Just a few years ago, the conventional tube (CRT) monitor was still the classic display but it has since been totally ousted by TFT LCD screens. LCD stands for the use of liquid crystals in the individual pixels of the screen and TFT for tiny transistor components which control the alignment of the liquid crystals and thus their light-transmitting qualities. The name Active Matrix Display is also often used for the TFT.
- TFT = Thin Film Transistor
- LCD = Liquid Cristal Display
A flat-screen display consists of individual pixels. Each pixel consists of three LCD cells (sub-pixels) which correspond to the colours red, green and blue. A 15 inch screen with XGA resolution therefore consists of a total of 786,432 pixels or approximately 2.4 million LCD cells.
A liquid crystal (LCD) cell functions similarly to Polaroid sunglasses: if two Polaroid lenses are held one over the other and rotated, less and less becomes visible through them until the point where nothing is visible at all. This effect occurs because Polaroid glass only lets through light waves which resonate within a certain layer. If two such glasses are held one over the other and rotated 90 degrees, some of the light can still pass through the first lens but not the second, because it is at right angles to the approaching light waves and filters them out.
An LCD cell works according to the same principle. It consists of two polarising filters laid over one another at 90 degrees through which no light can pass. Between them is a layer of liquid crystals which are naturally able to rotate the resonating layer of light. The liquid crystal layer is just thick enough to be able to bend back the light which passes through the first polarising filter by 90 degrees. It is then able to pass through the second polarising filter and becomes visible for the viewer. If the liquid crystals are then turned away from their natural position by the application of a certain voltage, less light can pass through the cell and the pixel becomes dark.
The voltage is produced by a TFT (thin film transistor) component belonging to each LCD cell. The light for the LCD display is created in the rear part of the screen housing by tiny fluorescent tubes (CFL backlights) such as are used in larger sizes for room lighting. So-called LED backlights are, however, becoming increasingly popular; they have a longer useful life and shallower installation depths.
Sunshine readable TFT
The legibility of the display is a particularly important factor for outdoor applications. Sunshine readable TFTs are particularly suitable for precisely these applications. These are modified with special filters and film packets so that the incident sunlight is reflected and the TFT remains legible. The electronic configuration, power consumption and useful life of the TFT are entirely unaffected by this modification.
It should not be forgotten that component cooling may be necessary depending on the application. Here we can help with advice based on our own experience.
We use TFT panels from all well-known manufacturers, but prefer those made by AUO and CMO. In addition, we purchase Samsung, NEC and Hitachi products worldwide. In addition to cost-effective solutions we also offer industry-standard panels which feature long-term availability.