Ultrasonic element, ultrasonic device, and air tactile sensation device

Abstract

The ultrasonic element is provided with: a piezoelectric element that generates ultrasonic waves of 20 kHz to 100 kHz; and an acoustic matching layer that is provided on the piezoelectric element and contains a resin, the maximum thickness from a surface of the piezoelectric element that is on the opposite side from a surface on which the acoustic matching layer is disposed to a surface of the acoustic matching layer that is on the opposite side from a surface on which the piezoelectric element is disposed being 1.5 mm or less.

Description

Technical Field

[0001] This disclosure relates to an ultrasonic element, an ultrasonic device, and an airborne tactile sensing device. Background Technology

[0002] In recent years, with the popularization of virtual reality technology, the demand for aerial haptic devices that stimulate skin sensations without physical contact has increased.

[0003] Airborne haptic devices, for example, collect ultrasonic waves generated by time differences from multiple ultrasonic transducers arranged in a two-dimensional array and synthesize them into a composite wave, forming a focal point at a target location, thereby generating a large acoustic radiation pressure at that focal point and stimulating the human skin sensation non-contactly.

[0004] As an air-sensing device, for example, there is a device disclosed in Non-Patent Document 1 below, which arranges ultrasonic elements with an outer diameter of about 10 mm and a thickness of about 7 mm in two dimensions on a printed circuit board and connects them with solder to form an array.

[0005] Non-patent literature 1: Journal of the Japan Society for Acoustics, Vol. 76, No. 5 (2020), pp. 271-278 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] In an airborne tactile sensor device that is formed by arraying ultrasonic elements with an outer diameter of about 10 mm and a thickness of about 7 mm, the overall size of the device is large due to the large size of each ultrasonic element, making it difficult to use as a component in a small device.

[0008] The purpose of this disclosure is to provide an ultrasonic element capable of generating high sound pressure and applicable to small air tactile devices, as well as an ultrasonic device and an air tactile device using said ultrasonic element.

[0009] [Technical means to solve the problem]

[0010] The means used to solve the aforementioned problem include the following forms.

[0011] <1>

[0012] An ultrasonic element comprising: a piezoelectric element for generating ultrasonic waves from 20 kHz to 100 kHz; and

[0013] An acoustic matching layer, disposed on the piezoelectric element and comprising resin,

[0014] The maximum thickness from the side of the piezoelectric element opposite to the side where the acoustic matching layer is disposed to the side of the acoustic matching layer opposite to the side where the piezoelectric element is disposed is 1.5 mm or less.

[0015] <2>

[0016] According to the ultrasonic element described in <1>, the difference between the maximum thickness and the minimum thickness of the acoustic matching layer is more than 1 μm.

[0017] <3>

[0018] According to the ultrasonic element described in <1> or <2>, the surface of the acoustic matching layer opposite to the side on which the piezoelectric element is disposed is a curved surface.

[0019] <4>

[0020] The ultrasonic element according to any one of <1> to <3>, wherein the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is disposed is convex.

[0021] <5>

[0022] According to any one of <1> to <3>, the ultrasonic element wherein the surface of the acoustic matching layer opposite to the side on which the piezoelectric element is disposed is concave.

[0023] <6>

[0024] According to any one of <1> to <5>, the ultrasonic element, when viewed from above, has a maximum diameter of 8 mm or less.

[0025] <7>

[0026] The ultrasonic element according to any one of <1> to <6>, wherein the acoustic matching layer is grounded to the piezoelectric element.

[0027] <8>

[0028] The ultrasonic element according to any one of <1> to <6>, wherein a metal plate is further provided between the piezoelectric element and the acoustic matching layer.

[0029] <9>

[0030] The ultrasonic element according to any one of <1> to <8> further comprises, on the side opposite to the side where the acoustic matching layer is disposed in the piezoelectric element, at least one of an acoustic wave reflecting layer comprising resin and an acoustic wave attenuating layer comprising resin.

[0031] <10>

[0032] An ultrasonic device, comprising:

[0033] Support; and

[0034] The ultrasonic element according to any one of <1> to <9> is disposed on the support body, and a plurality of them are arranged in two dimensions.

[0035] <11>

[0036] The ultrasonic device described in <10> is used in an air-to-air tactile device.

[0037] <12>

[0038] An airborne tactile device comprising an ultrasonic device as described in <10> or <11>.

[0039] [The effects of the invention]

[0040] This disclosure provides an ultrasonic element capable of generating high sound pressure and applicable to small air tactile devices, as well as an ultrasonic device and an air tactile device using the ultrasonic element. Attached Figure Description

[0041] Figure 1 This is a partial end view schematically showing a cross-section of an example of an ultrasonic element according to one embodiment.

[0042] Figure 2 This is a partial end view schematically showing a cross-section of another example of an ultrasonic element according to one embodiment.

[0043] Figure 3 This is a partial end view schematically showing a cross-section of another example of an ultrasonic element according to one embodiment.

[0044] Figure 4 This is a partial end view schematically showing a cross-section of another example of an ultrasonic element according to one embodiment.

[0045] Figure 5 This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0046] Figure 6 This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0047] Figure 7 This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0048] Figure 8This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0049] Figure 9 This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0050] Figure 10 This is a schematic end view of a cross-section of another example of an ultrasonic element according to one embodiment.

[0051] Figure 11 This is a perspective view showing an example of the ultrasonic device according to the first embodiment.

[0052] Figure 12 It is a schematic representation in Figure 11 The diagram shows a cross-section obtained by cutting the ultrasonic device along its thickness direction.

[0053] Figure 13 This is a schematic cross-sectional view of an example of the ultrasonic device according to the second embodiment.

[0054] Figure 14 This is a perspective view showing an example of an existing airborne haptic device.

[0055] Figure 15 yes Figure 14 A three-dimensional view of the ultrasonic wave generating device in the air-sensing device shown.

[0056] Figure 16 yes Figure 15 A schematic cross-sectional view of the ultrasonic generating device shown. Detailed Implementation

[0057] The following describes in detail the forms used to implement the present invention. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless specifically stated otherwise. Similarly, numerical values ​​and their ranges are not limiting to the present invention.

[0058] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that, even if they cannot be clearly distinguished from other processes, are included as long as the purpose of the process is achieved.

[0059] In this disclosure, the numerical values ​​recorded before and after “~” in the numerical range represented by “~” are respectively the minimum value and the maximum value.

[0060] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced by the upper or lower limit of another numerical range described in other stages. Furthermore, the upper or lower limit of the numerical ranges described in this disclosure can also be replaced by the values ​​shown in the embodiments.

[0061] In this disclosure, each component may comprise multiple equivalent substances. Where multiple equivalent substances are present in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the composition.

[0062] In this disclosure, multiple particles corresponding to each component may also be included. In the case where multiple particles corresponding to each component are present in the composition, unless otherwise specified, the particle size of each component refers to a value related to the mixture of the multiple particles present in the composition.

[0063] In this disclosure, the terms "layer" or "film" include, in addition to the case where the layer or film is formed entirely in the region where it is observed, the case where it is formed only in a portion of the region.

[0064] In this disclosure, the term "stack" means to stack layers, which may combine two or more layers together or allow two or more layers to be detached.

[0065] In this disclosure, "(meth)acryloyl" means at least one of acryloyl and methacryloyl, and "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid.

[0066] In this disclosure, embodiments are described with reference to the accompanying drawings, but the structure of the embodiments is not limited to the structure shown in the drawings. Furthermore, the sizes of the components in the figures are conceptual, and the relative sizes of the components are not limited thereto.

[0067] Ultrasonic Components

[0068] An ultrasonic element according to one embodiment of this disclosure includes: a piezoelectric element that generates ultrasonic waves of 20 kHz to 100 kHz; and an acoustic matching layer disposed on the piezoelectric element and comprising resin, the maximum thickness of which is 1.5 mm or less from the side of the piezoelectric element opposite to the side on which the acoustic matching layer is disposed to the side of the acoustic matching layer opposite to the side on which the piezoelectric element is disposed. Hereinafter, the maximum thickness from the side of the piezoelectric element opposite to the side on which the acoustic matching layer is disposed to the side of the acoustic matching layer opposite to the side on which the piezoelectric element is disposed will also be referred to as "specific thickness".

[0069] As an existing air-sensing device, for example, as mentioned above, a device formed by arraying ultrasonic elements with an outer diameter of about 10 mm and a thickness of about 7 mm can be cited.

[0070] An example of an existing air-based haptic device is shown. Figure 14 In. Figure 14 In the air-sensing device 500 shown, multiple ultrasonic elements 510 arranged in two dimensions are connected to a printed circuit board 502 using solder.

[0071] exist Figure 15 and Figure 16 The diagram shows a perspective view and a schematic cross-sectional view of the ultrasonic element 510. The ultrasonic element 510 includes an ultrasonic generating section 520 that generates ultrasonic waves and a connecting section 512 that is connected to a printed circuit board 502. The ultrasonic generating section 520 includes a metal plate 522, a piezoelectric ceramic 524 in contact with one side of the metal plate 522, and a funnel-shaped resonator 526 partially in contact with the other side of the metal plate 522. Furthermore, the metal plate 522, the piezoelectric ceramic 524, and the resonator 526 are covered by a frame 528 having a sound emission hole 528A.

[0072] exist Figure 14 In the air haptic device shown, as described above, each ultrasonic element, with an outer diameter of approximately 10 mm and a thickness of approximately 7 mm, has an ultrasonic wave generating section. Therefore, the air haptic device is large, heavy, and expensive overall. Specifically, for example, an air haptic device with 100 (10×10) ultrasonic elements connected to a printed circuit board has a size of approximately 170 mm × 170 mm × 20 mm. Therefore, it is difficult to apply, for example, to components in small devices such as Virtual Reality (VR) glasses, Augmented Reality (AR) glasses, Mixed Reality (MR) glasses, and hearable devices.

[0073] On the other hand, the ultrasonic element of this embodiment includes: a piezoelectric element that generates ultrasonic waves of 20 kHz to 100 kHz; and an acoustic matching layer disposed on the piezoelectric element and comprising resin.

[0074] When ultrasonic waves are emitted directly into the air from a piezoelectric element without passing through an acoustic matching layer, the sound pressure of the ultrasonic waves may decrease due to the large acoustic impedance difference at the interface, which may be caused by the attenuation of the intensity of the ultrasonic waves emitted into the air or the disturbance of the waveform.

[0075] In contrast, in this embodiment, by providing an acoustic matching layer, the acoustic impedance difference between the piezoelectric element and the acoustic matching layer, and the acoustic impedance difference between the ultrasonic element and air, are reduced compared to the acoustic impedance difference between the piezoelectric element and air. Therefore, for example, even if it is less than... Figure 16 The funnel-shaped resonator 526, as shown in the ultrasonic element 510, can also efficiently radiate ultrasonic waves into the air. Furthermore, by making the maximum thickness (i.e., a specific thickness) from the side of the piezoelectric element opposite to the side where the sound matching layer is disposed to the side of the sound matching layer opposite to the side where the piezoelectric element is disposed 1.5 mm or less, it becomes an ultrasonic element that can generate high sound pressure and can also be applied to small air-sensing devices.

