JPH106461A - Polyester film, metallized polyester film and film condenser - Google Patents

Abstract

(57) Abstract: A film comprising a biaxially oriented polyester film on at least one surface of which a film made of a polyester resin and / or a polyester urethane resin is formed, wherein the water absorption of the film is 3 wt% or less, A polyester film having a resin resistance of 2 to 5. [Effect] The polyester film of the present invention is superior to conventional films in resistance to moist heat under high temperature and high humidity.
A polyester film having a small increase in tan δ, hardly causing a capacitor breakdown at a low voltage, and having excellent environmental resistance and suitable for a capacitor was obtained.

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 use in a capacitor, and more particularly to a polyester film excellent in handling properties such as withstand voltage, low dielectric loss, slipperiness and winding property, and wet heat resistance, The present invention relates to a polyester film having excellent resin resistance.

[0002]

2. Description of the Related Art Conventionally, a polyester film or the like is disclosed in Japanese Patent Publication No. 1-19343 in which an aqueous polyurethane having a carboxyl base on its surface is mixed and coated with an epoxy compound having two or more epoxy groups. It is also known as
A water-soluble or water-dispersible polyurethane having a carboxyl group or a salt thereof in a side chain of ８8 wt% and / or a polyester mixed with and containing an epoxy compound having two or more epoxy groups, applied, and provided with a metal deposition layer. Japanese Patent Publication 7-81179
It is known that these materials are coated with a specific coating agent to improve the adhesiveness and the water-resistant adhesiveness between various materials and vapor-deposited metals and the base polyester film.

[0003] A metal-deposited polyester film capacitor comprising a resin selected from the group having a carboxyl group, a hydroxyl group or a salt thereof and containing at least one of an isocyanate compound, an epoxy compound and an amine compound. Japanese Patent Laid-Open No. 5-2521
No. 59 is known. All of these are known to improve the adhesion between the vapor-deposited metal and the base polyester film and the water-resistant adhesion by coating them, and to prevent a decrease in capacitance when the capacitor is placed under high temperature and high humidity. I have.

[0004]

However, in the above-mentioned method, although a certain effect can be expected for the purpose, further improvement of the moist heat resistance is required, and the humidity resistance under a higher temperature is required due to severe use conditions. There is a need for improved thermal life characteristics. Further, in the above method, when a capacitor is used, the coating material absorbs a large amount of water, and the dielectric loss increases under high temperature and high humidity. As a result, the capacitor is destroyed at a low voltage. In addition, the resin (including the undercoat) that forms the exterior of the capacitor has a problem that dielectric loss increases and the capacitor is destroyed (has no resin resistance).

[0005] The present invention is intended to further improve the moist heat life characteristics in the above-mentioned capacitor applications and to improve the moist heat life characteristics at higher temperatures (hereinafter, the moist heat resistance is referred to as including both). The purpose of the present invention is to prevent the capacitor from being destroyed at a low voltage.

[0006]

According to the present invention, there is provided a biaxially oriented polyester film having at least one surface coated with a polyester resin and / or a polyester urethane resin. Is a polyester film characterized by having a water absorption of 3 wt% or less and a resin resistance of 2 to 5 in the film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester used for the polyester film in the present invention is a crystalline thermoplastic resin composition which has been polymerized by esterification. Such a polyester comprises a dicarboxylic acid component and a glycol component. Is obtained by polycondensation.

As the dicarboxylic acid component, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenylethanedicarboxylic acid and the like are used. As the glycol component, ethylene glycol, propylene glycol, tetramethylene glycol, cyclohexanedimethanol are used. Are 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 or blended with these polymers.

Further, the M / P (described below) of the polyester of the present invention is preferably 1.8 or less, more preferably 1.4 or less, further preferably 1.2 or less, and particularly preferably 1 or less. Is preferable because the insulation resistance at room temperature and high temperature is improved. Further, it is preferable because the wet heat resistance property is also improved.

