Air filter medium and air filter and air purification device using the same

摘要

PROBLEM TO BE SOLVED: To achieve both low pressure loss and high dust collection efficiency of an air filter medium and an air filter.SOLUTION: An air filter 3 is provided with a filter medium part 10, and a shape holding part 11 which holds the filter medium part 10 in a pleat shape. The filter medium part 10 comprises a base material layer 14, and a fine fiber layer 15 and a protective layer 16 which are provided on the surface of the base material layer 14. A first fiber diameter of first fibers 17 composing the base material layer 14 is made larger than a second fiber diameter of second fibers 18 composing the fine fiber layer 15, and in the base material layer 14, the back surface-side density is made lower than the front surface-side density.