JPH09194603A - Polyester film for condenser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a film for condensers having excellent adhesion to the metal layer of an electrode, giving high electric and moisture/heat resistant characteristics when used as a dielectric for a metal vapor deposition film condenser, and being able to contribute to the improvement of long-term reliability of condensers. SOLUTION: This film contains 0.1-2.0wt.% calcium carbonate particles having a mean particle size (d50) of 0.5-3.0μm and a particle size distribution (d25/d75) of less than 3.0 and 0.1-2.0wt.% silica particles having a mean particle size (d50) of 0.8-4.0μm, and has a film thickness of 0.3-2.0μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film for a capacitor. More specifically, the present invention provides a capacitor dielectric capable of preventing problems such as heat loss of the film in the vapor deposition process and imparting high electrical characteristics when the vapor deposition capacitor is manufactured using an extremely thin film. The present invention relates to a biaxially oriented polyester film for body.

[0002]

2. Description of the Related Art Biaxially oriented 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. Widely used as industrial materials for packaging, plate making, etc. Among them, for capacitors, demand for capacitors manufactured from a polyester film, which can be miniaturized, is rapidly increasing as electric devices are miniaturized. In recent years, with the development of electronic devices and the like, it has been required to improve the properties of polyester films for capacitors. One of such required characteristics is that the film is an extremely thin film in order to cope with miniaturization of electronic devices. Even for polyester films with excellent mechanical properties, for example, in the case of a thin film of 2 μm or less,
It is necessary to adjust the roughness of the film surface within an appropriate range in order to improve the handleability and the running property during processing.
On the other hand, if the film contains a large amount of particles or contains large particles in order to improve handleability, the electrical characteristics are 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.

Such electrical characteristics include withstand voltage characteristics and insulation resistance characteristics, and in particular, it is necessary to have advanced characteristics in a wide temperature range from normal temperature to high temperature. 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.
In order to improve the handleability of the film, a method of adding fine particles to the film is employed. However, foreign substances such as aggregates and coarse particles contained in the fine particles affect the withstand voltage characteristics. In addition, some particles contain a metal component, which may cause a problem of deteriorating insulation resistance characteristics.
In addition to the above electrical characteristics, basic characteristics such as dielectric constant and dielectric loss as a capacitor dielectric are also required to be good, and these characteristics are also good and change in a wide temperature range from normal temperature to high temperature. It needs to be small. Recently, in addition to such advanced electrical properties, the cost of the film itself is required to be low, and not only can high-cost methods be practically adopted, but also methods that can further reduce costs are required. I have.

[0004]

The object of the present invention is to provide excellent adhesion to the electrode metal layer, and when used as a dielectric for a metal-deposited film capacitor, provide high electrical characteristics and resistance to humidity and heat, and Another object of the present invention is to provide a film for capacitors which can contribute to the improvement of long-term reliability.

[0005]

The inventors of the present invention have conducted extensive studies in view of the above-mentioned problems, and as a result, if a film made of polyester containing two specific types of particles is used, even if it is produced as an extremely thin film. The present invention has been completed by discovering that troubles such as film heat loss during film processing can be prevented, high electrical characteristics, good characteristics can be obtained in a wide temperature range, and excellent characteristics as a capacitor dielectric are obtained. Came to.

That is, the gist of the present invention is that the average particle size (d5
0) is 0.5-3.0 μm, particle size distribution value (d25 / d75)
0.1-2.0% by weight of calcium carbonate particles of less than 3.0 and an average particle size (d50) of 0.8-4.0μ
The biaxially oriented polyester film for capacitors is characterized by containing 0.1 to 2.0% by weight of silica particles of m and having a film thickness of 0.3 to 2.0 μm.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester constituting the film of the present invention 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 1,1. Polyesters having 4-cyclohexylene dimethylene terephthalate units are preferred. Further, such a polyester may have another third component copolymerized. As the aromatic dicarboxylic acid component,
Besides 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.) and the like can be used. As the glycol component, one or more of diethylene glycol, triethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like can be used in addition to ethylene glycol and 1,4-cyclohexanedimethanol. Further, a mixture of these polyesters may be used.

