JP2020048794A - Composition for acoustic wave probe, acoustic lens using this composition, acoustic wave probe, acoustic wave measuring device, ultrasonic diagnostic device, photoacoustic wave measuring device, and ultrasonic endoscope - Google Patents

Abstract

To provide a composition for an acoustic wave probe capable of achieving provision of an acoustic wave probe in which a temporal increase in an acoustic wave attenuation amount is suppressed, an acoustic lens using the composition as a component, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope.SOLUTION: There is provided a composition for an acoustic wave probe containing a polymer including a structural unit having a polysiloxane bond and a structural unit having at least one kind of specific bond or structure, and at least one kind of antioxidizing agent and photostabilizer, an acoustic lens using the composition as a component, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, an ultrasonic endoscope, and a method for manufacturing the acoustic lens.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an acoustic wave probe composition, an acoustic lens using the composition, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope.

  In the acoustic wave measuring device, an acoustic wave probe that irradiates an acoustic wave to a subject or a part (hereinafter, also simply referred to as an object), receives a 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 subject is visualized and observed.

As the acoustic wave, one having an appropriate frequency, such as an ultrasonic wave and a photoacoustic wave, is selected according to a test object and / or measurement conditions.
For example, an ultrasonic diagnostic apparatus transmits an ultrasonic wave toward the inside of a subject, receives an ultrasonic wave reflected by a tissue inside the subject, and displays the image as an image. The photoacoustic wave measuring device receives an acoustic wave radiated from the inside of a test subject by a 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. (Typically, ultrasonic waves).
Since the acoustic wave measurement device transmits and receives acoustic waves to and from a living body to be examined, it is necessary to match acoustic impedance with a living body (typically, a human body) and reduce acoustic wave attenuation. It is required to satisfy.

  For example, a probe for an ultrasonic diagnostic apparatus (also referred to as an ultrasonic probe), which is one type of an 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 oscillated 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 waves are reflected on the surface of the living body, so that the ultrasonic waves are not efficiently input into the living body. Therefore, it is difficult to obtain good resolution. 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. Further, the acoustic wave probe is required to have sufficient mechanical strength in addition to the acoustic characteristics described above. That is, since the acoustic wave probe is used by rubbing it against a living body and sometimes pressing it, the mechanical strength (for example, hardness and tear strength) of the acoustic lens directly affects the product life of the acoustic wave probe.

Silicone resin or rubber (hereinafter, also referred to as “silicone resin or the like” as a combination of silicone resin and rubber) is the acoustic impedance of a living body (1.40 to 1.70 × 10 ⁶ kg / m ² / sec for a human body). ) And a small amount of ultrasonic attenuation, it has been conventionally used as one of the materials for acoustic lenses. By including an inorganic filler (also referred to as an inorganic filler) in the silicone resin or the like, the specific gravity of the silicone resin or the like can be increased, and the acoustic impedance of the silicone resin or the like can be made closer to that of a living body.

  Patent Document 1 describes an acoustic wave probe resin material containing a polymer having a structural unit having a polysiloxane bond and at least one of an acryloyloxy structural unit, an acrylamide structural unit, and a styrene structural unit. ing. Patent Document 1 discloses that the acoustic impedance is close to the value of a living body, the acoustic wave attenuation is reduced even at high frequencies, and excellent hardness is obtained from the acoustic wave probe resin material without using an inorganic filler. It is described that a resin sheet having the same can be obtained.

International Publication No. WO 2018/061991

  The present inventors have studied and found that the resin sheet for a probe described in Patent Literature 1 satisfies desired acoustic characteristics and exhibits excellent hardness. In some cases, it was found that there is room for improvement in suppressing the increase in acoustic wave attenuation over time. This phenomenon has not been observed in a conventional silicone resin containing an inorganic filler. From the viewpoint of ensuring long-term quality and diagnostic performance of the acoustic wave probe, it is desired that the acoustic wave probe has a long life. Since an increase in the amount of acoustic wave attenuation during storage affects the service life of the acoustic wave probe, it is required to suppress an increase in the amount of acoustic wave attenuation over time.

Therefore, an object of the present invention is to provide a composition for an acoustic wave probe that can provide an acoustic wave probe in which an increase in acoustic wave attenuation over time is suppressed.
Further, the present invention provides an acoustic lens, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope in which an increase in acoustic wave attenuation over time is suppressed. That is the task.

In view of the above problems, the present inventors have made intensive studies on the probe resin described in Patent Document 1, and as a result, the polymer has a structural unit having a polysiloxane bond and a structural unit having a specific structural portion. It has been found that a composition is prepared by combining the polymer with at least one additive of an antioxidant and a light stabilizer, and that the above-mentioned problem can be solved by using this composition.
The present invention has been further studied based on these findings, and has been completed.

式中、Ｒ^１〜Ｒ^６は各々独立に、水素原子又は１価の有機基を示し、Ｌ^１は２価の連結基を示し、ｎ１は３〜１０,０００である。

式中、Ｒ^７及びＲａは各々独立に、水素原子又は１価の有機基を示す。

式中、Ｒ^８、Ｒｂ^１及びＲｂ^２は各々独立に、水素原子又は１価の有機基を示す。

式中、Ｒ^９及びＲｃ^１〜Ｒｃ^５は各々独立に、水素原子又は１価の有機基を示す。 The above problem has been solved by the following means.
[1]
(A1) a polymer containing a structural unit having a polysiloxane bond and (a2) a polymer having a structural unit having at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from an aromatic vinyl; A composition for an acoustic wave probe, comprising a light stabilizer and at least one additive (B).
[2]
The composition for an acoustic wave probe according to [1], wherein the additive (B) has an SP value of 7 to 10 (cal / cm ³ ) ^1/2 .
[3]
The composition for an acoustic probe according to [1], wherein the additive (B) is incorporated as a copolymer component in the polymer.
[4]
The composition for an acoustic wave probe according to any one of [1] to [3], wherein the additive (B) has a saturated aliphatic hydrocarbon group having 4 or more carbon atoms.
[5]
The composition for an acoustic wave probe according to any one of [1] to [4], wherein the structural unit (a2) has at least one of an acryloyloxy structural unit, an acrylamide structural unit, and a styrene structural unit.
[6]
The structural unit of (a1) is represented by the following formula (1), the acryloyloxy structural unit is represented by the following formula (2), the acrylamide structural unit is represented by the following formula (3), and the styrene structural unit is Is represented by the following formula (4): The composition for an acoustic wave probe according to [5].

In the formula, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a monovalent organic group, L ¹ represents a divalent linking group, and n 1 is 3 to 10,000.

In the formula, R ⁷ and Ra each independently represent a hydrogen atom or a monovalent organic group.

In the formula, R ⁸ , Rb ¹ and Rb ² each independently represent a hydrogen atom or a monovalent organic group.

In the formula, R ⁹ and Rc ^{1 to} Rc ⁵ each independently represent a hydrogen atom or a monovalent organic group.

[7]
The composition for an acoustic wave probe according to [5] or [6], wherein the structural unit (a2) has at least one of the acryloyloxy structural unit and the styrene structural unit.
[8]
The composition for an acoustic wave probe according to any one of [1] to [7], wherein the polymer contains a fluorine atom.
[9]
The composition for an acoustic wave probe according to [8], wherein the structural unit (a2) contains 5 or more fluorine atoms per structural unit.
[10]
An acoustic lens using the composition for an acoustic wave probe according to any one of [1] to [9].
[11]
An acoustic wave probe having the acoustic lens according to [10].
[12]
An acoustic wave measuring device comprising the acoustic wave probe according to [11].
[13]
An ultrasonic diagnostic apparatus comprising the acoustic probe according to [11].
[14]
A photoacoustic wave measurement device including the acoustic lens according to [10].
[15]
An ultrasonic endoscope comprising the acoustic lens according to [10].

In this specification, unless otherwise specified, when there are a plurality of substituents, linking groups, structural units, and the like (hereinafter, referred to as substituents) represented by a specific code or formula, or when a plurality of Alternatively, when they are alternatively specified, the respective substituents and the like may be the same or different from each other. This holds true for the definition of the number of substituents and the like.
In the present specification, the “group” of each group described as an example of each substituent is used to mean both an unsubstituted form and a form having a substituent. For example, “alkyl group” means an alkyl group which may have a substituent. Further, when the number of carbon atoms of the group is limited, the number of carbon atoms of the group means the total number of carbon atoms including the substituent unless otherwise specified.
In the present invention, the term “compound” is used to include not only the compound itself but also its salt and its ion. Also, it is meant to include a structure in which a part of the structure is changed, as long as the effects of the present invention are not impaired. Further, a compound that is not specified to be substituted or unsubstituted may have any substituent within a range that does not impair the effects of the present invention. This is the same for the substituent and the linking group.
In this specification, the term “acryl or acryloyl” broadly refers to a group of structures having an acryloyl group, and includes a structure having a substituent (eg, an alkyl group) at the α-position.
In this specification, the term “styrene structural unit” broadly refers to a group of structures having a styrene structure, and includes a structure having a substituent (eg, an alkyl group) at the α-position and a substituent (eg, a halogen atom, an alkyl group) on the benzene ring. Group).
In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” 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) of gel permeation chromatography (GPC) unless otherwise specified.
Specifically, the mass average molecular weight is determined by preparing a PC device HLC-8220 (manufactured by Tosoh Corporation), using tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) as an eluent, and using TSKgel (registered trademark) G3000HXL + TSKgel (registered trademark) as a column. ) It can be measured using G2000HXL at a temperature of 23 ° C. and a flow rate of 1 mL / min using an RI detector.

