JPH0126602B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to highly dielectric polymeric materials, and more particularly to highly dielectric polymeric materials comprising vinylidene fluoride/trifluoroethylene copolymer films having improved high dielectric constants. In recent years, there has been a desire for smaller electronic devices, and there has been an increasing demand for smaller capacitors as components incorporated therein. The capacitance (C) of the capacitor is
C=ε′εo(S/d) ε′: Relative permittivity of dielectric material εo: Relative permittivity of vacuum = 0.0885PF/cm S: Area of capacitor d: Expressed by thickness of capacitor, it is clear from this formula In order to develop a small-sized, large-capacity capacitor, it is necessary to increase ε' and S, and to decrease d. Due to its processing characteristics, polymeric substances can easily be formed into large-area, thin films, but ε' is generally as small as 2 to 5. In order to miniaturize and improve the performance of capacitors, which require a polymer material with a large ε', a highly dielectric polymer material with a high dielectric constant is necessary. The binary copolymer of vinylidene fluoride (hereinafter referred to as VdF) and trifluoroethylene (hereinafter referred to as TrFE) listed above is one of the well-known polymeric substances with a high dielectric constant. It is. The relative dielectric constant of this material is 1.5 to 2.0 times higher than that of polyvinylidene fluoride, which was previously well known as a highly dielectric polymer material.
ε′ = 15 (room temperature, 1KHz) is obtained. Furthermore, highly dielectric polymer compounds can also be applied as dispersants for ZnS particles in planar light emitters, which have recently attracted attention. In such a situation, the inventors have determined that VdF/
As a result of intensive research on the dielectric properties of TrFE copolymers, we discovered that when this polymer is irradiated with radiation, the relative dielectric constant of the film reaches over 35 (24°C, 1KHz), which led us to complete the present invention. Ivy. That is, the gist of the present invention resides in a highly dielectric polymeric material obtained by irradiating a vinylidene fluoride/trifluoroethylene copolymer with radiation, and a method for producing the same. The VdF/TrFE copolymer used in the present invention has a
Contains 80 mol% VdF, preferably 40-80 mol%. Furthermore, the VdF/TrFE copolymer is a multi-component copolymer in which a small amount of hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), vinyl fluoride, etc. are copolymerized as the third and fourth components. Also includes polymers. The method for synthesizing the copolymer is described in detail in JP-A-52-69000 and JP-A-58-112329. A film of VdF/TrFE copolymer can be obtained by a casting method using a solvent such as methyl ethyl ketone (MEK), a hot pressing method, or a film extrusion method. This VdF/TrFE copolymer film is exposed to radiation.
Preferably, electron beams or gamma rays are irradiated. In particular, electron beams are more preferable because they can achieve high dose irradiation at a specific temperature in a short time. The radiation dose varies depending on the type of radiation, but is generally between 20 and 300 Mrad. During irradiation,
Keep the copolymer film above the Curie temperature. In this way, a film having a higher dielectric constant than conventional VdF/TrFE copolymer films is obtained. To make a capacitor from the highly dielectric polymeric material of the present invention, a metal such as aluminum, silver, or nickel is coated on the surface of the copolymer film to a thickness of 0.05 mm.
It may be used as an electrode by vapor deposition to a thickness of ~2 μm. Further, instead of the metal vapor-deposited film, a metal foil may be laminated as an electrode. Next, examples and comparative examples will be shown to specifically explain the present invention. Example 1 and Comparative Examples 1 to 2 A VdF/TrFE copolymer containing 65 mol% of VdF (Curie point: 102°C) was formed into a film with a thickness of 30 to 35 μm using a film extruder heated to 200°C. Electron beam irradiation was performed at the temperature and dose shown in Table 1. Example 1 and Comparative Example 2 Next, aluminum was vacuum-deposited on both sides of the film to form electrodes, and Yokogawa-Hewlett
−4274A MULTI manufactured by Packard−
The capacitor capacitance was measured using a FREQUENCY LCRmeter and the relative dielectric constant was obtained. Further, as Comparative Example 1, the same film was used except that it was not irradiated with an electron beam, and the dielectric constant was measured. The results are shown in Table 1.

[Table] Comparative Examples 3 to 4 A VdF/TrFE copolymer containing 52 mol% of VdF (Curie point: 70°C) was formed into a film with a thickness of 30 to 35 μm using a film extruder heated to 260°C. Electron beam irradiation was performed at the temperature and dose shown in the table, and the dielectric constant was measured in the same manner as in Example 1. (Comparative Example 3). Further, as Comparative Example 4, the same film was used except that it was not irradiated with an electron beam, and the dielectric constant was measured. The results are shown in Table 2.

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Claims (1)

[Scope of Claims] 1. High-energy radiation obtained by irradiating a vinylidene fluoride/trifluoroethylene copolymer film containing 10 to 80 mol% of vinylidene fluoride with high-energy radiation at a temperature equal to or higher than the Curie point of this copolymer. Dielectric polymer material. 2. The highly dielectric polymeric material according to claim 1, wherein the copolymer film is a vinylidene fluoride/trifluoroethylene copolymer film containing 40 to 80 mol% vinylidene fluoride. 3. The highly dielectric polymeric material according to claim 1, wherein the radiation is an electron beam or a gamma ray.