Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-05-30
2002-02-26
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06350017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a print head of an ink-jet printer, which has resistance against corrosion by ink, thus, reliability is improved, and a method of manufacturing the print head.
2. Description of the Related Art
One of well known printers is an ink-jet printer. The ink-jet printer has a print head in which multiple nozzles for outputting ink droplets to a recording sheet of paper or textile are disposed, thus, images and characters are printed thereon. The ink-jet printer has several merits, for example, quiet operation, no fixing treatment, and easy full-color printing.
There are some methods for outputting the ink droplets. Typical ones are piezoelectric ink-jet, thermal ink-jet, and the like.
The piezoelectric ink-jet printer uses electromechanical transducers such as piezoelectric elements which mechanically deform ink chambers to produce alteration in ink pressure. The pressure alteration causes output of ink droplets through minute nozzles.
The thermal ink-jet printer employs minute heating elements in firing chambers. The heating elements forms bubbles of vapor in the ink in very short periods when electric current applied to the heating elements. Expansion of the bubble pushes out an ink droplet through a nozzle. The thermal ink-jet print head is categorized into two types, side shooter and roof shooter. In the side shooter type head, a bubble generated by a heating element expands and pushes ink in the direction parallel to the heating element surface to output an ink droplet through a nozzle which is placed away from the heating element. On the contrary, the roof shooter type head features that nozzles are formed just above heating elements. A bubble generated by the heating element pushes out ink in the vertical direction to output an ink droplet through the nozzle. It has been known that required power consumption of the roof shooter type head is less than that of the side shooter type head.
A roof shooter type head comprises multiple (for example, 64, 128, or 256) heating elements, drive circuits which drive the heating elements individually, ink passages, and nozzles. During manufacturing process, the roof shooter type heads formed on a silicon wafer having diameter of equal to or larger than 6 inch (approx. 15.24 cm). The wafer has 90 or more blocks (approx. 10×15 mm each), and the heads are formed at once so that one head is formed in one block. At that time, silicon LSI formation technique or thin film formation technique is used to form the print heads to have monolithic structure.
FIG. 1A
is a plan view showing an ink output surface of a roof shooter type print head
1
for an ink-jet printer (hereinafter, referred to simply as print head
1
).
FIG. 1B
is an enlarged diagram showing an area indicated by a broken-line square “a” in FIG.
1
A.
FIG. 1C
is a cross sectional view along a line C-C′ in FIG.
1
B. In
FIG. 1B
, components under an orifice plate
14
are shown through it.
Drive circuits (not shown) are formed on a chip substrate
2
by LSI formation technique. A common ink supply groove (not shown) is formed on the chip substrate
2
by etching or the like. An insulation layer
3
(oxidized film) is formed on the chip substrate
2
on which the drive circuits and the common ink supply groove have been formed.
Plural lines (64, 128, or 256 lines) of heating resistor
4
is formed with thin film formation technique such as photolithography, between the drive circuits and the common ink supply groove. Further, common electrodes
6
and individual electrodes
7
for driving heating areas
5
on the heating resistor
4
are formed so that the heating area
5
of the heating resistor
4
are exposed. A set of one heating area
5
, one common electrode
6
, and one individual electrode
7
is a unit of one heating element.
The individual electrodes
7
are connected to electrode terminals of the drive circuits. A connection terminal
8
for connecting the common electrodes
6
to peripherals and another set of connection terminals
9
for connecting the drive circuits to peripherals are formed on the chip substrate
2
.
A wall material layer is deposited onto the chip substrate
2
except the portion where the connection terminals
8
and
9
are formed. Then photolithography is performed to pattern the wall material layer, thus a wall
11
is formed. The wall
11
determines an ink flow passage
13
.
The wall
11
includes comb like extensions
11
-
1
. The wall
11
and its extensions
11
-
1
surrounds three sides of each heating area
5
to separate them from each other. Separated spaces above the heating areas
5
are firing chambers
12
. Open side of each firing chamber
12
is connected to an ink flow passage
13
which is communicated with the common ink supply groove.
An orifice plate
14
is deposited onto the wall
11
. Multiple nozzles
15
are formed in the orifice plate
14
so that a set of the nozzles
15
forms a nozzle line
16
being along a line of the heating areas
5
. Thus, multiple print heads
1
are formed on the silicon wafer. The silicon wafer is finally diced so that chip substrates
2
each having the formed print head
1
thereon are separated from each other.
In the printer, ink is supplied to the firing chambers
12
via the common ink supply groove and the ink flow passage
13
. For printing, electric current is selectively applied to the heating areas
5
in accordance with print data. Upon reception of the electric current, the heating area
5
heats ink for a very short time period, thus a bubble of vapor is generated at bottom of the ink layer. The bubble expands and pushes out an ink droplet through the ink nozzle
15
above the heating area
5
. Size of the ink droplet is almost the same as that of the nozzle diameter when output. When the droplet reaches a sheet, it is broadened almost twice as large as the initial size.
Aluminum (Al) is a major material for electrodes such as the common electrode
6
and the individual electrode
7
because good conductivity is available with low cost. Since aluminum is amphoteric metal, it will be corroded gradually under ordinary acid or alkaline ink.
Gold (Au) is one of corrosion resistant material, therefore, it is suitable one for the common electrodes
6
and the individual electrodes
7
. However, Au is likely to cause migration which diffuses ink into boundary between electrodes
617
and the heating resistor
4
. This ink migration will separate the Au electrode from the heating resistor
4
eventually.
Such the corrosion of the electrodes
6
and
7
or separation of the electrodes from the heating resistor
4
will deteriorate print head performance, and the print head
1
will be broken eventually. Even if the electrodes
6
and
7
are not corroded by ink, humidity in the air causes the migration, therefore, the print head disorder may be prolonged but it will be also broken eventually.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink-jet printer head having resistance against corrosion and migration caused by ink, thus reliability is improved. It is another object of the present invention to provide a method for easy manufacture of a print head for an ink-jet printer having resistance against corrosion and migration caused by ink, thus reliability is improved.
An ink-jet printer head according to a first aspect of the present invention is an ink-jet printer head in which ink is pressed out in predetermined directions by vapor bubbles generated by heating the ink, the ink-jet printer head comprises:
an insulation substrate at least a surface thereof is an insulator;
a plurality of heating resistors which are formed on the insulation substrate, each of which has a heating area which emits heat when a predetermined voltage is applied thereto;
a pair of electrodes which is electrically connected to each of the heating areas;
a wall which is formed on the insulation substrate to determine an ink flow passage; and
a barrier layer, having resistance again
Casio Computer Co. Ltd.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Gordon Raquel Yvette
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