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DESCRIPTION JP2008011494

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DESCRIPTION JP2008011494
PROBLEM TO BE SOLVED: To provide an array provided with an uppermost acoustic matching
layer having a low attenuation rate, dicing processability, heat resistance, excellent adhesion with
upper and lower layers, and suitable acoustic impedance among three or more acoustic matching
layers. An ultrasonic probe is provided. A plurality of channels are arranged with a space, each
having a piezoelectric element and three or more acoustic matching layers formed on the
piezoelectric element, and the piezoelectric elements of the respective channels are provided. A
grooved backing at a location corresponding to the channel space, and an acoustic lens formed to
at least cover the surface of the acoustic matching layer on the top layer of each channel, the
acoustic matching layer on the top layer An array type ultrasonic probe comprising a silicone
resin-containing mixture and having a Shore hardness D of 40 or more at 25 ° C. and an
acoustic impedance of 1.8 to 2.5 MRayls. [Selected figure] Figure 1
Array type ultrasonic probe and ultrasonic diagnostic apparatus
[0001]
The present invention relates to an array-type ultrasound probe for transmitting and receiving
ultrasound signals to a subject or the like and an ultrasound diagnostic apparatus having the
array-type ultrasound probe.
[0002]
Medical ultrasonic diagnostic apparatuses and ultrasonic image inspection apparatuses transmit
ultrasonic signals to an object, receive reflection signals (echo signals) from the inside of the
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object, and image the inside of the object It is.
As this medical ultrasonic diagnostic apparatus and ultrasonic image inspection apparatus, an
electronically operated array type ultrasonic probe having an ultrasonic signal transmitting /
receiving function is mainly used.
[0003]
The arrayed ultrasound probe has a structure comprising a backing, a plurality of channels
adhered on the backing and arranged in an array at desired spaces, and an acoustic lens adhered
on the channels . The plurality of channels are respectively formed on the backing, and a
piezoelectric element having a structure in which electrodes are attached to both sides of a
piezoelectric made of, for example, lead zirconate titanate (PZT) -based piezoelectric ceramic
material or relaxor-based single crystal material; And an acoustic matching layer formed on the
piezoelectric element. In some cases, grooves may be formed in the backing corresponding to the
spaces of the respective channels.
[0004]
Such an array-type ultrasonic probe contacts the acoustic lens side with the subject at the time of
diagnosis and drives the piezoelectric elements of each channel, whereby ultrasonic signals are
transmitted from the front of the piezoelectric element to the inside of the subject, that is, the
human body. Send. The ultrasonic signal is focused at a desired position in the subject by
electronic focusing according to the drive timing of the piezoelectric element and focusing by the
acoustic lens. At this time, an ultrasonic signal can be transmitted to a required range in the
subject by controlling the drive timing of the piezoelectric element, and an ultrasonic image of
the required range (an echo image from the subject is received) Tomogram is obtained. In driving
the piezoelectric element of the ultrasonic probe, an ultrasonic signal is emitted also to the back
side of the piezoelectric element. Therefore, a backing is disposed on the back of the piezoelectric
element of each channel, and the ultrasound signal to the back side is absorbed (attenuated) by
this backing, and the normal ultrasound signal is an ultrasound signal from the back side
(reflected signal) It avoids the adverse effect of being transmitted into the subject.
[0005]
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Heretofore, the acoustic matching layer is known to have a single-layer structure, a two-layer
structure or a multilayer gradient structure of three or more layers. In particular, in recent years,
three or more acoustic matching layers are preferably used for broadening the bandwidth (see
Non-Patent Document 1).
[0006]
On the other hand, Patent Document 1 discloses a general method of manufacturing an
ultrasonic probe. That is, piezoelectric elements having electrodes formed on both sides of a
piezoelectric body made of a piezoelectric material such as PZT are attached to a rubber plate as
a backing, and an acoustic matching layer is adhered on the piezoelectric elements to form a
laminate. In this bonding step, a heat treatment at 80 to 150 ° C. may be performed to cure the
adhesive layer. Therefore, it is important that the acoustic matching layer has heat resistance.
Subsequently, the laminate is cut in an array to a width of about 50 to 300 μm from the acoustic
matching layer side by a dicer to form a plurality of channels. By cutting the acoustic matching
layer in an array, crosstalk between each channel is prevented. For this reason, it is important to
have high dicing processability in the array cutting of the acoustic matching layer. Subsequently,
the resilient grooves between the channels are filled with a relatively soft resin, such as low
acoustic impedance and high damping silicone rubber, to maintain mechanical strength. After
this, the ultrasonic probe is manufactured by bonding an acoustic lens on the acoustic matching
layer of the plurality of channels.
[0007]
The acoustic lens is made of a mixed material obtained by adding an inorganic filler to silicone
rubber, and a material having an acoustic impedance of 1.3 to 1.7 M Rayls at room temperature
of 25 ° C. is used. The thermal expansion coefficient of these acoustic lenses is about 200 ppm /
° C. in the range of room temperature to 40 ° C. For adhesion between the acoustic matching
layer and the acoustic lens, a silicone rubber-based adhesive or a modified silicone rubber-based
adhesive is used.
[0008]
When driving such an array-type ultrasonic probe, ultrasonic energy emitted from the
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piezoelectric elements of the plurality of channels is absorbed and attenuated by the acoustic
matching layer and the acoustic lens. At this time, since a part of the ultrasonic energy is
converted to heat, the temperature of the acoustic matching layer may be 60 ° C. or higher, for
example, in the ultrasonic probe for a circulatory organ. In addition, the ultrasound probe is
constantly applied to the acoustic matching layer through the acoustic lens at all times during
use. Due to thermal expansion differences between the acoustic lens and the acoustic matching
layer due to these thermal effects and factors of mechanical pressure, the acoustic matching
layer between the acoustic lens and the top acoustic matching layer, and the acoustic matching
layer below the acoustic matching layer Peeling may occur between layers. As a result, variations
in sensitivity occur within the ultrasonic probe, resulting in reduced reliability. In extreme cases,
the ultrasound probe stops functioning. These phenomena are serious problems, especially when
the epoxy resin is used as the top acoustic matching layer material, because the difference in
thermal expansion coefficient with silicone rubber, which is an acoustic lens, reaches 150 ppm /
° C. or more. .
