DE69427837T2 - Ink jet head and method of making and controlling the same - Google Patents

Description

Technical area

The invention relates to an inkjet head that selectively arranges ink drops on an image recording medium, and to methods for manufacturing and controlling the same.

Technical background

Of non-impact printers, which are rapidly increasing their market share today, inkjet printers are the simplest in principle, and are also suitable for color printing. Of the inkjet printers, the most popular are so-called drop on demand (DOD) type inkjet printers, which eject ink drops only at the time of dot formation.

As representative head systems in DOD type ink jet printers, for example, a Kaiser type as disclosed in Japanese Patent Publication No. 53-12138 or a thermal jet type as disclosed in Japanese Patent Publication No. 61-59914 may be mentioned.

However, the Kaiser type ink jet head as described in Japanese Patent Publication 53-12138 has considerable problems in making it small, while the thermal jet type ink jet head as described in Japanese Patent Publication 61-59914 must apply heat of high temperature to the ink, so that the ink dries up and adheres to the head.

As an ink jet head which eliminates both of the above-mentioned disadvantages, one which uses a piezoelectric element having a piezoelectric voltage coefficient d33 (hereinafter referred to as "d33 mode type") is known.

The d33 mode type ink jet head includes in its schematic structure a strip of piezoelectric material (piezoelectric element) and electrodes each formed on both of the opposing surfaces of the piezoelectric element, the piezoelectric element being polarized in the same direction as an electric field formed across the electrodes to obtain the d33 mode type piezoelectric shear constant. The piezoelectric element is expanded and contracted in the direction of d33 by the electric field applied between the electrodes to apply pressure to an ink pressurizing chamber.

As the d33 mode type ink jet head, the separate liquid chamber type head as disclosed in Japanese Patent Publication 4-52213 and the extension liquid chamber type head as disclosed in Japanese Patent Publication 4-48622 are already known.

Of the d33 mode type ink jet heads, a structure of the separate liquid chamber type is shown in Fig. 19.

A plurality of pressurizing chambers 202 formed by covering a top plate 201 made of polysulfane, on the surface of which a plurality of grooves for an ink flow path are formed, with a thin membrane 203 made of polysulfane. A plurality of electrode patterns are formed on the membrane 203.

On the other hand, a plurality of electrodes 206 are formed on a piezoelectric element 204 which is divided by slits 207. The piezoelectric element 204 is arranged adjacent to the pressurizing chambers 202 such that the electrodes 206 are connected to their corresponding electrode patterns 208 on the diaphragm 203.

An electrode 205 is formed on the surface of the piezoelectric element 204 on the side opposite to the electrodes 206. A U-shaped rigid material 209 forming a common electrode 210 is formed on a surface forming the electrode 205. laminated. Furthermore, the rigid material 209 is bonded to edge regions of the upper plate 201 where ink flow paths are not formed by the membrane 203.

Each of the electrode patterns 208 formed on the diaphragm 203 is electrically connected to each of the electrodes 206 provided at one end of the piezoelectric element 204, while the common electrode 210 is electrically connected to the electrode 205 provided at the other end of the piezoelectric element 204.

When a voltage is externally applied between each of the electrode patterns 208 formed on the diaphragm 203 and the common electrode 210 to generate an electric field in a same direction as that of polarization of the piezoelectric element 204, the piezoelectric element 204 divided by the slits 207 expands in the direction of the electric field.

If the rigid material 209 and the top plate 201 are firmly bonded together, and the rigid material 209 is made rigid enough to withstand the stress of the piezoelectric element 204, the piezoelectric element 204 bulges the diaphragm 203 to pressurize ink to fill the pressurization chambers 202. As a result, it is possible to eject ink via nozzles 211.

Fig. 20 shows a d33 mode type ink jet head according to another example of a prior art.

The ink jet head as shown in this drawing includes a laminated piezoelectric actuator 214 formed by alternately laminating a plate-shaped piezoelectric material 212 and internal electrodes 213 made of conductive material, in place of the piezoelectric element 204 in the ink jet head as shown in Fig. 19.

This structure, in which the deformation of the plate-shaped piezoelectric material 212 is multiplied by the number of laminations, can achieve a deformation in the thickness direction (d₃₃ direction) large enough to eject ink drops for the laminated piezoelectric actuator 214.

At this time, the laminated piezoelectric actuator 214 is also deformed in the direction perpendicular to the polarization (d31 direction). However, the deformation in the d33 direction in which the amount of deformation is summed up by the number of laminations can generate a larger pressure in the pressurizing chambers 202.

Fig. 21 shows the structure of an extension liquid chamber type ink jet head of d₃₃ mode type.

It is formed from piezoelectric elements 222, each of which is formed as a piezoelectric material strip, such as PZT (lead zirconium titanium), wherein the piezoelectric elements 222 are arranged in parallel between a conductive carrier plate 221 and an insulation cover plate 223 and are attached thereto.

A plurality of narrow channels are formed between the piezoelectric elements 222. These channels consist of ink flow channels 225 serving as ink chambers/paths and dummy channels 226 serving as spacers, with the ink flow channels 225 and the dummy channels 226 being arranged alternately.

The ink flow channels 225 are connected to a common ink chamber 227 which supplies ink to the ink flow channels 225 at one end thereof. The open ends of the ink flow channels 225 serve as print nozzles.

The piezoelectric elements 222 are polarized in the direction perpendicular to the support plate 221 as indicated by an arrow 230, and the electrodes 224 are provided corresponding to the ink flow channels 225 on the upper surface of the piezoelectric elements 222 on the side of the cover plate 223. Each of the electrodes 224 is provided for each pair of piezoelectric elements.

When a voltage is applied between the electrode 224 and the conductive support plate 221, the piezoelectric elements 222 arranged on both sides of an ink flow channel 225 expand in the thickness direction and contract in the width direction. As a result of the deformation, the capacity of the ink flow channel 225 is increased.

When the application of voltage to the electrode 224 is stopped, the two piezoelectric elements 222 return to their original shape, thereby abruptly reducing the capacity of the ink flow path. As a result, an ink drop 228 is ejected from a print nozzle formed at the end portion of the path.

The purpose of the invention is to solve the following problems associated with an ink jet head having a structure in which strips of piezoelectric material are polarized in the direction of the electric field to obtain the piezoelectric voltage coefficient d₃₃ as described above, that is, the d₃₃ mode type ink jet head.

A first problem is that the d33 mode type inkjet head is structurally difficult to miniaturize by increasing the density of the arrangement of the printing nozzles and the degree of integration thereof.

For example, in the case of the separate liquid chamber type ink jet head as shown in Fig. 19, the piezoelectric elements 204 are arranged in a line in front of the slits 207 between them to separate adjacent piezoelectric elements 204, so that the manufacturing limit of the slits 207 determines the pitch of the printing nozzles 211, and consequently, it is impossible to condense the nozzle pitch. The limit of manufacturing the slits using the wire saw electron discharge method is about 150 to 200 slits per inch.

In addition, as shown in Fig. 21, the extension liquid chamber type ink jet head has a limited arrangement pitch of the piezoelectric elements 222, similar to the separate liquid chamber type head, and also requires Dummy channels 226, which do not eject ink, in every other row, making it more difficult to arrange nozzles at high density.

A second problem is that it is difficult to electrically connect the power supply source to the piezoelectric elements for driving them, and that the number of manufacturing steps is increased and the reliability of the electrical connection is reduced.

For example, in the case of the separate liquid chamber type as shown in Fig. 19, the electrodes 205 and 206 on the surface side of the piezoelectric element 204 opposite to the diaphragm 203 and on the surface side opposite to the rigid material 209 must be separately manufactured.

Furthermore, the control of the piezoelectric elements 204 by these electrodes 205 and 206 alone requires a tight connection that leaves no space between them, which was difficult in terms of manufacturing technology.

Furthermore, there was a disadvantage that in case of forming the other electrode on the piezoelectric element 204, the manufacturing cost was increased.

Furthermore, when external signal lines are connected to the electrodes, troublesome work is required to connect them individually because the electrode patterns 208 on the diaphragm 203 and the common electrode 210 are arranged differently.

Further, the electrode patterns 208 must be previously formed on the diaphragm 203 in advance, and also the material of the diaphragm 203 is limited to a non-conductive one.

Also in the case of the extension liquid chamber type, as shown in Fig. 21, the external signal lines must be electrically and separately connected to the electrodes 224 and the conductive support plate 221 serving as the common electrode.

A third problem is that the nozzle holes used to eject the ink drops are prone to clogging or ink loss.

Since the nozzles for ink ejection are formed at the end portions of the piezoelectric elements with high density in both the separate liquid chamber type and the extension liquid chamber type, it is impossible to ensure space for setting up a shutter mechanism to prevent evaporation of moisture from menisci, the liquid levels of ink in the nozzle holes, or a suction mechanism used when the nozzle holes are clogged with ink.

Even if the ink jet head includes a nozzle plate having a relatively large surface area and the nozzle holes formed at the end portions of the piezoelectric elements, it is difficult to seal the nozzle plate to prevent ink leakage because very thin members such as the base plate, the piezoelectric elements, the diaphragm, etc. must be bonded to the nozzle plate.

Also in case of using a metal nozzle plate, since the upper plate 201 made of polysulfane and the membrane 203 have different coefficients of linear expansion, a change in temperature causes the deformation of members, resulting in the breakage of the structure.

A fourth problem is that the energy loss or interference between pressurizing chambers easily occurs, resulting in insufficient or changing ink ejection force to reduce the performance of the inkjet head.

When the piezoelectric element is pre-displaced in the thickness direction (d33 direction), the displacement occurs in the direction (d31 direction) perpendicular to it.

Since the piezoelectric element and the diaphragm or the base plate are connected via an electrode, the d31 directional displacement of the piezoelectric element causes a unimorph deformation between the diaphragm and the piezoelectric element.

