DIELECTRIC RESIN FILM AND FILM CONDENSER

Abstract

A dielectric resin film capable of forming a film capacitor with excellent self-healing properties and an electrostatic capacitance that hardly decreases at high voltage. The dielectric resin film comprises: a dielectric resin film body having two opposing main surfaces; and at least one insulating projection arranged on at least one of the main surfaces, the projections, each identical to the at least one insulating projection, having a density of 1 piece / cm² when viewed from a normal direction to the main surfaces. 2 or more and 10 pieces / cm 2 or less, the protrusions have an average height of 2 µm or more and the protrusions have an average area of ​​550 µm² 2 or more.

Description

TECHNICAL FIELD

[0001] The present invention relates to a dielectric resin film and a film capacitor. STATE OF THE ART

[0002] Film capacitors are known to have a high self-healing capability. Patent Document 1 proposes dispersing a large number of nanoparticles on the surface of a dielectric film to further improve the self-healing capability. PRIOR ART DOCUMENT PATENT DOCUMENT

[0003] Patent Document 1: JP-A-2014-107394 PRESENTATION OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] However, in the method in Patent Document 1, a large number of dispersed nanoparticles serve as the starting point for insulation breakdown, and the electrostatic capacitance of a film capacitor therefore tends to decrease when a high voltage is applied.

[0005] An object of the present invention is therefore to provide a dielectric resin film capable of forming a film capacitor having an excellent self-healing ability and an electrostatic capacitance that hardly decreases when a high voltage is applied. SOLUTIONS TO THE PROBLEMS

[0006] The present invention relates to a dielectric resin film comprising: a dielectric resin film body having two main surfaces opposite each other; and at least one insulating protrusion disposed on at least one of the main surfaces, wherein the protrusions, each of which is identical to the at least one insulating protrusion, have a density of 1 piece / cm when viewed from a normal direction of the main surfaces 2 or more and 10 pieces / cm 2or less, the projections have an average height of 2 µm or more and the projections have an average area of ​​550 µm 2 or more.

[0007] The resin film body may contain a cured product of a curable resin.

[0008] The cured product of the curable resin may have a urethane bond.

[0009] 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.

[0010] The first organic material may further comprise an aromatic ring.

[0011] The present invention also relates to a film capacitor comprising: two or more dielectrics opposed to each other; a first metal layer sandwiched between the dielectrics; and a second metal layer opposed to the first metal layer, one of the dielectrics being sandwiched between the first and second metal layers, wherein at least one of the dielectrics comprises the above-described dielectric resin film. EFFECTS OF THE INVENTION

[0012] According to the present invention, it is possible to provide a dielectric resin film capable of forming a film capacitor having an excellent self-healing ability and an electrostatic capacitance that hardly decreases when a high voltage is applied. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig.1 is a diagram for explaining a method for calculating the average height of projections. [ Fig. 2] Fig. 2 is a longitudinal sectional view showing an example of a film capacitor of the present invention. [ Fig. 3] Fig. 3 is an image after a dielectric resin film prepared in Example 1 was photographed by a line sensor camera and subjected to image processing. DETAILED DESCRIPTION[Dielectric Resin Film]

[0013] A film capacitor comprises two or more dielectrics facing each other, a first metal layer sandwiched between the dielectrics, and a second metal layer facing the first metal layer, with one of the dielectrics sandwiched between them. A dielectric resin film (hereinafter referred to simply as a film) is typically used as the dielectric. The metal layer is usually formed on at least one major surface of the film. The film capacitor may comprise a plurality of films (hereinafter referred to as metallized films) formed in a laminated state or wound in an overlapped state, each film having this metal layer (the former may be referred to as a laminated film capacitor, and the latter may be referred to as a wound film capacitor).

[0014] The film capacitor has a so-called self-healing function. The self-healing function is a function of dispersion when a local insulation breakdown occurs in a film, a metal layer due to a short-circuit current flowing at the breakdown point to ensure insulation. Furthermore, the film is decomposed by the short-circuit current, so that gas is generated. In a case where there is a gap between the opposing films (in this case, "side by side") and the metal layer is sandwiched between them, the gas originating from the films is easily released to the outside of the capacitor, and the self-healing function is thus easily recognized. On the other hand, the electrostatic capacitance of the film capacitor is generally greatly reduced because the area of ​​the metal layer is reduced.

[0015] In the present disclosure, bulky protrusions are arranged in low density on at least one main surface of a dielectric resin film body, while a sufficient gap is provided between the films to reduce film defects. The average height of one or more bulky protrusions is 2 µm or more, and the average area is 550 µm. 2 or more. The density of the protrusions is 1 piece / cm 2 or more and 10 pieces / cm 2 or less. Therefore, both the high self-healing capability and the minimization of a decrease in electrostatic capacity are achieved.

[0016] The self-healing capability is determined by a failure mode, for example, when a high voltage is applied to the film capacitor, causing it to fail. If the failure occurs in an open mode, it can be determined that the film capacitor has a high self-healing capability. In a case where the failure occurs in a short-circuit mode, it can be determined that the film capacitor has a lower self-healing capability.

