JPS58141222A - High-dielectric film - Google Patents

Abstract

PURPOSE:The titled film whose dielectric constant is increased without increasing its dielectric loss tangent, prepared by adding a specified strong dielectric composition to a thermoplastic polymer film. CONSTITUTION:A ferroelectric composition is obtained by mixing 100-50wt% strontium titanate with 0-50wt% stannate, zirconate and at least one titanate other than strontium titanate, e.g., Mg2TiO4, baking the mixture at about 1,300 deg.C and grinding the formed solid solution into a size of several mu. Then, this ferroelectric composition is added to a thermoplastic polymer (e.g., polyethylene terephthalate), the mixture is heated and molten in an extruder, extruded through a T die and cooled and solidified by a cooling roll to obtain a high- dielectric film.

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 used and the thickness and area of the film. Some of them, such as fluorine-based compounds, exhibit a dielectric constant of about 10, but the reality is that they are rarely used due to cost and insulation performance considerations. On the other hand, efforts have been made to reduce the thickness of the film in order to increase the capacitance, but there are limits due to increased cost and workability, and increasing the area of the film is also limited by the shape of the capacitor. In the end, there was a need to inexpensively improve the dielectric constant of the dielectric film. 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 in AC When used for commercial purposes, there were problems such as heat generation, which needed to be improved.

As a result of considering these problems, the present invention has developed a single-layer or multi-layer thermoplastic polymer film containing (-) strontium titanate alone, or (-) strontium titanate and (b) stannate. For use in capacitors, which increases the dielectric constant by containing a ferroelectric material mixture consisting of at least one type of titanate different from zirconate or strontium titanate, and does not increase the dielectric voltage contact. The present invention provides a film for piezoelectric elements. 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.
Examples include sulfides, mixtures and copolymers thereof, but the thermoplastic polymers of various sizes can be used without being limited thereto. Among these, polyethylene terephthalate and polypropylene are particularly preferred in terms of electrical performance, workability, cost, etc.

As mentioned above, the ferroelectric material in the present invention is
When barium titanate is used as the main component, the dielectric constant can be dramatically increased, but on the other hand, the dielectric loss tangent also increases in proportion to the dielectric constant, and is extremely low compared to the dielectric loss tangent of the base thermoplastic polymer. begins to take a large value. In order to prevent this, in the present invention, strontium titanate alone,
Alternatively, a combination of strontium titanate and at least one of a stannate, a zirconate, and a titanate different from the strontium salt of titanic acid is used. Strontium titanate alone has a dielectric constant of 260 to 280 and a dielectric loss tangent of 0.03%, and by adding it to a thermoplastic polymer, the dielectric constant can be increased without increasing the dielectric loss tangent. but,
Furthermore, as a method for increasing the dielectric constant, a method can be adopted in which at least one kind of a stannate, a zirconate, or a titanate different from a strontium salt of titanate is added to strontium titanate.

These amounts are generally strontium titanate 10
Although it is 0 to 50% by weight relative to 0 to 50% by weight, it is not particularly limited. In addition, specific examples of titanates different from stannate, zirconate, and strontium titanate include BaSnO3, B12 (Sn05
)5, CaSnO3, PbSnO3.

MgSnO3, 5rSn05 * Zn5n05 r
B'aZr03, CaZrO3゜PbZrO3, M
gZrO3, 5rZr05, ZnZrO3.

BaTiO3, B12(Ti05)5, CaT
iO3, CoTiO3*PbTiO3, NjTiO
, MgTiO3, Mg2Ti011.

Examples include znTIO5 and Zn2T10II, but are not limited to kerala and cholera. These blended additives are added to strontium titanate and then fired at approximately 1300°C to form a solid solution.These blended additives change the crystal structure of strontium titanate, resulting in The dielectric constant is changed by changing a single Curie point.

Generally, when the dielectric constant increases, the dielectric loss tangent also increases, but since the dielectric loss tangent unique to strontium titanate is originally small, it is unlikely to become larger than the dielectric loss tangent of a thermoplastic polymer, even if it is added to a thermoplastic polymer. It is unlikely that the overall dielectric loss tangent will increase. In addition, when reducing the dielectric constant, adding it to a thermoplastic polymer cannot greatly increase the overall dielectric constant, but it can improve the temperature characteristics of the overall dielectric loss tangent, and it can be used for temperature compensation, etc. I can do it. Among these, a typical combination is S r
T i 05 and P b T i O5 or B12 (
combination with Ti05)5 or 5rTi05 and C
It is a combination with a T i O5, Mg 2 T i Oq or BaTiO3.

