Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R17/00—Piezoelectric transducers; Electrostrictive transducers

Definitions

• the present disclosure relates to ultrasonic elements, ultrasonic devices, and airborne haptic devices.
• an aerial haptic device collects ultrasonic waves generated with a time delay from a large number of ultrasonic transducers arranged in two dimensions, creates a composite wave, and forms a focus at a targeted location, generating a large acoustic radiation pressure at the focus and stimulating human skin sensations without contact.
• a known example of an aerial haptic device is an array in which ultrasonic elements with an outer diameter of approximately 10 mm and a thickness of approximately 7 mm are arranged two-dimensionally on a printed circuit board and connected with solder, as disclosed in the following non-patent document 1.
• Non-Patent Document 1 Journal of the Acoustical Society of Japan, Vol. 76, No. 5 (2020), pp. 271-278
• an airborne haptic device that uses an array of ultrasonic elements with an outer diameter of about 10 mm and a thickness of about 7 mm, the individual ultrasonic elements are large, which makes the entire device large, making it difficult to use as a component in a small device.
• the purpose of this disclosure is to provide an ultrasonic element that generates high sound pressure and can be applied to a small airborne haptic device, as well as an ultrasonic device and an airborne haptic device that use the same.
• Means for solving the above problems include the following aspects.
• ⁇ 3> The ultrasonic element according to ⁇ 1> or ⁇ 2>, wherein a surface of the acoustic matching layer opposite to a surface on which the piezoelectric element is arranged is a curved surface.
• ⁇ 4> The ultrasonic element according to any one of ⁇ 1> to ⁇ 3>, wherein a surface of the acoustic matching layer opposite to a surface on which the piezoelectric element is arranged is convex.
• ⁇ 5> 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 arranged is concave.
• ⁇ 6> The ultrasonic element according to any one of ⁇ 1> to ⁇ 5>, wherein, when the ultrasonic element is viewed in a plane, a maximum diameter of the entire ultrasonic element is 8 mm or less.
• ⁇ 7> The ultrasonic element according to any one of ⁇ 1> to ⁇ 6>, wherein the acoustic matching layer is provided in contact with the piezoelectric element.
• ⁇ 8> The ultrasonic element according to any one of ⁇ 1> to ⁇ 6>, further comprising a metal plate between the piezoelectric element and the acoustic matching layer.
• ⁇ 10> A support;
• An ultrasonic device comprising: ⁇ 11>
• An air haptic device comprising the ultrasonic device according to ⁇ 10> or ⁇ 11>.
• the present disclosure provides an ultrasonic element that generates high sound pressure and can be applied to a small airborne haptic device, as well as an ultrasonic device and an airborne haptic device that use the same.
• FIG. 1 is an end view that illustrates a schematic view of a portion of a cut surface of an example of an ultrasonic element according to an embodiment.
• FIG. 13 is an end view that illustrates a schematic view of a portion of a cut surface in another example of an ultrasonic element according to an embodiment.
• FIG. 13 is an end view that illustrates a schematic view of a portion of a cut surface in another example of an ultrasonic element according to an embodiment.
• FIG. 13 is an end view that illustrates a schematic view of a portion of a cut surface in another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 11 is an end view that illustrates a schematic cross section of another example of an ultrasonic element according to an embodiment.
• FIG. 1 is a perspective view illustrating an example of an ultrasonic device according to a first embodiment.
• 12 is a schematic diagram showing a cross section of the ultrasonic device shown in FIG.
• FIG. 10 is a schematic diagram illustrating a cross section of an example of an ultrasonic device according to a second embodiment.
• FIG. FIG. 1 is a perspective view showing an example of a conventional mid-air haptic device.
• FIG. 15 is a perspective view of an ultrasonic wave generating device in the air haptic device shown in FIG. 14 .
• 16 is a schematic cross-sectional view of the ultrasonic generating device shown in FIG. 15.
• the term "step” includes not only a step that is independent of other steps, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.
• the numerical ranges indicated using “to” include the numerical values before and after "to” as the minimum and maximum values, respectively.
• the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.
• the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
• each component may contain multiple types of the corresponding substance.
• the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.
• the particles corresponding to each component may include multiple types.
• the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.
• the terms "layer” and “film” include cases where the layer or film is formed over the entire area when the area in which the layer or film is present is observed, as well as cases where the layer or film is formed over only a portion of the area.
• the term “lamination” refers to stacking layers, where two or more layers may be bonded together or two or more layers may be removable.
• a "(meth)acryloyl group” means at least one of an acryloyl group and a methacryloyl group
• a "(meth)acrylic acid” means at least one of acrylic acid and methacrylic acid.
• An ultrasonic element includes 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, and the maximum thickness from the surface of the piezoelectric element opposite to the surface on which the acoustic matching layer is disposed to the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is disposed is 1.5 mm or less.
• the maximum thickness from the surface of the piezoelectric element opposite to the surface on which the acoustic matching layer is disposed to the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is disposed is also referred to as the "specific thickness".
• a conventional air haptic device may be, for example, an array of ultrasonic elements each having an outer diameter of about 10 mm and a thickness of about 7 mm.
• An example of a conventional air haptic device is shown in Fig. 14.
• a plurality of ultrasonic elements 510 arranged two-dimensionally are connected to a printed circuit board 502 by soldering.
• 15 and 16 show a perspective view and a schematic cross-sectional view of the ultrasonic element 510.
• the ultrasonic element 510 is composed of an ultrasonic generating unit 520 that generates ultrasonic waves and a connection unit 512 that connects to a printed circuit board 502.
• the ultrasonic generating unit 520 is provided with a metal plate 522, a piezoelectric ceramic 524 that contacts one surface of the metal plate 522, and a funnel-shaped resonator 526 that partially contacts the other surface of the metal plate 522.
• the metal plate 522, the piezoelectric ceramic 524, and the resonator 526 are covered by a housing 528 having a sound emission hole 528A.
• each ultrasonic element has an outer diameter of about 10 mm and a thickness of about 7 mm and has one ultrasonic generating unit. Therefore, the entire airborne haptic device is large, heavy, and expensive. Specifically, for example, the size of an airborne haptic device in which 100 (10 x 10) ultrasonic elements are connected to a printed circuit board is about 170 mm x 170 mm x 20 mm. Therefore, it is difficult to apply it as a component of small devices such as VR (Virtual Reality) glasses, AR (Augmented Reality) glasses, MR (Mixed Reality) glasses, and hearable devices.
• VR Virtual Reality
• AR Augmented Reality
• MR Mated Reality
• the ultrasonic element of this embodiment has 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 large difference in acoustic impedance at the interface can cause the intensity of the ultrasonic waves radiated into the air to attenuate and the waveform to become distorted, resulting in a decrease in the sound pressure of the ultrasonic waves.
• the acoustic impedance difference between the piezoelectric element and the acoustic matching layer and the acoustic impedance difference between the ultrasonic element and the air are smaller than the acoustic impedance difference between the piezoelectric element and the air. Therefore, even if a funnel-shaped resonator 526 is not provided as in the ultrasonic element 510 shown in Fig. 16, ultrasonic waves can be efficiently emitted into the air.
• the ultrasonic element since the maximum thickness (i.e., the specific thickness) from the surface of the piezoelectric element opposite to the surface on which the acoustic matching layer is arranged to the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is arranged is 1.5 mm or less, the ultrasonic element generates high sound pressure and is applicable to a small air haptic device. Furthermore, by applying the ultrasonic element of this embodiment to a small aerial haptic device, ultrasonic waves are emitted into the air from each ultrasonic element while maintaining their intensity and waveform, making it possible to generate high acoustic radiation pressure at the targeted location.
• the ultrasonic element of the present embodiment may have at least a piezoelectric element and an acoustic matching layer, and may have other layers as necessary.
• the other layers include a metal plate provided between the piezoelectric element and the acoustic matching layer, an acoustic reflection layer, an acoustic attenuation layer, etc. provided on the side of the piezoelectric element opposite to the side where the acoustic matching layer is provided, and the like.
• Examples of layer configurations in the ultrasonic element of this embodiment are shown in Figures 1 to 4, but the ultrasonic element of this embodiment is not limited to these.
• Each of Figures 1 to 4 is a schematic diagram showing a part of a cross section cut in the thickness direction of a piezoelectric element in an example of the ultrasonic element of this embodiment.
• the ultrasonic element 200 shown in Fig. 1 has a piezoelectric element 16 and an acoustic matching layer 20 provided in contact with at least a part of one surface of the piezoelectric element.
• the acoustic matching layer 20 is the outermost layer in contact with air.
• the maximum thickness i.e., the specific thickness
• 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 the air.
• the ultrasonic wave generated from the piezoelectric element 16 can be efficiently radiated into the air. Therefore, even if the specific thickness is within the above range, a high sound pressure can be obtained, and the ultrasonic element 200 can be applied to a small aerial haptic device.
