JP6442372B2 - Composition for acoustic wave probe, silicone resin for acoustic wave probe using the same, acoustic wave probe and ultrasonic probe, acoustic wave measuring device, ultrasonic diagnostic device, photoacoustic wave measuring device and ultrasonic endoscope - Google Patents

Description

  The present invention relates to a composition for an acoustic wave probe, a silicone resin for an acoustic wave probe using the same, an acoustic wave probe, and an ultrasonic probe. Furthermore, the present invention relates to an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope.

  In the acoustic wave measuring apparatus, an acoustic wave probe that irradiates a subject with an acoustic wave, receives the reflected wave (echo), and outputs a signal is used. The electric signal converted from the reflected wave received by the acoustic wave probe is displayed as an image. Thereby, the inside of the test object is visualized and observed.

As the acoustic wave, one having an appropriate frequency is selected from an ultrasonic wave, a photoacoustic wave, or the like according to an object to be examined and measurement conditions.
For example, the ultrasonic diagnostic apparatus transmits an ultrasonic wave toward the inside of the subject, receives the ultrasonic wave reflected by the tissue inside the subject, and displays it as an image. The photoacoustic wave measuring apparatus receives an acoustic wave radiated from the inside of the subject to be examined by the photoacoustic effect and displays it as an image. The photoacoustic effect means that when a test object is irradiated with an electromagnetic pulse such as visible light, near-infrared light, or microwave, the test object absorbs the electromagnetic wave, generates heat, and thermally expands. This is a phenomenon in which ultrasonic waves are typically generated.
Since the acoustic wave measuring device transmits and receives acoustic waves to and from a living body that is a subject to be examined, requirements such as acoustic impedance matching with a living body (typically a human body) and reduction of acoustic wave attenuation are required. It is required to satisfy.

For example, a probe for an ultrasonic diagnostic apparatus (also referred to as an ultrasonic probe), which is a kind of acoustic wave probe, includes a piezoelectric element that transmits and receives ultrasonic waves and an acoustic lens that is a part that contacts a living body. The ultrasonic wave emitted from the piezoelectric element passes through the acoustic lens and enters the living body. If the difference between the acoustic impedance (density × sound speed) of the acoustic lens and the acoustic impedance of the living body is large, the ultrasonic waves are reflected on the surface of the living body, and thus cannot be efficiently incident on the living body. Therefore, it is difficult to obtain a good resolution. In order to transmit and receive ultrasonic waves with high sensitivity, it is desired that the acoustic lens has a small ultrasonic attenuation.
For this reason, as one of the materials of the acoustic lens, a silicone resin that is close to the acoustic impedance of a living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec in the case of a human body) and has a small ultrasonic attenuation amount is used. It is used.

  As an acoustic lens composition, for example, Patent Document 1 describes an acoustic lens composition containing silicone rubber and zinc oxide powder. Patent Document 2 describes a filled silicone composition comprising a silicone resin and nano-particle monoclinic alpha phase bismuth oxide.

JP 2005-125071 A JP 2009-240782 A

Silicone resin alone is soft and has low mechanical strength. Therefore, for the purpose of improving hardness and mechanical strength, an inorganic filler (also referred to as an inorganic filler) is blended in a composition for forming a silicone resin as in Patent Documents 1 and 2 described above.
However, silicone resins prepared from the compositions described in Patent Documents 1 and 2 have a problem in bending durability.
Therefore, the silicone resin prepared from the compositions described in Patent Documents 1 and 2 satisfies all of the resin hardness, bending durability, and acoustic wave attenuation reduction required for the acoustic wave probe at a high level. It is difficult.

  In view of the above situation, the present invention can greatly improve the hardness and mechanical strength (tear strength and bending durability) of the silicone resin, with the acoustic impedance being close to the value of a living body and the amount of acoustic wave attenuation being reduced. Provided acoustic wave probe composition, silicone resin for acoustic wave probe using the same, acoustic wave probe, ultrasonic probe, acoustic wave measuring device, ultrasonic diagnostic device, photoacoustic wave measuring device, and ultrasonic endoscope The task is to do.

  Further, in a ultrasonic probe, a photoacoustic wave measuring apparatus, and an ultrasonic endoscope that use a capacitive micromachined ultrasonic transducer (cMUT) as a transducer array for ultrasonic diagnosis, the sensitivity is improved. Another object of the present invention is to provide a composition for an acoustic wave probe and a silicone resin for an acoustic wave probe that can be used.

  As a result of intensive studies on inorganic compounds to be added to the silicone resin, the present inventors have found that a silicone prepared using a composition containing zinc oxide and silica having an average primary particle size within a specific range and a polysiloxane. It has been found that the resin has an acoustic impedance close to that of a living body, an acoustic wave attenuation is reduced, is excellent in hardness and mechanical strength, and can be suitably used for an acoustic wave probe. The present invention has been made based on this finding.

The above problem has been solved by the following means.
<1> Acoustic wave probe containing a polysiloxane having a vinyl group, a polysiloxane having two or more Si-H groups in a molecular chain, zinc oxide and a polysiloxane mixture containing silica having an average primary particle size of less than 12 nm Composition.
<2> The composition for acoustic wave probes according to <1>, wherein the average primary particle diameter of silica is 10 nm or less.
<3> The composition for acoustic wave probes according to <2>, wherein the average primary particle diameter of silica is less than 10 nm.
< 4 > The composition for an acoustic wave probe according to any one of <1> to <3> , wherein 0.1 to 14.9 parts by mass of zinc oxide is contained in a total of 100 parts by mass of the polysiloxane mixture.
<5> Total in 100 parts by weight of polysiloxane mixture by silica contains 0.1 to 30 parts by mass <1> to the acoustic wave probe composition according to any one of <4>.
<6> mass ratio of the content of Cie Rica against the content of zinc oxide (the content of the content / zinc oxide shea silica) is from 0.2 to 3.0 <1> to <5> The composition for acoustic wave probes as described in any one of these.
< 7 > In a total of 100 parts by mass of the polysiloxane mixture, 10 to 99.4 parts by mass of the polysiloxane having a vinyl group, and 0.5 to 3 of the polysiloxane having two or more Si—H groups in the molecular chain. The composition for acoustic wave probes according to any one of <1> to < 6 >, containing 90 parts by mass.
<8> shea silica is one which is surface treated with a silane compound <1> to the acoustic wave probe composition according to any one of <7>.
<9> shea silica is one which is surface treated with a trimethylsilyl agent <1> to the acoustic wave probe composition according to any one of <8>.
< 10 > The composition for an acoustic wave probe according to any one of <1> to < 9 >, in which the polysiloxane having a vinyl group has a phenyl group.
< 11 > The composition for acoustic wave probes according to any one of <1> to < 10 >, wherein the polysiloxane having a vinyl group has a mass average molecular weight of 10,000 to 200,000.
< 12 > The composition for an acoustic wave probe according to any one of <1> to < 11 >, wherein the polysiloxane having a vinyl group has a mass average molecular weight of 30,000 to 150,000.
< 13 > The composition for an acoustic wave probe according to any one of <1> to < 12 >, wherein the polysiloxane having two or more Si—H groups in the molecular chain has a phenyl group.
< 14 > The composition for an acoustic wave probe according to any one of <1> to < 13 >, containing 0.0001 to 0.1 part by mass of platinum or a platinum-containing compound with respect to 100 parts by mass of the polysiloxane mixture. .

< 15 > A silicone resin for acoustic wave probes obtained by curing reaction of the composition for acoustic wave probes according to any one of <1> to < 14 >.
< 16 > An acoustic wave probe having at least one selected from the group consisting of an acoustic lens and an acoustic matching layer , comprising the silicone resin for acoustic wave probes according to < 15 >.
< 17 > An ultrasonic probe comprising an acoustic lens comprising a capacitive micromachine ultrasonic transducer and the silicone resin for an acoustic wave probe according to < 15 >.
< 18 > An acoustic wave measuring device including the acoustic wave probe according to < 16 >.
< 19 > An ultrasonic diagnostic apparatus including the acoustic wave probe according to < 16 >.
< 20 > A photoacoustic wave measurement apparatus including an acoustic lens including the silicone resin for an acoustic wave probe according to < 15 >.
< 21 > An ultrasonic endoscope comprising an acoustic lens comprising the silicone resin for acoustic wave probes according to < 15 >.

In the description of the present invention, when groups having the same symbols are present in the general formula, these may be the same or different from each other unless otherwise specified, and groups specified by each group (for example, alkyl groups) May be further substituted with a substituent.
In the description of the present invention, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In addition, unless otherwise indicated, the mass average molecular weight in this invention is a measured value (polystyrene conversion) by gel permeation chromatography (Gel Permeation Chromatography: GPC).

