topcoats applied over litho-printed materials are designed to provide:
- Increased gloss
- Rub resistance
- Chemical resistance
Functional improvements such as heast-sealable blister packaging The three types of
coatings are (1) Overprint varnishes, (2) Water-based, and (3) UV and Electron Beam-cured
Overprint varnishes are solvent-based, inexpensive, lower quality coatings which are
easy to use. This segment is seeing declining market share.
Water-based coatings provide higher quality than Overprint. They contain 30-50% solids and
are made up of acrylic and styrene/acrylic polymers and some water-based urethanes along
with specialty additives peculiar to a particular task. The acrylics have a far lower
yellowing tendency than Overprint. Forced air or infrared heating is required to dry them.
Water-based coatings are expanding their market share.
UV and Electron beam-cured coatings offer the highest performance of the three options at
the highest price. They are made from energy-cured polymers and monomers with specialty
additives. Like Overprint, they can be applied on a standard printing press, and like
water-based, require a separate curing unit. They are expanding from a small market share.
Author: Don P. Duncan
Source: GATF 1999 Technology Forecast, p. 30.