JP6641723B2 - Ultrasonic transducer and manufacturing method thereof, ultrasonic probe, and ultrasonic imaging apparatus - Google Patents

Description

  The present invention relates to an ultrasonic transducer and a method for manufacturing the same, an ultrasonic probe, and an ultrasonic imaging apparatus.

  An ultrasonic transducer is used for an ultrasonic probe used for a medical ultrasonic diagnostic device for a living body, a nondestructive inspection device, and the like, and its performance is required to be improved. The ultrasonic vibrator has a piezoelectric body, and the piezoelectric body is generally partitioned by a groove in accordance with an element unit in order to enhance piezoelectric characteristics. In general, the larger the area of the piezoelectric body or the more favorable the aspect ratio, the more the piezoelectric properties are expected to be improved. In recent years, a processing technique for forming a narrow groove in a piezoelectric body has been developed, and it has become possible to process the piezoelectric body with a larger area or an optimum aspect ratio.

  The groove is generally filled with a joint material to secure the mechanical strength of the ultrasonic vibrator. The joint material is generally formed by filling the groove with a curable material such as an epoxy resin and curing the material. With such a configuration, the restraining force on the piezoelectric body that is about to vibrate can be reduced, so that the piezoelectric body can be more easily vibrated. In addition, the acoustic impedance of the joint material is preferably low from the viewpoint that the acoustic impedance of the composite piezoelectric material is low and matching with the acoustic matching layer is easy.

  In order to lower the acoustic impedance of the joint, air bubbles are generally introduced into the joint. As an example of the method of introducing bubbles into the joint material, there is known a method in which a filler having curability and foaming is filled in a groove of a piezoelectric body and then cured (for example, Patent Document 1). reference). Further, as an example of the method of introducing bubbles into the joint material, a method is known in which a filler having curability and containing a hollow filler is filled in the groove and then cured (for example, Patent Reference 2).

JP-A-02-057099 JP 2007-235795 A

  On the other hand, as described above, the width of the groove in the ultrasonic vibrator is smaller, and the groove is generally bottomed. On the other hand, the flowability of the filler containing bubbles or hollow fillers is generally low, so that when the grooves are filled with the material, the bubbles are not sufficiently filled, and the bubbles are unevenly distributed in the grooves. It's easy to do.

  When the bubbles are deviated between the grooves or in the depth direction of the grooves, the characteristics between the grooves fluctuate, the acoustic characteristics of the ultrasonic vibrator fluctuate for each element, and as a result, the directivity of the ultrasonic probe and The variation in sensitivity may be large. Filling the groove with the filler so that the bubbles are even in the groove becomes more difficult as the width of the groove becomes narrower, and the variation becomes more remarkable as the width of the groove becomes narrower.

  A first object of the present invention is to provide an ultrasonic vibrator in which bubbles are more evenly present in a joint material even in a narrow groove. Further, a second object of the present invention is to provide an ultrasonic probe and an ultrasonic imaging apparatus having the ultrasonic transducer.

  The present invention provides a groove forming step of forming a groove for partitioning a piezoelectric body into element units in the piezoelectric body, a step of filling the groove with unfoamed particles, and foaming the unfoamed particle filled in the groove. A step of filling the groove after foaming the unexpanded particles with an uncured filler having curability, and a step of curing the filler filled in the groove. And a method of manufacturing the acoustic transducer.

  Further, the present invention is an ultrasonic vibrator having a piezoelectric body, a groove that partitions the piezoelectric body into element units, and a joint material filling the groove, wherein the joint material includes bubbles. The average porosity of the joint material in the ultrasonic vibrator is 10% or more, and the porosity of an arbitrary region having a depth of 40 μm in the groove has a variation of ± 15% or less with respect to the average porosity. To provide a child.

  Further, the present invention provides an ultrasonic probe including the above-described ultrasonic transducer and an acoustic lens adhered to an acoustic matching layer adhered to the piezoelectric body.

  Further, the present invention provides an ultrasonic imaging apparatus having the above-described ultrasonic probe.

  According to the present invention, it is possible to provide an ultrasonic vibrator in which bubbles are more evenly present in the joint material even in a narrow groove, and the sensitivity and directivity variation are small, and excellent sensitivity and An ultrasonic probe and an ultrasonic imaging device having directivity can be provided.

FIG. 1A is a perspective view schematically illustrating a first embodiment of a piezoelectric body having a groove according to the present invention, and FIG. 1B is a perspective view schematically illustrating a modification of the first embodiment. FIG. 1C is a perspective view schematically showing a second mode of the piezoelectric body. FIG. 2A is a perspective view schematically illustrating a first mode of the arrangement of the grooves in the ultrasonic transducer having the piezoelectric body and the acoustic matching layer, and FIG. 2B is a perspective view of the arrangement of the grooves in the ultrasonic transducer. It is a perspective view which shows 2 aspects typically. FIG. 3A is a perspective view schematically showing a third mode of the arrangement of the grooves in the ultrasonic transducer, and FIG. 3B is a schematic view of a fourth mode of the arrangement of the grooves in the ultrasonic transducer. FIG. FIG. 4A is a perspective view schematically showing a fifth mode of the arrangement of the grooves in the ultrasonic transducer, and FIG. 4B is a schematic view of a sixth mode of the arrangement of the grooves in the ultrasonic transducer. FIG. 5A to 5C are diagrams schematically showing a first embodiment in the manufacturing method of the present invention. 6A to 6D are diagrams schematically showing a second embodiment in the manufacturing method of the present invention. 7A to 7F are views schematically showing a third embodiment in the manufacturing method of the present invention. FIG. 8A is a diagram schematically illustrating a configuration of an embodiment of an ultrasonic imaging apparatus according to the present invention, and FIG. 8B is a block diagram illustrating an electrical configuration of the ultrasonic imaging apparatus. It is a figure showing typically composition of an ultrasonic probe in the above-mentioned ultrasonic imaging device. It is a figure for showing typically composition of an ultrasonic transducer of one embodiment of the present invention. FIG. 11A is a photograph taken by a scanning electron microscope at a magnification of 200 times when an example of the foaming agent used in the present invention is foamed, and FIG. 11B is a photograph obtained by scanning the cross section at a magnification of 500 times. It is a photograph taken with a microscope. It is the photograph which image | photographed the cross section of an example of the ultrasonic transducer of this invention by the scanning electron microscope at the magnification of 150 times. It is the photograph which image | photographed the cross section of an example of the said ultrasonic vibrator by the scanning electron microscope at 1000 times magnification. It is the photograph which image | photographed the cross section of an example of the hardened | cured material of the conventional filler containing the conventional hollow filler by the scanning electron microscope at 100 times magnification. It is the photograph which image | photographed the cross section of an example of the conventional ultrasonic vibrator by the scanning electron microscope at 200 times magnification.

Hereinafter, embodiments of the present invention will be described.
The ultrasonic transducer according to the present embodiment includes a piezoelectric body, a groove that partitions the piezoelectric body into element units, and a joint material that fills the groove.

  The piezoelectric body is an object that exhibits a phenomenon (piezoelectricity) that generates positive and negative charges on the surface when stress is applied to the surface thereof. For example, a substance, a mixture, a compound, a compound, a composite compound, or the like that is known to exhibit piezoelectricity is provided. Solid solutions and compositions. The piezoelectric body may be one kind or more, and may be an inorganic substance or an organic substance. The shape of the piezoelectric body is usually plate-shaped, but may be any shape as long as it can be used as an ultrasonic vibrator. For example, the piezoelectric body may be composed of only one plate-shaped piezoelectric body, or may be a laminate of a plurality of piezoelectric plates having different impedances.

