JP2001025094A - 1-3 composite piezoelectric body - Google Patents

Abstract

(57) [Summary] [Problem] Desired weighting [weighting of amplitude (sound pressure)]
The present invention provides a 1-3 composite piezoelectric body having a desired weight on the piezoelectric body itself so as to perform the above at low cost. SOLUTION: In a 1-3 composite piezoelectric body composed of a piezoelectric ceramic and a polymer material, the 1-3 composite piezoelectric body has a structure in which the volume fraction of the piezoelectric ceramic is changed. That is, the ratio between the volume of the piezoelectric ceramic and the volume of the polymer material in the 1-3 composite piezoelectric body is partially changed along the slice direction at the time of manufacturing the ultrasonic probe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1-3 composite piezoelectric material suitable for an ultrasonic probe.

[0002]

2. Description of the Related Art A 1-3 composite piezoelectric material is manufactured by combining a piezoelectric ceramic having a high electromechanical coupling coefficient with a polymer material having a low acoustic impedance, has a high electromechanical coupling coefficient, and As a piezoelectric vibrator having a low acoustic impedance, it is suitably used for an ultrasonic probe.

[0003] In an ultrasonic probe using a piezoelectric vibrator, an acoustic lens is generally provided, and an ultrasonic lens is provided by the acoustic lens in a direction (slice direction, elevation direction) orthogonal to the arrangement direction of the piezoelectric vibrators. Focusing the beam has been performed. That is, the ultrasonic beam is narrowed down by the electronic focus in the arrangement direction (electronic scanning direction), and the ultrasonic beam is narrowed down by the acoustic lens in the slice direction.

However, although the convergence of the ultrasonic beam by the acoustic lens is good near the focal point, in a region other than the focal point, particularly in the region near the ultrasonic probe, a good slice is obtained by only the acoustic lens. Since the resolution in the direction cannot be obtained, conventionally, acoustic apodization (weighting of amplitude (sound pressure)) is performed along the slice direction to reduce the above problem. For example, a method of changing the polarizability in the slice direction, a method of changing the electrode density, and the like are employed.

However, these methods have a problem that apodization cannot be easily performed at low cost.

For example, in the method of changing the polarizability, the process for the polarization process is complicated, and the manufacturing cost increases.
In this method, the polarizability becomes unstable in a region where the polarizability does not reach 100%. On the other hand, the method of changing the electrode density requires a precise etching technique and the like, and also in this case, the manufacturing cost increases. Further, Japanese Unexamined Patent Application Publication No. 5-76
Japanese Patent Publication No. 527 proposes that apodization is performed by arranging a plurality of piezoelectric plates having different electromechanical coupling coefficients. However, in this case as well, the process is very complicated and the manufacturing cost is increased.

In addition, in the apodization method as described above, weighting of at most about three steps is a limit in terms of manufacturing and cost.

As described above, conventionally, apodization has been performed through a complicated process in order to obtain a higher-performance ultrasonic probe, but the apodization can be performed without such a complicated process. Further, there is a demand for a piezoelectric body having a weight given to itself.

According to the present invention, a piezoelectric element having a desired weight is provided so that the desired weight can be obtained at low cost without using the apodization method as described above.
A third object is to provide a composite piezoelectric body.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made in consideration of a 1-3 composite piezoelectric body comprising piezoelectric ceramics and a polymer material.
The composite piezoelectric body has a structure in which the volume fraction of the piezoelectric ceramic is changed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, examples of piezoelectric ceramics include lead zirconate titanate (PZT).
, Lead titanate, barium titanate, bismuth titanate, and other piezoelectric ceramics can be used. In particular, PZT (ie, lead zirconate titanate, but hereinafter referred to as “PZT”) Piezoelectric ceramics (simplified) are preferred because they have higher electromechanical coupling coefficients and dielectric constants.

In the present invention, as the polymer material, for example, polyurethane resin, epoxy resin, silicone resin,
Acrylic resin or the like can be used, and can be selectively used from soft to hard depending on the application.

Next, the structure of the 1-3 composite piezoelectric body of the present invention will be described with reference to the drawings. Prior to this, a general 1-3 composite piezoelectric body will be described with reference to FIG.
The three-composite piezoelectric body 1 is composed of a piezoelectric ceramic 2 and a polymer material 3 in terms of material, and is structurally
Is embedded in a three-dimensional matrix of the polymer material 3. FIG. 4 shows a case where the one-dimensional thin rod of the piezoelectric ceramics 2 is a prism. However, the thin rods of the piezoelectric ceramics 2 in the 1-3 composite piezoelectric body are not limited to the prisms, and may have a columnar shape. Other shapes may be used. This is not limited to the case of the general 1-3 composite piezoelectric body shown in FIG. 4, but the same applies to the 1-3 composite piezoelectric body of the present invention.

