Fire-spread prevention sheet, method for manufacturing same, and battery

Abstract

[Problem] Provided are: a fire-spread prevention sheet capable of achieving elastic deformation that efficiently absorbs expansion of a heat source while achieving reflection of heat from the heat source; and a battery comprising the same.　[Solution] The present invention relates to: a fire-spread prevention sheet that is interposed between heat sources and is capable of preventing the spread of fire between the heat sources, and has a laminate structure having a plurality of layers, wherein a metal-film-equipped rubber sheet 17, in which a metal film 13 is provided on at least one surface in the thickness direction of a first rubber sheet 11, is provided inside the fire-spread prevention sheet in the thickness direction, and the metal film 13 is a film in which metal particles 15 are deposited; a method for manufacturing the fire-spread prevention sheet; and a battery.

Description

Fire prevention sheet, its manufacturing method, and battery Cross Reference

[0001] This application claims priority under the Paris Convention based on Japanese Patent Application No. 2024-147066, filed in Japan on August 29, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a fire prevention sheet, a method for manufacturing the same, and a battery.

[0003] Automobile power sources are shifting from engines that use fossil fuels such as gasoline and diesel to motors that use electricity from batteries. Lithium-ion batteries, one type of battery, generally have multiple battery cells (also simply called "cells") arranged in a housing.

[0004] Battery cells may generate heat during charging and discharging. If a battery cell overheats abnormally, the heat may be transferred to adjacent battery cells, resulting in overheating of the entire battery and an increased risk of fire. To prevent this, it is preferable to interpose a material that reduces thermal conduction between the battery cells between the battery cells. Various methods have been studied to prevent the transfer of heat from an abnormally high temperature battery cell to surrounding battery cells. For example, a method of providing a fire-prevention sheet, such as a fire-resistant material or a heat-insulating layer, between multiple battery cells is known (see Patent Document 1).

[0005] On the other hand, when a battery cell overheats, the battery cell container expands. To absorb such expansion, it is preferable to interpose a material that is highly elastically deformable between the battery cells. Prior to the present invention, the inventor of the present application developed a fire spread prevention sheet including a rubber sheet made of a rubber-like elastic material, heat insulating sheets laminated on both sides of the rubber sheet to reduce heat transfer between multiple adjacent heat sources, and adhesive layers interposed between the rubber sheet and the heat insulating sheet to bond the heat insulating sheet to both sides of the rubber sheet (see, for example, Patent Document 2).

[0006] JP 2018-206604 A JP 2023-062546 A

[0007] Based on the findings of the above-mentioned conventionally known fire spread prevention sheets, the inventors have further developed the sheet and have come up with the following improvements. One is to make it easier to reflect heat emitted from heat sources such as battery cells. The other is to enable the fire spread prevention sheet to achieve elastic deformation sufficient to more reliably absorb the expansion of the heat source.

[0008] When a laminated sheet with high thermal conductivity metal plates, such as aluminum, placed on both sides of the rubber sheet in the thickness direction is sandwiched between heat sources, the heat from the overheated heat source is quickly transferred to the metal plates. This results in the metal plates themselves becoming hot, which is undesirable. Furthermore, using ordinary metal plates inhibits the elastic deformation of the rubber sheets that make up the laminated sheet. As a result, when the heat source expands, the rubber is unable to elastically deform in response to the expansion.

[0009] Based on the above findings, the present invention aims to provide a fire prevention sheet that can reflect heat from a heat source while also achieving elastic deformation that efficiently absorbs the expansion of the heat source, and a battery equipped with the same.

[0010] (1) To achieve the above object, a fire spread prevention sheet according to one embodiment is a fire spread prevention sheet that can be interposed between heat sources to prevent the spread of fire between the heat sources, the fire spread prevention sheet having a laminate structure with multiple layers, and a metal film-attached rubber sheet having a metal film on at least one surface of a first rubber sheet in the thickness direction inside the fire spread prevention sheet, the metal film being a film in a state in which metal particles are deposited. (2) In a fire spread prevention sheet according to another embodiment, preferably, the metal film may be formed 1 mm or more inside from both surfaces in the thickness direction of the fire spread prevention sheet. (3) In a fire spread prevention sheet according to another embodiment, preferably, the outer surfaces of the multiple layers may be covered with an insulating film. (4) In a fire spread prevention sheet according to another embodiment, preferably, the first rubber sheet may be a sponge-like porous sheet. (5) In a fire spread prevention sheet according to another embodiment, preferably, the first rubber sheet may be silicone rubber. (6) In another embodiment of the fire spread prevention sheet, the plurality of layers may further include a second rubber sheet, and the second rubber sheet may be disposed opposite the metal film-containing surface of the metal film-covered rubber sheet. (7) In another embodiment of the fire spread prevention sheet, at least one of the first rubber sheet and the second rubber sheet may be a sponge-like porous sheet. (8) In another embodiment of the fire spread prevention sheet, at least one of the first rubber sheet and the second rubber sheet may be silicone rubber. (9) In another embodiment of the fire spread prevention sheet, the metal film may be a thin film primarily composed of aluminum, copper, silver, or gold, or a thin film of an alloy containing at least one of aluminum, copper, silver, or gold. (10) In another embodiment of the fire spread prevention sheet, a metal oxide-containing heat insulating sheet may be provided on the metal film side of the metal film-covered rubber sheet. (11) In another embodiment of the fire spread prevention sheet, a second rubber sheet may be provided on the side of the heat insulating sheet opposite the metal film.(12) In another embodiment of the fire spread prevention sheet, a metal oxide-containing heat insulating sheet may be provided on at least one outer surface in the thickness direction of the fire spread prevention sheet. (13) In another embodiment of the fire spread prevention sheet manufacturing method for achieving the above object, the fire spread prevention sheet is a method for manufacturing a fire spread prevention sheet that can be interposed between heat sources to prevent fire spread between the heat sources, wherein the fire spread prevention sheet has a laminate structure having multiple layers, and the manufacturing method includes: a metal film forming step of forming a metal film in which metal particles are deposited on at least one surface in the thickness direction of a first rubber sheet, which is one of the multiple layers, to manufacture a metal film-coated rubber sheet; and a laminating step of laminating the first rubber sheet with one or two other layers. (14) In another embodiment of the fire spread prevention sheet manufacturing method, preferably, the laminating step is followed by a covering step of covering the outer surfaces of the multiple layers with an insulating film. (15) In another embodiment of the fire spread prevention sheet manufacturing method, preferably, one or two of the other layers may include a second rubber sheet. (16) In another embodiment of the method for manufacturing a fire spread prevention sheet, preferably, one or two of the other layers may include a heat insulating sheet containing a metal oxide. (17) In another embodiment of the method for manufacturing a fire spread prevention sheet, preferably, the metal film forming step may be performed by vapor deposition or sputtering of the metal. (18) In another embodiment of the method for manufacturing a fire spread prevention sheet, preferably, a primer treatment step may be performed on one surface of the first rubber sheet in the thickness direction prior to the metal film forming step to facilitate the formation of the metal film. (19) In one embodiment of the battery for achieving the above object, the battery includes a plurality of battery cells arranged side by side, and any one of the above-described fire spread prevention sheets is interposed between the battery cells serving as heat sources. (20) In another embodiment of the fire spread prevention sheet for achieving the above object, the fire spread prevention sheet is a sheet that can be interposed between heat sources to prevent fire spread between the heat sources, and has a laminate structure in which a metal film is sandwiched between a first rubber sheet and a second rubber sheet, and the metal film is a film in a state in which metal particles are deposited.(21) In another embodiment of the fire spread prevention sheet, preferably, at least one of the first rubber sheet and the second rubber sheet may be a sponge-like porous sheet. (22) In another embodiment of the fire spread prevention sheet, preferably, at least one of the first rubber sheet and the second rubber sheet may be silicone rubber. (23) In another embodiment of the fire spread prevention sheet, preferably, the metal film may be one or more films of aluminum, copper, tin, or an alloy containing at least one of these elements. (24) To achieve the above object, a method for manufacturing a fire spread prevention sheet according to one embodiment of the present invention includes a metal film forming step of forming a metal film on one thickness-wise surface of a first rubber sheet, and a lamination step of laminating a second rubber sheet on the metal film surface of the first rubber sheet. (25) In another embodiment of the fire spread prevention sheet manufacturing method, preferably, prior to the metal film forming step, a primer treatment step may be performed on one thickness-wise surface of the first rubber sheet to facilitate the formation of the metal film. (26) In the method for manufacturing a fire spread prevention sheet according to another embodiment, the metal film forming step may be performed by vapor deposition or sputtering of the metal. (27) In one embodiment for achieving the above object, a battery is a battery including a plurality of battery cells arranged side by side, and any of the above fire spread prevention sheets is interposed between the battery cells.

