JP7625897B2 - Ultrasound transducer, ultrasound probe, and ultrasound diagnostic device - Google Patents

Description

The present invention relates to an ultrasonic transducer, an ultrasonic probe, and an ultrasonic diagnostic device.

An ultrasound diagnostic device is a device that performs diagnosis by applying an ultrasound probe to or inserting it into a subject to be examined, including humans and other animals, irradiating the subject with ultrasound, and receiving and analyzing the reflected waves. With this ultrasound diagnostic device, it is possible to obtain images or videos of, for example, the shape and movement of biological tissue. Ultrasound diagnostic devices have the advantage that they are highly safe and can be used for repeated examinations.

The ultrasound probe used in the ultrasound diagnostic device has built-in ultrasound transducers for transmitting and receiving ultrasound waves. The ultrasound transducers receive electrical signals (transmission signals) from the diagnostic device, convert the received transmission signals into ultrasonic signals, and transmit them. They also receive ultrasonic waves reflected within the subject under test, convert them into electrical signals (reception signals), and transmit them to the diagnostic device.

An ultrasonic transducer includes a piezoelectric material for converting signals into ultrasonic waves and converting received ultrasonic waves into electrical signals, a matching layer for matching the acoustic impedance between the piezoelectric material and the object being inspected, and an acoustic lens for focusing ultrasonic waves at a desired position. In order to increase the directivity of such ultrasonic transducers, the piezoelectric material in the piezoelectric material has traditionally been divided into multiple regions and a filler material has been placed between these regions. The filler material can reduce damage to the piezoelectric material due to external impacts and crosstalk between adjacent piezoelectric materials.

For example, Patent Document 1 proposes filling the gaps between piezoelectric materials with an epoxy resin having a predetermined bulk modulus. Patent Document 2 proposes filling the gaps between piezoelectric materials with a silicone resin.

JP 2016-25611 A Japanese Unexamined Patent Publication No. 63-164700

The inventors have studied and found that, as in Patent Document 1, placing a relatively hard resin such as epoxy resin between piezoelectric materials increases the mechanical strength of the ultrasonic transducer and improves its durability against external impacts. However, there is a problem that the directionality of the ultrasonic transducer is easily reduced. On the other hand, as in Patent Document 2, placing a relatively soft resin such as silicone resin between piezoelectric materials has a good directionality of the ultrasonic transducer, but there is a problem that the mechanical strength of the ultrasonic transducer cannot be sufficiently increased.

The present invention has been made in consideration of these problems. The purpose of the present invention is to provide an ultrasonic transducer that has high mechanical strength and good directionality, as well as an ultrasonic probe and ultrasonic diagnostic device that include the same.

The present invention provides the following ultrasonic transducer.
An ultrasonic transducer comprising a piezoelectric material including a piezoelectric material and a matching layer disposed on the piezoelectric material, wherein the piezoelectric material further has at least one first groove dividing the piezoelectric material into a plurality of regions, the first groove of the piezoelectric material being filled with a filler including an epoxy resin and an organic filler, and a cumulative percentage 10% value in a cumulative particle size distribution of the organic filler is 0.9 μm or more.

The present invention also provides an ultrasound probe including the above-mentioned ultrasound transducer. Furthermore, the present invention also provides an ultrasound diagnostic device including the above-mentioned ultrasound probe.

The present invention provides an ultrasonic transducer with high mechanical strength and good directionality, as well as an ultrasonic probe and ultrasonic diagnostic device that include the ultrasonic transducer.

FIG. 1 is a cross-sectional view showing an example of the overall structure of an ultrasonic transducer according to an embodiment of the present invention. FIG. 2 is a plan view illustrating the structure of the piezoelectric material of the ultrasonic transducer shown in FIG. FIG. 3 is a diagram showing the configuration of an ultrasonic diagnostic apparatus including an ultrasonic transducer according to an embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

1. Ultrasonic transducer The present invention relates to an ultrasonic transducer for use in an ultrasonic diagnostic device having an ultrasonic probe as described below. The ultrasonic transducer of the present invention may have at least a piezoelectric material and a matching layer, but usually has a backing material, an electric terminal lead-out layer, an acoustic lens, etc. FIG. 1 is a cross-sectional view showing an example of the overall structure of an ultrasonic transducer 100 according to an embodiment of the present invention. As shown in FIG. 1 of this embodiment, the ultrasonic transducer 100 includes at least a backing material 110, an electric terminal lead-out portion (flexible printed circuit board) 120 arranged on the backing material 110, a piezoelectric material 130 arranged on the electric terminal lead-out portion 120, a matching layer 140 arranged on the piezoelectric material 130, and an acoustic lens 150 arranged on the matching layer 140. The piezoelectric material 130 has a piezoelectric material 130a and at least one first groove 130b that divides the piezoelectric material 130a into a plurality of regions, and the first groove 130b is filled with a filler 160. In this embodiment, the matching layer 140 is composed of three layers, and a part of the matching layer 140 (the first matching layer 140a and the second matching layer 140b) has a second groove 140d connected to the first groove 130b, and the second groove 140d is also filled with a filler 160. Signal electrodes 170a and 170b are disposed on the electrical terminal lead-out portion 120 side and the matching layer 140 side of the piezoelectric material 130, respectively.

As mentioned above, in conventional ultrasonic transducers, it has been proposed to fill the spaces between the piezoelectric material divided into multiple regions with epoxy resin, silicone resin, or the like. However, when epoxy resin is used, the hardness of the filler is high and ultrasonic waves are easily transmitted, so the directionality of the resulting ultrasonic transducer tends to be low. On the other hand, when silicone resin is used, the strength of the filler is insufficient and it easily deforms when subjected to mechanical shock due to being dropped, etc., resulting in an issue that the piezoelectric material cannot be adequately protected.

