Piezoelectric single crystal composite vibrator

Abstract

To provide a piezoelectric single crystal composite resonator with a high electromechanical coupling coefficient and excellent productivity.SOLUTION: A piezoelectric single crystal composite resonator according to the present invention includes multiple piezoelectric single crystal columns, and a resin placed between the piezoelectric single crystal columns, and is a 2-2 type that is polarized in the thickness direction and utilizes an electromechanical coupling coefficient of a vibration mode parallel to the thickness direction, the column of the piezoelectric single crystal includes a column (1) and a column (2) having different widths, when the thickness is t (mm), the width of the column (1) is w1 (mm), and the width of the column (2) is w2 (mm), w1 / t is 0.3 to 0.6, w2 / t is greater than 0.6, and w2 / w1 is 1.5 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric single crystal composite vibrator that has a high electromechanical coupling coefficient and is highly manufacturable. [Background technology]

[0002] Piezoelectric vibrators have been used in devices that have a mechanism for converting electrical signals into displacement, such as ultrasonic equipment, and devices that have a mechanism for converting displacement into electrical signals, such as acceleration sensors. Composite vibrators that combine piezoelectric ceramics with resin (polymer) are known as such vibrators, but in recent years, composite vibrators that use piezoelectric single crystals instead of piezoelectric ceramics have also been developed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2005-139064 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a piezoelectric single crystal composite vibrator, for example, a method is used in which grooves are formed in the piezoelectric single crystal by machining, the grooves are filled with resin, and then the bottom of the groove in the piezoelectric single crystal is polished to expose the surface of the resin filled in the groove. A piezoelectric single crystal composite vibrator obtained by this manufacturing method has the end faces of the resin exposed in two directions, in the x, y, and z directions of the piezoelectric composite vibrator, and is called a 2-2 type piezoelectric single crystal composite vibrator.

[0005] In addition, piezoelectric single crystal composite vibrators are generally required to have a high electromechanical coupling coefficient, and to meet this requirement, it is desirable to narrow the space between the grooves formed in the piezoelectric single crystal and the adjacent grooves, reduce the width of the piezoelectric single crystal pillars located between these grooves (i.e., between the resin in the piezoelectric single crystal composite vibrator), and increase the number of these pillars.

[0006] In order to form many narrow piezoelectric single crystal pillars in a piezoelectric single crystal composite vibrator, it is necessary to form many grooves in the piezoelectric single crystal. However, forming grooves is not easy, and forming many of them requires a considerable amount of processing time. As a result, there are certain limitations on the productivity of piezoelectric single crystal composite vibrators with a high electromechanical coupling coefficient.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric single crystal composite vibrator that has a high electromechanical coupling coefficient and is easy to produce. [Means for solving the problem]

[0008] The piezoelectric single crystal composite vibrator of the present invention is a 2-2 type vibrator that includes a plurality of piezoelectric single crystal pillars and a resin disposed between the piezoelectric single crystal pillars, is polarized in the thickness direction, and utilizes an electromechanical coupling coefficient of a vibration mode parallel to the thickness direction. The piezoelectric single crystal pillars include pillars (1) and (2) of different widths, and are characterized in that, when the thickness is t (mm), the width of pillar (1) is w1 (mm), and the width of pillar (2) is w2 (mm), w1 / t is 0.3 to 0.6, w2 / t is greater than 0.6, and w2 / w1 is 1.5 or greater. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a piezoelectric single crystal composite vibrator that has a high electromechanical coupling coefficient and is highly manufacturable. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view schematically illustrating an example of a piezoelectric single crystal composite vibrator according to the present invention. [Figure 2] 1 is a diagram illustrating a method for manufacturing a piezoelectric single crystal composite vibrator according to the present invention. [Figure 3] 1 is a diagram illustrating a method for manufacturing a piezoelectric single crystal composite vibrator according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The piezoelectric single crystal composite vibrator of the present invention is a 2-2 type vibrator that includes multiple piezoelectric single crystal pillars and resin disposed between the pillars, is polarized in the thickness direction, and utilizes an electromechanical coupling coefficient of a vibration mode parallel to the thickness direction. The vibrator includes pillars (1) and (2) with different widths, and when the thickness is t (mm), the width of pillar (1) is w1 (mm), and the width of pillar (2) is w2 (mm), w1 / t is 0.3 to 0.6, w2 / t is greater than 0.6, and w2 / w1 is 1.5 or greater.

