JP3258111B2 - Ultrasonic transmitting / receiving element, ultrasonic probe, and ultrasonic transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transmitting / receiving element, an ultrasonic probe, and a transmitter for an ultrasonic therapy apparatus.

[0002]

2. Description of the Related Art An ultrasonic probe has an ultrasonic transmitting / receiving element having a piezoelectric element. The ultrasonic probe,
It is used to image the internal state of the object by irradiating the object with ultrasonic waves and receiving reflected echoes from interfaces having different acoustic impedances in the object. An ultrasonic imaging apparatus incorporating such an ultrasonic probe is applied to, for example, a medical diagnostic apparatus for inspecting the inside of a human body and an inspection apparatus for detecting flaws inside metal welding.

In recent years, as one of the medical diagnostic apparatuses,
In addition to a tomographic image (B-mode image) of the human body, the color of the blood flow can be displayed in two dimensions using the Doppler shift caused by the ultrasonic blood flow in the heart, liver, carotid artery, and the like. A method adopting the "flow mapping (CFM) method" was developed, and the diagnostic capability of the medical diagnostic device was dramatically improved. The medical diagnostic device employing the CFM method can be used for any organ of the human body such as the uterus, liver, spleen,
Research is being carried out for a device that can be used to diagnose organs and that can also diagnose coronary thrombi.

[0004] In the case of the former B-mode image, it is required that a high-resolution image be obtained with high sensitivity so that small lesions and voids due to physical changes can be clearly seen to a deep part. In the case of the Doppler mode in which the latter CFM image can be obtained, since a reflected echo from a minute blood cell having a diameter of about several μm is used, the obtained signal level is smaller than that in the case of the B mode. Higher sensitivity is required.

Conventionally, the ultrasonic transmitting / receiving element constituting the ultrasonic probe has the following structure in view of its performance.

(1) Ultrasonic attenuation when a living body is irradiated with ultrasonic waves by an ultrasonic probe is 0.5 to 1 except for bones and the like.
Since it is about dB / MHz · cm, it is preferable to lower the frequency of the ultrasonic wave emitted from the ultrasonic transmitting / receiving element in order to obtain a highly sensitive signal from the living body. However, if the frequency is excessively lowered, the wavelength of the ultrasonic wave becomes longer and the resolution may be reduced. Therefore, the ultrasonic wave having a frequency of 2 to 10 MHz is usually emitted.

(2) The piezoelectric body of the ultrasonic transmission / reception element may be formed of a material having a large dielectric constant, which has a large electromechanical coupling coefficient and is easily matched with a transmission / reception circuit having a small loss due to cables and device stray capacitance. is necessary.
For this reason, the piezoelectric body is mainly formed of lead zirconate titanate (PZT) -based ceramic.

(3) An array type ultrasonic probe in which several tens to 200 ultrasonic transmitting / receiving elements each having a strip-shaped piezoelectric body are arranged has a high resolution.

However, the conventional ultrasonic probe has the following problems.

(A) The ultrasonic transmitting / receiving element normally emits ultrasonic waves by utilizing resonance of thickness vibration of the piezoelectric body. In order to reduce the effect of ultrasonic attenuation on a living body, it is necessary to reduce the frequency of the ultrasonic waves as described above. In order to reduce the frequency of the ultrasonic wave, it is necessary to increase the thickness of the piezoelectric body in the vibration direction. For example, in order to radiate an ultrasonic wave having a frequency of 2.5 MHz, the piezoelectric body made of the PZT-based ceramic needs to have a thickness in the vibration direction of 600 μm. As described above, when the thickness of the piezoelectric body is increased, various problems occur. That is, to process a strip-shaped piezoelectric body from a block-shaped PZT-based ceramic, a dicer used for cutting a semiconductor silicon wafer or the like is used. When the thickness of the piezoelectric body in the vibration direction increases,
The depth of cut when cutting at a predetermined pitch becomes deeper. For this reason, when cutting is performed using a thin blade, the cut grooves are inclined, the cut portions meander, and the piezoelectric body is easily damaged. When processing is performed using a thick blade in order to avoid this, the cutting depth increases, and the size of the block-shaped PZT-based ceramic before processing is constant. The area of the sound wave transmitting / receiving surface is reduced. As a result, the sensitivity decreases and
The side lobe (grating lobe) level increases.

(B) When the array-type ultrasonic probe is brought into contact with a living body, the diameter of the ultrasonic wave emitting surface cannot be increased, so that the number of ultrasonic transmitting / receiving elements increases and the number of ultrasonic transmitting / receiving elements per piezoelectric body increases. The impedance becomes high, making it difficult to match with the transmission / reception circuit. The matching property can be avoided by using a PZT-based ceramic having a large relative dielectric constant as the piezoelectric body. However, since the PZT-based ceramic has a property that the electromechanical coupling coefficient becomes small when the relative dielectric constant exceeds 3000, a new problem that the sensitivity is lowered arises.

In order to solve the above-mentioned problem (b), matching with a transmission / reception circuit is performed by forming the piezoelectric body into a laminated structure or incorporating an impedance converter. However, in the stacked structure, although the transmission sensitivity increases according to the number of layers, the reception sensitivity is inversely proportional to the number of layers. For this reason, applicable fields are limited to special applications such as when the piezoelectric body is smaller than usual and when the cable is long. Further, when an impedance converter such as an emitter follower is used, the size of the ultrasonic probe is increased, and a band is narrowed due to a frequency characteristic inherent to the impedance converter.

On the other hand, it is known that a piezoelectric material made of a polymer material such as lead metaniobate, polyvinylidene fluoride or a copolymer thereof has a small frequency constant and can be made thinner than a PZT ceramic even at a low frequency. Have been. However, the polymer material is not practical because of its small dielectric constant and electromechanical coupling coefficient.

[0014]

As described above, in order to obtain an ultrasonic probe driven by a low frequency with a small amount of ultrasonic attenuation of a living body in order to increase the sensitivity, a conventional PZT ceramic becomes thick. For this reason, when a thin blade is used for cutting into strips, the cut grooves are inclined, the cut portions meander, and the piezoelectric body is likely to be damaged. In addition, when a thick blade is used, the area of the ultrasonic transmitting / receiving surface of one piezoelectric body becomes smaller as the cut-out portion increases, and the sensitivity decreases and the side lobe level increases. Further, when the piezoelectric body is thick, the electrical impedance increases, so that it becomes difficult to match with the transmitting / receiving circuit.

An object of the present invention is to provide an ultrasonic transmitting / receiving element which can achieve low-frequency driving, can reduce the thickness of a piezoelectric body in the vibration direction, can easily match with a transmitting / receiving circuit, and can achieve higher sensitivity. It is something to offer.

An object of the present invention is to provide an ultrasonic transmitting / receiving element which can achieve low-frequency driving, can reduce the thickness of a piezoelectric body in the vibration direction, can easily match a transmitting / receiving circuit, and can achieve higher sensitivity. It is an object of the present invention to provide an ultrasonic probe provided with such an ultrasonic probe.

Another object of the present invention is to provide an array type ultrasonic wave capable of keeping the frequency of the ultrasonic wave radiated from the ultrasonic transmitting / receiving surface of each ultrasonic transmitting / receiving element and obtaining a high-resolution sound beam. It is intended to provide a probe.

Another object of the present invention is to provide a transmitter for an ultrasonic therapy apparatus capable of generating a shock wave that is powerful and has good controllability.

[0019]

SUMMARY OF THE INVENTION An ultrasonic transmitting / receiving element according to the present invention comprises a piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate; an ultrasonic transmitting / receiving surface of the piezoelectric body; And a pair of electrodes respectively provided on surfaces opposite to each other, and the piezoelectric body has an ultrasonic transmission / reception surface and a surface opposite to the ultrasonic transmission / reception surface of 0.4 μm each.
m and an average surface roughness of 4 μm or less.