Accordingly, in the case of the separate liquid chamber type ink jet head, the unimorph deformation causes the warpage of the diaphragm 203. As a result, a loss in the thickness direction displacement of the piezoelectric element 204 occurs, so that additional energy is required for ejecting ink.

In the case of the extension liquid chamber type ink jet head, the unimorph deformation warps the support plate 221 and the insulating cover plate 223 to generate interference between ink flow channels.

A fifth problem is that it requires high precision in assembly and is difficult to manufacture.

In the case of the separate liquid chamber type ink jet head as shown in Fig. 19, the piezoelectric element 204 and the rigid material 209 must be bonded to the diaphragm 203 with high accuracy in positioning, allowing no deviation, in order to transmit slightest deformation of the piezoelectric element 204 to the diaphragm 203.

However, in the case of the conventional structure in which the electrodes 206 are formed at one end of the piezoelectric element 204 and brought into contact with the diaphragm 203, it is impossible to smooth the portions of the rigid material 209 and the piezoelectric element 204 that are bonded to the diaphragm 203 by performing processing such as surface grinding. Accordingly, it was difficult to bond with high accuracy.

JP 3-272856(A) discloses an inkjet head according to the preamble of claim 1, wherein the deformation of the piezoelectric actuators occurs parallel to the surface of the base plate.

The object of the invention is to solve such problems in the D₃₃ mode type ink jet head as described above and to provide an ink jet head which causes little energy loss and can be efficiently driven and manufactured at low cost due to its simple and small structure and which has high reliability and density, and a method for manufacturing such an ink jet head.

This object is achieved by an inkjet head according to claim 1 and a method according to claim 7, respectively.

Further developments of the invention are specified in the subclaims.

An ink jet head according to a first aspect of the invention includes a base plate, a plurality of partitions formed by laminating plate-shaped piezoelectric material layers polarized in the thickness direction by conductive material layers interposed therebetween, a cover, and a sealing member, the plurality of partitions being arranged on the base plate with given gaps therebetween, the gaps being sealed with the cover at the upper portion and by the sealing member at the peripheral portions to form the pressurizing chambers, and a nozzle opening being formed at a portion of each of the pressurizing chambers.

Such a structure can provide an ink jet head that is made with a small number of members and that has good ink ejection performance.

Furthermore, in the ink jet head according to the first aspect of the invention, the partitions are formed as laminated piezoelectric actuators having the piezoelectric stress coefficient d33, which are deformed in the thickness direction when voltage is applied thereto.

An ink jet head according to a second aspect of the invention includes a base plate, a plurality of partitions formed by alternately laminating plate-shaped piezoelectric material layers polarized in the thickness direction with conductive material layers disposed therebetween, a cover and a sealing member, the plurality of partitions being arranged in a matrix with predetermined gaps therebetween on the base plate, the gaps being covered with the cover at the upper portion and by the sealing member at the edge portions thereof to form pressurizing chambers, a nozzle hole for each pressurizing chamber is formed at a portion of each pressurizing chamber in each base plate or the cover, and an ink supply port formed at a portion of each pressurizing chamber on the base plate, the sealing member or the cover, each partition being deformed in the thickness direction by applying stress to the conductive material layers of the Partition is applied to change the capacity of each pressurizing chamber filled with ink so as to eject ink drops via each nozzle hole. Such a structure can also provide an ink jet head having a small number of members as well as good ink ejection performance. In the case of the ink jet head according to the first and second aspects of the invention, the gaps formed between the partitions may alternately be pressurizing chambers for supplying ink in a direction of lamination and dummy spaces that do not supply ink.

Due to the above structure, it is possible to eject an ink droplet simultaneously from adjacent nozzles.

The ink jet head according to the first and second aspects of the invention may also be constructed such that the pressurizing chambers are covered with individual covers. As a result, it is possible to reduce interference between the pressurizing chambers.

The ink jet head according to the first and second aspects of the invention may be constructed such that the gaps forming the dummy spaces are smaller in width than those forming the pressurizing chambers, thereby increasing the pitch of the nozzle holes.

The ink jet head according to the first and second aspects of the invention may be constructed such that insulation cover films are provided on the partitions on the surfaces thereof facing the pressurizing chambers, thereby enabling the water-soluble ink, insulation can be ensured for electrodes formed of conductive material exposed on the surface of the partitions.

Short description of the drawings

Fig. 1 is a front cross-sectional view of an ink jet head showing its structure according to a first example useful for understanding but not an embodiment of the invention.

Fig. 2 is a side cross-sectional view of an ink jet head showing its structure according to the first example.

Fig. 3A is a perspective view of a laminated piezoelectric element block constituting the ink jet head, showing a method of manufacturing the same according to the first example.

Fig. 3B is a perspective view of a laminated piezoelectric element block constituting the ink jet head, showing the method of manufacturing the same following the preceding drawing according to the first example.

Fig. 3C is a perspective view of the laminated piezoelectric element block constituting the ink jet head, showing a method of manufacturing the same following the foregoing drawing according to the first example.

Fig. 4 is a perspective view of a piezoelectric actuator constituting the ink-jet head, showing a method of manufacturing the same according to the first example.

Fig. 5 is an exploded perspective view of an ink jet head showing its structure according to a second example useful for understanding, but not an embodiment of the invention.

Fig. 6 is a front cross-sectional view of an ink jet head showing its structure according to the second example.

Fig. 7 is a perspective view of a laminated piezoelectric actuator constituting the ink jet head, showing a method of manufacturing the same according to the second example.

Fig. 8 is a partial cross-sectional plan view of an ink jet head according to a third example useful for understanding but not an embodiment of the invention.

Fig. 9 is a front cross-sectional view of an ink jet head showing its structure according to a fourth example useful for understanding, but not an embodiment of the invention.

Fig. 10 is an enlarged front cross-sectional view of an ink jet head according to a fifth example useful for understanding but not an embodiment of the invention.

Fig. 11 is a perspective view of an ink jet head showing its structure according to a first embodiment of the invention.

Fig. 12 is a front cross-sectional view of the ink jet head showing its structure according to the first embodiment of the invention.

Fig. 13A is a perspective view of a piezoelectric element block of the ink-jet head, showing the method of manufacturing the same according to the first embodiment of the invention.

Fig. 13B is a perspective view of the piezoelectric element block of the ink-jet head, showing a method of forming the same, following the foregoing drawing according to the first embodiment of the invention.

Fig. 13C is a perspective view of the piezoelectric element block of the ink-jet head, showing the process of forming the same, following the foregoing drawing according to the first embodiment of the invention.

Fig. 14 is a perspective view of the piezoelectric element block of the ink-jet head, showing the process of forming the same, following the foregoing drawing according to the first embodiment of the invention.

Fig. 15 is a perspective view of a laminated piezoelectric actuator of the ink-jet head, showing a method of forming the same according to the first embodiment of the invention.

Fig. 16 is a perspective view of an ink jet head showing a structure thereof according to a second embodiment of the invention.

Fig. 17 is a side cross-sectional view of the ink jet head showing its structure according to the second embodiment of the invention.

Fig. 18 is a cross-sectional view of the ink jet head according to a modified example of the first and second embodiments of the invention.

Fig. 19 is a perspective view of an ink jet head showing its structure according to a prior art.

Fig. 20 is a cross-sectional view of an ink jet head showing its structure according to another prior art.

Fig. 21 is a perspective view of an ink jet head showing its structure according to still another prior art.

Best mode for carrying out the invention

An ink jet head according to the embodiments of the invention will be described below with reference to the drawings.

Figs. 1 and 2 show an ink jet head according to a first example useful for understanding but not an embodiment of the invention, wherein Fig. 1 is a front cross-sectional view and Fig. 2 is a side cross-sectional view.

As shown in Fig. 1, the ink jet head according to this example includes a pair of laminated piezoelectric actuators 111 and 111. These pairs of laminated piezoelectric actuators 111 and 111 are formed by alternately laminating plate-shaped piezoelectric material layers 130 of piezoelectric ceramic made of a composite material of lead zirconium oxide and lead titanium, and conductive material 130 of silver palladium to expose the conductive material layers 131 from the end surfaces thereof.

The pairs of laminated piezoelectric actuators 111 and 111 are arranged in series on a base plate 110 made of ceramics, etc. so as to form a matrix-laminated piezoelectric actuator unit 112, a plurality of rows of which are perpendicular to the surface of the paper (see Fig. 2).

An electrode film is formed on the outer end surface of each laminated piezoelectric actuator 111 on which the conductive material layers 131 are exposed, the electrode film serving as a drive collecting electrode 113a to which voltage can be applied from the outside.

On the other hand, since the central region side end surfaces of the pair of laminated piezoelectric actuators 111 face each other, the electrode film continuously covering these end surfaces is formed as a common collecting electrode 113b serving as a common electrode for the conductive material layers 131 exposed on the end surfaces. The common collecting electrode 113b serving as a common electrode for the conductive material layers 131 thus serves as a common electrode for the pair of laminated piezoelectric actuators 111 (see Fig. 1).

With this structure, each laminated piezoelectric actuator 111 can be driven by applying a voltage between each drive collecting electrode 113a and the common collecting electrode 113b serving as a common electrode.

As shown in Fig. 1, the electrode films of the drive collecting electrodes 113a and the common collecting electrode 113b may extend onto the base plate 110 so as to facilitate electrical connection to the outside.

Using the opposite central end surfaces of the pair of laminated piezoelectric actuators 111 as a common electrode as described above can reduce the distance therebetween, so that the laminated piezoelectric actuators 111 can be mounted at high density. In addition, it also has the advantage that the number of contacts for electrical connection to the outside can be reduced.