• the ultrasonic element 200 does not have a metal plate between the piezoelectric element 16 and the acoustic matching layer 20, flexibility is imparted to the entire ultrasonic element 200 by using a piezoelectric resin sheet, which will be described later, as the piezoelectric element 16.
• the ultrasonic element 210 shown in Fig. 2 has a piezoelectric element 16, a metal plate 28 provided on one side of the piezoelectric element 16, and an acoustic matching layer 22 provided on the side of the metal plate 28 opposite to the side on which the piezoelectric element 16 is arranged. That is, the ultrasonic element 210 has the metal plate 28 between the piezoelectric element 16 and the acoustic matching layer 22.
• the acoustic matching layer 22 is the outermost layer in contact with air.
• the maximum thickness from the side 16A opposite to the side on which the acoustic matching layer 22 is arranged in the piezoelectric element 16 to the side 22A opposite to the side on which the piezoelectric element 16 is arranged in the acoustic matching layer 22 is 1.5 mm or less.
• 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 the air.
• the ultrasonic element 210 by having the 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 if the specific thickness is within the above range, a high sound pressure can be obtained and the device can be applied to a small aerial haptic device.
• the ultrasonic element 220 further includes an acoustic reflection layer 24 on the side of the piezoelectric element 16 opposite to the side on which the acoustic matching layer 20 is provided.
• an acoustic attenuation layer may be provided instead of or in addition to the acoustic reflection layer 24.
• the order of arrangement is not particularly limited, and the acoustic reflection layer 24 and the acoustic attenuation layer may be provided in this order from the piezoelectric element 16 side, or the acoustic attenuation layer and the acoustic reflection layer 24 may be provided in this order.
• the ultrasonic element 220 may have at least one of the acoustic reflection layer 24 and the acoustic attenuation layer on the side opposite to the side on which the acoustic matching layer 20 is arranged in the piezoelectric element 16.
• the maximum thickness from the surface 16A opposite to the surface on which the acoustic matching layer 20 is arranged in the piezoelectric element 16 to the surface 20A opposite to the surface on which the piezoelectric element 16 is arranged in the acoustic matching layer 20 is 1.5 mm or less.
• the entire child 200 is given flexibility.
• 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 the air, so that the ultrasonic waves generated from the piezoelectric element 16 can be efficiently radiated into the air.
• the ultrasonic waves generated from the piezoelectric element 16 on the side opposite to the side on which the acoustic matching layer 20 is arranged are reflected by the sound wave reflection layer 24 and efficiently radiated to the acoustic matching layer 20 side.
• the ultrasonic waves are efficiently radiated into the air, and even if the specific thickness is within the above-mentioned range, a high sound pressure can be obtained, and it is applicable to a small-sized aerial haptic device.
• the entire ultrasonic element 220 becomes flexible by using a piezoelectric resin sheet described later as the piezoelectric element 16.
• the ultrasonic element 230 shown in Figure 4 has a piezoelectric element 16, a metal plate 28 provided on one side of the piezoelectric element, an acoustic matching layer 22 provided on the side of the metal plate 28 opposite to the side on which the piezoelectric element 16 is arranged, and an acoustic wave reflecting layer 24 provided on the side of the piezoelectric element 16 opposite to the side on which the acoustic matching layer 22 is arranged, with the acoustic matching layer 22 being the outermost layer in contact with air.
• an acoustic attenuation layer may be provided instead of or in addition to the acoustic reflection layer 24.
• the order of arrangement is not particularly limited, and the acoustic reflection layer 24 and the acoustic attenuation layer may be provided in this order from the piezoelectric element 16 side, or the acoustic attenuation layer and the acoustic reflection layer 24 may be provided in this order.
• the maximum thickness from the surface 16A opposite to the surface on which the acoustic matching layer 22 of the piezoelectric element 16 is arranged to the surface 22A opposite to the surface on which the piezoelectric element 16 is arranged is 1.5 mm or less.
• 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 the air, so that the ultrasonic waves generated from the piezoelectric element 16 and amplified by the metal plate 28 can be efficiently radiated into the air.
• the ultrasonic element 230 by having the acoustic wave reflection layer 24 on the surface opposite to the surface on which the acoustic matching layer 22 is arranged in the piezoelectric element 16, a part of the ultrasonic waves generated from the piezoelectric element 16 is reflected by the acoustic wave reflection layer 24, amplified by the metal plate 28, and then efficiently radiated from the acoustic matching layer 22 into the air.
• the ultrasonic element 230 ultrasonic waves are efficiently radiated into the air, and even if the specific thickness is within the above-mentioned range, a high sound pressure can be obtained, and it is applicable to a small air haptic device.
• the specific thickness of the ultrasonic element is 1.5 mm or less, as described above, 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.
• the thickness of the entire ultrasonic element may be, for example, 2 mm or less, preferably 1.5 mm or less, and more preferably 1.3 mm or less.
• the thickness of the entire ultrasonic element may be 0.1 mm or more.
• the thickness of the entire ultrasonic element includes the thickness of the acoustic reflection layer and the acoustic attenuation layer.
• the ultrasonic element further has other members such as a housing in the thickness direction of the ultrasonic element, the thickness of the entire ultrasonic element including the housing, etc. is meant.
• the thickness of the layer or member can be measured using a micrometer or the like.
• the thickness of the layer or member can be measured directly, it is measured using a micrometer.
• the thickness of the layer or member cannot be measured directly, such as when measuring the thickness of one layer or the total thickness of multiple layers, it may be measured by observing the cross section of the layer to be measured using an electron microscope.
• the shape of the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is arranged is not particularly limited, and may be a flat surface, a curved surface, or a combination of a flat surface and a curved surface.
• the shape of the surface of the acoustic matching layer on the piezoelectric element side is not particularly limited, and may be a shape according to the surface shape of the layer (piezoelectric element, metal plate, etc.) that the acoustic matching layer is in contact with.For example, when the acoustic matching layer is provided in contact with the piezoelectric element and the surface of the piezoelectric element on the acoustic matching layer side is a flat surface, the surface of the acoustic matching layer on the piezoelectric element side may be a flat surface.
• the surface of the acoustic matching layer opposite to the surface on which the piezoelectric elements are arranged that is, the surface from which ultrasonic waves generated by the piezoelectric elements are radiated, will also be referred to as the "radiation surface.”
• the radiation surface in the ultrasonic element of this embodiment is preferably shaped such that the difference between the maximum thickness and the minimum thickness in the acoustic matching layer is 1 ⁇ m or more.
• the difference between the maximum thickness and the minimum thickness in the acoustic matching layer is more preferably 50 ⁇ m or more, even more preferably 100 ⁇ m or more, particularly preferably 200 ⁇ m or more, and most preferably 400 ⁇ m or more.
• the radiation surface in the ultrasonic element of this embodiment is preferably shaped such that the difference between the maximum thickness and the minimum thickness in the acoustic matching layer is 1 mm or less.
• the difference between the maximum thickness and the minimum thickness in the acoustic matching layer is more preferably 800 ⁇ m or less, even more preferably 600 ⁇ m or less, and particularly preferably 500 ⁇ m or less.
• the difference between the maximum thickness and the minimum thickness of the acoustic matching layer is preferably from 1 ⁇ m to 1 mm, more preferably from 50 ⁇ m to 800 ⁇ m, further preferably from 100 ⁇ m to 600 ⁇ m, and particularly preferably from 200 ⁇ m to 500 ⁇ m.
• Examples of the shape of the radiation surface of an acoustic matching layer having a difference between the maximum thickness and the minimum thickness within the above range include a convex shape in which the central part of the radiation surface is higher than the peripheral part, a concave shape in which the central part of the radiation surface is lower than the peripheral part, and an uneven shape in which multiple convex parts and multiple concave parts are arranged alternately.
• each of the ultrasonic elements shown in Figures 5 to 10 has a piezoelectric element 16 and an acoustic matching layer 20, but is not limited to this and may have other layers.
• Each of Figures 5 to 10 shows a schematic cross section cut in the thickness direction of the piezoelectric element in an example of the ultrasonic element of this embodiment.
• the radiation surface of the acoustic matching layer 20, i.e., the surface 20A opposite to the surface on which the piezoelectric element 16 is arranged in the acoustic matching layer 20, is curved and convex, and the central part of the radiation surface is higher than the peripheral part. Therefore, in the surface direction of the acoustic matching layer 20 (i.e., the surface direction perpendicular to the thickness direction), the thickness of the acoustic matching layer 20 at the central part is thicker than the thickness of the acoustic matching layer 20 at the peripheral part.
• the radiation surface of the acoustic matching layer 20 is flat and the thickness of the acoustic matching layer 20 is uniform.