[0012] Fig. 1 shows a perspective view that schematically illustrates an example of a piezoelectric single crystal composite vibrator of the present invention. However, Fig. 1 is intended to facilitate understanding of the structure of the piezoelectric single crystal composite vibrator, and the size of each element is not necessarily accurate (this also applies to Figs. 2 and 3 described below). Also, the crystal orientation is shown on the left side of Fig. 1 (this also applies to Figs. 2 and 3 described below).

[0013] The piezoelectric single crystal composite vibrator 1 is polarized in the thickness direction (vertical direction in the figure, i.e., the

[0001] orientation) and utilizes the electromechanical coupling coefficient of the vibration mode parallel to the thickness direction. The piezoelectric single crystal composite vibrator 1 contains piezoelectric single crystal pillars 21 and 22 and a resin 3, with the resin 3 disposed between each of the piezoelectric single crystal pillars. The pillars 21 and 22 have different widths in the direction perpendicular to the thickness direction (horizontal direction in the figure, i.e., the

[0100] orientation). The piezoelectric single crystal composite vibrator also has electrodes 4, 4 on the (001) plane (top and bottom surfaces in the figure) of the piezoelectric single crystal composite containing the piezoelectric single crystal pillars 21 and 22 and the resin 3.

[0014] In the piezoelectric single crystal composite vibrator of the present invention, when the thickness is t (mm), the narrower piezoelectric single crystal pillar (pillar 21 in the figure) is pillar (1) with a ratio of its width w1 to its thickness t: w1 / t of 0.3 to 0.6, and the wider piezoelectric single crystal pillar (pillar 22 in the figure) is pillar (2) with a ratio of its width w2 to its thickness t: w2 / t of greater than 0.6. The ratio of the width w1 of pillar (1) to the width w2 of pillar (2): w2 / w is 1.5 or greater. Note that the thickness t of the piezoelectric single crystal composite vibrator referred to in this specification means the thickness excluding the electrode portion (the thickness of the piezoelectric single crystal composite portion containing the piezoelectric single crystal pillar and resin, as shown in FIG. 1).

[0015] In this way, the piezoelectric single crystal composite vibrator of the present invention has multiple piezoelectric single crystal pillars of different widths that satisfy a specific relationship with respect to each other, thereby ensuring an electromechanical coupling coefficient that is equal to or close to that of a piezoelectric single crystal composite vibrator in which pillars are uniformly formed with a width-to-thickness ratio similar to that of narrower pillars (1). Furthermore, by having wider pillars (2), the piezoelectric single crystal composite vibrator of the present invention can reduce the number of grooves (grooves for filling with resin) formed during manufacturing compared to a piezoelectric single crystal composite vibrator in which pillars are uniformly formed with a width-to-thickness ratio similar to that of pillars (1), thereby shortening the processing time and thereby ensuring excellent productivity.

[0016] Furthermore, piezoelectric single crystal composite vibrators in which pillars with a width-to-thickness ratio similar to that of pillar (1) are uniformly formed are prone to breakage during manufacturing due to the need to form many thin grooves for filling with resin, and the rate of defective products is relatively high. However, with the piezoelectric single crystal composite vibrator of the present invention, for example, the number of grooves for filling with resin can be reduced, which reduces the number of defective products during manufacturing, and from this perspective as well, high productivity can be ensured.