[0076] Furthermore, by applying the ultrasonic elements of this embodiment to a small airborne tactile device, ultrasonic waves that maintain their intensity and waveform are emitted into the air from each ultrasonic element, thereby generating high acoustic radiation pressure at the target location.

[0077] <Layer Structure>

[0078] The ultrasonic element in this embodiment only needs to have at least a piezoelectric element and an acoustic matching layer, and may also have other layers as needed. Examples of other layers include: a metal plate disposed between the piezoelectric element and the acoustic matching layer; a sound wave reflecting layer, a sound wave attenuating layer, etc., disposed in the piezoelectric element on the side opposite to the side where the acoustic matching layer is disposed.

[0079] An example of the layered structure of the ultrasonic element in this embodiment is shown below. Figures 1-4 However, the ultrasonic element in this embodiment is not limited to these examples. Figures 1-4 A portion of the cut surface obtained by cutting the piezoelectric element in the thickness direction is shown in a schematic representation of an example of the ultrasonic element in this embodiment.

[0080] Figure 1 The ultrasonic element 200 shown includes a piezoelectric element 16 and an acoustic matching layer 20, which is grounded to at least a portion of one side of the piezoelectric element. The acoustic matching layer 20 is the outermost layer in contact with air. Furthermore, in the ultrasonic element 200, the maximum thickness (i.e., a specific thickness) from the surface 16A of the piezoelectric element 16 opposite to the surface where the acoustic matching layer 20 is disposed to the surface 20A of the acoustic matching layer 20 opposite to the surface where the piezoelectric element 16 is disposed is 1.5 mm or less.

[0081] In the ultrasonic element 200, for example, the acoustic impedance of the acoustic matching layer 20 is a value between the acoustic impedance of the piezoelectric element 16 and the acoustic impedance of air. Furthermore, in the ultrasonic element 200, by having the acoustic matching layer 20 between the piezoelectric element 16 and the air, the ultrasonic waves generated from the piezoelectric element 16 can be efficiently radiated into the air. Therefore, even with a specific thickness within the aforementioned range, high sound pressure can be obtained, and it can be applied to small air-sensing devices.

[0082] Furthermore, in the ultrasonic element 200, since no metal plate is provided between the piezoelectric element 16 and the acoustic matching layer 20, the ultrasonic element 200 as a whole is made flexible by using a piezoelectric resin sheet described later as the piezoelectric element 16.

[0083] Figure 2 The ultrasonic element 210 shown includes: a piezoelectric element 16; a metal plate 28 disposed on one side of the piezoelectric element 16; and an acoustic matching layer 22 disposed on the side of the metal plate 28 opposite to the side where the piezoelectric element 16 is disposed. That is, the ultrasonic element 210 has a metal plate 28 between the piezoelectric element 16 and the acoustic matching layer 22. Furthermore, the acoustic matching layer 22 is the outermost layer in contact with air. Moreover, in the ultrasonic element 210, the maximum thickness from the side 16A of the piezoelectric element 16 opposite to the side where the acoustic matching layer 22 is disposed to the side 22A of the acoustic matching layer 22 opposite to the side where the piezoelectric element 16 is disposed is 1.5 mm or less.

[0084] In the ultrasonic element 210, for example, the acoustic impedance of the acoustic matching layer 22 is a value between the acoustic impedance of the metal plate 28 and the acoustic impedance of air. Furthermore, in the ultrasonic element 210, by having an acoustic matching layer 22 between the metal plate 28 and the air, the ultrasonic waves generated from the piezoelectric element 16 and amplified by the metal plate 28 can be efficiently radiated into the air. Therefore, even with a specific thickness within the aforementioned range, high sound pressure can be obtained, and it can be applied to small air-sensing devices.

[0085] Figure 3 The ultrasonic element 220 shown includes: a piezoelectric element 16; an acoustic matching layer 20, which is grounded to at least a portion of one side of the piezoelectric element; and an acoustic wave reflecting layer 24, which is disposed on the other side of the piezoelectric element 16, with the acoustic matching layer 20 being the outermost layer in contact with air. That is, the ultrasonic element 220 also has an acoustic wave reflecting layer 24 on the side of the piezoelectric element 16 opposite to the side where the acoustic matching layer 20 is disposed.

[0086] In the ultrasonic element 220, a sound wave attenuation layer may be provided instead of the sound wave reflecting layer 24, or it may be provided on the basis of the sound wave reflecting layer 24. When the sound wave attenuation layer is provided on the basis of the sound wave reflecting layer 24, the arrangement order is not particularly limited; it may be arranged from the piezoelectric element 16 side in the order of the sound wave reflecting layer 24 and the sound wave attenuation layer, or it may be arranged in the order of the sound wave attenuation layer and the sound wave reflecting layer 24. That is, the ultrasonic element 220 may also have at least one of the sound wave reflecting layer 24 and the sound wave attenuation layer on the side of the piezoelectric element 16 opposite to the side where the sound matching layer 20 is disposed. Furthermore, in the ultrasonic element 220, the maximum thickness from the surface 16A of the piezoelectric element 16 opposite to the side where the sound matching layer 20 is disposed to the surface 20A of the sound matching layer 20 opposite to the side where the piezoelectric element 16 is disposed is 1.5 mm or less.

[0087] The entire Pair 200 is made soft.

[0088] In the ultrasonic element 220, similarly to the ultrasonic element 200, for example, the acoustic impedance of the acoustic matching layer 20 is a value between the acoustic impedance of the piezoelectric element 16 and the acoustic impedance of air, allowing the ultrasonic waves generated from the piezoelectric element 16 to be efficiently radiated into the air. Furthermore, in the ultrasonic element 220, by having an acoustic wave reflecting layer 24 on the other side of the piezoelectric element 16, the ultrasonic waves generated from the piezoelectric element 16 on the side opposite to the side where the acoustic matching layer 20 is located are reflected by the acoustic wave reflecting layer 24 and efficiently radiated to the acoustic matching layer 20 side. Thus, in the ultrasonic element 220, ultrasonic waves are efficiently radiated into the air, achieving high sound pressure even with a specific thickness within the aforementioned range, and enabling application in small airborne haptic devices.

[0089] Furthermore, in the ultrasonic element 220, since no metal plate is provided between the piezoelectric element 16 and the acoustic matching layer 20, the ultrasonic element 220 as a whole becomes flexible by using a piezoelectric resin sheet described later as the piezoelectric element 16.

[0090] Figure 4 The ultrasonic element 230 shown includes: a piezoelectric element 16; a metal plate 28 disposed on one side of the piezoelectric element; an acoustic matching layer 22 disposed on the side of the metal plate 28 opposite to the side on which the piezoelectric element 16 is disposed; and an acoustic wave reflecting layer 24 disposed on the side of the piezoelectric element 16 opposite to the side on which the acoustic matching layer 22 is disposed, wherein the acoustic matching layer 22 is the outermost layer in contact with the air.

[0091] In the ultrasonic element 230, a sound wave attenuation layer can be provided instead of the sound wave reflecting layer 24, or it can be provided on the basis of the sound wave reflecting layer 24. When the sound wave attenuation layer is provided on the basis of the sound wave reflecting layer 24, the arrangement order is not particularly limited. It can be arranged from the piezoelectric element 16 side in the order of sound wave reflecting layer 24 and sound wave attenuation layer, or it can be arranged in the order of sound wave attenuation layer and sound wave reflecting layer 24. Moreover, in the ultrasonic element 230, the maximum thickness from the surface 16A of the piezoelectric element 16 opposite to the side where the sound matching layer 22 is disposed to the surface 22A of the sound matching layer 22 opposite to the side where the piezoelectric element 16 is disposed is 1.5 mm or less.

[0092] In ultrasonic element 230, similarly to ultrasonic element 210, for example, by using an acoustic impedance layer 22 that is between the acoustic impedance of the metal plate 28 and the acoustic impedance of air, ultrasonic waves generated from piezoelectric element 16 and amplified by metal plate 28 can be efficiently radiated into the air. Furthermore, in ultrasonic element 230, by having a sound wave reflecting layer 24 on the side of piezoelectric element 16 opposite to the side where the acoustic matching layer 22 is disposed, a portion of the ultrasonic waves generated from piezoelectric element 16 is reflected by the sound wave reflecting layer 24, amplified by metal plate 28, and then efficiently radiated into the air from the acoustic matching layer 22. Thus, in ultrasonic element 230, ultrasonic waves are efficiently radiated into the air, achieving high sound pressure even with a specific thickness within the aforementioned range, and enabling application in small airborne tactile devices.

[0093] <Thickness of ultrasonic element>

[0094] As described above, the specific thickness of the ultrasonic element is 1.5 mm or less, preferably 1.3 mm or less, and more preferably 1.0 mm or less. The specific thickness of the ultrasonic element may be 0.1 mm or more.

[0095] The overall thickness of the ultrasonic element can be, for example, 2 mm or less, preferably 1.5 mm or less, and even more preferably 1.3 mm or less. The overall thickness of the ultrasonic element can also be 0.1 mm or more. When the ultrasonic element further comprises at least one of a sound wave reflecting layer and a sound wave attenuating layer, the overall thickness of the ultrasonic element includes the thicknesses of both the sound wave reflecting layer and the sound wave attenuating layer. Furthermore, when the ultrasonic element also comprises other components such as a frame in the thickness direction of the ultrasonic element, the overall thickness of the ultrasonic element refers to the thickness of the entire ultrasonic element including the frame, etc.

[0096] Here, the thickness of a layer or component can be measured using a micrometer or similar instrument. When the thickness of a layer or component can be directly measured, a micrometer is used. On the other hand, when the thickness of a layer or component cannot be directly measured, such as when measuring the thickness of a single layer or the total thickness of multiple layers, the thickness can be measured by observing a cross-section of the layer being measured using an electron microscope.

[0097] <Surface shape of the sound matching layer>

[0098] In the ultrasonic element of this embodiment, the shape of the surface of the acoustic matching layer opposite to the side where the piezoelectric element is disposed is not particularly limited; it can be a plane, a curved surface, or a combination of a plane and a curved surface. Furthermore, the shape of the surface of the acoustic matching layer on the piezoelectric element side is not particularly limited; shapes corresponding to the surface shape of the layer (piezoelectric element, metal plate, etc.) in contact with the acoustic matching layer can be listed. For example, when the acoustic matching layer and the piezoelectric element are grounded and the surface of the piezoelectric element on the acoustic matching layer side is a plane, a plane can be listed as the surface of the piezoelectric element side in the acoustic matching layer.

[0099] Hereinafter, the surface in the acoustic matching layer that is opposite to the side where the piezoelectric element is located, i.e., the surface that radiates ultrasonic waves generated by the piezoelectric element, will also be referred to as the "radiating surface".

