JPH07106652A - Multilayer electrostriction effect device - Google Patents

Abstract

PURPOSE:To provide a while surface electrode type multilayer electrostriction effect device in which deterioration of the mechanical strength and electrical characteristics of the device due to formation of the insulator layer on the side face by selective removing method is eliminated while reducing the cost as compared with a device where the insulator layer is formed selectively. CONSTITUTION:An insulator layer 51A for insulating the part of an inner electrode layer 2 exposed to the side of laminate and an outer electrode layer 31A for connecting every other inner electrode layer 2 are formed by screen printing. The insulator layer 51A is formed into a continuous stripe so that the exposed parts of all inner electrode layer 2 are insulated by one insulator layer 51A. The outer electrode layer 31A is formed such that the part being connected with the exposed part of the inner electrode layer 2 projects pectinately from the stripe insulator layer 51A. Reliability of the device is enhanced furthermore when a recess being described by a continuous line is provided at a part surrounded by the pectinated part in the side of the insulator layer 51A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated electrostrictive effect element, and more particularly to a full surface electrode type laminated electrostrictive element in which the planar shape of a ceramic layer and the internal electrode layer exhibiting the electrostrictive effect are the same. Regarding the effect element.

[0002]

2. Description of the Related Art As shown in a perspective view of FIG. 6, a laminated type electrostrictive effect element has a ceramic thin layer which generates strain due to the electrostrictive effect and an external power supply circuit (not shown). The ceramic layer 1 generates an electric field according to the driving voltage applied.
And a thin layer of an internal electrode for applying to the electrode are alternately and repeatedly stacked so as to be on top of each other. The internal electrode layers 2 are divided into two groups so that they have the same electric potential every other layer, and the external electrode layers 3A and 3B (left side surface) provided on each of the opposite side surfaces of the element for each group. The upper external electrode layer 3B is hidden and invisible). With such a structure, when a driving voltage is applied from the power supply circuit placed outside between the two external electrode layers 3A and 3B, the driving voltage is applied between the internal electrode layers 2 sandwiching the respective ceramic layers 1. Ceramic layer 1
Since an electric field is applied to each of the ceramic layers 1, strain is generated in each ceramic layer 1 according to the driving voltage.

A piezoelectric effect is known in addition to the electrostrictive effect as a phenomenon that causes distortion in response to an electric field applied from the outside. The following description will be made about the electrostrictive effect element using the electrostrictive effect, but the difference between the piezoelectric effect and the electrostrictive effect is
The generated strain is proportional to the electric field (piezoelectric effect)
Or only proportional to the square of the electric field (electrostrictive effect), so in the following description, "electrostrictive" is all "piezoelectric".
Can be read as In the present invention, the electrostrictive effect element refers to an element that causes a strain in accordance with an electric field applied from the outside, and is defined to include both an element using the electrostrictive effect and an element using the piezoelectric effect.

In the electrostrictive effect element having the above-mentioned structure, the thickness of the ceramic layer 1 in which strain is generated is, for example, 100.
Since the ceramic layers 1 are as thin as about μm and the strains generated are laminated in series, a large displacement is generated between both end faces of the device as a whole even in the case of a low driving voltage. It has the feature of being able to do. In particular, in the full surface electrode type laminated electrostrictive effect element which is the object of the present invention, the planar shape of the ceramic layer 1 and the planar shape of the internal electrode layer 2 are the same, and the entire surface of each ceramic layer 1 is covered. Since a uniform electric field is applied to the substrate, it is excellent in the magnitude of the generated displacement and the reliability when it is repeatedly used.

As is clear from the above-mentioned structure, generally, in the laminated electrostrictive effect element, the technique of electrically connecting the internal electrode layers every other layer is essential. As such a technique, for example, a technique of a through hole or a via hole used in a multilayer printed wiring board or the like can be applied. According to this method, as shown in the sectional view of the laminated body in FIG. 7, a through hole is opened in the ceramic layer 1 and the connecting conductor 4 is formed in this through hole.
Can be formed, and the upper and lower internal electrode layers can be sequentially connected to each other. However, in this case, for example, with respect to the through holes for connecting the odd-numbered internal electrode layers, an insulating space is provided around the through holes in the even-numbered internal electrode layers in order to avoid contact with the connection conductor 4. Must be provided. Therefore, the electric field is not applied to the peripheral portion of the through hole of each ceramic layer 1, and the strain is not generated. As a result, when a drive voltage is applied, a portion where strain is generated and a portion where strain is not generated occur in one ceramic layer, and a large stress is generated at the boundary portion thereof, so the displacement generated by the element is reduced. At the same time, reliability will be impaired. Therefore, in the full surface electrode type electrostrictive effect element,
Such a through-hole (or via-hole) technique, in other words, a technique of connecting internal electrode layers inside a laminated body is difficult to apply, and by way of example, as shown in FIG. The layers must be connected one after the other.