[0009]
Moreover, the characteristic etc. of the acoustic matching layer used for an ultrasonic probe are
concretely illustrated by the said patent document 1. FIG. For example, among the plurality of
acoustic matching layers, it is described that the topmost acoustic matching layer in contact with
the acoustic lens uses a material whose acoustic impedance is closer to that of the human body
(1.4 to 1.6 MRayls).
[0010]
As the acoustic matching layer described above, materials based on polyurethane rubber,
polyethylene, silicone rubber and epoxy resin are conventionally used. Specifically, Patent
Document 2 discloses an acoustic matching layer provided between a piezoelectric element and a
surface of a living body as a solution in order to reduce the amount of heat transferred from a
heating element inside an ultrasonic probe to the body surface. It is disclosed to use a low
thermal conductivity acoustic matching layer which has low thermal conductivity and at least
one of them. The low thermal conductivity acoustic matching layer is described to be formed by
adding and dispersing low thermal conductivity fine particles made of a material having low
thermal conductivity such as silicone resin in a base material made of epoxy resin etc. There is. In
addition, Non-Patent Documents 2 and 3 disclose an acoustic matching layer having a structure
in which a polyurethane resin is filled with polyethylene fiber or carbon fiber. However, these
materials have the low damping factor required as an acoustic matching layer, and are excellent
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and appropriate in properties such as dicing processability, heat resistance, adhesion between
upper and lower layers, matching of thermal expansion coefficient with acoustic lens, etc. It does
not satisfy all the acoustic impedances.
[0011]
Patent Document 3 discloses an acoustic lens material for an ultrasonic probe with high
hardness. Table II of this patent document 3 shows that the sound velocity of trimethylsiloxy
methacryloxypropylsilane (TRIS) is around 1650 m / s. However, it is neither described nor
suggested that this acoustic lens material can be applied to the acoustic matching layer. Further,
even if the materials of methyl methacrylate (Example I) and tetrabutylstyrene (Example II)
described in Patent Document 3 are applied, desired sound speed, attenuation factor, acoustic
impedance, etc. as an acoustic matching layer, etc. In addition to that, it is not excellent in
processability as an acoustic matching layer, heat resistance, adhesion to upper and lower layers,
matching of thermal expansion coefficient with an acoustic lens, and the like.
[0012]
Further, Patent Documents 4 and 5 disclose a material including a silicone resin with high
hardness used for Laser Emission Diode (LED). However, information on acoustic characteristics
such as the sound velocity, attenuation rate, acoustic impedance and the like of these LED
silicone materials is not disclosed, and application to an ultrasonic probe and the like are not
mentioned. JP, 2005-198261, A JP, 10-75953, A U.S. Patent No. 5,505, 205, JP, 2004-339, A 48
JP, A, 2005-272697, A. T. Inoue et al., IEEE, UFFC, vol. 34 No. 1, 1987, pp. 8-15 Toshio Kondo
and Hiroyuki Fujimoto, Proceedings 2003 IEEE Ultrasonic Symposium p. 1318-1321. Toshio
Kondo, Mitsuyoshi Kitatuji and Mikio Izumi, Proceedings, 2004 IEEE Ultrasonic Symposium p.
1659-1662.
[0013]
Among the three or more acoustic matching layers, the present invention is excellent in matching
with low attenuation, dicing processability, heat resistance, adhesiveness with upper and lower
layers, coefficient of thermal expansion with the acoustic lens, and appropriate acoustic
impedance. An object of the present invention is to provide an array-type ultrasonic probe
provided with a topmost acoustic matching layer.
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[0014]
An object of the present invention is to provide an ultrasonic diagnostic apparatus provided with
the array type ultrasonic probe.
[0015]
According to the present invention, a plurality of channels are arranged spaced apart and each
has a piezoelectric element and three or more acoustic matching layers formed on the
piezoelectric element; the piezoelectric elements of the respective channels are provided; A
grooved backing at a location corresponding to the channel space; and an acoustic lens formed to
at least cover the surface of the acoustic matching layer on the top layer of the channels; the
acoustic matching layer on the top layer The present invention provides an array-type ultrasonic
probe comprising a silicone resin-containing mixture and having a Shore hardness D of 40 or
more at 25 ° C. and an acoustic impedance of 1.8 to 2.5 MRayls.
[0016]
Further, according to the present invention, there is provided an ultrasonic diagnostic apparatus
comprising: an array type ultrasonic probe having the above-described configuration; and an
ultrasonic probe controller connected to the ultrasonic probe through a cable.
[0017]
According to the present invention, among acoustic matching layers of three or more layers, it is
the best with the low attenuation rate, dicing processability, heat resistance, adhesion with upper
and lower layers, excellent matching of thermal expansion coefficient, and appropriate acoustic
impedance. It is possible to provide a high performance, highly reliable arrayed ultrasound probe
with an upper acoustic matching layer and small cross coupling.
[0018]
Further, according to the present invention, it is possible to provide an ultrasonic diagnostic
apparatus in which cross-talk is reduced and a high performance and high reliability array type
ultrasonic probe is incorporated to improve the image quality and sensitivity of tomogram. .
[0019]
Hereinafter, an array-type ultrasonic probe and an ultrasonic diagnostic apparatus according to
an embodiment of the present invention will be described in detail with reference to the
drawings.
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[0020]
FIG. 1 is a perspective view of an essential part of an array-type ultrasonic probe according to an
embodiment, and FIG. 2 is a partial cross-sectional view of the array-type ultrasonic probe of FIG.
