Dielectric resin film and film capacitor

Abstract

Provided is a dielectric resin film that makes it possible to form a film capacitor that has excellent self-recovery capability and does not easily lose capacitance when high voltage is applied. A dielectric resin film according to the present invention comprises: a dielectric resin film body that has two opposite principal surfaces; and one or more insulating protrusions that are provided on at least one of the principal surfaces. The density of the protrusions is at least 1 / cm2 but no more than 10 / cm2, the average height of the protrusions is at least 2 μm, and the average area of the protrusions as seen from the normal direction to the principal surface is at least 550 μm2.

Description

[Technical Field]

[0001] The present invention relates to a dielectric resin film and a film capacitor. [Background technology]

[0002] Film capacitors are known to have a high self-healing function. To further enhance this self-healing function, Patent Document 1 proposes dispersing a large number of nanoparticles on the surface of the dielectric film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-107394 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of Patent Document 1, many dispersed nanoparticles become the starting points for dielectric breakdown, and the capacitance of the film capacitor is likely to decrease when a high voltage is applied. An object of the present invention is to provide a dielectric resin film that can be used to form a film capacitor that has an excellent self-healing function and is resistant to a decrease in capacitance when a high voltage is applied. [Means for solving the problem]

[0005] The present invention provides a dielectric resin film body having two opposing main surfaces, and at least one insulating protrusion disposed on at least one of the main surfaces, the protrusion having a density of 1 piece / cm 2 More than 10 pieces / cm 2 The average height of the convex portions is 2 μm or more, and the average area of the convex portions as viewed from the normal direction of the main surface is 550 μm or less. 2 The above relates to the dielectric resin film.

[0006] The resin film body may include a cured product of a curable resin.

[0007] The cured product of the curable resin may have a urethane bond.

[0008] The resin film body may contain a reaction product of a first organic material having two or more hydroxyl groups in one molecule and a second organic material having two or more isocyanate groups in one molecule.

[0009] The first organic material may further include an aromatic ring.

[0010] The present invention also relates to a film capacitor comprising two or more dielectrics facing each other, a first metal layer interposed between the dielectrics, and a second metal layer facing the first metal layer via the dielectrics, wherein at least one of the dielectrics includes the above-mentioned dielectric resin film. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a dielectric resin film that can be used to form a film capacitor that has an excellent self-healing function and is resistant to a decrease in capacitance when a high voltage is applied. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 10 is a diagram illustrating a method for calculating the average height of a convex portion. [Figure 2] 1 is a longitudinal sectional view showing an example of a film capacitor of the present invention. [Figure 3] 1 is an image of the dielectric resin film produced in Example 1 photographed with a line sensor camera and processed. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Dielectric resin film] A film capacitor comprises two or more dielectrics facing each other, a first metal layer interposed between the dielectrics, and a second metal layer facing the first metal layer across the dielectric. A dielectric resin film (hereinafter sometimes simply referred to as a film) is typically used as the dielectric. A metal layer is usually formed on at least one main surface of the film. A film capacitor can be constructed by stacking or winding multiple films (hereinafter sometimes referred to as metallized films) with this metal layer (the former can be called a stacked film capacitor, and the latter can be called a wound film capacitor).

[0014] Film capacitors have a so-called self-healing function. When localized dielectric breakdown occurs in the film, the short-circuit current flowing at the breakdown point causes the metal layer to scatter, ensuring insulation. The short-circuit current also decomposes the film, generating gas. If there is a gap between films facing each other (in this case, "adjacent") via a metal layer, gas from the film is more likely to be released outside the capacitor, making the self-healing function more likely to be realized. However, since the area of the metal layer is reduced, the capacitance of the film capacitor usually decreases significantly.

[0015] In the present disclosure, in order to provide sufficient gaps between films and reduce film defects, bulky protrusions are arranged at a low density on at least one main surface of a dielectric resin film body. The average height of one or more bulky protrusions is 2 μm or more, and the average area is 550 μm. 2 The density of the protrusions is 1 / cm 2 More than 10 pieces / cm 2 This allows for both a high self-healing function and suppression of capacitance reduction.

[0016] The self-healing function can be evaluated by the failure mode when a high voltage is applied to a film capacitor for evaluation purposes. If the failure occurs in the open mode, the film capacitor can be judged to have a high self-healing function. If the failure occurs in the short mode, the film capacitor can be judged to have a poor self-healing function.

[0017] The rated voltage of a film capacitor is generally about 100V to 2000V. From the viewpoint of reliability, it is required that the capacitance does not decrease easily even when a voltage of about 115% to 250% (at least about 115% to 130%) of the rated voltage is applied to the film capacitor. A capacitor including a film according to the present disclosure does not decrease in capacitance even when a high voltage is applied. For example, even when a voltage of 115% or more of the rated voltage is applied to a capacitor including a film according to the present disclosure, 50% of the initial capacitance can be maintained. A small decrease in capacitance suggests a small degree of dielectric breakdown. Even when the degree of dielectric breakdown is small, failure due to a short circuit mode of the film capacitor is unlikely to occur.

[0018] (Convex part) The protrusions are insulating. One or more protrusions are arranged on at least one main surface of the resin film body (hereinafter sometimes simply referred to as the film body). The protrusions contribute to the formation of gaps between films. The protrusions can also be the starting point for dielectric breakdown.