The polyester of the present invention has an intrinsic viscosity [η] of preferably at least 0.5 dl / g, more preferably at least 0.6 dl / g, further preferably at least 0.65 dl.
/ G or more, particularly preferably 0.7 dl / g or more, for a capacitor, in terms of pressure resistance, mechanical properties, and wet heat resistance, and also in terms of recoverability.

This polyester film needs to be biaxially stretched (oriented), and is preferable in terms of mechanical properties, thermal properties, and electrical properties. The coating layer may be in an oriented state or an unoriented state.

The resin forming the film of the present invention must be a polyester resin and / or a polyester urethane resin from the viewpoint of the wet heat resistance and the reduction of dielectric loss.

The polyester resin can be obtained by polycondensing a dicarboxylic acid component and a glycol component. Examples of the carboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and trimethyladipin. 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-
Naphthalic acid, diphenic acid, 4,4'-oxybenzoic acid, 2,5-naphthalenedicarboxylic acid and the like are used. The carboxylic acid may be an acid anhydride, an ester, a chloride and the like, for example, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl terephthalate, diphenyl terephthalate and the like. Is used. Among them, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and the like are preferable because the water absorption can be kept low, and the glass transition temperature can be raised, the dielectric loss can be suppressed, and the breakdown voltage of the capacitor can be suppressed. Used.

The glycol component includes 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 are used. Among them, ethylene glycol, diethylene glycol, neopentyl glycol, and the like are preferably used because they can suppress the water absorption rate, suppress an increase in dielectric loss, and suppress a decrease in breakdown voltage of the capacitor.

Further, the polyester resin preferably has a carboxylic acid on the surface of the polyester film.
The use of a terminal carboxylic acid as disclosed in JP-B-60-23983 does not provide sufficient wet heat resistance and easy adhesion, and preferably has a carboxylic acid in the side chain or pendant.

Examples of polyester resins having a carboxylic acid in the side chain include JP-A-54-46294, JP-A-60-209073, and JP-A-62-240318.
JP-A-53-26828, JP-A-53-28828
26829, JP-A-53-98336, JP-A-56-116718, and JP-A-61-1246.
No. 84, etc., and can be produced using a resin obtained by copolymerizing a trivalent or higher polycarboxylic acid. Also, other methods may be used.

The trivalent or higher polycarboxylic acid includes
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,
For example, 2,2 ', 3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylenetetracarboxylic acid and the like are used. Among them, particularly preferred is a polyester copolymer, in which the molecular weight decreases with increasing temperature and increases with decreasing temperature (the molecular weight does not need to be the original molecular weight). Those that change are preferable because they do not easily cause a decrease in melt viscosity at the time of reuse, coloring, generation of foreign substances due to gelation, and foaming. Examples of this are 5,
(2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid and the like are used.

The polyester resin may be formed by a composite film forming method such as hot melt or melt extrusion, or may be made water-soluble and / or water-dispersible using a neutralizing agent such as ammonia or triethylamine to form a coating method (inline,
Offline).

Examples of the polyester urethane-based resin include JP-B-53-38760, JP-B-6-80121 (JP-A-61-228030), and JP-B-8-82030.
For example, water-soluble and / or water-dispersible resins described in Japanese Patent No. 22900 (JP-A-61-36314) are used.

The polyester component and the glycol component are specific components similar to the polyester resin, which can suppress the water absorption, increase the glass transition temperature, suppress the dielectric loss, and suppress the breakdown voltage of the capacitor. It is preferable because the decrease can be suppressed.

The isocyanate component includes tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lysine diisocyanate, and isophorone diisocyanate. , Trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate,
Naphthalene diisocyanate, tetrahydronaphthalene diisocyanate and the like are used, and among these, tolylene diisocyanate is particularly preferred from the viewpoint of reducing the water absorption and the dielectric loss.

In order to obtain a specific surface carboxylic acid concentration, it is preferable that the urethane resin has a carboxylic acid in a side chain. Specific examples thereof include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid,
2,2-dimethylolvaleric acid and the like are used. This manufacturing method is disclosed in Japanese Patent Publication No.
No. 1-228030) and Japanese Patent Publication No. 8-22900 (Japanese Unexamined Patent Publication No. 61-36314).

