Liquid Crystal Televisions

Liquid Crystals aren't a New Age charm, they're high-tech Television

LCD stands for liquid crystal on silicone. The basic principle behind the LCD display has been around for decades, as the first LCD displays appeared in wristwatches and calculators. This monochrome iteration of the LCD display was used because of its very low-energy requirements - a tiny battery charge could keep an LCD display working for days, even weeks. Full-color LCD displays are still valued for their low-energy requirements and used in notebook computers, pocket PCs and cell phones - virtually anything that uses a display and runs on battery is liable to use LCD technology.

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The basic principle behind the technology is that of liquid crystal, a substance that was discovered more than 100 years ago. These liquid crystals respond to temperature and predictably undergo transitions when voltages are applied. This double-melting material is used as the basis of an LCD panel, a matrix of transistors that can apply voltages to a pixel of liquid crystal. Full-color displays result when the transistors are used to regulate voltages to three sub-pixels of red, green and blue. The amount of energy required to regulate each liquid crystal is very small and on a working full-color LCD panel these crystals regulate light passing through the panel to create astonishing modern LCD displays.

There are two types of LCD monitors or TVs - the LCD panel and rear-projection LCD TVs. The flat-panel LCD TV is a large panel of transistors regulating liquid crystal sub-pixels that in turn regulates the light passing through each pixel. The basic panel is recreated in miniature for an LCD rear projector. A rear projector has three chips; each chip is a separate mini-LCD panel, one for each primary color red, green and blue. The liquid crystal material regulates light reflecting off the chip and into a series of lenses and on to a lenticular screen for viewing. The reflection of light is projected through these lenses, giving a very large display from a small source.

LCD Pluses
  • LCD TVs use less energy.
  • Burn-in is impossible on an LCD display.
  • LCD panel TVs can be wafer-thin and very lightweight.
LCD Minuses
  • LCD displays can behave strangely in adverse temperatures.
  • LCD TVs cost significantly more than CRTs.
  • LCD dead or stuck pixels is a problem with current manufacturing.
  • LCD can give the "screen door" effect.

The benefits to the LCD are first and foremost that they give a fantastic fixed-pixel display. Any of the newer fixed-pixel display types are very pleasing to the eye. A good LCD panel or projector can give very bright and precise images. A good LCD panel can be indistinguishable from a plasma panel that costs almost twice as much as LCD. Also, LCD TVs won't suffer burn-in. You can leave a static image on an LCD panel indefinitely and it can't "burn in" as there is nothing to burn. It's simply a position of liquid crystal that is causing the picture; the liquid crystal will always respond to predictably to the input voltages.

The negative aspect to consider with LCD, especially on a rear-projection model, is the so-called "screen door". The screen door is where images look like they're being viewed through a screen, in other words a visible grid is overlaid upon the images. Generally this is only noticeable (on sets where it's noticeable at all) in very bright scenes. This occurs because of the way any LCD panel is really a matrix of transistors with circuit trace running between each pixel so as to supply the pixel with voltage. It's impossible to achieve 100% coverage on the viewable area with LCD technology. The result is visible with projection models because the spaces between pixels are actually projected along with each pixel. Most well-made LCD projection TVs make clever use of the lenses and can hide this affect so it's barely noticeable. It would require some personal viewing to determine if you're susceptible to this effect or not, as not everyone can see the screen door.

The other major thing to watch out for with the LCD technology is the "dead pixel." A dead or stuck pixel is a pixel on the LCD panel that no longer changes color and is stuck in one color all the time. This is very annoying and noticeable when the pixel is in the middle of the screen or there are a series of them on any one screen. This can literally ruin the affect of watching a home theater. Usually most people won't even notice a dead pixel on a display until it's pointed out, then suddenly it's all they notice.

To deal with fixed pixels you must work with your retailer and manufacturer. Make sure when you buy any LCD-based TV you reserve the right to return the TV no questions asked. This means if it suffers from a dead pixel out of the box you must verify you can return it. Don't be too sure you can without making sure and getting this promise in writing. Most manufacturers don't recognize the dead pixel as a problem but rather a feature of LCD technology. At current levels of technology, due to the small size of the micro-transistors used to regulate the voltages to the liquid crystal, sometimes they'll be unresponsive. Most factories that create LCD panels or chips have an acceptable ratio of dead pixels per display. If your display has less than what the manufacturer deems "acceptable" you won't get any satisfaction from the manufacturer warranty and are subject to the charity of the retailer. The retailer isn't getting covered from the manufacturer either, so you can't expect a positive response from them unless you've coordinated this ahead of time. So, always get the retailer's policy on a product return. Make sure they know you're going to looking for dead pixels on your display and would like a new one if any are evident. Fortunately, this is a manufacturing defect so it's unlikely to occur after you've gotten your panel home. They don't usually just "go bad" after viewing - but are rather born bad.