• the radiation surface of the acoustic matching layer 20 is conical. Therefore, in the surface direction of the acoustic matching layer 20, the thickness of the acoustic matching layer 20 in the center part is thicker than the thickness of the acoustic matching layer 20 in the peripheral part, and a higher sound pressure can be obtained compared to the case where the thickness of the acoustic matching layer 20 is uniform, as in the ultrasonic element 200A shown in Fig. 5.
• the radiation surface of the acoustic matching layer 20 is curved and concave, and the central part of the radiation surface is lower than the peripheral part. Therefore, in the surface direction of the acoustic matching layer 20, the thickness of the acoustic matching layer 20 at the central part is thinner than the thickness of the acoustic matching layer 20 at the peripheral part. As a result, a higher sound pressure can be obtained compared to when the radiation surface of the acoustic matching layer 20 is flat and the thickness of the acoustic matching layer 20 is uniform.
• the radiation surface of the acoustic matching layer 20 is in an inverted cone shape.
• the thickness of the acoustic matching layer 20 in the center part is thinner than the thickness of the acoustic matching layer 20 in the peripheral part, and a higher sound pressure can be obtained compared to the case where the thickness of the acoustic matching layer 20 is uniform, as in the ultrasonic element 200C shown in Fig. 7.
• the radiation surface of the acoustic matching layer 20 is composed of a plurality of curved surfaces and has an uneven shape, with a plurality of convex portions and a plurality of concave portions arranged alternately. Therefore, the thickness of the acoustic matching layer 20 at the convex portions is thicker than the thickness of the acoustic matching layer 20 at the concave portions. As a result, a higher sound pressure can be obtained compared to a case where the radiation surface of the acoustic matching layer 20 is flat and the thickness of the acoustic matching layer 20 is uniform.
• the radiation surface of the acoustic matching layer 20 is formed of a plurality of quadrangular pyramids and has an uneven shape. Therefore, the thickness of the acoustic matching layer 20 at the convex portions is thicker than the thickness of the acoustic matching layer 20 at the concave portions, and a higher sound pressure can be obtained compared to the case where the thickness of the acoustic matching layer 20 is uniform, as in the ultrasonic element 200E shown in FIG.
• the maximum diameter of the entire ultrasonic element is preferably 8 mm or less.
• the spatial resolution of the acoustic radiation pressure can be increased. Specifically, for example, by arranging ultrasonic elements whose entire maximum diameter is within the above range in two dimensions, the interval between the ultrasonic generating units can be reduced, and it is considered that the spatial resolution of the acoustic radiation pressure can be increased.
• the maximum diameter of the entire ultrasonic element refers to the largest diameter of the entire ultrasonic element in the surface direction of the piezoelectric element.
• the maximum diameter means the long diameter
• the maximum diameter means the length of the diagonal.
• the piezoelectric element is not particularly limited as long as it is an element that generates ultrasonic waves of 20 kHz to 100 kHz, and among them, an element that generates ultrasonic waves of 20 kHz to 80 kHz is preferable, and an element that generates ultrasonic waves of 40 kHz to 70 kHz is more preferable.
• Examples of the piezoelectric element include piezoelectric ceramics, piezoelectric resin sheets, and piezoelectric single crystals.
• the piezoelectric ceramics may be a ceramic piezoelectric body provided with electrodes, and examples of the ceramic piezoelectric body include lead zirconate titanate (PZT), barium titanate, and lead titanate.
• the maximum thickness of the piezoelectric ceramic is, for example, 200 ⁇ m or less.
• the shape of the piezoelectric ceramic in the surface direction is not particularly limited, and examples of the shape include a circle, a polygon, etc.
• the maximum diameter of the piezoelectric ceramic in the surface direction is, for example, 6.5 mm or less.
• the acoustic impedance of the piezoelectric ceramic is, for example, 30 MRayls.
• the acoustic impedance of the piezoelectric ceramic is not limited to 30 MRayls, but may be 25 MRayls to 50 MRayls.
• the piezoelectric resin sheet may be a sheet-shaped piezoelectric body made of resin with electrodes provided thereon.
• materials for the resin piezoelectric body include polyvinylidene fluoride (PVDF) and polylactic acid (PLA).
• PVDF polyvinylidene fluoride
• PLA polylactic acid
• the acoustic impedance of the piezoelectric resin sheet is, for example, 4.5 MRayls.
• the acoustic impedance of the piezoelectric resin sheet is not limited to 4.5 MRayls, and may be 1 MRayls to 25 MRayls.
• the acoustic matching layer is a layer that contains at least a resin and propagates ultrasonic waves generated from a piezoelectric element into the air while maintaining its strength and waveform.
• the acoustic impedance value of the acoustic matching layer is set to a value between the acoustic impedance of the layer that the acoustic matching layer contacts and the acoustic impedance of air.
• the acoustic matching layer 20 is provided in contact with the piezoelectric element 16 as in the ultrasonic element 200 shown in FIG.
• 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.
• the acoustic impedance value 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.
• the acoustic matching layer may have a single layer structure or a multi-layer structure.
• An example of an acoustic matching layer with a multi-layer structure is a layer in which an acoustic matching layer having an acoustic impedance value close to the acoustic impedance of the layer it contacts and an acoustic matching layer having an acoustic impedance value close to the acoustic impedance of air are stacked together.
• the ultrasonic waves generated from the piezoelectric element are more likely to propagate through the air while maintaining their intensity and waveform.
• the acoustic matching layer has a multi-layer structure, it may have a two-layer structure or a stacked structure of three or more layers.
• the acoustic impedance value of the entire acoustic matching layer is preferably a value between the acoustic impedance of air (e.g., 0.0004 MRayls) and the acoustic impedance of the layer with which the acoustic matching layer is in contact, and is preferably set according to the acoustic impedance value of the layer with which the acoustic matching layer is in contact.
• the acoustic impedance of the entire acoustic matching layer is preferably 0.01 MRayls to 1 MRayls.
• the acoustic impedance of the entire acoustic matching layer is preferably 0.001 MRayls to 1 MRayls. Furthermore, when the acoustic matching layer is provided in contact with a metal plate, the acoustic impedance of the entire 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.
• the value of acoustic impedance in the entire acoustic matching layer means the value of the entire multi-layer structure when the acoustic matching layer has a multi-layer structure.
• the acoustic matching layer has a multi-layer structure, it is sufficient that the acoustic impedance of the entire multi-layer structure is within the above range, and the acoustic impedance of each layer constituting the multi-layer structure may be within the above range, or the acoustic impedance of at least one layer may be outside the above range.
• the acoustic impedance of the entire multi-layer structure may be within the above range, and the acoustic impedance of at least one layer constituting the multi-layer structure may be outside the above range.
• the acoustic matching layer having a multi-layer structure may be, for example, configured to include a first acoustic matching layer provided on the layer side with which the acoustic matching layer is in contact and having an acoustic impedance value of 3 MRayls or more, and a second acoustic matching layer provided on the air side of the first acoustic matching layer and having an acoustic impedance value of less than 3 MRayls.
• the acoustic impedance of the acoustic matching layer can be calculated from the sound velocity and density of the acoustic matching layer, which will be described later, according to the following formula.
• Acoustic impedance (speed of sound x density)
• the density can be determined, for example, by preparing a sample of 10 mm square and measuring the average thickness and mass of the sample.
• Methods for controlling the value of the acoustic impedance of the acoustic matching layer include, for example, selecting the type of resin contained in the acoustic matching layer, adjusting the content of resin in the entire acoustic matching layer, incorporating a filler in the acoustic matching layer and adjusting the type of filler and the content of the filler in the entire acoustic matching layer, incorporating air bubbles in the acoustic matching layer, and the like.
• the method for controlling the acoustic impedance value of the acoustic matching layer is selected depending on the desired acoustic impedance value.
• acoustic matching layer A an acoustic matching layer having an acoustic impedance of 3 MRayls or more
• acoustic matching layer B an acoustic matching layer having an acoustic impedance of less than 3 MRayls
• Acoustic matching layer A and acoustic matching layer B will each be described.
• An example of the acoustic matching layer A having an acoustic impedance of 3 MRayls or more is a cured film of a resin composition containing a resin and a filler having a specific gravity of 2.0 or more.
• Specific examples of the resin include epoxy resin and acrylic resin among the specific examples of the resin described later.
• Examples of the filler having a specific gravity of 2.0 or more include insulating fillers such as aluminum oxide and bismuth oxide among the specific examples of the filler described later.
• the sound velocity in the acoustic matching layer A is not particularly limited, and may be, for example, 1500 m/s to 5000 m/s, and preferably 1900 m/s to 4500 m/s.
• the sound velocity in the acoustic matching layer is determined by using an ultrasonic sound velocimeter (ZX-5, manufactured by Minnesota Japan) and inputting the thickness of the acoustic matching layer actually measured with a micrometer.
