‍In the process of flexographic plate making, we need to obtain a printing plate with stable surface tension. Only when the surface tension of the printing plate is stable can we establish a reliable platform that matches the surface tension of the ink. So, how can the plate making process ensure stable surface tension for the flexographic printing process? In fact, there should be a way to stabilize the surface tension of the printing plate during the flexographic plate making process.
Follow the requirements of the flexible version supplier
Strictly follow the procedures provided by the flexible version supplier for distillation, measurement, compensation, and other environmentally friendly solvents. Do not take it for granted to take shortcuts, but instead take detours and take the wrong path. The problem is how to use solvents while protecting commercial interests. The method provided by the supplier is indeed somewhat vague, but following it first is the only feasible solution. It is necessary to strengthen the monitoring of the surface tension of the printed plate after production. A simple and practical method is to use a corona pen to test and use a high-power magnifying glass to inspect the smoothness of the concave area of the printed plate.
Stable solubility of plate washing solvent
The traditional washing solvent of tetrachloroethylene n-butanol has its own uniqueness in terms of solubility stability, but the toxicity of tetrachloroethylene is too high. From the standard of "flexographic printing is recognized as an environmentally friendly printing method", it is indeed not appropriate to use tetrachloroethylene for washing plates. But besides the factor of solvent cost, is there any reason why the stability of plate making quality is indeed higher when using this method for plate washing? This is just like in the gravure printing industry, it is generally believed that toluene based inks have better printing suitability than benzene free and ketone free inks. What we should obtain from this method is the idea that mixed solvents must be measured and directionally supplemented, while abandoning the environmentally friendly nature of solvents.
Wash plate with water-soluble solution
The organic solvents contained in water-soluble plate washing solution have high boiling points and are not easily volatile. Moreover, because they are mixed with water with high latent heat of evaporation, the comprehensive balance problem of the solvent is masked, and the contradiction is not prominent. However, water-soluble plate washing solution, after all, dissolves uncured resin in it. Therefore, as the solid increases, its concentration will also decrease, and the decrease in solubility will rely more on the action of the brush, thereby increasing the surface tension of the printing plate, and the surface tension of the printing plate will also fluctuate. This is something that needs to be noted. After the water washed plate is made, it is said that contact with ethanol is safe, and the printing plate does not swell. However, in practice, if swelling is found, the supplier suggests not using ethanol and instead using a 1:1 mixture of isopropanol and methanol. This case demonstrates the need for further research on water washable plates, and the toxicity indicators of water-based additives are not optimistic.
Thermal Plate Making Technology
The plate making process that can truly eliminate the interference of plate washing solution (including organic solvents and water-based solvents) on the surface tension of the printing plate is thermosensitive plate making technology. The characteristic of this plate making process is to change the uncured photosensitive resin from solid to liquid by heating, and then apply pressure to its surface using a pressure roller, similar to how a gravure transfer unit sucks out the ink from the printing plate mesh hole through the pressure roller. The non-woven fabric wrapped on the pressure roller will suck out the liquefied resin on the printing plate, completing the separation of cured and uncured photosensitive resin. The surface tension of the thermal plate completely reflects the characteristics of the solid itself, avoiding the impact of the solution of plate washing solution on the dissolution and desorption of solid materials and other processes, and avoiding the surface tension fluctuation of the printing plate in the process of plate making.
The thermal version can withstand criticism in terms of environmental protection, but the operational data provided by the thermal version supplier now results in a much lower level of precision in the printing plate produced. At the same time, the magnitude of pressure is also a problem, as too much pressure can cause the edge of the dot to collapse, affecting the accuracy of the dot. In addition, the surface characteristics of non-woven fabrics are not simply a matter of long and short fibers, but rather their ability to adsorb liquid resins. Overall, thermosensitive plate making technology is further refined and improved to obtain fine printing plates while ensuring stable surface tension, which is what we need.
When the plate making process can provide a stable surface tension printing plate for the flexographic printing process, the next problem is the ink. Our goal is to require ink that effectively matches the surface tension of the printing plate, whether it is solvent based ink, water-based ink, or UV ink. This stick should and can be handed over to the ink industry.
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