| 摘要 |
PROBLEM TO BE SOLVED: To provide an electret sheet for holding high piezoelectricity even if used under a high temperature.SOLUTION: An electret sheet is provided in which at least two layers of a porous sheet containing a synthetic resin are integrally laminated and charges are injected into a laminated porous sheet having eleven or more of the average number of vacancies in the cross section in the thickness direction to be charged. The electret sheet exhibits excellent piezoelectricity and can maintain such an excellent piezoelectricity over a long period of time even under a high temperature. |
