POLYPROPYLENE FILM, POLYPROPYLENE FILM INTEGRATED WITH METAL LAYER, AND FILM CAPACITOR

Abstract

Provided is a polypropylene film having a high dielectric breakdown strength at high temperatures. Provided is a polypropylene film in which a polypropylene resin constituting the polypropylene film has a molecular-weight distribution (Mw/Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of has a Z-average molecular weight Mz of 950,000-1,500,000, and has a weight proportion w of 2.6-4.2% in an integral molecular-weight distribution curve when the logarithmic molecular weight Log(M) is 4.0.

Claims

1. A polypropylene film comprising a polypropylene resin, the polypropylene resin having a molecular-weight distribution (Mw/Mn) of a weight-average molecular weight Mw to a number-average molecular weight Mn of 5.0 or more and 6.9 or less, having a Z-average molecular weight Mz of 950,000 or more and 1,500,000 or less, and having a weight proportion w of 2.6% or more and 4.0% or less when a logarithmic molecular weight Log(M) is 4.0 in an integral molecular-weight distribution curve.

2. A capacitor comprising the polypropylene film according to claim 1.

3. The polypropylene film according to claim 1, wherein the polypropylene film is a biaxially stretched film.

4. The polypropylene film according to claim 1, wherein a density as measured according to Method D in JIS K7112:1999 is 919 kg/m.sup.3 or more and 925 kg/m.sup.3 or less.

5. The polypropylene film according to claim 1, wherein a dielectric breakdown strength (DCES) at a direct current voltage at 120 C. is 530 V/m or more.

6. The polypropylene film according to claim 1, wherein the polypropylene resin contains a polypropylene resin A and a polypropylene resin B different from the polypropylene resin A, an Mw of the polypropylene resin A is 250,000 or more and less than 350,000, a molecular-weight distribution (Mw/Mn) of the polypropylene resin A is 5.5 or more and 10.0 or less, a melt flow rate (MFRA) of the polypropylene resin A is 3.0 g/10 min or more and 10.0 g/10 min or less, and a content of the polypropylene resin A in the polypropylene resin is larger than a content of the polypropylene resin B in the polypropylene resin.

7. The polypropylene film according to claim 1, wherein the polypropylene resin contains a polypropylene resin A and a polypropylene resin B different from the polypropylene resin A, an Mw of the polypropylene resin B is 300,000 or more and 550,000 or less, a molecular-weight distribution (Mw/Mn) of the polypropylene resin B is 5.0 or more and 11.0 or less, a melt flow rate (MFRB) of the polypropylene resin B is 0.1 g/10 min or more and 3.0 g/10 min or less, and a content of the polypropylene resin A in the polypropylene resin is larger than a content of the polypropylene resin B in the polypropylene resin.

8. The polypropylene film according to claim 6, wherein a ratio of a mass of the polypropylene resin A to a total mass of the polypropylene resin A and the polypropylene resin B is 55 mass % or more and 75 mass % or less.

9. The polypropylene film according to claim 1, wherein a thickness of the polypropylene film is 1.0 m or more and 2.4 m or less.

10. A polypropylene film comprising a polypropylene resin, the polypropylene resin having a Z-average molecular weight Mz of 950,000 or more and 1,500,000 or less and having a dielectric breakdown strength (DCES) at a direct current voltage at 120 C. of 530 V/m or more.

11. A metal layer-integrated polypropylene film comprising: the polypropylene film according to claim 1; and a metal layer laminated on one surface or both surfaces of the polypropylene film.

12. A film capacitor comprising the wound metal layer-integrated polypropylene film according to claim 11 or a configuration in which a plurality of the metal layer-integrated polypropylene films according to claim 11 are laminated.

13. The film capacitor according to claim 12, wherein an insulation resistance value at an ambient temperature of 115 C. is 20 M.Math.F or more.

14. A metal layer-integrated polypropylene film comprising: the polypropylene film according to claim 10; and a metal layer laminated on one surface or both surfaces of the polypropylene film.

15. A film capacitor comprising the wound metal layer-integrated polypropylene film according to claim 14 or a configuration in which a plurality of the metal layer-integrated polypropylene films according to claim 11 are laminated.

