PURPOSE: To make it possible to improve diaphragm characteristics while evading undesired deformation by enabling procession efficiently in a short time at a low temperature, by performing microwave plasma nitrification as to a metal substrate.
CONSTITUTION: A microwave transmitted through waveguide 2 is led out by antenna 21 made of a copper pipe inserted into waveguide 2 and supplied to sealed container 5. As cooling gas 24, nonoxidative gas such as inert gas and nitrogen gas is flowed inside of antenna 21 to cool antenna 21 and cylinder 22 covering it. Then, sealed container 5 is evacuated and while nitrogen gas and hydrogen gas mixed at a proper ratio are supplied, the microwave leads electric power, so that the surface of metal substrate 17 will be nifrified. After this nitrification, the part of this metal substrate 17 is dissolved and removed by being etched to obtain a disphragm made of only the nitrified layer.
| WO/1993/021743 | PLANAR-TYPE LOUDSPEAKER WITH DUAL DENSITY DIAPHRAGM |
IRIE HIDEYUKI
HIROSE MASAHIKO