The ultrasonic probe according to the present invention is characterized in that the ultrasonic transmitting / receiving element, an acoustic matching layer provided on the ultrasonic transmitting / receiving surface of the ultrasonic transmitting / receiving element, and a sound provided on the acoustic matching layer. A lens and a backing material provided on a surface of the ultrasonic transmitting / receiving element opposite to the ultrasonic transmitting / receiving surface.

Hereinafter, an ultrasonic transmitting / receiving element and an ultrasonic probe according to the present invention will be described in detail with reference to FIG.

A plurality of piezoelectric bodies 1 made of a solid solution single crystal of lead zinc niobate-lead titanate are bonded separately on a backing material 2. Each of the piezoelectric bodies 1 vibrates in the direction of arrow A in the figure. The first electrode 3 is formed from the ultrasonic transmission / reception surface of each of the piezoelectric bodies 1 to a side surface thereof and a part of a surface opposite to the transmission / reception surface. The second electrode 4 is formed on a surface of each of the piezoelectric bodies 1 opposite to the transmission / reception surface at a desired distance from the first electrode 3. The piezoelectric body 1 and the first and second electrodes 3 and 4 constitute an ultrasonic transmitting / receiving element. The acoustic matching layer 5 includes the first electrodes 3
Are formed on the ultrasonic transmitting / receiving surface of each of the piezoelectric bodies 1 including: The acoustic lens 6 is formed over the entire acoustic matching layer 5. The earth electrode plate 7
It is connected to each of the first electrodes 3. A flexible printed wiring board 8 having a plurality of conductors (cables) is connected to each of the second electrodes 4 by, for example, soldering.

The ultrasonic probe having the structure shown in FIG. 1 is manufactured by, for example, the following method.

First, a block-shaped lead zinc niobate is used.
A conductive film is vapor-deposited on a solid solution single crystal piece of lead titanate by a sputtering method, and the conductive film is left on an ultrasonic transmitting / receiving surface by a selective etching technique and on a surface opposite to the transmitting / receiving surface. Subsequently, after connecting the ground electrode 7 to the end of the conductive film on the ultrasonic transmission / reception surface side of the single crystal piece by, for example, soldering, an acoustic matching layer is formed on the surface of the single crystal piece which is to be the ultrasonic transmission / reception surface. Form. Subsequently, after connecting the flexible printed wiring board 8 having a plurality of conductors (cables) to the end of the conductive film located on the surface of the single crystal piece opposite to the ultrasonic transmitting / receiving surface by, for example, soldering, On the backing material 2. After that, by using a blade to cut a plurality of times from the acoustic matching layer over the conductive film located on the surface opposite to the ultrasonic transmission and reception surface of the single crystal piece, the first on the backing material 2, A plurality of separated piezoelectric bodies 1 having second electrodes 3 and 4 and a plurality of acoustic matching layers 5 arranged on the respective piezoelectric bodies 1 are formed. Next, an ultrasonic probe is produced by forming an acoustic lens 6 on the acoustic matching layer 4.

The lead zinc niobate constituting the piezoelectric body 1
The solid solution single crystal of lead titanate is produced, for example, by the following method.

First, as a starting material, chemically pure P
After using bO, ZnO, Nb ₂ O ₅ , and TiO ₂ to correct their purity, they were weighed so that lead zinc niobate (PZN) and lead titanate (PT) had a desired molar ratio. And the same amount of PbO is added. Pure water is added to the powder and mixed for a desired time in a ball mill containing ZrO ₂ balls, for example. After removing the water content of the obtained mixture, the mixture is sufficiently pulverized with a pulverizer such as a raikai machine, and further placed in a rubber container, and subjected to rubber pressing at a desired pressure. The solid material taken out of the rubber mold is put into a container of a desired volume made of, for example, platinum and melted at a desired temperature. After cooling, the solid is further placed in the container, sealed with a lid made of, for example, platinum, and the container is placed at the center of the electric furnace. The temperature is raised to a temperature higher than the melting temperature, gradually cooled to a temperature close to the melting temperature at a desired cooling rate, and then cooled to room temperature. Thereafter, nitric acid of a desired concentration is added to the container, and the mixture is boiled to take out a solid solution single crystal, thereby producing the same.

The solid solution single crystal of lead zinc niobate-lead titanate can be similarly produced by, for example, the Bridgman method, the kiloproth method, or the hydrothermal growth method, in addition to the flux method described above. is there.

As the solid solution single crystal of lead zinc niobate-lead titanate, it is desirable to use a composition in which the molar fraction of lead titanate is 20% or less (at a molar ratio of 0.20 or less). By using such a solid solution-based single crystal piezoelectric body, the speed of sound can be reduced by 20% or more as compared with a piezoelectric body made of PZT ceramic, so that an ultrasonic probe with higher sensitivity can be obtained. Becomes possible.

[0029] In particular, the general formula _{Pb A [(Zn 1/3 Nb 2/3} ) 1-x Ti x] B O 3 ( here, x is 0.05 ≦ x ≦ 0.20, stoichiometric ratio A
/ B indicates 0.98 ≦ A / B <1.00) It is preferable to use a solid solution single crystal of lead zinc niobate-lead titanate having a composition represented by the following formula:

The reason why x in the above general formula is specified is as follows. If the value x is less than 0.05, the Curie temperature of the solid solution single crystal is low, and the solid solution single crystal may be depolarized when soldering the flexible printed wiring board 7 and the ground electrode plate 8 or cutting the solid solution single crystal. There is. On the other hand, if the value of x exceeds 0.20, not only a large electromechanical coupling coefficient cannot be obtained, but also the dielectric constant may be reduced, making it difficult to match acoustic impedance of the transmitting and receiving circuit. More preferable x is 0.06 to 0.1.
2.

If the A / B in the general formula deviates from the above range, the reliability of the obtained ultrasonic probe at the time of actual operation may be reduced.

The piezoelectric body 1 has a thickness of 200 in the vibration direction.
It is preferably from 400 to 400 μm.

The piezoelectric body 1 has an ultrasonic transmission / reception surface and a surface opposite to the ultrasonic transmission / reception surface of 0.4 μm each.
m and a maximum surface roughness of 4 μm or less. If the average surface roughness and the maximum surface roughness exceed 0.4 μm and 4 μm, respectively, long-term reliability such as sensitivity may decrease. More preferably, the average surface roughness and the maximum surface roughness are each 0.1.
3 μm or less, 3 μm or less.

The piezoelectric body 1 has an ultrasonic transmitting / receiving surface of (00).
1) The surface is desirable. Such a piezoelectric body 1 is
It is produced by cutting the solid solution single crystal perpendicularly to the [001] axis (C axis).

The first and second electrodes 3 and 4 are made of, for example, Ti
/ Au, Ni / Au or Cr / Au two-layer conductive film,
Alternatively, it is formed by baking silver containing glass frit or the like.

The arrangement of the electrodes 3 and 4 and the manner in which the ground electrode plate 7 and the flexible printed wiring board 8 are attached to the electrodes 3 and 4 are not limited to those shown in FIG. For example, the bonding of the ground electrode plate 7 and the flexible printed wiring board 8 to the electrodes 3 and 4 may be performed by a method using a conductive paste or resistance welding in addition to soldering.

Although the array type ultrasonic probe is shown in FIG. 1 described above, the present invention includes an ultrasonic probe having a single ultrasonic transmitting / receiving element.

