Flexographic printing is rather simple process – liquid instant drying ink is transferred on relief printing plate and then directly on substrate by anilox roll, which serves as metering roll as well. Ink transfer is defined by anilox specification – bigger more open cell (low screen) transfers more ink and contrary smaller cell (high screen) less ink. To change applied ink amount you need remove one anilox roll and change it by another. This limits ink metering to some defined steps when offset has ability for infinitely variable ink metering and more precise color matching. But this limitation is the biggest flexo advantage, because it lets simply reproduce once defined color (repeat order) and keep it stable during all printing process. Moreover it allows using simple and not expensive machinery and is less demanding for personnel qualification.
Biggest discoveries that pushed flexo technology to these days glory and power:
· Photopolymer plates discovered by Du Pont greatly simplified plate making process and enhanced high resolution (150 lpi) reproduction;· Computer to plate (CTP) laser engraving technology pushed plate making technology to new heights enabling ultra high (175-200 lpi) resolution reproduction;· Ceramic laser engraved aniloxes allowed to wet and print high resolution small dot, reproduced in photopolymer plate;· UV and EB ink technologies enabled small printed dot remain the same small (low dot gain) and enough dense (high pigmentation) on substrate creating the highest quality result.
Improvements in anilox engraving, plate making and prepress technologies as well as new inks development enabled flexo to claim for its share of high quality printing market segment once exclusively occupied by offset and gravure printing. Now flexographic printing technology dominates flexible packaging, corrugated cardboard, self adhesive label printing markets and increases it share in carton box decoration, publishing or wallpaper printing traditionally dominated by offset and gravure.