JPH10284340A - Thermoplastic resin film for capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent trouble like thermal yield of a film in a vapor deposition process and obtain high withstand voltage and durability, by defining the maximum height of the film surface and the film thickness wherein specified weight of particles having specified mean grain diameter and grain size distribution value is contained. SOLUTION: In order to simultaneously improve film handling property and electric characteristics, particles of 0.01-1.0 wt.% whose mean grain diameter d50 is 0.3-2.0 μm and whose grain size distribution value d25/d75 is at most 2.0 are contained. The thickness of a film is made very thin, i.e., 0.3-3.0 μm, and the maximum height Rmax of the surface of the film is set to be 1.5 μm. Percentage of contraction in the longitudinal direction of the film after treatment at 180 deg.C for 3 minutes is preferably at most 5.0 %. A sheet is stretched in two axial directions and made into a film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented thermoplastic resin film for a capacitor. More specifically, the present invention is to prevent troubles such as heat loss of a film in a vapor deposition process when manufacturing a vapor deposition capacitor using an extremely thin film, and to provide high withstand voltage characteristics and durability. The present invention relates to a biaxially oriented thermoplastic resin film for a capacitor dielectric.

[0002]

2. Description of the Related Art In recent years, with the development of electronic devices and the like, required characteristics of capacitors used therein have become more severe. Such required characteristics include good electrical characteristics, durability, miniaturization, low cost, and the like. In order to meet such a demand, a so-called multilayer capacitor has recently been used in which an extremely thin film is subjected to vapor deposition and a dielectric is formed by lacquering to form an element having a multilayer structure. The film used for such a capacitor must satisfy extremely high required characteristics in addition to being extremely thin.
That is, for example, in the case of a thin film of 3 μm or less,
It is necessary to adjust the roughness of the film surface to an appropriate range in order to improve the handleability and the running property during processing and to prevent deterioration in characteristics due to scratches or the like. On the other hand, if the film contains a large amount of particles or contains large particles in order to improve the handleability, the electrical properties and durability will be adversely affected. Therefore, a film that does not have such an adverse electrical effect and has excellent handleability is demanded as a dielectric for a small capacitor used in future electronic devices.

[0003] As electrical characteristics that are particularly demanded to be improved,
It is required to have advanced characteristics in a wide temperature range from normal temperature to high temperature, such as withstand voltage characteristics and insulation resistance characteristics. When the film is thin, particularly good withstand voltage characteristics and insulation resistance are required. Factors that have an adverse effect on the withstand voltage characteristics include foreign substances present in the film and uneven thickness. To improve the handling of the film,
Although a method of adding fine particles to the film is employed, foreign substances such as aggregates and coarse particles contained in the fine particles affect the withstand voltage characteristics. Furthermore, the uniformity of the lacquer layer may be reduced due to coarse protrusions on the film surface or uneven thickness of the film, which may cause a decrease in withstand voltage characteristics. From these viewpoints, the surface of the film must be kept extremely uniform and have a specific projection shape.

Recently, in addition to such advanced electrical characteristics,
The cost of the film itself is required to be low, and a method that requires a high cost cannot be practically adopted, and a method that can further reduce the cost is required. Among the biaxially oriented thermoplastic resin films, polyester films have various properties such as mechanical properties, heat resistance, electrical properties, and chemical resistance in a highly balanced manner and are excellent in cost performance. However, there is a strong demand for further improvement in properties, and a film that satisfies these requirements is desired.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a film used as a dielectric for a vapor-deposited film capacitor, which prevents problems such as heat loss of the film in the vapor-deposition step, and has high withstand voltage characteristics and durability. And to provide a biaxially oriented thermoplastic resin film for a capacitor dielectric which can provide the following.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems. As a result, if a thermoplastic resin film containing specific particles and having a designed surface shape is used, an extremely thin film is obtained. Even if manufactured as
The present invention has been found to be able to prevent troubles such as loss of film heat during film processing, to obtain high withstand voltage characteristics, and to obtain good electric characteristics in a wide temperature range, and to have excellent characteristics as a capacitor dielectric. Was completed.

That is, the gist of the present invention is that the average particle size (d
50) is 0.3 to 2.0 μm and the particle size distribution value (d25 / d
75) contains 0.01 to 1.0% by weight of particles A having a particle size of 2.0 or less, and has a maximum film surface height (Rmax) of 1.5 μm.
m or less, and has a film thickness of 0.3 to 3.0 μm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Examples of the thermoplastic resin constituting the film in the present invention include resins such as polyester, polypropylene, polymethylpentene, polycarbonate, polyphenylene sulfide, and polyether ether ketone. Among them, polyester is preferred because it has good electrical and mechanical properties and is relatively inexpensive.

