JPH09302111A - Polyester film for capacitors - Google Patents

Abstract

(57) [Summary] A polyester film having an M / P of 0.8 to
A polyester film for a capacitor having a maximum roughness Rmax of 4 and a maximum roughness Rmax of 0.1 to 2 μm, and a capacitor using the film. [Effects] According to the present invention, the withstand voltage is excellent, especially the withstand voltage characteristics at high temperature and long time load, the insulation resistance is not lowered, the casting speed can be increased, and the productivity is improved as compared with the conventional film. An excellent polyester film for capacitors is obtained. Also, withstand voltage, especially high temperature
It is possible to obtain a capacitor that has excellent withstand voltage characteristics under a long-time load and has a small decrease in insulation resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film suitable for a capacitor, and more specifically, it has excellent withstand voltage characteristics, high insulation resistance characteristics, low tan δ characteristics, and slipperiness and winding property. The present invention relates to a polyester film for capacitors which has excellent handling properties such as properties.

[0002]

2. Description of the Related Art Conventionally, in polyester films and the like, M / P (M and P are metal (excluding antimony metal) and phosphorus remaining amount (equivalent amount) in polymer, respectively) and melting specific resistance are increased. As a result, we have realized and provided an excellent polyester film for capacitors.

However, increasing the M / P and the melting specific resistance leads to poor productivity (the castability is poor and the production speed is slow).
A casting method having a polyester having a P as low as 0.5 to less than 0.8 and a water film is proposed in JP-B-5-18688.

Further, it is possible to improve the castability and the uniformity of thickness by utilizing a polyester having an M / P of 0.8 to 5 in a polyester film.
No. 94 publication, magnetic tape applications, electrical insulation,
It is disclosed in the publication that it is used for capacitor applications and the like.

[0005]

However, although the above method can be expected to have some effect on its purpose, the former method has a problem of low withstand voltage. Particularly, the latter method has a withstand voltage characteristic. And the insulation resistance is low.

It is an object of the present invention, in particular, to obtain a polyester film for capacitors which has excellent withstand voltage characteristics and insulation resistance characteristics.

[0007]

The present invention has the following constitution in order to achieve the above-mentioned object.

That is, polyester film M / P
Is 0.8 to 4 and the maximum roughness Rmax is 0.1.
It is a polyester film for capacitors, characterized in that it is ˜2 μm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the polyester used for the polyester film is a crystalline thermoplastic resin composition which is polymerized by esterification, and such a polyester has a dicarboxylic acid component and a glycol. It is obtained by polycondensing the components.

As the dicarboxylic acid component, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenylethanedicarboxylic acid, etc. can be used, and as the glycol component, ethylene glycol, propylene glycol, tetramethylene glycol, cyclohexane. For example, dimethanol can be used.

Of these, terephthalic acid and naphthalene-2,6-dicarboxylic acid are preferable as the acid component, and ethylene glycol is preferable as the glycol component.

The melting point of the polyester is preferably 250 ° C. or higher from the viewpoint of heat resistance, and is preferably 300 ° C. or lower from the viewpoint of productivity. As such a preferable polyester, polyethylene terephthalate, polyethylene-2,6-naphthalate, and poly-1,4-cyclohexylene dimethylene terephthalate can be used.

Other components may be copolymerized and blended with these polymers.

Further, M of the polyester film of the present invention
It is important that / P is 0.8 to 4, preferably 1 to 3.5, and more preferably 1.2 to 3. If it is less than 0.8, there is a problem that the withstand voltage, particularly the withstand voltage at high temperature for a long time, is lowered, and the castability of the electrostatic printed matter is poor, and the productivity is lowered. On the other hand, if it exceeds 4, there arises a problem that the insulation resistance is excessively decreased. In addition, the moisture and heat resistance life characteristic tends to deteriorate.

The polyester according to the present invention preferably has an intrinsic viscosity [η] of 0.5 dl / g or more, more preferably 0.6 dl / g or more, still more preferably 0.65 dl / g or more, most preferably Preferably 0.7d
A value of 1 / g or more is preferable in that it can achieve pressure resistance, heat resistance, mechanical characteristics, and moisture and heat resistance life characteristics in a capacitor, and also in terms of recoverability.

It is essential that this polyester film is at least uniaxially or biaxially stretched (orientated), and is particularly preferable in terms of obtaining good mechanical properties, thermal properties, and electrical properties. .

