Laminated film, method for producing laminated film, laminated structure, current collector, electrode for bipolar battery, and secondary battery

Abstract

This laminated structure has an Al layer, an adhesive layer, and a Cu layer in the stated order. The thickness of the Cu layer is 0.5-5.0 μm. The indentation hardness of the surface of the Cu layer on the side opposite to the Al layer as measured by a nanoindentation method is 1.40 GPa or more. The present invention provides: a current collector which is suitable for weight reduction and in which it is possible to suppress deterioration of the adhesive layer due to water vapor or a component derived from an electrolyte, and to suppress decrease in the adhesion strength due to gas generated from the adhesive layer; and the Cu layer for achieving the current collector.

Description

Laminated film, method for manufacturing a laminated film, laminated structure, current collector, electrode for a bipolar battery, and secondary battery

[0001] The present invention relates to laminated films, laminates, components, and current collectors suitably used in wiring boards, secondary batteries, bipolar lithium-ion batteries, and the like.

[0002] Portable devices such as smartphones and laptop computers, as well as electric vehicles, are equipped with lithium-ion secondary batteries (LIBs), and in recent years, there has been a demand for increased energy density in order to further reduce weight and improve performance.

[0003] A lithium-ion battery (LIB) is primarily composed of electrode materials, a battery separator, an electrolyte, and a current collector. The current collector collects and outputs the generated current, and aluminum foil or copper foil is used for this purpose. One measure to improve the gravimetric energy density of an LIB is to thin the metal foil used in the current collector. However, thin metal foil has poor mechanical strength, making it difficult to handle and process, which can lead to decreased yield and reduced reliability in LIB manufacturing.

[0004] To solve this problem, a method has been devised that utilizes a metallized film (hereinafter referred to as a film current collector) in which a thin metal layer is deposited on a lightweight resin film substrate by vacuum deposition technology or plating (Patent Documents 1 to 4). Patent Document 5 also discloses a current collector in which electrode layers suitable for the positive and negative electrodes are laminated, and as a specific example, a current collector in which Al foil and Cu foil are joined with an adhesive.

[0005] Japanese Patent Publication No. 2018-113242, International Publication No. 2011 / 092938, Japanese Patent Publication No. 2019-179732, International Publication No. 2015 / 005116, Japanese Patent Publication No. 2024-67946

[0006] Current collectors made by bonding aluminum foil and copper foil with adhesive still face the challenge of reducing the weight of the current collector. Furthermore, it has been found that there is a problem of reduced adhesion due to gases generated from the adhesive.

[0007] On the other hand, when film current collectors are applied to LIBs for the purpose of weight reduction, pinholes in the metal film, which are likely to occur if the metal film thickness is thin, can allow water vapor and components derived from the electrolyte to permeate, potentially leading to undesirable reactions.

[0008] The present invention aims to provide a current collector that can suppress deterioration of the adhesive layer due to water vapor and electrolyte-derived components, as well as a reduction in adhesion strength due to gases generated from the adhesive layer, and is suitable for weight reduction, and a laminated film having a metal layer for realizing the current collector.

[0009] A preferred embodiment of the present invention is as follows: (1) A laminated film having a metal layer on at least one side of a film substrate, wherein the metal layer includes a layer made of Cu (Cu layer), the peeling force when peeling the metal layer from the film substrate is 0.01 N / cm or more and 2.00 N / cm or less, the total area of ​​pinholes when observing a 10 mm × 10 mm area of ​​the metal layer is 0.03% or less of the area of ​​the observation range, and the water vapor transmission rate of the laminated film at a temperature of 40°C and a humidity of 90% RH is 0.0001 g / m ２ / day or more 10g / m ２(1) A laminated film having a density of 0.5 μm or less per day. (2) The laminated film according to (1), wherein the thickness of the Cu layer is 0.5 μm or more and 5.0 μm or less. (3) The laminated film according to (1) or (2), wherein the thickness of the Cu layer is 0.7 μm or more and 2.0 μm or less. (4) The laminated film according to any one of (1) to (3), wherein the film substrate has a laminated structure. (5) The laminated film according to any one of (1) to (4), wherein the film substrate has a substrate layer and a release layer, and the release layer is located on the surface layer on the metal layer side of the film substrate. (6) The laminated film according to (5), wherein the release layer contains one or more selected from the group consisting of melamine resin, silicone resin, fluororesin, cellulose derivative, urea resin, polyolefin resin, paraffin resin, and composites thereof, Cr, Ni, Co, Fe, Mo, Ti, W, P, or alloys thereof, graphite, and diamond-like carbon, and the total amount thereof is 80% by mass or more. (7) The laminated film according to any one of (1) to (6), wherein the metal layer contains a rust-preventive layer, and the rust-preventive layer is located on the surface of the metal layer closer to the film substrate than the Cu layer. (8) The laminated film according to (7), wherein the peeling force when peeling the metal layer from the film substrate is 0.01 N / cm or more and 2.00 N / cm or less, and the surface resistance of the rust-preventive layer after transferring the metal layer and performing a heat treatment for 500 hours in an atmosphere of 85°C and 85% RH is 0.1 Ω / □ or less. (9) The laminated film according to (7) or (8), wherein the rust-preventive layer contains 20% by mass or more of any element selected from the group consisting of Ni, Cr, and Ti. (10) The laminated film according to any one of (1) to (9), wherein the arithmetic mean roughness Sa of the surface of the metal layer opposite to the film substrate is 20 nm or more and 200 nm or less, and the arithmetic mean roughness Sa of the surface of the metal layer on the film substrate side is 10 nm or more and 50 nm or less. (11) A method for manufacturing the laminated film according to any one of (1) to (10), wherein the metal layer is formed using a method that includes at least one of vacuum deposition, sputtering, or plating. (12) The method for manufacturing the laminated film according to (11), wherein the metal layer is formed using a method that includes at least two of vacuum deposition, sputtering, or plating.(13) A laminated structure having an Al layer, an adhesive layer, and a metal layer in this order, wherein the metal layer includes a layer made of Cu (Cu layer), the thickness of the Cu layer is 0.5 μm or more and 5.0 μm or less, and the indentation hardness of the surface of the Cu layer opposite to the adhesive layer by nanoindentation method is 1.40 GPa or more. (14) The laminated structure according to (13), characterized in that the indentation hardness of the surface of the metal layer opposite to the adhesive layer by nanoindentation method is measured at 9 points (3 x 3 intersections) arranged in a grid at 1 mm intervals, and the standard deviation of the measured values ​​of the indentation hardness at the 9 points is 0.30 GPa or less. (15) The laminated structure according to (14), wherein the metal layer has a rust-preventive layer on the side of the Cu layer opposite to the adhesive layer side. (16) The laminated structure according to (15), wherein the surface resistance of the rust-preventive layer after the laminated structure has been heat-treated for 500 hours in an atmosphere of 85°C and 85% RH is 0.1 Ω / □ or less. (17) The laminated structure according to (16), wherein the rust-preventive layer contains one or more elements selected from the group consisting of Ni, Cr and Ti. (18) The laminated structure according to (13), wherein the arithmetic mean roughness Sa of the surface of the Cu layer opposite to the adhesive layer side is 10 nm or more and 50 nm or less. (19) The laminated structure according to (15) or (16), wherein the arithmetic mean roughness Sa of the surface of the rust-preventive layer opposite to the Cu layer side is 10 nm or more and 50 nm or less. (20) A current collector having the laminated structure according to any one of (13) to (19). (21) An electrode for a bipolar battery comprising a negative electrode active material layer on one side of the surface layer of a laminated structure according to any of (13) to (19), and a positive electrode active material layer on the opposite side of the surface layer. (22) A secondary battery comprising a bipolar battery electrode according to (21) wherein the positive electrode active material layer and the negative electrode active material layer are laminated in at least two layers with an electrolyte in between.

[0010] This invention makes it possible to provide a current collector that can suppress deterioration of the adhesive layer due to water vapor and electrolyte-derived components, as well as a reduction in adhesion strength due to gases generated from the adhesive layer, and is suitable for weight reduction, and a laminated film having a metal layer for realizing such a current collector.

[0011] Hereinafter, a preferred embodiment of the laminated film, the method for producing the laminated film, the laminated structure, the current collector, the electrode for a bipolar battery, and the secondary battery of the present invention will be described in more detail.

[0012] As one aspect of the present invention, there is a laminated film having a metal layer on at least one side of a film substrate.

[0013] <Metal layer> The metal layer in the present invention comprises a layer made of Cu (Cu layer), and the metal layer may have a layer containing 10% by mass or more of other metals. The metal layer in the present invention is preferably formed on the film substrate or the intermediate layer using a method including at least one of vacuum evaporation, sputtering, or plating in physical vapor deposition, and more preferably formed using a method including at least two of vacuum evaporation, sputtering, or plating.

[0014] Vacuum evaporation methods include induction heating evaporation, resistance heating evaporation, laser beam evaporation, electron beam evaporation, etc. Any evaporation method may be used, but from the viewpoint of making it difficult to generate film defects such as pinholes, induction heating evaporation or electron beam evaporation is preferably used. During evaporation, evaporation may be performed while cooling the film so that the temperature of the substrate does not rise.

[0015] The Cu layer in the present invention is preferably a metal layer in which at least 90% by mass or more is Cu. The Cu layer in the present invention is preferably formed on the film substrate by vacuum evaporation in physical vapor deposition.

[0016] Vacuum evaporation methods include induction heating evaporation, resistance heating evaporation, laser beam evaporation, electron beam evaporation, etc. Any evaporation method may be used, but from the viewpoint of making it difficult to generate film defects such as pinholes, induction heating evaporation or electron beam evaporation is preferably used. During evaporation, evaporation may be performed while cooling the film so that the temperature of the substrate does not rise.

[0017] When observing the 10 mm × 10 mm range of the metal layer in the present invention, it is preferable that the total area of pinholes (hereinafter sometimes referred to as pinhole area) is 0.03% or less of the area of the observation range. If the pinhole area exceeds 0.03%, when the metal layer is used as the current collector of the LIB, the adhesive layer may deteriorate due to components derived from water vapor or electrolytic solution, which may reduce the reliability of the LIB. From the same viewpoint, the pinhole area is more preferably 0.02% or less of the area of the observation range, and even more preferably 0.01% or less. The measurement method of the pinhole area is as described in the examples.

[0018] When peeling the metal layer from the film substrate of the laminated film of the present invention, the peeling force is preferably 0.01 N / cm or more and 2.00 N / cm or less. If the peeling force is less than 0.01 N / cm, the metal layer may peel off naturally. If the peeling force exceeds 2.00 N / cm, the metal layer may crack during transfer, or a part of the release layer or the film substrate may adhere to the peeled metal layer. The measurement method of the peeling force is as described in the examples. More preferably, it is 0.03 N / cm or more and 1.40 N / cm or less.

