Liquid Crystal Display (LCD)

What is LCD Monitor?

An LCD monitor is a short for Liquid Crystal Display monitor. There is a liquid crystal solution in between two flexible sheets of polarizing material.

This is a flat panel monitor that uses LCD technology to display images that are much better than the images displayed by CRT technology.

The LCD backlights offer light to each pixel set in a rectangular framework containing a sub-pixel, red, green, and blue that can be switched on or off.

Understanding LCD Monitor

A flat-panel, LCD monitor is an optical device that is electronically modulated and designed on the light modulating properties of liquid crystals used in it in combination with the polarizers.

The liquid crystals in an LCD monitor do not give off light directly but use a reflector or a backlight instead to produce the images. These images can be produced either in color or in monochrome.

In the general purpose computers, when LCD monitors are used, they produce fixed images or arbitrary images.

Ideally, the LCD technology is further enhanced by the additional optical filters to the white on blue that helps it to produce a more characteristic appearance.

One of the most significant aspects of the LCD monitor design is that it does not use phosphors and therefore seldom suffer from image burn-in while displaying a static image on a screen for a long time.

Another useful attribute of the LCD monitors is low power consumption which helps in saving the battery life in laptop computers.

Parts

The LCD monitors have different parts that work in perfect harmony to display the best possible image on the screen.

The main parts of it are:

The panel
The cables and
The stand.

Features

The LCD monitors are superior to the CRT monitors due to the useful features that they come with. These are:

Lightweight design
Wider viewing angles
Higher color accuracy
Energy efficiency
Cheaper than CRT monitors
Better contrast ratio
Longer life expectancy
Better response time
Higher refresh rate and
Higher resolutions.

With all these features, the LCD monitors deliver sharp and clear images of high quality and resolution, more vivid colors, and more brightness.

Resolution Support

Depending on the support provided by the other components of your computer, you can use an LCD monitor of higher or lower resolution.

However, the common resolutions that you will get in an LCD monitor are:

1280 x 1024 pixels
1366 x 768 pixels, referred to as High Definition or HD resolution
1920 x 1080 pixels, referred to as Full High Definition or FHD resolution
1920 x 1200 pixels, referred to as Wide Ultra Extended Graphics Array or WUXGA resolution
2560 x 1440 pixels, referred to as Quad High Definition or QHD resolution
3840 x 2160 pixels, referred to as 4K or Ultra High Definition or UHD resolution and
7,680x 4,320 pixels, referred to as 8K resolution.

Power Consumption

As said earlier, the LCD monitors consume low power which makes it suitable for use in computers.

However, the power consumption rate may vary according to the size and model of the display along with its resolution, brightness, and other factors. For example:

The power consumption of a 15-inch LCD monitor on an average is about 15 watts
The power consumption of a 19-inch LCD monitor on an average is about 20 watts
The power consumption of a 22-inch LCD monitor on an average is about 30 watts
The power consumption of a 37-inch LCD monitor on an average is about 60 watts and
The power consumption of a 42-inch LCD monitor on an average is about 80 watts.

Therefore, as it is evident, the power consumption is pretty low even for the LCD monitor with the largest size.

With such a rate, it is also quite evident that these specific types of monitors used in a computer will have an exceptionally long life expectancy.

In fact, according to records, the average life expectancy of an LCD monitor is anywhere between 30,000 hours and 60,000 hours.

This means that the LCD monitors can last anywhere from 10 years and up to 20 years for normal usage.

Usefulness

The LCD monitors are useful for users of any profession as well as for those who only play games on their computers.

It is needless to say that the average users will find these monitors to be more than just useful to them.

Whether it is for video editing or graphics designing, watching movies or playing games, you can make the best use of the useful features of the LCD monitors to have a better user experience.

For example:

The graphics designers will like its improved color rendition and faster response time
The photographers will like the sharper, crispier, and brighter images displayed by it with brighter colors and sharper blacks
The architects will like its optimal resolution and color performance with clearer details in the images
The traders will like the large size of the screen and clear images that are flicker free not to strain their eyes or cause headaches and
The programmers will like its customizability and business style features that are needed for their kind of jobs.

