As in previous stages, the quality of lenticular lens used also plays a large role in the finishing stage of a great lenticular piece. Be sure you take the time to choose the lens that best suits your needs. Most lenticular projects will also require some type of finish applied after the lenticular image has been printed. This is necessary to prevent the image from being translucent, as well as to facilitate printing on the back of the finished piece.
Lenticular printing has been used for a variety of applications. Products range from labels to postcards, memberships and giftcards, P.O.P. displays to cups, and so much more. With such a large range of applications, the spectrum of finishes can be endless. For example, printed lenticular sheets can be laminated to paper or poly barrier film to help with opacity. Cards can be imprinted with static or variable print, then diecut, round-cornered, and/or drilled as well. Not all sheets need to be laminated. So as you can see, finishing is very project-by-project dependent.
Most lenticular projects will require a coat of opaque white. Achieving the desired opacity for Lithographic Opaque whites depends on a few factors:
- The opacity of the ink varies from manufacturer to manufacturer and brand to brand.
- The amount of ink film applied.
- How many hits or passes.
Depending on these factors, good results can be achieved with two hits, and other times as many as five hits are required to achieve the desired amount of opacity. If the final product is to have printing on the back, the goal is to have ample opacity that will prevent the backside print from showing through the front, or lenticular action side, of the piece.
It is a good idea to keep the backside graphics as simple as possible. Go easy on the amount of color and graphics. The more color intensive the back art the greater the chances are that it will show through and may require many hits of opaque white or even the need to have a barrier film laminate applied to eliminate it. On occasion the back art will need to be screened back or reduced to prevent showing through.
There are detriments to applying too many layers or hits of the Litho Opaque white. One thing to watch for is a phenomenon caused by poor opaque white ink adhesion or reticulation. This causes a grainy or screening look in the lenticular effect. When viewed through a loop you will notice that the opaque white appears to have a dotted look or blotted appearance. This pattern will be magnified on the lenticular side. To help remove this, another pass of the litho opaque white needs to be applied, possibly as many as two hits to fill the voids, making for a smooth white.
Occasionally a metallic silver is mixed into the opaque white in a small percentage in an attempt to increase the opacity if the white. This causes the white to turn a bit on the gray side and in turn darkens the lenticular side, which means this is not a suitable option.
Flexographic Opaque whites
More and more litho offset presses are being equipped with an Ultraviolet Flexo coater. This style of coating device can produce a thicker ink film with smooth coverage. There have been several projects printed as four-color process with two hits of opaque white and coated with the Flexo opaque white, all in a single pass that delivered a very nice result.
Another process to finish a lenticular piece with a back side print is to laminate a printed paper backer to the lens.
First the lenticular portion is printed and opaque white is applied. This is not only to achieve opacity but also to hide the adhesive used to adhere the paper to the lens. The backside print is on the paper stock. Text to cover weights are commonly used. Typically the paper backer is printed and sent to the laminator along with the printed lens for the laminating process.
A big advantage of paper laminate is great opacity that will allow for almost any high density, color-intensive backside graphics. Paper laminate is less costly than a poly barrier film laminate.
Unfortunately curling can be an issue. It is advisable to run the grain of the paper perpendicular to the direction of the lens. Use the minimum amount of roller or nip pressure possible. An adhesive with a low moisture content should be used.
Paper has a tendency of fraying or pealing at the corners with use over time. The paper laminate could add substantial weight. If your piece is a mailer this may effect the postage and/or shipping costs.
Barrier Film Laminate
There are two types of barrier film laminate: thermographic and pressure sensitive. They both have choices in opacity, from whatever the manufacturer offers up to 100%.
The thermographic barrier film adhesive is activated by heat during the laminating process. The laminating machine has a controlled heating device that warms the barrier film just as it is being married to the lens.
Thermo Barrier film laminate has great adhesion and has a choice of finishes like matte or gloss. It has very good color display when printed. It is thin and very light weight, less costly than pressure-sensitive film and even some paper laminates.
Due to heating and amount of pressure needed on the laminating machine’s rollers, there may be a degree of curling. There are some new products on the market called “low melt” or “ low heat”, meaning that they have been designed to activate their adhesive at a much lower temperature. Just as with the paper laminate, roller pressure or nip is a factor. The least amount of pressure or nip required while still ensuring a good bond will help keep any amount of curl to a minimum.
Pressure Sensitive Barrier Film
Pressure Sensitive barrier film has a wet adhesive with a liner. When the liner is removed, the adhesive is exposed and the barrier film is married to the lens via pressure. Once again, the amount of roller or nip pressure is important to prevent curling. However, because heat is not used and the adhesive has a very high tack the roller or nip pressure can be very light.
Pressure Sensitive Barrier Film is less likely to cause curling. It has great opacity and great adhesion and is available in a choice of finishes like matte and gloss. It’s thin and very light weight and has good color display when printed.
Unfortunately Pressure Sensitive Barrier Film is expensive. When compared to thermographic barrier film, it can approach double the cost.
Printing on Barrier Film
Typically the lens will have the poly barrier film applied and then the sheets are ready for printing on the back side or barrier film side.
Dyne is the amount surface energy in your substrate and ink. The Dyne level is a very important factor to good ink adhesion to the barrier film. As a general rule the dyne of the substrate should be higher than the dyne of the ink.
Target Dyne levels:
- Corona treated polyester – range up to 72 dynes/cm
- Adhesion treated polyester – range 42 – 46 dynes/cm
- Untreated polyester – range 40 – 44 dynes/cm
Due to the multitude of finishing options, choosing the finish that best suits your projects needs may be overwhelming.
For more information, consult your printer or contact us and we'll see if we can help you find the answer.