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DESCRIPTION JP2001069594

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DESCRIPTION JP2001069594
[0001]
TECHNICAL FIELD The present invention relates to an ultrasonic probe in which a piezoelectric
element, an acoustic matching layer, and an acoustic lens are sequentially laminated, and in
particular, the characteristic deterioration due to the propagation loss of ultrasonic waves. The
present invention relates to an ultrasonic probe that can improve the sensitivity characteristic.
[0002]
2. Description of the Related Art As a conventional ultrasonic probe, for example, as described in
JP-A-9-149496, a piezoelectric element, an acoustic matching layer, and an acoustic lens are
sequentially laminated. Ultrasound probes are known. In the following description, the front of
the ultrasound probe means the direction in which the ultrasound is emitted toward the subject.
[0003]
FIG. 5 shows a schematic cross-sectional view of such an ultrasonic probe. The ultrasonic probe
includes a piezoelectric element 6 which is an electro-acoustic transducer, an acoustic matching
layer 7 of one or more layers (two layers shown) laminated on the front surface of the
piezoelectric element 6, and an acoustic The acoustic lens 9 is laminated on the front surface of
the matching layer 7 via the adhesive layer 8.
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[0004]
The acoustic matching layer 7 is made of, for example, a material such as epoxy resin, and has a
function of acoustically matching the piezoelectric element 6 and the subject. The acoustic lens 9
is made of, for example, a material such as silicone rubber, and performs focusing, divergence,
and deflection of ultrasonic waves. The adhesive layer 8 is made of an adhesive using silicone
rubber.
[0005]
The acoustic lens 9 made of silicone rubber provided on the front surface of the acoustic
matching layer 7 is, in the case of a room temperature curing type (RTV) silicone rubber, cast
directly onto the front surface of the acoustic matching layer 7. However, this RTV type silicone
rubber is not widely used at present because of its low abrasion resistance. Most acoustic lenses
9 made of silicone rubber currently used are of high wear resistance type (HTV), which are
pressurized and vulcanized at high temperature. After the acoustic lens 9 is molded, the acoustic
lens 9 is fixed on the front surface of the acoustic matching layer 7 with the adhesive layer 8 to
be laminated as shown in FIG.
[0006]
In the ultrasonic probe having the above configuration, the ultrasonic wave generated from the
piezoelectric element 6 is irradiated to the subject through the acoustic matching layer 7, the
adhesive layer 8 and the acoustic lens 9. The ultrasonic wave reflected by the object is received
by the piezoelectric element 6 through the acoustic lens 9, the adhesive layer 8, and the acoustic
matching layer 7, converted into an electric signal, and processed.
[0007]
The piezoelectric element 6, the acoustic matching layer 7 and the acoustic lens 9 constituting
the ultrasonic probe have specific acoustic impedances specific to each material, and the specific
acoustic impedance is the density and the speed of sound of the material. It is expressed by the
product. For example, the specific acoustic impedance of the acoustic matching layer 7 is about 3
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MRayl, the acoustic lens 9 is 1.4 to 1.6 MRayl close to the specific acoustic impedance of the
subject, and the adhesive layer 8 is an adhesive having high adhesive strength. In addition, the
thickness can not be made very thin, and the specific acoustic impedance is 1 to 1.2 MRayl.
[0008]
However, in the above-mentioned conventional ultrasonic probe, the specific acoustic impedance
of the adhesive layer 8 provided between the acoustic matching layer 7 and the acoustic lens 9 is
the acoustic matching layer. It is not a value between the intrinsic acoustic impedance of 7 and
the intrinsic acoustic impedance of the acoustic lens 9, but a value smaller than them. As a result,
acoustic mismatch occurs at the interfaces between the adhesive layer 8 and the acoustic
matching layer 7 and the acoustic lens 9, causing a propagation loss of ultrasonic waves and
degrading the sensitivity of the ultrasonic probe. is there. Furthermore, there is a problem that
the thickness of the adhesive layer 8 adversely affects the frequency characteristics of the
ultrasonic probe.
[0009]
The present invention solves the above-mentioned conventional problems and can prevent the
occurrence of acoustic mismatch and the deterioration of frequency characteristics by the
adhesive layer formed between the acoustic matching layer and the acoustic lens. It is an object
of the present invention to provide an ultrasonic probe.
