UV Curing Applications For Printing
UV technology... open a whole new world of possibilities
- UV Flexo Printing
- UV Offset Printing
- UV Cold Foil Printing
- UV Lamination
- UV Rotary & Flatbed Screen Printing
- UV Coating
- UV Inkjet Printing
The world of UV curing opens up many doors to new markets and provides converters with green alternatives when using UV curing technology. UV cured inks, coatings, adhesives, silicones and specialty coatings provide outstanding physical and chemical properties which are paramount in the success of most UV curing applications. Medium pressure mercury vapor and metal halide UV lamp chemistries are ideal for use in UV cured print applications including UV flexo, UV offset, UV screen, UV coating& UV inkjet applications. UV curing technology promotes outstanding environmental and waste saving benefits which most governments recognize as "Green" due to the fact that they dramatically reduce the emission of harmful Volatile Organic Compounds (VOC's).
Ultraviolet Curing has been employed successfully for over ten years in the flexographic printing industry, as it offers outstanding print quality compared to solvent or water-based ink systems. UV flexo printing uses 100% solid ink systems which include monomers, oligomers and photo-initiators that when exposed to intense ultraviolet light provide outstanding durability, chemical resistance and graphic brilliance well beyond that of water or solvent ink systems.
Offset printing has largely been used in commercial applications with high volume print runs that require high quality graphics. In recent years, many commercial web and sheet fed offset printers have chosen to utilize UV curing technology as a means to improve production throughput and print quality. Standard offset ink technology typically takes more than 24 hours to dry prior to being converted or die cut to prevent ink smearing and ink transfer on to the opposing side of the substrate. UV offset ink systems are similar to that of UV flexo ink systems in that they employ the same three
For many years, converters have been utilizing rotary hot foil stamping to decorate labels, cartons and flexible packaging. This process requires an investment in expensive etched and engraved rotary hot stamp dies to transfer the foil image to the substrate.
Today, many printers employ UV cold foil transfer as a means of decorating the substrate with colored foils. This process involves the following steps:
- Printing an adhesive in a flexo print station on the base substrate using a photopolymer printing plate that has the desired foil design.
- The adhesive coated substrate is brought into contact with the colored foil or holographic film through a nip roll assembly.
- The laminated substrates are directed through a UV curing system to cure the adhesive permanently bonding the two substrates together in the areas where the adhesive was printed.
- Finally, the two substrates are separated leaving the foil image adhered to the base substrate while the foil waste is rewound.
There are significant cost savings to this method of foil decorating as there is no expensive “Tooling” to purchase. A converter only needs a flexo plate, adhesive, cold foil film, a laminating unwind, a nip assembly, a UV unit and a foil rewind. Since most flexo equipment already includes the auxiliary unwinds, rewinds and UV, the balance of the costs are nominal.
Ultraviolet Curing has many benefits to converters that desire to improve overall product quality as well as reduce material and manufacturing costs. Many converters must laminate the printed or converted product to protect it and enhance the image. Traditional lamination involves unwinding a laminating film that has pressure sensitive adhesive on the back side of it so that it will adhere to the base substrate when nip roll pressure is applied. Pressure sensitive laminating film can be quite expensive and is typically supplied as self-wound or with a liner.
UV Lamination offers significant cost savings as the processes uses only wound film and a UV laminating adhesive. This process involves the following steps:
- Flood coating a UV adhesive to the base substrate using a flexo print station and a rubber tint sleeve.
- Unwinding the laminating film and bringing it in contact with the base substrate using nip roll pressure.
- Directing the laminated materials through a UV curing system which cures the laminating adhesive through the film creating a permanent bond
This process allows converters to save significant material costs while creating a more permanent chemical bond between the two substrates.
Rotary screen printing has improved the quality and aesthetic appearance of many printed products we see in the consumer market today. Rotary screen printing is typically used in-line with flexo or web offset printing to apply brilliant colors, opaque whites or specialty coatings for printing and security applications. Rotary screen printing is similar to flat screen in that a viscous ink is forced through the openings in the screen mesh where the emulsion is not present. The main difference is that the screen material is made into a cylinder by seaming the leading and trailing edges together and attaching it to a precise set of end rings and gears. The squeegee is then placed on an adjustable bar inside the screen cylinder on the same access as the impression roll to force ink through the screen and transfer it to the substrate. In-line applications are best suited for UV cured ink systems due to higher line speeds and the requirement of 100% cured ink so that water based or UV inks can be printed over them. Typically, in-line presses utilize special screen printing UV lights at 600 WPI or metal halide UV bulb chemistry to achieve optimum results.
Most high quality printed products are either laminated or overprint varnished to protect the printed product from harsh chemicals or abrasive elements, while providing outstanding shine and brilliance for higher aesthetic properties.
Inkjet printing is a primary source for printing variable information on almost any substrate such as consecutive numbering, lot numbers, batch codes, personalized information and many others. This technology has largely used solvent based ink chemistries over the years which provide lower inkdensity resulting in relatively dull colors.