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DESCRIPTION JP2014147452

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DESCRIPTION JP2014147452
Abstract: The present invention provides an ultrasonic probe, an ultrasonic diagnostic imaging
apparatus, and a method of manufacturing an ultrasonic probe, which are provided with a
composite piezoelectric layer excellent in high sensitivity and wide band and having high
durability and stability. An ultrasonic probe for outputting an ultrasonic wave based on a drive
signal to be received, a composite piezoelectric layer in which a piezoelectric material and a
polymer material are alternately arranged in a one-dimensional or two-dimensional array. And an
acoustic reflection layer having an acoustic impedance higher than the acoustic impedance of the
composite piezoelectric layer, and an adhesive layer for joining the composite piezoelectric layer
and the acoustic reflection layer. In the bonding surface of the composite piezoelectric layer with
the acoustic reflection layer, the portion formed of the polymer material is recessed to the
opposite side to the acoustic reflection layer side with respect to the portion formed of the
piezoelectric material Form. [Selected figure] Figure 3A.
ULTRASONIC PROBE, ULTRASONIC IMAGING DEVICE, AND METHOD FOR MANUFACTURING
ULTRASONIC PROBE
[0001]
The present invention relates to an ultrasonic probe, an ultrasonic diagnostic imaging apparatus,
and a method of manufacturing an ultrasonic probe, each of which comprises a composite
piezoelectric layer capable of achieving high sensitivity and wide band.
[0002]
As for the ultrasound diagnostic imaging apparatus, one with higher image quality is required,
and one of the methods for realizing high image quality is to increase the sensitivity and wide
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band of the ultrasound probe.
[0003]
The ultrasonic probe is configured to excite an elastic vibration whose thickness corresponds to
1⁄4λ to the piezoelectric material, and to irradiate the object with an ultrasonic wave by the
elastic vibration.
The ultrasonic energy irradiated in the direction opposite to the direction in which the object is
located is irradiated because the ultrasonic wave is reflected to the object side by the acoustic
reflection layer having high acoustic impedance disposed on the side opposite to the direction of
the object Ultrasonic energy is increased to realize high sensitivity.
[0004]
In addition, a composite piezoelectric layer is used as a member for generating an ultrasonic
wave.
The composite piezoelectric layer is obtained by alternately arranging and integrating a
piezoelectric material such as lead zirconate (PZT) and a polymer material such as a resin in a
direction perpendicular to the direction of an object to be irradiated. The composite piezoelectric
layer can reduce the acoustic impedance by including the polymer material, and can achieve high
sensitivity and wide band by approaching the acoustic impedance of the subject whose acoustic
impedance is lower than that of the piezoelectric material.
[0005]
However, high sensitivity and wide band can not be realized only by taking the above-mentioned
measures. FIG. 11 shows that the thickness of the adhesive layer between the piezoelectric
material and the acoustic reflection layer is related to the width of the frequency band. The
horizontal axis is the frequency (MHz), and the vertical axis is the response sensitivity of the
piezoelectric material to the frequency in dB (dB). The curve A has a thickness of 1.5 μm
between the piezoelectric material and the acoustic reflection layer, the curve B has a thickness
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of 1.0 μm, and the curve C has a thickness of 0.5 μm. It shows. As is clear from this, the thinner
the thickness of the adhesive layer that bonds the piezoelectric material and the acoustic
reflection layer, the wider the range of frequency bands in the response sensitivity of the desired
piezoelectric material. Therefore, even in a composite piezoelectric layer in which the
piezoelectric material and the polymer material are alternately arranged in a direction
perpendicular to the direction of the object to be irradiated, the adhesive layer bonding the
portion of the piezoelectric material of the composite piezoelectric layer and the acoustic
reflection layer The thinner the thickness, the wider the frequency band. That is, reducing the
thickness of the adhesive layer for bonding the portion of the piezoelectric material of the
composite piezoelectric layer and the acoustic reflection layer is important for achieving further
broadening the bandwidth.
[0006]
For that purpose, the bonding surface of the composite piezoelectric layer bonded to the acoustic
reflection layer by the adhesive layer is mirror-polished and smoothed before bonding, and then
bonded by the adhesive layer to form the piezoelectric material portion and the acoustic
reflection layer of the composite piezoelectric layer It is necessary to thin the adhesive layer with
However, since the hardness of the piezoelectric material such as PZT and the polymer material
made of resin or the like constituting the piezoelectric material is different from each other, when
trying to mirror-finish the bonding surface of the composite piezoelectric layer, the piezoelectric
material side is more polished than the polymer material. As a result, unevenness occurs in the
bonding surface of the piezoelectric material and the polymer material, so that the piezoelectric
material portion can not be sufficiently smoothed, and the thickness of the adhesive layer can not
be sufficiently thin and uniform. In view of such a problem, in the technique described in Patent
Document 1, the piezoelectric material is cut halfway without cutting to the bottom, and the
composite piezoelectric layer is poured into the gap formed by cutting the piezoelectric material.
