JP2000143335A - Ceramic material, ultrasonic probe, piezoelectric oscillator and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alley-type ultrasonic probe and a piezoelectric oscillator having a backing layer comprising a ceramic material having high acoustic impedance and giving an elastomer matching with a piezoelectric material and applicable to a versatile medical ultrasonic diagnostic apparatus. SOLUTION: The objective alley-type ultrasonic probe 1 is produced by at least one-dimensionally arranging a piezoelectric material 2 to transmit and receive ultrasonic wave, a backing layer 3 placed at the back of the piezoelectric material and having an acoustic impedance larger than that of the piezoelectric material and a number of ultrasonic transmitting and receiving elements 10 provided with a backing material 4 having an acoustic impedance smaller than that of the backing layer. A ceramic material produced by adding <=5 wt.% of manganese oxide to a composite perovskite oxide composed mainly of lead, lanthanum, titanium, zinc and niobium and expressed by compositional formula: XLa(Zn2/3Nb1/3)O3-(1-X)PbTiO3 (X is 0.05 to 0.35) is used as the backing layer having an acoustic impedance larger than that of the piezoelectric material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe, an acoustic matching porcelain material used for an ultrasonic transmitting / receiving element of the above ultrasonic probe, and a porcelain material for a piezoelectric vibrator.

[0002]

2. Description of the Related Art In an ultrasonic probe conventionally used in the fields of measurement such as medical treatment and flaw detection, a piezoelectric body for transmitting and receiving ultrasonic waves has a half wavelength for efficiently generating ultrasonic waves having a desired center frequency fc. A resonant vibration mode is used.

FIG. 9 is a sectional view of a conventional ultrasonic probe. 9, 1 is an ultrasonic probe, 2 is a piezoelectric body, 4 is a backing material, 5 is a first matching layer, 6 is a second matching layer, 11
Numerals are electrodes provided on both end surfaces of the piezoelectric body, and numeral 12 is a signal line for coupling the electrode 11 to a transmitting / receiving circuit (not shown).

In the configuration shown in FIG.
When a drive signal from a transmission circuit is applied through the piezoelectric element 2, a strain in the thickness direction is generated inside the piezoelectric body 2, and as a result, a half-wave resonance, which is a fundamental resonance of the longitudinal vibration in the thickness direction, is strongly excited to generate ultrasonic waves. Radiated. Therefore, the thickness of the piezoelectric body 2 is substantially equal to a half wavelength of the frequency of the emitted ultrasonic wave.

In this case, the electric power entering the piezoelectric body is also distributed as acoustic power to the backing material 4, so that the acoustic power to the subject is small and the efficiency of the ultrasonic probe is reduced. It has become. As a structure for improving the efficiency of the ultrasonic probe by providing a layer different from the piezoelectric body on the back side of the piezoelectric plate, for example, an ultrasonic probe described in JP-A-53-2539 is known. ing. FIG. 10 is a perspective view of an ultrasonic probe described in Japanese Patent Application Laid-Open No. 53-2539.

In FIG. 10, 1 is an ultrasonic probe, 2 is a piezoelectric body, 3 is a back layer, 4 is a backing material, and 11 is an electrode layer. In the above configuration, the piezoelectric body 2 is used and has a thickness of 1/4 wavelength of the center frequency.
And, it has an acoustic impedance larger than that of the backing material 4 and is designed to have a thickness of 1/4 wavelength or an odd multiple thereof. The material of the piezoelectric body 2 is a piezoelectric material such as zinc oxide, and is formed on the back layer 3 by a process such as sputtering. By applying a drive voltage to the electrode 14, the piezoelectric body 2 performs quarter-wave resonance and emits ultrasonic waves.

