JPH09141809A - Polyester film for capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize excellent long-term moist heat resistance reliability, in a biaxially oriented polyester film having a coating layer at least on the single surface thereof, by adding a urethane resin and an age resistor to the coating layer. SOLUTION: Polyethylene terephthalate with intrinsic viscosity of 0.66 containing 0.3% of silica particles with an average particle size of 1.2μm is melted and extruded at 290 deg.C to obtain an amorphous sheet. Subsequently, this sheet is longitudinally stretched by 4.2 times at 90 deg.C. Thereafter, a coating soln. composed of 100 pts. (in terms of a dry solid) of polyurethane containing a synthetic age resistor and containing water as a medium is applied to both surfaces of the film. Next, the coated film is laterally stretched by 3.9 times at 110 deg.C and heat-treated at 230 deg.C to obtain a biaxlally stretched polyester film wherein the thickness of the coating layer is 0.055μm and the thickness of the base material polyester film is 6μm. The film thus obtained is used to produce a metal vapor deposition film condenser and a metal vapor deposition polyester film capacitor excelelnt in voltage-resistant characteristics and moist heat-resistance characteristics is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film for a capacitor. More specifically, the present invention relates to a biaxially oriented polyester film for a capacitor dielectric, which has excellent adhesiveness to an electrode metal layer and can impart high electrical characteristics and high humidity and heat resistance characteristics to the capacitor.

[0002]

2. Description of the Related Art Polyester films typified by polyethylene terephthalate are widely used as base films for capacitors because they have excellent mechanical properties, heat resistance and electrical properties. . However, with the recent development of various electronic devices and the like, there is an increasing demand for high-performance polyester films. As one of the requirements for high performance,
There is a demand for long-term moist heat resistance stability. That is, the dielectric constant, the dielectric loss, and the like, which are the basic characteristics of the capacitor dielectric, are required to be good and small in a wide temperature range from normal temperature to high temperature. In order to solve the above-mentioned problems, Japanese Unexamined Patent Publication No. 4-245414 discloses a metal vapor-deposited polyester film capacitor using a polyester film having a polyester polyurethane coating layer. A metal-deposited polyester film capacitor using a polyester film having a polycarbonate polyurethane coating layer is disclosed as a capacitor having excellent wet heat resistance.

However, the polyurethane-based coating agents described in the above publications undergo thermal decomposition and hydrolysis when exposed to high temperature and high humidity for a long time, and the performance of the capacitor is sufficiently high under high temperature and / or high humidity environment. Is not retained.
As the thickness of the polyester film decreases, the proportion of the coating layer in the dielectric increases, and the effect of the characteristics of the coating layer becomes more significant. For example, properties such as dielectric loss usually have a detrimental effect on a coating agent having a structure containing many polar groups. Since the above decomposition products are low molecular weight polar compounds, they have a significant adverse effect on the capacitor performance. Recent development of various electronic devices is remarkable,
The demand for long-term reliability, particularly long-term wet heat resistance, of capacitors has been further increased. Therefore, the demand for a polyester film as a capacitor dielectric has become more severe. In addition, there is a strong demand for miniaturization of capacitors accompanying the miniaturization of electric equipment products in recent years, and it is indispensable to reduce the thickness of the film used as the dielectric, and it is necessary to improve the overall characteristics including the influence of the coating layer described above. It has become to.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that a metal-deposited polyester film capacitor element using a polyester film having a specific coating layer as a dielectric is excellent in long-term use. They have found that they can exhibit wet heat resistance reliability, and have completed the present invention. That is, the gist of the present invention is a biaxially oriented polyester film having a coating layer on at least one surface,
A polyester film for a capacitor, wherein the coating layer contains a urethane resin and an antioxidant.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester of the polyester film in the present invention means polyethylene terephthalate in which 80 mol% or more of its constituent units is ethylene terephthalate, polyethylene naphthalate in which 80 mol% or more of its constituent units is ethylene naphthalate, or its constituent units. 80
Poly-1,4-cyclohexanedimethylene terephthalate in which the mol% is 1,4-cyclohexanedimethylene terephthalate. Examples of the copolymerization component other than the above-mentioned dominant constituent components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium. Dicarboxylic acid components such as sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid and its ester-forming derivatives, oxymonocarboxylic acids such as oxybenzoic acid and its ester-forming derivatives, etc. Can be used.

