JPS648476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a linear piezoelectric or pyroelectric material in which an internal electrode is provided inside a hollow tube of a tubular piezoelectric or pyroelectric material made of a stretched and orientation-polarized polymeric material; It concerns the manufacturing method.

A tubular piezoelectric material or pyroelectric material can directly detect changes in the pressure of a fluid flowing therein to control its flow rate, and can also detect changes in temperature of the fluid. In addition, tubular, especially capillary (with an inner diameter of several mm)
The following piezoelectric materials or pyroelectric materials
This is a useful form for determining temperature changes in minute local areas. In order to obtain such a shape, first of all, good workability is required. Inorganic crystal materials and ferroelectric ceramics, which have problems in this respect, are not practical. In addition, in this shape, the inner electrode must be formed in a state in which the inner electrode and the piezoelectric material or pyroelectric material have good adhesion within the tube, which is a narrow space. In this respect, polyvinylidene fluoride or polyvinyl fluoride does not exhibit piezoelectricity or pyroelectricity unless it is stretched, but as pointed out in JP-A-54-37299, stretching However, it is difficult to cover and utilize a linear electrode in terms of adhesion, and these methods have not been realized yet. Therefore,
Materials that exhibit piezoelectricity without stretching and have good processability are used, such as composites of polyvinylidene fluoride and ferroelectric ceramics, whose main component is ferroelectric ceramics, and synthetic polypeptides. It just came.

However, the piezoelectricity of these materials that have been considered to be practical is at most d ₃₁ = 7 to 10×
It was about 10 ^-12 C/N, so it could not be said that it had great piezoelectricity.

The present invention overcomes the drawbacks of the prior art described above, and provides a tubular piezoelectric or pyroelectric material made of a polymeric material that is stretched and orientation-polarized to impart piezoelectricity or pyroelectricity, which has been difficult to manufacture in the past. The present invention provides a piezoelectric or pyroelectric material comprising a piezoelectric material, and an interior made of a conductor having fluidity at a temperature below the melting point of the polymer material, inside a hollow tube of a tubular body of a piezoelectric polymer material. It is characterized by providing an electrode. This invention focused on the fact that when this internal electrode is injected into the hollow tube of a tubular piezoelectric material or pyroelectric material, it is in a fluid state, so that it can have very good adhesion to the inner surface of the tubular body. It is.

The present invention will be explained in detail below.

The piezoelectric polymer material according to the present invention means a polymer substance that has piezoelectricity or pyroelectricity due to orientation polarization treatment, or a piezoelectric material containing the polymer substance,
Typical examples include polyvinylidene fluoride resins and polyvinyl fluoride resins. Here, the polyvinylidene fluoride resin refers to a polyvinylidene fluoride homopolymer, a copolymer containing 50 mol % or more of vinylidene fluoride, a composition mainly containing any of these, and the like. Similarly, the polyvinyl fluoride resin refers to a polyvinyl fluoride homopolymer, a copolymer containing 50 mol % or more of vinyl fluoride, a composition mainly containing any of these, and the like. As is known from the above examples, it goes without saying that the piezoelectric material or pyroelectric material in the present invention includes cases in which the piezoelectric material or the pyroelectric material includes both a piezoelectric material and a pyroelectric material.

The polymer material to which piezoelectricity or pyroelectricity is imparted by the above-mentioned orientation polarization treatment may be used alone or in combination with a coaxial resin, which may be superimposed or not superimposed, for example, by a known hollow fiber manufacturing method. It is formed into a tubular shape using, etc. Next, an internal electrode made of a conductor having flow conductivity at a temperature below the melting point of the polymer material is formed inside the hollow tube of the polymer material tube to which piezoelectricity or pyroelectricity is imparted. be done. still,
The interior of the hollow tube may be the entire hollow portion of the hollow tube, but it may also be the inner wall of a polymeric tubular body imparted with piezoelectricity or pyroelectricity, for example. The conductor is used as one electrode of a pyroelectric material or a piezoelectric material, and may also be used as an electrode during orientation polarization in some cases. Therefore, depending on the purpose of the electrode to be used, before use, the conductor of the present invention may be made in a flowable state and injected into the hollow tube of the tubular body to form an internal electrode made of the conductor. Ru. Therefore, the conductor needs to have flow conductivity at a temperature below the melting point of the above-mentioned polymer material.
It goes without saying that when forming the internal electrode made of the conductor of the present invention at a temperature higher than the stretching temperature after stretching the polymeric material, the tubular body must be kept under tension.