[0011] According to the present invention, it is possible to provide a fire prevention sheet that can reflect heat from a heat source while also achieving elastic deformation that efficiently absorbs the expansion of the heat source, and a battery equipped with the same.

[0012] FIG. 1 shows an enlarged view of the main part of a battery according to a first embodiment of the present invention, and a part A thereof. FIG. 2 shows a perspective view of a fire spread prevention sheet according to a first embodiment of the present invention. FIG. 3 shows the main manufacturing steps of the fire spread prevention sheet of FIG. 2. FIG. 4 shows the first stage of the manufacturing steps of the fire spread prevention sheet of FIG. 2. FIG. 5 shows a stage subsequent to the state of FIG. 4. FIG. 6 shows a stage subsequent to the state of FIG. 5. FIG. 7 shows an evaluation method (7A) and evaluation results (7B) of the fire spread prevention performance of an example of the fire spread prevention sheet according to the first embodiment. FIG. 8 shows an exploded perspective view of a fire spread prevention sheet according to a second embodiment. FIG. 9 shows the main manufacturing steps of the fire spread prevention sheet of FIG. 8. FIG. 10 shows an exploded perspective view of a fire spread prevention sheet according to a third embodiment. FIG. 11 shows the main manufacturing steps of the fire spread prevention sheet of FIG. 10. FIG. 11A shows an exploded perspective view of a fire spread prevention sheet according to a fourth embodiment. FIG. 11B shows an exploded perspective view of a fire spread prevention sheet having a different structure from that of FIG. 11A. FIG. 11C shows an exploded cross-sectional view of a fire spread prevention sheet including a metal film-coated rubber sheet in which a metal film is formed on both thickness-wise sides of a first rubber sheet, and a cross-sectional view after assembly. FIG. 11D shows a longitudinal cross-sectional view illustrating the laminated structure of a fire spread prevention sheet according to another modification. FIG. 11E shows the main manufacturing process of the fire spread prevention sheet of FIG. 11D. FIG. 12 shows a schematic diagram of the layer structure of the foamed silicone rubber sheets of Examples 1 and 2 and Comparative Examples 1 and 2. FIG. 13 shows a photograph of a thermal resistance measuring device used to measure the thermal resistance and thermal conductivity of three samples of Examples 1 and 2 and Comparative Example 1. FIG. 14 shows a photograph of Samples A, B, and C sandwiched between an upper rod (Reference material) and a lower rod (Reference material). FIG. 15 shows a schematic diagram of the sample sandwiched between the upper and lower rods. (15A) shows the heat flow from the heat source to the upper rod, sample, lower rod, and heat sink (cooling part), the state in which the sample is compressed between the upper and lower rods, and the locations where four thermocouples are fixed. (15B) shows the thermal resistance (R ｔｈ，Ｂｕｌｋ), the thermal resistance between the sample and the upper rod (Rth,contact Ref-sample), the thermal resistance between the sample and the lower rod (Rth,contact Ref-sample), and the equation for measuring thermal conductivity. FIG. 16 shows the changes in thermal resistance (16A) and thermal conductivity (16B) when increasing pressure is applied to Sample A of Example 1, Sample B of Example 2, and Sample C of Comparative Example 1. FIG. 17 shows a graph of the relationship between thickness and stress when Sample A of Example 1, Sample C of Comparative Example 1, and Sample D of Comparative Example 2 are compressed in their thickness direction. FIG. 18 shows an optical microscope photograph (observation magnification: 500x) of the thin aluminum film of Sheet a constituting Sample A. FIG. 19 shows scanning electron microscope photographs (observation magnifications: 1000x, 3000x, and 10000x) of the thin aluminum film of Sheet a.

[0013] 1...battery, 5...battery cell (an example of a heat source), 10, 10a, 10b, 10c, 10d, 10e, 10f...fire prevention sheet, 11...first rubber sheet (e.g., a sponge-like porous sheet), 12...second rubber sheet (e.g., a sponge-like porous sheet), 13...metal film, 14...holes, 15...metal particles, 17...rubber sheet with metal film, 31, 32...heat insulating sheets.

[0014] Next, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0015] First Embodiment First, a fire spread prevention sheet, a method for manufacturing a fire spread prevention sheet, and a battery according to a first embodiment of the present invention will be described.

[0016] FIG. 1 shows an enlarged view of the main part of a battery according to a first embodiment of the present invention and a part A thereof.

[0017] The battery 1 according to this embodiment is, for example, a battery for an electric vehicle, preferably a lithium-ion battery. The battery 1 includes a large number of battery cells (also simply referred to as "cells") 5 arranged side by side, with a fire-prevention sheet 10 sandwiched between the battery cells 5. The fire-prevention sheet 10 is designed to minimize the spread of fire to adjacent battery cells 5 even if some of the battery cells 5 overheat and, in the worst case scenario, ignite. The fire-prevention sheet 10 is also elastically deformable in its thickness direction. The battery cells 5 are compressed in their arranging direction and set within the battery 1. At this time, the fire-prevention sheet 10 is compressed and deformed by the battery cells 5. On the other hand, when the battery cells 5 are released from compression, the fire-prevention sheet 10 returns to its original thickness. Furthermore, the fire-prevention sheet 10 is elastically deformable in response to the deformation of the battery cells 5 due to thermal expansion of the battery cells 5, which are an example of a heat source.

[0018] FIG. 2 shows a perspective view of the fire spread prevention sheet according to the first embodiment of the present invention.

[0019] The fire spread prevention sheet 10 according to this embodiment is a sheet that can be interposed between battery cells 5, which are an example of a heat source, to prevent the spread of fire between the battery cells 5, and has a laminate structure having multiple layers. Most fire spread prevention sheets 10 are provided within the battery 1 so that both sides in the thickness direction of the fire spread prevention sheets 10 contact the battery cells 5. However, at least one of the multiple fire spread prevention sheets 10 may be provided within the battery 1 so that one side in the thickness direction of the fire spread prevention sheets 10 contacts the battery cells 5 and the other side contacts the housing (not shown) of the battery 1.

