JP4522070B2 - Piezoelectric ceramics for piezoelectric actuator, manufacturing method thereof, and hard disk device using the same - Google Patents

Description

  The present invention relates to piezoelectric ceramics for piezoelectric actuators that have both stable piezoelectric characteristics and sufficient mechanical strength and can be used in ink jet recording heads, fans, ultrasonic motors, magnetic disk devices, and the like, and more particularly to the piezoelectric ceramics. In particular, the present invention relates to a piezoelectric ceramic for a piezoelectric actuator for driving a magnetic recording head and a hard disk device using the same.

  In recent years, information devices have been refined, and there is an increasing demand for actuators that require minute movement distances on the order of submicrons or nanometers. For example, an actuator that can move and control a minute distance is required for focus correction and tilt angle control of an optical system, a printer of a printer, a head actuator of a magnetic disk device, and the like.

  Among such information devices, the magnetic disk device is one of the key devices of multimedia devices that have rapidly expanded in recent years. In multimedia devices, in order to handle a large amount of images and sounds at high speed, it is desired to develop a device with a larger storage capacity. Increasing the capacity of a magnetic disk device is generally realized by increasing the storage capacity per disk. However, in order to increase the recording density of the magnetic recording disk device without changing the diameter of the disk, it is essential to increase the number of tracks per unit length, that is, to narrow the track width. And if the storage density is increased rapidly, the track width will become narrower. Therefore, it is a technical problem how to accurately position the head element that reads and writes to the recording track. There is a demand for a head actuator that can be used.

  As a solution to this problem, attempts have been made to generally improve the rigidity of movable parts such as a carriage and raise the main resonance point frequency in the in-plane direction. However, there is a limit to the improvement of the resonance point, and even if the in-plane resonance point of the movable part can be significantly increased, resonance occurs due to the bearings supporting the movable part exhibiting spring characteristics. Therefore, it was difficult to increase the servo bandwidth.

  Therefore, as one means for solving these problems, an arm (magnetic recording head support mechanism) is connected to a first actuator composed of a voice coil motor or the like attached to the magnetic disk device main body to drive the magnetic recording head. It is known to do. However, it is very difficult to drive the magnetic recording head on the submicron order by driving only with the first actuator. For this purpose, a second actuator composed of a piezoelectric element for positioning the magnetic recording head on the track is provided at the intermediate portion or the tip of the magnetic recording head support mechanism. Has been done. The second actuator slightly moves the magnetic recording head installed at the tip of the arm independently of the operation of the first actuator.

  An example in which the second actuator for fine driving of the magnetic recording head as described above is provided is disclosed in Patent Document 1. In other words, the second actuator is provided between the first actuator and the magnetic recording head to drive the magnetic recording head minutely. FIG. 3 shows a piezoelectric element provided in the second actuator. That is, a magnetic recording disk, a magnetic recording head for recording and reproducing information on the information recording surface of the magnetic recording disk, and a radius of the magnetic recording disk for positioning the magnetic recording head on a recording track of the magnetic recording disk A first actuator that moves in a direction, and the magnetic recording head that is provided in a part of the first actuator is moved a small distance in the radial direction of the magnetic recording disk independently of the operation of the first actuator. The second actuator comprises a first arm having a magnetic recording head held at the tip thereof and a second arm connected to the first arm via a piezoelectric element. A hard disk drive that moves the magnetic recording head by driving the first arm by a minute drive of the piezoelectric element; Displaces the two piezoelectric elements 13 so as to reverse the difference in the longitudinal direction of the second arm 15. Since the two piezoelectric elements 13 are connected by the spring mechanism 14, each can be independently piezoelectrically displaced. Thereby, the magnetic recording head can be finely driven.

  Moreover, although the example shown in the said patent document 1 is an example which installed the 2nd actuator in the intermediate part of the arm of the above-mentioned actuator, the example which has installed the mechanism which has the same function in the front-end | tip part of this arm is also possible. Proposed.

  Multi-component ceramics have been conventionally used as piezoelectric elements used for micro driving of these magnetic recording heads, and lead zirconate titanate (PZT) has been widely used as the material composition. .

  When the PZT material is used as the above-mentioned piezoelectric ceramics for micro drive of the magnetic recording head, the mechanical characteristics, electrical characteristics, thermal characteristics, etc. of the conventional piezoelectric ceramics are required characteristics of the piezoelectric ceramic used for the piezoelectric actuator. In order to improve this, a specific compound is added, or the main component is replaced with another component.

For example, in order to obtain piezoelectric ceramics having a high piezoelectric strain constant, Patent Documents 2 to 5 disclose that Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (PbZrO ₃ —PbTiO _{3) is} a two-component composition. Zn _1/3 Nb _2/3 ) O ₃ , Pb (Ni _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Sb _2/3 ) O _{3 and the} like are added as a third component perovskite type A multi-component ceramic made of an oxide is disclosed.

  In addition, the mechanical properties, electrical properties, thermal properties, etc. of multi-component ceramics are improved by controlling the pulverized particle size, specific surface area, etc. of the ceramic raw material powder, and controlling the molding and firing conditions. Has been done.

Patent Document 6 discloses a piezoelectric ceramic whose electromechanical coupling coefficient and mechanical strength are controlled by containing a specific amount of carbon.
Japanese Patent Laid-Open No. 3-69072 JP-A-53-62199 Japanese Patent Laid-Open No. 49-21696 JP 48-97094 A JP 49-27897 A JP 2001-19542 A

  Conventional piezoelectric ceramics are formed and fired using a starting material having a controlled material composition, processed as desired, and completed as a ceramic sintered body. However, since the material composition after firing changes from the material composition at the starting material due to evaporation of Pb and Zn, which are the main components, from the ceramic sintered body during firing, characteristics such as piezoelectric strain constant of piezoelectric ceramics There were problems such as deterioration and fluctuation.

  In addition, the mechanical properties, electrical properties, and thermal properties of the resulting ceramic sintered body are controlled by the manufacturing method that controls the pulverized particle size, specific surface area, etc. of the ceramic raw material powder, and controls the molding and firing conditions. In general, it is necessary to finely grind the pulverized particle size of the ceramic raw material powder. However, the finely pulverized powder has a problem that it is difficult to handle and a problem that a crack occurs during molding.

  In addition, the piezoelectric ceramic described in Patent Document 6 has a problem in that the piezoelectric strain constant decreases because carbon that greatly affects the value of the piezoelectric strain constant exists only in the solid state. This is considered due to the following reasons. Solid-state carbon generates lattice defects within the crystal and at grain boundaries. Lattice defects in the crystal generate lattice distortion of the piezoelectric ceramics or distort the regularity of the crystal lattice, so that the piezoelectric characteristics, for example, the piezoelectric strain constant is lowered.

  In addition, since the piezoelectric ceramic described in Patent Document 6 has a low piezoelectric strain constant, the following problem has occurred which is used as a constituent member of the second actuator for fine driving of the magnetic recording head described above. That is, for example, the piezoelectric element using the piezoelectric ceramic of Patent Document 6 has a problem that the amount of heat generated from the piezoelectric element increases because the piezoelectric element displacement for minute driving must be performed by applying a high voltage. there were. Therefore, there is a problem that the piezoelectric element is thermally expanded and it is difficult to finely drive the magnetic recording head with high accuracy.

