TW202025524A - Porous piezoelectric material molded body, method of manufacturing same, and probe using said molded body - Google Patents

Abstract

To provide a porous piezoelectric material molded body which has high utility as a constituent member of a piezoelectric vibrator suitable for, in particular, a probe for an ultrasound medical diagnostic device. A porous piezoelectric material molded body in which 1000 or more per cubic millimeter of spherical pores having an average pore diameter in a range of 2 to 70 [mu]m are dispersed and formed. The porous piezoelectric material molded body is characterized in that the spherical pores do not include substantially pores with a pore diameter exceeding 50 [mu]m, and that the pores occupying 80% or more of the entire volume of the pores constituting the spherical pores have a pore diameter of within ±20% with respect to the average pore diameter.

Description

Porous piezoelectric material molded body and its manufacturing method, and probe using the molded body

The present invention relates to a porous piezoelectric material molded body useful as a constituent material of a piezoelectric vibrator, and a manufacturing method thereof. In particular, it relates to a porous piezoelectric material molded body with high usefulness as a piezoelectric vibrator, which is the main constituent member of an array probe used in a medical ultrasonic diagnostic device, and a method for manufacturing the molded body, and a probe using the molded body needle.

Regarding piezoelectric materials that convert mechanical vibration (amplitude) into electrical signals, convert electrical signals into mechanical vibrations (amplitude), and convert electrical signals into mechanical vibrations (amplitude), and then convert the reflected waves into electrical signals again , Known a variety of inorganic and organic materials. Its utilization form can be roughly divided into (A) vibrator, (B) converter (but not a clear classification, close to synonyms). (A) As the commonly used oscillators around, there are electronic quartz clocks (various clocks represented by watches) in which crystal oscillators using artificial single crystal (quartz) piezoelectric materials are assembled. Since the crystal is oscillated as the reference for time travel, and its clock pulse is used, it can obtain obvious accuracy compared with the previous mechanical method of using clockwork and gears to travel time. In particular, the vibrator is characterized by being housed in an airtight container, which eliminates the adverse effects of gas molecules on the vibration of the crystal vibrator in a vacuum environment, and seeks to improve accuracy. In addition, the ultrasonic probe used in medical ultrasonic diagnostic devices has the advantage of being able to diagnose patients non-invasively. Therefore, internal medicine and surgery are represented by various diagnostics in ophthalmology, and they have made inestimable contributions. The probe is constantly being updated. The probe uses element-type polycrystalline piezoelectric ceramics or recently single crystal piezoelectric materials. The thickness of these components is determined by the inherent physical properties and oscillation frequency of the piezoelectric materials used. Since the high frequency probe is designed to have a thickness of tens of μm to 300 μm and a width of 40-60% of the thickness, ultra-fine processing is required. (B) As a converter, inorganic or organic piezoelectric materials are widely used in numerous fields for various industrial purposes. That is, liquid level gauge, traffic flow measurement, speed detector, thickness gauge, fish detector, sonar, flow rate, flow rate meter, washing machine, humidifier, electric welding machine, or piezoelectric pump, printer, acceleration sensor Various actuators such as sensor and piezoelectric ignition device.

In this way, piezoelectric materials used in all fields are roughly classified as follows. As single crystal piezoelectric materials, crystals, lithium niobate, and the like have been known. Recently, the lead compound (PMN) of the element called RELAXA with the addition of Mg (magnesium) and Nb (niobium), and the compound of lead titanate (PT) (PMN-PT) with PZT (zirconium) Lead acid, lead titanate) are mixed, and the mixed raw materials are cultured at high temperature for a long time to obtain a single crystal (commonly known as PMN-PT single crystal). There are various RELAXA additives represented by single crystals. The single crystal piezoelectric material is being developed as a probe (probe) for medical ultrasonic diagnostic devices. On the other hand, among polycrystalline ceramic piezoelectric materials, barium titanate, lead titanate, (titanic acid, lead zirconate, 2-component PZT, called PZT) are widely known. Nowadays, stimulated by the progress and results of the research and development of PMN-PT single crystal, in order to improve and improve the piezoelectric properties, the same as the PMN-PT single crystal, polycrystalline PZT added with RELAXA component (collectively referred to as 3-component PZT) is being developed. ). In particular, polycrystalline PZT has naturally become a research object for a long time due to its performance as a piezoelectric material in industrial applications or medical fields. As an organic piezoelectric material, polyvinylidene fluoride (PVDF) is known. The point that these piezoelectric materials have in common is that if the piezoelectric effect corresponding to various use purposes cannot be expected, of course they cannot be put into practical use. That is, in medical-related applications, high relative permittivity (εs), high electromechanical coupling coefficient (Kt), and large piezoelectric constant (d33) are required.

Recently, the trend of the probes (probes) of medical ultrasonic diagnostic devices is shifting to the use of single crystal piezoelectric materials with very excellent piezoelectric properties. (1) Through single crystalization, the characteristics of piezoelectric materials that have not been seen before have been greatly improved. That is, the value of the relative permittivity (εs) is very large, the mechanical electrical coupling coefficient (Kt) is high, and the piezoelectric constant (d33) is large. (2) In addition, compared with the previous polycrystalline PZT, the frequency range is particularly excellent and wider; (3) Simultaneously with item (2), the sensitivity has been improved by 4-8 dB; (4) On the other hand, these single crystal piezoelectric materials are very fragile and have extremely poor processability; (5) In addition, the crystal growth of single crystal piezoelectric materials is slow, it takes a long time to manufacture, and the shape is limited. Therefore, the raw materials are very expensive; In addition, because it is mechanically very brittle, the workability is poor. Moreover, compared with the polycrystalline PZT that has been generally used as a probe (probe), the price is 5-8 times (the substrate of the same shape after plating and finishing). (6) Except for (5), for the same reason in the manufacturing steps, the yield of the steps until the probe (probe) is made is extremely poor. The reasons why single crystal piezoelectric materials have the above-mentioned fatal shortcomings are still becoming the trend of probes (probes). The reasons are as follows. First, the piezoelectric characteristics are greatly improved, and the frequency range is significantly wider than the previous PZT ceramic piezoelectric materials. Therefore, two probes (probes) of 2.5 MHz and 5 MHz (probes) were needed. , But now it can meet the requirements with a 3.5 MHz probe (probe). Considering that the price of the probe (probe) ranges from tens of thousands of yen to hundreds of thousands of yen per probe, its economic effect is outstanding. The increased sensitivity enables high-quality images of the deep parts of the human body to be obtained, which is also an important reason. In addition, the frequency of the ultrasonic pulse used in in vivo diagnosis is determined by considering the depth of the body surface from the organ and the attenuation of the ultrasonic wave. It is known that in the circulatory organs or abdomen, the center frequency is 2 to 5 MHz, in children, breasts, and peripheral parts it is 5 to 7.5 MHz, and in the blood vessel is 10 to 30 MHz.

數厘米，厚度亦為同樣之尺寸，因此對於孔隙之存在形態之約束並非相當嚴格，其平均值反應於特性，頻帶較寬，且短脈衝性超越先前之轉換器之特性，有助於與先前機種之差別化。 然而，現階段，醫療用探頭(探針)中所使用之陣列型元件之探頭(探針)中，其實用化尚未達成。However, as described above, the improvement of polycrystalline piezoelectric ceramics, which tends to deteriorate in electrical characteristics compared to single-crystal piezoelectric ceramics, is being continuously improved. In particular, the RELAXA component, which is effective for the crystallization of single crystal piezoelectric materials, brings a dramatic effect to the improvement of the characteristics of polycrystalline piezoelectric ceramic materials. That is, the characteristics of the 3-component PZT polycrystalline ceramic piezoelectric material made by adding RELAXA to the previous PZT are infinitely close to the characteristics of single crystal PMN-PT. Especially the electrical characteristics are in a very attractive state. That is, it is more excellent than the single crystal material for the pulse characteristics at almost the same level in the frequency band. On the other hand, we have been focusing on the development of porous piezoelectric ceramics that use polycrystalline piezoelectric ceramic materials as the base material and make the polycrystalline piezoelectric ceramic porous as a further improvement measure. Mass-pressure ceramic materials have been partially put into practical use in the fields of fish exploration or sonar. It is believed that because the frequency of use is relatively low in the frequency band of 200～500 KHz, the shape of the converter is

A few centimeters, the thickness is also the same size, so the constraints on the existence of the pores are not very strict. The average value reflects the characteristics, the frequency band is wider, and the short pulse is beyond the characteristics of the previous converter, which helps to compare with the previous Differentiation of models. However, at this stage, the practical application of the array element probe (probe) used in the medical probe (probe) has not yet been achieved.

