Backing material for ultrasonic probe

Abstract

To provide a novel backing material for an ultrasonic probe possessing excellent thermal insulation in the thickness direction and ultrasonic attenuation properties.SOLUTION: As shown in Figure 1, a backing material 10 for ultrasonic probes contains a binder resin 12 and hollow particles 14 dispersed within the binder resin 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a backing material for an ultrasonic probe. [Background technology]

[0002] Medical ultrasound diagnostic devices and ultrasound imaging devices transmit ultrasound signals to an object and receive reflected signals (echo signals) from within the object to create an image of the object. These ultrasound diagnostic devices and ultrasound imaging devices mainly use array-type ultrasound probes (ultrasound probes) that have the ability to transmit and receive ultrasound signals.

[0003] An ultrasonic probe generally comprises, from the object side, an acoustic lens, an acoustic matching layer, a piezoelectric element, and a backing material, in this order. The backing material constituting such an ultrasonic probe is required to have performance such as good ultrasonic attenuation to improve sensitivity and high thermal conductivity to prevent overheating of the piezoelectric element. Various types of such backing materials have been proposed.

[0004] Patent Document 1 discloses an ultrasonic probe having a piezoelectric element and a backing material containing a matrix resin and thermally conductive particles, which is arranged on one side of the piezoelectric element, and in which the ratio of thermal conductivity in the thickness direction to the horizontal direction of the backing material is 3 or more.

[0005] Patent Document 2 discloses an ultrasonic probe comprising: a transducer array consisting of a plurality of transducers that transmit and receive ultrasonic waves; an electronic circuit disposed below the transducer array and electrically connected to the transducer array; an ultrasonic isolation layer disposed between the transducer array and the electronic circuit and having sound insulation properties that block ultrasonic waves propagating downward from the transducer array; and a thermal isolation layer disposed between the ultrasonic isolation layer and the electronic circuit and having heat insulation properties that limit the upward propagation of heat generated in the electronic circuit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-62170 [Patent Document 2] JP 2017-56124 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a novel backing material for an ultrasonic probe, which has good thermal insulation properties and ultrasonic attenuation properties in the thickness direction. [Means for solving the problem]

[0008] The present inventors have conducted extensive research and found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows: <Aspect 1> A backing material for an ultrasonic probe, comprising a binder resin and hollow particles dispersed in the binder resin. <Aspect 2> The backing material for an ultrasonic probe according to Aspect 1, wherein the content of the hollow particles is 35% by volume or more and 95% by volume or less relative to the volume of the backing material for an ultrasonic probe. <Aspect 3> The backing material for an ultrasonic probe according to Aspect 1 or 2, wherein the hollow particles are organic hollow particles. <Aspect 4> A backing laminate having an intermediate layer and two backing materials for an ultrasonic probe according to any one of Aspects 1 to 3, each of which is disposed on either side of the intermediate layer. <Aspect 5> The backing laminate according to aspect 4, wherein the intermediate layer contains a binder resin and scale-like particles dispersed in the binder resin. Aspect 6: An ultrasonic probe comprising an acoustic lens, an acoustic matching layer, a piezoelectric element, and the backing material for an ultrasonic probe according to any one of Aspects 1 to 3. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a novel backing material for an ultrasonic probe, which has good heat insulation properties and ultrasonic attenuation properties in the thickness direction. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side cross-sectional view of a backing material for an ultrasonic probe according to the present invention. [Figure 2] FIG. 2 is an explanatory diagram of the measurement of ultrasonic attenuation rate. [Figure 3] FIG. 3 is a cross-sectional side view of a backing laminate of the present invention. [Figure 4] FIG. 4 is a side cross-sectional view of the ultrasonic probe of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Backing material for ultrasonic probes> As shown in FIG. 1, a backing material 10 for an ultrasonic probe according to the present invention contains a binder resin 12 and hollow particles 14 dispersed in the binder resin 12 .

[0012] With conventional backing materials, efforts have been made to increase the thermal conductivity in order to dissipate heat from the piezoelectric element in the direction opposite the acoustic lens. However, when the thermal conductivity of the backing material is increased, heat generated by electronic components on the opposite side of the acoustic lens can flow toward the acoustic lens.

[0013] The inventors have found that the above-described structure provides good through-thickness thermal insulation and ultrasonic attenuation. Without wishing to be bound by theory, this is believed to be due to the fact that binder resins generally have high ultrasonic attenuation and that heat transfer is suppressed in the hollow portions of the hollow particles, thereby improving thermal insulation.

[0014] The thermal conductivity of the backing material of the present invention in accordance with JIS R1611-2010 can be 1.0 W / m·K or less. This thermal conductivity can be 1.0 W / m·K or less, 0.9 W / m·K or less, 0.8 W / m·K or less, 0.7 W / m·K or less, 0.6 W / m·K or less, 0.5 W / m·K or less, 0.4 W / m·K or less, or 0.3 W / m·K or less.

