Support film for current collector of semi-solid state battery, semi-solid state battery, and method for producing support film for current collector of semi-solid state battery

Abstract

Provided is a support film for a current collector of a semi-solid state battery, said support film comprising a resin base material and an adhesive layer which is disposed on one surface of the resin base material, wherein the adhesive layer contains an ethylene-methacrylic acid copolymer and / or an ethylene-vinyl acetate copolymer, and the thickness of the resin base material is not less than 6 μm. In the support film, the adhesive layer may contain an ethylene-methacrylic acid copolymer. In the support film, the adhesive layer may contain an ethylene-vinyl acetate copolymer.

Description

Support film for current collector for semi-solid battery, semi-solid battery, and method for manufacturing support film for current collector for semi-solid battery

[0001] The present invention relates to a support film for a current collector for a semi-solid battery, a semi-solid battery, and a method for producing a support film for a current collector for a semi-solid battery.

[0002] In recent years, semi-solid batteries have attracted attention because they are safer and can achieve higher energy densities than liquid batteries, which use liquid electrolytes. Semi-solid batteries have a gel, clay, or other electrolyte and electrodes (positive and negative electrodes), and the electrodes are composed of a positive electrode current collector, a positive electrode active material, a separator, a negative electrode active material, and a negative electrode current collector, in this order.

[0003] The electrodes are sealed with a support film to form a single pouch (unit cell), and in secondary batteries, multiple unit cells are stacked to form a battery assembly (stack cell) to improve battery capacity. The support film isolates the active material, current collector, etc. from the outside, protects them from moisture and other foreign matter, and prevents short-circuiting between adjacent electrodes. Such unit cells are fabricated, for example, by the method described in Patent Document 1.

[0004] Special Publication No. 2023-545410

[0005] First, the support film must be in close contact with the current collector to protect it from moisture and other foreign matter, and the support film must have sufficient dielectric breakdown strength to prevent short circuits with adjacent electrodes.

[0006] Therefore, one aspect of the present disclosure aims to provide a support film for a current collector for a semi-solid battery, which has excellent adhesion to the current collector and sufficient dielectric breakdown strength, thereby capable of suppressing the occurrence of short circuits.

[0007] In Patent Document 1, a current collector and the like are laminated to a support film by heat sealing. If the adhesion between the support film and the current collector is insufficient, poor adhesion occurs, which may allow the intrusion of foreign matter such as moisture or cause a short circuit with adjacent cells.

[0008] Therefore, the inventors considered that by making it possible to visually identify defective parts when poor adhesion occurs, it would be easier to remove defective products during semi-solid battery manufacturing, and it would be possible to provide safe semi-solid batteries.

[0009] One aspect of the present disclosure provides a support film that makes it easy to visually recognize poor adhesion.

[0010] The third problem is that the support film must be in close contact with the current collector to protect it from moisture and other foreign matter. However, when an excessive load is applied to the battery, the support film may peel off from the current collector. If water or other foreign matter enters the current collector while the support film is peeled off, the electrodes may short-circuit, potentially causing a fire or other problem.

[0011] Therefore, one aspect of the present disclosure aims to provide a support film for a current collector for a semi-solid battery, which has excellent adhesion to the current collector, and even when the support film is peeled off, the adhesive layer of the support film remains on the current collector, thereby suppressing the occurrence of a short circuit.

[0012] Fourth Problem: The support film must be in close contact with the current collector to protect the current collector from moisture and other foreign matter. However, the adhesive layer of the support film sometimes suffers from localized in-plane adhesion defects during thermocompression bonding to the current collector.

[0013] Therefore, an object of one aspect of the present disclosure is to provide a support film for a current collector for a semi-solid battery that has excellent adhesion to the current collector and is less likely to cause poor adhesion when thermocompression bonded to the current collector.

[0014] Fifth Problem: The support film must be in close contact with the current collector to protect it from moisture and other foreign matter. Therefore, the adhesive layer of the support film must have excellent adhesion. However, if the adhesive strength of the adhesive layer is too strong, blocking may occur when the support film is wound into a roll.

[0015] Therefore, an object of one aspect of the present disclosure is to provide a support film for a current collector for a semi-solid battery, which has excellent adhesion to the current collector and can suppress the occurrence of blocking.

[0016] Regarding the first problem of the first invention group, one aspect of the present disclosure includes, for example, the following inventions. [1] A support film for a current collector for a semi-solid battery, comprising a resin substrate and an adhesive layer disposed on one surface of the resin substrate, wherein the adhesive layer contains at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer, and the thickness of the resin substrate is 6 μm or more. [2] The support film according to [1], wherein the adhesive layer contains an ethylene-methacrylic acid copolymer. [3] The support film according to [1], wherein the adhesive layer contains an ethylene-vinyl acetate copolymer. [4] The support film according to any one of [1] to [3], wherein the resin substrate is a polyester resin. [5] The support film according to any one of [1] to [4], wherein the adhesive layer has a thickness of 1 μm or more and 30 μm or less. [6] The support film according to any one of [1] to [5], wherein the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.05 or more. [7] The support film according to any one of [1] to [6], having a thickness of 25 μm or less. [8] The support film according to any one of [1] to [7], wherein the adhesive layer is a layer formed by a wet coating method. [9] The support film according to any one of [1] to [3], wherein the adhesive layer has a thickness of 1 to 8 μm.

[10] The support film according to any one of [1] to [8], wherein the resin substrate has a thickness of 15 μm or less.

[11] The support film according to any one of [1] to

[10] , wherein the adhesive layer has an adhesion strength B1 to the copper foil of 2 N / 15 mm or more, as measured by the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of copper foil (thickness 18 μm, surface roughness 0.33 μm), and thermocompression bonding is performed using a heat seal tester by applying heat only to the copper foil side of the support film. The compression bonding conditions are 150°C, 0.2 MPa, and 1 second.According to JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine, and the interface between the adhesive layer and the copper foil is peeled at a 180-degree angle at a speed of 300 mm / min. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength B1.

[12] The support film according to any one of [1] to

[11] , wherein the adhesive layer contains an ethylene-vinyl acetate copolymer, the adhesive layer has a thickness of 1 to 3 μm, the resin substrate has a thickness of 11 to 13 μm, the resin substrate is a polyester resin, the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.15 to 0.20, and the thickness is 12 to 20 μm.

[13] The support film according to any one of [1] to

[11] , wherein the adhesive layer contains an ethylene-vinyl acetate copolymer, the adhesive layer has a thickness of 5 to 7 μm, the resin substrate has a thickness of 8 to 10 μm, the resin substrate is a polyester resin, the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.60 or more and 0.70 or less, and the thickness is 13 to 20 μm.

[14] A semi-solid battery comprising the support film according to any one of [1] to

[13] and a current collector.

[15] A method for producing the support film according to any one of [1] to

[13] , comprising a step of forming the adhesive layer on the resin substrate by a wet coating method.

[0017] Second Invention Group With regard to the second problem, one aspect of the present disclosure includes, for example, the following inventions. [1] A support film for a current collector for a semi-solid battery, comprising: a substrate; and an adhesive layer disposed on one surface of the substrate, wherein a haze change rate (unit: %) calculated by ((A1-A2) / A1) x 100 is 25% or more when a first test piece obtained by superposing the support films together with the adhesive layers facing each other has a haze of A1 and a second test piece obtained by thermocompression bonding the first test piece has a haze of A2. [2] The support film according to [1], in which A1 is 7 or more. [3] The support film according to [1] or [2], in which the adhesive layer has an arithmetic mean roughness Ra of 0.4 μm or more. [4] The support film according to any of [1] to [3], in which the substrate has a thickness of 4 to 100 μm. [5] The support film according to any one of [1] to [4], wherein the adhesive layer contains an organic filler. [6] The support film according to any one of [1] to [5], wherein the adhesive layer has a thickness of 1 to 30 μm.

[0018] Third Invention Group With respect to the third problem, one aspect of the present disclosure includes, for example, the following invention. [1] A support film for a current collector for a semi-solid battery, comprising a substrate and an adhesive layer disposed on one surface of the substrate, wherein the adhesive layer has an adhesion strength A1 to a copper foil of 2 N / 15 mm or more as measured in the following peel test, and the adhesion strength A1 is greater than the adhesion strength A2 of the adhesive layer to the substrate as measured in the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm), a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. According to JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the adhesive layer and the electrolytic copper foil are peeled at a 180° angle at a rate of 300 mm / min at the interface between the adhesive layer and the electrolytic copper foil. The peel strength is measured every 0.01 s from the maximum peak at the start of peeling for 4.00 seconds, and the average of the measured values ​​is defined as adhesion strength A1. The adhesive layer and the substrate are peeled at a 180° angle at a rate of 300 mm / min at the interface between the adhesive layer and the substrate. The peel strength is measured every 0.01 s from the maximum peak at the start of peeling for 4.00 seconds, and the average of the measured values ​​is defined as adhesion strength A2. [2] The support film according to [1], wherein, after the support film is adhered to the copper foil, peeling occurs at the interface between the substrate and the adhesive layer when the substrate is peeled. [3] The support film according to [1] or [2], wherein the substrate contains polyester, and the adhesive layer contains a thermoplastic resin. [4] The support film according to any one of [1] to [3], wherein the substrate has a thickness of 4 to 100 μm. [5] The support film according to any one of [1] to [4], wherein the adhesive layer has a thickness of 2 to 30 μm. [6] The support film according to any one of [1] to [5], wherein the adhesive layer is formed by a wet coating method.

