JP7150466B2 - Piezoelectric devices, vibrators, vibration wave motors, optical devices and electronic devices - Google Patents

Description

The present invention relates to a piezoelectric element, a vibrator using the piezoelectric element, a vibration wave motor, an optical device, and an electronic device.

A piezoelectric element has a structure in which a piezoelectric material layer and an electrode layer are laminated, and a large deformation strain can be obtained at a low voltage. When an elastic body for controlling vibration is attached to a piezoelectric element, it becomes a piezoelectric vibrator, and the piezoelectric vibrator can be used for various actuators. For example, a vibration wave motor can be obtained by attaching a moving body to a piezoelectric vibrator so that the moving body portion is moved by a voltage.

Lead zirconate titanate (hereinafter referred to as PZT) is generally used for the piezoelectric material layer of the piezoelectric element. However, since PZT contains lead as a main component, the lead component dissolves into the soil when it is discarded, and its impact on the environment, such as the possibility of harming the ecosystem, is viewed as a problem. For this reason, the use of so-called lead-free piezoelectric materials, which do not contain lead, for piezoelectric elements has been studied.

However, Patent Literature 1 describes that lead-free piezoelectric materials have lower piezoelectric characteristics than lead-based piezoelectric ceramics, and have the problem that a sufficiently large amount of generated displacement cannot be obtained. As one solution to this problem, a piezoelectric element using a potassium niobate-based material has been disclosed. However, the piezoelectric constant was still small due to insufficient firing temperature and oxygen content, and the vibration velocity was not sufficient when this element was used in a laminated piezoelectric vibrator.

On the other hand, Patent Literature 2 discloses a technique for increasing the piezoelectric constant converted from the strain rate by increasing the average particle size of the lead-free piezoelectric material after sintering to a maximum of 60.9 μm. However, the piezoelectric material layer of the piezoelectric element is preferably made as thin as, for example, about 20 μm to 70 μm for the purpose of suppressing power consumption. Sintering is common. Therefore, if the sintering temperature is simply raised to increase the grain size, the flatness of the piezoelectric material layer will be lost, the shape and thickness of the electrode layer will become uneven, and the entire element will warp or delaminate. There was a problem that occurred. As a result, there is a problem that the electrical loss of the piezoelectric element becomes large, resulting in excessive power consumption.

Japanese Patent Application Laid-Open No. 2007-258280 JP-A-2003-128460

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lead-free piezoelectric element that can be driven with high efficiency in order to deal with the problems of insufficient vibration speed and excessive power consumption.

A piezoelectric element as one aspect of the present invention is a piezoelectric element in which piezoelectric material layers and electrode layers are alternately laminated,
The piezoelectric material layer has a plurality of crystal grains and a plurality of voids,
At least one of the piezoelectric material layers comprises:
T _P is the average thickness in the stacking direction of the piezoelectric material layer, D _G is the average circle equivalent diameter of the plurality of crystal grains, and _LV is the maximum length in the stacking direction of the plurality of gaps that are not in contact with the electrode layer. , where TE is the average thickness of the electrode layer in contact with at least one of the piezoelectric material layers, _{0.07T P} ≤ DG ≤ _{0.33T P} , _{TE ≤ LV ≤ 0.3T P , and} lead The content is less than 1000 ppm ,
In the cross-sectional observation field of view of the piezoelectric element, the length of the piezoelectric material layer in the lamination direction is TE + _{TP +} TE , and the length in the direction intersecting the lamination direction is TE _{+ TE} . For a length greater than T _P + T _E ,
In the cross _{- sectional} observation field of view, the area _SV occupied by the void portion is characterized in that the ratio PV to the area SP of the piezoelectric material layer is 3 area % or more and 10 area % or less .

According to the present invention, it is possible to provide a lead-free piezoelectric element that can be driven with high efficiency. In addition, it is possible to provide vibrators, vibration wave motors, optical devices, and electronic devices that can be driven with high efficiency.

1A and 1B are a cross-sectional view and an external view showing an embodiment of a piezoelectric element of the present invention; It is a cross-sectional schematic diagram which shows an example of embodiment of the piezoelectric material layer of the piezoelectric element of this invention, and an electrode layer. 1 is a cross-sectional view of a schematic structure showing an embodiment of a vibrator of the present invention; FIG. 1 is a cross-sectional view of a schematic structure showing an embodiment of a vibration wave motor of the present invention; FIG. 1 is a cross-sectional view of a schematic structure showing an embodiment of an optical device of the present invention; FIG. 1 is a conceptual diagram showing an embodiment of an electronic device of the present invention; FIG. It is a figure which shows the cross-sectional structure of the piezoelectric element of the Example of this invention. FIG. 4 is a correlation diagram showing features of piezoelectric elements of examples of the present invention and comparative examples. 1 is a schematic diagram showing the structure of a liquid ejection head as an example of an electronic device of the present invention; FIG.

(Piezoelectric element of the present invention)
A piezoelectric element of the present invention is a piezoelectric element having piezoelectric material layers and electrode layers alternately laminated, wherein the piezoelectric material layers have a plurality of crystal grains and a plurality of voids. At least one of the piezoelectric material layers has a thickness T _P in the stacking direction of the piezoelectric material layer, an average circle equivalent diameter of the crystal grains D _G , and a maximum thickness in the stacking direction of the gap portion not in contact with the electrode layer. Let L _V be the length, and T _E be the average thickness of the electrode layer in contact with the piezoelectric material layer. At that time, it is characterized by 0.07 T _P ≦D _G ≦0.33 T _P , T _E ≦L _V ≦0.3 T _P and a lead content of less than 1000 ppm.

FIG. 1(a) is a schematic cross-sectional view showing one embodiment of the piezoelectric element of the present invention. A piezoelectric element according to the present invention has at least one or more piezoelectric material layers 2 and one or more electrode layers (1 and 3 in the case of FIG. 1(a)), and the piezoelectric material layers and the electrode layers are alternately arranged. Laminated.

In FIG. 1B, one or more piezoelectric material layers 54 and one or more electrode layers 55 are alternately laminated, and the laminated structure is sandwiched between a first metal electrode 51 and a second metal electrode 53. 1 is a schematic cross-sectional view of a piezoelectric element of the present invention, shown in FIG. The piezoelectric element according to the present invention is composed of piezoelectric material layers 54 and electrode layers including electrode layers 55, which are alternately laminated. The electrode layer may include external electrodes such as the first metal electrode 51 and the second metal electrode 53 in addition to the electrode layer 55 .

As shown in FIG. 1C, the number of piezoelectric material layers and electrode layers may be increased, and the number of layers is not limited, but the preferable number of layers is 2 to 60 as piezoelectric material layers. By using two or more piezoelectric material layers, the effect of obtaining a large piezoelectric strain and a high vibration velocity at a low voltage can be expected as compared with the case of a single layer. On the other hand, since the number of piezoelectric material layers is 60 or less, effects such as miniaturization of the piezoelectric element and reduction in electrode cost can be expected.

In the case of the piezoelectric element shown in FIG. 1C, nine piezoelectric material layers 504 and eight electrode layers 505 (505a or 505b) are alternately laminated. The laminated structure has a structure in which a piezoelectric material layer 504 is sandwiched between a first electrode 501 and a second electrode 503, and external short-circuit electrodes 506a and 506b for short-circuiting the alternately formed electrode layers 505. have The shape and arrangement of the electrodes for short-circuiting the electrode layer 505 are not limited to the example in FIG. 1(c). The electrode for short-circuiting the electrode layers may be an external short-circuit electrode or a short-circuit electrode provided in a hole (through-hole) passing through the laminated structure. The electrode layer 505 may be short-circuited by wiring such as a conductive wire instead of the short-circuit electrode.

