LCD (Liquid Crystal Display) Technology

LCD (Liquid Crystal Display) is the technology used for displays in notebook, smaller computers, portable devices including Mobile Telecoms (Telecommunication) pagers, phones, PDAs, EPOS and other instrumentation monitors. Like light-emitting diode and gas-plasma technologies, LCDs allow displays to be much thinner than cathode ray tube (CRT) technology. Liquid crystal Displays consume much less power than LED and gas displays because they work on the principle of shuttering light rather than emitting it.

LCD fluids are selectable for individual display projects, with TN the original technology and HTN, STN and F-STN being developments. Liquid crystal displays are the most popular display medium for applications large and small.

An LCD is made with either a passive matrix or an active matrix display grid. The active matrix LCD is also known as a thin film transistor (TFT) display. The passive matrix LCD has a grid of conductors with pixels located at each intersection in the grid. A current is sent across two conductors on the grid to control the light for any pixel. An active matrix has a transistor located at each pixel intersection, requiring less current to control the luminance of a pixel. For this reason, the current in an active matrix display can be switched on and off more frequently, improving the screen refresh time (your mouse will appear to move more smoothly across the screen, for example).

A typical liquid crystal display will incorporate the LCD fluid (either TN, STN, HTN or F-STN) in a glass envelope with ITO coatings to the internal glass surfaces. The basic liquid crystal display, either statically driven or multiplexed, is frequently incorporated onto a PCB (Printed Circuit Board) with the LCD display driver hardware and often backlighting, LED EL, or CCFL.

Liquid crystal displays do not suffer degradation over time, the LCD fluids always return to their normal state when a voltage is not applied. Temperature does affect liquid crystal displays however, with extreme low temperature causing the LCD to respond very slowly. The required bias voltage across the liquid crystal display also alters with ambient temperature.

Some passive matrix liquid crystal displays have dual scanning, meaning that they scan the grid twice with current in the same time that it took for one scan in the original technology. However, active matrix is still a superior technology.

Temperature does affect liquid crystal displays, however with extreme low temperature causing the LCD to respond very slowly. The required bias voltage across the liquid crystal display also alters with ambient temperature.

...click here to see how a 7 segment LCD works