[0019] The water vapor transmission rate of the laminated film is preferably 0.0001 g / m ２ / day or more, more preferably 0.01 g / m ２ / day or more, and even more preferably 0.05 g / m ２ / day or more. When the water vapor transmission rate is less than 0.01 g / m ２ / day, due to the heat load in the lamination process with the Al layer, volatile components containing water vapor from the adhesive layer are blocked by the Cu layer, and there is a high possibility that the layer adhesion is destroyed by the sudden vaporization of the volatile components. If the water vapor transmission rate of the laminated film is 0.0001 g / m ２ / day or more, the possibility of layer adhesion being destroyed is reduced, and if it is 0.01 g / m ２ / day or more, the possibility of being destroyed is further reduced. Furthermore, if the water vapor transmission rate of the laminated film is 0.05 g / m ２If the day is longer than 10 g / m³, the likelihood of destruction decreases. Also, the water vapor transmission rate is 10 g / m³. ２ Preferably less than / day, and 5 g / m ２ It is more preferable that the amount is less than or equal to 3 g / m² / day. ２ It is even more preferable that the water vapor transmission rate is 10 g / m³ or less. ２ If the number of days exceeds [number], it is assumed that there are many pinholes and cracks in the metal layer, and deterioration of the adhesive layer due to water vapor and electrolyte-derived components may occur, raising concerns about insufficient performance of the current collector.

[0020] In the present invention, the thickness of the metal layer is preferably 0.5 μm or more and 5.0 μm or less. A thickness of 0.5 μm or more is desirable for use as a current collector in a lithium-ion battery. If the thickness is less than 0.5 μm, the required charge and discharge current performance may not be satisfied. On the other hand, if the thickness exceeds 5.0 μm, the amount of heat applied to the substrate during deposition increases, and there is a risk that the film substrate will be thermally deformed. Also, the increased hardness may worsen the followability during transfer. Therefore, it is more preferable that the thickness of the metal layer is 0.5 μm or more and 2.0 μm or less, and even more preferable that it is 0.7 μm or more and 2.0 μm or less.

[0021] In the present invention, the thickness of the Cu layer is preferably 0.5 μm or more and 5.0 μm or less. A thickness of 0.5 μm or more is desirable for use as a current collector in a lithium-ion battery. If the thickness is less than 0.5 μm, the required charge and discharge current performance may not be satisfied. On the other hand, if the thickness exceeds 5.0 μm, the amount of heat applied to the substrate during deposition increases, and there is a risk that the film substrate will be thermally deformed. Also, the increased hardness may worsen the followability during transfer. Therefore, it is more preferable that the thickness of the Cu layer is 0.5 μm or more and 2.0 μm or less, and even more preferable that it is 0.7 μm or more and 2.0 μm or less.

[0022] <Film Substrate> The film substrate used in the present invention is not particularly limited, but various resins can be used as materials constituting the film substrate, such as polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resins such as polypropylene and polyethylene; cellulose resins such as diacetylcellulose and triacetylcellulose; polysulfone resins, polyetheretherketone resins, polyethersulfone resins, polyphenylene sulfide resins, polyetherimide resins, polyimide resins, polyamide resins, acrylic resins, cyclic olefin resins, and polycarbonate resins.

[0023] The thickness of the film substrate is preferably less than 100 μm, more preferably less than 75 μm, and particularly preferably less than 50 μm. Furthermore, the thickness of the film substrate is preferably 10 μm or more, and particularly preferably 25 μm or more.

[0024] Making the film substrate relatively thin is preferable because it reduces the bending rigidity of the release film, and consequently reduces the peeling force required when peeling the release film from the film to be transferred.

[0025] Furthermore, by using a thin film substrate, the mass per unit length becomes relatively smaller, allowing for a longer maximum length for a single winding roll. This longer winding roll improves productivity when continuously producing laminated films using a roll-to-roll method.

[0026] On the other hand, if the film substrate is made relatively thin and the maximum length of a single winding roll is made long, strong pressure is applied to the underwinding portion of the winding roll. As a result, the release layer, the anti-corrosion layer, and the Cu layer laminated on top of them are strongly affected by the opposite side of the film substrate. However, this effect can be mitigated by making the arithmetic mean roughness Sa of the opposite side of the film substrate less than 10 nm.

[0027] In other words, the laminated film of the present invention is beneficial in improving productivity by using a relatively thin film substrate and increasing the maximum length of a single winding roll. From the above viewpoint, the maximum length of a single winding roll is preferably 1,000 m or more, more preferably 2,000 m or more, and particularly preferably 4,000 m or more. The upper limit is about 10,000 m. Furthermore, the widthwise length of the winding roll is not particularly limited, but is suitable in the range of 300 to 3,000 mm, preferably in the range of 500 to 2,000 mm, and particularly preferably in the range of 700 to 1,700 mm.

[0028] The film substrate used in the present invention is preferably a polyester film, and more preferably a biaxially oriented polyester film. Among the polyester films, polyethylene terephthalate film is preferred.

[0029] Here, it is preferable that the polyester is obtained by polymerization of monomers comprising at least 70 mol% or more aromatic dicarboxylic acids and diols.

[0030] Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, with terephthalic acid being particularly preferred. These acid components may be used individually or in combination of two or more, and other aromatic dicarboxylic acids such as isophthalic acid, or fatty acids, may be partially copolymerized.

[0031] Examples of diol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, and neopentyl glycol. Ethylene glycol is preferred among these. These diol components may be used individually or in combination of two or more.

[0032] Preferably, the polyesters include polyethylene terephthalate, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, and further, polyhexamethylene terephthalate and its copolymers, polyhexamethylene naphthalate and its copolymers, and polyethylene terephthalate is particularly preferred.

[0033] Polyesters can be produced by conventionally known methods. For example, one method involves directly esterifying an acid component with a diol component, then heating the product under reduced pressure to remove excess diol components while polycondensing. Another method involves using a dialkyl ester as the acid component, transesterifying it with the diol component, and then polycondensing it in the same manner as described above. In this case, conventionally known alkali metals, alkaline earth metals, manganese, cobalt, zinc, antimony, germanium, titanium compounds, etc., can be used as reaction catalysts as needed.

[0034] Furthermore, the arithmetic mean roughness Sa of the surface of the film substrate opposite to the surface on which the metal layer is provided is preferably 10 nm or less, more preferably 8 nm or less, and particularly preferably 7 nm or less. In addition, the arithmetic mean roughness Sa is preferably 1 nm or more, and particularly preferably 2 nm or more.

[0035] The film substrate of the present invention may be a laminated film having a laminated structure. The layers forming the laminated structure may be made by laminating the materials that constitute the film substrate as described above, or a layer made of an inorganic material, an organic material, etc., may be laminated on a layer made of the materials that constitute the film substrate as described above. The inorganic material is preferably made of Cr, Ni, Co, Fe, Mo, Ti, W, P, Cu, Al, or alloys thereof, or nitrides thereof, or oxides thereof. The organic material may be either a silicone-based compound or a non-silicone-based compound. Furthermore, the laminated structure may consist of multiple layers.

[0036] <Release Layer> The laminated film of the present invention has a film substrate having a substrate layer and a release layer, and the release layer may be located on the surface layer of the film substrate on the metal layer side.

[0037] The release layer of the present invention may contain one or more selected from the group consisting of (i) to (iii) below: (i) melamine resins, silicone resins, fluororesins, cellulose derivatives, urea resins, polyolefin resins, paraffin resins, and composites thereof; (ii) Cr, Ni, Co, Fe, Mo, Ti, W, P, and alloys thereof; (iii) graphite, diamond-like carbon.

[0038] A so-called release film may be used, in which these release layers are pre-formed on at least one surface of the base film.

[0039] Silicones are polymers consisting of a main chain formed by alternating bonding of silicon atoms with organic groups (such as alkyl groups or phenyl groups) and oxygen atoms. For example, silicone compounds with dimethylpolysiloxane as their basic skeleton are well known.

[0040] Non-silicone compounds refer to compounds other than the silicone compounds described above. In this invention, non-silicone compounds include non-silicone mold release agents, non-silicone binder resins, non-silicone crosslinking agents, and the like.

[0041] In the laminated film of the present invention, when the film substrate has a substrate layer and a release layer, it is preferable that the release layer mainly contains a non-silicone compound. The statement that the release layer mainly contains a non-silicone compound means that it contains 80% by mass or more of the non-silicone compound based on 100% by mass of the total solid content of the release layer. More preferably, it contains 90% by mass or more of the non-silicone compound based on 100% by mass of the total solid content of the release layer. The upper limit is 100% by mass.

[0042] In the present invention, the release layer preferably does not contain silicone compounds. Examples of non-silicone release agents that can be included in the release layer as non-silicone compounds include fluororesins, rubber resins, polyolefin resins, alkylated melamine formaldehyde resins, and long-chain alkyl compounds. Among these, long-chain alkyl compounds, alkylated melamine formaldehyde resins, and polyolefin resins are preferred, and long-chain alkyl compounds and alkylated melamine formaldehyde resins are even more preferred, with long-chain alkyl compounds being particularly preferred from the viewpoint of coating properties and release properties.

[0043] Examples of fluororesins include ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer.

[0044] Examples of rubber-based resins include butadiene-based, styrene-butadiene-based, coloroprene-based, butyl-based, ethylene-propylene-based, and acrylic-based rubbers.

[0045] Examples of polyolefin resins include homopolymers of polyethylene, polypropylene, polybutene, and polyhexene, as well as copolymers thereof.

[0046] Examples of alkylated melamine formaldehyde resins include alkylated melamine formaldehyde resins having an alkyl group with 6 to 20 carbon atoms. These resins can be obtained, for example, by adding formaldehyde as an auxiliary to a melamine monomer to produce methylolated melamine, and then introducing an alkyl group with 6 to 20 carbon atoms to the resulting methylol group. Long-chain alkyl compounds refer to compounds having a straight-chain or branched alkyl group (also called a long-chain alkyl group) with 8 or more carbon atoms. Specifically, examples include long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing ether compounds, and long-chain alkyl group-containing amine compounds.

[0047] The number of carbon atoms in the long-chain alkyl group is preferably 8 or more, more preferably 10 or more, and particularly preferably 12 or more. The number of carbon atoms in the long-chain alkyl group is preferably 30 or less, more preferably 28 or less, and particularly preferably 25 or less.