100 μm之甲基丙烯酸樹脂，向PZT原料混合0～20重量%之該樹脂，對其進行加壓後燒成，觀察相對於燒成溫度之孔隙率之變化。即，描述了於壓電材料中形成孔隙之一方法。 (乙)描述了如下手法：使作為壓電原材料之PT(鈦酸鉛)之結晶尺寸限於約44～75 μm之範圍，準備4種PZ(鋯酸鉛)之結晶之尺寸，以適合於作為目標之PZT之組成進行混合，改變燒成溫度，藉由兩結晶之體膨脹率之差形成孔隙。於此基礎上，利用系統性之實驗考察與利用(甲)之方法獲得之多孔PZT壓電材料之各種電氣特性(εs、d33、g33及Y33等)之關係。於孔隙率20%以上之區域進行實驗。有關於燒成體之中之孔隙為70～120 μm之記載，但沒有關於其分散性或均勻性等之記載。 又，對於利用(乙)之方法獲得之多孔PZT壓電材料燒成體，於孔隙率幾乎固定之區域內，利用系統性之實驗考察結晶尺寸與各種電氣特性(εs、d33、g33及S33等)等之關係。改變原材料所使用之各材料之結晶尺寸，藉由其體膨脹率之差形成孔隙之想法係非常獨特之構想。有存在於壓電材料中之孔隙分佈於30～60 μm之範圍內之記載，但沒有關於其形狀或分散狀態、以及其等之控制之記載。Next, the porous piezoelectric material will be described. The development of porous piezoelectric ceramic materials has a long history. Non-Patent Document 2 is cited as a relatively systematic research report. As a pore formation method, (A) use

100 μm methacrylic resin, 0-20% by weight of the resin is mixed with the PZT raw material, pressurized and fired, and the change in porosity relative to the firing temperature is observed. That is, one method of forming pores in piezoelectric materials is described. (B) Describes the following method: the crystal size of PT (lead titanate) as the piezoelectric material is limited to the range of about 44-75 μm, and 4 kinds of PZ (lead zirconate) crystal sizes are prepared to be suitable as The composition of the target PZT is mixed, the firing temperature is changed, and the pores are formed by the difference between the bulk expansion rates of the two crystals. On this basis, the relationship between the various electrical properties (εs, d33, g33, Y33, etc.) of the porous PZT piezoelectric material obtained by the method (a) is investigated by systematic experiments. Experiment in an area with a porosity above 20%. It is stated that the pores in the fired body are 70 to 120 μm, but there is no description about the dispersibility or uniformity. In addition, for the porous PZT piezoelectric material fired body obtained by the method of (B), the crystal size and various electrical characteristics (εs, d33, g33, S33, etc.) were investigated by systematic experiments in a region where the porosity was almost constant. ) And so on. The idea of changing the crystal size of each material used in the raw material to form pores by the difference in volume expansion rate is a very unique concept. There is a description that the pores in the piezoelectric material are distributed in the range of 30-60 μm, but there is no description about the shape or dispersion state, and the control thereof.

Similarly, in Patent Document 5, the electrical and mechanical properties of porous piezoelectric materials are described. The content is the porosity and various characteristics (piezoelectric expansion constant, tensile strength and acoustic impedance) in the area with pore diameter of 20～105 μm due to the difference of pore size. It is inferred that a relatively large pore diameter and large sensor is prepared. There is no description of the state of the pores in any patent literature.

Patent Document 1 has the following description: Piezoelectric vibrators (piezoelectric elements) that use the piezoelectric effect of piezoelectric ceramic materials are used as electro-mechanical conversion elements in various fields, and piezoelectric vibrators are used as medical ultrasonic waves The ultrasonic transducer of the diagnostic device is a device used to extract information from the living body. The cited document 1 further states that: medical transducers made of piezoelectric ceramics have difficulty in supplying short pulses required to improve resolution, and for the transmission/reception of ultrasound in a wider frequency band Insufficient, as an improvement to solve this problem, it can be seen that there is a description of the following theme: theoretically and experimentally, it has been confirmed that the use of porous piezoelectric ceramics is effective. In addition, Patent Document 1 describes a method for producing a porous piezoelectric ceramic molded body (ie, a porous piezoelectric ceramic molded body) through the following steps: mixing the powder of piezoelectric ceramic as a pore forming material For ceramic powders of different types from piezoelectric ceramics, the ceramic powder composition obtained by mixing is shaped and then fired to remove the pore-forming material.

The porous piezoelectric ceramic molding system obtained by the manufacturing method described in Patent Document 1 is manufactured by firing (ie, sintering) the molded body of the powdery piezoelectric ceramic. Although it is not specifically described, it is understood It is a formed body of piezoelectric ceramic polycrystalline.

In Patent Document 2, as a method for manufacturing a porous piezoelectric element with uniformly distributed fine pores, high mechanical strength, and excellent workability, the following method is described: mixing piezoelectric material powder, bonding material, and heating A mixture of gasification (i.e., combustible) pore-forming materials is sprayed with compressed air in hot air to form a composite powder whose surface is coated with piezoelectric material powder. After being formed into a molded body, it is fired to obtain a porous piezoelectric element. In addition, Patent Document 2 describes that by using the above-mentioned manufacturing method, the pore-forming material does not undergo connection and aggregation, so that a porous piezoelectric element having fine independent pores can be obtained. However, there is no description about the uniformity of the size of the majority of the pores formed in the porous piezoelectric element. Moreover, in the examples, only the average particle diameter of the polymethyl methacrylate resin balls used as the pore-forming material The record is 5 μm.

In Patent Document 3, the description of each paragraph of (Technical Method to Solve the Problem) of (Problem to be Solved by the Invention) is to refer to the comparison of piezoelectric materials suitable for high-frequency piezoelectric vibrators. The target value of the best form does not have any specific solutions. That is, although a porous dielectric sheet (understood as a sheet-like porous piezoelectric material polycrystalline body) is described, the target piezoelectric material essentially consists of only pore diameters within 25 μm. Pore structure, and the average pore diameter in the range of 5-25 μm is within the range of 1/1000～1/10 of the thickness of the sheet, and its apparent density is within 5/10 of the true density , The thickness is within the range of 0.05～2.0 mm, but there is no specific content about how to solve the most important problem. In addition, as the manufacturing method cited from Patent Document 2, that is, the manufacturing method of the porous dielectric sheet, a method including the following operations is described: mixing zirconium titanate with an average particle diameter in the range of 0.1 to 2.0 μm A mixture of lead acid powder, binder, and thermally decomposable particles with an average particle size of 5 μm (preferably those with a narrower particle size distribution range), which is made by spraying with a gas under pressure Granules to obtain a granular powder. After the granular powder is formed, the formed body is heated and fired at a temperature higher than the thermal decomposition temperature of the thermally decomposable particles to obtain a porous fired body , And further cut or polish the porous fired body to a specific thickness. In addition, there is a description that the thermally decomposable particles are preferably those with a narrower particle size distribution range, and they remain in the porous dielectric sheet of the invention because the pores of the porous dielectric sheet are uniformly dispersed, so it is used as a porous array piezoelectric vibrator Use materials with better records. However, regarding the heat-decomposable particles of polymethyl methacrylate resin powder used in the examples, there is a record of an average particle size of 10 μm, regarding the pores of the pores of the dielectric sheet obtained in this example Diameter, only the average pore diameter of the pores in the range of 5-15 μm is recorded as 10 μm.

As described above, ultrasonic vibrators are used in a wide range of fields as industrial applications. In particular, ultrasonic diagnosis in the medical field can easily obtain tomographic images of internal organs or blood vessels in real time, and can be used for non-invasive diagnosis, regardless of surgical internal medicine. Furthermore, recently, for the purpose of obtaining a three-dimensional image of a fetus in an organ or a uterus, a probe (probe) composed of a two-dimensional array type array is being developed and provided for practical use.