According to the present invention, the acoustic impedance is close to the value of a living body, the acoustic wave (particularly preferably, ultrasonic wave) attenuation is reduced, and the hardness and mechanical strength (tear strength and bending durability) of the silicone resin can be greatly improved. To provide a composition for a possible acoustic wave probe, a silicone resin for an acoustic wave probe using the composition (hereinafter also simply referred to as “silicone resin”), an acoustic wave probe, an acoustic wave measuring device, and an ultrasonic diagnostic device. it can.
In addition, it is possible to provide an ultrasonic probe, a photoacoustic wave measurement apparatus, and a silicone resin for an acoustic wave probe that can improve sensitivity in an ultrasonic endoscope using cMUT as an ultrasonic diagnostic transducer array.

It is a perspective transmissive view about an example of a convex type ultrasonic probe which is one mode of an acoustic wave probe.

<Composition for acoustic wave probe>
The composition for an acoustic wave probe of the present invention (hereinafter also simply referred to as “composition”) includes a polysiloxane having a vinyl group, a polysiloxane having two or more Si—H groups in a molecular chain, zinc oxide, and The composition for an acoustic wave probe contains a polysiloxane mixture containing at least silica having an average primary particle size of less than 12 nm.

The content of zinc oxide in the total 100 parts by mass of the polysiloxane mixture is not particularly limited, but is preferably 0.1 to 14.9 parts by mass, more preferably 1.0 to 14.5 parts by mass, and 5.0 ˜13.0 parts by mass is particularly preferred.
When the content of zinc oxide is within the above range, the acoustic impedance of the silicone resin for acoustic wave probes can be made closer to the human body, and bending durability and acoustic wave sensitivity can be further improved.

The content of silica having an average primary particle diameter of less than 12 nm in a total of 100 parts by mass of the polysiloxane mixture is not particularly limited, but is preferably 0.1 to 30 parts by mass, more preferably 5 to 25 parts by mass, 20 parts by mass is particularly preferred.
When the content of silica having an average primary particle diameter of less than 12 nm is within the above range, tear strength, bending durability, and acoustic wave sensitivity are increased.

The mass ratio of silica having an average primary particle diameter of less than 12 nm relative to zinc oxide (content of silica less than 12 nm / content of zinc oxide) is preferably 0.1 to 4.0, and preferably 0.2 to 3. 0 is more preferable, and 0.5 to 2.5 is particularly preferable.
When the content of silica having a mass ratio of less than 12 nm is within the above range, the balance between tear strength and acoustic wave sensitivity is excellent.

Further, the content of the polysiloxane having a vinyl group in the total 100 parts by mass of the polysiloxane mixture is preferably 10 to 99.4 parts by mass, and the polysiloxane having two or more Si—H groups in the molecular chain. The content is preferably 0.5 to 90 parts by mass. In addition, the content of the polysiloxane having a vinyl group is more preferably 50 to 90 parts by mass, and the content of the polysiloxane having two or more Si—H groups in the molecular chain is more preferably 1 to 50 parts by mass. preferable.
The polysiloxane mixture is a mixture that does not contain a catalyst for cross-linking polymerization of a polysiloxane having a vinyl group and a polysiloxane having two or more Si-H groups in the molecular chain. Therefore, the polysiloxane mixture contains zinc oxide and silica having an average primary particle size of less than 12 nm, and does not contain a catalyst.

Each polysiloxane contained in the polysiloxane mixture may be any polysiloxane as long as it has a vinyl group or two or more Si-H groups in the molecular chain. However, in the present invention, polyorganosiloxane (A) having a vinyl group and polyorganosiloxane (B) having two or more Si—H groups in the molecular chain are preferred.
Therefore, in the present invention, in the polyorganosiloxane mixture, a polyorganosiloxane (A) having a vinyl group, a polyorganosiloxane (B) having two or more Si-H groups in a molecular chain, zinc oxide and an average primary It is preferable to contain at least silica having a particle size of less than 12 nm.
In the following detailed description, the polyorganosiloxane (A) having a vinyl group and the polyorganosiloxane (B) having two or more Si—H groups in the molecular chain are described as preferred embodiments. However, the present invention is not limited to the embodiments described below.

<Polyorganosiloxane having vinyl group (A)>
The polyorganosiloxane (A) having a vinyl group used in the present invention (hereinafter also simply referred to as polyorganosiloxane (A)) has two or more vinyl groups in the molecular chain.
As the polyorganosiloxane (A) having a vinyl group, for example, a polyorganosiloxane (a) having vinyl groups at least at both ends of the molecular chain (hereinafter, also simply referred to as polyorganosiloxane (a)), or in the molecular chain. And polyorganosiloxane (b) having at least two —O—Si (CH ₃ ) ₂ (CH═CH ₂ ) (hereinafter also simply referred to as polyorganosiloxane (b)). Among these, polyorganosiloxane (a) having vinyl groups at least at both ends of the molecular chain is preferable.
The polyorganosiloxane (a) is preferably linear, and the polyorganosiloxane (b) is a polyorganosiloxane in which —O—Si (CH ₃ ) ₂ (CH═CH ₂ ) is bonded to Si atoms constituting the main chain. Organosiloxane (b) is preferred.

  The polyorganosiloxane (A) having a vinyl group is hydrosilylated by reaction with a polyorganosiloxane (B) having two or more Si—H groups in the presence of a platinum catalyst. A crosslinked structure is formed by this hydrosilylation reaction (addition curing reaction).

The vinyl group content of the polyorganosiloxane (A) is not particularly limited. From the viewpoint of forming a sufficient network with each component contained in the composition for acoustic wave probes, for example, the content of vinyl groups is preferably 0.01 to 5 mol%, and 0.05 to 2 mol. % Is more preferable.
The polyorganosiloxane (A) preferably has a phenyl group, and the content of the phenyl group is not particularly limited. From the viewpoint of mechanical strength when a silicone resin for acoustic wave probes is used, for example, the phenyl group content is preferably 1 to 80 mol%, more preferably 2 to 40 mol%.

Here, the content of the vinyl group is the mol% of the vinyl group-containing siloxane unit when all the units constituting the polyorganosiloxane (A) are 100 mol%, and the Si—O unit constituting the main chain. And when all the Si atoms of the terminal Si are substituted with at least one vinyl group, it becomes 100 mol%.
Similarly, the phenyl group content is the mol% of the phenyl group-containing siloxane unit when the total units constituting the polyorganosiloxane (A) are 100 mol%, and the Si—O unit constituting the main chain and When all the Si atoms of the terminal Si are substituted with at least one phenyl group, it becomes 100 mol%.
In addition, a unit means the Si-O unit which comprises a principal chain, and terminal Si.

  The degree of polymerization and specific gravity are not particularly limited. The degree of polymerization is preferably 200 to 3000, more preferably 400 to 2000, and the specific gravity is 0.9 to 1 from the viewpoint of improving the mechanical strength, hardness, chemical stability, etc. of the silicone resin for acoustic wave probes obtained. .1 is preferred.

  The weight average molecular weight of the polyorganosiloxane having a vinyl group is preferably 10,000 to 200,000, more preferably 20,000 to 200,000, from the viewpoint of mechanical strength, hardness, and ease of processing. 000 to 150,000 is more preferable, and 40,000 to 120,000 is particularly preferable.

  For example, GPC apparatus HLC-8220 (manufactured by Tosoh Corporation) is prepared, toluene (Shonan Wako Pure Chemical Industries, Ltd.) is used as the eluent, and TSKgel (registered trademark) G3000HXL + TSKgel (registered trademark) is used as the column. Using G2000HXL, measurement can be performed using an RI detector under conditions of a temperature of 23 ° C. and a flow rate of 1 mL / min.

Kinematic viscosity at 25 ° C. is preferably ^{1 × 10 -5 ~10m 2 / s} , more preferably ^{1 × 10 -4 ~1m 2 / s} , 1 × 10 -3 ~0.5m 2 / s is more preferable.
The kinematic viscosity can be determined according to JIS Z8803 by measuring at a temperature of 23 ° C. using an Ubbelohde viscometer (for example, trade name SU, manufactured by Shibata Chemical Co., Ltd.).

  The polyorganosiloxane (a) having vinyl groups at least at both ends of the molecular chain is preferably a polyorganosiloxane represented by the following general formula (A).

In the general formula (A), R ^a1 represents a vinyl group, and R ^a2 and R ^a3 each independently represents an alkyl group, a cycloalkyl group, an alkenyl group, or an aryl group. x1 and x2 each independently represents an integer of 1 or more. Here, the plurality of R ^a2 and the plurality of R ^a3 may be the same as or different from each other. Further, each group of R ^a2 and R ^a3 may be further substituted with a substituent.

1-10 are preferable, as for carbon number of the alkyl group in R ^{< a2>} and R ^<a3> , 1-4 are more preferable, 1 or 2 is more preferable, and 1 is especially preferable. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl and n-decyl.

3-10 are preferable, as for carbon number of the cycloalkyl group in R ^{< a2>} and R ^<a3 >, 5-10 are more preferable, and 5 or 6 is still more preferable. The cycloalkyl group is preferably a 3-membered ring, 5-membered ring or 6-membered ring, more preferably a 5-membered ring or 6-membered ring. Examples of the cycloalkyl group include cyclopropyl, cyclopentyl, and cyclohexyl.