[0100] From the viewpoint of obtaining higher sound pressure levels, the radiating surface of the ultrasonic element in this embodiment is preferably shaped such that the difference between the maximum and minimum thickness of the acoustic matching layer is 1 μm or more. From the viewpoint of obtaining high sound pressure levels, the difference between the maximum and minimum thickness of the acoustic matching layer is more preferably 50 μm or more, more preferably 100 μm or more, particularly preferably 200 μm or more, and most preferably 400 μm or more.

[0101] Furthermore, from the viewpoint of obtaining higher sound pressure levels, the radiating surface of the ultrasonic element in this embodiment is preferably shaped such that the difference between the maximum and minimum thickness of the acoustic matching layer is 1 mm or less. From the viewpoint of setting a specific thickness within the aforementioned range, the difference between the maximum and minimum thickness of the acoustic matching layer is more preferably 800 μm or less, more preferably 600 μm or less, and particularly preferably 500 μm or less.

[0102] The difference between the maximum and minimum thickness of the acoustic matching layer is preferably 1 μm to 1 mm, more preferably 50 μm to 800 μm, even more preferably 100 μm to 600 μm, and particularly preferably 200 μm to 500 μm.

[0103] Examples of the shapes of the radiating surface of the acoustic matching layer, where the difference between the maximum and minimum thickness is within the specified range, include: a convex shape where the central portion of the radiating surface is higher than the peripheral portion; a concave shape where the central portion of the radiating surface is lower than the peripheral portion; and a concave-convex shape where multiple convex portions and multiple concave portions are arranged alternately.

[0104] The following examples illustrate ultrasonic elements with convex, concave, or irregularly shaped radiation surfaces in their acoustic matching layers. Figures 5-10 In this embodiment, the ultrasonic element is not limited to these examples. Figures 5-10 The ultrasonic elements shown all have a piezoelectric element 16 and an acoustic matching layer 20, but are not limited to these; other layers may also be present. Furthermore, Figures 5-10 The cut surface obtained by cutting the piezoelectric element in the thickness direction in one example of the ultrasonic element in this embodiment is shown in a schematic manner.

[0105] exist Figure 5 In the ultrasonic element 200A shown, the radiating surface of the acoustic matching layer 20, i.e., the surface 20A of the acoustic matching layer 20 opposite to the side where the piezoelectric element 16 is disposed, is curved and convex, with the central portion of the radiating surface being higher than the peripheral portion. Therefore, the thickness of the acoustic matching layer 20 at its central portion in the surface direction (i.e., the direction of the surface perpendicular to the thickness direction) is greater than the thickness of the acoustic matching layer 20 at its peripheral portion. Thus, compared to the case where the radiating surface of the acoustic matching layer 20 is planar and the thickness of the acoustic matching layer 20 is the same, a higher sound pressure level can be obtained.

[0106] In addition, Figure 6 In the ultrasonic element 200B shown, the radiating surface of the acoustic matching layer 20 is conical. Therefore, the thickness of the acoustic matching layer 20 at its central portion in the planar direction is greater than the thickness of the acoustic matching layer 20 at its periphery. Figure 5 Similarly, the ultrasonic element 200A shown can achieve a high sound pressure level compared to the case where the thickness of the acoustic matching layer 20 is the same.

[0107] exist Figure 7 In the ultrasonic element 200C shown, the radiating surface of the acoustic matching layer 20 is curved and concave, with the central portion of the radiating surface being lower than the peripheral portion. Therefore, the thickness of the acoustic matching layer 20 at the central portion in the planar direction is thinner than the thickness of the acoustic matching layer 20 at the peripheral portion. Consequently, compared to the case where the radiating surface of the acoustic matching layer 20 is planar and the thickness of the acoustic matching layer 20 is the same, a higher sound pressure level can be obtained.

[0108] In addition, Figure 8 In the ultrasonic element 200D shown, the radiating surface of the acoustic matching layer 20 is an inverted cone shape. Therefore, the thickness of the acoustic matching layer 20 at its central portion in the planar direction is thinner than the thickness of the acoustic matching layer 20 at its periphery. Figure 7Similarly, the ultrasonic element 200C shown can achieve a high sound pressure level compared to the case where the thickness of the acoustic matching layer 20 is the same.

[0109] exist Figure 9 In the ultrasonic element 200E shown, the radiating surface of the acoustic matching layer 20 includes multiple curved surfaces and is concave-convex, with multiple protrusions and multiple concave portions arranged alternately. Therefore, the thickness of the acoustic matching layer 20 at the protrusions is greater than the thickness of the acoustic matching layer 20 at the concave portions. As a result, a higher sound pressure level can be obtained compared to the case where the radiating surface of the acoustic matching layer 20 is planar and the thickness of the acoustic matching layer 20 is the same.

[0110] In addition, Figure 10 In the ultrasonic element 200F shown, the radiating surface of the acoustic matching layer 20 comprises multiple square pyramids and is irregularly shaped. Therefore, the thickness of the acoustic matching layer 20 at the convex portion is greater than the thickness of the acoustic matching layer 20 at the concave portion. Figure 9 Similarly, the ultrasonic element 200E shown can achieve a high sound pressure level compared to the case where the thickness of the sound matching layer 20 is the same.

[0111] <Diameter of ultrasonic element>

[0112] When viewed from above, the maximum diameter of the ultrasonic element is preferably 8 mm or less.

[0113] By applying ultrasonic elements with a maximum overall diameter within the aforementioned range to an airborne tactile sensing device, the spatial resolution of acoustic radiation pressure can be improved. Specifically, it is believed that, for example, by arranging ultrasonic elements with a maximum overall diameter within the aforementioned range in a two-dimensional manner, the spacing between ultrasonic wave generating parts can be reduced, thereby improving the spatial resolution of acoustic radiation pressure.

[0114] Here, the maximum diameter of the ultrasonic element as a whole refers to the largest diameter among the diameters of the ultrasonic element as a whole in the plane direction of the piezoelectric element. For example, if the shape of the ultrasonic element as a whole in the plane direction is elliptical, the maximum diameter refers to the major axis; if the shape is square, the maximum diameter refers to the length of the diagonal.

[0115] The layers constituting the ultrasonic element of this embodiment will be described below.

[0116] <Piezoelectric elements>

[0117] The piezoelectric element is not particularly limited as long as it is an ultrasonic element that generates ultrasonic waves in the range of 20 kHz to 100 kHz. Among them, it is preferred to be an ultrasonic element that generates ultrasonic waves in the range of 20 kHz to 80 kHz, and more preferably an ultrasonic element that generates ultrasonic waves in the range of 40 kHz to 70 kHz.

[0118] Examples of piezoelectric elements include piezoelectric ceramics, piezoelectric resin sheets, and piezoelectric single crystals.

[0119] Piezoelectric ceramics include those in which electrodes are provided on a ceramic piezoelectric body. Materials used in ceramic piezoelectric bodies include lead zirconate titanate (PZT), barium titanate, and lead titanate.

[0120] For example, the maximum thickness of piezoelectric ceramics can be 200 μm or less.

[0121] The shape of the piezoelectric ceramic in the face direction is not particularly limited; for example, circles and polygons can be included. The maximum diameter in the face direction of the piezoelectric ceramic can be, for example, 6.5 mm or less.

[0122] For example, the acoustic impedance of piezoelectric ceramics can be 30 MRayls. However, the acoustic impedance of piezoelectric ceramics is not limited to 30 MRayls; it can also be 25 MRayls to 50 MRayls.

[0123] Examples of piezoelectric resin sheets include those with electrodes disposed on a sheet-like piezoelectric body made of resin. Examples of materials used for resin-made piezoelectric bodies include polyvinylidene fluoride (PVDF) and polylactic acid (PLA).

[0124] For example, the acoustic impedance of a piezoelectric resin sheet can be 4.5 MRayls. However, the acoustic impedance of a piezoelectric resin sheet is not limited to 4.5 MRayls; it can also be 1 MRayls to 25 MRayls.

[0125] <Sound Matching Layer>

[0126] The acoustic matching layer is a layer comprising at least resin that allows ultrasonic waves generated by a piezoelectric element to propagate into the air while maintaining their intensity and waveform. Specifically, the acoustic impedance of the acoustic matching layer is set to a value between the acoustic impedance of the layer in contact with the acoustic matching layer and the acoustic impedance of the air. For example, such as... Figure 1 As shown in the ultrasonic element 200, when the acoustic matching layer 20 and the piezoelectric element 16 are grounded, the acoustic impedance value of the acoustic matching layer 20 is set to a value between the acoustic impedance of the piezoelectric element 16 and the acoustic impedance of air. Additionally, for example, as... Figure 2As shown in the ultrasonic element 210, when the acoustic matching layer 22 is grounded to the metal plate 28, the acoustic impedance of the acoustic matching layer 22 is set to a value between the acoustic impedance of the metal plate 28 and the acoustic impedance of air. As a result, the acoustic impedance difference between the layer in contact with the acoustic matching layer and the air is reduced, and the ultrasonic waves generated by the piezoelectric element are less likely to be reflected at the interface between the ultrasonic element and the air, and can easily propagate into the air while maintaining their intensity and waveform.

[0127] The acoustic matching layer can be a single-layer structure or a multi-layer structure. Examples of multi-layer acoustic matching layers include: an acoustic matching layer having an acoustic impedance value close to that of the layer adjacent to it, and a layer composed of stacked acoustic matching layers having an acoustic impedance value close to that of air. By causing the acoustic impedance to change in stages from the piezoelectric element side of the acoustic matching layer to the air side, the ultrasonic waves generated from the piezoelectric element can more easily propagate into the air while maintaining their intensity and waveform. In the case of a multi-layer acoustic matching layer, it can be a two-layer structure or a stacked structure with three or more layers.

[0128] The acoustic impedance of the acoustic matching layer as a whole is preferably a value between the acoustic impedance of air (e.g., 0.0004 MRayls) and the acoustic impedance of the layer connected to the acoustic matching layer, and is preferably set according to the acoustic impedance of the layer connected to the acoustic matching layer.

[0129] For example, when the acoustic matching layer is grounded to the piezoelectric element which is a piezoelectric ceramic, the overall acoustic impedance of the acoustic matching layer is preferably 0.01 MRayls to 1 MRayls.

[0130] Furthermore, when the acoustic matching layer is grounded to the piezoelectric element which is a piezoelectric resin sheet, the overall acoustic impedance of the acoustic matching layer is preferably 0.001 MRayls to 1 MRayls.

[0131] Furthermore, when the acoustic matching layer is grounded to the metal plate, the overall acoustic impedance of the acoustic matching layer is preferably 0.01 MRayls to 1 MRayls, more preferably 0.03 MRayls to 0.5 MRayls, and even more preferably 0.05 MRayls to 0.3 MRayls.

[0132] Here, when the acoustic matching layer is a multi-layer structure, "the overall acoustic impedance value of the acoustic matching layer" refers to the overall value of the multi-layer structure.