Examples of the inorganic piezoelectric material include quartz, lithium niobate, barium titanate, lead titanate, lead metaniobate, zinc oxide, PbZrO ₃ / PbTiO ₃ solid solution (PZT), and Pb (Mg _1/3 Nb _2/3 ). O ₃ / PbTiO ₃ solid solution (PMN-PT) and Pb (Zn _1/3 Nb _2/3 ) O ₃ / PbTiO ₃ solid solution (PZN-PT) are included.

  Examples of the organic piezoelectric material include polyvinylidene fluoride-ethylene trifluoride copolymer (P (VDF-3FE)), a kneaded product of P (VDF-3FE) and polyurethane, and P (VDF-3FE) and silicone. Kneaded product, kneaded product of polyvinylidene fluoride and nylon, PVDF copolymer obtained by copolymerization of vinylidene fluoride and chlorotrifluoroethylene, polybutadiene-N, N-methylenebisacrylamide-styrene copolymer, poly ( γ-benzyl-L-glutamate), polyurea by vapor deposition polyaddition of methane diisocyanate and diaminofluorene, polyurea by vapor deposition polyaddition of xylylene diisocyanate and p-diaminobenzene, and tetrafluoroethylene-hexafluoropropylene And polymer electrets.

  Further examples of inorganic and organic composite piezoelectrics include PZT-siloxane-poly (meth) acrylate composites and composites of polylactic acid with calcium phosphate or montmorillonite.

  The groove is formed in the piezoelectric body, and divides the piezoelectric body according to an element unit when the piezoelectric body is viewed in plan. The element unit includes a main unit partitioned up to the electrode and a subunit sharing the electrode, and the groove may be a groove forming any of the units. Usually, a plurality of the grooves are formed in the piezoelectric body and may be arranged in parallel in one direction or in two intersecting directions (for example, two directions orthogonal to each other).

  The narrower the width of the groove, the more the piezoelectric body can be partitioned. From such a viewpoint, the width of the groove is preferably 5 to 50 μm, and more preferably 10 to 30 μm.

  The depth of the groove can be appropriately determined according to the structure of the ultrasonic transducer. For example, the depth of the groove may be less than the thickness of the piezoelectric body, or may be more than the thickness.

  FIG. 1A is a perspective view schematically showing a first embodiment of a piezoelectric body having a groove. The piezoelectric body 10 has a plurality of parallel grooves 20, as shown in FIG. 1A. The groove 20 has a depth less than the thickness of the piezoelectric body 10. FIG. 1B is a perspective view schematically showing a modification of the first embodiment. The groove 20 of the piezoelectric body 10 may have a depth corresponding to the thickness of the piezoelectric body 10. The modified example can be manufactured, for example, by polishing the lower surface of the piezoelectric body 10 shown in FIG. 1A.

  Note that, in illustrating the embodiment of the present invention, components other than the piezoelectric body such as an adhesive, an FPC, an electrode, and a backing material may be appropriately omitted. Therefore, it should be noted that the configuration shown in the above drawings should not be interpreted as not having these other configurations because the above other configurations are not shown.

  FIG. 1C is a perspective view schematically showing a second mode of the piezoelectric body having a groove. As shown in FIG. 1C, the piezoelectric body 11 is a laminate in which a first piezoelectric plate 11a, a second piezoelectric plate 11b, and a third piezoelectric plate 11c are stacked in this order. Each of the first piezoelectric plate 11a, the second piezoelectric plate 11b, and the third piezoelectric plate 11c may be a piezoelectric plate having the same characteristics or a piezoelectric plate having different characteristics. For example, even if each of the first piezoelectric plate 11a to the third piezoelectric plate 11c has a predetermined acoustic impedance from the first piezoelectric plate 11a to the third piezoelectric plate 11c, the acoustic impedance gradually decreases. Good. The piezoelectric body 11 has grooves 21a to 21c. The groove 21a has a depth from the surface of the third piezoelectric plate 11c to the first piezoelectric plate 11a. The groove 21b has the same depth as the sum of the thickness of the third piezoelectric plate 11c and the thickness of the second piezoelectric plate 11b. The groove 21c has the same depth as the thickness of the third piezoelectric plate 11c.

  The joint material fills the groove. The joint material may be made of a usual material known as a joint material of an ultrasonic transducer. Examples of the joint material include a cured product of a curable epoxy resin and a cured product of a curable silicone.

  The joint material contains air bubbles. The air bubbles may be formed directly in the joint material, or may be an internal space of hollow microcapsules dispersed in the joint material.

  The average porosity of the joint material in the ultrasonic transducer is 10% or more. If the average porosity is too low, the acoustic impedance of the joint material becomes too high, and the joint material may excessively restrict the vibration of the piezoelectric body. The average porosity is preferably 50% or more, and more preferably 70% or more, from the viewpoint of suppressing acoustic impedance and restraint of the piezoelectric body, and from the viewpoint of making the distribution of the voids in the grooves more uniform. More preferred. The average porosity is preferably as high as possible from the viewpoint of facilitating vibration of the piezoelectric body, but is preferably 90% or less from the viewpoint of securing sufficient mechanical strength of the ultrasonic vibrator.

  The joint material uniformly contains the air bubbles in both the length direction and the depth direction of the groove. The uniform existence of the bubbles in the joint material can be evaluated based on the area of the bubbles in the cross section to be evaluated in a region of the groove having a sufficient depth including a sufficient number of bubbles. For example, the variation of the porosity of an arbitrary region having a depth of 40 μm in the groove with respect to the average porosity is within ± 15%. The width of the region is the same as the width of the groove, and the length of the region is 40 μm. In the present invention, the width of the groove is equal to or smaller than the size of the bubble, as is apparent from the manufacturing method described later. If the variation is too large, the variation in piezoelectric characteristics between the sections becomes large, and the desired piezoelectric characteristics of the ultrasonic vibrator may not be exhibited.

  From the viewpoint of suppressing the variation in the piezoelectric characteristics between the sections, the variation is preferably ± 15% or less, and more preferably ± 10% or less. The smaller the variation, the better, but the smaller the variation, the better the yield.

  The average porosity may be, for example, an area of 40 μm depth in the cross section of the groove from the cross section along the depth direction of the groove and the cross section in the direction crossing the groove in the ultrasonic vibrator. The porosity can be obtained by selecting each portion and obtaining the average value of the porosity in those regions.

  The variation may be, for example, from each of a cross section along the depth direction of the groove and a cross section in a direction crossing the groove in the ultrasonic transducer, a region having a length of 40 μm in the cross section of the groove (the same as the width of the groove). (A region having a width and a length in the depth direction of the groove or a length in the plane direction of the groove) is arbitrarily selected at three places, and the variation of the porosity of each region with respect to the average porosity is calculated according to a common method. It can be obtained by doing.

  The size of the bubble may be in a range that can be accommodated in the groove. From the viewpoint of realizing the above average porosity and variation, the size of the bubble is preferably 0.2 to 1.0 times, and preferably 0.3 to 0.7 times the width of the groove. Is more preferred. The size of the bubble may be a value representative of the size of the bubble, and may be, for example, an average value of arbitrarily selected maximum diameters in each region of the bubble.

  In the ultrasonic transducer, the groove has a sufficient porosity. Therefore, the joint material is unlikely to restrain the vibration of the piezoelectric body. Further, in the above-described ultrasonic vibrator, the porosity of the groove that partitions the piezoelectric body is substantially uniform. Therefore, the acoustic impedance in the groove becomes uniform. Also, there is substantially no variation in piezoelectric characteristics between the sections of the piezoelectric body.

  The joint material may further include a further material as long as the effects of the present embodiment can be obtained. For example, the joint material may further contain spacer particles.

  The spacer particles are added for the purpose of adjusting the acoustic impedance of the joint material. The size of the spacer particles can be determined from a range in which the grooves can be filled and that does not substantially affect the sound. From the above viewpoint, the size of the spacer particles is preferably 20 μm or less, more preferably 5 μm or less. Examples of the material of the spacer particles include silicone and epoxy.

