Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-09-25
2003-12-16
Stephens, Juanita (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06663228
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a base board for forming an ink-jet head (hereinafter, it may be referred to “head” for simplicity) which prints letters, signs, images, or the like on recording medium such as paper, plastic sheet, fabric, ordinary objects, and the like, by ejecting functional liquid, for example, ink, onto the recording medium. It also relates to an ink-jet head comprising such a base board, a recording unit, for example, an ink-jet pen, comprising an ink storage portion for storing the ink supplied to such an ink-jet head, and an ink-jet apparatus in which such an ink-jet head is installed.
There are various configuration for a recording unit, such as an ink-jet pen, in accordance with the present invention. One of such configurations is a cartridge. A cartridge may comprise an integral or independent combination of an ink-jet head and an ink storing portion. An ink-jet recording unit is structured so that it can be removably mounted on a carrying means, and as a carriage, on the main assembly side of an image forming apparatus.
An ink-jet apparatus with which the present invention is compatible includes a copying apparatus combined with an information reading device or the like, a facsimile apparatus enabled to send or receive information, a machine for printing on fabric, and the like, in addition to an ink-jet apparatus integrated, as an output terminal, with an information processing device such as a word processor, a computer, or the like.
Ink-jet recording apparatuses are distinctive in that they can print highly precise images at a high speed by ejecting ink in the form of a microscopic droplet from orifices. Recently, such ink-jet recording apparatuses that employ electrothermal transducers, which have a portion formed of exothermic resistant material, as a means for generating the energy used for ejecting ink, and that use the bubbling, that is, boiling, or ink caused by the thermal energy generated by the electrothermal transducers, have been attracting attention, because they are particularly suitable for forming high precision images, are capable of recording at a high speed, and make it possible to reduce in size, and/or colorize a recording head as well as a recording apparatus (for example, those disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796).
Generally, a head used for ink-jet recording comprises: a plurality of ejection orifices; a plurality of ink paths leading to the ejection orifices one for one; and a plurality of electrothermal transducers for generating the thermal energy used for ejecting ink. Each electrothermal transducer has an exothermic resistant portion and electrodes, and is coated with electrically insulative film so that it is insulated from the others. Each ink path is connected to a common liquid chamber, at the side opposite to the ejection orifice. In the common liquid chamber, the ink supplied from an ink container as an ink holding portion is stored. After being supplied into the common liquid chamber, ink is led into each of the ink paths, and is retained therein, forming a meniscus adjacent to the outward edge of the ejection orifices. While the head is in this state, the thermal energy generated by selectively driving the electrothermal transducers is used to suddenly heat the ink in contact with the surface of the driven electrothermal transducer to boil the ink. As the ink boils, or the state of the ink changes from liquid to gas, pressure is generated, and ink is ejected by this pressure.
When ink is ejected, the portion of the ink-jet head, which thermally interacts with ink, is subjected to not only the intense heat generated by the exothermic resistant material, but also the shocks (cavitation shocks) caused by the formation and collapsing of ink bubbles. Also, it is chemically affected by the ink itself. In other words, it is subjected to the compound effects of those factors.
Thus, this thermally interactive portion of the ink-jet head is generally covered with a top portion protecting layer for protecting the electrothermal transducer from the cavitation shocks, and also for preventing ink from chemically affecting the electrothermal transducer.
Next, referring to
FIG. 3
, the generation and collapse of a bubble on the aforementioned thermally interactive portion, and the related matters, will be described in detail.
A curved line (a) in
FIG. 3
shows the change in the surface temperature of the top portion protecting layer, which began the moment a voltage Vop (pulse), which was 1.3× Vth (Vth is the threshold voltage at which ink began boiling) in amplitude, 6 kHz in driving frequency, and 5 &mgr;sec in pulse width, was applied to a heat generating member (exothermic resistant member). A curved line (b) in
FIG. 3
shows the growth of the generated bubble, which began the moment the voltage was applied to the heat generating member. As the curved line (a) shows, the temperature began to rise after the application of the voltage, and reached its peak slightly after the end of the pulse with a predetermined duration (it took a short time for the heat from the heat generating member to reach the top portion protecting layer). After reaching its peak, it began to fall due to heat dissipation. On the other hand, as shown by the curved line (b), the bubble began to grow when the temperature of the top portion protecting layer reached approximately 300° C., and began collapsing after reaching its maximum size. In an actual operation, the above described process was repeated in the head. The surface temperature of the top portion protecting layer reached nearly 600° C., for example, as the bubble grew. In other words, it is evident from
FIG. 3
how high the level was of the temperature at which ink-jet recording was carried out.
The top portion protecting layer which comes into contact with ink is required to be superior in heat resistance, mechanical strength, chemical stability, oxidization resistance, alkali resistance, and the like properties. As to the material for the top portion protecting layer, precious metals, transition metals with a high melting point, their alloys, nitride, boride, silicide, carbide, amorphous silicon, and the like have been known.
For example, Laid-Open Japanese Patent No. 145158/1990 proposes a recording head superior in durability and reliability, which is realized by placing a top layer formed of Mx (Fe
100−y−x
Ni
y
Cr
z
)
100−x
(M stands for one or more elements selected from among Ti, Zr, Hf, Hb, Ta, and W; and x, y and z stand for atom percentages (at. %) in a range of 20-70 at. %, a range of 5-30 at. %, and a range of 10-30 at. %, correspondingly), of the insulative layer which is on the exothermic resistance layer.
In recent years, demands have been increasing for further improvement of an ink-jet recording apparatus in terms of image quality and recording speed, and in order to realize an ink-jet recording apparatus which satisfies these demands, various attempts have been made to improve an ink-jet recording apparatus in many aspects, for example, the head structure, and also to improve the ink itself.
FIG. 2
illustrates an example of the structure of a base board, that is, one of the portions which make up an ink-jet head.
In the base board illustrated in FIG.
2
(
a
), a protective layer
2006
and a top portion protecting layer
2007
are accumulated on an electrothermal transducer which is made up of an exothermic resistance layer
2004
and an electrode layer
2005
. The base board illustrated in FIG.
2
(
b
) is a version of the base board illustrated in FIG.
2
(
a
), in which the protective layer has been improved. More specifically, the protective layer of the base board illustrated in FIG.
2
(
b
) has been divided into two sub-layers so that the thermal energy from the exothermic resistant layer
2004
acts more effectively upon ink at a thermally interactive portion
2008
. Further, the thickness of the protective layer has been reduced, below the thermally interactive portion
2008
. When
Kubota Masahiko
Mochizuki Muga
Ogawa Masahiko
Ozaki Teruo
Saito Ichiro
Canon Kabushiki Kaisha
Stephens Juanita
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