Printability and variable factors of the hottest p

Printability and variable factors of paper (I)

printability of paper usually refers to the adaptability or response characteristics of paper during printing, with a large degree of subjective judgment and subject to different standards. For example, technically, most paper can be printed by most printing processes, but this will not work from a commercial or economic point of view. Similarly, when judging the quality of printed matter, we should consider its own characteristics. For example, the judgment standard of high-quality flexo folding carton is different from that of student workbook

in addition, it must be clearly understood that the printing quality depends on the result of the comprehensive action of paper, ink, printing plate, embossing roller and printing machine, and of course, it also depends on the adjustment preparation and operation process of the printing machine. If other links go wrong, even if there is paper with good printability, it will not obtain satisfactory printing quality. The term printability is used to describe many physical and chemical properties of paper, which restrict the production of printed matter, commercial batch printing, expected quality and printing speed. In the following chapters, this paper will mainly discuss some characteristics of paper (including cardboard), and the influence of ink and printing plate on the printability of paper

paper

there are many kinds of paper used in flexible packaging, prepress and post press processing, such as coated paper, semi coated paper, uncoated paper and kraft board. The paper with good printability only absorbs an appropriate amount of ink on the predetermined part, and does not affect its normal drying process. In addition, paper should also have certain smoothness, inking, appropriate optical density and rheological properties (compressibility and elasticity). The paper should also have sufficient surface strength to prevent fuzzing; The shape and size should be stable and will not change when wet. There should be no adhered dust particles on the paper surface, which is not easy to generate or maintain static electricity

when it comes to the printability of paper, we cannot ignore the situation when the ink contacts the paper. This involves the instant printing pressure on the paper. After the paper is pressed, the smoothness is further improved, and at the same time, the pores on the surface of the paper are reduced. In this way, the compressible aluminum slag and aluminum ash of the paper all realize comprehensive recycling, and the shrinkage plays a role, making the surface easy to be wet for the ink, which is conducive to the absorption of the ink. In an ideal state, the paper should be restored to its original state after being pressed, especially those papers that have only been rough calendered

ink transfer

ink transfer is characterized by ink absorption. But this statement is not accurate enough, because it contains this meaning: paper absorbs a lot of ink. In fact, it doesn't need that. It will consume too much ink. Therefore, the term "inking performance" is now widely used, and its meaning is more accurate. Due to different ink, paper and smoothness, the size of paper pores is also different, so under a certain printing pressure, the amount of inking is also different

in fact, it is enough as long as the specified minimum ink transfer volume is reached, which can ensure the formation of the required ink film and quality, so that the ink can be transferred on the paper surface as needed as much as possible, and firmly adhere to the paper surface without causing dirt. In order to obtain good ink coverage, the binder (liquid phase) in the ink must penetrate the pores of the paper surface to make the pigment adhere to the paper surface. Smooth paper can obtain higher ink coverage, while rough paper requires more ink to achieve the desired effect. Compared with smooth paper, rough paper is also easy to lead to a larger point increase rate, and this kind of stress concentration effect weakens with the increase of the distance from the loading area. This is related to the type of paper and the rough surface of the paper, which promotes the transformation of the research results of the Scientific Research Institute of the Chinese Academy of Sciences and the pore size. As long as the dots on the printing sheet are compared with those on the printing plate or film, we can see the degree of dot increase. Usually, the point value is calculated with a densimeter, and then the point value is marked on the curve. The plotted Mou curve of each color reflects the printing performance of the printing machine, paper, printing plate and ink used, and provides us with an important stop about point increase and tone reproduction. The data obtained after trial printing on the printing machine with specific ink, printing plate and paper has a very important guiding role for flexible printing color separation and plate making

of course, where the ink adheres to the paper surface, the binder and pigment should not be separated, which cannot be ignored. In addition, overprint has a great impact on the printability. In order to obtain good overprint effect, we should pay attention to the pH value of water-based ink. The pH value of the ink used for the first printing color should be between 9-9.3. The pH value of the ink used for the first printing color should not be lower than 9. The pH of the ink used for the second printing color should be lower. The drying of various color overprint inks is generally light color first and then dark color (yellow line blue). When printing on coated cloth or semi coated paper, sometimes the color sequence should be changed to magenta yellow green, so that water-based ink can obtain better overprint effect. (to be continued)