2-10 are preferable, as for carbon number of the alkenyl group in R ^{< a2>} and R ^<a3 >, 2-4 are more preferable, and 2 is more preferable. Examples of the alkenyl group include vinyl, allyl, and butenyl.

6-12 are preferable, as for carbon number of the aryl group in R ^{< a2>} and R ^<a3 >, 6-10 are more preferable, and 6-8 are more preferable. Examples of the aryl group include phenyl, tolyl, and naphthyl.

These alkyl group, cycloalkyl group, alkenyl group and aryl group may have a substituent. Examples of such a substituent include a halogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a silyl group, and a cyano group.
Examples of the group having a substituent include a halogenated alkyl group.

R ^a2 and R ^a3 are preferably an alkyl group, an alkenyl group or an aryl group, more preferably an alkyl group having 1 to 4 carbon atoms, a vinyl group or a phenyl group, and further preferably a methyl group, a vinyl group or a phenyl group.
In particular, R ^a2 is preferably a methyl group, and R ^a3 is particularly preferably a phenyl group. More preferably, both R ^{a3 in} the repetition of x1 are phenyl groups.

x1 is preferably an integer of 1 to 3000, and more preferably an integer of 5 to 1000.
x2 is preferably an integer of 1 to 3000, and more preferably an integer of 40 to 1000.

Polyorganosiloxane having vinyl groups at least at both ends of the molecular chain is, for example, a trade name, DMS series (for example, DMS-V31, DMS-V31S15, DMS-V33, DMS-V35, DMS-V35R, DMS, manufactured by Gelest). -V41, DMS-V42, DMS-V46, DMS-V51, DMS-V52), product names made by Gelest, PDV series (for example, PDV-0341, PDV-0346, PDV-0535, PDV-0541, PDV- 1631, PDV-1635, PDV-1641, PDV-2335, PMV-9925, PVV-3522, FMV-4031, and EDV-2022).
In addition, since DMS-V31S15 is previously blended with fumed silica, kneading with a special apparatus is unnecessary.

  The polyorganosiloxane (A) having a vinyl group in the present invention may be used alone or in combination of two or more.

<Polyorganosiloxane (B) having two or more Si-H groups in the molecular chain>
The polyorganosiloxane (B) having two or more Si—H groups in the molecular chain used in the present invention (hereinafter also simply referred to as polyorganosiloxane (B)) has two or more Si in the molecular chain. It has a -H group.
By having two or more Si—H groups in the molecular chain, a polyorganosiloxane having at least two polymerizable unsaturated groups can be crosslinked.

The polyorganosiloxane (B) has a linear structure and a branched structure, and a linear structure is preferable.
The mass average molecular weight of the linear structure is preferably from 500 to 100,000, more preferably from 1,500 to 50,000, from the viewpoint of mechanical strength and hardness.

The polyorganosiloxane (B) preferably has a phenyl group, and the content of the phenyl group is not particularly limited. From the viewpoint of mechanical strength when a silicone resin for an acoustic wave probe is used, it is, for example, 1 to 80 mol%, preferably 10 to 60 mol%.
Here, the content of the phenyl group is a content calculated by replacing the polyorganosiloxane (A) with the polyorganosiloxane (B) in the content of the phenyl group in the polyorganosiloxane (A).

In the present invention, it is preferable that both polyorganosiloxanes (A) and (B) have a phenyl group in order to improve compatibility.
Since the silicone resin for a silicone acoustic wave probe of the present invention has a bulky phenyl group, the sound speed can be increased and the hardness and specific gravity can be increased. Therefore, the acoustic impedance can be increased efficiently. As a result, the amount of zinc oxide added can be reduced, and the acoustic wave sensitivity can be maintained high.

  The polyorganosiloxane (B) having a linear structure having two or more Si-H groups in the molecular chain is preferably a polyorganosiloxane represented by the following general formula (B).

In the general formula (B), R ^b1 and R ^b2 each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or —O—Si (R ^b5 ) ₂ (R ^b4 ). R ^b4 and R ^b5 each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group or an aryl group. R ^b3 represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, or —O—Si (R ^b7 ) ₂ (R ^b6 ). R ^b6 and R ^b7 each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group. y1 represents an integer of 0 or more, and y2 represents an integer of 1 or more. Here, the plurality of R ^b1 , the plurality of R ^b2 , the plurality of R ^b3 , the plurality of R ^b4 , the plurality of R ^b5 , the plurality of R ^b6, and the plurality of R ^b7 may be the same as or different from each other. , R ^{b1 to} R ^b7 may be further substituted with a substituent. However, it has two or more Si-H groups in the molecular chain.

The alkyl group, cycloalkyl group and aryl group in R ^b1 and R ^{b2 have the same meanings as} the alkyl group, cycloalkyl group and aryl group in R ^a2 and R ^a3 , and the preferred ranges are also the same. The alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^{b3 have the same meanings as} the alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^a2 and R ^a3 , and the preferred ranges are also the same.

The alkyl group, cycloalkyl group and aryl group in R ^b4 and R ^b5 of —O—Si (R ^b5 ) ₂ (R ^b4 ) have the same ^{meanings as} the alkyl group, cycloalkyl group and aryl group in R ^b1 and R ^b2 . The preferred range is also the same.

The alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^b6 and R ^b7 of —O—Si (R ^b7 ) ₂ (R ^b6 ) are the same as the alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^b3 . It is synonymous and the preferable range is also the same.

R ^b1 and R ^b2 are preferably a hydrogen atom, an alkyl group, an aryl group, or —O—Si (R ^b5 ) ₂ (R ^b4 ), a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or —O—Si. (CH ₃ ) ₂ H is more preferred.
R ^b3 is preferably a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or —O—Si (R ^b7 ) ₂ (R ^b6 ), and is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a vinyl group, a phenyl group or — _{O-Si (CH 3) 2} H are more preferable.
Among these, R ^b1 and R ^b2 are preferably a hydrogen atom, an alkyl group or an aryl group, more preferably a hydrogen atom or an alkyl group, and even more preferably a hydrogen atom or a methyl group.
R ^b3 is preferably a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or —O—Si (R ^b7 ) ₂ (R ^b6 ), more preferably a hydrogen atom or an aryl group, and particularly preferably a hydrogen atom or a phenyl group.

In the present invention, when R ^b3 is a phenyl group, R ^b1 is preferably a hydrogen atom, more preferably R ^b1 is a hydrogen atom, and it is more preferable that the following condition is satisfied.
1) One R ^{b2 in} the repetition of y1 is a hydrogen atom, the remaining R ^b2 is an alkyl group, and R ^{b2 in} the repetition of y2 is an alkyl group, and R ^b3 is a phenyl group 2) y1 is 0, R ^{2b in} the repetition of y2 is an alkyl group, R ^b3 is a phenyl group 3) y1 is 0, and R ^{b2 in} the repetition of y2 is —O—Si (R ^b5 ) ₂ (R ^b4 ) in ^{still R b3} is a phenyl group, in the above ^3), when in ^{R b4} is a hydrogen atom, and ^{R b5} is an alkyl group, in which preferable.

y1 is preferably an integer of 0 to 2000, more preferably an integer of 0 to 50, and still more preferably an integer of 0 to 30.
y2 is preferably an integer of 2 to 2000, more preferably an integer of 2 to 50, and still more preferably an integer of 2 to 30.
y1 + y2 is preferably an integer of 5 to 2000, more preferably an integer of 7 to 1000, still more preferably 10 to 50, and particularly preferably an integer of 15 to 30.

As a combination of R ^{b1 to} R ^b3 , R ^b1 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ^b2 is an alkyl group having 1 to 4 carbon atoms, and R ^b3 is a combination of hydrogen atoms, and R ^b1 is A combination of an alkyl group having 1 to 4 carbon atoms, R ^b2 being an alkyl group having 1 to 4 carbon atoms, and R ^b3 being a hydrogen atom is more preferable.
In this preferable combination, the content of the hydrosilyl group represented by y2 / (y1 + y2) is preferably more than 0.1 and 1.0 or less, more preferably more than 0.2 and 1.0 or less, more preferably 0.4 And more preferably 1.0 or less.
Here, when any of R ^{b1 to} R ^b3 is a phenyl group, y2 / (y1 + y2) is preferably 100, and when any of R ^{b1 to} R ^b3 is not a phenyl group, y2 / (y1 + y2) is , More than 0.4 and less than 0.6 is particularly preferable.