[0133] When the acoustic matching layer is a multi-layer structure, it is sufficient that the overall acoustic impedance of the multi-layer structure is within the specified range. The acoustic impedance of each layer constituting the multi-layer structure can be within the specified range, or the acoustic impedance of at least one layer can deviate from the specified range. That is, the overall acoustic impedance of the multi-layer structure can be within the specified range, and the acoustic impedance of at least one layer constituting the multi-layer structure can deviate from the specified range. For example, a multi-layer acoustic matching layer may include the following layers: a first acoustic matching layer disposed on the layer side in contact with the first acoustic matching layer and having an acoustic impedance value of 3 MRayls or more; and a second acoustic matching layer disposed on the air side closer to the first acoustic matching layer and having an acoustic impedance value less than 3 MRayls.

[0134] The acoustic impedance of the acoustic matching layer is calculated based on the sound velocity and density of the acoustic matching layer, as described later, using the following formula.

[0135] Formula: Acoustic impedance = (Sound velocity × Density)

[0136] Furthermore, the density can be determined, for example, by preparing a 10 mm square sample and calculating it based on the average thickness and mass of the sample.

[0137] Methods for controlling the acoustic impedance of the acoustic matching layer include, for example, selecting the type of resin contained in the acoustic matching layer; adjusting the resin content relative to the overall acoustic matching layer; including filler in the acoustic matching layer and adjusting the type of filler and the filler content relative to the overall acoustic matching layer; and including air bubbles in the acoustic matching layer.

[0138] The method for controlling the acoustic impedance value of the acoustic matching layer can be selected based on the target acoustic impedance value.

[0139] Hereinafter, acoustic matching layers with an acoustic impedance of 3 MRayls or more will be referred to as "acoustic matching layer A", and acoustic matching layers with an acoustic impedance of less than 3 MRayls will be referred to as "acoustic matching layer B". Acoustic matching layer A and acoustic matching layer B will be explained respectively.

[0140] Examples of acoustic matching layers A with an acoustic impedance of 3 MRayls or higher include hardened films comprising a resin composition of a resin and a filler with a specific gravity of 2.0 or higher. Specific examples of resins include epoxy resin and acrylic resin, which will be discussed later. Furthermore, examples of fillers with a specific gravity of 2.0 or higher include insulating fillers such as alumina and bismuth oxide, which will be discussed later.

[0141] The sound velocity of the acoustic matching layer A is not particularly limited, for example, it can be 1500 m / s to 5000 m / s, preferably 1900 m / s to 4500 m / s. The sound velocity of the acoustic matching layer is determined by using an ultrasonic velocimeter (manufactured by Dakota Japan, ZX-5) and inputting the thickness of the acoustic matching layer as measured by a micrometer.

[0142] The density of the acoustic matching layer A is not particularly limited; for example, 1.0 g / cm³ is acceptable. 3 ~6.0 g / cm 3 The preferred value is 1.2 g / cm³. 3 ~5.5 g / cm 3 The density of the acoustic matching layer can be determined, for example, by preparing a 10 mm square sample and calculating it based on the average thickness and mass of the sample.

[0143] From the viewpoint of controlling the sound velocity within the aforementioned range, the elastic modulus of the sound matching layer A at 20°C is preferably 1.0 GPa or more, more preferably 7.0 GPa or more, and even more preferably 10.0 GPa or more.

[0144] The elastic modulus of the sound matching layer at 20°C was determined as follows: using a viscoelasticity measuring device DMA7100 (Hightech Corporation), the measurement was performed in tensile mode at a heating rate of 5°C / min and a frequency of 10 Hz.

[0145] For example, the volume resistivity of acoustic matching layer A can be 1.0 × 10⁻⁶. 6 For values ​​above Ω·cm, the range can be 1.0 × 10⁻⁶. 7 The range above Ω·cm can also be 1.0×10. 8 The range is above Ω·cm. There is no particular upper limit to the volume resistivity of the acoustic matching layer A; for example, 1.0 × 10⁻⁶ can be cited. 16 Ω·cm.

[0146] The volume resistivity of the acoustic matching layer can be measured using an insulation resistance meter (e.g., Advantest 8340A) according to Japanese Industrial Standards (JIS) C 2139-3-1:2018, and the volume resistivity can be calculated based on the area and thickness of the electrode contact surface.

[0147] Examples of acoustic matching layer B with an acoustic impedance of less than 3 MRayls include: a cured film comprising a resin composition containing a resin and a filler with a specific gravity of less than 2.0; a cured film comprising a resin composition containing a resin and a foaming agent; and a cured film comprising a resin composition containing a resin, a filler with a specific gravity of less than 2.0, and a foaming agent. Specific examples of resins mentioned later include epoxy resin and acrylic resin.

[0148] The sound velocity of the sound matching layer B is not particularly limited, for example, it can be 500 m / s to 3000 m / s, preferably 500 m / s to 2000 m / s, and more preferably 500 m / s to 1500 m / s.

[0149] The density of the acoustic matching layer B is not particularly limited; for example, 0.1 g / cm³ can be used. 3 ~2.0 g / cm 3 Preferably 0.1 g / cm 3 ~1.3 g / cm 3 More preferably 0.1 g / cm³ 3 ~1.0 g / cm 3 .

[0150] From the viewpoint of controlling the sound velocity within the aforementioned range, the elastic modulus of the sound matching layer B at 20°C is preferably 4 GPa or less, more preferably 0.01 GPa or less. From the viewpoint of controlling the sound velocity within the aforementioned range, the elastic modulus of the sound matching layer B at 20°C is preferably 0.001 GPa or more.

[0151] For example, the volume resistivity of acoustic matching layer B can be 1.0 × 10⁻⁶. 6 For values ​​above Ω·cm, the range can be 1.0 × 10⁻⁶. 7 The range above Ω·cm can also be 1.0×10. 8 The range is above Ω·cm. There is no particular upper limit to the volume resistivity of the acoustic matching layer B; for example, 1.0 × 10⁻⁶ can be listed. 16 Ω·cm.

[0152] The acoustic matching layer only needs to be provided on at least a portion of the layer (e.g., a piezoelectric element or a metal plate) that is in contact with the acoustic matching layer. Preferably, the acoustic matching layer is provided on 50% or more of the area in the surface direction of the layer that is in contact with the acoustic matching layer, more preferably on 80% or more, and even more preferably covering the entire layer that is in contact with the acoustic matching layer.

[0153] Furthermore, the side of the acoustic matching layer opposite to the side where the piezoelectric element is disposed (i.e., the radiating surface) is preferably in contact with air at least a portion, more preferably with more than 50% of the area of ​​the radiating surface in contact with air, and even more preferably with more than 80% in contact with air.

[0154] The maximum thickness of the acoustic matching layer can be 1 mm or less, for example, but from the viewpoint of miniaturization of the ultrasonic element, it is preferably 900 μm or less, more preferably 800 μm or less. From the viewpoint of maintaining the intensity of the ultrasonic wave, the maximum thickness of the acoustic matching layer is preferably 200 μm or more, more preferably 400 μm or more, and even more preferably 500 μm or more. The method for measuring the thickness is as described above.

[0155] As described above, the acoustic matching layer contains at least resin.

[0156] The resin content relative to the overall acoustic matching layer can be adjusted according to the type of resin and the target acoustic impedance value.

[0157] From the viewpoint of achieving flexibility in the acoustic matching layer, the resin content relative to the overall acoustic matching layer can be 2% by mass or more, or 3% by mass or more, or 4% by mass or more. From the viewpoint of achieving membrane flexibility, it can be 9% by mass or more, or 10% by mass or more, or 13% by mass or more. Furthermore, relative to the overall acoustic matching layer, the resin content can be 100% by mass or less, or 99% by mass or less, or 95% by mass or less, or 25% by mass or less, or 12% by mass or less, or 10% by mass or less, or 9% by mass or less.

[0158] Examples of resins include resins contained in resin compositions described below, or their cured forms.

[0159] As mentioned above, the acoustic matching layer may also include filler material if necessary.

[0160] The content of filler relative to the overall acoustic matching layer can be adjusted according to the type of filler and the target acoustic impedance value.

[0161] For example, when the acoustic matching layer is the acoustic matching layer A and the insulating filler described later is used as the filler, the content of the insulating filler relative to the acoustic matching layer A as a whole can be 90% by volume or less, or 80% by volume or less, or 70% by volume or less, or less than 50% by volume, or 45% by volume or less, or 35% by volume or less, or 25% by volume or less, or 15% by volume or less. Furthermore, the content of the insulating filler relative to the acoustic matching layer A as a whole can be 1% by volume or more, or 5% by volume or more, or 15% by volume or more, or 25% by volume or more, or 35% by volume or more, or 50% by volume or more, or 60% by volume or more, or 70% by volume or more.

[0162] As a type of insulating filler, the insulating fillers contained in the resin compositions described below can be listed.

[0163] Similarly, when the acoustic matching layer is the acoustic matching layer B and hollow particles (described later) are used as filler, the content of hollow particles relative to the acoustic matching layer B as a whole can be 90% by volume or less, 80% by volume or less, 70% by volume or less, less than 50% by volume, 45% by volume or less, 35% by volume or less, 25% by volume or less, or 15% by volume or less. Furthermore, the content of hollow particles relative to the acoustic matching layer B as a whole can be 1% by volume or more, 5% by volume or more, 15% by volume or more, 25% by volume or more, 35% by volume or more, 50% by volume or more, 60% by volume or more, or 70% by volume or more.

[0164] Examples of hollow particles include those contained in the resin compositions described later.

[0165] The acoustic matching layer may also contain other components besides resin and filler, as required. The types and contents of these other components are the same as those of the other components contained in the resin composition described later, and their contents relative to all solid components of the resin composition.

[0166] The acoustic matching layer may also contain air bubbles as needed. Examples of acoustic matching layers containing air bubbles include hardened films of resin compositions containing foaming agents described later.

[0167] When the sound matching layer B is a sound matching layer containing bubbles, the bubble content relative to the entire sound matching layer B can be 90% by volume or less, or 80% by volume or less, or 70% by volume or less, or less than 50% by volume, or 45% by volume or less, or 35% by volume or less, or 25% by volume or less, or 15% by volume or less. Alternatively, the bubble content relative to the entire sound matching layer B can be 1% by volume or more, or 5% by volume or more, or 15% by volume or more, or 25% by volume or more, or 35% by volume or more, or 50% by volume or more, or 60% by volume or more, or 70% by volume or more.

[0168] The bubble content was determined by the water immersion method and by using the relationship between the apparent density (ρ) and true density (ρ0) of the sample.

[0169] Formula: Porosity (%) = {1 - (ρ / ρ0)} × 100

[0170] Furthermore, the apparent density (ρ) is determined as follows: using the gravimetric method in water (immersion method), the weight in the atmosphere and the weight in water are measured, and the apparent volume is calculated according to Archimedes' principle. The apparent volume is then divided by the weight in the atmosphere. Alternatively, the sample is thoroughly pulverized to eliminate pores, and the true density (ρ0) is determined using a Gay-Lussac type hydrometer (pycnometer method). Specifically, the voids in the sample are completely degassed and replaced with liquid, and the relationship between its weight and volume is calculated to determine the true density.

