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| Typically, the following four techniques are employed
to improve the glossiness of the ink surface after color
printing, and for promoting scratch- and rub-resistance,
as well as chemical tolerance. |
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OP Varnish (oxidative polymerization
type) |
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- After the ink dries, apply the OP varnish with
an additional pass through the press.
- To avoid any curling or surface distortion,
be sure to use a varnish which has been specifically
formulated for use with YUPO®.
- Depending on the type of varnish, some yellowing
may occur over time. Please consult with your
ink manufacturer.
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UV Varnish Coating (UV
varnish) |
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- The application of a coat of varnish is the
most effective way to protect the ink surface
and improve gloss.
- To prevent distortion due to heat, including
deformation and curling, be sure to use a low-heat
type UV lamp (water-cooled or infrared-filtered).
When dealing with the high-volume lighting necessary
for dark color projects, even water-cooled systems
may produce high temperatures, which may result
in distortion of YUPO®. As a rule,
avoid stacking sheets of YUPO®
in temperature conditions exceeding 50°C.
- In the case of oil-based offset printing (oxidative
polymerization-type inks), coatings should be
applied offline. So as not to detract from the
glossiness of the finished coating, limit the
use of spray powder during printing as much as
possible, or remove the powder from the printing
surface prior to application of the UV varnish
coating.
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Inline Aqueous Varnish
Coating |
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- After the application of the varnish, use a
drier with a long delivery and maximize air speed
and pressure to ensure adequate drying.
- Additionally, make any necessary adjustments
to ensure that sheets of YUPO®
is delivered at a temperature not exceeding 35°C.
This will prevent blocking of the varnish.
- In addition to safeguarding the print surface,
this type of varnish coating is also effective
in reducing both the use of spray powder and any
blocking trouble with the pile.
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This method is not
used in Japan. |
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Vinyl Coating (Glazing) |
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This method is not suitable for use with
YUPO®. |
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