Ink-jet head and method for manufacturing the same

The present invention relates to an inkjet head that ejects ink onto a recording medium for recording.

[0002] Conventional Art In an inkjet head used in a conventional inkjet printer, ink supplied from an ink tank to a manifold is distributed to a plurality of pressure chambers, and pressure is selectively applied to each pressure chamber. It is configured to eject ink from the ejection nozzle. As a means for applying pressure to each pressure chamber, there is a means for reducing the volume of the pressure chamber by deforming a piezoelectric element arranged on the pressure chamber. In this case, in general, an electric field is applied to the piezoelectric element to deform it by outputting a drive signal to the electrodes installed in the piezoelectric element. Here, the electrodes of the piezoelectric element are joined to the terminals of a printed circuit board such as a flexible printed cable (hereinafter referred to as FPC), and the drive signal from the driver IC further connected to the printed circuit board is sent to the piezoelectric element via the printed circuit board. It is designed to be transmitted to the electrodes of.

[0003] In the conventional technique, the terminals of a printed circuit board and the electrodes of a piezoelectric element are generally bonded by interposing solder between them and heat-bonding them (see, for example, Patent Document 1).

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 7-156376 [0005] [Problems to be Solved by the Invention] Here, adhesion between the actuator unit and the flow path unit is performed in each of the pressure chambers in the flow path unit. It is customary to form an adhesive layer on the wall that separates the parts, position the actuator unit on the flow path unit, and press a heater or the like from the actuator unit side to heat and press it. is there.

[0006] Under such circumstances, it is customary that the land portion electrically connected to the electrode of the piezoelectric element is formed in a convex shape on the actuator unit. Further, this land portion is usually arranged in a portion corresponding to a portion of a wall portion that partitions the pressure chamber. By doing so, in the case of the above-mentioned pressure joining, only the convex land portion is in direct contact with the pressing surface of the heater, and the brittle actuator unit can be avoided from being damaged. Further, if the land portion having a raised volume and a large volume is solder-bonded to the terminal, disconnection during soldering can be avoided as compared with the case where the electrode of the piezoelectric element is directly soldered to the terminal. There are also merits.

[0007] However, it is customary to provide one convex land portion for each electrode of the piezoelectric element in a dot shape. Therefore, when the actuator unit is pressure-bonded to the flow path unit, it is difficult to evenly transmit the force, resulting in uneven thickness of the adhesive layer between the two. The non-uniformity of the thickness of the adhesive layer causes non-uniformity of the pressure generated in the pressure chamber, and causes deterioration of the image quality of the formed image due to the variation of the discharge characteristics. In extreme cases, ink may leak between the pressure chambers.

[0008] Although a configuration in which a plurality of land portions are electrically connected and arranged with respect to one electrode of the piezoelectric element is conceivable, the number of land portions (the number of soldering portions) increases, and the substrate The configuration for electrical connection to the terminals of is complicated.

[Means for Solving the Problems] The problems to be solved by the present invention are as described above, and next, the means for solving the problems will be described.

[0010] That is, the inkjet head according to claim 1 includes a flow path unit, a plurality of pressure chambers formed in the flow path unit so as to be arranged adjacent to each other along the surface of the flow path unit, and the like.<u style="single">Previous</u>Flow flow unit<u style="single">In contact with</u>With a common electrode that is worn and kept at a constant potential<u style="single">The plurality of</u>In the position corresponding to the pressure chamber<u style="single">Respectively</u>Includes at least a piezoelectric sheet sandwiched between a plurality of individual electrodes arranged<u style="single">, To change the volume of the pressure chamber</u>An inkjet head including an actuator unit, wherein each of the individual electrodes is formed on the surface of the actuator unit at a position corresponding to one end of the pressure chamber.<u style="single">Convex</u>It is electrically connected to the feed line via the land portion, and is not electrically connected to the surface of the actuator unit at a position opposite to the center of the pressure chamber of the land portion.<u style="single">Convex</u><u style="single">of</u>The metal member is arranged, and the height of the top of the land portion and the height of the top of the metal member are equal to each other and higher than the thickness of the individual electrodes protruding from the surface of the actuator unit.<u style="single">Neither the projective range in which the land portion and the metal member are projected onto the surface of the flow path unit is included in the region where the pressure chamber is formed on the surface of the flow path unit.</u>It is characterized by that.

[0011] The inkjet head according to claim 2 is<u style="single">The inkjet head according to claim 1, wherein the actuator unit extends so as to straddle the two pressure chambers. The inkjet head according to claim 3 is</u>The individual electrodes are arranged in a matrix in the two-dimensional direction in the actuator unit.

[0012] Claim<u style="single">4</u>In the inkjet head described in the above, in addition to the land portion and the metal member of the individual electrode, at least one of the land portion or the metal member of the individual electrode adjacent to the individual electrode is formed around each individual electrode. It is characterized by being arranged.<u style="single">The inkjet head according to claim 5 is characterized in that the land portion and the metal member are arranged so as to surround the pressure chamber.</u>[0013] Claim<u style="single">6</u>In the inkjet head according to the above, the center of the pressure chamber corresponding to the individual electrode is sandwiched, and at least one of the land portion or the metal member of the individual electrode adjacent to one side of the individual electrode is arranged on one side. On the other hand, at least one of the land portion or the metal member of the individual electrode adjacent to the other side of the individual electrode is arranged.