[0021]
The array type ultrasound probe 1 is provided with a backing 2.
A plurality of channels 3 are arranged on the backing 2 with a desired space 4 therebetween.
Grooves 5 are respectively formed in the backing 2 corresponding to the spaces 4 between the
plurality of channels 3.
The space 4 between the channels 3 may be filled with a relatively soft resin such as, for
example, low acoustic impedance and high damping silicone rubber to maintain mechanical
strength.
This resin may be filled not only in the space 3 but also in the groove 5 of the backing 2 below it.
[0022]
Each of the channels 3 has a piezoelectric element 6 and three or more, for example, three
acoustic matching layers formed on the piezoelectric element 6, that is, first to third acoustic
matching layers 71 to 73.
The piezoelectric element 6 is, as shown in FIG. 2, a piezoelectric body 8 made of, for example,
lead zirconate titanate (PZT) -based piezoelectric ceramic material or relaxor-based single crystal
material, and a first one formed on both sides of the piezoelectric body 8 It comprises the second
electrodes 91 and 92.
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The first electrode 91 of the piezoelectric element 6 is adhered and fixed on the backing 2 by, for
example, an epoxy resin adhesive layer (not shown).
The first acoustic matching layer 71 is adhered and fixed on the second electrode 92 of the
piezoelectric element 6 by, for example, an epoxy resin adhesive layer (not shown).
The second acoustic matching layer 72 is bonded and fixed onto the first acoustic matching layer
71 by, for example, an epoxy resin adhesive layer (not shown). The third acoustic matching layer
(uppermost acoustic matching layer) 73 is adhered and fixed on the second acoustic matching
layer 72 by, for example, an epoxy resin adhesive layer (not shown).
[0023]
The acoustic lens 10 is provided from the surface of the third acoustic matching layer 73 in the
uppermost layer of the channel 3 to the side surfaces of the third, second, and first acoustic
matching layers 73, 72, 71, the piezoelectric element 6 side, and the piezoelectric element 6. It is
formed so that the side part of backing 2 located may be covered. The acoustic lens 10 is bonded
and fixed to the surface of the third acoustic matching layer 73 by a rubber-based adhesive layer
(not shown). The rubber-based adhesive is preferably a modified silicone-based adhesive having
an acoustic impedance of 1.3 to 1.8 MRayls at 25 ° C.
[0024]
The backing 2, the plurality of channels 3 and the acoustic lens 10 are housed in a case (not
shown). In this case, a signal processing circuit (not shown) including a control circuit for
controlling the drive timing of the piezoelectric element 6 of each channel 3 and an amplifier
circuit for amplifying the received signal received by the piezoelectric element 6 is provided. It is
built-in. The first and second electrodes 91 and 92 of the piezoelectric element 6 are connected
to extended signal lines and ground lines (not shown), and extend from the case opposite to the
acoustic lens 10 to the outside. Is connected to a control circuit (not shown). A signal line may be
connected to the second electrode 92 of the piezoelectric element 6, and an earth line may be
connected between the second acoustic matching layer 72 and the third acoustic matching layer
73.
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[0025]
In the array-type ultrasonic probe having such a configuration, a voltage is applied between the
first and second electrodes 91 and 92 of the piezoelectric element 6 in each channel 3 to
resonate the piezoelectric body 8 in each channel 3. Ultrasonic waves are emitted (transmitted)
through the acoustic matching layers (first to third acoustic matching layers 71, 72, 73) and the
acoustic lens 10. At the time of reception, ultrasonic waves received through the acoustic lens 10
and the acoustic matching layer (first to third acoustic matching layers 71, 72, 73) of each
channel 3 vibrate the piezoelectric body 8 of the piezoelectric element 6 in each channel 3 This
vibration is electrically converted into a signal to obtain an image.
[0026]
The third acoustic matching layer (uppermost acoustic matching layer) 73 contains a silicone
resin-containing mixture, and has a Shore hardness D of 40 or more at 25 ° C. and an acoustic
impedance of 1.8 to 2 at 25 ° C. It has the characteristics of 5 MRayls. Here, the Shore hardness
D can be obtained using, for example, a durometer type D in accordance with JIS K 6253. The
third acoustic matching layer 73 (uppermost acoustic matching layer) has an attenuation factor
of 5 dB / cm MHz or less measured at 5 MHz at 25 ° C., and an attenuation factor of 900 m / s
which is the product of the attenuation factor and the speed of sound. More preferably, it is at
most dB / mm / MHz.
[0027]
The silicone resin-containing mixture comprises, for example, a two-component mixture of an
organopolysiloxane and a silicone-based mixture containing an epoxy-terminated siliconemodified organic resin compound.
[0028]
Here, as said organopolysiloxane, the material which contains a methyl group and a vinyl group
is mentioned, for example to organopolysiloxane.
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The silicone-modified organic resin compound is, for example, a block copolymer of a silicone
resin and an organic resin, and is obtained by the reaction of a silicone intermediate for
modification and an organic resin having a functional group. Although various silicone-modified
resins can be made depending on the type of organic resin, alkyd silicone and epoxy silicone can
be mentioned as typical materials.
[0029]
As the silicone resin-containing mixture, for example, SCR1004, SCR1011, and SCR1012, which
are silicone resin-containing mixtures for LED commercially available from Shin-Etsu Chemical
Co., Ltd., can be used. As the silicone resin-containing mixture of the above-mentioned
characteristics, DE 6665 commercially available from Dow Corning can be used. Among these
silicone resin-containing mixtures, especially SCR 1011 is preferred because of its low damping
factor.
[0030]
Moreover, as said silicone resin containing mixture, what consists of 2 liquid-type mixtures of
organopolysiloxane and the silicone type mixture containing an alkyl silicone compound can also
be used, for example. Here, as an alkyl silicone compound, SR2107 of Toray Dow Corning, etc.
are mentioned, for example.
