UV-cure liquid coating technology has been around for years. Primarily used in the lithographic and screen printing industries, UV-curable liquid coatings were also used to either achieve a specific, finished look or to provide abrasion protection to printed images.
“Originally, the coaters on the market 10 years ago were pretty straightforward—basic three-roll transfer coaters if you will, coupled with secondary, independent curing units that offered little versatility in what you could do with them,” says Jim Tatum, owner/managing member of Advanced Print & Finishing Technologies (AFT) in Hickory, North Carolina. “The result was that these devices quickly became outdated and somewhat unusable except for the very basics of liquid laminating.”
New Class of Coaters
Tatum says more recently there is a need for greater versatility to match a wider spectrum of markets that are adopting UV print technologies, and this has ushered in a new crop of UV coaters that feature a bevy of options and capabilities.
“The UV-cure coaters on the market today have to be able to handle a much wider gamut of potential issues from soft-cured inks—which can offset when trying to coat them—to working with an ever changing range of substrates from PSA vinyl roll stock and wall coverings to aluminum and rubber composites to glass/Plexiglas,” he says. “There is also a trend in offering more high-tech features that make life easier on the operator and ensure a greater sense of reliability and job consistency and repeatability through automated process control features such as application or job memory creation and intuitive control systems that even alert the operator to when maintenance is required on the machine.”
The Process
Tatum says UV-cure coaters work differently, depending on the type of coater used. There are four basic types: a slot die coater, a curtain coater, a reverse roll coater and a standard three-roll coater.
- Slot-Die Coater—Uncured UV coating liquid is routed into a chamber and forced through a special die that is output in a specific amount and deposited onto the substrate that runs beneath it.
- Curtain Coater—Uncured UV coating flows through a specifically sized slit in a bar down in front of the substrate between a gap in the transport belts. This creates a curtain of coating through which the substrate is fed.
- Reverse Roll Coater—Uncured UV coating liquid is transferred from a supply tray through a series of rollers and ultimately is transferred onto the substrate by an application roller running back against the substrate.
- Three-Roll Coater—Uncured UV coating liquid is jetted into a valley between two rollers and is transferred down onto the substrate running beneath it.
Certain features allow for control of lay-down thickness and smoothness with each of the coater types, which is essential for today’s graphics providers. The coated product is then fed into a curing unit, introducing the coating to a specific range of light waves (ranging from 280 to 365nm, depending on the application) that instantly cures the coated product at speeds of up to 100 linear feet per minute and either output onto a table, in a bin or onto a take up roll, depending on the feature set of the coater.
Applications
Tatum points out some of the more typical applications include: gloss, satin and matte lamination to standard banners, decals and standard rigid signage. Other, lesser known applications include creating dry erase boards and wall maps, antimicrobial/chemical resistant panels for highly traveled public spaces like hospitals, printed pool liners for in-ground and above-ground pools, fire retardant surface treatment, tactile surface treatment for membrane switches, providing alternatives to powder coating on metal surfaces, stampable/writable surfaces for underwater applications, creating custom water marks or security markings and protective coatings for leather surface treatments and more, he adds.