Exterior material for a storage device, and method for manufacturing an exterior material for a storage device

Abstract

The present invention relates to an outer casing for a capacitor device having a structure in which at least a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, wherein the substrate protective layer is a cured product of a raw material comprising a polyester resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the polyester resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60 and the hydroxyl group value of the polyester resin is 10 to 70 KOH mg / g.

Description

Technology Field

[0001] The present invention relates to an outer casing for a storage device and a method for manufacturing an outer casing for a storage device. Background Technology

[0002] Energy storage devices include, for example, secondary batteries such as lithium-ion batteries, nickel-hydrogen batteries, and lead-acid batteries, as well as electrochemical capacitors such as electric double-layer capacitors. Due to the miniaturization of portable devices and limitations on installation space, further miniaturization of energy storage devices is required, and lithium-ion batteries with high energy density are attracting attention. Conventionally, metal cans were used as casing materials for lithium-ion batteries, but multilayer films that are lightweight, have high heat dissipation, and can be manufactured at low cost are being used.

[0003] In lithium-ion batteries using the above-mentioned multilayer film as an outer layer, a configuration is adopted in which the battery contents (positive electrode, separator, negative electrode, electrolyte, etc.) are covered by an outer layer including an aluminum foil layer to prevent moisture from entering the interior. A lithium-ion battery that adopts such a configuration is called an aluminum laminate type lithium-ion battery.

[0004] Aluminum laminate type lithium-ion batteries are known, for example, embossed type lithium-ion batteries in which a concave portion is formed by cold forming in a part of the outer material, the battery contents are received within the concave portion, and the remaining part of the outer material is folded back and sealed with a heat seal (see, for example, Patent Document 1). In such lithium-ion batteries, the deeper the concave portion formed by cold forming, the more battery contents can be received, and thus the energy density can be increased. Prior art literature

[0005] Japanese Patent Publication No. 2013-101765 The problem to be solved

[0006] However, when deep concave molding is performed on conventional casings for lithium-ion batteries to form deep concave sections, fracture of the adhesive layer and the metal foil layer may occur. Therefore, good deep concave moldability is required for the casing.

[0007] In order to improve such moldability, a nylon film is sometimes used as a substrate layer on the outermost layer of the exterior material. However, since the nylon film is basic, there is a problem in that when it comes into contact with the electrolyte (acidic) for lithium-ion batteries, the nylon film melts and cannot exhibit its characteristics as an exterior material.

[0008] In addition, a protective layer may be additionally formed on the outer layer for the purpose of protecting the substrate layer from external stimuli, such as the aforementioned electrolyte. However, since the substrate layer undergoes thermal shrinkage due to heating during lamination or drying in the manufacturing process of the exterior material, the adhesion between the substrate layer and the protective layer may decrease. Such a decrease in adhesion is prone to occur not only in high-temperature environments during lamination or drying, but also in hot water or high-temperature, high-humidity environments.

[0009] The present invention has been made in consideration of the above circumstances, and its first objective is to provide an outer casing for a capacitor device having good moldability and electrolyte resistance, as well as excellent adhesion between the substrate layer and the protective layer. The present invention also aims to provide a method for manufacturing such an outer casing for a capacitor device.

[0010] In addition, the present invention has a second objective of providing an outer casing for a capacitor device having good moldability and electrolyte resistance. The present invention also has an objective of providing a method for manufacturing such an outer casing for a capacitor device. means of solving the problem

[0011] <First Invention>

[0012] To achieve the above first objective, the present first invention provides an outer casing for a capacitor device having a structure in which at least a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, wherein the substrate protective layer is a cured product of a raw material comprising a polyester resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the polyester resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60 and the hydroxyl group value of the polyester resin is 10 to 70 KOH mg / g.

[0013] The outer casing for a storage device according to the first invention has good moldability and electrolyte resistance, and also exhibits excellent adhesion between the substrate layer and the protective layer. Generally, in outer casings for consumer lithium-ion batteries, a nylon film is sometimes used as the outermost layer to improve moldability. However, since nylon films are basic, if they come into contact with the electrolyte (acidic) for lithium-ion batteries, the nylon melts and cannot be used as a battery cell. To resolve such problems caused by the film used, the present invention further forms a coating layer, in which a polyester resin is blended with polyisocyanate, as a substrate protective layer on the outermost layer of the film. At that time, by using the polyester resin or polyisocyanate defined as above, it is possible to impart suitable characteristics to the coating layer.

[0014] <Second Invention>

[0015] To achieve the above second objective, the present second invention provides an outer casing for a capacitor device having a structure in which at least a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, wherein the substrate protective layer is a cured product of a raw material comprising an aromatic polyesterurethane resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the aromatic polyesterurethane resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 20.

[0016] The outer casing for a storage device according to the second invention has good moldability and electrolyte resistance, and also exhibits excellent adhesion between the substrate layer and the protective layer. Generally, in outer casings for consumer lithium-ion batteries, a nylon film is sometimes used as the outermost layer to improve moldability. However, since nylon films are basic, if they come into contact with the electrolyte (acidic) for lithium-ion batteries, the nylon melts and cannot be used as a battery cell. To resolve such problems caused by the film used, the present invention further forms a coating layer on the outermost layer of the film as a substrate protective layer, wherein the coating layer is formed by combining an aromatic polyester urethane resin with a polyisocyanate. At that time, by using the aromatic polyester urethane resin and the polyisocyanate in the mixing ratio specified as above, it is possible to impart suitable characteristics to the coating layer. In addition, since the aromatic polyester used as a raw material for aromatic polyester urethane resin has excellent resistance to hydrolysis (by acid), it is possible to protect the nylon film without causing deterioration of the substrate protective layer even when it comes into contact with an electrolyte.

[0017] In the present invention, it is preferable that the insulation resistance between the layers be 2000 MΩ or higher when a constant voltage of 100 V is applied for 3 minutes between the substrate protection layer and the metal foil layer while water is attached to the substrate protection layer. Accordingly, even if, for example, a film that easily absorbs moisture (such as a Ny film) is used as the substrate layer, the risk of current flowing to the metal foil layer and affecting battery performance can be reduced. In particular, in environments where there is a possibility of high humidity or immersion in rainwater, such as for automotive applications or power tools, it is preferable to have this level of insulation while water is attached to the substrate protection layer.

[0018] In the present invention, it is preferable that the polyisocyanate comprises 50 mass% or more of a polyisocyanate that does not have a cycloaliphatic structure. In particular, it is preferable that the polyisocyanate that does not have a cycloaliphatic structure is an aliphatic polyisocyanate, and it is more preferable that it is an adduct or biuret of an aliphatic polyisocyanate. Accordingly, the electrolyte resistance and alcohol resistance of the substrate protective layer can be further improved.

[0019] In the second invention, from the perspective of achieving a balance of the hardness and other properties of the resin, it is preferable that the aromatic polyesterurethane resin be a blend of two or more aromatic polyesterurethane resins having different glass transition temperatures (Tg).

[0020] The above-mentioned raw material for forming the substrate protective layer may also include a filler. Accordingly, it is possible to further improve the slipperiness of the exterior material and also impart an aesthetic appearance to the exterior material.

[0021] In addition, the present invention provides a method for manufacturing an outer casing for a capacitor device, comprising the steps of: bonding a substrate layer to one side of a metal foil layer through an adhesive layer; forming a substrate protective layer on a side opposite to the adhesive layer of the substrate layer; and forming a sealant layer on a side opposite to the adhesive layer of the metal foil layer through a sealant adhesive layer, wherein the substrate protective layer is a cured product of a raw material comprising a polyester resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the polyester resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60, and the hydroxyl group value of the polyester resin is 10 to 70 KOH mg / g.

[0022] In addition, the present invention provides a method for manufacturing an outer casing for a capacitor device, comprising the steps of: laminating a substrate layer to one side of a metal foil layer through an adhesive layer; forming a substrate protective layer on a side opposite to the adhesive layer of the substrate layer; and forming a sealant layer on a side opposite to the adhesive layer of the metal foil layer through a sealant adhesive layer, wherein the substrate protective layer is a cured product of a raw material comprising an aromatic polyesterurethane resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the aromatic polyesterurethane resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 20. Effects of the invention

[0023] According to the first invention, an outer casing for a capacitor device can be provided that has good moldability and electrolyte resistance, and excellent adhesion between the substrate layer and the protective layer. In addition, according to the second invention, an outer casing for a capacitor device having good moldability and electrolyte resistance can be provided. Furthermore, according to the present invention, a method for manufacturing such an outer casing for a capacitor device can be provided. Brief explanation of the drawing

[0024] FIG. 1 is a schematic cross-sectional view of an outer casing for a capacitor device related to one embodiment of the present invention. FIG. 2 is a drawing showing an embossed type outer material obtained using an outer material for a capacitor device related to one embodiment of the present invention, (a) is a perspective view thereof, and (b) is a longitudinal cross-sectional view along line bb of the embossed type outer material shown in (a). FIG. 3 is a perspective view showing a process for manufacturing a secondary battery using an exterior material for a storage device related to an embodiment of the present invention, (a) shows a state in which an exterior material for a storage device is prepared, (b) shows a state in which an exterior material for a storage device processed into an embossed type and a battery element are prepared, (c) shows a state in which a part of the exterior material for a storage device is folded back and the end is melted, and (d) shows a state in which both sides of the folded-back part are folded back upward. Specific details for implementing the invention

[0025] Suitable embodiments of the present invention will be described in detail below with reference to the drawings. In addition, identical or substantial parts in the drawings are denoted by the same reference numerals, and redundant descriptions are omitted.

[0026] <First Embodiment>

[0027] [Exterior material for capacitor devices]

[0028] FIG. 1 is a cross-sectional view schematically illustrating one embodiment of an exterior material for a capacitor device according to the present invention. As shown in FIG. 1, the exterior material (exterior material for a capacitor device) (10) of the present embodiment is a laminate in which a substrate layer (11), a substrate protection layer (12) formed on one side of the substrate layer (11), an adhesive layer (13) formed on the opposite side of the substrate protection layer (12) of the substrate layer (11), a metal foil layer (14) having corrosion-prevention treatment layers (15a, 15b) on both sides formed on the opposite side of the adhesive layer (13) of the substrate layer (11), a sealant adhesive layer (16) formed on the opposite side of the adhesive layer (13) of the metal foil layer (14), and a sealant layer (17) formed on the opposite side of the metal foil layer (14) of the sealant adhesive layer (16) are laminated. Here, the anti-corrosion treatment layer (15a) is formed on the side of the adhesive layer (13) of the metal foil layer (14), and the anti-corrosion treatment layer (15b) is formed on the side of the sealant adhesive layer (16) of the metal foil layer (14). In the outer layer (10), the substrate protection layer (12) is the outermost layer and the sealant layer (17) is the innermost layer. That is, the outer layer (10) is used with the substrate protection layer (12) facing the outside of the capacitor device and the sealant layer (17) facing the inside of the capacitor device. Each layer will be described below.

[0029] (Recording layer (11))

[0030] The substrate layer (11) provides heat resistance during the sealing process when manufacturing the capacitor device and suppresses the occurrence of pinholes that may occur during molding or distribution. In particular, for the exterior material of a capacitor device for large applications, scratch resistance, chemical resistance, and insulation can also be provided.

[0031] The substrate layer (11) is preferably a layer made of a resin film formed by a resin having insulating properties. Examples of resin films include stretched or unstretched films such as polyester film, polyamide film, and polypropylene film. The substrate layer (11) may be a single-layer film composed of any of these resin films, or a laminated film composed of two or more of these resin films.

[0032] Among these films, as the substrate layer (11), a polyamide film is preferred in terms of excellent moldability, and a biaxially stretched polyamide film is more preferred. Examples of polyamide resins for forming the polyamide film include nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylyleneadipamide (MXD6), nylon 11, nylon 12, etc. Among these, nylon 6 (ONy) is preferred in terms of excellent heat resistance, puncture strength, and impact strength.