The resin forming the coating film of the present invention has a glass transition temperature of at least one resin of more than 80 ° C., preferably more than 85 ° C., and more preferably 85 to 160 ° C.
It is preferred that If the temperature is lower than 80 ° C., the dielectric loss increases and the withstand voltage decreases, and when used as a capacitor, problems such as destruction occur. In particular, the dielectric loss increases in a high temperature region, and deteriorates remarkably in a low frequency region.
In addition, the self-heel property tends to deteriorate, which is not preferable. At a temperature exceeding 160 ° C., the stretchability deteriorates, and a film cannot be obtained stably, or problems such as surface defects occur. In addition, it causes poor adhesion and deteriorates wet heat resistance, or when it is used as a multilayer capacitor,
There is a problem that the shape retention is poor, the lamination is easily broken, the handling during production is difficult, and the yield is reduced.

In order to obtain this glass transition temperature, in the case of the above-mentioned polyester resin or polyester urethane resin of the coating resin, 2,6-naphthalenedicarboxylic acid, phenylindanedicarboxylic acid, benzophenonedicarboxylic acid, As the glycol component, 1,2-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, bisphenol A, dihydroxybenzophenone, xylylene glycol, or the like may be appropriately combined for copolymerization or as described later. Obtained by copolymerizing pyromellitic acid, naphthalenetetracarboxylic acid, 5, (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid of a polyvalent carboxylic acid, or the like. La 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 carboxylic acid concentration on the surface thereof is preferably 0.003 to 0.003.
0.05, further preferably 0.005 to 0.05, more preferably 0.008 to 0.05, and 0.003
If the amount is less than the above range, the improvement of the moist heat resistance and the easy adhesion property of the capacitor becomes insufficient, which is not preferable. Further, if the amount is more than necessary, the wet heat resistance, the recoverability and the like tend to deteriorate, which is not preferable.

The polyester film of the present invention must have a water absorption of 3 wt% or less, and preferably has a water absorption of 0.3 wt% or less.
2 to 2.5 wt%. If it exceeds 3 wt%,
The dielectric loss increases, and the dielectric breakdown voltage decreases for a long time under high temperature and high humidity conditions. On the other hand, if it is too small, a charging phenomenon occurs in the winding of the capacitor element, and the winding yield tends to decrease, and the productivity tends to decrease.

The polyester film of the present invention must have a resin resistance (to be described later) of from 2 to 5, preferably from 3 to 5. If it is less than 2, when the capacitor is used, there is a problem that the resistance is increased at the terminal lead-out portion, heat is generated, and in severe cases, the capacitor is broken.

It is preferable to apply a crosslinking agent such as melamine, epoxy, or isocyanate to the water-soluble and / or water-dispersible coating agent of the above-mentioned resin of the polyester film of the present invention. It is preferable because it maintains the life and has excellent resin resistance. Further, an epoxy compound having two or more epoxy groups, preferably three to five epoxy groups, is preferable in terms of wet heat resistance, dielectric loss, and resin resistance.

The amount of the epoxy added is 7
To 30 parts by weight, more preferably 10 to 25 parts by weight.
If the amount is less than 7 parts by weight (based on the solid content of the coating agent), the resin resistance is poor, which leads to an increase in dielectric loss and a destruction of the capacitor. If the amount is more than 30 parts by weight, problems such as an increase in water absorption, an increase in dielectric loss, a decrease in wet heat resistance, and a decrease in pot life of a coating solution occur.

Preferred epoxy compounds in this method include polyepoxy compounds having at least two or more oxirane rings in the molecule, for example, epichlorohydrin / bisphenol A type epoxy resin represented by the structural formula (1):

Embedded image A chain epoxy resin represented by the structural formula (2),

Embedded image A novolak type epoxy resin represented by the structural formula (3),

Embedded image A flame-retardant epoxy resin represented by the structural formula (4),

Embedded image A cycloaliphatic epoxy resin represented by the structural formula (5),

Embedded image Further, those having two or more epoxy groups in the molecule and having the following structure are used.

