Backing material, ultrasonic probe, ultrasonic diagnostic device, ultrasonic endoscope, and curable resin composition

Abstract

Provided are: a backing material for an ultrasonic probe, the backing material containing thermally conductive particles and a resin, wherein the resin is a cured reaction product of a polyamine compound and a polyisocyanate compound containing a polyether-modified polyisocyanate compound represented by general formula (1); an ultrasonic probe; an ultrasonic diagnostic device; an ultrasonic endoscope; and a curable resin composition. In the formula, L1 represents an amide bond, L2 represents a specific polyether chain, and X represents a group including an isocyanato group and an aromatic ring. The amide bond of L1 is attached to L2 on the side of >C(=O).

Description

Backing material, ultrasonic probe, ultrasonic diagnostic device, ultrasonic endoscope, and curable resin composition

[0001] The present invention relates to a backing material, an ultrasonic probe, an ultrasonic diagnostic apparatus, an ultrasonic endoscope, and a curable resin composition.

[0002] An ultrasonic measurement device uses an ultrasonic probe that irradiates an object or region under test (hereinafter simply referred to as the object) with ultrasonic waves, receives the reflected waves (echoes), and outputs a signal. The reflected waves received by this ultrasonic probe are converted into electrical signals and displayed as an image. This allows the inside of the object to be visualized and observed.

[0003] During diagnosis, an ultrasound probe transmits an ultrasound signal from the front surface of the piezoelectric element into the subject by, for example, contacting the acoustic lens side of the ultrasound probe with the subject and driving the piezoelectric element. This ultrasound signal is focused at a desired location within the subject by electronic focusing based on the drive timing of the piezoelectric element and focusing by the acoustic lens. Controlling the drive timing of the piezoelectric element allows ultrasound signals to be transmitted to a desired area within the subject, and echo signals from the subject are received and processed to obtain an ultrasound image (tomographic image) of the desired area. Driving the piezoelectric element also emits ultrasound signals from the back surface. Therefore, a backing material is placed on the back surface of the piezoelectric element to absorb (attenuate) the ultrasound signals to the back surface, preventing the normal ultrasound signal from being transmitted into the subject along with the ultrasound signal (reflected signal) from the back surface. In addition to the high ultrasound attenuation, the backing material must have high heat dissipation properties to efficiently dissipate heat emitted from the piezoelectric element when the ultrasound probe is driven. Durability is also required to prevent cracks and other damage caused by repeated driving of the ultrasound probe.

[0004] A technique for imparting high heat dissipation properties to a backing material by adding a thermally conductive filler has been known. For example, Patent Document 1 describes an acoustic backing composition containing an ethylene-vinyl acetate copolymer with a vinyl acetate content of 20 to 80% by weight and a filler with excellent thermal conductivity. Furthermore, Patent Document 2 describes a backing material (backing material) for an ultrasonic probe, which contains a main material made of nitrile rubber, butyl rubber, or urethane rubber and a thermally conductive filler made of aluminum nitride, silicon carbide, copper, boron nitride, or graphite.

[0005] JP 2006-033801 A JP 2000-165995 A

[0006] The present inventors have conducted studies and found that, although the acoustic backing composition described in Patent Document 1 and the backing load material (backing material) described in Patent Document 2 provide acoustic backing materials that combine high heat dissipation and high ultrasonic attenuation, cracks and the like occur when the ultrasonic probe is repeatedly driven. To clarify the cause of this, the present inventors conducted further studies and found that heat emitted from the ultrasonic vibrator (piezoelectric element) when the ultrasonic probe is driven causes the backing material to heat up and cool to room temperature, which accelerates cracks and the like. In particular, it has been found that the occurrence of cracks due to the repeated temperature changes is more pronounced in ultrasonic probes in which the backing material has a curved surface. An object of the present invention is to provide a backing material that combines excellent ultrasonic attenuation and excellent durability against temperature changes, in which heat dissipation is enhanced by the incorporation of thermally conductive particles, as well as an ultrasonic probe, an ultrasonic diagnostic device, and an ultrasonic endoscope that include this backing material, and a curable resin composition for forming this backing material.

[0007] The above-mentioned problems of the present invention have been solved by the following means: [1] A backing material for an ultrasonic probe, comprising thermally conductive particles and a resin, wherein the resin comprises a reaction-cured product of a polyamine compound and a polyisocyanate compound, the reaction product including a polyether-modified polyisocyanate compound represented by the following general formula (1): In the above formula, L １ indicates an amide bond, and L ２ represents a polyether chain represented by the following general formula (p), and X represents a group containing an isocyanato group and an aromatic ring. １ The amide bond as ２ and combine. In the above formula, L ３ represents an alkylene group, and n is 1 or more. * represents a bond. [2] The above L ２ The backing material according to [1], having a chemical formula weight of 50 to 6000. [3] The backing material according to [1] or [2], wherein the glass transition temperature of the backing material is 10°C or lower. [4] The backing material according to any one of [1] to [3], wherein the content of the resin in the backing material is 30 to 80% by volume. [5] The backing material according to any one of [1] to [4], wherein the thermally conductive particles include at least one of metal particles and ceramic particles. [6] An ultrasonic probe comprising the backing material according to any one of [1] to [5]. [7] An ultrasonic diagnostic device using the ultrasonic probe according to [6]. [8] An ultrasonic endoscope equipped with the ultrasonic probe according to [6]. [9] A curable resin composition for forming the backing material according to any one of [1] to [5], the curable resin composition comprising the thermally conductive particles and, as a resin component, a combination of a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by the general formula (1) and a polyamine compound.

[0008] In the present invention, unless otherwise specified, the components constituting the backing material of the ultrasonic probe (such as resins, reaction cured products, thermally conductive particles, and other components) may each be contained in the backing material of the ultrasonic probe, either singly or in combination of two or more. This also applies to the components constituting the curable resin composition (such as compounds, thermally conductive particles, and other components), and each may each be contained in the curable resin composition, either singly or in combination of two or more. In the present invention, the term "composition" encompasses not only mixtures in which the component concentrations are constant (each component is uniformly dispersed), but also mixtures in which the component concentrations vary within a range that does not impair the intended function. In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits.

[0009] The backing material of the present invention is a backing material that has heat dissipation properties due to the incorporation of thermally conductive particles, and has excellent ultrasonic attenuation and durability against temperature changes. The ultrasonic probe, ultrasonic diagnostic device, and ultrasonic endoscope of the present invention also include the backing material having the above properties. The curable resin composition of the present invention is suitable for forming the backing material.

[0010] FIG. 1 is a perspective view of an example of a convex ultrasonic probe, which is one aspect of an ultrasonic probe.

[0011] [Backing Material] The backing material of the present invention is a backing material for an ultrasonic probe, comprising thermally conductive particles and a resin, wherein the resin is a reaction cured product of a polyamine compound and a polyisocyanate compound, including a polyether-modified polyisocyanate compound represented by the general formula (1) described below. The details of why the backing material of the present invention is excellent in ultrasonic attenuation and durability against temperature changes are not clear, but are thought to be as follows.