[0014] Claim<u style="single">7</u>In the inkjet head according to the above, the pressure chamber is formed in a square shape on the surface of the flow path unit, and the land portion and the metal member are arranged in a hexagonal shape as a whole around the pressure chamber. It is characterized by being.

[0015] Claim<u style="single">8</u>The inkjet head according to the above is characterized in that the quadrangular shape is a rhombus shape and the hexagonal shape is a regular hexagonal shape.<u style="single">In the inkjet head according to claim 9, the individual electrode has a rhombus shape, and one of the acute-angled portions of the rhombus shape has an extending portion, and the extending portion of the extending portion. The land portion is provided at the tip thereof. The inkjet head according to claim 10 is characterized in that the land portion and the metal member are arranged symmetrically with respect to the center of the pressure chamber. The inkjet head according to claim 11 is characterized in that the actuator unit is made of a laminated body in which a plurality of piezoelectric sheets are laminated. In the inkjet head according to claim 12, the individual electrodes are arranged on the surface of the laminate most separated from the flow path unit, and only the piezoelectric sheet most separated from the flow path unit is the individual electrode. The common electrode is arranged at a position sandwiched with the common electrode. The inkjet head according to claim 13 is a cable bonded to the surface of the actuator unit, and includes two insulating sheet members and a feeder line sandwiched between the two sheet members. A flexible cable that penetrates one of the two sheet members and has a terminal electrically connected to the feeder is further provided, and the terminal is the surface of the actuator unit. It is characterized in that it is arranged only at a position where it is electrically connected to the land portion when it is adhered to the land portion.</u>BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First, the overall configuration of the inkjet head according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is an external perspective view of the inkjet head 1 according to the present embodiment.

[0018] The inkjet head 1 is formed with a head unit 70 having a rectangular planar shape extending in the main scanning direction for ejecting ink to paper, and a flow path of ink supplied to the head unit 70. It is equipped with a base block 71. The base block 71 has a grip portion 72a accommodating the base block 71 and a pair of flat plate members 72b extending from the upper surface of the grip portion 72a along a direction orthogonal to the plane of the base block 71 at a predetermined interval. And is supported by a holder 72, including.

Further, the FPC 50 is pulled out from the head unit 70, and the FPC 50 is arranged along the surface of the flat plate member 72b of the holder 72 via an elastic member 83 such as a sponge. Then, the driver IC80 is installed on the portion of the FPC50 arranged on the surface of the flat plate portion 72b of the holder 72. Inside the FPC50, a conductor pattern is provided as a feeder line for transmitting the drive signal output from the driver IC80 to the actuator unit 21 (detailed later) of the head unit 70.

[0020] Further, the heat sink 82 is arranged so as to be in close contact with the outer surface of the driver IC 80 so that the heat generated by the driver IC 80 is released to the heat sink 82. Further, a substrate 81 is provided above the driver IC 80 and the heat sink 82 on the FPC 50 installed on the surface of the flat plate portion 72b of the holder 72.

Next, with reference to FIG. 2, the configurations of the head unit 70, the base block 71, and the like shown in FIG. 1 will be described in more detail. FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

[0022] The head unit 70 includes a flow path unit 4 in which an ink flow path is formed, and an actuator unit 21 bonded to the upper surface of the flow path unit 4 via an adhesive. Both the flow path unit 4 and the actuator unit 21 have a configuration in which a plurality of thin plates are laminated and adhered to each other. Further, the FPC 50 is adhered to the upper surface of the actuator unit 21.

[0023] On the upper surface of the flow path unit 4, the base block 71 is fixed to a portion where the actuator unit 21 is not adhered. The actuator unit 21 is arranged in the recess 71a provided on the outside of the lower surface of the base block 71, and is not adhered to the base block 71.

[0024] The base block 71 is made of a metal material such as stainless steel, and is adhesively fixed in the grip portion 72a of the holder 72. Further, the base block 71 is provided with an ink reservoir 3 having two substantially rectangular parallelepiped hollow regions, which will be described in detail later.

The heat sink 82 arranged on the surface of the flat plate portion 72b is fixed to the substrate 81 and the FPC 50 via the sealing member 84. Further, the FPC 50 is fixed to the tip of the grip portion 72a in the holder 72 and the upper surface of the actuator unit 21 via the seal member 85.

Next, the flow of ink from the ink sump 3 formed in the base block 71 to the head unit 70 will be described with reference to FIGS. 3 to 6.

[0027] FIG. 3 is a plan view of the head unit 70 shown in FIG. From FIG. 3, it can be seen that in the longitudinal direction of the head unit 70, the two ink pools 3 also shown in FIG. 2 extend in parallel with each other at a predetermined interval. Each of the two ink reservoirs 3 has an opening 3a at one end, and is communicated with an ink tank (not shown) through the opening 3a and is always filled with ink. In addition, each ink sump 3 is provided with two openings 3b in pairs. The openings 3b provided in the two ink reservoirs 3 are arranged at predetermined intervals in the extending direction so as not to overlap in the width direction of the head unit 70.