Referring again to FIG. 6, in the full-surface electrode type laminated electrostrictive effect element shown in this figure, the exposed portion of the odd-numbered (from the upper side of the drawing) internal electrode layer is insulated on the right side surface of the laminated body. A plurality of insulating layers 5A are formed. Further, an external electrode layer 3A is formed in a band shape on the external electrode layer 3A. Therefore, even-numbered (same) internal electrode layers of the internal electrode layers 2 are electrically connected to the external electrode layers 3A at the portions exposed on the right side surface of the stacked body, and all have the same potential. On the other hand, on the left side surface facing the side surface where the insulator layer 5A and the external electrode layer 3A are formed, an insulator layer 5B for insulating exposed portions of the even-numbered internal electrode layers and odd-numbered internal electrodes are provided. External electrode layer 3B that connects exposed parts of the layer (hidden and invisible)
And are formed.

In the context of the present invention, what is characteristic of the conventional electrostrictive effect element shown in FIG. 6 is that the internal electrode layer 2 and the external electrode layer 3 cover the exposed portions of the internal electrode layer 2 on the side surfaces of the laminate.
That is, the insulator layers 5A and 5B that insulate A and 3B are formed independently for each internal electrode layer. In order to form a plurality of independent insulating layers as described above, a method of selectively forming the insulating layer on a predetermined portion and a method of forming the insulating layer entirely and then leaving only the insulating layer on the predetermined portion selected There is a method to remove it.

As a selective forming method, Japanese Patent Publication Sho 63-1
As disclosed in Japanese Patent Application No. 7354 (Japanese Patent Application No. 57-78444, hereinafter referred to as the first publication), there is a method using a screen printing method. In addition, Japanese Patent Application Laid-Open No. 59-115579 (Japanese Patent Application No. 57-225169, hereinafter referred to as a second publication) describes an insulator by an electrophoretic method as another method for forming a selective insulator layer. A technique of forming a layer and then firing is disclosed.

On the other hand, as an insulating layer forming method by selective removal, Japanese Patent Application Laid-Open No. 63-84174 (Japanese Patent Application No. 61-84174) is available.
-228464 publication. Hereinafter, there is a method disclosed in the third publication). In this method, first, the insulating material is applied to the entire side surface of the laminate by screen printing or brush coating and baked, and then the insulating material in the unnecessary portion is removed by precision processing such as laser processing or water jet processing,
The internal electrode layers are exposed every other layer.

As described above, one of the major characteristics of the laminated electrostrictive effect element is that the thickness of the ceramic layer 1 is, for example,
It is as thin as about 100 μm or less. Along with this, the width of the insulating layers 5A and 5B in the stacking direction (the element displacement direction shown by the arrow in FIG. 6) is also very narrow, around 100 μm. Therefore, in particular, in the case of the whole-surface electrode type laminated electrostrictive effect element, in order to reliably connect and insulate the internal electrode layer and the external electrode layer,
A technique for forming high-quality insulator layers 5A and 5B having a thickness of about 50 μm and a width of about 100 μm at dimensional accuracy and at accurate positions is indispensable. Each of the above publications is intended to solve such a technical problem.

[0011]

As described above, in all of the conventional full-surface electrode type laminated electrostrictive effect elements, the insulator layer formed on the side surface of the element is different for each exposed portion of each internal electrode layer. It consists of multiple independent parts. In the above-mentioned first and second publications, such an insulator layer is selectively formed by screen printing or electrophoresis. In the third publication, it is formed by forming it on the entire surface and then selectively removing it.

However, a characteristic of this type of laminated electrostrictive effect element, that is, by providing a structure in which the ceramic layer is thin and sandwiched between the internal electrode layers from above and below, a high electric field is applied to the ceramic layer even at a low driving voltage. In order to fully exert the feature of being able to achieve the above, it may be difficult to reduce the cost of the element according to the conventional technique, and in some cases, the reliability of the element may be sacrificed. The description will be given below.

