JPH10156939A - Polypropylene film and capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance long-term dielectric breakdown characteristics at high temp. and to suppress the deterioration in yield at a time of the production of a condenser by specifying the isotacticity and isotactic pendant ratio and surface orientation coefficient of a biaxially oriented polypropylene film. SOLUTION: The isotacticity of a biaxially oriented polypropylene film is 98.5-99.5% and the isotactic pendant ratio mmmm displaying the stereoregularity of the film evaluated on the basis of a pendant ratio by the absorption peak of a methyl group measured by<13> C-NMR exceeds 99%. Further, the surface orientation coefficient of the biaxially oriented polypropylene film is 0.012-0.015. If the surface orientation coefficient is below 0.012, slitting properties are bad and, when said coefficient exceeds 0.015, slitting properties are good but, since the orientation of the film at a time of production is too high, the rupture of the film is frequently generated and productivity is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene film and a capacitor using the same, and more particularly to a biaxially oriented polypropylene film having excellent heat resistance and dielectric breakdown resistance, and heat resistance and resistance using the same as a dielectric. The present invention relates to a capacitor having excellent dielectric breakdown characteristics.

[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. For this purpose, it is necessary to maintain the performance at a temperature higher than 85 ° C., which is the maximum operating temperature of the conventional polypropylene film capacitor, and for a long time.

[0005] To this end, (1) mechanical deformation due to rapid heating for a short time, that is, a heat shrinkage rate is appropriately 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.

[0006] The reason for the above (1) is that, when a capacitor element is produced, a heat treatment is applied at a certain temperature at the stage when the polypropylene film is wound on the electrode so as to give an appropriate heat shrinkage and cause tightness. It is common to maintain the form and expel air between the film layers by performing the heat treatment. However, 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.

[0007] Further, with the miniaturization of electric devices, there has been a demand for improvement of the above-mentioned characteristics, while a demand for further miniaturization of the film capacitor itself has been increasing. 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.

However, as the film becomes thinner, various problems have arisen with respect to workability and electrical characteristics when handling the film. The slitting process before winding the element in the manufacturing process of film capacitors is one of them.If the workability at the time of slitting is poor, the phenomenon that the slitted part rises up or the yield in the slit decreases due to film breakage. was there. When the slitted portion rises, the uniformity of the thickness as a capacitor film is impaired, and not only the yield at the time of manufacturing the element may be deteriorated, but also the quality of electric characteristics such as dielectric breakdown strength may be varied. . Furthermore, in order to connect the external electrode terminals of the film capacitor with the metal deposited on the film surface, which is an internal electrode, after winding the element, there is a step of spraying a metal called metallikon on both sides of the element. If the part is disturbed, it may cause thermal spray spots, resulting in poor contact and poor insulation.

[0009] Further, as the film becomes thinner, the defect that the surface of the film provided with the metal layer becomes white due to heat loss by the flying metal in the vapor deposition process of providing the metal layer on the film surface increases rapidly, and the capacitor element becomes insulated. In some cases, this could cause a defect or cause a hole (pinhole) in the film, leading to a break in the film or poor insulation of the capacitor element.

On the other hand, in reducing the size of the capacitor element, the slit width is also reduced in addition to reducing the film thickness. If the slit width is too small, it is difficult to control the winding tension. Insulation failure due to failure was sometimes caused.

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 content 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.
There is a disclosure of a propylene polymer in the range of 995 and a molded article using the same.

However, as disclosed in these publications, a biaxially oriented polypropylene film having a high isotactic pentad fraction of a boiling n-heptane-insoluble component simply has an 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. The so-called highly crystalline biaxially oriented polypropylene film, which has an extremely high isotacticity, has an extremely poor film-forming property due to insufficient stereoregularity, and has excellent heat resistance and dielectric breakdown resistance. It has not been established as an industrially useful technique for producing a polypropylene film.