The electrode layers 55, 505, the external short-circuit electrodes 506a, 506b, the first metal electrodes 51, 501, and the second metal electrodes 53, 503 need not necessarily have the same size and shape as the piezoelectric material layers 54, 504. Moreover, it may be divided into a plurality of parts.

The thickness of the electrode layers 55, 505, the external short-circuit electrodes 506a, 506b, the first metal electrodes 51, 501 and the second metal electrodes 53, 503 is about 5 nm to 10 μm.

The material of the electrode layers 55, 505, the external short-circuit electrodes 506a, 506b, the first metal electrodes 51, 501 and the second metal electrodes 53, 503 is not particularly limited as long as it is a conductive metal. , Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, Cu and other metals, alloys, and laminates. Moreover, each electrode may be made of a different material.

The material of the electrode layers 55 and 505 contains Ag and Pd, and when these are the main components, for example, when the total of Ag and Pd accounts for 90% by weight or more and 100% by weight or less of the electrode layers, workability during manufacturing is improved. , is preferable in terms of conductivity, shape uniformity, and cost as an electrode layer. It is preferable that the weight ratio M1/M2 between the Ag content M1 and the Pd content M2 is 0.25≦M1/M2≦4.0. More preferably, 0.3≤M1/M2≤3.0. If the weight ratio M1/M2 is less than 0.25, the sintering temperature of the electrode layer becomes high, which is undesirable. On the other hand, if the weight ratio M1/M2 is greater than 4.0, the electrode layer becomes island-shaped, which is undesirable because it causes non-uniformity in the plane. More preferably, 0.3≤M1/M2≤3.0.

The lead component contained in the piezoelectric element of the present invention is less than 1000 ppm. More preferably, it is 500 ppm or less. A method for quantifying the lead component contained in the piezoelectric element is not particularly limited, but examples thereof include X-ray fluorescence spectrometry (XRF), ICP emission spectrometry, and atomic absorption spectrometry. Among these, ICP emission spectroscopy is suitable for quantifying trace amounts of lead components.

If the lead content in the piezoelectric element is less than 1000 ppm, even if the product using the piezoelectric element of the present invention is discarded and exposed to various harsh environments, the lead in the product affects the natural environment and living organisms. Reduced impact. Among the members constituting the piezoelectric element of the present invention, it is more preferable that the lead component contained in the piezoelectric material layer from which the lead component is particularly difficult to separate during recycling is less than 1000 ppm. Also, in the laminated piezoelectric vibrator, vibration wave motor, optical device, and electronic device using the piezoelectric element of the present invention, it is more preferable that the lead content in the entire constituent members is less than 1000 ppm. The method of quantifying the lead component in laminated piezoelectric vibrators, vibration wave motors, optical devices, and electronic devices is the same as that for piezoelectric elements.

FIG. 2(a) is a schematic cross-sectional view showing an example of an embodiment of the piezoelectric material layer and the electrode layer of the piezoelectric element of the present invention. As shown, the piezoelectric material layers 504 and 505a, 505b are alternately laminated. FIG. 2(a) is an image of an observation field of view in which a part of the piezoelectric element in FIGS. 1(a), (b) and (c) is enlarged. The piezoelectric material layer 504 and the electrode layers 505a and 505b continuing to the left and right of are omitted.

The piezoelectric material layer 504 is composed of an aggregate 5041 of a plurality of crystal grains (in the figure, white-painted portions and grain boundaries of crystal grains are omitted) and an aggregate of a plurality of gaps 5042 . The voids include voids in contact with the electrode layers 505a and 505b (hereinafter referred to as electrode adjacent voids) and voids not in contact with the electrode layers 505a and 505b (hereinafter referred to as electrode independent voids). All of the gaps flatten the interface where the piezoelectric material layer contacts the electrode layer, and produce the effect of reducing the dielectric loss tangent of the piezoelectric element. Since it interferes, the smaller one is preferable. For example, the ratio between the number N _V1 of the electrode-adjacent voids and the number N _V2 of the electrode-independent voids in the cross-sectional observation field of the piezoelectric element preferably satisfies the relationship N _V2 /N _V1 ≧3.

Further, the ratio _Pv of the area _Sv occupied by the void in the cross-sectional observation field of the piezoelectric element to the area _Sp of the piezoelectric material layer is preferably 3 area % or more and 10 area % or less. When the _PV is 3 area % or more and 10 area % or less, the dielectric loss tangent can be suppressed without disturbing the vibration of the piezoelectric element of the present invention. If the _PV is less than 3% by area, the flatness of the interface between the piezoelectric material layer and the electrode layer may be impaired and the dielectric loss tangent of the piezoelectric element may increase. On the other hand, if the _PV is more than 10% by area, the void part will partially absorb the deformation of the piezoelectric material layer, and the piezoelectric element or the laminated piezoelectric vibrator using the piezoelectric element will not be able to achieve the desired vibration speed and torque. It may not work.

In calculating N _V1 , N _V2 , S _V , S _P , and P _V , it is actually difficult to observe all locations of the piezoelectric element at once at a high magnification. Therefore, the cross section of the piezoelectric element is observed with a scanning electron microscope (SEM) at a magnification of about 100 to 500 times, and representative observation images are obtained at about 5 locations for each piezoelectric material layer, thereby calculating the parameters and their magnitudes. Relationship determinations can be made.

Let _TP be the thickness in the stacking direction of the piezoelectric material layer 504 to be observed. T _P is the average thickness of one piezoelectric material layer 504 and may be different thickness for each piezoelectric material layer. The TP of an arbitrary piezoelectric material layer can be easily calculated by image processing a cross _- sectional observation image by SEM. In a piezoelectric element, the thickness of the same piezoelectric material layer generally varies little depending on the location. Therefore, the _TP value may be obtained from a representative SEM image of one location, but it is more desirable to obtain SEM images of five or more locations for the same piezoelectric material layer and use the average _TP value.

Although the size of T _P is not particularly limited, it is preferably 20 μm or more and 70 μm or less from the viewpoint of design and manufacture of the piezoelectric element. If T _P is less than 20 μm, it is necessary to increase the number of layers in order to increase the admittance of the piezoelectric element. On the other hand, if the thickness is more than 70 μm, the voltage required for obtaining a large displacement of the piezoelectric element increases, and as a result, the cost of the power supply may increase.

Let LV be the maximum length in the stacking direction of the voids (electrode independent voids) present in the voids ₅₀₄₂ that are not in contact with the electrode layer, that is, that are surrounded by crystal grains. In the case of FIG. 2(a), since the gap 50421 is the longest in the stacking direction, the length of the gap ₅₀₄₂₁ in the stacking direction is defined as LV. Since it is difficult to determine the maximum length with only one narrow observation field, the maximum length is obtained by observing the entire observed area sandwiched between electrode layers for the same piezoelectric material layer to determine the average thickness _TP . It is desirable to determine the length _LV . The length of the void in the stacking direction can be easily calculated by image processing of a cross-sectional observation image by SEM. FIG. 2B is an enlarged view of the gap 50241. FIG. _LV is the maximum length of a line segment inscribed in the direction perpendicular to the electrode layer with respect to the cross-sectional periphery of the gap.

