Raster film for photopolymer clichés

   
 

Raster film for photopolymer clichés 200,250,300,350 lpi (80, 100, 120, 140 l/cm). A4 size. It is used for rasterization of alcohol-and water-wash clichés for pad printing.

To achieve optimal results after the exposure of the plate, it is necessary to carry out its rasterization. Raster film is a raster range with a round transparent point, made on a photofilm with a matte emulsion layer. It is necessary for the formation on the printing elements of the reference points that prevent lowering the squeegee in the recesses of the printing elements. Otherwise, the squeegee will remove the paint not only from the surface of the blank elements, but also from the depth of the printing elements, which will lead to uneven paint layer on the print. At the same time, tiny whitespace elements in the form of points are created over the entire surface of the printing elements.

The plates are rasterized in a completely similar way, as well as the exposure, instead of the original layout using raster film. The scanning should be carried out directly after exposure. It is recommended to use raster film ( 120 l/cm) to print thin lines, logos or line drawings.

Why is it necessary to rasterize the cliché and what is the raster film used in pad printing?

Polymer clichés have a fairly soft surface. The squeegee knife moves along the cliché under a certain pressure and therefore plunges deeper into those parts of the image (dies) that are parallel to the edge of the knife, so that the printing area appears with different density of paint. This effect is called "scooping". In most cases, it is impossible to get rid of it completely either by multiple images or by rotating the image. To eliminate this effect, re-exposure of the cliché through the raster film (grid) is used (to obtain the so-called "reference raster"). At the same time, the" die " ceases to be an open deep area on the cliché and becomes a set of small projections.

These projections serve the following purposes:

  • support the doctor blade and eliminate " scooping";
  • reduce surface stresses in the paint, so that the paint layer becomes more smooth;
  • hold the paint on the "dies", not allowing it to smear on the cliche during the movement of the doctor knife;
  • make more even colorful layer on the swab during the intake of paint with clichés.
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