JPS58141221A - 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 strong dielectric composition is prepared by mixing 50- 100wt% calcium titanate with 50-0wt% stannate, zirconate and at least one titanate other than calcium 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, at least 15wt% this strong dielectric composition is added to a thermoplastic polymer (e.g., polyethylene terephalate). The mixture is heated and molten in an extruder, then 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 sensors or pressure-sensitive elements.

Generally, the amount of electrostatic charge in a film capacitor or piezoelectric element is determined by the dielectric constant of the polymer used and the thickness and area of the film. It is at most 5th place,
Some of them, such as fluorine-based compounds, have 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 the total capacitance, but there are limits due to increased cost and workability.
Furthermore, the increase in the area of the film is also restricted by the shape of the capacitor, and as a result, it is 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 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 (a) calcium titanate alone, or (a) calcium titanate and (b) stannate. A ferroelectric substance distribution consisting of at least one type of titanate different from zirconate or calcium salt of titanate? The present invention provides a film for capacitors or pressure elements which increases the dielectric constant but does not increase the dielectric loss tangent.

The present invention will now be described in detail.

Thermoplastic polymers used in the present invention include polyethylene terephthalate, polypropylene, polyethylene, polycarbonate, polyarylate, phoriamite, polyvinylidene fluoride, polysulfone, polyphenylene sulfide, and mixtures and copolymers thereof. Various thermoplastic polymers can be used without being limited to these VCs. Among these, polyethylene terephthalate and polypropylene are particularly preferred in terms of electrical performance, workability, cost, etc.

As mentioned above, when barium titanate is used as the main component of the ferroelectric material in the present invention III, the 14-power ratio can be dramatically increased, but on the other hand, the 11-power dissipation factor is also The dielectric loss tangent increases in accordance with the dielectric loss tangent of the base thermoplastic polymer, and the dielectric loss tangent becomes very low (i?i) compared to the dielectric loss tangent of the base thermoplastic polymer. A compound consisting of at least one type of titanate different from stannate, zirconate, and calcium titanate is used.In the case of calcium titanate alone, the dielectric constant is 160 to 170. , the dielectric loss tangent is 0.02%, and the dielectric constant can be increased without increasing the dielectric loss tangent by adding it to a thermoplastic polymer. However, as a method to further increase the dielectric constant, stannate A method can be adopted in which at least one of titanates different from calcium titanate, zirconate, and titanate is blended with calcium titanate.The amount of these blends is generally 100 to 50% by weight of calcium titanate. The weight ratio is 0 to 50% by weight, but it is not particularly limited.In addition, specific examples of titanates different from stannate, zirconate, and calcium salt of titanic acid include BaSn
O3, Bi, (5nO3)s, Ca5nOs, PbS
nO3, Mg5nOs, 5rSnOs, Zn5nO
s, Ba1rns, CaZr0a, PbZrO3,
MgZrOs, 5rZrOs% ZnZrO3, B
aTiO3, B12(TiOs)3, CoTiO3,P
bTi0. , N1TjO5, MgTiO3, Mg5nO
s, ZnTiO3, Zn2Tto.

Then, it is fired at about 1300°C to form a solid solution and used.
However, these positional additives change the crystal structure of calcium titanate, change the Curie point of calcium titanate, and change the dielectric constant. in general,
When the dielectric constant increases, the dielectric loss tangent also increases, but since the dielectric loss tangent unique to calcium titanate is inherently small,
The dielectric loss tangent is rarely larger than that of the thermoplastic polymer, and even when added to the thermoplastic polymer, the overall dielectric loss tangent is unlikely to 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 is useful for temperature compensation, etc. be able to. Among these, the typical rate decreases, but the rate of temperature change can be made smaller.

The method for incorporating the above-mentioned material containing the ferroelectric substance into a thermoplastic polymer film is to crush the mixture 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 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.

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, the thermoplastic polymer film formed by dissolving or dispersing the thermoplastic polymer in a solution may have a single layer or multiple layers, but the method for forming the entire film is particularly limited. The method is not limited to, and extrusion lamination method, dry lamination method, solution coating method, hot melt coating method, coextrusion method, etc. can be applied.

