JPS63313878A - Composite electrostrictive material and ultrasonic probe - Google Patents

Abstract

PURPOSE:To control piezoelectricity from the outside, and to reduce mechanical linkage in the cross direction by using the composite electrostrictive material of an electrostrictive material, in which piezoelectricity is induced by a biassed electric field, and organic matter. CONSTITUTION:A large number of columnar electrostrictive materials 12, in which piezoelectricity is induced by a biassed electric field, are buried vertically to a sheet surface in a sheet-shaped organic matter 11. That is, since the mechanical linkage in the cross direction of a composite electrostrictive material, in which the electrostrictive material, an electromechanical coupling factor of which is increased suddenly from a certain electric field strength Ec, and the flexible organic matter are brought to a composite state, is weakened, an array vibrator in which each vibration element is independently operated effectively only by patterning array electrodes can be composed. Since only a section under the electrode to which a biassed electric field is applied is brought to a piezoelectric active state, the drive of peripheral elements in the leakage electric field of a driving electric field can be prevented when the biassed electric field is selectively applied previously only to a section to which a driving pulse electric field is applied.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an ultrasound probe used in an ultrasound diagnostic device, particularly an electronic scanning probe, and an electroacoustic transducer material for the ultrasound probe. It is something.

[Prior Art] In a conventional electronic scanning probe, a large number of rectangular vibrating elements are arranged one-dimensionally, and the ultrasonic beam pattern seen from the arrangement direction (long axis direction) is determined by the number of driving elements (therefore, It can be controlled by changing the aperture) and the phase of the electrical signal applied to each drive element. However, since the aperture and focal point are fixed in the direction perpendicular to the arrangement direction (short axis direction), a problem arises in that the resolution in the short axis direction is insufficient depending on the depth.

Therefore, in order to solve this problem, we divided the electrodes on both the upper and lower surfaces of the piezoelectric vibrator along the long axis direction and the short axis direction, respectively, and changed the aperture in the short axis direction as well as in the long axis direction. Ultrasonic probes based on
-21057). However, with this ultrasonic probe, even if a driving electric field is selectively applied between the divided electrodes on the upper and lower surfaces of the piezoelectric vibrator, the leakage electric field and mechanical coupling will also excite the surrounding area, making it insufficiently effective. may not be obtained.

[Problems to be Solved by the Invention] One object of the present invention is that piezoelectricity can be externally controlled;
Another object of the present invention is to provide a composite electrostrictive material that is a novel material that can be used as an electro-acoustic transducer element with small mechanical coupling in the lateral direction.

Another object of the present invention is to effectively utilize the properties of the composite voltage material to drive peripheral elements by the leakage electric field and mechanical coupling generated when a driving electric field is selectively applied between the divided electrodes on the upper and lower surfaces. The purpose of the present invention is to provide an ultrasonic probe with a variable aperture that will never be used.

[Means for Solving the Problems] The present invention is characterized by a composite electrostrictive material having a structure in which a large number of columnar electrostrictive materials whose piezoelectricity is induced by a bias electric field are embedded perpendicularly to the sheet surface in a sheet-like organic material. In strained materials.

Another feature of the present invention resides in an ultrasonic probe using the above-mentioned composite electrostrictive material in an electro-ultrasonic conversion section.

[Function] The electrostrictive material described in the present invention is a material that exhibits piezoelectricity only when a bias electric field is applied.As shown in Figure 2, the electromechanical coupling coefficient is extremely low when the bias electric field is small. There are also materials whose electromechanical coupling coefficient suddenly increases from a small electric field strength E0. Composite electrostrictive materials (Fig. 1), which are a combination of such electrostrictive materials and soft organic matter, have weak lateral mechanical bonds, so they can be made effectively by simply patterning array electrodes. It is possible to construct an array vibrator in which each vibrating element operates independently. Furthermore, since only the part under the electrode to which the bias electric field is applied is piezoelectrically active, if the bias electric field is selectively applied only to the part to which the driving pulse electric field is applied, the leakage electric field of the driving electric field can be reduced. Even if the voltage is applied to these elements, these peripheral elements will not be driven.