Making is disclosed. The composite piezoelectric layer formed by the method described above is
a piezoelectric material because the entire bonding surface with the acoustic reflection layer is a
piezoelectric material, and therefore even if mirror polishing is performed, no unevenness occurs
due to the difference in hardness between the piezoelectric material and the polymer material. It
is disclosed that it is possible to make
[0007]
JP, 2009-61112, A
[0008]
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However, in the technology described in Patent Document 1, there is a defect that the effect as
the composite piezoelectric layer becomes thin because the joint surface with the acoustic
reflection layer is not cut.
Therefore, in order to enhance the effect, it is necessary to cut the piezoelectric material of the
portion to be cut to the limit of the joint surface with the acoustic reflection layer. Therefore, a
crack is easily formed on the bonding surface, there is a problem in maintaining the durability
and stability of the composite piezoelectric layer, and desired ultrasonic waves can not be
generated stably.
[0009]
Therefore, the present invention provides an ultrasonic probe, an ultrasonic diagnostic imaging
apparatus, and a method for manufacturing an ultrasonic probe, which are provided with a
composite piezoelectric layer excellent in high sensitivity and wide band and having high
durability and stability. With the goal.
[0010]
In order to solve the above problems, according to a first aspect of the present invention, in an
ultrasonic probe for outputting an ultrasonic wave based on a received drive signal, a
piezoelectric material and a polymer material in a one-dimensional or two-dimensional array
shape And an acoustic reflection layer having an acoustic impedance higher than an acoustic
impedance of the composite piezoelectric layer, and an adhesive layer for joining the composite
piezoelectric layer and the acoustic reflection layer. An ultrasonic probe comprising: a portion of
the bonding surface of the composite piezoelectric layer to the acoustic reflection layer, the
portion formed of the polymer material being a portion formed of the piezoelectric material It is
dented and formed in the opposite side to the said acoustic reflection layer side.
[0011]
The second aspect is the ultrasonic probe according to the first aspect, wherein the thickness t
(μm) of the adhesive layer between the bonding surface of the piezoelectric material of the
composite piezoelectric layer and the acoustic reflection layer ) Is 0 <t ≦ 1.0.
[0012]
The third aspect is the ultrasonic probe according to the first or second aspect, wherein the
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surface roughness Ra (μm) of the piezoelectric material of the composite piezoelectric layer on
the acoustic reflection layer side satisfies Ra ≦ 0.4. It is.
[0013]
According to a fourth aspect, in the ultrasonic diagnostic imaging apparatus, the ultrasonic probe
according to the first, second, or third aspect, a transmitting unit that generates the drive signal,
and the ultrasonic probe. An image generation unit that generates ultrasound image data for
displaying an ultrasound image based on the received signal output by
[0014]
According to a fifth aspect, in the ultrasonic diagnostic imaging apparatus according to the fourth
aspect, the drive signal is a rectangular wave having a plurality of pulses, and the pulse width of
at least one of the plurality of pulses is , And pulse widths of other pulses.
[0015]
According to a sixth aspect, in the ultrasonic diagnostic imaging apparatus according to the
fourth or fifth aspect, the drive signal includes a first pulse signal and a second pulse different in
polarity from the first pulse signal. And a third pulse signal equal in polarity to the first pulse
signal, and having a pulse width of the first pulse signal, a pulse width of the second pulse signal,
and the third pulse signal, The pulse widths are all different.
[0016]
According to a seventh aspect of the present invention, there is provided a composite
piezoelectric layer in which a piezoelectric material and a polymer material are alternately
arranged in a one-dimensional or two-dimensional array, and an acoustic impedance higher than
the acoustic impedance of the composite piezoelectric layer. And a reflective layer, which is
formed by bonding the composite piezoelectric layer and the acoustic reflective layer by an
adhesive layer, and producing an ultrasonic probe for outputting an ultrasonic wave based on a
received drive signal. A method of forming a composite piezoelectric layer in which the
piezoelectric material and the polymer material are alternately arranged, and a portion of the
polymer material in the bonding surface of the composite piezoelectric layer to the acoustic
reflection layer, A removal step of partially removing the portion of the polymer material so as to
be recessed on the opposite side to the side of the acoustic reflection layer to be joined with
respect to the portion of the piezoelectric material; Performing a smoothing process by polishing
against Comprising a smoothing step, a bonding step of bonding by the adhesive layer junction
surface between the said acoustic reflection layer of the composite piezoelectric layer.
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[0017]
The eighth aspect is the method of manufacturing an ultrasonic probe according to the seventh
aspect, wherein the partial removal of the polymer material in the removal step is performed
using an etching method.
[0018]
In a ninth aspect, in the method of manufacturing an ultrasonic probe according to the seventh
aspect, partial removal of the polymer material in the removal step is performed using a dicing
method.