[0020] The fire spread prevention sheet 10 in this embodiment has a laminate structure in which a metal film 13 is sandwiched between a first rubber sheet 11 and a second rubber sheet 12. The second rubber sheet 12 is one of multiple layers constituting the laminate structure. The second rubber sheet 12 is disposed opposite the surface of a metal film-coated rubber sheet 17 (first rubber sheet 11 + metal film 13) described below, which has the metal film 13. The metal film 13 is a thin film formed on the first rubber sheet 11, more specifically, a film in which metal particles are deposited. Note that in this application, metal particles (=metal particles) are broadly interpreted to include metal atoms.

[0021] The thicknesses of the first rubber sheet 11 and the second rubber sheet 12 may be relatively larger or may be the same, but are preferably the same. As a result, the metal film 13 is disposed exactly in the center of the thickness of the fire spread prevention sheet 10. There are no particular restrictions on the range of the thickness of the first rubber sheet 11 and the second rubber sheet 12, but it is preferably 0.5 mm or more and 10 mm or less, and more preferably 1 mm or more and 7 mm or less. The metal film 13 has a form in which one or more layers of metal particles are deposited.

[0022] The first rubber sheet 11 and the second rubber sheet 12 are preferably made of a thermosetting elastomer such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), or styrene butadiene rubber (SBR); a thermoplastic elastomer such as a urethane-based, ester-based, styrene-based, olefin-based, butadiene-based, or fluorine-based elastomer, or a composite thereof. Silicone rubber sheets with excellent heat resistance are preferred for the first rubber sheet 11 and the second rubber sheet 12. The first rubber sheet 11 and the second rubber sheet 12 may contain fillers such as silica and graphite. Furthermore, porous sheets (also referred to as sponge-like porous sheets) with high elasticity are preferred for the first rubber sheet 11 and the second rubber sheet 12. In this embodiment, porous silicone rubber sheets (also referred to as foamed silicone rubber sheets) are more preferably used for the first rubber sheet 11 and the second rubber sheet 12. If the first rubber sheet 11 and the second rubber sheet 12 have small pores containing air inside, the heat insulating properties of the sheets can be further improved.

[0023] The first rubber sheet 11 and the second rubber sheet 12 do not have to be made of the same type of rubber. For example, only one of the first rubber sheet 11 or the second rubber sheet 12 may be made of silicone rubber, and the other may be made of non-silicone rubber. Also, only one of the first rubber sheet 11 or the second rubber sheet 12 may be a spongy porous sheet, and the other may be a non-spongy sheet.

[0024] While there are no particular restrictions on the type of metal used for the metal film 13, it is preferably a thin film primarily composed of aluminum, copper, tin, silver, or gold, or a thin film of an alloy containing at least one of aluminum, copper, tin, silver, or gold. The metal film 13 may be a film of a single metal component, or a laminated film of two metal components. The metal film 13 may be, for example, an aluminum film, a copper film, a tin film, a silver film, a gold film, an aluminum alloy film, a copper alloy film, a tin alloy film, a silver alloy film, or a laminated film of two or more of the above films. The metal film 13 is a thin film composed of metal particles (preferably crystal grains) formed in island or scale shapes, and is different from metal films or metal sheets formed by rolling or other methods. As can be seen from the exemplary thicknesses described above, the metal film 13 is very thin. This reduces the risk that the metal film 13 will impede the elastic deformation of the fire spread prevention sheet 10 in the thickness direction. The thickness of the metal film 13 is preferably 50 nm to 700 nm, more preferably 60 nm to 600 nm, even more preferably 100 nm to 500 nm, and especially preferably 100 nm to 300 nm. Furthermore, the metal film 13 is present inside the fire spread prevention sheet 10 in the thickness direction, and is not present on the outer surface of the fire spread prevention sheet 10 in the thickness direction. The metal film 13 is preferably formed at least 1 mm inside from both surfaces in the thickness direction of the fire spread prevention sheet 10 (thickness: preferably 4 to 10 mm, more preferably 5 to 8 mm). This also applies to the fire spread prevention sheets 10a, 10b, 10c, 10d, 10e, and 10f described below. The metal film 13 is a film formed on the sheet surface from within the pores of a sponge-like sheet (porous sheet), and is not a film adhered only to the sheet surface. The metal portions in the pores of the metal film 13 are extremely fine needle-like portions that enhance the adhesion between the film and the sheet. That is, the metal film 13 has a shape like a pinholder, with parts of the metal film 13 inserted into the holes of the sheet. Therefore, as the porous sheet continues to expand, the metal film 13 follows the deformation of the porous sheet and is less likely to peel off.

[0025] Figure 3 shows the main manufacturing process of the fire spread prevention sheet of Figure 2. Figures 4 to 6 show perspective views of the manufacturing process of the fire spread prevention sheet of Figure 2 in stages. Figure 5 shows an enlarged view of a portion B1 of the metal film 13, and also shows an enlarged view of B2 within B1.

[0026] The manufacturing method of the fire spread prevention sheet 10 according to this embodiment preferably includes a primer treatment (S100), a metal film forming step (S200), and a first lamination step (S300) as a lamination step, as shown in Fig. 3. The primer treatment is an optional step and is not an essential step.

[0027] (1) Primer Treatment (S100) This step, prior to the Metal Film Formation Step (S200), facilitates the formation of the metal film 13 on one surface of the first rubber sheet 11 in the thickness direction. The primer treatment can be performed in various ways depending on the material of the first rubber sheet 11. For example, when the first rubber sheet 11 is made of silicone rubber, the primer treatment can be performed by applying a silane coupling agent. Examples of silane coupling agents include epoxy-functional alkoxysilanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto-functional alkoxysilanes such as γ-mercaptopropyltrimethoxysilane; amine-functional alkoxysilanes such as γ-aminopropyltrimethoxysilane and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane; and methacryl-functional alkoxysilanes such as 3-methacryloxypropyltrimethoxysilane.

[0028] (2) Metal Film Forming Step (S200) As shown in FIG. 5 , this step is a step of forming a metal film 13, in which metal particles 15 are deposited, on at least one surface in the thickness direction of a first rubber sheet 11, which is one of the multiple layers constituting the fire spread prevention sheet 10, to produce a metal-film-coated rubber sheet 17. When the primer treatment step (S100) is performed, the metal film 13 is formed on the primer-treated surface of the first rubber sheet 11. The metal film forming step (S200) is preferably performed by metal vapor deposition or sputtering. Vapor deposition is a method of heating and evaporating metal in a vacuum chamber to form the metal film 13 on one surface of the first rubber sheet 11. Examples of methods for vapor-depositing metal include a resistance heating method, an electron beam irradiation method, a laser heating method, and a high-frequency induction method. Sputtering is a method in which a metal is used as a target in a vacuum chamber, and an inert gas such as argon is made to collide with the target as ions, causing metal atoms to fly out of the target and forming a metal film 13 on the first rubber sheet 11. As the metal film forming step (S200), sputtering is preferred as it can form a film with a relatively high density. The preferred degree of vacuum in the vacuum chamber before sputtering is 8×10 ―４ The pressure is equal to or less than Pa. Examples of the type of sputtering include magnetron sputtering, RF sputtering, reactive sputtering, DC sputtering, and two-pole sputtering.

