On June 5th, NuLight Technology and Delta Electronics, both of Taiwan, announced their jointly developed mercury-free Flat Fluorescent Lamp (FFL) backlight panel has received certification by the VDE Institute of Germany. This lamp is intended as a backlight for a 32" LCD panel, replacing the standard cold-cathode florescent lamps containing mercury.
Insight Media Analyst
Instead of mercury emission stimulating phosphors to get the desired visible light, this lamp uses a xenon gas fill to generate the UV light. UV light from xenon is typically shorter wavelength than the UV from mercury. This shorter wavelength UV then allows a wider choice of phosphor materials to convert the light into visible light allowing for wider color gamuts. In addition, normal glass is opaque to this short wave UV, preventing any leakage of UV outside the lamp.
While the European Union RoHS regulations have a generic ban on mercury in electronics, lamps including CCFLs and UHP-type lamps have an exemption, at least for the time being. Electronics manufacturers all over the world are looking for substitutes for mercury and other banned substances such as lead. RoHS compliance, in fact, has become a significant selling point for component manufacturers in their advertisements to the trade. So far as Insight Media knows, however, it has not (yet) become a selling point in consumer advertising. Consumer advertising of "Greener" products has become common, even without reference to RoHS.
"Unlike conventional optoelectronic inverting technology that uses mercury for a lighting material, NuLight uses xenon (Xe)," said C.T. Tsai, the CTF of NuLight. "This technology offers an alternative solution to the mercury-based lamps used in the millions of TFT-LCD TVs produced globally each year."
In addition to RoHS compliance, a FFL with xenon offers a number of other advantages including:
1) More uniform light distribution reduces or eliminates some back light components
2) "Instant On" operation, with 100% light output in milliseconds. CCFLs can take as long as two minutes to warm up to full brightness.
3) Operation over a much wider temperature range than mercury-based lamps
In addition to manufacturing problems, which hopefully Delta and NuLight have solved, FFLs have a couple of problems compared to CCFLs. First, typically they are less efficient. Second, they have been more expensive.
Since neither the Delta/NuLight announcement nor the NuLight website touched on these problems, presumably they are still there. For LCD-TV, they may not represent a barrier to introduction, especially in high-end models.
I have always been a proponent of edge-illuminated LED backlight units for LCDs. They have all the advantages of a FFL, as well as some of the disadvantages. LEDs can be more efficient than CCFLs and are already used in some laptops to increase battery life. Time and the marketplace will determine if or when either of these technologies will replace the entrenched CCFL for LCD-TV.