The intrinsic viscosity of the polyester is usually 0.45 or more, preferably 0.50 to 1.0, more preferably 0.52 to 0.80. If the intrinsic viscosity is less than 0.45, the productivity during film production may decrease, or the mechanical strength of the film may decrease. On the other hand, it is preferable that the intrinsic viscosity does not exceed 1.0 from the viewpoint of melt extrusion stability of the polymer. Further, since the polyester of the present invention highly satisfies the insulation resistance characteristics of the film, it has a volume specific resistance value (ρ value) of 1.0 when melted.
It is preferably more than × 10 ⁸ Ω · cm. 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. When the ρ value is 1.0 × 10 ⁸ Ω · cm or less, the insulation resistance characteristic of the film tends to be lowered particularly in the temperature range of 80 ° C. or higher. A method of adding a phosphoric acid or a phosphorus compound such as a phosphoric acid ester in order to reduce the amount of the catalyst metal added during the production of the polyester in order to make the ρ value of the polyester within the above range or to reduce the activity of the metal. Is used. The addition amount [P] of the phosphorus compound is such that [P] / [M] is a molar ratio of 0.1 to the metal amount [M] of the esterification or transesterification catalyst.
It may be selected so as to fall within the range of 7 to 2.0.

The polyester film of the present invention contains particles in the polyester for the purpose of imparting slipperiness to the film to improve the handleability and preventing the occurrence of scratches during the film production, so that the film surface can have appropriate protrusions. However, the feature of the present invention resides in the use of two kinds of particles having a specific particle size range as such particles. That is, according to the knowledge of the present inventors, when a specific amount of calcium carbonate particles and silica particles in a specific particle size range is contained, the film handling property and the electrical property are simultaneously improved. That is, the average particle size (d50) is 0.5 to 3.0 μ.
m, preferably 0.7 to 2.0 μm, particle size distribution value (d25
/ D75) is less than 3.0, preferably less than 2.0, calcium carbonate particles of 0.1 to 2.0% by weight, preferably 0.1.
2 to 1.0% by weight and an average particle size (d50) of 0.8 to
0.1 to 2.0% by weight, preferably 0.2 to 1.0, of silica particles of 4.0 μm, preferably 1.0 to 3.0 μm.
A high degree of properties is obtained when it is contained by weight.

The average particle size of the calcium carbonate particles is 0.5 μ
less than m or the average particle size of silica particles is 0.8 μm
If it is less than the above range, the effect of improving the running property of the film becomes insufficient, and further, there arises a problem that the insulation resistance characteristic of the film deteriorates. The reason why the insulation resistance decreases is not always clear, but the particles are small and the surface area is relatively large, so the metal components contained in the particles are easily dissolved in the polyester, which causes the insulation resistance value to decrease. It is supposed to do. On the other hand, if the average particle size is larger than the above range, the surface roughness may cause a decrease in insulating properties and withstand voltage characteristics, or particles may fall off the film surface to cause insulation defects. Is not preferable. Further, if the particle size distribution value of the calcium carbonate particles is larger than the above range, it will include extremely fine particles and coarse particles, and if the average particle diameter is too small, respectively, the same problem as when too large Will be generated. In particular, calcium carbonate particles have a property of being dissolved in polyester although the amount is very small, and therefore it is necessary not to include fine particles.

If the particle content is less than the above range, the projections 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. In the present invention, in addition to the calcium carbonate particles and the silica particles satisfying the above conditions, other particles may be contained in one kind or two or more kinds. Examples of such particles include calcium phosphate, kaolin, talc, titanium dioxide, alumina,
Examples thereof include inorganic particles such as barium sulfate, calcium fluoride, lithium fluoride, zeolite and molybdenum sulfide, crosslinked polymer particles, organic particles such as calcium oxalate, and precipitated particles produced during polyester polymerization. However, the total content of other particles is 2000ppm.
It is preferable that the amount is less than the above in order to obtain the excellent effects of the present invention. In the production of polyester containing particles, the particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When adding during the synthesis reaction,
A method in which particles are dispersed as a slurry in ethylene glycol or the like and added at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to polyester, it is used as dry particles, or as water or a boiling point of 200 ° C.
The method of adding and mixing the polyester as a slurry dispersed in the following organic solvent using a twin-screw kneading extruder is preferable. The particles to be added may be previously subjected to treatments such as disintegration, dispersion, classification and filtration, if necessary.

