white paper l 11 February 2013 I LUX Membrane 200
LUX with Membrane 200:
Engineered Surface Roughness Improves
Solid Print Quality
white paper l 11 February 2013 I LUX Membrane 200
EXECUTIVE SUMMARY
MacDermid LUX® membrane and exposure technology delivers
a unique flat-topped dot shape that improves print quality and
consistency, while delivering exceptional versatility for the
platemaker.
Using LUX Membrane 200, we can emboss an engineered
surface texture into plates made with LUX, which allows solid ink
density (SID) to be increased and mottle to be decreased. This
effect is evident in plates processed by both solvent and LAVATM
thermal processing methods.
The use of Membrane 200 is a quick and effective means of
improving solid print without the need to add special screening to
artwork, while retaining all the advantages of the LUX dot
structure throughout the remainder of the tone range.
LUX Membrane 200 boosts solid ink
density (SID) when used to image plates
processed with solvent or LAVA thermal
systems
LUX Membrane 200 reduces print mottle
when used to image plates processed
with solvent or LAVA thermal systems
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Ink: Making the most from the least
The amount of ink applied to a flexo plate on press is determined
by the volume of the anilox roll, so changes in anilox volume will
have a profound influence on color density. However, for a
variety of economic and operational reasons, it is preferable to
use the minimum amount of ink required to achieve the needed
print quality. Doing so obviously reduces ink costs, but perhaps
even more importantly, it allows crisp reproduction of halftones
and more consistent (i.e. “cleaner”) print runs.
However, the amount of ink applied to the plate is only half the
story. The way that the ink is distributed on the surface of the
substrate plays a major role in its appearance as well. It is during
the ink transfer step that the plate can play a major role in
improving both the solid ink density (SID, the intensity of the
color) and the uniformity (most commonly measured as mottle)
of the ink on the package.
The LUX Process
LUX adds a single step to digital flexo platemaking, using a
lamination process to cover the digital mask after ablation, prior
to UV exposure (see workflow diagram below).
The LUX process adds a lamination step to the platemaking workflow
Lamination of the LUX membrane blocks the effects of oxygen
on the photopolymer during UV-induced crosslinking, causing
three major differences compared to standard digital
platemaking:
1. LUX dots have a flat top, but retain the steep shoulder
angle of digital dots. This combination of geometric
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factors gives LUX dots exceptional stability and low dot
gain characteristics.
2. LUX dots are ‘type high’, meaning that dot tops are the
same height as solids. Press startup is simplified
because all print elements contact the substrate at the
same impression level.
3. LUX allows the photopolymer to image 1:1 to the mask
image. There is little or no bump curve, and the mask
image is translated into the photopolymer with a high
degree of fidelity.
By blocking oxygen and shaping the UV
light, LUX creates dots with flat tops,
steep shoulders, and 1:1 fidelity with the
mask image
The print benefits of the LUX dot shape have been proven
repeatedly. This new class of dot shape has become an enabling
technology for advanced screening because of the exceptional
stability of LUX highlight dots. In addition, the LUX dot shape
reduces the impression sensitivity of the plate, giving more
consistent print results throughout a run and from run-to-run with
the same plate.
Lamination allows surface modification
The LUX lamination process includes the ability to modify the
surface of the plate by embossing a pattern into the unexposed
photopolymer. This patented LUX capability is unique; no other
flat-top dot process can achieve plate surface modification
directly.
There are two membranes available for LUX – Membranes 100
and 200. LUX Membrane 100 is a smooth membrane that gives
the LUX dot structure and 1:1 imaging, with a surface very
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comparable to standard digital plates. LUX Membrane 200
imparts an engineered surface roughness to a digital plate during
the lamination process, as well as having the same unique LUX
dot shape and 1:1 imaging capability.
LUX Membrane 200 adds an engineered surface roughness to the plate, along with the high fidelity imaging
inherent in the LUX process
The surface texture imparted has a roughness of about 400 nm,
very similar to that of MacDermid capped digital plates such as
Digital Epic® and Digital MCH. In these capped plates, this
roughness frequency had been proven over thousands of
kilometers of printing to deliver improved solid ink density (SID)
and reduced mottle, so we targeted this same roughness for our
LUX process as well. The surface pattern is present throughout
the tone range, improving the ink transfer of both dots and solids.
The surface pattern is random, and thus cannot create
interference patterns (e.g. moiré) with any other screening
elements used in the artwork.
LUX Membrane 200 adds a random
surface pattern throughout the tone
range, to both solid and dot surfaces
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The pattern has proven highly durable too, as it remains visible
on the plate surface even after 100,000+ meter print runs. This
ensures that solid ink density and gain remain consistent
throughout a print job.
LUX Membrane 200-treated dots before and after a 579,000 meter print run
Print effects
On press, LUX Membrane 200-treated plates deliver significantly
higher SID and lower mottle than either standard digital or LUX
Membrane 100-treated plates. And this improvement is apparent
on both solvent- or thermally-processed plates.
Solid Ink Density (SID) is improved
significantly by the use of LUX
Membrane 200
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Mottle is decreased significantly by the
use of LUX Membrane 200
While numbers quantify the effect well, they do not give one a full
appreciation of the impact that the improved print brings.
Visually, the effects of Membrane 200 are often quite striking.
LUX Membrane 200-treated plates give better ink laydown and color density on white polypropylene
The benefits of LUX M200 are available on most substrates from
envelope stock to coated papers to polymeric films.
SID is increased and mottle is
decreased for Digital MAX
imaged with LUX Membrane 200
(right) compared to Digital MAX
imaged in standard digital format
(left), both printed on paper.
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Simplicity is a virtue
One of the nicest things about LUX Membrane 200 is its
simplicity. There is no extensive testing required to find the right
surface pattern and the digital imager can be run at its maximum
throughput because there is no need for fine details to be etched
into the solid portions of the mask.
Conclusions
LUX and Membrane 200 offer a combination of benefits no other
imaging technique can bring to package printers. The LUX dot
shape gives exceptional highlight dot stability, low mechanical
gain, and uniform dot height. LUX Membrane 200 imparts a
surface roughness to the plate that is durable, random, and
optimized to increase SID and reduce mottle in print.
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