[0019]
In a tenth aspect of the present invention, there is provided a composite piezoelectric layer in
which a piezoelectric material and a polymer material are alternately arranged in a onedimensional or two-dimensional array, and an acoustic impedance having an acoustic impedance
higher than that of the composite piezoelectric layer. And a reflective layer, which is formed by
bonding the composite piezoelectric layer and the acoustic reflective layer by an adhesive layer,
and producing an ultrasonic probe for outputting an ultrasonic wave based on a received drive
signal. Filling the polymer material in the gaps of the piezoelectric materials arranged at a
predetermined distance, and forming a composite piezoelectric layer in which the piezoelectric
material and the polymer material are alternately arranged After the filling step, a polishing and
smoothing step of smoothing the bonding surface of the composite piezoelectric layer by
polishing the bonding surface, and bonding the bonding surface of the composite piezoelectric
layer and the acoustic reflection layer with an adhesive layer Process, and, In the filling step, in
the bonding surface of the composite piezoelectric layer to the acoustic reflection layer, the
portion of the polymer material is recessed to the opposite side to the side of the acoustic
reflection layer to be joined than the portion of the piezoelectric material. As described above, the
polymer material is filled.
[0020]
According to the invention of the present application, since the adhesive layer between the
piezoelectric material portion of the composite piezoelectric layer and the acoustic reflecting
material can be made thin, it is possible to irradiate a broad band ultrasonic wave to the object,
and Since the bonding surface is also composed of a surface in which the piezoelectric material
and the polymer material are alternately arranged, it is possible to provide an ultrasonic probe
provided with a composite piezoelectric layer having improved durability and stability.
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[0021]
It is a figure showing the appearance composition of an ultrasound probe.
It is a figure showing the outline of an ultrasound probe.
It is a figure showing the outline of a compound piezoelectric layer.
It is a figure showing the outline of other examples of a compound piezoelectric layer.
It is a flowchart showing the manufacturing method of an ultrasound probe.
It is a figure which shows the general position of an electrode layer and a flexible printed circuit
board.
It is a figure which shows the external appearance structure of an ultrasound diagnostic imaging
apparatus.
It is a block diagram which shows schematic structure of an ultrasound diagnostic imaging
apparatus.
It is a block diagram which shows schematic structure of a transmission part.
It is a figure explaining the drive waveform of a pulse signal.
It is a figure explaining the waveform of the pulse signal to transmit.
It is a related figure of the thickness of an adhesion layer, and the zone which can be irradiated.
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[0022]
Hereinafter, the ultrasonic probe 1 and the ultrasonic diagnostic imaging apparatus 2 according
to the present invention will be described with reference to the drawings.
FIG. 1 is a view showing an appearance configuration of an ultrasound probe 1 in the present
embodiment. The ultrasound probe comprises an acoustic lens 16 in direct contact with the
subject, a housing support 19 and a cable 203.
[0023]
FIG. 2A is a view showing a part of the appearance configuration of the ultrasound probe 1. FIG.2
(b) is a schematic sectional drawing about the dotted line part of the ultrasound probe 1 shown
by FIG. 2 (a). As shown in FIG. 2B, the ultrasound probe 1 in the present embodiment is
integrated with the backing layer 11, the flexible printed board 12, the acoustic reflection layer
13, the piezoelectric material 14a and the polymer material 14b from the lower surface. It is
laminated by the composite piezoelectric layer 14, the acoustic matching layer 15, and the
acoustic lens 16, and the respective layers are formed by being bonded by an adhesive layer.
[0024]
The composite piezoelectric layer 14 is formed by alternately arranging and integrating a
piezoelectric material and a polymer material 14b such as an epoxy resin in a direction
perpendicular to the direction of emitting ultrasonic waves to the object. Since the piezoelectric
material 14a and the polymer material 14b are integrated, the composite piezoelectric layer can
lower the acoustic impedance as compared to the piezoelectric material 14a while the
electromechanical coupling coefficient is substantially equal to that of the piezoelectric material
14a. . Thereby, the acoustic impedance difference with the acoustic matching layer 15 can be
reduced, and the resonance frequency characteristic can have a wide frequency band.
[0025]
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The acoustic impedance of the composite piezoelectric layer can be determined using the
volumes of the piezoelectric material and the polymer material constituting the composite
piezoelectric layer. For example, assuming that the acoustic impedance of the piezoelectric
material is 30 MR and the acoustic impedance of the polymer material is 1.5 MR, the acoustic
impedance of the composite piezoelectric layer = {volume of piezoelectric material × 30 +
volume of polymer material × 1.5} / composite piezoelectric It can be determined by the volume
of the layer (1).
[0026]
The composite piezoelectric layer 14 according to the present embodiment will be described in
detail below with reference to FIGS. 3A and 3B. FIG. 3A is a schematic view of a composite
piezoelectric layer obtained by enlarging the composite piezoelectric layer 14 shown in FIG. As
shown in FIG. 3A, the composite piezoelectric layer 14 in the form of a one-dimensional array is
obtained by alternately arranging and integrating a piezoelectric material 14a and a polymer
material 14b in one direction. A two-dimensional array of composite piezoelectric layers 14 as
shown in FIG. 3B can also be used. The composite piezoelectric layer 14 according to the present
invention is not limited to the composite piezoelectric layer 14 described above, and has a
structure in which the polymer material 14 b is recessed inside the piezoelectric material 14 a
with respect to the direction of the acoustic reflection layer 13. Just do it. In the above
description, the piezoelectric material and the polymer material are arranged in a onedimensional or two-dimensional matrix array as the composite piezoelectric material, but the
“two-dimensional array” in the present invention means concentrically When the piezoelectric
material and the polymer material are alternately arranged, the two-dimensional ones other than
the linear one are also included.
