• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2

# How LCD screens work.

Extracts from this document...

Introduction

How LCD screens work

Although the term liquid crystal sounds like an oxy moron, it is in fact describing a solid whose particles are free to move around each other almost like a heavy molecular level.

Crystals are either categorised as thermotropic or lyotropic. Thermotropic crystals are affected by changes in temperature and some times pressure. They are either isotropic (with no particular arrangement) or nematic (with a pattern).

Ferro electric crystals use nematic crystals with a spiral pattern to allow for microsecond switching. It is necessary to have a layer of glass to maintain a certain pressure and to alow for even quicker switching.

There are four facts that allow for liquid crystals to work in the way they do

• Light can be polarized.
• Liquid crystals can transmit and change polarized light.
• The structure of liquid crystals can be changed by electric current.
• There are transparent substances that can conduct electricity.

Middle

Active-matrix LCDs depend on thin film transistors (TFT). Basically, TFTs are tiny switching transistors and capacitors. They are arranged in a matrix on a glass substrate. To address a particular pixel, the proper row is switched on, and then a charge is sent down the correct column. Since all of the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor is able to hold the charge until the next refresh cycle. And if we carefully control the amount of voltage supplied to a crystal, we can make it untwist only enough to allow some light through. By doing this in very exact, very small increments, LCDs can create a gray scale. Most displays today offer 256 levels of brightness per pixel.

Conclusion

resolutions up to 1,024x768. If we multiply 1,024 columns by 768 rows by 3 subpixels, we get 2,359,296 transistors etched onto the glass! If there is a problem with any of these transistors, it creates a "bad pixel" on the display. Most active matrix displays have a few bad pixels scattered across the screen.

Display size is limited by the quality-control problems faced by manufacturers. Simply put, to increase display size, manufacturers must add more pixels and transistors. As they increase the number of pixels and transistors, they also increase the chance of including a bad transistor in a display. Manufacturers of existing large LCDs often reject about 40 percent of the panels that come off the assembly line. The level of rejection directly affects LCD price since the sales of the good LCDs must cover the cost of manufacturing both the good and bad ones. Only advances in manufacturing can lead to affordable displays in bigger sizes.

This student written piece of work is one of many that can be found in our GCSE Sliding Puzzle section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
• Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to