The polyester film according to the present invention is
It is important that the maximum surface roughness Rmax is 0.1 to 2 μm, preferably 0.2 to 1.5 μm, and more preferably 0.25 to 1.2 μm. When the thickness is less than 0.1 μm, the device winding property of the capacitor and the winding property of the film or the metallized film are deteriorated, so that the value is practically poor, and when the thickness is more than 2 μm, the withstand voltage characteristic aimed at by the present invention is obtained. Is difficult to obtain, and as a result, the withstand voltage characteristic is significantly deteriorated especially at high temperature for a long time, which is not desirable.

The surface roughness Ra of the polyester film of the present invention is preferably 0.003 to 0.8 μm, more preferably 0.01 to 0.6 μm. If it is less than 0.003 μm, the slipperiness may be deteriorated, blocking may occur depending on the material, and the handling may be difficult or the winding property may be deteriorated. Also,
This is because when the thickness exceeds 0.8 μm, the smoothness is poor, and problems may occur in terms of moisture and heat life resistance, withstand voltage characteristics, and the like.

The polyester film of the present invention is preferably formed with a coating containing a polyester resin, a polyurethane resin, an acrylic resin, or the like, from the viewpoints of resistance to moisture and heat life, reduction of tan δ, and the like.

The composition of the coating is preferably a polyester resin, a polyester urethane resin and a mixture thereof.

This polyester resin can be obtained by polycondensing a dicarboxylic acid component and a glycol component, and as the carboxylic acid component, there are terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid and trimethyladipine. Acid, sebacic acid, malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, fumaric acid, maleic acid, itaconic acid, 1,3-cyclopentanedicarboxylic acid 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-
Naphtalic acid, diphenic acid, 4,4′-oxybenzoic acid, 2,5-naphthalenedicarboxylic acid and the like can be used. The carboxylic acid may be an acid anhydride, an ester, a chloride, or the like, for example, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl terephthalate, diphenyl terephthalate Etc. can be used. Among them, terephthalic acid, isophthalic acid, 2,
6-naphthalenedicarboxylic acid and the like are preferable because the water absorption can be suppressed small, the glass transition temperature can be increased, the increase of tan δ can be suppressed, and the decrease of breakdown voltage of the capacitor can be suppressed.

As the glycol component, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-
2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1 , 5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4 , 4-Tetramethyl-1,3-
Cyclobutanediol, 4,4′-thiodiphenol,
Bisphenol A, 4,4′-methylenediphenol,
4,4 '-(2-norbornylidene) diphenol,
4,4'-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4'-isopropylidenephenol, 4,4'-isopropylidenebis (2,6-dichlorophenol), 2,5- Naphthalene diol, p-xylene diol, cyclopentane
1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol and the like can be used. Among them, ethylene glycol, diethylene glycol, neopentyl glycol and the like are preferable because they can suppress the water absorption rate to a small level, suppress the rise of tan δ and suppress the breakdown voltage of the capacitor.

Further, this polyester resin is used in order to obtain the following carboxylic acid concentration on the polyester film surface:
As described in Japanese Patent Publication No. 60-23983, those utilizing a terminal carboxylic acid are not sufficient in moisture heat resistance life property and easy adhesiveness, and those having a carboxylic acid in a side chain or a pendant are preferable.

As a method for producing a polyester resin having a carboxylic acid in its side chain, JP-A-54-46294, JP-A-60-209073 and JP-A-62-2 are known.
40318, JP-A-53-26828, JP-A-53-26829, and JP-A-53-98336.
JP, JP-A-56-116718, JP-A-61
It can be produced from a resin obtained by copolymerizing a polyvalent carboxylic acid having a valency of 3 or more as described in JP-A-124684.
Also, other methods may be used.

Examples of the trivalent or higher polycarboxylic acid include
For example, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,
2,3,4-butanetetracarboxylic acid, 1,2,3,4
-Pentanetetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 5, (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene-
1,2-dicarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate,
2,2 ', 3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylenetetracarboxylic acid, etc. can be used.

Among them, particularly preferable one is that when the polyester copolymer is used, the molecular weight decreases (decreases) with temperature rise, but the molecular weight increases with temperature decrease, that is, the molecular weight changes reversibly. It is preferable to use those that do not easily cause a decrease in melt viscosity upon reuse, coloring, generation of foreign matter due to gelation, foaming and the like. As a specific example thereof, 5, (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid or the like can be used.