The polyorganosiloxane (B) having a linear structure is, for example, a methylhydrosiloxane-dimethylsiloxane copolymer (trimethylsiloxane terminated) manufactured by Gelest, HMS-064 (MeHSiO: 5-7 mol%), HMS- 082 (MeHSiO: 7-8 mol%), HMS-301 (MeHSiO: 25-30 mol%), HMS-501 (MeHSiO: 50-55 mol%), HPM-502 (MeHSiO: MeHSiO: methylhydrosiloxane-phenylmethylsiloxane copolymer) 45-50 mol%) and HMS-991 (MeHSiO: 100 mol%) which is a methylhydrosiloxane polymer.
Here, mol% of MeHSiO is synonymous with y2 / (y1 + y2) × 100.

  In addition, it is preferable that both the linear structure and the branched structure have no vinyl group from the viewpoint of preventing the progress of the cross-linking reaction in the molecule, and in particular, the branched structure does not have a vinyl group. It is preferable.

The branched polyorganosiloxane (B) having two or more Si—H groups in the molecular chain has a branched structure and two or more hydrosilyl groups (Si—H groups).
The specific gravity is preferably 0.9 to 0.95.
The branched structure polyorganosiloxane (B) is preferably represented by the following average composition formula (b).

Average composition formula (b): [H _a (R ^b8 ) _3-a SiO _1/2 ] _y3 [SiO _4/2 ] _y4

Here, R ^b8 represents an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group, a represents 0.1 to 3, and y3 and y4 each independently represents an integer of 1 or more.

The alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^{b8 have the same meanings as} the alkyl group, cycloalkyl group, alkenyl group and aryl group in R ^a2 and R ^a3 , and the preferred ranges are also the same.
a is preferably 1.
The content of the hydrosilyl group represented by a / 3 is preferably more than 0.1 and less than 0.6, more preferably more than 0.1 and less than 0.4.

On the other hand, when the polyorganosiloxane (B) having a branched structure is represented by a chemical structural formula, a polyorganosiloxane in which —O—Si (CH ₃ ) ₂ (H) is bonded to Si atoms constituting the main chain is preferable. Those having a structure represented by the following general formula (Bb) are more preferable.

  In the general formula (Bb), * means that it is bonded to at least a Si atom of siloxane.

Examples of the branched polyorganosiloxane (B) include HQM-107 (trade name, manufactured by Gelest, hydrogenated Q resin), HDP-111 (trade name, manufactured by Gelest, polyphenyl- (dimethylhydroxy) siloxane. (Hydrogen end), [(HMe ₂ SiO) (C ₆ H ₅ Si) O]: 99-100 mol%).

  In the present invention, the polyorganosiloxane (B) having two or more Si-H groups in the molecular chain may be used alone or in combination of two or more. Further, a linear polyorganosiloxane (B) and a branched polyorganosiloxane (B) may be used in combination.

<Zinc oxide>
In the present invention, zinc oxide is added to increase acoustic impedance and reduce acoustic attenuation.
On the other hand, the addition of fine particle filler is effective in improving the mechanical properties such as resin hardness, tear strength, and repeated bending fatigue, and the smaller the particle diameter, the higher the mechanical properties can be expressed with respect to the added amount. . In the present invention, by replacing a part of zinc oxide with silica having an average primary particle diameter within a specific range, which will be described later, both acoustic characteristics and mechanical characteristics can be achieved. This is presumably because silica having a small average primary particle size functions as a stopper when mechanical stress is applied to the silicone resin for acoustic wave probes. In particular, since the average primary particle diameter is small, the distance between the particles is small, so that the function as a stopper is more exhibited and the tear strength of the silicone resin is greatly improved.
As a result, it is considered that the increase in acoustic wave attenuation is suppressed, and the hardness and mechanical strength (tear strength and bending durability) of the silicone resin for acoustic wave probes are improved.

  The average primary particle diameter of zinc oxide used in the present invention is preferably less than 1 μm, more preferably more than 5 nm and less than 500 nm, more preferably 10 nm from the viewpoint of suppressing an increase in acoustic wave attenuation of the silicone resin and improving tear strength. More preferably less than 100 nm and more preferably more than 15 nm and less than 50 nm. In addition, it is preferable that the average primary particle diameter is in the above range and is small because the tear strength is high and the acoustic wave sensitivity is excellent.

The average primary particle diameter is described in the catalog of the zinc oxide manufacturer. However, a product whose average primary particle size is not described in the catalog or a newly produced product can be obtained by averaging the particle size measured by a transmission electron microscope (TEM). That is, the short diameter and the long diameter are measured for one particle of an electron micrograph taken by TEM, and the average value is obtained as the particle diameter of one particle. In the present invention, the particle diameters of 300 or more particles are averaged to obtain the average primary particle diameter.
Moreover, when the surface treatment mentioned later is given to zinc oxide, the average primary particle diameter in the state by which the surface treatment was carried out is meant.

Commercially available zinc oxide can be used. For example, FINEX-30S-LPT, FINEX-50S-LPT, FINEX-30, FINEX-30W-LP2, and FINEX-25-LPT (all products are manufactured by Sakai Chemical Industry Co., Ltd.) Name).
Zinc oxide may be used alone or in combination of two or more.

The zinc oxide used in the present invention is preferably zinc oxide particles having a surface treated, and more preferably zinc oxide particles having a surface treated with a silane compound.
Surface treatment of zinc oxide particles with a silane compound enhances the interaction with the silicone resin and increases the affinity with the silicone resin, enabling fine dispersion of zinc oxide particles with a small average primary particle size. It is considered to be. For this reason, it is considered that the zinc oxide fine particles exhibit a function as a stopper when mechanical adaptability is applied, and improve the hardness and mechanical strength of the silicone resin.
The surface treatment method may be a normal method. Examples of the surface treatment method with a silane compound include a method of surface treatment with a silane coupling agent and a method of coating with a silicone compound. In the present invention, a method of coating with a silicone compound is preferable.

(I) Silane coupling agent The silane coupling agent is preferably a silane coupling agent having a hydrolyzable group from the viewpoint of improving the hardness and mechanical strength of the silicone resin. The hydrolyzable group in the silane coupling agent is hydrolyzed with water to form a hydroxyl group, and this hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the zinc oxide particle, whereby the surface modification of the zinc oxide particle is performed and obtained. The hardness and mechanical strength of the silicone resin are improved. Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, and a halogen atom.
When the surface of the zinc oxide particles is hydrophobically modified, the affinity between the zinc oxide particles and the polyorganosiloxane (A) and (B) is improved, and the hardness and mechanical strength of the resulting silicone resin Is preferable.

  Examples of the silane coupling agent having a hydrophobic group as a functional group include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, and n-propyltrisilane. Alkoxysilanes such as methoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; methyltrichlorosilane, dimethyldichlorosilane (DDS), trimethylchlorosilane, phenyltrichlorosilane Chlorosilane; hexamethyldisilazane (HMDS).

  Examples of the silane coupling agent having a vinyl group as a functional group include methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, and vinyltriethoxy. Examples thereof include alkoxysilanes such as silane, vinyltrimethoxysilane and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; divinyltetramethyldisilazane.

The zinc oxide particles surface-treated with a silane coupling agent are preferably zinc oxide particles treated with a trialkylsilylating agent, and more preferably zinc oxide particles treated with a trimethylsilylating agent.
Examples of the silane compound include the above silane coupling agents and silane coupling agents in which functional groups in the silane coupling agent are substituted with alkyl groups.
Examples of the trimethylsilylating agent include trimethylchlorosilane and hexamethyldisilazane (HMDS) described in the above silane coupling agent and trimethylmethoxysilane which is a silane coupling agent in which a functional group is substituted with an alkyl group. It is done.

Examples of commercially available silane coupling agents include hexamethyldisilazane (HMDS) (trade name: HEXAMETHYLDISILAZAN (SIH6110.1), manufactured by Gelest).
Hydroxyl groups present on the surface of zinc oxide particles are covered with trimethylsilyl groups by reaction with hexamethyldisilazane (HMDS), and the surface of zinc oxide particles is modified to be hydrophobic.

(Ii) Silicone Compound The silicone compound that coats the zinc oxide particles may be a polymer composed of siloxane bonds.
Examples of the silicone compound include a silicone compound in which all or part of the side chain or terminal of polysiloxane is a methyl group, a silicone compound in which part of the side chain is a hydrogen atom, or all or one of the side chain or terminal. Examples thereof include a modified silicone compound in which an organic group such as an amino group or an epoxy group is introduced into the part, and a silicone resin having a branched structure. The silicone compound may have a linear or cyclic structure.

  Examples of silicone compounds in which all or part of the side chain or terminal of polysiloxane are methyl groups include polymethylhydrosiloxane (hydrogen terminal), polymethylhydrosiloxane (trimethylsiloxy terminal), polymethylphenylsiloxane ( Hydrogen-terminated), monomethylpolysiloxanes such as polymethylphenylsiloxane (trimethylsiloxy-terminated), such as dimethylpolysiloxane (hydrogen-terminated), dimethylpolysiloxane (trimethylsiloxy-terminated), and dimethylpolysiloxanes such as cyclic dimethylpolysiloxane. Can be mentioned.

