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Vacuum evaporation is a process by which an extremely thin and uniform metal film is deposited onto a substrate by melting and evaporating the metal material. This technology is used to form the magnetic recording layer on metal-evaporated tape requiring high recording density. Metal-evaporated tape was originally developed by Panasonic.
The raw material (cobalt) heated in a vacuum chamber evaporates, and cobalt molecules adhere to the surface of the base film to form a film with uniform thickness.
Coated tape is produced by using an adhesive to coat iron oxide or other magnetic particles onto the tape, and metal-evaporated tape is produced by melting a metallic magnetic material such as cobalt, and then depositing it onto the base film by an evaporation process.
Panasonic uses cobalt to produce metal-evaporated tape because cobalt is ferromagnetic and has an excellent crystal structure. By improving the diffusion and fluidity characteristics of cobalt molecules based on the use of evaporation technology, Panasonic forms a thin (2/10,000 mm), high-density recording film with high data retaining performance.
Cobalt in a vacuum chamber must be heated to high temperatures of 2,000°C or above in order to melt and evaporate. Panasonic uses the world's largest-class 40,000-V electron beam irradiation equipment to melt cobalt. The chamber, which is equipped with a vacuum pump, is made of iron plate measuring 75 mm in thickness to ensure that the chamber can withstand the extremely high internal pressure (several tens of tons) resulting from the reduction of pressure to 1/10,000,000 of atmospheric pressure. In comparison, the thickness of iron plate used to construct a 300-m-long ship is about 30 mm*. This shows how thick the iron plate of the evaporation chamber is.
High recording density cannot be achieved unless crystal columns in the magnetic layer are arranged uniformly in high density. By positioning a seed layer on the surface of the base film, Panasonic made it possible to minimize the cobalt magnetic column size, which dramatically raises the recording density.
To effectively utilize the cobalt that is used as the magnetic material, Panasonic re-melts scraps and also reuses cobalt that is recovered from waste materials by using electrolysis separation technology. In 2009, the rate of cobalt utilization reached 98%, clearly indicating the effectiveness of Panasonic's utilization method.