[0019] Fourth Invention Group With regard to the fourth problem described above, one aspect of the present disclosure includes, for example, the following invention: [1] A support film for a current collector for a semi-solid battery, comprising: a substrate; and an adhesive layer disposed on one surface of the substrate, wherein, when the adhesive layer has a thickness T1 and a copper foil, as measured in the following peel test, has an adhesion strength A1, and the adhesive layer has a thickness T2 (where T2 > T1) and a copper foil, A2, (A2 - A1) / (T2 - T1) is 0.7 [(N / 15 mm) / μm] or less, and A1 is 2 N / 15 mm or more. <Peel Test> The adhesive layer (thickness T1 or T2) of the support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm). A PET film was placed on the surface of the support film opposite the substrate, and the support film was sandwiched between them. Using a heat seal tester, heat was applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions were 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film was adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film was fixed to the grip of an autograph tester. The interface between the adhesive layer and the electrolytic copper foil was peeled at a speed of 300 mm / min at a 180° angle. The peel strength was measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​was recorded as adhesion strength A1 and A2. [2] The support film according to [1], wherein the adhesive layer comprises at least one selected from the group consisting of modified polyolefins, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, and ionomers. [3] The support film according to [1] or [2], wherein the substrate comprises polyester. [4] The support film according to any one of [1] to [3], wherein the substrate has a thickness of 4 to 100 μm. [5] The support film according to any one of [1] to [3], wherein the adhesive layer has a thickness of 1 to 30 μm. [6] The support film according to any one of [1] to [3], wherein the adhesive layer is formed by a wet coating method.

[0020] Fifth Invention Group: Regarding the fifth problem, one aspect of the present disclosure includes, for example, the following invention. [1] A support film for a current collector for a semi-solid battery, comprising: a substrate; and an adhesive layer disposed on one side of the substrate; the arithmetic mean roughness Ra of the adhesive layer on the surface opposite the substrate is 0.2 μm or more; and the adhesive strength A1 of the adhesive layer to a copper foil measured in the following peel test is 1 N / 15 mm or more. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm), a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Thermocompression bonding is performed using a heat seal tester by applying heat only from the adhesive layer side of the support film. The compression bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the electrolytic copper foil is peeled at a 180° angle at a rate of 300 mm / min. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as the adhesion strength A1. [2] The support film according to [1], wherein the adhesive layer contains a thermoplastic resin and a filler, and the content of the filler is 1% by mass or more and less than 30% by mass with respect to the thermoplastic resin. [3] The support film according to [2], wherein the filler is a filler made of a thermoplastic resin. [4] The support film according to [2] or [3], wherein the average particle size of the filler is 1 to 100 μm. [5] The support film according to any one of [1] to [4], wherein the surface has an uneven shape formed by a shaping treatment. [6] The support film according to any one of [1] to [5], wherein the substrate has a thickness of 4 to 100 μm. [7] The support film according to any one of [1] to [6], wherein the adhesive layer has a thickness of 2 to 30 μm. [8] The support film according to any one of [1] to [7], wherein the adhesive layer is formed by a wet coating method.

[0021] According to a first invention group representing one aspect of the present disclosure, a support film for a current collector for a semi-solid battery can be provided, which has excellent adhesion to the current collector and sufficient dielectric breakdown strength to suppress the occurrence of short circuits. According to a second invention group representing one aspect of the present disclosure, a support film is provided in which poor adhesion is easily visible. According to a third invention group representing one aspect of the present disclosure, a support film for a current collector for a semi-solid battery can be provided, which has excellent adhesion to the current collector and, even when the support film is peeled off, the adhesive layer of the support film remains on the current collector, thereby suppressing the occurrence of short circuits. According to a fourth invention group representing one aspect of the present disclosure, a support film for a current collector for a semi-solid battery can be provided, which has excellent adhesion to the current collector and is less likely to cause poor adhesion when thermocompression bonded to the current collector. According to a fifth invention group representing one aspect of the present disclosure, a support film for a current collector for a semi-solid battery can be provided, which has excellent adhesion to the current collector and is capable of suppressing the occurrence of blocking.

[0022] FIG. 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment.

[0023] Hereinafter, embodiments of the present disclosure will be described in detail, but the present invention is not limited to the following embodiments.

[0024] In the numerical ranges described herein, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the lower and upper limits of a numerical range can be arbitrarily combined with the lower or upper limit of another numerical range. When a numerical range is described as "A to B," the values ​​A and B at both ends are included as the lower and upper limits of the numerical range, respectively. In this specification, for example, "10 or more" means 10 and a value greater than 10, and this also applies when the numerical values ​​differ. Furthermore, for example, "10 or less" means 10 and a value less than 10, and this also applies when the numerical values ​​differ. Furthermore, unless otherwise specified, each component and material exemplified herein may be used alone or in combination of two or more types. In this specification, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified.

[0025] First Embodiment A first embodiment of the present disclosure will be described below.

[0026] 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a resin substrate 1 and an adhesive layer 2 disposed on one surface of the resin substrate 1.

[0027] (Resin substrate) Examples of resins constituting the resin substrate include polyolefin resins (LLDPE, PP, COP, CPP, etc.), polyester resins (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamide resins, polyimide resins, etc. The resin substrate may contain a polyester resin. The transparency of the resin substrate makes it easy to check the contents (for example, the current collector), and makes it easy to detect any abnormalities that may occur. The resin substrate may be a laminate of multiple resin substrates.

[0028] It is believed that the larger the volume resistance value of the resin substrate at 23°C and 50% RH, the more excellent the dielectric breakdown strength. １２Ω・cm or more, 10 １４ Ω cm or more, or 10 １６ The volume resistivity of the resin substrate at 23°C and 50% RH may be 10 １９ The volume resistivity of the resin substrate at 23° C. and 50% RH is a value measured in accordance with JIS K 6911.

[0029] The thickness of the resin substrate is 6 μm or more from the viewpoint of easily suppressing the occurrence of short circuits due to excellent dielectric breakdown strength. The thickness of the resin substrate may be 8 μm or more, 10 μm or more, 11 μm or more, or 12 μm or more from the viewpoint of more easily suppressing the occurrence of short circuits due to excellent dielectric breakdown strength, and may be 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less, 13 μm or less, or 10 μm or less from the viewpoint of improving loading efficiency and enabling high capacity by thinning the support film. From these viewpoints, the thickness of the resin substrate may be 6 to 100 μm, 8 to 100 μm, 10 to 50 μm, 12 to 25 μm, 8 to 10 μm, or 11 to 13 μm.

[0030] (Adhesive Layer) The adhesive layer contains at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer. The adhesive layer may contain at least one of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer. The adhesive layer may contain an ethylene-vinyl acetate copolymer from the viewpoint of providing better adhesion to the current collector and from the viewpoint of providing better dielectric breakdown strength and thus more easily suppressing the occurrence of short circuits.

[0031] The inventors' studies have revealed that when the resin substrate of the support film is thick to a certain extent and the adhesive layer contains at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer, the adhesive layer provides excellent adhesion to the current collector and excellent dielectric breakdown strength, thereby suppressing the occurrence of short circuits. The inventors' studies have revealed that, in particular, when the resin substrate of the support film is thick to a certain extent and the adhesive layer contains at least one of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer, the adhesive layer provides excellent adhesion to the current collector and excellent dielectric breakdown strength, thereby suppressing the occurrence of short circuits. Specifically, when the resin substrate is thick, the dielectric breakdown strength is excellent, making it easier to suppress the occurrence of short circuits. Furthermore, when the resin substrate is thick, it becomes more difficult for heat to escape to the surroundings during thermocompression bonding, which tends to improve adhesion. Furthermore, when the adhesive layer contains at least one of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer, the adhesive layer provides excellent adhesion to the current collector and, compared to cases where other resins are contained, the adhesive layer provides excellent dielectric breakdown strength, thereby suppressing the occurrence of short circuits, even when the resin substrate is thin to a certain extent.

[0032] Examples of the unsaturated carboxylic acid used to obtain the ethylene-unsaturated carboxylic acid copolymer include methacrylic acid, crotonic acid, acrylic acid, fumaric acid, and maleic acid.

[0033] Examples of vinyl esters used to obtain ethylene-vinyl ester copolymers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, and vinyl benzoate.

[0034] The content of the ethylene-unsaturated carboxylic acid copolymer in the adhesive layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total mass of the adhesive layer, from the viewpoint of better adhesion to the current collector and better dielectric breakdown strength, which makes it easier to suppress the occurrence of short circuits. If the content of the ethylene-unsaturated carboxylic acid copolymer in the adhesive layer is more than 50% by mass, it can be said that the ethylene-unsaturated carboxylic acid copolymer is a main component of the adhesive layer.

[0035] From the viewpoint of achieving better adhesion to the current collector and of more easily suppressing the occurrence of short circuits due to better dielectric breakdown strength, the content of the ethylene-methacrylic acid copolymer in the adhesive layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total mass of the adhesive layer. When the content of the ethylene-methacrylic acid copolymer in the adhesive layer is more than 50% by mass, it can be said that the ethylene-methacrylic acid copolymer is a main component of the adhesive layer.

[0036] From the viewpoint of achieving better adhesion to the current collector and making the support film less prone to curling, the content of the ethylene-vinyl ester copolymer in the adhesive layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total mass of the adhesive layer. When the content of the ethylene-vinyl ester copolymer in the adhesive layer is more than 50% by mass, it can be said that the ethylene-vinyl ester copolymer is the main component of the adhesive layer.

[0037] From the viewpoint of achieving better adhesion to the current collector and of more easily suppressing the occurrence of short circuits due to better dielectric breakdown strength, the content of the ethylene-vinyl acetate copolymer in the adhesive layer may be more than 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, based on the total mass of the adhesive layer. If the content of the ethylene-vinyl acetate copolymer in the adhesive layer is more than 50% by mass, it can be said that the ethylene-vinyl acetate copolymer is the main component of the adhesive layer.