  Examples of the spacer particles include silicone powders. Examples of the silicone powders include KMP series and X-52 series manufactured by Shin-Etsu Chemical Co., Ltd. and EP manufactured by Dow Corning Toray Co., Ltd. And the DY series, and the Tospearl series manufactured by Momentive (“Tospearl” is a registered trademark of the company).

  Further, the ultrasonic transducer may further include an acoustic matching layer bonded to the piezoelectric body. The acoustic matching layer has acoustic characteristics between the acoustic characteristics of the piezoelectric body and the acoustic characteristics of the subject irradiated with the ultrasonic waves generated from the piezoelectric body. A known acoustic matching layer can be used as the acoustic matching layer.

  The acoustic matching layer may further include an additional groove that defines the acoustic matching layer, and an additional joint material that fills the additional groove. FIG. 2A is a perspective view schematically illustrating a first mode of the arrangement of the grooves in the ultrasonic transducer having the piezoelectric body and the acoustic matching layer, and FIG. 2B is a perspective view of the arrangement of the grooves in the ultrasonic transducer. It is a perspective view which shows 2 aspects typically. FIG. 3A is a perspective view schematically showing a third mode of the arrangement of the grooves in the ultrasonic transducer, and FIG. 3B is a schematic view of a fourth mode of the arrangement of the grooves in the ultrasonic transducer. It is a perspective view shown typically. Further, FIG. 4A is a perspective view schematically showing a fifth mode of the arrangement of the grooves in the ultrasonic transducer, and FIG. 4B is a schematic view of a sixth mode of the arrangement of the grooves in the ultrasonic transducer. It is a perspective view shown typically.

  For example, as shown in FIG. 2A, the ultrasonic transducer has a piezoelectric body 12 having a plurality of parallel grooves 22 having the same depth as its thickness, and an acoustic matching layer 50 having no grooves. May be. Further, for example, as shown in FIG. 2B, the ultrasonic transducer may have a piezoelectric body 13 having grooves 20 and grooves 22 alternately and an acoustic matching layer 50. The number of the grooves 20 may be one or more than one between the grooves 22.

  Further, for example, as shown in FIG. 3A, the ultrasonic transducer may include the piezoelectric body 12 having the groove 22 and the acoustic matching layer 51 having the groove 61. The groove 61 has the same depth as the thickness of the acoustic matching layer 51 and communicates with the groove 22 in the direction in which the piezoelectric body 21 and the acoustic matching layer 51 overlap. Further, for example, as shown in FIG. 3B, the ultrasonic transducer may include the piezoelectric body 13 and the acoustic matching layer 52 having the groove 62. The groove 62 has the same depth as the thickness of the acoustic matching layer 52, is arranged corresponding to the groove 22, and communicates with the groove 22 in the overlapping direction. The number of the grooves 20 may be one or more than one between the grooves 22.

  Further, for example, the ultrasonic transducer may include the piezoelectric body 13 and the acoustic matching layer 51 as shown in FIG. 4A. Each of the grooves 61 communicates with each of the grooves 20 and 22 in the overlapping direction. The number of the grooves 20 may be one or more than one between the grooves 22. Further, for example, as shown in FIG. 4B, the ultrasonic vibrator may include the piezoelectric body 14 having the grooves 22 and 23 and the acoustic matching layer 53 having the grooves 61 and 63. . The groove 22 and the groove 23 both have the same depth as the thickness of the piezoelectric body 14 and extend in directions orthogonal to each other. Both the groove 61 and the groove 63 have the same depth as the thickness of the acoustic matching layer 53, and extend in directions orthogonal to each other. The groove 61 communicates with the groove 22 and the groove 63 communicates with the groove 23 in the overlapping direction.

  It is preferable that the further joint material includes bubbles evenly, similarly to the joint material of the piezoelectric body, from the viewpoint of suppressing variation in acoustic characteristics of each section of the acoustic matching layer. That is, the additional joint material contains air bubbles, the average porosity of the additional joint material in the acoustic matching layer is 10% or more, and the average porosity of the porosity of an arbitrary region having a depth of 40 µm in the additional groove. It is preferable from the above viewpoint that the variation with respect to the rate is within ± 15%.

  The further joint material may be the same as that of the piezoelectric body or may be different. Similarly, the average porosity in the further joint material and the variation in the further groove can be determined in the same manner as the corresponding one in the piezoelectric body, and the same as the corresponding one in the piezoelectric body. Or may be different.

  As shown in FIG. 3B, the additional groove may communicate with a part of the groove that divides the piezoelectric body in the laminating direction of the piezoelectric body and the acoustic matching layer. As shown in FIG. 4A and FIG. 4B, in the lamination direction, it may communicate with all of the grooves that partition the piezoelectric body.

  The joint material for filling the series of grooves may be made of the same material (foamed particles and filler) for the portion corresponding to the piezoelectric body and the portion corresponding to the acoustic matching layer. Is advantageous from the viewpoint of simplification of manufacturing. In addition, the joint material may be formed of different materials in a portion corresponding to the piezoelectric body and a portion corresponding to the acoustic matching layer. This is preferable from the viewpoint of adjusting the acoustic characteristics more precisely.

  Further, the ultrasonic vibrator may further have a configuration other than the above, for example, a backing member for absorbing ultrasonic waves, an electrode carried on the backing member, and carrying the piezoelectric body. . These further configurations can be configured similarly to those in known ultrasonic transducers.

  The ultrasonic vibrator can be manufactured by the following manufacturing method. The manufacturing method includes a groove forming step of forming a groove for partitioning the piezoelectric body into element units in the piezoelectric body, a step of filling the groove with unfoamed particles, and expanding the unfoamed particle filled in the groove. (Hereinafter referred to as “expanded particles”) and a step of filling an uncured filler having curability into the grooves after the unexpanded particles are expanded. And a step of curing the filler filled in the groove. The expanded foamed particles become the air bubbles, and the cured filler becomes the joint material.

  The groove forming step can be performed by using a known processing method of the piezoelectric body. For example, if the thickness of the piezoelectric body is 10 μm or more, the groove can be formed by a known processing machine such as a diamond cutter. If the thickness is less than 10 μm, the groove is formed by Micro Electro Mechanical Systems (MEMS) processing. be able to. By the groove forming step, for example, a plurality of grooves 20 shown in FIG. 5B are formed in the piezoelectric body 10 shown in FIG. 5A.

  The unfoamed particles are filled in the grooves in an unfoamed state. The unfoamed particles may be one kind or more. Examples of the unexpanded particles include expandable microcapsules in which a volatile liquid is contained in resin microcapsules. More specifically, Matsumoto Microsphere F and FN series (Matsumoto Yushi Pharmaceutical Co., Ltd., “Matsumoto Microsphere” is a registered trademark of the company) and Expancel unexpanded grade (Akzo Nobel, “Expancel” is a registered trademark of the company).

  The unexpanded particles can be filled in the grooves as they are or dispersed in a liquid medium. The filling of the unexpanded particles may be performed under normal pressure or under reduced pressure. It is preferable to perform the filling of the unexpanded particles under reduced pressure from the viewpoint of sufficiently spreading the unexpanded particles to the end of the groove.

  The step of expanding the unexpanded particles can be performed by placing a piezoelectric body under conditions according to the unexpanded particles. For example, in the case of the unexpanded particles, the unexpanded particles can be expanded by heating to a temperature of about 130 ° C. The foaming of the unfoamed particles may be performed under normal pressure or under reduced pressure. It is preferable to perform the expansion of the unexpanded particles under reduced pressure from the viewpoint of performing the expansion of the unexpanded particles at a lower temperature and suppressing a decrease in the piezoelectricity of the piezoelectric body due to heating for the expansion.

