JP6660990B2 - 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, ultrasonic endoscope, and acoustic wave Method for producing silicone resin for probe - 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. Further, the present invention relates to an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope. The present invention also relates to a method for producing a silicone resin for an acoustic wave probe.

  In the acoustic wave measuring device, an acoustic wave probe that irradiates an acoustic wave to an object, receives a reflected wave (echo) thereof, and outputs a signal is used. By displaying the image as an image based on the electric signal converted from the reflected wave received by the acoustic wave probe, the inside of the object is visualized and observed.

As the acoustic wave, an appropriate frequency, such as an ultrasonic wave or a photoacoustic wave, is selected according to an object to be inspected 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 the image as an image. The photoacoustic wave measurement device receives an acoustic wave radiated from the inside of the subject due to the photoacoustic effect, and displays the image as an image. The photoacoustic effect means that when an object is irradiated with an electromagnetic wave pulse such as visible light, near-infrared light, or microwave, the object absorbs the electromagnetic wave, generates heat, and thermally expands. Is a phenomenon in which ultrasonic waves are generated.
Since the acoustic wave measuring device transmits and receives acoustic waves to and from a living body, it is required to satisfy requirements such as acoustic impedance matching with the living body and low acoustic wave attenuation.

For example, a probe for an ultrasonic diagnostic apparatus (also referred to as an ultrasonic probe), which is a type of acoustic wave probe, includes a piezoelectric element that transmits and receives ultrasonic waves and an acoustic lens that is a part that comes into contact with a living body. Ultrasonic waves emitted from the piezoelectric element pass through the acoustic lens and enter the living body. If the difference between the acoustic impedance (density x sound velocity) of the acoustic lens and the acoustic impedance of the living body is large, the ultrasonic wave is reflected on the surface of the living body, so that it is not efficiently incident on the living body and it is difficult to obtain high resolution. is there. In addition, in order to transmit and receive ultrasonic waves with high sensitivity, it is desired that the ultrasonic lens has a small amount of ultrasonic attenuation.
For this reason, as a material of the acoustic lens, a silicone resin having a small ultrasonic attenuation and being close to the acoustic impedance of a living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec) is mainly used ( Patent Document 1).

  In addition, since the acoustic lens is used in contact with the subject, mechanical strength that can withstand long-term use is required. Therefore, in Patent Document 2, as a composition for an acoustic lens satisfying acoustic lens characteristics (acoustic impedance, ultrasonic attenuation, mechanical strength, etc.), a composition containing metal oxide particles coated with silicone rubber and silica is used. Proposed.

JP-A-62-089765 JP-A-2011-072702

Silicone resin alone is soft and has low mechanical strength. For the purpose of improving hardness and mechanical strength, while increasing the molecular weight of the vinyl silicone resin at both ends, an inorganic filler such as silica (also called an inorganic filler) or Incorporation of a vinyl group-containing resin (also referred to as a reinforcing agent) has been performed. However, in order to achieve the required mechanical strength, the amount of the inorganic filler or vinyl group-containing resin added to the silicone resin is inevitably increased, which results in the silicone resin having a large acoustic wave attenuation. was there.
Therefore, it has been difficult for conventional silicone resins to satisfy high resin hardness, high mechanical strength, and low acoustic wave attenuation at a high level.
Therefore, in view of the above circumstances, in the present invention, while maintaining a low acoustic wave attenuation, a composition for an acoustic wave probe capable of significantly improving the hardness and mechanical strength of a silicone resin, an acoustic wave using the same, It is an object to provide a silicone resin for a probe, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, and a method for producing a silicone resin for an acoustic wave probe.

  In addition, an ultrasonic probe using a capacitive micromachined ultrasonic transducer (cMUT: Capacitive Micromachined Ultrasonic Transducers) having insufficient sensitivity as an ultrasonic diagnostic transducer array, and the amount of ultrasonic waves generated by photoacoustic waves is small. The photoacoustic wave measurement device has low sensitivity and it is difficult to observe deep inside the human body, and the sensitivity is low because the signal line cable is longer than that for the body surface. 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, which are capable of improving sensitivity in a certain ultrasonic endoscope.

  The present inventors have studied silica added to a silicone resin, and as a result, have found that the above problem can be solved by using silica particles having a specific particle diameter.

The above problem has been solved by the following means.
<1> A composition for an acoustic wave probe comprising, in a polysiloxane mixture, at least a polysiloxane, an organic peroxide, and silica having an average primary particle diameter of less than 12 nm.
<2> The composition for an acoustic wave probe according to <1>, wherein 0.1 to 30 parts by mass of silica having an average primary particle diameter of less than 12 nm is contained in a total of 100 parts by mass of the polysiloxane mixture.
<3> The composition for an acoustic wave probe according to <1> or <2>, wherein the polysiloxane is a vinyl group-containing polysiloxane.
<4> The composition for an acoustic wave probe according to any one of <1> to <3>, wherein silica having an average primary particle size of less than 12 nm is surface-treated with a silane compound.
<5> The composition for an acoustic wave probe according to any one of <1> to <4>, wherein the silica having an average primary particle diameter of less than 12 nm is surface-treated with a trimethylsilylating agent.
<6> The composition for an acoustic wave probe according to any one of <1> to <5>, wherein the polysiloxane has a mass average molecular weight of 20,000 to 1,000,000.
<7> The composition for an acoustic wave probe according to any one of <1> to <6>, wherein the polysiloxane has a mass average molecular weight of 40,000 to 300,000.
<8> The composition for acoustic wave probe, wherein the following acoustic wave (ultrasonic) sensitivity of the silicone resin sheet having a thickness of 2 mm obtained with the composition for acoustic wave probe is -72 dB or more. 7> The composition for an acoustic wave probe according to any one of the above items.
[Acoustic wave (ultrasonic wave) sensitivity]
An acoustic wave (ultrasonic wave) generated with respect to the voltage peak value Vin of the input wave passes through the sheet, and is obtained when the ultrasonic oscillator receives an acoustic wave (ultrasonic wave) reflected from the opposite surface of the sheet. The voltage value is Vs, and is a numerical value given by acoustic wave (ultrasonic wave) sensitivity = 20 × Log (Vs / Vin).
<9> The composition for an acoustic wave probe according to any one of <1> to <8>, wherein the average primary particle diameter of the silica is more than 3 nm and less than 12 nm.
< 10 > A silicone resin for an acoustic wave probe obtained by curing the composition for an acoustic wave probe according to any one of <1> to < 9 >.
< 11 > An acoustic wave probe having an acoustic lens and / or an acoustic matching layer made of the silicone resin for an acoustic wave probe according to < 10 >.
< 12 > An ultrasonic probe comprising: a capacitive micromachined ultrasonic transducer as an ultrasonic transducer array; and an acoustic lens made of the silicone resin for an acoustic wave probe according to < 10 >.
< 13 > An acoustic wave measurement device including the acoustic wave probe according to < 11 >.
< 14 > An ultrasonic diagnostic apparatus including the acoustic probe according to < 11 >.
< 15 > A photoacoustic wave measurement device including an acoustic lens made of the silicone resin for an acoustic wave probe according to < 10 >.
< 16 > An ultrasonic endoscope comprising an acoustic lens made of the silicone resin for an acoustic wave probe according to < 10 >.
< 17 > An organic peroxide is added to a polysiloxane mixture containing at least a polysiloxane and silica having an average primary particle diameter of less than 12 nm to form a composition for an acoustic wave probe, and then the composition for an acoustic wave probe is cured. A method for producing a silicone resin for an acoustic wave probe.