A metal diaphragm 115 is bonded to the upper surface of the laminated piezoelectric actuators 111. A metal flow path plate 118 including a plurality of pressurizing chambers 116 and a common ink flow path 117 communicating with an external ink tank (not shown) formed thereon is bonded to the upper surface of the metal diaphragm 115.

Each pressurizing chamber 116 to be filled with ink is formed at the position adjacent to its corresponding laminated piezoelectric actuator 111 through the diaphragm 115 therebetween.

The flow path plate 118 and the metal membrane 115 may be formed as an integrated member, not as separate members.

A metal nozzle plate 120 having a plurality of nozzle holes is bonded to the upper surface of the flow path plate 118. Each nozzle hole 119 is located at the position where it communicates with its corresponding pressurization chamber 116.

As shown in Fig. 2, of the plurality of laminated piezoelectric actuators 111 arranged on the base plate 110, the laminated piezoelectric actuators 126 and 126 arranged at frontmost and rearmost positions are inactive ones that are not driven. These non-driven piezoelectric actuators 126 and 126 ensure a sufficient width compared with the driven laminated piezoelectric actuators 111, and have high rigidity.

The base plate 110 and the flow path plate 118 containing the pressurizing chambers 116 formed thereon are fixedly connected to each other via the non-driven laminated piezoelectric actuators 126 and 126.

The diaphragm 115 is not disposed between the non-driven inactive laminated piezoelectric actuators 126 and 126 and the flow path plate 118, so that the diaphragm 115 is not bonded to these laminated piezoelectric actuators 126 and 126.

When the laminated piezoelectric actuator 111 is driven to press the diaphragm 115 towards its corresponding pressurizing chamber 116 due to the deformation of the laminated piezoelectric actuator 111, the deformed diaphragm 115 is supported by the partitions 118a of the flow path plate 118. If the partitions 118a are made of a hard material and bonded to the metal diaphragm 115 through a bonding surface having a sufficient width, the supporting condition of the diaphragm 115 is considered to be firmly fixed to both ends of a beam.

However, in order to assemble them at high density, each of the partitions 118a of the flow path plate 118 cannot secure more than a width of several tens of µm, so that it cannot have sufficient rigidity. Accordingly, it is inevitable that the diaphragm 115 is somewhat elastically supported. In particular, when the flow path plate 118 is formed of a material with low rigidity such as plastic, etc., the diaphragm 115 is more elastically supported.

If the diaphragm 115 extends to the non-driven laminated piezoelectric actuators 126 and 126, which ensure sufficient width and high rigidity so as to be clamped by the laminated piezoelectric actuators 126 and 126 and the flow path plate 118, the support condition of the metal diaphragm 115 becomes rigid at both ends thereof but remains elastic at its central portion, so that the performance of transmitting oscillation distributed across the diaphragm 115 becomes uneven.

As a result, the pressure applied to the pressurizing chambers 116 varies with the position, so that a phenomenon occurs such that the property of ejecting ink drops becomes uneven over the entire ink jet head.

In an ink jet head having such a structure, even if the flow path plate 118 is formed of a metal material having high rigidity, a difference of 10 and several percent was observed in the speed of ejection of ink drops between a nozzle hole 119 at the central portion and a nozzle hole 119 adjacent to the non-driven laminated piezoelectric actuators 126 and 126. Moreover, when the flow path plate 118 was formed of plastic such as PSF, etc. having high rigidity, a difference of about 30% was observed in the speed of ejection of ink drops.

When the speed of ejection of ink drops varies with position as described above, in the case of a so-called serial printer that forms characters or images by scanning a paper with a print head, a change in time occurs until the ink drops reach the paper serving as a printing medium. As a result, the position of a pixel formed by an ink drop adhering to the paper deviates, deteriorating the print quality.

On the other hand, when the ink jet head has a structure in which the non-driven laminated piezoelectric actuators 126 and 126 and the diaphragm 115 are not bonded to each other, the support condition between the metal diaphragm 115 and the flow path plate 118 is the same, so that the speed of ejection of ink drops is uniform over the entire ink jet head when an ink jet from a pressurization chamber 116 by driving its corresponding laminated piezoelectric actuator 111.

Furthermore, if the pressurizing chambers 116 adjacent to the non-driven laminated piezoelectric actuator 126 are dummy chambers and ink is not ejected from them, the problem of uneven speed of ejected ink drops as described above can be almost eliminated. However, the provision of such dummy pressurizing chambers 116 results in a waste of space and is not favorable for miniaturization.

A method of manufacturing the matrix-laminated piezoelectric actuator unit 112 in the above-mentioned ink-jet head is described below.

3A, 3B, 3C and 4 are perspective views showing the method of manufacturing the matrix-laminated piezoelectric actuator unit 112 as described above, with the manufacturing steps shown in order.

As shown in Fig. 3A, the first conductive material layer 131 is formed by the printing method on a first ceramic sheet made of piezoelectric ceramic and is the plate-shaped piezoelectric material layer 130. At this time, the central region of the plate-shaped piezoelectric material layer 130 is not covered with the first conductive material layer 131 to form a first exposed region 130a.

As shown in Fig. 3B, a second ceramic sheet, which becomes the plate-shaped piezoelectric material layer 140, is laminated on the first conductive material layer 131, and then a second conductive material layer 141 is formed by printing on the upper surface of the piezoelectric material layer 140. At this time, both end surfaces of the plate-shaped piezoelectric material layer 140 are left uncovered by the second conductive material layer 141 to form a second exposed region 140a.

In this way, the ceramic sheets, the plate-shaped piezoelectric material layers and the conductive material layers are laminated on each other and then subjected to the pressure sintering process to form a piezoelectric element block 150 as shown in Fig. 3C.

Next, as shown in Fig. 4, the piezoelectric element block 150 is bonded to the base plate 110, and a first gap 160 reaching the base plate 110 is sequentially formed by using a cutting tool such as a diamond cutter, etc.

Subsequently, a gold (Au) thin film is formed on the entire piezoelectric element block 150 and the base plate 110 by thin film forming means such as vacuum deposition and the like, whereby an electrode film 161 is formed on the upper surface of the base plate 110, the end surfaces of the piezoelectric element block 150, and the inner surface of the first gap 160.

Subsequently, the electrode film 161 is removed from the upper surface of the piezoelectric element block 150 and other unnecessary surfaces by means of surface grinding, etc. to form a laminated piezoelectric actuator block 162 as shown in Fig. 4.

The second slots 163, as shown in Fig. 2 (not shown in Fig. 4), are formed in the consequently formed laminated piezoelectric actuator block 162 in a direction substantially perpendicular to the first slot 160 with a diamond cutter, etc. The second slots 163 reach the base plate 110, but are narrower than the first slot 160. The sequential formation of the second slots 163 at a given pitch completes the laminated piezoelectric actuator 111.

According to the above manufacturing steps, the electrode film 161 is divided into a plurality of patterns as shown in Fig. 4 so as to be able to drive each laminated piezoelectric actuator 111 individually. The laminated piezoelectric Actuators 111 are subjected to the polarization process in the thickness direction by applying a sufficient voltage thereto via the electrode film 161.

The inventor of the invention used 22 plate-shaped piezoelectric material layers 130 each having a thickness of 20 µm and 21 first conductive material layers 131 to construct a laminated piezoelectric actuator 111 having a thickness of about 0.5 mm by laminating them on each other.

Since the laminated piezoelectric actuator 111 was 0.5 mm thick and bonded to the base plate 110 at the bottom portion thereof with high rigidity at the connection, the laminated piezoelectric actuators 111 arranged on the base plate 110 were not likely to fall off due to processing, etc. As a result, the arrangement pitch of the laminated piezoelectric actuators 111 could be more than 150 per inch.

Moreover, a distance between the pair of opposing laminated piezoelectric actuators 111 can be less than 0.5 mm since a common electrode is formed by electrically connecting the opposite sides of the paired laminated piezoelectric actuators 111 to each other at the central portion of the base plate while individual driving electrodes of the laminated piezoelectric actuators 111 are formed on the outer sides thereof. By using such a simple processing method, it is possible to construct a laminated piezoelectric actuator with high mounting density on a plane.

Moreover, according to the structure of the matrix-laminated piezoelectric actuator unit 112 and the method of manufacturing the same as mentioned above, no conductive material layer 131 is formed on the upper surface of the uppermost plate-shaped piezoelectric material layer 130 of the laminated piezoelectric actuator 111 and on the lower surface of the lowermost plate-shaped piezoelectric material layer 130 Consequently, the top and bottom plate-shaped piezoelectric material layers 130 are dummy layers to which no voltage is applied.

When voltage is applied to a laminated piezoelectric actuator 111 polarized in the thickness direction, it expands in a thickness direction (d33 direction). At the same time, individual plate-shaped piezoelectric material layers 130 contract in a longitudinal direction (d31 direction) perpendicular thereto. However, when the uppermost and lowermost plate-shaped piezoelectric material layers 130 are dummy layers as described above, they do not generate such deformation, so that they do not exert an obligatory deformation force on the metal diaphragm 115 and the base plate 110 which are bonded to the upper and lower surfaces of the uppermost and lowermost plate-shaped piezoelectric material layers 130, respectively.

When the uppermost and lowermost plate-shaped piezoelectric material layers 130 of the laminated piezoelectric actuator 111 are dummy layers, the deformation of the laminated piezoelectric actuator 111 in the longitudinal direction thereof can be absorbed into the laminated piezoelectric actuator 111 which is a relatively soft member, so as to prevent the metal diaphragm 115 and the base plate 110 connected thereto from being deformed.

As a result, it is possible to prevent energy loss due to longitudinal deformation of the metal diaphragm 115 and crosstalk between laminated piezoelectric actuators 111 due to the deformation of the base plate 110.

