JP2000021681A - Dielectric polyester film for capacitor and polyester capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric polyester film for a capacitor that does not cause blocking, and to further provide a capacitor using the dielectric polyester film. SOLUTION: In this dielectric polyester film for a capacitor, a surface or both surfaces of the polyester film are coated with polyester paint. A polyester resin forming the polyester paint has a Tg between 0 and 40 deg.C and an average molecular weight between 1,000 and 17,000 (referred to as a polyester resin A). For the surface roughness, the coated layer surface of the polyester resin has a surface roughness (Ra) between 20 and 60 nm at the center line, and a P-V value is not more than 15 times the Ra.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric polyester film for a capacitor and a 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
In JP-A-3-140511, a film in which a polyester obtained by copolymerizing isophthalic acid is laminated by co-extrusion is known as a film for exterior of a capacitor.

[0003] Aluminum deposited film and polyester coating film (dielectric film for capacitors)
Are alternately wound, it is necessary to completely adhere the two types of films. In other words, the improvement of the adhesion between the aluminum-deposited film and the film coated with the polyester resin prevents the impregnating agent such as epoxy resin from infiltrating into the aluminum-deposited surface after being wound, and improves the yield of the final product and the capacitor. Is to improve the service life.

In general, in order to improve the adhesion, the softening point of the coating material to be coated should be as low as possible.
A method of thermocompression bonding at 00 ° C. to 200 ° C. is used. For this purpose, a polyether-based coating obtained by copolymerizing various dicarboxylic acid components and glycol components is used.

[0005] However, in the prior art, even when the temperature is increased at the time of thermocompression bonding, a sufficient adhesion cannot be obtained, and the performance of the product is degraded. Also, after coating with paint, if left at room temperature for a long time, blocking phenomenon often occurs between the polyester resin coating layer and the polyester base film, or between the polyester resin coating layers when applied on both sides of the base film. It is causing trouble.

Further, when the polyester film is coated on both sides of the base film, the step of impregnating the epoxy resin or the like can be omitted. However, in the conventional paint, the performance such as withstand voltage is inferior to that of the resin-impregnated capacitor.
The main reason is that when the coated surface of the polyester coating film and the uncoated polyester are wound, slippage between the two is poor and voids are easily formed between the two.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to have a high adhesion to an aluminum vapor-deposited film by thermocompression bonding at a low temperature, and to apply the film between a polyester resin coating layer and a polyester base film or on both sides of a base film. In addition to providing a capacitor dielectric polyester film that does not cause a blocking phenomenon between the polyester resin coating layers, when sliding the coated surface of the polyester coating film and the uncoated polyester, slippage between both will occur. It is an object of the present invention to provide a capacitor using the dielectric polyester film for a capacitor.

[0008]

As a result of investigations to solve the above problems, the present inventors have determined that the structure and composition of the polyester resin, which is the main component of the polyester-based coating, can be controlled at a low temperature by controlling the specific range. High adhesion is obtained by thermocompression bonding,
Further, they have found that an effect of preventing blocking during storage can be obtained. That is, the Tg of the polyester resin A constituting the polyester coating applied on one or both sides is 0 ° C. or more and 40 ° C. or less and the average molecular weight is 10,000.
Not less than 170,000 and the surface roughness of the coated surface (Ra)
20 to 60 nm and a value of PV / Ra of 15 or less to enhance the adhesion between the capacitor dielectric film and the aluminum vapor-deposited film and minimize the change in capacitance when the film capacitor is used. Can be
In addition, the inventors have found that the breakdown voltage can be increased, and that the winding disturbance during the winding of the element can be prevented.
That is, the above-mentioned object of the present invention has been industrially advantageously achieved by the following present invention.

[1] A dielectric polyester film for a capacitor in which one or both surfaces of a polyester film are coated with a polyester-based paint, wherein the polyester resin constituting the polyester-based paint has a Tg of 0 ° C. or more and 40 ° C. or less; Average molecular weight of 1,000 or more 17
000 or less (referred to as polyester resin A), the surface roughness of the coating layer of the polyester resin is 20 to 60 nm in center line surface roughness (Ra), and the PV value is 15 times or less of Ra. A dielectric polyester film for capacitors, characterized by the following.

[2] The dielectric polyester film for a capacitor according to the above [1], wherein the polyester resin constituting the polyester resin paint has a Tg of 5 ° C. or more and 35 ° C. or less.