In each of the general formulas in the present specification, unless otherwise specified, when there are a plurality of groups with the same sign, these may be the same or different from each other, and a group specified by each group (for example, Alkyl group and the like) may be further substituted with a substituent.
In this specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit and an upper limit.
In addition, the mass average molecular weight in this specification is a measured value (in terms of polystyrene) by gel permeation chromatography (GPC) unless otherwise specified.

Advantageous Effects of Invention According to the present invention, a composition for an acoustic wave probe capable of greatly improving the hardness and mechanical strength of a silicone resin while maintaining a low acoustic wave (particularly preferably ultrasonic) attenuation, an acoustic wave using the same A silicone resin for a probe, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, and a method for producing a silicone resin for an acoustic wave probe can be provided.
Further, it is possible to provide an ultrasonic probe, a photoacoustic wave measuring device, and a silicone resin for an acoustic wave probe capable of improving sensitivity in an ultrasonic endoscope using the cMUT as a transducer array for ultrasonic diagnosis.

Such an effect is considered to be because silica having a small average primary particle diameter functions as a stopper when a mechanical stress is applied to the silicone resin for an acoustic wave probe. In particular, since the average primary particle diameter is small, the distance between the particles is reduced, so that the function as a stopper is further exhibited, and the tear strength of the silicone resin is greatly improved.
As a result, it is considered that the increase in the amount of acoustic wave attenuation is suppressed, and the hardness and mechanical strength of the silicone resin for the acoustic wave probe are improved.

FIG. 3 is a perspective transmission view of a convex 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 a composition) comprises a polysiloxane mixture containing a polysiloxane (A) (hereinafter, also referred to as a polyorganosiloxane (A)) and an organic peroxide. (B) and at least silica (C) having an average primary particle diameter of less than 12 nm.

  Hereinafter, details will be described in order of the polyorganosiloxane (A), the organic peroxide (B), and the silica (C) having an average primary particle diameter of less than 12 nm.

<Polyorganosiloxane (A)>
The polyorganosiloxane (A) in the present invention may be any polyorganosiloxane as long as it is a millable silicone crosslinked by a radical curing reaction with the organic peroxide (B).
Here, millable silicone is similar to natural rubber or ordinary synthetic rubber unvulcanized compounded rubber before curing, and can be plasticized and mixed with a kneading roll machine, closed mixer, etc. It is a general term for those which are distinguished from liquid silicone which is a paste or a liquid in a state before curing.

Hereinafter, specific millable silicones will be described using linear and branched polyorganosiloxanes as examples.
The polyorganosiloxane (A) is not limited to the polyorganosiloxane described below, and may be, for example, a linear polyorganosiloxane having a partially branched structure.

[Linear polyorganosiloxane]
Examples of the linear polyorganosiloxane include those represented by the following general formula (A1).

In the general formula (A1), R ^a1 each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group, and R ^a2 and R ^a3 each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group. Represents a group, an alkenyl group, an aryl group or —O—Si (R ^a5 ) ₂ (R ^a4 ). R ^a4 and R ^a5 each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group. x1 and x2 each independently represent an integer of 1 or more. Here, the plurality of R ^a1 , the plurality of R ^a2 , the plurality of R ^a3 , the plurality of R ^a4, and the plurality of R ^a5 may be the same or different from each other. Further, each group of R ^{a1 to} R ^a5 may be further substituted with a substituent.

R ^a1 to R number of carbon atoms in the alkyl group in ^a5 preferably 1 to 10, more preferably 1 to 4, more preferably 1 or 2, 1 is particularly preferred. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl, and n-decyl.

The carbon number of the cycloalkyl group in R ^{a1 to} R ^a5 is preferably 3 to 10, more preferably 5 to 10, and even more preferably 5 or 6. Further, the cycloalkyl group is preferably a three-membered ring, a five-membered ring or a six-membered ring, more preferably a five-membered ring or a six-membered ring. Examples of the cycloalkyl group include cyclopropyl, cyclopentyl, and cyclohexyl.

R ^a1 to R number of carbon atoms of the alkenyl group in ^a5 is preferably 2 to 10, more preferably 2 to 4, 2 is more preferred. Alkenyl groups include, for example, vinyl, allyl and butenyl.

R ^a1 to R number of carbon atoms of the aryl group in ^a5 preferably 6 to 12, more preferably 6 to 10, 6 to 8 is more preferred. 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 ^a1 is preferably an alkyl group or an alkenyl group, more preferably an alkyl group having 1 to 4 carbon atoms or a vinyl group, still more preferably a methyl group or a vinyl group, particularly preferably a vinyl group, and both R ^a1 are a vinyl group. Is most preferred.
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 or a vinyl group.
^Ra2 is particularly preferably a methyl group. R ^a3 is among others, preferably a vinyl group when R ^a1 is not a vinyl group, when two R ^a1 are both vinyl group is preferably a methyl group.

The group represented by —O—Si (R ^a5 ) ₂ (R ^a4 ) is preferably —O—Si (CH ₃ ) ₂ (CH ＝ CH ₂ ).

x1 is preferably an integer of 200 to 3000, more preferably an integer of 400 to 2000.
x2 is preferably an integer of 1 to 1000, more preferably an integer of 40 to 700.