[0012] The backing material of the present invention is a backing material containing thermally conductive particles and a resin containing a reaction cured product of a polyamine compound and a polyisocyanate compound containing a polyether-modified polyisocyanate compound represented by the general formula (1) described below, and can exhibit excellent ultrasonic attenuation and excellent durability against temperature changes while exhibiting high heat dissipation due to the thermally conductive particles. This is because the polyether-modified polyisocyanate compound represented by the general formula (1) described below is a backing material containing thermally conductive particles and a resin containing a reaction cured product of a polyamine compound and a polyisocyanate compound. ２ One of the reasons for this is thought to be that, since the polyisocyanate compound has a polyether chain represented by the general formula (p) described below, a flexible chain can be introduced into the urea cross-linked linking portion formed by the reaction of a polyisocyanate compound including the polyether-modified polyisocyanate compound with a polyamine compound.

[0013] The backing material of the present invention will be described in detail below.

[0014] <Resin> The resin contained in the backing material of the present invention includes a reaction cured product of a polyamine compound and a polyisocyanate compound containing a polyether-modified polyisocyanate compound represented by the following general formula (1). In the reaction cured product of a polyamine compound and a polyisocyanate compound containing a polyether-modified polyisocyanate compound represented by the following general formula (1), a polyisocyanate compound other than the polyether-modified polyisocyanate compound represented by the following general formula (1) (polyisocyanate compound X described below), such as a polyisocyanate compound used as a raw material for the polyether-modified polyisocyanate compound represented by the following general formula (1), may react with the polyamine compound to form a urea bond and be incorporated into the reaction cured product. Details will be described in detail below in the section on polyisocyanate compound X.

[0015] (Polyether-modified polyisocyanate compound represented by general formula (1))

[0016] In the above formula, L １ indicates an amide bond, and L ２ represents a polyether chain represented by the general formula (p) described below, and X represents a group containing an isocyanato group and an aromatic ring.１ The amide bond as ２ and combine.

[0017] (1) L １ L １ represents an amide bond. １ The amide bond as ２ and combine.

[0018] (2) L ２ : a polyether chain represented by general formula (p)

[0019] In the above formula, L ３ represents an alkylene group, and n is 1 or more. * represents a bond.

[0020] L ３ The alkylene group represented by L may be linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, even more preferably 2 to 4 carbon atoms, and particularly preferably 2 or 3 carbon atoms. ３ The number of carbon atoms contained in the shortest chain connecting the two carbon atoms that are the bonds of L is preferably 0 to 2, more preferably 0 or 1, and even more preferably 0. ３ The number of carbon atoms contained in the shortest chain connecting the two carbon atoms that are the bonds of L is 1 for a 1,3-propanediyl group and 0 for an ethylene group. ３ Specific examples of the alkyl group include an ethylene group, a 1,2-propanediyl group, a 1,3-propanediyl group, a 1,2-butanediyl group, a 1,3-butanediyl group, and a 1,4-butanediyl group. An ethylene group, a 1,2-propanediyl group, or a 1,3-propanediyl group is preferred, and an ethylene group is more preferred.

[0021] n is 1 or more and means the average number of repetitions. For example, n is preferably 1 to 140, more preferably 1 to 90, and even more preferably 1 to 170. In the present invention, the "average" in the average number of repetitions means a number average, and is a value measured and calculated by GPC (gel permeation chromatography) or NMR (nuclear magnetic resonance analysis).

[0022] L２ The chemical formula weight of the above "L" is preferably 50 to 6000, more preferably 50 to 4000, and even more preferably 50 to 3000. ２ The chemical formula weight of "L ２ In the present invention, L ２ The chemical formula weight is a value measured and calculated by GPC (gel permeation chromatography) or NMR (nuclear magnetic resonance analysis), and when the chemical formula weight exceeds 100, the value is rounded to the nearest tenth place, and when the chemical formula weight is 100 or less, the value is rounded to the nearest oneth place.

[0023] The polyether-modified polyisocyanate compound represented by the general formula (1) is L １ is an amide bond (-NHC(=O)-), so two Xs are connected to L via a urethane bond. ２ and linked by a group in which oxygen atoms have been removed from both ends.

[0024] (3) X X represents a group containing an isocyanato group and an aromatic ring. The aromatic ring contained in X may be a monocyclic ring or a fused ring. When the aromatic ring contained in X is a monocyclic ring, the number of ring members is preferably a 6-membered ring. When the aromatic ring contained in X is a fused ring, the number of rings constituting the fused ring is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2. The number of ring members is preferably a 6- or 8-membered ring, and even more preferably a 6-membered ring. The number of carbon atoms in the aromatic ring contained in X is preferably 6 to 40, more preferably 6 to 30, even more preferably 6 to 20, and particularly preferably 6 to 10. Of these, the aromatic ring contained in X is preferably a benzene ring. The number of aromatic rings contained in X may be one or more, preferably 1 to 4, more preferably 2 to 4, even more preferably 2 or 3, and particularly preferably 2. The number of isocyanato groups contained in X may be one or more, preferably one to three, more preferably one or two, and even more preferably one.

[0025] X may contain a structure other than an aromatic ring and an isocyanato group, and a preferred example thereof is an alkylene structure. The alkylene structure that X may contain may be linear or branched, and preferably contains 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, still more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom. Specific examples thereof include a methylene structure, an ethylene structure, and an n-propylene structure, and the methylene structure (-CH ２ -) is preferred.

[0026] X is L １ The bonding site to the alkyl group is preferably an arylene group containing an isocyanato group, and -arylene-alkylene-arylene-(NCO) ｍ m is an integer of 1 to 3, preferably 1 or 2, and more preferably 1. The same applies to m hereinafter. -arylene-alkylene-arylene-(NCO) ｍ The arylene group in the formula (I) is a group obtained by removing two hydrogen atoms from the aromatic ring contained in X, and is -arylene-alkylene-arylene-(NCO) ｍ The alkylene group in the formula (I) is the same as the alkylene structure that X may contain. In particular, X is -phenylene-methylene-phenylene-(NCO) ｍ The bonding position of NCO to the methylene may be any of the 2- to 6-positions of the phenylene, and is preferably at least one of the 2- and 4-positions of the phenylene. -phenylene-methylene-phenylene-(NCO) ｍ Phenylene and methylene (-CH ２-) may be unsubstituted or may have a substituent. Examples of the substituent that may be possessed include an alkyl group, an alkoxy group, a halogen atom, a cycloalkyl group, an alkenyl group, and an aryl group. The number of carbon atoms in the alkyl group moiety of the alkyl group and alkoxy group that the phenylene group may have is preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4. Examples of the halogen atom that the phenylene group may have include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with fluorine and chlorine atoms being preferred. The number of carbon atoms in the cycloalkyl group that the phenylene group may have is preferably 3 to 11, more preferably 3 to 9, and even more preferably 3 to 7. The number of carbon atoms in the alkenyl group that the phenylene group may have is preferably 2 to 12, more preferably 2 to 8, and even more preferably 2 to 4. The number of carbon atoms in the aryl group that the phenylene group may have is preferably 6 to 40, more preferably 6 to 30, even more preferably 6 to 20, and particularly preferably 6 to 10. -phenylene-methylene-phenylene-(NCO) ｍ Phenylene and methylene (-CH ２ -) is preferably unsubstituted.

