Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-12-17
2003-05-13
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S063000
Reexamination Certificate
active
06561625
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet printhead. More particularly, the present invention relates to a bubble-jet type ink-jet printhead having a hemispherical ink chamber and a manufacturing method thereof.
2. Description of the Related Art
Ink-jet printing heads are devices for printing a predetermined color image by ejecting small droplets of printing ink at desired positions on a recording sheet. Ink ejection mechanisms of an ink-jet printer are generally categorized into two types: an electro-thermal transducer type (bubble-jet type), in which a heat source is employed to form a bubble in ink causing an ink droplet to be ejected, and an electromechanical transducer type, in which a piezoelectric crystal bends to change the volume of ink causing an ink droplet to be expelled.
FIG. 1A
is a cross-sectional, perspective view showing an example of the structure of a conventional bubble-jet type ink-jet printhead as disclosed in U.S. Pat. No. 4,882,595.
FIG. 1B
is a cross-sectional view illustrating a process of ejecting an ink droplet from the printhead of FIG.
1
A. The conventional bubblejet type ink-jet printhead shown in
FIGS. 1A and 1B
includes a substrate
10
, a barrier wall
12
disposed on the substrate
10
for forming an ink chamber
13
filled with ink
19
, a heater
14
disposed in the ink chamber
13
, and a nozzle plate
11
having a nozzle
16
for ejecting an ink droplet
19
′. The ink
19
is introduced into the ink chamber
13
through an ink feed channel
15
, and the ink
19
fills the nozzle
16
connected to the ink chamber
13
by capillary action. In a printhead of the current configuration, if current is supplied to the heater
14
, the heater
14
generates heat to form a bubble
18
in the ink
19
within the ink chamber
13
. The bubble
18
expands to exert pressure on the ink
19
present in the ink chamber
13
, which causes an ink droplet
19
′ to be expelled through the nozzle
16
. Then, ink
19
is introduced through the ink feed channel
15
to refill the ink chamber
13
.
There are multiple factors and parameters to consider in making an ink-jet printhead having a bubble-jet type ink ejector. First, it should be simple to manufacture, have a low manufacturing cost, and be capable of being mass-produced. Second, in order to produce high quality color images, the formation of minute, undesirable satellite ink droplets that usually trail an ejected main ink droplet must be avoided. Third, when ink is ejected from one nozzle or when ink refills an ink chamber after ink ejection, cross-talk with adjacent nozzles, from which no ink is ejected, must also be avoided. To this end, a backflow of ink in a direction opposite to the direction ink is ejected from a nozzle must be prevented during ink ejection. Fourth, for high speed printing, a cycle beginning with ink ejection and ending with ink refill in the ink channel must be carried out in as short a period of time as possible. That is, an operating frequency must be high. Fifth, the printhead needs to have a small thermal load imposed due to heat generated by a heater and the printhead should operate stably for long periods of time at high operating frequencies.
The above requirements, however, tend to conflict with one another. Furthermore, the performance of an ink-jet printhead is closely associated with and affected by the structure and design of an ink chamber, an ink channel, and a heater, as well as by the type of formation and expansion of bubbles, and the relative size of each component.
In an effort to overcome problems related to the above requirements, ink-jet printheads having a variety of structures have been proposed in U.S. Pat. Nos. 4,339,762; 5,760,804; 4,847,630; and 5,850,241 in addition to the above-referenced U.S. Pat. No. 4,882,595; European Patent No. 317,171; and Fan-Gang Tseng, Chang-Jin Kim, and Chih-Ming Ho, “A Novel Microinjector with Virtual Chamber Neck,” IEEE MEMS '98, pp. 57-62. However, ink-jet printheads proposed in the above-mentioned patents and publication may satisfy some of the aforementioned requirements but do not completely provide an improved ink-jet printing approach.
FIG. 2
illustrates a back-shooting type ink ejector of another example of a conventional bubble-jet type ink-jet printhead, as disclosed in IEEE MEMS '98, pp. 57-62. In this configuration, a back-shooting technique refers to an ink ejection mechanism in which an ink droplet is ejected in a direction opposite to the direction in which a bubble expands.
As shown in
FIG. 2
, in the back-shooting type printhead, a heater
24
is disposed around a nozzle
26
formed in a nozzle plate
21
. The heater
24
is connected to an electrode (not shown) for applying current and is protected by a protective layer
27
of a predetermined material formed on the nozzle plate
21
. The nozzle plate
21
is formed on a substrate
20
and an ink chamber
23
is formed for each nozzle
26
in the substrate
20
. The ink chamber
23
is in flow communication with an ink channel
25
and is filled with ink
29
. The protective layer
27
for protecting the heater
24
is coated with an anti-wetting layer
30
, thereby repelling the ink
29
. In the ink ejector configured as described above, if current is applied across the heater
24
, the heater
24
generates heat to form a bubble
28
within the ink
29
, thereby filling the ink chamber
23
. Then, the bubble
28
continues to expand by the heat supplied from the heater
24
and exerts pressure on the ink
29
within the ink chamber
23
, thus causing the ink
29
near the nozzle
26
to be ejected through the nozzle
26
in the form of an ink droplet
29
′. Then, ink
29
is absorbed through the ink channel
25
to refill the ink chamber
23
.
However, the conventional back-shooting type ink-jet printhead has a problem in that a significant percentage of heat generated by the heater
24
is conducted and absorbed into portions other than the ink
29
, such as the anti-wetting layer
30
and the protective layer
27
near the nozzle
26
. It is desirable that the heat generated by the heater be used for boiling the ink
29
and forming the bubbles
28
. However, a significant amount of heat is absorbed into other portions and the remainder of heat is actually used for forming the bubbles
28
, thereby wasting energy supplied to form the bubble
28
and consequently degrading energy efficiency. This also increases the period from formation to collapse of the bubble
28
. Thus, it is difficult to operate the ink-jet printerhead at a high frequency.
Furthermore, the heat conducted to other portions significantly increases the temperature of the overall printhead as a print cycle runs thereby making long-time stable operation of the printhead difficult due to significant thermal problems. For example, the heat produced by the heater is easily conducted to the surface near the nozzle
26
to increase the temperature of that portion excessively, thereby burning the anti-wetting layer
30
near the nozzle
26
and changing the physical properties of the anti-wetting layer
30
.
SUMMARY OF THE INVENTION
In an effort to solve the above problems, it is a feature of an embodiment of the present invention to provide a bubble-jet type ink-jet printhead with a structure that satisfies the above-mentioned requirements and has an adiabatic layer disposed around a heater so that energy supplied to the heater for bubble formation may be effectively used, as well as provide a manufacturing method thereof.
Accordingly, an embodiment of the present invention provides a bubble-jet type inkjet printhead including: a substrate integrally having a manifold for supplying ink, an ink chamber filled with ink to be ejected, and an ink channel for supplying ink from the manifold to the ink chamber; a nozzle plate on the substrate, the nozzle plate having a nozzle through which ink is ejected at a location corresponding to a central portion of the ink chamber; a heater formed in an annular sha
Kim Hyeon-cheol
Kuk Keon
Lee Sang-wook
Maeng Doo-jin
Oh Yong-soo
Barlow John
Lee & Sterba, P.C.
Samsung Electronics Co,. Ltd.
Stephens Juanita
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