[0019] The convex portions are identified by the following method. First, a probe beam is irradiated from one side of the film body, and the brightness of the reflected or transmitted light is measured. The average brightness value of the entire observation area is calculated, and a brightness value that is half or less of the average brightness value is determined within a certain area (e.g., 0.5 μm 2A continuous area (above) is identified. The area is specified to exclude dust and the like. This area is not on the same plane as other areas in the observation range, and includes parts that protrude from the above-mentioned surface of the film body, parts that are recessed from the above-mentioned surface of the film body, and crater-shaped areas with raised edges and recessed centers. Of the identified areas, those that include parts that protrude from the above-mentioned surface of the film body are considered to be convex parts. Convex parts also include areas that include partially recessed parts, such as the crater-shaped area mentioned above.

[0020] Whether or not the identified region includes a protruding portion can be determined, for example, by a method of determining using image analysis technology based on the captured image and the amount of change in brightness, a method of capturing an image of the region from diagonally above, etc. The protruding portion may be identified using a surface defect inspection device (for example, OMI-UL28 manufactured by Ayaha Engineering Co., Ltd.).

[0021] The protrusions may be arranged on at least one of the main surfaces of the film body. The protrusions arranged on at least one of the main surfaces may satisfy the above-mentioned size and density, and no protrusions may be arranged on the other main surface. Furthermore, protrusions that do not satisfy the above-mentioned size and density may be arranged on the other main surface. In particular, it is preferable that the protrusions be arranged on only one of the main surfaces of the film body, as this makes it easier to control the self-healing function and to suppress a decrease in capacitance.

[0022] The density of the convex parts is 1 piece / cm 2 More than 10 pieces / cm 2 The density of the protrusions is 1 / cm or less. 2 If the density is less than 2 / cm, it is difficult to form sufficient gaps between the films. 2 More than 3 pieces / cm is preferable. 2 More preferably, the density of the protrusions is 10 / cm 2 If the density exceeds , the number of breakdown points will be excessively large, resulting in a large decrease in capacitance. From the viewpoint of capacitance, the density of the protrusions should be 8 / cm 2 Preferably less than 6 pieces / cm 2The following is more preferred:

[0023] Even with such a low density, the large average height of the convex portions allows for sufficient gaps between the films. Furthermore, because the area of the convex portions is large, even when the film body is pressed in its thickness direction, the convex portions are less likely to be crushed, and gaps between the films are maintained. In the capacitor manufacturing process, multiple films are stacked or wound in an overlapping state, and may be pressed after stacking or winding. At this time, the film body may be pressed in its thickness direction.

[0024] The density of the convex portions was calculated by counting all the convex portions identified by the irradiation of the probe light in the observation area and dividing the number of convex portions by the area of the observation area. 2 More than 50cm 2 The following applies.

[0025] The average height of the convex portions is 2 μm or more. If the average height of the convex portions is less than 2 μm, it is difficult to form sufficient gaps between the films at the above density. In order to more easily form gaps between the films, the average height of the convex portions is preferably 2.5 μm or more, and more preferably 3 μm or more. The higher the convex portions, the more easily a sufficient gap is formed between the films. From the viewpoint of miniaturization and ensuring capacitance, the average height of the convex portions may be 20 μm or less, 15 μm or less, 8 μm or less, or 5 μm or less.

[0026] The size and density of the protrusions can also be determined from the film (or metallized film) extracted by disassembling the film capacitor.

[0027] The method for calculating the average height of the convex portions will be described with reference to FIG. First, six adjacent fields (Fields 1 to 6) are determined on the film. The size of each field is 1 cm. 2The six visual fields are arranged in two columns and three rows. The distance between the centers of the visual fields arranged horizontally is 2 cm. The distance between the centers of the visual fields arranged vertically is also 2 cm.

[0028] Using a laser microscope, the film thickness Hp is measured at all convex portions observed in each field of view. Separately, one point is arbitrarily selected from the areas other than the convex portions in each field of view, and the film thickness (i.e., the thickness of the film body) at the areas other than the convex portions is measured in the same manner. The average value of the thicknesses of the film body at these six points is the average thickness Ha of the film body. The average value of the values (Hp-Ha) obtained by subtracting the average thickness Ha from the thickness Hp of each convex portion is the average height of the convex portions. When convex portions are arranged on both main surfaces of the film body, the average height of the convex portions is calculated for each main surface.

[0029] It is not necessary for there to be any convexities within one field of view. However, the fields of view must be determined so that a total of 10 or more convexities are observed across the six fields of view. When viewed from the normal direction of the film, convexities that are entirely contained within the field of view are the subject of measurement; convexities that are only partially contained within the field of view are excluded.

[0030] The average area of the convex parts is 550 μm 2 The average area of the convex portions is 550 μm or more. 2 If the average area of the projections is less than 580 μm, it is difficult to maintain the gap between the films at the above density. 2 More than 650 μm is preferable. 2 More preferably, 700 μm or more 2 From the viewpoint of further suppressing the decrease in capacitance, the average area of the protrusions is preferably 2,000 μm 2 may be less than 1,500 μm 2 may be less than 1,000 μm 2 It may be the following:

[0031] The average area of the protrusions is calculated from the same observation range of the image as that used to calculate the density of the protrusions. The areas of all the protrusions identified as above are measured when viewed from the normal direction of the main surface of the film body, and the average value of these is the average area of the protrusions. When the protrusions are arranged on both main surfaces of the film body, the average area of the protrusions is calculated for each main surface.

