Matte paper printing off ink problem solving

In the printing process of matt paper, there is often such a problem that the drying performance is poor, the drying speed is slow, and it is easy to “discard ink” during the post-press processing, especially when printing black ink in the field, to give product quality, The production cycle has had an impact. Problems Digital presses, that is, poor drying performance, slow drying speed, and easy to “discard ink” during post-press processing, especially when printing black ink in the field, have an impact on product quality and production cycle.

For this Agfa, we look for the reasons from the following aspects.

First, the pH of the paper is tested. Because the pH value of the paper is one of the main factors affecting the drying of the print, acidic paper is less dry. After monitoring several common brands of matt paper, the pH value is between 7-8, which is a neutral-alkaline color management and all in the normal range. At the same time, the moisture content of matt paper was also monitored and monitored. The value ranged from 8% to 9%, which was within the normal range.

Secondly, the pH of the fountain solution was tested on X-Rite. The pH of the fountain solution was basically stable between 4.8 and 5.2. At the same time, the amount of water is strictly controlled. In the production process, the amount of water is continuously reduced, basically meeting the requirement of water-ink balance, and minimizing the degree of ink emulsification.

Third, analyze the ink thickness. Although black ink is actually processed on the Dalian line, it is not overprinted, and the high-level part of the black ink gently rubs off the ink, indicating that the thickness of the ink layer is not greatly affected.

Fourth, control the ambient temperature and humidity. The temperature was controlled at 25°C and the relative humidity was controlled at 65%. At the same time, the delivery of paper will also minimize the delivery height, which is basically 200 to 300 sheets.

Fifth, choose special inks that are specially suitable for printing on matt paper, and also try to add driers to the ink. publishing

In view of the above factors that may have an impact on the drying of blots, one by one, corresponding measures were taken to investigate the quality of the seals, but the results were not satisfactory and the problems were not solved.

The author analyzed that the main reasons for the poor drying of the matte paper imprints are the particularity of the matt paper itself and the particularity of the black ink pigment.

Due to the low sizing degree of CTP in China, matt paper causes loose structure and rough surface, so its absorption is strong, and the binder in the ink can be quickly absorbed. The yellow, magenta, and cyan pigments are generally made of inorganic or organic pigments, while the black ink uses carbon black (elemental carbon) as the pigment, and the carbon black is a non-drying design. In general, black ink is better than other colors. The ink dries slowly. In addition, the adhesion of carbon black and the binder is lower than other inorganic or organic pigments. This causes the matte paper to absorb the binder in the ink too quickly and float the carbon black on the surface of the paper.

The use of matt paper is becoming more and more widespread. Some printing companies use post-printing oils to alleviate this problem. This will not only increase the cost, and extend the production cycle of the printing of fine research, and the biggest danger is to change the original characteristics of the matt paper, and the color is also affected.

In order to meet the customer's requirement for black ink on the matte paper and solve the problem of “discarding ink” at the same time, the author made some attempts. First, the yellow, magenta, and cyan inks were used as the black and white ink to obtain black The second is the use of color to prevent false printing, the yellow, magenta, cyan ink mixed black ink to avoid the black ink in the "carbon black." Because pigments in yellow, magenta, and cyan are basically inorganic pigments, their drying properties and adhesion are significantly better than those of carbon black.