JPH05198860A - Laminated piezoelectric displacement element and ink jet type print head - Google Patents

Abstract

PURPOSE:To obtain displacement having directivity in single direction, enable thin cut for high density constitution because cracks are not generated in the outermost layer at the time of machining, obtain necessary displacement amount with a low voltage, and obtain displacement of little distortion. CONSTITUTION:Piezoelectric bodies 3 are alternately arranged in a sandwich type, in the manner in which a conducting layer constituting one electrode and a conducting layer 2 constituting the other electrode are in parallel with each other. The part position sandwiched by the conducting layere 1, 2 is an active part 6, and the part positions 5, 5a which are not sandwiched are inactive parts. The outermost layer 4 is thicker than the inside layer (between the conducting layers 1 and 2). In order that an electric field may be applied also to the outermost layer 4 to generate displacement, the outermost electrodes 10b, 10a are constituted on the outermost layer end surfaces, so as to be in parallel with the conducting layers 1, 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric displacement element used for a print head of an ink jet printer and an ink jet print head using the same.

[0002]

2. Description of the Related Art A conventional ink jet print head is
As shown in Japanese Examined Patent Publication No. 60-8953, a plurality of nozzle openings are formed on the wall surface of a container constituting an ink tank, and piezoelectric elements are arranged so that the expansion and contraction directions are aligned so as to face each nozzle opening. It is constructed and set up. This print head applies a drive signal to a piezoelectric element to expand and contract the piezoelectric element, and the dynamic pressure of ink generated at this time causes ink droplets to be ejected from nozzle openings to form dots on printing paper.

In a print head of this type,
It is desirable that droplet formation efficiency and flight force are large. However, since the unit length of the piezoelectric element and the expansion / contraction rate per unit voltage are extremely small, it is necessary to apply a high voltage in order to obtain the flying force required for printing, which complicates the drive circuit and electrical insulation measures. The problem is that

In order to solve such a problem, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent Laid-Open No. 3-295269, there is proposed a laminated piezoelectric displacement element for an inkjet print head in which electrodes and piezoelectric materials are alternately laminated in a sandwich shape. According to this laminated piezoelectric displacement element, the distance between the electrodes can be made as small as possible, so that the voltage of the drive signal can be lowered.

[0005]

However, it is difficult to form such a laminated piezoelectric displacement element into a small size, and there is a problem that its application is limited.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laminated piezoelectric displacement element having high operation efficiency and high reliability, and to provide an ink jet type print head capable of easily miniaturizing the piezoelectric element. ..

[0007]

A laminated piezoelectric displacement element in which at least piezoelectric bodies and electrodes are alternately laminated, wherein the outermost layer is thicker than the inner layer of the laminated piezoelectric displacement element.

Furthermore, in the laminated piezoelectric displacement element,
It is characterized in that an electrode is also formed on the end face of the outermost layer in parallel with the internal electrode so that the electric field is applied to the outermost layer and the outermost layer is also displaced.

In an ink jet type print head in which a piezoelectric element is arranged corresponding to a nozzle opening, and ink is discharged from the nozzle opening to the outside by a drive signal to the piezoelectric element, the piezoelectric element is at least a piezoelectric body and an electrode. And a layered piezoelectric displacement element alternately laminated, wherein the outermost layer is thicker than the inner layer of the layered piezoelectric displacement element.

Further, in the laminated piezoelectric displacement element used in the ink jet print head, an electrode is also formed on the end face of the outermost layer in parallel with the inner electrode so that an electric field is applied to the outermost layer and the outermost layer is also displaced. Is characterized by.