That is, Non-Patent Document 1 and Non-Patent Document 7 describe an array probe, which is composed of a plurality of short strip-shaped piezoelectric vibrator elements with a width of 0.15 mm and a height of 0.25 mm and a length of about 10 mm. The state is fixed on the surface of the sheet-like backing material, and is covered by an acoustic integration layer and an acoustic lens. In addition, this Non-Patent Document 1 does not describe the height (or thickness) of the short-striped piezoelectric vibrator. However, in a normal array probe, a piezoelectric material is used in the longitudinal vibration mode. As a requirement for piezoelectric materials to vibrate in the longitudinal vibration mode, there is a limit of geometric size. That is, in order to vibrate the element longitudinally, the frequency of use is first determined. According to the frequency characteristics of the piezoelectric material, the height (or thickness) of the frequency of the specified longitudinal vibration mode is determined. After determining the height, the width of the element is based on the design criteria of the longitudinal vibration mode well known in the field, and needs to be specified to be 0.6 times or less of the height, and more preferably 0.4 times or less. Therefore, the design of the component is carried out under this restriction. It is inferred that the size of the short strip piezoelectric vibrator element described above is also designed in accordance with the design criteria. In order to obtain a three-dimensional image, it is necessary to set the array-type element containing piezoelectric material to a two-dimensional (XY plane), but even in this case, the design criteria constituting each element must satisfy the above-mentioned restrictions. Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2-90579 Patent Document 2: Japanese Patent Laid-Open No. 4-300253 Patent Document 3: Japanese Patent Laid-Open No. 2000-119063 Patent Document 4: Japanese Patent Laid-Open No. 63-78700 Patent Document 5: Japanese Patent Laid-Open No. 1-172281 Non-patent literature

Non-Patent Document 1: "The Basics and Devices of Ultrasonic Waves: A Four-Fourth Calibration Edition", issued by VECTOR CORE Co., Ltd.: Issued on January 10, 2013 Non-Patent Document 2: Effect of Porous Structure to Piezoelectric Properties of PZT Ceramics: K. Hikita, K. Yamada, M. Nishioka and M. OnoR&d Laboratory. Mitubishi Mining and Cement Co., LTD JjAP vol. 22(1983) Supp. 22-2 pp 64-66 Non-Patent Document 3: Effect of Size Distribution on Relation Between Coorination Number and Void Fraction of Spheres in Randomly Packed Bed, M. Suzuki and Others.: Advanced Powder Technology, 10, 353-365 (1999) Non-Patent Document 4: The influence of particle size distribution on the compression properties of micropowders: Michitaka Suzuki et al., Papers of the Chemical Industry: The Society of Powder Engineering (Osaka 1989.5) Non-Patent Document 5: Effect of Distribution Tapping Properties of Fine Powder Mr. M. Suzuki, Others: Powder Technology, 118, 53-57 (2001) Non-Patent Document 6: Handbook of Powder Engineering: edited by the Society of Powder Engineering, Hirota, etc.: Nikkan Kogyo Newspaper (1998) Non-Patent Document 7: Research Paper: Research on Lead-based Piezoelectric Single Crystals for Medical Ultrasonic Probes: Toshiba Research and Development Center, Hosono Yasushiharu (2004-4)

[The problem to be solved by the invention]

Although part of the description is repeated, the sheet-shaped piezoelectric ceramic forming system that is generally used as the constituent material of the piezoelectric vibrator described so far forms the basic material. Conventionally, in order to manufacture array probes (probes) used in medical ultrasonic diagnostic devices, sintered bodies (polycrystals) of piezoelectric ceramic powder have been used as the material. However, until recently, in order to meet various requirements from the ultrasonic medical diagnosis field, the use of single crystal piezoelectric materials with excellent electrical or electrical-mechanical conversion characteristics has become the mainstream. However, since single-crystal piezoelectric materials have problems with their economy or processability, research has begun to use porous sheet-shaped piezoelectric ceramics with excellent economy or processability. Although porous sheet-shaped piezoelectric ceramics have reached the level of electrical or electro-mechanical conversion characteristics that can meet the requirements as a whole, when they are used as elements of arrayed vibrators, the following major problems remain: In the micron part related to the difference in size or the uniform dispersion of pores, uniform density (g/cubic centimeter) cannot be ensured, so the relative permittivity, electrical-mechanical coupling coefficient of each element, or various electrical characteristics and mechanical strength, etc. The homogeneity has not been ensured, and it has not reached the level that can fully meet the requirements as the constituent material of the probe. It is considered that this problem is a fundamental problem related to the uniform mixing of powders containing two components, and it is very difficult to fundamentally solve it. That is, with regard to the proposal of uniformly mixing at least two types of substances with different masses at the required volume ratio, there is only a method of physically stirring and mixing. There is no other method other than to achieve as much homogenization as possible by stirring and mixing with time. Patent references and non-patent references do not cover this point, and there is no description of the method of controlling porosity. Presumably, it is believed that the references are all those who rely on the above-mentioned stirring and mixing method to produce porous piezoelectric materials. Therefore, in essence, there is a fate that a uniform density (g/cm3) cannot be ensured in the micron part related to the difference in pore size or the uniform dispersion of pores. The creator of the present invention succeeded in breaking away from the so-called stirring and mixing method, and determined the porosity near the single pore-forming material, so that the processed product of the pore-forming material was spread over the required product forming mold and overlapped By this, it is possible to freely control the uniform pore diameter, uniform porosity, and controlled distance between pores. [Technical means to solve the problem]

The creator of the present invention has verified the contents and results described in reference patent documents and non-patent documents in detail in paragraphs (0007) to (0011), and obtained the following results. That is, the creator of the invention in this application came to the following conclusion: When the well-known porous sheet-shaped piezoelectric ceramic formed body is used as the vibrator element of the array probe, the reason why it cannot exhibit the electrical or electro-mechanical conversion characteristics and mechanical characteristics that can fully meet the requirements is: (1) The non-uniformity of the size of the pores that constitute the porous structure of the porous sheet-shaped piezoelectric ceramic body; (2) The unevenness of pore dispersion (the location of pores is not controlled); (3) The uniform distribution of porosity is not controlled.

Taking these known techniques into consideration, as a result, the creator of the present invention confirmed that most of the pores contained in the molded body made of porous piezoelectric materials have substantially the same pore diameter, and that the pores are in The method of adjusting the dispersion state (dispersion state) of high homogeneity and artificially controlling the porosity of the porous piezoelectric material molded body can obtain the piezoelectric material molded body that is not only the denser molded body used previously And single-crystal piezoelectric material, compared with the porous piezoelectric material formed body known so far, the porous piezoelectric material formed body that exhibits significantly superior electrical or electro-mechanical conversion characteristics and mechanical characteristics, therefore Complete the present invention.

(球體之體積占容器體積之比率)。已知有較理想而言，於被裝滿之相同直徑之球體於結晶結構學採用六方最密填充結構或面心晶格結構之情形時，空間填充率最大，該填充率

為0.74左右。若將空間率(存在於球體間之空間體積占容器體積之比率)設為η，則利用η＝1－

求出η。因此，空間率為0.26左右。 然而，在考慮產業界中之製造過程中，使某空間區域利用球體進行最密填充之實例時，上述理想性之結晶結構模型之實現困難。表1中模型化地表示經選粒之相同直徑之粒子被撒入至成形用之模具之狀態。若計算具有相同直徑之粒子之空間填充率及空間率，則如表1所示，各為0.523及0.477。此處，較重要的係空間填充率與球體之形狀(大小)無關而是唯一地決定。但，實際上，被進行最密填充之球體於某平面之一邊排列有n個，於下一段排列有(n－1)個，再下一段排列有n個・・・之重複，且空間構成係正方或者立方體構成，若考慮到此情況，則現實中於壁面無法完成理論上之排列，而該處係成為空間，因此較上述模型之最密填充空間率而言實際存在之空間變大。但是，可知無論任何實例中，空間率均相當高。 表2中，對存在於粒子間之空間中內接於各粒子之小球體之大小進行考察、研究。可知具有粒子之半徑之約15%左右之半徑之小球體能夠存在於該空間。於該情形時，表示與粒子之尺寸無關，該關係式成立，且係與球體之最密填充之問題一併成為本發明之基礎之非常重要之數值。 [數1]

[數2]

When the powder is handled in the manufacturing step, the transportation problem of the powder is bound to occur. That is, for example, when the powder of the prescribed drug is put into the mold of the tablet in order to manufacture the tablet, the powder will not flow freely if the powder of the drug is directly used, so spray is usually used. Desiccator to make granules (particle-like tiny spheres). In this way, the processing of the powder in the step can be said to be free because the particles have fluidity. Even in the step of manufacturing the piezoelectric material sheet, in the so-called dry method, powder pressure is also used. Therefore, when using this technique, the raw material powder of the piezoelectric material is made into pellets in advance. In this patent, the viewpoint of the handling of the powder, especially the transportation of the powder, is centered on the regularity of the arrangement of the particles formed by the piezoelectric material placed in the mold for the powder forming. Research from the perspective of crystal engineering. That is, when considering the case where the sphere is filled in the space, an example of the densest packing density of the sphere is performed. Generally speaking, the atoms forming the substance are spheres, which complete the arrangement for the densest packing of the crystalline core. Based on this fact, consider the space filling rate when a container is filled with spheres of the same diameter

