JPH11204365A - Dielectric plastic film for capacitor and plastic film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To positively change capacitance of a capacitor against a frequency, by setting content of powder constituting coating, and showing a specified powder frequency characteristic index to be specified weight % against resin. SOLUTION: Porous silica, barium titanate, titanium oxide, barium stannate, calcium carbonate in a range where powder frequency characteristic index is not less than 15% are used as powder contained in the coating layer of a plastic film. When powder is distributed in a resin layer and it is applied on the plastic film, the content of powder is set to be 20-80 weight % against whole application quantity. The surface ratio resistance of the coating layer is set to be not more than 10<12> Ω/(square). The content of organic solvent is to be to 0.1-3.0 ppm and ethyl acetate, methyl ethylketone, methyl isobutyl ketone, toluene, xylene and cyclohexanone exist for organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dielectric polyester film for a capacitor and a plastic film capacitor using the same as a dielectric.

[0002]

2. Description of the Related Art Conventionally, a dielectric film for a capacitor in which a polyester film is provided with a coating layer made of polyester and a capacitor using the same have been disclosed in, for example,
It is known from US Pat. In addition, Japanese Unexamined Patent Publication
Japanese Patent Application Publication No. 3-140511 discloses a film in which a polyester obtained by copolymerizing isophthalic acid is laminated by coextrusion as an exterior film of a capacitor. Conventionally, it has been considered preferable in a film capacitor that a change in capacitance due to an external factor is small. JP 54
Japanese Patent No. -20358 discloses a technique for preventing a decrease in capacitance by forming a structure in which a part or the entire outer periphery of a capacitor element is in contact with a polyurethane resin and the element is cut off from the outside air.

[0005] However, recently, a capacitor corresponding to a frequency has changed in a circuit corresponding to a high-definition television or a wide-vision television.

Heretofore, regarding the capacity of a film capacitor, it has been desirable that the change in the capacity be as small as possible with respect to external factors such as temperature. Therefore, there has been no known technique for positively changing the capacity of the capacitor with respect to the frequency as described above.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dielectric polyester film for a capacitor capable of positively changing the capacitance of the capacitor with respect to the frequency, and a plastic film capacitor using the same as a dielectric. It is something you want to do.

[0006]

As a result of intensive studies to solve the above problems, the present inventors have found that certain powders have a frequency dependence of capacitance when used as a dielectric of a capacitor. It has been found. By using these powders effectively, we have found that film capacitors can be made frequency dependent. That is, a dielectric polyester film for a capacitor coated with a paint in which a powder having a powder frequency characteristic index defined in the specification of 15% or more is dispersed in a resin, and the content of the powder constituting the paint. It has been found that the frequency dependence of the capacity can be made to a sufficient level when the content is 20% by weight or more and 80% by weight or less with respect to the resin.

That is, the above object of the present invention has been industrially advantageously achieved by the present invention described below.

[1] The powder frequency characteristic index defined in the specification is 15 on one side or both sides of a plastic film.
% Or more of a dielectric plastic film for a capacitor coated with a paint obtained by dispersing a powder of at least 20% by weight in a resin, wherein the content of the powder constituting the paint is 20% by weight or more and 80% by weight with respect to the whole dry coating layer. % Or less, which is a dielectric plastic film for capacitors.

[2] The surface resistivity of the coated surface is 1
The dielectric plastic film for capacitors according to the above [1], wherein the dielectric plastic film has a resistivity of 0 ^-10 Ω / □ or less.

[3] The resin according to the above [1] or [2], wherein the resin in which the powder constituting the paint is to be dispersed is a polyester resin having a Tg of 0 ° C. or more and 100 ° C. or less. Dielectric plastic film for capacitors.

[4] The above-mentioned [1] to [1], wherein the paint is applied to both sides of a plastic film.
The dielectric plastic film for a capacitor according to any one of [3].

[5] A plastic film capacitor using the dielectric plastic film for a capacitor according to any one of [1] to [4] as a dielectric.