Therefore, in this embodiment, a filler 160 containing an epoxy resin and an organic filler is placed in the first groove 130b of the piezoelectric material 130 and the second groove 140d of the matching layer 140. In addition, the cumulative percentage 10% value in the cumulative particle size distribution of the organic filler is adjusted to be 0.9 μm or more.

When the filler 160 contains epoxy resin in this way, the hardness of the filler 160 becomes sufficiently high, and even if it receives an external impact, the piezoelectric material 130 is less likely to be affected. On the other hand, when the filler 160 contains an organic filler having the above-mentioned cumulative particle size distribution, the ultrasonic waves are attenuated or scattered by the organic filler. Therefore, ultrasonic waves are less likely to be transmitted between adjacent piezoelectric materials 130a, and not only the mechanical strength but also the directionality is improved.

The components of the ultrasonic transducer 100 of this embodiment are described below. In this specification, the acoustic lens 150 side of the ultrasonic transducer is also referred to as the top side, and the backing material 110 side is also referred to as the back side.

(Backing material)
The backing material 110 is a member for supporting an electric terminal outlet 120, which will be described later, the piezoelectric material 130, etc., and also functions as a member for attenuating ultrasonic waves traveling from the piezoelectric material 130 to the rear surface side.

In this embodiment, the backing material 110 is composed of a single layer, but the backing material 110 may be composed of multiple layers. In addition, the backing material 110 of this embodiment has multiple grooves (not shown) on the interface side with the electrical terminal outlet 120. The planar shape of the groove is the same as the planar shape of the first groove 130b formed in the piezoelectric material 130 described below, and the groove is connected to the first groove 130b. In addition, the grooves of the backing material 110 are filled with the filler material 160 described below. However, the backing material 110 does not have to have a groove. On the other hand, the groove may extend from the electrical terminal outlet 120 side to the back side of the backing material 110.

The material of the backing material 110 is not particularly limited, and examples include organic materials such as synthetic rubber, natural rubber, epoxy resin, silicone resin, and thermoplastic resin filled with a material for adjusting the acoustic impedance, inorganic materials such as Macol glass, and organic-inorganic composite materials. The backing material 110 may also be composed of a porous material having fine voids inside.

Here, the shape of the backing material 110 is not particularly limited as long as it can attenuate the transmitted ultrasonic waves.

(Electrical terminal outlet)
The electrical terminal lead-out portion 120 is a member for transmitting signals to the piezoelectric material 130a in the piezoelectric material 130 via the signal electrodes 170a, 170b, and for receiving signals from the piezoelectric material 130 via the signal electrodes 170a, 170b. The electrical terminal lead-out portion 120 is disposed between the backing material 110 and the piezoelectric material 130 described below. It is also electrically connected to an external power source, a diagnostic device, and the like.

In this embodiment, the electrical terminal outlet 120 includes a flexible printed circuit board (hereinafter also referred to as "FPC"), which is divided by a number of grooves (not shown). The FPC has wiring that serves as electrodes for the piezoelectric material 130. The FPC may be a commercially available product as long as it has an appropriate pattern. The planar shape of each groove is the same as the planar shape of the first groove 130b of the piezoelectric material 130 described below, and the grooves are connected to the first groove 130b. The grooves are filled with a filler 160 described below.

(Piezoelectric material)
The piezoelectric material 130 includes a piezoelectric material 130a arranged on the electrical terminal outlet 120 (in this embodiment, on the electrical terminal outlet 120 via the signal electrode 170a) and a first groove 130b dividing the piezoelectric material 130a into multiple regions.

The planar shape of the piezoelectric material 130 is shown in FIG. 2. FIG. 2 shows the shape of the piezoelectric material 130 when the signal electrode 170b, the matching layer 140, and the acoustic lens 150 are removed from the ultrasonic transducer 100. In the piezoelectric material 130, a first groove 130b is provided to divide the piezoelectric material 130a. The first groove 130b divides the piezoelectric material 130a as long as the first groove 130b divides the area of the piezoelectric material 130a on the matching layer 140 side into multiple areas, and for example, the divided piezoelectric materials 130a may be connected to each other on the electrical terminal outlet 120 side.

In this embodiment, the shapes of the multiple piezoelectric materials 130a divided by the first grooves 130b are all the same. However, the shape of each piezoelectric material 130a is appropriately selected depending on the application of the ultrasonic transducer 100, and they do not all need to be the same shape. Also, in this embodiment, the shape of the piezoelectric material 130a divided by the first grooves 130b is a rectangular parallelepiped, but the shape of the piezoelectric material 130a divided by the first grooves 130b is not limited to a rectangular parallelepiped, and is not particularly limited as long as it is possible to oscillate ultrasonic waves in a desired direction.

The thickness of the piezoelectric material 130 is appropriately selected depending on the type of ultrasonic transducer and the frequency at which the ultrasonic transducer oscillates, but is, for example, 50 μm or more and 400 μm or less.

The width of each of the first grooves 130b in the piezoelectric material 130 is 15 to 45 μm. When the piezoelectric material 130a is not completely divided by the first grooves 130b, the depth of the first grooves 130b is preferably about 80 to 90% of the thickness of the piezoelectric material 130. On the other hand, when the piezoelectric material 130a constituting the piezoelectric material 130 is completely divided by the first grooves 130b and no grooves are provided in the matching layer 140, it is preferable that the depth of the grooves, which is the sum of the first grooves 130b, the grooves (not shown) formed in the electrical terminal extraction portion 120, and the grooves formed in the backing material 110, is 10 to 100 μm longer than the thickness of the piezoelectric material 130a. On the other hand, when the piezoelectric material 130a constituting the piezoelectric material 130 is completely divided by the first groove 130b and a groove is also provided in the matching layer 140, it is preferable that the depth of the grooves including the first groove 130b, the second groove 140d described below, the groove (not shown) formed in the electrical terminal outlet 120, and the groove formed in the backing material 110 is 10 to 100 μm longer than the thickness of the piezoelectric material 130a and the thickness of the matching layer to be cut. The distance between adjacent first grooves 130b is 150 to 600 μm, but can be changed as appropriate.