(The ratio of the volume of the sphere to the volume of the container). It is known that ideally, when a filled sphere of the same diameter adopts the hexagonal closest packing structure or face-centered lattice structure in the crystal structure, the space filling rate is the largest, and the filling rate

It is around 0.74. If the space ratio (the ratio of the volume of the space existing between the spheres to the volume of the container) is set to η, then use η = 1-

Find η. Therefore, the space ratio is about 0.26. However, when considering an example of the densest filling of a certain space area with spheres in the manufacturing process in the industry, it is difficult to realize the above-mentioned ideal crystal structure model. Table 1 shows the state in which the selected particles of the same diameter are cast into the mold for molding. If the space filling rate and space rate of particles with the same diameter are calculated, as shown in Table 1, they are 0.523 and 0.477 respectively. Here, the more important system space filling rate is determined uniquely regardless of the shape (size) of the sphere. However, in fact, the most densely filled spheres are arranged on one side of a plane with n pieces, (n-1) in the next stage, and n in the next stage, and there are n repeats of ... It is a square or cube structure. If this situation is taken into account, the theoretical arrangement on the wall surface cannot be completed in reality, and the system becomes a space, so the actual space becomes larger than the densest filling space rate of the above model. However, it can be seen that in any instance, the space ratio is quite high. In Table 2, the size of the small sphere inscribed in each particle in the space between the particles is investigated and studied. It can be seen that small spheres with a radius of about 15% of the radius of the particle can exist in this space. In this case, it means that it has nothing to do with the size of the particles, the relational expression holds, and the problem of the densest packing of the sphere together becomes a very important value for the foundation of the present invention. [Number 1]

[Number 2]

為0.74～0.52，空間率η為0.26～0.48左右。 本發明之著眼點以下述特徵為基礎：於具有某容積之容器中無限地使相同直徑之球體進行最密填充之情形時， (1)其空間率約為48%，較大；(2)空間非常規整地存在；(3)與填充體之球體所出現之空間內接之小球體之半徑為填充體之球體之半徑之約15%，相對較小；(4)空間率較大，該值可較大地有助於作為目標之多孔質壓電體之孔隙率之控制；(5)球體非常規整排列；(6)使球體填充之初始狀態於其後之製造全步驟中得到維持等。 回歸結晶結構學及粉體工學之基礎，捕捉其特徵，於其基礎上，完成先前不可能之(甲)孔隙之尺寸之控制(乙)人為地控制孔隙之位置及排列之獨立性(丙)完全實現孔隙率之人為控制等劃時代之發明。 即，發明出一種劃時代之製造方法，其於確保存在於壓電材料中孔隙之規則性、分佈之均勻性及尺寸選擇之自由度與其整齊性等之基礎上，能夠經濟地製造多孔質壓電材料。除此以外，能夠實現多孔質壓電材料之功能設計，使得壓電材料之用途增多，有利於超音波感測器之功能提高。 多孔質壓電材料製品製造之過程中，可將其製造方法大致分為兩種。即， (a)使孔隙形成材料存在於含有壓電材料等之粒子之中之方法，換言之，製作使球形孔隙形成材料之表面經壓電材料微粉末覆蓋而成之被覆複合粒子，並使用該被覆複合粒子之方法。 (b)使孔隙形成材料存在於由含有壓電材料等之粒子所構成之空間之方法。 無論製造方法(a)及(b)之任一方法中，與先前之製造方法有較大不同之點在於利用以下特性：發現孔隙形成材料及壓電材料之幾何學構成係自初始之設定狀態至全部製造步驟中被得到確保並成為製品之特徵。As mentioned above, theoretically or calculated the densest filling rate of the space

It is 0.74 to 0.52, and the space ratio η is about 0.26 to 0.48. The focus of the present invention is based on the following features: when spheres of the same diameter are filled infinitely in a container with a certain volume, (1) the space ratio is about 48%, which is relatively large; (2) Unconventional space preparation exists; (3) The radius of the small sphere inscribed in the space where the sphere of the filler body appears is about 15% of the radius of the sphere of the filler body, which is relatively small; (4) The space ratio is large, the The value can greatly contribute to the control of the porosity of the targeted porous piezoelectric body; (5) Unconventional alignment of the spheres; (6) The initial state of the filling of the spheres is maintained throughout the subsequent manufacturing steps. Return to the foundation of crystalline structure and powder engineering, capture its characteristics, and complete the previously impossible (a) pore size control (b) artificially control the independence of the position and arrangement of pores (C) ) Completely realize the epoch-making invention of artificial control of porosity. That is, invented an epoch-making manufacturing method, which can economically manufacture porous piezoelectric materials on the basis of ensuring the regularity and uniformity of the pores in the piezoelectric material, the degree of freedom in size selection, and the orderliness. material. In addition, the functional design of porous piezoelectric materials can be realized, which increases the use of piezoelectric materials, which is beneficial to the improvement of the function of ultrasonic sensors. In the process of manufacturing porous piezoelectric material products, the manufacturing methods can be roughly divided into two types. That is, (a) a method of making the pore-forming material exist in particles containing piezoelectric materials, in other words, producing coated composite particles in which the surface of the spherical pore-forming material is covered with piezoelectric material fine powder, and using the Method of coating composite particles. (b) A method of allowing the pore-forming material to exist in a space composed of particles containing piezoelectric materials and the like. Regardless of the manufacturing methods (a) and (b), the major difference from the previous manufacturing method is the use of the following characteristics: It is found that the geometric composition of the pore forming material and the piezoelectric material is from the initial setting state It is ensured in all manufacturing steps and becomes a feature of the product.

One of the proposals of the present invention is a method of manufacturing a porous piezoelectric material with controlled pores and porosity by using composite particles coated with fine powder of piezoelectric material PZT in the carbon particles of the pore forming material shown in FIG. 2. The product forming mold 14 shown in FIG. 3 is most densely filled with covered composite particles 13 formed by covering the periphery of the pore-forming material with piezoelectric material. It is mentioned that the space formed by these composite particles is not filled with The porosity P1 in the case of any material. (A) The densest filling rate of the space of the spheres with the same infinite diameter is relatively low, but the spheres are arranged regularly; (b) The space where the spheres can be arranged regularly is larger, and the arrangement is completed geometrically, etc., Based on the above, it can be proved that the targeted porous piezoelectric material can be produced with uniformly dispersed pores. That is, the porosity is determined by a function of the volume ratio of the composite sphere (radius: R, thickness of the coating layer: t) coated with the piezoelectric material and the volume ratio of the particles of the pore-forming material (radius: r). The porosity is artificially determined based on the ratio of the radius of the piezoelectric material to the pore-forming material. Therefore, it becomes possible to set the porosity under limited conditions. In this case, the space formed by the coated composite particles 13 regularly filled is maintained in a hollow state, and is reduced by the pressure received in the powder forming step. The porosity P1 obtained by this method is determined by the volume ratio of the piezoelectric material PZT coated with the pore-forming material to the volume of the pore-forming material as described previously. The mathematical formula required for the theoretical investigation is shown in (Numeral 3), and the calculation result of the porosity P1 is shown in (Table 1). [Number 3]

[表1]

In the method of the preceding paragraph, in order to obtain a relatively low porosity, the surface of the spherical pore forming material must be thickly coated with the piezoelectric material. However, it may become difficult to coat thickly to a certain extent, or the piezoelectric coating layer may peel off depending on the situation. In the present invention, on the basis of the densest filling of the coated composite particles 13 formed by the piezoelectric material in the product forming mold, the piezoelectric material containing about 15% of the diameter of the coated composite particles as the largest diameter The fine particles 15 are filled in the space formed by the coated composite particles, thereby solving the above-mentioned problems. If the ultrafine particles 15 composed of only the raw material of the piezoelectric material alone, and the particles 13 formed by coating the carbon particles of the pore-forming material with the piezoelectric material are simultaneously placed into the molding die of the workpiece, the coating The space formed between the composite particles is filled with fine particles 15 containing piezoelectric materials, thereby solving this problem. As a result, the total amount of piezoelectric materials becomes more than the amount of space ratio. The total amount can be freely controlled according to the thickness of the piezoelectric material covered. This brings about porosity control as a result. It can be seen that if this process is applied to the manufacture of porous piezoelectric materials, all the defects and abnormalities in the previous manufacturing can be eliminated, which is a very epoch-making manufacturing method. That is, the size or distribution of pores cannot be controlled at all in the previous manufacturing steps, and although it is known that its characteristics are better, the road to productization is quite narrow. By introducing the method of the present invention, on the basis of the conditions under which the porosity is controlled, the size, uniformity and distribution of the pores can be freely designed according to the purpose. The theoretical calculation method of the porosity in this example is shown in (Number 4), and the calculation results of the porosity P2 are combined and shown in (Table 1). [Number 4]