[3] Polyester B having a Tg of more than 40 ° C. and an average molecular weight of 18,000 or more and 40,000 or less is used in combination with the polyester-based paint,
The dielectric polyester film for a capacitor according to the above [1] or [2], wherein the constituent molar ratio of the polyester resin A is larger than the constituent molar ratio of the polyester resin B.

[4] A dielectric polyester film for capacitors, wherein the polyester-based paint described in any one of [1] to [3] is applied to both sides of a polyester film.

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

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The polyester base film of the dielectric polyester film for a capacitor in the present invention is not particularly limited, but polyethylene terephthalate whose constituent unit is at least 80 mol% of ethylene terephthalate,
Polyethylene naphthalate in which 80% by mole or more of the structural unit is ethylene naphthalate, or poly-1,4-cyclohexane dimethylene terephthalate in which 80% by mole of the structural unit is 1,4-cyclohexane dimethylene terephthalate. Is particularly preferable, and polyethylene terephthalate is particularly preferable. Examples of the copolymer 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;
Dicarboxylic acid components such as 6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and its ester-forming derivatives, and oxymonocarboxylic acids such as oxybenzoate and its ester-forming derivatives. But are not limited to these. 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. Desirably, the melting point of the polyester base film is higher than 255 ° C.

In the present invention, it is preferable that the surface roughness of the base film is in the range of 10 to 50 nm so that the surface roughness of the coating film falls within the scope of the first aspect.

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.

The thickness of the polyester base film used in the present invention, that is, the polyester film coated with the polyester-based paint is preferably 2 μm or more and 20 μm or less. If it is less than 2 μm, 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.

The polyester paint in the present invention is:
It is a paint made of a polyester resin, and the Tg of the polyester resin A constituting the polyester resin is 0 ° C. or more and 40 ° C.
° C or less and the average molecular weight is 10,000 or more and 1700 or less.
00 or less, and the surface roughness (Ra) of the coated surface is 20 to 6
It is necessary that 0 nm and the value of PV / Ra be 15 or less. If the Tg is lower than 0 ° C., blocking tends to occur due to adhesion at room temperature, and if the Tg exceeds 40 ° C., the level of adhesion is not satisfactory. A more preferable range of Tg is 5 ° C. or more and 35 ° C. or less. If the average molecular weight is less than 10,000, the coating film has high tackiness and tends to cause blocking. On the other hand, when the average molecular weight exceeds 17000, the fluidity of the coating film at a high temperature is reduced, and voids are easily generated at the time of thermocompression bonding. As a result, the withstand voltage characteristics of the film capacitor may be reduced, which is not preferable.

In the present invention, the center line surface roughness (Ra) of the polyester resin coating film surface to be coated on one or both surfaces of the polyester film is 20 to 60 nm and the value of PV / Ra is 15 or less. There is a need to. By keeping the surface shape of the polyester resin coating film surface within the above range, it is possible to minimize the change in capacitance when the film capacitor is used, and to increase the breakdown voltage, and in the film capacitor manufacturing process. In the element winding step, winding disturbance can be prevented.

Center line surface roughness Ra, PV value and Ra
In order to make the ratio within the range of the present invention, the average particle diameter of the particles to be added to the polyester-based paint is 0.3 μm or more, and the average particle diameter of the particles is 0.5 to 1.times.
Means may be taken such as increasing the size to 5 times, or using a burnisher to scrape off the extremely protruding projections on the coating surface, or crushing the projections on the coating surface that protrude extremely high with a calender roll. Further, the surface roughness of the base film is preferably in the range of 10 to 50 nm.

It is desirable that 60 mol% or more of the dicarboxylic acid component of the polyester resin constituting the polyester resin is an aromatic carboxylic acid having a benzene ring. In the present invention, the ratio of ethylene glycol in the diol component of the polyester resin is 30.
It is desirably about 90% by mole. In addition, components other than the above-mentioned glycol component may be copolymerized or blended as necessary. However, the range of copolymerization and blending amount which does not deviate from the present invention is usually 5 to the total weight of the dry coating film. % Or less.