[0015] The acoustic impedance of the backing material of the present invention can be 1.0 Mrayl or more and 5.0 Mrayl or less. This acoustic impedance can be 1.0 Mrayl or more, 1.3 Mrayl or more, 1.5 Mrayl or more, or 1.8 Mrayl or more, and can be 5.0 Mrayl or less, 4.5 Mrayl or less, 4.0 Mrayl or less, 3.5 Mrayl or less, 3.0 Mrayl or less, or 2.8 Mrayl or less.

[0016] The above acoustic impedance is calculated by the following formula: Acoustic impedance (Z: Mrayl) = Density (ρ: g / cm 3 )×Sound velocity (C:m / sec) / 10 3

[0017] Here, the above-mentioned sound velocity may be the sound velocity measured in accordance with, for example, JIS Z 2353-2003.

[0018] The density of the backing material having the above structure is 1.10 g / cm 3 The density can be 1.10 g / cm or less. 3 Below 1.05g / cm 3 Below 1.00g / cm 3 Below, 0.95g / cm 3 or less, or 0.90 g / cm 3 can be less than or equal to 0.50 g / cm 3 More than 0.55g / cm 3 More than 0.60g / cm 3 More than 0.65g / cm 3 More than 0.70g / cm 3 or more, or 0.75 g / cm3 It can be more than that.

[0019] The backing material of the present invention may have an ultrasonic attenuation rate of 2.5 dB / mm or more at a frequency of 1 MHz, which may be 2.5 dB / mm or more, 3.0 dB / mm or more, 3.5 dB / mm or more, 4.0 dB / mm or more, 4.5 dB / mm or more, 5.0 dB / mm or more, 5.5 dB / mm or more, 6.0 dB / mm or more, 6.5 dB / mm or more, 7.0 dB / mm or more, 7.5 dB / mm or more, 8.0 dB / mm or more, or 8.5 dB / mm or more.

[0020] 2, this ultrasonic attenuation rate can be obtained by filling a water tank 20 with water 22 at 25°C, arranging a transmitting probe 40, a backing material 10, and a receiving probe 30 in that order, transmitting ultrasonic waves at a frequency of 1 MHz toward the backing material 10, receiving the ultrasonic waves that have passed through the backing material 10 with the receiving probe 30, and measuring the amplitude of the ultrasonic waves as they pass through the water (before passing through the backing material) and after passing through the backing material 10. The attenuation rate can be calculated using the ratio A / B of the amplitude A as they pass through the water (before passing through the backing material) to the amplitude B after passing through the backing material, and the thickness T of the backing material, using the following formula: Attenuation rate (dB / mm) = {20log 10 (A / B)} / T

[0021] The backing material for an ultrasonic probe of the present invention can be obtained, for example, by a method including kneading the hollow particles and binder resin that constitute the backing material to obtain a precursor composition, and molding this precursor composition by, for example, press molding.

[0022] The thickness of the backing material for an ultrasonic probe of the present invention may be 1 mm or more and 100 mm or less. This thickness may be 1 mm or more, 2 mm or more, or 3 mm or more, or may be 100 mm or less, 90 mm or less, 80 mm or less, 70 mm or less, 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, 25 mm or less, 20 mm or less, 15 mm or less, 12 mm or less, 10 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, or 5 mm or less.

[0023] Each component of the present invention will be described below.

[0024] <Binder resin> As the binder resin, rubber-based resins such as nitrile butadiene rubber (NBR), acrylic rubber, and urethane rubber, and thermoplastic resins such as vinyl chloride resin, vinyl acetate resin, and ethylene-vinyl acetate copolymer can be used.

[0025] The binder resin content may be 5% by volume or more and 65% by volume or less, based on the volume of the backing material. This content may be 5% by volume or more, 8% by volume or more, 10% by volume or more, 15% by volume or more, 15% by volume or more, 20% by volume or more, or 25% by volume or more, and may be 65% by volume or less, 62% by volume or less, 60% by volume or less, 55% by volume or less, 50% by volume or less, 45% by volume or less, 40% by volume or less, 35% by volume or less, or 30% by volume or less.

[0026] <Hollow particles> As the hollow particles, organic hollow particles such as acrylic hollow particles and urethane hollow particles, and non-metallic inorganic hollow particles such as silica hollow particles and volcanic ash hollow particles can be used, and among these, the use of organic hollow particles is preferred from the viewpoint of ultrasonic attenuation rate.