As used herein, the polyester refers to a polyester comprising an aromatic dicarboxylic acid component and a glycol component. In particular, 80% or more of the repeating units are ethylene terephthalate units or ethylene-2,6-naphthalate units or 1,4. Polyesters having cyclohexylene dimethylene terephthalate units are preferred. Further, such a polyester may have another third component copolymerized. As the aromatic dicarboxylic acid component, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid,
For example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, oxycarboxylic acid (eg, p-oxyethoxybenzoic acid, etc.) can be used. As the glycol component, in addition to ethylene glycol and 1,4-cyclohexanedimethanol, for example, one or more of diethylene glycol, triethylene glycol, propylene glycol, butanediol, neopentyl glycol, and the like can be used. Further, a mixture of these polyesters may be used.

The intrinsic viscosity of such a polyester is usually 0.45 or more, preferably 0.50 to 1.0, and more preferably 0.52 to 0.80. If the intrinsic viscosity is less than 0.45, the productivity at the time of producing the film may decrease, or the mechanical strength of the film may decrease. On the other hand, from the viewpoint of melt extrusion stability of the polymer, the intrinsic viscosity preferably does not exceed 1.0.

In addition, the thermoplastic resin of the present invention has a volume resistivity (ρ value) of more than 5.0 × 10 ⁸ Ω · cm when melted in order to satisfy the insulation resistance of the film to a high degree. Is preferred. The ρ value here is a resistance value measured by melting the film, keeping the temperature at the extrusion molding temperature, and inserting an electrode. For example, in the case of polyethylene terephthalate, the measurement is performed at 285 ° C. ρ value is 5.0 ×
In the case of 10 ⁸ Ω · cm or less, the insulation resistance characteristic of the film tends to decrease particularly in a temperature range of 80 ° C. or more.
In the case of polyester, phosphoric acid is used to reduce the amount of the catalyst metal added during the production of the polyester, or to reduce the activity of the metal, in order to keep the ρ value in the above range.
Alternatively, a method of adding a phosphorus compound such as a phosphoric ester is used. The addition amount [P] of the phosphorus compound is based on the metal amount [M] of the esterification or transesterification catalyst,
The molar ratio may be selected so that [P] / [M] is in the range of 0.8 to 2.0.

When a polyester is produced, a metal component is used as a reaction catalyst, which is contained in the polyester. Therefore, the upper limit of the ρ value is usually 1.0 × 10 ¹⁰ Ω · cm.
It is about. In the present invention, for the purpose of improving the handleability by giving the film a slippery, for the purpose of preventing the occurrence of scratches during film production, containing particles in the film,
Moderate protrusions are formed on the film surface, and the feature of the present invention is that specific particles are used as such particles. That is, according to the knowledge of the present inventors, when specific particles are contained, the film handling properties and the electrical properties are simultaneously improved. That is, the average particle size (d50)
When particles A having a particle size distribution of 0.3 to 2.0 [mu] m and a particle size distribution value (d25 / d75) of 2.0 or less are contained in an amount of 0.01 to 1.0% by weight, high properties can be obtained.

When the average particle size of the particles A is larger than the above range, the insulation resistance of the film itself is reduced, insulation defects occur due to the particles falling off from the film surface, and the uniformity of the thickness of the lacquer layer is caused by the film surface roughening. Is reduced, and problems such as deterioration of the insulation resistance characteristics of the lacquer layer existing as a dielectric material occur, which is not preferable. Particle A
Has an average particle size of preferably 1.7 μm or less, more preferably 1.5 μm or less.

If the particle size distribution value of the particles A is larger than the above range, coarse particles will be contained, causing the same problem as when the average particle size is too large. The particle size distribution value is preferably 1.8 or less, more preferably 1.7.
It is as follows. The lower limit of the particle size distribution value is usually 1.1, preferably 1.2, from the viewpoint of particle production efficiency, cost and the like. On the other hand, when the average particle diameter of the particles A is less than 0.3 μm, the effect of improving the running property of the film becomes insufficient, and the insulation resistance characteristic is lowered due to, for example, scratching of the film. Problems arise. The average particle size of the particles A is preferably 0.4 μm or more, more preferably 0.1 μm or more.
5 μm or more.