[0031]
The silicone resin-containing mixture more preferably has C̶H stretching vibration of a benzene
nucleus and C̶H out-of-plane vibration of a benzene nucleus in a spectrum obtained by
measurement of a Fourier transform infrared spectrophotometer.
[0032]
Even if the third acoustic matching layer (the topmost acoustic matching layer) 73 is made of the
silicone resin-containing mixture alone having the above-mentioned characteristics, it is
preferable to use a silicone resin-containing mixture for the purpose of further improving
adhesion, processability and heat resistance. It may be made from the addition of fillers.
[0033]
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The uppermost acoustic matching layer 73 made of a composite material obtained by adding a
filler to such a silicone resin-containing mixture has, for example, a structure shown in FIGS.
[0034]
The acoustic matching layer 73 shown in FIG. 3 has a structure in which, for example, organic
substance-filled particles 12 are dispersed in an amount of 30% by volume or less in the matrix
11 of the silicone resin-containing mixture.
The uppermost acoustic matching layer in which the organic filler particles are dispersed in the
silicone resin-containing mixture exhibits a longitudinal sound velocity of 1750 to 2200 m / s at
25 ° C.
[0035]
The organic filler particles may be, for example, at least one selected from silicone rubber
particles, fluorocarbon resin particles, and urethane rubber particles, and can be used alone or in
the form of a mixture.
The organic filler particles have an effect of adjusting the speed of sound.
The organic filler particles are, for example, spherical. The spherical organic filler particles
preferably have an average diameter of 1 to 10 μm, for example.
[0036]
When the volume fraction of the organic filler particles exceeds 30% by volume, the attenuation
rate tends to be large, and the strength is further reduced, and the processability may be
reduced. The more preferable dispersed amount of the organic substance-filled particles in the
silicone resin matrix is 10% by volume or less.
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[0037]
In the acoustic matching layer 73 shown in FIG. 4, an inorganic filler (for example, spherical
silicon oxide particles 13 and inorganic fibers 14) having a density of 6 g / cm <3> or less is
dispersed in 10% by volume or less in the matrix 11 of the silicone resin-containing mixture. It
has the following structure. Such an acoustic matching layer has an attenuation factor of 5 dB /
cm / MHz or less measured at 25 ° C. and 5 MHz, and a product of attenuation factor and sound
velocity (attenuation performance index) of 900 (unit: m / s · dB / mm) It becomes possible to
control easily to the characteristic below / MHz). Further, the acoustic matching layer to which
the inorganic filler is added can effectively improve the processing strength, the adhesion, and
the heat resistance as compared with the non-added acoustic matching layer.
[0038]
The inorganic filler has, for example, a powdery or fibrous form. These types of inorganic fillers
can be contained alone or as a mixture in the silicone resin-containing mixture.
[0039]
Examples of the powdery inorganic filler include zinc oxide powder, zirconium oxide powder,
alumina powder, silica powder such as aerosil silica, titanium oxide powder, silicon carbide
powder, aluminum nitride powder, carbon powder or boron nitride powder. be able to. The
powdered inorganic fillers can be used alone or in the form of a mixture. The powdered inorganic
filler desirably has an average particle size of 0.5 μm or less, more preferably 0.1 μm or less.
The uppermost acoustic matching layer 73 in which such a fine powdered inorganic filler is
further dispersed in the silicone resin-containing mixture makes it possible to obtain excellent
processability while keeping the attenuation factor low.
[0040]
Examples of the fibrous inorganic filler include carbon fibers, silicon carbide fibers, zinc oxide
fibers, alumina fibers and glass fibers. The fibrous inorganic filler can be used alone or in the
form of a mixture.
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[0041]
The fibrous inorganic filler is particularly preferably glass fiber. As glass fiber, quartz glass fiber,
soda glass fiber etc. can be used, for example. In addition, conductive carbon fibers can also be
used. As a carbon fiber, the thing of various grades, such as pitch system carbon fiber and PAN
system carbon fiber, can be used, for example. Besides carbon fibers, carbon nanotubes can be
used. The fibrous inorganic filler is not limited to one made of one type of material, and for
example, the surface of carbon fibers may be coated with a resin.
[0042]
The fibrous inorganic filler preferably has a diameter of 10 μm or less and a length of 5 times or
more of the diameter. An acoustic matching layer containing a fibrous inorganic filler of such
dimensions allows the attenuation factor measured at 5 MHz to be easily reduced to 5 dB / cm /
MHz or less with a small amount of compounding, and thus an ultrasonic signal It becomes
possible to transmit and receive without deterioration in the acoustic matching layer. In addition,
the acoustic matching layer is provided with sufficient strength required during the dicing
process. Furthermore, the acoustic matching layer can further improve the heat resistance and
the processability during the dicing process. In particular, by using a fibrous inorganic filler
having a diameter of 5 μm or less, it is possible to realize an acoustic matching layer whose
attenuation factor is further reduced. By using a fibrous inorganic filler having a length of 20
times or more of the diameter, an acoustic matching layer with further improved heat resistance
and processability can be realized.
[0043]
When the dispersion amount of the inorganic filler with respect to the matrix of the silicone
resin-containing mixture exceeds 10% by volume, the attenuation factor of ultrasonic waves
rapidly increases, and as a result, the value of acoustic impedance exceeds 2.5 MRayls and low
acoustic impedance There is a risk that the acoustic matching layer of The dispersion amount of
the more preferable inorganic filler to the matrix of the silicone resin-containing mixture is 2 to
5% by volume.
[0044]
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The inorganic filler may be added to the silicone resin-containing mixture together with the
organic filler particles.
[0045]
When the acoustic matching layer has a laminated structure of three layers, the acoustic
matching layer other than the acoustic matching layer 73 of the uppermost layer described
above, that is, the lower acoustic matching layer in contact with the piezoelectric element 6 (first
acoustic matching layer 71 Preferably has an acoustic impedance of 10 to 15 MRayls at 25 ° C.,
and an intermediate acoustic matching layer (second acoustic matching layer 72) has an acoustic
impedance of 2.7 to 8 M Rayls at 25 ° C.