And, the non-professionals as well as the daily users will also find the screen to be of great help when they work on word docs, spreadsheets, send emails or simply surf the internet.

Background

The nature of liquid crystals was discovered by Friedrich Reinitzer way back in 1888 from the nature of cholesterol extracted from carrots!

It involved the generation of colors and two melting points.

Later, in 1911, first experimentation of liquid crystals was made by Charles Mauguin confining between plates in emaciated layers.

Further, in 1922, the properties and structure of liquid crystals was described by Georges Friedel and according to him these were classified into three groups namely:

Nematics
Smectics and
Cholesterics.

The electrically switched light valve was devised by Vsevolod Frederiks in 1927 which is the most vital effect of LCD technology.

The practical application of this technology was however patented by the Marconi Wireless Telegraph company in 1936.

The fact that the liquid crystals had a few exciting electro-optic properties was found by Richard Williams in 1962 when he applied voltage to the liquid crystals.

He explained that it was due to the electro-hydrodynamic effects caused within the liquid crystals, which is an instability forming in it and was called ‘Williams domains.’

Later, in 1964, George H. Heilmeier worked on these domains and found the scattering effects of liquid crystals.

This was considered to be the first operational LCD based on DSM or the Dynamic Scattering Mode.

It was found during this work that with a considerable amount of current flowing through the liquid crystals turned the transparent crystals into a turbid and milky state.

It was only in 1968 that Bernard Lechner conceived the idea of a TFT-based Liquid-Crystal Display.

He, along with E.O. Nester, F.J. Marlowe, and J. Tults demonstrated this idea using an 18×2 matrix Dynamic Scattering Mode LCD by utilizing the standard discrete MOSFETs.

The TN or Twisted Nematic field effect in liquid crystals was patented on December 4, 1970 by Hoffmann-La Roche in Switzerland naming Wolfgang Helfrich and Martin Schadt as the inventors.

This paved the path for the creation of TN displays for wristwatches, digital quartz wristwatches, and several other applications.

In 1972, T Peter Brody and his team prototyped the conception of the active-matrix thin film transistor liquid crystal display panel at Westinghouse, in Pittsburgh, Pennsylvania.

Along with J. A. Asars and G. D. Dixon, the first TFT LCD was demonstrated.

A lot of products flooded the market such as calculators and wristwatches with DSM LCDs since then.

Then, in 1983, the STN or Super Twisted Nematic structure was invented by the researchers at Brown, Boveri & Cie Research Center in Switzerland for the passive matrix addressed LCDs. It was used in video equipment, telephones and others.

However, the STN LCDs had a slow response time and it was resolved with the invention of a video speed-drive scheme in 1984 by researchers Theodorus Welzen and Adrianus de Vaan in Philips.

This produced high quality images with high resolution and smooth rendering.

In 1985, low-voltage, CMOS-based drive electronics were used which resulted in solving the high-resolution STN-LCDs.

Philips inventors Theodorus Welzen and Adrianus de Vaan applied this in the battery-operated portable products such as mobile phones and notebook computers.

A lot of products with an LCD screen were then developed that included microphones and speakers right from mobile phones to TVs.

Since then, there have been a lot of changes made in the LCD technology to finally design and develop the modern LCD monitors that are used in computers today.

Based on a span of two decades, these developments include and are not limited to:

Electro optical effects with the use of inter digital electrodes
IPS or In Plane Switching technology
Interconnecting TFT array as a matrix
Optimization of the shape of the electrodes to improve the viewing angle
Implementation of large screen LCDs
Flat-panel computer monitors and TVs
Adoption and widespread use of Tracking Gate-line in Pixel or TGP technique for narrow bezels and
High contrast ratio to the tune of 1,000,000:1.

Also, dual layer and panel or Light Modulating Cell Layer or LMCL LCDs were put into mass production later on which used two liquid crystal layers rather than one along with quantum dot sheets and a mini-LED backlight.

Characteristics

Here are a few general characteristics of LCD that differentiates it and makes it better than the traditional CRT.

