Invention History of Liquid Crystal Display (LCD)
The history and development of the Liquid Crystal Display (LCD) is
rather complex. The story of the LCD had an unusual beginning by an
Austrian botanist in the 19th century. Though the LCD made a different
and unstable start, its development proceeded from early successes like
the pocket calculator to the key milestone of a flat panel television
display that can be hung on a wall. The origin and development of the
LCD spans the world’s major industrial centers including the US, Japan
and Europe.
Liquid Crystals – Discovery
Liquid
crystals were first observed by an Austrian botanist, Friedrich
Reinitzer, in the year 1888. He discovered a strange material that
exhibited a mesophase between the solid state and liquid state. At a
temperature of 145 degree Celsius, it melted, probably becoming white
and viscous. When he increased the temperature to 179 degree Celsius, it
became isotropic and clear. The material discovered by him was
cholesteryl benzoate. Regarding this, he wrote a letter to Otto Lehmann,
professor of Physics at the Technical University Karlsruhe of Germany
on 14th of March, 1889. In the letter, he had written in detail about
the two melting points. Lehmann studied the material comprehensively and
discovered that the liquid at the mesophase was found to exhibit a
double refraction effect, which is a characteristic of a crystal. As the
material had the characteristics of both liquid and crystal, Lehmann
named it “fliessende krystalle” and the English equivalent name “liquid
crystal” was ultimately born.
The Then-unpopular Liquid Crystals
These
liquid crystals were not popular among the scientists and researchers
in the early 20th century; in fact, the material remained an element of
scientific curiosity for nearly 80 long years. Here, it should be
mentioned that E. Merck of Darmstadt, Germany sold liquid crystals as
early as 1907 for analytical purposes. Even in the early 1960s, only a
few institutions and corporations were involved in research on these
liquid crystals. The conditions for designing liquid crystals with
particular physical properties hardly existed and naturally, no one was
motivated to use these in a commercial product. Eventually, liquid
crystals remained unknown to the common man.
The Early Breakthrough – Williams Domain
The
development of LCDs began at the RCA Laboratories in Princeton, New
Jersey. In the year 1962, an RCA researcher Richard Williams discovered
that liquid crystals exhibited some interesting electro-optic
characteristics. Williams generated stripe patterns in a thin layer of
liquid crystal material by applying voltage. The pattern produced
consisted of long parallel regions which he referred to as “domains.”
Williams
concluded that the domains were generated due to ordering the liquid of
a kind that had previously not been recognized. He demonstrated the
possibility of liquid crystals as electro-optical elements for display
devices. This, indeed, was a forerunner of the LCD. The phenomenon
discovered by Williams is now referred to as the “Williams domain.”
The Major Breakthrough in the LCD Technology – The Role of George H Heilmeier
In
the year 1961, George H. Heilmeier was a young talent who had just
completed his written and oral examination for the Ph.D. degree at the
Princeton University. RCA Laboratories sponsored his studies. In fact,
in those days, there was a big demand for young engineers and
scientists. RCA Laboratories recruited and encouraged the best talents
and financed their graduate education simultaneously enabling them to
work part time at their laboratory on sensible research projects. In the
first two years, Heilmeier worked in the then emerging field of solid
state microwave devices. Nevertheless, being an ambitious and passionate
young scientist, he was in a dilemma whether he should stay in the well
established solid state microwave field or enter the more interesting
and risky field of organic semiconductors. It was around that time that
Heilmeier was pulled towards the experiments on the Williams domain.
Guest-Host Mode
Heilmeier
worked sincerely on the Williams domain and after great efforts, he
proposed the guest-host mode. The device was drawing a small amount of
electric current, less than a microwatt of power per square centimeter
and it was capable of switching color with voltages substantially
smaller than those of the CRTs, that is, less than 10 V for liquid
crystal dye mixture versus more than 1000 V for CRTs!! This was
demonstrated in the fall of 1964. Heilmeier predicted that a wall sized
flat panel color television was just round the corner. However, it took
about a quarter century for his thought to be realized.
