LCD monitors (Liquid Crystal Displays) are based on the fact that liquid crystals influence the polarization direction of light when a certain level of electrical voltage is applied. A characteristic of liquid crystals is that they do not produce light themselves, consequently they require a backlight. The spiral-shaped liquid crystals wind up to a greater or lesser extent depending on the current strength, allowing more or less light to pass through accordingly. Thus, each pixel is transmitted as a gray value. However, polarized light is needed and thus polarization filters in front of the light source. For color, additional layers are needed, the color filters. Because of the many layers, very thin displays are more difficult with this screen technology.
Light-emitting diodes are processed in LED screens (Light Emitting Diodes). These convert current into light. The brightness is proportional to the current intensity. Unlike liquid crystals (LCD), LEDs can directly generate a colored image. LEDS are available in the primary colors red, green and blue, and all possible colors can be formed by superimposing them. LED materials are crystalline, which means that they can be deposited in thin layers on glass under high temperatures and vacuum.
Organic light emitting diodes (OLEDs) generate colored images directly, just as LEDs do. However, they are made from completely different materials than LEDs, as they are based on carbon, which is why they can be manufactured in a completely different way than LEDs. OLED materials dissolve in water or solvents, and can thus be sprayed or printed onto a support medium. Since an OLED screen basically consists of a single layer, it is possible to manufacture displays that are very thin.
So which technology is the right one?
The simpler the question, the harder the answer. Whereas OLEDs are still in their infancy, not least due to their higher price and shorter lifespan, LED screens have practically become the benchmark for professional digital signage screens over the past ten years. However, experts believe that due to the better picture quality, OLEDs will catch up strongly in the next few years.
However, LCD screen technology is far from dead. Instead of LED screen, we should actually speak of “LED-backlit LCD screens”. A complicated expression – we admit it… But technically, virtually all LED screens are just that. Because, as mentioned above, liquid crystal displays themselves do not emit any light and do not produce any colors, LEDs are usually installed behind the liquid crystal display as a light and color source for the two-dimensional illumination.
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