Examples of the piezoelectric material 130a include piezoelectric ceramics such as lead zirconate titanate (PZT)-based piezoelectric ceramics; piezoelectric single crystals such as lead magnesium niobate-lead titanate solid solution (PMN-PT) and lead zinc niobate-lead titanate solid solution (PZN-PT); and composite piezoelectric materials made by combining these materials with polymeric materials.

The multiple signal electrodes 170a and 170b arranged on both sides of the piezoelectric material 130 are electrodes for applying a voltage to the piezoelectric material 130. There are no particular limitations on the signal electrodes 170a and 170b as long as they are electrically connected to the electrical terminal lead-out portion 120 described above and can sufficiently transmit and receive signals between the piezoelectric material 130, and they can be layers made of gold, silver, copper, etc., for example.

(Matching layer)
The matching layer 140 is a layer disposed on the piezoelectric material 130 (in this embodiment, on the signal electrode 170b of the piezoelectric material 130a) and serves to match the acoustic characteristics between the piezoelectric material 130 and the acoustic lens 150. The matching layer 140 may be composed of a single layer, but is usually composed of multiple layers with different acoustic impedances. There is no particular limit to the number of layers in the matching layer, and two or more layers are generally used. As shown in FIG. 1, in this embodiment, the matching layer 140 is a laminate including a first matching layer 140a, a second matching layer 140b, and a third matching layer 140c.

The acoustic impedance of each layer constituting the matching layer 140 can be adjusted as appropriate depending on the components constituting each layer. For example, if each of the matching layers 140a, 140b, and 140c is a layer containing a resin and a filler, the acoustic impedance of each layer can be adjusted by adjusting the type and amount of these fillers. Note that each of the matching layers 140a, 140b, and 140c may be a layer containing the same resin and the same filler, or may be a layer containing different resins and/or different fillers. Furthermore, the thickness of each layer may be the same or different.

The type of resin and the type of filler contained in the matching layer 140 are not particularly limited. Examples of resins include epoxy resins, etc. On the other hand, examples of fillers include inorganic fine particles such as ferrite, and organic fine particles such as silicone fine powder. In this embodiment, the composition of the third matching layer 140c is different from the composition of the filler 160 described below. However, the composition of the third matching layer 140c may be the same as the composition of the filler 160.

In this embodiment, the first matching layer 140a and the second matching layer 140b have a second groove 140d connected to the first groove 130b of the piezoelectric material 130 described above. The planar shape of the second groove 140d is the same as the planar shape of the first groove 130b. On the other hand, the top layer of the matching layer 140 closest to the acoustic lens 150 (the third matching layer 140c in this embodiment) does not have the second groove 140d. However, this is not limited to this embodiment, and the top layer (the third matching layer 140c) may have the second groove 140d. Also, the top layer may have a groove that communicates with only a portion of the multiple second grooves 140d. In this case, the groove may be filled with the filler 160, may be a void, or may be filled with a filler having a composition different from that of the filler 160.

(Acoustic Lens)
The acoustic lens 150 is a member for focusing ultrasonic waves transmitted from the piezoelectric material 130. As shown in Fig. 1, in this embodiment, the acoustic lens 150 is a cylindrical type acoustic lens that extends in the Y direction in Fig. 1 and protrudes in the Z direction. The cross-sectional shapes perpendicular to the X direction are all the same. In addition, the acoustic lens 150 focuses ultrasonic waves oscillated by each piezoelectric material 130a in the Z direction and emits them to the outside of the ultrasonic transducer 100.

The acoustic lens 150 is made of a material having acoustic properties suitable for the object to be inspected, such as a living body. For example, it is preferable that the acoustic lens 150 is made of a material, such as silicone rubber, that has an acoustic impedance relatively close to that of the object to be inspected.

(Filling material)
The filler 160 is a material filled in the first groove 130b of the piezoelectric material 130 described above, the second groove 140d of the matching layer 140, and the grooves of the backing material 110 and the electrical terminal outlet portion 120, and is a material for suppressing ultrasonic interference between adjacent piezoelectric materials 130a to increase the directionality of the ultrasonic transducer 100, increasing the strength of the ultrasonic transducer 100, and increasing the mechanical resistance to external impacts.

It is preferable that the filler 160 is filled without gaps in the first groove 130b of the piezoelectric material 130, the second groove 140d of the matching layer 140, the groove of the backing material 110, and the groove of the electrical terminal lead-out portion 120. However, if necessary, some voids may be present. Furthermore, the first groove 130b of the piezoelectric material 130, the second groove 140d of the matching layer 140, the groove of the backing material 110, and some of the grooves of the electrical terminal lead-out portion 120 may be filled with a filler having a composition different from the filler 160 containing the epoxy resin and organic filler.

The filler 160 contains an epoxy resin and an organic filler having a cumulative percentage 10% value in the cumulative particle size distribution of 0.9 μm or more. In the filler 160, the epoxy resin acts as a binder, and the organic filler is dispersed in the binder.

The epoxy resin contained in the filler 160 is not particularly limited, and examples include bisphenol type epoxy resins such as bisphenol A type and bisphenol F type; novolac type epoxy resins such as resol novolac type and phenol modified novolac type; polycyclic aromatic type epoxy resins such as naphthalene structure containing type, anthracene structure containing type, and fluorene structure containing type; hydrogenated alicyclic epoxy resins; liquid crystalline epoxy resins, etc. The filler 160 may contain only one type of epoxy resin, or two or more types.

Of the above epoxy resins, from the viewpoint of chemical resistance, epoxy resins having multiple epoxy groups are preferred, and the number of epoxy groups in one molecule can be, for example, 3 to 4. In addition, those with a high glass transition temperature (Tg) and high crosslinking density are also preferred. Therefore, of the above, novolac-type epoxy resins are preferred.

