Capacitor and manufacturing method thereof

Abstract

To provide a capacitor in which capacitance change is suppressed even in a high temperature and high voltage environment.SOLUTION: A capacitor includes a metallized film having a metal layer on one or both sides of a polypropylene film, and the polypropylene film contains a secondary antioxidant, the content of the secondary antioxidant in the polypropylene film is 1450 ppm or more, and the capacitor has a C-IR product of 15 ks or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a capacitor and a method for manufacturing the same. [Background technology]

[0002] 2. Description of the Related Art Capacitors such as film capacitors have been used in electronic and electrical devices. Examples of such capacitors include high-voltage capacitors, filter capacitors for converters and inverters, and smoothing capacitors.

[0003] For the above-mentioned capacitor, a polypropylene film is preferably used since it can exhibit excellent electrical properties such as high voltage resistance and low dielectric loss properties, as well as high moisture resistance.

[0004] When polypropylene films are used for applications such as capacitors, antioxidants are added to improve long-term storage stability. For example, Patent Document 1 discloses a polyolefin film capacitor containing an antioxidant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 63-070409 Summary of the Invention [Problem to be solved by the invention]

[0006] The antioxidant can suppress oxidation of polypropylene during storage or use of the polypropylene film, thereby improving the long-term high-temperature stability of a capacitor manufactured using the polypropylene film.

[0007] In addition, the antioxidant contained in the polypropylene film decreases with each process of manufacturing the capacitor, from pelletization, to film formation, and capacitor manufacturing. If the manufactured capacitor does not contain an antioxidant, there is a problem that high-temperature, high-voltage stability cannot be obtained. In other words, when the antioxidant in the polypropylene film that constitutes the capacitor is oxidized and deteriorated by heat, the insulation resistance (IR) deteriorates and the capacitance decreases, which causes a problem of capacitance change of the capacitor in a high-temperature, high-voltage environment.

[0008] In addition, the higher the insulation resistance of the capacitor element, the better. If the insulation resistance is low, when a high voltage is applied at high temperature, leakage current flows, and the resulting Joule heat causes a rise in temperature, resulting in deterioration of the capacitor. However, antioxidants generally lower the insulation resistance.

[0009] Therefore, there is a demand for the development of a capacitor in which capacitance change is suppressed even in a high-temperature, high-voltage environment, since the polypropylene film contains an antioxidant and thus has excellent long-term high-temperature, high-voltage stability.

[0010] An object of the present invention is to provide a capacitor in which capacitance change is suppressed even in a high-temperature, high-voltage environment. [Means for solving the problem]

[0011] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned object can be achieved by a capacitor including a metallized film having a metal layer on one or both sides of a polypropylene film, wherein the polypropylene film contains a secondary antioxidant in a specific range amount, and the capacitor has a C·IR product of 15ks or more, and have thus completed the present invention.

[0012] That is, the present invention relates to the following capacitor and manufacturing method thereof. 1. A capacitor comprising a metallized film having a metal layer on one or both sides of a polypropylene film, The polypropylene film contains a secondary antioxidant; The content of the secondary antioxidant in the polypropylene film is 1450 ppm or more; The capacitor has a C·IR product of 15ks or more. A capacitor characterized by: 2. The capacitor according to item 1, wherein the C·IR product is 23ks or more. 3. The capacitor according to item 1 or 2, wherein the content of the secondary antioxidant in the polypropylene film is 2000 ppm or more. 4. The capacitor according to any one of items 1 to 3, wherein the secondary antioxidant has a melting point of 100 to 260° C. 5. The capacitor according to any one of items 1 to 4, wherein the secondary antioxidant has a weight average molecular weight of 500 to 2,000. 6. The capacitor according to any one of items 1 to 5, wherein the secondary antioxidant is a hindered phenol-based antioxidant. 7. A method for producing a capacitor comprising a metallized film having a metal layer on one or both sides of a polypropylene film, comprising: Step 1 of laminating or winding the metallized film; The polypropylene film contains a secondary antioxidant; The capacitor has a C·IR product of 15ks or more. A method for manufacturing a capacitor comprising the steps of: 8. After the step 1, a step 2 of heating the laminated or wound metallized film is provided, Item 8. The method according to item 7, wherein the heating time in step 2 is 1 to 20 hours. 9. The method according to item 8, wherein the heating temperature in step 2 is 100 to 130°C. Effect of the Invention

[0013] The capacitor of the present invention is suppressed from changing in capacitance even in a high-temperature, high-voltage environment. Furthermore, the manufacturing method of the present invention can easily manufacture the capacitor of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In this specification, the expressions "contain" and "include" include the concepts of "contain", "include", "consist essentially of" and "consist only of".

[0015] In this specification, the expression "capacitor" includes the concepts of "capacitor," "capacitor element," and "film capacitor."

