LCD - Liquid Crystal Display


  • Author Andy Mccarthy
  • Published March 4, 2011
  • Word count 627

LCD stands for liquid crystal display, and connotes the technology behind flat screens growing in popularity among today's electronics consumers. There are several benefits of LCDs over plasmas and cathode ray tubes. LCD is lighter in weight, more compact in size and more portable than its counterparts. It is also more reliable and less expensive, a unique combination. In the safety realm, it is safer for the eyes, has less emission of low frequency radiation, and does not use phosphors, resulting in no image burn. Environmentally speaking, the technology uses 1/3 to 1/2 the electricity, since there are no phosphors that light up. Finally, the screens are flat, which leads to less picture distortion due to a screen's curve, and there is a wider range of screen size options.

Due to these preferential characteristics of Liquid Crystal Displays, by 2008 they had begun surpassing the sale of cathode ray tube units, which are 90% bulkier, inches thicker, and many pounds heavier in comparison.

Liquid crystal displays are composed of five layers. The first of which is backlight, to make colors and images visible since liquid crystals do not emit their own light. Next is a sheet of polarized glass, followed by a mask of colored pixels. Fourth, a layer of liquid crystal solution, which reacts to a wire grid organized into x and y coordinates. And finally a second sheet of polarized glass, coated in a polymer to hold the liquid crystals

These components of the display work together to positioning pixels composed of liquid crystals in front of a backlight to make color images visible to its viewers. Electrical currents of varying voltages stimulate the liquid crystals to open and shut as manipulated, like miniature shutters, either passing or blocking light to manipulate the images on the screen. When light is allowed to pass through open shutters of pixels of a particular color, then those colors illuminate the display with the image we see on the screen. Since the crystals don't produce light on their own, these images are only made visible to the viewer with the support of the built-in backlight. When the shutters of certain pixels are off, they don't emit the backlight, and when the shutters are open, the backlight is able to pass through to create the intended image.

Specs to consider for LCD purchases:

• Contrast ratio, which refers to the visual difference between the screen's brightest whites and darkest blacks. When it comes to contrast ratio, the higher the better, as the colors on the screen are truer to life, more vivid, and less subject to wash out than at lower ratios. For those reasons, high contrast ratios also indicate wider viewing angles. Less impressive screens lean toward a contrast ratio of about 350:1, whereas higher end LCD's offer contrast ratios upwards of 500:1.

• Brightness, which should range anywhere between 250-300 nits, since any higher will probably necessitate adjustment downward.

• Viewing angle, which refers to how many degrees vertically or horizontally a viewer can stray from the center of a screen before the picture begins to wash out, so the wider the better. Minimum recommendations are at least 140 degrees horizontally and 120 degrees vertically.

• Response time refers to how much time is required for pixels to shift from their lightest, to their darkest, and back again. In this case, the smaller the value, the better, since fewer milliseconds indicate a faster response time. Screens with slow response time impose ghosting of images and trailing of images in fast motion. In general, 25 milliseconds is decent, while 17 is ideal.

Overall, LCD panels are much thinner and flatter than the cathode ray tube displays they have replaced in technological devices including computers, television monitors, cell phones, and calculators. Other products using this technology include both personal and promotional digital picture frames.

Andy has over 10 years experience in the promotional product field, with a focus on promotional digital picture frames.

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