Let TE be the average thickness of the electrode layer in contact with at least one piezoelectric material layer ₅₀₄ to be observed. Specifically, T _E =(T _E1 +T _E2 )/2, where T _E1 is the average thickness of the electrode layer 505a and T _E2 is the average thickness of the electrode layer 505b. The length of the electrode layers in the stacking direction can be easily calculated by image processing of a cross-sectional observation image by SEM.

Although the size of _TE is not particularly limited, it is preferable that _TE is 3.5 μm or more and 10 μm or less. When the _TE of the electrode layer is 3.5 μm or more, the conductivity of the electrode layer is increased, and a desired voltage can be applied to the piezoelectric material layers 54 and 504 efficiently. On the other hand, when the _TE of the electrode layer is 10 μm or less, the piezoelectric element can be made smaller and less expensive while maintaining sufficient vibration performance of the piezoelectric element.

FIG. 2(c) is a schematic cross-sectional view showing an example of an embodiment of the piezoelectric material layer 504 and the electrode layers 505a and 505b of the piezoelectric element of the present invention. An aggregate of crystal grains (no figure number, white areas in the figure) and an aggregate of voids (no figure number, black areas in the figure) constituting the piezoelectric material layer 504 are shown schematically. .

When there are N crystal grains in the same piezoelectric material layer, the equivalent circle diameter of the n-th metal oxide is _DGn . The "equivalent circle diameter" in the present invention represents the "projected area equivalent circle diameter" generally referred to in microscope observation, and represents the diameter of a perfect circle having the same area as the projected area of a crystal grain. In the present invention, the method for measuring the equivalent circle diameter is not particularly limited, but it can be obtained by image processing a photographic image obtained by photographing a cross section of the piezoelectric element with an SEM. An average equivalent circle diameter of N crystal grains in the same piezoelectric material layer is defined as an average equivalent circle diameter _DG .

It is difficult to calculate the equivalent circle diameters of all crystal grains in one piezoelectric material layer. Inside the piezoelectric material layer, there is variation in the equivalent circle diameter in the stacking direction corresponding to the vertical direction in FIG. Therefore, as shown in FIG. 2(c), an SEM image is obtained in which the thickness _TP of one piezoelectric material layer 504 in the stacking direction is entirely within the field of view, and the equivalent circle diameters of the crystal grains within the field of view are averaged. Then, a value of _DG that is sufficiently reliable can be obtained. For example, it is sufficient to calculate the average circle-equivalent diameter _DG of 100 or more crystal grains covering the stacking direction of the piezoelectric material layers.

Although the size of the average equivalent circle diameter _DG is not particularly limited, it is preferable that _DG is 5 μm or more and 15 μm or less. By setting the average equivalent circle diameter _DG of the crystal grains forming the piezoelectric material layer within this range, the piezoelectric material layer has a large piezoelectric constant. When _DG is less than 5 μm, the piezoelectric constant becomes insufficient compared to when _DG is 5 μm or more and 15 μm or less, and as a result, the vibration velocity of the piezoelectric element may be insufficient.

The piezoelectric constant _d33 of the piezoelectric material layer can be approximated by, for example, measuring the apparent piezoelectric constant _d33 ^*sum of the entire _{piezoelectric} element and dividing _d33 ^*sum by the number of piezoelectric material layers. can be asked for. The apparent piezoelectric constant d ₃₃ ^*sum of the entire piezoelectric element can be measured using, for example, a commercially available d ₃₃ meter. If a _d33 meter is used, the dielectric loss tangent of the piezoelectric element can also be measured at the same time. The dielectric loss tangent of the piezoelectric element and the dielectric loss tangent of the piezoelectric material layer may be regarded as having the same value. Normally, the piezoelectric constant d ₃₃ ^*sum and the dielectric loss tangent are measured at room temperature, eg, 25° C., and the d ₃₃ and the dielectric loss tangent of the piezoelectric material layer are calculated.

On the other hand, when D _G exceeds 15 μm, it is difficult for crystal grains to densely fill a piezoelectric material layer having a thickness T _P of about 20 to 70 μm, compared to when D _G is 5 μm or more and 15 μm or less. can be In some cases, the proportion of voids is as large as 20 area % or more with respect to the area of the piezoelectric material layer in the cross-sectional image. As a result, the mechanical strength and dielectric loss tangent of the piezoelectric material layer may be impaired. In any case, the user of the piezoelectric element of the present invention may arbitrarily determine the size of the average circle equivalent diameter _DG according to the application.

Also, the equivalent circle diameter D _Gn of each crystal grain is preferably D _Gn ≦20 μm. The presence of crystal grains having an equivalent circle diameter D _Gn exceeding 20 μm may impair the mechanical strength and dielectric loss tangent of the piezoelectric material layer.

The piezoelectric element of the present invention has at least one piezoelectric material layer satisfying 0.07 T _P ≦D _G ≦0.33 T _P and T _E ≦L _V ≦0.3 T _P . More preferably, all the piezoelectric material layers that contribute to the piezoelectric vibration of the piezoelectric element satisfy the relationships of _{0.07T P} ≤ DG ≤ 0.33T _P and _TE ≤ LV ≤ _{0.3T P} .

In the piezoelectric element of the present invention, the piezoelectric constant of the piezoelectric material layer increases when the average circle equivalent diameter D _G of the crystal grains is 0.07 times or more the thickness T _P of the piezoelectric material layer in the stacking direction. For example, when a barium titanate-based material is used for the piezoelectric material layer, the piezoelectric constant d ₃₃ is as large as ≧160 pm/V. On the other hand, if DG is less than _{0.07T P} , the piezoelectric constant of the piezoelectric material layer becomes small, and sufficient vibration velocity cannot be obtained. For example, when a barium titanate-based material is used for the piezoelectric material layer, the piezoelectric constant d ₃₃ is reduced to 100 pm/V.

In addition, when D _G is 0.33 times or less than T _P , three or more crystal grains can be expected to be stacked in the stacking direction of the piezoelectric material layer, and the mechanical strength of the piezoelectric material layer can be sufficiently obtained. and the dielectric loss tangent of the piezoelectric material layer becomes sufficiently small. On the other hand, if DG is greater than _{0.33 T P} , the proportion of crystal grain boundaries, that is, voids increases, resulting in a loss of mechanical strength and dielectric loss tangent of the piezoelectric material layer.

Since the maximum length _LV of the void in the stacking direction is greater than the average thickness _TE of the electrode layer in contact with the piezoelectric material layer, a plurality of locations in the piezoelectric material layer with imperfect filling of the crystal grains can be removed. The gap of the buffer. As a result, the flatness of the interface between the electrode layer and the piezoelectric material layer is improved. Therefore, the electric field applied from the metal electrode to the piezoelectric material becomes uniform, and the dielectric loss tangent of the piezoelectric element becomes small.

If the crystal grains push the electrode layer due to the growth or movement of the crystal grains and the electrode layer is deformed beyond the layer thickness, the electrode layer may break. The fact that _LV is larger than _TE means that the gap can absorb the deformation corresponding to the thickness of the electrode layer. Since _LV is the maximum length of the air gap in the stacking direction, there are many smaller air gaps inside the piezoelectric material layer. These small voids are traces of large voids receiving growth and movement of crystal grains in order to suppress deformation of the electrode layer.

