Resin composition

Abstract

The present invention provides a resin composition which is low in attenuation and can be coated. A resin composition according to an embodiment is a resin composition that is a precursor of an acoustic matching layer of an ultrasonic transducer in an ultrasonic transducer unit having an array transducer provided with a piezoelectric body and an electrode, the resin composition containing particles of a resin and an inorganic material, the acoustic impedance of the acoustic matching layer being set to Z, and the acoustic impedance of the acoustic matching layer being set to Z; if the density of the particles of the inorganic material is set as [rho], 2.3 < = Z / [square root of] [rho] < = 3.4 is satisfied.

Description

[0001] CROSS - REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Japanese Patent Application No. 2023 - 214214 filed on December 19, 2023, Japanese Patent Application No. 2024 - 006408 filed on January 18, 2024, and Japanese Patent Application No. 2024 - 223602 filed on December 18, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The embodiments disclosed in this specification and the accompanying drawings relate to a resin composition. BACKGROUND ART

[0004] In an ultrasonic diagnostic apparatus, the piezoelectric element and the acoustic matching layer are required to be thinned. In addition, the element size of the array oscillator is also required to be miniaturized in accordance with the higher frequency of transmitting and receiving ultrasonic waves.

[0005] Here, conventionally, the acoustic matching layer has been formed by laminating a glass plate, a carbon plate, etc. using an adhesive. However, as the acoustic matching substrate of the acoustic matching layer has been thinned, the operation of the substrate and the lamination using the adhesive have become difficult. In addition, the technical difficulty of processing the substrate of the acoustic matching layer has also increased.

[0006] Therefore, for example, as shown in Patent Document 1 (Japanese Patent No. 5415086), the following method has been considered: adjusting the acoustic impedance by mixing a high - density ceramic or metal filler obtained by mixing nano - sized particles and micro - sized particles in a resin, and laminating the acoustic matching layer by coating the mixture on the acoustic matching layer.

[0007] However, this method is limited to the case where the density of the ceramic particles is high. In addition, since it is a method of mixing particles of different sizes, there are problems in maintaining the in - plane uniformity of the impedance of the thin - film acoustic matching layer. SUMMARY OF THE INVENTION

[0008] One of the problems to be solved by the embodiments disclosed in this specification and the accompanying drawings is to produce a resin composition with low attenuation and capable of being coated. However, the problems to be solved by the embodiments disclosed in this specification and the accompanying drawings are not limited to the above problems. Problems corresponding to the respective effects brought about by the respective configurations shown in the following embodiments may also be defined as other problems.

[0009] ADVANTAGEOUS EFFECTS OF THE INVENTION

[0010] According to the resin composition of the embodiment, a resin composition with low attenuation and capable of being coated can be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram showing an example of the configuration of the ultrasonic diagnostic apparatus 100 according to an embodiment.

[0012] Figure 2 This is a diagram showing an example of the configuration of the ultrasonic transducer according to an embodiment.

[0013] Figure 3 This is a diagram for explaining the background of an embodiment.

[0014] Figure 4 This is a diagram for explaining the background of an embodiment.

[0015] Figure 5 This is a diagram for explaining the experimental results related to the acoustic matching layer composition of an embodiment.

[0016] Figure 6 This is a diagram for explaining the manufacturing method of the resin composition of an embodiment.

[0017] Figure 7 This is a diagram showing an example of the configuration of the ultrasonic transducers according to the first and second embodiments.

[0018] Figure 8 This is a diagram for explaining the background of an embodiment.

[0019] Figure 9 This is a diagram for explaining the manufacturing method of the resin composition of an embodiment.

[0020] Figure 10 This is a diagram for explaining the experimental results related to the acoustic matching layer composition of an embodiment.

[0021] Figure 11 This is a diagram for explaining the experimental results related to the acoustic matching layer composition of an embodiment.

[0022] Figure 12 This is a diagram showing an example of the configuration of the ultrasonic transducer according to the third embodiment. Detailed Embodiments

[0023] Hereinafter, embodiments of the resin composition will be described in detail with reference to the accompanying drawings.

[0024] (First Embodiment)

[0025] First, use Figure 1 , to explain an example of the configuration of an ultrasonic diagnostic apparatus incorporating an ultrasonic transducer generated using the resin composition of the embodiment.

[0026] As Figure 1As shown in [Fig.], the ultrasonic diagnostic apparatus 100 includes an ultrasonic probe 1, a monitor 2, an input device 3, and a device main body 10.

[0027] The ultrasonic probe 1 has an ultrasonic oscillator unit that transmits ultrasonic waves and receives reflected waves.

[0028] Figure 2 A partial configuration of the ultrasonic oscillator unit is shown in [Fig.].

[0029] The ultrasonic oscillator unit is built into the ultrasonic probe 1 and transmits and receives ultrasonic waves to and from a living body contacted by the probe. The ultrasonic oscillator unit is composed of, for example, a plurality of ultrasonic oscillators 23 arranged two-dimensionally, a flexible printed circuit (FPC) 22 that arranges the plurality of ultrasonic oscillators 23, and an acoustic lens. Each of the plurality of ultrasonic oscillators 23 is composed of a piezoelectric element 21, an acoustic matching layer 20, and a back matching layer (not shown). The element size 24 of the ultrasonic oscillator 23 is, for example, 40 μm.

[0030] The piezoelectric element 21 is an element having piezoelectricity. For example, the piezoelectric element 21 is a piezoelectric element such as PZT (lead zirconate titanate / Pb(Zr,Ti)O3), PMN-PT (lead magnesium niobate-lead titanate / Pb(Mg 1 / 3 Nb 2 / 3 )O3 - PbTiO3). In the embodiment, the plurality of ultrasonic oscillators 23 are arranged on a predetermined surface of the flexible printed circuit board 22. A signal electrode is provided on the surface (ultrasonic wave radiation surface) of the piezoelectric element 21 on the side that radiates ultrasonic waves. In addition, a ground electrode is provided on the surface (back surface) of the piezoelectric element 21 on the side opposite to the ultrasonic wave radiation surface side.

[0031] The piezoelectric element 21 is driven by a drive signal from the transmission / reception circuit 11 and radiates ultrasonic waves from the surface on the signal electrode side. In addition, when the piezoelectric element 21 receives a reflected wave, it converts the received reflected wave into a reflected wave signal and outputs the converted reflected wave signal from the signal electrode. The thickness of the piezoelectric element 21 is, for example, 40 μm.

[0032] The acoustic matching layer 20 is a layer for gradually reducing the acoustic impedance from the piezoelectric element 21 to the living body and making the piezoelectric element 21 acoustically match the living body. The acoustic matching layer 20 may be composed of only one layer, or may have a plurality of layers in order to make the acoustic impedance gradually decrease as smoothly as possible toward the living body. As the acoustic matching layer 20, for example, in order to have conductivity, a resin mixed with a conductive filler can be used. This resin can be, for example, an epoxy resin. The thickness of the acoustic matching layer 20 is, for example, 30 μm.

[0033] In addition, the back matching layer is made of a material having a higher acoustic impedance than the piezoelectric element, and serves as a resonance layer, integrated with the piezoelectric element to transmit and receive ultrasonic waves.

[0034] In addition, the flexible printed circuit board 22 is an FPC (Flexible Printed Circuit), and electrically connects the signal electrode and the ground electrode to the transceiver circuit 11 through the wiring provided in each layer of the ultrasonic transducer.

[0035] In addition, between the piezoelectric element 21 and the acoustic matching layer 20, for example, an adhesive may be filled, or it may be formed by laminate coating without using an adhesive.

[0036] When ultrasonic waves are transmitted from the ultrasonic probe 1 to the subject P, the transmitted ultrasonic waves are successively reflected at the discontinuity surfaces of the acoustic impedance in the body tissues of the subject P, and are received by the plurality of ultrasonic transducers 23 included in the ultrasonic probe 1 as reflected waves. The reflected waves are converted into reflected wave signals as electrical signals by the piezoelectric elements 21 of the ultrasonic transducers 23 that have received the reflected waves. The amplitude of the reflected wave signal depends on the difference in acoustic impedance at the discontinuity surface where the ultrasonic waves are reflected. It should be noted that when the transmitted ultrasonic pulse is reflected by the surface of a moving blood flow or the heart wall, etc., the reflected wave signal is frequency-shifted due to the Doppler effect, depending on the velocity component of the moving object relative to the ultrasonic wave transmission direction.

[0037] The monitor 2 displays a GUI (Graphical User Interface) for the operator of the ultrasonic diagnostic apparatus 100 to input various setting requirements using the input device 3, or displays ultrasonic images generated in the apparatus main body 10, etc.

[0038] The input device 3 includes a trackball, a switch, a dial, a touch command screen, etc. The input device 3 receives various setting requirements from the operator of the ultrasonic diagnostic apparatus 100 and transfers the received various setting requirements to the apparatus main body 10.

[0039] The apparatus main body 10 is a device that controls the transmission and reception of ultrasonic waves by the ultrasonic probe 1 and generates an ultrasonic image based on the reflected waves received by the ultrasonic probe 1. As shown in Figure 1 , the apparatus main body 10 includes a transceiver circuit 11, a B-mode processing circuit 12, a Doppler processing circuit 13, a processing circuit 14, and a memory 15.

[0040] The transceiver circuit 11 includes a trigger generation circuit, a delay circuit, a pulse generator circuit, etc., and supplies a drive signal to the ultrasonic probe 1.

[0041] The B-mode processing circuit 12 receives reflected wave data from the transceiver circuit 11, performs logarithmic amplification, envelope detection processing, etc., and generates data (B-mode data) in which the signal intensity is represented by the brightness of the luminance.

[0042] The Doppler processing circuit 13 performs frequency analysis on the velocity information based on the reflected wave data received from the transceiver circuit 11, extracts blood flow, tissue, and contrast agent echo components based on the Doppler effect, and generates data (Doppler data) in which moving body information such as average velocity, variance, and power is extracted for multiple points.

[0043] The processing circuit 14 is constituted by, for example, a control processor (CPU: Central Processing Unit) that realizes the functions of an information processing device (computer).

[0044] The processing circuit 14 generates an ultrasonic image from the data generated by the B-mode processing circuit 12 and the Doppler processing circuit 13 through an image generation function. In addition, through a control function, the processing circuit 14 controls the processing of the transceiver circuit 11, the B-mode processing circuit 12, the Doppler processing circuit 13, etc., based on various setting requirements input by the operator through the input device 3, or various control programs and various data read from the memory 15.

[0045] The memory 15 is a memory that stores the ultrasonic image generated by the processing circuit 14 through the image generation function 14a. In addition, the memory 15 can also store the data generated by the B-mode processing circuit 12 or the Doppler processing circuit 13.

[0046] Next, the background of the embodiment will be described. In the ultrasonic diagnostic apparatus 100, for the purpose of improving the resolution of the acquired image, or for the purpose of obtaining three-dimensional space information, etc., the array oscillator tends to be required to be composed of more ultrasonic oscillators 23. On the other hand, the ultrasonic probe 1 is required to transmit and receive ultrasonic waves at a higher frequency (shorter wavelength). Therefore, the piezoelectric element 21, the acoustic matching layer 20, etc. tend to be required to be thinned.

[0047] In addition, the element size 24 of the ultrasonic oscillator 23 is also preferably miniaturized in accordance with the high-frequencyization of the transmitted and received ultrasonic waves.

[0048] Here, conventionally, the acoustic matching layer 20 is generated by laminating a glass plate, a carbon plate, etc. using an adhesive, but due to the progress of the thinning of the acoustic matching substrate of the acoustic matching layer 20, the operation of the substrate and the lamination through the adhesive have become difficult. In addition, the technical difficulty of processing the substrate of the acoustic matching layer 20 has also increased.

