JP2001196656A - Manufacturing method for laminated piezoelectric material and manufacture product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a laminated piezoelectric body excellent in reliability by forming a uniform glass insulation layer with suppressed defects in a side where the end of an internal electrode layer of a laminated piezoelectric material is exposed, and to provide its manufactured product. SOLUTION: This is a method for manufacturing a laminated piezoelectric material 1 to form an insulation by electrodepositing fine particles consisting of a glass insulation material on a part where an internal electrode layer 3 by electrophoresis to a laminated piezoelectric material having an interlaminated structure of a plurality of piezoelectric ceramic layers 2 and internal electrode layers 3 with exposed end faces of the internal electrode layers 3, wherein a glass insulating layer 4 consisting of a glass insulating material is so constituted as to be uniform on only the exposed part of the said internal electrode layer 3, or on both exposed part of the said internal electrode layer 3 and the surface of the piezoelectric ceramic layer 2 between the internal electrode layers 3, 3 by combining the said electrophoresis and a heat treating at a predetermined temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer piezoelectric body, and more particularly to a method for manufacturing a multilayer piezoelectric body with improved reliability.

[0002]

2. Description of the Related Art At present, laminated piezoelectric bodies are frequently used as thin piezoelectric actuators. In general, the laminated piezoelectric body is formed by alternately laminating a plurality of plate-like piezoelectric ceramic layers and film-like internal electrode layers for applying a voltage, and external electrodes are provided at predetermined positions on end faces of the internal electrode layers. Having a given structure.

When the laminated piezoelectric body is small or has a complicated shape, there may be a portion where the end face of the internal electrode layer is exposed on the side surface of the laminated piezoelectric body. As described above, when a voltage is applied to the internal electrode layer and the multilayer piezoelectric body is driven in a state where moisture can permeate the end face, the metal or the like constituting the internal electrode layer is ionized and moves between the electrodes according to the electric field. That is, a so-called migration phenomenon is induced. In addition, an alloy containing silver as a main component, for example, a silver (Ag) -palladium (Pd) alloy is generally used for the internal electrode layer due to cost and other restrictions. However,
In an internal electrode layer made of an alloy containing Ag, migration is likely to occur, and in extreme cases, a metal bridge made of Ag or the like is formed between the internal electrode layers facing each other. As a result, cross-linking of the metal may cause an electrical short between the internal electrode layers facing each other, which may impair reliability.

[0004] Such migration is particularly promoted under high temperature, high humidity and high electric field. Therefore, the following measures have been taken to improve the moisture resistance of the multilayer piezoelectric body. (1) A method of coating the outer surface of the laminated piezoelectric body with an insulating material made of a resin film or a glass insulating layer.

(2) A method of coating the outer surface of the laminated piezoelectric body with an insulating material made of silica (SiO ₂ ).
For example, Japanese Patent Application Laid-Open No. 61-15382 discloses a technique in which an insulating film made of silica is uniformly formed on an exposed portion of an internal electrode layer by a low-pressure CVD method, and the exposed portion of the internal electrode layer is coated with a silica film. Have been.

(3) A method of forming a glass insulating layer on the outer surface of the laminated piezoelectric body by a dry or wet transfer method.
For example, in Japanese Patent Application Laid-Open No. 7-7193, dry transfer paper,
Alternatively, there is disclosed a technique in which a glass insulating material paste is formed on a wet transfer paper and then separated, and then the glass insulating material paste is attached to four side surfaces of the laminated piezoelectric body and heated to coat the glass insulating material.

(4) A method of selectively coating an insulator made of an inorganic material or a polymer material only on a portion where the internal electrode layer of the laminated piezoelectric body is exposed on the side surface. For example, in Japanese Patent Application Laid-Open No. 7-176802, particles made of an inorganic substance such as piezoelectric ceramics or a polymer insulator such as polyimide are exposed by electrophoresis to a portion where the internal electrode layer of the laminated piezoelectric body is exposed. There is disclosed a technique of selectively fixing and coating only on the surface.

(5) In the above-mentioned laminated piezoelectric body having a structure in which a hole is provided, a filler is filled in the hole, and a portion of the inner surface where the end face of the internal electrode layer is exposed is coated. Structure. For example, Japanese Patent Application Laid-Open No. H10-1366
No. 65 discloses a structure in which a hole is provided in the laminated piezoelectric body, in which the hole is filled with a flexible filler such as a silicone resin or a urethane resin. By coating the portion of the portion where the end face of the internal electrode layer is exposed, the effect of improving the moisture resistance is also provided.

[0009]

However, even with the above-mentioned measures, it is difficult to say that it is still sufficient to improve the reliability of the laminated piezoelectric material in the following points. According to the measure (1), when the outer surface of the multilayer piezoelectric body is coated with a resin film, the effect of imparting moisture resistance is small, and a problem remains in reliability. Further, when the outer surface of the laminated piezoelectric body is coated with a glass insulating layer by a normal method, moisture resistance is improved, but when the laminated type is driven, the elastic modulus between the glass insulating layer and the piezoelectric ceramic is large. If different, the glass insulating layer may hinder the displacement of the piezoelectric ceramic.