The polyester resin film is formed by a composite film forming method such as hot melt or melt extrusion, or a water-soluble and / or water-dispersible coating method (in-line, by using a neutralizing agent such as ammonia or triethylamine).
Offline).

As the polyester urethane resin, Japanese Patent Publication No. 53-38760 and Japanese Patent Laid-Open No. 62-22803.
The water-soluble and / or water-dispersible resin described in JP-A-0 can be used.

The polyester component and the glycol component are the same components as the above-mentioned polyester resin, but the water absorption can be suppressed to be small, and the glass transition temperature can be increased.
This is preferable because it can suppress an increase in tan δ and suppress a decrease in the breakdown voltage of the capacitor.

As the isocyanate component, tolylene diisocyanate, phenylene diisocyanate,
Use of diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate, naphthalene diisocyanate, tetrahydronaphthalene diisocyanate, etc. Among these, tolylene diisocyanate is particularly preferable because it can reduce the water absorption and tan δ.

Even with this urethane resin, one having a carboxylic acid in the side chain is preferable in order to obtain the following specific surface carboxylic acid concentration. As a concrete example, 2,
2-Dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, etc. can be used. This manufacturing method is disclosed in JP-A-61-2280.
It is manufactured by the method described in Japanese Patent Laid-Open No. 30-30.

In the present invention, as the acrylic resin, alkyl acrylate, alkyl methacrylate and the like can be used.

The resin forming the coating film of the present invention preferably has a glass transition temperature of at least one resin of higher than 80 ° C., more preferably 85 ° C. or higher, further preferably 85 to 160 ° C. , Decrease of tan δ (especially in high temperature region and low frequency region) and improvement of withstand voltage, resistance to moisture and heat, form retention when used as a multilayer capacitor, and resistance to destruction when used as a capacitor, It is preferable in terms of film formability (stability) and self-healing property.

In order to obtain this glass transition temperature, in the case of the polyester resin or polyester urethane resin of the above-mentioned coating resin, 2,6-naphthalenedicarboxylic acid, phenylindanedicarboxylic acid, benzophenonedicarboxylic acid, as its dicarboxylic acid component, As the glycol component, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, bisphenol A, dihydroxybenzophenone, xylylene glycol and the like may be appropriately combined and copolymerized, or may be described later. Obtained by a method of copolymerizing a carboxylic acid such as pyromellitic acid, naphthalenetetracarboxylic acid, and 5, (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid. From That. It can also be obtained by appropriately combining an acid and a glycol component other than these.

In the polyester film of the present invention, the concentration of carboxylic acid on the surface is preferably 0.003 or more, more preferably 0.008 or more, and further preferably 0.015 to 0.07. It is preferable in terms of life, easy adhesion, and collectability.

The polyester film according to the present invention is
Its water absorption is preferably 0.4 to 3% by weight,
More preferably, the range of 0.45 to 2.5% by weight is tan δ, the dielectric breakdown voltage at high temperature and high humidity for a long time,
It is preferable in terms of element winding property.

The polyester film according to the present invention is
It is preferable that the resin resistance described later is 2 to 5, and more preferably 3 to 5 is a point for preventing a decrease in resistance and heat generation at a terminal lead portion when a capacitor is used, and preventing the capacitor from being destroyed. Is preferred.

It is preferable to add a cross-linking agent such as melamine, epoxy, or isocyanate to the coating agent for the polyester film of the present invention. Among them, cross-linking with epoxy is preferable because it maintains the wet heat life resistance and is excellent in resin resistance. Further, the number of epoxy groups is 2 or more, preferably 3
Epoxy compounds having 5 to 5 epoxy groups are preferable from the viewpoints of resistance to wet heat and heat, reduction of tan δ, resin resistance, and improvement of crosslinking rate (excellent in productivity).

The amount of epoxy added is 7
-30 parts by weight is preferable, and more preferably 10-25 parts by weight. If it is less than 7 parts by weight, the resin resistance is poor,
When used as a condenser, it increases tan δ and destroys the condenser. If it exceeds 30 parts by weight, the water absorption rate increases and tan δ increases, and problems such as deterioration in wet heat life resistance and blocking occur.

As a curing agent for this epoxy, a curing agent such as diethylenetriamine, triethylenetetramine, benzylmethylamine, metaphenylenediamine, diaminodiphenylmethane, xylylenediamine or ethylmethylimidazole may be used.