[0017] The film capacitor generally has a rated voltage of about 100 V to 2000 V. From the viewpoint of reliability, it is required that the electrostatic capacitance hardly decreases 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. In the capacitor using the films according to the present disclosure, the electrostatic capacitance hardly decreases even when a high voltage is applied. For example, even when a voltage of 115% or more of the rated voltage is applied to the capacitor using the films according to the present disclosure, 50% of the original electrostatic capacitance can be maintained. The fact that the electrostatic capacitance hardly decreases indicates that the degree of insulation breakdown is low. Even if the degree of insulation breakdown is low, failure due to a short circuit of the film capacitor hardly occurs. (Projection)

[0018] A protrusion has an insulating property. One or more protrusions are arranged on at least one main surface of the resin film body (hereinafter referred to simply as the film body). The protrusions contribute to the formation of a gap between the films. The protrusions can also serve as a starting point for insulation breakdown.

[0019] The protrusions are determined according to the following procedure. First, a surface of the film body is irradiated with probe light, and the luminance of the reflected or transmitted light is measured. The average luminance value of the entire observation area is calculated to define a range in which luminance values ​​equal to or less than half of the average luminance value continue in a constant range (for example, 0.5 µm). 2or more). The area is selected such that dust and other contaminants are removed. This area is not coplanar with the other area of ​​the observation area and includes a part protruding from the above-described surface of the film body, a part recessed from the above-described surface of the film body, a crater-shaped part in which the edge is raised and the central part is recessed, and other parts. Among the specified areas, an area having portions protruding from the above-described surface of the film body is defined as projections. The projections also include an area having a partially depressed portion such as in the above-described crater shape.

[0020] Whether the specified area has protrusions can be determined, for example, by a determination method using an image analysis technique based on a captured image and luminance variation, a method of obliquely scanning the area, or other methods. The protrusions can be determined 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 main surface of the film body. It is sufficient that the protrusions arranged on at least one main surface satisfy the above-described size and density, and the protrusions may not be arranged on the other main surface. Furthermore, protrusions that do not satisfy the above-described size and density may be arranged on the other main surface. In particular, the protrusions are preferably arranged only on one main surface of the film body in order to easily control the self-healing ability and minimize a decrease in electrostatic capacity.

[0022] The density of the protrusions is 1 piece / cm 2 or more and 10 pieces / cm 2 or less. In a case where the density of the protrusions is less than 1 piece / cm 2, it is difficult to create a sufficient distance between the films. The density of the projections is preferably 2 pieces / cm 2 or more, and particularly preferably 3 pieces / cm 2 or more to facilitate the formation of a gap between the films. In a case where the density of the projections is more than 10 pieces / cm 2 , the number of insulation breakdown points is too high, resulting in a sharp decrease in electrostatic capacity. From the perspective of electrostatic capacity, the density of the protrusions is preferably 8 pieces / cm 2 or less, and particularly preferably 6 pieces / cm 2 or less.

[0023] Since the average height of the protrusions is high, sufficient spacing can be achieved between the films even when the density is low as described above. Furthermore, since the area of ​​the protrusions is large, the protrusions are hardly crushed, and the spacing between the films is maintained even when the film body is pressed in its thickness direction. In a method for manufacturing the capacitor, a plurality of films may be wound in a laminated or overlapped state, and optionally pressed after lamination or winding. In this case, the film body may be pressed in its thickness direction.

[0024] The density of protrusions is determined by counting all protrusions determined by the irradiation of the probe light in the observation area and dividing the number of these protrusions by the area of ​​the observation area. The observation area is 40 cm. 2 or more and 50 cm 2or less.

[0025] The average height of the protrusions is 2 μm or more. In a case where the average height of the protrusions is less than 2 μm, it is difficult to form a sufficient gap between the films at the above-described density. The average height of the protrusions is preferably 2.5 μm or more, and more preferably 3 μm or more, to facilitate the formation of a gap between the films. The higher the protrusions are, the easier it is to form a sufficient gap between the films. From the viewpoint of miniaturization and ensuring electrostatic capacity, the average height of the protrusions 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 are also determined from a foil (or metallized foil) obtained by decomposing the film capacitor.

[0027] A method for calculating the average height of the projections is described with reference to Fig. 1 described.

[0028] First, six adjacent fields of view (fields 1 to 6) are determined on a slide. The size of each field of view is 1 cm. 2 The six fields of view are arranged in two horizontal rows and three vertical rows. The distance between the centers of the horizontally aligned fields of view is 2 cm. The distance between the centers of the vertically aligned fields of view is 2 cm.

[0029] The thicknesses Hp of all film protrusions observed in each field of view are measured using a laser microscope. Separately, an arbitrary point is selected from the area not belonging to the protrusions in each field of view, and the film thickness (i.e., the thickness of the film body) at the area not belonging to the protrusions is measured in the same way. The average value of the film body thicknesses at the six points is defined as the average thickness Ha of the film body. The mean of the values ​​(Hp - Ha), obtained by subtracting the average thickness Ha from the thicknesses Hp of each protrusion, is the average height of the protrusions. If the protrusions are located on both main surfaces of the film body, the average height of the protrusions is calculated for each main surface.

[0030] No protrusions may be present in a field of view. However, the fields of view are defined such that a total of 10 or more protrusions are observed in the six fields of view. When viewed from the normal direction of the film, a protrusion that is completely contained within the field of view is subject to measurement, and a protrusion that is only partially contained within the field of view is not subject to measurement.

[0031] The average area of ​​the protrusions is 550 µm 2 or more. In a case where the average area of ​​the projections is less than 550 µm 2 , it is difficult to maintain a gap between the films with the density described above. The average area of ​​the projections is preferably 580 µm 2 or more, more preferably 650 µm 2 or more and particularly preferably 700 µm 2or more to make it easier to maintain the gap between the films. The average area of ​​the projections can be 2000 µm 2 or less, 1500 µm 2 or less or 1000 µm 2 or less to further minimize a decrease in electrostatic capacity.