According to the measure (2), the moisture resistance is improved, but when the laminated piezoelectric body is driven and tensile stress is repeatedly applied to the silica film, cracks are easily generated in the silica film. When a crack occurs in the silica film, the end face of the internal electrode layer is exposed again, which impairs reliability.

Also, forming the silica film to a predetermined thickness requires a relatively long processing time, which causes a problem of an increase in cost.

According to the above-mentioned measure (3), the outer surface of the laminated piezoelectric body is coated with a glass insulating layer to improve moisture resistance and reduce the rate of occurrence of defects when used under high humidity. If the elastic modulus of the glass insulating layer is significantly different from that of the piezoelectric ceramic as in (1), the glass insulating layer may hinder the displacement of the piezoelectric ceramic.

According to the above-mentioned measure (4), the moisture resistance is improved, and further, only the portion where the internal electrode layer is exposed is selectively coated with an insulator, so that the multilayer piezoelectric body is driven. This makes it possible to suppress the occurrence of cracks even when tensile stress repeatedly acts on the inorganic coating layer. Therefore, the reliability can be greatly improved. In addition, according to the electrophoresis method, the coating time of the insulator is shortened as compared with the method (2), and the increase in cost can be suppressed.

However, since the insulator is formed only in the portion where the internal electrode layer is exposed, the moisture resistance of the portion where the insulator is not formed, for example, the piezoelectric ceramic layer between the internal electrode layers is not sufficient. In particular, when fine pores exist in the piezoelectric ceramic layer, there is a risk that the reliability may be impaired.

According to the above-mentioned measure (5), the moisture resistance of the portion exposed in the hole is improved, but a coating layer is separately provided on the portion where the internal electrode layer is exposed on the outer surface. Required.

Therefore, the present invention provides a multilayer piezoelectric body having excellent reliability by forming a uniform glass insulating layer with suppressed defects on the side face where the end face of the internal electrode layer of the multilayer piezoelectric body is exposed. And a product thereof.

Here, the "glass insulating layer" refers to a coating layer made of an amorphous inorganic compound and having defects sufficiently suppressed so as to prevent penetration of moisture.

[0018]

Means for Solving the Problems The present inventors have found that, in order to solve the above-mentioned problems, the above-mentioned object can be achieved by configuring as follows, and have led to the creation of the present invention.

According to a first aspect of the present invention, there is provided a method of manufacturing a laminated piezoelectric body having a structure in which a plurality of piezoelectric ceramic layers and internal electrode layers are alternately laminated and an end surface of the internal electrode layer is exposed. On the side surface of the laminated piezoelectric body where the internal electrode layer is exposed, fine particles made of a glass insulating material are electrodeposited by an electrophoresis method, and then heat-treated at a predetermined temperature to form a surface of the laminated piezoelectric body from the glass insulating material. The glass insulating layer is formed only on the exposed portion of the internal electrode layer or on both the exposed portion of the internal electrode layer and the surface of the piezoelectric ceramic layer between the internal electrode layers.

According to a second aspect of the present invention, in the first aspect, the thickness of the glass insulating layer is 0.3 to 10 μm.
It is preferred that

According to a third aspect of the present invention, in the first or second aspect, the heat treatment temperature of the glass fine particles and the glass insulating layer is lower than the firing temperature of the laminated piezoelectric material.
The glass component is a single component system, or a mixed component system comprising a plurality of the glass components, or a component system in which piezoelectric ceramics are dispersed in the single component glass matrix, or the mixed component system glass It is desirable to be composed of one selected from component systems in which piezoelectric ceramics are dispersed in a matrix.

The softening point of such a glass insulating material is preferably 500 to 900 ° C.

According to a fourth aspect of the present invention, in the third aspect, when the glass insulating layer contains piezoelectric ceramics, the piezoelectric ceramics are the same as the piezoelectric ceramics constituting the laminated piezoelectric body. convenient.

The fifth aspect of the present invention is the same as the first aspect.
Or the glass fine particles according to any of the third aspects,
And the glass insulating layer contains 10 to 80% by mass of PbO,
iO _TwoFrom 10 to 80% by mass, Al_TwoO_Three0 to 50 mass
%, The same as the piezoelectric ceramics of the multilayer piezoelectric body
From 0 to 50% by mass.

According to a sixth aspect of the present invention, the laminated piezoelectric body according to the first to fifth aspects may be used for a piezoelectric actuator.

According to a seventh aspect of the present invention, there is provided a method according to the first aspect.
This was configured as a laminated piezoelectric body manufactured according to the fifth aspect.

[0027]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic perspective view showing the configuration of a laminated piezoelectric element 1 according to the present invention, FIG. 2 (a) is a cross-sectional view taken along line AA of FIG. 1, and FIG. It is BB sectional drawing. 1 and 2 (a)
As shown in (b), the laminated piezoelectric body 1 has a piezoelectric ceramic layer 2, an internal electrode layer 3 for applying an electric field to the piezoelectric ceramic layer 2, and a portion where an end face of the internal electrode layer 3 is exposed. And a glass insulating layer 4 for insulating the piezoelectric ceramic layer 2 between the internal electrode layers 3 and 3 from the outside, and an external electrode (not shown) for applying a voltage to the internal electrode layer 3. The electrode layer 3 has such a structure that every other end face is exposed to the outside of the piezoelectric ceramic layer 2.