[0010]
The ultrasonic probe according to the present invention comprises a piezoelectric element, an
acoustic matching layer laminated on the front surface of the piezoelectric element, and an
adhesive layer on the front surface of the acoustic matching layer. And an acoustic lens
laminated via the first to third layers, wherein the specific acoustic impedance ZM (MRayl) of the
acoustic matching layer, the specific acoustic impedance ZL (MRayl) of the acoustic lens, and the
specific property of the adhesive layer The acoustic impedance ZB (MRayl) has a relationship of
ZM ≧ ZB ≧ ZL.
According to this configuration, it is possible to transmit and receive ultrasonic waves efficiently
without acoustic mismatch, and to prevent deterioration of frequency characteristics.
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[0011]
Further, according to the ultrasonic probe of the present invention, a piezoelectric element, an
acoustic matching layer laminated on the front surface of the piezoelectric element, and an
acoustic layer laminated on the front surface of the acoustic matching layer through an adhesive
layer. An ultrasonic probe having a lens, a polymer film is formed on a back surface of the
acoustic lens, and specific acoustic impedances of the acoustic matching layer, the adhesive layer,
and the polymer film are substantially the same. Has a configuration set to a value. According to
this configuration, it is possible to transmit and receive ultrasonic waves efficiently without any
acoustic mismatch, to prevent deterioration of the frequency characteristics, and to prevent the
erosion of the piezoelectric element, the acoustic matching layer, and the adhesive layer.
[0012]
DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be
described in detail with reference to the drawings.
[0013]
(First Embodiment) In the first embodiment of the present invention, the specific acoustic
impedance of the adhesive layer is equal to or higher than the specific acoustic impedance of the
acoustic lens and equal to or lower than the specific acoustic impedance of the acoustic matching
layer. Configured.
[0014]
FIG. 1 is a schematic cross-sectional view of an ultrasonic probe according to a first embodiment
of the present invention.
This ultrasonic probe is laminated via the adhesive layer 3 on the front surface of the
piezoelectric element 1, the acoustic matching layer 2 of one or more layers laminated on the
front surface of the piezoelectric element 1, and the acoustic matching layer 2. And an acoustic
lens 4.
[0015]
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The piezoelectric element 1 is made of a PZT-based piezoelectric ceramic, a single crystal, or a
polymer such as PVDF, and transmits and receives ultrasonic waves.
The acoustic matching layer 2 is made of, for example, a material such as epoxy resin, and has a
function of acoustically matching the piezoelectric element 1 and the subject. The acoustic lens 4
is made of, for example, a material such as silicone rubber, and performs focusing, divergence,
and deflection of ultrasonic waves. The adhesive layer 3 is made of a silyl group-containing
polymer adhesive and bonds the acoustic lens 4 on the surface of the acoustic matching layer 2.
[0016]
In the ultrasonic probe configured as described above, the ultrasonic wave generated by the
piezoelectric element 1 is irradiated to the subject through the acoustic matching layer 2, the
adhesive layer 3 and the acoustic lens 4. Further, the ultrasonic wave reflected by the object is
received by the piezoelectric element 1 through the acoustic lens 4, the adhesive layer 3 and the
acoustic matching layer 2, converted into an electric signal, and processed by the main body
(ultrasound diagnostic apparatus etc.) Be done.
[0017]
Here, the acoustic matching layer 2, the adhesive layer 3 and the acoustic lens 4 are configured
to satisfy the relationship of ZM ≧ ZB ≧ ZL, where ZM, ZB and ZL are specific acoustic
impedances of the respective components. Specifically, the acoustic matching layer 2 and the
acoustic lens 4 are respectively the same epoxy resin and silicone rubber as in the conventional
example, and their specific acoustic impedances are about 3 MRayl and 1.4 to 1.6 MRayl,
respectively.
[0018]
As characteristics required of the material of the adhesive layer 3, it is premised that the
adhesive strength is high. There are many adhesives in the adhesive that can bond epoxy resin
such as the acoustic matching layer 2. On the other hand, there are few materials that can bond
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the acoustic lens 4 to the acoustic matching layer 2 such as silicone rubber, and the material is
limited to materials such as silicone rubber. However, when this silicone rubber adhesive has
high adhesive strength, as described in the prior art, there are only ones having specific acoustic
impedance of 1 to 1.2 MRayl.
[0019]
Therefore, in the present embodiment, a silyl group-containing polymer adhesive is used as the
adhesive layer 3 as a material having a high adhesive strength and a specific acoustic impedance
satisfying the relationship of ZM ≧ ZB ≧ ZL. As this adhesive, there is, for example, Super X of
Cemedine Corporation. This silyl group-containing polymer adhesive satisfies the relationship of
ZM ≧ ZB ≧ ZL because the sound velocity is 1500 m / s and the intrinsic acoustic impedance
has a value of 2 MRayl.
