JPH079865B2 - Exterior polyester film capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel polyester film capacitor. More specifically, the present invention relates to a polyester film capacitor that does not require an exterior.

[Prior Art] Conventionally, as a packaging method of a polyester film capacitor, a resin dip coating or a resin molding coating in which a capacitor element is wrapped by dipping or molding in a resin, or an adhesive tape is wrapped around the outside of the capacitor element and then sealed with a resin. In general, a tape wrap exterior for stopping, a metal case exterior for enclosing and sealing a capacitor element in a container made of metal or resin, and a resin case exterior are generally adopted.

[Problems to be Solved by the Invention] However, polyester film capacitors are now widely used for electronic devices and the like. For TVR, audio device capacitors, etc., the size and weight of which are being further reduced The accompanying increase in size and weight has become non-negligible, and the conventional externally mounted capacitor cannot sufficiently satisfy such requirements.

Further, in the case of using the resin, the coating or dipping of the resin and the drying and curing of the resin are repeated, so that there is a drawback that the processing step becomes long.

An object of the present invention is to provide a capacitor and an insulating polyester film with an exterior function, thereby reducing the size of the capacitor and omitting the exterior process without deteriorating the electrical characteristics.

[Means for Solving the Problems] The present invention relates to a capacitor in which at least a polyester film layer (A), a thermal adhesive layer (B) and a thin metal layer (C) are laminated and a lead wire is inserted and wound. Arranging the thermal adhesive layer (B) on at least one side of the thin metal layer (C),
Further, the present invention relates to a non-coated polyester film capacitor which simultaneously satisfies the following expressions (I) and (II).

1000 ≦ (Tg1 + Tg2) × (Tm1−Tm2) ≦ 9500 …… (I) D / L ≦ 1500 …… (II) Where, Tg1: Glass transition temperature of polyester film layer (A) (℃) Tg2: Thermal bonding Glass transition temperature of layer (B) (° C) Tm1: Melting point of polyester film layer (A) (° C) Tm2: Melting point of thermal adhesive layer (B) (° C) L: Thickness of thermal adhesive layer (B) (μm) D: Wire diameter of lead wire (μm) The polyester film layer in the present invention is selected from ethylene terephthalate, butylene terephthalate, ethylene naphthalate and arylate, and the unit thereof is 70 mol% or more, preferably 80 mol% or more. Say. Of course, within the above range, various dicarboxylic acid components (for example,
Isophthalic acid, adipic acid, etc.) or a diol component (eg, diethylene glycol, polyethylene glycol, neopentyl glycol, etc.) may be copolymerized. Further, it may be a polymer blend of two or more kinds of the above polyesters or a copolymerized product by an exchange reaction. Among these, a polyester film layer containing polyethylene terephthalate as a main component is particularly preferably used from the viewpoints of balance of electric characteristics, strength, cost performance and the like.

On the other hand, the heat-adhesive layer of the present invention includes a film layer mainly composed of a thermoplastic polymer having excellent electrical properties such as polyester, polypropylene, polyolefin, polyamide, polycarbonate, etc., but a polyester film layer, a thin metal layer and a lead wire. Polyester is preferably used in terms of adhesion with and mechanical properties. In particular, polyester having a solubility parameter similar to that of the dielectric film layer is suitable.

Further, in any of the polyester film layer or the heat-adhesive layer, titanium oxide, calcium carbonate, calcium silicate, barium titanate, calcium sulfate, barium sulfate, calcium phosphate, for the purpose of improving slipperiness and electrical properties, if desired. Aluminum oxide, magnesium oxide,
Inorganic particles such as silica, kaolinite, talc, mica and zeolite can be added.

The polyester film layer (A) and the thermal adhesive layer (B) of the present invention are required to satisfy the following thermal characteristic formula (I). That is, 1000 ≦ (Tg1 + Tg2) × (Tm1−Tm2) ≦ 9500 (I) where, Tg1: glass transition temperature (° C.) of polyester film layer (A) Tg2: glass transition temperature of thermal bonding layer (B) (° C.) Tm1: Melting point of polyester film layer (A) (° C.) Tm2: Melting point of thermal adhesive layer (B) (° C.) More preferably, 3000 ≦ (Tg1 + Tg2) × (Tm1-Tm2) ≦ 8000.