[0027] The polyether-modified polyisocyanate compound represented by general formula (1) may be a compound synthesized by a conventional method, or a commercially available product. The polyether-modified polyisocyanate compound represented by general formula (1) can be obtained, for example, by reacting a polyisocyanate compound such as diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) with a polyether diol compound, and forming a urethane bond through a reaction between the terminal hydroxy group of the polyether diol compound and the isocyanato group of the polyisocyanate compound. In the present invention, when simply referring to diphenylmethane diisocyanate (MDI), this is used to mean that any of the three structural isomers, 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI, may be included. Examples of commercially available products include the SUPRASEC series manufactured by HUNTSMAN (trade names: SUPRASEC2058, SUPRASEC2067, SUPRASEC7112, SUPRASEC7808, SUPRASEC7802N, etc.) and the Coronate series manufactured by Tosoh Corporation (trade name: Coronate 1120, etc.).

[0028] In addition to the polyether-modified polyisocyanate compound represented by general formula (1), the commercially available products may contain polyisocyanate compounds such as diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) as raw materials. These polyisocyanate compounds, such as MDI and TDI, may be incorporated into a cured reaction product of a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by general formula (1) and a polyamine compound. The polyisocyanate compound (hereinafter referred to as "polyisocyanate compound X") that may be incorporated into the cured reaction product of a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by general formula (1) and a polyamine compound may be any polyisocyanate compound having two or more isocyanate groups, and may be either an aliphatic isocyanate compound (a compound in which an isocyanate group is bonded to an aliphatic chain or aliphatic ring) or an aromatic isocyanate compound (a compound in which an isocyanate group is bonded to an aromatic ring), or a mixture thereof. The polyisocyanate compound X may have a ring structure. The number of isocyanato groups in the polyisocyanate compound X is preferably 2 to 4, more preferably 2 or 3, and even more preferably 2. Examples of the polyisocyanate compound X include diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), metaxylylene diisocyanate (XDI), norbornane diisocyanate (NBDI), and 1,4-bis(isocyanatomethyl)cyclohexane (1,4-H6XDI).

[0029] The proportion of the polyether-modified polyisocyanate compound represented by general formula (1) in the polyisocyanate compound is not particularly limited as long as it can achieve both excellent ultrasonic attenuation properties and excellent durability against temperature changes, and may be, for example, 40 to 100 mass%, preferably 45 to 100 mass%, and more preferably 50 to 100 mass%.

[0030] The isocyanato group content of the polyisocyanate compound (also referred to as the "NCO content" in the present invention) is not particularly limited and is, for example, preferably 1 to 40% by mass, more preferably 2 to 35% by mass. The isocyanato group content is the amount of isocyanato groups present in the polyisocyanate compound expressed as a mass percentage (% by mass). Therefore, when the polyisocyanate compound contains polyisocyanate compound X, the isocyanato group content is calculated as the proportion (% by mass) of the "total amount of isocyanato groups contained in the mixture of the polyether-modified polyisocyanate compound represented by general formula (1) and polyisocyanate compound X" to the "total mass of the mixture of the polyether-modified polyisocyanate compound represented by general formula (1) and polyisocyanate compound X."

[0031] (Polyamine Compound) The polyamine compound to be reacted with the polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by general formula (1) can be any polyamine compound having two or more amino groups, and is generally preferably a polyamine compound used to obtain a urea-crosslinked resin by chemical reaction with a polyisocyanate compound. The polyamine compound may be any aliphatic polyamine compound (a chain aliphatic polyamine compound, a cyclic aliphatic polyamine compound, or an aliphatic polyamine compound having an aromatic ring) or an aromatic polyamine compound, or a mixture thereof. The chain aliphatic polyamine compound is a polyamine compound having an amino group bonded to an aliphatic chain. The cyclic aliphatic polyamine compound is a polyamine compound having an amino group bonded to an aliphatic ring. However, the cyclic aliphatic polyamine compound may have a nitrogen atom constituting an amino group as a ring-constituting atom of the aliphatic ring. The aliphatic polyamine compound having an aromatic ring is an aliphatic polyamine compound having an amino group bonded to an aliphatic chain or aliphatic ring, and also having an aromatic ring. The aromatic polyamine compound is a polyamine compound in which an amino group is directly bonded to an aromatic ring. The polyamine compound may contain heteroatoms such as oxygen atoms in addition to nitrogen atoms, and preferably has a polyether structure. The polyether structure is preferably a polyether structure having a number average molecular weight of 200 to 6000, and more preferably, among the polyether chains represented by the general formula (p) above, a polyether structure having a number average molecular weight of 200 to 6000 is used. The number average molecular weight is determined by the above-mentioned L ２ The description of the chemical formula weight can be applied, and it is preferably 200 to 4000, more preferably 200 to 2000. The number of amino groups in the polyamine compound may be two or more, preferably two or three, more preferably two. The two or more amino groups that the polyamine compound has in the compound may be amino groups having active hydrogen, and specifically, unsubstituted amino groups (—NH ２ ) and a position-substituted amino group having one active hydrogen atom, and ２). The monosubstituted amino group having one active hydrogen may be incorporated into the compound in the form of >NH. The polyamine compound may have a disubstituted amino group (amino group without active hydrogen) in addition to the two or more amino groups (amino groups having active hydrogen) that the polyamine compound has. The number of active hydrogens derived from the amino groups that the polyamine compound has may be two or more, preferably 3 to 6, and more preferably 4 to 6. Among these, the polyamine compound preferably has an unsubstituted amino group (-NH ２ ), and preferably has two or more unsubstituted amino groups (—NH ２ It is more preferable that the alkyl group has two or three unsubstituted amino groups (—NH ２ The polyamine compound may be a low molecular weight compound or a high molecular weight compound.

[0032] Specific examples of polyamine compounds include the following: For example, examples of chain aliphatic polyamine compounds include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, diethylaminopropylamine, hexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and tris(2-aminoethyl)amine, and examples of polymeric chain aliphatic polyamine compounds include ANCAMINE 2678 (trade name, manufactured by Evonik Japan). Examples of the chain aliphatic polyamine compound containing an oxygen atom include chain aliphatic polyamine compounds having a polyether structure (hereinafter also referred to as "chain aliphatic polyetheramine compounds"), such as JEFFAMINE D-230, JEFFAMINE D-400, JEFFAMINE D-2000, JEFFAMINE T-403, and JEFFAMINE T-5000 (all trade names, manufactured by HUNTSMAN). Examples of the cyclic aliphatic polyamine compound include N-aminoethylpiperazine, 4,4'-methylenebis(2-methylcyclohexane-1-amine), menthenediamine, isophoronediamine, bis(4-aminocyclohexyl)methane, and 1,3-bis(aminomethyl)cyclohexane. Examples of aliphatic polyamine compounds having an aromatic ring include m-xylylenediamine, Gascamine 240, and Gascamine 328 (all trade names, manufactured by Mitsubishi Gas Chemical Company, Inc.). Examples of aromatic polyamine compounds include m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, 2,4-diamino-3,5-diethyltoluene, and 2,6-diamino-3,5-diethyltoluene. Examples of polyamine compounds classified as aromatic polyamine compounds having a polyether structure (hereinafter also referred to as "aromatic polyetheramine compounds") include Elastomer 250P, Elastomer 650P, Elastomer 1000P, and Heartcure 10 (all trade names, manufactured by Kumiai Chemical Co., Ltd.).

