I just bought a CD at a thrift store, and I was struck by the beautiful artwork printed on the face of the disk. So I wondered how it had been printed. Then I pulled out a number of my CDs and noticed that some were printed differently from others. Unsure of what the options were, I went online and did some research. This is what I found.
Screen Printed CDs
CDs decorated with custom screen printing have a thick surface of ink. The ink has texture and gives an opulent sense to the product. Unfortunately, the surface of a CD has a number of different sections. Printing even the thick silkscreen inks directly over these three distinct portions (the regular surface, mirror band, and stacking ring of the CD) would produce an image with visible shifts from section to section. Therefore, laying down an initial background of white ink is preferable. The white is opaque, so it evens out the differences in the various “rings” of the CD.
In addition, the white ink also lightens colors printed over this background (since some custom screen printing inks are translucent). This avoids any dulling effect that might otherwise occur, since the unprinted, mirrored surface of the CD has a bit of a grayish tone (i.e., it is not pure white).
Halftones can be printed on CDs along with type and solid areas of ink. Many custom screen printing shops use lower frequency screens due to the thickness of the screen printing inks (such as a 100 lpi halftone screen). Because of this, fine detail in halftones can be lost. Therefore, it is wise to consider this limitation when choosing images for a CD label.
Some print shops, however, can print up to 200 lpi screens, which are more suited to the detail of full-color CMYK images.
Another thing to consider is the range of tones that can be captured on a screen printed CD. Unlike offset printing on paper, which may be able to hold detail from a 2 percent dot in the highlights to 90 percent dot in the shadows, a screen printed image may only have a tonal range of 15 percent to 85 percent. (Below 15 percent, the image would not print; above 85 percent, it would be solid ink.)
Finally, it’s wise to avoid gradations (also known as blends, which transition gradually from a lower to higher ink percentage). Since gradations are produced with halftone dots, since dot gain is a problem in custom screen printing, and since the photographic transfer of a gradation from film to the printing screen is not precise, there can be visible tonal jumps that show up as banding in screen printed gradations.
Even with all these caveats, screen printing is still ideal for longer runs of CD labels. The set up charge is higher than with digital printing (inkjet), but a long run will yield a much lower per-unit cost than will digital printing. In addition, the ink is thick and lush. I personally prefer the look. However, it does require forethought and the avoidance of certain problematic design elements.
Inkjet Printed Labels Affixed to CDs
I have seen labels that can be printed on inkjet printers, then peeled off a backing sheet (like a Crack’N Peel label) and affixed to the CD surface. This looks like an easy solution, but the labels do peel off the CDs occasionally and may damage the CD player (or computer optical drive). The main benefit I can see in adhesive labels for CDs, though, is the white background. As with screen printed CDs that have a white layer laid down beneath the colored ink, the white background of the paper CD labels does provide a bright, even ground for the inkjet inks.
Unlike screen printed CD labels, which require so much set-up work as to only be practical for very long runs, an adhesive label printed via inkjet technology can have a press run of a single CD label, and you can do the printing at home on your own inkjet printer.
Inkjet Printed CDs (Direct to CD)
Fortunately, inkjet printing has evolved over the years, and a number of inkjet printers now can print directly on the surface of a CD. The benefit of this process is that the label cannot peel up and damage the CD player or computer optical drive. The overall effect is also more aesthetically pleasing than a separate inkjet label (i.e., it avoids having a second layer).
If you look online, you will see images of inkjet printers with CD trays that can hold one, or even six or eight (or more) CDs in position for inkjet printing. These trays can be fed through small tabletop inkjet printers or larger commercial inkjet presses. In this way the CDs can be held in place and protected during the custom printing process.
Based on my research, it looks like the pretreated CDs for direct imaging have a layer of white (like gesso on a primed canvas board or stretched canvas). As noted in the description of the custom screen printing process, this white ground will both brighten the resulting inkjet image and also make it appear more consistent across the surface of the CD.
Unfortunately, due to the thinner consistency of inkjet inks, the printed image will not have the same thick, tactile feel as a screen printed product. However, it will allow you to print only a few (or a short run of) CDs with labels, since digital inkjet printing requires only minimal set-up time compared to custom screen printing.
This entry was posted
on Saturday, December 20th, 2014 at 2:53 pm and is filed under Label Printing.
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