Ink, OPV's & Primers
Overprint varnishes, commonly termed "OPV's", provide the finishing touch
to printed media. These clear coatings impart a glossy depth of image, or a soft
matte touch, for a dramatic visual effect, while protecting the underlying ink from
damage. OPV's are exposed to harsh conditions during processing and afterwards in
shipping, handling, and storage yet must look perfect when finally placed on display.
For these reasons, wax surface modifiers are a critical ingredient of many OPV formulations,
providing slip control, rub/scratch resistance, and other specialty barrier properties.
Printed media are created by several different techniques (flexographic, lithographic,
etc.) and OPV's may be recommended for any and all. The OPV's are most commonly
water-based or UV-curable, with solvent-borne also used. Various types of wax-based
slip/rub additives are formulated into all types of OPV. For example, a fine particle
size ultra-low-VOC (water-based) wax emulsion is the best choice for a High Gloss
Proper selection of wax surface modifiers also depends on the end use of the printed
media. Folding cartons, labels, and publications are high volume uses for OPV's.
Many specialty paper and film products also require OPV's that often must comply
with food contact regulations. In these cases a specialty OPV may be selected to
provide an effective barrier to water, oil, or grease, to provide release properties,
and/or to increase heat resistance. Paper plates are a good example of a food contact
application requiring barrier as well as efficient high speed processing.
Another specialty OPV application that uses wax surface modifier technology is preprinted
liner board, which is paper that has been printed and varnished, to be subsequently
corrugated (ultimately for box manufacturing). The corrugating process is temperature
and pressure intensive, demanding a specialty heat resistant OPV.
As with OPV's, wax surface modifiers are the essential additive to an ink formulation,
providing slip control, rub resistance, and scratch resistance, all critical to
maintaining the integrity of a graphic design. Marring or abrasion of the dried
ink simply "blurs the message" and ruins the dramatic visual effect that
the designer intended.
Many types of inks are used in industry, to fit the various printing processes,
which include: lithographic/offset, flexographic, gravure, screen, letterpress,
and now, of course, digital printing. Wax surface modifiers are selected for their
compatibility with the specific ink system that's being used as well as for their
Besides inks and OPV's, primers are sometimes used to prepare the media for printing.
Primers enhance the ink receptivity of surfaces, improving ink adhesion, rub resistance,
and image quality.