[0032] When the average height of the convex portions is less than 2 μm, the density of the convex portions is 1 / cm 2 More than 10 pieces / cm 2 If the average height of the projections is less than 2 μm, it is not possible to form sufficient gaps between the films, and therefore the self-healing function is low. If the average height of the projections is less than 2 μm, the density of the projections is 10 / cm. 2 Over (e.g., 25 pieces / cm 2 However, the dielectric breakdown point increases, which tends to result in a large decrease in capacitance.

[0033] The average area of the convex parts is 550 μm 2 If the average area of the convex portions is less than 550 μm, the convex portions will be crushed by the force pressing the film body in the thickness direction, regardless of the density of the convex portions. Therefore, it is not possible to maintain the gap between the films. 2 If the density of the convex parts is less than 10 pieces / cm 2 Over (e.g., 25 pieces / cm 2 However, as mentioned above, the dielectric breakdown point increases, which tends to result in a large decrease in capacitance.

[0034] The material of the protrusions is not particularly limited as long as it is insulating. Representative insulating materials (insulators) include organic materials such as resins and rubber, and inorganic materials such as ceramics and glass.

[0035] The method for forming the convex portions is not particularly limited. The convex portions may be formed by disposing insulating particles on the surface of the film body. In this case, from the viewpoint of density control, it is desirable that the particles are fixed to the surface of the film body. The convex portions may be formed by subjecting the film body to roughening processing. The convex portions may be formed by forming an organic material containing insulating particles into a film. Alternatively, the convex portions may be formed integrally from the same material as the film body. In particular, from the viewpoints of productivity and suppression of contamination, it is preferable that the convex portions be formed integrally from the same material as the film body.

[0036] The protrusions formed integrally from the same material as the film body are formed, for example, by aggregation of a portion of the curable organic material when it is formed into a film or cured. In this case, various protrusions are formed irregularly on the surface of the film body. The aggregation of the organic material can be controlled by the film formation conditions, curing conditions, composition of the organic material, etc. The protrusions are more likely to be formed, for example, by increasing the proportion of the curing agent (the second organic material described below) or the proportion of the curing agent that is a polymer.

[0037] The shape of the protrusions is not particularly limited. The shape of the protrusions when viewed from the normal direction of the main surface of the film body may be, for example, circular (including elliptical), rectangular, other polygonal, or irregular. The shape of the protrusions when viewed from the thickness direction of the film body may also be semicircular, circular (including elliptical), rectangular, other polygonal, or irregular.

[0038] (organic material) The film body is dielectric. The film body contains, for example, a cured product of an organic material. The content of the cured product in the film body can be, for example, 90% by mass or more, further 95% by mass or more, particularly 98% by mass or more, with the upper limit being 100% by mass. The content of the cured product can be measured based on the change in mass before and after immersing the film body (or film) in a solvent such as toluene for 24 hours or more.

[0039] The film body may contain a cured product of a curable resin. The curable resin may be thermosetting or photocurable. Thermosetting resin refers to a resin that can be cured by heat. The curing method for obtaining a cured product of the thermosetting resin is not particularly limited. The curing method for the thermosetting resin may be heating or a method other than heating (e.g., irradiation with active energy rays, addition of a polymerization initiator, reaction with a curing agent, or self-polymerization). Photocurable resin refers to a resin that can be cured by active energy rays. The curing method for obtaining a cured product of the photocurable resin is also not particularly limited. The curing method for the photocurable resin may be irradiation with active energy rays or a method other than irradiation with active energy rays (e.g., heating, addition of a polymerization initiator, reaction with a curing agent, or self-polymerization). Examples of active energy rays include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays; electromagnetic waves such as X-rays and gamma rays; electron beams; proton beams; and neutron beams. A cured product of the curable resin can be obtained by curing a thermosetting resin or a photocurable resin by heating, irradiating with active energy rays, or by other methods.

[0040] The film body may contain a cured product of a curable resin as a main component, which can improve heat resistance. The main component is a component that accounts for 50% or more by mass of the film body.

[0041] Examples of the curable resin include phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, silicone resin, phenoxy resin, and curable polyimide.

[0042] The cured product of the curable resin may contain at least one of a urethane bond and a urea bond. The presence of a urethane bond and a urea bond can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR). The cured product of the curable resin may contain a urethane bond.

[0043] The film body may contain a reaction product of a first organic material (base material) having two or more hydroxyl groups per molecule and a second organic material (curing agent) having two or more isocyanate groups per molecule. This reaction product has urethane bonds. The hydroxyl groups of the first organic material react with the isocyanate groups of the second organic material to form urethane bonds, which are crosslinked structures, resulting in a cured product.

[0044] <First organic material> The first organic material has two or more hydroxyl groups per molecule. The hydroxyl equivalent of the first organic material may be, for example, 150 g / eq or more, further 200 g / eq or more, particularly 220 g / eq or more, and may be, for example, 400 g / eq or less, further 350 g / eq or less, particularly 300 g / eq or less.

[0045] The first organic material may be a compound further having an epoxy group. The number of epoxy groups in one molecule is 1 to 4, typically 2 to 3, and particularly 2. The epoxy group is typically bonded to the end of the main chain of the first organic material.

[0046] The first organic material may be linear or branched, and is typically linear.

