WATERPROOFING SOUND-TRANSMITTING FILM, PROCESS FOR PRODUCING SAME, AND ELECTRICAL PRODUCT EMPLOYING SAME

摘要

The present invention provides a water-proof sound-transmitting membrane including a polytetrafluoroethylene (PTFE) porous membrane, in which the waterproofness is enhanced further with little lowering of the sound transmittance. The water-proof sound-transmitting membrane includes the PTFE porous membrane. The PTFE, porous membrane includes a first porous layer, and a second porous layer stacked on and integrated with the first porous layer by a binding force acting between PTFE matrices. The first porous layer and the second porous layer each are composed of PTFE with a number-average molecular weight of 5.0 × 10 7 or more determined by a standard specific gravity method. At least one layer selected from the first porous layer and the second porous layer has an average pore diameter of 1 µm or less. The water-proof sound-transmitting membrane has a surface density of 1 g/m 2 to 10 g/m 2 . The water-proof sound-transmitting membrane has a tensile strength of 10 MPa to 100 MPa. A value obtained by dividing a puncture strength of the water-proof sound-transmitting membrane by the surface density of the membrane is 25 kPa · m 2 /g to 50 kPa · m 2 /g.