Every pixel of it comprises a layer of molecules in between two transparent electrodes.

These are made of Indium-Tin Oxide and there are two polarizing filters, one parallel and one perpendicular.

In most of the cases, the axes of transmission are at right angles to each other.

The liquid crystals used in the LCDs may not be the same because the chemical formula of each may vary.

The technique followed in most of the color LCD systems is the same where color filters are used to produce red, green, and blue sub-pixels.

The optical effect in the voltage-on state of a TN device is not as dependent on the thickness of the device as it is in the voltage-off state.

Separate electrodes can be used in each segment of the displays to get a small number of fixed symbols and separate digits.

The LCD glass substrate may vary in size depending on the generations and may range anywhere between 200 mm to 300 mm in length and 200 mm to 400 mm in height as it is in the Gen 1 models and up to 2940 mm in length and 3370 mm in height as it is in the Gen 11 models.

Types and Technologies

The technologies used in the LCD monitors of computers today are also different which determines the types of these optical devices. These are:

IPS or In Plane Switching Panel Technology – These panels offer the best viewing angles, color accuracy, and image quality.
PLS or Super Plane to Line Switching technology – This LCD panel is almost the same as IPS technology but it offesr 10% more brightness, wider viewing angles and is also quite economical to produce.
VA or Vertical Alignment Panel Technology – These panels are in between the TN and IPS LCD technology. These panels offer better color quality, higher contrast ratio, and wider viewing angles but come with lower response time, color shifting issues and uneven distribution of brightness across the screen.
TN or Twisted Nematic Panel Technology – These are one of the most commonly used LCD panel technology types that offer faster response time. They are cheaper to produce but their viewing angles, color production ability, and contrast ratio are on the lower side.

LCDs typically need an external source of light to produce the images since they cannot produce their own light.

This is usually called the backlight in active matrix LCDs.

In passive LCDs, both back lights and reflectors are used in isolation to create an ambient light for illumination.

There are different types of LCD backlight technologies used and the most common ones are:

CCFL – A short for Cold Cathode Fluorescent Lamps, two of these are placed at opposite sides of the display. However a set of these lamps arranged in parallel may also be used in the case of larger displays. There is also a PMMA acrylic plastic diffuser known by different names such as light guide, guiding plate or wave that evenly spreads the light across the entire screen.
EL-WLED – There is a row of white light in an LCD panel to light up the whole screen. These are located at one or more edges of the display. The light diffuser spreads the light evenly all across the screen. There may be a Quantum Dot Enhancement Film or QDEF placed on top of the diffuser to protect the layer from heat and humidity. The QDEF may also be placed on the color filter of the LCD to replace the commonly used resists. This produces the thinnest display and is a popular design in desktop computer monitors.
WLED array – Here an entire array of white LEDs light up the LCD panel. These are located behind the diffuser. This technology gives the LCD panels the power to dim or entirely turn off the lights in the dark areas of the image. This eventually increases the contrast ratio.
RGB-LED array – This is same as WLED array except that the panel is lit by an arrangement of RGB LEDs that offers higher color gamuts.
Monochrome LEDs – This is used in smaller passive monochrome LCDs.
Mini-LED – This arrangement offers high contrast ratio and deeper blacks with a support of more than a thousand Full-area Local Area Dimming or FLAD zones.

Most LCD screens today are made more efficient with the use of optical films or a prism sheet.

This adds to the light required for the reflective polarizing films.

Monochrome passive-matrix LCDs were used commonly in the early laptops while its color variant was the norm for the modern laptops.

However, modern LCD computer monitors use active-matrix architecture for high-resolution color display.

Connections

Different types of connectors with different specifications and features are used to attach an LCD monitor to the computer.

The list includes, and is not limited to:

HDMI or High-Definition Multimedia Interface
DVI or Digital Visual Interface
DisplayPort and
VGA or Video Graphics Array cable.

The one to be used depends entirely on the needs of the user based on the pros and cons of each offered.