[0049] Therefore, as shown in Patent Document 1, the following process has been proposed: The acoustic impedance Z is adjusted by mixing a filler of high-density ceramics or metal in which nano-sized particles and micro-sized particles are mixed in a resin, and the acoustic matching layer 20 is laminated by coating the mixture on the acoustic matching layer 20.

[0050] However, the method of Patent Document 1 is a method limited to the case where the density ρ of the ceramic particles is high. In addition, since it is a method of mixing particles of different sizes, there is a problem in terms of in-plane uniformity of the impedance of the thin-film acoustic matching layer.

[0051] The resin composition of the embodiment is based on the above background. The resin composition of the embodiment is a resin composition as a precursor of the acoustic matching layer 20 of the ultrasonic oscillator 24 in an ultrasonic oscillator unit having an array oscillator including a piezoelectric body having a piezoelectric element 21 and an electrode. The resin composition contains a resin and inorganic material particles. If the acoustic impedance of the acoustic matching layer 20 is set to Z and the density of the ceramic particles is set to ρ, then it satisfies Here, in the first embodiment, the inorganic material particles are ceramic particles. That is, in the first embodiment, the resin composition contains a resin and ceramic particles. If the acoustic impedance of the acoustic matching layer 20 is set to Z and the density of the ceramic particles is set to ρ, then it satisfies

[0052] Here, if we explain this quantity, generally speaking, if the acoustic impedance is set to Z and the density of the substance is set to ρ, then it becomes a quantity associated with the bulk modulus. That is, it becomes a quantity that roughly represents the deformability resistance of the substance. However, in the embodiment, for the resin composition containing a resin and ceramic particles, it is not the density of the resin composition itself, but the density ρ of the added ceramic particles that is used to evaluate the value.

[0053] Here, regarding the relationship between the value and the properties of the resin composition, Figure 3 is used for explanation. Figure 3 is a graph for explaining the properties of the resin composition with the design value of the acoustic impedance Z on the horizontal axis and the density ρ of the ceramic particles added in the resin on the vertical axis.

[0054] Here, in Figure 3 the curves 50, 51, and 52 respectively become The curve, the region between curve 50 and curve 52, for example, region 41 denoted as region B becomes the optimal composition of the resin composition. On the other hand, the low-viscosity region 42 on the left side of curve 50 denoted as region A and the high-viscosity region 43 on the right side of curve 52 denoted as region C become inappropriate regions as the resin composition.

[0055] If explained in more detail, regarding the low-viscosity region 42, it becomes a region where the density of the added ceramic particles is high, and sedimentation of the ceramic particles with high density occurs. In addition, regarding the low-viscosity region 42, it becomes a region where the density of the ceramic particles is high, there is a lot of reflection scattering, and attenuation occurs strongly. That is, due to the sedimentation of the ceramic particles and the attenuation in reflection scattering in the low-viscosity region 42, it becomes an inappropriate region as the resin composition.

[0056] On the other hand, regarding the high-viscosity region 43, since a paste with high viscosity and high thixotropy is formed, mixing, degassing, and spreading / coating become technically difficult. As an example, regarding the high-viscosity region 43, in the process of forming a uniform thin film (<100 μm) by coating using a slit coater or a coater, sufficient coating accuracy cannot be obtained, and manufacturing problems occur. That is, due to manufacturing problems, the high-viscosity region 43 becomes an inappropriate region as the resin composition.

[0057] Therefore, if the first advantage of the resin composition of the embodiment is explained, by satisfying it becomes a resin composition with low attenuation and can be coated, and is a suitable resin composition.

[0058] That is, the resin composition of the embodiment becomes a composition with low attenuation within the proper design range of the acoustic impedance Z, that is, 3.0 to 15 MRayl. In addition, the resin composition of the embodiment, for example, has a viscosity such that it can be coated within the range of 1 < Cp < 500 [Pas] at the shear viscosity during coating using a slit coater or a coater.

[0059] In addition, if the second advantage of the resin composition of the embodiment is explained, the resin composition of the embodiment does not mix particles of different sizes, but uses ceramic particles with a unimodal particle size to produce the resin composition.

[0060] If this is simply explained, regarding the particle size of the ceramic particles added to the resin, in order to ensure the in-plane uniformity of the impedance of the thin film acoustic matching layer, a small particle size is required. Here, for example, when mixing particles with two peak particle sizes as in Patent Document 1 or Patent Document 2 (Japanese Patent Laid-Open No. 2003-169397), although the viscosity adjustment becomes easy, it becomes difficult to avoid mixing of large particle size fillers. As a result, in the part where there are many large particle size fillers, the acoustic impedance Z becomes uneven in the thickness direction. In addition, ifFigure 4 When large-diameter fillers dispersed in the acoustic matching layer 20 slip 32 or remain 31 during the cutting process in forming the ultrasonic oscillator 23 as shown, it becomes a cause of unevenness in the acoustic impedance Z between the ultrasonic oscillators 23. Particularly for the ultrasonic oscillator 23 in which the transmitted ultrasonic wave is high-frequencyized, since the element size 24 is miniaturized, the unevenness between the elements of the ultrasonic oscillator 23 becomes significant. Therefore, the particle size distribution of the average particle size of the ceramic particles in the embodiment is preferably a unimodal distribution. When generating a resin composition by adding ceramic particles with a unimodal particle size, the in-plane uniformity of the impedance Z of the acoustic matching layer 20 is improved, and the unevenness of the acoustic impedance Z between the array oscillators becomes smaller.

[0061] The resin composition of the embodiment becomes a material in a form containing a resin such as an epoxy resin and ceramic particles, and the ceramic particles are uniformly dispersed and do not contain fine bubbles or the like that are factors causing attenuation. The uniformly dispersed state can be achieved by the stirring method described later.

[0062] [Regarding ceramic particles]

[0063] As the ceramic particles added to the resin composition of the embodiment, ceramic particles generally used as small-diameter fillers can be widely used. As an example, the ceramic particles contain a substance composed of at least one of Mg, Ca, Ba, B, Al, Y, Hf, Ce, Ti, W, Si and at least one of O, C, N, and S. Typically, as described above, from the viewpoint of the relationship with the viscosity of the acoustic matching layer composition and suppressing the unevenness of the acoustic impedance between the array oscillators, the average particle size (average primary particle size) of the ceramic particles becomes a small particle size of 0.3 μm or more and 2.0 μm or less. As an example, the ceramic particles may also contain particles with a particle size of 2.0 μm or less or 0.005 μm or more in an amount of 5% by volume or less. The ceramic particle material and each content can be appropriately adjusted within the range of for the designed acoustic impedance Z.

[0064] [Regarding resin]

[0065] As the resin constituting the resin composition of the embodiment, for example, epoxy resins can be cited. More specifically, ordinary epoxy resins can be cited, such as aliphatic cyclic (alicyclic) epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and phenol novolac-type epoxy resins. In the embodiment, in order to coat the filler dispersion composition, a low-viscosity epoxy resin is preferably used. The viscosity of the epoxy resin is preferably 500 mPas or less at 24°C.

[0066] The epoxy resin used in the embodiments is not particularly limited, and epoxy resins generally used as the main component of epoxy adhesives can be widely used. As a specific example, for instance, CELLOXIDE 2021P (registered trademark), an aliphatic cyclic (alicyclic) epoxy resin, can be cited. Compared with general epichlorohydrin / bisphenol A type epoxy resins, it is characterized by being a low-viscosity liquid with extremely low chlorine content and has the advantage of being easily applicable in the coating process.

[0067] It should be noted that the epoxy resin can be composed of the above-mentioned epoxy resin, or in addition to the above-mentioned epoxy resin, other epoxy resins can be contained within the scope that does not impair the effects of the present embodiments. The epoxy resin can be used alone as one type, or two or more types can be used in combination.

[0068] The curing agent can be used without particular limitation as a known curing agent for epoxy resins. As an example, a thermosetting resin can be used as the curing agent for epoxy resins. As typical examples of curing agents, for instance, tertiary amines, imidazoles, Lewis acids, Bronsted bases, acid anhydrides, aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, phenolic resins, etc. can be cited. As curing agents that can avoid affecting the viscosity of epoxy resins and maintain the low viscosity of the main component, catalyst-type tertiary amines, imidazoles, Lewis acids, and Bronsted bases are easy to apply. As specific examples, borate-based cationic polymerizers, SI series manufactured by SAN AID (registered trademark) company, etc. are useful.

[0069] [Regarding the mixing ratio of resin and ceramic particles]

[0070] The epoxy content in the laminate of the embodiments is preferably 60 to 80% by mass. In addition, the ceramic content in the laminate of the embodiments is preferably 20 to 40% by mass. That is, typically, the content of ceramic particles in the resin composition is 20% by volume or more and 40% by volume or less.

[0071] [Regarding the mixing process of resin and ceramic particles]

[0072] As points to be noted for the mixing process of resin and ceramic particles, the following three points can be cited. That is, as points to be noted, it can be cited that: First, each component can be uniformly mixed; Second, the air mixed in can be well degassed; Third, the mixing is carried out under low-temperature conditions that can suppress the initiation of the heat curing reaction. As a mixing method, for example, it is preferable to use a self-rotating and revolving mixer with a vacuum degassing mechanism for kneading, but in this case, heat is generated by the friction between the fillers. As an example of the process flow of the mixing process, detailed content will be described in the following examples.

[0073] [Regarding the coating process and curing]

[0074] The coating process of the acoustic matching layer composition of the embodiment will be described. The acoustic matching layer composition refined by the above method can be coated. As an example of a specific coating method, coating using a slit coater or a spreader can be cited. If coating using a spreader is taken as an example, the thickness of the matching layer can be controlled by the gap of the spreader or the coating speed.

[0075] It should be noted that the structure of the matching layer is not limited to a single layer. For example, after finishing the coating of the first layer, by changing the gap of the spreader, the second layer of the matching layer can be coated on the coated matching layer of the first layer, and the third layer of the matching layer can be coated on the coated matching layer of the second layer, and so on. With such a structure, the acoustic matching layer composition having multiple acoustic impedances can be laminated and coated without using an adhesive. In addition, the coated matching layer can be heat-cured using a clean oven to obtain a sheet-like single-layer or multi-layer acoustic matching sheet.

[0076] [Regarding curing]

[0077] Curing shrinkage generated during the curing of the resin matching layer or linear expansion generated during the heating process can be a cause of warping of the resin matching layer. Therefore, as the curing resin, a room temperature curing resin or a UV curing resin is recommended. However, when a room temperature curing resin is used as in Patent Document 1, sometimes the fillers come into contact with each other during the mixing process of the resin and the filler, heat up due to frictional heat, and initiate a polymerization reaction and cure. In addition, when a photo-curing resin is used as in Patent Document 2, since the filler absorbs and scatters light, curing unevenness sometimes occurs in the depth direction.

[0078] In contrast, the above coating process is a high-precision coating process that does not induce warping of the resin acoustic matching layer even when a heat-curing resin (cured at 150 °C) is used.

[0079] The above is a general description of the resin composition of the embodiment. Hereinafter, specific examples will be given to illustrate the resin composition of the embodiment. In the first embodiment of the first embodiment, with the idea of manufacturing an ultrasonic probe 1 having a center frequency of 20 - 30 MHz, the case of adding alumina (Al2O3) will be described. In the second embodiment, with the idea of manufacturing an ultrasonic probe 1 having a center frequency of about 30 MHz, the case of adding tungsten carbide (WC) will be described.

