White light makes right: will LEDs replace the light bulb?

Japan, Inc., Nov, 2004 by Alex Stewart

IN the US, Light Emitting Diodes (LEDs) now account for 30 to 40 percent of all new signage. In Japan, that figure has hovered at less than 5 percent. But at Tokyo's annual Sign and Display Show this past September, there was ample evidence to prove that LEDs are a rising force-especially if they're white.

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ONE-HUNDRED AND SEVENTY-SIX companies exhibited, including lighting companies, sign makers, LED manufacturers and various companies involved in printing or electronic displays. There were many variations of LED solutions exhibited--with white LEDs heavily featured.

White represents a revolution in LEDs. The technology on which they depend is blue, but mixing blue from the ultraviolet end of the light spectrum with red and green enables engineers to produce white.

The revolutionary impact of white is that it opens up the possibility that LEDs could eventually replace other illumination devices--including the light bulb--and thereby create a completely new lighting market, with several attendant environmental benefits.

Maverick breakthrough

While it is relatively easy for LEDs to produce warm colors at the wider end of the spectrum, it becomes progressively more difficult to generate cool colors like blue.

It took twenty years before the breakthrough occurred in 1998, when a maverick corporate research warrior, Shuji Nakamura (see JI, July 2001) almost singlehandedly developed a method of using indium nitride as the semiconductor material which could generate blue light.

Everything about the story of how the blue laser diode was developed defied conventional wisdom.

The company where Nakamura conducted his research, Nichia Chemical, is located on the remote island of Shikoku in Japan's Inland Sea. Nichia's research budget was minuscule compared with the huge budgets available to the major lighting and semiconductor companies, but no other company in the multi-billion dollar semiconductor and lighting industries believed indium nitride was a candidate material.

Nakamura pursued his unorthodox research and was eventually proven right. Nichia then cross-licensed the technology and began commercializing blue LEDs.

As reported in these pages in May, Nichia was ordered earlier this year by the Tokyo Disctrict Court to pay [yen]20 billion to Nakamura as compensation for an original payment that was just 0.0000017 percent of the profits made on the blue LED. Nakamura subsequently left Nichia for a post at the University of California, Santa Barbara, where he is hoping to consolidate his achievements and continue his research in this field.

Fierce competition

Nakamura's blue light diode produced a pure green initially, which earlier technology could not achieve. He then found a way to produce a white light by developing a special phosphor. This generated enough lumens for commercial applications such as flashlights, which consumed so little battery power they could run for days rather than hours.

He also set himself up to become somebody who could follow in Edison's shoes as an entrepreneur-cum-researcher by throwing himself into the hurly-burly of Silicon Valley.

There are now many companies that have concluded cross-licensing agreements with Nichia. As a result, competition in the LED market is fierce, which is good for accelerating the development of white light applications. The value of further progress in producing white light by producing the right balance of brightness with longevity is substantial because of the environmental benefits.

Lighting accounts for over 20 percent of all electricity consumed in the US. On the other hand, LEDs use only 20 percent or less of the energy consumed by traditional lighting. This implies that LEDs could have the single biggest impact on demand for energy in the next two decades--and possibly as much impact on the problem of global warming.

How quickly this happens will depend on the speed with which the technology is adopted by the specialist end of the illumination market, notably in sign and display illumination, another multi-billion dollar market.

Signage is the driver

Sign and display illumination is where white LEDs will make their first significant contribution. Adopting white LED technology will help to promote the development of brighter white LEDs at more affordable prices.

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Traditionally, neon or fluorescent lighting has been used to illuminate displays and signs. These systems have their strengths still, but for most applications it is likely that LEDs will replace them.

The reason lies in the total cost of ownership. LEDs consume up to 80 percent less energy than neon, need almost zero maintenance and have both a long life (up to 100,000 hours) and extensive warranty coverage (up to five years). Because of these benefits, many companies can start earning a return only one year after substituting LED for neon.

One display which stood out at this year's Sign Show was produced by Osaka-based Daikan Company Ltd. Not only it did feature the brightest stand, it was also attracting more people.