The amount of the epoxy resin in the filler 160 is preferably 40 parts by mass or more and 60 parts by mass or less, more preferably 40 parts by mass or more and 55 parts by mass or less, and even more preferably 40 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total amount of the filler 160. When the proportion of the epoxy resin is 40 parts by mass or more, the strength of the ultrasonic transducer is increased. On the other hand, when the proportion of the epoxy resin is 60 parts by mass or less, the amount of the organic filler becomes relatively large, and the directionality of the ultrasonic transducer 100 becomes good.

On the other hand, the organic filler is not particularly limited as long as it contains an organic resin and is a particle having a specified particle size, but it is preferable that the organic filler is an elastomer particle. Examples of the elastomer contained in the elastomer particles include silicone, urethane, acrylic, butadiene, etc.

Here, the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler is 0.9 μm or more. When the 10% cumulative percentage value of the organic filler is 0.9 μm or more, as described above, excellent directionality can be obtained while maintaining the durability (mechanical strength) of the ultrasonic transducer.

The cumulative particle size distribution is calculated based on the particle diameter of about 200 particles measured by a scanning electron microscope (SEM). As a method for separating the organic filler from the filler composition before curing, the epoxy resin in the filler composition is dissolved or removed with an organic solvent such as ethanol, and only the organic filler is taken out. On the other hand, when measuring the cumulative particle size distribution from the filler 160, the ultrasonic transducer 100 is cut out along the Y direction using a dicing saw or a diamond cutter, and the filler 160 is subjected to elemental analysis by energy dispersive X-ray analysis (EDS) or wavelength dispersive X-ray analysis (WDS). As a result, the element derived from the organic filler (Si in the case of silicone) is mapped, and the organic filler is identified. Then, the particle size of the identified organic filler is measured by a scanning electron microscope (SEM), and the cumulative particle size distribution is calculated. The 10% cumulative percentage value refers to the particle size at a cumulative frequency of 10% from the smallest particle size side in the cumulative particle size distribution measured by the above method (hereinafter also referred to as " _D10 "). Furthermore, when the filler 160 contains multiple organic fillers, the cumulative particle size distribution is measured in a mixed state of all of these.

In addition, in this embodiment, it is preferable that the particle size distribution of the organic filler is wide. When the particle size distribution of the organic filler is wide, a large number of large and small particles are present, and small particles tend to be filled between the large particles. As a result, the path of ultrasonic waves transmitted from one piezoelectric material 130a to an adjacent piezoelectric material 130a tends to be interrupted. As a result, ultrasonic waves are less likely to be transmitted between adjacent piezoelectric materials 130a, and the directionality of the ultrasonic transducer 100 tends to be high.

The 50% cumulative percentage value and 90% cumulative percentage value in the cumulative particle size distribution are indicators of the broad particle size distribution of the organic filler. The greater the difference between the 50% cumulative percentage value and the 90% cumulative percentage value and the 10% cumulative percentage value, the broader the particle size distribution. The 90% cumulative percentage value is preferably 1.5 μm or more and 3.5 μm or less, more preferably 1.75 μm or more and 3.0 μm or less, and more preferably 2.0 μm or more and 2.5 μm or less. When the 90% cumulative percentage value is within this range, it becomes easier to obtain excellent directionality while maintaining the durability (strength) of the ultrasonic transducer.

Here, the filler 160 may contain only one type of organic filler, but preferably contains two or more types of organic fillers. When the filler 160 contains two or more types of organic fillers, it becomes easier to satisfy the above-mentioned 10% cumulative percentage value, 50% cumulative percentage value, and 90% cumulative percentage value.

At least one of the multiple organic fillers is preferably an organic filler having a structure capable of reacting with epoxy resin (hereinafter, also referred to as a "reactive organic filler"). Here, the structure capable of reacting with epoxy resin refers to an epoxy group, an amino group, or the like. When the filler 160 contains a reactive organic filler, the dispersibility of the organic filler in the filler 160 is improved, and the directionality of the ultrasonic transducer is improved. Note that whether the filler 160 contains a reactive organic filler, that is, whether the organic filler has a structure capable of reacting with epoxy resin, can be confirmed by observing the cross section of the filler 160 with a scanning electron microscope (SEM) or the like. For example, when the filler 160 contains a reactive organic filler, the epoxy resin and the reactive organic filler are in close contact with each other, and no gaps are observed. On the other hand, when the filler 160 does not have a structure capable of reacting with epoxy resin, gaps are observed between the epoxy resin and the filler.

The filler 160 may contain only one type of reactive organic filler, or may contain two or more types.

The particle diameter of the reactive organic filler is preferably 0.1 μm or more and 5.5 μm or less, more preferably 0.1 μm or more and 5.0 μm or less, and even more preferably 0.1 μm or more and 4.5 μm or less. The average particle diameter is measured by a scanning electron microscope. On the other hand, if the average particle diameter of the reactive organic filler is 1.2 μm or more, it becomes easier to satisfy the above-mentioned cumulative particle size distribution.

The amount of reactive organic filler is preferably 10 parts by mass or more and 30 parts by mass or less, more preferably 10 parts by mass or more and 25 parts by mass or less, and even more preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the total amount of organic filler. When the proportion of reactive organic filler is 10 parts by mass or more, the dispersibility of the organic filler in the filler 160 is good. On the other hand, when the proportion of reactive organic filler is 30 parts by mass or less, the viscosity of the filler composition when preparing the filler 160 does not increase excessively, and the above-mentioned first groove 130b, second groove 140d, etc. can be filled without gaps.

As mentioned above, reactive organic fillers have a high affinity with binder resins, so if a large amount is used, it may become difficult to fill the first grooves 130b etc. with the filler 160. Therefore, it is preferable that the organic filler contains, in addition to the reactive organic filler, a filler that is not reactive with epoxy resins and has a particle size different from that of the reactive organic filler (hereinafter also referred to as "non-reactive organic filler").

