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Many of the advancements in screen-printing technology that we've seen over the years have been driven by the specific needs of niche markets. This is very true of the compact-disc field, which has been of real benefit to the screen-printing industry as a whole. Disc manufacturers presented the ideal set of circumstances for suppliers to develop their products: An easily identified, lucrative market where printing would be done in a generally controlled environment onto a reasonably consistent substrate.
The quality demanded by these clients has also driven the technology. Artists and recording companies are not interested in the limitations of screen printing. They just want the print on the CD or DVD to look like the litho-printed insert. The unavailability of a color-control strip to measure dot gain and density made it all the harder for CD printers to control the process in order to meet these quality expectations.
The print surface of the CD or DVD is coated with a UV lacquer, which in itself poses a problem because if the lacquer is overcured, UV screen-printing inks won't adhere to it. CD printers have generally used conventional UV inks to get the ink adhesion necessary, but have struggled with controlling the ink-deposit thickness to get the best results. Water-based UV inks can allow for a thinner ink deposit and have been used by graphics screen printers for some time. But these inks have been impractical in the CD industry because of adhesion problems and curing difficulties caused by the higher ambient temperatures in enclosed multicolor printing machines.
Recently, however, water-based UV inks have been released that are designed specifically for the needs of CD printers. These stable formulations offer more control of ink-deposit thickness and allow users to print tonal ranges of 10-90% at 150 lines/in. This is a big improvement over traditional ink systems, where 120 and 133 lines/in. are the norm.
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