However, since the gap does not contribute to the vibration of the element due to the piezoelectric effect, there is an upper limit to the size of the gap. In the present invention, the upper limit of L _V is 0.3 times the thickness T _P in the stacking direction of the piezoelectric material layer, that is, L _V ≦0.3 T _P. If the LV is greater than _{0.3T P} , the gap will hinder the vibration of the piezoelectric element due to the piezoelectric effect when an electric field is applied to the piezoelectric element.

In the piezoelectric material layer _{satisfying 0.07T P ≤ DG ≤ 0.33T P and TE ≤ LV ≤ 0.3T P , the interface between the} piezoelectric material layer and the adjacent electrode layer is observed from the cross-sectional direction. It is preferable that the line average roughness Ra is 1 μm or less. The line average roughness Ra in this specification corresponds to the arithmetic average roughness Ra of the contour curve described in JIS B 0601. For example, a cross-sectional observation image by SEM is image-processed to clarify the contour line of the interface between the electrode layer and the piezoelectric material layer as shown in FIG. It can be calculated by integrating in the segment direction and averaging over the segment length. When the Ra of the portion is 1 μm or less, the parallelism of the two electrode layers sandwiching the piezoelectric material layer becomes high, and an electric field can be applied perpendicularly to the piezoelectric material layer, so that the vibration efficiency of the piezoelectric element increases. and power consumption is reduced. When Ra is 0.6 μm or less, the power consumption of the piezoelectric element is further reduced. The ideal Ra is 0 (zero), but the minimum value of Ra that can actually be manufactured is about 0.05 μm.

The metal oxide forming the piezoelectric material layer is preferably a barium titanate-based metal oxide. A barium titanate-based material has the advantage that it exhibits a high piezoelectric constant without using a lead component, and can reduce the dielectric loss tangent with a small amount of additive.

Here, the barium titanate-based material includes barium titanate (BaTiO ₃ ), barium calcium titanate ((Ba, Ca)TiO ₃ ), barium zirconate titanate (Ba(Ti, Zr)O ₃ ), titanic acid Barium calcium zirconate ((Ba, Ca) (Ti, Zr) O ₃ ), sodium niobate-barium titanate (NaNbO ₃ -BaTiO ₃ ), bismuth sodium titanate-barium titanate ((Bi, Na) TiO ₃ -BaTiO ₃ ), bismuth potassium titanate-barium titanate ((Bi, K)TiO ₃ -BaTiO ₃ ), barium titanate-bismuth ferrate (BaTiO ₃ -BiFeO ₃ ), etc. It refers to the material used as a component.

Among these exemplified materials, the barium titanate-based material is preferably an oxide containing Ba, Ca, Ti, and Zr from the viewpoint of achieving both the piezoelectric constant and the temperature stability of the piezoelectric material layer. As the piezoelectric constant of the piezoelectric material layer increases, the admittance of the piezoelectric element increases and a large displacement can be obtained. Further, when the piezoelectric constant of the piezoelectric material layer has high temperature stability, the vibration speed and power consumption of the piezoelectric element are stabilized depending on the operating temperature.

In the oxide containing Ba, Ca, Ti, and Zr, the molar ratio x of Ca to the sum of Ba and Ca is preferably 0.02≦x≦0.30.

More preferably, 0.10≤x≤0.20.

When x is 0.10 or more, the phase transition temperature between the tetragonal crystal structure and the rhombohedral crystal structure of the barium titanate-based material shifts to a low temperature, so the practical temperature range of the piezoelectric element, for example, 0 ° C. to 50 ° C. Vibration speed and power consumption are particularly stable. On the other hand, when x is 0.20 or less, the piezoelectric constant of the piezoelectric material layer can be kept particularly high, and the vibration velocity and torque required for the piezoelectric element can be obtained.

Further, in the oxide containing Ba, Ca, Ti and Zr, the value of y, which is the molar ratio of Zr to the sum of Ti and Zr, is preferably 0.01≤y≤0.09.

More preferably, 0.02≤y≤0.07.

When y is 0.02 or more, the piezoelectric constant of the piezoelectric material layer becomes particularly high, and vibration velocity and torque required for the piezoelectric element can be obtained. On the other hand, when y is 0.07 or less, the Curie temperature of the piezoelectric material layer can be particularly kept at 100° C. or more.

Further, the piezoelectric material layer contains a Mn component together with the oxide containing Ba, Ca, Ti, and Zr, and the content of Mn is 100 parts by weight of the oxide containing Ba, Ca, Ti, and Zr. is preferably 0.02 parts by weight or more and 0.40 parts by weight or less in terms of metal.

More preferably, the content of Mn is 0.04 to 0.40 parts by weight, and more preferably 0.08 to 0.30 parts by weight.

The content of Mn in "metal equivalent" constitutes a metal oxide from the content of each metal when the piezoelectric material is measured by X-ray fluorescence analysis (XRF), ICP emission spectrometry, atomic absorption analysis, etc. It is obtained by converting the element to oxide. When the total weight is 100, it is represented by the ratio of the total weight to the weight of the Mn metal. When converting to oxide, the crystal structure is specified in advance through an X-ray diffraction experiment (for example, a perovskite structure), and the oxygen number is calculated based on the specified crystal structure and the analysis result of the metal content. In the case of a perovskite structure oxide, it is generally represented by the compositional formula ABO ₃ , but from the viewpoint of charge balance and the like, the calculated oxygen number may deviate by several percent.

When the oxide containing Ba, Ca, Ti, and Zr contains Mn within the above range, the electrical insulation of the piezoelectric element of the present invention is improved and the dielectric loss tangent is reduced. As a result, the power consumption of the piezoelectric element is reduced, so the Mn content within the above range is preferable. If the Mn content is less than 0.04 parts by weight, the effect of improving the dielectric loss tangent may not be expected in comparison with oxides containing no Mn. On the other hand, when the content of Mn is more than 0.40 parts by weight, the piezoelectric constant may be lowered compared to an oxide containing no Mn. A user of the present invention can adopt a desired content according to the application.

When the room temperature piezoelectric constant d ₃₃ of the piezoelectric material layer constituting the piezoelectric element of the present invention satisfies d ₃₃ ≧160 pm/V, sufficient vibration velocity and torque are obtained when the piezoelectric element is applied to a vibrator or vibration wave motor. is obtained.

When the dielectric loss tangent of the piezoelectric element of the present invention and the piezoelectric material layer constituting the piezoelectric element at room temperature is 0.8% or less in the range of 100 to 1000 Hz, the adverse effect on the power consumption of the piezoelectric element is negligible. becomes.

(Manufacturing method of piezoelectric element)
Although the method of manufacturing the piezoelectric element according to the present invention is not particularly limited, a method of manufacturing the piezoelectric element using a barium titanate-based material as the metal oxide constituting the piezoelectric material layer will be exemplified below.

First, a slurry is obtained by adding a solvent to a powdery barium titanate-based material.

The powdery barium titanate-based material is pretreated with an oxide containing Ba, Ca, Ti and Zr components at 800° C. to 1100° C. in order to prevent warping and cracking of the laminated element during the subsequent firing process. It is preferable to use a so-called calcined powder that has been calcined at a temperature of about. A calcined powder may be obtained by adding a Mn oxide to the oxide and calcining the mixture. The mixing ratio of the Ba, Ca, Ti, Zr and Mn components contained in the calcined powder is the same as that of the target metal oxide.

