Press performance of frequency modulated screen printing on newsprint

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Title: Press performance of frequency modulated screen printing on newsprint
Author: Ma, Li-Yi
Abstract: Frequency Modulated (FM) screening has been praised for its apparent resolution advantage over conventional halftone screening. Studies showed FM screening can be processed with the existing technology, and it does bring about a visible improvement in image quality on newsprint. This study focused on the press performance of the FM halftone printing on newsprint. The fineness of conventional halftone screens can be described by indicating the screen rulings (lines per inch or lpi), and the fineness of FM screens is measured by the size of the micro dots (;pi or 10~6m). It is difficult to equate the microdot size in FM screen to the screen ruling in the conventional halftone. This research uses the concept of the total border length per unit area on a given % film dot area as a common parameter to characterize both FM and conventional screens. By comparing the border length difference between a number of FM screens to the 85-lpi conventional screen, the results show that the higher the border length ratio, the higher the dot gain of the screen in question. In addition, the maximum border length ratio for a given screen is where the maximum dot gain difference occurs. This research also investigated if there is significant color variation between FM and conventional screens when solid ink densities are varied. The Specifications for Non-Heat Advertising Printing (SNAP) recommends an 85- lpi conventional screen for newsprint. UGRA recommends 40(mew)m FM screen for newspaper printing. Therefore, in this study the 85-lpi conventional screen (AGFA Balanced screen) was used as the reference screen. The 42um FM screen (UGRA Velvet screen) was used for the color stability test. The test run was conducted on the Rockwell positive-feed keyless Newsliner newspaper press. Five inking levels were tested in the experiment with two inking levels lowered and two inking levels increased over the normal inking condition. The normal inking condition was set to conform to SNAP specifications. The results show that there is no significant color variation between FM and conventional screens over a wide range of solid ink density variation.
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Date: 1996-10

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