A study of the influence of mesh on light reflection in exposure of photosensitive screen printing stencils

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Wheeler, Suzanne
Screen printing; Stencils; Mesh
thesis / dissertation description
The mesh has been an interference factor in the making of close tolerance high resolution screen printing stencils. Radiation strikes the surface of the threads and is reflected into the light sensitive emulsion causing a deterioration in the sharpness of the stencil edge. This problem has been largely overcome by the introduction of dyed mesh. However, by purposely exploiting the reflective properties of the mesh, a random, or irregular pattern of dots can be produced. This is accomplished by exposing a continuous tone positive to a screen that has been coated with a photosensitive emulsion. Five screens of varying mesh counts were constructed. The test procedure involved experimenting with a number of variables including photosensitive materials, coating thickness and wash-out procedures. Comparisons of the differences in the random dot structure from one screen to another were made and analyzed. Results of this study showed that there is a correlation between thread frequency and the degree of hardening caused by undercut that is produced in the coating around these threads.