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Color eReader Tech Close to Prime Time

Electronic paper (e-paper) displays mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat-panel displays that are virtually unreadable in bright sunlight, electronic paper displays reflect light like paper making them more comfortable to read and providing a wider viewing angle. An ideal e-paper display can be read in direct sunlight without the image fading.

Electrophoretic, or electronic ink, is the technology behind e-readers. In its U.S. Consumer Technology Sales and Forecasts report, CTA projects 2018 e-reader sales of 5.36 million units valued at $395 million.

The optical component of film used in e-reader displays is made up of millions of tiny microcapsules, about the diameter of a human hair. Each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a positive or negative electric field is applied, corresponding particles move to the top of the microcapsule where they become visible to the viewer. This makes the surface appear white or black at that spot.

The particles lay suspended even when the electric field is removed. When the electric field is reversed, the particles exchange places. This means that the display is consuming power only when something changes.

New E-Paper Developments

E Ink Holdings, (E Ink) includes new additions to its Advanced Color ePaper (ACeP for short) technology along with traditional e-reader applications that include flexible display solutions.

ACeP is a "full color" reflective display at every pixel, without the use of a color filter. The technology was shown in a 32- and 13.3-inch diagonal, with 13.3-inch slated for commercial availability later this year. ACeP achieves all eight primary colors, using only colored pigments. It can also display more than 32,000 different
colors and has a resolution of 1600x2500 pixels and 150 pixels per inch (PPI). ACeP maintains the low-power and paper-like readability under all lighting conditions of regular e-paper. The initial application for ACeP is digital signage, with e-readers to follow.

CLEARink Displays focuses on 1.32-inch displays for wearables and 9.7-inch screens for e-readers. The company has increased the resolution of its color screens to 200 PPI due to a new color filter design. CLEARink is partnering with a leading tablet maker to supply displays in 2019 that feature up to 50 percent larger form factors. The company’s ePaper 2.0 uses a monochrome display with a color filter over the top to produce colors. It has no frontlight or backlight, and the screens can be produced in flexible form.

Professor Guofu Zhou’s team from the Electronic Paper Display Institute, South China Academy of Advanced Optoelectronics, South China Normal University (SCNU) recently demonstrated color video electronic paper displays. Since the team invented and stabilized a spacer technology for SCNU e-paper last year, he says it has made important modifications in the pixel structure, which is now optimized in both size and shape, increasing the display pixel aperture to more than 80 percent and the contrast ratio to over 10:1, making the display brighter. The team also has improved response time to three milliseconds, rivaling LCD. These features enable the display to show dynamic videos up to 100 frames per second.

Using a new 2.7-inch e-paper display, the SCNU team also demonstrated a real-time clock prototype. SCNU team member and Professor Alex Henzen, says, "This clock could work for years with a single coin battery and it can show high contrast images. This is a big step for e-paper."

Murray Slovick