First, in the electrostrictive effect element described in the above-mentioned third publication, after forming an insulating layer continuous in the longitudinal direction (laminating direction) of the laminated body, laser processing is performed with this insulating layer body placed every other layer. Although it is selectively removed by a thermal processing method or a mechanical processing method such as water jet processing, when the thermal processing method is used, the thermal adverse effect such as the generation of thermal cracks due to the heat generated during processing may cause a bad influence on the ceramic layer. Or induced in the insulating layer, the mechanical strength and electrical reliability of the device may decrease. Furthermore, when the insulating layer is an organic material, the electrical characteristics of the element may be deteriorated due to the adhesion of carbon that accompanies the combustion of the insulating material. On the other hand, the mechanical processing method may generate mechanical cracks such as micro cracks during processing, and like the thermal processing method, may cause deterioration of mechanical strength and reliability during element driving. Furthermore, the formation of the insulator layer by such selective removal requires an additional step of partially removing the insulator layer in addition to the step of forming the insulator layer. It is difficult to remove all the unnecessary portions of the insulating layer at once, and the unnecessary portions must be sequentially removed individually, which requires a lot of processing time and is very disadvantageous in terms of cost. These effects become more remarkable as the number of stacked layers is increased to improve the characteristics of the device.

On the other hand, in the method for selectively forming the insulator layer described in the first and second publications, the thermal / mechanical method as in the device described in the third publication is used. There is no problem such as deterioration of mechanical or electrical performance or deterioration of reliability due to stress. However, on the other hand, since it is necessary to selectively form the insulating layer in a narrow area, if the insulating layer is to have sufficient dielectric strength,
There are problems that the thinning of the ceramic layer is limited, and that it becomes difficult to reduce the cost.

For example, it is assumed that the practical electric field strength applied to the ceramic layer is about 1.5 kV / mm.
In addition, as an insulator layer, glass (dielectric breakdown strength: about 50k
V / mm or less) is used, and the strength of the dielectric breakdown of the glass is estimated to be 1/10 of the above value in consideration of the transient phenomenon of the driving voltage and the long-term reliability of the element. At this time, theoretically, the required dielectric strength can be obtained when the thickness of the glass insulator layer is about 30 μm.

Here, as in the first publication, when screen printing is used to form the insulator layer, it is unavoidable that a defective portion is generated in the actual insulator layer formed, so that insulation is not possible. At least 50 μm for practical use as a body layer
It needs a certain thickness. The thickness of this insulator layer is 50 μm
Is the minimum distance between the internal electrode layers, that is, the minimum thickness of the ceramic layer. A ceramic layer having such a thickness can be stably mass-produced even under the present circumstances due to the development of the laminated technology of the laminated ceramic capacitor, and it can be sufficiently thinned. On the other hand, in consideration of the alignment accuracy and the pattern dimensional accuracy in the current screen printing, a space of about 50 μm is required on each side of each insulator layer, and the thickness of the ceramic layer must be at least about 100 μm. Don't In this way, an element having a thickness of each ceramic layer of 100 μm, a thickness of each insulator layer of 50 μm, a width in the stacking direction of 100 μm, and a driving voltage of 150 V is obtained. In short,
In the case of an element that uses screen printing to form the glass insulator layer, the thickness of the ceramic layer is limited by the limit of the technology for forming the glass insulator layer and cannot be made sufficiently thin, and it can be said that the driving electric field cannot be further increased. .

On the other hand, in the insulator layer forming technique by the electrophoretic method disclosed in the second publication, the insulator layer does not cause a positional deviation with respect to the internal electrode layers due to its forming principle. It is suitable for forming a fine and high-quality glass insulating layer as compared with the insulating layer forming by. However, in the electrostrictive effect element to which this technique is applied, the step of forming the temporary electrode, the step of masking the exposed portion of the internal electrode layer, and the step of electrodeposition are each performed only for electrophoresis. It is necessary to make a total of twice, one for each side. Moreover, the electrical characteristics of the formed insulator layer are affected by the electrodeposition state of the insulator layer,
This electrodeposition state is sensitive to the temperature and concentration of the swimming bath, and its thickness and shape are easily influenced by the voltage and time during electrodeposition.Therefore, it is very important to control these electrodeposition conditions in the actual manufacturing process. If not strictly done, the rate of non-defective products will decrease.
As described above, in the electrostrictive effect element in which the insulator layer is formed by electrophoresis, the manufacturing process is complicated, the management of the manufacturing conditions is difficult, and the non-defective rate easily varies. It's not easy.