[0027] The content of hollow particles may be 35% by volume or more and 95% by volume or less, based on the volume of the backing material. This content may be 35% by volume or more, 38% by volume or more, 40% by volume or more, 45% by volume or more, 50% by volume or more, 55% by volume or more, 60% by volume or more, or 70% by volume or more, and may be 95% by volume or less, 92% by volume or less, 90% by volume or less, 85% by volume or less, 80% by volume or less, or 75% by volume or less.

[0028] The particle diameter of the hollow particles may be 1 μm or more and 50 μm or less, or 1 μm or more, 2 μm or more, or 3 μm or more, or 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 9 μm or less.

[0029] In the present invention, the "particle size" refers to the median size (D50) calculated on a volume basis by laser diffraction method.

[0030] The hollow particles may have a void ratio of 40% or more and 90% or less. This void ratio may be 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, or 70% or more, and may be 90% or less, 85% or less, or 80% or less.

[0031] Here, the hollow ratio can be calculated by the following formula. Hollowness ratio=(1-particle density / true density)×100 The true density of hollow particles can be measured, for example, by heating the hollow particles to a temperature equal to or higher than the melting point, then cooling them to remove voids, and then using a known density measuring device.

[0032] Backing laminate As shown in FIG. 3, the backing laminate 50 of the present invention has an intermediate layer 52 and two backing materials 10 for ultrasonic probes disposed on both sides of the intermediate layer.

[0033] By providing an intermediate layer, the heat insulating property can be further improved.

[0034] The intermediate layer and the backing material for an ultrasonic probe may be laminated via an adhesive layer or by fusion bonding.

[0035] <Middle class> As shown in FIG. 3, the intermediate layer 52 may contain a binder resin 522 and scale-like particles 524 dispersed in the binder resin 522 .

[0036] (binder resin) For the type and content of the binder resin, reference can be made to the description of the backing material for an ultrasonic probe, for example.

[0037] (scaly particles) As the scaly particles, non-metallic inorganic scaly particles such as boron nitride can be used.

[0038] The particle size of the scaly particles may be 1 μm or more and 50 μm or less. This particle size may be 1 μm or more, 3 μm or more, or 5 μm or more, or may be 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 8 μm or less.

[0039] 《Ultrasonic probe》 4, the ultrasonic probe 100 of the present invention has an acoustic lens 120, an acoustic matching layer 130, a piezoelectric element 140, and the above-mentioned backing material 10. In particular, the ultrasonic probe 100 of the present invention may have the acoustic lens 120, the acoustic matching layer 130, the piezoelectric element 140, and the above-mentioned backing material 10 in this order.

[0040] The ultrasonic waves emitted by the piezoelectric element 140 pass through the acoustic matching layer 130 and the acoustic lens 120 in this order before being transmitted to the target. In other words, the backing material 10 is provided on the piezoelectric element 140 that transmits the ultrasonic waves to the target, on the side opposite to the transmission direction of the ultrasonic waves from the piezoelectric element 140 to the target.

[0041] Acoustic Lens Acoustic lenses are typically positioned to use refraction to focus an ultrasound beam and improve resolution.

[0042] In the present invention, examples of materials that can be used to form the acoustic lens include conventionally known homopolymers such as silicone rubber, fluorosilicone rubber, polyurethane rubber, and epichlorohydrin rubber, and copolymer rubbers such as ethylene-propylene copolymer rubber obtained by copolymerizing ethylene and propylene.

[0043] <Piezoelectric element> A piezoelectric element generally has electrodes and a piezoelectric material, and is an element capable of converting an electrical signal into a mechanical vibration and vice versa, and capable of transmitting and receiving ultrasonic waves.

[0044] (Piezoelectric materials) The piezoelectric material may be a material capable of converting electrical signals into mechanical vibrations and vice versa. Examples of piezoelectric materials include piezoelectric ceramics such as lead zirconate titanate (PZT) ceramics and PbTiO3 ceramics, organic polymer piezoelectric materials such as vinylidene fluoride (VDF) polymers and vinylidene cyanide (VDCN) polymers, quartz, and Rochelle salt.

[0045] Examples of vinylidene fluoride (VDF) polymers include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), etc. Examples of vinylidene cyanide (VDCN) polymers include polyvinylidene cyanide (PVDCN) and vinylidene cyanide copolymers.

[0046] (electrode) For example, gold (Au), platinum (Pt), silver (Ag), palladium (Pd), copper (Cu), aluminum (Al), nickel (Ni), tin (Sn), etc. can be used for the electrodes.

[0047] <Acoustic matching layer> The acoustic matching layer generally matches the acoustic impedance between the ultrasonic transducer and the subject, and is made of a material having an acoustic impedance intermediate between that of the ultrasonic transducer and the subject.