[0080] (The first embodiment of the first embodiment)

[0081] In the first embodiment of the first embodiment, with the idea of manufacturing an ultrasonic probe 1 having a center frequency of 20 - 30 MHz, the case of using alumina (Al2O3) as the ceramic particles added to the resin will be described.

[0082] [Regarding the Selection of Ceramic Particles]

[0083] First, when manufacturing the ultrasonic probe 1 with a center frequency of 20 - 30 MHz, the reason for selecting alumina (Al2O3) as the ceramic particles added to the resin will be explained.

[0084] Regarding the factors of the acoustic matching layer, the designed value of the acoustic impedance is set to Z = 5.6 [MRayl], the designed value of the film thickness of the acoustic matching layer 20 is set to 30 μm, and the designed value of the element size 24 is set to 40 μm.

[0085] In addition, as a constraint condition, the attenuation coefficient of the acoustic matching layer composition caused by the reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at the center frequency of 20 - 30 MHz. The composition of the ceramic particles that can be achieved under the above - designed values and constraint conditions was studied.

[0086] Here, based on the relational formula between the acoustic impedance Z and the density ρ of the ceramic particles as the added filler Taking the intermediate value of these relational formulas the composition calculation was carried out. If the designed value of the acoustic impedance, i.e., Z = 5.6 [MRayl], is substituted, then ρ = [3.99 g·cm 3 . In the first embodiment of the first embodiment, as the small - particle - based filler with a density close to this value, considering various conditions such as general ceramic material groups, alumina (Al2O3: ρ = [3.8 g·cm 3 ) was selected.

[0087] [Regarding the Particle Size of Ceramic Particles]

[0088] Next, when studying the particle size of the ceramic particles as the added filler, if the upper limit value of the particle size has a defect of more than 5% relative to the matching layer film thickness or the element size, it will directly affect the non - uniformity of the acoustic characteristics of each array element. Therefore, the upper limit value of the particle size is preferably not more than 5% of the matching layer film thickness or the element size. Thus, considering the designed value of the matching layer film thickness of 30 μm and the designed value of the element size of 40 μm, the particle size of the ceramic particles as the added filler is preferably 1.5 μm or less.

[0089] Through the above research, in the first embodiment of the first embodiment, commercially available Al2O3 with an average particle size of 0.7 μm (ρ = [3.8 g·cm 3 ) was selected as the ceramic particles added in the first embodiment.

[0090] [Regarding the Case where the Designed Value of the Acoustic Impedance Z Changes]

[0091] If the density ρ of ceramic particles, which are the added filler, is substituted into the relational expression between the acoustic impedance Z and the density ρ of the filler as ρ = [3.8 g·cm 3 , then 4.48 < Z < 6.63 [MRayl]. Therefore, the acoustic impedance Z can be changed within this range. Figure 5 The experimental results obtained by changing the value of the acoustic impedance Z within the range of Z = 4.1 to 8 and investigating the properties of the generated acoustic matching layer composition are shown.

[0092] Here, for example, when Z = 4.1 [MRayl] in the low-viscosity region 42 corresponding to region A shown in Figure 3 , sedimentation of the filler occurs, and the filler is not uniformly dispersed in the outermost layer, forming only an epoxy thin film layer, which cannot be used as an acoustic matching layer composition. In addition, when Z = 7.2 to 8.0 [MRayl] in the high-viscosity region 43 corresponding to region C shown in Figure 3 , the viscosity is high, and precision coating with a designed film thickness t = 30 μm (coating error < + / −1 μm) by slit coating or coater coating methods is impossible. It should be noted that since samples for acoustic impedance measurement use substrates with thicknesses of 1 mm, 2 mm, and 3 mm, even materials with a certain degree of high viscosity can be formed and measured. In the region of Z = 4.6 to 6.3, such problems do not occur.

[0093] [Regarding the resin]

[0094] Next, the resin mixed with the ceramic particles will be described. As the resin mixed with the ceramic particles, for example, epoxy resin is considered. In the first embodiment of the first embodiment, as the epoxy resin mixed with the ceramic particles, for example, CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24°C) and is suitable for the acoustic matching layer composition for coating purposes.

[0095] [Regarding the mixing ratio of the resin and the ceramic particles]

[0096] Next, the mixing amount of the resin and the ceramic particles will be described. By appropriately adjusting the mixing ratio of the resin and the ceramic particles, the value of the acoustic impedance Z can be adjusted. If the density ρ of Al2O3 is substituted into the relational expression between the acoustic impedance Z and the density ρ of the ceramic particles, which are the added filler as ρ = [3.8 g·cm 3, 4.48 < Z < 6.63 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and the ceramic particles, the value of the acoustic impedance Z can be adjusted. In the embodiment, the addition of the ceramic particles as the filler in epoxy + curing agent + filler is set to 30 vol%, and as a result, the acoustic impedance Z of the obtained resin composition is Z = 5.6 [MRayl].

[0097] [Regarding the curing agent]

[0098] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerizer is considered for use. In the embodiment, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) Co., Ltd. is added. It should be noted that this is because it is difficult to uniformly disperse the solid-added curing agent in the resin. For example, it is considered to dilute the curing agent with MEK (methyl ethyl ketone) and add it in such a way that the addition amount of the curing agent becomes 0.15 vol%, and remove the MEK by vacuum degassing.

[0099] [Regarding the mixing process of the resin and the ceramic particles]

[0100] Next, the mixing process of the resin, the ceramic particles as the filler, and the curing agent will be described. Figure 6 An example of the mixing process is shown in. For the mixing of the resin, the ceramic particles, and the curing agent, for example, the case of using a self-rotating and revolving mixer with a vacuum degassing mechanism for mixing is considered.

[0101] Specifically, first, as the epoxy resin, 18.6 g of CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) is weighed (the first step). Next, 25.5 g of Al2O3 filler is weighed (the second step). Next, the Al2O3 filler as the ceramic particles weighed in the second step and CELLOXIDE 2021P (registered trademark) weighed in the first step are uniformly dispersed at 2000 rpm for 2 minutes (the third step). Next, after confirming the uniform dispersion, it is again stirred at 2000 rpm for 4 minutes by vacuuming to 0.2 Pa to remove the fine bubbles mixed in (the fourth step). Next, the mixed solution of the Al2O3 filler and CELLOXIDE 2021P heated by the high-speed rotation treatment is cooled to 25 °C (room temperature) (the fifth step). Next, the self-rotating and revolving mixer heated by the high-speed rotation treatment is cooled to 25 °C (room temperature) (the sixth step).

[0102] Next, a curing agent: SI-B3A at 0.15 vol% was dissolved in MEK and added to the composition obtained in the sixth step (seventh step). Next, a stabilizer at 0.005 vol% relative to CELLOXIDE 2021P (registered trademark) was dissolved in ethanol and added (eighth step). It should be noted that the eighth step can be omitted. Next, in order to suppress the temperature rise of the mixed solution during rotation, it was stirred in a vacuum at a low rotation speed (500 rpm) for 1 minute to remove the residual solvent and fine bubbles (ninth step). Next, vacuum core stirring was performed at 200 rpm for 8 minutes (tenth step). Next, after visually confirming that there was no degassing from the surface of the mixed solution (eleventh step), the mixed composition was reloaded into a syringe for dispensing (twelfth step). Next, the mixed solution of Al2O3 filler and CELLOXIDE 2021P (registered trademark) heated by high-speed rotation treatment was cooled to 25 °C (thirteenth step). Next, the planetary mixer heated by high-speed rotation treatment was cooled to 25 °C (room temperature) by a cooling jig (fourteenth step). Next, the bubbles remaining in the syringe were subjected to vacuum core stirring at 200 rpm for 4 minutes (fifteenth step).

[0103] Through the above steps, it became possible to mix the Al2O3 filler and CELLOXIDE 2021P (registered trademark) after adding the curing agent at 35 °C or lower. It became possible to control the pot life (viscosity change rate 2 hours after adding the curing agent) of the acoustic matching layer composition with Z = 5.6 [MRayl] to be less than 5% under the above mixing conditions.

[0104] In the slit coating or coater coating process, the viscosity change of the composition is not preferred from the viewpoint of film thickness controllability because it directly affects the coating film thickness. By coating to form a matching layer with a designed matching layer film thickness of 30 μm, it was confirmed that when the viscosity increase rate in the current process was less than 5%, the variation in the coating film thickness could be controlled to be less than +0.1 μm.

[0105] (Second Example of the First Embodiment)

[0106] In the second example of the first embodiment, when it is assumed that an ultrasonic probe 1 with a center frequency of 30 MHz is manufactured, the case of using tungsten carbide (WC) as the ceramic particles added to the resin will be described.

[0107] [Regarding the Selection of Ceramic Particles]

[0108] First, when manufacturing the ultrasonic probe 1 with a center frequency of 30 MHz, the reason for selecting tungsten carbide (WC) as the ceramic particles added to the resin will be described.

[0109] As a factor regarding the acoustic matching layer, the designed value of the acoustic impedance is set to be close to Z = 11 [MRayl] of the glass matching layer, the designed value of the matching layer film thickness 21 is set to 40 μm, and the designed value of the element size 24 is set to 40 μm.

[0110] In addition, as a constraint condition, the attenuation coefficient of the acoustic matching layer composition generated by the reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at the center frequency of 20 to 30 MHz, and the composition of the ceramic particles that can be achieved under the above-designed values and constraint conditions is studied.

[0111] Here, based on the relational expression between the acoustic impedance Z and the density ρ of the ceramic particles as the added filler To be the intermediate value of these relational expressions The composition calculation was carried out. If the designed value of the acoustic impedance, i.e., Z = 11 [MRayl], is substituted, then ρ = [14.9 g·cm 3 . In the second embodiment of the first embodiment, as the small particle series filler with a density close to this value, considering various conditions such as the general ceramic material group used, WC (ρ = [15.63 g·cm 3 is selected.

[0112] [Regarding the particle size of the ceramic particles]

[0113] Next, if the particle size of the ceramic particles as the added filler is studied, regarding the upper limit value of the particle size, if there are defects with a size of 5% or more relative to the matching layer film thickness and the element size, it will directly affect the non-uniformity of the acoustic characteristics of each array element. Therefore, the upper limit value of the particle size of the particles is preferably not more than 5% of the matching layer film thickness and the element size. Thus, if the designed value of the matching layer film thickness is considered to be 30 μm and the designed value of the element size is 40 μm, the particle size of the ceramic particles as the added filler is preferably 1.5 μm or less.

[0114] Through the above research, in the second embodiment of the first embodiment, a commercially available material of WC with an average particle size of 1.5 μm (ρ = [15.63 g·cm 3 is selected as the ceramic particles added in the second embodiment of the first embodiment.

[0115] [Regarding the resin]

[0116] Next, the resin mixed with ceramic particles will be described. As the resin mixed with ceramic particles, for example, an epoxy resin is considered. In the second embodiment of the first embodiment, similar to the first embodiment of the first embodiment, as the epoxy resin mixed with ceramic particles, for example, CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24°C) and is suitable for the acoustic matching layer composition for coating purposes.

[0117] [Regarding the mixing ratio of the resin and ceramic particles]

[0118] Next, the mixing amount of the resin and ceramic particles will be described. By appropriately adjusting the mixing ratio of the resin and ceramic particles, the value of the acoustic impedance Z can be adjusted. If the density ρ of the ceramic particles as the added filler is substituted into the relational expression of the acoustic impedance Z and the density ρ of WC = [15.63 g·cm 3 is substituted, then 9.1 < Z < 13.8 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and ceramic particles, the value of the acoustic impedance Z can be adjusted. In the embodiment, the addition of ceramic particles as the filler in epoxy + curing agent + filler is set to 30 vol%, and as a result, the acoustic impedance Z of the obtained resin composition is Z = 11.0 [MRayl].

