Whether your phone runs iOS, Android or Windows Phone, it most likely has a screen made out of three distinct parts: A liquid crystal display that generates colors, a set of wires that detects where you touch the screen, and a protective glass cover. A few models use emerging technologies, such as screens that integrate touch sensitivity directly into the LCD, but almost all phone screens consist of the same types of parts, regardless of screen resolution or manufacturer.
Liquid Crystal Display
Cell phone screens display images on a liquid crystal display. Just like the LCD screens in most TVs and computer monitors, phone LCD screens use an electrical current to adjust the color of each pixel. Whereas most TVs light their LCDs with a fluorescent back light, however, phones often use LED back lights to save space and power. Some phones bypass the need for any type of separate lighting by using an organic LED screen. OLED screens generate light internally when powered, and some models can even bend, allowing for curved phones.
Capacitive Touch Screen
Directly below the glass in a touch-screen capable phone lies a grid of tiny wires that generates an electrical field. When you put your finger on the screen, your skin interrupts the field, causing an electrical change that the phone can locate and interpret as a tap. Unlike a resistive touch screen, which detects pressure, a capacitive touch screen won't respond to a fingernail or a narrow stylus. For a capacitive touch screen to register a tap, you need to use something with similar conductivity to a human finger, such as a padded stylus designed specifically for smartphones.
The top layer of a phone screen consists of a hard glass. Unlike traditional glass panes, the glass used in phones -- often aluminosilicate glass, branded by Corning as Gorilla Glass -- is designed to resist shattering and scratching, even when dropped onto a hard floor or struck directly. Changes in phone design also help the glass remain intact. For example, between the iPhone 4S and iPhone 5, Apple sunk the edge of the glass screen farther into the metal side of the phone, protecting it from shattering on a side impact.
Although most phones follow the standard three-part screen, consisting of an LCD display, a capacitive layer and a glass cover, some companies have shifted to alternatives that use new technology. Samsung, for example, produced an OLED phone screen that has capacitive sensitivity built in, removing the need for a separate layer. As a replacement for aluminosilicate glass screens, some phones boast glass layers made out of lab-made sapphire, a naturally scratch-resistant material. Prior to the release of the iPhone 6, many articles predicted Apple's new phone would use a sapphire screen, but the prediction turned out false. Sapphire screens still have several hurdles to overcome to surpass aluminosilicate glass, including a higher cost, worse translucence and less resistance to drops.