The present invention relates to a reproducing stylus of a capacitance detection type for grooveless disc records in which signals are recorded in the form of minute pits and a method for manufacturing the stylus.
Capacitance detection type reproducing stylii are formed with a contact face, structured so that the stylus may rest over several recording tracks. An electrode is provided for reading just one information signal, recorded in a track, and tracking signals which may be recorded on either side thereof or on a common track with the information signal. Since the disc record is spun at a considerably high speed, the reproducing stylus is manufactured to tight tolerances to ensure a reasonable operating lifetime.
Various attempts have hitherto been made to improve life time for such stylii. One prior art attempt involves the use of a multifaced body of a hard, insulative material with the electrode being attached to a rear face of the body. To assure excellent operating performance, the stylus body is ground or abraded with utmost care so that it is structurally balanced with respect to its vertical axis. Furthermore, the adjoining faces of the stylus body must be carefully shaped so that the edges between adjacent faces are free of any chipped portions which might catch dust or small fragmentary objects that would eventually cause impairment of the record surface. Therefore, productivity of this type of stylus is quite low.
Another prior art approach involves the use of a cylindrical stylus body having a conically shaped portion. Although this approach eliminates the precision requirements as imposed on the multifaced type, the electrode must be deposited on a curved surface of the support body using a photoresist and a mask pattern to assure that the electrode has a predetermined width along its length. The latter approach involves various production process steps including exposure to light through the mask pattern, developing the photoresist and etching unnecessary parts of the photoresist. Because of the small dimensions of the stylus, coupled with the fact that it must be passed through a number of process steps, productivity is also not satisfactory.