Did you know that the graphic overlay (the top most layer of a membrane switch) is the most important layer? Sure the printed silver circuitry is extremely important, that is what makes the electronics work, however, the graphic layer is what tells the user where to push and what to expect. The graphic is the visual representation of the interface and is the only portion that the end user will see once a switch is mounted to an appliance, medical instrument or industrial control panel.
The graphic layer is screen printed – each color will have its own layer and each color will be perfectly color matched to the customers requirements.
There are two different kinds of inks that are typically used, conventional graphic ink and UV graphic ink:
Conventional ink
The chemistry of conventional ink contains evaporative solvents, pigments and binders which need heat to drive solvents out of the ink to harden – or dry. Conventional cure ovens use radiant heat. Like an oven at your house, they can be gas or electric.
UV ink
The chemistry of UV ink contains the pigments, binders and a photo initiator. When the ink is exposed to a certain light wavelength the photo initiator will start a cross linking molecular chain reaction which caused the ink to harden – or cure (no solvents comes out in the curing process, it’s a chemical reaction).
Side note: Drying time for conventional ink is measured in minutes, curing time for UV inks is measured in seconds.
The majority of the graphic overlay designs that Xymox prints use UV ink. Why you ask? UV ink contains no solvents which means:
- The ink is more environmentally friendly
- no solvents emitted into the air
- less energy is used to run the curing unit opposed to the gas tunnel oven used to dry solvent based inks
- Fine detailed printing will not dry on the screen during the screen printing process
- Because there are no solvents, the viscosity of the ink will not change on longer running jobs
- Because UV inks cure significantly faster, “drying time” is not a bottleneck for throughput. Basically, presses could run a lot faster
However, when customers want a backlit graphic, conventional ink is typically the ink of choice because it is more opaque than the UV graphic ink which helps the graphic better control and direct the backlighting to the areas it is intended to be seen.
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Xymox had a 35+ year old conventional radiant heat oven, until recently, it was replaced with a newer version to ensure nothing stands in the way of getting products through the factory and to our customers! Check out the 6 hour removal process, sped up to just 10 seconds!