JP2008160045A - Flexible pressure-sensitive material, piezoelectric element using the same, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible pressure-sensitive material, a piezoelectric element using the same, and manufacturing method therefor capable of reducing variation in an electric characteristic even when used under a high-temperature and high-moisture atmosphere, materializing a constantly stable piezoelectric characteristic, and requiring no complicated circuitry. <P>SOLUTION: The flexible pressure-sensitive material 1 contains a piezoelectric ceramic particle 3 and a flexible organic macromolecular material 4. The piezoelectric ceramic particle 3 has a coated layer 5 to suppress absorption of moisture on its surface, performs washing treatment after forming the coated layer 5, and removes components including residual metal elements. Accordingly, elution can be suppressed in a metal element residual in the piezoelectric ceramic particle 3, and in an unreacted metal element contained in the coated layer 5. Therefore, the flexible pressure-sensitive material can be obtained with high reliability, and variations can be reduced in electrostatic capacitance, electric resistance and piezoelectric characteristic. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flexible pressure-sensitive body obtained by blending a piezoelectric ceramic powder in an organic polymer, and more particularly to a piezoelectric element used as a flexible pressure-sensitive sensor and a manufacturing method thereof.

  This flexible pressure-sensitive body is obtained by uniformly dispersing, mixing and kneading the above materials using a processing machine such as a kneader or a roll, and is flexible because it contains a thermoplastic elastomer such as chlorinated polyethylene. It is processed into a sheet shape or a cable shape and used as a piezoelectric element (see, for example, Patent Document 1).

In the sheet-like piezoelectric element, first, piezoelectric powder and chlorinated polyethylene are kneaded with a roll, and then a flexible pressure-sensitive body is formed into a sheet shape by hot pressing, and a silver paste is applied to both surfaces of the sheet or applied to rubber. A pair of electrodes is formed by fusing a conductive sheet in which carbon is dispersed, and then obtained by applying a DC voltage of several tens of kV between both electrodes in order to develop piezoelectricity. be able to. When pressure is applied to a part or the entire surface of this electrode, the flexible pressure-sensitive body in that part is distorted. As a result, a voltage is induced between both electrodes, and the pressure is detected using this induced voltage. Therefore, it is applied as a pressure sensor.
JP 62-230071 A

  However, when a conventional piezoelectric element is used in a high-temperature and high-humidity environment, water vapor passes through the electrode and reaches the flexible pressure-sensitive body constituting the piezoelectric element. When the temperature inside the flexible pressure sensing element is lower than the outside or when the water vapor becomes supersaturated on the surface of the flexible pressure sensing element, the diffused water vapor condenses to produce water, and the flexible pressure sensing element A phenomenon occurs in which components and impurities of the constituent piezoelectric ceramic powder are eluted by water and ionized. As a result, problems such as changes in electrical resistance, capacitance, and piezoelectric characteristics occur, resulting in inferior durability. In addition, when used as a sensor, a circuit for detection and control becomes complicated. It was.

  In particular, piezoelectric ceramic powders containing alkali metals and alkaline earth metals belonging to Groups 1 and 2 of the periodic table have a low specific resistance and are easily eluted into water, so that a reduction in electrical resistance is a major issue.

  In addition, although the said subject was described with respect to the sheet-like piezoelectric element, while it has the same subject also in a cable shape and another shape, it has the same subject only in a flexible pressure sensitive body.

  The present invention solves the conventional problems, and even when used in a high-temperature and high-humidity environment, it suppresses the change in electrical characteristics, always realizes stable piezoelectric characteristics, and does not require a complicated circuit. An object of the present invention is to provide a flexible pressure-sensitive body, a piezoelectric element using the flexible pressure-sensitive body, and a manufacturing method thereof.

In order to solve the above-described conventional problems, the flexible pressure-sensitive body of the present invention is a flexible pressure-sensitive body including a piezoelectric ceramic powder and a flexible organic polymer, and the piezoelectric ceramic powder has moisture on the surface. A coating layer that suppresses the absorption of water is provided, and after the coating layer is formed, a cleaning process is performed to remove a compound containing a remaining metal element.

  As a result, the piezoelectric element is used in a high-temperature and high-humidity environment, and even when water vapor is generated by condensation inside the piezoelectric element, a coating layer that suppresses moisture absorption is provided on the surface of the piezoelectric ceramic powder. Absorption of moisture into the piezoelectric ceramic powder is suppressed. Furthermore, since the cleaning process is performed after the film is formed to remove the compound containing the remaining metal element, the metal element remaining in the piezoelectric ceramic powder and the unreacted metal element and compound containing the metal element contained in the coating layer are eluted. Is suppressed, and changes in capacitance and electric resistance are reduced. In addition, since the amount of water penetrating into the flexible pressure sensitive body is reduced, changes in electrical characteristics and piezoelectric characteristics when used as a piezoelectric element are further reduced.

  The piezoelectric element using the flexible pressure-sensitive body of the present invention and the method for manufacturing the piezoelectric element are obtained by washing and removing unreacted components remaining in the piezoelectric ceramic powder and the coating layer on the surface of the piezoelectric ceramic powder. Since the eluted metal elements and compounds containing metal elements can be reduced, the initial electrical characteristics can be maintained, changes over time can be prevented, and excellent durability and reliability can be achieved. Can be realized.

  The first invention is a flexible pressure-sensitive body comprising piezoelectric ceramic powder and a flexible organic polymer, wherein the piezoelectric ceramic powder is provided with a coating layer for suppressing moisture absorption on the surface, and the coating layer is formed. Since the compound containing the remaining metal element is removed after cleaning, the elution of the metal element remaining in the piezoelectric ceramic powder and the unreacted metal element contained in the coating layer can be suppressed. A highly flexible pressure sensitive body can be realized.

  According to a second aspect of the present invention, after the piezoelectric ceramic powder is cleaned, a coating layer that suppresses moisture absorption is formed on the surface of the piezoelectric ceramic powder, and after the coating layer is formed, the cleaning process is further performed, and the compound containing the remaining metal element is formed. It has been removed. Therefore, the metal element remaining in the piezoelectric ceramic powder can be efficiently removed, and a highly reliable flexible pressure sensitive body can be realized.

  In the third invention, in particular, by forming the coating layer on the particle surface of the piezoelectric ceramic powder of the first invention with a water repellent material, the water repellent effect can be made into a thin film coating layer, and flexible pressure sensitive In addition to preventing changes in the piezoelectric characteristics due to prevention of penetration into the body, it is possible to reduce the loss of applied voltage in the poling process performed to develop piezoelectricity, and excellent piezoelectricity even at low voltages Characteristics can be developed.

  Further, by coating the piezoelectric ceramic powder with a water-repellent material, the surface of the piezoelectric ceramic powder exhibits hydrophobicity, so that the compatibility with the organic polymer having flexibility is improved, and the kneadability of both is improved. As a result, the kneading process time can be shortened and the productivity can be improved.

  In the fourth aspect of the invention, in particular, excellent water repellency can be realized by configuring the coating layer with at least one of fatty acid, fatty acid salt, and monomolecular layer. In particular, when the first coating layer is formed of a monomolecular layer, when the thickness of the coating layer is a monomolecular layer of several nanometers, a single DC layer is applied during poling to apply a high DC voltage in order to develop piezoelectric characteristics. The voltage drop that occurs in the molecular layer is reduced, and the poling efficiency can be improved, and the polling processing time can be shortened or excellent piezoelectric characteristics can be realized.

  Moreover, since the amount of the water repellent material used can be reduced by making the coating layer a monomolecular layer, the cost of the water repellent piezoelectric element can be reduced.

  In the fifth aspect of the invention, in particular, the piezoelectric ceramic after the cleaning treatment is boiled, and the pH of the aqueous solution has a correlation with changes in electric characteristics such as capacitance, electric resistance, and piezoelectric characteristics. By making it below, the influence of the remaining metal element can be reduced, and stable electrical characteristics can be maintained over a long period of time. Furthermore, when used as a piezoelectric element, it is possible to prevent changes in capacitance, electrical resistance, and piezoelectric characteristics, and to simplify a circuit for detection and control when used as a sensor.