[0119] [Regarding the curing agent]

[0120] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerizer is considered for use. In the embodiment, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) is added. It should be noted that this is because it is difficult to uniformly disperse the curing agent in the resin when adding it in a solid state. For example, consider diluting the curing agent with MEK (methyl ethyl ketone) and adding it in such a way that the addition amount of the curing agent becomes 0.15 vol%, and removing MEK by vacuum degassing.

[0121] [Regarding the mixing process of the resin and ceramic particles]

[0122] Next, the mixing process of the resin, ceramic particles as the filler, and the curing agent will be described. By passing through Figure 6The same mixing process as that of the first embodiment of the first embodiment shown can mix resin, ceramic particles as fillers, and a curing agent. That is, for example, by using a planetary mixer with a vacuum degassing mechanism for mixing, resin, ceramic particles as fillers, and a curing agent can be mixed. It should be noted that the volume ratio of the mixed ceramic particles is about 30% as in the first embodiment of the first embodiment. However, in the second embodiment, since the WC of the mixed ceramic particles has a large density, the mixed weight is Figure 6 increased compared to

[0123] Through the above process, it becomes possible to mix WC filler and CELLOXIDE2021P (registered trademark) at 35°C or lower. It becomes possible to control the pot life (viscosity change rate 2 hours after adding the curing agent) of the acoustic matching layer composition with Z = 11.0 [MRayl] to be less than 5% under the above mixing conditions.

[0124] In the slit coating or coater coating process, the viscosity change of the composition directly affects the coating film thickness. Therefore, from the viewpoint of film thickness controllability, it is not preferred. By coating to form a matching layer with a designed matching layer film thickness of 30 μm, it can be confirmed that when the viscosity increase rate of the current process is less than 5%, the variation in the coating film thickness can be controlled to be less than +0.1 μm.

[0125] According to at least one of the embodiments described above, a resin composition with low attenuation and capable of being coated can be produced.

[0126] (Second Embodiment)

[0127] In the first embodiment, the case where the particles of the inorganic material are ceramic particles was described. In the second embodiment, the case where the particles of the inorganic material are metal particles will be described.

[0128] Figure 7 An example of a partial configuration of the ultrasonic oscillator unit 1070 of the second embodiment is shown.

[0129] The ultrasonic oscillator unit 1070 is built into the ultrasonic probe 1 and transmits and receives ultrasonic waves to and from the living body contacted by the probe. The ultrasonic oscillator unit 1070 is composed of, for example, a plurality of ultrasonic oscillators arranged two-dimensionally, a flexible printed circuit (FPC) 1022 on which the plurality of ultrasonic oscillators are arranged, and an acoustic lens. Each of the plurality of ultrasonic oscillators is composed of a piezoelectric element 1021, an acoustic matching layer 1020, and a back matching layer (not shown). The element size 1027 of the ultrasonic oscillator is, for example, 40 μm.

[0130] The piezoelectric element 1021 is an element having piezoelectricity. For example, the piezoelectric element 1021 is a piezoelectric element such as PZT (lead zirconate titanate / Pb(Zr,Ti)O3), PMN-PT (lead magnesium niobate-lead titanate / Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3). In an embodiment, a plurality of ultrasonic transducers are arranged on a predetermined surface of the flexible wiring board 1022. A signal electrode is provided on the surface (ultrasonic radiation surface) of the piezoelectric element 1021 on the side where ultrasonic waves are radiated. In addition, a ground electrode is provided on the surface (back surface) of the piezoelectric element 1021 on the side opposite to the ultrasonic radiation surface side.

[0131] The piezoelectric element 1021 is driven by a drive signal from the transceiver circuit 1011 and radiates ultrasonic waves from the surface on the signal electrode side. In addition, when the piezoelectric element 1021 receives a reflected wave, the received reflected wave is converted into a reflected wave signal, and the converted reflected wave signal is output from the signal electrode. The thickness of the piezoelectric element 1021 is, for example, 40 μm.

[0132] The acoustic matching layer 1020 is a layer for gradually reducing the acoustic impedance from the piezoelectric element 1021 to the living body and making the piezoelectric element 1021 and the living body acoustically matched. The acoustic matching layer 1020 may be composed of only one layer, or may have multiple layers in order to make the acoustic impedance gradually decrease as smoothly as possible toward the living body. As the acoustic matching layer 1020, for example, in order to have conductivity, a resin mixed with a conductive filler can be used. This resin can be, for example, an epoxy resin. The thickness of the acoustic matching layer 1020 is, for example, 30 μm.

[0133] In addition, the back surface matching layer is made of a material having a higher acoustic impedance than the piezoelectric element, and as a resonance layer, it is integrated with the piezoelectric element to transmit and receive ultrasonic waves.

[0134] In addition, the flexible wiring board 1022 is an FPC (Flexible Printed Circuit), and electrically connects the signal electrode and the ground electrode to the transceiver circuit 11 through wirings provided in each layer of the ultrasonic transducer.

[0135] In addition, between the piezoelectric element 1021 and the acoustic matching layer 1020, for example, an adhesive may be filled, or it may be formed by laminate coating without using an adhesive.

[0136] Next, the background of the second embodiment will be described. In the ultrasonic diagnostic apparatus 100, for the purpose of improving the resolution of the acquired image or for the purpose of obtaining three-dimensional space information, etc., the array oscillator tends to be required to be composed of more ultrasonic oscillators. On the other hand, the ultrasonic probe 1 is required to transmit and receive ultrasonic waves at a higher frequency (shorter wavelength). Therefore, the piezoelectric element 1021, the acoustic matching layer 1020, etc. tend to be required to be thinned.

[0137] In addition, the element size of the ultrasonic oscillator is preferably miniaturized in accordance with the high frequency of transmitting and receiving ultrasonic waves.

[0138] Here, conventionally, the acoustic matching layer 1020 is generated by laminating a glass plate, a carbon plate, etc. with an adhesive, but due to the progress of the thinning of the acoustic matching substrate of the acoustic matching layer 1020, the operation of the substrate and the lamination of the adhesive have become difficult. In addition, the technical difficulty of processing the substrate of the acoustic matching layer 1020 has also increased.

[0139] Therefore, as shown in Patent Document 1, the following process has been proposed: adjusting the acoustic impedance Z by mixing a high-density ceramic obtained by mixing nano-sized particles and micro-sized particles in a resin, and laminating the acoustic matching layer 1020 by coating the mixture on the acoustic matching layer 1020.

[0140] However, the method of Patent Document 1 is a method limited to the case where the density ρ of the ceramic particles is high, and in addition, since it is a method of mixing particles of different sizes, there are problems in terms of in-plane uniformity of the impedance of the thin film acoustic matching layer.

[0141] Based on the above background, the resin composition of the second embodiment is based on the method of adding metal particles. The resin composition of the embodiment is a resin composition as a precursor of the acoustic matching layer 1020 of the ultrasonic oscillator 1024 in an ultrasonic oscillator unit having an array oscillator including a piezoelectric body and an electrode including the piezoelectric element 1021. The resin composition contains a resin and metal particles. If the acoustic impedance of the acoustic matching layer 1020 is set to Z and the density of the metal particles is set to ρ, then it satisfies

[0142] Here, if an explanation is given for this quantity, generally, if the acoustic impedance is set to Z and the density of the substance is set to ρ, then becomes a quantity associated with the bulk modulus of elasticity. That is, becomes a quantity that roughly represents the non-deformability of the substance. However, in the embodiment, for the resin composition containing a resin and metal particles, it is not the density of the resin composition itself, but the density ρ of the added metal particles that is evaluated of the value.

[0143] Here, the relationship between the value of and the properties of the resin composition is described using Figure 8 . Figure 8 is a graph that shows the properties of the resin composition with the design value of the acoustic impedance Z on the horizontal axis and the density ρ of the metal particles added to the resin on the vertical axis.

[0144] Here, in Figure 8 , the straight lines 1050 and 1052 are respectively the values that become the lower limit and the upper limit of the inequality described above, and the straight line of 2.9. The straight line 1051 is a straight line where the value of ρ is in the middle of the values of the straight lines 1050 and 1052. The regions between the straight lines 1050 and 1052, such as the regions 1060a, 1060b, 1060c, 1060d, etc., become the optimal compositions as the resin composition. On the other hand, the low-viscosity region 1042 on the left side of the straight line 1050 and the high-viscosity region 1043 on the right side of the straight line 1052 become inappropriate regions as the resin composition.

[0145] If described in more detail, for the low-viscosity region 1042, it becomes a region where the density of the added metal particles is high and sedimentation of the high-density metal particles occurs. In addition, for the low-viscosity region 1042, due to the influence of the average inter-particle distance, a problem of strong attenuation caused by reflection scattering occurs. That is, the low-viscosity region 1042 becomes an inappropriate region as the resin composition due to the sedimentation of the metal particles and the attenuation in reflection scattering.

[0146] On the other hand, for the high-viscosity region 1043, since a paste with high viscosity and high thixotropy is formed, mixing, degassing, and spreading / coating become technically difficult. As an example, for the high-viscosity region 1043, in the process of forming a uniform thin film (<100 μm) by coating using a slit coater or a coater, sufficient coating accuracy cannot be obtained, and manufacturing problems occur. That is, the high-viscosity region 1043 becomes an inappropriate region as the resin composition due to manufacturing problems.

[0147] Therefore, if the first advantage of the resin composition of the embodiment is described, the metal particle material of the embodiment satisfies the relationship between the density ρ of the metal particle material and the design acoustic impedance Z becomes low attenuation and can be coated, and becomes a suitable resin composition.

[0148] That is, the resin composition of the embodiment becomes low attenuation when the sound impedance Z is designed within an appropriate range of 3.0 to 15 MRayl. In addition, the resin composition of the embodiment has a viscosity such that it can be coated within a range of 1 < Cp < 500 [Pas] at the coating shear rate using slit coating or a coater.

[0149] In addition, when explaining the second advantage of the resin composition of the embodiment, the resin composition of the embodiment does not mix metal particles of different sizes, but mainly uses metal particles with a small particle size and a unimodal particle size to produce the resin composition.

[0150] To briefly explain this point, for the particle size of the metal particles added to the resin, in order to ensure the in-plane uniformity of the impedance of the thin film acoustic matching layer, a small particle size is required. Here, for example, as in Patent Document 1 and Patent Document 2, when mixing particles with two peak particle sizes of different sizes, although the viscosity adjustment becomes easy, it becomes difficult to avoid the mixing of large particle size fillers. As a result, in the portion where there are many large particle size fillers, the sound impedance Z becomes uneven in the thickness direction. In addition, if the large particle size fillers dispersed in the acoustic matching layer 1020 slide or remain during the cutting process when forming the ultrasonic oscillator, it becomes a cause of unevenness in the sound impedance Z between the ultrasonic oscillators. Especially for ultrasonic oscillators in which the transmitted ultrasonic wave is high-frequencyized, due to the miniaturization of the element size, the unevenness between the elements of the ultrasonic oscillator becomes significant. Therefore, the particle size distribution of the average particle size of the metal particles of the embodiment is preferably a unimodal distribution with a small particle size. When adding metal particles with a unimodal particle size to produce the resin composition, the in-plane uniformity of the impedance Z of the acoustic matching layer 1020 is improved, and the unevenness of the sound impedance Z between the array oscillators becomes smaller. That is, it is possible to reduce the unevenness of the sound impedance between the array oscillators, and in addition, it is possible to provide a resin composition with low attenuation and can be coated.