[0007] At this time, since the impedance as viewed from the end face on the back layer side of the piezoelectric body 2 is increased, the radiation of energy to the back layer 3 side is reduced, thereby realizing a highly efficient ultrasonic probe.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned problems of the prior art, and uses a piezoelectric ceramic having a high piezoelectric constant, and has an acoustic impedance larger than that of the piezoelectric material. Porcelain materials with high precision, and by joining them precisely, the combined longitudinal vibration mode is reduced to a quarter of the fundamental standing wave. This enables a piezoelectric vibrator having a sub-band at twice the frequency in addition to the conventional vibration mode, and provides a method of manufacturing a high-sensitivity ultrasonic probe and a piezoelectric vibrator as the ultrasonic transmitting / receiving element. The purpose is to:

However, in the prior art, since the piezoelectric body is formed by a process such as sputtering, the thickness of the piezoelectric body is about several tens μm, and the frequency thereof is about several tens MHz. It cannot be applied to a frequency of about several MHz that is generally used, and the operating area is large with respect to the thickness of the piezoelectric body.
Since the driving method is the t mode, at least one of the elements is used.
One side is as narrow as the wavelength, and the Poisson's ratio has a significant effect on the characteristics, and furthermore, there is a problem that it cannot be directly applied to an array-type element requiring fine cutting. Further, a material having a large acoustic impedance has a hard and brittle property, so that processing is very difficult.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an array-type ultrasonic wave having a large acoustic impedance porcelain material on a back layer, which is an elastic material suitable for a piezoelectric material applicable to a current general-purpose medical ultrasonic diagnostic apparatus. It is an object to provide a probe and a piezoelectric vibrator.

[0011]

According to the present invention, a back layer made of a material having a higher acoustic impedance than the piezoelectric material and the backing material is provided between the piezoelectric material and the backing material. And the ratio of the width of each element constituting the array to the total thickness of the piezoelectric body and the back layer is 1 or less.

In order to solve this problem, as a porcelain material which is easily bonded to a piezoelectric ceramic and has a high acoustic impedance, a composite perovskite-type oxide containing lead, lanthanum, titanium, zinc and niobium as main components in the present invention has a composition formula There _{XLa (Zn 2/3 Nb 1/3} ) O 3 - (1-X) PbTi
The present invention provides a porcelain material represented by O ₃ , wherein X is in the range of 0.05 to 0.35, and further containing not more than 5% by weight of manganese oxide.

Furthermore, in order to realize the piezoelectric vibrator or the ultrasonic probe according to the present invention, in order to improve the bonding state with the piezoelectric ceramic, powder having a median diameter of 0.7 μm or less is made of a polymer material ( Nitrocellulose, polyvinyl alcohol, etc.) as a pressure-sensitive adhesive, a thin electrode of several μm or less is formed at the interface, and then baked to make the thickness of the bonding layer uneven at 0.5 μm or less, and a piezoelectric vibrator having desired characteristics Alternatively, an ultrasonic probe is obtained. According to these inventions, a high-sensitivity ultrasonic probe having an unprecedented frequency band characteristic can be obtained.

Further, the above-mentioned piezoelectric ceramic and the composition formula X
The manufacturing method for realizing the lamination of the ceramic material mainly composed of the material represented by La (Zn2 / 3Nb1 / 3) O3- (1-X) PbTiO3 was also specified.

According to the present invention, an array-type ultrasonic probe and a piezoelectric vibrator applicable to an ultrasonic diagnostic apparatus can be realized.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention
Consists mainly of lead, lanthanum, titanium, zinc and niobium
The composition formula of the complex perovskite oxide is XL
a (Zn_2/3Nb _1/3) O_Three-(1-X) PbTiO_ThreeCan be expressed as
X is in the range of 0.05 to 0.35 and manganese oxidation
Porcelain material characterized by the addition of 5% by weight or less
Combined with piezoelectric ceramic with high piezoelectric constant by using
High-sensitivity array-type ultrasonic probe
Wear.