Moreover, according to the structure of the matrix-laminated piezoelectric actuator unit 112 and the method of manufacturing the same as described above, it is possible to manufacture the ink-jet head easily and with high accuracy by sequentially laminating and bonding the laminated piezoelectric actuator unit 112, the metal diaphragm 115, the flow path plate 118 and the nozzle plate 120 together.

And it is possible to easily form a nozzle plate 120 with a large surface area to provide sufficient space for establishing the shutter mechanism to prevent evaporation of moisture from menisci as ink level in the nozzle holes 119 and to ensure sufficient space for establishing the suction mechanism used when the nozzle holes 119 are blocked by ink drops. Moreover, it is possible to easily form a seal to prevent ink leakage because the nozzle plate 120 and the flow path plate 118 are bonded to each other over a relatively large surface area.

The ejection operation of the above inkjet head is described below.

In a first step of the operation, voltage is applied between the drive collecting electrode 113a and the common collecting electrode 113b to form an electric field in the plate-shaped piezoelectric material layers 130 in their polarized direction, whereby the laminated piezoelectric actuator 111 gradually expands in the thickness direction (d33 direction). This action of the laminated piezoelectric actuator 111 presses a part of the diaphragm 115 into a pressurizing chamber 116 so as to reduce its capacitance in advance. At this time, the laminated piezoelectric actuator 111 is driven slowly enough to prevent ink inside the pressurizing chamber 116 from being ejected via the nozzle hole 119.

The inventor of the invention carried out the embodiments under the condition that the piezoelectric stress coefficient d33 of the laminated piezoelectric actuator 111 was 450 x 1012 m/V, and the number of the plate-shaped piezoelectric material layers 130 was 20 without the dummy layers. When a voltage of 30 V was applied between the drive collecting electrode 113a and the common collecting electrode 113b, the plate-shaped piezoelectric material layer 130 expanded by about 0.014 µm per layer in the thickness direction, so that the laminated piezoelectric actuator 111 expanded by 0.27 µm in total upon deformation of 20 of the plate-shaped piezoelectric material layers 130.

This deformation reduces the capacity of a pressurization chamber 116 by an amount substantially equal to that of one ink drop ejected at a time.

The operation then proceeds to a second step in which the electric field generated in the previous step is gradually weakened to reduce the displacement of the laminated piezoelectric actuator 111. As a result, the capacity of the pressurizing chamber 116 is increased compared with that in the first step of the operation, so that ink is supplied to the pressurizing chamber 116 via the common ink flow path 117 as shown in Fig. 1.

In a third step of the operation, an electric field is abruptly generated in the polarized direction of the plate-shaped piezoelectric material layers 130 to expand the laminated piezoelectric actuator 111 in the direction of thickness (d33 direction). At this time, the pressure in the pressurizing chamber 116 is abruptly increased to eject the ink filling the pressurizing chamber 116 via the nozzle hole 119.

Finally, in a fourth step of the operation, a voltage of the same level as in the first step is applied to the laminated piezoelectric actuator 111. The fourth step of the operation can be omitted by making the voltage applied in the first step equal to that in the third step.

According to such a driving method, since an electric field is always applied to the laminated piezoelectric actuator 111 in the same direction as the polarization, it is possible to prevent the generation of reverse polarization which weakens the polarization of the laminated piezoelectric actuator 111. Moreover, it is possible to make the ejection speed or diameter of the ink drops uniform because the oscillation of the liquid surfaces (menisci) in the nozzle holes 119 following the ink liquid generated in the pressurizing chambers 116 can be reduced by slowly adding ink in the second step of the operation.

5 and 6 show an ink jet head according to the second example, which is useful for understanding but not an embodiment of the invention, in which Fig. 5 is an exploded perspective view and Fig. 6 is a cross-sectional front view. The second example will be described below with alternate reference to Figs. 5 and 6.

As shown in Figs. 5 and 6, a pair of laminated piezoelectric actuators 111 are arranged in series on the base plate 110 made of ceramics, etc. The plural pairs of laminated piezoelectric actuators 111 are arranged in the longitudinal direction, thereby forming a matrix-laminated piezoelectric actuator unit 112. The laminated piezoelectric actuator is formed by alternately laminating plate-shaped piezoelectric material layers of piezoelectric ceramic made of a composite material of lead zirconium oxide and lead titanium and the conductive material layers of silver palladium, and baking them.

As shown in Fig. 6, the driving collecting electrodes 113a formed of thin films of gold (Au) by thin film forming means such as evaporation, etc. are formed on the outer end surfaces of the laminated piezoelectric actuators 111, and the common collecting electrode 113b is formed at the other end portions thereof by using a similar means.

As shown in Figs. 5 and 6, the ceramic supports 114a are bonded to both end portions of the base plate 110 so that the upper surfaces of the supports 114a are in the same plane as the upper surfaces of the laminated piezoelectric actuators 111. Similarly, the ceramic supports 114b are also formed between the pairs of laminated piezoelectric actuators 111.

The metal diaphragm 115 is bonded to the upper surfaces of the laminated piezoelectric actuators 111 and the supports 114a and 114b.

Then, a metal flow path plate 118 is bonded to the diaphragm 115. A plurality of pressurizing chambers 116 and a common ink flow path 117 communicating with an external ink tank not shown are formed on the flow path plate 118. Each pressurizing chamber and its corresponding laminated piezoelectric actuator 111 are arranged above and below the diaphragm 115, respectively, to face each other across the diaphragm 115.

The diaphragm 115 is clamped by the supports 114a and 114b of the matrix laminated piezoelectric actuator unit 112 and the partitions 118a of the flow path plate 118.

In addition, the metal nozzle plate 120 with the nozzle holes 119 is bonded to the upper surface of the flow path plate 118. Each nozzle hole 119 communicates with its corresponding pressurization chamber 116.

The wire patterns 123 are formed on a circuit substrate 121 with a pitch equal to the arrangement pitch of the laminated piezoelectric actuators 111. On the other hand, the wire patterns 122 electrically connected to the drive collecting electrodes 113a and the common collecting electrode 113b are formed on the base plate 110. These wire patterns 123 and the wire patterns 122 are bonded to each other by a conductive adhesive.

Further, the drive ICs 125 for driving the laminated piezoelectric actuators 111 by applying a voltage thereto are mounted on the circuit substrate 121. The drive ICs 125 are electrically connected to the wire patterns 123 and the wires 124.

When an external signal is supplied to the wires 124, the drive ICs 125 are operated to apply voltage between the drive collecting electrodes 113a of the laminated piezoelectric actuator 111 and the common collecting electrode 113b via the wiring patterns 123 and the wire patterns 122, and to generate an electric field in the plate-shaped piezoelectric material of the laminated piezoelectric actuator 111. This electric field deforms the plate-shaped piezoelectric material in the thickness direction (d33 direction), the plate-shaped piezoelectric material is polarized in the direction of the electric field.

In this way, the laminated piezoelectric actuator 111 expands in the thickness direction (d33 direction). At the same time, the laminated piezoelectric actuator 111 also contracts in the direction (d31 direction) perpendicular thereto. Consequently, small gaps are preferably provided between the laminated piezoelectric actuators 111 and the supports 114a adjacent thereto, or bonded together with an elastic bonding material. Such a structure prevents limitation of the laminated piezoelectric actuator 111 in the direction perpendicular to the thickness and generation of deformation loss in the thickness direction.

Although not shown in detail in the drawing, the laminated piezoelectric actuators 126 and 126 located at the longitudinal end portions of the base plate 110 as shown in Fig. 5 are not used to drive the diaphragm 115, but to electrically connect the common collecting electrode 113b as shown in Fig. 1 to the wire patterns 122 on the base plate 110, so that an internal electrode to be electrically connected to the common collecting electrode 113b is formed in each of the laminated piezoelectric actuators 126.

The material constituting each member is not limited to the above. For example, the base plate 110, the supports 114a and 114b may be formed of glass if they are insulating members. The diaphragm 115, the flow path plate 118 and the nozzle plate 120 may be formed of plastic, etc.

As described above, the materials for forming the base plate 110, the laminated piezoelectric actuator 111, the diaphragm 115, the flow path plate 116 and the nozzle plate 120 can be arbitrarily selected, however, the materials described above can minimize the deformation of the members caused by different thermal expansion between them because they have substantially the same coefficient of linear expansion, whereby the ejection performance of the ink jet head remains constant even when the temperature changes.

Furthermore, the base plate 110, the supports 114a and 114b can be integrally formed by using a part of the piezoelectric material of the laminated piezoelectric actuator.

In addition, the supports 114b, which have the function of firmly fixing the membrane 115 and the flow path plate 118, may be omitted if the flow path plate 118 is sufficiently rigid.

The partitions 118a provided between adjacent pressurizing chambers 116 in the flow path plate 118 are bonded to the upper surface of the diaphragm 115, while the opposite surface (lower surface) contacts the grooves formed between the laminated piezoelectric actuators 111. When the diaphragm 115 and the flow path plate 118 are bonded to each other with a bonding material, etc., it is preferable to first bond the diaphragm 115 and the flow path plate 118 together, and then bond the bonded diaphragm 115 and the flow path plate 118 to the laminated piezoelectric actuators 111, the supports 114a and 114b by pressing them together. In this way, it is possible to press the diaphragm 115 onto the laminated piezoelectric actuators 111 while supporting the diaphragm 115 with a jig inserted into the pressurizing chambers 116 formed by forming holes on the flow path plate 118.

In addition, when the diaphragm 115 is clamped by the partitions 118a of the flow path plate 118 and the supports 114a, it can be firmly fixed so that the diaphragm 115 stably functions as an elastic body. If the flow path plate 118 can be firmly bonded to the diaphragm 115 to stably support it, the supports 114a and the flow path plate 118 can be directly bonded to each other without interposing the diaphragm 115 therebetween.