An auxiliary agent is added to the calcined powder for the purpose of forming voids after sintering. When the auxiliary agent contains particulate SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ , the temperature at which shrinkage occurs due to grain growth during firing is lowered, and voids are formed inside the piezoelectric material layer. It is preferable because the part is generated. Preferable average particle diameters of particulate SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ are 0.5 μm or more and 2.0 μm or less.

In addition, the auxiliary agent may contain hollow particles in order to promote the formation of voids inside the piezoelectric material layer. As the material of the particles, a material that does not affect the piezoelectric properties after firing is preferable, and for example, SiO ₂ or an organic polymer can be used.

The addition ratio of the auxiliary agent to the calcined powder is preferably 0.05 parts by weight or more and 1.0 parts by weight or less. By setting the addition ratio of the auxiliary agent within the above range, it is possible to form a void inside the piezoelectric material layer without impairing the vibration speed of the piezoelectric element.

As a solvent to be added to the powdery barium titanate-based material, for example, toluene, ethanol, a mixed solvent of toluene and ethanol, n-butyl acetate, and water can be used. The amount of solvent is, for example, 1.0 to 2.0 times the weight of the metal compound powder. A solvent is added to the metal compound powder and mixed by a ball mill for 24 hours, and then a binder and a plasticizer are added. For example, PVA (polyvinyl alcohol), PVB (polyvinyl butyral), acrylic resin, or the like can be used as the binder. When PVB is used as the binder, PVB is weighed so that the weight ratio of the solvent to PVB is, for example, 88:12. Examples of plasticizers that can be used include dioctyl sebacate, dioctyl phthalate, and dibutyl phthalate. When dibutyl phthalate is used as the plasticizer, dibutyl phthalate is added in the same weight as the binder.

After adding the binder and plasticizer, the mixture is ball milled again overnight. The target viscosity of the slurry is 300 to 500 mPa·s, and the amount of solvent and binder may be increased or decreased to adjust the viscosity.

Next, the slurry is placed on a substrate to obtain a green sheet that is a precursor of the piezoelectric material layer.

A green sheet can be obtained, for example, by applying the slurry onto the base material using a doctor blade and drying it. For example, a fluorine-coated PET film can be used as the base material. The thickness of the green sheet is not particularly limited, and can be adjusted according to the intended thickness of the piezoelectric material layer. The thickness of the green sheet can be increased, for example, by increasing the viscosity of the slurry.

Next, an electrode layer is formed on the green sheet.

Small holes are formed in the green sheet to serve as through holes as required. Furthermore, the holes formed in the green sheet are filled with a paste made of a conductive powder material that will serve as a short-circuit electrode by screen printing. Furthermore, a paste made of a conductive powder material for forming an electrode layer is printed on the surface of the green sheet by screen printing.

A plurality of green sheets are stacked in order from the bottom as shown in FIG. 1, and heated and pressed by a heating/pressurizing device to laminate and form a laminate before firing.

Then, the laminated body is sintered at 1150.degree. C. to 1350.degree. C. in an air atmosphere. Next, the sintered body after sintering is subjected to polarization treatment. The conditions for the polarization treatment vary depending on the composition and structure of the piezoelectric material layer.

(Vibrator of the present invention)
The vibrator of the present invention includes a piezoelectric element, a first elastic body and a second elastic body sandwiching the piezoelectric element, and penetrating through the piezoelectric element, the first elastic body, and the second elastic body. The vibrator has a shaft and a nut provided on the shaft.

FIG. 3 is a cross-sectional view of a schematic structure showing one embodiment of the vibrator of the present invention.

As shown in FIG. 3, the piezoelectric element 10 is sandwiched between a first elastic body 21 and a second elastic body 22 in the stacking direction of the piezoelectric element 10 . Furthermore, the piezoelectric element 10 has a shaft 24 and a first nut 25 .

The first elastic body 21 and the second elastic body 22 have holes through which the shaft 24 is passed.

Shaft 24 passes through piezoelectric element 10 , first elastic body 21 and second elastic body 22 .

Furthermore, a first nut 25 is attached to said shaft 24 . Materials for the first elastic body 21, the second elastic body 22, the shaft 24, and the first nut 25 are not limited, but are preferably made of metal from the viewpoint of elastic modulus, and examples thereof include SUS material and brass. be.

The piezoelectric element 10 is joined to the first elastic body 21 and the second elastic body 22 using an adhesive or the like at the locations of the first electrode and the second electrode. It is preferable to perform the bonding while applying a pressure of about 1 MPa to 10 MPa. Also, the piezoelectric element 10 is tightened by the shaft 24 and the first nut 25 to apply a predetermined compressive force. By applying a compressive force to the piezoelectric element 10, it is possible to prevent the piezoelectric element 10 from breaking when the laminated piezoelectric vibrator vibrates with a large displacement.

(Vibration wave motor of the present invention)
A vibration wave motor of the present invention is characterized by having the vibrator and a moving body in contact with the first elastic body 21 of the vibrator.

FIG. 4 is a sectional view of a schematic structure showing one embodiment of the vibration wave motor of the present invention.

The vibration wave motor 40 of the present invention includes the piezoelectric element 10, the first elastic body 21, the second elastic body 22, the shaft 24, and the first nut 25, which constitute the vibrator 20, as well as the moving body 30. have. Further, the vibration wave motor 40 may have a flange 35 for attaching the vibration wave motor 40 to the device and a second nut 36 for pressing the moving body 30 against the vibrator 20, if necessary. The flange 35 is a member for attaching the vibration wave motor 40 to an external member (not shown) such as a frame of equipment on which the vibration wave motor 40 is mounted, and is fixed at a predetermined position by a second nut 36 .

Although the structure of the moving body 30 is not limited, the general structure shown in FIG. 4 has a rotor 31 as a main member for converting vibration of a piezoelectric element into rotational motion. Further, if necessary, the moving body 30 includes a sliding member 32 for suppressing abnormal noise during vibration, and a pressure spring for applying a frictional force to the contact surface between the first elastic body 21 and the moving body 30. 33. It may have a gear 34 for power transmission as shown.

The material of the sliding member 32 is preferably resin such as natural rubber or synthetic rubber. The rotor 31, the pressure spring 33, the gear 34, the flange 35, and the second nut 36 are preferably made of metal, such as SUS material or brass.

In the vibration wave motor 40, the first elastic body 21 of the vibrator 20, which is a constituent member, is in contact with the moving body 27 (sliding member 32 in the figure). When the first elastic body 21 and the moving body 27 are in contact with each other, vibration generated by applying a voltage to the vibrator 20 can be efficiently transmitted to the moving body 27 .

A lower end of the sliding member 32 is in contact with the upper surface of the first elastic body 21 . The rotor 31 is fixed to the sliding member 32 . The gear 34 is arranged above the rotor 31 , and the concave portion provided on the upper side of the rotor 31 and the convex portion provided on the lower side of the gear 34 are engaged. A pressure spring 33 is arranged between the rotor 31 and the gear 34 . The spring force of the pressure spring 33 positions the gear 34 and presses the rotor 31 downward. As a result, the lower end surface of the sliding member 32 fixed to the rotor 31 is pressed against the upper surface of the first elastic body 21 and comes into pressure contact, so that a predetermined frictional force is generated on the contact surface.