[0032]

Embedded image

Embedded image Also, when the coating material is a polyester urethane resin,
Self-crosslinking polyester urethane may be used.

The coating resin of the present invention contains a crosslinking accelerator for promoting the above-mentioned crosslinking, for example, diethylenetriamine, triethylenetetramine, benzylmethylamine,
Metaphenylenediamine, diaminodiphenylmethane,
The addition of xylylenediamine or the like promotes the cross-linking reaction and seems to improve the productivity. However, the addition of xylylenediamine lowers the wet heat resistance, so that it is preferably not added.

Another method is disclosed in JP-A-63-158.
No. 16, JP-A-63-256661, JP-A-6-287259, JP-A-7-292060, etc., as described as a method for producing a water-soluble and / or water-dispersible urethane resin. By using a cross-linked polyester urethane-based resin aqueous dispersion as a coating liquid cross-linked in a water-dispersed state, it has excellent wet heat resistance,
In addition, it is preferable because a resin having excellent resin resistance and excellent pot life of a coating solution can be obtained. In addition, these properties make it possible to obtain better wet heat resistance and resin resistance than those obtained by adding the epoxy compound to the coating agent later, and to greatly improve the pot life of the coating liquid. As the cross-linking agent, the above-mentioned epoxy compound or the like is used.
The same excellent characteristics can be obtained for the polyester-based resin in the same manner.

The coating resin of the present invention has a softening temperature of 14
It is preferably at least 0 ° C., more preferably 150 ° C.
C., more preferably 160 ° C. or higher. 14
The temperature of 0 ° C. or higher is preferable in terms of improving the resin resistance, the wet heat resistance, and the heat resistance of the capacitor.

The polyester film on which the coating of the present invention is formed preferably has a center line average roughness SRa of 100 nm or less, preferably 10 to 80 nm. 1
If the thickness exceeds 00 nm, the smoothness is poor and problems may occur in terms of wet heat resistance, withstand voltage and the like. Also,
If it is too small, the slipperiness is deteriorated, and depending on the material, blocking may occur, which may make handling difficult or windability worse.

The maximum height SRmax is 2000
nm or less, more preferably 500 to 150 nm.
0 nm is preferred. If the thickness exceeds 2,000 nm, the withstand voltage, particularly the step-up DC withstand voltage, decreases, and the wet heat resistance characteristic tends to decrease. If the diameter is too small, the air bleeding property is poor at the time of winding, which causes problems such as meandering of the film.

The heat shrinkage of the film of the present invention at 150 ° C. for 30 minutes is preferably 1.5% or less, more preferably 0.1 to 1.2%. When the content exceeds 1.5%, the capacitor is formed after vapor deposition, and when left at high temperature and high temperature and high humidity, irregularities are generated on the surface. As a result, the dielectric loss tends to increase, and the cause of the destruction of the capacitor is easily caused.
In addition, if it is too small, the same problem is likely to occur.

This coating layer is coated with a water-dispersible resin and / or a water-soluble resin of the above-mentioned coating resin before stretching in biaxial stretching film formation or before uniaxial stretching and before biaxial stretching, and is stretched. Although it is obtained, off-line or in-line coating may be performed using a solvent other than hot melt or water.

The thickness of the coating layer in the present invention is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm on at least one side, and if less than 0.01 μm, the surface roughness of the present invention cannot be obtained. In addition, the sliding property, the element winding property, etc. are poor, and the effect of improving the wet heat resistance is insufficient, which is not preferable. If the thickness exceeds 5 μm, in a capacitor application, various electric characteristics such as withstand voltage and corona discharge destruction, and self-healing property are deteriorated.

Fine particles may be added to the base polyester layer or the coating layer in order to improve the winding property and slip property of the film and the winding property of the capacitor element. The inorganic particles include silica, alumina, zirconia, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, and the like.The organic particles include acrylic acid, styrene, polyester, and the like. Are used. The surface roughness is preferably adjusted by the particle size and the amount of addition which constitute the surface roughness.