  Examples of silicone compounds in which a part of the side chain is a hydrogen atom include methylhydrosiloxane-dimethylsiloxane copolymer (trimethylsiloxy-terminated), methylhydrosiloxane-dimethylsiloxane copolymer (hydrogen-terminated), and polymethylhydrosiloxane (hydrogen-terminated). Polymethylhydrosiloxane (trimethylsiloxy-terminated), polyethylhydrosiloxane (triethylsiloxy-terminated), polyphenyl- (dimethylhydrosiloxy) siloxane (hydrogen-terminated), methylhydrosiloxane-phenylmethylsiloxane copolymer (hydrogen-terminated), methylhydro Examples thereof include siloxane-octylmethylsiloxane copolymer / terpolymer.

  Examples of the modified silicone introduced with an organic group include amino groups, epoxy groups, methoxy groups, (meth) acryloyl groups, phenol groups, carboxylic anhydride groups, hydroxy groups, mercapto groups, carboxy groups, and hydrogen atoms. Non-reactive silicones modified with, for example, polyethers, aralkyls, fluoroalkyls, long-chain alkyls, long-chain aralkyls, higher fatty acid esters, higher fatty acid amides, and polyether methoxys. It is done.

Zinc oxide particles coated with a silicone compound can be obtained by a conventional method. For example, it can be obtained by mixing and stirring zinc oxide particles in dimethylpolysiloxane for a certain period of time and filtering.
When reactive modified silicone is used as the silicone compound, the organic group reacts with the hydroxyl group on the surface of the zinc oxide particles to modify the surface of the zinc oxide particles, and the hardness and mechanical properties of the resulting silicone resin Strength is improved.

  Examples of commercially available silicone compounds include methyl hydrogen silicone oil (MHS) (trade name: KF-99, manufactured by Shin-Etsu Chemical Co., Ltd.), which is polymethylhydrosiloxane (trimethylsiloxy terminal).

The vinyl group possessed by the polyorganosiloxane (A) and the Si—H group possessed by the polyorganosiloxane (B) usually react in a stoichiometric ratio of 1: 1.
However, in the present invention, since the zinc oxide particles are closely packed in the gaps between the polyorganosiloxanes (A) and (B), the movement of the molecular chains of the polyorganosiloxanes (A) and (B) is limited. Has been.
Therefore, in order for all vinyl groups to react with the Si—H group, the equivalent of the Si—H group of the polyorganosiloxane (B) to the vinyl group of the polyorganosiloxane (A) is vinyl group: Si— H group is preferably 1: 1.1-1: 8, more preferably 1: 1.2-1: 5.

<Silica having an average primary particle size of less than 12 nm>
The polysiloxane mixture in the present invention further contains silica having an average primary particle diameter of less than 12 nm (hereinafter also simply referred to as silica particles).
Silica particles are components added for the purpose of improving the hardness and mechanical strength (tear strength and bending durability) of the silicone resin to be obtained, particularly for improving the tear strength.

By reducing the average primary particle size of the silica particles to less than 12 nm, it is considered that the increase in acoustic wave attenuation is suppressed and the tear strength and bending durability of the silicone resin can be improved.
That is, it is thought that the crack of the silicone resin due to mechanical stress is suppressed by the fine silica particles functioning as a stopper. In particular, it is estimated that the average primary particle size is small, so that the distance between particles is small, so that the function as a stopper is exhibited more and the tear strength and bending durability of the silicone resin are greatly improved.

  When the average primary particle diameter of the silica particles exceeds 12 nm, the interparticle distance of the inorganic particles becomes large and cracks are likely to grow. Therefore, a silicone resin produced from a composition containing silica particles having an average primary particle diameter exceeding 12 nm. Has low bending durability.

  Examples of the silica particles include fumed silica, calcined silica, precipitated silica, and vinyl group-containing silicone resin. Silica particles may be used alone or in combination of two or more.

The average primary particle diameter of the silica particles is less than 12 nm from the viewpoint of suppressing an increase in acoustic wave attenuation of the silicone resin and improving the tear strength, preferably more than 3 nm and less than 12 nm, more preferably more than 3 nm and less than 10 nm. preferable. In addition, since an average primary particle diameter exists in the said range, and since tear strength and bending durability are high, it is preferable.
The average primary particle diameter is described in the catalog of the silica particle manufacturer. However, in the case where the average primary particle diameter is not described in the catalog or a newly produced one can be obtained using TEM in the same manner as the zinc oxide.

Silica particles, from the viewpoint of improving the hardness and mechanical strength of the obtained silicone resin, the specific surface area is preferably ^{50~400m 2 / g, 100~400m 2 /} g is more preferable.

  The silica particles are preferably silica particles whose surfaces are surface-treated. As the surface treatment, silica particles treated with saturated fatty acid or silane are preferable, and silica particles treated with silane are particularly preferable.

In the silane treatment, the surface of the silica particles is preferably treated with a silane coupling agent. From the viewpoint of improving the hardness and mechanical strength of the silicone resin, a silane coupling agent having a hydrolyzable group is preferred. The hydrolyzable group in the silane coupling agent is hydrolyzed with water to form a hydroxyl group, and this hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particle, whereby the surface modification of the silica particle is performed, and the resulting silicone resin Hardness and mechanical strength are improved. Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, and a halogen atom.
If the surface of the silica particles is hydrophobically modified, the affinity between the silica particles and the polyorganosiloxane (A) and (B) is improved, and the hardness and mechanical strength of the resulting silicone resin are improved. Therefore, it is preferable.

  Examples of the silane coupling agent having a hydrophobic group as a functional group include those mentioned above in “(i) Silane coupling agent”.

The silica particles are preferably silica particles treated with a silane compound, more preferably silica particles treated with a trialkylsilylating agent, and even more preferably silica particles treated with a trimethylsilylating agent.
Examples of the silane compound include the above silane coupling agents and silane coupling agents in which functional groups in the silane coupling agent are substituted with alkyl groups.
Examples of the trimethylsilylating agent include trimethylchlorosilane and hexamethyldisilazane (HMDS) described in the above silane coupling agent and trimethylmethoxysilane which is a silane coupling agent in which a functional group is substituted with an alkyl group. It is done.

As a commercially available silane coupling agent, the said SIH6110.1 is mentioned, for example.
Silanol groups (Si—OH groups) present on the surface of the silica particles are covered with trimethylsilyl groups by reaction with hexamethyldisilazane (HMDS), and the silica particle surface is modified to be hydrophobic.

  Examples of commercially available silica particles include, for example, Aerosil (registered trademark) R812 (average primary particle diameter 7 nm, HMDS surface treatment), Aerosil (registered trademark) R812S (hydrophobic fumed silica manufactured by Nippon Aerosil Co., Ltd.). Average primary particle size 7 nm, HMDS surface treatment), Aerosil (registered trademark) RX300 (average primary particle size 7 nm, HMDS surface treatment), Aerosil (registered trademark) RX380S (average primary particle size 5 nm, HMDS surface treatment), Aerosil (registered) (Trademark) R976S (average primary particle diameter 7 nm, DDS surface treatment), Aerosil (registered trademark) 300 (average primary particle diameter 7 nm), Aerosil (registered trademark), both of which are hydrophilic fumed silica manufactured by Nippon Aerosil Co., Ltd. ) 300CF (average primary particle size 7nm), Aerosil ( (Registered trademark) 380 (average primary particle diameter 7 nm), Aerosil (registered trademark) RX380S (average primary particle diameter 5 nm, HMDS surface treatment), Aerosil R (registered trademark) 8200 average primary particle diameter 12 nm, HMDS surface treatment), Aerosil ( (Registered trademark) R972 (average primary particle diameter 16 nm, DDS surface treatment).

<Other ingredients>
The composition for an acoustic wave probe of the present invention includes a polyorganosiloxane having a vinyl group (A), a polyorganosiloxane having two or more Si—H groups in a molecular chain, zinc oxide, and an average primary particle size. In addition to silica of less than 12 nm, a catalyst for addition polymerization reaction, a curing retarder, a solvent, a dispersant, a pigment, a dye, an antistatic agent, an antioxidant, a flame retardant, a thermal conductivity improver, and the like are appropriately blended. be able to.

<Catalyst>
Examples of the catalyst include platinum or a platinum-containing compound (hereinafter also referred to as “platinum compound”). Any platinum or platinum compound can be used.
Specifically, platinum black, platinum supported on an inorganic compound or carbon black, chloroplatinic acid or chloroplatinic acid alcohol solution, chloroplatinic acid and olefin complex salt, chloroplatinic acid and vinylsiloxane complex salt Etc. A catalyst may be used individually by 1 type and may be used in combination of 2 or more type.

The content of the catalyst can be appropriately set within the range of the catalyst amount.
The catalyst is necessary in the hydrosilylation reaction in which the Si—H group of the polyorganosiloxane (B) is added to the vinyl group of the polyorganosiloxane (A). The polyorganosiloxane (A) is crosslinked with the polyorganosiloxane (B) by an addition curing reaction by hydrosilylation to form a silicone resin.
Here, the catalyst may be contained in the composition for acoustic wave probes of the present invention, or may be brought into contact with the composition for acoustic wave probes without being contained in the composition for acoustic wave probes. The latter is preferred.

