JP2797525B2 - Capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized and high-capacity capacitor having excellent heat resistance.

[Prior art] In order to increase the capacitance per volume of a film capacitor, the thickness of a conventional dielectric film has been reduced,
A method of increasing the dielectric constant of a film by mixing a high dielectric constant filler into the film has been adopted. Recently, a method has been developed in which a double-sided metallized film is provided with a dielectric layer having a high dielectric constant, wound and laminated to increase the capacity. JP-A-63-216323 uses a composite dielectric comprising a fine powder ceramic dielectric and polyphenylene oxide.
In -224313, a mixture of a cyanoethylated polymer dielectric and polyphenylene oxide is used as a dielectric.

[Problems to be Solved by the Invention] However, in order to increase the capacity, the thickness of the film is reduced, or a high dielectric constant filler is mixed to increase the dielectric constant because the mechanical properties of the film are deteriorated. There is a limit.
On the other hand, providing a dielectric layer having a high dielectric constant on a film metalized on both sides is a very effective method for miniaturization and large capacity. However, those obtained by the above method have disadvantages such as poor heat resistance and lack of solder resistance, and a large change in dielectric constant when used at high temperatures for a long period of time, resulting in poor reliability. In addition, the capacity per volume is not yet sufficiently high, and in order to further increase the dielectric constant, the mechanical characteristics of the dielectric film-like material are extremely deteriorated, and products cannot be obtained. The demand for higher performance has not yet been answered.

An object of the present invention is to solve the above-mentioned problems and to provide a capacitor which is excellent in heat resistance and can be reduced in size and increased in capacity.

[Means for Solving the Problems] The present invention provides a capacitor formed by providing a dielectric layer on one or both sides of a double-sided metallized film and winding or laminating the film, wherein the film is made of an aromatic polyamide or an aromatic polyimide. The dielectric layer is made of one or more selected polymers, and the dielectric layer is a film made of one or more polymers selected from aromatic polyamide and aromatic polyimide, and an inorganic filler having a high dielectric constant. It relates to a characteristic capacitor.

Sided metallized films of the present invention, or made of a polymer is an aromatic polyamide in the dielectric layer comprises the general formula _{-HN-Ar 1 -NHOC-Ar 2} -CO- In the repeating unit 70 mol% or more represented Is preferred.

Here, Ar ₁ and Ar ₂ contain at least one aromatic ring and may be the same or different, and representative examples thereof include the following.

Also, part of the hydrogen on these aromatic rings are halogen (especially chlorine), a nitro group, an alkyl group of C ₁ -C ₃ (especially methyl), such as alkoxy groups C ₁ -C ₃ Also includes those substituted with a substituent. X represents —O—, —CH _{2
-, - SO 2 -, -} S -, - CO- , and the like. These are included in the form of homopolymer or copolymer.

A polymer having an alkyl group or —CH ₂ — is preferable because the solubility in a polymer solution is higher than that having no substituent and the compatibility with an inorganic filler is improved. For example, And the like containing 50 mol% or more.

Further, the double-sided metallized film of the present invention, or the aromatic polyimide in the dielectric layer is a polymer containing at least one aromatic ring and at least one imide ring in the repeating unit of the polymer, a general formula Or Those containing 70 mol% or more of the repeating unit represented by are preferred.

Here, Ar ₃ and Ar ₅ contain at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar ₃ is derived from an aromatic tetracarboxylic acid or its anhydride. Representative examples include the following.

Here, Y _{is, -O -, - CH 2 -} , - SO 2 -, - S-,
—CO— and the like.

Ar ₅ is derived from tricarboxylic acid or its anhydride.

Ar ₄ and Ar ₆ contain at least one aromatic ring and are derived from aromatic diamines and aromatic diisocyanates. Further, it may contain an amide bond, a urethane bond, or the like. Ar ₄ , A
Typical examples of r ₆ include the following.

Here, some of the hydrogens on these aromatic rings are substituted with substituents such as halogen groups, nitro groups, C _{1 to} C ₃ alkyl groups, and C _{1 to} C ₃ alkoxy groups. Including. Z
_{Is, -O -, - CH 2 -} , - SO 2 -, - S -, - CO- , and the like. These are included in the form of homopolymer or copolymer.

