The basic difference between liquid crystal display and light emitting diode is that light emitting diode uses a PN junction diode to emit light, when current passes through it, but in case of liquid crystal display, liquid crystal or plasma is used to emit light. This liquid crystal material is filled b/w glass electrodes, on the passage of power, they cause light emission by being energized. LCDs display text or images in form of segments or dot matrix. LEDs show the numeric or alphanumeric characters and they use gallium arsenide and gallium phosphide to emit light on heating. However, basic purpose of both LED and LCD is to display images and texts.
An optical device which displays information in form of text or images in form of dots. Cold cathode fluorescent lamp provides the back light (A light used in monitors by using LCD technology. LCD monitors depend on light source to provide visible image as they can’t produce light by themselves) and it has low resolution. It needs less power and offers large display area with low price in market. It is manufactured by glass electrodes and liquid crystals. It has slow switching (needs more time for switching) time and direct current and reduce its life span. Mercury is used in its formation which pollutes the environment. The LCDs use liquid filaments and liquid crystal is filled b/w two glass electrodes and it is transparent in absence of potential. However, when power is applied then, it scatters light in all directions, which makes its look bright. It operates with AC with the frequency of 500 Hz.
The basic working principle of liquid crystal display is the blocking of light. LCD is manufactured by sandwiching a liquid crystal material b/w two pieces of polarized glass (substrates). Light produced from backlight passes through first substrate, instantly, molecules of liquid crystal align to allow the passage of current through to the 2nd substrate and hence creating the color and images that you see.
It is a type of PN junction diode which emits visible light when current passes through it. There is no back light in it and it has high resolution. It needs more power and its display area is small. It uses gallium arsenide phosphide with fast switching time and it is costly in market. Mercury is not used in it and direct current doesn’t affect it. It is formed by mixing of P and N-type semiconductor materials. When current passes through it then electrons and holes recombine, which results in the formation of light photons. The material used in LED is translucent (allows light to pass), so that light can be emitted through junction. LEDs are available in market in red, green and amber colors. They are used to display alpha numeric characters. It can operate with a wide range of temperature (zero to 70 degree Celsius), it can withstand with shocks and vibrations and it is very durable.
Basic principle of LED working is that, when current passes through it, then the electrons in lower energy state move to higher energy levels. Since electrons in excited state are unstable so they return back by emitting the photons, having energy equal to the difference of the energy levels of the two states.
LED has more advantages than LCD, so it is more common. But it cannot be used for large displays.
How to know which screen is LED or LCD?
An LCD screen will display a faint white glow on it when bright light will be shine on it, but an LED screen will remain truly dark even light is shine on it. Another point is that, if your display screen doesn’t contain any inverter (a long rectangular circuit placed at bottom of screen) then it is an LED.
Cold cathode lightening technology used in LCDs can affect our eyes too, so LED are recommended over LCDs as they have better color quality. But actually, you need to relax your eyes after one hour in case of both displays.
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