Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-29
2002-05-14
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06386685
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording method which are applied to an ink jet printer, particularly a bubble jet printer using bubbling phenomena, and the like.
2. Related Background Art
A bubble jet recording method is a recording method in which ink in a liquid path is locally heated to a high temperature by heating means to bubble the ink, pushing the ink out of a discharge port by a high pressure generated during bubbling, and allowing the ink to be deposited to a recording medium such as a recording paper and the like. A recording head applied to a bubble jet recording method generally includes fine structures such as a discharge port, a liquid path, heating means provided at a portion of the liquid path and used as an ink discharge energy generation portion, and the like.
In such bubble jet recording methods, as an ink jet recording head which discharges ink from discharge ports provided in a matrix in accordance with heating means, with heating means arranged longitudinally and transversely in a matrix in plural numbers, Japanese Patent Application Laid-Open No. 64-20151 discloses an ink jet recording head which disposes a plurality of longitudinal wiring and transverse wiring on a substrate, and includes a rectifying device through which an electric current is flowed only when a forward voltage is applied and an electric current is not flowed by the application of reverse voltage, and a heating resistor used as heating means connected to the rectifying device on the crossing portions of the longitudinal wiring and the transverse wiring. In this ink jet recording head, a voltage is applied to any of longitudinal wiring and any of transverse wiring to apply a forward voltage to a heating resistor on the crossing portion of the longitudinal wiring and the transverse wiring, so that this heating resistor is driven. In this case, to other heating resistors is flowed no electric current while keeping states where no voltage is applied thereto, or a reverse voltage is applied thereto. Thus, a predetermined heating resistor of a plurality of heating resistors is driven.
Further, Japanese Patent Application Laid-Open No. 57-36679 discloses an ink jet recording head in which a diode, which is heated by the energization of forward current and which a reverse current cannot be energized, is used as heating means, and these diodes are arranged in a matrix in the plural numbers on a substrate.
Further, in an ink jet recording head, an about 0.05 &mgr;m thick tantalum nitride (Ta
x
N
y
) thin-film resistor is usually used as heating means, and ink is heated and bubbled by the Joule heat generated when electric current is energized through this thin-film resistor. On such a thin-film resistor is usually provided an about 0.2 &mgr;m thick cavitation-resisting layer composed of a metal such as Ta or the like through an about 0.8 &mgr;m thick insulator of SiN or the like, to prevent damage of the surface of the thin-film resistor due to cavitation. As a method of forming the cavitation-resisting layer, a method of laminating three protective layers on a heating resistor, and the like have been proposed (refer to Japanese Patent Application Laid-Open No. 5-301345 and the like).
To make high definition images recordable by an ink jet recording method, a technique of discharging as minute an ink droplet as possible with high density is required. For the sake of this, it is basically important to form a fine liquid path and fine heating means.
As a method of forming such fine structures, a method of producing a high density recording head using the photolithography technology has been proposed, which utilizes the simplicity of the recording head structure in a bubble jet recording method (refer to Japanese Patent Application Laid-Open No. 8-156269 and the like).
Further, as a method of discharging a minute or fine ink droplet, the method using heating means having the heat value larger at the center portion compared to that in the edge portions has been proposed (refer to Japanese Patent Application Laid-Open No. 62-201254).
In a conventional ink jet recording head, when a plurality of heating means are selectively driven, a noise voltage is applied to non-selected heating means to waste energy and affect the driving voltage thereby to change the discharging amount of ink and possibly affect recording images. Particularly, in an ink jet recording head, in which a voltage is applied to a plurality of longitudinal wiring and a plurality of transverse wiring so that heating means provided in a matrix on the crossing of the longitudinal wiring and the transverse wiring are selectively driven, a voltage lower than the driving voltage is possibly applied to non-selected heating means, and when this voltage is applied in the forward direction, non-required heat is generated in non-selected heating means.
When a cavitation-resisting layer is provided on a heating resistor, the heating resistor indirectly contacts ink through the cavitation-resisting layer, and the cavitation-resisting layer prevents the heat transfer to the ink, whereby the heat is difficult to transfer to the ink. Thus, the application of electric energy is further required compared to a case where a cavitation-resisting layer is not provided, and the consumption electric power may be increased.
On the other hand, another method is known, in which a cavitation-resisting layer is not provided and a layer itself composed of a metal having the cavitation-resisting properties is used as a heating resistor. However, since the specific resistance of the metal having the cavitation-resisting properties is usually low (for example, the specific resistance of Ta is 2×10
−6
&OHgr;cm), when this metal film thickness is increased, the area of a conducting path is increased and the resistance is excessively reduced, whereby the function of the heating resistor is not effected. Therefore, in a method in which a layer itself composed of a metal having the cavitation-resisting properties is used as a heating resistor, to use the metal layer having a sufficiently increased film thickness is difficult.
Further, when a cavitation-resisting layer having a decreased film thickness is formed to improved the heat transfer, the functions of a heating resistor are possibly lost by the generation of a pin-hole due to cavitation or the like.
Further, in a case where the size of a heater is decreased to allow a fine ink droplet to discharge, when the heater portion and the wiring portion connected to the heater are miniaturized in the same ratio as the heater is miniaturized, an increase of the wiring resistance is invited. Thus, the miniaturization of the heater portion and the like has limitations.
Further, although the photolithography technology is excellent in the working precision, it is inferior in a mass production. On the contrary, although the printing technology is advantageous in a mass production, it is inferior in the working precision. That is, when a heater or the like is finely formed for the purpose of discharging a minute liquid droplet, it is difficult to satisfy both of the precision and mass productivity.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an ink jet recording head providing heating means which does not generate non-required heat even though a voltage such as a noise voltage lower than the driving voltage is applied to the heating means.
Further, another object of the present invention is to provide an ink jet recording head which has a resistance to cavitation and has a small consumption electric power.
Still another object of the present invention is to provide a liquid discharge device which can heat a minute spot-shaped area even when a heater film area cannot be formed in a sufficiently small size, and can discharge a minute liquid droplet, and is to provide an ink jet recording head and an ink jet apparatus, which have this liquid discharge device and can perform high precision rec
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