JP4325941B2 - Piezoelectric actuator and inkjet recording head - Google Patents

Description

  The present invention relates to a piezoelectric actuator and an ink jet recording head, and more particularly to a piezoelectric actuator and an ink jet recording head used in an ink jet recording head that can easily perform multi-gradation and color and can perform high density recording.

  In recent years, with the spread of personal computers and the development of multimedia, as a recording device that outputs information to a recording medium, it is equipped with a piezoelectric actuator that can easily increase the number of gradations and color and can keep running costs low. The use of inkjet recording devices is rapidly expanding. Such a recording apparatus is equipped with an ink jet recording head. In order to cope with the recent increase in density of piezoelectric actuator elements (displacement elements), an ink jet recording head in which a plurality of individual electrodes are formed at the center of the surface of the piezoelectric actuator has been proposed (for example, see Patent Document 1). ).

  FIG. 6 is a cross-sectional view showing the ink jet recording head as described above. As shown in the figure, the inkjet recording head includes a plurality of laminated piezoelectric ceramic layers 65 and 66, a common electrode 68 disposed between the piezoelectric ceramic layers 65 and 66, and the uppermost piezoelectric ceramic layer. A plurality of individual electrodes 79 arranged on the surface of the layer 65, and provided on the same plane as the individual electrodes 79 for discharging charges accumulated in the common electrode 68, and connected to the common electrode 68 by the through conductor 71. The piezoelectric actuator 73 provided with the extraction electrode 77 is mounted on the flow path member 57 including the plurality of ink flow paths 55 having the ink discharge ports 51 so that the positions of the ink flow paths 55 and the individual electrodes 79 are aligned. At the same time, a flexible flat cable 63 is connected to the extraction electrode 77 and the individual electrode 79 via a connection terminal 61. Reference numeral 67 denotes an adhesive layer between the piezoelectric actuator 73 and the flow path member 57.

  FIG. 7 is a plan view showing the piezoelectric actuator 73. As shown in the figure, the individual electrode 79 includes a drive unit 81 that contributes to piezoelectric drive, and a drive voltage application land unit 82 connected to one end of the drive unit 81. The extraction electrode 77 is formed in a rectangular shape having a long side and a short side.

In recent years, along with the demand for high-density recording, further increase in the elements constituting the piezoelectric actuator 73 and higher integration have been demanded. With the downsizing of the elements, the drive unit 81 constituting the individual electrode 79 and The land area 82 needs to be reduced in area.
JP 11-34321 A

  However, in the ink jet recording head as shown in FIGS. 6 and 7, further high integration of elements is required, and the area of the drive unit 81 and the land unit 82 constituting the individual electrode 79 is reduced. However, since the land portion 82 is miniaturized, the connection with the wiring pattern of the flexible flat cable 63 is weak, and it is difficult to release the connection due to vibration or the like or to maintain the connection for a long time.

  An object of the present invention is to provide a piezoelectric actuator and an ink jet recording head that can reliably and securely maintain an electrical connection with a wiring pattern of a flexible flat cable over a long period of time.

The piezoelectric actuator of the present invention includes a plurality of laminated piezoelectric ceramic layers, at least one common electrode formed between the piezoelectric ceramic layers, and a plurality of layers arranged on the surface of the uppermost piezoelectric ceramic layer. A piezoelectric actuator comprising: an individual electrode; and an extraction electrode provided on the same plane as the individual electrode and connected to the common electrode, wherein the individual electrode contributes to piezoelectric driving ; and a land portion for applying a driving voltage which is connected to one end of the driving unit, and said extraction electrode, to become arranged in a U-shape so as to surround the assembly constituted by the plurality of individual electrodes Features.

  In such a piezoelectric actuator, for example, the leading end portion of the flexible flat cable and both sides thereof can be joined to the lead electrode by providing a U-shaped lead electrode so that the direction drawn by the flexible flat cable opens. For this reason, the wiring pattern of the flexible flat cable can be reliably connected to the land portions of the extraction electrode and the individual electrode for a long period of time.

  Furthermore, in the piezoelectric actuator of the present invention, it is preferable that the interval between the land portions of the adjacent individual electrodes is 4 mm or less. In such a piezoelectric actuator, since the distance between the land portions is 4 mm or less, the area to be connected to the flexible flat cable tends to be small and the connection strength tends to be lowered, so that the present invention can be used particularly effectively.