If the content of the particles A is less than the above range, the protrusions on the film surface are insufficient and the slipperiness is insufficient. On the other hand, if the content is too large, the particles easily fall off or the particles aggregate to form coarse projections, which causes problems such as insulation defects. The content of the particles A is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and is preferably 1.0% by weight or less, more preferably 0.8% by weight or less.

Further, in addition to the particles A satisfying the above requirements, particles B having an average particle size of less than 0.5 μm and a particle size distribution value of 3.0 or less are added in an amount of 2.0% by weight or less, preferably 1.0% by weight or less.
It can be contained in the following range. By simultaneously containing such particles B having a small average particle size, it is possible to prevent the occurrence of surface flaws in the film manufacturing process and the processing process, and to prevent the deterioration of the insulation resistance characteristics of the capacitor. The average particle size of such particles is more preferably less than 0.4 μm, particularly preferably less than 0.3 μm. On the other hand, if the average particle diameter of the particles B is less than 0.1 μm, the effect of preventing scratches is reduced. Even when aggregated or chain-like particles are used as such small particles, they can be used as long as the average particle diameter measured by the method described later is in the above range.

Examples of particles usable in the present invention include calcium carbonate, silica, calcium phosphate, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite,
In the case of inorganic particles such as molybdenum sulfide, crosslinked polymer particles, organic particles such as calcium oxalate, and polyester, precipitated particles formed during polymerization can be mentioned.

In the present invention, calcium carbonate and calcium oxalate are particularly preferably used as the particles A satisfying the above-mentioned requirements of an average particle size of 0.3 to 2.0 μm and a particle size distribution value of 2.0 or less. In the case of such particles, the particles do not easily fall off and good electrical characteristics can be provided. On the other hand, it is preferable to contain substantially spherical silica particles or spherical crosslinked polymer particles as particles A satisfying the requirements of an average particle size of 0.3 to 2.0 μm and a particle size distribution value of 2.0 or less. Absent. The substantially spherical particles referred to here include, for example, spherical silica particles as described in JP-A-63-317533 and JP-A-6-317533.
The term refers to spherical crosslinked polymer particles as described in JP-A-3-178144 and JP-A-63-191838, in which the particles have a specific ratio of major axis to minor axis or a specific range. It refers to those having a volume shape factor. Such spherical particles are not preferred because they may fall off the film in the film manufacturing process or the capacitor manufacturing process, causing problems such as fouling the process and causing insulation defects. In particular, spherical silica particles are not preferred because the productivity of deposition may be significantly reduced due to contamination in the process due to falling off.

However, it is possible to contain particles satisfying the requirements of the present invention and, in addition, spherical particles having a particle diameter smaller than the average particle diameter of the particles A. Also in this case, the diameter of the spherical particles is preferably less than 0.5 μm,
More preferably, it is less than 3 μm. Further, the content of the spherical particles is preferably 0.5% by weight or less, more preferably 0.3% by weight or less.

As the particles B satisfying the requirements of an average particle size of less than 0.5 μm and a particle size distribution of 3.0 or less, fine silica particles or crosslinked polymer particles which are not substantially spherical are preferable in the present invention. . Such particles are excellent in electrical characteristics, and thus can improve the insulation resistance and withstand voltage characteristics of the film. In producing a thermoplastic resin containing particles, the particles may be added during the production of the resin or may be directly added to the resin. Particularly, in the case of adding polyester during the synthesis reaction, a method of adding the slurry as a slurry in which particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to the resin, a method of adding and mixing the resin as a dried particle or a slurry dispersed in water or an organic solvent having a boiling point of 200 ° C. or lower using a twin-screw kneading extruder is preferable. . In addition, the particles to be added may be subjected to processing such as crushing, dispersion, classification, and filtration as needed.

As a method of adjusting the content of particles, a master material containing particles at a high concentration is prepared by the above-described method, and is diluted with a material substantially free of particles at the time of film formation. A method of adjusting the particle content is effective. In addition, as additives other than the above-mentioned projection-forming agent, if necessary, an antistatic agent, a stabilizer, a lubricant, a cross-linking agent, an anti-blocking agent, an antioxidant, a coloring agent, a light-blocking agent, an ultraviolet absorber, etc. May be contained in a range that does not deteriorate the capacitor characteristics.

