JPS62261300A - Compound piezoelectric material for ultrasonic probe - Google Patents

Abstract

PURPOSE:To suppress an unnecessary vibration to thickness, height and vibration by making the shape of a pillar-shaped piezoelectric piece into the parallel plane to which only both main surfaces in the thickness direction face, forming it to the polygonal shape which is not orthogonal to an adjoining sude surface, filling up a linking material between respective pillar-shaped piezoelectric pieces and making it into a compound piezoelectric plate. CONSTITUTION:A compound piezoelectric material 1 arranges plural pillar- shaped piezoelectric bodies 2 composed of a PZT. The plane shape of the pillar- shaped piezoelectric bodies 2 is made into an equilateral triangle. A linking material 3 composed of an organic material at the clearance between respective pillar-shaped piezoelectric bodies 2. Actually, an electrode 4 is formed at both main surfaces of the compound piezoelectric material 1, a lead wire not shown in the figure is derived and a driving pulse is impressed. Since the distance sides (b) and (c) to for example the side (a) of a main surface comes to be successively smaller with a vertical angle point A as maximum, a resonance phenomenon is not shown in a special frequency in a transverse (length) direction. For such a reason, for the unnecessary ultrasonic wave in the horizontal direction, an energy level in the height direction is lowered.

Description

Detailed Description of the Invention (Field of Application of the Invention) The field of the present invention is a composite piezoelectric material for an ultrasonic probe in which a large number of piezoelectric bodies are connected by a bonding material. This invention relates to a composite piezoelectric material that suppresses .

(Background of the Invention) Ultrasonic probes used in, for example, medical ultrasonic diagnostic devices usually use a piezoelectric material as a source for transmitting and receiving ultrasonic waves. This piezoelectric material includes, for example, lead zirconate titanate (
There are piezoelectric materials made of inorganic materials such as PZT (hereinafter referred to as PZT), piezoelectric ceramics, and lithium niobate, and polymer piezoelectric materials made of recently developed organic materials. Inorganic piezoelectric materials have a relatively high electro-mechanical coupling coefficient and have a high electro-acoustic conversion efficiency. However, since the acoustic impedance is extremely high, the radiation efficiency of ultrasonic waves to water or the human body, where this value is small, is poor. On the other hand, a polymeric piezoelectric material has flexibility and low acoustic impedance, and therefore has excellent ultrasonic radiation efficiency. However, since the electromechanical coupling coefficient is considerably lower than that of PZT and the like, it is inferior in terms of electro-acoustic conversion efficiency. For this reason, efforts have been made to develop piezoelectric materials that combine the features of both inorganic piezoelectric materials and polymeric piezoelectric materials, that is, have a high electromechanical coupling coefficient, low acoustic impedance, and are flexible. ing. For example, PZ, which is rich in resources and has the highest electromechanical coupling coefficient among inorganic piezoelectric materials,
There is a composite piezoelectric material in which Ts are connected with a binding material. (Reference publication: Japanese Patent Publication No. 1985-85700 "Ultrasonic probe and its manufacturing method, etc.") (Prior art) Figures 3 and 4 are diagrams explaining this type of composite piezoelectric material. be. Note that Figure (a) is a plan view, and Figure (b) is a diagram of a columnar piezoelectric body.

This composite piezoelectric material 10 consists of a plurality of small columnar piezoelectric bodies 11 made of PZT with a rectangular (FIG. 3) or circular (FIG. 4) planar shape arranged in a row, and a polymer or resin in the gap between each columnar piezoelectric body 11. A bonding material 12 made of an organic material such as rubber or silicone is filled in to bond the columnar piezoelectric bodies together, forming one piezoelectric plate as a whole. Note that when the columnar piezoelectric body 11 is made into a rectangle, for example, first prepare a desired large piezoelectric plate (not shown), cut the piezoelectric plate finely into a rectangular column shape of an appropriate size, and then cut the piezoelectric plate into a rectangular column shape. This shape is more practical than a circular shape because it can be formed by filling the bonding material 12 into the shape.

The acoustic impedance of the composite piezoelectric material 10 formed in this manner can generally be considerably lower than the acoustic impedance of the inorganic piezoelectric material itself. However, it differs depending on the ratio of piezoelectric material and bonding material per unit volume. The electromechanical coupling coefficient can also be maintained at a value that is not extremely smaller than the value of the piezoelectric material itself, and these values can be controlled by the ratio of the piezoelectric material and the bonding material.

(Disadvantages of the Prior Art) By the way, when each piezoelectric piece forming a composite piezoelectric plate is a square prism with a rectangular planar shape, this square prism piezoelectric body has the following:
As shown in FIG. 5, there is inherent thickness vibration determined by the dimensions of height 61 width w1 length in one direction. Roughly speaking, the resonant frequency of the thickness vibration in each direction is v/2, which is obtained by dividing the sound speed V of the ultrasonic wave by twice the thickness L in each direction.
It becomes t. Then, when each dimension is in a state where w and l are close to each other and h = w = 1, even if electrodes are formed only on the main surface in the height direction and vibration is excited in the thickness direction,
In reality, ultrasonic waves of the same frequency are emitted in both the width and length directions. The ultrasonic waves in the width and length directions have a negative impact on the required main vibration in the height direction, for example, reducing detection accuracy. For this reason, in the past, for example, the ratios h/w and h/l of width W and length l to height h were set to 0.6.
The influence of vibrations in the width and length directions on the thickness vibration Ft in the height direction was made as follows.

However, in recent years, there has been a trend toward using high-frequency ultrasound to increase resolution and information density. Therefore, since the height dimension of the piezoelectric body becomes smaller, the above-mentioned side ratio h/w and h71 approach 1, and as mentioned above, the width and length direction vibrations have a negative effect on the thickness height vibration. There was a problem.

