Familiar applications for screen printing (also referred to as silkscreen) include t-shirts and other textiles. It is also the technique used for printing on compact discs. It involves a thick layer of ink poured onto a stencil with the excess scraped off, forcing the remaining ink through the holes in the stencil to create the image on the surface of the disc.
A silk screen is prepared by exposing a film to a screen covered in a layer of light-sensitive emulsion. After processing the resulting image is a clear area on the screen which allows the ink through during printing. Most discs are silk screen printed because very high-quality results are obtained. Silk screen printing can bring the vibrant colors of your disc to life but detailed shading is best for photo offset imprinting. Due to the fact that silk screens are slightly coarser than litho plates, screen imprinting is generally not suitable where the reproduction of a picture or photo or a design with tinting and shading is required.
In the silk screening printing process, printing plates are prepared (usually from films); there are as many plates as there are colors to be printed – usually 4,5 or 6. Each plate picks up ink from a roller, and lays down its color image on the printed object.
The idiosyncracies of screen printing and the surface of the CD that can affect your designs include:
- The standard line screen for images on disc is a low 85 dpi, the same as for newspaper printing, up to about 100 dpi resulting in a possible loss of image detail.
- The thick applications of ink required for screen printing can make fine lines and detail disappear (including very small type and serifs).
- Spot color rather than CMYK printing is the norm. Although CMYK printing is possible, it can cost more and produce less than ideal results.
- Because the disc surface is metallic silver, not white, you may need to add an additional color to your design (for spot or CMYK colors) if you want to design for a white background.
- Rarely can you precisely match the spot color inks on the face of the CD or DVD to the CMYK colors you may use on printed inserts.
- The same color of ink appears differently on the clear inner hub, the mirror hub, and the main silver surface of the disc.
- Designs with gradual fades from one color to another may reproduce poorly due to dot gain and tonal jump that make colors darker and produce pronounced dots in the image.