Backing material and acoustic wave probe

Abstract

To provide a backing material which has high dicing workability of an acoustic wave probe, can improve an attenuation rate of an acoustic wave, and does not deteriorate vibration characteristics of a piezoelectric element generating the acoustic wave, and to provide the acoustic wave probe using the backing material.SOLUTION: The backing material contains resins and fillers, wherein the resins are addition reaction type silicone resins, the fillers are made of inorganic materials, densities of the fillers are 5. 0g / cm3 or more and 20. 0g / cm3 or less, and 200 pts. mass or more of the fillers are contained with respect to 100 pts. mass of the resins.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a backing material and an acoustic wave probe using the same. [Background technology]

[0002] An acoustic wave measurement device, which is an example of a non-destructive testing device, is equipped with an acoustic wave probe that irradiates an acoustic wave toward an object to be measured, receives reflected waves (echoes) reflected according to the structure of the object to be tested, and outputs a measurement signal. The measurement signal converted from the reflected waves received by such an acoustic wave probe is output as, for example, an image. This allows the internal structure of the object to be observed non-destructively.

[0003] The acoustic wave to be irradiated during measurement may be, for example, an ultrasonic wave or a photoacoustic wave, and an appropriate wavelength range is selected depending on the constituent material of the object to be measured, the measurement conditions, and the like. For example, an ultrasound diagnostic device that uses ultrasound (generally with a frequency of 20 kHz or higher), which is an example of acoustic waves, irradiates ultrasound toward the inside of a subject to be measured, receives the ultrasound reflected by tissue inside the subject, and outputs an image of the ultrasound.

[0004] In such an ultrasound diagnostic device, ultrasonic waves are transmitted and received via an acoustic wave probe. A typical acoustic wave probe is provided with a piezoelectric element (vibrator) that performs electroacoustic conversion. An acoustic matching layer and an acoustic lens are provided in this order on the ultrasonic wave transmitting / receiving surface side (measurement object side) of the piezoelectric element. A backing material is provided on the back side (power supply side), which is the opposite side from the measurement object side. An adhesive layer may also be provided between each component.

[0005] Among the components of such acoustic wave probes, the backing material is provided to hold the piezoelectric element and to acoustically damp it, thereby suppressing excess vibration and shortening the pulse interval of the ultrasound. If the pulse interval of the ultrasound can be shortened in this way, it will be possible to improve the axial resolution in ultrasound diagnostic images, for example.

[0006] One of the properties required for such a backing material is that sound waves are efficiently absorbed inside the backing material.

[0007] As a method for satisfying the required characteristics of the backing material as described above, for example, Patent Document 1 discloses a configuration in which the backing material contains thermally conductive particles, non-thermally conductive particles, and a matrix resin that is a thermosetting resin, and the thermal conductivity is 2.0 W / mk or more, and the content of the thermally conductive particles is less than 30% by volume of the total volume of the backing material. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-130943 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in recent years, the technology described above has not been sufficient to meet the demand for further improvement in the acoustic damping characteristics of backing materials, and there is a need for backing materials that can achieve further improvements in the attenuation rate of acoustic waves, and for acoustic wave probes using such backing materials. Furthermore, conventional backing materials have problems such as element collapse during dicing of the acoustic wave probe, and they are prone to clogging due to shavings generated during dicing.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a backing material that has high dicing processability for acoustic wave probes and can improve the attenuation rate of acoustic waves, and an acoustic wave probe using the same. [Means for solving the problem]

[0011] In order to solve the above problems, the backing material and acoustic wave probe of one embodiment of the present invention propose the following means. (1) A backing material according to a first aspect of the present invention comprises a resin and a filler, the resin being an addition reaction type silicone resin, and the filler being an inorganic material having a density of 5.0 g / cm. 3 More than 20.0g / cm 3 The filler is contained in an amount of 200 parts by mass or more per 100 parts by mass of the resin.

[0012] (2) A second aspect of the present invention is the backing material of the first aspect, wherein the filler has an average primary particle size of 100 μm or less.

[0013] (3) A third aspect of the present invention is the backing material of the first or second aspect, wherein the filler is metal particles.

[0014] (4) In a fourth aspect of the present invention, the backing material of any one of the first to third aspects has a flexural modulus of elasticity of 0.2 MPa or more.

[0015] (5) A fifth aspect of the present invention is the backing material of any one of the first to fourth aspects, wherein the attenuation rate at a frequency of 5.0 MHz is 120 dB / cm or more.