[0151] In addition, in the embodiment, by using a single material, a material with an appropriate density that can be used with an appropriate powder particle size can be found. That is, by mixing the resin and the metal particles in an appropriate volume ratio, it becomes very easy to coat by forming a paste with viscosity and thixotropy, and manufacturing problems can be solved. In addition, the reflection and scattering attenuation caused by the addition of the filler can be controlled to low attenuation.

[0152] In addition, the resin composition of the embodiment is a material in a form that contains a resin such as an epoxy resin and metal particles, and the metal particles are uniformly dispersed, and does not contain fine bubbles or the like that are factors causing attenuation. The uniform dispersion state can be achieved by the stirring method described later.

[0153] [Regarding the resin]

[0154] Here, as the resin constituting the resin composition of the embodiment, for example, epoxy resins can be cited. More specifically, ordinary epoxy resins can be cited, such as aliphatic cyclic (alicyclic) epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and phenol novolac type epoxy resins. In the embodiment, in order to coat the filler dispersion composition, a low-viscosity epoxy resin is preferably used. The viscosity of the epoxy resin is preferably 500 mPas or less at 24°C.

[0155] The epoxy resin used in the embodiment is not particularly limited, and epoxy resins generally used as the main component of epoxy adhesives can be widely used. As a specific example, for example, an aliphatic cyclic (alicyclic) epoxy resin, CELLOXIDE 2021P (registered trademark), can be cited. Compared with general epoxy chloropropane / bisphenol A type epoxy resins, it is characterized by being a low-viscosity liquid with extremely low chlorine content, and has the advantage of being easily applied in the coating process.

[0156] It should be noted that the epoxy resin can be composed of the above-mentioned epoxy resins, or in addition to the above-mentioned epoxy resins, other epoxy resins can be contained within the range that does not impair the effects of this embodiment. The epoxy resin can be used alone as one kind, or two or more kinds can be used in combination.

[0157] [Regarding the curing agent]

[0158] The curing agent can be used without particular limitation as a curing agent known for epoxy resins. As an example, a thermosetting resin can be used as the curing agent for the epoxy resin. As typical examples of the curing agent, for example, tertiary amines, imidazoles, Lewis acids, Bronsted bases, acid anhydrides, aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, phenolic resins, etc. can be cited. As a curing agent that can avoid the influence of the epoxy resin on the viscosity and maintain the low viscosity of the main component, catalyst-type tertiary amines, imidazoles, and Lewis acids are easy to apply. As specific examples, borate-based cationic polymerization agents, SI series manufactured by SAN AID (registered trademark) company, etc. are useful.

[0159] [Regarding metal particles]

[0160] The metal particles added to the resin composition as an embodiment can be widely used as the metal particles generally used as small particle size fillers. As an example, the metal particles include a substance composed of at least one of Au, Ag, Pt, Cu, Cr, Zr, Zn, Ta, Ti, Mg, Ni, Ca, Ba, Al, Y, Hf, Ce, Ti, Mo, W, Si, Pd, Ir, Sn, Fe, Pb, Pd, Nd. Typically, as described above, from the viewpoint of the relationship with the viscosity of the acoustic matching layer composition and suppressing the unevenness of the acoustic impedance between the respective array oscillators, the average particle size (average primary particle size) of the metal particles is a small particle size of 1.0 μm or more and 4 μm or less. The metal particle material and each content are appropriately adjusted within the range of with respect to the designed acoustic impedance Z. The metal particles may also contain particles having a particle size of 2.0 μm or less or 0.005 μm or more in an amount of 5% by volume or less.

[0161] [Regarding the mixing ratio of the resin and the metal particles]

[0162] The epoxy content in the laminate of the embodiment is preferably 60 to 80% by mass. In addition, the metal particle content in the laminate of the embodiment is preferably 20 to 40% by mass. That is, typically, the content of the metal particles in the resin composition is 20% by volume or more and 40% by volume or less.

[0163] [Regarding the mixing process of the resin and the metal particles]

[0164] As the points to be noted for the mixing process of the resin and the metal particles, the following three points can be cited. That is, as the points to be noted, it can be cited that: First, each component can be uniformly mixed; Second, the air mixed in can be well degassed; Third, the mixing is carried out under low temperature conditions capable of suppressing the initiation of the heat curing reaction. As a mixing method, for example, a rotation revolution mixer with a vacuum degassing mechanism can be used for kneading.

[0165] [Regarding the coating process]

[0166] The acoustic matching layer composition refined by the above method can be coated. As an example of a specific coating method, coating using a slit coater or a coater can be cited. If coating using a coater is taken as an example, the matching layer film thickness can be controlled by the gap of the coater and the coating speed.

[0167] It should be noted that the matching layer is not limited to a single layer. For example, after the coating of the first layer is completed, by changing the gap of the coater, the matching layer of the second layer can be coated on the coating matching layer of the first layer, and the matching layer of the third layer can be coated on the coating matching layer of the second layer, and so on. With such a structure, it is possible to stack and coat the acoustic matching layer compositions having multiple acoustic impedances without using an adhesive. In addition, the coated matching layer can be heat-cured using a clean oven to obtain a sheet-like single-layer or multi-layer acoustic matching sheet.

[0168] [Regarding the curing method]

[0169] Next, the curing method after coating the resin matching layer is mentioned. The curing shrinkage generated during the curing of the resin matching layer and the linear expansion generated during the heating process will be the causes of the warping of the resin matching layer. Therefore, it is recommended to use room temperature curing resin and UV curing resin. However, for example, in the case of using room temperature curing resin, the fillers come into contact with each other during the mixing process of the resin and the filler, and the temperature rises due to frictional heat, triggering a polymerization reaction and curing. In addition, in the case of using photo-curing resin, since the filler absorbs and scatters light, curing unevenness occurs in the depth direction.

[0170] Therefore, we have studied the curing method after coating the resin matching layer. As a result, a high-precision coating process has been established that does not induce warping of the resin acoustic matching layer even when using a heat-curing resin (cured at 150 °C).

[0171] Hereinafter, the specific embodiments will be described with reference to the first embodiment of the second embodiment to the third embodiment of the second embodiment. In the first embodiment of the second embodiment, the case of selecting copper as the metal particles is described. In the second embodiment of the second embodiment, the case of selecting tungsten as the metal particles is described. In the third embodiment of the second embodiment, an example of the case where the acoustic matching layer is set to two layers is described.

[0172] (The first embodiment of the second embodiment)

[0173] In the first embodiment of the second embodiment, when it is assumed that an ultrasonic probe 1 with a center frequency of 20 - 30 MHz is manufactured, the case of using copper (Cu) as the metal particles added to the resin is described.

[0174] [Regarding the selection of metal particles]

[0175] First, when manufacturing an ultrasonic probe 1 with a center frequency of 20 - 30 MHz, the reason for selecting copper (Cu) as the metal particles added to the resin is described.

[0176] As a factor regarding the acoustic matching layer, the designed value of the acoustic impedance is set to Z = 7.6 [MRayl], the designed value of the film thickness of the acoustic matching layer 20 is set to 30 μm, and the designed value of the element size 27 is set to 40 μm.

[0177] In addition, as a constraint condition, the attenuation coefficient of the acoustic matching layer composition generated by the reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at the center frequency of 20 - 30 MHz. The composition of the metal particles that can be achieved under the above-designed values and constraint conditions was studied.

[0178] Here, based on the relational expression between the acoustic impedance Z and the density ρ of the metal particles as the added filler To be the intermediate value of these relational expressions Composition calculations were carried out. If the designed value of the acoustic impedance, i.e., Z = 7.6 [MRayl], is substituted, then ρ = [8.883 g·cm 3 . In the first embodiment, as small particle size fillers having a density close to this value, considering various conditions such as the material groups commonly used, copper (Cu: ρ = [8.96 g·cm 3 ) was selected.

[0179] [Regarding the particle size of the metal particles]

[0180] Next, if the particle size of the metal particles as the added filler is studied, regarding the upper limit value of the particle size, since if there are defects with a size of 10% or more relative to the matching layer film thickness and the element size, it will directly affect the non-uniformity of the acoustic characteristics of each array element. Therefore, the upper limit value of the particle size of the particles is preferably not more than 10% of the matching layer film thickness and the element size. Thus, if the designed value of the matching layer film thickness is considered to be 30 μm and the designed value of the element size is 40 μm, the particle size of the metal particles as the added filler is preferably 3 μm or less.

[0181] Through the above research, in the first example of the second embodiment, a commercially available material of Cu (ρ = [8.96 g·cm 3 with an average particle size of 2.1 μm was selected as the metal particles added in the first example of the second embodiment.

[0182] [Regarding the resin]

[0183] Next, the resin mixed with metal particles will be described. As the resin mixed with metal particles, for example, an epoxy resin is considered. In the first embodiment of the second embodiment, as the epoxy resin mixed with metal particles, an aliphatic cyclic (alicyclic) epoxy resin, for example, CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark), is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24°C) and is suitable for a sound matching layer composition for coating purposes.

[0184] [Regarding the mixing ratio of the resin and metal particles]

[0185] Next, the mixing amount of the resin and metal particles will be described. By appropriately adjusting the mixing ratio of the resin and metal particles, the value of the acoustic impedance Z can be adjusted. If the density ρ of the metal particles as the added filler is substituted into the relational expression of the acoustic impedance Z with the density ρ of copper = [8.96 g·cm 3 , then 6.88 < Z < 8.68 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and metal particles, the value of the acoustic impedance Z can be adjusted. In the embodiment, the addition of the metal particles as the filler in epoxy + curing agent + filler is set to a volume ratio of 33 vol%, and as a result, the acoustic impedance Z of the obtained resin composition is Z = 7.6 [MRayl].

[0186] [Regarding the curing agent]

[0187] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerization agent is considered for use. In the embodiment, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) is added. It should be noted that this is because it is difficult to uniformly disperse the curing agent in the resin when adding it as a solid. For example, the curing agent is diluted with acetone and added in such a way that the addition amount of the curing agent becomes 0.15 vol%, and the acetone is removed by vacuum degassing.

[0188] [Regarding the mixing process of the resin and metal particles]

[0189] Next, the mixing process of the resin, the metal particles as the filler, and the curing agent will be described. Figure 9 An example of the mixing process is shown. For the mixing of the resin, metal particles, and curing agent, for example, the case of using a planetary mixer with a vacuum degassing mechanism for mixing is considered.

[0190] Specifically, first, as the epoxy resin, 18 g of CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) was weighed (first step). Next, 73.5 g of copper filler was weighed (second step). Next, the copper filler, which is the metal particles weighed in the second step, and CELLOXIDE 2021P (registered trademark) weighed in the first step were uniformly dispersed at 2000 rpm for 2 minutes (third step). Next, after confirming uniform dispersion, it was stirred again at 1000 rpm for 6 minutes under a vacuum of 0.2 Pa to remove the mixed fine bubbles (fourth step). Next, the mixed solution of copper filler and CELLOXIDE 2021P heated by high-speed rotation treatment was cooled to 25°C (room temperature) (fifth step). Next, the rotating and revolving mixer heated by high-speed rotation treatment was cooled to 25°C (room temperature) (sixth step).

[0191] Next, 0.15 vol% of the initiator: SI-B3A was dissolved in an acetone solution and added to the composition obtained in the sixth step (seventh step). It should be noted that, depending on the situation, stabilizers and retarders can also be adjusted. Next, in order to suppress the temperature rise of the mixed solution during rotation, it was stirred at a low speed (500 rpm) in a vacuum for 1 minute to remove the residual solvent and fine bubbles (eighth step). Next, vacuum core stirring was performed at 200 rpm for 15 minutes (ninth step). Next, after visually confirming that there was no defoaming from the surface of the mixed solution (tenth step), the mixed composition was reloaded into a syringe for dispensing (eleventh step). Next, the mixed solution of copper filler and CELLOXIDE 2021P (registered trademark) heated by high-speed rotation treatment was cooled to 25°C (twelfth step). Next, the rotating and revolving mixer heated by high-speed rotation treatment was cooled to 25°C (room temperature) by a cooling jig (thirteenth step). Next, the bubbles remaining in the syringe were subjected to vacuum core stirring at 200 rpm for 4 minutes (fourteenth step).