  In the sixth aspect of the invention, in particular, the piezoelectric ceramic after the cleaning treatment is boiled, and the conductivity of the aqueous solution is correlated with changes in electrical characteristics such as capacitance, electrical resistance, and piezoelectric characteristics. By setting it to / cm or less, the influence of the remaining metal element can be reduced, and stable electrical characteristics can be maintained over a long period of time. Furthermore, when used as a piezoelectric element, it is possible to prevent changes in capacitance, electrical resistance, and piezoelectric characteristics, and to simplify a circuit for detection and control when used as a sensor.

  In the seventh aspect of the invention, in particular, the piezoelectric ceramic after the cleaning treatment is boiled, and the sodium ions in the aqueous solution are correlated with changes in electrical characteristics such as capacitance, electrical resistance, and piezoelectric characteristics. By setting it to 300 μg / g or less, the influence of the remaining metal element can be reduced, and stable electrical characteristics can be maintained over a long period of time. Furthermore, when used as a piezoelectric element, it is possible to prevent changes in capacitance, electrical resistance, and piezoelectric characteristics, and to simplify a circuit for detection and control when used as a sensor.

  In the eighth aspect of the invention, in particular, the piezoelectric ceramic powder of the first aspect of the invention can be more effective in cleaning by including at least the elements of Group 1 of the periodic table and Group 2 of the periodic table. In particular, piezoelectric ceramic powders containing Group 1 and Group 2 alkali metals and alkaline earth metals of the periodic table have low resistivity and are easily eluted into water, so they were greatly affected by humidity. By performing the coating layer and the cleaning treatment, a change with respect to humidity can be reduced.

  In the ninth aspect of the invention, in particular, the piezoelectric ceramic powder containing the elements of Group 1 of the periodic table and Group 2 of the periodic table of the eighth invention includes at least one of barium, sodium, potassium, bismuth, and lithium. As a result, the dielectric constant of the piezoelectric ceramic powder can be lowered, so that a high voltage can be applied to the piezoelectric ceramic powder when performing the poling process for applying the DC voltage to develop the piezoelectric characteristics. The polling efficiency can be increased, and the voltage output constant can be increased. As a result, when the piezoelectric element is used as a pressure-sensitive sensor, the output voltage of the sensor with respect to the applied pressure can be increased, so that the sensitivity can be improved.

  In the tenth aspect of the invention, in particular, the piezoelectric ceramic powder containing the elements of Group 1 and Periodic Table Group 2 of the eighth aspect is sodium niobate, potassium niobate, lithium niobate, bismuth sodium titanate, By including at least one of barium titanate and bismuth titanate, the dielectric constant of the piezoelectric ceramic powder can be further reduced, so that the poling efficiency for expressing the piezoelectric characteristics can be further increased. In addition, since the amplification factor of the detection circuit can be lowered by increasing the sensitivity of the sheet-like piezoelectric element, when the piezoelectric element is used as a pressure-sensitive sensor, the output voltage of the sensor with respect to the applied pressure is increased. As a result, the sensitivity can be improved and a pressure sensor that is strong against electrical noise can be obtained. .

  In the eleventh aspect of the invention, in particular, by performing the cleaning treatment with water, it is possible to increase the removal efficiency of the components including the elements of Group 1 and Group 2 of the periodic table remaining in the piezoelectric ceramic powder.

In the twelfth aspect of the invention, in particular, a component containing the elements of the periodic table group 1 and the periodic table group 2 remaining in the piezoelectric ceramic powder to be removed by performing the cleaning treatment of the eleventh invention with acidic water. Since it is alkaline, it can be efficiently dissolved in acidic water, and higher removal efficiency can be obtained in a shorter time than water.

  In the thirteenth aspect of the invention, the elements of the periodic table group 1 and periodic table group 2 remaining in the piezoelectric ceramic powder by heating the water or the acidic water for performing the cleaning treatment of the eleventh or twelfth invention, in particular. The elution of the component containing can be promoted, and still higher removal efficiency can be realized.

  According to a fourteenth aspect of the present invention, there is provided a piezoelectric element comprising a first electrode connected to a flexible pressure sensitive body and a second electrode connected to the flexible pressure sensitive body and insulated from the first electrode. By doing so, since an electrical output can be obtained easily, application development of a sensor etc. becomes easy. In addition, when the piezoelectric element is used in a high-temperature and high-humidity environment, even if water vapor is condensed inside the piezoelectric element to produce water, no unreacted components remain in the piezoelectric ceramic powder in the condensed water. Elution can suppress elution. Therefore, changes in the capacitance, electrical resistance, and piezoelectric characteristics of the piezoelectric element can be prevented. As a result, stable electrical characteristics can be maintained over a long period of time, and a circuit for detection and control when used as a sensor can be simplified.

  According to the fifteenth aspect of the invention, in particular, the flexible pressure-sensitive body covers the first electrode, and the second electrode is a cable-shaped piezoelectric element configured to cover the flexible pressure-sensitive body. Since not only vibration but vibration in the direction of the center can be detected, even if the flat plate shape is limited in use, the cable can be applied to facilitate application development. Furthermore, since it has flexibility and is shaped like a cable, it can be used for arrangements including bent portions and space-saving arrangements with a limited mounting width. In addition, when the piezoelectric element is used in a high-temperature and high-humidity environment, even if water vapor is condensed inside the piezoelectric element to produce water, no unreacted components remain in the piezoelectric ceramic powder in the condensed water. Elution can suppress elution. Therefore, changes in the capacitance, electrical resistance, and piezoelectric characteristics of the piezoelectric element can be prevented. As a result, stable electrical characteristics can be maintained over a long period of time, and a circuit for detection and control when used as a sensor can be simplified.

  In the sixteenth aspect of the invention, in particular, the piezoelectric ceramic powder and the metal element eluting from the coating layer and the compound containing the metal element are removed by washing away unreacted components remaining in the coating layer on the surface of the piezoelectric ceramic powder. Since it can be reduced, initial electrical characteristics and piezoelectric characteristics can be maintained, changes with time can be prevented, and excellent durability and reliability can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a sheet-like piezoelectric element according to the first embodiment of the present invention. In FIG. 1, a sheet-like piezoelectric element is configured by forming an electrode 2 </ b> A as a first electrode and an electrode 2 </ b> B as a second electrode on both surfaces of a sheet-like flexible pressure-sensitive body 1.

  FIG. 2 is a schematic diagram showing a partial cross section of the flexible pressure-sensitive body 1. In FIG. 2, a sheet-like flexible pressure-sensitive body 1 is composed of a piezoelectric ceramic powder 3 containing elements of Groups 1 and 2 of the periodic table and an organic polymer 4 having flexibility. Further, a coating layer 5 for suppressing moisture absorption is formed on the surface of the piezoelectric ceramic powder 3, and the piezoelectric ceramic powder 3 and the organic polymer 4 are in a state of being uniformly dispersed.

  The compound of the piezoelectric ceramic powder 3 containing elements of Group 1 and Group 2 of the periodic table used in the present embodiment includes at least one of barium, sodium, potassium, bismuth, and lithium, specifically Includes at least one of sodium niobate, potassium niobate, lithium niobate, bismuth / sodium titanate, barium titanate, and bismuth titanate, and includes a ceramic material that exhibits piezoelectricity by poling treatment.

  In addition, the piezoelectric ceramic powder 3 containing the elements of Group 1 of the periodic table and Group 2 of the periodic table is a raw material (for example, nitrate) containing the elements of Group 1 of the periodic table and Group 2 of the periodic table so as to have a predetermined composition. , Carbonate, sulfate, etc.), and then calcined at a high temperature. At this time, in the ceramic produced by firing, there are impurities, unreacted elements and compounds, or compounds having a composition that cannot exhibit piezoelectric characteristics, in addition to the compound having a crystal structure that exhibits piezoelectric characteristics. . In the present invention, a compound that does not exhibit the piezoelectric characteristics existing in the piezoelectric ceramic powder 3 is defined as a compound containing a remaining metal element.

  The sheet-like piezoelectric element according to the first embodiment is manufactured as follows. This manufacturing process is shown in FIG. First, the piezoelectric ceramic powder 3 containing the elements of Group 1 of the periodic table and Group 2 of the periodic table was diluted with a suitable solvent and adjusted to a predetermined concentration, or heated to a melting temperature. Piezoelectric ceramic powder 3 in which a coating layer 5 of water repellent material is formed on piezoelectric ceramic powder 3 by dipping in a solution of water repellent material and drying, or by mixing piezoelectric ceramic powder 3 with a predetermined amount of water repellent material powder. (S1).

  Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed is immersed in a container containing water, and the metal element is eluted from the compound containing the residual metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 while stirring. A cleaning process is performed (S2). If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the piezoelectric ceramic powder 3 and the flexible organic polymer 4 are uniformly mixed and dispersed in the flexible organic polymer 4 using a processing machine such as a kneader or a roll. The mixture is kneaded so as to be in a heated state (S3). At this time, a titanium coupling agent may be added to improve kneading. After kneading, it is processed using a processing machine such as a roll or a hot press to produce a sheet-like flexible pressure-sensitive body 1 (S4).

  Next, a conductive paste or conductive paint in which conductive powder and an organic polymer are mixed is applied to both surfaces of the sheet-like flexible pressure-sensitive body 1, and the conductive powder is made flexible such as rubber or thermoplastic elastomer. Electrodes 2A and 2B that are insulated from each other are formed by either fusing the conductive sheet mixed / dispersed in the organic polymer having it, and depositing the conductive material by any material and forming method (S5). Thereafter, a poling process is performed by applying a DC high voltage between the electrodes 2A and 2B in the air or in a silicon oil bath in order to develop piezoelectricity (S6), and a sheet-like piezoelectric element is manufactured. The polling process (S6) is performed after the electrodes 2A and 2B are formed (S5). However, after the sheet-like flexible pressure-sensitive body 1 is manufactured (S4), two pseudo electrodes are used. You may go.

  The operation and action of the sheet-like piezoelectric element configured as described above will be described below.

As described above, the piezoelectric characteristics of the sheet-like piezoelectric element are manifested by applying a high direct-current voltage between the electrodes 2A and 2B and poling the flexible pressure-sensitive body 1. When a temporally changing pressure is applied to a part or the entire surface of a sheet-like piezoelectric element that exhibits piezoelectric characteristics, vibration corresponding to the acceleration generated in that part is applied between the first electrode 2A and the second electrode 2B. A voltage is induced. The pressure can be detected using this induced voltage. Sensors installed on automobile doors to prevent pinching, touch sensors installed on door handles to control unlocking, sensors installed on nursing beds, etc. to detect body movement, placed on handrails on verandas, etc. It can be used as a pressure-sensitive sensor such as a sensor that detects the intrusion of the water.

  Pressure sensors such as those mentioned above may be used outdoors or when installed in automobiles, in high-temperature steam environments during rainy seasons or in the rain in summer, and incontinence or sweat when installed in nursing beds. If it is mounted on bedding, there is a high possibility that it will be used in a high-temperature and high-humidity environment such as washing and cleaning to maintain sanitation.

  When a conventional piezoelectric element is used as a pressure-sensitive sensor in such a high temperature and high humidity environment, water vapor passes through the electrode and diffuses into the sheet-like piezoelectric element. When the temperature of the flexible pressure sensitive body is lower than the outside or when the water vapor is supersaturated on the surface of the flexible pressure sensitive body, the diffused water vapor is condensed and water is generated, and this water is generated in the flexible pressure sensitive body. Penetration causes a phenomenon in which compounds and impurities remaining in the piezoelectric ceramic powder 3 are eluted. As a result, the capacitance of the sheet-like piezoelectric element increases and the electrical characteristics change, such as a decrease in electrical resistance. This results in inferior durability and detection when used as a pressure sensor. In addition, it is necessary to make it possible to cope with the initial change in electrical characteristics of the control circuit, which makes the circuit a complicated configuration.

  However, when the sheet-like piezoelectric element of the present embodiment is used in a high-temperature and high-humidity environment, the water vapor passes through the electrodes 2A and 2B, and the water vapor is condensed on the surface of the flexible pressure-sensitive body 1 to form water. Even if it forms, since the coating layer 5 which suppresses absorption of moisture is provided on the surface of the piezoelectric ceramic powder 3, absorption of moisture itself into the piezoelectric ceramic powder can be suppressed. Further, after the coating layer 5 is formed, a cleaning process is performed to remove the metal element remaining in the piezoelectric ceramic powder 3 and the coating layer 5, so that even if water vapor is generated by the condensation of the flexible pressure-sensitive body 1, The elution of the metal element remaining in the piezoelectric ceramic powder 3 and the unreacted metal element contained in the coating layer 5 is suppressed, and changes in electrical resistance and piezoelectric characteristics as a sheet-like piezoelectric element can be prevented. As a result, the initial electrical characteristics of the sheet-like piezoelectric element can be maintained, and excellent durability and reliability can be realized. In addition, since the initial change in electrical characteristics can be prevented, a circuit configuration for correcting the change in electrical characteristics is not required, and a circuit for detection and control can be simplified.

  The piezoelectric characteristics of the sheet-like piezoelectric element used in the present embodiment are manifested by applying a high DC voltage between both electrodes and performing a poling process. However, the sheet-like piezoelectric element of the present embodiment is pressure sensitive. When used as a sensor, an important piezoelectric characteristic is a voltage output constant that serves as an index of the generated voltage.

  A flexible pressure-sensitive body 1 constituting the sheet-like piezoelectric element of the present embodiment is composed of a composite of piezoelectric ceramic powder 3 and flexible organic polymer 4, and the relative dielectric constant ( The dielectric constant of the material (dielectric constant / vacuum dielectric constant) is several hundred to several thousands, whereas the organic polymer 4 having flexibility has several tens of dielectric constants. Since the DC voltage applied during the poling process is distributed in inverse proportion to the ratio of the dielectric constant of the piezoelectric ceramic powder 3 and the flexible organic polymer 4, the DC voltage is flexible with a low dielectric constant. A high voltage is applied to the organic polymer 4 having In other words, when the same organic polymer 4 having flexibility is used, a higher voltage is applied to the organic polymer 4 having flexibility as the dielectric constant of the piezoelectric ceramic powder 3 is higher. .

Therefore, when the piezoelectric ceramic powder 3 of the flexible pressure-sensitive body 1 is composed of lead zirconate titanate having a relative dielectric constant of about 2000 and bismuth sodium titanate having a relative dielectric constant of about 600, the flexibility of both When a constant DC voltage is applied to the pressure body 1, a voltage higher than that of lead zirconate titanate is applied to bismuth / sodium titanate having a low relative dielectric constant, so that the poling efficiency can be increased. The constant increases. As a result, when a sheet-like piezoelectric element is used as a pressure-sensitive sensor, the output voltage of the sensor with respect to the applied pressure can be increased, so that the sensitivity can be improved and the sheet-like piezoelectric element can be improved. Since the amplification factor of the detection circuit can be lowered by increasing the sensitivity, a pressure-sensitive sensor that is strong against electrical noise can be obtained.

  The lower the relative dielectric constant of the piezoelectric ceramic powder 3 is, the better. However, when the piezoelectric ceramic powder 3 is 1000 or less, a voltage output constant that is three times or more superior to that when the piezoelectric ceramic powder 3 of lead zirconate titanate is used is obtained. In that respect, the useful piezoelectric ceramic powder 3 includes at least one of barium, sodium, potassium, bismuth, and lithium as the compound of the piezoelectric ceramic powder 3 including elements of Group 1 and Group 2 of the Periodic Table. Specific examples include those containing at least one of sodium niobate, potassium niobate, lithium niobate, bismuth / sodium titanate, barium titanate, and bismuth titanate.

  In addition, since the piezoelectric ceramic powder 3 used in the present embodiment does not contain lead, the sheet-like piezoelectric element is disposed of, and even if it is exposed to an environment such as acid rain, there is no elution of lead and there is a possibility of environmental pollution. Absent.

  According to the present embodiment, the coating layer 5 of the water repellent material is formed on the surface of the piezoelectric ceramic powder 3. In order to suppress the penetration of water into the flexible pressure-sensitive body 1 and to significantly reduce changes in the electrical characteristics, piezoelectric characteristics, and mechanical strength of the sheet-like piezoelectric element in a high temperature and high humidity environment, the flexible feeling It is necessary to develop excellent water repellency on the entire surface of the pressure body 1, and for this purpose, the water repellency of the first coating layer 5 needs to be remarkably increased. Therefore, the coating layer 5 is preferably a water repellent material having a contact angle with distilled water of 125 ° or more. In other words, if the contact angle of the coating layer 5 with distilled water is 125 ° or more, the surface of the flexible pressure-sensitive body 1 can have high water repellency with respect to condensed water even in a high temperature environment. The effect of suppressing the penetration of water into the flexible pressure sensitive body 1 can be enhanced. Since the contact angle is less than 180 ° by definition, a water repellent material having a contact angle with distilled water of 125 ° or more and less than 180 ° is preferable. Desirably, a super water-repellent material having a contact angle with distilled water of 150 ° or more is preferable.

