JPH01289015A - Manufacture of dielectric - Google Patents

Abstract

PURPOSE:To strengthen the bonding between a film base and a fluorine containing polymer layer without influencing the thickness of the film base by treating the surface of the film base with fluorine to form the fluorine containing polymer layer on the surface thereof. CONSTITUTION:A fluorine containing polymer layer is formed on a surface of a film base by treating the surface with fluorine. In general, polyolefine resin is used as the film base. The fluorine containing polymer layer is formed by fluorination treatment method utilizing fluorine gas. For example, a method wherein the fluorination treatment is effected by using fluorine gas upon molding the film base according to tubular film process, or a method wherein the fluorination treatment is effected by using fluorine gas after molding the film base according to tubular film process, T die extruder and casting process, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a dielectric material made of a fluorinated polyolefin in which the surface of a polyolefin film is modified in order to improve the dielectric properties of the base film.

[Prior art and problems to be solved by the invention] Conventionally, there are inorganic and organic dielectric materials, such as T
There are inorganic dielectric materials such as io Ta O B a T i OP b T 103. Although these exhibit high dielectric properties, they are difficult to form into thin films and are not flexible. Furthermore, molding also has drawbacks such as requiring high temperature conditions. Therefore, recently, inexpensive and flexible dielectric materials such as polyester resin, polyethylene resin, polypropylene resin, polystyrene resin,
Polymer films such as polycarbonate resin have come into use. However, the dielectric constant of these polymer films is as small as 2 to 3, and the film thickness is thin due to film manufacturing technology, and the limit for polyester resin and polycarbonate resin films is about 4 to 6 μm. Furthermore, even for fluororesins, especially polyvinylidene fluoride, which have a high dielectric constant (approximately 8 to 11) in polymer films, the film thickness is limited to 6 μm, and the films are expensive and have a dielectric loss tangent (tan δ) of approximately 6 μm. 0. '1, which causes a large loss of electrical energy (furthermore, the low mechanical modulus of elasticity causes trouble in the film winding process.Therefore, as an improvement method, polyolefin-based A method in which a polyvinylidene fluoride solution is cast on a polymeric film substrate such as a resin to form a thin film, or a thin film is laminated by polymerizing vinylidene fluoride monomer in the gas phase on the surface of the film substrate using plasma polymerization method etc. A method has been proposed (for example, Japanese Unexamined Patent Application Publication No. 188110/1983) in which polyvinylidene fluoride can be made into a thin film.
There was a problem in the adhesion between this polyvinylidene fluoride thin film and the surface of the film base material, and there was a risk that it would peel off during use, resulting in a decrease in capacitance. Furthermore, in these methods,
Although the dielectric constant of the obtained dielectric is improved, since it is laminated on a polymer film base, it is necessarily thicker than the original base material.

As a result, when such a base material is used as a film capacitor, it has the disadvantage that the capacitance is smaller than that of a capacitor having the same volume and dielectric constant due to the thick film.

Therefore, it has a high dielectric constant and a small dielectric loss tangent, and in the process of imparting dielectric properties to such a base material, there is no change in the film thickness of the film base material used, and furthermore, the film base material and the fluorine-containing polymer layer are in strong contact. The development of a polymer film for capacitors is desired.

[Means for Solving the Problems] In view of the above-mentioned current situation, the present inventors have developed a thin film based on polyolefin resin that has a high dielectric constant and a dielectric loss tangent (ta).
nδ) is small, does not change the thickness of the film base material used in the process of imparting dielectric properties to such a base material, and also has a strong bond between the film base material and the fluorine-containing polymer layer. We conducted intensive research to obtain a molecular film.

As a result, the inventors discovered that a desired capacitor film could be obtained by forming a fluorine-containing polymer layer on the surface of the film base material, and completed the present invention.

That is, the method for manufacturing a dielectric is characterized in that a fluorine-containing polymer layer is formed on the surface of a film base material made of a polyolefin resin by fluorinating the surface using fluorine gas.

According to the present invention, a material having a dielectric constant higher than the original dielectric constant is provided by treating the surface of the film base material with fluorine to form a fluorine-containing polymer layer on the surface. It is thus possible to increase the dielectric constant of the film substrate by as much as 15% or more.

The present invention will be explained in detail below.

Polyolefin resins are generally used as the film base material of the present invention, such as high density, low density, linear low density, ultra-high molecular weight polyethylene, polypropylene, 1-butene, 1-hexene, 4-methyl-1 -Pentene, 3-
α of methyl-1-pentene, 3-methyl-1-butene, etc.
- Olefin homopolymers or copolymers consisting of 2F1 or more thereof, and other monomers copolymerizable with the above α-olefins, such as styrene, acrylonitrile, vinyl chloride, vinylidene chloride, and vinyl acetate.

Copolymers with methacrylic acid and its derivatives, blends with other polymers, and block copolymers.

It is a known polymer film such as a graft polymer. The polymer film used as the film base material preferably has a dielectric loss tangent as small as possible and a thickness of 1 to 150 microns. Furthermore, from the viewpoint of economy and availability, high density, low density, linear low density polyethylene, and polypropylene are preferred.

Further, the method of forming a fluorine-containing polymer layer on the surface of the film base material as described above according to the present invention is a fluorination treatment method using fluorine gas. For example, when molding a film base material by the inflation method, fluorine treatment is performed using fluorine gas, or after the film base material is molded by the inflation method, T-die extruder, or casting method, it is fluorinated using fluorine gas. method is adopted.