[0028] Actuator units 21 having a trapezoidal planar shape are arranged between the pair of openings 3b, respectively. More specifically, each actuator unit 21 has a trapezoidal planar shape having parallel opposing sides (upper side and lower side) along the longitudinal direction of the head unit 70, and is arranged in a staggered pattern with adjacent hypotenuses. Overlaps in the width direction of the head unit 70.

[0029] FIG. 4 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG. From FIG. 4, it can be seen that the opening 3b provided in each ink reservoir 3 communicates with the manifold 5, and the tip of each manifold 5 branches into two to form a sub-manifold 5a. Further, in a plan view, two sub-manifold 5a branched from the adjacent openings 3b extend from each of the two hypotenuse sides of the actuator unit 21. That is, in a plan view, a total of four sub-manifold 5a extend along the parallel facing sides of the actuator unit 21.

[0030] In the lower surface of the flow path unit 4 (see FIG. 2) arranged below the actuator unit 21, ink ejection nozzles 8 are arranged in a matrix in the projection region of the actuator unit 21, and ink is ejected. A region is formed (Fig. 4). Although the discharge nozzles 8 are partially shown in FIG. 4, they are arranged in the entire projection region of the actuator unit 21 on the lower surface of the flow path unit 4.

FIG. 5 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG. FIG. 6 is a cross-sectional view of a main part of the head unit 70 and the FPC 50 arranged on the upper surface thereof. As shown in FIG. 6, the uppermost plate in the flow path unit 4 (that is, the cavity plate 22 to which the actuator unit 21 is adhered to the surface, which will be described in detail later) is formed with an opening corresponding to the pressure chamber 10. ing. Since this pressure chamber 10 is formed inside the head unit 70, it should be drawn with a broken line in FIGS. 4 and 5 showing the lower surface of the head unit 70, but it is drawn with a solid line for the sake of clarity. There is. The pressure chambers 10 are formed so as to be adjacent to each other along the surface of the flow path unit 4.

Further, as shown in FIG. 6, the pressure chamber 10 and the sub-manifold 5a communicate with each other via the aperture 12. As shown in FIG. 5, the aperture 12 is arranged at one end in the region of the sub-manifold 5a and the other end in the acute-angled portion of the pressure chamber 10 having a substantially rhombic shape.

[0033] From FIG. 5, it can be seen that the two apertures 12 are arranged so as to overlap each other with respect to one pressure chamber 10. This is achieved by providing the pressure chamber 10 and the aperture 12 at different heights. This makes it possible to arrange the pressure chambers 10 at a high density and to realize high-resolution image formation with the inkjet head 1 having a relatively small occupied area.

[0034] In the present embodiment, the pressure chamber 10 projects the actuator unit 21 in two directions, a longitudinal direction (first arrangement direction) of the head unit 70 and a direction slightly inclined from the width direction (second arrangement direction). It is formed in a matrix in the region.

[0035] Further, as shown in FIG. 5, the ink ejection nozzle 8 is a portion on the plane of the head unit 70 that is outside the range of the sub-manifold 5a and substantially corresponds to one acute angle in each of the substantially diamond-shaped pressure chambers 10. Is located in. In the present embodiment, the discharge nozzles 8 are arranged at 50 dpi in the first arrangement direction, and the pressure chambers 10 are arranged so that a maximum of 12 pressure chambers 10 are included in the region corresponding to each actuator unit 21 in the second arrangement direction. .. Then, the length of the 12 pressure chambers 10 arranged in the second arrangement direction occupying the first arrangement direction corresponds to the length occupied by the two pressure chambers 10 adjacent to the first arrangement direction. There is. That is, in the two pressure chambers 10 adjacent to each other in the first arrangement direction, there are 12 discharge nozzles 8 in the width direction of the inkjet head 1 within the range between the discharge nozzles 8 arranged at the acute angles. ing. The hypotenuse portion of the actuator unit 21 (see FIG. 4) satisfies the above condition by having a complementary relationship with the hypotenuse portion of the actuator unit 21 facing in the width direction of the inkjet head 1.

Therefore, according to the inkjet head 1 in the present embodiment, a large number of ejection nozzles 8 arranged in a matrix as the paper moves relative to the inkjet head 1 in the sub-scanning direction (see FIG. 3). Printing can be performed at 600 dpi in the main scanning direction by sequentially ejecting ink droplets from the ink jet.

As described above, the inkjet head 1 of the present embodiment is tapered from an ink tank (not shown) through an ink reservoir 3, a manifold 5, a sub-manifold 5a, an aperture 12, and a pressure chamber 10. An ink flow path 32 (see FIG. 6) is formed up to the ejection nozzle 8 formed at the tip of the ejection nozzle 8 having a shape.

Next, with reference to FIGS. 6 to 8, the cross-sectional configuration of the head unit 70 and the FPC 50 arranged on the upper surface thereof will be described in more detail.