After electrodes are formed on the upper and lower surfaces of the above-mentioned 1-3 composite piezoelectric body by a sputtering method or the like,
By applying a predetermined DC voltage to the above-described 1-3 composite piezoelectric body at a predetermined temperature and performing polarization processing, a composite piezoelectric vibrator having a desired electromechanical coupling coefficient and a desired dielectric constant can be obtained.

However, in the conventional 1-3 composite piezoelectric body 1 as shown in FIG. 4, the ratio of the volume of the piezoelectric ceramics 2 to the volume of the polymer material 3 is constant. In other words,
The volume ratio of the piezoelectric ceramic in the 1-3 composite piezoelectric body is constant. This is the same even when the thin rod of the piezoelectric ceramics 2 is a cylinder or another shape.

The structure in which the volume fraction of the piezoelectric ceramic in the present invention is changed means that acoustic apodization (weighting) is performed along a slice direction at the time of manufacturing an ultrasonic probe.
In this case, the ratio of the volume of the piezoelectric ceramic in the 1-3 composite piezoelectric material to the volume of the polymer material is partially changed along the slice direction.

FIGS. 1 and 2 show an example in which weighting is performed in three stages in the 1-3 composite piezoelectric material of the present invention. The piezoelectric ceramics 2 has a prismatic shape, and the upper surface thereof is shown in FIGS. 1 and 2 as a rectangular shape having three different areas, but when weighted in three stages as described above, the A zone , The zone B and the zone C have a structure in which the volume fraction of the piezoelectric ceramic is changed along the slice direction at the time of producing the ultrasonic probe, and the volume fraction of the piezoelectric ceramic in the zone A is the largest, Next, the volume fraction of the piezoelectric ceramic in the zone B is large, and the volume fraction of the piezoelectric ceramic in the zone C is smallest. This Figure 1
Also, the 1-3 composite piezoelectric body of the present invention shown in FIG. 2 is made of a piezoelectric ceramic 2 and a polymer material 3 and is made of a one-dimensional thin rod of the piezoelectric ceramic 2 (in this example, a prism is used. , Its shape may be another shape such as a columnar shape)
4 except that the upper surface is embedded in a three-dimensional matrix of the polymer material 3 except for the upper surface.
Is the same as the general 1-3 composite piezoelectric material shown in FIG. 1, except that the volume fraction of the piezoelectric ceramics 2 in the 1-3 composite piezoelectric material of the present invention changes along the slice direction. -3 composite piezoelectric body. FIG.
Although the three composite piezoelectric bodies are schematically shown, the arrangement direction is shorter than the slice direction, but in an actual 1-3 composite piezoelectric body, the arrangement direction is longer than the slice direction. Many. 1 and 2, the number of piezoelectric ceramic fine bars arranged in the A zone, the B zone, and the C zone is also smaller than that described in the later-described embodiment.

Electrodes are formed on the upper and lower surfaces of the 1-3 composite piezoelectric body. After the 1-3 composite piezoelectric body is polarized, an ultrasonic probe is assembled according to a conventional method, and its transmission sound pressure is set. When the distribution was examined, as shown in FIG.
Three levels of sound pressure distribution corresponding to the B zone and the C zone are shown. In FIG. 3, the horizontal axis is the distance (mm) from the center of the piezoelectric body (1-3 composite piezoelectric body) in the slice direction, and the vertical axis is the transmission relative sound pressure. The direction in which the 1-3 composite piezoelectric body is cut in manufacturing the ultrasonic probe is parallel to the slice direction shown in FIG.

In the present invention, of course, the volume fraction of the piezoelectric ceramic can be variously changed according to the transmission sound pressure distribution of the ultrasonic probe to be manufactured. Also, by changing the volume fraction of the piezoelectric ceramic in any number of steps as desired, the steps of the sound pressure distribution can be finely set.

In the present invention, as a method of changing the volume fraction of the piezoelectric ceramic, there are a method of changing the volume of the piezoelectric ceramic in units of area, a method of changing the volume of the polymer material in units of area, and a method of changing both in units of area. is there.

Next, an example of a method for producing the 1-3 composite piezoelectric material of the present invention will be described.