[0038] The adhesive layer is a layer formed from a resin composition containing at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer as a binder resin and a liquid medium for dissolving and dispersing the binder resin. The binder resin may be composed of at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer, or may be a mixture of an ethylene-unsaturated carboxylic acid copolymer or an ethylene-vinyl ester copolymer with a resin other than the ethylene-unsaturated carboxylic acid copolymer or the ethylene-vinyl ester copolymer (for example, a thermoplastic resin, a thermosetting resin).

[0039] The adhesive layer is a layer formed from a resin composition containing at least one of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer as a binder resin and a liquid medium to dissolve and disperse the binder resin in. The binder resin may be composed of at least one of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer, or may be a mixture of an ethylene-methacrylic acid copolymer and an ethylene-vinyl acetate copolymer with a resin other than the ethylene-methacrylic acid copolymer and the ethylene-vinyl acetate copolymer (for example, a thermoplastic resin, a thermosetting resin).

[0040] Examples of thermoplastic resins (excluding ethylene-unsaturated carboxylic acid copolymers and ethylene-vinyl ester copolymers) include polyolefin resins such as polypropylene resins, polyethylene resins, polybutene resins, and polypentene resins; modified polyolefin resins, polyester resins, polystyrene resins, acrylonitrile-butadiene-styrene copolymers, methyl methacrylate-butadiene-styrene copolymers, ethylene-propylene copolymers, polycarbonate resins, polyphenylene ether resins, acrylic copolymers, polyamide resins, polyvinyl chloride resins, polyvinyl alcohol resins (PVA), polyvinyl acetal resins, and ionomers. The adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefin resins, polyester resins, and ionomers, from the viewpoints of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits.

[0041] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane resin, polyisocyanate resin, polyisocyanurate resin, and polyvinyl ether resin.

[0042] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0043] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0044] The resin composition may further contain a filler, which may be an organic filler or an inorganic filler, in order to more easily prevent blocking when the support film is wound into a roll.

[0045] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0046] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0047] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0048] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0049] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0050] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 4 μm or more from the viewpoints of better adhesion to the current collector and of allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of a short circuit, and from the viewpoints of improving loading efficiency and enabling higher capacity by making the support film thinner, and of suppressing deterioration of handleability due to curling of the support film, the thickness of the adhesive layer may be 50 μm or less, 30 μm or less, 10 μm or less, 8 μm or less, 7 μm or less, or 3 μm or less. From these viewpoints, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1 to 8 μm, 1 to 3 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, 2 to 8 μm, or 5 to 7 μm. In the support film according to this embodiment, even if the adhesive layer has a thickness as thin as 1 to 8 μm, 1 to 3 μm, or 5 to 7 μm, the adhesive layer contains at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer, and the resin substrate has a thickness of 6 μm or more, so that the support film has excellent adhesion to the current collector and sufficient dielectric breakdown strength.

[0051] The ratio of the thickness of the adhesive layer to the thickness of the resin substrate (thickness of adhesive layer / thickness of resin substrate) may be 0.05 or more, 0.1 or more, 0.15 or more, 0.3 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.9 or more, 1.1 or more, 1.3 or more, or 1.5 or more from the viewpoint of better adhesion to the current collector, and may be 2 or less, 1.5 or less, 1.2 or less, 1 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.4 or less, or 0.2 or less from the viewpoint of making the support film less prone to curling.

[0052] The total thickness of the resin substrate and the adhesive layer may be 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, or 20 μm or more from the viewpoint that the dielectric breakdown strength is better and the occurrence of short circuits is more easily suppressed, and from the viewpoint that the loading efficiency is improved by thinning the support film and high capacity is possible, it may be 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, or 25 μm or less. From these viewpoints, the total thickness of the resin substrate and the adhesive layer may be 10 to 150 μm, 10 to 60 μm, or 10 to 25 μm.

[0053] The adhesive strength B1 of the adhesive layer to the copper foil (hereinafter also simply referred to as "adhesion strength B1") may be 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesive strength B1 may be 20 N / 15 mm or less, 15 N / 15 mm or less, or 10 N / 15 mm or less. The adhesive strength B1 can be adjusted by the type of binder resin, the type of filler, etc., contained in the resin composition that forms the adhesive layer.

[0054] The adhesion strength B1 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of copper foil (thickness 18 μm, surface roughness 0.33 μm), and heat is applied only from the copper foil side of the support film using a heat seal tester to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester. The interface between the adhesive layer and the copper foil is peeled at a rate of 300 mm / min at a 180° angle. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength B1.

[0055] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a resin substrate, forming a coating film, and then drying the resulting film. The resin composition can be applied by a wet coating method, which facilitates uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. In other words, the method for producing a support film according to this embodiment may include, for example, a step of forming an adhesive layer on a resin substrate by a wet coating method. If the adhesive layer is formed by extrusion lamination, it is difficult to control the film thickness of the adhesive layer, and differences in the in-plane film thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0056] The support film may further include layers other than the resin substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite to the resin substrate.

[0057] The thickness of the support film may be 10 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, or 20 μm or more from the viewpoint that a better dielectric breakdown strength makes it easier to suppress the occurrence of short circuits, and from the viewpoint that a thinner support film improves loading efficiency and enables higher capacity, the thickness may be 150 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. From these viewpoints, the thickness of the support film may be 10 to 150 μm, 10 to 60 μm, 10 to 25 μm, 12 to 20 μm, or 13 to 20 μm.

[0058] The support film can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0059] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0060] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0061] (Examples 1-1 to 1-7, Comparative Example 1-1) Aquatex EC1700 (ethylene vinyl acetate copolymer, manufactured by Japan Coating Resins Co., Ltd.) was applied using a bar coater onto a PET substrate having the thickness shown in Table 1. After coating, the substrate was dried at 100°C for 1 minute to produce a support film having an adhesive layer on the substrate having the thickness shown in Table 1.

[0062] (Examples 1-8 to 1-14, Comparative Example 1-2) Aquatex AC3100 (ethylene methacrylic acid copolymer, manufactured by Japan Coating Resins Co., Ltd.) was applied using a bar coater onto a PET substrate having the thickness shown in Table 2. After coating, the substrate was dried at 100°C for 1 minute to produce a support film having an adhesive layer on the substrate having the thickness shown in Table 2.

[0063] (Examples 1-15 to 1-16) Aquatex EC1700 (ethylene vinyl acetate copolymer, manufactured by Japan Coating Resins Co., Ltd.) was applied to a nylon substrate having a thickness of 15 μm using a bar coater. After coating, the substrate was dried at 100° C. for 1 minute to produce a support film having an adhesive layer on the substrate with a thickness shown in Table 3.

[0064] (Examples 1-17 to 1-18) Aquatex EC1700 (ethylene vinyl acetate copolymer, manufactured by Japan Coating Resins Co., Ltd.) was applied to a 20 μm thick CPP substrate using a bar coater. After coating, the substrate was dried at 100° C. for 1 minute to produce a support film having an adhesive layer on the substrate with the thickness shown in Table 3.

[0065] (Comparative Examples 1-3 to 1-4) Arrowbase SE-1030N (acid-modified olefin, manufactured by Unitika Ltd.) was applied using a bar coater onto a PET substrate having the thickness shown in Table 3. After coating, the substrate was dried at 100°C for 1 minute to produce a support film having an adhesive layer having the thickness shown in Table 3 on the substrate.

[0066] Reference Examples 1 to 4 PET substrates having the thicknesses shown in Table 4 were prepared.

[0067] <Thermocompression bonding> The adhesive layer of the prepared support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm, product name: 4-1592-02, manufactured by AS ONE), and the support film was sandwiched between PET films (thickness 25 μm, product name: Lumirror S10, manufactured by Toray) in the following order: PET film / electrolytic copper foil / support film / PET film. Thermocompression bonding was performed by applying heat only from the electrolytic copper foil side using a heat seal tester (product name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.). The bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0068] <Peel test> In accordance with JIS K 6854-2, a thermocompression-bonded support film was adjusted to a width of 15 mm, and the end of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation), and the interface between the adhesive layer and the electrolytic copper foil was peeled at a speed of 300 mm / min at an angle of 180°. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of each measurement value was taken as the adhesion strength. The measurement results are shown in Tables 1 to 3.

[0069] <Measurement of Dielectric Breakdown Strength> The prepared support film was cut into a size of 50 mm x 50 mm and sandwiched in the plane direction between the terminals of a withstand voltage / insulation resistance tester (Kikusui Electronics Model TOS9201). The presence or absence of dielectric breakdown when a specific voltage was applied was evaluated in accordance with JIS C2110. At this time, 30 μL of pure water was dropped on the resin substrate side before sandwiching between the terminals. The film surface measurement conditions were DC current, applied voltage (1.0 kV or 3.6 kV), and measurement time 60 seconds. Dielectric breakdown was evaluated as occurring when a current of 10 mA or more flowed. The evaluation criteria were as follows, and the evaluation results are shown in Tables 1 to 3. A: No dielectric breakdown occurred even when 3.6 kV was applied. B: Dielectric breakdown occurred when 3.6 kV was applied, but not when 1.0 kV was applied. C: Dielectric breakdown occurred when 1.0 kV was applied.

[0070]

[0071]

[0072]

[0073]

[0074] The support films produced in Examples 1-1 to 1-18 had an adhesion strength of 3 N / 15 mm or more and sufficient dielectric breakdown strength. On the other hand, Comparative Examples 1-1, 1-3, and 1-4 all had an adhesion strength of 2 N / 15 mm or more, but insufficient dielectric breakdown strength. Comparative Example 1-2 had sufficient dielectric breakdown strength, but the adhesion strength was less than 2 N / 15 mm, so adhesion to the current collector was insufficient.

[0075] Second Embodiment A second embodiment of the present disclosure will now be described.

