JP2820791B2 - Multilayer piezoelectric element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an element utilizing the electrostriction effect,
More specifically, the present invention relates to a laminated piezoelectric element formed by laminating a piezoelectric plate such as a piezoelectric ceramic and an electrode plate, and a method of manufacturing the same.

[Prior art]

Conventionally, a laminated piezoelectric actuator has been known as a drive source for an electromechanical component. One type of element that uses the electrostriction longitudinal effect, which is used as this piezoelectric actuator, is to form a metal sheet on the surface of a piezoelectric plate that becomes an electrostrictive material such as a green sheet of a piezoelectric ceramic or a piezoelectric ceramics plate, and then stack a large number of them. , Sintering or bonding. In order to drive, as an actuator, a laminated piezoelectric element in which such a piezoelectric plate and an electrode plate are sequentially laminated, it is necessary to electrically connect every other electrode plate between the piezoelectric bodies. As a configuration of an element for connecting each electrode plate, for example, as shown in FIG. 3, one end of an electrode plate 32 is formed slightly shorter than the piezoelectric plate 31 on a tomographic plane of the piezoelectric element 3. is there. That is, the electrode plate formed on the thin plate surface of the flat piezoelectric body is not formed on only one side of the thin plate surface, and conversely, the other side is stacked on the side of the element when the other side is laminated. The surface on which the electrode plate is formed is provided to be smaller than the surface of the thin plate so that is exposed. The electrode plates 32 are alternately laminated so as to be exposed every other layer, and are connected in parallel by external electrodes 34a and 34b every other layer using the electrode plate exposed on the side surface of the element. In order to improve the distortion characteristics of the element, as shown in FIG. 4, the piezoelectric element 4 forms an electrode plate on the entire surface of the piezoelectric plate, and the piezoelectric plate 41 and the electrode plate 42 are alternately stacked. The thing laminated | stacked sequentially is known. In this case, since the edges of the electrode plate are exposed on both sides of the element in both layers, an insulating material 43 is applied alternately on both sides of the edge of the electrode plate 42, and the external electrodes 44a are formed thereon. , 44b are formed. (Japanese Patent Publication No. 63-17354).

[Problems to be solved by the invention]

In these conventional laminated piezoelectric elements, as shown in FIG. 3, electrode plates are alternately exposed on both sides of the element, that is, the electrode surface is separated from the surface of the piezoelectric plate by one side of the element. In the one whose edge is formed slightly shorter on the side,
There is an advantage that the configuration of the external electrodes is extremely simple, and the electrode plates can be easily and alternately connected alternately. However, when such a piezoelectric element is driven as an actuator, there is a non-displacement part that does not expand and contract piezoelectrically inside the element near both external electrodes, and this non-displacement part suppresses the occurrence of distortion. At the same time, the element was destroyed due to the concentration of stress. Therefore, if the internal electrode plate is formed on the entire surface of the piezoelectric plate and electrically connected alternately outside the laminated device as shown in FIG. There are no parts. Therefore, since concentration of stress can be prevented without suppressing generation of distortion, an element having high electromechanical conversion efficiency such as displacement can be configured. On the other hand, such an element in which an electrode plate is formed on the entire surface of a piezoelectric plate has the following problems. Normally, in order to manufacture a piezoelectric element, roughly, a slip mainly composed of ceramic powder is formed by a film forming machine, and a solvent in the slip is dried to form a thin green sheet. An electrode plate is created by screen printing the electrode surface. Then, an element is obtained by sintering a product formed by laminating and pressing a large number of sheets. At this time, a paste-like ink such as silver, palladium, or platinum is used as an electrode material on the electrode surface printed on the green sheet to form a single electrode plate. In some cases, the adhesion strength between the electrode material and the ceramic is improved by, for example, mixing a material which is familiar with the ceramic into the material in advance. However, if a large amount of the above impurities are mixed in the electrode material, the internal resistance of the electrode plate is increased. On the other hand, if the purity of the electrode material is increased, the electrode surface is provided on the entire surface of the piezoelectric plate. The strength is low, and there has been a problem that the electrode plate and the piezoelectric plate are peeled off by repeated application or application of a high voltage for a long time or a long time. Therefore, the present invention has been made in view of the above problems,
The purpose is that there is no non-displacement part inside the piezoelectric body, so that the element does not break down due to stress concentration, and the electrode plate is applied for a long time, long-term repetition, or high voltage application. An object of the present invention is to provide an improved laminated piezoelectric element which does not cause separation from a piezoelectric plate and a method for producing the same.

