JPS5915340B2 - High dielectric constant film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor film with significantly improved dielectric constant.

In general, the capacitance of a film capacitor is determined by the dielectric constant of the polymer used and the thickness and area of the film ζ The dielectric constant of the polymer used is usually at most 5th in the case of organic polymeric materials. Some of them, such as fluorine 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 capacitance, but there are limits due to increased cost and workability, and there are even restrictions on increasing the area of the film due to 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. When used for AC applications, etc., there were problems such as heat generation, which needed to be improved. 10 As a result of considering these problems, the present invention has developed a monolayer or multilayer thermoplastic polymer film containing (a) calcium titanate alone, or (a) calcium titanate and (b) stannate. For capacitors that increase the dielectric constant and do not increase the dielectric loss tangent by containing a ferroelectric material compound consisting of at least 15 types of titanates different from calcium salts of titanate, zirconate, and titanate. It provides film.

The present invention will be explained in detail below. 20 Thermoplastic polymers used in the present invention include polyethylene terephthalate, polypropylene, polyethylene, polycarbonate,
polyarylate, polyamide, polyvinylidene fluoride,
Examples include polysulfone, polyphenylene sulfide, etc., or mixtures and copolymers thereof.
Various thermoplastic polymers can be used without being limited to these.

Among these, polyethylene terephthalate and polypropylene are particularly preferred in terms of electrical performance, workability, cost, etc. 30 As mentioned above, when barium titanate is the main component of the ferroelectric material in the present invention, the dielectric constant can be dramatically increased, but on the other hand, the dielectric loss tangent also increases in accordance with the dielectric constant. However, compared to the dielectric loss tangent of the base thermoplastic polymer, the dielectric loss tangent takes on an extremely large value of 35.

In order to prevent this, in the present invention, calcium titanate alone or calcium titanate and stannate, zirconate, etc.
A formulation comprising at least one titanate different from the calcium salt of titanic acid is used.
In the case of calcium titanate alone, the dielectric constant is 160 to 1.
70, the dielectric loss tangent is a value of 0.02%, and the dielectric constant can be increased without increasing the dielectric loss tangent by adding it to a thermoplastic polymer. As a method of further increasing the dielectric constant, stannate , zirconate, and a titanate different from the calcium salt of titanate can be mixed with calcium titanate. The amount of these compounds is generally 0 to 50% by weight based on 100 to 50% by weight of calcium titanate, but is not particularly limited. Also, stannate,
Specific examples of titanates different from calcium salts of zirconate titanate include BasnO3, Bi2 (SnO
3) 3, CasnO3pbsnO3, MgsnO3, S
rsnO3, ZnsnO3, BazrO3, CazrO
3, PbzrO3, MgzrO3, SrZrO,, Zn
zrO3, BaTlO3, Bi2(TiO3),, CO
TlO3, PbTlO3, NiTiO3, MgTiO3
, MgTlO4, ZnTiO3, Zn2TiO4, etc. (but not limited to these) These blended additives are added to calcium titanate and then heated to about 1300°C.
(These additives change the crystal structure of calcium titanate, change the cue point of calcium titanate, and change the dielectric constant. Generally, When the dielectric constant increases, the dielectric loss tangent also increases, but since the dielectric loss tangent unique to calcium titanate is originally small, it is unlikely to become larger than the dielectric loss tangent of the thermoplastic polymer. However, the total dielectric loss tangent is rarely increased.
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. Can be done. Among these, a typical combination is a combination of CaTiO3 and Mg2TlO4. In this case, the dielectric constant decreases by increasing Mg2TiO4, but the temperature change rate can be reduced. As a means of incorporating the above-mentioned ferroelectric substance-containing compound into a thermoplastic polymer film, the 4-round compound was crushed into a powder of several μm in size, mixed with a thermoplastic polymer, and melt-extruded 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 extruder, calender roll, etc., but the method is not particularly limited to these. isn't it. 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 have a single layer or multiple layers, but the average content of the ferroelectric substance compound in the entire film should be 1.
5% by weight or more is desirable.

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 material 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. (or at least one layer each of a thermoplastic polymer layer containing less than 5% by weight of a ferroelectric material blend and at least one layer of a thermoplastic polymer containing less than 5% by weight of a ferroelectric material blend) By forming such a composite film into a shape and then stretching it, stretching becomes possible and various strengths can be increased.

The stretching method may be uniaxial 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.

That is, after microslitting the above film,
A capacitor can be made by stacking it with aluminum foil and winding it, or by applying metal vapor deposition on one or both sides of the above film in the form of a band, micro-slitting it, and winding it. Alternatively, it can be manufactured in the form of a multilayer capacitor. That is, the above-mentioned vapor-deposited film is laminated without any treatment or after coating the surface with hot melt adhesive,
This is a method of cutting into small chips and integrating them. Hereinafter, this will be described in detail with reference to Examples.

Example 1 CaTiO3 powder having an average particle size of 1.5 μm was blended with polyethylene terephthalate chips in an amount of 50% by weight, mixed into a twin-screw extruder, and heated and melt-extruded to produce blended chips.

This blend chip is heated and melted 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 simultaneously biaxially stretched to 3x3.5 times at 95°C using a simultaneous biaxial stretching machine.
Heat setting was performed 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 A mixture of CaTi03wt% and Mg2TiO44O wt% was calcined at 1300°C for about 3 hours, and then ground in a hammer mill and a vibration mill to produce a ferroelectric material composition with an average particle size of 1.7μ. Uses a twin-screw extruder, calendar roll kneader, and mixer together. The mixture was kneaded with polyethylene terephthalate to produce blend chips with a content of 60% by weight.

This blend chip and polyethylene terephthalate virgin chips containing no ferroelectric material compound were separately placed into a coextrusion device and extruded from a T-die. A laminated unstretched film was prepared. The film thickness of each layer was 40 μm for the film layer containing a ferroelectric substance, and 0 μm for the film layer not containing a ferroelectric substance. This laminated unstretched film was simultaneously biaxially stretched to 3x3.5 times at 95°C and heat set at 230°C.

Claims (1)

[Claims] 1 A single layer or multiple layers of thermoplastic polymer film,
A ferroelectric material consisting of (a) calcium titanate alone, or (a) calcium titanate and (b) at least one type of titanate different from stannate, zirconate, or calcium salt of titanate. A high dielectric constant film characterized by containing a substance combination.