[0029] As shown in the enlarged view of a portion B1 in FIG. 5 and the enlarged view of a portion B2 therein, the metal film 13 is a film on which metal particles 15 are deposited. When the first rubber sheet 11 is a sponge-like porous sheet, the metal film 13 is formed on the outermost surface of the first rubber sheet 11. The first rubber sheet 11 also has holes 14 that are recessed inward on the outermost surface. The metal particles 15 are deposited so as to penetrate into the holes 14 or to block the holes 14. Therefore, the metal film 13 is formed on the first rubber sheet 11 in a form that extends from the outermost surface of the first rubber sheet 11 into the holes 14.

[0030] (3) First Lamination Step (S300) This step is a step of laminating the first rubber sheet 11 and one or two other layers. In this embodiment, the first lamination step is a lamination step of laminating a second rubber sheet 12, which is an example of another layer, on the surface of the metal film 13 of the first rubber sheet 11, as shown in FIG. 6 . Prior to this step, the surface of the second rubber sheet 12 that comes into contact with the metal film 13 may be subjected to a treatment similar to the primer treatment step (S100). Furthermore, in the first lamination step (S300), heating or a combination of heating and pressure may be performed. Furthermore, lamination may be performed using a heat-resistant adhesive.

[0031] Next, a preliminary experiment will be described.

[0032] 7A and 7B show an evaluation method (7A) and evaluation results (7B) of the fire spread prevention performance of an example of the fire spread prevention sheet according to the first embodiment. The horizontal axis of the graph in (7B) represents elapsed time (sec), and the vertical axis represents temperature (°C).

[0033] As shown in (7A), the fire spread prevention performance was measured by sandwiching Sample X between a heating element (800°C) 20 and a temperature measurement plate 21, and applying pressure between the heating element 20 and the temperature measurement plate 21 when the heating element reached 800°C. The pressure applied was 0.1 MPa. Temperature measurements were performed at the position of the temperature measurement plate 21. The following three types of Sample X were used. The first sample was a 4.2 mm thick foamed silicone rubber sheet (specific gravity: 0.36) used as a comparative material (Sample A). The second sample was a sheet used as an example of this embodiment (Sample B), and was a sheet in the form of a laminated film consisting of a 1 μm thick copper thin film and a 0.3 μm thick tin-based alloy (Sn—Ag—P alloy) thin film sandwiched between two 2.1 mm thick foamed silicone rubber sheets (specific gravity: 0.36). The copper thin film was formed by vapor deposition on one side of a 2.1 mm thick foamed silicone rubber sheet. The tin alloy thin film was formed by vapor deposition on the surface of the copper thin film. Vacuum deposition was performed using a batch vapor deposition system (model: LP1300BSD) manufactured by ULVAC, with the degree of vacuum in the chamber set to 1×10. ―４ ~1 x 10 ―６The deposition was performed within a pressure range of 100 Pa. The deposition was performed by heating the metal for deposition using a resistance heating method. The third sample was a sheet used as a comparative material (Sample C), which was a sheet in the form of two 2.1 mm thick foamed silicone rubber sheets (specific gravity: 0.36) with 10 μm thick aluminum foil sandwiched between them. The foamed silicone rubber sheet is also called a silicone sponge.

[0034] As shown in (7B), Sample A, Sample B, and Sample C all showed a temperature increase over time. All Samples maintained a temperature below 400°C, demonstrating a significant temperature increase suppression effect compared to the temperature of the heating element (800°C). Sample B also demonstrated a greater temperature increase suppression effect than Sample A. Furthermore, Sample C demonstrated a greater temperature increase suppression effect than Sample B. However, in the case of a structure in which aluminum foil is sandwiched between foamed silicone rubber sheets, as in Sample C, it was found that compression was difficult even when a load was concentrated in the center of the laminated sheet. This is thought to be because the aluminum foil is difficult to stretch, and the foil suppressed deformation of the foamed silicone rubber sheet. This phenomenon was not observed in the structure of Sample B. From the above results, it was determined that Sample B, which has a relatively large heat-shielding effect and minimizes the deformation of the silicone rubber, has an overall superior structure.

[0035] Second Embodiment Next, a fire spread prevention sheet, a method for manufacturing a fire spread prevention sheet, and a battery according to a second embodiment of the present invention will be described. In the second embodiment, descriptions of parts common to the first embodiment will be omitted as appropriate.

[0036] FIG. 8 shows an exploded perspective view of the fire spread prevention sheet according to the second embodiment.

[0037] The fire spread prevention sheet 10a according to the second embodiment has a structure in which a laminate of a metal film-coated rubber sheet 17 and a second rubber sheet 12 is sandwiched between heat insulating sheets 31 and 32 on the outer side of the fire spread prevention sheet 10 according to the first embodiment. The heat insulating sheets 31 and 32 are metal oxide-containing sheets that are located on both sides of the thickness of the laminate and function to enhance the thermal insulation of the fire spread prevention sheet 10a. The heat insulating sheets 31 and 32 are preferably sheets primarily containing talc, diatomaceous earth, silica, aerogel (e.g., silica aerogel), mullite, cordierite, steatite, forsterite, titania, or zirconia, and more preferably sheets primarily containing talc, diatomaceous earth, silica, or aerogel. Talc is generally a ceramic primarily composed of hydrated magnesium silicate and contains small amounts of impurities such as iron oxide. The type and amount of impurities vary depending on the source of the talc ore, but the talc contained in the heat insulating sheets 31 and 32 is not particularly limited in these respects.

[0038] The term "mainly" used herein means that the mass ratio of the metal oxides, such as talc, diatomaceous earth, silica, aerogel, mullite, cordierite, steatite, forsterite, titania, or zirconia, to the total mass of the insulating sheets 31, 32 exceeds 50% by mass. The content of the metal oxides in the insulating sheets 31, 32 as a whole is preferably 51% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. In addition to the metal oxides, the insulating sheets 31, 32 may also contain relatively heat-resistant materials such as silicone rubber, aramid fiber, and polyphenylene sulfide. The insulating sheets 31, 32 may also be composed almost entirely or entirely of the metal oxides. There are no particular restrictions on the manufacturing method of the insulating sheets 31, 32, but examples include a manufacturing method that includes a process similar to the papermaking process in paper manufacturing, a method in which the insulating sheet material is placed in a mold and molded, and a method in which a molten material containing the material is formed into a sheet shape using a 3D printer.

[0039] FIG. 9 shows the main manufacturing steps of the fire prevention sheet of FIG.

[0040] As shown in Fig. 9, the method for manufacturing a fire spread prevention sheet according to this embodiment preferably includes a metal film forming step (S200), a first lamination step (S300) which is the first of two lamination steps, and a second lamination step (S400) which is the second of the two lamination steps. As with the method for manufacturing a fire spread prevention sheet according to the first embodiment, the method for manufacturing a fire spread prevention sheet according to the second embodiment may optionally include a primer treatment (S100).

[0041] The metal film forming step (S200) and the first laminating step (S300) are the same as those in the first embodiment, and therefore, redundant explanations will be omitted.