[0016] 1. Capacitor The capacitor of the present invention is a capacitor including a metallized film having a metal layer on one or both sides of a polypropylene film, the polypropylene film containing a secondary antioxidant, the content of the secondary antioxidant in the polypropylene film being 1450 ppm or more, and the capacitor having a C·IR product of 15 ks or more. The capacitor of the present invention having the above characteristics is characterized in that the polypropylene film contains a secondary antioxidant, so that oxidation of polypropylene can be suppressed, and the long-term high-temperature high-voltage stability of a capacitor manufactured using the polypropylene film can be improved. In addition, the capacitor of the present invention has a C·IR product of 15 ks or more, so that, together with the content of the secondary antioxidant being within a specific range, leakage current due to voltage application in a high-temperature, high-voltage environment caused by a decrease in insulation resistance due to the inclusion of an antioxidant can be suppressed, and deterioration of the capacitor is suppressed, and a decrease in the high-temperature, high-voltage stability of the capacitor is suppressed. That is, the capacitor of the present invention is characterized in that the polypropylene film contains a secondary antioxidant in a content within a specific range, and the capacitor has a C·IR product of 15 ks or more, so that a change in capacitance is suppressed even in a high-temperature, high-voltage environment.

[0017] The capacitor of the present invention has a C·IR product of 15ks or more. If the C·IR product is less than 15ks, the suppression of capacitance change in a high-temperature, high-voltage environment is insufficient. The C·IR product is preferably 23ks or more, more preferably 30ks or more, and even more preferably 35ks or more. There is no particular upper limit to the C·IR product, and the larger the better, but it may be, for example, 200ks or less.

[0018] In this specification, the C·IR product of the capacitor is measured by the method described in the Examples.

[0019] Each of the components constituting the capacitor of the present invention will now be described in detail.

[0020] (Polypropylene film) The polypropylene film constituting the capacitor of the present invention preferably contains polypropylene resin as a main component. It is more preferable that the resin component constituting the polypropylene film is polypropylene resin. The above-mentioned "main component" means that the polypropylene film contains 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, calculated as solid content.

[0021] The polypropylene film constituting the capacitor of the present invention may be a biaxially oriented polypropylene film. When the polypropylene film constituting the capacitor of the present invention is a biaxially oriented polypropylene film, the stretching ratio in the machine direction is preferably 3.0 times or more and 7.0 times or less, more preferably 4.0 times or more and 6.0 times or less. In addition, the stretching ratio in the transverse direction is preferably 6 times or more and 11 times or less, more preferably 9 times or more and 11 times or less.

[0022] The polypropylene resin is not particularly limited, and can be widely used from those that can be used to form polypropylene films. Examples of polypropylene resins include propylene homopolymers such as isotactic polypropylene and syndiotactic polypropylene; long-chain branched polypropylene; and ultra-high molecular weight polypropylene. Among them, propylene homopolymers are preferred from the viewpoint of heat resistance, and isotactic polypropylene obtained by homopolymerizing propylene in the presence of an olefin polymerization catalyst is even more preferred. The polypropylene resin may be one type alone or a blend of two or more types.

[0023] The polypropylene film may be formed from a polypropylene resin composition containing a polypropylene resin and a secondary antioxidant (hereinafter, in this specification, also simply referred to as a "polypropylene resin composition"), which is used in the production method described below. That is, the polypropylene film may be a polypropylene film derived from a polypropylene resin composition containing a polypropylene resin and a secondary antioxidant.

[0024] The weight average molecular weight (Mw) of the polypropylene resin in the polypropylene resin composition is preferably 200,000 to 550,000, more preferably 200,000 to 500,000, even more preferably 200,000 to 450,000, and particularly preferably 250,000 to 400,000. When such a polypropylene resin is used, appropriate resin fluidity is obtained during biaxial stretching, making biaxial stretching easier. For example, it becomes easier to obtain a thin biaxially stretched polypropylene film suitable for a small and high-capacity capacitor. In addition, it is preferable because unevenness in the thickness of the biaxially stretched polypropylene film is suppressed. In addition, the weight average molecular weight (Mw) of the polypropylene resin in the polypropylene resin composition is more preferably 250,000 or more from the viewpoint of the uniformity of the thickness of the polypropylene film, mechanical properties, thermo-mechanical properties, etc. In addition, the weight average molecular weight (Mw) of the polypropylene resin in the polypropylene resin composition is more preferably 400,000 or less from the viewpoint of the fluidity of the polypropylene resin and the stretchability when obtaining a thin biaxially stretched polypropylene film.