In the acoustic matching layer having such a three-layered laminated structure, the thickness of
the acoustic matching layer changes with the speed of sound. The thickness of the uppermost
acoustic matching layer 73 is typically λ / 4 (where λ is the wavelength of ultrasonic waves),
and the thickness is preferably 30 to 200 μm.
[0046]
Next, a method of producing such an acoustic matching layer will be described.
[0047]
First, for example, a liquid two-component silicone resin is weighed at a predetermined ratio and
thoroughly mixed.
Subsequently, the mixture is placed in a polyethylene container, defoamed, and cured at room
temperature to 85 ° C. for 2 hours and at 125 ° C. for 2 hours to prepare an acoustic matching
layer.
[0048]
In addition, at the time of preparation of the said acoustic matching layer, you may mix | blend at
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least one filler chosen from the organic filler particle mentioned above and an inorganic filler.
Among the fillers, the fibrous inorganic filler is preferably, for example, vacuum impregnated
before curing the mixture. When the viscosity of the mixture is high, the viscosity may be
reduced using an organic solvent such as normal hexane or toluene.
[0049]
Next, a method of manufacturing the ultrasonic probe according to the embodiment will be
described.
[0050]
First, on the backing, the piezoelectric element, the first acoustic matching layer, the second
acoustic matching layer, and the third acoustic matching layer described above are arranged in
this order, for example, by interposing a low viscosity epoxy resin adhesive between these
members. , To stack.
Subsequently, the laminate is heated, for example, at 120 ° C. for about one hour, and the
respective epoxy resin adhesives are cured to cure the backing and the piezoelectric element, the
piezoelectric element and the first acoustic matching layer, and the first acoustic matching layer.
The second acoustic matching layer, the second acoustic matching layer, and the third acoustic
matching layer are adhered and fixed, respectively.
[0051]
Then, the third acoustic matching layer is subjected to dicing processing at a width (pitch) of, for
example, 50 to 200 μm with a dicing blade, for example, from the third acoustic matching layer
to a plurality of divisions in an array, and the piezoelectric element and the first, second, and
third Form a plurality of channels with an acoustic matching layer. At this time, grooves are
formed in the backing surface layer corresponding to the spaces of the plurality of channels.
Subsequently, if necessary, the space between the channels is filled with a relatively soft resin
such as low acoustic impedance and high damping silicone rubber to maintain the mechanical
strength of each channel. Thereafter, an acoustic lens is adhesively fixed to the third acoustic
matching layer of each channel with a silicone rubber-based adhesive layer, and the backing, the
plurality of channels and the acoustic lens are housed in a case to manufacture an ultrasonic
probe.
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[0052]
An ultrasonic diagnostic apparatus provided with an ultrasonic probe according to the
embodiment will be described with reference to FIG.
[0053]
A medical ultrasonic diagnostic apparatus (or ultrasonic image inspection apparatus) for
transmitting an ultrasonic signal to an object, receiving a reflected signal (echo signal) from the
object, and imaging the object An array type ultrasound probe having a sound wave signal
transmitting / receiving function is provided.
This ultrasonic probe has the structure shown in FIGS. 1 and 2 described above. The ultrasonic
probe 1 is connected to an ultrasonic diagnostic apparatus main body 22 through a cable 21.
The ultrasonic diagnostic apparatus main body 22 is provided with an ultrasonic probe controller
(not shown) for transmitting and receiving ultrasonic signals of the ultrasonic probe, a display
23, and the like.
[0054]
The array type ultrasonic probe according to the embodiment described above is arranged with a
space, and has a plurality of channels each having a piezoelectric element and three or more
acoustic matching layers formed on the piezoelectric element, and these channels And an
acoustic lens formed to at least cover the surface of the acoustic matching layer on the top layer
of each of the channels. The acoustic matching layer of the top layer includes a silicone resincontaining mixture, and has a Shore hardness D of 40 or more at 25 ° C. and an acoustic
impedance of 1.8 to 2.5 MRayls, as follows: Play an important role.
[0055]
(1) The acoustic matching layer on the top layer has a low attenuation rate and an appropriate
acoustic impedance, so it is possible to provide a high-performance array-type ultrasonic probe
capable of effectively transmitting and receiving ultrasonic energy.
[0056]
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(2) The topmost acoustic matching layer is excellent in dicing processability, so that it is possible
to precisely form a channel having a target width by dicing with a diamond saw, for example.
As a result, since crosstalk between channels can be reduced, a high resolution arrayed
ultrasound probe can be realized.
[0057]
(3) The acoustic matching layer of the uppermost layer is excellent in heat resistance, and with
respect to a silicone-based adhesive layer and an epoxy-based adhesive layer interposed between
the upper and lower layers (acoustic lens and acoustic matching layer in the lower layer). The
acoustic matching layer between the acoustic lens and the top acoustic matching layer, even if
mechanical energy is applied, due to absorption of ultrasonic energy, heating of the acoustic
matching layer accompanying attenuation, and mechanical stress. It is possible to prevent
peeling between the and the acoustic matching layer below it.
As a result, it is possible to provide an arrayed ultrasound probe having high long-term reliability
with uniform sensitivity among channels.
[0058]
In particular, the acoustic matching layer of the uppermost layer in a form in which a powdery
inorganic filler having a density of 6 g / cm <3> or less such as silica powder is dispersed in 10%
by volume or less in the silicone resin matrix is an epoxy adhesive and And the processability at
the time of dicing can be further improved.
[0059]
Further, by using a fibrous inorganic filler such as glass fiber, it is possible to suppress an
increase in the damping rate and to further improve the processability and mechanical strength
at the time of dicing treatment.
