UV Technology for In-Mold Labeling

UV Technology Feature for In-Mold Labeling

By Ronald B. Schultz V-cured inks and coating have part. This pre-formed insert is placed become an important part of the into an injection mold where it is production of in-mold labels backfilled with resin to form the final Ufor packaging (IML) and in-mold part. Examples of IMD products are decoration of durable products (IMD). cell phone faceplates, automotive For 2013, 25% of in-mold labels in dashboards and name plates, and North America and 20% of those washing machine control panels. produced in Europe were printed with The in-mold labeling process UV-cured inks. This is especially true requires inks and overcoats with for labels produced on narrow web superior heat resistance for both the flexo and web offset presses. blow mold (IML-B) and injection In-mold labeling (IML-I) molding process. The IML-I is different from process is especially demanding where pressure-sensitive, resin is injected at high pressure heat-transfer or glue-on and temperature against a reverse Printed on 70µ oriented labeling which are post- printed label. Conventional inks polypropylene mold operations. In IML, with inadequate heat and chemical (OPP) by UV Offset the in-mold label is placed resistance can be washed away by the in the mold before the hot resin as it is injected behind the Printed UV Flexo plastic container resin is injected or label into the mold cavity. on OPP blown into the mold. As the resin flows UV-cured inks provide superior into the mold, the label is embedded in properties on in-mold labels, including: the wall of the container, making the • High gloss label an integral, non-removable part of • Abrasion resistance the container. All post-mold operations • Chemical resistance and equipment are eliminated. In-mold • Resistance to injection “washout” labeled containers include laundry detergent bottles, cream cheese and ice • Good bonding to backfill resin for cream containers, and motor oil bottles. insert molding IMD is similar to IML in principal, • High durability for outdoor but the “labels” are more robust and exposure the in-mold decorated parts are of • Low or no volatile organic much higher value and intended for compounds continuous or even harsh outdoor • Rapid cure service. Many such products are made in multistep processes. The Despite the attractive performance initial “label” may be a 10- or 20-mil properties of UV inks for IML/IMD, clear polycarbonate which is first they are more challenging to use in a reverse printed with a UV ink. The number of ways. printed film is then thermoformed • Curl—In order to feed smoothly and die cut to the shape of the final from label magazines, in-mold labels

16 RADTECH REPORT ISSUE 3 2014 must be as flat as possible. Any can hang up in the mold causing with print-to-print and curl introduced by the converting the molding machine to shut down. print-to-cut registration. process can be a serious problem at Another artifact of inadequate • Odor—UV inks often have residual the molding machine. UV inks and cure is poor slip which affects label odors which are particularly coatings have been known to create feeding for magazines. objectionable on labels for food Feature curled labels as they cure. • Over cure—Over-cured UV inks packaging applications. • Undercure—Undercured UV and coatings can be brittle, causing Despite these mostly controllable inks and coatings can cause label hairline cracks along bend radii and issues, UV inks and coatings are blocking and offsetting of ink to the corners. Water-based overprints are becoming increasingly popular for inside of often applied over UV inks to avoid printing in-mold labels and decorating the mold. this problem as well as to avoid curl. durable molded products. When this • Heat Management—UV lamps For more information about happens, generate significant heat, especially in-mold labeling for packaging the label on narrow web presses. IML and in-mold decoration of durable substrates are thin, goods, visit the IMDA website at unsupported www.imdassociation.com. w polyolefin films which are quite —Ronald B. Schultz is executive director of the In-Mold Decorating extensible under Association in Scottsdale, Ariz. tension and heat. Stretching of the

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