Next, the manufacturing method of the present invention will be described, but the present invention is not necessarily limited thereto.

First, polyester as a base material is melt-extruded by an extruder, cooled on a cooling roll to a temperature lower than the glass transition point, cast, heated to a temperature higher than the glass transition point, and then 2.8-7. Stretch 5 times and coat with the above-mentioned coating resin (the surface of the substrate is subjected to corona discharge treatment if necessary)
Then, with a stenter, Tg of the base polyester ~ 1
After preheating to 70 ° C, the film is stretched 3 to 12 times in the width direction, and is relaxed if necessary, at a temperature lower than the melting point of the base polyester, preferably 235 ° C or lower, more preferably 225 or lower.
C., more preferably 220-200.degree. C., is preferred for reducing dielectric loss.

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

As the evaporation source, a boat type of resistance heating type, a crucible type by radiation or high frequency heating,
There is a method using electron beam heating, but there is no particular limitation.

The metals used for this deposition are Al, Z
Metals such as n, Mg and Sn are preferred, but Ti, In,
Cr, Ni, Cu, Pb, Fe and the like 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 this case, aluminum is particularly preferable in terms of productivity and cost. Aluminum is deposited on at least one side to provide an aluminum deposited film. At this time, for example, Ni, Other metal components such as Cu, Au, Ag, Cr, Zn can also be deposited.

The thickness of the aluminum varies depending on the purpose of use, but is preferably from 10 to 200 nm from the viewpoint of capacitor characteristics, particularly self-healing properties.

For use in capacitors, the aluminum oxidation index of the surface of the deposited aluminum film is preferably 1.65 or less, more preferably 1.45 to 1.45.
1.6 further improves the moist heat resistance.

The polyester film of the present invention has the following properties:
The heat shrinkage at 50 ° C. for 30 minutes is preferably 1.5% or less, more preferably 1% or less at least in the longitudinal direction after forming the condenser.

[0051]

【Evaluation method】

(1) Intrinsic viscosity [η] of polyester Polyester is dissolved in o-chlorophenol,
Was measured.

(2) Water Absorption Polyester films were layered and cut into 2 cm squares, placed in a weighing bottle, vacuum dried at room temperature for 48 hours, and
Let it be 1. This sample was allowed to stand at 60 ° C. and 80% RH, and the weight was measured over time. The weight at the time of the parallel state was defined as W2, and the water absorption was determined by the following equation (W2 is the time of water absorption. The change was within 10%).

Water absorption (%) = (W2−W1) × 100 / W1

(3) Resin Resistance Sample Preparation Aluminum was coated on the evaluation surface of the polyester film to be evaluated by a vapor deposition machine with a surface resistance of 1 to 5 Ω / □ or 20 to 10
Evaporation was performed to a thickness of 0 nm. For a capacitor made of a metallized film, its vapor deposition surface is evaluated.

Evaluation procedure An epoxy resin SR-10 manufactured by Sanyuresin Co., Ltd. and its curing agent H-330 were applied on the vapor deposition surface of the vapor deposition film in a ratio of 100: 8.
The mixture mixed at a ratio of 0 (weight ratio) is applied or dropped, left at room temperature for 30 minutes, then left in a hot air oven at 105 ° C for 1 hour, and observes the surface change of the applied or dropped portion (enlarged observation such as under a microscope). And the following evaluation criteria.

When a certain change such as a wrinkle or a squamous shape is recognized, the change is represented by the size of the largest part of the change. Number). The following five-step evaluation was performed.

5: No change: less than 0.05 mm (good and usable) 4: 0.05 to less than 0.1 mm (slightly problematic,
Available: 3: 0.1 to less than 0.2 mm (problematic, but can be used depending on application) 2: 0.2 to less than 0.3 mm (very problematic, but usable depending on application) 1: 0.3 mm Above (cannot be used)

(4) Center line average roughness Ra of the film is measured according to JIS-B0601. ET-30K
(Manufactured by Kosaka Seisakusho) by a stylus method.