Therefore, according to the present invention, in the laminated electrostrictive effect element of the whole surface electrode type, the mechanical strength of the element is lowered and the electrical strength is reduced due to the formation of the insulating layer on the side surface of the laminated body by the selective removal method. It is an object of the present invention to provide a laminated electrostrictive effect element which does not deteriorate in characteristics and can be manufactured at a lower cost than an element in which an insulating layer is selectively formed.

[0019]

In the laminated electrostrictive effect element of the present invention, ceramic layers exhibiting an electrostrictive effect and internal electrode layers having the same planar shape as the ceramic layers are alternately laminated. On the first side surface parallel to the axis along the stacking direction of the laminated body formed by the above, and continuously covering the exposed portion of the internal electrode layer to the first side surface, which is continuous in the stacking direction in a strip shape. An insulating layer is electrically connected to an exposed portion of the first internal electrode layer provided on the first insulating layer and arranged every other layer of the internal electrode layer to the first side surface. A first external electrode layer is provided, and on the second side surface parallel to the axis along the stacking direction of the stacked body, the strip-like continuous shape is formed in the stacking direction to the second side surface of the internal electrode layer. A second insulator layer that partially covers the exposed part of the internal insulator, and the internal insulator that is provided on the second insulator layer. A second outer electrode layer electrically connecting an exposed portion of the second inner electrode layer different from the first inner electrode layer to the second side surface of the layer, and the first outer electrode A laminated electrostrictive effect element having a structure in which a planar shape of the layer and the second external electrode layer is formed in a shape in which a portion connected to each internal electrode layer protrudes in a comb shape from each insulator layer.

In the laminated electrostrictive effect element of the present invention, the planar shape of the first insulator layer and the second insulator layer is the first external electrode on a side parallel to the stacking direction. The laminated electrostrictive effect element is characterized in that a layer and a portion of the second external electrode layer sandwiched between the comb-teeth shaped protrusions have a shape having a recess drawn by a continuous line.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the first embodiment of the present invention. Referring to FIGS. 1 and 6, the present embodiment is different from the conventional full-surface electrode type laminated electrostrictive effect element in that the insulator layers 51A and 51B (the insulator layer 51B is hidden in the laminate). (Not shown in the figure because it is formed on the side surface on the side) and the external electrode layers 31A and 31B (same)
2 is a plane shape when viewed from a direction perpendicular to the side surface of the element. The insulator layers in the present embodiment are laminated while the conventional insulator layers 5A and 5B of each element are composed of an exposed portion of each internal electrode layer and an isolated portion covering only the periphery thereof. It has a continuous strip shape in the direction. Further, the external electrode layer 31A (31B) of this embodiment is provided in a strip shape on the above-mentioned insulator layer 51A (51B). Only the portion of the internal electrode layer 2 that is connected to the exposed portion protrudes from the insulator layer 51A (51B) like a comb and electrically connects the odd-numbered (even number) internal electrode layers 2. The insulator layer and the external electrode layer are formed by a screen printing method as described later. The thickness of the ceramic layer 1 is 110 μm.

The present inventor produced this embodiment as described below. First, for example, Pb (Zr, Ti) O
A multi-component solid solution ceramic powder having a perovskite crystal structure as described above is mixed with polyvinyl butyral resin powder as an organic binder to form a green sheet. Then, a silver-palladium paste to be the internal electrode layer is screen-printed on the entire surface and dried, and then 80
A laminated sintered body is formed by stacking layers and sintering at a temperature of 1000 ° C. or higher.

Next, of the opposing side surfaces of the laminated sintered body, first, the right side surface is screen-printed with a glass paste to be the insulator layer 51A and dried. At this time, a band-shaped pattern as shown in FIG. 1 is used. This band-shaped glass paste has a thickness of 50 μm or more, and the width (width in the direction along the exposed portion of the internal electrode layer) is ⅓ of the width (same) of the laminated sintered body. Similarly, glass paste to be the insulating layer 51B (which is hidden and invisible) is screen-printed on the opposite left side surface in the same manner and dried, and then the glass pastes on both sides are simultaneously fired at a temperature of 650 ° C. for glass insulation. Body layers 51A, 5
1B (the same) is formed.