• the density of the acoustic matching layer A is not particularly limited, and may be, for example, 1.0 g/cm 3 to 6.0 g/cm 3 , and preferably 1.2 g/cm 3 to 5.5 g/cm 3.
• the density of the acoustic matching layer can be determined, for example, by preparing a sample of 10 mm square and measuring the average thickness and mass of the sample.
• the elastic modulus of the acoustic 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.
• the elastic modulus of the acoustic matching layer at 20° C. is determined by measuring in tension mode using a viscoelasticity measuring device DMA7100 (Hitachi High-Technologies Corporation) at a temperature rise rate of 5° C./min and a frequency of 10 Hz.
• the volume resistivity of the acoustic matching layer A is, for example, in the range of 1.0 ⁇ 10 ⁇ cm or more, may be in the range of 1.0 ⁇ 10 ⁇ cm or more, or may be in the range of 1.0 ⁇ 10 ⁇ cm or more.
• the upper limit of the volume resistivity of the acoustic matching layer A is not particularly limited, and may be, for example, 1.0 ⁇ 10 ⁇ cm.
• the volume resistivity of the acoustic matching layer can be calculated in accordance with JIS C 2139-3-1:2018 by measuring the insulation resistance value with an insulation resistance meter (for example, 8340A manufactured by Advantest) and calculating the volume resistivity from the area and thickness of the electrode contact surface.
• Examples of the acoustic matching layer B having an acoustic impedance of less than 3 MRayls include a cured film of a resin composition containing a resin and a filler having a specific gravity of less than 2.0, a cured film of a resin composition containing a resin and a foaming agent, a cured film of a resin composition containing a resin, a filler having a specific gravity of less than 2.0, and a foaming agent, etc.
• Specific examples of the resin include epoxy resin, acrylic resin, etc., among the specific examples of resins described later.
• the sound velocity in the acoustic matching layer B is not particularly limited, and may be, for example, 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.
• the density of the acoustic matching layer B is not particularly limited, and may be, for example, 0.1 g/cm 3 to 2.0 g/cm 3 , preferably 0.1 g/cm 3 to 1.3 g/cm 3 , and more preferably 0.1 g/cm 3 to 1.0 g/cm 3 .
• the elastic modulus of the acoustic matching layer B at 20° C.
• the elastic modulus of the acoustic matching layer B at 20° C. is preferably 0.001 GPa or more, from the viewpoint of controlling the sound velocity within the above range.
• the volume resistivity of the acoustic matching layer B is, for example, in the range of 1.0 ⁇ 10 ⁇ cm or more, may be in the range of 1.0 ⁇ 10 ⁇ cm or more, or may be in the range of 1.0 ⁇ 10 ⁇ cm or more.
• the upper limit of the volume resistivity of the acoustic matching layer B is not particularly limited, and may be, for example, 1.0 ⁇ 10 ⁇ cm.
• the acoustic matching layer may be provided on at least a part of a layer (e.g., a piezoelectric element or a metal plate) that the acoustic matching layer contacts.
• the acoustic matching layer is provided on preferably 50% or more, more preferably 80% or more of the surface area of the layer that the acoustic matching layer contacts, and further preferably covering the entire layer that the acoustic matching layer contacts.
• the radiation surface it is preferable that at least a portion of the surface of the acoustic matching layer opposite to the surface on which the piezoelectric element is arranged (i.e., the radiation surface) is in contact with air, and it is more preferable that 50% or more of the area of the radiation surface is in contact with air, and even more preferable that 80% or more of the area of the radiation surface is in contact with air.
• the maximum thickness of the acoustic matching layer is, for example, 1 mm or less, and from the viewpoint of miniaturization of the ultrasonic element, 900 ⁇ m or less is preferable, and 800 ⁇ m or less is more preferable. From the viewpoint of maintaining the strength of the ultrasonic waves, the maximum thickness of the acoustic matching layer is preferably 200 ⁇ m or more, more preferably 400 ⁇ m or more, and even more preferably 500 ⁇ m or more. The method for measuring the thickness is as described above.
• the acoustic matching layer contains at least a resin.
• the content of the resin in the entire acoustic matching layer is adjusted according to the type of resin and the desired acoustic impedance value.
• the resin content may be 2% by mass or more, 3% by mass or more, or 4% by mass or more with respect to the entire acoustic matching layer from the viewpoint of obtaining flexibility of the acoustic matching layer, and may be 9% by mass or more, 10% by mass or more, or 13% by mass or more with respect to the viewpoint of obtaining flexibility of the film.
• the resin content may 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 with respect to the entire acoustic matching layer.
• the type of resin may be a resin contained in a resin composition described below or a cured product thereof.
• the acoustic matching layer may contain a filler, if necessary.
• the content of the filler in the entire acoustic matching layer is adjusted according to the type of filler and the desired acoustic impedance value. For example, when the acoustic matching layer is the acoustic matching layer A and an insulating filler described later is used as the filler, the content of the insulating filler may be 90 volume % or less, 80 volume % or less, 70 volume % or less, less than 50 volume %, 45 volume % or less, 35 volume % or less, 25 volume % or less, or 15 volume % or less, based on the entire acoustic matching layer A.
• the content of the insulating filler may be 1 volume % or more, 5 volume % or more, 15 volume % or more, 25 volume % or more, 35 volume % or more, 50 volume % or more, 60 volume % or more, or 70 volume % or more, based on the entire acoustic matching layer A.
• the type of insulating filler there can be mentioned the insulating filler contained in the resin composition described below.
• the content of the hollow particles may be 90 volume % or less, 80 volume % or less, 70 volume % or less, less than 50 volume %, 45 volume % or less, 35 volume % or less, 25 volume % or less, or 15 volume % or less, based on the entire acoustic matching layer B.
• the content of the hollow particles may be 1 volume % or more, 5 volume % or more, 15 volume % or more, 25 volume % or more, 35 volume % or more, 50 volume % or more, 60 volume % or more, or 70 volume % or more, based on the entire acoustic matching layer B.
• the type of hollow particles hollow particles contained in a resin composition described below can be mentioned.
• the acoustic matching layer may contain other components in addition to the resin and filler as necessary.
• the types and contents of the other components are the same as the types of other components contained in the resin composition described below and their contents relative to the total solid content of the resin composition.
• the acoustic matching layer may contain bubbles, if necessary.
• An example of an acoustic matching layer containing bubbles is a cured film of a resin composition containing a foaming agent, which will be described later.
• the content of the bubbles may be 90 volume % or less, 80 volume % or less, 70 volume % or less, less than 50 volume %, 45 volume % or less, 35 volume % or less, 25 volume % or less, or 15 volume % or less, based on the entire acoustic matching layer B.
• the content of the bubbles may be 1 volume % or more, 5 volume % or more, 15 volume % or more, 25 volume % or more, 35 volume % or more, 50 volume % or more, 60 volume % or more, or 70 volume % or more, based on the entire acoustic matching layer B.
• the air bubble content is measured according to the water immersion method, and is determined using the relationship between the apparent density ( ⁇ ) and true density ( ⁇ 0) of the measurement sample.
• Formula: Porosity (%) ⁇ 1-( ⁇ / ⁇ 0) ⁇ 100
• the apparent density ( ⁇ ) is determined by measuring the weight in air and in water using the underwater gravimetric method (underwater immersion method), determining the apparent volume from Archimedes' principle, and dividing the weight in air by the apparent volume.
• the true density ( ⁇ 0) is determined by thoroughly pulverizing the sample to eliminate open pores, and using a Gay-Lussac-type pycnometer method. Specifically, the voids in the sample are completely degassed and replaced with liquid, and the relationship between the weight and volume is calculated to determine the true density.
• the acoustic matching layer may be, for example, a cured film of a resin composition containing a resin.
• the cured film may be a film obtained by curing a dried film of a resin composition, or may be a film obtained by curing a resin composition without going through the process of drying a film.
• the cured film may be a film whose hardness has been increased by having a chemical structure different from that before curing due to a chemical reaction, or a film whose hardness has been increased by solidifying a molten resin composition whose chemical structure remains the same as before curing.
• an acoustic matching layer that is a cured film of a resin composition will be described below.
• the resin composition contains at least a resin, and may contain a filler, a solvent, other components, and the like, as necessary.
• the type of resin is not particularly limited, and may be a thermosetting resin, a thermoplastic resin, or a combination thereof.
• the resin may be in the form of a monomer having a functional group capable of undergoing a polymerization reaction upon heating, or may be in the form of an already polymerized polymer.
• the resin is preferably a resin having a polar group.
• a polar group refers to an atomic group having polarity due to the bond between atoms with different electronegativity.
• Examples of polar groups include groups having heteroatoms other than carbon atoms and hydrogen atoms, and more specifically, groups containing at least one heteroatom selected from the group consisting of nitrogen atoms, oxygen atoms, sulfur atoms, boron atoms, phosphorus atoms, and silicon atoms.