[0017] Furthermore, when evaluating the vibration characteristics of a piezoelectric single crystal composite vibrator using a logarithmic graph with frequency on the horizontal axis and impedance on the vertical axis, for example, in a vibrator in which piezoelectric single crystal pillars are uniformly formed with a width (w) to thickness (t) ratio (w / t) of approximately 0.3 to 0.6, only the primary vibration (i.e., vibration in the thickness direction) tends to be observed. However, in a vibrator in which pillars are uniformly formed with a w / t ratio exceeding 0.6, not only the primary vibration (i.e., vibration in the thickness direction) but also vibration in the width direction (horizontal direction in Figure 1) appears as unwanted vibration. Because these unwanted vibrations are located in a frequency band close to the primary vibration, a piezoelectric single crystal composite vibrator with a large w / t ratio of the piezoelectric single crystal pillars (i.e., large pillar width) as described above cannot effectively extract only the primary vibration that should be utilized in the applicable device. However, in the piezoelectric single crystal composite vibrator of the present invention, although unwanted vibration in the width direction occurs, it is located in a frequency band that does not overlap with the primary vibration in the thickness direction, making it possible to effectively extract the primary vibration in the thickness direction required for the applicable device.

[0018] Examples of piezoelectric single crystals that constitute the piezoelectric single crystal composite vibrator include solid solution single crystals containing lead titanate. Specifically, examples include lead composite perovskite compositions containing niobium oxide and at least one of magnesium oxide and indium oxide, and lead composite perovskite compositions containing zinc oxide and niobium oxide. Examples of the lead composite perovskite compositions include lead magnesium niobate-lead titanate [Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT), lead indium niobate-lead magnesium niobate-lead titanatePb(In1 / 2 Nb 1 / 2 )O3-Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PIN-PMN-PT), lead zinc niobate-lead titanatePb(Zn 1 / 3 Nb 2 / 3 )O3-PbTiO3](PZN-PT), etc.

[0019] Commercially available raw single crystal substrates can be used for the piezoelectric single crystals. Specific examples of commercially available products that can be used as raw single crystal substrates include "X2B (product name)" (PMN-PT) manufactured by TRS Technologies, Inc., and PMN-28PT (Type A) and PMN-32PT (Type B) manufactured by CTS Corporation.

[0020] The resin used to form the piezoelectric single crystal composite vibrator and to be placed between the piezoelectric single crystal pillars is not particularly limited, as long as it can be filled between the piezoelectric single crystal pillars to form a piezoelectric single crystal composite vibrator and has the necessary insulating properties. Specific examples of resins include thermosetting resins (cured products of these thermosetting resins) such as unsaturated polyester resin, allyl resin, epoxy resin, urethane resin, urea resin, melamine resin, and phenolic resin; and thermoplastic resins such as acrylonitrile copolymer resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, polyacetal resin, polycarbonate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, and polymethyl methacrylate resin. It is desirable to select a thermoplastic resin with a melting point or glass transition temperature higher than the temperature at which the electrodes of the piezoelectric single crystal composite vibrator are formed to prevent softening during electrode formation.

[0021] The piezoelectric single crystal pillars (1) in the piezoelectric single crystal composite vibrator have a w1 / t of 0.6 or less, and providing such narrow pillars (1) can increase the electromechanical coupling coefficient of the piezoelectric single crystal composite vibrator. However, if the width of the pillars (1) is made too small, it may be difficult to form them, and the effect of improving productivity may be reduced. Therefore, the w1 / t of the pillars (1) is 0.3 or more.

[0022] Furthermore, the piezoelectric single crystal pillars (2) in the piezoelectric single crystal composite vibrator have a w2 / t ratio greater than 0.6, and by providing such wide pillars (2) together with narrow pillars (1), productivity of the piezoelectric single crystal composite is improved. The upper limit of w2 / t may be any value that satisfies the above range of w1 / t and the range of w2 / w1 described below.

[0023] Furthermore, in the piezoelectric single crystal composite vibrator, the ratio of the width w1 of the pillar (1) to the width w2 of the pillar (2): w2 / w1 is 1.5 or more, and preferably 2 or more. In this way, by making the width of the pillar (2) larger than the width of the pillar (1) by a certain amount, a good balance is achieved between the effect of improving the electromechanical coupling coefficient and the effect of improving productivity. If the value of w2 / w1 becomes too large, the above balance tends to deteriorate, so the value of w2 / w1 is preferably 4 or less.