When a voltage is applied to the piezoelectric element 10, bending vibration is generated in the vibrator 20, and the sliding member 32, the rotor 31, the gear 34, and the pressure spring 33, which constitute the moving body 30, are united to move the axis of the shaft 24. rotate around. Rotation output can be taken out from any one of the sliding member 32 , the rotor 31 and the gear 34 .

(Optical device of the present invention)
The optical apparatus of the present invention is characterized by having the vibration wave motor 40 and an optical member dynamically connected to the vibration wave motor 40 .

FIG. 5 is a perspective view showing a schematic structure of a digital camera (imaging device) 200, which is an example of the optical equipment of the present invention.

A lens barrel 202 is attached to the front surface of the digital camera 200. Inside the lens barrel 202, a lens and a camera shake correction optical system 203 are arranged.

An imaging element 208 is arranged on the main body side of the digital camera 200, and light passing through the lens barrel 202 forms an image on the imaging element 208 as an optical image. The imaging device 208 is a photoelectric conversion device such as a CMOS sensor or CCD sensor, and converts an optical image into an analog electrical signal. An analog electrical signal output from the image pickup device 208 is converted into a digital signal by an A/D converter (not shown), and then undergoes predetermined image processing by an image processing circuit (not shown) to form image data (video data). It is stored in a storage medium such as a semiconductor memory (not shown).

A lens group (not shown) movable in the optical axis direction is arranged in the lens barrel 202 . The vibration wave motor 100 is mechanically connected to an optical member such as a lens barrel through a gear train (not shown) or the like, and drives a lens group arranged in the lens barrel 202 . The vibration wave motor 100 can be used in the digital camera 200 to drive a zoom lens, a focus lens, and the like.

Here, a digital camera has been described as an optical device of the present invention. In addition, the present invention can be applied to optical equipment having a vibration wave motor in its drive unit, regardless of the type of camera, such as an interchangeable lens barrel of a single-lens reflex camera, a compact camera, an electronic still camera, and a mobile information terminal with a camera. be able to.

(Electronic device of the present invention)
An electronic device according to the present invention is characterized by including an electronic component and the piezoelectric element 10 as a drive source.

FIG. 6 is a schematic diagram showing one embodiment of the electronic device of the present invention.

The laminated piezoelectric vibrator of the present invention can be used in electronic devices such as liquid ejection heads, vibration devices, piezoelectric sound collectors, piezoelectric sound generators, piezoelectric actuators, piezoelectric sensors, piezoelectric transformers, ferroelectric memories, and power generators.

An electronic device of the present invention, as shown in FIG. 6, includes the laminated piezoelectric vibrator of the present invention, and has at least one of means for applying voltage to the laminated piezoelectric vibrator and means for extracting power. “Electric power extraction” may be either an act of extracting electrical energy or an act of receiving an electrical signal. An electronic device uses the vibrator vibration generated by the voltage applying means for its function. Alternatively, the electric power generated in the laminated vibrator vibrated by an external action is detected by the electric power extracting means and used by the electronic device for its function.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

(Example 1)
First, a powdery barium titanate-based material was prepared as a starting material for the piezoelectric material layer.

Specifically, barium carbonate (BaCO ₃ ), calcium carbonate (CaCO ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ) and trimanganese tetroxide (Mn ₃ O ₄ ) are added to the sum of Ba and Ca. The value of x, which is the molar ratio of Ba to They were weighed and mixed so as to be 0.30 parts by weight in terms of metal with respect to 100 parts by weight of the oxide contained. This mixed powder was calcined at 900° C. for 4 hours to obtain a calcined powder made of a barium titanate-based material.

0.1 part by weight of an auxiliary agent was added to 100 parts by weight of the calcined powder. A mixture of particulate SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ having an average particle diameter of 1.0 μm was used as the auxiliary agent. The weight ratio of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ contained in the auxiliary agent was 5:2:2:1 as anhydride.

Next, calcined powder mixed with an auxiliary agent and 3 parts by weight of a binder (PVB) with respect to 100 parts by weight of calcined powder were added to water as a solvent and mixed to obtain a slurry.

Using the obtained slurry, a green sheet having a thickness of 60 μm was obtained by a doctor blade method.

A conductive paste for internal metal electrodes was printed on the green sheet. A 60% Ag-40% Pd alloy (Ag/Pd=1.50) paste was used as the conductive paste. A sintered body was obtained by stacking 36 green sheets coated with a conductive paste and firing the stack at a maximum temperature of 1250° C. for 5 hours.

The composition of the piezoelectric material portion of the sintered body thus obtained was evaluated by ICP emission spectroscopic analysis. As a result, the main component is an oxide represented by the chemical formula ( _Ba0.87Ca0.13 ) _{( Ti0.97Zr0.03} ) _{O3 ,} and Mn was found to contain 0.30 parts by weight. The components of Ba, Ca, Ti, Zr, and Mn matched the weighed composition and the composition of the piezoelectric material after sintering.

The thickness of the sintered body in the stacking direction was 2.0 mm.

The sintered body was cut into a cylindrical shape with an outer diameter of 6 mm, and a through hole with an inner diameter of 2 mm was formed in the center of the circular surface by a cutting process. A pair of metal electrodes (a first electrode and a second electrode) for alternately short-circuiting the internal electrode layers are formed on the outer surface of the cylindrical element by Au sputtering, thereby forming a piezoelectric element as shown in FIG. 1(c). made. Next, the laminated sintered body was subjected to polarization treatment to obtain the piezoelectric element of the present invention. Specifically, the sample was heated to 135° C. on a hot plate, an electric field of 14 kV/cm was applied between the first electrode and the second electrode for 30 minutes, and cooled to room temperature while the electric field was applied.

When the lead component contained in the piezoelectric element was evaluated by ICP emission spectroscopic analysis, it was found that the piezoelectric element contained about 2 ppm of lead component. The lead component contained in the piezoelectric material layer portion was also approximately 2 ppm.

Observation of the side section of the piezoelectric element with a microscope of 25 magnifications revealed that 36 piezoelectric material layers and 35 electrode layers were alternately laminated. The layer thickness _TP of each piezoelectric material layer was 55 μm. The layer thickness _TE of the electrode layers was 6 μm for all electrode layers.

Furthermore, using a scanning electron microscope, the side cross section of the piezoelectric element was observed at a high magnification of 400 times. FIG. 7 shows a backscattered electron image of a side section of the piezoelectric element of Example 1. As shown in FIG. In FIG. 7, white portions with high brightness are electrode layers, and colored portions with low brightness sandwiched between a plurality of electrode layers are piezoelectric material layers. The black portions inside the piezoelectric material layer are voids, and the neutral-colored portions are aggregates of crystal grains. Metal oxide particles have different brightness of backscattered electrons. The black band at the bottom of the figure is artificially colored to show the scale bar and has nothing to do with the structure of the piezoelectric element.

Each of the three piezoelectric material layers seen in FIG. 7 was formed of aggregates of multiple crystal grains and multiple voids.

Here, attention is focused on the second piezoelectric material layer from the bottom in FIG. For the piezoelectric material layer, five backscattered electron images of the same magnification are acquired at different observation points, and from these observed images, the average thickness _TP in the stacking direction of the piezoelectric material layer and the thickness of the electrode layer in contact with the piezoelectric material layer are calculated. The average thickness T _E was calculated to be T _P of 55 μm and T _E of 6.0 μm. Next, when the average circular equivalent diameter D _G of the crystal grains was calculated from the same observed image of the piezoelectric material layer, it was 8.5 μm, which was larger than 0.07 times smaller than 0.33 times T _P .