The composition for an acoustic wave probe of the present invention can provide a molded article in which the increase in acoustic wave attenuation over time is sufficiently suppressed by molding the composition. To provide an acoustic lens, an acoustic wave probe, an acoustic wave measuring device, an ultrasonic diagnostic device, a photoacoustic wave measuring device, and an ultrasonic endoscope in which an increase in acoustic wave attenuation over time is sufficiently suppressed. Is possible.
Further, the acoustic lens, the acoustic wave probe, the acoustic wave measuring device, the ultrasonic diagnostic device, the photoacoustic wave measuring device, and the ultrasonic endoscope of the present invention are members formed using the composition for an acoustic wave probe of the present invention. And the time-dependent increase in the amount of acoustic wave attenuation is sufficiently suppressed.

FIG. 1 is a perspective transmission diagram illustrating an example of a convex ultrasonic probe which is an embodiment 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”) comprises (a1) a structural unit having a polysiloxane bond, and (a2) an ester bond, an amide bond, a urethane bond, a urea bond, A polymer containing a structural unit having at least one kind of a structure derived from an aromatic vinyl (hereinafter, also referred to as “polymer (A)”), and at least one kind of additive (B) of an antioxidant and a light stabilizer (Hereinafter also referred to as “additive (B)”).
In the description of the present invention, the structure derived from vinyl aromatic ring means a component of a polymer formed by addition polymerization of a vinyl group of a vinyl aromatic compound.
Hereinafter, (a1) the structural unit having a polysiloxane bond is also simply referred to as “structural unit (a1)”. Further, (a2) a structural unit having at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from aromatic vinyl is also simply referred to as “structural unit (a2)”. (A2) does not have a structural unit having a polysiloxane bond.
The “ester bond, amide bond, urethane bond and urea bond” may be included in a monovalent group.

  The specific structure of the polymer (A) is not particularly limited, and includes a random, block, or graft polymer.

The composition for an acoustic wave probe of the present invention is preferably in the form of a composition in which the polymer (A) and the additive (B) are homogeneously mixed.
The composition for an acoustic wave probe of the present invention may be in a form having fluidity when mixed with a solvent or the like, or may be in the form of pellets formed into a predetermined shape.
The composition for an acoustic wave probe of the present invention can be molded into a desired acoustic characteristic such that the acoustic impedance is close to the value of a living body and the amount of acoustic wave attenuation (particularly, the amount of acoustic wave attenuation at high frequencies) is reduced. It is possible to obtain a molded article having mechanical properties (hardness and the like) and suppressing an increase in acoustic wave attenuation over time. Therefore, it can be suitably used for forming members constituting the acoustic wave probe.
The polymer (A) used in the present invention has (a1) a structural unit having a polysiloxane bond and (a2) at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from an aromatic ring vinyl. And structural units. The formed article formed from the composition of the present invention has a certain density even without containing an inorganic filler, and can bring the acoustic impedance close to the value of a living body. As a result, the amount of acoustic wave attenuation can be suppressed. Further, the structural unit (a2) is a structure having a high elastic modulus, and can increase the hardness of the formed product. Further, an element or a structure having a high specific gravity can be introduced into the structural unit (a2), and the acoustic impedance can be appropriately adjusted so as to be closer to a living body.

The polymer (A) may have at least one of an ester bond, an amide bond, a urethane bond, and a urea bond in any of the main chain and the side chain. When the ester bond and the amide bond are located on the side chain rather than on the main chain of the polymer, the molecular mobility decreases and the initial acoustic wave attenuation is easily reduced. , An ester bond and an amide bond.
When the urethane bond and the urea bond are located on the main chain rather than on the side chains of the polymer, the interaction between the main chains becomes stronger and the mechanical strength is improved. Therefore, the polymer (A) has It preferably has at least one of a urethane bond and a urea bond.
The polymer (A) may have a polysiloxane bond in either the main chain or the side chain. For example, the polymer (A) can be appropriately selected in relation to the structural unit (a2). Is preferred.

  Here, “main chain” means that, among all molecular chains in the polymer (A), all molecular chains other than the main chain (long molecular chains and / or short molecular chains) can be regarded as pendants to the main chain. It means a linear molecular chain. Typically, the longest chain among the molecular chains constituting the polymer (A) is the main chain.

((A1) Structural unit having polysiloxane bond)
In the polymer (A) used in the present invention, the structural unit (a1) is not particularly limited as long as it has a polysiloxane bond. The structural unit (a1) is preferably a structural unit represented by the following formula (1).
In the description of the present invention, when the structural unit having a polysiloxane bond has a structure derived from an ester bond, an amide bond, a urethane bond, a urea bond, or an aromatic vinyl, not the structural unit (a2), It is classified into structural units (a1).

In the formula, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a monovalent organic group, L ¹ represents a divalent linking group, and n 1 represents an average number of repetitions (may be a decimal number). 3 to 10,000, more preferably 10 to 500, and particularly preferably 50 to 300. This is because when n1 is within the above range, the mobility for acoustic waves is low, or the compatibility with hard segments is high, so that phase separation can be suppressed and the amount of acoustic wave attenuation can be further reduced.
The average number of repetitions can be calculated by, for example, NMR (Nuclear Magnetic Resonance) measurement or the like.

Examples of the monovalent organic group represented by R ^{1 to} R ⁶ include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an alkylthio group, and an arylthio group. , Heteroarylthio, alkylamino, arylamino, heteroarylamino, alkyloxycarbonyl, aryloxycarbonyl, heteroaryloxycarbonyl, alkylaminocarbonyl, arylaminocarbonyl, heteroarylaminocarbonyl And a halogen group, and any one of an alkyl group, a cycloalkyl group, an alkenyl group, and an aryl group is preferable. The details are described below.
The alkyl group represented by R ^{1 to} R ⁶ preferably has 1 to 10 carbon atoms, more preferably 1 to 4, more preferably 1 or 2, and particularly preferably 1. The alkyl group represented by R ⁶ preferably has 1 to 10 carbon atoms, more preferably has 1 to 8 carbon atoms, and particularly preferably has 1 to 4 carbon atoms. 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 represented by R ^{1 to} R ⁶ 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. Cycloalkyl groups include, for example, cyclopropyl, cyclopentyl and cyclohexyl.
The carbon number of the alkenyl group represented by R ^{1 to} R ⁵ is preferably 2 to 10, more preferably 2 to 4, and still more preferably 2. Alkenyl groups include, for example, vinyl, allyl and butenyl.
The aryl group represented by R ^{1 to} R ⁶ preferably has 6 to 12 carbon atoms, more preferably has 6 to 10 carbon atoms, and still more preferably has 6 to 8 carbon atoms. Aryl groups include, for example, phenyl, tolyl and naphthyl.
The heteroaryl group represented by R ^{1 to} R ⁶ is a 5- or 6-membered heteroaryl group having a hetero atom (preferably at least one of an oxygen atom, a sulfur atom and a nitrogen atom) as a ring-constituting atom. Is preferred. The heteroaryl group may be condensed, and the condensed ring is preferably a benzene ring or an alicyclic ring. The number of carbon atoms constituting the heteroaryl group is preferably from 2 to 20, and more preferably from 2 to 12. Heteroaryl groups include, for example, thienyl, pyridyl and indolyl.
Alkyl group represented by R ¹ to R ^6, cycloalkyl group, a description of the aryl group and heteroaryl group, represented by R ¹ to R ^6, alkyl group, cycloalkyl group, aryl group and heteroaryl group It can be applied as a description of an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group (for example, an alkyl group in an alkoxy group and an aryl group in an aryloxy group) which constitute a group having any of them.

These alkyl group, cycloalkyl group, alkenyl group and aryl group may have a substituent. Such a substituent includes, for example, a halogen atom (eg, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, Arylthio, silyl and cyano groups.
Examples of the group having a substituent include an alkyl group having a fluorine atom.

R ^{1 to} R ⁶ are preferably an alkyl group, an alkenyl group or an aryl group, and more preferably an alkyl group having 1 to 4 carbon atoms. R ^{1 to} R ⁵ are particularly preferably a methyl group from the viewpoint of reduction of acoustic wave attenuation, and R ⁶ is particularly preferably a butyl group.

