Ink recording apparatus provided with shutter

An ink recording apparatus used with printers or the like and manufactured by applying semiconductor device manufacturing techniques. One wall of an ink chamber is formed of a single-crystal substrate and an ink jet port is formed by etching on the single-crystal substrate. A shutter and electrodes composed of polycrystalline-silicon film are formed on the single-crystal substrate by film forming in the LPCVD method and patterning through plasma etching. A front wall is formed by coating the shutter and electrodes further with a polycrystalline-silicon film. The shutter is movable between the wall surface of the ink chamber and the front wall, being driven through electrostatic attracting force produced between voltage-applied electrodes and the shutter. The electrodes are formed at positions corresponding to those where the shutter blocks the ink jet port and releases the same.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
The present invention relates to an ink recording apparatus for use in 
printers or the like. It is to be noted that the word `recording` herein 
used refers to the fact that any desired patterns of characters, symbols, 
or the like are written down onto a printed material such as paper with 
ink jetted out by an apparatus of the present invention. 
2. Description of the Related Art 
A conventional ink recording apparatus is shown in the Japanese magazine 
"Nikkei Mechanical", issued on May 29, 1989, pp. 90 to 91, the apparatus 
exemplifying such ink recording apparatus that are currently used in 
printers featuring compactness suitable for office or personal use 
thereof. 
FIG. 10 shows a construction of such a conventional ink recording 
apparatus. In the figure, a slit plate 1 is provided with a plurality of 
slits 2 having a width of 50 .mu.m and a length of 8 mm in place of 
nozzles. The slit plate 1 has also a plurality of auxiliary holes 3 equal 
in number to a plurality of heating elements 5 formed on a base plate 4, 
with an ink reservoir 6 as well provided on the slit plate. On the base 
plate 4 there are formed a plurality of electrodes 7 in correspondence to 
the heating elements 5 and moreover a plurality of fluid resistance 
elements 8 shaped into a long, narrow protrusion. Besides, between the 
slit plate 1 and the base plate 4 there is disposed a spacer 9, which in 
conjunction with the slit plate 1 and base plate 4 defines a portion 
serving as an ink chamber 11 illustrated in FIGS. 11a to 11d. Under the 
base plate 4 there is provided an ink tank 10, whereon all the units are 
piled up to make up a head. The heating elements 5 are formed by piling up 
a glass layer, resistors, electrodes, and a protective coat on the base 
plate 4, as in a common thermal head. 
A conventional ink recording apparatus having a construction as described 
above will jet ink droplets while carrying out steps as shown in FIGS. 11a 
to 11d. Each step is detailed below: 
(a) First, when pulse voltage is applied to the heating elements 5 on the 
base plate 4 to heat the ink contained in the ink chamber 11, the ink in 
the vicinity of the heating elements 5 vaporizes to make a large number of 
small bubbles 12; 
(b) Second, the small bubbles 12 merge together and grow into a larger 
bubble 13 that overcomes the surface tension, causing ink swells to be 
produced at the slits 2; 
(c) Third, when the heating elements 5, on completion of heating, are 
cooled down to stop the bubble 13 from being produced, the swelling of ink 
is intercepted to produce ink droplets 14; and 
(d) Finally, the ink droplets 14 are jetted out through the slits 2 by the 
power of growing bubble 13. 
If a number of heating elements 5 share the slits 2 and the ink chamber 11 
with one another as in the above conventional apparatus, there arises a 
problem that the ink droplets 14 derived from adjoining heating elements 5 
may interfere with each other. In the conventional apparatus, however, the 
fluid resistance elements 8 provided between adjoining heating elements 5, 
5, as shown in FIG. 10, will serve to prevent pressure waves from being 
horizontally propagated while the bubbles are being produced, thereby 
allowing the ink droplets 14 to be formed and jetted out without being 
adversely affected by such pressure waves. Furthermore, the auxiliary 
holes 3 provided to the slit plate 1 will absorb the pressure waves, so 
that pressure waves may be prevented also from being reflected. 
In the conventional apparatus arranged as described above, however, even if 
no problems occur during the recording operation thereof, the apparatus 
may have some problems if left out of recording operation in a long 
period, such as dried and solidified ink at some slits 2 or dust 
aggression from outside, which is likely to cause some recording failure 
or head damage. 
