Incremental printing of symbolic information – Ink jet – Ejector mechanism
Patent
1995-02-28
1998-02-17
Fuller, Benjamin R.
Incremental printing of symbolic information
Ink jet
Ejector mechanism
347 50, 347 68, B41J 2045, B41J 214
Patent
active
057196060
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP93/00921 filed Jul. 5, 1993.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an ink jet head of a drop-on-demand (DOD) type, and, more specifically, relates to an ink jet head of a piezoelectric type.
2. Background Art
Use of ink jet printers of non-impact printers is expanding in the market since such printers operate on a simple principle and are suitable for color printing. It can be said that an ink jet printer of a so-called DOD type that jets ink drops only on formation of dots is the leading of such printers.
Typical examples of a DOD type printer are a kaiser type disclosed in Japanese Patent Publication No. 12138/1978 and a thermal jet type disclosed in Japanese Patent Publication No. 59914/1986. Both have a very difficult problem: the former is hard to miniaturize, and in the latter ink is burned due to high heat imparted thereto.
To avoid such problems, there have been proposed an expanding mode type disclosed in Japanese Laid-Open Patent Publication No. 159358/1984 and a shearing mode type disclosed in Japanese Laid-Open Patent Publication No. 252750/1988 using a chip of a piezoelectric material.
A shearing mode type will be described briefly with reference to FIG. 14 and FIG. 15. A pressure chamber 1a is constituted by forming a slot in a piezoelectric base 1 and covering it with a flat plate-like upper lid 2. A driving electrode 4 is provided on an inner wall of slot 1 and voltage is applied onto a barrier 1c that is a part of the piezoelectric base 1 to deform barrier 1c. If the polarization of the piezoelectric base 1 is left in the direction to the upper lid 2 from base 1, shearing deformation shown by broken lines occurs when an electric field by voltage is in the direction of shown arrows. The state of the barrier 1c after deformation is shown on an exaggerated scale to illustrate the deformation of the barrier clearly. The volume of the pressure chamber 1a is reduced by such deformation and ink supplied into chamber 1a is pressurized, thereby jetting ink drops from a nozzle hole provided in correspondence to the pressure chamber to thus perform printing.
Generally, an electroconductive aqueous ink is used in an ink jet printer of a DOD type. Therefore, in a shearing mode type with no insulating film as shown in FIG. 15, the driving electrode 4 and the ink come into direct contact with each other, thus causing a short circuit of adjacent driving electrodes or the electrolysis of the ink itself. Hence, it is necessary to apply an insulating film 6 between the ink and a driving electrode 4 as a countermeasure to such short circuiting, as shown in FIG. 14.
It is necessary to connect an external driving circuit and the driving electrode 4 electrically in order to apply voltage to the driving electrode 4. Since high-density printing is performed in an ink jet printer, the layout of the above pressure chamber 1a becomes very minute, with approximately a 100 .mu.m pitch. Hence, wiring involves difficulties.
For example, Japanese Laid-Open Patent Publication No. 252750/1988 discloses a method of forming an electroconductive pattern on the upper surface of a piezoelectric base for wiring between a driving electrode and an IC (semiconductor integrated circuit) and from the IC to the exterior. In addition, Japanese Laid-Open Patent Publication No. 182133/1992 discloses a method of providing a shallow connection slot at the end part extended from a slot of a pressure chamber and joining an electrode in such connection slot and an electrode of a circuit base having a driving circuit with a copper foil wire. The driving electrode 4 achieves connection with the IC or copper foil wire electrically (generally at an end part opposite to the ink jetting side). For this, the electroconductive surface of the driving electrode usually must be exposed at a position where such connection is achieved. No insulating film is applied at a position not coming into contact with ink. Alternatively, wiring is conducted after partial removal of an ins
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Hiraishi Hisato
Ikeda Tomoo
Kigawa Keisuke
Nagashima Yoshiyuki
Uga Masayasu
Anderson L.
Citizen Watch Co. Ltd.
Fuller Benjamin R.
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