[0027]
Next, a method of manufacturing the ultrasonic probe 1 including the composite piezoelectric
layer 14 described above will be described below with reference to FIG. Here, for the sake of
convenience, a method of manufacturing an ultrasonic probe having a primary array of
composite piezoelectric layers will be described.
[0028]
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In the first step, in order to align the piezoelectric material 14a and the polymer material 14b in
a primary array on the substrate, the piezoelectric material is removed by etching or dicing at a
predetermined distance (FIG. 4b), A gap for filling the material 14b is formed. Thereafter, the
polymer material 14b is filled in the gap (FIG. 4c) to form a composite piezoelectric layer in
which the polymer material 14b and the piezoelectric material 14a are alternately arrayed in a
primary array and integrated. .
[0029]
In the above process, the piezoelectric material 14a and the polymer material 14b may be
arranged in a primary array, for example, after the piezoelectric material 14a is arranged on the
substrate with a predetermined gap, the polymer material 14b is placed in the gap. By filling, the
polymer material 14 b and the piezoelectric material 14 a can be arranged in a primary array on
the base without using an etching method or a dicing method.
[0030]
In the second step (polymer material removal step), of the piezoelectric material 14a and the
polymer material 14b arranged in a primary array on the substrate, a part of the polymer
material 14b is removed using an etching method or a dicing method. By removing it, a
composite piezoelectric layer can be formed in which the surface opposite to the base surface of
the polymer material is recessed from the surface opposite to the base surface of the
piezoelectric material (FIG. 4 d).
That is, the bonding surface of the composite piezoelectric layer at the time of bonding using an
acoustic reflection layer and an adhesive layer, which will be described later, is recessed on the
opposite side to the acoustic reflection layer side where the polymer material is bonded than the
piezoelectric material. Remove a portion of the polymer material to form a bonding surface. The
etching method and the dicing method will be described later.
[0031]
In the third step (polishing and smoothing treatment), mirror surface polishing is performed on
the bonding surface of the piezoelectric material 14a located on the opposite side of the
substrate surface in contact with the substrate, and smoothing of the portion composed of the
piezoelectric material among the bonding surfaces Do (Figure 4e). In the second step, the
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composite piezoelectric layer is formed such that the surface opposite to the base surface of the
polymer material is recessed from the surface opposite to the base surface of the piezoelectric
material, so that it contacts the base Only the bonding surface of the piezoelectric material 14a
opposite to the base surface can be mirror-polished, and the bonding surface can be smoothed.
Although the hardness of the piezoelectric material and the surface roughness Ra (μm) of the
portion formed of the piezoelectric material differ depending on the acoustic reflection layer to
be joined, the adhesive layer can be made thin and can be used in a wide frequency band. From
the viewpoint, it is preferable to perform smoothing so that Ra ≦ 0.4.
[0032]
In addition, the piezoelectric material is scraped off by polishing to smooth the bonding surface
of the piezoelectric material 14a located on the opposite side to the substrate surface in contact
with the substrate among the bonding surfaces of the composite piezoelectric layer, thereby
bonding the polymer material. It is possible to reach the surface. Therefore, for example, when
the surface roughness of the bonding surface of the piezoelectric material 14a opposite to the
substrate surface in contact with the substrate is 0.4 μm or less, the piezoelectric material and
the polymer material as described above are simultaneously polished. It is preferable that the
polymer material be recessed inward by 2.0 μm or more with respect to the acoustic reflection
layer from the viewpoint of preventing the occurrence of the problem. On the other hand,
considering that it is difficult to form the electrode layer described later and the durability of the
composite piezoelectric layer, the high polymer material is 50% or less of the height of the
piezoelectric material with respect to the acoustic reflection layer. It is preferable to form so as
not to be dented inward until the end.
[0033]
In the fourth step (bonding step), an adhesive layer is applied to the bonding surface subjected to
the mirror polishing described above, and the bonding surface bonded to the acoustic reflection
layer of the composite piezoelectric layer 14 and the bonding surface of the acoustic reflection
layer 13 Bond (Figure 4f). In order to bond the bonding surface of the piezoelectric material
portion of the composite piezoelectric layer and the bonding surface of the acoustic reflection
layer, an adhesive layer is required. However, in terms of broadening the bandwidth, the bonding
surface of the piezoelectric material portion of the composite piezoelectric layer and the acoustic
The adhesive layer between the reflective layer and the bonding surface is preferably thinner. For
example, in consideration of use at a central frequency band of 7 MHz or more, the thickness t
(μm) of the adhesive layer in the above portion is 0 <t It is preferable to adjust so as to be ≦ 1.0.
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In addition, when forming the adhesive layer described above, the depression of the polymer
material caused by the removal of the polymer material in the second step (polymer removal
step) is filled with the adhesive layer.