[0025] The number average molecular weight (Mn) of the polypropylene resin in the polypropylene resin composition is preferably 30,000 to 60,000, more preferably 40,000 to 60,000, and even more preferably 40,000 to 50,000. When such a polypropylene resin is used, appropriate resin fluidity is obtained during biaxial stretching, making biaxial stretching easier. For example, it becomes easier to obtain a thin biaxially stretched polypropylene film suitable for a small and high-capacity capacitor. In addition, this is preferable because unevenness in the thickness of the biaxially stretched polypropylene film is suppressed. In addition, the number average molecular weight (Mn) of the polypropylene resin in the polypropylene resin composition is more preferably 50,000 or less from the viewpoint of the fluidity of the polypropylene resin and the stretchability when obtaining a thin biaxially stretched polypropylene film.

[0026] The average molecular weight distribution (Mw / Mn) of the polypropylene resin in the polypropylene resin composition, calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 4 to 12, more preferably 5.5 to 10, and even more preferably 6 to 8. When such a polypropylene resin is used, appropriate resin fluidity is obtained during biaxial stretching, making it easier to obtain a thin biaxially stretched polypropylene film with uniform thickness. In addition, such a polypropylene resin is also preferable from the viewpoint of further improving the dielectric breakdown strength of the polypropylene film.

[0027] The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the polypropylene resin in the polypropylene resin composition can be measured by the following method using SEC (size exclusion chromatography). Apparatus: HLC-8321GPC / HT (detector: differential refractometer (RI)) (manufactured by Tosoh Corporation) Column: TSKgel guard column HHR(30)HT(7.5mmI.D.×7.5cm)×1 + TSKgel GMHHR-H(20)HT(7.8mmI.D.×30cm)×3 (Tosoh Corporation) Eluent: 1,2,4-trichlorobenzene (Fujifilm Wako Pure Chemical GPC grade) + BHT (0.05%) Flow rate: 1.0mL / min Detection condition: polarity-(-) Injection volume: 0.3mL Column temperature: 140℃ System temperature: 40℃ Sample concentration: 1mg / mL Sample pretreatment: Weigh the sample, add a solvent (1,2,4-trichlorobenzene with 0.1% BHT) and dissolve by shaking at 140°C for 1 hour. Then, heat filter through a 0.5μm sintered filter. Calibration curve: Create a calibration curve of a quintic approximation curve using standard polystyrene from Tosoh Corporation. However, the molecular weight is converted to the molecular weight of polypropylene using the Q-factor. From the calibration curve and SEC chromatogram obtained by the above method, the number average molecular weight (Mn) and weight average molecular weight (Mw) can be obtained using analysis software for the measurement device. The molecular weight distribution (Mw / Mn) can be calculated from Mw and Mn.

[0028] The layer structure of the polypropylene film is not particularly limited, and may be formed of multiple layers or may be a single layer. The polypropylene film is preferably a single layer from the viewpoint of excellent dielectric properties since the metal oxide is uniformly distributed throughout the polypropylene film.

[0029] The thickness of the polypropylene film is preferably 1 to 20 μm, more preferably 1 to 10 μm, and still more preferably 1 to 6 μm. When the lower limit of the thickness is within the above range, the voltage resistance is ensured and the breakage of the polypropylene film is further suppressed. When the upper limit of the thickness is within the above range, the shape of the capacitor can be made smaller for the same capacitance.

[0030] The thickness of the polypropylene film was measured by the method described in the Examples.

[0031] (Secondary antioxidant) The polypropylene film constituting the capacitor of the present invention contains a secondary antioxidant.

[0032] Antioxidants are generally used for two purposes. One purpose is to suppress thermal and oxidative degradation in an extruder, and the other purpose is to contribute to suppressing degradation during long-term use as a capacitor film and improving capacitor performance. In this specification, an antioxidant that suppresses thermal and oxidative degradation in an extruder is called a "primary antioxidant," and an antioxidant that contributes to improving capacitor performance is called a "secondary antioxidant."

[0033] The secondary antioxidant is not particularly limited as long as it is a secondary antioxidant used in the polypropylene film constituting the capacitor, and a known secondary antioxidant can be used. Examples of such secondary antioxidants include hindered phenol-based antioxidants and amine-based antioxidants. Among these, hindered phenol-based antioxidants are preferred.

[0034] Examples of the hindered phenol-based antioxidants include triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (trade name: Irganox 245), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 259), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010), and 2,2-thio-diethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 103). 5), N,N'-hexamethylenebis(3,5-di-tertiary-butyl-4-hydroxy-hydrocinnamamide) (trade name: Irganox 1098), 4,4',4''-[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(2,6-di-tert-butylphenol) (trade name: Irganox 1330), 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (trade name: Irganox 3114), octadecyl-3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate (trade name: Adekastab AO-50), and the like.Among these, triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (trade name: Irganox 245), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010), N,N'-hexyl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1020), and N,N'-hexyl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1030) are preferred from the viewpoint of further suppressing the change in capacitance under high temperature and high voltage environments due to their moderate melting points. 4,4',4''-[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(2,6-di-tert-butylphenol) (trade name: Irganox 1330), 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5 -triazine-2,4,6(1H,3H,5H)-trione (trade name: Irganox 3114) is preferred, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide) (trade name: Irganox 1098), 4,4',4''-[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(2,6-di-tert-butylphenol) (trade name: Irganox 133) are preferred. 0), 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (trade name: Irganox 3114) is more preferred, and 4,4',4''-[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(2,6-di-tert-butylphenol) (trade name: Irganox 1330) is even more preferred.