FIG. 3 is a view showing a flow of a process for manufacturing the laminated piezoelectric body 1 according to the present invention, and FIG. 4 is a schematic view showing a main part of FIG. As shown in FIG. 3, first, the raw material fine particles of the piezoelectric ceramic are weighed and
After mixing with an O ₂ ball (S1) and drying, pre-firing is performed (S2). Next, this is pulverized in water using a ZrO ₂ ball (S3), dried, and kneaded with an organic solvent and a resin component to form a paste (S4). Then, this paste is applied on a PET film and formed into a sheet to form a green sheet (S5).

On the green sheet containing such piezoelectric ceramics, the internal electrode layer 3 is formed in a predetermined pattern by a printing method or the like using a conductive paste containing Ag and Pd as main components (S6). A green sheet laminate is formed (S10), which is processed into a shape and laminated in a predetermined number of layers (S7 to S9). After performing a binder removal treatment (S11) and firing (S12) on the green sheet laminate,
Processing is performed (S13) to form a molded body 7 having a predetermined shape.
This molded body 7 has a structure in which the internal electrode layer 3 is exposed on the side surface, as shown in FIG. 4, for example. Then, the external electrodes 5 and 5 were formed on the molded body 7.
5) Then, predetermined glass particles are electrodeposited on the exposed end surface of the internal electrode layer 3 by electrophoresis (S16), dried (S17), and heat-treated (S18), and the laminated piezoelectric body 1 is formed.
Is produced (S19).

[Glass insulating layer] FIGS. 1 and 2 (a)
As shown in (b), the glass insulating layer 4 formed on the multilayer piezoelectric body 1 according to the present invention has only a portion where the end face of the internal electrode layer 3 is exposed to the outside of the piezoelectric ceramic layer 2, or
The end surface of the internal electrode layer 3 is formed on both the portion of the piezoelectric ceramic layer 2 exposed to the outside and the surface of the piezoelectric ceramic layer between the internal electrode layers 3, 3, thereby improving the moisture resistance of the multilayer piezoelectric body 1. In addition to improving the reliability, the inhibition of displacement during driving of the multilayer piezoelectric body 1 is sufficiently suppressed to enhance reliability.

(Method of Forming Glass Insulating Layer) The method of forming such a glass insulating layer 4 requires the following items. (A) The glass insulating layer 4 can be formed at least in a portion where the internal electrode layer 3 is exposed to the outside of the piezoelectric ceramic layer 2. (B) The glass insulating layer 4 can be formed uniformly at a predetermined thickness with good controllability, and further excellent in thickness accuracy. (C) The speed at which the glass insulating layer 4 is formed is sufficiently fast so as not to hinder productivity.

As a method for forming the glass insulating layer 4 that satisfies such requirements, there is a method combining electrophoresis and heat treatment. Hereinafter, a method for forming the glass insulating layer 4 using the electrophoresis method will be described with reference to FIGS.

(Electrophoresis Method) The electrophoresis method used in the present invention is not particularly limited, and a conventionally known method can be used. In this electrophoresis method, as shown in FIG. 5, an external electrode 5 for electrophoresis is first placed on an exposed portion of the internal electrode layer 3 in a suspension 11 in which predetermined glass particles 10 are dispersed. The molded body 7 provided with 5 and the counter electrode 6 are immersed. The external electrodes 5, 5 and the counter electrode 6
And are electrically connected. Next, a predetermined voltage is applied from a power supply provided between the counter electrode 6 and the external electrodes 5 and 5. In this way, the glass particles 10 dispersed in the suspension 11 are moved along the electric field toward the portion where the internal electrode layer 3 is exposed, and
The glass electrodeposited molded body 8 in which the glass fine particles 10 are selectively electrodeposited on the exposed end face can be formed.

Thereafter, the glass electrodeposition molded body 8 is heat-treated at a predetermined temperature in the air to form a uniform glass insulating layer 4. At this time, the temperature of the heat treatment is set to a temperature equal to or higher than the softening point of the glass microparticles 10 and equal to or lower than the firing temperature of the laminated piezoelectric material, and the defects are sufficiently suppressed by softening the glass microparticles 10 and appropriately flowing the same. Thus, a uniform glass insulating layer 4 can be formed. At this time, if the heat treatment is performed at a relatively low temperature or for a relatively short time so as to suppress the flow range of the softened glass fine particles 10, for example, as shown in (b-1) of FIG. like,
It is possible to form the glass insulating layer 4 uniformly only near the portion where the internal electrode layer 3 is exposed.

On the other hand, the temperature of the heat treatment is set to a temperature equal to or higher than the softening point of the glass fine particles 10, and a relatively high temperature or a relatively long time is set so as to appropriately expand the flow range of the softened glass fine particles 10. If the heat treatment is performed in the step (b), for example, as shown in (b-2) of FIG. It can be formed on both surfaces of the ceramic layer 2.