Further, the aromatic polyamide and the aromatic polyimide in the double-sided metallized film of the present invention are blended with a lubricant, an antioxidant, other additives, and other polymers to such an extent that the physical properties of the film are not impaired. Is also good. Further, an inorganic filler having a high dielectric constant as described later may be added.

Furthermore, the aromatic polyamide used for the double-sided metallized film, the aromatic polyimide used for the dielectric layer and the aromatic polyamide used for the dielectric layer and the aromatic polyimide may be the same or different. It is preferable to select a polymer that is hardly affected by the solvent even when applied.

As the inorganic filler having a high dielectric constant used in the present invention, a metal oxide is preferable in consideration of compatibility with a polymer. Specifically, barium titanate, zinc titanate, strontium titanate, titanium calcium oxide, lead titanate, magnesium titanate, titanium oxide,
Barium antimonate, magnesium antimonate, strontium antimonate, calcium antimonate,
Examples thereof include magnesium antimonate, lead antimonate, barium stannate, and strontium stannate, and a composite compound, a solid solution, or a simple mixture thereof may be used.
The shape of the inorganic filler may be spherical, scale-like, nail-like, irregular, etc., and the temporary particle size is such that the thickness of the obtained dielectric layer is 10 μ or less, and these particles have a particle size distribution, Those having a range of from 10 μm to 5 μm are preferable, and those having a range of 20 μm to 2 μm are preferable.

The amount of the filler added depends on the desired dielectric constant, but preferably ranges from 30 to 7000 relative to 100 parts by weight of the polymer.
Parts by weight, more preferably 150 to 5,000 parts by weight. If the amount is less than 30 parts, high capacity cannot be expected and 7000
If the amount is more than 10 parts by weight, the film characteristics will be extremely deteriorated, and it will be difficult to form a dielectric layer. At this time, the dielectric constant of the dielectric layer is preferably 10 to 200. The dielectric loss tangent tan δ (1KHz)
Is preferably 50% or less.

The dielectric breakdown voltage (BDV) is
It is preferably 0.1 KV or more. If it is less than 0.1 KV, it is not practical. More preferably, it is 0.2 KV or more.

For the purpose of further improving the mechanical properties of the film-like material, silane-based, titanate-based, and alumina-based dielectric layers composed of one or more polymers selected from aromatic polyamide and aromatic polyimide, and an inorganic filler having a high dielectric constant. Addition of a coupling agent or a surfactant such as a system may be used without any problem.

The thickness of the dielectric layer of the present invention is preferably 0.1 to 10 μm. 0.1
If it is thinner than μ, the electrical and mechanical properties are poor. If it is thicker than 10 μm, it is not possible to reduce the size. More preferably 0.2-5μ
It is.

The thickness of the double-sided metallized film of the present invention is preferably thinner for the purpose of miniaturization, but preferably 1 to 10 μm,
More preferably, it is 1-5 μm.

The heat shrinkage at 250 ° C. in at least one direction of the film used for the double-sided metallized film of the present invention is preferably 5% or less, more preferably 2% or less, and the strength and elongation are at least one direction. Is preferably 5 kg / mm ² or more and 5% or more, more preferably 8 kg / mm ² or more and 10% or more.
Further, the moisture absorption of the film is preferably 5% or less, more preferably 4% or less. If it is more than 5%, the fluctuation of the dielectric constant due to the humidity increases, which may cause a practical problem.

Next, the method for producing a film-like material of the present invention will be described, but the present invention is not limited thereto.

First, in the case of an aromatic polyamide, from an acid chloride and a diamine, in an aprotic organic polar solvent such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide, a solution polymerization or an aqueous medium is used. It is synthesized by interfacial polymerization or the like. When acid chloride and diamine are used as monomers in a polymer solution, hydrogen chloride is produced as a by-product.To neutralize this, an inorganic neutralizer such as calcium hydroxide or an organic neutralizer such as ethylene oxide is used. Add the agent. The reaction between the isocyanate and the carboxylic acid is performed in an aprotic organic polar solvent in the presence of a catalyst.

These polymer solutions may be used as a stock solution for forming a film as it is, or the polymer may be isolated once and then redissolved in the above solvent to prepare a stock solution. In some cases, an inorganic salt, such as calcium chloride or magnesium chloride, is added as a dissolution aid to the film forming stock solution. The polymer concentration in the film forming stock solution is preferably about 2 to 4% by weight.