  The piezoelectric actuator of the present invention is characterized in that the area of the extraction electrode is larger than the area of the land portion of the individual electrode. In such a piezoelectric actuator, even if the degree of integration of the displacement elements is increased and the land area of the individual electrode is reduced, the connection with the flexible flat cable can be ensured by the extraction electrode. Can be reliably connected to the land portion of the individual electrode over a long period of time.

The piezoelectric actuator of the present invention, it is preferable that the thickness of the La-end portion and the extraction electrode are substantially the same thickness. In such a piezoelectric actuator, the load applied to the extraction electrode and the land portion can be made substantially the same, and the bonding strength between the flexible flat cable, the land portion, and the extraction electrode can be further improved.

  An ink jet recording head of the present invention is provided with the piezoelectric actuator, a flexible flat cable connected to the extraction electrode of the piezoelectric actuator and land portions of the plurality of individual electrodes, and a plurality of ink flow paths having ink discharge ports. The ink flow path and the individual electrodes are aligned, and a flow path member attached to the lowermost piezoelectric ceramic layer of the piezoelectric actuator is provided, and the flexible flat cable includes the extraction electrode and the It is connected so that a several separate electrode may be covered.

In such a piezoelectric actuator, for example, an ink jet recording head is configured by connecting a wiring pattern of a flexible flat cable to a land portion of an extraction electrode and an individual electrode. In the present invention, the extraction electrode of the actuator is an individual electrode. Since the U-shape is provided so as to surround the assembled assembly, both sides of the flexible flat cable in the width direction can be joined to the extraction electrode, and the wiring pattern of the flexible flat cable can be securely connected to the land of the extraction electrode and individual electrode. And can be connected for a long time. Thereby, even when the flexible flat cable swings due to vibration, the connection reliability between the wiring pattern of the flexible flat cable, the land portion of the individual electrode, and the extraction electrode can be improved.

  According to the piezoelectric actuator of the present invention, since the lead electrode of the actuator is provided in a U shape so as to surround the assembly of individual electrodes, both sides in the width direction of the flexible flat cable can be reliably joined to the lead electrode, The flexible flat cable can be reliably connected to the land portion of the individual electrode between the extraction electrodes over a long period of time. Thereby, even when the flexible flat cable swings due to vibration, the connection reliability between the wiring pattern of the flexible flat cable, the land portion of the individual electrode, and the extraction electrode can be improved.

  Hereinafter, a piezoelectric actuator and an ink jet recording head according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing a piezoelectric actuator, and FIG. 2 is a cross-sectional view showing the piezoelectric actuator.

  As shown in FIGS. 1 and 2, the piezoelectric actuator 1 includes laminated piezoelectric ceramic layers 2 and 3, a common electrode 5 formed between these piezoelectric ceramic layers 2 and 3, and an uppermost piezoelectric ceramic layer. A plurality of individual electrodes 7 arranged on the surface of the layer 2, and provided on the same plane as the individual electrodes 7 for discharging the charges accumulated in the common electrode 5, and are connected to the common electrode 5 through the through conductors 8. An extraction electrode 9 that is electrically connected is provided.

  The individual electrode 7 includes a drive unit 11 that contributes to piezoelectric drive and a drive voltage application land unit 10 connected to one end of the drive unit 11. In the present invention, it is preferable that the thickness t1 of the land portion 10 and the thickness t2 of the extraction electrode 9 are substantially the same. Here, “substantially the same” means that t1 and t2 satisfy the relationship of | t1-t2 | ≦ 2 μm. Further, the thickness t1 of the land portion 10 and the thickness t2 of the extraction electrode 9 are 3 to 20 μm, preferably 5 to 15 μm. The thickness of the drive unit 11 is 0.3 to 3 μm, preferably 0.5 to 1 μm, which is thinner than the thickness t1 of the land unit 10 and the thickness t2 of the extraction electrode 9.

  The land portion 10 has a two-stage shape including a lower stage 10a and an upper stage 10b. Further, the width w1 of the lower stage 10a and the width w2 of the upper stage 10b in the direction of the opposing extraction electrode 9 satisfy the relationship of (w2 / w1) <1, and this is because the printing position accuracy is improved. Preferably, the relationship of (w2 / w1) ≦ 0.9 is satisfied. The width w1 of the lower stage 10a is 100 to 250 μm, preferably 150 to 200 μm, and the width w2 of the upper stage 10b is 80 to 200 μm, preferably 120 to 160 μm.

