JPH0481113A - Piezoelectric resonance element - Google Patents

Abstract

PURPOSE:To realize a piezoelectric resonance element whose polarity degree is accurately controlled to a desired value by forming the resonator with a part of a piezoelectric ceramic substrate polarized with a tilt in the broadwise direction and with a vibration electrode. CONSTITUTION:Since electrodes 2a, 2b and 3a, 3b are opposed to each other at a prescribed position with a substrate 1 inbetween, polarization P1 is formed perpendicular to the broadwise direction of the substrate 1 from the electrodes 2a, 2b with a negative voltage applied to them to the electrodes 3a, 3b with a positive voltage applied to them in a very stable state. Similarly, since electrodes 3a, 3b and 4a, 4b are opposed to each other at a prescribed position with a substrate 1 inbetween, polarization P2 is formed at a tilt angle theta in the broadwise direction of the substrate 1 from the electrodes 4a, 4b with a negative voltage applied to them to the electrodes 3a, 3b with a positive voltage applied to them in a very stable state. After the polarization P1, P2 is formed in this way, the electrodes 2a-4b for polarization processing is removed. Then the degree of polarization is adjusted by varying a tilt angle of polarization in the broadwise direction of the piezoelectric ceramics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric resonant element constituting a piezoelectric resonant component used in filter circuits, oscillation circuits, and the like.

Prior Art and Problems As this type of piezoelectric resonant element, those shown in FIGS. 9 to 11 are known. As the substrates 30, 35, and 40, piezoelectric ceramic substrates subjected to polarization treatment are used. Vibrating electrodes 31a, 31b, 36a, 36b, 4 are provided on the surfaces of these piezoelectric substrates 30, 35, 40, respectively.
1a.

41b is provided. Conventionally, substrate 30.35.40
When polarization treatment is applied to the substrate 30, the polarization P5 is parallel to the thickness direction (see Fig. 9), as is the case with the substrate 30.
Polarization P6 is perpendicular to the thickness direction as shown in 5 (see Figure 10), or parallel to the thickness direction as in the case of the substrate 40.
and polarization P7. in the opposite direction. P7'l (see Figure 11).

By the way, in the polarization process, when controlling the degree of polarization to a desired value in order to adjust the electromechanical coupling coefficient, a method is adopted in which the value of the DC applied voltage for the polarization process is increased or decreased. There is. However, there is a problem that when the applied voltage value is low, it is difficult to accurately control the degree of polarization to a desired value.

Therefore, an object of the present invention is to provide a piezoelectric resonant element whose degree of polarization can be accurately controlled to a desired value.

In order to solve the above problems, the piezoelectric resonant element according to the present invention has a piezoelectric resonant element in which at least a portion of a piezoelectric ceramic substrate is tilted and polarized in the thickness direction, and the piezoelectric ceramic of the polarized portion is polarized. The present invention is characterized in that the substrate and the vibrating electrode constitute at least one resonator.

In the above-described structure, the piezoelectric ceramic substrate and the vibrating electrode constitute a resonator that is polarized at an angle in the thickness direction, so that the degree of polarization can be determined by the angle of inclination of the polarization with respect to the thickness direction. In other words, the degree of polarization is not adjusted by increasing or decreasing the voltage applied for polarization treatment as in the past, but by changing the angle of inclination of polarization with respect to the thickness direction of the piezoelectric ceramic substrate. be done.

At this time, the polarization processing voltage is always set to a high voltage (for example, the limit voltage of the piezoelectric ceramic substrate material), and the polarization processing is performed in an extremely stable state.

EXAMPLE Hereinafter, an example of a piezoelectric resonant element according to the present invention will be described with reference to the accompanying drawings.

1 and 2 show a method for polarizing a piezoelectric ceramic substrate 1. FIG. For the substrate 1, BaTiOs, Pb(Zrli)O, or the like is used. On the front and back surfaces of the substrate 10, polarization processing electrodes 2a, 2b, 3a, 3b,
4a and 4b are brought into contact with each other, and a high DC voltage for polarization treatment, for example, the limit voltage of the substrate 1, is applied to each electrode 2a to 4b. Electrodes 2a and 2b, 3a and 3b, 4
A and 4b are at the same potential and are connected to each other.

The polarization states of the substrate 1 at portions AA' and BB' in FIG. 1 are shown in FIGS. 3 and 4, respectively. In Figure 3,
Since the electrodes 2a, 2b and 3a, 3b face each other at the same position with the substrate 1 in between, the electrodes 2a, 2b and 3a, 3b to which a negative voltage is applied,
Electrode 3a to which a positive voltage is applied from electrode 2b.