[0048] Materials that can be used for the acoustic matching layer include aluminum, aluminum alloys (e.g., AL-Mg alloys), magnesium alloys, Macor glass, glass, fused silica, copper graphite, polyethylene (PE), polypropylene (PP), polycarbonate (PC), ABC resin, polyphenylene ether (PPE), ABS resin, AAS resin, AES resin, nylon (PA6, PA6-6), PPO (polyphenylene oxide), PPS (polyphenylene sulfide: can also contain glass fiber), PPE (polyphenylene ether), PEEK (polyether ether ketone), PAI (polyamide imide), PETP (polyethylene terephthalate), PC (polycarbonate), epoxy resin, urethane resin, etc.

[0049] The acoustic matching layer may be a single layer or multiple layers. [Example]

[0050] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0051] <<Making the backing material>> Example 1 50 parts by mass of hollow silica particles (density 0.15 g / cm 3 , particle diameter 3.6 μm, hollow rate 70% or more), and 50 parts by mass of nitrile butadiene rubber (NBR) (density 1.0 g / cm ) as a binder resin. 3 ) were mixed in a mixer and then kneaded using a three-roll mill to obtain a precursor composition.

[0052] The resulting precursor composition was then press-molded to obtain a 4 mm-thick backing material of Example 1. The respective volumetric contents of the hollow particles and binder resin used were calculated from their mass parts and densities. The density of the resulting backing material was also calculated from its volume and mass.

[0053] Examples 2 to 4 and Comparative Examples 1 and 2 Backing materials of Examples 2 to 4 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the type and content of each component was changed as shown in Table 1. The "acrylic hollow particles" shown in Table 1 are acrylic hollow particles with a particle diameter of 8 μm and a hollow ratio of approximately 50%.

[0054] "evaluation" <Thermal conductivity> The thermal conductivity of the prepared backing material in the thickness direction was measured using a laser flash thermal property measuring device (LFA457, NETZSCH).

[0055] <Ultrasonic attenuation rate> As shown in Figure 2, a water tank 20 was filled with water at 25°C, and a transmitting probe 40, a backing material 10, and a receiving probe 30 were arranged in that order. Ultrasonic waves with a frequency of 1 MHz were transmitted from the transmitting probe 40 toward the backing material, and the ultrasonic waves that passed through the backing material were received by the receiving probe 30. The ultrasonic attenuation rate in the thickness direction of each backing material was evaluated by measuring the amplitude of the ultrasonic waves before and after they passed through the backing material.

[0056] <Acoustic Impedance> In accordance with JIS Z 2353-2003, the sound velocity in the thickness direction of each prepared backing material was measured at 25°C using a sing-around sound velocity measuring device. The acoustic impedance was calculated using the calculated density and the measured sound velocity.

[0057] <Workability> The precursor compositions used to manufacture the backing materials of Examples 1 to 4 and Comparative Examples 1 and 2 were pressed in the same manner as above using a mold having multiple concaves and convexes corresponding to more than 50% of the thickness of the backing material to form backing materials, and the processability of the backing materials was evaluated. The evaluation criteria were as follows: A: No molding defects occurred. B: Defective molding such as cracking occurred.

[0058] Table 1 shows the configurations and evaluation results of the examples and comparative examples.

[0059] [Table 1]

[0060] From Table 1, it can be seen that the backing materials for ultrasonic probes of the examples, which contain a binder resin and hollow particles dispersed in the binder resin, have low acoustic impedance and thermal conductivity, high ultrasonic attenuation, and good processability. [Explanation of symbols]

[0061] 10 Backing material for ultrasonic probes 12 Binder resin 14 Hollow particles 20 aquarium 22 water 30 Receiving probe 40 Transmitting transducer 50 Backing laminate 52 Central layer 522 Binder resin 524 Scaly particles 100 Ultrasonic transducer 120 Acoustic Lens 130 Acoustic matching layer 140 Piezoelectric element

Claims

1. A backing material for an ultrasonic probe, comprising a binder resin and hollow particles dispersed in the binder resin.

2. 2. The backing material for an ultrasonic probe according to claim 1, wherein the content of the hollow particles is 35% by volume or more and 95% by volume or less with respect to the volume of the backing material for an ultrasonic probe.

3. 3. The backing material for an ultrasonic probe according to claim 1, wherein the hollow particles are organic hollow particles.

4. A backing laminate comprising an intermediate layer and two backing materials for an ultrasonic probe according to claim 1 or 2, each of which is disposed on either side of the intermediate layer.

5. 5. The backing laminate according to claim 4, wherein the intermediate layer contains a binder resin and scaly particles dispersed in the binder resin.

6. An ultrasonic probe comprising an acoustic lens, an acoustic matching layer, a piezoelectric element, and the backing material for an ultrasonic probe according to claim 1.

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