Tag Archive for: Infra-Red

Can I hurt a touch screen by touching it? – Ben Harris, Cucamonga, CA

Ah Ben, the question we Touch guys have always feared. I assume your question is akin to asking, “Does it hurt a tire if you use it on the road?” However, I think what you really mean is, “Does touching the screen wear it out”?

Well in the early days of touch (1970’s), some touch sensors did wear out when finger oils, ladies’ hand creams and Hawaiian-breezes corroded the thin films. (Hmm, wonder what those creams did to their hands?)

Today, all sensors are advertised to withstand a minimum of 5 million touches. It is even rumored that the president of one unnamed touch company (Microtouch) hired a homeless guy to actually touch the screen that many times. Each of the technologies wear out differently and there is a difference between electrical wear (it does not work anymore) and cosmetic wear (the display is hard to read).

The newest entry into the touch arena is also the most vulnerable to electrical failure. When the in-cell technology fails, it is going to take your display with it, so it’s a double whammy on the checkbook. This happens because you must actually touch and depress the LCD surface itself, which puddles the liquid crystal and scratches the first surface. (Remember your mother telling you to keep your hands off the TV?)

Surface capacitive is the most vulnerable to electrical wear. Touching the same spot multiple times will actually wear through the thin film, down to the glass substrate, rendering it non-linear. Of course, a big scratch from a diamond ring will do-it-in quickly. And bye-bye to SAW technology when that same guy puts a big ‘ol scratch in it too.

In terms of electrical and cosmetic failures, resistive 4-wire touch screens are the most vulnerable. Touching in one place will rub a shiny spot in the hard coat of the top polyester (PET) layer. Touching in this same spot will also wear and crack the top conductive layer and leave it an electrical basket-case. The same number of touches on a 5-wire resistive will not damage it electrically; however the same glossy spot will appear.

In the end, the winners in the wear-me-out contest are projected capacitive (p-cap) and Infra-Red which work without needing to touch anything. Nothing to wear, no electrical surface to scratch and thus these two touch technologies can advertise infinite electrical life.

So Benny, as is the case with that tire, there are 10,000 mile touch screens and 1,000,000 mile touch screens, it just depends.

Until next time,
Touch Guy