JP2003174209A - Laminated piezoelectric actuator element - Google Patents

Abstract

(57) Abstract: Provided is a multilayer piezoelectric actuator having an element structure in which an insulating portion does not deteriorate even in a driving environment in which a large displacement is repeated over a long period of time. SOLUTION: The laminated body has a laminated body in which piezoelectric ceramic layers and internal electrode layers are alternately laminated, and the internal electrodes exposed on the side surfaces of the laminated body are covered with an insulating material every other layer, and the insulating material is covered with a layer. In a laminated piezoelectric actuator element formed of an external electrode that is electrically connected to an internal electrode every other time, the insulating material is made of resin, and the external electrode is made of a conductive resin. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating part structure and an external electrode structure of a laminated piezoelectric actuator element which requires a large amount of displacement and repeated durability.

[0002]

2. Description of the Related Art The internal electrode structure of a laminated piezoelectric actuator element is similar to that of a laminated ceramic capacitor.
There is a partial electrode structure as shown in FIG. In this electrode structure, since there is a portion that does not expand or contract even when a voltage is applied to the outer edge portion, strain is often generated at the boundary portion and cracks easily occur in the insulating portion. On the other hand, in a laminated piezoelectric actuator element having a structure in which internal electrodes are formed and laminated on the entire surface of a piezoelectric ceramic sheet as shown in FIG. In addition, there is no problem that a crack is generated in the insulating portion and a crack is generated unlike the partial electrode structure element. In the device having this structure, the end faces of the internal electrodes exposed on the side faces are covered by every other layer of the glass insulating layer, and formed by printing or baking an external electrode paste of silver or silver-palladium having a thickness of about 10 μm from the top. ing. This external electrode paste contains a small amount of low-melting-point glass frit for sticking to the ceramic layer.

On the other hand, patents relating to resin insulation of a laminated piezoelectric actuator include, for example, Japanese Patent Publication No. 2-56830.
There is. However, the patent does not specifically disclose the structure of the external electrode, and only describes "burning the external electrode at a predetermined position" in the examples, so that the glass having a low melting point is used. It is considered to be the adhesion due to the chemical reaction between the frit material and the ceramic.

[0004]

Even in the case of a device having a full internal electrode structure, if the insulating layer is made of a hard material such as glass, a high voltage is applied to increase the elongation of the piezoelectric device. Since the insulating layer itself does not stretch, there is a risk of strain occurring at the interface between the insulating layer and the piezoelectric ceramic layer, causing microcracks inside the insulating layer and reducing the insulation properties. ing. For this reason, it is necessary to finely select the material and forming conditions of the inorganic material that are optimal according to the specifications required for the application of the element and the piezoelectric ceramic material. Further, when the insulating layer is a resin, a conventional electrode material containing glass frit,
For example, when a paste such as silver particles is printed or baked, there is a problem that the insulating material is deteriorated and the insulating performance is remarkably deteriorated. Even if the element is made of a soft material and can withstand large expansion and contraction of the element, the external electrode formed so as to cover the insulating layer may be cut off.

Therefore, an object of the present invention is to provide a laminated piezoelectric actuator having an element structure in which the insulating portion does not deteriorate even in a driving environment in which a large displacement is repeated for a long period of time. .

[0006]

In order to solve the above-mentioned problems, in the present invention, a resin material which can follow the expansion and contraction of the piezoelectric material is used as the insulating layer.

Since it is necessary to form every other insulating layer, an electrodeposition coating solution is used so that the resin is selectively formed only at the exposed inner electrode end portions and their vicinity. The resin material is selected from polyimide resin, acrylic resin and fluororesin.

The ionic form of the electrodeposition resin may be either a cation or an anion, but the cation is preferred when the internal electrode contains a material which is easily ionized.

The external electrode material formed after baking the insulating layer is composed of a resin mainly containing conductive particles such as silver, silver palladium, and copper so that the insulating resin does not deteriorate. Moreover, since the external electrode material is made of a soft resin, expansion and contraction of the element and the insulating layer are not restricted.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A laminated piezoelectric actuator according to an embodiment of the present invention will be described with reference to FIG.

