Inkjet recording head

An inkjet recording head includes a nozzle plate, chamber plate, and a diaphragm plate. The nozzle plate includes a plurality of nozzles for ejecting ink droplets, a plurality of connecting channels in communication with the nozzles and pressure chambers. The nozzles are formed in a row at a uniform pitch. The connecting channels extend from the nozzles alternately in opposite directions in a staggered formation and are offset a prescribed angle to a direction orthogonal to the row of nozzles. The chamber plate includes the pressure chambers, restrictors, and common ink chambers formed therein. Each pressure chamber has an elongated shape extending in a direction orthogonal to the row of nozzles. The pressure chambers are formed in rows, one on either side of the row of nozzles, so that the pressure chambers in one row oppose the corresponding pressure chambers in the other row. The diaphragm plate has a vibration plate that seals the pressure chambers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inkjet recording head having a superposed plate construction.

2. Description of the Related Art

One type of recording head well known in the art is configured of nozzles for ejecting ink droplets, pressure chambers in communication with the nozzles, a vibration plate that seals the pressure chambers, and piezoelectric elements for deforming the vibration plate in order to expand and contract the pressure chambers and eject ink droplets from the nozzles. In recent years, there has been a heightened demand for recording devices using these types of recording heads with a denser arrangement of nozzles in order to achieve faster and higher quality printing.

To achieve this, Japanese Patent Publication No. SHO-62-111758 proposes a recording head that includes narrow, elongated pressure chambers confronting each other longitudinally, and nozzles are formed in a row at a uniform pitch. Another recording head disclosed in Japanese Patent Publication No. HEI-7-195685 attempts to improve nozzle-density with a plurality of superposed plates in which are formed pressure chambers, nozzles, and connecting channels that grow gradually smaller from the pressure chambers to the nozzles.

Another recording head disclosed in Japanese Patent Publication No. 2002-205394 includes a plurality of elongated pressure chambers, each having one longitudinal end formed narrower than the main portion of the pressure chamber. The pressure chambers are formed in two adjacent rows with the narrow ends of the pressure chambers in one row juxtaposed with those in the other row to form a staggered arrangement, thus enabling the nozzles to be arranged at a high density. Further, another recording head disclosed in Japanese Patent Publication No. 2004-181798 includes means for increasing nozzle density using pressure chambers with narrow ends.

SUMMARY OF THE INVENTION

Since the conventional inkjet recording heads described above are formed of a plurality of superposed plates, deviations in the relative positions of the plates are likely to occur when the plates are superposed and bonded together, resulting in a different volume of ink flowing among individual pressure chambers and, consequently, a variation in ejection properties for ink droplets ejected from each nozzle. Further, when the plates are bonded together with adhesive, the tendency for adhesive to protrude into the ink channels increases the greater the number of plates being superposed. This protruding adhesive disturbs the flow of ink in the channel portions. This disturbance induces cavitation and leads to the production of air bubbles that may hinder ink ejection.

Further, although the nozzle density can be increased by crisscrossing the ends of the pressure chambers near the nozzles in a staggered arrangement, it is also necessary to form the piezoelectric elements corresponding to the pressure chambers in a staggered arrangement. In other words, piezoelectric element groups divided into individual piezoelectric elements must be offset from each other at one-half their pitch and must be aligned with high precision. In another technique, bulk piezoelectric elements are disposed over the pressure chambers and machined with a dicing saw, forming individual piezoelectric elements corresponding to each of the pressure chambers. However, this technique requires more machining time as the number of pressure chambers increases and high precision in machining as the pitch of the pressure chambers becomes finer.

Further, the narrow parts of the pressure chambers are narrower the greater the nozzle density. The nozzles are formed in a nozzle plate as a separate component from the pressure chambers and superposed over the narrow parts of the pressure chambers. Accordingly, there is little margin for error in positioning the narrow portions of the pressure chambers with the nozzles, requiring extremely high precision. Another problem occurs when driving neighboring nozzles with a prescribed delay to prevent cross talk that occurs when adjacent nozzles are driven at the same time. Since it is necessary to shift the position of the nozzles to provide this delay, both the nozzle plate and the chamber plate must be manufactured in accordance to this amount of shift.