[0024] The width w1 of the pillar (1) is preferably 0.01 mm or more, more preferably 0.03 mm or more, and preferably 3 mm or less, more preferably 1 mm or less. The width w2 of the pillar (2) is preferably 0.02 mm or more, more preferably 0.09 mm or more, and preferably 9 mm or less, more preferably 3 mm or less.

[0025] Furthermore, the thickness t of the piezoelectric single crystal composite vibrator is preferably 0.02 mm or more, more preferably 0.04 mm or more, and is preferably 3 mm or less, more preferably 1 mm or less.

[0026] Furthermore, the width of the resin in the piezoelectric single crystal composite vibrator (the horizontal length in FIG. 1) is preferably 0.005 mm or more, more preferably 0.015 mm or more, and is preferably 3 mm or less, more preferably 1 mm or less.

[0027] Furthermore, the length L of the piezoelectric single crystal composite vibrator in the depth direction shown in FIG. 1 is preferably 1 mm or more, more preferably 3 mm or more, and is preferably 30 mm or less, more preferably 10 mm or less.

[0028] Furthermore, in order to ensure a better improvement in the electromechanical coupling coefficient in the piezoelectric single crystal composite vibrator, it is preferable that the number of pillars (1) is two or more when the number of pillars (2) is one. However, if the number of pillars (1) is too large relative to the number of pillars (2), there is a risk that the productivity improvement effect will be reduced. Therefore, in order to ensure a better productivity in the piezoelectric single crystal composite vibrator, it is preferable that the number of pillars (1) is five or less when the number of pillars (2) is one, and more preferably three or less.

[0029] The pillars (1) of the piezoelectric single crystal composite vibrator may all be the same width, some may have different widths, or all may have different widths, as long as w1 / t satisfies the above value, but from the perspective of improving productivity, it is preferable that they all have the same width. Also, the pillars (2) of the piezoelectric single crystal composite vibrator may all be the same width, some may have different widths, or all may have different widths, as long as w2 / t satisfies the above value, but from the perspective of improving productivity, it is preferable that they all have the same width.

[0030] Furthermore, there are no particular limitations on the arrangement of the pillars (1) and pillars (2) in the piezoelectric single crystal composite vibrator, but several narrow pillars (1) may be arranged in succession, while it is preferable that the wide pillars (2) are not arranged in succession. From the viewpoint of achieving a better balance between improved productivity and improved characteristics, it is more preferable that several (e.g., about 3 to 5) consecutively arranged pillars (1) and one adjacent pillar (2) are arranged as one set, as shown in Figure 1 (however, in this case, the outermost piezoelectric single crystal pillars may all be pillars (2)).

[0031] Next, an example of a method for manufacturing a piezoelectric single crystal composite vibrator will be described with reference to the drawings. Fig. 2 is a perspective view schematically showing an example of a piezoelectric single crystal plate for forming a piezoelectric single crystal composite vibrator. As shown in Fig. 2, grooves 23 for filling with resin are formed in the piezoelectric single crystal plate 2 parallel to the

[0010] direction. A precision cutting device such as a dicing saw can be used to form the grooves.

[0032] Next, the grooves formed in the piezoelectric single crystal plate are filled with a resin. In the case of a thermosetting resin, the resin is generally in liquid form, so a method of injecting the liquid into the grooves and curing the thermosetting resin according to a standard method, such as heating, can be used. Furthermore, when a thermoplastic resin is used, a method of injecting a solution or dispersion of the thermoplastic resin into the grooves and removing the solvent in the solution or dispersion by heating can be used to fill the resin into the grooves.

[0033] The bottom of the grooves in the piezoelectric single crystal plate is then polished to expose the resin surface that was located at the bottom of the grooves, and piezoelectric single crystal pillars (1) and (2) are formed to obtain a piezoelectric single crystal composite. A grinder or the like can be used to polish the piezoelectric single crystal plate.