[0042] Second Laminating Step (S400) This step is one of the laminating steps for laminating the first rubber sheet 11 and one or two other layers, and is a step for laminating a laminate in which the second rubber sheet 12 is laminated on the surface of the metal film 13 of the metal film-coated rubber sheet 17, sandwiching the laminate from both sides in the thickness direction between the heat insulating sheets 31, 32. The heat insulating sheets 31, 32 and the rubber sheets 11, 12 may be fixed by any method, but for example, they can be fixed using an adhesive.

[0043] Instead of laminating the heat insulating sheets 31, 32 after the completion of the laminate, the heat insulating sheets 31, 32 may be attached to the rubber sheets 11, 12 before laminating the first rubber sheet 11 and the second rubber sheet 12 together or before forming the metal film 13. Therefore, in the flow of Fig. 9, the second laminating step (S400) may be performed immediately before the metal film forming step (S200) or immediately before the first laminating step (S300). Therefore, the second laminating step can be divided into a step of laminating the heat insulating sheet 31 to the first rubber sheet 11 and a step of laminating the heat insulating sheet 32 ​​to the second rubber sheet 12.

[0044] The battery according to the second embodiment has the same configuration as the battery 1 according to the first embodiment, so a description of the battery according to the second embodiment will be omitted.

[0045] Third Embodiment Next, a fire spread prevention sheet, a method for manufacturing a fire spread prevention sheet, and a battery according to a third embodiment of the present invention will be described. In the third embodiment, descriptions of parts common to the first and second embodiments will be omitted as appropriate.

[0046] FIG. 10 shows an exploded perspective view of a fire spread prevention sheet according to the third embodiment.

[0047] The fire spread prevention sheet 10b according to the third embodiment has a structure in which the second rubber sheet 12 is removed from the fire spread prevention sheet 10a according to the second embodiment. That is, the fire spread prevention sheet 10b has a structure in which a first rubber sheet 11 having a metal film 13 formed on one side thereof is sandwiched between heat insulating sheets 31 and 32 on both sides in the thickness direction. Therefore, one side of the metal film 13 is in contact with the first rubber sheet 11, while the other side of the metal film 13 is in contact with the heat insulating sheet 32. An adhesive layer may be interposed between the metal film 13 and the heat insulating sheet 32. The configuration and manufacturing method of the heat insulating sheets 31 and 32 are the same as those described in the second embodiment.

[0048] FIG. 11 shows the main manufacturing steps of the fire prevention sheet of FIG.

[0049] The method for manufacturing a fire spread prevention sheet according to this embodiment preferably includes a metal film forming step (S200) and a second lamination step (S400), as shown in Fig. 11. As with the method for manufacturing a fire spread prevention sheet according to the first embodiment, the method for manufacturing a fire spread prevention sheet according to the third embodiment may optionally include a primer treatment (S100).

[0050] The metal film forming step (S200) is the same as in the first embodiment, and therefore a duplicated description will be omitted.

[0051] Second Lamination Step (S400) This step is a type of lamination step, in which heat insulating sheets 31 and 32 are attached to both sides in the thickness direction of the metal film-coated rubber sheet 17, which has the metal film 13 formed on one side of the first rubber sheet 11. The heat insulating sheets 31 and 32 and the metal film-coated rubber sheet 17 may be fixed by any method, for example, using an adhesive. Note that part of the second lamination step (S400) may be performed before the metal film formation step (S200). In this case, the heat insulating sheet 31 is attached to one side of the first rubber sheet 11, and then the metal film 13 is formed on the side of the first rubber sheet 11 opposite the heat insulating sheet 31, and the heat insulating sheet 32 ​​is attached to the metal film 13 side.

[0052] The battery according to the third embodiment has the same configuration as the battery 1 according to the first embodiment, so a description of the battery according to the third embodiment will be omitted.

[0053] Fourth Embodiment Next, a fire spread prevention sheet, a method for manufacturing a fire spread prevention sheet, and a battery according to a fourth embodiment of the present invention will be described. In the fourth embodiment, descriptions of parts common to the first, second, or third embodiment will be omitted as appropriate.

[0054] Fig. 11A shows an exploded perspective view of a fire spread prevention sheet according to a fourth embodiment, and Fig. 11B shows an exploded perspective view of a fire spread prevention sheet having a different structure from that shown in Fig. 11A.

[0055] The fire spread prevention sheet 10c according to the fourth embodiment includes a metal oxide-containing heat insulating sheet 32 ​​on the metal film 13 side of the metal film-coated rubber sheet 17. The fire spread prevention sheet 10d according to a modification of the fourth embodiment includes a second rubber sheet 12 on the heat insulating sheet 32 ​​opposite the metal film 13.

[0056] That is, the fire spread prevention sheet 10c has a structure in which the heat insulating sheet 31 is removed from the fire spread prevention sheet 10b according to the third embodiment. An adhesive layer may be interposed between the metal film 13 and the heat insulating sheet 32. The configuration and manufacturing method of the heat insulating sheet 32 ​​are the same as those described in the second embodiment.

[0057] The fire spread prevention sheet 10d has a structure in which the heat insulating sheet 32 ​​of the fire spread prevention sheet 10c according to the fourth embodiment is further provided with a second rubber sheet 12. That is, the fire spread prevention sheet 10d has a structure in which a metal film-covered rubber sheet 17, a heat insulating sheet 32 ​​disposed on the metal film 13 side, and a second rubber sheet 12 are laminated in this order. An adhesive layer may be interposed between the heat insulating sheet 32 ​​and the second rubber sheet 12.

[0058] The method for manufacturing the fire spread prevention sheet 10c according to the fourth embodiment preferably includes a metal film forming step (S200) and a second lamination step (S400), similar to the method shown in Fig. 11. The metal film forming step (S200) is the same as that of the first embodiment, and therefore a duplicated description will be omitted.

[0059] The second lamination step (S400) is slightly different from the third embodiment and is a step of attaching a heat insulating sheet 32 ​​to the metal film 13 side of the metal film-coated rubber sheet 17 in a state in which the metal film 13 has been formed on one side of the first rubber sheet 11. There is no heat insulating sheet 31. The heat insulating sheet 32 ​​and the metal film-coated rubber sheet 17 may be fixed by any method, for example, by using an adhesive.

[0060] The method for manufacturing the fire spread prevention sheet 10d relating to a modified example of the fourth embodiment is a method in which the first lamination step (S300) and the second lamination step (S400) are reversed in order in the steps shown in Figure 9 above, and the second lamination step (S400) is the same as the second lamination step (S400) in the above-mentioned fourth embodiment, i.e., only the insulating sheet 32 ​​is attached.

[0061] The battery according to the fourth embodiment has the same configuration as the battery 1 according to the first embodiment, so a description of the battery according to the fourth embodiment will be omitted.

[0062] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways.

[0063] In the above-described embodiment, both the first rubber sheet 11 and the second rubber sheet 12 are sponge-like porous sheets, but only one of the rubber sheets 11, 12 may be a sponge-like porous sheet, or both of the rubber sheets 11, 12 may be non-sponge-like rubber sheets.

[0064] In the above-described embodiment, the metal film 13 is formed on the entire area of ​​one side of the first rubber sheet 11. However, the metal film 13 may be formed on one or more parts of a part of the one side.

[0065] The metal film 13 may also be formed on both sides of the first rubber sheet 11 in the thickness direction.