Since the structure of laminating the nozzle plate 120 to the flow path plate 118 can bond them together with a large surface area, it does not matter even if the bonding material is squeezed out of the nozzle holes 119. As a result, no strict requirements on bonding quality are required to enable the manufacture of a product.

In addition, since the nozzle plate 120 can ensure a large surface area, it is easy to mount thereon the shutter mechanism to ensure the quality of menisci, i.e., the liquid levels in the nozzle holes 119, and a suction mechanism to remove the ink blocking the nozzle holes 119.

According to the embodiment experimented by the inventor, it was possible to provide a laminated piezoelectric actuator 111, 3 mm in length and 0.5 mm in thickness, and having high rigidity and high frequency. As a result, the continuous ink ejection performance was improved.

The laminated piezoelectric actuator 111 has high rigidity to be less likely to break, and furthermore, the arrangement of the common electrode at the central region and the drive electrodes at outer end surfaces enables the provision of electrical connection with a minimum space, thereby increasing the mounting density of the laminated piezoelectric actuator 111 on a plane.

In addition, since the supports 114a are arranged on the end surfaces of the laminated piezoelectric actuators 111 to bond the base plate 110 and the flux path plate 118, even if each laminated piezoelectric actuator 111 is individually controlled , its reactive force and the pressure thereby generated in its corresponding pressurizing chamber 116 do not produce pressure loss in the pressurizing chamber 116 by changing the distance between the base plate 110 and the flow path plate 118 or do not produce interference between the pressurizing chambers 116 by deformation of the base plate 110 and the flow path plate 118.

Moreover, since the diaphragm 115 is firmly clamped by the supports 114a and 114b and the partitions 118a of the flow path plate 118, the oscillation system of the diaphragm 115 becomes stable and excessive oscillation is not generated even when the pressurizing chamber 116 is pressed by the laminated piezoelectric actuator 111, so that it has excellent efficiency, and little interference occurs between adjacent pressurizing chambers 116.

Although not described in detail in the above structure, the use of the top plate-shaped piezoelectric material layer of the laminated piezoelectric actuator 111 as a dummy layer that does not function enables the laminated piezoelectric actuator 111 and the supports 114a and 114b to be smoothed by means of surface grinding, etc., and thus bonded to the diaphragm 115 with high accuracy and without gaps therebetween.

In addition, if the lowermost plate-shaped piezoelectric material layer of the laminated piezoelectric actuator 1111 is formed of a dummy layer that does not function, even if the laminated piezoelectric actuator 111 is deformed in the d31 direction, the dummy layer can absorb the deformation to relieve the stress in the bonding surface between the base plate 110 and the laminated piezoelectric actuator 111.

The ink ejection operation of the above-mentioned ink jet head will be described below mainly with reference to Fig. 6.

First, in a first step of the operation, voltage is applied between the drive collecting electrode 113a and the common collecting electrode 113b to generate an electric field in the plate-shaped piezoelectric material in the direction of polarization and to gradually expand the laminated piezoelectric actuator 111 in the thickness direction (d33 direction).

The capacity of the pressurizing chamber 116 is reduced in advance by this operation of pressing the diaphragm 115 into the pressurizing chamber 116. At this time, the laminated piezoelectric actuator 111 is driven sufficiently slowly so as not to eject ink inside the pressurizing chamber 116 via the nozzle hole 119.

The operation then proceeds to the second step, wherein the electric field generated in the previous step is gradually weakened to reduce the displacement of the laminated piezoelectric actuator 111. This operation increases the capacity of the pressurizing chamber 116, compared with the operation of the first step, to supply ink to the pressurizing chamber 116 via the common ink flow path 117 as shown in Fig. 5.

In a third step of the operation, an electric field is sequentially generated in the plate-shaped piezoelectric material in the direction of polarization to greatly expand the laminated piezoelectric actuator 111 in the direction of thickness. At this time, the pressure in the pressurizing chamber 116 is increased abruptly to eject the ink that has filled the pressurizing chamber 116 from the nozzle hole 119.

Finally, in the fourth step, voltage applied to the laminated piezoelectric actuator 111 is reduced until it has the same level as in the first step. The fourth step of the operation can be omitted by making the voltage applied to the laminated piezoelectric actuator 111 in the first step equal to that in the third step.

According to such a driving method, since an electric field is constantly applied to the laminated piezoelectric actuator 111 in the direction of polarization, no reverse polarization occurs which weakens the polarization of the laminated piezoelectric actuator 111. Moreover, since the oscillation of the liquid surfaces (menisci) in the nozzle holes 119 following that of ink generated in the pressurizing chambers 116 can be weakened by gradually supplying the ink at the second step of the operation, it is possible to make the ejection speed or diameter of the ink droplets uniform even when the laminated piezoelectric actuator 111 is driven at different frequencies.

The method of manufacturing the laminated piezoelectric actuator unit 112 in the above-mentioned ink jet head will be described below with reference to Figs. 3A, 3B, 3C and 7.

The manufacturing process of the piezoelectric element block 150 shown in Figs. 3A to 3C is substantially identical to that of the laminated piezoelectric actuator unit 112 according to the first example described above.

As shown in Fig. 3A, the first conductive material layer 131 is formed by printing method on a first ceramic sheet made of piezoelectric ceramic, and is the plate-shaped piezoelectric material layer 130. At this time, the central region of the plate-shaped piezoelectric material layer 130 remains uncovered by the first conductive material layer 131 so as to be the first exposed region 130a.

Then, as shown in Fig. 3B, a second ceramic sheet as the plate-shaped piezoelectric material layer 140 is laminated on the first conductive material layer 131, and the second conductive material layer 141 is formed by printing method on the upper surface of the plate-shaped piezoelectric material layer 140. At this time, the both end surfaces of the plate-shaped piezoelectric Material layer 140 uncovered by the second conductive material layer 141 so as to form the second exposed region 140a.

The piezoelectric element block 150, as shown in Fig. 3C, is formed by laminating the ceramic sheets on each other to form the plate-shaped piezoelectric material layers and the conductive material layers, and then applying the pressure sintering process thereto.

Then, as shown in Fig. 7, the piezoelectric element block 150 is bonded to the base plate 110, and sequentially, the first slits 160a and 160b reaching the base plate 110 are formed in the piezoelectric element block 150 by using a cutting tool such as a diamond cutter, etc.

Subsequently, a thin film of gold (Au) is formed over the entire piezoelectric element block 150 and the base plate 110 by using thin film forming means such as vacuum deposition, and the electrode film 161 is formed on the upper surface of the base plate 110, on the end surfaces of the piezoelectric element block 150, and on the inner surfaces of the first slots 160a and 160b.

Then, the electrode film 161 is removed from the upper surface of the piezoelectric element block 150 or other unnecessary surfaces by surface grinding, etc., so as to form the laminated piezoelectric actuator block 162 as shown in Fig. 4.

The second slots 163 (not shown in Fig. 7) are formed on the formed laminated piezoelectric actuator block 162 in the direction substantially perpendicular to the first slots 160a and 160b by using a diamond cutter, etc. The second slots 163 reach the base plate 110, but are narrower than the first slots 160a and 160b. Successive formation of the second slots 163 at a given pitch completes the manufacture of the laminated piezoelectric actuator 111.

In the manufacturing step as described above, the electrode film 161 is divided into a plurality of patterns as shown in Fig. 7 so as to individually drive each laminated piezoelectric actuator 111.

Then, as shown in Fig. 5, the supports 114a are bonded to the base plate 110 and the upper surfaces of the laminated piezoelectric actuators 111, and the supports 114a and 114b are simultaneously subjected to surface grinding.

The step of surface grinding and the step of forming the second slots 163, as mentioned above, may be performed in the reverse order.

According to the structure of the ink jet head and the method of manufacturing the laminated piezoelectric actuator 111, it is possible to easily form the electrical connection structure for driving the piezoelectric actuator 111 by using the thin film forming means and grinding.

Moreover, due to its structure, the protruding portions of the laminated piezoelectric actuator 111 are small, so that damage such as breakage hardly occurs. Furthermore, since it does not involve a heavy manufacturing step, each member can be formed with high accuracy, and it can be easily assembled by laminating the members and bonding them together, the manufacturing cost is low.

An ink jet head according to a third example, which is useful for understanding but is not an embodiment, will be described below.

The ink jet head according to the third embodiment has a structure in which the arrangement of the nozzle holes 119 and the laminated piezoelectric actuators 111 in the ink jet head described in the first and second embodiments is changed. Accordingly, other parts except for the above-described substantially identical to those of the first and second embodiments, so that a description thereof is omitted.

Fig. 8 is a partial cross-sectional view showing the nozzle plate 120, the flow path plate 118, the diaphragm 115, and the laminated piezoelectric actuator unit 112.

In Fig. 8, the axes marked with X1 and X2 are those that cross the nozzle holes 119 provided on the nozzle plate 120 and show the arrangement direction of the nozzle holes 119. The axes marked with Y is an axis that cross the axes X1 and X2 at right angles on the nozzle plate 120.

According to this example, the pairs of laminated piezoelectric actuators 111 and 111 are arranged in series, with each laminated piezoelectric actuator 111 arranged along an axis Z, θ° relative to the axis Y.

Moreover, the plural pairs of laminated piezoelectric actuators 111 are arranged in series in the direction of the axes X1 and X2 with arrangement intervals of P1 .

Each of the plurality of pressurizing chambers 116 formed in the flow path plate 118 is also arranged parallel to the axis Z, inclined by θ° relative to the axis Y corresponding to each laminated piezoelectric actuator 111.

The nozzle plate 120 contains the nozzle holes 119, each of which communicates with its corresponding pressurization chamber 116.