Further, by observing the entire cross section of the piezoelectric material layer, the maximum length _LV in the _stacking direction of the void portion present in the portion surrounded by the crystal grains and not in contact with the electrode layer was determined. , 10 μm which is larger than T _E and smaller than 0.3 times T _P .

When the line average roughness Ra of the interface between the piezoelectric material layer of interest and the adjacent electrode layer was calculated from the same observed image, Ra was 0.42 μm as the average value of the two interfaces.

From the same observed image, the ratio PV of the total cross-sectional area of the _voids to the cross-sectional area of the piezoelectric material layer was 6.2% by area.

The apparent piezoelectric constant d ₃₃ ^*sum of the entire piezoelectric element obtained in this example was measured with a d ₃₃ meter at room temperature, and the measured value d ₃₃ ^*sum was divided by ₃₆ , which is the number of layers. was 200 pm/V. At the same time, the loss tangent obtained with the d ₃₃ meter was 0.5% at 160 Hz.

Subsequently, a laminated piezoelectric vibrator was produced using the obtained piezoelectric element.

First, the piezoelectric element was treated with a primer and pressure-bonded to the first elastic body made of SUS. Subsequently, an electric wiring made of a flexible printed circuit board was sandwiched between a second elastic body made of SUS and the surface of the piezoelectric element to which the first elastic body was not adhered. Finally, after the shaft made of SUS was passed through the piezoelectric element, the first elastic body and the second elastic body, the first nut made of SUS was used to pressurize and tighten the laminated piezoelectric vibrator of the present invention. got

(Examples 2 to 7)
A piezoelectric element of the present invention was obtained in the same manner as in Example 1, except that the mixing ratio of raw materials, the thickness of the green sheet, the Ag/Pd ratio of the conductive paste, and the maximum firing temperature of the laminate were changed.

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, in all piezoelectric elements, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. . The lead component contained in the piezoelectric element and the piezoelectric material layer was less than 10 ppm in all piezoelectric elements. Table 1 shows the manufacturing conditions of the piezoelectric element.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. Table 2 shows the measurement results of each parameter. The PV _obtained in the same manner as in Example 1 was within the range of 3 to 10 area %.

Next, in the same manner as in Example 1, laminated piezoelectric vibrators using the piezoelectric elements of Examples 2 to 7 were produced.

(Example 8)
As an auxiliary agent for the calcined powder, in addition to a mixture of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ , 0.1 part by weight of solid content per 100 parts by weight of the calcined powder A piezoelectric element of the present invention was obtained in the same manner as in Example 1, except that silica fine particles were added in the form of an IPA dispersion.

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. The lead component contained in the piezoelectric element and piezoelectric material layer was about 3 ppm.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. Table 2 shows the measurement results of each parameter. PV obtained in the same manner as in Example 1 was _9.0 area %.

Next, in the same manner as in Example 1, a laminated piezoelectric vibrator using the piezoelectric element of Example 8 was produced.

(Comparative example 1)
A comparative piezoelectric element was prepared in the same manner as in Example 1, except that the Ag/Pd ratio of the conductive paste was changed from 6:4 to 4:6 and the maximum firing temperature of the laminate was changed from 1250°C to 1400°C. Obtained.

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. Table 1 shows the manufacturing conditions of the piezoelectric element.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. As a result, _TP was 55 μm, _DG was 20.1 μm, _LV was _19.0 μm, and TE was 6.0 μm. That is, D _G was 0.36 times T _P and L _V was greater than T _E and 0.35 times T _P . Table 2 shows the measurement results of each parameter. PV obtained in the same manner as in Example 1 was _13.7 area %.

Next, in the same manner as in Example 1, a laminated piezoelectric vibrator using the piezoelectric element of Comparative Example 1 was produced.

(Comparative example 2)
The thickness of the green sheet, the Ag/Pd ratio of the conductive paste, and the maximum firing temperature of the laminate are changed, and the amount of the auxiliary agent added is set to 1.0 part by weight per 100 parts by weight of the calcined powder. A piezoelectric element for comparison was obtained in the same manner as in Example 1, except that the amount was increased to .

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. Table 1 shows the manufacturing conditions of the piezoelectric element.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. As a result, _TP was 30 μm, _DG was _12.3 μm, _LV was 10 μm, and TE was 6 μm. That is, D _G was 0.40 times T _P and L _V was greater than T _E and 0.33 times T _P . Table 2 shows the measurement results of each parameter. PV obtained in the same manner as in Example 1 was _10.4 area %.

Next, in the same manner as in Example 1, a laminated piezoelectric vibrator using the piezoelectric element of Comparative Example 2 was produced.

(Comparative Example 3)
A comparative piezoelectric element was obtained in the same manner as in Example 1, except that the thickness of the green sheet, the Ag/Pd ratio of the conductive paste, and the maximum firing temperature of the laminate were changed.

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. Table 1 shows the manufacturing conditions of the piezoelectric element.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. As a result, _TP was ₄₅ μm, _DG was 1.9 μm, LV was 1.2 μm, and _TE was 6.0 μm. That is, D _G was 0.04 times T _P and L _V was less than T _E . Table 2 shows the measurement results of each parameter. PV obtained in the same manner as in Example 1 was _2.8 area %.

Next, in the same manner as in Example 1, a laminated piezoelectric vibrator using the piezoelectric element of Comparative Example 3 was produced.

(Comparative Example 4)
By changing the Ag/Pd ratio of the conductive paste and the maximum firing temperature of the laminate, the component ratio of the auxiliary agent was changed to 7:3:0 by weight ratio of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ and Na ₂ CO ₃ . A piezoelectric element for comparison was obtained in the same manner as in Example 1, except that the pair was 0.

When the composition of the piezoelectric material portion was evaluated by ICP emission spectroscopic analysis, the weighed composition of Ba, Ca, Ti, Zr, and Mn matched the composition after sintering. Table 1 shows the manufacturing conditions of the piezoelectric element.

In the same manner as in Example 1, T _P , T _E , D _G , L _V , Ra, d ₃₃ and dielectric loss tangent of the piezoelectric element were measured. As a result, _TP was 55 μm, _DG was 10.0 μm, _LV was 0.8 μm, and _TE was 6.0 μm. That is, D _G was 0.18 times T _P and L _V was less than T _E. Table 2 shows the measurement results of each parameter. PV obtained in the same manner as in Example 1 was _1.1 area %.

Next, in the same manner as in Example 1, a laminated piezoelectric vibrator using the piezoelectric element of Comparative Example 4 was produced.

FIG. 8 shows the relationship between the values of T _P and D _G and T _P and L _V of the piezoelectric elements of Examples 1-8 and the piezoelectric elements of Comparative Examples 1-4. ♦ indicates values plotted for the example, and ◯ indicates values for the comparative example. In FIG. 8(a), the horizontal axis represents T _P and the vertical axis represents D _G , the solid line represents the range of 0.07 T _P ≦D _G ≦0.33 T _P , and the dotted line represents the range of 5 μm≦D _G ≦15 μm. It is shown as an auxiliary.

On the other hand, in FIG. 8(b), the horizontal axis represents T _P , the vertical axis represents L _V , and the solid line indicates the range of L _V ≦0.3 T _P.