[0034] An oblique view of an example of a piezoelectric single crystal composite obtained in this manner is shown in Figure 3. Piezoelectric single crystal composite 10 has piezoelectric single crystal pillars (1) 21 and (2) 22, and resin 3 is placed between these pillars.

[0035] Typically, electrodes are formed on the top and bottom surfaces (i.e., the (001) plane) of this piezoelectric single crystal composite, and polarization processing is performed in the thickness direction to obtain a piezoelectric single crystal composite vibrator as shown in Figure 1.

[0036] The electrodes can be formed by sputtering, plating, vapor deposition, etc. using one or more metals such as Ni, Cr, Ti, Au, Pt, Pd, Ag, Cu, and Al. The thickness of the electrodes is preferably 100 to 2000 nm.

[0037] The polarization treatment can be carried out by applying a DC voltage between the electrodes of the piezoelectric single crystal substrate after electrode formation. The DC voltage applied during the polarization treatment can be, for example, 0.1 to 2.0 kV / mm, and the treatment time can be, for example, 10 seconds to 30 minutes.

[0038] In the piezoelectric single crystal composite vibrator obtained in this manner, when the impedances at the resonance point and anti-resonance point of the main vibration are Zr1 and Za1, respectively, and the impedances at the resonance point and anti-resonance point of the unwanted vibration are Zr2 and Za2, respectively, the unwanted vibrations (vibrations in the width direction) that are a problem in vibrators having wide piezoelectric single crystal pillars can be reduced by setting "[log(Za2)-log(Zr2)] / [log(Za1)-log(Zr1)]" to between 0 and 0.4.

[0039] In the case of a vibrator of the present invention, in which electrodes are attached to the (001) plane and polarized in the

[0001] direction, the "principal vibration" refers to the vibration in the thickness direction, which is the vibration that coincides with the polarization direction and is the largest vibration excited when an AC or pulsed electric field is applied to the attached electrodes. In measuring the impedance characteristics versus frequency, the maximum impedance value of the obtained peak is measured as the anti-resonant impedance Za, and the minimum impedance value is measured as the resonant impedance Zr. In the measured frequency band, the vibration that is the thickness direction vibration mode and shows the largest peak is defined as the principal vibration. The anti-resonant impedance of the principal vibration is denoted by Za1, and the resonant impedance is denoted by Zr1. Furthermore, "unwanted vibration" refers to vibration other than the above "principal vibration," which is excited by a combination of column width vibration and higher-order width vibration, and is vibration in a direction perpendicular to the vibration direction of the "principal vibration." The peak closest to the principal vibration on the high-frequency side is defined as the unwanted vibration, and its anti-resonant impedance is denoted by Za2, and its resonant impedance is denoted by Zr2.

[0040] The piezoelectric single crystal composite vibrator of the present invention can be preferably applied to applications in which conventionally known piezoelectric single crystal composite vibrators are used, including sensing materials that convert electrical signals into displacements in medical ultrasound devices, airborne ultrasound devices, underwater ultrasound devices, solid-state ultrasound devices, and other ultrasound devices; sensing materials that convert displacements in acceleration sensors, etc.; and the like. [Example]

[0041] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0042] Example 1 Pb(Mg 1 / 3 Nb 2 / 3Both major surfaces ((001) planes) of a raw material single crystal plate of PMN-PT, manufactured by TRSS Technologies, Inc., under the trade name "X2B" were polished using a grinder (manufactured by Disco Corporation) to a thickness of 0.50 mm. This single crystal plate was then cut using a dicing saw (manufactured by Disco Corporation) so that the cut surfaces were the (100) and (010) planes, yielding PMN-PT single crystal plates with a length L of 30 mm in the

[0100] orientation and a width W of 15 mm in the

[0010] orientation.