  Further, when the piezoelectric ceramic of Patent Document 6 is used, there is a case where a piezoelectric displacement constant is low and, for example, a sufficient piezoelectric displacement enough to slightly drive the magnetic recording head cannot be obtained. There is a problem that it is difficult to use the second actuator mounted.

  Furthermore, in recent years, with the increase in recording density of hard disk devices, the flying gap between the magnetic recording head and the magnetic recording disk has become very narrow as 30 nm or less. When mounting the battery, it is required to reduce the amount of particles generated from the piezoelectric ceramic as much as possible. In order to reduce the amount of particles generated from the piezoelectric ceramic, it was necessary to reduce the surface roughness of the piezoelectric ceramic. For this reason, the piezoelectric ceramic used for the second actuator for minute driving is processed to reduce the surface roughness. However, the conventional piezoelectric ceramic of Patent Document 6, for example, has large closed pores and a large closed porosity after firing. Therefore, when this is processed, the processing abrasive grains used in the processing and the piezoelectric ceramic crystals peeled off by the processing There is a problem that the particle pieces remain as particles on the surface of the piezoelectric ceramic, or crystal grains of the piezoelectric ceramic are separated as particles after processing. Such particles enter between the magnetic recording head and the magnetic recording disk, causing malfunction of magnetic recording or damaging the magnetic recording head.

  Therefore, the present invention has been devised in view of the above-mentioned problems, and has a high piezoelectric strain constant. When used as a piezoelectric actuator for a hard disk device component or the like, the present invention is not damaged by mechanical stress applied to the piezoelectric ceramic. An object of the present invention is to provide a piezoelectric ceramic with high mechanical strength that can be prevented. It is another object of the present invention to provide a piezoelectric ceramic that generates less particles from piezoelectric ceramics. It is another object of the present invention to provide a hard disk device using the piezoelectric ceramic of the present invention.

The piezoelectric ceramic for a piezoelectric actuator according to the present invention is a piezoelectric ceramic for a piezoelectric actuator in which a magnetic recording head supported by an arm is micro-driven by the piezoelectric ceramic, and a gas containing CO ₂ is contained in the closed pores of the piezoelectric ceramic. The carbon content is less than 40 ppm by mass, and the surface roughness is 0.5 μm or less in terms of the center line average roughness Ra.

  The average pore diameter of the closed pores is 1 to 5 μm, and the closed porosity is 2% by volume or less.

The amount of gas containing CO ₂ in the closed pores is 5 mass ppm or more in terms of carbon element.

  Further, the method for producing a piezoelectric ceramic for a piezoelectric actuator according to the present invention includes a step of wet-mixing raw material powder before forming a piezoelectric ceramic and an organic binder to prepare a slurry, a step of filtering the slurry, and the filtration A step of forming a molded body using a later slurry, a step of firing the molded body in an atmosphere containing oxygen, and a step of processing the sintered body after firing and ultrasonically washing the sintered body. Features.

  In the step of firing the compact, the oxygen concentration in the atmosphere is 90% by volume or more.

  Further, the processed sintered body is washed with an ultrasonic cleaner in a solution containing 1 to 30% by mass of a surfactant, and further washed with pure water.

  The hard disk device of the present invention also includes a magnetic recording disk, a magnetic recording head for recording and reproducing information on the information recording surface of the magnetic recording disk, and a recording disk for positioning the magnetic recording head on a recording track of the magnetic recording disk. A first actuator for moving the magnetic recording head in the radial direction of the magnetic disk, and a second actuator for moving the magnetic recording head provided in a part of the first actuator by a minute distance in the radial direction of the magnetic disk independently of the operation of the first actuator. The second actuator has a first arm having a magnetic recording head held at the tip and a second arm connected to the first arm via a piezoelectric element. In a hard disk drive that moves the magnetic recording head by driving the first arm with a minute drive, the second actuator A piezoelectric element used in, characterized by using a piezoelectric ceramic for the piezoelectric actuator.

In a piezoelectric ceramic for a piezoelectric actuator that slightly drives a magnetic recording head supported by an arm, a gas containing CO ₂ is contained in the closed pores of the piezoelectric ceramic in an amount less than 40 ppm by mass in terms of carbon element with respect to the mass of the sintered body. By using the piezoelectric ceramic for the piezoelectric actuator, the displacement amount and mechanical strength of the piezoelectric ceramic can be increased. Therefore, even when used for micro drive of a magnetic recording head, it is possible to drive the magnetic recording head minutely without being damaged by mechanical stress and with the displacement of the piezoelectric ceramic being displaced in a wider range than before. It becomes. Further, since the center line average surface roughness Ra is set to 0.5 μm or less, the amount of particles generated particularly from the processed surface of the piezoelectric ceramic can be reduced, and the particles have entered between the magnetic recording head and the magnetic recording disk. In addition, it is possible to prevent information read / write errors caused by damage to the recording layer of the magnetic recording disk.

  In addition, by making the average pore diameter of closed pores 1 to 5 μm and the closed porosity 2 volume% or less, the mechanical strength can be further improved and the piezoelectric strain constant can be improved. It becomes possible to prevent the processing abrasive grains and the piezoelectric ceramic crystal particle pieces separated by the processing from entering the concave portions of the surface exposed by the processing of the piezoelectric ceramic.

In addition, a process for producing a slurry by wet mixing raw material powder and an organic binder before forming a piezoelectric ceramic, a process for filtering the slurry, a process for forming a molded body using the slurry after filtration, and a molding By manufacturing piezoelectric ceramics by a process of firing the body in an atmosphere containing oxygen, the gas containing CO ₂ in closed pores present in the obtained piezoelectric ceramics is 40 masses in terms of carbon element with respect to the mass of the sintered body. It can be contained in an amount of less than ppm, whereby a piezoelectric ceramic with improved piezoelectric strain constant and mechanical properties can be produced. Furthermore, by processing the sintered body after firing and ultrasonically washing the sintered body, it is possible to manufacture a piezoelectric ceramic in which generation of particles is suppressed.

  Moreover, after processing the sintered body in a solution containing 1 to 30% by weight of a surfactant with an ultrasonic cleaner, and further cleaning with pure water, processing marks and processing after processing This makes it possible to remove particles remaining in the recesses appearing on the surface of the piezoelectric ceramic porcelain, and when used as piezoelectric ceramics for piezoelectric actuators, it is possible to produce piezoelectric ceramics with further reduced generation of particles.