[0192] Through the above steps, it became possible to mix the copper filler and CELLOXIDE 2021P (registered trademark) after adding SI-B3A as the initiator at 35°C or lower. By being able to perform mixing at a low temperature, it became possible to suppress the initiation of the polymerization reaction and suppress the viscosity change (pot life) of the acoustic matching layer composition.

[0193] In slit coating or coater coating processes, viscosity changes in the composition are not preferred from the perspective of film thickness controllability because they directly affect the coating film thickness. A matching layer with a designed matching layer film thickness of 40 μm was formed by coating, and as a result, it was confirmed that the viscosity increase rate of the current mixing process became less than 10% 1 hour after the initiator was added, and the variation in the coating film thickness could be controlled to be less than +0.2 μm.

[0194] In addition, as described above, the acoustic matching layer composition can adjust the control design impedance within the range of the above-mentioned relational expression between the design acoustic impedance and the filler density. That is, when selecting copper filler with ρ = [8.96 g·cm , for the acoustic impedance Z, an acoustic matching layer composition in the range of 6.88 < Z < 8.68 [MRayl] can be formed. The experimental results obtained by changing the design acoustic impedance of the acoustic matching layer composition using copper filler are shown in 3 . Figure 10 in.

[0195] A list of the composition and evaluation results with respect to the design impedance is shown. For the composition region (Z = 6.9 [MRayl]) in the low viscosity region 42 shown in Figure 8 , it was found that sedimentation of the filler occurred, and the filler was not evenly dispersed in the outermost layer, forming a thin film layer of only epoxy, making it impossible to use as an acoustic matching layer composition. On the other hand, for the composition region (Z = 10.0 [MRayl]) in the high viscosity region 43 shown in Figure 8 , precise coating (coating error < + / −1 μm) with a high viscosity and a designed film thickness t = 40 μm was impossible by the above slit coating or coater coating method. It should be noted that since samples for acoustic impedance measurement use substrates with thicknesses of 1 mm, 2 mm, and 3 mm, even materials with a certain degree of high viscosity can be formed and measured.

[0196] (Second Embodiment, Second Example)

[0197] In the second example of the second embodiment, it is assumed that an ultrasonic probe 1 with a center frequency of about 30 MHz is manufactured, and the case of using tungsten (W) as the metal particles added to the resin will be described.

[0198] [Regarding the Selection of Metal Particles]

[0199] First, in the case of manufacturing an ultrasonic probe 1 with a center frequency of about 30 MHz, the reason for selecting tungsten (W) as the metal particles added to the resin will be described.

[0200] As a factor regarding the acoustic matching layer, the designed value of the acoustic impedance is set to be close to Z = 11.2 [MRayl] of the glass matching layer, the designed value of the film thickness of the acoustic matching layer 20 is set to 40 μm, and the designed value of the element size 24 is set to 40 μm.

[0201] In addition, as a constraint condition, the attenuation coefficient of the acoustic matching layer composition generated by the reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at the center frequency of 20 - 30 MHz. The composition of the metal particles that can be achieved under the above design values and constraint conditions was studied.

[0202] Here, based on the relational expression between the acoustic impedance Z and the density ρ of the metal particles as the added filler To be the intermediate value of these relational expressions The composition calculation was carried out. If the designed value of the acoustic impedance, i.e., Z = 11.2 [MRayl], is substituted, then it becomes ρ = [19.291 g·cm 3 . In the second embodiment of the second embodiment, as a small particle size filler with a density close to this value, considering various conditions such as the generally used material group, tungsten (W: ρ = [19.3 g·cm 3 ) was selected.

[0203] [Regarding the particle size of the metal particles]

[0204] Next, if the particle size of the metal particles as the added filler is studied, regarding the upper limit value of the particle size, since if there are defects with a size of 10% or more relative to the matching layer film thickness and the element size, it will directly affect the non-uniformity of the acoustic characteristics of each array element, the upper limit value of the particle size of the particles is preferably not more than 10% of the matching layer film thickness and the element size. Thus, if the designed value of the matching layer film thickness is 40 μm and the designed value of the element size is 40 μm, the particle size of the metal particles as the added filler is preferably 4 μm or less.

[0205] Through the above research, in the second embodiment of the second embodiment, a commercially available material of W with an average particle size of 2.2 μm (ρ = [19.3 g·cm 3 ) was selected as the metal particles added in the second embodiment of the second embodiment.

[0206] [Regarding the resin]

[0207] Next, the resin mixed with metal particles will be described. As the resin mixed with metal particles, for example, an epoxy resin is considered. In the second embodiment of the second example, as the epoxy resin mixed with metal particles, an aliphatic cyclic (alicyclic) epoxy resin, for example, CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark), is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24°C) and is suitable for the acoustic matching layer composition for coating purposes.

[0208] [Regarding the mixing ratio of the resin and metal particles]

[0209] Next, the mixing amount of the resin and metal particles will be described. By appropriately adjusting the mixing ratio of the resin and metal particles, the value of the acoustic impedance Z can be adjusted. If the density ρ of tungsten is substituted into the relational expression of the acoustic impedance Z and the metal particles as the added filler 3 , then 10.1 < Z < 12.7 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and metal particles, the value of the acoustic impedance Z can be adjusted. In the example, the addition of metal particles as the filler in epoxy + curing agent + filler was set to 33.2 vol%, and as a result, the acoustic impedance Z of the obtained resin composition was Z = 11.2 [MRayl].

[0210] [Regarding the curing agent]

[0211] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerization agent is considered for use. In the example, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) is added. It should be noted that this is because it is difficult to uniformly disperse the curing agent in the resin when adding it in solid form. For example, the curing agent is diluted with acetone, added in such a way that the addition amount of the curing agent becomes 0.15 vol%, and the acetone is removed by vacuum degassing.

[0212] [Regarding the mixing process of the resin and metal particles]

[0213] Next, the mixing process of the resin, metal particles as the filler, and the curing agent will be described. Although it is common with the first example of the second embodiment, Figure 9 an example of the mixing process in the second example of the second embodiment is shown in

[0214] Specifically, first, as the epoxy resin, 18 g of CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) was weighed (first step). Next, 145 g of tungsten filler was weighed (second step). Next, the tungsten filler, which is the metal particles weighed in the second step, and CELLOXIDE 2021P (registered trademark) weighed in the first step were uniformly dispersed at 2000 rpm for 2 minutes (third step). Next, after confirming uniform dispersion, it was stirred again at 1000 rpm for 6 minutes under a vacuum of 0.2 Pa to remove the mixed fine bubbles (fourth step). Next, the mixed solution of tungsten filler and CELLOXIDE 2021P heated by high-speed rotation treatment was cooled to 25°C (room temperature) (fifth step). Next, the planetary mixer heated by high-speed rotation treatment was cooled to 25°C (room temperature) (sixth step).

[0215] Next, 0.15 vol% of the initiator: SI-B3A was dissolved in an acetone solution and added to the composition obtained in the sixth step (seventh step). It should be noted that, depending on the situation, stabilizers and inhibitors can also be adjusted. Next, in order to suppress the temperature rise of the mixed solution during rotation, it was stirred at a low speed (500 rpm) in a vacuum for 1 minute to remove the residual solvent and fine bubbles (eighth step). Next, vacuum core stirring was performed at 200 rpm for 15 minutes (ninth step). Next, after visually confirming that there was no defoaming from the surface of the mixed solution (tenth step), the mixed composition was reloaded into a syringe for dispensing (eleventh step). Next, the mixed solution of tungsten filler and CELLOXIDE 2021P (registered trademark) heated by high-speed rotation treatment was cooled to 25°C (twelfth step). Next, the planetary mixer heated by high-speed rotation treatment was cooled to 25°C (room temperature) by a cooling jig (thirteenth step). Next, the bubbles remaining in the syringe were subjected to vacuum core stirring at 200 rpm for 4 minutes (fourteenth step).

[0216] Through the above steps, it became possible to mix the tungsten filler and CELLOXIDE 2021P (registered trademark) after adding SI-B3A as the initiator at 35°C or lower. By being able to perform mixing at a low temperature, it became possible to suppress the initiation of the polymerization reaction and suppress the viscosity change (pot life) of the acoustic matching layer composition.

[0217] In the slit coating or coater coating process, the viscosity change of the composition directly affects the coating film thickness, so it is not preferred from the viewpoint of film thickness controllability. A matching layer with a designed matching layer film thickness of 40 μm was formed by coating. As a result, it was confirmed that the viscosity increase rate of the current mixing process became lower than 10% 1 hour after the initiator was added, and the coating film thickness variation amount could be controlled to be less than +0.2 μm.

[0218] In addition, as described above, the acoustic matching layer composition controls the design impedance and can be adjusted within the relational expression of the above-described designed acoustic impedance and filler density. That is, when tungsten filler with ρ = [19.3 g·cm is selected, the acoustic impedance Z of the acoustic matching layer composition can form a range of 10.1 < Z < 12.7 [MRayl]. The experimental results obtained by changing the designed acoustic impedance of the acoustic matching layer composition using tungsten filler are shown in 3 . Figure 11

[0219] A list of the composition and evaluation results with respect to the design impedance is shown. Regarding the composition region (Z = 9.0 [MRayl]) of the low-viscosity region 1042 shown in Figure 8 , it is known that sedimentation of the filler occurs, the filler is not uniformly dispersed in the outermost layer, and a thin film layer composed only of epoxy is formed, making it impossible to use it as an acoustic matching layer composition. On the other hand, regarding the composition region (Z = 13.4 [MRayl]) of the high-viscosity region 1043 shown in Figure 8 , precise coating with a high viscosity and a designed film thickness t = 40 μm (coating error < ±1 μm) is impossible by the above slit coating or coater coating method. It should be noted that since samples for acoustic impedance measurement use substrates with thicknesses of 1 mm, 2 mm, and 3 mm, even materials with a certain degree of high viscosity can be formed and measured.

[0220] (Third Embodiment of the Second Embodiment)

[0221] In the first embodiment of the second embodiment and the second embodiment of the second embodiment, the case of manufacturing a single-layer matching layer has been described, but the embodiment is not limited thereto, and it may also be the case of manufacturing an acoustic matching layer including multiple layers. In the third embodiment of the second embodiment, the case where the acoustic matching layer includes multiple layers, for example, a two-layer matching layer, is described. In the case where the acoustic matching layer includes multiple layers, for example, after finishing the coating of the first layer, by changing the gap of the coater, processes such as coating the second-layer matching layer on the coating matching layer of the first layer and then coating the third-layer matching layer on the coating matching layer of the second layer can be performed, making it possible to stack and coat multiple acoustic matching layer compositions having acoustic impedance without using an adhesive.

[0222] Figure 12 A partial configuration of the ultrasonic oscillator unit in the case where the acoustic matching layer is a two-layer matching layer is shown in

[0223] ​In the third embodiment, the acoustic matching layer 1020 includes a first acoustic matching layer 1020a and a second acoustic matching layer 1020b. That is, the ultrasonic oscillator unit 1070 includes a flexible wiring board 1022, a piezoelectric element 1021, the first acoustic matching layer 1020a, and the second acoustic matching layer 1020b. The element size 1027 of each ultrasonic oscillator 1071 in the ultrasonic oscillator unit 1070 is, for example, 40 μm. The thickness of the piezoelectric element 1021 is, for example, 40 μm. The thickness of the first acoustic matching layer 1020a is, for example, 40 μm. In addition, the thickness of the second acoustic matching layer 1020b is, for example, 30 μm.