(Objective of the Invention) An object of the present invention is to provide a composite piezoelectric plate that suppresses unnecessary vibration in the horizontal direction, especially in relation to the thickness vibration in the height direction.

(Means for Solving the Invention) The present invention has the shape of the columnar piezoelectric pieces as parallel planes in which only both main surfaces in the thickness direction face each other, the adjacent side surfaces are formed in a polygonal shape that is not orthogonal, and the piezoelectric pieces are bonded between each columnar piezoelectric piece. The solution is to form a composite piezoelectric plate by filling the piezoelectric material with a material.

(Function of the invention) Since the plurality of columnar piezoelectric pieces forming the composite piezoelectric plate are parallel planes facing each other only in the thickness direction, and the adjacent side surfaces are polygonal shapes that do not intersect at right angles, the ultrasonic radiation emitted from the sides other than the thickness direction is This has the effect of dispersing the frequency of the sound waves and lowering the energy level of the ultrasonic waves in the height direction. The present invention will be explained in detail below.

(Example) FIG. 1 is a diagram illustrating a composite piezoelectric material of the present invention. Note that Figure (a) is a plan view of the composite piezoelectric material, Figure (b) is a diagram of a columnar piezoelectric material, and Figure (c) is an x-x diagram of Figure (a) with electrodes attached.
'This is a cross-sectional view.

That is, in this composite piezoelectric material 1, a plurality of columnar piezoelectric bodies 2 made of PZT are arranged. The planar shape of the columnar piezoelectric body 2 is an equilateral triangle. For example, a single piezoelectric plate is fixed on a holding table with an adhesive such as glue, grooves are provided, and the plate is cut into equilateral triangles having a predetermined area.

Then, as described above, the gap between each columnar piezoelectric body 2 is filled with a binding material 3 made of an organic material. In reality, electrodes 4 are formed on the bidirectional surfaces of the composite piezoelectric material 1, lead wires (not shown) are led out, and driving pulses are applied.

Therefore, this composite piezoelectric material 1 has a frequency based on the height h,
Ultrasonic waves are sent in a direction perpendicular to the plate surface. Since each columnar piezoelectric body 2 has an equilateral triangular planar shape, ultrasonic waves are not transmitted at a specific frequency in the horizontal direction. That is, since the distance between, for example, the side A of the main surface and the sides A and C gradually decreases from the maximum at the vertex point A, a resonance phenomenon does not occur at a specific frequency in the width (length) direction. For this reason, the energy of horizontal unnecessary ultrasonic waves is dispersed in each frequency range, so that the energy Sibels in the height direction decreases. Therefore, even if the height h of each columnar piezoelectric body 2 is reduced to be close to each side a, b, and c, the influence of unnecessary ultrasonic waves can be prevented.

(Other Embodiments) FIG. 2 is a diagram showing another embodiment of the present invention, and FIG.
is a plan view, and FIG. 3(b) is a diagram of a columnar piezoelectric body.

That is, in this embodiment, the shape of each columnar piezoelectric body 6 constituting the composite piezoelectric material 5 is not fixed, but is randomly formed into polygons such as three shapes 6a, a square 6b, a pentagon 6c, and a hexagon. There is. That is, the planar shape of any polygon is such that adjacent sides are not perpendicular to each other. Then, in the same manner as described above, a bonding material 7 is filled between each columnar piezoelectric body 6, and electrodes (not shown) are formed to form a composite piezoelectric material 5.

Therefore, in this composite piezoelectric material 5, as described above, ultrasonic waves are transmitted from each columnar piezoelectric body 6 at a predetermined frequency in the height direction, and are dispersed in frequency in the horizontal direction, so that the ultrasonic waves are transmitted in the height direction. can increase your energy level. and,
In this embodiment, since the flat plate shape of each columnar piezoelectric body 6 is randomly configured, the degree of frequency dispersion is further increased.

(Effects of the Invention) The present invention has the shape of the columnar piezoelectric pieces as parallel planes in which only the bidirectional surfaces in the thickness direction face each other, the adjacent side surfaces are formed in a polygonal shape that is not perpendicular to each other, and a bonding material is placed between each columnar piezoelectric piece. By filling the composite piezoelectric plate, we hope to be able to provide a composite piezoelectric plate that suppresses unnecessary vibrations due to thickness and height vibrations.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the composite piezoelectric plate of the present invention.
) is a plan view of the composite piezoelectric material, (b) is a diagram of a columnar piezoelectric body, and (C) is a cross-sectional view taken along line x-X' in (n) of the same figure. FIG. 2 is a diagram of a composite piezoelectric plate illustrating another embodiment of the present invention; FIG. 2(a) is a plan view of the composite piezoelectric material, and FIG. 2(b) is a diagram of a columnar piezoelectric material. Figures 3 and 4 (a) and (b) are diagrams for explaining conventional composite piezoelectric plates, in which figure (a) is a plan view of the composite piezoelectric material, and figure (b)
) is a diagram of a columnar piezoelectric body. 1.5 Composite piezoelectric material, 2.6 Column piezoelectric material, 3.7 Binding material. Figure 1

Claims (2)

[Claims] (1) In a composite piezoelectric material for an ultrasonic probe formed by filling a binder between a large number of columnar piezoelectric bodies, the shape of the columnar electric bodies is a parallel plane in which only both main surfaces in the thickness direction face each other. A composite piezoelectric material for an ultrasonic probe, characterized in that it is formed into a polygonal columnar body in which adjacent side plate surfaces are not perpendicular to each other. (2) A composite piezoelectric material for an ultrasound probe according to claim 1, characterized in that the piezoelectric body is a triangular prism-shaped body.