  A magnetic recording disk; a magnetic recording head that records and reproduces information on an information recording surface of the magnetic recording disk; and a magnetic recording head that moves in a radial direction of the recording disk in order to position the magnetic recording head on a recording track of the magnetic recording disk. And a second actuator that is provided in a part of the first actuator and moves the magnetic recording head by a minute distance in the radial direction of the magnetic disk independently of the operation of the first actuator. The actuator 2 has a first arm having a magnetic recording head held at the tip and a second arm connected to the first arm via a piezoelectric element, and the first arm is driven by a minute drive of the piezoelectric element. As a piezoelectric element used for the second actuator in a hard disk drive that moves the magnetic recording head by driving Of the use of the piezoelectric ceramic for a piezoelectric actuator, it is possible to increase the displacement amount of the piezoelectric ceramic can than conventional and extensive micro drive capable hard disk drive. In addition, the reliability and life of the hard disk device can be increased.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic view of an example of a hard disk device using the piezoelectric ceramic for a piezoelectric actuator of the present invention. 2A is a schematic diagram of an example of a second actuator equipped with the piezoelectric ceramic for piezoelectric actuator of the present invention, which is a part of FIG. 1, and FIG. 2B is a part of FIG. 2A. The schematic diagram shown in FIG. 2C is a cross-sectional view taken along line XX in FIG.

  1 includes a magnetic recording disk 12, a magnetic recording head 11 for recording and reproducing information on the information recording surface of the magnetic recording disk 12, and positioning the magnetic recording head 11 on a recording track of the magnetic recording disk 12. For this purpose, the first actuator 8 that moves in the radial direction of the magnetic recording disk 12 and the magnetic recording head 11 provided in a part of the first actuator 8 are operated independently of the operation of the first actuator 8. 12 includes a second actuator 10 that is moved by a minute distance in the radial direction. The second actuator 10 includes a first arm 9a having a magnetic recording head 11 held at the tip and a piezoelectric element on the first arm 9a. 20 and the second arm 9b connected via the piezoelectric element 20, and the first arm 9a is driven by the minute driving of the piezoelectric element 20. In the hard disk device 7 for moving the magnetic recording head 11 Te, the piezoelectric element 20 used in the second actuator 10 is formed by using a piezoelectric ceramic 5 for the piezoelectric actuators of the present invention to be described later.

  The first actuator 8 includes a voice coil motor 34 attached to the main body of the magnetic recording disk 12, and the second arm 9 b supported by the bearing 26 rotates to move the magnetic recording head 11 to the magnetic recording disk 12. Drive roughly in the radial direction. Since it is difficult to finely drive the magnetic recording head 11 only by the rough drive only by the first actuator 8, the second can drive the magnetic recording head 11 independently of the first actuator 8. In this way, the magnetic recording head 11 is slightly driven, which is difficult with only the first actuator 8.

A method for minutely driving the magnetic recording head 11 will be described with reference to FIGS. The piezoelectric element 20 includes electrodes 28 formed on both main surfaces of the piezoelectric ceramics 5a and 5b. Each of the two main surfaces of the piezoelectric element 20 is connected to the conductive first arm 9a and the conductive second arm 9b through the conductive adhesive 32. The first arm 9a is formed by connecting the conductive plate 4a and the conductive plate 4b by an insulating layer 36 such as an insulating adhesive, and the conductive plate 4a and the conductive plate 4b are electrically insulated. The second arm 9b is composed of a conductive plate 4c and a conductive plate 4d connected by an insulating layer 36 such as an insulating adhesive, and the conductive plate 4c and the conductive plate 4d are electrically insulated. Conductive plates 4b and 4d are connected to a conductive wire 30 whose outer peripheral surface is coated with an insulating layer, and a DC voltage can be applied from the conductive wire 30. The piezoelectric ceramics 5a and 5b are arranged in directions in which the polarization directions are opposite to each other. By applying a DC voltage between the electrodes 28 from the first arm 9a and the second arm 9b, the piezoelectric element 20 is first arm 9a, which piezoelectric displacement in _{d 15} mode in the longitudinal direction of the second arm 9b. Due to this piezoelectric displacement, the first arm 9a is deformed in the directions of arrows A and B, and the first arm 9a on which the magnetic recording head 11 is mounted can be slightly driven in the direction of arrow C. Further, the minute drive in the reverse direction of the arrow C is performed by applying a voltage to the first arm 9a and the second arm 9b so that the expansion and contraction of the piezoelectric ceramic 5 is in the reverse direction to the arrows A and B. Can do. In FIG. 2C, the insulating layer 36 is provided on both the first arm 9a and the second arm 9b, but may be provided on at least one of them.

The piezoelectric ceramic 5 for a piezoelectric actuator of the present invention contains a gas containing CO ₂ in closed pores in an amount of less than 40 ppm by mass in terms of carbon element with respect to the mass of the sintered body. Thereby, a piezoelectric ceramic having a high piezoelectric strain constant and high mechanical strength can be obtained. Since the piezoelectric ceramic 5 of the present invention has a large piezoelectric strain constant, the amount of displacement when a DC voltage is applied to the piezoelectric ceramic 5 increases. When the piezoelectric element 20 having a large displacement is used as a micro-driving piezoelectric actuator for the magnetic recording head 11, the magnetic recording head 11 can be micro-driven over a wide range. In addition, since the piezoelectric ceramic 5 has high mechanical strength, the piezoelectric ceramic 5 is not cracked or broken even if the magnetic recording head 11 is finely driven over a wide range.

  Here, the reason why the piezoelectric ceramic 5 of the present invention has a high piezoelectric strain constant and a high mechanical strength is considered as follows.

  The piezoelectric ceramic for a piezoelectric actuator of the present invention is made of a polycrystalline sintered body. When carbon remaining in a piezoelectric ceramic made of a polycrystalline sintered body exists in a solid state, the solid state carbon exists as a solid solution in a crystal grain or precipitates at a crystal grain boundary. Such solid-state carbon generates lattice defects within the crystal and at grain boundaries. Lattice defects in the crystal generate lattice distortion of the piezoelectric ceramics or distort the regularity of the crystal lattice, so that the piezoelectric characteristics, for example, the piezoelectric strain constant is lowered. In addition, lattice defects at the crystal grain boundaries become line defects, and the mechanical strength of the grain boundary phase is lowered, so that the mechanical strength of the piezoelectric ceramic is lowered. In order to suppress such a decrease in piezoelectric strain constant and a decrease in mechanical strength, it is important that carbon present in the piezoelectric ceramic be present not only in a solid state but also in a gas state.

  If carbon can be contained in a piezoelectric ceramic made of a polycrystalline sintered body in a gaseous state, lattice strain and the lattice defects can be remarkably reduced, so that mechanical strength is improved and piezoelectric strain constant is improved. Piezoelectric ceramics can be obtained. The reason for this is not clear, but is considered as follows.

  Compared to the case where carbon exists only in the solid state in the piezoelectric ceramic, when carbon is present in both the solid state and the gas state, when the piezoelectric ceramic is polarized by applying a voltage to the piezoelectric ceramic, Solid state carbon and carbon-containing gas are electrically coupled during polarization so that the polarization is uniform. This electrical coupling serves to make the direction of spontaneous polarization of crystals in the piezoelectric ceramic very uniform during polarization. Thereby, the piezoelectric characteristics such as the piezoelectric strain constant after polarization can be improved.