[Table 1]

In the present invention, using the method described above, a porous piezoelectric material molded body can be manufactured as follows: the average pore diameter of the spherical pore group in the piezoelectric material is in the range of 2-50 μm per 1 mm ³ volume A porous piezoelectric material molded body formed by dispersing more than 1,000 pieces, the number of pores with a pore diameter exceeding 50 μm is 1% or less (preferably 0.5% or less) based on the number, and constitutes the pores of the spherical pore group The pores above 80% by volume of the total volume have a pore diameter within ±20% based on the above average pore diameter.

Furthermore, in the present invention, the average pore diameter of the spherical pore group in the porous piezoelectric material formed body, the number of spherical pore groups per 1 mm ³ volume, the number of pores with a pore diameter exceeding 50 μm, constitute a spherical shape The total volume of the pores of the pore group and the pore diameter of each spherical pore can be measured by X-ray CT observation of the porous piezoelectric body. That is, the above-mentioned measurement values can be obtained by performing image analysis on the stereoscopic image of the porous piezoelectric material molded body obtained by X-ray CT. In addition, it can also be confirmed by the following method: after cutting the porous piezoelectric material formed body and grinding the cut surface, using an electron microscope (SEM), the distribution of the pore diameter of the pores appearing on the cut surface Determination.

In addition, in the present invention, the so-called "spherical pores" are not spherical pores in the exponential meaning, but refer to pores having a shape called spherical in common sense.

In the porous piezoelectric material molded body of the present invention, it is more desirable that "the interval between two spherical pores that are adjacent to each other through the piezoelectric material region is substantially the same throughout the inner region", and it is more desirable to exist in the porous body The pores in the inner pore group exist independently in all directions of up and down, left and right, and front and rear, without deviating from the inside of the porous body. Here, the "substantially the same interval" in the expression "the interval between two spherical pores is substantially the same in the entire inner region" refers to the interval between adjacent spherical pores relative to the interval between all spherical pores The average value is distributed within a range of ±60%, preferably within a range of ±40%, and more preferably within a range of ±20%.

The above-mentioned porous piezoelectric material molded body of the present invention can be manufactured by using a manufacturing method including the following steps: preparing coated composite particles, which are pore-forming material particles having an average particle diameter in the range of 2 to 70 μm, and using The average particle diameter of the particles is in the range of 1/100 to 1/5 of the average diameter of the piezoelectric material powder and the binder mixture is coated, and the particle diameter of the coated composite particles constituting the coated composite particle group The coated composite particles distributed within ±50% of the average particle diameter of the coated composite particle group occupy more than 60% by volume (preferably more than 80% by volume) of the entire coated composite particle group; press the coated composite particle group Next, the molded body is obtained by molding; and then the molded body is fired, the pore-forming material particles and the binder are burned and removed, and then sintered.

In addition, the porous piezoelectric material molded body of the present invention can be used to produce the porous piezoelectric material of the present invention efficiently and reliably by a method including the following steps: the porous piezoelectric material has an average particle diameter in the range of 2 to 70 μm and From the pore forming material particles whose average particle size error is within ±20%, use piezoelectric material powder and binder with an average diameter in the range of 1/100 to 1/5 of the average particle size of the particle The mixture is coated to produce coated composite particles; particle size sorting is performed on the coated composite particle group, whereby the particle size distribution of the coated composite particles constituting the coated composite particle group is the average particle size of the coated composite particle group Coated composite particles within ±50% of the diameter occupying 60% by volume or more (preferably 80% by volume or more) of the entire coated particle group are recovered; the recovered coated composite particle group is formed under pressure Obtaining a compact: and then firing the compact, burning and removing the pore-forming material particles and the binder, and then sintering.

In addition, the porous piezoelectric material molded body of the present invention can be used to produce the porous piezoelectric material of the present invention efficiently and reliably by a method including the following steps: the porous piezoelectric material has an average particle diameter in the range of 2 to 70 μm and From the pore-forming material particles whose average particle size error is within ±20%, use the powder and bonding of piezoelectric material particles with an average diameter in the range of 1/100～1/5 of the average particle size of the particle The coated composite particle group is coated with a mixture of agents to produce a coated composite particle group; the particle size sorting process is performed on the coated composite particle group, whereby the particle size distribution of the coated composite particles constituting the coated composite particle group is The coated composite particles with an average particle diameter within ±10% (preferably within ±5%) occupy more than 80% by volume (preferably more than 90% by volume) of the total coated composite particle group; recover the coated composite particles; The recovered coated composite particle group is molded under pressure to obtain a molded body; and then, by firing the molded body, the pore-forming material particles and the binder are burned and removed, and then sintered.

The present invention further relates to an array type vibrator, comprising: a piezoelectric vibrator row formed by arraying piezoelectric vibrators containing the porous piezoelectric material molded body of the present invention; and an acoustic device attached to the surface of the piezoelectric vibrator row The integration layer; the backing material attached to the back of the piezoelectric vibrator row; and the acoustic lens attached to the surface of the acoustic integration layer.

Hereinafter, preferred aspects of the porous piezoelectric material molded body of the present invention will be described. (1) Spherical pores that constitute more than 90% by volume of the total spherical pore volume of the spherical pore group have a pore diameter within ±20% based on the average pore diameter. (2) Spherical pores that constitute more than 80% by volume of the total spherical pore volume of the spherical pore group have a pore diameter within ±10% based on the average pore diameter. (3) Spherical pores that constitute more than 90% by volume of the total spherical pore volume of the spherical pore group have a pore diameter within ±10% based on the average pore diameter. (4) The interval between the two spherical pores existing adjacent to each other through the piezoelectric material is substantially the same in more than 80% by volume of the entire internal area. (5) The average pore diameter of the spherical pore group is substantially 15 μm or less. (6) The height and width of the porous molding system are both within the range of 0.05-2 mm, and the length of the porous molding system is within the range of 5-50 mm. (7) The piezoelectric material contains lead zirconate titanate (2-component PZT) or 3-component PZT. (8) The apparent density is in the range of 5/10 to 9/10 relative to the true density, and more preferably in the range of 50/100 to 99/100. (9) In a sheet or short strip of porous piezoelectric material molded body, the average pore diameter is within the range of 1/1000 to 1/10 of the thickness of the sheet or strip.

Furthermore, when implementing the method of manufacturing the porous piezoelectric material molded body of the present invention, in the step of forming the coated composite particle group under pressure to obtain the molded body, a particle size of 15% or less of the coated composite particle size is prepared in advance. Fine particles (using a spray dryer, etc. to make a slurry containing piezoelectric material powder and binder into tiny particles), and the volume ratio of the piezoelectric material powder to the coated composite particle group is calculated as the former relative to the latter In the range of 1/1 to 10/1, prepare a group of fine particles of piezoelectric material. The following method can also be used: after sequentially injecting the coated composite particles and the piezoelectric fine particles into a molding die, they are molded under pressure to form a molded body. By using this method of manufacturing a molded body, it becomes possible to artificially adjust the porosity of the porous piezoelectric material molded body. [Effects of Invention]