[0034]
In the etching method, a desired portion (polymer material 14b) can be removed by coating a
portion (piezoelectric material 14a) not to be removed by etching with an etching mask and then
performing etching using plasma, gas or the like. it can.
[0035]
For the etching mask, one having an etching rate lower than that of the piezoelectric material is
used.
For example, SiO2, Si3 N4 and calcium fluoride formed by CVD, nickel by electrolytic plating,
copper, and resinous resist can be used as they are.
[0036]
On the other hand, in the dicing method, a gap is formed by penetrating the piezoelectric
material left on the substrate to the substrate with a dicing saw to form a gap for filling the
polymer material 14b, or a part of the polymer material Is removed by shaving using a dicing
saw, and is used when forming a composite piezoelectric layer in which a polymer material is
recessed more inward than the piezoelectric material with respect to the acoustic reflection layer.
The dicing saw can be made of a diamond grindstone or the like. The method of etching the
polymer material 14b by etching will be described below.
[0037]
The etching according to the present invention can also be performed by masking the
piezoelectric material portion with the etching mask as described above, but for example, the
desired etching rate of the piezoelectric material 14a and the polymer material 14b is utilized
The location can also be etched.
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[0038]
The etching speed of the piezoelectric material 14a is extremely slow as compared with the
material used for the polymer material 14b, and the polymer material 14b is more than the
piezoelectric material 14a by utilizing the difference in etching resistance between the
piezoelectric material 14a and the polymer material 14b. Since the material is etched and
removed first, the polymer material 14b can be scraped so as to be inside.
[0039]
In the above manufacturing method, although the composite piezoelectric layer is formed, the
polymer material is partially removed by etching or the like to form a recess. However, the recess
is formed by forming the composite piezoelectric layer. When the polymer material 14b is filled
in the space of the piezoelectric material, the surface of the polymer material opposite to the
substrate surface is recessed from the surface of the piezoelectric material opposite to the
substrate surface. It can also be formed by filling while adjusting the filling amount.
In this case, the polymer removal step described above can be omitted.
[0040]
Examples of materials used for the piezoelectric material 14 a include piezoelectric ceramics
such as lead zirconate titanate (PZT), relaxor-based, lead niobate-based and lead titanate-based
ceramics, lead zinc niobate titanate (PZNT), Single crystals such as magnesium niobate titanic
acid (PMNT) are preferred.
[0041]
As the polymer material 14b, organic synthetic polymer materials such as epoxy resin, silicone
resin, urethane resin, polyethylene resin, polyurethane resin and the like can be used.
In addition, you may apply organic natural polymer materials, such as natural rubber.
These organic polymer materials have a large specific heat and a small thermal conductivity as
compared with the above-described piezoelectric materials, so that thermal damage such as
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frictional heat generated when using the dicing method in the first process described above can
be suppressed it can. For example, an epoxy resin has a thermal conductivity of about 0.2 W / (m
· K), which is advantageous in terms of specific heat and thermal conductivity. In addition, these
organic polymer materials can prevent physical damage to the piezoelectric material during the
cutting process.
[0042]
As the organic polymer material applied to the present embodiment, a hard resin having a
predetermined hardness is preferably applied in order to improve cutting accuracy when using
the dicing method, and, for example, the Rockwell hardness is 80 or more. Is preferred. In
addition, in order to improve the element characteristics after arraying, the speed of sound of the
polymer material is preferably 1 km / s or more. In the present embodiment, an epoxy resin
having a sound velocity of 2 km / s or more and a Rockwell hardness of M80 or more is applied.
In addition, it may replace with an organic polymer material and may apply an inorganic polymer
material.
[0043]
Next, the electrode layer 18 and the flexible printed board will be described with reference to
FIG. An electrode layer 18 is provided on the entire surface on which the composite piezoelectric
layer 14 is formed. The electrode layer 18 applies a power supply voltage from a signal
extraction flexible printed circuit (FPC) to the composite piezoelectric layer 14. When
manufacturing the ultrasound probe which concerns on this application, it is preferable to form
an electrode layer after the grinding | polishing process of a 3rd process. Hereinafter, a method
of electrically connecting the flexible printed board and the composite piezoelectric layer after
the third step will be described in detail. After the third step, an electrode layer is formed on the
entire surface of the composite piezoelectric layer by sputtering or the like. Thereafter, the
acoustic reflection layer and the composite piezoelectric layer in which the electrode layer is
formed on the surface of the composite piezoelectric layer are bonded by an adhesive layer. After
bonding, it is scraped off from the acoustic reflection layer on the side facing the composite
piezoelectric layer to the direction of the composite piezoelectric layer on the acoustic reflection
layer side by dicing, and the electrode layer disposed on the composite piezoelectric layer on the
acoustic reflection layer side is scraped off and insulated Remove to position. The cut holes
formed by dicing are filled with an adhesive to form the insulator 17. By the formation of the
insulator 17, as shown in FIG. 5, the central portion separated by the insulator 17 is electrically
connected to the composite piezoelectric material and the ground electrode layer of the flexible
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printed board through the acoustic reflection layer which is conductive. On the other hand, both
ends separated by the insulator 17 are electrically connected to the flexible printed board.