[0047] Examples of the first organic material include polyvinyl acetal such as polyvinyl acetoacetal; polyhydroxy polyether such as phenoxy resin; and polyester polyol. Among them, the first organic material may have an aromatic ring and may be polyhydroxy polyether. The first organic material may be used alone or in combination of two or more.

[0048] The phenoxy resin may be, for example, a reaction product of a bisphenol compound, such as bisphenol A, bisphenol B, bisphenol C, bisphenol E, bisphenol F, or bisphenol G, with epichlorohydrin.

[0049] The weight-average molecular weight of the first organic material is not particularly limited. The weight-average molecular weight of the first organic material may be, for example, less than 75,000, 70,000 or less, or 40,000 or less. The weight-average molecular weight of the first organic material may be, for example, 2,000 or more, or 5,000 or more. In one embodiment, the weight-average molecular weight of the first organic material is 2,000 or more and less than 75,000.

[0050] In this specification, the weight average molecular weight can be measured by gel permeation chromatography (GPC) and can be specified as a converted value using polystyrene as a standard sample.

[0051] <Second organic material> The second organic material has two or more isocyanate groups per molecule. The isocyanate group equivalent of the second organic material may be, for example, 50 g / eq or more, further 70 g / eq or more, particularly 100 g / eq or more, and may be, for example, 200 g / eq or less, further 160 g / eq or less, particularly 140 g / eq or less.

[0052] Examples of the second organic material include monomers of compounds having an isocyanate group and their multimers. Examples of the monomers include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate; and modified products of the aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Examples of the multimers include dimers, trimers, and higher multimers of the aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples of the multimers include dimers such as uretdione compounds; trimers such as adducts, isocyanurates, and biurets; and polymeric polyisocyanates. The second organic material may be used alone or in combination of two or more.

[0053] Increasing the proportion of the polymeric second organic material makes it easier to form convex portions that satisfy the above-mentioned size. From this perspective, the molar occupancy rate of the polymeric second organic material of the entire second organic material is preferably 20 mol% or more, more preferably 25 mol% or more, and particularly preferably 30 mol% or more. From the same perspective, the molar occupancy rate of the polymeric second organic material of the entire second organic material is preferably 70 mol% or less, more preferably 60 mol% or less, and particularly preferably 50 mol% or less. In one embodiment, the molar occupancy rate of the polymeric second organic material of the entire second organic material is 20 mol% or more and 70 mol% or less.

[0054] When the proportion of the polymeric second organic material does not need to be considered in forming the convex portions, the molar proportion of the polymeric second organic material relative to the total second organic material may be 5 mol% or more, or 10 mol% or more. Similarly, the molar proportion of the polymeric second organic material relative to the total second organic material may be 70 mol% or less, 60 mol% or less, or 50 mol% or less. In one embodiment, the molar proportion of the polymeric second organic material relative to the total second organic material is 5 mol% or more and 70 mol% or less.

[0055] The mass ratio of the first organic material to the second organic material is not particularly limited. Increasing the proportion of the second organic material makes it easier to form convex portions that satisfy the above-mentioned size. In this respect, the mass ratio of the second organic material to the total of the first organic material and the second organic material is preferably 15% by mass or more, more preferably 20% by mass or more, and particularly preferably 25% by mass or more. In order to easily control the density of the convex portions within the above range, the mass ratio of the second organic material to the above total is preferably 50% by mass or less, more preferably 45% by mass or less, and particularly preferably 40% by mass or less. In one embodiment, the mass ratio of the second organic material to the above total is 15% by mass or more and 50% by mass or less.

[0056] When the proportion of the second organic material does not need to be considered in forming the convex portions, the mass proportion of the second organic material with respect to the total may be 10% by mass or more, 20% by mass or more, or 30% by mass or more. Similarly, the mass proportion of the second organic material with respect to the total may be 80% by mass or less, 70% by mass or less, or 60% by mass or less. In one embodiment, the mass proportion of the second organic material with respect to the total is 10% by mass or more and 60% by mass or less.

[0057] The molar ratio (NCO / OH) of the isocyanate groups contained in the second organic material to the hydroxyl groups contained in the first organic material may be, for example, 0.9 or more, or even 1 or more, and particularly 1.1 or more, and may be, for example, 2 or less, or even 1.5 or less, and particularly 1.3 or less.

[0058] (others) The film body may contain other additives, such as a leveling agent. The additives may be physically or chemically bonded to the cured product of the first organic material and the second organic material, or may not be bonded. If the additive has a hydroxyl group, an epoxy group, a silanol group, a carboxyl group, or the like, the additive may be chemically bonded (covalently bonded) to the cured product of the first organic material and the second organic material.

[0059] The film body may contain unreacted first and / or second organic materials. In this case, the film body has one or both of hydroxyl groups and isocyanate groups. The presence of hydroxyl groups or isocyanate groups in the film body can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0060] The average thickness Ha of the film body is not particularly limited. The average thickness Ha of the film body may be 5 μm or less, 3.5 μm or less, or 3.4 μm or less. The average thickness Ha of the film body may be 0.5 μm or more. The average thickness Ha of the film body is the average thickness of the film in the portions other than the convex portions, and is calculated as described above.

[0061] [Method of manufacturing dielectric resin film] A method for manufacturing a film having protrusions integrally formed from the same material as the film body will be described below, although the method for manufacturing a film according to the present disclosure is not limited thereto.