[0039] As shown in FIG. 6, the flow path unit 4 includes a cavity plate 22, a base plate 23, an aperture plate 24, a supply plate 25, a manifold plates 26, 27, 28, and a cover in this order from the adhesive side with the actuator unit 21. A total of nine plates constituting the plate 29 and the nozzle plate 30 are laminated and adhered to each other. These plates are made of a metal such as stainless steel.

[0040] From the exploded perspective view of the main part of FIG. 7, notches and penetrations are made in each of the nine plates 22 to 30 constituting the flow path unit 4 described above, the actuator unit 21 laminated on the plates 22 to 30, and the FPC 50. You can see that the holes are provided.

Here, as shown in FIG. 6, the uppermost cavity plate 22 in the flow path unit 4 is a metal plate provided with a large number of substantially rhombic openings corresponding to the pressure chamber 10. The base plate 23 is a metal plate provided with a communication hole between each pressure chamber 10 and the aperture 12 formed in the cavity plate 22 and a communication hole from the pressure chamber 10 to the discharge nozzle 8. The aperture plate 24 is a metal plate provided with a communication hole to the discharge nozzle 8 that communicates with the communication hole formed in the aperture 12 and the base plate 23. The supply plate 25 is a metal plate provided with a connecting hole between the aperture 12 and the sub-manifold 5a and a connecting hole to the discharge nozzle 8 communicating with the connecting hole formed in the aperture plate 24. The manifold plates 26, 27, and 28 are metal plates provided with a connecting hole to the discharge nozzle 8 communicating with the connecting hole formed in the sub-manifold 5a and the supply plate 25. The cover plate 29 is a metal plate provided with a connecting hole to the discharge nozzle 8 which is smaller than the connecting holes of the manifold plates 26, 27, and 28. The nozzle plate 30 is a metal plate provided with a large number of ink ejection nozzles 8.

[0042] The flow path unit 4 is formed by stacking these nine plates 22 to 30 so as to form the ink flow path 32 shown in FIG. 6 so as to be aligned with each other. The ink flow path 32 extends upward from the sub-manifold 5a, extends horizontally at aperture 12, then further upwards, extends horizontally again in the pressure chamber 10, and then diagonally away from aperture 12 for some time. From downward, it goes vertically downward toward the discharge nozzle 8.

Further, the spatial shapes corresponding to the ink flow paths 32 shown in FIG. 6 are shown in FIGS. 8 (a) and 8 (b) as a plan view and a perspective view, respectively. Note that FIGS. 8A and 8B show a filter 13 provided at the boundary between the aperture 12 and the sub-manifold 5a. The filter 13 is for removing impurities contained in the ink.

Next, the configuration of the actuator unit 21 laminated on the uppermost cavity plate 22 in the flow path unit 4 will be described with reference to FIGS. 9 and 10. FIG. 9 is an enlarged cross-sectional view of the region surrounded by the alternate long and short dash line drawn in FIG. 6, and FIG. 10 is a plan view showing the shapes of the individual electrodes and the land portion provided on the surface of the actuator unit 21.

As shown in FIG. 9, the actuator unit 21 is laminated with four piezoelectric sheets 41, 42, 43, and 44, which are continuous flat plate layers. Each of these piezoelectric sheets 41, 42, 43, and 44 is made of lead zirconate titanate (PZT) -based ceramic material, which is highly processable and has ferroelectricity, and has a thickness of approximately 15 μm. These piezoelectric sheets 41 to 44 constitute a piezoelectric element, and are arranged across a large number of pressure chambers 10 formed in one ink ejection region in the inkjet head 1. As a result, the mechanical rigidity of the piezoelectric element is maintained high, and the responsiveness of the ink ejection performance of the inkjet head 1 is enhanced.

[0046] On the top-layer piezoelectric sheet 41, an individual electrode 35 having a planar shape shown in FIG. 10 is formed. Further, as shown in FIG. 9, between the top-layer piezoelectric sheet 41 and the piezoelectric sheet 42 below it, and between the piezoelectric sheet 43 and the piezoelectric sheet 44 below it, the entire surface of the sheet is formed. A common electrode 34a with a thickness of approximately 2 μm is interposed. No electrode is arranged between the piezoelectric sheet 42 and the piezoelectric sheet 43. Both the individual electrodes 35 and the common electrodes 34a and 34b are made of a metal material such as Ag-Pd system, and as will be described in detail later, the pressure chamber 10 is deformed by applying an electric field to the piezoelectric sheets 41 to 44. It is for changing the volume of.

As shown in FIG. 10, the individual electrode 35 has a thickness of about 1 μm and has a substantially rhombic (length 850 μm, width 250 μm) planar shape similar to that of the pressure chamber 10. One of the acute-angled portions of the substantially rhombic individual electrode 35 is extended, and a circular land portion 36 electrically connected to the individual electrode 35 is provided at the tip thereof. The land portion 36 has a thickness (top height) of 10 μm and a diameter of approximately 160 μm, and is adhered to the surface of the extending portion of the individual electrode 35 as shown in FIG. The material of the land portion 36 is, for example, gold containing a glass frit.

[0048] As shown in FIGS. 9 and 10, on the opposite side of the land portion 36 and the center of the pressure chamber 10, a circular dummy land portion (metal) having the same thickness and diameter as the land portion 36. Member) 37 is provided. The dummy land portion 37 is made of the same material as the land portion 36 (gold including glass frit), but is not electrically connected to the individual electrode 35.