The film of the present invention provides a capacitor having excellent electrical characteristics by satisfying the above requirements, but exerts its effect when the film has a very small thickness of 0.3 to 3.0 μm. That is, the effect of the surface characteristics of the film of the present invention is particularly exhibited in the case of a capacitor formed by applying a thin lacquer layer as a dielectric layer to the film surface. In the case of a thick film, such a film is rarely used for such an application, and a measure for improving the insulating properties by increasing the thickness of the lacquer layer can be adopted. Therefore, the necessity for a flat surface as in the present invention is low. On the other hand, a thin film having a film thickness of less than 0.3 μm has extremely poor film production productivity due to problems of strength and thickness unevenness, and is not in a practically usable range. When the film thickness is preferably 0.5 to 2.5 μm, more preferably 1.0 to 2.5 μm, the effects of the present invention are more highly exhibited, and the contribution to miniaturization of the capacitor is increased.

The film of the present invention may have a multilayer structure as long as the properties finally obtained satisfy the requirements of the present invention. Alternatively, a method may be used in which a film is produced by laminating a target film, a peelable polymer layer and the resin layer of the present invention by a coextrusion method or the like, and a biaxially oriented film is peeled off. The film of the present invention may be provided with a coating layer on one side or both sides of the film in order to enhance the adhesion to the deposited metal. As components constituting the coating layer, polyester, polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate,
Examples thereof include resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, and polyurethane, and copolymers of these resins. One or two or more such resins may be simultaneously contained, and, if necessary, a projection forming agent such as fine particles, an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, a blocking inhibitor, an antioxidant. , An antifoaming agent, a thickening agent, a coating improver, and the like may be contained within a range that does not deteriorate the capacitor characteristics.

As a method of applying the above-mentioned coating solution to a film, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater or the like other than those described in “Coating System”, published by Yuji Harasaki, Maki Shoten, 1979, can be used. A coating device can be used.
The coating layer may be provided in the film manufacturing process, or may be applied after the film is manufactured. In particular, from the viewpoint of uniformity of the coating thickness and production efficiency, a coating method in the film manufacturing process is preferable.

As a method of applying in the film manufacturing process, a coating solution is applied to an unstretched film, and sequentially or
Simultaneous biaxial stretching, coating on a uniaxially stretched film, and further stretching in a direction perpendicular to the uniaxial stretching direction, or applying to a biaxially stretched film and further stretching in the transverse and / or longitudinal directions There are methods. The thickness of the coating layer is usually in the range of 0.005 to 0.5 μm,
Preferably it is in the range of 0.01 to 0.2 μm. It is preferable that the thickness of the coating layer be reduced in view of a demand for miniaturization of the capacitor. In particular, when the thickness of the coating layer exceeds 0.5 μm, the electrical characteristics may be deteriorated. On the other hand, when the thickness of the coating layer is less than 0.005 μm, there is a tendency that coating unevenness and coating slippage tend to occur.

The maximum height (Rmax) of the surface of the film of the present invention thus obtained is 1.5 μm or less, preferably 1.3 μm or less, more preferably 1.1 μm or less. When Rmax exceeds 1.5 μm, the surface is too rough, and the withstand voltage characteristics of the film itself deteriorate, the wet heat resistance of the capacitor deteriorates, and the uniformity of the thickness of the lacquer layer decreases. In some cases, a problem may occur that the insulation resistance characteristics of the semiconductor device deteriorate.

On the other hand, the lower limit of Rmax is usually 0.3 μm in order to satisfy the handling property of the film and the winding characteristics.
Preferably, it is 0.5 μm. In addition to the maximum projection height on the film surface, the center line average roughness (Ra) is preferably 0.020 to 0.20 μm, and more preferably 0.02 to 0.20 μm.
When the thickness is in the range of 30 to 0.12 μm, the film can be easily handled, and the deterioration of the capacitor insulation characteristics due to scratches can be prevented.

Further, the shape of the surface of the film of the present invention
About, it was measured by the method described later using a three-dimensional roughness meter
Regarding the number of protrusions, the height of the film surface is 0.1 μm or more.
Number of protrusions is 1000 / mm^TwoAbove, preferably 1500
Pieces / mm^TwoAbove, 50 protrusions with a height of 1.2 μm or more
/ Mm^TwoBelow, preferably 30 pieces / mm^TwoWhen is
Handling properties and electrical properties
This is preferable. 100 protrusions with a height of 0.1 μm or more
0 / mm^TwoIf the value is less than
Running performance during construction may be poor, resulting in scratches
Capacitor insulation characteristics may be degraded. Meanwhile, height
The number of protrusions of 1.2 μm or more is 50 / mm ^TwoExceeds
Is the same as in the case where Rmax is too large.
There is a possibility that the insulation resistance characteristics may be reduced.