When the coating material is a polyurethane resin, it may be a self-crosslinking type polyurethane.

This coating layer is, for example, coated with a water-dispersible resin and / or a water-soluble resin of the above-mentioned coating resin before stretching in biaxially stretched film formation and before uniaxial stretching and before biaxial stretching. Obtained by the method, hot melt,
Off-line or in-line coating may be performed using a solvent other than water, or the above-mentioned extrusion by a melt extrusion method or blending with another resin may be used.

The thickness of the coating layer in the present invention is 0.01
The thickness is preferably in the range of ˜5 μm, more preferably 0.02 to 2 μm. By being in these ranges, slipperiness, element winding property, moisture and heat resistance, voltage resistance,
The improvement of various electrical characteristics such as the prevention of corona discharge destruction and the good self-healing property are achieved.

Fine particles may be added to the base material polyester layer or the coating layer in order to improve the winding property, the slip property of the film, and the winding property of the capacitor element. As the particles, inorganic particles or organic particles may be added. Can be used. For example,
As the inorganic particles, silica, alumina, zirconia, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide or the like can be used, and as the organic particles, those having acrylic acid, styrene, polyester or the like as a constituent component can be used. When using the particles, the particle size and the addition amount may be determined so as to constitute the maximum roughness and the surface roughness described above.

Next, the method for producing the polyester film for capacitors of the present invention will be explained, but the present invention is not necessarily limited to this.

First, a polyester as a base material is melt-extruded by an extruder, cooled on a cooling roll to below the glass transition point, cast, and heated to above the glass transition point, and then 2.8 to 7. The film is stretched 5 times, coated with the above-mentioned coating resin as needed (corona discharge treatment is applied to the surface of the base material if necessary), and further preheated to Tg to 170 ° C. of the base polyester with a stenter, and then 3 to 12 In order to reduce the dielectric loss, it is preferable to stretch the film in the width direction twice and to heat-set it at a temperature lower than the melting point of the base polyester, preferably 235 ° C. or lower, while relaxing if necessary.

Next, vapor deposition of a metal to be an internal electrode in the case of a capacitor is obtained by a vacuum vapor deposition method, a metal is vapor deposited from an evaporation source, and a vapor deposition film is formed on the polyester film of the present invention.

As the evaporation source, a resistance heating type boat type, a crucible type by radiation or high frequency heating,
There is a method using electron beam heating, but the method is not particularly limited.

As the metal used for this vapor deposition, Al, Z
Metals such as n, Mg and Sn are preferable, but Ti, In,
Cr, Ni, Cu, Pb, Fe, etc. can also be used. These metals have a purity of 99% or more, preferably 99.5%.
% Or more, processed into a granular, rod, tablet, wire or crucible shape.

In the case of this vapor deposition, aluminum is particularly preferable from the viewpoint of productivity and cost, and aluminum is vapor-deposited on at least one side to provide an aluminum vapor deposition film. At this time, for example, nickel or copper is simultaneously or sequentially provided with aluminum. Other metal components such as gold, silver, chromium, zinc can also be deposited.

Although the thickness of the aluminum depends on the purpose of use, it is preferably in the range of 20 to 1000 angstroms from the viewpoint of the capacitor characteristics, especially the self-healing property.

Further, in the capacitor application, the aluminum oxidation index on the surface of the vapor-deposited aluminum film is preferably 1.65 or less, and more preferably 1.45 to 1.6, the moisture and heat resistance is further improved. Therefore, it can be said that it is preferable.

Further, the polyester film of the present invention is
The heat shrinkage rate after 30 minutes at 150 ° C. is preferably 2% or less in the longitudinal direction, more preferably 1.5% or less, still more preferably 1 after forming a capacitor.
% Or less.

A capacitor using the film of the present invention generally has, for example, an insulation resistance value of 2,500 to 420.
It becomes as large as 00 MΩ, and can achieve a DC long-term withstand voltage of about 1000 to 1600 V at high temperatures, which is about 600 to 1100 V of the conventional product.
It can be said that it was able to be greatly improved in view of the fact that it was only a degree, and at the same time, since the casting speed and the element winding property can be improved, the productivity improving effect is also great.

[0055]

【Evaluation method】

(1) Intrinsic viscosity of polyester [η] Dissolve polyester in orthochlorophenol,
Measured in ° C. (2) Determination of M / P M and P represent the residual amount (equivalent amount) of metal (excluding antimony metal) and phosphorus in the polymer, respectively, as described above.