8 μm之孔隙占98%，且孔隙之數量為2,500個/mm³ 以上之多孔質壓電材料。 如此，由於本發明之多孔質壓電材料成形體中，存在於含有壓電材料之成形體之內部之孔隙直徑之均勻性較高之孔隙群均勻地散佈，故與至今為止所知之多孔質壓電材料成形體相比，係明顯不同之成形體。 表2係將為了測定於使孔隙率變化之情形時，多孔質壓電材料之各物性值表現出何種舉動而實驗性地獲得之數值進行繪圖而成者(孔隙率0%之各特性值表示所使用之多晶壓電材料燒成體之值)。 作為壓電元件之感測器之輸出(感度)Sp由感測器之電壓V與相對介電常數ε33及電氣機械耦合係數K33決定。 於電壓固定之情形時，重要因數集中於相對介電常數ε33與電氣機械耦合係數k33。 根據圖表可知，伴隨孔隙率之增加，相對介電常數大幅下降，但達到一定之孔隙率之前電氣機械耦合係數不斷增加。 即，孔隙率達到～15%左右之前，作為感測器之輸出表示超過作為基底之壓電材料之數值。與單晶壓電材料相比，約為90%之數值。 另一方面，超音波探頭(探針)之設計中，由於Eastek(股)PiezoCAD(超音波探針設計開發支援軟體)之模擬值與實測值之關聯性非常高，故於該業界中廣泛地使用且受到較高評價。 使用該軟體，對作為基底之PZT壓電材料、使用其之孔隙率15%之多孔質PZT及單晶壓電材料之應用厚度振動之於3.5 MHz振盪下之電氣的特性(頻帶特性及脈衝特性)進行比較。 (註：本實驗資料係以利用其他PZT材料所獲得之資料為基礎，於加成性成立之條件下，對3成分系PZT之特性進行推測之資料) 將其結果示於表3。電氣頻帶特性表現出與使用單晶壓電材料製得之壓電振子匹配或者其以上之特性。脈衝特性中，獲得淩駕於其之上之特性。進而，製造上無較大之阻礙及困難性，又，機械特性(牢固性)或加工性(加工之容易程度)亦優異。 若以根據該厚度振動獲得之資料為基礎，類推排列型探針之特性，則可期待以下內容。 先前根據所需之診斷活體之不同而準備診斷用之探針，但若如上所述般使用本發明之多孔質壓電材料準備中心頻率為3.5 MHz之探針，則能夠涵蓋2～5 MHz之頻帶，故準備1根探針即可滿足要求。 根據專利參考文獻2，有獲得孔隙率為0.1～0.75較佳為0.30～0.65之較佳之特性之探針，且若孔隙率未達0.1，則無法活用多孔質壓電體之特徵之記述。但，本發明之實證實驗結果中，可預測孔隙率為0.01～0.25較佳為0.15以下時，發揮極其較佳之特性。 [表2]

[表3]

Using X-ray CT to scan the 5 mm□×8 mmH porous piezoelectric material obtained in the present invention, the state of the pores was observed, and the result showed that the pores were 17.4 mm ³ , the PZT of the base material was 200 mm ³ , and the volume ratio of the pores was approximately Is 9%. Get average diameter

A porous piezoelectric material with pores of 8 μm accounting for 98%, and the number of pores is 2,500/mm ³ or more. In this way, in the porous piezoelectric material molded body of the present invention, the pore groups with high uniformity of the pore diameter existing in the piezoelectric material-containing molded body are uniformly dispersed, so it is different from the known porous body. Compared with the piezoelectric material formed body, it is a significantly different formed body. Table 2 is the result of plotting experimentally obtained values in order to determine the behavior of each physical property value of the porous piezoelectric material when the porosity is changed (the characteristic values of porosity 0% It represents the value of the fired polycrystalline piezoelectric material used). The output (sensitivity) Sp of the sensor as the piezoelectric element is determined by the voltage V of the sensor, the relative permittivity ε33 and the electromechanical coupling coefficient K33. When the voltage is fixed, the important factors focus on the relative permittivity ε33 and the electromechanical coupling coefficient k33. According to the graph, the relative permittivity decreases drastically with the increase in porosity, but the electromechanical coupling coefficient continues to increase before reaching a certain porosity. That is, before the porosity reaches ~15%, the output of the sensor indicates a value exceeding the value of the piezoelectric material as the substrate. Compared with single crystal piezoelectric materials, the value is about 90%. On the other hand, in the design of ultrasonic probes (probes), due to the high correlation between the analog values of Eastek (stock) PiezoCAD (ultrasonic probe design and development support software) and the measured values, it is widely used in the industry. Used and received high evaluation. Using this software, the electrical characteristics (band characteristics and pulse characteristics) of thickness vibration under 3.5 MHz oscillation are applied to PZT piezoelectric materials as the substrate, porous PZT with a porosity of 15%, and single crystal piezoelectric materials. )Compare. (Note: This experimental data is based on the data obtained by using other PZT materials. Under the condition that the additive property is established, the properties of the 3-component system PZT are estimated.) The results are shown in Table 3. The electrical frequency band characteristics show matching or higher characteristics with piezoelectric vibrators made of single crystal piezoelectric materials. Among the pulse characteristics, the characteristics above it are obtained. Furthermore, there are no major obstacles and difficulties in manufacturing, and the mechanical properties (firmness) and processability (easy of processing) are also excellent. Based on the data obtained from the thickness vibration and analogy with the characteristics of the array probe, the following can be expected. Previously, probes for diagnosis were prepared according to the different living organisms required for diagnosis. However, if the porous piezoelectric material of the present invention is used to prepare probes with a center frequency of 3.5 MHz as described above, it can cover the range of 2 to 5 MHz. Frequency band, so prepare one probe to meet the requirements. According to Patent Reference 2, there is a description that a probe having a better characteristic with a porosity of 0.1 to 0.75, preferably 0.30 to 0.65, and if the porosity is less than 0.1, the characteristics of the porous piezoelectric body cannot be utilized. However, in the results of the empirical experiments of the present invention, it can be predicted that when the porosity is 0.01 to 0.25, preferably 0.15 or less, extremely favorable characteristics are exhibited. [Table 2]

[table 3]

Next, the porous piezoelectric material molded body and its manufacturing method of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of the structure of the porous piezoelectric material molded body of the present invention in the form of a conceptual diagram. In FIG. 1, the porous piezoelectric material molded body 1 of the present invention includes a sintered body 11 of piezoelectric material powder, and a large number of fine spherical shapes dispersed in an almost aligned state (that is, in a uniformly dispersed state) inside it的孔12。 The pore 12. Figure 1 is a two-dimensional conceptual diagram, and the same is true for a three-dimensional conceptual diagram.

As the piezoelectric material powder obtained by obtaining the sintered body of the piezoelectric material powder constituting the porous piezoelectric material molded body of the present invention, for example, lead zirconate titanate (PZT), which is the most general powder, can be cited. However, the piezoelectric material powder is not limited to the 2-component system PZT or the 3-component system PZT, as long as it is a powder of a material exhibiting piezoelectricity, it can be used without particular limitation. The piezoelectric material powder that can be used is described in more detail in Patent Documents 1 to 3. Therefore, the contents of these patent documents are included in this specification. In addition, the piezoelectric material powder may also be an aggregate of hollow piezoelectric material particles.

The piezoelectric material powder preferably has an average diameter in the range of 1/100 to 1/5 of the average particle diameter of the pore forming material particles described later. That is, the piezoelectric material particles constituting the piezoelectric material powder are preferably an aggregate of piezoelectric material powders whose powder diameter is sufficiently small relative to the pore-forming material particles, and the powder diameter is as uniform as possible.

Fig. 2 is a conceptual diagram illustrating the steps of obtaining a molded body by molding the coated composite particle group used in the production of the porous piezoelectric material molded body of the present invention under pressure. That is, in the production of the porous piezoelectric material of the present invention, as described above, in the first step, first, the preparation of the coated composite particle powder is performed as follows: the coated composite particle powder contains a powder having an average particle size Pore-forming material particles (ie, particles with a highly consistent particle size) in the range of 2～70 μm and the error of the average particle diameter is within ±20%, using the average within the range of 1/100～1/5 Coated composite particle group formed by coating a mixture of piezoelectric material powder and binder with diameter, and the particle size distribution of the coated composite particles constituting the coated composite particle group is ±50% of the average particle size of the coated composite particle group The covered composite composite particles occupy more than 60% by volume of the entire covered particle group.

As the pore forming material particles used in the first step, synthetic resin particles such as spherical carbon powder (spherical carbon particles), spherical polymethyl methacrylate particles, or thermosetting epoxy particles are generally used. Other examples of the pore-forming material particles that can be used in the production of the porous piezoelectric material molded body of the present invention are described in more detail in the above-mentioned Patent Documents 1 to 3. Therefore, the contents of these patent documents are included in this specification. .

