JP2919946B2 - Laminated electrostrictive element and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated electrostrictive element that can be driven at a low voltage and a method for manufacturing the element.

[Conventional technology]

As mechatronics evolved, it became smaller and lighter,
It is desired that an element capable of fine positioning or an element having a large generating force and a high response speed be supplied in large quantities and at low cost. In the past, most of these elements used electromagnetic force typified by motors, solenoids, voice coils, and the like. Recently, however, elements using the electrostrictive properties of ceramics have been developed and are attracting attention. In particular, elements utilizing the electrostriction longitudinal effect have attracted particular attention because of their large generating force and high response speed. However, the strain of the electrostrictive material due to this effect is as small as ^10-3 at most even under an electric field of 10 kV / cm, so that in order to obtain a large displacement, the electrodes and the thin electrostrictive material are alternately stacked, and mechanically in series. Some devices have been proposed to be electrically parallel, and some have been put to practical use.

Among such stacked electrostrictive longitudinal effect elements, those proposed relatively early are called stack type, and have a thickness of, for example, 0.
100 sheets of 5 to 1 mm electrostrictive material and electrodes of the same shape were alternately laminated to obtain a displacement of at most about 100 μm when a high voltage of about 1000 V was applied (for example, Shuji Yamashita, Jpn. J. App.
l.Phys.vol.20 (1981) Suppl.pp93-95. This stack-type device has a relatively large size and requires a high voltage to drive the device, which limits its application.

On the other hand, Takahashi et al. Used the green sheet method in JP-A-58-196068 to reduce the thickness of each electrostrictive material, and to further reduce the number of electrodes (internal electrodes) sandwiched between the electrostrictive materials. It has been proposed to realize a structure similar to a stack type device by forming the device over the entire surface of the material and drive the device at a low voltage.
In order to industrially manufacture such an element, it was necessary to devise a method of electrically connecting the internal electrode end faces exposed on the element side end face to every other layer, but Ochi et al. Disclosed in JP-A-59-115579. By electro-depositing a glass-based inorganic material only on the exposed part of the internal electrode and the electrostrictive material in the vicinity of it using electrophoresis, an insulating layer is formed, and an independent insulating layer is formed for each internal electrode layer It suggested that the above difficulties could be overcome. It is said that this proposal has reduced the thickness of the electrostrictive material to 0.1 to 0.2 mm and reduced the driving voltage to about 100 V. However, even if such a method is used, it is difficult to realize reliable insulation, and various improvements regarding the electrophoresis method have been proposed by the same applicant. Also, many internal electrode insulation methods using a method different from the electrophoresis method have been proposed.

These proposals aim at miniaturization of the element and low-voltage driving, but there is no practical use that can reduce the thickness of the electrostrictive material to 0.1 mm or less until now.

[Problems to be solved by the invention]

In order to drive the laminated electrostrictive longitudinal effect element at a lower voltage than conventional products, it is necessary to make the electrostrictive material thinner. To this end, an insulating layer for insulating the end face of the internal electrode exposed at the side end face of the element must be formed finely and accurately. However, if the exposed end face of the internal electrode is insulated every other layer and the insulating layer is made to be an independent insulating layer for each layer of the internal electrode, as the thickness of the electrostrictive material becomes thinner, there are restrictions on the operation, the insulating material and the electrostriction. Internal electrodes that should not be insulated due to wettability of the material are also insulated, and internal electrodes that do not conduct at all with the external electrodes are created. As a result, the amount of displacement as designed cannot be realized. There is.

The present inventors have studied an insulating material as one means for solving the above problem, and formed a coating layer by depositing polyamic acid by electrophoresis on the exposed end of the internal electrode, and then heating the coating layer by heating. A method of imidizing the polyamic acid resin of the layer and forming an insulating layer with the obtained polyimide resin was previously filed (Japanese Patent Application No. 1-171854). The method according to the present application is epoch-making not only in that it has been conventionally difficult to solve the problem with an organic material, but also in that the thickness of one layer of the laminate can be reduced to 100 microns or less. However, the method of this application has a disadvantage that bubbles are easily encapsulated in the insulating layer, and when the bubbles are encapsulated, insulation breaks down from the foam, resulting in a large variation in withstand voltage of the product. Was.

An object of the present invention is to provide a laminated electrostrictive effect element free from the above-mentioned disadvantages and a method for manufacturing the same.

The present inventors have also found that the above-mentioned problem arises because an independent insulating layer is formed for each internal electrode layer. SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to insulate only a necessary portion of an internal electrode exposed portion even if the electrostrictive material is thinned, and thus to obtain an element structure capable of taking out a displacement amount as designed and its insulation. It is to provide a method.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have found that, when polyamic acid is deposited on the element end exposed portion of the internal electrode, the insulating filler is deposited at the same time. The present inventors have found out what should be done and completed the present invention.

In addition, the present inventors have found that it is sufficient to insulate three or more odd-numbered internal electrodes with the same insulating layer, and have completed the present invention.

That is, the laminated electrostrictive effect element of the first aspect of the present invention,
A film or thin plate of electrostrictive material and an internal electrode are alternately laminated, and in the laminated electrostrictive element in which the internal electrode is formed over the entire surface of the thin film or thin plate of the electrostrictive material,
An insulating layer that insulates only the electrostrictive material on the exposed end face of the internal electrode exposed on the side end face of the element and the vicinity thereof has a general formula (I) (Wherein X is a phenyl group; a biphenyl group; and at least one of the phenyl group and the biphenyl group is O, CO, S, CH ₂ , C
A tetravalent group selected from the group consisting of a polyphenyl group linked by at least one of (CH ₃ ) ₂ and C (CF ₃ ) ₂ , wherein Y is a phenyl group; a biphenyl group; a phenyl group and a biphenyl group At least one of O, CO, S, SO ₂ , CH ₂ , C (C
H ₃ ) ₂ and a divalent group selected from the group consisting of a polyphenyl group, an alkylene group, and a xylylene group, which are linked by at least one of C (CF ₃ ) _2. It is characterized by comprising a polyimide resin and an insulating filler.