[0076] <Support Film> Figure 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a substrate 1 and an adhesive layer 2 disposed on one surface of the substrate 1. When a first test piece obtained by overlapping two support films 10 with their adhesive layers 2 facing each other has a haze of A1 and a second test piece obtained by thermocompression bonding the first test piece has a haze of A2, the haze change rate (unit: %) calculated by ((A1-A2) / A1) x 100 is 25% or more.

[0077] From the viewpoint of making poor adhesion more easily visible, the haze change rate may be 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. The haze change rate may be, for example, 99.9% or less. The haze change rate may be 30% or more and 99.9% or less, 40% or more and 99.9% or less, 50% or more and 99.9% or less, 60% or more and 99.9% or less, 70% or more and 99.9% or less, 80% or more and 99.9% or less, or 90% or more and 99.9% or less.

[0078] The above A1 may be 7% or more, 20% or more, or 50% or more, and may be 80% or less, 60% or less, or 30% or less, from the viewpoint that having a certain degree of haze before thermocompression bonding makes poor adhesion more easily visible.

[0079] Methods for controlling the haze change rate, A1, and A2 include a method for controlling the film formation of a granular resin in the adhesive layer, a method for adding a filler to the adhesive layer, a method for forming an uneven shape on the surface of the adhesive layer by shaping treatment, and a method for forming islands by adding a material with low compatibility to the adhesive layer.

[0080] The above-mentioned A1 is measured as follows. That is, a pair of support films 10 is prepared. The pair of support films 10 are overlapped with each other so that the adhesive layers 2 face each other to obtain a first test piece. Using a haze meter, the haze is measured in a state where the first test piece is fixed so that light entering an integrating sphere from a light source passes through the first test piece in the thickness direction. This allows the above-mentioned A1 to be measured.

[0081] The above A2 is measured as follows. That is, a pair of support films 10 is prepared. The pair of support films 10 is overlapped with each other so that the adhesive layers 2 face each other to obtain a first test piece. The first test piece is thermocompression bonded using a hot stamping device to obtain a second test piece in which the support films are in close contact with each other. The thermocompression bonding conditions are a temperature of 140°C on the contact surface of the member in contact with the first test piece of the hot stamping device, a diameter of the contact surface of 2 cm, 300 kgf, and a time of 3 seconds. Using a haze meter, the haze is measured in a state in which the second test piece is fixed so that light entering an integrating sphere from a light source passes through the second test piece in the thickness direction. This allows the above A2 to be measured.

[0082] (Substrate) The substrate may be a resin substrate (resin film). Examples of resins constituting the substrate include polyolefins (LLDPE, PP, COP, CPP, etc.), polyesters (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamides, polyimides, etc. The substrate is transparent, making it easier to check the contents (e.g., current collectors) and to detect any abnormalities. The substrate may be a laminate of multiple substrates.

[0083] The thickness of the substrate may be 4 μm or more, 5 μm or more, or 6 μm or more from the viewpoint of easily preventing a short circuit when an overvoltage is applied, and may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of improving loading efficiency and enabling a high capacity by making the support film thinner. From these viewpoints, the thickness of the substrate may be 4 to 100 μm, 5 to 50 μm, or 6 to 25 μm.

[0084] (Adhesive Layer) The adhesive layer is a layer formed from a resin composition containing a binder resin and a liquid medium that dissolves and disperses the binder resin. The binder resin may be a thermoplastic resin, a thermosetting resin, or a mixture thereof.

[0085] Examples of thermoplastic resins include polyolefins such as polypropylene, polyethylene, polybutene, and polypentene; modified polyolefins, polyesters, polystyrenes, acrylonitrile-butadiene-styrene copolymers, methyl methacrylate-butadiene-styrene copolymers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, polycarbonates, polyphenylene ethers, acrylic copolymers, polyamides, polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetal, and ionomers. From the viewpoints of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits, the adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefins, polyesters, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, and ionomers.

[0086] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane, polyisocyanate, polyisocyanurate, and polyvinyl ether.

[0087] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0088] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0089] The resin composition may further contain a filler from the viewpoint of suppressing the occurrence of blocking when the support film is wound into a roll. The filler may be an organic filler or an inorganic filler.

[0090] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0091] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0092] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0093] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0094] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0095] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, or 2 μm or more from the viewpoint of achieving better adhesion to the current collector, and allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of a short circuit, or may be 50 μm or less, 30 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of improving loading efficiency by making the support film thinner, enabling a higher capacity, and suppressing deterioration in handleability due to curling of the support film. From these viewpoints, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, or 2 to 8 μm.

[0096] The arithmetic mean roughness Ra of the surface of the adhesive layer may be 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1 μm or more, from the viewpoint of sufficiently imparting a blocking suppression effect to the adhesive layer. The arithmetic mean roughness Ra of the surface of the adhesive layer may be 2.0 μm or less, or 1.5 μm or less, from the viewpoint of better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The arithmetic mean roughness Ra of the surface of the adhesive layer can be measured using a contact surface roughness meter (e.g., Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. The arithmetic mean roughness Ra of the surface of the adhesive layer can be adjusted, for example, by performing a shaping treatment on the surface of the adhesive layer or by adding a filler to the resin composition forming the adhesive layer.

[0097] The surface of the adhesive layer may have an uneven shape. The uneven shape may be formed by a shaping treatment, and by performing the shaping treatment, it is possible to suppress blocking with the surface of the substrate on which the adhesive layer is not provided when the film is formed into a roll shape. The formation of the uneven shape by the shaping treatment can be confirmed using an optical microscope or a laser microscope, a surface roughness meter, a white light interference microscope, or the like. The uneven shape may also be formed by the resin composition forming the adhesive layer containing a filler, and the filler protruding from the surface of the adhesive layer. When the filler is made of a thermoplastic resin, the formation of an uneven shape on the surface of the adhesive layer by the filler suppresses blocking, and when the support film and the current collector are bonded by heating and / or pressure, the filler made of a thermoplastic resin melts, making it easier to achieve excellent adhesion to the current collector.

[0098] The adhesive strength B1 of the adhesive layer to the copper foil (hereinafter also simply referred to as "adhesion strength B1") may be 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesive strength B1 may be 20 N / 15 mm or less, 15 N / 15 mm or less, or 10 N / 15 mm or less. The adhesive strength B1 can be adjusted by the type of binder resin, the type of filler, etc., contained in the resin composition that forms the adhesive layer.

[0099] The adhesion strength B1 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of copper foil (thickness 18 μm, surface roughness 0.33 μm), and heat is applied only from the copper foil side of the support film using a heat seal tester to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester. The interface between the adhesive layer and the copper foil is peeled at a rate of 300 mm / min at a 180° angle. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength B1.

[0100] The adhesive strength B2 of the adhesive layer to the aluminum foil (hereinafter also simply referred to as "adhesion strength B2") may be 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, or 5 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesive strength B2 may be 10 N / 15 mm or less, 8 N / 15 mm or less, 7 N / 15 mm or less, or 4 N / 15 mm or less. The adhesive strength B2 can be adjusted by the type of binder resin, the type of filler, etc. contained in the resin composition that forms the adhesive layer.

[0101] The adhesion strength B2 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film is superimposed on the glossy side of aluminum foil (thickness 7 μm, surface roughness 0.98 μm), and heat is applied only from the aluminum foil side of the support film using a heat seal tester to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the aluminum foil is peeled at a rate of 300 mm / min at a 180° angle. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength B2.

[0102] The self-adhesion strength of the adhesive layer may be 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, or 5 N / 15 mm or more from the viewpoint of suppressing the intrusion of foreign matter such as moisture and the occurrence of short circuits. The self-adhesion strength may be 10 N / 15 mm or less, 8 N / 15 mm or less, 7 N / 15 mm or less, or 4 N / 15 mm. The self-adhesion strength can be adjusted by the type of binder resin, the type of filler, etc. contained in the resin composition that forms the adhesive layer.

[0103] The self-adhesion strength can be measured by the following peel test. <Peel Test> A pair of support films are overlapped with their respective adhesive layers facing each other, and a heat seal tester is used to apply heat only to one of the support films to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layers is peeled at a rate of 300 mm / min at a 180° angle. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as the self-adhesion strength.

[0104] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a substrate, forming a coating film, and then drying the coating. The resin composition can be applied by a wet coating method, which makes it easier to achieve a uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. If the adhesive layer is formed by extrusion lamination, it is difficult to control the thickness of the adhesive layer, and differences in the in-plane thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0105] The support film may further include layers other than the substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite the substrate.

[0106] The support film can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0107] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0108] [Examples] The second embodiment will be specifically described below using examples, but the present invention is not limited to the following examples.

[0109] <Preparation of Support Film> (Example 2-1) Aquatex EC-1700 (manufactured by Japan Coating Resins, EVA) was applied as an adhesive composition onto a PET substrate (manufactured by Toray Industries, Inc., thickness: 12 μm) using a bar coater so that the thickness after drying would be 2 μm. After coating, the coating was dried at 100° C. for 1 minute to prepare a support film.

[0110] (Comparative Example 2-1) A support film was produced in the same manner as in Example 2-1, except that Aquatex AC3100 (manufactured by Japan Coating Resins, EMAA) was used as the adhesive layer composition, and the composition was applied so that the adhesive layer had a thickness of 4 μm after drying.

[0111] <Thermocompression bonding 1> A pair of support films from each Example and Comparative Example was overlapped with each other with the adhesive layers facing each other to obtain a first test piece. The first test piece was thermocompression bonded using a hot stamping device (NAVITAS V10) to obtain a second test piece in which the support films were in close contact with each other. The thermocompression bonding conditions were as follows: the temperature of the contact surface of the member in contact with the first test piece in the hot stamping device was 140°C (the set temperature of the hot stamping device was 150°C), the diameter of the contact surface was 2 cm, and the pressure was 300 kgf for 3 seconds.

