Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-07-19
2003-07-22
Nguyen, Thinh (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S094000
Reexamination Certificate
active
06595627
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inkjet printhead and a manufacturing method thereof, and more particularly, to a bubble-jet type inkjet printhead having improved structures of an ink chamber and ink channels, and a manufacturing method thereof.
2. Description of the Related Art
Ink ejection mechanisms of an inkjet printer are largely categorized into two types: an electro-thermal transducer type (bubble-jet type) in which a heat source is employed to form bubbles in ink to eject the ink, and an electromechanical transducer type in which ink is ejected by a change in ink volume due to deformation of a piezoelectric element.
According to a bubble growing direction and a droplet ejecting direction, electro-mechanical transducer types are classified into top-shooting, side-shooting, and back-shooting types. In a top-shooting type printhead, bubbles grow in the same direction that ink droplets are ejected. In a side-shooting type printhead, bubbles grow in a direction perpendicular to the direction that ink droplets are ejected. In a back-shooting type printhead, bubbles grow in a direction opposite to a direction in which ink droplets are ejected.
A bubble-jet type inkjet printhead needs to meet the following conditions. First, a simplified manufacturing process, a low manufacturing cost, and mass production must be allowed. Second, in order to produce high quality color images, creation of minute satellite droplets that trail ejected main droplets must be prevented. Third, when ink is ejected from one nozzle or an ink chamber is refilled with ink after the ink ejection, a cross-talk between the nozzle and its adjacent nozzle through ink which is not ejected, must be prevented. To this end, a back flow of ink, that is, a phenomenon that ink flows in an opposite direction to a normal ejection direction, must be avoided during the ink ejection. Fourth, for a high speed printing, a refill cycle after the ink ejection must be as short as possible. That is, an operating frequency must be high.
Considering the above conditions, the performance of an inkjet printhead is closely associated with structures of the ink chamber, ink channels, and a heater, the type of formation and expansion of bubbles, and the relative size of each component.
FIG. 1
is a schematic cross-sectional view of a conventional inkjet printhead disclosed in a U.S. Pat. No. 6,019,457.
Referring to
FIG. 1
, an ink chamber
15
having a hemispherical shape is formed in an upper portion of a substrate
10
made of silicon, etc., and an ink supply manifold
16
supplying the ink chamber
15
with ink is formed in a lower portion of the substrate
10
. An ink channel
13
communicating with the ink chamber
15
and the ink supply manifold
16
is formed between the ink chamber
15
and the ink supply manifold
16
.
A nozzle plate
20
having a nozzle
11
through which an ink droplet
16
is ejected, is disposed on a surface of the substrate
10
to form an upper wall of the ink chamber
15
. The nozzle plate
20
includes a thermal insulation layer
20
a
and a chemical vapor deposition (CVD) overcoat layer
20
b.
In the nozzle plate
20
, an annular heater
12
surrounding the nozzle
11
is formed in the vicinity of the nozzle
11
. The annular heater
12
is located at an interface between the thermal insulation layer
20
a
and the CVD overcoat layer
20
b
. Meanwhile, the heater
12
is connected to an electric line (now shown) through which a current pulse is supplied to the annular heater
12
.
In the above-described configuration, in a state that the ink chamber
15
is filled with ink supplied through the manifold
16
and the ink channel
13
, if the current pulse is supplied to the annular heater
12
, heat generated by the annular heater
12
is transmitted through the underlying thermal insulation layer
20
a
, and the ink under the heater
12
is boiled to form a bubble B. Thereafter, as the heat is continuously generated from the annular heater
12
so that the bubble B expands, a pressure is applied to the ink contained in the ink chamber
15
, and the ink around the nozzle
11
is ejected in a form of an ink droplet
18
through the nozzle
11
. Then, new ink is introduced through the ink channel
13
to refill the ink chamber
15
.
In the conventional inkjet printhead, since the ink chamber
15
has the hemispherical shape and is formed on the substrate
10
by isotropically etching, the degree of accuracy and reproducibility of the inkjet printhead deteriorates when the ink chamber
15
is manufactured. Also, the amount of ink contained in the ink chamber
15
is relatively small in view of a volume of the ink chamber
15
. Also, the hemispherical ink chamber
15
is configured such that the ink may be easily ejected to the ink channel
13
in a case where the ink around the annular heater
12
is pushed away by a bubble pressure.: caused when the bubble B is formed. When the ink is ejected, and when the bubble B is contracted, it is difficult to smoothly refill the ink chamber
15
with the new ink.
Although the ink channel and the nozzle are aligned to make an ink flowing direction substantially linear, a problem occurring in the aforementioned conventional inkjet printhead is that the ink flow is not smooth during the ink ejection. This results in undesirable frequency characteristics of the inkjet printhead.
Since only a single ink channel is formed for each ink chamber, it is difficult to adjust a transferring amount of ink passing through the ink channel. A manufacturing process of such an ink channel is also complicated.
SUMMARY OF THE INVENTION.
To solve the above and other problems, it is an object of the present invention to provide a bubble-jet type inkjet printhead having improved structures of an ink chamber and an ink channel to improve an ejection performance.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above and other objects according to an embodiments of the present invention, there is provided an inkjet printhead including a substrate, a substantially cylindrical ink chamber formed in an upper portion of the substrate to store ink to be ejected, a manifold supplying ink to the ink chamber and formed in a bottom portion of the substrate, a channel-forming layer disposed between the ink chamber and the manifold and having an ink channel communicating between the ink chamber and the manifold, a nozzle plate stacked on a top surface of the upper portion of the substrate and having a nozzle at a location corresponding to a central portion of the ink chamber, a heater formed to surround the nozzle of the nozzle plate, and electrodes electrically connected to the heater to supply current to the heater.
Here, the inkjet printhead,may include a nozzle guide formed on a periphery of the nozzle to extend toward the ink chamber.
Also, according to an aspect of the present invention, a plurality of ink channels are formed in the ink chamber at equal, intervals along a circumference having a predetermined radius.
The channel-forming layer may include a first material layer forming a bottom of the ink chamber. Here, the first material layer is a silicon oxide material layer. The channel-forming layer may further include a second material layer formed on the first material layer as a buffer layer of the first material layer. The second material layer is a polycrystalline silicon layer.
In accordance with another aspect of the present invention, there is provided a method of manufacturing an inkjet printhead. The method includes forming a nozzle plate on the a surface of a substrate, forming a heater on the nozzle plate, forming electrodes electrically connected to the heater on the nozzle plate, forming a nozzle by etching the nozzle plate, forming a manifold by etching the bottom portion of the substrate by a predetermined depth, forming a channel-forming la
Cho Seo-hyun
Jung Myung-song
Min Jae-sik
Park Sung-joon
Nguyen Thinh
Staas & Halsey , LLP
Stephens Juanita
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