[0048] Among long-chain alkyl compounds, long-chain alkyl-containing polyvinyl resins and long-chain alkyl-containing acrylic resins are preferred from the viewpoint of having good peelability.

[0049] Non-silicone binder resins that can be included as non-silicone compounds in the release layer include polyurethane resins, acrylic resins, polyester resins, melamine resins, alkyd resins, and epoxy resins. Among these, polyurethane resins and melamine resins are preferred.

[0050] Non-silicone crosslinking agents that can be included in the release layer as non-silicone compounds include epoxy crosslinking agents, isocyanate crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, and melamine crosslinking agents. Among these, melamine crosslinking agents are preferred from the viewpoint of reducing peeling force.

[0051] When using an inorganic release layer, it is preferable to form it using at least one inorganic component selected from the group consisting of Cr, Ni, Co, Fe, Mo, Ti, W, P, or alloys or compounds mainly composed of these, or a carbon material such as graphite or diamond-like carbon. Methods for forming these inorganic release layers include vacuum deposition and electrodeposition. Examples of vapor deposition methods include arc ion plating, magnetron sputtering, high-frequency plasma CVD, pulsed DC plasma CVD, ionization deposition, and plasma ion implantation deposition. Magnetron sputtering, which can be relatively easily implemented, is preferred.

[0052] The thickness of the release layer is preferably in the range of 10 to 1000 nm, more preferably in the range of 20 to 600 nm, even more preferably in the range of 20 to 300 nm, and particularly preferably in the range of 50 to 250 nm.

[0053] From the perspective of ensuring good coating properties of the transfer film laminated on the release layer of the release film and reducing peeling force, the surface free energy of the release layer is 20 to 35 mJ / m ２ Preferably, it is in the range of 21 to 32 mJ / m ２ A range of 22 to 30 mJ / m is more preferable. ２ A range of 20 mJ / m² is particularly preferred. ２ If the value falls below 35 mJ / m, the coating properties of the film to be transferred may deteriorate, while 35 mJ / m ２ As the size increases, the peeling force may become stronger.

[0054] Here, the surface free energy can be measured using a contact angle meter, such as the "Drop Master DM501" from Kyowa Interface Science Co., Ltd.

[0055] The surface free energy of the release layer is 20–35 mJ / m ２ To adjust the range, it is preferable to use a non-silicone-based release agent as the release agent contained in the release layer, and in particular, it is preferable to use a long-chain alkyl compound.

[0056] From the viewpoint of controlling the arithmetic mean roughness Sa of the metal layer of the present invention to 200 nm or less, the arithmetic mean roughness Sa of the release layer on the metal layer side of the film substrate is preferably 200 nm or less, more preferably 150 nm or less, and particularly preferably 100 nm or less. Furthermore, from the viewpoint of controlling the arithmetic mean roughness Sa of the metal layer to 20 nm or more, the arithmetic mean roughness Sa of the release layer on the Cu layer side of the film substrate is preferably 20 nm or more, and particularly preferably 30 nm or more.

[0057] <Rust-preventive layer> The metal layer of the present invention may include a rust-preventive layer. In particular, in the metal layer, it is preferable that the rust-preventive layer be located on the surface layer closer to the film substrate than the Cu layer.

[0058] The material used for the rust-preventive layer in this invention is a metal or a metal compound, but it is particularly preferable to use a metal with a stable oxide film or a noble metal that is stable in its elemental form. Specifically, it is preferable to use a metal layer containing any of Ti, Cr, Ni, Mo, W, Au, or Pt, preferably containing 10% by mass or more of any of Ti, Cr, Ni, Mo, W, Au, or Pt, and more preferably containing Ti, Cr, or Ni as the main component. As long as moisture resistance can be obtained, the aforementioned metals may be used individually or as alloys. If the rust-preventive layer is an alloy, it is preferable to contain 10% by mass or more of a metal that has a rust-preventive effect. By having 10% by mass or more, the effects of water vapor, oxygen, and oxidizing agents can be reduced. If it is less than 10% by mass, a sufficient rust-preventive effect cannot be obtained. In addition, localized corrosion is likely to progress, and a uniform rust-preventive effect cannot be obtained. For the same reason, it is preferable that the amount of metal with a rust-preventive effect be 15% by mass or more, and preferably 20% by mass or more.

[0059] Furthermore, the thickness of the rust-preventive layer is controlled to be between 0.1 nm and 100 nm to produce a moisture-resistant laminate. If rust prevention performance can be achieved, a thicker rust-preventive layer is preferable to ensure moisture resistance, and a thickness of 1 nm or more is more preferable. Also, since the metal used in the rust-preventive layer has a low deposition rate or is a precious metal, a thinner film thickness is preferable from the standpoint of productivity and production cost, and a thickness of 20 nm or less is even more preferable.

[0060] In this invention, the anti-corrosion layer is preferably formed by sputtering or vacuum deposition in physical vapor deposition. For sputtering, two-electrode sputtering, magnetron sputtering, dual magnetron sputtering (DMS), ion beam sputtering, etc., can be used individually or in combination of two or more. Furthermore, the target application method can be DC (direct current) sputtering, DC pulse sputtering, AC (alternating current) sputtering, or RF (radio frequency) sputtering. Vacuum deposition methods include induction heating deposition, resistance heating deposition, laser beam deposition, and electron beam deposition. While any method may be used, considering the desired film thickness for adhesion and production stability, magnetron sputtering using a DC pulse power supply is preferably used. During film formation, the film may be cooled to prevent the substrate temperature from rising.

[0061] In the deposition of the anti-corrosion material layer, using high-pressure sputtering gas pressure of 0.5 Pa or higher causes the deposited particles to undergo numerous collisions before reaching the substrate, reducing their kinetic energy. This suppresses particle diffusion on the substrate surface, promoting random and dense particle deposition. As a result, voids in the film are reduced, blocking the entry of oxygen and water vapor, thereby suppressing oxidative degradation in humid and hot environments. Furthermore, setting the substrate temperature to a low temperature of approximately -20°C to 50°C suppresses crystallization of the anti-corrosion material layer, making it easier to form amorphous or microcrystalline films. Such structures have fewer grain boundaries and restrict the diffusion pathways of oxygen and moisture, thus improving moisture resistance. In addition, amorphous films are structurally uniform, contributing to the stability of surface resistance. Moreover, the formation of fine irregularities on the film surface by high-pressure sputtering creates a mechanical anchoring effect with the Cu layer deposited in a subsequent process, improving adhesion between the films. This suppresses film peeling even in post-transfer processing, improving the reliability of the battery current collector. By employing the above film formation conditions, it becomes possible to maintain the surface resistance of the anti-corrosion layer at 0.1 Ω / □ or less, more preferably 0.01 Ω / □ or less, even after 500 hours of heat treatment in an atmosphere of 85°C and 85% RH, thereby contributing to improved battery performance.

[0062] In the laminated film of the present invention, when the metal layer includes a rust-preventive layer, and the rust-preventive layer is located on the surface of the metal layer closer to the film substrate than the Cu layer, it is preferable that the surface resistance of the rust-preventive layer after transferring the metal layer to the substrate under the conditions described later, and then performing a heat treatment for 500 hours in an atmosphere of 85°C and 85% RH, is 0.1 Ω / □ or less. A lower change in the sheet resistance value of the metal layer in a humid heat environment suppresses the effects of oxidation and deterioration during the processing steps after the metal layer is transferred to the substrate and exposed to oxygen and water vapor. This reduces the loss of current flowing in the in-plane and perpendicular directions when the transferred metal layer is used as a battery current collector, improving the performance when a secondary battery is constructed. For similar reasons, it is more preferable that the surface resistance of the rust-preventive layer after transferring the metal layer to the substrate, and then performing a heat treatment for 500 hours in an atmosphere of 85°C and 85% RH, is 0.05 Ω / □ or less, and even more preferable that it is 0.01 Ω / □ or less.

[0063] <Al Layer> The Al layer that can be used in the present invention is typically provided in the form of rolled Al foil. As the material for the Al layer, high-purity Al or Al alloys to which Si, Mn, Cr, Fe, etc. have been added can also be used. In this specification, when the term "Al layer" is used alone, it shall also include Al alloy layers.

[0064] In the laminated structure of the present invention, which has an Al layer, an adhesive layer, and a Cu layer in that order, the Al layer is the component responsible for the mechanical properties of the laminated structure. In the Al layer, which is unwound under tension from the Al layer roll and transported between each roll, in order to achieve both resistance to wrinkles and stretching and flexibility for neat winding, the thickness of the Al layer is preferably 20 μm to 80 μm, and more preferably 30 μm to 60 μm.

[0065] <Adhesive Layer> The adhesive layer of the present invention is not particularly limited as long as it can fix the metal layer and the transfer layer, but it is preferable to use a conductive adhesive layer having an adhesive resin composition and a conductive filler. The adhesive resin composition is not particularly limited, but thermoplastic resin compositions such as styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, amide resin compositions, or acrylic resin compositions, or thermosetting resin compositions such as phenol resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, or alkyd resin compositions can be used. These may be used alone or in combination of two or more.

[0066] The adhesive layer may optionally contain curing accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, UV absorbers, defoamers, leveling agents, fillers, flame retardants, and viscosity modifiers.

[0067] The thickness of the adhesive layer is not particularly limited and can be set as appropriate as needed, but is preferably 3 μm to 10 μm, and more preferably 4 μm to 7 μm.

[0068] The conductive filler is not particularly limited, but for example, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. Examples of the metal fillers include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder, and these metal powders can be produced by electrolysis, atomization, or reduction.

[0069] Furthermore, in order to facilitate contact between the fillers, it is preferable that the average particle size of the conductive filler be 3 μm or more and 50 μm or less. In addition, examples of conductive filler shapes include spherical, flake, dendritic, and fibrous shapes. Among these, from the viewpoint of connection resistance and cost, it is preferable that at least one is selected from the group consisting of silver powder, silver-coated copper powder, and copper powder.

[0070] By including conductive fillers in the adhesive layer, it can be made into an anisotropic conductive adhesive layer or an isotropic conductive adhesive layer.

[0071] The amount of conductive filler added can be in the range of more than 39 parts by mass and up to 400 parts by mass per 100 parts by mass of adhesive in the adhesive layer when it is an isotropic conductive adhesive layer. When it is an anisotropic conductive adhesive layer, it can be added in the range of 3% by mass or more and up to 39% by mass relative to the total amount of adhesive layer.

