JP2016052531A - Ultrasonic probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic probe which can improve the conversion efficiency and S/N of a reception signal in a plurality of organic piezoelectric elements while having excellent acoustic transmissivity with respect to an ultrasonic beam transmitted from a plurality of inorganic piezoelectric elements, correctly match the arrangement positions of the plurality of inorganic piezoelectric elements and the plurality of organic piezoelectric elements with each other, and maintain the characteristics of the organic piezoelectric elements at the high level even after device completion.SOLUTION: A backing material 1, an inorganic piezoelectric element layer, an acoustic matching layer, an organic layer and a conductive layer are sequentially laminated, then the positions of respective fragments of the plurality of inorganic piezoelectric elements 2, the first acoustic matching layer 3, a lower side organic layer 42 and a signal electrode layer 44 are aligned and sequentially laminated by performing dicing from the conductive layer to the inorganic piezoelectric element layer in the lamination direction at any pitch, and then an upper side organic layer 41 and a ground electrode layer 43 are overlapped and joined on the signal electrode layer 44. A plurality of organic piezoelectric elements 5 constituted by the signal electrode layer 44, the upper side organic layer 41 and the ground electrode layer 43 is formed as described above.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic probe, and more particularly to an ultrasonic probe in which a plurality of inorganic piezoelectric elements and a plurality of organic piezoelectric elements are stacked on each other.

  Conventionally, in the medical field, an ultrasonic diagnostic apparatus using an ultrasonic image has been put into practical use. In general, this type of ultrasonic diagnostic apparatus transmits an ultrasonic beam from an ultrasonic probe into a subject, receives an ultrasonic echo from the subject with the ultrasonic probe, and receives the received ultrasonic echo. An ultrasonic image is generated by electrically processing the signal.

In recent years, in order to perform more accurate diagnosis, harmonic imaging that receives and visualizes harmonic components generated by distortion of an ultrasonic waveform due to nonlinearity of a subject has become mainstream. In recent years, photoacoustic imaging, which is a new diagnostic method using ultrasonic waves, is focused on photo-irradiation by irradiating a living body with laser and receiving weak and broadband elastic waves generated by adiabatic expansion. .
As an ultrasonic probe suitable for this harmonic imaging or photoacoustic imaging, for example, as disclosed in Patent Document 1, an inorganic piezoelectric material such as lead zirconate titanate (Pb (Zr, Ti) O ₃ ) is used. A plurality of laminated inorganic piezoelectric elements using a plurality of organic piezoelectric elements using an organic piezoelectric material such as polyvinylidene fluoride (PVDF) has been proposed.
A high-power ultrasonic beam can be transmitted by the inorganic piezoelectric element, and a harmonic signal can be received with high sensitivity by the organic piezoelectric element. In addition, a normal ultrasonic reception signal can be acquired by the inorganic piezoelectric element, and a wide-band signal of photoacoustic imaging can be received with high sensitivity by the organic piezoelectric element.

International Publication No. 2008/010509

Here, since the ultrasonic beams output from the plurality of inorganic piezoelectric elements are transmitted through the organic piezoelectric body and then transmitted from the ultrasonic probe into the subject, the thickness of the organic piezoelectric body is determined by the ultrasonic wave. Designed to increase the acoustic transmission of the beam. Specifically, the organic piezoelectric body is designed in the vicinity of a thickness that satisfies the λ / 4 resonance condition with respect to the wavelength λ of the fundamental wave transmitted from the plurality of inorganic piezoelectric elements. For this reason, the organic piezoelectric material cannot be designed freely, and has to be designed with a certain thickness in order to satisfy the above resonance condition. On the other hand, since the organic piezoelectric material has a small relative dielectric constant, when the organic piezoelectric element is formed thick, the electric capacity is reduced, and a reception signal generated by the ultrasonic wave received by the organic piezoelectric element is efficiently acquired on the circuit. It was difficult. Further, since the thermal noise increases when the electric capacity is small, the S / N with the acquired signal tends to be disadvantageous.
In addition, when an organic piezoelectric body is stacked on an inorganic piezoelectric element, if the positions of the electrodes do not coincide with the beam transmission direction, focus deviation and reception efficiency decrease. Therefore, it is desirable that the electrode positions of the organic piezoelectric element laminated with the inorganic piezoelectric element match as much as possible with respect to the beam transmission direction, but it is difficult to accurately match with the conventional configuration and manufacturing method. It was.
Furthermore, since the degree of crystallinity of an organic piezoelectric body gradually decreases as the temperature rises, there is a use upper limit temperature at a temperature considerably lower than the Curie point. For example, in a typical polyvinylidene fluoride (PVDF), the use upper limit temperature is 80 ° C., and in a polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)), it is 100 ° C. Therefore, if this temperature is exceeded during the process, the ferroelectricity deteriorates and depolarization occurs. Although repolarization is an effective means for recovering the deterioration of ferroelectricity, the coercive electric field (Ec) of the organic piezoelectric material is extremely large, about 400 kV / cm to 450 kV / cm. Accordingly, it is necessary to apply an extremely high voltage to repolarize the organic piezoelectric material once depolarized on the device, which is difficult in terms of process. From the above, when an organic piezoelectric material is laminated on an inorganic piezoelectric material, it is necessary to fabricate it with as low a temperature process as possible and with a small number of thermal histories. However, a process that hardly applies thermal history is difficult with conventional configurations and manufacturing methods. Met.