The ultrasonic probe according to the present invention comprises a piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, an ultrasonic transmitting / receiving surface of the piezoelectric body, and an opposite side of the ultrasonic transmitting / receiving surface. A plurality of ultrasonic transmission / reception elements each having a pair of electrodes provided on a surface; an acoustic matching layer provided on the ultrasonic transmission / reception surface of each of the plurality of ultrasonic transmission / reception elements; provided on the acoustic matching layer An acoustic lens; a backing material provided on a surface of the ultrasonic transmission / reception element opposite to the ultrasonic transmission / reception surface; and the piezoelectric body has a direction in which the ultrasonic transmission / reception surface is orthogonal to the arrangement direction. The concave ultrasonic wave transmitting and receiving surface has a maximum electromechanical coupling coefficient, and has a maximum thickness.

Hereinafter, an ultrasonic probe (array type ultrasonic probe) according to the present invention will be described in detail with reference to FIG.

A plurality of piezoelectric bodies 11 made of a solid solution single crystal of zinc zinc niobate-lead titanate are bonded to a backing material 12 separately from each other. Each of the piezoelectric bodies 11
Has a shape in which the ultrasonic transmitting and receiving surface is concavely curved in a direction perpendicular to the arrangement direction and has a constant thickness, and the central portion of the concave ultrasonic transmitting and receiving surface has a maximum electromechanical coupling coefficient. Each of the piezoelectric bodies 11 vibrates in the direction of arrow A in FIG. The first electrodes 13 are respectively formed on the concave ultrasonic transmission / reception surfaces of each of the piezoelectric bodies 11. The second electrodes 14 are interposed between the backing material 12 and the convex surfaces of the respective piezoelectric bodies 11 opposite to the transmitting and receiving surfaces, and are in good contact with the respective piezoelectric bodies 11. The piezoelectric body 11 and the first and second electrodes 13 and 14 constitute an ultrasonic transmitting / receiving element. The acoustic matching layer 15 is formed on each of the first electrodes 13. The acoustic matching layer 15 has a shape in which the surface is curved concavely in a direction perpendicular to the arrangement direction and has a constant thickness, similarly to the piezoelectric body 11.
The ground electrode 16 is interposed between each of the first electrodes 13 and each of the acoustic matching layers 15 along the direction in which the piezoelectric bodies 11 are arranged, and is connected to each of the first electrodes 13. A flexible printed wiring board 17 having a plurality of conductors (cables) is interposed between the respective second electrodes 14 and the backing material 12 along the direction in which the piezoelectric bodies 11 are arranged. It is connected to the.

The array type ultrasonic probe having the structure shown in FIG. 2 is manufactured by the following method, for example.

First, the ultrasonic transmitting / receiving surface is curved in a concave shape,
And a solid solution type single crystal piece of lead zinc niobate-lead titanate having a constant thickness and a convex curved surface on the side opposite to the transmitting / receiving surface is formed, and a conductive film is formed on the single crystal piece. It is deposited by a sputtering method. Subsequently, a ground electrode 16 is adhered to the end of the conductive film on the concave surface side of the single crystal piece by using a conductive paste along a direction orthogonal to the bending direction of the single crystal piece. An acoustic matching layer is formed on the conductive film on the concave surface side including the ground electrode 16, similarly to the single crystal piece, having a constant thickness and a concave surface. Subsequently, the flexible printed wiring board 17 having a plurality of conductors (cables) on the end of the conductive film positioned on the convex surface of the single crystal piece is electrically conductive along a direction orthogonal to the bending direction of the single crystal piece. After bonding using a paste, these are bonded on the backing material 12. Next, the first and second electrodes 13 are cut on the backing material 12 by cutting a plurality of times from the acoustic matching layer to the single crystal piece using a blade so as to be parallel to the bending direction of the single crystal piece. , 1
An array type ultrasonic probe having a plurality of piezoelectric bodies 11 separated from each other and a plurality of acoustic matching layers 5 formed on each of the piezoelectric bodies 11 is manufactured.

The solid solution single crystal of lead zinc niobate-lead titanate constituting the piezoelectric body 11 has a composition in which the molar fraction of lead titanate is 20% or less (at a molar ratio of 0.20 or less). It is desirable to use In particular, the general formula Pb
_{A [(Zn 1/3 Nb 2/3)} 1-x Ti x] B O 3 ( here, x is 0.05 ≦ x ≦ 0.20, stoichiometric ratio A / B is 0.98 ≦ A / B <1.00) It is preferable to use a solid solution single crystal of lead zinc niobate-lead titanate having a composition represented by the following formula:

In order to make the central part of the concave ultrasonic transmitting / receiving surface of the piezoelectric body 11 the maximum electromechanical coupling coefficient, for example, the crystal orientation of the central part of the concave ultrasonic transmitting / receiving surface is maximized by the electromechanical coupling coefficient. Can be adopted. Specifically, this is achieved by setting the crystal orientation at the center of the concave ultrasonic transmitting / receiving surface to the (100) plane.

The piezoelectric body 11 has a thickness of 20 in the vibration direction.
It is preferably from 0 to 400 μm.

In the piezoelectric body 11, the concave ultrasonic transmitting and receiving surface and the convex surface opposite to the ultrasonic transmitting and receiving surface each have an average surface roughness of 0.4 μm or less, and a maximum surface roughness of 4 μm or less. Preferably. The average surface roughness and the maximum surface roughness are each 0.4 μm,
If it exceeds 4 μm, long-term reliability such as sensitivity may decrease. More preferably, the average surface roughness and the maximum surface roughness are each 0.3 μm or less and 3 μm or less.

The first and second electrodes 13 and 14 are formed by, for example, a two-layer conductor film of Ti / Au, Ni / Au or Cr / Au, or baking silver containing glass frit.

Further, a transmitter for an ultrasonic therapy apparatus according to the present invention comprises a piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, an ultrasonic wave generating surface of the piezoelectric body and an ultrasonic wave generating surface. A plurality of ultrasonic generating elements each having a pair of electrodes provided on a surface opposite to the surface; and an acoustic matching layer provided on each of the ultrasonic transmitting and receiving surfaces of the plurality of ultrasonic transmitting and generating elements. The plurality of ultrasonic wave transmitting / generating elements are densely arranged.

The piezoelectric body has an ultrasonic wave generating surface of (001).
Surface is desirable. Such a piezoelectric body is manufactured by cutting out the [001] axis (C axis) of the solid solution single crystal perpendicularly.

As the solid solution single crystal of lead zinc niobate-lead titanate, it is desirable to use a composition in which the molar fraction of lead titanate is 20% or less (at a molar ratio of 0.20 or less). In particular, the general formula Pb _A [(Zn _1/3 Nb _2/3 )
_{1-x Ti x] B O} 3 ( here, x is 0.05 ≦ x ≦ 0.
20, stoichiometric ratio A / B is 0.98 ≦ A / B <1.00
It is desirable to use a solid solution single crystal of lead zinc niobate-lead titanate having a composition represented by the following formula:

The electrodes are made of, for example, Ti / Au, Ni / A
It is formed by u or Cr / Au two-layer conductor film, silver baking including glass frit, or the like.

[0052]

The ultrasonic probe shown in FIG. 1 according to the present invention uses a solid solution single crystal of lead zinc niobate-lead titanate as the piezoelectric body 1. Therefore, a dielectric constant of about 2200 can be obtained by forming an electrode on the piezoelectric body made of the solid solution single crystal and performing a polarization treatment. Further, the ultrasonic transmitting / receiving element cuts the solid solution single crystal perpendicularly to, for example, the [001] axis to obtain a maximum electromechanical coupling coefficient (k _33).
(1) is obtained by forming a strip-shaped piezoelectric body whose (001) plane is an ultrasonic transmitting / receiving surface, and forming first and second electrodes 3 and 4 on the (001) plane of the piezoelectric body, respectively. It is made. Such an ultrasonic transmitting / receiving element has a sound speed of 2700 to 3000 m / s (frequency constant of 1350 to 3000 m / s) from the ultrasonic transmitting / receiving surface having the orientation of the (001) plane of the piezoelectric body 1.
(1500 Hz · m). For this reason, the ultrasonic transmission / reception element has the same sound speed (4000) as that of a conventional ultrasonic transmission / reception element having a piezoelectric body made of PZT ceramic.
m / s) can be reduced by about 30%. In particular, the molar fraction of titanic acid, a component that increases the speed of sound, is set at 20.
% (At a molar ratio of 0.20 or less), the use of a piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate can further reduce the sound speed.