The divalent linking group for L ¹ is not particularly limited as long as the effects of the present invention are not impaired, but a single bond, an ester group (ester bond), or an alkylene group (having preferably 1 to 12 carbon atoms, and 1 to 8 carbon atoms) Is more preferable, 1 to 6 is more preferable, and 1 to 3 is particularly preferable.Specific examples include methylene, ethylene, n-propylene, isopropylene, n-butylene, t-butylene and n-octylene. ), An arylene group (the number of carbon atoms is preferably 6 to 18, more preferably 6 to 14, and particularly preferably 6 to 12. Specific examples include phenylene, tolylene and naphthylene.), Oxyalkylene Group (The number of carbon atoms is preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, and particularly preferably 1 to 3. Specifically, for example, Oxymethylene, oxyethylene, oxypropylene, and oxydimethylethylene are listed.) And an oxyarylene group (the carbon number is preferably 6 to 18, more preferably 6 to 14, and particularly preferably 6 to 12). Specific examples include oxyphenylene, oxytolylene, and oxynaphthylene.), And combinations thereof, and any one of an ester group, an alkylene group, an oxyalkylene group, and a combination thereof is preferable. As a specific example of the above combination, "-carbonyloxy-alkylene group-" can be mentioned.
The oxyalkylene group and oxyarylene group may be bonded to adjacent Si on any side, and preferably bonded to adjacent Si by an alkylene group and an arylene group. The alkylene group or the arylene group bonded to the adjacent Si is preferably any one of an ethylene group, a propylene group, and a phenylene group. Further, the above-mentioned “-carbonyloxy-alkylene group-” is preferably bonded to adjacent Si by an alkylene group.

((A2) a structural unit having at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from an aromatic vinyl)
The polymer (A) has, in addition to the structural unit (a1), a structural unit (a2) having at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from an aromatic ring vinyl. The structural unit (a2) preferably has at least one of (a21) an acryloyloxy structural unit, (a22) an acrylamide structural unit, and (a23) a styrene structural unit, from the viewpoint of acoustic wave sensitivity. That is, in the polymer (A), at least a part of the structural units (a2) present in the polymer (A) is (a21) an acryloyloxy structural unit, (a22) an acrylamide structural unit, or (a23) a styrene structural unit. Preferably, there is.

  When the polymer (A) has an acroyloxy structural unit as the structural unit (a2), the dipole interaction between the ester bonds in the acroyloxy structure increases the interaction between the polymers and increases the hardness. Further, by improving the copolymerizability of the structural unit (a1) and the structural unit (a2), the compatibility between the structural unit (a1) and the acroyloxy structural unit is further improved, and the initial acoustic wave attenuation Can be further suppressed.

  When the polymer (A) has an acrylamide structural unit as the structural unit (a2), the structural unit (a2) has a higher elastic modulus. Due to the high elasticity, the ultrasonic response is reduced, and the initial acoustic wave attenuation can be further suppressed. In this respect, the structural unit (a2) is preferably (a22) an acrylamide structural unit.

  When the polymer (A) has a styrene structural unit as the structural unit (a2), the structural unit (a2) has a nonpolar structure. Therefore, the compatibility between the structural unit (a2) and the structural unit (a1) is increased, and the initial acoustic wave attenuation can be further suppressed. In this respect, the structural unit (a2) is preferably (a23) a styrene structural unit.

Among the (a21) acryloyloxy structural units, (a22) acrylamide structural units and (a23) styrene structural units, the polymer (A) is excellent in suppressing the initial amount of acoustic wave attenuation. It preferably has at least one of a unit and (a23) a styrene structural unit.
Hereinafter, the (a21) acryloyloxy structural unit is also simply referred to as “structural unit (a21)”. The (a22) acrylamide structural unit is also simply referred to as “structural unit (a22)”. Further, the (a23) styrene structural unit is also simply referred to as “structural unit (a23)”.

((A21) acryloyloxy structural unit)
In the polymer (A) used in the present invention, the structural unit (a21) is preferably a structural unit represented by the following formula (2).

In the formula, R ⁷ and Ra each independently represent a hydrogen atom or a monovalent organic group.

Examples of the monovalent organic group represented by R ⁷ include the monovalent organic group represented by R ¹ in the above formula (1).
R ⁷ is preferably a hydrogen atom or an alkyl group.
The carbon number of the alkyl group in R ⁷ is preferably 1 to 10, more preferably 1 to 4, still more preferably 1 or 2, and particularly preferably 1. Examples of the alkyl group for R ⁷ include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl and n-decyl.

Specific examples of the monovalent organic group represented by Ra include the monovalent organic group represented by R ¹ in the above formula (1).
Ra is preferably a hydrogen atom, an alkyl group or an aryl group.
The number of carbon atoms of the alkyl group in Ra is preferably from 1 to 10, and more preferably from 1 to 6. Examples of the alkyl group for Ra include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl and n-decyl.
The carbon number of the aryl group in Ra is preferably from 6 to 12, more preferably from 6 to 10, further preferably from 6 to 8, and particularly preferably 6. The aryl group for Ra includes, for example, phenyl, tolyl and naphthyl.

The monovalent organic group represented by R ⁷ and Ra may have a substituent. Examples of such a substituent include a halogen atom (eg, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), an alkyl group, a cycloalkyl group, an alkenyl group (preferably a vinyl group), an aryl group, an alkoxy group, and an aryl group. Oxy groups, alkylthio groups, arylthio groups, silyl groups, cyano groups, epoxy groups, and ureido groups, and combinations thereof.
Among these substituents, a halogen atom is preferable, and a fluorine atom is more preferable, from the viewpoint of reducing acoustic wave attenuation and realizing an acoustic impedance closer to a biological value.
Examples of the group having a substituent include an alkylureidoalkyl group, an alkyl group having a fluorine atom (preferably, a perfluoroalkyl group), and an aryl group having a fluorine atom.

((A22) acrylamide structural unit)
In the polymer (A) used in the present invention, the structural unit (a22) is preferably a structural unit represented by the following formula (3).

In the formula, R ⁸ , Rb ¹ and Rb ² each independently represent a hydrogen atom or a monovalent organic group.

Specific examples of the monovalent organic group represented by R ⁸ include the monovalent organic group represented by R ¹ in the above formula (1).
R ⁸ is preferably a hydrogen atom or an alkyl group, and more preferably an alkyl group.
The carbon number of the alkyl group in R ⁸ is preferably 1 to 10, more preferably 1 to 4, still more preferably 1 or 2, and particularly preferably 1. Examples of the alkyl group for R ⁸ include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl and n-decyl.

The monovalent organic group represented by R ⁸ , Rb ¹ and Rb ² 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 an alkyl group having a fluorine atom and an aryl group having a fluorine atom (preferably, a perfluoroaryl group).

((A23) Styrene structural unit)
In the polymer (A) used in the present invention, the structural unit (a23) is preferably a structural unit represented by the following formula (4).

In the formula, R ⁹ and Rc ^{1 to} Rc ⁵ each independently represent a hydrogen atom, a halogen atom or a monovalent organic group.

Specific examples of the monovalent organic group represented by R ⁹ include the monovalent organic group represented by R ¹ in the above formula (1). R ⁹ is preferably a hydrogen atom.

Specific examples of the monovalent organic group represented by Rc ^{1 to} Rc ⁵ include a monovalent organic group represented by R ¹ in the above formula (1).
Rc ^{1 to} Rc ⁵ are preferably a hydrogen atom, a halogen atom or an alkyl group, more preferably a hydrogen atom or a halogen atom.
The carbon number of the alkyl group in Rc ^{1 to} Rc ⁵ is preferably 1 to 10, more preferably 1 to 4, still more preferably 1 or 2, and particularly preferably 1. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, n-octyl, 2-ethylhexyl and n-decyl.
As the halogen atom in R ⁹ and Rc ^{1 to} Rc ^{5, a} fluorine atom or a bromine atom is preferable, and a fluorine atom is more preferable.

The monovalent organic group represented by R ⁹ and Rc ^{1 to} Rc ⁵ 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 an alkyl group having a fluorine atom and an aryl group having a fluorine atom.

  In the polymer (A) used in the present invention, the structural unit (a1) is represented by the above formula (1), the structural unit (a21) is represented by the above formula (2), and the structural unit (a22) is represented by the above formula ( It is preferable that the structural unit (a23) is represented by the formula (4). Such a polymer (A) has a structure that is difficult to respond to an acoustic wave, has a good reduction in the amount of acoustic wave attenuation, and has a mechanical strength (hardness) because the polymer (A) has a rigid structure. Is increased.

  The specific structure of the polymer (A) is not particularly limited, and includes a random, block, or graft polymer.