Next, a silver paste to be the external electrode layer 31A is screen-printed and dried on the side surface on which the glass insulator layer 51A is formed. As shown in FIG. 1, the print pattern of this silver paste is continuous in a strip shape on the insulator layer 51A, and a part of the print pattern protrudes like a comb in the direction perpendicular to the strip portion. 2 is a pattern connected to the exposed portion of the internal electrode layer 2 of FIG. Similarly, the external electrode layer 31B is formed on the side surface on which the glass insulator layer 51B is formed.
Screen-print the silver paste that becomes (hidden and invisible). The print pattern of this silver paste is a pattern to be connected to the exposed portion of the even-numbered internal electrode layers (from the upper side of the paper) of the internal electrode layers. After that, both surfaces are simultaneously fired at a temperature of 650 ° C. to simultaneously form the external electrode layers 31A and 31B. Each of these external electrode layers has a thickness of 10 μm and has a width in the stacking direction of the comb-teeth portion that makes electrical contact with the internal electrode layers.
The width of the strip-shaped portion on the glass insulator layer (width in the direction along the exposed portion of the internal electrode layer) is 2/3 of the width of the glass insulator layer (the same).

After that, lead wires (the same) for connecting to an external driving power supply circuit (not shown) are soldered to the external electrode layers 31A and 31B to complete this embodiment.

In this embodiment, the width of the external electrode layers in the stacking direction of the comb-teeth-shaped protrusions for establishing electrical continuity with the exposed portions of the internal electrode layers 2 is 30 μm, but this width is made wider than necessary. No need. This is because the electrostrictive effect element is basically a voltage drive type element rather than a current drive type element. That is, in the electrostrictive effect element, contact between the exposed portion of the internal electrode layer and the external electrode layer only needs to be in electrical contact and to transmit only the voltage. Therefore, it is not necessary to increase the contact area in consideration of the voltage drop due to the contact resistance between the internal electrode layer and the external electrode layer and the voltage drop due to the resistance component of the external electrode layer. On the other hand, in the electrostrictive effect element described in the first publication, according to the strength of the electric field applied to the ceramic layer, in other words, the electric field applied between the internal electrode layer and the external electrode layer with the glass insulator layer interposed therebetween. ,
This limits the thickness of the ceramic layer, since the glass insulator layer must have a certain width or more.

Now, referring to FIG. 2 (a), which is an enlarged view of a main portion of a side surface of a conventional electrostrictive effect element in which an independent insulator layer is formed for each internal electrode layer, the thickness of each ceramic layer 1 is referred to. Sa t
_{It is} assumed that _C1 and the width of the insulator layer 5A are w ₁ and that the insulator layer 5A is displaced from the normal position (shown by the solid line in the figure) by a distance d with respect to the internal electrode layer 2 _{n + 1} (the same, Shown with a broken line).
At this time, since the insulator layer 5A should not cover the adjacent internal electrode layer 2 _n , (1/2) w ₁ + d <t _C1 must be satisfied. On the other hand, since the dielectric strength between the internal electrode layer 2 _{n + 1} and the external electrode layer must be ensured, (1/2) w ₁ −d ≧ t _BD must be satisfied (however, t _BD is the thickness of the insulator layer 5A for obtaining the necessary dielectric strength).

Therefore, the minimum value t of the thickness of the ceramic layer 1 is
_From the equations, _C1min is represented by t _C1min > t _BD + 2d.

On the other hand, referring to FIG. 2 (b) which is an enlarged view of the essential parts of the element side surface of this embodiment, each ceramic layer 1
Is t _C2 , and the width of the comb-teeth portion of the external electrode layer 31A is w.
₂ , where the amount of positional displacement of the external electrode layer 31A with respect to the internal electrode layer 2 _{n + 1} is d, the external electrode layer 31 that has caused positional displacement
(Shown by a broken line) A is from having to keep the contact with the internal electrode layer 2 _{n + 1} and not contacting the internal electrode layer 2 _n, the thickness t _C2 of each ceramic layer 1 , (1/2) w ₂ + d <t _C2 and (1/2) w ₂ −d> 0.