Assuming that the frequency of the ultrasonic wave radiated from the ultrasonic transmitting / receiving element is f ₀ , the sound velocity of the ultrasonic wave is v, and the thickness of the piezoelectric body of the element in the vibration direction is t, f ₀ is given by the following equation. expressed.

F ₀ = v / 2t Therefore, since the ultrasonic transmission / reception element can emit an ultrasonic wave having a low sound velocity as described above, even if the frequency (f ₀ ) is set to a lower value according to the above equation, The thickness of the piezoelectric body can be reduced. In other words, low-frequency driving for obtaining a high-sensitivity signal can be performed, and the thickness of the piezoelectric body made of the solid-solution single crystal in the vibration direction can be reduced.

For this reason, when processing the solid-solution single crystal into a strip shape, the cutting depth of the blade of the dicing machine can be made shallow, and even if a thin blade is used, the cutting portion can be straightened without any meandering. You can cut it. In addition, the cutting amount in the cutting step can be reduced. As a result, the manufacturing yield can be improved, and the ultrasonic transmitting and receiving surface of the piezoelectric body can be maintained at a desired area, so that a high-performance ultrasonic probe with reduced side lobes can be obtained.

As described above, the piezoelectric body made of the solid solution single crystal has a relative dielectric constant equal to or higher than that of the conventional piezoelectric body made of a PZT ceramic, so that the matching with the transmission / reception circuit is improved. Therefore, the loss due to the cable and the stray capacitance of the device can be reduced, and a highly sensitive signal can be obtained.

Further, the ultrasonic transmitting / receiving element is a solid solution single crystal of lead zinc niobate-lead titanate, which is composed of Pb
_{A [(Zn 1/3 Nb 2/3)} 1-x Ti x] B O 3 ( here, x is 0.05 ≦ x ≦ 0.20, stoichiometric ratio A / B is 0.98 ≦ A / B <1.00), and the solid solution single crystal is, for example, [00
1] The (001) plane obtained by cutting out perpendicularly to the axis and obtaining the maximum electromechanical coupling coefficient (k ₃₃ ′) is processed into a strip shape to be an ultrasonic transmission / reception plane, and electrodes are respectively formed on the (001) plane. It is constituted by forming. In such an ultrasonic transmitting / receiving element, the sound velocity from the ultrasonic transmitting / receiving surface having the orientation of the (001) plane is 2700 to 3000 m / s (frequency constant 1350 to 1500 Hz · m), and the k ₃₃
'Is a large value of 80 to 85%. As a result, even when the ultrasonic probe having the ultrasonic transmitting / receiving element is connected to a diagnostic apparatus and a test is performed for about 1000 hours at a pulse voltage of 50 to 150 V, which is an actual operating condition, and a repetition frequency of 3 to 15 kHz. Good sensitivity can be maintained at the initial stage of the movement.

Further, the piezoelectric body constituting the ultrasonic transmitting / receiving element has an ultrasonic transmitting / receiving surface and a surface opposite to the ultrasonic transmitting / receiving surface, each having an average surface roughness of 0.4 μm or less, and a surface roughness of 4 μm or less. When formed from a solid solution single crystal of lead zinc niobate-lead titanate having the maximum surface roughness, for example, a pulse voltage of 50 to 150 V which is an actual operating condition, 3
Even if an actual operation test is performed for 1000 hours or more at a repetition frequency of １５15 kHz, no decrease in sensitivity is observed, and an ultrasonic probe with excellent long-term reliability can be realized.

The array type ultrasonic probe shown in FIG. 2 according to the present invention has a form in which a plurality of ultrasonic transmitting / receiving elements having a piezoelectric body 11 made of a solid solution single crystal of lead zinc niobate-lead titanate are arranged. None, each of the piezoelectric bodies 11 has a shape in which an ultrasonic transmitting / receiving surface is concavely curved in a direction orthogonal to the arrangement direction and has a constant thickness, and a central portion of the concave ultrasonic transmitting / receiving surface has a maximum electric power. It has a mechanical coupling coefficient. For this reason, the ultrasonic transmitting and receiving element is
, The electromechanical coupling coefficient can be reduced toward the end of the concave ultrasonic transmission / reception surface. As a result, the frequency of the ultrasonic wave radiated from the ultrasonic transmitting / receiving surface of each ultrasonic transmitting / receiving element can be kept constant, and the electromechanical coupling coefficient can have a distribution. Therefore, side lobes can be suppressed, and a high-resolution sound beam can be obtained. The array type ultrasonic probe shown in FIG. 2 can focus an ultrasonic beam without using an acoustic lens like the ultrasonic probe of FIG. 1 described above. For this reason,
Ultrasonic attenuation due to the arrangement of the acoustic lens can be avoided, and the S / N can be significantly improved.

The piezoelectric body constituting the ultrasonic transmitting / receiving element has a concave ultrasonic transmitting / receiving surface and a surface (convex surface) opposite to the ultrasonic transmitting / receiving surface, each having an average surface roughness of 0.4 μm or less. And a solid solution single crystal having a maximum surface roughness of 4 μm or less, an actual operation test is performed for 1000 hours or more at a pulse voltage of 50 to 150 V, which is an actual operating condition, and a repetition frequency of 3 to 15 kHz. However, a decrease in sensitivity is not observed, and an array-type ultrasonic probe with excellent long-term reliability can be realized.

Further, in the transmitter for an ultrasonic therapy apparatus according to the present invention, electrodes are provided on the ultrasonic wave generating surface of a piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate and on the surface opposite to the ultrasonic generating surface. Since a large electric field can be applied to the piezoelectric body made of the solid solution single crystal provided with the formed ultrasonic wave generating elements, the radiated sound waves can be increased. As a result, a transmitter for an ultrasonic therapy apparatus having the above-mentioned ultrasonic generating element emits a shock wave from the outside of the body to crush finely hepatic stones and gallstones and naturally discharge and treat the stones. Can be applied to the source.

The specific gravity of the piezoelectric body made of the solid solution single crystal is 8.2 to 8.5 and the specific gravity of the conventional piezoelectric body made of PZT ceramic having a specific gravity of 7.5 to 8.0 (7 .
5 to 8.0) and can be made thinner than the conventional piezoelectric body, so that the weight can be reduced by about 25%. As a result, the transmitter incorporating the ultrasonic generating element having the piezoelectric body made of the solid solution single crystal can realize a lightweight calculus breaking device. Such a calculus crushing device can adjust the transmitter to a delicate position of the calculus with good controllability, so that crushing efficiency can be improved and the drive mechanism can be downsized.

[0063]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

Example 1 First, chemically high-purity PbO and Zn were used as starting materials.
O, Nb ₂ O ₅ and TiO ₂ are used, and after correcting their purity, lead zinc niobate (PZN) and lead titanate (PT)
Were weighed such that the molar ratio of PbO was 91: 9, and the same amount of PbO was added as a flux. Pure water is added to the powder, and the powder is added to a ball mill containing ZrO ₂ balls.
Mix for hours. After removing the water content of the obtained mixture, the mixture was sufficiently pulverized by a raikai machine, and further placed in a rubber-type container.
Rubber pressing was performed at a pressure of ton / cm ² . 600 g of the solid material taken out of the rubber mold is 50 mm in diameter, and has a capacity of 25.
The mixture was placed in a 0 cc platinum container and heated to 900 ° C. for 4 hours to dissolve. After cooling, the solids were further
Then, the container was closed with a platinum lid, and the container was placed at the center of an electric furnace. Raise the temperature to 1250 ° C in 5 hours,
After slowly cooling to 800 ° C. at a rate of 0.8 ° C./hr, it was cooled to room temperature. Thereafter, nitric acid at a concentration of 20% was added to the platinum container, and the mixture was boiled for 8 hours to take out a solid solution single crystal.