[0044]
In the above process, the step of insulating the electrode layer formed on the entire surface of
the composite piezoelectric layer at a desired position is performed after bonding the acoustic
reflection layer and the composite piezoelectric layer, but may be performed before bonding. In
this case, the acoustic reflection layer is cut by dicing or the like according to the insulating
portion of the electrode layer formed on the surface of the composite piezoelectric layer before
bonding to form a cutting hole, and the adhesive is filled.
[0045]
Materials used for the electrode layer 18 include gold (Au), platinum (Pt), silver (Ag), palladium
(Pd), copper (Cu), aluminum (Al), nickel (Ni), tin (Sn), etc. Can be mentioned. In the electrode layer
21 and the common electrode layer 22, first, an underlying metal such as titanium (Ti) or
chromium (Cr) is formed to a thickness of 0.002 to 1.0 μm by a sputtering method, and then the
above metal element is mainly used. Metal materials comprising these metals and their alloys,
and, if necessary, partially insulating materials, by sputtering, vapor deposition, or any other
suitable method, to a thickness of 0.02 to 10 .mu.m. These electrode layers can also be formed by
screen printing, dipping, or thermal spraying other than sputtering, using a conductive paste in
which metal powder of fine powder and low melting point glass are mixed.
[0046]
The acoustic reflection layer 13 is a reflection layer that reflects the ultrasonic waves generated
in the composite piezoelectric layer 14, is bonded to the surface of the composite piezoelectric
layer 14 opposite to the object, and faces the bonding surface with the composite piezoelectric
layer 14. The bonding surface is bonded to the backing layer 11. The acoustic reflection layer 13
reflects, in the direction of the subject, the ultrasonic waves of the composite piezoelectric layer
14 irradiated in the direction opposite to the direction of the subject, and increases the power of
the ultrasonic waves incident on the subject.
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[0047]
Since the acoustic reflection layer 13 is used to reflect ultrasonic waves, the acoustic impedance
of the acoustic reflection layer may be an acoustic impedance relatively higher than the acoustic
impedance of the composite piezoelectric layer calculated by the above equation (1). Just do it.
Tungsten or the like can be used as the acoustic reflection layer.
[0048]
The acoustic reflection layer 13 is also a substance having high conductivity at the same time,
and electrically connects the flexible printed board 12 described later and the composite
piezoelectric layer 14. The acoustic reflection layer 13 has a cutting hole and is in a state of
being electrically insulated according to the insulating portion of the electrode layer 18 of the
composite piezoelectric layer 14.
[0049]
The backing layer 11 is made of an ultrasonic absorber that supports the acoustic reflection layer
13, the composite piezoelectric layer 14, and the acoustic matching layer 15 and can absorb
unnecessary ultrasonic waves. The backing layer 11 is mounted on a plate surface of the
composite piezoelectric layer 14 opposite to the direction in which ultrasonic waves are
transmitted and received, and among ultrasonic waves generated on the opposite side of the
object direction, ultrasonic waves transmitted through the acoustic reflection layer Absorb.
[0050]
As a backing material constituting backing layer 11, natural rubber, ferrite rubber, epoxy resin,
tungsten oxide, titanium oxide, ferrite, polyvinyl chloride, polyvinyl butyral (PVB), ABS resin,
polyurethane (PUR), polyvinyl alcohol Add thermoplastics such as alcohol (PVAL), polyethylene
(PE), polypropylene (PP), polyacetal (POM), polyethylene terephthalate (PETP), fluorine resin
(PTFE) polyethylene glycol, polyethylene terephthalate-polyethylene glycol copolymer etc. It is
possible to apply a rubber-based composite material and an epoxy resin composite material
which are press-molded.
[0051]
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The backing material is preferably composed of a mixture of a rubber-based composite material
and an epoxy resin composite material.
The shape of the backing layer can be appropriately selected in accordance with the shape of the
composite piezoelectric layer 14 and the shape of the ultrasonic probe 1 including the same.
[0052]
The acoustic matching layer 15 matches the acoustic impedance between the composite
piezoelectric layer 14 and the subject and suppresses reflection at the interface. The acoustic
matching layer 15 is mounted on the object side of the composite piezoelectric layer 14 in the
transmission / reception direction in which transmission / reception of ultrasonic waves is
performed. The acoustic matching layer 15 has an acoustic impedance that is approximately
midway between the composite piezoelectric layer 14 and the subject.
[0053]
The acoustic matching layer 15 may be a single layer or a plurality of layers, but is preferably
two or more layers, more preferably four or more layers. The layer thickness of the acoustic
matching layer 15 is preferably determined to be λ / 4, where λ is a wavelength of ultrasonic
waves. If the layer thickness of the acoustic matching layer 15 is not properly made, a plurality of
unnecessary spurs may appear at frequency points different from the original resonance
frequency, and the basic acoustic characteristics may greatly fluctuate. As a result, the
reverberation time may increase, and the sensitivity or S / N may be reduced due to waveform
distortion of the reflection echo. The thickness of the acoustic matching layer 15 is generally in
the range of about 20 to 500 μm.
