ISP - March/April 2013 - 23

W

hat is one of the hottest growth markets in package printing? Shrink sleeves.
Research over the last five years has shown
shrink sleeves growing twice as fast as the
rest of the market. To see this, you don’t
need to read volumes of market research;
simply go to your local grocery store and
walk the aisles.
Shrink sleeves are a true phenomenon
in the modern packaging world—a real
innovation that has transformed the face
of the retail shelves. They offer head-totoe container coverage and 360°, full-color
graphic label/package decoration (Figure
1). They can be applied to any package
shape and can provide differential shrinkage over different areas of the container
(Figure 2).
Shrink sleeves give the package graphic
visibility, with eye-catching design and
its ability to conform to nearly any shape.
Market growth over the last five years has
enabled the introduction of new films, and
we now have a number of different films
with different properties and end uses.
challenging demands on the ink
While there is much discussion of the
shrink factors achievable with shrink sleeving, this is only half the equation. To make
a sleeve label, you need to print it, and that
entails the use of inks that, of course, need
to shrink along with the substrate subscribing to the contour of the container.
Ink technology has been challenged by
the shrink-sleeving process (Figure 3), but
ink suppliers have been able to use their
expertise in ink chemistry to develop solutions that really meet market needs.
Inks for shrink sleeves have to combine
two conflicting performance parameters:
creating an ink film on the substrate that
cures at high speeds and also shrinks as
required while providing strong adhesion
to the film substrate with good scratch
resistance. The ability to cope with varying
degrees of film shrinkage across an entire
container is the hardest requirement.
Originally, most sleeves were gravure
printed, but flexo printers wanted to gain
access to this market. This demand for
high-quality flexo inks pushed the supply
chain to improve. Early on we saw specially
formulated inks for specific films and
specific printing applications. This created
complexity, high inventories, and waste as
multiple ink systems were required for the

variety of different films. Ultimately,
universal ink systems were needed.
But a universal system is not easily created; shrink-film printing is a
unique application. The inks must
be capable of adhering to different substrate surfaces: PE, PVC,
PETG, OPS, PLA, and more.
The substrate will shrink
more than 70% in some
cases, and the inks cannot
crack. During shrinking, the inks must
have good heat
and steam resistance. In most
cases, the inks
are inside the
sleeve but
must still have
good scratch
resistance so
they don’t scratch
while being applied
to the container. The inks need all of these
performance properties while still providing
high-fidelity printing of good, solid density
with smooth lay and great dots.
ideal conversion parameters
First, to cope with the issues associated in
shrink-sleeve printing with UV inks, ink
suppliers need to help converters achieve
high opacity coupled with good shrinkage.
Opacity is generally associated with a thick
ink layer. But that can be difficult to cure,
and can cause poor shrink performance.
On the pack, heavy ink layers can also
result in an unattractive relief effect. For
example, experience shows that using two
base layers of opaque white printed in dots
(in high-shrink applications they will look
like solids) will give good opacity—but care
should be taken to use as little white ink
as possible in areas that will experience
the most shrink. Metallic inks have proven
to be a problem area—they can lose their
sheen when shrunk—but they can be successfully used in low-shrink applications, at
20-30% shrinkage.
Sleeves are generally solvent welded
to create a tube post-printing and prior
to application and shrinking, with the
printed web passing through nip rollers
and then being rewound. This creates
stress on ink-layer adhesion. The application process involves slipping a tube of

Figure 1 Shrink sleeves provide more area
for brand marketing, create 360° shelf appeal, and accommodate a variety of package
shapes and sizes.

printed film over the top of the pack to be
sleeved. The sleeved container then passes
along a conveyor into a heated shrink tunnel
which may use IR, hot air, or steam, or a
combination of these to provide the different
levels of warmth needed to create required
shrinkage levels. The inks used have to be
able to withstand these additional processes,
while shrinking with the film to deliver the
prescribed morphed image.
materials
Today, the importance of color and
graphic design on a label or package is
well understood for the success of products
in being selected by the consumer. A package has an estimated five seconds to make
an impression; thus, it is very important for
the ink designed into the product packaging to catch consumers’ attention. Any
failure with the ink on the label or package
during the lifecycle of the product will be
disastrous to the product’s success in the
marketplace.
The label cannot fade in a storefront
window or on the container in the greenhouse. It cannot bleed off a shampoo bottle
march/april 2013 | 23
ISP - March/April 2013

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