In the 1-3 composite piezoelectric body of the present invention, for example, a groove is formed on a piezoelectric ceramic plate by a dicing machine,
After the grooves are filled with a polymer material and cured, both sides are lapped and polished with a lapping machine.

At this time, the volume fraction of the piezoelectric ceramic can be changed by changing the width of the groove to be formed and the interval between the grooves.

[0024]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 Using a dicing machine, grooves having a width of 30 μm were formed in a PZT piezoelectric ceramic plate along the arrangement direction.
At that time, from the edge of the piezoelectric ceramic plate, the grooves to be formed are arranged in the order of 30 lines at intervals of 20 μm, 21 lines at intervals of 40 μm, 44 lines at intervals of 60 μm, 21 lines at intervals of 40 μm, and 30 lines at intervals of 20 μm. Along with the number of grooves.

Next, an epoxy resin was poured into the groove, and after degassing in a vacuum, the epoxy resin was cured. Then
After forming grooves having a width of 30 μm at intervals of 60 μm along the slice direction, an epoxy resin was poured into the grooves, and after vacuum degassing, the epoxy resin was cured.

The upper and lower surfaces of the piezoelectric ceramic-polymer composite were lapped and polished with a double-sided lapping machine. The width of the A zone was 3.96 mm, and the width of the B zone was 1.times. 47mm, C zone width is B
Each of the two sides of the zone has a thickness of 1.50 mm and a thickness of 380 μm, and the structure is schematically shown in FIGS.
Three composite piezoelectric bodies were obtained.

In the A zone of the 1-3 composite piezoelectric body manufactured as described above, one unit is 60 μm × 60 μm.
The structure was such that an epoxy resin was surrounded with a width of 30 μm around a prism of × 380 μm PZT-based piezoelectric ceramics, and the volume fraction of the piezoelectric ceramics was 44%.

In the B zone, one unit is 40 μm.
It has a structure in which an epoxy resin is surrounded by a 30 μm width around a prism of m × 60 μm × 380 μm PZT piezoelectric ceramics, and the volume fraction of the piezoelectric ceramics is 38%.
Met.

In the C zone, one unit is 20 μm × 6
The structure was such that an epoxy resin was surrounded by a 30 μm width around a prism of 0 μm × 380 μm PZT piezoelectric ceramics, and the volume fraction of the piezoelectric ceramics was 27%.

After forming electrodes on the upper and lower surfaces of the 1-3 composite piezoelectric body by gold sputtering, the 1-3 composite piezoelectric body which has been subjected to polarization processing is assembled into an ultrasonic probe according to a conventional method. When examining the sound pressure distribution of the transmitted wave,
The transmission sound pressure distribution was as shown in FIG.

In the first embodiment described above, three levels of weighting are used. In the present invention, the length of one unit of the piezoelectric ceramic or the width of the polymer material is finely changed in the slice direction. Thus, weighting can be performed in any number of stages.

To change the shape of the transmission sound pressure distribution,
This can be performed by changing the volume fraction of the piezoelectric ceramic in the zone. For example, in order to sharpen the distribution, it is possible to lower the volume fraction of the piezoelectric ceramic in the B zone or the C zone.

[0034]

As described above, according to the present invention,
It is possible to provide a 1-3 composite piezoelectric body that can be easily weighted at a low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing one embodiment of a 1-3 composite piezoelectric body of the present invention.

FIG. 2 is an enlarged plan view showing a part of the 1-3 composite piezoelectric body shown in FIG.

FIG. 3 is a diagram showing an example of a transmission sound pressure distribution when the 1-3 composite piezoelectric material of the present invention is used.

FIG. 4 is a perspective view schematically showing an example of a general 1-3 composite piezoelectric body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1-3 Composite piezoelectric material 2 Piezoelectric ceramics 3 Polymer material

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[Procedure amendment]

[Submission date] April 14, 2000 (2004.1.
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a 1-3 composite piezoelectric material having a desired weight on the piezoelectric material itself so that the desired weight can be obtained at low cost without using the apodization method as described above. The purpose is to provide the body.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyuki Minoba 1-3-47 Funamachi, Taisho-ku, Osaka Teika F-term (reference) 4C301 EE17 GB10 GB14 GB33 GB36 GB37 GB39 5D019 AA01 BB02 BB04 BB05 BB19 FF03 GG03

Claims (1)

[Claims] 1. A 1-3 composite piezoelectric body comprising a piezoelectric ceramic and a polymer material, wherein the 1-3 composite piezoelectric body has a structure in which the volume fraction of the piezoelectric ceramic is changed. Composite piezoelectric body.