[0020]
FIG. 2 is a view showing the characteristics of the ultrasonic probe according to the present
embodiment, and FIG. 3 is a diagram showing a conventional ultrasonic probe (sonic velocity
1000 m / s, silicone rubber bonding with an intrinsic acoustic impedance 1.1 MRayl) Is a
diagram showing the calculation results of the characteristics of using an agent). In these figures,
(a) is a pulse response waveform and (b) is a frequency characteristic. The thickness of the
adhesive layer 3 at this time is 10 μm.
[0021]
Comparing the voltages of the pulse response waveforms shown in FIGS. 2 (a) and 3 (a), the Vpp
value of this embodiment is +1.3 dB {20 × log 10 (202 mv / 173 mV) = +1.3 dB higher.
Moreover, when the frequency characteristics shown in FIG. 2 (b) and FIG. 3 (b) are compared in
the ratio band (-6 dB), it is 50% in the conventional ultrasonic probe, but in the present
embodiment It is 65% and has wide band characteristics. Moreover, it can be seen that the shape
of the conventional frequency characteristic is largely deformed, and the adhesive has an adverse
effect. On the other hand, in the present embodiment, since the frequency characteristic has a
straightforward shape, the pulse response waveform also has a favorable characteristic with little
ringing.
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[0022]
As apparent from the comparison of the characteristics, the diagnostic image extracted by
connecting the ultrasonic probe of the present embodiment to the ultrasonic diagnostic
apparatus has a deep examination depth and a high resolution. Become.
[0023]
Further, the adhesive layer 3 of the present embodiment has a sound velocity of 1500 m / s,
which is 1.5 times faster than the sound velocity of 1000 m / s of the conventional silicone
rubber.
For this reason, even if the thickness of the adhesive layer 3 is the same as that of the
conventional adhesive, the influence of the adhesive layer 3 of the present embodiment is
extremely small with respect to the wavelength of ultrasonic waves. Therefore, the control of the
thickness of the adhesive layer 3 becomes gentle, and the manufacture of the ultrasonic probe
becomes easy.
[0024]
In the present embodiment, the case where a silyl group-containing polymer adhesive is used as
the adhesive has been described, but an adhesive having a specific acoustic impedance
relationship satisfying ZM ≧ ZB ≧ ZL as described above may be used. For example, similar
effects can be obtained by using other adhesives such as cyano adhesives. Further, although the
case of the ultrasonic probe having a single piezoelectric element has been described in the
present embodiment, the same may be applied to a so-called array-type ultrasonic probe in which
a plurality of piezoelectric elements are arrayed. The effect of
[0025]
As described above, according to the ultrasonic probe of the first embodiment of the present
invention, the specific acoustic impedance ZM of the acoustic matching layer 2, the specific
acoustic impedance ZL of the acoustic lens 4, and the adhesive layer 3 Since the specific acoustic
impedance ZB is configured to satisfy the relationship ZM ≧ ZB ≧ ZL, the occurrence of acoustic
mismatch is prevented, and as a result, efficient transmission and reception of ultrasonic waves
and prevention of deterioration of frequency characteristics can be realized. become.
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[0026]
Second Embodiment In the second embodiment of the present invention, a polymer film is
formed on the back of an acoustic lens, and each of an acoustic matching layer, an adhesive
layer, and a polymer film is provided. By setting the intrinsic acoustic impedance to
approximately the same value, prevention of the occurrence of acoustic mismatch and erosion of
the piezoelectric element, the acoustic matching layer, and the adhesive layer were realized.
[0027]
FIG. 4 is a schematic cross-sectional view of an ultrasonic probe according to a second
embodiment of the present invention.
Here, constituent elements that are the same as or correspond to those in FIG. 1 are given the
same reference numerals as the reference numerals used in FIG. 1, and descriptions thereof will
be omitted.
[0028]
The second embodiment of the present invention is different from the first embodiment in that a
thin polymer film 5 is provided on the surface of the acoustic lens 4 on the acoustic matching
layer 2 side.
The polymer film 5 has a function of preventing the piezoelectric element 1, the acoustic
matching layer 2, and the adhesive layer 3 from being attacked by chemicals such as a
disinfectant.
[0029]
For example, polyparaxylylene is used as the polymer film 5. As this material, there is Parylene C,
D of Union Carbide. This material is formed on the silicone rubber of the acoustic lens 4 by vapor
deposition. And, it can be formed firmly with a small thickness of 1 to 10 μm.