[0035] The melting point of the secondary antioxidant is preferably 50 to 260°C, more preferably 130 to 260°C, further preferably 150 to 255°C, particularly preferably 200 to 255°C, and most preferably 230 to 250°C. By setting the lower limit of the melting point within the above range, the content (residual amount) of the secondary antioxidant in the polypropylene film constituting the capacitor is increased, the insulation resistance (IR) is further improved, and the capacitance change of the capacitor in a high temperature and high voltage environment is further suppressed. By setting the upper limit of the melting point within the above range, oxidation of the polypropylene film is further suppressed.

[0036] The weight average molecular weight of the secondary antioxidant is preferably 500-2,000, more preferably 600-1,000, further preferably 700-900, and particularly preferably 750-800.

[0037] The content of the secondary antioxidant in the polypropylene film (biaxially oriented polypropylene film) constituting the capacitor is 1450 ppm or more. 1500 ppm is preferable, 2000 ppm or more is more preferable, and 2300 ppm or more is even more preferable. The content of the secondary antioxidant is preferably 4000 ppm or less, more preferably 3500 ppm or less, and even more preferably 3000 ppm or less. By setting the lower limit of the content of the secondary antioxidant within the above range, the decrease in capacitance of the capacitor in a high-temperature, high-voltage environment is further suppressed, and the capacitance change is further suppressed. By setting the upper limit of the content of the secondary antioxidant within the above range, the decrease in insulation resistance (IR) is further suppressed.

[0038] The content of the secondary antioxidant in the polypropylene film is the content of the secondary antioxidant relative to the weight of the polypropylene film including all components constituting the polypropylene film, such as polypropylene, primary antioxidant, secondary antioxidant, and additives.

[0039] The content of the secondary antioxidant in the polypropylene film constituting the capacitor is the content in the polypropylene film constituting the capacitor after the capacitor has been manufactured, and is not the content in the polypropylene film prepared as a material for manufacturing the capacitor.

[0040] The content of the secondary antioxidant in the polypropylene film is measured by the method described in the Examples.

[0041] (Primary antioxidant) The polypropylene film constituting the capacitor of the present invention may contain a primary antioxidant, which further suppresses thermal and oxidative degradation of the polypropylene resin composition in an extruder for producing the polypropylene film, and further suppresses thermal and oxidative degradation of the polypropylene film during the production of a capacitor.

[0042] The primary antioxidant is not particularly limited as long as it can suppress thermal and oxidative degradation of the polypropylene film, and for example, it is preferable to use 2,6-di-tert-butyl-p-cresol (BHT).

[0043] The primary antioxidant in the polypropylene film constituting the capacitor is almost entirely consumed during the molding process in the extruder and during the production of the capacitor, and almost none remains in the polypropylene film constituting the capacitor. Therefore, the content of the primary antioxidant in the polypropylene film constituting the capacitor may be 50 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 1 ppm or less, or may be 0 ppm.

[0044] The content of the primary antioxidant in the polypropylene film constituting the capacitor is the content in the polypropylene film constituting the capacitor after the capacitor has been manufactured, and is not the content in the polypropylene film prepared as a material for manufacturing the capacitor.

[0045] (Additives) The polypropylene film constituting the capacitor of the present invention may further contain additives, such as chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, and colorants.

[0046] (Metallized film) The capacitor of the present invention comprises a metallized film having a metal layer on one or both sides of the polypropylene film described above.

[0047] The metal layer functions as an electrode. Examples of metals that can be used for the metal layer include simple metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, mixtures of multiple types of these, and alloys of these. Among these, zinc and aluminum are preferred in terms of environmental load, economic efficiency, and excellent capacitor performance.

[0048] The method for laminating a metal layer on at least one side (one side or both sides) of a polypropylene film is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, etc. From the viewpoint of excellent productivity and economic efficiency, a vacuum deposition method is preferred. Examples of the vacuum deposition method include a crucible method and a wire method, and the most suitable method can be appropriately selected.

[0049] The margin pattern when laminating a metal layer by vapor deposition is not particularly limited, but from the viewpoint of further improving the safety of the capacitor and further suppressing destruction and short circuits of the capacitor, it is preferable to apply a pattern including a so-called special margin, such as a fishnet pattern or a T-margin pattern, on one side of the polypropylene film.