[0112] <Haze Measurement> A pair of support films in each Example and Comparative Example was overlapped with each other with the adhesive layers facing each other to obtain a first test piece. The haze was measured using a haze meter (BYK-Gardner Haze-Guard Plus, manufactured by BYK) with the first test piece fixed so that light entering an integrating sphere from a light source passed through the first test piece in the thickness direction.

[0113] In addition, a second test piece in which the support films were closely attached to each other was obtained by thermocompression bonding the first test piece using a hot stamping machine (NAVITAS V10). The thermocompression bonding conditions were: the temperature of the contact surface of the member in contact with the first test piece of the hot stamping machine was 140 ° C (the set temperature of the hot stamping machine was 150 ° C), the diameter of the contact surface was 2 cm, 300 kgf, and 3 seconds. The haze of the second test piece was also measured in the same manner as the first test piece. The haze of the first test piece was designated A1, and the haze of the second test piece was designated A2, and these are shown in Table 5. The haze change rate calculated by ((A1 - A2) / A1) × 100 was also calculated. When the haze change rate was 25% or more, it was determined that the visibility in the event of poor adhesion was high and the result was good, and it was given an "A" rating. When the haze change rate was less than 25%, it was determined that the visibility in the event of poor adhesion was low and the result was poor, and it was given a "B" rating. The results are shown in Table 5.

[0114] <Thermocompression bonding 2> The adhesive layer side of the support film was overlapped with copper foil (thickness 18 μm, surface roughness 0.33 μm), and pressure bonding was performed by applying heat from the copper foil using a heat seal tester TP-701-B (Tester Sangyo). The pressure bonding conditions were 150°C, 0.2 MPa, and 1 second. This resulted in a third test piece. A fourth test piece was obtained in the same manner as the third test piece, except that aluminum foil was used instead of copper foil. For each of the pair of support films in each example and comparative example, the adhesive layers were overlapped with each other so that they faced each other, and pressure bonding was performed by applying heat from one of the support film sides using a heat seal tester TP-701-B (Tester Sangyo). The pressure bonding conditions were the same as for the third test piece. This resulted in a fifth test piece.

[0115] <Peel Strength Test> The adhesion strength of the third test piece was measured in accordance with JIS K 6854-2. Specifically, each test piece was adjusted to a width of 15 mm, the end of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation), and peeled at a rate of 300 mm / min at a 180° angle. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of each measured value was taken as the adhesion strength with copper. Similarly to the third test piece, the peel strength of the fourth test piece was also measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of each measured value was taken as the adhesion strength with aluminum. Similarly to the third test piece, the peel strength of the fifth test piece was also measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of each measured value was taken as the self-adhesion strength. The results are shown in Table 5.

[0116] <Measurement of arithmetic mean roughness Ra> The arithmetic mean roughness Ra of the surface of the adhesive layer of each support film (the surface opposite to the PET substrate) was measured using a contact surface roughness meter (manufactured by Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. Ra was measured at five different points on the surface of the adhesive layer, and the average was taken as the surface roughness of the adhesive layer. The results are shown in Table 5.

[0117]

[0118] The support film of Example 2-1 had a haze A1 of 7 or more and a haze change rate of 25% or more, which resulted in high visibility in the event of poor adhesion, and was a good result. Furthermore, both films had high metal adhesion, making them suitable for use as support films for semi-solid batteries. On the other hand, Comparative Example 2-1 had a low haze change rate, making it difficult to detect poor adhesion.

[0119] Third Embodiment A third embodiment of the present disclosure will now be described.

[0120] 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a substrate 1 and an adhesive layer 2 disposed on one surface of the substrate 1.

[0121] (Substrate) The substrate may be a resin substrate (resin film). Examples of resins constituting the substrate include polyolefins (LLDPE, PP, COP, CPP, etc.), polyesters (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamides, polyimides, etc. The substrate is transparent, making it easier to check the contents (e.g., current collectors) and to detect any abnormalities. The substrate may be a laminate of multiple substrates.

[0122] The thickness of the substrate may be 4 μm or more, 5 μm or more, or 6 μm or more from the viewpoint of easily preventing a short circuit when an overvoltage is applied, and may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of improving loading efficiency and enabling a high capacity by making the support film thinner. From these viewpoints, the thickness of the substrate may be 4 to 100 μm, 5 to 50 μm, or 6 to 25 μm.

[0123] (Adhesive Layer) The adhesive layer is a layer formed from a resin composition containing a binder resin and a liquid medium that dissolves and disperses the binder resin. The binder resin may be a thermoplastic resin, a thermosetting resin, or a mixture thereof.

[0124] Examples of thermoplastic resins include polyolefins such as polypropylene, polyethylene, polybutene, and polypentene; modified polyolefins, polyesters, polystyrenes, acrylonitrile-butadiene-styrene copolymers, methyl methacrylate-butadiene-styrene copolymers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, polycarbonates, polyphenylene ethers, acrylic copolymers, polyamides, polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetal, and ionomers. From the viewpoints of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits, the adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefins, polyesters, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, and ionomers.

[0125] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane, polyisocyanate, polyisocyanurate, and polyvinyl ether.

[0126] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0127] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0128] The resin composition may further contain a filler from the viewpoint of suppressing the occurrence of blocking when the support film is wound into a roll. The filler may be an organic filler or an inorganic filler.

[0129] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0130] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0131] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0132] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0133] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0134] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, or 2 μm or more from the viewpoint of achieving better adhesion to the current collector, and allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of a short circuit, or may be 50 μm or less, 30 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of improving loading efficiency by making the support film thinner, enabling a higher capacity, and suppressing deterioration in handleability due to curling of the support film. From these viewpoints, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, or 2 to 8 μm.

[0135] The arithmetic mean roughness Ra of the surface of the adhesive layer may be 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1 μm or more, from the viewpoint of sufficiently imparting a blocking suppression effect to the adhesive layer. The arithmetic mean roughness Ra of the surface of the adhesive layer may be 2.0 μm or less, or 1.5 μm or less, from the viewpoint of better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The arithmetic mean roughness Ra of the surface of the adhesive layer can be measured using a contact surface roughness meter (e.g., Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. The arithmetic mean roughness Ra of the surface of the adhesive layer can be adjusted, for example, by performing a shaping treatment on the surface of the adhesive layer or by adding a filler to the resin composition forming the adhesive layer.

[0136] The surface of the adhesive layer may have an uneven shape. The uneven shape may be formed by a shaping treatment, and by performing the shaping treatment, it is possible to suppress blocking with the surface of the substrate on which the adhesive layer is not provided when the film is formed into a roll shape. The formation of the uneven shape by the shaping treatment can be confirmed using an optical microscope or a laser microscope, a surface roughness meter, a white light interference microscope, or the like. The uneven shape may also be formed by the resin composition forming the adhesive layer containing a filler, and the filler protruding from the surface of the adhesive layer. When the filler is made of a thermoplastic resin, the formation of an uneven shape on the surface of the adhesive layer by the filler suppresses blocking, and when the support film and the current collector are bonded by heating and / or pressure, the filler made of a thermoplastic resin melts, making it easier to achieve excellent adhesion to the current collector.

[0137] The adhesive strength A1 of the adhesive layer to the copper foil is 2 N / 15 mm or more. The adhesive strength A1 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm) are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The compression conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine, and the interface between the adhesive layer and the electrolytic copper foil is peeled at an angle of 180° at a speed of 300 mm / min. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of the measured values ​​is recorded as adhesion strength A1.

[0138] The adhesion strength A1 may be 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesion strength A1 may be 10 N / 15 mm or less, 8 N / 15 mm or less, 6 N / 15 mm or less, or 4 N / 15 mm. The adhesion strength A1 can be adjusted by the type of binder resin, the type of filler, etc., contained in the resin composition that forms the adhesive layer.

[0139] The adhesion strength A1 is greater than the adhesion strength A2 of the adhesive layer to the substrate. The adhesion strength A2 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and a test substrate identical to the substrate are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the test substrate is peeled 180 degrees at a speed of 300 mm / min. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength A2.

[0140] The adhesion strength A2 may be 8 N / 15 mm or less, 7 N / 15 mm or less, 6 N / 15 mm or less, 5 N / 15 mm or less, 4 N / 15 mm or less, 3 N / 15 mm or less, or 2 N / 15 mm or less, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The adhesion strength A2 may be 0.5 N / 15 mm or more, 1 N / 15 mm or more, 2 N / 15 mm or more, or 3 N / 15 mm or more, from the viewpoint of excellent adhesion to the substrate. The adhesion strength A2 can be adjusted by the type of binder resin, the type of filler, etc., contained in the resin composition that forms the adhesive layer.

[0141] The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 0.4 N / 15 mm or more, 0.8 N / 15 mm or more, 1 N / 15 mm or more, 1.2 N / 15 mm or more, 1.4 N / 15 mm or more, 1.6 N / 15 mm or more, 1.8 N / 15 mm or more, or 2 N / 15 mm or more, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 5 N / 15 mm or less, 4 N / 15 mm or less, 3 N / 15 mm or less, or 2 N / 15 mm or less.

[0142] The support film may be one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). That is, the support film may be one that does not peel off at the interface between the adhesive layer and the copper foil when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). If the support film is one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1), the adhesive layer of the support film remains on the current collector even when the support film is peeled off from the current collector, thereby further suppressing the occurrence of a short circuit.

[0143] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a substrate, forming a coating film, and then drying the coating. The resin composition can be applied by a wet coating method, which makes it easier to achieve a uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. If the adhesive layer is formed by extrusion lamination, it is difficult to control the thickness of the adhesive layer, and differences in the in-plane thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0144] The support film may further include layers other than the substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite the substrate.

[0145] The support film can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0146] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0147] [Examples] The third embodiment will be specifically described below using examples, but the present invention is not limited to the following examples.