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[0030]
The specific acoustic impedance of the polymer film 5 thus formed has a value of 2.8 to 3 MRayl
substantially the same as the specific acoustic impedance of the epoxy resin used for the acoustic
matching layer 2. Further, as the adhesive layer 3 for bonding the acoustic matching layer 2 and
the polymer film 5, a material having an intrinsic acoustic impedance substantially the same as
the intrinsic acoustic impedance of the acoustic matching layer 2 and the intrinsic acoustic
impedance of the polymer film 5 is used. It is desirable to prevent acoustic inconsistencies from
occurring. An adhesive such as epoxy resin can be used as the material.
[0031]
Although an epoxy resin can not be used when bonding a silicone rubber acoustic lens not
having the polymer film 5 to the acoustic matching layer, in the present embodiment, the
polymer film 5 is provided to make the epoxy It became possible to bond with resin. Therefore,
since it is possible to firmly bond and to match the specific acoustic impedance, it is possible to
improve the sensitivity and frequency characteristics, and to obtain a highly reliable ultrasonic
probe.
[0032]
The same effect can be obtained by using an undercoat for silicone rubber as the polymer film 5.
Examples of this material include Aron silicone rubber primer manufactured by Toagosei
Chemical Co., Ltd.
[0033]
In the present embodiment, the case where an adhesive of epoxy resin is used as the adhesive
layer 3 has been described. In addition to the above, the specific acoustic impedance is the same
as the specific acoustic impedance of the acoustic matching layer 2 and the polymer film 5. The
same effect can be obtained by using any adhesive that is made of a material having
approximately the same inherent acoustic impedance as the inherent acoustic impedance.
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Further, although the case of the ultrasonic probe having a single piezoelectric element has been
described in the present embodiment, the same may be applied to a so-called array-type
ultrasonic probe in which a plurality of piezoelectric elements are arrayed. There is an effect of
[0034]
As described above, in the second embodiment of the present invention, the polymer film 5 is
formed on the back surface of the acoustic lens 4, and each of the acoustic matching layer 2, the
adhesive layer 3 and the polymer film 5 is formed. Since the intrinsic acoustic impedances of
these components are set to approximately the same value, the acoustic mismatch is eliminated
to efficiently transmit and receive the ultrasonic wave, and the deterioration of the frequency
characteristic is prevented, and further the piezoelectric element 1, the acoustic matching layer 2
and the adhesive layer The erosion of 3 can be prevented.
[0035]
As described above, according to the present invention, the piezoelectric element, the acoustic
matching layer laminated on the front surface of the piezoelectric element, and the adhesive
layer on the front surface of the acoustic matching layer In the ultrasonic probe comprising the
laminated acoustic lens, the specific acoustic impedance of the adhesive layer is equal to or
higher than the specific acoustic impedance of the acoustic lens and equal to or lower than the
specific acoustic impedance of the acoustic matching layer. Therefore, an ultrasonic probe can be
provided which has an excellent effect that ultrasonic waves can be transmitted and received
efficiently because no acoustic mismatch occurs, and deterioration of frequency characteristics
can be prevented.
[0036]
Further, according to the present invention, a piezoelectric element, an acoustic matching layer
laminated on the front surface of the piezoelectric element, and an acoustic lens laminated on the
front surface of the acoustic matching layer via an adhesive layer are provided. In the ultrasonic
probe, a polymer film is formed on the back surface of the acoustic lens, and the specific acoustic
impedances of the acoustic matching layer, the adhesive layer, and the polymer film are set to
approximately the same value. Since there is no acoustic mismatch, it is possible to transmit and
receive ultrasonic waves efficiently, yet it has the excellent effect of preventing deterioration of
frequency characteristics and preventing erosion of piezoelectric elements, acoustic matching
layers, and adhesive layers. An acoustic probe can be provided.
[0037]
Brief description of the drawings
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[0038]
1 is a schematic cross-sectional view of an ultrasonic probe according to a first embodiment of
the present invention,
[0039]
2 shows a pulse response waveform and frequency characteristics of the ultrasonic probe
according to the first embodiment of the present invention,
[0040]
Figure 3 shows the pulse response waveform and frequency characteristics of a conventional
ultrasound probe;
[0041]
4 is a schematic cross-sectional view of an ultrasonic probe according to a second embodiment of
the present invention,
[0042]
5 is a schematic cross-sectional view of a conventional ultrasonic probe.
[0043]
Explanation of sign
[0044]
Reference Signs List 1 piezoelectric element 2 acoustic matching layer 3 adhesive layer 4
acoustic lens 5 polymer film
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