The polyvalent carboxylic acid constituting the polyester resin in the present invention includes terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid,
6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-
Sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid,
Succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium trimellitic acid and their ester-forming derivatives and the like can be used. Is ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentadiol, 4-cyclohexanedimethanol, p-xylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol Dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolesulfonate, potassium dimethylolpropionate, and the like. From these compounds, one or more can be appropriately selected, and the polyester resin can be synthesized by a conventional polymerization reaction. However, when the ratio of the aromatic carboxylic acid is less than 60 mol%, the polyester base film is formed. This is not preferred because the adhesiveness with the adhesive may decrease. Also, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid,
Aliphatic carboxylic acids such as succinic acid are also preferably used, but since the Tg of the polyester resin is limited to a range of 0 ° C. or higher, the copolymerization amount is substantially less than 40 mol%.

In the present invention, these polyester resins may be blended and used as required. Also,
When blocking resistance is particularly required, Tg is 40 ° C.
Above the polymer is blended to the extent not beyond the scope of the invention. In this case, the molecular weight of the polymer to be blended is 1
The molecular ratio of the polymer to be blended is preferably lower than the molar ratio of the polymer having Tg of 40 ° C. or lower. If the molecular weight of the polymer having a Tg of more than 40 ° C. is less than 18,000, the effect on the blocking resistance is not remarkably obtained, and if the molecular weight exceeds 40,000, the viscosity of the coating liquid is liable to increase. Is not preferred because it becomes difficult.

The coating material to be coated preferably contains calcium carbonate, silicon oxide, aluminum oxide or the like having an average particle diameter of 1 μm or less, in an amount of 1% by weight or more and 20% by weight or less based on the polyester resin, preferably 2% by weight. Above, 15
% By weight or less is more preferred. The purpose of blending these additives is to improve the anti-blocking effect. By blending these additives, a polyester resin having a lower softening point can be used. If the amount is less than 1% by weight,
If the blocking effect is insufficient, and if it exceeds 20% by weight, the secondary aggregated particles increase, the coated surface becomes rough, and the adhesion performance is reduced.

The polyester film coated with the polyester-based paint of the present invention can be brought into close contact with an aluminum vapor-deposited film by low-temperature thermocompression bonding to reduce the incidence of problems such as blocking. The concentration is preferably 0.1 ppm or more and 3.0 ppm or less, more preferably 0.5 ppm or more and 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 polyester resin used in 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 preferable. 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 coating material, 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 polyester film, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater or the like other than those described in “Coating System”, published by Yuji Harazaki, Maki Shoten, 1979, are used. Using a coating device of
A method of applying the coating solution outside the biaxially stretched polyester film manufacturing process, or a method of applying the coating solution within the film manufacturing process may be used.

The coating of the present invention may be applied on only one side of the polyester film, and the coating amount is 0.1 g / m ^2.
As described above, the content is preferably 1.0 g / m ² or less.
More preferably, it is 3 g / m ² or more and 0.8 g / m ² or less. When the coating amount is less than 0.1 g / m ^2, it is difficult to obtain a uniform coating amount, so that not only the coating unevenness is likely to occur on the product, but also the adhesive strength tends to decrease, and 1.0 g / m ^2.
If it exceeds m ² , not only the adhesion strength is saturated, but also blocking tends to occur, which is not practical. The present invention is to improve the adhesion between a polyester film coated with a polyester film-based paint and a metallized dielectric film, but the metallized dielectric film used in the present invention is a general polyester film. It is a film on which metal is deposited, and the metal to be deposited is aluminum, palladium, zinc, nickel, gold,
Silver, copper, indium, tin, chromium, titanium and the like can be mentioned, and the most preferred metal is aluminum (Al). The thickness of the metal deposition film is preferably in the range of 10 to 5000 angstroms. The method of vapor deposition is generally a vacuum vapor deposition method, but may be a method such as an electroplating method or a sputtering method. In addition, the metal deposition layer may be provided on both sides of the polyester film.

The present invention is to improve the adhesion between a polyester film coated with a polyester paint and a metallized dielectric film.
The two films are superposed so that the metallized surface and the paint-coated surface are in contact with each other to form a pair, which is wound to form a capacitor element. The capacitor element can be made into a capacitor by performing, for example, hot pressing, taping, metallikon, voltage treatment, sealing at both ends, attaching lead wires, etc., according to a standard method.
However, it is not limited to these.

Further, the polyester paint of the present invention can be suitably applied to both sides of a polyester film. In this case, the thickness of the polyester-based coating film (coating A) to be adhered to metal deposition or metal foil is 0.1 μm.
m or more and 1.0 μm or less, and a polyester film (coating B) to be adhered to a polyester film or a polypropylene film on a surface opposite to one surface of the polyester film provided with the polyester resin coating. ) Is provided, and it is desirable that the thickness of the coating film B is 0.2 μm or more and 2 μm or less and larger than the thickness of the coating film A.

By doing so, the metal deposition surface,
It is possible to improve all the adhesion to the metal foil surface or the raw polyester film surface.

The polyester resin constituting the coating film A to be adhered to a metal film or a metal foil has an average molecular weight of 10,000 or more and 17000 or less, and the polyester film on which the polyester resin coating film A is provided. The polyester resin constituting the polyester resin-based coating film B to be adhered to the polyester film or the polypropylene film provided on one surface opposite to the one surface has an average molecular weight of 19000 or more and the polyester resin constituting the coating film A Is desirably larger than the average molecular weight. By doing so, the slipperiness between the coating surface and the raw polyester film surface can be improved, and as a result, voids are less likely to be formed between the two.

[0034]

The present invention will be described in more detail with reference to the following examples. In addition, the physical property in an Example was measured as follows.

A. Glass transition point of polyester resin (T
g) Measurement was performed using a differential scanning calorimeter (DSC) according to the technique of measuring fibers and polymers (edited by the Society of Fiber Science and Technology).

B. Adhesive strength of film 50m wide film coated with polyester paint
m, cut to a length of 200 mm. On the coating layer side of this film, an aluminum vapor-deposited film also cut into a width of 50 mm and a length of 200 mm was superimposed, and the temperature was set at 120 ° C. ±
On a 2 ° C flat hot plate, 1 with a 2100 g silicone rubber roll
After thermocompression bonding the sample at a speed of 00 mm / min, the sample width is 25 m
m and a universal pulling tester, pulling speed 300m
/ Min was measured for adhesion.

C. 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.

D. Surface Roughness (Ra, PV) Measurement was performed using a non-contact type surface shape measuring instrument (manufactured by WYKO Corporation) under the following measurement conditions. Measurement area: 230 μm × 230 μm An average value of n = 5 was determined.

E. Withstand voltage characteristics Sheet BVD (dielectric breakdown voltage) was measured according to JIS-2110. A 100 μm-thick 10 cm square aluminum foil electrode was used for the cathode, and a brass 25 mmφ, 500 g electrode was used for the anode. A film was sandwiched between the electrodes, and a high-voltage DC power supply was applied while increasing the pressure at a rate of 100 V / sec. The case where the above current flowed was regarded as the breakdown, and this was measured ten times and indicated by the voltage of the average value.

Example 1 Methyl ethyl ketone (hereinafter M
40 parts, toluene 37 parts, average particle size 0.4μ
m, 3 parts of calcium carbonate and terephthalic acid and isophthalic acid in a molar ratio of 80:20 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. Toluene and xylene were added to this coating stock solution, and a coating thickness of 0.5 μm was applied to a 12 μm polyester film having a width of 1000 mm at a speed of 100 m / min. The oven temperature was controlled to 80 ° C. at the entrance, 140 ° C. at the middle and 100 ° C. at the exit. Using a general gravure coater, coating and drying were performed to obtain dielectrics having physical properties shown in Table 1.

Example 2 The Tg of the polyester resin in Example 1 was substantially unchanged and the coating thickness was 0.4 μm.
A paint was prepared in the same manner as in Example 1 except that
Application was performed.

Example 3 The polyester resin A in Example 1 was prepared using terephthalic acid as a polyvalent carboxylic acid and a resin containing 60 mol% of ethylene glycol and 40 mol% of triethylene glycol as a glycol component. Example 1 except that the values shown in Table 1 were obtained.
A coating material was prepared and applied in the same manner as described above.

Examples 4 and 5 In Examples 4 and 5, terephthalic acid (50 mol%) and isophthalic acid (50 mol%) were used as the polyester resin B for 100 parts of the same polyester resin A as in Examples 2 and 3, respectively. Coating was carried out in the same manner as in Examples 2 and 3, except that 20 parts of a copolymer of (50 mol%) ethylene glycol (50 mol%) and neopentyl glycol (50 mol%) were blended.

Comparative Example 1 The average particle size of calcium carbonate added to the polyester-based paint in Example 1 was 1.4.
The coating was performed in the same manner as in Example 1 except that the coating thickness was set to 1.0 μm and the coating film thickness was set to 1.0 μm.

Comparative Example 2 In Example 1, terephthalic acid and adipic acid were used as the polycarboxylic acid constituting the polyester resin in a molar ratio of 50:50 and a molecular weight of 16,000.
The coating was performed in the same manner as in Example 1 except that the above conditions were satisfied.