  The extraction electrode 9 is rectangular and has a two-stage shape including a lower stage 9a and an upper stage 9b. The width w3 of the lower stage 9a and the width w4 of the upper stage 9b in the direction of the opposing extraction electrode 9 satisfy the relationship of (w4 / w3) <1, and preferably (w4 / w) because the printing position accuracy is improved. w3) It is preferable that the relationship <0.9 is satisfied. The width w3 of the lower stage 9a may be 100 to 400 μm, preferably 150 to 300 μm, and the width w4 of the upper stage 9b may be 80 to 300 μm, preferably 120 to 250 μm.

  In the present invention, a large number of individual electrodes 7 are formed on the surface of the piezoelectric ceramic layer 2, and these individual electrodes 7 are arranged to form a rectangular assembly A (indicated by a one-dot chain line). On both sides of the body A, a plurality of extraction electrodes 9 are arranged in a row at a predetermined interval, and these arranged extraction electrodes 9 are opposed to each other through the assembly A.

  In other words, the extraction electrodes 9 are arranged in a line at a predetermined interval along the opposing sides of the assembly A of rectangular individual electrodes 7.

  Further, the distance L between the land portions 10 of the individual electrodes 7 provided adjacent to each other in the direction of the opposing extraction electrode 9 is set to 4 mm or less. In such a piezoelectric actuator, the displacement element can be highly integrated, and the area of the land portion 10 is reduced, so that the bonding strength between the land portion 10 and the flexible flat cable tends to decrease. The significance of using the invention is great.

  Further, the area of the upper stage 9 b of the extraction electrode 9 is larger than the area of the upper stage 10 b of the land portion 10 of the individual electrode 7. Thereby, the joint strength between the upper stage 9b of the extraction electrode 9 and the flexible flat cable is improved, and the connection between the upper stage 10b of the land portion 10 and the wiring pattern of the flexible flat cable can be maintained for a long period of time.

  Piezoelectric ceramic layers 2 and 3 include lead zirconate titanate (PZT), lead magnesium niobate (PMN), lead nickel niobate (PNN), or piezoelectric ceramics mainly composed of at least one of these. Are preferably used. The piezoelectric ceramic layer 2 is polarized in the direction opposite to each other in the thickness direction. The thickness of the piezoelectric ceramic layers 2 and 3 is 8 to 100 μm, preferably 10 to 30 μm.

  The common electrode 5 is desirably formed of Ag, Pd, Pt, Rh, Au, Ni alone or a combination of two or more, preferably an Ag—Pd alloy, and is common to the piezoelectric ceramic layers 2 and 3. The electrode 5 is fired simultaneously. The common electrode 5 has a thickness of 0.5 to 5 μm, preferably 1 to 3 μm.

  The individual electrode 7 composed of the drive unit 11 and the land unit 10 is made of Ag, Pd, Pt, Rh, Au-based material, Ni alone or a combination of two or more, preferably the drive unit 11 is made of Au-based material. Therefore, the land portion 10 is preferably formed of an Ag—Pd alloy. The extraction electrode 9 can use the same material as that of the individual electrode 7. Preferably, like the land portion 10, it is desirable to be formed of an Ag—Pd alloy.

  The piezoelectric actuator 1 is preferably used for an ink jet recording head. FIG. 3 is a cross-sectional view showing an ink jet recording head 41 provided with the piezoelectric actuator 1. The ink jet recording head 41 includes a piezoelectric actuator 1, a flexible flat cable 43 connected to the extraction electrode 9 and the individual electrode 7 via a connection terminal 42, and a plurality of ink flow paths 45 having ink discharge ports 44. A flow path member 46 is provided in which the positions of the ink flow path 45 and the drive unit 11 of the individual electrode 7 are aligned and laminated and bonded to the lowermost piezoelectric ceramic layer 3 via an adhesive layer 47.

  The flow path member 46 is obtained by a rolling method or the like, and the ink discharge hole 44 and the ink flow path 45 are provided by being processed into a predetermined shape by etching. The flow path member 46 is preferably formed of at least one selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, and is made of a material particularly excellent in corrosion resistance to ink. Desirably, the Fe-Cr system is more preferable.

