Introduction to LCD Televisions

LCD televisions can be easily mistaken for plasma TVs. Just like a plasma TV, an LCD television is flat and very thin. But LCD is a completely different technology.

LCD (liquid crystal display) technology is the "workhorse" of portable device displays. Its light weight, small size, thin dimensions, and low consumption of electricity make it perfect for use in calculators, digital watches, PDAs, and portable computers.

The RCA company was the first to produce an experimental LCD in 1968. LCDs were popularized in pocket calculators and digital watches throughout the 70s. And now, with improved manufacturing techniques, high resolution LCDs can be made very large, for use as flat panel televisions, or very small for use in front and rear projection TVs.

LCDs contains a liquid substance, the "liquid crystal", composed of long, bipolar, molecules that can be untwisted and oriented in one direction using an electric field. When the molecules are all aligned in one direction, they act as a light filter and block light waves polarized in the other direction. Screen pixels are formed by applying electric fields to locations on the screen using a grid of tiny electrodes made of a transparent conductor.

Back lit LCDs, such as in laptop computers and LCD televisions, have florescent lights shinning through from the back to create a bright image. Non-lit LCDs, such as in digital watches and calculators, rely on a reflective surface at their back to form the image using reflected outside light.

• LCDs are very thin and consume little electricity. LCD televisions are even thinner than plasma televisions and consume half the electricity.
• LCD televisions are not susceptible to screen burn-in like television technologies that rely on phosphorous materials for illumination, such as CRT and plasma. Screen burn-in happens when static screen images illuminate the same sections of phosphor for long periods of time, causing discoloration. This problem was ubiquitous in CRT computer screens, leading to the advent of "screen savers".
• LCD televisions have a very long operational life time. The only part that's susceptible to failure is the LCD's back light. But it is a single component that can be easily replaced.
• Since LCD televisions are lit by a back light that is separate from the image producing elements, it can be made arbitrarily bright. Therefore LCD televisions are good at displaying a clear picture despite the presence of bright outside light.
• LCD televisions are often designed to easily double up as computer screens, and are very suitable for the job.

• LCD televisions have a limited viewing angle, as they appear dark and discolored when viewed from the side.
• LCDs have a relatively low contrast, which is the difference between the brightest and darkest color possible, and have trouble displaying complete black.
• LCDs tend to have large gaps between pixels, which lead to a visible grid effect in large screens. In high resolution LCDs this effect is often minimized.
• LCDs are difficult to manufacture in large sizes. Manufactured LCDs often have bad pixels, and a large percentage of LCDs that come off the production line are rejected. The price of LCDs has to compensate for the rejected ones. A large number of pixels on an LCD increases the chance of having more bad pixels, and therefore more rejected displays.
• The liquid crystal in LCDs has a narrow range of operational temperatures. Therefore an LCD television should only be used under normal room temperatures.