  When the unfoamed particles are dispersed in a liquid medium and filled in the grooves, it is preferable to remove the liquid medium from the grooves after the unfoamed particles are foamed. The liquid medium may be sucked out from the groove, or may be evaporated under reduced pressure, for example. If it does not dissolve in the filler to be filled in the groove later and its specific gravity is sufficiently smaller than that of the filler, it is discharged from the groove by replacing the filler in the groove. You may.

  The filler is filled in the groove after expanding the unexpanded particles. The filler has curability and can be appropriately selected from ordinary components used as joint materials for grooves of the ultrasonic vibrator. The filler may be one kind or more. Examples of the filler include a one- or two-part silicone resin, an epoxy resin, a urethane resin (polyurethane) having high fluidity, and a precursor thereof.

  Examples of the silicone resin include TSE3663 and XE12-B2543 manufactured by Momentive, KE471W, KE108, KE118, KE66 and KE200 manufactured by Shin-Etsu Chemical Co., Ltd., and SE9206L, EE-9000, and EE-9000 manufactured by Dow Corning Toray Co., Ltd. 9100.

  Examples of the epoxy resin include C1163 manufactured by Tesque Corporation and Struct Bond EH-455NF manufactured by Mitsui Chemicals, Inc.

  Filling the groove with the filler under reduced pressure is preferable from the viewpoint of sufficiently spreading the filler to the gap between the foamed foam particles and the bottom of the groove. It is preferable to sufficiently spread the filler in the groove from the viewpoint of sufficiently increasing the mechanical strength of the ultrasonic vibrator.

  The curing of the filler can be performed by placing the piezoelectric body under conditions corresponding to the filler. For example, it is possible to cure the filler by curing the piezoelectric body in which the groove is filled with the uncured filler at a temperature of room temperature to 70 ° C. Performing the curing of the filler under reduced pressure is preferable from the viewpoint of suppressing a decrease in piezoelectricity of the piezoelectric body due to heating for curing.

  When the filler is cured, the grooves are filled with the foamed foam particles and the cured filler that fills the gaps between the grooves. In this way, as shown in FIG. 5C, the joint material 40 containing the uniformly dispersed bubbles 30 is configured.

  The above manufacturing method may further include other steps other than the above steps as long as the effects according to the present embodiment can be obtained. For example, the manufacturing method may further include a step of filling the groove with spacer particles.

  The step of filling the grooves with the spacer particles can be performed at any timing before the filler is cured. The spacer particles are usually filled in the groove for the purpose of adjusting the acoustic impedance of the joint material. For example, the spacer particles may be mixed with the unfoamed particles, mixed with the liquid medium, mixed with the filler, or filled in the groove with the spacer particles as they are.

  In addition, in the manufacturing method, a step of bonding the acoustic matching layer 50 to the piezoelectric body 10 before forming the groove as illustrated in FIG. 6A as illustrated in FIG. 6B (also referred to as a “pre-adhesion step”). May be further included. In this case, in the groove forming step, a groove 24 that partitions both the piezoelectric body 10 and the acoustic matching layer 50 into the element units as shown in FIG. 6C is formed. Bonding of the acoustic matching 50 to the piezoelectric body 10 can be performed using a known adhesive. The groove 24 can be formed in the same manner as the groove of the piezoelectric body 10. According to the manufacturing method including the pre-adhesion step, an ultrasonic transducer having the joint material 41 filling the series of grooves 24 from the acoustic matching layer 50 to the piezoelectric body 10 as shown in FIG. 6D is manufactured.

  Alternatively, the manufacturing method includes a step of bonding an acoustic matching layer 50 as shown in FIG. 7D to the piezoelectric body 10 after curing the filler as shown in FIGS. 7A to 7C (“post bonding step”). 7E), as shown in FIG. 7E, a step of forming an additional groove 64 in the acoustic matching layer 50 for dividing the acoustic matching layer 50 in an element unit in a section corresponding to the element unit, A step of filling the particles, a step of foaming the unfoamed particles filled in the groove 64, a step of filling the uncured filler in the groove 64 after the foaming of the unfoamed particles, and a step of filling the groove 64 Curing the filled filler. According to the manufacturing method including the post-adhesion step, for example, as shown in FIG. 7F, a part of the groove 64 of the acoustic matching layer 50 communicates with the groove 20 of the piezoelectric body 10, and the respective grooves 20, 64 The ultrasonic vibrator having the joint members 40 and 42 satisfying the following conditions is manufactured.

  Furthermore, the above manufacturing method may further include a repolarization step. The additional polarization step is a step of restoring the polarization characteristics in which the piezoelectric body has been damaged by heating for expanding the unexpanded particles or curing the filler, for example. The additional polarization step can be performed, for example, by applying a voltage of 1.5 to 3 times the voltage corresponding to the coercive electric field to the ultrasonic transducer at room temperature to 60 ° C. The step of performing additional polarization can be performed at any timing in the above manufacturing method.

  Further, the manufacturing method may further include a step of attaching the piezoelectric body having the groove formed thereon to, for example, a base material including a backing material and a flexible printed board. In this case, it is preferable that the groove has a depth less than the thickness of the piezoelectric body, for example, as shown in FIG. 5B, from the viewpoint of making the width of the groove of the piezoelectric body uniform. It is preferable to further include the above-described step, since the piezoelectric body can be arranged on a convex curved surface having a radius of curvature of about 5 to 100 mm, for example, from the viewpoint of forming a medical ultrasonic probe. In addition, the width of the groove of the piezoelectric body attached to the convex curved surface slightly increases from the bottom toward the opening. Foamed foamed particles are generated in the groove, and a fine gap is formed between the groove and the foamed particle. For this reason, the filler easily flows into the gap and hardly flows out due to the capillary phenomenon. Therefore, it is more effective when a relatively easy-to-flow filler such as a silicone-based filler is used.

  The ultrasonic transducer may be manufactured by a method other than the above-described manufacturing method. For example, the ultrasonic vibrator mixes a slurry of a foaming agent having a foaming property such as foamed polyurethane or foamed silicone (for example, TSE5000) with an additive for controlling the surface tension of the slurry and fills the groove with the additive. And then filling the grooves with a filler and curing. By controlling the surface tension of the slurry, it is possible to control foaming of polyurethane foam or silicone foam, and it is possible to control the size and porosity of the bubbles in the grooves. According to this method, it is possible to manufacture the above-described ultrasonic vibrator using a foaming agent having a foaming property.

  Further, the ultrasonic vibrator, the soluble particles sufficiently smaller than the width of the groove is mixed with the filler and filled in the groove, and then, or after curing the filler, the soluble particles May be dissolved in the solvent by immersion in a solvent or the like to form voids in the filler (joint material). The soluble particles are particles that are dissolved by the solvent, and may be one or more types. Examples thereof include acrylic resin-based particles and polystyrene-based particles. Further, the solvent is a liquid that dissolves the soluble particles without substantially dissolving the filler before or after curing, and examples thereof include acetone, chloroform, and dichloromethane.

  The ultrasonic transducer having the acoustic matching layer is suitably used for an ultrasonic probe. That is, the ultrasonic probe has the ultrasonic transducer and an acoustic lens bonded to the acoustic matching layer. The acoustic lens is a member that gives a desired focus to the ultrasonic wave irradiated toward the subject, and a known acoustic lens can be used as the acoustic lens. The ultrasonic probe can be configured in the same manner as a known ultrasonic probe, except that the ultrasonic probe according to the present embodiment is provided.

  The ultrasonic probe is suitably used for an ultrasonic imaging device. The ultrasonic imaging apparatus can be configured in the same manner as a known ultrasonic imaging apparatus except that it has the above-described ultrasonic probe. The ultrasonic imaging apparatus is suitable for, for example, a medical ultrasonic diagnostic apparatus or a non-destructive ultrasonic inspection apparatus.