16. The film capacitor according to claim 15, wherein an insulation resistance value at an ambient temperature of 115 C. is 20 M.Math.F or more.

Description

EXAMPLES

[0145] Hereinafter, the present disclosure will be specifically described with reference to Examples and Comparative Examples. However, the present disclosure is not limited to Examples.

[0146] <<Resin>>

[0147] Details of resins (PP resins A1 to A7 and PP resins B1 to B8) used in Examples and Comparative Examples are summarized in Table 1 below and methods for measuring respective physical properties are described.

TABLE-US-00001 TABLE 1 Value using differential molecular-weight distribution Mn Mw Mz Log (M) = Log (M) = DM 4.5 10000 10000 10000 Mw/Mn Mz/Mn 4.5 6.0 6.0 PP resin A1 4.2 34 150 8.1 35.7 31.4 26.6 4.8 PP resin A2 3.3 31 140 9.4 42.4 33.5 24.5 9.0 PP resin A3 4.7 27 75 5.7 16.0 29.9 21.4 8.6 PP resin A4 3.4 34 155 10.0 45.5 35.0 24.8 10.2 PP resin A5 3.6 31 120 8.6 33.3 34.0 23.0 11.0 PP resin A6 4.7 27 75 5.7 16.0 30.2 21.2 10.0 PP resin A7 4.7 27 75 5.7 16.0 30.0 21.2 8.8 PP resin B1 4.6 38 160 8.3 34.8 27.3 30.9 3.6 PP resin B2 7.6 46 190 6.1 25.0 20.8 37.1 16.3 PP resin B3 4.2 32 120 7.6 28.6 32.0 25.4 6.6 PP resin B4 4.6 39 160 8.5 34.8 27.3 30.9 3.6 PP resin B5 4.4 35 150 8.0 34.8 32.3 25.3 7.0 PP resin B6 4.5 34 130 7.6 28.9 31.3 27.7 3.6 PP resin B7 4.6 38 160 8.3 34.8 27.4 30.8 3.4 PP resin B8 4.6 38 160 8.3 34.8 27.4 30.8 3.4 Weight proportion w HI MFR % % g/10 min Manufacturer PP resin A1 4.5 98.5 4.0 Borealis AG PP resin A2 6.4 97.3 4.9 Prime Polymer Co., Ltd. PP resin A3 4.1 97.8 5.6 Prime Polymer Co., Ltd. PP resin A4 6.2 97.3 4.5 Prime Polymer Co., Ltd. PP resin A5 6.0 97.2 4.6 Prime Polymer Co., Ltd. PP resin A6 4.3 97.7 5.6 Prime Polymer Co., Ltd. PP resin A7 4.3 97.8 5.5 Prime Polymer Co., Ltd. PP resin B1 3.3 98.8 2.3 Korea Petrochemical Ind. Co., LTD. PP resin B2 2.0 98.9 0.7 Korea Petrochemical Ind. Co., LTD. PP resin B3 4.6 98.5 3.0 Samsung Total Petrochemicals Co., Ltd. PP resin B4 3.7 98.8 2.1 Korea Petrochemical Ind. Co., LTD. PP resin B5 4.6 98.6 3.0 Korea Petrochemical Ind. Co., LTD. PP resin B6 4.5 98.6 3.1 Korea Petrochemical Ind. Co., LTD. PP resin B7 3.8 98.7 2.3 Korea Petrochemical Ind. Co., LTD. PP resin B8 3.8 98.8 2.1 Korea Petrochemical Ind. Co., LTD. PP resin A1: manufactured by Borealis AG PP resins A2 to A7: manufactured by Prime Polymer Co., Ltd. PP resin B1: manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B2: trade name S800 manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B3: trade name HU300 manufactured by Samsung Total Petrochemicals Co., Ltd. PP resin B4: manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B5: manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B6: manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B7: manufactured by Korea Petrochemical Ind. Co., LTD. PP resin B8: manufactured by Korea Petrochemical Ind. Co., LTD.