M is 700 g of 2 g of polyester in air.
The polymer is incinerated by igniting at 2 ° C. for 2 hours, then dissolved in hydrochloric acid, and the metal equivalent is determined by an atomic absorption method according to a conventional method.

For P, after wet ashing the polyester in the presence of sulfuric acid and perchloric acid, color was developed with ammonium molybdate in an acidic sulfuric acid solution, and the absorbance at 845 mμ was measured and quantified by a calibration curve. .

(3) Water absorption rate Polyester film is piled up and cut into 2 cm square pieces, put in a weighing bottle, and vacuum dried at room temperature for 48 hours.
Let it be 1. This sample was allowed to stand at 60 ° C. and 80% RH, the weight was measured over time, the weight when it was in a parallel state was W2, and the water absorption was determined by the following formula. (W2 is the time when the change in moisture absorption rate is within 10%.) (W2-W1) × 100 / W1 = water absorption rate (%) (4) Resin resistance Sample preparation: Evaluation of polyester film to be evaluated Aluminum was vapor-deposited on the surface by a vapor deposition machine so as to have a surface resistance of 1 to 5 Ω / □ or 200 to 2000 angstrom. This film was cut into a sample having a width of 2 cm and a size of 10 cm to obtain a sample.

Evaluation procedure: A mixture of epoxy resin SR-10 manufactured by Sanyu Resin Co., Ltd. and its curing agent H-330 at a ratio of 100: 80 (weight ratio) was applied to the vapor deposition surface of the vapor deposition film in a size of 2 × 2 cm. Apply or drip on the width, and at room temperature 3
After leaving it for 0 min, leave it in a hot air oven at 105 ° C for 1 hour, and observe the surface change of the coating or dropping part, and if there is no change, mark as ○, and change is recognized, large wrinkle, crushed change Is recognized, and the size of one is 1.
Marks less than mm are indicated by △, those exceeding 1 mm are marked ×
It is indicated by a mark.

Then, the above-mentioned evaluation sample was exposed and strongly rubbed to evaluate the adhesiveness as follows.

The case where the vapor-deposited layer did not peel at all was marked as good, and the mark ○ indicates that the vapor-deposited layer peeled off only slightly, and the mark X indicates that the layer completely peeled was unusable.

This evaluation was made into the following 5 grades.

5: Surface: ○, Peeling: ○ Good and usable 4: Surface: △, Peeling: ○ Slightly problematic, usable 3: Surface: △, Peeling: △ Problematic but usable 2: Surface: ×, peeling: △ There is a considerable problem, but it can be used depending on the application 1: Surface: ×, peeling: × Cannot be used (5) Maximum roughness Rmax of film, surface roughness Ra Measured according to JIS B0601.

(6) Aluminum Oxidation Index of Aluminum Vapor Deposition Film Surface The vapor deposition film surface is analyzed by soft X-ray photoelectron spectroscopy. If the sample is a capacitor, disassemble it and expose the vapor deposition surface to the air to use it as a sample. From the ratio of the number of atoms obtained by correcting the peak area ratio obtained by the measurement with the relative sensitivity factor of each atom and the component ratio obtained by dividing the peak shifted depending on the bonding state of each atom, the aluminum oxidation index O / Al was calculated. It is calculated by the equation (1).

O / Al = [O (Al oxide) / Al (Total)] / [Al (III) / Al (Total)] (1) Here, [Al (III) / Al (Total)] is the abundance ratio of Al (III) obtained by dividing the peak of aluminum atom, and [O (Aloxide) / Al (Total)] is the total oxygen concentration with respect to aluminum, and oxygen other than oxygen alone and aluminum It is obtained by subtracting the oxygen concentration bound to the element. That is, for example, the concentration of oxygen bound to carbon can be obtained by dividing the carbon peak. At this time,
It is estimated that the most oxygen is bonded to carbon when the amount of oxygen cannot be specified, because some functional groups containing oxygen are considered, or the energy cannot be separated due to the close bond energy. Similarly, the amount of bound oxygen is determined for oxygen bound to other elements, and the total value is subtracted from the total oxygen concentration.

The measurement conditions are shown below.

Equipment: Shimadzu ESCA750 Excited X-ray: MgKα1.2 ray (1253.6 eV) Energy correction: The binding energy of the C1S main peak is set to 284.6 eV.