[0016] (6) The acoustic wave probe of the sixth aspect of the present invention is formed using the backing material of any one of the first to fifth aspects. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a backing material that has high dicing processability for an acoustic wave probe and is capable of improving the attenuation rate of acoustic waves, and an acoustic wave probe using the same. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating the configuration of an acoustic wave probe according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram for explaining an evaluation method of the backing material in the examples. [Figure 3]FIG. 2 is an explanatory diagram for explaining an evaluation method of the backing material in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a backing material and an acoustic wave probe according to one embodiment of the present invention will be described with reference to the drawings. Note that the embodiment shown below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show essential parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as those in reality.

[0020] [Backing material] The backing material according to one embodiment of the present invention is disposed on the side opposite to the ultrasonic wave irradiation side of a piezoelectric element (vibrator) that constitutes an acoustic wave probe, which will be described later. The backing material of this embodiment contains at least a resin and a filler.

[0021] (resin) The resin may be an addition reaction type silicone resin that undergoes polymerization by an addition reaction. The silicone resin is not particularly limited, but examples thereof include dimethyl silicone, methyl phenyl silicone, phenyl silicone, modified silicone, etc. Among these, dimethyl silicone and methyl phenyl silicone are preferred.

[0022] Of these silicone resins, the resin of this embodiment is preferably a cured product of an addition reaction type liquid silicone resin. Here, addition reaction type liquid silicone resins are classified into one-component type and two-component mixed type, and when the addition reaction type liquid silicone resin is a two-component mixed type, the cured product refers to the entire product obtained by curing the mixture of the two components. By using such an addition reaction type silicone resin, it is possible to suppress the generation of outgassing during curing.

[0023] In the following description, when simply referred to as "silicone resin," it refers to the cured product as described above, i.e., the silicone resin after polymerization, and when referred to as "liquid silicone resin," it refers to a silicone resin oligomer that is an uncured (unpolymerized) silicone resin as a raw material, such as the addition reaction type liquid silicone resin described above. In other words, the "liquid silicone resin" in this embodiment is a precursor of the silicone resin as a cured product.

[0024] (filler) High-density particles such as ferrite and tungsten have traditionally been used as fillers. These high-density particles are dispersed in resin and have the effect of damping the vibration of sound waves propagating through the backing material. The following two mechanisms are thought to be responsible for the damping of vibrations by high-density particles. First, (a) the particles are dense, so a large amount of energy is required to vibrate them. Second, (b) the high-density particles vibrate more slowly than the surrounding resin, so when vibrations are applied, they lag behind the resin. This delay creates an anti-phase vibration, which cancels out the surrounding vibrations.

[0025] In this embodiment, the filler is an inorganic material having a density of 5.0 g / cm 3 More than 20.0g / cm 3 or less, preferably 7.0 g / cm 3 More than 20.0g / cm 3 It was composed of the following particles.

[0026] The filler made of such an inorganic material has a density of, for example, 5.0 g / cm 3 More than 20.0g / cm 3 It is preferable that the material be made of metal particles formed by granulating metals in the following ranges. Furthermore, preferred examples of such metal particles include particles containing stainless steel (SUS). The average primary particle size of the filler is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

[0027] The density of the filler is based on the value described in the product catalog, safety data sheet, etc., and if the value cannot be obtained from the catalog, etc., a value measured by a known method may be used, for example, a value measured using a true density measuring device.

[0028] The amount of filler to be blended is 200 parts by mass or more, preferably 230 parts by mass or more, and more preferably 260 parts by mass or more, per 100 parts by mass of silicone resin (resin). The upper limit of the amount of filler to be blended may be selected depending on ease of mixing and moldability, but is, for example, 500 parts by mass or less.

[0029] The average primary particle diameter of the filler is preferably 100 μm or less. The average primary particle diameter of the filler is determined based on the value described in the product catalog, safety data sheet, etc. If the value cannot be obtained from the catalog, etc., it may be determined by a known method, for example, by using a laser diffraction particle size distribution analyzer to obtain a cumulative particle size distribution, and the particle diameter at a cumulative percentage of 50% (D50) may be used.

[0030] In this embodiment, the density of the inorganic material is 5.0 g / cm 3 More than 20.0g / cm 3 By mixing the following filler in an amount of 200 parts by mass or more with respect to 100 parts by mass of silicone resin, it is possible to maintain a high attenuation rate of acoustic waves.

[0031] (Other ingredients) Furthermore, the backing material 4 may further contain components other than those described above, as necessary, such as colorants, crosslinking agents, curing agents, curing accelerators, curing retarders, solvents, dispersants, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers.

