by David DeAgazio

There is just no stopping them. Long the dominant illumination technology employed by the smaller displays used in mobile phones and other portable/handheld devices, LEDs are rapidly displacing fluorescents as the illumination technology of choice for LCDs used in notebook computers, automotive and aircraft-cockpit displays, and even large-sized LCD TVs.

The reasons are clear: LEDs have higher brightness, longer life, a wider operating temperature range and color gamut, better solid-state durability, lower power consumption and voltage drive, wider dimming range, a more compact form factor for increased design and styling flexibility, and, of course, mercury-free RoHS (Restriction of Hazardous Substances) compliance.

And LEDs are getting better and better. New advances in LED fabrication technology are improving light-extraction efficiency, increasing luminance, and reducing power consumption. In addition, LED manufacturers are working closely with backlighting manufacturers to ensure that LED packages, sizes, and emission patterns are optimized. LED backlights are getting thinner, with improved light-extraction efficiency that reduces the number of LEDs required for a backlight and lowers manufacturing costs. Advances in thermal design are providing more efficient ways to conduct heat away from the LEDs to maintain a low LED junction temperature, which is critical to long-life operation of LED-backlighting modules.

These design advances, combined with the superior performance of LEDs, are also beginning to overcome one of the main obstacles that has heretofore prevented manufacturers from implementing LEDs in many applications – cost. In automotive LCDs, for example, the crossover point in price/performance ratio was passed in 2007, with the result that more and more new automotive LCD backlight designs will be LED- based.

LEDs are also adding versatility, color control, and dimming. Light sensors that match what the human eye sees are enabling LED-backlit LCDs to be more sensitive to changes in ambient lighting.

The three LED-based articles in this issue of Information Display address many of these exciting new developments from different perspectives. The first article is by Francis Nguyen of OSRAM Opto Semiconductors, a provider of solutions based on semiconductor technology for the lighting, sensor, and visualization sectors, and a subsidiary of OSRAM. Nguyen examines advances in LED design and fabrication technology that are addressing the technical challenges associated with avionics displays and improving the display of critical information in aircraft cockpits.

My own article addresses how LED-based backlight units (BLUs) are utilizing performance advances in high-brightness LEDs in consumer-product displays to meet the ever-increasing demands for thinner displays with smaller form factors, and how advances in light-extraction efficiency and edge-lighting technology are enabling LED BLUs to meet performance demands while using fewer LEDs.

The article by Evan O'Sullivan and Bob Pantalone of Jabil Circuit, Inc., examines the challenges involved in the high-volume manufacturing of large LED-backlit LCDs from the viewpoint of a systems integrator and manufacturer.

I hope you will find these articles interesting, and, well, illuminating.