[0171] As an acoustic matching layer, examples include hardened films of resin compositions containing resin.

[0172] The hardened film can be a film obtained by hardening a dried film of a resin composition, or a film obtained by hardening a resin composition without a dried film.

[0173] Here, the hardened film can be a film whose hardness is increased by utilizing a chemical reaction to have a different chemical structure than before hardening, or it can be a film whose hardness is increased by curing a resin composition that is molten without changing its chemical structure compared to before hardening.

[0174] Hereinafter, as an example of an acoustic matching layer, an acoustic matching layer that is a hardened film of a resin composition will be described.

[0175] (Resin composition)

[0176] The resin composition contains at least a resin, and may also contain fillers, solvents, other components, etc., as needed.

[0177] -Resin-

[0178] There are no particular restrictions on the type of resin; it can be a thermosetting resin, a thermoplastic resin, or a combination of these.

[0179] In addition, the resin can be a monomer having functional groups that can undergo a polymerization reaction when heated, or it can be a polymer that has already been polymerized.

[0180] The resin is preferably a resin with polar groups. By using a resin with polar groups as the resin, the interaction with the surfaces of the components being bonded is improved, thereby obtaining a layer with high adhesion.

[0181] A polar group refers to an atomic group that is polar through the bonding of atoms with different electronegativity. Examples of polar groups include those containing heteroatoms other than carbon and hydrogen atoms; more specifically, groups containing at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur, boron, phosphorus, and silicon atoms. Preferably, a polar group contains at least one heteroatom selected from the group consisting of nitrogen, oxygen, and sulfur atoms. More specifically, examples of polar groups include: amino, amide, imide, cyano, nitro, epoxy, hydroxyl, carboxyl, carbonyl, thiol, sulfonyl, sulfinyl, ester bond, ether bond, thioether bond, carbamate bond, urea bond, etc., preferably at least one selected from the group consisting of amide, imide, epoxy, hydroxyl, amino, carboxyl, carbonyl, ether bond, and urea bond. Polar groups can exist in the main chain of the resin or in the side chain.

[0182] Resins with polar groups include, specifically, vinyl polymer resins, acrylic resins, polyamide resins, polyimide resins, polyamide-imide resins, polyurethane resins, polyester resins, polyether resins, epoxy resins, oxazine resins, bismaleimide resins, phenolic resins, unsaturated polyester resins, silicone resins, phenoxy resins, etc. Among these, resins with polar groups are preferably at least one selected from the group consisting of polyamide-imide resins, epoxy resins, acrylic resins, polyester resins, and polyether resins. Resins with polar groups can be used alone or in combination of two or more.

[0183] In addition to resins with polar groups, resin compositions may also contain resins without polar groups. Examples of resins that do not have polar groups include: styrene-butadiene random copolymer resins (styrene-butadiene rubber (SBR) resins), styrene-butadiene block copolymer resins (styrene-butadiene-styrene (SBS) resins), styrene-isoprene block copolymers (styrene-isoprene-styrene (SIS)), styrene-ethylene-butene block copolymer resins (styrene-ethylene-butylene-styrene (SEBS)), styrene-ethylene-propylene block copolymer resins (styrene-ethylene-propylene-styrene (SEPS)), polyethylene, polypropylene, polybutadiene, polyisoprene, polystyrene, and cyclic olefin polymers, as well as their hydrogenated products.

[0184] The content of resin with polar groups relative to the total amount of resin is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The content of resin with polar groups relative to the total amount of resin may be 100% by mass or 95% by mass or less.

[0185] From the viewpoint of durability, the resin is preferably a thermosetting resin, and more preferably a thermosetting resin having a polar group. The thermosetting resin may have aromatic rings, or it may have condensed rings formed by the condensation of two or more aromatic rings. Examples of condensed rings include naphthalene rings, anthracene rings, and phenanthrene rings.

[0186] Examples of thermosetting resins with polar groups include epoxy resins, phenolic resins, melamine resins, urea resins, thermosetting polyimide resins, acrylic resins, and polyurethane resins. Among these, from the viewpoint of durability, epoxy resins, phenolic resins, and acrylic resins are preferred as thermosetting resins with polar groups, and epoxy resins are more preferred.

[0187] There are no particular limitations on epoxy resins as long as they have two or more epoxy groups in one molecule.

[0188] Specific examples of epoxy resins include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, phenolic varnish type epoxy resin, cresol phenolic varnish type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, biphenyl type epoxy resin, biphenyl phenolic varnish type epoxy resin, cyclic aliphatic epoxy resin, etc.

[0189] Furthermore, as preferred specific examples of epoxy resins, epoxy resins having substituents such as ether groups or alicyclic epoxy groups can be cited. Preferably, the epoxy resin has heteroatoms other than oxygen atoms derived from the epoxy group or glycidyl group of the epoxy resin.

[0190] Epoxy resins can be, for example, epoxy resins containing nitrogen atoms and hydrogen atoms bonded to the nitrogen atoms. In a preferred embodiment, the epoxy resin may have a heterocyclic structure containing nitrogen atoms and hydrogen atoms bonded to the nitrogen atoms. Examples of such heterocyclic structures include the glycourea structure.

[0191] There is no particular limitation on the molecular weight of epoxy resin. For example, it can be 100-1500, 150-1000, or 200-500.

[0192] When the resin composition contains epoxy resin, the epoxy resin content relative to the total resin may be 80% by mass or more, 90% by mass or more, or 100% by mass. Alternatively, the epoxy resin content relative to the total resin may be 10% by mass to 90% by mass, 20% by mass to 80% by mass, 30% by mass to 80% by mass, or 40% by mass to 80% by mass.

[0193] There are no particular limitations on acrylic resins as long as they have two or more (meth)acryloyl groups in their molecules.

[0194] Specific examples of acrylic resins include: 1,9-nonanediol diacrylate, ethylene glycol diacrylate, propylene glycol diacrylate, and other polyfunctional (meth)acrylates.

[0195] When the resin composition contains the acrylic resin, the resin composition may also contain acrylic compounds other than the acrylic resin. Examples of acrylic compounds other than the acrylic resin include: acrylic nitrile monoacrylates such as acrylonitrile and methacrylonitrile; monofunctional (meth)acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, tert-butyl acrylate, 3-ethoxypropyl acrylate, tetramethoxycarbonyl acrylate, methyl acrylate, isopropyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, n-propyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, ethyl methacrylate, 2-nitro-2-methylpropyl methacrylate, 1,1-diethylpropyl methacrylate, methyl methacrylate, isodecanyl acrylate, tricyclodecyl acrylate, and glycidyl methacrylate.

[0196] When the resin composition contains acrylic resin, the total content of acrylic resin and acrylic compounds other than acrylic resin relative to the total amount of resin may be 5% to 100% by mass, or 10% to 50% by mass.

[0197] When the resin contains a thermosetting resin, the resin composition may also contain a curing agent. For example, when using epoxy resin as the thermosetting resin, addition curing agents such as acid anhydride-based curing agents, amine-based curing agents, phenol-based curing agents, and thiol-based curing agents, as well as latent curing agents such as imidazole, may be used. Furthermore, when using acrylic resin as the thermosetting resin, curing agents such as peroxides and azo compounds may also be used.

[0198] When the resin is polymerized with a curing agent, the polar groups contained in the resin with polar groups can be polar groups generated as a result of the polymerization reaction.

[0199] From the viewpoint of flexibility, the resin preferably comprises a thermoplastic resin, and more preferably a thermoplastic resin having a polar group.

[0200] Examples of thermoplastic resins include phenoxy resins, polyamide-imide resins, polyethylene resins, polypropylene resins, and SBR resins. Among these, from the viewpoint of flexibility, phenoxy resins, polyamide-imide resins, polyethylene resins, and SBR resins are preferred, and polyamide-imide resins, phenoxy resins, and SBR resins are more preferred.

[0201] There are no particular limitations on phenoxy resins as long as they have a phenoxy structure in their molecular structure. Here, "phenoxy structure" refers to the structure in which an oxygen atom is bonded to a benzene ring, including not only phenoxy groups (C6H5-O-), but also structures in which a portion of the phenoxy group is substituted, or structures in which a portion of the phenoxy group undergoes a reaction such as hydrogenation.

[0202] Examples of phenoxy resins include: phenoxy resins with a bisphenol backbone, phenoxy resins with a phenolic varnish backbone, phenoxy resins with a naphthalene backbone, and phenoxy resins with a biphenyl backbone. From a general viewpoint, phenoxy resins with a bisphenol backbone are preferred.

[0203] Examples of phenoxy resins with a bisphenol backbone include: bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol A and bisphenol F copolymer phenoxy resin, bisphenol S type phenoxy resin, brominated bisphenol A type phenoxy resin, hydrogenated bisphenol A type phenoxy resin, etc.

[0204] These phenoxy resins can be used alone or in combination with two or more.

[0205] Polyamide-imide resins are resins having amide bonds and imide bonds in their main chain. Preferred examples of polyamide-imide resins include those having at least one structure selected from the group consisting of polyepoxide structures and polysiloxane structures. These polyamide-imide resins are preferred from the viewpoint of mitigating stress through deformation of the polyamide-imide resin. These polyamide-imide resins may also be polyamide-imide resins synthesized, for example, using polyepoxide-modified diamines and polysiloxane-modified diamines.

[0206] The polyepoxide structure that can be included in the polyamide-imide resin is preferably an epoxy alkane structure with 1 to 10 carbon atoms, more preferably an epoxy alkane structure with 1 to 8 carbon atoms, and even more preferably an epoxy alkane structure with 1 to 4 carbon atoms. Among these, a polyepoxide-propylene structure is preferred. The alkylene groups in the epoxy alkane structure can be linear or branched. The polyepoxide structure can have one or more unit structures.

[0207] Examples of polysiloxane structures that can be included in polyamide-imide resins include: polysiloxane structures in which part or all of the silicon atoms are substituted with alkyl groups having 1 to 20 carbon atoms or aryl groups having 6 to 18 carbon atoms.

[0208] In addition, as a preferred form of polyamide-imide resin, examples include polyamide-imide resins having structural units derived from diimide carboxylic acids or their derivatives, and structural units derived from aromatic diisocyanates or aromatic diamines.

[0209] There are no particular limitations on SBR resin as long as it is a copolymer of styrene and butadiene. Furthermore, there are no limitations on the ratio of styrene-derived units to butadiene-derived units constituting the SBR resin, nor on the molecular weight of the SBR resin. SBR resin can be a resin with residual unsaturated double bonds derived from butadiene units for reaction with thermosetting resins, or it can be a resin obtained by hydrogenating the unsaturated double bonds to improve durability.

[0210] When the resin contains a thermoplastic resin, from the viewpoint of improving the strength of the film after film formation and suppressing hardening shrinkage during hardening, the thermoplastic resin can be combined with the thermosetting resin.