[0032] Among these, thermal conductivity improvers are components that are blended to impart heat dissipation. Examples of such thermal conductivity improvers include carbon, crystalline or amorphous silica, aluminum oxide, and magnesium oxide. These components may be used alone or in combination of two or more.

[0033] The colorant is a component added for the purpose of identification or confirmation of cleanliness. Examples of such colorants include pigments and dyes such as carbon, titanium oxide, and ferrite. These components may be used alone or in combination of two or more. The content of the colorant is not particularly limited, but is preferably 5 parts by mass or less, and preferably 3 parts by mass or less, per 100 parts by mass of the silicone resin.

[0034] (hardness) The backing material 4 of this embodiment conforms to JIS K6253-3:2012 and has a hardness (A hardness) measured with a type A durometer of 80 or more, preferably 85 or more. Also, the hardness (D hardness) measured with a type D durometer is 15 or more, preferably 20 or more. If the A hardness and D hardness are within the above ranges, the cut elements will not collapse after dicing and will be able to maintain their self-supporting properties.

[0035] (flexural modulus) The backing material of this embodiment conforms to JIS K7171:2016 and has a flexural modulus (MPa) of 0.2 or more, preferably 0.25 or more, where σ1 and σ2 are the stresses for 0.05% and 0.25% strain, respectively, and the flexural modulus is the value obtained by dividing the difference in stress (σ2 - σ1) by the difference in strain. If the flexural modulus is within the above range, collapse of the cut elements and clogging between adjacent elements during dicing are suppressed, making it possible to maintain good processability.

[0036] (density) The density of the backing material of this embodiment is, for example, 2.0 g / cm 3 More than 5.0g / cm 3 or less, preferably 2.5 g / cm 3 More than 4.0g / cm3 If the density is within the above range, it is possible to satisfy the high attenuation rate of acoustic waves required for a backing material.

[0037] (acoustic characteristics) The acoustic properties of the backing material can be evaluated, for example, by the attenuation rate of acoustic vibration. The attenuation rate of the backing material of this embodiment at a frequency of 5.0 MHz is 120 dB / cm or more, preferably 200 dB / cm or more. With such an attenuation rate, when used as a constituent material of an acoustic wave probe, it is possible to maintain a large amount of attenuation of acoustic vibration propagating to the side opposite the ultrasonic transmission / reception surface of the piezoelectric element (vibrator), and the backing material exhibits excellent acoustic properties.

[0038] [Backing material manufacturing method] An example of a method for producing a backing material according to one embodiment of the present invention will be described below. Note that the method for producing a backing material is not limited to the steps described below, and any steps and procedures can be performed as necessary.

[0039] (Step of obtaining resin composition material (before curing)) First, the liquid silicone resin, filler, and other components, if necessary, are prepared and weighed out in appropriate amounts to achieve a predetermined blend ratio. The weighing can be performed by a known method, and the blend ratio of each component is the same as the content in the backing material described above, unless otherwise specified.

[0040] Next, the components prepared as described above are mixed to prepare a resin composition material. In this embodiment, the dispersibility, workability, and moldability can be improved by mixing the liquid silicone resin described above with a filler.

[0041] Furthermore, the method for mixing the above-mentioned components is not particularly limited as long as a resin composition material in which the filler is dispersed in the liquid silicone resin can be obtained, and any known method can be used. Examples of such mixing methods include stirring with a rotor blade, stirring with a planetary stirring mixer, etc.

[0042] Such mixing is preferably carried out under reduced pressure. By continuing mixing under reduced pressure and degassing, bubble entrapment is suppressed, the added filler is uniformly dispersed and maintained, and a resin composition material can be suitably obtained. The degree of vacuum during the degassing may be any degree that can be achieved by a general vacuum degassing machine.

[0043] (Step of curing the resin composition material) The resin composition material obtained as described above is molded into a predetermined shape and cured. The molding method is not particularly limited and can be performed by a known method, for example, a method in which the mixed resin composition material is poured into a molding die, and then the die is clamped and cured.

[0044] The molded shape is not particularly limited, and may be a desired shape depending on the type of use, etc., or the cured product may be formed into a predetermined shape by post-processing (e.g., shaping such as cutting, milling, or polishing). The heating temperature and curing time may be appropriately set depending on the curing temperature of the resin used.

[0045] (Optional processing steps) The method for producing the backing material may include other steps as necessary in addition to the steps described above. It is also preferable to optionally perform various treatments to improve chemical resistance, water resistance, abrasion resistance, adhesiveness, etc., as long as the sonic vibration damping effect is not affected.