According to a second aspect of the present invention, there is provided a piezoelectric body for transmitting and receiving ultrasonic waves, a back layer having a larger acoustic impedance than the piezoelectric body on the back side of the piezoelectric body, and a backing material having a smaller acoustic impedance than the back layer. In an array type ultrasonic probe in which a number of ultrasonic transmitting / receiving elements having at least one are arranged in at least one dimension, a composition formula is used in a composite perovskite type oxide mainly containing lead, lanthanum, titanium, zinc, and niobium as a back layer. Is XLa (Zn _2/3 Nb
_1/3 ) O _3- (1-X) PbTiO ₃ , where X is 0.05 to 0.35
A high-sensitivity array-type ultrasonic probe combined with a piezoelectric ceramic having a high piezoelectric constant is realized by using a porcelain material characterized by adding manganese oxide in an amount of 5% by weight or less. can do.

According to a third aspect of the present invention, there is provided the piezoelectric vibrator according to the first aspect, wherein the thickness of the back layer is 0.05 to 0.25 times the wavelength at the center frequency. Yes, by setting the thickness of the piezoelectric body in the above range, it is possible to obtain the maximum sensitivity at a desired center frequency.

According to a fourth aspect of the present invention, when the ultrasonic probe according to the second aspect is manufactured, the porcelain material and the piezoelectric ceramic material according to the first aspect are formed into green sheets, electrodes are formed at the interface, and firing is performed. This makes it possible to obtain a highly sensitive ultrasonic probe.

According to a fifth aspect of the present invention, when manufacturing the piezoelectric ceramic resonator according to the third aspect, the porcelain material and the piezoelectric ceramic material according to the first aspect are formed into a green sheet, and electrodes are formed at an interface, and then fired. It is possible for the piezoelectric ceramic vibrator formed by the above to obtain the maximum output at a desired center frequency.

According to a sixth aspect of the present invention, there is provided a viscous material obtained by finely dividing the porcelain material according to the first aspect and mixing with a polymer material, and a viscous material having a particle size of 5 μm or less as a precursor for the piezoelectric ceramic according to the third aspect. Manufacturing a viscous body in which dielectric particles are mixed with a polymer material into a desired structure in advance, forming electrodes at desired positions, and then sintering to produce a piezoelectric vibrator having a desired shape. Becomes possible.

According to a seventh aspect of the present invention, the green sheet on which the electrodes are formed is processed into a desired structure in advance, inserted into a mold containing carbon or platinum as a main component, and then sintered to obtain a desired structure. It becomes possible to manufacture a piezoelectric vibrator having a shape.

According to an eighth aspect of the present invention, it is possible to manufacture a desired two-dimensional or three-dimensional piezoelectric ceramic resonator by subjecting a green sheet to laser processing into a desired structure in advance and then sintering the green sheet. Become.

Next, a specific example of the present invention will be described. (Example 1) First, a composite perovskite-type oxide containing lead, lanthanum, titanium, zinc, and niobium as main components according to the present invention has a composition formula of XLa (Zn _2/3 Nb _1/3 ) O ₃ −.
(1−X) PbTiO ₃ , wherein X is in the range of 0.05 to 0.35, and a manganese oxide is added in an amount of 5% by weight or less, and a porcelain material and a ceramic material having piezoelectric characteristics are formed into powder. I do.

The above composition XLa (Zn _2/3 Nb _1/3 ) O _3-
(1-X) PbTiO ₃ is, lanthanum oxide, zinc oxide, 800 niobium pentoxide, titanium oxide, lead oxide as a starting material
A powder that has been temporarily calcined several hours at a temperature of from 900C to 900C is used. At this time, the powder is pulverized and classified so that the average particle size is 0.7 μm or less and the maximum particle size is 5 μm or less, and then polyvinyl alcohol (PVA), which is a polymer material, is used.
Or an organic solvent containing polyvinyl butyral (PVB) is added to each powder and mixed to form a clay. Piezoelectric ceramic materials are similarly ground and classified, mixed with a polymer solution, and made into a clay state. Next, the shrinkage ratio at the time of sintering is measured in advance so as to have the final dimensional shape, and the shape of each sheet is determined.

Here, the XLa (Zn _2/3 Nb _1/3 ) O of the present invention is used.
It is important to match the contraction rates of the _3- (1-X) PbTiO ₃ -based ceramic material and the piezoelectric ceramic material. For this purpose, the calcination temperature of both materials was adjusted to match the dimensions after sintering. At this time, when a thin green sheet is formed, the viscosity is reduced, and the thin green sheet is poured out from between narrow slits and laid on a polyethylene terephthalate sheet and dried to obtain a thin green sheet having flexibility.