[0033] Examples of stretching methods for biaxially stretched films include sequential biaxial stretching, tubular biaxial stretching, and simultaneous biaxial stretching. It is preferable that the biaxially stretched film be stretched by the tubular biaxial stretching method to obtain superior deep cross-forming properties.

[0034] The thickness of the substrate layer (11) is preferably 6 to 40 μm, and more preferably 10 to 30 μm. By having a thickness of 6 μm or more of the substrate layer (11), the pinhole resistance and insulation properties of the outer casing (10) for the energy storage device can be improved. If the thickness of the substrate layer (11) exceeds 40 μm, the total thickness of the outer casing (10) for the energy storage device increases, and it is not desirable because there may be cases where the electrical capacity of the battery must be reduced.

[0035] (Material protection layer (12))

[0036] The substrate protective layer (12) is a layer formed on one side of the substrate layer (11), and is formed using a polyester resin (which has hydroxyl groups in its side chains that react with the isocyanate groups of the polyisocyanate) and a polyisocyanate. That is, the substrate protective layer (12) is a cured product of a raw material containing a polyester resin and a polyisocyanate.

[0037] Polyester resins (polyester polyols) having hydroxyl groups in their side chains are polyester resins that have hydroxyl groups in their side chains in addition to the hydroxyl groups at the ends of the repeating units. Examples of such polyester resins include polyester resins obtained by reacting one or more dicarboxylic acids with one or more compounds having three or more hydroxyl groups. The unreacted portions among the hydroxyl groups of the compounds having three or more hydroxyl groups become the hydroxyl groups of the side chains of the polyester resin. As for the dicarboxylic acids, either aliphatic dicarboxylic acids or aromatic dicarboxylic acids can be used; specifically, examples include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, souveric acid, azelaic acid, sebacic acid, and brasylic acid; and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, and naphthalene dicarboxylic acid. Compounds having three or more hydroxyl groups include, for example, hexanetriol, trimethylolpropane, pentaerythritol, etc.

[0038] The above polyester resin may be a compound in which a diol is reacted with a compound having three or more hydroxyl groups in addition to a dicarboxylic acid and a hydroxyl group, if necessary. Examples of diols include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; and aromatic diols such as xylylene glycol.

[0039] In terms of solubility, it is preferable that the number average molecular weight (Mn) of the polyester resin be 3,000 to 10,000.

[0040] In this embodiment, the hydroxyl value of the polyester resin is 10 to 70 mg / g KOH. If the hydroxyl value is less than 10, it becomes difficult to sufficiently exhibit adhesion between the substrate protective layer (12) and the substrate layer (11), even if the polyester resin and polyisocyanate are appropriately blended as described below. On the other hand, if it exceeds 70, the molecular weight of the polyester resin tends to become excessively small, so there is a risk that the film strength will decrease or the cross-linked structure will become too dense and brittle. From this perspective, it is preferable that the hydroxyl value of the polyester resin be 30 to 70 mg / g KOH. The hydroxyl value can be measured by, for example, using acetic anhydride to acetylate the hydroxyl groups in the sample and titrating the unused acetic acid with a potassium hydroxide solution.

[0041] As polyisocyanates, various types of aromatic, aliphatic, and alicyclic polyisocyanates may be used. Specific examples include aliphatic hexamethylene diisocyanate (HDI), etc.; aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), etc.; alicyclic isophorone diisocyanate (IPDI), etc.; and polyfunctional isocyanate modified products from one or more of these diisocyanates.

[0042] In addition, among aromatic, aliphatic, and alicyclic polyisocyanates, in this embodiment, a polyisocyanate that does not have an alicyclic structure (is not alicyclic) is preferred from the perspective of improving electrolyte resistance, and an aliphatic polyisocyanate is more preferred. In particular, an adduct or biuret of hexamethylene diisocyanate is suitablely used to impart electrolyte resistance. Furthermore, when 50 mass% or more of a polyisocyanate that does not have an alicyclic structure is used based on the total mass (100 mass%) of the polyisocyanate, alcohol resistance also tends to be exhibited. For example, when a battery cell manufacturer prints using an inkjet printer for lot trace management, there are cases where incorrect information is printed. In such cases, the printed area is wiped off with alcohol and printed again, but such a type of polyisocyanate is effective in improving resistance to wiping off with alcohol.

[0043] The mixing ratio of the main component, polyester resin, and the curing agent, polyisocyanate, is such that when the number of moles of hydroxyl groups in the polyester resin is [OH] and the number of moles of isocyanate groups in the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60. It is believed that resistance to electrolyte is influenced by the cross-linking structure of the substrate protection layer (12). Therefore, the inventor believes that it is necessary to mix the isocyanate groups of the polyisocyanate in excess with respect to the hydroxyl groups of the polyester resin and to make the cross-linking density dense. If [NCO] / [OH] is less than 5, the cross-linking structure becomes insufficient, making it difficult to provide good resistance to electrolyte. On the other hand, if it exceeds 60, the cross-linking structure becomes excessively dense (the substrate protection layer (12) becomes excessively hard), which may have an undesirable effect on molding, etc. In addition, if the polyisocyanate ratio is low, it becomes difficult to obtain adhesion between the substrate protective layer (12) and the substrate layer (11), so it is desirable to keep it within the above range. In this regard, [NCO] / [OH] is preferably 20 to 60.

[0044] As described above, the substrate protective layer (12) is formed using a raw material comprising polyester resin and polyisocyanate. The raw material may include various additives such as fillers, flame retardants, lubricants (slip agents), anti-blocking agents, antioxidants, light stabilizers, tackifiers, leveling agents to provide coating stability, defoaming agents, catalysts to prevent blocking after coating (promoting the reaction of the coating solution), and reaction retardants to control the pot life of the coating solution (acetylacetone is suitably used).

[0045] Since the raw material contains a filler, a matte treatment can be applied to the outer surface of the substrate protection layer (12). In this embodiment, the substrate protection layer (12) is a coating layer formed from polyester resin and polyisocyanate, so compared to, for example, nylon (the substrate layer itself), it tends to have lower slipperiness because it is a system involving a reaction, and there is a risk that moldability will be reduced. Therefore, by adjusting the surface roughness through matte treatment, the slipperiness of the surface of the substrate protection layer (12) is improved, and it becomes easier to suppress the exterior material (10) from adhering excessively to the mold during cold forming, thus making it easier to secure good moldability. In addition, since a gloss removal effect is also obtained through matte treatment, the exterior material (10) can be given an appearance design by adjusting the amount of filler.

[0046] As fillers, fine particles of inorganic materials such as silica, acrylic, alumina, barium sulfate, calcium carbonate, and titanium oxide (inorganic fillers), or acrylic beads, urethane beads, and polyester beads (organic fillers) may be used. Among these, fine particles of silica are preferred because resin cracking (whitening due to fine cracks) does not easily occur during the press molding of the outer casing. In addition, the average particle size of the filler can be selected as needed, but since thickness control is difficult for outer casings for capacitor devices, the filler size is preferably submicron (on the order of nm) to less than 10 μm. At that time, fillers having different particle size distributions may be blended. The average particle size can be measured by the Coulter counter method.

[0047] The filler content ratio (filler content ratio relative to the total mass of the substrate protection layer (12)) in the substrate protection layer (12) is preferably 1 to 50 mass%, and more preferably 5 to 50 mass%. By making the filler content ratio 1 mass% or more, it becomes easier to impart activity to the surface of the substrate protection layer (12). Also, by making the filler content ratio 50 mass% or less, it becomes easier to prevent roughening of the surface of the substrate protection layer (12). Accordingly, it is possible to prevent defects in the appearance of the surface of the exterior material (10).

[0048] In addition, examples of activators include fatty acid amides such as oleamide, erucamide, stearamide, beheninamide, ethylenebisoleamide, and ethylenebiserucamide. As for anti-blocking agents, various filler-based anti-blocking agents such as silica are preferred.

[0049] The additives described above may be used as a single type or in combination of two or more types.

[0050] The thickness of the substrate protection layer (12) is selected according to the required characteristics for the exterior material (10), but for example, it can be about 1 to 10 μm. If the thickness is less than 1 μm, the substrate protection effect tends to be insufficient, and if it exceeds 10 μm, the substrate protection effect is sufficient, but conversely, because it is excessively thick, the influence on other characteristics as an exterior material is also at risk.

[0051] In this embodiment, when a constant voltage of 100 V is applied for 3 minutes between the substrate protection layer (12) and the metal foil layer (14) while water is attached to the substrate protection layer (12), the insulation resistance between the layers is preferably 2000 MΩ or more, and more preferably 10000 MΩ or more. Accordingly, even if a film that is prone to moisture absorption (such as a Ny film) is used as the substrate layer, the risk of current flowing to the metal foil layer and affecting battery performance can be reduced. In particular, in environments where there is a possibility of high humidity or flooding with rainwater, such as for automotive applications or power tools, it is desirable to have this level of insulation even when water is attached to the substrate protection layer. Furthermore, the insulation resistance between the substrate protection layer (12) and the metal foil layer (14) specifically refers to the insulation resistance in the laminated portion of the substrate protection layer (12), the substrate layer (11), the adhesive layer (13), and the metal foil layer (14). On one or both sides of the metal foil layer (14), an anti-corrosion treatment layer (15a, 15b) may be formed, and the presence or absence of these layers has a negligible effect on the insulation resistance value.

[0052] (Adhesive layer (13))

[0053] The adhesive layer (13) is a layer that bonds the substrate layer (11) and the metal foil layer (14). The adhesive layer (13) has the necessary adhesion force to firmly bond the substrate layer (11) and the metal foil layer (14), and also has a followability (performance to reliably form the adhesive layer (13) on the member without peeling even if the member is deformed or stretched) to prevent the metal foil layer (14) from breaking due to the substrate layer (11) when cold forming.

[0054] As an adhesive constituting the adhesive layer (13), for example, a two-component curing type polyurethane adhesive having a main component composed of a polyol such as polyester polyol, polyether polyol, or acrylic polyol, and a curing agent composed of an isocyanate such as an aromatic or aliphatic type may be used. In the adhesive, the molar ratio of the isocyanate groups of the curing agent to the hydroxyl groups of the main component (= [NCO] / [OH]) is preferably 1 to 10, and more preferably 2 to 5.

[0055] The above polyurethane-based adhesive, by aging at 40°C for 4 days or more after coating, for example, allows the reaction between the hydroxyl group of the main component and the isocyanate group of the curing agent to proceed, thereby enabling a stronger bond between the substrate layer (11) and the metal foil layer (14).

[0056] The thickness of the adhesive layer (13) is preferably 1 to 10 μm and more preferably 2 to 6 μm from the perspective of obtaining the desired adhesive strength, conformability, and processability.

[0057] In the adhesive layer (13), an appropriate amount of pigment may be added to give it a decorative appearance. The pigment may be an organic pigment, an inorganic pigment, or a mixture of the pigments.

[0058] The type of pigment is not particularly limited as long as it does not impede the adhesiveness of the adhesive layer (13). Examples of organic pigments include azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-thioindigo-based, perinone-perylene-based, isoindolenin-based, etc. Examples of inorganic pigments include carbon black-based, titanium oxide-based, cadmium-based, lead-based, chromium oxide-based, etc. In addition, fine powder of mica, fish scales, etc. may be used.

[0059] Specific examples of organic pigments include, for example, the following pigments.

[0060] Yellow: Isoindolinone, isoindolin, quinophthalone, anthraquinone (flavanthrone), azomethine, xanthen, etc.

[0061] Orange: Diketopyrrolopyrrol, perylene, anthraquinone, perinone, quinacridone, etc.