Examples of such conductors include polymer melting point solders, such as the registered trademark "Kyosei Solder-62", which is a solder with a melting point of 62°C manufactured by Senju Metal Industries, and "Kyosei Solder-78", which has a melting point of 78°C. metal alloys with a melting point lower than that of the polymer material; electrolyte solutions such as aqueous sodium chloride and copper sulfate solutions; Conductive resin, resin solder, conductive rubber, etc. may be used. These can be formed inside a hollow tube by, for example, suctioning from one end of the tubular body and injecting it from the other end; coextruding conductive resin; or injecting conductive rubber in an uncrosslinked state and then Known methods such as crosslinking may be used. It is desirable for these conductors to be in a fluid state even at room temperature in order to use the tubular polymer material as a piezoelectric material or pyroelectric material, but it is not necessary that they be in a fluid state when filling the hollow tube. It's good to have.

By the way, the piezoelectric constant d ₃₁ increases as the Young's modulus of the element decreases. That is, the smaller the Young's modulus, the greater the strain with respect to a constant stress, and as a result, the amount of charge generated increases. Therefore, even if it cannot flow at room temperature, if it is a conductor that can flow when injected into a hollow space and has a relatively low Young's modulus at room temperature, it can be used as a piezoelectric material or a pyroelectric material. When used as an electric body, it can be used as is as an inner electrode. If the Young's modulus is large, another conductor with a relatively small Young's modulus may be used instead. For example, Young's modulus of copper is 12×10 ¹⁰ N/m ²
On the other hand, the Young's modulus of "low-temperature solder-62", which is a solder with a melting point of 62°C manufactured by Senju Metal Industry, a low-melting metal alloy that can be used in the present invention, is approximately 3 × 10 ¹⁰ N/m. It is ² .

The above conductor may not be used during orientation polarization and may be used only when the tubular polymer material is used as a piezoelectric material or pyroelectric material, but in that case, for example, a hollow fiber or the like may be used as the internal electrode during orientation polarization. A method may be adopted in which a metal wire thinner than the inner diameter of a stretched tube is used as an internal electrode to cause corona discharge. On the other hand, the outer electrode is not necessary when using an electron beam for orientational polarization and for piezoelectric or pyroelectric action, but it is usually necessary, and is similar to the electrode formation of film-like piezoelectric or pyroelectric elements. A vapor-deposited metal film, a conductive paint, a conductive rubber, etc. can be used.

When using the internal electrode made of the above-mentioned conductor as an internal electrode during orientation polarization, the conductor may be injected into the hollow before or after stretching the polymer material. Since the diameter is larger before stretching than after stretching, there is an advantage in manufacturing that it is easier to inject into the hollow. Furthermore, there is an unexpected effect that the stretching ratio can be increased by about 10 to 15% compared to stretching without filling the hollow space with anything, and as a result, piezoelectricity and pyroelectricity are improved. be able to.

In this case, it is desirable to seal both ends after injection. In that case, it is desirable to prevent non-conductors such as air from being included in the hollow, but there is no practical problem even if a certain amount is included.

The stretching operation may be performed simultaneously with the orientation and polarization, or may be performed before the orientation and polarization, and can be performed by a known method similar to that for films. As is well known, in the case of polyvinylidene fluoride resin, it is necessary to form a structure mainly consisting of a β structure by a stretching operation in order to impart piezoelectricity or pyroelectricity. For this purpose, as is well known, the lower the stretching temperature or the higher the stretching ratio, the easier it is to obtain a β structure, so by appropriately selecting the stretching ratio and stretching temperature and stretching, the β structure can be obtained as the main component. Note that for tubular bodies, it is certain to examine the extent to which the β structure is contained by X-ray analysis.

