JPH01164080A - Electrostrictive effect element - Google Patents

Abstract

PURPOSE:To completely eliminate the production of a crack in an insulating layer due to expansion and contraction even when a voltage is impressed on an electrostrictive effect element in order to cause the expansion and contraction due to an electrostrictive effect and to completely eliminate a disturbance action of the expansion and contraction due to a non-electric field part when the insulating layer has been formed by a method wherein an inorganic insulating layer is formed only in an exposed part of an internal electrode sheet on a side end face of the element and on an electrostrictive material near the exposed part. CONSTITUTION:An electrostrictive effect element is constituted in such a way that only exposed parts on element side faces of internal electrode sheets 2, 2' exposed to the outside and parts near the internal electrodes on the element side faces of electrostrictive material films 1 are coated with outside electrodes 3, 3'. Because an insulating layer is divided, a stretch is hardly exerted on the insulating layer and a bending stress is not exerted. Accordingly, even when the electrostrictive effect element is expanded and contracted, it is possible to completely eliminate a problem that a crack is produced in the insulating layer or that the insulating layer is stripped off.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrostrictive element that utilizes longitudinal effects.

(Prior art and problems to be solved by the present invention) When an element with a multilayer chip capacitor structure as shown in Fig. 3 is constructed using a material with a large electrostrictive effect, a large strain occurs at low voltage. An effect element is obtained. That is, as shown in FIG. 3(a), a film or thin plate 1 made of an electrostrictive material
In this structure, positive internal electrode plates 2 and negative internal electrode plates 2'' are alternately sandwiched and stacked in between, and the internal electrode plates 2 and 2'' are connected to external electrodes 3 and 3', respectively.However, as described above, As can be seen from the plan view of FIG. 2(b), in the conventional electrostrictive effect element, the overlapping part with the internal electrode plates 2 and 2' is smaller than the total area between the elements, and the picture electrode do not overlap.Therefore, when a voltage is applied between the external electrodes 4 and 4', the electric field strength is weak only in the overlapping part of the electrodes, and the electric field strength in the peripheral part is weak.For this reason, the peripheral part of the element not only does not deform; This has the disadvantage that it inhibits the deformation of the entire element and makes it impossible to obtain the amount of strain inherent to the material.Furthermore, stress concentration occurs at the boundary between the deformed part and the non-deformed part, and when high voltage application, repeated application, or long There is also a drawback that the element is destroyed like a wave due to the application of time.

In order to improve the above-mentioned drawbacks, a structure as shown in FIGS. 4(a) and 4(b) may be considered. In other words, the same figure (
As shown in a), internal electrode plates 2, 2'' are alternately formed and stacked on the entire surface of an electrostrictive material film (or thin plate) 1, and the ends of a plurality of internal electrode plates 2 are connected to each other. The structure is such that the internal electrode plates 2' are connected to the external terminal A, and the plurality of internal electrode plates 2' are connected to the external terminal B. Therefore, as shown in FIG.
and 2' are formed on the entire surface of the element, so when a voltage is applied between electrode terminals A and B, the electric field distribution in the electrostrictive material film 1 becomes uniform, the element deforms uniformly, and stress concentration is also reduced. It doesn't happen. In other words, the element exhibits an amount of deformation that is almost inherent to the material and becomes difficult to break. However, since the internal electrode plates 2 and 2' are close to each other, it is very difficult to electrically connect the internal electrode plates 2 to each other and the internal electrode plates 2' to each other.

In view of the above-mentioned circumstances, an object of the present invention is to propose an electrostrictive effect element in which an insulating layer is formed only on the electrostrictive material in the vicinity of the surface of the internal electrode plate formed on the entire surface of the element.

(Means for Solving the Problems) That is, the present invention provides an electrostrictive effect element in which films or thin plates of electrostrictive material and internal electrodes are alternately laminated and sintered as a unit. The end face of the internal electrode plate is exposed, and an inorganic insulating layer is formed on the entire surface or every other layer of the electrode exposed on this side end face in a range including the periphery of the exposed electrode.

When insulating electrodes with inorganic materials, dip methods, screen methods, etc. are generally used. However, in these methods, the structure of the insulating layer is such that the insulating layer covers not only the periphery of the exposed electrode but also the entire surface of the element, and when the element expands and contracts due to the electrostrictive effect as in the present invention, the inorganic insulation Problems such as cracks occurring in the layer, loss of insulation, and a reduction in the electrostrictive effect due to the inorganic insulating layer made it difficult to put it into practical use.

This is thought to be because the electrostrictive element expands and contracts when a voltage is applied, but the inorganic insulating layer does not, causing strain at the interface between the inorganic insulating layer and the electrostrictive element.

Moreover, as the size of the element increases, the difference in elongation also increases, resulting in 100% cracking.

One possible solution to this problem is to form an insulating layer using a stretchable soft organic material, but organic insulation has poor adhesion to ceramics, metals, etc., and the organic material itself has poor moisture resistance compared to inorganic materials. In particular, it is difficult to put it into practical use as an insulation for electrostrictive elements to which high voltage is applied. In particular, in stacked electrostrictive elements, the interval between internal electrodes is extremely narrow, on the order of tens of microns to one millimeter, and a high voltage of several tens to hundreds of volts is applied between these electrodes, so an insulating layer containing organic matter is required. Therefore, it is difficult to put it into practical use.

The present invention solves all of these problems, and provides inorganic insulation with high insulation properties and reliability without causing cracks even when the electrostrictive element is expanded and contracted, and without inhibiting the expansion and contraction rate of the electrostrictive element. It is an electrostrictive effect element formed with layers.

(Example) Next, the present invention will be described in detail with reference to drawings showing examples.