[0062] Red: Anthraquinone, quinacridone, diketopyrrolopyrrol, perylene, indigoid, etc.

[0063] Purple: Oxazine (dioxazine), quinacridone, perylene, indigoid, anthraquinone, xanthen, benzimidazolone, violanthrone, etc.

[0064] Blue: Phthalocyanines, anthraquinones, indigoids, etc.

[0065] Green: Phthalocyanine, perylene, azomethine, etc.

[0066] Specific examples of inorganic pigments include, for example, the following pigments.

[0067] White: zinc oxide, lead white, lithopone, titanium dioxide, precipitated barium sulfate, barite powder, etc.

[0068] Red: Lead oxide, iron oxide, etc.

[0069] Yellow: yellow lead, zinc sulfur (zinc sulfur type 1, zinc sulfur type 2), etc.

[0070] Blue: Ultramarine blue, Prussian blue (potassium iron ferrocyanide), etc.

[0071] Black: Carbon Black, etc.

[0072] Based on the total mass of the adhesive layer (13), the pigment content is preferably 1 mass% or more, and more preferably 5 mass% or more, in order to obtain higher reliability. Also, it is preferably 50 mass% or less, and more preferably 20 mass% or less, in order to obtain excellent adhesion.

[0073] (metal thin layer (14))

[0074] Various metal foils such as aluminum and stainless steel can be used as the metal foil layer (14), and in terms of moisture resistance, processability such as ductility, and cost, the metal foil layer (14) is preferably aluminum foil. The aluminum foil may be general soft aluminum foil, but it is preferable to use aluminum foil containing iron in terms of excellent pinhole resistance and ductility during forming.

[0075] In an aluminum foil (100 mass%) containing iron, the iron content is preferably 0.1 to 9.0 mass%, and more preferably 0.5 to 2.0 mass%. By having an iron content of 0.1 mass% or more, an exterior material (10) having better pinhole resistance and ductility can be obtained. By having an iron content of 9.0 mass% or less, an exterior material (10) with better flexibility can be obtained.

[0076] In addition, as for the aluminum foil, a soft aluminum foil that has undergone annealing treatment (for example, an aluminum foil made of 8021 or 8079 materials as defined in the JIS standard) is more preferable in that it can impart desired ductility during forming.

[0077] For the metal foil used in the metal foil layer (14), it is preferable that, for example, degreasing treatment be performed to obtain the desired electrolyte resistance. Also, for the sake of simplifying the manufacturing process, it is preferable that the surface of the metal foil not be etched. For example, wet-type degreasing treatment or dry-type degreasing treatment may be used for the degreasing treatment, but dry-type degreasing treatment is preferred from the perspective of simplifying the manufacturing process.

[0078] As for the above dry-type degreasing treatment, for example, a method of performing degreasing treatment by extending the treatment time during the annealing process of a metal foil can be cited. Sufficient electrolyte resistance is obtained even with the degree of degreasing treatment performed simultaneously during the annealing process performed to soften the metal foil.

[0079] Furthermore, for the above-mentioned dry-type degreasing treatment, treatments other than the above-mentioned annealing treatment, such as frame treatment and corona treatment, may be used. Additionally, for the above-mentioned dry-type degreasing treatment, for example, a degreasing treatment that oxidatively decomposes and removes contaminants by means of active oxygen generated when ultraviolet rays of a specific wavelength are irradiated onto a metal foil may be used.

[0080] For the above wet-type degreasing treatment, treatments such as acid degreasing and alkaline degreasing may be used. For example, inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid may be used as the acid used for the above acid degreasing treatment. These acids may be used individually or in combination of two or more types. In addition, for the alkali used for the alkaline degreasing treatment, sodium hydroxide, which has a high etching effect, may be used. Furthermore, alkaline degreasing treatment may be performed using a material that is a mixture of a weakly alkaline material and a surfactant. The above-described wet-type degreasing treatment may be carried out by, for example, the immersion method or the spray method.

[0081] The thickness of the metal foil layer (14) is preferably 9 to 200 μm in terms of barrier properties, pinhole resistance, and processability, more preferably 15 to 150 μm, and even more preferably 15 to 100 μm. Since the thickness of the metal foil layer (14) is 9 μm or more, it does not break easily even when stress is applied by forming process. Since the thickness of the metal foil layer (14) is 200 μm or less, the increase in mass of the outer material can be reduced, and the decrease in the weight energy density of the capacitor device can be suppressed.

[0082] (Corrosion-resistant treatment layer (15a, 15b))

[0083] The corrosion prevention treatment layers (15a, 15b) serve to suppress corrosion of the metal foil layer (14) caused by the electrolyte, or hydrofluoric acid generated by the reaction between the electrolyte and water. Additionally, the corrosion prevention treatment layer (15a) serves to increase the adhesion between the metal foil layer (14) and the adhesive layer (13). Additionally, the corrosion prevention treatment layer (15b) serves to increase the adhesion between the metal foil layer (14) and the sealant adhesive layer (16). The corrosion prevention treatment layer (15a) and the corrosion prevention treatment layer (15b) may be layers of the same composition or layers of different composition.

[0084] The corrosion-resistant treatment layer (15a, 15b) can be formed, for example, by performing degreasing treatment, hydrothermal modification treatment, anodic oxidation treatment, chemical treatment, a coating-type corrosion-resistant treatment in which a coating agent having corrosion-resistant ability is applied, or a combination of these treatments on the layer that serves as the base material of the corrosion-resistant treatment layer (15a, 15b).

[0085] Among the treatments described above, degreasing treatment, hydrothermal modification treatment, and anodic oxidation treatment, in particular hydrothermal modification treatment and anodic oxidation treatment, are treatments that dissolve the surface of a metal foil (aluminum foil) with a treatment agent to form a metal compound (aluminum compound (boehmite, alumite)) with excellent corrosion resistance. For this reason, such treatments are sometimes included in the definition of chemical treatment in order to obtain a structure in which a co-linked structure is formed from the metal foil layer (14) to the corrosion-resistant treatment layer (15a, 15b).

[0086] Degreasing treatments include acid degreasing and alkaline degreasing. Acid degreasing methods include using an acid degreasing agent obtained by using inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid described above, either alone or in a mixture thereof. Additionally, as an acid degreasing agent, by using an acid degreasing agent in which a fluorine-containing compound such as monosodium difluoride ammonium is dissolved in the inorganic acid, it is possible to not only degreasing the metal foil layer (14) but also to form a fluoride of the passivated metal, and it is effective in terms of hydrofluoric acid resistance. Alkaline degreasing methods include using sodium hydroxide.

[0087] For the above hydrothermal modification treatment, for example, a boehmite treatment obtained by immersing the metal foil layer (14) in boiling water to which triethanolamine has been added may be used. For the above anodic oxidation treatment, for example, an anodizing treatment may be used. Also, for the above chemical treatment, for example, a chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or a combination of two or more of these may be used. It is preferable to perform the degreasing treatment described above beforehand for these hydrothermal modification treatments, anodic oxidation treatments, and chemical treatments.

[0088] In addition, the above chemical treatment is not limited to a wet method; for example, a method of mixing the treatment agent used for these treatments with a resin component and applying it may be used. Furthermore, regarding the above corrosion prevention treatment, a coating-type chromate treatment is preferred from the perspective of waste liquid treatment while maximizing the effect.

[0089] Examples of coating agents used in a corrosion prevention treatment of the coating type, which involves applying a coating agent having corrosion prevention performance, include coating agents containing at least one selected from the group consisting of rare earth element oxide sol, anionic polymer, and cationic polymer. In particular, a method using a coating agent containing a rare earth element oxide sol is preferred.

[0090] The method of using a coating agent containing a rare earth element oxide sol is a pure coating-type corrosion prevention treatment, and by using this method, it is possible to impart a corrosion prevention effect to the metal foil layer (14) even with a general coating method. In addition, the layer formed using the rare earth element oxide sol has a corrosion prevention effect (inhibitor effect) on the metal foil layer (14) and is also a material suitable in terms of the environment.

[0091] In the rare earth element oxide sol, fine particles of the rare earth element oxide (e.g., particles with an average particle size of 100 nm or less) are dispersed in a liquid dispersion medium. Examples of rare earth element oxides include cerium oxide, yttrium oxide, neodymium oxide, and lanthanum oxide. Among these, cerium oxide is preferred. Accordingly, the adhesion between the metal foil layer (14) and the sol can be further improved. As the liquid dispersion medium for the rare earth element oxide sol, various solvents such as water, alcohol-based solvents, hydrocarbon-based solvents, ketone-based solvents, ester-based solvents, and ether-based solvents can be used. Among these, water is preferred. The rare earth element oxide included in the corrosion-prevention treatment layer (15a, 15b) can be used as a single type or in combination of two or more types.

[0092] In order to stabilize the dispersion of rare earth element oxide particles, the rare earth element oxide sol preferably contains inorganic acids such as nitric acid, hydrochloric acid, and phosphoric acid, organic acids such as acetic acid, malic acid, ascorbic acid, and lactic acid, and their salts as dispersion stabilizers. Among these dispersion stabilizers, it is particularly preferable to use phosphoric acid or phosphate. Accordingly, in addition to the dispersion stabilization of rare earth element oxide particles, effects such as improved adhesion between the metal foil layer (14) and the casing material for capacitor devices using the chelating ability of phosphoric acid, imparting resistance to electrolyte by capturing metal ions leached out by the influence of hydrofluoric acid (forming passivation), and improved cohesion of the rare earth element oxide layer due to the ease of causing dehydration condensation of phosphoric acid even at low temperatures can be expected. Examples of phosphoric acid or phosphate used as dispersion stabilizers include orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, alkali metal salts of these, ammonium salts, etc. Among these, condensed phosphoric acids such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, and ultrametaphosphoric acid, or their alkali metal salts and ammonium salts, are preferred for exhibiting function as outer materials for capacitor devices. In particular, when considering the drying film-forming properties (drying ability, heat quantity) when forming a layer containing rare earth oxides by various coating methods using a coating composition containing a rare earth element oxide sol, an agent with excellent reactivity at low temperatures is preferred, and a sodium salt is preferred in that it has excellent dehydration condensation synthesis at low temperatures. As for the phosphate, a water-soluble salt is preferred. The phosphoric acid or phosphate included in the corrosion-preventing treatment layer (15a, 15b) may be used as a single type or in combination of two or more types.

[0093] Regarding the amount of phosphoric acid or its salt mixed in the rare earth element oxide sol, it is preferable to have at least 1 part by mass and more preferably 5 parts by mass or more per 100 parts by mass of the rare earth element oxide. If it is at least 1 part by mass, it is easy to satisfy the function as an outer material for a capacitor device while ensuring good stabilization of the sol. The upper limit of the amount of phosphoric acid or its salt mixed in per 100 parts by mass of the rare earth element oxide should be within a range that does not lead to a decrease in the function of the rare earth element oxide sol, and it is preferable to have 100 parts by mass or less per 100 parts by mass of the rare earth element oxide, more preferable to have 50 parts by mass or less, and even more preferable to have 20 parts by mass or less.

[0094] However, since the layer formed from the rare earth element oxide sol described above is an aggregate of inorganic particles, the cohesive strength of the layer itself is low even after undergoing a drying and curing process. Therefore, in order to supplement the cohesive strength of this layer, it is suitable to composite it with an anionic polymer.

