China's newsprint is divided into four grades of A, B, C, and D according to quality standards. Among them, A and B grades are suitable for high-speed rotary offset presses, while color newspaper printing is generally carried out on high-speed rotary presses.
Ink absorption
1. The influence of the absorbency of newsprint on the printing quality of color newspapers
Color newspapers are generally printed on high-speed rotary offset presses. Due to the fast printing speed, newsprint is required to have strong ink absorption, that is, the ink dries faster on newsprint.
There is no coating layer on the surface of newsprint, which is relatively loose and has strong ink absorption. Ink drying is mainly done by the penetration of the solvent. After the ink is transferred to the paper surface, the solvent in it quickly penetrates into the paper, so that the ink is fastened and dried on the paper surface. However, if the newsprint is too loose and the ink absorption is too strong, and the ink used has a low viscosity and a large printing pressure, the ink will penetrate the back of the paper and the through-printing phenomenon will occur, and the thickness of the conjunctiva of the ink layer will be affected, so that the imprint cannot be The paper presents the proper color saturation, which affects the quality of the printed matter.
2. Properly reduce ink viscosity and improve fluidity
In high-speed operation, this drying method based on penetration requires that the viscosity of the ink must be appropriately reduced and the fluidity must be improved. When printing a newspaper, the viscosity of the ink is too large or too small, which is not good for printing. If the viscosity is too large, it will cause hair loss and powder loss, and it is also easy to cause uneven ink transfer; if the viscosity is too small, it will easily cause ink emulsification, unbearable imprinting, and low printing gloss. Unlike adhesion, as the printing speed increases, the viscosity of the ink increases during printing.
3. The increase of dots affects the printing quality of color newspapers
From the main characteristics of newsprint, compared with general coated paper, newsprint has poor image clarity, small color reproduction range, low color purity, bright tone dots are easy to lose, dark tone dots are easy to merge, and tone level The range is small and the flat screen is difficult to print evenly. The reason is that the sizing degree of newsprint is too low (generally not sizing), the fluidity of the ink is too large and the printing pressure is too large.
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