The polymer (A) used in the present invention preferably contains a fluorine atom from the viewpoint of reducing the amount of acoustic wave attenuation and increasing the acoustic wave impedance, and more preferably the structural unit (a2) contains a fluorine atom. preferable. In order to further increase the density, it is more preferable that the structural unit (a2) contains 5 or more fluorine atoms per structural unit, and (a21) an acryloyloxy structural unit, (a22) an acrylamide structural unit, and (a23) It is particularly preferred that at least one of the styrene structural units contains 5 or more fluorine atoms per structural unit.
The content of fluorine atoms in the polymer (A) is preferably 1 to 100 mmol / g, more preferably 2 to 50 mmol / g, and still more preferably 3 to 20 mmol / g.
Here, the content of the fluorine atom in the polymer (A) can be calculated by analyzing the composition ratio in the polymer by NMR.
The content of fluorine atoms in the polymer (A) present in an acoustic lens or the like can also be measured by an analysis method such as NMR or elemental analysis.

Specific examples of the fluorine atom-containing structural unit (hereinafter, also referred to as “fluorine-containing structural unit”) that can be used as the structural unit (a2) include the following compounds.
Examples of the (a21) acryloyloxy structural unit containing a fluorine atom include pentafluorophenyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,2-trifluoropropyl methacrylate, and 2,2,3. 3,3-pentafluoropropyl methacrylate, 1H, 1H, 2H, 2H-nonafluorohexyl methacrylate, 2- (perfluorobutyl) ethyl methacrylate, 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 2- (per (Fluorooctyl) ethyl methacrylate, 3- (perfluorooctyl) -2-hydroxypropyl methacrylate, 2- (perfluorodecyl) ethyl methacrylate, 2- (perfluoro-3-methylbutyl) ethyl methacrylate, 3 (Perfluoro-3-methylbutyl) -2-hydroxypropyl methacrylate, 2- (perfluoro-5-methylhexyl) ethyl methacrylate, 3- (perfluoro-5-methylhexyl) -2-hydroxypropyl methacrylate, 2- ( Perfluoro-7-methyloctyl) ethyl methacrylate, 3- (perfluoro-7-methyloctyl) ethyl methacrylate, tetrafluoropropyl methacrylate, octafluoropentyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, hexadecafluorononyl methacrylate , 1- (trifluoromethyl) trifluoroethyl methacrylate, hexafluorobutyl methacrylate, pentafluorophenoxy methacrylate 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, pentafluorobenzyl methacrylate, methyl α-trifluoromethyl methacrylate, 2,2,2-trifluoroethyl acrylate, 2,2,3 , 3,3-Pentafluoropropyl acrylate, 2- (perfluorobutyl) ethyl acrylate, 3- (perfluorobutyl) -2-hydroxypropyl acrylate, 2- (perfluorohexyl) ethyl acrylate, 3- (perfluoro Hexyl) -2-hydroxypropyl acrylate, 2- (perfluorooctyl) ethyl acrylate, 3- (perfluorooctyl) -2-hydroxypropyl acrylate, 2- (perfluorodecyl) ethyl acrylate, 2- (perfluoro-3) -Methylbutyl) Butyl acrylate, 3- (perfluoro-3-methoxybutyl) -2-hydroxypropyl acrylate, 2- (perfluoro-5-methylhexyl) ethyl acrylate, 3- (perfluoro-5-methylhexyl) -2-hydroxy Examples include structural units derived from propyl acrylate, 2- (perfluoro-7-methyloctyl) -2-hydroxypropyl acrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, and dodecafluoroheptyl acrylate.
Examples of the fluorine atom-containing (a22) acrylamide structural unit include, for example, structures derived from N, N-bis (perfluoromethyl) acrylamide, N- (perfluoroisopropyl) acrylamide and N- (perfluorot-butyl) acrylamide Units.
Examples of the (a23) styrene structural unit containing a fluorine atom include structural units derived from p-fluorostyrene, pentafluorostyrene and 3,5-bis (trifluoromethyl) styrene.

  The type of the structural unit (a2) present in the polymer (A) may be one, or two or more. Further, the polymer (A) may have one type of the structural units (a21) to (a23), or may have two or more types.

  The polymer (A) used in the present invention preferably contains a high Tg structure (a structure having a high glass transition temperature (Tg)) in order to increase mechanical strength. When the polymer (A) has the above-mentioned fluorine-containing structural unit and high Tg structure, it is possible to effectively improve both acoustic characteristics and mechanical strength. The high Tg structure is a polymer structure. The structural unit of the polymer structure having a high Tg structure is preferably a homopolymer having a Tg of 60 ° C. or higher, more preferably 80 ° C. or higher, assuming a homopolymer composed of only the structural unit. . The upper limit of the Tg of this homopolymer is practically 200 ° C. or less. In calculating Tg, the degree of polymerization of the homopolymer assumed above is 300. Examples of the structural unit having a high Tg structure include a methacrylate ester structural unit, a styrene structural unit, a methacrylamide structural unit, a structural unit having an alicyclic structure, and a structural unit having an aromatic ring.

In the polymer (A), the proportion of the structural unit (a1) having a polysiloxane bond is preferably 20% by mass or more from the viewpoint that the acoustic impedance approaches the value of a living body and the amount of acoustic wave attenuation is reduced. 85 mass% is more preferable, and 40 to 60 mass% is still more preferable.
Further, in the polymer (A), the proportion of the structural unit (a2) is preferably 15 to 70% by mass, and is preferably 40 to 60% by mass from the viewpoint of imparting high hardness and bringing the acoustic impedance close to the value of a living body. % Is more preferable.
Here, the content of the structural unit (a1) and the content of the structural unit (a2) in the polymer (A) can be calculated, for example, from the charged amount (mass ratio) of the monomer at the time of synthesis.

When the structural unit (a1) is a structural unit having a polysiloxane bond in the main chain of the polymer (A), the weight average molecular weight of the structural unit (a1) is preferably 500 or more, more preferably 800 or more. preferable. The upper limit is not particularly limited, but is preferably 50,000 or less, more preferably 30,000 or less.
When the structural unit (a1) is a structural unit having a polysiloxane bond in a side chain of the polymer (A), the structural unit (a1) preferably has a weight average molecular weight of 3,000 or more, and 4,000 or more. More preferably, it is the above. The upper limit is not particularly limited, but is preferably 50,000 or less, more preferably 30,000 or less.
This is because when the mass average molecular weight of the structural unit (a1) is within the above range, the amount of acoustic wave attenuation can be more effectively reduced.
Here, the mass average molecular weight in the polymer (A) can be measured by, for example, NMR analysis of the polymer (A) or hydrolysis treatment of the polymer (A) and GPC measurement.

The acoustic impedance of the formed article formed by the composition for an acoustic wave probe of the present invention is preferably close to the value of a living body, and is preferably 1.3 Mrayls, that is, 1.30 × 10 ⁶ kg / m ² / s or more. more preferable, it is preferred that the density of the polymer (a) is 1.05 g / cm ³ or more, and more preferably 1.10 g / cm ³ or more. There is no particular limitation on the upper limit of the density is preferably at 1.90 g / cm ³ or less, more preferably 1.60 g / cm ³ or less.
Here, the value of the density is a value obtained by rounding off the third decimal place. The density of the polymer (A) can be measured, for example, by the method described below, or can be calculated from the density of each monomer.
The density of the polymer (A) at 25 ° C. is determined by an electronic hydrometer (trade name “SD-200L” manufactured by Alpha Mirage Co., Ltd.) according to the density measurement method of Method A (in-water substitution method) described in JIS K7112 (1999). ).

The polymer (A) used in the present invention preferably has a structural unit other than the structural unit (a1) and a structural unit other than the structural unit (a2) (hereinafter, referred to as “other structural units”).
Other structural units can be introduced without any particular limitation as long as the effects of the present invention are not impaired. Examples thereof include structural units having at least one of an imide bond and an ether bond.
The proportion of other structural units in the polymer (A) is preferably from 0 to 30% by mass, and more preferably from 0 to 20% by mass, from the viewpoint of reducing the amount of acoustic wave attenuation.

