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APPLICATIONS OF UV COATING
UV curable coatings find a variety
of applications in paper and board, graphic arts, compact
discs, optical fibers, automobile paints, plastic coating,
wood coatings, parquet floorings, adhesives, photopolymer
resists, for joining glass to glass, dental materials,
release coating for labels laminates, sealant, printed
circuits, metal coating etc.
The bulk usage is in the overprint
varnishes and inks in graphic arts, packaging and wood
coating industry internationally.
Procedure for coating of UV curable products for the
printing and packaging industry.
UV curable overprint varnishes (UV-OPV)
are used widely in the printing and packaging industry.
The liquid UV-OPV are coated /applied to the substrate
by one of the many possible methods and subsequently
exposed to high energy source of UV light, the liquid
coating on exposure to the UV light polymerizes and
becomes a solid film.
UV curable coatings are available
for a whole range of application methods UV-OPV are
applied by silk screen manual process, rotary screen
printing, roller coating, varnishing machines, flexography
coating using analog roller, letterpress, offset printing
machine through the duct as dry offset. Spot coating,
window coating or patch coating can be done using traditional
screen printing or by the use of photopolymer plates
in traditional printing machines like the offset machine.
As you can see a whole lot of methods
of applications are possible for UV coating. Different
grades of UV-OP varnishes are available for different
application method depending on the rhelogy involved
for the application. A UV coating formulations must
be suitable, in terms of rheology, to the method that
will be used to apply to the substrate. The UV-OP varnish
grade also depends on the final properties the printer
desires to obtain from the coating e.g. glue ability,
gloss etc.etc.
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UV curable inks are also available for different printing
equipment like flexo, offset, letterpress etc for a
variety of substrates.
UV curing equipment comes as an optional
attachment after every printing station on a lot of
flexographic printing machines, and offset printing
machines nowadays. For UV-OP Varnish drying, conveyorized
UV equipment can be installed in conjunction with any
of the coating machines.
ADVANTAGES OF UV CURABLE COATINGS
There is a debate whether UV curing
coatings are developed for environmental reasons or
they were developed because of being highly energy efficient
coatings and environmental advantages were an incidental
advantage, but one thing is sure the industry has benefited
from this new technology. It is an environmentally safe
process since there are nil or almost nil volatile contents
in and UV curable coating.
UV coating can provide very high gloss
and smoothness and are replacing traditional film laminations.
These coatings are environmentally safe being biodegradable,
whereas the film lamination is not a biodegradable coating
and is being eliminated from most developed countries
as a waste disposal hazard. Also, UV cured coating don't
wrinkle up like film lancination does.
Very high production speeds are achievable
with UV curing coating. UV curable coatings are almost
instantaneous curing or drying, line speeds of 100 m/min
are achievable, and theses coating take a fraction of
a second to dry. With UV technology you can plan on
faster job turn around and Just-in-Time (JIT) inventory
management.
The process is a low heat generating
process can be used on heat sensitive substrates. Special
equipment design allows for minimizing heat generation.
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