Separator having heat resistant insulation layers

A separator having heat resistant insulation layers for an electric device, the separator comprising:

• a resin porous substrate;
• and
• heat resistant insulation layers formed on both surfaces of the resin porous substrate and containing heat resistant particles having a melting point or a thermal softening point of 150° C. or higher,
• wherein a parameter X represented by the following mathematical formula 1 is greater than or equal to 0.15:
• X
• =
• (
• A
• ′
• +
• A
• ″
• )
• C
• ×
• (
• A
• ′
• /
• A
• ″
• )
• 2
• [
• Math
• ⁢
• ⁢
• 1
• ]
• where A′ and A″ represent thicknesses (μm) of the respective heat resistant insulation layers formed on both surfaces of the resin porous substrate while fulfilling a condition of A′>A″, and C represents an entire thickness (μm) of the separator having the heat resistant insulation layers,
• wherein C is greater than or equal to 24.5 μm, and
• wherein a parameter Y represented by the following mathematical formula 2 is in a range from 0.3 to 0.7:
• Y
• =
• X
• (
• D
• /
• 100
• )
• [
• Math
• ⁢
• ⁢
• 2
• ]
• where D represents a porosity (%) of the respective heat resistant insulation layers.