[0148] Example 3-1 Chemipearl S300 (ethylene-unsaturated carboxylic acid copolymer, manufactured by Mitsui Chemicals, Inc.) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the coating was dried at 100°C for 1 minute to produce a support film having an adhesive layer of 8.5 μm thickness on the substrate.

[0149] (Example 3-2) A support film was prepared in the same manner as in Example 3-1, except that Aquatex EC1700 (ethylene methacrylic acid copolymer, manufactured by Japan Coating Resin Co., Ltd.) was used instead of Chemipearl S300, and the thickness of the adhesive layer after drying was 2.0 μm.

[0150] Example 3-3 A support film was prepared in the same manner as in Example 3-2, except that the thickness of the adhesive layer after drying was 3.6 μm.

[0151] Example 3-4 A support film was prepared in the same manner as in Example 3-2, except that the thickness of the adhesive layer after drying was 5.0 μm.

[0152] (Example 3-5) A support film was prepared in the same manner as in Example 3-1, except that Aquatex AC3100 (ethylene methacrylic acid copolymer, manufactured by Japan Coating Resin Co., Ltd.) was used instead of Chemipearl S300, and the thickness of the adhesive layer after drying was 4.0 μm.

[0153] <Thermocompression bonding> (Thermocompression bonding with copper foil) The adhesive layer of the prepared support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm, product name: 4-1592-02, manufactured by AS ONE), and the support film was sandwiched between PET films (thickness 25 μm, product name: Lumirror S10, manufactured by Toray) in the following order: PET film / electrolytic copper foil / support film / PET film. Thermocompression bonding was performed by applying heat only from the electrolytic copper foil side using a heat seal tester (product name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.). The bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0154] (Thermocompression bonding with substrate) The adhesive layer of the prepared support film and a test PET substrate (manufactured by Toray Industries, Inc., trade name: P60, thickness: 12 μm) were superimposed, and the support film was sandwiched using a PET film (thickness 25 μm, trade name: Lumirror S10, manufactured by Toray) in the order PET film / test PET substrate / support film / PET film, and thermocompression bonding was performed by applying heat only from the test PET substrate side using a heat seal tester (trade name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.). The compression bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0155] <Peel Test> In accordance with JIS K 6854-2, a thermocompression-bonded support film was adjusted to a width of 15 mm, and the edge of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation). The adhesive layer was peeled at a speed of 300 mm / min at a 180° angle from the interface between the adhesive layer and the electrolytic copper foil or the test PET substrate. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of the measured values ​​was taken as the adhesion strength. The adhesion strength to the copper foil was designated A1, and the adhesion strength to the test PET substrate was designated A2. The measurement results are shown in Table 6.

[0156]

[0157] The support films produced in Examples 3-1 to 3-5 had an adhesive strength A1 of 2 N / 15 mm or more, and had a relationship of adhesive strength A1>adhesive strength A2.

[0158] Fourth Embodiment A fourth embodiment of the present disclosure will now be described.

[0159] 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a substrate 1 and an adhesive layer 2 disposed on one surface of the substrate 1.

[0160] (Substrate) The substrate may be a resin substrate (resin film). Examples of resins constituting the substrate include polyolefins (LLDPE, PP, COP, CPP, etc.), polyesters (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamides, polyimides, etc. The substrate is transparent, making it easier to check the contents (e.g., current collectors) and to detect any abnormalities. The substrate may be a laminate of multiple substrates.

[0161] The thickness of the substrate may be 4 μm or more, 5 μm or more, or 6 μm or more from the viewpoint of easily preventing a short circuit when an overvoltage is applied, and may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of improving loading efficiency and enabling a high capacity by making the support film thinner. From these viewpoints, the thickness of the substrate may be 4 to 100 μm, 5 to 50 μm, or 6 to 25 μm.

[0162] (Adhesive Layer) The adhesive layer is a layer formed from a resin composition containing a binder resin and a liquid medium that dissolves and disperses the binder resin. The binder resin may be a thermoplastic resin, a thermosetting resin, or a mixture thereof.

[0163] Examples of thermoplastic resins include polyolefins such as polypropylene, polyethylene, polybutene, and polypentene; modified polyolefins, polyesters, polystyrenes, acrylonitrile-butadiene-styrene copolymers, methyl methacrylate-butadiene-styrene copolymers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, polycarbonates, polyphenylene ethers, acrylic copolymers, polyamides, polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetal, and ionomers. From the viewpoints of achieving better adhesion to the current collector and making it less likely that poor adhesion will occur during thermocompression bonding with the current collector, the adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefins, polyesters, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, and ionomers.

[0164] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane, polyisocyanate, polyisocyanurate, and polyvinyl ether.

[0165] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0166] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0167] The resin composition may further contain a filler, which may be an organic filler or an inorganic filler, in order to more easily prevent blocking when the support film is wound into a roll.

[0168] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0169] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0170] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0171] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0172] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0173] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, or 2 μm or more from the viewpoint of achieving better adhesion to the current collector, and allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of a short circuit, or may be 50 μm or less, 30 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of improving loading efficiency by making the support film thinner, enabling a higher capacity, and suppressing deterioration in handleability due to curling of the support film. From these viewpoints, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, or 2 to 8 μm.

[0174] The arithmetic mean roughness Ra of the surface of the adhesive layer is 0.2 μm or more. From the viewpoint of sufficiently imparting a blocking suppression effect to the adhesive layer, the arithmetic mean roughness Ra may be 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1 μm or more. From the viewpoint of better adhesion to the current collector, the arithmetic mean roughness Ra of the surface of the adhesive layer may be 2.0 μm or less, or 1.5 μm or less. The arithmetic mean roughness Ra of the surface of the adhesive layer can be measured using a contact surface roughness meter (e.g., Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. The arithmetic mean roughness Ra of the surface of the adhesive layer can be adjusted, for example, by performing a shaping treatment on the surface of the adhesive layer or by adding a filler to the resin composition forming the adhesive layer.

[0175] The surface of the adhesive layer may have an uneven shape. The uneven shape may be formed by a shaping treatment, and by performing the shaping treatment, it is possible to suppress blocking with the surface of the substrate on which the adhesive layer is not provided when the film is formed into a roll shape. The formation of the uneven shape by the shaping treatment can be confirmed using an optical microscope or a laser microscope, a surface roughness meter, a white light interference microscope, or the like. The uneven shape may also be formed by the resin composition forming the adhesive layer containing a filler, and the filler protruding from the surface of the adhesive layer. When the filler is made of a thermoplastic resin, the formation of an uneven shape on the surface of the adhesive layer by the filler suppresses blocking, and when the support film and the current collector are bonded by heating and / or pressure, the filler made of a thermoplastic resin melts, making it easier to achieve excellent adhesion to the current collector.

[0176] When the adhesive strength of an adhesive layer having a thickness of T1 to a copper foil is A1 and the adhesive strength of an adhesive layer having a thickness of T2 (where T2 > T1) to a copper foil is A2, (A2 - A1) / (T2 - T1) is 0.7 [(N / 15 mm) / μm] or less. Having (A2 - A1) / (T2 - T1) equal to or less than a specific value reduces the likelihood of poor adhesion during thermocompression bonding with a current collector. The reason for this is that the larger the (A2 - A1) / (T2 - T1) ratio, the greater the variation in adhesion strength relative to the thickness of the adhesive layer, making it more likely that localized poor adhesion will occur within the surface of the adhesive layer. However, a small (A2 - A1) / (T2 - T1) ratio ensures uniform adhesion throughout the adhesive layer, reducing the likelihood of poor adhesion. Adhesion strengths A1 and A2 are measured using the following peel test. T1 may be 4 μm or less, and T2 may be 5 μm or more. (T2 - T1) may be 3 μm or more. <Peel Test> The adhesive layer of a support film (thickness T1 or T2) was superimposed on the glossy side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm). A PET film was placed on the surface of the support film opposite the substrate, and the support film was sandwiched. Using a heat seal tester, heat was applied only from the adhesive layer side of the support film to perform thermocompression bonding. The bonding conditions were 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film was adjusted to a width of 15 mm, and the edge of the thermocompression-bonded support film was fixed to the grip of an autograph tester. The interface between the adhesive layer and the electrolytic copper foil was peeled at a speed of 300 mm / min at a 180° angle. The peel strength was measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of each measurement value was measured as adhesion strength A1 and A2.

[0177] From the viewpoint of making poor adhesion less likely to occur during thermocompression bonding with the current collector, (A2-A1) / (T2-T1) may be 0.6 [(N / 15 mm) / μm] or less, 0.5 [(N / 15 mm) / μm] or less, 0.4 [(N / 15 mm) / μm] or less, 0.3 [(N / 15 mm) / μm] or less, 0.2 [(N / 15 mm) / μm] or less, or 0.1 [(N / 15 mm) / μm] or less.

[0178] The adhesive strength A1 of the adhesive layer to the copper foil is 2 N / 15 mm or more. From the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits, the adhesive strength A1 may be 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more. The adhesive strength A1 may be 20 N / 15 mm or less, 15 N / 15 mm or less, 10 N / 15 mm, 8 N / 15 mm or less, or 4 N / 15 mm. The adhesive strength A1 can be adjusted by the type of binder resin, the type of filler, etc. contained in the resin composition forming the adhesive layer.

[0179] The support film may be one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). That is, the support film may be one that does not peel off at the interface between the adhesive layer and the copper foil when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). If the support film is one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1), the adhesive layer of the support film remains on the current collector, and the occurrence of a short circuit can be suppressed.

[0180] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a substrate, forming a coating film, and then drying the coating. The resin composition can be applied by a wet coating method, which makes it easier to achieve a uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. If the adhesive layer is formed by extrusion lamination, it is difficult to control the thickness of the adhesive layer, and differences in the in-plane thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0181] The support film may further include layers other than the substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite the substrate.