[0060]
Furthermore, the uppermost acoustic matching layer having a thermal expansion coefficient
difference of 50 ppm / ° C. or less with the acoustic lens is unlikely to be peeled off even when
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heat generated during driving is repeatedly applied, and a highly reliable ultrasonic probe You
can get
[0061]
The ultrasound diagnostic apparatus according to the embodiment includes the highperformance, high-reliability array-type ultrasound probe with small crosstalk, and therefore can
improve the image quality and the sensitivity of the tomographic image.
[0062]
Hereinafter, embodiments of the present invention will be described in more detail.
[0063]
Example 1 Two liquid silicone resins, SCR1011 resin A and SCR1011 resin B manufactured by
Shin-Etsu Chemical Co., Ltd., were weighed accurately at a weight ratio of 100: 100.
The silicone resin-based mixture was placed in a polyethylene container, and stirred for 3
minutes with a rotary mixer and uniformly mixed.
The liquid resin was degassed in a vacuum container for 10 minutes and then placed in a
container made of Teflon (registered trademark).
Subsequently, after pre-curing at 85 ° C. for 1 hour, main curing was performed at 125 ° C. for
2 hours to prepare a third acoustic matching layer material made of a silicone resin-containing
mixture.
[0064]
The cured product of the silicone resin-containing mixture (material for the third acoustic
matching layer) obtained in Example 1 was subjected to a thermogravimetric analyzer /
differential thermal analyzer (TG / DTA; thermogravimetric analyzer / differential thermal
analyzer) under the following conditions: The TG / DTA curve was measured.
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Also, the FTIR spectrum of the cured silicone resin was analyzed by Fourier transform infrared
spectrophotometer (FTIR) under the following conditions.
The TG / DTA curve is shown in FIG. 6 and the FTIR spectrum is shown in FIG.
[0065]
<Conditions of TG / DTA> Device used: TG / DTA320U manufactured by SII Nano Technology Inc.
Heating conditions: Temperature rising from room temperature to 600 ° C. at 20 ° C./min.
Atmospheric gas: Air current (200 mL / min) Reference: Sapphire 9.6 mg Sample amount: 10 mg
<Analytical conditions of FTIR> Device used: FTS-6000 / UMA 500 manufactured by Varian
Technologies Japan Detector: MCT Integration frequency: 200 times Measurement method: Total
reflection measurement (ATR: Attenuation For comparison, TG / DTA curves and FTIR spectra of
cured products of general purpose silicone resin (Momentive Performance Material Co., Ltd. [old
name: GE Toshiba Silicon Co., Ltd .; former TSE 3032) are measured under the same conditions.
did. The TG / DTA curve is shown in FIG. 8 and the FTIR spectrum is shown in FIG.
[0066]
As is clear from FIGS. 6 and 8, the cured product of the silicone resin-containing mixture
obtained in Example 1 has a second-stage decomposition initiation temperature higher than that
of the cured general-purpose silicone resin, and the weight reduction also applies to the generalpurpose silicone A difference of about 10% was observed compared to the resin cured product.
[0067]
In addition, the cured product of the silicone resin-containing mixture obtained in Example 1 is,
as shown in FIG. 7, C̶ of the benzene nucleus, which is an absorption band derived from a
benzene nucleus, which does not appear in the general purpose silicone resin cured product (FIG.
9). H stretching vibrations (indicated by arrow A) and C̶H out-of-plane bending vibrations
(indicated by arrow B) of the benzene nucleus appear.
[0068]
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19
(Examples 2 to 9) As shown in Table 1 below, using SCR1012, SCR1011, and SCR1004
manufactured by Shin-Etsu Chemical Co., Ltd. as a two-liquid silicone resin (silicone resin-based
mixture), the third method is performed in the same manner as Example 1. Each material for the
acoustic matching layer was produced.
Of these materials, certain fillers were dispersed in some.
As the filler, silicone rubber particles having an average diameter of 3 μm, epoxy resin particles
having an average diameter of 10 μm, powdered silicon oxide having an average diameter of 20
nm, powdered zinc oxide having an average diameter of 30 nm, and powder having an average
diameter of 50 nm Titanium oxide, fibrous glass having an average diameter of 5 μm and an
average length of 100 μm, and fibrous carbon having an average diameter of 7 μm and an
average length of 100 μm were used.
[0069]
Examples 10 and 11 and Comparative Examples 1 to 6 As shown in Table 2 below, SCR1011,
SCR1012, polyurethane rubber, silicone rubber manufactured by Shin-Etsu Chemical Co., Ltd. as
a mixture of two liquid silicone resins (a silicone resin-based mixture) Example using an epoxy
resin, polyethylene, high hardness silicone resin (trade name: KER2500 manufactured by ShinEtsu Silicone Co., Ltd.) and (Momentive Performance Material Co., Ltd. [old name: GE Toshiba
Silicon Co., Ltd .; trade name; IVSM4500) as a base resin The materials for the third acoustic
matching layer were produced respectively in the same manner as in No. 1. Of these materials,
certain fillers were dispersed in some. As the filler, silicone rubber particles having an average
diameter of 3 μm, powdered silicon oxide having an average diameter of 20 nm, powdered
alumina having an average diameter of 100 nm, fibrous silicon oxide having an average diameter
of 5 μm and an average length of 100 μm are used. It was.
[0070]
About the obtained raw material for the third acoustic matching layer of Examples 1 to 10 and
Comparative Examples 1 to 6, the following methods were used for density, sound velocity,
acoustic impedance (Z), attenuation factor, processability, heat resistance and adhesiveness.
Evaluated.
[0071]
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1) Density The density was determined using a disk-shaped acoustic characteristic evaluation
sample of 50 mm diameter × 3 mm thickness obtained by polishing the material for the third
acoustic matching layer.
The density was measured by measuring the weight of the sample at 25 ° C. in air and water
and using the Archimedean method.
