Flexo Microcell Screening Technology—Part 1

1.Key Conclusions

01. Microcell are not simply a type of halftone dot; they are an integrated system.

High-precision laser imaging, flat-top dot architecture, and plate surface engineering are all essential. Any claim that a RIP alone can generate microcell dots overlooks two critical physical processes: LAMS black mask ablation and UV exposure-based image formation.

02. Three different approaches achieve the same physical result.

Esko: Generates microcell patterns through direct file-based RIP screening, followed by laser energy-modulated imaging. Compatible with a range of plates.

Kodak: Applies a secondary microcell pattern to the screened dot file through a laminated mask micro-patterning process. Compatible only with its own plates.

XSYS: Applies secondary screening and engraving to the screened dot file through the imaging device. Compatible with a range of plates.

Final microcell structure: An array of micro-pits or grooves, 5–10 μm deep with a spacing of 12.7–18 μm.

03. Screening frequency determines the compatible anilox roller.

A frequency of 1,400 lpi (18 μm spacing) corresponds to an 800–1,050 lpi anilox roller, while 2,000 lpi (12.7 μm spacing) corresponds to an anilox roller of 1,000–1,200 lpi or higher. A mismatch between microcell frequency and anilox specifications can actually introduce ink streaking and uneven ink transfer.

04. Flat-top dots are a prerequisite, not an optional feature.

Creating microcells on rounded-top dots is like carving pits into a sloped roof: after plate washing, the cell walls may collapse and cell depth becomes difficult to control. Flat-top dots can be achieved through one of four approaches: flat-top plate technology, high-energy LED exposure, oxygen-removing lamination, or an inert-gas environment.

05. The ink system determines the maximum achievable benefit.

Solvent-based and water-based inks generally benefit the most. Conventional free-radical UV inks, due to their high viscosity and poor leveling, offer relatively limited improvement in solid-area ink density. Cationic UV inks, with viscosity potentially reduced to below 22 seconds under the specified measurement conditions, work particularly well with microcells and may enable a single white-ink pass to replace two passes.

06. Plate selection is more likely to be the wrong choice than equipment selection.

The plate must satisfy four requirements simultaneously: flat-top capability, a sufficiently smooth surface, compatibility between the LAMS black mask and imaging energy, and inclusion on the equipment supplier's approved plate list. A plate described as high-hardness or high-definition is not necessarily suitable for microcell production.

07. 2024 marked a turning point.

Quartz Edition advanced microcell technology from 1,400 lpi to 2,000 lpi, reducing spacing from 18 μm to 12.7 μm. Microcells consequently evolved from a solid-area enhancement technique into a surface-engineering approach applicable across the tonal range, from highlights to solids.

08. Acceptance testing must cover three stages, not density alone; appearance matters even more.

Quantitative criteria are required at all three stages: black-mask engraving, plate formation after washing, and final printing results. Measuring only solid ink density (SID) can miss the most critical defect: excessive microcell depth variation, which may cause progressive print-density loss along the production run.