Dot Reproduction of CTP Plates on Paper Author: Yung-Cheng Hsieh(Associate Professor in the Deparpment of Graphic Communication Arts,National Taiwan University of Arts)、Yu-Ju Wu (Associate Professor in the Departpment of Graphic Communication Art,National Taiwan University of Arts)

Vol.&No.：Vol. 49, No.1
Date：April 2004
Pages：1-28
DOI：10.6210/JNTNULL.2004.49(1).01

Abstract：

Computer-to-plate (CTP) is a completely electronic system that produces print- ing plates for direct mounting on the printing press without the use of film. With CTP technology, text and graphics are digitally transferred directly from the computer to the printing plate, making the image on the plate a potentially more accurate repro- duction than one done from film. Computer-to-plate reduces the plate-making process to minutes instead of hours. Compared with the conventional printing method, the CTP technology can save manpower and production time for printers, as well as reduce pollution. The adaptation of, and investment in, CTP techno- logies has been a major issue in Taiwan's printing industry since 1998. The main considerations regarding CTP investment include CTP's production time, cost and dot-reproduction stability and quality. Therefore, the stability of the CTP plates and their quality of tone reproduction are the two major concerns of potential CTP investors.
This experimental study investigated the differences between three major CTP plates and one conventional Pre-sensitized (PS) plate in Taiwan, with regard to dot- reproduction quality, stability, and relative capability on paper. The CTP plate materials used in this experiment included Silver Halide, Photopolymer, Thermal and PS plates. A digital test form and color con- trol bars were designed for the three CTP plates, and a film generalized from the test form and color bars was also developed for exposing the PS plates. Twenty sets of plates were used for each of the four plate types, and their dot images were measured by GretagMacbeth D118C. The plate readings were then entered onto statistics soft- ware for analysis and the best 5 sets of plates were selected for the final press runs. One hundred sheets were printed for each set of plates and 50 of them were randomly selected for the final analysis. Therefore, a total of 1000 printed sheets were sampled and read by a Gretag SpectroEye. The dot reproduction attributes of dot gain size, print contrast, and solid ink density were determined statistically.
The results of this study can not only evaluate, for the printing industry, the adaptation of CTP technologies, but also provide a comparison of CTP and conven- tional PS plates with regard to the stability and quality of dot reproduction on paper.

Keywords：Computer to Plate (CTP), Printing Technology, Dot Reproduction Attribute, Solid Ink Density, Print Contrast, Dot Gain

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