These fluorination methods have the advantage that the thickness of the fluoropolymer layer can be controlled arbitrarily by using an inert gas and arbitrarily determining the fluorine gas concentration. In this way, forming a fluorine-containing polymer layer by fluorinating the surface of the film base material using fluorine gas improves the adhesion and thinning of the film compared to the conventional method of forming a polyvinylidene fluoride thin film on the film base layer. It is extremely effective as a method for solving problems.

Furthermore, to describe the fluorination method specifically, argon is used.

Zero fluorine gas with inert gas such as helium or nitrogen
．． It is used after being diluted to 1-20% by volume. Preferably 0.1
-10% by volume. Further, any pressure can be used for the processing pressure, but it is preferable to use a relatively low pressure in order to easily perform reaction operation and control.
More preferably, the pressure is at most atmospheric pressure. There is no particular limit to the format of the fluorination treatment, and a known batch method, continuous method, or inflation method can be used.

The temperature of the fluorination treatment can be appropriately selected depending on the resin and molding method, but is preferably 10 to 40°C.

The fluorination treatment time depends on the concentration and pressure of the fluorine gas used,
The time is preferably from 10 seconds to 24 hours, and more preferably from 20 seconds to 1 hour, although it varies depending on the required amount of fluorine bonding to the film base material, processing temperature, etc.

If the treatment time is less than 10 seconds, no improvement in dielectric constant will be observed, and if it exceeds 24 hours, productivity will decrease, which is not preferable.

When performing the fluorination treatment of the present invention in a batch manner, the film substrate is placed in a reactor in advance, degassed under reduced pressure, and residual gas is replaced using an inert gas such as nitrogen, argon, or helium. After that, it is preferable to introduce a gas containing fluorine. Further, after the fluorination treatment, unreacted gas in the reaction vessel is removed, and the inside of the reaction vessel is sufficiently replaced and ventilated with an inert gas to obtain a fluorinated polyolefin resin film.

Moreover, when creating the fluorinated film of the present invention by an inflation molding method, the following method can be mentioned. For example, argon is used as a suction gas when molten resin is inflated.

This method uses a mixed gas in which fluorine gas is diluted with an inert gas such as helium or nitrogen to obtain a fluorinated polyolefin resin at the same time as film forming (Japanese Patent Application Laid-Open No. 140821/1982).

[Example] The dielectric constant and dielectric voltage contact (tan δ) in the following examples were measured using ■ Rheolograph Solid S-, a new product manufactured by Toyo Seiki Co., Ltd.
1 at -100 to 150° C. and a frequency of 10 kHz.

Example 1 A polypropylene film base material with a thickness of 40 μm (product name: rDS5C-13J manufactured by UCC) was inserted into a reaction container (container area: 1.5×10 m ) capable of airtight gas replacement.
After degassing to a vacuum level of 1 mmHg, gas replacement was performed three times with nitrogen gas. Next, fluorine gas diluted to 10% by volume with nitrogen gas was introduced at 760 mmHg and reacted at 20° C. for 10 minutes. After the reaction, the reaction vessel was degassed, and the inside of the reaction vessel was subsequently replaced with nitrogen gas three times, and then the sample was taken out. The dielectric constant and dielectric loss tangent (tan δ) of the film base material prepared by the above method were measured at 1'0) kHz and room temperature, and the results were 2.428 and 0.00148, respectively.

Comparative Example 1 The dielectric constant and dielectric loss tangent (tan δ) of the polypropylene film base material used in Example 1 were measured at 10 kHz and room temperature, and the results were 2.068 and 0.00, respectively.
It was 341.

Example 2 Low-density polyethylene (manufactured by Tosoh Corporation, trade name: Petrocene 175J) was extruded from an annular die of an extruder in a molten state at 154°C, the tip of the extruded material was held between pinch rolls, and a resin film was placed inside. 1 with a sufficient amount of nitrogen gas to match the amount of fluorine consumed in fluorinating the inner surface of the bubble and to maintain the bubble at a predetermined size.
Fluorine gas diluted to 0% by volume was fed. In addition, in order to ensure that a constant concentration of fluorine gas always existed within the bubble, a gas outlet was provided at the same time as the gas inlet to circulate the fluorine gas. This inflates the resin film into an annular tube shape and continuously cools the material at a line speed of 10 m.
A film base material having a thickness of 40 μm was prepared by winding the film at a speed of 40 μm.

The blow ratio at this time was 165.

The dielectric constant and dielectric loss tangent (tan δ) of the film substrate prepared by the above method were measured at 10 kHz at room temperature and were 2.528 and 0.01777, respectively.
Met.

Comparative Example 2 Low-density polyethylene (manufactured by Tosoh Corporation, trade name "Betrocene 175J"
) A 40 μm film base material was prepared. The dielectric constant and dielectric loss tangent (tan) of the film base material prepared by the above method
δ) measured at 10 kHz at room temperature were 2.108 and 0.00516, respectively.

[Effects of the Invention] As is clear from the above description, according to the present invention, a dielectric material in which a fluorine-containing polymer layer is uniformly formed on the surface of a film base material can be manufactured. This dielectric has a dielectric constant higher than that of the original dielectric, and has a dielectric loss tangent (ta).
Its industrial value as a polymer film for capacitors has a small nδ), there is no change in the film thickness of the film base material during the process of imparting dielectric properties to the thin film, and the problem of adhesion to the film base material has been improved. is expensive.

Claims (1)

[Claims] (1) A method for producing a dielectric, which comprises forming a fluorine-containing polymer layer on the surface of a film base material made of a polyolefin resin by fluorinating the surface using fluorine gas.