  As a commercially available platinum catalyst, a platinum compound (Brand name: PLATINUM CYCLOVINYLMETHYLSLOOXANE COMPLEX IN CYCLIC METHYLVINYLSILOXANES (SIP6832.2), Pt density | concentration 2 mass%, the product made from Gelest) is mentioned, for example.

  When the catalyst is present with respect to the polysiloxane mixture, the amount of the catalyst present is preferably 0.00001 parts by mass or more and 0.00002 parts by mass as the Pt amount with respect to 100 parts by mass of the polysiloxane mixture from the viewpoint of reactivity. Part or more is more preferable, 0.00005 part by weight or more is more preferable, and 0.0001 part by weight or more is particularly preferable. On the other hand, it is preferably 0.1 parts by mass or less, more preferably 0.05 parts by mass or less, still more preferably 0.01 parts by mass or less, and particularly preferably 0.005 parts by mass or less.

  Further, the curing temperature can be adjusted by selecting an appropriate platinum catalyst. For example, platinum-vinyldisiloxane is used for room temperature curing (RTV) at 50 ° C. or lower, and platinum-cyclic vinylsiloxane is used for high temperature curing (HTV) at 130 ° C. or higher.

<Method for Producing Acoustic Wave Probe Composition and Silicone Resin for Acoustic Wave Probe>
The composition for acoustic wave probes of the present invention can be prepared by a conventional method.
For example, the components constituting the composition for acoustic wave probes can be obtained by kneading with a kneader, a pressure kneader, a Banbury mixer (continuous kneader), or a two-roll kneader. The mixing order of each component is not particularly limited.
From the viewpoint of obtaining a uniform composition, first, a polyorganosiloxane having a vinyl group (A) and a polyorganosiloxane having two or more Si—H groups in the molecular chain (B), zinc oxide and A polyorganosiloxane mixture in which silica having an average primary particle size of less than 12 nm is dispersed is preferable. Thereafter, a catalyst is added to a polyorganosiloxane mixture in which zinc oxide and silica having an average primary particle size of less than 12 nm are dispersed, and the composition for acoustic wave probes can be prepared by degassing under reduced pressure.

  The silicone resin for acoustic wave probes of the present invention can be obtained by curing the composition for acoustic wave probes of the present invention thus obtained. Specifically, for example, a silicone resin for acoustic wave probes can be obtained by heat curing at 20 to 200 ° C. for 5 to 500 minutes.

<Mechanical strength and acoustic wave characteristics of silicone resin>
Hereinafter, the mechanical strength and acoustic wave characteristics of the silicone resin will be described in detail.
Here, the acoustic wave characteristic describes the ultrasonic characteristic. However, the acoustic wave characteristic is not limited to the ultrasonic characteristic, but relates to the acoustic wave characteristic of an appropriate frequency selected according to the object to be examined, measurement conditions, and the like.

[hardness]
The hardness is preferably 30 or more, and more preferably 35 or more. The practical upper limit is 80 or less. By being in the said range, the deformation | transformation at the time of incorporating and using as a part of acoustic wave probe can be prevented.
In addition, the hardness of a silicone resin sheet can be calculated | required with the measuring method as described in the term of the below-mentioned Example.

[Tear strength test]
The tear strength is preferably 10 N / cm or more, more preferably 15 N / cm or more, further preferably 20 N / cm or more, and particularly preferably 30 N / cm or more. The realistic upper limit is 100 N / cm or less.
The tear strength can be determined by the measuring method described in the section of the examples described later.

[Bending durability test]
For a silicone resin sheet having a thickness of 2 mm, in accordance with JIS K6260 (2010), the resistance to bending cracks (the number of bendings required to reach the third grade) is measured using a Demach bending tester (manufactured by Toyo Seiki).
From the viewpoint of bringing the acoustic wave probe into contact with the living body, 10,000 times or more is preferable, and 20,000 times or more is more preferable. The realistic upper limit is 100,000 times or less.

[Acoustic impedance]
The acoustic impedance of the silicone resin sheet of the present invention is preferably closer to that of a living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec), and preferably 1.2 to 1.8 kg / m ² / sec. Preferably, 1.3 to 1.7 kg / m ² / sec is more preferable, and 1.4 to 1.6 kg / m ² / sec is particularly preferable.
The acoustic impedance can be obtained by the method described in the section of the example described later.

[Acoustic wave (ultrasonic wave) sensitivity]
In the evaluation system in the present invention, the acoustic wave (ultrasonic wave) sensitivity is preferably −74 dB or more, more preferably −73 dB or more, further preferably −72 dB or more, and particularly preferably −71 dB or more.
The acoustic wave (ultrasonic wave) sensitivity can be obtained by the method described in the section of Examples described later.

The composition for an acoustic wave probe of the present invention is useful for a medical member, and can be preferably used for, for example, an acoustic wave probe or an acoustic wave measuring device. The acoustic wave measuring device of the present invention is not limited to an ultrasonic diagnostic device or a photoacoustic wave measuring device, but refers to a device that receives an acoustic wave reflected or generated by a test object and displays it as an image or signal intensity. .
In particular, the composition for an acoustic wave probe of the present invention is provided between an acoustic lens of an ultrasonic diagnostic apparatus or a piezoelectric element and an acoustic lens, and has a role of matching acoustic impedance between the piezoelectric element and the acoustic lens. Acoustic matching layer material, acoustic lens material in photoacoustic wave measuring device and ultrasonic endoscope, and acoustic in ultrasonic probe with capacitive micromachined ultrasonic transducer (cMUT) as ultrasonic transducer array It can be suitably used for a lens material or the like.
Specifically, the silicone resin for an acoustic wave probe of the present invention is, for example, an ultrasonic diagnostic apparatus described in JP-A-2005-253751, JP-A-2003-169802, or JP-A-2013-202050. , Preferably for acoustic wave measuring devices such as the photoacoustic wave measuring devices described in JP 2013-188465 A, JP 2013-180330 A, JP 2013-158435 A, JP 2013-154139 A, etc. Applied.

<Acoustic wave probe (probe)>
Hereinafter, the configuration of the acoustic wave probe of the present invention will be described in more detail based on the configuration of the ultrasonic probe in the ultrasonic diagnostic apparatus shown in FIG. In addition, an ultrasonic probe is a probe which uses an ultrasonic wave especially as an acoustic wave in an acoustic wave probe. Therefore, the basic structure of the ultrasonic probe can be applied to the acoustic wave probe.

<Ultrasonic probe>
The ultrasonic probe 10 is a main component of the ultrasonic diagnostic apparatus, and has a function of generating ultrasonic waves and transmitting / receiving ultrasonic beams. As shown in FIG. 1, the configuration of the ultrasonic probe 10 is provided in the order of the acoustic lens 1, the acoustic matching layer 2, the piezoelectric element layer 3, and the backing material 4 from the tip (surface contacting the living body to be examined). ing. In recent years, for the purpose of receiving high-order harmonics, a transmitting ultrasonic transducer (piezoelectric element) and a receiving ultrasonic transducer (piezoelectric element) are made of different materials to form a laminated structure. Has also been proposed.

<Piezoelectric element layer>
The piezoelectric element layer 3 is a part that generates ultrasonic waves, and electrodes are attached to both sides of the piezoelectric element. When a voltage is applied, the piezoelectric element repeatedly vibrates and expands and expands to generate ultrasonic waves. .

As a material constituting the piezoelectric element, a single crystal such as quartz, LiNbO ₃ , LiTaO ₃ , KNbO ₃ , a thin film such as ZnO or AlN, or a sintered body such as Pb (Zr, Ti) O ₃ system is subjected to polarization treatment. So-called ceramic inorganic piezoelectric materials are widely used. In general, piezoelectric ceramics such as PZT: lead zirconate titanate with high conversion efficiency are used.
In addition, a piezoelectric element that detects a received wave on the high frequency side needs sensitivity with a wider bandwidth. For this reason, an organic piezoelectric body using an organic polymer material such as polyvinylidene fluoride (PVDF) is used as a piezoelectric element suitable for a high frequency and a wide band.
Furthermore, Japanese Patent Application Laid-Open No. 2011-071842 uses MEMS (Micro Electro Mechanical Systems) technology that exhibits excellent short pulse characteristics and wide band characteristics, and that provides an array structure with excellent mass productivity and little variation in characteristics. cMUT is described.
In the present invention, any piezoelectric element material can be preferably used.

<Backing material>
The backing material 4 is provided on the back surface of the piezoelectric element layer 3, and reduces the pulse width of the ultrasonic wave by suppressing excessive vibration, thereby contributing to the improvement of the distance resolution in the ultrasonic diagnostic image.

