Coat solution and layered porous film

The invention relates to a layered porous film having a heat-resistant layer that is suitable for use in a separator for a non-aqueous electrolytic solution secondary battery having excellent cycle characteristics, and to a coat solution for forming the heat-resistant layer. The coat solution contains a filler, a binder and a solvent, the hydrophilicity parameter A of the filler as defined by formula (1) being 0.35 to 0.65. Hydrophilicity parameter A = BET1/BET2... (1) BET1: Specific surface area of the filler calculated using the BET method, from a difference adsorption isotherm obtained by subtracting a secondary adsorption isotherm from a primary adsorption isotherm measured by adsorbing water vapor onto the filler BET2: Specific surface area of the filler calculated using the BET method, from an adsorption isotherm measured by adsorbing nitrogen onto the filler.