[0050] The method for forming the margin is not particularly limited, and the margin may be formed by a known method such as a tape method or an oil method.

[0051] The film resistance of the metal layer is not particularly limited, but is preferably 5 to 25 Ω / □, and more preferably 10 to 20 Ω / □.

[0052] The capacitor of the present invention is a capacitor including the above-mentioned metallized film. The metallized film can be laminated or wound by a conventionally known method to form a film capacitor.

[0053] The film capacitor may have a structure in which a plurality of metallized films are laminated, or may have a wound metallized film. Such a film capacitor can be suitably used as a capacitor for an inverter power supply device that controls a drive motor of an electric vehicle, a hybrid vehicle, etc. It can also be suitably used for railroad cars, wind power generation, solar power generation, general home appliances, etc.

[0054] 2. Polypropylene film manufacturing method The method for producing the polypropylene film used in producing the capacitor of the present invention is not particularly limited, and the film can be produced, for example, by a method including a step of melting a polypropylene resin composition containing at least a polypropylene resin and a secondary antioxidant, preferably at a temperature of 225°C or higher and 270°C or lower.

[0055] The method for preparing the polypropylene resin composition is not particularly limited, and examples thereof include a method in which a polymer powder or pellets of a polypropylene resin is mixed with a secondary antioxidant and other additives added as necessary, and then dry-blended using a mixer or the like, or a method in which the mixture is supplied to a kneader and melt-kneaded.

[0056] The mixer and kneader are not particularly limited. The kneader may be any of a single screw type, a twin screw type, and a multi-screw type having three or more screws. In the case of a twin or more screw type, the screws may rotate in the same direction or in opposite directions.

[0057] In the case of kneading by melt kneading, the kneading temperature is not particularly limited as long as a good kneaded product is obtained. In general, the kneading temperature is in the range of 200°C to 300°C, and from the viewpoint of suppressing deterioration of the resin, 230°C to 270°C is preferable. In addition, in order to suppress deterioration during kneading and mixing of the resin, an inert gas such as nitrogen may be purged into the kneader. The melt kneaded resin may be pelletized to an appropriate size using a generally known granulator. This allows the preparation of polypropylene resin pellets.

[0058] In the method for producing the polypropylene film, first, polypropylene resin pellets, dry-blended polypropylene resin pellets, or mixed polypropylene resin pellets previously prepared by melt kneading are fed into an extruder and heated to melt.

[0059] The polypropylene resin composition is preferably melted at 170° C. or more and 320° C. or less, and specifically, the extruder temperature during heating and melting the polypropylene resin composition is preferably set to 225° C. or more and 270° C. or less, which further improves the dielectric breakdown strength of the produced polypropylene film.

[0060] Next, the molten polypropylene resin composition is extruded into a sheet using a T-die, and cooled and solidified on at least one metal drum to form an unstretched cast sheet. The surface temperature of the metal drum (the temperature of the metal drum that first comes into contact after extrusion) is preferably 10° C. or higher and 105° C. or lower, more preferably 15° C. or higher and 100° C. or lower. The surface temperature of the metal drum can be determined depending on the physical properties of the polypropylene resin used, etc.

[0061] The thickness of the cast sheet is not particularly limited, but is preferably 50 μm or more and 2000 μm or less, and more preferably 100 μm or more and 1000 μm or less.

[0062] When the polypropylene film is a biaxially stretched polypropylene film, the biaxially stretched polypropylene film can be produced by subjecting the cast sheet to a biaxial stretching process. The stretching is preferably biaxial stretching in which the film is oriented biaxially in the longitudinal and transverse directions, and the stretching method is preferably a sequential biaxial stretching method. In the sequential biaxial stretching method, for example, the cast sheet is first kept at a temperature of 100°C to 180°C (preferably 120°C to 170°C) and stretched in the flow direction by passing it between rolls with a speed difference. The stretching ratio in the flow direction is preferably 3.0 times to 7.0 times, more preferably 4.0 times to 6.0 times. Next, the sheet is introduced into a tenter and stretched in the transverse direction. The temperature during the transverse stretching is preferably 160°C to 180°C, and the stretching ratio in the transverse direction is preferably 3 times to 11 times. Next, after the transverse stretching, the sheet is relaxed, heat-set, and wound up.

[0063] The biaxially oriented polypropylene film may be subjected to corona discharge treatment online or offline after the stretching and heat setting processes in order to further improve the adhesive properties in a post-process such as a metal deposition process. The corona discharge treatment can be performed using a known method. It is preferable to use air, carbon dioxide gas, nitrogen gas, or a mixture of these gases as the atmospheric gas.

[0064] A polypropylene film can be produced by the production method described above.

[0065] 3.Metallized film manufacturing method In the production of the capacitor of the present invention, a metallized film having a metal layer on one or both sides of the polypropylene film is used. The metallized film having such a configuration can be effectively used as a metallized film for a capacitor.