Examples of non-reactive organic fillers include silicone particles, urethane particles, acrylic particles, butadiene, etc. Among these, silicone particles are particularly preferred because they can maintain the elastic modulus of rubber even at low temperatures. The filler 160 may contain only one type of non-reactive organic filler, or may contain two or more types.

The particle diameter of the non-reactive organic filler is preferably 0.3 μm or more and 10.0 μm or less, more preferably 0.5 μm or more and 7.5 μm or less, and preferably 0.7 μm or more and 5.0 μm or less. The average particle diameter is measured by a scanning electron microscope. If the average particle diameter of the non-reactive organic filler is 2.0 μm or more, it becomes easier to satisfy the above-mentioned cumulative particle size distribution.

The non-reactive organic filler is preferably 70 parts by mass or more and 90 parts by mass or less, more preferably 75 parts by mass or more and 90 parts by mass or less, and even more preferably 80 parts by mass or more and 90 parts by mass or less, relative to 100 parts by mass of the total amount of the organic filler. When the proportion of the non-reactive organic filler is 90 parts by mass or more, the viscosity of the filler composition when preparing the filler 160 does not increase excessively, and the filler 160 can be easily formed without gaps in the first groove 130b and the second groove 140d described above. On the other hand, when the proportion of the non-reactive organic filler is 70 parts by mass or less, the amount of the reactive organic filler becomes sufficiently large, and the organic filler is easily dispersed uniformly in the filler 160.

The content (total amount) of the organic filler is preferably 40 parts by mass or more and 60 parts by mass or less, more preferably 45 parts by mass or more and 60 parts by mass or less, and even more preferably 50 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the filler. When the proportion of the organic filler is 60 parts by mass or more, the directionality of the ultrasonic transducer 100 is increased. On the other hand, when the proportion of the organic filler is 40 parts by mass or less, the proportion of the epoxy resin becomes sufficiently large, and the strength of the ultrasonic transducer 100 is increased.

In addition to the epoxy resin and organic filler, the filler 160 may contain other components as necessary, as long as the purpose and effect of the present invention are not impaired. Examples of other components include coupling agents. When the filler 160 contains a coupling agent, the dispersibility of the non-reactive organic filler described above is improved. Examples of coupling agents include silane coupling agents containing epoxy groups or amino groups, titanium coupling agents, etc.

The coupling agent may be a commercially available product, examples of which include A-186, A-187, A-1871, A-1100, A-1110, A-1120, A-2120, and Y-9669 (all trade names, manufactured by Momentive Corporation); KBM-602, KBM-603, KBM-903, KBE-903, KBE-9103P, KBM-573, KBM-575, KBM-303, KBM-402, KBM-403, KBE-402, and KBE-403 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.); DOWSIL Z-6610 Silane, DOWSIL Z-6011 Silane, and XIAMETER OFS-6020. Silane, DOWSIL Z-6094 Silane, DOWSIL Z-6883 Silane, XIAMETER OFS-6032 Silane, DOWSIL Z-6269 Silane, DOWSIL SZ 6032 Silane, XIAMETER OFS-6040 Silane, DOWSIL Z-6044 Silane, DOWSIL Z-6043 Silane (all trade names, DOWSIL and XIAMETER are registered trademarks, manufactured by Dow Corning Toray Co., Ltd.); S310, S320, S330, S340, S350, S510, S530 (all trade names, manufactured by JNC Corporation); PLENACT Contains 44 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), which contains an amino group.

Filler 160 may contain a small amount of inorganic particles, but the amount of inorganic particles is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the total amount of filler 160. If the amount of inorganic particles in filler 160 is 1 part by mass or less, the amount of epoxy resin and organic filler will be relatively sufficient, making it easier to obtain the polarity and directionality described above.

(Method of manufacturing ultrasonic transducer)
The method for manufacturing the ultrasonic transducer described above is not particularly limited as long as it can form the above-mentioned structure. An example is shown below, but the method is not limited to this method.

In this manufacturing method, a backing material without a groove, a flat electrical terminal lead-out portion without a groove, and a flat piezoelectric material having signal electrodes formed on both sides and no first groove are bonded together (bonding process). A matching layer is then formed on the piezoelectric material (signal electrode) (matching layer forming process), and multiple grooves are formed from the matching layer side toward the backing material (groove forming process). After that, the grooves formed in the groove forming process are filled with a filler composition and cured (filler forming process), and an acoustic lens is attached onto the matching layer (acoustic lens attachment process). Other processes may be included as necessary.

- Bonding process In the bonding process, a flat backing material without a groove, an electric terminal lead-out part having a desired circuit or the like arranged on a single film without a groove, and a flat piezoelectric material having signal electrodes formed on both sides and having no first groove are bonded together. The order of bonding is not particularly limited, and the backing material and the electric terminal lead-out part may be bonded together first, or the piezoelectric material and the electric terminal lead-out part may be bonded together. The method of bonding these is not particularly limited, and for example, they may be bonded together using an adhesive or the like.

The method of forming the signal electrodes on the surface of the piezoelectric material is not particularly limited. For example, they may be formed by evaporating or sputtering gold and silver. Silver may also be baked onto the piezoelectric material. Furthermore, a conductor such as copper may be attached to the piezoelectric material and patterned.

Matching layer forming process In the matching layer forming process, a matching layer is formed on the piezoelectric material (here, one of the signal electrodes). The method of forming the matching layer is not particularly limited, and previously prepared matching layers may be attached one by one, or multiple matching layers may be previously stacked and then attached to the piezoelectric material. Furthermore, a process of applying a matching layer composition onto the piezoelectric material and curing it may be repeated. The matching layer formed in the matching layer forming process does not have a second groove.

Note that although all of the matching layers may be formed in the matching layer formation process, if the second groove is to be provided only in a portion of the matching layer, only the matching layer in which the groove is to be provided is formed.