[0011]

1 is a perspective view showing an embodiment of a laminated piezoelectric displacement element of the present invention. In the figure, 1 is a conductive layer that constitutes one of the electrodes. Reference numeral 2 is a conductive layer that constitutes the other electrode, and the conductive layers are alternately arranged in parallel with each other in a piezoelectric body 3, for example, a titanate / lead zirconate-based composite perovskite ceramic. The portion sandwiched between the conductive layers 1 and 2 is the inner layer. Reference numeral 90 denotes a dummy electrode layer, which does not generate an electric field for displacing the laminated piezoelectric displacement element, and when manufacturing the laminated piezoelectric displacement element, the number of layers of the active portion 6 and the inactive portion 5 is the same. It is necessary to prevent distortion such as warpage. The conductive layer 1 and the dummy electrode layer 90, which are one of the electrodes, are connected to the outermost electrode 10a, and the conductive layer 2 that is the other electrode is connected to the other outermost electrode 10b. The outermost electrodes 10a and 10b become positive or negative, and accordingly, the conductive layers 1 and 2 are electrically arranged in parallel. The inactive portion 5 is necessary for fixing, and its length is determined by fixing conditions. The active portion 6 is a portion that is actually displaced in the direction of the end face 7 in the displacement direction when an electric field is applied. The inactive portion 5a is necessary to prevent the conductive layer 1 and the outermost electrode 10b from being connected to each other. The outermost layer 4 is thicker than the inner layer and has a bilaterally symmetrical thickness. Since the outermost layer 4 is thicker than the conventional one,
It serves as a guide to obtain a directional displacement in a single direction, and further reduces chipping during dicing and cutting with a wire saw. However, if it is too thick, the effect as a guide and the effect of less chipping during cutting are enhanced, but since the displacement is reduced by restraining the inner layer, a high voltage is required to obtain the required displacement. become. According to experiments, it can be said that about twice the inner layer is suitable.

FIG. 2 is a perspective view showing an embodiment in which electrodes are formed on the end faces of the outermost layers in parallel with the internal electrodes in the laminated piezoelectric displacement element of FIG. At this time, at least in the active portion 6, the outermost layer 4 is the outermost electrode 10a and the conductive layer 2 or the outermost electrode 10.
It is configured to be sandwiched between b and the conductive layer 1. Therefore, an electric field is applied to the outermost layer and the outermost layer is also displaced, so that the required displacement amount can be obtained at a low voltage and the displacement with less strain can be obtained.

Since the number of laminated layers is odd in FIG. 2, the outermost layer 4 is the outermost electrode 10a and the conductive layer 2 or the outermost electrode 10.
It was configured to be sandwiched between b and the conductive layer 1. However, when the number of stacked layers is an even number as shown in FIG. 3, both outermost layers 4 can be configured to be sandwiched between the outermost electrode 10b and the conductive layer 2 at least in the active portion 6. Similarly, depending on the number of layers, both outermost layers 4 may be sandwiched between the outermost electrode 10a and the conductive layer 1. The outermost electrodes 10a, 10b are formed by vapor deposition of gold, copper, or the like, have good conductivity, have few breaks during processing, and can be thinly cut for high density. When the outermost electrodes 10a and 10b are formed of a thick material such as plating, they are often dragged during cutting and chipped or burred. In order to increase the adhesion with the laminated piezoelectric displacement element, nickel-chromium is first vapor-deposited with a thickness of about 0.125 μm, and gold with a sheet resistance of 1Ω or less is vapor-deposited thereon. For vapor deposition of copper, nickel
Use chrome instead of chrome. The thickness of gold and copper is
If it was made too thick to reduce the resistance value, there were many chips and burrs during processing, similar to plating. About 0.5 μm
The rank seems appropriate.