  The present invention has been made to solve such a conventional problem, and has a plurality of organic piezoelectric elements while having excellent acoustic transmittance with respect to ultrasonic beams transmitted from a plurality of inorganic piezoelectric elements. Improve the conversion efficiency and S / N of the received signal in the element, accurately match the electrode position of the inorganic piezoelectric element that transmits and receives ultrasonic waves and the position of the organic piezoelectric element dedicated to ultrasonic reception in the beam transmission direction, and An object of the present invention is to provide an ultrasonic probe capable of maintaining high characteristics of an organic piezoelectric element even after the device is completed.

  The ultrasonic probe according to the present invention includes a backing material, a plurality of inorganic piezoelectric elements arranged on the surface of the backing material, a first acoustic matching layer disposed on the plurality of inorganic piezoelectric elements, A second acoustic matching layer disposed on the first acoustic matching layer, wherein the second acoustic matching layer includes a plurality of upper organic layers constituting the plurality of organic piezoelectric elements and a plurality of upper organic layers. A plurality of organic piezoelectric elements including a sheet-like upper organic layer, a ground electrode layer extending over the surface of the upper organic layer, and a lower organic layer. A plurality of signal electrode layers arranged on the back surface of the upper organic layer facing the side organic layer, and separating each layer from the plurality of signal electrode layers to the plurality of inorganic piezoelectric elements into a plurality of pieces, Plural components extending in parallel at the same pitch in the stacking direction By further comprising a section, a plurality of organic piezoelectric elements and a plurality of inorganic piezoelectric elements are arranged at the same pitches.

Here, the upper organic layer is preferably formed thinner than the lower organic layer.
Also, each piece constituting a plurality of inorganic piezoelectric elements, or each piece constituting each of a plurality of inorganic piezoelectric elements and a first acoustic matching layer, or a plurality of inorganic piezoelectric elements and a first acoustic matching layer A sub die forming groove extending in the stacking direction may be provided so that each of the pieces constituting the lower organic layer of the two acoustic matching layers is further separated into a plurality of sub dice.
The plurality of organic piezoelectric elements is used as a receiving device that receives ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements, and the upper organic layer efficiently acquires the received ultrasonic echoes as received signals on the circuit. In addition, in order to improve S / N, it is formed with a thickness having a predetermined electric capacity, and the sum of the thickness of the upper organic layer and the thickness of the lower organic layer is transmitted from a plurality of inorganic piezoelectric elements. It is preferable to form the value so that desired acoustic matching is performed with respect to the ultrasonic wave.

The upper organic layer and the lower organic layer preferably have an acoustic impedance within a range of ± 10%. The lower organic layer preferably has an acoustic impedance larger than that of the upper organic layer and smaller acoustic impedance than that of the first acoustic matching layer.
Preferably, the plurality of inorganic piezoelectric elements include a plurality of inorganic piezoelectric bodies separated from each other, and a plurality of signal electrode layers and a plurality of ground electrode layers respectively disposed on both surfaces of the plurality of inorganic piezoelectric bodies.

Further, the plurality of inorganic piezoelectric materials can be composed of a Pb-based perovskite oxide such as lead zirconate titanate (Pb (Zr, Ti) O ₃ ) or magnesium niobate / lead titanate solid solution (PMN-PT). . The upper organic layer can be composed of only an organic material, and the lower organic layer can be composed of an organic material or a composite material of an organic material and an inorganic material. Furthermore, the upper organic layer and the lower organic layer can be composed of a vinylidene fluoride compound such as polyvinylidene fluoride (PVDF) or polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)).
Moreover, the acoustic lens arrange | positioned on the some organic piezoelectric element can be further provided. In addition, a protective layer for protecting the plurality of organic piezoelectric elements can be further provided between the plurality of organic piezoelectric elements and the acoustic lens.

Further, an organic piezoelectric element amplifier directly connected to each of the plurality of organic piezoelectric elements can be further provided.
In addition, the light irradiation unit further irradiates the subject with irradiation light, and the ultrasonic wave induced from the subject by irradiation of the irradiation light from the light irradiation unit is applied to a plurality of organic piezoelectric elements or a plurality of inorganic substances. It can be received by a piezoelectric element.

According to this invention, the second acoustic matching layer includes an upper organic layer constituting a plurality of organic piezoelectric elements, and a lower organic layer for performing acoustic matching with respect to the plurality of inorganic piezoelectric elements in combination with the upper organic layer. So that the acquisition efficiency of the received signals generated in the plurality of organic piezoelectric elements is improved while having excellent acoustic transmittance for the ultrasonic beams transmitted from the plurality of inorganic piezoelectric elements, and S / N can be improved.
In addition, the position of the electrode of the inorganic piezoelectric element that transmits and receives ultrasonic waves and the position of the organic piezoelectric element dedicated to ultrasonic reception in the beam transmission direction must be accurately matched, and the characteristics of the organic piezoelectric element can be maintained high even after the device is completed. Is also possible.