As a method of adjusting the content of particles, a master material containing particles at a high concentration is prepared in advance by the above-mentioned method, and is diluted with a material substantially free of particles during film formation. A method of adjusting the particle content is effective. Further, as an additive other than the above-mentioned protrusion forming agent, if necessary, an antistatic agent, a stabilizer, a lubricant, a cross-linking agent, an antiblocking agent, an antioxidant, a colorant, a light blocking agent, an ultraviolet absorber, etc. May be contained within a range that does not deteriorate the capacitor characteristics. The polyester film of the present invention provides a capacitor having excellent electric characteristics by satisfying the above requirements, but the film thickness is 0.3.
The effect is exhibited in the case of an extremely thin film of ˜2.0 μm. That is, when the film thickness is thick, it has a certain withstand voltage characteristic originally, and when a large amount of relatively large particles is contained as in the present invention, the surface roughness is too large, or the particles are aggregated. The probability of the presence of foreign matter increases,
On the contrary, it may cause deterioration of characteristics. When the film thickness is as thin as 2.0 μm or less, the number of particles per area of the film is small, and therefore the blending of specific particles as in the present invention is effective. On the other hand, the film thickness is 0.
A thin film having a thickness of less than 3 μm has extremely poor productivity in film production due to problems of strength and thickness unevenness, and is not in a practical range. The film thickness is preferably 0.3 to 1.8.
In the case of μm, and more preferably 0.5 to 1.5 μm, the effect of the present invention is exerted to a higher degree, and the contribution to miniaturization of the capacitor becomes large.

The polyester film of the present invention may have a multi-layer structure as long as the finally obtained properties satisfy the requirements of the present invention. Alternatively, a method in which a film in which a polyester film, a peelable polymer layer, and the polyester layer of the present invention are laminated by a coextrusion method or the like is manufactured, and then a biaxially oriented film is peeled off may be used.
The film of the present invention may be provided with a coating layer in order to enhance the adhesiveness with the vapor-deposited metal. Examples of the components constituting the coating layer include resins such as polyester, polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, and polyurethane, and copolymers of these resins. Can be mentioned. 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 liquid to a polyester film, Yuji Harazaki, Maki Shoten, 1979, reverse roll coater, gravure coater, rod coater, air doctor coater or others shown in "Coating system" Can be used. The coating layer may be provided in the film production process or may be applied after the film production. In particular, the method of coating in the film manufacturing process is preferable from the viewpoint of uniformity of coating thickness and production efficiency. As a method of applying in the film manufacturing process, a coating solution is applied to a polyester unstretched film and then sequentially or simultaneously, a method of biaxially stretching, a method of applying to a uniaxially stretched polyester film, and further perpendicular to the uniaxially stretching direction. And a biaxially stretched polyester film and then stretched in the transverse and / or longitudinal direction. The thickness of the coating layer is usually in the range of 0.005 to 1.0 μm, preferably 0.01 to 0.5 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, if the thickness of the coating layer exceeds 1.0 μm, the electrical characteristics may deteriorate. On the other hand, when the thickness of the coating layer is less than 0.005 μm, coating unevenness or coating drop tends to occur.

The coating layer may be provided on only one side of the polyester film, but it is preferably provided on both sides. In addition, when coated on only one side, a coating layer other than the above-mentioned coating solution may be formed on the opposite side, if necessary, to impart other properties to the polyester film of the present invention. Note that the film may be subjected to a chemical treatment or a discharge treatment before application in order to improve the coating property and adhesion of the coating agent to the film. It is particularly preferable to perform the corona discharge treatment in terms of treatment efficiency, cost, and simplicity of the treatment. Further, in order to improve the adhesiveness, coatability and the like of the coat layer of the biaxially stretched polyester film of the present invention, the coat layer may be subjected to a discharge treatment after forming the coat layer. The center line average roughness (Ra) of the surface of the film of the present invention thus obtained is preferably in the range of 0.01 to 0.5 μm, more preferably in the range of 0.05 to 0.3 μm, and particularly preferably The range is preferably 0.02 to 0.1 μm. Ra is 0.01μ
If it is less than m, the slipperiness of the film may be insufficient. On the other hand, when Ra exceeds 0.5 μm, the surface may be too rough, and the withstand voltage characteristics and the wet heat resistance may deteriorate.

