Liquid crystal displays, or LCDs, have become an integral part of our digital world, powering screens large and small. This article will provide a comprehensive look at the development, working principles, types, applications and future trends of this ubiquitous display technology.
A Brief History of LCDs
The discovery of liquid crystals dates back to 1888 when Austrian scientist Friedrich Reinitzer observed a strange behavior in cholesteryl benzoate compounds extracted from carrots. The compounds appeared to have an intermediate phase between solid and liquid. Reinitzer collaborated with German physicist Otto Lehmann, who coined the term "liquid crystals" in his 1904 book Flüssige Kristalle (Liquid Crystals).
Otto Lehmann, who coined the term "liquid crystals" in 1904. (Image: Public domain)
For several decades, liquid crystals were a scientific curiosity looking for real-world application. The breakthrough came in 1964 when RCA researchers George Heilmeier, Louis Zanoni and Lucian Barton experimented with liquid crystals under electric fields and realized their potential for displays.
Heilmeier in particular is considered the father of LCDs – he developed the first working liquid crystal display in 1968 and holds over 100 patents in LC technology. Through innovations by other engineers at RCA and Westinghouse, the first LCD wristwatch was created in 1972.
Companies in Switzerland, Japan and the USA commercialized LCDs through the 1970s-90s. The advent of thin-film transistor (TFT) technology in the 90s enabled the production of high-quality color displays, paving the way for LCD televisions, monitors and phones.
How Do LCDs Work?
Structure of a twisted nematic LCD. (Image: ResearchGate)
An LCD sandwich contains the following key components:
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Polarizing filters: These filters only let light waves vibrating in one direction pass through. In LCDs, two polarizing filters are placed perpendicular (90°) to each other.
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Glass substrate: The polarizers and liquid crystals sit between two glass sheets that protect the inner components.
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Liquid crystals: These long-chain organic molecules can be aligned by electric signals. Common types used are twisted nematic and in-plane switching crystals.
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Color filters: Red, blue and green filters are alternately placed over pixel regions to enable color displays.
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Backlight: LCDs do not produce their own light – a strong backlight like CCFL or LED provides illumination.
When no voltage is applied, light entering from the backlight gets twisted 90° by the liquid crystals and passes through the front polarizer to brightly illuminate that pixel. When voltage is applied, crystals untwist and block light transmission through that area, making it appear darker.
Millions of tiny pixel regions can be controlled like this across the display to produce images in color.
Passive vs. Active Matrix LCDs
LCDs use either a passive matrix or active matrix arrangement of pixels.
In passive matrix LCDs, pixel rows and columns form a grid that is used to control pixels through the timing of voltage signals. They have slower response times and are difficult to produce in large sizes.
Modern LCDs predominantly use active matrix technology, first patented by T. Peter Brody in 1972. Each pixel has its own control circuit with capacitors and transistors that maintain the pixel state while other parts of the display are addressed. This enables faster response, better viewing angles and larger possible screen sizes.
Major Applications of LCD Technology
Since commercialization in the 70s, LCDs have steadily conquered markets occupied by heavy, space-consuming CRT displays:
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Mobile phones and tablets: LCDs enabled the transition to large yet sleek touchscreen devices. Active matrix LCDs can scale to any size while remaining energy efficient.
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Computer monitors and televisions: LCD monitors overtook CRTs in 2008 to become the most popular display for PCs. LCD TVs now comprise over 90% of global TV shipments due to falling prices and better picture quality.
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Portable electronics: Watches, calculators, camcorders and other gadgets have used LCDs for compact form factors combined with lower power than LED displays. Special LCDs are even used on spaceships due to limited weight considerations!
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Industrial and medical devices: Rugged small-format LCDs bring displays into test equipment, point-of-sale devices, heart monitors and more while avoiding bulky CRTs. Custom LCD variants like OLEDs and e-paper target emerging niches.
LCD shipments crossed 1.1 billion units worldwide in 2021. They have become indispensable for digital systems, enabling interactivity through screens that were unthinkable 50 years ago.
Recent Advances Expanding LCD Capabilities
While LCD principles have remained similar over the decades, innovation continues to push boundaries:
In-Plane Switching (IPS): IPS LCDs move the liquid crystal switching into a horizontal plane for massively improved viewing angles compared to older twisted nematic tech.