[0062] The dielectric resin film is manufactured by a method including, for example, the steps of: (1) mixing the first organic material, the second organic material, and a solvent to prepare a resin solution; (2) applying the resin solution to a substrate to form a coating film; (3) drying the coating film to remove the solvent to form a dry coating film; and (4) heating and curing the dry coating film.

[0063] (1) Resin solution preparation process In this step, the first organic material, the second organic material, and a solvent are mixed together. The solvent is not particularly limited as long as it can dissolve the first organic material and the second organic material. Examples of the solvent include ketone solvents such as methyl ethyl ketone and diethyl ketone; and ether solvents such as tetrahydrofuran and tetrahydropyran. The solvents may be used alone or in combination of two or more.

[0064] Among these, a mixture of a ketone solvent and an ether solvent is preferred. The proportion of the ketone solvent in the mixture may be, for example, 10% by mass or more, further 30% by mass or more, particularly 40% by mass or more, and may be, for example, 90% by mass or less, further 70% by mass or less, particularly 60% by mass or less.

[0065] The total concentration of the first organic material and the second organic material in the resin solution can be, for example, 15% by mass or more and 25% by mass or less. When the mass ratio of the second organic material is 15% by mass or more and 50% by mass or less of the total of the first organic material and the second organic material, convex portions satisfying the above-mentioned size and density are easily formed. When the molar ratio of the polymeric second organic material is 5% by mol or more and 70% by mol or less of the total second organic material, convex portions satisfying the above-mentioned size and density are easily formed.

[0066] The resin solution may contain a catalyst, which can increase the reaction rate between the first organic material and the second organic material. Examples of the catalyst include amine compounds such as triethylamine, tributylamine, and triethylenediamine; organometallic compounds such as titanium tetrabutoxide, dibutyltin oxide, dibutyltin dilaurate, zinc naphthenate, cobalt naphthenate, tin octoate, and dibutyltin dilaurate; and inorganic compounds such as iron chloride and zinc chloride.

[0067] The prepared resin solution may be subjected to high-pressure homogenization, mechanical homogenization, or ultrasonic homogenization, which further enhances the dispersibility of each organic material.

[0068] (2) Coating process In this step, the prepared resin solution is applied to a substrate so that the average thickness Ha of the film body after curing is 0.5 μm or more and 5 μm or less.

[0069] A typical example of the substrate is a resin substrate, and examples of the resin constituting the resin substrate include polyester resins such as polyethylene terephthalate.

[0070] Examples of the coating method include roll coating methods such as reverse roll coating, gravure coating, roll coating, die coating and bar coating; curtain coating; spray coating; and dip coating.

[0071] (3) Drying process In this step, the coating film is dried. Drying is typically carried out by heating. The drying temperature may be, for example, 40°C or higher, further 50°C or higher, particularly 60°C or higher, and may be, for example, 150°C or lower, further 130°C or lower, particularly 120°C or lower.

[0072] (4) Curing process In this step, the coating film is heated to a temperature equal to or higher than the drying temperature, which promotes the reaction between the first organic material and the second organic material, resulting in a cured film.

[0073] The temperature at which the coating is cured (curing temperature) may be, for example, 100°C or higher, further 120°C or higher, particularly 140°C or higher, and may be, for example, 170°C or lower, further 165°C or lower, particularly 160°C or lower.

[0074] [Film capacitors] A film capacitor comprises two or more dielectrics facing each other, a first metal layer interposed between the dielectrics, and a second metal layer facing the first metal layer across the dielectric. Two adjacent dielectrics face each other across the metal layer. In a film capacitor, the metal layers and dielectrics are usually arranged alternately. A film is typically used as the dielectric.

[0075] At least one dielectric includes the dielectric resin film according to the present disclosure. The dielectrics may be the same or different in configuration. From the viewpoint of self-healing function and suppression of capacitance reduction, it is preferable that all of the dielectrics be the dielectric resin film according to the present disclosure.

[0076] (metal layer) The first metal layer and the second metal layer (hereinafter sometimes collectively referred to as the metal layers) function as internal electrodes. The metal layer may contain, for example, at least one selected from the group consisting of aluminum, titanium, zinc, magnesium, tin, and nickel, and may typically contain aluminum. The configurations of the metal layers may be the same or different.

[0077] The thickness of each metal layer is, for example, 5 nm to 40 nm, and can be measured by cutting the metallized film in the thickness direction and observing the cut surface using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

[0078] The metal layer can be formed on at least one main surface of the film by, for example, vapor deposition or sputtering. Alternatively, the metal layer can be a metal foil. By laminating the metal foil on the film and pressing or rolling, the metal foil and the film are brought into close contact with each other. In particular, when the metal layer is formed by vapor deposition, a thin metal layer that is in close contact with the film can be obtained, and an excellent self-healing function can be easily obtained.

[0079] A metal layer is typically formed on one main surface of a film. For example, a first metal layer is formed on one main surface of a film. A second metal layer is formed on one main surface of another film. In this case, a film including the first metal layer (first metallized film) and a film including the second metal layer (second metallized film) are arranged so that either film is interposed between the first metal layer and the second metal layer.

[0080] The metal layer formed on the dielectric resin film according to the present disclosure may be provided on the main surface on which the convex portions are arranged, or on the other main surface. Typically, the metal layer is provided on the main surface on which the convex portions of the film are arranged.