[0148] <<Measurement of Number-Average Molecular Weight (Mn), Weight-Average Molecular Weight (Mw), z-Average Molecular Weight (Mz), Molecular-Weight Distribution (Mw/Mn), Molecular-Weight Distribution (Mz/Mn), and Weight Proportion w of Polypropylene Resin>>

[0149] First, the average molecular weight and molecular-weight distribution of each polypropylene resin were measured by size exclusion chromatography (SEC) under the following conditions. [0150] Device: HLC-8321GPC/HT (detector: differential refractometer (RI)) (manufactured by Tosoh Corporation) [0151] Column: one TSKgel guardcolumn HHR(30)HT column (7.5 mm I.D.7.5 cm)+three TSKgel GMHHR-H(20)HT (7.8 mm I.D.30 cm) columns (manufactured by Tosoh Corporation) [0152] Eluent: 1,2,4-trichlorobenzene (for GPC, manufactured by FUJIFILM Wako Pure Chemical Corporation)+BHT (0.05%) [0153] Flow rate: 1.0 mL/min [0154] Detection condition: polarity-() [0155] Injected amount: 0.3 mL [0156] Column temperature: 140 C. [0157] System temperature: 40 C. [0158] Sample concentration: 1 mg/mL [0159] Sample pretreatment: A sample was weighed, a solvent (1,2,4-trichlorobenzene added with 0.1% BHT) was added, and the sample was dissolved by shaking at 140 C. for 1 hour. Thereafter, the resultant was heated and filtered through a 0.5-m sintered filter. [0160] Calibration curve: A calibration curve of the fifth-order approximate curve was prepared using polystyrene standard manufactured by Tosoh Corporation. However, the molecular weight was converted into the molecular weight of polypropylene using the Q-factor.

[0161] From the obtained calibration curve and SEC chromatogram, analysis software for the measurement device was used to plot the molecular weight (logarithmic values) on the horizontal axis and the integral value of the concentration fraction on the vertical axis, thereby obtaining an integral molecular-weight distribution curve. A differential value of the integral molecular-weight distribution curve (slope of the integral molecular-weight distribution curve) at each molecular weight was determined, and a differential molecular-weight distribution curve was obtained by plotting the molecular weight (logarithmic values) on the horizontal axis and the differential value on the vertical axis.

[0162] From these curves, the number-average molecular weight Mn, the weight-average molecular weight Mw, and the Z-average molecular weight Mz were obtained. The Mw and Mn values were used to obtain a molecular-weight distribution (Mw/Mn). A value when the logarithmic molecular weight Log(M) is 4.0 in the integral molecular-weight distribution curve was designated as the weight proportion w. The weight proportion w indicates the weight proportion of a molecule at a logarithmic molecular weight Log(M) of 4.0, that is, a molecular weight of 10,000 or less.

[0163] <<Measurement of Differential Distribution Value when Logarithmic Molecular Weight Log(M) is 4.5, Differential Distribution Value when Logarithmic Molecular Weight Log(M) is 6.0, and Difference in Molecular Weight Differential Values (DM)>>

[0164] For each polypropylene resin, the differential distribution value when the logarithmic molecular weight Log(M) is 4.5 and the differential distribution value when the logarithmic molecular weight Log(M) is 6.0 were obtained by the following method. First, a time curve (elution curve) of intensity distribution detected by an RI detector was converted into a distribution curve with respect to the molecular weight M (Log(M)) of the above polystyrene standard using the calibration curve produced using the polystyrene standard. Next, after an integral distribution curve with respect to Log(M) when the total area of the distribution curve was regarded as 100% was obtained, the integral distribution curve was differentiated by Log(M), thereby obtaining a differential distribution curve with respect to Log(M). Differential distribution values when Log(M) is 4.5 and Log(M) is 6.0 were read from this differential distribution curve. A difference between the differential distribution value when Log(M) is 4.5 and the differential distribution value when Log(M) is 6.0 was designated as the difference in molecular weight differential values (DM). The series of operations until the differential distribution curve was obtained was performed using analysis software provided in the GPC measurement apparatus.

[0165] <<Measurement of Heptane Insoluble (HI)>>

[0166] Each polypropylene resin was press-molded to 10 mm35 mm0.3 mm to prepare about 3 g of a measurement sample. Next, about 150 mL of heptane was added, and Soxhlet extraction was performed for 8 hours. The heptane insoluble was calculated from the sample mass before and after extraction.

