An Analysis on the Quality of Baking Plates for Improving the Printing Rate of PS Plates (I)

Under the condition of high temperature heating, the photosensitive film of the positive PS type plate is heat-modified to make the cross-linking effect of a cresol-formaldehyde resin between the film formers, from linear to body-shaped structure, and the photosensitive film is printed. The stability, corrosion resistance, and mechanical strength of the text section. The roasting plate can increase the printing rate of the PS plate by 3-5 times and reach 30-50 thousand lines, thus reducing the production cost and improving the economic benefits. However, if it is not properly handled in the actual production work, the baking version will have quality problems.

In the following, we will analyze the quality of the roasting plates that we can often meet in production so that we can better analyze and judge when problems occur in production.

First, the plate should be processed first before baking. For example, the surface of the plate is cleaned, the development is correct, and so on. Here are some problems with plate quality due to unsatisfactory plate processing before baking.

(1) Light red after baking

This light red color is caused by a trace amount of photosensitive layer in the blank portion of the printing plate that has been baked. If it is treated with a developer, it will not get dirty; if the light red remains on the plate after being processed, it must be dirty. This situation can be used in addition to dirty agent treatment, and then ink inspection, generally can be resolved.

(2) Underexposure or incomplete development

Insufficient exposure or incomplete development will result in insufficient decomposition of the non-graphical part of the photosensitive resin, leaving a residue in the blank part, and the residual part is strongly adsorbed on the plate base during the baking process, and is difficult to remove, so that ink will be absorbed during printing. Dirty. In general, this situation can only be reprinted.

(3) Before grilling, the layout contamination causes the front plate of the plate on the plate to be dirty and the PS plate must be handled cleanly, and the traces of dirt, impurities, traces of dirt, etc. must be thoroughly and thoroughly cleaned. These stains will be firm after baking. Adsorption onto the plate, causing the plate to be dirty.

(4) Dirty dirt

The actual production often sees, the reason is very simple too, it is that the dirty mark that has been corroded by the dirt remover is not rinsed completely in time, the dirty mark that is identical to the dirt remover is reflected when printing. In order to prevent such dirty marks from appearing, be sure to thoroughly clean the dirt remover with a sponge or a wet towel after washing and then rinse with water, and then wipe the protective solution to start baking. Avoid dirtiness.

Second, we found that there are many problems in the baking plate on the baking plate protection agent, either due to improper use of the protective agent or due to improper formulation of the protective agent itself.

We first understand the role of the protective agent on the surface of the printing plate before baking. The most important role of the protective agent is to protect the blank part of the printing plate during the baking process, so that the pores of the oxide film that has been subjected to the sealing treatment at the high temperature of the baking plate do not reopen and are activated again to generate ink absorption. Dirty phenomenon.

Let's take a look at the following situations:

(1) Dirty plates after baking

Dirty on the PS version of the baking plate is a relatively common failure in production, and it is often difficult to solve. We should first find out the cause of this kind of filthy problem, and then take a corresponding approach. If the dirty version uses gasoline to wash off the ink, there is a reddish-brown baking layer on the bottom, which means that the development is not complete, there is residual sensitizer baking hardening, the ink is dirty, this dirty has a solid foundation, Generally can not afford to go, if forced to remove, the surrounding reticulation will suffer. This dirty version can prevent recurrence only by increasing the time or intensity of the printing. If there is no red-brown baking layer beneath the dirty plate, it may be that the concentration of the protective liquid is low, the coating is too thin, and there is no effect of protecting the plate from contamination, and the micropores of the aluminum plate oxide film at high temperature are renewed. Open and contaminated. This dirty version will show up after the ink is drawn or printed, but it will not be observed at ordinary times.

(2) Shallow streaks appear on the layout text, and the ink-reporting ability of the layout decreases.

The printing plate cannot faithfully reproduce the tonality of the original, and light-colored stripes appear. This is often caused by improper protection of the eraser. As the concentration of the protective agent is too high or the streak left by the rubbing is not uniform, it hardly dissolves in water after being baked and hardened on the plate, resulting in no ink absorption. In this case, the alkaline solution slightly thicker than the normal developer can be re-exposed and then neutralized with 3% phosphoric acid.

(to be continued)