Understanding of the impact of paper on printing
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Paper is a general term for paper and paperboard. It is composed of plant fibers, fillers, colorants, and rubber compounds. In the process of packaging and printing, to ensure the quality of printed products, there should be five major factors: people, machines, materials, methods, and rings. Then, paper is one of the five factors — What is the impact of the paper quality problem on the printing of the main ingredient in the material?
First, the smoothness of the paper is not good for printing
Smoothness refers to the flatness of the surface of the paper, which depends on the topography of the paper surface and reflects the surface structural characteristics of the paper. In order to obtain good quality of printed products, the smoothness of the paper is a necessary condition. During the printing process, the degree of contact between the surface of the paper and the surface of the inked blanket affects whether the transfer of the ink is comprehensive and the image is clear. First, because the smoothness of the paper is poor, the amount of ink required for the paper is affected, and the thickness of the ink film on the blanket is different, which will increase the unevenness of the ink color of the printed product, resulting in an enlargement of the graphic image dot and an increase in the mechanical dot gain. Big. Second, due to the poor smoothness of the paper, it affects the uniformity of the ink in the paper, causing the printed product to be embossed and imaginary, and there is a serious phenomenon of dot loss.
Second, the impact of paper compression deformation characteristics on printing
For printing paper, not only should it have better compression deformation, but also be suitable for multiple-color printing, and it has the characteristics of quick recovery at the moment of pressure removal. This is because during the printing process, the paper is deformed under the printing pressure, which can produce a cushioning effect, and the paper and the blanket cylinder can be in good contact, so that the ink can be uniformly transferred. If the printing paper used has only a high compression ratio and does not have a high elastic recovery rate, in multi-color printing, after multiple compression deformations, it cannot be quickly recovered, and the paper becomes large or shrinks, which seriously affects the printing product. Overprint quality.
Third, the paper surface strength is poor, the impact on printing
Surface strength refers to the bond strength between the surface fibers of the paper, the size of the compound, between the fillers, or between the coating particles on the surface of the paper and between the coating and the paper base. In the printing process, if the surface of the printed paper is inferior, the surface of the paper is separated from the inked blanket, the separation force of the ink is greater than the bonding force between the particles on the surface of the paper, and the edge of the printed matter will see white edges or The phenomenon of printing is false, faint, etc. This is the phenomenon of pulling in printing. There are two main effects on printing:
1. Cause pollution in the graphic part. Mainly reflected in: 1 paper particles peeled off, because of the white spots caused by the ink. 2 is due to contamination caused by paper dust or fine coating.
2. The increase in the number of times the blanket and the ink roller are cleaned in the offset printing. Due to the poor surface degree of the paper, it is easy to drop the material and drop the powder, and the cleaning time of the blanket is obviously increased, thereby greatly affecting the printing production.
Fourth, the acidity and alkalinity of paper on the printing
In the printing process, the normal range of the pH of the dampening solution is 4.8~5.2. Due to the different acidity and alkalinity of the paper used for printing, different phenomena may occur, which have different effects on printing. The acidity of the paper causes corrosion and sticking of the plate, which directly affects the drying of the oxidized conjunctiva of the print. It is known from the usual printing of different papers that the higher the acidity, the faster the drying speed of the ink, because the acid paper absorbs the desiccant in the ink, thereby suppressing the effect of the oxidative conjunctiva. On the contrary, the paper is alkaline, and the alkaline substance in the paper is transferred to the water tank, neutralizing with the dampening solution in the water tank, directly affecting the control of the pH value, thereby emulsification of the ink, resulting in partial staining of the printed product, affecting product quality.
Since paper has a great influence on printing, when using the printed paper out of the warehouse, it is necessary to strictly check the smoothness, compression deformation characteristics, surface strength, acidity and alkalinity of the paper to avoid the influence of printing paper. Quality of products.