Further, when the number of projections of the surface shape of the film of the present invention measured by a method described later using a three-dimensional roughness meter is within the following range, the handling property and the electrical property are highly satisfied. It is preferable because Ie height 0.5μ
The number of protrusions of m or more is 500 / mm ² or more, preferably 7
00-5000 pieces / mm ² , more preferably 900-3
It is in the range of 000 pieces / mm ² , and the number of protrusions with a height of 1.0 μm or more is less than 300 pieces / mm ² , preferably 200 pieces / mm ^2.
less than mm ^2, further preferably in the range of less than 150 / mm ^2. Such a surface shape has a height of 0.5.
There are many relatively large protrusions with a size of μm or more, and 1.0
The feature is that there are few coarse protrusions of μm or more,
It is obtained by containing particles having a sharp particle size distribution. In addition to such surface characteristics, the coefficient of friction with the metal pin of the film measured under the conditions described below is 0.38 or less,
When it is preferably 0.35 or less, the running property in the vapor deposition step becomes good and the adhesion to the cooling can becomes good, so that
This is preferable because problems such as heat loss do not occur.

In addition to the surface characteristics of the film, when the Young's modulus in the longitudinal direction of the film is 5.0 GPa or more, preferably 5.5 GPa or more, the electrical characteristics and the handling property during vapor deposition become higher. 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 will 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. In addition to this, the Young's modulus in the longitudinal direction of the film at 100 ° C. is 1.0 GPa or more, preferably 1.2 GPa.
If it is a or more, it is less likely to be damaged by the heat at the time of vapor deposition, so that the electrical characteristics of the capacitor are more highly satisfied.

Further, the film of the present invention is 3 ° C. at 120 ° C.
The shrinkage in the longitudinal direction after treatment for 0 minutes is preferably less than 3.0%, more preferably less than 2.5%.
When the heat shrinkage ratio in the longitudinal direction is large, the film undergoes dimensional changes in the process of receiving heat during the manufacturing of the capacitor, which causes problems such as deterioration of productivity and shortening of the life of the capacitor. Next, the method for producing the film of the present invention will be specifically described. 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 thus obtained is biaxially stretched to form a film, and the orientation which is a feature of the film of the present invention can be obtained by adjusting the stretching and heat treatment conditions to appropriate ranges. And 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. Stretching temperature range is 70-150
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.
It is preheated to a temperature range of 0 ° C. and further stretched 2.5 to 5 times, preferably 3.0 to 4.5 times at about the same temperature to obtain a biaxially oriented film. In addition, it is preferable to perform stretching in the first axial direction 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.

The thus-obtained film is heat-treated for 1 second to 5 minutes under an elongation of 30%, a limited shrinkage, or a fixed length. At this time, re-stretching may be performed in the longitudinal direction, the transverse direction, or both directions within or after the heat treatment step. In the present invention, the film density is 1.3990 g.
/ Cm ³ , more preferably less than 1.3980 g / cm ^3, and in order to satisfy such characteristics, the temperature of the heat treatment step is appropriately selected. The heat treatment temperature is
Although it depends on the stretching conditions, it is preferably in the range of 180 to 250 ° C, more preferably 200 to 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, if the heat treatment temperature is less than 180 ° C, the heat shrinkage rate of the film becomes large, causing dimensional changes in the process of receiving heat during capacitor manufacturing, which deteriorates the productivity of the capacitor and deteriorates the capacitor characteristics such as withstand voltage. There may be problems such as doing.

When a capacitor is produced using the film of the present invention and an electrode is formed by metal vapor deposition, the metal to be vapor deposited is aluminum, palladium, zinc, nickel, gold, silver, copper, indium, tin or chromium. , Titanium, etc., but a particularly preferred metal is aluminum. The above-mentioned metals include metal oxides.
The thickness of the metal vapor-deposited film is preferably in the range of 10 to 2000 °, and the vapor deposition method is generally a vacuum vapor deposition method, but may be a method such as an electroplating method or a sputtering method. In addition, the metal deposition layer may be provided on both sides of the polyester film. After the metal deposition, a surface treatment of the deposited metal layer or a coating treatment with another resin may be performed. Two metal-deposited polyester films thus obtained are superposed and wound (including winding of a double-sided metal-deposited polyester film and other films including the polyester film of the present invention), or a large number of layers are laminated. Capacitor elements can be formed and subjected to, for example, heat pressing, taping, metallikon, voltage treatment, both end surface sealing, lead wire attachment, etc., according to a conventional method to obtain capacitors, but of course not limited to these. .

[0022]

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 (d50) (μm) of particles and particle size distribution value (d25 / d75) Centrifugal sedimentation type particle size distribution analyzer (SA-CP, manufactured by Shimadzu Corporation)
3), the average particle size (d50) is the particle size with an integrated volume fraction of 50% accumulated from the large particle side in the equivalent spherical distribution.
And Further, the values of the cumulative volume fractions of 25% and 75% are d25 and d75, respectively, and the value of the ratio (d25 /
d75) was used as the particle size distribution value. The smaller the particle size distribution value, the sharper the particle size distribution of the particles.