SUMMARY OF THE INVENTION 
The present invention has been accomplished to effectively solve the 
above-described technical problems and, accordingly, an essential object 
of the present invention is to provide an ink recording apparatus which 
can prevent ink from drying and also can prevent external contaminations 
of dust and, even when left unused for a long time period, and which is 
free of any recording failure or head damage. 
Another important object of the present invention is to provide an ink 
recording apparatus which is internally protected from any touch of an 
operator's hands or fingers, thereby being highly reliable in its 
performance. 
In accomplishing these and other objects, according to one preferred 
embodiment of the present invention, there are provided an ink chamber for 
being filled with ink, an ink jet port provided in the ink chamber, a 
shutter formed of a thin film and provided in the vicinity of the ink jet 
port and movable between a shut-off position for shutting off the ink 
passing through the ink jet port and a passing position for allowing the 
ink to pass therethrough, and shutter driving means for not only driving 
the shutter but also holding the shutter in the shut-off position while 
the apparatus is out of recording operation, the shutter driving means 
having electrodes provided in correspondence to each of the shut-off 
position and passing position for the shutter, a power supply for applying 
voltage to the electrodes, and a control circuit, whereby the shutter is 
driven by virtue of electrostatic attracting force acting between the 
surfaces of the electrodes and the surface of said shutter. 
With the above-mentioned arrangement of the first embodiment of the ink 
recording apparatus according to the invention, the shutter disposed in 
the vicinity of the ink jet port is held in the shut-off position while 
the apparatus is out of recording operation. Thus the shutter can prevent 
ink from drying and also avoid contamination by any foreign matter from 
outside the apparatus and, even if the apparatus is left unused for a long 
period, keeping it free of any recording failure or head damage. 
According to another preferred embodiment of the present invention, there 
are provided an ink chamber for being filled with ink, an ink jet port 
provided in the ink chamber, a shutter formed of a thin film and provided 
outside of the ink chamber and also in the vicinity of the ink jet port 
and movable between a shut-off position for shutting off the ink passing 
through the ink jet port and a passing position for allowing the ink to 
pass therethrough, shutter driving means for not only driving the shutter 
but also holding the shutter in the shut-off position while the apparatus 
is out of recording operation, the shutter driving means having electrodes 
provided in correspondence to each of the shut-off position and passing 
position for the shutter, a power supply for applying voltage to the 
electrodes, and a control circuit, whereby the shutter is driven by virtue 
of electrostatic attracting force acting between the surfaces of the 
electrodes and the surface of said shutter and a wall formed of a thin 
film and disposed outside of the shutter for covering the external surface 
of the shutter. 
With the above-mentioned arrangement of the second embodiment of the ink 
recording apparatus according to the invention, the following operational 
effects can be obtained in addition to those of the ink recording 
apparatus of the first embodiment. That is, even if the shutter is subject 
to ink pressure in its shut-off position, the wall disposed on the rear 
side thereof supports the shutter to prevent the shutter from being 
deformed. The wall also prevents the internal structure of the apparatus 
including the shutter from being touched by hands, fingers, or other 
foreign matters from outside the apparatus, thus enhancing the reliability 
of the apparatus more than of the first embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
Before the description of the present invention proceeds, it is to be noted 
that like parts are designated by like reference numerals throughout the 
accompanying drawings. 
Referring first to FIGS. 1 to 3, a single-crystal silicon substrate 21 has 
an ink jet port 21a provided in the center thereof and an ink sump 21b 
provided on its side adjoining an ink chamber 20. The ink jet port 21a is 
formed by being bored from the ink sump 21b through an oxide film 22 and a 
nitride film 23. Electrodes 24a to 24h formed of polycrystalline-silicon, 
the wiring of which is omitted in the figures, each have on their surfaces 
a nitride film 23 formed as an insulating layer (not shown). A shutter 25 
formed of polycrystalline-silicon has an ink passing hole 25a provided in 
its center and guide slots 25b, 25c provided on opposite sides thereof. On 
the surfaces of the shutter 25 except the underside thereof there is 
formed nitride films (not shown) as lubricating layers. Guide pins 27b, 
27c are formed also of polycrystalline-silicon. A front wall 28 
illustrated by single dotted chain lines in FIG. 1, as integrated with the 
guide pins 27b, 27c, has an opening 28a provided in its center. On the 
other hand, the ink chamber 20 and the ink sump 21b are charged with ink 
31 composed of insulating material. The ink 31 is subject to working 
pressures corresponding to recording signals through ordinary means such 
as a pressure device comprising a piezoelectric element or a heating 
element as shown in FIG. 10, which means is not shown. 
