Printed matter is a general term for all kinds of finished products produced by printing technology. In daily life, people come into contact with newspapers, books and magazines, trademarks, labels, business cards, packaging boxes, gift boxes, etc.
The quality of printed matter, especially book printing depends on many factors. Which the characteristics of paper are undoubtedly an important factor? The paper with excellent performance can complete the ink transfer completely. So that the image and text can be clearly and fully reproduced on the paper. Thus obtaining a satisfactory reproduction effect. Here are some key points for printing paper.
The influence of paper characteristics on the gloss of printed matter
In the printing process, the ink film is transferred to the paper surface and filled with the unevenness of the paper surface. So that the printed surface is quite smooth. The specular reflection of light from the ink film surface of printed matter determines the gloss of printed matter. And the ink film surface is closely related to the characteristics of paper.
Ink film thickness
The ink film thickness is the main factor affecting the gloss of printed matter. After the paper absorbs the ink binder to the largest extent, the remaining binder remains in the ink film. Which can effectively improve the luster of the printed matter. The thicker the ink film is, the more binders remain. Which is more conducive to improving the luster of the printed matter.
The gloss increases with the ink film thickness, which is different for different papers. When the ink film of high gloss coated paper is thin. The gloss of its printed matter decreases with the increase of the ink film thickness. This is because the ink film covers up the original high gloss of the paper itself. While the gloss formed by the ink film itself decreases due to the absorption of the paper. With the increase in ink film thickness. The higher gloss of the paper itself is more difficult to be reflected through the ink film. When the ink film thickness reaches 1.5 μ M, the absorption of paper to the binder is basically saturated. After that, as the ink film thickness continues to increase, the more binders are retained, the gloss will continue to improve. The gloss of coated paperboard prints increases rapidly with the increase in ink film thickness when the ink film is thin. And the ink film thickness increases to 3.8 μ After m, the gloss no longer increases with the increase of ink film thickness. But, no matter what kind of paper, the amount of gloss increases with the increase in ink film thickness should have a certain limit.
The influence of paper characteristics on the gloss of printed matter
The paper forms a capillary network structure due to fiber interweaving. Which has many pores and becomes the basis for absorbing ink. The balance between the absorption time and fixation time of the ink binder in the paper capillary network. Determines the degree of binder penetration when the luster of printed matter is formed. Generally, the gloss of printed matter decreases with the increase in paper absorption capacity.
Paper smoothness and its own gloss affect the gloss of printed matter. The high smoothness is conducive to the formation of a uniform and smooth ink film, thereby improving the luster of the printed matter. The good gloss of the paper itself can improve the reflectivity of the ink film, especially for transparent ink. The correlation between the gloss of printed matter and the gloss of paper itself is stronger than that between the gloss of printed matter and the absorption capacity of paper.
The influence of paper characteristics on the step reproduction of printed images
The ideal step reproduction is the most important process to get high-quality printing images. Most of the bad prints are caused by the step reproduction problems.
The primary need for image reproduction is that the copied image visually matches the original. But, in most cases, the density range of the original document is larger than that of the printed image. And as the paper quality decreases, the density range that can be copied is smaller, as is the case for saturation and color.
The solution is to compress the gradient range of the original to match the density range that can be reproduced on paper, etc.
The influence of paper characteristics on dot gain
Increase of outlets
The effect of dot gain on the color change of copy is greater than any other variable. The amount of ink printed on the paper will affect the dot gain, and the dot gain will affect the printing contrast. When printing black-and-white or color halftone images. Dot gain will change the contrast of the image and cause loss of image detail and definition. In multi-color printing, the increase of dot will lead to the loss of contrast, dark image. Dot paste and cause sharp color changes.
Impact of paper characteristics on dot gain
The smooth surface of the ink produces the best solid density on high-quality paper. When the paper quality decreases, the solid ink density decreases, resulting in a certain dot gain. Which affects the quality of the printed matter.
The higher the number of screen lines, the smaller the dot diameter. And the small pits on the paper can also distort or omit small printing plate dots. Thus, the higher the number of fine printing lines, the higher the smoothness of the paper is required. This is a principle of paper selection. But in actual work, it is also possible to adjust some properties of the ink. Or change the process parameters to adapt to this characteristic of the paper.
The influence of paper characteristics on overprint accuracy
For fine print, the registration requirements are high, and the allowable error is generally within 0.05mm. In multi-color printing, there are many reasons for inaccurate overprint. But the paper deformation caused by the change of water content in the printing process is an important factor.
As we all know, the change of paper moisture content not only leads to the expansion or contraction of the paper. But also changes the local size of the paper due to the change in moisture content. Resulting in other forms of deformation, such as crimping, folding, etc.
To keep the moisture content of the paper uniform on the entire paper surface. And adapt to the temperature and humidity of the printing workshop. At the same time, to reduce the sensitivity of the paper to environmental humidity and improve the stability of the paper size. Moisture conditioning treatment is generally required before printing.
How to ensure printing quality
1. Balanced production and orderly scheduling
2. Strong product quality control
3. Raw and auxiliary materials, timely supply
4. Strict discipline and strict assessment
5. The equipment is in good condition and operates normally
6. Safety first, eliminate hidden dangers
7. Stacked neatly, civilized production
8. Original records, neat, accurate, fast and clear
9. High morale and coordination