(5) Aluminum Oxidation Index on the Surface of Aluminum Vapor Deposition Film The surface of the vapor deposition film is analyzed by X-ray photoelectron spectroscopy. If the sample is a capacitor, disassemble it and expose the evaporation surface to air to make 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 by the bonding state of each atom, the aluminum oxidation index O /
Al is determined by equation (1).

O / Al = [O (Al oxide) / Al (Total)] / [Al (III) / Al (Total)] (1) where [Al (III) / Al (Total)] Is the abundance ratio of Al (III) obtained by dividing the peak of aluminum atoms, and [O (Al oxide) / Al (Total)] is combined with simple oxygen and elements other than aluminum from the total oxygen concentration with respect to aluminum. It is determined by subtracting the oxygen concentration. That is, for example, the concentration of oxygen bonded to carbon is obtained by dividing the peak of carbon. At this time, when the amount of oxygen cannot be specified, such as when several oxygen-containing functional groups are considered or separation is impossible due to close binding energy, the most oxygen is bonded to carbon. Estimate. 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.

Apparatus: ES manufactured by Shimadzu Corporation
CA750 Excitation X-ray: MgKα1,2 (1253.6e
V) Energy correction: binding energy of C1S main peak is 284.6 eV. Photoelectron escape angle: 90 degrees.

(6) Moisture / Heat Resistance of Capacitors The capacitors were placed in an atmosphere of 60 ° C. and 95% RH for 400 hours.
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.

The moist heat resistance under further high temperature was the same except that the ambient temperature was 85 ° C.

(7) Average withstand voltage of sheet Measured with a sheet BDV (dielectric breakdown voltage) DC according to JIS-2110. 100μm thickness, 10c on cathode
m square aluminum foil electrode, anode made of brass 25mmφ, 500g
The electrode was used, and a film was sandwiched between them, and a voltage was applied at a rate of 100 V / sec using a high voltage DC power supply manufactured by Kasuga Electric Co., Ltd. And this is measured 30 times,
The average voltage was shown.

(8) Production of Capacitor Aluminum was vacuum-deposited on one side of the film so that the surface resistance was 2 Ω / □. At this time, vapor deposition was performed in a stripe shape having a margin portion running in the longitudinal direction (the vapor deposition portion had a width of 8.0 mm and the margin portion had a width of 1.0 mm repeatedly).
Next, a blade was inserted into the center of each vapor deposition section and the center of each margin section, slitted, wound up into a 4.5 mm-wide tape having a left or right margin of 0.5 mm, and formed into a reel.

Each of the reels having the left margin and the right margin of the obtained reel was overlapped and wound, and a wound body having a capacitance of about 0.047 μF was obtained. At this 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 the wound body,
Pressing was performed at a temperature and pressure of 50 ° C. and 1 MPa for 5 minutes. Metallicon was sprayed on both ends to form external electrodes, and lead wires were welded to the metallikon to obtain a wound capacitor element.

An epoxy resin SR-10 manufactured by Sanyuresin Co., Ltd. and a curing agent H-33 were added to the capacitor element.
0 was mixed at a ratio of 100: 80 (weight ratio) and impregnated (from the end face) and coated (overall). (Impregnation time: 30
Seconds) However, a capacitor element previously heated at 120 ° C. for 1 hour is quickly impregnated. Then, it was cured at 100 ° C.

(9) Glass transition temperature (Tg) “Robot” DSC-RDC manufactured by Seiko Electronic Industry Co., Ltd.
220, using SSC5200 HDIS STATION, sample 2 to 5 mg, and heat up at 20 ° C /
It was measured in minutes and determined. 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 substrate with a solvent, the solvent was removed, and only the coating resin was taken out. If this was difficult, only the coating layer was scraped off 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.

(10) Concentration of Carboxylic Acid on Surface Using ESCA750 manufactured by Shimadzu Corporation, it was measured under the following conditions.