  As the adhesive layer 47, a well-known layer can be used, but in order not to affect the piezoelectric actuator 1 and the flow path member 46, an epoxy resin, phenol resin, polyphenylene having a thermosetting temperature of 130 to 250 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of ether resins. By heating to the thermosetting temperature using such an adhesive layer 47, the piezoelectric actuator 1 and the flow path member 46 can be heat-bonded, whereby the ink jet recording head 41 can be obtained.

  The flexible flat cable 43 has a wiring pattern corresponding to each of the individual electrodes 7 formed on the upper surface of the piezoelectric actuator 1, and as described above, the wiring pattern and the land portion 10 of the individual electrode 7, the extraction electrode 9. Are connected by a connection terminal 42, and the piezoelectric actuator 1 can be displaced to a desired range.

  As the connection terminal 42, a low melting point metal made of any one of solder (Pb-Sn), lead-free solder containing at least Sn as a main component, and the like can be suitably used. In particular, solder is more preferable in terms of bonding reliability.

  In the ink jet recording head 41 as described above, by applying a voltage between the individual electrode 7 and the common electrode 5, the piezoelectric ceramic layer 2 constituting the piezoelectric actuator 1 has d31, d33, and d15. Displacement is performed in at least one vibration mode selected from the group. As a result, a predetermined amount of ink is ejected from the ink ejection port 44.

  In the ink jet recording head configured as described above, the lead electrode 9 of the actuator is provided so as to be opposed to each other via the assembly A of the individual electrodes 7, so that both sides in the width direction of the flexible flat cable 43 are joined to the lead electrode 9. The flexible flat cable 43 can be reliably connected to the individual electrode 7 over a long period of time. Thereby, even when the flexible flat cable 43 is swung by vibration, the connection reliability between the wiring pattern of the flexible flat cable 43 and the land portion 10 of the individual electrode 7 and the extraction electrode 9 can be improved.

  According to the present invention, as shown in FIG. 4, it is important to arrange a plurality of extraction electrodes 9 in a U-shape so as to surround the assembly A of individual electrodes 7 at a predetermined interval. In this case, the bonding strength between the wiring pattern of the flexible flat cable 43, the land portion 10 of the individual electrode 7, and the extraction electrode 9 can be improved. Further, as shown in FIG. 5, an extraction electrode 49 formed in a U shape so as to surround the aggregate A of the individual electrodes 7 may be provided.

  In the above embodiment, the case where the extraction electrode and the land portion have a two-stage shape has been described as an example. However, in the piezoelectric actuator and the ink jet recording head of the present invention, the extraction electrode and the land portion have at least their thicknesses. However, it is sufficient that the above-mentioned predetermined relationship is satisfied.

  First, a piezoelectric sheet was formed using a PZT system as the piezoelectric ceramic powder, and then a through hole was formed in the piezoelectric sheet. Moreover, the common electrode pattern which consists of Ag-Pd alloy was formed in the substantially whole surface using screen printing on the piezoelectric material sheet. Next, the piezoelectric sheet on which the common electrode pattern was formed was laminated with the piezoelectric sheet on which the through holes were formed so as to sandwich the common electrode pattern.

  A through-conductor filling portion made of an Ag—Pd alloy is formed on the laminated body having the through holes by screen printing, and the laminated body is cut into a predetermined shape and then fired at 1000 ° C. An actuator body was formed.

  Next, an Au paste is printed on the surface of the piezoelectric actuator body to form a drive portion for individual electrodes, which is baked at 800 ° C., and then an extraction electrode pattern and a land portion pattern are formed and baked at 600 ° C. 1 and FIG. 2 were obtained.

The land portion and the extraction electrode have a two-stage structure, and the dimensions of W1 to W4 are 600 μm, 500 μm, 600 μm, and 500 μm, respectively. The thicknesses t1 and t2 of the individual electrodes and the extraction electrodes were 10 μm, the thickness of the piezoelectric ceramic layer was 15 μm, and the distance L between the land portions of the individual electrodes was 1 mm. Further, the interval between the extraction electrodes was set to 300 μm. Furthermore, the area of the upper layer of the extraction electrode (joint area with the flexible flat cable) and the area of the upper layer of the land portion of the individual electrode (joint area with the flexible flat cable) were set to 0.025 mm ² , which were the same area.