It is a fragmentary perspective view which shows the ultrasonic probe which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the ultrasonic probe which concerns on embodiment. It is sectional drawing which shows the manufacturing method of the ultrasonic probe which concerns on embodiment to process order. It is sectional drawing which shows the structure of the ultrasonic probe which concerns on a modification. It is a figure which shows the structure of the ultrasonic probe which concerns on another modification.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 and 2 show the configuration of an ultrasonic probe according to an embodiment of the present invention.
A plurality of inorganic piezoelectric elements 2 are arranged at a pitch P on the surface of the backing material 1. The plurality of inorganic piezoelectric elements 2 have a plurality of inorganic piezoelectric bodies 21 separated from each other, a signal electrode layer 22 is bonded to one surface of each inorganic piezoelectric body 21, and a ground electrode layer 23 is bonded to the other surface. It is joined. That is, each inorganic piezoelectric element 2 is formed of a dedicated inorganic piezoelectric body 21, signal electrode layer 22, and ground electrode layer 23.
The first acoustic matching layer 3 is bonded on the plurality of inorganic piezoelectric elements 2. The first acoustic matching layer 3 is divided into a plurality of pieces and arranged at the same pitch P as the plurality of inorganic piezoelectric elements 2.

In addition, it is preferable to form each piece constituting the plurality of inorganic piezoelectric elements 2 separately into a plurality of sub-dies. For example, each piece constituting each of the plurality of inorganic piezoelectric bodies 21, the signal electrode layer 22, and the ground electrode layer 23 (the plurality of inorganic piezoelectric elements 2), or the plurality of inorganic piezoelectric bodies 21, the signal electrode layer 22, the ground electrode A sub die forming groove extending in the stacking direction can be formed so as to further divide each piece constituting the layer 23 and the first acoustic matching layer 3 into a plurality of pieces. Also, the stacking direction is such that each piece constituting the plurality of inorganic piezoelectric bodies 21, the signal electrode layer 22, the ground electrode layer 23, the first acoustic matching layer 3 and the lower organic layer 42 is further separated into a plurality of pieces. It is also possible to form a sub-die forming groove extending toward.
At this time, it is preferable to form one or two sub die forming grooves for each inorganic piezoelectric element 2 to form two or three sub dice. Thus, by forming a plurality of sub-dies, the piezoelectric multiplier of the plurality of inorganic piezoelectric elements 2 can be improved, and the transmission / reception sensitivity of the ultrasonic probe can be improved.

A second acoustic matching layer 4 is bonded on the first acoustic matching layer 3. The second acoustic matching layer 4 has two layers, an upper organic layer 41 and a lower organic layer 42.
The lower organic layer 42 is divided into a plurality of pieces and arranged on the first acoustic matching layer 3 at the same pitch P as the plurality of inorganic piezoelectric elements 2. On the other hand, the upper organic layer 41 has a sheet-like shape and extends over the entire lower organic layer 42 without being divided into a plurality of pieces. The sum of the thickness of the upper organic layer 41 and the thickness of the lower organic layer 42 is formed to a value such that desired acoustic matching is performed on the ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements. For example, the sum of the thickness of the upper organic layer 41 and the thickness of the lower organic layer 42 is the fundamental wave of the ultrasonic wave transmitted from the plurality of inorganic piezoelectric elements 2 (the center frequency of the −6 dB band of the maximum sensitivity of the inorganic piezoelectric material 21). ), The second acoustic matching layer 4 including the upper organic layer 41 and the lower organic layer 42 includes a plurality of layers. It can have excellent acoustic transmittance with respect to the ultrasonic wave transmitted from the inorganic piezoelectric element.

  Furthermore, the upper organic layer 41 constitutes a plurality of organic piezoelectric elements 5. That is, a ground electrode layer 43 extending over the surface is joined to the upper organic layer 41 and separated from each other at the same pitch P as the plurality of inorganic piezoelectric elements 2 on the back surface facing the lower organic layer 42. Thus, the plurality of signal electrode layers 44 are joined, whereby the upper organic layer 4 functions as an organic piezoelectric body of the plurality of organic piezoelectric elements 5. Each organic piezoelectric element 5 arranged in this manner is composed of a dedicated signal electrode layer 44, and an upper organic layer 41 and a ground electrode layer 43 common to the plurality of organic piezoelectric elements 5. Therefore, the arrangement pitch of the plurality of organic piezoelectric elements 5 is determined only by the arrangement pitch of the plurality of signal electrode layers 44 bonded on the back surface of the upper organic layer 41, and the plurality of organic piezoelectric elements 5 is a plurality of inorganic piezoelectric elements. They are arranged at the same pitch P as the elements 2.