Also, for orientation polarization, a known method used for films is adopted, and it is desirable to apply an electric field as close to the dielectric strength as possible, and orientation polarization is performed at a temperature above the glass transition temperature of the polymer and below the melting point. .

Examples are shown below.

Example 1 Melt extrusion of polyvinylidene fluoride into hollow fibers,
Obtain hollow fibers with an inner diameter of 500μ and an outer diameter of 800μ, then at 70°C.
A capillary tube with an inner diameter of 300μ and an outer diameter of 500μ was obtained by stretching 3.3 times, and aluminum was vapor-deposited on the tube surface. Next, inject a saturated aqueous solution of aluminum chloride into the hollow tube,
Both ends were sealed, and a lead wire connected to the saturated sodium chloride aqueous solution was taken out without touching the aluminum vapor-deposited film. Further, the lead wire was taken out from the aluminum vapor-deposited surface, and a DC electric field of 600 KV/cm was applied at 60° C. for 15 minutes, and then cooled to room temperature while the electric field was applied. The piezoelectric constant d ₃₁ was 20×10 ⁻²¹ C/N. This value is approximately equivalent to the piezoelectric constant d ₃₁ of a normal polyvinylidene fluoride uniaxially stretched film.
Here, the electrode area in the measurement of the piezoelectric constant is the harmonic average of the electrode area in contact with the inner diameter of the tubular body and the electrode area in contact with the outer diameter. The same applies to the following examples.

Comparative Example 1 The same procedure as in Example 1 was conducted except that a copper wire with a diameter of 300 μm was forcibly inserted into the hollow instead of the saturated sodium chloride aqueous solution in Example 1, and the piezoelectric constant d ₃₁ was 0.

Example 2 "Low-temperature solder-62", a solder with a melting point of 62°C, manufactured by Senju Metal Industries, was injected at 67°C into the tube of the unstretched hollow fiber of Example 1, and both ends were sealed with chucks. , stretched 3.5 times at 80℃, inner diameter 250μ,
A capillary body with an outer diameter of 450μ was obtained. Aluminum was vapor-deposited on the outside of this capillary body, the lead wire was taken out as in Example 1, and a DC voltage of 600 KV/cm was applied at 90°C for 15 minutes.
The voltage was applied for a minute, and the voltage was further cooled to room temperature while the voltage was being applied. The piezoelectric constant d ₃₁ was 7×10 ⁻¹² C/N when measured using the solder as an internal electrode.

Example 3 After the orientational polarization in Example 2, the solder is removed by heating to 70°C, and a saturated aqueous solution of sodium chloride is injected instead, and this is used as the internal electrode.
The piezoelectric constant d ₃₁ was 2.3×10 ⁻¹¹ C/N.

Example 4 Polyvinylidene fluoride was melt-extruded into a hollow fiber shape with an inner diameter of 700 μm and an outer diameter of 1200 μm, the same “low temperature solder-62” as in Example 2 was injected into the tube at 67°C, and it was stretched 5.0 times at 80°C. A capillary body with an inner diameter of 350μ and an outer diameter of 600μ was obtained.
Polarization was carried out in the same manner as in Example 2, and the piezoelectric constant d ₃₁ was determined to be 1×10 ⁻¹¹ C/N. When this was done in the same manner as in Example 3, it was 3×10 ^-11 C/N.

Example 5 Same as Example 4 except that the order of injection operation and stretching operation of "low temperature solder-62" was reversed.
When _carried out similarly ^to
It was N. When this was done in the same manner as in Example 3, it was 2.7×10 ^-11 C/N.

Example 6 When the change in the amount of polarization, that is, the pyroelectric effect, due to the temperature change of the capillary voltage pyroelectric body obtained in Example 4 was measured after removing irreversible components, the pyroelectric coefficient was
It was 3.5×10 ^-9 C/cm ²・deg.