(Vibrator generated displacement)
A DC electric field of 3 kV/mm was applied to the laminated piezoelectric vibrators of Examples 1 to 8 and Comparative Examples 1 to 4, and the strain rate was measured with a laser displacement meter. The strain rate here is a percentage obtained by multiplying the value obtained by dividing the measured strain amount by the thickness of the laminated portion and multiplying by 100.

The oscillator distortion rates of Examples 1 to 8 were all in the range of 0.10% or more and 0.15% or less, while the oscillator distortion rates of Comparative Examples 1, 2, and 4 were 0.08%. was small in extent. In particular, the oscillator strain rate of Comparative Example 3 was as small as about 0.04%.

(Fabrication of vibration wave motor)
In the laminated piezoelectric vibrators of Examples 1 to 8 and Comparative Examples 1 to 4, a moving body comprising a rubber sliding member, a SUS rotor, a SUS pressure spring, and a SUS gear, and a SUS A flange and a second SUS nut were attached to fabricate a vibration wave motor having the structure shown in FIG.

An alternating voltage of 15 Vrms was applied to the produced vibration wave motor to rotate the vibration wave motor. The frequency of the applied voltage was brought close to the resonance frequency, and the power consumption of the motor portion was measured with a wattmeter for the vibration wave motor whose rotational speed reached 700 rpm. Table 3 shows the measurement results.

As shown in Table 3, the power consumption of the vibration wave motors of the examples at 700 rpm was all 1.7 W or less, while the power consumption of Comparative Examples 1, 2, and 4 under the same conditions was 2.3W or more. In addition, the vibration wave motor of Comparative Example 3 did not reach a maximum rotation speed of 700 rpm when a voltage was applied.

As can be seen from FIG. 8(a), the average equivalent circle diameter _D.sub.G exerts excellent effects by being within an appropriate range with respect to the thickness _T.sub.P in the lamination direction of the piezoelectric material layers. In addition, as can be seen from FIG. 8(b), the maximum length of the gap in the stacking direction, _LV , is also excellent when it falls within an appropriate range with respect to _TP . According to each example and each comparative example described in Table 2, the example satisfying the above conditions showed a favorable value of piezoelectric constant _d33 of 170 pC/N or more, which is 10% or more higher than that of the comparative example. rice field. Also, as can be seen from Table 3, the power consumption of each example was 1.7 W or less, which was a good value lower than that of the comparative example by more than 20%.

(Number of piezoelectric material layers)
Although the number of piezoelectric material layers in the piezoelectric elements, laminated piezoelectric vibrators, and vibration wave motors of Examples 1 to 8 is 36, the number of layers can be changed from 2 to 60 in the same manner. We were able to. In particular, the vibration wave motor having 25 to 55 layers could be driven at 700 rpm with the power consumption of the motor close to Table 3.

(optical equipment)
The vibration wave motors of Examples 1 to 8 and Comparative Examples 1, 2, and 4 were mechanically connected to a lens barrel as an optical member to produce an optical apparatus as shown in FIG. Autofocus operation in response to the application of the alternating voltage could be confirmed in any optical device, but the power consumption of the optical device of the example was 20% or more smaller than that of the optical device of the comparative example. .

(Electronics)
Using the piezoelectric elements of Examples 1 to 8, the liquid ejection head shown in FIG. 9 was manufactured. The liquid ejection head shown in FIG. 9 has the piezoelectric element 101 (consisting of an electrode 1011, a laminated portion 1012, and an electrode 1013) of the embodiment. Further, it has an ejection port 105 , an individual liquid chamber 102 , a communication hole 106 connecting the individual liquid chamber 102 and the ejection port 105 , a liquid chamber partition 104 , a common liquid chamber 107 , a vibration plate 103 and a piezoelectric element 101 . Liquid ink can be stored in the liquid chamber.

When an electric signal was input to the liquid ejection head, it was confirmed that the ink was ejected following the signal pattern. This liquid ejection head was incorporated into an ink jet printer, and ejection of ink onto recording paper was confirmed.

According to the present invention, a piezoelectric element having highly efficient drive characteristics can be provided. Further, according to the present invention, it is possible to provide vibrators, vibration wave motors, optical devices, and electronic devices that have highly efficient drive characteristics. Furthermore, the laminated element of the present invention can be applied to piezoelectric devices using laminated elements in general.

REFERENCE SIGNS LIST 1 electrode layer 2 piezoelectric material layer 3 electrode layer

Claims (12)

In a piezoelectric element in which piezoelectric material layers and electrode layers are alternately laminated,
The piezoelectric material layer has a plurality of crystal grains and a plurality of voids,
At least one of the piezoelectric material layers comprises:
T _P is the average thickness in the stacking direction of the piezoelectric material layer, D _G is the average circle equivalent diameter of the plurality of crystal grains, and _LV is the maximum length in the stacking direction of the plurality of gaps that are not in contact with the electrode layer. , where TE is the average thickness of the electrode layer in contact with at least one of the piezoelectric material layers, _{0.07T P} ≤ DG ≤ _{0.33T P} , _{TE ≤ LV ≤ 0.3T P , and} lead The content is less than 1000 ppm ,
In the cross-sectional observation field of view of the piezoelectric element, the length of the piezoelectric material layer in the lamination direction is TE + _{TP +} TE , and the length in the direction intersecting the lamination direction is TE _{+ TE} . For a length greater than T _P + T _E ,
A piezoelectric element in which, in the cross _{- sectional} observation field, the ratio PV of the area _SV occupied by the void portion to the area SP of the piezoelectric material layer is 3 area % or more and 10 area % or less . 2. The piezoelectric element according to claim 1, wherein the average circle equivalent diameter _DG is 5 [mu]m or more and 15 [mu]m or less. 3. The piezoelectric element according to claim 1, wherein the line average roughness Ra of the interface of the electrode layer in contact with the piezoelectric material layer is 1 [mu]m or less when observed from the cross section in the stacking direction. 4. The piezoelectric element according to claim 1, wherein the piezoelectric material layer has an average thickness _TP of 20 [mu]m or more and 70 [mu]m or less in the stacking direction. The piezoelectric element according to any one of claims 1 to 4, wherein an average thickness _TE of the electrode layer in contact with the at least one piezoelectric material layer is 3.5 µm or more and 10 µm or less. 6. The piezoelectric element according to any one of claims 1 to 5, wherein the piezoelectric material layer comprises oxides of titanium and barium. 7. The piezoelectric element of claim 6, wherein said oxides of titanium and barium include Ba, Ca, Ti, and Zr. In the piezoelectric material layer, x, which is the molar ratio of Ca to the sum of Ba and Ca, is 0.02≦x≦0.30, and the molar ratio of Zr to the sum of Ti and Zr. 7. The method according to claim 6, wherein y is 0.01≦y≦0.09, and 0.02 parts by weight or more and 0.40 parts by weight or less of Mn in terms of metal is contained with respect to 100 parts by weight of the oxide. piezoelectric element. A vibrator comprising the piezoelectric element according to any one of claims 1 to 8, and a first elastic body and a second elastic body that sandwich the piezoelectric element. 10. A vibration wave motor comprising the vibrator according to claim 9 and a moving body in contact with the vibrator. 11. An optical apparatus comprising the vibration wave motor according to claim 10 and an optical member movably held by the vibration wave motor. An electronic device comprising an electronic component and the piezoelectric element according to claim 1 .

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