Advantages and Disadvantages of TN LCD

Advantages and Disadvantages of TN LCD Panel

Twisted nematic or TN LCD is a thin-film transistor liquid crystal display or TFT-LCD and one of the general examples of LCD technologies that is often used in various inexpensive consumer electronic devices such as digital clocks and wristwatches, calculators, computer monitors, and mobile phones. It was once the most popular display technology in the market

Subsequent technological developments resulted in the emergence of better technologies. These include plasma panel display or PDP technology, in-plane switching or IPS LCD technology, and organic light-emitting diode or OLED display technology.

It is still important to underscore the fact that the introduction of TN LCD beginning in 1970 marked a technological breakthrough that later resulted in the commercialization of LCD. It made the use of digital electronic displays in consumer electronic devices affordable and practical while rendering monolithic LED and CRT displays obsolete.

This article discusses the pros and cons or advantages and disadvantages of TN LCD in consideration of the features and characteristics of other LCD technologies such as VA LCD and IPS LCD and other display technologies such as OLED and AMOLED.

Background: Explaining TN LCD Technology

At the heart of TN LCD is the twisted nematic effect that is based on the controlled realignment of liquid crystal materials between different ordered molecular configurations under the action of an applied electric field. A particular panel is made of liquid crystal molecules sandwiched between two plates of glass substrates that are coated with a transparent indium-tin-oxide surface. This surface is further coated with aligners that both rub in one direction.

The liquid crystal materials are twisted at an angle in their natural state. The application of an electric current changes the orientation of these twisted materials into an untwisted state. This untwisting enables light to pass through. The materials can be twisted back and untwisted again through the switching of electric current. This twisting-and-untwisting mechanism represents pixel control and it creates images from the patterns of light and dark pixels.

Benefits: Notable Advantages of TN LCD Panel

The advantages of TN LCD panels have made twisted nematic LCD technology a dominant and almost universal display technology used in portable electronics starting from the 1990s. Take note of the following advantages of TN LCD panels over other display technologies:

1. Inexpensive Cost and End-Use Price

One of the key advantages of twisted nematic LCD panels stems from the uncomplicated implementation of the twisted nematic effect. This translated to simpler production processes and cheaper manufacturing costs that translated further to the inexpensive pricing of consumer electronic products equipped with TN LCD panels.

The popularization of twisted nematic LCD pushed out other common display technologies such as monolithic LED and CRT displays. The fact that TN LCD panels are easier and cheaper to manufacture makes them a more practical alternative to IPS LCD panels and AMOLED display panels for affordable consumer electronic devices.

2. Low and Efficient Power Consumption

It also does not require a current flow to operate and it runs under low operating voltages. These characteristics correspond to low power consumption. Take note that VA LCD and IPS LCD are not as efficient as TN LCD. A basic monochromatic twisted nematic LCD panel can even have the same power draw as a passive-matrix OLED panel.

The low power consumption advantage of TN LCD panels ushered in an era of lightweight electronic displays and low-powered electronic devices. These are the preferred panels in portable and simpler consumer electronic products such as digital watches and calculators that are powered using small batteries and small solar cells.

3. Better Response Time and Refresh Rate

Pixel response time is the duration it takes a single pixel in a panel to transition from one state to another. This is measured in milliseconds. The screen refresh rate is the frequency at which the image on a screen is refreshed and displayed. This is measured in hertz. A low pixel response time is better while a high screen refresh rate is also better.

A panel with a high pixel response time and low refresh rate tends to produce ghosting effects on moving images and motion blurs around a particular image or graphical element. This is more noticeable in fast-moving images. TN LCD panels have a better native response time of 2 milliseconds and a native refresh rate of 60 seconds than IPS LCD.

Drawbacks: Main Disadvantages of TN LCD Panel

The limitations and disadvantages of twisted nematic LCD technology have restricted it from more modern and wider applications. IPS LCD and OLED have addressed its inherent drawbacks and issues. Below are the specific disadvantages of TN LCD panels:

1. Limited Viewing Angle

A notable disadvantage of TN LCD panels is a narrow viewing angle or viewing cone. A user needs to look at this panel from a straight-up 90-degree angle to appreciate its viewability. Colors appear duller and images look darker when viewed from other angles. These color shifts and image distortion are negligible in OLED and high-end IPS LCD.

This narrow viewing angle compels a particular user to remain fixed or seated dead straight in front of a TN LCD panel. Color shifts and image distortion are a problem in larger TN LCD panels because changing the angles at which these panels are viewed is sometimes unavoidable. This also translates to poorer visual experience and overall user experience.

2. Poorer Color Reproduction

These LCD panels also suffer from inaccurate color reproduction compared to other types of LCD technologies such as vertical alignment or VA and in-plane switching or IPS LCD technologies. The colors are duller and this is noticeable when compared to VA LCD and IPS LCD. The narrow viewing angle also results in color shifts.

Nevertheless, because of its poor color reproduction, a particular LCD panel based on the twisted nematic technology is not suitable for use in color-critical use cases. Examples include photo editing, graphics design, and video editing. A high-end and pixel-dense IPS LCD such as the Liquid Retina panels from Apple are more suited for these applications.

3. Variability in Quality

Note that the quality of TN LCD panels depends on the manufacturers. Low-end panels tend to exhibit extreme instances of the inherent disadvantages of the technology. Inexpensive feature phones and PC monitors are notable examples. The panels used in these devices can demonstrate extreme color shifts even at slight changes in the viewing angle.

Images in low-end TN LCD panels can also be indiscernible when viewed under direct sunlight because of the inherent poor color reproduction and low-powered backlighting. Another disadvantage is the susceptibility of these panels to dead pixels. This problem is more pronounced in cheaper and low-end TN LCD panels.

Conclusion: Pros and Cons of TN LCD Panel

Twisted nematic LCD technology was a breakthrough innovation that popularized the use of digital electronic displays in various consumer electronic devices. TN panels remain a popular display option because of their notable qualities and advantages that revolve around simpler manufacturing that translates to cheaper end-user price points.

However, because of IPS LCD and AMOLED technologies, TN LCD is becoming more archaic. IPS LCD remains the best LCD option because of its better visual performance and mature manufacturing process. OLED has also become popular across mid-range and premium consumer electronic devices because of its unique advantages.

The low cost of producing a TN LCD panel and the low price point at which it is sold in the market still makes it somewhat unrivaled. The low power consumption has made it a suitable choice for low-powered devices such as digital watches and calculators. The faster response time and high refresh rate also make it an inexpensive PC monitor option.

Note twisted nematic would not be able to compete against display technologies for high-quality visual experience. Technologies such as Mini-LED backlighting and IGZO TFT or LTPO materials are improving further better LCD technologies. The emergence of MicroLED and quantum dot technologies have provided newer and better alternatives.

FURTHER READINGS AND REFERENCES: Several information from the article are culled from the following scholarly article: Kim, K. H. & Song, K. J. (2009). “Technical evolution of liquid crystal displays.” NPG Asia Materials. 1(1). DOI: 10.1038/asiamat.2009.3