JPS58158909A - High dielectric constant film - 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 The present invention relates to a film for capacitors or piezoelectric elements that has a significantly improved dielectric constant.

In general, the capacitance of a film capacitor or piezoelectric element is determined by the dielectric constant of the polymer or polymer used, and the thickness and area of the film. In the case of organic polymer materials, the dielectric constant of the polymer used is usually at most 5th. Some of them, such as those of fluorine series compounds, exhibit a dielectric constant of about 10, but the reality is that they are rarely used due to cost and insulation performance considerations. - Efforts have been made to reduce the thickness of the film in order to increase capacitance, but there are limits due to increased cost and workability.
The increase in the area of the film was still limited by the shape of the capacitor, and as a result, it was necessary to improve the dielectric constant of the dielectric film at low cost. One way to improve this is to add a ferroelectric compound containing barium titanate as the main component, but while this method can increase the dielectric constant, it also tends to increase the dielectric loss tangent, especially When used for AC applications, etc., there were problems such as heat generation, which needed to be improved.

As a result of studies on this problem, the present invention has been developed to increase the dielectric constant by completely containing a ferroelectric material mixture made of alumina or alumina porcelain in a single-layer or multi-layer thermoplastic polymer film, and to increase the dielectric constant. This makes it possible to provide a film for capacitors or piezoelectric elements that does not increase tangent. The present invention will be explained in detail below.

Thermoplastic polymers used in the present invention include polyethylene terephthalate, polypropylene, polyethylene, polycarbonate, polyarylate, polyamide, polyvinylidene fluoride, polysulfone, polyphenylene sulfide, poly4-methylpe/tene-1, etc., or mixtures thereof. Examples include, but are not limited to, copolymers. Among these, polyethylene terephthalate and polypropylene have particularly good electrical performance.
It is suitable in terms of workability, price, etc.

The ferroelectric material used in the present invention is alumina (At20
3) or a compound made of alumina porcelain. Alumina porcelain can be made by sintering alumina, but if the alumina content exceeds 99%, it must be sintered at a temperature of 1,800°C or higher, so in order to lower the sintering temperature,
io2. MnO2, Fe2O3.

(40) 0% Mg is added, or clay, silica, etc. are often added. The dielectric constant of alumina or alumina porcelain is about 5 to 8, and the dielectric loss tangent is about 3×4 10 .

Alumina or alumina porcelain is dispersed in a thermoplastic polymer in the form of a powder with an average particle size of several microns, and then formed into a film by melt extrusion. The mixing method includes adding it during the polymerization of the thermoplastic polymer and directly blending it into the polymerized thermoplastic polymer using a twin-screw extrusion machine, calender roll, etc., but it is particularly limited to these methods. It's not a thing. Furthermore, a method of forming a film from a conventional thermoplastic polymer can be applied to the film forming method. That is, a thermoplastic polymer containing a ferroelectric material mixture can be heated and melted using an extruder, extruded from a T-die, and cooled and solidified using a cooling roll to form a film. Alternatively, it is also possible to adopt a method in which the compound is added to a solution in which a thermoplastic polymer is dissolved or dispersed, and then a film is formed and only the solvent is evaporated.

The thermoplastic polymer film formed may have a single layer or multiple layers, but it is preferable that the average content of the ferroelectric substance blend relative to the entire film is 5% by weight or more. The method for forming a multilayer film is not particularly limited, and extrusion lamination, dry lamination, solution coating, hot melt coating, coextrusion, and the like can be applied.

When the content of the ferroelectric substance compound is large, especially exceeding 40% by weight, or when the stretchability of the thermoplastic polymer is particularly poor, the unstretched film is used as a capacitor dielectric without stretching. Alternatively, at least one layer of a thermoplastic polymer containing less than 5% by weight of a ferroelectric substance blend and one layer of a thermoplastic polymer containing 5% by weight or more of a ferroelectric substance blend are laminated. By forming the composite film into a shape and then stretching it, stretching becomes possible and various strengths can be increased.

The stretching method may be -axial stretching, sequential biaxial stretching, or simultaneous biaxial stretching.

The method for manufacturing a capacitor using the obtained capacitor film as a dielectric is not particularly limited, but it is common to apply a manufacturing method for a normal wound type capacitor. In other words, the capacitor can be fabricated by micro-slitting the above film, overlapping it with aluminum foil and winding it, or by applying metal vapor deposition on one or both sides of the film in the form of a belt, micro-slitting it, and then winding it. can be made. Alternatively, it can be manufactured in the form of a multilayer capacitor. That is, this is a method in which the above-mentioned vapor-deposited films are laminated without any treatment or after coating the surface with a hot-melt adhesive, and the films are cut into small chips and integrated.

Hereinafter, this will be described in detail with reference to Examples.

Example 40% by weight of alumina powder having an average particle size of 1 μm was added to polyethylene terephthalate chips and mixed in a twin-screw extruder to produce blend chips. This blend chip was heated and melted at 280° C. using a single-screw extruder, extruded from a T-die, and formed into a film on a cooling roll to form a film with a thickness of 50 μm.

This unstretched film was simultaneously biaxially stretched 3×3.5 times at 95°C and heat set at 230°C.

When the dielectric constant and dielectric voltage contact of the obtained film were measured, the results were good as shown in Table 1.

Table-1 Patent Applicant Unitika Co., Ltd. Procedural Amendment April 18, 1980 Mr. Kazuo Wakasugi, Commissioner of the Office of Special Correction 1. Indication of the case 1982 Patent Application No. 40188 2. Name of the invention High dielectric constant film 3. Amendment Relationship with the case of a person who does the following Patent applicant address: 1-50 Higashihonmachi, Amagasaki City, Hyogo Prefecture Name: f4
50] Unitika Co., Ltd. Representative Hei 1) Yutaka 4, Agent 105 Telephone 501-4552
Address Shimazaki Building 4, 1-2-14 Toranomon, HigashiF Miyako-ku
Floor 5. Date of amendment order. Voluntary amendment. 6. Number of inventions increased by amendment. 7. Subject of amendment (1) "-or film for piezoelectric element" in line 11 of page 1 of the specification. Line 13 to 1
Correct "or the capacitance of the piezoelectric element" and "capacitance of the piezoelectric element" in the fourth line.

(2) Delete “or for piezoelectric elements” on page 2, line 17 of the specification.

Claims (1)

[Claims] A high dielectric constant film comprising a single layer or multiple layers of a thermoplastic polymer film containing a ferroelectric substance compound made of alumina or alumina porcelain.