The single crystal obtained by such a flux method was amorphous, but had a size of about 7 mm square. When a part of the single crystal was pulverized and subjected to X-ray diffraction, it was confirmed that the single crystal had a good crystal structure. Chemical analysis of the powder by ICP confirmed that lead zinc niobate (PZN) and lead titanate (PT) had a composition of 91PZN-9PT having a molar ratio of 91: 9.

The orientation of the [001] axis of the single crystal was determined using a Laue camera, and the single crystal was cut perpendicularly to this axis with a cutter. Subsequently, Ni / Au electrodes were formed on the (001) plane of the cut single crystal piece by a sputtering method.
After applying an electric field of 1 kV / mm in silicone oil at 50 to 200 ° C. for 30 minutes, cooling was performed while applying the electric field. This single crystal piece was cut into strips, and the capacitance, resonance, and antiresonance frequency were measured. As a result, the relative dielectric constant is 2200,
The sound velocity is 2850 m / s, and the electromechanical coupling coefficient k ₃₃ ′ is 80
８５85%.

Further, the above-mentioned array type ultrasonic probe shown in FIG. 1 was manufactured using the single crystal of 91PZN-9PT. That is, first, a single crystal piece having a thickness of 400 μm is formed from the single crystal of 91PZN-9PT, a Ti / Au conductor film is deposited on the (001) plane of the single crystal piece by a sputtering method, and the etching is performed by a selective etching technique. A part of the conductive film located on one side surface of the piezoelectric body and a part of the conductive film located on a surface opposite to the transmitting / receiving surface were removed. Subsequently, after connecting the ground electrode 7 to the end of the conductive film on the ultrasonic transmission / reception surface side of the single crystal piece by, for example, soldering, an acoustic matching layer is formed on the surface of the single crystal piece which is to be the ultrasonic transmission / reception surface. Formed. Subsequently, after connecting the flexible printed wiring board 8 to the end of the conductive film located on the surface opposite to the ultrasonic transmitting / receiving surface of the single crystal piece by, for example, soldering, these were bonded on the backing material 2. . Thereafter, using a blade having a thickness of 30 μm, a cut depth of 1 mm and a pitch of 0.19 mm are formed from the acoustic matching layer to the conductive film located on the surface of the single crystal piece opposite to the ultrasonic transmitting / receiving surface. And cut into strips. By this cutting, a plurality of piezoelectric bodies 1 having first and second electrodes 3 and 4 on the backing material 2 are separated from each other.
And a plurality of acoustic matching layers 5 respectively formed on the piezoelectric bodies 1. When the cut portion after cutting was observed from above and from the side with a microscope, no meandering or inclined cut was observed. Next, an acoustic lens 6 was formed on the acoustic matching layer 4, and a cable having a capacitance of 110 pF / m and a length of 2 m was connected to the flexible printed wiring board 7 to manufacture an array-type ultrasonic probe.

When the reflected echoes of the ultrasonic probe were measured by the pulse echo method, echoes having a center frequency of about 2.5 MHz were received from all the ultrasonic transmitting and receiving elements.

Comparative Example An ultrasonic probe similar to that of Example 1 was manufactured using a piezoelectric body made of PZT-based ceramic having a relative dielectric constant of 2000.
At this time, in order to manufacture an ultrasonic probe that emits an echo having a center frequency of about 2.5 MHz, the thickness of the piezoelectric body made of the PZT-based ceramic needs to be 600 μm. Therefore, when cutting a PZT-based ceramic block that is to be a piezoelectric body using a blade, the cutting depth must be about 1.3 mm, and the thickness is 30 mm.
When the strip was cut from the acoustic matching layer to the conductive film on the lower surface of the ceramic block using a μm blade, the blade entered obliquely into the ceramic block. As a result, when the impedance characteristics of the ultrasonic transmitting / receiving element after cutting were measured, 5% of the elements became defective.

Therefore, the blade was replaced with a blade having a thickness of 50 μm and cut in the same manner. Then, an array-type ultrasonic probe having the same structure as that shown in FIG. 1 was manufactured, and pulse echo was measured. As a result, the echo sensitivity was -3 dB compared to the first embodiment.
Dropped.

A sound field measurement was performed on the ultrasonic probes of Example 1 and Comparative Example, and the side lobe level was measured while the beam was deflected by 60 ° by controlling the delay time of the applied pulse. As a result, the ultrasonic probe of Example 1 had a side lobe level lower by about 10 dB than the same probe of Comparative Example.

Further, the ultrasonic probes of Example 1 and Comparative Example were examined for longitudinal sound velocity. As a result, the sound speed of Example 1 was 2800 m / s, and the sound speed of Comparative Example was 4
It was confirmed that it was about 30% slower than 000 m / s.

Examples 2 to 4 and Reference Examples 1 to 3 First, chemically high-purity PbO and Zn were used as starting materials.
Using O, Nb ₂ O ₅ , and TiO ₂ , the purity of these materials was corrected, these raw materials were weighed to a predetermined amount, and the same amount of PbO was added as a flux. Alcohol is added to this powder, and the powder is added to a ball mill containing ZrO ₂ balls.
Mix for hours. After removing the alcohol from the obtained mixture, the mixture was pulverized sufficiently with a raikai machine, further placed in a rubber-type container, and subjected to rubber press at a pressure of 2 ton / cm ² .
1000g of solid material taken out from rubber mold is 50m in diameter
m, placed in a 250 cc platinum container, sealed with a platinum lid, and then placed in the center of an electric furnace. 10
The temperature is raised to a temperature of 00 to 1300 ° C. in 5 hours,
It was gradually cooled to 700 to 900 ° C. at a rate of 5 ° C./hr. In this slow cooling step, 10 to 100
Air was blown at a flow rate of 0 ml / min to selectively cool the lower part of the vessel and then to room temperature. Thereafter, nitric acid of 50% concentration was added to the platinum container, and the mixture was boiled for 8 hours to dissolve the flux portion, and a solid solution single crystal was taken out.

By controlling the amount of flux, the maximum temperature, and the cooling rate in the single crystal production step, six types of single crystals having a pale yellow to dark brown perovskite structure were obtained. Each of these single crystals was amorphous, but had a size of about 10 mm square. A portion of each of the single crystals was crushed and subjected to X-ray diffraction. As a result, it was confirmed that the single crystal had a good crystal structure. The results of chemical analysis of each powder by ICP are shown in Table 1 below. The composition of each single crystal was Pb _A [(Zn _1/3 Nb _2/3 ) _1-x T
The i _x] stoichiometric ratio A / B when expressed in _B O ₃ are also shown in Table 1.

[0075]

[Table 1]

The single crystal was oriented in the [001] axis direction using a Laue camera and cut by a cutter perpendicular to this axis. Then, the cut single crystal piece (001)
Ni / Au electrodes were formed on the surfaces by sputtering, respectively, and were exposed to 1 kV /
After applying an electric field of 30 mm for 30 minutes, cooling was performed while applying an electric field. These single crystal pieces were cut into strips, and the capacitance, resonance, and antiresonance frequency were measured. As a result, the relative dielectric constant is 2
000-2800, sound speed 2700-3000m / s,
It was confirmed that the electromechanical coupling coefficient k ₃₃ ′ was 80 to 85%.

Further, the array type ultrasonic probe (96 elements) shown in FIG. 1 described above was manufactured in the same manner as in Example 1 using each of the single crystals. Reflection echoes of these ultrasonic probes were measured by a pulse echo method. As a result, echoes having a center frequency of about 2.5 MHz were received from all the ultrasonic transmitting / receiving elements.