In order to solve these drawbacks, Japanese Patent Publication No.
No. 28727 discloses that the isotactic pentad fraction is in the range of 0.960 to 0.990 and the boiling n-
A crystalline polypropylene film having excellent moldability has been proposed in which the total amount of the extract to be extracted sequentially with hexane and boiling n-heptane is 3.0 to 6.0%. However, this polypropylene film did not have a sufficient isotactic pentad fraction and had insufficient dielectric breakdown resistance at high temperatures.

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 distortion 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, 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 isotacticity and stereoregularity of this film are conventional, and the dielectric breakdown resistance at high temperatures, which is the object of the present invention, for responding to future high demands, was not always sufficient. .

[0017]

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, the long-term deterioration at high temperatures is suppressed by the variation in quality. The present inventors have found that a small capacitor can be obtained and a thin film suitable for miniaturization of the capacitor can be obtained, which has led to the present invention.

It is an object of the present invention to provide a polypropylene film which is excellent in heat resistance and long-term dielectric breakdown resistance at high temperatures, furthermore, suppresses deterioration of the yield in the capacitor manufacturing process and reduces quality variations. It is in.

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

[0020]

Means for Solving the Problems The present invention achieves the above object, and the polypropylene film of the present invention is a biaxially oriented polypropylene film having an isotacticity of 98.
９９99.5%, the isotactic pentad fraction exceeds 99%, and the plane orientation coefficient is 0.012 to 0.015.
It is a polypropylene film characterized by these.

The capacitor of the present invention uses the above polypropylene film as a dielectric.

[0022]

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. And 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, and 1-butene.
Pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allyl Benzene, cyclopentene, norbornene, 5-methyl-2
-Norbornene and the like. The copolymerization amount or blend amount is 1 from the viewpoint of dielectric breakdown resistance and heat resistance.
Preferably, it is less than 10 mol% and less than 10% by weight of the blend.

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
In producing a biaxially oriented film as disclosed in Japanese Patent Publication No. 236709, 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 99.5% for good film forming property, heat resistance and dielectric breakdown resistance, and more preferably 9 to 99.5%.
8.7 to 99.3% is preferred.

In order to obtain a polypropylene film having such isotacticity, the proportion of a low molecular weight component which is easily soluble in the boiling n-heptane of the polypropylene resin as a raw material or a so-called atactic portion having low stereoregularity is 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, as described in T.W. 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 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. The mmmm of the polypropylene film of the present invention is preferably 99.1% or more, more preferably 99.2% or more, and still more preferably 99.3% or more in terms of high heat resistance and high dielectric breakdown resistance. It is.

In order 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 can be achieved by selecting a catalyst system (solid catalyst, externally added electron donating compound) and purifying them when polymerizing polypropylene. M of raw material polypropylene resin
The higher the mmm, the mmm of the polypropylene film
m tends to be high, but 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 adjusted. Selected.

In the polymerization process of the polypropylene 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 if necessary after the polymerization, if necessary. Competition can be evaluated by determining the amount of metal oxide remaining after the resin has been completely burned, and this is referred to as ash in the present invention. 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 is lowered, and the dielectric strength of a capacitor using the film may be lowered. In order to keep the ash content within such a 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, reducing the bleed time to 1 hour A method such as the above-mentioned 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 modifier may be added to the polypropylene used in the polypropylene film of the present invention. And a coloring inhibitor.

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. Although various examples are given as specific examples thereof, for example, 2,6-di-t-
Butyl-p-cresol (BHT: molecular weight 220.4)
Together with 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:
It is preferable to use a compound having a molecular weight of 1177.7) or the like. The total content of these antioxidants is preferably in the range of 0.03 to 1% by weight (300 to 10000 ppm) based on the total amount of polypropylene. If the content is small, the long-term heat resistance may be poor. If the content is too large, the antioxidant may bleed out and block at a high temperature, which 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 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. As a 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, film forming stability, thickness uniformity, described later In order to control the plane orientation coefficient to be formed, a film formed by a stenter sequential biaxial stretching method is preferably used.

