All types of smartphone screens

LCD, TFT, IPS, AMOLED, P-OLED, QLED is an incomplete list of display technologies that can now be found on the mass market of consumer electronics. When you go buy a regular gadget, you constantly face this and scold yourself that you did not understand it in time.

So here’s the chance. Read about the specifics of each and how they differ …

Liquid Crystal Display, that is, a liquid crystal display – it was this technology in the late 1990s that made it possible to turn monitors and TVs out of comfortable mattress beds for seals with harmful electron beam tubes inside into thin, elegant devices. It also opened the way to the creation of compact gadgets: laptops, PDAs, smartphones.

Liquid crystals are a substance that is both fluid and fluid, and anisotropic, like a crystal. The latter quality means that with different orientations of the molecules of liquid crystals, optical, electrical, and other properties change.

Crystalline, liquid crystal, liquid: crystals are transformed into another aggregate state under the influence of temperature

In displays, this property of the LCD is used to control the light conductivity: depending on the signal from the transistor, the crystals are oriented in a certain way. Before them is a polarizer, “collecting” light waves in the plane of the crystals. After them, the light passes through the RGB filter and turns red, green or blue, respectively. Then, if not blocked by the front polarizer, it appears on the screen as a sub-pixel. Several such light streams are connected to each other, and on the display we see a pixel of the expected color, and its combination with neighboring pixels is able to produce a gamut of sRGB-spectrum.

LCD pixel scheme

When the display is on, the backlighting is carried out by white LEDs located around the perimeter of the display, and evenly distributed over the entire area thanks to a special substrate. Hence, there are known “diseases” of the LCD. For example, to the pixels that should be black, the light still comes. In old and substandard displays, “black glow” is easily discernible.

It happens that the crystals are “stuck”, that is, they do not move even when receiving a signal from the transistor, then the “broken pixel” appears on the display. Because of the specifics of the light source, white light can be seen along the edges of LCD monitors, and smartphones with LCD can not be absolutely frameless, although both generations of Xiaomi Mi Mix and Essential Phone are striving for this.