JPH0786651A - Laminated electrostrictive transducer and laminated ceramic actuator, and their manufacture - Google Patents

Abstract

PURPOSE:To strengthen withstand voltage on the outer surface of ceramics material and to surely prevent migration, short circuit, and creeping discharge. CONSTITUTION:A plurality of ceramics piezoelectric bodies 1 consisting of zirconium acid titanate group piezoelectric material, on both sides of which electrodes 2 and 2' are formed, are laminated and bonded together, with an external electrode 3 in between, so that a lamination body is produced. The lamination body is oxidized in an oxidizing atmosphere, for an oxide 10 to be formed. Then, the entire surface of the lamination body is coated with an insulation coating resin 11, and then, the external electrodes 3, protruding themselves from the resin 11, are alternately connected with lead wires 4 for the same electric potential, thus a laminated electrostrictive transducer 12 is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated electric / strain conversion element that expands and contracts according to an applied voltage, a laminated ceramic actuator and a method for manufacturing the same.

[0002]

2. Description of the Related Art Recently, in precision positioning devices such as optical or magnetic disk heads, various optical devices, precision machine tools, etc., for example, Japanese Patent Laid-Open No. 63-136581 "Layered Piezoelectric Body", Japanese Patent Publication No. 63-17354. As disclosed in the publication “Electrostrictive effect element” and the like, a large number of piezoelectric elements are formed by stacking, and the piezoelectric elements are expanded and contracted according to an applied voltage to be used as a micro-driving actuator. There is.

FIG. 2 is a cross-sectional view showing the basic structure of such a laminated electric / strain conversion element. A plurality of thin-film ceramic piezoelectric bodies (ceramic elements) having electrodes 2 and 2'on the front and back surfaces are formed. ) 1 is laminated and bonded via external electrodes 3 made of a copper metal plate or the like, and every other external electrode 3 is connected to a power source via lead wires 4 and 5 so as to have the same potential, and each ceramic piezoelectric element is connected. The body 1 is electrically connected in parallel to form a laminated electric / strain conversion element 6, to which a high voltage (eg:
1 KV / mm or more) to generate a strain in each ceramic piezoelectric body 1, and when an external force is applied to deform the ceramic piezoelectric body 1 on the contrary, an electric charge is generated on the surface of the piezoelectric body in proportion to the external force to generate a voltage. It was done. This property is called piezoelectric. In FIG. 2, 7 is an insulator.

[0004]

In such a laminated type electric / strain conversion element, when a large displacement is applied to a ceramic material composed of a piezoelectric element or an electrostrictive element, a large displacement of 1 KV / mm or more is applied to both ends of the element. It is necessary to apply an electric field, and if water or conductive dust adheres to the side surface of the ceramic material to which the large electric field is applied, there is a problem that short-circuiting or creeping discharge easily occurs and the reliability is significantly reduced.
That is, normally, silver, nickel, etc. are used as the electrode film of the ceramic material, but if there is a little moisture,
On the side surface of the material to which an electric field is applied, metal ions are generated from the positive electrode, which are electrically attracted to receive electrons at the negative electrode to deposit metal. This phenomenon is called migration. When the migration occurs, the distance between the electrodes becomes shorter and the insulating property deteriorates. As a result, short circuits and creeping discharges easily occur. In addition, if voids are present in the areas where migration has occurred, short circuits and creeping discharges are particularly likely to occur.

Therefore, as a countermeasure, for example, a method of covering with an insulating resin or grease or the like to prevent the ingress of moisture from the outside, a gap between the ceramic piezoelectric elements and a viscous insulating material on the side surfaces of the ceramic piezoelectric elements. (Japanese Patent Application Laid-Open No. 63-136581), the insulating material is applied to the end faces of the internal electrodes on one side surface of the laminated chip every other layer, and then the conductive material to be the one electrode is formed. Then, on the other side, a method of forming a conductive substance to be the other electrode from the one side where the insulating substance is not applied on the one side face is coated with the insulating substance on every other end face of the internal electrode plate (the above-mentioned special feature). Kosho 63-173
No. 54) is proposed and implemented.

However, the above-mentioned method is not sufficient to prevent migration, which is a problem even with a small amount of moisture, because the resin usually has hygroscopicity and moisture permeability, and it is a resin and an inorganic substance which are organic substances. Since it is difficult to chemically bond the interface with the ceramics, it has weaknesses such as weak adhesive strength and easy formation of voids. On the other hand, in all of the above methods, since it is necessary to partially coat the insulating material on the side surface of the thin piezoelectric element, high positioning accuracy is required,
There was a problem that the work was troublesome.

Therefore, as a result of conducting various experiments while changing the surface state of the ceramic material, the present inventor has found that when the surface is covered with an oxide which is an insulator, creeping discharge or migration which is an electrochemical reaction on the surface is caused. I confirmed that it was hard to get up.

Therefore, the present invention has been made on the basis of the above-mentioned conventional problems and experimental results, and its purpose is to provide a simple structure in which an insulating oxide is formed on the outer surface of a ceramic material. Accordingly, it is an object of the present invention to provide a laminated electric / strain conversion element, a laminated ceramic actuator and a method for manufacturing the same, which can increase the withstand voltage and reliably prevent migration, short circuit and creeping discharge.