  In particular, the water repellent material having a contact angle with respect to distilled water of the first coating layer 5 formed by water repellent treatment of 150 ° or more includes the aforementioned fatty acid, fatty acid salt, fatty acid amide, fluorine-based resin, and silicon-based resin. And silane compounds.

  In particular, the fatty acids include caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadencanic acid, arachic acid, behenic acid, lignoceric acid , Serotic acid, heptacosanoic acid, montanic acid, acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, erucic acid, pracidic acid, sorbic acid, linoleic acid, linolenic acid.

  Examples of the fatty acid salt include compounds of the above-described fatty acids and calcium, zinc, sodium, potassium, magnesium, copper, and lead metal elements, and at least one of these fatty acid salts.

Examples of fatty acid amides include caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadencanic acid, arachic acid, behenic acid, lignoserine. Acid, serotic acid, heptacosanoic acid, montanic acid, acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, pracidic acid, sorbic acid, linoleic acid, linolenic acid What substituted the hydrogen group by the amino group is used.

  In addition, as a fluorine-based resin, polytetrafluoroethylene (PTFE), perfluoroalkylethyl acrylate, as a silicon-based resin, dimethylpolysiloxane, diethylpolysiloxane, a silicon-acrylic block copolymer, and as an acrylic resin, Examples include methacrylic acid esters and acrylic acid ester polymers.

  Examples of the silane compound include dialkylsilane compounds and fluorosilane compounds having at least a siloxane bond on the surface of the piezoelectric ceramic powder 5 and having at least an alkyl group or a fluoroalkyl group. The coating layer 5 formed by applying a water repellent material to the aforementioned silane compound can be formed as a monomolecular layer. Since the monomolecular layer is an ultra-thin film having a thickness of several nanometers, the monomolecular layer is formed when a high-voltage DC voltage is applied in the poling process performed for producing the piezoelectric characteristics after the flexible pressure-sensitive body 1 is produced. Can reduce the voltage drop in the battery, improve the polling efficiency, reduce the processing time, achieve excellent piezoelectric characteristics, and reduce the amount of water repellent material used. Since it can be remarkably reduced, the cost of the sheet-like piezoelectric element can be reduced.

  In S1, the first coating layer 5 formed by performing the water repellent treatment is prepared by immersing the piezoelectric ceramic powder 3 in a solvent suitable for the water repellent material after the water repellent material is heated and melted. Put the water repellent material and immerse the piezoelectric ceramic powder 3 in a solution adjusted to an appropriate concentration, and then dry or mix the water repellent material powder and the piezoelectric ceramic powder 3 when the water repellent material is solid. Formed by any of the methods. Moreover, the water repellent material may be used alone or in combination of two or more.

  In the present embodiment, as a means for removing the metal elements remaining in the piezoelectric ceramic powder 3 and the coating layer 5, the crystal structure capable of expressing the piezoelectric characteristics of the piezoelectric ceramic powder 3 is destroyed by performing a cleaning process with water. The metal element can be eluted from the compound containing the remaining metal element without performing. In particular, when a fatty acid salt of a water-repellent material is used as the coating layer 5, there is a possibility that a metal element as a salt is eluted when an unreacted fatty acid salt remains. Therefore, the elution of the metal element remaining in the coating layer 5 can be suppressed by performing the cleaning after the water repellent treatment. Even when a water repellent material that does not contain a salt such as a fatty acid is used as the material of the coating layer 5, the unreacted water repellent material can be obtained by washing after the formation of the coating layer 5. Since elution into the molecule 4 can also be suppressed, the characteristic change hardly occurs and the reliability is improved.

  In addition, in the washing treatment with water, elution of the metal element from the compound containing the remaining metal element can be promoted by heating the water to a boiling temperature or a temperature of 50 ° C. or higher. Higher removal efficiency can be achieved in a shorter time than when no heating is performed.

  In addition, by using acidic water as the liquid for the cleaning treatment, the components containing the elements of Group 1 and Group 2 of the periodic table remaining in the piezoelectric ceramic powder to be removed are alkaline, which is efficient. Therefore, it is possible to obtain a high removal efficiency in a shorter time than water. Furthermore, in the washing treatment with the acidic water, by heating the acidic water, the elution of the metal element from the compound containing the remaining metal element can be promoted, and the removal efficiency is higher in a shorter time than when not heating. Can be realized.

Examples of the flexible organic polymer 4 used in the present embodiment include a material containing at least one of a thermoplastic elastomer and rubber. Since these flexible polymers 4 can impart excellent elasticity and flexibility to the sheet-like piezoelectric element, the sheet-like piezoelectric element has a large repulsive force and displacement amount against the applied pressure. Can be obtained, and the piezoelectric characteristics can be improved.

  In particular, as the above-mentioned thermoplastic elastomer, chlorinated polyethylene and chlorosulfonated polyethylene can increase the content of the piezoelectric ceramic powder 3 in the flexible pressure-sensitive body 1, so that the piezoelectric characteristics of the sheet-like piezoelectric element are improved. Can be improved.

  The electrode 2A and the electrode 2B of the sheet-like piezoelectric element of the present embodiment can be composed of an elastic body containing at least one of a thermoplastic resin, a thermoplastic elastomer, and rubber and a conductive layer of conductive powder. In this configuration, the electrode 2A and the electrode 2B can be extended and excellent in flexibility, so that a sheet-like piezoelectric element having high bending resistance and excellent durability can be obtained. This conductive layer is a flexible pressure-sensitive material obtained by extruding an elastic material containing at least one of a thermoplastic resin, a thermoplastic elastomer, and rubber and a conductive powder using a processing machine such as an extruder. 1 is formed.

  Alternatively, the electrodes 2A and 2B may be formed of a conductive paint whose main component is a mixture of a conductive powder and an organic polymer, or a coating film of a conductive paste. In this configuration, the adhesiveness between the flexible pressure-sensitive body 1 and the electrodes 2A and 2B can be increased, and an air layer is less interposed between the electrodes 2A and 2B and the flexible pressure-sensitive body 1. Therefore, the voltage drop between the electrodes 2A and 2B and the flexible pressure-sensitive body 1 during the polling process can be suppressed, and the effective voltage of the polling process can be increased.

  Further, the electrode 2A and the electrode 2B can be formed of a vapor-deposited film of a conductive material. In this configuration, since the electrodes 2A and 2B can be formed as thin films, the excellent flexibility of the flexible pressure-sensitive body 1 can be maintained, and the piezoelectric characteristics of the flexible pressure-sensitive body 1 can be reduced. Can be prevented. This thin film is formed on the flexible pressure-sensitive body 1 by vapor deposition using an apparatus such as vacuum vapor deposition, sputtering, or CVD.

  The conductive powder and conductive material described above can achieve particularly excellent conductivity and corrosion resistance by using at least one of C, Pt, Au, Pd, Ag, Cu, Al, and Ni. .

  In addition, a conductive layer made of a conductive film in which at least one foil of C, Pt, Au, Pd, Ag, Cu, Al, and Ni is bonded to both surfaces of a polymer film such as polyethylene terephthalate and the both surfaces are made conductive is provided. It may be used.

  As a result of evaluating the change in capacitance, resistance, and piezoelectric characteristics after leaving the piezoelectric element manufactured in the above manufacturing process at 85 ° C. and 85% high temperature and high humidity for 20 hours, it was compared with the piezoelectric element not subjected to cleaning treatment. Each change was reduced by about 60%. Therefore, since the piezoelectric element of the present invention is excellent in humidity characteristics, it can maintain stable electrical characteristics over a long period of time, and can simplify a circuit for detection and control when used as a sensor.

  Further, after the coating layer 5 is formed and subjected to a cleaning treatment, the piezoelectric ceramic powder 3 from which the compound containing the remaining metal element is removed is boiled with distilled water or ion-exchanged water, and the pH of the boiled solution and the piezoelectric element are set to 85. FIG. 4 shows the rate of change in capacitance after standing for 20 hours at a high temperature and high humidity of 85 ° C.