On the other hand, a solution of aromatic polyimide or polyamic acid is obtained as follows. That is, polyamic acid is N-
It can be prepared by reacting tetracarboxylic dianhydride with an aromatic diamine in an aprotic organic polar solvent such as methylpyrrolidone, dimethylacetamide and dimethylformamide. The aromatic polyimide can be prepared by heating a solution containing the above-mentioned polyamic acid or adding an imidizing agent such as pyridine to obtain a polyimide powder, which is dissolved in a solvent again. The polymer concentration in the film forming solution is preferably about 5 to 40% by weight.

This film forming stock solution is formed into a film by a so-called solution film forming method. The solution casting method includes a wet-dry method, a dry method,
There are a wet method and the like, but a dry-wet method and a dry method are preferable for obtaining a film having good surface properties. The viscosity at the time of casting is 10
It is preferable to adjust the polymer concentration and temperature of the membrane-forming stock solution so as to be 0 to 10,000 poise.

Here, the viscosity refers to a value measured with a rotary B-type viscometer under the same conditions (concentration and temperature) as at the time of casting.

Casting is performed on a support such as a metal drum or an endless metal belt where the thin film is self-supporting to promote the drying or imidization reaction. At this time, it is necessary to adjust so that the solvent does not suddenly scatter and cause surface roughness, and is generally room temperature to 300 ° C, preferably 50 to 250 ° C.
In less than 60 minutes.

The self-retaining film is peeled off from the support and introduced into a wet bath when a dry-wet process is employed. This bath is generally composed of an aqueous medium, and may contain an organic solvent, an inorganic salt or the like in addition to water. In the bath, the remaining solvent, inorganic salt and imidating agent in the film are extracted.

Further, the film is stretched or relaxed in the longitudinal direction of the film. The film exiting the bath is then dried, stretched, relaxed and heat treated.

 These treatments are generally performed at 100 to 500 ° C.

In the case of the dry method, the self-holding film is generally separated from the support by at least 3 vol.
Drying, stretching relaxation, and heat treatment are performed until the amount becomes less than the weight percent. These treatments are generally performed at 150 ° C to 500 ° C.

As described above, in any of the film forming methods of the dry-wet method and the dry method, stretching or relaxation is performed at an area magnification of preferably 0.8 to 5.0 times, more preferably 1.1 to 3.0 times.
The area magnification refers to the product of the stretching ratio in the film longitudinal direction (MD direction) and the stretching ratio in the width direction (TD direction).

Next, as a method of metallizing a film, a metal thin film is formed by a method such as vacuum deposition, plating, sputtering, or ion plating. Examples of the metal at this time include aluminum, zinc, nickel, and nickel-chromium alloy. Of these, alnium is preferred in terms of vapor deposition properties and characteristics.

Next, the aromatic polyamide used for the dielectric layer, the mixture of the aromatic polyimide and the inorganic filler, before polymerization of the polymer,
The reaction may be performed during or after the polymerization.

The method of applying a mixture of a polymer and an inorganic filler on the aromatic polyamide or aromatic polyimide film is performed by a known method, and includes a gravure coater or a reverse roll coater, a rod coater, an air doctor coater, and the like. It is not limited.

Next, a film provided with a dielectric layer on the film metallized on both sides as described above is wound or laminated, and further provided with an external electrode and a package to obtain a capacitor of the present invention. The change in capacitance before and after the capacitor is immersed in a 260 ° C. solder bath for 30 seconds is preferably 10% or less, more preferably 7% or less.
% Or less. In addition, the withstand voltage change before and after storage in an atmosphere at 150 ° C. for 1000 hours is preferably 10% or less,
It is more preferably at most 7%. Both are not practical for use outside of this range.

[Effect of the Invention] As described above, in the method of providing the dielectric layer on the double-sided metallized film, by using the film and the dielectric having the above composition, a small-sized and high-capacitance capacitor having excellent heat resistance can be produced. . In addition, since the same type of polymer is used for the double-sided metallized film and the dielectric layer, the adhesion between them is excellent, and the adhesion with the metal surface is also good, and the long-term stability is particularly excellent. .