[0095] Examples of anionic polymers include polymers having carboxyl groups, such as poly(meth)acrylic acid (or its salt), or copolymers copolymerized with poly(meth)acrylic acid as the main component. The copolymer components of the copolymer include alkyl (meth)acrylate monomers (alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.); (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide (alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc.), N-alkoxy (meth)acrylamide, N,N-dialkoxy (meth)acrylamide, (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), N-methylol (meth)acrylamide, Examples include monomers containing amide groups such as N-phenyl(meth)acrylamide; monomers containing hydroxyl groups such as 2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl(meth)acrylate; monomers containing glycidyl groups such as glycidyl(meth)acrylate and allylglycidyl ether; silane-containing monomers such as (meth)acryloxypropyltrimethoxysilane and (meth)acryloxypropyltriethoxylan; and monomers containing isocyanate groups such as (meth)acryloxypropylisocyanate. In addition, examples include styrene, α-methylstyrene, vinylmethyl ether, vinylethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth)acrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, etc.

[0096] An anionic polymer plays a role in improving the stability of the corrosion-resistant treatment layer (15a, 15b) (oxide layer) obtained using a rare earth element oxide sol. This is achieved by the effect of protecting the hard and brittle oxide layer with an acrylic resin component, and by the effect of capturing (cation capture) ion contamination (especially sodium ions) derived from phosphate contained in the rare earth oxide sol. In short, if alkali metal ions or alkaline earth metal ions, such as sodium, are contained in the corrosion-resistant treatment layer (15a, 15b) obtained using a rare earth element oxide sol, the corrosion-resistant treatment layer (15a, 15b) is prone to deterioration starting from the location containing those ions. Therefore, by immobilizing sodium ions, etc., contained in the rare earth oxide sol with an anionic polymer, the resistance of the corrosion-resistant treatment layer (15a, 15b) is improved.

[0097] The corrosion-resistant treatment layer (15a, 15b) combined with an anionic polymer and a rare earth element oxide sol has corrosion-resistant performance equivalent to that of the corrosion-resistant treatment layer (15a, 15b) formed by performing chromate treatment on the metal foil layer (14). The anionic polymer is preferably a polyanionic polymer that is essentially water-soluble and has a cross-linked structure. Examples of cross-linking agents used to form the structure include compounds having isocyanate groups, glycidyl groups, carboxyl groups, and oxazoline groups. Furthermore, it is also possible to introduce cross-linking sites having siloxane bonds using a silane coupling agent.

[0098] Examples of compounds having isocyanate groups include, for instance, diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or its hydrogenated derivative, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate or its hydrogenated derivative, isophorone diisocyanate; or polyisocyanates such as adducts obtained by reacting these isocyanates with polyhydric alcohols such as trimethylolpropane, biurets obtained by reacting them with water, or isocyanurates which are triprates; or blocked polyisocyanates obtained by blocking these polyisocyanates with alcohols, lactams, oximes, etc.

[0099] Examples of compounds having a glycidyl group include epoxy compounds formed by reacting glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol with epichlorohydrin, epoxy compounds formed by reacting polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, and sorbitol with epichlorohydrin, and epoxy compounds formed by reacting dicarboxylic acids such as phthalic acid, terephthalic acid, oxalic acid, and adipic acid with epichlorohydrin.

[0100] Examples of compounds having a carboxyl group include various aliphatic or aromatic dicarboxylic acids, and furthermore, it is also possible to use poly(meth)acrylic acid and alkali (earth) metal salts of poly(meth)acrylic acid.

[0101] Examples of compounds having an oxazoline group include, for instance, low molecular weight compounds having two or more oxazoline units, or, when using polymerizable monomers such as isopropenyloxazoline, compounds copolymerized with acrylic monomers such as (meth)acrylic acid, (meth)acrylic acid alkyl ester, and (meth)acrylic acid hydroxyalkyl.

[0102] Examples of silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-isocyanatepropyltriethoxysilane. In particular, considering the reactivity with anionic polymers, epoxysilane, aminosilane, and isocyanatesilane are preferred.

[0103] The amount of crosslinking agent is preferably 1 to 50 parts by mass and more preferably 10 to 20 parts by mass per 100 parts by mass of anionic polymer. If the ratio of the crosslinking agent is 1 part by mass or more per 100 parts by mass of anionic polymer, a crosslinked structure is easily formed sufficiently. If the ratio of the crosslinking agent is 50 parts by mass or less per 100 parts by mass of anionic polymer, the pot life of the coating solution is improved.

[0104] The method of crosslinking an anionic polymer is not limited to the above-mentioned crosslinking agent, but may also be a method of forming ionic crosslinks using titanium or zirconium compounds, etc. In addition, these materials may be used to form a coating composition that forms an anti-corrosion treatment layer (15a).

[0105] In the corrosion-preventing treatment layers (15a, 15b) described above, the corrosion-preventing treatment layers (15a, 15b) formed by chemical treatment, such as chromate treatment, are treated on the metal foil layer (14) using a chemical treatment agent specifically composed of hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, or salts thereof, in order to form a gradient structure with the metal foil layer (14), and then a chromium-based or non-chromium-based compound is applied to form a chemical treatment layer on the metal foil layer (14). However, since the chemical treatment uses acid in the chemical treatment agent, the above chemical treatment entails deterioration of the working environment and corrosion of the coating device.

[0106] Meanwhile, the aforementioned coating-type corrosion-prevention treatment layers (15a, 15b), unlike chemical treatment represented by chromate treatment, do not require forming a gradient structure on the metal foil layer (14). Therefore, the properties of the coating agent are not subject to restrictions such as acidity, alkalinity, or neutrality, and a good working environment can be realized. Furthermore, the coating-type corrosion-prevention treatment layers (15a, 15b) are preferred because an alternative is required for environmental hygiene purposes regarding chromate treatment using chromium compounds.

[0107] The corrosion-resistant treatment layer (15a, 15b) may, if necessary, have a laminated structure in which a cationic polymer is additionally laminated. Examples of cationic polymers include polyethyleneimine, an ionic polymer complex composed of polyethyleneimine and a polymer having a carboxylic acid, a primary amine graft acrylic resin in which a primary amine is grafted onto an acrylic main frame, polyallylamine or derivatives thereof, and aminophenol resin.

[0108] Examples of “polymers having carboxylic acids” that form ionic polymer complexes include polycarboxylic acids (salts), copolymers in which a comonomer is introduced to a polycarboxylic acid (salt), and polysaccharides having carboxyl groups. Examples of polycarboxylic acids (salts) include polyacrylic acid or its ionic salts. Examples of polysaccharides having carboxyl groups include carboxymethylcellulose or its ionic salts. Examples of ionic salts include alkali metal salts and alkaline earth metal salts.

[0109] Primary amine grafted acrylic resin is a resin in which a primary amine is grafted onto an acrylic main frame. Examples of the acrylic main frame include various monomers used as acrylic polyols described above, such as poly(meth)acrylic acid. Examples of primary amines grafted onto the acrylic main frame include ethyleneimine.

[0110] As polyallylamine or its derivatives, homopolymers or copolymers such as allylamine, allylamineamide sulfate, diallylamine, and dimethylallylamine may be used. Furthermore, these amines may be used as free amines or as stabilizers using acetic acid or hydrochloric acid. Additionally, maleic acid, sulfur dioxide, etc., may be used as copolymer components. Furthermore, a type in which thermal crosslinkability is imparted by partially methoxylating a primary amine may also be used. These cationic polymers may be used as a single type or in combination of two or more types. Among the above, at least one type selected from the group consisting of polyallylamine and its derivatives is preferred as the cationic polymer.

[0111] It is preferable to use a cationic polymer in combination with a crosslinking agent having a functional group capable of reacting with amines / imines, such as a carboxyl group or a glycidyl group. As a crosslinking agent used in combination with a cationic polymer, a polymer having a carboxylic acid that forms an ionic polymer complex with polyethyleneimine may also be used. Examples include polycarboxylic acids (salts) such as polyacrylic acid or its ionic salt, copolymers in which a comonomer is introduced thereto, and polysaccharides having carboxyl groups such as carboxymethylcellulose or its ionic salt.

[0112] In this embodiment, a cationic polymer is also described as one component constituting the corrosion-prevention treatment layer (15a, 15b). The reason for this is that, as a result of using various compounds and conducting thorough examinations to impart electrolyte resistance and hydrofluoric acid resistance required for the outer casing material for the capacitor device, it was found that the cationic polymer itself is a compound capable of imparting electrolyte resistance and hydrofluoric acid resistance. It is presumed that this factor is suppressing damage to the metal foil layer (14) by capturing fluoride ions with cationic groups (anion capture). Furthermore, the cationic polymer is also highly desirable in terms of improving the adhesion between the corrosion-prevention treatment layer (15b) and the sealant adhesive layer (16). Additionally, since the cationic polymer is water-soluble like the aforementioned anionic polymer, water resistance can be improved by forming a cross-linked structure using the cross-linking agent. In this way, since a cross-linked structure can be formed even when using a cationic polymer, when a rare earth oxide sol is used to form the corrosion-preventing treatment layer (15a, 15b), a cationic polymer may be used instead of an anionic polymer as the protective layer.

[0113] From the above, examples of combinations of the corrosion prevention treatment of the coating type described above include (1) only rare earth oxide sol, (2) only anionic polymer, (3) only cationic polymer, (4) rare earth oxide sol + anionic polymer (layered composite), (5) rare earth oxide sol + cationic polymer (layered composite), (6) (rare earth oxide sol + anionic polymer: layered composite) / cationic polymer (multilayer), (7) (rare earth oxide sol + cationic polymer: layered composite) / anionic polymer (multilayer), etc. Among these, (1) and (4) to (7) are preferred, and (4) to (7) are more preferred. Also, in the case of the corrosion prevention treatment layer (15a), (6) is particularly preferred in that it can realize both the corrosion prevention effect and the anchor effect (adhesion improvement effect) in a single layer. In addition, (6) and (7) are particularly preferred in that the corrosion prevention treatment layer (15b) makes it easier to maintain the electrolyte resistance on the side of the sealant layer (17). However, this embodiment is not limited to the above combinations. For example, as an example of selecting a corrosion prevention treatment, since a cationic polymer is a very desirable material in that it has good adhesion to the modified polyolefin resin exemplified in the description of the sealant adhesive layer (16) described later, when the sealant adhesive layer (16) is composed of a modified polyolefin resin, it is possible to design the cationic polymer to form on the surface in contact with the sealant adhesive layer (16) (e.g., configurations (5) and (6), etc.).

[0114] However, the corrosion-prevention treatment layer (15a, 15b) is not limited to the layer described above. For example, it may be formed using a compound of phosphoric acid and chromium in a resin binder (such as aminophenol resin), as in the known coating chromate. By using such a treatment agent, it is possible to form a layer that combines both corrosion prevention function and adhesion. In addition, regarding the chemical treatment layer described above (a layer formed by degreasing treatment, hydrothermal modification treatment, anodic oxidation treatment, chemical treatment, or a combination of these treatments), in order to improve adhesion, it is possible to perform a complex treatment using the cationic polymer and / or anionic polymer described above, or to laminate the cationic polymer and / or anionic polymer as a multilayer structure for a combination of these treatments. In addition, although it is necessary to consider the stability of the coating solution, a coating agent obtained by pre-liquefying the rare earth oxide sol and the cationic polymer or anionic polymer described above can be used to create a layer that combines both corrosion prevention and adhesion.

[0115] The mass per unit area of ​​the corrosion-prevention treatment layer (15a, 15b) is preferably in the range of 0.005 to 0.200 g / m², and more preferably in the range of 0.010 to 0.100 g / m². If it is 0.005 g / m² or higher, it is easy to impart a corrosion-prevention function to the metal foil layer (14). Also, even if the mass per unit area exceeds 0.200 g / m², the corrosion-prevention function becomes saturated and does not change much. On the other hand, when using a rare earth oxide sol, if the coating film is thick, the curing by heat during drying becomes insufficient, and there is a risk of a decrease in cohesiveness. Also, although the above description is written in terms of mass per unit area, if the specific gravity is known, it is also possible to calculate the thickness from it.

