TouchGuy_Basic

Do you have a question for Touch Guy?

Send him an e-mail at asktouchguy@touchintl.com.

Would an “iPad” type touch screen work in Antarctica?

Dear Mr. Abominable,

You are not alone in the cold my friend. First, this “iPad” type touch screen you are referring to is using projected capacitive (PCAP) technology. Without diving into detail, a “touch” is sensed when you make contact with the screen, basically grounding out the circuit. That’s right, no matter what anyone has said about your personality, make no mistake that you sir are electric. The problem in Antarctica isn’t so much the temperature, it’s the fact that you certainly do not want to take off your gloves in those temperatures. Now, quite a few companies manufacture “phone friendly” gloves with a little strip of conductive material woven on the pointer finger from the inside out to bridge the gap from finger to screen. Maybe I shop at the wrong places, but most of these gloves seem a little light for sub-zero death freeze. Since that may not be an option, some PCAP screens can be tuned to handle gloves – but again, it’s the thickness of the material separating man and machine that gets in the way and can result in an overly sensitive touch screen when the gloves come off.

I apologize for throwing my “sales guy” hat on in advance, but let’s switch gears and talk new technology. For this exact reason (ok there’s a few others) the mad scientists here at TI have developed a new technology that gives your freezing fingers the freedom to be covered in any glove you choose and still get the benefits of a multi-touch interface on whatever device you’re using. It’s called PCAP Plus. I don’t want to drill down too far, but what we’ve done is combine the best of resistive touch screen technology, with the features of PCAP (multi-touch, gesture, etc) and created “Frankenscreen.” Ok well I wanted to call it “Frankentouch” but they wouldn’t let me. Now there are far more benefits than just using gloves with this new technology, especially for the military, but for you and whatever device you may be trying to develop here – this is the technology for you.

While touch may be a pita while roaming the frozen tundra, I think you may be overlooking a potentially bigger problem – the display. LCD’s and I have a lot in common – we’re square and we don’t like the cold. The colder it gets, the longer it takes for your LCD to display an image, and the dimmer your image gets. If you dip to around or below -35 degrees C, you can have permanent display damage from the liquid crystal actually freezing. Fortunately, there is a solution around this problem. Transparent heaters (sometimes simply referred to as LCD heaters) are exactly what they sound like. We take a piece of glass, coat it in a conductive material (most commonly ITO) and then give it power. You can tweak the coating depending on how much power you need and how big of a display you have. The heater is then bonded to the LCD using a UV curable, optically clear adhesive. Finally, your touch screen is attached on top of that (most likely using the same adhesive), creating a sandwich of functional touch display goodness. This will keep your display nice and toasty while you freeze to death, giving you the “instant on” that I’ll be getting from my iPad in the comfort of my living room.

So, pioneer of the great frozen unknown, I hope I answered your question and then some. Now if you’ll excuse me, I have sudden urge to make hot cocoa and s’mores.

Cheers to the good life,
-Touch Guy

Hey Touch Guy, I’m working on a sort of digital signage / kiosk type application that will hopefully be everywhere from hotel lobbies to office buildings. The plan is to start out around 32” and eventually grow to 60”. I’m thinking I want Projected Capacitive for the touch screens for all the usual reasons , but people are telling me optical touch is the way to go due to size. So who’s right and what’s the best? PCAP or optical? -The Sign Guy

Hey Sign Guy,

The big ones, usually defined as over 32 inch LCD’s, have long been the domain of optical systems with an occasional sighting of an acoustic (external and internal noise generator) or surface capacitive sensor, as well as a smattering of the other touch technologies. Optical is defined as IR beam or corner camera type. Recent advances in optical touch systems have added the ability to do multi-touch which had been one of the drawbacks. Frankly sign guy, optical is your best choice today. But do not sign any long term commitments. The market wants p-cap with pen for large format displays. Why, you inquire? The same reasons the small display guys want it….low cost, high reliability/durability, multi-touch, gestures, and good image quality – in addition to the twelve other things people like about the technology. The holy-grail of big formats seems to be white-boards (think every school room and meeting chamber) as opposed to the slow growing digital signage market (for touch displays). But, as Touch Guy has pointed out, p-cap has changed the sleepy old days of resistive touch manufacturing to major advances every six months…..that 82 inch, $35,000 p-cap touch panel you saw at the trade show last year will be in your budget within 12 months. Already 32 inch p-cap is common and cheap, due to advances in the materials, IC’s, and manufacturing techniques. Passive pen is not quite ready for the big ’uns yet, but when it is, Touch Guy advises you buckle your seat belt.