[0066] FIG. 11C shows an exploded cross-sectional view of a fire spread prevention sheet including a metal film-coated rubber sheet in which metal films are formed on both sides of a first rubber sheet in the thickness direction, and a cross-sectional view after assembly.

[0067] 11C includes a metal film-coated rubber sheet 17 having metal films 13 formed on both thickness-wise surfaces of a first rubber sheet 11, and heat insulating sheets 31 and 32 sandwiching the metal film-coated rubber sheet 17 from both thickness-wise surfaces. The fire spread prevention sheet 10e includes the metal film 13 on both thickness-wise surfaces of the first rubber sheet 11 in the fire spread prevention sheet 10b according to the third embodiment, but not on either thickness-wise surface of the first rubber sheet 11.

[0068] Fig. 11D is a longitudinal cross-sectional view showing the laminated structure of a fire spread prevention sheet according to another modification, and Fig. 11E shows the main manufacturing steps of the fire spread prevention sheet of Fig. 11D.

[0069] Another modified fire spread prevention sheet 10f includes an insulating film 40 that covers the outside of the multiple layers that make up the fire spread prevention sheet. The fire spread prevention sheet 10f has a structure in which the outside of the fire spread prevention sheet 10e is covered with the insulating film 40. However, the insulating film 40 may also cover the outside of the other fire spread prevention sheets 10, 10a, 10b, 10c, and 10d.

[0070] The insulating film 40 has the function of reducing the risk of electrical conduction between the fire spread prevention sheets 10, 10a, 10b, 10c, 10d, and 10e and the device (including the battery 1) equipped with the sheets. The insulating film 40 is not particularly limited as long as it is made of a resin with excellent insulating properties, and is formed of, for example, an olefin-based resin such as polyethylene (PE) or polypropylene (PP); a polyester-based resin such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT); or other resins such as polycarbonate (PC) or polyurethane (PU). The insulating film 40 preferably has a bag-like shape that covers the entirety of the multiple layers. The insulating properties of the insulating film 40, expressed in terms of volume resistivity, are preferably 10 ８ ~10 １８ It is Ω·cm.

[0071] 11E, the manufacturing method of the fire spread prevention sheet 10f preferably includes a metal film forming step (S200) and a second laminating step (S400), and then a coating step (S500) after laminating is completed. Even when coating other fire spread prevention sheets 10, 10a, 10b, 10c, and 10d, the coating step (S500) is performed after the step of forming the metal film 13 and the laminating step of laminating the first rubber sheet 11 with one or two other layers. The manufacturing method of the fire spread prevention sheet 10f may also include a primer treatment (S100) as an option.

[0072] The fire spread prevention sheets 10, 10a, 10b, 10c, 10d, 10e, and 10f may be disposed not only between the battery cells 5 but also between the battery cells 5 and the housing that stores the battery cells 5. Furthermore, the fire spread prevention sheets 10, 10a, 10b, 10c, 10d, 10e, and 10f may be disposed not only on the battery 1 but also between circuit boards, between electronic components, or between a circuit board and an electronic component in an electronic device.

[0073] The fire spread prevention sheet 10 is a sheet that can be interposed between heat sources to prevent the spread of fire between the heat sources. It has a laminate structure in which a metal film 13 is sandwiched between a first rubber sheet 11 and a second rubber sheet 12, and the metal film 13 is a film in which metal particles 15 are deposited. At least one of the first rubber sheet 11 and the second rubber sheet 12 is preferably a sponge-like porous sheet. At least one of the first rubber sheet 11 and the second rubber sheet 12 is preferably made of silicone rubber. The metal film 13 may be formed on at least one surface in the thickness direction of the second rubber sheet 12. The metal film 13 of the first rubber sheet 11 and the metal film 13 of the second rubber sheet 12 may be arranged opposite each other. An adhesive layer and heat insulating sheets 31, 32 may be disposed between the metal films 13.

[0074] The method for manufacturing the fire spread prevention sheet may include a metal film forming step of forming a metal film 13 on one surface in the thickness direction of the first rubber sheet 11, and a lamination step of laminating the second rubber sheet 12 on the surface of the metal film 13 of the first rubber sheet 11. Prior to the metal film forming step, a primer treatment step may be performed on one surface in the thickness direction of the first rubber sheet 11 to facilitate the formation of the metal film 13. The metal film forming step may also be performed by a metal vapor deposition or sputtering film formation process.

[0075] The battery 1 includes a plurality of battery cells 5 arranged side by side, and any one of the fire spread prevention sheets 1 described above is interposed at least between the battery cells 5 .

[0076] The metal film 13 may be formed on at least one surface of the second rubber sheet 12 in the thickness direction, and may also be formed on the surface of the first rubber sheet 11 facing the metal film 13. The second rubber sheet 12 is preferably a sponge-like porous sheet. The metal film 13 is preferably formed so as to penetrate into the surfaces of the porous sheet other than the pores and into the interior of the pores.

[0077] The components or steps of the above embodiments may be combined in any combination except where they are incombinable. In particular, the claims may be combined in any combination.

[0078] Next, examples of the present invention will be described, but the present invention is not limited to the contents of the following examples.

[0079] 1. Production of Fire Spread Prevention Sheets FIG. 12 shows a schematic diagram of the layer structure of the foamed silicone rubber sheets of Examples 1 and 2 and Comparative Examples 1 and 2.

[0080] Example 1 (1) Production of Foamed Silicone Rubber Sheets Foamed silicone rubber sheets serving as the first and second rubber sheets were produced under the following conditions. First, 100 parts by mass of a curable silicone rubber composition (product number KE-9710U manufactured by Shin-Etsu Chemical Co., Ltd.), 0.3 parts by mass of an organic peroxide crosslinking agent (product number C-1A manufactured by Shin-Etsu Chemical Co., Ltd.), 2.0 parts by mass of an organic peroxide crosslinking agent (product number C-3 manufactured by Shin-Etsu Chemical Co., Ltd.), and 2.0 parts by mass of an addition reaction type crosslinking agent (product number C-25A manufactured by Shin-Etsu Chemical Co., Ltd.) were prepared, to which 1.0 part by mass of a foaming agent and 1.0 part by mass of a colorant were added, and the mixture was kneaded using a mixing roll. Here, 1 part by mass corresponds to 1 g. This also applies to the following examples. The kneaded mixture was dispensed into a sheet using a mixing roll, and a polyethylene terephthalate (PET) film was attached to one side of the sheet-like molded product. Next, the dispensed sheet-like molded product was peeled off from the mixing roll, and the PET film was attached to the other side. This sheet-like molded product was placed in a thermostatic chamber heated to 195°C and subjected to primary vulcanization for 5 minutes. The sheet-like molded product was then removed from the thermostatic chamber, and the PET films attached to both sides were peeled off. This was then subjected to secondary vulcanization at 200°C for 4 hours, producing a foamed silicone rubber sheet approximately 2.1 mm thick. The sheet was then cut into a rectangular sheet measuring 100 mm wide and 300 mm long in plan view. (2) Formation of Aluminum Film Next, a thin aluminum film was formed on one side of one foamed silicone rubber sheet. The thin film was formed under the following conditions. The thin aluminum film was formed by sputtering. The foamed silicone rubber (referred to as the substrate) was placed in the vacuum chamber of a carousel-type batch-type sputtering device (method: DC magnetron sputtering). Pure Al was used as the sputtering target. The vacuum in the vacuum chamber was approximately 5 x 10 ―４After the pressure was adjusted to Pa, the substrate temperature was 25°C, the sputtering power was 9 kW, the Ar flow rate was 650 sccm, and the film formation pressure was 3 × 10 ―１ Sputtering was performed under conditions of 0.1 Pa. After 10 minutes of sputtering, an aluminum film approximately 100 nm thick was formed on one side of the substrate. The film thickness was measured using a Bruker stylus step profiler (model: DXT-E). (3) Production of Laminate: Two foamed silicone rubber sheets with a thin aluminum film were attached to one another with an adhesive (manufactured by Cemedine Co., Ltd., product number: SuperX) so that the thin aluminum film was on the inside. Next, a heat insulating sheet containing talc, silica, and aerogel (manufactured by Awa Paper Co., Ltd., product number: I-80F, thickness 0.8-1.0 mm) was adhered to both outer surfaces of the laminate using the adhesive. As a result, a fire prevention sheet consisting of heat insulating sheet / foamed silicone rubber sheet / thin aluminum film / foamed silicone rubber sheet / heat insulating sheet was completed. The total thickness of the fire prevention sheet was approximately 6.8 mm. The sample manufactured under the conditions of Example 1 was designated "A."