<Acoustic matching layer>
The acoustic matching layer 2 is provided in order to reduce the difference in acoustic impedance between the piezoelectric element layer 3 and the test object and to efficiently transmit and receive ultrasonic waves.
The composition for an ultrasonic probe of the present invention is preferably used as a material for an acoustic matching layer because it has a small difference from the acoustic impedance (1.4 to 1.7 × 10 ⁶ kg / m ² / sec) of the human body. Can do. The acoustic matching layer of the present invention preferably contains 10% by mass or more of a silicone resin for acoustic wave probes obtained by curing reaction of the composition for acoustic wave probes of the present invention.

<Acoustic lens>
The acoustic lens 1 is provided to focus the ultrasonic wave in the slice direction using refraction and improve the resolution. In addition, the ultrasonic wave is brought into close contact with the living body to be examined and the ultrasonic wave is matched with the acoustic impedance of the living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec in the human body), and the acoustic lens 1 The ultrasonic attenuation amount of the device itself is required to be small.
That is, as the material of the acoustic lens 1, if the sound speed is sufficiently smaller than the sound speed of the human body, the attenuation of the ultrasonic wave is small, and the acoustic impedance is close to the value of the skin of a living body like the human body, the transmission / reception sensitivity of the ultrasonic wave Will be better.
The composition for ultrasonic probes of the present invention can be preferably used also as an acoustic lens material. The acoustic lens used in the present invention preferably contains 10% by mass or more of a silicone resin for acoustic wave probes obtained by curing reaction of the composition for acoustic wave probes of the present invention.

  The operation of the ultrasonic probe 10 having such a configuration will be described. A voltage is applied to the electrodes provided on both sides of the piezoelectric element to resonate the piezoelectric element layer 3, and an ultrasonic signal is transmitted from the acoustic lens to the object to be examined. At the time of reception, the piezoelectric element layer 3 is vibrated by a reflected signal (echo signal) from the subject to be examined, and this vibration is electrically converted into a signal to obtain an image.

In particular, the acoustic lens obtained from the composition for an ultrasonic probe of the present invention can confirm a remarkable sensitivity improvement effect at an ultrasonic transmission frequency of about 5 MHz or more as a general medical ultrasonic transducer. Particularly significant sensitivity improvement effect can be expected at an ultrasonic transmission frequency of 10 MHz or more.
Hereinafter, an apparatus in which the acoustic lens obtained from the composition for an ultrasonic probe according to the present invention particularly functions will be described in detail.
In addition, the composition for ultrasonic probes of this invention shows the outstanding effect also with respect to apparatuses other than what is described below.

<Ultrasonic probe provided with cMUT (capacitive micromachine ultrasonic transducer)>
When the cMUT device described in JP 2006-157320 A, JP 2011-71842 A, or the like is used for a transducer array for ultrasonic diagnosis, it is generally compared with a transducer using general piezoelectric ceramics (PZT). Specifically, the sensitivity becomes low.
However, it is possible to compensate for the lack of sensitivity of cMUT by using an acoustic lens obtained from the composition for acoustic wave probes of the present invention. Thereby, the sensitivity of the cMUT can be brought close to the performance of the conventional transducer.
Since the cMUT device is manufactured by the MEMS technology, it is possible to provide an ultrasonic probe having a higher productivity and a lower cost than the piezoelectric ceramic probe to the market.

<Photoacoustic wave measurement device by photoacoustic imaging>
Photoacoustic imaging (PAI) described in Japanese Patent Application Laid-Open No. 2013-158435 or the like is a supersonic wave generated when a human body tissue is adiabatically expanded by irradiating light (electromagnetic waves) into the human body. Displays the image of the sound wave or the signal strength of the ultrasonic wave.
Here, since the sound pressure of the ultrasonic wave generated by light irradiation is very small, there is a problem that it is difficult to observe the deep part of the human body.
However, by using an acoustic lens obtained from the acoustic wave probe composition of the present invention, an effective effect on this problem can be exhibited.

<Ultrasound endoscope>
Since the ultrasonic wave in the ultrasonic endoscope described in Japanese Patent Application Laid-Open No. 2008-311700 is longer than the body surface transducer due to its structure, the improvement of the sensitivity of the transducer due to the cable loss is a problem. is there. Moreover, it is said that there is no effective sensitivity improvement means for this problem for the following reasons.

First, in the case of an ultrasonic diagnostic apparatus for the body surface, an amplifier circuit, an AD conversion IC, etc. can be installed at the tip of the transducer. On the other hand, since the ultrasonic endoscope is used by being inserted into the body, there is no installation space for the transducer and it is difficult to install it at the tip of the transducer.
Second, the piezoelectric single crystal employed in the transducer in the ultrasonic diagnostic apparatus for the body surface is difficult to apply to a transducer having an ultrasonic transmission frequency of 7 to 8 MHz or more due to its physical characteristics and process suitability. . However, since the ultrasonic waves for endoscopes are generally probes having an ultrasonic transmission frequency of 7 to 8 MHz or higher, it is difficult to improve the sensitivity with the piezoelectric single crystal material.

However, it is possible to improve the sensitivity of the endoscope ultrasonic transducer by using an acoustic lens obtained from the composition for acoustic wave probes of the present invention.
Even when the same ultrasonic transmission frequency (for example, 10 MHz) is used, it is particularly effective when the acoustic lens obtained from the acoustic wave probe composition of the present invention is used in an ultrasonic transducer for an endoscope. Is demonstrated.

Hereinafter, the present invention will be described in more detail based on examples using ultrasonic waves as acoustic waves. Note that the present invention is not limited to ultrasonic waves, and an acoustic wave having an audible frequency may be used as long as an appropriate frequency is selected in accordance with an object to be examined and measurement conditions.
In the following examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, "-" used in a table | surface means not having the composition.

[Example 1]
As the polyorganosiloxane (A), a vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer (component (A) in Table 1 below, manufactured by Gelest, trade name “PDV-1641”, mass average molecular weight 55,000, diphenylsiloxane amount 16 mol% ) 68.0 parts by mass, polyorganosiloxane (B), methylhydrosiloxane-phenylmethylsiloxane copolymer (component (B) in Table 1 below, manufactured by Gelest, trade name “HPM-502”, mass average molecular weight 4, 500) 2.0 parts by mass, zinc oxide (“FINEX (registered trademark) -30S-LPT” manufactured by Sakai Chemical Industry Co., Ltd., average primary particle size 35 nm, silicone surface treatment), 12.0 parts by mass, fumed silica (“Aerosil”) (Registered trademark) RX300 ", average primary particle diameter 7 nm, hexamethyl The kneader silazane (HMDS) surface-treated product) 18.0 parts by mass, and kneaded for 2 hours at a temperature 23 ° C., to give a uniform paste (polysiloxane mixture). A platinum catalyst solution (Gelest, trade name “SIP6832.2”, Pt concentration: 2% by mass) was added to and mixed with 500 ppm, then degassed under reduced pressure (1 mmHg), 150 mm long × 150 mm wide × depth. It was put into a metal mold having a thickness of 2 mm and heat-treated at 60 ° C. for 3 hours to produce a silicone resin for acoustic wave probes (150 mm long × 150 mm wide × 2 mm thick sheet). Hereinafter, the silicone resin for acoustic wave probes produced in this way is referred to as a “silicone resin sheet”.

[Examples 2 to 25, Comparative Examples 1 to 4]
A predetermined silicone resin sheet was obtained in the same manner as in Example 1 except that the composition of the polysiloxane mixture of Example 1 was changed to the composition described in Table 1 below.
Here, Comparative Example 2 is a follow-up test simulating an example of Japanese Patent Application Laid-Open No. 2005-125071.

<Evaluation of mechanical strength and ultrasonic characteristics>
The following evaluation was performed about the silicone resin sheet of Examples 1-25 and Comparative Examples 1-4.

[hardness]
About the obtained 2 mm-thick silicone resin sheet, according to JIS K6253-3 (2012), the type A durometer hardness was measured using the rubber hardness meter (the Excel company make, brand name "RH-201A").

[Tear strength test]
About the obtained 2 mm-thick silicone resin sheet, a trouser type test piece was prepared according to JIS K6252 (2007), and tear strength was measured.

[Bending durability test]
For the obtained silicone resin sheet having a thickness of 2 mm, in accordance with JIS K6260 (2010), the bending crack resistance (number of bendings required to reach the third grade) was measured using a Demacha bending tester (manufactured by Toyo Seiki Co., Ltd.). did.

[Acoustic impedance]
For the obtained silicone resin sheet having a thickness of 2 mm, an electronic hydrometer (trade name, manufactured by Alpha Mirage Co., Ltd.) was used in accordance with the density measurement method of A method (underwater substitution method) described in JIS K7112 (1999). “SD-200L”). The ultrasonic sound velocity was measured at 25 ° C. using a sing-around sound velocity measuring device (trade name “UVM-2 type” manufactured by Ultrasonic Industry Co., Ltd.) according to JIS Z2353 (2003), and the measured density and sound velocity were measured. The acoustic impedance was obtained from the product.