When
Heilmeier showcased this effect within the lab, the people there became
really excited. Vladimir Zworkin, the father of television, heard about
the experiment and called Heilmeier to his office to know why people in
the RCA were so excited. Heilmeier elaborated on how he had “stumbled”
onto the guest-host color switching effect. Zworkin made a remarkable
reply: “Stumbled perhaps, but to stumble, one must be moving.” In 1982,
the guest-host mode combined with an AM drive was used in a wristwatch
television!!
The Successful Dynamic Scattering Mode
Despite a lot of appreciations, there were several problems with the guest-host effect. The dyes used and their liquid crystal hosts did not remain stable for long periods of time in applied fields; besides, the effect was sensitive to surface orientation effects and needed heating to maintain the host in its nematic phase. Scientists at the RCA tried solving these problems in all ways possible.
The Successful Dynamic Scattering Mode
Despite a lot of appreciations, there were several problems with the guest-host effect. The dyes used and their liquid crystal hosts did not remain stable for long periods of time in applied fields; besides, the effect was sensitive to surface orientation effects and needed heating to maintain the host in its nematic phase. Scientists at the RCA tried solving these problems in all ways possible.
It
was in late 1964 that they observed an interesting effect in several
classes of nematic liquid crystals, those with n-type. The materials
that gave the best performance were found to be the members of a class
of organic compounds called Schiff’s bases. They found the compound
anisylidene para-aminophenylacetate (APAPA) to be of specific interest.
Its nematic range was from 83 to 100 degree Celsius. In an applied
field, these materials seemed to exhibit a remarkable turbulence that
they turned milky white from transparent white. Perhaps, the milk white
appearance did not require any polarizer to observe; it was merely a
light scattering effect.
Heilmeier
found a very efficient way to control the reflection of light by
electronic means. The rise time of 1-5 ms and decay times of less than
30 ms together with DC operating voltages in the 10-100 V range made the
new mode quite attractive for applications like alphanumeric
indicators. He was able to demonstrate reflective contrast ratios of
better than 15 to 1 with efficiencies of 45 % of the standard white. He
referred to this phenomenon as DSM; With DSM as the basis, he achieved
the first operational liquid crystal display. This was, in fact, the
first demonstration to show that the so-called vague materials called
liquid crystals could be made into something useful. And, voila! The LCD
was born!!
Heilmeier
was inducted in the National Inventors Hall of Fame and was credited
with the invention of LCD or the Liquid Crystal Display.
In
May 1968, RCA held a press conference and announced the proud discovery
of a completely new type of electronic display which was significantly
different from the traditional CRTs. The new display was lightweight,
consumed very little electrical power and was slim and sleek. The
conference captured the attention of industrial and scientific
communities across the globe. This announcement led to the development
of digital watches in the US, Japan, and Germany as well as the work on
pocket calculators in Japan. At the same point of time, it also led to
further research work in Switzerland, the UK and Germany, specifically,
for the production of new liquid crystal materials that would be
appropriate for use in various display applications.
Drawbacks of Heilmeier’s LCD
As
mentioned earlier, LCD developed by Heilmeier employed what he called
DSM wherein an electrical charge is applied that rearranges the
molecules resulting in scattering of light. This DSM design performed
poorly and seemed to be too power hungry; eventually, this design was
replaced by a much improved version invented by James Fergason in the
year 1969.
Improved Version of LCD by James Fergason
James
Fergason, an Associate Director at the Kent State University’s Liquid
Crystal Institute, was creating a liquid-crystal-based breast cancer
screening apparatus in the 1960s. It was during this time that he made
the discovery that formed the basis of his best invention. As we know,
the liquid crystal displays developed in RCA labs applied voltage in
dynamic scattering mode; it consumed much power with meager results. In
1969, Fergason utilized his “twisted nematic field effect” discovery of
liquid crystals to channel the current through the crystals effectively,
ultimately resulting in displays that provided excellent contrast and
long life on minimal power.
Twisted
nematic liquid crystal displays were unquestionably superior to the
earlier dynamic scattering displays, and soon became popular. The
technology was patented in the United States by Fergason in the year
1971. Fergason formed his own company, ILIXCO or International Liquid
Crystal Company, in 1968 to manufacture liquid crystal displays. His
first customers were the Bulova Watch Company and Gruen Watch Company
which employed the technology to market the first LCD watches that used
this technology. By the end of the decade, most of the world’s digital
watches employed this kind of LCD display.
LCD has seen tremendous development year after year and the annual sales of television with LCD screens are exceeding year after year and with the more and more use of the LCDs, the CRT almost became obsolescent for most purposes.
Stands for "Liquid Crystal Display." LCD is a flat panel display technology commonly used in TVs and computer monitors. It is also used in screens for mobile devices, such as laptops, tablets, and smartphones.
LCD displays don't just look different than bulky CRT monitors, the way they operate is significantly different as well. Instead of firing electrons at a glass screen, an LCD has backlight that provides light to individual pixels arranged in a rectangular grid. Each pixel has a red, green, and blue RGB sub-pixel that can be turned on or off. When all of a pixel's sub-pixels are turned off, it appears black. When all the sub-pixels are turned on 100%, it appears white. By adjusting the individual levels of red, green, and blue light, millions of color combinations are possible.
How an LCD works:
The backlight in liquid crystal display provides an even light source behind the screen. This light is polarized, meaning only half of the light shines through to the liquid crystal layer. The liquid crystals are made up of a part solid, part liquid substance that can be "twisted" by applying electrical voltage to them. They block the polarized light when they are off, but reflect red, green, or blue light when activated.
Each LCD screen contains a matrix of pixels that display the image on the screen. Early LCDs had passive-matrix screens, which controlled individual pixels by sending a charge to their row and column. Since a limited number of electrical charges could be sent each second, passive-matrix screens were known for appearing blurry when images moved quickly on the screen. Modern LCDs typically use active-matrix technology, which contain thin film transistors, or TFTs. These transistors include capacitors that enable individual pixels to "actively" retain their charge. Therefore, active-matrix LCDs are more efficient and appear more responsive than passive-matrix displays.
NOTE: An LCD's backlight may either be a traditional bulb or LED light. An "LED display" is simply an LCD screen with an LED backlight. This is different than an OLED display, which lights up individual LEDs for each pixel. While the liquid crystals block most of an LCD's backlight when they are off, some of the light may still shine through (which might be noticeable in a dark room). Therefore OLEDs typically have darker black levels than LCDs.
LCD has seen tremendous development year after year and the annual sales of television with LCD screens are exceeding year after year and with the more and more use of the LCDs, the CRT almost became obsolescent for most purposes.
Stands for "Liquid Crystal Display." LCD is a flat panel display technology commonly used in TVs and computer monitors. It is also used in screens for mobile devices, such as laptops, tablets, and smartphones.
LCD displays don't just look different than bulky CRT monitors, the way they operate is significantly different as well. Instead of firing electrons at a glass screen, an LCD has backlight that provides light to individual pixels arranged in a rectangular grid. Each pixel has a red, green, and blue RGB sub-pixel that can be turned on or off. When all of a pixel's sub-pixels are turned off, it appears black. When all the sub-pixels are turned on 100%, it appears white. By adjusting the individual levels of red, green, and blue light, millions of color combinations are possible.
How an LCD works:
The backlight in liquid crystal display provides an even light source behind the screen. This light is polarized, meaning only half of the light shines through to the liquid crystal layer. The liquid crystals are made up of a part solid, part liquid substance that can be "twisted" by applying electrical voltage to them. They block the polarized light when they are off, but reflect red, green, or blue light when activated.
Each LCD screen contains a matrix of pixels that display the image on the screen. Early LCDs had passive-matrix screens, which controlled individual pixels by sending a charge to their row and column. Since a limited number of electrical charges could be sent each second, passive-matrix screens were known for appearing blurry when images moved quickly on the screen. Modern LCDs typically use active-matrix technology, which contain thin film transistors, or TFTs. These transistors include capacitors that enable individual pixels to "actively" retain their charge. Therefore, active-matrix LCDs are more efficient and appear more responsive than passive-matrix displays.
NOTE: An LCD's backlight may either be a traditional bulb or LED light. An "LED display" is simply an LCD screen with an LED backlight. This is different than an OLED display, which lights up individual LEDs for each pixel. While the liquid crystals block most of an LCD's backlight when they are off, some of the light may still shine through (which might be noticeable in a dark room). Therefore OLEDs typically have darker black levels than LCDs.