Color e-paper trials begin on Tokyo trains

On three commuter trains some traditional paper advertisements have been replaced with color e-paper displays. The displays, while technologically advanced, proved difficult to read during a demonstration Thursday.

The 13.1-inch displays are made by Hitachi Ltd. and based on Bridgestone Corp.'s "electronic liquid powder" technology. There are two such displays on each of the three trains, mounted on the carriage wall at either end of the train.

Each display is connected to a smaller unit which contains companion electronics and an 8M-byte memory that can hold 37 advertisements. Each advertisement is shown for two minutes in a continuous cycle.

Electronic paper is still in its infancy. While it has been shown in prototype form for several years, the technology has only recently started making its way into commercial products. One of the highest profile uses is Sony Corp.'s Sony Reader electronic book, but it uses only a monochrome display. Color e-paper development lags.

The displays in the trains offer relatively low resolution, at 50 dpi (dots per inch), and can only display eight colors. There's also no backlight, so on-screen images appeared quite dark and advertisements utilizing dark colors, such as red and black, were relatively difficult to read. Reflections on the display's protective plastic cover also caused problems.

The month-long tests are relatively high-profile because the trains in question run on East Japan Railway Co.'s Yamanote Line, which runs in a loop around the center of Tokyo. It's used by about 3.5 million people each weekday, making it one of the city's most important and heavily used railway lines.

The trial will gauge feedback from travellers and see how the system performs in a real-world environment, said Nobuyuki Ogura, a senior manager with Hitachi's transportation information systems division in Tokyo. They follow a trial last year in which a monochrome e-paper display replaced a wall poster at Tokyo Station, he said.

Hitachi will continue working on the screens and hopes to have a commercial panel ready for use by March 2008, he said.

The Yamanote Line has 52 trains and on each 11-car train there are 1,414 advertisements, for a total of 73,528 on the entire line. While 96 of the advertisements on each train are LCD displays, the rest must be changed by hand. The use of more digital advertisements would mean new content could be quickly transmitted to each display panel with little fuss.

The trial system that begins Thursday includes the ability to update advertisements via a 802.11b wireless LAN link to the panels.

Hitachi isn't the only company working on color e-paper. Earlier this year Fujitsu Ltd. showed a prototype 7.8-inch panel that can display up to 4,096 colors. The display, which is the same size as a sheet of A5 paper, was built into a thin case in the form of an electronic book reader and was on show at the Ceatec exhibition in October.