IPS LCDs enable much wider viewing angles (Image: ResearchGate)
Quantum Dots: Adding a quantum dot layer improves color saturation and brightness through pure emitted light. QD-enhanced LCD TVs can match OLED-level quality at lower cost.
Local Dimming: Thousands of LED zones on the backlight of premium LCD TVs can selectively dim or boost illumination for far better blacks and contrast than conventional edge lighting.
MiniLED Backlights: Shrinking LED sizes increases granularity of backlight dimming for thousands of virtual dimming zones on LCD TVs and monitors.
The Threat from OLEDs and MicroLEDs
Despite rapid improvement, LCD technology has serious up-and-coming competitors with their own pros and cons:
OLEDs: Organic light-emitting diode displays can be manufactured on flexible plastic substrates for lighter and thinner panels. As each pixel emits its own light, OLEDs enable perfect blacks, infinite contrast and superior viewing angles to LCDs. Downsides are higher production costs, possible burn-in and lower peak brightness.
MicroLEDs: This futuristic technology shrinks LEDs to microscopic sizes – each becoming its own pixel. Benefits include perfect blacks, high speed, wide color gamut, no burn-in and astonishing peak brightness and contrast. High density assembly remains extremely challenging and expensive, restricting microLEDs to niche applications for now.
OLED TV sales are projected to overtake LCD TVs worldwide by 2026-27. Meanwhile high-end LCDs continue dominating the monitor and large-format display category for the foreseeable future thanks to lower costs.
LCD Panel Production and Market Forces
China has become the manufacturing hub for LCD panels – major suppliers like BOE Technology, China Star Optoelectronics and CSOT churn out millions of LCD screens annually for both domestic use and export overseas. Other top suppliers are based in South Korea and Japan – LG Display, Samsung Display and Japan Display being the heavyweights.
Global LCD TV unit sales forecast to decline slowly as OLED TVs gain share (Image: Statista)
According to [OMDIA research](https://technology.ihs.com/ encourage readers to click link) , LCD panel makers produced nearly 1.3 billion square meters of LCDs in 2021. The equivalent of over 200 million TV panels helps meet continuous demand from manufacturers and retailers. With LCD monitors, mobile devices, automotive displays and embedded gadgets added to the mix, LCD shipments easily crossed 1.1 billion units last year.
However Statista forecasts predict that global LCD TV shipments will peak by 2023 before slowly declining over the late 2020s as other technologies like OLED TVs bite into market share. Nevertheless, LCD technology still has tremendous staying power due to lower production costs and technical advantages holding back alternatives like microLEDs.
The Road Ahead for LCDs
Liquid crystal display technology has progressed enormously from early monochrome watches to vivid widescreen TVs and monitors. While OLEDs pose a disruptive challenge, improved LCDs also continue raising the bar through quantum dots, full array local dimming (FALD), MiniLED and MicroLED backlights.
Gamers and videophiles will accelerate the uptake of advanced LCD monitors with extreme refresh rates, high resolution and MiniLED backlights. On the other extreme, low-cost commodity LCD panels and devices will keep spreading across the developing world.
In industrial roles, smaller LCD innovations could embed interactive displays onto surfaces like car windshields and retail storefronts through flexible plastic or glass substrates. Once confined to bulky CRTs, LCD technology has successfully poured visual information into almost every facet of society – a trend that has miles still left to run thanks to sustained enhancements and cost efficiencies that cannot be ignored.
Frequently Asked Questions
What is an LCD?
A liquid crystal display (LCD) is a thin panel containing liquid crystals sandwiched between polarizing filters and glass substrates. Applying electric signals controls crystal alignment to let variable amounts of backlight through for illuminating pixels.
Who invented the LCD?
While liquid crystals were discovered in 1888, RCA researcher George Heilmeier is considered the father of LCDs for realizing their potential for displays and constructing the first working LCD in 1968 based on his own patented ideas.
How do LCDs produce color?
Alternating red, green and blue color filters over LCD pixels let white backlight pass through to create full-color images. Advanced LCD TVs also use quantum dots to enhance color brightness and saturation.
Why are LCDs flat and thin compared to CRTs?
LCDs modulate external backlight rather than having to electronically aim and fire photons from the back of the screen like bulky cathode ray tubes. This enables extremely compact and lightweight construction.
Do LCDs use more power than OLED displays?
For equivalent sizes and resolutions LCDs generally consume more power due to requiring strong backlighting. OLED displays are emissive, so blacks use no energy – giving OLED TVs clear power efficiency advantages.
