JPH1197759A - Method for polarizing piezoelectric ceramic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a discharge short-circuiting when a high voltage is applied from being generated between electrodes by forming a covering for withstand voltage that covers the ceramic foundation surface between electrodes from an insulation paste where an inorganic insulator is mixed to an organic macromolecular material and applying a high voltage to the double-sided electrode of the piezoelectric ceramic element in atmosphere. SOLUTION: A ceramic foundation surface 4 is formed so that it is exposed as the insulation gap of double-sided electrodes 2 and 3 being located on the same surface. Also, a covering 5 for withstand voltage is formed in a ring shape so that the ceramic foundation surface 4 is covered from an insulation paste where an inorganic insulator is mixed to a macromolecular material before polarization treatment due to the application of a high voltage to a piezoelectric ceramic element 1. An electric field of 1,000 V/mm or larger is applied to the double-sided electrodes 2 and 3 in the piezoelectric ceramic element 1, thus performing polarization treatment in atmosphere. By using the mixture between silica and alumina as the inorganic insulator of the insulation paste, electrical insulation property and a large volume resistivity can be given, thus preventing a discharge short-circuiting when a high voltage is applied from being generated between the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to obtaining a piezoelectric ceramic element for a piezoelectric ceramic component by applying a high voltage to both electrodes of a piezoelectric ceramic element in the atmosphere and performing polarization processing of the piezoelectric ceramic element. The present invention relates to a method for polarizing a piezoelectric ceramic element.

[0002]

2. Description of the Related Art Conventionally, as a method of polarizing a piezoelectric ceramic element by applying a high voltage to both electrodes of the piezoelectric ceramic element in the atmosphere, a method of preventing a discharge short circuit between the electrodes when a high voltage is applied is used. It has been proposed to form an oil compound as a withstand voltage coating on a porcelain ground between electrodes using insulating oil obtained by mixing silicon oil with silicon oil or the like (JP-A-4-179287).

If the oil compound is formed on the porcelain ground between the electrodes as a withstand voltage coating, it is possible to prevent a discharge short circuit between the electrodes when a high voltage is applied. However, since insulating oil such as silicon oil has a bad effect on adhesion or soldering in later processes, painting of insulating paint, etc., it is usually removed using a carbon chloride-based solvent after polarization treatment of piezoelectric ceramic elements. ing.

However, it is difficult to completely remove the insulating oil such as silicon oil from the base surface of the piezoelectric ceramic element, and it is unavoidable that it adversely affects the bonding or soldering, the coating of the insulating paint, etc. in a later process. . Also, using a carbon chloride-based solvent requires measures to prevent the effects on the environment.

[0005]

SUMMARY OF THE INVENTION In the present invention, a coating for withstand voltage is formed on a porcelain ground between electrodes without using an insulating oil such as silicon oil, and polarization treatment of a piezoelectric ceramic element is performed in air. It is an object of the present invention to provide a method of polarizing a piezoelectric ceramic element which can prevent a discharge short circuit between electrodes when a high voltage is applied.

Further, the present invention forms a withstand voltage coating which can be completely removed afterwards in a simple cleaning step on the porcelain ground between the electrodes, so that bonding or soldering in a later step can be performed.
In addition to preventing adverse effects on the coating of insulating paint, etc.,
It is an object of the present invention to provide a polarization method of a piezoelectric ceramic element capable of performing a polarization process such that a discharge short circuit does not occur between electrodes when a high voltage is applied.

Further, the present invention provides a piezoelectric device capable of performing a polarization treatment such that a discharge short circuit does not occur between the electrodes when a high voltage is applied by printing a withstand voltage coating capable of completely covering the porcelain ground between the electrodes. An object of the present invention is to provide a method for polarizing a porcelain element.

[0008]

According to a first aspect of the present invention, there is provided a method for polarizing a piezoelectric ceramic element, wherein an insulating paste in which an inorganic insulating material is mixed with an organic polymer material covers a porcelain ground between electrodes. A coating for voltage is formed, and a high voltage is applied to the double-sided electrodes of the piezoelectric ceramic element in the atmosphere.

According to a second aspect of the present invention, in the method for polarizing a piezoelectric ceramic element, a withstand voltage film is formed from an insulating paste obtained by mixing an inorganic insulator with a water-soluble organic polymer material. .

According to a third aspect of the present invention, there is provided a method for polarizing a piezoelectric ceramic element, comprising mixing an inorganic insulator of silica or alumina or a mixed inorganic insulator of silica and alumina with an organic polymer material in an amount of 40 to 80 wt%. A coating for withstand voltage is formed by printing from the paste.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, the illustrated embodiment sinters a disc-shaped piezoelectric ceramic element 1 from a ceramic material such as PZT as shown in FIGS. 1a and 1b. After forming and baking the double-sided electrodes 2 and 3 from the conductive material containing silver (Ag) as a main component on the ground surface of the piezoelectric ceramic element 1, an electric field of 1000 V / mm or more is applied to the double-sided electrodes 2 and 3. This is applied to perform polarization processing of the piezoelectric ceramic element 1 in the atmosphere.

