What’s The Difference Between LCD and LED?

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Technically speaking, the main difference between the LED and the LCD is that the LED uses the PN-junction diode which emits light when the electrons flow through it, whereas LCD uses liquid crystal (or plasma in some cases) for  emission of visible light.

LCD and LED are two words that seem to be thrown at us from every billboard and advertisement on TV, and any conversation about television innovation would be incomplete without referring to them. Let us now look into more details about the two prominent TV technologies.

The Technology

Both LCD and LED TVs use the same basic technology. Over time, however, televisions became bigger and bulkier, as well as more power-intensive. These beasts took up far too much space, ate up too much electricity and were too difficult to produce. Thus, the age of liquid crystal technology dawned.

For the longest time, human beings were under the impression that matter could only exist in three states: solid, liquid and gaseous. However, following a discovery made by Friedrich Reinitzer in 1888, we found a new state for matter to be in – a kind of middle ground between the solid and liquid states. This state was termed “liquid crystal”. The molecules in this state tend to maintain their orientation, like a solid, but also have certain properties of fluid, like a liquid.

If you apply electricity to a certain phase of liquid crystals, the molecules straighten out. This property of liquid crystals makes them very useful in the manufacture of LCD televisions.

lcd-pictures-of-liquid

LCD stands for ‘liquid crystal display’. It consists of two layers of polarizing film stuck close to each other. Between these two films, there is a layer composed of liquid crystals. When electric current is passed through it, these liquid crystals allow light to pass through, or alternatively, allow light to be blocked.

LCD

LCD technology brought several unprecedented advantages alone with it. For one, LCD televisions are incredibly light and thin. The thickness of most LCD TVs hardly ever exceeds 3 inches, while some LCD screens are even smaller – just 1 inch thick! These display panels also do not emit harmful electromagnetic radiation. The images produced by an LCD TV are of remarkably better quality than the images from older CRT television models. LCD technology also helps to conserve energy. CCFL-based LCD screens save twenty to thirty percent more electricity than even the most energy-efficient plasma TVs!

Sony_KDL-S19A10

An LCD screen

However, what must be remembered is that the liquid crystals in an LCD screen do not produce any light on their own. The light has to be externally manufactured in the television itself. There are a number of fluorescent lights at the back of the screen that produce this light. Millions of tiny shutters are placed in a grid to control the passage of light – opening to release the light that is needed and closing to trap the light that isn’t. With the help of these florescent lights, the crisp images displayed by the liquid crystals become visible to the viewer.

LED

LED TVs, on the other hand, don’t use these kinds of fluorescent lights. LED stands for ‘light-emitting diodes’, which are exactly what an LED TV uses to illuminate the images displayed on the screen. This is the basic and main difference between LCD and LED TVs.

Also, the placement of the lights on an LED screen can differ. The fluorescent lights in an LCD TV are always behind the screen. On an LED screen, however, the light-emitting diodes can be placed either behind the screen or around its edges.

800px-IPod_Touch_2G_Backlight

Diodes at the edge of an LED screen of a phone

With Edge Lighting, LED TVs produce light from a series of diodes arranged outside the edge of the screen. On the other hand, backlit LEDs (better known as Full Array Lighting) has the light-producing diodes behind the screen. Full Array Lighting offers more control over the brightness of the image, as these diodes can be independently controlled.

The different lighting technology used in LED TVs ensures that most LED screens are slimmer than LCD screens. The image quality is also much better, with LED screens producing colors that are sharper and more realistic than LCD screens. In addition to this, LED technology significantly reduces the energy consumption of the television unit. If LCD TVs are 20-30% more efficient than plasma TVs, LEDs can be up to 50% more efficient! 

LCD_TV_與_LED_TV比較2_小

Source: Wikipedia

Edge Lighting has its own problems, though. It does not guarantee satisfactory angle-viewing of the screen, which isn’t as much of a problem with a backlit LCD screen. A backlit LED TV usually offers better angle viewing than a backlit LCD TV.

LCD vs Edgelit LED vs Backlit LED Source: Wikipedia

LCD vs Edgelit LED vs Backlit LED
Source: Wikipedia

So there you go! Now that you know the difference, you’re officially a more enlightened consumer. Happy shopping!

References

  1. Central Information Technology Services (University of Wisconsin)
  2. Academia
  3. Television (TV) Buying Guide
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About the Author:

Vaishnavi has a bachelor’s degree in Sociology/Anthropology from St. Xavier’s College, Mumbai (India) and is currently pursuing a Master’s Degree in Global Studies (whatever that is) from Humboldt University, Berlin (Germany). She loves to read and to sing, especially to avoid awkward situations. She claims she has learned a lot through traveling but she still ends up pulling a door marked ‘Push’, so the jury is still out on that one.

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