Therefore, the ceramic layer 1 in this embodiment
The minimum value of the thickness t _C2min is t _C2 ≧ 2d based on the equation and the equation. Here, comparing the equation with the equation, the conventional electrostriction in which an insulator layer is independently formed for each internal electrode layer is used. In the effect element, even if the accuracy of the insulating layer formation is improved, the thinning of the ceramic layer is limited by the dielectric strength of the insulating layer. It can be seen that the ceramic layer can be made thinner by increasing the accuracy. Particularly, in the electrostrictive effect element described in the first publication in which screen printing is used for forming the insulating layer as in the case of this example, the difference in effect from this example is remarkable.

Moreover, in this embodiment, since the insulator layer and the external electrode layer are formed by screen printing, unlike the electrostrictive effect element described in the second publication, there is no need for forming the insulator layer. No new technology or manufacturing process is required, and of course, manufacturing equipment and complicated manufacturing condition management for it are not required. Therefore, this embodiment can greatly reduce the manufacturing cost as compared with the electrostrictive effect element described in the second publication. In this example, as an example, the processing man-hours per 1000 pieces could be reduced to 1/3 of the case of the electrophoresis method.

Further, as in the electrostrictive effect element described in the third publication, the thermal / electrical characteristics are not deteriorated and the reliability is not deteriorated due to the selective removal of the insulating layer. .

In this embodiment, the insulator layer 51A (51B)
Since the planar shape of is a continuous strip, it is already known that the strip-shaped inorganic insulator layer restrains the strain generation of the ceramic layer on the side surface of the element, resulting in a decrease in displacement and repeated displacement. In the point of failure occurrence due to stress applied to the insulating layer when the
It is somewhat disadvantageous as compared with the electrostrictive effect element described in the above publication and the second publication. However, since the use of this type of electrostrictive effect element has become widespread in recent years, for example, a mass flow controller (precision gas flow rate control device) used in a semiconductor manufacturing apparatus, a positioning device for an optical fiber, or a mirror for an optical device is used. Displacement of 10 μm for position control, etc.
It has the advantage of low cost in applications that are relatively small (less than or equal to a certain level), applications that perform a DC servo operation that does not repeat displacement frequently, and further that replacement is easy when a failure occurs. be able to.

Here, in order to reduce the decrease in displacement and the occurrence of failure due to the above-mentioned band-shaped inorganic insulating layer, as described in the second publication, the material itself is made of an organic material system having elasticity. It is preferable to use an insulating layer. Conventionally, the strength of dielectric breakdown of organic insulating materials has not been sufficient as compared with inorganic insulating materials, but in recent years, the electrical characteristics of organic materials have been significantly improved. Since the strength of dielectric breakdown is several hundred kV / mm, which is not inferior to that of glass, it can be sufficiently put to practical use as a material for an insulator layer of the electrostrictive effect element of the present invention.

In the above-mentioned embodiment, the insulating layer 51A is used.
And a side surface (right side surface) on which the external electrode layer 31A is formed,
Although the side surface (left side surface) on which the insulator layer 51B and the external electrode layer 31B are formed are different from each other, these surfaces may be the same side surface. Further, as shown in the perspective view of FIG. 3, the external electrode layer 31A and the external electrode layer 31B may have a structure in which the same one insulator layer 51 is shared on the same side surface.

Next, a description will be given of a second embodiment in which the reduction of the displacement amount caused by the above-mentioned strip-shaped insulator layer and the occurrence of failure are further reduced. FIG. 4 is a perspective view of the second embodiment of the present invention. In the following description, in order to avoid complication of the description, the insulator layer 52A on the right side surface of the two insulator layers facing each other will be described as an example.

Referring to FIG. 4, this embodiment is different from the first embodiment shown in FIG. 1 in the pattern of the insulating layer 52A. In the pattern of the insulator layer 52A in this embodiment, as shown in FIGS. 4 and 5A, a semicircular recess 6 is provided in a portion between the comb-teeth-shaped protrusions of the external electrode layer 31A. It has a shape.

By providing the recess 6, the contact area between the side surface of the laminate and the insulating layer 52A is reduced. Further, for example, as can be seen from the comparison between the straight cylindrical metal pipe and the bellows-shaped metal pipe, the insulating layer 52A is made stretchable due to the shape effect of providing the recessed portion 6. In the present embodiment, the contact area is reduced and the elasticity is imparted, so that the restraint force of the insulating layer 52A against the displacement of the laminate and the accompanying reduction in the generated displacement amount are reduced.