[0046] Through the above steps, a backing material containing no air bubbles and in which the filler is dispersed in the silicone resin can be obtained.

[0047] [Acoustic wave probe] The backing material of the above-described embodiment can be suitably used as a constituent material of an acoustic wave probe. FIG. 1 is a schematic diagram showing the configuration of an acoustic wave probe according to one embodiment of the present invention. The acoustic wave probe 10 has, in order from the ultrasound transmitting / receiving surface side (measurement object side), an acoustic lens 1, an acoustic matching layer 2, a piezoelectric element (vibrator) 3, and a backing material 4 of this embodiment, and further has a housing 5 that houses these. The acoustic wave probe 10 can be produced by laminating the backing material 4 obtained as described above, the piezoelectric element 3, the acoustic matching layer 2, and the acoustic lens 1 using an adhesive or the like.

[0048] [Dicing process] The dicing process is performed by bonding the backing material 4, piezoelectric element 3, and acoustic matching layer 2 together using an adhesive or the like, cutting the piezoelectric element 3 from the acoustic matching layer 2 side before laminating the acoustic lens 1, and dicing at a predetermined pitch in one go to form grooves several hundred microns deep in the backing material 4. The dicing method is not particularly limited, and examples include blade dicing and laser ablation dicing. The acoustic wave probe 10 can be fabricated by laminating the diced acoustic matching layer 2 and the acoustic lens 1 together using an adhesive or the like.

[0049] By using the backing material 4 of the above-described embodiment, an acoustic wave probe 10 can be realized that has high dicing processability, maintains a high acoustic wave attenuation rate, and is equipped with a backing material 4 that does not affect the vibration characteristics of the piezoelectric element.

[0050] Although one embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Example]

[0051] In the following examples, the resin composition materials of the present invention and comparative examples were cured to form backing materials, and their physical properties were examined. (Example 1 of the present invention) As the silicone resin, 50 parts by mass of a two-component silicone resin A liquid (KE-1204-A: manufactured by Shin-Etsu Chemical Co., Ltd.) and 50 parts by mass of a two-component silicone resin B liquid (KE-1204-B: manufactured by Shin-Etsu Chemical Co., Ltd.) (total 100 parts by mass) were used. Furthermore, as the filler, SUS particles (AKT-410L(10): manufactured by Mitsubishi Steel Corporation (density 8.4 g / cm 3 140 parts by mass of silicone resin (average primary particle diameter: 9.63 μm) was used. The silicone resin solution A and solution B described above consisted of, in addition to the resin component, crystalline silica, iron oxide as a colorant, and a polyfunctional siloxane as a crosslinking agent. The resulting resin composition material contained 126 parts by mass of crystalline silica, 2.3 parts by mass of iron oxide, 0.8 parts by mass of polyfunctional siloxane, and 321 parts by mass of SUS particles, based on 100 parts by mass of the resin component.

[0052] (Comparative Example 1) Instead of the two-component silicone resin of Invention Example 1, 100 parts by mass of silicone resin (KE-106: manufactured by Shin-Etsu Chemical Co., Ltd.) and 10 parts by mass of curing agent (CAT-RG) were used, and further, alumina particles (AO-502: manufactured by Admatechs Co., Ltd. (density 3.7 g / cm) were added in addition to 140 parts by mass of SUS particles as a filler. 3 )) 125 parts by mass, and further amorphous silica particles (R-8200: manufactured by Nippon Aerosil Co., Ltd. (density 2 g / cm 3)) 10 parts by mass was used. Other than that, it was the same as in Example 1 of the present invention.

[0053] (Comparative Example 2) Instead of the two-component silicone resin used in Invention Example 1, 100 parts by mass of an epoxy resin (jER-828, manufactured by Mitsubishi Chemical Corporation) and 1.4 parts by mass of a curing agent (2E4MZ, manufactured by Shikoku Chemical Industries Co., Ltd.) were used. No filler was added. The rest of the procedure was the same as Invention Example 1.

[0054] (Comparative Example 3) Instead of the two-component silicone resin of Invention Example 1, 100 parts by mass of epoxy resin (jER-828: manufactured by Mitsubishi Chemical Corporation) and 1.4 parts by mass of curing agent (2E4MZ: manufactured by Shikoku Chemical Industries Co., Ltd.) were used, and in addition to 140 parts by mass of SUS particles as a filler, amorphous silica particles (AEROSIL200: manufactured by Nippon Aerosil Co., Ltd. (density 2.2 g / cm 3 )) 20 parts by mass was used. Other than that, it was the same as in Example 1 of the present invention.