When the glass insulating layer 4 is formed on both the internal electrode layer 3 and the piezoelectric ceramic layer 2 between the internal electrode layers 3 as described above, the piezoelectric ceramic layer 2
When fine pores are present on the surface of the piezoelectric ceramic layer 2, since the softened glass particles 10 enter the pores, the pores can be filled with the glass insulating layer 4 as well. It is possible to prevent moisture from penetrating into the body 1.

As described above, the glass particles 10 are electrodeposited by electrophoresis on the portion where the internal electrode layer 3 of the molded body 7 is exposed. By performing the heat treatment at a temperature equal to or lower than the above-described predetermined time, either the portion where the internal electrode layer 3 is exposed, or both the portion where the internal electrode layer 3 is exposed and the piezoelectric ceramic layer 2 between the internal electrode layers 3 and 3 are formed. The glass insulating layer 4 can be formed in such a form. In this manner, since the glass insulating layer 4 can be formed according to the properties of the molded body 7 and the required characteristics of the laminated piezoelectric body 1, performance and cost can be satisfied at a favorable harmony point.

(Electrodeposition of Glass Fine Particles by Electrophoresis)
FIG. 6A shows that the glass microparticles 10 are formed by electrophoresis.
FIG. 3B schematically shows a process of electrodepositing the compact 7 on the molded body 7. FIG. 2B shows a layer formed by electrodepositing the glass particles 10 on the compact 7 as shown in FIG. It is a figure which shows the state in which the glass insulating layer was formed typically.

As shown in FIG. 6A, in the electrophoresis method, first, an electrodeposit such as glass fine particles 10 moves along the electric field from the counter electrode 6 to the external electrode 5 and moves to the internal electrode layer 3. To form an initial nucleus (not shown). Thereafter, the initial nucleus grows, for example, into a substantially hemispherical island-shaped layer N having a radius r. It is known that the radius r of the island-shaped layers N gradually increases, and when the adjacent island-shaped layers N come into contact with each other, they are united to form a relatively flat layer (not shown). ing.

The layered structure composed of the island-like layer N formed by such an electrophoresis method or a relatively flat layer is referred to herein as a “glass electrodeposition layer”.

In the present invention, as shown in FIG. 6 (a), the molded body 7 is subjected to an electrophoresis method, and the glass electrodeposition layer is subjected to a heat treatment at a predetermined temperature to sufficiently suppress defects. The glass insulating layer 4 is formed to have a uniform thickness efficiently.

By subjecting such a glass electrodeposition layer to heat treatment, the glass fine particles 10 are melted to form a uniform amorphous glass insulating layer 4. The shape of the glass insulating layer 4 thus formed can be one of the following two types by appropriately setting the temperature and time of the heat treatment. That is, if the temperature of the heat treatment is set to be relatively low or the time is set to be relatively short, the vicinity of the portion where the internal electrode layer 3 is exposed as shown in (b-1) of FIG. Only when the glass electrodeposition layer 4 can be formed, and when the temperature of the heat treatment is set relatively high or the time is set relatively long, (b-2) in FIG. As shown in (1), the glass electrodeposition layer 4 can be formed on both the exposed portion of the internal electrode layer 3 and the piezoelectric ceramic layer 2 between the internal electrode layers 3 and 3. As described above, by appropriately setting the conditions of the heat treatment, the shape of the glass insulating layer 4 can be adapted to the quality or characteristics required for the laminated piezoelectric body 1.

In the present invention, the glass electrodeposition layer 4
Are the piezoelectric ceramic surface on the upper surface of the uppermost internal electrode layer 3 and the lower surface of the lowermost internal electrode layer 3, in addition to the exposed portion of the internal electrode layer 3 and the surface of the piezoelectric ceramic layer 2 between the internal electrode layers 3 and 3. May be formed on both or at least a part of either of the piezoelectric ceramic surfaces.

(Heat Treatment Temperature for Forming Glass Insulating Layer) As a requirement for the heat treatment temperature for forming the glass insulating layer 4 according to the present invention, the heat treatment temperature has an adverse effect on the piezoelectric ceramic layer 2 and the internal electrode layer 3. And the electrodeposited glass fine particles can be softened to form a uniform layer. When the piezoelectric ceramic layer 2 is made of a PZT {Pb (Zr, Ti) O ₃ } -based ceramic material and the internal electrode layer 3 is made of the above-mentioned Ag-Pd alloy, the glass electrodeposition layer to the glass insulating layer 4 Is desirably 1000 ° C. or lower, which is lower than the firing temperature of the laminated piezoelectric material, for the heat treatment for forming the substrate.

(Thickness of Glass Insulating Layer) As a requirement for the thickness of the glass insulating layer 4 according to the present invention, it is necessary that the glass insulating layer 4 sufficiently suppress the displacement of the laminated piezoelectric body 1 during driving, and Insulating the exposed portion of the internal electrode layer 3 of the multilayer piezoelectric body 1 from the outside world and imparting sufficient moisture resistance can be mentioned. Glass insulating layer 4 satisfying such requirements
Preferably has a thickness of 0.3 μm to 10 μm. If the thickness of the glass insulating layer 4 is less than 0.3 μm, the moisture resistance is not sufficiently imparted. If the thickness is more than 10 μm, the displacement of the laminated piezoelectric body 1 during driving becomes excessively large. Inconvenience may occur.