[0116] The thickness of the corrosion-resistant treatment layer (15a, 15b) is preferably 10 nm to 5 μm, for example, in terms of corrosion resistance and function as an anchor, and more preferably 20 to 500 nm.

[0117] (Sealant adhesive layer (16))

[0118] The sealant adhesive layer (16) is a layer that bonds the metal foil layer (14), on which the corrosion-resistant treatment layer (15b) is formed, and the sealant layer (17). The exterior material (10) is broadly divided into a thermal laminate composition and a dry laminate composition depending on the adhesive component that forms the sealant adhesive layer (16).

[0119] In the thermal laminate composition, the adhesive component forming the sealant adhesive layer (16) is preferably an acid-modified polyolefin resin obtained by grafting a polyolefin resin with acid. Since the acid-modified polyolefin resin has polar groups introduced into a part of the non-polar polyolefin resin, it can adhere strongly to both the sealant layer (17), which is composed of a non-polar polyolefin resin film, etc., and the corrosion-prevention treatment layer (15b), which often has polarity. In addition, by using an acid-modified polyolefin resin, the resistance to contents such as the electrolyte of the outer material (10) is improved, and even if hydrofluoric acid is generated inside the battery, it is easy to prevent a decrease in adhesion strength due to the deterioration of the sealant adhesive layer (16).

[0120] Examples of polyolefin resins for acid-modified polyolefin resins include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymer; polypropylene; and propylene-α-olefin copolymer. In the case of a copolymer, the polyolefin resin may be a block copolymer or a random copolymer. Also, as a polyolefin resin, a copolymer obtained by copolymerizing a polar molecule such as acrylic acid or methacrylic acid with the above-mentioned material, or a polymer such as a cross-linked polyolefin, may be used. Examples of acids that modify the polyolefin resin include carboxylic acids, epoxy compounds, and acid anhydrides, and maleic anhydride is preferred. The acid-modified polyolefin resin used in the sealant adhesive layer (16) may be one type or two or more types.

[0121] The sealant adhesive layer (16) of the thermal laminate composition can be formed by extruding the adhesive component with an extrusion device. The thickness of the sealant adhesive layer (16) of the thermal laminate composition is preferably 8 to 50 μm.

[0122] As an adhesive component forming the sealant adhesive layer (16) of the dry laminate composition, for example, the same adhesive as exemplified in the adhesive layer (13) may be used. In this case, in order to suppress swelling by the electrolyte and hydrolysis by hydrofluoric acid, it is desirable to design the composition of the adhesive so that it is a component of a framework that is difficult to hydrolyze and also has a composition that allows for an improvement in crosslinking density.

[0123] In order to improve crosslinking density, for example, a dimer fatty acid, an ester or hydrogenated derivative of a dimer fatty acid, a reducing glycol of a dimer fatty acid, or a reducing glycol of an ester or hydrogenated derivative of a dimer fatty acid may be added to the adhesive. The dimer fatty acid is an acid obtained by dimerizing various unsaturated fatty acids, and examples of its structure include acyclic, monocyclic, polycyclic, and aromatic types.

[0124] The fatty acid used as the starting material for the dimer fatty acid is not particularly limited. In addition, it is acceptable to introduce a dibasic acid used as a conventional polyester polyol, using such a dimer fatty acid as an essential component. As a curing agent for the main component constituting the sealant adhesive layer (16), it is possible to use, for example, an isocyanate compound that can also be used as a chain elongator for polyester polyol. Accordingly, the crosslinking density of the adhesive film is increased, leading to improved solubility and swelling properties, and as the concentration of urethane groups is increased, improved adhesion to the substrate can also be expected.

[0125] Since the sealant adhesive layer (16) of the dry laminate composition has highly hydrolyzable bonding parts such as ester groups and urethane groups, it is preferable to use an adhesive component of the heat laminate composition as the sealant adhesive layer (16) for applications requiring higher reliability. For example, the sealant adhesive layer (16) is formed by mixing the various curing agents described above into a coating solution in which an acid-modified polyolefin resin is dissolved or dispersed in a solvent such as toluene or methylcyclohexane (MCH), and then applying and drying it.

[0126] When the sealant adhesive layer (16) is formed by extrusion molding, the adhesive resin tends to be oriented in the MD direction (extrusion direction) due to stress generated during extrusion molding. In this case, to alleviate the anisotropy of the sealant adhesive layer (16), an elastomer may be added to the sealant adhesive layer (16). For example, an olefin-based elastomer, a styrene-based elastomer, etc., may be used as the elastomer added to the sealant adhesive layer (16).

[0127] The average particle size of the above elastomer is preferably such that it improves the compatibility between the elastomer and the adhesive resin and also improves the effect of mitigating the anisotropy of the sealant adhesive layer (16). Specifically, the average particle size of the above elastomer is preferably, for example, 200 nm or less.

[0128] In addition, the average particle size of the elastomer is determined, for example, by taking an enlarged photograph of a cross-section of the elastomer composition using an electron microscope, and then measuring the average particle size of the dispersed cross-linked rubber component through image analysis. The above elastomer may be used as a single type or in combination of two or more types.

[0129] When an elastomer is added to the sealant adhesive layer (16), the amount of elastomer added to the sealant adhesive layer (16) (100 mass%) is, for example, preferably 1 to 25 mass%, and more preferably 10 to 20 mass%. By making the amount of elastomer added 1 mass% or more, compatibility with the adhesive resin is improved, and the effect of mitigating the anisotropy of the sealant adhesive layer (16) tends to be improved. Also, by making the amount of elastomer added 25 mass% or less, the effect of suppressing swelling of the sealant adhesive layer (16) by the electrolyte tends to be improved.

[0130] As a sealant adhesive layer (16), for example, a dispersion-type adhesive resin liquid in which the adhesive resin is dispersed in an organic solvent may be used.

[0131] In the case of a thermal laminate composition, the thickness of the sealant adhesive layer (16) is preferably 8 to 50 μm, and more preferably 20 to 40 μm. By having a thickness of 8 μm or more of the sealant adhesive layer (16), it is easy to obtain sufficient adhesive strength between the metal foil layer (14) and the sealant layer (17), and by having a thickness of 50 μm or less, it is easy to reduce the amount of moisture penetrating the internal battery element from the cross-section of the exterior material. In addition, in the case of a dry laminate composition, the thickness of the sealant adhesive layer (16) is preferably 1 to 5 μm. Since the thickness of the sealant adhesive layer (16) is 1 μm or more, sufficient adhesive strength between the metal foil layer (14) and the sealant layer (17) can be easily obtained, and since the thickness is 5 μm or less, the occurrence of cracks in the sealant adhesive layer (16) can be suppressed.

[0132] (Sealant layer (17))

[0133] The sealant layer (17) is a layer that provides sealing properties to the outer material (10) by heat sealing, and is a layer that is placed on the inside and heat-fused during assembly of the capacitor device. As for the sealant layer (17), a resin film made of a polyolefin resin or an acid-modified polyolefin resin in which an acid such as maleic anhydride is grafted onto a polyolefin resin may be used. Among these, a polyolefin resin that improves the barrier properties against water vapor and allows the capacitor device to be formed without being excessively crushed by the heat seal is preferred, and polypropylene is particularly preferred.

[0134] Examples of polyolefin resins include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymers; polypropylene; and propylene-α-olefin copolymers. In the case of copolymers, the polyolefin resin may be a block copolymer or a random copolymer. These polyolefin resins may be used as a single type or in combination of two or more types.

[0135] In addition, for each of the above types of polypropylene, namely random polypropylene, homopolypropylene, and blocked polypropylene, anti-blocking agents (AB agents) such as low-crystallinity ethylene-butene copolymer, low-crystallinity propylene-butene copolymer, terpolymer composed of a three-component copolymer of ethylene, butene, and propylene, silica, zeolite, acrylic resin beads, etc., and fatty acid amide-based slip agents may be added.

[0136] Acid-modified polyolefin resins include, for example, the same as those exemplified in the sealant adhesive layer (16).

[0137] The sealant layer (17) may be a single-layer film or a multi-layer film, and can be selected according to the required function. For example, to provide moisture resistance, a multi-layer film containing a resin such as an ethylene-cyclic olefin copolymer and polymethylpentene can be used.

[0138] In addition, the sealant layer (17) may contain various additives such as flame retardants, slip agents, anti-blocking agents, antioxidants, light stabilizers and tackifiers.

[0139] When a heat-weldable film formed by extrusion molding is used as the sealant layer (17), the heat-weldable film tends to be oriented in the extrusion direction. Therefore, in order to mitigate the anisotropy of the sealant layer (17) due to orientation, an elastomer may be added to the heat-weldable film. Accordingly, when the outer material (10) for the capacitor device is cold-formed to form a concave part, the sealant layer (17) can be suppressed from becoming white.

[0140] As the elastomer constituting the sealant layer (17), for example, the same material as the material exemplified as the elastomer constituting the sealant adhesive layer (16) may be used. If the sealant layer (17) is a multilayer film structure, at least one layer among the plurality of layers constituting the multilayer film structure may be configured to include an elastomer. For example, in the case of a three-layer laminated structure consisting of a laminated random polypropylene layer / block polypropylene layer / random polypropylene layer as the sealant layer (17), the elastomer may be blended only in the block polypropylene layer, blended only in the random polypropylene layer, or blended in both the random polypropylene layer and the block polypropylene layer.

[0141] In addition, a lubricant may be included to impart slipperiness to the sealant layer (17). Thus, by having the sealant layer (17) contain a lubricant, when forming a concave portion in the outer material (10) for a capacitor device by cold forming, it becomes possible to suppress the excessive elongation of the side or corner portion of the concave portion, which has a high elongation rate, in the outer material (10) for a capacitor device. Accordingly, it is possible to suppress delamination between the metal foil layer (14) and the sealant adhesive layer (16), as well as breakage and whitening caused by cracks in the sealant layer (17) and the sealant adhesive layer (16).

[0142] When a lubricant is included in the sealant layer (17), the amount of lubricant in the sealant layer (17) (100 mass%) is preferably 0.001 to 0.5 mass%. If the amount of lubricant is 0.001 mass% or more, the sealant layer (17) tends to be more suppressed from whitening during cold forming. Also, if the amount of lubricant is 0.5 mass% or less, the decrease in adhesion strength between the surface of the sealant layer (17) and the surface of another layer in contact with it tends to be suppressed.

[0143] The thickness of the sealant layer (17) is preferably 10 to 100 μm, and more preferably 20 to 60 μm. By having a thickness of 20 μm or more, sufficient heat seal strength can be obtained, and by having a thickness of 60 μm or less, the amount of water vapor intrusion from the end of the exterior material can be reduced.

[0144] [Method for manufacturing exterior materials]

[0145] Next, the manufacturing method of the exterior material (10) will be described. In addition, the manufacturing method of the exterior material (10) is not limited to the following methods.

[0146] As a method for manufacturing the exterior material (10), for example, a method having the following processes S11 to S14 can be cited.

[0147] Process S11: A process of forming an anti-corrosion treatment layer (15a) on one side of a metal foil layer (14) and forming an anti-corrosion treatment layer (15b) on the other side of a metal foil layer (14).

[0148] Process S12: A process of bonding the substrate layer (11) to the side opposite to the metal foil layer (14) of the corrosion-prevention treatment layer (15a) through an adhesive layer (13).

[0149] Process S13: A process of forming a substrate protective layer (12) on the opposite side of the adhesive layer (13) of the substrate layer (11).

[0150] Process S14: A process of forming a sealant layer (17) through a sealant adhesive layer (16) on a surface opposite to the metal foil layer (14) of the corrosion-resistant treatment layer (15b).