The component parts shown in FIGS. 1 to 3, as detailed later, are 
integrally manufactured onto the substrate 21 using semiconductor device 
manufacturing processes including lithography and etching. The result is 
that the component parts are substantially compact in size, light in 
weight, and of high precision, being comparable to semiconductor products. 
FIG. 4 is a block diagram showing a driving circuit for driving the ink 
recording apparatus. In the figure, a control circuit 41 receives a 
recording signal from the apparatus main body (not shown) via an input 
terminal 42, subsequently deciding the status of the signal to control 
switches 43 to 45. The switch 43 serves to turn on and off a power supply 
46, while the switches 44 and 45 serve to control one group of connected 
electrodes 24a, 24b, 24e, and 24f and the other group of like electrodes 
24c, 24d, 24g, and 24h, respectively, so as to render the two groups of 
electrodes oppositely phased. More specifically, while a voltage is 
applied to the side of the electrodes 24a, 24b, 24e, and 24f, the 
electrodes 24c, 24d, 24g, and 24h are grounded; and vice versa. 
Now the ink recording apparatus arranged as stated above will be explained 
with respect to its operation. The state thereof shown in FIGS. 1 to 3 is 
such that the control circuit 41 judges the apparatus to be in recording 
operation according to an input signal delivered from the apparatus main 
body via the input terminal 42, turning on the switch 43 and activating 
the switches 44, 45, with the result that a voltage of several times 10 V 
or so is applied to the side of the electrodes 24a, 24b, 24e, and 24f. In 
this state, the shutter 25 is stably positioned as shown in the figures 
with its ends 25p, 25q, 25r, and 25s sucked up by virtue of electrostatic 
attracting force acting between the ends and the surfaces of the 
electrodes 24a, 24b, 24e, and 24f, where the ink passing hole 25a of the 
shutter 25 is aligned with the ink jet port 21a provided to the substrate 
21. Then, due to the pressure within the ink chamber 20, the ink 31 
charged in the ink sump 21b passes through the ink jet port 21a and ink 
passing hole 25a and further through the opening 28a of the front wall 28, 
thus making ink droplets 32 to be jetted out. 
At this point of the state of the apparatus, setting recording paper at the 
outside of the front wall 28 allows the ink droplets 32 to record any 
patterns of characters, symbols, and the like. Moreover, the front wall 28 
surrounding the shutter 25 for coverage serves to protect an operator's 
hands or fingers or prevent other foreign matters from touching the 
shutter from outside, thereby preventing the internal structure including 
the shutter 25 from being damaged resulting in high reliability thereof. 
Succeedingly to the above-described state, even if the control circuit 41 
turns off the switch 43 to de-energize the electrodes 24a, 24b, 24e, and 
24f, the shutter 25 will remain stable at rest position thereof primarily 
by virtue of surface force. 
Next, with reference to FIGS. 5 and 6, the ink recording apparatus will be 
described in its states in which the shutter 25 has moved away from the 
position shown in FIG. 1. In this case, the control circuit 41 judges when 
the apparatus has completed the recording operation according to an input 
signal delivered from the apparatus main body via the input terminal 42, 
changing the condition of the switches 44, 45, with a result that a 
voltage is applied to the side of the electrodes 24c, 24d, 24g, and 24h. 
In this case, as shown in FIG. 5, the shutter 25 is stably positioned at 
rest having moved from the position shown in FIG. 1 with its ends 25p, 
25q, 25r, and 25s sucked up by virtue of electrostatic attracting force 
acting between the ends and the surfaces of the electrodes 24c, 24d, 24g, 
and 24h, where the ink jet port 21a is shut off by the shutter 25, thus 
effectively preventing the ink from drying and solidifying and further 
avoiding contaminations by any foreign matter from outside. 