As a result, the lower the pH of the solution after boiling, the lower the change in capacitance, and a correlation was obtained between the pH and the change in capacitance. Therefore, it is desirable that the pH is low in order to suppress changes in capacitance. In addition, since the pH decreases as the number of cleaning treatments is increased, the pH of the treatment solution is effective as a residual element residual index, and the pH can be easily measured, which is suitable for the residual element residual index.

The output voltage (V) and capacitance (C) of the piezoelectric element are expressed by the equation (1) and show an inversely proportional relationship. Here, Q is a charge generation amount, which is a value specific to the material.
V = Q / C (1)
It can be seen from equation (1) that the output voltage decreases as the capacitance increases.

  In particular, when used for applications such as a switch sensor, a certain threshold value is generally provided, and control is performed such that the threshold value is ON when the threshold value is exceeded and OFF when the threshold value is not more than the threshold value. If the threshold value is lowered, the sensor output is likely to be affected by other vibrations and external noise. If the threshold value is increased, detection may be impossible. Therefore, the sensor output is often set to about 1.3 to 1.5 times the threshold value. . In that case, if the capacitance increases by 30% or more, the sensor output may drop to a threshold value and cause a malfunction. Therefore, it is desirable to suppress at least a change in the capacitance to 30% or less. It is desirable to suppress to 8.0 or less.

  More desirably, a pH of 7 or less that can suppress the change in capacitance to 20% or less leads to improved detection accuracy and reliability.

  In addition, when the change in capacitance is large, a design that takes into account a decrease in output voltage due to the change in capacitance is required, and thus the ratio between the output voltage and the threshold needs to be increased. In other words, what required a high-power piezoelectric element can suppress the decrease in output voltage due to capacitance change, so the ratio between sensor output and threshold can be lowered, and the same can be achieved without a high-sensitivity design. Since an output can be obtained, it leads to low cost.

  In addition, the piezoelectric ceramic powder 3 subjected to the cleaning treatment after the coating layer 5 is formed is boiled with distilled water or ion-exchanged water, and the electric conductivity of the boiled solution and the piezoelectric element are heated at 85 ° C. and 85% under high temperature and high humidity. FIG. 5 shows the rate of change in capacitance after standing for a period of time.

  As a result, the lower the conductivity of the treatment solution, the lower the capacitance change, and a correlation was obtained between the conductivity and the capacitance change. In particular, when the number of washings is repeated, the conductivity decreases, so that the conductivity of the treatment solution is effective as a residual element residual index, and the conductivity can be easily measured, which is suitable as a residual element residual index.

  When used as a sensor as described above, the change in capacitance needs to be suppressed to 30% or less, and therefore, the conductivity is desirably suppressed to 50 μs / cm or less.

  More desirably, the detection accuracy is improved and the reliability is improved by setting the capacitance to 40 μs / cm or less that can suppress the change in capacitance to 20% or less.

  In addition, the piezoelectric ceramic powder 3 subjected to the cleaning treatment after forming the coating layer 5 is boiled with distilled water or ion-exchanged water, and the sodium ion concentration of the boiling solution and the piezoelectric element are set to 20 at 85 ° C. and 85% under high temperature and high humidity. FIG. 6 shows the rate of change in capacitance after standing for a period of time.

  As a result, the lower the sodium ion concentration of the treatment solution, the lower the change in capacitance, and a correlation was obtained between the change in conductivity and capacitance. In particular, when the number of washings is repeated, the conductivity decreases, so the sodium ion concentration of the treatment solution is effective as a residual element residual index, which is suitable for the residual element residual index.

As described above, when used as a sensor, the change in capacitance needs to be suppressed to 30% or less, so that the sodium ion concentration is preferably suppressed to 300 μg / g or less.

  More desirably, the detection accuracy is improved and the reliability is improved by setting the output voltage to 200 μg / g or less that can suppress the change in the output voltage to 20% or less.

(Embodiment 2)
FIG. 7 is a diagram for explaining the manufacturing process of the sheet-like piezoelectric element according to the second embodiment of the present invention. The difference from the manufacturing method of the first embodiment is that the piezoelectric ceramic powder 3 is cleaned. Then, after removing metal elements from the metal elements and metal element compounds remaining in the piezoelectric ceramic particles 3, a coating layer 5 of a water-repellent material is formed on the surface of the piezoelectric ceramic particles 3, and the piezoelectric ceramic powder formed with the coating layer 5 is formed. This is a point where a cleaning process is performed. In particular, when fatty acid salts or metal soaps are used as water repellent treatment materials, electrical properties such as capacitance, electrical resistance, and piezoelectric properties are generated due to the phenomenon that unreacted salts are eluted by water and ionized. It suppresses the change of

  The sheet-like piezoelectric element in the present embodiment is manufactured as follows. The manufacturing process will be described with reference to FIG. First, the piezoelectric ceramic powder 3 containing the elements of Group 1 of the periodic table and Group 2 of the periodic table is immersed in a container containing water, and the metal from the compound containing the remaining metal elements contained in the piezoelectric ceramic powder 3 is stirred. The element is eluted (S12). If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the washed piezoelectric ceramic powder 3 is immersed in a solution containing a water repellent material diluted to a predetermined concentration by dilution with an appropriate solvent, or a solution of a water repellent material heated to a melting temperature and dried. Alternatively, the piezoelectric ceramic powder 3 is mixed with a predetermined amount of water-repellent material powder to form the water-repellent material coating layer 5 on the piezoelectric ceramic powder 3 to produce the water-repellent piezoelectric ceramic powder 3 (S13). ).

  Next, the water-repellent piezoceramic powder 3 is immersed in a container containing water, and a cleaning process is performed to elute the metal element from the compound containing the remaining metal element contained in the piezoceramic powder 3 while stirring (S14). ). If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the piezoelectric ceramic powder 3 and the flexible organic polymer 4 are uniformly mixed and dispersed in the flexible organic polymer 4 using a processing machine such as a kneader or a roll. The mixture is kneaded so as to be in a heated state (S15). At this time, a titanium coupling agent may be added to improve kneading. After kneading, it is processed using a processing machine such as a roll or a hot press to produce a sheet-like flexible pressure-sensitive body 1 (S16).

  Next, a conductive paste or conductive paint in which conductive powder and an organic polymer are mixed is applied to both surfaces of the sheet-like flexible pressure-sensitive body 1, and the conductive powder is made flexible such as rubber or thermoplastic elastomer. Electrodes 2A and 2B that are insulated from each other by any material and formation method of fusing the conductive sheet mixed and dispersed in the organic polymer and depositing the conductive material are formed (S17). Thereafter, a poling process is performed by applying a DC high voltage between the electrodes 2A and 2B in the air or in a silicon oil bath in order to develop piezoelectricity (S18), and a sheet-like piezoelectric element is produced. The polling process (S18) is performed after the electrodes 2A and 2B are formed (S17). However, after the sheet-like flexible pressure-sensitive body 1 is manufactured (S16), two pseudo electrodes are used. You may go.

As a result of evaluating the change in capacitance, resistance, and piezoelectric characteristics after leaving the piezoelectric element manufactured in the above manufacturing process at 85 ° C. and 85% high temperature and high humidity for 20 hours, it was compared with the piezoelectric element not subjected to cleaning treatment. Each change could be reduced by about 70%. Therefore, the piezoelectric element of the present invention can reduce elution of unreacted components of the water-repellent treatment material by washing the piezoelectric ceramic powder 3 on which the water-repellent coating layer 5 is formed. It is possible to prevent changes in the piezoelectric characteristics of the capacitance and electric resistance of the element.

  As a result, the initial electrical characteristics of the piezoelectric element can be maintained, and excellent durability and reliability can be realized.

  In the present embodiment, the washing treatment is performed with water. However, as in the first embodiment, unreacted water can be efficiently reacted by using heated water, acidic water, or heated acidic water. Since residual components can be dissolved, high removal efficiency can be realized in a short time.