  FIG. 8A is a diagram schematically illustrating the configuration of the ultrasonic imaging apparatus according to the present embodiment, and FIG. 8B is a block diagram illustrating the electrical configuration of the ultrasonic imaging apparatus.

  As shown in FIG. 8A, the ultrasonic imaging apparatus 200 is disposed on the apparatus main body 201, an ultrasonic probe 202 connected to the apparatus main body 201 via a cable 203, and the apparatus main body 201. An input unit 204 and a display unit 209.

  As shown in FIG. 8B, the apparatus main body 201 includes a control unit 205 connected to the input unit 204, a transmission unit 206 and a reception unit 207 connected to the control unit 205 and the cable 203, a reception unit 207, And an image processing unit 208 connected to each of the control units 205. Note that the control unit 205 and the image processing unit 208 are connected to the display unit 209, respectively.

  The input unit 204 is a device for inputting a command for instructing the start of a diagnosis or the like or data such as personal information of a subject, and is, for example, an operation panel or a keyboard having a plurality of input switches.

  The control unit 205 includes, for example, a microprocessor, a storage element, peripheral circuits thereof, and the like, and includes an ultrasonic probe 202, an input unit 204, a transmission unit 206, a reception unit 207, an image processing unit 208, and a display unit 209. Is a circuit that controls the entire ultrasonic diagnostic apparatus 200 by controlling the functions according to the respective functions.

  The transmission unit 206 transmits a signal from the control unit 205 to the ultrasonic probe 202, for example. The receiving unit 207 receives, for example, a signal from the ultrasonic probe 202 and outputs the signal to the control unit 205 or the image processing unit 208.

  The image processing unit 208 is a circuit that forms an image (ultrasound image) representing the internal state of the subject based on the signal received by the receiving unit 207 under the control of the control unit 205, for example. For example, the image processing unit 208 includes a Digital Signal Processor (DSP) that generates an ultrasonic image of a subject, and a digital-analog conversion circuit (DAC circuit) that converts a signal processed by the DSP from a digital signal to an analog signal. ).

  The display unit 209 is a device for displaying an ultrasonic image of the subject generated by the image processing unit 208 under the control of the control unit 205, for example. The display unit 209 is, for example, a display device such as a CRT display, a liquid crystal display (LCD), an organic EL display, a plasma display, or a printing device such as a printer.

  FIG. 9 is a diagram schematically illustrating the configuration of the ultrasonic probe 202. As shown in FIG. 9, the ultrasonic probe 202 has an ultrasonic transducer 100 and a holder 210 that houses the ultrasonic transducer 100. The holder 210 holds the ultrasonic transducer 100 so that the acoustic lens 170 is exposed on the surface of the ultrasonic probe 202. The FPC 120 of the ultrasonic transducer 100 is connected to a connector 211 disposed at the end of the cable 203. In FIG. 9, a part of the configuration of the ultrasonic transducer 100 is omitted.

  FIG. 10 is a diagram schematically illustrating the configuration of the ultrasonic transducer 100. The ultrasonic transducer 100 includes a backing layer 110, a flexible printed circuit (FPC) 120, a piezoelectric body 130, grooves 140 and 141, joint materials 150, an acoustic matching layer 160, and an acoustic lens 170.

  The backing layer 110 is made of a backing material, is an ultrasonic absorber that supports the piezoelectric body 130 and can absorb unnecessary ultrasonic waves. That is, the backing layer 110 is attached to the surface (back surface) of the piezoelectric body 130 opposite to the direction in which ultrasonic waves are transmitted and received by the subject, for example, a living body, and absorbs ultrasonic waves generated on the opposite side of the direction of the subject. .

  Examples of the material of the backing layer 110 include a natural rubber, an epoxy resin, a thermoplastic resin, and a resin-based composite material obtained by press-molding a mixture of at least one of these materials and a powder of tungsten oxide, titanium oxide, ferrite, or the like. , Is included. Examples of the thermoplastic resin include vinyl chloride, polyvinyl butyral, ABS resin, polyurethane, polyvinyl alcohol, polyethylene, polypropylene, polyacetal, polyethylene terephthalate, fluororesin, polyethylene glycol, and polyethylene terephthalate-polyethylene glycol copolymer. included. Among them, a resin-based composite material, and among them, a rubber-based composite material or an epoxy resin-based composite material is particularly preferable. The shape of the backing layer 110 can be appropriately determined according to the planar shape of the piezoelectric body 130 and the shape of the ultrasonic transducer 100 and the ultrasonic probe 202 including the same.

  The FPC 120 has, for example, a wiring pattern connected to a pair of electrodes for the piezoelectric body 130 and corresponding to an ultrasonic transducer described later. Electrodes are attached to each ultrasonic vibrator by the FPC 120, and arbitrary beam forming can be performed by transmitting and receiving ultrasonic waves programmed by a computer. For example, the FPC 120 has a signal lead-out line serving as one electrode and a ground lead-out line connected to the other electrode (not shown). The FPC 120 may be a commercially available product as long as it has the above-described appropriate pattern.

  Examples of the electrode material include gold, platinum, silver, palladium, copper, aluminum, nickel, tin, and alloys containing these metal elements. For example, the electrode is formed by first forming a base metal such as titanium or chromium to a thickness of 0.002 to 1.0 μm by a sputtering method, and then partially coating the above-mentioned material and, if necessary, an insulating material. It is formed by forming it to a thickness of 0.02 to 10 [mu] m by a sputtering method, a vapor deposition method or another appropriate method. The electrode can also be manufactured by forming a conductive paste layer obtained by mixing a fine metal powder and a low-melting glass by screen printing, dipping, or thermal spraying.

  In addition, the backing layer 110 and the FPC 120 can be bonded with, for example, an adhesive (for example, an epoxy-based adhesive) generally used in the technical field.

  The piezoelectric body 130 is the above-described piezoelectric body according to the present embodiment, and the grooves 140 and 141 that partition the piezoelectric body into element units have joint materials 150 in which bubbles are dispersed. For example, the piezoelectric body 130 is formed of the above-described laminate, and the thickness of the piezoelectric body 130 is, for example, 0.05 to 0.4 mm. The piezoelectric body 130 is bonded to the FPC 120 by, for example, a conductive adhesive. The conductive adhesive is, for example, an adhesive containing a conductive material such as silver powder, copper powder, and carbon fiber.

  The groove 140 has a depth from the surface of the piezoelectric body 130 to the backing layer 110, and the groove 141 has a depth from the surface of the piezoelectric body 130 to the inside of the piezoelectric body 130. The groove 140 divides a main unit of the ultrasonic transducer, and the groove 141 divides three subunits arranged in parallel in one main element. Each of the grooves 140 and 141 is formed by, for example, a groove cutting process using a dicing saw, and has a width of, for example, 15 to 30 μm.

  The pitch (the distance between the centers of the grooves 140) in the main unit is, for example, 0.15 to 0.30 mm, and the pitch (the distance between the centers of the adjacent grooves (the grooves 141 or the grooves 140)) in the subunit is , For example, 0.05 to 0.15 mm.

  The joint material 150 fills the grooves 140 and 141. As described above, examples of the material of the joint material 150 include a cured product of an epoxy resin, silicone, and a mixture thereof.

  The epoxy resin is, for example, a cured product of a prepolymer composition containing a prepolymer of an epoxy resin and a filler for forming a crosslinked network between the prepolymers.

  Examples of the above prepolymer include phenol novolak resins, cresol novolak resins, phenol aralkyl (including phenylene and biphenylene skeleton) resins, naphthol aralkyl resins, triphenol methane resins, and phenol resins such as dicyclopentadiene-type phenol resins. .

  Examples of the filler include an amine-based filler, and examples of the amine-based filler include ethylenediamine, triethylenediamine, hexamethylenediamine, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)] triazine compounds such as ethyl-s-triazine, 1,8-diazabicyclo [5,4,0] undecene-7 (DBU), triethylenediamine, benzyldimethylamine, and triethanolamine.

