If you are looking for information concerning LCD TVs, you have come to the right place. LCD TVs have a great display. If you want to know more about LCD TVs, you’d have to read through this guide.
LCD stands for liquid crystal display. The liquid crystals block or allow light to pass through them. The different colors and brightness levels created by the liquid crystals and various filters become the picture on the screen. The liquid crystals don’t create a light, though; that job falls to the backlight
What’s different about LCDs?
For many people, the most attractive thing about LCD TVs is not the way they make a picture but their flat, compact screen. Unlike an old-style TV, an LCD screen is flat enough to hang on your wall. That’s because it generates its picture in an entirely different way.
You probably know that an old-style cathode-ray tube (CRT) television makes a picture using three electron guns. Think of them as three very fast, very precise paintbrushes that dance back and forth, painting a moving image on the back of the screen that you can watch when you sit in front of it.
Flatscreen LCD and plasma screens work in a completely different way. If you sit up close to a flatscreen TV, you’ll notice that the picture is made from millions of tiny blocks called pixels (picture elements). Each one of these is effectively a separate red, blue, or green light that can be switched on or off very rapidly to make the moving color picture.
The pixels are controlled in completely different ways in plasma and LCD screens. In a plasma screen, each pixel is a tiny fluorescent lamp switched on or off electronically. In an LCD television, the pixels are switched on or off electronically using liquid crystals to rotate polarized light.
That’s not as complex as it sounds! To understand what’s going on, first, we need to understand what liquid crystals are; then we need to look more closely at a light and how it travels.
What are liquid crystals?
We’re used to the idea that a given substance can be in one of three states: solid, liquid, or gas—we call them states of matter—and up until the late 19th century, scientists thought that was the end of the story.
Then, in 1888, an Austrian chemist named Friedrich Reinitzer (1857–1927) discovered liquid crystals, which are another state entirely, somewhere in between liquids and solids. Liquid crystals might have lingered in obscurity but in fact that they turned out to have some very useful properties.
Solids are frozen lumps of matter that stay put all by themselves, often with their atoms packed in a neat, regular arrangement called a crystal (or crystalline lattice). Liquids lack the order of solids and, though they stay put if you keep them in a container, they flow relatively easily when you pour them out. Now imagine a substance with some of the order of a solid and some of the fluidity of a liquid.
What you have is a liquid crystal—a kind of halfway house in between. At any given moment, liquid crystals can be in one of several possible “substates” (phases) somewhere in a limbo-land between solid and liquid. The two most important liquid crystal phases are called nematic and smectic:
- When they’re in the nematic phase, liquid crystals are a bit like a liquid: their molecules can move around and shuffle past one another, but they all point in broadly the same direction. They’re a bit like matches in a matchbox: you can shake them and move them about but they all keep pointing the same way.
- If you cool liquid crystals, they shift over to the smectic phase. Now the molecules form into layers that can slide past one another relatively easily. The molecules in a given layer can move about within it, but they can’t and don’t move into the other layers (a bit like people working for different companies on particular floors of an office block). There are actually several different smectic “subphases,” but we won’t go into them in any more detail here.
Televisions used to be hot, heavy, power-hungry beasts that sat in the corner of your living room. Not any more! Now they’re slim enough to hang on the wall and they use a fraction as much energy as they used to. LCD TV is a television display technology based on a liquid crystal display. LCD TVs consume much less power.
A liquid-crystal display (LCD) is a flat-panel display or another electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly, instead of using a backlight or reflector to produce images in color or monochrome.
LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden, such as preset words, digits, and seven-segment displays, as in a digital clock.
They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement.
For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.
LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in LCD projectors and portable consumer devices such as digital cameras, watches, digital clocks, calculators, and mobile telephones, including smartphones.
LCD screens are also used on consumer electronics products such as DVD players, video game devices, and clocks. LCD screens have replaced heavy, bulky cathode ray tube (CRT) displays in nearly all applications. LCD screens are available in a wider range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to very large television receivers.
How LCDs use liquid crystals and polarized light
An LCD TV screen uses the sunglasses trick to switch its colored pixels on or off. At the back of the screen, there’s a large bright light that shines out toward the viewer. In front of this, there are the millions of pixels, each one made up of smaller areas called sub-pixels that are colored red, blue, or green.
Each pixel has a polarizing glass filter behind it and another one in front of it at 90 degrees. That means the pixel normally looks dark. In between the two polarizing filters, there’s a tiny twisted, nematic liquid crystal that can be switched on or off (twisted or untwisted) electronically.
When it’s switched off, it rotates the light passing through it through 90 degrees, effectively allowing light to flow through the two polarizing filters and making the pixel look bright. When it’s switched on, it doesn’t rotate the light, which is blocked by one of the polarizers, and the pixel looks dark.
Each pixel is controlled by a separate transistor (a tiny electronic component) that can switch it on or off many times each second.
Advantages of LCD Over Plasma TV
- No burn-in of static images.
- Cooler running temperature.
- No high altitude use issues.
- Increased image brightness over Plasma, which makes LCD TVs better for viewing in brightly lit rooms.
- Screen surface on most LCD TVs is less reflective than Plasma TV screen surfaces, making them less susceptible to glare.
- Lighter weight (when comparing the same screen sizes) than Plasma TVs of the same screen size.
- Longer display life, but the gap has narrowed.
Disadvantages of LCD vs. Plasma TV
- The lower real-contrast ratio is not as good as rendering deep blacks, although the increasing incorporation of LED backlighting has narrowed this gap.
- Not as good at tracking motion (fast-moving objects may exhibit lag artifacts). However, this has with the implementation of 120Hz screen refresh rates and 240Hz processing in most LCD sets, but that can result in the “Soap Opera Effect,” in which film-based content sources look more like a videotape than film.
- Narrower effective side-to-side viewing angle than Plasma. On LCD TVs, it is common to notice color fading or color shifting as you move your viewing position further to either side of the center point.
- Although LCD TVs do not suffer from burn-in susceptibility, single pixels can burn out, causing small but visible, black or white dots to appear on the screen. Individual pixels are not fixable. Replacing the whole screen is the sole option if the pixel burnout becomes unbearable.
- An LCD TV was typically more expensive than an equivalent-sized (and equivalent featured) Plasma TV. However, that is no longer a factor, since companies have ceased manufacturing Plasma TVs.
LCD TVs without LED backlights are rare, so if you’re shopping for a new LCD TV, you’re more likely to find ones listed as LED. At the same time, you shouldn’t be put off if the TV is listed as LCD. It’s possible that it still has an LED backlight, but, as it still has an LCD display, it’s not an inaccurate listing.