Further, when a vertical force is applied to the insulating layer 52A as the laminated body is displaced in the vertical direction of the paper surface,
In the recessed portion 6, the tensile force with respect to the side portion of the insulator layer 52A is dispersed. Therefore, for example, as shown in FIG. 5A, even if a minute defect occurs during screen printing in the recessed portion 6, the concentration of stress on the minute defect is as shown by a short arrow in FIG. Will be alleviated. On the other hand, in the linear insulator layer 51A shown in FIG. 5B, the tensile force is not dispersed in the side portion of the insulator layer 51A as described above. As a result, when a minute defect similar to the one described above occurs in the peripheral portion of the insulator layer 51A, large stress concentration occurs in this defect portion as indicated by a long arrow in the figure, and displacement is repeated. Accordingly, the breakage of the insulator layer 51A progresses from this defect. Therefore, the density of minute defects generated on the side portion of the insulator layer is the same as that of the second embodiment shown in FIG.
If it is the same as that of the linear insulator layer shown in (b), the probability of breakage from minute defects in the insulator layer is lower in the present embodiment, and accordingly, there are less failures when the element is repeatedly displaced. . The shape of the recess 6 is not limited to the semicircle. It may be part of an ellipse or part of a sine curve. Further, it may have a shape formed by smoothly connecting a plurality of straight lines.

In the second embodiment described above, the insulator layer 52
The recessed portion 6 of A and other portions are discontinuously connected. Therefore, there is a slight possibility that the portion where the minute defect is generated during screen printing coincides with the discontinuous connection point or the linear portion other than the recessed portion 6 and the stress is concentrated there to cause the element to fail. Remain. The failure of the element due to such a cause can be further reduced by forming the pattern of the insulating layer into the shape shown in FIG. That is, referring to FIG. 5C, in the pattern of the insulator layer 53A shown in this figure, the portion corresponding to the comb-shaped protruding portion of the external electrode layer is formed in a semicircular convex shape, and the concave portion 6 and the smooth portion are smooth. Connected to. In the insulator layer 53A having such a shape, the tensile force is dispersed in any of the peripheral portions of the insulator layer.
The occurrence of device failure due to minute defects is reduced. Here, in this example, the convex semi-circle and the concave semi-circle are continuous, but the respective shapes are not limited to the semi-circle. The same effect can be obtained by using a part of an ellipse or a sine curve.

In the above-mentioned second embodiment, the pattern of the external electrode layer 31A is formed in such a manner that the comb-teeth-like protrusions project in both directions with respect to the strip-shaped portion, as shown in FIG.
That is, the two comb-teeth-shaped protrusions are provided back to back, but this pattern may have a shape in which the comb-teeth-shaped protrusions project only to one side, as shown in FIG. . Also, two insulator layers may be formed on the same side surface of the laminate, and at this time, two external electrode layers may share the same insulator layer. Is the same as in the embodiment.

[0042]

As described above, according to the present invention, in the laminated electrode electrostrictive effect element of the full-surface electrode type, the insulating layer for insulating the exposed portion of the internal electrode layer exposed on the side surface of the laminated body from the external electrode layer. And, the external electrode layers for connecting every other internal electrode layer are formed by screen printing, and the shape of the insulating layer is such that all the internal electrode layers are insulated by one insulating layer continuous in a strip shape. Also, the external electrode layer is shaped such that the portion connected to the exposed portion of the internal electrode layer protrudes like a comb from the strip-shaped portion of the insulator layer.

Thus, according to the present invention, the thickness of the ceramic layer is not limited by the dielectric strength of the insulator layer, but can be determined only by the screen printing accuracy of the external electrode layer. Therefore, compared with the conventional electrostrictive effect element in which an independent insulator layer is formed for each internal electrode layer, the ceramic layer can be made thinner and can be driven by a high electric field.

Moreover, unlike the element in which the insulator layer is formed by the electrophoretic method, no new process is required to form the insulator layer and the external electrode layer, and the manufacturing conditions need to be strictly controlled. Therefore, the manufacturing cost can be greatly reduced.

Further, as compared with the device in which the insulating layer is formed by the selective removal method, there is no thermal or mechanical damage at the time of manufacturing the device, so that the electrical and mechanical characteristics associated with these damages are There are no problems such as deterioration or deterioration of reliability.