Groove Forming Step In the groove forming step, grooves are formed from the matching layer side to the backing material. The method of forming the grooves is not particularly limited, and is appropriately selected depending on the widths of the first and second grooves described above, the thickness of the piezoelectric material, etc. For example, cutting may be performed with a dicing saw or a diamond cutter, or cutting may be performed by Micro Electro Mechanical Systems (MEMS) processing.

Filler Forming Step In the filler filling step, a filler composition is introduced into the groove formed in the above-mentioned groove forming step and hardened. At this time, in addition to filling the groove with the filler composition, the filler composition may be applied to the above-mentioned matching layer and hardened to form a part of the matching layer (for example, the above-mentioned third matching layer 140c). In this case, the matching layer formed in the filler forming step (for example, the above-mentioned third matching layer 140c) does not have the second groove 140d.

The method for filling the grooves with the filler composition is not particularly limited, and the filler composition may be injected, for example, with a spatula or the like. The method for forming the filler composition on the matching layer is also not particularly limited, and the filler composition may be applied, for example, with a spatula or the like used when injecting the filler composition into the grooves.

The filler composition is a composition containing the above-mentioned epoxy resin precursor (hereinafter also referred to as "prepolymer"), the above-mentioned organic filler, and, if necessary, a curing agent, a coupling agent, etc.

Examples of prepolymers include the epoxy resin monomers and oligomers described above. The organic fillers and coupling agents are the same as those described above.

On the other hand, examples of curing agents for curing the prepolymer include triazine compounds such as ethylenediamine, triethylenediamine, hexamethylenediamine, and 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine; 1,8-diazabicyclo[5,4,0]undecene-7 (DBU); triethylenediamine; benzyldimethylamine; triethanolamine; linear aliphatic polyamines; aliphatic polyamines such as cyclic aliphatic polyamines and aliphatic aromatic polyamines; aromatic amines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone; and modified amines such as amine adducts and ketimines.

Examples of the above-mentioned linear aliphatic polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine and diethylaminopropylamine.

Examples of the cyclic aliphatic polyamines include N-aminoethylpiperazine, Lamiron C-260, Araldit HY-964, menthene diamine, isophorone diamine, SCure 211, SCure 212, Wondamin HM, and 1.3BAC (all manufactured by ThreeBond Co., Ltd.).

Examples of the above aliphatic aromatic polyamines include m-xylylenediamine, Shawamine X, Amine Black, Shawamine Black, Shawamine N, Shawamine 1001 and Shawamine 1010 (all manufactured by ThreeBond Co., Ltd.).

The method for hardening the filler composition is appropriately selected depending on the type of hardener in the filler composition, but it is usually preferable to harden the composition by heating. The heating temperature is appropriately selected. Heating can be performed by a known method, for example, by using a heater or a thermostatic bath.

Acoustic Lens Attachment Step After the filler formation step, an acoustic lens is attached onto the matching layer. There are no particular limitations on the method for attaching the acoustic lens, and it can be attached, for example, with an adhesive or the like.

2. Ultrasonic Probe and Ultrasonic Diagnostic Apparatus The above-mentioned ultrasonic transducer can be used in, for example, an ultrasonic probe 100a and an ultrasonic diagnostic apparatus 10 as shown in Fig. 3. The ultrasonic diagnostic apparatus 10 includes an ultrasonic probe 100a equipped with the above-mentioned ultrasonic transducer, a main body 11, a connector 12, a display 13, and the like.

The ultrasonic probe 100a only needs to include the ultrasonic transducer (not shown) and is connected to the main body 11 via a cable 14 connected to the connector 12.

An electrical signal (transmission signal) from the main body 11 is transmitted to the piezoelectric material of the ultrasound probe 100a via the cable 14. This transmission signal is converted into ultrasound by the piezoelectric material and transmitted into the object being inspected. The transmitted ultrasound is reflected within the object being inspected. A portion of the reflected wave is then received by the piezoelectric material, converted into an electrical signal (received signal), and transmitted to the main body 11. The received signal is converted into image data in the main body 11 of the ultrasound diagnostic device 10 and displayed on the display 13.

An ultrasound diagnostic device equipped with the ultrasound transducer of the above-mentioned embodiment has high directionality and enables accurate diagnosis. Furthermore, the above-mentioned ultrasound transducer has high strength and can withstand impacts such as dropping, so it can be used in ultrasound diagnostic devices in a variety of fields.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these.

1. Preparation of ultrasonic transducer Comparative Example 1
A backing material and a flexible printed circuit board (electrical terminal lead-out portion) were adhered in this order on the fixed plate with an adhesive. A piezoelectric material made of lead zirconate titanate (PZT) measuring 4.6 mm x 42.5 mm and having signal electrodes on both sides was prepared. The piezoelectric material and the flexible printed circuit board were then adhered together so that one of the signal electrodes was adjacent to the flexible printed circuit board.

Next, a dicing saw was used to create grooves perpendicular to the layered surface of each component in the piezoelectric material and flexible printed circuit board. Note that multiple grooves were formed in the piezoelectric material so that they were parallel when viewed in a plane and were equally spaced apart. The width of the groove was 20 μm. At this time, the depth of the groove was adjusted so that the backing material was not completely cut.

Next, the filler composition was prepared as follows: Epoxy resin 1 (product name: C1163A, manufactured by Tesque), organic filler-containing epoxy resin 2 (product name: EP2240, manufactured by Evonik (organic filler surface contains a structure capable of reacting with epoxy resin), filler particle size: 0.1 to 3 μm), amine-based hardener 1 (product name: C1163B, manufactured by Tesque), and amine-based hardener 2 (product name: ST12, manufactured by Mitsubishi Chemical) were mixed in a mass ratio of 33:37:17:13.

