Screen printing is used for on-disc printing. It is also commonly used for t-shirts, and occasionally for posters. It is less precise than offset printing, but it has many advantages, and a distinct personality. The layer of ink that is applied is several times thicker than the layer of ink applied by an offset press - some 10-30 times thicker.
Step 1 - Preparing the screen
A fine fabric mesh is coated with a photosensitive emulsion. The mesh is stretched over a frame.
Step 2 - Creating the stencil
The positive films are laid directly on top of the mesh. Ultraviolet light is shown onto the assembly. Where there is an image on the positive film, no light gets through to the emulsion on the screening assembly beneath, leaving it unexposed. Where the film is clear, the light passes through and hits the emulsion, causing it to harden. When the development process is complete, the unexposed, soft areas of emulsion are washed away, leaving only the porous fabric mesh.
Step 3 - Printing
The stencil is placed directly on top of the item that will receive the ink. Ink is poured on top of the stencil, and a squeegee is scraped over the top, forcing ink through the image area of the stencil, and onto the printable surface.
Step 4 - Drying
In order to speed the process, it is typical that the ink will be cured with ultraviolet light right away, so that subsequent colors can be applied without difficulty, and so that printed items can be stacked on top of each other immediately.
Step 5 - Repeat steps 1-4 for each color
If there is more than one color to be printed, as is often the case with CDs, a seperate screen is produced for each ink. For CDs, as many as 5 colors can be printed at once. |
