JPH10156938A - Polypropylene film and capacitor using the same as dielectric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance long-term dielectric breakdown characteristics at high temp. and the permeability and swelling resistance between film layers at a time of the immersion in insulating oil by specifying the isotacticity and isotactic pendant ratio of a biaxially oriented polypropylene film and the center line average surface roughness of both surfaces thereof. SOLUTION: The isotacticity of a biaxially oriented polypropylene film is 98.5-99.5%. The isotacticity is defined by the ratio of the wt. of the insoluble component in the film to the wt. of the film before extraction when the film is extracted with boiling n-heptane. The stereoregularity of the polypropylene film is evaluated on the basis of a pendant ratio by an absorption peak of a methyl group measured by<14> C-NMR and the isotactic pendant ratio mmmm of this film exceeds 99%. Further, the max. roughness of both surfaces of the biaxially oriented polypropylene film is pref. 0.1-4.0μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene film and a capacitor using the same as a dielectric material, and more particularly to a capacitor having excellent heat resistance and dielectric breakdown resistance, few insulation defects, and immersion in insulating oil. Biaxially oriented polypropylene film with excellent penetration of insulating oil between film layers and swelling resistance, and excellent heat resistance, dielectric breakdown resistance, corona resistance and long-term heat resistance using it as a dielectric It concerns the condenser.

[0002]

2. Description of the Related Art Biaxially oriented polypropylene films are excellent in optical properties such as transparency and glossiness, mechanical properties such as rupture strength and elongation at break, as well as water vapor barrier properties and excellent electrical properties. Widely used for applications, tapes, capacitors, etc.

[0003] Such a biaxially oriented polypropylene film is one of the typical materials used as a dielectric material of a film capacitor. However, the biaxially oriented polypropylene film has a lower heat resistance than a polyester film which is another typical material. As the maximum use temperature was limited to about 85 ° C. The reason for this is that when the operating temperature rises, the dielectric breakdown strength, which should be a feature of the polypropylene film, suddenly drops due to the effects of the amorphous portion of the film and foreign substances, and it can withstand long-term use. This is because it sometimes disappeared.

[0004] On the other hand, with the miniaturization of electric devices, the density and temperature of elements have been increased, and there has been an increasing demand for further increasing the maximum operating temperature of conventional polypropylene film capacitors. Especially for capacitors mounted in AC circuits, polypropylene films that have a characteristic of low dielectric loss have been used as dielectrics because of the need to suppress heat generation from inside the capacitor elements, but the environment surrounding the AC circuit becomes high temperature in accordance with,
It is becoming difficult to use it, which is one of the obstacles to miniaturization of electric devices. The reason for this is that the circuit in which the heat source is located close to it has been installed at a certain distance from the heat source so that the temperature of the circuit does not rise due to the heat source, or the heat source and the circuit are cut off with a heat insulating material. However, there has been an increasing demand for installing a circuit in the vicinity of a heat source without a heat insulator due to miniaturization. Representative examples of such a demand are an AC circuit and a motor control circuit used for a lighting stabilizer such as a street light. To meet this demand, the maximum operating temperature of conventional polypropylene film capacitors, 85
It was necessary to maintain the performance at a temperature higher than ℃ and for a long period of time.

[0005] For this reason, polypropylene films used as dielectrics have (1) that the mechanical deformation due to rapid heating in a short time, that is, the heat shrinkage is moderately small;
It has been required that (2) the film has excellent electrical properties at high temperatures and (3) the electrical properties have a small decrease with time at high temperatures.

The reason for the above (1) is that when a capacitor element is produced, a heat treatment is applied at a certain temperature at a stage when the polypropylene film is wound on the electrode so that a proper heat shrinkage is caused to cause tightness. It is common practice to maintain the shape and expel air between the film layers, but if the heat shrinkage is too large, the deformation of the element may cause a reduction in the capacity of the capacitor or the destruction of the element. On the other hand, if the heat shrinkage is too small, the tightness of the winding is insufficient, and the element may be broken due to an increase in the dielectric loss tangent during long-term high-temperature use.

Further, in some cases, corona generated by impregnating the capacitor element with insulating oil is suppressed to suppress a decrease in capacity of the capacitor, dielectric breakdown, and an increase in leakage current during continuous use. When the insulating oil is impregnated in this way, the polypropylene oil used as a dielectric is uniformly wound between the film layers at the stage of being wound as a capacitor element,
(4) It was necessary to design the shape of the film surface, and (5) it was necessary to suppress dimensional changes and swelling due to insulating oil.

As described above, with the miniaturization of electric devices,
While the above-mentioned properties are desired to be improved, there is a growing demand for further downsizing the film capacitor itself. For this purpose, it is necessary to increase the capacitance per unit volume of the capacitor, and it is necessary to reduce the thickness of the dielectric film.

To solve such a problem, Japanese Patent Application Laid-Open No. 6-236
Japanese Patent Application Publication No. 709 discloses a polymer insulating material having low ash content, having a boiling n-heptane soluble content of 1 to 10% by weight, and having excellent workability, and having excellent electrical insulation from room temperature to 80 ° C. It is suggested that those having an isotactic pentad fraction of 90% or more in the boiling n-heptane-insoluble portion are preferable.

Japanese Patent Application Laid-Open No. 7-25946 also discloses that the boiling heptane-insoluble component is 80% by weight or more, particularly preferably 96% by weight or more, and the isotactic pentad fraction of the boiling heptane-insoluble component is 0%. .970-0.9
Propylene polymers in the range of 95 and molded articles using the same have been proposed.

However, as proposed in these publications, a biaxially oriented polypropylene film having only a high isotactic pentad fraction of the boiling n-heptane-insoluble portion simply has a high insulation resistance at a high temperature exceeding 85 ° C. The breaking characteristics and the long-term heat resistance of the capacitor element using this film as a dielectric were insufficient. That is, the biaxially oriented polypropylene film having a high stereoregularity according to the conventional technique described above has a high isotactic pentad fraction in the boiling n-heptane-insoluble portion, but has an n-heptane-soluble isotactic pen. Since the tod fraction was low, the isotactic pentad fraction as a film was low as a result, and the stereoregularity was insufficient.