Further, in the method for manufacturing a laminated electrostrictive effect element according to the first aspect of the present invention, a film or thin plate of an electrostrictive material and internal electrodes are alternately laminated, and the internal electrode is a thin film of the electrostrictive material. Alternatively, the electrostrictive element in which the end face of the internal electrode is exposed at the side end face of the laminated electrostrictive effect element formed over the entire surface of the thin plate is represented by the general formula (II): (Wherein X is a phenyl group; a biphenyl group; and at least one of the phenyl group and the biphenyl group is O, CO, S, CH ₂ , C
A tetravalent group selected from the group consisting of a polyphenyl group linked by at least one of (CH ₃ ) ₂ and C (CF ₃ ) ₂ , wherein Y is a phenyl group; a biphenyl group; a phenyl group and a biphenyl group At least one of O, CO, S, SO ₂ , CH ₂ , C (C
H ₃ ) ₂ and a divalent group selected from the group consisting of a polyphenyl group, an alkylene group, and a xylylene group, which are linked by at least one of C (CF ₃ ) _2. A carboxyl group of the polyamic acid resin in a composition comprising a polyamic acid resin and an insulating filler dispersed in the resin is neutralized with a base, and immersed in a film-forming electrophoresis bath obtained by diluting with water. Electrophoresis is performed using the internal electrode of the electrostrictive effect element as an anode, and only the exposed portion of the internal electrode on the side end surface of the electrostrictive effect element and the electrostrictive material in the vicinity thereof are exposed to the polyamic acid and the insulating material. The conductive filler is precipitated to form a coating layer, which is then subjected to a heat treatment to imidize the polyamic acid resin of the coating layer. (Wherein X and Y are as defined above). An insulating layer comprising a polyimide resin having a repeating unit represented by the following formula and an insulating filler is formed.

Further, the laminated electrostrictive effect element of the second aspect of the present invention,
In a laminated electrostrictive element in which the thin film or thin plate of the electrostrictive material and the internal electrode are alternately laminated, and the internal electrode is formed over the entire surface of the thin film or the thin plate of the electrostrictive material,
There are m (m) insulating layers that insulate only the exposed end face of the internal electrode exposed on the side end face of the element and the electrostrictive material in the vicinity thereof.
Is an even number of 4 or more), and the insulating layer of the first group insulates the (m × n + 1) th (n is 0 or a positive integer) other internal electrode, The insulating layers of the group insulate the internal electrodes other than the (m × n + 2) -th internal electrode, and the insulating layers of the third group form the (m × n +
3) The other internal electrodes are insulated. Similarly, the m-th group of insulating layers insulates the (m × n + m) -th internal electrodes, and furthermore, the m stacked layers. An external electrode electrically connected to each internal electrode is provided on the insulating layer of each group.

Further, the method for manufacturing a laminated electrostrictive effect element according to the second aspect of the present invention is characterized in that m laminated sintered bodies in which thin films or thin plates of an electrostrictive material and internal electrodes are alternately laminated (m is 4 or more) Are formed, and at this time, the first temporary external electrode is electrically connected to the (m × n + 1) -th (n is 0 or a positive integer) other internal electrode. Then, the second temporary external electrode is electrically connected to the (m × n + 2) -th internal electrodes,
Of the (m × n + 3) -th internal electrode is electrically connected to the (m × n + 3) -th internal electrode.
+ M) a first step of forming external electrodes so as to conduct to the internal electrodes other than the (m) -th internal electrode, and providing a lead wire to each temporary external electrode; M groups of insulating layers are formed by electrophoresis on the exposed end face of the internal electrode and the electrostrictive material in the vicinity thereof, and at this time, the first group of insulating layers is the (m × n + 1) th (n
Is an integer other than 0 or a positive integer), the second group of insulating layers insulates other than the (m × n + 2) th internal electrode, and the third group of insulating layers is the (mx n +
3) a second step of forming an insulating layer so as to insulate the other internal electrodes other than the (m × n + m) th inner electrode, and the second step; Forming, from above each of the m groups of insulating layers obtained above, external electrodes that are electrically connected to the internal electrodes of each of the stacked m layers, and further attaching a lead wire to the external electrodes; The method is characterized in that a step of separating the lead wire from the m temporary external electrodes attached in the first step is performed.

The electrostrictive material referred to in the present invention refers to any material in which a substance is distorted when a voltage is applied, and more specifically, a piezoelectric material in which the strain is substantially proportional to the magnitude of the electric field and a strain in which the strain is substantially proportional to the square of the magnitude of the electric field. Electrostrictive material.

The polyamic acid resin used in the production method of the present invention may be partially imidized in advance.

In the polyimide resin having the repeating unit represented by the general formula (I) and the polyamide resin having the repeating unit represented by the general formula (II), specific examples of X include the following: Further, specific examples of Y include the following: From the viewpoint of adhesion and heat resistance of the polyimide resin having the repeating unit represented by the general formula (I) to the electrostrictive element substrate, X is Is particularly preferred.

