JP2589489B2 - Manufacturing method of piezoelectric composite material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a piezoelectric composite material containing piezoelectric ceramic powder such as lead titanate particles in an organic base material made of synthetic rubber.

<Art> example, lead titanate (PbTiO ₃₎ is a ferroelectric material having a perovskite structure have been widely used as various piezoelectric materials and pyroelectric materials, piezoelectric constant d _n in water, especially in recent years Since (d ₃₃ + 2d ₃₁ ) and g _n (= d _n / ε) are large, they have attracted attention as piezoelectric materials for underwater acoustic transducers such as hydrophones.

In addition, such a material for an underwater acoustic transducer efficiently emits or receives acoustic waves or ultrasonic waves into water and has good acoustic matching with water, and strength enough to withstand the water pressure even when immersed deeply in water. Therefore, a piezoelectric material having low density and high flexibility is required. To meet such demands, there has been proposed a composite material in which particles of lead titanate are prepared, mixed and dispersed in an organic base material made of synthetic rubber.

In addition, various piezoelectric ceramic powders, not limited to lead titanate particles, are dispersed in an organic base material and applied to various uses as a piezoelectric composite material.

<Problems to be Solved by the Invention> In the manufacturing process of this piezoelectric composite material, piezoelectric ceramic powder is mixed into an organic base material made of synthetic rubber, and then molded into a predetermined shape. Will be applied.

By the way, in the process of mixing the organic base material and the piezoelectric ceramic powder, air is mixed into the material. Then, an air layer is formed at the grain boundary between the piezoelectric ceramic powder and the organic base material.

For this reason, when the piezoelectric composite material is used under a high pressure such as in water, the air layer is compressed and its characteristics are changed. Therefore, when the piezoelectric composite material is used at different depths (pressures), the output varies, and the output needs to be corrected, and the signal processing becomes complicated.

An object of the present invention is to provide a manufacturing method that enables manufacturing of a piezoelectric composite material having no pressure dependency.

<Means for Solving the Problems> The first invention of the present application is to mix a piezoelectric ceramic powder into an organic base material made of synthetic rubber, form the mixture into a predetermined shape, and then apply hydrostatic pressure in an unvulcanized state. Pressing is performed.

In the second invention, steam vulcanization is performed after performing the hydrostatic pressing in the unvulcanized state as described above.

<Effect> When a hydrostatic press is performed in an unvulcanized state after molding, the material receives pressure from the entire circumference, and the air layer is compressed and divided, and dispersed in the material.

For this reason, even when a composite material is used under high pressure, the influence of a change in the air layer around the porcelain powder is small, and the pressure incompatibility is reduced.

Further, when steam vulcanization is performed after the isostatic pressing, the material is pressurized at a high temperature from the entire circumference of the material, and the same effect as the above-described hydrostatic pressing is produced.

<Test Example> FIG. 1 shows a manufacturing process of a piezoelectric composite material according to the present invention, in which lead titanate particles and chloroprene rubber are mixed at 60:40 vol%.
Alternatively, they were mixed at a mixing ratio of 65:35 vol%, and Pb ₃ O ₄ , ZnO and dibenzothiazyl disulfide (trade name; Noxeller DM) were further mixed as vulcanizing agents. The compounding ratio of the vulcanizing agent is 100 parts by weight of chloroprene rubber, and Pb ₃ O ₄ : Zn
O: Noxeller DM = 20 parts by weight: 5 parts by weight: 0.5 parts by weight (step).

Using a universal stirrer, the mixture is stirred for 25 to 30 minutes to sufficiently disperse the lead titanate particles in the chloroprene rubber (step), dried, mixed with a roll machine, and mixed in a linear or sheet form. (Step ~
).

Then, the molded product was subjected to isostatic pressing (step). That is, the molded product was stored in a pressurized water tank, and the water pressure was applied by 1 ton or 2 tons, and pressure was applied from the entire circumference of the molded product.

By this pressurizing treatment, during mixing of the steps, the air layer mixed in the chloroprene rubber gel and formed at the grain boundaries around the lead titanate particles is broken, and is atomized and dispersed in the chloroprene rubber gel. Further, the molded product was placed in a steam pot, confined in an atmosphere of 5.4 kg / cm ² and 164 ° C. for 40 minutes, and vulcanized (step). Press vulcanization was performed for comparison (step).

And apply silver paste to the front and back of this sheet,
An electrode was formed, and further immersed in an insulating solution at 20 ° C., and a DC voltage of 100 KV / cm was continuously applied in the solution for 1 hour to perform a polarization treatment, thereby obtaining a sheet-like piezoelectric composite material (step). ,
).