[0072] <Metal Layer of Laminated Structure> To suppress deterioration of the adhesive layer, the metal layer of the laminated structure is preferably dense. Denseness reduces liquid penetration pathways such as pinholes, cracks, and grain boundaries, which can improve safety and yield when the laminated structure is applied to a bipolar battery. Denseness can be indicated by the indentation hardness using a nanoindenter, and it is preferable that it is 1.40 GPa or higher. More preferably, it is 1.50 GPa or higher, and even more preferably, 1.80 GPa or higher. From the viewpoint of suppressing the decrease in adhesion force due to gas generated from the adhesive layer, the indentation hardness is preferably 2.50 GPa or lower, and more preferably 2.20 GPa or lower. There are no particular limitations on the method of controlling the indentation hardness, but for example, by lowering the temperature of the transport roll of the apparatus during deposition to lower the temperature of the substrate in contact with it, the crystal growth of the deposited metal is inhibited, and the nanocrystallization and amorphous formation of the metal layer is promoted, increasing the number of interfaces and thus increasing the indentation hardness through the Hall-Petch effect, etc. Furthermore, increasing the rate of metal layer deposition suppresses metal layer crystal growth, promoting nanocrystallization and amorphous formation. This increases the number of interfaces, which in turn increases the indentation hardness through effects such as the Hall-Petch effect.

[0073] When using a metal layer as a current collector or electrode, it is preferable that the metal layer of the laminated structure be uniform in order to ensure uniformity of current and to suppress localized film rupture during the bonding process. If the in-plane uniformity of the metal layer is high, the bias in the current distribution when the laminated structure is used as a current collector can be suppressed, and the risk of localized heat generation and degradation can be reduced. In addition, it is possible to prevent localized film rupture and stress concentration during the bonding process, thereby contributing to improved stability of the manufacturing process and product reliability. When the indentation hardness of the surface of the metal layer of the laminated structure opposite to the adhesive layer is measured by nanoindentation at nine points (3x3 intersections) arranged in a grid at 1 mm intervals, it is preferable that the standard deviation of the measured indentation hardness at the nine points is 0.30 GPa or less. More preferably, it is 0.25 GPa or less, and even more preferably 0.20 GPa or less.

[0074] <Method for Manufacturing a Film Laminate> The film laminate of the present invention preferably has a configuration in which a metal layer is provided on at least one side of the film substrate, the metal layer includes a layer made of Cu (Cu layer), the film substrate has a laminated structure, and the laminated structure preferably includes a release layer to facilitate the separation of the Cu layer from the film substrate, and a rust-preventive layer to suppress corrosion of the surface of the Cu layer after transfer.

[0075] In the present invention, there are no particular limitations on the method for forming a metal layer on a film substrate, but methods such as vapor deposition, sputtering, or electroplating under vacuum conditions or reduced pressure conditions with an inert gas such as argon sealed inside are preferred. In particular, from the viewpoint of continuously forming a metal layer on a substrate film using a long roll of film substrate, it is preferable to use a roll-to-roll type vacuum film deposition apparatus.

[0076] When using the vacuum deposition method, it is preferable to pre-install a polyester roll in a vacuum chamber, and while the unwound film is in close contact with a cooling roll, heated and vaporized metal and / or metal compounds are solidified and deposited onto the surface of the polyester film to form a deposition layer, and then the film is wound up again as a film roll.

[0077] Here, the inside of the vacuum chamber is 9.0 × 10 －３ Under vacuum conditions below Pa, or by sealing with an inert gas such as argon, 9.0 × 10 －３ Pa or more 1×10 －１ Any of the reduced pressure conditions below Pa can be suitably used. Furthermore, from the viewpoint of suppressing pinholes, it is preferable to perform two or more film formation processes in succession, such as first forming a first Cu layer or rust-preventive layer by sputtering, followed by a second Cu layer by vacuum deposition, or conversely, first forming a Cu layer by vacuum deposition, followed by a second Cu layer or rust-preventive layer by sputtering.

[0078] Furthermore, when selecting the vacuum deposition method, one deposition cycle (defined as the process of evaporating Cu from a single evaporation source and forming a film on a film substrate) may be made sufficiently smaller than the target final thickness, and this thin film deposition may be repeated multiple times to form the target total thickness.

[0079] The reason for dividing the metal layer deposition process into multiple stages is that vacuum deposition and sputtering tend to form nuclei from the surface of the film substrate where deposition begins, and as metal particles are deposited, columnar crystals easily grow in the thickness direction of the film, starting from these nuclei. If there are areas on the film substrate where no crystal nuclei are formed, or if the bond between the crystal nuclei and the film substrate is weak, columnar Cu crystals will not grow in those areas, and pinholes are likely to form. Therefore, by dividing the metal layer deposition process into multiple stages, the crystal growth process can be reset and a new crystal growth process can be started, thereby reducing the number of pinholes.

[0080] When forming a metal layer using a combination of vacuum deposition and sputtering, sputtering produces particles with higher kinetic energy, making it easier to nucleate on the film substrate and thus less likely to form pinholes. On the other hand, vacuum deposition has the advantage of a high deposition rate, and it is more efficient to deposit the majority of the total film thickness using the vacuum deposition method. Furthermore, for the vacuum-deposited layer, which makes up the majority of the Cu layer, it is preferable to have a film with higher conductivity (a film with lower volume resistivity). Higher conductivity allows for a smaller Cu layer thickness, results in a film with fewer defects, and is also preferable in terms of flexibility, i.e., suitability for roll-to-roll processes. To achieve such a highly conductive film, it is necessary to reduce impurities in the Cu layer and increase the film density. To reduce impurities, it is advisable to use the aforementioned induction heating method or electron beam heating method, or to select a highly pure Cu material for the evaporation source. A Cu purity of 99.9% to 99.999% is preferable. Increasing the purity too much will increase material costs. Films with increased conductivity achieved by vacuum deposition in this way also have high gas permeability. In particular, it has the effect of suppressing the penetration of water vapor, which is a cause of corrosion of the Cu film and the Al layer that forms the base material of the current collector formed by the transfer. The water vapor transmission rate at a temperature of 40°C and a humidity of 90% RH is 0.0001 g / m ２ / day or more 10g / m ２ A range of 0.01 g / m³ or less is preferable, and among these, 0.01 g / m³ is particularly preferable. ２ / day or more 5g / m ２ / day, plus 0.05 g / m ２ / day or more 5g / m ２ / day is preferable. If water vapor is completely blocked, after the metal layer is transferred to the Al layer via the adhesive, the moisture contained in the adhesive layer cannot be removed, which can lead to air bubbles remaining or, in some cases, peeling of the metal layer. Therefore, it is better to allow some water vapor to pass through.

[0081] Based on the characteristics described above, when a metal layer is formed by sputtering followed by vacuum deposition, the sputtering, which facilitates nucleation, results in a film with a relatively small crystal size. The metal layer deposited on top of it by vacuum deposition starts with a relatively small crystal size at the beginning of deposition, following the crystal size of the sputtered metal film, but as it approaches the surface, it becomes a film with a larger crystal size. For this reason, the surface roughness on the film substrate interface side of the metal layer is small, while the surface roughness on the surface side is large. The arithmetic mean roughness Sa of the dense metal layer formed by sputtering is in the range of 10 nm to 50 nm, preferably 15 nm to 40 nm, and more preferably 20 nm to 35 nm. On the other hand, the arithmetic mean roughness Sa of the surface of the Cu layer derived from vacuum deposition is in the range of 20 nm to 100 nm, preferably 30 nm to 100 nm.

[0082] In the laminated film of the present invention, it is preferable that the arithmetic mean roughness Sa of the surface of the metal layer opposite to the film substrate is 20 nm or more and 200 nm or less. Being within this range allows for close adhesion with the adhesive layer due to the anchoring effect during substrate transfer, making partial peeling less likely. If it exceeds 200 nm, localized stress loading may occur when pressing it against the adhesive layer during the lamination process, potentially causing tearing or other damage. From the same viewpoint, it is more preferable that the arithmetic mean roughness Sa of the surface of the metal layer opposite to the film substrate is 30 nm or more and 100 nm or less, and particularly preferable that it is 50 nm or more and 80 nm or less.

[0083] The arithmetic mean roughness Sa of the surface of the metal layer on the film substrate side is preferably 10 nm or more and 50 nm or less. Within this range, the metal layer can be easily transferred without tearing when the metal layer and film substrate of the film laminate are peeled apart. Furthermore, the surface of the metal layer on the film substrate side is exposed to the surface after the laminate structure is created. At this time, it is preferable that the arithmetic mean roughness Sa is 10 nm or more and 50 nm or less. If it exceeds 50 nm, cracks are easily generated in the metal layer by external force or thermal deformation, and these cracks tend to become pathways for electrolyte permeation. On the other hand, if the arithmetic mean roughness Sa is less than 10 nm, the electrode active material coating solution is easily repelled during application, and the electrode active material may flatten, reducing the number of sites for lithium ions to enter and potentially degrading battery performance.

[0084] In a laminated structure, it is preferable that the arithmetic mean roughness Sa of the surface of the metal layer opposite the adhesive layer is between 10 nm and 50 nm. If it exceeds 50 nm, cracks are more likely to occur in the metal layer due to external force or thermal deformation, and these cracks tend to become pathways for electrolyte permeation. On the other hand, if the arithmetic mean roughness Sa is less than 10 nm, the electrode active material coating solution is more likely to be repelled during application, potentially leading to flattening of the electrode active material and a reduction in the number of sites for lithium ions to enter, thus degrading battery performance.

[0085] In a laminated structure, it is preferable that the arithmetic mean roughness Sa of the surface of the Cu layer opposite the adhesive layer is between 10 nm and 50 nm. Being within this range makes the metal layer of the laminated structure less susceptible to cracking under external force and thermal deformation, reducing the risk of it becoming a pathway for electrolyte permeation. Furthermore, if Sa is less than 10 nm, the electrode active material coating solution is more likely to be repelled during application, leading to flattening of the active material and a decrease in lithium ion diffusion sites, potentially degrading battery performance. Therefore, having Sa between 10 nm and 50 nm makes it possible to achieve both stability and reliability in battery performance.

[0086] In a laminated structure, it is preferable that the arithmetic mean roughness Sa of the anti-corrosion layer surface on the side of the metal layer opposite the adhesive layer is between 10 nm and 50 nm. Being within this range makes the metal layer of the laminated structure less susceptible to cracking due to external forces and thermal deformation, reducing the risk of it becoming a pathway for electrolyte permeation. Furthermore, if Sa is less than 10 nm, the electrode active material coating solution is more likely to be repelled during application, leading to increased planarization of the active material and a decrease in lithium ion diffusion sites, potentially degrading battery performance. Therefore, having Sa between 10 nm and 50 nm makes it possible to achieve both stability and reliability in battery performance.