Next, electrodes were formed at predetermined positions on the green sheet of piezoelectric ceramic material by vapor deposition or printing, processed into a desired shape, and the ceramic material sheet of the present invention and the piezoelectric ceramic sheet were laminated. It is fired in an electric furnace or the like in the state.

At this time, the substrate is once held at a temperature of 400 to 700 ° C. or lower for several hours to remove PVA or PVB as a binder, and then fired at 1100 to 1250 ° C. for about 2 hours to obtain a desired piezoelectric vibrator. It was created.

Here, X, which is a porcelain material according to the present invention, is used.
FIG. 1 shows the acoustic impedance characteristics of La (Zn _2/3 Nb _1/3 ) O _3- (1-X) PbTiO ₃ based porcelain material. The maximum value is obtained when the molar ratio X is 0.2, and the range of 0.05 to 0.35 is effective depending on the combination with the piezoelectric ceramic material. Exceeding this range results in a value comparable to the acoustic impedance of the piezoelectric ceramic material.

Further, XLa (Zn _2/3 Nb _1/3 ) O _3- (1
-X) When a small amount (5% by weight or less) of manganese oxide was added to the PbTiO ₃ -based porcelain material and fired, the speed of sound was improved by about 5%.

As the piezoelectric ceramic material at this time, a ferroelectric material of a perovskite oxide or a ferroelectric material having a tungsten bronze structure was used. Specifically, the present invention can be implemented by an oxide piezoelectric material containing two or more elements of lead, barium, strontium, zinc, niobium, tantalum, magnesium, titanium, zirconium, and lanthanide.

In addition, instead of a piezoelectric ceramic material, a ferroelectric single crystal XLa (Zn _2/3 Nb _1/3 ) of a perovskite oxide containing lead as a piezoelectric material having a low acoustic impedance is used.
It could be combined with O _3- (1-X) PbTiO ₃ (X is 0.08 to 0.15). As the electrode material, platinum, palladium containing silver, or nickel was used.

On the other hand, the XLa (Zn _2/3 Nb _1/3 ) O of the present invention
_{When the 3-} (1-X) PbTiO ₃ -based porcelain material and the piezoelectric material are in the form of a sintered body or a single crystal plate, the porcelain material of the present invention and the piezoelectric material which are to be the back layers have a surface roughness of 0.25 μm or less. Then, the adhesive layer was bonded with an adhesive so as to have a thickness of 0.5 μm or less. In this case, an electrode material such as silver, gold, platinum, or copper was formed by vapor deposition.

In order to increase the bonding strength, chromium or titanium was formed on the interface between the electrode and the piezoelectric material at a thickness of 100 nm or less.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 8 for an ultrasonic probe and a piezoelectric vibrator using the porcelain material of the present invention.

Embodiment 1 FIG. 2 is a perspective view of an ultrasonic probe according to Embodiment 1 of the present invention. In FIG. 2, 1 is an ultrasonic probe, 2 is a piezoelectric body for transmitting and receiving ultrasonic waves,
Is a backing layer provided on the backside of the piezoelectric body 2, 4 is a backing material provided behind the backing layer and supports the entire ultrasonic probe 1, and 5 and 6 are acoustic waves with the subject (not shown). A first and a second matching layer for performing a target matching, 7 is an acoustic lens for performing focusing in a short axis direction, 8 is a dicing gap provided for forming an array, 9 is a dicing gap filled in the dicing gap, and A filler 10 for maintaining the mechanical strength of the acoustic probe is an ultrasonic transmitting / receiving element constituting an array.