For the array type ultrasonic probes of Examples 2 to 4 and Reference Examples 1 to 3 having 96 elements, a repetition frequency of 5 kHz, a voltage of 100 V, a load ratio (duty ratio) of 1: 1 and a pulse width of 0. It is 10 for 2 rectangular waves of 2 μs
After performing the actual operation test for 00 hours, the peak value of the reflected echo was measured. When the obtained peak value was deteriorated by 30 or more compared to the value before the actual operation test, it was defined as a failure, and the number of failures of 96 elements incorporated in the probe was examined. The results are shown in Table 2 below.

[0079]

[Table 2]

As is clear from Table 2, the stoichiometric ratio A
The array-type ultrasonic probes of Examples 2 to 4 using a piezoelectric material made of a single crystal having a ratio / B of 0.98 ≦ A / B <1.00 can maintain high reliability for a long period of time. Understand.

The amount of lead titanate in the lead zinc niobate-lead titanate solid solution single crystal was changed in the range of 5 to 20 mol% (molar ratio: 0.05 to 0.20). An ultrasonic probe shown in FIG. 1 was manufactured using a piezoelectric body cut out of a single crystal. Such an ultrasonic probe had almost the same effect on the long-term reliability due to the stoichiometric ratio.

Embodiment 5 FIG. 3 is a schematic diagram showing an ultrasonic probe and an apparatus having a function of controlling heat generation of the probe. 21 in the figure is
This is an array-type ultrasonic probe having the same structure as that of FIG. 1 described above having a piezoelectric body made of a solid solution single crystal of 91PZN-9PT similar to that of the first embodiment. The 91PZN-9P
FIG. 4 shows the relationship between temperature and relative permittivity of a solid solution single crystal of T.
As described above, a phase transformation from rhombohedral to tetragon occurs at 50 to 90 [deg.] C., and the relative dielectric constant increases accordingly. Specifically, the solid solution single crystal has a relative dielectric constant of about 2200 at room temperature, but has a relative dielectric constant of 3500 at 50 ° C. due to the phase transformation.

A pulser 22 for generating a pulse is connected to the ultrasonic probe 21 through a cable. The receiver 23 is connected to the ultrasonic probe 21 through a cable. Impedance detection circuit 2
4 is connected to the ultrasonic probe 21 through a cable. The impedance detection circuit 24 detects a change in impedance correlated with the relative permittivity of the ultrasonic probe 21. The detection circuit 24 is connected to the pulser 22, and a pulse (voltage) applied from the pulser 22 to the ultrasonic probe 21 is controlled based on a detection result by the detection circuit 24. For example, the detection circuit 24 includes the ultrasonic probe 2
When 1 has an impedance that is ／ times the impedance when no voltage is applied to the ultrasonic probe 21, the voltage applied from the pulsar 22 to the ultrasonic probe 21 is reduced to １ ／. Control.

When the ultrasonic probe 21 of the apparatus shown in FIG. 3 is inserted into a body cavity and a voltage is applied from the pulsar 22 to the ultrasonic probe 21, the generated ultrasonic wave is applied to a predetermined part of the living body. Other than that, the acoustic matching layer, acoustic lens,
Generates heat when absorbed by the backing material. When the ultrasonic probe 21 generates heat as described above, the ultrasonic probe 2
The relative dielectric constant of the solid solution single crystal, which is the piezoelectric body of item 1, is increased as shown in FIG. Since the ultrasonic probe 21 is connected to an impedance detection circuit 24 for detecting an impedance correlated with the relative permittivity, the relative permittivity of the piezoelectric body of the ultrasonic probe 21 is a certain value or more (for example, 3500 or more). ), A signal is output from the impedance detection circuit 24 to the pulser 22, and a voltage that is ２ of the voltage before the signal is output is applied from the pulser 22 to the ultrasonic probe 21, and the ultrasonic probe 21 Excessive heat generation is suppressed.

In fact, a thermocouple was installed on the surface of the acoustic lens of the ultrasonic probe 21 to measure heat generation when left in the air. As a result, a characteristic diagram showing the time change of the temperature difference from the outside air shown in FIG. 5 was obtained. From this FIG.
It can be seen that, in the apparatus described above, when the ultrasonic probe 21 becomes higher than room temperature by 10 ° C., feedback is applied from the impedance detection circuit 24 to the pulser 22, and the heat generated by reducing the driving voltage to １ ／ can be reduced.

As described above, according to the apparatus of the fifth embodiment, the calorific value of the ultrasonic probe 21 is determined by the relative dielectric constant of the piezoelectric body made of a solid solution single crystal of 91PZN-9PT incorporated in the ultrasonic probe 21. The change can be read as an impedance change by the impedance detection circuit 24. Therefore, since the drive voltage to the ultrasonic probe 21 can be controlled based on the impedance change, it is possible to prevent the body cavity of the patient from being excessively heated and causing a low-temperature burn. In addition, since the drive voltage can be increased when the ultrasonic probe 21 generates low heat, a highly sensitive signal can be obtained, and the diagnostic performance can be improved. For example, when the impedance detection circuit is not provided, the driving voltage is set to 5 due to the heat generation of the ultrasonic probe.
Although it was necessary to suppress the voltage to 7 V, the apparatus of the fifth embodiment can set the voltage to 96 V, which is 4.5 dB higher than that. As a result, in the sensitivity measurement using a phantom of 0.5 dB / MHz · cm, the apparatus of the fifth embodiment, in which the drive voltage can be increased to 96 V, is improved by about 2 cm in comparison with the prior art in which the drive voltage can be set only to 57 V. We were able to.

Example 6 A single crystal of 91PZN-9PT obtained in Example 1 was cut out at the (001) plane, and then processed into a concave shape so that the (001) plane was at the center, and the thickness was constant. Was formed. Ti / Au electrodes were formed on the concave surface (ultrasonic radiation surface) and the convex surface of this single crystal piece by sputtering, respectively, and were placed in a silicone oil at 150 to 200 ° C. for 1 k.
After applying an electric field of V / mm for 30 minutes, cooling was performed while applying the electric field. The single crystal piece and the electrode were cut into strips along the bending direction of the single crystal piece to produce an ultrasonic transmitting and receiving element in which electrodes were formed on concave and convex surfaces of a curved piezoelectric body. The element is divided into five in a direction orthogonal to the bending direction of the piezoelectric body, and the electromechanical coupling coefficient (k
₃₃ ') was measured. FIG. 6 shows the result. FIG.
The horizontal axis represents the length of the ultrasonic transmitting / receiving element in the bending direction.
_0, and indicates the length from one end of the element to the five division elements when a l, a position of the respective dividing element as l / l _0.

As is clear from FIG. 6, an element having a piezoelectric body having an ultrasonic radiation surface having a concave shape and having a (001) crystal orientation at the center has a large electromechanical coupling coefficient at the center, It turns out that it becomes small as it goes to a part.

The above-mentioned array type ultrasonic probe shown in FIG. 2 was manufactured by using a 91PZN-9PT single crystal piece having a constant thickness processed so as to be concave so that the (001) plane was the center. That is, a conductive film of Ti / Au was formed on the concave surface and the convex surface of the single crystal piece by sputtering. Subsequently, a ground electrode 17 was adhered to the end of the conductive film on the concave surface side of the single crystal piece by using a conductive paste along a direction orthogonal to the bending direction of the single crystal piece.
On the conductor film on the concave surface side including the ground electrode 17, an acoustic matching layer having a shape whose surface is curved concavely and has a constant thickness is formed similarly to the single crystal piece. Subsequently, the flexible printed wiring board 18 having a plurality of conductors (cables) on the end of the conductive film located on the convex surface of the single crystal piece is electrically conductive along a direction orthogonal to the bending direction of the single crystal piece. After bonding using a paste, these are bonded on the backing material 12 with an epoxy resin. Then, using a 30 μm-thick blade, a 1 mm cut depth of 0.19 m was formed from the acoustic matching layer to the single crystal piece so as to be parallel to the bending direction of the single crystal piece.
It was cut into strips at a pitch of m. By this cutting, a plurality of separated piezoelectric bodies 11 having first and second electrodes 13 and 14 on the backing material 12 and a plurality of acoustic matching layers 5 arranged on each of the piezoelectric bodies 11 are formed. As a result, an array-type ultrasonic probe was manufactured.