Excitation X-ray: MgKα1,2 (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 performed for both the standard sample and the measurement sample.

R-COOH + CF ₃ CH ₂ OH + C ₆ H
₁₁ NCNC ₆ H ₁₁ → R-COOCH ₂ CF ₃ + C ₆ H ₁₁
NHCONHC ₆ H ₁₁

A sample film and a PAA film as a standard sample were cut into about 1 cm squares, and pyridine and dicyclohexylcarbodiimide (DC) were placed in a desiccator under an air atmosphere.
C) was used as a catalyst to esterify the carboxylic acid on the film surface with trifluoroethanol (TFE) (the sample film and the PAA film were performed in the same batch).

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

(11) Element winding property In the above-described method for manufacturing a capacitor, the element wound was disassembled before entering the pressing step, and judgment was made based on the meandering state of the 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 △.

(12) Slipperiness Evaluation was made based on the coefficient of friction. AS is a method of evaluating the coefficient of friction.
According to TM-D1894.

(13) Change in tan δ The tan δ after preparing the condenser was measured, and
The difference from anδ was shown.

A change of ± 3% or less is regarded as good, and ± 3%
超 え indicates ± 5% or less and ± 5% ± 7% or less
In this case, Δx exceeding ± 7% and ± 10% or less was indicated by Δ ×, and ± 10% or more was indicated by × as unusable.

(14) Softening Temperature The coating resin was dried under vacuum at 100 ° C., and further dried at 230 ° C. for 15 minutes. The temperature of the coating resin lowered to normal temperature under vacuum was evaluated and measured as follows.

Using the above resin with a Koka type flow tester,
A load of 10 kg was applied to a nozzle having a diameter of 1.0 mm, a nozzle length of 5 mm, and a cylinder diameter of 10 mm, and the temperature was raised at a rate of 4 ° C./min.

(15) M / P The residual amount (equivalent) of metal (M) (excluding antimony metal) and phosphorus (P) in the film was determined by X-ray fluorescence spectroscopy.

[0083]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Comparative Example 1 Polyethylene terephthalate (IV = 0.65) was used as a polyester resin, dried in vacuum at 180 ° C., supplied to an extruder, melted at 285 ° C., discharged from a T-die, cooled. Cast on drums.

This film was heated to 90 ° C., stretched 3.3 times in the longitudinal direction, stretched 4 times in the width direction, and subsequently stretched 215 times.
A 3.5% relaxation treatment was performed at ℃ to obtain a 5.4 μm biaxially stretched film.

Comparative Example 2 0.14 mol of terephthalic acid, 0.86 mol of isophthalic acid and 0.35 mol of diethylene glycol were used as coating agents.
1, 0.67 mol of neopentyl glycol in the presence of a catalyst at 190 to 220 ° C. while removing water distilled
The mixture was reacted for 1 hour at 250 ° C. under reduced pressure for 1 hour to obtain a prepolymer, which was then treated with 5- (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2 -0.14 mol of dicarboxylic anhydride
And subjected to a selective monoesterification reaction at 140 ° C. for 3 hours to obtain a polymer. This polymer has an oxidation of 66 KOH
mg / g. The polymer was neutralized with ammonia to obtain an aqueous solution. This coating agent was formed into a film under the same conditions as in Comparative Example 1. At this time, after stretching in the longitudinal direction, the coating agent was applied to both surfaces so as to have a coating thickness of 0.1 μm. A biaxially stretched film having a total film thickness of 5.4 μm was obtained.

Examples 1 to 4 As a coating agent, 100 parts by weight of the same polymer as in Comparative Example 2 was used.
Epoxy compound CR-5L having 4 to 5 epoxy groups
(Manufactured by Dainippon Ink and Chemicals, Inc.) to 7 (Example 1),
10 (Example 2), 20 (Example 3), and 35 parts by weight (Example 4) were added to obtain a biaxially stretched film under the same film forming conditions as Comparative Example 2.

