408-754-4176 | info@reachtech.com

by Reach Technology, a Novanta Company
Support > CCFL vs. LED Backlighting

CCFL vs. LED Backlighting

As an engineer whose main area of expertise is not embedded LCD technology, it is easy to become overwhelmed with the details in selecting the right touch screen to add to your embedded product.

“There’s a comfort in working with somebody like Reach that knows what they are talking about when it comes to embedded LCD displays.”

How Embedded LCD Backlights Work

Liquid crystal displays (LCDs) do not produce light while functioning because the pixels are like little shutters that vary their opacity accordingly to the amount of electric current they receive. The lighting problem is solved by placing a light source behind the color pixel panel.

Cold Cathode Fluorescent Lamps (CCFL) Backlights

Use a single straight glass tube, which works much like a regular fluorescent lamp. The tube contains a low-pressure mercury vapor that when ionized starts to emit ultraviolet light. Human eyes cannot see in ultraviolet wavelengths, so a coat of phosphorus inside the tube converts it to visible bright white light.

Light-Emitting Diode (LED) Backlights

Use 10 to 18 white LEDs arranged in a uniform pattern. White LEDs are blue LEDs with a yellow phosphor coating to give the impression of white light. LED backlights are most commonly used in small, inexpensive LCD panels.

Which backlight should you use?

From an industrial design point of view, embracing the latest and greatest can be risky. There are good reasons to stick with tried-and-true CCFLs that have been the standard in backlighting. They offer high brightness, long lifetime, and great uniformity.

By contrast white LED backlights are relatively new, but are the way of the future. In some cases, new formats are only available with an LED backlight (i.e. 4.3” unit). LEDs degrade at a faster rate than CCFLs, but do offer high brightness, do not require an inverter, are cost effective, and are durable.