The plane orientation coefficient of the biaxially oriented polypropylene film of the present invention needs to be 0.012 to 0.015. When the plane orientation coefficient is less than 0.012, the slitting property aimed at by the present invention is poor, the yield in the element winding process is deteriorated, and not only the contact failure in the metallikon process is caused, but also the dielectric breakdown strength at high temperatures is deteriorated. Tend to. On the other hand, when the plane orientation coefficient exceeds 0.015, the slitting property is good, but the film is frequently broken during production of the film because the orientation is too high, and the productivity is reduced. The preferred range of the plane orientation coefficient is 0.0125 to
0.0145, more preferably 0.0128 to
0.014.

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 biaxially oriented polypropylene film preferably has a curl degree in the width direction of 10% or less. If the degree of curl exceeds 10%, the film may meander or bend when winding the film after slitting. Also, when winding the capacitor element, similar meandering and creases of the film occur, which not only reduces the productivity, but also leads to poor insulation even with a capacitor that seems to have good element winding. There are cases. The degree of curl is more preferably 5% or less,
More preferably, it is 3% or less. In order to reduce the curl degree to 10% or less, it is necessary to devise a method of equalizing the amount of heat received on the front and back of the film in the process of manufacturing the film.

In the present invention, the thickness of the biaxially oriented polypropylene film is preferably from 2 to 30 μm, and more preferably from 2.5 to 30 μm, from the viewpoint of film forming properties, mechanical properties and electrical properties.
20 μm. If the thickness of the film is too small, the dielectric breakdown strength and mechanical strength may be poor, and the film may be damaged due to metallization, particularly heat loss. On the other hand, 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 capacitance per volume is undesirably small. When a metal layer is formed on the biaxially oriented polypropylene film of the present invention and used, it is preferable to perform a corona discharge treatment or a plasma treatment on the surface on which the metal layer is 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 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 used by being wound together with a metal foil used as an internal electrode.
The internal electrode may be wound and used as a metallized film in which a metal layer is provided on at least one surface of the film surface in advance. Those wound and used as a metallized film provided with a layer are more preferred. In addition, by providing a metal layer on at least one surface of the film surface as an internal electrode, the capacitor is provided with a self-healing capability of a dielectric breakdown portion, which is called self-healing, to further maintain security.

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 metal layer.

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

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, the dielectric loss tends to deteriorate. 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.

The value of the film resistance was determined by cutting out a vapor-deposited film sample in the longitudinal direction at a width of 2 mm and a length of 50 mm, and measuring the longitudinal resistance value of the cut out sample by a four-point contact method.
Calibrate with width and voltage measurement terminal gap.

In the present invention, the specification of the margin provided when the metal layer is formed on the biaxially oriented 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) is usually specified. It can be adopted according to the purpose, such as various types provided with a fuse mechanism other than the type, and is not particularly limited.

The type of the condenser of the present invention is a dry type,
An oil immersion type or the like may be used, but is not particularly limited.

The slit width of the polypropylene film used as a dielectric in the capacitor of the present invention is not particularly limited, but a slit width of 5 to 50 mm is preferable because both the miniaturization of the capacitor and the yield at the time of manufacturing the capacitor are compatible. .

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 / μm
This is because a value four times or more of this is preferable 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 use a method such as sealing the inside of a metal can after oil or oil impregnation, or blocking the contact with the outside air (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.

First, a polypropylene raw material was supplied to an extruder, heated and melted, and passed through a filtration filter.
Melt extrusion from a slit die at a temperature of 320 ° C, 40
It is wound around a casting drum maintained at a temperature of 85 ° C. and solidified by cooling to produce an unstretched film. At this time, if the casting drum temperature is too high, the crystallization of the film proceeds too much, and it becomes difficult to stretch in the subsequent process,
The heat shrinkage may become too large.

In order to reduce the degree of curl of the film after biaxial stretching, the film wound around a casting drum and cooled and solidified is cooled in a process of cooling to room temperature.
It is preferable to gradually cool with a cooling roll maintained in a temperature range of 5 ° C. to 5 ° C. lower than the casting drum temperature.