The polymer (A) used in the present invention can be synthesized by a conventional method. For example, a monomer capable of forming or forming the structural unit (a1) and a monomer capable of forming or forming the structural unit (a2) By a conventional method. As the polymerization reaction, anionic polymerization, cationic polymerization, radical polymerization, polyaddition, polycondensation and the like can be appropriately selected according to the structure of the target polymer (A). In addition, reaction conditions such as a reaction temperature, a reaction time, a solvent and a catalyst in each polymerization reaction, and purification conditions can be appropriately selected according to a conventional method.
The structural unit having a urethane bond is obtained, for example, from a polyaddition reaction between a diisocyanate compound and a diol compound. The structural unit having a urea bond is obtained by a polyaddition reaction between a diisocyanate compound and a diamine compound. The structural unit having an ester bond is obtained, for example, from a polycondensation reaction between a dicarboxylic acid compound and a diol compound. The structural unit having an amide bond is obtained, for example, from a polycondensation reaction between a dicarboxylic acid compound and a diamine compound. In these polyaddition or polycondensation reactions, by using any one of a diisocyanate compound, a diol compound, a diamine compound and a dicarboxylic acid compound having a polysiloxane bond, a polysiloxane bond and a urethane bond and a urea bond in the polymer main chain. (A) having an ester bond or an amide bond.
Further, for example, a vinyl compound such as an acrylic compound having a urethane bond or a urea bond, obtained by reacting an isocyanate group of a vinyl compound such as an acrylic compound having an isocyanate group with a hydroxy group of an alcohol compound or an amino group of an amine compound. Polymers having a structural unit having a urethane bond or a urea bond in a side chain and a polymer having a structural unit having a polysiloxane bond in a side chain (A) are obtained by chain-polymerizing a base compound with a vinyl compound having a polysiloxane bond in a side chain. ) Can be obtained.
Further, for example, a vinyl compound such as an acrylic compound having an ester bond or an amide bond obtained by reacting a carboxy group of a vinyl compound such as an acrylic compound having a carboxy group with a hydroxy group of an alcohol compound or an amino group of an amine compound. A polymer having a structural unit having an ester bond or an amide bond in a side chain and a polymer having a structural unit having a polysiloxane bond in a side chain (A) are obtained by chain-polymerizing a base compound with a vinyl compound having a polysiloxane bond in a side chain. ) Can be obtained.
Each of the above reactions may be performed alone, or may be performed in combination of two or more reactions.

  The composition of the present invention may contain one kind of the polymer (A), or may contain two or more kinds of the polymer (A).

(At least one additive (B) of an antioxidant and a light stabilizer)
The composition for an acoustic wave probe of the present invention contains at least one additive (B) of an antioxidant and a light stabilizer (hereinafter, also simply referred to as “additive (B)”). The composition for an acoustic wave probe of the present invention contains the polymer (A) having the specific structure described above in combination with the additive (B), so that the acoustic wave probe formed using this composition can be used over time. It is possible to make it difficult to cause a large increase in acoustic wave attenuation.
This additive (B) is at least one of an antioxidant and a light stabilizer, and is generally assumed to suppress the degradation of the polymer with time. However, as shown in the examples described below, the polymer (A) having a specific structure hardly causes a change with time in mechanical properties even when the additive (B) is not present. That is, it is considered that the polymer (A) alone is unlikely to deteriorate with time due to its structural characteristics. However, in a molded article (for example, a sheet) using the polymer (A), the acoustic wave attenuation increases with time, although the cause is not clear. The additive (B) has an effect of effectively suppressing an increase in acoustic wave attenuation in a molded article using the polymer (A). The reason for this is not clear, but the additive (B) does not suppress the decomposition of the polymer (A) by an antioxidant effect or the like, but rather, the acoustic wave attenuation through the physicochemical interaction with the polymer (A). It is presumed to be acting to suppress the increase in
The additive (B) used in the present invention may be a low molecular compound, an oligomer or a polymer.

When the additive (B) is an oligomer or a polymer, the oligomer or polymer (hereinafter, also collectively referred to as “polymer additive (Ib)”) has a structural part exhibiting an antioxidant action or a light stabilizing action. It has a structural unit (hereinafter, also referred to as “structural unit (Z)”).
The polymer additive (Ib) may have a structural unit other than the structural unit (Z) (hereinafter, referred to as other structural units). Other structural units are not particularly limited as long as they are copolymerizable with the structural unit (Z). The polymer additive (Ib) is preferably an aliphatic hydrocarbon polymer in which the polymer main chain is mainly formed by carbon-carbon bonds. Examples of the structural unit capable of forming such an aliphatic hydrocarbon polymer include a structural unit derived from a vinyl monomer. For example, a structural unit derived from a vinyl monomer having the structural unit (Z) and a (meth) acryloyl Polymers having at least one structural unit derived from a group-containing monomer, a styrene-based monomer, and acrylonitrile are exemplified. From the viewpoint of exhibiting high compatibility with the polymer (A), the other structural units are preferably the structural units (a1) or (a2) of the polymer (A).
Although the ratio of the structural unit (Z) in the polymer additive (Ib) is not particularly limited, it is preferably 1 to 100% by mass, more preferably 3 to 40% by mass, and still more preferably 5 to 20% by mass.
The mass average molecular weight (Mw) of the polymer additive (Ib) is preferably from 1,000 to 100,000, more preferably from 3,000 to 50,000, and still more preferably from 5,000 to 30,000.
Regarding the method of synthesizing the polymer additive (Ib), the description of the method for synthesizing the polymer (A) and the method for synthesizing the polymer (A) using the following additive (B) as a copolymer component may be applied as appropriate. it can.

Solubility parameters of the additive (B) (SP value) is 7-10 preferably (cal ^/ cm ³⁾ is ^1/2, 7 to 9 (cal ^/ cm ^{3) 1/2,} more preferably, 7 -8 (cal / cm ³ ) ^1/2 is more preferable. When the additive (B) has the above SP value, the compatibility with the polymer (A) having an SP value of about 7 to 10 (cal / cm ³ ) ^1/2 is high as described below, and the additive (B) ) Is more uniformly dispersed in the polymer (A), whereby the increase in acoustic wave attenuation over time can be more effectively suppressed.
The SP value of the additive (B), including the SP value described in the examples, is determined by the following method.

The SP value is a value obtained by the Okitsu method. The Okitsu method is one of the well-known methods for calculating the SP value in the art. 29, no. 6 (1993) pp. 249-259. Since the SP value of the polysiloxane bond structure in the structural unit of (a1) is about 7.4 (cal / cm ³ ) ^1/2 , the SP value of the polymer (A) is the same as that of the structural unit of (a2) and (a1). ) And (a2), but slightly varies from 7 to 10 (cal / cm ³ ) ^1/2 .
Therefore, the SP value of the additive (B) is preferably close to the SP value of the polymer (A). The difference between the SP value of the polymer (A) and the SP value of the additive (B) is preferably 3.0 (cal / cm ³ ) ^1/2 or less, and 2.5 (cal / cm ³ ) ^1/2 or less. And more preferably 1.8 (cal / cm ³ ) ^1/2 or less, particularly preferably 1.1 (cal / cm ³ ) ^1/2 or less, and 0.5 (cal / cm ³ ) ^1/2. The following are most preferred.

The additive (B) preferably has a saturated aliphatic hydrocarbon group having 4 or more carbon atoms. The number of carbon atoms of this saturated aliphatic hydrocarbon group is preferably 8 or more, more preferably 12 or more. The upper limit of the carbon number of the saturated aliphatic hydrocarbon group is preferably 30 or less, more preferably 20 or less. Since the additive (B) has a saturated aliphatic hydrocarbon group having a specific number of carbon atoms as described above, the additive (B) is uniformly dispersed in the polymer (A). Can be more effectively suppressed.
Here, the saturated aliphatic hydrocarbon group is a group formed only by a carbon atom and a hydrogen atom, and forms a bond (for example, -C-O-C-) via an atom other than a carbon atom. When it contains, it does not correspond to a saturated aliphatic hydrocarbon group.
The number of carbon atoms of the saturated aliphatic hydrocarbon group is calculated as follows. The carbon number of the saturated aliphatic hydrocarbon group described in the examples is also a value calculated by the following method.

The carbon number of the saturated aliphatic hydrocarbon group indicates the carbon number of the longest saturated aliphatic hydrocarbon chain in the molecular structure, and the saturated aliphatic hydrocarbon chain is a linked chain (alkylene group, alkane It may be a divalent or higher valent group such as an yl group) or a group (alkyl group) attached to the end of the molecular structure. When the saturated aliphatic hydrocarbon chain is a branched chain, the total is the total number of carbon atoms including the number of carbon atoms in the branched portion.
Taking the additive (B) used in the examples as an example, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate is used in 1,2,2,6,6-pentamethyl-4-piperidyl. Has an alkanetriyl group having 9 carbon atoms.
For the polymer additive (Ib), the carbon number of the saturated aliphatic hydrocarbon chain excluding the polymer main chain is calculated.

The fact that the additive (B) is incorporated into the polymer (A) by forming a chemical bond with the polymer (A) also improves the compatibility between the additive (B) and the polymer (A). This is preferable from the viewpoint of more effectively suppressing an increase in acoustic wave attenuation over time. The form in which the additive (B) is incorporated into the polymer (A) is not particularly limited as long as it depends on the chemical bond. Examples thereof include a form in which the additive (B) is incorporated as a copolymer component and a method in which a chemical bond is formed with the polymer during kneading. No. Above all, the additive (B) is incorporated as a copolymer component in the polymer (A), that is, the polymer (A) is a polymer (A) having the additive (B) as a copolymer component. Is preferred.
The reaction mechanism for forming the polymer (A) having the additive (B) as a copolymer component is not particularly limited, and chain polymerization (radical polymerization, anionic polymerization, cationic polymerization, ring-opening polymerization, and coordination polymerization) and sequential polymerization ( (Polyaddition and polycondensation), preferably chain polymerization, more preferably radical polymerization or cationic polymerization, and still more preferably radical polymerization. It is preferable to simultaneously react and copolymerize the additive (B) and the monomer component constituting the polymer (A), since the synthesis is easy.
The form of the polymer (A) containing the additive (B) as a copolymer component is not particularly limited, and may be any form such as random, block and graft as long as the effects of the present invention are not impaired. .