The powder frequency characteristic index referred to in the present invention is L
When measuring the capacitance with a CR meter, only the powder is filled between the electrodes to measure the capacitance, and the rate of change of the capacitance at a frequency of 10 KHz and the capacitance at a frequency of 30 KHz. It is an index to be shown.

That is, It is.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The base film of the plastic film in the present invention is not particularly limited, but its constituent unit 8
Polyethylene terephthalate in which 0 mol% or more is ethylene terephthalate, polyethylene naphthalate in which 80 mol% or more of its constituent units are ethylene naphthalate, or poly in which 80 mol% of its constituent units is 1,4-cyclohexane dimethylene terephthalate -1,
Preferred are 4-cyclohexane dimethylene terephthalate, polyphenylene sulfide (PPS), aromatic polyamide or Kapton, and particularly preferred are polyethylene terephthalate, polyethylene naphthalate and aromatic polyamide. Examples of the copolymerization components other than the above-mentioned superior components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol and polytetramethylene glycol, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium glycol. Examples include, but are not limited to, dicarboxylic acid components such as dium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and its ester-forming derivatives, and oxymonocarboxylic acids such as oxybenzoate and its ester-forming derivatives. Not something. The polyester film may be blended with titanium oxide, carbon, or the like, or may be blended with silicon oxide, calcium carbonate, or the like for roughening the surface of the film. The melting point of the polyester base film is 255
Desirably higher than ℃.

In general, a plastic film capacitor may be formed by co-winding a metalized film and a resin-coated film, as well as a raw film that is not metallized or coated. In some cases, a polypropylene film may be used in addition to the polyester film.

In the present invention, the thickness of the coating layer is
0.5 μm or more and 20 μm or less, preferably 0.7 μm
Above, it is 15 μm or less. If the thickness is less than 0.5 μm, a sufficiently large change in the capacitor capacity cannot be obtained when the film capacitor is used. Also, 20
If it exceeds μm, there is a disadvantage that the capacitor becomes too large.

The thickness of the base film used in the present invention, that is, the thickness of the plastic film coated with the polyester coating is preferably 2 μm or more and 20 μm or less. If it is 2 μm or less, it is difficult to obtain a sufficient capacitor capacity, and if it exceeds 20 μm, there is a disadvantage that the capacitor becomes too large.

As the resin used for the coating layer in the present invention, polyurethane resins, polyester resins, acrylic resins, olefin resins and the like are preferably used, and polyester resins are preferably used. The Tg of the resin constituting the coating layer is desirably 0 ° C or higher and 100 ° C or lower. When Tg is lower than 0 ° C, blocking tends to occur due to adhesion at room temperature, and when Tg exceeds 100 ° C, the level of adhesion may not be satisfactory. A more preferable range of Tg is 5 ° C or more and 40 ° C or less.

Further, the surface roughness (Ra) of the coating surface is set to 20 to
When the value of PV / Ra is 60 nm and the value of PV / Ra is 15 or less, it is preferable that occurrence of winding deviation and wrinkling does not occur in the step of winding the coated film and the element winding step in the film capacitor manufacturing step. In order to keep the surface roughness Ra and the ratio of the PV value to the Ra within the above preferred range, the average particle diameter of the particles added to the polyester-based coating material is 0.3 μm or more, and the average particle diameter of the particles is further dried and applied. 0.5 to 1.5 times the thickness of the film, or use a burnisher to scrape off the extremely protruding projections on the coating surface. And other means. In addition, the surface roughness of the base film is set to 10
It is preferably in the range of 範 囲 50 nm.

As the powder to be contained in the coating layer of the plastic film of the present invention, it is necessary to select a powder having a powder frequency characteristic index of 15% or more, preferably 30% or more. More preferably 4
0% or more. If the powder frequency characteristic index is less than 15%, the capacity variability with respect to frequency is not sufficient. Examples of the powder having a powder frequency characteristic index of 15% or more include porous silica, barium titanate, titanium oxide, barium stannate, and calcium carbonate. Particularly effective are porous silica and barium titanate. Among them, porous silica is particularly preferred.