In the formula (I), if (Tg1 + Tg2) × (Tm1-Tm2) (hereinafter, referred to as thermal characteristic parameter) is less than 1000,
Non-uniform adhesion between capacitor element layers causes deterioration of capacitance, insulation resistance and dielectric loss tangent due to moisture absorption in the outside air.
If it exceeds, the durability of the element interlayer adhesive portion is insufficient, and it is adversely affected by environmental temperature changes, ultraviolet rays, harmful gases, and the like.

Further, the polyester film layer and the heat-adhesive layer of the present invention may be laminated at the time of winding, or may be previously formed into a composite film by coextrusion, laminating of a polyester derivative film and a heat-adhesive film, and heat-adhesion to the surface of a polyester dielectric film. Composite lamination may be performed by polymer coating or the like. Further, in addition to the polyester film, a plastic film other than polyester or thin paper may be laminated as a dielectric for the purpose of improving the capacitor characteristics.

The conductive materials used in the present invention include thin metal layers and lead wires. The thin metal layer is a metal foil made of aluminum, tin, zinc, etc. and laminated simultaneously with the polyester film layer and the heat-adhesive layer at the time of winding, or a metal film is previously formed on the surface of the polyester film layer and the heat-adhesive layer by vapor deposition. However, in order to fix the lead wire joined to the thin metal layer without covering it, a thermal adhesive layer must be arranged on at least one side of the thin metal layer. Furthermore, the wire diameter D of the lead wire and the heat-bonding layer (B) are determined by the following fixed characteristic formula (I
It is necessary to satisfy I).

That is, D / L ≦ 1500 (II) where L: thickness of heat-bonding layer (B) (μm) D: wire diameter of lead wire (μm) More preferably, 50 ≦ D / L ≦ 900 is there.

The thickness L of the thermal adhesive layer (B) here is the total thickness of the thermal adhesive layer in contact with each thin metal layer, and the wire diameter of the lead wire is the diameter of the lead wire at the position in contact with the thermal adhesive layer.

If D / L (hereinafter referred to as lead wire fixing parameter) in formula (II) exceeds 1500, the fixing of the lead wire by the thermal bonding layer becomes insufficient, and practical strength against pulling, twisting and bending of the lead wire is obtained. If the lead wire and the thin metal layer are peeled off at the stage of being incorporated into an electronic device or the like, the sheet becomes defective.

The capacitor according to the present invention that does not require an outer package can be manufactured by, for example, the following method, but the invention is not limited thereto. That is, in the conventional metal foil piece polyester film capacitor, the lead wire is inserted between the polyester film and the aluminum foil, and simultaneously wound up,
Taping, hot pressing, epoxy resin for undercoating and resin hardening for exterior packaging,
Then, after finishing resin coating and curing are repeated again, the product is marked. On the other hand, in the case of the capacitor of the present invention which does not require an outer package, a polyester film satisfying the requirements of the present invention, a heat-adhesive layer and an aluminum foil with lead wires inserted and wound up at the same time is higher than the conventional capacitor element 15
A product can be obtained by marking after hot-pressing for 50 to 250 seconds while applying a pressure of 1 to 50 kg / cm ² per pressed area at a temperature of 0 to 210 ° C.

The method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows.

(1) Thermal characteristic parameters The glass transition temperature and melting point used for the thermal characteristic parameters are determined by using a differential scanning calorimeter (DSC) in accordance with the technology for measuring fibers and polymers (edited by the Textile Society of Japan), and a sample of 10 mg is subjected to nitrogen gas flow. The temperature was raised to a melting point + 25 ° C at a heating rate of 16 ° C / min, rapidly cooled to 50 ° C, and measured again with a second run.