When the Young's modulus in the longitudinal direction of the film is 4.5 GPa or more, preferably 5.0 GPa or more, in addition to the surface characteristics of the film, the electrical characteristics and the handling property during deposition are further enhanced. That is, in the step of performing metal vapor deposition on a film, the film is unwound and vapor-deposited while running under a certain tension. Therefore, if the film does not have sufficient strength against the tension, that is, does not have a high Young's modulus, the film cannot withstand the tension, and may be greatly damaged by heat generated by vapor deposition.
According to the knowledge of the present inventors, when such damage is caused, the heat-resistant dimensional stability of the vapor-deposited film is reduced, so that the yield at the time of manufacturing the capacitor is reduced or the electrical characteristics of the obtained capacitor are reduced. Tend to do so. If the Young's modulus of the film in the longitudinal direction is within the range of the present invention, such electric properties are highly satisfied.

Further, the film of the present invention has a viscosity of 3 ° C. at 180 ° C.
The shrinkage in the longitudinal direction after the treatment for 5 minutes is preferably 5.0% or less, more preferably 4.0% or less. If the heat shrinkage in the longitudinal direction is too large, the film undergoes dimensional change in the step of receiving heat during the production of the capacitor, causing problems such as a decrease in productivity and a reduction in the life of the capacitor. On the other hand, the heat shrinkage is preferably 1.0% or more, more preferably 2.0% or more. If the heat shrinkage is too small, the adhesion between the film and the cooling can becomes insufficient in the vapor deposition step, and the film becomes susceptible to thermal damage. The effect tends to be difficult to obtain. On the other hand, the shrinkage rate in the width direction under the same conditions is preferably smaller than the shrinkage rate in the longitudinal direction,
And less than 2%.

Next, the method for producing the film of the present invention will be specifically described with respect to a polyester film which is the most preferred embodiment of the present invention. First, a polyester raw material is supplied to an extruder, melt-extruded at a temperature equal to or higher than the melting point of the polyester, and extruded as a molten sheet from a slit die. Next, the molten sheet is quenched and solidified on a rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed. In the present invention, the sheet obtained in this way is stretched biaxially to form a film, but by setting the stretching and heat treatment conditions in an appropriate range, the orientation and the characteristic of the film of the present invention can be obtained. Young's modulus can be achieved. Specifically, the biaxial stretching conditions are as follows. The unstretched sheet is first stretched in the first axial direction so that the birefringence (Δn) is usually 0.08 or more, preferably 0.09 or more. The stretching temperature range is 70 to 150
C., the stretching magnification is in the range of 2.5 to 6 times, and the desired birefringence is obtained by appropriately combining the temperature and the magnification. Stretching can be performed in one step or two or more steps. Next, the uniaxially oriented film is once cooled below the glass transition point in the second axis direction, that is, in a direction orthogonal to the first axis direction, or without cooling, for example, 80 to 15 minutes.
Preheat to a temperature range of 0 ° C.
The film is stretched to 5 to 5 times, preferably 3.0 to 4.5 times to obtain a biaxially oriented film.

It is preferable that stretching in the first axial direction is performed in two or more steps because good thickness uniformity can be achieved. In addition, a method of further stretching in the longitudinal direction after the transverse stretching is possible, but in any case, it is preferable to set the total stretching ratio in the longitudinal direction to 3.5 times or more. Elongation, limited shrinkage within 20%,
Alternatively, heat treatment is performed at a constant length for 1 second to 5 minutes. At this time, re-stretching may be performed in the longitudinal direction, the lateral direction, or both directions during or after the heat treatment step.

[0033] In the present invention, when the polyester film is less than the density of 1.4050g / cm ^3, more desirably to less than 1.4030g / cm ^3, in order to satisfy such characteristics, the heat treatment step described above The temperature is appropriately selected. The heat treatment temperature depends on the stretching conditions, but is preferably 180 to 250 ° C, more preferably 200 to 250 ° C.
It is in the range of 240 ° C. If the heat treatment temperature exceeds 250 ° C., the film density becomes too high, and high electrical characteristics may not be obtained. On the other hand, when the heat treatment temperature is 180
If the temperature is lower than ℃, the heat shrinkage of the film becomes large, causing dimensional change in the step of receiving heat during the production of the capacitor, causing problems such as deterioration of the productivity of the capacitor and deterioration of the capacitor characteristics such as withstand voltage. Sometimes.