The mechanism by which these powders exhibit frequency dependence is not clear, but the complexity of the shape and the degree of distortion of the crystalline or amorphous structure of the powder with respect to changes in the electric field cause frequency dependence. It is considered a factor. Further, a high dielectric constant tends to show such frequency dependence of the capacitance.

In the present invention, the powder having the frequency characteristic index in the range of 15% or more is dispersed in a resin layer and coated on a plastic film. It is necessary that the content be 20% by weight or more and 80% by weight or less. If it is less than 20%, the frequency dependence of the film capacitor will not be exhibited, and if it exceeds 80% by weight, powder drop will easily occur in the film capacitor manufacturing process.

The surface resistivity of the coating layer is preferably 10 ¹² Ω / □ or less. If the surface specific resistance exceeds 10 ¹² Ω / □, even when a powder having a frequency characteristic index of 15% or more is used, when a film capacitor is used, the capacitance variability with respect to frequency may not be exhibited. A more preferred range of the surface resistivity is 10 ⁴ to 10 ¹² Ω /.
□.

The plastic film of the present invention can be brought into close contact with an aluminum vapor-deposited film by low-temperature thermocompression bonding, and the content of the organic solvent in the film is 0.1 ppm or more in order to reduce the occurrence of problems such as blocking. .0
ppm or less, preferably 0.5 ppm or more,
Preferably, the content is 2.0 ppm or less. When the content is less than this range, stable adhesion cannot be obtained, and when the content is large, blocking tends to occur.

Examples of the organic solvent for dissolving the resin used in the coating layer of the present invention include ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene and cyclohexanone. Among them, aromatic solvents such as toluene and xylene are preferred. Are preferred. However, it is not limited to this.

The amount of the organic solvent can be controlled by adjusting the type and amount of the organic solvent used in the paint, the drying temperature after coating, the drying speed, and the like.

As a method for applying the coating material of the present invention to a plastic film, there are provided a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, and the like described in “Coating System”, published by Yuji Harazaki, Maki Shoten, 1979. A method of applying the coating liquid outside the plastic film manufacturing process using a coating device other than the above, or a method of applying the coating liquid within the plastic film manufacturing process.

Further, it is preferable to carry out a calendering treatment after coating, because it has the effect of increasing the degree of filling of the powder or improving the smoothness of the surface.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. .

The physical properties in the examples were measured as follows.

A. Blocking evaluation Ten samples cut into a square of 50 mm were overlapped so that the film surface and the coated surface were in contact with each other, sandwiched with a glass plate, and a load of 1 g / cm ² was applied thereto.
It was left for 7 days. Thereafter, the sealed film was cut into a width of 25 mm, and a force when peeled at a rate of 200 mm / min in a 180-degree direction using a tensile tester was measured, and the measured force was used as an index of the blocking property. If this value is 30 g or less, there is no practical problem, but it is preferably 20 g or less.

B. Capacitance Capacity of Powder and Film Capacitance was measured using an Ando Electric Co., Ltd. AG-4311B LCR meter, using a rectangular aluminum foil of 10 cm × 3 cm as an electrode and a voltage between electrodes of 5 V. The measurement was performed while changing the frequency of the AC voltage between the electrodes to 10 KHz and 30 KHz. The measurement of the capacitor capacity of the powder was performed by filling the powder between the electrodes, and the measurement of the capacitor capacity of the film was performed by sandwiching one film between the electrodes.

Using the capacitance values at 10 KHz and 30 KHz, the frequency characteristic index of the powder and the film was determined according to the following equation.