(2) Decrease rate of electrostatic capacity After placing the capacitor in an atmosphere of 95% RH at 60 ° C for 500 hours, measure the electrostatic capacity, divide the decrease from the initial capacity by the initial capacity, and multiply by 100% indicate. As a matter of course, the smaller this rate of capacitance decrease, the better the capacitor.

(3) Insulation resistance and dielectric loss tangent After leaving the capacitor in an atmosphere of 95% RH at 60 ° C for 500 hours, the insulation resistance and the dielectric loss tangent were measured according to JIS C5112 to evaluate the moisture resistance of the uncoated capacitor. Naturally, the larger the insulation resistance and the smaller the loss tangent, the better the capacitor.

(4) Lead wire fixability The lead wire fixability was determined by grasping the capacitor so as not to press the lead wire insertion part and measuring the pullout resistance of the lead wire. The pull-out resistance is the maximum resistance per 7 mm of lead wire embedded in the capacitor.

◯: Pullout resistance 4.5 kg or more (particularly preferable in practical range) △: Pullout resistance 3.5 kg or more, less than 4.5 kg (within practical range) X: Pullout resistance less than 3.5 kg (within practical range) (Example) The present invention will be described in more detail by the following examples.

Example 1 Polyethylene terephthalate (Tg1 = 80) having an intrinsic viscosity of 0.65
(° C, Tm1 = 256 ° C) as the inner layer, and laminated on both sides with a thermal adhesive layer of polyethylene terephthalate ([η] = 0.63, Tg2 = 76 ° C. Tm2 = 211 ° C) copolymerized with 17.5 mol% of isophthalic acid. The film extruded from the die was stretched at 90 ° C. in the longitudinal direction by 3.3 times and in the transverse direction by 3.4 times. Then heat-treated at 180 ℃, the total thickness is 6.0μm, and the thickness of the thermal adhesive layer is 1.0 on each side.
A composite film with a thermal property parameter of 7020 in μm was obtained. The resulting 3-layer composite film was micro-slit to a width of 7 mm and laminated alternately with aluminum foil of a width of 4 mm to obtain a wire diameter of 500 μm.
In the hot press process after winding while inserting the lead wire of
We integrally formed it at 200 ℃ for 60 seconds while applying a pressure of 1 Kg / cm ² , and obtained a DC capacitor with a lead wire fixing parameter of 250 and a rated capacity of 1000 PF with no external packaging.

Compared to the conventional resin-dipped exterior product, this capacitor not only made the capacitor volume 75%, but also eliminated the exterior process and made it possible to reduce the length of the capacitor manufacturing process to 1/4. Further, the electrical characteristics such as dielectric breakdown strength, electric capacity, insulation resistance, and their durability were superior to those of the conventional external capacitors.

Comparative Example 1 A single-layer film having a thickness of 6.0 μm and containing only the copolymerized polyethylene terephthalate used for the exterior of Example 1 was formed by the same method. Subsequently, when a capacitor without a sheath was manufactured under the same conditions as in Example 1, the crystal of polyethylene terephthalate and the fine structure of the orientation region were deteriorated by hot pressing, and the electrical characteristics as a film capacitor were deteriorated.

Comparative Example 2 Polyethylene terephthalate copolymerized with 2 mol% of isophthalic acid as the heat-bonding layer of Example 1 ([η] = 0.65, Tg
2 = 79 ℃, Tm2 ＝ 251 ℃)
In the non-exterior capacitor using the composite film of 95, the adhesion between the element layers was uneven and the seal with the outside air was incomplete, so the electrostatic capacity and insulation resistance were significantly degraded at high temperatures and high humidity.

Comparative Example 3 Polyethylene terephthalate copolymerized with 30 mol% of isophthalic acid as the heat-bonding layer of Example 1 ([η] = 0.63, Tg
2 = 71 ° C., Tm2 = 179 ° C.) and the film was formed under the same conditions as in Example 1 except that heat treatment was performed at 150 ° C.
627 composite films were obtained. The adhesive seal part of the non-exterior capacitor using this film had low durability against heat, moisture, ultraviolet rays and harmful gas, and had a high short circuit failure rate during long-term use.