[0167] <<Measurement of Melt Flow Rate (MFR)>>

[0168] The melt flow rate (MFR) in the form of raw material resin pellets used in the Examples and Comparative Examples was measured using the melt index of Toyo Seiki Co., Ltd. according to the condition M of JIS K 7210. Specifically, first, a sample weighed to 4 g was inserted into a cylinder set at a test temperature of 230 C., and preheated under a load of 2.16 kg for 3.5 minutes. Thereafter, the weight of the sample extruded from the bottom hole for 30 seconds was measured, and MFR (unit: g/10 min) was determined. The above measurements were repeated 3 times, and the average value was taken as the measured value of MFR.

Examples 1 to 6 and Comparative Examples 1 to 15

[Production of Biaxially Stretched Polypropylene Film and Evaluation of Properties Thereof]

[0169] According to Table 2, the polypropylene resins A and B were weighed and mixed at the weight ratios shown in Table 2, thereby obtaining dry-blended resin compositions. Next, each dry-blended resin composition was supplied to an extruder and melted at the melting temperature and shear rate shown in Table 2. This molten resin was extruded using a T-die, wound around a metal drum whose surface temperature was maintained at 95 C. and solidified to produce a cast rolled sheet. The unstretched cast rolled sheet was maintained at a temperature of 140 C., passed between rolls having different speeds, stretched by a factor of 4.5 in the flow direction, and immediately cooled to room temperature. Subsequently, after the stretched film obtained by stretching in the flow direction was guided to a tenter and stretched by a factor of 10 in the width direction at a traverse stretching temperature of 158 C., relaxation at a relaxation rate of 12% and thermal solidification were performed, and then the biaxially stretched polypropylene film with a width of about 5 m and a thickness of 2.3 m was wound around an iron core with a diameter of 400 mm by about 80,000 m under the atmosphere shown in Table 2 and wound as a jumbo roll. The wound biaxially stretched polypropylene film was subjected to an aging treatment in an atmosphere of 35 C. for 24 hours.

