We are in the very early stages of developing a new product and are attempting to identify the type of LCD screen backlight we want to use. We are using a regular segment LCD glass screen, the type that connects to the PCB via a zebra connector. We have identified a screen on another product that is absolutely beautiful and we're trying to determine what type it is. We suspect it's the backlight that is making the different, that is giving in the high quality look. It appears that the backlight is a solid sheet of light rather than a few single LEDs on the perimeter of the glass.
Here are two example photos and I'm hoping someone here can give some additional information on what kind of screen this is:
Here is another example:
It's the uniform distribution and blue-gray color that we find appealing. I've read that there are three common backlight technologies used:
- LED
- EL
- CCFL
Of those 3 options I suspect we're wanting a LED backlight. Furthermore there is edge layout and array layout. I'm sure there are even more options. I'm hoping that given the two above images you will be able to determine what backlight technology is used.
Best Answer
For a single large planar backlight with very even lighting, the backlight technology of choice is the electroluminescent sheet or EL sheet / EL panel.
EL panels come in a variety of colors depending on the material used, and in a variety of sizes. Also, they can typically be cut to a desired size. For instance, see these EL panels from this eBay listing:
The lighting is very even across the panel. There is some color and intensity variation visible with change of EL excitation frequency, but with a good inverter design, that is rarely of concern.
LED backlights can be made even and smooth, but at the cost of an added diffusion layer, that loses some of the light intensity.
The second display in the question is most likely equipped with a sidelit LED backlight, going by the intensity pattern, 3 LEDs at the top.(Invalid hypothesis, OP's image editing gave a misleading impression)CCFL is commonly used for small or narrow displays, i.e. edge layout, or sometimes for large displays as well (some TVs for instance), but at the cost of a laser etched prism matrix sheet (or sometimes merely a diffusion sheet), again leading to some light loss.
Many common laptop displays use edge lighting with CCFL tubes. For instance, with my Lenovo laptop, I can actually see the bright sliver of edge lighting generated by a CCFL tube on each side of the display, if I flex the screen a bit. The light suffers a small amount of fall-off as one moves away from the edge, but that may not be evident to the naked eye: I can only spot it if I have a solid light color edge to edge on the display.