Effect of waterless offset ink on dot gain
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Waterless offset printing refers to an offset printing method that does not require a conventional aqueous solution dampening, using an ink-repellent silicone rubber layer as a non-image portion of a printing plate, and using a special ink to complete printing.
Waterless offset printing has higher quality due to the elimination of dampening solution. Such a promising printing method, the related material requirements are relatively high, and ink as an important material basis for printing plays a very important role in this printing process.
At present, the internationally common waterless offset ink is K+E in Germany, and the key parameter for evaluating the quality of ink is to analyze the common parameters of conventional prints in a dynamic printing process. Because the increased dot size of the print directly affects the quality of the print. In this paper, the German K E waterless offset ink is taken as an example to analyze the influence of ink on the dot gain during the waterless offset printing process, so that the printing suitability parameters of the ink can be obtained.
Test introduction
experiment material
The test strip printed by Heidelberg QKDI-46 waterless printing machine, the test strip printed by Heidelberg GTO four-color water offset printing machine.
Test Instruments
X-Rite 508 Density Meter.
Test conditions
A test strip obtained by printing a coated paper having a basis weight of 157 g/m2 and a screen line of 175 lines/inch under standard printing conditions (i.e., a temperature of 20 ° C and a relative humidity of 56%) was used. Under the standard test conditions (ie, temperature 20 ° C, relative humidity 65%), 6 samples were randomly selected from 500 samples to be tested, and finally the average value was taken.
The data for analyzing the increase of the four-color dot is the overall dot gain of the coated paper having a basis weight of 157 g/m2.
Data analysis
It can be analyzed that the highest dot area percentage of 157g/m2 coated paper for Y, M, C, BK four-color inks is 85%, 95%, 96%\75%, respectively. The copy of the smallest dot is 2%, 1%, 1%, and 1%, respectively.
In the 40% to 50% area, the dot gain is the largest. It can be seen from the figure that the waterless offset printing dot is increased by about 7% to 8%. Water offset printing is generally 20% to 25%.
It can be analyzed that the highest dot area percentage of 200g/m2 coated paper which can be replicated for Y, M, C and BK four-color inks is 85%, 95%, 96%. The area of the smallest dot that can be copied is Y2%, M1%, C1%/BK1%. As shown in Fig. 2, the dot gain is relatively small, and the largest dot gain is concentrated in the region of about 50%, which is about 7% to 8%.
Test Conclusions
It can be seen from the above that the increase of the waterless offset dot is not serious, and the influence of the fountain solution on the dot gain is eliminated. The dot gain in the highlight region is small, and the midpoint region (ie, in the 45% to 55% region) is the largest dot gain, and the largest dot gain region is between 7% and 8%.