FIG. 3 is a schematic sectional view of an ultrasonic probe according to the first embodiment of the present invention. In FIG. 3, reference numeral 11 denotes an electrode layer provided on both end surfaces of the piezoelectric body 2, and 12 denotes signal lines connected to the electrode layers of the piezoelectric body, which are connected to a transmitting / receiving circuit circuit (not shown) in the main body. I have. Also one
Reference numeral 3 denotes an adhesive layer for joining the piezoelectric body 2 and the back layer 3. Here, the bonding layer 13 can be made zero by a manufacturing method.

A description will be given of an example of a method of manufacturing the ultrasonic probe 1 configured as described above. First, the center frequency of the ultrasonic wave used for measurement is determined. The center frequency is determined based on the size of the measurement target, the distance to the measurement target, a desired resolution, and the like. After the center frequency is determined, the thickness of the piezoelectric body 2 is set to about 0.2 to 0.3 times the wavelength determined by the relationship between the set center frequency and the sound speed of the piezoelectric body 2, and the piezoelectric body 2 having a predetermined thickness is set.
Is prepared by grinding or polishing. In addition, dimensions other than the thickness may be determined in consideration of the use environment of the ultrasonic probe 1, the measurement object, and the like, and may be processed in advance to a predetermined size using a dicer, a wire saw, or the like.

The material of the piezoelectric body 2 is a piezoelectric ceramic such as PZT,
Any material having piezoelectricity such as a piezoelectric composite material or a piezoelectric polymer material may be used, but a material having a large electromechanical coupling coefficient is desirable. Baking on both sides of this piezoelectric body 2
The electrode 11 is formed by printing, sputtering, or the like. The electrode material may be a metal having good conductivity, and it is preferable that the electrode is formed as thin as possible from the viewpoint of acoustic characteristics.

On the back side of the piezoelectric body 2 on which the electrode 11 is formed,
The back layer 3 made of a material having a higher acoustic impedance than the piezoelectric body 2 is processed into a predetermined size, and then joined with an adhesive. The thickness of the back layer 3 is 0.05 to 0.25 with respect to the wavelength determined by the relationship between the center frequency fc and the sound velocity Vb of the back layer 3.
Set to about twice and make by grinding, polishing, etc.

In the bonding step, it is necessary to make the bonding layer 13 as thin as possible by using a die set or a dedicated bonding jig. The material of the back layer 3 may be any material having an acoustic impedance higher than that of the piezoelectric body 2.
It is desirable to use a material having a good bonding property with the material and a good cutting property in order to form an array.

The porcelain material effective as the back layer 3 according to the present invention has an acoustic impedance of 33 Mkg / (m 2 · s).
With the above structure, even if a PZT-based piezoelectric ceramic having an acoustic impedance of about 32 Mkg / (m 2 · s) is used as the piezoelectric body, it is a suitable material for the back layer. XLa which is a porcelain material according to the present invention
_{(Zn 2/3 Nb 1/3) O 3} - acoustic impedance characteristics of the (1-X) PbTiO ₃ based ceramic material was not meet this condition.

After bonding the piezoelectric body 2 and the back layer 3, the backing agent 4, the first matching layer 5, and the second matching layer 6 are bonded, and a dancing gap 8 is formed using a dicer or the like. At this time, the ratio of the width W of each ultrasonic transmitting / receiving element 1 to the total thickness T of the piezoelectric body 2 and the back layer 3 is 0.8 or less, preferably 0.6.
Set as follows. When the ultrasonic probe 1 requires mechanical strength, the dicing gap 8 is filled with a filler 9.

As the filler, for example, an epoxy resin, a silicone resin, or a polyurethane resin having a low hardness may be used in order to suppress the crosstalk between the array elements to a low level. Acoustic lens 7 after filling with filler 9
Glue. It is sufficient that the signal line 11 can be electrically connected to the upper and lower electrodes 10 of the piezoelectric body 2.
Alternatively, after the bonding, the electrodes 10 are bonded by soldering, conductive paste, wire bonding, or the like.

According to the above-described manufacturing method, the piezoelectric body 2
Back layer 3 and backing material 4, piezoelectric body 2 and first matching layer 5, first matching layer 5
3, an adhesive layer exists between the second matching layer 6 and the acoustic lens 7, but is omitted in FIG.