[Example] Zircon lead titanate Pb (Zr(1
4. So-called PLZT ceramics, which is Ti(1,35)03 doped with L'a, was used. Although the bias electric field dependence of piezoelectric characteristics differs depending on the amount of La doped, PLZT ceramics containing 10 mol % of La1i-Pb was used here. In this case, E in FIG. The value was 2.5 KV/cm.

80 mm square of PLZT ceramic with the above composition, thickness 0.
A 4 mm flat plate was adhered onto a ferrite substrate using electron wax. This ceramic plate was cut into a mesh shape with a diamond blade having a thickness of 30 μm. A sheet-like composite electrostrictive material with a thickness of 0.4111 m obtained by filling the grooves created by cutting with polyurethane resin and solidifying it was peeled off from the ferrite substrate by melting the electron wax.

A rectangular plate 31 cut out from such a composite electrostrictive material is formed with ground electrodes 32, 33° 34 divided into three parts along the long axis direction as shown in FIG. A hot electrode array 35 was formed on the surface. This rectangular plate was glued to a backing material with the hot electrode side facing down, an acoustic matching layer was provided on the ground electrode, and an electronic scanning linear probe was assembled. In such an ultrasonic probe, only when a DC bias electric field is applied between the hot electrode and the ground electrode, the portion where the electrodes face each other becomes piezoelectrically active. Therefore, by applying a bias electric field only between the hot electrode and the ground electrode used, the aperture in the minor axis direction can be effectively changed.

As a result of actual ultrasonic beam forming experiments, we found that when a bias electric field is applied only between the hot electrode and the central earth electrode, the bias electric field is applied between the hot electrode and all earth electrodes. It was found that the width of the ultrasonic beam as seen from the short axis direction was narrower at short distances compared to the case where the ultrasonic beam was used as a beam. This is considered to be because the aperture in the short axis direction is effectively reduced. In other words, it was confirmed that the ultrasonic beam pattern viewed from the short axis direction can be controlled by changing the distribution of the bias electric field.

In the above embodiment, the number of divisions of the earth electrode was set to 3, but
It is obvious that it is not limited to this and may be divided into any number of parts.

[Effects of the Invention] As explained above, by using an electrostrictive material whose piezoelectricity is induced by a bias electric field and a composite electrostrictive material of an organic material, an electronic scanning linear probe whose aperture in the short axis direction is variable is created. However, according to the present invention, any bias electric field distribution can be given not only to such an ultrasonic probe but also generally.

It is clear that it is possible to realize a probe that can control an ultrasound beam by giving an arbitrary weight distribution to the electroacoustic conversion efficiency. For example, by providing a two-dimensional bias electric field distribution, it is possible to realize a two-dimensionally arrayed ultrasound probe that can selectively transmit and receive ultrasound beams.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the concept of the composite electrostrictive material of the present invention, Figure 2 is a diagram showing the concept of the composite electrostrictive material of the present invention.
The figure is a diagram showing an example of the characteristics of an electrostrictive material, and FIG. 3 is a diagram showing an embodiment of the ultrasonic probe of the present invention. 11... Organic substance, 12... Electrostrictive material whose piezoelectricity is induced by a bias electric field, 21... An example of the bias electric field dependence of the electromechanical coupling coefficient of an electrostrictive material, 31...
Composite electrostrictive material, 32-34... Earth electrode, 3.5.
...Hot electrode array.

Claims (1)

[Claims] 1. A composite electrostrictive material having a structure in which a large number of columnar electrostrictive materials whose piezoelectricity is induced by a bias electric field are embedded perpendicularly to the sheet surface in a sheet-like organic material. 2. A composite electrostrictive material having a structure in which a large number of columnar electrostrictive materials whose piezoelectricity is induced by a bias electric field are embedded perpendicularly to the sheet surface in a sheet-like organic material is used in the electro-ultrasonic converter. Ultrasonic probe. 3. A sheet of composite voltage material having a structure in which a large number of columnar electrostrictive materials whose piezoelectricity is induced by a bias electric field are embedded perpendicularly to the sheet surface in a sheet-like organic material has array electrodes on one side; An ultrasonic probe comprising an array of electrodes on the other surface in a direction perpendicular to the array direction of the array electrodes.