Among them, the linear polyorganosiloxane preferably has one or more vinyl groups in the molecular chain, and more preferably has two or more vinyl groups in the molecular chain.
As the polyorganosiloxane having a vinyl group, for example, at least a polyorganosiloxane having a vinyl group at a molecular chain terminal, or at least a vinyl group or —O—Si (CH ₃ ) ₂ (CH ＝ CH ₂ ) in a molecular chain. A polyorganosiloxane having one is exemplified.
Among them, a polyorganosiloxane having a vinyl group at least at a molecular chain terminal is preferable, and a polyorganosiloxane having a vinyl group at least at both molecular chain terminals is more preferable.

  The degree of polymerization and specific gravity are not particularly limited. The degree of polymerization is preferably from 200 to 3,000, and more preferably from 400 to 2,000, from the viewpoint of improving the mechanical properties, hardness, chemical stability and the like of the obtained silicone resin for an acoustic wave probe (hereinafter also simply referred to as silicone resin). Is more preferable, and the specific gravity is preferably 0.9 to 1.1.

  The mass average molecular weight of the polyorganosiloxane having a vinyl group is preferably from 20,000 to 1,000,000, more preferably from 40,000 to 300,000, from the viewpoint of mechanical strength, hardness and ease of processing. , 45,000 to 250,000.

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

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 polyorganosiloxane having a vinyl group at least at both molecular chain terminals is, for example, a product name manufactured by Gelest, a DMS series (for example, DMS-V31, DMS-V31S15, DMS-V33, DMS-35, DMS-35R, DMS). -V41, DMS-V42, DMS-V46, DMS-V51, DMS-V52), trade name of Gelest, PDV series (for example, PDV-0341, PDV-0346, PDV-0535, PDV-0541, PDV- 01631, PDV-01635, PDV-01641, PDV-2335, PMV-9925, PVV-3522, FMV-4031, EDV-2022).
Note that DMS-V31S15 does not require kneading with a special device because fumed silica is previously blended.

[Branched polyorganosiloxane]
Examples of the branched polyorganosiloxane include those represented by the following general formula (A2).

In Formula (A2), R ^{1 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, or —O—Si (R ⁶ ) ₂ (R ⁵ ). R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group. m represents an integer of 1 or more, and n represents 0 or an integer of 1 to 5. Here, a plurality of R ¹ , a plurality of R ² , a plurality of R ³ , a plurality of R ⁴ , a plurality of R ⁵ , a plurality of R ^6, and a plurality of m may be the same or different from each other, Each of R ^{1 to} R ⁶ may be further substituted with a substituent.

  In the general formula (A2), the polyorganosiloxane in which n is 0 can be represented by the following general formula (a2).

In the general formula (a2), R ^{1 to} R ⁴ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, or —O—Si (R ⁶ ) ₂ (R ⁵ ). R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group. m represents an integer of 1 or more. Here, a plurality of R ² , a plurality of R ³ , a plurality of R ⁴ , a plurality of R ⁵ , a plurality of R ^6, and a plurality of m may be the same or different from each other, and R ^{1 to} R ^6. May be further substituted with a substituent.

In the general formulas (A2) and (a2), the above groups in R ^{1 to} R ⁶ have the same ^{meanings as} the corresponding groups in R ^{a2 to} R ^a5 in the general formula (A1). Is the same as
In addition, at least two or more of the plurality of R ¹ and R ⁴ are preferably a vinyl group, and more preferably at least two or more of the plurality of R ⁴ are a vinyl group.

The n, m, and mass average molecular weight in the general formulas (A2) and (a2) are not particularly limited, and may be any millable silicone having a kinematic viscosity at 25 ° C. in a raw rubber state.
The specific value of the kinematic viscosity is the same as the preferable range of the kinematic viscosity described for the linear polyorganosiloxane.

The polyorganosiloxane (A) in the present invention is preferably a vinyl group-containing polysiloxane having one or more vinyl groups in the molecular chain.
When the polyorganosiloxane (A) has a vinyl group, the content of the vinyl group is not particularly limited. In addition, from a viewpoint of forming a sufficient network by the organic peroxide (B), it is, for example, 0.01 to 5 mol%, and preferably 0.05 to 2 mol%.
Here, the content of the vinyl group is a mol% of the vinyl group-containing siloxane unit when all the units constituting the polyorganosiloxane (A) are taken as 100 mol%. And one vinyl group.
The unit refers to a Si—O unit constituting the main chain and terminal Si.

  As the polyorganosiloxane (A) in the present invention, only one type may be used alone, or two or more types may be used in combination. In addition, 2 or less types are preferable and 1 type alone is more preferable.

<Organic peroxide (B)>
The organic peroxide (B) in the present invention includes a hydroperoxide, a dialkyl peroxide, a peroxyester, a diacyl peroxide, a peroxydicarbonate, a peroxyketal, and a ketone having an —O—O— bond in a molecule. Commonly used organic peroxides such as peroxides are exemplified.

Specifically, the following organic peroxides can be mentioned.
-Hydroperoxide: p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, etc.

Dialkyl peroxide: bis (2,4-dichlorobenzoyl) peroxide, bis (4-chlorobenzoyl) peroxide, bis (2-methylbenzoyl) peroxide, bis (2-t-butylperoxyisopropyl) benzene, Dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide and 2, 5-bis (t-butylperoxy) -2,5-dimethyl-3-hexyne and the like

-Peroxyester: t-butyl peroxybenzoate, cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, t- Butyl peroxy neodecanoate, t-butyl peroxy neoheptanoate, t-hexyl peroxy pivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 2,5- Bis (2-ethylhexylperoxy) -2,5-dimethylhexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxymaleate, t-butylperoxy-3,5,5-trimethyl Hexanoate, t-butyl peroxy laurate, t-butyl peroxyisopropyl monocarbonate Tert-butylperoxy-2-ethylhexyl monocarbonate, tert-hexylperoxybenzoate, 2,5-bis (bensoylperoxy) -2,5-dimethylhexane, tert-butylperoxyacetate and tert-butyl Peroxy-3-methylbenzoate, etc.

Diacyl peroxide: diisobutyryl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, bis (3-carboxypropionyl) peroxide, bis (3-methylbenzoyl) peroxide, Benzoyl (3-methylbenzoyl) peroxide, dibenzoyl peroxide, bis (4-methylbenzoyl) peroxide, 1,6-hexanediol-bis (t-butylperoxycarbonate) and the like

-Peroxydicarbonate: di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, bis (2-ethylhexyl) peroxydicarbonate and di-sec -Butyl peroxydicarbonate, etc.

-Peroxyketal: 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-butyl) Peroxy) -2-methylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) butane, n-butyl4,4-bis (t-butylperoxy) Oxy) valerate and 2,2-bis (4,4-bis (t-butylperoxy) cyclohexyl) propane

・ Ketone peroxide: Methyl ethyl ketone peroxide, cyclohexanone peroxide, acetylacetone peroxide, etc.