[0033] Among these polyamine compounds, from the viewpoint of further improving ultrasonic attenuation properties and durability against temperature changes, at least one of polyamine compounds having a polyether structure, linear aliphatic polyamine compounds, and cyclic aliphatic polyamine compounds is preferred, and at least one of linear aliphatic polyetheramine compounds, aromatic polyetheramine compounds, linear aliphatic polyamine compounds, and cyclic aliphatic polyamine compounds is more preferred. In the description of preferred compounds as these polyamine compounds, compounds simply described as "linear aliphatic polyamine compounds, cyclic aliphatic polyamine compounds" do not have a polyether structure.

[0034] The amino group equivalent of the polyamine compound is not particularly limited and is, for example, preferably 30 to 12,000 g / mol, more preferably 30 to 3,000 g / mol, and even more preferably 30 to 1,200 g / mol. The amino group equivalent means the mass (g) of the polyamine compound per 1 mol of amino groups.

[0035] The content of the reaction cured product of a polyisocyanate compound, including the polyether-modified polyisocyanate compound represented by the general formula (1) above, and a polyamine compound in the resin contained in the backing material of the present invention is not particularly limited as long as the effects of the present invention are achieved, and can be, for example, 15% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more, even more preferably 50% by volume or more, and particularly preferably 70% by volume or more. It is also preferable that all of the resin contained in the backing material of the present invention is composed of a reaction cured product of a polyisocyanate compound, including the polyether-modified polyisocyanate compound represented by the general formula (1) above, and a polyamine compound.

[0036] The resin content in the backing material of the present invention is preferably 30 to 80% by volume.

[0037] <Thermal Conductive Particles> As the thermal conductive particles, either inorganic or organic particles may be used as long as they have thermal conductivity (preferably a thermal conductivity of 30 W / m·K or more), and any thermal conductive particles that impart heat dissipation properties to the backing material may be used without any particular limitation. The shape of the particles is not particularly limited, and various shapes such as amorphous, spherical, fibrous, branched fibrous, and tabular shapes may be used. A spherical shape is preferred because it can increase the packing density. On the other hand, an anisotropic shape such as a fibrous or tabular shape is preferred because it can increase particle contact and improve heat dissipation. Furthermore, irregular particles are preferred because they can randomly reflect ultrasonic waves, thereby improving the ultrasonic attenuation of the backing material.

[0038] Examples of inorganic particles include metal particles made of metals such as silver, copper, gold, aluminum, iron, brass, tungsten, molybdenum, and zinc. Among these, tungsten or molybdenum particles are preferred due to their low electrical conductivity. Oxides, carbides, or nitrides of the above metal particles are also preferred, and examples of these include aluminum trioxide (alumina, sapphire), zinc oxide, aluminum nitride, tungsten oxide, molybdenum oxide, tungsten carbide, and molybdenum carbide. Inorganic particles such as silicon carbide and boron nitride are also preferred. That is, metal particles, ceramic particles, and the like are preferred as inorganic particles. Examples of organic particles include graphite, carbon nanotubes, and diamond. Of these, diamond is preferred due to its low electrical conductivity. The thermal conductivity of the thermally conductive particles is preferably 30 W / m·K or higher. The surfaces of the metal particles may be surface-treated. Examples of surface treatments include UV (ultraviolet) surface treatment, plasma surface treatment, corona surface treatment, silane coupling treatment, titanium coupling treatment, aluminum coupling treatment, and phosphate treatment. Surface treatment can change the functional groups on the particle surface, improve particle dispersibility in resin, and improve thermal conductivity and ultrasonic attenuation by changing the interparticle distance. The thermally conductive particles preferably include at least one of metal particles and ceramic particles.

[0039] The particle size of the thermally conductive particles is not particularly limited. From the viewpoint of maintaining high mechanical strength of the backing material (cured product) of the present invention while keeping the viscosity of the curable resin composition described below low, the particle size of the thermally conductive particles is, for example, preferably 1 to 300 μm, more preferably 5 to 100 μm, and even more preferably 8 to 30 μm. The "particle size" of the thermally conductive particles is the number-average particle size. The number-average particle size of the particles is calculated by observing the edge of the backing material sheet using a scanning electron microscope (e.g., SU8030 (trade name) manufactured by Hitachi High-Technologies Corporation) in a field of view containing 500 or more particles, randomly selecting 500 particles from the field of view, and measuring the particle diameters of these particles. Backing material sheets whose edge cannot be observed using a scanning electron microscope are observed using ice-embedded transmission electron microscopy. Ice embedding is performed using, for example, Vitrobot Mark IV (trade name) manufactured by FEI, and 500 particles are randomly selected from the field of view using a transmission electron microscope (for example, JEM-2010 (trade name) manufactured by JEOL Ltd.), and the particle diameters of these particles are measured and calculated. Note that if the particles are not perfectly round, particles with a maximum diameter to diameter ratio of 0.7 or more are selected and measured.

[0040] The proportion of thermally conductive particles in the total amount of components other than the resin in the backing material is preferably 50% by volume or more, more preferably 60% by volume or more, and even more preferably 65% ​​by volume or more. It is also preferable that all components other than the resin in the backing material of the present invention are thermally conductive particles. The content of thermally conductive particles in the backing material is preferably, for example, 20 to 70% by volume. One type of thermally conductive particle may be used alone, or two or more types may be used in combination. In the present invention, the proportion and content of thermally conductive particles refer to the total amount when two or more types of thermally conductive particles are contained.

[0041] <Other Components> The backing material of the present invention may contain other components in addition to the above-mentioned resin and thermally conductive particles. It is preferable that the other components include hollow particles. By including hollow particles, ultrasonic attenuation can be further improved. As the hollow particles, any hollow particles commonly used to exhibit the effect of improving acoustic wave attenuation or ultrasonic wave attenuation can be used without any particular limitation. Either hollow glass particles or hollow resin particles may be used, with hollow resin particles being preferred. Preferred examples of hollow particles include glass balloons, hollow silica, senolite, phenolic resin microballoons, urea resin microballoons, and plastic microballoons such as polymethyl methacrylate balloons. Furthermore, as hollow particles, plastic microballoons whose surfaces are coated with an inert inorganic powder such as calcium carbonate may be used. Examples include the Matsumoto Microsphere series MFL-81GCA, MFL-SEVEN, MFL-HD30CA, MFL-HD60CA, and MFL-100MCA (all trade names, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.). One type of hollow particle may be used alone, or two or more types may be used in combination. In the present invention, the content of hollow particles refers to the total amount when two or more types of hollow particles are contained. The particle size of the hollow particles is not particularly limited. From the viewpoint of maintaining a high mechanical strength of the backing material (cured product) of the present invention while keeping the viscosity of the curable resin composition described below low, the particle size of the hollow particles is, for example, preferably 1 to 300 μm, more preferably 5 to 100 μm, and even more preferably 20 to 80 μm. The "particle size" of the hollow particles is synonymous with the "particle size" of the thermally conductive particles described above. That is, the "particle size" of the hollow particles is the number average particle size, and is a value measured by the method described above.