In addition, a plurality of pieces separated at the same pitch P in each of the plurality of inorganic piezoelectric elements 2, the first acoustic matching layer 3, the lower organic layer 42 and the signal electrode layer 44 of the second acoustic matching layer 4, A plurality of layers constituting the layers from the plurality of inorganic piezoelectric elements 2 to the signal electrode layer 44 are formed by aligning the positions between the layers and aligning them in the stacking direction, and filling each column with a filler. A separation part 6 for separating the fragments is formed. That is, the separation portions 6 extend in parallel at the same pitch P in the stacking direction so as to penetrate each layer from the surface of the signal electrode layer 44 to the surface of the backing material 1.
Furthermore, an acoustic lens 8 is bonded on the plurality of organic piezoelectric elements 5 via a protective layer 7.

The inorganic piezoelectric element 21 of the inorganic piezoelectric element 2 is formed of an inorganic material for a piezoelectric body such as a Pb-based perovskite structure oxide. For example, Pb-based piezoelectric ceramic represented by lead zirconate titanate (Pb (Zr, Ti) O ₃ ), or magnesium niobate / lead titanate solid solution (PMN-PT) and zinc niobate / lead titanate It can be formed from a relaxor-type piezoelectric single crystal typified by a solid solution (PZN-PT). On the other hand, the upper organic layer 41 of the organic piezoelectric element 5 is formed of an organic material for a piezoelectric body such as a vinylidene fluoride (VDF) material. For example, it can be formed from a polymer piezoelectric element such as polyvinylidene fluoride (PVDF) or polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)).

The backing material 1 supports a plurality of inorganic piezoelectric elements 2 and absorbs ultrasonic waves emitted backward, and can be formed from a rubber material such as ferrite rubber.
The first acoustic matching layer 3 is for efficiently allowing the ultrasonic beams from the plurality of inorganic piezoelectric elements 2 to enter the subject, and is intermediate between the acoustic impedance of the inorganic piezoelectric element 2 and the acoustic impedance of the living body. It is formed from a material having a value acoustic impedance.
The second acoustic matching layer 4 is for efficiently allowing the ultrasonic beams from the plurality of inorganic piezoelectric elements 2 to enter the subject, and the lower organic layer 42 is an organic material or an organic material and an inorganic material. It is composed of composite materials. For example, the lower organic layer 42 is made of polyvinylidene fluoride (VDF) such as polyvinylidene fluoride (PVDF) or polyvinylidene fluoride trifluoride copolymer (P (VDF-TrFE)) used in the upper organic layer 41. ) It can be formed from organic materials including system materials. The lower organic layer 42 can also be formed from a composite material of an organic material and an inorganic material in which zirconia particles are dispersed in, for example, an epoxy resin.
The upper organic layer 41 and the lower organic layer 42 are preferably formed of materials having the same or close acoustic impedance as each other. For example, if the mutual acoustic impedance is within a range of ± 10%, ultrasonic waves The second acoustic matching layer 4 can be configured without affecting the acoustic matching. Further, the lower organic layer 42 may be formed of a material having an acoustic impedance larger than that of the upper organic layer 41 and having an acoustic impedance smaller than that of the first acoustic matching layer 3.

The filler forming the separation portion 6 is for fixing the position and posture of adjacent pieces, and is formed of, for example, an epoxy resin.
The protective layer 7 protects the ground electrode layer 43 of the organic piezoelectric element 5 and is formed of, for example, polyvinylidene fluoride (PVDF). If the protection of the ground electrode layer 43 is not hindered, the acoustic lens 8 can be directly bonded onto the plurality of organic piezoelectric elements 5 by forming the protective layer 7 except the protective layer 7.
The acoustic lens 8 narrows the ultrasonic beam using refraction and improves the resolution in the elevation direction, and is made of silicon rubber or the like.

Next, the operation of this embodiment will be described.
In operation, for example, the plurality of inorganic piezoelectric elements 2 are used as transducers dedicated to ultrasonic transmission, and the plurality of organic piezoelectric elements 5 are used as transducers dedicated to ultrasonic reception.
When a pulsed or continuous wave voltage is applied between the signal electrode layer 22 and the ground electrode layer 23 of the plurality of inorganic piezoelectric elements 2, the inorganic piezoelectric body 21 of each inorganic piezoelectric element 2 expands and contracts to be pulsed or continuous. Wave ultrasound is generated. These ultrasonic waves enter the subject through the first acoustic matching layer 3, the second acoustic matching layer 4, the protective layer 7, and the acoustic lens 8, and are combined with each other to form an ultrasonic beam. Propagates through the subject.

Subsequently, when the ultrasonic echoes propagated and reflected in the subject are incident on the respective organic piezoelectric elements 5 through the acoustic lens 8 and the protective layer 7, the upper organic layer 41 is subjected to ultrasonic harmonics. The component expands and contracts in response to high sensitivity, an electric signal is generated between the signal electrode layer 44 and the ground electrode layer 43, and is output as a received signal.
In this way, a harmonic image can be generated based on the reception signals output from the plurality of organic piezoelectric elements 5. Here, since the plurality of inorganic piezoelectric elements 2 and the plurality of organic piezoelectric elements 5 are aligned with each other in the stacking direction and arranged at the same pitch P, the subject is at the same arrangement position as the transmission position of the ultrasonic beam. Can receive the ultrasonic echoes, and can generate a harmonic image with high accuracy.