The nozzle holes 119 on the axis X1 and those on the axis X2 are each arranged in the direction of the axes with the distance of P1. Provided that the x-component of the distance between a nozzle hole 119 on the axis X1 and its Neighboring nozzle hole 119 on the axis X2 is P2 and the distance between the axes X1 and X2 is S, the nozzle holes 119 are arranged to satisfy the expression:

P2 = S · tanθ = P1/2

When the ink jet head having such a structure is moved in the Y-axis direction in Fig. 8 relative to a printing medium such as paper, etc. to print characters, the arrangement pitch of the nozzle holes 119 in the X1(X2) axis direction becomes 1/2 compared with the first and second embodiments, so that printed pixels have double density and an image with extremely good quality can be obtained.

According to the example experimented by the inventor, the arrangement pitch of the nozzle holes 119 can be set to 300 dpi by forming grooves on the laminated piezoelectric body bonded to the base plate 110 at a pitch of 150 dpi. At this time, the inclination angle θ was quite small, on the order of 0.03 rad, so that, in particular, the shape of the laminated piezoelectric actuators 111 or the pressurizing chamber 116 did not deviate from a rectangular shape to a parallelogram shape as shown in Fig. 8.

A fourth example, which is useful for understanding but is not an embodiment of the invention, is described below mainly with reference to Fig. 9.

The structure of the ink jet head according to this example is identical to that of the second example as mentioned above, except for a laminated piezoelectric actuator unit 170 which will be described later.

The laminated piezoelectric actuator unit 170 is described below according to its manufacturing steps.

A laminated piezoelectric body 171 is formed by laminating plate-shaped piezoelectric material layers and conductive material layers and by subjecting the thus laminated material layers to a pressure sintering process, as in the second embodiment.

First slits 172a and 172b are formed on the central portion of the laminated piezoelectric body 171, and the drive collecting electrodes 173a and the common collecting electrodes 173b are formed on both end surfaces of the laminated piezoelectric body 171 and inside the first slits 172a and 172b, respectively.

The second slits, similar to the second slits 163 (see Fig. 5) in the second embodiment, are laminated in the thus formed laminated piezoelectric body 171 in the direction substantially perpendicular to the first slits 172a and 172b at a given pitch, thereby completing the laminated piezoelectric actuator unit 170.

The drive collecting electrodes 173a are separated from each other by forming slits having the same pitch as the second slits mentioned above to serve as individual drive electrodes corresponding to the respective laminated piezoelectric blocks 171.

Then, the diaphragm 115, the flow path plate 118 and the nozzle plate 120 are laminated and bonded together to form an ink jet head, as in the second embodiment.

The feature of this example lies in forming the base plate 110 and the supports 114a and 114b of the ink jet head of the second embodiment from the laminated piezoelectric actuator itself, instead of forming them as other members.

One of the pairs of first conductive material layers 131 and second conductive material layers 141 facing each other for driving each plate-shaped piezoelectric material layer 130 and each plate-shaped piezoelectric material layer 140 does not exist on the bottom portion, the outer end portions, and around the central portion of the laminated piezoelectric blocks 171. As a result, the portions do not deform even when voltage is applied thereto. Thus, the bottom portion and the outer end portions and the central portion of the laminated piezoelectric blocks 171 are used as the base plate and the supports, respectively, to reduce the number of members.

According to the fourth example, the cost of the members and the number of manufacturing steps can be reduced, so that the ink jet head can be easily manufactured.

The fifth example, which is useful for understanding but is not an embodiment of the invention, is described below with reference to Fig. 10.

The ink jet head according to this example is also similar to those of the first to fourth examples mentioned above, except for a laminated piezoelectric actuator unit 180 which will be described later.

The ink jet head of this example has a structure in which the connection structure of the laminated piezoelectric actuators, the diaphragm and the flow path plate in the above-mentioned first to fourth examples is modified.

As shown in Fig. 10, a plurality of laminated piezoelectric actuator units 180 are arranged in a row at a given pitch, the rows of the driven actuators 183 and the rows of the non-driven actuators 184 are arranged alternately, and the non-driven actuators 184 are arranged every other rows used as supports.

A diaphragm 181 is connected to the upper end surfaces of the driven actuators 183 and the non-driven actuators 184, which serve as supports, and further a flow path plate 182 is connected to the upper surface of the diaphragm 181. The diaphragm 181 is clamped by the non-controlled actuators 184 and the partitions of the flow path plate 182.

In addition, the nozzle plate 120 is bonded to the upper end surface of the flow path plate 182.

Such a structure makes the supporting condition of the diaphragm 181 constant, so that it is possible to prevent the uneven ink ejection performance and interference between adjacent pressurizing chambers.

An ink jet head according to a first embodiment of the invention will be described below with reference to Figs. 11 and 12.

The ink jet head according to the first and later embodiments has substantially the same structure with respect to the laminated piezoelectric actuator unit as the ink jet head according to the first to fifth examples mentioned above, but the former are quite different from the latter in the structure of the pressurizing chambers and the principle of ink ejection.

The ink jet head according to the first to fifth examples has a structure in which a laminated piezoelectric actuator provided outside a pressurizing chamber presses it to eject ink drops therefrom, but in the ink jet head according to the sixth and later embodiments, the pressurizing chamber is formed in the laminated piezoelectric actuator.

Consequently, the members are designated with new reference numerals for explanation in the drawings (Figs. 11 to 18) showing the first and later embodiments.

As shown in Figs. 11 and 12, a first plate-shaped piezoelectric material layer 1a and a second plate-shaped piezoelectric material layer 1b bonded together with a first conductive material layer 2a interposed therebetween. Further, the second plate-shaped piezoelectric material layer 1b and the third plate-shaped piezoelectric material layer 1c are bonded together with a second conductive material layer 2b interposed therebetween.

The first plate-shaped piezoelectric material layer 1a is polarized in the thickness direction, while the second plate-shaped piezoelectric material layer 1b is polarized in the direction reverse to that of the first plate-shaped piezoelectric material layer 1a. The third plate-shaped piezoelectric material layer 1c is polarized in the direction reverse to that of the second plate-shaped piezoelectric material layer 1b.

Each of the partitions 10 is formed by successively laminating the necessary number of conductive material layers and the plate-shaped piezoelectric material layers in a similar structure.

A first collecting electrode 3a made of a thin gold (Au) film, etc., formed by using thin film forming means such as a vacuum evaporation method, is provided on the end surface of the partitions 10. The first conductive material layer 2a, the third conductive material layer 2c, etc. are electrically connected to the first collecting electrode 3a.

On the other hand, the second collecting electrode 3b is provided on the other end surfaces of the partitions 10 by using the means similar to the first collecting electrode 3a, and the second conductive material layer 2b, a fourth conductive material layer 2d, etc., are electrically connected to the second collecting electrode 3b.

When a voltage is applied between the first collecting electrode 3a and the second collecting electrode 3b in the ink jet head having such a structure, a potential difference is generated between the conductive material layers to generate an electric field in the plate-shaped piezoelectric material layer in the direction of thickness. As a result, the partitions 10 function as piezoelectric element blocks.

A plurality of these partitions 10 are arranged in a matrix on a base plate 11, on which an ink supply port 13 has an opening. These partitions 10 are bonded to the base plate 11 with a bonding agent to form longitudinal gaps 20 and 21 and a transverse gap 29 between the partitions 10.

Furthermore, a sealing member 22 is fixed on the base plate 11 by bonding so as to contact the longitudinal outer end surfaces of the partitions 10. A cover 14 covers the longitudinal gaps 20 and 21 and the upper surface of the sealing member 22 to form a plurality of pressurizing chambers 15 surrounded by these partitions 10, the sealing member 22 and the cover 14.

A plurality of nozzle holes 23, each communicating with a corresponding pressurizing chamber 15, are formed in the cover 14.

Wiring patterns 25 electrically connected to the collecting electrodes 3a and 3b of the partitions 10 are provided on the upper surface of the base plate 11. These wiring patterns 25 are connected to flexible wiring boards 26, and an external drive voltage is applied to the collecting electrodes 3a and 3b of the partitions 10 via these flexible wiring boards 26 and the wiring patterns 25.

Although not shown in Figs. 11 and 12, ink may be supplied from the ink supply port 13 from a common ink tank of an ink cartridge.

Although the ink supply port 13 is formed on the base plate 11 according to this embodiment, it may be formed in the sealing member 22, the cover 14, or the like.

In the ink jet head as described above, the partitions 10 as laminated piezoelectric actuators are arranged in two rows so that the nozzle holes 23 can be opened in the thickness direction to realize the high density of mounting of the partitions 10. The partitions 10 may also be arranged in one row depending on their use.

The operation of the ink jet head according to the above embodiment will be described below with reference to Figs. 11 and 12.

When electric power is supplied to the first and second collecting electrodes 3a and 3b from the flexible wiring plates 26 connected thereto through the wiring patterns 25, a voltage is generated between the first conductive material layers 2a and the second conductive material layers 2b. An electric field is generated in the second plate-shaped piezoelectric material layer 1b in the thickness direction.

The second plate-shaped piezoelectric material layer 1b is pre-polarized in advance in the direction opposite to that of the electric field. As a result, the second plate-shaped piezoelectric material layer 1b contracts in the thickness direction (d33 direction).

Assuming that the thickness of the second plate-shaped piezoelectric material layer 1b is t, the strain is δt, the voltage applied thereto is V, and the piezoelectric stress coefficient in the thickness direction is d33, the following expression can be formed since the stress is proportional to the strength of the electric field:

δ/t = d₃₃V/t

δ = d₃₃V

The above expression means that the deformation is proportional to the voltage, and does not depend on the thickness of the piezoelectric material layer.

Each of the laminated piezoelectric material layers is deformed similarly to the second plate-shaped piezoelectric material layer 1b so that the total deformation in the thickness direction is proportional to the number m of the laminated piezoelectric material layers on both surfaces of which electrodes are formed to be m · δt, thereby obtaining a large deformation m times as large as that of a single layer.