  Further, the mechanical strength of the piezoelectric ceramic is improved as the lattice defects and the lattice strain are reduced. The reason for this is that when carbon is present in the piezoelectric ceramics in a gas state as well as in a solid state, lattice defects and lattice strains existing in the piezoelectric ceramics before polarization are reduced by the polarization, and as a result, the mechanical strength of the piezoelectric ceramics is reduced. improves.

In the piezoelectric ceramic for a piezoelectric actuator of the present invention, a gas containing CO ₂ as a gas containing carbon is contained in the closed pores in an amount of less than 40 ppm by mass in terms of carbon element with respect to the mass of the sintered body. If it is 40 mass ppm or more, the above-mentioned lattice strain and lattice defects cannot be remarkably reduced, so that the mechanical strength cannot be remarkably improved and the piezoelectric strain constant cannot be remarkably improved. For this reason, it is because a piezoelectric actuator cannot be minutely driven with high accuracy at 40 mass ppm or more. The gas containing carbon means a gas containing carbon element, for example, CO ₂ or CO.

Further, it is preferable that the gas containing CO ₂ does not substantially contain CO. Since CO is electrochemically unstable at a low temperature, for example, room temperature, piezoelectric ceramics containing a large amount of CO in closed pores cannot significantly improve the piezoelectric strain constant, so that the piezoelectric actuator cannot be micro-driven with extremely high accuracy. It is.

The kind and content of the gas contained in the closed pores of the piezoelectric ceramic for piezoelectric actuator of the present invention are measured, for example, as follows. After putting the sintered body in a sealed container and evacuating the inside of the container, high purity inert gas or nitrogen gas from which O ₂ , CO and CO ₂ are substantially removed is purged into the container. Subsequently, the sintered body is pulverized while the sintered body is put in the container, and the gas contained in the closed pores of the sintered body is diffused into the container. Thereafter, the CO ₂ concentration contained in the gas in the container is measured by a CO ₂ sensor or a gas chromatograph. Using the measured value of CO ₂ concentration, the mass of the sintered body and the volume in the container, and the amount of gas purged in the container, the content of CO ₂ with respect to the sintered body mass contained in the closed pores of the sintered body is calculated. Calculated in terms of carbon element. Furthermore, the amount of CO ₂ contained in the closed pores of the sintered body can be measured more accurately by using at least one of a carbon analyzer and a charged particle activation analysis.

  Furthermore, the piezoelectric ceramic for piezoelectric actuator of the present invention has a surface roughness of 0.5 μm or less in terms of centerline average roughness Ra. As a result, the amount of particles generated particularly from the processed surface of the piezoelectric ceramic 5 can be reduced, and the recording layers of the magnetic recording head 11 and the magnetic recording disk 12 are damaged because particles enter between the magnetic recording head 11 and the magnetic recording disk 12. It is possible to prevent information read / write errors and the like caused by this. The reason is as follows.

  The reason why Ra is 0.5 μm or less is that when Ra is larger than 0.5 μm, the abrasive grains used for processing the piezoelectric ceramic and the crystal particle pieces of the piezoelectric ceramic separated by the processing are used as the particles. Or crystal grains of the piezoelectric ceramic are separated from the piezoelectric ceramic as particles after processing. If a piezoelectric ceramic having such particles is generated in a hard disk, for example, as a piezoelectric element for a piezoelectric actuator, for example, a magnetic recording head micro-drive actuator, The particles fall on the magnetic recording disk in the hard disk device due to vibration or impact generated when a personal computer or the like with a built-in hard disk device is moved. Then, the fallen particles enter between the magnetic recording head and the magnetic recording disk to inhibit information recording, or in some cases damage the recording layer on the magnetic recording head or the magnetic recording disk, making it impossible to record or take out information. I will. In particular, the Ra is preferably 0.3 μm or less, whereby the amount of particles generated from the piezoelectric ceramic can be further reduced.

  In the piezoelectric ceramic for a piezoelectric actuator of the present invention, it is preferable that the average pore diameter of the closed pores is 1 to 5 μm and the closed porosity is 2% by volume or less. This is because this improves the mechanical strength and the piezoelectric strain constant. When the piezoelectric ceramic 5 having an average pore diameter of 1 to 5 μm and a closed porosity of 2% by volume or less is used as the piezoelectric element 20 for minutely driving the first arm 9a, magnetic recording is performed with higher accuracy. The head 11 can be finely driven.

  On the other hand, when the closed porosity exceeds 2% by volume, or when the average pore diameter is less than 1 μm or exceeds 5 μm, the mechanical strength and the piezoelectric strain constant are not significantly improved. Cannot be driven minutely. Further, when the average pore diameter exceeds 5 μm, the closed pores appear as large open pores (recesses) on the ceramic surface due to the processing of the piezoelectric ceramics 5, and particles (processing for use when the piezoelectric ceramics 5 are processed) are formed in the recesses. Abrasive grains or crystal particle pieces of the piezoelectric ceramic 5 generated during processing may enter and remain, which is not preferable. Further, when the closed porosity is more than 2% by volume, the probability that the closed pores appear as open pores (concave portions) on the magnetic surface is increased by the processing of the piezoelectric ceramic 5. When the particles enter the recess, when a vibration or impact is applied to the hard disk device 7, the particles fall on the magnetic recording disk 12, and the recording layer formed on the magnetic recording head 11 or the magnetic recording disk 12. May be hurt. In particular, the lower limit of the average pore diameter is preferably 1.5 μm, and the upper limit is preferably 3 μm. Further, the closed porosity is particularly preferably 1% by volume or less.

  Moreover, it is preferable that the piezoelectric ceramic 5 for actuators of this invention has lead zirconate titanate as a main component. The reason for this is that the piezoelectric strain constant can be further increased. Therefore, for example, when the piezoelectric ceramic 5 is used as a piezoelectric ceramic for an actuator such as a magnetic recording head micro drive, the displacement is large and the displacement can be controlled with high accuracy. This is because since the piezoelectric element is obtained, the position of the magnetic recording head 11 can be controlled with high accuracy within a range of ± 1 μm.

  More preferably, the piezoelectric ceramic 5 is made of a composite perovskite oxide having an A site and a B site, the A site contains Pb as a main component, and further contains Sr and / or Ba, and the B site contains Zr. And Ti are the main components. Thereby, the evaporation of Pb during the synthesis of the piezoelectric ceramic is prevented, and the piezoelectric ceramic 5 having further improved piezoelectric characteristics can be obtained. Pb evaporation is suppressed because the chemical potential for moving Pb in the crystal lattice of the perovskite oxide increases, and Pb in the piezoelectric ceramic 5 diffuses from the inside of the sintered body to the outside of the sintered body. This is thought to be because the speed at which it is performed decreases.

  Particularly preferably, the B site contains at least one of Zn, Sb, Ni, Te, rare earth elements, Nb and Ta. As a result, vacancies are formed at the Pb sites of lead zirconate titanate, and domain walls can be easily moved through the vacancies to facilitate polarization. Therefore, the piezoelectric ceramic 5 having a high piezoelectric strain constant can be obtained. Obtainable. Most preferably, the B site contains Zr, Ti, Zn and Nb as essential elements in order to particularly improve the piezoelectric strain constant.