The acoustic matching layer 160 is a layer for matching acoustic characteristics between the piezoelectric body 130 and an acoustic lens 170 described later. The acoustic matching layer 160 adheres each of the piezoelectric body 130 and the acoustic lens with an adhesive, for example. The acoustic matching layer 160 has an acoustic impedance Za (Mrayl (= × 10 ⁶ kg / (m ² seconds)) approximately intermediate between the piezoelectric body 130 and the acoustic lens 170. The piezoelectric body 130 is arranged on the subject side (surface side), for example, via the other electrode described above.

  The acoustic matching layer 160 may be a single layer or a laminate, but is preferably a laminate of a plurality of layers having different acoustic impedances from the viewpoint of adjustment of acoustic characteristics, for example, two or more layers, more preferably four or more layers. is there. The thickness of the acoustic matching layer 160 is preferably λ / 4. λ is the wavelength of the ultrasonic wave. The acoustic matching layer 160 can be made of, for example, various materials. The Za of the acoustic matching layer 160 is preferably set so as to gradually or continuously approach the Za of the acoustic lens toward the acoustic lens. Can be adjusted.

  Examples of the above materials include aluminum, aluminum alloys (e.g., Al-Mg alloys), magnesium alloys, macor glass, glass, fused quartz, copper graphite, and resins. Examples of the resin include polyethylene, polypropylene, polycarbonate, ABS resin, AAS resin, AES resin, nylon such as nylon 6 and nylon 66, polyphenylene oxide, polyphenylene sulfide, polyphenylene ether, polyether ether ketone, polyamide imide, and polyethylene terephthalate. , Epoxy resins and urethane resins. Examples of the above additives include zinc white, titanium oxide, silica and alumina, red iron oxide, ferrite, tungsten oxide, yttrium oxide, barium sulfate, tungsten, molybdenum, glass fiber and silicone particles.

  From the viewpoint of adjusting the Za of the acoustic matching layer 160, for example, it is preferable that the surface of the acoustic matching layer 160 is made of an epoxy resin and contains silicone particles. As will be described later, when silicone, which is the material of the acoustic lens 170, is dispersed in the base material of the acoustic matching layer 160, the Za of the acoustic matching layer 160 can be made closer to that of the acoustic lens 170.

  In addition, each layer of the acoustic matching layer 160 is adhered with, for example, an adhesive (for example, an epoxy-based adhesive or a silicone-based adhesive) generally used in the technical field.

  For example, the silicone-based adhesive is a curable compound or composition containing silicone as a base material. The silicone-based adhesive is an additive for increasing the affinity for the acoustic matching layers 160 or for both the acoustic matching layer 160 and the acoustic lens 170, and an additive for matching the acoustic characteristics of both to be adhered. Various additives such as an agent may be further contained.

  The silicone-based adhesive may be a liquid rubber (RTV rubber) that cures at room temperature or a liquid rubber that is cured by heating. Further, the silicone adhesive may be a one-part type or a two-part type. Examples of the silicone based adhesive include KE-441, KE-445, KE-471W, KE-1600, KE-1604, KE-1884, KE-1885, KE-1886, KE-4895, KE-4896, KE-4897 and KE-4898 (all manufactured by Shin-Etsu Chemical Co., Ltd.), TN3005, TN3305, TN3705, TSE3976-B, ECS0600, and ECS0601 (all manufactured by Momentive Performance Materials Japan GK) Is included.

  The acoustic lens 170 is made of, for example, a soft polymer material having an intermediate Za between the subject and the acoustic matching layer 160. Examples of the polymer material include silicone rubber, butadiene rubber, polyurethane rubber, epichlorohydrin rubber, and ethylene-propylene copolymer rubber obtained by copolymerizing ethylene and propylene. Above all, the above-mentioned polymer material is preferably made of silicone rubber and butadiene rubber.

  Examples of the silicone rubber include silicone rubber and fluorine silicone rubber. In particular, silicone rubber is preferable from the viewpoint of the characteristics of the acoustic lens. The silicone rubber refers to an organopolysiloxane having a molecular skeleton composed of Si—O bonds and a plurality of organic groups mainly bonded to Si atoms. Usually, the main component is methylpolysiloxane, and the entirety thereof is methylpolysiloxane. 90% or more of the organic groups are methyl groups. In the silicone rubber, at least a part of the methyl group of the methyl polysiloxane may be replaced with a hydrogen atom, a phenyl group, a vinyl group, or an allyl group.

  The silicone rubber can be obtained, for example, by kneading a curing agent (vulcanizing agent) such as benzoyl peroxide with an organopolysiloxane having a high degree of polymerization, heating and vulcanizing and curing. An organic or inorganic filler such as silica or nylon powder, or a vulcanization aid such as sulfur or zinc oxide may be further added according to the purpose of adjusting the speed of sound or adjusting the density of the acoustic lens 170.

  Examples of the butadiene rubber include butadiene rubber, which is a homopolymer of butadiene, and a copolymer rubber composed mainly of butadiene and copolymerized with a small amount of styrene or acrylonitrile. Particularly, butadiene rubber is preferable from the viewpoint of the characteristics of the acoustic lens. Butadiene rubber refers to a synthetic rubber obtained by polymerization of butadiene having a conjugated double bond. Butadiene rubber can be obtained by polymerizing butadiene having a conjugated double bond alone at the 1,4-position or at the 1,2-position. The butadiene rubber may be further vulcanized with sulfur or the like.

  The acoustic lens 170 made of silicone rubber and butadiene rubber can be produced, for example, by mixing silicone rubber and butadiene rubber and vulcanizing and curing. For example, the acoustic lens 170 can be obtained by mixing silicone rubber and butadiene rubber in an appropriate ratio with a kneading roll, adding a vulcanizing agent such as benzoyl peroxide, and vulcanizing by heating to crosslink (cur). Can be.

  In the above case, zinc oxide may be further added as a vulcanization aid. Zinc oxide can promote vulcanization without substantially impairing the lens characteristics of the acoustic lens 170, and can shorten the vulcanization time. In addition, other additives may be added within a range that does not impair the properties of the colorant and the acoustic lens. The mixing ratio of the silicone rubber and the butadiene rubber can be appropriately set. For example, Za of the acoustic lens 170 is set so that it is close to that of the subject, the sound velocity in the acoustic lens 170 is lower than that of the subject, and the attenuation of Za of the acoustic lens 170 is smaller. Is preferred. From such a viewpoint, the mixing ratio of the silicone rubber and the butadiene rubber is preferably 1: 1.

  Note that the ultrasonic transducer 100 may include a protective layer that seals a part of the ultrasonic transducer 100 other than the acoustic lens 170. The protective layer is, for example, a layer that integrally covers the acoustic matching layer 160 in the ultrasonic transducer 100 and the configuration on the piezoelectric body 130 side with respect to the acoustic matching layer 160. Is a layer for protecting the configuration of The protective layer is preferably made of a material having physical and chemical stability, for example, made of a relatively physically and chemically stable resin such as an epoxy resin or polyparaxylylene. Can be done. The protective layer is made, for example, by the above-described parylene coating.

  The thickness of the protective layer can be appropriately determined as long as the desired function is exhibited and the desired acoustic characteristics of the ultrasonic transducer 100 can be exhibited. The thickness of the protective layer is, for example, 2 to 4 μm. With this thickness, even if the acoustic impedance of the protective layer is higher than that of the acoustic matching layer 160 and the acoustic lens 170, the desired acoustic characteristics of the ultrasonic transducer 100 can be sufficiently exhibited. It is.

  When the ultrasonic transducer 100 has the protective layer, the acoustic lens 170 is adhered to the protective layer. In this case, it is preferable that the thickness of the protective layer be sufficiently thin as much as possible from the viewpoint of realizing the desired acoustic characteristics of the ultrasonic transducer 100.