In the direction 3b, polarization PI perpendicular to the thickness direction of the substrate 1 can be formed in an extremely stable state. Similarly, in FIG. 4, the electrodes 3a, 3b and 4a, 4b are opposed to each other with the substrate 1 in between, so that the electrode 4 to which a negative voltage is applied is
In the direction of electrodes 3a and 3b to which a positive voltage is applied from a and 4b, polarization P is generated at an inclination angle θ with respect to the thickness direction of the substrate 1.
2 is formed in an extremely stable state. Thus the polarization P
After I and P2 are formed, the polarization processing electrodes 2a to 4b are removed.

As shown in FIGS. 5 and 6, polarization P1. The substrate 1 on which P2 is formed has polarization P1. Vibrating electrodes 5a, 5b, 5c and 6a, 6b, 6c are provided on the portion where P2 is formed.
is provided.

In this way, a resonator F1 is constituted by the vibrating electrodes 5a, 5b, 5c and the polarization P1 forming part, and the vibrating electrodes 6a, 6
A resonator F2 is constituted by the portions b and 6c and the polarization P2 forming portion. At this time, the resonators F1 and F2 are arranged so that the vibrations generated by each resonator do not interfere with each other.

The obtained piezoelectric resonant element is sandwiched, for example, between upper and lower sealing substrates to form a piezoelectric resonant component. The piezoelectric ceramic substrate 1 of this piezoelectric resonant element has a resonator F2 having a desired degree of polarization by changing the inclination angle θ of the polarization P2.
is obtained, and since the polarization treatment voltage value is high, stable polarization treatment is possible.

By the way, the direction and arrangement of polarization formed on the piezoelectric ceramic substrate 1 are arbitrary, and as shown in FIG.
are sandwiched between the substrates 1 and brought into contact with each other at shifted positions, and the polarization P is inclined in the thickness direction of the substrate 1 from the electrode 10b to which a negative voltage is applied to the electrode 10a to which a positive voltage is applied.
3 may be formed.

Further, as shown in FIG. 8, three single poles 15a, 15b, and 15c for polarization treatment are brought into contact with the front and back surfaces of the substrate 1 at shifted positions with the substrate 1 sandwiched between them, and a negative voltage is applied. The electrodes 15a, 1 to which a positive voltage was applied from the electrode 15c
Polarization P4.5b in two directions. F4' may also be formed.

Furthermore, in addition to the polarized portions tilted in the thickness direction, polarized portions parallel to the thickness direction and polarized portions perpendicular to the thickness direction are arranged in arbitrary combinations on a single piezoelectric ceramic 7X substrate. It's okay.

Furthermore, the direction of polarization and the positional relationship between the vibrating electrodes are arbitrary. For example, when multiple resonators are provided on a single piezoelectric ceramic substrate, the vibrations of the resonators should be adjusted so that their vibrations do not interfere with each other. It is possible to provide electrodes, or to combine the directions of polarization of each resonator so that the resonators mutually compensate for temperature in order to reduce the temperature characteristics of the resonant frequency.

Effects of the Invention As described above, according to the present invention, since a resonator is constituted by a piezoelectric ceramic substrate and a vibrating electrode which are polarized at an angle in the thickness direction, the degree of polarization can be adjusted depending on the angle of inclination of polarization. Moreover, by always setting the polarization processing voltage value to a high value, stable polarization processing is possible. As a result, a piezoelectric resonant element whose degree of polarization is accurately controlled to a desired value is obtained.

Further, since the polarization direction of the piezoelectric ceramic substrate and the positional relationship between the vibrating electrode can be set arbitrarily, the degree of freedom in designing the piezoelectric resonant element is increased.

[Brief explanation of the drawing]

1 to 6 show an embodiment of a piezoelectric resonant element according to the present invention, and FIGS. 1 and 2 are a perspective view and a plan view showing polarization treatment of a piezoelectric ceramic substrate, respectively;
3 and 4 are schematic diagrams showing the polarization state of the portions AA' and BB' in Figure 1 and the positional relationship between the polarization processing electrodes, and Figure 5 is a perspective view of the piezoelectric resonant element. , FIG. 6 is a schematic diagram showing the polarization state of the portion c-c' in FIG. 5 and the positional relationship between the vibrating electrode. FIGS. 7 and 8 are schematic diagrams showing other polarization states of the piezoelectric ceramic substrate and the positional relationship between the polarization processing electrodes. FIG. 9, FIG. 10, and FIG. 11 are perspective views showing the polarization states of conventional piezoelectric resonant elements, respectively. 1... Piezoelectric ceramic substrate, 6a, 6b, 6
c... Vibrating electrode, F2... Resonator, F2. F3.
F4. P4°...Polarization, θ...Polarization inclination angle. Patent applicant Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A piezoelectric resonator element, characterized in that at least a portion of a piezoelectric ceramic substrate is polarized at an angle in the thickness direction, and the polarized portion of the piezoelectric ceramic substrate and a vibrating electrode constitute at least one resonator.