Application principle of flexo printing photosensitive resin plate III

There are a lot of technologists who can solve this problem and try to understand the exposure latitude of using plates (that is, the limits of the physical properties of materials/systems). This information can be known by the supplier or through actual exposure test in the field. Obtain. These test steps can also provide the minimum exposure time for fine dot exposures and the time for the maximum number of inverted fine segments not to be filled. This also provides the underline of the exposure latitude of the plate. If there are occasionally more plates than this underline, the staff can choose to partially cover the fine parts after the main exposure in order to continue with the highlights of the small dots. Exposure (this is an example of the use of exposure time and exposure space)

It is a practical method to expose light in units of exposure, without timing. At the same time, the continuous testing at intervals and the exposure lamination tests for different batches of plates are also recommended for the same reasons as the exposure described above.

When we focus on the test of exposure, there are many factors that can affect latitude in the process of washing the plate. For example, when the potency of the platewashing solution is not completely replenished or the brush is not properly adjusted, it may cause reversal. The white part cannot be washed. Like these may be misled to think that it is a problem of tolerance. The entire plate-making system must operate effectively, and the VU image test procedure is only a part of this system.

※ Digital Printing Plate

The digital photosensitive resin plate has greatly improved the quality of flexographic printing since it was introduced in the mid-1990s. Many of the reasons for improving quality are due to improvements in prepress, platemaking, and printing departments.
The digital resin plate uses a coating (black) that is comprehensive on the layout and is erased by infrared laser light (burning) to form an image portion. The role of this coating is equivalent to the role of the film plus the suction film to reduce the amount of light lost and affect the fine and anti-white thin lines of light. This effect of reducing light scattering greatly increases the effect of exposure to light. Another interesting phenomenon is the formation of UV images without photosynthesis during photopolymerization so that exposure to light is also accompanied by an oxidation effect. The chemical reaction effectively changes the image formation on the plate.

<Figure 5> Oxidative inhibition effect

As shown in Fig. 5, the right digital plate forms a side reaction due to the fact that the molecules of oxygen increase their mobility due to the absence of the backsheet and the insulating film. The free radicals (R) quickly formed oxygen molecules to complete the exposure process. The reactive oxygen molecules of the leaf silkworms react with the monomer resin. This reaction is slower than the interaction between the active monomer and the monomer resin. This result allows the oxygen molecules to act as inhibitory effects on the monomer resin to make the entire light. The formation of a staggered network of polymerization slowed down.

What the dream of the plate-making industry dreams of is that this effect will make the dot more sharp.

As shown in Fig. 5, the staggered network effect has formed a wide shoulder during exposure through the film + film because the dots are surrounded by uniform ambient air. In such a balanced environment, because there are enough oxygen molecules, the photopolymerization becomes a staggered network and thus slows down.

The real result is that dots that are not on the film/film will be smaller and the shoulders will be steeper than the dots that pass through the film.

Does the sharpness of outlets have an impact on printing? Of course there are influences and the influence is very great. Recently, the quality of flexible printing plates has been surging. The most important factor is the sharp results of such outlets. The smaller the more solid the network, the brighter part of the fine network can be more when printed. At the same time, the broader part of the anti-white depression (given by the effect of oxygen molecules) makes the shadow part more clearly visible.

Since the sharpening of digital outlets is a comprehensive layout effect, digitalized prepress operations can prevent the loss of tone values ​​and make the picture more realistic. It is also digitally sensitive, and the high print reproducibility of the resin sheet enables comparison with the quality of the color print or gravure.

---Long Chen Printing Technology Network