TABLE-US-00002 TABLE 2 Raw material Production conditions Film physical properties Number Number Melting Weight of parts Blend of parts temperature Shear rate Thickness Mz proportion w Base resin Parts resin Parts C. s.sup.1 m 10000 Mw/Mn % Example 1 Resin A1 65 Resin B1 35 250 2000 2.3 110 6.3 3.5 Example 2 Resin A1 70 Resin B1 30 250 2000 2.3 110 6.9 3.9 Example 3 Resin A1 55 Resin B1 45 250 2000 2.3 111 6.7 3.8 Example 4 Resin A2 70 Resin A1 30 250 2000 2.3 104 6.6 4.0 Example 5 Resin A1 60 Resin B1 40 260 5000 2.3 110 6.4 3.7 Example 6 Resin A1 75 Resin B1 25 230 2000 2.3 106 6.8 3.9 Comparative Resin A1 95 Resin B1 5 250 2000 2.3 108 8.0 4.1 Example 1 Comparative Resin B1 90 Resin A1 10 250 2000 2.3 114 8.0 3.5 Example 2 Comparative Resin A2 65 Resin B1 35 250 2000 2.3 100 6.7 4.9 Example 3 Comparative Resin A3 75 Resin B1 25 250 2000 2.3 72 5.2 3.6 Example 4 Comparative Resin B3 100 250 2000 2.3 118 7.6 4.6 Example 5 Comparative Resin B2 100 250 2000 Unstretchable 180 6.1 2.0 Example 6 Comparative Resin A1 80 Resin B7 20 230 2000 2.3 100 7.0 4.0 Example 7 Comparative Resin A1 75 Resin B1 25 250 16000 2.3 100 6.8 4.1 Example 8 Comparative Resin A1 70 Resin B1 30 290 2000 2.3 100 7.0 4.2 Example 9 Comparative Resin A2 65 Resin B2 35 250 2000 2.3 120 8.7 4.2 Example 10 Comparative Resin A2 65 Resin B4 35 250 2000 2.3 100 6.7 4.9 Example 11 Comparative Resin A4 65 Resin B5 35 250 2000 2.3 101 7.8 5.9 Example 12 Comparative Resin A5 65 Resin B6 35 250 2000 2.3 98 7.3 6.0 Example 13 Comparative Resin A6 75 Resin B7 25 250 1800 2.3 70 6.4 4.3 Example 14 Comparative Resin A7 75 Resin B8 25 260 1800 2.3 70 6.4 4.3 Example 15 Film physical properties Element physical properties Volume resistivity Element- DCES 100 C. DCES 120 C. Density 5 minute 10 minute Deposition winding V/m V/m kg/m.sup.3 value .Math. cm value .Math. cm Lifetime processability processability Example 1 587 547 922 3 10.sup.15 3 10.sup.15 Example 2 582 541 922 3 10.sup.15 3 10.sup.15 Example 3 577 535 922 3 10.sup.15 3 10.sup.15 Example 4 574 534 921 2 10.sup.15 3 10.sup.15 Example 5 582 544 922 3 10.sup.15 3 10.sup.15 Example 6 580 535 922 3 10.sup.15 3 10.sup.15 Comparative 566 527 919 2 10.sup.15 2 10.sup.15 X Example 1 Comparative 556 518 922 1 10.sup.15 1 10.sup.15 X Example 2 Comparative 580 528 919 2 10.sup.15 2 10.sup.15 X Example 3 Comparative 565 529 922 1 10.sup.15 2 10.sup.15 Example 4 Comparative 555 503 913 1 10.sup.14 1 10.sup.14 X Example 5 Comparative Example 6 Comparative 573 534 922 2 10.sup.15 2 10.sup.15 Example 7 Comparative 575 535 922 2 10.sup.15 2 10.sup.15 Example 8 Comparative 575 536 922 2 10.sup.15 2 10.sup.15 Example 9 Comparative 560 491 922 1 10.sup.15 2 10.sup.15 Example 10 Comparative 566 530 919 2 10.sup.15 2 10.sup.15 Example 11 Comparative 551 521 919 2 10.sup.15 2 10.sup.15 Example 12 Comparative 551 518 919 2 10.sup.15 2 10.sup.15 Example 13 Comparative 547 516 920 1 10.sup.15 2 10.sup.15 Example 14 Comparative 547 515 920 1 10.sup.15 2 10.sup.15 Example 15

[0170] In the film physical properties described in Table 2, the Mz of Comparative Example 5 using Resin 3 as a base resin is 1,180,000, the Mz of Comparative Example 6 using Resin 2 is 1,800,000, whereas the Mz of Resin 3 described in Table 1 is 1,200,000, the Mz of Resin 2 is 1,900,000, and the values of Mz in the film physical properties are slightly small. This is considered to mean that a high-molecular-weight component is decomposed by melting or the like when a film is produced using a polypropylene resin.

[0171] The methods for measuring the thickness, density, and dielectric breakdown strength of the biaxially stretched polypropylene film obtained in each of Examples and Comparative Examples, the method for performing thermomechanical analysis (TMA), and the method for evaluating the winding quality (wrinkles) of the jumbo rolls during aging are shown below. The results of each measurement and evaluation are also shown in Table 2.

[0172] <<Measurement of Polypropylene Film Thickness>>

[0173] A paper thickness measuring instrument MEI-11 (measurement pressure: 100 kPa, descent speed: 3 mm/sec, measuring terminal =16 mm, measuring force: 20.1 N) manufactured by Citizen Seimitsu Co., Ltd. was used in an environment of a temperature 232 C. and a humidity 505% RH. The sample was cut out from the roll with 10 or more sheets stacked, and handled so that wrinkles or air did not enter the film during cutting. The thickness of the 10 stacked samples was measured 5 times, and the average value of the 5 measurements was divided by 10 to calculate the thickness.