As shown in FIGS. 9 and 5, the land portion 36 is provided at a position corresponding to one end of the pressure chamber 10, and the dummy land portion 37 sandwiches the center of the pressure chamber 10 of the land portion 36. It is provided at the opposite position. In the stacking direction of the piezoelectric sheets 41 to 44, the projection region of the individual electrode 35 is arranged so as to be included in the region of the pressure chamber 10, but the projection region of both the land portion 36 and the dummy land portion 37 is pressure. Not included in the area of room 10.

[0050] As shown in FIGS. 4 and 5, a large number of grounding electrodes 38 are separated from each other in the vicinity of the outer edge of the actuator unit 21. Although this grounding electrode 38 is not shown in FIG. 9, it is printed on the surface of the piezoelectric sheet 41 on the uppermost layer of the actuator unit 21, and both are connected to the common electrode 34a through a through hole formed in the piezoelectric sheet 41. Has been done. The common electrode 34a and the other common electrode 34b are connected to each other via through holes formed in the piezoelectric sheets 42 and 43.

Although not shown, the FPC 50 has a grounding terminal connected to the grounding electrode 38 in addition to the conductor pattern 53, which is a wiring connected to the driver IC 80 described later, and is grounded. A conductor pattern, which is the wiring of the above, and a grounding terminal that is electrically connected to the grounding electrode 38 are provided. When the grounding terminal (not shown) of the FPC50 and the grounding electrode 38 are joined, the common electrodes 34a and 34b connected to the grounding electrode 38 have the same ground potential in the region corresponding to all the pressure chambers 10. It is designed to be kept.

[0052] Here, a method of driving the actuator unit 21 according to the present embodiment will be described.

[0053] The polarization direction of the piezoelectric sheets 41 to 44 in the actuator unit 21 is the thickness direction thereof, which is a so-called unimorph type configuration. First, by controlling the driver IC80, the individual electrodes 35 are set to positive or negative predetermined potentials via the FPC50. For example, if the electric field and the polarization are in the same direction, the piezoelectric sheet 41, which is the active layer, shrinks in the direction perpendicular to the polarization direction, and the other piezoelectric sheets 42 to 44 do not shrink spontaneously because they are not affected by the electric field. At this time, there is a difference in distortion in the polarization direction between the piezoelectric sheets 41 and the lower piezoelectric sheets 42 to 44, and the entire piezoelectric sheets 41 to 44 are deformed to be convex toward the inactive side, that is, the pressure chamber 10 side (unimorph). Deformation) occurs. Then, the volume of the pressure chamber 10 decreases, the pressure of the ink rises, and the ink is ejected from the ejection nozzle 8 shown in FIG. After that, when the application of the driving voltage to the individual electrodes 35 is stopped, the piezoelectric sheets 41 to 44 return to their original shapes, the volume of the pressure chamber 10 also returns to the original volume, and ink is sucked from the manifold 5 side.

Further, for example, when the electric field and the polarization are in opposite directions, the piezoelectric sheet 41 which is an active layer extends in a direction perpendicular to the polarization direction, and the piezoelectric sheets 41 to 44 become concave toward the pressure chamber side due to the piezoelectric lateral effect. Curved like. Then, the volume of the pressure chamber 10 increases and ink is sucked from the manifold 5 side. After that, when the application of the drive voltage to the individual electrodes 35 is stopped, the piezoelectric sheets 41 to 44 return to their original shapes, the volume of the pressure chamber 10 also returns to the original volume, and ink is ejected from the ejection nozzle 8. ..

[0055] As another driving method, there is also a method in which a voltage is applied to the individual electrodes 35 in advance, the application of the voltage is temporarily stopped each time there is a discharge request, and then the voltage is applied again at a predetermined timing. .. In this case, the piezoelectric sheets 41 to 44 return to their original shapes when the voltage application is stopped, so that the volume of the pressure chamber 10 increases as compared with the initial state (the state in which the voltage is applied in advance). Ink is sucked in from the manifold 5 side. After that, when the voltage is applied again, the piezoelectric sheets 41 to 44 are deformed so as to be convex toward the pressure chamber 10, the pressure on the ink rises due to the decrease in the volume of the pressure chamber 10, and the ink is ejected from the ejection nozzle 8. Will be done.

[0056] The adhesion of the actuator unit 21 to the flow path unit 4 as described above is performed on the flow path unit 4 (specifically, on the portion of the wall portion that separates the pressure chambers 10 formed in the cavity plate 22 from each other. ), The adhesive layer g is formed by an appropriate method such as transfer, the actuator unit 21 is aligned and arranged on the flow path unit 4, and the ceramic heater is pressed from above on the flow path unit 4. It is done by pressing and heating.

[0057] Here, in the present embodiment, the land portion 36 is formed in a convex shape on the piezoelectric sheet 41 of the actuator unit 21, and the dummy land portion 37 is also formed in a convex shape. The heights of the tops of the land portion 36 and the dummy land portion 37 are both about 10 μm and are equal. Further, this height of 10 μm is larger than the thickness (1 μm) of the individual electrode 35 protruding from the surface of the actuator unit 21.