[0042] Other components may be included, such as dispersants, diluents, colorants, viscosity modifiers, plasticizers, and curing accelerators. The content of other components in the backing material may be, for example, 5 to 30% by volume.

[0043] A preferred embodiment of the backing material of the present invention is, for example, a backing material comprising thermally conductive particles and a resin containing a cured product of a reaction between a polyisocyanate compound, including the polyether-modified polyisocyanate compound represented by the general formula (1), and a polyamine compound. Note that this embodiment does not contain hollow particles. In this embodiment, the content of each component in the backing material is preferably 30 to 80 vol%, more preferably 40 to 80 vol%, and even more preferably 40 to 70 vol%, for the resin, and preferably 20 to 70 vol%, more preferably 20 to 60 vol%, and even more preferably 30 to 60 vol% for the thermally conductive particles. Another preferred embodiment of the backing material of the present invention is, for example, a backing material comprising thermally conductive particles and a resin containing a cured product of a reaction between a polyisocyanate compound, including the polyether-modified polyisocyanate compound represented by the general formula (1), and a polyamine compound, wherein the hollow particles are included. In this embodiment, with regard to the contents of each component in the backing material, the resin content is preferably 30 to 80 vol%, more preferably 35 to 65 vol%, and even more preferably 40 to 60 vol%; the thermally conductive particle content is preferably 20 to 70 vol%, more preferably 30 to 65 vol%, and even more preferably 35 to 55 vol%; and the hollow particle content is preferably 5 to 30 vol%, more preferably 5 to 25 vol%, and even more preferably 10 to 20 vol%.

[0044] (Glass Transition Temperature) The glass transition temperature of the backing material of the present invention is preferably 10°C or lower, more preferably 5°C or lower, and even more preferably 0°C or lower. The practical lower limit of the glass transition temperature is usually -40°C or higher. The glass transition temperature is a value measured by the following method. A test piece cut into a strip having a thickness of 0.5 mm and a width of 5 mm is subjected to measurement of storage modulus using a dynamic viscoelasticity measuring device (for example, manufactured by IT Measurement & Control Co., Ltd., trade name "Vibron DVA-225") under conditions of a grip distance of 20 mm, a heating rate of 2°C / min, a measurement temperature range of -150°C to 250°C, and a frequency of 5 Hz. A semi-logarithmic plot is made with the storage modulus measured at each temperature on the vertical axis and the measurement temperature on the horizontal axis, with the vertical axis as the logarithmic axis and the horizontal axis as the linear axis. The glass transition temperature (Tg) of the obtained curve is determined based on the method described in "9.3 Determination of glass transition temperature (see Figure 3)" of JIS (Japanese Industrial Standards) K7121 (1987). Note that the DTA (differential thermal analysis) or DSC (differential scanning calorimetry) curve in 9.3 of JIS K7121 (1987) is used by replacing it with the curve obtained by the dynamic viscoelasticity measurement.

[0045] (Attenuation rate of backing material) The attenuation rate of the backing material of the present invention is preferably more than 1.0 dB / (mm MHz), more preferably more than 3.0 dB / (mm MHz), and even more preferably more than 8.0 dB / (mm MHz). The upper limit of the attenuation rate is usually 30 dB / (mm MHz) or less. The attenuation rate of the backing material is measured by the method described in the Examples below.

[0046] <Curable Resin Composition> The backing material of the present invention is preferably formed using the curable resin composition of the present invention. The curable resin composition of the present invention is a curable resin composition for forming the backing material of the present invention, and this curable resin composition contains thermally conductive particles and, as resin components, a combination of a polyisocyanate compound including the polyether-modified polyisocyanate compound represented by the above-mentioned general formula (1) and a polyamine compound.

[0047] The resin component in the curable resin composition of the present invention corresponds to the resin in the backing material of the present invention by forming the backing material of the present invention. Therefore, the polyamine compound contained as a resin component can be applied to the polyamine compound described above in the backing material of the present invention. Furthermore, the thermally conductive particles in the curable resin composition of the present invention correspond to the thermally conductive particles in the backing material of the present invention. Therefore, the thermally conductive particles in the curable resin composition of the present invention can be applied to the thermally conductive particles in the backing material of the present invention. Furthermore, the curable resin composition of the present invention can also contain other components described above in the backing material of the present invention.

[0048] (Viscosity of curable resin composition) The viscosity of the curable resin composition of the present invention is preferably 5000 Pa sec or less, more preferably 3000 Pa sec or less, more preferably 2000 Pa sec or less, even more preferably 1000 Pa sec or less, and particularly preferably 800 Pa sec or less, at 25 ° C. and a shear rate of 0.01 / sec from the viewpoint of having sufficient fluidity to be poured into a mold and being molded into a desired shape. The viscosity of the curable resin composition of the present invention is measured using a rheometer (for example, a HAAKE MARS 40 rheometer (trade name) manufactured by Thermo Fisher Scientific) under the conditions of temperature: 25 ° C., shear rate: 0.01 / sec, sensor: C35 2 ° / Ti, measurement mode: oscillation mode, frequency: 0.03 Hz.

[0049] The content of the thermally conductive particles and resin components in the curable resin composition of the present invention is not particularly limited as long as the backing material of the present invention can be obtained. The content of the polyisocyanate compound, including the polyether-modified polyisocyanate compound represented by the general formula (1), and the polyamine compound in the resin components of the curable resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved. For example, it may be 15% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more, even more preferably 50% by volume or more, and particularly preferably 70% by volume or more. There is no particular upper limit and it can be 100% by volume or less. The content of the resin components in the curable resin composition of the present invention is preferably 25 to 50% by volume, more preferably 30 to 50% by volume. The proportion of the thermally conductive particles in the total amount of components other than the resin components in the curable resin composition of the present invention is preferably 50% by volume or more, more preferably 60% by volume or more, and even more preferably 70% by volume or more. It is also preferable that all components other than the resin components in the curable resin composition of the present invention are thermally conductive particles. The content of the thermally conductive particles in the curable resin composition of the present invention is, for example, preferably 30 to 60% by volume, more preferably 30 to 55% by volume, and even more preferably 30 to 50% by volume. Furthermore, when the curable resin composition of the present invention contains the other components described above, the content of the other components in the curable resin composition of the present invention can be, for example, 10 to 20% by volume.

[0050] Preferred embodiments of the curable resin composition of the present invention include, for example, a form containing thermally conductive particles and a resin component containing a polyamine compound and a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by the general formula (1) described above (however, this form does not contain hollow particles), and a form containing thermally conductive particles and a resin component containing a polyamine compound and a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by the general formula (1) described above. In these embodiments, the contents of each component in the curable resin composition can be determined in the same manner as those described above for the contents of the corresponding components in the backing material of the present invention.

[0051] <Method for Producing Backing Material> The curable resin composition of the present invention can be prepared by a conventional method. For example, the curable resin composition of the present invention can be obtained by kneading the components constituting the curable resin composition, which include the thermally conductive particles described above, a resin component containing a polyisocyanate compound including the polyether-modified polyisocyanate compound represented by the general formula (1) described above, and a polyamine compound, as well as other components as appropriate, using a kneading device such as a rotation-revolution device such as a rotation-revolution mixer, a kneader, a pressure kneader, a Banbury mixer (continuous kneader), or a two-roll mill. The order in which the components are mixed is not particularly limited. The kneading conditions are not particularly limited, as long as the thermally conductive particles and other components that may be contained as appropriate are dispersed in the resin component.

