Flexible Screens
Fold the world around you
I have grown up watching science fiction movies fantasizing about having a watch whose display goes around my wrist, a 13-inch laptop that can be folded down to the size of a diary, a smartphone which is also a tablet, and most of all a television screen which can roll to hide. But today, these aren’t imaginations anymore. Flexible display is the hero behind the transition of this technology from being a part of science fiction to reality.
Are flexible screens the future of smartphones, smartwatches, smart televisions & gaming industry?
Well, they are the future, but they have also been part of our past. Yes, the idea of flexible screens started way back in the 1960s, and research was done by Xerox PARC (Palo Alto Research Company). The first flexible display was made in 1974 by Nicholas K. Sheridon, a PARC employee, who then called it e-paper (electronic paper) display. Later, many others continued the research, and in 1992 the first flexible LED display was made by Santa Barbara Unix Corporation. These displays weren’t very bright and ineffective, but they laid the foundation for new age flexible displays that we are experiencing now. In 2014, Royole Corporation made the world’s thinnest OLED (Organic light-emitting diode) display with 0.01mm thickness and stated, “Foldable screens are the future.”
What held back the development of foldable devices for 5 years?
Before answering that, let’s go back into history again. Tech giants like Nokia, Sony, Samsung, LG, Xiaomi, etc. started their research and came up with conceptual models at the end of the 2000s. In 2013, Samsung came up with Galaxy Round, the first rounded, flexible AMOLED (Active Matrix Organic Light-emitting Diode) display mobile. Later, Samsung continued and pioneered the field of flexible AMOLED display. They came up with a curved edge display, which was a massive success in the market. This was done by attaching the flexible display to the curved base and gluing it to a curved glass layer.
Now, let us talk about what OLED displays are. Previously most of the screens were LCDs (Liquid Crystal Displays), though they were a huge step up from cathode-ray displays; they had some setbacks compared to OLED displays.
OLED displays are comparatively thinner, have high contrast, better colors, and have faster refresh rates. Each pixel produces light individually, eliminating the need for a backlight and thus making it potentially thinner. This is one of the biggest reasons for its bendability. The color of the light emitted by an LED depends upon the semiconductor and metal compounds inside it. In OLED screens, the semiconductor materials (like Si, Ge & Ga) are replaced by some special conductive organic compounds like Bis[2(diphenylphosphino)phenyl] ether oxide and Tris-(8-hydroxyquinolinato) aluminum. These are electroluminescent dyes.
The OLED is basically sandwiched between layers that transport electrons between an anode and a cathode. The anode is on the top surface and needs to be transparent as the light from OLED can pass through it. ITO (Indium Tin Oxide) is the most widely used anode. The OLEDs are built on a glass substrate with super-thin layers of the chemicals mentioned above deposited on it.
The substrate also incorporates a grid of thin-film transistors which make up the active matrix in Samsung’s AMOLED displays. And this whole thing is encapsulated in a thin layer of glass or metal because the compounds in an OLED breakdown in contact with air and are quickly degraded by water. As these require high temperatures like 1800 F, it starts damaging the glass layer when big screens are made. So, scientists found out new methods (Low-Temperature Poly Silicon) where this process can be done at 800F. And now, these temperatures are suitable to build the OLED on plastic. The Samsung Fold, the first foldable smartphone, is built on a plastic called polyimide, which is super heat resistant and can bear more than 2,85,000 folds. They use colorless polyimides for the front screen and orangish polyimides for the backplate. To be folded, the screen needs to be flexible, but ITO, the common anode used in OLEDs, is brittle and can break after a few folds.
PEDOT: PSS (Poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) is a super-thin transparent conducting material. However, it is hydrophilic (water-loving), it absorbs water when moisture is above 50%. It should be appropriately sealed to avoid damage. For this, Samsung SDI has developed optically clear adhesives for foldable smartphones, and these are responsible for holding everything tight.
Apart from innovation and necessity, the tech market is also concerned about portability, accessibility, and durability. The companies have given their best in innovating, solving portability issues, but there are still questions regarding availability and durability. Samsung unveiled its new phone Galaxy Z Flip, with bendable glass resolving the issue of sustainability.
I hope someday we’ll have flexible OLED skins, using which we can be a ShapeShifter or use it to blend into surroundings and have HARRY POTTER’S INVISIBLE CLOAK or one day become an actual HOLLOW MAN.
After using the OLED skin:
As said, Imagination has no boundaries and neither does technology.
Make yourselves ready to unfold the Foldable World.
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