Furthermore, particles having pore-forming material particles with an average particle diameter in the range of 2 to 70 μm and a particle diameter within ±20% of the average particle diameter error (that is, particles with uniform particle diameters) can be obtained from Japan Carbon (stock ), Soken Chemicl (shares), Japan Exlan (shares), IBIDEN (shares), or GUN EI Chemial Industry (shares) and other companies. If necessary, you can also use commercially available precision grading devices to The spherical pore-forming material particles (precision sieving device) obtained by the required enterprises are classified, so that they can be easily obtained.

As the adhesive used in the above-mentioned first step, a mixture of polyvinyl alcohol in the form of an aqueous solution and a water-soluble acrylic resin can be used, but there is no particular limitation on the adhesive. Other examples of the adhesive are described in more detail in the above-mentioned Patent Documents 2 to 3, so the contents of these patent documents are included in this specification.

In order to produce a group of coated composite particles coated with a mixture of piezoelectric material particles and a binder, for example, the following method can be used: the powder of piezoelectric particles is dispersed in a binder that is made into a dilute aqueous solution. After obtaining the slurry, for example, using a spray drying device such as an atomizer type spray dryer, the slurry and the pore forming material particles are spray-dried. Using spray drying, the binder aqueous solution slurry and pore-forming material particles formed by dispersing piezoelectric particle powder are coated with a mixture of piezoelectric material powder and binder to produce a coated composite particle group. There are more detailed descriptions in the above-mentioned patent documents 2 to 3, so the contents of these patent documents are included in this specification.

For the purpose of manufacturing the porous piezoelectric material molded body of the present invention, it is preferable to appropriately adjust the concentration or the binder aqueous solution when manufacturing the coated composite particle group coated with a mixture of piezoelectric material powder and a binder. The mixing ratio of the binder aqueous solution and the piezoelectric material powder, as well as the spray drying (or spray granulation) conditions, etc., so that the particle size distribution of the coated composite particles constituting the coated composite particle group is the average of the coated composite particle group The coated composite particles within ±50% of the particle size occupy 60% by volume or more (preferably 80% by volume or more) of the entire coated particle group.

However, when manufacturing the coated composite particle group that is coated by the mixture of the piezoelectric material particle powder and the binder, even by adjusting the concentration of the binder aqueous solution or the mixing ratio of the binder aqueous solution and the piezoelectric material powder, and spraying It is also difficult to obtain the particle size distribution of the coated composite particles constituting the coated composite particle group under the drying conditions within ±50% of the average particle size of the coated composite particle group. The coated composite particles occupy 60% by volume of the total coated particle group. In this case, the above-mentioned coated composite particle group can also be added with the following step: by subjecting the obtained coated composite particle group to a well-known particle size sorting process, the coated composite particles constituting the target coated composite particle group are recovered The particle size distribution is that the coated composite particles within ±50% of the average particle size of the coated composite particle group occupy 60% by volume or more (preferably 80% by volume or more) of the entire coated particle group. The particle size sorting process can be performed by a precision classifier such as an ultrasonic precision classifier manufactured and sold by a classifier manufacturer such as Aishin Nano Technologies Co., Ltd. When particles other than the coated composite particles are mixed, that is, in case it is inconvenient to mix the particles containing piezoelectric material monomers, the Aerosol mass analyzer manufactured and sold by KANOMAX Co., Ltd. can also be used to perform the above treatment.

Second, the distribution of the particle size of the coated composite particles constituting the obtained coated composite particle group is within ±50% of the average particle diameter of the coated composite particle group. The coated composite particles occupy 60% by volume or more of the total coated particle group. The particles are subjected to the following steps: forming under pressure to obtain a formed body.

Fig. 3 shows a schematic diagram of a step of forming a group of coated composite particles coated with a mixture containing the electrical material powder and a binder used in the production of the porous piezoelectric material molded body of the present invention under pressure. That is, the coated composite particles 13 are introduced into the container 14 for pressure treatment, and the pressure treatment is performed. Regarding the molding process under pressure for the coated composite particles 13 coated with a mixture containing piezoelectric material particles and a binder, the above-mentioned Patent Documents 2 to 3 have more detailed descriptions, and therefore the description of these patent documents The content is recorded in this manual.

Then, the molded body obtained by the molding process of the above-mentioned coated composite particle powder under pressure is subjected to a firing process at a temperature higher than the thermal decomposition temperature of the pore-forming material particles, and the pores are removed by the firing process The particles of the forming material and the binder are burned and removed, and then further heated at a high temperature to sinter them. The sintering of the molded body obtained by using the coated composite particle group to perform a molding process under pressure, thereby burning and removing the pore-forming material particles and the binder, and sintering, the above process is also described in the above patent Documents 2 to 3 have more detailed descriptions, so the contents of these patent documents are included in this specification.

In addition, when it is desired to obtain a porous piezoelectric material molded body with a low porosity suppressed as a porous piezoelectric material molded body prepared by the above method, the following method can also be used: In the step of molding under pressure to obtain a molded body, as described above, the volume ratio of the piezoelectric material fine powder and the coated composite particle is, for example, the former to the latter in the range of 1/1 to 1/10 for addition and mixing. After the mixture is prepared, the mixture is molded under pressure to obtain a molded body. That is, by using such a manufacturing method of a molded body, the porosity of the porous piezoelectric material molded body can be artificially finely adjusted.

Furthermore, for the purpose of obtaining a porous piezoelectric material molded body whose porosity is suppressed to be low, a wet method is used. In this example, when manufacturing PZT-coated composite particles, a water-soluble binder and PZT fine powder slurry were used. Therefore, the coated composite particles have very weak properties against moisture. A hydrophobic solution, such as acetone, is sprayed on the surface of the coated composite particles in advance. After putting the coated composite particle group that has been surface-processed in advance into the required mold, the PZT micropowder slurry with a water-soluble binder is filled in the space that appears between the coated composite particles, thereby achieving low Porous piezoelectric material molded body with porosity. For example, it is sufficient to prepare a PZT fine powder slurry obtained by adding and mixing the volume ratio of the former to the latter in the range of 1/1 to 1/10. That is, it is also possible to freely adjust the porosity of the porous piezoelectric material molded body by the manufacturing method of the molded body by such a wet method. Furthermore, when the PZT fine powder slurry using a water-soluble binder is filled in the space that appears between the coated composite particles, if the entire forming mold is turned into a reduced pressure environment using a vacuum pump or the like, the filling operation becomes even greater. Efficient. Example

Example 1 PZT powder (2-component PZT powder) with a particle size in the range of 0.1 to 1 μm was selected as the piezoelectric material particle powder, and 50 parts by mass of the PZT powder was combined with an aqueous binder solution (polyvinyl alcohol 1% by weight). 50 parts by mass of a mixture of the aqueous solution and the water-soluble acrylic resin 1% by weight aqueous solution) were mixed to prepare a PZT powder slurry. In addition, a spherical carbon powder with a particle size of about 10 μm (average particle size of 10 μm, particle size distribution within ±50%) is prepared separately. 100 parts by mass of the above-mentioned PZT powder slurry and 100 parts by mass of carbon powder with a particle size of about 10 μm are spray-dried using an atomizer-type spray dryer to obtain a PZT powder and binder Coated composite particles (average particle size: 20 μm) covered by a coating layer with a thickness of approximately 5 μm. In addition, the particle size distribution of the coated composite particles was measured, and the results showed that the coated composite particles did not belong to the coated composite particles whose particle size distribution was within ±50% of the average particle diameter of the coated composite particles, occupying 60% of the total coated composite particles. Volume% or more of the coated composite particles, so by using an ultrasonic classifier to perform classification processing, the particle size distribution of the coated composite particles can be recovered to be within ±50% of the average particle size of the entire coated composite particles Coated composite particles occupying more than 60% by volume of the entire coated particle group. The coated composite particles recovered by the above classification process are accommodated in the molding die 14 shown in FIG. 2, and a pressure of 1 to 1.5 ton/cm ^{2 is} applied to the accommodated coated composite particles to perform a pressure molding process. A formed body is obtained. Furthermore, visual observation under a high-magnification microscope could not confirm the existence of voids in the molded body obtained by the press molding process. Fig. 3 shows the dispersion state of the coated composite particle powder contained in the forming mold in the form of a conceptual diagram. Next, the above-mentioned formed body obtained by pressurizing the coated composite particle group was calcined in air at 450°C for 1 hour to sublime and remove the carbon particles, and then calcined at 1250°C (sintering treatment) ), thereby obtaining a porous PZT compact (sintered body) in which a spherical pore group with an average pore diameter of about 10 μm is formed in an aligned state in a three-dimensional direction at a position where carbon particles are present . After cutting the porous PZT molded body and grinding the cut surface, the pore diameter distribution of the pores appearing on the cut surface was measured. As a result, the pore diameter distribution of the pores that constitute more than 90% by volume of the pore group was determined. Within ±10% of the above average pore diameter (about 10 μm). In addition, it can also be known that the interval between the two spherical pores that exist adjacent to each other through the piezoelectric material area is distributed in a range of ±20% in more than 60% of the entire internal area. In addition, the density of the obtained porous PZT molded body was measured, and the result was 5.25 g/cm ³ , so if the density of the PZT used (6.70 g/cm ³ ) was calculated, the porosity was 22 volumes %. In addition, by X-ray CT observation, the number of spherical pores formed in the porous PZT molded body with an average pore diameter in the range of 2-50 μm was measured, and the result confirmed that the volume per 1 mm ³ The number is more than 1,000.