[0066] The metal layer functions as an electrode. Examples of metals that can be used for the metal layer include simple metals such as zinc, lead, silver, chromium, aluminum, copper, and nickel, mixtures of multiple types of these, and alloys of these. Among these, zinc and aluminum are preferred in terms of environmental load, economic efficiency, and excellent capacitor performance.

[0067] The method for laminating a metal layer on at least one side (one side or both sides) of a polypropylene film is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, etc. From the viewpoint of excellent productivity and economic efficiency, a vacuum deposition method is preferred. Examples of the vacuum deposition method include a crucible method and a wire method, and the most suitable method can be appropriately selected.

[0068] The margin pattern when laminating a metal layer by vapor deposition is not particularly limited, but from the viewpoint of further improving the safety of the capacitor and further suppressing destruction and short circuits of the capacitor, it is preferable to apply a pattern including a so-called special margin, such as a fishnet pattern or a T-margin pattern, on one side of the polypropylene film.

[0069] The method for forming the margin is not particularly limited, and the margin may be formed by a known method such as a tape method or an oil method.

[0070] The thickness of the metallized film is not particularly limited, and is preferably 1 to 20 μm, more preferably 1 to 10 μm, and even more preferably 1 to 6 μm.

[0071] The capacitor of the present invention is a capacitor including the metallized film. The metallized film can be used in the method for producing the capacitor of the present invention described below.

[0072] 4. Capacitor manufacturing method The method for producing a capacitor of the present invention is a method for producing a capacitor including a metallized film having a metal layer on one or both sides of a polypropylene film, the method comprising a step 1 of laminating or winding the metallized film, the polypropylene film containing a secondary antioxidant, and the capacitor having a C·IR product of 15ks or more. According to the production method of the present invention, the capacitor of the present invention can be easily produced. The production method of the present invention will be described below.

[0073] (Process 1) Step 1 is a step of laminating or winding a metallized film. The metallized film constituting the capacitor of the present invention described above can be used as the metallized film. By manufacturing a capacitor using the metallized film described above, the C·IR product of the capacitor can be adjusted to 15ks or more.

[0074] There are no particular limitations on the method for laminating or winding (element winding) the metallized film, and the film capacitor may be formed by laminating or winding using a conventionally known method.

[0075] The film capacitor may have a structure in which a plurality of metallized films are laminated, or may have a wound metallized film. Such a film capacitor can be suitably used as a capacitor for an inverter power supply device that controls a drive motor of an electric vehicle, a hybrid vehicle, etc. It can also be suitably used for railroad cars, wind power generation, solar power generation, general home appliances, etc.

[0076] In the manufacturing method of the present invention, after step 1, the wound metallized film may be subjected to a flattening treatment. The flattening treatment reduces unnecessary space and minimizes the volume of the element. The capacitance of the capacitor can be adjusted to an appropriate capacitance. The method of the flattening treatment is not particularly limited, and examples thereof include a method in which the metallized film wound around the element is pressed by a known method such as a press machine.

[0077] The manufacturing method of the present invention preferably includes a step of spraying metallikon onto the element end faces after the flattening treatment. By spraying metallikon onto the element end faces, it is possible to form lead electrodes on the capacitor.

[0078] (Process 2) The manufacturing method of the present invention may include step 2 of heating the laminated or wound metallized film after step 1. By including step 2 in the manufacturing method of the present invention, it becomes easier to adjust the C·IR product of the capacitor to 15ks or more.

[0079] The heating method is not particularly limited, and may be a conventionally known heating method. For example, the capacitor may be placed in a heating device such as a high-temperature bath or a vacuum thermostatic bath and heated. From the viewpoint of suppressing oxidation of the polypropylene film constituting the capacitor, it is preferable to heat the capacitor under vacuum conditions using a vacuum thermostatic bath.

[0080] The heating time (aging time) in step 2 is preferably 0.5 to 30 hours, more preferably 1 to 20 hours, even more preferably 1.5 to 18 hours, and particularly preferably 2 to 15 hours. When the lower limit of the heating time is within the above range, the insulation resistance (IR) is further improved, the C·IR product can be more easily adjusted to 15ks or more, and the capacitance change of the capacitor in a high-temperature, high-voltage environment is further suppressed. When the upper limit of the melting point is within the above range, the decrease in the content (residual amount) of the secondary antioxidant in the polypropylene film constituting the capacitor is suppressed, and the stability of the polypropylene film is further improved.

[0081] The heating temperature (aging temperature) in step 2 is preferably 100 to 130°C, and more preferably 105 to 120°C. By setting the lower limit of the heating temperature within the above range, the insulation resistance (IR) is further improved, the C·IR product can be more easily adjusted to 15ks or more, and the capacitance change of the capacitor in a high-temperature, high-voltage environment is further suppressed. By setting the upper limit of the heating temperature within the above range, the decrease in the content (residual amount) of the secondary antioxidant in the polypropylene film constituting the capacitor is suppressed, and the stability of the polypropylene film is further improved.