The operation of the ultrasonic probe 1 configured as described above will be described with reference to FIG. When the probe according to the first embodiment of the present invention shown in FIG. 2 is designed, the thickness of the piezoelectric body 2 is set to 0.2 to 0.3 wavelength, and the thickness of the piezoelectric body 2 is increased by using a conventional half wavelength resonance. It is designed to be thinner than an acoustic probe.

When the driving voltage V is applied, the electric field strength generated inside the piezoelectric body is inversely proportional to the thickness of the piezoelectric body. Therefore, the ultrasonic probe of the present invention has a larger internal strength than a conventional ultrasonic probe. Has a large electric field strength, and thus a large distortion occurs. Dimensionally, the thickness of the piezoelectric body 2 in this embodiment is:
Since the thickness of the piezoelectric body 2 is about half the thickness of the conventional piezoelectric body 2, the piezoelectric body 2
The distortion caused by the electric field inside is about twice that of the conventional one.

When the thickness of the piezoelectric body 2 is reduced and the electric field strength is increased to increase the internal strain, the two end faces of the piezoelectric body 2 vibrate in a nearly free state, so that half-wave resonance in the thickness direction is strongly excited. Although the center frequency increases, the ultrasonic probe 1 according to the present embodiment
XLa (Zn _2/3 Nb _1/3 ) O ₃ −, which is a porcelain material according to the present invention, is used as the back layer 3 having higher acoustic impedance.
By providing the (1-X) PbTiO ₃ ceramic material,
Vibration on the back layer side of the piezoelectric body 2 was suppressed, and large strain was able to be generated in a state where the increase in the center frequency was suppressed. As a result, an ultrasonic probe with high transmission efficiency and high reception sensitivity was obtained.

In order to construct a highly efficient array type ultrasonic probe, the relationship between the thickness of the piezoelectric body 2 and the width of the ultrasonic transmitting / receiving element 10 is important. It is said that the ratio of the width to the thickness of the body is preferably 1 or less, preferably 0.6 or less. In the case of the ultrasonic probe 1 according to the first embodiment of the present invention, the vibration characteristics when the piezoelectric body 2 and the back layer 3 are considered integrally are important.

FIG. 4 shows the results of simulating impedance characteristics by changing the relationship between the width of the ultrasonic transmitting / receiving element 10 and the thickness of the combined piezoelectric body 2 and back layer 3 as T. FIG. 4A shows W / T = 0.5, and FIG. 4B shows W / T =
0.6 and (c) are the results when W / T = 0.8.

In FIGS. 4A and 4B, 5 MHz to 4 MHz
A large longitudinal vibration resonance appears around MHz,
In (c), it can be seen that horizontal resonance occurs in the anti-resonance part, which affects the longitudinal vibration characteristics as a whole.
FIG. 4 shows that the ultrasonic transmitting / receiving element 10 in the present embodiment
In order to increase the efficiency of the ultrasonic transmission / reception element 10
And the ratio W / of the thickness T of the piezoelectric body 2 and the back layer 3 together
It is necessary to design T to be 0.8 or less, preferably 0.6 or less.

The thickness and acoustic impedance of the back layer 3 affect the sensitivity of the ultrasonic probe, and have different effects on transmission sensitivity and reception sensitivity. FIGS. 5 and 6 show the relationship between the sensitivity characteristic of the ultrasonic probe and the thickness and acoustic impedance of the back layer 4 in the present embodiment, where the vertical axis represents the relative sensitivity and the horizontal axis represents the center frequency. This is the thickness of the back layer normalized by wavelength. Figure 5 shows the transmission sensitivity,
FIG. 6 shows the receiving sensitivity. As shown in FIG. 5, the transmission sensitivity reaches the maximum value when the thickness of the back layer is around 0.15 wavelength.