  Specific additives (B) include, for example, the following additives. Further, as the polymer additive (Ib), a polymer having a polymerizable additive as a structural unit among the following additives is also preferably exemplified. However, it is not limited to these. Further, when composites are sold as commodities, they may be used.

[Antioxidant]
(Radical chain inhibitor and radical scavenger)
As phenols, 4,4′-butylidenebis (6-tert-butyl-m-cresol), 2-tert-butyl-4,6-dimethylphenol, 2,5-bis ( 1,1,3,3-tetramethylbutyl) hydroquinone, butylhydroxytoluene, 2,5-di-tert-pentylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylphenol, Stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,6-di-tert-butyl-4-ethylphenol, 3,6-dihydroxybenzonorbornane, 3,5-di -Tert-butyl-4-hydroxybenzylphosphonate diethyl, 4,6-di-tert-butylbenzene -1,3-diol, 3- (3,5-di-tert-butyl-4-hydroxyphenyl) -N '-[3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanoyl] Propane hydrazide, galvinoxyl free radical, N, N '-(hexane-1,6-diyl) bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], 2,2'- Methylenebis (6-tert-butyl-4-ethylphenol), 2,2′-methylenebis [6- (1-methylcyclohexyl) -p-cresol], 2,2′-methylenebis (6-cyclohexyl-p-cresol) Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], bis (5-tert Butyl-4-hydroxy-2-methylphenyl) sulfide, 2,4,6-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) mesitylene, 2,2 ′, 6,6 ′ -Tetra-tert-butyl-4,4'-dihydroxybiphenyl, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4 , 6 (1H, 3H, 5H) -trione and bis [3- [3- (tert-butyl) -4-hydroxy-5-methylphenyl] propanoic acid] 2,4,8,10-tetraoxaspiro [5 .5] phenolic antioxidants such as undecane-3,9-diylbis (2-methylpropane-2,1-diyl) and the like;
As amines, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, N, N′-diphenyl-1,4-phenylenediamine, N, N′-di-sold by Tokyo Chemical Industry Co., Ltd. 2-naphthyl-1,4-phenylenediamine, N, N'-di-sec-butyl-1,4-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-1,4-phenylene Adecastab LA (trade name, hindered amine) such as amine-based antioxidants such as diamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N-phenyl-1-naphthylamine and 4-isopropylaminodiphenylamine LA-52, LA-57, LA-63P, LA-68, LA-72, LA-77Y, LA-7 of the series light stabilizer (manufactured by ADEKA) G, LA-81, LA-82, LA-87, and LA-402AF, like LA-502XP, and the like.
(Peroxide decomposer)
Phosphorus (such as zinc dialkyldithiophosphate and zinc diallyldithiophosphate) and sulfur (such as sulfurized fats and oils, dibenzyldisulfide and dicetylsulfide) and the like can be mentioned.
Of these, sulfur-based peroxide decomposers are preferred.
(Metal deactivator)
Examples of the hydrazine series include ADK STAB CDA (trade name, manufactured by ADEKA) series CDA-1, CDA-1M, CDA-6, and CDA-10.

[Light stabilizer]
(Light shielding agent)
Examples include carbon black, white carbon, dark pigments, titanium oxide and zinc oxide.
(UV absorber)
As benzotriazoles, 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -4- Methyl-6- (2-propenyl) phenol, 2- (3,5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (5-chloro-2-benzotriazolyl) -6-tert-butyl-p-cresol, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (3,5- Di-tert-amyl-2-hydroxyphenyl) benzotriazole, 2- (5-tert-butyl-2-hydroxyphenyl) ben Triazole, 2- [2-hydroxy-5- [2- (methacryloyloxy) ethyl] phenyl] -2H-benzotriazole, 2,2′-methylenebis [6- (benzotriazol-2-yl) -4-tert- Octylphenol]), etc.
Benzophenones include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone)
As triazines, 2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-n-octyloxyphenyl) -1,3,5-triazine, 2- (2,4-dihydroxy Phenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- (2,4-dihydroxyphenyl) -4,6-diphenyl-1,3,5-triazine, Ethylhexyl triazone, 2- (2-hydroxy-4-methoxyphenyl) -4,6-diphenyl-1,3,5-triazine, N, N ′, N ″ -tri (m-tolyl) -1,3,3 5-triazine-2,4,6-triamine) and the like.
Examples thereof include cyanoacrylates, oxanilides, salicylates, and formamidines.
Among these, a benzotriazole-based or benzophenone-based ultraviolet absorber is preferable.
(Other)
Quenchers (nickel-based) and the like can be mentioned.

  Among the above, the additive (B) is a radical chain inhibitor, a radical scavenger, a peroxide decomposer, a metal deactivator, and an ultraviolet absorber, since the additive (B) can further suppress an increase in the amount of acoustic wave attenuation over time. At least one of an agent and a quencher is preferable, and at least one of a radical chain inhibitor, a radical scavenger, a peroxide decomposer, a metal deactivator, and an ultraviolet absorber is more preferable.

The composition of the present invention may contain one type of additive (B), or may contain two or more types.
The content of the additive (B) in the composition of the present invention is preferably 0.001 to 15 parts by mass, more preferably 0.01 to 10 parts by mass, and more preferably 0.01 to 10 parts by mass, based on 100 parts by mass of the polymer (A). 0.1 to 10 parts by mass is more preferable, and 1 to 8 parts by mass is particularly preferable.
When the additive (B) is contained as a copolymer component in the polymer (A), the content of the additive (B) with respect to 100 parts by mass of the polymer (A) is such that the polymer (A) It is read as the blending amount of the additive (B) with respect to 100 parts by mass (specifically, the components constituting the structural units of (a1) and (a2)) of the components other than the additive (B).
When the additive (B) is the polymer additive (Ib), the content of the additive (B) with respect to 100 parts by mass of the polymer (A) is such that the polymer additive ( It is read as the amount of the structural unit derived from the agent in Ib).

(C) Other Components The composition for an acoustic wave probe of the present invention may contain, in addition to the polymer (A) and the additive (B), components other than these components as long as the effects of the present invention are not impaired. Good. For example, conventional additives or additional functions such as organosiloxanes such as vinyl silicone and hydrosilicone, fillers, catalysts, solvents, dispersants, pigments, dyes, antistatic agents, flame retardants, and thermal conductivity improvers are exhibited. The optional components described above can be appropriately blended.
In the composition of the present invention, the total content of the polymer (A) and the additive (B) is preferably from 80 to 100% by mass, and more preferably from 90 to 100% by mass.

<Production method of composition for acoustic wave probe>
The composition for an acoustic wave probe of the present invention can be obtained, for example, by mixing components constituting the composition for an acoustic wave probe. This mixing method is not particularly limited as long as each component can be uniformly mixed. For example, kneading can be performed using a stirrer or a kneader (a kneader, a pressure kneader, a Banbury mixer (continuous kneader), or a two-roll kneader). The same applies to the case where components other than the polymer (A) and the additive (B) are mixed, and the mixing order of each component is not particularly limited.

  The composition for an acoustic wave probe of the present invention obtained in this manner is, for example, formed into a desired shape by a forming method such as hot pressing, cutting and dicing into a desired thickness or shape as required. By doing so, a molded article (for example, a sheet) for an acoustic wave probe can be obtained. The hot pressing method is not particularly limited, and can be performed by a conventional method. For example, there is an embodiment in which an apparatus such as Mini Test Press-10 (trade name, manufactured by Toyo Seiki Co., Ltd.) is used and hot pressed at 50 to 200 ° C. for 1 to 10 minutes at a pressure of 5 to 30 MPa.

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

<< Acoustic wave probe >>
The configuration of the acoustic wave probe of the present invention will be described in more detail below 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 can be 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 the living body to be inspected). ing. 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, and electrodes are attached to both sides of the piezoelectric element. When a voltage is applied, the piezoelectric element repeatedly expands and contracts and expands, thereby generating ultrasonic waves. I do.

As a material constituting the piezoelectric element, quartz, a single crystal such as LiNbO ₃ , LiTaO ₃ and KNbO _3, a thin film such as ZnO and AlN, and a sintered body such as a Pb (Zr, Ti) O ₃ system were subjected to polarization treatment. 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 which exhibits excellent short pulse characteristics and wide band characteristics, is excellent in mass productivity, and can obtain 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 test subject, and to efficiently transmit and receive ultrasonic waves.