(Embodiment 3)
FIG. 8 is a partial cross-sectional view of a cable-shaped piezoelectric element according to the third embodiment of the present invention. As shown in FIG. 8, the cable-shaped piezoelectric element has a flexible flexible pressure-sensitive body 1 formed on the outer surface of the core electrode 6 that is the first electrode, and the outer surface of the flexible pressure-sensitive body 1. A flexible outer electrode 7 as a second electrode is formed, and a protective layer 8 made of an electrically insulating elastic body is further formed. The core electrode 6 and the outer electrode 7 are insulated by the flexible pressure sensitive body 1.

  The core electrode 6 has a configuration in which a metal such as copper is wound around a single or a plurality of metal wires, or converging wires of many polyester fibers.

  The flexible pressure-sensitive body 1 is composed of a piezoelectric ceramic powder 3 containing an element of Group 1 of the periodic table and Group 2 of the periodic table and an organic polymer 4 having flexibility. A material obtained by performing a cleaning process with the coating layer 5 of the embodiment to remove the remaining metal element is used.

  As with the electrodes 2A and 2B in the first embodiment, the outer electrode 7 has at least one of C, Pt, Au, Pd, Ag, Cu, Al, and Ni on both surfaces of a polymer film such as polyethylene terephthalate. A conductive layer formed by winding a conductive film with a seed foil attached around a flexible flexible pressure-sensitive body 7 having at least one of C, Pt, Au, Pd, Ag, Cu, Al, and Ni A conductive layer formed by extrusion molding a flexible conductive composition prepared by kneading powder and a flexible organic polymer such as rubber or thermoplastic elastomer, and dispersing the above-mentioned conductive powder in the organic polymer The conductive film coated with the conductive paint (paste) applied, at least one conductive material of C, Pt, Au, Pd, Ag, Cu, Al, Ni is vacuum-deposited on the flexible pressure-sensitive body 7, sputtering, CVD and other methods Vapor deposition film of the formed thin film is used.

  The protective layer 8 uses the material of the protective layer 5 described in the first embodiment, and is formed by extrusion molding of this material.

  A manufacturing process of the cable-like piezoelectric element in the present embodiment will be described with reference to FIG. First, the piezoelectric ceramic powder 3 is immersed in a solution containing a water-repellent material diluted with an appropriate solvent and adjusted to a predetermined concentration, stirred and mixed, and then dried or heated to a melting temperature. The piezoelectric ceramic powder 3 is subjected to a water repellent treatment by either being immersed in a solution and then mixed and then cooled, or the piezoelectric ceramic powder 3 is mixed with a predetermined amount of a water repellent material powder to thereby coat the coating layer 5. Is formed (S14).

Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed is immersed in a container containing water, and the metal element is eluted from the compound containing the residual metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 while stirring. A cleaning process is performed (S15). If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed and the organic polymer 4 are uniformly mixed with the organic polymer 4 by using a processing machine such as a kneader or a roll. -Knead to be in a dispersed state (S16).

  Next, the kneaded product is made into a sheet-like flexible pressure-sensitive body using a roll processing machine (S17), and the sheet-like pressure-flexible pressure-sensitive body is formed into a pellet using a processing machine such as a pelletizer. Process (S18).

  Next, the core electrode 6 is used as a core material, and a pellet-like flexible pressure-sensitive body is extruded using an extrusion molding machine to form a layer of the flexible pressure-sensitive body 1 around the core electrode 6. That is, the layer of the flexible pressure sensitive body 1 is provided around the core electrode 6 (S19).

  Next, the outer electrode 7 is formed using any of the materials and processing means described above (S20).

  Next, the protective layer 8 is formed by extrusion molding using an organic polymer such as a thermoplastic elastomer or rubber having elasticity (S21).

  Thereafter, a poling process is performed by applying a DC high voltage between the core electrode 6 and the outer electrode 11 in the air or in a silicon oil bath in order to develop piezoelectricity (S22), and a cable-shaped piezoelectric element is manufactured. Is done.

  The polling process (S22) is performed after forming the protective layer 12 (S21). However, after forming the layer of the flexible pressure-sensitive body 1 around the core electrode 6 (S19), the core electrode and the outer side are formed. It may be performed using a pseudo electrode corresponding to the electrode, or may be performed after forming the outer electrode 7 (S20).

  The cable-like piezoelectric element thus manufactured is controlled by removing the protective layer 8 and the flexible pressure-sensitive body 1 at one end and exposing the core electrode 6 and the outer electrode 7 as shown in FIG. It is connected to a circuit and used as a pressure sensitive sensor.

  The operation and action of the cable-shaped piezoelectric element configured as described above will be described below.

  When a time-varying pressure is applied to a part or the entire surface of the cable-shaped piezoelectric element, the acceleration generated in the cable-shaped piezoelectric element in that part is between the core electrode 6 and the outer electrode 7. A corresponding oscillating voltage is induced. The pressure can be detected using this induced voltage.

  When the cable-shaped piezoelectric element having the above-described configuration is used as a pressure-sensitive sensor in a high-temperature and high-humidity environment as in the first embodiment, the protective layer 8 is present. The amount of diffusion of can be reduced. However, since the gap between the organic polymer three-dimensional network molecular structure of the protective layer 8 is larger than the size of one molecule of water vapor, the protective layer 8 cannot completely prevent the diffusion of water vapor. Similarly to the embodiment, the water passes through the outer electrode 6 and water is condensed on the surface of the flexible pressure-sensitive body 7 to generate water.

In the cable-shaped piezoelectric element of the present embodiment, the metal element is removed from the compound containing the metal element remaining from the piezoelectric ceramic powder 3 constituting the flexible pressure-sensitive body 1, so that the flexible pressure-sensitive body 1 uses water vapor. Even if water is condensed to form water, elution of the metal element from the compound containing the metal element remaining in the piezoelectric ceramic powder 3 and the coating layer 5 is suppressed, and the electrical resistance and piezoelectric characteristics of the cable-shaped piezoelectric element are changed. Can be prevented. As a result, the initial electrical characteristics of the sheet-like piezoelectric element can be maintained, and the same effect as in the first embodiment can be realized.

  Further, even when a long cable-shaped piezoelectric element of several kilometers or more is processed, the cable is cut by removing the metal element from the compound containing the metal element remaining from each particle of the piezoelectric ceramic powder 3 in advance. The above-described effect can be exhibited at any part of the cable shape including the surface, and a cable-shaped piezoelectric element having always stable electrical characteristics can be obtained.

  Furthermore, since the cable-like piezoelectric element of the present invention has flexibility and is shaped like a cable, it can be applied to arrangements including bent portions and space-saving arrangements with a limited mounting width. In addition, even when used in a high-temperature and high-humidity environment, it has excellent characteristics that the initial electrical characteristics, piezoelectric characteristics, and mechanical strength can be maintained. Therefore, it is most suitable as a sensor for detecting pressure and vibration for outdoor use that requires such arrangement conditions and characteristics. Specifically, sensors are installed on devices and parts that require opening and closing, such as car sliding doors, hatchback doors, trunks, and power windows, and they are installed on car door handles to control door unlocking. Touch sensor.

  In addition, body motion sensors used for nursing beds and the like need to ensure a large area detection, but the cable-like piezoelectric element of the present invention has a large area by being meandered on the bed. In addition, it can be detected, and it is an optimum configuration as a body motion sensor for a nursing bed in consideration of usage conditions such as a humid environment such as incontinence and sweat and washing for hygiene maintenance.

  In addition, it can be used as a pressure-sensitive sensor such as a sensor for detecting an intrusion from the outside by placing it on a handrail of a veranda or an entrance door in an apartment or a detached house. In this case as well, the cable-shaped piezoelectric element is exposed to high-temperature and high-humidity environments because it is outdoors, but because it can maintain stable piezoelectric characteristics even in such an environment, malfunctions can be prevented and it can be used as a security sensor. can do.

  In addition, the cable-shaped piezoelectric element produced by the manufacturing method of the present invention can detect a large area by being meandered on the bed, and is optimal as a body motion sensor for a nursing bed. It is a configuration.

(Example 1)
In order to investigate the water-repellent effect of the piezoelectric ceramic powder 3 coated with the water-repellent material, the piezoelectric ceramic powder is a solid solution of bismuth sodium titanate and barium titanate having an average particle diameter of about 1 μm (Bi _1/2 Na _{1 / 2} ) Piezoelectric ceramic powder 3 on which coating layer 5 was formed using _0.85 Ba _0.15 TiO ₃ and the following various water materials.

