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Basic Things You Need to Know About LCDDisplay
LCD display screens are everywhere. Youprobably own one or more devices with an LCD display screen at home and work.This includes your TV, computer monitor, watches, clocks, smartphones, and evencalculators.
But have you ever wondered about how yourLCD screen works, its lifespan, components, and how it holds up to otheremerging display technologies today?
Knowing all these things about your LCDdisplay lets you appreciate your screen all the more. Caring for your devicebecomes easier when you’re armed with this knowledge.
Without further ado, here are the basicthings you need to know about LCD display.
How Does LCD Display Screens Work?
LCD screens make use of Liquid CrystalDisplay (LCD) technology. The screen is embedded with liquid crystals, asubstance that has properties in between a conventional liquid and a solidcrystal. Liquid crystals can flow, but their molecules carry a crystal-likesolid orientation.
Liquid crystals are responsible forproducing an image flashed onto the LCD screen. They don’t emit light, though.Backlights are used to illuminate these crystals.
A display screen is made up of several tinycolor blocks called pixels. The term is a portmanteau of “picture” and“element”, denoting pixels as little elements making up an entire screenpicture. A screen is typically made up of millions of pixels.
Every pixel on the display screen is madeup of red, blue, and green light. These lights can be quickly turned on or offto create an overall moving picture or image.
Now, in LCD displays, pixels are regulatedby using liquid crystals for rotating polarized light. Polarized light denoteslight waves with vibrations occurring in a single plane. In LCDs, this isachieved by using polarized layers.
Each pixel has polarizing filters on bothits front and back. Tiny nematic (twisted) liquid crystals are placed inbetween these filters. The liquid crystals can be switched on or offelectronically through tiny electronic transistors.
When the liquid crystal is turned off,electricity controlled by the transistor stops flowing. The pixel is thenturned on, brightening up due to the 90-degree twisting of the nematic liquidcrystal. This allows light to pass through both polarizing filters on thepixel, illuminating the pixel by letting light pass through.
When the liquid crystal is turned on,electricity flows through the nematic liquid crystals. They completelystraighten out from their twisted state. The polarizing filter in front of theliquid crystal blocks out the light, resulting in the pixel turning off andbecoming dark.
A single LCD contains millions of pixels,nematic liquid crystals, polarizing filters, and transistors. They all worktogether to create images on the screen.
LCD Display Lifespan
LCD display lifespan depends on severalfactors such as:
• Backlight source of the LCD screen
• Display screen size
• Storage conditions
• Status of electrical components accompanying theLCD screen
• Frequency of use
• Operating environment of the screen (is it usedindoors or outdoors)
Most LCD monitors have a lifespan rangingfrom 30,000 to 60,000 hours. That's equivalent to 5-7 years using the monitorfor 24 hours per day. It could also translate to 10-20 years with running themonitor for 8 hours a day, 5 days a week.
The backlight's life expectancy is the biggest factor in determining the LCDdisplay lifespan. It's because liquid crystals do not give off light fromthemselves. The liquid crystals depend on the backlight for illuminating them.Hence, the LCD screen wears off when the backlights dim as it reaches itsmaximum lifespan.
LCD Display Components
Several components make up an LCD display screen. We'll explain each one here:
1. Backlight
The backlight serves as the illuminator of the entire LCD display device.Without a backlight, the LCD device remains darkened and hard to use.Backlights are installed directly behind the LCD panel to lighten up thedisplay.
Simple devices such as pocket calculatorsdon’t use a backlight for their LCD screens. Users rely on natural light to seethe numbers displayed on such calculators. However, the majority of modern LCDscreens such as televisions, computer monitors, smartphones, aviation screenpanels, outdoor signages, and medical monitoring devices use backlights astheir internal light source.
There are various types of backlights used in LCDs, and here are some of them:
a. Light Emitting Diode (LED)
This type of backlight is the most popularand widely-used light source for LCDs today. Light-emitting diodes aresemiconductors that emit light once electric current flows into it. Particlescarrying the electric current are called electrons holes. These combine withelectrons in the semiconductor, releasing photons (light particles).
Band separations called bandgaps determinethe photons’ energy. Furthermore, the photon’s energy dictates which color theLED emits, depending on the emitted light’s wavelength. Various kinds ofsemiconductors and their corresponding varying bandgaps create different lightcolors.