Therefore, when a ceramic heater having a flat pressing surface is brought into contact with the actuator unit 21 to be pressed, the pressing surface does not come into contact with the individual electrodes 35, and the land portion 36 and the dummy land portion 37 are used. Will be in contact with. At the time of bonding, the dummy land portion 37 in addition to the land portion 36 also contributes to transmitting the pressing force of the ceramic heater to the adhesive layer g side. Therefore, since the unevenness of the pressing force is reduced and the thickness of the adhesive layer g is made uniform, the variation in the ejection characteristics from the ejection nozzle 8 is reduced, and the ink leakage between the pressure chambers 10 can be avoided.

[0059] As described above, in the stacking direction of the piezoelectric sheets 41 to 44, the projection region of neither the land portion 36 nor the dummy land portion 37 is included in the region of the pressure chamber 10. That is, the land portion 36 and the dummy land portion 37 are located on the adhesive layer g on the wall portion that partitions the pressure chamber 10. Therefore, both the land portion 36 and the dummy land portion 37 effectively contribute to transmitting the pressing force from the ceramic heater to the adhesive layer g.

[0060] As shown in FIG. 10, the land portion 36 and the dummy land portion 37 are arranged symmetrically with the center of the pressure chamber 10 in a pair. As a result, the thickness of the adhesive layer g around the pressure chamber 10 becomes uniform, and the discharge characteristics are stabilized.

Further, in the present embodiment, as shown in FIG. 12, the individual electrodes 35 are arranged in a matrix in the two-dimensional direction in the actuator unit 21. As a result, a periodic arrangement pattern of the land portion 36 and the dummy land portion 37 is realized, and it is possible to achieve both uniform discharge characteristics and high resolution.

[0062] As shown in FIG. 12, around each individual electrode 35, in addition to the land portion 36 and the dummy land portion 37 of the individual electrode 35, the land of the individual electrode 35 adjacent to the individual electrode 35 is said. The portion 36 and the dummy land portion 37 are arranged.

[0063] Therefore, since the land portion 36 and the dummy land portion 37 of the adjacent individual electrodes 35 also contribute to transmitting the pressing force to the adhesive layer g, the adhesive layer g around each pressure chamber 10 is formed. The thickness can be further made uniform.

[0064] Further, as shown in FIG. 13, when focusing on one individual electrode 35 *, the center of the pressure chamber 10 corresponding to the individual electrode 35 * is sandwiched, and the individual electrode 35 * is placed on one side. The land portion 36 of the adjacent individual electrode (35A / 35X) adjacent to one side is arranged. Further, the dummy land portion 37 of the adjacent individual electrode (35B / 35Y) adjacent to the other side of the individual electrode 35 * is also arranged on the other side of the center.

[0065] Therefore, since the land portion 36 and the dummy land portion 37 are paired and arranged symmetrically with respect to the center of the pressure chamber 10, the thickness of the adhesive layer g around each pressure chamber 10 becomes more uniform. , Contributes to stabilization of discharge characteristics.

Further, as shown in FIG. 12, the pressure chamber 10 is formed on the surface of the flow path unit 4 in a quadrangular shape (specifically, a rhombus shape). Further, as shown by the chain line in FIG. 12, the land portion 36 and the dummy land portion 37 form a hexagonal shape as a whole (specifically, a substantially regular hexagonal shape) around the pressure chamber 10. It is arranged.

[0067] Therefore, the adhesive layer g formed around the pressure chamber 10 is pressed by a large number of points (that is, six land portions 36 or dummy land portions 37 located at the vertices of the hexagon). Therefore, the pressing force becomes more uniform, and the discharge characteristics become uniform. This effect is further enhanced by forming the pressure chamber 10 into a rhombus shape and arranging the land portion 36 and the dummy land portion 37 into a regular hexagonal shape.

Next, a method of joining the land portion 36 arranged on the surface of the individual electrode 35 and the terminal of the FPC 50 will be described with reference to FIGS. 14 (a) and 14 (b).

[0069] Before explaining the joining method, first, the configuration of the FPC 50 will be described with reference to FIG. 14 (a). The FPC50 includes a base film 51 having a thickness of about 25 μm, a conductor pattern 53 having a thickness of about 9 μm formed on the lower surface thereof, and a cover film 52 having a thickness of about 20 μm provided so as to cover almost the entire surface of the base film 51. And, including. A plurality of through holes 52a having an area smaller than the plane of the conductor pattern 53 are formed in the cover film 52, and by making the center of the through hole 52a correspond to the center of the conductor pattern 53, the through hole 52a is formed through the through hole 52a. The conductor pattern 53 and the terminal 54 described later are in contact with each other. The outer peripheral edge of the conductor pattern 53 is covered with the cover film 52.

[0070] Both the base film 51 and the cover film 52 are sheet members having an insulating property. In the present embodiment, the base film 51 is made of a polyimide resin, and the cover film 52 is made of a photosensitive material. By using a photosensitive material as the cover film 52 in this way, a large number of through holes 52a can be easily formed.