Among these organic peroxides, those having a 10-hour half-life decomposition temperature of 100 ° C. to 120 ° C. are preferable because the half-life decomposition temperature is compatible with the processing temperature. Specifically, dicumyl peroxide, , 5-Dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, bis (2-t-butylperoxyisopropyl) benzene, t-butyl Peroxybenzoate, 2,5-bis (bensoylperoxy) -2,5-dimethylhexane, t-butylperoxyacetate, 2,2-bis (t-butylperoxy) butane or n-butyl 4,4 -Bis (t-butylperoxy) valerate is preferred.
The organic peroxides may be used alone or in combination of two or more.

The amount of the organic peroxide (B) to be added is preferably 0.1 to 15 parts by mass, more preferably 0.2 to 10 parts by mass, based on 100 parts by mass of the polyorganosiloxane (A) component.
When the amount is within the above range, the crosslinking reaction proceeds sufficiently, and deterioration in physical properties such as a decrease in hardness of the silicone resin, insufficient rubber strength, and an increase in compression set are suppressed. In addition, it is economically preferable, and by suppressing the generation of decomposition products of the curing agent, deterioration in physical properties such as an increase in compression set and discoloration of the obtained silicone resin sheet are suppressed.

<Silica (C) having an average primary particle diameter of less than 12 nm>
Silica (C) having an average primary particle diameter of less than 12 nm (hereinafter, also simply referred to as silica particles (C)) in the present invention is intended to improve the hardness and mechanical strength of the obtained silicone resin, particularly to improve the tear strength. It is a component to be added.

In the present invention, by reducing the average primary particle diameter of the silica particles (C) to less than 12 nm, it is possible to suppress an increase in the amount of acoustic wave attenuation and to improve the tear strength of the silicone resin. I think that the.
That is, it is considered that cracks in the silicone resin due to mechanical stress are suppressed by the fine silica particles (C) functioning as stoppers. In particular, it is presumed that since the average primary particle diameter is small, the distance between the particles becomes small, so that it functions more as a stopper and the tear strength of the silicone resin is greatly improved.
It is also presumed that the use of a high-molecular-weight vinyl silicone will greatly improve the tear strength.

  The content of the silica particles (C) in the present invention in a total of 100 parts by mass of the polysiloxane mixture is preferably 0.1 to 30 parts by mass, more preferably 1 to 25 parts by mass, and further preferably 5 to 20 parts by mass. preferable.

  Examples of the silica particles (C) include fumed silica, calcined silica, precipitated silica, and vinyl group-containing silicone resin. As the silica particles (C), one type may be used alone, or two or more types may be used in combination.

  The average primary particle diameter of the silica particles (C) in the present invention is less than 12 nm, preferably more than 3 nm and less than 12 nm, more preferably less than 12 nm, from the viewpoint of suppressing an increase in the amount of acoustic wave attenuation of the silicone resin and improving the tear strength. Is more preferably less than 10 nm. Note that a smaller average primary particle diameter is preferable because the tear strength is higher and the acoustic wave sensitivity is better.

  The average primary particle diameter is described in a catalog of a silica particle manufacturer. However, those having no average primary particle diameter described in the catalog or newly manufactured particles can be determined by averaging the particle diameters measured by a transmission electron microscope (TEM). That is, the minor axis and major axis are measured for one particle in an electron micrograph taken by TEM, and the average value is determined as the particle diameter of one particle. In the present specification, the particle diameters of 300 or more particles are averaged and determined as an average primary particle diameter.

Silica particles (C) in the present invention, 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 (C) in the present invention are preferably silica particles whose surfaces are surface-treated. As the surface treatment, silica particles treated with a 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 preferable. The hydrolyzable group in the silane coupling agent is hydrolyzed by water to form a hydroxyl group, and the 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 obtained silicone resin Hardness and mechanical strength are improved. Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, and a halogen atom.
When the surface of the silica particles is hydrophobically modified, the affinity between the silica particles (C) and the polyorganosiloxane (A) becomes good, and the hardness and mechanical strength of the obtained silicone resin are improved. Therefore, it is preferable.

Examples of the silane coupling agent having a hydrophobic group as a functional group include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrisilane. Alkoxysilanes such as methoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; such as methyltrichlorosilane, dimethyldichlorosilane (DDS), trimethylchlorosilane, phenyltrichlorosilane Chlorosilane; hexamethyldisilazane (HMDS).
Examples of the silane coupling agent having a vinyl group as a functional group include, for example, methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, and vinyltriethoxy. Alkoxysilanes such as silane, vinyltrimethoxysilane and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane.

The silica particles (C) in the present invention are preferably silica particles treated with a silane compound, more preferably silica particles treated with a trialkylsilylation agent, and still more preferably silica particles treated with a trimethylsilylation agent.
Examples of the silane compound include the above-mentioned silane coupling agent and a silane coupling agent in which a functional group in the silane coupling agent is substituted with an alkyl group.
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. Can be

Examples of commercially available silane coupling agents include, for example, hexamethyldisilazane (HMDS) (trade name: HEXAMETHYLDISILAZANE (SIH6110.1), manufactured by Gelest).
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 surface of the silica particles is modified to be hydrophobic.

  Examples of commercially available silica particles (C) include, for example, Aerosil (registered trademark) R812 (average primary particle diameter 7 nm, HMDS surface treatment), and Aerosil (registered trademark), all of which are hydrophobic fumed silica manufactured by Nippon Aerosil Co., Ltd. ) R812S (average primary particle diameter 7 nm, HMDS surface treatment), Aerosil (registered trademark) RX300 (average primary particle diameter 7 nm, HMDS surface treatment), Aerosil (registered trademark) RX380S (average primary particle diameter 5 nm, HMDS surface treatment), Aerosil (registered trademark) R976S (average primary particle diameter 7 nm, DDS surface treatment) and Aerosil (registered trademark) 300 (average primary particle diameter 7 nm), both of which are hydrophilic fumed silica manufactured by Nippon Aerosil Co., Ltd. (Registered trademark) 300CF (average primary particle diameter 7nm), Aero Le (R) 380 (average primary particle diameter 7 nm) can be mentioned.