A plurality of inorganic piezoelectric elements 2 can also be used as transducers for transmitting and receiving ultrasonic waves. In this case, the ultrasonic echoes received by the organic piezoelectric element 5 via the acoustic lens 8 and the protective layer 7 are further transmitted to the respective inorganic piezoelectric elements via the second acoustic matching layer 4 and the first acoustic matching layer 3. 2, the inorganic piezoelectric body 21 expands and contracts mainly in response to the fundamental wave component of the ultrasonic wave, and generates an electric signal between the signal electrode layer 22 and the ground electrode layer 23.
Based on the reception signal corresponding to the fundamental wave component obtained from the plurality of inorganic piezoelectric elements 2 in this way and the reception signal corresponding to the harmonic component obtained from the organic piezoelectric element 5, the fundamental wave component and the harmonics are obtained. A compound image in which wave components are combined can be generated.

  Also at this time, since the plurality of inorganic piezoelectric elements 2 and the plurality of organic piezoelectric elements 5 are aligned with each other in the stacking direction and arranged at the same pitch P, the fundamental component and the harmonic component of the ultrasonic echo are It is possible to receive at the same arrangement position, and it is possible to generate a compound image in which the fundamental wave component and the harmonic component are combined with high accuracy.

Such an ultrasonic probe can be manufactured as follows.
First, as shown in FIG. 3A, an inorganic piezoelectric element layer 91a extending over the entire surface of the backing material 1 is bonded onto the surface of the backing material 1 with an adhesive or the like. In this inorganic piezoelectric element layer 91a, conductive layers 92 and 93 are formed on both surfaces of the inorganic piezoelectric layer 91 extending over the entire surface of the backing material 1, respectively.
Next, as shown in FIG. 3B, an acoustic matching layer 94 extending over the entire area of the inorganic piezoelectric element layer 91a is bonded onto the conductive layer 93 at a temperature of 80 ° C. to 100 ° C., for example. At this time, when forming the sub-dies on the plurality of inorganic piezoelectric bodies 21, the dice forming groove is formed by dicing the inorganic piezoelectric element layer 91a or each layer of the acoustic matching layer 94 from the inorganic piezoelectric element layer 91a in the stacking direction. Can be formed.
Then, as shown in FIG. 3C, the organic layer 95 is bonded on the acoustic matching layer 94. The organic layer 95 has a size sufficient to extend over the entire surface of the acoustic matching layer 94, and a conductive layer 96 is formed in advance on the entire surface opposite to the surface facing the acoustic matching layer 94.

Subsequently, as shown in FIG. 3D, each layer of the conductive layer 96, the organic layer 95, the acoustic matching layer 94, and the inorganic piezoelectric element layer 91a is diced at a pitch P to separate each layer into a plurality of pieces. To do. At this time, since the dicing is performed so as to completely divide each layer from the conductive layer 96 to the inorganic piezoelectric element layer 91a, each piece of each divided layer is aligned and aligned in the stacking direction. As a result, a plurality of inorganic piezoelectric elements 2 arranged at the arrangement pitch P are formed on the surface of the backing material 1, and the first acoustic matching layer 3 and the lower organic layer are formed on each inorganic piezoelectric element 2. 42 and the signal electrode layer 44 are formed so as to overlap each other in sequence. Further, between each row in which a plurality of pieces of each layer are arranged in the stacking direction at a pitch P, a plurality of flat grooves 97 that penetrate each layer in the stacking direction are formed by dicing.
In this way, by dicing each layer from the conductive layer 96 to the inorganic piezoelectric element layer 91a with the pitch P, each layer is easily separated into a plurality of pieces and each piece of each separated layer is positioned in the stacking direction. Can be combined. The signal electrode layers 44 of the plurality of organic piezoelectric elements 5 and the signal electrode layers 22 and the ground electrode layers 23 of the plurality of inorganic piezoelectric elements 2 can be accurately aligned with each other.

  Next, the inside of the plurality of grooves 97 formed by dicing is filled with a filler, and as shown in FIG. 3 (E), the separation portion 6 that fixes the position and posture of the plurality of pieces of each layer is formed. After that, the upper organic layer 41 is pressure-bonded onto the plurality of signal electrode layers 44 at a temperature of about 80 ° C., for example. The upper organic layer 41 has a size that extends over the whole of the plurality of signal electrode layers 44, and the ground electrode layer 43 is previously formed on the entire surface on the opposite side of the surface facing the plurality of signal electrode layers 44. Is formed.