The thickness of the glass insulating layer 4 is as follows:
In order to more stably exhibit the performance of the multilayer piezoelectric body 1,
Alternatively, the thickness is more preferably 0.5 μm to 7 μm from the viewpoint of minimizing variation in product quality.

(Chemical Component of Glass Insulating Layer) The chemical component of the glass insulating layer 4 of the multilayer piezoelectric body 1 according to the present invention is a layer having a uniform thickness with relatively few defects in a portion where the internal electrode layer 3 is exposed. In order to form the multilayer piezoelectric element 1, it is necessary that the internal electrode layer 3 be heat-treated at a temperature and time that does not adversely affect the internal electrode layer 3 so that the multilayer piezoelectric element 1 can be formed to a thickness that does not hinder the displacement during driving.

As a constituent material of the glass insulating layer 4 having a suitably large heat treatment temperature range and an elastic modulus as described above, for example, a glass insulating material such as PbO, SiO ₂ , and Al ₂ O ₃ can be mentioned.

Further, in order to make the elastic modulus of the glass insulating layer 4 closer to the elastic modulus of the laminated piezoelectric body 1, piezoelectric ceramics are added to the glass matrix having the glass component so that the amorphous property of the glass insulating layer 4 is reduced. An appropriate amount may be added as long as it is not inhibited.

That is, it is desirable that the glass insulating layer 4 that satisfies the above-described requirements is composed of the following components. (1) The glass component is a single component system. (2) A mixed component system comprising a plurality of the glass components. (3) A component system in which piezoelectric ceramics are dispersed in the single-component glass matrix. (4) A component system in which piezoelectric ceramics are dispersed in the mixed component glass matrix.

Further, in the case of the above (3) or (4), by making the piezoelectric ceramics the same as the piezoelectric ceramics 2 of the laminated piezoelectric body 1, the elastic modulus of the glass insulating layer 4 and the laminated piezoelectric body The elastic modulus of No. 1 is more preferable.

Then, the glass insulating layer 4 is made of PbO: 10
80 wt%, SiO _2: 10~80 wt%, Al ₂ O
₃ : 0 to 50% by mass, and the same piezoelectric ceramics as the multilayer piezoelectric body 1: 0 to 50% by mass, the displacement of the multilayer piezoelectric body 1 at the time of driving is suppressed sufficiently, and
The laminated piezoelectric body 1 has improved humidity resistance to improve reliability and durability, and has a relatively low cost.

[Internal Electrode Layer] The internal electrode layer 3 of the multilayer piezoelectric body 1 according to the present invention generates a displacement in the piezoelectric ceramic layer 2 by applying a predetermined voltage to drive the multilayer piezoelectric body 1. It is to let. This internal electrode layer 3
It is formed in a film shape having a predetermined pattern shape on a green sheet made of piezoelectric ceramics, and by laminating the green sheets, a plurality of piezoelectric ceramic layers 2 and internal electrode layers 3 are alternately stacked, and an electric field is applied to the piezoelectric ceramic layer 2. To act as a counter electrode.

(Requirements for Internal Electrode Layer) The requirements for the internal electrode layer 3 include the following. (A) It can be easily formed at a predetermined position on the green sheet. (B) It can be formed on a green sheet with good adhesion. (C) The function as an electrode can be maintained even after firing at a predetermined temperature. (D) Being able to be displaced in accordance with the displacement of the piezoelectric ceramic layer 2 while maintaining a predetermined electrode structure.

The internal electrode layer that satisfies the requirements (a) to (d) and satisfies the above requirements at the best possible harmony point in view of economy is usually based on Ag. Ag-Pd alloy obtained by adding an appropriate amount of Pd to Pb is used. The internal electrode layer 3 configured as described above is, for example,
Paste Ag-Pd alloy with other metals, metal oxides,
Alternatively, at least one of the organometallic compounds may be added. Further, a piezoelectric ceramic layer 2 as a so-called lid is formed further outside the internal electrode layer 3 at the outermost position of the multilayer piezoelectric body 1.

(Method of Forming Internal Electrode Layer) The method of forming such an internal electrode layer 3 is not particularly limited, and a conventionally known method can be used. For example, in the case of forming using a conductive paste, a stamp or a roller having a predetermined pattern shape, a screen, or a mask, or the like, may be applied on a green sheet, that is, a so-called printing method. . When the internal electrode layer 3 is formed by a dry film forming method such as a sputtering method or a vapor deposition method, first, a photoresist film is formed on the surface of the green sheet, and an exposure process is performed using a predetermined mask. A photoresist film may be formed in a predetermined pattern shape by a photolithography method, and then, the internal electrode layer 3 may be formed by the dry film formation method. Alternatively, the internal electrode layer 3 may be formed by an electroless plating method in which a green sheet is immersed in an electrolytic solution containing a predetermined metal or the like.

