JPH09215094A - Ultrasonic probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe which also improves formability at the time of making an element into recessed face concerning this element having satisfactory characteristics for transmitting/receiving ultrasonic waves by composing piezoelectric materials. SOLUTION: This ultrasonic probe is composed of a base 1 having a recessed face 1a, a compound reflector 2 as the compound film of piezoelectric ceramics materials and organic piezoelectric materials to be laminated on the recessed face 1a, and a polymeric piezoelectric body 3 as an organic piezoelectric film laminated on the compound reflector 2. In this case, the compound reflector 2 is used for oscillating ultrasonic waves and the polymeric piezo-electric body 3 is used for receiving the ultrasonic waves. Therefore, characteristics for transmitting and receiving the ultrasonic waves are improved and since this ultrasonic probe is provided on the base 1 having the recessed face 1a, the characteristics are further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe in which piezoelectric films are combined to improve ultrasonic wave transmission and reception characteristics.

[0002]

Conventionally, for example, the actual Kaihei 4
JP-A-128499 discloses an ultrasonic probe in which a piezoelectric ceramic material such as PZT and an organic piezoelectric material such as PVDF are combined, and the piezoelectric ceramic material is used for transmitting ultrasonic waves, and the organic piezoelectric material is used. It has been shown to be excellent in receiving ultrasonic waves.

In recent years, the use of elements for detecting ultrasonic waves has progressed, and the internal state of an object to be examined can be detected nondestructively. Therefore, in the medical field, the internal state of the human body, the size of a tumor, etc. are detected. There is. As described above, in the element used in recent years, it is necessary to sufficiently detect the output at a specific position, and the surface of the element is made concave to focus the light. Further, an annular element in which a concave element is divided into rings and the focal lengths thereof are individually shifted is also used. As described above, if the surface of the element is to be concave, the ceramic material has a problem in formability.

The present invention is an element which is composed of a piezoelectric material and is excellent in the characteristics of transmitting and receiving ultrasonic waves. The ultrasonic wave using the element is excellent in formability when the surface of the element is made concave. The purpose is to obtain a probe.

[0005]

The present invention provides a base having a concave surface, a composite film of a piezoelectric ceramic material and an organic piezoelectric material laminated on the concave surface, and an organic piezoelectric film laminated on the composite film. Is to have. This composite film may be one in which powder of a piezoelectric ceramic material is mixed to form an organic piezoelectric material, and as the piezoelectric ceramic material, PZ is used.
T, barium titanate or lead titanate is used,
As the organic piezoelectric material, PVDF, VDF / TrFE copolymer, or the like can be used.

By providing this composite film, since the strength is high, the reflecting plate which is necessary because the organic piezoelectric material alone is too flexible is unnecessary. Further, if the piezoelectric ceramic material is directly provided on the base instead of the composite film, it is difficult to form the concave surface.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

In the figure, a backing material 1 made of phenolic resin or the like having a concave surface 1a as a base, and a concave surface 1a
PZT (lead titanium zirconate) as a piezoelectric ceramic material and PVDF as an organic piezoelectric material to be laminated on
A composite reflector 2 which is a composite film of (polyvinylidene fluoride) or a copolymer (VDF / TrFE (tetrafluoroethylene)) containing the same as a main material, and an organic piezoelectric film laminated on the composite reflector 2. A polymer piezoelectric body 3 made of VDF / TrFE of the same as above is shown.

Then, the composite reflector 2 and the piezoelectric polymer 3
Electrodes 4, 5 and 6 are formed on the space and on the upper and lower surfaces by vapor deposition of gold or the like. Further, since FIG. 1 is a single type and FIG. 2 is an annular type, the electrodes 4 and 5 are shown in FIG.
2 may be integrated, but in FIG. 2, the structure is such that the output is obtained individually by being divided into rings. Although not described in detail, the respective electrodes 4, 5, 6 are connected to the oscillation circuit TX and the reception circuit RX, and ultrasonic waves are emitted from the composite reflector 2 via the electrodes 4, 5 by the oscillation circuit TX. It is oscillated and a reception output by the polymer piezoelectric material 3 via the composite reflector 2 is obtained via the electrodes 4 and 6 by the reception circuit RX.

The composite reflector 2 is formed by mixing a powder of a piezoelectric ceramic material and polymerizing an organic piezoelectric material, and has a moldability as compared with a single piezoelectric ceramic material. Optimal PZT as a piezoelectric ceramic material
As the organic piezoelectric material, the polymer piezoelectric body 3 similarly uses VDF / TrFE having excellent piezoelectricity. In addition to PZT, barium titanate, lead titanate, or the like is used as the piezoelectric ceramic material, and polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer is used as the organic piezoelectric material, in addition to PVDF or VDF / TrFE. Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer,
Polychlorotrifluoroethylene, polyvinyl fluoride, etc. can be used.