  Here, the upper organic layer 41 constitutes a part of the second acoustic matching layer 4 for acoustic matching of ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements 2. It is sufficient that the combined thickness of the side organic layer 42 is formed so that a desired acoustic matching is performed with respect to the ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements 2. When attention is paid, the electric capacity of the organic piezoelectric element 5 can be increased by forming the upper organic layer 41 thin without being limited by acoustic matching. That is, the upper organic layer 41 is formed with a desired thickness having an electric capacity such that the ultrasonic echo received by the organic piezoelectric element 5 is efficiently converted into a received signal. By adding the thickness of the lower organic layer 42, the combined thickness of the upper organic layer 41 and the lower organic layer 42 is a range in which acoustic matching is performed on ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements 2. To fit in. As described above, the upper organic layer 41 is formed thinner than the lower organic layer 42, so that the second acoustic matching layer 4 is acoustically matched to the ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements 2. A plurality of organic piezoelectric elements 5 can be formed thin while being formed within the range. The sum of the thickness of the upper organic layer 41 and the thickness of the lower organic layer 42 is in the vicinity of a value that satisfies the λ / 4 resonance condition with respect to the wavelength λ of the fundamental wave transmitted from the plurality of inorganic piezoelectric elements 2. Preferably it is formed.

Further, the upper organic layer 41 has a use upper limit temperature at a temperature considerably lower than the Curie point because the crystallinity is gradually lowered as the temperature rises. For example, when a high temperature of 80 ° C. to 100 ° C. used when laminating each layer such as the acoustic matching layer 94 is applied, it is easily depolarized, but the upper organic layer 41 excludes the protective layer 7 and the acoustic lens 8. It is laminated after the other layers are laminated. Therefore, the upper organic layer 41 can be prevented from being depolarized without being exposed to a high temperature when another layer is laminated or when the filler 97 is filled with the filler.
Furthermore, each layer laminated below the upper organic layer 41, that is, the signal electrode layer 22, the inorganic piezoelectric body 21, the ground electrode layer 23, the first acoustic matching layer 3, the lower organic layer 42, and the signal electrode layer 44 are formed. Since the upper organic layer 41 does not exist until they are sequentially bonded, these layers can be bonded to each other at a high temperature and laminated with a high adhesive force.
After the upper organic layer 41 is laminated on the plurality of signal electrode layers 44 in this way, the acoustic lens 8 is bonded to the ground electrode layer 43 of the plurality of organic piezoelectric elements 5 via the protective layer 7. Thus, the ultrasonic probe shown in FIGS. 1 and 2 is manufactured.

For example, the frequency of ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements 2 is about 7 MHz, the acoustic impedance of the first acoustic matching layer 3 is about 8.9 Mrayl (kg / m ² s), and the second acoustic matching layer In the case of producing a linear probe having an acoustic impedance of about 4.0 Mrayl, lead zirconate titanate (Pb (Zr, Ti) O ₃ ) is used as the inorganic piezoelectric body 21 and the thickness thereof is about 190 μm. The thickness of the first acoustic matching layer 3 can be formed to about 80 μm. Then, PVDF is used for each of the lower organic layer 42 and the upper organic layer 41, the lower organic layer 42 is formed to have a thickness of approximately 60 μm, and the upper organic layer 41 is formed to have a thickness of approximately 20 μm. By setting the total thickness to about 80 μm, the plurality of organic piezoelectric elements 5 can be formed with a desired thickness while the second acoustic matching layer 4 satisfies the resonance condition for the plurality of inorganic piezoelectric elements 2. .

  When the lower organic layer 42 of the second acoustic matching layer 4 is composed of a composite material of an organic material and an inorganic material, for example, the upper organic layer 41 is made of a polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)) and a thickness of about 10 μm, and the lower organic layer 42 is 70 μm using zirconia particles dispersed in an epoxy resin so that the acoustic impedance is about 5 to 6 Mrayl. It is formed to a thickness of about. And the 1st acoustic matching layer 3 is formed in the thickness of about 100 micrometers using what disperse | distributed the zirconia particle to the epoxy resin so that acoustic impedance may be set to about 8 Mrayl. By configuring the first acoustic matching layer 3 and the second acoustic matching layer 4 in this manner, the second acoustic matching layer 4 satisfies a resonance condition for the plurality of inorganic piezoelectric elements 2 and a plurality of organic piezoelectric elements. 5 can be formed in a desired thickness.

Thus, the second acoustic matching layer 4 has a two-layer structure of the upper organic layer 41 and the lower organic layer 42, and the upper organic layer 41 constituting the plurality of organic piezoelectric elements 5 is formed with a desired thickness. By forming the second acoustic matching layer 4 so that the combined thickness of the upper organic layer 41 and the lower organic layer 42 satisfies the resonance condition, it is superior to an ultrasonic beam transmitted from a plurality of inorganic piezoelectric elements. The acquisition efficiency of the received signals in the plurality of organic piezoelectric elements 5 can be improved while maintaining the sound transmittance.
In addition, since the plurality of inorganic piezoelectric elements 2 and the plurality of organic piezoelectric elements 5 are aligned with each other, high-accuracy harmonic images and compound images can be generated.
Furthermore, when the ultrasonic probe is manufactured, the upper organic layer 41 that functions as the organic piezoelectric body of the organic piezoelectric element 5 is rarely exposed to a high temperature, so that the upper organic layer 41 can be prevented from being depolarized. it can.