LED has many sub-categories, including:
• Edge-Lit White LED (EL-WLED) – One or more LED rows are placed on the screen’s edge. A speciallight diffuser is used to scatter the light evenly across the entire displayscreen. Computer monitors, laptops, notebooks, and even HDTVs are now lit inthis way.
• White LED (WLED) –The LCD panel’s rear side is lit up with several white-colored LEDs. A diffuseris set in front of the LEDs to help evenly smooth out the light throughout thescreen. Some computer monitors and large-screen LCD TVs use this LEDtechnology.
• Red-Green-Blue LED (RGB LED) – This technology works like WLED. The difference is that it usesred, green, and blue LED combination lights instead of white lights. Betterpicture quality and higher color gamut are its advantages over WLED andEL-WLED.
b. Electroluminescence Panel (ELP)
ELP uses electroluminescent materials suchas colored phosphors instead of heat to create light. This material is placedin between two conductor layers. The material emits light as a result of anelectric current flowing through it. ELPs are mostly used in small LCD screens.
c. Cold Cathode Fluorescent Lamps (CCFL)
CCFL backlight uses a cold cathode fluorescentlamp as its main light source. This lamp consists of a cathode that isn’theated electrically by a filament, hence the connotation “cold”. A diffuser is placed in front of the CCFLlamp to evenly distribute light across the entire screen.
The cathodes used in CCFL produce light bycreating a non-heated thermionic emission of electrons. This is accomplished byusing discharges in mercury vapor to create an ultraviolet light. This light,in turn, creates a fluorescent coating inside the lamp, resulting in visiblelight.
Neon lamps are also considered a type ofCCFL. Such lamps emit light through gas molecule excitation.
Computer monitors and TV screenspredominantly used CCFLs for backlights. However, modern manufacturers opt forLED technology instead of CCFL for their devices’ backlights.
d. Hot Cathode Fluorescent Lamps (HCFL)
HCFL backlights have filaments that need tobe heated to excite mercury atoms, cause the current to flow, and ultimatelyemit light. HCFLs are often used in LCD equipment such as medical devices,custom task-oriented lamps, scanners, and outdoor LCD signs.
2. Liquid Crystals
Liquid crystals are the heart of an LCD display. This unique substance flowslike a liquid but retains many characteristics of solid crystals. They havelong and cylindrical-shaped molecules that can twist when changes in molecularorientation happen.
Different liquid crystal families are usedin LCD displays. One requirement of such liquids is to exhibit mutualattraction. Also, the molecules in the liquid crystal need to be anisotropic.This means that the liquid crystal molecules have that average structural orderalong a molecular axis.
Liquid crystals are often sandwiched in between the color filters and thepolarizers. They twist and straighten in response to electrical currentsapplied to them. The movement of liquid crystals controls whether polarizedlight will pass through the filters or not.
Liquid crystals have three basic phases ofmovement:
a. Nematic
The nematic phase is characterized by thecrystal molecules freely moving around the liquid. However, these moleculespoint themselves to one direction only, making it unique from pure liquidmolecules. Nematic liquid crystals are the most common liquid used in LCDscreens.
b. Smectic
In the smectic phase, the liquid crystalskeep their similar orientation and direction. But the molecules are now liningthemselves into layers. The smectic layers have restricted movement, creating asolid-like state in the liquid crystals.
c. Cholesteric
Also known as the chiral nematic phase, thecholesteric phase happens when the liquid crystal molecules align themselves ata slight angle to each other. The molecules become stacked in very thin layersas well. The cholesteric phase also allows molecules to change color fromexposure to different temperatures.
Now, molecules in liquid crystals move as areaction to an electric field. Their arrangement changes as a voltage areapplied to them. This allows liquid crystals to control polarized light, which,in turn, defines which pixels on a screen will be illuminated or not.
3. Color Filters
Color filters are found in between theliquid crystals. These filters determine whether the pixel shows red, green, orblue colors when activated. The filters work by independently controlling thepixel’s red, green, and blue sub-pixels. With this, the LCD screen canreproduce all possible colors found in the color space.
The color filters aren’t active elements,though. It’s the liquid crystal molecules that control the light passingthrough the filters. The color filters simply determine the color the pixelshows based on how much light is passing through them, as determined by theapplied electric voltage and the movement of the liquid crystal molecules.
4. Polarizing Filters
An LCD cell is made up of two polarizingfilters. They enclose the liquid crystals and color filters. One polarizingfilter is located in front of the backlight and is horizontal in orientation.The other one is found just beneath the pixel in front and is vertical inorientation. Polarizing filters are typically made of transparent crystals orglass substrates.
The role of polarizing filters is tocontrol which light patterns can pass through the LCD screen. Without thesefilters, visual images generated by the LCD panel will have a poor contrastratio and an inferior quality image.
Now, light emitted by your panel’sbacklight source enters the first horizontal polarizing filter. It then passesthrough the liquid crystals. The polarized light vibrates vertically if theliquid crystals are in a twisted state. Hence, these light waves can then passthrough the second vertical polarizing filter. The pixel on the screen turns onand is illuminated properly.
Meanwhile, if the liquid crystals are arrangedin a straightened way, the horizontal light waves that came from the firstpolarizing filter will be blocked from entering the vertical polarizing filter.The pixel is then turned off and no light illuminates it.
The two polarizing filters need to bevertical and horizontal in orientation, respectively. If the filters areoriented in the same way (ie; both horizontal or both vertical) will block allthe light passing through, displaying nothing on the screen.
5. Thin-Film Transistors (TFT)
TFTs are tiny electrical components etchedon the polarizing glass substrates. Amorphous silicon transistors are oftenused for LCD panels.
TFTs are responsible for providingelectrical voltage to the liquid crystals. Each screen pixel has acorresponding transistor, enabling the pixels to easily be controlled in unisonthrough changes in electrical current.
Using TFTs requires less charge and lesspower to operate the LCD screen successfully. TFT use also leads to sharperimages because each pixel has its own transistor controlling it. The chargegiven to a certain pixel can be actively maintained even if the screen isrefreshed to display another image.
LCD Display VS OLED Display
A new form of display technology calledOrganic Light-Emitting Diode (OLED) is sweeping the display world today. Let’stake a look at what OLED display is and how it stacks up to LCDs.
OLED display uses a light-emitting diode(LED) that features an organic compound as its emissive electroluminescentlayer. Electric current is applied to the diode, activating the organiccompound film and giving off light as a result. The organic compound film istypically situated between two electrodes, one of which is transparent.
OLEDs are mostly used in smartphones andlimited releases of high-end smart televisions. It can also be used in computermonitors and handheld game consoles.
Now, here’s a comparison of LCD display vsOLED display:
Light Emission
OLED displays naturally emit light, sousing them on a display panel doesn’t require a backlight. Meanwhile, LCDs needbacklights because the liquid crystals cannot create light on their own. OLED’snatural light emission also paves the way for creating lighter screen devicesthan those using LCDs.
Brightness
LCD displays are brighter than OLED. Thisis due to LCD’s use of backlights that can brightly light up the entire screen.While OLEDs emit good brightness levels from their light, it can never matchthe brightness that LCD backlights have.
Black Levels
OLED wins in the black levels feature. It’sbecause OLEDs can perfectly turn off a pixel, causing it to become completelyblack. LCDs can’t create perfect black screens even with their full-array localdimming feature. LCDs are also prone to blooming, where a bright part spoilsthe darkness of an adjacent black area.
Viewing Angle
OLED screens have better viewing anglesthan LCDs. Some LCDs improve their viewing angles by using in-plane switchingpanels (IPS). However, the clarity of images and videos can’t match that ofOLEDs when viewed from extreme side angles. This is because LCDs inherentlyblock light due to its filtering layers, and that creates added depth whichmakes LCD viewing angles limited.
Energy Consumption
LCD displays are a bit moreenergy-efficient than OLEDs. Energy consumption in OLED displays depends on thescreen brightness. Less brightness used means lower power consumption, but thismay not be ideal because the contrast ration will suffer when brightness isreduced. This is not ideal if, for instance, you’re using an OLED smartphoneunder bright sunlight.
Meanwhile, the backlights form the bulk ofpower consumption in LCD displays. Putting the backlight to a lower settingsignificantly improves the energy efficiency of LCD displays. For instance,reducing the backlight brightness of an LCD TV with a LED backlight won’taffect the picture quality but will draw less power consumption than an OLEDTV.
Both OLED and LCD create high-qualityimages with wide color gamut on a screen. OLED display wins over LCD displayregarding blackness levels and viewing angle. However, LCD display takes thecake for brightness and energy efficiency.
LCD Display VS AMOLED Display
AMOLED is another emerging displaytechnology lately. It stands for Active Matrix Organic Light-Emitting Diodes.AMOLED is a type of OLED display used in several smartphones, digital cameras,televisions, and media players.
Active Matrix technology is utilized inAMOLED displays. This refers to how the OLEDs in the display panel arecontrolled and arranged.
Thin film transistors (TFTs) and capacitorsare attached to each pixel LED component of the panel. At least two TFTs areattached to one pixel – one to control the capacitor’s charging and another togive a voltage source.
The voltage source allows continuous,constant current to the pixel. Hence, there is a better level of controlexerted over pixels, allowing you to quickly dim or turn off and on individualpixels.
Let’s move on to a quick comparison of LCDdisplay vs AMOLED display:
Color Accuracy
AMOLED displays have better color accuracythan LCDs. What makes the color more accurate in AMOLED displays is largely dueto the precise pixel control achieved by AMOLED panels.
Whites and blacks appear perfect in AMOLEDdisplays. Whites produced by LCDs may carry a bluish tint due to the backlight.Blacks don’t completely appear dark in LCDs, too.
Color Gamut
AMOLED provides a greater color gamut thanLCDs. AMOLEDs (and all OLED displays in general) have additional blue and greensaturation. While these hues greatly widen AMOLED’s color options, some peoplefind the resulting colors a bit unnatural to look at.
Meanwhile, LCDs have subdued greens andquite compelling red hues. Its color gamut may not be as wide as AMOLED’s, butmany people still find it satisfying. That’s because LCD’s color range closelymatches the Standard RBG color gamut profile, the one most utilized in videosand images.
Color Balance
LCD’s backlights help maintain the colorbalance of the entire screen. The backlights ensure that color balance remainsconsistent across the display. Meanwhile, AMOLED tends to suffer from veryslight color balance drifts because of variances in the diodes’ light-emittingcapacity over time.
Contrast Ratio
LCDs often have a lower contrast ratio andare prone to light bleeds. That’s due to the backlights remaining open even iflight has been blocked and the pixels are supposed to show black color. This isnot a problem with AMOLED displays because the panel can simply switch off thepixel to create a pure black color. AMOLEDs have a better contrast ratio asexhibited by their pure black and white levels.
Component Lifespan
AMOLED’s different RGB components candegrade at different rates. Hence, AMOLED may experience problems and degradationat a faster rate than LCDs.
Suitability for Mobile Devices
Since AMOLED displays do not requirefiltering layers and backlights, they’re more suited for use in handheld mobiledevices such as smartphones and gaming consoles. LCD may be used in mobiledevices as well, but the filtering layers and backlights tend to add a slightbulk to the device. Hence, many manufacturers are now switching to thinner andlighter AMOLED displays.
To sum up this part, AMOLED displays farebetter than LCDs in terms of color gamut, accuracy, contrast, and mobile devicesuitability. However, LCDs have the potential for longer lifespans and carry abetter color balance across the display device.
Color LCD VS Display P3
Display P3 is an Apple-developed colorspace heavily used in American films and digital movie projection. It allowsdevices to display richer, vibrant, and more lifelike colors that are demandedin videos and movies. It’s also created for adapting to computer displays.
Display P3 has a color space based on theDCI-P3 primaries. It uses the D65 white point which is typically used in colorspaces for computer displays. Display P3 also utilizes the sRGB transfer curvein place of the DCI-P3’s 1/2.6 pure gamma curve.
If you compare color LCD vs Display P3,you’ll find a significantly wider color range in Display P3 than the typicalsRGB used in color LCDs. LCD monitors, especially those used in computers andlaptops, are configured to accurately represent the sRGB gamut as precisely aspossible. Meanwhile, Display P3 has been consistently used in Apple productssince 2015, starting with the iMac desktop.
Display P3 is not limited to Apple devices,though. Several devices have been configured to support Display P3 as well.These include smartphones from Samsung, OnePlus, Google, and HTC. EvenWindows-based laptops from Acer and Asus support Display P3 color gamut.
Conclusion
That’s all the basic information you needto know about LCD display screens. Now, you know how an LCD screen works, itspossible lifespan, components, and how it compares to other displaytechnologies.
Armed with this information, you can betterappreciate and take care of your LCD devices. And in case you’re planning toadd display devices to your business, the information you’ve learned will helpyou make educated choices regarding the display technologies you’ll utilize.
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