[0032] The average protrusion area is calculated from the observation area of ​​the same image used to calculate the protrusion density. The area of ​​all protrusions specified as described above, viewed from the normal direction of the main surface of the film body, is measured, and the average value is used as the average protrusion area. In a case where the protrusions are located on both main surfaces of the film body, the average protrusion area is calculated for each main surface.

[0033] In a case where the average height of the protrusions is less than 2 µm and the density of the protrusions is 1 piece / cm 2 or more and 10 pieces / cm 2 or less, a sufficient gap cannot be formed between the films. Therefore, the self-healing ability decreases. In a case where the average height of the protrusions is less than 2 µm, the self-healing ability can be improved if the density of the protrusions is more than 10 pieces / cm 2 (for example about 25 pieces / cm 2 ). However, as the number of insulation breakdown points increases, the decrease in electrostatic capacity is likely to be large.

[0034] In a case where the average area of ​​the projections is less than 550 µm 2, the protrusions are crushed by the force pushing the film body in the direction of its thickness, regardless of the density of the protrusions. Therefore, a distance between the films cannot be maintained. In a case where the average area of ​​the protrusions is less than 550 µm 2 the ability of self-healing can be improved if the density of the protrusions is more than 10 pieces / cm 2 (for example about 25 pieces / cm 2 ). However, since the number of insulation breakdown points increases as described above, the decrease in electrostatic capacity is likely to be large.

[0035] There are no restrictions regarding the material of the protrusions, as long as the material has insulating properties. Typical examples of a material with insulating properties (insulators) are organic materials such as resin and rubber, and inorganic materials such as ceramics and glass.

[0036] The method for forming the protrusions is not limited. The protrusions may be formed by applying insulating particles to the surface of the film body. In this case, the particles are desirably fixed to the surface of the film body from the viewpoint of density control. The protrusions may be formed by embossing the film body. The protrusions may be formed by forming a film from an organic material containing insulating particles. Alternatively, the protrusions may be formed from the same material as the film body. Particularly from the viewpoints of productivity, pollution reduction, and other factors, the protrusions are preferably formed from the same material as the film body.

[0037] The protrusions, which are integrally formed from the same material as that of the film body, are formed, for example, by a portion of a curable organic material aggregating during film formation or curing. In this case, various protrusions are irregularly formed on the surface of the film body. The aggregation of the organic material can be controlled by the film formation conditions, the curing conditions, the composition of the organic material, and other conditions. The protrusions can be easily formed, for example, by increasing the proportion of a curing agent (a second organic material described later), by increasing the proportion of a curing agent as a multimer, or by other means.

[0038] The shape of the protrusions is not limited. The shape of the protrusions, viewed from the normal direction of the main surface of the film body, can be, for example, a circle (including an ellipse), a rectangle, another polygon, or an indeterminate shape. The shape of the protrusions viewed from the thickness direction of the film body can also be, for example, a circle (including an ellipse), a rectangle, another polygon, or an indeterminate shape. (Organic material)

[0039] The film body is dielectric. The film body contains, for example, a cured product made of an organic material. In the film body, the content of the cured product can be, for example, 90 mass percent or more, furthermore 95 mass percent or more, or particularly 98 mass percent or more, and the upper limit can be 100 mass percent. The above-described content of the cured product can be measured by the mass change before and after immersing the film body (or film) in a solvent such as toluene for 24 hours or more.

[0040] The film body may contain a cured product of a curable resin. The curable resin may be thermosetting or light-curing. A thermosetting resin is a resin that can be cured by heat. A curing method for obtaining a cured product of a thermosetting resin is not limited. A method for curing the thermosetting resin may be heating or a method other than heating (for example, irradiation with active energy rays, addition of a polymerization initiator, reaction with a curing agent, and self-polymerization). A photocurable resin is a resin that can be cured by active energy rays. A curing method for obtaining a cured product of the photocurable resin is also not limited.A method for curing the photocurable resin can be irradiation with high-energy rays or a method other than irradiation with high-energy rays (for example, heating, addition of a polymerization initiator, reaction with a curing agent, and self-polymerization). Examples of high-energy rays include light rays such as far ultraviolet, ultraviolet, near ultraviolet, and infrared; electromagnetic waves such as X-rays and γ-rays; electron beams, proton beams, and neutron beams. The cured product of the curable resin is obtained by curing the thermosetting resin or the photocurable resin by heating, irradiation with active energy rays, or other methods.

[0041] The film body can contain the cured product of the curable resin as the main component. This can improve heat resistance. The main component is a component that accounts for 50% or more by mass of the film body.

[0042] Examples of the curable resin are a phenolic resin, an epoxy resin, a melamine resin, a urea resin, an unsaturated polyester resin, a silicone resin, a phenoxy resin and a curable polyimide.

[0043] The cured product made from the curable resin may contain at least one urethane bond or one urea bond. The presence of a urethane bond or a urea bond can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR). The cured product made from the curable resin may contain a urethane bond.

[0044] The film body may contain a reaction product of a first organic material (base agent) having two or more hydroxyl groups in one molecule and a second organic material (curing agent) having two or more isocyanate groups in one molecule. This reaction product has a urethane bond. The hydroxyl groups of the first organic material and the isocyanate groups of the second organic material react with each other to form a urethane bond, which is a crosslinked structure, thereby obtaining a cured product. <Erstes organisches Material>

[0045] The first organic material has two or more hydroxyl groups in one molecule. The hydroxyl equivalent of the first organic material can be, for example, 150 g / eq. or more, furthermore 200 g / eq. or more, in particular 220 g / eq. or more, and can be, for example, 400 g / eq. or less, furthermore 350 g / eq. or less, in particular 300 g / eq. or less.

