Myoung-Seop Song

Low-Power Flexible Organic Light-Emitting Diode Display Device

Demands in extending fl at panel approaches to attain ultra-thin fl exible displays, which are lightweight, portable, and unbreakable for head-up displays, security identifi cation documents, conformable products, and electronic papers are ever increasing. [ 1‐3 ] A typical fl exible display comprises two major parts: i) driving circuitry to switch and address the display device, and ii) a fl exible display device to display an image and enhance outdoor readability. Signifi cant progress has been made in achieving stable rollable or bendable driving circuitry based on flthin fi lm transistors (TFTs), such as oxide transistors based on gallium indium zinc oxide (GIZO) [ 4 ] or hafnium indium zinc oxide (HIZO), [ 5 ] low temperature poly-Si (LTPS) on a plastic substrate (polyimide), [ 6 ] nanotube and nanowire-based transistors, [ 2 , 7 , 8 ] and organic thin fi lm transistors (OTFTs). [ 9 ] On the other hand, challenges to integrate a fl exible display device to realize full-color, low power, and outdoor readability have still not been addressed. Liquid crystal displays (LCDs) are widely used to fabricate commercial displays, but their optical system to switch a light source (backlight unit or light-emitting diode (LED) through a red/ green/blue (RGB) color fi lter) consists of a constant thick layer of liquid crystal molecules aligned between electrodes, and two polarization fi lms having the axes of transmission perpendicular to each other. Bending a LCD causes liquid crystal molecules to deform. The light that passes through the deformed liquid crystal molecules and two surrounding polarizing fi lms with perpendicular polarization axes is distorted causing display malfunction. In comparison, OLEDs do not suffer from such bending malfunctions, which makes OLEDs strong candidates for integration with fl exible electronics to achieve fl exible color displays. Current-generation OLEDs can afford a high performance and fl exibility, but this technology requires a polarization (POL) fi lm to enhance the contrast ratio for outdoor readability, and glass encapsulation to protect the OLED from oxygen and water. The fragile nature of these components limits their utility in fl exible OLED display devices. An advanced material to overcome the fragile components is required to allow the fl exible properties. In order to achieve a highly fl exible OLED display device, the following characteristics are needed: i) a low temperature process to prevent deformation in plastic substrates, ii) a new optical architecture providing both fl exibility and high outdoor readability, iii) a thinner and lighter platform than for current OLED technologies that allows bending and folding, iv) mechanical and electrical stability during repetitive folding, and v) optical reliability without malfunction from an ambient environment, especially water and oxygen.

18.4: A New Seamless Foldable OLED Display Composed of Multi Display Panels

A new seamless foldable OLED display composed of multi display panels is proposed. To verify seamless viewing and robust folding-unfolding reliability, a 138 ppi resolution, 5.4″ diagonal size AM-OLED seamless foldable display prototype is fabricated.

7.3: Auto-Stereoscopic Swing 3D Display

We have developed auto-stereoscopic swing 3D display for the first time in the world. It makes us to feel stereoscopically the images of portrait and landscape mode simultaneously by rotating the display. We have designed a black and white liquid crystal display as parallax barrier so that it is convertible electrically between 2D and 3D mode. We have used 2.2″ QVGA AM TFT LCD as 2D imager for mobile application. To improve 3D image quality we have designed and developed the various patterns of liquid crystal barrier and to improve 3D brightness we have designed and developed the new backlight schemes of LCD module.

55.2: Auto-stereoscopic 3D Display Apparatus using Projectors and LC Image-splitter

We have developed a prototype of auto-stereoscopic 3-dimensional display system with 2 projectors and new LC Image splitter. We use two LCD projectors, one for the right and the other for the left stereoscopic image. The polarizations of light from each projector are perpendicular to each other. We specially designed a projection screen comprised of Fresnel lenses, LC image splitter and lenticular lens to separate right and left images for certain ranges of viewing angle.

P‐50: 42‐inch PDP Autostereoscopic 3D Display

We have made a 42-inch PDP autostereoscopic three-dimensional display. A sheet of lenticular lens is placed in front of a 42-inch PDP of full color XGA. The surface temperature of a PDP can be high during its operating times. The pitch of lenticular lens may be expanded. It makes an undesirable problem of deteriorating the 3D image quality. To overcome this problem, we have developed a 3D simulator to design a lenticular lens properly and measured the thermal expansion ratio of the lenticular lens and the surface temperature of the PDP. These two measured values have been used in the design of lenticular lens.