Comparative Example 3 A coating was performed in the same manner as in Example 1 except that the polyester B was used alone as the polyester resin A.

Table 1 shows the physical properties of these dielectrics.

[0048]

[Table 1] It can be seen that all of those within the scope of the present invention show a high level of adhesion to the aluminum deposited film and are less likely to cause blocking.

[Example 6, Example 7, and Comparative Example 4]
A polyester film for a dielectric was obtained in the same manner as in Example 1, except that the coating material of Example 1 was applied to both surfaces of the polyester base film at the application thickness shown in Table 2 (A layer, B layer). Comparative Example 4 was performed in the same manner as in Comparative Example 1 except that the paint of Comparative Example 3 was applied to both surfaces of the polyester base film at the application thickness shown in Table 2 (A layer, B layer). A film was obtained.

Example 8 The procedure of Example 7 was repeated except that the polyester paint used in Example 2 was used as the coating for the coating layer (layer B) having a thickness of 1 μm. Was done.

Table 2 shows the physical properties of these dielectrics. In this table, in evaluating the adhesion of the layer B, the center line surface roughness (Ra) was used instead of the aluminum vapor-deposited film.
Was performed using a raw polyester film of 50 nm. Also, after winding the coating film for dielectric and the raw polyester film, 10-6To under reduced pressure.
Perform air void elimination treatment for 8 hours under the conditions of rr and 40 ° C., then gradually raise the temperature to 120 ° C. under reduced pressure at 10-3 Torr and heat treatment at 120 ° C. for 2 hours. Was evaluated visually.

[0052]

[Table 2] Any of those within the scope of the present invention exhibit a high level of adhesion to an aluminum vapor-deposited film, have excellent adhesion to a raw polyester film, and can also reduce the area of voids on the bonded surface of the polyester film. I understand.

[0053]

According to the dielectric polyester film for a capacitor in which one or both surfaces of a polyester film are coated with a polyester coating, the polyester resin A constituting the polyester coating has a Tg of 0 ° C. or more and 40 ° C. or less and an average molecular weight. Is 10,000 or more 17
000 or less, and the surface roughness (Ra) of the coated surface is 20 to
By setting the value of 60 nm and the value of PV / Ra to 15 or less, the adhesion between the capacitor dielectric film and the aluminum vapor-deposited film can be increased, and the change in capacitance when the film capacitor is used can be minimized. In addition, the breakdown voltage can be increased, and furthermore, winding disturbance during element winding can be prevented.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshihisa Kinashi 33-1 Nagafushi, Mishima-shi, Shizuoka Pref. F-term (reference) in the Mishima Plant of Toyo Metallizing Co., Ltd. CC01C DA20 DD07C EH66 EJ17 EJ42 GB41 JA05A JA05C JA07A JA07C JG05 JK14A JL11 YY00A YY00C 5E082 AB04 BC14 BC35 EE03 EE07 EE08 EE23 EE24 EE37 FF14 FF15 FG06 FG22 BB36 AB02 PP23 BB04

Claims (5)

[Claims] 1. A dielectric polyester film for a capacitor in which one or both surfaces of a polyester film are coated with a polyester-based paint, wherein the polyester resin constituting the polyester-based paint has a Tg of 0 ° C. or more and 40 ° C. or more.
° C or lower and the average molecular weight is 1000 or more and 17000
Below (referred to as polyester resin A), the surface roughness of the coating layer of the polyester resin is 20 to 60 nm in center line surface roughness (Ra), and the PV value is 15 times or less of Ra. Characteristic dielectric polyester film for capacitors. 2. The dielectric polyester film for a capacitor according to claim 1, wherein the polyester resin constituting the polyester resin paint has a Tg of 5 ° C. or more and 35 ° C. or less. 3. The polyester-based paint further has a Tg of more than 40 ° C. and an average molecular weight of 18,000 or more.
2,000 or less polyester B is used in combination, and the constituent molar ratio of polyester resin A is polyester resin B.
2. The composition molar ratio is larger than
3. The dielectric polyester film for a capacitor according to any one of items 1 to 2. 4. A dielectric polyester film for a capacitor, wherein the polyester paint according to claim 1 is applied to both sides of a polyester film. 5. A polyester film capacitor using the dielectric polyester film for a capacitor according to claim 1 as a dielectric.