  Next, a film of piezoelectric ceramic powder 3 in which a first coating layer made of various water repellent materials is formed on a glass plate, and the contact angle of polka dots formed by dropping distilled water on the film is determined. It was measured. The contact angle was measured using a contact angle meter CA-DT type manufactured by Kyowa Interface Science Co., Ltd. For comparison, the contact angle is measured only for the piezoelectric ceramic powder.

  Table 1 shows the names of the water-repellent materials used for the measurement and the measurement results of the contact angle.

  As is clear from this result, it can be seen that the piezoelectric ceramic powder 3 formed with the first coating layer of the water repellent material exhibits a large contact angle, and this large contact angle has a flexible feeling that constitutes the piezoelectric element. It is considered that the effect of suppressing the penetration of water into the pressure body 1 is expressed.

(Example 2)
The piezoelectric ceramic powder 3 is a solid solution of bismuth sodium titanate and barium titanate having an average particle size of about 1 μm (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO ₃ and an average particle system of about Using Pb (Zr · Ti) O ₃ , a solid solution of 1 μm lead titanate and lead zirconate, using calcium oleate (fatty acid salt) and heptadecafluorodecyltrichlorosilane (silane compound) as water repellent materials The water-repellent-treated piezoelectric ceramic powder 3 was manufactured by forming the coating layer 5 of the water-repellent material on the surface of each piezoelectric ceramic powder 3 in the same manner as in Example 1.

  Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed is immersed in a container containing water, and the metal element is eluted from the compound containing the residual metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 while stirring. The washing process was performed. If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the water-repellent piezoceramic powder 3 is kneaded with a roll machine so that the volume of the piezoceramic powder 3 is about 60% by volume and the organic polymer 4 having flexibility is about 35% by volume. A sheet of the pressure body 1 was produced, and pellets were produced using a pelletizer.

  Using the flexible pressure-sensitive body 1 pellets, a core electrode is obtained by winding a copper foil around a converging line of a number of polyester fibers having a diameter of 0.45 mm, and is flexible around the core electrode using an extrusion molding machine. The pressure sensitive body 1 was coated so as to have a thickness of about 0.6 mm.

  Next, a flexible pressure-sensitive body 1 in which a core film is covered with a conductive film in which an aluminum foil having a width of 3 mm and a thickness of 10 μm is bonded to both surfaces of a polymer film of polyethylene terephthalate having a width of 3 mm and a thickness of 12 μm. The outer electrode was wound by winding so that a part of the conductive film overlapped on the surface. In addition, the outer layer of the outer electrode is coated with a protective layer so that the thickness of the olefinic thermoplastic elastomer becomes about 0.5 mm by using an extrusion molding machine, to produce a cable-shaped piezoelectric element, and to express piezoelectricity. A poling treatment was performed by applying a DC voltage of 5 kV / mm to the core electrode and the outer electrode in air at 100 ° C.

  Various cable-shaped piezoelectric elements produced as described above were adjusted so that the effective length was 150 mm, and a high-temperature and high-humidity test under the same conditions as in Example 1 was performed for 20 hours. After the test, the electrical resistance and capacitance were measured at room temperature. The measuring instrument was an LCR high tester 3522 manufactured by Hioki Electric Co., Ltd., and measured at a frequency of 1 kHz. Further, the piezoelectric constant d33 was evaluated as an index of piezoelectric characteristics. The measurement was performed at a frequency of 110 Hz using a piezotest piezometer system PM-3000.

  For comparison, a cable-like piezoelectric element was also manufactured for the piezoelectric ceramic powder 3 that was not subjected to the cleaning treatment after the coating layer 5 was formed, and the coating ceramic layer 3 that was not formed with the coating layer 5 and was not subjected to the cleaning treatment. Carried out.

  (Table 2) shows the rate of change of electrical resistance after 20 hours of high temperature and high humidity test, (Table 3) shows the rate of change of capacitance after 20 hours of high temperature and high humidity test, and (Table 4) shows 20 hours of high temperature and high humidity test. The rate of change of the subsequent piezoelectric constant d33 is shown.

  As is apparent from this result, the cable-like piezoelectric element using the piezoelectric ceramic powder 3 that has been subjected to the cleaning treatment after the formation of the coating layer 5 has small changes in electrical resistance, capacitance, and piezoelectric constant d33. As can be seen, piezoelectric elements having different shapes were able to achieve the same effects as sheet-shaped piezoelectric elements.

The electrical resistance of the cable-like piezoelectric element decreases under a high temperature and high humidity environment. It is considered that this is because condensed water penetrates into the flexible pressure-sensitive body 1 and the components of the piezoelectric ceramic powder 3 dissolve in the penetrated water. In addition, the change in electric resistance is such that the cable-like piezoelectric element using the piezoelectric ceramic powder of (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO ₃ has Pb (Zr · Ti) O ₃ . Although the result is larger than that of the cable-like piezoelectric element using the piezoelectric ceramic powder 3, this indicates that the alkali component contained in the piezoelectric ceramic powder is easily dissolved in water.

On the other hand, the specific resistance of both of them is (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO in the cable-like piezoelectric element using the piezoelectric ceramic powder of Pb (Zr · Ti) O _3. Cable-shaped piezoelectric element using piezoelectric ceramic powder ₃ of (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO _3. It can be seen that the piezoelectric element has a low specific resistance and further decreases in a high temperature and high humidity environment. If the cable-shaped piezoelectric element becomes longer, the electrical resistance further decreases, so it may not be possible to use it as a pressure-sensitive sensor in a circuit configuration in which a constant voltage is constantly applied to the piezoelectric element to detect pressure. In the case of using a long cable-shaped piezoelectric element using the piezoelectric ceramic powder 3 containing in a high temperature and high humidity environment, it can be said that formation of a coating layer of the piezoelectric ceramic powder is indispensable in order to prevent elution of alkali components.

In addition, the change in capacitance is also larger for the piezoelectric ceramic powder of (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO _{3 than for} the piezoelectric ceramic powder of Pb (Zr · Ti) O _3. However, it is considered that there is a difference in the hygroscopicity with respect to water of the components contained in the piezoelectric ceramic powder.

Furthermore, the change of the piezoelectric constant d33 is also larger for the piezoelectric ceramic powder of (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO _{3 than for} the piezoelectric ceramic powder of Pb (Zr · Ti) O _3. However, it is considered that there is a difference in the hygroscopicity with respect to water of the components contained in the piezoelectric ceramic powder 3.

  The high-temperature and high-humidity test was conducted for 1000 hours, but the electrical resistance, capacitance, and piezoelectric constant d33 at the level of 20 hours were maintained, and it was confirmed that the water-repellent effect was excellent.

  Thus, after forming the coating layer 5 of the water repellent material on the piezoelectric ceramic powder 3, the unreacted metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 is eluted, It was confirmed that changes in both the capacitance and the piezoelectric constant d33 can be reduced.

(Example 3)
The piezoelectric ceramic powder 3 is a solid solution of bismuth sodium titanate and barium titanate having an average particle size of about 1 μm (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO ₃ and an average particle system of about By washing each piezoelectric ceramic powder 3 of Pb (Zr · Ti) O ₃ , which is a solid solution of 1 μm of lead titanate and lead zirconate, from the metal elements and metal element compounds remaining in the piezoelectric ceramic particles 3 Metal elements were removed. Thereafter, calcium oleate (fatty acid salt) and heptadecafluorodecyltrichlorosilane (silane compound) are used as the water repellent material, and the surface of each piezoelectric ceramic powder 3 washed by the same method as in Example 2 is applied to the surface. A water-based coating layer 5 was formed to produce a water-repellent piezoelectric ceramic powder 3.

  Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed is immersed in a container containing water, and the metal element is eluted from the compound containing the residual metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 while stirring. The washing process was performed. If necessary, this cleaning process is repeated several times and a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  Next, the water-repellent piezoceramic powder 3 is kneaded with a roll machine so that the volume of the piezoceramic powder 3 is about 60% by volume and the organic polymer 4 having flexibility is about 35% by volume. A sheet of the pressure body 1 was produced, and pellets were produced using a pelletizer.

  Using the flexible pressure-sensitive body 1 pellets, a core electrode is obtained by winding a copper foil around a converging line of a number of polyester fibers having a diameter of 0.45 mm, and is flexible around the core electrode using an extrusion molding machine. The pressure sensitive body 1 was coated so as to have a thickness of about 0.6 mm.