[0081] In the film capacitor, the first metallized film and the second metallized film may be wound in a superimposed state, or may be a laminated type in which the first metallized film and the second metallized film are laminated in the thickness direction. The film capacitor may further include a winding shaft used for winding. Hereinafter, a wound body and a laminated body including a dielectric (typically a dielectric resin film) and a metal layer may be collectively referred to as a capacitor element.

[0082] The cross-sectional shape of the capacitor element may be circular, elliptical, or oval, and from the viewpoint of miniaturization and low profile, it may be typically elliptical or oval. By pressing a capacitor element having a circular cross-sectional shape, a capacitor element having an elliptical or oval cross-sectional shape can be obtained.

[0083] The configuration of the capacitor element is not limited to one comprising a first metallized film and a second metallized film, but may have any suitable configuration as long as it comprises two or more dielectrics facing each other, a first metal layer interposed between the dielectrics, and a second metal layer facing the first metal layer via the dielectric.

[0084] (external terminal electrode) The film capacitor further includes external terminal electrodes. The external terminal electrodes are usually arranged on two opposing end faces of the capacitor element. For example, in a wound film capacitor, two external terminal electrodes are arranged so as to cover both end faces of the capacitor element in the direction of the winding axis. One of the external terminal electrodes (first external terminal electrode) is electrically connected to the first metal layer. The other external terminal electrode (second external terminal electrode) is electrically connected to the second metal layer. The configurations of the external terminal electrodes may be the same or different.

[0085] The external terminal electrodes are typically formed by metal spraying. Examples of metal species include zinc, aluminum, tin, and zinc-aluminum alloys. The thickness of the external terminal electrodes is not particularly limited. For example, the thickness of the external terminal electrodes is 0.5 mm or more and 3 mm or less.

[0086] Hereinafter, a film capacitor according to the present disclosure will be described in detail with reference to the drawings. However, the shape and arrangement of the film capacitor and each component of the following embodiments are not limited to the examples shown in the drawings.

[0087] FIG. 1 shows a wound film capacitor 1. The film capacitor 1 includes a capacitor element 5, a first external terminal electrode 6a, and a second external terminal electrode 6b. The capacitor element 5 is formed by winding a first metallized film 4a and a second metallized film 4b in a stacked state. The first external terminal electrode 6a and the second external terminal electrode 6b are formed at both ends of the capacitor element 5 in the width direction (winding axis direction) W, and are electrically connected thereto (more specifically, to the first metal layer 3a and the second metal layer 3b, respectively, as described below).

[0088] The first metallized film 4a comprises a first film 2a and a first metal layer 3a provided on one surface of the first film 2a. The second metallized film 4b comprises a second film 2b and a second metal layer 3b provided on one surface of the second film 2b. At least one of the first film 2a and the second film 2b is a film according to the present disclosure.

[0089] The first film 2a and the second film 2b face each other. The first metal layer 3a and the second metal layer 3b face each other with the first film 2a or the second film 2b interposed therebetween. The first metal layer 3a is electrically connected to the first external terminal electrode 6a. The second metal layer 3b is electrically connected to the second external terminal electrode 6b.

[0090] The first metal layer 3a is formed on one surface of the first film 2a so as to reach one side edge of the first film 2a but not the other side edge. Typically, the first metal layer 3a is formed so as to reach the side edge on the side where the first metal layer 3a is electrically connected to the first external terminal electrode 6a but not the opposite side edge. The second metal layer 3b is formed on one surface of the second film 2b so as to not reach one side edge of the second film 2b but the other side edge. Typically, the second metal layer 3b is formed so as to reach the side edge on the side where the second metal layer 3b is electrically connected to the second external terminal electrode 6b but not the opposite side edge.

[0091] In the capacitor element 5, the first metallized film 4a and the second metallized film 4b are arranged so as to be offset from each other in the width direction W. Typically, the first metallized film 4a is arranged so that the end of the first metallized film 4a, where the first metal layer 3a reaches the side edge of the first film 2a, is exposed from the second metallized film 4b, and the second metallized film 4b is arranged so that the end of the second metallized film 4b, where the second metal layer 3b reaches the side edge of the second film 2b, is exposed from the first metallized film 4a. The first metallized film 4a and the second metallized film 4b are thus overlapped with an offset and wound to form the capacitor element 5. In the capacitor element 5, the first metal layer 3a and the second metal layer 3b are exposed at their ends.

[0092] 1, second metallized film 4b is overlapped and wound around first metallized film 4a so as to be located outside first metallized film 4a in radial direction T. First metallized film 4a is arranged so that the main surface on which first metal layer 3a is provided faces inward in radial direction T, and second metallized film 4b is arranged so that the main surface on which second metal layer 3b is provided faces inward in radial direction T.

[0093] The first external terminal electrode 6a contacts an exposed end of the first metal layer 3a, thereby electrically connecting the first external terminal electrode 6a and the first metal layer 3a. Typically, the first metal layer 3a contacts the first external terminal electrode 6a while protruding in the width direction W relative to the first external terminal electrode 6a. The second external terminal electrode 6b contacts an exposed end of the second metal layer 3b, thereby electrically connecting the second external terminal electrode 6b and the second metal layer 3b. Typically, the second metal layer 3b contacts the second external terminal electrode 6b while protruding in the width direction W relative to the second external terminal electrode 6b.

[0094] [Film capacitor manufacturing method] A method for manufacturing a wound film capacitor including a metallized film will be described below, although the method for manufacturing a film capacitor according to the present disclosure is not limited thereto.

