Storable electrotype, esp. for mfg. video and audio disks - where original positive disk is protected against corrosion by nickel coating, and is used to make press dies

摘要

A master recording, i.e. a cut foil, is used to make an original positive disk(P). Disk(P) is used to make dies for pressing disks on which high density data are stored. The data side of disk(P) is cleaned and passivated, and coated with a thin nickel layer(NS) with low internal stress. Layer(NS) extends over the edge of disk(P) and provides protection against corrosion during storage of the disk(P). Layer(NS) is pref. 3-10 microns thick; to make a die it is activated and thickened except on its edge. The edge is then cut off and the thick layer is detached from the disk(P) and used as a press die. Disk(P) can be used for the repeated intermittent mfr. of press dies. After each use, a new layer(NS) is applied to protect disk(P) until it is required at some future date.