Using the ultrasonic probe, a sound field was measured in a cutting direction of the piezoelectric body. FIG. 7 shows the result.

For comparison, 91PZN-9P was used for comparison.
An array-type ultrasonic probe having the same structure as that of FIG. 2 described above was manufactured except that the piezoelectric body made of a single crystal of T was made flat and an acoustic lens was provided on the acoustic matching layer. FIG. 8 shows the result of the same sound field measurement performed on this ultrasonic probe.

As is clear from FIGS. 7 and 8, the ultrasonic probe of Example 6 showed a remarkable difference particularly in the beam width of −20 dB as compared with the ultrasonic probe having a flat piezoelectric material. Further, it was confirmed that the ultrasonic probe of Example 6 became a narrow beam due to suppression of the side lobe level. Further, it was confirmed that the ultrasonic probe of Example 6 improved the signal S / N by 5 dB as compared with the ultrasonic probe using the acoustic lens.

In the sixth embodiment, the bonding between the ground electrode plate 17 and the conductive film and the bonding between the flexible printed wiring board 18 and the conductive film are performed by soldering or resistance welding in addition to the method using the conductive paste. The method may be performed.

Example 7 The single crystal of 91PZN-9PT obtained in Example 1 was oriented in the [001] axis direction using a Laue camera and cut with a cutter perpendicular to this axis. Subsequently, a Ti / Au electrode was formed on the (001) plane of the cut single crystal piece by sputtering, and an electric field of 1 kV / mm was applied in silicone oil at 150 to 200 ° C. for 30 minutes. While cooling. Subsequently, the single crystal piece and the electrode were cut into a regular hexagon, and the capacitance, resonance, and antiresonance frequency were measured. As a result, the relative dielectric constant is 2200,
Speed of sound is 3250m / s, the electromechanical coupling coefficient k _t 70~
It was confirmed to be 75%.

Further, using the single crystal of 91PZN-9PT, a transmitter 36 having a plurality of ultrasonic generating elements 35 shown in FIG. 9 was manufactured. That is, as shown in FIG. 10, a piezoelectric body 31 having a thickness set so as to have a resonance frequency of 500 kHz is cut out from the single crystal.
After the Ti / Au electrodes 32 and 33 were formed on the (001) plane by sputtering, respectively, an acoustic matching layer 34 was formed on the upper electrode 32 side to produce an ultrasonic wave generating element 35. Subsequently, a plurality of the ultrasonic wave generating elements 35 were densely arranged in a substantially spherical shell shape having a diameter of 330 mm and a curvature of 260 mm to constitute the above-described transmitter 36 shown in FIG.

In the transmitter 36, the thickness of the piezoelectric body 31 incorporated in each of the ultrasonic wave generating elements 35 is about 3.
The thickness was 2 mm, which was smaller than the thickness (4 mm) of a piezoelectric body made of a conventional PZT ceramic. As a result, each of the ultrasonic wave generating elements 35 can apply an electric field 25% larger than the electrodes 32 and 33 to the piezoelectric body 31 as compared with the ultrasonic wave generating element having a piezoelectric body made of PZT-based ceramic. The sound pressure could also be increased in proportion to the electric field. Further, the weight of each of the ultrasonic generating elements 35 can be reduced by 20% as compared with the conventional ultrasonic generating element, and the weight is reduced.

In the seventh embodiment, although a regular hexagonal ultrasonic wave generating element is used and these elements are densely arranged to constitute a transmitter, the present invention is not limited to this. For example, FIG.
The transmitters 36 and ultrasonic wave generating element 35 ₂ of the trapezoid and fan-shaped ultrasonic generating elements 35 ₁ and different opposing sides curvature lengths densely arranged in spherical shell as shown in (b) You may comprise.

Examples 8 to 12 and Reference Examples 4 and 5 First, as a starting material, chemically high-purity PbO and Zn were used.
Using O, Nb ₂ O ₅ , and TiO ₂ , the purity of these materials was corrected, these raw materials were weighed to a predetermined amount, and the same amount of PbO was added as a flux. Alcohol is added to this powder, and the powder is added to a ball mill containing ZrO ₂ balls.
Mix for hours. After removing the alcohol from the obtained mixture, the mixture was pulverized sufficiently with a raikai machine, further placed in a rubber-type container, and subjected to rubber press at a pressure of 2 ton / cm ² .
1000g of solid material taken out from rubber mold is 50m in diameter
m, placed in a 250 cc platinum container, sealed with a platinum lid, and then placed in the center of an electric furnace. 10
The temperature is raised to a temperature of 00 to 1280 ° C in 5 hours,
It was gradually cooled to 700 to 900 ° C. at a rate of 5 ° C./hr. Then, 30% nitric acid was added to the platinum container,
The mixture was boiled for 4 hours to dissolve the flux portion, and a solid solution single crystal was taken out. The single crystal obtained by such a flux method was amorphous, but the large one was about 20 mm square. When a part of the single crystal was pulverized and subjected to X-ray diffraction, it was confirmed that the single crystal had a good crystal structure. When the powder was subjected to chemical analysis by ICP,
Zinc niobate (PZN) and lead titanate (PT) are 9
It was confirmed that the composition was 91PZN-9PT having a molar ratio of 1: 9.

Next, the [001] axis orientation of the single crystal was determined using a Laue camera, and the single crystal was cut perpendicularly to this axis by a cutter to form seven single crystal pieces. Both surfaces of each single crystal piece, that is, the (001) surface which is the surface opposite to the ultrasonic transmitting / receiving surface and the transmitting / receiving surface is made of abrasive grains of alumina or silicon carbide of # 400 to # 8000 or cerium oxide powder of 1 μm. The paste was polished. The surface roughness of each polished single crystal piece was measured at 10 points at intervals of 1 mm using a contact surface roughness meter. Table 3 below shows the maximum surface roughness and average surface roughness obtained by this measurement. Subsequently, Ni / Au electrodes were formed on the polished surfaces (both surfaces) of each of the single crystal pieces by a sputtering method, and an electric field of 0.5 to 1 kV / mm was applied in silicone oil at 150 to 200 ° C. for 15 minutes. Then, it cooled to 40 degreeC, applying an electric field. Subsequently, the single crystal pieces and the electrodes were cut into strips each having a width of 80 μm, and the capacitance, resonance, and antiresonance frequency were measured. As a result, the relative dielectric constant is 3000 and the sound speed is 2850 m
/ S. The electromechanical coupling coefficient k ₃₃ ′ was a value shown in Table 3 below.

[0100]

[Table 3]

Further, the thickness of the single crystal in the vibration direction is 3
Cut out to a thickness of 00 μm and polished with a paste containing abrasive grains or cerium oxide powder as described above. The array type ultrasonic probe shown in FIG. In addition, cutting with a blade of 30 μm width is performed with a cutting depth of 1 mm and 0.13 m.
The measurement was performed at a pitch of m, and the obtained 96 piezoelectric bodies had a width of about 80 μm.

The reflection echo was measured for each of the ultrasonic probes by the pulse echo method. As a result, echoes having a center frequency of about 2.5 MHz were received from all the ultrasonic transmission / reception elements.

