Flexible Display is a kind of the holy grail for the display indsutry as it is a revolutionary form factor change, which can bring extremely new value for the devices. But the challenges for making a flexible display is always there. Polymer Vision in 2007 unveiled the Readius, the world’s first prototype of a functional e-book reader with a roll-up screen (4.5-inch electrophoretic display with a resolution of 320 x 240). However, initial awe and fad over e-book readers and electrophoretic displays waned as commercial demand in smartphones and tablet PCs started to evolve entirely around high-definition LCD and OLED displays in 2008. The innovative Readius was chucked away before it formerly debuted on the market.
A foldable display again stepped into the limelight at the Consumer Electronics Show (CES) 2013 when Samsung Electronics Co. unveiled a demonstration video on a tablet with foldable OLED display technology. Since then, a number of companies rushed to showcase various prototypes with foldable OLED displays in exhibitions and conferences. A few panel makers even pledged to mass produce foldable displays by 2016, indicating that the race is in full swing on the foldable OLED.
In what forms will foldable displays be available in the near future? First of all, it is important to gauge demand from set makers.
The concept foldable tablet PC Samsung Electronics unveiled in 2013 was a tablet with smartphone features. This device allows a relatively heavier and bulky tablet to be folded into a regular smartphone size. When the device is folded once (1-point folding), the separated smartphone screen is placed on top, and the screen of the foldable display of the tablet would go inside (in-folding).
What matters is the screen size and radius of curvature, or the size and thickness of the display to support the design and function of the hardware. For example, an 8-inch tablet becomes 6.1 inches when folded once and 4.6 inches when folded twice. The smaller it becomes, the better it will be as a tablet-smartphone hybrid. However, the display could become thicker when folded several times. The size and thickness of the device would hinge on how many times the display is folded.
The next important factor to consider is the direction of the folded display – or whether the screen is facing out or in when folded (out-folding or in-folding) that directly affects the design of an application. It also can determine the device’s exposure to external tensions. An in-folding feature would require lower curvature than out-folding embodiment to keep the two sides of the display close, suggesting that the folded direction could affect the display’s durability, internal structure, and materials.
Another factor that can affect the device design depends on where and how many hinges (the number of points) go on the display in completely folded state. Along with the folded direction, the hinge location on the device can be mostly affected by repeated stress. It is important to note that most of the early defects in foldable feature phones that came out about a decade ago stemmed from hinges.
Lastly, it is important whether to maintain the same pixel per inch (PPI) across the smartphone and table screens. When the two displays are separate as in the concept demo Samsung Electronics had released, they would come in with different PPIs. When the smartphone and tablet screens are physically in a single display, the PPI should be identical. However, since a PPI of premium smartphone’s display generally comes in higher than that of a tablet, whether the phone-tablet hybrid device comes in single or dual screens could again determine the specifications.
Meanwhile, interest in oxide thin film transistor (TFT) technology increased with Sharp Corp. agreeing to supply 9.7-inch oxide-TFT LCDs for Apple’s iPad in 2012. LG Display Co. also started to manufacture 55-inch OLED displays for LG Electronics Inc. in 2013, heightening expectations that oxide TFTs can become the next phenomenon that may change the paradigm in the display market.
So far, application of oxide-TFT displays on the key display devices such as smartphones, tablets, monitors, and TVs has been lower than expected. Overall capital investment in the oxide-TFT display fabs has been also below expectations. The recent rapid development in the display industry can explain why oxide-TFT technology could not be in more popular use.
Foldable display market forecast
The flexible display market that started with e-paper technology has reached a new turning point in terms of technology through the mass production of flexible OLED displays in 2013. Still e-book readers, bendable smartphones, and curved smartphones employing flexible display technology remain as niche markets. Various factors, including design, durability, and differentiated features that can determine the success of a display application as much as the screen technology, still lack in flexible form.
Once foldable OLED displays are mass produced in 2016 as planned, it is important to make sure foldable applications can offer maximized usability of foldable display technology so the flexible display industry can be taken to a new level.
The Flexible Display Technology & Market Report – 2015 published by IHS forecasts foldable displays to take a 51.9% share in the entire flexible display market in 2020 because application of foldable displays is expected to increase gradually across a wide range of mobile devices such as tablet PCs and smartphones starting from 2016 in a bid to enhance the mobility of such handheld gadgets.
David Hsieh is a display senior analyst for IHS
Posted on 20 September 2015