Until next time,
-Touch Guy

I can’t seem to find a straight answer on this. What are the differences (if any) in anti-reflective, anti-fingerprint, anti-smudge, and anti-glare?? Every piece of information I find ends up as a sales pitch. Can you clarify things for me?

Touch guy thought that the new fad of taking and sharing selfies meant everyone wanted to see themselves (a lot), so he wonders why there are so many requests for anti-reflective/anti-fingerprint films (AR/AF) on his products. He is so out-of-touch (haha). Ok, enough cracking myself up.

What customers want when they ask for AR coatings is to reduce the ability to see oneself when looking at the display, especially when you are outside. Ultimately, AR coatings make the display easier to see.

In legacy touch products, glare reduction was done using anti-glare (AG) coatings. AG treatments are made by either coating the touch surface with silica “bumps” or lightly etching the glass. The result is that some of the light hitting the touch surface is diffused or scattered, and not reflected back at the user. This was good enough for 25 years of touch technology.

Then along comes Apple and their beautiful high resolution displays to upset the cart. To preserve that super display image, polished glass was used on the iPhone instead of the traditional AG treatment. It is kind of OK for mobile devices because you can tilt the surface to reduce reflections, but less easy to “fix” on bigger devices such as pads.

So the market is asking for something that reduces reflections but preserves that pretty little picture on the display. This has traditionally been done using anti-reflection treatments. Reflection reduction can be achieved in a number of ways, including moth-eye treatments, circular polarizers, eliminating the reflective surface, or that which I will talk about, multi-layer thin film interference coatings.

AR thin film treatments work by “trapping” the light. OK, English majors, stay up with me here….if you took a physics class you know that most energy can be represented by a wave of peaks and valleys (sine pattern). In your physics class you probably also played with a 3 by 5 card with slits, or (as touch guy did) a wave generator made of Popsicle sticks which showed that light can “cancel” itself. Angstroms wide thin films, made up of multiple layers of transparent materials, are put down (on the touch surface) to a precise thickness relative to a visible wave length (550nm) so that light (from your smiling face) passes into the thin film, reflects on the touch surface, and then is reflected back on itself by the thin film, and, as if by magic, the reflection is gone (canceled). Another benefit of AR coatings is that because the light is not reflected, much more light from the display passes through the AR coating so the display is actually brighter. (OK, physics majors, I know this is not a compete explanation, but I might have lost most readers by now)

Touch Guy finds that customers want less than 1% of the light (your pretty face) to be reflected, and that is pretty commonly (though still not cheaply) achieved. If you have enough money (and don’t mind parting with a chunk of it), you can get an AR stack to have less than 0.1% reflection. It used to be that only a few companies could make production quantities of AR coated material but the demand for this stuff has dramatically reduced the cost and increased the number of suppliers, both on plastic and glass.

There are two problems with AR coatings on touch screens. The finger print problem has been fixed with anti-finger print (AF) coatings. Recalling the description above, you know that the thin film coating must be the precise thickness of a light wave (say ¼ of the width) to work. Along comes your dirty, oily finger tip, laden with hand cream, to touch the screen. Boom, the oil you left on the AR coating has changed the thickness of the coating which reduces the ability to trap the light and most often shows up as a finger print. AF coatings work by resisting the ability of the oil on your finger to “stick” to the AR coating; these are called hydrophobic (fear of water) coatings. Of course, for the AR coating to work, the AF coating must be built into the precise thickness of the thin-film stack. Touch Guy is not impressed with the after market spray-on AF coatings over AR stacks. Not impressed at all.

AR problem number two is that it wears off…think about it, angstroms thick material in an abrasive and chemically active environment, and you have limited time before its anti-reflection properties go away, especially on frequently touched areas. There seem to be two solutions…the first is that the AF coating on the AR stack is made of (secret) tough material that will wear-off your finger tip (just kidding) before it gives up. The other is to use thicker, but less effective (2% reflection) organic AR coatings, that seem to have better resistance to finger wear.

Another way around the AR wear problem is to eliminate the reflective surfaces in the first place. Touch International is a big supplier of optically bonded (touch panel to display) products which increased the ruggedness of the display while eliminating the internal reflections. An AG coating and an optically bonded p-cap touch panel eliminates the wear, and anti-finger print issues, with only a minor loss in display sharpness. And the new p-cap+ product has a secret method of AR reduction.

Until next time,
Touch Guy