[Means for Solving the Problems]

In order to solve the above problems, the present invention is a laminated piezoelectric element in which a piezoelectric plate and an electrode plate are alternately laminated, wherein the electrode plate is configured by juxtaposing a plurality of electrode pieces, The piezoelectric plates adjacent in the thickness direction are mutually connected by the piezoelectric electrostrictive material filled in the gap between the pieces, and the arrangement pattern of the electrode plates is changed to a strip-shaped electrode exposed on the upper surface side of the electrode plates. The strips and the strip-shaped electrode strips exposed on the lower surface side of the electrode plate have a pattern in which they are alternately arranged with overlapping portions. Next, the manufacturing method of the present invention includes a step of forming a plurality of electrode pieces in a strip shape on a piezoelectric plate, a step of applying a piezoelectric electrostrictive material from above the electrode pieces, and a step of further applying the piezoelectric electrostrictive material. A method of manufacturing a laminated piezoelectric element as described above, comprising a material and a step of forming a plurality of electrode pieces from above. Further, in the manufacturing method described above, in the step of forming a plurality of electrode pieces from above the piezoelectric electrostrictive material, a piezoelectric plate having a plurality of electrode pieces is overlapped from above the piezoelectric electrostrictive material to form a piezoelectric element. A plurality of electrode pieces may be formed on the electrostrictive material, and after this step, the stacked piezoelectric plates may be pressed in a direction approaching each other to join the electrode pieces together.

[Action]

The electrode plate provided on the surface of the piezoelectric plate includes a first electrode piece having a pattern divided in a plane and a second electrode piece formed in a pattern complementary to the first electrode piece. Since the electrodes are formed, the upper and lower piezoelectric plates become a uniform electrode plate with no electrode absent. When a voltage is applied during element driving, a uniform electric field is generated between the electrode plates. Further, a coupling layer made of a piezoelectric electrostrictive material, which is filled and interposed between the first electrode layer and the second electrode layer, enters into the gap between the respective electrode pieces, and integrates the laminated upper and lower piezoelectric thin films. Tightly bound to