[0081] Example 2 The foamed silicone rubber sheet was manufactured and the aluminum film was formed in the same manner as in Example 1. The laminate was manufactured differently from Example 1, in that a heat insulating sheet (manufactured by Awa Paper Co., Ltd., product number I-80F, thickness 0.8 to 1.0 mm) was bonded to both sides of a foamed silicone rubber sheet with a thin aluminum film using an adhesive (manufactured by Cemedine Co., Ltd., product number SuperX). As a result, a fire prevention sheet consisting of heat insulating sheet / foamed silicone rubber sheet / thin aluminum film / heat insulating sheet was completed. The total thickness of the fire prevention sheet was approximately 4.5 mm. The sample manufactured under the conditions of Example 2 was designated "B".

[0082] Comparative Example 1 A foamed silicone rubber sheet was produced using the same formulation as in Example 1, except that the thickness was increased from 2.1 mm to 4.2 mm. The cut size was the same as in Example 1. The laminate was produced differently from Example 1, with a heat insulating sheet (manufactured by Awa Paper Co., Ltd., product number I-80F, thickness 0.8 to 1.0 mm) adhered to both sides of the foamed silicone rubber sheet using an adhesive (manufactured by Cemedine Co., Ltd., product number SuperX). This resulted in a fire spread prevention sheet consisting of heat insulating sheet / foamed silicone rubber sheet / heat insulating sheet. The total thickness of the fire spread prevention sheet was approximately 6.6 mm. The fire spread prevention sheet of Comparative Example 1 had a layer structure similar to that of Example 1, except that the thin aluminum film was removed. The sample produced under the conditions of Comparative Example 1 was designated "C."

[0083] (Comparative Example 2) A foamed silicone rubber sheet was produced under the same conditions as in Example 1. A laminate was produced by sandwiching aluminum foil (manufactured by Toyo Aluminum K.K., thickness: approximately 11 μm) between two foamed silicone rubber sheets via the adhesive used in Example 1. Next, the heat insulating sheet used in Example 1 was adhered to both outer surfaces of the laminate using the adhesive. As a result, a fire spread prevention sheet of heat insulating sheet / foamed silicone rubber sheet / aluminum foil / foamed silicone rubber sheet / heat insulating sheet was completed. The total thickness of the fire spread prevention sheet was approximately 6.8 mm. The sample produced under the conditions of Comparative Example 2 was designated "D".

[0084] 2. Evaluation of Fire Spread Prevention Sheet Characteristics (1) Experiment 1 (Evaluation of Thermal Resistance and Thermal Conductivity) Figure 13 shows a photograph of a thermal resistance measuring device used to examine the thermal resistance and thermal conductivity of three types of samples from Examples 1 and 2 and Comparative Example 1. Figure 14 shows a photograph of each of Samples A, B, and C sandwiched between an upper rod (also called the reference material) and a lower rod (also called the reference material). Figure 15 shows a schematic diagram of the sample sandwiched between the upper and lower rods. (15A) shows the heat flow from the heat source to the upper rod, sample, lower rod, and heat sink (cooling section), the state in which the sample is compressed between the upper and lower rods, and the locations where four thermocouples are fixed. (15B) shows the thermal resistance (R ｔｈ，Ｂｕｌｋ), the existence of thermal resistance between the sample and the upper rod (Rth, contact Ref-sample), the existence of thermal resistance between the sample and the lower rod (Rth, contact Ref-sample), and the measurement formula for thermal conductivity are shown.

[0085] The thermal resistance measuring device (TIM tester manufactured by ZFW) in Figure 13 is equipped with a system that supplies heat from the upper rod to heat the sample, as well as a unit that can compress the sample using hydraulic pressure and a device that optically measures the thickness of the sample (indicated by dx or Gap). The area (Area) of the end faces of the upper and lower rods is 706.86 mm ２ The thermal resistance measuring device shown in FIG. 13 is a device for measuring thermal resistance and thermal conductivity based on ASTM D5470-17, which is a standard for evaluating thermal resistance and thermal conductivity. ｔｈ，Ｂｕｌｋ The total of three thermal resistances, R , contact Ref-sample, the thermal resistance between the sample and the upper rod, and the thermal resistance between the sample and the lower rod, are R ｔｈ，ａｐｐ As shown in FIG. 15 (15B), the thermal resistance measuring device of FIG. 13 measures the sum of the three thermal resistances, R ｔｈ，ａｐｐ Measure dx / Area·R ｔｈ，ａｐｐ By calculating the thermal conductivity (λ ｅｆｆ or λ ａｐｐ ) can be obtained.

[0086] Tables 1, 2, and 3 show output data when sample A of Example 1, sample B of Example 2, and sample C of Comparative Example 1 were measured using the thermal resistance measuring device of FIG. 13. In the tables, Gap represents the thickness when the sample was compressed, Force represents the load when the sample was compressed, and R ｔｈ，ａｐｐ is the thermal resistance (as mentioned above), λ ａｐｐ is the thermal conductivity, R ｔｈ，ａｐｐ ・A is R ｔｈ，ａｐｐ is multiplied by the area, Pressure is the pressure caused by the load applied to the sample, and T ｓａｍｐｌｅ is the sample temperature, and Q ｂｏｔｔｏｍ and denote the heat flow through the sample, respectively.

[0087] FIG. 16 shows the changes in thermal resistance (16A) and thermal conductivity (16B) when increasing pressure is applied to Sample A of Example 1, Sample B of Example 2, and Sample C of Comparative Example 1.

[0088]

[0089]

[0090]

[0091] As shown in Tables 1-3 and Figure 16, a common trend for each sample was observed: as the pressure applied to the sample increased, the thickness decreased, the thermal resistance decreased, and the thermal conductivity increased. However, Samples A and B (Examples 1 and 2) clearly showed a smaller decrease in thermal resistance and a smaller increase in thermal conductivity than Sample C (Comparative Example 1). This result indicates that forming a thin aluminum film inside the fire spread prevention sheet can maintain high thermal resistance and, as a result, low thermal conductivity, even when pressure is increased, compared to a sheet without such a thin film. Therefore, it is believed that the thin aluminum film can prevent heat transfer from one side of the fire spread prevention sheet to the other.