  Next, the flexible flat cable was joined to the land portion of the extraction electrode and the individual electrode in the piezoelectric actuator obtained as described above by pressure heating through a connection terminal formed of solder. Next, on the flow path member in which a plurality of ink flow paths having ink ejection openings are arranged, the piezoelectric ceramic layer on which the individual electrode and the extraction electrode are not formed is placed down, and the ink flow path and the drive unit for the individual electrode are provided. The ink jet recording head shown in FIG. 3 was obtained by aligning the positions of the piezoelectric actuators and joining the piezoelectric actuators.

  The connection state between the flexible flat cable of the obtained ink jet recording head and the individual electrode and the extraction electrode was evaluated. Evaluation was made by pulling the flexible flat cable perpendicularly to the piezoelectric actuator with a force of 0.5 kgf, and confirming the connection between the individual electrode and the extraction electrode in that case. There was no peeling from the part.

  A recording head was produced and evaluated in the same manner as in Example 1 except that the interval L between the land portions of the individual electrodes was changed to 4 mm and 2 mm. As a result, the flexible flat cable, the extraction electrode, and the land portions of the individual electrodes There was no peeling.

  Further, as shown in FIGS. 4 and 5, a recording head was prepared in the same manner as described above except that an extraction electrode was formed, and evaluated with a pulling force of 0.5 kgf. There was no peeling from the land portions of the electrodes and the individual electrodes.

Furthermore, the area of the upper layer of the extraction electrode is 0.025 mm ² , the area of the upper layer of the land portion of the individual electrode is 0.01 mm ^2, and the extraction area is larger than the bonding area between the land portion of the individual electrode and the flexible flat cable. A recording head was prepared in the same manner as in Example 1 except that the bonding area between the electrode and the flexible flat cable was increased, and evaluated with a tensile force of 0.5 kgf. There was no peeling from the land portions of the electrodes and individual electrodes.

(Comparative example)
A recording head was prepared in the same manner as in Example 1 except that the extraction electrode was formed on one side of the assembly of individual electrodes, and evaluated with a tensile force of 0.5 kgf. Separation from the land was observed.

It is a top view which shows a piezoelectric actuator. It is sectional drawing which shows a piezoelectric actuator. An inkjet head is shown, (a) is sectional drawing, (b) is a top view. It is a top view which shows the state which arranged the several extraction electrode in the U shape at predetermined intervals. It is a top view which shows the state in which the U-shaped extraction electrode was formed. It is sectional drawing which shows the conventional inkjet recording head. It is a top view which shows the conventional piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator 2, 3 ... Piezoceramic layer 5 ... Common electrode 7 ... Individual electrode 9 ... Extraction electrode 10 ... Land part 11 ... Drive part 41 ... Inkjet Recording head 43 ... Flexible flat cable 44 ... Ink ejection port 45 ... Ink channel 46 ... Channel member

Claims (4)

A plurality of piezoelectric ceramic layers stacked, a common electrode of at least one layer formed between the piezoelectric layer, and a plurality of individual electrodes arranged on the surface of the uppermost layer of the piezoelectric ceramic layer, the individual by provided on the electrodes and the same plane, and a piezoelectric actuator and a connected lead electrodes to said common electrode, said individual electrodes, and contributes driver to the piezoelectric drive, connected to one end of the drive unit A piezoelectric actuator, wherein the lead-out electrode is provided in a U-shape so as to surround the assembly composed of the plurality of individual electrodes. 2. The piezoelectric actuator according to claim 1, wherein an area of the extraction electrode is larger than an area of a land portion of the individual electrode. Claim 1 or 2 piezoelectric actuator, wherein the thickness of the extraction electrode and the front Symbol land portions are substantially identical thickness. A piezoelectric actuator according to any one of claims 1 to 3, a flexible flat cable connected to land portions of the extraction electrode and the plurality of individual electrodes of the piezoelectric actuator, and a plurality of ink streams having ink discharge ports A path member is provided, and the ink flow path and the individual electrode are aligned, and a flow path member is attached to the lowermost piezoelectric ceramic layer of the piezoelectric actuator. An ink jet recording head, wherein the ink jet recording head is connected so as to cover an electrode and the plurality of individual electrodes.

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