[0224] Here, the first acoustic matching layer 1020a is an acoustic matching layer made by adding metal particles such as tungsten to resin. In addition, the second acoustic matching layer 1020b is an acoustic matching layer made by adding ceramic particles such as alumina to resin.

[0225] It should be noted that the embodiment is not limited to this. For example, the order of the first acoustic matching layer 1020a and the second acoustic matching layer 1020b can be reversed, and in addition, the materials of the first acoustic matching layer 1020a and the second acoustic matching layer 1020b can be other than the above materials.

[0226] [Regarding the selection of metal particles in the first acoustic matching layer 1020a]

[0227] For the first acoustic matching layer 1020a, based on the following research, tungsten (W) is used as the metal particles added to the resin.

[0228] As a factor regarding the acoustic matching layer, the design value of the acoustic impedance is set to Z = 11.2 [MRayl], the design value of the film thickness of the first acoustic matching layer 1020a is set to 40 μm, and the design value of the element size 24 is set to 40 μm.

[0229] In addition, as a constraint condition, the attenuation coefficient of the acoustic matching layer composition generated by reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at a center frequency of 20 - 30 MHz. The composition of the metal particles that can be achieved under the above design values and constraint conditions was studied.

[0230] Here, based on the relational expression between the acoustic impedance Z and the density ρ of the metal particles as the added filler To be an intermediate value of these relational expressions Composition calculation was performed. If the design value of the acoustic impedance, i.e., Z = 11.2 [MRayl], is substituted, then it becomes ρ = [19.291 g·cm 3 . As small particle size fillers having a density close to this value, considering various conditions such as a general material group, tungsten (W: ρ = [19.3 g·cm3 )。

[0231] [First acoustic matching layer 1020a: Regarding the particle size of metal particles]

[0232] Next, if the particle size of the metal particles used as the added filler is studied, regarding the upper limit value of the particle size, if there are defects with a size of 10% or more relative to the film thickness of the matching layer and the element size, it will directly affect the non-uniformity of the acoustic characteristics of each array element. Therefore, the upper limit value of the particle size of the particles is preferably not more than 10% of the film thickness of the matching layer and the element size. Thus, if the designed value of the film thickness of the matching layer is 40 μm and the designed value of the element size is 40 μm, the particle size of the metal particles used as the added filler is preferably 4 μm or less.

[0233] Through the above research, in the third embodiment of the second embodiment, a commercially available material with an average particle size of 2.2 μm of W (ρ = [19.3 g·cm 3 is selected as the metal particles added in the third embodiment of the second embodiment.

[0234] [First acoustic matching layer 1020a: Regarding resin]

[0235] Next, the resin mixed with the metal particles will be described. As the resin mixed with the metal particles, for example, epoxy resin is considered. Specifically, as the epoxy resin mixed with the metal particles, an aliphatic cyclic (alicyclic) epoxy resin, such as CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark), is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24 °C) and is suitable for the acoustic matching layer composition for coating purposes.

[0236] [First acoustic matching layer 1020a: Regarding the mixing ratio of resin and metal particles]

[0237] Next, the mixing amount of the resin and the metal particles will be described. By appropriately adjusting the mixing ratio of the resin and the metal particles, the value of the acoustic impedance Z can be adjusted. If in the relational expression of the acoustic impedance Z and the density ρ of the metal particles used as the added filler the density ρ = [19.3·cm of tungsten is substituted 3 , then 10.1 < Z < 12.7 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and the metal particles, the value of the acoustic impedance Z can be adjusted. In the embodiment, the addition of the metal particles as the filler in epoxy + curing agent + filler is set to a volume ratio of 33.2 vol%, and as a result, the acoustic impedance Z of the obtained resin composition is Z = 11.2 [MRayl].

[0238] [First acoustic matching layer 1020a: Regarding the curing agent]

[0239] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerizing agent is considered. In the examples, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) is added. It should be noted that this is because it is difficult to uniformly disperse the curing agent in the resin when adding it in solid form. For example, the curing agent is diluted with acetone and added in such a way that the addition amount of the curing agent becomes 0.15 vol%, and the acetone is removed by vacuum degassing.

[0240] [First acoustic matching layer 1020a: Regarding the mixing process of resin and metal particles]

[0241] Next, the mixing process of the resin, metal particles as fillers, and the curing agent will be described. As described before, Figure 9 An example of the mixing process is shown. For the mixing of the resin, metal particles, and the curing agent, for example, the case of using a planetary mixer with a vacuum degassing mechanism for mixing is considered.

[0242] Specifically, first, as the epoxy resin, 18 g of CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) is weighed (first step). Next, 145 g of tungsten filler is weighed (second step). Next, the tungsten filler, which is the metal particles weighed in the second step, and CELLOXIDE 2021P (registered trademark) weighed in the first step are uniformly dispersed at 2000 rpm for 2 minutes (third step). Next, after confirming uniform dispersion, it is again stirred at 1000 rpm for 6 minutes under a vacuum of 0.2 Pa to remove the fine bubbles mixed in (fourth step). Next, the mixed solution of tungsten filler and CELLOXIDE 2021P heated by the high-speed rotation treatment is cooled to 25 °C (room temperature) (fifth step). Next, the planetary mixer heated by the high-speed rotation treatment is cooled to 25 °C (room temperature) (sixth step).

[0243] Next, 0.15 vol% of the initiator: SI-B3A was dissolved in an acetone solution and added to the composition obtained in the sixth step (seventh step). It should be noted that the stabilizer and retarder can also be adjusted according to the situation. Next, in order to suppress the temperature rise of the mixed solution during rotation, it was stirred in a vacuum at a low rotation speed (500 rpm) for 1 minute to remove the residual solvent and fine bubbles (eighth step). Next, vacuum core stirring was carried out at 200 rpm for 15 minutes (ninth step). Next, after visually confirming that there is no defoaming from the surface of the mixed solution (tenth step), the mixed composition was reloaded into a syringe for dispensing (eleventh step). Next, the mixed solution of tungsten filler and CELLOXIDE 2021P (registered trademark) heated by high-speed rotation treatment was cooled to 25 °C (twelfth step). Next, the planetary mixer heated by high-speed rotation treatment was cooled to 25 °C (room temperature) by a cooling jig (thirteenth step). Next, the bubbles remaining in the syringe were subjected to vacuum core stirring at 200 rpm for 4 minutes (fourteenth step).

[0244] Through the above steps, it became possible to mix the tungsten filler and CELLOXIDE 2021P (registered trademark) after adding SI-B3A as an initiator at 35 °C or lower. By being able to perform mixing at a low temperature, it became possible to suppress the initiation of the polymerization reaction and suppress the viscosity change (pot life) of the acoustic matching layer composition.

[0245] In the slit coating or coater coating process, the viscosity change of the composition directly affects the coating film thickness, so it is not preferred from the viewpoint of film thickness controllability. A matching layer with a designed matching layer film thickness of 40 μm was formed by coating. As a result, it was confirmed that the viscosity increase rate of the current mixing process became less than 10% 1 hour after the initiator was added, and the variation in the coating film thickness could be controlled to be less than +0.2 μm.

[0246] [Second Acoustic Matching Layer 1020b: Selection of Ceramic Particles]

[0247] In the second acoustic matching layer 1020b, ceramic particles are used as the substance added to the resin. Specifically, alumina (Al2O3) is selected.

[0248] As factors regarding the acoustic matching layer, the designed value of the acoustic impedance is set to Z = 5.6 [MRayl], the designed value of the film thickness of the acoustic matching layer 1020b is set to 30 μm, and the designed value of the element size 1024 is set to 40 μm.

[0249] In addition, as a restrictive condition, the attenuation coefficient of the acoustic matching layer composition generated by the reflection and scattering of the filler is set to be less than 0.6 dB / MHz / mm at a center frequency of 20 - 30 MHz. Research is conducted on the composition of ceramic particles that can be achieved under the above design values and restrictive conditions.

[0250] Here, based on the relational expression between the acoustic impedance Z and the density ρ of the ceramic particles as the added filler To be an intermediate value of these relational expressions Composition calculations were performed. If the design value of the acoustic impedance, i.e., Z = 5.6 [MRayl], is substituted, then ρ = [3.99 g·cm 3 . In the first embodiment, as small particle-based fillers that have a density close to this value, considering various conditions such as general ceramic material groups commonly used, alumina (Al2O3: ρ = [3.8 g·cm 3 ) is selected.

[0251] [Second acoustic matching layer 1020b: Regarding the particle size of ceramic particles]

[0252] Next, if the particle size of the ceramic particles as the added filler is studied, regarding the upper limit value of the particle size, if there are defects with a size of 5% or more relative to the matching layer film thickness and the element size, it will directly affect the non-uniformity of the acoustic characteristics of each array element. Therefore, the upper limit value of the particle size of the particles is preferably not more than 5% of the matching layer film thickness and the element size. Thus, if the design value of the matching layer film thickness is considered to be 30 μm and the design value of the element size is 40 μm, the particle size of the ceramic particles as the added filler is preferably 1.5 μm or less.

[0253] Through the above research, commercially available alumina with an average particle size of 0.7 μm (ρ = [3.8 g·cm 3 ) is selected as the ceramic particles added in the second acoustic matching layer 1020b. It should be noted that if the density ρ = [3.8 g·cm of the filler is substituted into the relational expression between the acoustic impedance Z and the density ρ of the ceramic particles as the added filler 3 , then 4.48 < Z < 6.63 [MRayl]. Therefore, the acoustic impedance Z can be changed within this range.

[0254] [Second acoustic matching layer 1020b: Regarding the resin]

[0255] Next, the resin mixed with ceramic particles will be described. As the resin mixed with ceramic particles, for example, an epoxy resin is considered. As the epoxy resin mixed with ceramic particles, for example, CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) is selected. This material is a liquid epoxy resin with a low viscosity (250 mPas @ 24°C) and is suitable for the acoustic matching layer composition for coating purposes.

[0256] [Second acoustic matching layer 1020b: Regarding the mixing ratio of resin and ceramic particles]

[0257] Next, the mixing amount of the resin and ceramic particles will be described. By appropriately adjusting the mixing ratio of the resin and ceramic particles, the value of the acoustic impedance Z can be adjusted. If the density ρ of the ceramic particles as the added filler is substituted into the relational expression of the acoustic impedance Z and the density ρ of Al2O3 = [3.8 g·cm 3 is substituted, then 4.48 < Z < 6.63 [MRayl] can be obtained. Therefore, by changing the mixing amount of the resin and ceramic particles, the value of the acoustic impedance Z can be adjusted. In the example, the addition of ceramic particles as the filler in epoxy + curing agent + filler is set to 30 vol%, and as a result, the acoustic impedance Z of the obtained resin composition is Z = 5.6 [MRayl].

[0258] [Second acoustic matching layer 1020b: Regarding the curing agent]

[0259] Next, the curing agent will be described. As the curing agent, a borate-based cationic polymerization agent is considered for use. In the example, 0.15 vol% of SI-B3A (registered trademark) manufactured by SAN AID (registered trademark) is added. It should be noted that since it is difficult to uniformly disperse the curing agent in the resin when adding it in a solid state, for example, it is considered to dilute the curing agent with acetone and add it in such a way that the addition amount of the curing agent becomes 0.15 vol%, and the acetone is removed by vacuum degassing.