Example 2 Using the same method as the method described in Example 1, coated carbon particles (average particle size: 14 μm) coated with a coating layer containing PZT particle powder and a binder with a thickness of about 2 μm were obtained After the powder, the classification process is carried out to recover the particle size distribution of the coated composite particles within ±50% of the average particle size of the entire coated composite particle group. The coated composite particles occupy more than 80% by volume of the entire coated composite particle group. Coated composite particle group. In addition, PZT powder in the range of 0.1-1 μm is used to prepare particles (particles) of PZT fine powder with a particle size of 1 to 2 μm (approximately 15% of the coated composite particles). 100 parts by volume of the above-mentioned coated composite particles recovered by classification were put into the raw material supply funnel. Next, put 50 parts by volume of the above-mentioned particles separately prepared into the funnel. Vibration is applied by the vibration device attached to the funnel, and when the particles placed later become invisible, the on-off valve set at the bottom of the funnel is opened, and the pressure in the funnel is injected into the forming mold through the supply pipe. Electric raw materials. The piezoelectric material put into the forming mold in the same manner as in Example 1 (in a conceptual diagram in FIG. 4, the dispersed state of the coated composite particles 13 and PZT particles (particles) 15 contained in the forming mold 14 is shown) after forming , Calcining and firing treatments are performed to obtain a porous PZT molded body. The density of the obtained porous PZT molded body was measured, and the result was 6.85 g/cm ^3. Therefore, if the density of the PZT used (7.60 g/cm ³ ) is taken into consideration, the porosity is 10% by volume. In addition, the porous PZT molded body was cut, and the cut surface was polished, and the distribution of the pore diameter of the pores appearing on the cut surface was measured. As a result, it was found that more than 90% by volume of the pores constituting the pore group The pore diameters are distributed within ±10% of the above average pore diameter (about 10 μm). In addition, it can also be known that the interval between the two spherical pores that exist adjacent to each other through the piezoelectric material area is distributed in the range of ±20% in more than 60% of the entire internal area. Furthermore, by X-ray CT observation, the number of spherical pores formed in the porous PZT molded body with an average pore diameter in the range of 2-50 μm was measured. As a result, it was confirmed that the number of spherical pores per 1 mm ³ volume The number is more than 1,000.

1: Porous piezoelectric material molded body 11: Piezoelectric materials 12: Porosity 13: Coated composite particles 14: Forming mold 15: Micro-powder particles (particles) made of piezoelectric materials

Fig. 1 is a conceptual diagram showing an example of the structure of the porous piezoelectric material molded body of the present invention. Fig. 2 is a diagram illustrating the concept of obtaining the most densely packed composite particles used in the manufacture of the porous piezoelectric material molded body of the present invention to obtain the basic molded body of this patent. Fig. 3 is a conceptual diagram illustrating the arrangement of coated composite particles in the step of obtaining the formed body of the coated composite particle group shown in Fig. 2 in the form of a two-dimensional diagram. Fig. 4 is a method of forming a molded body by adding a group of coated composite particles of piezoelectric material particles (particles) used in one example of the production of the porous piezoelectric material molded body of the present invention under pressure A conceptual diagram illustrating the steps.

1: Porous piezoelectric material molded body

11: Piezoelectric materials

12: Porosity

Claims (14)

A method for manufacturing a porous piezoelectric material, which is characterized in that: in a powder compact containing piezoelectric material, spherical piezoelectric material particles are most densely filled in the powder forming mold or the spherical pore forming material is coated and pressed Based on the conditions of composite particles made of electrical materials, in the space formed by the particles in a regular arrangement, when the composite particles are covered, if necessary, spherical particles containing piezoelectric materials are filled. In spherical piezoelectric particles In this case, the spherical pores are filled to form material particles and the porosity is controlled. The method for manufacturing a porous piezoelectric material according to claim 1, wherein the particle size of the material filled in the space formed by the particles is less than 0.155 times the particle size. The method for manufacturing a porous piezoelectric material according to claim 2, wherein the particle size of the material filled in the space formed by the particles is within a region less than 0.155 times the particle size. The upper and lower limits are specified and only used Material particles within this range are used as space fillers. A porous piezoelectric material molded body characterized in that it is formed in a piezoelectric material obtained by the manufacturing method as claimed in claim 1, and has a spherical pore group with an average pore diameter in the range of 2 to 70 μm per 1 volume of 1000 mm ³ or more is made by forming a dispersion, and a number of spherical pores over pore diameter of 50 μm to the number of basis is 1% or less, and 80 constituting the spherical volume of the total pore volume of spherical pores% or more of the group The pores have a pore diameter within ±20% based on the above average pore diameter. Such as the porous piezoelectric material molded body of claim 4, wherein more than 90% by volume of the total volume of the spherical pores constituting the spherical pore group has a pore diameter within ±20% based on the average pore diameter. Such as the porous piezoelectric material molded body of claim 4, in which the spherical pores more than 80% by volume of the total volume of the spherical pores constituting the spherical pore group have a pore diameter within ±10% based on the average pore diameter. Such as the porous piezoelectric material molded body of claim 4, wherein more than 90% by volume of the total volume of the spherical pores constituting the spherical pore group has a pore diameter within ±10% based on the average pore diameter. For example, the method of manufacturing a porous piezoelectric material molded body of claim 1, which includes the following steps: preparing a group of coated composite particles, which will have an average particle diameter in the range of 2 to 70 μm and the error from the average particle diameter is ±20 The pore-forming material particles with a particle size of less than% are coated with a mixture of piezoelectric material powder and a binder having an average powder diameter in the range of 1/100 to 1/5 of the average particle size of the particle, And the distribution of the particle size of the coated composite particles constituting the coated composite particle group is within ±50% of the average particle diameter of the coated composite particle group. The coated composite particles occupy more than 60% by volume of the entire coated composite particle group; The composite particle group is molded under pressure to obtain a molded body; and then the molded body is fired, whereby the pore forming material particles and the binder are burned and removed, and then sintered. For example, the method for manufacturing a porous piezoelectric material molded body of claim 1, which includes the following steps: forming pores with an average particle diameter in the range of 2 to 70 μm and the error from the average particle diameter within ±20% The material particles are coated with a mixture of piezoelectric material powder and a binder having an average powder diameter in the range of 1/100 to 1/5 of the average particle size, thereby producing voids covered by the mixture of powder and binder. Material particles (coated composite particles); by subjecting the coated composite particle group to the particle size sorting process, the particle size distribution of the coated composite particles constituting the coated composite particle group is the average particle size of the coated composite particle group Within ±10% of the coated composite particles are recovered; the recovered coated composite particles are molded under pressure to obtain a molded body; and then the molded body is fired to thereby combine the pore-forming material particles and the binder Burned and removed, and then sintered. An array probe, comprising: a row of piezoelectric vibrators composed of piezoelectric vibrators containing a porous piezoelectric material molded body as in claim 4; an acoustic integration layer attached to the surface of the row of piezoelectric vibrators; A backing material attached to the back of the piezoelectric vibrator row; and an acoustic lens attached to the surface of the acoustic integration layer. A probe, which is a probe used for an array element of an ultrasonic diagnostic device, is characterized in that the piezoelectric material forming system used in the probe is composed of porous ceramics. For example, the probe of claim 11 uses porous ceramics with more than 1000 pores separated from each other and existed independently per cubic millimeter. Such as the probe of claim 12, wherein the porosity of the porous ceramic is in the range of 0.1-15%, preferably 0.1-10%. Such as the probe of claim 13, wherein the porous ceramic material used is 2 series or 3 series PZT.

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