[0092] (2) Experiment 2 (Evaluation of Stress-Strain) Figure 17 shows a graph of the relationship between thickness and stress when Sample A of Example 1, Sample C of Comparative Example 1, and Sample D of Comparative Example 2 are compressed in their thickness direction. The horizontal axis of the graph is thickness (mm), and the vertical axis is stress (MPa). "Stress Strain" in the graph means stress-strain. For this evaluation, the same apparatus used in Experiment 1 (see Figure 13) was used.

[0093] As shown in Figure 17, a tendency for stress to increase with decreasing sample thickness was observed for all samples. However, it was found that Samples A and C maintained lower stress when compressed in the thickness direction than Sample D. Sample C has a structure in which a foamed silicone rubber sheet is sandwiched between insulating sheets. Sample A has the same structure as Sample C, but with an aluminum thin film sandwiched inside the foamed silicone rubber sheet. Sample D has aluminum foil instead of the aluminum thin film of Sample C. These results indicate that even when a thin aluminum film is included within the fire spread prevention sheet, the sheet has low stress-strain characteristics equivalent to those of a fire spread prevention sheet without such a thin film. On the other hand, it was found that when aluminum foil is included within the fire spread prevention sheet, stress-strain increases. These results indicate that aluminum foil inhibits the low stress-strain characteristics of the foamed silicone rubber sheet, but the thin aluminum film does not inhibit the low stress-strain characteristics of the foamed silicone rubber sheet.

[0094] 3. Evaluation of the Aluminum Thin Film and Aluminum Foil in the Fire Prevention Sheet (1) To investigate the cause of the results of Experiment 2, the electrical conductivity of Sample A was examined using a foamed silicone rubber sheet with an aluminum thin film formed on one side (Sheet a), and Sample D using a foamed silicone rubber sheet with aluminum foil attached on one side (Sheet d). The electrical conductivity of Sheet d was examined using a four-terminal resistance meter (Model: MCP-T600) manufactured by Mitsubishi Chemical Corporation. As a result, Sheet d exhibited extremely high electrical conductivity (electrical resistance value: 0.0024 Ω / □). Meanwhile, the electrical conductivity of Sheet a was examined using a Hiresta (Model: MCP-HT450) manufactured by Mitsubishi Chemical Analytech. The results showed that Sheet a conducted almost no electricity (electrical resistance value: Over Load, meaning that the electrical resistance value was infinite).

[0095] (2) Observation of Microstructure Fig. 18 shows an optical microscope photograph (observation magnification: 500x) of the aluminum thin film of sheet a constituting sample A. Fig. 19 shows scanning electron microscope photographs (observation magnifications: 1000x, 3000x, and 10000x) of the aluminum thin film of sheet a.

[0096] Observation of the thin film using an optical microscope and a scanning electron microscope revealed that the thin film contained numerous fine cracks and was composed of tiny scales rather than a single film. In other words, aluminum foil is in the form of a single sheet, while the thin aluminum film is composed of multiple small pieces. This difference in morphology is thought to be related to the phenomenon where aluminum foil inhibits the low-stress strain characteristics of the foamed silicone rubber sheet, while the thin aluminum film does not. This difference in morphology is also thought to be related to the phenomenon where aluminum foil exhibits excellent electrical conductivity, while the thin aluminum film barely conducts electricity.

[0097] The present invention can be used, for example, in automobile batteries.

Claims

1. A fire prevention sheet that can be placed between heat sources to prevent the spread of fire between the heat sources, the fire prevention sheet having a laminated structure with multiple layers, and a metal film-covered rubber sheet having a metal film on at least one surface in the thickness direction of a first rubber sheet inside the thickness direction of the fire prevention sheet, the metal film being a film in which metal particles are deposited.

2. A fire prevention sheet according to claim 1, characterized in that the metal film is formed at least 1 mm inside from both surfaces of the fire prevention sheet in the thickness direction.

3. A fire prevention sheet according to claim 1 or 2, characterized in that the outer surfaces of the plurality of layers are covered with an insulating film.

4. A fire prevention sheet according to any one of claims 1 to 3, characterized in that the first rubber sheet is a sponge-like porous sheet.

5. A fire prevention sheet according to any one of claims 1 to 4, characterized in that the first rubber sheet is made of silicone rubber.

6. A fire prevention sheet as described in any one of claims 1 to 5, characterized in that the plurality of layers further comprise a second rubber sheet, the second rubber sheet being arranged opposite the surface of the metal film-coated rubber sheet that has the metal film.

7. The fire prevention sheet according to claim 6, wherein at least one of the first rubber sheet and the second rubber sheet is a sponge-like porous sheet.

8. A fire prevention sheet according to claim 6 or 7, characterized in that at least one of the first rubber sheet and the second rubber sheet is made of silicone rubber.

9. A fire prevention sheet as described in any one of claims 1 to 8, characterized in that the metal film is a thin film primarily made of aluminum, copper, tin, silver or gold, or a thin film of an alloy containing at least one of the elements aluminum, copper, tin, silver or gold.

10. A fire prevention sheet according to any one of claims 1 to 9, characterized in that a heat insulating sheet containing metal oxide is provided on the metal film side of the metal film-covered rubber sheet.

11. The fire prevention sheet according to claim 10, characterized in that the heat insulating sheet is provided with a second rubber sheet on the side opposite the metal film.

12. A fire prevention sheet as described in any one of claims 1 to 11, characterized in that a metal oxide-containing heat insulating sheet is provided on at least one outer side in the thickness direction of the fire prevention sheet.

13. A method for manufacturing a fire spread prevention sheet that can be placed between heat sources to prevent the spread of fire between the heat sources, wherein the fire spread prevention sheet has a laminate structure having a plurality of layers, and the method includes: a metal film forming step of forming a metal film in a state in which metal particles are deposited on at least one surface in the thickness direction of a first rubber sheet, which is one of the plurality of layers, to manufacture a rubber sheet with a metal film; and a lamination step of laminating the first rubber sheet with one or two other layers.

14. The method for manufacturing a fire spread prevention sheet according to claim 13, characterized in that after the laminating step, a covering step is carried out in which the outside of the plurality of layers is covered with an insulating film.

15. A method for manufacturing a fire prevention sheet as described in claim 13 or 14, characterized in that one or two of the other layers includes a second rubber sheet.

16. A method for manufacturing a fire prevention sheet according to any one of claims 13 to 15, characterized in that one or two of the other layers comprises a heat insulating sheet containing a metal oxide.

17. A method for manufacturing a fire spread prevention sheet as described in any one of claims 13 to 16, characterized in that the metal film formation process is carried out by vapor deposition or sputtering of the metal.

18. A method for manufacturing a fire spread prevention sheet described in any one of claims 13 to 17, characterized in that prior to the metal film formation process, a primer treatment process is performed on one thickness-wise surface of the first rubber sheet to facilitate the formation of the metal film.

19. A battery comprising a plurality of battery cells arranged in a row, characterized in that a fire prevention sheet according to any one of claims 1 to 12 is interposed between the battery cells serving as a heat source.