[0174] <<Measurement of Polypropylene Film Density>>

[0175] The density of the polypropylene films was measured according to Method D in JIS K7112 (1999). [0176] Measurement device: density gradient tube-type specific gravity measuring device, Type A, manufactured by SHIBAYAMA SCIENTIFIC CO., LTD. [0177] Gradient liquid: ethanol aqueous solution [0178] Measurement temperature: 230.5 C. [0179] Number of measurements: n=3

[0180] <<Measurement of Dielectric Breakdown Strength of Polypropylene Film: Direct Current (DC)>>

[0181] The dielectric breakdown voltage (BDV) of the polypropylene film at 100 C. or 120 C. was measured 16 times under the following test conditions with the electrode configuration described in 17.2.2 (Plate electrode method) of JIS C2151 (2006). The applied voltage at the time when the leakage current of the following upper limit reference value was detected during the pressure rise was defined as BDV. BDV was divided by the thickness (m) of the film, and the average value of 12 points excluding the upper 2 points and the lower 2 points in the 16 measurement results was taken as the dielectric breakdown strength DCES (V/m). [0182] Specimen: about 150 mm150 mm [0183] Specimen condition adjustment: 30 minutes under atmospheric conditions [0184] Power source: direct current [0185] Atmosphere: in the air, 100 C. or 120 C. [0186] Tester: DC withstanding voltage/insulation resistance tester TOS9213AS manufactured by KIKUSUI ELECTRONICS CORPORATION [0187] Voltage rise rate: 100 V/s [0188] Current detection response speed: MID [0189] Upper limit reference value: 5 mA

[0190] <<Volume Resistivity>>

[0191] <Measurement of Volume Resistivity V>

[0192] A specific measurement procedure of the volume resistivity is described below, but as for conditions not specifically described, the volume resistivity was measured as follows based on JIS C 2139-3-1:2018

[0193] First, a jig for measuring volume resistivity (hereinafter, also simply referred to as a jig) was placed in a thermostatic chamber in an environment of 100 C. The configuration of the jig is as follows. A DC power supply and a DC ammeter were connected to the jig.

[0194] <Jig for Measuring Volume Resistivity> [0195] Main electrode (diameter: 50 mm) [0196] Counter electrode (diameter: 85 mm) [0197] Annular guard electrode surrounding main electrode (outer diameter: 80 mm, inner diameter: 70 mm)

[0198] Each electrode is made of gold-plated copper, and a conductive rubber is attached to a surface in contact with a sample. The conductive rubber used is EC-60BL (W300) manufactured by Shin-Etsu Silicone Co., Ltd., and the conductive rubber is attached so that the glossy surface of the conductive rubber is in contact with the gold-plated copper.

[0199] Next, the resin films (hereinafter, also referred to as samples) of Examples and Comparative Examples were set in the jig in the thermostatic chamber. Specifically, the main electrode and the guard electrode were brought into close contact with one surface of the sample, the counter electrode was brought into close contact with the other surface, and the sample and each electrode were brought into close contact with each other at a load of 5 kgf. Thereafter, the obtained product was left to stand still for 30 minutes.

[0200] Next, a voltage was applied to the sample so that the potential gradient was 200 V/m.

[0201] The current values at 5 minutes and 10 minutes after the application of the voltage were read, and the volume resistivity was calculated by the following equation. For the voltage application and current value measurement, 6517B (electrometer/insulation resistance meter) manufactured by Keithley was used.

Volume resistivity=[(Effective electrode area)(Applied voltage)]/[(Thickness of sample)(Current value)]

[0202] The effective electrode area was determined by the following equation.

(Effective electrode area)=Ratio of circumference of circle to its diameter[[[(Diameter of main electrode)+(Inner diameter of guard electrode)]/2]/2].sup.2

[0203] This was repeated three times, and the arithmetic average value obtained in one significant digit was taken as the volume resistivity (SI cm).

[Production of Film Capacitor and Evaluation of Properties Thereof]

[0204] The biaxially stretched polypropylene film obtained in each of Examples and Comparative Examples was used to produce a film capacitor by the following procedure.

[0205] A special deposition pattern margin and an insulation margin for imparting the film capacitor safety were formed on the biaxially stretched polypropylene film, and aluminum deposition was applied so that the metal film had a surface resistivity of 20/, thereby obtaining a metal layer-integrated polypropylene film. Next, after the metal layer-integrated polypropylene film was silt to an arbitrary width, the two metal layer-integrated polypropylene films were combined, and the metal layer-integrated polypropylene films were wound using an automatic winder 3KAW-N2 Type manufactured by KAIDO MANUFACTURING CO., LTD. at a winding speed of 4 m/sec, a winding tension of 180 g, and a contact roller contact pressure of 260 g while setting the number of turns so that the element capacitance was 50 F.

