Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-03-27
2003-07-22
Nguyen, Thinh (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S063000
Reexamination Certificate
active
06595622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid ejecting apparatus to be used in, for example, an ink jet recording head of an ink jet printer for recording an image by shooting ink droplets and, in particular, to a liquid ejecting apparatus which is of high accuracy and which is capable of forming a high quality image through high accuracy shooting of ink droplets and achieving an improvement in terms of yield. The present invention also relates to an ink jet printer using such a liquid ejecting apparatus.
2. Description of the Related Art
A thermal ink jet, which rapidly vaporizes a portion of ink through heating by a heater and causes ink droplets to be ejected through nozzles (orifices) by its expansion force or the like, is utilized in various types of printers (See JP 48-9622 A, JP 54-51837 A, etc.).
Apart from this, a printer is known which utilizes an electrostatic ink jet in which an oscillation plate is caused to oscillate by an MEM (micro electronic machine) utilizing static electricity, ejecting ink droplets through nozzles by the energy thereof (See JP 11-309850 A, etc.).
Of those,
FIGS. 7A and 7B
schematically show an example of a thermal ink jet recording head.
FIG. 7A
is a plan view of an ink jet recording head as seen from the ink ejecting direction, and
FIG. 7B
is a sectional view taken along the line IV—IV of FIG.
7
A.
As shown in
FIG. 7A
, in a recording head
150
, a large number of nozzles
20
for ejecting ink are arranged in one direction (in
FIG. 7B
, in a direction perpendicular to the plane of the drawing). In the example shown, the nozzles
20
are arranged in two rows (hereinafter referred to as nozzle rows), thereby increasing the nozzle density.
In this recording head
150
, there are directly formed on the surface of a semiconductor substrate such as an Si (silicon) substrate
152
heaters (not shown) corresponding to the individual nozzles
20
and serving as ink ejecting devices, a driving LSI
14
for driving each heater, a partition
15
forming ink flow passages to the nozzles
20
, etc. The nozzles (orifices)
20
are formed in an orifice plate
22
laminated/glued to the Si substrate
152
(partition
15
).
Further, formed in the silicon substrate
152
of the recording head
150
are an ink groove
16
for supplying ink to the ink flow passages and ink supply holes
18
for supplying ink to the ink groove
16
. The ink groove
16
is formed by digging the surface of the silicon substrate
152
and extends in the nozzle row direction. The ink supply holes
18
, which make the back side of the Si substrate
152
communicate with the ink groove
16
, are formed and arranged at predetermined intervals in the nozzle row direction.
In the recording head
150
, ink is supplied to the ink supply holes
18
from the back side of the Si substrate
152
and introduced into the ink groove
16
communicating therewith. From the ink groove
16
, the ink flows through the ink passages formed by the partition
15
and leading to the nozzles
20
before it is ejected through the nozzles
20
by being heated by the heaters.
Usually, this recording head
150
is not handled in the form of an Si chip (semiconductor chip) based on the Si substrate
152
; it is glued (mounted) to a frame
24
and attached, for example, to a head unit (e.g., a so-called cartridge) of an ink jet printer.
Further, formed in the frame
24
is an ink flow passage
26
for supplying ink from an ink tank of the head unit to the ink supply holes
18
of the recording head
150
.
In the recording head
150
(including not only the thermal ink jet shown but also the above-mentioned electrostatic type), in which ink ejecting devices such as heaters are formed in the Si substrate
152
, one of the factors leading to a deterioration in product accuracy and yield is warpage (curving) of the recording head
150
(Si substrate
152
).
Such warpage naturally leads to positional error of the nozzles
20
, i.e., a deterioration in image quality. In extreme cases, the product becomes defective (NG). When the recording head
150
is elongated, this warpage is aggravated and the relative mechanical strength of the head deteriorates, with the result that the above problem becomes more serious.
Various attempts have been made to overcome the problem of such warpage. For example, provision of a reinforcing layer (counter layer) on the back side of the Si substrate
152
and reconsideration of the material of the orifice plate
22
have been proposed. However, no sufficient effect has been achieved yet.
It might be possible to eliminate such warpage of the recording head
150
by mounting to the frame
24
the recording head
150
in a straight state by using a strong adhesive. However, that would make it necessary to keep the recording head
150
in a pressed state until the adhesive cures completely, which is very disadvantageous in terms of productivity and operability. Further, it would be very difficult to straighten the recording head
150
in a stable manner. Moreover, such a method involves application of an excessive force to the recording head
150
, so that, in many cases, the method will lead to breakage of the recording head
150
instead of straightening it.
According to this method however, even if the recording head
150
can be straightened well, when the strength is reduced due to secular changes, the recording head
150
may be warped again or be broken because of the residual stress being applied, whereupon the service life of the recording head
150
may be shortened.
SUMMARY OF THE INVENTION
The present invention has been made with a view toward solving the above problem in the prior art. It is an object of the present invention to provide a liquid ejecting apparatus for use in an ink jet recording head or the like in which liquid ejecting devices such as heaters and MEMs are formed on an Si (silicon) substrate prepared by using, for example, a semiconductor manufacturing technique, in which little warpage is involved, which has a long service life and wherein it is possible to obtain a high accuracy product with high yield even in the case where the apparatus has a line structure with a long nozzle row.
Another object of the present invention is to provide an ink jet printer using the liquid ejecting apparatus as an ink jet recording head.
In order to attain the object described above, the first aspect of the present invention provides a liquid ejecting apparatus comprising: a plurality of liquid ejecting devices which are arranged in one direction on a silicon substrate; and a plurality of liquid ejecting nozzles which are arranged in correspondence with the plurality of liquid ejecting devices, wherein at least part of the silicon substrate has a thickness of not less than 700 &mgr;m.
Preferably, the at least part of the silicon substrate which has the thickness of not less than 700 &mgr;m is positioned along the one direction in which the plurality of liquid ejecting devices are arranged.
Preferably, the silicon substrate has a portion of which the thickness is continuously not less than 700 &mgr;m from end to end in the one direction in which the plurality of liquid ejecting devices are arranged.
Preferably, the plurality of liquid ejecting devices form a length of not less than 10 mm in the one direction in which the plurality of liquid ejecting devices are arranged.
Preferably, a liquid is ejected in a direction substantially perpendicular to a surface of the silicon substrate.
Preferably, the liquid ejecting apparatus is an ink jet recording head.
Preferably, the silicon substrate has a length of not less than 10 mm in the one direction in which the plurality of liquid ejecting devices are arranged.
Preferably, the plurality of liquid ejecting nozzles have a nozzle density of 600 nozzles/inch or more.
Preferably, the silicon substrate has an aspect ratio of 2 to 20 in terms of a ratio of length to width.
In order to attain the object described above, the second aspect of the present invention provides an ink jet pr
Nguyen Thinh
Stephens Juanita
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