Secindary Research - Flexography

Frequently used for printing on plastic, foil, acetate film, brown paper, and other materials used in packaging, flexography or flexographic printing uses flexible printing plates made of rubber or plastic. The inked plates with a slightly raised image are rotated on a cylinder which transfers the image to the substrate. Flexography uses fast-drying inks, is a high-speed print process, can print on many types of absorbent and non-absorbent materials, and can print continuous patterns (such as for giftwrap and wallpaper).
Some typical applications for flexography are paper and plastic bags, milk cartons, disposable cups, and candy bar wrappers. Flexography printing may also be used for envelopes, labels, and newspapers.

Benefits

• Because 100% of the material applied to the substrate remains after curing, there is potential to achieve greater densities than with conventional inks. Due to the higher viscosities, UV inks tend to stay where they are placed. Dot gain is negligible resulting in exceptional image sharpness. For that reason, UV inks work well for printing fine line, process and vignettes.
• Cured UV ink provides many desirable end use qualities including excellent rub resistance, chemical resistance, exceptional color consistency and superior gloss. Although functions of the pigment, UV inks also provide lightfastness and opacity.
• UV inks come press-ready. Consequently, set-up times are reduced and less waste is generated. UV inks also present another advantage in that operator involvement is reduced. There is less variability from operator to operator and press run to press run because the ink consistency is not manipulated at press side.
• One of the greatest advantages of UV inks is that they do not change consistency due to evaporation or pH. Without manipulation, the ink maintains consistency throughout the duration of a press run. UV inks provide additional benefits because the ink does not dry in the cells. Significant savings can be realized in terms of labor, consumables, anilox roll cleaning expenses, and roll refurbishment.
• With typical water and solvent based inks, evaporation results in a system where the constant is variability. Over time, the ink changes viscosity and affects lay down. Ink resins dry in the cells of the anilox roll resulting in further changes to the lay down. Press operators, attempting to correct for changes in ink density, add extenders and other additives to the ink. Degradation of the print quality results as the anilox roll continues to plug. The ink is further altered until its consistency has little resemblance to the ink the job was started with.
• Because of the tendency of traditional inks to plug the anilox rolls, it is necessary to pay extremely careful attention to press-side housekeeping practices. Even rolls idling for minutes can begin to plug. When this happens, the rolls must be removed from the press and cleaned with aggressive chemicals or harsh agitation action, either of which can damage the fragile engraved cell structure.
• Some water-based inks have a catalyst component. These undertake a chemical reaction that links the chemical structure to create an ink layer almost impervious to all but the harshest cleaning approaches. When these inks harden, they do not re-wet and predicate the need for the anilox roll to be refurbished at considerable expense.
• To reduce the likelihood or at least slow the process of cell plugging, printers must clean the rolls on press before each occasion when the press will be idling as well as between print. jobs. To purge the cells and plates of any residual ink and cleaning chemicals, the press is run until the web is clean. Over time, repetitive cleanings can result in substantial costs associated with waste materials and disposal.
• When the press is down for cleaning, it is not producing. Press operators and maintenance people have to spend their time manually cleaning the rolls. Manual cleaning is messy and time consuming and with the growing tendency toward higher cellcounts, often has limited effectiveness. Unfortunately, sooner or later even the best efforts at cleaning will succumb to cell plugging. This does not happen with UV ink because it stays wet and maintains consistency until it is exposed to concentrated UV energy. Over the course of a year, improvements in press utilization can be substantial.

Drawbacks

• Printing with UV inks does have some drawbacks. While some waste and maintenance costs are less with UV, start-up and operating costs are higher. Because the inks are not manipulated, print color is adjusted by the choice of anilox roll. This may predicate the need for having a wider assortment of anilox rolls in-house and more precisely specifying cell characteristics for a given print job. To shorten the learning curve, it may be advantageous to test print results with a banded anilox roll. In any event, switching to a new system invariably results in expenses, errors and waste until the system is understood and the parameters fine-tuned.
• Because UV inks do not dry, any small spill can end up being a large mess. Ink can be tracked from department to department on people's shoes. UV ink can damage clothes and irritate the skin. Some press operators even experience allergic reactions to UV ink chemistry. Care must always be taken to prevent direct contact with the skin.
• UV inks do not adhere well to some poly substrates. In order to raise the surface tension sufficiently to achieve good adhesion, the web must first receive corona treatment. Because UV inks are thick and do not flow easily, (the same characteristics that make them ideal for fine line and process work), they have problems printing smooth, consistent solids. This is particularly the case with anilox rolls engraved to 60 where the microscopic turbulence and surface tension result in extensive pinholing. There seems to be almost universal agreement the pinholing is reduced with a 30 cell placement pattern.
• UV inks require special lamps that focus UV energy onto the web surface. The purchase of the lamps represents a significant up-front capital cost. In addition, it may be necessary to purchase equipment to dissipate some of the heat from the press. Even daily operation costs tend to be higher due to typically higher energy consumption for the UV lamps. Printers already achieving desired print quality levels may wish to carefully consider if the potential quality improvements are worth the price.
• While the curing mechanism is the UV spectral component of the light, the lamps emit a significant amount of infrared energy. The IR energy offers no benefit and actually has the negative effect of inducing heat onto the web surface. During an idle cycle, the web can scorch and even break. This potential can be reduced and energy savings realized by adjusting the output power of the UV lamps relative to press speeds and ink thicknesses delivered at a given print station. There are many brands and styles of lamps available including parabolic, elliptical, surface-coated, water and air-cooled. It is important to specify lamps with reflectors suited to ink film thicknesses most often encountered.

This is a print created through flexography. This is a very crisp finish which you would not achieve through printing on to this material in most other ways. I like the bright block colours they have used with the design. This is therefore also good because it is waterproof and then ink will not rub off when wet etc...