On the other hand, the conductor pattern (feed line) 53 arranged between the base film 51 and the cover film 52 is formed of copper foil. The conductor pattern 53 is a wiring connected to the driver IC 80 shown in FIGS. 1 and 2, and is provided so as to form a predetermined pattern on the lower surface of the base film 51.

[0072] As described above, the terminal 54 adhered to the conductor pattern 53 through the through hole 52a of the cover film 52 is made of a conductive material such as nickel. The terminal 54 is formed so as to close the through hole 52a and to protrude from the through hole 52a so as to be convex from the lower surface of the cover film 52 toward the piezoelectric sheet 41. The diameter of the terminal 54 is about 50 μm, and the thickness from the lower surface of the cover film 52 is about 30 μm.

[0073] The FPC 50 is provided with a large number of terminals 54, each of which is configured to correspond to one land portion 36. Therefore, each individual electrode 35 electrically connected to each land portion 36 is connected to the driver IC 80 via an independent conductor pattern 53 in the FPC 50, respectively. This makes it possible to control the potential for each pressure chamber 10.

[0074] The terminal 54 is not provided for the dummy land portion 37. The dummy land portion 37 is not conductive with the individual electrode 35, and is only for uniformly transmitting the pressing force of the ceramic heater to the adhesive layer g when the actuator unit 21 is adhered to the flow path unit 4. Because it is formed.

[0075] Next, an example of a method of joining the terminal 54 of the FPC 50 configured as described above and the land portion 36 will be described. First, the work of adhering the solder 60 to the surface of the terminal 54 is performed. By this operation, as shown in FIG. 14A, the entire surface of the terminal 54 is covered with the solder 60 having a thickness of about 10 μm.

Next, the terminals 54 having the solder 60 on the surface are brought into contact with the land portion 36 while being aligned as shown in FIG. 14 (b), and for example, a ceramic heater (not shown) is attached to the FPC 50. It is installed on the surface of the base film 51 side and heated. By this heating work, the solder 60 can be melted and the terminal 54 and the land portion 36 can be electrically connected to each other.

Although the embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the configuration of the above embodiment, and various transformations are possible as long as the gist of the present invention is not deviated.

[0078] For example, in the above embodiment, the metal member (dummy land portion 37) is made of the same material as the land portion 36 (gold with glass frit), but the material is not limited to this, and the material of the dummy land portion 37 is not limited to this. May be different from the land portion 36 as long as it is a metal. However, if the material of the dummy land portion 37 is the same as that of the land portion 36, the land portion 36 and the dummy land portion 37 can be formed on the surface of the actuator unit 21 at the same time, and the manufacturing man-hours can be simplified. desirable.

[0079] Further, the present invention can be similarly applied to a configuration in which individual electrodes are further arranged between the piezoelectric sheet 42 and the piezoelectric sheet 43 in the actuator unit 21. In this case, the individual electrodes 35 on the piezoelectric sheets 41 and the individual electrodes sandwiched between the piezoelectric sheets 42 and 43 are electrically connected via the through holes formed in the piezoelectric sheets 41 and 42. Just do it.

[0080] Further, the land portion 36 and the terminal 54 of the FPC are not limited to joining by solder, but are electrically joined by using, for example, ACP (Anisotropic Conductive Paste) having heat curability. You may.

[Effects of the Invention] Since the present invention is configured as described above, the following effects are exhibited.

That is, as shown in claim 1, the flow path unit and a plurality of pressure chambers formed in the flow path unit so as to be adjacent to each other along the surface of the flow path unit.<u style="single">Previous</u>Flow flow unit<u style="single">In contact with</u>With a common electrode that is worn and kept at a constant potential<u style="single">The plurality of</u>In the position corresponding to the pressure chamber<u style="single">Respectively</u>Includes at least a piezoelectric sheet sandwiched between a plurality of individual electrodes arranged<u style="single">, To change the volume of the pressure chamber</u>An inkjet head including an actuator unit, wherein each of the individual electrodes is formed on the surface of the actuator unit at a position corresponding to one end of the pressure chamber.<u style="single">Convex</u>It is electrically connected to the feed line via the land portion, and is not electrically connected to the surface of the actuator unit at a position opposite to the center of the pressure chamber of the land portion.<u style="single">Convex</u>The metal member is arranged, and the height of the top of the land portion and the height of the top of the metal member are equal to each other and higher than the thickness of the individual electrodes protruding from the surface of the actuator unit.<u style="single">Neither the projective range in which the land portion and the metal member are projected onto the surface of the flow path unit is included in the region where the pressure chamber is formed on the surface of the flow path unit.</u>Therefore, not only the land portion but also the metal member transmits the pressing force when adhering the actuator unit to the flow path unit to the adhesive layer between the two. Therefore, since the thickness of the adhesive layer becomes uniform, it is possible to avoid variations in ejection characteristics and ink leakage between pressure chambers. Further, since the land portion and the metal member are paired and arranged symmetrically with the center of the pressure chamber in between, the thickness of the adhesive layer around the pressure chamber becomes uniform, and the discharge characteristics are stabilized.