The multilayer piezoelectric body 1 according to the present invention includes:
An external electrode connected to a predetermined position on the end face of the internal electrode layer 3 is provided. The external electrode is led to an external power supply via a lead terminal (not shown) or the like.

The number of layers and the size (area, thickness, width, etc.) of the piezoelectric ceramic layer 2 and the internal electrode layer 3 are not particularly limited in the multilayer piezoelectric body 1 according to the present invention. What is necessary is just a laminated | stacked piezoelectric body consisting of two layers.

Furthermore, the shape of the laminated piezoelectric element 1 according to the present invention is not particularly limited as long as the glass insulating layer 4 having the above-described configuration can be formed. For example, it may have a shape in which a hole is provided inside the multilayer piezoelectric body 1.

The multilayer piezoelectric body 1 according to the present invention
There is no particular limitation on the displacement direction at the time of driving, and any of a so-called piezoelectric longitudinal effect that displaces in a direction perpendicular to the plane of each layer, or a so-called piezoelectric transverse effect that changes in a direction parallel to the plane of each layer. May have the above piezoelectric effect.

[0061]

Embodiments of the present invention and comparative examples will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing the configuration of the multilayer piezoelectric body 1 of the present embodiment, FIG. 2A is a cross-sectional view taken along line AA of FIG. 1, and FIG. BB
It is a line sectional view. As shown in FIGS. 1, 2 (a) and 2 (b), the laminated piezoelectric body 1 includes a piezoelectric ceramic layer 2 and an internal electrode layer 3 for applying an electric field to the piezoelectric ceramic layer 2.
A glass insulating layer 4 for insulating a portion where the end face of the internal electrode layer 3 is exposed and the piezoelectric ceramics layer 2 between the internal electrode layers 3 and 3; and an external for applying a voltage to the internal electrode layer 3. And electrodes (not shown).
Are exposed outside the piezoelectric ceramic layer 2 every other layer.

[Method of Manufacturing Laminated Piezoelectric Material] FIG. 3 is a diagram showing a flow of a process of manufacturing the laminated piezoelectric material 1 of this embodiment, and FIG. 4 is a schematic diagram showing a main part of FIG. is there. 3 and 4, first, a paste is prepared by kneading piezoelectric ceramic fine particles, a binder, an organic solvent, and the like, which are raw materials of the piezoelectric ceramic layer 2, (S1 to S4), and the paste is formed to produce a green sheet. (S5). Separately, a conductive material, a binder, an organic solvent and the like were kneaded to prepare an internal electrode layer paste.

Next, after a predetermined pattern of the internal electrode layer paste is printed on the green sheet (S6), it is cut into a predetermined size (S7), and 30 sheets are laminated (S6).
8) Pressing (S9) to form a green sheet laminate in which green sheets are laminated (S10), removing the binder (S11), and firing (S1).
2) Molded body 7 of predetermined shape with internal electrode layer 3 exposed on the side
(S13). Then, an external electrode 5 is formed at a predetermined position of the exposed portion of the internal electrode layer 3 of the molded body 7.
14) After the baking treatment (S15), an electrophoresis method as shown in FIG. 5 was performed.

That is, the laminated piezoelectric material is immersed in the suspension 11 in which the glass fine particles 10 are dispersed,
The glass fine particles 10 are moved along the electric field by connecting the counter electrode 6 to the power supply 11 and applying a voltage, so that the glass fine particles 1
0 was electrodeposited (S16) to form a glass electrodeposited molded body 8 including the external electrode 5 and the glass electrodeposition layer. Thereafter, the glass electrodeposition molded body 8 is dried (S17), and is subjected to a heat treatment at a predetermined temperature (S18) to form the glass insulating layer 4;
A test sample of the multilayer piezoelectric body 1 was produced (S19).

In the above-mentioned electrophoresis method, by applying an appropriate voltage to the applied voltage, the examples (1 to 7) in which the thickness of the glass insulating layer 4 is within the specified range of the present invention, Were formed (S16 to S19), and Comparative Example 9 in which the thickness of the glass insulating layer 4 was out of the specified range of the present invention.

Then, the initial electrical characteristics such as insulation resistance and capacitance are measured and evaluated for each of the test samples prepared as described above (S20), and at high temperature and high humidity to promote the migration phenomenon from the internal electrode layer 3. Was evaluated by a moisture resistance test (S21), and the cumulative failure rate at each test time (10 to 1000 hours) was examined.

Further, in order to examine the dependency of the thickness of the glass insulating layer 4 on the displacement inhibition suppression rate, which is the rate of suppressing the displacement inhibition during the operation of the multilayer piezoelectric body 1, the polarization treatment of each of the test samples is performed. The displacement was measured using an eddy current type displacement measuring device. The configuration of each test sample and the conditions of the moisture resistance test are shown below. Table 1 shows the test results.