[Acoustic wave (ultrasonic wave) sensitivity]
A 5 MHz sine wave signal (1 wave) output from an ultrasonic oscillator (Iwadori Measurement Co., Ltd., function generator, product name “FG-350”) is input to an ultrasonic probe (Japan Probe Co., Ltd.). Then, an ultrasonic pulse wave having a center frequency of 5 MHz was generated from the ultrasonic probe in water. The amplitude of the generated ultrasonic wave before and after passing through the obtained 2 mm thick silicone resin sheet is measured with an ultrasonic receiver (Matsushita Electric Industrial Co., Ltd., oscilloscope, trade name “VP-5204A”). Thus, the acoustic wave (ultrasonic wave) attenuation amount of each material was compared by measuring in an environment with a water temperature of 25 ° C. and comparing the acoustic wave (ultrasonic wave) sensitivity.
The acoustic wave (ultrasonic wave) sensitivity is such that the generated acoustic wave (ultrasonic wave) passes through the sheet with respect to the voltage peak value Vin of the input wave having a half-value width of 50 nsec or less by the ultrasonic oscillator, and from the opposite side of the sheet. The voltage value obtained when the ultrasonic wave (ultrasonic wave) reflected was received by the ultrasonic oscillator was defined as Vs, and was calculated from the following calculation formula.

    Acoustic wave (ultrasound) sensitivity = 20 x Log (Vs / Vin)

The results obtained are summarized in Table 1 below.
In Table 1 below, the mass average molecular weights of the polyorganosiloxanes (A) and (B) are simply described as molecular weights, and the name of each component is a trade name.

<Notes on the table>
[Polyorganosiloxane component (A)]
All of them are PDV (trade name), DMS (trade name) series, PDV-1641, trade name, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, mass average molecular weight 55,000, diphenylsiloxane amount 16 mol% manufactured by Gelest.
PDV-1635: trade name, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, mass average molecular weight 35,300, diphenylsiloxane amount 16 mol%
PDV-1631: trade name, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, weight average molecular weight 19,000, diphenylsiloxane amount 16 mol%
PDV-0541: trade name, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, mass average molecular weight 60,000, diphenylsiloxane amount 5 mol%
PDV-0535: trade name, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, mass average molecular weight 47,500, diphenylsiloxane amount 5 mol%
DMS-V41: trade name, vinyl-terminated polydimethylsiloxane, mass average molecular weight 62,700
[Polyorganosiloxane component (B)]
HPM-502: trade name, methyl hydrosiloxane-phenylmethylsiloxane copolymer manufactured by Gelest, weight average molecular weight 4,500
HMS-991: trade name, methyl hydrosiloxane polymer manufactured by Gelest, mass average molecular weight 1,600
[Zinc oxide]
In either case, zinc oxide manufactured by Sakai Chemical Industry Co., Ltd., FINEX (registered trademark) series, and in the above table, “FINEX-” is omitted.
FINEX-30S-LPT: trade name, average primary particle diameter 35 nm, silicone surface treatment FINEX-50S-LPT: trade name, average primary particle diameter 20 nm, silicone surface treatment FINEX-30: trade name, average primary particle diameter 35 nm, no surface treatment • FINEX-30W-LP2: trade name, average primary particle diameter 35 nm, silica / silicone surface treatment • FINEX-25-LPT: trade name, average primary particle diameter 60 nm, silicone surface treatment [silica]
Fumed silica manufactured by Nippon Aerosil Co., Ltd., Aerosil (registered trademark) series, and in the above table, “Aerosil” is omitted. HDK H 20 is made of Asahi Kasei Wacker Silicone. In the above table, “HDK” is omitted.
Aerosil RX300: trade name, average primary particle diameter 7 nm, hexamethyldisilazane (HMDS) surface treatment Aerosil R976S: trade name, average primary particle diameter 7 nm, dimethyldichlorosilane (DDS) surface treatment Aerosil 300: trade name, Average primary particle diameter 7 nm, no surface treatment Aerosil RX380S: trade name, average primary particle diameter 5 nm, HMDS surface treatment Aerosil R8200: trade name, average primary particle diameter 12 nm, HMDS surface treatment Aerosil R972: trade name, average primary Particle diameter 16 nm, DDS surface treatment / HDK H 20: trade name, average primary particle diameter 10 nm, HMDS surface treatment

  As is clear from Table 1, the silicone resins for acoustic wave probes of Examples 1 to 25 have an acoustic impedance close to that of a living body, and all have an acoustic wave (ultrasonic wave) sensitivity of −74 dB or more. Since the sensitivity is −74 dB or more, it can be seen that the acoustic wave attenuation is reduced. Furthermore, the silicone resins for acoustic wave probes of Examples 1 to 25 were excellent in hardness, tear strength, and bending durability. On the other hand, all of the silicone resins for acoustic wave probes of Comparative Examples 1 to 4 had insufficient bending durability.

  This result shows that the composition for acoustic wave probes of this invention is suitable for a medical member. Moreover, it turns out that the silicone resin of this invention can be used suitably also for the acoustic lens and / or acoustic matching layer of an acoustic wave probe, an acoustic wave measuring apparatus, and an ultrasonic diagnostic apparatus. In particular, the composition for acoustic wave probes and the silicone resin for acoustic wave probes are used for the purpose of improving sensitivity in ultrasonic probes, photoacoustic wave measuring apparatuses and ultrasonic endoscopes using cMUT as a transducer array for ultrasonic diagnosis. It can be used suitably.

DESCRIPTION OF SYMBOLS 1 Acoustic lens 2 Acoustic matching layer 3 Piezoelectric element layer 4 Backing material 7 Case 9 Code 10 Ultrasonic probe (probe)

Claims (21)

  Composition for acoustic wave probe comprising polysiloxane having vinyl group, polysiloxane having two or more Si-H groups in the molecular chain, zinc oxide and polysiloxane mixture containing silica having an average primary particle diameter of less than 12 nm . The composition for an acoustic wave probe according to claim 1, wherein the silica has an average primary particle diameter of 10 nm or less. The composition for an acoustic wave probe according to claim 2, wherein the silica has an average primary particle diameter of less than 10 nm. The composition for acoustic wave probes according to any one of claims 1 to 3 , wherein 0.1 to 14.9 parts by mass of the zinc oxide is contained in 100 parts by mass of the polysiloxane mixture. Wherein the total of 100 parts by weight of polysiloxane mixture, the acoustic wave probe composition according to any one of claims 1-4, containing prior 0.1-30 parts by weight of carboxymethyl Rica. The mass ratio of the content of pre-carboxymethyl Rica to the content of zinc oxide, the acoustic wave probe composition according to any one of claims 1 to 5 which is 0.2 to 3.0. In a total of 100 parts by mass of the polysiloxane mixture, 10 to 99.4 parts by mass of the polysiloxane having the vinyl group, and 0.5 to 3 of the polysiloxane having two or more Si—H groups in the molecular chain. The composition for an acoustic wave probe according to any one of claims 1 to 6 , containing 90 parts by mass. Before carboxymethyl Rika, acoustic wave probe composition according to any one of claims 1 to 7 which has been surface-treated with a silane compound. Before carboxymethyl Rika, either acoustic wave probe composition according to one of claims 1-8 in which surface-treated with trimethylsilyl agent. The composition for acoustic wave probes according to any one of claims 1 to 9 , wherein the polysiloxane having a vinyl group has a phenyl group. The composition for an acoustic wave probe according to any one of claims 1 to 10 , wherein the polysiloxane having a vinyl group has a mass average molecular weight of 10,000 to 200,000. The composition for acoustic wave probes according to any one of claims 1 to 11 , wherein the polysiloxane having a vinyl group has a mass average molecular weight of 30,000 to 150,000. The composition for acoustic wave probes according to any one of claims 1 to 12 , wherein the polysiloxane having two or more Si-H groups in the molecular chain has a phenyl group. The polysiloxane mixture relative to 100 parts by weight, of platinum or platinum-containing compound an acoustic wave probe composition according to any one of claims 1 to 13 containing 0.0001 parts by weight. Claim 1-14 any one acoustic wave acoustic wave probe silicone resins probe composition obtained by curing reaction described in. An acoustic wave probe having at least one selected from the group consisting of an acoustic lens and an acoustic matching layer, comprising the silicone resin for an acoustic wave probe according to claim 15 . An ultrasonic probe comprising an acoustic lens comprising a capacitive micromachine ultrasonic transducer and the silicone resin for an acoustic wave probe according to claim 15 . An acoustic wave measuring apparatus provided with the acoustic wave probe of Claim 16 . An ultrasonic diagnostic apparatus comprising the acoustic wave probe according to claim 16 . A photoacoustic wave measuring apparatus provided with the acoustic lens containing the silicone resin for acoustic wave probes of Claim 15 . An ultrasonic endoscope comprising an acoustic lens comprising the silicone resin for an acoustic wave probe according to claim 15 .

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