Although smaller than the deformation in the thickness direction (d33 direction) as mentioned above, the piezoelectric material partitions 10 also expand in the longitudinal direction (d31 direction), thereby reducing the capacity of the pressurizing chambers 15.

The deformation of the laminated piezoelectric material in the thickness direction (d33 direction) as mentioned above generates a strong force, thereby reducing the capacity of the pressurizing chamber by S · m · δt, assuming that the cross-section of the pressurizing chamber 15 is S. The reduction in capacity, i.e., the change in volume, generates pressure in the pressurizing chamber 15, which can eject an ink drop 17 via the nozzle hole 23.

The formation of an ink drop 17 requires a given change in the capacitance of the pressurizing chamber 15, but the ink jet head according to the embodiment as described above can obtain a sufficient change in the capacitance even with a single-layer piezoelectric element block. As a result, an ink drop 17 having a stable size can be formed.

Moreover, in the ink jet head according to the embodiment, as described above, the deformation of one layer of the piezoelectric element block can be multiplied by m, so that it is possible to form the cross section 5 of a pressurizing chamber to be 1/m of the cross section in the case of the single-layer piezoelectric element block, so that the pressurizing chamber can be made small.

As a result, it is possible to reduce the length of the pressurization chamber, which is advantageous in terms of ink supply, as described below.

In order to successively form the ink droplet 17, it is necessary to supply ink from the ink supply port 13 to the pressurizing chamber 15 as quickly as the ink droplet 17 is ejected therefrom. In the above-mentioned embodiment, the ink supply port 13 is provided at an end portion of the pressurizing chamber 15 opposite to the nozzle hole 23.

Accordingly, the ink flow path formed in the pressurizing chamber 15 in the longitudinal direction thereof preferably has a small flow resistance and a small length.

In the ink jet head according to this embodiment, the dimension of the partitions 10 each formed of laminated piezoelectric element blocks in the thickness direction, that is, the height of the pressurizing chamber 15 depends on the thickness of the plate-shaped piezoelectric material layer and the number of laminated layers. The height of the pressurizing chamber 15 can be increased by increasing the number of plate-shaped piezoelectric material layers so as to increase the change in capacity of the pressurizing chamber 15.

Basically, the pressure generated is proportional to [change in capacity]/[capacity of pressurizing chamber]. Consequently, the increased capacity can be compensated by the change in capacity so that the ejection force is not reduced.

The cross-section of the pressurizing chamber 15 can be increased by increasing the height of the partitions 10. As a result, the flow resistance of the ink flow path formed in the pressurizing chamber 15 can be made small, and furthermore, the ink flow path can be made short. Accordingly, it is possible to improve the ink supply performance so as to successively To form ink droplets 17 having a stable size, thereby improving the efficiency of successive ejection of the ink droplet 17.

A similar structure using single-layer type partitions cannot change the change of the capacity of the pressurization chamber, but on the contrary can increase the capacity of the pressurization chamber following the increase of the height of the pressurization chamber, so that the pressure generated therein is reduced.

To increase the pressure generated in it, the voltage applied to it can be increased, but it is not practical to increase the voltage by more than 150 V.

Furthermore, in the ink jet head according to the embodiment, the piezoelectric element block is formed by laminating a plurality of plate-shaped piezoelectric material layers, so that the deformation of the plate-shaped piezoelectric material layer can be increased in proportion to the number of layers. As a result, it is possible to reduce the applied voltage necessary to obtain a certain deformation compared with a single-layered plate-shaped piezoelectric material, thereby enabling the piezoelectric element block to be driven with a low voltage of less than 50 V.

Furthermore, the most important feature of the ink jet head according to this embodiment is that a plurality of pressurizing chambers 15 can be arranged in a matrix on the base plate 11 to realize a two-dimensional arrangement. As a result, it is possible to form a pressurizing chamber 15a and a pressurizing chamber 15b which are independent of each other in a longitudinal gap 21 as shown in Fig. 11.

In this way, it is possible to form a plurality of rows of nozzle holes 23 by arranging independent pressurizing chambers 15 as a matrix on the base plate 11 and by forming individual nozzle holes 23 each corresponding to each of the pressurizing chambers 15 corresponding to each other. As a result, it is possible to realize a multi-nozzle inkjet head.

This property occurs due to the formation of the partitions 10 from laminated plate-shaped piezoelectric material layers and the driving of the same to obtain a large deformation. Since a large deformation can be obtained, it becomes possible to miniaturize each pressurizing chamber 15 and thus to arrange a plurality of independent pressurizing chambers 15 as a matrix on the base plate 11.

Although ink is ejected by contracting the piezoelectric element block according to the Examples and the embodiments described above, it is also possible that the electric field is generated in the same direction as the polarization of the plate-shaped piezoelectric material layers to expand them in the thickness direction to increase the capacity of the pressurizing chambers 15, thereby stopping the application of the voltage to return the piezoelectric element block to its original state, thereby generating a pressure for ejecting ink.

In Fig. 11, the longitudinal gaps 20 serve as pressurization chambers 15 filled with ink, and the longitudinal gaps 21 adjacent thereto form dummy spaces not filled with ink.

It becomes possible to separately control the adjacent pressurizing chambers 15, which form the longitudinal gaps 20 and 20a, by forming therebetween the dummy space, which is not filled with ink.

As a result, it becomes possible to control the pressurization chambers 15 independently of time, e.g. to eject ink inside adjacent pressurization chambers 15 simultaneously or with a time delay.

In the case where the longitudinal gap 21 is not used as a dummy space that is not filled with ink, the partition 10 between the adjacent pressurizing chambers 15 is used in common for controlling them. Accordingly, it is necessary to set the conditions such that when one of the pressurizing chambers 15 is controlled, an ink drop is not ejected from the other pressurizing chamber.

Concretely, a laborious setting is required to prevent the partitions 10 from being offset by more than a given value by selecting the timing for driving the partitions 10 so that ink is not ejected in synchronism with the oscillation level of the meniscus in the nozzle hole or the like.

Since the longitudinal gap 21 serving as a dummy space is formed only to allow the partitions of adjacent pressurizing chambers 15 to function independently, it may have a sufficient width to prevent adjacent partitions 10 from coming into contact with each other.

Reducing the dimension of the width of the longitudinal gap 21 forming a dummy space to its manufacturing limit is effective in increasing the pitch of the arrangement of the pressurizing chambers 15. Accordingly, it is possible to obtain a small head with a high density nozzle pitch.

The method of manufacturing the ink jet head according to the above-mentioned embodiments will be described below with reference to Figs. 13A, 13B, 13C, 14 and 15.

As shown in Fig. 13A, first, the first conductive material layer 2a is formed by printing method on the upper surface of a first ceramic sheet made of piezoelectric ceramic, and is the first plate-shaped piezoelectric material layer 1a. At this time, the central surface region 41a of the first plate-shaped piezoelectric material layer 1a is uncovered by the first conductive material layer 2a to be in an exposed state.

Second, as shown in Fig. 13B, a new second ceramic sheet constituting the second plate-shaped piezoelectric material layer 1b is laminated on the first conductive material layer 2a, and the second conductive material layer 2b is formed on the surface thereof by printing. At this time, both edge portions of the second plate-shaped piezoelectric material layer 1b are left uncovered by the second conductive material layer 2b to be exposed.

In this way, it is possible to form a piezoelectric element block 60 as shown in Fig. 13C by alternately laminating a given number of ceramic sheets which are the plate-shaped piezoelectric material layer and the conductive material layer and then applying the pressure sintering process thereto.

Then, as shown in Fig. 14, the piezoelectric element block 60 is bonded to the upper surface of the base plate 11 made of glass material, etc.

Subsequently, a portion of the piezoelectric element block 60 and the base plate 11 is cut by using a cutting tool such as a diamond cutter, etc. to form the transverse gap 29.

Moreover, a thin film of a conductive material such as gold (Au) or the like is formed on the entire piezoelectric element block 60 and the base plate 11 by means of vacuum deposition, etc. while masking the upper surface 61 of the piezoelectric element block 60 to form an electrode 70.

In this way, the first conductive material layer 2a, the second conductive material layer 2b, etc. in the piezoelectric element block 60 are electrically connected to the electrode 70 formed on the side surfaces 70a and 70b.

As shown in Fig. 15, the piezoelectric element block 60 and a portion of the base plate 11 are successively cut by a cutting tool such as a diamond cutter, etc. in a direction perpendicular to the transverse gap 29. As a result, the partitions 10, the longitudinal gap 20 and the longitudinal gap 21 are formed to divide the piezoelectric element block 60 and the electrode 70.

Then, as shown in Fig. 11, the sealing member 22 is bonded to the end portions of the partitions 10, and the cover 14 formed of a glass material, etc., and in which the nozzle holes 23 are formed are bonded to the partitions 10 to form the pressurization chambers 15.

According to the above-mentioned manufacturing method, as shown in Fig. 15, a first collecting electrode 80a, a second collecting electrode 80b, and a third collecting electrode 80c, each of which has a conductive material for driving the piezoelectric element block connected thereto, can be easily formed at both end portions of each of the partitions 10.

Moreover, as shown in Fig. 15, the provision of the first collecting electrodes 80a and the second collecting electrodes 80b at both end portions of the partitions 10 in the first row, and the provision of the second collecting electrode 80b and the third collecting electrode 80c at both end portions of the partitions 10 in the second row is effective because it enables the electrical connection to external drive lines.

According to the above-mentioned manufacturing method, as shown in Fig. 15, wiring patterns 81 for supplying electric power to the first collecting electrodes 80a on the base plate 11, the wiring patterns 82 for supplying electric power to the second collecting electrodes 80b, and the wiring patterns 83 for supplying electric power to the third collecting electrodes 80c can be formed simultaneously.