[Evaluation Method of Characteristics] (1) Solder Resistance The sample was immersed in a solder bath at 260 ° C. for 30 seconds, and the change in capacitance before and after was measured.

Capacity change rate (%) = (capacity before immersion−capacity after immersion) /
Capacity before immersion × 100 (2) Long-term heat resistance The sample was stored in an atmosphere at 150 ° C. for 1000 hours, and a change in withstand voltage before and after was measured.

Charge rate (%) = (Dielectric strength before storage−Dielectric strength after storage) / Dielectric strength before storage × 100 [Examples] Hereinafter, the present invention will be described with reference to Examples, but is not limited thereto. is not.

 Table 1 summarizes examples and comparative examples.

Example 1 (1) Production of double-sided metallized film 2-chloro-p-phenylenediamine (CPA), 4,4 '
-An NMP (N-methylpyrrolidone) solution of a polymer synthesized from diaminodiphenyl ether (DAE) and terephthalic acid chloride (TPC) was cast on a stainless steel endless belt and dried with hot air at 150 ° C until it became self-supporting. . The gel film with self-supporting property was continuously peeled off from the belt, then introduced into a water tank to extract the solvent, and further dried and heat-treated in a stenter to a thickness of 2.0 μm. A film was obtained. This film is referred to as Film 1.

(2) Production of dielectric A polymer synthesized from CPA and 2-chloroterephthalic acid chloride (CTPC) is once isolated, dissolved again in NMP at a concentration of 10 wt%, and barium titanate having a particle size of 0.1 μm is solidified. And stirred for 1 hour.
This was diluted so that the polymer concentration became 3% to obtain a coating liquid 1.

(3) Metallization and Formation of Derivative Layer Aluminum was vacuum-deposited on both surfaces of the film-shaped material 1 so that the surface resistance became 2Ω. At this time, vapor deposition was performed in a stripe shape having a margin portion running in the longitudinal direction, and the coating liquid 1 was applied so as to leave the electrode taken out on the vapor deposition.

(4) Production of Wound Body The slit tape was wound on a reel having a diameter of 50 cm.

(5) Production of Capacitor A 5 mm cut-out of this wound body was sprayed with metallikon on both end surfaces to form external electrodes, and a lead wire was connected to the metallikon to obtain a wound capacitor (2.1 μF). The evaluation results of the solder resistance and the long-term heat resistance of this capacitor are shown in Table 1, and the capacitor had good capacitor characteristics.

Example 2 N, N-dimethylacetamide (DMA) of polyamic acid obtained by the reaction of pyromellitic dianhydride (PMDA) with DAE
C) Cast the solution on a stainless steel drum,
And dried by hot air until self-supporting. The gel film with self-supporting properties was continuously peeled off from the drum, led to a 400 ° C stenter, and thermally closed and dried.
A film having a thickness of 5 μm was obtained (film 2). Using this film 2 and coating liquid 1, a capacitor (1.5 μF) was produced in the same manner as in Example 1, and showed good characteristics.

Example 3 CPA, 4,4'-diaminodiphenyl sulfone (DAS) and T
A film 3 (2.5 μm) synthesized from PC, 4,4′-diaminodiphenylmethane (DAM), and a polymer synthesized from CTPC, obtained by adding barium titanate having a particle size of 0.3 μm to a solid content of 70 wt%. Using the coating liquid 2 thus obtained, a capacitor (1.7 μF) was produced in the same manner as in Example 1 and showed good characteristics.

Comparative Example 1 Polyphenylene oxide was dissolved in trichlene at a concentration of 10% by weight, and 0.2% of the solid content was added to this solution at a concentration of 60% by weight.
1 μm of titanium oxide was added to obtain a coating liquid 3.
Using the film 1 and the coating solution 3, a capacitor (2.1 μF) was produced in the same manner as in Example 1. Although the solder resistance and the long-term heat resistance were tested, there was no heat resistance, and neither the capacity nor the withstand voltage could be measured.

Claims (1)

(57) [Claims] A capacitor formed by providing a dielectric layer on one or both sides of a double-sided metallized film and winding or laminating the dielectric layer, wherein the film is made of at least one polymer selected from aromatic polyamide and aromatic polyimide. Wherein the dielectric layer is a film made of at least one polymer selected from aromatic polyamide and aromatic polyimide and an inorganic filler having a high dielectric constant.