| 摘要 |
PROBLEM TO BE SOLVED: To provide an air filter filtering medium suppressing an increase of pressure loss in long-term use, while maintaining high collection efficiency.SOLUTION: A filtering medium part 10 includes a base material layer 14, and a fine fiber layer 15 provided on the surface of the base material layer 14. The fine fiber layer 15 has a multilayer structure comprising fine fiber assemblies of four layers or more, and is configured such that a first fine fiber assembly 17 formed of fine fibers with thick fiber diameters and a second fine fiber assembly 18 formed of fine fibers of thin fiber diameters are alternately stacked, and also the first fine fiber assembly 17 is disposed on the farthest side of the base material layer 14 in the fine fiber layer 15, and further, a weight amount of each layer constituting the second fine fiber assembly 18 is reduced as separated from the base material layer 14 side. Accordingly, a high collection efficiency is ensured while reducing an initial pressure loss in thin fine fibers, and a collection amount of large powder dust is ensured in thick fine fibers, thereby suppressing an increase of the pressure loss in long-term use. |