[0046] The first organic material may be a compound further comprising an epoxy group. The number of epoxy groups in a molecule is 1 or more and 4 or less, typically 2 or more and 3 or less, and especially 2. The epoxy group in the first organic material is typically bonded to one end of the main chain.

[0047] The first organic material can be linear or branched, but is usually linear.

[0048] Examples of the first organic material include polyvinyl acetal such as polyvinyl acetoacetal, polyhydroxypolyethers such as a phenoxy resin, and polyester polyols. In particular, the first organic material may have an aromatic ring and be a polyhydroxypolyether. The first organic material is used alone or in combination with two or more types.

[0049] The phenoxy resin can, for example, be a reactant of a bisphenol compound such as bisphenol A, bisphenol B, bisphenol C, bisphenol E, bisphenol F or bisphenol G and epichlorohydrin.

[0050] The weight-average molecular weight of the first organic material is not 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.

[0051] In the present specification, the weight-average molecular weight can be measured by gel permeation chromatography (GPC) and expressed as a conversion value using polystyrene as a standard sample. <Zweites organisches Material>

[0052] The second organic material has two or more isocyanate groups in one molecule. The isocyanate equivalent of the second organic material can be, for example, 50 g / eq or more, furthermore 70 g / eq or more, in particular 100 g / eq or more, and, for example, 200 g / eq or less, furthermore 160 g / eq or less, in particular 140 g / eq or less.

[0053] Examples of the second organic material include a monomer of a compound having an isocyanate group and a multimer thereof. Examples of the monomer include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate; and modified products of the above-described aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Examples of multimers include dimers, trimers, and higher multimers of aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Specific examples of multimers include dimers such as uretdione; trimers such as adducts, isocyanurates, and biurets; polymeric polyisocyanates, and other multimers.The second organic material is used alone or in combination of two or more types of it.

[0054] In a case where the proportion of the second organic material as a multimer is increased, a protrusion satisfying the above-described size is easily formed. From this point of view, the proportion of the second organic material as a multimer is preferably 20 mol% or more, more preferably 25 mol% or more, and particularly preferably 30 mol% or more, on a molar basis, of the total second organic material. From the same point of view, the fractional occupancy of the second organic material as a multimer is preferably 70 mol% or less, more preferably 60 mol% or less, and particularly preferably 50 mol% or less, on a molar basis, of the total second organic material. In one aspect, the fractional occupancy of the second organic material as a multimer is preferably 20 mol% or more and 70 mol% or less, on a molar basis, of the total second organic material.

[0055] In the formation of the protrusions, in a case where the proportion of the second organic material as a multimer does not need to be considered, the proportion of a multimer on a molar basis may be 5 mol% or more, or 10 mol% or more. Similarly, the proportion of a multimer on a molar basis with respect to the entire second organic material may be 70 mol% or less, 60 mol% or less, or 50 mol% or less. In one aspect, the proportion of the second organic material as a multimer on a molar basis is 5 mol% or more and 70 mol% or less of the entire second organic material.

[0056] The mass ratio between the first organic material and the second organic material is not limited. In a case where the proportion of the second organic material is increased, a protrusion satisfying the above-described size is easily formed. In this connection, the mass proportion of the second organic material with respect to the total amount of the first organic material and the second organic material is preferably 15 mass % or more, more preferably 20 mass % or more, and particularly preferably 25 mass % or more. The mass proportion of the second organic material with respect to the total amount described above is preferably 50 mass % or less, more preferably 45 mass % or less, and particularly preferably 40 mass % or less, from the viewpoint that the density of the protrusions can be easily controlled within the above-described range.In one embodiment, the mass fraction of the second organic material with respect to the total amount described above is 15 mass percent or more and 50 mass percent or less.

[0057] In the formation of the protrusions, in a case where the proportion of the second organic material need not be considered, the mass fraction of the second organic material with respect to the above-described total amount may be 10 mass % or more, 20 mass % or more, or 30 mass % or more. Similarly, the mass fraction of the second organic material with respect to the above-described total amount may be 80 mass % or less, 70 mass % or less, or 60 mass % or less. In one embodiment, the mass fraction of the second organic material with respect to the above-described total amount is 10 mass % or more and 60 mass % or less.

[0058] The molar ratio of the isocyanate groups contained in the second organic material to the hydroxyl groups contained in the first organic material (NCO / OH) may be, for example, 0.9 or more, furthermore 1 or more, in particular 1.1 or more, and for example 2 or less, furthermore 1.5 or less, in particular 1.3 or less. (More)

[0059] The film body may contain further additives. Examples of an additive include a leveling agent and other additives. The additive may or may not be physically or chemically bonded to the cured product of the first organic material and the second organic material. If the additive has a hydroxyl group, an epoxy group, a silanol group, a carboxyl group, or other functional groups, the additive may be chemically (covalently) bonded to the cured product of the first organic material and the second organic material.