In the piezoelectric ceramic element 1 shown in the figure, a ceramic ground 4 is formed so as to be exposed as an insulating gap between the double-sided electrodes 2 and 3 located on the same plane. As shown in FIGS. 2A and 2B, the piezoelectric ceramic element 1 is coated with an insulating paste in which an inorganic insulating material is mixed with an organic polymer material before the polarization treatment by applying a high voltage. Coating 5 is formed in a ring shape.

As the inorganic insulator of the insulating paste,
Silica (SiO ₂ ), alumina (Al ₂ O ₃ ) or a mixture of silica and alumina can be used. When these inorganic insulators are mixed, it is possible to impart not only electrical insulation properties but also a large volume resistivity.

An organic polymer material has been adopted as a binder which can be easily washed and removed with water, alcohol or the like after the polarization treatment of the piezoelectric ceramic element 1. In particular, when a water-soluble organic polymer material is used, a simple removal step of washing and removing can be applied. Examples of the water-soluble organic polymer material include water-soluble polyvinyl hirolidone (PVP).

If screen printing or the like is applied using the insulating paste, a high-precision coating film 5 for withstand voltage without exposing the porcelain ground 4 can be easily formed by printing.
Considering this printability, the case where silica is used as an inorganic insulator is exemplified.
It is good to mix 0 wt%. This is because if the mixing ratio of the inorganic insulator is 40 wt% or less, the withstand voltage coating 5 becomes inferior in electrical insulation, while if it is 80 wt% or more, good printability cannot be obtained. .

When a mixture with alumina or silica is used, it is preferable to mix about 60 wt% with an organic polymer material as a preferable example of both electric insulation and printability.
After forming a withstand voltage film 5 between the edges of the double-sided electrodes 2 and 3 using these insulating pastes, the withstand voltage film 5 is formed.
Can be obtained as a piezoelectric ceramic element 1 before polarization by heating and drying in the atmosphere.

The piezoelectric ceramic element 1 has 1000 V / m
By applying an electric field of m or more to the double-sided electrodes 2 and 3, polarization processing is performed in the air. As shown in FIG. 3, the polarization process includes a power supply 10 for applying a voltage, and a contact pin 11 connected to the power supply 10 and a jig for the piezoelectric ceramic element 1 on which the coating 5 for withstand voltage is formed. A polarization processing device including the table 12 can be applied.

In the polarization processing apparatus, the piezoelectric ceramic element 1 is placed on a plate surface by bringing the electrode 2 on one side into surface contact with the metal base 12, and the contact pin 11 is placed on the electrode 3 on the other side.
The DC voltage from the power supply 10 is applied to the piezoelectric ceramic element 1 so that the piezoelectric ceramic element 1 can be polarized in the atmosphere.
Further, the metal stage 12 is provided with a heater 13, and the polarization process can be promoted by heating the piezoelectric ceramic element 1 from the metal stage 13 with the application of a high voltage.

In order to confirm the effectiveness of the above-described polarization method, a piezoelectric ceramic element obtained by baking the double-sided electrode shown in FIG. 1 was obtained as a piezoelectric ceramic element, and a conventional example was used as a sample 1 without providing a withstand voltage coating. . On the other hand, as a comparative example, an insulating paste in which silica or alumina was mixed with an organic polymer material in which water-soluble polyvinyl pyrrolidone was dissolved in butyl carbitol was prepared in order to provide a coating for withstand voltage.

As the insulating paste, silica is mixed with the above organic polymer material at a mixing ratio of 20 wt%, 40 wt%,
A mixture of 60 wt%, 80 wt%, and 90 wt% was prepared. Samples 2 to 7 with the respective mixing ratios were printed on the porcelain ground of the piezoelectric ceramic element. Samples 2 to 6 with the mixing ratio of 20 to 80 wt% had a ring-shaped withstand voltage for which the base was not exposed. Printing was good as a coating. But
Sample 7 having a mixing ratio of 90 wt% could not be printed as a withstand voltage film due to its viscosity.

Also, an insulating paste in which alumina was mixed with the same organic polymer material at 60 wt% was prepared, and the insulating paste was printed as a sample 8 on the porcelain ground of the piezoelectric ceramic element. It was printed well as a ring-like withstand voltage coating with no bare ground. Except for Sample 7, Samples 2 to 6 and Sample 8 were subjected to a drying treatment in the atmosphere at a temperature of 100 ° C. for 10 minutes to obtain a piezoelectric ceramic element before polarization. Each of these samples including Sample 1 was prepared in the same number.