In the piezoelectric ceramic for a piezoelectric actuator of the present invention, it is preferable that a gas containing CO ₂ as a gas containing carbon is contained in the closed pores in an amount of 5 mass ppm or more with respect to the sintered body mass in terms of carbon element. This is because if it is less than 5 ppm by mass, the mechanical strength and piezoelectric strain constant of the piezoelectric ceramic 5 are not significantly improved.

  Next, a method for producing a piezoelectric ceramic for a piezoelectric actuator according to the present invention will be described.

  The method for producing a piezoelectric ceramic for a piezoelectric actuator according to the present invention includes a step of wet-mixing raw material powder and an organic binder before forming a piezoelectric ceramic to produce a slurry, a step of filtering the slurry, and a step after the filtration It is important to have a step of forming a formed body using the slurry, a step of firing the formed body in an atmosphere containing oxygen, and a step of processing and washing the sintered body after firing. Thereby, it is possible to obtain the piezoelectric ceramic 5 having high mechanical strength and high piezoelectric strain constant and less generation of particles.

  In the method for manufacturing a piezoelectric ceramic for a piezoelectric actuator according to the present invention, a raw material powder before forming a piezoelectric ceramic and an organic binder are wet mixed to produce a slurry. This is because segregation of the organic binder in the resulting molded body can be reduced. By firing a compact with little segregation of the organic binder, the pore size of the resulting ceramic sintered body can be reduced and evenly dispersed. Therefore, even if mechanical stress is applied to the ceramic sintered body, As a result, it is possible to suppress cracking or cracking, and as a result, it is possible to manufacture a piezoelectric ceramic having high mechanical strength.

  On the other hand, when the raw material powder before forming the piezoelectric ceramic and the organic binder are molded after dry mixing, segregation of the organic binder occurs in the resulting molded body. Therefore, the segregated organic binder is evaporated during firing of the molded body. Large pores are generated. When mechanical stress is applied to the piezoelectric ceramics having large pores, cracks are generated or cracked starting from the large pores. Furthermore, when such large pores exist, large open pores (concave portions) appear on the surface of the processed piezoelectric ceramic 5, which is not preferable because particles easily enter the concave portions.

Further, in the method for producing a piezoelectric ceramic for a piezoelectric actuator of the present invention, the step of filtering the slurry and the step of forming a molded body using the slurry after the filtration are primarily segregation of an organic binder. The piezoelectric ceramic 5 having a high mechanical strength can be manufactured with a particular reduction, and secondly, the piezoelectric ceramic 5 obtained by removing the large piezoelectric ceramic particles contained in the raw material powder before forming and then forming the piezoelectric ceramic 5 is obtained. This is because the strain constant can be improved. Further, in the manufacturing method of the present invention, the piezoelectric ceramic molded body is fired in an atmosphere containing oxygen. A gas containing CO ₂ as a gas containing carbon is contained in the closed pores in the obtained sintered body. This is for containing less than 40 mass ppm in terms of carbon element with respect to the mass of the sintered body.

A gas containing carbon (a gas containing CO ₂ ) contained in the closed pores of the piezoelectric ceramic of the present invention made of a sintered body is mainly a carbonate, which is a starting material of the piezoelectric ceramic, and carbon contained in an organic binder. It remains in the state (CO ₂ ). In order to produce the piezoelectric ceramic of the present invention having a high mechanical strength and a large piezoelectric strain constant, the raw material powder before molding and an organic binder are uniformly mixed, and further, the large piezoelectric ceramic particles in the molded body are removed, In addition, it is important to perform firing in an atmosphere containing oxygen so that a gas containing carbon is generated in the closed pores in the obtained piezoelectric ceramic.

  Further, in the manufacturing method of the present invention, the sintered body after firing is cleaned and cleaned (particles for processing used when processing the piezoelectric ceramic 5 or piezoelectric ceramics 5 generated during processing). This is for removing the crystal particle pieces from the surface of the piezoelectric ceramic 5. As a result, the generation of particles can be suppressed when the piezoelectric ceramic for a piezoelectric actuator according to the present invention is used for the piezoelectric element 20 for minute driving of the magnetic recording head 11.

  Next, the method for producing a piezoelectric ceramic for a piezoelectric actuator according to the present invention will be described more specifically.

  The piezoelectric ceramic for a piezoelectric actuator of the present invention is manufactured as follows, for example.

  Using each powder of lead oxide, zirconium oxide, titanium oxide, strontium carbonate, barium carbonate, zinc oxide, niobium oxide, antimony oxide, etc. as a starting material, after weighing to a desired ratio, add pure water, Wet mixing and pulverization are performed by a mill using zirconia balls or the like for 10 to 30 hours until the average particle size of the mixed raw material becomes 2.0 μm or less. The mixture is dried and calcined at 800 to 1000 ° C. for 1 to 10 hours. 3 to 8 parts by weight of an organic binder and 70 to 200 parts by weight of pure water are added to 100 parts by weight of the obtained calcined powder (raw material powder before molding) and wet-mixed with a ball mill or the like. The obtained slurry after wet mixing is filtered through a stainless mesh of 100 to 400 mesh, and the permeated slurry is granulated by a known method such as spray drying. The obtained granulated body is molded by a desired molding means such as a die press, cold isostatic pressing, extrusion molding and the like to obtain a molded body. Most of the organic binder is removed by heating the obtained molded body at a temperature at which the organic binder burns and decomposes in the air or in an atmosphere containing oxygen, that is, 500 to 800 ° C. In the organic binder removal treatment by heating, the piezoelectric ceramic molded body is placed in the mortar and the treatment is performed by opening the lid of the mortar at 500 to 800 ° C. In the closed pores of the obtained piezoelectric ceramic. This is preferable because the amount of gas containing carbon can be controlled with high accuracy to less than 40 ppm in terms of carbon element with respect to the mass of the sintered body. Next, the calcined body obtained by removing the organic binder is housed in a mortar, and the mortar is sealed and baked at about 1000 to 1200 ° C. in the atmosphere or in an oxygen stream. The inventive piezoelectric ceramic is obtained. The reason why the mortar is sealed during firing is that it is preferable in order to suppress evaporation of the metal element contained in the piezoelectric ceramic and to improve the piezoelectric strain constant.

In order to leave the carbon component remaining in the calcined body subjected to the organic binder removal treatment as a gas containing carbon in the closed pores during firing, particularly preferably in an atmosphere containing 90% by volume or more of oxygen. Bake. The reason for this is that by firing while replacing the pores in the calcined body after the removal of the organic binder with oxygen having a high oxygen concentration, the gas in the closed pores once becomes a high oxygen concentration during sintering, and then sintered. As the process proceeds, the carbon contained in the crystal and grain boundaries diffuses into the closed pores, and this carbon combines with the oxygen present in the closed pores, producing a gas containing carbon in the closed pores. is there. In order to contain CO ₂ in the gas containing carbon present in the closed pores, in the firing step, sufficient oxygen, specifically, oxygen gas having a volume 1000 times or more the volume of the obtained sintered body is used. Supply. Moreover, it is particularly preferable to smoothly exhaust the gas discharged from the firing furnace. On the other hand, when the calcined body is fired in an atmosphere substantially free of oxygen, a gas containing carbon is not substantially generated in the closed pores in the obtained piezoelectric ceramic, and the carbon is separated from the crystal and grain boundaries. Therefore, the piezoelectric ceramic for a piezoelectric actuator of the present invention cannot be manufactured. In addition to oxides and carbonates, starting materials such as acetates, nitrates, hydroxides, and the like may be used as compounds that can generate oxides by heat treatment in an oxidizing atmosphere.