The polyamic acid resin having a repeating unit represented by the general formula (II) used in the production method of the present invention is represented by the general formula (III) (Wherein X is as defined above) and a tetracarboxylic anhydride having the general formula (IV) (Wherein Y is as defined above).

As the above tetracarboxylic anhydrides, for example,
Pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4, 4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2, 2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride,
Bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,
3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-
Preferred are perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like. Of these, particularly preferred tetracarboxylic dianhydrides are pyromellitic dianhydride, 3,3 ′, 4,
4'-benzophenonetetracarboxylic dianhydride, 3,
3 ', 4,4'-biphenyltetracarboxylic dianhydride and bis (3,4-dicarboxyphenyl) ether dianhydride.

Examples of the above diamines include 3,3'-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene, 4,4'-bis (3-aminophenoxy) biphenyl, and 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3- Meta-position diamines such as amino [phenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl] sulfone; Alternatively, two or more kinds are used in combination.

The reaction between the tetracarboxylic anhydride and the diamine is usually performed in an organic solvent. As the organic solvent, for example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, pyridine, dimethylsulfone, hexamethylphosphoramide, tetramethylurea, N-methylcaprolactam, tetrahydrofuran, m-dioxane, p
-Dioxane, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, bis [2- (2-methoxyethoxy)
Ethyl] ether and the like. These organic solvents may be used alone or in combination of two or more. The reaction temperature is generally 200 ° C or lower and -20 ° C or higher, preferably 50 ° C or lower and -10 ° C or higher, more preferably 0 ° C or lower and about room temperature. The reaction pressure is not particularly limited, and the reaction can be sufficiently performed at normal pressure. The reaction time may vary depending on the type of the solvent, the reaction temperature and the diamine or acid dianhydride used, but it is usually 2 to 40 hours, preferably 4 hours, for reacting for a time sufficient to complete the formation of the polyamic acid. About 24 hours is enough.

The polyamic acid solution thus obtained is a solution containing about 5 to 40% by weight of polyamic acid, and has a logarithmic viscosity of 0.5 to 0.5%.
About 4 dl / g (temperature measured at 35 ° C., a value measured as a concentration of 0.5 g per ml of N, N-dimethylacetamide solution) as the water solubility and the physical properties of the polyimide film after heat treatment. It is desirable because it is excellent.

The core of the present invention is that an insulating filler is added to the polyamic acid obtained as described above. As a method of addition, any method such as roll kneading and a ball mill may be used as long as the insulating filler is sufficiently dispersed in the polyamic acid. The addition amount of the insulating filler is preferably about 2 to 70% by volume. If the addition amount is too small, the effect of addition will not appear, and if it is too large, the insulating filler will precipitate in the final electrophoresis bath, which is not preferable.

The insulating filler used in the present invention has a resistivity of 10 ⁵ Ωcm
An inorganic compound or an organic compound may be used as long as it exhibits an electrical resistance of at least a certain level. As inorganic compounds used as such an insulating filler, beryllium, magnesium, calcium, aluminum, boron, silicon, scandium, yttrium, lanthanum, titanium, zirconium, hafnium and rare earth oxides and composite oxides, aluminum, boron, Examples thereof include nitrides such as silicon, titanium, zirconium, and hafnium, oxynitrides, and carbides such as silicon carbide. Also, the organic compound must be one that does not dissolve in the electrophoresis bath,
Such materials include silicone resins, fluororesins represented by Teflon, phenolic resins, furan resins,
Epoxy resins, acrylic resins and the like are exemplified.

In the present invention, the shape of the insulating filler is particulate,
The size is arbitrary irrespective of the fibrous shape or the like, but the dimensions are determined in relation to the required thickness of the insulating layer film. That is,
It is necessary that the maximum diameter of the insulating filler is smaller than the minimum thickness of the insulating layer film. Further, considering that it is important to maintain a good dispersion state in an electrophoresis bath from an industrial viewpoint, it is desirable that the average diameter of the insulating filler is 20 μm or less, preferably 10 μm or less.

In the production method of the present invention, the polyamic acid resin having a repeating unit represented by the general formula (II) containing an insulating filler dispersed therein is prepared by adding a base such as an amine or an alkali metal ion in the presence of water. ,That
COOH groups can be dissociated into COO- ions and become soluble in water or can be stably colloidally dispersed, and can be precipitated and insolubilized by electrophoresis on a laminated electrostrictive element as an anode. .

Examples of the base include ammonia: secondary amines such as dialkylamine, diethanolamine, and morpholine: triethylamine, tributylamine, triethanolamine, triisopropanolamine, dimethylethanolamine, dimethylisopropanolamine, diethylethanolamine, dimethylbenzylamine, and the like. Tertiary amines: Inorganic bases such as caustic soda and caustic potash are used, but tertiary amines are particularly preferable in view of stability after dilution with water and properties of a coating film obtained.

The amount of base required for imparting water dilutability is 30 to 110 mol% based on the carboxyl equivalent of the polyamic acid to be neutralized.
In general, and particularly preferably 40 to 100 mol%. By performing the neutralization in this manner, the polyamic acid becomes completely water-soluble or partially solubilized to become a suspended state and becomes water-dilutable.

By diluting the neutralized composition with water, a suspension containing a polyamic acid capable of being subjected to electrophoresis and an insulating filler coated with the polyamic acid is provided as a film-forming electrophoresis bath. You can do it.

The coating layer composed of the polyamic acid resin and the insulating filler thus precipitated is subjected to a heat treatment to obtain the general formula (I) (Where X is as described above) is converted into an insulating layer composed of a polyimide resin having a repeating unit represented by the following formula and an insulating filler. The heating temperature at this time is about 80 to 300 ° C, preferably about 150 to 280 ° C.

