When I first came into this industry I was perplexed by the difference between CD, DVD & Blu-ray replication & duplication. I even asked the question in my job interview for HDC New Media.
Prior to my interview I searched for a definition high and low (online), but I was no closer to an answer than when I began. The definitions I came across were near enough identical; “the action of copying or reproducing something/the action or process of duplicating something”. So when the interview drew to a close and the archetypal question about your question was asked, I tossed my hat into the ring in the form of the aforementioned pondering, to which I was greeted by the following response from our managing director, Dean:
“The terms, as you have stated, are in reference to the different production processes adopted in order to manufacturer CD, DVD & Blu-Ray. The deciding factor, which decides which process is utilised, is typically quantity.”
Duplication is a great process for low volume orders, and/or orders which require to be produced in a couple of days. This process is great for bands wanted to have demos or EP’s made or independent companies who do not have a requirement for more than 500 discs.
For short run orders, of 50 units and above, we will use the duplication process. This process is no different from the one used by a commercial disc burner, which you may have in your own PC. The disc which you wish to write the information to, a CD-R for example, is made up of 4 layers; the back of the disc is made out of polycarbonate plastic which has grooves pre pressed into it, with a layer of photosensitive dye on top, which has a reflective metal, typically aluminium, placed on top and finished off with a surface which can be printed on by the use of commercial inks. When the disc is brand new the photosensitive dye is translucent, but once the laser begins to burn the data to the disc, moving from the inside out, areas of the dye become opaque. The microscopic translucent & opaque areas of the dye then behave like binary code which the read laser, within the disc drive, is able to read, which is then translated into a digital file.
The production process for replication is longer and more complex, although the finished product behaves in the same way as its duplicated counterpart. The main reason for longevity is due to the set up process, as in order to replicate the required data a glass master has to be produced.
As the name suggests the master is made of glass and is slightly larger than a standard disc, one of the sides is polished so it is extremely smooth and must be free from even the most miniscule blemish. The glass master is then cleaned before being coated with a photoresist coating. Once the coating has dried the glass substrate is ready for mastering. The master is then placed in a laser beam recorder in order to write the data required to be replicated, like the duplication process the laser creates a series of bumps & flats, moving from the inside out, which can be translated into binary code.
The master is then ready for next stage in the process, electroforming. Placed in a bath, which typically contains a solution of nickel sulfamate, the master is spun until the side which contains the data is evenly coated. Once enough solution has gathered, typically around 0.3mm, the layer of nickel sulfamate is peeled off as a single piece, subsequently creating a negative version of the data on the glass master, this is known as the father. The electroforming is then repeated using the father, rather than the glass master, in order to create a mirror version of the father; the second nickel sulfamate layer to be created is known as the mother (you can probably see a pattern emerging here). Next up the sons are required to be made, this is done by the electroforming process being repeated over & over, with the mother alone, until the number of sons match the amount of discs which are to be replicated. When the required number of sons is produced the family is now finished and the electroforming process is now complete, phew!
The sons are then trimmed of any excess nickel, so that they are the same size as an optical media disc, so they can be used as the stampers in the final stage of the replication process, the replication itself. The father is kept safe, in case another mother has to be created, as well as the mother, in case further sons are needed. Replication begins with the sons being placed into a disc moulding machine where they are injection moulded with poly carbonate, on the reverse side to the data, which takes between 3-5 seconds to complete. The disc is then placed into a small chamber called a metaliser where a metallic alloy covers the data side of the disc through a process known as an anode-cathode transfer. Said alloy creates the reflective layer you can visibly see on the back of the disc, the reflective layer is what allows the read laser within your disc drive to read the binary code created by the bumps and flats on the son. Finally the reflective alloy is coated with a lacquer and cured with UV light; this last stage not only protects the reflective alloy from damage, but creates the substrate on the face of this which can then be printed.
Obviously, as now explained, the replication process is pretty arduous in comparison to the duplication process, because of this the production schedule can take quite a few days longer, typically around 10-12 working days in total. However once the master family has been created the actual replication process is much quicker than that of the duplication process, allowing the unit cost of the disc to be driven down – so it is a great option for customers requiring more than 500 discs.
“So there you have it, the difference is not just in the spelling!”
I then nodded my head in agreement, trying to let the information sink in, simultaneously wishing I’d asked a different question. The interview came to close and I never had to listen to another word about optical media duplication and replication again. With this in mind it was almost bitter sweet when I received a call later that week, offering me the position. What had I let myself in for!
If you are looking to place an order for CD, DVD or Blu-Ray and are still unsure about which process would be best for you then why don’t you get in contact with us, and see how we can help you get your order finalised.