  And after obtaining the sintered compact by the said process, the piezoelectric ceramic 5 is processed by grinding etc. FIG. When the processing is performed by grinding, the processing is preferably performed by a grinding machine such as a wet surface grinder, a universal grinder, or a milling machine, and the processing is performed until a predetermined shape and thickness are obtained. Thereafter, polishing is performed if necessary, but a polishing machine such as a lapping machine is used as a polishing method. At this time, the surface roughness of the finished surface is preferably 0.5 μm or less according to JIS B 0601-1992.

  Further, the processed piezoelectric ceramic is washed. Cleaning is performed by putting water containing a surfactant into a water tank of an ultrasonic cleaning machine and immersing the piezoelectric ceramics in the water tank. Thereafter, the piezoelectric ceramic is taken out from the ultrasonic cleaner, the cleaning liquid in the water tank is replaced with pure water, and the piezoelectric ceramic is immersed in pure water to perform ultrasonic cleaning.

  Here, the surfactant is preferably contained in an amount of 1 to 30% by mass with respect to the total of water and the surfactant. If the surface activity is less than 1% by mass, particles adhering to the surface of the piezoelectric ceramic cannot be removed. If the surface activity exceeds 30% by mass, the surfactant penetrates into the pores of the piezoelectric ceramic and is difficult to remove. The agent may remain in the piezoelectric ceramic. If a hard disk drive that includes a piezoelectric element made using piezoelectric ceramics with residual surfactant is installed in the computer manufacturing process, the surfactant may gasify during the computer manufacturing process, which may adversely affect the computer. It is not preferable.

  Moreover, about the said ultrasonic cleaner, it is preferable to use the thing of the frequency band allocated by the 10-100kHz radio wave method, and the said pure water uses ion-exchange water etc ..

  The piezoelectric ceramic for a piezoelectric actuator of the present invention manufactured by the above-described manufacturing method is a rectangular thin plate as shown in FIG. 2 and is incorporated in the hard disk device 7 as the piezoelectric element 20 of the second actuator 10. For example, when a driving test is performed by applying a frequency of 20 kHz to the second actuator 10 at a voltage of 20 V and adding a 10 10th driving, a displacement amount and a piezoelectric strain constant are measured after the driving test and at the initial stage of the driving test. Each change can be very small or no change. Even after such a driving test, the piezoelectric ceramic for piezoelectric actuator of the present invention mounted on the second actuator 10 is not damaged.

  Furthermore, the piezoelectric element 20 made of the piezoelectric ceramic for a piezoelectric actuator of the present invention has few particles that fall on the magnetic recording disk 12 in the hard disk device 7 due to vibration, impact, or the like. Therefore, the magnetic layer formed on the magnetic recording head 11 and the magnetic recording disk 12 is not easily damaged by particles, and the life of the hard disk device 7 can be extended.

  Examples of the present invention will be described below.

First, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , ZnO, Nb ₂ O ₅ , Yb ₂ O ₃ , SrCO ₃ , BaCO ₃ , Sb ₂ O ₅ , NiO, TeO ₂ , Lu ₂ O ₃ are used as starting materials. Each powder was weighed to have the composition shown in Table 1, and mixed and ground using a zirconia ball in a ball mill using water as a solvent until the average particle size became 0.3 to 1 μm. Next, this mixed pulverized product was dehydrated, dried, calcined at 850 to 950 ° C. for 1 to 3 hours, and then crushed by pulverization using a zirconia ball in a ball mill with water as a solvent, and pulverization was average The process was performed until the particle size became 0.4 to 1 μm. Thereafter, an aqueous acrylic emulsion resin binder is added to the slurry of the pulverized product, mixed, filtered through a stainless steel 325 mesh, the slurry that has passed through the mesh is granulated by spray drying, and the resulting granulated powder is obtained. The mold was filled, and several disk-shaped compacts having a diameter of 60 mm and a thickness of 13 mm were press-molded at a molding pressure of 1.5 × 10 ⁸ N / m ² . At this time, the amount of the binder to be added was changed as shown in Table 1.

  A calcining treatment for removing most of the organic binder at 600 to 800 ° C. for 3 hours in the atmosphere with the lid of the mortar open while the molded body is placed in a magnesia mortar. Went. The obtained calcined body was placed in a magnesia mortar and sealed in the mortar, while the oxygen concentration in the firing atmosphere was controlled to the concentration (volume%) shown in Table 1 at 1150 ° C. Baked for 3 hours.

  After polishing both surfaces of the obtained sintered body with a surface grinder by about 0.2 mm, a paste containing silver as a main component is applied as an electrode and held at 500 to 600 ° C. for 30 minutes for baking. And applying a voltage of electric field strength of 0.5 to 1.5 kV / mm at 50 to 200 ° C. in silicon oil to obtain a piezoelectric ceramic.

Next, in order to produce an element for measuring the electromechanical coupling coefficient k ₁₅ in accordance with Japan Electronic Materials Industry Standard EMAS-6100, a piezoelectric ceramic having a shape of 10 mm × 2.5 mm × 0.25 mm is ground and diced. Cut out. A gold electrode having a thickness of about 0.1 μm was vapor-deposited on both main surfaces of this element, and an electromechanical coupling coefficient k ₁₅ was measured. Further, the dielectric constant, the Young's modulus was measured and calculated the piezoelectric strain constant d _15.

  The mechanical strength was measured in accordance with Japanese Industrial Standard JIS B R1601, using a sample obtained by cutting a 40 mm × 4 mm × 3 mm test piece by grinding from a piezoelectric ceramic after polarization treatment.

  In addition, after cutting a sintered body having a diameter of 50 mm × 10 mm to a thickness of 0.8 mm with a wire saw, lapping is performed to make both main surfaces into a mirror state, and then using a stereomicroscope, the closed pore diameter of the piezoelectric ceramics (Long diameter), the number of closed pores was measured.

Further, the concentrations of CO and CO _{2 in} the gas contained in the closed pores of the sintered body were measured as follows. The sintered body was put in a sealed container and the inside of the container was evacuated, and then the container was purged with high-purity Ar gas from which CO and CO ₂ had been removed. Subsequently, the sintered body was pulverized while the sintered body was put in the container, and the gas contained in the closed pores of the sintered body was diffused into the Ar gas in the container. Thereafter, the concentration P ₂ of the gas containing carbon, except for Ar contained in the gas in the container was measured at 250 to 550 ° C. The following gas sensor.

