JPS609115A - Method of producing eectret - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a method for producing electrets, and particularly to a method for producing electrets with excellent stability and long life.

[Prior art and its problems]

The following methods are known for producing electrets from dielectric materials. For example, an organic polymer material is heated to a temperature around its softening point or melting point, a DC high voltage is applied to it for a certain period of time, and then it is slowly cooled to room temperature (with the DC high voltage still applied), or the DC high voltage described above is Instead of applying a strong static magnetic field, a so-called thermal electret or magnetoelectret is obtained. A method is also known in which a photoelectret is obtained by polarizing a photoconductive substance such as zinc sulfide or cadmium sulfide by applying a DC high voltage while irradiating it with light at room temperature. According to these electret production methods, electrets with positive or negative polarity can be obtained arbitrarily, but in the case of thermal electrets or magnetic electrets, the organic polymer material is subjected to a temperature cycle of room temperature → high temperature → room temperature. Since an electric field or a magnetic field is applied while giving the electret, the operation is not only complicated, but also it takes a long time to form an electret.

Moreover, when looking at the obtained electret material, the distribution of charge is uneven, and its lifespan is easily controlled by the external atmosphere, so there are definite defects that make it impossible to apply it to electroacoustic transducers, switches, memory devices, etc. . On the other hand, in the case of food electrets (the second type uses a photoconductive substance, it cannot be used in bright places, and although it is used as a memory element in the field of electrophotography, its sensitivity is not sufficient, and it cannot be used as an electroacoustic transducer. Application to the other side is difficult.

Method for obtaining the above-mentioned electret (polarization method) 1: On the other hand, a method called a charged body injection method is also known.

For example, an electret can be obtained by applying a high voltage of about 105 V 7' cm to a polymer film with high electrical resistance, such as tetrafluoroethylene polymer or polyethylene terephthalate, by applying a high voltage of about 105 V 7' cm and injecting charge. . According to this charged body injection method, an electret with a large initial charge amount and a uniform charge distribution can be obtained within a short time. However, according to this charge injection method, the polarity can be changed arbitrarily (if the electret has positive polarity (-), the stability of the charge is poor, and the specified performance as an electret (life) is several steps compared to the case with negative polarity. It can only be maintained for a certain period of time.

That is, although this charged body injection method is excellent as a method for producing electrets with negative electrode characteristics, it is not suitable for producing electrets with positive electrode characteristics.

The inventors of the present invention proceeded with studies to address these points, and found that when ultraviolet rays are irradiated while applying an electric field to an ultraviolet curable resin layer, the initial charge amount is large regardless of polarity, and temperature and humidity It has been found that it is possible to obtain an electret that is stable against changes and therefore maintains a predetermined performance over a long period of time (1 to 5 A).

[Purpose of the invention]

Based on this knowledge, the present invention can be easily used without requiring complicated operations, has a large initial M charge amount, good uniformity of charge distribution, and excellent stability, and can be used for a long period of time (1° [place]). The present invention aims to provide a method for producing electrets that maintains reasonable profits and losses.

[Summary of the invention]

The present invention will be described in detail below.1 The present invention is a method for producing an electret characterized by curing an ultraviolet curable resin layer (= irradiation with ultraviolet rays) under an electric field. Figure 1 is a partially cutaway sectional view showing an example of the configuration of an apparatus suitable for carrying out the method of the present invention.
1) is supplied into the device. The device has sequential coaters (2
), a transport roll (3) and a take-up roll (4) are arranged. A charger (5) is provided above the device (2), and one end is connected to the brain pressure power source (6). Also, (7) is a light shielding plate that prevents the irradiation of ultraviolet rays (8) before being charged. (9) is the ground roll that comes into contact with the base film (-) during charging.

FIG. 2 is a cross-sectional view showing the simultaneous exposure and charging steps after applying an ultraviolet curable resin suitable for carrying out the method of the present invention. At least one side (second side) of the base film (1) is provided with a conductive layer fil, and on the conductive layer α1 (one ultraviolet curing resin layer aυ
is coated. Conductive layer (11) Grounding roll (9)
While grounded, an electric field is applied using a charger (5) connected to one end (two high-voltage power sources (6)). Under the electric field, ultraviolet rays (8) are irradiated to cure the ultraviolet curing resin layer (11).

