LCD TFT displays are the most popular type of active matrix LCD display currently on the market. LCD TFT displays, or liquid crystal display using thin film transistor technology, can display crisp and vibrant visuals for multimedia applications for television, computing, projection displays, and mobile applications such as hand held video games, mobile phones, and digital assistants.
Passive matrix LCD technology, such as that used in calculators and digital watches applies voltage to a pixel, altering the orientation of the liquid crystal to show part of the image. This pixel cell acts as a capacitor, slowly bleeding off it’s voltage and allowing the crystal to return naturally to it’s original position. This works well for data oriented displays that don’t require a quick refresh rate.
LCD TFT displays actively change the position of the liquid crystal from off to on and back again using a transistor in each cell. This prevents ghosting, and blurring of moving objects displayed on screen. The use of LCD TFT displays with their active matrix design allows LCD technology to be used for multimedia applications with rapidly changing elements such as video games and live action movies.
The transistor layer of an LCD TFT display is made up of a thin film of semiconductor on top of a glass substrate. In color LCD TFT displays, each pixel is made up of a blue, red and green cell to produce the entire range of visible light. Each of these cells has it’s own transistor and liquid crystal material. Liquid crystal can change position quickly as a liquid but also has the ability to remain in an arranged crystalline position. In essence, each cell is a window with the transistor being the hand that opens the liquid crystal blinds to either release or withhold light. When millions of these cells work together, they produce a working image.
The source of the light depends on the type of LCD TFT displays. In a reflective TFT display, ambient light from the environment enters the monitor and is bounced back by a mirrored surface behind the pixel matrix. This type of display requires good lighting conditions in order to be effective. Back lighting, side lighting and front lighting have been used to actively produce light for the display in low lighting conditions, but these can appear washed out in bright light and hard to see.
CCFL, or cold cathode fluorescent lamps, are commonly used in LCD TFT displays for back lighting. These lights are very similar to overhead fluorescent lighting used in offices. They are inexpensive and replaceable. The current trend is moving towards LED back lighting. LED technology has only recently matured to the point of adequately displaying enough white light to effectively work in this application. LED back lighting has many benefits such as being durable and more energy efficient.
The basic technology of LCD TFT displays has been around for years. Supplemented by new back lighting technology, LCD TFT has retained market importance and is a current leading option for display devices.