When a capacitor is produced by using the film of the present invention, when an electrode is formed by metal vapor deposition, the metal to be vapor-deposited is aluminum, palladium, zinc, nickel, gold, silver, copper, indium, tin, chromium. , Titanium and the like, and a particularly preferred metal is aluminum. The above-mentioned metals include metal oxides. A plurality of types of metals may be mixed or deposited in a stacked state.

The thickness of the metal deposited film is preferably in the range of 1 to 200 nm. The method of vapor deposition is generally a vacuum deposition method, but may be a method such as an electroplating method or a sputtering method. The metal deposition layer is provided on both sides or one side of the film. After the metal deposition, a surface treatment of the deposited metal layer or a coating treatment with another resin may be performed.

A lacquer layer is formed on the metal-deposited film thus obtained by coating, and a large number of the obtained films are laminated to form a capacitor element.
For example, a capacitor can be formed by performing metallikon, voltage treatment, sealing both end faces, forming an exterior, and the like, but is not limited thereto.

[0037]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “parts” means “parts by weight”. (1) Intrinsic viscosity of polymer [η] (dl / g) 1 g of polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in 100 ml of a mixed solvent.
Measured in ° C. (2) Average particle size of particles (d50) (μm) and particle size distribution value (d25 / d75) Centrifugal sedimentation type particle size distribution analyzer (SA-CP, manufactured by Shimadzu Corporation)
The average particle diameter (d50) was the particle diameter at 50% of the integrated volume fraction integrated from the large particle side in the equivalent spherical distribution measured by type 3). The values of the integrated volume fractions of 25% and 75% were d25 and d75, respectively, and the ratio value (d25 / d75) was taken as the particle size distribution value. The smaller the particle size distribution value, the sharper the particle size distribution of the particles. (3) Volume resistivity value (ρ value) (Ω · cm) at the time of melting The film was melted at 285 ° C., and air bubbles were removed by a method such as reducing the pressure in the system. In the polymer kept at the same temperature,
Two 5m electrodes having an area of stainless steel 1 cm ²
It was fixed and inserted at intervals of m. A voltage of 100 V was applied between the electrodes, and the specific resistance was calculated from the value of the flowing current. The current value was recorded on a recorder, and the value one second after the voltage was applied was read. (4) Maximum height (Rmax) and center line average roughness (R
a) (μm) It was determined as follows using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Co., Ltd. That is, a portion of the reference length L (2.5 mm) is extracted from the film cross-sectional curve in the direction of the center line, and the center line of the extracted portion is the x-axis, and the direction of the vertical magnification is the y-axis. When represented by f (x), the value given by the following equation was defined as the center line average roughness (Ra) and represented by [μm].

The maximum height (Rmax) is 2 parallel to the average line of the extracted portion of the film cross-section curve obtained above.
When the sampled portion is sandwiched by straight lines, the value obtained by measuring the distance between these two straight lines in the direction of the longitudinal magnification of the sectional curve is the maximum height (Rma).
x) and expressed in [μm]. The maximum height and the center line average roughness were obtained by obtaining ten cross-sectional curves from the surface of the sample film, and expressing the average values of the values of the extracted portions obtained from these cross-sectional curves. The tip radius of the stylus is 2μ.
m, the load is 30 mg, and the cutoff value is 0.08 mm
And

[0039]

(Equation 1) (5) Number of surface protrusions Three-dimensional surface roughness tester (SE-3A) manufactured by Kosaka Laboratory Co., Ltd.
Using K), the tip radius of the stylus is 5 μm, the stylus pressure is 30 mg, the measurement length is 0.5 mm, the sampling pitch is 1.0 μm, the cutoff is 0.25 mm, the vertical magnification is 20,000 times, and the horizontal magnification is 20.
The projection height and the number of projections were measured under the condition of 0 times and 500 scanning lines. Here, the projection height (X, μm) is defined as the height of the point where the number of projections is the maximum, and the height from this level is defined as the projection height. The number of projections (Y, / Mm ² ) was graphically represented as a distribution curve.

