Hunet Inc., a Tokyo-based construction company diversifying into LCD business, is making a different approach to the high density of quarter VGA in a diagonal 1.5-inch display panel employing field sequential technology which does not require a color filter.

Masaya Okita, executive vice president and chief technology officer of Hunet, said, "it's possible to achieve 400 ppi resolution using conventional TN [twisted nematic] liquid crystals with field sequential technology, but the practical resolution is limited by current color-filter technology."

NEC claims to have overcome that hurdle with its "color filter on TFT" (thin-film transistor) technology, which uses photolithography to form color filters over the TFT circuitry on the lower glass substrate rather than on the top glass substrate, as is usual with conventional methods.

That technique gets around the problem of having to have an extremely precise alignment of the two substrates, allowing NEC to achieve 211-pixel-per-inch resolution in a 9.4-inch-diagonal LCD panel with 1,600 x 1, 200-pixel UGA resolution.

The company is pursuing print-quality LCDs to expand LCD applications into areas such as electronic book viewers, picture viewers and medical monitoring equipment. The aperture ratio of the LCD is over 50 percent, making the display far more efficient than the norm. NEC expects to bring LCD modules based on the new technology to production by the end of next year.

For its part, Hunet discussed a 1.5-inch, QVGA (320 x 240-pixel) LCD that gets around the resolution limitation by implementing field-sequential color LCD technology. Field-sequential LCDs need a high-speed driver to drive liquid crystals at more than three times the speed of conventional LCDs. Hunet developed its own driving technology for that task.

Hunet expects to have a working sample of the 266-pixel/inch panel ready by the end of this year, with cellular phone applications in mind. When they offer the display module to customers, the company said the price would be around $20.

And Hunet is aiming higher than just making display modules. "The 1.5-inch LCD module is just the first step of our project. Making the display as the core, we want to offer a one chip solution of cellular phone which integrate the LCD drivers, graphics controller, VRAM, microprocessor or DSP with an operating system as well."

Field sequential LCDs need a high-speed driver to drive liquid crystals at more than three times faster than conventional LCDs. Hunet developed its own driving technology for this task. "If parts such as the driver and the controller are on separate chips, there is a big power consumption loss." said Okita. Hunet is now negotiating with major U.S. semiconductor manufacturers to collaborate on a one-chip solution to cut power consumption.