[0052] The backing material of the present invention can be obtained by curing the curable resin composition of the present invention obtained in this manner. The curing conditions can be adjusted depending on the chemical reaction of the resin components contained in the curable resin composition of the present invention. For example, the backing material can be obtained by heat curing at 20 to 200°C for 5 to 500 minutes. The shape of the backing material is not particularly limited. For example, it may be formed into a shape suitable for a backing material, such as a cylindrical shape, using a mold during curing. Alternatively, a sheet-shaped backing material may be obtained and then cut by dicing or the like to obtain the desired backing material. The backing material of the present invention can be used in various ultrasonic probes, such as convex and radial types, and is particularly suitable for radial type ultrasonic probes in which the backing material has a curved surface.

[0053] The backing material of the present invention is useful for medical devices, and can be preferably used in, for example, acoustic wave probes and acoustic wave measuring devices, and more preferably in ultrasound probes and ultrasound diagnostic devices. Note that, in the present invention, the term "acoustic wave measuring device" is not limited to an ultrasound diagnostic device or a photoacoustic wave measuring device, but refers to a device that receives acoustic waves reflected by or generated by an object and displays them as an image or signal intensity. In particular, the backing material of the present invention can be preferably used as a backing material for ultrasound probes, a backing material for photoacoustic wave measuring devices or ultrasound endoscopes, and a backing material for ultrasound probes equipped with capacitive micromachined ultrasound transducers (cMUTs) as an ultrasound transducer array. Specifically, the backing material of the present invention is preferably applied to, for example, the ultrasonic diagnostic apparatus described in JP-A-2003-169802, and the acoustic wave measuring apparatus such as the photoacoustic wave measuring apparatus described in JP-A-2013-202050 and JP-A-2013-188465.

[0054] <<Acoustic Wave Probe>> The configuration of an acoustic wave probe using the backing material of the present invention will be described in more detail below based on the configuration of an ultrasonic probe in an ultrasonic diagnostic device shown in Fig. 1. Note that an ultrasonic probe is a probe that uses ultrasonic waves, in particular, as the acoustic wave in an acoustic wave probe. Therefore, the basic structure of an ultrasonic probe can be applied directly to an acoustic wave probe.

[0055] [Ultrasonic Probe] The configuration of the ultrasonic probe of the present invention will be described in more detail below based on the configuration of an ultrasonic probe in an ultrasonic diagnostic device shown in Figure 1. The ultrasonic probe 10 is a major component of an ultrasonic diagnostic device and has the functions of generating ultrasonic waves and transmitting and receiving ultrasonic beams. As shown in Figure 1, the ultrasonic probe 10 is configured such that, from the tip (the surface that contacts the living body being examined), an acoustic lens 1, an acoustic matching layer 2, a piezoelectric element layer 3, and a backing material 4 are provided in this order. In recent years, a laminated structure has been proposed in which the transmitting ultrasonic transducer (piezoelectric element) and the receiving ultrasonic transducer (piezoelectric element) are made of different materials in order to receive higher-order harmonics.

[0056] <Piezoelectric Element Layer> The piezoelectric element layer 3 is a part that generates ultrasonic waves. Electrodes are attached to both sides of the piezoelectric element. When a voltage is applied, the piezoelectric element vibrates by repeatedly expanding and contracting, thereby generating ultrasonic waves.

[0057] The materials that make up the piezoelectric element include quartz crystal and LiNbO ３ , LiTaO ３ and KNbO ３ single crystals such as ZnO and AlN, thin films such as Pb(Zr,Ti)O ３Inorganic ceramic piezoelectric materials, which are obtained by polarization-treating sintered bodies such as those based on the PZT system, are widely used. Generally, piezoelectric ceramics such as PZT (lead zirconate titanate), which have good conversion efficiency, are used. Furthermore, piezoelectric elements that detect high-frequency received waves require sensitivity over a wider bandwidth. For this reason, organic piezoelectric materials using organic polymeric materials such as polyvinylidene fluoride (PVDF) are used as piezoelectric elements suitable for high frequencies and wide bandwidths. Furthermore, Japanese Patent Laid-Open Publication No. 2011-071842 and other publications describe cMUTs that utilize MEMS (Micro Electro Mechanical Systems) technology, exhibiting excellent short-pulse and wide-band characteristics, and enabling mass production with minimal characteristic variation, resulting in an array structure. Any of these piezoelectric element materials can be preferably used in the present invention.

[0058] <Backing Material> The backing material 4 is provided on the back surface of the piezoelectric element layer 3, and by suppressing excess vibrations, it shortens the pulse width of ultrasound and contributes to improving the axial resolution in ultrasound diagnostic images. In the ultrasonic probe of the present invention, the backing material 4 includes the backing material of the present invention. The backing material of the present invention has excellent ultrasonic attenuation properties and durability against temperature changes, and also exhibits high heat dissipation properties due to the thermally conductive particles. Therefore, by using the backing material of the present invention or the curable resin composition of the present invention, it is possible to obtain a backing material 3 that can suppress excess vibrations radiated from the piezoelectric element layer 3 to the back surface side when the ultrasonic probe is driven, and can efficiently dissipate heat emitted from the piezoelectric element layer 3, thereby suppressing the occurrence of cracks due to repeated use of the ultrasonic probe.

[0059] <Acoustic Matching Layer> The acoustic matching layer 2 is provided to reduce the difference in acoustic impedance between the piezoelectric element layer 3 and the subject to be examined, and to efficiently transmit and receive ultrasonic waves.

[0060] <Acoustic Lens> The acoustic lens 1 is provided to utilize refraction to focus ultrasonic waves in the slice direction and improve resolution. It is also required to be in close contact with the living body being examined, and to match the ultrasonic waves to the acoustic impedance of the living body (1.4 to 1.7 Mrayl for the human body). In other words, the acoustic lens 1 is made of a material whose acoustic speed is sufficiently slower than that of the human body and whose acoustic impedance is close to that of human skin, thereby improving the ultrasonic transmission and reception sensitivity.

[0061] The operation of the ultrasonic probe 10 configured as described above will now be described. A voltage is applied to the electrodes provided on both sides of the piezoelectric element layer 3 to resonate the piezoelectric element layer 3, and an ultrasonic signal is transmitted to the subject through the acoustic lens 1. During reception, the piezoelectric element layer 3 is vibrated by a reflected signal (echo signal) from the subject, and this vibration is electrically converted into a signal to obtain an image.

[0062] - Ultrasonic probe equipped with a cMUT (capacitive micromachined ultrasonic transducer) - When a cMUT device described in JP 2006-157320 A, JP 2011-71842 A, or the like is used in an ultrasonic transducer array, the sensitivity is generally lower than that of a transducer using a general piezoelectric ceramic (PZT). Note that, because a cMUT device is fabricated using MEMS technology, it is more easily mass-produced than a piezoelectric ceramic probe, and low-cost ultrasonic probes can be provided to the market.

