Ink recording apparatus

Abstract: An ink recording apparatus used with printers or the like and manufactured by applying semiconductor device manufacturing techniques. One wall of an ink chamber (20) is formed of a single-crystal substrate (21) and an ink jet port (21a) is formed by etching on the single-crystal sub­ strate (21). A shutter (25) and electrodes (24a to 24h) 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 (28) is formed by coating the shutter (25) and electrodes (24a to 24h) further with a polycrystalline-silicon film. The shutter (25) is movable between the wall surface of the ink chamber (20) and the front wall (28), being driven through electrostatic attracting force produced between voltage-ap­ plied electrodes (24a to 24h) and the shutter (25). The electrodes (24a to 24h) are formed at positions correspond­ ing to those where the shutter (25) blocks the ink jet port (21a) and releases the same.

Description: BACKGROUND OF THE INVENTION Field of the invention The present invention relates to 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. Description of the related art From US-A-4 199 767 from which the invention proceeds, there is known an arrangement for ink jet printers, comprising an ink jet port provided to an ink chamber, a shutter provided in the vicinity of the ink jet port, the shutter being movable between a shut-off position for shutting off ink from passing through the ink jet port and a passing position for allowing ink to pass through, and shutter driving means for not only driving the shutter but also holding the shutter in the shut-off position while the printer is out of recording operation. A similar 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 their 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 µm 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 to 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 is 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 taking 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 overcome 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 having arranged as described above, however, even if no problems occur during the recording operation thereof, the apparatus may be involved in 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 external, likely causing some recording failure or head damage. SUMMARY OF THE INVENTION The present invention has been accomplished to effectively solve the above-mentioned 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 as unused for a long time period, 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 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 disposed in the ink chamber, a shutter disposed 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, characterized in that the shutter and the shutter driving means are formed simultaneously in the same process using semiconductor manufacturing techniques. When using such techniques, the shutter and the shutter driving means are formed at their correct positions during the manufacturing process. This means, that any difficult assembling of the shutter and the shutter driving means being very small parts is not necessary. Therefore, a plenty of shutters can be regularly arranged in high-accuracy in a small area what is very suitable for a small-sized ink head of an ink jet printer. Further embodiments of the invention are defined in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features for the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which: Fig. 1 is a plan view showing the construction of an ink recording apparatus of a first embodiment according to the present invention; Fig. 2 is a sectional view taken along line II - II of Fig. 1; Fig. 3 is a sectional view taken along line III - III of Fig. 1; Fig. 4 is a block diagram showing a driving circuit of the ink recording apparatus of Fig.1; Fig. 5 is a view illustrating the operation of the ink recording apparatus of Fig. 1; Fig. 6 is a sectional view taken along line VI - VI of Fig. 5; Figs. 7a to 7n are views illustrating the manufacture processes of the ink recording apparatus of Fig. 1; Fig. 8 is a plan view showing the construction of a second embodiment of the present invention; Fig. 9 is a plan view showing the construction of an ink recording apparatus of a third embodiment of the invention; Fig. 10 is a perspective view showing the construction of an ink recording apparatus according to the prior art; and Figs. 11a to 11d are views illustrating the operation of the apparatus of Fig. 10. 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 as 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, have 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, comparable to semiconductor products. Fig. 4 is a block diagram showing a driving circuit for driving the ink recording apparatus here mentioned. 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 operator's hands or fingers or other foreign matters from touching the shutter from external, thereby preventing the internal structure including the shutter 25 from being damaged with the result of high reliability thereof. Succeedingly to the above-mentioned 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 as stable in rest in the same 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 that the apparatus 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 such 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 in rest as 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 of any foreign matter from external. 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 such a possibility that some careless mishandling, accident, or other troubles may cause any external stains due to the ink. Moreover, even if any pressure is applied within the ink chamber 20 as above, where the shutter 25 is subject to an ink jet pressure, the shutter 25 is supported as 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 in 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 operator's hands or fingers or other foreign matters from touching the shutter from external, 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 be prevented from 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 with the internal protection from any touch of operator's hands or fingers or other foreign matters. Next, with reference to Figs. 7a to 7n, the ink recording apparatus of the above-mentioned embodiments will be described in its manufacturing method, 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 of common knowledge thereof. (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 (SiO₂) is made 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°C, and the film 22 is etched using a buffered hydrofluoric acid, as shown in Fig. 7b. (c) The nitride film 23 (Si₃N₄) 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°C, followed by etching using the buffered hydrofluoric acid. (e) A polycrystalline-silicon layer 34 is entirely deposited at approximately 610 to 630°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 therewith 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°C by the LPCVD method. The oxide film 35 will serve as a protection film for the RIE later performed. (g) The polycrystalline-silicon layer 34 and the oxide film 35 are subjected to patterning by plasma etching as shown in Fig. 7g, thereby shaping into the electrodes 24a to 24h and the shutter 25. In this process, end points are detected with 30% overetching, and annealing are performed to remove the residual stress. (h) A nitride (Si₃N₄) 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 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°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. (l) A polycrystalline-silicon layer 37 is deposited by the LPCVD method at approximately 610 to 630°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 up 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 the 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 which features their 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, the one 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 in 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 the 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 made 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 in the foregoing method.

Claims: An ink recording apparatus comprising: an ink chamber (20) for being filled with ink; an ink jet port (21a) provided to said ink chamber (20); a shutter (25) provided in the vicinity of said ink jet port (21a), said shutter (25) being movable between a shut-off position for shutting off ink from passing through said ink jet port (21a) and a passing position for allowing ink to pass through; and shutter driving means (24a to 24h, 41 to 46) for not only driving said shutter but also holding said shutter (25) in said shut-off position while the apparatus is out of recording operation; characterized in that said shutter (25) and said shutter driving means (24a to 24h, 41 to 46) are formed simultaneously in the same process using semiconductor manufacturing techniques. An ink recording apparatus as claimed in claim 1, characterized in that said shutter (25) is formed of a thin film. An ink recording apparatus as claimed in claim 1 or 2, characterized in that said shutter driving means (24a to 24h, 41 to 46) comprise: electrodes (24a to 24h) provided in correspondence to each of said shut-off position and passing position for said shutter (25); a power supply (46) for applying voltage to said electrodces (24a to 24h); and a control circuit (41), whereby said shutter (25) is driven by virtue of electrostatic attracting force acting between the surfaces of said electrodes (24a to 24h) and the surface of said shutter (25). An ink recording apparatus as claimed in claim 1 comprising a wall (28) provided outside of said shutter (25) for covering the external surface of said shutter (25). An ink recording apparatus as claimed in claim 1 or 2, wherein said shutter driving means includes an elastic member (25d) for biasing said shutter (25) toward said shut-off position.

Inventors: MIMA SOICHIRO, SHIBAIKE NARITO, MIMA, SOICHIRO, SHIBAIKE, NARITO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: B41J2
IPC codes: B41J2