First, the CO ₂ concentration P ₂ CO ₂ of the concentration P ₂ is the _{same as that} described in MRS Bulletin, June 1999, pages 37 to 43, Gas Sensors Using Solid Electrolytes. a conductor NASICON _{(eg: Na 3 Zr 2 Si 2 PO} 12) to the auxiliary layer _{(NaCO 3 -BaCO 3, Li 2} CO 3 -BaCO 3, Li 2 CO 3 either -BaCO ₃₎ the provided Nernst The electromotive force generated according to the above law was measured and converted into CO ₂ concentration. If the concentration P _2CO2 is close to the measurement limit was determined concentration by extrapolation from the relationship between the electromotive force and the CO ₂ concentration.

The concentration _{P 2CO} of CO of concentration _{P 2,} apart from the _{P 2CO2} concentration measurement were determined by Co. Round Science Ltd. trace reducing gas analyzer TRA-1 or TRA-1000.

The measure of the concentration _{P 2 (P 2CO2, P 2CO} ), the mass of the sintered body, using the amount of Ar purged in volume and container in the container, the carbon contained in the closed pores of the sintered body The amount of gas contained was determined in terms of carbon element relative to the mass of the sintered body.

  Moreover, the crystal phase of each sample was identified by the X-ray diffraction method.

Next, the piezoelectric element 20 was produced and evaluated as follows. That is, a 1.8 × 1.4 × 0.16 mm sintered body is cut out from the obtained sintered body with a wire saw, and the surface roughness of the sample after cutting is adjusted as necessary. Polishing was performed using a board. Thereafter, a cleaning liquid in which 15% by mass of a surfactant is mixed with ion exchange water having a water temperature of 20 ° C. is put into a water tank of an ultrasonic cleaning machine, and an ultrasonic wave of a frequency of 100 kHz is applied in this water tank for 10 minutes. In order to wash off the cleaning liquid adhering to the sample after the first cleaning, the first cleaning that performs sonic cleaning and the second cleaning in which cleaning is further performed in ion-exchanged water for 10 minutes was performed. The sample after washing was dried. A Ni—Cr layer was deposited as an electrode 28 on both main surfaces of each sample after drying, and then Au was further deposited to produce the piezoelectric element 20. Then, 3 kHz between the electrodes 28 of the resultant piezoelectric element 20 by applying a DC voltage of 20V, the piezoelectric element 20 is a piezoelectric displacement d ₁₅ mode, and measuring the displacement of a laser Doppler displacement meter.

As a result, as shown in Table 2, the sample No. 1 of the present invention. Nos. 1 to 11 all contained a gas containing carbon in the closed pores, the strength was 80 MPa or more, k ₁₅ was 70% or more, d ₁₅ was 850 pm / V or more, and the displacement amount was 100 to 114 nm and was highly stable. In particular, Sample No. _{2 in which the} amount of CO ₂ in the closed pores was converted to carbon element was 5 to 39 ppm relative to the mass of the sintered body. 2-9 _{d 15} was as high as 900pm / V. Sample No. 1 having an average pore diameter of 1 to 5 μm was used. The strength of 3 to 9 was as high as 100 MPa or more. Sample No. The crystal phases 1 to 11 consisted of complex perovskite oxides.

  Next, the hard disk device 7 of FIGS. 1 and 2 was manufactured as follows using the piezoelectric element 20, and a drive test was performed.

  One main surface of the piezoelectric element 20 and the first arm 9a (the conductive plate 4a and the conductive plate 4b are joined with an insulating epoxy adhesive), the other main surface of the piezoelectric element 20 and the second arm 9b (the conductive plate 4c and the conductive plate 4d joined together with an insulating epoxy adhesive) are joined together using the conductive epoxy resin adhesive 32 as shown in FIGS. 2B and 2C. did. Here, the conductive plates 4a, 4b, and 4d are made of SUS. The conductive plate 4c was made of SUS on the piezoelectric element 20 side and made of an Mg alloy on the bearing 26 side. Further, the conductive wires 30 are connected to the conductive plate 4b and the conductive plate 4d, respectively, so that a DC voltage can be applied to the first arm 9a and the second arm 9b. Next, the hard disk device 7 was manufactured as follows.

Magnetic recording disk 12: 2.5 inch diameter spindle motor 22: 7200 rpm
Storage capacity per track: 20480 bytes Storage capacity (storage capacity per track x storage capacity per sector x number of sectors per track): distance between 360 Mbyte magnetic recording disk 12 and magnetic recording head 11: 20 to 25 nm
Applied voltage to the piezoelectric element 20: -30 to 30V
Using the produced hard disk device 7, information was read and written as a hard disk drive test. The second actuator 10 was finely driven in a state where the movement of the first actuator 8 was stopped when reading and writing information.

  As a result, in the hard disk device 7 manufactured using the sample of the piezoelectric ceramic 5 of the present invention, the displacement amount of the magnetic recording head 11 is ± 0 in the radial direction of the magnetic recording disk 12 by controlling the voltage applied between the electrodes 28. It was possible to control within the range of 4 μm. The hard disk device 7 shown in FIG. 2 manufactured using the piezoelectric ceramic 5 of the present invention is magnetic even when the gap between the tracks is 0.2 to 0.3 μm due to the high density of the magnetic recording disk 12. It was possible to read and write various data by slightly driving the recording head 11. Further, since the mechanical strength of the piezoelectric ceramic has increased, the reliability of the hard disk device 7 has been greatly improved. Further, even when the hard disk device 7 was driven for 500 hours or longer (data reading / writing was performed continuously), no error occurred during data reading / writing during this time.

In contrast, the raw material powder before molding and the organic binder are dried, that is, pulverized and pulverized without adding a solvent, or a slurry is added to the raw material powder before molding to form a slurry. Sample No. which was not filtered or baked in an oxygen-free atmosphere The 12-15 piezoelectric ceramics did not contain carbon-containing gas in the closed pores. Sample No. 12-15 strength 65MPa or _{less, k 15} following the low _{65%, d 15} was bought low as less than 750 pM / V.

Sample No. A hard disk device was fabricated using 12 to 15 piezoelectric ceramics in the same manner as in the example. As a result, sample no. In a hard disk drive equipped with 12 to 15 piezoelectric ceramics, since the displacement of the piezoelectric element is small, the positioning accuracy of the magnetic recording head can be controlled within a range of ± 0.2 μm or less on the track on the magnetic recording disk. could not. Further, when the hard disk drive was driven for 1 to 2 hours, a data write error occurred.

  Next, with respect to the composition of D, which showed good characteristics in Example 1, it was evaluated how the particle amount would be according to the surface roughness and the cleaning method.

  The surface of the sintered body was processed with a surface grinder and then polished with a lapping machine as necessary to adjust the surface roughness.