[0006] The polyester film of the present invention may contain additive particles, precipitated particles, and other catalyst residues that form protrusions on the surface of the film, as long as the characteristics of the capacitor described later are not deteriorated. Further, as an additive other than the above-mentioned protrusion forming agent, if necessary, an antistatic agent, a stabilizer, a lubricant, a cross-linking agent, an antiblocking agent, an antioxidant, a colorant, a light blocking agent, an ultraviolet absorber, etc. May be contained within a range that does not deteriorate the capacitor characteristics.
The polyester film of the present invention may have a multilayer structure as long as the properties finally obtained satisfy the requirements of the present invention. In the case of a multilayer structure, some of the layers may be other than the polyester layer. The coating layer of the film of the present invention contains a urethane resin. The urethane-based resin in the present invention is a general term for polymer compounds having a urethane bond, and is composed of polyol, polyisocyanate, chain extender, crosslinking agent and the like. Examples of polyols include dehydration reaction between glycols containing polyoxyethylene glycol, polyoxypropylene glycol, polyethers such as polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polycaprolactone, etc. and dicarboxylic acid. Examples of the polyesters, polycarbonates having a carbonate bond, acrylic polyols, castor oil and the like.

Examples of polyisocyanates include tolylene diisocyanate, phenylene diisocyanate,
4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and the like can be mentioned. In particular, the polyurethane in the present invention is preferably selected from aromatic polyisocyanates and / or isophorone diisocyanates having excellent heat resistance. When using aromatic polyisocyanate and / or isophorone diisocyanate, the proportion of aromatic polyisocyanate and / or isophorone diisocyanate in the isocyanate component is preferably 50 mol% or more, more preferably 70 mol% or more. Examples of chain extenders or crosslinking agents are ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, Examples include water.

The urethane resin in the present invention is preferably a coating agent containing water as a medium for safety and hygiene.
An organic solvent may be contained as an auxiliary agent for the water-soluble or water-dispersible resin within the scope of the present invention. When water is used as the medium, it may be a urethane resin forcedly dispersed by a surfactant or the like, but is preferably a hydrophilic nonionic component such as a polyether or a quaternary ammonium salt. It is a self-dispersion type coating agent having a cationic group, and more preferably a water-soluble or water-dispersible urethane resin having an anionic group. The water-soluble or water-dispersible urethane resin having an anionic group is a resin having a compound having an anionic group bonded to the resin by copolymerization or grafting, and includes a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group. From groups and their salts, etc.
It is appropriately selected. In order to impart water solubility to the resin, the counterion of the anionic group is preferably an alkali metal ion. However, for the purpose of improving the heat and humidity resistance of the capacitor, which will be described later, it is preferable that the counter ion of the anionic group is selected from amine-based onium ions including ammonium ions. The amount of anionic groups in the water-soluble or water-dispersible coating agent having anionic groups is preferably 0.05 to 8% by weight. When the amount of the anionic group is less than 0.05% by weight,
The water solubility or water dispersibility of the resin tends to deteriorate,
If the amount of the anionic group exceeds 8% by weight, the water resistance of the undercoat layer after coating may be poor, or the films may stick to each other due to moisture absorption or the wet heat resistance may be deteriorated.