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 to be examined, and the ultrasonic wave is matched with the acoustic impedance of the living body (1.40 to 1.70 × 10 ⁶ kg / m ² / sec for the human body). It is required that the ultrasonic attenuation of itself is small.
That is, as the material of the acoustic lens 1, 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. Sensitivity improves.

  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 cause the piezoelectric element layer 3 to resonate, 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 test 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 acoustic wave 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 acoustic wave probe of the present invention particularly exerts a function on a conventional problem will be described in detail.
In addition, the composition for acoustic wave probes of the present invention exhibits excellent effects also 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.
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 measuring 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 the human body (especially after aging).
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 longer signal line cable than the body surface transducer due to its structure. It is an issue. 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, the installation space for the transducer is narrow, and it is difficult to install an amplifier circuit, an AD conversion IC, and the like at the tip of the transducer.
Secondly, it is difficult to apply a piezoelectric single crystal employed as a transducer in a body surface ultrasonic diagnostic apparatus 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 ultrasonic waves for endoscopes are generally probes having a transmission frequency of ultrasonic waves of 7 to 8 MHz or more, it is difficult to improve sensitivity 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. Room temperature means 25 ° C.

[Example]
(1) Synthesis of polymer (synthesis of polymer 1)
50 parts by mass of methacryl-modified silicone KF-2012 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd., weight average molecular weight 4,600), 50 parts by mass of methyl methacrylate, 100 parts by mass of propylene glycol-1-monomethyl ether-2-acetate On the other hand, under a nitrogen atmosphere at 80 ° C., 0.1 parts by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added and reacted for 2 hours. Thereafter, 0.1 parts by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was reacted at 80 ° C. for 2 hours. Further, 0.1 part by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added and reacted at 80 ° C. for 2 hours. By adding the obtained reaction solution to a mixed solvent of 1000 parts by mass of isopropyl alcohol and 200 parts by mass of methanol, a white solid was produced. The resulting white solid was washed with methanol and dried to obtain Polymer 1. In the following formula, the structure enclosed in parentheses is a repeating structure, and X represents a monovalent organic group.

(Synthesis of Polymers 2 to 6)
Polymers 2, 3, 5 and 6 were obtained in the same manner as in the synthesis of Polymer 1 except that methyl methacrylate was changed to the compounds described in column (a2) of Table 1 below.
Further, as a polymer constituent, 50 parts by mass of methacryl-modified silicone KF-2012 at one end, 45 parts by mass of methyl methacrylate, and 5 parts by mass of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate are used. Polymer 4 having 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate as a copolymer component was obtained in the same manner as in the synthesis of Polymer 1 except for the above.

(Synthesis of Polymer 7)
Both ends hydroxy-modified silicone KF-6000 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd.) 79 parts by mass, tetrahydrofuran 50 parts by mass and N-methylpyrrolidone 50 parts by mass, 4,4'-diphenylmethane diisocyanate 21 parts by mass, K- 0.1 parts by mass of KAT348 (trade name, bismuth carboxylate, manufactured by Kusumoto Kasei Co., Ltd.) was added and reacted at 80 ° C. for 1 hour. Thereafter, a white solid was produced by adding the reaction solution to 500 parts by mass of methanol. The resulting white solid was washed with water, washed with methanol, and dried to obtain Polymer 7.
(Synthesis of Polymer 8)
23 parts by mass of 4,4'-diphenylmethane diisocyanate was added to 77 parts by mass of amino-terminal modified silicone KF-8010 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd.), 50 parts by mass of tetrahydrofuran and 50 parts by mass of N-methylpyrrolidone. The reaction was carried out at room temperature for 2 hours. Thereafter, a white solid was produced by adding the reaction solution to 500 parts by mass of methanol. The resulting white solid was washed with water, washed with methanol, and dried to obtain Polymer 8.
(Synthesis of Polymer 9)
18 parts by mass of terephthaloyl chloride and 30 parts by mass of triethylamine are added to 82 parts by mass of a hydroxy-modified silicone having both ends KF-6000 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd.), 100 parts by mass of tetrahydrofuran and 100 parts by mass of N-methylpyrrolidone. The mixture was added and reacted at room temperature for 5 hours. Thereafter, a white solid was produced by adding the reaction solution to 500 parts by mass of methanol. The resulting white solid was washed with water, methanol, and dried to obtain Polymer 9.
(Synthesis of Polymer 10)
19 parts by mass of terephthaloyl chloride was added to 81 parts by mass of amino-terminal modified silicone KF-8010 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd.), 100 parts by mass of tetrahydrofuran and 100 parts by mass of N-methylpyrrolidone, and the mixture was added at room temperature. The reaction was performed for 5 hours. Thereafter, a white solid was produced by adding the reaction solution to 500 parts by mass of methanol. The resulting white solid was washed with water, methanol, and dried to obtain Polymer 10.

(2) Synthesis of Additive (B) (Synthesis of Polymer Additive I)
80 parts by mass of methacryl-modified silicone KF-2012 (trade name, manufactured by Shin-Etsu Silicone Co., Ltd.), 20 parts by mass of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, propylene glycol-1-monomethyl ether- 0.1 parts by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 100 parts by mass of 2-acetate at 80 ° C. under a nitrogen atmosphere. Allowed to react for hours. Thereafter, 0.1 parts by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was reacted at 80 ° C. for 2 hours. Further, 0.1 part by mass of dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) (manufactured by Wako Pure Chemical Industries, Ltd.) was added and reacted at 80 ° C. for 2 hours. The obtained reaction solution was added to 1000 parts by mass of methanol to separate into a methanol phase and a polymer phase. The polymer additive I was obtained by collecting the separated polymer phase (liquid phase). The weight average molecular weight of the polymer additive I was 10,000.

(3) Production of sheet (production of sheet No. 101)
100 parts by mass of the polymer 1 obtained above were mixed with 5 parts by mass of p-methoxyphenol using a spatula and subjected to a hot press treatment to obtain a sheet No. having a length of 60 mm, a width of 60 mm and a thickness of 2 mm. 101 was produced.
The heat press treatment was performed at 150 ° C. for 2 minutes while applying a pressure of 10 MPa.
(Production of Sheet Nos. 102 to 124 and c11 to c19)
Except for using the polymer (A) and the additive (B) described in Table 1 below, the sheet Nos. 101 in the same manner as in the production of sheet No. 101. 102 to 124 and c11 to c19 were produced.
The sheet No. No. 121 uses the polymer 4 in which the additives described in the column (B) are incorporated into the polymer (A) described in Table 1 below by copolymerization, and thus the polymer 4 is subjected to hot press treatment to prepare a sheet. did.
Further, sheet Nos. C11 to c19 were prepared by applying a hot press treatment to the polymer (A) described in Table 1 below without using the additives described in the column (B).
Table 1 below summarizes the compositions of the prepared sheets.

<Note for Table 1>
(A) Monomer for polymer constitution KF-2012: trade name, manufactured by Shin-Etsu Silicone Co., one-terminal methacryl-modified silicone, mass average molecular weight 4,600
KF-6000: trade name, manufactured by Shin-Etsu Silicone Co., both ends hydroxy-modified silicone, mass average molecular weight 933
KF-8010: trade name, manufactured by Shin-Etsu Silicone Co., amino-modified silicone at both terminals, mass average molecular weight 860
For the polymers 7 to 10, for convenience, a monomer having a polysiloxane bond is described in the column of the structural unit (a1) forming monomer, and a monomer other than the monomer having a polysiloxane bond is described in the column of the structural unit (a2) forming monomer. Are described.
(B) Additives BHT, ADK STAB AO-50 and CDA-6 (all trade names) are compounds having the structures shown below.
The SP value and carbon number of titanium oxide are not described because they cannot be calculated or do not correspond.
No. The SP value in column 117 is not described because the additive (B) is incorporated as a co-component in the polymer (A).
(C) Other No. Additive (B) at 115 is only added to polymer (A) and is not incorporated as a copolymer component in polymer (A). On the other hand, no. The additive (B) in 117 is incorporated as a copolymer component in the polymer (A).
The unit of “SP value” is (cal / cm ³ ) ^1/2 .
"Carbon number" is the carbon number of the saturated aliphatic hydrocarbon group.
"Blending amount" is parts by mass.

(4) Evaluation The acoustic characteristics of each sheet produced above were evaluated as described below.
Specifically, the initial test (before heating) sensitivity of the acoustic wave (ultrasonic wave) was evaluated for each of the sheets prepared above by the following test.
After heating each sheet prepared above at 100 ° C. for 24 hours, the sheet was allowed to cool to 25 ° C. in a 25 ° C. environment and subjected to an acceleration test.
The acoustic wave (ultrasonic) sensitivity after heating was measured for each sheet after the acceleration test, similarly to the sheet before heating. Based on these results, the amount of change in acoustic wave (ultrasonic) sensitivity before and after heating was evaluated.
In addition, the acoustic wave impedance obtained by the following method for each of the sheets prepared above is in the range of 1.1 × 10 ^{6 to} 2.0 × 10 ⁶ kg / m ² / s, and is practical. Value.

