Novel Display Technologies Panel
August 6, 2013, Emerging Display Technologies Conference, San Jose, CA-Charles Annis from NPD DisplaySearch moderated a panel on novel display technologies. Panelists were Bil Cowell from Amorphyx, Andrew Loxley from ClearInk Displays, Yao-Dong Ma from MacroDisplay, and Roger Hajjar from Prysm.
Cowell noted that despite the drive to reduce costs through improved glass, the complexity in display manufacturing is increasing as new features, integrated touch, etc. are added to the panels. One alternative is to reduce costs by reducing complexity with non-linear resistors in a diode-based backplane. The aluminum oxide devices are deposited in a 10nm thick layer that is flexible and has low registration requirements, as this is only a two-terminal device.
There are many technical benefits to this simplified process which takes two masks plus the color filters. As a result of being diodes, the devices are rad hard.
Loxley proposed reflective displays for good visual performance in high brightness environments. Although e-ink has been around for a while, it suffers from limited grey scale and very slow response that is adequate for reading, but not for any moving images. users want color and video on their mobile devices. The use cases for outdoor viewing is limited due to the lack of display intensity in most emissive and LCD displays.
Their display has a retro-reflective surface over an array of nano-particles that are moved by electromotive forces in an electric field towards or away from the reflector film. When the particles are near the active matrix electrode array, the display reflects almost all of the incident light. When the particles are driven to the reflector film, the display looks dark.
This technology has shown greater brightness than paper and is scalable to large areas like signs. They have achieved moving images at 28 fps, up to 90 percent brightness, and 40:1 contrast ratio.
Ma agreed that sunlight-readable displays are important, but instead opted for LCD as the underlying technology. The increase in mobile devices has raised the need for displays that work in bright light. The problem is that higher brightness requires more power, an already limited resource. One solution is to use a light guide to mix backlight and directed sunlight for the standard LCD display.
The directional light guides are combined with a window structure to provide backlight, allowing the electrical backlight to be dimmed or turned off while in bright light. A couple of film layers with different angular arrangements and a diffuser are added to a standard LCD display. So far, the backlight features work well in all lighting conditions at the cost of a loss in contrast. The addition of a liquid crystal shutter allows the auxiliary sunlight illumination to be modulated.
Hajjar is involved in large format displays for signage and pubic displays in commercial markets. They have combined the technologies from color CRTs, laser printers, and Blu-Ray disks to make a laser phosphor display. Laser scanners activate the phosphors in tiles that are 20×15 inches. These bevel-less tiles use the raster scan techniques from CRTs to build up large displays.
A closed loop video control system adjusts each tile for brightness and color uniformity. The modulated laser light source is a set of 20 LEDs producing 6.6 lumens per watt input. The images can be on a non-planar surface like one that is 60 feet wide and spans 180 degrees field of view. The displays can also be touch enabled.
Electron mobility?
Cowell offered the high fields cause tunneling. Roll-to-roll processing is coming.
Microvision and other company IP?
Hajjar responded that Microvision uses a set of RGB lasers to scan the image and need a special surface. We are scanning with UV on phosphors. Outdoors we use more laser power and brighter phosphors.
Plans?
Ma plans to license the IP and supply the key materials. Their first production is setting up in China.
Specifications of drivers and pixel size?
Hajjar stated that the LED drivers use a constant drive. The ganged array of LEDs and scanning mechanisms require 14-inches of depth. Since bezels are objectionable, they keep the gaps to less than 300 microns. There are cost issues for smaller area signage.
Materials, media, front layers?
Loxley commented that various vendors are building backplanes and other functional assemblies. The front film is just a patterned, hemispherical set of microlenses. They use existing materials, so there is no issue with availability.