(3) Specific resistance when polymer is melted (Ω · c
m) 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) Center Line Average Roughness (Ra) (μm) It was determined as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory 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 represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portions obtained from the 10 section curves obtained from the surface of the sample film. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08.
mm.

[Equation 1]

(5) Number of surface protrusions Three-dimensional surface roughness measuring device (SE-3A) manufactured by Kosaka Laboratory 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. Protrusion height 0.5 μm or more, and 1.0 μ
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 film thickness was determined by a gravimetric method. That is, 10cm
The total weight of 100 films cut into a square of × 10 cm was measured and calculated using the density of the film. The density of the film was measured using a density gradient tube of n-heptane / carbon tetrachloride. (7) Young's modulus (GPa) Intesco Co., Ltd. Tensile tester Intesco Model 20
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, a sample film having a length of 300 mm and a width of 25 mm is stretched at a strain rate of 10% / min, and is calculated by the following equation using the first linear portion of the tensile stress-strain curve.

## EQU2 ## E = Δσ / Δε (where E is the tensile modulus, Δσ is the stress difference due to the original average cross-sectional area between the two points on the straight line, and Δε is the strain difference between the same two points).

(8) Coefficient of dynamic friction with metal pin (μd) Fixed stainless steel pin (diameter 6 mm, surface finish 2
A film is wound around S) at an angle of 135 °, and
A load of g (T2) was applied to one end, the vehicle was run at a speed of 1 m / min, and the resistance (T1 (g)) of the other end was measured. The friction coefficient (μd) during running was determined by the following equation.

(Equation 3)

(9) Evaluation of electrical characteristics (i) Withstand voltage characteristics Measurement was performed according to JIS C-2319. That is, using a 10 kV DC withstand voltage tester, 23 ° C., 50%
Under an atmosphere of RH, the voltage was increased at a rate of 100 V / sec, and the voltage when the film was broken and short-circuited was read. (Ii) Insulation Resistance Characteristics (Manufacture of Capacitor) A capacitor was manufactured and evaluated as follows. That is, aluminum was vapor-deposited to a thickness of 350 A on the film surface by using a resistance heating type metal vapor deposition device while setting the pressure in the vacuum chamber to 10 ⁻⁴ Torr or less. At that time, the polyester film was vapor-deposited in a stripe shape having a margin portion in the longitudinal direction (width of vapor deposition portion: 8 mm, margin:
Repeated width of gin 1mm). The obtained vapor-deposited polyester film was slit into a 4.5 mm width tape shape having a margin portion of 1 mm width on the left or right. The obtained left and right margin vapor-deposited polyester films were wound one by one to obtain a wound body. At this time, the two films were wound while being shifted so that the vapor deposition portion protruded by 0.5 mm in the width direction. This wound body was pressed at a temperature of 140 ° C. and a pressure of 50 kg / cm ² for 5 minutes. After the metal wire was sprayed on both end surfaces of the wound body after pressing, a lead wire was attached thereto, an impregnation layer of a liquid bisphenol A type epoxy resin and a powdered epoxy resin were heated and melted to a minimum thickness of 0. A 5 mm exterior was formed to obtain a film capacitor having a capacitance of 0.1 μF.

(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. The measurement was performed in an atmosphere of 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 was applied for 1 minute, and the current value was recorded on the recorder during that period. The current value shows the maximum value immediately after the voltage is applied and then decreases, and the maximum value is taken as the measured value R. The measurement was performed at 23 ° C and 105 ° 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. It takes 4 hours 2
The temperature was raised to 30 ° C. to substantially complete the transesterification reaction. Then, 1.0 part of silica particles having a particle diameter of 1.5 μm was added as ethylene glycol slurry. After the addition of the slurry, 0.06 part of phosphoric acid and antimony trioxide were added.
04 parts was added, the reaction system was gradually depressurized, the temperature was raised and the polycondensation reaction was carried out for 4 hours to obtain a polyester (a) having an intrinsic viscosity of 0.66. Similarly, an average particle size of 1.4 μm,
1.0% by weight of calcium carbonate particles having a particle size distribution value of 1.4
A polyester (b) having an intrinsic viscosity of 0.65 was obtained. A polyester (c) was obtained in the same manner except that it did not contain particles. A raw material obtained by mixing 50 parts of polyester (a), 40 parts of polyester (b) and 10 parts of polyester (c) was dried by an ordinary method and supplied to an extruder,
It was melted at 290 ° C., extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous sheet.
The obtained sheet is stretched in the longitudinal direction by using a roll stretching method.
The film was stretched 2.9 times at 70 ° C and then 1.5 times at 70 ° C. Next, the film was guided to a tenter, and 11
The film was stretched 4.1 times at 0 ° C. and heat-treated at 230 ° C. to obtain a biaxially stretched polyester film having a film thickness of 1.5 μm. The center line average roughness (Ra) was 0.120 μm. As shown in Table 1 below, the metal-evaporated film capacitor obtained using this film was a metal-evaporated polyester film capacitor having excellent withstand voltage characteristics and insulation resistance characteristics.