[0206] After the element-wound element was pressed and flattened, zinc metal was sprayed on the element end surface to form an electrode extraction portion while the press load was applied, followed by heat treatment at 120 C. for 15 hours for thermal curing.

[0207] After thermal curing, leads were soldered to the element end surface and sealed with an epoxy resin to obtain a flat film capacitor. The capacitance of all of the obtained film capacitors was 50 F (3 F).

[0208] The methods for evaluating deposition processability and element-winding processability in the production process of the film capacitor obtained in each of Examples and Comparative Examples, and the methods for evaluating the lifetime characteristics and thermal shock resistance of the film capacitor are shown below The results of each evaluation are also shown in Table 2.

[0209] <<Deposition Processability>>

[0210] A case where a wrinkle formation rate due to thermal deformation in the film after deposition is less than 5% was regarded as , and a case where a wrinkle formation rate is 5% or more was regarded as x.

[0211] <<Element-Winding Processability Evaluation>>

[0212] Of the small rolls obtained by deposition and slitting, a left-margin winding reel and a right-margin winding reel were used to wind two superimposed films so that the deposition portions protruded beyond the margin portions in the width direction (element-winding process). The winding was performed for 1360 turns at a winding tension of 200 g using an automatic winder 3KAW-N2 Type manufactured by KAIDO MANUFACTURING CO., LTD. At that time, the films were visually observed from the start of winding to the end of winding, those with wrinkles or misalignment were determined to be rejected, and the ratio of the number of rejected products to the total number of products produced was expressed as a percentage and used as an index of processability (hereinafter, referred to as element-winding yield). A higher element-winding yield is more preferable. An element-winding yield of 95% or more was evaluated as good , and an element-winding yield of less than 95% was evaluated as poor x.

[0213] <<Lifetime Characteristics (Capacitance Change Rate))>>

[0214] The initial capacitance of the obtained capacitor before the test was evaluated by an LCR Hi-Tester 3522-50 manufactured by HIOKI E.E. CORPORATION. Next, a direct current voltage of 800 V (348 V/m) was continuously applied to the capacitor for 500 hours in a high-temperature chamber at 115 C. The capacitance of the capacitor after 500 hours was measured in the same manner, and the capacitance change rate before and after voltage application was calculated by the following equation. The test was conducted using two samples, and the average value thereof was used for evaluation.

(Capacitance change rate)=[(Capacitance after voltage application)(Initial capacitance)]/(Initial capacitance)100(%)

[0215] A capacitance change rate within 4% after 500 hours was regarded as good , a capacitance change rate of more than 4% and 6% or less was regarded as , and a capacitance change rate of more than 6% was regarded as poor x.

[0216] <<Insulation Resistance at High Temperatures (High-Temperature IR)>>

[0217] For each capacitor obtained above, the insulation resistance at 115 C. was measured by the following method. A shielding box SME-8350 was connected to a super insulation resistance meter DSM8104 manufactured by HIOKI E.E. CORPORATION. A metallized film capacitor element was placed in the shielding box, and a direct current voltage of 750 V was applied. The insulation resistance value [unit: M] after the lapse of 1 minute was read. The value was rounded off to the first decimal place. The measurement conditions other than those described herein were in accordance with 4.2.4 Insulation resistance in JIS C 5101-16:2009.

[0218] The product (CIR product) of the measured value and the nominal capacitance value (50 F) of the capacitor element is shown in Table 3.

TABLE-US-00003 TABLE 3 Insulation resistance value at high temperatures of capacitor (M .Math. F) Example 1 20 Example 2 20 Example 3 20 Example 4 20 Example 5 20 Example 6 20 Comparative Example 1 15 Comparative Example 2 15 Comparative Example 3 10 Comparative Example 4 10 Comparative Example 5 5 Comparative Example 6 Comparative Example 7 15 Comparative Example 8 10 Comparative Example 9 10 Comparative Example 10 10 Comparative Example 11 10 Comparative Example 12 10 Comparative Example 13 10 Comparative Example 14 10 Comparative Example 15 10