The inventors of the present invention have previously filed an application in that the insulating layer composed of the polyimide resin and the insulating filler obtained as described above has excellent dielectric strength and very good adhesion to metal ( Japanese Patent Application No. 1-1171854) The performance is the same as that of the insulating layer made of polyimide resin alone, but as is clear from the examples described later, the rate of occurrence of defective products that cause dielectric breakdown at low voltage is lower than that of polyimide resin alone. And has the advantage of being significantly lower.

The laminate according to the present invention includes not only a laminate formed by a so-called green sheet method but also a laminate obtained by laminating a sintered thin plate called a stack type with an adhesive or the like.

In the present invention, it is not yet clear how the insulating filler functions to reduce the defective rate. However, many small air bubbles are often seen in a polyimide resin alone film that breaks down at low voltage, but considering that there are few or almost no air bubbles in a system with an insulating filler added, It is supposed that the filler prevents bubbles from being trapped in the insulating film during electrophoresis, and promotes the formation of an insulating film having a uniform thickness.

FIG. 1 shows an example of a laminated electrostrictive longitudinal effect element according to the present invention. In the device of the present invention, the number of the insulating layers is m, for example, 4
Group exists, and the insulating material is (m
-1) There are internal electrodes that are continuously formed on the internal electrodes and the electrostrictive material in the vicinity thereof and are not insulated for every m layers. The insulating layer having such a structure is realized by an electrophoresis method described later, but requires an insulating material as compared with the conventional device (FIG. 2) in which two independent insulating layers are provided every other layer. Since it is locally attached only to a critical part, insulation of a fine shape is possible. Although the present inventors do not use a special theory, if the insulating layers are made continuous every (m-1) layers in this way, compared to the case where an independent insulating layer is formed for each layer of the conventional element, It is presumed that the end face of the internal electrode to be exposed is not covered with an insulating layer, and only a necessary portion can be insulated. The m obtained in this way
An external electrode is formed on each of the insulating layers of the group, and when the m external electrodes are connected to a power source, the external electrodes are connected such that the polarity of the internal electrodes is reversed for each layer (FIG. 1
The group (G ₁ ) and the third group (G ₃ ), and the second group (G ₂ ) and the fourth group (G ₄ ) have the same polarity.

The insulating material used in the second embodiment of the present invention may be an inorganic material, but is preferably an organic material. An inorganic material lacks elasticity, so that cracks and the like are likely to occur during driving of the element, leaving unreliability in reliability. However, an organic material is preferable without such a defect. Among organic materials, a polyimide resin containing an insulating filler is also excellent in solder heat resistance and is particularly preferable. The polyimide resin and the insulating filler that can be used in the second embodiment of the present invention are as described above.

In the present invention, the element shape may be, for example, any of a cylinder, a truncated cone, a truncated pyramid, an octagonal prism, and a truncated octagonal pyramid.
Further, the formation position of m, for example, four insulating layer groups is also arbitrary. Furthermore, in FIG. 1, the inner electrode side end faces other than the four insulating layer groups and the vicinity thereof are exposed, but in the present invention, there is no problem even if these parts are covered with the insulating layer.

The manufacturing method of the electrostrictive effect element of the present invention is roughly as follows. First, the production of a laminated sintered body is performed by an almost known method. That is, in the case of the doctor blade method, first, a green sheet of an electrostrictive material is made, and a paste for an internal electrode such as silver, a silver-palladium alloy, platinum, nickel, or copper is printed on the obtained green sheet. Are laminated and thermocompression-bonded, and the laminated body is degreased and sintered to form a laminated sintered body.

In the case of performing the bonding method, first, a molded body of the electrostrictive material is formed and sintered to obtain a block-shaped sintered body. Next, this is cut out into a thin plate shape to have a predetermined thickness, and this is alternately laminated with a metal thin film or a thin plate with an adhesive to obtain a laminated sintered body.

What is important when producing a laminated sintered body in any of the methods is that, in a first step to be described later, m parts, for example, four temporary external electrodes are provided along a laminating direction as shown in FIG. In other words, the internal electrode is formed in such a shape that a portion where the internal electrode does not reach the side end face of the laminated sintered body is formed for every m layers.

In the element of the present invention, as described above, m temporary external electrodes are formed on the laminated sintered body thus obtained, and a first step of providing a lead wire to each temporary external electrode, A second step of forming m groups of insulating layers by electrophoresis, a step of forming external electrodes from above the m groups of insulating layers, and attaching a lead wire to each external electrode;
It is manufactured through a process of separating the lead wires from the m temporary external electrodes attached in the process.

In the following description, a case where m is 4 will be described for simplicity.

In the first step, a temporary external electrode is provided by applying a conductive paste to the laminated sintered body prepared as described above at four locations. At this time, the first temporary external electrode is electrically connected to the (4n + 1) th (n is 0 or a positive integer) other internal electrode, and the second temporary external electrode is other than the (4n + 2) th internal electrode. , The third temporary external electrode is conductive to the (4n + 3) -th internal electrode, and so on, and the m-th temporary external electrode is conductive to the (4n + m) -th internal electrode. To do it. Next, a lead wire is provided for each temporary external electrode.