Next, this unstretched film is biaxially stretched,
Make it biaxially oriented. First, the unstretched film is
The sheet is preheated by passing through a roll maintained at 0 ° C., and subsequently, the sheet is passed through a roll provided with a peripheral speed difference maintained at a temperature of 140 ° C. to 150 ° C., stretched 2 to 6 times in the longitudinal direction, and immediately at room temperature. Cool. 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

The stretching speed in the longitudinal direction is set
It is important to carry out at 1,000,000% / min in order to obtain the plane orientation of the present invention.
000% / min. The stretching speed in the longitudinal direction is 200
If it is less than 00% / min, the plane orientation of the film becomes insufficient, so that the slitting property of the film is poor, the yield in the element winding process is deteriorated, and the contact failure in the metallikon process is caused, and the dielectric breakdown at a high temperature is caused. The strength tends to deteriorate. On the other hand, 1,000,000% / min
If it exceeds, stretching may occur or tear, making it impossible to form a film.

Subsequently, the stretched film was guided to a stenter and 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 140 to 160 ° C.

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

The obtained film is set in a vacuum vapor deposition device, and a metal suitable for the purpose is vapor-deposited on a predetermined 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, the capacitor is wound into an element shape, hot-pressed and formed into a flat shape, and is subjected to metal spraying (metallicon process) at the end, a lead is taken out, and a capacitor is formed through the exterior.

The biaxially oriented polypropylene film of the present invention can be used in various packaging applications, such as lamination with a heat seal layer, by utilizing heat resistance, cut moldability, and low heat shrinkage in addition to the above-mentioned capacitor applications. It can also be suitably used as an adhesive tape or a polished film (print laminate).

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
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) Measurement of Plane Orientation Coefficient In accordance with the method specified in JIS-K7105, the refractive index in the longitudinal direction, the width direction, and the 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 is 260 mm long in the machine direction and the width direction.
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 = [(L ₀ −L ₁ ) / L ₀ ] × 100 (%)

(5) Ash content According to JIS-C-2330. The 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. to measure the weight W _1, it was determined from the following equation.

Ash content = (W ₁ / W ₀ ) × 1,000,000 (ppm) W ₀ : initial weight (g) W ₁ : ashing weight (g)

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

(7) 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), and a voltage was applied while increasing the voltage at a rate of 200 V / sec. The voltage when the element was broken was determined, and the average value of 10 measured elements was defined as the element breakdown strength.

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

(9) Workability at the time of slitting The degree of swelling of the slit portion when the polypropylene film was slit was divided into four ranks by observing it with an electron microscope.

A: Almost no swelling and good winding appearance of the capacitor element after winding B: Slightly swelling (0.1 μm or less) C: Swelling (0.3 μm or less) Although there is no practical problem D: The swell is large (exceeding 0.3 μm), and the end portion when wrapped swells to cause a practical problem.

(10) Evaluation of the yield in the metallurgical process The end of the capacitor element manufactured up to the pressing process was sprayed with a metal mainly composed of aluminum, and connected to a DC high-voltage stabilized power supply manufactured by Kasuga Electric Co., Ltd. The voltage was applied while increasing the voltage at a rate of 50 V / sec at 65% RH, and the voltage when the element was destroyed was determined. At this time, 1000 devices were measured, and the number of defective devices having a breakdown voltage of less than 100 V / μm was determined and divided into three ranks as follows.

A: The number of defects is 3 or less, and the yield is good. B: The number of defects is 4 to 10, but there is no problem. C: The number of defects exceeds 10 and there is a problem in practical use.

(11) Measurement of the degree of curl 100 or more film samples wound on a roll are bundled and cut in the width direction, and the obtained film cut sheet (100 or more bundles) is cut in the width direction. The center of one side is fixed with a clip, and the length along the film in the film width direction of one side in the width direction opposite to the side fixed with the clip when the cut sample is hung with the clip (the length of the arc) is: M ₀₎ and both edges of the film width direction (becomes horizontal direction when suspended) linear distance (chord length of: M ₁₎ were measured to determine the degree of curl by the following equation.