[0060] The film body may contain unreacted substances of the first organic material and / or the second organic material. In this case, the film body has either a hydroxyl group or an isocyanate group, or both. The presence of a hydroxyl group or an isocyanate group in the film body can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0061] The average thickness Ha of the film body is not limited. The average thickness Ha of the film body can be 5 µm or less, 3.5 µm or less, or 3.4 µm or less. The average thickness Ha of the film body can be 0.5 µm or more. The average thickness Ha of the film body is an average thickness of the film at a portion other than the protrusions, which is calculated as described above. [Method for producing a dielectric resin film]

[0062] A method for producing a film provided with protrusions formed integrally from the same material as the film body will be described below. However, the method for producing a film according to the present disclosure is not limited thereto.

[0063] The dielectric resin film is manufactured, for example, by a method comprising: (1) a step of preparing a resin solution by mixing the first organic material, the second organic material, and a solvent; (2) a step of coating a base material with the resin solution to form a coating film; (3) a step of drying the coating film and removing the solvent to form a dry coating film; and (4) a step of heating and curing the dry coating film. (1) Step for preparing the resin solution

[0064] In this step, the first organic material, the second organic material and the solvent are mixed.

[0065] The solvent is not 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 solvent can be used alone or in combination with two or more types.

[0066] In particular, 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 mass percent or more, furthermore 30 mass percent or more, especially 40 mass percent or more, and may be, for example, 90 mass percent or less, furthermore 70 mass percent or less, especially 60 mass percent or less.

[0067] The total concentration of the first organic material and the second organic material in the resin solution may be, for example, 15 mass % or more and 25 mass % or less. In a case where the mass fraction of the second organic material is 15 mass % or more and 50 mass % or less of the total amount of the first organic material and the second organic material, protrusions satisfying the above-described size and density are easily formed. In a case where the molar fraction of the second organic material as a multimer is 5 mol % or more and 70 mol % or less of the total second organic material, protrusions satisfying the above-described size and density are easily formed.

[0068] The resin solution may contain a catalyst. This 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 octylate, and dibutyltin dilaurate; inorganic compounds such as ferric chloride and zinc chloride; and other catalysts.

[0069] The prepared resin solution can be subjected to high-pressure homogenization, mechanical homogenization, or ultrasonic homogenization. This further improves the dispersibility of any organic material. (2) Coating step

[0070] In this step, the base material is coated with the prepared resin solution. For example, the resin solution is coated so that the average thickness Ha of the film body after curing is 0.5 µm or more and 5 µm or less.

[0071] Typical examples of the base material include a resin base material. Examples of a resin constituting the resin base material include polyester resins such as polyethylene terephthalate.

[0072] Examples of a coating method include roll coating methods such as reverse roll coating method, gravure coating method, roller coating method, die coating method and bar coating method, curtain coating method, spray coating method and dip coating method. (3) Drying step

[0073] In this step, the coating film is dried. Drying is usually achieved by heating.

[0074] The drying temperature may be, for example, 40°C or higher, furthermore 50°C or higher, in particular 60°C or higher, and it may be, for example, 150°C or lower, furthermore 130°C or lower, in particular 120°C or lower. (4) Curing step

[0075] In this step, the coating film is heated to a temperature equal to or higher than the drying temperature. This heating accelerates the reaction between the first organic material and the second organic material to produce a cured film.

[0076] The temperature for curing the coating film (curing temperature) may be, for example, 100°C or higher, furthermore 120°C or higher, in particular 140°C or higher, and may be, for example, 170°C or lower, furthermore 165°C or lower, in particular 160°C or lower. [Film capacitor]

[0077] A film capacitor contains two or more dielectrics facing each other, a first metal layer sandwiched between the dielectrics, and a second metal layer opposite the first metal layer, with one of the dielectrics sandwiched between them. The two adjacent dielectrics are arranged opposite each other, with a metal layer sandwiched between them. In a film capacitor, the metal layers and the dielectrics are typically arranged alternately. A film is typically used as the dielectric.

[0078] At least one dielectric comprises the dielectric resin film according to the present disclosure. The dielectrics may have the same or different configurations. It is preferable that all dielectrics be the dielectric resin film according to the present disclosure from the perspective of self-healing capability and minimizing a decrease in electrostatic capacitance. (metal layer)

[0079] A first metal layer and a second metal layer (hereinafter collectively referred to as the metal layer) serve as internal electrodes. The metal layer contains, for example, at least one element from the group consisting of aluminum, titanium, zinc, magnesium, tin, and nickel, and can typically contain aluminum. Each metal layer can have the same or a different configuration.

[0080] The thickness of each metal layer is, for example, 5 nm or more and 40 nm or less. The thickness of the metal layer can be measured by cutting a metallized film in the thickness direction and observing the cut surface with an electron microscope, such as a field emission scanning electron microscope (FE-SEM).

[0081] The metal layer can be formed on at least one main surface of the film, for example, by vapor deposition or sputtering. Alternatively, the metal layer can also be a metal foil. The metal foil is laminated onto the film, and the metal foil and the film are pressed and wound to bring them into close contact with each other. Particularly, in a case where the metal layer is formed by vapor deposition, a thin metal layer in close contact with the film can be obtained, and excellent self-healing ability can be easily obtained.

[0082] The metal layer is typically formed on at least one main surface of the foil. For example, the first metal layer is formed on one main surface of one foil. The second metal layer is formed on one main surface of another foil. In this case, a foil (first metallized foil) provided with the first metal layer and a foil (second metallized foil) provided with the second metal layer are arranged such that any foil is sandwiched between the first metal layer and the second metal layer.

