Nonaqueous electrolyte battery separator and nonaqueous electrolyte battery

A nonaqueous electrolyte battery separator comprising:

• a porous base material made of a polyolefin-based resin;
• a porous front-side protective layer formed on a front surface of the porous base material to protect the porous base material such that the porous base material is not thermally deformed or thermally contracted;
• a porous front-side flame retardant layer formed on the front-side protective layer and containing solid flame retardant having a melting point lower than an ignition temperature of a nonaqueous electrolyte;
• and
• the front-side flame retardant layer is formed such that a surface area of the front-side retardant layer is 60 to 80% per a surface area of the font-side protective layer.

A nonaqueous electrolyte battery separator comprising:

• a porous base material made of a polyolefin-based resin;
• a porous front-side protective layer formed on a front surface of the porous base material to protect the porous base material such that the porous base material is not thermally deformed or thermally contracted;
• a porous back-side flame retardant layer formed on a back surface of the porous base material and containing solid flame retardant having a melting point lower than an ignition temperature of the nonaqueous electrolyte;
• and
• the back-side flame retardant layer is formed such that a surface area of the back-side retardant layer is 60 to 80% per a surface area of the back surface of the porous base material.