In the present invention, since the average primary particle diameter of the silica particles (C) is small and the gaps between the polyorganosiloxanes (A) are densely packed, the motion of the molecular chains of the polyorganosiloxane (A) is restricted. I have.
Further, since the radical curing reaction proceeds by the organic peroxide (B), the use of a polyorganosiloxane having a vinyl group is more excellent in mechanical strength than a polyorganosiloxane having no vinyl group in the molecule. It is preferable because a silicone resin can be obtained.
Among them, polyorganosiloxanes having a vinyl group at the terminal of the molecular chain are more preferable in view of the reactivity of the polyorganosiloxane (A) in a state where the molecular chain motion is restricted, and a high molecular weight vinyl group-containing polyorganosiloxane. Is more preferable in terms of mechanical strength and reactivity.

<Other materials>
The composition for an acoustic wave probe of the present invention comprises, in addition to polyorganosiloxane (A), organic peroxide (B) and silica (C) having an average primary particle diameter of less than 12 nm, a platinum catalyst for an 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 can be appropriately compounded.

− Curing retarder −
The curing retarder is used for delaying a radical addition reaction by an organic peroxide or an addition polymerization reaction by a platinum catalyst. For example, a low molecular weight vinylmethylsiloxane homopolymer (trade name: VMS-005, manufactured by Gelest) is used. No.
The curing speed, that is, the working time, can be adjusted by the content of the curing retarder.

<Method for producing composition for acoustic wave probe and silicone resin for acoustic wave probe>
The composition for an acoustic wave probe of the present invention can be prepared by a known method.
For example, it can be obtained by kneading the components constituting the composition for an acoustic wave probe using a kneader, a pressure kneader, a Banbury mixer (continuous kneader), a two-roll kneader, or the like.

From the viewpoint of obtaining a uniform composition for an acoustic wave probe, first, silica (C) having an average primary particle diameter of less than 12 nm is dispersed in polyorganosiloxane (A), and then organic peroxide (B) Is preferably added.
When the composition for an acoustic wave probe of the present invention contains other materials in addition to the polyorganosiloxane (A), the organic peroxide (B) and the silica particles (C), the polyorganosiloxane (A It is preferable to add the organic peroxide (B) after obtaining a mixture in which the silica particles (C) and other materials are dispersed.

The silicone resin for an acoustic wave probe of the present invention is obtained by adding an organic peroxide (B) to a polysiloxane mixture containing at least a polyorganosiloxane (A) and silica particles (C). After that, the composition can be manufactured by curing the composition for acoustic wave probes. In addition, each component can be kneaded by the method described above.
Specifically, for example, the composition for an acoustic wave probe of the present invention obtained by the above-described method is cured by heating at 50 to 180 ° C for 5 to 240 minutes, and optionally at 100 to 220 ° C. The silicone resin for an acoustic wave probe can be obtained by secondary crosslinking for up to 5 hours.
In particular, since the organic peroxide (B) is used in the present invention, the secondary crosslinking by reheating contributes to heat removal of the decomposition product of the organic peroxide (B) and stabilization of the properties of the silicone resin.

<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 an ultrasonic characteristic. However, the acoustic wave characteristic is not limited to the ultrasonic wave characteristic, but relates to an acoustic wave characteristic of an appropriate frequency selected according to a test object, measurement conditions, and the like.

[hardness]
For a silicone resin sheet having a thickness of 2 mm, a type A durometer hardness is measured using a rubber hardness meter (for example, “RH-201A” manufactured by Excel Co., Ltd.) according to JIS K6253-3 (2012).
If it is too soft, it may be deformed when used as a part of an acoustic wave probe. Therefore, the hardness is preferably 20 or more, and more preferably 30 or more. Note that a practical upper limit is 80 or less.

[Tensile test]
For a 1 mm thick silicone resin sheet, a dumbbell-shaped test piece is prepared according to JIS K6251 (2010), and the tensile strength at break and the tensile elongation at break (elongation) are measured.
The tensile breaking strength is preferably 1.0 MPa or more, more preferably 1.9 MPa or more, and the tensile breaking elongation is preferably 400% or more, more preferably 500% or more, and even more preferably 600% or more. As a practical upper limit, the tensile strength at break is 10 MPa or less, and the tensile elongation at break is 1500% or less.

[Tear strength test]
For a silicone resin sheet having a thickness of 2 mm, a trouser-type test piece is prepared according to JIS K6252 (2007), and the tear strength is measured.
The tear strength is preferably at least 20 N / cm, more preferably at least 30 N / cm. Note that a practical upper limit is 100 N / cm or less.

[Acoustic impedance]
The density at 25 ° C. of the silicone resin sheet having a thickness of 2 mm was measured by an electronic hydrometer (for example, “SD- manufactured by Alpha Mirage Co., Ltd.,” according to the density measurement method of Method A (underwater replacement method) described in JIS K7112 (1999)). 200L "). According to JIS Z2353 (2003), the sound velocity of the acoustic wave was measured at 25 ° C. using a sing-around type sound velocity measuring device (for example, “UVM-2” manufactured by Ultrasonics Industries, Ltd.), and the measured density and sound velocity were measured. The acoustic impedance is determined from the product of

[Acoustic wave (ultrasonic wave) attenuation, sensitivity]
A 5 MHz sine wave signal (one wave) output from an ultrasonic oscillator (for example, Function Generator “FG-350” manufactured by Iwatsu Keisoku Co., Ltd.) is input to an ultrasonic probe (for example, manufactured by Japan Probe Co., Ltd.). Then, an ultrasonic pulse wave having a center frequency of 5 MHz is generated from the ultrasonic probe in water. The magnitude of the amplitude before and after the generated ultrasonic wave passes through the silicone resin sheet having a thickness of 2 mm is measured by an ultrasonic receiver (for example, an oscilloscope “VP-5204A” manufactured by Matsushita Electric Industrial Co., Ltd.) using a water temperature of 25. The acoustic wave (ultrasonic) attenuation of each material is compared by measuring in an environment of ° C. and comparing the acoustic wave (ultrasonic) sensitivity.
Note that the acoustic wave (ultrasonic) sensitivity means that an acoustic wave (ultrasonic wave) generated by an ultrasonic oscillator with respect to a voltage peak value Vin of an input wave such as a rectangular wave or a spike wave having a half width of 50 nsec or less is a sheet. , And the voltage value obtained when the ultrasonic oscillator receives the acoustic wave (ultrasonic wave) reflected from the facing surface of the sheet is denoted by Vs, and is a numerical value given by the following formula.

    Acoustic wave (ultrasonic wave) sensitivity = 20 × Log (Vs / Vin)

  In the evaluation system of the present invention, the acoustic (ultrasonic) sensitivity is preferably -72 dB or more, more preferably -71 dB or more.