[0009]

In order to achieve the above object, a laminated electric / strain conversion element according to the first invention comprises a plurality of piezoelectric or electrostrictive materials having electrodes formed on the front and back surfaces. Multi-layer type with ceramic materials laminated and bonded
In the strain conversion element, the ceramic material has an oxide formed on the outer surface. A multilayer ceramic actuator according to a second invention uses the multilayer electric / strain conversion element according to the first invention. A method of manufacturing a laminated electric / strain conversion element according to a third aspect of the present invention includes a step of laminating and bonding a plurality of ceramic materials made of a piezoelectric material or an electrostrictive material having electrodes formed on the front and back surfaces, and the laminating and bonding. The ceramic material is oxidized in an oxidizing atmosphere to form an oxide.

[0010]

In the present invention, when the outer surface of the ceramic material is coated with an oxide which is an insulator, the withstand voltage is higher than when it is not coated with an oxide, and migration or creeping discharge which is an electrochemical reaction on the outer surface. Is rare. As a method of oxidizing the outer surface, it is suitable to perform the oxidizing treatment in an oxygen atmosphere, an ozone atmosphere, or the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a laminated electric / strain conversion element according to the present invention. In addition, in FIG.
Components that are the same as those in FIG. Further, the thickness and size of each part in the drawing are exaggerated for ease of understanding, and are different from actual dimensions. In this embodiment, a plurality of thin-film ceramic piezoelectric bodies 1 made of lead zirconate titanate-based piezoelectric material and having electrodes 2 and 2 ′ formed on the front and back surfaces are used as an external electrode 3 made of a copper metal plate or the like. And is laminated and bonded through, and the laminate is subjected to an oxidation treatment in ozone at room temperature to form an oxide 10.
Thereafter, the entire surface of this laminate is covered with an insulating coating resin 11 such as an acrylic resin to a thickness of 0.5 mm by a normal process, and every other external electrode 3 protruding from the resin 11 to the same potential. The laminated electric / strain conversion element 12 is manufactured by connecting with the lead wires 4 and 5 so as to be. The laminated electric / strain conversion element 12 having such a configuration is
It is used as a laminated ceramic actuator which is connected to a power source and expands and contracts when a high voltage is applied between the electrodes 2 and 2'of each ceramic piezoelectric body 1 to finely drive the movable part of the device.

In the laminated electric / strain conversion element 12 having such a structure, the oxide 10 which is an insulator formed on the outer surface of the ceramic piezoelectric body 1 has a withstand voltage higher than that when the surface is not oxidized. Is large, and migration or creeping discharge, which is an electrochemical reaction, can be prevented.

The laminated electric / strain conversion element 12 having the above structure was placed in a constant temperature and humidity chamber and an atmosphere of 90% was set at 40 ° C. Further, an accelerated durability test was also performed for comparison of the same laminated electric / strain conversion element which was not oxidized and was coated with an epoxy resin to a thickness of 0.5 mm. Furthermore, when an electric field of 1300 V / mm was continuously applied to the actuator, it was confirmed that no discharge occurred even after 1000 hours or more in the laminated electric-strain conversion element subjected to the oxidation treatment. Laminated electricity without treatment
Discharge was observed in the strain conversion element after about 500 hours.

In the above embodiment, the external electrode 3 is made of a metal plate made of copper. However, the invention is not limited to this. Silver paste is applied and fired along the side surface of the ceramic piezoelectric body 1 to form the external electrode. It may be

[0015]

As described above, in the laminated electric / strain conversion element according to the present invention, since the outer surface of the ceramic material is oxidized to form an oxide, the withstand voltage increases and the electrochemical reaction occurs. It is possible to prevent migration and creeping discharge. Therefore, the reliability and durability of the element can be improved. In addition, since the oxidation process only needs to leave the element in the oxidizing atmosphere for the required time, the work is significantly easier than the conventional method of partially covering with the insulating coating resin, and troublesome positioning work is required. Therefore, productivity can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a laminated electric / strain conversion element according to the present invention.

FIG. 2 is a cross-sectional view showing a basic configuration of a laminated electric / strain conversion element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic piezoelectric body 2, 2'internal electrode 3 External electrode 4 Lead wire 5 Lead wire 6 Laminated electric / strain conversion element 10 Oxide 11 Insulation coating resin 12 Laminated electric / strain conversion element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihiko Yoshino 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (3)

[Claims] 1. A laminated electric / strain conversion element in which a plurality of ceramic materials made of a piezoelectric material or an electrostrictive material having electrodes formed on the front and back surfaces are laminated and adhered, and the ceramic material has an oxide formed on the outer surface. A laminated electric / strain conversion element characterized in that 2. A multilayer ceramic actuator using the multilayer electric / strain conversion element according to claim 1. 3. A step of laminating and adhering a plurality of ceramic materials made of a piezoelectric material or an electrostrictive material having electrodes formed on the front and back surfaces, and an oxidation treatment of the laminated and adhering ceramic materials in an oxidizing atmosphere. And a step of forming a laminated electric / strain conversion element.