[0063] Photoacoustic wave measurement device using photoacoustic wave imaging Photoacoustic wave imaging (PAI), as described in JP 2013-158435 A and other publications, irradiates the inside of the human body with light (electromagnetic waves) and displays an image of ultrasound waves generated when the irradiated light causes adiabatic expansion of human tissue, or the signal intensity of the ultrasound waves.

[0064] - Ultrasonic endoscope - The ultrasonic endoscope described in JP 2008-311700 A and the like includes an insertion section inserted into the body and an operating section connected to the proximal end of the insertion section. An ultrasonic probe is provided at the tip of the insertion section. By using a backing material containing the backing material of the present invention as the backing material constituting the ultrasonic probe, excess vibrations applied to the ultrasonic endoscope are suppressed, thereby improving the acoustic characteristics of the ultrasonic endoscope.

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not to be construed as being limited thereto. Note that room temperature means 25°C.

[0066] Example <1> Preparation of Backing Material Compositions Backing material compositions (curable resin compositions) having the formulations shown in Table 1 were prepared. Specifically, the resin raw material (P), resin compounding components (R), thermally conductive particles (TH), and hollow particles (B) were weighed out in the blending ratios shown in Tables 1-1 to 1-6 (collectively referred to as "Table 1") below, and mixed using a centrifugal mixer (product name: Awatori Rentaro Vacuum Type ARV-310, manufactured by Thinky Corporation) to prepare backing material compositions Nos. 101 to 139 and c11 to c36. The components used in each backing material composition are as shown in Tables A-1 and A-2 (collectively referred to as "Table A") below.

[0067] <2> Preparation of Backing Material Sheets The backing material composition prepared above was poured into a square mold with a side length of 30 mm and the desired depth, and cured by heating at 100°C for 4 hours to prepare square backing material sheets with a side length of 30 mm and the desired thickness, which were used for the following measurements and evaluations. Backing material sheet Nos. 101 to 139 are backing materials of the present invention, and backing material sheet Nos. c11 to c36 are comparative backing materials. The depth of the mold used and the thickness of the resulting sheets were 2 mm and 0.5 mm, respectively.

[0068] <3> Measurement and Evaluation The backing material composition and backing material sheet were subjected to the following measurements and evaluations. The results are shown in Table 1.

[0069] (1) Glass Transition Temperature (Tg) A square backing material sheet with a thickness of 0.5 mm was cut into 5 mm wide strips to prepare test specimens. The storage modulus of the prepared test specimens was measured using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., product name "Vibron DVA-225") under the following conditions: a grip distance of 20 mm, a heating rate of 2°C / min, a measurement temperature range of -150°C to 250°C, and a frequency of 5 Hz. A semi-logarithmic plot was made, with the storage modulus measured at each temperature on the vertical axis and the measurement temperature on the horizontal axis, with the vertical axis as the logarithmic axis and the horizontal axis as the linear axis. The glass transition temperature (Tg) was determined from the obtained curve based on the method described in "9.3 Method for Determining Glass Transition Temperature (see Figure 3)" of JIS (Japanese Industrial Standards) K7121 (1987). The DTA (differential thermal analysis) or DSC (differential scanning calorimetry) curve in 9.3 of JIS K7121 (1987) was used by replacing it with the curve obtained by the dynamic viscoelasticity measurement.

[0070] (2) Attenuation Rate Based on the method described in JIS (Japanese Industrial Standards) Z 2354 (2012) "Method for measuring ultrasonic attenuation coefficient of solids," the intensity of the reflected echo was measured using a sing-around sound velocity measuring device (manufactured by Ultrasonic Industries, product name "Ultrasonic Sound Velocity Measuring Device UVM-2 Type"). The measurement was performed using a 2 MHz measuring probe in water at 25°C, using a 2 mm thick backing material sheet as the measurement test piece. The attenuation rate was calculated from the difference in the intensity of the reflected echo with and without the measurement test piece and the thickness of the measurement test piece, and evaluated based on the following criteria. - Evaluation Criteria (Attenuation Rate) - S: The attenuation rate is greater than 8.0 dB / (mm MHz). A: The attenuation rate is greater than 3.0 dB / (mm MHz) and equal to or less than 8.0 dB / (mm MHz). B: The attenuation rate is greater than 1.0 dB / (mm MHz) and equal to or less than 3.0 dB / (mm MHz). C: The attenuation rate is 1.0 dB / (mm·MHz) or less.

[0071] (3) Durability against temperature change The backing material composition prepared above was applied to the outer periphery of a cylindrical SUS (Steel Use Stainless Steel) rod with a diameter of 1 cm and a length of 40 mm so that the thickness after curing was 1 mm, and then heated to 100 ° C for 4 hours to cure, thereby obtaining a test sample. The obtained test sample was subjected to the following temperature cycle test using a high-rate chamber (manufactured by ESPEC Corporation, trade name "HRS-306L", high-power high-rate large type). Specifically, the test sample was cooled from room temperature to -20 ° C at a temperature change rate of -5 ° C / min (preparation step), held at -20 ° C for 10 minutes (step 1), heated to 100 ° C at a temperature change rate of 5 ° C / min (step 2), held at 100 ° C for 10 minutes (step 3), and then cooled to -20 ° C at a temperature change rate of -5 ° C / min (step 4). 1000 cycles were performed, with steps 1 to 4 considered as one cycle. After the temperature cycle test, the test samples were visually inspected for the presence or absence of cracks on the surface of the cured backing material composition, and durability against temperature changes was evaluated according to the following criteria. - Evaluation criteria (durability against temperature changes) - S: No cracks occurred during 1000 cycles. A: Cracks occurred during 700 to 999 cycles. B: Cracks occurred during 300 to 699 cycles. C: Cracks occurred during up to 299 cycles.

[0072] (4) Effect of improving damping rate by adding hollow particles Among the backing sheets prepared above, for the backing sheets containing hollow particles, the increase U of the damping rate due to the addition of hollow particles (hereinafter simply referred to as "increase U") was calculated using the following formula. The calculated increase U was applied to the following criteria to evaluate the effect of improving damping rate due to the addition of hollow particles. Increase U of damping rate due to the addition of hollow particles = damping rate ＨＰ - Decay rate ＳＴ In the above formula, the attenuation rate ＨＰ indicates the attenuation rate of the backing sheet containing hollow particles, and the attenuation rate ＳＴindicates the attenuation rate of the reference backing sheet that does not contain hollow particles. ＨＰ The backing material composition used to prepare the backing sheet exhibiting the above characteristic was prepared in the same manner as in the preparation of the backing material composition used to prepare the backing sheet exhibiting the characteristic, except that hollow particles were not blended in, and the backing material composition was prepared in the same manner as in the preparation of the backing material composition used to prepare the backing sheet exhibiting the characteristic. The attenuation rate of each backing sheet was measured using the method described in (2) Attenuation Rate above. - Evaluation criteria (effect of improving attenuation rate by adding hollow particles) - S: The increase U is more than 5 dB / (mm MHz). A: The increase U is more than 4 dB / (mm MHz) and is 5 dB / (mm MHz) or less. B: The increase U is 4 dB / (mm MHz) or less.