On the other hand, as shown in FIG. 6, the reception sensitivity has little dependence on the acoustic impedance of the back layer 4. In this case, the overall sensitivity becomes maximum around 0.2 to 0.25 wavelength, and the relative sensitivity increases as the ratio of the acoustic impedance of the back layer 3 to the piezoelectric body 3 increases.
By utilizing the difference between the thickness of the back layer and the effect of the acoustic impedance as shown in FIGS. 5 and 6, the ultrasonic waves having different transmission sensitivities or reception sensitivities can be used without making significant changes to other structures such as the piezoelectric body 2. The probe can be easily designed and manufactured.

Further, the piezoelectric body 2 and the back layer 3 are bonded by bonding.
In this case, the thickness and the acoustic impedance of the adhesive layer 13 in FIG. FIG. 7 shows an ultrasonic probe 1 in the case where the thickness of the adhesive layer 13 is constant and the acoustic impedance Z of the adhesive is changed from 0 to 10.
12 is a simulation result of a change in the band characteristic of FIG. FIG.
As shown in (1), when the acoustic impedance is low, the band characteristic is narrowed and the sensitivity is remarkably reduced.

FIG. 8 shows a decrease in sensitivity when the thickness normalized by the acoustic impedance and the center frequency of the adhesive layer is changed. It is actually impossible to make the thickness of the adhesive layer zero, and the acoustic impedance of a commonly used polymer adhesive such as epoxy resin has an acoustic impedance of 10 Mkg /
(M ² · s) or less. It is indispensable to forgive a slight decrease in sensitivity, and if the sensitivity is to be reduced to within -3 dB with respect to the theoretical sensitivity, the adhesive layer is required to have a thickness of 0.0.
It is necessary to control the wavelength to one wavelength or less.

As described above, according to the present embodiment, the piezoelectric body for transmitting and receiving the ultrasonic wave, the back layer having a larger acoustic impedance than the piezoelectric body on the back side of the piezoelectric body are provided, and the ultrasonic transmitting and receiving element is provided. The ratio of the width to the thickness of the piezoelectric body and the back layer should be 0.8 or less, and the adhesive layer between the piezoelectric body and the back layer should be 0.01
By controlling the wavelength to be less than the wavelength, a highly efficient ultrasonic probe can be realized. Further, by changing the thickness and the acoustic impedance of the back layer, the transmission sensitivity and the reception sensitivity can be changed, and the design flexibility of the ultrasonic probe can be expanded.

In realizing the present embodiment, a porcelain material according to the present invention, ie, XLa (Zn _2/3 Nb _1/3 ) O _3- (1-X)
A PbTiO ₃ -based porcelain material is used for the back layer 3, and XLa (Zn _2/3 Nb _1/3 ) O _3- (1-X) PbTiO ₃ is used as the piezoelectric body 2.
System piezoelectric ceramic material and single crystal XLa (Zn _2/3 Nb _1/3 ) O _3-
This prediction was consistent with (1-X) PbTiO ₃ .

Further, as a processing method, a sintered body or a single crystal is cut and polished into a desired shape and then joined, and a method of sintering after processing using a laser in a green sheet stage before sintering. Were performed, but both obtained the same result as the design prediction.

Further, after cutting the green sheet and forming electrodes, etc., the processed green sheet is inserted into a previously designed mold mainly composed of platinum or carbon, and then sintered, so that the green sheet is sintered as shown in FIG. In addition to the flat plate shape as shown in FIG. 3, a concave or convex piezoelectric body and a back layer laminated type piezoelectric vibrator or an ultrasonic probe using the same were formed.

[0060]

As described above, according to the ultrasonic probe provided with the piezoelectric vibrator using the high acoustic impedance porcelain material of the present invention, the efficiency is higher than that of the conventional ultrasonic probe. Since an ultrasonic probe can be configured, transmission / reception sensitivity is improved, and high-sensitivity measurement can be performed. Further, according to the structure of the ultrasonic probe of the present invention, it is possible to control settings such as transmission sensitivity and reception sensitivity by changing the thickness of the back layer and the acoustic impedance, thereby expanding the degree of freedom in designing the ultrasonic probe. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram relating to acoustic impedance and density of a porcelain material of the present invention.

