ELECTRET SHEET AND PIEZOELECTRIC SENSOR

摘要

The present invention provides an electret sheet which makes it possible to maintain a high generated voltage even if considerable pressure is applied. This electret sheet is characterized by comprising an electrostatically charged propylene-based resin foam sheet including a cross-linked propylene-based resin that contains 60 wt% or more of a propylene-α-olefin random copolymer having a weight-average molecular weight of 370,000 to 420,000 and that has a gel fraction of 30 to 50 wt%, the propylene-based resin foam sheet having a mean thickness of 90 to 150 μm and a mean number of bubbles in the thickness direction of two to four.