• the polar group is preferably a group containing at least one heteroatom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms. More specifically, examples of polar groups include amino groups, amide groups, imide groups, cyano groups, nitro groups, epoxy groups, hydroxy groups, carboxy groups, carbonyl groups, thiol groups, sulfo groups, thionyl groups, ester bonds, ether bonds, sulfide bonds, urethane bonds, urea bonds, and the like, and at least one selected from the group consisting of amide groups, imide groups, epoxy groups, hydroxy groups, amino groups, carboxy groups, carbonyl groups, ether bonds, and urea bonds is preferred.
• the polar group may be present in the main chain or side chain of the resin.
• resins having polar groups include vinyl polymerization resins, acrylic resins, polyamide resins, polyimide resins, polyamideimide resins, polyurethane resins, polyester resins, polyether resins, epoxy resins, oxazine resins, bismaleimide resins, phenolic resins, unsaturated polyester resins, silicone resins, and phenoxy resins.
• the resin having a polar group includes at least one selected from the group consisting of polyamideimide resins, epoxy resins, acrylic resins, polyester resins, and polyether resins. Resins having polar groups may be used alone or in combination of two or more types.
• the resin composition may contain a resin having no polar group in addition to the resin having a polar group.
• the resin having no polar group include SBR resin (styrene-butadiene-random copolymer resin), SBS resin (styrene-butadiene block copolymer resin), SIS (styrene-isoprene block copolymer), SEBS (styrene-ethylene-butylene block copolymer resin), SEPS (styrene-ethylene-propylene block copolymer resin), polyethylene, polypropylene, polybutadiene, polyisoprene, polystyrene, and cycloolefin polymer, as well as hydrogenated versions of these.
• SBR resin styrene-butadiene-random copolymer resin
• SBS resin styrene-butadiene block copolymer resin
• SIS styrene-isoprene block copo
• the content of the resin having a polar group relative to the total amount of the 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 the resin having a polar group relative to the total amount of the resin may be 100% by mass or may be 95% by mass or less.
• the resin preferably contains a thermosetting resin, and preferably contains a thermosetting resin having a polar group.
• the thermosetting resin may have an aromatic ring, or may have a condensed ring in which two or more aromatic rings are condensed. Examples of the condensed ring include a naphthalene ring, an anthracene ring, and a phenanthrene ring.
• thermosetting resins having polar groups examples include epoxy resins, phenolic resins, melamine resins, urea resins, thermosetting polyimide resins, acrylic resins, polyurethane resins, etc.
• epoxy resins, phenolic resins, and acrylic resins are preferred as thermosetting resins having polar groups, with epoxy resins being more preferred.
• the epoxy resin is not particularly limited as long as it has two or more epoxy groups in one molecule.
• Specific examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, hydrogenated bisphenol A type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, biphenol type epoxy resins, biphenyl novolac type epoxy resins, and cyclic aliphatic epoxy resins.
• epoxy resins include the above-mentioned epoxy resins having a substituent such as an ether group or an alicyclic epoxy group.
• an epoxy resin having a heteroatom other than an oxygen atom derived from the epoxy group or glycidyloxy group of the epoxy resin is preferable.
• the epoxy resin may be, for example, an epoxy resin containing a nitrogen atom and a hydrogen atom bonded to the nitrogen atom.
• the epoxy resin may have a heterocyclic structure containing a nitrogen atom and a hydrogen atom bonded to the nitrogen atom.
• An example of such a heterocyclic structure is a glycoluril structure.
• the molecular weight of the epoxy resin is not particularly limited, and may be, for example, 100 to 1500, or may be 150 to 1000 or 200 to 500.
• the content of the epoxy resin relative to the total amount of resin may be 80% by mass or more, 90% by mass or more, or even 100% by mass.
• the content of the epoxy resin relative to the total amount of 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.
• the acrylic resin is not particularly limited as long as it has two or more (meth)acryloyl groups in the molecule.
• Specific examples of the acrylic resin include polyfunctional (meth)acrylic acid esters such as 1,9-nonanediol diacrylate, ethylene glycol diacrylate, and propylene glycol diacrylate.
• the resin composition may further contain an acrylic compound other than the acrylic resin.
• acrylic compounds other than the acrylic resin include acrylic nitrile group-containing monomers such as acrylonitrile and methacrylonitrile; monofunctional (meth)acrylic acid esters such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, 3-ethoxypropyl acrylate, oxycarbonyl tetramethacrylate, 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, isodecyl acryl
• the total content of the acrylic resin and acrylic compounds other than the acrylic resin relative to the total amount of the resin may be 5% by mass to 100% by mass, or 10% by mass to 50% by mass.
• the resin composition may further contain a curing agent.
• a curing agent such as an acid anhydride curing agent, an amine curing agent, a phenolic curing agent, a polyaddition type curing agent such as a mercaptan curing agent, or a latent curing agent such as imidazole may be used in combination.
• an acrylic resin is used as the thermosetting resin
• a curing agent such as a peroxide or an azo compound may be used in combination.
• the polar group contained in the resin having a polar group may be a polar group formed as a result of the polymerization reaction.
• the resin preferably contains a thermoplastic resin, and more preferably contains a thermoplastic resin having a polar group.
• the thermoplastic resin include phenoxy resin, polyamideimide resin, polyethylene resin, polypropylene resin, SBR resin, etc.
• the thermoplastic resin is preferably phenoxy resin, polyamideimide resin, polyethylene resin, or SBR resin, and more preferably polyamideimide resin, phenoxy resin, or SBR resin.
• the phenoxy resin is not particularly limited as long as it has a phenoxy structure in its molecular structure.
• the "phenoxy structure” refers to a structure in which an oxygen atom is bonded to a benzene ring, and includes not only the phenoxy group (C 6 H 5 -O-), but also those in which a part of the phenoxy group has been substituted, and those in which a part of the phenoxy group has been reacted by hydrogenation or the like.
• the phenoxy resin examples include phenoxy resins having a bisphenol skeleton, phenoxy resins having a novolac skeleton, phenoxy resins having a naphthalene skeleton, phenoxy resins having a biphenyl skeleton, etc.
• the phenoxy resin is preferably a phenoxy resin having a bisphenol skeleton from the viewpoint of versatility.
• phenoxy resins having a bisphenol skeleton examples include bisphenol A type phenoxy resins, bisphenol F type phenoxy resins, copolymer phenoxy resins of bisphenol A and bisphenol F, bisphenol S type phenoxy resins, brominated bisphenol A type phenoxy resins, and hydrogenated bisphenol A type phenoxy resins. These phenoxy resins may be used alone or in combination of two or more.
• Polyamide-imide resins are resins having amide bonds and imide bonds in the main chain.
• Preferred examples of polyamide-imide resins include polyamide-imide resins having at least one structure selected from the group consisting of polyalkylene oxide structures and polysiloxane structures. These polyamide-imide resins are preferred from the viewpoint of mitigating stress caused by deformation of the polyamide-imide resin.
• These polyamide-imide resins may be polyamide-imide resins synthesized using, for example, polyalkylene oxide-modified diamines and polysiloxane-modified diamines, respectively.
• an alkylene oxide structure having 1 to 10 carbon atoms is preferable, an alkylene oxide structure having 1 to 8 carbon atoms is more preferable, and an alkylene oxide structure having 1 to 4 carbon atoms is even more preferable.
• the polyalkylene oxide structure is preferably a polypropylene oxide structure.
• the alkylene group in the alkylene oxide structure may be linear or branched.
• the unit structure in the polyalkylene oxide structure may be one type or two or more types.
• polysiloxane structure examples include polysiloxane structures in which some or all of the silicon atoms in the polysiloxane structure are substituted with an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 18 carbon atoms.
• a preferred embodiment of the polyamideimide resin is a polyamideimide resin having a structural unit derived from a diimide carboxylic acid or a derivative thereof and a structural unit derived from an aromatic diisocyanate or an aromatic diamine.
• the SBR resin is not particularly limited as long as it is a copolymer of styrene and butadiene. There is also no limitation on the ratio of the units derived from styrene and the units derived from butadiene that constitute the SBR resin, and there is also no particular limitation on the molecular weight of the SBR resin.
• the SBR resin may be one in which the unsaturated double bonds of the units derived from butadiene are left intact in order to react with a thermosetting resin, or the unsaturated double bonds may be hydrogenated to increase durability.
• the thermoplastic resin may be combined with a thermosetting resin to improve the strength of the film after film formation and to suppress shrinkage during curing.
• the total content of the resin in the resin composition may be 2% by mass or more, 3% by mass or more, or 4% by mass or more, and from the viewpoint of obtaining flexibility of the film, may be 9% by mass or more, 10% by mass or more, or 13% by mass or more.
