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The Heidelberg website glossary explains, in alphabetical order, a multitude of terms relevant to printing, as well as some terms used in Heidelberg's product catalogue.

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Uncoated paper

Paper without an additional protective coating; "untreated" paper. The application of a colorless coat of glossy or matte varnish as final printing step, either as an overprint varnish applied on-press or a water-based preparation applied by a separate coating machine. Varnishes enhance the appearance of print products and, especially on matte-finished stock, improve the rub resistance of printing inks.

Under Color Addition

Under Color Addition (UCA) is a variation of achromatic synthesis used for 4c color sets. Equal components of the three chromatic colors cyan, magenta and yellow in the CMYK color system replace part of the neutral color component generated here with black. Under Color Addition is a good means for improving print quality vis-à-vis pure achromatic synthesis.

Unicode

Unicode is a method for coding characters for electronic processing and uses 16-digit binary numbers (16-bit numbers). Unlike ASCII and other codes, which work with 8-bit numbers, Unicode is capable of representing 65,536 different characters. This covers all the characters is every commonly used script in the world. Unicode is already in widespread use today.

Universal Mobile Telecommunications System

Universal Mobile Telecommunications System - to be introduced by 2003/4 to replace existing GSM/GPRS mobile telephone networks; the maximum data transmission speed is 2 megabits per second.

Upstream

All information and data sent from PC to Internet.

UV coating

UV coatings (UV stands for ultra-violet) are coating systems based on unsaturated polyesters or polyacrylates, or a combination of the two. For both, ultra-violet light triggers the drying process. This high-energy light breaks chemical bonds in the coating material’s molecules. These then link up to form long, highly-branched chains, causing the material to solidify.The drying process takes only seconds, which means that UV coatings can be worked quickly. These coatings contain no volatile substances either, making the layer thickness of the liquid coating similar to that when it is dry. They can also be applied inline, i.e. in the press, in very high layer thicknesses (up to 8 µm). UV coatings achieve excellent gloss and can be barely distinguished from laminated products (film-lamination). UV coatings, however, are not entirely odor-free.

UV inks

UV inks are printing inks that are cured with ultraviolet (UV)light. For this purpose, these inks do not contain any volatile substances. Rather, in addition to color pigments, they contain individual molecules and short molecular chains that can link to form polymers and so-called photo-initiators. The latter decompose when exposed to UV light and form highly reactive fragments. These radicals trigger a polymerization process in which stable, three-dimensional network structures are formed. UV inks are primarily used to print non-absorbent materials, such as metal (sheet metal) and plastic, but also high-quality paper boards and labels.

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