【0083】<u style="single">As shown in claim 2, since the actuator unit extends so as to straddle the two pressure chambers,</u><u style="single"> The mechanical rigidity of the piezoelectric sheet is maintained high, and the responsiveness of the ink ejection performance of the inkjet head is enhanced.</u>[0084] Claim<u style="single">3</u>As shown in the above, since the individual electrodes are arranged in a matrix in the two-dimensional direction in the actuator unit, it is possible to achieve both uniform discharge characteristics and high resolution.

[0085] Claim<u style="single">4</u>As shown in the above, in addition to the land portion and the metal member of the individual electrode, at least one of the land portion or the metal member of the individual electrode adjacent to the individual electrode is arranged around each individual electrode. Therefore, the land portion / metal member of the adjacent individual electrode also contributes to transmitting the pressing force to the adhesive layer, so that the thickness of the adhesive layer around each pressure chamber can be further made uniform.

【0086】<u style="single">In the present invention, as shown in claim 5, the land portion and the metal member may be arranged so as to surround the pressure chamber.</u>[0087] Claim<u style="single">6</u>As shown in the above, at least one of the land portion or the metal member of the individual electrode adjacent to one side of the individual electrode is arranged on one side of the center of the pressure chamber corresponding to the individual electrode, and on the other side. Also, since at least one of the land portion or the metal member of the individual electrode adjacent to the other side of the individual electrode is arranged, the land portion / metal member is paired and arranged symmetrically with the center of the pressure chamber in between. Therefore, the thickness of the adhesive layer around each pressure chamber becomes more uniform, which contributes to the stabilization of discharge characteristics.

[0088] Claim<u style="single">7</u>As shown in the above, the pressure chamber is formed in a square shape on the surface of the flow path unit, and the individual electrodes and the metal member are arranged in a hexagonal shape as a whole around the pressure chamber. Therefore, the adhesive layer formed around the pressure chamber is pressed by a large number of points (that is, six lands / metal members located at the vertices of the hexagon), so that the pressing force is higher. It becomes uniform, and uniform discharge characteristics are realized.

[0089] Claim<u style="single">8</u>As shown in the above, the quadrangular shape is a rhombus shape, and the hexagonal shape is a regular hexagonal shape. Therefore, due to the symmetry of the arrangement shape of the land portion / metal member, the pressing force becomes more uniform and the discharge characteristic. Good uniformity is achieved.

【0090】<u style="single">In the present invention, as shown in claim 9, the individual electrode has a rhombic shape, and one of the acute-angled portions of the rhombus shape has an extended portion, and the extension portion is provided. The land portion may be provided at the tip of the protruding portion.</u><u style="single">【0091】</u><u style="single"> As shown in claim 10, since the land portion and the metal member are arranged symmetrically with respect to the center of the pressure chamber,</u><u style="single"> The thickness of the adhesive layer around the pressure chamber becomes uniform, and the discharge characteristics are stabilized.</u><u style="single">【0092】</u><u style="single"> In the present invention, as shown in claim 11, the actuator unit may be made of a laminated body in which a plurality of piezoelectric sheets are laminated. As shown in claim 12, the individual electrodes are arranged on the surface of the laminate farthest from the flow path unit, and the front electrode is arranged.</u><u style="single">The common electrode may be arranged at a position where only the piezoelectric sheet farthest from the flow path unit is sandwiched with the individual electrodes.</u><u style="single">【0093】</u><u style="single">Further, as shown in claim 13, the present invention is a cable bonded to the surface of the actuator unit, and is sandwiched between two insulating sheet members and the two sheet members. A flexible cable having a feed line and a terminal penetrating one of the two sheet members and electrically connected to the feed line is further provided, and the terminal is the flexible cable and the flexible cable is the actuator. It may be arranged only at a position where it is electrically connected to the land portion when it is adhered to the surface of the unit.</u>BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external perspective view of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a plan view of the head unit shown in FIG.

FIG. 4 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG.

FIG. 5 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG.

FIG. 6 is a cross-sectional view of a main part of a head unit and an FPC arranged on the upper surface thereof.

FIG. 7 is an exploded perspective view of a main part of a head unit and an FPC.

8 (a) is a plan view of the space forming the ink flow path drawn in FIG. 6, and FIG. 8 (b) is a perspective view.

FIG. 9 is an enlarged cross-sectional view of the area surrounded by the alternate long and short dash line drawn in FIG.

FIG. 10 is a plan view showing the shapes of individual electrodes and land portions adhered to the surface of the actuator unit.

FIG. 11 is an enlarged cross-sectional view showing a state in which an actuator unit is pressure-bonded to a flow path unit with a heater.

FIG. 12 is a plan view showing the arrangement of individual electrodes, land portions, and dummy land portions on the surface of the actuator unit.

FIG. 13 is a plan view showing the arrangement of individual electrodes, land portions, and dummy land portions on the surface of the actuator unit.

FIG. 14 is a diagram showing stepwise the process of solder joining between the terminals of the FPC and the land portion.

[Code description] 1 Inkjet head 4 Flow path unit 10 Pressure chamber 21 Actuator unit 34a / 34b Common electrode 35 Individual electrode 36 Land part 37 Dummy land part (metal member) 41 ~ 44 Piezoelectric sheet 53 Conductor pattern (feed line)