• the total content of the resin in the resin composition may 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, based on the solid content of the resin composition.
• examples of the insulating filler used in producing the acoustic matching layer A include oxides such as aluminum oxide, zirconium oxide, titanium oxide, bismuth oxide, silicon dioxide, cerium oxide, tantalum oxide, tungsten oxide, and sintered uranium oxide; barium titanate, tungsten carbide, tungsten, zirconium, etc.
• the insulating fillers may be used alone or in combination of two or more kinds.
• the insulating filler preferably contains at least one selected from the group consisting of aluminum oxide, zirconium oxide, titanium oxide, bismuth oxide, silicon dioxide, tantalum oxide, and tungsten oxide. Furthermore, from the viewpoints of high hardness and uniform particle shape, the insulating filler preferably contains at least one selected from the group consisting of aluminum oxide, zirconium oxide, titanium oxide, barium titanate, and bismuth oxide, and more preferably contains at least one selected from the group consisting of aluminum oxide, zirconium oxide, and bismuth oxide.
• the volume resistivity of the insulating filler at 25° C. is preferably 1 ⁇ 10 6 ⁇ cm or more, more preferably 1 ⁇ 10 8 ⁇ cm or more, and even more preferably 1 ⁇ 10 10 ⁇ cm or more.
• the volume average particle diameter D50 of the insulating filler is preferably 5.0 ⁇ m or less, more preferably 3.0 ⁇ m or less, and even more preferably 2.0 ⁇ m or less.
• the lower limit of the volume average particle diameter D50 of the insulating filler is not particularly limited, and may be 0.001 ⁇ m or more.
• the volume average particle diameter D50 of the insulating filler is preferably 0.001 ⁇ m to 5.0 ⁇ m, more preferably 0.001 ⁇ m to 3.0 ⁇ m, and even more preferably 0.001 ⁇ m to 2.0 ⁇ m.
• the volume average particle diameter D50 of the insulating filler contained in the resin composition and the volume average particle diameter D50 of the insulating filler contained in the film formed using the resin composition are determined as follows. Specifically, the particle size at which the cumulative amount from the small diameter side reaches 50% in a volume-based particle size distribution curve is defined as the volume average particle size D50.
• the particle size distribution curve of the insulating filler contained in the resin composition can be obtained by observing a cross section of a cured product of the resin composition with a scanning electron microscope (SEM) and determining the circle equivalent diameter of 20 insulating filler particles.
• the volume average particle size D50 of the insulating filler alone for example, an insulating filler that is a raw material of a resin composition
• it may be determined by a laser diffraction scattering type particle size distribution measurement method using a particle size distribution measurement device that utilizes a laser light scattering method (for example, "SALD-3000" manufactured by Shimadzu Corporation).
• the shape of the insulating filler is not particularly limited, and may be spherical, powdery, needle-like, fibrous, plate-like, angular, polyhedral, scaly, etc. From the viewpoint of thinning the resin composition layer, the shape of the insulating filler is preferably polyhedral or spherical, and more preferably spherical. 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 a cross section of a cured product of the resin composition with a scanning electron microscope (SEM) and calculating the average aspect ratio of 20 insulating fillers.
• SEM scanning electron microscope
• the specific gravity of the insulating filler is not particularly limited, and may be appropriately adjusted according to the application of the resin composition.
• the specific gravity of the insulating filler may be 2.0 or more, 3.0 or more, 5.0 or more, 6.0 or more, or 7.0 or more.
• the upper limit of the specific gravity of the insulating filler is not particularly limited.
• the specific gravity of the insulating filler may be, for example, 10.0 or less.
• the specific gravity of a filler represents the ratio of the true specific gravity of a measurement sample to the true specific gravity of water, which is measured in accordance with JIS K 0061:2001 and JIS Z 8807:2012 as the ratio of the mass of a measurement sample to the mass of the same volume of pure water under atmospheric pressure.
• the specific gravity of the filler refers to the value for the mixture of the fillers contained in the resin composition.
• the content of the insulating filler in the total solid content of the resin composition may be 90 vol. % or less, 85 vol. % or less, 80 vol. % or less, less than 50 vol. %, 45 vol. % or less, 35 vol. % or less, 25 vol. % or less, or 15 vol. % or less.
• the content of the insulating filler in the total solid content of the resin composition may be 1 vol. % or more, 5 vol. % or more, 15 vol. % or more, 25 vol. % or more, 35 vol. % or more, 50 vol. % or more, 55 vol. % or more, or 60 vol. % or more.
• the content of the insulating filler in the total solid content of the resin composition may be 99 mass% or less, and from the viewpoint of achieving both flexibility and wide range of acoustic impedance control, it may be 87 mass% or less, 70 mass% or less, 65 mass% or less, less than 65 mass%, 60 mass% or less, 50 mass% or less, or 40 mass% or less.
• the content of the insulating filler in the total solid content of the resin composition may be 1 mass% or more, 5 mass% or more, 20 mass% or more, 70 mass% or more, 80 mass% or more, 88 mass% or more, 90 mass% or more, or 92 mass% or more.
• examples of the hollow particles used in the production of the acoustic matching layer B include hollow inorganic particles and hollow organic particles.
• examples of hollow inorganic particles include hollow oxide particles such as hollow silica particles, hollow titania particles, hollow zirconia particles, and hollow tin oxide particles; hollow silicon particles; and hollow carbon particles.
• examples of the hollow organic particles include hollow polymer particles.
• hollow organic particles include hollow particles of vinyl polymerization resins, acrylic resins, polyamide resins, polyimide resins, polyamideimide 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 copolymer resins), SBS resins (styrene-butadiene block copolymer resins), SIS (styrene-isoprene block copolymers), SEBS (styrene-ethylene-butylene block copolymer resins), SEPS (styrene-ethylene-propylene block copolymer resins), polyethylene, polypropylene, polybutadiene, polyisoprene, polystyrene, and cycloolefin polymers, as well as hydrogenated
• the volume average particle diameter D50 of the hollow particles is preferably 100.0 ⁇ m or less, more preferably 50.0 ⁇ m or less, and even more preferably 30.0 ⁇ m or less.
• the lower limit of the volume average particle diameter D50 of the hollow particles is not particularly limited, and may be 1 ⁇ m or more. From the viewpoint above, the volume average particle diameter D50 of the hollow particles is preferably 1 ⁇ m to 100.0 ⁇ m, more preferably 1 ⁇ m to 50.0 ⁇ m, and even more preferably 1 ⁇ m to 30.0 ⁇ m.
• the volume average particle diameter D50 of the hollow particles contained in the resin composition and the volume average particle diameter D50 of the hollow particles contained in a film formed using the resin composition are determined in the same manner as the volume average particle diameter D50 of the insulating filler described above.
• the shape of the hollow particles is not particularly limited, and examples thereof include spherical shapes.
• the specific gravity of the hollow particles is not particularly limited and may be adjusted appropriately depending on the application of the resin composition.
• the specific gravity of the hollow particles may be less than 2.0, may be 0.1 or less, or may be 0.01 or less.
• foaming agent examples include organic foaming agents and inorganic foaming agents.
• examples of the organic foaming agent include azodicarbonamide (ADCA), N,N-dinitrosopentamethylenetetramine (DPT), 4,4-oxybisbenzenesulfonylhydrazide (OBSH), and hydrazodicarbonamide (HDCA).
• the inorganic foaming agent may, for example, be sodium hydrogen carbonate.
• the decomposition temperature of the foaming agent is not particularly limited, and may be, for example, 50°C to 200°C, or may be 80°C to 200°C, or may be 130°C to 200°C.
• the content of the foaming agent in the resin composition is preferably set appropriately depending on the type of foaming agent, etc.
• the content of the organic foaming agent in the resin composition is preferably within the range of 0.05% by mass to 1.0% by mass, and more preferably within the range of 0.1% by mass to 0.5% by mass.
• the resin composition may contain a solvent from the viewpoint of adjusting the viscosity.
• the solvent is preferably a solvent having a boiling point of 70° C. or more, more preferably a solvent having a boiling point of 100° C. or more, from the viewpoint of preventing the composition from drying in the process of applying the composition.
• the solvent is more preferably a solvent having a boiling point of 300° C. or less in order to suppress the generation of voids.
• the type of solvent is not particularly limited, and examples include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, aromatic hydrocarbon-based solvents, ester-based solvents, and nitrile-based solvents.
• examples of the solvent include methyl isobutyl ketone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, ⁇ -butyrolactone, sulfolane, cyclohexanone, methyl ethyl ketone, dimethylpropanamide, 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,
• the solvent content is preferably 60 mass% or less, more preferably 40 mass% or less, and even more preferably 20 mass% or less, relative to the total amount of the resin composition.
• the resin composition may not contain a solvent.