In view of the foregoing, it is an object of the present invention to provide an inkjet recording head, the construction facilitating the processing and assembly of components constituting the recording head, and achieving a high-density nozzle arrangement and high-quality printing.

This and other objects of the invention will be attained by an inkjet recording head including a first plate, a second plate, a third plate, and a pressure generating member.

The first plate is formed with a plurality of nozzles arranged in a row for ejecting ink droplets and a plurality of connecting channels each having a first end in fluid communication with a corresponding one of the plurality of nozzles. The plurality of connecting channels extend from a respective first end to a corresponding second end alternately in opposite directions that are angularly shifted from a direction orthogonal to the row of the nozzles. The second plate is formed with a plurality of pressure chambers in fluid communication with a respective second end of the connecting channels in a one-on-one correspondence to the nozzles. The pressure chambers are formed in two rows parallel to the row of nozzles. One row of the pressure chambers is on one side of the row of nozzles and the other row of pressure chambers is on the other side of nozzles. At least one region of each of the pressure chambers in one row is aligned with another region of one of the pressure chambers in the other row in the direction orthogonal to the row of nozzles. The third plate has a vibration plate that seals the pressure chambers. The pressure generating member has a plurality of drive elements that contact portions of the vibration plate opposing the regions of the pressure chambers.

In another aspect of the invention, there is provided an inkjet recording head including a first plate, a second plate, a third plate, and a pressure generating member.

The first plate is formed with a plurality of nozzles arranged in a row for ejecting ink droplets and a plurality of connecting channels each having a first end in fluid communication with a corresponding one of the plurality of nozzles and extend from a respective first end the to respective second ends alternately in opposite directions orthogonal to the row of nozzles. The plurality of connection channels extend along their centerlines in a direction orthogonal to the row of the nozzles. The second plate is formed with a plurality of pressure chambers. The pressure chambers are formed in two rows parallel to the row of nozzles. The row of nozzles is located between the two rows of the pressure chambers. Each pressure chamber has a first portion in fluid communication with a second end of the corresponding connecting channel and a second portion in fluid communication with the first portion. The first portion of each pressure chamber slants with respect to the direction orthogonal to the row of the nozzles. The second portion of each pressure chamber extends along its centerline in the direction orthogonal to the row of the nozzles. The centerline of each pressure chamber is separated a prescribed distance from the centerline of a neighboring connecting channel. The second portion of each pressure chamber in one row is aligned with the second portion of one of the pressure chambers in the other row in a direction orthogonal to the row of nozzles. The third plate has a vibration plate that seals the pressure chambers. The pressure generating member has a plurality of drive elements that contact the vibration plate opposing the another portions of the pressure chambers.

In another aspect of the invention, there is provided an inkjet recording head including a first plate, a second plate, a third plate, and a pressure generating member.

The first plate is formed with a plurality of nozzles arranged in a row for ejecting ink droplets and a plurality of connecting channels each having a first end in fluid communication with a corresponding one of the plurality of nozzles. The plurality of connecting channels extend from their respective first ends to respective second ends alternately in opposite directions orthogonal to the row of nozzles. The second plate is formed with a plurality of pressure chambers. Each pressure chamber has a first end portion in fluid communication with the second end of a corresponding connecting channel. The pressure chambers are formed in two rows parallel to the row of nozzles. The row of nozzles is located between the two rows of the pressure chambers. Each of the pressure chambers in one row is aligned with one of the pressure chambers in the other row in the direction orthogonal to the row of nozzles. A width of each first end portion of the pressure chambers in a direction parallel to the row of the nozzles gradually decreases in a direction defined from a second end portion to the first end portion. The third plate has a vibration plate that seals the pressure chambers. The pressure generating member has a plurality of drive elements that contact a portion of the vibration plate opposing the pressure chambers.

In another aspect of the invention, there is provided an inkjet recording head including a first plate, a second plate, a third plate, and a pressure generating member.