FIG. 1 and FIG. 2 are a perspective view and a sectional view, respectively, showing an embodiment of the present invention. That is, in the electrostrictive effect element of the present invention, only the exposed portions of the internal electrode plates 2, 2' exposed to the outside on the side surfaces of the device and the portions of the electrostrictive material film 1 on the side surfaces of the device close to the internal electrodes are used as the external electrodes 3.3'. Since the structure is coated with , the strain caused by expansion and contraction of the electrostrictive material is extremely small, resulting in a structure in which cracks in the insulating layer are completely eliminated.

As an example, a length of 10 mm of Pb(Mgl/3Nb2/
3) A laminated electrostrictive effect element was prototyped using an electrostrictive material containing 03 as a main component, and when a voltage of IKV/mm was applied, it expanded to a length of 10.01 mm.

Therefore, if an insulating layer is formed over the entire surface, a force such as a total thickness of 10.01 mm will be applied to the insulating layer as well. Furthermore, when an insulating layer is formed on the entire surface of the laminated electrostrictive element and the electrostrictive element is expanded or contracted, since the insulating layer does not expand or contract, bending stress is applied to the element, which also causes cracks in the insulating layer and the element. It causes peeling.

However, by dividing the insulating layer as in the present invention, almost no elongation is applied to the insulating layer, and furthermore, no bending stress is applied to the insulating layer. Therefore, even when the electrostrictive element is expanded or contracted, problems such as cracks and peeling in the insulating layer can be completely eliminated.

The structure of the present invention will be explained based on examples. First, powder of an electrostrictive material containing magnesium niobate Pb(Mgl/3Nb2/3)03 as a main component is dispersed in a solvent together with an organic binder to form a slurry. This is made into a ceramic raw sheet having a uniform thickness of 30 μm to 200 pm by a casting method using a doctor blade. This ceramic raw sheet is punched out into a rectangle of 60 mm x 40 mm, and platinum paste is printed on the surface as an internal electrode material by screen printing.

II i ceramic green sheets including this ceramic green sheet are laminated and pressed together to form an integral laminate. This laminate is sintered at a temperature of 900°C to 1200°C to obtain a sintered laminate.

This sintered body is cut into small rectangular pieces of 5 mm x 5 mm using a diamond cutter. For example, an electrode paste is formed by coating or printing every other layer on two opposing surfaces of the four exposed internal electrode layers of the cut small piece element, and baked as electrodes for electrophoresis. The electrodes may be deposited using a predetermined mask. At this time, the internal electrode layers forming the two electrodes are further shifted from each other so that electrodes are not attached to the image side of the same internal electrode layer on the two surfaces. Lead wires are connected to the electrodes thus formed, and these are assembled into a book. This element is placed in an electrophoresis tank, and a DC voltage of 50 V is applied between the lead wire and the counter electrode for 30 seconds to form an insulating layer on the exposed internal electrode surface and its vicinity. At this time, an organic material is formed on the exposed parts of the internal electrodes where it is not desired to form an insulating layer, and in order to form an insulating layer with a uniform thickness, the counter electrode is moved around the element while a DC electric field is applied. Alternatively, it is desirable to arrange a counter electrode on the circumferential surface of the element. A DC electric field is applied for a predetermined period of time, and the device with the insulating layer formed is heated to 900°C.
When the heat treatment is performed at -10 minutes at -10 minutes, the insulating layer is baked onto the surface of the element.

FIG. 5 shows an example of an apparatus for forming an insulating layer on exposed internal electrodes of an electrostrictive element by electrophoresis. Here, 5 is an electrostrictive element, 6 is a counter electrode, 7 and 7' are lead wires, and 8
9 indicates a slurry of insulating powder, 9 indicates a DC power supply, and 10 indicates a glass container.

In this example, the following composition was used as a slurry for electrophoresis of an inorganic insulating material.

Lead borosilicate glass 10wt% ethanol
85wt% polyvinyl butyral
5 wt% Even if an AC voltage of 300 V and 50 Hz was applied to the electrostrictive effect element with an external insulating layer formed in this manner, and stretching vibration was performed continuously for 100 hours, there were no problems with insulation or other electrical properties. No cracks or peeling occurred in the insulating layer, and it was confirmed that it could be put to practical use as an electrostrictive element.

(Effects of the Invention) As is clear from the above embodiments, according to the structure of the present invention, the insulating layer is independent for each layer of the internal electrode. There is no cracking of the insulating layer due to expansion/contraction even if the expansion/contraction occurs, and there is no interference with expansion/contraction due to the no-electric field area caused by the formation of the insulating layer.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a sectional view similarly showing an embodiment of the present invention. In FIGS. 1 and 2, 1 is an electrostrictive material, 2 is an internal electrode, 3 and 3' are inorganic insulating layers. Figures 3(a) and (b) are a cross-sectional view and a plan view showing an example of a conventional multilayer chip capacitor type electrostrictive effect element, and Figures 4(a) and (b) are internal electrode plates shown on the entire surface of the element. 3 and 4, 1 is an electrostrictive material, 2 and 2' are internal electrodes, and 4 and 4' are external electrodes. . FIG. 5 is a sectional view of an apparatus for forming an insulating layer by electrophoresis. In FIG. 5, 5 is an electrostrictive element, 6 is a counter electrode, 7, 7' are lead wires, 8 is an insulating powder noslurry, and 9 is an electrostrictive element. A DC power supply and 10 are glass containers.

Claims (1)

[Claims] 1. An electrostrictive effect element in which films or thin plates of electrostrictive material and internal electrodes are alternately laminated and sintered as one body,
An electrostrictive effect element characterized in that an inorganic insulating layer is directly formed only on the exposed internal electrode plate portion on the side end face of the element and the electrostrictive material in the vicinity thereof.