PURPOSE: To obtain a diaphragm for speakers of higher resonance frequencies by using a composite film wherein a polybisphenol phthalate type resin is combined with needle or fibrous fillers having a moduls of elasticity higher than specific values.
CONSTITUTION: The polybisphenol phthalate resin having the structural formula shown in the figure is used as a resin for molding of the above-mentioned diaphragm and whiskers (fine single crystal fibers, ≥2,800,000kg/cm2 modulus of elasticity) of potassium titanate (K2O.6TiO2) are used as fillers. The fillers are combined with the above-mentioned resin at 15wt%. The modulus of elasticity of the composite film is 41,000kg/cm2 and the loss is 0.019. The diaphragm is molded by a vacuum molding method, whereby the cone type diaphragm of 40mm diameter and 80μm thickness is obtained. Since the speaker using such diaphragm has a high modulus of elasticity, the speaker has higher resonance frequencies and improved reproduction in a high sound range.
MURATA KOUSAKU
YAMAMOTO TOORU
YAMAMOTO KAZUMASA
