6540 South Glacier
Street Suite 120 Seattle, Wa 98188 Phone:(425) 656-8210 (877) 656-8210
Fax: (425) 656-4400
Latest Newsletter | Services | Library | Links | Map | Contacts | Employment | Forms | Search | Home
UV Coating Technical TipsUV coating has become widespread as a very effective way to add gloss to a printed sheet. The current generation of UV curable inks contains virtually no volatile organic compounds (VOC’s) and are considered to be environmentally friendly. When the wet coating applied comes in contact with UV light within the coater it undergoes a chemical reaction which converts the wet coating into a hard film. This occurs almost instantaneously so very fast production speeds are possible. UV coating is available in a variety of formulas. Gloss is the most common but matte is also available. There are also special formulas for coating sheets produced on various digital presses as well as glueable formulas. Some tips to improve the quality of the finished product: Quick Summary – use wax, silicon and Teflon free ink, avoid alcohol substitutes and one step fountain solutions because they may contain glycol which may contain oil and UV coating materials will not adhere to oil. Avoid alkali pigment inks High substrate holdout – the ability of the substrate to resist or slow the penetration of ink will also help keep the coating on the top of the sheet Ink matching – use inks that are formulated to accept UV coatings. This includes: wax, silicon and teflon free inks, no alkali sensitive pigments such as reflex blue, rhodamine, methyl violet, Red Lake C, or barium pigments Hard drying inks also enhance the success rate. The heat of the UV lamp can soften the ink and create offsetting issues Low VOC and low water pick up inks – these properties will tend to slow drying and inhibit adherence of the coating Dry Back inks such as metalics and florescents will result in poor UV coating adherence and should be avoided. Fake metallic formulas may be an alternative. Varnishes should be water based that are compatible with UV coating. Solvent based varnishes usually prevent the UV coating from adhering and should be avoided Ink should be dry before top coating on the press. If water is trapped under the coating it will prevent the UV coating from adhering Spray power left on the sheet will cause a sandpapering effect. Our press has a crusher unit designed to remove press powder, but it is best to remove it at the source Clay coated sheets may have a porous surface that can absorb UV coating and cause a streaking affect. Kromekote and King James are examples of stocks that can cause UV coating problems Uncoated stocks will result in an unacceptable finished product and should be avoided. They absorb the coating and prevent an acceptable finished product Acid free stock is preferable since the acid can cause yellowing of the finished product and may create adhesion problems. Foil stamping should be done before UV coating using foil designed for UV Embossing and debossing should be done after UV coating Scoring should be done after UV coating. Some flaking or cracking of ink coatings may happen even after scoring. Stock thickness should be .006 or greater. Thinner stocks will tend to curl and may crack when folded Sources: Actega Kelstar UV Coatings Technical Publication November 2009 |
|
|