[0054]
Materials used for the acoustic matching layer 15 include aluminum, aluminum alloy (for
example, AL-Mg alloy), magnesium alloy, macor glass, glass, fused quartz, copper graphite, PE
(polyethylene), PP (polypropylene), PC (polycarbonate) ), ABC resin, ABS resin, AAS resin, AES
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17
resin, nylon (PA6, PA6-6), PPO (polyphenylene oxide), PPS (polyphenylene sulfide: may be
contained in glass fiber), PPE (polyphenylene ether), PEEK (poly Ether ether ketone), PAI
(polyamide imide), PETP (polyethylene terephthalate), epoxy resin, urethane resin and the like
can be used. It is preferable to use a thermosetting resin such as epoxy resin as a filler, which is
formed by adding zinc flower, titanium oxide, silica or alumina, bengara, ferrite, tungsten oxide,
ytterbium oxide, barium sulfate, tungsten, molybdenum, etc. Applicable
[0055]
Next, the ultrasound diagnostic imaging apparatus 2 will be described using the drawings. FIG. 6
is a side view showing a schematic configuration of the ultrasound diagnostic imaging apparatus
2 in the present embodiment.
[0056]
An ultrasound diagnostic imaging apparatus 2 according to the present embodiment includes an
ultrasound diagnostic imaging apparatus main body 201 and an ultrasound probe 1. The
ultrasonic probe 1 transmits an ultrasonic wave (transmission ultrasonic wave) to a subject such
as a living body (not shown) and receives a reflected wave (reflected ultrasonic wave: echo) of the
ultrasonic wave reflected by the subject. Do. The ultrasonic diagnostic imaging apparatus main
body 201 is connected to the ultrasonic probe 1 via the cable 203, and transmits a drive signal of
an electric signal to the ultrasonic probe 1 so that the ultrasonic probe 1 is a subject To the
transmitting ultrasonic wave, and based on the received signal which is an electrical signal
generated by the ultrasonic probe 1 in response to the reflected ultrasonic wave from the inside
of the subject received by the ultrasonic probe 1. Thus, the internal state inside the subject is
imaged as an ultrasound image.
[0057]
For example, as shown in FIG. 7, the ultrasonic diagnostic imaging apparatus main body 201
includes an operation input unit 211, a transmission unit 212, a reception unit 213, an image
generation unit 214, a memory unit 215, and a DSC (Digital Scan Converter). ), A display unit
217, and a control unit 218.
[0058]
The operation input unit 211 includes, for example, various switches, buttons, a track ball, a
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mouse, a keyboard, and the like for inputting a command for instructing start of diagnosis and
data such as personal information of the subject. It outputs to the control unit 218.
[0059]
The transmission unit 212 is a circuit that supplies a drive signal, which is an electrical signal, to
the ultrasound probe 1 via the cable 203 according to the control of the control unit 218, and
causes the ultrasound probe 1 to generate transmission ultrasound. .
More specifically, as shown in FIG. 8, the transmission unit 212 includes, for example, a clock
generation circuit 121, a pulse generation circuit 122, a pulse width setting unit 123, and a delay
circuit 124.
[0060]
The clock generation circuit 121 is a circuit that generates a clock signal that determines the
transmission timing and transmission frequency of the drive signal.
The pulse generation circuit 122 is a circuit for generating a pulse signal as a drive signal at a
predetermined cycle. For example, as shown in FIG. 9, the pulse generation circuit 122 can
generate a rectangular pulse signal by switching and outputting a ternary voltage. At this time,
although the amplitude of the pulse signal is made the same in positive polarity and negative
polarity, it is not limited to this. The configuration may be such that a binary voltage is switched
to generate a pulse signal.
[0061]
The pulse width setting unit 123 sets the pulse width of the pulse signal output from the pulse
generation circuit 122. That is, the pulse generation circuit 122 outputs a pulse signal having a
pulse waveform according to the pulse width set by the pulse width setting unit 123. The pulse
width can be changed, for example, by an input operation by the operation input unit 211.
Further, by identifying the ultrasonic probe 1 connected to the ultrasonic diagnostic imaging
apparatus main body 201, the pulse width corresponding to the identified ultrasonic probe 1
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may be set.
[0062]
As shown in FIG. 7, the receiving unit 213 is a circuit that receives a received signal of an
electrical signal from the ultrasound probe 1 via the cable 203 according to the control of the
control unit 218. The receiving unit 213 includes, for example, an amplifier, an A / D conversion
circuit, and a phasing addition circuit. In the amplifier, the reception signal has a portion
surrounded at both ends by the insulator 17 of the composite piezoelectric layer as one element
(shown in FIG. 2), and a predetermined amplification preset for each individual path
corresponding to each element It is a circuit for amplifying at a rate. The A / D conversion circuit
is a circuit for analog-digital conversion (A / D conversion) of the amplified reception signal. The
phasing addition circuit adjusts the phase by giving a delay time to the A / D converted received
signal for each individual path corresponding to each element of the composite piezoelectric
layer, and adds them (phasing addition) It is a circuit for generating sound ray data.