[0211] The total resin content in the resin composition, relative to the solids content, can be 2% by mass or more, 3% by mass or more, or 4% by mass or more. From the viewpoint of obtaining membrane flexibility, it can be 9% by mass or more, 10% by mass or more, or 13% by mass or more. Furthermore, the total resin content in the resin composition, relative to the solids content, can be 100% by mass or less, 99% by mass or less, 95% by mass or less, 25% by mass or less, 12% by mass or less, 10% by mass or less, or 9% by mass or less.

[0212] -filler-

[0213] Among the fillers used in the manufacture of acoustic matching layer A, insulating fillers include, for example, oxides such as alumina, zirconium oxide, titanium oxide, bismuth oxide, silicon dioxide, cerium oxide, tantalum oxide, tungsten oxide, and sintered uranium oxide; barium titanate, tungsten carbide, tungsten, and zirconium. One type of insulating filler may be used alone, or two or more may be used in combination.

[0214] Among these, the insulating filler is preferably at least one selected from the group consisting of alumina, zirconium oxide, titanium oxide, bismuth oxide, silicon dioxide, tantalum oxide, and tungsten oxide. Furthermore, from the viewpoint of high hardness and uniform particle shape, the insulating filler is preferably at least one selected from the group consisting of alumina, zirconium oxide, titanium oxide, barium titanate, and bismuth oxide, and more preferably at least one selected from the group consisting of alumina, zirconium oxide, and bismuth oxide.

[0215] The volume resistivity of the insulating filler at 25°C is preferably 1×10⁻⁶. 6 Ω·cm or more, more preferably 1×10 8 Ω·cm or higher, and more preferably 1×10 10 Ω·cm or higher.

[0216] From the viewpoint of thin-film formation of the resin composition layer, the volume average particle size D50 of the insulating filler is preferably 5.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less. The lower limit of the volume average particle size D50 of the insulating filler is not particularly limited and can be 0.001 μm or more. From the above viewpoint, the volume average particle size D50 of the insulating filler is preferably 0.001 μm to 5.0 μm, more preferably 0.001 μm to 3.0 μm, and even more preferably 0.001 μm to 2.0 μm.

[0217] Here, the volume average particle size D50 of the insulating filler contained in the resin composition and the volume average particle size D50 of the insulating filler contained in the film formed using the resin composition are determined as follows.

[0218] Specifically, in the volume-based particle size distribution curve, the particle size at which the cumulative total from the small diameter side becomes 50% is set as the volume average particle size D50.

[0219] The particle size distribution curve of the insulating filler contained in the resin composition was obtained by observing the cross-section of the cured resin composition using a scanning electron microscope (SEM) and determining the equivalent diameter of the circle for 20 insulating fillers.

[0220] Furthermore, when determining the volume average particle size D50 of an insulating filler monomer (e.g., an insulating filler that serves as a raw material for a resin composition), it can be determined, for example, by using a particle size distribution measuring device employing laser light scattering (e.g., Shimadzu Corporation's "SALD-3000"), through laser diffraction scattering particle size distribution measurement.

[0221] The shape of the insulating filler is not particularly limited and can be spherical, powdery, needle-like, fibrous, plate-like, angular, polyhedral, or scaly. From the viewpoint of thin-film formation of the resin composition layer, the shape of the insulating filler is preferably polyhedral or spherical, and more preferably spherical.

[0222] From the viewpoint of thinning the resin composition layer, the aspect ratio of the insulating filler is preferably 5 or less, more preferably 4 or less, and more preferably 3 or less. The aspect ratio of the insulating filler contained in the resin composition is determined by observing the cross-section of the cured resin composition using a scanning electron microscope (SEM) as the average of the aspect ratios of the 20 insulating fillers.

[0223] There is no particular limitation on the specific gravity of the insulating filler, which can be adjusted appropriately according to the intended use of the resin composition. The specific gravity of the insulating filler can be 2.0 or higher, or 3.0 or higher, or 5.0 or higher, or 6.0 or higher, or 7.0 or higher. There is no particular upper limit on the specific gravity of the insulating filler. For example, the specific gravity of the insulating filler can be 10.0 or lower.

[0224] In this disclosure, the specific gravity of the filler is expressed according to JIS K 0061:2001 and JIS Z 8807:2012, as the ratio of the mass of the test sample to the mass of pure water at atmospheric pressure of the same volume, which is the ratio of the true specific gravity of the test sample to the true specific gravity of water.

[0225] Furthermore, when the resin composition contains two or more fillers, the specific gravity of the filler refers to a value related to the mixture of fillers contained in the resin composition.

[0226] The content of insulating filler in all solid components of the resin composition may be less than 90% by volume, less than 85% by volume, less than 50% by volume, less than 45% by volume, less than 35% by volume, less than 25% by volume, or less than 15% by volume.

[0227] In addition, from the viewpoint of improving the acoustic impedance of the membrane, the content of insulating filler in all solid components of the resin composition can be 1% or more by volume, or 5% or more by volume, or 15% or more by volume, or 25% or more by volume, or 35% or more by volume, or 50% or more by volume, or 55% or more by volume, or 60% or more by volume.

[0228] The content of insulating filler in all solid components of the resin composition may be 99% by mass or less, or, from the viewpoint of balancing flexibility and wide acoustic impedance control, 87% by mass or less, 70% by mass or less, 65% by mass or less, less than 65% by mass, 60% by mass or less, 50% by mass or less, or 40% by mass or less.

[0229] In addition, the content of insulating filler in all solid components of the resin composition may be 1% by mass or more, or 5% by mass or more, or 20% by mass or more, or 70% by mass or more, or 80% by mass or more, or 88% by mass or more, or 90% by mass or more, or 92% by mass or more.

[0230] Among the fillers, hollow particles used in the manufacture of acoustic matching layer B can include hollow inorganic particles and hollow organic particles.

[0231] Examples of hollow inorganic particles include: hollow silicon dioxide particles, hollow titanium dioxide particles, hollow zirconium oxide particles, hollow tin oxide particles, and other hollow oxide particles; hollow silicon particles; and hollow carbon particles.

[0232] Hollow organic particles can be categorized as hollow polymer particles, specifically including: vinyl polymer resins, acrylic resins, polyamide resins, polyimide resins, polyamide-imide resins, polyurethane resins, polyester resins, polyether resins, epoxy resins, oxazine resins, bismaleimide resins, phenolic resins, unsaturated polyester resins, silicone resins, phenoxy resins, SBR resins (styrene-butadiene-random copolymers), SBS resins (styrene-butadiene block copolymers), SIS (styrene-isoprene block copolymers), SEBS (styrene-ethylene-butene block copolymers), SEPS (styrene-ethylene-propylene block copolymers), polyethylene, polypropylene, polybutadiene, polyisoprene, polystyrene, and cyclic olefin polymers, as well as their hydrogenation products, etc.

[0233] From the viewpoint of thin-film formation of the resin composition layer, the volume average particle size D50 of the hollow particles is preferably 100.0 μm or less, more preferably 50.0 μm or less, and even more preferably 30.0 μm or less. The lower limit of the volume average particle size D50 of the hollow particles is not particularly limited and can be 1 μm or more. From the above viewpoint, the volume average particle size D50 of the hollow particles is preferably 1 μm to 100.0 μm, more preferably 1 μm to 50.0 μm, and even more preferably 1 μm to 30.0 μm.

[0234] The volume average particle size D50 of the hollow particles contained in the resin composition and the volume average particle size D50 of the hollow particles contained in the film formed using the resin composition are determined by the same method as the volume average particle size D50 of the insulating filler.

[0235] There are no particular restrictions on the shape of hollow particles; examples include spherical particles.

[0236] The specific gravity of the hollow particles is not particularly limited and can be adjusted appropriately according to the intended use of the resin composition. The specific gravity of the hollow particles can be less than 2.0, less than 0.1, or less than 0.01.

[0237] -Foaming agent-

[0238] As foaming agents, examples include organic foaming agents and inorganic foaming agents.

[0239] Examples of organic foaming agents include: azodicarbonamide (ADCA), N,N-dinitroso pentamethylene tetramine (DPT), 4,4-oxybisbenzenesulfonyl hydrazide (OBSH), and hydrazodicarbonamide (HDCA).

[0240] Examples of inorganic foaming agents include sodium bicarbonate.

[0241] There is no particular limitation on the decomposition temperature of foaming agents. For example, it can be 50℃~200℃, 80℃~200℃, or 130℃~200℃.

[0242] The content of the foaming agent in the resin composition is preferably set appropriately according to the type of foaming agent, etc. For example, when azodicarbonamide, which is an organic foaming agent, is used as the foaming agent, from the viewpoint of foaming properties, the content of the organic foaming agent in the resin composition is preferably in the range of 0.05% by mass to 1.0% by mass, and more preferably in the range of 0.1% by mass to 0.5% by mass.

[0243] -solvent-

[0244] From the viewpoint of adjusting viscosity, the resin composition may contain a solvent. From the viewpoint of preventing the composition from drying during the process of applying the composition, the solvent is preferably a solvent with a boiling point of 70°C or higher, more preferably a solvent with a boiling point of 100°C or higher. In addition, in order to suppress the formation of voids, the solvent is more preferably a solvent with a boiling point of 300°C or lower.

[0245] There are no particular restrictions on the types of solvents, such as: alcohol solvents, ether solvents, ketone solvents, amide solvents, aromatic hydrocarbon solvents, ester solvents, and nitrile solvents. More specifically, examples include: methyl isobutyl ketone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, γ-butyrolactone, sulfolane, cyclohexanone, methyl ethyl ketone, dimethylpropionamide, 2-(2-hexyloxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol, diethylene glycol monoethyl ether, terpineol, stearyl alcohol, tripropylene glycol methyl ether, diethylene glycol, propylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol-n-butyl ether, 1,3-butanediol, 1,4-butanediol, p-phenylphenol, propylene glycol phenyl ether, tributyl citrate, 4-methyl-1,3-dioxacyclopentan-2-one, paraffin, toluene, etc. A single solvent or two or more solvents can be used.

[0246] From the viewpoints of viscosity and shortening the heating process, the solvent content relative to the total amount of the resin composition is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 20% by mass or less. There is no particular limitation on the lower limit of the solvent content, and the resin composition may also be solvent-free. The solvent content may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or less.

[0247] -Other ingredients-

[0248] The resin composition may also contain other components as needed. Examples of other components include additives such as dispersants, coupling agents, and thixotropic agents.

[0249] From the viewpoint of the dispersibility of fillers, resin compositions may also contain dispersants.

[0250] Dispersants that are compatible with resins can be listed as examples. By using dispersants that are compatible with resins, fillers can be properly dispersed, tending to improve adhesion to the substrate. Specifically, examples of dispersants include phosphates, carboxylates, and amine carboxylates.

[0251] The content of the dispersant relative to all solid components of the resin composition can be 0.01% to 5% by mass, 0.05% to 3% by mass, 0.1% to 1% by mass, or 0.1% to 0.5% by mass.

[0252] There is no particular limitation on the type of coupling agent. Examples of coupling agents include silane compounds, titanium compounds, aluminum chelate compounds, and aluminum / zirconium compounds. Among these, silane coupling agents are preferred from the viewpoint of adhesion to substrates such as glass. A single coupling agent or two or more can be used in combination.