[Acoustic wave (ultrasonic wave) sensitivity]
A 10 MHz sine wave signal (one wave) output from an ultrasonic oscillator (Iwatsu Measurement Co., Ltd., function generator, product name "FG-350") is input to an ultrasonic probe (Japan Probe Co., Ltd.). An ultrasonic pulse wave having a center frequency of 10 MHz was generated in water from an ultrasonic probe. The magnitude of the amplitude before and after the generated ultrasonic wave passes through the obtained sheet having a thickness of 2 mm is measured by an ultrasonic receiver (Oscilloscope, manufactured by Matsushita Electric Industrial Co., Ltd., trade name “VP-5204A”). The measurement was performed in an environment at a water temperature of 25 ° C., and the acoustic wave (ultrasonic wave) attenuation of each material was compared by comparing the acoustic wave (ultrasonic) sensitivity.
The acoustic wave (ultrasonic wave) sensitivity is a numerical value given by the following formula.
In the following formula, Vin represents a voltage peak value of an input wave having a half width of 50 nsec or less and generated by the ultrasonic oscillator. Vs represents a voltage value obtained when the generated acoustic wave (ultrasonic wave) passes through the sheet and the ultrasonic wave (ultrasonic wave) reflected from the opposite surface of the sheet is received by the ultrasonic oscillator. The higher the acoustic wave (ultrasonic wave) sensitivity, the smaller the amount of acoustic wave (ultrasonic wave) attenuation.

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

The acoustic wave (ultrasonic) sensitivity before heating was evaluated according to the following evaluation criteria.
(Evaluation criteria)
A: -66 dB or more B: -68 dB or more and less than -66 dB C: -70 dB or more and less than -68 dB D: less than -70 dB

  The sensitivity change amount calculated from the following equation was evaluated according to the following evaluation criteria. In this test, a rating of “D” or higher is a pass level.

Sensitivity change amount = [Acoustic wave (ultrasonic) sensitivity before heating]-[Acoustic wave (ultrasonic) sensitivity after heating]

(Evaluation criteria)
A: less than 2 dB B: 2 dB to less than 4 dB C: 4 dB to less than 6 dB D: 6 dB to less than 8 dB E: 8 dB to less than 10 dB F: 10 dB or more

[Acoustic impedance]
The density of the obtained sheet having a thickness of 2 mm at 25 ° C. was measured by an electronic hydrometer (manufactured by Alpha Mirage Co., Ltd. under the trade name “SD”) in accordance with 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 device (trade name “UVM-2” manufactured by Ultrasonic Industry Co., Ltd.), and the measured density and sound velocity were measured. The acoustic impedance was determined from the product.

As is evident from Table 2, No. 1 consisting of a composition not satisfying the requirements of the present invention. All of the sheets c11 to c19 were inferior in acoustic wave sensitivity as a result of the heating acceleration test.
On the other hand, No. 1 comprising the composition of the present invention. It can be seen that the sheets 101 to 124 have a small change in the acoustic wave sensitivity due to the heating acceleration test, and are excellent in the maintenance ratio of the acoustic wave sensitivity over time.

[Reference example]
(1) Evaluation The mechanical properties of each sheet prepared above and each sheet after the acceleration test were evaluated as described below.
Specifically, the initial (before heating) hardness and tear strength of each of the sheets prepared above were evaluated by the following tests. Further, for each sheet after the accelerated test, the hardness and tear strength after heating were measured in the same manner as the sheet before heating. Based on these results, the respective amounts of change in hardness and tear strength before and after heating were evaluated.

(1-1) Hardness In accordance with JIS K6253-3 (2012), a type A durometer hardness of the obtained sheet having a thickness of 2 mm was measured using a rubber hardness meter (trade name “RH-201A” manufactured by Excel Co., Ltd.). It was measured. In this test, a rating of “C” or higher is a pass level.
(Evaluation criteria)
A: 40 degrees or more B: 30 degrees or more and less than 40 degrees C: 20 degrees or more and less than 30 degrees D: 10 degrees or more and less than 20 degrees E: 5 degrees or more and less than 10 degrees F: less than 5 degrees

  The hardness change amount calculated from the following equation was evaluated according to the following evaluation criteria. In this test, a rating of “C” or higher is a pass level.

Hardness change = [hardness before heating]-[hardness after heating]

(Evaluation criteria)
A: less than 2 degrees B: 2 degrees or more and less than 5 degrees C: 5 degrees or more and less than 10 degrees D: 10 degrees or more and less than 15 degrees E: 15 degrees or more and less than 20 degrees F: 20 degrees or more

(1-2) Tear Strength Test A trouser-type test piece was prepared from the obtained sheet having a thickness of 2 mm in accordance with JIS K6252 (2007), the tear strength was measured, and the tear strength was evaluated according to the following evaluation criteria. In this test, a rating of “C” or higher is a pass level.
(Evaluation criteria)
A: 2.0 N / cm or more B: 1.5 N / cm or more and less than 2.0 N / cm C: 1.0 N / cm or more and less than 1.5 N / cm D: 0.5 N / cm or more and less than 1.0 N / cm E: 0.1 N / cm or more and less than 0.5 N / cm F: less than 0.1 N / cm

  The hardness change amount calculated from the following equation was evaluated according to the following evaluation criteria. In this test, a rating of “C” or higher is a pass level.

Change in tear strength = [tear strength before heating]-[tear strength after heating]

(Evaluation criteria: Change)
A: less than 0.5 N / cm B: 0.5 N / cm or more and less than 0.75 N / cm C: 0.75 N / cm or more and less than 1.0 N / cm D: 1.0 N / cm or more and less than 1.5 N / cm E: 1.5 N / cm or more and less than 2.0 N / cm F: 2.0 N / cm or more

As is evident from Table 3, the composition No. 3 does not satisfy the requirements of the present invention. Nos. c11 to c19, and No. 1 comprising the composition of the present invention. No substantial difference was found between the sheets 101 to 124 in the initial hardness and the tear strength and the changes in the hardness and the tear strength before and after the heating acceleration test.
From the results in Tables 2 and 3, the sheet composed of the composition of the present invention containing the polymer (A) and the additive (B) was more heated than the sheet composed of the composition not containing the additive (B). In the accelerated test, it was found that there was no difference in the maintenance ratio between the hardness and the tear strength (mechanical strength), while there was a difference in the maintenance ratio of the acoustic wave attenuation (the increase suppression ratio of the acoustic wave attenuation). That is, it can be seen that the additive (B) does not substantially affect the mechanical properties of the polymer but specifically acts on the acoustic wave characteristics.

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 (15)

  (A1) a polymer containing a structural unit having a polysiloxane bond and (a2) a polymer having a structural unit having at least one of an ester bond, an amide bond, a urethane bond, a urea bond, and a structure derived from an aromatic vinyl; A composition for an acoustic wave probe, comprising a light stabilizer and at least one additive (B). The SP value of the additive (B) is ^{7~10 (cal / cm 3) 1/2} , the acoustic wave probe composition according to claim 1.   The composition for an acoustic wave probe according to claim 1, wherein the additive (B) is incorporated as a copolymer component in the polymer.   The composition for an acoustic wave probe according to any one of claims 1 to 3, wherein the additive (B) has a saturated aliphatic hydrocarbon group having 4 or more carbon atoms.   The composition for an acoustic wave probe according to any one of claims 1 to 4, wherein the structural unit (a2) has at least one of an acryloyloxy structural unit, an acrylamide structural unit, and a styrene structural unit. The structural unit (a1) is represented by the following formula (1), the acryloyloxy structural unit is represented by the following formula (2), the acrylamide structural unit is represented by the following formula (3), and the styrene structural unit is The composition for an acoustic wave probe according to claim 5, wherein is represented by the following formula (4).

In the formula, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a monovalent organic group, L ¹ represents a divalent linking group, and n 1 is 3 to 10,000.

In the formula, R ⁷ and Ra each independently represent a hydrogen atom or a monovalent organic group.

In the formula, R ⁸ , Rb ¹ and Rb ² each independently represent a hydrogen atom or a monovalent organic group.

In the formula, R ⁹ and Rc ^{1 to} Rc ⁵ each independently represent a hydrogen atom or a monovalent organic group.   The composition for an acoustic wave probe according to claim 5 or 6, wherein the structural unit (a2) has at least one of the acryloyloxy structural unit and the styrene structural unit.   The composition for an acoustic wave probe according to any one of claims 1 to 7, wherein the polymer contains a fluorine atom.   The composition for an acoustic wave probe according to claim 8, wherein the structural unit (a2) contains 5 or more fluorine atoms per structural unit.   An acoustic lens using the composition for an acoustic wave probe according to claim 1.   An acoustic probe having the acoustic lens 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 measurement device comprising the acoustic lens according to claim 10.   An ultrasonic endoscope comprising the acoustic lens according to claim 10.

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