Once the glass master copy of the CD or DVD has been produced and is ready to be replicated, a replicating machine is then used to generate the required number of copies. This process of generating a copy of the master disc is quicker and more efficient for higher volumes than writing (or burning) the data onto each disc individually as the Replicating machines can ‘stamp’ or mould the discs very quickly, up to 900 an hour.
CDs are made out of Polycarbonate, a thermoplastic polymer group of plastics that are easily moulded as they can be melted at relatively low temperatures, while also solid and relatively strong at room temperature. The CD and DVD Replicating machines first dry this polycarbonate at about 130°C before being vacuum fed into the injection chamber where it is heated to its melting point of about 210-320°C and then injected into the mould that contains the data print. Once full, water is passed over the mould so that the disc solidifies enough to be removed and still maintain its form with the data intact. This whole process takes a few seconds, before the disc is removed and placed on the cooling station where it fully solidifies and prepared for the final stages of the development of the disk
Although the disc now contains the data print, there is no reflective layer that actually reflects the laser and tells the reading device what the data is. The disc surface is also too fragile in its current state to be used in reading devices.
To resolve these two issues, firstly the disc undergoes what is known as ‘sputtering’, where a metal layer is added to the disc. Each disc is individually passed into the processing position in a chamber called the metaliser vacuum, which contains aluminium, known as the target. Argon gas is then added to the chamber before an electric direct current of about 700 volts is passed through, resulting in the production of a plasma from the aluminium. This plasma vapour settles on the data side of the disc, coating it in a reflective material that is varied by the peaks and pits on the data side and can be read by the recording device.
The final stage of the CD and DVD Replication process is adding a layer of protection to the reflective side to prevent damage and corrosion. This is achieved by applying a lacquer to the disc using UV curable lacquer. To do this, a ‘spin coater’ machine is used to spin the disc very fast while the lacquer is applied to the disc. This is done so that only a very thin layer of the lacquer is applied, enough to protect the disc but not affect the reflective properties of the data side. Then, the disc is exposed to a UV lamp to ‘cure’ the lacquer, done at high intensity so that it is done quickly.
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Post time: 02-26-2017