The first plate is formed with a plurality of nozzles arranged in a row for ejecting ink droplets and a plurality of connecting channels each having a first end in fluid communication with a corresponding one of the plurality of nozzles and extending from the first end to a second end alternately in opposite directions orthogonal to the row of nozzles. The first plate has a first wall defining each of the connecting channels. The second plate is formed with a plurality of pressure chambers. The second plate has a second wall defining each of the pressure chambers. The pressure chambers are formed in two rows parallel to the row of nozzles. The row of nozzles is located between the two rows of the pressure chambers. Each pressure chamber has a first portion in fluid communication with the second end of the corresponding connecting channel and a second portion in fluid communication with the first portion. At least either one of the first wall defining each of the connecting channels and the second wall defining the first portion of each of the pressure chambers slants relative to the direction orthogonal to row of nozzles. At least the second portion of each pressure chamber in one row opposes the second portion of one of the pressure chambers in the other row in the direction orthogonal to the row of nozzles. The third plate has a vibration plate that seals the pressure chambers. The pressure generating member has a plurality of drive elements that contact the vibration plate opposing the another portions of the pressure chambers,

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An inkjet recording head according to a first embodiment of the present invention will be described with reference toFIGS. 1 through 5C.

As shown inFIG. 1, a recording head1includes a channel substrate3, a piezoelectric actuator40, and a housing50.

The channel substrate3includes a nozzle plate10, a chamber plate20, and a diaphragm plate30that are superposed and fixed together.

The nozzle plate10includes a plurality of nozzles11(seeFIG. 3) for ejecting ink droplets, a plurality of connecting channels12(seeFIG. 3) in communication with the nozzles11and pressure chambers21described later, and positioning holes10aformed each side of the nozzle plate10in a longitudinal direction thereof.

The nozzle plate10is configured of a silicon single-crystal substrate with a (110) plane. The nozzles11, the connecting channels12, and the positioning hole10aare formed in the nozzle plate10by dry etching. As shown inFIG. 2, steps are formed in the nozzles11so that the ink channel becomes gradually narrower. As shown inFIG. 3, the nozzles11are formed in a row at a uniform pitch. In the preferred embodiment, the nozzles11are formed at a pitch of 1/200 of an inch. The connecting channels12are elongated with one longitudinal end in communication with the respective nozzles11and the other end in communication with the respective pressure chambers21via the through-holes24described later. The connecting channels12extend from the nozzles11alternately in opposite directions in a staggered formation and are offset a prescribed angle to a direction orthogonal to the row of nozzles11. The connecting channels12are narrower than the channel width of the pressure chambers21.

The chamber plate20includes the pressure chambers21, restrictors22, common ink chambers23, through-holes24, and positioning holes20aformed therein. The chamber plate20is configured of a silicon single-crystal substrate with a (110) plane. In the preferred embodiment, the chamber plate20has a thickness of approximately 300 μm. One end of each through-hole24is in communication with the respective connecting channel12, while the other end is in communication with the respective pressure chamber21. The depth of the pressure chambers21is no greater than one-third the thickness of the chamber plate20. Each pressure chamber21has an elongated shape extending in a direction orthogonal to the row of nozzles11, with one end opposing an end of the respective connecting channel12. The pressure chambers21are formed in rows, one on either side of the row of nozzles11, so that the pressure chambers21in one row oppose the corresponding pressure chambers21in the other row. The pressure chambers21must have a relatively large volume and thus are arranged at a pitch twice that of the nozzles11, thereby facilitating processing of the pressure chambers21and improving precision. Further, one end of each restrictors22is in communication with a corresponding pressure chamber21, while the other end is in communication with one of the common ink chambers23. The restrictors22are configured with a smaller cross-sectional area in the inner ink channel than that of the pressure chambers21.

The diaphragm plate30includes a vibration plate31and a support plate32that are bonded together, and positioning holes30apenetrating both of the plates31and32. The vibration plate31is formed of polyimide in the shape of a thin plate 5-20 μm thick. The support plate32is formed of stainless steel in the shape of a thin plate 20-30 μm thick. Hence, the support plate32is sufficiently thick with relatively high rigidity for maintaining a seal over the restrictors22serving as ink channels. Depressions33and35are formed in portions of the support plate32opposing the pressure chambers21and common ink chambers23, respectively, through the vibration plate31. Hence, the vibration plate31is exposed in the depressions33and35. The depressions33and35are formed by etching the support plate32. A plurality of holes are formed in the vibration plate31in regions corresponding to the depressions35, which holes function collectively as filters34. The diameter of the holes in the filters34is preferably smaller than the diameter of the nozzles11. For example, if the diameter of the nozzles11is 30 μm, the holes in the filters34have a diameter of no greater than about 20 μm.