The degree of curl = [(M ₀ −M ₁ ) / M ₀ ] × 100 (%)

[0077]

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

(Example 1) II was 99.1%, mmmm
Is 99.8%, ash content is 18ppm, intrinsic viscosity is 1.6d
l / g, a melt flow rate of 3.2 g / 10 min, a raw material of polypropylene, 3000 ppm of 2,6-di-t-butyl-p-cresol (BHT), telakis [methylene-3 (3,5-di-t- Butyl-4-hydroxyphenyl) propionate] methane (Irganox1010) 4000
ppm was added to the extruder and melted at a temperature of 280 ° C., and extruded into a sheet shape from a T-type die.
The sheet was wound around a casting drum having a temperature of ℃ 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.

Next, the obtained sheet was preheated at 143 ° C., and then passed between rolls having a peripheral speed difference maintained at a temperature of 148 ° C., and a stretching speed in the longitudinal direction of 600,000% / m.
The film was stretched 5 times under the condition of in. 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 150 ° C. while giving 10% relaxation in the width direction.
To obtain a biaxially oriented polypropylene film having a thickness of 5 μm. Further, a corona discharge treatment was performed in the atmosphere at a treatment intensity of 30 W · min / m ² . II of the obtained film was 99.0%, mmmm was 99.7%, and the plane orientation coefficient was 0.0130.

This film was set in a vacuum evaporation machine, copper was used as a nucleating 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. 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 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 1) II was 98.0%, mmmm
99.3%, ash content 23ppm, intrinsic viscosity 1.6d
1 / g, using a polypropylene raw material having a melt flow rate of 3.2 g / 10 min, and a polypropylene film (II: 97.5%, mmmm: 9
9.1% and a plane orientation coefficient of 0.0128) were obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 2) II was 99.8%, mmmm
Is 99.9%, the ash content is 12 ppm, and the intrinsic viscosity is 1.8 d.
1 / g, using a polypropylene raw material having a melt flow rate of 2.4 g / 10 minutes, an attempt was made to produce a polypropylene film in the same manner as in Example 1, but the film was frequently torn after stretching in the width direction and was stable. And no film could be collected. Film II that can be collected without tearing
Was 99.7%, mmmm was 99.9%, and the plane orientation coefficient was 0.0165.

(Comparative Example 3) II was 98.4%, mmmm
98.9%, ash 21ppm, intrinsic viscosity 1.5d
1 / g, using a polypropylene raw material having a melt flow rate of 3.9 g / 10 min, and using the same method as in Example 1, a polypropylene film (II: 98.2%, mmmm: 9 mm)
8.5% and a plane orientation coefficient of 0.0132) were obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 4) The same polypropylene raw material as in Example 1 was used, and the stretching speed in the longitudinal direction was 10,000% / m.
In the same manner as in Example 1 except that the film thickness was changed to in, the polypropylene film (II was 99.0%, mmmm was 99.7%).
%, The plane orientation coefficient was 0.0105), and a capacitor element was obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Examples 2 and 3) Using the same polypropylene raw material as in Example 1, the preheating temperature and the stretching temperature in the longitudinal direction were 148 ° C. and 153 ° C. (Example 2), and 138 ° C. and 1
A polypropylene film and a capacitor element were obtained in the same manner as in Example 1 except that the temperature was changed to 43 ° C. (Example 3).
II of the polypropylene film of Example 2 was 99.0.
%, Mmmm is 99.7%, and the plane orientation coefficient is 0.012.
1. The II of the polypropylene film of Example 3 is 99.
0%, mmmm: 99.7%, plane orientation coefficient: 0.014
It was 3. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 4 The same polypropylene raw material as in Example 1 was used, and the longitudinal stretching speed was 40000% / m.
In the same manner as in Example 1 except that the film thickness was changed to in, the polypropylene film (II was 99.0%, mmmm was 99.7%).
%, The plane orientation coefficient was 0.0126), and a capacitor element was obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 5 The raw materials of polypropylene used in Example 1 and the raw materials of polypropylene used in Comparative Example 2 were:
Except that the dry blended raw material was used, polypropylene film (II: 99.4) was used in the same manner as in Example 1.
%, Mmmm is 99.8%, and the plane orientation coefficient is 0.013.
9) and a capacitor element were obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 6 The polypropylene raw material used in Example 1 and the polypropylene raw material used in Comparative Example 1 were the following:
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%, and the plane orientation coefficient is 0.012.
9) and a capacitor element were obtained. Table 1 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 7 II: 99.1%, mmmm
Is 99.8%, ash content is 18ppm, intrinsic viscosity is 1.6d
l / g, a melt flow rate of 3.2 g / 10 min, a raw material of polypropylene, 3000 ppm of 2,6-di-t-butyl-p-cresol (BHT), telakis [methylene-3 (3,5-di-t- Butyl-4-hydroxyphenyl) propionate] methane (Irganox1010) 4000
ppm was added to the extruder and melted at a temperature of 280 ° C., and extruded into a sheet shape from a T-type die.
The sheet was wound around a casting drum having a temperature of ℃ 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.