[0082] In the manufacturing method of the present invention, the content of the secondary antioxidant in the polypropylene film constituting the capacitor is preferably 1450 ppm or more, more preferably 1500 ppm, even more preferably 2000 ppm or more, and particularly preferably 2300 ppm or more. The content of the secondary antioxidant is preferably 4000 ppm or less, more preferably 3500 ppm or less, and even more preferably 3000 ppm or less. By setting the lower limit of the content of the secondary antioxidant within the above range, the decrease in capacitance of the capacitor in a high-temperature, high-voltage environment is further suppressed, and the capacitance change is further suppressed. By setting the upper limit of the content of the secondary antioxidant within the above range, the decrease in insulation resistance (IR) is further suppressed.

[0083] The manufacturing method of the present invention preferably includes a step of attaching a lead to the extraction electrode formed by the metallikon spraying after step 2. The material forming the lead is not particularly limited as long as it is conductive, and a known metal wire used as a capacitor lead, such as a copper wire, can be used.

[0084] In the manufacturing method of the present invention, after the leads are attached to the extraction electrodes as described above, the manufacturing method preferably includes the steps of placing the capacitor in a resin case, filling the gaps with epoxy resin, and curing the epoxy resin. Through these steps, a capacitor coated with epoxy resin can be obtained. EXAMPLES

[0085] The present invention will be described more specifically with reference to examples. However, these examples are for the purpose of illustrating the present invention and are not intended to limit the present invention in any way.

[0086] The raw materials used in the examples and comparative examples are as follows. (Polypropylene resin) Polypropylene resin: Prime Polymer Co., Ltd. MFR5g / 10min (Primary antioxidant) ·BHT: 2,6-di-tertiary-butyl-para-cresol (Secondary antioxidant) Secondary antioxidant A: Molecular weight 637, melting point 158.5±3℃, density 1.04g / cm 3 , Hindered phenol-based antioxidants that do not have a carbonyl group Secondary antioxidant B: Molecular weight 784, melting point 220.5±3℃, density 1.00g / cm 3 , Hindered phenol-based antioxidants that do not have a carbonyl group Secondary antioxidant C: molecular weight 775, melting point 242.5±3℃, density 1.05g / cm 3 , Hindered phenol-based antioxidants that do not have a carbonyl group Secondary antioxidant D: Molecular weight 587, melting point 77.5±1.5℃, density 1.14g / cm 3 , Hindered phenol-based antioxidants having a carbonyl group Secondary antioxidant E: Molecular weight 1178, melting point 117.5±7.5℃, density 1.15g / cm 3 , Hindered phenol-based antioxidants having a carbonyl group

[0087] Manufacturing of biaxially oriented polypropylene films <Examples and Comparative Examples> A primary antioxidant was added to the polypropylene resin described above at a content (prescription amount) of 1500 ppm. In addition, a secondary antioxidant shown in Table 1 was added at a content (prescription amount) of 3500 ppm. The mixture was then fed to an extruder and melt-kneaded at a temperature of 250°C to prepare resin pellets.

[0088] The resin pellets prepared as described above were fed to an extruder, melted under a temperature condition of a resin temperature of 250°C, and then extruded using a T-die. Next, the unstretched cast raw sheet 1 was produced by winding it around a metal drum whose surface temperature was kept at 95°C and solidifying it. The unstretched cast raw sheet 1 was kept at a temperature of 140°C, passed between rolls with a speed difference, stretched 4.5 times in the flow direction, and immediately cooled to room temperature. Next, the cast raw sheet 1 was introduced into a tenter, stretched 10 times in the width direction at a transverse stretching temperature of 158°C, and then relaxed and heat-set, and a biaxially stretched polypropylene film having a thickness of 2.3 μm was wound up. After the biaxially stretched polypropylene film was wound up, it was placed in an atmosphere of about 20 to 45°C for 24 hours and aged to produce a biaxially stretched polypropylene film.

[0089] Capacitor manufacturing A metallized film was produced by depositing aluminum on one side of the obtained biaxially oriented polypropylene film by vacuum deposition to form a metal layer. The metallized film was rolled to prepare an element, which was then pressed and flattened. The winding (element winding) was performed using an automatic winder 3KAW-N2 manufactured by Kaito Seisakusho Co., Ltd., by winding the laminated metallized films 1,350 turns under the conditions of a winding tension of 250 g, a contact pressure of 880 g, and a winding speed of 4 m / s. Metallicon was then sprayed onto the element end surface of the flattened element to form a film electrode lead-out portion.

