Flat top dot is the holy grail of flexography. The result of the search for the perfect tonal transition. Until its invention, oxygen inhibition was considered salutary because it oxidized the dot tops. Minimal differences in height between the dots relative to solid areas resulted in full layer distribution and fine dot printing. Unfortunately, standardizing oxygen inhibition never came to pass, and this caused undesirable differences in printing.
Today, the race for the flattest dots is on, and polymer manufacturers achieve this effect using a variety of techniques, such as plate lamination or exposure in a special gas. All of these processes do work, but they complicate the entire process of manufacturing a printing plate, driving up the cost because they require specialized equipment.
For many years now, the QS and QZ plates by the Japanese company TOYOBO have been used for high-quality printing. Polymer development is driven by customer requirements and rasterization technology. 200 LPI and modern hybrid rasters have already become a standard in numerous printing houses. However, not all plates can handle large print runs with a “scattering” of small, free-standing dots in these rasters.
The Japanese company TOYOBO has developed a plate that prevents oxygen interference in the exposure process, completely eliminating the effect of oxygen inhibition without unnecessary additional treatments.
Typical dot vs. new QZ
QZ, Toyobo’s new-generation of printing plates, make it possible to achieve a stable and always uniform base thickness even when an imperfect exposing unit is used, such as one with large exposure energy spikes and power drops. At the same time, when using a moderately sensitive plate, during backlight exposure, the upper layer responsible for building the dot tops is very sensitive. As a result, the dot top is created with great precision, and a barrier separating the polymer from oxygen interference allows to obtain an ideally flat dot with sharp edges.
“Finally, fine dot printing without the fear of damaging the print is possible. Going down to 0% was previously reserved for solvent plates, but now it has become achievable with eco-friendly water-wash technology. Hybrid raster printing is no longer a challenge with this plate.” — Tomasz Fiebich — Production Coordinator — NATALII
The middle polymer layer creates a very stable and strong base for the dots. This allows even the smallest rasters on the plate to gain a base and shape that allows stable printing at high print runs and speeds, without picking up ink, but more on that later.
The multilayer nature of the polymer structure means that we can achieve the smallest dots in high lights on the plate while maintaining a wide gradient in shadows.
The QZ printing plate by TOYOBO completely eliminates the problem that is the bane of numerous printers — ink being picked up by the plate during printing and the need to wash the plate during operation. The composition of compounds used to build the photopolymer is responsible for eliminating this problem.
“Printers have no problem with plate cleanliness throughout the whole print run, and washing and storage of plates in the archives are trouble-free. The use of the new plates resulted in an improved production process while maintaining colour stability, perfect rasterization and most importantly filled solid areas.” — Rafał Kostrz — Production Manager, Member of the Board — ETYFLEX.
It allows our customers to make considerable savings as they do not have to stop the machines mid-process.
TOYOBO’s QZ water-wash flexo plate meets all customer expectations. It is appreciated for its environmental aspects such as the elimination of solvents from the process and the savings in time and energy, as the plate is ready for use within 50 minutes. However, the plate is mainly praised for its high-quality characteristics. Fine flat dots, long-lasting even with very long print runs, without the problem of picking up ink, is what customers appreciate it most for.
Expert, experienced photopolymer plate processing and flexographic printing practitioner. Vice President and co-owner of the company Print Systems. Responsible for the implementation and maintenance of technology based on water-wash plates by the Japanese company Toyobo. He advises and cooperates with all the major labels and packaging printers in Poland, Italy and the Balkans.