Specifications

There are a few specific specifications of the LCD monitors used in the computer. These are:

The resolution – This refers to the number of rows and columns pixels, for example, 1024 × 768 pixels. Depending on the resolution it is determined whether the LCD will display HD, FHD, QHD or other quality images.
The spatial performance – Since the computer monitors are supposed to be viewed from a close distance, display density should be consistent across the entire screen so that the images can be seen clearly from all angles.
Temporal performance – This refers to the ability of the unit to accurately display the changing images as well as the number of times per second the data given is drawn by the display. If the refresh rate and response time is lower, it will result in undesired visual effects such as smearing or ghosting.
Color performance – This depends on the color gamut, color depth, and color range. It also depends on specific types of color management such as gamma and white point correction. This helps in determining what exactly a white color is and how other colors are to be displayed with respect to it.
Brightness and contrast ratio – This refers to the maximum output of light of the LCD. This can vary according to the brightness of the backlights as well as on the transparency of the LCD. If brightness is high, the contrast and HDR or High Dynamic Range will be high but that will come at the cost of high power consumption.

It is the difference in each of these specifications that makes one LCD computer monitor better than the other.

Working Process

The molecules of the liquid crystals used in these monitors are typically anisotropic which demonstrate mutual attraction.

Different types of chemicals are used to make the LCD work but the most common of all is the polarizable rod-shaped molecules.

The basic working principle is to switch off and switch on the pixels in order to display a particular color.

Since liquid crystals are used in the LCD monitors, the molecules untwist on the application of electric current on them.

This changes the angle of the light as well as the polarizing filter at the top.

The individual area of the display is used to let the polarized glass allow only a small amount of light to pass through.

This means that some of the areas will be dark.

Therefore, it can be said safely that the working process of the LCD is based on the principle of blocking the light rather than allowing it to pass through.

There is a reflected mirror and an electrode plane used at the top and a polarized glass consisting of polarizing film at the bottom.

And, a common electrode is used to enclose the whole area of the LCD. The liquid crystal material is found above it.

There is also a polarizing film at the top and another piece of glass with an electrode placed at right angles.

When there is no current in the light passing through the front of the panel, it is reflected by the mirror and bounced back.

There is a screen in front of the light. This is made up of red, green, and blue colored pixels.

The liquid crystals turn the filter on or off either to keep the pixel black or to display specific colors on the screen.

Pros and Cons

It is due to the working process of the LCD monitors of the computers that they consume much less power than the CRT monitors to the tune of 10% to 25% less.

In addition to that, these monitors offer a lot of other significant benefits such as:

A very compact design
Thin and light in weight
Less heat generation during operation
No geometric deformation
Better backlight technology and refresh rate resulting in little or no flicker
Sharper images with no smearing or bleeding
No undesired electromagnetic radiation
Permitting stacked resolution
Larger screen size that offer more viewing area
Masking effect of grayscale and spatial quantization
Unmoved by magnetic fields
Better connectivity that needs no conversion to analog signals
Enhanced battery life for the laptops
Takes less space
High peak intensity for more brightness
No burn-in and
Narrow bezels that allow adding multiple screens side by side.

There are also a few disadvantages of using an LCD with a computer such as:

Cheaper and older models offer limited viewing angle, color saturation, varying contrast and brightness
Older TNs and IPS may offer uneven backlighting resulting in brightness distortion
Use of PWM or Pulse Width Modulation may dim the display resulting in screen flicker
Unable to display more than one native resolution without a video scaler otherwise it will cause jagged edges and blurriness
Preset bit depth
Input lag caused due to the waiting of the A/D converter to output a frame completely before drawing it to the panel.
Thermalization in a constant-on condition and
Slower response time and low brightness in extremely low or extremely high temperature conditions.

However, the disadvantages of the LCD computer monitor will depend on the type and quality of it as well as the support provided to it by the other components of the computer system.

Conclusion

So, now you know a lot about the LCD monitors that are used in computers today.

Thanks to this article, you can now surely make up your mind quite easily and confidently whether or not you will upgrade your system and your viewing pleasure with an LCD monitor or stick to the old CRT model.