  Next, a flexible pressure-sensitive body 1 in which a core film is covered with a conductive film in which an aluminum foil having a width of 3 mm and a thickness of 10 μm is bonded to both surfaces of a polymer film of polyethylene terephthalate having a width of 3 mm and a thickness of 12 μm. The outer electrode was wound by winding so that a part of the conductive film overlapped on the surface. In addition, the outer layer of the outer electrode is coated with a protective layer so that the thickness of the olefinic thermoplastic elastomer becomes about 0.5 mm by using an extrusion molding machine, to produce a cable-shaped piezoelectric element, and to express piezoelectricity. A poling treatment was performed by applying a DC voltage of 5 kV / mm to the core electrode and the outer electrode in air at 100 ° C.

  Various cable-shaped piezoelectric elements produced as described above were adjusted to have an effective length of 150 mm, and a high temperature and high humidity test under the same conditions as in Examples 1 and 2 was performed for 20 hours. After the test, the electrical resistance and capacitance were measured at room temperature. The measuring instrument was an LCR high tester 3522 manufactured by Hioki Electric Co., Ltd., and measured at a frequency of 1 kHz. Further, the piezoelectric constant d33 was evaluated as an index of piezoelectric characteristics. The measurement was performed at a frequency of 110 Hz using a piezotest piezometer system PM-3000.

  (Table 5) shows the rate of change in electrical resistance after 20 hours of high-temperature and high-humidity test, (Table 6) shows the rate of change of capacitance after 20 hours of high-temperature and high-humidity test, and (Table 7) shows 20 hours of high-temperature and high-humidity test. The rate of change of the subsequent piezoelectric constant d33 is shown.

  As is clear from this result, the cable-like piezoelectric element using the piezoelectric ceramic powder 3 subjected to the cleaning treatment before and after the formation of the coating layer 5 has a small change in electric resistance, change in capacitance, and change in the piezoelectric constant d33. As can be seen, piezoelectric elements having different shapes were able to obtain the same effects as the sheet-like piezoelectric elements.

  The high-temperature and high-humidity test was conducted for 1000 hours, but the electrical resistance, capacitance, and piezoelectric constant d33 at the level of 20 hours were maintained, and it was confirmed that the water-repellent effect was excellent.

Example 4
The piezoelectric ceramic powder 3 is a water-repellent material using (Bi _1/2 Na _1/2 ) _0.85 Ba _0.15 TiO ₃ which is a solid solution of bismuth sodium titanate and barium titanate having an average particle diameter of about 1 μm. Calcium oleate (fatty acid salt) and heptadecafluorodecyltrichlorosilane (silane compound) are used as the coating layer 5 of the above water-repellent material on the surface of each piezoelectric ceramic powder 3 in the same manner as in Example 1. A water-repellent treated piezoelectric ceramic powder 3 was produced.

  Next, the piezoelectric ceramic powder 3 on which the coating layer 5 is formed is immersed in a container containing water, and the metal element is eluted from the compound containing the residual metal element contained in the piezoelectric ceramic powder 3 and the coating layer 5 while stirring. The washing process was performed. Further, a drying process is performed to produce the piezoelectric ceramic powder 3 from which the remaining metal elements are removed.

  At this time, the washing treatment is performed with water, warm water, and acidic water, and the washed piezoelectric ceramic powder 3 is boiled with distilled water or ion-exchanged water, and the sodium ion concentration of the boiling solution is measured (Table 8). Show.

  As is clear from this result, elution of the metal element from the compound containing the remaining metal element can be promoted by using warm water or acidic water for cleaning, and high removal efficiency is realized in a short time. It was confirmed that it was possible.

  As described above, since the piezoelectric element according to the present invention can suppress the water absorption of the flexible pressure-sensitive body 1 even when used in a high-temperature and high-humidity environment, the initial electrical characteristics, piezoelectric characteristics, mechanical It is possible to prevent the change in the tensile strength, and to realize excellent durability and reliability. Therefore, it can be applied to a wide range of applications such as pressure-sensitive sensors that prevent car doors and windows from being caught in high-temperature, high-humidity environments, and pressure detection devices that detect the presence of a person by detecting the movement of a person with a nursing bed. is there.

Sectional drawing of the sheet-like piezoelectric element in Embodiment 1 of this invention Schematic diagram showing a partial cross section of the flexible pressure-sensitive body according to Embodiment 1 of the present invention. Explanatory drawing which shows the manufacturing process of the sheet-like piezoelectric element in Embodiment 1 of this invention Relational diagram showing the relationship between pH and capacitance change in Embodiment 1 of the present invention Relational diagram showing the relationship between conductivity and capacitance change in the first embodiment of the present invention Relationship diagram showing the relationship between sodium ion concentration and capacitance change in Embodiment 1 of the present invention Explanatory drawing which shows the manufacturing process of the sheet-like piezoelectric element in Embodiment 2 of this invention Sectional drawing of the cable-shaped piezoelectric element in Embodiment 3 of this invention Explanatory drawing which shows the manufacturing process of the cable-shaped piezoelectric element in Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible pressure sensitive body 2A 1st electrode 2B 2nd electrode 3 Piezoelectric ceramic powder 4 Organic polymer 5 Coating layer 6 Core electrode 7 Outer electrode 8 Protective layer

Claims (16)

In a flexible pressure-sensitive body comprising a piezoelectric ceramic powder and a flexible organic polymer, the piezoelectric ceramic powder is provided with a coating layer that suppresses moisture absorption on the surface, and after the coating layer is formed, is washed and remains. A flexible pressure-sensitive body having a structure in which a compound containing a metal element to be removed is removed. The flexible pressure-sensitive body according to claim 1, wherein the piezoelectric ceramic powder is provided with a coating layer that suppresses moisture absorption on the surface of the piezoelectric ceramic powder after being washed. The flexible pressure-sensitive body according to claim 1 or 2, wherein the coating layer is made of a water-repellent material. The flexible pressure-sensitive body according to any one of claims 1 to 3, wherein the coating layer is formed of at least one of a fatty acid, a fatty acid salt, and a monomolecular layer. The flexible pressure-sensitive body according to any one of claims 1 to 4, wherein the piezoelectric ceramic from which the compound containing the remaining metal element is removed is boiled, and the pH of the aqueous solution is 8.0 or less. The flexible pressure-sensitive body according to any one of claims 1 to 5, wherein the piezoelectric ceramic from which the compound containing the remaining metal element is removed is boiled, and the electrical conductivity of the aqueous solution is 50 µS / cm or less. The flexible pressure-sensitive body according to any one of claims 1 to 6, wherein the piezoelectric ceramic from which the compound containing the remaining metal element is removed is boiled, and the sodium ion of the aqueous solution is 300 µg / g or less. The flexible pressure-sensitive body according to any one of claims 1 to 7, wherein the piezoelectric ceramic powder contains at least an element of Group 1 of the periodic table and Group 2 of the periodic table. The flexible pressure-sensitive body according to claim 8, wherein the piezoelectric ceramic powder containing an element of Group 1 of the periodic table and Group 2 of the periodic table contains at least one of barium, sodium, potassium, bismuth, and lithium. The piezoelectric ceramic powder containing the elements of Group 1 and Group 2 of the periodic table contains at least one of sodium niobate, potassium niobate, lithium niobate, bismuth / sodium titanate, barium titanate, and bismuth titanate. The flexible pressure-sensitive body according to claim 8 or 9. The flexible pressure sensitive body according to any one of claims 1 to 10, wherein the cleaning treatment is performed with water. The flexible pressure sensitive body according to any one of claims 1 to 10, wherein the washing treatment is performed with acidic water. The flexible pressure-sensitive body according to claim 11 or 12, wherein water or acid water for performing the washing treatment is heated. The first electrode connected to the flexible pressure-sensitive body, and the second electrode connected to the flexible pressure-sensitive body and insulated from the first electrode. Piezoelectric element. The cable-shaped piezoelectric element according to any one of claims 1 to 13, wherein the flexible pressure-sensitive body covers the first electrode, and the second electrode covers the flexible pressure-sensitive body. The method for producing a flexible pressure-sensitive body or piezoelectric element according to claim 1, wherein the compound containing the remaining metal element is removed by a cleaning treatment.

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