[0043] The PMN-PT single crystal plate was grooved with a dicing saw to a width of 0.035 mm and a depth of 0.3 mm, with the width of the w / t=0.5 pillars being 0.1 mm and the width of the w / t=1.5 pillars being 0.3 mm, resulting in 32 pillars with a width of 0.1 mm and 16 pillars with a width of 0.3 mm.

[0044] The resulting grooved PMN-PT single crystal plate was filled with epoxy resin (EPO-TEK 301 (product name) manufactured by Epoky Technology, Inc.) and cured by heating to produce a piezoelectric single crystal composite. The resulting piezoelectric single crystal composite was ground to a thickness of 0.2 mm using a grinder to expose the resin located at the bottom of the grooves.

[0045] Electrodes having a 50 nm thick underlayer made of chromium and a 200 nm thick top layer made of gold were formed on both main (001) surfaces of the obtained piezoelectric single crystal composite using a sputtering device (manufactured by Shibaura Mechatronics Co., Ltd.) The piezoelectric single crystal composite with the electrodes formed thereon was then subjected to polarization treatment by applying a DC electric field of 5 kV / cm at 25°C, resulting in a piezoelectric single crystal composite vibrator with the appearance shown in Figure 1.

[0046] Examples 2 to 4, Comparative Examples 1 to 3 A piezoelectric single crystal composite vibrator was obtained in the same manner as in Example 1, except that grooves were formed with the pillar width and number of pillars shown in Table 1.

[0047] For the piezoelectric single-crystal composite oscillators of the examples and comparative examples, the following evaluations were performed.

[0048] <Impedance Characteristic Evaluation with Respect to Frequency> The impedance characteristics with respect to the frequency of the thickness-direction vibration of each piezoelectric single-crystal composite oscillator of the examples and comparative examples were measured at 25°C in the thickness-direction vibration mode (the

[0001] azimuth in FIG. 1) using an "Impedance Analyzer 4294A (trade name)" manufactured by Keysight Technologies. Then, from the resonance frequency fr and the anti-resonance frequency fa of each obtained piezoelectric single-crystal composite oscillator, according to the method described in the standard JEITA EM-4501A (Electrical Test Methods for Piezoelectric Ceramic Oscillators) of the Electronics and Information Technology Industries Association, the electromechanical coupling coefficient k t (%) was calculated.

[0049] Also, the vibration showing the maximum peak obtained in the above measurement was defined as the main vibration, and the maximum impedance value of that peak was defined as the anti-resonance impedance Za1, and the minimum impedance value was defined as the resonance impedance Zr1. Also, the peak closest to the high-frequency side with respect to the peak of the main vibration in the above measurement was defined as the unwanted vibration, and its anti-resonance impedance was defined as Za2 and the resonance impedance was defined as Zr2. Then, the ratio of the difference in the anti-resonance and resonance impedances of the unwanted vibration to the difference in the anti-resonance and resonance impedances of the main vibration was expressed as "[log(Za2) - log(Zr2)] / [log(Za1) - log(Zr1)]". This ratio represents the magnitude ratio of the unwanted vibration to the main vibration.

[0050] Note that for the piezoelectric single-crystal composite oscillator of Comparative Example 1, since no vibration that could be evaluated as an unwanted vibration was observed, "[log(Za2) - log(Zr2)] / [log(Za1) - log(Zr1)]" was not obtained.

[0051] <Productivity Evaluation during Grooving of PMN-PT Single-Crystal Plate> The productivity during groove processing of the PMN-PT single crystal plate during the fabrication of the piezoelectric single crystal composite vibrators of Example 2 and Comparative Examples 1 to 3 was evaluated in terms of processing time and yield. The yield was evaluated in terms of the percentage of non-defective pillars formed. The pillars formed by groove processing were visually inspected for defects such as "collapse," "cracks," and "splits," and pillars free of such defects were deemed to be non-defective. Evaluation was performed on three pillars for each Example and Comparative Example, and the percentage (%) of non-defective pillars was taken as the yield during groove processing. Piezoelectric single crystal composite vibrators obtained using PMN-PT single crystal plates with high productivity during groove processing can be judged to have high productivity.