Photoelectron escape angle: 90 ° (7) Moisture and heat resistance of the condenser The condenser was set to 400 at 60 ° C. in an atmosphere of 95% RH.
VDC was applied, aged, and the capacitance change rate was measured. The time until the capacitance change rate ΔC / C was reduced by 10% was shown as the result of the moisture resistance life test. The longer this time, the better the moist heat resistance. Here, C is the capacitance before aging, and ΔC is the capacitance change before and after aging.

(8) Sheet average withstand voltage In accordance with JIS 2110, sheet BDV (dielectric breakdown voltage)
Measured at DC. A 100 μm-thick 10 cm square aluminum foil electrode is used for the cathode, a 25 mmφ, 500 g electrode for the anode is used as the anode, and a film is sandwiched between the electrodes, and a voltage is applied at a rate of 100 V / sec using a high voltage DC power supply manufactured by Kasuga. The case where a current of 10 mA or more flowed was regarded as a breakdown, and this was measured 30 times, and indicated as a voltage of an average value.

(9) High-temperature long-time withstand voltage The capacitor prepared in (10) below is placed in an atmosphere of 105 ° C., 1 hour later, a DC voltage is applied, and a voltage of 25 V is boosted every 5 minutes. When the current of 10 mA or more flowed, it was considered as a breakdown, and this was repeated 5 times to show the highest voltage.

(10) Production of Capacitor Aluminum was vacuum-deposited on one surface of the film so that the surface resistance value was 2Ω. At this time, vapor deposition was performed in a stripe shape having a margin portion running in the longitudinal direction (width of vapor deposition portion: 8.
0 mm, width of the margin part 1.0 mm). Next, a blade was placed at the center of each vapor deposition section and the center of each margin section and slitted to form a take-up reel in the form of a tape having a width of 4.5 mm and a margin of 0.5 mm to the left or right.

The reels having a left margin and a right margin, respectively, were wound one by one and wound to obtain a wound body having an electrostatic capacity of about 0.047 μF. At that time, the two films were wound while being shifted so that the vapor deposition portion protruded from the margin portion by 0.5 mm in the width direction.

Remove the core material from this wound body and
Pressing was performed at a temperature and pressure of 50 ° C. and 1 MPa for 5 minutes. Metallicon was thermally sprayed on both end faces of this to form external electrodes, and lead wires were welded to the metallicon to obtain a wound-type capacitor element.

(11) Glass transition temperature (Tg) Robot DSC, RDC22 manufactured by Seiko Instruments Inc.
0, using an SSC5200 HDIS STATION, sampling 2 to 5 mmg, and heating at a rate of 20 ° C. /
It was determined by measuring at min. If the temperature is not detected by this measurement, raise the temperature to 250 ° C, quench with liquid nitrogen,
The temperature was measured again under the above conditions. In addition, when a glass transition temperature was observed in both, the one that appeared higher was used.

The coating layer was dissolved from the base material with a solvent, the solvent was removed, and only the coating resin was taken out. If difficult, only the coating layer was scraped to obtain a measurement sample. When the resin of the base material and the coating layer was clear, the material was used as a sample.

(12) Concentration of Carboxylic Acid on Surface Using ESCA750 manufactured by Shimadzu Corporation, measurement was performed under the following conditions.

Excited X-ray: MgKα 1,2 ray (1253.6 eV) Photoelectron escape angle θ: 90 ° As a standard sample, a polyacrylic acid (PAA) film was used.

The following gas phase chemical modification reaction was carried out for both the standard sample and the measurement sample.

R-COOH + CF3CH2OH + C6H11NCNC6H11 → R-CO
OCH2CF3 ＋ C6H11NHCONHC6H11 Approximately 1c of sample film and standard sample PAA film
Cut into m-squares and esterify the carboxylic acid on the film surface with trifluoroethanol (TFE) using pyridine and dicyclohexylcarbodiimide (DCC) as catalysts in an air atmosphere in a desiccator (Sample film and PAA film are the same batch). I did it in).

From the PAA standard sample, the reaction rate (r) with TFE and the residual rate (m) of DCC used as a reaction catalyst were determined, and the peak areas of C1S and F1S of each sample were taken into consideration in terms of r and m and the film surface. Carboxylic acid concentration (-COOH / C [to
tal]).

