POROUS FILM, SEPARATOR FOR AN ELECTRICITY STORAGE DEVICE, AND ELECTRICITY STORAGE DEVICE

• Main Authors: OKURA MASATOSHI, TAMURA NAOKO, IKOMA HIROSHI
• Format: Patent
• Language: English; Japanese
• Published: 04.12.2014
• Subjects: AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; BASIC ELECTRIC ELEMENTS; CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES ORLIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE; CHEMISTRY; COMPOSITIONS BASED THEREON; ELECTRICITY; GENERAL PROCESSES OF COMPOUNDING; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSIONOF CHEMICAL INTO ELECTRICAL ENERGY; THEIR PREPARATION OR CHEMICAL WORKING-UP; WORKING-UP

PROBLEM TO BE SOLVED: To provide a porous film exhibiting, when used as a separator for an electricity storage device, a low battery resistance, excellent in terms not only of the homogeneity of surface apertures but, due to the low thermal shrinkage of the porous film, also of heat resistance, capable of realizing the maximal heat resistance of a heat-resistant protective layer, and excellent in terms also of battery characteristics.SOLUTION: The provided porous film includes a thermoplastic resin as a main component in a state where the relation of the surface aperture ratio (S) and porosity (P) thereof satisfies the following formula (1) and where the range of the surface aperture ratio (S) is 45% or higher: 0.3<porosity (P)/surface aperture ratio (S)<1.0 (1). 【課題】 蓄電デバイス用セパレータとして使用したとき、セパレータとして用いた際の電池抵抗が低く、表面開口の均一性に優れており、さらには多孔性フィルムの熱収縮率が低いために耐熱性に優れ、また耐熱保護層の耐熱性を最大限発揮することができ、電池特性にも優れた多孔性フィルムを提供することにある。【解決手段】 熱可塑性樹脂を主成分とし、表面開口率（Ｓ）と空孔率（Ｐ）の関係が下記式（１）を満足し、表面開口率（Ｓ）の範囲が４５％以上である多孔性フィルム。０．３ ＜ 空孔率（Ｐ）／表面開口率（Ｓ） ＜１．０ ・・・（１）【選択図】なし