The filler composition was then applied to the piezoelectric material with a spatula and vacuum degassed for 3 minutes. Three matching layers (first matching layer, second matching layer, and third matching layer) were formed on the signal electrode of the piezoelectric material. Each matching layer was a hardened product of a mixture of epoxy resin and ferrite or silicone fine powder. After heating at 60°C for 4 hours, an acoustic lens was bonded to the third matching layer with adhesive to obtain ultrasonic transducer 1.

The above filler composition was placed in ethanol, the epoxy resin in the filler composition was removed, and only the organic filler was taken out. The particle diameter of about 200 particles of the organic filler was measured using a scanning electron microscope (SEM), and the particle diameter was calculated based on the measurement results. The cumulative percentage of the cumulative particle size distribution of the organic filler at 10% was determined to be 0.4 μm.

Comparative Example 2
A backing material and a flexible printed circuit board (electrical terminal lead-out portion) were bonded in this order on the fixed plate with an adhesive. A piezoelectric material made of lead zirconate titanate (PZT) measuring 4.6 mm x 42.5 mm and having signal electrodes on both sides was prepared. The piezoelectric material and the flexible printed circuit board were then bonded together so that one of the signal electrodes was adjacent to the flexible printed circuit board. As in Comparative Example 1, two matching layers (first and second matching layers) were formed on the signal electrodes of the piezoelectric material.

Next, a dicing saw was used to create grooves perpendicular to the layered surface of each component in the matching layers (first matching layer and second matching layer), the piezoelectric material layer, and the flexible printed circuit board. Note that multiple grooves were formed so that they were parallel when viewed in a plane and were equally spaced apart. The groove width was 20 μm. At this time, the groove depth was adjusted so that the backing material was not completely cut.

Next, a filler composition was prepared as follows: Silicone resin (product name: KE-1604, manufactured by Shin-Etsu Chemical Co., Ltd.) and amine-based curing agent 3 (product name: CAT1604, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed in a mass ratio of 90:10.

The grooves were filled with the filler composition by applying with a spatula and vacuum degassing for 3 minutes. A third matching layer was then attached and heated at 60°C for 2 hours. After that, an acoustic lens was attached with an adhesive onto the matching layer (third matching layer) to obtain ultrasonic transducer 2.

Comparative Example 3
The filler composition was prepared by mixing epoxy resin 1 (product name: C1163A, manufactured by Tesque), organic filler-containing epoxy resin 2 (product name: EP2240, manufactured by Evonik (the organic filler surface contains a structure capable of reacting with the epoxy resin)), amine-based hardener 1 (product name: C1163B, manufactured by Tesque), and amine-based hardener 2 (product name: ST12, manufactured by Mitsubishi Chemical Corporation) in a mass ratio of 33:37:17:13, and heating the mixture at 60° C. for 4 hours. Except for this, ultrasonic transducer 3 was obtained in the same manner as in Comparative Example 2.

In the same manner as in Comparative Example 1, only the organic filler in the obtained filler was diluted with an organic solvent and extracted, and the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler was determined by a scanning electron microscope (SEM) in the same manner as in Comparative Example 1, and was found to be 0.4 μm.
Comparative Example 4
A filler composition was prepared by adding 30 parts by mass of tungsten trioxide powder to 100 parts by mass of the filler composition of Comparative Example 3, and ultrasonic transducer 4 was produced in the same manner as in Comparative Example 2, except that the filler composition was heated at 60° C. for 4 hours.

Using the same method as in Comparative Example 1, only the organic filler in the resulting filler was diluted with an organic solvent and extracted, and the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler was measured using a scanning electron microscope (SEM) using the same method as in Comparative Example 1, and was found to be 0.4 μm.

Comparative Example 5
A filler composition was prepared by adding 50 parts by mass of a silicone composite powder (product name: KMP-605, manufactured by Shin-Etsu Chemical Co., Ltd., particle size: 0.7 to 5 μm) to 100 parts by mass of the filler composition of Comparative Example 3. The ultrasonic transducer 5 was prepared in the same manner as in Comparative Example 2, except that the filler composition was heated at 60° C. for 4 hours.

Using the same method as in Comparative Example 1, only the organic filler in the resulting filler was diluted with an organic solvent and extracted, and the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler was measured using a scanning electron microscope (SEM) using the same method as in Comparative Example 1, and was found to be 0.8 μm.

Example 1
A filler composition was prepared by adding 75 parts by mass of a silicone composite powder (product name: KMP-605, manufactured by Shin-Etsu Chemical Co., Ltd., particle size: 0.7 to 5 μm) to 100 parts by mass of the filler composition of Comparative Example 3. The ultrasonic transducer 6 was prepared in the same manner as in Comparative Example 2, except that the filler composition was heated at 60° C. for 4 hours.

Using the same method as in Comparative Example 1, only the organic filler in the resulting filler was diluted with an organic solvent and extracted, and the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler was measured using a scanning electron microscope (SEM) using the same method as in Comparative Example 1, and was found to be 0.9 μm.

Example 2
An ultrasonic transducer 7 was produced in the same manner as in Comparative Example 2, except that a filler composition was prepared by adding 100 parts by mass of a silicone composite powder (product name: KMP-605, manufactured by Shin-Etsu Chemical Co., Ltd., particle size: 0.7 to 5 μm) to 100 parts by mass of the filler composition of Comparative Example 3, and heating the composition at 60° C. for 4 hours.

Using the same method as in Comparative Example 1, only the organic filler in the resulting filler was diluted with an organic solvent and extracted, and the 10% cumulative percentage value in the cumulative particle size distribution of the organic filler was measured using a scanning electron microscope (SEM) using the same method as in Comparative Example 1, and was found to be 1.0 μm.

2. Evaluation The directivity and intensity of each of the ultrasonic transducers were evaluated by the following methods. The results are shown in Table 1.

