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[Co., Ltd.] manufacturing method of polymer electret 特 願 Japanese Patent Application No. 4583686 [Phase] application A. 45 (1970) Sept. 21 石 塚 同 原 市 55 吾 蔭 55 伏 光 伏 津 津 津 同
同 敏 敏 彦 彦 太 字 太 字 太 字 太 字 太 字 太 字 太 字 太 字 南 南 垣 垣 出 願 500 applicants チ
尼 有 Higashihoncho 1 50 DETAILED DESCRIPTION OF THE INVENTION Attorney Docket Kozo
Kodama Yuko, an Attorney Attorney Attorney Docket # Int'l The present invention is
characterized in that the polymer substance dissolved in a solvent is oriented and polarized in a
direct current strong electric field without evaporating the solvent. The present invention relates
to a method for producing an electret. In the present invention, the term electret refers to a
dielectric material in which both sides of the film or plate are charged through the material
cylinder with opposite sign and has permanent polarization which is not just the surface charge.
Applications such as electrometers, voltmeters, condenser microphones, radiation calibration
meters, DC high-voltage power supplies, dust collectors, electrostatic storage devices, etc., are
considered using the electrostatic characteristics of the work and turret, that is, the permanent
electrostatic field to the outside. ing. Conventionally, as a method for producing electrets, a
dielectric plate made of a polymer substance is kept at a temperature which can be higher than
the second order transition point, or in some cases, in a molten state, and rl 111 111 parts of
ions or dipoles are frozen. In this state, a DC high electric field is applied between the metallic
electrodes disposed on both sides of the dielectric plate to cause movement of ions, arrangement
of dipoles, and movement of charges from the electrodes to the dielectric. After a certain period
of time, the heating of the dielectric is stopped, and it is cooled and solidified as it is. After the
dielectric temperature is cooled back to room temperature, the electric field is removed to obtain
an electret in a permanently oriented polarization state. It is known. However, in such a known
method, it is inappropriate to use a polymeric material which is easily thermally decomposed at
high temperature, and electretized at a temperature slightly higher than the second order
transition point to avoid thermal decomposition. In some cases, only a small fraction of the
surface charge density is obtained, and only a significant reduction of the surface charge by oral
administration is obtained. Moreover, even when using a polymer substance which is not easily
thermally decomposed, it is a polymer substance, so the movement of the molecule at high
temperature is incomplete and it is difficult to form an electret which is sufficiently oriented and
polarized. The surface charge density is low and the life is short. The present invention is
intended to provide a novel method for improving the drawbacks of the electret manufacturing
method as described above, and it is a thermal decomposition at high temperature where
electretization has hitherto been regarded as impossible or very difficult. A high performance
electret is to be manufactured from a polymer dielectric which can be easily electretized and can
not be put into practical use because of insufficient surface charge and insufficient stability.
According to the present invention, the polymer substance is dissolved in a suitable solvent, and
the polymer substance is oriented and polarized while evaporating the solvent in a strong direct
electric field, and solidified to have a sufficient surface charge density and oral change. Good
performance electrets with little or no performance are easily obtained. In the method of the
present invention, the strength of the field is preferably strong within the range in which the
surface of the polymer solution is not disturbed, and heating [111111] EndPage: 1 is preferred to
promote the evaporation of the solvent. However, heating should be avoided above the boiling
point at which the polymer solution surface is disturbed. That is, as described above, the present
invention is a method of dissolving a polymer substance in a solvent to form a polymer solution,
and subjecting the polymer solution to a solvent by evaporating the solvent to dryness under a
strong direct electric field. The mobility of the molecule is large compared to when electretizing
the polymer substance at or above the second-order transition point or in the solution state, and
the orientation of the dipole in the polymer by the action of the DC strong electric field is It is
characterized by the fact that the fixation of orientation proceeds with evaporation of the solvent,
which is much easier. Therefore, it is very effective in producing an electret with high surface
charge density, high storage stability and stability. Furthermore, in the application of the method
of the present invention, if the specific crystalline polymer described below is selected, the
molecular chain is formed by the action of an electric field in the process of evaporation of the
solvent in which the formation and growth of crystal nuclei proceed. The arrangement is
advantageously performed to further enhance the effects of the method of the present invention.
That is, a polymer having a dipole in a polymer structural unit and a polymer having a dipole unit
which does not cancel dipolarity in a crystal unit lattice, or a polymer substance dissolved in a
solvent has a rod-like or socks molecular structure. When the method of the present invention is
applied to a polymer in which the orientation of the child is oriented in a specific direction, an
excellent electret can be obtained. Examples of such polymers and the former include
polyacrylonitrile, polyvinylidene fluoride, mn type polyamide or polyester (where m and n are
both odd numbers), and examples of the latter include poly-γ-benzyl-L. -Include glutamate. Polyγ-benzyl-L-'fA tamate is dissolved in methylene bromide solvent as a Hessock structure and
dissolved, and when a direct current strong electric field is applied, the electric field is realized by
the dipole efficiency in the helical axial direction and the rigid structure of the helical molecule
Under the action of (1), the direction of the helical axis in the direction of the electric field forms
a so-called liquid crystal phase having both the fluidity of the liquid and the optical anisotropy of
the crystal.
When the solvent is evaporated while maintaining this orientation state by a direct current
strong electric field, a sheet having a remarkable molecular orientation parallel to the electric
field direction is obtained. The present invention will now be described in detail by way of
examples, which should not be construed as limiting the invention in any manner. 0 [111111]
Example 11 parts by weight (same weight or less same) of polyacrylonitrile A particulate Th 10
parts The solution heated and dissolved in dimethylformamide was placed in a quartz glass
container and held between a grounded copper lower electrode and a copper upper electrode
connected to a DC power supply. Such a system was set in a thermostat, and the atmosphere was
replaced with nitrogen gas. When the temperature in the constant-temperature bath heated by
the heater reaches 100 ° C., apply a DC voltage of 20 kv between the two electrodes, and cut off
the heater 3 hours after evaporation of dimethylformamide, the solvent, The application of
voltage was stopped when the temperature in the thermostat returned to 30 ° C. At this time,
the thickness of the quartz glass container is 20 mm 1 when the polyacrylonitrile sample
thickness is 1.0 mm, the air gap length between the sample surface and the upper electrode is
120 mm, and the obtained electret film has an electric field direction by X-ray photograph The
surface electrode density was [email protected] coulomb / cm @ 2, and even after 5000 hours
after production, the surface charge density was almost the same as that immediately after
production. The surface charge density immediately after the production of the polyacrylonitrile
molded product which has been oriented and polarized under the known production conditions
is at most [email protected] quantum / cm @ 2 and disappears after 1000 hours. EXAMPLE 21 1
part of poly-.gamma.-benzyl-L-glutamate was dissolved in 7 parts of methylene bromide and set
in a thermostat in the same manner as in Example 1. When the temperature in the thermostat
reaches 70 ° C, apply a DCk of 20 kv between the two electrodes, keep in this state for 4 hours
until the solvent is evaporated, then turn off the heater 9 and the temperature in the thermostat
The application of the voltage was stopped when the temperature returned to The
surface charge density of the formed poly-γ-ben-) ru L-glutamate electret film immediately after
production is 4.6 × 10 −9 coulomb /. Even after the passage of m 2.5,000 hours, 4. It
maintained a high value of 1 × 10 −9 kron / cm 2.
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