The reason why the overall ink becomes lighter in the printing process

A print-making colleague asked me a question: During the printing, the surface ink on the finished product became very light, white stains, seemingly related to the lack of ink, but how to mix the amount of ink is not OK, on ​​the printing press The amount of water used, blankets, etc. have also been dealt with or not. In the end, why should I deal with the reasons behind this? How can I deal with it? Because I did not understand the actual situation on the scene, I only made the following analysis.

First, from the analysis of the printing plate, nothing more than the following four aspects

1 Influence of raw materials

The quality of the PS plates used in printing plates is of utmost importance, especially for the PS plates produced by some small factories. They will cut corners in their recipes. For example, the proportion of photosensitive emulsion and water is seriously misaligned, and the raw material concentration of ingredients is often too diluted, which has a certain impact on the printing quality, such as the decrease of the strength of ink-pro-moting (lower performance) and the reduction of the resistance to printing force. The PS version produced by regular manufacturers rarely arises in this area. If a similar situation occurs, the PS version should be replaced immediately, and it cannot be used.

2 Influence of the quality of the bottom plate

In the imposition, you must first check whether the texture density of the used original plate meets the requirements, and whether the surface of the bottom plate is a positive or negative character (usually the typeface is an inverted character). If the density of the bottom texture is too light, the exposure time and the developing speed will be affected. Because the density of the bottom plate texture is too shallow, the ultraviolet rays can be directly transmitted to the photosensitive layer on the surface of the PS plate through the reticulation to varying degrees, so that the photosensitive layer is damaged to varying degrees. During development, the damaged photosensitive layer will be developed to varying degrees, making the hydrophilic area hydrophilic, which will reduce the amount of ink used, and the ink will be diluted with water to varying degrees (at this time the water will start To dilute the effect, similar to a kind of lighter agent), the printed matter will naturally be printed with white ink as a whole. If the word on the bottom page is a positive word, then the imposition must be literally attached to the surface of the film used for the imposition. When printing the printing plate in this way, the contact distance between the literal surface and the photosensitive layer of the PS plate is intangibly increased. Therefore, when exposed, ultraviolet rays can penetrate through this distance to varying degrees, making the photosensitive layer that should remain on the PS plate damaged. Damaged parts of the development will be developed or incompletely developed. From the surface, this part will appear imaginary or lighter, let alone print.

Sometimes, due to mistakes made by the operator during the imposition, the layout is reversed, or when the printing plate is printed, the assembled version is reversed. In this type of situation, the appearance of the word and the PS version will also appear. There is an extra distance between the layers. In this way, after exposure, the resulting plate is developed, and the whole part of the ink-printed area appears imaginary. If there is a similar situation above, the mistake should be promptly corrected. This is an unsuitable version of the original and should be re-emitted. This should be repelled or reversed, and should be re-fighted or re-placed and placed in position.

3 The impact of actual operation

When the PS plate is exposed and developed, the operator should handle it according to the actual situation, and it should not be stereotyped. Relatively shortening or prolonging the exposure time prevents unnecessary damage to the photosensitive layer that should be inked. After exposure, the operator should pay attention to the development of the PS plate. The developer should be treated differently according to different conditions. The development time should be controlled well. If you go too far, the photosensitive layer of the ink-receiving area will be damaged to varying degrees, and lighter ones will greatly reduce the ink receptivity. Therefore, there will be a shortage of ink on the whole page of the printed matter, which will appear white stains. If this happens, the basic skills of the operators should be improved.

Second, from the printing ink and printing machine

Before printing, the operator should check the ink used for printing. Do not look at the ink is just bought, printing quality can not be guaranteed. Because some ink manufacturers now have different ink processes. Some inks must be stored for a certain period of time. The hue can be used to achieve the best results, and some must add a certain amount of auxiliary materials. If the storage period is insufficient, the amount of ink used will no longer achieve the best results in its hue. Therefore, the ink color of printed matters must not be required, and there is no lack of white ink. If the storage period is too long, beyond the shelf life, such ink can not be used, its ink is erratic, hue is unstable, it is difficult to blend well. Not to mention the print quality?

At the time of printing, the machine started and should not be printed immediately. Otherwise, due to the uneven ink, the print will appear dark and uneven. But should fight for a while, through the drum of non-stop transfer, so that the ink-printed parts of the printing plate full ink, and then start proofing or printing. During the printing process, the amount of ink and the amount of water used should be properly adjusted. If the amount of water is too large, the water will act as a lighter, thereby reducing the amount of ink used, removing the ink's ink color and making the entire ink lighter. The blanket on the printing press should be cleaned and kept clean. Generally speaking, the smooth and clean surface of the blanket is not easily lost when printing, and the ink coverage is good. When the surface roughness is not clean, the printing dots will be irregular. Or, when the blanket surface layer is formed into a very smooth, aged film due to exposure to light, heat, and long use time, the properties of the surface of the blanket can be completely masked to increase its hydrophilicity and decrease the pro-inking performance. The printed ink is whitish. If a similar situation occurs, shut down immediately and clean or replace the blanket.