Anti-glare • Anti-fingerprints • Anti-scratch • Anti-smudge
Is it possible to have them all? The simple answer, no, HOWEVER, there are things suppliers can do to get you pretty darn close.
First, determine what is more important on your membrane switch:
- Having a crystal clear display?
- Anti-glare surface?
- Survival in sunlight (if used outdoors)?
Crystal clear display vs. anti-glare surfaces:
Many companies want a material that is crystal clear while also being anti-glare. To ensure the display is anti-glare, a .007” thick anti-glare polyester graphic material is often used, the downside: it has a slightly matte appearance, which, as you guessed it...reduces the clarity.
There are fine and velvet (a slightly coarser texture) graphic materials, these have a textured hard coat that help resist fingerprints and smudges. If the part has a display window, a window ‘clarifier’ can be printed, this flattens the texture and gives the window a glossy finish. However, this window ‘clarifier’ does not make for a perfect display window - the ‘clarifier’ does not actually eliminate the textured surface, it just fills in the grooves in the texture, and adds a smooth, glossy look. The light passing through is still somewhat distorted by the original textured surface.
The preferred material for a graphic with a display window is polyester with a glossy hard coat. A textured hard coat can be selectively printed, leaving the window clear. This provides a much clearer window, while the printed texture hard coat helps resist fingerprints and smudges, however, it is not completely anti-glare.
Survival in sunlight:
One other thing to consider, is whether the part will be used indoors or outdoors. Parts used outdoors must survive UV light exposure from the sun. Long exposure to sun light will degrade the polyester substrate, turning it yellow and making it brittle. The only material meant to survive UV light outdoors comes with either a fine or velvet textured hard coat. So, if the outdoor part has a need for a non-textured display window, the only option is printing the window clarifier meant for outdoor use. As mentioned above, this does not create a perfect window.
All of the materials used for graphic overlays can have a hard coat to make the front surface scratch-resistant. If a selective texture is printed, that also acts as a hard coat.
How are these issues addressed for capacitive touch sensors?
Anti-scratch:
If glass is desired - regular soda lime and borosilicate (glass) can be scratched, Gorilla Glass® is more scratch resistant however, it can be scratched - below is a snippet about Apple investing $200 million to develop scratch resistant glass:
Apple to invest $200 million in scratch-resistant glass - May 12, 2017 by Adam Beam
Apple says it will invest $200 million in a rural Kentucky facility that it credits with rescuing the company's signature smartphone from a design flaw that would have led to scratched screens.
The California-based company announced Friday [May 12th] it would give the money to Corning Inc. to use at its facility in Harrodsburg, Kentucky.
Apple and Corning first teamed up 10 years ago when former Apple CEO Steve Jobs ordered the plastic screen on the company's first iPhone to be replaced with a scratch-resistant glass just a few months before the product was to launch.
Since then, Corning says it has made 552 million square feet (51 million square meters) of its Gorilla Glass product for iPhones and iPads, or roughly enough glass to cover 10,000 football fields.
"All of that work happened right here in Harrodsburg, and Apple owes you a big thank you," Apple Chief Operating Officer Jeff Williams told workers at Corning's Harrodsburg facility on Friday.
Williams said the money is the first of $1 billion the company plans to spend on US-based companies from its Advanced Manufacturing Fund.
"It's only fitting that the first commitment from that fund be for Corning and specifically for Harrodsburg, where so much of our history is," Williams said. Williams was joined by U.S. Senate Majority Leader Mitch McConnell of Kentucky and Corning CEO Wendell Weeks.
Read more at: https://phys.org/news/2017-05-apple-invest-million-scratch-resistant-glass.html#jCp
Standard acrylic can be scratched but there is an abrasion resistant version available. Xymox has yet to identify a distributor producing a AR (abrasion resistant) coated, 1.5mm thick acrylic sheet, as a standard product, so in the meantime, Xymox is producing 3mm thick acrylic lenses with an AR coating to customers that require it.
Crystal-clear display:
Kodak HCF material can be used for applications needing crystal-clear displays. Xymox processes Kodak HCF film coated with Heraeus PEDOT:PSS clear conductive polymer to produce a durable, flexible and transparent PCAP sensor.
Anti-glare & survival in sunlight:
Anti-glare and UV inhibitors can be coated directly onto the overlay material (ex: glass or acrylic), however, these can have a slight impact on clarity.