[Configuration of Test Sample] External dimensions: 5.0 × 5.0 × 3.0 mm Piezoelectric ceramic layer: Chemical composition: Pb _0.96 Sr _0.04 ｛(Co _1/3 Nb _2/3 ) _0.01 Ti _0.48 Zr
_0.53 ｝ O ₃ + WO ₃ , thickness: 25 μm Internal electrode layer: Ag—Pd alloy (chemical composition ratio; Ag / Pd = 70 mass%)
/ 30 mass%), thickness: 2 μm Number of layers: 30 (combination of piezoelectric ceramic layer 1 and internal electrode layer 1 is one layer) External electrode: Ag-Pd alloy

[Preparation Conditions of Test Sample] Firing temperature of green sheet: 1100 ° C. (conditions of electrophoresis) Composition of suspension: glass fine particles + dispersion medium (dispersion medium: acetic anhydride) Chemical component composition of glass fine particles: PbO: 60% by mass, SiO ₂ : 20% by mass, Al ₂ O ₃ : 20% by mass, having the same chemical composition as the piezoelectric ceramic layer 2;
% By mass of glass fine particles in the suspension; 1% by mass Processing conditions: applied voltage; C. 10 to 100 V Processing time; 30 seconds Processing temperature; 25 ° C. Heat treatment conditions for glass electrodeposited layer; 800 ° C., 20 minutes

[Reliability Evaluation Test] Conditions for moisture resistance test: atmosphere in test tank; 85 ° C./85% RH Applied voltage when driving test sample; C. 50V (2k
V / mm) Reliability evaluation criteria: Insulation resistance was compared with the initial value. If the order was reduced by three digits, it was evaluated as defective, and if less than two digits, it was evaluated as acceptable. Displacement measurement condition: A voltage of 50 V (2 kV / mm) was applied at room temperature.

[0071]

[Table 1]

[Results of Displacement Measurement and Reliability Test Evaluation] Table 1 shows the thickness (μm) of each glass insulating layer 4 and the displacement measurement in Examples (1-7) and Comparative Examples (8, 9). Displacement (μm), the displacement (0.85 μm) of Comparative Example 8 which is a bare laminated piezoelectric body having no glass layer 4 formed thereon
) As a reference (100%), the displacement inhibition suppression ratio representing the degree of suppressing the displacement inhibition, and 10 to 100.
It represents the cumulative failure rate in a moisture resistance test performed at 0 hours.

According to Table 1, in Comparative Example 8 in which the glass insulating layer 4 was not formed, the cumulative defective rate was 60 after 10 hours.
%, And 100% after 50 hours, indicating that the reliability is extremely low. In addition, the glass insulating layer 4
In Comparative Example 9 having a thickness of 15 μm, the cumulative failure rate was 0% after 1000 hours, and the reliability was dramatically improved. This is only 72% of Example 1, and the displacement performance as the piezoelectric actuator is greatly reduced.

On the other hand, in Examples 1 to 7 in which the thickness of the glass insulating layer 4 was 0.3 to 10 μm, the displacement inhibition suppression rate was 80 to 95%, and the inhibition of displacement was sufficiently suppressed. The rate was determined in Example 1 (thickness of glass insulating layer 4:
0.3%), 60% after 500 hours, and 0% even after 1000 hours in Examples 2 to 7 (thickness of glass insulating layer: 0.5 to 10 μm). It has been dramatically improved.

As shown in the results of the above Examples (1 to 7) and Comparative Examples (8, 9), in the laminated piezoelectric body 1 according to the present invention, the formed glass insulating layer 4 has a displacement during driving. And the displacement performance can be sufficiently exhibited by inhibiting the inhibition of the deformation. In addition, the glass insulating layer 4 can sufficiently secure the reliability and durability even under high temperature and high humidity, and can exhibit the expected performance without any restriction. .

The present invention is not limited to the present embodiment, and various modifications are possible as long as the effects of the present invention can be obtained. The composition of the piezoelectric body is not limited to the PZT-based ceramic material as long as it causes a displacement. The piezoelectric body may be formed by appropriately modifying PZT or a composition containing no lead.

Further, it is a preferable object of the present invention that the internal electrode contains a metal component which causes migration. In addition, the external electrode may be any electrode as long as the function can be sufficiently maintained even after the glass is heat-treated, and may be an electrode having a chemical composition other than that used in this embodiment. In addition, the present invention is not limited to the scope of application only to the actuator. For example, even when the present invention is applied to a device having a relatively low applied voltage, such as a laminated piezoelectric transformer, the moisture resistance is improved by the same configuration. ,
As a result, reliability can be improved.

[0078]

With the configuration described above, the present invention has the following effects. According to the first aspect of the invention, since the glass insulating layer is formed only on the exposed portion of the internal electrode layer or on both the exposed portion of the internal electrode layer and the surface of the piezoelectric ceramic layer between the internal electrode layers, the moisture resistance is improved. And a laminated piezoelectric body having excellent reliability and durability can be provided.

Further, by combining the electrophoresis method and the heat treatment performed at a predetermined temperature, a glass insulating layer can be formed with a uniform thickness on the piezoelectric ceramic layer between the internal electrode layers with high accuracy. When fine pores are present, the glass layer can penetrate into the pores as well, so that it is possible to provide a laminated piezoelectric body in which penetration of moisture into the pores is prevented.