As described above, the channel substrate3is formed by superposing and fixing the nozzle plate10, chamber plate20, and diaphragm plate30together. An adhesive may be used as the method of bonding these plates. However, since the nozzle plate10and chamber plate20are configured of silicon single-crystal substrates, these plates may also be joined through anodic bonding. The nozzle plate10, chamber plate20, and diaphragm plate30may all be integrally formed through anodic bonding if the diaphragm plate30is also formed of the same material.

The piezoelectric actuator40is bonded to the diaphragm plate30for expanding and contracting the volume of the pressure chambers21via the vibration plate31. As shown inFIG. 5C, the piezoelectric actuator40includes a support substrate41, common electrodes42, a plurality of individual electrodes43, flexible cables45, a plurality of piezoelectric elements66, and external electrodes64A and64B. The support substrate41is shaped like a rectangular parallelepiped with a groove48formed on a side surface thereof. The common electrodes42are formed one on either longitudinal end of the support substrate41. The individual electrodes43are formed at regular intervals between the common electrodes42. The piezoelectric elements66are disposed on one side surface of the support substrate41. The piezoelectric elements66are pole-shaped and are formed by alternately superposing an electrically conductive material62with a piezoelectric material63. As shown inFIG. 2, one end of the piezoelectric elements66is bonded to the vibration plate31by adhesive.

As shown inFIG. 5C, the external electrodes64A and64B are formed on side surfaces of the piezoelectric elements66and are electrically connected to the electrically conductive material62. The external electrodes64B are also electrically connected to the common electrodes42by a conductive adhesive65a. The external electrodes64A are also electrically connected to the individual electrodes43via a conductive adhesive65b. The flexible cables45are connected to both the common electrodes42and the individual electrodes43.

The housing50includes an opening51through which the piezoelectric actuator40can be inserted, the opening51, common ink channels52, and positioning holes50aformed therein. The housing50is bonded to the channel substrate3. The common ink channels52are in communication with the respective common ink chambers23via the filters34. Ink is supplied from an ink reservoir (not shown) to the common ink channels52via supply channels (not shown). As shown inFIG. 2, the housing50is stacked on and bonded to the channel substrate3using the positioning holes10a,20a,30a, and50aas positioning references.

With this construction, ink from the ink reservoir (not shown) is supplied to the nozzles11via the common ink channels52, filters34, common ink chambers23, restrictors22, pressure chambers21, through-holes24, and connecting channels12. The vibration plate31is vibrated based on a signal applied to the piezoelectric elements66. The vibrations compress the pressure chambers21and cause ink droplets to be ejected through the nozzles11.

The recording head1described above can simplify processing and assembly of an inkjet recording head and improve ejection properties while achieving a high nozzle density. The high nozzle density can be easily achieved by forming connecting channels with a staggered arrangement in a nozzle plate with nozzles formed therein.

The inkjet recording head of the present invention can also achieve a compact recording head structure with a high nozzle density. Accordingly, the inkjet recording head can print at high speeds and can eject microdroplets of ink capable of achieving high resolution printing quality. Hence, the inkjet recording head can be used in a wide range of applications, from printing devices for office use to industrial printing applications.

Further, the ink channels in the nozzles11grow gradually narrower, preventing air bubbles from generating and accumulating due to cavitation in the ink flow and ensuring that ink droplets are ejected with greater stability. Further, there is always some error in manufacturing regardless of how precise the manufacturing process. When providing channels equivalent to the connecting channels12in the chamber plate20of the conventional structure, the accuracy required for positioning the connecting channels12and nozzles11, which are the finest sections of the channel portions, is severe. However, in the present invention, the nozzles11and connecting channels12that require the most exact precision are both formed in the nozzle plate10, and the chamber plate20in which are formed the pressure chambers21is bonded to the nozzle plate10. Since the connecting channels12and pressure chambers21are the components being positioned in this construction, the adverse effects of errors in positioning are eliminated and a larger margin of error is possible.