[0063]
The image generation unit 214 performs envelope detection processing, logarithmic
amplification, and the like on the sound ray data from the reception unit 213, performs gain
adjustment, and the like, and performs luminance conversion to generate image data. That is, the
image data represents the intensity of the received signal by luminance. The image data
generated by the image generation unit 214 is transmitted to the memory unit 215.
[0064]
The memory unit 215 is formed of, for example, a semiconductor memory such as a dynamic
random access memory (DRAM), and stores the image data transmitted from the image
generation unit 214 in frame units. That is, the memory unit 215 can be stored as ultrasound
diagnostic image data configured in frame units. The ultrasound diagnostic image data stored in
the memory unit 215 is read according to the control of the control unit 218 and transmitted to
the DSC 216.
[0065]
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The DSC 216 converts the ultrasound diagnostic image data received from the memory unit 215
into an image signal according to a television signal scanning method, and outputs the image
signal to the display unit 217.
[0066]
As the display unit 217, a display device such as a liquid crystal display (LCD), a cathode-ray tube
(CRT) display, an organic EL (Electronic Luminescence) display, an inorganic EL display, a plasma
display, or the like is applicable.
The display unit 217 displays an ultrasound diagnostic image on the display screen in
accordance with the image signal output from the DSC 216. Note that, instead of the display
device, a printing device such as a printer may be applied.
[0067]
The control unit 218 includes, for example, a central processing unit (CPU), a read only memory
(ROM), and a random access memory (RAM), reads out various processing programs such as a
system program stored in the ROM, and , And centrally control the operation of each part of the
ultrasonic diagnostic imaging apparatus 2 in accordance with the developed program. The ROM
is constituted by a nonvolatile memory such as a semiconductor, and stores a system program
corresponding to the ultrasound diagnostic imaging apparatus 2, various processing programs
that can be executed on the system program, various data, and the like. These programs are
stored in the form of computer readable program code, and the CPU sequentially executes
operations according to the program code.
[0068]
The RAM forms a work area for temporarily storing various programs executed by the CPU and
data related to these programs.
[0069]
The shape of the drive signal is not particularly limited, and may be appropriately selected from a
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sine wave, a cosine wave, a rectangular wave, and the like.
Alternatively, a signal obtained by combining these plural signals may be used. From the
viewpoint of being able to be configured by a simple and small circuit, it is preferable to set the
drive signal as a rectangular wave having a plurality of pulses. At this time, at least one pulse of
the plurality of pulses is preferably configured to have a pulse width (duty) different from that of
the other pulses. As a result, the frequency bandwidth of the drive signal is increased, so that the
frequency bandwidth of the ultrasonic waves to be transmitted can be further increased, and the
time resolution, that is, the distance resolution in the depth direction can be further improved.
[0070]
An example of such a drive signal shape is shown in FIG. The drive signal illustrated in FIG. 10
includes a first pulse signal (pulse width A), a second pulse signal (pulse width B) different in
polarity from the first pulse signal, and the first pulse signal. And a third pulse signal (pulse
width A) of the same polarity. The pulse signal to be transmitted is set to have a cycle of 2T, and
the pulse widths of the first pulse signal, the second pulse signal, and the third pulse signal may
be set individually such that T = 2A + B. . Thus, the pulse signal can be easily designed by
combining the first and third pulse signals having the same polarity with the third pulse signal
having a different polarity. Also, the illustrated rectangular wave is a drive signal in which the
pulse width of the first pulse signal and the pulse width of the third pulse signal are equal, but
the pulse width of the first pulse signal, the pulse of the second pulse signal When the width and
the pulse width of the third pulse signal are set to 16 ns, 56 ns, and 104 ns, respectively, the
pulse widths of the first to third pulses can all be made different. As described above, by
changing the pulse width, the position of the peak indicated by the frequency response
characteristic of the ultrasonic probe can be changed to a desired frequency band, so that the
frequency bandwidth of the drive signal is made larger. Can.
[0071]
By providing the ultrasonic probe 1 in the ultrasonic diagnostic apparatus as described above, an
ultrasonic diagnostic apparatus can be provided which can irradiate a wide band ultrasonic wave
to the subject and provide a high resolution ultrasonic image. .
[0072]
Reference Signs List 1 ultrasonic probe 11 backing layer 12 flexible printed board 13 acoustic
reflection layer 14 composite piezoelectric layer 14 a piezoelectric material 14 b polymer
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material 15 acoustic matching layer 16 acoustic lens layer 17 insulator 18 electrode layer 19
case holding portion 2 ultrasonic wave Image diagnostic apparatus 201 Ultrasonic diagnostic
imaging apparatus main body 203 Cable 121 Clock generation circuit 122 Pulse generation
circuit 123 Pulse width setting unit 124 Delay circuit 211 Operation input unit 212
Transmission unit 213 Reception unit 214 Image generation unit 215 Memory unit 216 DSC
217 Display unit 218 control unit
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