[0095] A wound film capacitor is manufactured by a method including, for example, a step of forming a metal layer on one main surface of a dielectric resin film to obtain a metallized film, a step of stacking and rolling two or more metallized films to obtain a capacitor element, and a step of forming external terminal electrodes on both ends of the capacitor element in the winding axis direction. At least one of the dielectric resin films constituting the metallized film is a film according to the present disclosure.

[0096] The metal layer is formed by, for example, vapor deposition. The metal layer is typically provided on the main surface of the film on which the protrusions are arranged. The external terminal electrodes are formed by, for example, metal spraying. [Example]

[0097] The present disclosure will be explained in more detail with reference to the following examples, but the present disclosure is not limited thereto. [Example 1] (i) Preparation of dielectric resin film A reaction vessel was charged with 56 parts by mass of polyhydroxypolyether (phenoxy resin (bisphenol A-type epoxy resin) which is a reaction product of bisphenol A and epichlorohydrin, weight average molecular weight 50,000, hydroxyl group equivalent 284 g / eq, containing epoxy groups) as the first organic material and 30 parts by mass of 4,4'-diphenylmethane diisocyanate (MDI, a mixture of monomers and polymers) as the second organic material, and the resulting mixture was mixed with 400 parts by mass of a mixed solvent of methyl ethyl ketone (MEK) and tetrahydrofuran (THF) in a mass ratio of 1:1 to obtain a resin solution.

[0098] The resulting resin solution was applied to a polyethylene terephthalate (PET) substrate using a gravure coater so that the thickness after curing would be 3.5 μm. The coating was then heated to 100°C or higher in a drying oven and thoroughly dried until the solvent content was 0.5% or less, yielding a dried coating film. The resulting dried coating film was cured by heat treatment at 150°C for approximately 4 hours, yielding a dielectric resin film. Multiple protrusions were formed on the main surface of the dielectric resin film opposite the substrate.

[0099] (ii) Fabrication of film capacitors Fluorine-based oil was applied to the main surface of the dielectric resin film on which the protrusions were formed to form an electrode pattern. Aluminum was vapor-deposited onto this main surface of the film using a vacuum vapor deposition device to produce a metallized film with an electrode pattern. The resulting metallized film was cut to a specified width and length. Two cut sheets of metallized film were then stacked and wound together to obtain a capacitor element. External terminal electrodes were formed on both ends of the capacitor element in the winding axis direction by metal spraying, resulting in a film capacitor (rated voltage 850 V).

[0100] [Examples 2 to 3, Comparative Examples 1 to 3] Dielectric resin films and film capacitors were prepared in the same manner as in Example 1, except that the mass ratio of the second organic material to the total of the first organic material and the second organic material and / or the molar ratio of the polymer in the second organic material were changed as shown in Table 1.

[0101] [Example 4] Dielectric resin films and film capacitors were produced in the same manner as in Example 1, except that polyvinyl acetoacetal (weight average molecular weight 120,000) was used as the first organic material, tolylene diisocyanate (TDI, a mixture of monomers and polymers) was used as the second organic material, and the mass ratio of the second organic material to the total of the first organic material and the second organic material and the molar ratio of polymers in the second organic material were changed as shown in Table 1.

[0102] [Example 5] A film capacitor was produced in the same manner as in Example 1, except that a dielectric resin film was produced as follows. (i) Preparation of dielectric resin film A mixed resin solution was prepared by adding 0.1 wt% imidazole as a catalyst for the thermosetting reaction to a mixed resin prepared by mixing phenoxy resin and epoxy resin (novolac-type epoxy resin) in a ratio of phenoxy resin / epoxy resin = 80% by mass / 20% by mass. 100 parts by mass of the mixed resin solution obtained was mixed with 400 parts by mass of a mixed solvent prepared by mixing methyl ethyl ketone (MEK) and toluene in a mass ratio of 1:1 in a reaction vessel to obtain a resin solution.

[0103] The resulting resin solution was applied to a PET substrate using a gravure coater so that the thickness after curing would be 3.5 μm. The coating was then heated to 100°C or higher in a drying oven and thoroughly dried until the solvent content was 0.5% or less, yielding a dried coating film. The resulting dried coating film was cured by heat treatment at 150°C for approximately 4 hours, yielding a dielectric resin film. Multiple protrusions were formed on the main surface of the dielectric resin film opposite the substrate.

[0104] [evaluation] The dielectric resin film and film capacitor obtained were evaluated as follows. The evaluation results are shown in Table 1.

[0105] (1) Calculating the density of the convex parts and measuring the area The principal surface of the film opposite the substrate was photographed from the normal direction using a line sensor camera (OMI-UL28, manufactured by Ayaha Engineering Co., Ltd., resolution 2.8 μm), and the image was processed to identify the convexities present within an observation range of 45 mm × 95 mm. The number of identified convexities was counted and divided by the area of the observation range (45 mm × 95 mm) to calculate the density of the convexities.

[0106] Furthermore, the areas of all the identified convex portions were measured. The average of these areas was taken as the average area of the convex portions. Figure 3 shows an image of the film of Example 1 taken with a line sensor camera and processed. The dots represent the convex portions. 43 convex portions were identified in this image.