[0073] (5) Overall Evaluation The evaluation results of (2) attenuation rate and (3) durability against temperature change were applied to the following criteria for an overall evaluation. - Overall evaluation criteria - S: The evaluation results of (2) and (3) above were both rated "S". A: One of the evaluations of (2) and (3) above was rated "A", and the other was rated "S" or "A". B: One of the evaluations of (2) and (3) above was rated "B", and the other was rated "S", "A", or "B". C: At least one of the evaluations of (2) and (3) above was rated "C".

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] (P): Resin raw material (I): Polyisocyanate compound, I-1 to I-11 are as described in Table A below. (A): Polyamine compound, A-1 to A-9 are as described in Table A below. (E): Epoxy compound, E-1 and E-2 are as described in Table A below. NBR-1 is liquid acrylonitrile butadiene rubber, and EVAC-1 is ethylene-vinyl acetate copolymer resin, details of which are as described in Table A below. (R): Resin compounding component R-1 is a diluent, and R-2 is a defoamer, details of which are as described in Table A below. (TH): Thermally conductive particles SiC-1 is silicon carbide particles, WC-1 is tungsten carbide particles, BN-1 is boron nitride particles, and WO3-1 is tungsten oxide particles, details of which are as described in Table A below. (B): Hollow Particles B-1 are hollow resin particles, the details of which are as shown in Table A below.

[0081] The composition column lists the amount of each component used in preparing the backing material composition (curable resin composition), and these amounts are based on mass. A "-" in the table indicates that the component is not contained. The content ratio column lists the content ratio of each component, i.e., resin component, thermally conductive particles, and hollow particles, in the backing material sheet, expressed in volume percent. The glass transition temperature is expressed in °C. A "\ (diagonal line (downward to the right))" in the table indicates that the effect of adding hollow particles to improve the attenuation rate was not evaluated, or could not be evaluated because hollow particles were not contained.

[0082]

[0083]

[0084] (P): Resin raw material (I): Polyisocyanate compound (A): Polyamine compound (E): Epoxy compound (R): Resin compounding component (TH): Thermally conductive particles (B): Hollow particles PEPO: Polyether polyol PPG: Polypropylene glycol PEsPO: Polyester polyol MDI: Diphenylmethane diisocyanate TDI: Toluene diisocyanate Polymeric MDI: Polymethylene polyphenyl polyisocyanate, meaning a mixture of 4,4'-MDI and a high molecular weight polyisocyanate. The particle sizes of the thermally conductive particles and hollow particles are number average particle sizes measured by the following method. The hollow particles were confirmed to be present as hollow particles in the backing material sheet by cutting the backing material sheet with a razor blade and observing the cross section with a tabletop microscope, Miniscope TM4000 (trade name, manufactured by Hitachi High-Technologies Corporation).

[0085] (Measurement of number average particle diameter of particles) The number average particle diameter of the particles was calculated by observing the edge of the backing material sheet in a field of view containing 500 or more particles using a scanning electron microscope (SU8030 (trade name) manufactured by Hitachi High-Technologies Corporation), randomly selecting 500 particles from the field of view, measuring the particle diameters of these particles. For backing material sheets whose edge cannot be observed using a scanning electron microscope, observation was performed using ice-embedding transmission electron microscopy. Ice embedding was performed using a Vitrobot Mark IV (trade name) manufactured by FEI, and 500 particles were randomly selected from the field of view using a transmission electron microscope (JEOL Ltd., JEM-2010 (trade name)), measuring the particle diameters of these particles, and calculating the particle diameter. In addition, when the particles were not perfectly round, particles with a maximum ratio of vertical to horizontal diameter of 0.7 or more were selected and measured. In the details of the polyisocyanate compound, "Mn" means the number average molecular weight measured and calculated by the method described above, "Formula (I):" represents the proportion (unit: mass%) of the polyether-modified polyisocyanate compound represented by general formula (1) in the polyisocyanate compound, and "NCO:" represents the amount of isocyanato groups present in the polyisocyanate compound expressed as a mass percentage (mass%). The CAS (main component) column lists the CAS number of the main component.

[0086] As shown in Table 1, comparative backing material sheets Nos. c11 to c31 contain a cured reaction product of a polyamine compound and a polyisocyanate compound that does not fall under the polyether-modified polyisocyanate compound represented by general formula (1) defined in the present invention. These comparative backing material sheets Nos. c11 to c31 received an overall rating of C or B, indicating poor ultrasonic attenuation and / or durability against temperature changes. Reference example backing material sheets Nos. c32 to c34, which contain a reaction compound of a polyepoxy compound and a polyamine compound, also received an overall rating of C, indicating poor ultrasonic attenuation and durability against temperature changes. Comparative backing material sheets Nos. c35 and c36, which use ethylene-vinyl acetate copolymer resin or liquid acrylonitrile butadiene rubber, known as the base material for backing materials, received an overall rating of C, indicating poor ultrasonic attenuation and durability against temperature changes. In contrast, backing material sheets Nos. c35 and c36, which satisfy the definition of the present invention, received an overall rating of C, indicating poor ultrasonic attenuation and durability against temperature changes. It was found that Nos. 101 to 139 have improved heat dissipation properties due to the incorporation of thermally conductive particles, and are also excellent in both ultrasonic attenuation and durability against temperature changes. When the glass transition temperature of the backing material is 10°C or lower, they have the effect of improving ultrasonic attenuation and durability against temperature changes. The relationship between this improvement effect and the glass transition temperature was not known until now, and this is an unexpected effect.

[0087] This application claims priority based on Japanese Patent Application No. 2024-050289, filed on March 26, 2024, the contents of which are incorporated herein by reference as part of the present specification.

[0088] REFERENCE SIGNS LIST 1 acoustic lens 2 acoustic matching layer 3 piezoelectric element layer 4 backing material 7 housing 9 cord 10 ultrasonic probe

Claims

1. A backing material for an ultrasonic probe, comprising thermally conductive particles and a resin, wherein the resin comprises a reaction-cured product of a polyamine compound and a polyisocyanate compound, including a polyether-modified polyisocyanate compound represented by the following general formula (1): In the above formula, L １ indicates an amide bond, and L ２ represents a polyether chain represented by the following general formula (p), and X represents a group containing an isocyanato group and an aromatic ring. １ The amide bond as ２ and combine. In the above formula, L ３ represents an alkylene group, and n is 1 or more. * represents a bond.

2. Said L ２ 2. The backing material of claim 1, wherein the formula weight of the backing material is 50 to 6000.

3. The backing material of claim 1, wherein the glass transition temperature of the backing material is 10°C or less.

4. The backing material according to claim 1, wherein the content of said resin in said backing material is 30 to 80% by volume.

5. The backing material of claim 1, wherein the thermally conductive particles include at least one of metal particles and ceramic particles.

6. An ultrasonic probe comprising a backing material according to any one of claims 1 to 5.

7. An ultrasonic diagnostic device using the ultrasonic probe according to claim 6.

8. An ultrasonic endoscope comprising the ultrasonic probe according to claim 6.

9. A curable resin composition for forming the backing material according to any one of claims 1 to 5, comprising the thermally conductive particles and, as a resin component, a combination of a polyisocyanate compound containing the polyether-modified polyisocyanate compound represented by general formula (1) and a polyamine compound.

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