The protrusion height is 0.5 μm or more and 1.0 μm.
m or more, the projection height by the above method is 0.5 μm
And the total number of protrusions corresponding to protrusions exceeding 1.0 μm. The measurement was performed at three points in the longitudinal direction of the film and three points in the direction perpendicular to the longitudinal direction, for a total of six points, and the average value was used as the measured value. Note that the measurement film is set on a smooth glass sample table, but is adhered to the glass without any liquid, air, or the like between the film and the glass. (6) Film thickness (μm) The thickness of the film was determined by a gravimetric method. That is, 10
The total weight of 100 pieces of the film cut into a square of cm × 10 cm was measured, and calculated using the density of the film. In addition, the density of the film was measured at 25 degreeC using the density gradient tube by n-heptane / carbon tetrachloride. (7) Shrinkage (%) The film was heat-treated in an oven maintained at 180 ° C. for 3 minutes in a non-tension state, and the length of the film before and after the heat treatment was measured.

[0041]

(Equation 2) (In the above formula, L0 is the film length (mm) before heat treatment, L
1 means the film length (mm) after the heat treatment.) The measurement was performed at 10 points each in the longitudinal direction and the width direction, and the average value was obtained. (8) Young's modulus (GPa) Tensile tester Intesco Model 20 manufactured by Intesco Corporation
The measurement was performed in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH using a Model 01. That is, length 300m
The sample film having a width of 25 mm and a width of 25 mm is pulled at a strain rate of 10% / min, and is calculated by the following equation using the first straight line portion of the tensile stress-strain curve.

[0042]

E = Δσ / Δε (where E is the tensile modulus, Δσ is the stress difference due to the original average cross-sectional area between two points on the straight line, and Δε is the strain difference between the same two points) (9) Evaluation of electrical characteristics (Manufacture of capacitor) A capacitor was manufactured and evaluated as follows. That is, using a resistance heating type metal vapor deposition apparatus on both surfaces of the film, the pressure in the vacuum chamber was set to 10 ^-4 Torr
Aluminum was deposited to a thickness of 40 nm as follows.
At this time, vapor deposition was performed in a stripe shape having a margin portion in the longitudinal direction of the film. A lacquering dielectric film made of polyphenylene oxide was provided on the surface of the obtained evaporated polyester film by coating. A plurality of such films were laminated, and a cover film having a polyphenylene oxide film on the surface of a polyester film was provided on both surfaces thereof. The thus obtained plurality of rows of capacitor bodies were divided in the row direction. After heat treatment and metallikon treatment of the obtained capacitor body, it is cut with a saw blade in the direction perpendicular to the strip direction, and further lead to each capacitor element, voltage processing,
An epoxy exterior treatment was applied to make a capacitor. (I) Withstand voltage characteristics Using a 10 kV DC withstand voltage tester, 23 ° C., 50% RH
Under the atmosphere described above, the voltage was increased at a step-up rate of 10 V / second, and the voltage was read when the capacitor was short-circuited and no longer functioned as a capacitor. The measurement was performed for 110 capacitors, and the average of the values at 100 points was calculated excluding 5 points from the larger value and 5 points from the smaller value. (Ii) Insulation Resistance Characteristics (Measurement of Capacitance) Using a LCR meter 4284A (trade name) manufactured by Yokogawa Hewlett-Packard Company, the capacitance C [F] of the obtained capacitor was measured. Measurement is 23
C. and 50% RH. (Measurement of insulation resistance value) Using a high resistance meter 4329A (trade name) manufactured by Yokogawa Hewlett-Packard Company, a DC voltage of 100 V was applied between the electrodes of the obtained capacitor, and the resistance value R [Ω] of the capacitor was measured. It was measured. The voltage application was performed for 1 minute, and the current value was recorded on the recorder during that time. The current value showed a maximum value immediately after voltage application and then decreased. The maximum value was defined as a measured value R. The measurement was performed at 23 ° C and 130 ° C. The evaluation of the insulation resistance of the capacitor is C × R (CR
Value) [Ω · F]. Larger CR values indicate better insulation resistance.

Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of calcium acetate monohydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. 4 hours, 2
The temperature was raised to 30 ° C. to substantially complete the transesterification reaction.

Next, the particle size was 1.4 μm, and the particle size distribution value was 1.
1.0 part of calcium carbonate particles of No. 6 was added as an ethylene glycol slurry. After the addition of the slurry, 0.06 parts of phosphoric acid and 0.04 parts of antimony trioxide were further added, and the reaction system was gradually reduced in pressure, the temperature was increased, and the polycondensation reaction was performed for 4 hours. a) was obtained.

