Laser recording method on gramophone record - involves covering unexposed surfaces with metallic layer and etching to form deep groove

摘要

Process of recording or mechanically or optically reproducible information, has bandwidth of several K Hz. A spiral groove is produced on a flat disc whose surface is covered with a photosensitive lacquer film. During recording the film is exposed to a laser or electron beam and the film is then etched to remove the unexposed portions. The surface areas from which the lacquer has been removed are then covered up with a metal layer (i.e. gold) in order that the remaining parts can be cleared of lacquer and an etching made into the record. The etching medium is made of 10 vol. % H2SO4; 10 vol. % H3PO4; 30 vol. % KNO3; and 50 vol. % methano carboxylic acid. And is applied for 20 sec. after etching the gold layer is removed with 37.5g. potassium iodate, 55 gm. of iodine and 20 m.l. of water.