A so-called highly crystalline biaxially oriented polypropylene film having extremely high isotacticity is
Due to insufficient stereoregularity, the film-forming properties are extremely poor,
It has not been established as an industrially useful technique for producing a biaxially oriented polypropylene film having excellent heat resistance and dielectric breakdown resistance.

As a technique for solving this drawback, Japanese Patent Publication No. 4-28727 discloses that the isotactic pentad fraction is in the range of 0.960 to 0.990, and that boiling n-hexane and boiling A crystalline polypropylene film excellent in moldability has been proposed by setting the total amount of the extract to be extracted sequentially with n-heptane to 3.0 to 6.0%. However, the isotactic pentad fraction was not sufficient, and the dielectric breakdown resistance at high temperatures was insufficient.

Further, Japanese Patent Application Laid-Open No. Hei 5-217799 discloses a high-rigidity vapor-deposited metal obtained by vapor-depositing a metal on a high-rigidity polypropylene film having a specific heat deformation temperature and Young's modulus, a high degree of crystallinity and a good stereoregularity. A vapor-deposited film capacitor using a functionalized film has been proposed. However, the stereoregularity was at most about 90%, and the dielectric breakdown characteristics at high temperatures were insufficient.

Further, JP-A-7-50224 discloses that
A metallized polypropylene film having a heat shrinkage at 20 ° C. of 4.0% or less in the length direction and 0.8% or less in the width direction has been proposed. However, the isotacticity and stereoregularity of the film are conventional, and the dielectric breakdown resistance at high temperatures, which is the object of the present invention, in order to meet future high demands, has not always been sufficient.

[0016]

DISCLOSURE OF THE INVENTION The present inventors have made it possible to form a polypropylene film having extremely high isotacticity by controlling the isotacticity and stereoregularity of the polypropylene film to a high degree. By adopting appropriate film forming conditions, the dielectric breakdown resistance characteristic of polypropylene film, which could not be achieved with the conventional technology, is further improved, and furthermore, such characteristics decrease at high temperatures and long-term deterioration at high temperatures The present inventors have found that a capacitor with a reduced variation in quality can be obtained, and have reached the present invention.

An object of the present invention is to provide a polypropylene film which is excellent in heat resistance and long-term dielectric breakdown resistance at high temperatures, has few insulation defects, and has excellent permeability and swelling resistance between film layers when immersed in insulating oil. Is to provide.

Another object of the present invention is to provide a capacitor using the above-mentioned polypropylene film as a dielectric and having excellent heat resistance, long-term dielectric breakdown resistance at high temperatures, and corona resistance.

[0019]

In order to achieve the above object, the present invention provides a biaxially oriented polypropylene film having an isotacticity of 98 to 98.
99.5%, the isotactic pentad fraction exceeds 99%, and the center line average surface roughness of both surfaces is 0.01 to 0.4 μm. It is characterized by the following. And the capacitor using the polypropylene film of the present invention as a dielectric is suitably used as a capacitor for heat-resistant AC circuits.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene used in the polypropylene film of the present invention mainly comprises a homopolymer of propylene, but contains other unsaturated hydrocarbon copolymer components and the like within a range not to impair the object of the present invention. Or a polymer other than propylene alone may be blended.

Examples of such copolymer components and monomer components constituting the blend include ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1,1-hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl- 2-
Norbornene and the like can be mentioned. The copolymerization amount or blend amount is 1 m from the viewpoint of dielectric breakdown resistance and heat resistance.
ol% and the blend is preferably less than 10% by weight.

In the present invention, the isotacticity of the polypropylene film needs to be 99.5% or less from the viewpoint of film forming properties. Here, the isotacticity is defined by the ratio of the weight of the insoluble content to the weight of the film before extraction when the film is extracted with boiling n-heptane. If the isotacticity is too high, the
When a biaxially oriented film is produced as disclosed in Japanese Patent No. 6709, stretchability is poor and film formation becomes extremely difficult. Further, the isotacticity needs to be 98% or more in terms of heat resistance and dielectric breakdown resistance.

More preferable isotacticity is 98.5 to 9 for good film forming property, heat resistance and dielectric breakdown resistance.
It is 9.5%, and more preferably 98.7 to 99.3%. In order to obtain a polypropylene film having such isotacticity, a low molecular weight component which is easily soluble in boiling n-heptane of a polypropylene resin as a raw material,
It is possible to adopt a method of selecting a material having a low stereoregularity, that is, a material having an appropriately low ratio of so-called atactic portions.

In the present invention, the stereoregularity of the polypropylene film can be evaluated by a pentad fraction based on an absorption peak of a methyl group measured by ¹³ C-NMR. Generally, 5 in the polypropylene molecular chain
The conformation of the repeating units (pentads) is mmm
m, mmmr, rmmr, ..., rrrr, mrrr,
mrrm. Here, m is a meso (me
so) and r show the conformation of racemo. The pentad fraction of the polypropylene film is, for example, T.D. Report of Hayashi et al. [Polymer, 2
9,138～143 (1988)], etc. As in the ratio of the segment having the above-described conformation ¹³ C-NMR
Can be obtained from Among these, the ratio of the conformation of mmmm to the absorption intensity of all methyl groups, that is, the isotactic pentad fraction (hereinafter sometimes abbreviated as mmmm) is m (mmmm) m, m (mmmm) r,
r (mmmm) is defined as the sum of the three heptad fractions of r.

The isotactic pentad fraction mmmm of the polypropylene film of the present invention exceeds 99%. Since such a film is made of polypropylene composed of molecules having extremely long isotactic segments, it can provide a film having high crystallinity, high heat resistance, and high dielectric breakdown resistance.

Mmm of the polypropylene film of the present invention
m is preferably 9 in terms of high heat resistance and high dielectric breakdown resistance.
It is at least 9.1%, more preferably at least 99.2%, further preferably at least 99.3%. To impart such stereoregularity, it is effective to control the stereoregularity of the polypropylene resin as a raw material to a high degree. A method for producing such a raw material is achieved by using a catalyst system (solid catalyst, externally added electron-donating compound) and their purity when polymerizing polypropylene. The higher the mmmm of the polypropylene resin as the raw material, the higher the mmmm of the polypropylene film is observed.However, extreme thermal deterioration in the extrusion system of the raw material also reduces the mmmm. Structural measures such as avoiding stagnation and extrusion conditions are appropriately selected.

In the process of polymerizing the polypropylene used for the polypropylene film of the present invention, it is general to use a compound containing a metal as a catalyst, and to remove this residue after polymerization, if necessary. Can be evaluated by determining the amount of metal oxide remaining after completely burning the resin, and this is called ash.

The ash content of the polypropylene film of the present invention is preferably at most 30 ppm, more preferably at most 25 ppm, even more preferably at most 20 ppm. If the ash content is too large, the dielectric breakdown resistance of the film may decrease, and the dielectric strength of a capacitor using the film may decrease. In order to keep the ash content within this range, it is important to use a raw material with little residual catalyst, but a method such as minimizing contamination from the extrusion system during film formation, for example, bleeding time of 1 hour or more is required. Such a method can be adopted.

Known additives such as a nucleating agent, an antioxidant, a heat stabilizer, a sliding agent, an antistatic agent, an antiblocking agent, a filler, and a viscosity modifier are added to the polypropylene used in the polypropylene film of the present invention. And an anti-coloring agent may be contained within a range that does not deteriorate the characteristics of the present invention.

Of these, the selection of the type and amount of the antioxidant is important for long-term heat resistance. The antioxidant to be added to the polypropylene film of the present invention is a phenolic compound having steric hindrance, and at least one of them is preferably a high molecular weight type having a molecular weight of 500 or more for preventing scattering during melt extrusion.

Specific examples thereof include various ones. For example, together with 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4), 1,3,5-trimethyl-2,4 , 6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (for example, Irganox 1330 manufactured by Ciba-Geigy: molecular weight 775.2) or tetrakis [methylene-3 (3,5-di-t-butyl-4) −
[Hydroxyphenyl) propionate] methane (for example, Irganox 1010 manufactured by Ciba-Geigy: molecular weight 1177.7) is preferably used in combination.

The total content of these antioxidants is 0.03 to 1% by weight (300 to 100%) based on the total amount of polypropylene.
00 ppm) is preferred. If it is less than 0.03% by weight, the long-term heat resistance may be inferior. If it exceeds 1.0% by weight, blocking at a high temperature due to bleed out of these antioxidants may adversely affect the capacitor element. A more preferred content is 0.1 to 0.9.
% By weight, and more preferably 0.2 to 0.8% by weight.
It is.

The addition of a crystal nucleating agent affects the surface roughness and transparency of the film, but the dielectric breakdown strength tends to deteriorate. Therefore, the addition amount is preferably less than 0.1% by weight, more preferably. Is preferably not substantially added.

In the present invention, the intrinsic viscosity of the polypropylene having excellent stereoregularity used for the polypropylene film is not particularly limited.
Those in the range of dl / g are preferred. 230 ° C,
The melt flow rate under a load of 2.16 kg is preferably 2 to 5 g / 10 min from the viewpoint of film forming properties. In order to set the intrinsic viscosity and the melt flow rate to the above values, a method of controlling the average molecular weight and the molecular weight distribution and the like are adopted.

The polypropylene film of the present invention is obtained by using a raw material capable of giving the above-mentioned properties and performing biaxial orientation. An unoriented film cannot provide a film having high crystallinity, high heat resistance, and high dielectric breakdown resistance, which is the object of the present invention. The method of biaxial orientation can be obtained by any of the following methods: inflation simultaneous biaxial stretching method, stenter simultaneous biaxial stretching method, and stenter sequential biaxial stretching method. Among them, film forming stability, thickness uniformity From the viewpoint of controlling the surface roughness described below, a film formed by a stenter sequential biaxial stretching method is preferably used.

The biaxially oriented polypropylene film of the present invention has a center line average surface roughness of 0.01
０．４0.4 μm. If the center line average roughness is too large, air will enter between the layers when the films are laminated, leading to deterioration of the capacitor element, and when a metal layer is formed on the film, holes will be formed in the metal layer and the like at the time of high temperature. The dielectric breakdown strength and the element life are reduced, and electric charges are concentrated when a voltage is applied, which causes insulation defects. On the other hand, if it is too small, the film will slip poorly, and the handling properties will be poor, or if the capacitor element is impregnated with insulating oil, the insulating oil will not uniformly penetrate between the film layers, resulting in a large capacity change during continuous use. A more preferable range of the center line average surface roughness of both surfaces of the film is 0.03 to 0.3 μm, more preferably 0.04 to 0.25 μm.

The biaxially oriented polypropylene film of the present invention preferably has a difference (Δd) of 0.01 to 0.5 μm or less according to a method of measuring a film thickness defined by the following formula (1). , More preferably 0.02-
It is 0.4 μm, most preferably 0.03 to 0.3 μm.

Δd = d (MMV) −d (WMV) (1) [where d (MMV) is the thickness of a 10-layer micrometer film (μm), and d (WMV) is the weight of a gravimetric film ( μm)] When Δd exceeds 0.5 μm, when a capacitor is used,
A gap is formed between the wound film layers due to the unevenness of the film surface, which causes corona discharge at the end of the electrode, lowering the withstand voltage and lowering the electric capacity. Since the contact area of the film is large, an electrostatic defect generated when the roll-shaped film is unwound may cause insulation defects in the film.

The maximum roughness of both surfaces of the biaxially oriented polypropylene film of the present invention is 0.1 to 4.0 μm.
Is more preferable, and more preferably 0.3 to 3.0 μm.
m. If the maximum roughness is less than 0.1 μm, the slipperiness is deteriorated, the air escape is poor, vertical wrinkles and the like are formed, and the winding property and the handling property may be reduced. On the other hand, when Rt exceeds 4.0 μm, the surface is too roughened, so that when the films are laminated, air enters between the layers and not only leads to deterioration of the capacitor element, but also causes film breakage and lowers productivity. May be.

In the biaxially oriented polypropylene film of the present invention, the sum of the heat shrinkage in the machine direction and the width direction when heated at 120 ° C. for 15 minutes is preferably in the range of 1.5 to 3.5%. . If the heat shrinkage is too large, dimensional changes occur when the metal layer as an electrode is formed, wrinkles are formed in the film roll, and mechanical deformation due to heat during the production of the capacitor element is too large, so that the film roll and the external electrode and Stress may occur at the contact portion of the capacitor, and the capacity of the capacitor may be greatly reduced or the element may be destroyed. If the heat shrinkage is too low, the tightness due to heat treatment during the production of the capacitor element becomes insufficient, which may adversely affect the shape retention and the rate of change in capacity. The more preferable heat shrinkage ratio is 1.6 to 3.3% of the above sum, further 1.7 to 3%, further 1.8 to 2.8%, particularly 1.8 to 2.5%. % Is preferred.

In the present invention, the thickness of the biaxially oriented polypropylene film (film thickness by ten-layer micrometer method) is preferably from 2 to 30 μm, more preferably from the viewpoint of film forming properties, mechanical properties and electrical properties. Is 2.5 ~
It is 20 μm, more preferably 2.5 to 10 μm. If the thickness of the film is too small, the dielectric strength or mechanical strength may be poor, and the film may be damaged due to metallization, particularly heat loss. If the thickness of the film is too large, it is difficult to form a film having a uniform thickness, and if it is used as a dielectric for a capacitor, the capacity per volume is undesirably small.

The biaxially oriented polypropylene film of the present invention preferably has a weight change rate of 5 to 12% when immersed in dodecylbenzene. This weight change rate corresponds to the swelling property of the film, and the weight change rate is 12%.
Exceeding the limit, in the process of impregnating the capacitor element with insulating oil, the film swells greatly at the element edge, which is the penetration path of the insulation oil, and an appropriate gap between the film layers, which is the penetration path, is closed. Insulation oil is prevented from penetrating to the point where not only the effect of imparting corona resistance by the insulation oil is not sufficiently obtained, but also excessive stress is applied to the film serving as the dielectric of the capacitor element due to swelling, and the dielectric breakdown strength is reduced. May decrease. If the weight change rate is less than 5%, the affinity between the film surface and the insulating oil decreases, and the penetration speed of the insulating oil between the film layers decreases, so that the inside of the element is not evenly filled. Cannot sufficiently obtain the effect of imparting corona resistance. A more preferred range of the weight change rate is 6 to 11%, most preferably 7 to 11%.

The biaxially oriented polypropylene film of the present invention preferably has a dimensional change rate in the longitudinal direction of the film of -1 to 1% when immersed in dodecylbenzene. If the rate of dimensional change in the longitudinal direction of the film exceeds 1%, in the process of impregnating the capacitor element with the insulating oil, tight winding occurs and an appropriate gap between the film layers is closed, so that the insulating oil penetrates into the element. Therefore, the effect of imparting corona resistance by the insulating oil cannot be sufficiently obtained. Also, the dimensional change rate in the longitudinal direction of the film is-
If it is less than 1% (that is, −2%, −3%, etc.), the film partially bends inside the capacitor element, and the dielectric loss becomes worse. A more preferred range of the dimensional change in the longitudinal direction of the film is from -0.8 to 0.8%, most preferably from -0.6 to 0.6%.

The biaxially oriented polypropylene film of the present invention preferably has a dimensional change rate in the width direction of the film of -2 to 2% when immersed in dodecylbenzene. If the rate of dimensional change in the width direction of the film exceeds 2%, poor contact with metallikon occurs, and dielectric loss worsens.
If the dimensional change rate in the width direction of the film is less than -2% (that is, -3%, -4%, or the like), the film partially bends inside the capacitor element, and the dielectric loss similarly deteriorates. A more preferable range of the dimensional change rate in the width direction of the film is -1.5 to 1.5%, and most preferably -1 to 1.5%.
1%.

When a metal layer is formed on the biaxially oriented polypropylene film of the present invention, the surface on which the metal layer is formed is preferably subjected to a corona discharge treatment or a plasma treatment in order to increase the adhesive strength. A known method can be used for the corona discharge treatment, but treatment is preferably performed in air, carbon dioxide gas, nitrogen gas, or a mixed gas thereof as an atmosphere gas. For the plasma treatment, a method in which various gases are put into a plasma state and the film surface is chemically denatured can be adopted, for example, a method described in JP-A-59-98140.

The biaxially oriented polypropylene film used as a dielectric in the capacitor of the present invention may be wound together with a metal foil used as an electrode, or may be a metallized electrode in advance. In order to reduce the size, it is more preferable to use a metallized and wound metal.

The metal for forming the metal layer on the biaxially oriented polypropylene film of the present invention is not particularly limited, but aluminum, zinc, copper, tin, silver, nickel, etc. may be used alone or in combination. This is preferable in terms of durability and productivity of the metallized layer.

The method for forming a metal layer on the biaxially oriented polypropylene film of the present invention includes, but is not particularly limited to, a vacuum deposition method, a sputtering method, and an ion beam method.