【Example】

Embodiments of a method for manufacturing a multilayer piezoelectric element of the present invention and a multilayer piezoelectric element obtained thereby will be described with reference to FIG. 1 and FIG. The piezoelectric element 1 is formed such that piezoelectric plates 11 made of piezoelectric ceramics and electrode plates 12 are alternately stacked in multiple layers. Although exaggerated in the drawing, the piezoelectric plate 11
Is a rectangular shape formed in a thin plate or thin film, or
Although not shown, it has a circular shape, in which a plurality of electrode plates 12 are provided on the surface of the piezoelectric plate 11 and stacked. First, the piezoelectric plate (piezoelectric ceramic) 11 is made of Pb (Mg _1/3 N
b _2/3 ) A slip formed by mixing a solvent, a dispersant, a binder, and a plasticizer with ceramic powder containing O ₃ as a main component is formed into a thin film by a film forming machine used for manufacturing a multilayer capacitor. Then, the solvent in the thin film is evaporated and dried to obtain a green sheet. The obtained green sheet molded into a predetermined shape is used as the piezoelectric plate 11. next,
An electrode plate 12 is provided on the surface of the piezoelectric plate 11. The electrode plate 12
As a material for the electrode, a paste-like ink obtained by mixing a glass frit with silver, paridium, platinum, or the like is used, and printed by a screen printing machine. In the present invention, when forming the electrode plate 12, first electrode pieces 121,... Are first formed as shown in FIG. 2 (b). A plurality of first electrode pieces 121 are provided in a band shape on the surface of the piezoelectric plate 11 in parallel to a certain side, and each band-shaped electrode piece is formed in a pattern having a gap between each other. After the first electrode pieces 121,... Are formed, a piezoelectric electrostrictive material made of a paste-like piezoelectric material or an electrostrictive material, which becomes the same or near quality piezoelectric ceramics as the piezoelectric plate 11, is applied to the entire surface of the piezoelectric plate 11. To
The bonding layer 123 is formed by being applied from above the first electrode piece 121. The bonding layer 123 is initially a soft paste made of a mixture of an electrostrictive material or a piezoelectric material powder and a glass frit that have been heat-treated at the firing temperature of the piezoelectric electrostrictive material. Is a filler which exhibits some fluidity. Next, as shown in FIG. 2A, a second electrode piece 122,
, Are printed and created in the same manner as the first electrode piece 121. At this time, the second electrode piece 122 is formed complementarily on the gap 124 between the plurality of band-shaped patterns of the first electrode piece 121. That is, the electrode pattern of the first electrode piece 121 and the electrode pattern of the second electrode piece 122 are separated from the upper and lower surfaces in the thickness direction of the formed electrode plate 12 with the piezoelectric electrostrictive material-filled coupling layer 123 therebetween. Are arranged alternately and complementarily. Then, when pressure-bonded by lamination, the piezoelectric electrostrictive material-filled coupling layer 123 was transferred fluidly, and the electrodes were arranged without gaps over the entire surface of the piezoelectric plate 11 with the electrode pieces 121 and 122. It is configured as follows. A first electrode piece 121 and a second electrode piece 122 are provided on the surface of the piezoelectric plate 11.
Are provided to form the electrode plate 12, and a predetermined number of the piezoelectric plates 11 are laminated in a predetermined number according to the application, and the piezoelectric plates 11 are pressed by a hot press. Thereafter, the laminate is cut into a predetermined size and sintered. In sintering, main sintering is performed after pre-firing for removing binders. Subsequently, external electrodes 14a, 14b were provided on the outer surface of the obtained laminate.
Is provided. To this end, an insulating band 13 for insulating the external electrode 14a (14b) to be formed from the electrode plate 12 is formed on an edge of the electrode plate 12 exposed on both side surfaces of the laminate, Connect each pattern of electrode pieces 121 and 122 for each plate, and
A conductive band 15 for connecting the external electrode 14a (14b) to the electrode plate 12 is provided. The insulating bands 13 and the conductive bands 15 are provided alternately every other layer and alternately on both side surfaces. Subsequently, external electrodes 14a and 14b are formed on the insulating band 13 and the conductive band 15 in the laminating direction on both side surfaces. Insulation strip 1
3. Application of an insulating material or a conductive material for the conductive band 15 or the external electrodes 14a and 14b can be performed by screen printing or the like, similarly to the electrode plate 12. Also, the electrode plate is usually used for the polarization treatment of the element.
It is sufficient to apply voltages of different polarities to the external electrodes 14a and 14b so that the polarities of the 12, 12,... The piezoelectric element 1 of the present invention thus manufactured is
An electrode plate 12 is provided on the piezoelectric plate 11 and a large number of the electrode plates 12 are laminated, and the electrode plate 12 is configured to have a first electrode piece 121 and a second electrode piece 122 in each plate. I have. The pattern of each electrode piece is complementary, and the first electrode piece 121 and the second electrode piece 122 are arranged via the piezoelectric electrostrictive material-filled coupling layer 123 filling the gap. It has become. Next, the operation of the piezoelectric element 1 configured as described above will be described. An electrode plate provided on the surface of the piezoelectric plate 11
12 is formed by a first electrode piece 121 and a second electrode piece 122, and when driving a device, when a voltage is applied, like the electrode plate to be integrated, between the electrode plates 12, 12, Produces a uniform electric field throughout. That is, as shown in FIGS. 2B and 2A, the first electrode piece is used to form the electrode plate 12.
After the formation of the piezoelectric plate 11, the piezoelectric plate 11 is
To form a piezoelectric electrostrictive material-filled bonding layer 123 over the entire surface,
Since the second electrode piece 122 is formed and the piezoelectric plate is laminated and pressed, the bonding layer 123 in the form of a paste has a gap 124 between the electrode patterns of the first electrode piece 121 and a gap between the electrode patterns of the second electrode piece. Go into 125. Moreover, the printed electrode pieces 12
Since 1,122 is slightly rolled, no electrodes are absent on the upper and lower piezoelectric plates to be laminated, and a uniform electrode plate is obtained as described above. Further, the piezoelectric electrostrictive material-filled coupling layer 123 is formed on the first electrode piece 1.
Even if there is a slight overlap between the electrode pattern 21 and the electrode pattern of the second electrode piece 122, the electrode pattern is not completely divided, and the upper and lower piezoelectric plates 1
It firmly joins 1,11 together. The above is an embodiment by the green sheet method of the present invention. Next, an embodiment by the pressure bonding method of the present invention will be described with reference to FIG. 1 and FIG. First, the baked piezoelectric or electrostrictive material block is polished to form the piezoelectric plate 11. A first electrode piece 121 is formed on the surface of the piezoelectric plate 11 by printing a paste-like electrode material to which glass frit is added by means such as screen printing. Next, the piezoelectric electrostrictive material-filled coupling layer 123 is formed of an electrostrictive material heat-treated at the firing temperature of the glass frit and the electrostrictive material or the piezoelectric material, or a paste containing piezoelectric material powder. Further, the second electrode piece 122 is formed from the electrode material in a pattern that complements the first electrode piece 121. Then, the piezoelectric plate 1
1 are laminated and pressure-bonded by a hot press to form a laminate. Then, as in the green sheet method described above,
13 and the conductive band 15, and the external electrodes 14a and 14b are formed. In the embodiment of the present invention, the patterns of the electrode pieces 121 and 122 provided on the electrode plate 12 are shown in the form of two strips in the drawings, but a plurality of the pieces may be provided as desired. A variety of pattern shapes can be implemented. Furthermore, in the method of manufacturing the piezoelectric plate 11 in the embodiment, a so-called green sheet method and a pressure bonding method are used. However, from the characteristics of the present invention, another bonding method may be used. For the piezoelectric plate 11, an electrostrictive material having a history or a piezoelectric material having no history may be used.

