DIAPHRAGM FOR SPEAKER

PROBLEM TO BE SOLVED: To provide a lightweight and rigid diaphragm for a speaker of a mobile phone having little changes in rigidity even at high temperatures that can meet requests for downsizing, thickness reduction, power saving, and sound improvement.SOLUTION: A thermoplastic resin particle foam film made up by a process where thermoplastic resin particle foam compacts of foam particles in a particular size are thinly sliced is high in surface uniformity, lightweight, and rigid as well as has little changes in its rigidity at a high temperature of 85°C. This film alone as well as a multilayer material laminated with aluminum foils on both sides of the film can be used appropriately as a diaphragm for a speaker.