In the present invention C2, the ultraviolet curable resin that serves as the base material of the electret may contain, for example, a low molecular weight monomer and/or oligomer containing an average of 5 to 5 free saturated hydrocarbon groups and/or phenyl groups by weight. It is growing. A low molecular weight mono-, jatri- or tetra-acrylic ester is used and a photosensitive catalyst such as an aromatic carbonyl compound such as benzoin isobutyl ether is added to this. An example of an acrylic ester is 2-ethylhexyl acrylate.

These include ethyl acrylate, phenyl acrylate, 2-ethoxyethyl acrylate, and octadecyl acrylate. These materials are merely examples, and are not limited in any way as long as they are resins that harden when irradiated with ultraviolet rays.

In addition, when irradiating the ultraviolet curable resin layer (1) with ultraviolet rays, for example, when performing corona charging using a charger, charge may be applied directly in a N or gas atmosphere, or by contacting the ultraviolet curable resin layer with a transparent electrode such as Nesa. In the above embodiments, the ultraviolet curable resin is coated on the flexible base film (1), but it may also be coated on a conductive substrate such as a metal plate.

〔Effect of the invention〕

According to the method of the present invention, which consists of irradiating a predetermined ultraviolet curable resin layer with ultraviolet rays under an electric field, curing it, and electrifying it, it is easy to operate and it is possible to obtain any desired electret by selecting the operating conditions. can. In other words, the method of applying the electric field and the electric field strength.

By selecting C2, such as the type of ultraviolet curable resin, it is possible to easily obtain an electret that has a large initial surface charge density, has excellent stability, and retains a predetermined charge for a long period of time. Thus, the method of the present invention can be said to be a method for producing electrets that provides many practical advantages in terms of ease of operation, good reproducibility, and the ability to obtain electrets of various properties.

[Embodiments of the invention]

Next, examples of the present invention will be described.

EXAMPLE 1 A charger and an ultraviolet lamp are installed in a closed device that is replaced with perforation gas. An epoxy acrylate-based ultraviolet curing resin is applied in advance to a thickness of 100 μm on a 700 μm thick A/substrate, and is supplied 0.5 cm below the charger. At room temperature, a DC high voltage of 8 KV was applied, and 80 W/Cm of ultraviolet rays were applied to the cell, which was then charged by corona discharge.
It was irradiated for 5 seconds and cured to obtain a positive polarity electret. Thus obtained electrets) H1 (1”-6 to 1
It had an initial surface charge density of 0-7 coulombs/cpl, and the difference in surface charge density was within 3 inches, with good uniformity.

For comparison, 1100 was installed on a 700 pm thick plate.
A direct current of 8V was applied to a p-thick FEP piece for 40 minutes at room temperature to charge it by corona discharge to obtain a positive polarity electret. This corona electret is 10"-'~10
Although the initial surface charge density was ``'' Coulomb/d, a difference of about 10% was observed in the surface charge density.

As a life test for both of these electrets, an example in which changes in surface potential of the electrets were measured after being left under (a) υ is shown in FIG. In Figure 3 (2), curve A is for the example, and curve a is for the comparative example.As is clear from Figure 3, the electret according to the present invention has almost no attenuation of the surface potential, The length of is shown.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway sectional view showing an example of the configuration of an electret production apparatus suitable for carrying out the method of the present invention, and Fig. 2 is a partially cutaway sectional view showing a configuration example of an electret production apparatus suitable for carrying out the method of the present invention. A cross-sectional view showing an example, and FIG. 3 is a diagram showing the change in surface charge density of electrets obtained by the method of the present invention and electrets obtained by corona discharge when they are left at 60°C. 1. Hepar. Su 741L Mu 1 Da Training Pi%
, S ° Hikaruzo, patent attorney Norichika Kensuke (and 1 others)
Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A method for producing a cutlet, characterized in that a resin layer cured by ultraviolet rays provided on a substrate is irradiated with ultraviolet rays in double daylight.