• the solvent content may be 0.1 mass% or more, 0.5 mass% or more, or 1 mass% or less.
• the resin composition may contain other components as necessary, such as additives including a dispersant, a coupling agent, and a thixotropic agent.
• the resin composition may contain a dispersant from the viewpoint of dispersibility of the filler.
• the dispersant may be a dispersant compatible with the resin.
• the filler tends to be suitably dispersed and the adhesion to the substrate tends to be improved.
• the dispersant may be a phosphate, a carboxylate, or an amine carboxylate.
• the content of the dispersant may be 0.01% by mass to 5% by mass, 0.05% by mass to 3% by mass, 0.1% by mass to 1% by mass, or 0.1% by mass to 0.5% by mass, based on the total solid content of the resin composition.
• the type of coupling agent is not particularly limited, and examples of the coupling agent include silane-based compounds, titanium-based compounds, aluminum chelate compounds, aluminum/zirconium-based compounds, etc. Among them, silane coupling agents are preferred from the viewpoint of adhesion to substrates such as glass.
• the coupling agents may be used alone or in combination of two or more. When the resin composition contains a coupling agent, the adhesion of the resulting film to a substrate tends to be improved.
• silane coupling agents examples include silane coupling agents having a vinyl group, an epoxy group, a methacryl group, an acrylic group, an amino group, an isocyanurate group, a ureido group, a mercapto group, an isocyanate group, an acid anhydride group, or the like.
• silane coupling agents having an epoxy group or an amino group are preferred, and silane coupling agents having an epoxy group or an anilino group are more preferred.
• the resin when at least one resin selected from the group consisting of polyamideimide resins and epoxy resins is used as the resin, it is preferred to use a silane coupling agent having an epoxy group or an amino group, and it is more preferred to use a silane coupling agent having an epoxy group or an anilino group, from the viewpoint of good compatibility with polyamideimide resins and epoxy resins.
• silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-ureidopropyltriethoxysilane,
• the content of the coupling agent in the resin composition is not particularly limited, but is preferably 0.05% by mass to 5% by mass, and more preferably 0.1% by mass to 2.5% by mass, based on the solid content of the resin composition.
• Thixotropic agents include 12-hydroxystearic acid, 12-hydroxystearic acid triglyceride, ethylene bisstearic acid amide, hexamethylene bisoleic acid amide, N,N'-distearyl adipic acid amide, fumed silica, etc.
• One type of thixotropic agent may be used alone, or two or more types may be used in combination.
• the content of the thixotropic agent is not particularly limited, and may be 0.01% by mass to 5% by mass, 0.05% by mass to 3% by mass, or 0.1% by mass to 1% by mass, based on the total solid content of the resin composition.
• the resin composition may or may not contain a conductive filler as another component.
• the content of the conductive filler relative to the total solid content 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 %, from the viewpoint of obtaining a film having insulating properties.
• the conductive filler refers to a filler having a volume resistivity at 25° C. of less than 1 ⁇ 10 6 ⁇ cm.
• the conductive filler may include metals, conductive metal oxides, carbon black, and the like.
• the method for preparing the resin composition is not particularly limited, and examples thereof include a method in which the above-mentioned components contained in the resin composition are mixed in predetermined amounts using a mixer or the like.
• the viscosity of the resin composition is preferably 10 Pa ⁇ s to 300 Pa ⁇ s at 25°C, 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 in accordance with JIS Z 3284-3:2014 using an E-type rotational viscometer equipped with an SPP rotor at 25°C, at a rotation speed of 2.5 revolutions per minute (rpm) for 144 seconds, and is the average value of two measurements.
• the acoustic matching layer is obtained, for example, as follows. Specifically, for example, the above-mentioned resin composition is first applied to an object on which the acoustic matching layer is to be provided to form a resin composition layer, and the resin composition layer is then dried and cured to obtain an acoustic matching layer which is a cured film of the resin composition.
• the above-mentioned resin composition may be applied to the surface of a substrate to form a resin composition layer, the resin composition layer may be dried to obtain a dry film, and the dry film may then be peeled off from the surface of the substrate and placed on an object to be fitted with the acoustic matching layer, and cured to obtain an acoustic matching layer which is a cured film of the resin composition.
• the above-mentioned resin composition may be applied to the surface of a substrate to form a resin composition layer, the resin composition layer may be dried and cured to obtain a cured film of the resin composition, and the cured film may then be peeled off from the surface of the substrate and provided on an object to be fitted with an acoustic matching layer, thereby obtaining an acoustic matching layer which is a cured film of the resin composition.
• a cured film that is a molded body of the resin composition may be obtained by injection molding, extrusion molding, or the like, and then the cured film may be provided on the object on which the acoustic matching layer is to be provided, thereby obtaining an acoustic matching layer that is a cured film of the resin composition.
• the acoustic matching layer may be a cured film obtained by curing a laminate in which multiple dry films are stacked.
• the acoustic matching layer may be a cured film obtained by peeling dry films formed on multiple different substrates from the substrates, bonding them together, and curing them to form an integrated film.
• the acoustic matching layer may be a cured film obtained by further applying a resin composition onto the dry film, drying it to obtain a laminate in which multiple dry films are stacked, and curing the laminate.
• the method for applying the resin composition is not particularly limited, and examples thereof include spraying, screen printing, rotary coating, spin coating, bar coating, and the like.
• the substrate to which the resin composition is applied is not particularly limited, and examples thereof include glass, metal, resin material, metal vapor deposition film, metal oxide, ceramic, nonwoven fabric, glass fiber, aramid fiber, carbon fiber, glass fiber prepreg, aramid fiber prepreg, and carbon fiber prepreg.
• the method for drying the resin composition layer is not particularly limited, and examples of the method include a method of heat treatment using a device such as a hot plate or an oven, a method of natural drying, etc.
• the conditions for drying by heat treatment are not particularly limited as long as the solvent in the resin composition is sufficiently evaporated, and may be 80° C. to 150° C. for about 5 minutes to 120 minutes.
• the method of curing to obtain a cured film is not particularly limited, and curing can be performed by heat treatment or the like. Curing by heat treatment can be performed using a box dryer, hot air conveyor type dryer, quartz tube furnace, hot plate, rapid thermal annealer, vertical diffusion furnace, infrared curing furnace, electron beam curing furnace, microwave curing furnace, laminator, hot plate press, etc.
• a cured film can be obtained by curing the resin composition by heat treatment during molding using a molding machine such as an injection molding machine or extrusion molding machine.
• the metal plate is provided as necessary, and serves to amplify ultrasonic waves generated from the piezoelectric element and propagate the amplified waves to the acoustic matching layer.
• the material of the metal plate is not particularly limited, and examples thereof include aluminum, stainless steel, iron, copper, and the like.
• the maximum thickness of the metal plate is, for example, 500 ⁇ m or less, and from the viewpoint of obtaining a high sound pressure and of setting the specific thickness within the above range, it is preferably 100 ⁇ m to 500 ⁇ m.
• the metal plate may be provided on at least a part of the surface of the piezoelectric element facing the acoustic matching layer, and from the viewpoint of efficiently amplifying ultrasonic waves generated by the piezoelectric element, it is preferable that the metal plate is provided so as to cover the entire surface of the piezoelectric element facing the acoustic matching layer.
• the size of the metal plate in the planar direction may be larger than that of the surface of the piezoelectric element facing the acoustic matching layer.
• the shape of the metal plate in the planar direction is not particularly limited, and examples of the shape include a circle, a polygon, etc. When the metal plate is viewed in a plan view, the maximum diameter of the metal plate is, for example, 8 mm or less.
• the sound wave reflection layer contains at least a resin and reflects ultrasonic waves generated from the piezoelectric element to the opposite side of the acoustic matching layer.
• the acoustic impedance value of the sound wave reflection layer is set to a value significantly different from the acoustic impedance value of the layer with which the sound wave reflection layer is in contact. This makes it easier for the ultrasonic waves generated from the piezoelectric element to be reflected at the interface between the sound wave reflection layer and the layer with which the sound wave reflection layer is in contact.
• the acoustic impedance value of the sound wave reflecting layer can be controlled by the same method as that for controlling the acoustic impedance value of the acoustic matching layer described above.
• the composition and formation method of the sound wave reflecting layer are the same as those of the acoustic matching layer described above, except that the acoustic impedance value is different.
• the average thickness of the sound wave reflection layer is not particularly limited, and may be, for example, 500 ⁇ m or less. The definition of the average thickness and the method for measuring the thickness are as described above.
• the acoustic attenuation layer contains at least a resin and attenuates ultrasonic waves generated from the piezoelectric element on the opposite side to the acoustic matching layer.