[0151] (Process S11)

[0152] In process S11, a corrosion-prevention treatment layer (15a) is formed on one side of the metal foil layer (14), and a corrosion-prevention treatment layer (15b) is formed on the other side of the metal foil layer (14). The corrosion-prevention treatment layers (15a and 15b) may be formed separately, or both may be formed at once. Specifically, for example, a corrosion-prevention treatment agent (base material of the corrosion-prevention treatment layer) is applied to both sides of the metal foil layer (14), and then drying, curing, and baking are performed sequentially to form the corrosion-prevention treatment layers (15a and 15b) at once. Additionally, a corrosion-preventing treatment agent may be applied to one side of the metal foil layer (14), and then drying, curing, and baking may be performed sequentially to form a corrosion-preventing treatment layer (15a), and then a corrosion-preventing treatment layer (15b) may be formed in the same manner on the other side of the metal foil layer (14). The order of forming the corrosion-preventing treatment layers (15a and 15b) is not particularly limited. Also, the corrosion-preventing treatment agent may be different for the corrosion-preventing treatment layer (15a) and the corrosion-preventing treatment layer (15b), or the same may be used. For example, a corrosion-preventing treatment agent for coating-type chromate treatment may be used as the corrosion-preventing treatment agent. The method of applying the corrosion-preventing treatment agent is not particularly limited, but for example, methods such as gravure coating, gravure reverse coating, roll coating, reverse roll coating, die coating, bar coating, kiss coating, and comma coating may be used. In addition, as the metal foil layer (14), an untreated metal foil layer may be used, or a metal foil layer that has been degreased by wet-type degreasing treatment or dry-type degreasing treatment may be used.

[0153] (Process S12)

[0154] In process S12, the surface opposite to the metal foil layer (14) of the corrosion-preventive treatment layer (15a) and the substrate layer (11) are bonded by a method such as dry lamination using an adhesive that forms an adhesive layer (13). In process S12, to promote adhesion, an aging (curing) treatment may be performed in the range of room temperature to 100°C. The aging time is, for example, 1 to 10 days.

[0155] (Process S13)

[0156] In process S13, a substrate protective layer (12) is formed on the side opposite to the adhesive layer (13) of the substrate layer (11). First, a raw material (coating solution: a mixture of polyisocyanate and polyester resin diluted with a solvent) for forming the substrate protective layer (12) is prepared. Next, this coating solution is applied onto the substrate layer (11) using a known method and heated and dried. Examples of such coating methods include gravure direct, gravure reverse (direct, kiss), bar coater, etc. Furthermore, when incorporating the filler described above, a slurry in which the filler is dispersed in a solvent beforehand may be mixed into the varnished resin, or the filler may be directly dispersed into the already varnished resin coating solution. It is also possible to add other additives, such as a curing agent, to these filler mixtures. Additionally, the timing of forming the substrate protective layer (12) is not limited to this embodiment.

[0157] (Process S14)

[0158] After process S13, a sealant layer (17) is formed on the side opposite to the metal foil layer (14) of the corrosion-resistant treatment layer (15b) of a laminate in which a substrate protection layer (12), a substrate layer (11), an adhesive layer (13), a corrosion-resistant treatment layer (15a), a metal foil layer (14), and a corrosion-resistant treatment layer (15b) are laminated in this order, through a sealant adhesive layer (16). The sealant layer (17) may be laminated by dry lamination and sandwich lamination, etc., or may be laminated by co-extrusion together with the sealant adhesive layer (16). For the sake of improved adhesion, it is preferable for the sealant layer (17) to be laminated by, for example, sandwich lamination, or laminated by co-extrusion together with the sealant adhesive layer (16), and it is more preferable for it to be laminated by sandwich lamination.

[0159] An exterior material (10) is obtained by the processes S11 to S14 described above. In addition, the process sequence of the method for manufacturing the exterior material (10) is not limited to the method of sequentially carrying out the processes S11 to S14. For example, the order of the processes carried out may be appropriately changed, such as carrying out process S12 and then carrying out process S11.

[0160] [Capacitor Device]

[0161] Next, a storage device having an exterior material (10) as a container will be described. The storage device has a battery element (1) including an electrode, a lead (2) extending from the electrode, and a container for accommodating the battery element (1). The container is formed such that a sealant layer (17) is on the inside of the exterior material (10) for the storage device. The container may be obtained by overlapping two exterior materials with their sealant layers (17) facing each other and heat-fusing the periphery of the overlapping exterior materials (10), or by overlapping one exterior material by folding it back and likewise heat-fusing the periphery of the exterior material (10). Additionally, the storage device may have an exterior material (20) as a container. The exterior material of this embodiment can be used in various storage devices. Examples of such storage devices include secondary batteries such as lithium-ion batteries, nickel-hydrogen batteries, and lead-acid batteries, and electrochemical capacitors such as electric double layer capacitors.

[0162] The lid (2) is clamped and sealed by an outer material (10) that forms a container with the sealant layer (17) on the inside. The lid (2) may also be clamped by the outer material (10) through a tab sealant.

[0163] [Method for manufacturing a capacitor device]

[0164] Next, a method for manufacturing a storage device using the exterior material (10) described above will be explained. Additionally, here, the case of manufacturing a secondary battery (40) using an embossed type exterior material (30) will be explained as an example. FIG. 2 is a drawing showing the embossed type exterior material (30). FIG. 3 (a) to (d) are perspective views showing the manufacturing process of a single-sided molded battery using the exterior material (10). The secondary battery (40) may be a double-sided molded battery manufactured by forming two exterior materials such as the embossed type exterior material (30) and laminating them while adjusting the alignment. Also, the embossed type exterior material (30) may be formed using the exterior material (20).

[0165] A secondary battery (40) that is a unilaterally molded processed battery can be manufactured, for example, by the following processes S21 to S25.

[0166] Process S21: A process for preparing an outer material (10), a battery element (1) including an electrode, and a lead (2) extending from the electrode.

[0167] Process S22: A process of forming a recess (32) for placing a battery element (1) on one side of an exterior material (10) (see FIG. 3(a) and FIG. 3(b)).

[0168] Process S23: A process of placing a battery element (1) in a molding processing area (concave portion (32)) of an embossed type exterior material (30), folding and overlapping the embossed type exterior material (30) so that the cover portion (34) covers the concave portion (32), and applying pressure and heat-fusion to one side of the embossed type exterior material (30) to clamp a lead (2) extending from the battery element (1) (see FIG. 3(b) and FIG. 3(c)).

[0169] Process S24: A process of leaving one side other than the side that clamps the lead (2), pressing and heat-sealing the other side, then injecting an electrolyte from the remaining side, and pressing and heat-sealing the remaining side under vacuum (see FIG. 3(c)).

[0170] Process S25: A process of cutting the end of the pressure heat-fusion side other than the side that clamps the lead (2), and folding and bending it toward the forming processing area (concave part (32)) (see FIG. 3(d)).

[0171] (Process S21)

[0172] In process S21, an outer casing (10), a battery element (1) including an electrode, and a lead (2) extending from the electrode are prepared. The outer casing (10) is prepared based on the embodiment described above. There are no particular limitations on the battery element (1) and the lead (2), and known battery elements (1) and leads (2) may be used.

[0173] (Process S22)

[0174] In process S22, a recess (32) is formed on the sealant layer (17) side of the exterior material (10) to accommodate a battery element (1). The planar shape of the recess (32) is a shape that matches the shape of the battery element (1), for example, a rectangular shape when viewed from a planar perspective. The recess (32) is formed by pressing a pressing member, for example, having a rectangular pressure surface, against a part of the exterior material (10) in the thickness direction. Also, the pressing position, i.e., the recess (32), is formed at a position offset from the center of the rectangularly cut exterior material (10) to one end in the longitudinal direction of the exterior material (10). Accordingly, after the molding process, the other end side that does not have the recess (32) formed can be folded back and bent to form a cover (cover part (34)).

[0175] More specifically, a method for forming the concave portion (32) may be formed using a mold (deep-cross forming). As a forming method, a female mold and a male mold are arranged to have a gap greater than the thickness of the exterior material (10), and the male mold is pushed into the female mold together with the exterior material (10). By adjusting the amount of pressing of the male mold, the depth of the concave portion (32) (deep-cross amount) can be adjusted to a desired amount. By forming the concave portion (32) in the exterior material (10), an embossed type exterior material (30) is obtained. This embossed type exterior material (30) has a shape as shown in FIG. 2, for example. Here, FIG. 2(a) is a perspective view of an embossed type exterior material (30), and FIG. 2(b) is a longitudinal section view along the bb line of the embossed type exterior material (30) shown in FIG. 2(a).

[0176] (Process S23)

[0177] In process S23, a battery element (1) composed of a positive electrode, a separator, and a negative electrode is placed within the molding processing area (concave portion (32)) of the embossed-type exterior material (30). Additionally, a lead (2) extending from the battery element (1) and joined to the positive electrode and the negative electrode, respectively, is drawn out from the molding processing area (concave portion (32)). Afterward, the embossed-type exterior material (30) is folded back at approximately the center in the longitudinal direction, and the sealant layers (17) are overlapped so that they face inward, and one side of the embossed-type exterior material (30) that grips the lead (2) is heat-fused under pressure. The heat-fused under pressure is controlled by three conditions of temperature, pressure, and time and is appropriately set. It is preferable that the temperature of the heat-fused under pressure be higher than the temperature at which the sealant layer (17) melts.

[0178] Additionally, the thickness of the sealant layer (17) before heat fusion is preferably 40% or more and 80% or less of the thickness of the lead (2). Since the thickness of the sealant layer (17) is greater than or equal to the lower limit value, the heat fusion resin tends to sufficiently fill the end of the lead (2), and since it is less than or equal to the upper limit value, the thickness of the end of the outer material (10) of the secondary battery (40) can be appropriately suppressed, thereby reducing the amount of moisture intrusion from the end of the outer material (10).

[0179] (Process S24)

[0180] In process S24, one side other than the side that clamps the lead (2) is left intact, and pressure heat fusion is performed on the other side. After that, an electrolyte is injected from the remaining side, and the remaining side is pressure heat fused under vacuum. The conditions for pressure heat fusion are the same as in process S23.

[0181] (Process S25)

[0182] The end of the perimeter edge pressure heat-fusion side other than the side that clamps the lead (2) is cut, and the sealant layer (17) that protrudes from the end is removed. Then, the perimeter edge pressure heat-fusion side is folded back toward the molding processing area (32) (concave part (32)), and by forming the folded part (42), a secondary battery (40) is obtained.

[0183] <Second Embodiment>

[0184] [Exterior material for capacitors]

[0185] The description regarding the outer casing for a storage device of the present embodiment shall be in accordance with the description of the first embodiment. That is, FIG. 1 is a cross-sectional view schematically showing the outer casing for a storage device of the present embodiment. In the present embodiment, the substrate protective layer is a cured product of a raw material comprising an aromatic polyesterurethane resin and a polyisocyanate, and the ratio of the number of moles of hydroxyl groups of the aromatic polyesterurethane resin to the number of moles of isocyanate groups of the polyisocyanate is within a specific range. Accordingly, moldability and electrolyte resistance can be improved.

[0186] (Material protection layer (12))

[0187] The substrate protective layer (12) is a layer formed on one side of the substrate layer (11), and is obtained by reacting an aromatic polyester urethane resin with a polyisocyanate. That is, the substrate protective layer (12) is a cured product of raw materials containing an aromatic polyester urethane resin and a polyisocyanate. Originally, since the polyester urethane resin has urethane groups in its structure, it can be a good protective layer with excellent adhesion to the substrate, but according to the inventors' knowledge, it has been revealed that it is desirable to use a polyisocyanate in combination with the polyester urethane resin in order to provide the substrate protective layer with even better resistance to electrolytes.

[0188] Aromatic polyester urethane resin is a resin obtained by reacting an aromatic polyester resin with an isocyanate, which acts as a curing agent. In other words, aromatic polyester urethane resin can be described as an aromatic polyester resin whose chains have been extended by a polyisocyanate.