As shown in FIG. 4A, such a laminated piezoelectric displacement element block 20 is bonded to the base 8. The laminated piezoelectric displacement element block 20 thus bonded is cut into a predetermined width and arranged at regular intervals to form a laminated piezoelectric displacement element row 21 as shown in FIG. 4B. In FIGS. 4A and 4B, the fixed state of the laminated piezoelectric displacement element is a cantilevered state. Therefore, the outermost layer 4 is easily bent during cutting, and the outermost layer 4 is liable to be chipped. The outermost electrode 10a has an independent lead member 3
2 is connected to the outermost electrode 10b and a common lead member 31
Connect. The independent lead member 32 is directly joined to the outermost electrode 10a in FIG.
Wiring to the laminated piezoelectric displacement element block 20 and the base 8
If an electrically conductive material is used as the adhesive between them, or if the adhesive is thinned and pressure-bonded so that electrical continuity can be obtained, the independent lead member 32 may be joined to the base 8, and the laminated piezoelectric displacement element. The workability was greatly improved without falling or scratching the laminated piezoelectric displacement element in an attempt to directly bond it with.
If there is no electrode on the outermost layer end face of the outermost electrode 10b, the common lead member 31 is connected to the end face 7 in the displacement direction. The spring plate member 45 is bonded to the end face 7 in the displacement direction as shown in FIG. 6, and is not suitable for connecting the lead member 31. Furthermore, if the common lead member is connected to the active portion 6 where the laminated piezoelectric displacement element actually displaces, it is not suitable for connection because it inhibits displacement. In order to escape this, the outermost electrode 10b is extended to the portion of the inactive portion 5, and the inactive portion 5 is connected.

The operation of the laminated piezoelectric displacement element will be described with reference to FIG. The charging switch 6 as shown in FIG.
1 is inserted between the conductive layers 1 and 2 of the active part 6 and the outermost electrode 1
An electric field is applied between 0a and the conductive layer 2 and between the outermost electrode 10b and the conductive layer 1. Then, the piezoelectric body 3 of the active portion 6 contracts in the direction of arrow 51. When the discharge switch 62 is turned on as shown in FIG. 5B, the electric field between the electrodes is released and the active portion 6 is released.
The piezoelectric body 3 extends in the direction of arrow 52 and returns to the length before applying the electric field.

On the other hand, in the conventional technique, the piezoelectric layers 73 are alternately arranged so that the conductive layers 71 and 72 are parallel to each other as shown in FIG.
It is similar that they are arranged in a sandwich form. However, the outermost layer 74 is about the same as between the inner electrodes. Furthermore, the outermost electrodes 80 (a), 80
(B) is not formed on the end face of the outermost layer.

When a voltage is applied to such a laminated piezoelectric displacement element, the piezoelectric body 73 sandwiched between the conductive layers 71 and 72 contracts in the direction of arrow 91 as shown in FIG. 6B, but the outermost layer has an electric field. Since no is added, the displacement type becomes distorted only by being dragged. When such a distorted displacement occurs, the adhesive force between the end face 7 and the spring plate member 45 (FIG. 6) in the displacement direction weakens and peels off, or peeling occurs at the electrode at the boundary between the outermost layer and the inner layer. ..

When the laminated piezoelectric displacement element is applied to a Kaiser type laminated piezoelectric displacement element longitudinal vibration type head which is an ink jet recording apparatus shown in FIG. 7A, the directivity of vibration in a single direction without distortion. It is possible to obtain a certain displacement. Therefore, an enlarged view of the driving unit when FIG. 7A is cut along the plane A and viewed from the Z direction is shown in FIG. 7B, and a process until ink droplets are ejected from the nozzle openings 44 will be described.

In FIG. 7B, when a voltage is applied to the laminated piezoelectric displacement element 41 facing the nozzle opening formed in the nozzle plate 44a where dots are to be formed, the laminated piezoelectric displacement element 41 is rich in elasticity. The spring plate member 45 can be expanded while being deformed to push out the partition wall 42 disposed on the facing surface of the laminated piezoelectric displacement element and the ink 43 in the partition wall, and ejected as an ink droplet from the nozzle opening.

[0020]

As described above, the piezoelectric element in which the piezoelectric material and the conductive material are alternately laminated in layers,
By configuring the outermost layer thicker than the inner layer, the outermost layer serves as a guide, so a displacement with directivity in a single direction can be obtained.
The outermost layer is less likely to be chipped during cutting, and an electrode is also formed on the outermost layer end face in parallel with the internal electrodes, so an electric field is applied to the outermost layer as well. Was obtained, and it became possible to obtain a displacement with less distortion.

