The mechanism of image-formation in photopolymer flexographic relief printing plates is reviewed. In addition to the identified factors, it was hypothesized that the level of exposure could influence the plate shoulder angle. It was further hypothesized that an optimization of shoulder angle with respect to halftone dot area may reduce the dot gain of the printing process. An experiment was conducted using a novel method of plate exposure. Continuous-tone masks were placed in contact with the plate back and the halftone negative used on the plate face. The resulting shoulder angles were measured and analyzed for significant fit to a linear mathematical model. For many dot sizes the face exposure level was significant in determining shoulder angle. The plates were printed on a flexographic press, and prints were analyzed to identify any benefits in dot gain reduction. Regression analysis showed very inconsistent correlations between shoulder angle and dot gain for individual dot sizes printed at an optimized level of impression.
Print Media (MS)
Department, Program, or Center
School of Photographic Arts and Sciences (CIAS)
Brier, Bruce, "The effect of the relief plate shoulder angle on flexographic dot gain" (1986). Thesis. Rochester Institute of Technology. Accessed from
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