According to the second aspect of the present invention, since the thickness of the glass insulating layer is defined, in addition to the effects described above,
Defects in the glass insulating layer and inhibition of displacement of the multilayer piezoelectric body are reliably suppressed to a low level, and the reliability and durability of the multilayer piezoelectric body can be more stably improved.

According to the third aspect of the present invention, the heat treatment at the time of forming the glass insulating layer does not adversely affect the internal electrode layer, and the glass insulating layer suppresses the inhibition of displacement during driving of the laminated piezoelectric body. In addition to defining the heat treatment temperature of the glass insulating layer, and configuring the components of the glass insulating layer so that it can be adapted to various needs of the laminated piezoelectric body, in addition to the above-described effects, in addition to the expected performance, It is possible to provide a laminated piezoelectric material that can be sufficiently exerted and that further meets needs.

According to the fourth aspect of the present invention, since the piezoelectric ceramic added to the glass insulating layer is composed of the same component as the piezoelectric ceramic of the laminated piezoelectric body, the glass insulating layer is driven when the laminated piezoelectric body is driven. The displacement can be substantially the same as the displacement, and in addition to the above-described effects, the inhibition of the displacement of the multilayer piezoelectric body can be suppressed as much as possible.

According to the fifth aspect of the present invention, the glass insulation
The layer is made of PbO, SiO_Two, Al_TwoO _Three, And stacked pressure
It is composed of the same piezoelectric ceramic as the conductor,
Since the amount is specified, the effects and costs described above are preferable.
We can provide a laminated piezoelectric material that satisfies the harmony point
You.

According to the invention of claim 6, it is possible to provide a piezoelectric actuator having the above-mentioned effects.

According to the seventh aspect of the present invention, reliability, performance,
Since a multilayer piezoelectric body with improved cost, accuracy, and durability can be obtained, applications of the multilayer piezoelectric body can be expanded.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a configuration of a multilayer piezoelectric body according to the present invention.

FIG. 2A is a sectional view taken along line AA of FIG. (B) It is BB sectional drawing of FIG.

FIG. 3 is a diagram showing a flow of a process for manufacturing a multilayer piezoelectric body according to the present invention.

FIG. 4 is a schematic view showing a main part of a process flow according to the present invention.

FIG. 5 is a schematic view showing one example of an electrophoresis method according to the present invention.

FIG. 6 (a) is a view showing a process in which glass particles are electrodeposited on an internal electrode layer by the electrophoresis method according to the present invention. (B) It is a schematic diagram which shows the form of the glass insulating layer formed by performing heat processing to the glass electrodeposition layer electrodeposited by the electrophoresis method concerning this invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric body 2 Piezoelectric ceramic layer 3 Internal electrode layer 4 Glass insulating layer 5 External electrode 6 Counter electrode 7 Molded body 8 Glass electrodeposited molded body 10 Glass fine particles 11 Suspension N Island layer r Island layer ( Radius of approximately hemisphere)

Claims (7)

[Claims] 1. A laminated piezoelectric body having a structure in which a plurality of piezoelectric ceramic layers and internal electrode layers are alternately laminated, and an end face of the internal electrode layer is exposed. What is claimed is: 1. A method for manufacturing a laminated piezoelectric body, comprising forming an insulating portion by electrodepositing fine particles made of a glass insulating material, wherein the electrophoresis method and a heat treatment performed at a predetermined temperature are combined to form a glass made of a glass insulating material. A method of manufacturing a laminated piezoelectric element, wherein an insulating layer is uniformly formed only on the exposed portion of the internal electrode layer or on both the exposed portion of the internal electrode layer and the surface of the piezoelectric ceramic layer between the internal electrode layers. . 2. The method according to claim 1, wherein the thickness of the glass insulating layer is 0.3 to 1
2. The method according to claim 1, wherein the thickness is 0 [mu] m. 3. The glass insulating layer, wherein a heat treatment temperature is lower than a firing temperature of the laminated piezoelectric material, and the glass insulating layer is constituted by any one of the following component systems (1) to (4). A method for manufacturing a multilayer piezoelectric body according to claim 1. (1) The glass component is a single component system. (2) A mixed component system comprising a plurality of the glass components. (3) A component system in which piezoelectric ceramics are dispersed in the single-component glass matrix. (4) A component system in which piezoelectric ceramics are dispersed in a glass matrix of the mixed component system. 4. The multilayer piezoelectric body according to claim 3, wherein when the glass insulating layer contains piezoelectric ceramics, the piezoelectric ceramics are the same as the piezoelectric ceramics of the multilayer piezoelectric body. Production method. 5. The glass insulating layer according to claim 1, wherein PbO: 10 to 8
0 wt%, SiO _2: 10~80 wt%, Al ₂ O _3:
The method for producing a multilayer piezoelectric body according to claim 1, wherein the piezoelectric ceramic is composed of a chemical composition of 0 to 50 mass% and the same piezoelectric ceramic as the multilayer piezoelectric body: 0 to 50 mass%. . 6. The method for manufacturing a multilayer piezoelectric body according to claim 1, wherein the multilayer piezoelectric body is used for a piezoelectric actuator. 7. A multilayer piezoelectric body manufactured by the method according to claim 1. Description: