JPH11162779A - Polypropylene film for capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene film for supplying a capacitor with high maintenance, by reducing electrical insulation defect, making dielectric breakdown strength excellent, and reducing the change of an electrostatic capacity with lapse of time. SOLUTION: A two-axial orientation polypropylene film having at least one resin layer in which more than one kind of resin selected from oil resin which does not substantially include any double bond or polar group, and terpene resin which does not substantially include any double bond or polar group which is 5-50 by weight is mixed with polypropylene resin which is 100 by weight, is provided. The center line mean surface roughness of at least one face of the film is more than 0.03 μm and 0.5 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene film suitably used as a dielectric of a capacitor, and more particularly, to a film having few insulation defects.
The present invention relates to a polypropylene film having excellent dielectric breakdown strength and capable of supplying a capacitor with high security because the change in capacitance with time is small.

[0002]

2. Description of the Related Art Polypropylene films have been widely used as dielectrics, that is, insulating materials for capacitors, because of their excellent electrical properties.

[0003] However, such polypropylene film capacitors also have the following serious disadvantages. (1) When a film on which a metal such as aluminum or zinc is vapor-deposited is used as a wound capacitor, the capacity of the capacitor decreases with use, and when the change is large, the change is as large as 10%. (2) When metal is deposited on the film, the yield is poor due to poor thermal dimensional stability.
(3) A capacitor with a high potential gradient per unit thickness cannot be designed due to insulation defects inherent in the film. (4) The lower limit of the thickness of the biaxially stretched film is equivalent to 3 μm. If the thickness is smaller than this, not only the film cannot be formed, but also since the handleability is extremely poor, the capacitor can be miniaturized by thinning the film. Absent.

To solve such a problem, Japanese Patent 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 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
There are disclosures of propylene polymers in the range of 95 and molded articles using the same.

However, as proposed in these, a biaxially oriented polypropylene film having only a high isotactic pentad fraction of the boiling n-heptane-insoluble portion has few insulation defects aimed at by the present invention and has a low dielectric breakdown strength. It was excellent, and the change in capacitance with time was small, so that a capacitor with high security could be supplied, and the long-term heat resistance was insufficient.

Japanese Patent Application Laid-Open No. 7-25946 discloses a stretched film to which a specific high stereoregularity polypropylene and a specific terpene resin and / or a specific petroleum resin are added. Is for packaging,
For a capacitor, it was not usable in terms of surface roughness and was not excellent in terms of dielectric breakdown strength.

Further, Japanese Patent Application Laid-Open No. 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 components constituting the film were conventional, and the insulation defects and the dielectric breakdown characteristics were insufficient.

Further, Japanese Patent Application Laid-Open No. 7-50224 discloses that
The heat shrinkage at 120 ° C. is 4.0% or less in the length direction,
There is a disclosure of a metallized polypropylene film that is 0.8% or less in the width direction. However, the components that make up the film are conventional, in order to respond to future advanced requirements,
The dielectric breakdown resistance, one of the objects of the present invention, was not always sufficient.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene film for a capacitor which has solved the above-mentioned disadvantages.

[0011] That is, an object of the present invention is to provide a polypropylene film which can supply a capacitor with high security because it has few insulation defects, has excellent dielectric breakdown strength, and has little change in capacitance with time.

[0012]

Means for Solving the Problems The present invention achieves the above object, and a polypropylene film of the present invention comprises a petroleum resin substantially free of double bonds and polar groups in 100 parts by weight of a polypropylene resin. A polypropylene film having at least one resin layer in which at least one resin selected from a resin and a terpene resin substantially free of a double bond and a polar group is mixed in an amount of 5 to 50 parts by weight. A polypropylene film for a capacitor having a center line average surface roughness of at least one side exceeding 0.03 μm and not more than 0.5 μm.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene resin used in the polypropylene film of the present invention is mainly composed of a propylene homopolymer, but other copolymerizable components such as unsaturated hydrocarbons may be used as long as the object of the present invention is not impaired. It may be contained, or a polymer other than propylene alone may be blended. Examples of such a copolymer component or a monomer component constituting the blend include ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, and 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. The copolymerization amount or the blend amount is preferably less than 1 mol% from the viewpoint of dielectric breakdown resistance and heat resistance, and the blend amount is preferably less than 10% by weight.

In the present invention, the isotacticity of the polypropylene film is preferably 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 JP-A-36709, stretchability is deteriorated and film formability is deteriorated.

Further, the isotacticity is preferably 98% or more from the viewpoint of dielectric breakdown resistance. More preferable isotacticity is 98.5 to 99.5% for good film forming property and dielectric breakdown resistance, and further 98.7.
~ 99.3% is preferred.

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 and a proportion of a so-called atactic portion having low stereoregularity are appropriate. For example, a method such as selecting a lower one can be adopted.

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. [Polyme
r, 29, 138 to 143 (1988)], the ratio of the segments having each of the above-mentioned conformations is ¹³ C-
It can be determined from NMR. 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 (mmm
m) defined as the sum of three heptad fractions, r and r (mmmm) r.

The isotactic pentad fraction mmmm of the polypropylene film of the present invention preferably exceeds 99%. Since such a film is made of a polypropylene resin composed of molecules having an extremely long isotactic segment, it can provide a film having high crystallinity, high heat resistance, and high dielectric breakdown characteristics. The mmmm of the polypropylene film of the present invention is preferably 99.1% or more, more preferably 99.2% or more, and even more preferably 99.
3% or more.

In order to impart such stereoregularity, it is effective to control the stereoregularity of the raw material polypropylene resin to a high degree. A method for producing such a raw material is achieved by a catalyst system (solid catalyst, externally added electron donating compound) and the purity thereof when polymerizing a polypropylene resin. Mm of raw polypropylene resin
The higher the mm, the mmmm of the polypropylene film
However, extreme thermal degradation of the raw material in the extrusion system also reduces mmmm, so structural measures such as avoiding long-term stagnation of the raw material in the high-temperature extrusion system and extrusion conditions are appropriately selected. Is done.

In the process of polymerizing the polypropylene resin used in 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 the polymerization, if necessary. Competition can be evaluated by determining the amount of metal oxide remaining after the resin is completely burned, 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 there is too much ash,
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 crystal nucleating agent, an antioxidant, a heat stabilizer, a sliding agent, an antistatic agent, an antiblocking agent, a filler, and a viscosity control agent may be added to the polypropylene resin used in the polypropylene film of the present invention. And an anti-coloring agent.

Among these, 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 a high molecular weight type having a molecular weight of 500 or more when melt-pressed. It is preferable for preventing the scattering of water. Various examples thereof include, for example, 1,3 and 2,3-di-t-butyl-p-cresol (BHT: molecular weight 220.4).
5-trimethyl-2,4,6-tris (3,5-di-t
-Butyl-4-hydroxybenzyl) benzene (for example, Irganox 1330 manufactured by Ciba Geigy: molecular weight 77)
5.2) or tetrakis [methylene-3 (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (for example, Irganox 10 manufactured by Ciba Geigy)
10: molecular weight 1177.7). The total content of these antioxidants is 0.03 to 1% by weight (300 to 10,000) based on the total amount of the polypropylene resin.
ppm) is preferred. If it is less than 0.03% by weight, the long-term heat resistance may be poor.
Blocking at a high temperature due to bleed-out of these antioxidants may adversely affect the capacitor element. A more preferable content is 0.1 to 0.9% by weight, and further preferably 0.2 to 0.8% by weight.

In the present invention, the intrinsic viscosity of the polypropylene resin used for the polypropylene film is not particularly limited, but is preferably in the range of 1 to 10 dl / g from the viewpoint of film forming properties. The melt flow rate at 230 ° C. and a load of 2.16 kg is 2 to 5 g from the viewpoint of film forming properties.
/ 10 minutes is preferred. 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 petroleum resin substantially free of polar groups is
A hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO ₃ Y, Y is H, Na, etc.) and a petroleum resin having no polar group made of their modified product, i.e. petroleum It is a resin mainly composed of a cyclopentadiene-based or higher olefin-based hydrocarbon using an unsaturated hydrocarbon directly as a raw material.

Further, the glass transition temperature of the petroleum resin measured by a differential calorimeter is preferably 50 ° C. or more, and more preferably 76 ° C. or more, from the viewpoint that the dielectric loss is not deteriorated in the temperature range in which the capacitor is used.

A hydrogenated petroleum resin obtained by adding hydrogen to the petroleum resin and having a hydrogenation ratio of 80% or more, more preferably 95% or more, is suitable for the film of the present invention.

Further, the petroleum resin is preferably amorphous (ie, substantially no crystal melting is observed when the petroleum resin is measured by a differential calorimeter) from the viewpoint of compatibilization with the polypropylene resin, The number average molecular weight is 1
000 or less is preferable. If the petroleum resin is not compatible with the polypropylene resin, stretching unevenness is caused during biaxial stretching, and cavities are formed inside the film, so that the dielectric breakdown strength may decrease.

The terpene resin having substantially no polar group includes a hydroxyl group (—OH), an aldehyde group (—CHO), a ketone group (—CO—), a carboxyl group (—COOH),
Halogen group, sulfonic acid group (—SO ₃ Y, Y is H, Na
And terpene resins having no polar group, such as modified hydrocarbons having a composition of (C ₅ H ₈ ) _n and modified compounds derived therefrom. Note that n is a natural number of about 2 to 20. Terpene resins are sometimes referred to as terpenoids. Representative compound names include pinene, dipentene, kalen, myrcene, ocimene, limonene, tervinolene, terpion, sapinene, tricyclene, pisapolene, zingiperene, santalen, camphorene, millen, totalene, and the like. %, More preferably 90% or more, and particularly preferably hydrogenated β-pinene and hydrogenated dipentene.

It is important in the present invention to use such a hydrogenated resin, and the bromine value is preferably 10 or less, more preferably 5 or less, and particularly preferably 1 or less.

The polypropylene film of the present invention is characterized in that 100 parts by weight of the above polypropylene resin contains 5 to 50 parts by weight of at least one kind of the petroleum resin or terpene resin substantially containing no polar group and double bond. Is 10
It is a film having at least one resin layer in which about 20 parts by weight are mixed.

It is necessary that the mixing amount of the resin containing no polar group and no double bond is 50 parts by weight or less.
When the amount exceeds 0 parts by weight, not only the chemical resistance of the film, particularly the oil resistance against aromatic hydrocarbon solvents and the like is weakened, but also the thermal dimensional stability of the film is deteriorated.

It is necessary that the mixing amount of the above resin is not less than 5 parts by weight, and if it is less than 5 parts by weight, the object of the present invention is to have few insulation defects, excellent dielectric breakdown strength, and static with time. Since the change in electric capacity is small, a polypropylene film capable of supplying a capacitor with high security cannot be obtained.

The polypropylene film of the present invention is obtained by using the above-described raw materials and generally being biaxially oriented. As the method of biaxial orientation, inflation simultaneous biaxial stretching method, Stenter simultaneous biaxial stretching method, obtained by any prescription of Stenter sequential biaxial stretching method,
Among them, a film formed by a stenter sequential biaxial stretching method is preferably used in view of film forming stability and thickness uniformity.

The center line average surface roughness of at least one surface of the polypropylene film of the present invention exceeds 0.03 μm,
It is necessary that the thickness be 0.5 μm or less.

The centerline average surface roughness of the polypropylene film is timely selected depending on the type of capacitor used with the film, and capacitors in which the capacitors are not impregnated with insulating oil (ie, dry capacitors)
The center line average surface roughness of at least one side of the polypropylene film exceeds 0.03 μm and 0.15 μm in order to maintain a proper air layer between the film layers of the wound capacitor element after winding. The following is preferred. .

On the other hand, in a capacitor in which the capacitor is impregnated with insulating oil (ie, a wet capacitor), the film is wound so that the insulating oil is uniformly impregnated from the end of the wound capacitor element over the entire film surface. In order to maintain an appropriate air layer between the layers, the center line average surface roughness of at least one surface of the polypropylene film is preferably 0.1 μm or more and 0.5 μm or less.

If the center line average surface roughness of both surfaces of the film is 0.03 μm or less, the films wound on the rolls adhere to each other, and peeling discharge occurs at the time of unwinding.
It causes insulation defects. If the center line average surface roughness of both sides of the film exceeds 0.5 μm, even if it is used as a wet capacitor, an excessive air layer will be provided between the film layers when it is used as a wound capacitor element, so that insulating Since excessive oil infiltration is caused, the shape of the capacitor is not stable, the capacitance of the capacitor changes with time, and the dielectric breakdown strength decreases.

When the center line average surface roughness of both surfaces of the polypropylene film used in the dry condenser exceeds 0.15 μm, an excessive air layer is provided between the film layers of the dry condenser, so that the static electricity is caused by corona discharge. The capacitance may change over time. In addition, when the center line average surface roughness of both surfaces of the polypropylene film used in the wet condenser is less than 0.1 μm, since an appropriate air layer is not provided between the film layers as the wet condenser, the insulating oil covers the entire film surface. Therefore, a corona discharge may occur in a place where the insulating oil does not spread, and the capacitance may change with time.

The method for setting the center line average surface roughness of at least one surface of the film within the above range is not particularly limited. For example, when the raw material is melted and extruded into a sheet, the temperature of the casting drum is set high. By slowing down the rate of cooling and solidifying by doing, laminating a polypropylene resin layer with a high growth rate of spherulites and a method to make the growth of spherulites of polypropylene sufficient on at least one side of the film,
There is a method of generating large spherulites only on the film surface, or a method of laminating polyolefin resin layers having different stretching behaviors and intentionally causing stretching unevenness in the polyolefin resin layer at the time of stretching to optimize the surface by stretching unevenness. .

The above-mentioned polypropylene resin can be used as the polypropylene resin layer in which spherulites grow rapidly. However, petroleum resins, terpene resins, and the like have an effect of inhibiting spherulite growth of the polypropylene resins. It is preferable that neither petroleum resin nor terpene resin be mixed.

In the present invention, the expression that substantially no petroleum resin or terpene resin is mixed means that the addition amount is within a range that does not inhibit the spherulite growth of the polypropylene resin. It means that the addition amount is 1 part by weight or less based on 100 parts by weight of the resin.

Further, there is a half-crystallization time as an index indicating that the growth of spherulites is fast. Since the half-crystallization time is a value inversely proportional to the growth rate of the spherulite, the smaller this value is, the faster the spherulite grows. In the present invention, as the resin constituting the polypropylene resin layer for optimizing the surface roughness, the half-crystallization time at 125 ° C. is preferably 250 seconds or less.

Furthermore, a half-crystallization time at 125 ° C. of a resin layer obtained by mixing the above-mentioned specific polypropylene resin and the above-mentioned specific petroleum resin and / or terpene resin with the polypropylene film of the present invention as a laminated film of two or more layers. The time is preferably at least 200 seconds in order to suppress insulation defects, which is the object of the present invention, and to form a film having excellent dielectric breakdown strength. It is considered that the reason for this is that if the growth of spherulites inside the film is too large, cavities are formed inside the film when the film is stretched, and the cavities serve as a starting point for insulation defects and dielectric breakdown.

Next, the resin constituting the polyolefin resin layer is preferably a blend of polyethylene and a random copolymer of propylene and another olefin because a uniform center line average surface roughness can be obtained. .

As other olefins, for example, ethylene,
Butene-1, 4-methyl-pentene-1, propylene
Ethylene rubber, propylene / ethylene / diene terpolymer rubber, butadiene, styrene and the like. Among them, a random copolymer using ethylene is preferable because a uniform center line average surface roughness can be obtained. The surface of the polyolefin resin layer is roughened by stretching.

The copolymerization ratio of propylene to another olefin is preferably in the range of 99: 1 to 85:15 (% by weight). The intrinsic viscosity of the random copolymer of propylene and another olefin is not particularly limited, but is preferably in the range of 1 to 5 dl / g from the viewpoint of film forming properties and dispersibility with polyethylene. Further, the melt flow rate at 230 ° C. under a load of 2.16 kg is preferably 5 to 10 g / 10 min from the viewpoint of film forming properties and dispersibility with polyethylene.
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.

As the polyethylene constituting the polyolefin resin layer, high-density polyethylene is preferable because of its good dispersibility with the above random copolymer. As the high-density polyethylene, the density is 0.9 to 1 g / cm ³ , and the intrinsic viscosity is not particularly limited, but is preferably in the range of 1 to 5 dl / g from the viewpoint of dispersibility with the above random copolymer. Further, the melt flow rate at 190 ° C. and a load of 2.16 kg is preferably from 0.1 to 0.5 g / 10 min from the viewpoint of dispersibility with the above random copolymer.

When the polyolefin resin layer is a blend of a random copolymer of propylene with another olefin and polyethylene, the blend ratio is 85:15 to 15:15.
The range of 70:30 (% by weight) is preferable because uniform and appropriate center line surface roughness can be obtained.

Further, inorganic particles may be added to the polyolefin resin layer. Examples of the inorganic particles include calcium carbonate, magnesium carbonate, magnesium oxide, alumina, silica, aluminum silicate, kaolin, kaolinite, talc, clay, diatomaceous earth, montmorillonite, titanium oxide, and zeolite. The average particle size of these inorganic particles is 0.1 to 5 μm, preferably 0.2 to 2 μm.
The addition amount is 1 to 20%, preferably 5 to 20% based on the polymer.
１５15%.

Further, known additives such as a crystal nucleating agent, an antioxidant, a heat stabilizer, a sliding agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, and a coloring inhibitor are added to the polyolefin resin layer. You may make it contain.

Further, in the polyolefin resin layer,
Since petroleum resins and terpene resins have the effect of reducing the effect of causing polyolefin resin to cause unevenness in stretching, it is preferable that substantially neither petroleum resin nor terpene resin is mixed.

Further, the biaxially oriented polypropylene film of the present invention has a heat of crystal fusion of 85 J / g or more,
More preferably, it is 90 J / g or more. The reason for this is that the dielectric breakdown may be based on the above-described cavity, but the amorphous portion is considered to have a lower breakdown strength than the crystalline portion of the film.

The plane orientation coefficient of the polypropylene film of the present invention is preferably 0.012 to 0.015.
When the plane orientation coefficient is less than 0.012, the dielectric breakdown strength tends to deteriorate. On the other hand, when the plane orientation coefficient exceeds 0.015, the film is frequently oriented during the production of the film, so that the film is frequently torn and the productivity may be reduced. The preferred range of the plane orientation coefficient is 0.012 to 0.014, and more preferably 0.0125 to 0.0138.

The polypropylene film of the present invention has 12
The heat shrinkage in the longitudinal direction when heating at 0 ° C. for 15 minutes is 1.5 to
Preferably it is in the range of 3%. 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 in the longitudinal direction is too low, the tightening by heat treatment at the time of producing the capacitor element becomes insufficient, which may adversely affect the shape retention and the capacity change rate. More preferably, the heat shrinkage in the longitudinal direction is 1.6 to 2.8%, and more preferably 1.7 to 2.5%.
Is preferable.

The polypropylene film of the present invention has 12
Heat shrinkage in the width direction when heated at 0 ° C. for 15 minutes is 0 to 2.5
% Is preferable. If the heat shrinkage in the width direction is too large, dimensional changes may occur during the formation of the metal layer as an electrode, wrinkles may be formed on the film roll, and metallikon metal may not be uniformly adhered during metallikon. If the heat shrinkage in the width direction is too low, the shape of the capacitor is deformed or peeling occurs between film layers, which may result in a decrease in capacity or a decrease in dielectric breakdown strength. A more preferable heat shrinkage in the width direction is in the range of 0.5 to 2%.

In the present invention, the thickness of the polypropylene film is preferably 2 to 2 in terms of film forming properties, mechanical properties and electrical properties.
0 μm is preferred. 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.

When a metal layer is formed on the polypropylene film of the present invention, it is preferable to perform a corona discharge treatment or a plasma treatment on the surface on which the metal layer is to be formed 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 kept in a plasma state to chemically modify the film surface can be adopted.
There is a method described in Japanese Patent Application Laid-Open Publication No. HEI 10-202, for example.

The polypropylene film used as the dielectric of the capacitor of the present invention may be wound with a metal foil used as an electrode, or may be metallized in advance as an electrode. It is more preferable that the metal is wound after being metallized.

The metal for forming the metal layer on the polypropylene film of the present invention is not particularly limited.
It is preferable to use aluminum, zinc, copper, tin, silver, nickel or the like alone or in combination in view of the durability and productivity of the metallized layer. In addition, it is preferable that the surface of the film on which the metal layer is formed has a relatively small center line average surface roughness on the front and back sides, because a decrease in capacitance can be minimized.

The method for forming a metal layer on the 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 is too large, when the deposited film clears during the application of electricity, the film is likely to disappear and the change in capacitance may be large. 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, the specifications of the margin provided when the metal layer is formed on the polypropylene film (the portion without the metal layer provided on the surface on which the metal layer is formed for the purpose of electrical insulation, etc.) are different from those of the normal type in that the fuse mechanism is used. Can be adopted according to the purpose, such as those provided with, and are not particularly limited.

The type of the capacitor using the polypropylene film of the present invention as a dielectric includes a dry type and an oil immersion type, but is not particularly limited.

Next, the method for producing the polypropylene film of the present invention will be described below, but is not necessarily limited thereto.

A mixture of a polypropylene resin raw material and a petroleum resin and / or a terpene resin is supplied to an extruder, melted by heating, passed through a filter, and then heated to 220 to 320 ° C.
Melt extrusion at a temperature of 70 to 105
It is wound around a casting drum maintained at a temperature of ° C. and cooled and solidified to form an unstretched film. Next, the unstretched film is biaxially stretched and biaxially oriented. First, the unstretched film is preheated by passing through a roll maintained at 120 to 150 ° C., and then the sheet is passed between rolls having a peripheral speed difference maintained at a temperature of 140 ° C. to 150 ° C.
Stretch ~ 6 times and immediately cool to room temperature. M of the present invention
In the case of a polypropylene film having a mmm of more than 99%, a preheating temperature of 130 ° C. or less and a stretching temperature of 140 ° C. or less may cause insufficient stretching due to insufficient heat, resulting in uneven film formation or tearing. This is very important. Subsequently, the stretched film was guided to a stenter, stretched 5 to 15 times in the width direction at a temperature of 155 to 165 ° C., and then relaxed by 2 to 20% in the width direction.
The film is heat-set at a temperature of 50 to 160 ° C. and wound.

Thereafter, in order to improve the adhesion 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 method for measuring and evaluating the characteristic values 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
13C-NMR was measured at z. For the assignment of the obtained spectra and the calculation of the pentad fraction, see T.W. Ha
Yashi et al. [Polymer, 29, 1]
38-143 (1988)], the peak derived from the methyl group had an mmmmmm peak of 21.85.
Each peak was assigned as 5 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 concentration: 15 to 20 wt% Solvent: o-dichlorobenzene (90 wt%) / benzene-D 6 (10 wt%) Measurement temperature: 120 to 130 ° C. Resonance frequency: 67.93 MHz Pulse width: 10 μsec (45 ° pulse) ) Pulse repetition time: 7.091 sec Data point: 32K Integration count: 8168 Measurement mode: Noise decoupling

(3) Measurement of Plane Orientation Coefficient In accordance with the method specified in JIS-K7105, the refractive index in the longitudinal direction, width direction and thickness direction was measured using an Abbe refractometer with sodium D line as a light source. Each n
MD, nTD, nZD). Here, the mounting liquid was measured using methyl salicylate at 25 ° C. and 65% RH. Next, the plane orientation coefficient was calculated by the following equation. In addition,
The measurement of the vapor-deposited film was performed after the vapor-deposited film was once immersed in a 1N aqueous solution of sodium hydroxide to dissolve the vapor-deposited metal and then washed with purified water.

Plane orientation coefficient = [(nMD + nTD) / 2] −nZD

(4) Heat shrinkage ratio The film was 260 mm long in the machine and width directions, respectively.
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 (%)

(5) 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)

(6) Film thickness The thickness was measured using a dial gauge type thickness gauge (JIS-B-7503).

(7) Center line average surface roughness 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

(8) Half-crystallization time, heat of crystal fusion As a differential scanning calorimeter, DS manufactured by Seiko Instruments Inc.
C (RDC220), using a disk station (SSC / 5200) manufactured by the company as a data analyzer, about 10 mg of a film sample was mounted on an aluminum packing, and the temperature was raised from room temperature to 280 ° C. at a rate of 20 ° C./min. For the endothermic peak observed at this time, the heat of crystal fusion was calculated from the peak area. The peak area is an area which shifts from the baseline to the absorption side by increasing the temperature, and further continues to increase the temperature until the temperature returns to the baseline.
I asked. Measured with In (indium) weighed to the same weight as the film sample under the same conditions to determine the area B,
The calorific value of the endothermic peak was determined by the following equation.

Heat quantity of endothermic peak (J / g) = 28.5 × A / B

The half-crystallization time was as follows: the sample heated to 280 ° C. was kept at 280 ° C. for 5 minutes, and then heated at 50 ° C./mi.
The temperature was lowered to 125 ° C. at n, and the time obtained by subtracting the time when the temperature reached 125 ° C. from the time of the exothermic peak observed when the temperature was maintained at 125 ° C. was defined as the half-crystallization time.

(9) Insulation Defects According to JIS-C-2330, films having a film thickness of 7.5 μm and a film thickness of 15 μm measured by a ten-sheet micrometer method were evaluated according to the following evaluation criteria.

：: The number of insulation defects is 2 or less Δ: The number of insulation defects is 3 to 5 ×: The number of insulation defects is 6 or more (cannot be used as a capacitor film) In the present invention, “O” and “Δ” are accepted.

(10) Element Dielectric Breakdown Strength The capacitor element was connected to a (DC or AC) high-voltage stabilized power supply manufactured by Kasuga Electric Co., Ltd. in an atmosphere of 23 ° C. and 65% RH, and was stepped up at a rate of 100 V / sec. While applying a voltage, the voltage at the time when the capacitor (element) was broken was determined, and the average value measured for ten capacitors (elements) was converted to a value per film thickness to obtain element dielectric breakdown strength.

(11) Capacitance change rate A DC voltage of 80 V / μm per film thickness is applied to ten capacitor elements, and the capacitance is changed to 1000 at 85 ° C. atmosphere.
After a lapse of time, the capacitance was measured, and the rate of change in capacitance (average of 10 elements) was determined by the following equation.

Capacitance change rate (%) = [(C−C ₀ ) / C ₀ ] × 100 C ₀ : initial capacitance before energization C: capacitance after 1000 hours of energization

[0089]

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

(Preparation of Polypropylene Resin) The properties of the polypropylene resin used are shown in Table 1.

[0091]

[Table 1]

(Preparation of Petroleum Resin) A mixture of dicyclopentadiene as a monomer, mixed xylene as a solvent and a mixed solution of benzene was placed in a stainless steel polymerization vessel and subjected to thermal polymerization at 270 ° C. After the completion of the reaction, the solvent and unreacted monomer were distilled off, and finally distilled under reduced pressure at 210 ° C./2 mmHg. The residue was collected as product resin. Next, hydrogen pressure 7
Hydrogenation was carried out at 0 kg / cm ² and 250 ° C. using Raney nickel as a catalyst. At this time, two types of petroleum resins having different thermal polymerization times were collected (petroleum resins 1 and 3). Petroleum resin 1 which was not subjected to hydrogenation was designated as petroleum resin 2. Table 2 shows the properties of each petroleum resin.

(Preparation of Terpene Resin) Cationic polymerization was carried out using β-pinene and dipentene as starting materials and aluminum chloride as a catalyst. Next, hydrogen pressure 70kg / c
Raney nickel was taken terpene resin 1 performs hydride as catalyst at m ^2, 250 ℃. Table 2 shows the properties of the terpene resin 1.

[0094]

[Table 2]

Example 1 Polypropylene resin 1 (2,
6-di-t-butyl-p-cresol (BHT) 300
0 ppm, telorakis [methylene-3 (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate]
9 ppm of methane (Irganox 1010) and 50 ppm of calcium stearate)
A mixture of 0% by weight and 10% by weight of petroleum resin 1 is supplied to an extruder, melted at a temperature of 280 ° C., extruded into a sheet from a T-type die, and wound around a casting drum at a temperature of 105 ° C. After cooling and solidifying, the sheet was peeled off from the casting drum, and then gradually cooled with a roll at 60 ° C. to return to room temperature. Next, the sheet was preheated at 143 ° C., passed through rolls having a peripheral speed difference maintained at a temperature of 148 ° C., and stretched 5.5 times in the longitudinal direction. Subsequently, the film was guided to a tenter, stretched 10 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 7.5 μm. Obtained. Further, 30 W · min /
The corona discharge treatment was performed in the atmosphere at a treatment intensity of m ² . The film was set in a vacuum vapor deposition machine, and an alloy metal of zinc and aluminum was vapor-deposited on the corona-treated surface so that the film resistance was 4.0 Ω / □. This film was slit to obtain a metallized film having a total width of 38 mm and a margin width of 1 mm. The element was wound using a pair of two reels of the obtained film, metal sprayed on an 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 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

(Example 2) A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was set to 5 times. Table 3 summarizes the composition of the raw materials used and the composition of the film. Table 4 shows the physical properties of the obtained polypropylene film and the evaluation results of the capacitor element.
Summarized in

Example 3 A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that 10% by weight of terpene resin 1 was used instead of petroleum resin 1. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Example 4 Polypropylene resin 2 was used instead of polypropylene resin 1 as the polypropylene resin.
(2,6-di-t-butyl-p-cresol (BHT)
3000 ppm, telorakis [methylene-3 (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate] methane (Irganox 1010) 4000 pp
m, and 50% by weight of calcium stearate) were used to obtain a polypropylene film and a capacitor element in the same manner as in Example 1 except for using 90% by weight. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Example 5 Polypropylene resin 2 (2,
6-di-t-butyl-p-cresol (BHT) 300
0 ppm, telorakis [methylene-3 (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate]
9 ppm of methane (Irganox 1010) and 50 ppm of calcium stearate)
0% by weight and 10% by weight of Petroleum Resin 1 were mixed and supplied to an extruder and melted at a temperature of 280 ° C. In addition, polypropylene resin 2 (2,6-di-t-butyl-p-cresol (BHT) 3000 ppm, telorakis [methylene-
3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (Irganox 101
0) 4000 ppm, calcium stearate 50 pp
is added to another extruder (sub-extruder) and melted at a temperature of 280 ° C. and melted by two extruders before being extruded into a sheet from a T-type die. The resin is combined and extruded into a sheet.
After being wound around a casting drum having a temperature of and cooled and solidified, and the sheet is peeled off from the casting drum,
The mixture was gradually cooled with a roll at 60 ° C. and returned to room temperature. At this time, the surface opposite to the surface in close contact with the casting drum (A surface)
And a polypropylene resin 2 was laminated thereon. Next, the sheet was preheated at 143 ° C., passed through rolls having a peripheral speed difference maintained at a temperature of 148 ° C., and stretched 5.5 times in the longitudinal direction. Subsequently, the film was guided to a tenter, stretched 10 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 7.5 μm. Obtained. Further, a corona discharge treatment was performed on the surface (Side B) in close contact with the casting drum in the atmosphere at a treatment intensity of 30 W · min / m ² . The film was set in a vacuum vapor deposition machine, and an alloy metal of zinc and aluminum was vapor-deposited on the corona-treated surface so that the film resistance was 4.0 Ω / □. This film was slit to obtain a metallized film having a total width of 38 mm and a margin width of 1 mm.
The element was wound using a pair of two reels of the obtained film, metal sprayed on an 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 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

(Example 6) The raw material supplied to the sub-extruder was polypropylene resin 1 (2,6-di-t-butyl-p-
Cresol (BHT) 3000 ppm, Telorakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (Irganox1
010) 4000 ppm, calcium stearate 50
ppm added) was changed to 100% by weight to obtain a polypropylene film and a capacitor element in the same manner as in Example 5. Table 3 shows the composition of the raw materials used and the composition of the film.
Table 4 summarizes the physical properties of the obtained polypropylene film and the evaluation results of the capacitor element.

Example 7 The raw material supplied to the sub-extruder was polypropylene resin 1 (2,6-di-tert-butyl-p-).
Cresol (BHT) 3000 ppm, Telorakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (Irganox1
010) 4000 ppm, calcium stearate 50
ppm) and 5% of petroleum resin 1
A polypropylene film and a capacitor element were obtained in the same manner as in Example 5, except that the content was changed to% by weight. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

(Example 8) A polypropylene film and a capacitor element were obtained in the same manner as in Example 5 except that the raw materials supplied to the sub-extruder were laminated on both sides of the film, and the temperature of the casting drum was set to 70 ° C. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Example 9 A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that 10% by weight of petroleum resin 2 was used instead of petroleum resin 1. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Example 10 A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that 10% by weight of petroleum resin 3 was used instead of petroleum resin 1. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Comparative Example 1 The raw materials to be supplied were polypropylene resin 1 (2,6-di-t-butyl-p-cresol (BHT) 3000 ppm, telakis [methylene-3]
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] Methane (Irganox 1010) 4
2,000 ppm and 50 ppm of calcium stearate), and a polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that the temperature of the casting drum was set to 85 ° C. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

Comparative Example 2 A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that the temperature of the casting drum was 70 ° C. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 4 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitor elements.

[0107]

[Table 3]

[0108]

[Table 4]

(Example 11) Polypropylene resin 2
(2,6-di-t-butyl-p-cresol (BHT)
3000 ppm, 1,3,5-trimethyl-2,4,6
-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (Irganox1330) 500p
pm, 50% by weight of calcium stearate) and 90% by weight of petroleum resin 1 were mixed and supplied to an extruder to be melted at a temperature of 280 ° C. Also,
Polypropylene resin 2 (2,6-di-t-butyl-p-
Cresol (BHT) 3000 ppm, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (Irgano)
x1330) 500 ppm, calcium stearate 5
100 ppm by weight) was fed to another extruder (sub-extruder) and melted at a temperature of 280 ° C.
Before extruding from a T-type die into a sheet, the resins melted by two extruders are combined and extruded into a sheet.
The sheet was wound around a casting drum having a temperature of 105 ° C. to be cooled and solidified. After the sheet was peeled off from the casting drum, the sheet was gradually cooled with a roll of 60 ° C. and returned to room temperature.
At this time, the polypropylene resin 2 was laminated on the surface (surface A) opposite to the surface in close contact with the casting drum. The sheet was then preheated at 144 ° C. and subsequently
It was kept at a temperature of 50 ° C., passed between rolls provided with a peripheral speed difference, and stretched 5.5 times in the longitudinal direction. Subsequently, the film was guided to a tenter, stretched 10 times in the width direction at a temperature of 163 ° C., and then subjected to 150 ° C. while giving 10% relaxation in the width direction.
To obtain a biaxially oriented polypropylene film having a thickness of 15 μm. Three of these films were wound between electrode foils to produce a wound capacitor element. Then, a plurality of wound capacitor elements were connected in parallel, integrated and stored in a tank, and impregnated with insulating oil to form a capacitor. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 5 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitors.