The laminated piezoelectric actuator shown in FIG. 3 has a plurality of plate-shaped piezoelectric ceramic layers 3a and a plurality of plate-shaped internal electrodes 3.
a laminated body 3 formed by laminating b and internal electrodes 3b thereof
And a pair of external electrodes 4 connected to each other on opposite side surfaces of the laminated body 3. On the opposite side surface of the laminated body 3, the internal electrode 3b
Are alternately covered with the insulating layer 3c. Therefore, the internal electrodes 3b are alternately connected to the pair of external electrodes 4. The external electrode 4 is formed by curing a polyimide resin containing silver particles, for example.

The manufacturing method will be described below based on the embodiments. Piezoelectric ceramic powder containing nickel and lead niobate as main components is dispersed in a solvent, and then a binder is added to form mud, which is film-formed on a carrier tape to form a green sheet having a thickness of 90 to 130 μm. . This sheet is printed with Ag / Pd internal electrode paste, dried, punched out, laminated and filled in a mold, and thermocompression bonded to form an integrated laminated body. After removing this binder from the binder, 1
Sinter at a temperature of 000 to 1150 ° C. After processing this laminated sintered body to a predetermined height, electrodes for conduction with internal electrodes are baked on both side surfaces, and the width is 5 mm and the length is about 100 m.
Cut into a rectangular shape of m. A silver electrode paste is printed and baked at a predetermined position of this cut piece as a base for external lead connection. The cut piece is dipped in a bath containing an electrodeposition paint, and a DC voltage of −50 to 200 V is applied to form a resin layer only on the exposed inner surface of the internal electrode and the surface of the piezoelectric material layer in the vicinity thereof. After formation, curing treatment is performed at 150 to 210 ° C. for 30 minutes to fix the resin insulating layer to the element surface. An external electrode is formed by printing a conductive resin paste on both surfaces of this cut piece having an insulating layer formed on every other side of the cut piece with a predetermined width and at a predetermined interval and curing at a temperature of 150 to 210 ° C. Further, the cut piece on which the external electrode is formed is cut into a small piece having a width of 5 mm, and a lead wire is attached to obtain a laminated piezoelectric actuator element.

[0013]

According to the structure and the manufacturing method of the present invention, since cracks in the insulating layer due to strain caused by expansion and contraction of the piezoelectric ceramic layer are completely eliminated, a failure occurs even when a high voltage is repeatedly applied for a long time. There is nothing to do.

[Brief description of drawings]

FIG. 1 is a side view of a prior art multilayer piezoelectric actuator element having a multilayer ceramic capacitor type partial electrode structure.

FIG. 2 is a side view of a laminated piezoelectric actuator element having an inorganic insulating layer according to the prior art of the present invention.

FIG. 3 is a side view of the laminated piezoelectric actuator element according to the embodiment of the present invention.

[Explanation of symbols]

1,2,3 laminate 1a, 2a, 3a Piezoelectric ceramic layer 1b, 2b, 3b internal electrodes 2c Inorganic insulation layer 3c Resin insulation layer 3 external electrodes (baked silver) 4 Conductive resin external electrode 5 External lead 6 Base electrode for external lead connection

Claims (3)

[Claims] 1. A laminated body comprising piezoelectric ceramic layers and internal electrode layers alternately laminated, wherein each of the internal electrodes exposed on the side surface of the laminated body is covered with an insulating material to cover the insulating material. A laminated piezoelectric actuator element, wherein external electrodes are formed every other layer so as to be electrically connected to internal electrodes, wherein the insulating material is made of resin and the external electrodes are made of conductive resin. 2. The laminated piezoelectric actuator element according to claim 1, wherein the external electrode is a composite material obtained by adding ceramic particles as a filler to a conductive resin. 3. The insulating resin is formed by electrodeposition,
The laminated piezoelectric actuator element according to claim 1, wherein the form of the resin ion in the electrodeposition liquid is a cation.