[0182] The support film can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0183] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0184] [Examples] The fourth embodiment will be specifically described below using examples, but the present invention is not limited to the following examples.

[0185] Example 4-1 Chemipearl S300 (manufactured by Mitsui Chemicals, Inc.) was applied to a PET substrate (manufactured by Toray Industries, Inc., product name: P60, thickness: 12 μm) using a bar coater. After coating, the substrate was dried at 100° C. for 1 minute to produce a support film having a 2.5 μm thick adhesive layer on the substrate and a support film having a 8.5 μm thick adhesive layer.

[0186] (Example 4-2) Support films were prepared in the same manner as in Example 4-1, except that Chemipearl V200 (ethylene vinyl acetate copolymer, manufactured by Mitsui Chemicals, Inc.) was used, and a support film having an adhesive layer thickness of 4 μm after drying and a support film having an adhesive layer thickness of 12 μm after drying were prepared.

[0187] (Example 4-3) Aquatex EC1700 (ethylene vinyl acetate copolymer, manufactured by Japan Coating Resin Co., Ltd.) was used, and a support film having an adhesive layer thickness of 3.6 μm after drying and a support film having an adhesive layer thickness of 6.7 μm after drying were prepared in the same manner as in Example 4-1.

[0188] (Example 4-4) Aquatex AC3100 (ethylene methacrylic acid copolymer, manufactured by Japan Coating Resin Co., Ltd.) was used, and a support film having an adhesive layer thickness of 4 μm after drying and a support film having an adhesive layer thickness of 10.5 μm after drying were prepared. A support film was prepared in the same manner as in Example 4-1.

[0189] <Measurement of arithmetic mean roughness Ra> The arithmetic mean roughness Ra of the surface of the adhesive layer of the prepared support film (surface opposite to the substrate) was measured using a contact surface roughness meter (manufactured by Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. The surface roughness was measured at five different points on the surface of the adhesive layer, and the average was taken as the arithmetic mean roughness Ra of the surface of the adhesive layer.

[0190] <Thermocompression bonding> (Thermocompression bonding with copper foil) The adhesive layer of the prepared support film was superimposed on the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm, product name: 4-1592-02, manufactured by AS ONE), and the support film was sandwiched between PET films (thickness 25 μm, product name: Lumirror S10, manufactured by Toray) in the following order: PET film / electrolytic copper foil / support film / PET film. Thermocompression bonding was performed by applying heat only from the electrolytic copper foil side using a heat seal tester (product name: TP-701-B, manufactured by Tester Sangyo Co., Ltd.). The bonding conditions were 150°C, 0.2 MPa, and 1 second.

[0191] <Peel test> In accordance with JIS K 6854-2, a thermocompression-bonded support film was adjusted to a width of 15 mm, and the end of the support film was fixed to the grip of an autograph testing machine (product name: AGS-X, manufactured by Shimadzu Corporation), and the interface between the adhesive layer and the electrolytic copper foil was peeled at a speed of 300 mm / min at an angle of 180°. The peel strength was measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of each measurement value was taken as the adhesion strength A1. The measurement results are shown in Table 7.

[0192] <Evaluation of Variation in Adhesion Strength> The above-mentioned peel test was performed on the thin support film among the prepared support films, and the maximum convex peak value M (excluding the maximum peak at the start of peeling) and the minimum concave peak value m were measured to evaluate the variation in adhesion strength (M-m) / adhesion strength A1 x 100 (%). Note that the greater the variation in adhesion strength, the more likely it is that poor in-plane adhesion will occur during thermocompression bonding between the current collector and the support film.

[0193]

[0194] The support films produced in Examples 4-1 to 4-4 had (A2-A1) / (T2-T1) of 0.7 [(N / 15 mm) / μm] or less and an adhesive strength A1 of 2 N / 15 mm or more.

[0195] Fifth Embodiment A fifth embodiment of the present disclosure will now be described.

[0196] 1 is a schematic cross-sectional view of a support film for a current collector for a semi-solid battery according to one embodiment. The support film 10 includes a substrate 1 and an adhesive layer 2 disposed on one surface of the substrate 1.

[0197] (Substrate) The substrate may be a resin substrate (resin film). Examples of resins constituting the substrate include polyolefins (LLDPE, PP, COP, CPP, etc.), polyesters (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamides, polyimides, etc. The substrate is transparent, making it easier to check the contents (e.g., current collectors) and to detect any abnormalities. The substrate may be a laminate of multiple substrates.

[0198] The thickness of the substrate may be 4 μm or more, 5 μm or more, or 6 μm or more from the viewpoint of easily preventing a short circuit when an overvoltage is applied, and may be 100 μm or less, 50 μm or less, or 25 μm or less from the viewpoint of improving loading efficiency and enabling a high capacity by making the support film thinner. From these viewpoints, the thickness of the substrate may be 4 to 100 μm, 5 to 50 μm, or 6 to 25 μm.

[0199] (Adhesive Layer) The adhesive layer is a layer formed from a resin composition containing a binder resin and a liquid medium that dissolves and disperses the binder resin. The binder resin may be a thermoplastic resin, a thermosetting resin, or a mixture thereof.

[0200] Examples of thermoplastic resins include polyolefins such as polypropylene, polyethylene, polybutene, and polypentene; modified polyolefins, polyesters, polystyrenes, acrylonitrile-butadiene-styrene copolymers, methyl methacrylate-butadiene-styrene copolymers, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, polycarbonates, polyphenylene ethers, acrylic copolymers, polyamides, polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetal, and ionomers. From the viewpoints of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits, the adhesive layer may be formed from a resin composition containing at least one selected from the group consisting of modified polyolefins, polyesters, ethylene-vinyl acetate copolymers, ethylene-methacrylic acid copolymers, and ionomers.

[0201] Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane, polyisocyanate, polyisocyanurate, and polyvinyl ether.

[0202] The liquid medium may be an organic solvent, such as a water-soluble solvent, including alcohols such as methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones such as acetone and methyl ethyl ketone; glycols such as ethylene glycol and diethylene glycol; and glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

[0203] The resin composition may further contain other components in addition to the binder resin and the liquid medium, such as a curing agent, a filler, a lubricant, a UV absorber, a matting agent, a flexibility imparting agent, a surfactant, etc.

[0204] The resin composition may further contain a filler, which may be an organic filler or an inorganic filler, in order to more easily prevent blocking when the support film is wound into a roll.

[0205] Examples of organic fillers include fillers made of thermoplastic resins. A filler made of a thermoplastic resin means a filler in which the proportion of the thermoplastic resin in the filler is 90 mass % or more. When the filler is made of a thermoplastic resin, the filler made of the thermoplastic resin melts when the support film and the current collector are bonded by heating and / or pressure, which makes it easier to achieve excellent adhesion to the current collector while suppressing the occurrence of blocking.

[0206] When the organic filler is a filler made of a thermoplastic resin, the thermoplastic resin may be a polyolefin resin or an acid-modified polyolefin resin from the viewpoint of achieving better adhesion to the current collector.

[0207] The particle size of the filler is not particularly limited as long as it is within a range that provides a blocking suppression effect in the adhesive layer, and can be appropriately adjusted depending on the type of thermoplastic resin used in the adhesive layer and the film thickness of the adhesive layer. The average particle size of the filler may be 1 μm or more, 3 μm or more, or 5 μm or more from the viewpoint of providing a sufficient blocking suppression effect in the adhesive layer, and may be 100 μm or less, 30 μm or less, or 20 μm or less from the viewpoint of providing better adhesion to the current collector. In this specification, "average particle size" means the median diameter (D50) and can be measured using a laser diffraction particle size distribution analyzer.

[0208] The filler content may be 1 mass% or more, 2 mass% or more, or 3 mass% or more relative to the total mass of the thermoplastic resin, from the viewpoint of providing the adhesive layer with a sufficient blocking suppression effect, and may be less than 30 mass%, 20 mass% or less, or 10 mass% or less, from the viewpoint of excellent formability of the adhesive layer.

[0209] The adhesive layer may be a single layer or may be composed of multiple layers. When the adhesive layer is composed of multiple layers, each adhesive layer may be formed based on the description regarding the resin composition described above.

[0210] The thickness of the adhesive layer may be 1 μm or more, 1.5 μm or more, or 2 μm or more from the viewpoint of achieving better adhesion to the current collector, and allowing the adhesive layer of the support film to remain on the current collector even when the support film is peeled off, thereby further suppressing the occurrence of a short circuit, or may be 50 μm or less, 30 μm or less, 10 μm or less, or 8 μm or less from the viewpoint of improving loading efficiency by making the support film thinner, enabling a higher capacity, and suppressing deterioration in handleability due to curling of the support film. From these viewpoints, the thickness of the adhesive layer may be 1 to 50 μm, 1 to 30 μm, 1.5 to 30 μm, 2 to 30 μm, 2 to 10 μm, or 2 to 8 μm.

[0211] The arithmetic mean roughness Ra of the surface of the adhesive layer is 0.2 μm or more. From the viewpoint of sufficiently imparting a blocking suppression effect to the adhesive layer, the arithmetic mean roughness Ra may be 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1 μm or more. From the viewpoint of better adhesion to the current collector, the arithmetic mean roughness Ra of the surface of the adhesive layer may be 2.0 μm or less, or 1.5 μm or less. The arithmetic mean roughness Ra of the surface of the adhesive layer can be measured using a contact surface roughness meter (e.g., Mitutoyo, model number: SJ-210) in accordance with JIS B 0601 and JIS B 0031. The arithmetic mean roughness Ra of the surface of the adhesive layer can be adjusted, for example, by performing a shaping treatment on the surface of the adhesive layer or by adding a filler to the resin composition forming the adhesive layer.