As an example, the nozzle plate10may have a thickness of 50-100 μm with the nozzles11arranged at a density of 200 dpi (dots per inch). If the diameter of the nozzles11at the surface from which ink is ejected is 25 μm, then the diameter of the nozzles11at the end abutting the connecting channels12is set to 50-70 μm, that is, at least twice the diameter at the ejection surface. Hence, the connecting channels12can be limited to a width of 50-70 μm, about the same as the diameter of the nozzles11on the connecting channels12end. However, since the pressure chambers21are arranged at a density of 100 dpi, about twice the pitch of the nozzles11, the pressure chambers21can be formed at a width of at least 0.15 mm, thereby increasing the tolerance for lateral offset relative to the connecting channels12. In other words, this configuration relaxes restrictions on assembly precision.

Further, when considering the inertance and fluid resistance in the nozzles11and connecting channels12in series, the connecting channels12can be allowed larger dimensions. Hence, by treating each corresponding nozzle11and connecting channel12as a series, the connecting channel12can be factored into the Helmholtz equation for finding oscillation period and damping. Since the number of time constant parameters increases as a result, there is greater freedom in designing the structure and drive waveform of the recording head, which can be useful for fine-tuning the ink ejection characteristics.

Further, despite having a somewhat long ink channel, the connecting channel12has a smaller longitude-latitude aspect ratio than the pressure chambers21and can be processed with greater precision. Further, the cross-sectional area of the ink channel portion of the restrictors22is smaller than that of the pressure chambers21, making it possible to optimize the amount of ink flowing from the common ink chambers23into the pressure chambers21when the volume of the pressure chambers21is expanded, as well as the amount of ink flowing in reverse from the pressure chambers21to the common ink chambers23when the volume in the pressure chambers21is contracted to eject an ink droplet. Further, the vibration plate31is configured of a thin plate that can be sufficiently displaced by the expansion and contraction of the piezoelectric elements66.

The filters34also trap foreign matter flowing from the ink channels52and the like, thereby preventing such matter from clogging the microchannels leading to the nozzles11and increasing the reliability of ink ejection.

The recording head1described above allows the nozzles11to be arranged very densely. Further, manufacturing processes for the recording head1are simplified by constructing the pressure chambers21and piezoelectric elements66at a pitch twice that of the nozzles11.

Since the pressure chambers21are provided independently of the connecting channels12and are not greatly influenced by the configuration of the connecting channels12, there is a greater degree of freedom in designing the shape of the connecting channels12, including the depth, width, and length. The channel substrate3configured of the nozzle plate10, chamber plate20, and diaphragm plate30requires an overall degree of stiffness, as pressure generated from displacement when the piezoelectric actuator40expands and contracts can deform the channel substrate3. Hence, the chamber plate20constituting part of the channel substrate3should be relatively thick. In the preferred embodiment, the thickness of the chamber plate20is increased, the depth of the restrictors22and pressure chambers21is set to about one-third the plate thickness, and the pressure chambers21are in fluid communication with the nozzles11via the narrow through-holes24and the connecting channels12. This configuration prevents both a decline in stiffness in the channel substrate3and the occurrence of structural cross talk. Although the structures of the nozzle plate10and chamber plate20are complex, these plates can easily be formed with high precision by performing dry etching of silicon single-crystal substrates.

Next, a method of manufacturing the nozzle plate10will be described with reference toFIGS. 4A through 4E. As shown inFIG. 4A, a thermal oxidation method or the like is used to form a silicon oxide layer15on the surface of a silicon wafer10A, which is a single-crystal substrate. Patterning is performed for prescribed regions using photolithography, and the silicon oxide layer15in the prescribed regions is completely removed by etching. Etching is performed with a fluorine and ammonium fluoride mixed liquid. When etching, the entire surface of the silicon oxide layer15excluding the prescribed regions is coated with resist to protect the silicon oxide layer15on the side that will become the surface of the nozzles11. Next, the portions of the silicon wafer10A exposed through the above etching process are removed to the required depth by dry etching.