In the second step, one temporary external electrode is connected to a DC power source such that the positive electrode and the counter electrode are negative, and the polyamic acid resin and the filler are exposed to the exposed end face of the internal electrode by electrophoresis in an electrodeposition tank. Three layers are continuously deposited on the electrostrictive material in the vicinity. Next, the resulting product is heated to change the polyamic acid resin into a polyimide resin to form one insulating layer group. This procedure is repeated four times for each temporary external electrode to form four groups of insulating layers. At that time, it is necessary to cover a portion where the polyamic acid resin and the filler are not desired to be precipitated in each operation using a tape or the like. At the end of this step, the element has four groups of insulating layers, and in each of the insulating layer groups, the insulating layer continuously insulates the exposed end faces of the internal electrodes by three layers and insulates one layer for every four layers. There are no exposed end faces of the internal electrodes. After forming one group of insulating layers, it is also possible to immediately proceed to the third step, to form external electrodes from above the insulating layer, and to provide lead wires before starting the formation of the next insulating layer group.

Up to the second step, a plurality of devices can be manufactured at the same time as described in the embodiments described later. Therefore, the devices may be cut out one by one before starting the next process. Further, the temporary external electrodes may be separated at this stage. In the third step, external electrodes are formed from above on each of the four insulating layer groups formed in the previous step so as to be electrically connected to the internal electrodes every four layers,
Further, a lead wire is provided for each external electrode. Therefore, the number of lead wires is usually four, but if two external electrodes are connected two by two so that opposing internal electrodes have polarities opposite to each other and two sets of external electrodes are electrically used, the number of lead wires is two. It can be a book.

The external electrodes may be formed by applying a conductive paste or by a vapor deposition method. Normally, solder is used to connect the external electrode and the lead wire, but a conductive adhesive may be used.

Generally, after the third step is completed, the four temporary external electrodes are separated from the lead wires. Further, when a large number of elements are formed together as in Example 1 described later, each element is separated into individual elements. Hereinafter, the present invention will be described in more detail by way of examples. Of course, the present invention is not limited to these examples.

Example 1 In a reaction vessel equipped with a stirrer, a reflux condenser and a nitrogen inlet tube, 53.0 g (0.25 mol) of 3,3'-diaminebenzophenone was dissolved in 240 ml of N, N-dimethylacetamide. To this solution was added powder of 78.6 g (0.244 mol) of 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride,
The mixture was stirred for 24 hours to obtain a polyamic acid solution. Alumina powder (AKP-30, manufactured by Sumitomo Chemical Co., Ltd.) was added to this solution for 620 minutes.
g was added and kneaded with a three-roll mill to prepare an alumina-dispersed polyamic acid varnish. 21.7 g of dimethylethanolamine (relative to carboxyl equivalent: 50 mol%) was gradually added to the varnish, and the mixture was stirred at room temperature for 20 minutes. Then, while stirring, 905.3 g of water was gradually added at room temperature to dilute with water. A polyamic acid suspension containing alumina powder was prepared.

In the case of a sample of a laminated body (one layer having a thickness of about 100 μm and 50 layers), one end face is exposed in every other layer, and the other end face is exposed in advance so that all internal electrodes are exposed. Oita. Silver electrodes were baked on the side where the internal electrodes were exposed every other layer, and lead wires were connected with solder. The suspension was put into a plastic tank, used as an electrophoresis bath for forming a film, and the laminate to be coated was infiltrated as an anode, and a lead wire was connected to the anode. Electrophoresis was performed by applying a voltage at 20 V for 5 seconds. Thereafter, the laminate was taken out, washed with an aqueous solution containing 20% by weight of N, N-dimethylacetamide, and then imidized by heat treatment at 150 ° C. for 2 hours and 280 ° C. for 2 hours. Next, the laminate was cut in the middle, a silver electrode was applied to the side where the imide resin insulating film was attached, and a lead wire was attached. By performing the same operation, a laminate having insulating layers on the left and right for each electrode was obtained. The thickness of this insulating layer was about 50 microns.

When the dielectric strength was measured for 100 laminates obtained in this manner, 98 of them had a dielectric breakdown voltage of 1000 V or more, and the other two had dielectric breakdown at about 90 V and 310 V.

Comparative Example 1 A varnish was prepared without adding alumina powder, and a polyamic acid aqueous solution for electrophoresis was prepared in exactly the same manner as in Example 1 except that 39.1 g of dimethylethanolamine was added to the varnish instead of 21.7 g. Using this polyamic acid aqueous solution, an insulating film was formed on the laminate in exactly the same manner as in Example 1 except that the electrophoresis conditions were set to 100 V for 20 seconds (the thickness of the insulating layer was about 50 μm).

When the dielectric strength was measured for 100 laminates obtained in this way, 78 had a dielectric breakdown voltage of 1000 V or more, and 17 had 100 V or less, and 3 had 100 to 200 V.
And 200-300V.

Example 2 In the method of Example 1, the imidization heat treatment was performed at 180 ° C.
Alternatively, the test was performed at 250 ° C., and in each case, the same result as in Example 1 was obtained.

Example 3 Instead of alumina powder, titania powder (average particle size 0.8
An experiment was performed in exactly the same manner as in Example 1 except that μm) was used. There were 97 pieces with a dielectric breakdown voltage of 1000 V or more, and the rest were two pieces at 200 to 300 V and one piece at 500 to 600 V.

Example 4 Instead of alumina powder, use silica powder (average particle size 0.5 μm).
The experiment was performed in exactly the same manner as in Example 1 except that m) was used. 99 pieces had a breakdown voltage of 1000 V or more, and the remaining one had a breakdown of 273 V.