[0212] The surface of the adhesive layer may have an uneven shape. The uneven shape may be formed by a shaping treatment, and by performing the shaping treatment, it is possible to suppress blocking with the surface of the substrate on which the adhesive layer is not provided when the film is formed into a roll shape. The formation of the uneven shape by the shaping treatment can be confirmed using an optical microscope or a laser microscope, a surface roughness meter, a white light interference microscope, or the like. The uneven shape may also be formed by the resin composition forming the adhesive layer containing a filler, and the filler protruding from the surface of the adhesive layer. When the filler is made of a thermoplastic resin, the formation of an uneven shape on the surface of the adhesive layer by the filler suppresses blocking, and when the support film and the current collector are bonded by heating and / or pressure, the filler made of a thermoplastic resin melts, making it easier to achieve excellent adhesion to the current collector.

[0213] The adhesive strength A1 of the adhesive layer to the copper foil is 1 N / 15 mm or more. The adhesive strength A1 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and the shiny side of an electrolytic copper foil (thickness 18 μm, surface roughness 0.33 μm) are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The compression conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the gripping portion of an autograph testing machine, and the interface between the adhesive layer and the electrolytic copper foil is peeled at an angle of 180° at a speed of 300 mm / min. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average value of the measured values ​​is recorded as adhesion strength A1.

[0214] The adhesion strength A1 may be 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, 6 N / 15 mm or more, 7 N / 15 mm or more, or 8 N / 15 mm or more, from the viewpoint of achieving better adhesion to the current collector, allowing the adhesive layer of the support film to remain on the current collector, and further suppressing the occurrence of short circuits. The adhesion strength A1 may be 15 N / 15 mm or less, 10 N / 15 mm or less, 8 N / 15 mm or less, 6 N / 15 mm or less, or 4 N / 15 mm. The adhesion strength A1 can be adjusted by the type of binder resin, the type of filler, etc. contained in the resin composition that forms the adhesive layer.

[0215] The adhesion strength A2 may be 8 N / 15 mm or less, 7 N / 15 mm or less, 6 N / 15 mm or less, 5 N / 15 mm or less, 4 N / 15 mm or less, 3 N / 15 mm or less, or 2 N / 15 mm or less, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The adhesion strength A2 may be 0.5 N / 15 mm or more, 1 N / 15 mm or more, 2 N / 15 mm or more, or 3 N / 15 mm or more, from the viewpoint of excellent adhesion to the substrate. The adhesion strength A2 can be adjusted by the type of binder resin, the type of filler, etc., contained in the resin composition forming the adhesive layer. The adhesion strength A2 can be measured by the following peel test. <Peel test> The adhesive layer of the support film and the same test substrate as the substrate are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The compression conditions are 150 ° C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, and the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester. The interface between the adhesive layer and the test substrate is peeled at a speed of 300 mm / min at a 180 ° peel angle. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of each measurement value is measured as adhesion strength A2.

[0216] The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 0.4 N / 15 mm or more, 0.8 N / 15 mm or more, 1 N / 15 mm or more, 1.2 N / 15 mm or more, 1.4 N / 15 mm or more, 1.6 N / 15 mm or more, 1.8 N / 15 mm or more, or 2 N / 15 mm or more, from the viewpoint that even when the support film is peeled off, the adhesive layer of the support film remains on the current collector and the occurrence of a short circuit is easily suppressed. The difference between the adhesion force A1 and the adhesion force A2 (adhesion force A1 - adhesion force A2) may be 5 N / 15 mm or less, 4 N / 15 mm or less, 3 N / 15 mm or less, or 2 N / 15 mm or less.

[0217] The adhesion strength A3 of the adhesive layer to the aluminum foil may be 1 N / 15 mm or more, 2 N / 15 mm or more, 3 N / 15 mm or more, 4 N / 15 mm or more, 5 N / 15 mm or more, or 6 N / 15 mm or more, from the viewpoint of better adhesion to the current collector. The adhesion strength A3 may be 10 N / 15 mm or less, 8 N / 15 mm or less, 6 N / 15 mm or less, or 4 N / 15 mm. The adhesion strength A3 can be adjusted by the type of binder resin contained in the resin composition forming the adhesive layer, the type of filler, etc. The adhesion strength A3 can be measured by the following peel test. <Peel Test> The adhesive layer of the support film and the glossy side of aluminum foil (alloy 8079, thickness: 7 μm, surface roughness: 0.98 μm) are overlapped, a PET film is placed on the surface of the support film opposite the substrate, and the support film is sandwiched between them. Using a heat seal tester, heat is applied only from the adhesive layer side of the support film to perform thermocompression bonding. The pressure bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the aluminum foil is peeled at a speed of 300 mm / min at an angle of 180°. The peel strength is measured every 0.01 s for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is measured as adhesion strength A3.

[0218] The support film may be one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). That is, the support film may be one that does not peel off at the interface between the adhesive layer and the copper foil when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1). If the support film is one that peels off at the interface between the substrate and the adhesive layer when the substrate is peeled off after the support film is adhered to copper foil (the copper foil used in measuring adhesion strength A1), the adhesive layer of the support film remains on the current collector, and the occurrence of a short circuit can be suppressed.

[0219] The adhesive layer can be formed by known methods. For example, the adhesive layer can be formed by applying a resin composition to a substrate, forming a coating film, and then drying the coating. The resin composition can be applied by a wet coating method, which makes it easier to achieve a uniform thickness of the adhesive layer, thereby preventing localized peeling of the adhesive layer of the support film from the current collector and further suppressing the occurrence of short circuits. If the adhesive layer is formed by extrusion lamination, it is difficult to control the thickness of the adhesive layer, and differences in the in-plane thickness may result in localized reduced adhesion. Examples of wet coating methods include gravure coating, comma coating, dip coating, curtain coating, spin coating, sponge roll coating, and die coating. The coating film can be dried, for example, at 60 to 100°C for 0.5 to 2 minutes.

[0220] The support film may further include layers other than the substrate and the adhesive layer. For example, the support film may include a release layer on the surface of the adhesive layer opposite the substrate.

[0221] The support film can be used as a support film for a current collector for a semi-solid battery. The support film can be adhered to the current collector for a semi-solid battery by applying heat and / or pressure to the current collector for a semi-solid battery.

[0222] The current collector for a semi-solid battery is, for example, a substrate, sheet, or foil containing a conductive material. The current collector for a semi-solid battery may contain aluminum, copper, lithium, nickel, stainless steel, tantalum, titanium, tungsten, vanadium, or an alloy of these metals. The current collector for a semi-solid battery may contain a non-metallic material such as carbon, carbon nanotubes, or a metal oxide. The current collector for a semi-solid battery may also be a mixture of these. From the viewpoint of enabling high capacity, the current collector for a semi-solid battery is preferably thin, and may be, for example, 20 μm or less.

[0223] 1...substrate, 2...adhesive layer, 10...support film

Claims

1. A support film for a current collector for a semi-solid battery, comprising a resin substrate and an adhesive layer disposed on one surface of the resin substrate, the adhesive layer containing at least one of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-vinyl ester copolymer, and the thickness of the resin substrate is 6 μm or more.

2. The support film of claim 1, wherein the adhesive layer comprises an ethylene-methacrylic acid copolymer.

3. The support film of claim 1, wherein the adhesive layer comprises an ethylene-vinyl acetate copolymer.

4. The support film according to any one of claims 1 to 3, wherein the resin substrate is a polyester resin.

5. A support film according to any one of claims 1 to 3, wherein the adhesive layer has a thickness of 1 to 30 µm.

6. A support film according to any one of claims 1 to 3, wherein the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.05 or more.

7. The support film according to any one of claims 1 to 3, having a thickness of 25 µm or less.

8. A support film according to any one of claims 1 to 3, wherein the adhesive layer is a layer formed by a wet coating method.

9. The support film according to any one of claims 1 to 3, wherein the adhesive layer has a thickness of 1 to 8 µm.

10. The support film according to any one of claims 1 to 3, wherein the resin substrate has a thickness of 15 μm or less.

11. The support film according to any one of claims 1 to 3, wherein the adhesive strength B1 of the adhesive layer to the copper foil, as measured by the following peel test, is 2 N / 15 mm or more. <Peel Test> The adhesive layer of the support film is superimposed on the shiny side of a copper foil (thickness 18 μm, surface roughness 0.33 μm), and thermocompression bonding is performed using a heat seal tester by applying heat only to the copper foil side of the support film. The bonding conditions are 150°C, 0.2 MPa, and 1 second. In accordance with JIS K 6854-2, the thermocompression-bonded support film is adjusted to a width of 15 mm, the end of the thermocompression-bonded support film is fixed to the grip of an autograph tester, and the interface between the adhesive layer and the copper foil is peeled at a 180° angle at a speed of 300 mm / min. The peel strength is measured every 0.01 second for 4.00 seconds from the maximum peak at the start of peeling, and the average of the measured values ​​is determined as the adhesion strength B1.

12. The support film according to claim 1, wherein the adhesive layer contains an ethylene-vinyl acetate copolymer, the adhesive layer has a thickness of 1 to 3 μm, the resin substrate has a thickness of 11 to 13 μm, the resin substrate is a polyester resin, the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.15 or more and 0.2 or less, and the thickness is 12 to 20 μm.

13. The support film according to claim 1, wherein the adhesive layer contains an ethylene-vinyl acetate copolymer, the adhesive layer has a thickness of 5 to 7 μm, the resin substrate has a thickness of 8 to 10 μm, the resin substrate is a polyester resin, the ratio of the thickness of the adhesive layer to the thickness of the resin substrate is 0.6 or more and 0.7 or less, and the thickness is 13 to 20 μm.

14. A semi-solid battery comprising the support film according to any one of claims 1 to 3 and a current collector.

15. A method for producing a support film according to any one of claims 1 to 3, comprising the step of forming the adhesive layer on the resin substrate by a wet coating method.

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