TouchGuy_Basic

Do you have a question for Touch Guy?

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

Our team is developing a touch module for boats. This thing will be getting a healthy dose of sun, water, and sometimes saltwater. At the same time, it will need to do everything from finding fish to navigating the open seas, giving system diagnostics, and providing entertainment. I understand water can be a problem for touch screens. Why is that? What’s the best solution for me?

Ahoy Mate!

Nautical displays have traditionally topped the list of most difficult touch applications. It seems that boats and ships just have it in for touch. First there is the corrosive effect of salt water, so the legacy surface capacitive was out. Then there was the water itself, whether from rain or the stuff that floats-the-boats, which ended the possibilities for SAW, IR, and projected capacitive (PCAP). Resistive would work, but the internal reflections from the touch surfaces made sunlight readable displays really hard to pull-off and the image quality is really lacking. Plus, no multi-touch certainly makes it difficult to zoom in on that school of fish cruising 50ft below you.

So, Touch Guy picked this question as a vehicle for (unabashed?) self-promotion of his new PCAP Plus. It works great in boats, in fact, that’s what we developed it for in the first place. Rain, salt-water, and spilled coffee (or beer) are ignored. You get your pretty picture from that high-end LCD back. Even better for any military guys out there, now you can clamp down on that EMI so the display will not be a beacon for the bad guys missile (or maybe NSA spying). Right out of the box it passes both DO-160G and MIL spec 461. You retain the ease of multi-touch and get a system that will never wear out – whoa, you got it all. There is a small premium over standard p-cap, but PCAP Plus is a complete nautical touch display problem solver!!

Just remember the words of Robert Rose, “Ships are the nearest things to dreams that hands have ever made.”

-Touch Guy

I’m developing a touch based gaming unit and I need it to take a beating. I’m told that there is a difference in my options for coverglass on PCAP – that it’s easiest to have thick glass instead of polycarb – is this true and why is that?

Gamer Dude,

Touch Guy knows about beating on gaming machines, and not only the one he beat after it stole his money.. At one time, during the heyday of S-cap in gaming machines, TI was the largest supplier to the Las Vegas repair market; we have photos of bullet holes, deep cuts from keys and diamond rings, and a brick being tossed at an outdoor gaming machine in Europe. So we can help you make your machine super-tough.

P-cap has yet to become the dominate force in gaming machines, mostly because the market is not expanding as fast as it once did, and many casinos are holding on to their machines longer than they did in the past. However, compared to the existing S-cap and IR systems, P-cap offers a lower cost, more reliable solution. But you knew that, and are asking about the touch surface. In Touch Guy’s experience, based upon outside, unsupervised machines, (ATM’s comes to mind), you will find a tempered glass first surface to be your best choice. Tempered glass, is a very low cost material and can be laminated with a standard p-cap sensor all the way up to the level of being bullet proof (literally). Automobile windows are laminated tempered glass. Should your machine need a curved touch screen, this would be the way to go as well. Bring on the pounding.

Chemically hardened plastics have been remarkably improved in the last two years, some claiming scratch resistance equal to that of glass….we have tested and can confirm that is TouchGuy_Basicaccurate. Touch uses these magic plastics in products it is shipping now and our customers are pleased with the performance. However, we need to warn you that they are extremely expensive. As a minor consideration, the image from the display is not quite as good, and the touch sensitivity may be a little bit less good than with glass. If you are one of the lucky ones that does not have a weight problem, I mean your machine does not have a weight budget, lower cost tempered glass, even chemically strengthened glass, is a better choice than any of the exotic plastics.

If you have not read the white paper on hardened glass you might take a look at http://touchinternational.com/literature/Glass-Substrates-Whitepaper.html

However, if you really want to use those expensive plastics, you might as well consider TI’s soon to be release PCAP Plus, which will add pressure sensing and immunity to the cuba libre dumped on your new machine while preserving the no-wear, great image, and mutl-touch features of the p-cap solution.

Until Next Time,
Touch Guy

What is the difference between liquid optical bonding and dry optical bonding?

Mr. Inquisitive,

At last, a question testing Touch Guy’s expertise. Touch International is an expert in all of the ways to assemble and laminate p-cap touch sensors including OCA or optically clear adhesive using pressure and heat, DFA or dry film adhesive using vacuum and heat, OCR or optically clear resin, using heat and UV radiation, and two-part epoxy, using chemical cross-linking.

Optical bonding, however, is a process which attaches the touch panel (or other filter or overlay) directly to the LCD, filling the small air gap between the front of the display and the back of the touch panel. The reason one chooses an optical bond is to make it easier to read the display through the overlay, especially in sunlight, and most importantly to make the touch screen/LCD assembly more rugged, sometimes called the Army boot-kick test. Touch guy only does liquid optical bonding, so he had to seek expertise of others to discuss the advantages and disadvantages of dry optical bonding.

There are three common ways to do optical bonding which include a two-part Epoxy using a long heat cure, OCR using UV radiation, and dry optical bonding using heat and pressure. The names for the optical bonding methods are not the same processes for same names used for the optical laminations described above; dry bonding is the same method as OCA lamination, and OCR optical bonding is unlike the OCR lamination process.

Now that you have read all of that as background, the answer is that, if you get a properly manufactured optically bonded assembly, there is almost no difference between the three methods. Almost all of the differences have to do with the manufacturer which does the optical bonding for you. The differences are in cost of equipment, manufacturing time, space requirements in the factory, skill levels (none of the methods are easy to do), cost of materials, damage to LCD, design of overlay, and the ability to rework parts with blemishes.

Here is a chart which shows the steps for liquid optical bonding (OCR) and dry optical bonding (OCA):

optical bonding process

In addition to the optical bonding line in the US, TI has recently opened its new China-based clean room line for optical bonding consumer products.

Throw some more questions at me! I’ll be happy to answer any more, until then…
Touch Guy