A piezoelectric element in which a piezoelectric material and a conductive material are alternately laminated in layers is fixed to the base at one end and is arranged so as to correspond to the nozzle opening with the other end as a free end. Since the outermost layer is made thicker, the outermost layer serves as a guide, so directional displacement can be obtained in a single direction, and the outermost layer is less likely to be chipped during cutting, and is thin for high density. It becomes possible to disconnect,
Furthermore, by forming an electrode on the end face of the outermost layer parallel to the inner electrode, an electric field is also applied to the outermost layer, so that the required displacement amount can be obtained at a low voltage and the displacement with less strain can be obtained. Therefore, a piezoelectric element array suitable for placement in the ink jet print head was obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a laminated piezoelectric displacement element of the present invention.

FIG. 2 is a perspective view showing another embodiment of the laminated piezoelectric displacement element of the present invention.

FIG. 3 is a perspective view showing another embodiment of the laminated piezoelectric displacement element of the present invention.

4A is a perspective view showing an example of a fixing structure of a laminated piezoelectric displacement element block having the layer structure of FIG.
4B is a partial perspective view showing a laminated piezoelectric displacement element row and a lead member obtained by cutting the laminated piezoelectric displacement element block of FIG. 4A.

5A and 5B are explanatory views of the operation of the laminated piezoelectric displacement element having the layer structure of FIG.

FIG. 6A is a perspective view showing an example of a conventional laminated piezoelectric displacement element. (B) is an explanatory view of the operation of the conventional laminated piezoelectric displacement element.

7A is a structural diagram showing a vertical vibration type inkjet head unit of a Kaiser type laminated piezoelectric displacement element using the laminated piezoelectric displacement element having the layer structure of FIG. 2. FIG. (B)
7A is an enlarged view of a drive unit when the Kaiser type laminated piezoelectric displacement element longitudinal vibration type inkjet head structure diagram of FIG.

[Explanation of symbols]

 1 ... Conductive layer constituting one electrode 2 ... Conductive layer constituting the other electrode 3 ... Piezoelectric body 4 ... Outermost layer 5 ... Inactive portion 5a.・ ・ ・ Inactive part 6 ・ ・ ・ Active part 7 ・ ・ ・ Displacement end face 8 ・ ・ ・ Base 10a ・ ・ ・ Outermost electrode 10b ・ ・ ・ Outermost electrode 20 ・ ・ ・Stacked piezoelectric displacement element block 21 ... Stacked piezoelectric displacement element row 31 .... Common lead member 32 .... Independent lead member 41 .... Stacked piezoelectric displacement element 42 .. Partition wall 43 ... Ink 44 ... Nozzle opening 44a ... Nozzle plate 45 ... Spring plate material 51 ... Arrow 52 .... Arrow 61 .... Charge switch 62・ ・ ・ ・ Discharge switch 71 ・ ・ ・ ・ Conductive layer 72 ・ ・ ・ ・Conductive layer 73 ... Piezoelectric body 74 ... Outermost layer 80a ... Outermost electrode 80b ... Outermost electrode 90 ... Dummy electrode layer

Front page continuation (72) Inventor Munehide Kanaya 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation

Claims (4)

[Claims] 1. A laminated piezoelectric displacement element in which at least piezoelectric bodies and electrodes are alternately laminated, wherein an outermost layer is thicker than an inner layer of the laminated piezoelectric displacement element. .. 2. In the laminated piezoelectric displacement element, an electrode is also formed on the end face of the outermost layer in parallel with the internal electrode so that an electric field is applied to the outermost layer and the outermost layer is also displaced. 1. The laminated piezoelectric displacement element according to 1. 3. In an ink jet type print head, wherein a piezoelectric element is arranged corresponding to a nozzle opening, and ink is discharged to the outside from the nozzle opening by a drive signal to the piezoelectric element. A laminated piezoelectric displacement element in which electrodes and electrodes are alternately laminated,
An ink jet type print head, wherein an outermost layer is thicker than an inner layer of the laminated piezoelectric displacement element. 4. In the laminated piezoelectric displacement element used in the ink jet type print head, electrodes are formed on the outermost layer end faces in parallel with the inner electrodes so that an electric field is applied to the outermost layers and the outermost layers are also displaced. 4. The method according to claim 3, wherein
The inkjet print head described.