In this state of the apparatus, even if the ink 31 charged in the ink sump 
21b is jetted out through the ink jet port 21a due to any externally 
induced pressure applied within the ink chamber 20, the shutter 25 will 
shut off the passage of the ink flow from the outside of the shutter, thus 
minimizing the possibility that some careless mishandling, accident, or 
other troubles may cause external stains due to the ink. Moreover, even if 
any pressure is applied within the ink chamber 20, where the shutter 25 is 
subject to an ink jet pressure, the shutter 25 is supported by being 
pressed against the front wall 28, thus being free of any distortion and 
therefore ensuring the substantially high reliability thereof. 
In such a state of the apparatus, even if the control circuit 41 turns off 
the switch 43 to suspend the continuity to the side of electrodes 24c, 
24d, 24g, and 24h, the shutter 25 will remain stably positioned at rest by 
virtue of surface force. The apparatus therefore, even if left unused for 
a long period, can prevent any recording failure or any head damage. 
Moreover, the front wall 28 surrounding the shutter 25 for coverage serves 
to protect against the operator's hands or fingers or other foreign 
matters from touching the shutter from outside, thereby preventing shutter 
25 from being moved therewith. 
As described heretofore, according to the present invention, it is possible 
to provide an ink recording apparatus which can prevent ink drying and 
also avoided contaminations, which is free of any recording failure or 
head damage even if left unused for a long period, and which can be highly 
reliable and protected against the interior being touched by an operator's 
hands or fingers or other foreign matters. 
Next, with reference to FIGS. 7a to 7n, the manufacturing method of the ink 
recording apparatus of the above-mentioned embodiments will be described, 
wherein, since the method utilizes the one generally used in semiconductor 
device manufacturing techniques, the description of individual processes 
will be simplified by omitting the details thereof which are common 
knowledge. 
(a) A concave portion 21a' as illustrated in FIG. 7a is formed on the 
surface of the single-crystal silicon substrate 21 by anisotropic etching. 
As the etching solution, an aqueous solution of potassium hydroxide (KOH) 
is used. Photoresist is removed by photo-resist stripping using oxygen 
plasma. The removing of photo-resist is carried out likewise in the 
following processes. 
(b) The oxide film 22 (SiO.sub.2) is to grow on the substrate 21, where the 
oxide film 22 is made grown by depositing a PSG (Phosphor Silicate Glass) 
layer 33 of a weight ratio of 8% by the method of LPCVD (Low Pressure 
Chemical Vapor Deposition) at a temperature of approximately 450.degree. 
C., and the film 22 is etched using a buffered hydrofluoric acid, as shown 
in FIG. 7b. 
(c) The nitride film 23 (Si.sub.3 N.sub.4) is deposited on the oxide film 
22, subjected to patterning by RIE (reactive-ion-etching). The nitride 
film 23 in combination with the oxide film 22 makes up an insulating 
layer, the dielectric breakdown voltage of which is more than 500 V. The 
nitride film 23 also serves to protect the oxide film 22 dissolved with 
the buffered hydrofluoric acid. 
(d) A PSG layer 33 of a weight ratio of 8% is deposited by the LPCVD method 
at approximately 450.degree. C., followed by etching using the buffered 
hydrofluoric acid. 
(e) A polycrystalline-silicon layer 34 is entirely deposited at 
approximately 610.degree. to 630.degree. C. by the LPCVD method and shaped 
as shown in the figures by plasma etching. The polycrystalline-silicon 
layer 34 forms the electrodes 24a to 24h and the shutter 25. Then, 
annealing is performed to remove the residual stress. In addition, the 
polycrystalline-silicon layer 34 may be imparted with electrical 
conductivity by diffusing phosphorus thereinto as required. 
(f) An oxide film 35 is made to grow on the polycrystalline-silicon layer 
34, where for the oxide film 35 a PSG layer of a weight ratio of 8% may be 
deposited at approximately 450.degree. C. by the LPCVD method. The oxide 
film 35 will serve as a protection film for the RIE later formed. 
(g) The polycrystalline-silicon layer 34 and the oxide film 35 are 
subjected to patterning by plasma etching as shown in FIG. 7g, thereby 
being shaped into the electrodes 24a to 24h and the shutter 25. In this 
process, end point is detected with 30% overetching, and annealing are 
performed to remove the residual stress. 