The composition for an acoustic wave probe of the present invention is useful for medical members, and can be preferably used for an acoustic wave probe and an acoustic wave measuring device. Note that 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 an 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. Material of acoustic matching layer, material of acoustic lens in photoacoustic wave measuring device and ultrasonic endoscope, and sound in ultrasonic probe provided with a capacitive micromachined ultrasonic transducer (cMUT) as an ultrasonic transducer array (cMUT: Capacitive Micromachined Ultrasonic Transducers) It can be suitably used for a lens material and the like.
The silicone resin for an acoustic wave probe of the present invention is specifically, for example, an ultrasonic diagnostic apparatus described in JP-A-2005-253751, JP-A-2003-169802, and JP-A-2013-202050. JP-A-2013-188465, JP-A-2013-180330, JP-A-2013-158435, and preferred for acoustic wave measurement devices such as the photoacoustic wave measurement device described in JP-A-2013-154139. Applied.

<< Acoustic wave 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. Note that the ultrasonic probe is a probe that particularly uses an ultrasonic wave as an acoustic wave in the acoustic wave probe. Therefore, the basic structure of the ultrasonic probe is directly 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 an ultrasonic wave and transmitting and receiving an ultrasonic beam. As shown in FIG. 1, the configuration of the ultrasonic probe 10 is such that an acoustic lens 1, an acoustic matching layer 2, a piezoelectric element layer 3, and a backing material 4 are provided in this order from the tip (the surface in contact with a living body as a subject). I have. In recent years, the transmitting ultrasonic vibrator (piezoelectric element) and the receiving ultrasonic vibrator (piezoelectric element) have been formed of different materials for the purpose of receiving high-order harmonics, and have a laminated structure. Has also been proposed.

<Piezoelectric element layer>
The piezoelectric element layer 3 is a portion that generates ultrasonic waves. Electrodes are attached to both sides of the piezoelectric element, and when a voltage is applied, the piezoelectric element repeatedly expands and contracts and expands to generate ultrasonic waves. .

As a material constituting the piezoelectric element, a quartz crystal, a single crystal such as LiNbO ₃ , LiTaO ₃ , KNbO ₃ , a thin film such as ZnO or AlN, or a sintered body such as a Pb (Zr, Ti) O ₃ system is polarized. So-called ceramic inorganic piezoelectric materials are widely used. Generally, piezoelectric ceramics such as PZT: lead zirconate titanate having high conversion efficiency are used.
In addition, a piezoelectric element that detects a reception wave on the high frequency side requires a wider bandwidth of sensitivity. For this reason, an organic piezoelectric material using an organic polymer material such as polyvinylidene fluoride (PVDF) has been used as a piezoelectric element suitable for high frequency and wide band.
Further, Japanese Patent Application Laid-Open No. 2011-071842 and the like use MEMS (Micro Electro Mechanical Systems) technology that exhibits excellent short pulse characteristics and wide band characteristics, is excellent in mass productivity, and provides an array structure with small characteristic variations. A cMUT is described.
In the present invention, any of the piezoelectric element materials 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 extra vibration, thereby contributing to the improvement of the distance resolution in an ultrasonic diagnostic image.

<Acoustic matching layer>
The acoustic matching layer 2 is provided to reduce the difference in acoustic impedance between the piezoelectric element layer 3 and the subject, and to transmit and receive ultrasonic waves efficiently.
The composition for an ultrasonic probe of the present invention has a small difference from the acoustic impedance of a living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec). Can be.

<Acoustic lens>
The acoustic lens 1 is provided to focus ultrasonic waves in the slice direction using refraction and improve resolution. In addition, the ultrasonic wave is brought into close contact with the living body, which is the subject, to match the ultrasonic wave with the acoustic impedance of the living body (1.4 to 1.7 × 10 ⁶ kg / m ² / sec), and the ultrasonic wave of the acoustic lens 1 itself. It is required that the amount of attenuation be small.
That is, as the material of the acoustic lens 1, if the sound speed is sufficiently lower 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 the human body, the transmission / reception sensitivity of the ultrasonic wave is improved.
The composition for an ultrasonic probe of the present invention can be preferably used also as an acoustic lens material.

  The operation of the ultrasonic probe 10 having such a configuration will be described. A voltage is applied to 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 subject. At the time of reception, the piezoelectric element layer 3 is vibrated by a reflected signal (echo signal) from the subject, 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 effect of improving sensitivity at an ultrasonic transmission frequency of about 5 MHz or more as a general medical ultrasonic transducer. Particularly at an ultrasonic transmission frequency of 10 MHz or more, a particularly remarkable sensitivity improvement effect can be expected.
Hereinafter, a device in which an acoustic lens obtained from the composition for an ultrasonic probe of the present invention particularly exerts a function on a conventional problem will be described in detail.
In addition, the composition for an ultrasonic probe of the present invention exhibits an excellent effect on devices other than those described below.

-Ultrasonic probe with cMUT (capacitive micromachined ultrasonic transducer)-
When the cMUT device described in JP-A-2006-157320, JP-A-2011-71842, or the like is used for a transducer array for ultrasonic diagnosis, the cMUT device is generally compared with a transducer using general piezoelectric ceramics (PZT). Typically, the sensitivity is reduced.
However, by using the acoustic lens obtained from the composition for an acoustic wave probe of the present invention, it is possible to compensate for the insufficient sensitivity of the cMUT. This allows the sensitivity of the cMUT to approach the performance of conventional transducers.
Since the cMUT device is manufactured by the MEMS technology, it is possible to provide a low-cost ultrasonic probe with higher productivity and lower cost than the piezoelectric ceramic probe to the market.

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

− Ultrasound endoscope −
The ultrasonic wave in the ultrasonic endoscope described in Japanese Patent Application Laid-Open No. 2008-311700, for example, has a problem that the signal line cable is longer than the body surface transducer due to its structure. is there. Further, it is said that there is no effective sensitivity improving means for this problem for the following reasons.

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

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

  Hereinafter, the present invention will be described in more detail based on embodiments using ultrasonic waves as acoustic waves. It should be noted that the present invention is not limited to ultrasonic waves, and an acoustic wave of an audible frequency may be used as long as an appropriate frequency is selected according to an object to be inspected, measurement conditions, and the like.