[0189] In addition, the aromatic polyester resin is a copolymer based on a dicarboxylic acid and a diol, at least one of which is aromatic.

[0190] As dicarboxylic acids, either aliphatic dicarboxylic acids or aromatic dicarboxylic acids may be used. Specifically, examples include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, souveric acid, azelaic acid, sebacic acid, and brasylic acid; and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, and naphthalene dicarboxylic acid.

[0191] Examples of diols include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; and aromatic diols such as xylylene glycol.

[0192] As the polyisocyanate used as a curing agent, various types of aromatic, aliphatic, and alicyclic polyisocyanates may be used. Specific examples include aliphatic hexamethylene diisocyanate (HDI), etc.; aromatic tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), etc.; alicyclic isophorone diisocyanate (IPDI), etc.; and polyisocyanate modified products derived from one or more of these diisocyanates.

[0193] The molecular weight of the aromatic polyester urethane resin is preferably such that the number average molecular weight (Mn) is 10,000 to 40,000 in terms of resistance to electrolyte and adhesion to the substrate layer (11).

[0194] The hydroxyl group value of the aromatic polyester urethane resin is preferably 2 to 20 KOH mg / g, and more preferably 3 to 6 KOH mg / g. If the hydroxyl group value is less than 2 KOH mg / g, further improvement in durability cannot be expected, and if it exceeds 20 KOH mg / g, the functionality due to crosslinking becomes saturated.

[0195] The glass transition temperature (Tg) of the aromatic polyesterurethane resin is not particularly limited, but it is preferably -3 to 100°C, and more preferably 20 to 50°C. However, in the present embodiment, it is preferable to have a blend of two or more aromatic polyesterurethane resins with different glass transition temperatures. Generally, when the glass transition temperature of the polyesterurethane resin is high (40°C or higher), there are many cases where a large number of aromatic units are included, and although the durability is excellent because it has a rigid structure, the elongation of the film tends to decrease and moldability tends to be poor. On the other hand, when the glass transition temperature is low (less than 40°C), the number of aromatic units is small and it has a flexible structure, so the flexibility (moldability) is excellent, but since the tack increases, blocking during coating winding tends to decrease. In this regard, from the perspective of achieving a balance of the resin's hardness and other properties, by blending aromatic polyesterurethane resins with different glass transition temperatures, it becomes easier to achieve excellent electrolyte resistance while making the moldability equivalent to that of a nylon film. As a suitable embodiment, it is preferable to use an aromatic polyesterurethane resin blended with a resin having a glass transition temperature of at least 20 to 30°C and a resin having a glass transition temperature of 40 to 50°C.

[0196] As the polyisocyanate to be reacted with the aromatic polyesterurethane resin, the above-mentioned polyisocyanate used when synthesizing the aromatic polyesterurethane resin may be appropriately used. However, among aromatic, aliphatic, and alicyclic polyisocyanates, in this embodiment, a polyisocyanate that does not have an alicyclic structure (is not alicyclic) is preferred from the perspective of improving electrolyte resistance, and an aliphatic polyisocyanate is more preferred. In particular, an adduct or burette of hexamethylene diisocyanate is suitablely used to impart electrolyte resistance. Furthermore, when 50 mass% or more of a polyisocyanate that does not have an alicyclic structure is used based on the total mass (100 mass%) of the polyisocyanate, alcohol resistance also tends to be exhibited. For example, when a battery cell manufacturer prints using an inkjet printer for lot trace management, there are cases where incorrect information is printed. In that case, the printing site is wiped with alcohol and re-printed, but such a polyisocyanate type is effective in that it improves resistance to wiping off alcohol.

[0197] The mixing ratio of the aromatic polyester urethane resin, which is the main component, and the polyisocyanate, which is the curing agent, is adjusted so that the ratio [NCO] / [OH] is 5 to 20, where [OH] is the number of moles of hydroxyl groups in the main component and [NCO] is the number of moles of isocyanate groups in the curing agent. If the ratio is less than 5, further improvement in durability cannot be expected, and if it exceeds 20, there is a risk that the film will become excessively hard because the crosslinking points due to urethane bonding become dense. From this perspective, it is preferable that [NCO] / [OH] be 5 to 20.

[0198] Other descriptions regarding the protective layer (12) are based on the description of the first embodiment, except that aromatic polyester urethane resin is used instead of polyester resin.

[0199] The descriptions regarding the substrate layer (11), adhesive layer (13), metal foil layer (14), corrosion prevention treatment layer (15a, 15b), sealant adhesive layer (16), and sealant layer (17) are based on the descriptions of the first embodiment, except that aromatic polyester urethane resin is used instead of polyester resin.

[0200] [Method for manufacturing exterior material, capacitor device, method for manufacturing capacitor device]

[0201] The description regarding these is based on the description of the first embodiment, except that an aromatic polyester urethane resin is used instead of a polyester resin.

[0202] Although preferred embodiments of the exterior material for a capacitor device and the method for manufacturing a capacitor device according to the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

[0203] Examples

[0204] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0205] [Experiment 1]

[0206] Regarding the first invention, an outer casing for a capacitor device was manufactured and its various characteristics were evaluated.

[0207] (Example 1-1)

[0208] In Example 1-1, an outer casing (10) for a capacitor device was manufactured by the following method. First, as a metal foil layer (14), a soft aluminum foil 8079 material (manufactured by Toyo Aluminum Co., Ltd.) with a thickness of 35 μm was prepared. Subsequently, on both sides of the metal foil layer (14), a sodium polyphosphate stabilized cerium oxide sol (corrosion prevention treatment agent) was applied by gravure coating using distilled water as a solvent and adjusted to a solid content concentration of 10 mass%. At this time, the phosphoric acid was 10 mass parts for every 100 mass parts of cerium oxide.

[0209] Next, the applied sodium polyphosphate-stabilized cerium oxide sol was dried, and then a baking treatment was sequentially performed to form an anti-corrosion treatment layer (15a) on one side of the metal foil layer (14) and an anti-corrosion treatment layer (15b) on the other side. At this time, the baking conditions were set such that the temperature was 150°C and the treatment time was 30 seconds.

[0210] Next, a nylon film (thickness 15 μm) was used as the substrate layer (11), and one side of the substrate layer (11) was corona treated.

[0211] Next, a polyurethane-based adhesive (thickness 3 μm) was applied as an adhesive layer (13) on the side of the corrosion-resistant treatment layer (15a) of the metal foil layer (14) opposite to the metal foil layer (14). Then, by dry lamination, the corona-treated surface of the metal foil layer (14) and the substrate layer (11) was bonded through the adhesive layer (13). After that, the structure consisting of the substrate layer (11), the adhesive layer (13), the corrosion-resistant treatment layer (15a), the metal foil layer (14), and the corrosion-resistant treatment layer (15b) was aged by leaving it in an atmosphere at a temperature of 60°C for 6 days.

[0212] Next, a coating solution for forming a substrate protective layer was prepared, and a substrate protective layer (12) with a thickness of 3 μm was formed by coating the surface opposite to the adhesive layer (13) of the substrate layer (11) and drying it. In addition, the coating solution for forming a substrate protective layer was prepared as follows. That is, a filler was directly dispersed in a varnished resin coating solution, and other additives such as a curing agent were mixed into the filler mixture to prepare the coating solution for forming a substrate protective layer.

[0213] Then, on the side opposite to the metal foil layer (14) of the corrosion prevention treatment layer (15b), a sealant adhesive layer (16) was formed by extruding maleic anhydride modified polypropylene (manufactured by Mitsui Chemical Co., Ltd., trade name: Admer), which serves as the base material. At this time, the thickness of the sealant adhesive layer (16) was set to 15 μm. Then, by the sandwich lamination method, a polyolefin film with a thickness of 20 μm (a film in which the side of the sealant adhesive layer (16) of an unoriented polypropylene film is corona treated) which serves as the sealant layer (17) was bonded (heat-pressed) at 180°C through the sealant adhesive layer (16) to the corrosion prevention treatment layer (15b). Accordingly, an outer casing (10) for a capacitor device was manufactured.

[0214] (Other examples and comparative examples)

[0215] An outer casing (10) for a capacitor device was manufactured in the same manner as Example 1-1, except that the substrate protective layer composition and configuration pattern shown in Table 1 were adopted. In Table 1, the ending -A in the curing agent type indicates an adduct body, and the ending -N indicates a nurate body. In addition, for some examples, the outer casing was manufactured by changing the order as follows.

[0216] (Examples 1-11 to 1-12)

[0217] Instead of forming the corrosion-resistant treatment layers (15a and 15b) using a sodium polyphosphate-stabilized cerium oxide sol, a treatment solution consisting of phenol resin, a chromium fluoride compound, and phosphoric acid was applied to both sides of the metal foil layer (14) to form a film, and a chromate treatment was performed by baking to form the corrosion-resistant treatment layers (15a and 15b). Except for this, the outer casing (10) for the capacitor device was manufactured in the same manner as in Example 1-1.

[0218] (Examples 1-13 to 1-14)

[0219] In the same manner as in Examples 1-11, a chromate treatment was performed to form an anti-corrosion treatment layer (15a and 15b). Additionally, on the side opposite to the metal foil layer (14) of the anti-corrosion treatment layer (15b), a polyurethane-based adhesive (thickness 5 μm) was applied, which is a polyisocyanate compounded with an acid-modified polyolefin dissolved in a mixed solvent of toluene and methylcyclohexane. Subsequently, by a dry lamination method, a polyolefin film with a thickness of 30 μm (a film in which the side of the sealant adhesive layer (16) of an unoriented polypropylene film has been corona-treated) which becomes the sealant layer (17) and the metal foil layer (14) were bonded through the sealant adhesive layer (16). After that, the structure comprising a substrate layer (11), an adhesive layer (13), an anti-corrosion treatment layer (15a), a metal foil layer (14), an anti-corrosion treatment layer (15b), a sealant adhesive layer (16), and a sealant layer (17) was aged by leaving it in an atmosphere at a temperature of 40°C for 6 days. Except for this, an outer casing (10) for a capacitor device was manufactured in the same manner as in Example 1-1.

[0220]

[0221] <Evaluation of Electrolyte Tolerance>

[0222] An electrolyte solution (ethylene carbonate / dimethyl carbonate / diethyl carbonate = 1:1:1 wt%, LiPF6, 1 M) with a small amount of water (1500 ppm) added was applied dropwise to the coating layer of the exterior material obtained in each example, and after a specified time, it was wiped off with isopropyl alcohol. Afterward, the appearance of the application site was evaluated according to the following criteria. The results are shown in Table 2.

[0223] ◎: After 15 minutes, the point where the electrolyte was dropped could not be identified.

[0224] ○: After 10 minutes, the spot where the electrolyte was dropped could not be identified, but after 15 minutes, an outline appeared.

[0225] △: After 5 minutes, the point where the electrolyte was dropped could not be identified, but after 10 minutes, an outline appeared.

[0226] ▲: After 3 minutes, the point where the electrolyte was dropped could not be identified, but after 5 minutes, an outline appeared.

[0227] ×: After 1 minute, the spot where the electrolyte was dropped could not be identified, but after 3 minutes, an outline appeared.

[0228] <Assessment of Alcohol Tolerance>

[0229] A cotton ball measuring 1 cm on each side, soaked in ethanol, was placed on the coating layer of the exterior material obtained in each example, and rubbed at a constant speed with a weight of 500 g applied from above (alcohol rubbing method). Then, after repeating the rubbing a prescribed number of times, the absence of peeling on the coating film was evaluated according to the following criteria. The results are shown in Table 2.

[0230] ◎: No peeling occurred even after repeating more than 20 times.

[0231] ○: After 15 repetitions, no peeling occurred, but after 20 repetitions, peeling occurred.