The method of incorporating the above-mentioned compound containing the ferroelectric substance into a thermoplastic polymer film is to crush the compound into a powder of several micrometers, mix it with a thermoplastic polymer, and melt-extrude it into a film. This method is generally adopted. The mixing method includes adding it during polymerization of the thermoplastic polymer, or directly blending it into the polymerized thermoplastic polymer using a twin-screw extruder, calender roll, etc., but it is particularly limited to these methods. It's not a thing.

Further, a method for forming a film from a normal thermoplastic polymer can be applied. 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 be a single layer or multiple layers. The method of forming a multilayer film is not particularly limited, and may include extrusion lamination,
Dry lamination method, solution coating method, hot melt coating method, coextrusion method, etc. can be applied.

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

The stretching method may be I@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 made 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 1 50% by weight of 5rTi05 powder with an average particle size of 1.5 μm was blended into polyethylene terephthalate chips, mixed into a twin-screw extruder, and heated and melted and extruded to produce blend chips. This blend chip was heated and melted using a single-screw extruder, extruded through a T-die, and formed into a film on a cooling roll to a thickness of 40 mm.
This unstretched film was prepared at 95°C using a simultaneous biaxial stretching machine.
The film was simultaneously biaxially stretched to 3x3.5 times and heat centrifuged at 230°C. When the dielectric constant and dielectric loss tangent of the obtained stretched film were measured, the results were good as shown in Table 1.

Example 2 SrT plate 03 60 M %, PbT
iC) 5 2 0 Weight Section.

B12(Ti03)3 20 weight ratio mixture'f: 13
After firing at 00°C for about 3 hours, the ferroelectric substance mixture was crushed with a mer mill and a vibration mill to produce a ferroelectric material compound with an average particle size of 1.7μ, which was then processed using a twin-screw pusher, a calendar roll mixer, and a vibration mill. The mixture was kneaded with polyethylene terephthalate using a mixer to produce blend chips with a content of 6ON. This blend chip and the polyethylene terephthalate virgin chip containing no ferroelectric substance compound were separately charged into a coextrusion apparatus and extruded from a T-die to produce a laminated unstretched film. The film thickness of each layer was 40 μm for the film layer containing a ferroelectric substance, and 10 μm for the film layer not containing a ferroelectric substance.

This laminated unstretched film was simultaneously biaxially stretched 3x3.5 times at 95°C and heat set at 230°C. When the dielectric constant and dielectric loss tangent of the obtained stretched film were measured, the results were good as shown in Table 2.

Table 2 Measurement temperature 20°C Example 3 SrTi05 70 i [amount %, CaTiO315
weight%.

A mixture of 5% by weight of Mg2Ti0ql was prepared in Example 2.
Blend chips were produced by calcination and pulverization in the same manner as above, and by adding 50% by weight of polyethylene terephthalate.

This blend chip was melted in a heating bath using a single-screw extruder, and T
It was extruded through a die and formed into a film on a cooling roll to form a film with a thickness of 40 μm.

This unstretched film was stretched and set in the same manner as in Example 1. When the performance of the obtained film was measured, the results were good as shown in Table 3.

Procedural amendment $58, 30,000, 30 days; Kazuo Wakasugi, Director General of the Patent Office, Incident Relation to the 1980 Sex License Application No. 9574
Patent application, representative 1991) Yutaka 4, agent 1015 telephone '501-
45521 Number of inventions increased by amendment 7, "Detailed description of the invention" column of the specification subject to amendment
``Film'' and ``or capacitance of piezoelectric element'' in lines 16 and 17 are corrected as ``No Seiden Valley.''

(2) Light opening #3 negative 3rd row 1 or for piezoelectric element
Delete.

-16:

Claims (1)

[Claims] A single or multi-layer thermoplastic polymer film containing (a
) A ferroelectric material combination consisting of strontium titanate alone, or (a) strontium titanate and (b) at least one type of titanate different from stannate, zirconate, or strontium salt of titanic acid. A high dielectric constant film characterized by containing a substance.