Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-10-24
2001-07-17
Fuller, Benjamin R. (Department: 2855)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C716S030000
Reexamination Certificate
active
06260960
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet print head and a method of manufacturing the same, and more particularly to an ink jet print head which uses piezoelectric elements as drive sources for drop generators for generating and discharging ink drops and a method of manufacturing the same.
There is known an ink jet print head which uses elements made of lead zirconate titanate (PZT) piezoelectric material (referred to as PZT element) for the drive sources for ink drop ejecting generators for generating ink drops or droplets, i.e., the elements for transducing electric energy into mechanical energy. The ink jet print head is generally formed with a head base, a vibrating plate, and PZT elements. A number of ink passages (ink cavities and the like) are formed in the head base. The vibrating plate is formed over the head base while covering all the ink passages formed therein. The PZT elements are formed on the regions on the vibrating plate, which correspond in position to the ink cavities. In operation, electric fields are selectively applied to the PZT elements, to thereby cause flexural displacements in these elements. With the displacements, inks contained in the ink passages associated with the PZT elements placed under the applied electric fields are forcibly shot forth in the form of ink drops or droplets, through the related ink discharge orifices formed in the nozzle plate.
In a case where the head base is formed of a single-crystal silicon substrate, the single-crystal silicon substrate is selectively subjected to wet etching process to form discrete ink passages in the substrate. This wet etching process is generally carried out using an alkaline aqueous solution of high concentration, e.g., a 5 wt % to 40 wt % potassium hydroxide solution.
For the formation of the nozzle plate, a thin plate (e.g., a stainless plate) having ink discharge orifices formed at predetermined determined positions is bonded onto the head base.
In the ink jet print head thus structured, in forming the head base by wet etching process, if the etching solution comes in contact with the PZT elements, the elements are frequently stripped off or damaged. Specifically, if the single-crystal silicon substrate is etched by use of, for example, an alkaline aqueous solution for an etching solution and the etching progresses to reach the vibrating plate, the alkaline solution or the etching reaction products pass through the vibrating plate to possibly damage the PZT elements, at the termination of the etching.
Meanwhile, the nozzle plate forming method in which a thin plate (e.g., a stainless plate) having ink discharge orifices formed at predetermined determined positions is bonded on the head base, requires complicated manufacturing process. Therefore, this method is not suitable for the mass production of ink jet print heads.
SUMMARY OF THE INVENTION
Accordingly, the present invention is made to solve the above problems, and has an object to provide an ink jet print head which has reliable piezoelectric elements such as a PZT element and is capable of ejecting a large amount of ink at high ejecting speed. Another object of the invention is to provide an ink jet print head which has reliable piezoelectric elements and is capable of ejecting a small amount of ink at high ejecting speed. Yet another object of the invention is to provide a method of manufacturing an ink jet print head which is capable of ejecting a large amount of ink at high ejecting speed without adversely affecting the piezoelectric elements of the print head. Still another object of the invention is to provide a method of manufacturing an ink jet print head which can form the nozzle plate of the head in a simple manner and is suitable for the mass production of the print heads.
An additional object of the present invention is to provide a method of manufacturing an ink jet print head having reliable piezoelectric elements in which wet etching process, which may adversely affect the piezoelectric elements, is carried out at the best timing in the manufacturing of the heads.
According to one aspect of the invention, there is provided an ink jet print head comprising: piezoelectric elements formed on a first surface of a single-crystal silicon substrate; ink cavities formed in the regions of the single-crystal silicon substrate, the regions corresponding in position to the piezoelectric elements; and a nozzle plate formed on a second surface of the single-crystal silicon substrate, the second surface being opposite to the first surface, and the nozzle plate having discharge orifices through which inks contained in the ink cavities are discharged therefrom; wherein in forming the ink cavities, anisotropical wet etching process is used to form a portion (first portion) of each ink cavity ranging from the second surface of the single-crystal silicon substrate to a position (referred to as a surface-region position) near the first surface, and anisotropical dry etching process is used to form a portion (second portion) of each ink cavity ranging from the surface-region position to the first surface of the single-crystal silicon substrate. In the ink jet print head thus constructed, the reliability of the piezoelectric elements is improved.
In the ink jet print head structured as mentioned above, a side wall (second side wall) of each ink cavity ranging from the surface-region position to the first surface of the single-crystal silicon substrate, is tapered toward the outer side of the ink cavity. This feature of the ink jet print head brings about the following advantages, in addition to the above-mentioned ones. Each piezoelectric element serving also as the vibrating plate may have a large compliance although the compliance of the side wall of each ink cavity is little different from that of the conventional one. Therefore, the piezoelectric element may have large flexural displacements, and the ink drop generator including the piezoelectric element and its associated ink cavity generates a large amount of ink drop and shoots forth the same at high speed.
Further, the second side wall of each ink cavity may be tapered toward the inner side of the ink cavity in the above-mentioned ink jet print head. This feature brings about the following advantage, in addition to the above-mentioned ones. The ink contained in each ink cavity may have a large inertance, and each of the piezoelectric elements may have a small compliance. Therefore, the ink jet print head is capable of discharging a small amount of ink drop at a high speed even if the displacement of the vibrating plate is small. In other words, the print head is capable of printing an image, which is higher in density and definition than that printed by the conventional one.
In the ink jet print head mentioned above, the second surface of the single-crystal silicon substrate may have a face (
110
), and in the anisotropical wet etching process an alkaline aqueous solution may be used for an etching solution.
Alternatively, the second surface of the single-crystal silicon substrate may have a face (
100
), and in the anisotropical wet etching process an alkaline aqueous solution may be used for an etching solution. In the present specification, the meaning of the “tapered surface” includes a “curved surface”.
The present invention also provides an ink jet print head comprising: piezoelectric elements formed on a first surface of a single-crystal silicon substrate; ink cavities formed in the regions of the single-crystal silicon substrate, the regions corresponding in position to the piezoelectric elements; and a nozzle plate formed on a second surface of the single-crystal silicon substrate, the second surface being opposite to the first surface, and the nozzle plate having discharge orifices through which inks contained in the ink cavities are discharged therefrom; wherein a side wall (second side wall) of each ink cavity ranging from a position (referred to as a surface-region position) near the first surface to the first surface of the single-crystal sili
Hashizume Tsutomu
Takahashi Tetsushi
Dickens C
Fuller Benjamin R.
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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