Tag Archive for: touch screen

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?

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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 display 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 wavelength (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 complete 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 fingerprint problem has been fixed with anti-fingerprint (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 fingertip, 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 fingerprint. 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 aftermarket 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 fingertip (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-fingerprint 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

Q&A Session with Mil/Aero Sales Engineer James Hunt

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What excites you most about diving into touch screen manufacturing?Mil/Aero Sales Engineer James Hunt
The touch screen industry itself is exciting because one can relate to the various applications in everyday life. Almost everywhere we go we encounter touch screens – supermarket, bank, doctor’s office, casinos, airport – the list is virtually endless.

In terms of touch screen manufacturing, it is interesting because every solution is different and comes with unique considerations and challenges. For the military, the important touch screen attributes are generally high optical performance and high reliability. Other segments require high volume and low cost. We encounter a wide array of needs and requirements that often vary by industry or application.

Another exciting aspect of Touch International right now is our improvement plan to the Austin facility. We have undertaken facility upgrades which include a new clean room, and are implementing processes to transfer our company into a lean organization which will ultimately better serve our customers.

What role do you see Touch International playing within the Mil/Aero market space?
Our role is not only to provide products to this market but also to help our customers find solutions throughout the concept, development, prototype and volume production stages. This process is even more important for the military/aerospace segment because of higher standards invoked on products from a reliability, performance, and traceability perspective. We see ourselves as a key custom solution supplier for these market segments.

Where do you think military electronics are headed in 2012 and beyond?
In terms of traditional military platforms, we expect to see some contraction in the electronics market. Having said this, Touch International does see opportunities in the existing platforms as well as new technologies being implemented in the same sector.

I do anticipate seeing a rise in the deployment of touch technology in military applications. Touch technology has proven itself to be highly versatile, and applications for touch screen devices are virtually countless. Although touch screen electronics have been in the mainstream for quite some time, military devices take a little bit longer to develop.

While there are many military applications for touch technology, one of the most obvious is the ability to communicate through mobile phones and touchpads. In recent weeks, US government agencies and contractors have publicized the development of secure software run on Android-based touch screen devices to be deployed to soldiers in the field. By providing soldiers with this kind of touch-enabled device, classified information containing the location of infantry or potentially dangerous areas can be sent directly to the soldier on a digital map.

This breakthrough is just one example of how touch screens are becoming a requirement in military electronics and provide key advantages in the field. Whether it is a large-format touch screen being used to view maps at a regional command post, or one of the thousands of hand-held devices used in the field for communication, or part of the control panel inside of an MRAP vehicle, the possibilities for touch technology in military electronics are virtually endless and will enjoy growth across the board.

What is Touch International working on right now in terms of military solutions?
The military is always seeking to have the best-trained soldiers, using the best equipment and the latest technologies to accomplish its mission. To that end, our goal is to provide award-winning touch screen and LCD enhancement solutions that meet these needs. In 2012 Touch International is focused on building sunlight readable displays with EMI shielding and a full bond to LCD solution; this solution provides optimal visibility in changing light conditions, noise suppression to remain undetected, and a ruggedized display to ensure accuracy even during challenging environments.

I am in need of an oddly-shaped, custom projected capacitive multi-touch display that is waterproof, able to work with varying pressure, and provides maximum velocity for input acquisition and transmission to controller. The dimensions of the sensor need to be 460mm long and the widths need to be 42mm and 58mm respectively; the boarder must be narrow at 1-2mm (maybe made of plastic or aluminum). It is also important that the electronics work with Linux.

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I have made mention of how we propeller-heads love the challenges you crazy design engineers give us. But, as exotic requests go, you have thrown us a soft ball. In the old days of resistive and surface capacitive, we have made Cartesian touch sensors that were circular, triangular, spherical, and even a hexagon or two. So your request is quite “doable”.

Recall that multi-touch projected capacitive is a digital technology that generates a high resolution analog coordinate from the row/column intersections. Within reason, the lengths of the rows or columns do not need to be the same. So making either end shorter will not change the output….just TouchGuy_Basicsome of the coordinates will not exist where there is no sensor. Some projected
capacitive electronics work best with different (invisible) ITO patterns, so you will need to pick one that anticipates your strange-dimensions, usually streets-and-alleys, diamonds, or snowflakes…..avoid telephone poles, zigzags, triangles and rings. But odd shapes – they do not trouble us.

So much for non-uniform dimensions, but now to the bigger problem….your one or two
millimeter border. First, I need to understand if you truly have such limited space at the edge. Almost all p-cap touch sensors have a top layer, called a cover glass or cover lens, which usually has an opaque ink on the back to hide the circuitry and replace the bezel, enabling in a flush
design. The opaque ink must be at least as large as the inactive border area, and usually is much wider. For a sensor that is 460mm long, it seems unlikely that you would only be allowed such a tiny edge area. Thus, me thinks you should have a traditional bezel and allow yourself more room.

However, if you persist…..you probably know that all touch screens need a border to deliver
signals to the sensor. In the case of p-cap, there needs to be one signal delivered to each row and column, which, for a 460mm length would be about 65 signal lines in the long dimension. The minimum width of these signal lines is usually 30 microns with a 30 micron separation between the conductive traces. You do the math, but you can see that you simply cannot fit that many signal
lines in 1-2mm space. Touch-International’s solution is to put the signal lines on a flex tail and bond that tail to connecting pads at the edge of the sensor glass. Rarely, we have also drilled holes in the glass and connected via the back, but bring your checkbook for this solution.

You have me wondering what you mean by extreme velocity….here in Texas, everybody is
packing and “extreme velocity” means a bullet is headed your way. As much as I want to say PCAP will last forever… when it comes to target practice, I am lying. However, we can use up to 6mm tempered glass if you are expecting trouble.

Until Next Time,
– Touch Guy