The sample 1, sample 2 to 6 and sample 8 were applied to the polarization processing apparatus shown in FIG.
Was applied to the double-sided electrode for 5 to 6 minutes. Along with the application of the high voltage, each piezoelectric ceramic element was heated at about 50 ° C. with a heater from a metal table of the polarization processing apparatus. Each piezoelectric ceramic element after the application of the voltage was returned to normal temperature and inspected for discharge failure. As shown in Table 1 below, 70% for the conventional sample 1, 60% for the sample 2, and 3% for the sample 2. Showed a discharge failure of 40%. In contrast, Samples 4 to 6 and Sample 8 did not show any discharge failure.

[0023]

[Table 1]

Prior to the inspection for the discharge failure, samples 2 to
6 and Sample 8 were subjected to an ultrasonic cleaning with water to remove the withstand voltage coating. Both coatings are made of an insulating paste with a binder made of an organic polymer material in which water-soluble polyvinyl pyrrolidone is dissolved in butyl carbitol, so they can be completely removed by simple equipment such as ultrasonic cleaning with water. Was completed.

Although the above embodiment has been described based on a piezoelectric ceramic element formed from a PZT-based ceramic material, the piezoelectric ceramic element is formed from a lead titanate-based ceramic material by appropriately setting an electric field value, a heating temperature, and the like. The same can be applied to piezoelectric ceramic elements. Also, the present invention is not limited to the case where the double-sided electrodes are provided on a disc-shaped piezoelectric ceramic element, and can be applied to polarization processing of piezoelectric ceramic elements formed in various shapes such as a square shape.

As a preferred example of the organic polymer material, a material obtained by dissolving water-soluble polyvinyl pyrrolidone with butyl carbitol is mentioned. Any organic polymer material having solubility can be used. Depending on the selected organic polymer material, the mixing ratio of the inorganic insulator can be appropriately set based on requirements such as electric insulation and printability.

[0027]

As described above, according to the polarization method of the piezoelectric ceramic element according to the first aspect of the present invention, the porcelain ground between the electrodes is covered with an insulating paste in which an inorganic insulator is mixed with an organic polymer material. By forming a film for withstanding voltage 4 and applying a high voltage to the double-sided electrodes of the piezoelectric ceramic element in the atmosphere,
It is possible to prevent the occurrence of a discharge short circuit between the electrodes when a high voltage is applied by using a coating not made of insulating oil such as silicon oil.

According to the method for polarizing a piezoelectric ceramic element according to claim 2 of the present invention, a withstand voltage film is formed from an insulating paste in which an inorganic insulator is mixed with a water-soluble organic polymer material. A coating for withstand voltage that can be completely removed by a simple process of washing with water can be formed on the porcelain ground between the electrodes,
Polarization can be performed so that short-circuiting does not occur between the electrodes when high voltage is applied. In addition, it is possible to prevent adverse effects on adhesion or soldering in the subsequent process, coating of insulating paint, etc., and a coating for withstand voltage. The effect on the environment by the removal is reliably suppressed.

According to the method for polarizing a piezoelectric ceramic element according to claim 3 of the present invention, an inorganic insulator of silica or alumina or a mixed inorganic insulator of silica and alumina is used in an amount of 40 to 8%.
Since a coating for withstand voltage is formed by printing from an insulating paste mixed with an organic polymer material at 0 wt%, a coating for withstand voltage that does not expose a bare ground can be formed with high precision even when an inorganic insulator is mixed. At the same time, it is possible to reliably prevent a discharge short circuit between the electrodes when a high voltage is applied.

[Brief description of the drawings]

FIG. 1a is a plan view showing a piezoelectric ceramic element before a withstand voltage coating is formed by a method according to the present invention.

FIG. 1b is a side sectional view showing the piezoelectric ceramic element of FIG. 1a.

FIG. 2a is a plan view showing a piezoelectric ceramic element after a withstand voltage coating is formed by a method according to the present invention.

2b is a side sectional view showing the piezoelectric ceramic element of FIG. 2a.

FIG. 3 is an explanatory view schematically showing a configuration of a polarization processing device together with a piezoelectric ceramic element having a withstand voltage coating formed by a method according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 piezoelectric ceramic element 2, 3 double-sided electrode 4 ceramic ground

Claims (3)

[Claims] 1. A method for polarizing a piezoelectric ceramic element by applying a high voltage to both electrodes of the piezoelectric ceramic element in the atmosphere, the method comprising a step of polarizing the piezoelectric ceramic element. A method for polarizing a piezoelectric ceramic element, comprising forming a withstand voltage coating for covering a ceramic ground between electrodes from a paste, and applying a high voltage in the atmosphere to both side electrodes of the piezoelectric ceramic element. . 2. The polarization method for a piezoelectric ceramic element according to claim 1, wherein a withstand voltage film is formed from an insulating paste obtained by mixing an inorganic insulator with a water-soluble organic polymer material. . 3. A voltage-resistant coating is formed by printing from an insulating paste in which an inorganic insulating material of silica or alumina or a mixed inorganic insulating material of silica and alumina is mixed with an organic polymer material in an amount of 40 to 80% by weight. 3. The method according to claim 1, wherein the piezoelectric ceramic element is polarized.