[0253] If the resin composition contains a coupling agent, the resulting film tends to have improved adhesion to the substrate.

[0254] Examples of silane coupling agents include those having vinyl, epoxy, methacrylate, acrylate, amino, isocyanurate, urea, mercapto, isocyanate, or anhydride groups. Among these, silane coupling agents having epoxy or amino groups are preferred, and those having epoxy or aniline groups are more preferred. Particularly when using at least one resin selected from the group consisting of polyamide-imide resins and epoxy resins, from the viewpoint of good compatibility with polyamide-imide resins and epoxy resins, it is preferable to use silane coupling agents having epoxy or amino groups, and more preferably silane coupling agents having epoxy or aniline groups.

[0255] Specifically, examples of silane coupling agents include: 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-ureopropyltriethoxysilane, etc.

[0256] When the resin composition contains a coupling agent, there is no particular limitation on the content of the coupling agent in the resin composition, but it is preferably 0.05% to 5% by mass relative to the solid content of the resin composition, and more preferably 0.1% to 2.5% by mass.

[0257] Examples of thixotropic agents include: 12-hydroxystearic acid, 12-hydroxystearic acid triglyceride, ethylene distearate, hexamethylene dioleate, N,N'-distearate adipamide, and fumed silica. A single thixotropic agent can be used, or two or more can be used in combination. The content of the thixotropic agent is not particularly limited; relative to all solid components of the resin composition, it can be 0.01% to 5% by mass, 0.05% to 3% by mass, or 0.1% to 1% by mass.

[0258] Furthermore, the resin composition may or may not contain conductive fillers as other components. From the viewpoint of obtaining an insulating film, the content of conductive fillers relative to the total solid components of the resin composition is preferably less than 1 volume, more preferably less than 0.1 volume, and even more preferably less than 0.01 volume.

[0259] In addition, conductive fillers refer to fillers with a volume resistivity of less than 1×10⁻⁶ at 25°C. 6 Ω·cm packing material.

[0260] Examples of conductive fillers include: metals, conductive metal oxides, and carbon black.

[0261] -Preparation and properties of resin compositions-

[0262] There are no particular limitations on the preparation method of the resin composition. For example, a method in which the components contained in the resin composition are mixed in a specified amount by means of a mixer or the like can be listed.

[0263] From a processability point of view, the viscosity of the resin composition at 25°C is preferably 10 Pa·s to 300 Pa·s, more preferably 20 Pa·s to 250 Pa·s, and even more preferably 30 Pa·s to 200 Pa·s. The viscosity of the resin composition is measured according to JIS Z 3284-3:2014, using an E-type rotational viscometer equipped with an SPP rotor, at 25°C, rotating at 2.5 rpm for 144 seconds, and is taken as the average of two measurements.

[0264] (Manufacturing method of acoustic matching layer)

[0265] The sound matching layer can be obtained, for example, in the following manner.

[0266] Specifically, for example, the resin composition is first applied to the acoustic matching layer setting object to form a resin composition layer, and the resin composition layer is dried and hardened to obtain a hardened film of the resin composition, namely the acoustic matching layer.

[0267] Alternatively, the resin composition can be applied to the surface of a substrate to form a resin composition layer, and the resin composition layer can be dried to obtain a dried film. Then, the dried film peeled off from the surface of the substrate is applied to the acoustic matching layer application object and hardened to obtain a hardened film of the resin composition, i.e., the acoustic matching layer.

[0268] Alternatively, the resin composition can be applied to the surface of a substrate to form a resin composition layer, and the resin composition layer can be dried and hardened to obtain a hardened film of the resin composition. Then, the hardened film peeled off from the surface of the substrate is disposed on the acoustic matching layer placement object to obtain the hardened film of the resin composition, i.e., the acoustic matching layer.

[0269] Alternatively, injection molding, extrusion molding, or other methods can be used to obtain a molded body of the resin composition, i.e., a hardened film, which is then placed on the acoustic matching layer placement object to obtain a hardened film of the resin composition, i.e., an acoustic matching layer.

[0270] When the acoustic matching layer has a multilayer structure, it can also be a hardened film formed by curing a laminate of multiple dried films. Specifically, it can be a hardened film formed by peeling dried films, which are formed on different substrates, from the substrates and then bonding them together, and then integrating them through curing. Alternatively, it can be a hardened film obtained by further coating a resin composition onto the dried film and drying it, thereby obtaining a laminate of multiple dried films, and then curing the laminate.

[0271] There are no particular limitations on the methods of applying resin compositions, and examples include: spraying, screen printing, spin coating, spool coating, and bar coating.

[0272] There are no particular limitations on the substrates to which the resin composition is applied, and examples include: glass, metal, resin materials, metal vapor-deposited films, metal oxides, ceramics, nonwoven fabrics, glass fibers, aramid fibers, carbon fibers, glass fiber prepregs, aramid fiber prepregs, carbon fiber prepregs, etc.

[0273] There are no particular limitations on the method for drying the resin composition layer. Examples include heat treatment using devices such as heating plates and ovens, and natural drying. The conditions for drying by heat treatment are not particularly limited as long as the solvent in the resin composition is sufficiently evaporated; it can be carried out at 80℃ to 150℃ for approximately 5 to 120 minutes.

[0274] There are no particular limitations on the method used to obtain a hardened film; hardening can be achieved through heat treatment, etc. Heat treatment can be performed using box dryers, hot air conveyor belt dryers, quartz tube furnaces, hot plates, rapid heat annealing furnaces, vertical diffusion furnaces, infrared curing furnaces, electron beam curing furnaces, microwave curing furnaces, laminators, hot plate presses, etc. Alternatively, a hardened film can be obtained by using molding machines such as injection molding machines and extrusion molding machines, where heat treatment during molding is used to harden the resin composition.

[0275] <Metal Plate>

[0276] The metal plate is a layer that is set as needed and amplifies and propagates the ultrasonic waves generated from the piezoelectric element to the acoustic matching layer.

[0277] There are no particular restrictions on the materials used for metal sheets; examples include aluminum, stainless steel, iron, and copper.

[0278] For example, a maximum thickness of 500 μm or less can be used as the maximum thickness of the metal plate. However, from the perspective of obtaining high sound pressure levels and setting a specific thickness within the range mentioned above, 100 μm to 500 μm is preferred.

[0279] From the viewpoint that efficiently amplifying the ultrasonic waves generated by the piezoelectric element can be achieved simply by having a metal plate disposed on at least a portion of the surface of the piezoelectric element on the acoustic matching layer side, it is preferable to have the metal plate disposed on the entire surface of the acoustic matching layer side. The size of the metal plate in the surface direction may be larger than the surface of the piezoelectric element on the acoustic matching layer side.

[0280] There are no particular limitations on the shape of the metal sheet in the face direction; for example, circles and polygons can be listed. When viewed from above, the maximum diameter of the metal sheet can be, for example, 8 mm or less.

[0281] <Sound wave reflector>

[0282] The acoustic wave reflecting layer comprises at least resin and reflects ultrasonic waves generated from the piezoelectric element on the opposite side to the acoustic matching layer. Specifically, the acoustic impedance of the acoustic wave reflecting layer is set to a value significantly different from the acoustic impedance of the layer in contact with it. Therefore, ultrasonic waves generated by the piezoelectric element are easily reflected at the interface between the acoustic wave reflecting layer and the layer in contact with it.

[0283] As a method for controlling the acoustic impedance value of the acoustic wave reflecting layer, the same method as the method for controlling the acoustic impedance value of the acoustic matching layer can be listed.

[0284] Apart from the difference in acoustic impedance, the composition and formation method of the acoustic wave reflecting layer are the same as those of the acoustic matching layer.

[0285] There is no particular limitation on the average thickness of the acoustic wave reflective layer; for example, it can be less than 500 μm. The definition of average thickness and the method for measuring thickness are as described above.

[0286] <Acoustic attenuation layer>

[0287] The acoustic attenuation layer comprises at least resin and is a layer that attenuates ultrasonic waves generated from the piezoelectric element on the opposite side to the acoustic matching layer. The acoustic attenuation layer can be any layer that makes sound waves impervious, such as a layer that makes sound waves impervious by reflecting sound waves, a layer that makes sound waves impervious by absorbing sound waves, or a layer that makes sound waves impervious by both reflecting and absorbing sound waves.

[0288] In the acoustic attenuation layer, similar to the acoustic reflection layer, the reflectivity of the acoustic wave can be increased by setting the acoustic impedance value to be significantly different from the acoustic impedance value of the layer connected to the acoustic attenuation layer, making the acoustic wave less likely to pass through.

[0289] In addition, in the acoustic attenuation layer, the signal strength of ultrasonic waves can be reduced during propagation through the conversion to heat energy, diffusion, scattering, and delay of ultrasonic waves.

[0290] Apart from the difference in acoustic impedance, the composition and formation method of the acoustic attenuation layer are the same as those of the acoustic matching layer.

[0291] There is no particular limitation on the average thickness of the acoustic attenuation layer; for example, it can be less than 500 μm. The definition of average thickness and the method for measuring thickness are as described above.

[0292] Furthermore, when the sound wave attenuation layer is a layer that increases the absorption rate of sound waves, it is preferable to increase the thermal conductivity of the sound wave attenuation layer so that the heat generated by the absorption of sound waves is less likely to accumulate.

[0293] Methods for improving the thermal conductivity of the acoustic wave attenuation layer include, for example, methods incorporating fillers with high thermal conductivity. Examples of fillers with high thermal conductivity include alumina.

[0294] Ultrasonic Devices

[0295] An ultrasonic device according to one embodiment of this disclosure includes: a support body; and multiple ultrasonic elements disposed on the support body and arranged in a two-dimensional manner. In this embodiment, since the ultrasonic elements of the present embodiment are used as ultrasonic elements, it can be applied to a small airborne tactile sensing device, and ultrasonic waves with maintained intensity and waveform can be emitted from each ultrasonic element into the air, generating high acoustic radiation pressure at a target location.

[0296] <Support>

[0297] The support can be any component that supports the ultrasonic element, and there are no special restrictions.

[0298] The following description uses the accompanying drawings to illustrate the structure of an example of the ultrasonic device of this disclosure, but the ultrasonic device of this disclosure is not limited to these examples.

[0299] <First Implementation>

[0300] Figure 11 This is a perspective view showing an example of the ultrasonic device according to the first embodiment. Figure 12 It is a schematic representation in Figure 11 A schematic diagram of a cross-section obtained by cutting the ultrasonic device along its thickness direction.

[0301] Figure 11 and Figure 12 The ultrasonic device 100 shown includes: a support 10; and a plurality of ultrasonic elements 12 disposed on the support 10. The plurality of ultrasonic elements 12 are ultrasonic elements according to the described embodiment, such as... Figure 11 As shown, they are arranged in two dimensions on the surface of the support 10 and arrayed.

[0302] The ultrasonic element 12 includes: a piezoelectric element 16, which is grounded to the support 10; and an acoustic matching layer 20, which is grounded to the piezoelectric element 16.