Example 5 Instead of alumina powder, silicon nitride powder (average particle size 0.8
An experiment was performed in exactly the same manner as in Example 1 except that μm) was used. 98 pieces had a breakdown voltage of 1000 V or more, and the remaining two pieces had breakdown at 260 and 543 V, respectively.

Example 6 In a container equipped with a stirrer, a reflux condenser and a nitrogen inlet tube,
2,2-bis [4- (3-aminophenoxy) phenyl]
41.0 g (0.1 mol) of propane and 200 ml of N, N-dimethylacetamide were charged, cooled to around 0 ° C., and a powder of 21.8 g (0.1 mol) of pyromellitic dianhydride was added under a nitrogen atmosphere. The mixture was stirred at around ° C for 2 hours. Next, the solution was returned to room temperature and stirred under a nitrogen atmosphere for about 20 hours.
The logarithmic viscosity of the polyamic acid thus obtained was 1.5 dl / g. Alumina powder (manufactured by Sumitomo Chemical Co., Ltd., trade name: AKP
−30), and add 3 until the alumina powder is sufficiently dispersed.
It was kneaded with this roll. To the obtained alumina powder-containing polyamic acid solution was gradually added 10.1 g of triethylamine (relative to a carboxyl equivalent of 50 mol%), and the mixture was stirred at room temperature for 1 hour. A polyamic acid suspension was prepared.

An insulating layer was provided in the same manner as in Example 1 using the same laminate and the above-mentioned polyamic acid suspension as in Example 1. This insulating layer also had a thickness of about 50 μm.

When the dielectric strength was measured for 100 of the laminates thus obtained, 97 of them had a dielectric breakdown voltage of 1000 V or more, and the remaining breakdown occurred at 16 V, 193 V, and 862 V.

Comparative Example 2 An aqueous polyamic acid solution for electrophoresis was prepared in exactly the same manner as in Example 6, except that the step of adding the alumina powder and kneading the rolls was omitted, and 20.2 g of triethylamine was added instead of 10.1 g. Using this polyamic acid aqueous solution, an insulating film was formed on the laminate in exactly the same manner as in Example 6 except that the electrophoresis conditions were set at 100 V for 20 seconds (the thickness of the insulating layer was about 50 μm).

When the dielectric strength was measured for 100 laminates obtained in this way, 84 dielectric breakdown voltages were 1000 V or more, 11 were 100 V or less, and 200 to 300 V were 2 or less.
There were three pieces, 500-600V.

Example 7 Instead of alumina powder, a fine-grained phenol resin (Unibex C, manufactured by Unitika Ltd.) was classified to give a particle size of 10 μm.
m), the experiment was carried out in exactly the same manner as in Example 1. Of the 100 laminates, 90 had a breakdown voltage of 1000 V or more.

Example _{8 (Pb x, Ba 1-} x) (Zr y, Ti 1-y) O 3 prepared powder (herein x = 0.73, y = 0.55) in a solid solution with a very small amount of additive, which Was divided into two.

One of the powders was put into a mold and press-molded at 1 ton / cm ² to obtain a disk-shaped compact. After sintering this molded body at 1320 ° C. for 3 hours, the surface was polished to obtain a disk-shaped sintered body having a thickness of 0.5 mm. Electrodes are formed on the upper and lower surfaces of this disc-shaped sintered body.
A voltage of 0 V was applied (electric field was 10 kV / cm), and the elongation in the voltage application direction was about 0.11%.

The other powder is about 0.1mm thick by doctor blade method
, And then cut into small pieces of 7 mm x 50 mm by a punching machine. Platinum paste was screen-printed on the 50 small pieces so as to have a shape as shown in FIG. 3A, and on another 50 pieces as shown in FIG. The printed green sheets pieces laminated in the order shown in FIG -4, 120 ° C. on a hot plate, after thermocompression bonding 150 Kg / cm ^2, the defatted slowly heated to 500 ° C. Put the degreasing furnace went. Next, the degreased body was transferred to a sintering furnace and sintered at 1320 ° C. for 3 hours. The distance between the internal electrodes of the obtained sintered body was 0.08 mm, and one layer did not reach every four internal electrodes near the four ridges as shown in FIG. Is always 3
It has a structure that reaches one ridge. Silver paste was applied near these four ridges to form temporary external electrodes, and lead wires were attached to each of them using solder.

Next, in order to prevent an insulating layer from being formed except for a necessary portion, the surface A′B ′ shown in FIG.
A protective tape is applied to the entire surface of C'D ', and a protective tape is applied to the surface ABCD as shown in FIG. 6 and then immersed in an electrodeposition tank. A temporary external electrode formed near the ridge A'D 'shown in FIG. 5 (a)) is connected to a DC power supply through a lead wire such that the positive electrode and the counter electrode are negative, and the alumina particles and the polyamide are electrophoretically electrophoresed. An acid was electrodeposited on the exposed end face of the internal electrode which is in conduction with the temporary external electrode and in the vicinity thereof (the polyamic acid used in this example was 3,3).
It is obtained by reacting 3'-diaminobenzophenone with 3,3 ', 4,4'-benzophenonetetracarboxylic acid dihydrate. Alumina is AKP-30 manufactured by Sumitomo Chemical Co., Ltd.
Is). After that, remove from the electrodeposition tank and drain the liquid, 200 ° C
And the polyamic acid was imidized to form a first insulating layer group.

By the same operation, the second, third and fourth temporary external electrodes (temporary external electrodes formed near the ridges AD, BC and B'C 'shown in FIG. 5A) and the DC power supply And a second insulating layer group were formed by connecting the positive electrode with a lead wire. At that time, the protective tape was changed so that the insulating layers of each group did not overlap.