(1) Directivity Evaluation Method An ultrasonic probe including the ultrasonic transducer described above was placed near the water surface of a water tank in which a spherical target was placed. A pulser receiver and an oscilloscope were electrically connected to the ultrasonic probe. The pulser receiver was an ultrasonic pulser receiver: MODEL5900PR manufactured by Olympus Corporation, and the oscilloscope was an oscilloscope: TDS5032 manufactured by TFF.

Then, ultrasonic waves were transmitted from the probe head of the ultrasonic probe immersed in water toward a spherical target, and the reflected waves were received to obtain the directivity of the ultrasonic probe. The directivity was evaluated when the angles between the spherical target and the element in the ultrasonic probe to be measured were set to -40°, -30°, -20°, -10°, 0°, +10°, +20°, +30°, and +40°, specifically, the presence or absence of ripples in the transmission and reception frequency characteristics at each angle. The case where the spherical target and the element in the ultrasonic probe to be measured are located on a straight line was set as 0°. The evaluation was based on the following criteria.
(Evaluation Criteria)
◯: In the transmission and reception frequency characteristics when the angle between the spherical target and the measurement target element of the ultrasonic probe to be measured is ±40°, the absolute value of the difference ΔS between the maximum sensitivity S _MAX and the minimum sensitivity S _MIN of the ripple portion is less than 10 dB. △: In the transmission and reception frequency characteristics when the angle between the spherical target and the measurement target element of the ultrasonic probe to be measured is ±40°, the absolute value ΔS of the difference between the maximum sensitivity S _MAX and the minimum sensitivity S _MIN of the ripple portion is 10 dB or more and less than 20 dB. ×: In the transmission and reception frequency characteristics when the angle between the spherical target and the measurement target element of the ultrasonic probe to be measured is ±40°, the absolute value ΔS of the difference between the maximum sensitivity S _MAX and the minimum sensitivity S _MIN of the ripple portion is 20 dB or more.

(2) Drop test evaluation method An ultrasonic probe having the ultrasonic transducer described above was prepared. Then, a weight with a steel ball at the tip and the same weight as the ultrasonic probe (excluding the cable and connector) was dropped onto the top surface of the acoustic lens of the ultrasonic probe. The weight was dropped from a height 10 cm higher than the acoustic lens, and was increased in 10 cm increments. Each time, the capacitance of the ultrasonic probe was evaluated, and the test was continued until a decrease in capacitance was observed, up to a maximum of 122 cm.
(Evaluation Criteria)
◯: When the capacitance Sa of the ultrasonic transducer after a weight is dropped from a height of 122 cm is compared to the capacitance Sb before the test, the difference Sa-Sb = ΔSc is -5 pF or less for none of the elements. ×: When the capacitance Sa of the ultrasonic transducer after a weight is dropped from a height of 122 cm is compared to the capacitance Sb before the test, the difference Sa-Sb = ΔSc is -5 pF or less for one or more channels of elements.

3. Results

As shown in Table 1 above, when the piezoelectric material has grooves (first grooves) separating the piezoelectric materials, the grooves contain epoxy resin and organic filler, and the 10% cumulative percentage value ( _D10 ) in the cumulative particle size distribution of the organic filler is 0.9 μm or more, the ultrasonic directionality is good and the drop test results are also good (Examples 1 and 2).

On the other hand, even if the filler contained an organic filler, when the cumulative percentage 10% (D ₁₀ ) in the cumulative particle size distribution was less than 0.9 μm, the directionality was likely to be low (Comparative Examples 1, 3 to 5). Also, when the filler was a silicone resin that did not contain an organic filler, the directionality was good, but the drop test results were low (Comparative Example 2).

The ultrasonic transducer of the present invention has high mechanical strength and excellent directionality. Therefore, it is useful for various ultrasonic diagnostic devices, etc.

REFERENCE SIGNS LIST 10 Ultrasonic diagnostic device 11 Main body 12 Connector 13 Display 14 Cable 100 Ultrasonic transducer 100a Ultrasonic probe 110 Backing material 120 Electrode terminal lead-out portion 130 Piezoelectric material 130a Piezoelectric material 130b First groove 140 Matching layer 140a First matching layer 140b Second matching layer 140c Third matching layer (top layer)
140d: second groove; 150: acoustic lens; 160: filling material; 170a, 170b: signal electrodes

Claims (9)

A piezoelectric material including a piezoelectric material;
at least one matching layer disposed on the piezoelectric material;
An ultrasonic transducer comprising:
the piezoelectric material further comprises at least one first groove dividing the piezoelectric material into a plurality of regions;
The width of the first groove is 15 to 45 μm;
the first groove of the piezoelectric material is filled with a filler including an epoxy resin and an organic filler;
the organic filler is an elastomer particle, and includes a reactive organic filler having a particle size of 0.1 to 3 μm and a non-reactive organic filler having a particle size of 0.7 to 10.0 μm;
The total amount of the organic filler is 50 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the filler,
The 10% cumulative percentage in the cumulative particle size distribution of the organic filler is 0.9 μm or more;
Ultrasonic transducer. the matching layer has a second groove connected to the first groove in the piezoelectric material;
The second groove is filled with the filler.
2. The ultrasonic transducer of claim 1. the matching layer is a stack of multiple layers, and a top layer of the multiple layers does not have the second groove;
3. The ultrasonic transducer according to claim 2. The composition of the top layer is the same as the composition of the filler.
4. The ultrasonic transducer according to claim 3. The organic filler contains at least one resin selected from the group consisting of silicone, urethane, acrylic, and butadiene.
The ultrasonic transducer according to any one of claims 1 to 4. the reactive organic filler has a structure on its surface that can react with the epoxy resin;
The ultrasonic transducer according to any one of claims 1 to 5. The filler comprises a coupling agent.
The ultrasonic transducer according to any one of claims 1 to 6. A method comprising the steps of:
Ultrasound probe. The ultrasonic probe according to claim 8,
Ultrasound diagnostic equipment.