When the content of the ferroelectric material mixture is high, especially exceeding 40%, or when the stretchability of the thermoplastic polymer is particularly low (
In worse cases, the unstretched film is not stretched and used as a capacitor dielectric, or the thermoplastic polymer layer and ferroelectric material blend containing less than 5% by weight of the ferroelectric material blend. By forming a composite film in which at least one layer is laminated with a thermoplastic polymer layer containing 5% by weight or more of 5% or more of thermoplastic polymer and then stretching it, it is possible to make stretching possible and improve various strengths.

Stretching) Any one of -axial stretching, sequential biaxial stretching, and simultaneous biaxial stretching may be used.

The method for manufacturing the entire capacitor using the obtained capacitor film as a dielectric is not particularly limited, but it is common to apply a manufacturing method for ordinary wound capacitors. 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 CaTiOs powder with an average particle size of 1.5 μm was blended with polyethylene terephthalate chips at 50% by weight, mixed into a twin-screw extruder, and heated and melted and extruded to produce blended chips. The blend chips were melted in a heating bath using a single-screw extruder V (heated bath), extruded through a T-die, and formed into a film on a cooling roll to a thickness of σ4.
To make a 0 μ film, this unstretched film was stretched at 95°C using a simultaneous biaxial stretching machine.
The film was simultaneously biaxially stretched to 3x35 times and heat set at 230°C. When the dielectric loss factor and dielectric loss tangent of the obtained stretched film were measured, the results were very good as shown in Table 1.

Table 1 Measurement temperature 20°C Example 2 CaTiO360% by weight, Mg2TiO440% by weight
After baking at 13oooC for about 3 hours, the mixture was crushed with a hammer mill and ('N vibration mill) to obtain an average particle size of 1.7.
A 9i1i current-visitor substance mixture of μ is made, and this is combined with a twin-screw presser, a calendar roll mixer, and a mixer.
Knead with C polyethylene terephthalate, content 600
Weight % blend chips were produced. This blend chip and the polyethylene terephthalate virgin chip containing no ferroelectric material compound were separately charged into a coextrusion apparatus and extruded from a T-die to produce a laminated unsoot stretched film. The film thickness of each layer was 40μ for the film layer containing a ferroelectric substance, and 10μ for the film layer not containing a ferroelectric substance.

This laminated unstretched film was simultaneously multiplied by 3×35 times at 95°C.
It was axially stretched and subjected to heat celatra at 230°C. When the dielectric constant and dielectric weight tangent of the obtained stretched film were measured,
The results were excellent as shown in Table 2.

Table 2 Procedural amendment March 30, 1980 Director of the Japan Patent Office Kazuo Wakasugi t 1 + f'l indication 1984.1157: + - Patent I No. 8965 No. 3, Relationship to the supplementary iE case Patent Applicant Oka y ji, j', 1-5 Higashihonmachi, Amagasaki City, Hyogo Prefecture
Address 0 lυ1'', (6th name) (450) Unitika Co., Ltd. Representative Hei 1) Yutaka 4, Agent 〒105 Telephone 501-45526
, hL++l: Number of inventions increased by 13+1 from e 7
, The subject of the amendment is the "Detailed Description of the Invention" column in +1l14. 8. Contents of the amendment (1) "Or film for pressure-sensitive elements" in line 14 of page 1 of the specification is changed to "film". Correct "or the capacitance of the piezoelectric element" in lines 16 and 17 with -f: respectively.

(2) Delete "or for piezoelectric elements" in the second and third lines of the third chapter of the specification.

Claims (1)

[Claims] A single layer or several layers of thermoplastic polymer film (a
) A ferroelectric substance combination consisting of calcium titanate alone or (a) calcium titanate and (b) at least one of stannate, zirconate, and a titanate different from a calcium salt of titanate. A film with a high dielectric constant of 1°C, characterized by the fact that it contains M.