[0107] (2) Measuring the height of the convex part Six visual fields were determined from the film (area 45 mm × 95 mm) according to Figure 1. Using a laser microscope (VK-8700, Keyence Corporation), the film thickness Hp of all convex portions observed in each visual field was measured. Separately, one point was arbitrarily selected from the area other than the convex portions in each visual field, and the film thickness (i.e., the thickness of the film body) of the area other than the convex portions was measured in the same manner. The average value of the film body thicknesses at these six points was taken as the average thickness Ha of the film body. The average value (Hp - Ha) obtained by subtracting the average thickness Ha from the thickness Hp of each convex portion was taken as the average height of the convex portions.

[0108] (3) Measurement of withstand voltage (evaluation of suppression of capacitance reduction) The capacitance when a voltage of 700V was applied to the film capacitor in an atmosphere of 125°C was taken as the initial value C0. The capacitance of the film capacitor was measured while the voltage applied was increased stepwise from 700V at an electric field strength of 50V / μm every hour. The applied voltage when the capacitance was 50% of the initial value C0 was taken as the withstand voltage. Film capacitors with a withstand voltage of 1000V or more were rated as good, those with a withstand voltage of 950V or more but less than 1000V were rated as acceptable, and film capacitors with a withstand voltage of less than 950V were rated as poor. It can be said that the higher the withstand voltage, the more the decrease in capacitance is suppressed.

[0109] (4) Self-healing function In the above-mentioned withstand voltage evaluation, the voltage was increased stepwise until the film capacitor failed, and the failure mode was confirmed. A film capacitor that had zero capacitance due to an open-mode failure was rated as good, and a film capacitor that had a short-mode failure was rated as bad.

[0110] [Table 1]

[0111] The films produced in Examples 1 to 3 had a density of 1 particle / cm 2 More than 10 pieces / cm 2 Average height is 2 μm or more, and average area is 550 μm or less 2 As a result, the resulting film capacitor exhibited excellent self-healing properties and high withstand voltage.

[0112] Although the materials of the main body and the protrusions of the films produced in Examples 4 and 5 were different from those of the films in Examples 1 to 3, the resulting film capacitors exhibited the same self-healing function and withstand voltage as those in Examples 1 to 3. This indicates that regardless of the materials of the main body and the protrusions, the film capacitors produced in Examples 4 and 5 exhibited the same self-healing function and withstand voltage as those in Examples 1 to 3. 2 More than 10 pieces / cm 2 Average height is 2 μm or more, and average area is 550 μm or less 2 If the above conditions are met, it is understood that an excellent self-healing function and a high withstand voltage can be obtained.

[0113] On the other hand, the density of the convex portions of the film produced in Comparative Example 1 was 1 / cm 2 More than 10 pieces / cm 2 and the average height is 2 μm or more, but the average area is 550 μm or less 2 Therefore, the resulting film capacitor has poor self-healing properties. This is thought to be because the protrusions were crushed during the production of the capacitor, and a sufficient gap could not be secured between the films.

[0114] The convex portions of the film produced in Comparative Example 2 had a density of 1 piece / cm 2 More than 10 pieces / cm 2 and the average area is 550 μm or less. 2 However, the average height is less than 2 μm, which means that sufficient gaps cannot be secured between the films, and the resulting film capacitor has poor self-healing properties.

[0115] The convex portions of the film produced in Comparative Example 3 had an average height of 2 μm or more and an average length of 30 μm or more, but the density was 1 / cm 2 Therefore, sufficient gaps cannot be secured between the films, resulting in poor self-healing properties. The convex portions of the film produced in Comparative Example 4 have an average height of 2 μm or more and an average area of 550 μm. 2 Although the density is 10 particles / cm 2 Therefore, the number of dielectric breakdown points increases, and the resulting film capacitor has poor withstand voltage. [Industrial Applicability]

[0116] The dielectric resin film of the present disclosure is used in a film capacitor. This film capacitor has an excellent self-healing function and is resistant to a decrease in capacitance when a high voltage is applied, and therefore is applicable to a variety of electronic devices.

[0117] This application claims priority based on Japanese Patent Application No. 2022-070235, filed on April 21, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0118] 1. Film capacitor 2a First Film 2b Second Film 3a First Metal Layer 3b Second metal layer 4a First metallized film 4b Second metallized film 5 Capacitor elements 6a First external terminal electrode 6b Second external terminal electrode W width direction T Radial direction

Claims

1. a dielectric resin film body having two opposing main surfaces; At least one insulating protrusion is disposed on at least one of the main surfaces, The density of the protrusions is 1 piece / cm ２ More than 10 pieces / cm ２ is as follows: The average height of the convex portions is 2 μm or more, The average area of the convex portions as viewed from the normal direction of the main surface is 550 μm ２ This is the dielectric resin film.

2. The dielectric resin film according to claim 1 , wherein the resin film body includes a cured product of a curable resin.

3. The dielectric resin film according to claim 2 , wherein the cured product of the curable resin has a urethane bond.

4. The dielectric resin film according to claim 1, wherein the resin film body comprises a reaction product of a first organic material having two or more hydroxyl groups per molecule and a second organic material having two or more isocyanate groups per molecule.

5. The dielectric resin film according to claim 4 , wherein the first organic material further has an aromatic ring.

6. Two or more dielectrics facing each other; a first metal layer interposed between the dielectric layers; a second metal layer facing the first metal layer with the dielectric interposed therebetween; A film capacitor, wherein at least one of the dielectrics comprises the dielectric resin film according to any one of claims 1 to 5.

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