Prepress technology of the hottest paper printing

Prepress process of paper printing

first, the main performance indicators of paper and the characteristics of newspaper printing

paper is the carrier of newspapers. The paper used in newspapers is mainly paper, which is also the main object of this paper. For a long time, we treat paper as medium and low-grade printing paper, but with the development of newspaper printing in recent years, we also put forward higher requirements for the quality of paper. Newspapers produced with high-quality paper are solid and neat, with plain and beautiful words and accurate color reproduction; With poor quality paper, the ink layer density is low, the dot damage is serious, and the dot enlargement rate is high, and the color level reproduction effect is poor. The quality difference of printing products caused by the quality of paper is quite obvious. Large quantities of imported paper with good quality are sent to the newspaper market, and the consumption is huge, which is enough to explain that the quality requirements of newspaper publishing on paper are constantly improving. Especially for the production of color newspapers, there are many overprinting times, rich layers and colors, and high requirements for dot reproduction quality. It is difficult to produce high-quality color newspapers with poor paper

the main performance indicators of paper include printing smoothness, whiteness, dimensional stability, ink absorption, surface strength, fracture length, etc. This paper only discusses the printing manufacturability indicators of paper related to printing, which directly affects the quality of printing products. In production, we often say which kind of paper is easy to use or not, which is actually the overall evaluation of the printability of the paper. The influence of various properties of paper on printing quality in production is also different. It also has a lot to do with the production environment of each factory. Different equipment, processes, product varieties, etc. will also have certain differences in the performance requirements of paper, such as the performance requirements of paper for printing double-sided photocopy and printing single-sided BS EN 1288 ⑶ ⑵ 000 glass for buildings There will be a great difference in the measurement of glass; There will also be certain differences in dimensional stability requirements between color newspapers and black-and-white newspapers, as well as between incremental machines and non tower batches

the characteristics of paper newspaper printing production mainly include the following aspects:

1. The high-speed newspaper printing machine is used for production. The machine speed is fast, and the running speed of paper tape in printing can reach 9-13m/s

2. The ink path of rotary printing machine adopts short ink path, and the ink rollers are generally about 7-11. 3. Generally, BB type imprinting is used to complete double-sided printing at one time

4. Newspaper printing is the continuous printing of paper tape, which adopts high-speed automatic paper receiving

5. The printing and page analysis are completed at one time, with a maximum of 80 pages and 10 folios at one time

6. Four color embossing in color newspaper printing is continuous wet press wet printing

7. Paper should have good breaking strength to ensure printing tension

8. The paper is mainly composed of filaments, and the surface smoothness is poor

9. There is no coating on the paper surface, with strong ink absorption ability, high dot expansion value and strong water absorption

10. The whiteness of the paper is low, and the color difference between different brand batches is large

11. The surface strength of the paper is low, and there is a certain degree of hair loss in printing

second, the influence of paper smoothness on printing quality

the so-called smoothness of paper refers to the surface roughness of paper. Paper smoothness is a very important paper performance index. There is a certain difference between paper smoothness and printing smoothness. As a discussion of its impact on printing quality, here only refers to the printing smoothness of paper. The smoothness of the paper is lower among all kinds of printing paper. Its 252 steel concrete composite structure is mainly composed of long fibers, filled with short fibers and properly calendered, and its surface smoothness is low. At present, offset printing technology has been widely used in newspaper production. Offset printing is produced by the principle that oil and water are immiscible. Its printing pressure is smaller than that of lead printing. In order to obtain good image and text quality, we must ensure that the paper has good surface smoothness. Newspapers produced with paper with a smooth surface can obtain higher dot quality and reproduce the pictures and texts clearly and fully on the paper because of better contact during embossing to transfer the ink. With the development of newspaper industry and the expansion of color newspaper production scale in recent years, the requirements for the surface smoothness of paper are also constantly improving

dots are the basic elements of printing tone reproduction. At 50% dots at 100lpi, the diameter is only about 0.2mm. If the surface smoothness of the paper is poor, the dots are prone to incomplete deformation and the loss of dots, which will affect the hierarchical reproduction of the picture and the quality of graphics and text, especially the reproduction of fine levels. In order to make the picture level coordinate and complete reproduction, we must ensure that the point on the paper must get a clear and accurate shape. We have such experience that the better the surface thirst of the paper, the higher the point reproduction quality, and the clearer the idea. From the microscopic point of view, the rough paper surface will not be able to fully transfer the dot ink here due to insufficient pressure in the concave, resulting in a certain degree of dot deformation or even incomplete, and the quality of the newspaper will be significantly affected; If the smoothness of the paper is high, the dots are not easy to be lost in the printing process, which can effectively ensure the rich levels of pictures and words and good color reproduction

in addition, the higher the number of lines in the same line, the richer the picture level, and the higher the number of lines hanging, the smaller the point diameter at the same coordination, which also requires that the paper with better surface smoothness is not printed. Therefore, there is also a large correlation between the number of hanging mesh and the smoothness of printed paper. However, the number of controlled items in newspapers is not fixed. Newspaper printing requires paper to have a good surface smoothness to try to improve the number of hanging same mesh and ensure the reproduction quality of pictures and words is more fine. The same amount of money for newspaper printing is generally about 80100lpi. Under the condition of ensuring the smoothness of the paper surface, appropriately improving the number of pictures is also one of the means to improve the printing quality of newspapers. In other words, the paper with good surface smoothness should be used for newspaper production as much as possible, and the number of hanging lines can be appropriately increased to improve the printing quality of newspapers

compared with black-and-white newspapers, point quality has a greater impact on printing quality. The color newspaper emphasizes the word "color". It is important to ensure the quality of important color elements such as pictures on the page and the tensile properties of asphalt waterproof coiled materials gb/t328.8 ⑵ 007 title, bottom and label, and it is important to improve the reproduction quality of points. The dots of black-and-white newspapers are mainly used for the hierarchical reproduction of pictures, and the dots of color newspapers are very important for the reproduction of color, hierarchy and coordination. In order to ensure the reproduction quality of pictures, the number of color newspapers is generally higher than that of black-and-white newspapers, so the paper clarity requirements of color newspapers are also higher

the surface thirst difference between the front and back of paper is also an important performance index. Reducing the surface thirst difference between the front and back is quite important to reduce the gap between the front and back of newspaper printing quality. The international 1910-89 standard has also greatly improved the poor surface smoothness of the front and back sides of the paper according to the old standard, and the requirement of class a paper is less than 15%. In recent years, the surface smoothness of major brands of paper has been greatly improved, and the difference between the surface smoothness of the front and back sides of some papers has been far smaller than this value, which provides a good condition for the publication of double-sided color newspapers