  In the ultrasonic imaging apparatus 200, the control unit 205 receives a signal from the input unit 204, outputs a signal for transmitting an ultrasonic wave (first ultrasonic signal) to a subject such as a living body to the transmission unit 206, and Then, the receiving unit 207 receives an electric signal corresponding to an ultrasonic wave (second ultrasonic signal) coming from inside the subject based on the first ultrasonic signal.

  The ultrasonic transducer 100 of the ultrasonic probe 202 uses the ultrasonic transducer 100. When ultrasonic waves are transmitted from the piezoelectric body 130, the ultrasonic waves travel through the acoustic matching layer 160 and the acoustic lens 170, and are transmitted to a subject such as a human body. Then, the light is reflected inside the subject, propagates through the acoustic lens 170 and the acoustic matching layer 160, and is received by the piezoelectric body 130. For example, the received ultrasonic waves are converted by the piezoelectric body 130 into electric signals corresponding to the amplitude and the frequency band.

  Since the grooves 140 and 141 are filled with the joint material 150 having sufficient and uniform air bubbles, the piezoelectric body 130 can sufficiently reduce the acoustic impedance of the joint material 150 and have sufficient mechanical strength. Can be expressed. For this reason, the restraint of the vibration of the piezoelectric body between the respective element units in the piezoelectric body 130 is reduced, and the variation in the acoustic characteristics is suppressed. As a result, the ultrasonic wave having small variation and high directivity and sensitivity is output. It is possible to do.

  The electric signal received by the receiving unit 207 is sent to the image processing unit 208 and processed into an image signal corresponding to the electric signal. The image signal is sent to the display unit 209, and an image corresponding to the image signal is displayed on the display unit 209. The display unit 209 also performs, based on information input from the input unit 204 and transmitted via the control unit 205, an image and an operation (display of a character, movement or enlargement of a displayed image, etc.) corresponding to the information. Is also displayed.

  The ultrasonic imaging apparatus 200 outputs ultrasonic waves with high directivity and sensitivity in ultrasonic measurement. For this reason, the ultrasonic imaging apparatus 200 can obtain higher spatial resolution as compared with the conventional ultrasonic imaging apparatus in which the number of bubbles in the joint material 150 is small or unevenly distributed, and therefore, more accurate and reliable. Higher measurement results can be obtained.

  The ultrasonic imaging apparatus 200 is applied to a medical ultrasonic diagnostic apparatus. In addition, the ultrasonic imaging apparatus 200 can be applied to an apparatus that displays an ultrasonic search result as an image or a numerical value, such as a fish finder (sonar) or a flaw detector for nondestructive inspection.

  As is clear from the above description, the ultrasonic vibrator has a piezoelectric body, a groove that partitions the piezoelectric body into element units, and a joint filling the groove. Wherein the average porosity of the joint material in the ultrasonic vibrator is 10% or more, and the porosity of an arbitrary region having a depth of 40 μm in the groove is within ± 15% of the average porosity. is there. Therefore, according to the present embodiment, it is possible to provide an ultrasonic transducer in which bubbles are more evenly present in the joint material even in a narrow groove.

  The fact that the air bubbles are constituted by the expanded particles contained in the joint material is even more effective from the viewpoint of easily adjusting the average porosity and the variation to a desired range.

  Further, it is more effective that the joint material further contains spacer particles from the viewpoint of easily adjusting the acoustic impedance of the joint material to a desired value.

  Further, it is more effective that the ultrasonic vibrator further includes an acoustic matching layer bonded to the piezoelectric body from the viewpoint of matching acoustic characteristics between the piezoelectric body and the subject.

  Further, the acoustic matching layer further includes a further groove that partitions the acoustic matching layer into element units, and a further joint material that fills the further groove, wherein the further joint material includes bubbles, and the additional joint material includes That the average porosity in the acoustic matching layer is not less than 10% and that the porosity of an arbitrary region having a depth of 40 μm in the further groove is within ± 15% with respect to the average porosity. This is even more effective from the viewpoint of matching the acoustic characteristics of the elements and outputting ultrasonic waves with high sensitivity and directivity.

  Further, in the laminating direction of the piezoelectric body and the acoustic matching layer, the additional groove communicates with a part or all of the groove that partitions the piezoelectric body. Are more effective from the viewpoint of easily manufacturing and adjusting the acoustic characteristics of adjacent elements.

  Further, the manufacturing method includes forming a groove for partitioning the piezoelectric body into element units in the piezoelectric body, filling the groove with unexpanded particles, and filling the groove with the unexpanded particles. And a step of filling the groove after the unfoamed particles are foamed with an uncured filler having curability, and a step of curing the filler filled in the groove. Including. Therefore, according to the present embodiment, it is possible to provide an ultrasonic transducer in which bubbles are more evenly present in the joint material even in a narrow groove.

  The fact that the manufacturing method further includes a step of filling the grooves with the spacer particles is more effective from the viewpoint of easily adjusting the acoustic impedance of the joint material to a desired value.

  Further, the manufacturing method further includes a step of bonding an acoustic matching layer to the piezoelectric body before forming the groove, and the groove forming step partitions both the piezoelectric body and the acoustic matching layer into the element units. The step of forming a groove is more effective from the viewpoint of easily manufacturing an ultrasonic transducer having an acoustic matching layer and matching acoustic characteristics of adjacent elements.

  Further, the manufacturing method may further include a step of adhering an acoustic matching layer to the piezoelectric body after curing the filler, and forming a further groove for dividing the acoustic matching layer into element units in sections corresponding to the element units. The step of forming the acoustic matching layer, the step of filling the additional grooves with unexpanded particles, the step of expanding the unexpanded particles filled in the additional grooves, and the step of expanding the unexpanded particles. Filling a further groove with uncured filler and curing the filler filled in the further groove further achieves a better joint material and acoustic properties by the acoustic matching layer. This is even more effective from the viewpoint of improving the directivity and sensitivity of the output ultrasonic waves.

  The ultrasonic probe includes the ultrasonic transducer and an acoustic lens adhered to the acoustic matching layer. Therefore, according to the present embodiment, it is possible to provide an ultrasonic probe capable of outputting ultrasonic waves with higher directivity and sensitivity.

  Further, the ultrasonic imaging apparatus includes the ultrasonic probe. Therefore, according to the present embodiment, it is possible to provide an ultrasonic imaging apparatus with higher resolution and sensitivity.

  Hereinafter, the present invention will be described with reference to examples.

[ Comparative Example 2 ]
A 800 μm-thick lead zirconate titanate (PZT) plate (PZT plate) was prepared as a piezoelectric body according to a conventional method. Then, a plurality of parallel grooves having a width of 15 μm were formed in the PZT plate by dicing. The distance between adjacent grooves is about 80 μm.

  Unexpanded particles (unexpanded foaming agent, “Microsphere FN-80GS” manufactured by Matsumoto Yushi Seiyaku Co., Ltd., average particle diameter: 6 to 10 μm) were filled in the grooves of the PZT plate. Next, the PZT plate was heated to around 140 ° C. to expand the unexpanded particles.

  FIGS. 11A and 11B show photographs of the cross section of the object obtained by heating the powder of the unexpanded particles and expanding the unexpanded particles with a scanning electron microscope. The unexpanded particles expand upon heating to form hollow expanded particles. In addition, although it is shown like a porous body in the photograph of illustration, this is because the aggregate of the unexpanded particles was heated.

  Next, the groove was filled with an epoxy resin (“C1163” manufactured by Tex Corporation) under reduced pressure, and filled with hollow expanded particles formed by expanding the unexpanded particles. Next, the PZT plate was heated to about 60 ° C. to cure the epoxy resin for 4 hours. Thus, the joint material 1 containing the foamed particles dispersed in the cured product of the epoxy resin was produced, and the ultrasonic transducer 1 was obtained.

