# US 8,785,032 B2 · Multilayer porous film, separator for batteries, and battery > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,032 B2 - Document ID: US8785032B2 - Status: Granted - Kind: B2 - Application number: 14/123,120 - Filed: 2012-05-31 - Published: 2014-04-10 - Granted: 2014-07-22 - Earliest claimed: 2011-06-02 - Assignees: Mitsubishi Plastics, Inc. - Applicants: Hiroto Yamada; Tomoyuki Nemoto - Inventors: Hiroto Yamada; Tomoyuki Nemoto - Web page: https://patentgrep.com/patent/US8785032B2 ## CPC - B32B 27/32: comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)} - C08J 7/042: {with two or more layers, where at least one layer of a composition contains a polymer binder} - C08J 7/043: Improving the adhesiveness of the coatings per se, e.g. forming primers (adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50) - C08L 69/00: Compositions of polycarbonates; Compositions of derivatives of polycarbonates - H01M 50/403: Manufacturing processes of separators, membranes or diaphragms - H01M 50/449: having a layered structure - C08J 2323/02: not modified by chemical after treatment - H01M 10/052: Li-accumulators - Y02E 60/10: Energy storage using batteries - Y10T 428/249953: Composite having voids in a component [e.g., porous, cellular, etc.] - Y10T 428/249981: Plural void-containing components - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06) - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The present invention is capable of providing a multilayer porous film used as a separator for a non-aqueous electrolyte secondary battery. A multilayer porous film which is obtained by laminating a coating layer that contains a filler and a resin binder on at least one surface of a polyolefin resin porous film that serves as a base layer. The ratio of the average particle diameter (Du) of the filler within 25% of the thickness of the coating layer from the surface of the multilayer porous film to the average particle diameter (Db) of the filler within 25% of the thickness of the coating layer from the interface with the base layer, namely, Du/Db is 1.2 to 10; and the average particle diameter (Du) is 0.5 μm or less. ## Claims ### Claim 1 A multilayer porous film, comprising: a coating layer, a filler, a resin binder, and a base layer comprising a porous polyolefin resin film, wherein said coating layer is laminated on at least one surface of the porous polyolefin resin film of said base layer, Du is an average particle diameter of said filler which is disposed downward from an upper surface of said coating layer composing an upper surface of said multilayer porous film and has a thickness within 25% of a thickness of said coating layer, Db is an average particle diameter of said filler which is disposed upward from an interface between said coating layer and said base layer and has a thickness within 25% of said thickness of said coating layer, a ratio of Db/Du is a value of from 1.2 to 10; and Du is not more than 0.5 μm. ### Claim 2 (depends on 1) The multilayer porous film according to claim 1, wherein Db is not less than 0.1 μm nor more than 3.0 μm. ### Claim 3 (depends on 1) The multilayer porous film according to claim 1, wherein Du is from 0.05 μm to 0.5 μm; Db is from 0.1 μm to 3.0 μm; an average particle diameter of said filler disposed in a region between the filler having the average particle diameter of Du and the filler having the average particle diameter of Db is a value between Du and Db; and said filler of said coating layer has an average particle diameter increasing from said upper surface of said coating layer to said interface between said coating layer and said base layer. ### Claim 4 (depends on 1) The multilayer porous film according to claim 1, wherein said filler has a density of not less than twice as a density of said resin binder. ### Claim 5 (depends on 1) The multilayer porous film according to claim 1, wherein said porous polyolefin resin film of said base layer comprises a layer comprising polypropylene resin as a main component thereof. ### Claim 6 (depends on 1) The multilayer porous film according to claim 1, wherein said porous polyolefin resin film of said base layer is a laminated film consisting of layer A comprising polypropylene resin as a main component thereof, and a layer, which is at least one of a layer B consisting of polyolefin resin other than said polypropylene resin and a layer consisting of resin other than said polyolefin resin and is laminated upon the layer A; and said coating layer is laminated on a surface of said base layer consisting of said laminated film. ### Claim 7 (depends on 1) The multilayer porous film according to claim 1, wherein said porous polyolefin resin film of the base layer has a β crystal activity. ### Claim 8 (depends on 1) The multilayer porous film according to claim 1, wherein a peel-off strength between said base layer and said coating layer is not less than 3N/15 mm. ### Claim 9 (depends on 1) The multilayer porous film according to claim 1, wherein said multilayer porous film has a thermal contraction rate of less than 25% at 150° C. ### Claim 10 (depends on 1) A separator, consisting of the multilayer porous film according to claim 1, wherein the separator is suitable for a nonaqueous electrolytic solution secondary battery. ### Claim 11 (depends on 10) A nonaqueous electrolytic solution secondary battery, comprising the separator according to claim 10. ### Claim 12 (depends on 1) A method of producing the multilayer porous film according to claim 1, the method comprising: obtaining a dispersion solution in which said filler and said resin binder are dissolved or dispersed in a solvent; applying the dispersion solution to the at least one surface of said porous polyolefin resin film, thereby obtaining said base layer; and setting the ratio of Db/Du to be from 1.2 to 10 either when said filler is settled toward said base layer before removing said solvent or while said solvent is removed. ### Claim 13 (depends on 1) A method of producing the multilayer porous film according to claim 1, the method comprising: applying a first dispersion solution comprising filler having a large average particle diameter to the at least one surface of said porous polyolefin resin film, and subsequently applying a second dispersion solution comprising filler having a small average particle diameter to the first dispersion solution to set the ratio of Db/Du to be from 1.2 to 10. ### Claim 14 (depends on 12) The method according to claim 12, further comprising: heat-treating said multilayer porous film at not less than 100° C. nor more than 170° C. before said applying or after forming said coating layer on said base layer, and subjecting said multilayer porous film to a relaxation treatment at 1 to 20%, while said multilayer porous film is heat-treated to set a thermal contraction rate at 150° C. to be less than 25%. ### Claim 15 (depends on 13) The method according to claim 13, further comprising: heat-treating said multilayer porous film at not less than 100° C. nor more than 170° C. before applying said first dispersion solution or after forming said coating layer on said base layer, and subjecting said multilayer porous film to a relaxation treatment at 1 to 20%, while said multilayer porous film is heat-treated to set a thermal contraction rate at 150° C. to be less than 25%.