[0036] [Example 1] Methyl ethyl ketone (hereinafter abbreviated as MEK) 4
0 parts, 40 parts of toluene and 80:20 molar ratio of terephthalic acid and isophthalic acid as polycarboxylic acids, and 60 mol% of ethylene glycol, 30 mol% of triethylene glycol and 10 mol% of neopentyl glycol as glycol components. 120 parts of the copolymerized polyethylene terephthalate copolymer (hereinafter referred to as polyester resin A) were mixed and dissolved at 50 ° C. for 12 hours. This paint stock solution is designated as A. Porous silica manufactured by Suzuki Yuka (average particle size of about 1 μm, S
-149) 100 parts by weight, 60 parts by weight of MEK and 60 parts by weight of toluene were mixed and dispersed in a ball mill, and then 50 parts by weight of a stock solution A was further added to dilute the mixture to prepare a paint B. This paint B was applied to a polyethylene terephthalate film having a width of 1000 mm and a thickness of 6 μm, and a coating thickness of 5 μm.
m, a speed of 50 m / min, an oven temperature of 80 ° C. at the entrance, 140 ° C. at the middle, and an outlet controlled at 100 ° C., using a general reverse roll coater, dried and dried. I got a body.

Example 2 A paint was prepared in the same manner as in Example 1 except that in the dilution step after dispersion, 80 parts by weight of a carbon paste having the following composition was used instead of the paint A as a diluent in the dilution step after dispersion. A dielectric having the physical properties shown in Table 1 was obtained.

Composition of carbon paste Coating A: 25 parts by weight Carbon black (Vulcan Xc-72 manufactured by Cabot Corporation): 45 parts by weight Toluene: 45 parts by weight MEK: 45 parts by weight [Example 3] Porous powder in Example 2 Barium titanate HPBT manufactured by Fuji Titanium Co., Ltd. instead of porous silica
A coating material was prepared and applied in the same manner as in Example 1 except that -1 was used, and a dielectric having the physical properties shown in Table 1 was obtained.

Example 4 6 μm of the paint in Example 3 was used.
m was obtained in the same manner as in Example 3 except that both sides of the polyethylene naphthalate film having a thickness of 4 m were each coated with a thickness of 4 μm. The physical properties are shown in Table 1.

[Comparative Example 1] A dielectric film was obtained in the same manner as in Example 1, except that instead of the porous silica, wet silica thyricia # 450 manufactured by Fuji Silysia was used as the powder. . The physical properties are shown in Table 1.

Comparative Example 2 A coating film was obtained in the same manner as in Example 1 except that the addition amount of the porous silica was changed to 14 parts by weight to obtain a dielectric film.

Table 1 shows the physical properties of this dielectric.

[0043]

[Table 1] As is clear from Table 1, what is within the scope of the present invention is:
It can be seen that the film shows a high film frequency characteristic index, shows a high level of adhesion to the aluminum vapor-deposited film, and hardly causes blocking.

[0044]

The dielectric plastic film for a capacitor in which one or both surfaces of a plastic film is coated with a paint in which a powder having a powder frequency characteristic index defined in the specification of 15% or more is dispersed in a resin. hand,
Since the content of the powder constituting the paint is 20% by weight or more and 80% by weight or less based on the whole dry coating layer,
It is now possible to support circuits for high-definition televisions and wide-vision televisions, which require capacitors whose capacity varies with frequency.

Claims (5)

[Claims] 1. A dielectric plastic film for capacitors comprising a plastic film coated on one or both sides with a coating material in which a powder having a powder frequency characteristic index defined in the specification of 15% or more is dispersed in a resin. hand,
A dielectric plastic film for a capacitor, wherein the content of the powder constituting the paint is 20% by weight or more and 80% by weight or less based on the whole dry coating layer. 2. The coated surface has a surface resistivity of 10 ¹² Ω.
2. The dielectric plastic film for capacitors according to claim 1, wherein the ratio is not more than / □. 3. The capacitor dielectric according to claim 1, wherein the resin in which the powder constituting the coating material is to be dispersed is a polyester resin having a Tg of 0 ° C. or more and 100 ° C. or less. Plastic film. 4. The dielectric plastic film for a capacitor according to claim 1, wherein said paint is applied to both surfaces of a plastic film. 5. A plastic film capacitor using the dielectric plastic film for a capacitor according to claim 1 as a dielectric.