Example 2 The particle content was 1.0% by weight in the same manner as the polyester (b) of Example 1 except that calcium carbonate particles having an average particle size of 1.3 μm and a particle size distribution value of 1.7 were used. A polyester (d) having an intrinsic viscosity of 0.64 was obtained. Using a raw material obtained by mixing 40 parts of polyester (d), 50 parts of polyester (a) and 10 parts of polyester (c), the film forming conditions were the same as in Example 1, and a biaxially oriented polyester film having a thickness of 1.5 μm was used. Obtained. Example 3 In Example 1, the film stretching conditions were changed as follows. That is, the stretching in the machine direction by the roll stretching method is made to be 2.4 times at 85 ° C. and then 1.2 times at 75 ° C.
4.5 times horizontal stretch at 110 ℃ in a tenter, and then 230
A heat treatment was performed at 0 ° C. to obtain a biaxially oriented polyester film having a thickness of 1.5 μm. Example 4 Polyester (a) was prepared in the same manner as in Example 1 except that the amount of phosphoric acid added after the transesterification reaction was 0.035 parts in the production of polyester.
Polyesters (e) and (f) containing the same amount of particles as in (b) were obtained. The intrinsic viscosities were both 0.66. 50 parts of polyester (e) and 5 parts of polyester (f)
A biaxially oriented polyester film having a thickness of 1.6 μm was obtained in the same manner as in Example 1 except that the starting material was mixed with 0 parts.

Comparative Example 1 A raw material prepared by mixing 60 parts of polyester (a) and 40 parts of polyester (c) was used, and the film forming conditions were the same as in Example 1 to obtain a biaxially oriented polyester film having a thickness of 1.5 μm. It was Comparative Example 2 A biaxially oriented polyester film having a thickness of 1.5 μm was obtained in the same manner as in Example 1 except that a raw material prepared by mixing 60 parts of polyester (b) and 40 parts of polyester (c) was used. Comparative Example 3 In the polyester (b) of Example 1, the average particle size was 1.
A polyester (h) having an intrinsic viscosity of 0.65 was manufactured in the same manner except that calcium carbonate particles having a particle size distribution of 3.5 μm and a particle size of 5 μm were used. A raw material obtained by mixing 50 parts of polyester (a) and 50 parts of polyester (h) was used, and the film forming conditions were the same as in Example 1 to obtain a biaxially oriented polyester film having a thickness of 1.6 μm.

Comparative Example 4 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. Comparative Example 5 In the polyester (a) of Example 1, the average particle size was 0.
A polyester (i) having an intrinsic viscosity of 0.64 was produced in the same manner except that silica particles of 2 μm were used and the addition amount was 0.8% by weight. Using a raw material obtained by mixing 60 parts of polyester (i) and 40 parts of polyester (b), the film forming conditions were the same as in Example 1 to obtain a biaxially oriented polyester film having a thickness of 1.5 μm. Tables 1 and 2 below show the physical properties of the films obtained in Examples and Comparative Examples and the characteristic evaluation results of vapor deposition capacitors prepared using them.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

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 (1)

[Claims] 1. The average particle size (d50) is 0.5 to 3.0 μm.
Silica particles containing 0.1 to 2.0% by weight of calcium carbonate particles having a particle size distribution value (d25 / d75) of less than 3.0 and an average particle size (d50) of 0.8 to 4.0 μm. To 0.1
~ 2.0 wt%, film thickness 0.3-2.0
A biaxially oriented polyester film for capacitors, which has a thickness of μm.