[Example 1]
82 parts by mass of vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V42", mass average molecular weight 72,000), fumed silica (manufactured by Nippon Aerosil Co., Ltd., "Aerosil (registered trademark) RX300", average primary particle size] 7 nm, hexamethyldisilazane (HMDS) surface treatment) 18 parts by mass were kneaded using a 6-inch double-roll kneader, and furthermore, 2,5-dimethyl-2,5-di- (t-butylpar) was kneaded. A molding compound was prepared by mixing 0.5 parts by mass of (oxy) hexane (“Perhexa 25B” manufactured by NOF CORPORATION) with a roll. This was press-molded at 165 ° C. for 10 minutes, and further subjected to secondary crosslinking at 200 ° C. for 2 hours to obtain silicone resin sheets having a thickness of 1 mm and 2 mm, respectively.

[Example 2]
Example 1 except that 18 parts by mass of fumed silica (Aerosil (registered trademark) R976S, manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 7 nm, dimethyldichlorosilane (DDS) surface treatment) was used as the silica particles. The same treatment was performed to obtain a predetermined silicone resin sheet.

[Example 3]
Except that 18 parts by mass of fumed silica ("Aerosil (registered trademark) 300" manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 7 nm, no surface treatment) was used as the silica particles, the same treatment as in Example 1 was carried out. A predetermined silicone resin sheet was obtained.

[Example 4]
The same treatment as in Example 1 was conducted except that 18 parts by mass of fumed silica ("Aerosil (registered trademark) RX380S", average primary particle diameter 5 nm, HDMS surface treatment, manufactured by Nippon Aerosil Co., Ltd.) was used as the silica particles. A predetermined silicone resin sheet was obtained.

[Example 5]
The same treatment as in Example 1 was carried out except that 82 parts by mass of polydimethylsiloxane containing no vinyl group (manufactured by Gelest, "DMS-T41", weight average molecular weight 60,000) was used as the polyorganosiloxane. A silicone resin sheet was obtained.

[Example 6]
The same treatment as in Example 1 was carried out except that 82 parts by mass of polydimethylsiloxane containing no vinyl group (manufactured by Gelest, "DMS-T46", mass average molecular weight 115,000) was used as the polyorganosiloxane. A silicone resin sheet was obtained.

[Example 7]
The same treatment as in Example 1 was carried out except that 82 parts by mass of polydimethylsiloxane containing no vinyl group (manufactured by Gelest, "DMS-T61", weight average molecular weight 230,000) was used as the polyorganosiloxane. A silicone resin sheet was obtained.

Example 8
The same treatment as in Example 1 was carried out except that 82 parts by mass of polydimethylsiloxane containing no vinyl group (manufactured by Gelest, "DMS-T63", weight average molecular weight 300,000) was used as the polyorganosiloxane. A silicone resin sheet was obtained.

[Example 9]
The same treatment as in Example 1 was carried out except that 82 parts by mass of polydimethylsiloxane containing no vinyl group (manufactured by Gelest, "DMS-T72", mass average molecular weight: 500,000) was used as the polyorganosiloxane. A silicone resin sheet was obtained.

[Example 10]
A silicone resin sheet treated in the same manner as in Example 1 except that 82 parts by mass of a vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V31", weight average molecular weight 28,000) was used as the polyorganosiloxane. I got

[Example 11]
A silicone resin sheet treated in the same manner as in Example 1 except that 82 parts by mass of a vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V35", weight average molecular weight 49,500) was used as the polyorganosiloxane. I got

[Example 12]
The same treatment as in Example 1 was carried out except that 82 parts by mass of vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V46", weight average molecular weight 117,000) was used as the polyorganosiloxane. I got

Example 13
Except that 82 parts by mass of vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V52", weight average molecular weight 155,000) was used as the polyorganosiloxane, the same silicone resin sheet as in Example 1 was used. I got

[Example 14]
88 parts by mass of vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V42", mass average molecular weight 72,000) as a polyorganosiloxane, and fumed silica (manufactured by Nippon Aerosil Co., Ltd., "Aerosil (registered trademark)" as silica particles. RX300 ", an average primary particle diameter of 7 nm, and hexamethyldisilazane (HMDS) surface treatment) except that 12 parts by mass were used, to thereby obtain a predetermined silicone resin sheet.

[Example 15]
76 parts by mass of vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V42", weight average molecular weight 72,000) as a polyorganosiloxane, and fumed silica (manufactured by Nippon Aerosil Co., Ltd., "Aerosil (registered trademark)" as silica particles. RX300 ", an average primary particle diameter of 7 nm, and hexamethyldisilazane (HMDS) surface treatment) except that 24 parts by mass were used, to thereby obtain a predetermined silicone resin sheet.

[Example 16]
Except that 0.5 parts by mass of dicumyl peroxide (manufactured by NOF CORPORATION, "Park Mill D") was used as the organic peroxide, the same treatment as in Example 1 was performed to obtain a predetermined silicone resin sheet.

[Example 17]
Except that 0.5 parts by mass of t-butyl peroxybenzoate (manufactured by NOF CORPORATION, "Perbutyl Z") was used as the organic peroxide, the same treatment as in Example 1 was performed to obtain a predetermined silicone resin sheet. Was.

[Comparative Example 1]
Except for using 18 parts by mass of fumed silica ("Aerosil (registered trademark) RX200", manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 12 nm, HMDS surface treatment) as silica particles, the same treatment as in Example 1 was carried out. A predetermined silicone resin sheet was obtained.

[Comparative Example 2]
100 parts by mass of a vinyl-terminated polydimethylsiloxane (manufactured by Gelest, "DMS-V42", weight average molecular weight 72,000) was used as the polyorganosiloxane, and an organic compound was prepared in the same manner as in Example 1 except that silica particles were not used. Thermal crosslinking with a peroxide was performed to obtain a predetermined silicone resin sheet.

[Comparative Example 3]
Except that 18 parts by mass of fumed silica (Aerosil (registered trademark) 200, manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 12 nm, no surface treatment) was used as the silica particles, the same treatment as in Example 1 was performed. A predetermined silicone resin sheet was obtained.

<Evaluation of mechanical strength and ultrasonic characteristics>
The following evaluation was performed about the silicone resin sheet of Examples 1-17 and Comparative Examples 1-3.

[hardness]
With respect to the obtained silicone resin sheet having a thickness of 2 mm, a type A durometer hardness was measured using a rubber hardness meter ("RH-201A" manufactured by Excel Co., Ltd.) in accordance with JIS K6253-3 (2012).

[Tensile test]
A dumbbell-shaped test piece was prepared from the obtained silicone resin sheet having a thickness of 1 mm in accordance with JIS K6251 (2010), and the tensile strength at break and the tensile strength at break were measured.