As shown in FIG. 7, the insulating layer formed in the above step was separated from the temporary external electrode, and further separated into a plurality of elements so as to provide an element having four insulating layer groups.
Finally, silver paste was applied from above the four insulating layer groups provided on the individual elements to form external electrodes, and lead wires were attached to each of them to complete the element (FIG. 8).

The lead wires of the device obtained in this way are connected in sets of two such that the internal electrodes of the device have the opposite polarity for each layer, and connected to a power supply, and a voltage of 80 V (10 kV / cm as an electric field) is applied. The elongation percentage in the voltage application direction was measured to be about 0.10%.

Example 9 In the same manner as in Example 8, a small green sheet piece having a thickness of 0.1 mm was obtained. Screen printing was performed on the 100 small pieces using the same platinum paste as in Example 8 so as to have the shape shown in FIG. 9. All printed green sheet pieces and one unprinted piece were laminated in the order shown in FIG. 10 and thermocompressed on a hot plate at 120 ° C. and 150 kg / cm ² .

The obtained laminate was degreased exactly in the same manner as in Example 8, and then sintered. The distance between the internal electrodes of the obtained sintered body was 0.08 mm, and the structure was such that one internal layer did not reach every two internal electrodes on two side surfaces. As shown in FIG. 11, conductive paste was applied to these two side surfaces to form temporary external electrodes, and lead wires were attached to each. Next, a protective tape was stuck on one of the two exposed side surfaces of the internal electrode where no temporary external electrode was provided, and then the alumina particles and the polyamic acid were electrophoresed in exactly the same manner as in Example 8 to form the first electrode. Electrodeposition was performed on the exposed end face of the internal electrode that is in conduction with the lead wire and in the vicinity thereof (the polyamic acid and alumina used in this example are exactly the same as in Example 8). Then, it was taken out of the electrodeposition tank in exactly the same manner as in Example 8 and drained.
The polyamic acid was imidized by heating to 0 ° C. to form a first insulating layer group. By the same operation, a second insulating layer group was formed using the second lead wire. At that time, the protective tape was changed so that the first insulating layer was not insulated again.

As shown in FIG. 12, a temporary external electrode is separated from the one having the insulating layer formed in the above step, and further divided into a plurality of elements so as to form an element having two insulating layer groups. Finally, silver paste was applied from above the two insulating layer groups provided on the individual devices to form external electrodes, and lead wires were attached to each of them to complete the device (FIG. 13).

The two leads of the device thus obtained were connected to a power supply, and a voltage of 80 V (an electric field of 10 kV / cm) was applied. The elongation in the voltage application direction was measured to be about 0.08%.

〔The invention's effect〕

As is clear from the above Examples and Comparative Examples, by adding an insulating filler, a laminate having a high insulating power can be efficiently produced, which greatly contributes to a reduction in production cost. Further, with the laminated electrostrictive longitudinal effect element structure of the present invention in which the exposed end faces of the internal electrodes are continuously insulated three layers at a time, even if the electrostrictive material is an extremely thin element, the internal electrodes to be electrically connected to the external electrodes must Since the insulating layer is formed only on a necessary portion without covering the exposed end surface of the electrode, an element which shows a large displacement even when driven at a low voltage, which has been conventionally difficult, can be easily manufactured.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (c) are a perspective view and a vertical sectional view along XY and X'-Y 'of an embodiment of the present invention. 2 (a) and 2 (b) are a perspective view and a vertical cross-sectional view along XY of a conventional laminated electrostrictive vertical effect element. FIG. 3 to FIG. 7 are a perspective view, a plan view, and a longitudinal sectional view shown in the order of steps for explaining the manufacturing method of the eighth embodiment. FIG. 8 is a perspective view of one laminated electrostrictive longitudinal effect element obtained in Example 8 and a longitudinal sectional view taken along XY and X'-Y '. FIG. 9 to FIG. 12 are a perspective view, a plan view, and a longitudinal sectional view shown in the order of steps for explaining the manufacturing method of the ninth embodiment. FIG. 13 is a perspective view of one laminated electrostrictive longitudinal effect element obtained in Example 9. In each figure, 1 is an electrostrictive material, 2 is a platinum internal electrode, 3 is an insulating layer, 4 is an external electrode, 5 is a lead wire, 6 is a solder, 7 is a green sheet, 8 is a platinum paste, 9 is a protective tape, 10
Is a temporary external electrode, 11 is a lead wire for electrophoresis, and 12 is a cutting line for cutting out each of the laminated electrostrictive longitudinal effect elements.

Claims (10)

