06183070
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an ink jet recording head and a process of manufacturing such an ink jet recording head. More particularly, the invention is directed not only to an ink jet recording head with improved ink injecting speed at which ink is jetted out of the ink cavities, but also to a process of manufacturing such an ink jet recording head.
An ink jet recording head using a piezoelectric body element as an ink jetting drive source, i.e., as an element for converting electric energy to mechanical energy has heretofore been known. The piezoelectric body element is formed by interposing lead titanate zirconate (hereinafter referred to as “PZT”) between a lower electrode and an upper electrode.
This ink jet recording head generally includes: a head substrate having a plurality of ink cavities formed therein; a vibrating plate mounted on the head substrate so as to cover all the ink cavities; a piezoelectric body element attached to portions of the vibrating plate corresponding to the ink cavities; and a nozzle plate arranged on the head substrate so as to close the ink cavities. It may be noted that the nozzle plate has ink jetting ports for jetting out ink contained within the ink cavities.
The thus constructed ink jet recording head is designed to displace the piezoelectric body element by applying an electric field thereto and to apply pressure to a desired ink cavity so that the ink contained in such a desired ink cavity is squeezed outward from a corresponding ink jetting port. Each of the cavities is formed to have such a capacity (volume) as to allow satisfactory printing to be carried out. Here, this ink jet recording head is designed to have as many ink cavities as possible in a narrow surface area so that reproducibility and artistic appearance of tiny characters, graphics, pictures, and the like can be improved. To achieve this object, the ink cavities are designed to be deep enough to reliably meet the aforementioned capacity (volume) requirement.
However, such a conventional ink jet recording head addresses the following problem. In the conventional ink jet recording head, the piezoelectric body element utilizing a thin-film piezoelectric mechanism is formed on the front surface of a silicon wafer and the ink cavities are laid out on the back surface of the silicon wafer at locations confronting the piezoelectric body element. Silicon wafers that can actually be handled during manufacturing processes are 100 mm in diameter and as thin as 200 &mgr;m, and if ink cavities are formed at such a high density as to allow high-definition printing to be achieved, side walls partitioning individual ink cavities must be thin. As a result, the side walls are susceptible to deformation, which in turn prevents ink particles from being jetted therethrough efficiently as well as speedily.
Further, if an inexpensive silicon wafer that is 150 mm or more in diameter is used, the silicon wafer thickness that can be handled becomes about 500 &mgr;m, which in turn requires that this wafer have deeper ink cavities. As a result, arises the problem that the side walls are susceptible to distortion and deformation due to displacement of the piezoelectric body element.
As a result, when pressure is applied to an ink cavity by displacement of the piezoelectric body element, it is difficult to utilize such pressure for correct and efficient ink jetting operation. Hence, the problem of impaired ink injecting speed occurs.
SUMMARY OF THE INVENTION
The present invention has been made to overcome these problems caused by the conventional art. The object of the invention is, therefore, to provide not only an ink jet recording head that prevents the side walls of an ink cavity from being deformed when pressure is applied to the ink cavity by displacement of the piezoelectric body element, so that ink injecting speed can be improved, but also a process of manufacturing such ink jet recording head.
To achieve the above object, the invention is applied to an ink jet recording head that includes: a piezoelectric body element being formed on a substrate; an ink cavity being formed at a location of the substrate corresponding to the piezoelectric body element; an ink jetting port for jetting ink contained within the ink cavity, wherein the ink cavity has a beamlike portion that is not only interposed between a pair of confronting side walls while coming in contact with desired regions of the side walls, but also formed so as to be distanced from other side walls. The thus constructed ink jet recording head is characterized as allowing the beamlike portion to support the confronting side walls of the ink cavity. Therefore, the side walls of an ink cavity are prevented from being distorted or deformed at the time of squeezing outward the ink contained in the ink cavity from the corresponding ink jetting port by displacing the piezoelectric body element while applying an electric field thereto. The displaced piezoelectric body element applies pressure to the ink cavity to thereby cause such pressure to squeeze the ink contained in the ink cavity outward.
The beamlike portion may be interposed between the pair of side walls so as to be substantially perpendicular to the side walls. As a result of such an arrangement, the pair of side walls can be supported more reliably.
Further, the desired regions may be located more toward the piezoelectric body element than a middle portion of the ink cavity. As a result of such an arrangement, ink jetting operation can be performed efficiently in addition to the aforementioned advantages.
The invention also provides a process of manufacturing an ink jet recording head having a piezoelectric body element being formed on a substrate, an ink cavity being formed at a location of the substrate corresponding to the piezoelectric body element, and an ink jetting port for jetting ink contained within the ink cavity, the process involving the steps of: selectively adding an impurity to a desired portion in a region of the substrate in which to form the ink cavity; forming the piezoelectric body element on the impurity-added substrate; and forming the ink cavity by selectively etching a portion of the substrate corresponding to the piezoelectric body element.
Further, the invention provides a process of manufacturing an ink jet recording head having a piezoelectric body element being formed on a substrate, an ink cavity being formed at a location of the substrate corresponding to the piezoelectric body element, and an ink jetting port for jetting ink contained within the ink cavity, the process including the steps of: selectively etching a desired portion of a region of the substrate in which to form the ink cavity; adding an impurity to the etched region of the substrate; charging silicon into the etched portion after the impurity has been added; flattening the silicon-charged surface of the substrate; forming the piezoelectric body element on the flattened substrate; and forming the ink cavity by selectively etching a portion of the substrate corresponding to the piezoelectric body element.
As a result of these steps, the beamlike portion that is not only interposed between the confronting side walls while coming in contact with the desired regions of the side walls but also formed so as to be distanced from other side walls, can be formed.
Further, the step of selectively etching a desired portion of a region of the substrate in which to form the ink cavity may be carried out at a location more toward the piezoelectric body element than the middle portion of the ink cavity.
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Patent Abstracts of Japan vol. 13, No. 147 (E-741) Apr. 11, 1989 & JP 63 308390 A (Yokogawa Electric Corp) Dec. 15
Barlow John
Gordon Raquel Yvette
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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