JPS5841791B2 - Polymer piezoelectric material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polymeric piezoelectric material whose piezoelectric constant polarity is reversed at a constant temperature and which can also be used as a temperature sensor.

Research and development of polymeric piezoelectric materials has been carried out to increase the piezoelectric constant by subjecting polyvinylidene fluoride and its copolymers to a stretching polarization treatment.

In other words, research and development has been conducted with the aim of obtaining materials with large piezoelectric constants by changing material selection and processing methods.

The purpose of this invention is to obtain a polymeric piezoelectric material whose piezoelectric constant polarity is reversibly reversed at a temperature below its melting point by polarizing a copolymer of vinylidene fluoride trifluoroethylene. The present invention aims to provide a polymeric piezoelectric material that can be used both as a piezoelectric material and as a temperature sensor.

Next, to explain this invention in detail, by thermoforming a copolymer of vinylidene fluoride and ethylene trifluoride and then subjecting it to polarization treatment, the polarity of the piezoelectric constant is reversed at a temperature within a range below the melting point. A polymer piezoelectric material can be obtained.

Next, specific examples are listed.

The copolymerization ratio of vinylidene fluoride is 45 mol to 90 mol.
The mol person is appropriate.

Specific example 1 A film thermoformed at 300°C with a vinylidene fluoride composition of 51m01% was stretched 3 times (to a thickness of 10 to 30μ), and then electrodes were attached by vapor deposition at 80°C and 400°C.
When polarization treatment is performed for 1 hour under the condition of KV/(1 m), a polymer piezoelectric material having a piezoelectric constant of 5.5xlO-7 (CGSESU: 25°C) is obtained.

Then, this material was cut into a width of 5 mm and a length of 30 to 50 mm, and the piezoelectric constant was measured at a frequency of 110 Hz.When the ambient temperature was increased (heating rate of 1 °C min to 3 °C m1 n), 1
The polarity of piezoelectric constant is reversed at 30°C.

Specific Example 2 Among the processing conditions of Specific Example 1 above, when stretching is performed at 3.7 times, piezoelectric constant: 6.5 XI 0-7 (cgs esu
: 25°C) was obtained, and when the measurement was carried out under the same conditions as those described above, the polarity of the piezoelectric constant was reversed at 105°C.

Specific Example 3 A film was obtained from the material having the composition of Specific Example 1 described above from a methyl ethyl ketone solution by Tsurubert casting, stretched 6 times (to a thickness of 5 to 13 μm), and electrodes were attached by vapor deposition at 80° C. and 400 KV/cm. When polarization treatment is carried out for 1 hour under the conditions of
A polymeric piezoelectric material with a temperature of 25° C. is obtained.

When this material is measured under the measurement conditions of Example 1, the polarity of the piezoelectric constant is reversed at 80°C.

Specific example 4 A film thermoformed at 300°C from a material with a vinylidene fluoride composition of 72 mo1% was made into an unstretched film (thickness: 40 μm), and then an electrode was attached by vapor deposition at 140'C12200KV/c.
When polarization treatment is performed for 1 hour under IrL conditions, the piezoelectric constant is 2.1.
A polymer piezoelectric material of XI 0-7 (cgs esu: 25°C) is obtained.

Then, this material was cut into pieces with a width of 5 mm and a length of 30 to 50 nIIn, and the piezoelectric constant was measured at a frequency of 110 Hz. When the ambient temperature was increased (heating rate of 1°C/min to 3°C/min)
) The polarity of piezoelectric constant is reversed at 130°C.

The measurement results of Specific Example 3 are shown in FIGS. 1 and 2.

As can be seen from this diagram, when the temperature is increased, the piezoelectric constant drops rapidly from 60'C, and when it reaches 80°C, the piezoelectric constant changes to the negative side.

Then, when the temperature is lowered, the piezoelectric constant increases, and at 80° C., the piezoelectric constant changes to the positive side (Fig. 2).

The black circles in the figure indicate changes in piezoelectric constant when the temperature continues to rise.

As described above, this invention is achieved by subjecting a copolymer of vinylidene fluoride and ethylene trifluoride to a stretching and polarization treatment.
Since the polarity of piezoelectricity changes at temperatures below the melting point, it can be used not only as a piezoelectric material but also as a temperature sensor, and it is also possible to change the inversion temperature by changing the processing conditions. In addition to being able to manufacture various types of sensors with different inversion temperatures, this method also has the advantage of being able to obtain a material with a sufficiently large piezoelectric constant.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in piezoelectric constant with respect to temperature of the polymeric piezoelectric material according to the present invention, and FIG. 2 is an enlarged diagram of a portion where the piezoelectric constant is reversed.

Claims (1)

[Claims] 1. A polymer piezoelectric material obtained by polarizing a copolymer of vinylidene fluoride and ethylene trifluoride at a temperature below the melting point so that the polarity of the piezoelectric constant is reversibly reversed at a temperature within the range below the melting point. .