Liquid Crystal Display (LCD)

An LCD (Liquid Crystal Display) can often define as a smooth board with the electronic visuals display which works through the light that has the standard of liquid crystal. LCDs are super-thin shows that are utilized as a component of tablet phone and level board screens. Smaller LCDs may be utilized as a component of handheld TVs, PDAs, and compact computer game gadgets.

LCDs are commonly used for portable electronic games, as viewfinders for digital cameras and camcorders, in video projection systems, for electronic billboards, as monitors for computers, and in flat-panel televisions. LCDs can either be normally on (positive) or off (negative), counting on the polarizer arrangement. As an example, a character positive LCD with a backlight will have black lettering on a background that’s the color of the backlight, and a character negative LCD will have a black background with the letters being of the identical color as the backlight. Optical filters are added to white on blue LCDs to allow them their characteristic appearance.

One way of constructing the display is to orient two polarizing filters to cross one another, effectively blocking out any light from passing through that “sandwich”. Top and bottom electrodes are oriented at 90-degree angles. As electricity is applied, the liquid crystals line up along the “twist” that produces, and the light starts to follow that twist and pass through the display. Varying the intensity of the voltage varies the quantity of light that’ll pass. Some LCD types do it the opposite way they begin with twisted crystals that untwist under the electrical field. Altogether color is added by filters arranged overactive portions of the LCD display.

Since LCD screens don’t use phosphors, they rarely suffer image burn-in when a static image is displayed on a screen for an extended time, e.g., the table frame for an airline flight schedule on an internal sign. LCDs are, however, prone to image persistence. The LCD screen is more energy-efficient and may be disposed of more safely than a CRT can. Its low wattage consumption enables it to be employed in battery-powered equipment more efficiently than a CRT is. By 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and therefore the CRT became obsolete for many purposes.

Liquid crystals are materials with a structure that’s intermediate between that of liquids and crystalline solids. As in liquids, the molecules of a liquid can flow past each other. As in solid crystals, however, they arrange themselves in recognizably ordered patterns. In common with solid crystals, liquid crystals can exhibit polymorphism; i.e., they will tackle different structural patterns, each with unique properties. LCDs utilize either nematic or smectic liquid crystals. The molecules of nematic liquid crystals align themselves with their axes in parallel, as shown within the figure. Smectic liquid crystals, on the opposite hand, arrange themselves in layered sheets; within different smectic phases, as shown within the figure, the molecules may tackle different alignments relative to the plane of the sheets.

An LCD monitor is one with a fluorescent panel and cold cathode technology. This type of monitor is an improvement over the older cathode ray tube (CRT) monitors, which used a vacuum tube to emit electrons onto the fluorescent panel. LCD offers improvements with almost half the power usage, a mercury-free environment, and low electromagnetic interference (EMI). Also of importance to consumers are the weight reduction and the much slimmer design of about 1/2-inch thick.

The origins and the complex history of liquid-crystal displays from the perspective of an insider during the early days were described by Joseph A. Castellano in Liquid Gold: The Story of Liquid Crystal Displays and the Creation of an Industry. Another report on the origins and history of LCD from a different perspective until 1991 has been published by Hiroshi Kawamoto, available at the IEEE History Center. A description of Swiss contributions to LCD developments, written by Peter J. Wild, can be found at the Engineering and Technology History Wiki.

The first LCDs became commercially available in the late 1960s and were based on a light-scattering effect known as the dynamic scattering mode. These displays were used in many watches and pocket calculators because of their low power consumption and portability. However, problems connected with their readability and the limited lifetime of their liquid crystal materials led to the development during the 1970s of twisted nematic (TN) displays, variants of which are now available in computer monitors and flat-panel televisions.

The first color LCD televisions were developed as handheld televisions in Japan. In 1980, Hattori Seiko’s R&D group began development on color LCD pocket televisions. In 1982, Seiko Epson released the primary LCD television, the Epson TV Watch, a wristwatch equipped with a tiny low active-matrix LCD television. In 1996, Samsung developed the optical patterning technique that permits multi-domain LCD. Multi-domain and In-Plane Switching subsequently remain the dominant LCD designs through 2006. Within the late 1990s, the LCD industry began shifting off from Japan, towards Asian countries and Taiwan, which later shifted to China. In 2016, Panasonic developed IPS LCDs with a contrast ratio of 1,000,000:1, rivaling OLEDs. This technology was later put into production as dual-layer or dual-panel LCDs. The technology uses 2 liquid layers rather than one and will be used together with a mini-LED backlight and quantum dot sheets.

While LCD monitors are 40 percent more efficient than the old CRT monitors. The LCDs used in projection systems are typically small reflective or transmissive panels illuminated by a powerful arc lamp source. A series of lenses magnifies the reflected or transmitted image and casts it onto a screen. In front-projection systems, the LCD is situated on the same side of the screen as the viewer, while in rear-projection systems the screen is illuminated from behind. Projectors of higher cost and performance may use three separate LCD panels, forming separate red, green, and blue images that combine to form a colored image on the screen.


Information sources:

  3. wikipedia