(Example 12) Polypropylene resin 2
(2,6-di-t-butyl-p-cresol (BHT)
3000 ppm, 1,3,5-trimethyl-2,4,6
-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (Irganox1330) 500p
pm, 50% by weight of calcium stearate) and 90% by weight of petroleum resin 1 were mixed and supplied to an extruder to be melted at a temperature of 280 ° C. Also,
Polyolefin resin (random copolymer resin of 98.5% by weight of propylene and 1.5% by weight of ethylene (intrinsic viscosity:
1.5 dl / g, melt index: 8.5 g / 1
0 minutes) and 75% by weight of high-density polyethylene (density: 0.
95 g / cm3, intrinsic viscosity 1.8 dl / g, melt index: 0.2 g / 10 min) and 25 wt%, and 2,6-di-t-butyl-p-cresol (BHT) was used as an additive. ) 3000 ppm, Telakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (Irganox1010) 50
0 ppm, and 50 ppm of calcium stearate) were supplied to another extruder (sub-extruder) and 280
Before extruding into a sheet from a T-type die, the resins melted by two extruders are merged, extruded into a sheet, wound around a casting drum at a temperature of 40 ° C, and cooled and solidified. After the sheet was peeled off from the casting drum, the sheet was gradually cooled with a roll at 30 ° C. and returned to room temperature. At this time, the polyolefin resin layer was laminated on the surface (surface A) opposite to the surface in close contact with the casting drum. Next, the sheet was preheated at 144 ° C., continuously kept at a temperature of 150 ° C., passed between rolls provided with a peripheral speed difference, and stretched 5.5 times in the longitudinal direction. Subsequently, the film was guided to a tenter, stretched 10 times in the width direction at a temperature of 163 ° 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 15 μm. . Three of these films were wound between electrode foils to produce a wound capacitor element. Then, a plurality of wound capacitor elements were connected in parallel, integrated and stored in a tank, and impregnated with insulating oil to form a capacitor. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 5 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitors.

Comparative Example 3 A capacitor was constructed in the same manner as in Example 12, except that the petroleum resin 1 was not added to the polypropylene resin 2. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 5 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitors.

Comparative Example 4 A capacitor was constructed in the same manner as in Example 12 except that the blend ratio of the random copolymer resin and the high-density polyethylene was changed to 50% by weight and 50% by weight. Table 3 summarizes the constitutions of the raw materials and the films used, and Table 5 summarizes the physical properties of the obtained polypropylene films and the evaluation results of the capacitors.

[0113]

[Table 5]

[0114]

By using the polypropylene film of the present invention as a dielectric, a capacitor having a small amount of insulation defects, an excellent dielectric breakdown strength, and a small change in capacitance with the passage of time can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 23:00 B29L 7:00

Claims (8)

[Claims] 1. One or more resins selected from petroleum resins substantially free of double bonds and polar groups and terpene resins substantially free of double bonds and polar groups per 100 parts by weight of polypropylene resin Is a polypropylene film having at least one resin layer in which 5 to 50 parts by weight is mixed, wherein the center line average surface roughness of at least one surface of the film is more than 0.03 μm and 0.5 μm or less. Polypropylene film for capacitors. 2. One or more resins selected from petroleum resins substantially free of double bonds and polar groups and terpene resins substantially free of double bonds and polar groups per 100 parts by weight of polypropylene resin Is characterized by using a polypropylene resin having an isotacticity of 98 to 99.5% and an isotactic pentad fraction of more than 99% as a polypropylene resin constituting a resin layer in which 5 to 50 parts by weight are mixed. The polypropylene film for a capacitor according to claim 1, wherein 3. The polypropylene film for a capacitor according to claim 1, wherein two or more layers are laminated in the thickness direction. 4. A laminate comprising two or more layers laminated in the thickness direction,
The polypropylene film for a capacitor according to claim 3, wherein the layer is a polypropylene resin layer containing substantially no petroleum resin or terpene resin. 5. One or more resins selected from petroleum resins substantially free of double bonds and polar groups and terpene resins substantially free of double bonds and polar groups per 100 parts by weight of polypropylene resin Of the resin layer in which 5 to 50 parts by weight are mixed, the half-crystallization time at 125 ° C. is 200 seconds or more, and the 125 ° C. of the polypropylene resin layer in which substantially no petroleum resin or terpene resin is mixed.
The polypropylene film for a capacitor according to claim 4, wherein the half-crystallization time in step (a) is 250 seconds or less. 6. A laminate of two or more layers in the thickness direction,
The polypropylene film for a capacitor according to claim 3, wherein the layer is a polyolefin resin layer containing substantially no petroleum resin or terpene resin. 7. The polypropylene film for a capacitor according to claim 1, wherein the crystal has a heat of crystal fusion of 85 J / g or more. 8. The heat shrinkage at 120 ° C. in the longitudinal direction of the film is 1.5 to 3%,
The polypropylene film for capacitors according to any one of claims 1 to 7, wherein the heat shrinkage at 0 ° C is 0 to 2.5%.