In the step, the piezoelectric composite material produced by this process is prepared by mixing lead titanate particles having a particle size of 21 μm with chloroprene rubber at a mixing ratio of 60:40 vol% as material A, A mixture of lead oxide particles and chloroprene rubber at a compounding ratio of 65:35 vol% is used as material B. Each material is divided into a linear material and a sheet material, and further 1 ton or 2 tons Hydrostatic pressing (step) and non-hydrostatic pressing, and vulcanization by steam vulcanization (step), and vulcanization by press vulcanization (conventional means, step) We measured the dielectric constant, tan δ, wave receiving sensitivity, pressure change, etc. of the sample.

Here, FIGS. 2 and 3 are characteristic diagrams showing the relationship between the change in pressure, the capacitance, and the wave receiving sensitivity, which was formed linearly from the materials A and B, and was subjected to steam vulcanization (step). In this case, the hydrostatic press (2 tons) and the non-hydrostatic press (conventional) are compared.

As shown in this figure, in the case of the conventional configuration, the capacitance and the wave receiving sensitivity greatly fluctuate according to the change in pressure, but in the case of the hydrostatic press, the amount of change is reduced. I understand.

Further, FIG. 4 shows a summary of each characteristic, that is, the case where no hydrostatic pressing was performed and the case where 1 and 2 tons were applied (both thereafter, steam vulcanization) before applying pressure. And the dielectric constant after application, tan δ, the wave receiving sensitivity, and also the amount of pressure change. Here, the pressure change amount is
It shows the maximum change amount when the pressure is changed in the range of 0 to 150 kg / cm ² as shown in FIGS. From this figure, it was confirmed that the pressure change amount can be reduced without causing a large change in the dielectric constant, tan δ, and wave receiving sensitivity.

In addition, conventionally, a polarization voltage of only 50 KV / cm could be applied, but a voltage of 100 KV / cm can be applied. This is understood that the polarization layer was efficiently applied to the piezoelectric layer as a result of the air layer becoming smaller and denser.

FIGS. 5 and 6 are characteristic diagrams of sheets formed from materials A and B, respectively, in the case where press vulcanization is performed, and where hydrostatic pressing (1 ton or 2 ton) is performed. And those that are not (conventional) are shown in comparison.

Similarly, as shown in these figures, the change in the capacitance and the receiving sensitivity corresponding to the pressure is greater in the case where the hydrostatic press (1 ton or 2 ton) is applied than in the case of the conventional structure. Was alleviated.

Further, FIG. 7 shows a sheet formed from materials A and B, respectively, which was subjected to hydrostatic pressing (step) and further subjected to steam vulcanization (2 tons). The pressure dependence of sensitivity is shown.

From these results, it was found that the pressure dependency was significantly reduced by using the hydrostatic press and steam vulcanization together.

Further, FIG. 8 shows a summary of each characteristic, one without hydrostatic pressing, one with 1 and 2 tons (both then press vulcanized), and two with hydrostatic pressing. The dielectric constant, tan δ, and wave receiving sensitivity before and after applying the pressure of the vulcanized vulcanized product after applying the pressure are shown. Also, the pressure change amount is shown. From this figure, it was confirmed that the pressure change amount could be reduced without a large change in the dielectric constant, tan δ, and wave receiving sensitivity. It was also found that the apparent piezoelectric constant decreased and the piezoelectric constant became a true piezoelectric constant.

In particular, in the case where the hydrostatic press and the steam vulcanization were used in combination, both the piezoelectric constant and the pressure change amount were significantly reduced.

<Effect of the Invention> The present invention provides an air layer formed at the grain boundary of piezoelectric ceramic powder as much as possible by adding a hydrostatic press or by using a hydrostatic press and steam vulcanization in a manufacturing process. Removed to reduce pressure dependency, so even when applied to places where pressure changes, such as in water, output characteristics do not vary and stable output can be obtained. Therefore, there is an excellent effect that the applicable range can be expanded and the usefulness of this kind of piezoelectric composite material can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the manufacturing process of the present invention, and FIG.
4 to 4 are characteristic diagrams showing a comparison of characteristics in a linear composite piezoelectric material, and FIGS. 5 to 8 are characteristic diagrams showing a comparison in characteristics of a sheet-like piezoelectric composite material.

Claims (2)

(57) [Claims] 1. A piezoelectric device comprising the steps of: mixing piezoelectric ceramic powder in an organic base material made of synthetic rubber, forming the mixture into a predetermined shape, and then performing hydrostatic pressing in an unvulcanized state. Manufacturing method of composite material. 2. A step of mixing piezoelectric ceramic powder into an organic base material made of synthetic rubber, forming the mixture into a predetermined shape, performing an unvulcanized hydrostatic press, and then performing steam vulcanization. A method for producing a piezoelectric composite material, comprising: