4 Types of LCD(Liquid Crystal Display)
4 Types of LCD(Liquid Crystal Display) - Table of contents:
What is LCD?
LCD is a flat display technology, which stands for “Liquid Crystal Display”, which is generally used in computer monitors, instrument panels, cell phones, digital cameras, TVs, laptops, tablets, and calculators.
LCD displays don’t just look different from bulky CRT (Cathode Ray Tube) monitors, the way they operate is significantly different as well.
Instead of firing electrons at a glass screen, an LCD has a backlight that provides a light source to individual pixels arranged in a rectangular grid.
Each pixel has a RGB (Red, Green, and Blue) sub-pixel that can be turned on or off. When all of a pixel’s sub-pixels are turned off, it appears black.
How LCD(Liquid Crystal Display) are Constructed?
An LCD screen includes a thin layer of liquid crystal material sandwiched between two electrodes on glass substrates, with two polarizers on each side. A polarizer is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. The electrodes need to be transparent, so the most popular material is ITO (Indium Tin Oxide).
As LCD can’t emit light itself, normally a backlight is placed behind an LCD screen in order to be seen in the dark environment. The light sources for the backlight can be LED (Light Emitting Diode) or CCFL (Cold Cathode Fluorescent Lamps). The LED backlight is most popular.
Of course, if you like to have a color display, a layer of the color filter can be made into an LCD cell. The color filter consists of RGB color. You can also add a touch panel in front of an LCD.
How LCDs Work?
The first LCD panel technology in mass production is called TN (Twisted Nematic). The principle behind the LCDs is that when an electrical field is not applied to the liquid crystal molecules, the molecules twist 90 degrees in the LCD cell.
When the light either from ambient light or from the backlight passes through the first polarizer, the light is polarized and twisted with the liquid crystal molecular layer. When it reaches the second polarizer, it is blocked. The viewer sees the display is black.
When an electric field is applied to the liquid crystal molecules, they are untwisted. When the polarized light reaches the layer of liquid crystal molecules, the light passes straight through without being twisted. When it reaches the second polarizer, it will also pass through, the viewer sees the display is bright.
Because LCD technology uses electric fields instead of electric current (electron passes through), it has low power consumption.
Types of LCDs
Types of LCDs include:
Twisted Nematic (TN)
– which are inexpensive while having high response times. However, TN displays have low contrast ratios, viewing angles and color contrasts.
In Panel Switching displays (IPS Panels)
– which boast much better contrast ratios, viewing angles and color contrast when compared to TN LCDs.
Vertical Alignment Panels (VA Panels)
– which are seen as a medium quality between TN and IPS displays.
Advanced Fringe Field Switching (AFFS)
– which is a top performer compared IPS displays in color reproduction range.
Advantages of LCD
LCD panels are increasingly rapidly and replacing CRT monitors and televisions in many homes and offices. These displays provide multiple benefits while comparing with CRT technology. Some advantages are discussed below:
LCD (Liquid Crystal Display) technology made display screens much thinner as compared to CRT technology, through which they take up much less space. LCD displays do not take space taken up by the cathode ray tube; therefore, they are also called flat panel screens.
Thus, there is much space on the table that allows keeping other documents and peripheral computer equipment easily on the desk. Hence, LCD panels have almost replaced the CRT displays.
One of the best advantages of LCD displays is less energy Consumption. It takes very less energy as compared to CRT technology. If the size increases of LCD monitors, its power consumption is also increased;
But it still takes low power while comparing with CRT monitors. On the basis of the size, the power consumption of LCD monitors is around 25 to 50 watts, but the same size of CRT monitor takes 60 to 80 watts. If the size of the CRT monitor is 19-inch, it will consume anything between 70 and 150 watts.
As compared to CRT technology, LCD monitors provide output with brighter pictures as they generate the high peak intensity. Due to high-intensity results, LCD panels illuminate the screen through a constant backlight.
Thus, LCD monitors are sufficient for use in brightly lit areas.
The screen viewing area is scanned as horizontal lines in CRT monitors. And, the rate at which the entire screen is scanned is called refresh rate. Typically, CRT monitors have a flickering effect as they contain a low refresh rate. The flickering effect can be caused to detrimental health and eye strain, and headaches if anyone is viewing for a long time period.
LCD monitors have a very high refresh rate in comparison to CRT monitors. They have a refresh rate of 75 and 85 hertz being common, which means the flickering effect is very low in LCD displays that made them much comfortable to use anywhere.
With the LCD displays, you can end up with a lot of static content (images that don’t change or move around) when you watch the stock ticker on MSNBC, play a lot of video games, or do other things.
But CRT displays involve those images and content that cannot end up. It is done with LCD because instead of creating its own light with phosphors, it utilizes a separate backlight. Hence, they are sufficient in this problem; however, plasmas are unable to do that.