Next, the obtained sheet was preheated at 143 ° C., and then passed between rolls having a peripheral speed difference maintained at a temperature of 148 ° C., and a stretching speed in the longitudinal direction of 600,000% / m.
The film was stretched 5 times under the condition of in. 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 150 ° C. while giving 10% relaxation in the width direction.
To obtain a biaxially oriented polypropylene film having a thickness of 3 μm. Further, a corona discharge treatment was performed in the atmosphere at a treatment intensity of 30 W · min / m ² . II of the obtained film was 99.0%, mmmm was 99.7%, and the plane orientation coefficient was 0.0128.

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. This film was slit to obtain a metallized film having a total width of 8 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 1.5 μF.
Table 2 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

Example 8 A polypropylene film (II was 98%) was peeled off from the casting drum and then returned to room temperature without being gradually cooled by a 60 ° C. roll. 0.9%, mmmm is 9
A capacitor element with a surface orientation coefficient of 9.5% and a surface orientation coefficient of 0.0129) was obtained. Table 2 summarizes the evaluation results of the obtained polypropylene films and capacitor elements. In this film, clipping occurred frequently in the tenter, and the productivity was reduced due to tearing. In addition, meandering and wrinkling of the film occurred during winding of the capacitor element, and the element winding yield was reduced.

Comparative Example 5 II: 98.0%, mmmm
99.3%, ash content 23ppm, intrinsic viscosity 1.6d
1 / g and a polypropylene material having a melt flow rate of 3.2 g / 10 min and a polypropylene film (II: 97.4%, mmmm: 9 mm) in the same manner as in Example 7.
9.1% and a plane orientation coefficient of 0.0127) were obtained. Table 2 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

(Comparative Example 6) The same polypropylene raw material as in Example 7 was used, and the stretching speed in the longitudinal direction was 10,000% / m.
In the same manner as in Example 7, except that the film thickness was changed to in, a polypropylene film (II was 99.0%, mmmm was 99.7%)
%, The plane orientation coefficient was 0.0104), and a capacitor element was obtained. Table 2 summarizes the evaluation results of the obtained polypropylene films and capacitor elements.

[0095]

[Table 1]

[0096]

[Table 2]

[0097]

According to the present invention, it is possible to obtain a polypropylene film which is excellent in heat resistance and long-term dielectric breakdown resistance at high temperatures, suppresses the deterioration of the yield in the capacitor manufacturing process, and reduces the variation in quality. Furthermore, it is possible to obtain a capacitor using this polypropylene film as a dielectric, having excellent heat resistance and long-term dielectric breakdown characteristics at high temperatures, and having reduced quality variations.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 31:34 C08L 23:00

Claims (5)

[Claims] 1. A biaxially oriented polypropylene film having an isotacticity of 98 to 99.5%, an isotactic pentad fraction of more than 99%, and a plane orientation coefficient. Is 0.012
A polypropylene film having a thickness of from 0.015 to 0.015. 2. The polypropylene film according to claim 1, wherein the curl degree in the width direction is 10% or less. 3. A capacitor comprising the polypropylene film according to claim 1 as a dielectric. 4. A capacitor comprising the polypropylene film according to claim 1 as a dielectric and a metal layer provided as an internal electrode on at least one side of the film surface. 5. The condenser according to claim 3, wherein a film having a slit width of 5 to 50 mm is wound.