Further, according to the present invention, a concave portion drawn by a continuous line is provided in a portion sandwiched between the comb-teeth-shaped protrusions of the external electrode layer with respect to a side extending in the stacking direction of the insulating layers. There is.
This reduces the amount of displacement that occurs when the insulating layer is formed into a strip-shaped continuous body, and reduces the occurrence of device failure due to breakage of the insulating layer when repeatedly displaced.

The electrostrictive effect element of the present invention is used for a comparatively small amount of displacement, for a DC servo-like operation in which displacement is not repeated frequently, and for easy replacement when a failure occurs. When it is used for, the advantage of its low cost is exerted.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 illustrates the relationship between the thickness of the ceramic layer and the width of the insulating layer and the relationship between the width of the ceramic layer and the width of the external electrode layer in the conventional electrostrictive effect element and the first embodiment of the present invention. FIG.

FIG. 3 is a perspective view showing another example of the structures of the insulator layer and the external electrode layer in the first example of the present invention.

FIG. 4 is a perspective view of a second embodiment of the present invention.

FIG. 5A is a diagram showing a state of stress when minute defects are generated in the insulating layer in the second embodiment of the present invention. FIG. 6B is a diagram showing a state of stress when minute defects are generated in the insulating layer in the first embodiment of the present invention. Separation diagram (c) is a diagram showing another example of the pattern of the insulator layer in the second embodiment of the present invention.

FIG. 6 is a perspective view of an example of a conventional laminated electrostrictive effect element.

FIG. 7 is a cross-sectional view of another example of a conventional laminated electrostrictive effect element.

[Description of Reference Signs] 1 ceramic layer 2 internal electrode layers 3A, 3B external electrode layer 4 connection conductors 5A, 5B insulator layer 6 recessed portions 31A, 31B external electrode layers 51, 51A, 51B, 52A, 52B, 53A, 53
B insulator layer

Claims (8)

[Claims] 1. A first parallel to a shaft along a stacking direction of a stack body in which a ceramic layer exhibiting an electrostrictive effect and an internal electrode layer having the same planar shape as the ceramic layer are alternately stacked. A first insulator layer that is continuous in a strip shape in the stacking direction and partially covers an exposed portion of the internal electrode layer that is exposed to the first side surface, and is provided on the first insulator layer. The
A first external electrode layer electrically connecting exposed portions of the first internal electrode layers arranged in alternate layers of the internal electrode layers to the first side surface, and the stacking direction of the stacked body. A second insulator layer continuous on the second side surface parallel to the axis extending along the stacking direction in a strip shape and partially covering the exposed portion of the internal electrode layer to the second side surface; A second insulating layer provided on the second insulator layer, for electrically connecting an exposed portion of the second inner electrode layer of the inner electrode layer different from the first inner electrode layer to the second side surface; 2 external electrode layers are provided, and the planar shape of the first external electrode layer and the second external electrode layer is made to have a shape in which a portion connected to each internal electrode layer protrudes in a comb shape from each insulator layer. The laminated electrostrictive effect element having the above structure. 2. The laminated electrostrictive effect element according to claim 1, wherein the first side surface and the second side surface are side surfaces facing each other. 3. The laminated electrostrictive effect element according to claim 1, wherein the first side surface and the second side surface are the same side surface. 4. The laminated electrostrictive effect element according to claim 3, wherein the first insulator layer and the second insulator layer are the same insulator layer. Strain effect element. 5. The laminated electrostrictive effect element according to claim 1, wherein the first insulator layer and the second insulator layer are made of an inorganic material such as silica glass or alumina glass. Characteristic multilayer electrostrictive effect element. 6. The laminated electrostrictive effect element according to claim 1, wherein the first insulator layer and the second insulator layer are made of an electrically insulating resin. Effect element. 7. The laminated electrostrictive effect element according to claim 1, wherein a planar shape of the first insulator layer and the second insulator layer is the first of the sides parallel to the stacking direction. A laminated electrostrictive effect element having a shape having a recess drawn by a continuous line in a portion sandwiched between the external electrode layer and the second external electrode layer between the comb-teeth-shaped protrusions. 8. The stacked electrostrictive effect element according to claim 7, wherein a side parallel to the stacking direction is formed by smoothly connecting the recess and a portion other than the recess by a continuous line. And a laminated electrostrictive effect element.