(57) [Claims] 1. A laminated electrostrictive element in which a film or a thin plate of an electrostrictive material and an internal electrode are alternately laminated, and the internal electrode is formed over the entire surface of the thin film or the thin plate of the electrostrictive material. The insulating layer that insulates only the exposed end face of the internal electrode exposed on the side end face of the element and the electrostrictive material in the vicinity thereof has a general formula (I) (Wherein X is a phenyl group; a biphenyl group; and at least one of the phenyl group and the biphenyl group is O, CO, S, CH ₂ , C
A tetravalent group selected from the group consisting of a polyphenyl group linked by at least one of (CH ₃ ) ₂ and C (CF ₃ ) ₂ , wherein Y is a phenyl group; a biphenyl group; a phenyl group and a biphenyl group At least one of O, CO, S, SO ₂ , CH ₂ , C (C
H ₃ ) ₂ and a divalent group selected from the group consisting of a polyphenyl group, an alkylene group, and a xylylene group, which are linked by at least one of C (CF ₃ ) _2. A laminated electrostrictive element comprising a polyimide resin and an insulating filler. 2. A laminated electrostrictive effect element in which a film or thin plate of an electrostrictive material and internal electrodes are alternately laminated, and the internal electrode is formed over the entire surface of the thin film or the thin plate of the electrostrictive material. The electrostrictive effect element having the end face of the internal electrode exposed at the side end face is represented by general formula (II) (Wherein X is a phenyl group; a biphenyl group; and at least one of the phenyl group and the biphenyl group is O, CO, S, CH ₂ , C
A tetravalent group selected from the group consisting of a polyphenyl group linked by at least one of (CH ₃ ) ₂ and C (CF ₃ ) ₂ , wherein Y is a phenyl group; a biphenyl group; a phenyl group and a biphenyl group At least one of O, CO, S, SO ₂ , CH ₂ , C (C
H ₃ ) ₂ and a divalent group selected from the group consisting of a polyphenyl group, an alkylene group, and a xylylene group, which are linked by at least one of C (CF ₃ ) _2. A carboxyl group of the polyamic acid resin in a composition comprising a polyamic acid resin and an insulating filler dispersed in the resin is neutralized with a base, and immersed in a film-forming electrophoresis bath obtained by diluting with water. Electrophoresis is performed using the internal electrode of the electrostrictive effect element as an anode, and only the exposed portion of the internal electrode on the side end surface of the electrostrictive effect element and the electrostrictive material in the vicinity thereof are exposed to the polyamic acid and the insulating material. The conductive filler is precipitated to form a coating layer, which is then subjected to a heat treatment to imidize the polyamic acid resin of the coating layer. The laminated electrostrictive effect according to claim 1, wherein an insulating layer comprising a polyimide resin having a repeating unit represented by the following formula (where X and Y are as defined above) and an insulating filler is formed. Device manufacturing method. 3. A laminated electrostrictive effect element in which thin films or thin plates of an electrostrictive material and internal electrodes are alternately laminated, and the internal electrodes are formed over the entire surface of the thin film or the thin plate of the electrostrictive material. A first group includes m (m is an even number of 4 or more) insulating layers for insulating only the exposed end face of the internal electrode exposed on the side end face of the element and the electrostrictive material in the vicinity thereof. Of the (m × n + 1) th (n
Is an integer other than 0 or a positive integer), the second group of insulating layers insulates other than the (m × n + 2) th internal electrode, and the third group of insulating layers The (m × n + 3) -th internal electrodes are insulated. Similarly, the m-th group of insulating layers insulate the (m × n + m) -th internal electrodes, and are further laminated. An external electrode, which is electrically connected to the internal electrodes of every m layers, is provided from above the insulating layers of each group. 4. The laminated electrostrictive effect element according to claim 3, wherein four insulating layers insulate only the exposed end face of the internal electrode exposed on the side end face of the element and the electrostrictive material near the exposed end face. The first group of insulating layers is the (4n +
The first (in which n is 0 or a positive integer) other than the (1) -th internal electrode is insulated, and the insulating layer of the second group is (4n + 2)
The third group of insulating layers insulates other than the (4n + 3) th internal electrodes, and the third group of insulating layers insulates the other (4n + 4) th internal electrodes. A laminated electrostrictive effect element, wherein external electrodes which are insulated and which are electrically connected to internal electrodes of each of the four laminated layers are provided on the insulating layers of each group. 5. The laminated electrostrictive element according to claim 3, wherein the insulating layer contains an organic material. 6. The laminated electrostrictive longitudinal effect element according to claim 5, wherein the organic material is the polyimide resin according to claim 1. 7. The laminated electrostrictive effect element according to claim 5, wherein said insulating layer contains the polyimide resin according to claim 1 and an insulating filler. 8. The multi-layer electrostrictive effect element according to claim 1, wherein the multi-layer electrostrictive effect element is a multi-layer electrostrictive longitudinal effect element.
8. The laminated electrostrictive effect element according to 6 or 7. 9. A m (where m is an even number equal to or greater than 4) temporary external electrode is formed on a laminated sintered body in which thin films or thin plates of an electrostrictive material and internal electrodes are alternately laminated. In addition, the first temporary external electrode is electrically connected to the (m × n + 1) th (n is 0 or a positive integer) other internal electrode, and the second temporary external electrode is (m × n + 2). The third temporary external electrode is conductive to the (m × n + 3) -th internal electrode except for the (m × n + 3) th internal electrode, and so on.
a first step of forming external electrodes so as to conduct to internal electrodes other than the (n + m) -th internal electrode, and providing a lead wire to each temporary external electrode; Forming m groups of insulating layers by electrophoresis on the exposed end face of the internal electrode and the electrostrictive material in the vicinity thereof,
The first group of insulating layers is the (m × n + 1) -th (n is 0
Or a positive integer), the second group of insulating layers insulates other than (m × n + 2) -th internal electrodes, and the third group of insulating layers (m × n + 3) A second step of forming an insulating layer so as to insulate the internal electrodes other than the (m × n + m) th internal electrode, and in the same manner, obtain an insulating layer of the m-th group. Forming, from above each of the m groups of insulating layers, external electrodes that are electrically connected to the internal electrodes of each of the stacked m layers, and further attaching a lead wire to the external electrodes; A method for manufacturing a laminated electrostrictive effect element, comprising a step of separating a lead wire from m temporary external electrodes attached in one step. 10. The method according to claim 9, wherein the second
The method according to claim 9, wherein the step is performed by the method according to claim 2.