In the present invention, the film resistance of the metallized film is preferably in the range of 1 to 40 Ω / □. More preferably, it is 1.2 to 30 Ω / □. If the film resistance is too small, the thickness of the deposited film is so large that heat loss occurs during the deposition, and an avatar-shaped surface defect or a hole in a thin film of about 4 μm may occur. If the film resistance value is too large, the dielectric loss tangent deteriorates, and the long-term breakdown voltage may not be maintained due to heat generated from the inside of the capacitor during AC application. In order to keep the film resistance within this range, a method of controlling the film resistance at the time of vapor deposition by monitoring is preferably adopted.

In the present invention, when a metal layer is formed on one surface of a biaxially oriented polypropylene film, and when there is a difference in the center line average surface roughness between the front and back surfaces, the surface roughness is increased. It is preferable to form a metal layer on a surface having a small size. By doing so, surface defects of the metal layer can be minimized, leading to an improvement in dielectric breakdown strength and element life.

In the present invention, a margin provided when a metal layer is formed on a biaxially oriented polypropylene film (a portion without a metal layer provided on a surface on which a metal layer is formed for the purpose of electrical insulation, hereinafter referred to as an insulating groove portion). Can be adopted according to the purpose, such as various types provided with a fuse mechanism in addition to the normal type. In particular, a metal layer is continuously formed at one end in the width direction of the film in the longitudinal direction of the film. The metal layer is separated into a plurality of islands in the longitudinal direction of the film by the insulating groove, and a continuous metal layer at the other end in the width direction of the film. It is preferable that the capacitor be formed so as to be connected by a bottleneck because a change in capacitance after continuous use of the capacitor can be minimized. Such a method is particularly preferably used for a capacitor for a heat-resistant AC circuit.

The method of providing the insulating groove portion includes a laser margin method, an oil margin method, a tape margin method and the like, and is not particularly limited, but a simple oil margin method is preferably employed.

In the present invention, when a metal layer is formed on a biaxially oriented polypropylene film, the type of the capacitor is such that a pair of two films having a metal layer (with a margin) provided on one side are wound together, and each is wound. A paired metal layer is connected to two external extraction electrodes (lead electrodes) so as not to be short-circuited. A film with a metal layer (with a margin) on both sides and one or more films without a metal layer are paired. And wound together, and each pair of metal layers is taken out of two external extraction electrodes (lead electrodes)
There is no particular limitation on the type of connection for preventing short circuit. Here, it is preferable to connect the metal layer provided on the film and the external extraction electrode via a sprayed metal called metallikon.

Further, in the present invention, the type of the capacitor in the case where the metal layer is formed on the biaxially oriented polypropylene film with a bottleneck is not particularly limited.
If one of the paired metal layers has a bottleneck, a change in capacitance after continuous use of the capacitor can be minimized.

The type of the capacitor of the present invention includes a dry type and an oil immersion type (oil impregnation type), which can be adopted according to the purpose. An oil impregnation type capacitor for an AC circuit is preferably used.

A film capacitor using the biaxially oriented polypropylene film of the present invention as a dielectric is described below.
AC breakdown strength at 05 ° C is 200V per unit thickness
/ Μm or more. The rated voltage of a polypropylene film capacitor is usually 45 to 50 V /
This is because the value is preferably 4 times or more in consideration of safety. More preferably, it is 210 V / μm or more. In order to keep the dielectric breakdown strength of the film capacitor within this range, it is effective to avoid wrinkles and scratches during processing into the capacitor.

A film capacitor using the biaxially oriented polypropylene film of the present invention as a dielectric is described below.
The life under AC voltage application of 60 V / μm per unit thickness (1.2 to 1.3 times the rated voltage) at 05 ° C. is 500 hours or more in terms of the warranty period of the device equipped with the capacitor. Preferably, more preferably 1000
More than an hour. To keep the service life within this range, add an appropriate amount of antioxidant, heat-treat the capacitor at about 100 ° C during processing, avoid wrinkles and scratches, and embed epoxy resin. It is effective to block the contact with the outside air by sealing the inside of a metal can after impregnation with resin or oil (outer packaging).

Next, a method for producing a biaxially oriented polypropylene film of the present invention and a capacitor using the same as a dielectric will be described below, but the present invention is not necessarily limited thereto.

The polypropylene raw material was supplied to an extruder, melted by heating, and passed through a filter.
Melt extrusion from a slit die at a temperature of 50 ° C.
It is wound around a casting drum maintained at a temperature of ° C. and cooled and solidified to form an unstretched film. At this time, if the casting drum temperature is too high, the crystallization of the film proceeds too much, and it may be difficult to perform stretching in the subsequent step, or the surface roughness may be too large. Sometimes too much. Also, as a method of adhesion to the cast drum, an electrostatic application method, an adhesion method using surface tension of water, an air knife method, a press roll method,
Any method such as an underwater casting method may be used, but as a method for obtaining the polypropylene film of the present invention, an air knife method having good flatness and capable of controlling the surface roughness is effective. In particular, the surface temperature of the film may be different due to the difference in cooling efficiency between the drum surface and the air on the surface opposite to the cast drum surface, and the polypropylene having high stereoregularity used for the film of the present invention has high crystallinity, so the surface temperature is high. The difference in temperature appears as a difference in the degree of crystallinity of the film surface, which greatly affects the difference in flatness and surface roughness of both surfaces.When using the air knife method, it is important to control the temperature of the blown air. is there. In order to obtain the film of the present invention, the temperature of the air used in the air knife method is preferably set to ((cast drum temperature) -70 ° C) to ((cast drum temperature) -20 ° C).

Next, the unstretched film is biaxially stretched and biaxially oriented. First, unstretched film is 120-150
Preheated by passing through a roll maintained at a temperature of 140 ° C. to 150 ° C., and subsequently passed between rolls provided with a peripheral speed difference at a temperature of 140 ° C. to 150 ° C., stretched 2 to 6 times in the longitudinal direction, and immediately brought to room temperature. Cooling. When the mmmm exceeds 99% of the polypropylene film of the present invention, if the preheating temperature is 130 ° C. or lower and the stretching temperature is 140 ° C. or lower, the calorific value may be insufficient to cause uneven stretching or tearing, and the film may not be formed. It is important to adopt

Subsequently, the stretched film is guided to a stenter, stretched 5 to 15 times in the width direction at a temperature of 155 to 165 ° C., and then, while giving 2 to 20% relaxation in the width direction,
Winding with heat setting at a temperature of 150 to 160 ° C.

Thereafter, in order to improve the adhesiveness of the deposited metal to the surface on which the deposition is performed, a corona discharge treatment is performed in air, nitrogen, carbon dioxide, or a mixed gas thereof, and the film is wound by a winder.

The obtained film is set in a vacuum deposition apparatus, and oil is applied to the film using a gravure coater or the like to form an insulating groove according to the purpose. Deposit on film resistance. This vapor deposition film is slit to form a pair of vapor deposition reels on two reels for producing a capacitor element. Thereafter, it is wound into an element shape, pressed into a flat shape by hot pressing, metal sprayed at the end (metallicon step), leads are taken out, and if necessary, an insulating oil is impregnated, and a capacitor is formed through an exterior.

The biaxially oriented polypropylene film of the present invention can suppress deformation due to heat during processing such as vapor deposition, printing, laminating, and heat sealing by utilizing heat resistance in addition to the above-mentioned capacitor use. For various packaging applications, for example, it can be used by laminating it with a heat seal layer, and can also be suitably used as an adhesive tape, a polished film (print laminate), and the like.

The measuring method and the evaluating method of the characteristic value in the present invention are as follows. (1) Isotacticity (isotactic index: II) A sample is extracted with n-heptane at a temperature of 60 ° C or less for 2 hours to remove additives to polypropylene. Then 13
Vacuum dry at 0 ° C. for 2 hours. From this, a sample of weight W (mg) is taken, placed in a Soxhlet extractor and extracted with boiling n-heptane for 12 hours. Next, the sample was taken out, sufficiently washed with acetone, vacuum-dried at 130 ° C. for 6 hours, and then cooled to room temperature, and the weight W ′ (mg) was measured and determined by the following equation.

II = (W '/ W) × 100 (%)

(2) Isotactic Pentad Fraction A sample was dissolved in o-dichlorobenzene, and JN
Using an M-GX270 device, a resonance frequency of 67.93 MH
The ¹³ C-NMR was measured at z. For the assignment of the obtained spectra and the calculation of the pentad fraction, see T.W. Hay
, et al. [Polymer, 29, 13]
8 to 143 (1988)], the peak derived from the mmmmmm was 21.855 for the spectrum derived from the methyl group.
Each peak was assigned as ppm, the peak area was determined, and the ratio to the total peak area derived from the methyl group was expressed as a percentage. Detailed measurement conditions are as follows.

Measurement solvent: o-dichlorobenzene (90
wt%) / benzene -D ₆ (10 wt%) Sample concentration: 15~20wt% Measurement temperature: 120 to 130 ° C. resonance frequency: 67.93MHz Pulse width: 10 .mu.sec (45 ° pulse) Pulse repetition time: 7.091Sec data points ： 32K Total number of times ： 8168 Measurement mode ： Noise decoupling

(3) Center line average surface roughness, maximum roughness (hereinafter referred to as Ra and Rt, respectively) Measured using a stylus type surface roughness meter according to JIS-B0601. In addition, using a high-precision thin film step measuring device (model: ET-10) manufactured by Kosaka Laboratory Co., Ltd., a stylus diameter cone type 0.5 μmR, load 5 mg, cut-off is 0.08 mm.
And

(4) Measurement of Δd Ten-layer micrometer method film thickness (d (MM
V) (μm)) was measured according to JIS-B7502. In addition, using a micrometer having a measuring force of 700 ± 100 gf and a minimum display amount of 0.0001 mm, a value obtained by stacking 10 films is divided by 10 to obtain d (MMV).
(Μm). In addition, the gravimetric film thickness (d (WM
V) (μm)) was obtained by cutting out a film into 10 cm square and measuring the weight W (g) measured with an electronic balance manufactured by Mettler Co., using the following formula.

D (WMV) = 100 × W / ρ [where d (WMV) is the thickness of the gravimetric film (μ
m), W is the film weight (g) of a 10 cm square, ρ is the density of the film (g / cm3), and ρ is JIS-K-7
It was measured at 23 ± 0.5 ° C. using an ethanol-water-based density gradient tube according to the 112-D method.] Next, using the obtained d (MMV) and d (WMV), Δd (μm) was calculated by the following equation. did.

△ d = d (MMV) −d (WMV)

(5) Heat Shrinkage Ratio The film was 260 mm long in the machine and width directions.
Sampling is performed 10 mm in width and a mark is placed at 30 mm from both ends to make the original size (L0: 200 mm). A weight of 3 g was applied to the lower end of this sample,
And heat-treat for 15 minutes. Thereafter, the sample was taken out, the marked length (L1) was measured, the heat shrinkage was calculated by the following equation, and the sum in the machine direction and the width direction was defined as the heat shrinkage.

Heat shrinkage = [(L0−L1) / L0] × 100 (%)

(6) Ash content According to JIS-C-2330. A biaxially oriented polypropylene film having an initial weight of W0 was placed in a platinum crucible, first sufficiently burned with a gas burner, and then completely treated with an electric furnace at 750 to 800 ° C. for about 1 hour to completely incinerate the obtained ash. The weight W1 was measured and determined from the following equation.

Ash content = (W1 / W0) × 1,000,000 (ppm) W0: Initial weight (g) W1: Ash weight (g)

(7) Insulation defect test According to JIS-C-2330, a film having a film thickness of 7.5 μm measured by a ten-sheet micrometer method was determined according to the following evaluation criteria.

：: The number of insulating defects is 2 or less Δ: The number of insulating defects is 3 to 5 ×: The number of insulating defects is 6 or more (cannot be used as a film for a capacitor)

(8) Element Dielectric Breakdown Strength A capacitor element maintained at 105 ° C. in a hot air oven was connected to an AC high-voltage stabilized power supply (frequency 60
Hz), a voltage was applied while increasing the voltage at a rate of 200 V / sec, and a voltage when the element was destroyed was determined. An average value of 10 measured elements was defined as an element dielectric breakdown strength, which was determined according to the following evaluation criteria. .

：: 200 V / μm or more Δ: 150 V / μm or more and less than 200 V / μm ×: less than 150 V / μm In the present invention, ○ and Δ are accepted.

(9) Element Life Test An AC voltage of 60 V / μm per film thickness (frequency 6
0 Hz) was applied to the capacitor element, the time until the element was destroyed in an atmosphere at 105 ° C. was measured, and the evaluation was made according to the following evaluation criteria.

：: 500 hours or more Δ: 400 hours or more and less than 500 hours ×: less than 400 hours In the present invention, ○ and Δ are accepted.

(10) Weight change rate and dimensional change rate after immersion in dodecyl benzene
After the treatment at 00 ° C. for 8 hours, a cycle of allowing to cool naturally at room temperature for 16 hours was performed three times, and each rate of change of the film was determined by the following equations (2) and (3). Here, the dimensional change rate was measured in the longitudinal direction (MD) and the width direction (TD) of the film. In addition, the same sample was measured five times, and the average value was set as the measured value.

Weight change rate (%) = (J ₀ −J ₁ ) / J ₀ × 100 (2) Dimension change rate (%) = (M ₀ −M ₁ ) / M ₀ × 100 (3) (where J ₀ and J ₁ is the weight of the film sample after immersion and before immersion in dodecylbenzene respectively, M ₀ and M ₁ are the dimensions of the film sample after immersion and before immersion in each dodecylbenzene).

(11) Evaluation of Corona Resistance AC voltage of 30 V / μm per film thickness (frequency 6
0 Hz) in the atmosphere of 105 ° C.
The voltage was applied for 0 hour, and the capacitance change rate of the device was obtained based on the equation (4), and evaluated as follows.

Capacity change rate (%) = (C ₁ −C ₀ ) / C ₀ × 100 (4) (where C ₀ is the capacity of the capacitor element before application, and C ₁ is the capacitor element after application. ○: Capacitance change rate <5% Good corona resistance Δ: 5% ≦ Capacity change rate ≦ 10% Level at which there is no problem in corona resistance ×: 10% <Capacity change rate Poor corona resistance The present invention ○ and △ are acceptable.

[0087]

EXAMPLES The present invention will be described in detail below based on examples and comparative examples.

(Example 1) II was 99.1%, mmmm
Is 99.7%, the ash content is 21 ppm, the melt flow rate is 4.2 g / 10 min, and 2,6-di-t-butyl-p-cresol (BHT) is 3000 pp.
m, to which 4,000 ppm of telorakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (Irganox1010) was added and fed to an extruder and melted at a temperature of 280 ° C. The sheet was extruded from the die into a sheet, wound around a casting drum at a temperature of 80 ° C. using an air knife method at an air temperature of 25 ° C., and solidified by cooling. Then, the sheet is heated to 143 ° C.
And then passed between rolls provided with a peripheral speed difference while maintaining the temperature at 148 ° C., and stretched 4.8 times in the longitudinal direction. Subsequently, the film was guided to a tenter, stretched 11 times in the width direction at a temperature of 161 ° C., and then subjected to a heat treatment at 150 ° C. while giving 10% relaxation in the width direction to obtain a biaxially oriented polypropylene film having a thickness of 7.50 μm. Obtained. 3 more
Corona discharge treatment was performed in the air at a treatment intensity of 0 W · min / m 2. II of the obtained film was 99.0%, m
mmm was 99.6%.

This film was set in a vacuum evaporation machine, copper was used as a nucleation metal, and zinc was applied to the corona-treated surface with a film resistance of 4.
It vapor-deposited so that it might be set to 0 ohm / square. At this time, as shown in FIG. 1, the metal layer 1 was vapor-deposited by the oil margin method so that an insulating groove 2 (margin part: length 1 mm in the width direction) was provided at one end in the width direction as shown in FIG. This film was slit to obtain a metallized film having a total width of 38 mm. An element is wound using the obtained film pair of two reels,
A metal spray was applied to the end face of the element, and a lead wire was taken out from the metal to form a capacitor element having a capacity of 5 μF. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 1) II was 98.0%, mmmm
The polypropylene film (II: 97%) was prepared in the same manner as in Example 1 except that a polypropylene raw material was 99.2%, an ash content was 21 ppm, and a melt flow rate was 3.1 g / 10 min. .8%, m
mm = 99.1%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 2) II was 99.8%, mmmm
Of 99.9%, ash content of 12 ppm, and melt flow rate of 2.4 g / 10 min using a polypropylene raw material in the same manner as in Comparative Example 1, but after stretching in the width direction, The film was frequently torn and the film could not be collected stably. The II of the film collected without breaking was 99.7%, and the mmmm was 9
9.9%.