[0087] <Method for Manufacturing a Laminated Structure> An example of a method for manufacturing the laminated structure of the present invention will be described. The laminated structure of the present invention can be manufactured by combining the steps of applying an adhesive layer coating solution onto an Al layer and drying it to form an adhesive layer, and laminating a laminated film so that the metal layer of the laminated film of the present invention is in contact with the adhesive layer. Conversely, it can also be manufactured by combining the steps of applying an adhesive layer coating solution onto the metal layer of a laminated film and drying it to form an adhesive layer, and laminating an Al layer so that one side of the Al layer is in contact with the adhesive layer.

[0088] As described above, the method for manufacturing the laminated structure of the present invention is not particularly limited, but a specific manufacturing method will be described below, which involves applying an adhesive layer coating solution onto an Al layer and drying it to form an adhesive layer.

[0089] When an adhesive layer is formed by applying an adhesive layer composition to the surface of the Al layer, the adhesive layer composition comprises a resin composition and a solvent. The resin composition is not particularly limited, but may be a thermoplastic resin composition such as a styrene-based resin composition, a vinyl acetate-based resin composition, a polyester-based resin composition, a polyethylene-based resin composition, a polypropylene-based resin composition, an imide-based resin composition, an amide-based resin composition, or an acrylic-based resin composition, or a thermosetting resin composition such as a phenol-based resin composition, an epoxy-based resin composition, a urethane-based resin composition, a melamine-based resin composition, or an alkyd-based resin composition. These may be used individually or in combination of two or more.

[0090] For example, solvents such as toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, and dimethylformamide can be used. Furthermore, if necessary, the adhesive layer composition may contain at least one of the following: a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity modifier. The ratio of the resin composition in the adhesive layer composition should be appropriately set according to the thickness of the adhesive layer, the coating method, the viscosity of the liquid, etc.

[0091] The method for applying the adhesive layer composition to the surface of the Al layer is not particularly limited, and lip coating, comma coating, gravure coating, or slot die coating can be used.

[0092] Then, after applying the adhesive layer composition to the surface of the Al layer, the adhesive layer is formed by heating and drying to remove the solvent. If necessary, such as when there is a long time until the process of laminating the laminated film onto the adhesive layer, a release film may be temporarily attached to the surface of the adhesive layer.

[0093] Next, the process of laminating the laminated film so that the metal layer is in contact with the side of the adhesive layer opposite to the Al layer will be described. The metal layer side of the laminated film is bonded to the side of the adhesive layer opposite to the Al layer, and the adhesive layer and the metal layer are joined by applying pressure perpendicular to the surfaces of the Al layer and the laminated film from the Al layer side and the film substrate side of the laminated film. Heating may be applied during the application of pressure if necessary. In some cases, a portion of the adhesive layer that has softened due to heating may flow into the uneven surface of the metal layer under pressure, increasing the adhesive strength. Examples of methods for applying pressure include the flat plate press method, in which the Al layer and laminated film are sandwiched between two flat plates; the roll press method, in which a flat plate is used on one side and a roll on the other, and pressure is continuously applied across the surface while the roll is rotated; and the nip roll method, in which the Al layer and laminated film are sandwiched between the contact points of two pressure rolls, and the rolls are rotated to continuously laminate them. In any of these methods, it is more preferable to use flat plates or rolls coated with rubber on the surface to apply pressure uniformly across the surface.

[0094] The process of forming the adhesive layer and laminating can be done by processing one sheet at a time on a single sheet of Al layer, but industrially, using a roll-to-roll coater or laminator to process laminated structures from rolls of Al layer and laminated film is suitable for mass production and reducing processing costs. The process in this case will be explained below. The Al layer is unwound from an unwinding device where the Al layer roll is set, and the Al layer is passed through a coater section where the adhesive layer composition is applied, and the adhesive layer composition is continuously applied to one side of the Al layer. The Al layer coated with the adhesive layer composition is then passed through a drying oven heated to a predetermined temperature, where the adhesive layer composition dries and the adhesive layer is formed. The laminated film is unwound from an unwinding device for the laminated film roll and transported to a pressurized section where the metal layer of the laminated film contacts the adhesive layer side of the Al layer that has come out of the drying oven. The Al layer and the laminated film are joined via the adhesive layer as they pass through the pressurized section. The laminated structure formed by joining the materials is transported to the winding section and wound into a roll.

[0095] As described above, the roll-to-roll process has the advantage of allowing the formation of the adhesive layer and lamination to be done in a single step.

[0096] The density of the metal layer in this laminated structure can be indicated by the indentation hardness measured by a nanoindenter. The indentation hardness measured by nanoindentation on the surface of the metal layer opposite to the adhesive layer is preferably 1.40 GPa or higher. More preferably 1.50 GPa or higher, and even more preferably 1.80 GPa or higher.

[0097] Preferably, the metal layer has a rust-preventive layer on the side of the Cu layer opposite to the adhesive layer side. The rust-preventive layer suppresses oxidation and deterioration of the Cu layer during processing and transportation, thereby maintaining the performance of the current collector and battery.

[0098] Furthermore, it is preferable that the surface resistance of the laminated structure having a rust-preventive layer on the side of the Cu layer opposite to the adhesive layer side is 0.1 Ω / □ or less after being heat-treated for 500 hours in an atmosphere of 85°C and 85% RH. When the surface resistance after the moist heat test is low, the resistance does not deteriorate even when exposed to oxygen or water vapor during the processing of the laminated structure, reducing the loss of current flowing in the in-plane direction and perpendicular direction, and improving the performance when a secondary battery is constructed. For similar reasons, it is more preferable that the surface resistance of the rust-preventive layer after being heat-treated for 500 hours in an atmosphere of 85°C and 85% RH after transferring the metal layer to the transfer substrate is 0.05 Ω / □ or less, and even more preferable that it is 0.02 Ω / □ or less.

[0099] <Current Collector> It is preferable to use the laminated structure of the present invention as the current collector of a bipolar LIB. By using a current collector with excellent conductivity in the thickness direction, when incorporated into a bipolar LIB, it is possible to achieve excellent current value stability as described later and suppress variations in battery characteristics. In addition, it has excellent mechanical properties, and a bipolar battery incorporating the current collector for bipolar batteries exhibits excellent durability against external stress such as deformation and impact. Furthermore, it enables stable battery operation even in high-temperature environments.

[0100] <Electrodes for Bipolar Batteries> The electrodes for bipolar batteries of the present invention consist of an electrode assembly including a positive electrode and a negative electrode, the positive electrode having a negative electrode active material layer on one side of the surface layer of the current collector and a positive electrode active material layer on the opposite side of the surface layer.

[0101] <Secondary Batteries> Examples of secondary batteries include lithium secondary batteries, lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-iron batteries, silver oxide-zinc batteries, manganese dioxide-lithium secondary batteries, lithium cobalt oxide-carbonate secondary batteries, and vanadium-lithium ion secondary batteries.

[0102] Among these, secondary batteries are preferred because they can be used for a long period of time, and lithium-ion secondary batteries, which achieve high energy density by using organic solvents, are even more preferred.

[0103] For the battery case, for example, an aluminum case, an iron case with a nickel-plated interior, or a case made of aluminum laminate film can be used.

[0104] Battery cases can take various shapes, including pouch type, cylindrical type, rectangular type, and coin type. Among these, the pouch type is preferred because it can achieve high energy density, is low-cost, and allows for flexible shape design.

[0105] The positive electrode consists of a positive electrode material comprising an active material, a binder resin, and a conductive additive, which are laminated on a current collector. The active material is LiCoO ２ LiNiO ２ , Li(NiCoMn)O ２ Lithium-containing transition metal oxides with layered structures, such as LiMn ２ O ４ spinel-type manganese oxides such as, and LiFePO ４ Examples include iron-based compounds. As a binder resin, a resin with high oxidation resistance should be used. Specifically, examples include fluorine-containing resins, acrylic resins, and styrene-butadiene resins. Examples of conductive additives include carbon materials such as carbon black and graphite.

[0106] The negative electrode consists of a negative electrode material made of an active material and a binder resin, which are laminated on a current collector. The active material may be carbon materials such as artificial graphite, natural graphite, hard carbon, or soft carbon; lithium alloy materials such as tin or silicon; metallic materials such as lithium; or lithium titanate (Li) ４ Ti ５ O １２ Examples include fluorine-containing resins, acrylic resins, and styrene-butadiene resins.

[0107] The electrodes for the bipolar battery of the present invention may be used as a secondary battery by connecting multiple electrodes in series to meet the application and required battery capacity of the secondary battery. In that case, it is preferable to have a secondary battery equipped with voltage control, temperature control, and safety devices by connecting multiple electrodes in series, or to have a secondary battery equipped with voltage control, temperature control, and safety devices by connecting multiple module units, each containing multiple electrodes connected in series and housed in a case, in series or parallel. It is preferable to connect the electrodes with tab lead wires (current extraction wires) and house them in a resin or metal module case to use them as a secondary battery.

[0108] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0109] [Evaluation Method] (1) Measurement of Peel Force The thickness of the metal layer (or the Cu layer if the metal layer consists only of a Cu layer) was standardized to 5 μm, and the peel force was measured. If the thickness of the metal layer was less than 5 μm, the thickness was increased by known methods such as plating, and if it exceeded 5 μm, the thickness was adjusted by etching or polishing. An adhesive was coated onto the surface of the metal layer, and a polyethylene terephthalate film (Toray Industries, Inc.'s biaxially oriented polyester film "Lumirror" (registered trademark) #25-S10) was laminated onto it. The adhesive consisted of DIC Graphics Corporation's adhesive "DIC Dry" (registered trademark) LX-500 (main component of the adhesive), KW-75 (curing agent), and ethyl acetate, which were mixed at room temperature with stirring in a ratio of 10:1:30 (mass ratio). This mixture was applied to the surface of the metal layer of the laminated film to a thickness of 2 μm using a bar coater and dried in a hot air oven set to 85°C for 30 seconds. After aging this laminate at 40°C for 48 hours, samples were obtained by cutting them into 10 mm wide strips and measuring them under the following conditions to obtain a peel force profile. For the measurement, the laminated film side of the sample was attached to a 1.5 mm thick SUS plate with double-sided tape (Nitto Denko Corporation double-sided tape No. 532, tape thickness 0.08 mm) and fixed with an air chuck. The attached PET film was then fixed with the other air chuck, and the PET film side was pulled for measurement. In the case of peeling, the surface layer of the film substrate may adhere to the surface of the metal layer, but in this case, it was considered that the metal layer had peeled off. Three measurements were taken for each sample, and the arithmetic mean value was taken as the peel force. Measurement device: Tensilon universal material tester RTG-1210, A&D Corporation Load cell: 50 N Peeling angle: 180° Peeling speed: 50 mm / min Measurement environment: Room temperature 23°C, humidity 50%.