Similarly, a polyester (b) having an intrinsic viscosity of 0.65 and containing 0.6% by weight of silica particles having an average particle size of 0.20 μm and a particle size distribution value of 1.9 was obtained. Also, a polyester (c) having an intrinsic viscosity of 0.66 was obtained in the same manner except that no particles were contained. 20 parts of polyester (a), 70 parts of polyester (b) and 10 parts of polyester (c)
The raw material obtained by mixing the components is dried by a conventional method, supplied to an extruder, melted at 290 ° C., extruded into a sheet, and quenched on a cooling roll using an electrostatic contact method to form an amorphous sheet. . The obtained sheet was stretched 2.9 times in the longitudinal direction at 84 ° C. using the roll stretching method, and further stretched 1.5 times at 70 ° C. Next, the film was guided to a tenter, stretched 4.1 times in the transverse direction at 110 ° C., heat-treated at 225 ° C., and further subjected to a 3% transverse relaxation treatment in a 200 ° C. zone. A 0 μm biaxially stretched polyester film was obtained. Center line average roughness (Ra) is 0.0
It was 60 μm 2.

As shown in Table 1 below, a metal-deposited film capacitor prepared using the obtained film was a metal-deposited polyester film capacitor having excellent withstand voltage characteristics and excellent insulation resistance characteristics. Examples 2 to 5 and Comparative Examples 1 to 4 Polyester containing particles was produced in the same manner as in Example 1, and a 2.0 μm-thick polyester film was obtained in the same manner as in Example. The average particle size, particle size distribution, and content of the particles contained in the film are as shown in Table 1.

In Example 5, white powder was generated at the portion in contact with the film during running in the film deposition step, and the productivity was inferior to those of the other Examples. However, in Comparative Example 3, the film could not be obtained in the form of a good roll because the handleability of the film was extremely poor. Therefore, although a small amount of film was obtained and the characteristics were measured, it was not possible to prepare and evaluate a capacitor.

Example 6 In Example 1, the film stretching conditions were changed as follows. That is, the longitudinal stretching by the roll stretching method,
First, the film was stretched 2.4 times at 85 ° C., then 1.2 times at 75 ° C., and then stretched 4.5 times at 110 ° C. with a tenter. By performing a relaxation treatment, a biaxially oriented polyester film having a thickness of 2.0 μm was obtained.

Example 7 A polyester raw material obtained in the same manner as in Example 1 except that the amount of phosphoric acid added after the transesterification reaction was changed to 0.035 part during the production of the polyester was used. The conditions for film formation were 1.8 μm in the same manner as in Example 1.
m biaxially oriented polyester film was obtained.

Comparative Example 5 Raw materials and film production conditions were the same as in Example 1.
By changing the raw material extrusion amount, a biaxially stretched film having a film thickness of 4.0 μm was obtained. A capacitor was made using the film. However, if it was attempted to obtain a capacity equivalent to that of the example, the capacitor itself became large, and the capacitor could not be used practically, and the effect of the present invention could not be exhibited.

Comparative Example 6 The raw materials and film production conditions were the same as in Example 1.
It was attempted to obtain a biaxially stretched film having a film thickness of 0.2 μm by changing the raw material extrusion amount, but the film thickness was too thin, and frequent breakage and removal of the tenter clip frequently occurred. No film was obtained.

The polyesters obtained in Examples and Comparative Examples, the physical properties of the films thereof, and the results of evaluating the properties of the vapor deposition capacitors prepared using them are shown in Tables 1 to 3 below.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

The film of the present invention, even though it is an extremely thin film, can be obtained without causing troubles such as heat loss in the vapor deposition process when used as a dielectric of a metal vapor-deposited film capacitor. The capacitor has high withstand voltage characteristics and insulation resistance characteristics, and can contribute to miniaturization and improvement of reliability of the capacitor, and its industrial value is high.

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Claims (4)

[Claims] An average particle size (d50) of 0.3 to 2.0 μm.
A having a particle size distribution value (d25 / d75) of 2.0 or less
Wherein the maximum height (Rmax) of the film surface is 1.5 μm or less and the film thickness is 0.3 to 3.0 μm. the film. 2. The method according to claim 1, wherein the particles B have an average particle size (d50) of less than 0.5 μm and a particle size distribution value (d25 / d75) of not more than 3.0 by 0.1 to 2% by weight. Item 6. The thermoplastic resin film for a capacitor according to Item 1. 3. The thermoplastic resin film for a capacitor according to claim 1, wherein the shrinkage in the longitudinal direction of the film after treatment at 180 ° C. for 3 minutes is 1.0 to 5.0%. . 4. The thermoplastic resin film for a capacitor according to claim 1, wherein the thermoplastic resin film is biaxially oriented.