For each of the array-type ultrasonic probes, two rectangular waves having a repetition frequency of 5 kHz, a voltage of 100 V, a load ratio (duty ratio) of 1: 1 and a pulse width of 0.2 μs were operated for 1000 hours and 3000 hours. After the test, the peak value of the reflected echo was measured. When the obtained peak value was deteriorated by 30 or more compared to the value before the actual operation test, it was defined as a failure, and the number of failures of 96 elements incorporated in the probe was examined. The results are shown in Table 4 below.

[0104]

[Table 4]

As is evident from Tables 3 and 4, the piezoelectric surface having an average surface roughness of 0.4 μm or less and a maximum surface roughness of 4 μm or less on the ultrasonic transmitting / receiving surface and the surface opposite to the ultrasonic transmitting / receiving surface, respectively. ultrasonic probe of example 8-12 with body, not only has high electromechanical coupling coefficient k ₃₃ ', it can be seen that the long-term reliability is excellent.

The amount of lead titanate in the lead zinc niobate-lead titanate solid solution single crystal may be changed in the range of 5 to 20 mol% (molar ratio of 0.05 to 0.20), The ultrasonic probe shown in FIG. 1 was manufactured using a piezoelectric material cut out of a single crystal having a composition partially containing magnesium or zirconium. Such an ultrasonic probe had almost the same effect on the long-term reliability due to the surface roughness.

[0107]

As described above, according to the present invention, low-frequency driving can be achieved, and the thickness of the piezoelectric body in the vibration direction can be reduced, so that matching with the transmitting / receiving circuit can be easily achieved, and higher sensitivity can be achieved. It is possible to provide an ultrasonic transmitting / receiving element capable of performing the above.

Further, according to the present invention, low-frequency driving can be achieved, and the thickness of the piezoelectric body in the vibration direction can be reduced, so that matching with the transmission / reception circuit is easy, and the ultrasonic transmission / reception which can further increase the sensitivity is achieved. It is possible to provide an ultrasonic probe having an element and useful for a medical diagnostic apparatus and the like.

Further, it is possible to provide a powerful ultrasonic wave transmitting device for an ultrasonic therapy apparatus which can generate a shock wave with good controllability and is suitable as a shock wave source for a calculus crushing apparatus and a thermal therapy apparatus.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ultrasonic probe according to the present invention.

FIG. 2 is a perspective view showing another ultrasonic probe according to the present invention.

FIG. 3 is a schematic diagram showing an apparatus having a function of controlling heat generation of an ultrasonic probe according to a fifth embodiment of the present invention.

FIG. 4 shows a temperature of a solid solution single crystal of 91PZN-9PT as a piezoelectric material used in the ultrasonic probe of FIG. 3;
FIG. 3 is a diagram showing a relationship between relative dielectric constants.

FIG. 5 is a characteristic diagram showing a time change of a temperature difference from outside air when heat generation control of an ultrasonic probe is performed in the apparatus of FIG. 3;

FIG. 6 is a characteristic diagram showing an electromechanical coupling coefficient along a slice direction of the piezoelectric body in an ultrasonic transmitting / receiving element having a piezoelectric body having a concave ultrasonic transmitting / receiving surface.

FIG. 7 is a characteristic diagram showing a sound field measurement result of the array type ultrasonic probe according to the sixth embodiment.

FIG. 8 is a characteristic diagram showing a sound field measurement result of an array-type ultrasonic probe having a flat piezoelectric body.

FIG. 9 is a plan view showing a transmitter according to a seventh embodiment of the present invention.

FIG. 10 is a perspective view showing an ultrasonic generator incorporated in the transmitter of FIG. 9;

FIG. 11 is a schematic view showing another example of the transmitter of the present invention.

[Explanation of symbols]

1, 11, 31 ... piezoelectric body, 3, 4, 13, 14, 32,
33 ... electrode, 5, 15, 34 ... acoustic matching layer, 6 ...
Acoustic lens, 7, 16 ... ground electrode, 8, 17 ... flexible printed wiring board, 36 ... wave transmitter.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mamoru Izumi 1 Tokoba, Komukai Toshiba-cho, Saisaki-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Shinichi Hashimoto Toshiba Komukai, Kochi-ku, Kawasaki-shi, Kanagawa No. 1, Toshiba Research and Development Center Co., Ltd. (56) References JP-A-54-34581 (JP, A) JP-A-56-115882 (JP, A) JP-A-56-115586 (JP, A) 56-71211 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 8/00-8/15 G01N 29/00-29/28 H01L 41/18 H04R 17/00 332 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, and a pair of electrodes provided on an ultrasonic transmitting / receiving surface of the piezoelectric body and a surface opposite to the transmitting / receiving surface, respectively. Wherein the piezoelectric body has an average surface roughness of 0.4 μm or less and a maximum surface roughness of 4 μm or less, respectively, on the ultrasonic transmission / reception surface and the surface opposite to the ultrasonic transmission / reception surface. An ultrasonic transmitting / receiving element characterized by the above-mentioned. Wherein said zinc niobate - solid-solution single crystal of lead _{titanate, Pb A [(Zn 1/3 Nb} 2/3) 1-x Ti x] B O 3 ( here, x is 0. 05 ≦ x ≦ 0.20, stoichiometric ratio A / B
The ultrasonic transmission / reception element according to claim 1, wherein the composition is represented by the following formula: 0.98 ≦ A / B <1.00. 3. The ultrasonic transmitting / receiving element according to claim 1, wherein: an acoustic matching layer provided on the ultrasonic transmitting / receiving surface of the ultrasonic transmitting / receiving element; and an acoustic lens provided on the acoustic matching layer. An ultrasonic probe, comprising: a backing material provided on a surface of the ultrasonic transmitting / receiving element opposite to the ultrasonic transmitting / receiving surface. 4. A piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, and a pair of ultrasonic transmitting / receiving surfaces of the piezoelectric body and a pair of surfaces provided on the surface opposite to the ultrasonic transmitting / receiving surface. An ultrasonic transmitting / receiving element having an electrode; an acoustic matching layer provided on the ultrasonic transmitting / receiving surface of the ultrasonic transmitting / receiving element; an acoustic lens provided on the acoustic matching layer; An ultrasonic probe, comprising: a backing material provided on a surface opposite to the transmitting / receiving surface. Wherein said zinc niobate - solid-solution single crystal of lead _{titanate, Pb A [(Zn 1/3 Nb} 2/3) 1-x Ti x] B O 3 ( here, x is 0. 05 ≦ x ≦ 0.20, stoichiometric ratio A / B
5. The ultrasonic probe according to claim 4, comprising a composition represented by: 0.98 ≦ A / B <1.00. 6. A piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, and a pair of ultrasonic transmitting and receiving surfaces of the piezoelectric body and a pair of surfaces provided on the surface opposite to the ultrasonic transmitting and receiving surface. A plurality of ultrasonic transmitting / receiving elements having electrodes; an acoustic matching layer provided on each of the ultrasonic transmitting / receiving surfaces of the plurality of ultrasonic transmitting / receiving elements; an acoustic lens provided on the acoustic matching layer; A backing material provided on a surface of the transmitting / receiving element opposite to the ultrasonic transmitting / receiving surface; and the piezoelectric body has a thickness such that the ultrasonic transmitting / receiving surface is concavely curved in a direction orthogonal to the arrangement direction thereof and has a thickness. Has a constant shape, and a central portion of the concave ultrasonic transmitting / receiving surface has a maximum electromechanical coupling coefficient. 7. A piezoelectric body made of a solid solution single crystal of lead zinc niobate-lead titanate, and a pair of ultrasonic wave generating surfaces of the piezoelectric body and a pair of surfaces provided on a surface opposite to the ultrasonic wave generating surface. A plurality of ultrasonic wave generating elements having electrodes; an acoustic matching layer provided on each of the ultrasonic transmitting and receiving surfaces of the plural ultrasonic wave transmitting and generating elements; A transmitter for an ultrasonic therapy device, which is disposed.