[0055] Samples were prepared from the backing materials of Inventive Example 1 and Comparative Examples 1 to 3 as described above, and the following items were inspected and measured. (1) Density: A sample of 2 mm thickness was cut into a size of 40 mm x 40 mm, and the density (g / cm) was measured by the underwater displacement method. 3 ) was sought. (2) Hardness: The hardness (A hardness, D hardness) of the composition was measured using a type A durometer and a type D durometer in accordance with JIS K6253-3:2012. (3) Flexural modulus: Based on JIS K7171:2016, when the stresses for strains of 0.05% and 0.25% on a precision universal testing machine (Shimadzu Corporation, AGS-X) are σ1 and σ2, respectively, the flexural modulus (MPa) was calculated by dividing the difference in stress (σ2 - σ1) by the difference in strain. The size of the sample used for evaluation was 80 mm x 15 mm x 7 mm. (4) Dicing processability: Because dicing processability can be evaluated without laminating a matching layer, this time a sample was prepared in which a backing material and a piezoelectric element were bonded using an adhesive, and dicing processability was evaluated. Dicing was performed as shown in Figure 2. The cut-out elements were then visually checked for collapse, chipping, and the generation of cutting debris. If none of these three occurred, it was marked as ◯, and if even one of them occurred, it was marked as ×. (5) Attenuation rate: As shown in Figure 3, ultrasonic waves with a transmission frequency of 2.25 MHz were incident on a reflector X placed underwater using a transmitting and receiving probe 20, and the received wave W1 observed was measured. Similarly, a measurement sample 4a with a thickness of 1 mm was placed and a received wave W2 observed in the same manner was measured. Then, the acoustic intensity difference ΔG at 5.0 MHz was calculated based on the following formula (1). Furthermore, the reflection loss Δη on the front and back of the sample calculated using the following formula (2) was taken into account, and the attenuation rate of the sample was calculated based on the following formula (3). ΔG = G1 - G2 [dB] (1) ΔG: Acoustic intensity difference at each frequency G1: Sound intensity without sample [dB] G2: Acoustic intensity with sample [dB] Δη=2×20log((Z+Zw)2 / 4ZZw)[dB] ···(2) Δη: Return loss on the front and back of the sample [dB] Z: Sample acoustic impedance [dB] Zw: Acoustic impedance of water [dB] Attenuation rate=(ΔG-Δη) / 2d[dB / cm] ···(3) d: sample thickness [mm]

[0056] The composition of each backing material as well as the test and measurement results are summarized in Table 1. [Table 1]

[0057] According to the results shown in Table 1, Example 1 of the present invention has excellent dicing processability and an attenuation rate of 200 (dB / cm) or more, and it was confirmed that this is a backing material that can achieve both high dicing processability and high attenuation rate.

[0058] On the other hand, in Comparative Example 1, there were problems with dicing processability, and in Comparative Example 2, the attenuation rate was only 20 (dB / cm), and in Comparative Example 3, the attenuation rate was only 18 (dB / cm). Therefore, a backing material that could achieve both high processability and high attenuation rate could not be obtained. [Industrial Applicability]

[0059] The backing material of the present invention and the acoustic wave probe using the same can realize, for example, an ultrasonic diagnostic device equipped with an ultrasonic probe using a backing material that has high dicing processability for the acoustic wave probe and excellent ultrasonic propagation characteristics, and therefore has industrial applicability. [Explanation of symbols]

[0060] 1...Acoustic lens 1a...Measurement sample 2…Acoustic matching layer 3...Piezoelectric element 4...Backing material 5. Housing 10...Acoustic wave probe

Claims

1. Contains a resin and a filler, the resin is an addition reaction type silicone resin, The filler is made of an inorganic material and has a density of 5.0 g / cm ３ 20.0g / cm or more ３ The backing material contains 200 parts by mass or more of the filler per 100 parts by mass of the resin.

2. 2. The backing material according to claim 1, wherein the filler has an average primary particle size of 100 μm or less.

3. The backing material according to claim 1 or 2, wherein the filler is metal particles.

4. 2. The backing material according to claim 1, wherein the backing material has a flexural modulus of 0.2 MPa or more.

5. 5. The backing material according to claim 1, wherein the attenuation rate at a frequency of 5.0 MHz is 120 dB / cm or more.

6. An acoustic wave probe using the backing material according to claim 1 or 4.

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