The structure in which the wiring patterns 81, 82 and 83 are formed on the base plate 11 as shown in Fig. 15 has an effect to enable the electrical connection with the flexible wiring plates 26 as shown in Fig. 11.

The second collecting electrodes 80b serve as common electrodes for driving first row partitions 10a and second row partitions 10b. As a result, all partitions 10 have the wiring patterns 82 as a common electrode, it is possible to reduce the number of electrical contacts between the flexible wiring boards 26 and the partitions 10.

Although the method for manufacturing the ink jet head according to the first embodiment has been described above, the invention is not limited to this structure.

For example, the base plate 11 is not limited to the glass material, but may also be formed of a material such as ceramic, plastic or the like.

Ceramic, plastic and metal materials can be used for the cover 14, with the exception of glass materials.

Although piezoelectric ceramic has been used as a plate-shaped piezoelectric material, an organic macromolecular piezoelectric film can also be used.

No electrodes are formed on the bonding surface between the partitions 10 and the base plate 11, and on the bonding surface between the partitions 10 and the cover 14. However, the plate-shaped piezoelectric material bonded to the base plate or the cover is also controllable by providing conductive material to form electrodes on the surfaces of the piezoelectric element block 60 where it contacts the base plate or the cover.

Although the vacuum deposition method was used to form the collecting electrodes, it is also possible to form the electrodes on the end surfaces of the piezoelectric element block by using the conductive coating to directly connect the collecting electrodes on the piezoelectric element block to the flexible wiring boards.

An ink jet head according to a second embodiment of the invention will be described below with reference to Figs. 16 and 17.

A plurality of partitions 10 are arranged in a row on the base plate 11 and bonded thereto.

The partitions 10 are identical in structure to those of the first embodiment. A first plate-shaped piezoelectric material layer 1a and a second plate-shaped piezoelectric material layer 1b are bonded with a first conductive material layer 2a disposed therebetween, and further, the second plate-shaped piezoelectric material layer 1b and a third plate-shaped piezoelectric material layer 1c are bonded with a second conductive material layer 2b disposed therebetween, thereby constructing a laminated piezoelectric actuator.

The first plate-shaped piezoelectric material layer 1a is polarized in the thickness direction, while the second plate-shaped piezoelectric material layer 1b is polarized in the direction opposite to that of the first plate-shaped piezoelectric material layer 1a. Further, the third plate-shaped piezoelectric material layer 1c is polarized in the direction opposite to that of the second plate-shaped piezoelectric material layer 1b.

The first collecting electrode 3a made of a thin gold (Au) film, etc. is formed by using the thin film forming means such as vacuum evaporation, etc. The first conductive material layer 2a, etc. is electrically connected to the first collecting electrode 3a.

On the other hand, the second collecting electrode 3b is provided on the other end surfaces of the partitions 10 by using similar means as the first collecting electrode 3a, and the second conductive material layer 2b, etc. is connected to the second collecting electrode 3b.

When voltage is applied between the first collecting electrode 3a and the second collecting electrode 3b of the ink jet head having such a structure, a voltage difference is generated between the conductive material layers to generate an electric field in the plate-shaped piezoelectric material layer in the thickness direction. As a result, the partitions 10 function as laminated piezoelectric actuators.

The longitudinal gaps 20 and 21 formed between these partitions 10 are closed at one longitudinal end surface with the sealing member 22. A nozzle plate 24 with nozzle holes 23 formed therein is provided at the other end surface. The nozzle plate 24 also functions as a sealing member for the longitudinal gaps 20 and 21.

In addition, the cover 14 is provided to cover the upper portions of the longitudinal gaps 20 and 21. The cover 14 is fixed to the upper surface of the partitions 10 by means of bonding.

In the arrangement described above, the gaps 20 form pressurization chambers 15. The gaps 21 are dummy spaces to which no ink is supplied, similarly to the first embodiment mentioned above.

The ink supply ports 13 are formed on the cover 14, from which ink is supplied to the pressurizing chambers 15.

In the ink jet head according to this embodiment, ink supplied to the pressurizing chambers 15 by means of the ink supply ports 13 is ejected in the longitudinal direction of the pressurizing chambers 15 via the nozzle holes 23. Also according to this embodiment, it is possible to form an ink droplet 17 having a stable size, similarly to the above-mentioned sixth embodiment.

Fig. 18 is a modified example of the above-mentioned first and second embodiments.

In the ink jet head according to the above-mentioned first and second embodiments, the longitudinal gaps 20 filled with ink may also be covered with independent caps 30.

In the ink jet head having such a structure, mechanical influence such as the displacement of the partitions 10 for ejecting ink drops or the transmission of oscillation due to the deformation of the caps 30 does not reach adjacent pressurizing chambers 15. As a result, it is possible to completely avoid interference between the pressurizing chambers 15.

Moreover, in the ink jet head according to the above-mentioned first and second embodiments, an insulating cover film is formed on the inner surface of the pressurizing chambers.

For example, a cover film 40 is formed on the inner surfaces of the partitions 10 constituting the pressurization chambers 15 as shown in Fig. 18 due to chemical evaporation with polyparaxylene resin, etc.

Driven electrodes electrically connected to conductive material layers are exposed on the inner surfaces of the partitions 10 forming the pressurization chambers 15. Accordingly, this structure has the disadvantage that available ink limited, e.g., water-soluble ink, etc. cannot be used without additional devices. Consequently, the cover film 40 having good electrical insulation properties is formed on the partitions 10 within the pressurizing chamber 15 to prevent ink from contacting the drive electrode.

As a result, a chemical change in the ink does not corrode the drive electrode; and does not generate gas, so that either water-soluble or oil-soluble (non-aqueous) ink is applicable.

In addition, if the piezoelectric element block is formed such that the conductive material is embedded in the partitions 10 forming the pressurizing chambers 15 in advance, various kinds of ink can be used without forming the cover film.

Commercial applicability

The inkjet head according to the invention can be used in various types of inkjet printers.

The invention makes it possible to provide a small and high-resolution inkjet head that can be effectively driven with little energy loss and that can be manufactured at low cost due to its simple structure and that has high reliability.

Claims (8)

1. Inkjet head with a base plate (11), a plurality of partitions (10) formed by laminating a plurality of plate-shaped piezoelectric material layers (1a-1c) polarized in a thickness direction with conductive material layers (2a-2d) disposed therebetween, a cover (14), and a sealing member (22), wherein the plurality of partitions (10) are arranged with given gaps (20, 21, 29) interposed therebetween on the base plate (11), the gaps (20, 21, 29) being closed by the cover (14) at their upper portions and by the sealing member (22) at their side portions to form pressurizing chambers (15), and a nozzle hole (23) is formed at a portion of each of the pressurizing chambers (15), characterized in that the direction of the thickness of the plate-shaped piezoelectric material layers extends between the base plate (11) and the cover (14); and the partitions (10) are laminated piezoelectric actuators, each of which has a piezoelectric stress coefficient d33 and is deformed in the thickness direction when a stress is applied thereto. 2. Ink jet head according to claim 1, characterized in that the uppermost layer and the lowermost layer of each of the laminated piezoelectric actuators (10) are formed of dummy layers which are not driven. 3. Ink jet head according to claim 1 or 2, characterized in that a plurality of drive electrodes, each electrically connected to a corresponding drive electrode of a corresponding laminated piezoelectric actuator (10), are formed on the base plate (11). 4. An ink jet head according to any one of claims 1 to 3, characterized in that the collecting electrodes formed on opposite end surfaces of the laminated piezoelectric actuators (3b, 80b) are formed at a central portion of the base plate (11) and are connected together to form a common electrode, while the collecting electrodes formed on other end surfaces of each of the laminated piezoelectric actuators (10, 10) are formed as drive electrodes (3a). 5. Ink jet head according to one of claims 1 to 4, characterized in that the plurality of partitions (10) are arranged in a matrix with given gaps (20, 21) interposed therebetween on the base plate (11), the gaps being closed by the cover (14) at upper portions and by the sealing member (22) at side portions to form the pressurizing chambers (15), the nozzle hole (23) is formed at a portion of each pressurizing chamber (15) on either the base plate (11) or the cover (14), and an ink supply port (13) is formed at a portion of each pressurizing chamber (15) on either the base plate (11), the sealing member (22) or the cover (14), and each partition (10) is deformed in the thickness direction by applying stress to the conductive material layers (2a-2d) of the partitions (10) to change a capacity of each pressurization chamber (15) to eject ink drops (17) via each nozzle hole (23). 6. Ink jet head according to one of claims 1 to 5, characterized in that the gaps (20, 21) formed between the partitions (10) one after the other are the pressurizing chambers (15) which supply ink in a row direction or dummy spaces (21) which do not supply ink, and/or that the cover consists of separate cover areas (30) and each of the pressurizing chambers (15) is closed by one of the cover areas (30) independently of each other, and/or that the gaps (20, 21) forming the dummy spaces (21) are narrower in width than those forming the pressurizing chambers (15), and/or that an insulating cover film (40) formed on a surface of each of the partitions (10) contacting the pressurizing chambers (15). 7. A method for producing an ink jet head according to any one of claims 1 to 6, comprising a first step of forming a first slot (29) at a central region of a laminated piezoelectric body (60), a second step of forming electrodes at both end portions of the laminated piezoelectric body (60) and at the first slot (160), a third step of forming a plurality of second and third slots (20, 21) narrower than the first slot (29) with a first pitch for the second slots (20) and a second pitch for the third slots (21) in a direction substantially perpendicular to the first slots (29) to form the plurality of laminated piezoelectric actuators (10) on the base plate (11), and a fourth step of smoothing the upper surfaces of the laminated piezoelectric actuators (10). 8. Method according to claim 7, characterized in that the third and fourth steps are interchanged.