Example 2 Polybutylene terephthalate ([η] = 0.8) was used as a heat-bonding layer on both surfaces of the polyester base layer shown in Example 1.
9, Tg1 = 35 ° C., Tm1 = 225 ° C.) was compounded by a coextrusion method, and after forming a film under the same conditions as in Example 1, a capacitor was also processed under the same conditions. The obtained unpackaged capacitor was compact and lightweight and had excellent electrical characteristics.

Example 3 Isophthalic acid 1 was added onto a polyethylene terephthalate film ([η] = 0.64, Tg1 = 80 ° C., Tm1 = 256 ° C.) having a thickness of 4 μm so that the coating thickness after drying was 1.5 μm.
A water-soluble polyester copolymerized with 2.5 mol% and sodium sulfonate of 12.5 mol% is coated on one side as a thermal adhesive layer, dried in hot air at 130 ° C., and has a total thickness of 5.5 μm and a thermal composite parameter of 9372. Got Further, this film processed into a capacitor with a lead wire fixing parameter of 333 and a rated capacity of 10,000 PF under the same conditions as in Example 1 has a small change in electric capacity and insulation resistance, has few failures, and is highly reliable. there were.

Example 4 25 μm thick polyethylene terephthalate film ([η] = 0.64, Tg1 = 80 ° C., Tm1 = 256 ° C.) aluminum foil and isophthalic acid were copolymerized at 117.5 mol% to a thickness of 2 μm.
m polyethylene terephthalate ([η] = 0.63, Tg2
= 76 ° C., Tm2 = 211 ° C.) are laminated in this order, and a lead wire plated with solder having a wire diameter of 1600 μm is inserted and wound, and then the same processing conditions as in Example 1 are used.
A 00PF uncoated capacitor was manufactured. The obtained capacitor has a thermal characteristic parameter of 7020, a lead wire fixing parameter of 800, and the seal between the element layers and the fixing of the lead wire are sufficient, so the capacitance reduction rate is small and the short circuit failure rate is the same as the conventional resin dip exterior product. Was excellent.

Comparative Example 5 A capacitor having a thermal characteristic parameter of 7020 and a lead wire fixing parameter of 1600 was produced under the same conditions except that the thickness of the thermal adhesive film of Example 4 was 1 μm. This capacitor was inferior in fixing and holding the seed wire, resulting in frequent short circuits between the aluminum foil and the lead wire joint.

[Advantages of the Invention] With the structure of the present invention, it is possible to easily obtain a small-sized and lightweight non-packaged capacitor, and such a capacitor has a variation in insulation resistance, a capacitance under a high temperature and high humidity atmosphere, a dielectric breakdown strength, and a dielectric loss tangent. , Insulation resistance change is small and failure is extremely small. Further, since the exterior process can be omitted, the space that is substantially occupied by the capacitor manufacturing process can be reduced, and the productivity can be greatly improved and the cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an embodiment of an uncoated polyester film capacitor according to the present invention, and FIGS. 2 (a) to (h) are sectional views of a capacitor laminated portion of the present invention. 1: Polyester film layer (A) 2: Thermal adhesive layer (B) 3: Thin metal layer (C) 4: Dielectric layer other than polyester film 5: Lead wire

Claims (1)

[Claims] 1. A capacitor obtained by laminating at least a polyester film layer (A), a heat-bonding layer (B) and a thin metal layer (C) and inserting a lead wire and winding the laminated thin film layer (C). The thermal adhesive layer (B) on at least one side of
An uncoated polyester film capacitor which simultaneously satisfies the following formulas (I) and (II). 1000 ≦ (Tg1 + Tg2) × (Tm1−Tm2) ≦ 9500 …… (I) D / L ≦ 1500 …… (II) Where, Tg1: Glass transition temperature of polyester film layer (A) (℃) Tg2: Thermal bonding Glass transition temperature of layer (B) (° C) Tm1: Melting point of polyester film layer (A) (° C) Tm2: Melting point of thermal adhesive layer (B) (° C) L: Thickness of thermal adhesive layer (B) (μm) D: Lead wire diameter (μm)