[0110] (2) Measurement of Pinhole Area The pinhole area was calculated by observation with a microscope and image analysis. A Keyence VHX-7000 microscope was used, with a lens magnification of 20x, and the light intensity of the backlight source was adjusted to 56,000 lux using an illuminometer. The image was taken in transmitted light observation mode, focusing on the surface of the copper film. The observation area was 10 mm x 10 mm. Areas where light from the backlight leaked out of the obtained image and appeared as bright spots were identified as pinholes, and the pinhole area was calculated by performing binarization processing using the automatic area measurement function of the particle analysis software built into the device. In automatic area measurement, the initial settings were used without changing the image preprocessing or threshold settings. The illuminance of the backlight was measured using a Sato Keiryoki illuminometer SATOSK-10LX, and the light intensity setting value of the microscope device was changed to make adjustments.

[0111] (3) Water vapor transmission rate: 0.01 g / m ２ Water vapor transmission rates of 0.01 g / m³ or higher were measured according to the method compliant with JIS K7129:2008 (infrared). Measurements were taken using a water vapor transmission rate meter (model name: Permatran® W3 / 31) manufactured by MOCON, USA, under conditions of 40°C and 90% RH humidity. Measurements were performed twice on each of two test specimens, and the four measured values ​​were averaged to two significant figures to obtain the water vapor transmission rate. The lower limit of measurement (0.01 g / m³) was measured using Permatran® W3 / 31. ２ For samples with a value less than 1 / day, the water vapor transmission rate was measured at a temperature of 40°C, humidity of 90% RH, and a measurement area of ​​50 cm². ２ Under these conditions, the water vapor transmission rate was measured using a water vapor transmission rate measuring device (model name: "DELTAPERM" (registered trademark)) manufactured by Technolox, a UK company. Two samples were taken per level. The data obtained from the two samples were averaged to two significant figures to determine the average value for that level, and this value was used to calculate the water vapor transmission rate (g / m³). ２ ( / day)

[0112] (4) Thickness of each layer The thickness of each layer was measured by observing the cross-section of the laminated film or laminated structure with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). If the thickness of each layer was greater than 0.05 μm, an SEM was used, and if it was 0.05 μm or less, a TEM was used.

[0113] When observing with a scanning electron microscope (SEM), the laminate was cut in the thickness direction and the cross-section of the laminate was observed. For cutting the laminate, a microtome RMS type manufactured by Japan Microtome Laboratory Co., Ltd. was used, and for the SEM, a Hitachi scanning electron microscope S-3400N manufactured by Hitachi High-Technologies Corporation was used. The observation magnification was changed according to the film thickness as described below, and three points were observed and the thickness was measured for each, and the average value was taken as the film thickness. The observation magnification was 2,000x for film thickness of 10 μm or more, 5,000x for film thickness of 5 μm or more and less than 10 μm, 10,000x for film thickness of 1 μm or more and less than 5 μm, 50,000x for film thickness of 0.1 μm or more and less than 1 μm, and 100,000x for thickness greater than 0.05 μm and less than or equal to 0.1 μm.

[0114] For TEM observation, the laminated film or components were thinned cross-sectionally using the cryo-FIB method and observed and measured using a scanning transmission electron microscope (STEM). The measurement device used was a JEOL Ltd. atomic resolution analytical electron microscope JEM-ARM200F, with three-point observation performed at an acceleration voltage of 200 kV and magnification of 2,000,000x. The thickness was measured from the observed photographs, and the average value was defined as the film thickness.

[0115] (5) Measurement of Arithmetic Mean Roughness Sa The arithmetic mean roughness Sa was measured using an atomic force microscope (AFM). The laminate was cut to an arbitrary size, and the surface of a 1 μm × 1 μm field of view was measured under the following conditions. Measurements were performed with n=2, and the value of Sa was the average of n=2. If other layers such as a hard coat layer exist on the measurement surface, these other layers should be removed before measurement. ・Measurement device: Bruker Dimension icon ・Measurement range: 1 μm × 1 μm ・Scan rate: 1 Hz ・Scan line: 512 ・Analysis software: Nanoscope Analysis The arithmetic mean roughness of the substrate-side surface of the Cu layer of the laminated film is measured by preparing the test piece as follows. Adhesive is coated onto the surface of the Cu layer (the side opposite to the substrate), and a polyethylene terephthalate film (Toray Industries, Inc.'s biaxially oriented polyester film "Lumirror" (registered trademark) #25-S10) is laminated onto it. The adhesive and coating method are the same as those used for measuring peel strength. After aging this laminate at 40°C for 48 hours, a sample is obtained by cutting it into 10 mm wide strips. Using the same procedure as for peel measurement, the film substrate of the film laminate is fixed, and the PET film side is pulled to separate the Cu layer from the film substrate. The arithmetic mean roughness Ra of the surface of the Cu layer on the film substrate side that was exposed after peeling is measured using the same method as for the Cu layer surface.

[0116] If the film laminate includes a rust-preventive layer, the surface roughness of the exposed rust-preventive layer is measured by delaminating it at the interface between the rust-preventive layer and the film substrate, and considering it to be the same as the roughness of the film substrate side of the Cu layer. If other layers, such as a release layer, exist on top of the Cu layer or rust-preventive layer, the measurement is taken by finding an area where no other layers are present, or by removing the other layers before measuring the surface roughness.

[0117] (6) Measurement of indentation hardness The indentation hardness was measured using the "ENT-2100" nanoindenter manufactured by Elionix Co., Ltd. The surface opposite to the measurement surface was fixed to a dedicated sample fixing stand via adhesive ("Aron Alpha®" manufactured by Toagosei Co., Ltd.), and the indentation hardness (HIT (GPa)) of the measurement surface was measured using a triangular pyramidal diamond indenter (Berkovich indenter) with a ridge angle of 115° under the following conditions. The measurement data was processed using the dedicated analysis software (version 6.18) for the "ENT-2100".

[0118] The indentation hardness was measured at nine points (3x3 intersections) arranged in a grid at 1 mm intervals. The measurement data from these nine points was averaged to two significant figures, and this value was taken as the indentation hardness. The standard deviation of the nine measurement points was calculated by squaring the difference between each measured value and the average value, summing these differences, dividing by the number of measurement points (9), and taking the square root of this value to two significant figures. Measurement mode: Load-unload test, holding time when maximum load is reached: 1 second, Loading speed, unloading speed: 10 mN / sec, Indentation depth: 1 / 10 of the film thickness, Poisson's ratio of the indenter: 0.07, Poisson's ratio of the sample: 0.33 (7) Measurement of adhesion reduction rate An A4-sized laminated structure was divided into two A5-sized sections, and a humidity and heat resistance test was performed on one of the laminated structures. A constant temperature and humidity chamber LH-114 (manufactured by ESPEC Corporation) was used for the humidity and heat resistance test. The laminate was placed on a metal tray with the side opposite the Al layer facing upwards, and the ends were secured with "Kapton" (registered trademark) tape. The metal tray with the laminate attached was placed in a constant temperature and humidity chamber and maintained at 85°C and 85% RH for 100 hours to conduct a heat resistance test. After 100 hours, the "Kapton" (registered trademark) tape on the ends was peeled off and the laminate was removed.

[0119] Subsequently, an adhesive layer coating solution was applied to the opposite side of the Al layer of both the laminated structure that had not undergone humidity and heat resistance testing and the laminated structure that had undergone testing. This solution consisted of DIC Graphics Co., Ltd.'s adhesive "DIC Dry" (registered trademark) LX-500 (main adhesive component), KW-75 (curing agent), and ethyl acetate mixed in a 10:1:30 (mass ratio) ratio at room temperature while stirring. The solution was then applied to a 2 μm thickness using a bar coater and dried in a hot air oven set to 85°C for 30 seconds to form the adhesive layer. A polyethylene terephthalate film (Toray Industries, Inc.'s biaxially oriented polyester film "Lumirror" (registered trademark) #25-S10) was then laminated onto the adhesive layer. Samples were obtained by cutting the samples to a width of 10 mm and measured under the following conditions to obtain the peel force profile. In the measurement, the sample was prepared by attaching the Al layer side to a 1.5 mm thick SUS plate with double-sided tape (Nitto Denko Corporation double-sided tape No. 532, tape thickness 0.08 mm) and fixing it with an air chuck. The attached PET film was then fixed with the other air chuck, and the PET film side was pulled and measured. Three measurements were taken for each sample, and the arithmetic mean value was taken as the peel force. Measurement device: Tensilon universal material tester RTG-1210 manufactured by A&D Co., Ltd. Load cell: 50N Peel angle: 180° Peel speed: 50 mm / min Measurement environment: Room temperature 23°C, humidity 50%. When the peel force of the laminated structure that has not undergone humidity and heat resistance testing is N1, and the peel force of the laminated structure that has undergone humidity and heat resistance testing is N2, the peel force reduction rate Nd (%) was calculated as Nd = (1 - N2 / N1) × 100, and the following evaluation was performed. A: Peel force reduction rate Nd (%) is 10 or less. B: The peeling force reduction rate Nd (%) is greater than 10 and 40 or less. C: The peeling force reduction rate Nd (%) is greater than 40. In terms of peeling force reduction rate, A and B are preferable, and among them A is the best.

[0120] (8) Weight calculation of the laminated structure Cut the prepared laminated structure into 10 cm squares and measure the weight using an electronic balance and ２ The weight per unit was calculated.

[0121] (9) Measurement of Metal Layer Surface Resistance The surface resistance of the rust-preventive layer surface (metal layer (rust-preventive layer) surface of the laminated structure) after transferring and heat-treating the metal layer of the laminated film under the following conditions was measured at room temperature using a low resistivity meter "Loresta" (registered trademark) AX (MCP-T370) manufactured by Nitto Seiko Analytics Co., Ltd., with a 4-terminal 4-probe statutory current application method. A series 4-probe probe was used. [Transfer and Heat Treatment Conditions] The following adhesive layer coating liquid was applied to an A4-sized Al layer with a thickness of 50 μm using a bar coater, and dried at 85°C for 1 minute to prepare the adhesive layer. [Adhesive Layer Coating Liquid] DIC Graphics Co., Ltd. adhesive DIC Dry LX-500 (main component of the adhesive), KW-75 (curing agent), and ethyl acetate were mixed at room temperature in a ratio of 10:1:30 (mass ratio) while stirring to obtain the coating liquid.