[0072]
2) Sound velocity and attenuation rate For measurement of 5 MHz in water at 25 ° C. using a
disk-shaped acoustic characteristic evaluation sample of 50 mm diameter × 3 mm thickness
obtained by polishing the material for the third acoustic matching layer The velocity of sound
and the rate of attenuation were measured using a probe. The stainless steel plate placed in
water, and the sample placed in place were transmitted from the ultrasonic probe, and their
reflection echoes were measured.
[0073]
The speed of sound was determined from the time difference between reflection echoes due to
the presence or absence of the sample and the sample thickness. The sound velocity (C) was
calculated using the following equation, using the time difference between the water and sample
transmission waveforms, with the sound velocity of water at each temperature as a reference.
[0074]
C = C0 / [L-C0 (Δt / d)] where C0 is the speed of sound of water, L is the distance between the
ultrasonic probe and the sample (object to be measured), d is the thickness of the sample, and Δt
is the water and the sample The time difference of the zero crossing point after passing the first
peak of the transmission waveform is shown.
[0075]
Similarly, the attenuation factor was determined by a predetermined method from the difference
in intensity of reflection echo depending on the presence or absence of a sample at a water
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temperature of 25 ° C. and the sample thickness.
[0076]
3) Acoustic impedance (Z) Z was determined as the product of the measured density and the
speed of sound.
[0077]
4) Sure hardness Determined at 25 ° C. using a durometer type D according to JIS K 6253.
[0078]
5) Processability 10 mm × 10 mm, 1.0 mm thick sample for processability evaluation obtained
by polishing the PZT piezoelectric element and the material for the third acoustic matching layer
on a backing obtained by adding ferrite to chloroprene rubber Laminated in this order via an
epoxy resin adhesive, cut this laminate with a 50 μm thick diamond blade to a pitch of 100 μm,
a depth of 200 μm to the backing, and rotate it by another 90 degrees, again A pitch of 100 μm
and a depth of 200 μm to the backing were cut.
The remaining portion (50 μm × 50 μm square) after cutting was observed with a microscope.
In this observation, the processability was evaluated from the inclination and linearity of the
sample for processability evaluation (third acoustic matching layer).
[0079]
If the remaining 50 μm square pieces have no problem at all: A: If the remaining 50 μm square
pieces have a defect of 2% or less: B, then the remaining 50 μm square pieces In the case where
a defect of 10% or less was observed: C, · In the case where a defect exceeding 10% was observed
in the remaining 50 μm square piece: D, it was classified into four stages.
[0080]
6) Heat Resistance The material for the third acoustic matching layer was polished to obtain a
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sample having a width of 25 mm, a length of 100 mm, and a thickness of 1.6 mm.
This sample is attached to a glass epoxy substrate (FR4) using an epoxy adhesive according to
the method of JIS-C6471 8.1, and after being cured at 60 ° C for 24 hours and subsequently at
125 ° C for 1 hour, tensilon tension The tensile shear strength was determined by pulling at a
speed of 30 cm / min with a tester.
In addition, the test made the sample of 10 sheets the average value of those.
[0081]
When the shear strength after heat treatment is 2.0 N / mm <2> or more: A, When the shear
strength after heat treatment is 1.5 N / mm <2> or more: B, · Heat treatment If the shear strength
after 1.0N / mm <2> or more: C, If the shear strength after heat treatment is 0.5N / mm <2> or
more: D, If the shear strength after heat treatment is 0.5N In the case of less than / mm <2>: E,
and five steps.
[0082]
7) Adhesiveness The material for the third acoustic matching layer was polished to obtain a
sample 25 mm wide, 100 mm long, and 1.6 mm thick.
This sample is a silicone rubber with a density of 1.5 g / cm 3 and a thickness of 5 mm that is an
acoustic lens material (an aluminum plate with a thickness of 5 mm is attached to the back
surface) according to the method of JIS-C6471 8.1. Adhesive; Cemedine Super X No. It stuck
using 8008 Clear (trademark) and was made to harden | cure at 60 degreeC for 72 hours.
Thereafter, it was placed in a heat cycle device, and heat cycles of -25 ° C and + 85 ° C were
performed 100 times, and thereafter it was pulled at a speed of 30 cm / min with a Tensilon type
tensile tester to determine peel strength. In addition, the test made the test piece of 10 sheets the
average value of those.
[0083]
The adhesion is judged as follows: ・ Peeling strength after heat treatment is 1.0N / mm <2> or
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more: A ・ When peeling strength after heat treatment is 0.75N / mm <2> or more: B ・ Heat
treatment When the peel strength after 0.5N / mm <2> or more: C, · When the peel strength after
heat treatment is 0.3N / mm <2> or more: D, · The peel strength after heat treatment is 0.3N In
the case of less than / mm <2>: E, and five steps.
[0084]
These results are shown in Table 3 below.
The Shore hardness D of each acoustic matching layer is shown in Table 3 below.
[0085]
The relationship between the acoustic impedance and the Shore hardness D in the third acoustic
matching layer material of Example 1 and Comparative Example 1-5 is shown in FIG. 10, and the
relationship between the acoustic impedance and the attenuation rate in each third acoustic
matching layer material is shown. It is shown in 11.
[0086]
[0087]
[0088]
As is apparent from Tables 1 to 3 and FIGS. 10 and 11, the third acoustic matching layers of
Examples 1 to 10 have low attenuation rates despite the fact that Z is 1.8 to 2.5 MRayls, which is
low. In addition, it is understood that it has excellent processability and adhesiveness.
[0089]
On the other hand, in the third acoustic matching layers of Comparative Examples 1 to 6, it is
understood that the attenuation factor is large, or either the processability or the adhesiveness is
inferior, and all of these characteristics are not satisfied.
[0090]
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The array type ultrasonic probe having such a third acoustic matching layer of Examples 1 to 10
can effectively transmit and receive the energy of ultrasonic waves, has uniform sensitivity
between channels, and has crosstalk between channels. It can be reduced and has high resolution
and long-term reliability.