• the acoustic attenuation layer may be any layer through which acoustic waves are difficult to transmit, such as a layer through which acoustic waves are difficult to transmit by reflecting acoustic waves, a layer through which acoustic waves are difficult to transmit by absorbing acoustic waves, or a layer through which acoustic waves are difficult to transmit by reflecting and absorbing acoustic waves.
• the acoustic impedance value is set to be significantly different from the acoustic impedance value of the layer with which the acoustic attenuation layer is in contact, thereby increasing the reflectivity of acoustic waves and making it more difficult for sound waves to transmit.
• the acoustic attenuation layer can attenuate the signal strength of ultrasonic waves during propagation by converting them into thermal energy, diffusing, scattering, delaying, etc., ultrasonic waves.
• the composition and formation method of the acoustic attenuation layer are the same as those of the acoustic matching layer described above, except that the acoustic impedance value is different.
• the average thickness of the acoustic attenuation layer is not particularly limited, and may be, for example, 500 ⁇ m or less. The definition of the average thickness and the method for measuring the thickness are as described above.
• the acoustic attenuation layer is a layer having a high acoustic absorption rate
• the thermal conductivity of the sound attenuation layer can be increased, for example, by including a highly thermally conductive filler such as aluminum oxide.
• An ultrasonic device includes a support and the ultrasonic elements provided on the support and arranged two-dimensionally.
• the ultrasonic elements according to the embodiment described above are used as the ultrasonic elements, so that the device is applicable to a small airborne haptic device, and ultrasonic waves with their intensity and waveform maintained are emitted into the air from each ultrasonic element, making it possible to generate a high acoustic radiation pressure at a targeted position.
• the support is not particularly limited as long as it is a member that supports the ultrasonic element.
• the support is not particularly limited as long as it is a member that supports the ultrasonic element.
• FIG. 11 is a perspective view showing an example of an ultrasonic device according to the first embodiment
• FIG. 12 is a schematic view showing a cross section of the ultrasonic device of FIG. 11 cut in the thickness direction.
• 11 and 12 includes a support 10 and a plurality of ultrasonic elements 12 provided on the support 10.
• Each of the plurality of ultrasonic elements 12 is an ultrasonic element according to the embodiment described above, and is two-dimensionally arranged and arrayed on the surface of the support 10 as shown in FIG.
• the ultrasonic element 12 has a piezoelectric element 16 provided in contact with the support 10 , and an acoustic matching layer 20 provided in contact with the piezoelectric element 16 . Since each ultrasonic element 12 has an acoustic matching layer 20, the ultrasonic waves generated from the piezoelectric element 16 are propagated into the air while maintaining their intensity and waveform.
• the spacing between the ultrasonic elements 12, i.e., the shortest distance between the centers of the piezoelectric elements 16, is not particularly limited, and may be, for example, 500 ⁇ m or less.
• the ultrasonic elements 12 are arranged in a square lattice pattern, but the arrangement shape of the ultrasonic elements 12 is not limited to this and may be a hexagonal lattice pattern or another arrangement shape.
• the number of ultrasonic elements 12 arranged in an array on the support 10 is not particularly limited.
• the maximum value of the overall thickness of the ultrasonic device 100 is, for example, 20 mm or less.
• the maximum value of the overall thickness of the ultrasonic device 100 can be measured using a micrometer or the like.
• the ultrasonic device 100 may or may not further include other layers, such as a cover layer, on the acoustic matching layer 20 .
• the surface of the piezoelectric element 16 opposite to the surface on which the support 10 is disposed is covered with an acoustic matching layer 20. Therefore, the piezoelectric element 16 is protected by the acoustic matching layer 20 even without a cover layer.
• FIG. 13 is a schematic diagram illustrating a cross section of an example of an ultrasonic device according to the second embodiment.
• the ultrasonic device according to the second embodiment has one sound wave reflecting layer between the support and the ultrasonic element so as to cover the entire surface of the support.
• the ultrasonic device 120 shown in FIG. 13 has a support 10, an acoustic reflection layer 24 containing a resin and provided in contact with the support 10, and a plurality of ultrasonic elements 12 provided on the acoustic reflection layer 24.
• the support 10 and the ultrasonic elements 12 in the ultrasonic device 120 are similar to the support 10 and the ultrasonic elements 12 in the ultrasonic device 100, and therefore a description thereof will be omitted.
• the ultrasonic device 120 has an acoustic matching layer 20 in the ultrasonic element 12, so that the ultrasonic waves generated from the piezoelectric element 16 are propagated into the air while maintaining their intensity and waveform. Furthermore, since the ultrasonic device 120 has an acoustic reflection layer 24, the ultrasonic waves generated from the piezoelectric element 16 and emitted in the direction of the support 10 are reflected by the acoustic reflection layer 24, making it easier to obtain the intensity of the ultrasonic waves propagating in the air.
• the ultrasonic device 120 may have an acoustic attenuation layer instead of or in addition to the acoustic reflection layer 24.
• the acoustic attenuation layer may be provided on the support 10 side or on the ultrasonic element 12 side with respect to the acoustic reflection layer 24.
• ultrasonic device 120 may or may not have other layers, such as a cover layer, on acoustic matching layer 20 of ultrasonic element 12, and if it has a cover layer, it may also have another acoustic matching layer on the side of the cover layer opposite to the side on which acoustic matching layer 20 is arranged.
• the details of the sound wave reflecting layer 24 in the ultrasonic device 120 are similar to those of the sound wave reflecting layer provided as necessary in the ultrasonic element described above, and therefore will not be described here.
• the ultrasonic device of the present disclosure is used for an air-based haptic device.
• the air-based haptic device of the present disclosure is not particularly limited as long as it includes at least the ultrasonic device of the present disclosure.
• the ultrasonic device according to the above-mentioned embodiment emits ultrasonic waves from each ultrasonic element into the air while maintaining its intensity and waveform, making it possible to generate high acoustic radiation pressure at a targeted location, and can also be made compact, making it particularly applicable as a component of a small aerial haptic device.
• small mid-air haptic devices include virtual reality (VR) glasses, augmented reality (AR) glasses, wearable devices such as hearable devices, and mixed reality (MR) glasses.
• Example 1 Using simulation software (manufactured by COMSOL, product name: COMSOL Multiphysisics), the following simulation conditions were set to determine the sound pressure level of the ultrasonic waves generated from the ultrasonic element in Example 1. The result was 112.2 dB at a distance of 30 mm from the ultrasonic element base.
• Example 2 Among the simulation conditions in Example 1, except that the shape of the radiation surface of the acoustic matching layer was curved and concave (maximum thickness: 600 ⁇ m, minimum thickness: 200 ⁇ m), the sound pressure level of the ultrasonic waves generated from the ultrasonic element in Example 2 was obtained in the same manner as in Example 1. The result was 109.8 dB at a distance of 30 mm from the ultrasonic element base.
• Example 3 Among the simulation conditions in Example 1, except that the shape of the radiation surface of the acoustic matching layer was flat and had a uniform thickness (maximum thickness and minimum thickness: 600 ⁇ m), the sound pressure level of the ultrasonic waves generated from the ultrasonic element in Example 3 was obtained in the same manner as in Example 1. The result was 97.9 dB at a distance of 30 mm from the ultrasonic element base.
• Example 1 ⁇ Comparative Example 1> Among the simulation conditions in Example 1, except that the layer structure was made up of only the piezoelectric element and the metal plate, the sound pressure level of the ultrasonic waves generated from the ultrasonic element in Comparative Example 1 was obtained in the same manner as in Example 1. The result was 80.8 dB at a distance of 30 mm from the ultrasonic element base.
• Example 1 Among the simulation conditions in Example 1, except that the layer structure was a piezoelectric element, a metal plate, and a resonator (material: aluminum, shape: funnel-shaped, maximum height: 1.0 mm), the sound pressure level of the ultrasonic waves generated from the ultrasonic element in Reference Example 1 was obtained in the same manner as in Example 1. The result was 113.9 dB at a distance of 30 mm from the ultrasonic element base.
• Ultrasonic element 10 Piezoelectric element 16A, 20A, 22A Surface 20, 22 Acoustic matching layer 24 Sound wave reflecting layer 26 Sound wave attenuation layer 28
• Metal plate 100, 120, 130 Ultrasonic device 200, 200A, 200B, 200C, 200D, 200E, 200F, 210, 220, 230 Ultrasonic element
• Air haptic device 502 Printed circuit board 510: Ultrasonic element 512: Connection section 520: Ultrasonic generator 522: Metal plate 524: Piezoelectric ceramics 526: Resonator 528: Housing 528A: Sound emission hole

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• 2023
  • 2023-06-30 JP JP2025529407A patent/JPWO2025004384A1/ja active Pending
  • 2023-06-30 CN CN202380099847.7A patent/CN121444481A/zh active Pending
  • 2023-06-30 WO PCT/JP2023/024522 patent/WO2025004384A1/ja not_active Ceased

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