[0083] The metal layer formed on the dielectric resin film according to the present disclosure may be provided on the main surface on which the protrusions are arranged or on the other main surface. Typically, the metal layer is applied to the main surface of the film on which the protrusions are arranged.

[0084] In the film capacitor, the first metallized film and the second metallized film may be a wound type in which the first metallized film and the second metallized film are wound in an overlapping state, and 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 axis 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.

[0085] The cross-sectional shape of the capacitor element can be circular, elliptical, or oval, and is typically elliptical or oval due to its small size and low profile. The capacitor element with a circular cross-sectional shape can be pressed to form a capacitor element with an elliptical or oval cross-sectional shape.

[0086] The configuration of the capacitor element is not limited to a configuration having the first metallized film and the second metallized film, and the capacitor element may have any suitable configuration as long as it is provided with two or more opposing dielectrics, a first metal layer interposed between the dielectrics, and a second metal layer opposing the first metal layer and interposing one of the dielectrics. (Outer connection electrode)

[0087] The film capacitor further includes external terminal electrodes. The external terminal electrodes are typically arranged at two opposite end faces of the capacitor element. In a wound film capacitor, for example, the external terminal electrodes are arranged at two locations 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 of the external terminal electrodes (second external terminal electrode) is electrically connected to the second metal layer. The external terminal electrodes can have the same or different configurations.

[0088] The external terminal electrodes are typically manufactured by metal spraying. Examples of metals include zinc, aluminum, tin, and zinc-aluminum alloys. There is no limit to the thickness of individual external terminal electrodes. For example, the thickness of each external terminal electrode is 0.5 mm or more and 3 mm or less.

[0089] The film capacitor according to the present disclosure will be described in detail below with reference to the drawings. However, the shape, arrangement, and other details of the film capacitor and each component of the following embodiments are not limited to the illustrated examples.

[0090] Fig.2 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 configured by winding a first metallized film 4a and a second metallized film 4b in a state where the first metallized film 4a and the second metallized film 4b overlap each other. The first external terminal electrode 6a and the second external terminal electrode 6b are respectively formed at both end portions in a width direction (winding axis direction) W of the capacitor element 5 and are electrically connected thereto (more specifically, as described later, to the first metal layer 3a and the second metal layer 3b, respectively).

[0091] The first metallized film 4a includes a first film 2a and a first metal layer 3a provided on a surface of the first film 2a. The second metallized film 4b includes a second film 2b and a second metal layer 3b provided on a surface of the second film 2b. At least one of the two films, the first film 2a or the second film 2b, is a film within the meaning of the present disclosure.

[0092] The first foil 2a and the second foil 2b are arranged opposite each other. The first metal layer 3a and the second metal layer 3b are arranged opposite each other, with the first foil 2a or the second foil 2b in between. 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.

[0093] The first metal layer 3a is formed on a surface of the first foil 2a such that it reaches one side edge of the first foil 2a, but not the other side edge. Typically, the first metal layer 3a is formed such that it reaches the side edge at which 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 a surface of the second foil 2b such that it does not reach one side edge of the second foil 2b, but reaches the other side edge. Typically, the second metal layer 3b is formed such that it reaches the side edge at which the second metal layer 3b is electrically connected to the second external terminal electrode 6b, but not the opposite side edge.

[0094] In the capacitor element 5, the first metallized film 4a and the second metallized film 4b are shifted from each other in the width direction W. Typically, the first metallized film 4a is arranged such that an end portion where the first metal layer 3a reaches a side edge of the first film 2a is exposed from the second metallized film 4b, and the second metallized film 4b is arranged such that an end portion where the second metal layer 3b reaches a 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 superimposed and wound in such a shifted manner, thereby forming the capacitor element 5. In the capacitor element 5, the first metal layer 3a and the second metal layer 3b are exposed at their end portions.

[0095] In Fig.2, the second metallized foil 4b is overlapped and wound to lie outside the first metallized foil 4a in a radial direction T. Furthermore, the first metallized foil 4a is arranged such that the main surface on which the first metal layer 3a is provided faces inward in the radial direction T, and the second metallized foil 4b is arranged such that the main surface on which the second metal layer 3b is provided faces inward in the radial direction T.

[0096] The first external terminal electrode 6a is in contact with the exposed end portion of the first metal layer 3a, so that the first external terminal electrode 6a and the first metal layer 3a are electrically connected. Typically, the first metal layer 3a is in contact with the first external terminal electrode 6a in a state where it protrudes in the width direction W with respect to the first external terminal electrode 6a. The second external terminal electrode 6b is in contact with the exposed end portion of the second metal layer 3b, so that the second external terminal electrode 6b and the second metal layer 3b are electrically connected. Typically, the second metal layer 3b is in contact with the second external terminal electrode 6b in a state where it protrudes in the width direction W with respect to the second external terminal electrode 6b. [Method for manufacturing a film capacitor]

[0097] A method for manufacturing a wound film capacitor with metallized films is described below. However, the method for manufacturing a film capacitor according to the present disclosure is not limited thereto.

[0098] The wound film capacitor is manufactured, for example, by a method including a step of forming a metal layer on a main surface of a dielectric resin film to obtain a metallized film; a step of overlapping and winding two or more metallized films to obtain a capacitor element; and a step of forming external terminal electrodes at both end portions in a winding axis direction of the capacitor element. At least one dielectric resin film constituting the metallized film is the film according to the present disclosure.