  FIGS. 12 and 13 show photographs of the cross section of the ultrasonic transducer 1 and its groove taken by a scanning electron microscope. As shown in FIGS. 12 and 13, the grooves of the ultrasonic vibrator 1 are uniformly and densely filled with bubbles made of the foamed particles. When three regions having a depth of 40 μm in the joint material 1 were arbitrarily selected, the porosity in these regions was determined, and the average porosity was determined. The average porosity of the joint material 1 was 72%. Further, the variation of the porosity of each of the regions with respect to the average porosity was within a range of ± 10%.

[Comparative Example 1]
The grooves of the PZT plate are filled with a filler having the following composition under reduced pressure, and the PZT plate is heated to about 70 ° C. to cure the epoxy resin, thereby producing a joint material C1, and an ultrasonic transducer C1. Obtained. The following hollow filler is “Expancel” (particle size: 20 to 30 μm) manufactured by Akzo Nobel.
Hollow filler volume ratio 50%
The above epoxy resin C1163 volume ratio 50%

  FIG. 14 shows a photograph taken by a scanning electron microscope of a cross section of a separately prepared cured product of the filler. The bubbles due to the hollow filler are dispersed in the epoxy resin, but when viewed in a region of about 100 μm square, the density of the bubbles is observed.

  FIG. 15 shows a photograph of the cross section of the ultrasonic transducer C1 and its groove taken by a scanning electron microscope. As shown in FIG. 15, air bubbles are sparsely and non-uniformly present in the grooves of the ultrasonic transducer C1. When three areas of the joint material C1 having a depth of 40 μm were arbitrarily selected, the porosity in these areas was determined, and the average porosity was determined. The average porosity of the joint material C1 was 25%. Further, the variation of the porosity of each of the regions with respect to the average porosity was within a range of ± 25%.

[simulation]
Next, in addition to the above-described ultrasonic vibrator C1, ultrasonic vibrators C2 and C3 were set. The ultrasonic transducer C2 has the joint material according to the present invention, and corresponds to Comparative Example 2 (the ultrasonic transducer 1) described above. The ultrasonic vibrator C3 uses silicone TSE3663 as a filler, and corresponds to one having an average porosity of 80%, which is the most preferable in the present invention. The variation with respect to the average porosity of both the ultrasonic transducers C2 and C3 was ± 10%.

  Each element factor (directivity) of each of the ultrasonic transducers C1, C2, and C3 was determined using piezoelectric wave analysis software “PZFlex” manufactured by Weidlinger Associates. More specifically, when the ultrasonic transducer is driven by an impulse and scanned in a fan shape around the sound emission point at the acoustic focal length in the elevation direction, the angle at which the amplitude of the echo pulse becomes the maximum value, the maximum angle The angle at which the value becomes -3 dB from the value and the angle at which the value becomes -6 dB from the maximum value were obtained.

  The maximum value is 0 ° because it is in the elevation direction (the front of the ultrasonic transducer). It can be seen that the larger the angle at -3 dB and the angle at -6 dB, the stronger the echo pulse is emitted over a wider range. Table 1 shows the acoustic impedance Za of the joint members of the ultrasonic transducers C1, C2, and C3 and the result of the simulation.

  In Table 1, “0 ° (dB)” indicates the front (0 °) of the ultrasonic transducers C2 and C3 when the sensitivity (the maximum value) at the front of the ultrasonic transducer C1 is “0 dB”. Represents the relative sensitivity. Further, “−3 dB (°)” and “−6 dB (°)” represent angles (°) when the relative sensitivities are −3 dB and −6 dB, respectively, in each ultrasonic transducer.

  As shown in Table 1, in the ultrasonic transducers C2 and C3 having the joint material including the bubbles dispersed uniformly, the numerical values of the sensitivity and the directivity are smaller than those of the ultrasonic transducer C1. Therefore, it can be seen that an ultrasonic probe with less variation in sensitivity and directivity can be obtained. Further, any numerical value and sensitivity of the directivity of the ultrasonic transducer C3 having a higher porosity of the joint material is higher than that of the ultrasonic transducer C2. Therefore, it can be seen that the higher the porosity due to the uniformly dispersed bubbles in the joint material, the higher the sensitivity and the better the directivity of the ultrasonic probe.

  According to the present invention, it is possible to provide an ultrasonic probe with small variations in sensitivity and directivity and good sensitivity and directivity. Therefore, according to the present invention, further spread of the ultrasonic imaging apparatus is expected.

10-14, 130 Piezoelectric body 11a First piezoelectric plate 11b Second piezoelectric plate 11c Third piezoelectric plate 20, 21a-21c, 22-24, 61-64, 140, 141 Groove 30 Bubbles 40-42, 150 Joint material 50 ~ 53,160 Acoustic matching layer 100 Ultrasonic transducer 110 Backing layer 120 Flexible printed circuit board (FPC)
170 acoustic lens 200 ultrasonic imaging apparatus 201 apparatus main body 202 ultrasonic probe 203 cable 204 input section 205 control section 206 transmission section 207 reception section 208 image processing section 209 display section 210 holder 211 connector

Claims (12)

A groove forming step of forming a groove for partitioning the piezoelectric body into element units in the piezoelectric body,
Filling the grooves with unexpanded particles,
Foaming the unfoamed particles filled in the grooves,
A step of filling the groove after the unfoamed particles are foamed with an uncured filler having curability,
And curing the filler filled in the groove, only including,
Before the foaming step, the method has a step of filling the grooves with spacer particles.
Manufacturing method of ultrasonic transducer. The method according to claim 1, wherein the spacer particles are filled in the groove in a state where the spacer particles are mixed with the unfoamed particles . Further comprising a step of bonding an acoustic matching layer to the piezoelectric body before forming the groove,
The groove forming step is a step of forming a groove that partitions both the piezoelectric body and the acoustic matching layer into the element units.
A method for manufacturing the ultrasonic transducer according to claim 1. A step of bonding an acoustic matching layer to the piezoelectric body after curing the filler,
Forming a further groove in the acoustic matching layer that partitions the acoustic matching layer in a section corresponding to the element unit;
Filling the further grooves with unexpanded particles;
Foaming the unfoamed particles filled in the further groove,
Filling the uncured filler having curability in the further groove after the unfoamed particles are expanded,
Curing the filler filled in the further groove;
The method for manufacturing an ultrasonic transducer according to claim 1, further comprising: An ultrasonic vibrator manufactured by the manufacturing method according to claim 1. An ultrasonic probe comprising the ultrasonic transducer according to claim 5 and an acoustic lens. Piezoelectric body, a groove that partitions the piezoelectric body into element units, and a joint material filling the groove, an ultrasonic vibrator having:
The joint material includes bubbles and spacer particles ,
The air bubbles are constituted by expanded particles contained in the joint material,
The average porosity in the ultrasonic transducer of the joint material is 10% or more.
Ultrasonic transducer. The ultrasonic transducer according to claim 7 , further comprising an acoustic matching layer bonded to the piezoelectric body. The acoustic matching layer further includes a further groove that partitions the acoustic matching layer into element units, and a further joint material that fills the further groove.
The further joint material includes air bubbles,
The bubbles contained in the further joint material are constituted by expanded particles contained in the joint material,
An average porosity of the additional joint material in the acoustic matching layer is 10% or more;
An ultrasonic transducer according to claim 8 . The ultrasonic transducer according to claim 9 , wherein the further groove communicates with a part or all of a groove that divides the piezoelectric body in a stacking direction of the piezoelectric body and the acoustic matching layer. An ultrasonic probe comprising: the ultrasonic transducer according to any one of claims 7 to 10 ; and an acoustic lens bonded to the acoustic matching layer. An ultrasonic imaging apparatus comprising the ultrasonic probe according to claim 11 .