[0090] The element with the film electrode lead-out portion formed was heated in a vacuum thermostatic chamber under the following thermal aging conditions by leaving it for the time shown in Table 1. Then, it was exposed to the atmosphere and left for an additional 30 minutes to produce a capacitor. [Heat aging conditions] Equipment: Espec vacuum thermostatic chamber (VAC-201) Heat aging temperature: 120℃ Pressure: Vacuum Aging time: The time shown in Table 1

[0091] For each of the examples and comparative examples, various characteristics were evaluated under the following measurement conditions.

[0092] Characterization The thickness of the biaxially oriented polypropylene film used in the manufacture of the capacitor was measured using an outside micrometer (high-precision digital micrometer MDH-25MB manufactured by Mitutoyo Corporation) according to the measurement method in accordance with JIS K 7130:199 Method A.

[0093] (Antioxidant content (residual amount) of biaxially oriented polypropylene film in capacitor) The biaxially oriented polypropylene film in the capacitor was taken and cut into pieces to prepare samples for extraction, which were then subjected to Soxhlet extraction with dichloromethane. The resulting extract was dissolved in methanol, and the secondary antioxidants in the extract were isolated using high performance liquid chromatography (HPLC) under the conditions shown below, and the content of the secondary antioxidants was quantitatively analyzed by absorbance. [HPLC measurement conditions] Measurement equipment: Waters Acquity UPLC-SQDetector2 Detector: Photodiode array detector Acquity PDA Column: ACQUITY BEH Phenyl (length 100 mm, inner diameter 2.1 mm, particle size 1.7 μm) Mobile phase: 100 mmol / L ammonium bicarbonate (containing 2.5% ammonia) / acetonitrile / water = 3 / 45 / 52 (v / v / v) → 3 / 94 / 3 (v / v / v) ·Flow rate: 0.6 mL / min, injection volume: 2 μL, quantitative wavelength: 220 nm

[0094] (C IR product) The capacitance (C) and insulation resistance (IR) were measured using the following method. The product of the measured capacitance (C) and insulation resistance (IR) was calculated to obtain the C·IR product.

[0095] <Capacitance (C)> A 4-Terminal Probe 9140 was attached to a Hioki E.E. Corporation LCR HiTester 3522-50. The two terminals (lead wires) of the capacitor were pinched with the 4-Terminal Probe 9140, and an AC voltage of 0.1 V, 1 kHz was applied using the built-in power supply of the LCR HiTester 3522-50. When the displayed value stabilized, the capacitance value was read. Measurement conditions other than those described here were in accordance with "4.2.2 Capacitance" of JIS C 5101-16:2009.

[0096] <Insulation resistance (IR)> A shielding box SME-8350 was connected to a Hioki E.E. Corporation super insulation resistance meter DSM8104. A capacitor was placed inside the shielding box and a DC voltage of 500V was applied. The insulation resistance value was read after 1 minute. Note that the measurement conditions other than those described here were in accordance with "4.2.4 Insulation resistance" of JIS C 5101-16:2009.

[0097] (Capacitance change rate during high temperature load test (life test)) The capacitor was placed in an environment of 115°C and a voltage of 750V was applied for 500 hours. The rate of change in capacitance before and after the test was calculated according to the following formula. Capacitance change rate (%) = {[(capacitance after test) - (capacitance before test)] / (capacitance before test)} x 100

[0098] The results of the above characteristic evaluations of the examples and comparative examples are shown in Table 1.

[0099] [Table 1]

Claims

1. A capacitor comprising a metallized film having a metal layer on one or both sides of a polypropylene film, The polypropylene film contains a secondary antioxidant; The content of the secondary antioxidant in the polypropylene film is 1450 ppm or more; The capacitor has a C-IR product of 15 ks or more. A capacitor characterized by:

2. 2. The capacitor of claim 1, wherein the C-IR product is greater than or equal to 23 ks.

3. 2. The capacitor of claim 1, wherein the content of the secondary antioxidant in the polypropylene film is 2000 ppm or more.

4. The capacitor of claim 1, wherein the secondary antioxidant has a melting point of 100 to 260°C.

5. 2. The capacitor of claim 1, wherein the weight average molecular weight of the secondary antioxidant is 500 to 2000.

6. 2. The capacitor of claim 1, wherein the secondary antioxidant is a hindered phenolic antioxidant.

7. 1. A method for producing a capacitor including a metallized film having a metal layer on one or both sides of a polypropylene film, comprising: Step 1 of laminating or winding the metallized film; The polypropylene film contains a secondary antioxidant; The capacitor has a C-IR product of 15 ks or more. A method for manufacturing a capacitor comprising the steps of:

8. After the step 1, a step 2 of heating the laminated or wound metallized film is provided, The method according to claim 7, wherein the heating time in step 2 is 1 to 20 hours.

9. The method according to claim 8, wherein the heating temperature in the step 2 is 100 to 130°C.

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