[0303] Each ultrasonic element 12 has an acoustic matching layer 20, so that the ultrasonic waves generated from the piezoelectric element 16 propagate into the air while maintaining their intensity and waveform.

[0304] The spacing between the ultrasonic elements 12, i.e., the shortest distance between the centers of each piezoelectric element 16, is not particularly limited, for example, less than 500 μm.

[0305] exist Figure 11 In the ultrasonic device 100, the ultrasonic elements 12 are arranged in a square grid, but the arrangement of the ultrasonic elements 12 is not limited to this, and can be a hexagonal grid or other arrangement shapes.

[0306] In the ultrasonic device 100, there is no particular limitation on the number of ultrasonic elements 12 arranged in an array on the support 10.

[0307] The maximum thickness of the ultrasonic device 100 as a whole, that is, the maximum combined thickness of the support 10 and the ultrasonic element 12, can be 20 mm or less, for example.

[0308] Here, the maximum thickness of the ultrasonic device 100 as a whole can be measured using a micrometer or similar tool.

[0309] The ultrasonic device 100 may have other layers such as a cover layer on the acoustic matching layer 20, or it may not have other layers such as a cover layer.

[0310] Furthermore, in the ultrasonic device 100, the side of the piezoelectric element 16 opposite to the side where the support 10 is disposed is covered by the acoustic matching layer 20. Therefore, even without the covering layer, the piezoelectric element 16 can be protected by the acoustic matching layer 20.

[0311] Furthermore, from the viewpoint of enabling ultrasound to propagate into the air while maintaining its intensity and waveform, the ultrasound device 100 is preferably such that at least a portion of the acoustic matching layer 20 is in contact with the air, and more preferably, the acoustic matching layer 20 does not have any other layers.

[0312] <Second Implementation>

[0313] Figure 13 This is a schematic cross-sectional view of an example of the ultrasonic device according to the second embodiment.

[0314] The ultrasonic device of the second embodiment has an acoustic wave reflecting layer between the support and the ultrasonic element to cover the entire surface of the support.

[0315] Specifically, Figure 13 The ultrasonic device 120 shown includes: a support 10; an acoustic wave reflecting layer 24, which is grounded to the support 10 and contains resin; and a plurality of ultrasonic elements 12 disposed on the acoustic wave reflecting layer 24.

[0316] The support 10 and ultrasonic element 12 in ultrasonic device 120 are the same as those in ultrasonic device 100, so their description is omitted.

[0317] By having an acoustic matching layer 20 within the ultrasonic element 12, the ultrasonic waves generated from the piezoelectric element 16 propagate into the air while maintaining their intensity and waveform.

[0318] Furthermore, since the ultrasonic device 120 has an acoustic wave reflecting layer 24, the ultrasonic waves generated from the piezoelectric element 16 and emitted toward the support 10 are reflected by the acoustic wave reflecting layer 24, making it easy to obtain the intensity of ultrasonic waves propagating in the air.

[0319] The ultrasonic device 120 can replace the acoustic wave reflecting layer 24 or have an acoustic wave attenuation layer on the basis of the acoustic wave reflecting layer 24. When the ultrasonic device 120 has an acoustic wave attenuation layer on the basis of the acoustic wave reflecting layer 24, the acoustic wave attenuation layer can be disposed on the side of the support 10 or on the side of the ultrasonic element 12 relative to the acoustic wave reflecting layer 24.

[0320] Similar to the ultrasonic device 100, the ultrasonic device 120 may have other layers such as a cover layer on the acoustic matching layer 20 of the ultrasonic element 12, or it may not have other layers such as a cover layer. If a cover layer is present, other acoustic matching layers may also be present on the side of the cover layer opposite to the side on which the acoustic matching layer 20 is disposed.

[0321] The details of the acoustic wave reflecting layer 24 in the ultrasonic device 120 are the same as those of the acoustic wave reflecting layer that is disposed in the ultrasonic element as needed, so the description is omitted.

[0322] <Uses>

[0323] The ultrasonic device disclosed herein is used for aerial haptic devices. The aerial haptic device disclosed herein is not particularly limited as long as it includes at least the ultrasonic device disclosed herein.

[0324] The ultrasonic device described in this embodiment radiates ultrasonic waves into the air from each ultrasonic element, maintaining the intensity and waveform of the waves. It can generate high acoustic radiation pressure at the target location and can be miniaturized. Therefore, it is particularly suitable as a component of a small airborne tactile device.

[0325] Examples of small, airborne haptic devices include VR (Virtual Reality) glasses, AR (Augmented Reality) glasses, wearable devices with audio capabilities, and MR (Mixed Reality) glasses.

[0326] [Example]

[0327] The embodiments of this disclosure are described in detail below, but the embodiments of this disclosure are not limited to these examples.

[0328] <Example 1>

[0329] Using simulation software (manufactured by COMSOL, product name: COMSOL Multiphyisics), the sound pressure level of the ultrasonic wave generated by the ultrasonic element of Example 1 was determined under the following simulation conditions. The result was 112.2 dB at a distance of 30 mm from the base of the ultrasonic element.

[0330] -Simulation Conditions-

[0331] Layered structure: piezoelectric element, metal plate, and sound matching layer

[0332] Specific thickness: 1.00 mm

[0333] The shape of the radial surface of the acoustic matching layer: curved and convex.

[0334] Maximum thickness of the acoustic matching layer: 400 μm

[0335] Minimum thickness of the acoustic matching layer: 200 μm

[0336] Maximum diameter of the ultrasonic element: 8000 μm

[0337] Metal plate: (Material: Iron, Maximum thickness: 400 μm, Density: 7.87 g / cm³) 3 (Elastic modulus 200 GPa, Poisson's ratio 0.29)

[0338] Piezoelectric element: Piezoelectric ceramic (material: lead zirconate titanate (PZT-5H)), maximum thickness: 200 μm, acoustic impedance: 30 MRayls, center frequency: 40 kHz, maximum diameter in the surface direction: 6.3 mm)

[0339] Acoustic impedance of the acoustic matching layer: 0.500 MRayls

[0340] The sound velocity in the sound matching layer: 500 m / s

[0341] Density of the acoustic matching layer: 1.0 g / cm³ 3

[0342] The elastic modulus of the acoustic matching layer at 20℃ is 0.0025 GPa.

[0343] <Example 2>

[0344] In the simulation conditions of Example 1, the shape of the radiating surface of the acoustic matching layer was set to curved and concave (maximum thickness: 600 μm, minimum thickness: 200 μm). Otherwise, as in Example 1, the sound pressure level of the ultrasonic wave generated from the ultrasonic element of Example 2 was determined. The result was 109.8 dB at a distance of 30 mm from the base of the ultrasonic element.

[0345] <Example 3>

[0346] In the simulation conditions of Example 1, the shape of the radiating surface of the acoustic matching layer was set to be planar and the thickness was the same (maximum and minimum thickness: 600 μm). Otherwise, the sound pressure level of the ultrasonic wave generated from the ultrasonic element of Example 3 was determined in the same manner as in Example 1. The result was 97.9 dB at a distance of 30 mm from the base of the ultrasonic element.

[0347] <Comparative Example 1>

[0348] In the simulation conditions of Example 1, the layer structure was set to consist only of a piezoelectric element and a metal plate. Otherwise, the sound pressure level of the ultrasonic wave generated by the ultrasonic element of Comparative Example 1 was determined in the same manner as in Example 1. The result was 80.8 dB at a distance of 30 mm from the base of the ultrasonic element.

[0349] <Reference Example 1>

[0350] In the simulation conditions of Example 1, the layer structure was set as a piezoelectric element, a metal plate, and a resonator (material: aluminum, shape: funnel-shaped, maximum height: 1.0 mm). Otherwise, as in Example 1, the sound pressure level of the ultrasonic wave generated by the ultrasonic element of Reference Example 1 was determined. The result was 113.9 dB at a distance of 30 mm from the base of the ultrasonic element.

[0351] All documents, patent applications and technical specifications set forth in this specification are incorporated herein to the same extent as those documents, patent applications and technical specifications which are incorporated herein by reference in their specific and individual instances.

[0352] Explanation of icon numbers

[0353] 10: Support structure

[0354] 12: Ultrasonic components

[0355] 16: Piezoelectric elements

[0356] 16A, 20A, 22A: Surface

[0357] 20, 22: Sound Matching Layer

[0358] 24: Sound wave reflecting layer

[0359] 26: Acoustic attenuation layer

[0360] 28: Metal plate

[0361] 100, 120, 130: Ultrasonic devices

[0362] 200, 200A, 200B, 200C, 200D, 200E, 200F, 210, 220, 230: Ultrasonic components

[0363] 500: Airborne Touch Device

[0364] 502: Printed substrate

[0365] 510: Ultrasonic Components

[0366] 512: Connecting part

[0367] 520: Ultrasonic generating unit

[0368] 522: Metal Plate

[0369] 524: Piezoelectric ceramics

[0370] 526: Resonator

[0371] 528: Frame

[0372] 528A: Sound hole

Claims

1. An ultrasonic wave element, comprising: a piezoelectric element that generates ultrasonic waves of 20 kHz to 100 kHz; and a sound matching layer that is provided on the piezoelectric element and contains a resin, a maximum thickness from a surface opposite to a surface on which the sound matching layer is provided in the piezoelectric element to a surface opposite to a surface on which the piezoelectric element is provided in the sound matching layer is 1.5 mm or less. A difference between the maximum thickness and a minimum thickness of the sound matching layer is 1 μm or more.

2. The ultrasonic wave element according to claim 1, wherein The surface opposite to the surface on which the piezoelectric element is provided in the sound matching layer is a curved surface.

3. The ultrasonic wave element according to claim 1, wherein The surface opposite to the surface on which the piezoelectric element is provided in the sound matching layer is convex.

4. The ultrasonic wave element according to claim 1, wherein The surface opposite to the surface on which the piezoelectric element is provided in the sound matching layer is concave.

5. The ultrasonic wave element according to claim 1, wherein A maximum diameter of the entire ultrasonic wave element is 8 mm or less when the ultrasonic wave element is viewed in plan.

6. The ultrasonic wave element according to claim 1, wherein The sound matching layer is provided in contact with the piezoelectric element.

7. The ultrasonic wave element according to claim 1, wherein A metal plate is further provided between the piezoelectric element and the sound matching layer.

8. The ultrasonic wave element according to claim 1, wherein At least one of a sound wave reflecting layer containing a resin and a sound wave attenuating layer containing a resin is further provided in the piezoelectric element at a side opposite to the side on which the sound matching layer is provided.

9. The ultrasonic wave element according to claim 1, wherein 10. An ultrasonic wave device, comprising: a support body; and the ultrasonic wave element according to any one of claims 1 to 9 is provided on the support body and is two-dimensionally provided in plurality.

11. The ultrasonic wave device according to claim 10, which is used for an air touch device.

12. An air touch device comprising the ultrasonic wave device according to claim 11. ​

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