Subsequently, the oxide layer for regions that will become the connecting channel12is removed, as shown inFIG. 4B. This portion of the silicon wafer10A is then removed to a required depth by dry etching, as shown inFIG. 4C. Next, an oxide mask is formed over the surface that was etched, as shown inFIG. 4D. The silicon oxide layer formed on the surface opposite the side on which etching was performed above is completely removed in areas corresponding to what will be the nozzles11. Next, etching is performed to form the nozzles11, as shown inFIG. 4E, and the remaining oxide film is completely removed to reveal the completed nozzle plate10, shown inFIG. 4F. The surface of the completed nozzle plate10from which ink droplets are ejected may also be subjected to an ink-repellant treatment to improve ink wettability.

The chamber plate20is manufactured according to a similar dry etching method. In this way, high precision processing can be performed according to a simple method to form members constituting the ink channels. Further, by reducing the number of superposed plates, it is possible to reduce the cumulative error in the ink channels.

Next, a method of manufacturing the piezoelectric actuator40will be described with reference toFIGS. 5A-5C. As shown inFIG. 5A, two rod-shaped piezoelectric members60formed by alternating superposed layers of the electrically conductive material62and piezoelectric material63are fixed parallel to each other on one surface of the support substrate41. The external electrodes64A and64B are formed on side surfaces of the piezoelectric members60so as to be electrically connected to the layers of electrically conductive material62in the piezoelectric members60. Specifically, the external electrodes64A are formed on outer side surfaces of both piezoelectric members60, while the external electrodes64B are formed on inner side surfaces (opposing surfaces) of the piezoelectric members60(only one of each electrode64A and64B is indicated inFIG. 5A). The groove48is formed in a center region of the support substrate41. The common electrodes42are connected to the piezoelectric members60via the conductive adhesive65aand the external electrodes64B, while the individual electrodes43are connected to the piezoelectric members60via the conductive adhesive65band the external electrodes64A. In the preferred embodiment, the common electrodes42and individual electrodes43have been preprinted using a screen printing technique or the like.

As shown inFIG. 5B, the two piezoelectric members60are cut with a dicing saw, wire saw, or the like to form a comb structure with comb-like teeth at a prescribed pitch so that the piezoelectric member60is separated into discrete parts on the individual electrodes43. The common electrodes42are connected together via the conductive adhesive65aformed in the groove48of the support substrate41. This process produces separated piezoelectric elements66that can function as individual actuators. The separated piezoelectric elements66are shaped like comb teeth at a uniform pitch corresponding to the pitch of the pressure chambers21. As shown inFIG. 5C, the individual electrodes43and common electrodes42are connected to the flexible cables45, thereby completing the piezoelectric actuator40.

Next, an inkjet recording head according to a second embodiment of the present invention will be described with reference toFIG. 6, wherein like parts and components are designated with the same reference numerals to avoid duplicating description.FIG. 6corresponds toFIG. 3of the first embodiment and is a plan view illustrating the positional relationship of the nozzles, connecting channels, through-holes, pressure chambers, restrictors, and common ink chambers according to the second embodiment.

The inkjet recording head according to the second embodiment includes a plurality of connecting channels12aformed in the nozzle plate10. The connecting channels12aextend alternately in opposite directions and are formed parallel to the direction orthogonal to the row of nozzles11. Each connecting channel12aextends along a first centerline L1passing through a center of each connecting channel12ain a width direction thereof and extending in the longitudinal direction of each connecting channel12a. A one end of each connecting channels12ais in communication with the respective nozzles11.

The inkjet recording head according to the second embodiment also includes a plurality of through-holes24aand a plurality of pressure chambers21aformed in the chamber plate20. Each of through-holes24ais in communication with the respective connecting channels12a. The pressure chambers21aare arranged in two rows, one on either side of the row of nozzles11. The pressure chambers21aof one row are positioned to oppose corresponding pressure chambers21ain the other row. Further, each pressure chamber21aextends along a second centerline L2passing through a center of each pressure chamber21ain a width direction thereof and extending in the longitudinal direction of each pressure chamber21a. The second centerline L2of pressure chamber21ais offset from the first centerline L1of neighboring connecting channels12aby about one-half the pitch of the nozzles11. The ends of the pressure chambers21aon the connecting channel12aside (portions communicating with through-holes24a) are bent toward the respective connecting channels12a. Bending the pressure chambers21ain this way enables the pressure chambers21ato be in fluid communication with the connecting channels12a. By gently curving the pressure chambers21atoward the connecting channels12ain this way, it is possible to ensure a smooth flow of ink thereto. Here, the width of the channels in the pressure chambers21ais preferably the same or greater than the width of the channels in the connecting channels12ain order to facilitate the removal of air bubbles when the connecting channels12aare filled with ink. The structure according to the second embodiment described above can obtain the same effects as the inkjet recording head according to the first embodiment.