In the present invention, the proportion of the urethane resin in the coating layer is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. When the content of the urethane resin in the coating layer is less than 30% by weight, the desired capacitor characteristics of the present invention may not be obtained. When water is used as a medium, it is preferable to add an antioxidant to be described later before water-solubilizing or water-dispersing the above urethane-based resin and simultaneously water-solubilize or water-disperse it. The coating layer in the present invention is
In addition to urethane-based resin, it also contains an antioxidant.
Here, the anti-aging agent is an antioxidant that acts by trapping radicals or decomposing peroxides. Suitable antioxidants that trap radicals include hindered phenols, secondary aromatic amines and hindered amines, and suitable antioxidants that decompose peroxides include trivalent phosphorus compounds such as triphenylphosphine. Examples include phyto and trialkyl phosphite. The most preferred antioxidant among these antioxidants is a hindered phenolic antioxidant. The hindered phenolic antioxidant is the following general formula

[0010]

Embedded image

(Wherein R ¹ is an alkyl group having 1 to 10 carbon atoms such as methyl, ethyl, propyl, tert-butyl, etc.), and a compound having a molecular weight of 500 to 5000 is preferable. As a hindered phenolic antioxidant, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,3 5-di-t-butyl-4-hydroxyphenyl) propionate, 2,4-bis- (n
-Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-t]
-Butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2-
Thiobis (4-methyl 6-t-butylphenol),
N, N'-hexamethylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-
Di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-
2,4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, bis (3,5-di-t-)
Butyl-4-hydroxybenzylphosphonate ethyl) calcium, tris- (3,5, -di-t-butyl-4-)
Examples thereof include hydroxybenzyl) -isocyanurate.

A compound having both a hindered phenol structure and a hindered amine structure in one molecule is particularly effective. As an example of this, 2- (3,5-di-t
Bis (1,2,2,6,6-pentamethyl-4) -butyl-4-hydroxybenzyl) -2-n-butylmalonate
-Piperidyl). The upper limit of the concentration of the antioxidant in the coating layer is preferably 20000 ppm,
More preferably 10000 ppm, even more preferably 5
000 ppm, most preferably 3000 ppm.
The lower limit of the concentration of the antioxidant in the coating layer is preferably 50.
The range is ppm, more preferably 100 ppm, even more preferably 300 ppm, and most preferably 400 ppm. If the concentration of the antioxidant is too low, the effect of improving the heat resistance by the antioxidant may not be obtained. However, since the antiaging agent is a relatively low molecular weight substance, if its concentration is too high, the capacitor characteristics may be deteriorated. The antiaging agent of the present invention may use a mixture of two or more antiaging agents. In that case, the total concentration is preferably within the above range.

The coating solution used in the present invention contains an isocyanate compound, an epoxy compound or an amine compound as a crosslinking agent in order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer. A compound, an aziridine compound, a silane coupling agent, a titanium coupling agent, a zirco-aluminate coupling agent, a peroxide, a heat- and photoreactive vinyl compound, a photosensitive resin and the like may be contained. Further, in order to improve the sticking property and the slipperiness, silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black, sulfide as inorganic fine particles in the coating liquid. It contains molybdenum, antimony oxide sol, etc. as organic fine particles such as polystyrene, polyethylene, polyamide, polyester, polyacrylic acid ester, epoxy resin, silicone resin, fluororesin, etc. within the range of the surface roughness described later. May be. Further, if necessary, it may contain an antifoaming agent, a coating property improving agent, a thickener, an antistatic agent, an organic lubricant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like.

The coating liquid used in the present invention includes
Acrylic resins other than the above-mentioned resins essential in the present invention,
A polyester resin, a vinyl resin or the like may be contained in order to improve the characteristics of the coating liquid or the coating layer. In particular, the polyester-based resin is preferably used because it improves the interlayer wet heat resistance adhesion between the base polyester film and the coating layer. However, the proportion of the polyester resin in the coating layer is preferably 30% by weight or less. The alkali metal content in the coating liquid used in the present invention is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 200 ppm or less in the solid content of the coating liquid. If the content of the alkali metal in the coating solution is high, the wet heat resistance of the capacitor is deteriorated, which is not preferable. In particular, it was found that when the capacitor was placed under high temperature and high humidity while applying a DC voltage, the capacitance of the capacitor was drastically reduced. Therefore, a desired coating liquid may be obtained by performing deionization treatment as needed.

As a method of applying the above-mentioned coating solution to a polyester film, Yuji Harazaki, Maki Shoten, 1979, published "River roll coater, gravure coater, rod coater, air doctor coater or these" Using a coating device other than
A method of applying the coating liquid outside the biaxially stretched polyester film production process, and more preferably, a method of applying the coating liquid inside the film production process can be mentioned. As a method of applying in the film manufacturing process, a coating solution is applied to a polyester unstretched film, and sequentially or simultaneously, a method of biaxially stretching,
There is a method in which it is applied to a uniaxially stretched polyester film and then stretched in a direction perpendicular to the uniaxially stretched direction, or a method in which it is applied to a biaxially stretched polyester film and further stretched in the transverse and / or longitudinal direction. The above-mentioned stretching step is preferably performed at 60 to 130 ° C., and the stretching ratio is at least 4 times or more, preferably 6 in terms of area ratio.
~ 20 times. The stretched film is 150-250
Heat treated at ℃. Furthermore, it is preferable to relax 0.2 to 20% in the vertical and horizontal directions in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet. Particularly, 2 to 6 by the roll drawing method at 60 to 130 ° C.
The coating solution is applied to the uniaxially stretched polyester film that has been double-stretched, and the polyester uniaxially stretched film is immediately dried in a direction perpendicular to the previous stretching direction at 80 to 130 ° C. by 2 to 6 times, with or without suitable drying. To 150 and
A method of performing heat treatment at 250 ° C. for 1 to 600 seconds is preferable.

According to this method, the coating layer can be dried at the same time as stretching, and the thickness of the coating layer can be thinned according to the stretching ratio. Therefore, a film suitable as a polyester film base material is relatively inexpensive. Can be manufactured. In the present invention, the coating liquid may be applied to only one side of the polyester film, or may be applied to both sides. When applied on only one side, a coating layer other than the above-mentioned coating solution may be formed on the opposite side, if necessary, to impart other properties to the polyester film of the present invention. Note that the film may be subjected to a chemical treatment or a discharge treatment before application in order to improve the coating property and adhesion of the coating agent to the film. Also,
In order to improve the adhesiveness, coatability, etc. of the coating layer of the biaxially stretched polyester film of the present invention, the coating layer may be subjected to discharge treatment after the coating layer is formed. The thickness of the coating layer is 0.0
The range is preferably from 0.5 to 1.0 μm. The thickness of the coating layer is
It is preferable to make it thinner because of the demand for smaller capacitors,
The upper limit of the coating thickness is preferably 0.5 μm, more preferably 0.3 μm. However, if the thickness of the coating layer is too thin, it is difficult to obtain a uniform coating layer, so that coating unevenness is likely to occur in the product, and the lower limit of the coating thickness is preferably 0.01.
μm, and more preferably 0.02 μm.

The coating layer formed as described above preferably has a water droplet contact angle of 60 ° or more. If the water droplet contact angle is less than 60 °, the water-resistant adhesion to the metal vapor deposition film is deteriorated, and it tends to be difficult to impart the moist heat resistance property to the capacitor of the present invention. Therefore, attention must be paid to the amount of hydrophilic groups, the amount of emulsifiers, and the amount of hydrophilic compounds of the coating and coating agent. The center line average roughness (Ra) of the coating layer surface formed as described above is preferably in the range of 0.005 to 0.5 μm, and more preferably in the range of 0.01 to 0.3 μm. , And most preferably 0.02 to 0.1 μm. When Ra is less than 0.005 μm, the slipperiness of the film is insufficient and workability tends to deteriorate. On the other hand, if Ra exceeds 0.5 μm, the surface may be too rough, and the resulting capacitor may have poor wet heat resistance and withstand voltage characteristics. The total thickness of the polyester film having the coating layer of the present invention is preferably 21 μm or less, more preferably 1 μm or less.
It is 6 μm or less, and most preferably 10 μm or less. When the polyester film having a coating layer is thick, the ratio of the coating layer to the dielectric is small, and therefore the influence of the characteristics of the coating layer tends not to appear remarkably.