As shown in FIG. 4, the inorganic piezoelectric element A / D converter 9 is connected to the signal line electrode layer 22 of each inorganic piezoelectric element 2, and the signal line electrode layer 44 of each organic piezoelectric element 5 is organically connected. The piezoelectric element amplifier 10 and the organic piezoelectric element A / D converter 11 can be sequentially connected.
Here, the electric capacity of the plurality of organic piezoelectric elements 5 can be increased by setting the thickness of the organic piezoelectric body to be small as described above. However, it is possible to obtain a received signal having sufficient strength by itself. Therefore, it is necessary to amplify by the organic piezoelectric element amplifier 10. At this time, in order to prevent the received signal from being attenuated during transmission from the organic piezoelectric element 5 to the organic piezoelectric element amplifier 10, the organic piezoelectric element amplifier 10 is placed near the signal line electrode layer 44 of the organic piezoelectric element 5. It is preferably connected or directly connected.
Further, the number of signal lines drawn from the ultrasonic probe can be reduced by arranging the multiplexer in the ultrasonic probe. For example, a multiplexer is disposed after the A / D converter 9 for the inorganic piezoelectric element and the A / D converter 11 for the organic piezoelectric element, and is drawn from the A / D converter 9 for the inorganic piezoelectric element and the A / D converter 11 for the organic piezoelectric element. These two signal lines can be combined into one.

In addition, the lower organic layer 95 in which the conductive layer 96 is previously formed on the surface is laminated on the first acoustic matching layer 94. However, the present invention is not limited to this. The lower organic layer 95 may be laminated, and then the conductive layer 96 may be formed on the surface of the lower organic layer 95.
Similarly, the upper organic layer 41 in which the ground electrode layer 43 is previously formed on the surface is bonded onto the plurality of signal electrode layers 44, but after the upper organic layer 41 is bonded onto the plurality of signal electrode layers 42. The ground electrode layer 43 may be formed on the surface of the upper organic layer 41.

In the above-described embodiment, ultrasonic waves generated by the plurality of inorganic piezoelectric elements 2 are transmitted toward the subject, and ultrasonic echoes reflected within the subject are transmitted to the plurality of inorganic piezoelectric elements 2 or the plurality of inorganic piezoelectric elements 2. Although received by the organic piezoelectric element 5, as shown in FIG. 5, irradiation is performed from the light irradiation unit 31 toward the subject by newly providing the light irradiation unit 31 that irradiates the irradiation light L toward the subject. For example, a plurality of organic piezoelectric elements 5 can receive photoacoustic waves U (ultrasonic waves) induced from the subject by irradiation with the light L. Thereby, what is called photoacoustic imaging (PAI: Photoacoustic Imaging) which images the inside of a subject using a photoacoustic effect can be performed.
The light irradiation unit 31 sequentially irradiates a subject with a plurality of irradiation lights L having different wavelengths, and may be composed of a semiconductor laser (LD), a light emitting diode (LED), a solid-state laser, a gas laser, or the like. it can. For example, the light irradiation unit 31 uses pulsed laser light as the irradiation light L and irradiates the subject with the pulsed laser light while sequentially switching the wavelength for each pulse.

When performing photoacoustic imaging, irradiation light L is irradiated from the light irradiation unit 31 toward the subject, and when the irradiated irradiation light L is irradiated to a predetermined biological tissue V in the subject, the living body The tissue V absorbs the light energy of the irradiation light L and emits a photoacoustic wave U (ultrasonic wave) that is an elastic wave.
For example, the object is sequentially irradiated with irradiation light L having a wavelength of about 750 nm and irradiation light L having a wavelength of about 800 nm from the light irradiation unit 31. Here, oxygenated hemoglobin (hemoglobin combined with oxygen: oxy-Hb) contained in a large amount in human arteries has a higher molecular absorption coefficient than the irradiation light L having a wavelength of 800 nm with respect to the irradiation light L having a wavelength of 750 nm. . On the other hand, deoxygenated hemoglobin (hemoglobin deoxy-Hb not bound to oxygen) contained in a large amount in veins has a lower molecular absorption coefficient for irradiation light L with a wavelength of 750 nm than irradiation light L with a wavelength of 800 nm. For this reason, when the irradiation light L having a wavelength of 800 nm and the irradiation light L having a wavelength of 750 nm are respectively irradiated to an artery and a vein, photoacoustic waves U having an intensity corresponding to the molecular absorption coefficient of the artery and vein are respectively emitted.
The photoacoustic wave U emitted from the artery or vein is received by the plurality of organic miscellaneous elements 5 of the ultrasonic probe in the same manner as in the above embodiment.