(h) A nitride (Si.sub.3 N.sub.4) film 26 is deposited as shown in FIG. 7h, 
where patterning is performed by the RIE. The nitride film 26 finally 
forms the above-mentioned nitride film (not shown), serving as a 
lubricating layer for reducing the friction between the shutter 25 and 
relevant portions and compensating for the brittleness of materials and 
also as an insulating layer (not shown) for the electrodes 24a to 24h. 
(i) A PSG layer 36 of a weight ratio of 8% is entirely deposited by the 
LPCVD method at approximately 450.degree. C. 
(j) The PSG layer 36 is etched using buffered hydrofluoric acid as shown in 
FIG. 7j. 
(k) The PSG layer 36 is subjected to patterning by plasma etching as shown 
in FIG. 7k. This patterning will enable the fixing of the guide pins 27b, 
27c and the front wall 28 (both shown in FIG. 1) to be later formed. The 
end points are detected with 30% overetching. 
(1) a polycrystalline-silicon layer 37 is deposited by the LPCVD method at 
approximately 610.degree. to 630.degree. C., subjected to patterning by 
plasma etching as shown in FIG. 71, thus forming the guide pins 27b, 27c 
and the front wall 28. Here, annealing is performed to remove the residual 
stress. 
(m) The PSG layers (or oxide films) 33, 36 are dissolved with a buffered 
hydrofluoric acid to form a movable member into which the 
polycrystalline-silicon layer 34 and the oxide film 35 are integrated, 
thereby forming the shutter 25 as shown in FIG. 1. 
(n) The substrate 21 is anisotropically etched from its rear side as shown 
in FIG. 7n to form the concave portion 21b' until it is bored through up 
to the concave portion 21a, first formed. This allows the ink jet port 21a 
and the ink sump 21b, as shown in FIG. 2, to be formed. 
Through the above processes, the ink recording apparatus of the first 
embodiment of the present invention can be manufactured. As seen here, the 
component structures are integrally manufactured using semiconductor 
device manufacturing processes, thereby allowing the structures to be 
integrated very simply and furthermore rendering them high in precision as 
well as steady in performance. Besides, the whole apparatus is so thin 
that it may be arranged in the clearance between recording paper and the 
head. Accordingly, the ink recording apparatus can be steadily 
mass-produced yet have remarkably high reliability, light weight and 
compactness, and further high precision. 
In addition, although in the foregoing first embodiment of the invention 
the front wall 28 is formed of the same material and constructed in the 
same manner as those in the shutter 25 and the like, a front wall produced 
by any other manufacturing method may be combined therewith. 
Moreover, although in the first embodiment of the invention one ink jet 
port 21a and one shutter 25 are combined with the ink jet port 21a, a 
plurality of ink jet ports 21a may also be provided for the combination 
with the ink chamber 20 as a second embodiment, as shown in FIG. 8. In 
FIG. 8, the front wall 28 is not illustrated and the ink sump 21b is 
indicated by broken lines. The ink recording apparatus of the second 
embodiment of the present invention can also be manufactured by the same 
manufacturing method as described above. 
The third embodiment of the invention can be arranged as shown in FIG. 9, 
wherein the shutter 25 may be integrally provided with an elastic member 
25d to produce a resilient force against the front wall 28, thereby 
holding its state mechanically. In this case, although it is impossible to 
cut off the feed to the electrodes 24a, 24b, 24e, and 24f while the 
recording is enabled as stated above, the shutter 25 may in turn be 
blocked by interrupting the feed to the electrodes, thereby allowing the 
electrodes to be reduced in number so that the shutter can be held blocked 
more steadily than in the first embodiment, with a result of further 
enhanced reliability. As a matter of course, the ink recording apparatus 
of the third embodiment can also be manufactured by the foregoing method. 
Although the present invention has been fully described in connection with 
the preferred embodiments thereof with reference to the accompanying 
drawings, it is to be noted that various changes and modifications will be 
apparent to those skilled in the art. Such changes and modifications are 
to be understood as included within the scope of the present invention as 
defined by the appended claims unless they depart therefrom.