The film of the present invention is particularly effective for improving the wet heat resistance of vapor-deposited capacitors. When the film of the present invention is used as a dielectric of a vapor deposition capacitor, the metal to be vapor deposited is aluminum, palladium, zinc, nickel,
Gold, silver, copper, indium, tin, chromium, titanium and the like can be mentioned, but the most preferable metal is aluminum. The above-mentioned metals include metal oxides. The thickness of the metal vapor deposition film is preferably in the range of 10 to 5000 Å. The vapor deposition method is generally a vacuum vapor deposition method, but may be an electroplating method, a sputtering method, or the like. In addition, the metal deposition layer may be provided on both sides of the polyester film. After the metal deposition, a surface treatment of the deposited metal layer or a coating treatment with another resin may be performed. Two metal-deposited polyester films thus obtained are superposed and wound (including a double-sided metal-deposited polyester film and another film including the polyester film of the present invention), or a large number of layers are laminated. Capacitor elements can be manufactured and subjected to, for example, heat pressing, taping, metallikon, voltage treatment, both end surface sealing, lead wire attachment, etc., according to a conventional method to obtain capacitors, but the invention is not limited thereto.

[0019]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, "part" means "part by weight". (1) Centerline average roughness (Ra) It was determined as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, the reference length L (2.55 mm) from the film section curve in the direction of the center line
The part of is drawn out, and the center line of this extracted part is the x-axis,
When the roughness curve y = f (x) is represented with the direction of the longitudinal magnification as the y-axis, the value given by the following equation is represented by [μm]. The center line average roughness is obtained by obtaining a sectional curve of 10 sample film surfaces,
The average value of the center line average roughness of the extracted portion obtained from these sectional curves was expressed. The tip radius of the stylus is 2μ.
m, load 30 mmg, cutoff value 0.8 mm
And

[0020]

(Equation 1)

(2) Water Droplet Contact Angle A contact angle meter (CA-DT-A type, manufactured by Kyowa Interface Chemical Co., Ltd.) was used to measure the contact angle between a sample film and distilled water in an atmosphere of temperature 23 ° C. and humidity 50% RH. ) Was used for the measurement. The contact angle is
A total of six points were measured at two points on the left and right and three points on the sample, and the average value was determined as the contact angle. The diameter of the water droplet was 2 mm,
The number after minutes was read. (3) Evaluation of electrical characteristics Change in capacitance (manufacture of capacitor) Aluminum was vapor-deposited to a thickness of 450 Å on the surface of the film by using a resistance heating type metal vapor deposition device with the pressure in the vacuum chamber being 10 ^-4 Torr or less. . At that time, the polyester film was vapor-deposited in a stripe shape having a margin portion in the longitudinal direction (width of vapor deposition portion: 8 mm, mark
Repeated width of gin 1mm). The resulting vapor-deposited polyester film was slit into a 4.5 mm wide tape having a left or right margin of 1 mm. Each of the obtained left margin and right margin vapor-deposited polyester films, one by one, was wound together to obtain a wound body. At this time, the two films were wound while being shifted so that the vapor deposition portion protruded by 0.5 mm in the width direction. The wound body was pressed at a temperature of 150 ° C. and a pressure of 50 kg / cm ² for 5 minutes. After applying a lead wire after spraying metallikon on both end surfaces of the wound body after pressing, impregnated layer with liquid bisphenol A type epoxy resin, and a minimum thickness of 0.5 mm by heating and melting the powdery epoxy resin. An exterior was formed to obtain a film capacitor having a capacitance of 0.1 μF. (Measurement of change in capacitance) While applying a DC voltage of 60 V / μm between the electrodes of the obtained capacitor, leave it in an atmosphere of temperature 85 ° C. and humidity 85% RH for 500 hours, and use the initial capacitance as a reference. The value was calculated as the rate of change in capacitance. That is, the value obtained by subtracting the initial capacitance from the capacitance after 500 hours was divided by the initial capacitance and expressed as a percentage.