【effect】

The present invention is configured as described above, and has the following effects. When the multilayer piezoelectric element of the present invention is driven as an actuator, there is no non-displacement portion that does not expand and contract piezoelectrically, and a uniform electrostrictive effect is obtained, and the element is caused by stress concentration. There is no destruction. In addition, there is no occurrence of peeling between the electrode plate and the piezoelectric thin plate due to long-term application, long-term repetitive application, or high-voltage application due to the problem of the adhesion strength of the electrode plate. This structure also disperses stress concentration at high / low temperatures or during cooling after firing due to the difference in the coefficient of thermal expansion between the electrode plate and the piezoelectric plate. Absent. According to the manufacturing method of the present invention, when driven as an actuator, there is no non-displacement part that does not expand and contract piezoelectrically inside the element, a uniform electrostrictive effect is obtained, and the element is concentrated by stress. An excellent multilayer piezoelectric element without breakage can be obtained. In addition, due to the problem of the adhesion strength of the electrode plate, there is no occurrence of peeling between the electrode plate and the piezoelectric thin plate due to long-time application, long-term repetitive application or high voltage application, and the coefficient of thermal expansion of the electrode plate and the piezoelectric plate. With a structure that can disperse even at high and low temperatures due to the difference in stress or during stress concentration during cooling after firing,
It is possible to obtain an excellent laminated piezoelectric element which does not cause separation between the electrode plate and the piezoelectric plate due to heat shock. Next, by pressing the stacked piezoelectric plates in a direction approaching each other to join the electrode pieces together, no electrode absent portion is generated with respect to the upper and lower piezoelectric plates to be stacked, and a uniform electrode is formed. Obtainable.

[Brief description of the drawings]

1 (a) and 1 (b) are side views showing an embodiment of the multilayer piezoelectric element of the present invention, FIGS. 2 (a) and (b) are views showing an embodiment of the configuration of an electrode plate, and FIG. FIG. 4 and FIG. 4 are side views of a conventional laminated piezoelectric element. 11: a piezoelectric plate, 12: an electrode plate, 121: a first electrode piece, 122: a second electrode piece, 123: a bonding layer filled with a piezoelectric electrostrictive material, 124, 125 ... a gap, 13: insulation Bands, 14a, 14b ... external electrodes, 15 ... conductive bands.

Claims (3)

(57) [Claims] 1. A laminated piezoelectric element in which piezoelectric plates and electrode plates are alternately laminated, wherein the electrode plate is configured by arranging a plurality of electrode pieces in parallel, and a gap between the electrode pieces is provided. The piezoelectric plates adjacent to each other in the thickness direction are connected to each other by the piezoelectric electrostrictive material filled in, and the arrangement pattern of the electrode plates is such that the band-shaped electrode pieces and the electrode plates exposed on the upper surface side of the electrode plates are arranged. A multilayer piezoelectric element, wherein a strip-shaped electrode piece exposed on the lower surface is a pattern arranged alternately having a superposed portion. 2. A laminated piezoelectric element comprising a piezoelectric plate and an electrode plate alternately laminated, wherein the electrode plate is configured by juxtaposing a plurality of electrode pieces, and fills a gap between the electrode pieces. The piezoelectric plates adjacent in the thickness direction are connected to each other by the formed piezoelectric electrostrictive material, and the arrangement pattern of the electrode plates is such that the strip-shaped electrode piece exposed on the upper surface side of the electrode plate and the lower surface side of the electrode plate A method of manufacturing a laminated piezoelectric element having a structure in which a strip-shaped electrode piece exposed to the substrate has a pattern in which the electrode pieces are alternately arranged having a polymerized portion, and a plurality of strip-shaped electrode pieces are formed on the piezoelectric plate. Forming, forming a plurality of electrode pieces from above the piezoelectric electrostrictive material, and applying a piezoelectric electrostrictive material from above the electrode pieces. Of manufacturing a piezoelectric element. 3. A method of forming a plurality of electrode pieces from above the piezoelectric electrostrictive material, wherein the step of forming a plurality of electrode pieces from above the piezoelectric electrostrictive material includes overlapping a piezoelectric plate having a plurality of electrode pieces from above the piezoelectric electrostrictive material. 3. A multilayer piezoelectric element according to claim 2, wherein, after this step, the laminated piezoelectric plates are pressed together in a direction approaching each other to join the electrode pieces together. Production method.