FIG. 2 is a perspective view of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of a cross section of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a change in impedance characteristics when the ratio of the width of the ultrasonic transmission / reception element of the ultrasonic probe and the thickness of the piezoelectric back layer in the ultrasonic probe according to the first embodiment of the present invention is changed.

FIG. 5 is a diagram showing the relationship between the thickness of the back layer, the acoustic impedance, and the transmission sensitivity of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the thickness of the back layer, acoustic impedance, and reception sensitivity of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a thickness of an adhesive layer between a piezoelectric body and a back layer of the ultrasonic probe, an acoustic impedance, and a band characteristic of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the thickness of an adhesive layer between the piezoelectric body and the back layer of the ultrasonic probe, the acoustic impedance, and the sensitivity characteristics of the ultrasonic probe according to the first embodiment of the present invention.

FIG. 9 is a sectional view of a conventional ultrasonic probe.

FIG. 10 is a sectional view of a conventional ultrasonic probe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Array type ultrasonic probe 2 Piezoelectric body 3 Back layer 4 Backing material 5 First matching layer 6 Second matching layer 7 Acoustic lens 8 Dicing gap 9 Filler 10 Ultrasonic transmitting / receiving element 11 Electrode layer 12 Signal line 13 Adhesive layer 14 Metal layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/22 H01L 41/22 Z (72) Inventor Masahiko Hashimoto 3-10 Higashimita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture No. 1 Matsushita Giken Co., Ltd. F term (reference) 2G047 CA01 CB01 EA05 GB32 GB35 4C301 EE06 GA20 GB02 GB20 GB33 HH45 4G031 AA09 AA11 AA14 AA19 AA26 AA32 AA39 BA10 CA08

Claims (8)

[Claims] 1. A composite perovskite-type oxide containing lead, lanthanum, titanium, zinc and niobium as main components and having a composition formula of XLa (Zn _2/3 Nb _1/3 ) O _3- (1-X) PbTiO ₃
Wherein X is in the range of 0.05 to 0.35 and manganese oxide is added in an amount of 5% by weight or less. 2. A plurality of ultrasonic waves comprising a piezoelectric body for transmitting and receiving ultrasonic waves, a back layer having a larger acoustic impedance than the piezoelectric body on the back side of the piezoelectric body, and a backing material having a smaller acoustic impedance than the back layer. An array-type ultrasonic probe in which transmitting and receiving elements are arranged in at least one dimension, wherein the porcelain material according to claim 1 is provided as a back layer having an acoustic impedance larger than that of the piezoelectric body. Tentacles. 3. A piezoelectric vibrator, wherein the porcelain material according to claim 1 is combined with a piezoelectric ceramic. 4. The ultrasonic probe according to claim 2, wherein the porcelain material and the piezoelectric material according to claim 1 are formed into a green sheet, an electrode is formed at an interface, and firing is performed. Probe. 5. A piezoelectric vibrator characterized in that when manufacturing the piezoelectric vibrator according to claim 3, the porcelain material and the piezoelectric material according to claim 1 are formed into a green sheet, electrodes are formed on an interface, and then fired. 6. A viscous body obtained by mixing the porcelain material according to claim 1 with fine particles having an average particle diameter of 0.7 μm or less and a maximum particle diameter of 5 μm or less and mixing with a polymer material, and a precursor to be a piezoelectric material according to claim 3 A viscous body obtained by mixing ferroelectric particles having an average particle diameter of 0.7 μm or less and a maximum particle diameter of 5 μm or less with a polymer material is processed into a desired structure in advance,
Further, a method of manufacturing a piezoelectric vibrator for manufacturing a vibrator having a desired shape by sintering after forming electrodes at desired positions. 7. A vibrator having a desired shape is manufactured by processing a green sheet on which an electrode is formed into a desired structure in advance, inserting the green sheet into a mold containing carbon or platinum as a main component, and then sintering. Manufacturing method of a piezoelectric vibrator. 8. A method for manufacturing a piezoelectric vibrator for manufacturing a vibrator having a desired shape by subjecting a green sheet to laser processing into a desired structure in advance and then sintering the green sheet.