[0260] [Second acoustic matching layer 1020b: Regarding the mixing process of resin and ceramic particles]

[0261] Next, the mixing process of the resin, the ceramic particles as the filler, and the curing agent will be described. As already described, Figure 9 shows an example of the mixing process. As the mixing of the resin, ceramic particles, and curing agent, for example, the case of using a planetary mixer with a vacuum degassing mechanism for mixing is considered.

[0262] Specifically, first, as the epoxy resin, 18.6 g of CELLOXIDE 2021P (registered trademark) of Daicel Corporation (registered trademark) was weighed (first step). Next, 25.5 g of Al2O3 filler was weighed (second step). Next, the ceramic particles, i.e., the Al2O3 filler weighed in the second step and the CELLOXIDE 2021P (registered trademark) weighed in the first step were uniformly dispersed at 2000 rpm for 2 minutes (third step). Next, after confirming uniform dispersion, it was stirred again at 2000 rpm for 6 minutes under a vacuum of 0.2 Pa to remove the mixed fine bubbles (fourth step). Next, the mixed solution of the Al2O3 filler and CELLOXIDE 2021P heated by the high-speed rotation treatment was cooled to 25 °C (room temperature) (fifth step). Next, the planetary mixer heated by the high-speed rotation treatment was cooled to 25 °C (room temperature) by a cooling jig (sixth step).

[0263] Next, 0.15 vol% of the curing agent: SI-B3A was dissolved in acetone and added to the composition obtained in the sixth step (seventh step). Next, in order to suppress the temperature rise of the mixed solution during rotation, it was stirred in a vacuum at a low speed (500 rpm) for 1 minute to remove the residual solvent and fine bubbles (eighth step). Next, vacuum core stirring was performed at 200 rpm for 15 minutes (ninth step). Next, after visually confirming that there was no defoaming from the surface of the mixed solution (tenth step), the mixed composition was reloaded into a syringe for dispensing (eleventh step). Next, the mixed solution of the Al2O3 filler and CELLOXIDE 2021P (registered trademark) heated by the high-speed rotation treatment was cooled to 25 °C (twelfth step). Next, the planetary mixer heated by the high-speed rotation treatment was cooled to 25 °C (room temperature) by a cooling jig (thirteenth step). Next, the bubbles remaining in the syringe were subjected to vacuum core stirring at 200 rpm for 4 minutes (fourteenth step).

[0264] Through the above steps, it became possible to mix the Al2O3 filler and CELLOXIDE 2021P (registered trademark) after adding the curing agent at 35 °C or lower. It became possible to control the pot life (viscosity change rate 2 hours after adding the curing agent) of the acoustic matching layer composition with Z = 5.6 [MRayl] to less than 5% under the above mixing conditions.

[0265] In the slit coating or coater coating process, the viscosity change of the composition directly affects the coating film thickness, so it is not preferred from the viewpoint of film thickness controllability. By coating to form a matching layer with a designed matching layer film thickness of 30 μm, it was confirmed that when the viscosity increase rate of the current process was less than 5%, the coating film thickness variation could be controlled to less than +0.1 μm.

[0266] [Manufacture of Two-Layer Matching Layers]

[0267] As described above, the manufacturing methods of the first matching layer 1020a and the second matching layer 1020b have been explained. Next, the manufacturing method of the entire matching layer composition and the like will be described.

[0268] As an example of the manufacturing method of the matching layer composition, the formation of the matching layer composition using a coater is considered. As an example, a method of manufacturing a sheet of a two-layer matching layer by coating the first matching layer 1020a and the second matching layer composition 1020b on a smooth substrate using a coater is considered. It should be noted that since the viscosities and thixotropic properties of the respective compositions are different, the coating film thickness varies depending on the coating speed and the gap of the coater. The coating conditions of the matching layer composition were studied. As a result, by coating the first matching layer composition on a smooth substrate with a gap of 70 μm and a coating speed of 10 mm / sec, and continuously coating the second matching layer composition on the first matching layer with a gap of 110 μm and a coating speed of 5 mm / sec, and then heating and curing at 130 °C and peeling off from the smooth substrate, it becomes possible to obtain Figure 12 a sheet of a two-layer matching layer with the first matching layer / second matching layer = 40 μm / 30 μm as shown in. After bonding the obtained sheet of the two-layer matching layer to the piezoelectric element and slicing it into an element size of 40 μm using a dicing blade array, it becomes possible to obtain Figure 12 the ultrasonic array element including two-layer matching as shown in.

[0269] Regarding the above embodiments, as one aspect and optional features of the invention, the following appended notes are disclosed.

[0270] (Appended Note 1)

[0271] The resin composition provided by one aspect of the present invention is a resin composition as a precursor of the acoustic matching layer of the ultrasonic oscillator in the ultrasonic oscillator unit, and the ultrasonic oscillator unit has an array oscillator including a piezoelectric body and an electrode.

[0272] The above resin composition contains a resin and ceramic particles.

[0273] If the acoustic impedance of the above acoustic matching layer is set as Z and the density of the above ceramic particles is set as ρ, then it satisfies

[0274] (Appended Note 2)

[0275] The above Z may also be in the range of 3.0 MRayl or more and 15 MRayl or less.

[0276] (Appended Note 3)

[0277] The particle size distribution of the average particle size of the above-mentioned ceramic particles may also be a unimodal distribution.

[0278] (Supplementary Note 4)

[0279] The content of the above-mentioned ceramic particles in the above-mentioned resin composition may also be 20% by volume or more and 40% by volume or less.

[0280] (Supplementary Note 5)

[0281] The average particle size of the above-mentioned ceramic particles may also be 0.3 μm or more and 2 μm or less.

[0282] (Supplementary Note 6)

[0283] The above-mentioned ceramic particles may also contain a substance composed of at least one of Mg, Ca, Ba, B, Al, Y, Hf, Ce, Ti, W, Si and at least one of O, C, N and S.

[0284] (Supplementary Note 7)

[0285] The above-mentioned ceramic particles may also contain particles with a particle size of 2.0 μm or less or 0.005 μm or more in an amount of 5% by volume or less.

[0286] (Supplementary Note 8)

[0287] The above-mentioned resin may also be an epoxy resin.

[0288] (Supplementary Note 9)

[0289] A thermosetting resin may also be used as a curing agent for the above-mentioned epoxy resin.

[0290] (Supplementary Note 10)

[0291] The above-mentioned ceramic particles may also be alumina.

[0292] (Supplementary Note 11)

[0293] The above-mentioned ceramic particles may also be tungsten carbide.

[0294] (Supplementary Note 12)

[0295] The resin composition provided by one aspect of the present invention is a resin composition as a precursor of an acoustic matching layer of an ultrasonic oscillator in an ultrasonic oscillator unit, and the ultrasonic oscillator unit has an array oscillator including a piezoelectric body and an electrode.

[0296] The above-mentioned resin composition contains a resin and metal particles.

[0297] If the acoustic impedance of the above-mentioned acoustic matching layer is set to Z and the density of the above-mentioned metal particles is set to ρ,

[0298] then it satisfies

[0299] (Supplementary Note 13)

[0300] The above-mentioned Z can also be in the range of 3.0 MRayl or more and 15 MRayl or less.

[0301] (Supplementary Note 14)

[0302] The particle size distribution of the average particle size of the above-mentioned metal particles can also be a unimodal distribution.

[0303] (Supplementary Note 15)

[0304] The content of the above-mentioned metal particles in the above-mentioned resin composition can also be 20% by volume or more and 40% by volume or less.

[0305] (Supplementary Note 16)

[0306] The average particle size of the above-mentioned metal particles can also be 1.0 μm or more and 4 μm or less.

[0307] (Supplementary Note 17)

[0308] The above-mentioned metal particles can also contain a substance composed of at least one of Au, Ag, Pt, Cu, Cr, Zr, Zn, Ta, Ti, Mg, Ni, Ca, Ba, Al, Y, Hf, Ce, Ti, Mo, W, Si, Pd, Ir, Sn, Fe, Pb, Pd, Nd.

[0309] (Supplementary Note 18)

[0310] The above-mentioned metal particles can also contain particles with a particle size of 2.0 μm or less or 0.005 μm or more in an amount of 5% by volume or less.

[0311] (Supplementary Note 19)

[0312] The above-mentioned resin can also be an epoxy resin.

[0313] (Supplementary Note 20)

[0314] A thermosetting resin can also be used as a curing agent for the above-mentioned epoxy resin.

[0315] (Supplementary Note 21)

[0316] The above-mentioned metal particles can also be copper or tungsten.

[0317] According to at least one of the embodiments described above, a resin composition with low attenuation and capable of being coated can be generated.

[0318] Several embodiments have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, changes, and combinations of the embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and similarly included in the invention described in the claims and its equivalents.

Claims

1. A resin composition as a precursor of an acoustic matching layer of an ultrasonic transducer in an ultrasonic transducer unit, wherein the ultrasonic transducer unit has an array transducer having a piezoelectric body and an electrode, The resin composition comprises resin and inorganic material particles, If the acoustic impedance of the acoustic matching layer is set to Z, and the density of the inorganic material particles is set to ρ, Then 2.3≤Z / √ρ≤3.4 is satisfied.

2. The resin composition according to claim 1, wherein The particles of the inorganic material are ceramic particles.

3. The resin composition according to claim 1, wherein The Z is in the range of 3.0 MRayl or more and 15 MRayl or less.

4. The resin composition according to claim 2, wherein The particle size distribution of the average particle size of the ceramic particles is unimodal.

5. The resin composition according to claim 2, wherein The content of the ceramic particles in the resin composition is 20 volume % or more and 40 volume % or less.

6. The resin composition according to claim 2, wherein The ceramic particles have an average particle size of 0.3 μm or more and 2 μm or less.

7. The resin composition according to claim 2, wherein The ceramic particles include a substance composed of at least one of Mg, Ca, Ba, B, Al, Y, Hf, Ce, Ti, W, and Si and at least one of O, C, N, and S.

8. The resin composition according to claim 2, wherein The ceramic particles contain 5 volume % or less of particles having a particle size of 2.0 μm or less or 0.005 μm or more.

9. The resin composition according to claim 1, wherein The resin is epoxy resin.

10. The resin composition according to claim 9, wherein Thermosetting resin is used as a curing agent for the epoxy resin.

11. The resin composition according to claim 2, wherein The ceramic particles are aluminum oxide.

12. The resin composition according to claim 2, wherein The ceramic particles are tungsten carbide.

13. The resin composition according to claim 1, wherein The particles of the inorganic material are metal particles, If the acoustic impedance of the acoustic matching layer is set to Z, and the density of the metal particles is set to ρ, Then 2.3≤Z / √ρ≤2.9 is satisfied.

14. The resin composition according to claim 13, wherein The particle size distribution of the average particle size of the metal particles is a unimodal distribution.

15. The resin composition according to claim 13, wherein The content of the metal particles in the resin composition is 20% by volume or more and 40% by volume or less.

16. The resin composition according to claim 13, wherein The metal particles have an average particle size of 1.0 μm or more and 4 μm or less.

17. The resin composition according to claim 13, wherein The metal particles include a substance composed of at least one of Au, Ag, Pt, Cu, Cr, Zr, Zn, Ta, Ti, Mg, Ni, Ca, Ba, Al, Y, Hf, Ce, Ti, Mo, W, Si, Pd, Ir, Sn, Fe, Pb, Pd, and Nd.

18. The resin composition according to claim 13, wherein The metal particles contain 5 volume % or less of particles having a particle size of 2.0 μm or less or 0.005 μm or more.

19. The resin composition according to claim 13, wherein The metal particles are copper or tungsten.

Images