[0122] Next, the surface of the A4-sized laminated film with the exposed metal layer (rust-preventive layer) on the adhesive layer was laminated under the following conditions, and then the film substrate of the laminated film was peeled off. Subsequently, a heat treatment was performed for 500 hours in an atmosphere of 85°C and 85% RH humidity. <Lamination conditions> - Lamination pressure: 0.2 MPa - Lamination speed: 1 m / min. [Peeling conditions] For peeling, an A&D Company, Limited Tensilon universal material testing machine RTG-1210 was used. A sample was cut to 5 cm x 5 cm, and the laminated film side was attached to a 1.5 mm thick SUS plate with double-sided tape (Nitto Denko Corporation double-sided tape No. 532, tape thickness 0.08 mm) and fixed with an air chuck, and a single-sided adhesive tape with a width of 20 mm and a length of 15 cm was attached to the laminated film. The single-sided adhesive tape was secured with the other end of the air chuck, and the peeling force was measured by pulling on the single-sided adhesive tape side. Measurement device: Tensilon universal material testing machine RTG-1210 manufactured by A&D Co., Ltd. Peeling angle: 180° Peeling speed: 100 mm / min.

[0123] (Example 1) A polyethylene terephthalate film with a thickness of 50 μm (Toray Industries, Inc.'s "Lumirror" (registered trademark) U48; arithmetic mean roughness Ra 0.6 nm) was used as the film substrate. The film was cooled to -5°C during sputtering and deposition.

[0124] First, a release layer was formed on one surface of the film substrate, and then a rust-preventive layer and a Cu layer were formed on top of the release layer in that order using a vacuum deposition apparatus.

[0125] [Release Layer] A non-silicone compound release coating solution was prepared by mixing and stirring 10 parts by mass (based on solid content) of a long-chain alkyl compound (Lion Specialty Chemicals Co., Ltd.'s "P-Royl" 1050) as a release agent, 2.5 parts by mass (based on solid content) of a melamine-based crosslinking agent (Mitsui Chemicals, Inc.'s "Uban" 28-60) as a crosslinking agent, 1.3 parts by mass (based on solid content) of p-toluenesulfonic acid (Teika Co., Ltd.'s "TAYCACURE" AC-700) as an acid catalyst, 400 parts by mass of toluene and 130 parts by mass of methyl ethyl ketone as solvents.

[0126] This release agent was applied to the surface of the film substrate using a gravure coater and dried to form a non-silicone organic release layer. The thickness of the release layer was 100 nm.

[0127] [Corrosion Prevention Layer] As a corrosion prevention layer, a 10 nm thick film of Cr was deposited on the surface of the release layer using the magnetron sputtering method. The sputtering conditions were as follows: a target of 50 mm x 550 mm size was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0128] [Cu Layer] First, a 20 nm Cu layer was formed on the surface of the Cr layer using magnetron sputtering. The sputtering conditions were as follows: a 50 mm × 550 mm target was used, and the vacuum level reached was 1 × 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0129] Next, Cu was vacuum-deposited onto the Cu layer formation surface of this release film using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min to a thickness of 1.8 μm.

[0130] Subsequently, a 20 nm thick Cu layer was formed again using the magnetron sputtering method. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0131] Next, test specimens were cut from the obtained samples, and various evaluations were performed. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0132] (Example 2) A laminated film was prepared in the same manner as in Example 1, except that the procedure for preparing the rust-preventive layer was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2. [Rust-preventive layer] Ni was deposited as a rust-preventive layer on the surface of the release layer by magnetron sputtering to a thickness of 10 nm. The sputtering conditions were as follows: a target of 50 mm × 550 mm size was used, and the vacuum level reached was 1 × 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0133] (Example 3) A laminated film was prepared in the same manner as in Example 1, except that the rust-preventive layer preparation procedure was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0134] [Corrosion Prevention Layer] As a corrosion prevention layer, a 10 nm film of Cr-Cu (mass ratio 50:50) was deposited on the surface of the release layer by magnetron sputtering. The sputtering conditions were as follows: a target of 50 mm x 550 mm size was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0135] (Example 4) A laminated film was prepared in the same manner as in Example 1, except that the rust-preventive layer preparation procedure was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0136] [Corrosion Prevention Layer] As a corrosion prevention layer, a 10 nm thin film of Ni-Cu (mass ratio 50:50) was deposited on the surface of the release layer using the magnetron sputtering method. The sputtering conditions were as follows: a target of 50 mm x 550 mm size was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0137] (Example 5) A laminated film was prepared in the same manner as in Example 1, except that a rust-preventive layer was not prepared. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0138] (Example 6) A laminated film was prepared in the same manner as in Example 1, except that the Cu layer preparation procedure was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0139] [Cu layer] Cu was vacuum deposited to a thickness of 1.8 μm on the anti-corrosion layer formation surface using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min.

[0140] Subsequently, a 20 nm thick Cu layer was formed again using the magnetron sputtering method. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0141] (Example 7) A laminated film was prepared in the same manner as in Example 1, except that the procedure for preparing the rust-preventive layer was the same as in Example 2, and the procedure for preparing the Cu layer was the same as in Example 6. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0142] (Example 8) A laminated film was prepared in the same manner as in Example 1, except that the procedure for preparing the rust-preventive layer was the same as in Example 3, and the procedure for preparing the Cu layer was the same as in Example 6. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0143] (Example 9) A laminated film was prepared in the same manner as in Example 1, except that the rust-preventive layer preparation procedure was the same as in Example 4 and the Cu layer preparation procedure was the same as in Example 6. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0144] (Example 10) A laminated film was prepared in the same manner as in Example 6, except that the film cooling temperature was set to -15°C. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0145] (Example 11) A laminated film was prepared in the same manner as in Example 1, except that a release layer was not formed. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0146] (Example 12) A laminated film was prepared in the same manner as in Example 5, except that a release layer and a rust-preventive layer were not formed. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0147] (Example 13) A laminated film was prepared in the same manner as in Example 5, except that the Cu layer preparation procedure was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0148] [Cu Layer] First, a 200 nm layer of Cu was formed on the surface of the release layer by repeating the formation of a 20 nm Cu layer 10 times using the magnetron sputtering method. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0149] Next, Cu was vacuum-deposited onto the Cu layer formation surface of this release film using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min to a thickness of 1.8 μm.

[0150] Subsequently, a 20 nm layer of Cu was formed by repeating the process 10 times using the magnetron sputtering method. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0151] (Comparative Example 1) A laminated film was prepared in the same manner as in Example 1, except that the film was cooled to -15°C during sputtering and deposition, and the Cu layer preparation procedure was changed as described below. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0152] [Cu layer] Cu was vacuum deposited to a thickness of 1.8 μm on the anti-corrosion layer formation surface using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min.

[0153] (Comparative Example 2) A laminated film was prepared in the same manner as in Example 10, except that a polyethylene terephthalate film with a thickness of 50 μm (Toray Industries, Inc.'s "Lumirror" (registered trademark) S10; arithmetic mean roughness Sa 6.9 nm) was used as the film substrate. The preparation conditions are shown in Table 1, and the measurement results are shown in Table 2.

[0154]

[0155]

[0156] The laminated films in the examples were found to have the target peel strength and water vapor permeability, and the pinhole area ratio was also confirmed to be reduced. In the examples in which anti-corrosion layer materials Cr, Ni, Cr-Cu alloy, and Ni-Cu alloy were deposited, the sheet resistance value after 500 hours of heat treatment at 85°C and 85% RH was below 0.1 Ω / □, indicating that oxidation was suppressed by the anti-corrosion effect and the deterioration of the resistance value was prevented. In Example 6, the film cooling temperature was higher than in Example 10, which promoted uniform diffusion of Cu crystals and resulted in a better pinhole area ratio. Examples 11 and 12 lacked a release layer and showed increased peel strength. In Example 13, the peel strength was increased by sputtering a thick layer of Cu.

[0157] On the other hand, in Comparative Example 1, since small crystal grains formed by sputtering were not present on the substrate surface before Cu layer deposition, it is thought that the Cu layer grown by EB deposition had a large number of gaps between crystals and a large pinhole area. In Comparative Example 2, a film substrate with a rough surface was used, resulting in a shorter diffusion distance of Cu atoms on the release layer surface during sputtering and deposition, and an increase in the pinhole area.

[0158] (Example 14) First, a film laminate was prepared under the conditions of Example 1. Next, the following adhesive layer coating liquid was applied to an Al foil with a thickness of 50 μm and size A4 using a bar coater, and the adhesive layer was prepared by drying at 85°C for 1 minute.

[0159] [Coating liquid for adhesive layer] A coating liquid was obtained by mixing DIC Graphics Co., Ltd.'s adhesive DIC Dry LX-500 (main component of the adhesive), KW-75 (curing agent), and ethyl acetate in a mass ratio of 10:1:30 at room temperature while stirring.

[0160] Next, the surface of the A4-sized film laminate with the Cu layer exposed was laminated onto the adhesive layer under the following conditions, and the laminated structure was obtained by peeling off the film substrate of the laminated film. Subsequently, test pieces were cut from the obtained sample and various evaluations were performed. The measurement results are shown in Table 3. <Laminating conditions> ・Laminating pressure: 0.2 MPa ・Laminating speed: 1 m / min (Example 15) First, a laminated structure was prepared in the same manner as in Example 14, except that the film laminate was prepared under the conditions of Example 2. The measurement results are shown in Table 3.

[0161] (Example 16) First, a laminated structure was prepared in the same manner as in Example 14, except that the film laminate was prepared under the conditions of Example 3. The measurement results are shown in Table 3.

[0162] (Example 17) First, a laminated structure was prepared in the same manner as in Example 14, except that the film laminate was prepared under the conditions of Example 4. The measurement results are shown in Table 3.

[0163] (Example 18) First, a laminated structure was prepared in the same manner as in Example 14, except that the film laminate was prepared under the conditions of Example 5. The measurement results are shown in Table 3.

[0164] (Example 19) First, a film laminate was prepared using the following process. The film was cooled to -15°C during sputtering and deposition.

[0165] Subsequently, the film laminate was laminated using the same procedure as in Example 6 to obtain a laminated structure. The measurement results are shown in Table 3.

[0166] [Film Laminate Fabrication Process] A polyethylene terephthalate film with a thickness of 50 μm (Toray Industries, Inc.'s "Lumirror" (registered trademark) U48; arithmetic mean roughness Ra 0.6 nm) was used as the film substrate.