  For cleaning the sample after processing, a cleaning liquid in which 15% by mass of a surfactant is mixed with ion-exchanged water having a water temperature of 20 ° C. is put into a water tank of an ultrasonic cleaning machine, and an ultrasonic wave having a frequency of 100 kHz is put in the water tank. First cleaning is performed for 1 to 10 minutes while applying pressure, and cleaning is further performed in ion-exchanged water for 10 minutes in the ultrasonic cleaning machine in order to wash off the cleaning solution adhering to the sample after the first cleaning. Two washes were performed. The cleaning time in Table 3 indicates the time for the first cleaning.

Particles generated from the washed sample were measured as follows. The piezoelectric ceramic was suspended in pure water in a beaker using a thin metal wire, and in that state, ultrasonic waves were applied for 1 minute with an ultrasonic cleaner. Then, the piezoelectric ceramics hung on the metal wire from the beaker were taken out, and the particles in the pure water were measured with a particle counter (DHA-1000 manufactured by BRANSON). The amount of particles in Table 3 is a value obtained by converting the measured number of particles into the number per 1 cm ² of the surface area of the piezoelectric ceramic.

As for particles, 0.5 μm or less particles and 2 μm or less particles are measured, and the particle amount of 2 μm or less is 0 / cm ² , and the particle amount of 0.5 μm or less is 2000 / cm ² or less. Was judged to be particularly good.

From Table 3, Sample No. 21-23, no. The surface roughness (Ra) of Nos. 25 to 27 has a good finished surface with a surface roughness (Ra) of 0.5 μm or less, the particle amount of 2 μm or less is 0 / cm ² , and the particle amount of 0.5 μm or less is 1880. The number / cm ² or less was good. Furthermore, the generation of particles decreased as the cleaning time increased. In addition, the sample having a small surface roughness (Ra) produced less particles even when the cleaning time was the same as that of the sample having a large surface roughness.

Also, the samples 21～23,25～27, to produce a piezoelectric element 20 for driving the same to _{d 15} mode as in Example 1, was subjected to the same hard disk drive test as in Example 1. As a result, the displacement amount of the magnetic recording head 11 could be controlled within a range of ± 0.4 μm. Further, even when the gap between tracks was 0.2 to 0.3 μm, the magnetic recording head 11 was slightly driven, and various data could be read and written. Furthermore, even when the hard disk device 7 was driven for 500 hours or more, no error occurred during data read / write during that time.

On the other hand, as a sample out of the scope of the present invention, the sample was prepared in the same manner as in the example and the sample was manufactured under the following conditions. That is, as a comparative example, a sample in which Ra after processing was increased to 0.6 μm, and ultrasonic cleaning was performed instead of washing with ion-exchanged water (flowing ion-exchanged water to the sample for 10 seconds at a flow rate of 2 ml / second). And a sample in which Ra was 0.6 μm and ultrasonic cleaning was not performed. The amount of particles generated from these samples was measured in the same manner as in the examples. As a result, sample No. In 16-19, the amount of particles of 2 μm or less was 0 to 260 particles / cm ² , and the amount of particles of 0.5 μm or less was 2500 particles / cm ² or more. Sample No. which was not subjected to ultrasonic cleaning was used. In 16, 20, and 24, the amount of particles of ² μm or less was 10 to 260 particles / cm ^2, and the amount of particles of 0.5 μm or less was 8500 to 25000 particles / cm ² . In particular, the sample No. 1 in which Ra was 0.6 μm and ultrasonic cleaning was not performed. In No. 16, many particles were generated with a particle amount of ² μm or less of 260 particles / cm ² and a particle amount of 0.5 μm or less of 25000 particles / cm ² .

Moreover, the hard disk drive test was done like the Example using the piezoelectric ceramic sample of a comparative example. As a result, sample no. In the case of using 16-20, 24, since many particles were generated, a data write error occurred when the hard disk drive was driven for 1-5 minutes.

1 is a schematic diagram of a hard disk device using piezoelectric ceramics for a piezoelectric actuator of the present invention. 2A is a schematic diagram of a second actuator that is a part of the hard disk device of FIG. 1, FIG. 2B is a schematic diagram showing a part of FIG. 2A, and FIG. It is sectional drawing in the XX line of FIG.2 (b). It is a schematic diagram which shows the piezoelectric element mounted in the conventional hard disk drive.

Explanation of symbols

4a, 4b, 4c, 4d: Conductor plates 5, 5a, 5b: Piezoelectric ceramics 7: Hard disk device 8: First actuator 9a: First arm 9b: Second arm 10: Second actuator 11: Magnetic recording Head 12: Magnetic recording disk 13, 20: Piezoelectric element 14: Spring mechanism 15: Arm 22: Spindle motor 24: Case 26: Bearing 28: Electrode 30: Conductor 32: Conductive adhesive 34: Voice coil motor 36: Insulating layer

Claims (7)

In a piezoelectric ceramic for a piezoelectric actuator in which a magnetic recording head supported by an arm is micro-driven by piezoelectric ceramic, the gas containing CO ₂ in the closed pores of the piezoelectric ceramic is 40 mass ppm in terms of carbon element with respect to the mass of the sintered body. Piezoelectric ceramics for a piezoelectric actuator, characterized in that the surface roughness is 0.5 μm or less in terms of centerline average roughness Ra. 2. The piezoelectric ceramic for a piezoelectric actuator according to claim 1, wherein the closed pores have an average pore diameter of 1 to 5 μm and a closed porosity of 2% by volume or less. 3. The piezoelectric ceramic for a piezoelectric actuator according to claim 1, wherein the amount of gas containing CO ₂ in the closed pores is 5 mass ppm or more in terms of carbon element. A step of wet-mixing the raw material powder before forming the piezoelectric ceramic and an organic binder to prepare a slurry; a step of filtering the slurry; and a step of forming a molded body using the slurry after the filtration; The piezoelectric ceramic for a piezoelectric actuator according to any one of claims 1 to 3, comprising a step of firing the molded body in an atmosphere containing oxygen and a step of processing the sintered body after firing and ultrasonically cleaning the sintered body. Manufacturing method. 5. The method for producing a piezoelectric ceramic for a piezoelectric actuator according to claim 4, wherein in the step of firing the compact, the oxygen concentration in the atmosphere is 90% by volume or more. 6. The piezoelectric actuator according to claim 5, wherein the processed sintered body is washed with an ultrasonic cleaner in a solution containing 1 to 30% by mass of a surfactant and then further washed with pure water. Method for manufacturing piezoelectric ceramics for use in automobiles. A magnetic recording disk, a magnetic recording head for recording and reproducing information on the information recording surface of the magnetic recording disk, and a radial direction of the magnetic recording disk for positioning the magnetic recording head on a recording track of the magnetic recording disk A first actuator that is moved, and a second actuator that is provided in a part of the first actuator and moves the magnetic recording head by a small distance in the radial direction of the magnetic recording disk independently of the operation of the first actuator. The second actuator has a first arm having a magnetic recording head held at the tip and a second arm connected to the first arm via a piezoelectric element, In the hard disk drive that moves the magnetic recording head by driving the first arm by minute driving of a piezoelectric element, the first arm A piezoelectric element used in the actuator, a hard disk drive, which comprises using a piezoelectric ceramic for a piezoelectric actuator according to claim 1.

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