[0232] △: Delamination did not occur after 10 repetitions, but delamination occurred after 15 repetitions.

[0233] ▲: After 5 repetitions, no peeling occurred, but after 10 repetitions, peeling occurred.

[0234] ×: Delamination did not occur on the first attempt, but occurred after 5 repetitions.

[0235] <Evaluation of Closeness>

[0236] For the exterior material obtained in each example, the adhesion between the substrate layer (11) and the substrate protection layer (12) was evaluated by the following method.

[0237] First, using a cutter knife on the test surface, 11 cuts were made with a spacing of 1 mm between cuts reaching the substrate to create 100 meshes. Then, cellophane tape was strongly pressed onto the meshes, and the ends of the tape were peeled off in one go at a 90° angle. The number of meshes where the coating film was not peeled off was counted visually, and evaluated according to the following criteria. The results are shown in Table 2.

[0238] ◎: 100 pieces

[0239] ○: 90 ~ 99 items

[0240] △: 80 ~ 89 items

[0241] ▲: 70 ~ 79 items

[0242] ×: Less than 70

[0243] <Evaluation of Plastic Surgery Depth>

[0244] For the exterior material obtained in each example, the forming depth capable of deep forming was evaluated by the following method. First, the exterior material (10) for the capacitor device was placed in a forming device such that the sealant layer (17) faced upward. The forming depth of the forming device was set to 5.0 to 7.5 mm for every 0.5 mm, and cold forming was performed under an environment of room temperature 23°C and dew point temperature -35°C. In addition, a punch die was used that had a rectangular cross-section of 70 mm × 80 mm, a punch radius (RP) of 1.00 mm on the bottom surface, and a punch corner radius (RCP) of 1.00 mm on the side surface. In addition, a die die was used that had a die radius (RD) of 1.00 mm on the upper surface of the opening. The presence or absence of fractures and pinholes in the cold-formed parts was visually inspected while illuminating the exterior material with light, and the maximum forming depth at which deep forming was possible without any fractures or pinholes was determined. In addition, the forming depth was evaluated according to the following criteria. The results are shown in Table 2.

[0245] ◎: A difference of 0.25 mm or less compared to the case without a substrate protective layer (Comparative Example 1-1).

[0246] ○: A difference of more than 0.25 mm and less than or equal to 0.50 mm compared to the case where there is no protective layer.

[0247] △: A difference of more than 0.50 mm and less than or equal to 1.0 mm compared to the case where there is no protective layer.

[0248] ▲: A difference of more than 1.0 mm and less than or equal to 1.5 mm compared to the case where there is no protective layer.

[0249] ×: A difference of more than 1.5 mm compared to the case without a protective layer.

[0250] <Evaluation of Insulation>

[0251] At the stage where a substrate protection layer, a substrate layer, an adhesive layer, and a metal foil layer having corrosion-resistant treatment layers on both sides are laminated in this order, an insulation performance evaluation was performed on the laminate. A withstand voltage and insulation resistance tester (manufactured by KIKUSUI, “TOS9201”) was used for the insulation performance evaluation. One electrode was fixed to the side of the exposed corrosion-resistant treatment layer, water was dropped onto the surface of the substrate protection layer, and the other electrode was brought into contact with the dropped area. A constant voltage of 100 V was applied for 3 minutes, and the insulation resistance of the laminate was measured. The insulation resistance was evaluated according to the following criteria. The results are shown in Table 2.

[0252] ◎: 20,000 MΩ or higher.

[0253] ○: 10,000 MΩ or more and less than 20,000 MΩ.

[0254] △: 2000 MΩ or more and less than 10000 MΩ.

[0255] ×: Less than 2000 MΩ.

[0256]

[0257] With the exterior material of this embodiment, electrolyte resistance, alcohol resistance, adhesion, and moldability can be expressed in a balanced manner. Particular attention is paid to the substrate protection layer. It is understood that by increasing the number of urethane bonds, adhesion to the substrate layer is improved, while by keeping the amount of polyisocyanate within a certain range, moldability and electrolyte resistance and alcohol resistance can be achieved simultaneously.

[0258] [Experiment 2]

[0259] Regarding the second invention, an outer casing for a capacitor device was manufactured and its various characteristics were evaluated.

[0260] (Example 2-1)

[0261] Except for forming the substrate protective layer (12) as described below, an outer material (10) for a capacitor device was manufactured in the same manner as in Example 1-1. Specifically, a coating solution for forming the substrate protective layer was prepared, and a substrate protective layer (12) with a thickness of 5 μm was formed by coating the surface opposite to the adhesive layer (13) of the substrate layer (11) and drying it. In addition, the coating solution for forming the substrate protective layer was prepared as follows. Specifically, the coating solution for forming the substrate protective layer was prepared by adding an aromatic polyester urethane resin A and / or B and an inorganic filler shown in Table 3 to an organic solvent, and then adding a polyisocyanate resin.

[0262]

[0263] (Other examples and comparative examples)

[0264] An outer casing (10) for a capacitor device was manufactured in the same manner as in Example 2-1, except that the substrate protective layer composition and configuration pattern shown in Table 4 were adopted. In Table 4, the ending -A in the isocyanate type indicates that it is an adduct. In addition, for some examples, the outer casing was manufactured by changing the order as follows.

[0265] (Example 2-17)

[0266] An outer casing (10) for a capacitor device was manufactured in the same manner as Example 2-1, except that a structure was obtained by the dry lamination method in the same manner as Example 1-13.

[0267] (Examples 2-18 to 2-19)

[0268] An outer casing (10) for a capacitor device was manufactured in the same manner as in Example 2-1, except that a corrosion-resistant treatment layer (15a and 15b) was formed in the same manner as in Example 1-11.

[0269] (Examples 2-20 to 2-21)

[0270] An outer casing (10) for a capacitor device was manufactured in the same manner as Example 2-1, except that an anti-corrosion treatment layer (15a and 15b) was formed in the same manner as Example 1-11, and a structure was obtained by a dry lamination method in the same manner as Example 1-13.

[0271]

[0272] <Evaluation of Electrolyte Tolerance>

[0273] In the same manner as Experiment 1, the electrolyte resistance of the exterior materials obtained in each example was evaluated according to the following criteria. The results are shown in Table 5.

[0274] ◎: After 15 minutes, the point where the electrolyte was dropped could not be identified.

[0275] ○: After 10 minutes, the spot where the electrolyte was dropped could not be identified, but after 15 minutes, an outline appeared.

[0276] △: After 5 minutes, the point where the electrolyte was dropped could not be identified, but after 10 minutes, an outline appeared.

[0277] ×: After 1 minute, the point where the electrolyte was dropped could not be identified, but after 5 minutes, an outline appeared.

[0278] <Assessment of Alcohol Tolerance>

[0279] In the same manner as Experiment 1, the alcohol resistance of the exterior materials obtained in each example was evaluated according to the following criteria. The results are shown in Table 5.

[0280] ◎: No peeling occurred even after repeating more than 20 times.

[0281] ○: After 15 repetitions, no peeling occurred, but after 20 repetitions, peeling occurred.

[0282] △: Delamination did not occur after 10 repetitions, but delamination occurred after 15 repetitions.

[0283] ×: Delamination did not occur on the first attempt, but occurred after 10 repetitions.

[0284] <Evaluation of Plastic Surgery Depth>

[0285] In the same manner as Experiment 1, the molding depth of the exterior materials obtained in each example was evaluated according to the following criteria. The results are shown in Table 5.

[0286] ◎: A difference of 0.25 mm or less compared to the case without a substrate protective layer (Comparative Example 2-1).

[0287] ○: A difference of more than 0.25 mm and less than or equal to 0.50 mm compared to the case where there is no protective layer.

[0288] △: A difference of more than 0.50 mm and less than or equal to 1.0 mm compared to the case where there is no protective layer.

[0289] ×: A difference of more than 1.0 mm compared to the case without a protective layer.

[0290] <Evaluation of Insulation>

[0291] In the same manner as Experiment 1, the insulation resistance of a laminate of metal foil layers having a substrate protection layer, a substrate layer, an adhesive layer, and corrosion-resistant treatment layers on both sides was evaluated according to the following criteria. The results are shown in Table 5.

[0292] ◎: 20,000 MΩ or higher.

[0293] ○: 10,000 MΩ or more and less than 20,000 MΩ.

[0294] △: 2000 MΩ or more and less than 10000 MΩ.

[0295] ×: Less than 2000 MΩ.

[0296]

[0297] If the exterior material of this embodiment is used, it can exhibit balanced resistance to electrolytes, resistance to alcohol, and moldability. Explanation of the symbols

[0298] 1: Battery element 2: Lead 10: Exterior material for capacitor devices (Exterior material) 11: Record layer 12: Material protection layer 13: Adhesive layer 14: Metal foil layer 15a, 15b: Corrosion-resistant treatment layer 16: Sealant adhesive layer 17: Sealant layer 30: Embossed type exterior material 32: Forming processing area (concave part) 34: Cover part 40: Secondary battery

Claims

Claim 1 An outer casing for a capacitor device, having a structure in which at least a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, wherein the substrate protective layer is a cured product of a raw material comprising a polyester resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the polyester resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60, and the hydroxyl value of the polyester resin is 10 to 70 KOH mg / g. Claim 2 An outer casing for a capacitor device having a structure in which at least a substrate protective layer, a substrate layer, an adhesive layer, a metal foil layer, a sealant adhesive layer, and a sealant layer are laminated in this order, wherein the substrate protective layer is a cured product of a raw material comprising an aromatic polyesterurethane resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the aromatic polyesterurethane resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 20. Claim 3 An outer casing for a capacitor device according to claim 1 or 2, wherein the insulation resistance between the layers is 2000 MΩ or more when a constant voltage of 100 V is applied for 3 minutes between the substrate protective layer and the metal foil layer while water is attached to the substrate protective layer. Claim 4 An outer casing for a capacitor device according to claim 1 or 2, wherein the polyisocyanate comprises 50 mass% or more of a polyisocyanate that does not have a cycloaliphatic structure. Claim 5 In claim 4, the outer casing for a capacitor device, wherein the polyisocyanate not having the above-mentioned alicyclic structure is an aliphatic polyisocyanate. Claim 6 In claim 4, the polyisocyanate not having the above-mentioned alicyclic structure is an adduct or burette chain of an aliphatic polyisocyanate, an outer casing for a capacitor device. Claim 7 An outer material for a capacitor device according to claim 2, wherein the aromatic polyesterurethane resin is a blend of two or more aromatic polyesterurethane resins having different glass transition temperatures (Tg). Claim 8 An outer material for a storage device according to claim 1 or 2, wherein the raw material also includes a filler. Claim 9 A method for manufacturing an outer casing for a capacitor device, comprising the steps of: laminating a substrate layer to one side of a metal foil layer through an adhesive layer; forming a substrate protective layer on the side of the substrate layer opposite to the adhesive layer; and forming a sealant layer on the side of the metal foil layer opposite to the adhesive layer through a sealant adhesive layer, wherein the substrate protective layer is a cured product of a raw material comprising a polyester resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the polyester resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 60, and the hydroxyl group value of the polyester resin is 10 to 70 KOH mg / g. Claim 10 A method for manufacturing an outer casing for a capacitor device, comprising the steps of: laminating a substrate layer to one side of a metal foil layer through an adhesive layer; forming a substrate protective layer on the side of the substrate layer opposite to the adhesive layer; and forming a sealant layer on the side of the metal foil layer opposite to the adhesive layer through a sealant adhesive layer, wherein the substrate protective layer is a cured product of a raw material comprising an aromatic polyesterurethane resin and a polyisocyanate, and when the number of moles of hydroxyl groups of the aromatic polyesterurethane resin is [OH] and the number of moles of isocyanate groups of the polyisocyanate is [NCO], the ratio [NCO] / [OH] is 5 to 20.

Images