Further, the pressure chambers21a, which communicate with the connecting channels12a, are formed with ink channels that grow narrower toward the connecting channels12a, thereby increasing the ability to remove air bubbles from the ink.

Next, an inkjet recording head according to a third embodiment of the present invention will be described with reference toFIG. 7, wherein like parts and components are designated with the same reference numerals to avoid duplicating description.FIG. 7corresponds toFIG. 3of the first embodiment and is a plan view illustrating the positional relationship of the nozzles, connecting channels, through-holes, pressure chambers, restrictors, and common ink chambers according to the third embodiment.

The chamber plate20according to the third embodiment is formed by anisotropic wet etching of a silicon single-crystal substrate with a (110) surface. As shown inFIG. 8, planes A, B, and C emerge when performing anisotropic wet etching of silicon single-crystal substrate with the (110) surface. Here, anisotropic wet etching is used to form (111) planes (planes A and B inFIG. 8) orthogonal to the (110) plane, and to produce depressed areas in the shape of parallelograms (pressure chambers21band through-holes24b) in which the planes A correspond to sides16and17and the planes B correspond to sides18and19inFIG. 7. This technique achieves an extremely high precision during the molding process.

The pressure chambers21bformed in the chamber plate20communicate with the connecting channels12avia corner parts of the through-holes24bforming an acute angle in the parallelogram. By forming the nozzle plate10through dry etching and the chamber plate20through anisotropic wet etching in this way, relative positioning between the two plates can be improved. Further, since the ink channels in the through-holes24bgrow narrower toward the connecting channels12a, this structure can facilitate removal of air bubbles, thereby improving the reliability of the recording head for ejecting ink droplets.

While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims. For example, the restrictors22may be configured of two or more narrow channels in order to obtain optimal flow resistance. Further, the filters34need not be formed integrally with the diaphragm plate30, but may be prepared separately as a filter plate that is disposed between the diaphragm plate30and the housing50. Further, while the diaphragm plate30in the embodiments described above is configured of the bonded vibration plate31and support plate32, these parts may be provided separately. For example, the vibration plate31may be replaced by a thin stainless steel plate no greater than 10 μm thick or a thin plate formed by nickel electroforming. Since the diaphragm plate30does not define the ink channels, the same effects as those described above can be obtained when treating the vibration plate31and support plate32as separate components. Similar to the nozzle plate10and chamber plate20, the diaphragm plate30may also be formed by etching a silicon substrate.

FIG. 9shows a piezoelectric actuator unit40A as a variation of the piezoelectric actuator40according to the preferred embodiments described above. While the piezoelectric actuator40A is manufactured by mounting two piezoelectric members60on a single support substrate41in the preferred embodiments described above, the piezoelectric actuator40A is configured of two individual piezoelectric actuators40ajoined by an intermediate support member49interposed therebetween. Each piezoelectric actuator40ahas a support substrate41aand a pole-shaped piezoelectric member60. Since the pressure chambers21oppose each other at corresponding positions across the row of nozzles, instead of being staggered, the piezoelectric elements66corresponding to each of the pressure chambers21can be formed by simultaneously machining the two piezoelectric members60with a dicing saw, thereby providing an inexpensive piezoelectric actuator40A.

While both the nozzle plate10and chamber plate20are formed from silicon substrates, these plates may also be formed of molded ceramic or molded resin, provide that microstructures can be formed therein. It is also possible to form the nozzle plate10and chamber plate20by etching stainless steel plates. However, since it is difficult to achieve sufficient precision in each of these methods, silicon substrates are preferable. Further, the actuator in the preferred embodiments described above is configured of a superposed type piezoelectric body. Here, the piezoelectric body may be configured to expand and contract in a direction parallel to the planes of the electrodes formed therein or in a direction orthogonal to the planes of the electrodes.