Example 1 (Production of Polyester Film) Polyethylene terephthalate having an intrinsic viscosity of 0.66 and containing 0.3% of silica particles having an average particle diameter of 1.2 μm was melt extruded at 290 ° C. to obtain an amorphous sheet according to a conventional method. Then, at 90 ° C. in the vertical direction 4.
After being stretched 2 times, 100 parts of polyurethane having the composition shown in the following Table 1 containing the anti-aging agent A synthesized according to a conventional method (dried solid content conversion, the same applies below) was used, and a coating solution containing water as a medium was applied to the film. Apply on both sides, then 11 across
It was stretched 3.9 times at 0 ° C. and heat-treated at 230 ° C. to obtain a biaxially stretched polyester film having a coating layer thickness of 0.055 μm and a base polyester film thickness of 6 μm. The content of alkali metal in the coating liquid was 5.0 ppm of Na and 1.8 ppm of K in terms of solid content of the coating liquid, and other alkali metals were below the detection limit. The contact angle of water droplets on the coating layer was 63 °, and the center line average roughness (Ra) was 0.025 μm. As shown in Table 2 below, the metal-evaporated film capacitor produced using the obtained film was a metal-evaporated polyester film capacitor having excellent withstand voltage characteristics and excellent wet heat resistance characteristics. Table 2 also shows the results of Examples and Comparative Examples described later.

Comparative Example 1 A polyester film was obtained in the same manner as in Example 1 except that the coating solution was not applied. Comparative Example 2 A polyester film was obtained in the same manner as in Example 1 except that the antioxidant was not added in the polyurethane aqueous dispersion synthesis process of Example 1.

Example 2 A polyester film was obtained in the same manner as in Example 1 except that the antiaging agent B was used instead of the antiaging agent A of Example 1. As shown in Table 1, the metal-evaporated film capacitor manufactured using the obtained film was excellent in withstand voltage characteristics and wet-heat resistance characteristics, and the metal-evaporated polyester film capacitor was more excellent than that in Example 1. Example 3 Polyurethane 80 containing Antiaging Agent A of Example 1
And 20 parts of a water-dispersible polyester A (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name Polyester WR-961) having ammonium carboxylate as a functional group, except that a coating solution using water as a medium is applied. A polyester film was obtained in the same manner as in 1. As shown in Table 1, the metal-evaporated film capacitor manufactured using the obtained film was excellent in withstand voltage characteristics and wet-heat resistance characteristics, and the metal-evaporated polyester film capacitor was more excellent than that in Example 1.

Comparative Example 3 99.75 parts of the above-mentioned polyester A, the antioxidant A0.
A polyester film was prepared in the same manner as in Example 1 except that the coating liquid was 25 parts and the coating liquid was water.

[0026]

[Table 1] (The abbreviations in Table 1 are as follows: TDI: toluene diisocyanate, PTMG: polytetramethylene glycol (molecular weight 2000), NPG: neopentyl glycol, DMPA: dimethylolpropionic acid, TMP: trimethylolpropane, TEA: triethylamine, Anti-aging agent A: triethylene glycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], anti-aging agent B: 2- (3,5-di-
t-Butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-
4-piperidyl)))

[0027]

[Table 2]

[0028]

EFFECT OF THE INVENTION The film of the present invention has excellent adhesion to the electrode metal, and when used as a dielectric of a metal-deposited film capacitor, it imparts a high degree of electrical characteristics and resistance to moisture and heat, improving the long-term reliability of the capacitor. It has a high industrial value.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 9:00

Claims (2)

[Claims] 1. A biaxially oriented polyester film having a coating layer on at least one surface, wherein the coating layer contains a urethane resin and an antioxidant, and a polyester film for capacitors. 2. The thickness of the coating layer is 0.005 to 1.0 μm.
The polyester film for a capacitor according to claim 1, wherein the polyester film having a coating layer has a thickness of 21 μm or less.