[0099] The metal layer is formed, for example, by vapor deposition. The metal layer is usually located on the main surface of the foil on which the projections are arranged. The external connection electrodes are formed, for example, by spraying metal. Examples

[0100] The present disclosure will be further described with reference to the following examples, but the present disclosure is not limited thereto. [Example 1](i) Preparation of a dielectric resin film

[0101] In a reaction vessel, 56 mass parts of polyhydroxypolyether (phenoxy resin (bisphenol A type epoxy resin), which is a reactant of bisphenol A and epichlorohydrin, weight-average molecular weight: 50,000, hydroxyl equivalent: 284 g / eq, containing epoxy groups) as the first organic material and 30 mass parts of 4,4'-diphenylmethane diisocyanate (MDI, mixture of monomer and multimer) as the second organic material were charged and mixed with 400 mass parts of a mixed solvent obtained by mixing methyl ethyl ketone (MEK) and tetrahydrofuran (THF) in a mass ratio of 1:1 to obtain a resin solution.

[0102] The resulting resin solution was coated onto a polyethylene terephthalate (PET) base material using a gravure coating machine to achieve a cured thickness of 3.5 µm. Subsequently, the coated base material was heated in a drying oven at 100°C or higher and sufficiently dried until the solvent content was 0.5% or less to obtain a dry coating film. The resulting dry coating film was cured by heat treatment at 150°C for about 4 hours to obtain a dielectric resin film. A plurality of protrusions were formed on a main surface opposite to the base material of the dielectric resin film. (ii) Manufacturing a film capacitor

[0103] A 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 then evaporated onto the main surface of this film using a vacuum evaporation system to produce a metallized film with an electrode pattern. The resulting metallized film was cut to a predetermined width and length. Then, the two cut metallized films were superimposed and wound to form a capacitor element. External terminal electrodes were formed at both end portions of the capacitor element in the direction of the winding axis by metal spraying to obtain a film capacitor (rated voltage: 850 V). [Examples 2 to 3, Comparative Examples 1 to 3]

[0104] Dielectric resin film and film capacitors were prepared in the same manner as in Example 1, except that the mass fraction of the second organic material with respect to the total amount of the first organic material and the second organic material and / or the molar fraction of the multimer in the second organic material were changed as shown in Table 1. [Example 4]

[0105] A dielectric resin film and a film capacitor were prepared 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 and tolylene diisocyanate (TDI, a mixture of monomer and multimer) was used as the second organic material, and the mass fraction of the second organic material to the total amount of the first organic material and the second organic material and the molar fraction of the multimer in the second organic material were changed as shown in Table 1. [Example 5]

[0106] A film capacitor was prepared in the same manner as in Example 1 except that a dielectric resin film was prepared as follows. (i) Preparation of a dielectric resin film

[0107] A mixed resin solution was prepared by adding 0.1 wt% of imidazole as a thermal curing reaction catalyst to a mixed resin obtained by mixing a phenoxy resin and an epoxy resin (novolak-type epoxy resin) in a mixing ratio of phenoxy resin / epoxy resin = 80 mass % / 20 mass %. In a reaction vessel, 100 parts by mass of the resulting mixed resin solution and 400 parts by mass of a mixed solvent obtained by mixing methyl ethyl ketone (MEK) and toluene in a mass ratio of 1:1 were mixed to obtain a resin solution.

[0108] The resulting resin solution was coated onto a PET base material using a gravure coating machine so that the curing thickness was 3.5 µm. Subsequently, the coated base material was heated in a drying oven at 100°C or higher and sufficiently dried until the solvent content was 0.5% or less to obtain a dry coating film. The resulting dry coating film was cured by heat treatment at 150°C for about 4 hours to obtain a dielectric resin film. A plurality of protrusions were formed on a main surface opposite to the base material of the dielectric resin film. [Evaluation]

[0109] The resulting dielectric resin film and film capacitor were evaluated as follows. The evaluation results are shown in Table 1. (1) Calculating the density of the protrusions and measuring the area

[0110] The main surface of the film opposite the base material was imaged from the normal direction by a line-scan camera (OMI-UL28, manufactured by AYAHA ENGINEERING CO., LTD., resolution: 2.8 µm), and image processing was performed to determine the protrusions present in the 45 mm × 95 mm observation area. The number of detected protrusions was counted and divided by the area (45 mm × 95 mm) of the observation area to calculate the protrusion density.

[0111] Furthermore, the areas of all indicated protrusions were measured. The average value of the areas was used as the average area of ​​the protrusions. Fig. Figure 3 is an image taken after the film in Example 1 was captured by the line-scan camera and subjected to image processing. The dots represent protrusions. 43 protrusions were identified in this image. (2) Measuring the height of the projection

[0112] From the foil (area 45 mm × 95 mm) six fields of view were cut according to Fig. 1. The thicknesses Hp of all the protrusions in the film observed in each field of view were measured using a laser microscope (VK-8700, manufactured by KEYENCE CORPORATION). Separately, an arbitrary point was selected from the area not belonging to the protrusions in each field of view, and the thickness of the film (i.e., the thickness of the film body) at the area not belonging to the protrusions was measured in the same way. The average value of the film body thicknesses at the six points was defined as the average thickness Ha of the film body. The mean of the values ​​(Hp - Ha), which is obtained by subtracting the average thickness Ha from the thicknesses Hp of each protrusion, is the average height of the protrusions. (3) Breakdown voltage measurement (evaluation of minimizing the reduction of electrostatic capacity)

