How does an LCD TV Work

In 2007, for the first time, LCD televisions surpassed sales of the conventional model based on CRT (Cathode Ray Tube). The Liquid Crystal Display (LCD) TV is based on the inter-active properties of liquid crystals and light, and the technology used is known as the Thin Film Transistor (TFT). These liquid crystals are broken down into small particles known as pixels, which are the smallest unit of screen resolution. The crystals are usually located between two electrodes and an equal number of sifts, vibrating in a single direction. The LCD technology has witnessed a lot of innovations over the years, to bring the LCD TV to what we have today.

Components of an LCD TV

• Liquid crystals
• Cold Cathode Fluorescent Lamps (CCFLs)
• Polarizer plates
• In-Plane Switching displays (IPS and S-IPS)
• Electrodes made of a transparent conductor like indium tin oxide
• Thin film transistor (TFT)

Basics of LCD Technology

LCD technology works by selective passage of light, which passes through millions of individual LCD shutters. These shutters are arranged in grids and constitute colored filters, allowing only the RGB (red, green, blue) portion of the light to pass through. This white light is typically provided by a series of CCFLs (Cold Cathode Fluorescent Lamps), which are at the rear of a screen. Every single sub-pixel is formed by a shutter-filter combination, and these sub-pixels blend together to form the whole picture.

The LCD shutters consist of three primary elements. There are two polarizers, set at right angles. These polarizers carry directors (a material with microscopic groves in it) in order to create the twisted structure, which is aligned to the other polarizer. Light flowing out of the rear polarizer follow the liquid crystal's twist, and exits from the front of the liquid crystal. Thus it gets rotated through the correct angle, which allows its passage through the front polarizer. Liquid crystals in LCDs are generally rod-shaped polymers which naturally mold to form thin layers. The particular direction of its alignment is set by placing it in contact with a director. The layer in contact, wit the director and aligns itself with the grooves, thus making the bulk material take on the director's alignment. The right angle between the two polarizer, aligns the layers in two directions. Thus, it creates a twisted structure with each layer aligned at a slightly different angle to the ones on either side.

The working of LCD shutters is assisted by an application of electric voltage. To turn a shutter off, an electrical voltage is applied across it from front to back, and by controlling the voltage applied across the crystal, the amount of remaining twist can be finely selected. This helps in controlling the transparency or capacity of the shutter. In order to improve the switching time, these liquid crystals are placed under pressure, which helps in re-alignment the directors, when the field is turned off.

Working of a LCD TV

In an LCD TV, there are two thin glass sheets which constitute the assembly of a typical shutter. The rear sheet polarizes the film, the active matrix components, addressing electrodes, and then the director. The only difference with the front sheet is absence of active matrix components, which is replaced by patterned color filters. There is liquid crystal placed between the two sheets which divides the liquid into individual shutters and maintains a precise distance between them.

The shutter assembly combines with control electronics and back light, for the production of an entire picture. The back light is generally provided by a single lamp in case of small sets, and a diffuser or frosted mirror is used to spread out the light. However, in case of larger displays, a single lamp is not bright enough and a number of separate lamps are used instead.

The LCD televisions provide high on image resolution, crystal-clear displays and distortion-free sound transmission. They deliver high-end, and consistent performance, and represent an exciting synthesis of design and technology.