[0091]
That is, a piezoelectric element with a thickness of 400 μm on a backing obtained by adding
ferrite to a chloroprene rubber with an acoustic impedance (Z) of 4 MRayls, a thickness of 420
μm, and a first acoustic matching layer made of borosilicate glass with a Z of 12 MRayls, a
thickness of 200 μm, A second acoustic matching layer in which 20% by volume of zinc oxide
powder is added to an epoxy resin of Z 5.0 MRayls and a third acoustic matching layer of the
same composition as Example 3 having a thickness of 150 μm and Z of 2.29 MRayls The
members were adhered to each other by heat curing with pressure in the order of 120 ° C. for
about 1 hour after overlapping and laminating an epoxy resin adhesive in the order and between
them.
The piezoelectric element used was one in which first and second electrodes made of Ni were
formed on both sides of a piezoelectric body made of PZT-based piezoelectric ceramic.
Subsequently, dicing was performed from the third acoustic matching layer toward the backing
with a diamond blade having a width of 50 μm so as to have a width of 200 μm and a cutting
depth of 200 μm on the backing.
By this dicing, 200 μm × 2 rows were made into one channel, and a total of 200 channels were
formed.
Subsequently, the space between each channel was filled with liquid silicone rubber and cured at
125 ° C. for 1 hour.
On each channel, an acoustic lens of Z 1.5 M Rayls made of silicone rubber was fixed with a
modified silicone rubber adhesive.
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Finally, the backing, the plurality of channels and the acoustic lens are housed in a case, and the
control circuit for controlling the drive timing of the piezoelectric element of each channel and
the received signal received by the piezoelectric element are housed in this case. A 3.5 MHz
arrayed ultrasound probe was assembled by incorporating a signal processing circuit including
an amplifier circuit for amplification.
[0092]
In addition, a piezoelectric element with a thickness of 400 μm on a backing obtained by adding
ferrite to a chloroprene rubber with an acoustic impedance (Z) of 4 MRayls, a first acoustic
matching layer made of single crystal silicon with a thickness of 480 μm and Z of 19 MRayls, a
thickness of 400 μm, A second acoustic matching layer of boron silica glass in which Z is 10
MRayls, a third matching layer in which the thickness is 250 μm, a glass epoxy resin of Z is 4.0
MRayls, and the same composition as in Example 8 having Z of 2.11 MRayls These members are
mutually bonded by heating and curing while pressing the fourth acoustic matching layer in the
following order, with an epoxy resin-based adhesive interposed therebetween, for about 1 hour
at 120 ° C. did. The piezoelectric element used was one in which first and second electrodes
made of Ni were formed on both sides of a piezoelectric body made of PZT-based piezoelectric
ceramic. Subsequently, dicing was performed from the fourth acoustic matching layer toward the
backing with a diamond blade having a width of 50 μm so as to have a width of 200 μm and a
cutting depth of 200 μm on the backing. By this dicing, 200 μm × 2 rows were made into one
channel, and a total of 200 channels were formed. Subsequently, the space between each channel
was filled with liquid silicone rubber and cured at 85 ° C. for 1 hour. On each channel, an
acoustic lens of Z 1.5 M Rayls made of silicone rubber was fixed with a modified silicone rubber
adhesive. Finally, the backing, the plurality of channels and the acoustic lens are housed in a
case, and the control circuit for controlling the drive timing of the piezoelectric element of each
channel and the received signal received by the piezoelectric element are housed in this case. A
3.5 MHz arrayed ultrasound probe was assembled by incorporating a signal processing circuit
including an amplifier circuit for amplification.
[0093]
When these array-type ultrasonic probes were connected to an imaging diagnostic apparatus and
their characteristics were evaluated, a better image was obtained as compared with the
conventional product.
[0094]
Furthermore, the array type ultrasonic probe was placed in a heat cycle tester at -25 ° C and 85
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° C, and an image was confirmed before and after the 100 cycle test, but no decrease in channel
failure or image quality deterioration was observed.
[0095]
BRIEF DESCRIPTION OF THE DRAWINGS The principal part perspective view of the array-type
ultrasonic probe which concerns on embodiment of this invention.
FIG. 2 is a cross-sectional view of main parts of the ultrasonic probe of FIG. 1;
The figure which shows typically the cross section of the 3rd acoustic matching layer integrated
in the array-type ultrasonic probe which concerns on embodiment of this invention. FIG. 7
schematically shows a cross section of another third acoustic matching layer incorporated in the
array-type ultrasonic probe according to the embodiment of the present invention. FIG. 1 is a
schematic view showing an ultrasonic diagnostic apparatus according to an embodiment of the
present invention. TG / DTA curve of the cured product of the silicone resin-containing mixture
obtained in Example 1 (material for the third acoustic matching layer). FTIR spectrum of the
cured product of the silicone resin-containing mixture (material for the third acoustic matching
layer) obtained in Example 1. TG / DTA curve of general purpose silicone resin cured product.
FTIR spectrum of a general purpose silicone resin cured product. The figure which shows the
relationship of the acoustic impedance and Shore hardness D in the raw material for 3rd acoustic
matching layer of Example 1 and Comparative Example 1-5. The figure which shows the
relationship of the acoustic impedance and attenuation factor in the raw material for 3rd acoustic
matching layer of Example 1 and Comparative Example 1-5.
Explanation of sign
[0096]
DESCRIPTION OF SYMBOLS 1 ... Array-type ultrasonic probe, 2 ... Backing, 3 ... Channel, 4 ...
Space 6 ... Piezoelectric element, 71 ... 1st acoustic matching layer, 72 ... 2nd acoustic matching
layer, 73 ... 3rd acoustic matching layer Upper layer acoustic matching layer), 10: acoustic lens,
11: silicone resin matrix, 12: organic filled particles, 13: silicon oxide particles, 14: inorganic
fiber, 21: cable, 22: ultrasonic diagnostic device main body, 23: display .
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