[0113] The electrostatic capacitance when a voltage of 700 V was applied to the film capacitor in an atmosphere of 125°C was defined as the initial value C0. The electrostatic capacitance of the film capacitor was measured while the applied voltage was gradually increased from 700 V every 1 hour at an electric field strength of 50 V / µm. The applied voltage at which the electrostatic capacitance reached 50% of the initial value C0 was defined as the breakdown voltage. A film capacitor with a breakdown voltage of 1000 V or more was evaluated as good, a film capacitor with a breakdown voltage of 950 V or more and less than 1000 V was evaluated as satisfactory, and a film capacitor with a breakdown voltage of less than 950 V was evaluated as poor. It can be said that the higher the breakdown voltage, the smaller the decrease in electrostatic capacitance. (4) Ability to heal oneself

[0114] In the breakdown voltage evaluation described above, the voltage was gradually increased until the film capacitor failed, and the failure mode was confirmed. A film capacitor whose electrostatic capacitance was zero due to an open-mode failure was rated as good, and a film capacitor that failed due to a short-mode failure was rated as poor. [Table 1] Conditions of film production projection Ability to heal oneself Breakdown voltage Proportion of the second organic material (mass%) Proportion of the multimer in the second organic material (mol%) Average height (µm) Average area (µm 2 ) Density (pieces / cm 2 ) Comparison example 1 40 50 3,8 323 9,85 Bad Fair Comparison example 2 30 20 0,8 743 2,83 Bad Good Comparison Example 3 20 50 3,8 683 0,58 Bad Good Comparison Example 4 40 10 3,8 623 17,50 Good Bad Example 1 35 30 3,9 599 7,93 Good Good Example 2 30 30 3,1 812 1,01 Good Good Example 3 35 40 2,0 713 1,68 Good Good Example 4 30 50 2,1 643 3,21 Good Good Example 5 - - 2,2 598 2,12 Good Good

[0115] In the films produced in Examples 1 to 3, the projections are formed with a density of 1 piece / cm 2 or more and 10 pieces / cm 2 or less, an average height of 2 µm or more and an average area of ​​550 µm 2 or more were formed. Therefore, the resulting film capacitors exhibited excellent self-healing ability and high breakdown voltage.

[0116] The films prepared in Examples 4 and 5 differed from the films in Examples 1 to 3 in the materials of the main body and the protrusions, but the obtained film capacitors had the same self-healing ability and breakdown voltage as those in Examples 1 to 3. It can be seen that, regardless of the materials of the main body and the protrusions, an excellent self-healing ability and a high breakdown voltage can be obtained in the case where the density of the protrusions is 1 piece / cm 2 or more and 10 pieces / cm 2 or less, the average height is 2 µm or more and the average area is 550 µm 2 or more.

[0117] In contrast, the protrusions of the film prepared in Comparative Example 1 have a density of 1 piece / cm 2 or more and 10 pieces / cm 2or less, and an average height of 2 µm or more, but an average area of ​​less than 550 µm 2 Therefore, the resulting film capacitor is inferior in terms of self-healing ability. This is believed to be due to the fact that the protrusions were crushed during capacitor manufacturing, and therefore sufficient spacing between the films could not be ensured.

[0118] The projections of the film produced in Comparative Example 2 have a density of 1 piece / cm 2 or more and 10 pieces / cm 2 or less and an average area of ​​550 µm 2 or more, but have an average height of less than 2 µm. Therefore, sufficient spacing between the films cannot be ensured, and the resulting film capacitor is inferior in self-healing ability.

[0119] The projections of the film prepared in Comparative Example 3 have an average height of 2 µm or more and an average length of 30 µm or more, but have a density of less than 1 piece / cm 2 Therefore, sufficient spacing between the films cannot be ensured, and the self-healing ability is inferior. The protrusions 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 or more, but have a density of more than 10 pieces / cm 2 . Therefore, the number of insulation breakdown points increases, and the resulting film capacitor is inferior in breakdown voltage. INDUSTRIAL APPLICABILITY

[0120] The dielectric resin film of the present disclosure is used for the film capacitor. Since this film capacitor has excellent self-healing ability and the electrostatic capacitance hardly decreases when a high voltage is applied, the film capacitor can be applied to various electronic devices.

[0121] This application claims priority to Japanese Patent Application No. 2022-070235, filed in Japan on April 21, 2022, the entire contents of which are incorporated herein by reference. LIST OF REFERENCE SYMBOLS 1 film capacitor 2a first slide 2b second slide 3a first metal layer 3b second metal layer 4a first metallized foil 4b second metallized foil 5 Capacitor element 6a first external connection electrode 6b second external connection electrode W latitude direction T Radial direction QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP-A-2014-107394

[0003]

Claims

[1] Dielectric resin film, comprising: a dielectric resin film body having two opposing main surfaces; and at least one insulating projection arranged on at least one of the main surfaces, where, viewed from a normal direction of the main surfaces, projections, each of which is identical to the at least one insulating projection, a density of 1 piece / cm 2 or more and 10 pieces / cm 2 or less, the projections have an average height of 2 µm or more, and the projections have an average area of ​​550 µm 2 or more. [2] The dielectric resin film according to claim 1, wherein the resin film body contains 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 contains 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. [5] The dielectric resin film according to claim 4, wherein the first organic material further comprises an aromatic ring. [6] Film capacitor, which has: two or more dielectrics facing each other; a first metal layer sandwiched between the dielectrics; and a second metal layer opposite the first metal layer, wherein one of the dielectrics is sandwiched between the first and second metal layers, wherein at least one of the dielectrics comprises the dielectric resin film according to any one of claims 1 to 5.

Images