Everything you need to know about flexible OLED displays

Samsung's Galaxy Round raises a lot of questions about what a flexible display is and isn't, what the word really means, and just what kinds of benefits a bendable display would bring to a smartphone or any other gadget.

We address your burning questions below, but if you have more, drop them in the comments.

Colloquially, "display" means the thing you see when you look at your phone and navigate around. But more technically, display refers to the electronic material that sits beneath the glass or plastic cover (the part you actually touch) and is responsible for lighting up your phone.

So when Samsung (or LG, or anyone) talks about a flexible display, they're talking about the organic light-emitting diode, or OLED, layer -- located beneath the cover glass -- that's now made using flexible materials (like plastic) rather than rigid glass.

Companies like LG and Samsung have spent years demoing flexible displays that sit on their own outside of any device. These eye-catching products faithfully show off the interface you're supposed to see -- say a grid of icons -- without bending or breaking. Samsung's Galaxy Round represents the first time that a phone maker is bringing a flexible display to market.

The Samsung Galaxy Nexus (and Nexus S) boasted a slightly curved screen that was meant to more snugly hug your cheek. In this case, it was the glass top that contoured, not the OLED material below.

No. For the Galaxy Round, Samsung is using a 5.7-inch "full HD super flexible AMOLED" display, but that doesn't mean it's going to flex in your hands. The device is deeply curved, but the phone's body is rigid and will not bend when you move it.

Part of the confusion stems from the many definitions of what flexible means. Like we mentioned, the flexion can refer to just the OLED or LCD, to the glass, or even to both.

Beyond that, there are many forms that a flexible display can take. In the case of the Galaxy Round, the display is conformable, meaning it's not flat. "Contoured" is another word that's often used.

Companies making such devices bend the display at some point, say vertically in the case of the Round, but then fix the whole caboodle in place. Another type of flexibility is "bendable." Think of these sort of like credit cards. They flex a little bit, but don't completely fold in half.

Then there's a third category, foldable displays, which do just what you think. Finally, there are rollable displays, often called the holy grail of flexible displays. To picture this type, just think about a perhaps less extreme version of a scroll, or a Fruit Rollup, and you can see where the concept's going.

As CNET has noted before, the benefits for a curved display like the Galaxy Round aren't immediately clear.

However, there are some pretty significant benefits for displays that can flex. For one, they could be more durable (especially when you drop them), largely because they might use plastic, which has some give, instead of glass. Plastic also can make the devices thinner and lighter, and it can allow for products in different shapes beyond the standard rectangular screen.

Note that this may not always be the case. Even plastic can break if you stress it enough, and glass-makers are also designing flexible glass, but more on that below.

Still, the durability issues raises the question: Why not just make a regular phone with a plastic display? We'll likely see that too, some experts say, but there are some things a flexible display can do that others can't.

Imagine being able to fold up your phone or tablet and put it in your pocket, or unroll a screen to serve as a map. These could even be incorporated into clothing or jewelry or other items where the screen needs to have some give. The future potential for flexible displays is huge if hurdles are overcome, even though we may not yet know exactly what their uses will be.

While some gadget-watchers are incredulous about the practicality of a scrollable phone, others see the benefit in trying to make them anyhow. NPD DisplaySearch analyst Paul Semenza is one of them. "I don't think anyone developing them knows the value of curvature or flexibility yet," he told CNET.

It takes much more than a bendy screen to make a phone you can flex. Right now, batteries and other circuitry are unyieldingly straight. The durability of a bendable phone and its internal parts are also in question. Depending on the design, you may need to have a flexible display, cover material (like plastic or glass), arching batteries, and forgiving silicon.

Some of this is already in the works. LG announced new battery tech for three kinds of juice packs that can curve, squeeze into tight spaces, and even contort like a pretzel. Time will tell if these produce and hold enough charge to competitively power a smartphone.

In addition, devices can be designed so they have a sort of rigid spine that stores the components that can't be flexed, while the rest of the gadget moves freely. We know that these various flexible designs are possible based on concept devices shown by Samsung and others.

Along with making the guts flexible comes another big challenge -- manufacturing these devices and displays at high volumes. Phones that move will undoubtedly cost more than standard smartphones when they first hit the market, but after the industry nails down more efficient manufacturing, the cost to make the phones will surely drop, along with their sticker price.

Even though the Galaxy Round's display is curved, not bendable, it's undoubtedly still tough to manufacture. That's likely a reason that Samsung is only releasing it in Korea (at least for now).

When companies show off displays being curved, bent, folded, or rolled, they're typically using OLED. While it's possible to curve an LCD, it's not as easy or as effective as curving OLED, according to the experts we spoke with.

LCDs, or liquid crystal displays -- the most common type out there -- are made of two sheets of glass that sandwich a liquid crystal material that modifies the light as it goes through it. They require a backlight of light-emitting chips to sort of pump light through the display. It's possible to curve LCDs, but is difficult because the distance between the two sheets of glass have to be consistent. Forget about doing things like rolling them up.

OLED, meanwhile, doesn't need chips to create light, and it only needs one piece of glass (or even plastic or metal) to serve as the substrate. Both these factors make it a better candidate for bending. OLEDs light up the screen with carbon-based materials that are deposited onto the surface, and that surface can then be shaped. Companies typically will add a second piece of glass afterward to protect the bottom layer.

We wish we could tell you for sure, but we just don't know yet. Samsung isn't sharing specific details, and none of the materials companies we reached out to would comment. There's some speculation that the company is using a plastic polymer screen, but it appears more likely that Samsung is using a thin layer of glass that has been bent into a curved shape.

Switching to a plastic display is what will allow a device to be truly flexible, but plastic comes with its own problems. It has different properties than glass, which means manufacturers have to find ways to use it without compromising the screen's crystal-clear image quality or responsiveness.

One big issue for plastic is that it's semipermeable, which could allow air and water to leak into the device. To avoid this, companies can coat the plastic and apply barrier layers, and some have experimented with glass/plastic hybrids. While there are still some hurdles to overcome, industry watchers say it's only a matter of time -- and money -- before this is no longer an issue.

"A lot of these problems can be solved with enough investment," said Sriram Peruvemba, chief marketing officer of Cambrios, a Silicon Valley company that makes technology used in flexible touch screens.

Not quite a year ago, CNET was the first to get its hands on Corning Willow Glass, an extremely thin, pliable glass that the Gorilla Glass-maker started developing in its R&D division. Corning described Willow glass as a material to go beneath and support the display, far away from tapping and swiping fingers.

Although we have yet to determine just how practical or even desirable a smartphone is that you can bend and twist, there are some good, practical uses for display technology that can be formed into S-curves and still respond to touch. Here's one: a wraparound touch display that covers the band of a smartwatch or other wearable. And here's another: an all-touch car dashboard that spills far beyond the confines of its usual 8-inch rectangular home.

Flexible displays -- on both the inside and out -- are going to be a hot topic in the months ahead. Whether gimmick or convenience, it's going to be fun to watch what happens next.

Source: CNET

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