As described above, the ultrasonic probe can be used not only for an ultrasonic image but also for a photoacoustic image, and various ultrasonic diagnosis can be performed by using one ultrasonic probe. It can be carried out.
The photoacoustic wave U induced from the subject by the irradiation of the irradiation light L can be received by the plurality of inorganic piezoelectric elements 2.

  DESCRIPTION OF SYMBOLS 1 Backing material, 2 Inorganic piezoelectric element, 3rd 1st acoustic matching layer, 4th 2nd acoustic matching layer, 5 Organic piezoelectric element, 6 Separation part, 7 Protective layer, 8 Acoustic lens, 9 A / D for inorganic piezoelectric elements Converter, 10 Amplifier for organic piezoelectric element, 11 A / D converter for organic piezoelectric element, 21 Inorganic piezoelectric body, 22, 44 Signal electrode layer, 23, 43 Ground electrode layer, 41 Upper organic layer, 42 Lower organic layer, 91 Inorganic piezoelectric layer, 91a Inorganic piezoelectric element layer, 92, 93, 96 conductive layer, 94 acoustic matching layer, 95 organic layer, 97 groove, 31 light irradiation part, P arrangement pitch, L irradiation light, U photoacoustic wave.

Claims (14)

Backing material,
A plurality of inorganic piezoelectric elements arranged on the surface of the backing material;
A first acoustic matching layer disposed on the plurality of inorganic piezoelectric elements;
A second acoustic matching layer disposed on the first acoustic matching layer,
The second acoustic matching layer includes an upper organic layer constituting a plurality of organic piezoelectric elements, and a lower organic layer for performing acoustic matching with the plurality of inorganic piezoelectric elements in combination with the upper organic layer,
The plurality of organic piezoelectric elements are:
The upper organic layer in sheet form;
A ground electrode layer extending over the surface of the upper organic layer;
A plurality of signal electrode layers arranged on the back surface of the upper organic layer facing the lower organic layer, and
By further comprising a plurality of separation portions extending in parallel at the same pitch in the stacking direction so as to separate each layer from the plurality of signal electrode layers to the plurality of inorganic piezoelectric elements into a plurality of pieces, An ultrasonic probe in which the organic piezoelectric element and the plurality of inorganic piezoelectric elements are arranged at the same pitch.   The ultrasonic probe according to claim 1, wherein the upper organic layer is formed thinner than the lower organic layer.   Each piece constituting the plurality of inorganic piezoelectric elements, or each piece constituting each of the plurality of inorganic piezoelectric elements and the first acoustic matching layer, or the plurality of inorganic piezoelectric elements and the first acoustic matching. The sub die formation groove | channel extended in the lamination direction is provided so that each fragment | piece which respectively comprises the layer and the said lower organic layer of a said 2nd acoustic matching layer may be further divided | segmented into a some sub die | dye. The described ultrasonic probe. The plurality of organic piezoelectric elements is used as a receiving device that receives ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements,
The upper organic layer is formed with a thickness having a predetermined capacitance in order to convert a received ultrasonic echo into a received signal,
The sum of the thickness of the upper organic layer and the thickness of the lower organic layer is formed to a value such that desired acoustic matching is performed with respect to ultrasonic waves transmitted from the plurality of inorganic piezoelectric elements. The ultrasonic probe as described in any one of 1-3.   The ultrasonic probe according to claim 1, wherein the upper organic layer and the lower organic layer have an acoustic impedance within a range of ± 10% of each other.   5. The ultrasonic probe according to claim 1, wherein the lower organic layer has an acoustic impedance larger than that of the upper organic layer, and has an acoustic impedance smaller than that of the first acoustic matching layer. Tentacles. The plurality of inorganic piezoelectric elements are:
A plurality of inorganic piezoelectric bodies separated from each other;
The ultrasonic probe according to claim 1, further comprising: a plurality of signal electrode layers and a plurality of ground electrode layers respectively disposed on both surfaces of the plurality of inorganic piezoelectric bodies.   The ultrasonic probe according to claim 7, wherein the plurality of inorganic piezoelectric bodies are made of a Pb-based perovskite structure oxide. The upper organic layer is composed only of an organic material,
The ultrasound probe according to claim 1, wherein the lower organic layer is made of an organic material or a composite material of an organic material and an inorganic material.   The ultrasonic probe according to claim 9, wherein the upper organic layer and the lower organic layer are made of a vinylidene fluoride-based material.   The ultrasonic probe according to claim 1, further comprising an acoustic lens disposed on the plurality of organic piezoelectric elements.   The ultrasonic probe according to claim 11, further comprising a protective layer for protecting the plurality of organic piezoelectric elements between the plurality of organic piezoelectric elements and the acoustic lens.   The ultrasonic probe according to any one of claims 1 to 12, further comprising an organic piezoelectric element amplifier directly connected to each of the plurality of organic piezoelectric elements. It further has a light irradiation unit that irradiates irradiation light toward the subject,
The ultrasonic wave induced from the subject by irradiating irradiation light from the light irradiation unit is received by the plurality of organic piezoelectric elements or the plurality of inorganic piezoelectric elements. Ultrasonic probe.

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