[0167] (Formation of the intermediate layer) A release layer was formed as an intermediate layer on one surface of the film substrate.

[0168] [Release Layer] A non-silicone compound release coating solution was prepared by mixing and stirring 10 parts by mass (based on solid content) of a long-chain alkyl compound (Lion Specialty Chemicals Co., Ltd.'s "P-Royl" 1050) as a release agent, 2.5 parts by mass (based on solid content) of a melamine-based crosslinking agent (Mitsui Chemicals, Inc.'s "Uban" 28-60) as a crosslinking agent, 1.3 parts by mass (based on solid content) of p-toluenesulfonic acid (Teika Co., Ltd.'s "TAYCACURE" AC-700) as an acid catalyst, 400 parts by mass of toluene and 130 parts by mass of methyl ethyl ketone as solvents.

[0169] This release agent was applied to the surface of the film substrate using a gravure coater and dried to form a non-silicone organic release layer. The thickness of the release layer was 100 nm.

[0170] [Cu Layer] First, a 20 nm Cu layer was formed on the surface of the release layer using magnetron sputtering. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0171] Next, Cu was vacuum-deposited onto the Cu layer formation surface of this release film using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 6.0 m / min to a thickness of 0.4 μm. During this electron beam evaporation, the vacuum level was increased to 8 × 10⁻¹⁴. －２ It was set to Pa or higher.

[0172] Subsequently, a 20 nm thick Cu layer was formed again using the magnetron sputtering method. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0173] (Example 20) First, a laminated film was prepared in the same manner as in Example 5, except that the Cu layer preparation conditions were changed as follows. The evaluation results of the film laminate are shown in Table 2.

[0174] [Cu Layer Fabrication] First, a 20 nm Cu layer was formed on the surface of the release layer using magnetron sputtering. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0175] Next, Cu was vacuum deposited onto the Cu layer formation surface of this release film using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min to a thickness of 1.8 μm. During this electron beam evaporation, the vacuum level was increased to 8 × 10⁻⁶. －２ The pressure was set to Pa or higher. This deposition process was repeated three times to deposit Cu to a thickness of 5.4 μm.

[0176] Next, the laminated film was laminated to an Al foil under the same conditions as in Example 6, and the film substrate of the laminated film was peeled off to obtain a laminated structure. The results are shown in Table 3.

[0177] (Example 21) First, a laminated structure was prepared in the same manner as in Example 14, except that the film laminate was prepared under the conditions of Example 13. The measurement results are shown in Table 3.

[0178] (Comparative Example 3) A laminated film was prepared in the same manner as in Example 5, except that the line speed was set to 16.0 m / min during Cu deposition, the Cu deposition thickness was 0.15 μm, and the Cu layer thickness was 0.19 μm. The evaluation results of the film laminate are shown in Table 2.

[0179] Next, the laminated film was laminated to an Al foil under the same conditions as in Example 6, and the film substrate of the laminated film was peeled off to obtain a laminated structure. The results are shown in Table 3.

[0180] (Comparative Example 4) First, a laminated film was prepared in the same manner as in Example 5, except that the Cu layer preparation conditions were changed as follows. The evaluation results of the film laminate are shown in Table 2.

[0181] [Cu Layer Fabrication] First, a 20 nm Cu layer was formed on the surface of the release layer using magnetron sputtering. The sputtering conditions were as follows: a 50 mm x 550 mm target was used, and the vacuum level reached was 1 x 10⁻⁶. －２ Below Pa, the sputtering output was set to 2 kW using a DC power supply.

[0182] Next, Cu was vacuum deposited onto the Cu layer formation surface of this release film using electron beam evaporation at a deposition rate of 2.0 μm / min and a line speed of 1.0 m / min to a thickness of 1.8 μm. During this electron beam evaporation, the vacuum level was increased to 8 × 10⁻⁶. －２ The pressure was set to Pa or higher. This deposition process was repeated four times, depositing Cu to a thickness of 7.2 μm.

[0183] Next, the laminated film was laminated to an Al foil under the same conditions as in Example 6, and the film substrate of the laminated film was peeled off to obtain a laminated structure. The results are shown in Table 3.

[0184] (Comparative Example 5) Thickness 6 μm, pinhole area ratio less than 0.001%, water vapor transmission rate 0.01 g / m ２ A laminated structure was obtained in the same manner as in Example 6, except that rolled copper foil with a yield of less than 1 / day and Al foil were laminated with an adhesive. The results are shown in Table 3.

[0185]

[0186] In Table 3, "metal layer indentation hardness" refers to "the indentation hardness of the surface of the metal layer opposite to the adhesive layer, measured by nanoindentation," "Cu layer surface" refers to "the surface of the Cu layer opposite to the adhesive layer," and "corrosion-preventive layer surface" refers to "the surface of the corrosion-preventive layer opposite to the Cu layer."

[0187] The results in Table 3 confirm that the laminated structures of the examples exhibit high indentation hardness. Depending on the film formation conditions of the laminated film before transfer, the grain boundaries and crystal defects of the transferred Cu layer are reduced, making it denser and improving the indentation hardness.

[0188] On the other hand, in Comparative Example 3, the Cu layer of the laminated film was thin and easily permeable to gas, so in the humid heat resistance test, water vapor permeated and embrittled the underlying adhesive layer, reducing the adhesion strength. Also, in Comparative Examples 4 and 5, the Cu layer was thick, so 1 m ２ The weight per unit area is heavy, making it unsuitable for electrodes in bipolar batteries. Furthermore, in comparative examples 4 and 5, gas generated from the adhesive layer accumulated between the Al foil and the rolled copper foil, causing a decrease in adhesion.

[0189] The laminated film and laminated structure of the present invention have excellent conductivity, a uniform in-plane conductivity distribution in the direction of the current collector, and are suitable for lightweight current collectors. As such, the current collector is made of a thin Cu layer, and is therefore suitable for use in wiring boards, secondary batteries, bipolar LIBs, etc., but its applications are not limited to these.

Claims

1. A laminated film having a metal layer on at least one side of a film substrate, wherein the metal layer includes a layer made of Cu (Cu layer), the peeling force when peeling the metal layer from the film substrate is 0.01 N / cm or more and 2.00 N / cm or less, the total area of ​​pinholes when observing a 10 mm × 10 mm area of ​​the metal layer is 0.03% or less of the area of ​​the observation range, and the water vapor transmission rate of the laminated film at a temperature of 40°C and a humidity of 90% RH is 0.0001 g / m². ２ / day or more 10g / m ２ Laminated film with a lifespan of / day or less.

2. The laminated film according to claim 1, wherein the thickness of the Cu layer is 0.5 μm or more and 5.0 μm or less.

3. The laminated film according to claim 1, wherein the thickness of the Cu layer is 0.7 μm or more and 2.0 μm or less.

4. The laminated film according to claim 1, wherein the film substrate has a laminated structure.

5. The laminated film according to claim 4, wherein the film substrate has a substrate layer and a release layer, and the release layer is located on the surface layer of the film substrate on the metal layer side.

6. The laminated film according to claim 5, wherein the release layer contains one or more selected from the group consisting of melamine resin, silicone resin, fluororesin, cellulose derivative, urea resin, polyolefin resin, paraffin resin, and composites thereof, Cr, Ni, Co, Fe, Mo, Ti, W, P, or alloys thereof, graphite, and diamond-like carbon, and the total amount thereof is 80% by mass or more.

7. The laminated film according to claim 1, wherein the metal layer includes a rust-preventive layer, and the rust-preventive layer is located on the surface of the metal layer closer to the film substrate than the Cu layer.

8. The laminated film according to claim 7, wherein the peeling force when peeling the metal layer from the film substrate is 0.01 N / cm or more and 2.00 N / cm or less, and the surface resistance of the rust-preventive layer after transferring the metal layer and performing a heat treatment for 500 hours in an atmosphere of 85°C and 85% RH is 0.1 Ω / □ or less.

9. The laminated film according to claim 8, wherein the rust-preventive layer contains 10% by mass or more of any element selected from the group consisting of Ni, Cr, and Ti.

10. The laminated film according to claim 1, wherein the arithmetic mean roughness Sa of the surface of the metal layer opposite to the film substrate is 20 nm or more and 200 nm or less, and the arithmetic mean roughness Sa of the surface of the metal layer on the film substrate side is 10 nm or more and 50 nm or less.

11. A method for manufacturing a laminated film according to any one of claims 1 to 10, wherein the metal layer is formed using a method comprising at least one of vacuum deposition, sputtering, or plating.

12. The method for manufacturing a laminated film according to claim 11, wherein the metal layer is formed using a method comprising at least two of the following: vacuum deposition, sputtering, or plating.

13. A laminated structure having an Al layer, an adhesive layer, and a metal layer in that order, wherein the metal layer includes a layer made of Cu (Cu layer), the thickness of the Cu layer is 0.5 μm or more and 5.0 μm or less, and the indentation hardness of the surface of the metal layer opposite to the adhesive layer by nanoindentation method is 1.40 GPa or more.

14. The laminated structure according to claim 13, characterized in that the indentation hardness of the surface of the metal layer opposite to the adhesive layer is measured by nanoindentation at nine points (3x3 intersections) arranged in a grid at 1 mm intervals, and the standard deviation of the measured indentation hardness at the nine points is 0.30 GPa or less.

15. The laminated structure according to claim 14, wherein the metal layer has a rust-preventive layer on the side of the Cu layer opposite to the adhesive layer side.

16. The laminated structure according to claim 15, wherein the surface resistance of the rust-preventive layer after the laminated structure has been heat-treated for 500 hours in an atmosphere of 85°C and 85% RH is 0.1 Ω / □ or less.

17. The laminated structure according to claim 16, wherein the rust-preventive layer comprises any element selected from the group consisting of Ni, Cr, and Ti as a main component.

18. The laminated structure according to claim 13, wherein the arithmetic mean roughness Sa of the surface of the Cu layer opposite to the adhesive layer side is 10 nm or more and 50 nm or less.

19. The laminated structure according to claim 15, wherein the arithmetic mean roughness Sa of the surface of the rust-preventive layer opposite to the Cu layer side is 10 nm or more and 50 nm or less.

20. A current collector having the laminated structure described in claim 13 or claim 15.

21. An electrode for a bipolar battery comprising a negative electrode active material layer on one side of the surface layer of the laminated structure according to claim 13 or claim 15, and a positive electrode active material layer on the side opposite to the surface layer.

22. A secondary battery comprising, according to claim 21, an electrode for a bipolar battery having a configuration in which the positive electrode active material layer and the negative electrode active material layer are stacked in at least two layers with an electrolyte in between.

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