(Comparative Example 3) II was 98.4%, mmmm
Using a polypropylene raw material of 98.9%, an ash content of 21 ppm, and a melt flow rate of 3.9 g / 10 min.
8.2%, mmmm is 98.5%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Comparative Example 4 A polypropylene film (I) was produced in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used and the temperature of the cast drum was 90 ° C.
I was 99.0% and mmmm was 99.6%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Comparative Example 5 A polypropylene film (I) was produced in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used and the temperature of the cast drum was set at 30 ° C.
I was 99.0% and mmmm was 99.6%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Example 2) A polypropylene film (I) was produced in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used and the temperature of the cast drum was 70 ° C.
I was 99.0% and mmmm was 99.6%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 3 A polypropylene film (II was prepared in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used, the cast drum temperature was set to 80 ° C., and the air temperature of the air knife was set to 0 ° C. 99.0%, m
mm = 99.6%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 4 A polypropylene film (II was prepared in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used, the cast drum temperature was 70 ° C., and the air temperature of the air knife was 50 ° C.) 99.0%,
mmmm is 99.6%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 5 A polypropylene film (II: 9) was prepared in the same manner as in Example 1 except that the same polypropylene raw material as in Example 1 was used and the air knife was not used.
9.0%, mmmm is 99.6%) to obtain a capacitor element. In addition, curl occurred in the width direction of the film at the time of film formation in Example 5, and the clip occasionally slipped off during transverse stretching, resulting in a decrease in yield. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 6 The raw materials of polypropylene used in Example 1 and the raw materials of polypropylene used in Comparative Example 1 were as follows:
2, a polypropylene film (II: 98.6) was prepared in the same manner as in Example 1 except that the raw materials which had been dry blended were used.
%, Mmmm is 99.2%) to obtain a capacitor element. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Example 7) The film used in Example 1 was set in a vacuum evaporation machine, copper was used as a nucleation metal, and zinc was evaporated on a corona-treated surface so that the film resistance became 4.0 Ω / □. . At this time, after slitting by the oil margin method, as shown in FIG. 2, the metal layer 1 has an insulating groove portion 2 (margin portion: continuous at one end in the width direction of the film in the longitudinal direction of the film).
(Length 1 mm in the width direction), and the metal layer 1 is separated into a plurality of islands in the longitudinal direction of the film by the insulating grooves 3 (width 1 mm in the longitudinal direction). Vapor deposition was carried out at intervals of 30 mm and connected so as to be connected to a continuous metal layer (1 mm in width) at the other end in the width direction of the film and a bottleneck 4 (1 mm in both the longitudinal and width directions). This film was slit to obtain a metallized film having a total width of 38 mm. An element was wound using the obtained film and the metallized film used in Example 1 as a pair, metal spraying was performed on the end face of the element, and a lead wire was taken out from the element to produce a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

Example 8 A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Example 2 was used, and the obtained film and the metallized film used in Example 2 were used. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

Example 9 A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Example 3 was used, and the obtained film and the metallized film used in Example 3 were used. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

Example 10 A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Example 5 was used, and the obtained film and the metallized film used in Example 5 were used. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

(Example 11) A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Example 6 was used, and the obtained film and the metallized film used in Example 6 were used. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

Example 12 A capacitor was produced in the same manner as in Example 8, except that the metallized film used in Example 1 was used as a pair of two reels. Table 2 summarizes the evaluation results of the obtained capacitors.

Comparative Example 6 A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Comparative Example 1 was used, and the obtained film and the metallized film used in Comparative Example 1 were used. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

Comparative Example 7 A metallized film was prepared in the same manner as in Example 7 except that the biaxially oriented polypropylene film of Comparative Example 4 was used, and the obtained film was compared with the metallized film used in Comparative Example 4. Were wound as a pair, and metal was sprayed on the end face of the element, and a lead wire was taken out from the element to form a capacitor element having a capacity of 5 μF. Table 2 summarizes the evaluation results of the capacitors obtained by impregnating the obtained capacitor elements with crystallin wax.

[0108]

[Table 1]

[Table 2]

[0109]

According to the present invention, there is provided a heat-resistant and dielectric-breakdown-resistant material having few insulation defects, and having excellent insulation oil permeability and swelling resistance between film layers when immersed in insulation oil. An axially oriented polypropylene film and a capacitor using this polypropylene film as a dielectric having excellent heat resistance, dielectric breakdown resistance, corona resistance, and long-term heat resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a polypropylene film provided with a metal layer on one side according to an embodiment of the present invention.

FIG. 2 shows a metal layer provided on one side according to an embodiment of the present invention;
FIG. 3 is a plan view of a polypropylene film in which electrodes are separated in an island shape.

[Explanation of symbols]

 1. 1. Metal layer (internal electrode) 2. Insulation groove (margin) 3. Insulating grooves (separate electrodes into islands) bottleneck

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 31:34 C08L 23:02

Claims (8)

[Claims] 1. A biaxially oriented polypropylene film having an isotacticity of 98 to 99.
5%, 99% isotactic pentad fraction
And the center line average surface roughness of both sides is 0.01
A polypropylene film having a thickness of about 0.4 μm. 2. The polypropylene film according to claim 1, wherein a difference (Δd) determined by a method of measuring a film thickness defined by the following formula (1) is 0.01 to 0.5 μm. Δd = d (MMV) −d (WMV) (1) [where d (MMV) is the thickness of a 10-layer micrometer film (μm), and d (WMV) is the weight of a gravimetric film (μm). is there] 3. The polypropylene film according to claim 1, wherein a weight change rate when immersed in dodecylbenzene is 5 to 12%. 4. A capacitor using the polypropylene film according to claim 1 as a dielectric. 5. The capacitor according to claim 4, wherein a metal layer is provided as an internal electrode on at least one surface of the film surface. 6. A metal layer is formed by providing an insulating groove continuous at one end in the width direction of the film in the longitudinal direction of the film, and the metal layer is formed by a plurality of insulating grooves in the longitudinal direction of the film. 6. The capacitor using a polypropylene film as a dielectric according to claim 5, wherein the capacitor is separated into islands and is connected to a continuous metal layer at the other end in the width direction of the film by a bottleneck. 7. A film provided with a metal layer is wound,
7. A capacitor using the polypropylene film according to claim 5 as a dielectric, wherein a film layer is impregnated with an insulating oil. 8. A capacitor for a heat-resistant AC circuit using the polypropylene film according to claim 5 as a dielectric.