The film formation of the composite reflection plate 2 can be performed by, for example, a casting method. A VDF / TrFE solution (solvent DMF) in which PZT powder was mixed was poured into a glass cast plate, and a vacuum dryer (50 ° C., 2
After suction drying for 30 hours while introducing nitrogen gas in (00 mmHg), the cast plate may be rapidly cooled in a refrigerant to separate the composite film, and after poling, it may be cut into a predetermined size. At this time, since it is necessary for the PZT powder to become organically compatible, it is preferable to pretreat the powder surface with MMA (methmethylacrylic acid) or the like, or to mix it in a solvent. However, it is necessary that the amount of MMA be small enough not to interfere with the interface between the two. Although the VDF / TrFE solution is used here, it may be polymerized as a monomer solution. Further, FIG. 3 shows a table of the results of the moldability of this composite together with the specific gravity and the electromechanical conversion constant Kt.
When VDF / TrFE is mixed with PZT, the moldability improves even at a ratio of 9: 1 (weight ratio).
As the amount of FE increases, the acoustic impedance decreases, and the effect as a reflector decreases. Basically, from this point, the ratio of VDF / TrFE to PZT can be up to about 6: 4. Also, in terms of the reception waveform λ / 4, the PZT alone has a frequency of 114 μm / 10 MHz, whereas the frequency of 6: 4 has a frequency of 88 μm / 10 MHz. Further, even when the ratio is changed and the shape is too soft to maintain the shape, the object can be achieved by adhering it to the base such as the backing material 1 shown in FIG.

FIG. 4 is a graph showing the piezoelectric characteristics of the above composite, with the vertical axis representing the electromechanical conversion constant Kt and the horizontal axis representing the weight ratio. From FIG. 4, when the ratio of VDF / TrFE to PZT is 7: 3 or more, there is no large difference in characteristics. Since VDF / TrFE is used as the polymer piezoelectric material, it is not necessary to stretch the film unlike PVDF alone, and piezoelectricity can be obtained by poling after heat treatment at an applied voltage of 100 V per 1 μm of thickness.

Each element thus formed is mounted on a main body (not shown) to form an ultrasonic probe. At that time, the upper side of each element comes to be arranged on the contact surface of the inspection target, but at that time, a protective film such as PET or a protective film such as a protective paste (not shown) is formed.
In addition, in each embodiment of the present invention, the composite reflector 2
Since it is not a single piezoelectric ceramic and has flexibility, it can be brought into contact with the concave surface 1a of the base 1, but a thickness is necessary to perform the role of a reflector.
If it is insufficient, it can be performed in the same manner as in the case of using an ordinary copper reflector. Furthermore, the concaved surface of the element has better characteristics than a flat surface, and cannot be used on a flat surface particularly when used as an annular type.

As described above, the base 1 having the concave surface 1a
A composite reflector 2 which is a composite film of a piezoelectric ceramic material and an organic piezoelectric material laminated on the concave surface 1a, and a polymer piezoelectric body 3 which is an organic piezoelectric film laminated on the composite reflector 2. By using the composite reflector 2 which is a composite film of a piezoelectric ceramic material and an organic piezoelectric material for the oscillation of ultrasonic waves, and the polymer piezoelectric body 3 which is an organic piezoelectric film for the reception, Since the characteristics of transmitting and receiving ultrasonic waves can be improved and the ultrasonic wave is provided on the base 1 having the concave surface 1a, the characteristics are further improved, which is also advantageous when used in an annular type.

The composite reflector 2 is formed into a film by mixing the powder of the piezoelectric ceramic material and polymerizing the organic piezoelectric material, so that the composite reflector 2 is superior in moldability to the piezoelectric ceramic material alone and has a concave surface of the base 1. It can be brought into contact with 1a.
PZT, barium titanate or lead titanate is used as the piezoelectric ceramic material, and PVDF, VDCN / VAc or VDF / Tr is used as the organic piezoelectric material.
An FE copolymer or the like can be used. As the organic piezoelectric material, VDF / TrFE has excellent piezoelectricity, and PZT is the best as the piezoelectric ceramic material.

The composite reflector 2 also eliminates the need for a reflector, which is required with organic piezoelectric materials. Moreover, it is difficult to form the piezoelectric ceramic material directly on the concave surface in place of the composite film.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment (single type) of the present invention.

FIG. 2 is a sectional view showing another embodiment (annular type) of the present invention.

FIG. 3 is a table relating to moldability of composites.

FIG. 4 is a graph relating to piezoelectric characteristics of a composite.

[Explanation of symbols]

 1 base 2 composite reflector 3 polymer piezoelectric

Claims (3)

[Claims] 1. A super-structure comprising a base having a concave surface, a composite film of a piezoelectric ceramic material and an organic piezoelectric material laminated on the concave surface, and an organic piezoelectric film laminated on the composite film. Sonic probe. 2. The ultrasonic probe according to claim 1, wherein the composite film is formed by mixing a powder of a piezoelectric ceramic material to form an organic piezoelectric material. 3. The ultrasonic probe according to claim 2, wherein the organic piezoelectric material used for the composite film is a copolymer containing vinylidene fluoride as a main material.