Example 5 "Polyester" (polyester water-dispersible resin) W0030 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) as a coating agent
25 parts by weight of the above-mentioned CR-5L was added to 0 parts by weight, and a film was formed under the same conditions as in Comparative Example 2 to obtain a biaxially stretched film. A biaxially stretched film having a coating thickness of 0.15 μm on both sides and a total film thickness of 5.4 μm was obtained.

Example 6 In addition to the coating material of Example 4, 5 parts by weight of "Epiclone" (alicyclic tetracarboxylic anhydride) B4400 (manufactured by Dainippon Ink and Chemicals, Inc.) ("Polyester" ( Polyester-based water-dispersible resin) based on 100 parts by weight of solids)
And a film was formed under the same conditions as in Comparative Example 2. Coating thickness 0.
A biaxially stretched film having a thickness of 15 μm and a total film thickness of 5.4 μm was obtained.

Comparative Example 3, Examples 7 to 9 Using "Hydran" (a polyester urethane-based water-dispersible resin) HW-350 (manufactured by Dainippon Ink and Chemicals, Inc.) as a coating agent (Comparative Example 3) , And CR-5
L (7 parts by weight in Example 7) and 20 parts by weight (Example 8) (based on 100 parts by weight of the solid content of HW-350) were added in the same manner as in Example 1 to obtain a total film thickness of 5. 4μ
m was obtained.

Example 9 was prepared by reducing the water absorption by vacuum-drying the same material as in Example 8 and then vacuum drying.

Example 10 "Hydran" (polyester urethane-based water-dispersible resin) HW-350 (manufactured by Dainippon Ink and Chemicals, Inc.) 5 parts by weight of CR-5L were added per 100 parts by weight of solids, and The mixture was stirred and mixed at 15 ° C. for 15 hours to obtain a coating agent as an aqueous dispersion of a polyester urethane resin crosslinked in an aqueous dispersion state.

Otherwise in the same manner as in Example 1, a biaxially stretched film having a total film thickness of 5.4 μm was obtained.

The results are shown in Table 1. As a result of having a specific coating, having a water absorption of 3 wt% or less, and having a resin resistance of 2 to 5, the increase in tan δ was small and the wet heat resistance was poor. An excellent polyester film for a condenser was obtained.

Further, by using a cross-linked water-dispersible polyester urethane, more excellent properties can be obtained, and the pot life property (Examples 1 to 9 show changes in the coating solution at 40 ° C. and 48 hours. In Example 10, no change was observed).

[0096]

[Table 1]

[0097]

The polyester film of the present invention has excellent resistance to moist heat under high temperature and high humidity, has a small increase in tan δ, is less likely to cause capacitor breakdown at low voltage, and has excellent environmental resistance as compared with conventional films. A polyester film suitable for a capacitor was obtained.

Claims (8)

[Claims] 1. A film comprising a polyester resin and / or a polyester urethane resin formed on at least one surface of a biaxially oriented polyester film, wherein the film has a water absorption of 3% by weight or less and a resin resistance of 2% or less. Polyester film characterized by the following formula: 2. A film is formed by applying and drying a water-soluble and / or water-dispersible crosslinked polyester resin and / or a water-soluble and / or water-dispersible crosslinked polyester urethane resin. The polyester film according to claim 1, wherein: 3. The polyester film according to claim 1, wherein the softening temperature of the coating resin is 140 ° C. or higher. 4. The method according to claim 1, wherein the surface carboxylic acid concentration of the coating is 0.003.
4. The method according to claim 1, wherein the value is from 0.05 to 0.05.
The polyester film according to any one of the above. 5. The polyester film according to claim 1, wherein the heat shrinkage of the film at 150 ° C. for 30 minutes is 1.5% or less. 6. The film has a center line average roughness SRa of 10
0 nm or less and the maximum height SRmax is 2000
The polyester film according to any one of claims 1 to 5, wherein the thickness is not more than nm. 7. A metallized polyester film obtained by forming a metal layer on at least one surface of the polyester film according to any one of claims 1 to 6. 8. A film capacitor obtained by winding or laminating the metallized polyester film according to claim 7.