[0052] Table 1 shows the pillar configurations of the piezoelectric single crystal composite vibrators of the examples and comparative examples, and Tables 2 and 3 show the evaluation results of the impedance characteristics versus thickness vibration frequency. Note that the number ratio "w / t 0.5:1.5" in Table 1 refers to the ratio between the number of pillars with w / t=0.5 and the number of pillars with w / t=1.5. Also, in Table 3, the "ratio of the magnitude of unwanted vibration to the main vibration" refers to the value of the above-mentioned "[log(Za2)-log(Zr2)] / [log(Za1)-log(Zr1)]."

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] In the piezoelectric single crystal composite vibrators of Examples 1 to 4, the pillars with a width of 0.1 mm (pillars with w / t = 0.5) correspond to "pillar (1)," and the pillars with a width of 0.3 mm (pillars with w / t = 1.5) correspond to "pillar (2)." As shown in Tables 1 to 3, the piezoelectric single crystal composite vibrators of Examples 1 to 4, which have pillars (1) and (2) with appropriate w / t values ​​in an appropriate ratio, have an electromechanical coupling coefficient k t However, it was higher than the piezoelectric single crystal composite vibrator of Comparative Example 3 in which pillars of w / t=1.5 were uniformly formed, and lower than the piezoelectric single crystal composite vibrator of Comparative Example 1 in which pillars of w / t=0.5 were uniformly formed, but was approximately the same as the piezoelectric single crystal composite vibrator of Comparative Example 2 in which pillars of w / t=0.75 were uniformly formed.

[0057] Furthermore, the piezoelectric single crystal composite vibrators of Examples 1 to 4 had a smaller ratio of the magnitude of unwanted vibrations to the main vibration, "[log(Za2)-log(Zr2)] / [log(Za1)-log(Zr1)]," than the piezoelectric single crystal composite vibrators of Comparative Examples 2 and 3, and were able to suppress unwanted vibrations.

[0058] Furthermore, the productivity evaluation results for groove processing of PMN-PT single crystal plates are shown in Table 4. The "processing time" in Table 4 is expressed as a relative value, with the time required to process the PMN-PT single crystal plate of Comparative Example 1 set as 1.00.

[0059] [Table 4]

[0060] As shown in Table 4, the PMN-PT single crystal plate for the piezoelectric single crystal composite vibrator of Example 2 had a shorter processing time for the groove processing, a higher yield, and superior productivity compared to the PMN-PT single crystal plate for the piezoelectric single crystal composite vibrator of Comparative Example 1, in which pillars with a w / t ratio of 0.5 were uniformly formed. [Explanation of symbols]

[0061] 1. Piezoelectric single crystal composite vibrator 10 Piezoelectric single crystal composite 2. Piezoelectric single crystal plate 21 Piezoelectric Single Crystal Pillar (1) 22 Piezoelectric Single Crystal Pillar (2) 23 Groove 3. Resin 4 electrodes

Claims

1. A 2-2 type piezoelectric single crystal composite vibrator including a plurality of piezoelectric single crystal pillars and a resin disposed between the piezoelectric single crystal pillars, polarized in a thickness direction, and utilizing an electromechanical coupling coefficient of a vibration mode parallel to the thickness direction, Each of the plurality of piezoelectric single crystal pillars is either a pillar (1) or a pillar (2) having a different width, and the pillars (1) have the same width, and the pillars (2) have the same width, A piezoelectric single crystal composite vibrator characterized in that, when the thickness is t (mm), the width of the pillar (1) is w1 (mm), and the width of the pillar (2) is w2 (mm), w1 / t is 0.3 to 0.6, w2 / t is greater than 0.6, w2 / w1 is 1.5 to 4, and t is 0.02 to 3 mm.

2. 2. The piezoelectric single crystal composite vibrator according to claim 1, wherein the number of said pillars (1) is two or more when the number of said pillars (2) is one.

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