[Tear strength test]
With respect to the obtained silicone resin sheet having a thickness of 2 mm, a trouser-type test piece was prepared in accordance with JIS K6252 (2007), and the tear strength was measured.

[Acoustic impedance]
With respect to the obtained silicone resin sheet having a thickness of 2 mm, the density at 25 ° C. was measured by an electronic hydrometer (Alfa Mirage, “SD”) according to the density measurement method of Method A (underwater replacement method) described in JIS K7112 (1999). -200 L "). According to JIS Z2353 (2003), the ultrasonic sound velocity was measured at 25 ° C. using a sing-around type sound velocity measuring apparatus (“UVM-2”, manufactured by Ultrasonic Industrial Co., Ltd.), and the product of the measured density and sound velocity was used. The acoustic impedance was determined.

[Acoustic wave (ultrasonic wave) sensitivity]
A 5 MHz sine wave signal (one wave) output from an ultrasonic oscillator (Iwatsu Keisoku Co., Ltd., function generator "FG-350") is input to an ultrasonic probe (Japan Probe Co., Ltd.), and an ultrasonic wave is input. An ultrasonic pulse wave having a center frequency of 5 MHz was generated from water in the probe. The magnitude of the amplitude before and after the generated ultrasonic wave passes through the obtained silicone resin sheet having a thickness of 2 mm is measured by an ultrasonic receiver (manufactured by Matsushita Electric Industrial Co., Ltd., oscilloscope "VP-5204A"). The measurement was performed in an environment of 25 ° C., and the acoustic wave (ultrasonic) sensitivity was compared to compare the acoustic wave (ultrasonic) attenuation of each material.
The acoustic wave (ultrasonic) 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 The voltage value obtained when the reflected ultrasonic wave (ultrasonic wave) was received by the ultrasonic oscillator was defined as Vs, and the voltage was calculated by the following formula.

    Acoustic wave (ultrasonic wave) sensitivity = 20 × Log (Vs / Vin)

The obtained results are summarized in Tables 1 to 3 below.
In addition, in the following Tables 1 to 3, the type of each material is described as a trade name. The trade name of the silica particles (C) is abbreviated to Aerosil (registered trademark).

  As shown in Tables 1 to 3, the silicone resins for acoustic wave probes of Examples 1 to 17 all have high resin hardness, tensile breaking strength, and tensile strength while maintaining acoustic wave (ultrasonic) sensitivity of -72 dB or more. Elongation at break and tear strength could be obtained. On the other hand, all of the silicone resins for acoustic wave probes of Comparative Examples 1 to 3 did not have sufficient tear strength.

  From these results, the composition for an acoustic wave probe of the present invention is useful for medical members and can be suitably used for the method for producing a silicone resin of the present invention. Further, the silicone resin of the present invention can be suitably used for an acoustic lens and / or an acoustic matching layer of an acoustic wave probe, an acoustic wave measuring device and an ultrasonic diagnostic device. In particular, the composition for the acoustic wave probe and the silicone resin for the acoustic wave probe are intended to improve sensitivity in an ultrasonic probe, a photoacoustic wave measuring device, and an ultrasonic endoscope using the cMUT as a transducer array for ultrasonic diagnosis. It can be suitably used.

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

Claims (17)

  A composition for an acoustic probe containing at least a polysiloxane, an organic peroxide, and silica having an average primary particle diameter of less than 12 nm in a polysiloxane mixture (provided that zinc oxide powder, platinum powder, Excluding platinum oxide powder and ytterbium oxide powder).   The composition for an acoustic wave probe according to claim 1, wherein the polysiloxane mixture contains 0.1 to 30 parts by mass of silica having an average primary particle diameter of less than 12 nm in 100 parts by mass in total.   3. The composition for an acoustic wave probe according to claim 1, wherein the polysiloxane is a vinyl group-containing polysiloxane.   The composition for an acoustic wave probe according to any one of claims 1 to 3, wherein the silica having an average primary particle diameter of less than 12 nm has been surface-treated with a silane compound.   The composition for an acoustic wave probe according to any one of claims 1 to 4, wherein the silica having an average primary particle diameter of less than 12 nm has been surface-treated with a trimethylsilylating agent.   The composition for an acoustic probe according to any one of claims 1 to 5, wherein the polysiloxane has a mass average molecular weight of 20,000 to 1,000,000.   The composition for an acoustic wave probe according to any one of claims 1 to 6, wherein the polysiloxane has a mass average molecular weight of 40,000 to 300,000. The composition for acoustic wave probes, wherein the following acoustic wave (ultrasonic) sensitivity of the silicone resin sheet having a thickness of 2 mm obtained with the composition for acoustic wave probes is -72 dB or more. Item 2. The composition for an acoustic wave probe according to Item 1.
[Acoustic wave (ultrasonic wave) sensitivity]
An acoustic wave (ultrasonic wave) generated with respect to the voltage peak value Vin of the input wave passes through the sheet, and is obtained when the ultrasonic oscillator receives an acoustic wave (ultrasonic wave) reflected from the opposite surface of the sheet. The voltage value is Vs, and is a numerical value given by acoustic wave (ultrasonic wave) sensitivity = 20 × Log (Vs / Vin). The composition for an acoustic wave probe according to any one of claims 1 to 8, wherein the average primary particle diameter of the silica is more than 3 nm and less than 12 nm. A silicone resin for an acoustic wave probe obtained by curing the composition for an acoustic wave probe according to any one of claims 1 to 9 . An acoustic wave probe having an acoustic lens and / or an acoustic matching layer made of the silicone resin for an acoustic wave probe according to claim 10 . An ultrasonic probe comprising: a capacitive micromachined ultrasonic transducer as an ultrasonic transducer array; and an acoustic lens made of the silicone resin for an acoustic wave probe according to claim 10 . An acoustic wave measuring device comprising the acoustic wave probe according to claim 11 . An ultrasonic diagnostic apparatus comprising the acoustic wave probe according to claim 11 . A photoacoustic wave measuring apparatus comprising an acoustic lens made of the silicone resin for an acoustic wave probe according to claim 10 . An ultrasonic endoscope comprising an acoustic lens made of the silicone resin for an acoustic wave probe according to claim 10 . It is a manufacturing method of the silicone resin for acoustic wave probes according to claim 10 ,
After adding an organic peroxide to a polysiloxane mixture containing at least polysiloxane and silica having an average primary particle diameter of less than 12 nm to form an acoustic wave probe composition, the acoustic wave curing the acoustic wave probe composition Method for producing silicone resin for probe.

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