(13) Element winding property In the above-described capacitor manufacturing method, the element winding completed product was disassembled before the pressing step, and judged by the meandering state of two films. A meandering of less than 0.5 mm was indicated by 良好 as good, and a meandering of 1.0 mm or more was indicated by X as unusable. In addition, the intermediate ones are indicated by △.

(14) Sliding property The friction coefficient was evaluated. AS is a method of evaluating the coefficient of friction.
According to TM D1894.

(15) Tan δ change rate (δ2-δ1) × 100 / δ1 = tan δ change rate Sample preparation: A sample in which circular aluminum with a diameter of 18 mm was vapor-deposited on both sides at 80 ° C. and 80% for measurement of dielectric loss.
After standing for 72 hours at 23 ° C. and 65% RH for 10 minutes, a sample (dielectric loss δ2 determined by the following measurement) was used. Next, do not leave it under high temperature and high humidity 23
The sample left to stand at 65 ° C. and 65% RH was used as a comparative sample (dielectric loss δ1 determined by the following measurement).

Measurement: DEA2970 (TA INSTR
Made by UMENTS) at 60 at 23 ° C. and 65% RH
The dielectric loss at Hz was obtained.

(16) Tan δ in condenser Measured by using LCR meter 4284A manufactured by HEWLETT PACKARD.

(17) Castability: In the electrostatically-charged cast, the cast speed is indicated by the upper limit of the casting speed at which no surface defect occurs.

[0087]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Comparative Examples 1-5, Examples 1-6 After the transesterification reaction from dimethyl terephthalate and ethylene glycol, the addition amounts of magnesium acetate and trimethyl phosphate were changed to obtain M / P as shown in Table 1. It was Further, in Comparative Examples 1 and 5 and Examples 1 to 3, 0.08 parts of aggregated silica particles having an average particle size of 1.1 μm are used.
Is 0.3 parts of the same particles, and Example 6 is 1.
5 parts, Example 5 was 0.08 part of aggregated silica particles having an average particle size of 0.6 μm, Comparative Example 4 was 0.2 parts of aggregated silica particles having an average particle size of 2.0 μm, and Comparative Example 3 was an average particle size. 0.1 part of 0.13 μm silica particles was made into ethylene glycol slurry and added before polymerization, and polymerization was carried out so that the intrinsic viscosity became 0.6, and the total amount of polymer was 100 parts to obtain a polyester resin. This polyester resin was vacuum dried at 180 ° C., supplied to an extruder and melted at 285 ° C.
The sheet was discharged from the die and cast on a cooling drum.

This film was heated to 90 ° C., stretched 3.3 times in the longitudinal direction and stretched in the width direction, and then stretched at 215 ° C. to 3.5 times.
% Relaxation treatment was performed to obtain a 5.4 μm biaxially stretched film. Each of the films thus obtained was used to make a capacitor, and the insulation resistance, high-temperature long-time withstand voltage characteristics, etc. were evaluated.

The evaluation results are shown in Table 1.

[0091]

[Table 1] As is clear from Table 1, M / P is 0.8 to
4. By setting the maximum roughness Rmax within the range of 0.1 to 2 μm, the insulation resistance is excellent, the high-temperature long-term withstand voltage property is also excellent, and the element winding property and the high-speed castability are also excellent. Can be obtained, and also excellent in productivity can be obtained.

[0092]

According to the present invention, compared with the conventional film,
It has excellent withstand voltage, especially withstand voltage at high temperature and long time load, less decrease in insulation resistance, high casting speed, high productivity, and excellent polyester film for capacitors. Further, according to the present invention, it is possible to provide a capacitor which is excellent in withstand voltage, particularly withstand voltage characteristics at high temperature and long time load, and has a small decrease in insulation resistance.

Claims (5)

[Claims] 1. A polyester film having an M / P of 0.8 to.
4. The polyester film for capacitors, which is 4 and has a maximum roughness Rmax of 0.1 to 2 μm. However, M and P represent the residual amount (equivalent amount) of metal (excluding antimony metal) and phosphorus in the polymer, respectively. 2. The polyester film for capacitors according to claim 1, which has a surface roughness Ra of 0.003 to 0.8 μm. 3. The polyester film for capacitors according to claim 1, which has a polyester, polyester urethane or acrylic resin coating on at least one surface. 4. A metallized polyester film having a metal layer formed on at least one surface of the polyester film according to claim 1. 5. A film condenser comprising the metallized polyester film according to claim 4.