The piezoelectric constant d ₃₁ of this sample is 8×12 ^-12 C/N when solder is used as the inner electrode, and 2.6×10 ^-11 C/N when a saturated aqueous sodium chloride solution is used.
It was N. This correspondence relationship between the piezoelectric constant d ₃₁ and the pyroelectric coefficient is in good agreement with that of the film-like polyvinylidene fluoride piezoelectric pyroelectric material, and even after one year at room temperature, the piezoelectricity and pyroelectricity remain stable. Obtained.

As is known from the above examples, the piezoelectric constant d ₃₁ exhibited by the conventional tubular piezoelectric material, a composite of a polymer material and ferroelectric ceramics, is at most 10×
10 ^-12 C/N, but in the present invention d ₃₁ is
A piezoelectric material with a value of 30×10 ^-12 C/N and a pyroelectric material with a pyroelectric constant of 3.5×10 ^-9 C/cm ²・deg were obtained, both of which are stable against changes over time. It has practical piezoelectricity and pyroelectricity. Furthermore, the piezoelectric effect of a film or sheet-like piezoelectric material has a clear correspondence with the amount of displacement, for example, due to the anisotropy of the piezoelectric effect or the shear component of the displacement in response to two-dimensional displacement. Therefore, only quantifiable responses can be obtained to stimuli in a specific direction. However, if a linear piezoelectric material is installed along the Z-axis and one end is left free, it is possible to obtain a response proportional to the displacement in the xy plane, even if the direction is arbitrary. It also has the feature that it can be used as a piezoelectric material, and has effects that cannot be obtained with film-like piezoelectric materials.

Claims (1)

[Claims] 1. An internal electrode made of a conductor that has fluidity at a temperature below the melting point of the polymer material is provided inside a hollow tube of a stretched and orientation-polarized piezoelectric polymer material. A linear piezoelectric or pyroelectric material characterized by: 2. The piezoelectric or pyroelectric body according to claim 1, wherein an internal electrode is provided throughout the hollow tube of the tubular body made of a piezoelectric polymer material. 3. The piezoelectric or pyroelectric material according to claim 1, wherein an internal electrode is provided on the inner wall of the tubular body made of a piezoelectric polymer material. 4. The piezoelectric or pyroelectric material according to any one of claims 1 to 3, characterized in that it is made of a metal alloy whose internal voltage has a melting point lower than that of the piezoelectric polymer material. 5. The piezoelectric or pyroelectric material according to any one of claims 1 to 3, wherein the internal electrode is made of an electrolyte solution. 6. The piezoelectric or piezoelectric material according to any one of claims 1 to 5, characterized in that the piezoelectric polymer material is made of polyvinylidene fluoride resin and mainly has a β-type crystal structure. Pyroelectric body. 7 A piezoelectric polymeric material is extruded into a hollow fiber shape to form a tubular body, and then a conductor having fluidity at a temperature below the melting point of the polymeric material is flowed into the hollow tube of the tubular body of the polymeric material. linear piezoelectric or Method of manufacturing pyroelectric material. 8 A piezoelectric polymeric material is extruded into a hollow fiber shape to form a tubular body, and then the tubular polymeric material is stretched, and then a conductor having fluidity at a temperature below the melting point of the polymeric material is stretched. Production of a linear piezoelectric or pyroelectric material by injecting the polymeric material in a fluid state into the hollow tube of a tubular body, and performing orientation polarization treatment on the polymeric material using the injected conductor as an internal electrode. Method. 9 Extrude a piezoelectric polymer material into a hollow fiber shape to form a tubular body, stretch the tubular polymer material, perform corona polarization using a metal wire as an internal electrode during or after the stretching, and Then, a conductor having fluidity at a temperature below the melting point of the polymeric material is injected in a fluid state into the hollow tube of the stretched, oriented and polarized tubular body of the polymeric material. A method for manufacturing a piezoelectric or pyroelectric substance.