Liquid Crystal Display

Name: CHEN YUK NGA ANNA

University ID: 2005179428

Title of Journal: Science in Hong Kong

Title of article: Liquid Crystal Display

In Hong Kong, laptop computers, mobile phones, portable game consoles and televisions have nowadays become an inseparable part of our daily life. These appliances all possess an essential component, the screen, which gives colourful and high quality display for entertainment. One of the most frequently used type of screen is the Thin Film Transistor Liquid Crystal Display or, in short, TFT LCD. This article will introduce the scientific principles behind the TFT LCD and its impact on Hong Kong people’s life.

Liquid Crystal is a special substance in an intermediate state between the conventional liquid and a crystalline solid1. It was first observed and studied by Austrian botanist Friedrich Reinitzer in 18881. However it was not until 1960s when companies started to investigate the possibility of using Liquid Crystal to create complex displays1.

Figure 1 Arrangement of the components between the electrodes inside one pixel of the TFT-LCD3.

Liquid Crystal Display consists of many rectangular pixels, each of which consists of two electrodes2. Liquid Crystals (LC) molecules are filled in between the electrodes, along with a colour filter and two polarizers that filter the light passing through the liquid crystal2. The arrangement of the components in a pixel is similar to that shown in fig. 1. When a voltage is applied across the electrodes, the electric field set up causes the alignment of the LC molecules along the same direction2. A change in the polarization of light passing out of LC molecules, and thus out of the pixel, results2. With different voltages are applied through each individual pixel, complex image display can be achieved2.

One of the challenges faced when developing LCD is that the change in current in one pixel might affect the pixels next to it, creating unwanted disruptions in images displayed1. Dr. Bernard Lechner at Radio Corporation of America (RCA) suggested a solution1, by which a Thin Film Transistor is introduced to drive the current through each individual pixel, and its effect on neighboring pixels can be minimized1. The first TFT-LCD was created by Dr. Fan Luo at RCA in 19721, which was also commonly known as the Active-matrices Liquid Crystal Display (AMLCD). The arrangement of the components is shown in fig. 1.

The pixels in the LCD are arranged in a matrix to form a large rectangular shaped screen1. The number of pixels controls the resolution of the image. For example, “1024x768 pixels” means that there are 1024 and 768 pixels along the horizontal and vertical edges of the screen respectively.

There are a lot of advantages of LCDs over the traditional Cathode Ray Tube (CRT) screens — the type of display used in conventional televisions and computer screen4. Firstly, LCDs are much lighter in size and consume less power2. This opens the opportunity for the development of many portable devices4. Secondly, the quality of image is improved to meet the increasing demand for quality display4. However, CRT Displays have not been completely replaced owing to its lower price4. With the reduced price of LCD monitor, LCDs are replacing CRT screens in many household appliances 5.

The introduction of LCDs brings a lot of business as well as research opportunities to Hong Kong. Hong Kong is currently engaging a lot in developing the LCDs. According the Noruma Research Institute, more than 20% of the world’s LCDs are manufactured in Hong Kong6. There are over 19 major commercial companies manufacturing and developing the LCDs6.There is also a government funded organization, Centre for Display Research at the Hong Kong University of Science and Technology, which aims to conduct research in the latest technology of LCDs and to provide technical support for local companies7.

Figure 2. Compaq’s first transportable computer at the Stanford Resources’ office in 19831.

The invention of LCDs greatly raises our quality of life by offering us more convenience. Laptop computers with CRT screens used to have the size of a sewing machine1 as shown in fig. 2. Nowadays laptops computers with LCDs are popularized with their size comparable to a book and their price reduced. According to a research conducted by the Chinese University of Hong Kong, 70% of Hong Kong people own at least one portable electronic device, including digital cameras, mobile phones, portable game consoles and laptop computers8. These products not only entertain our lives but also enable a variety way of communication to get people connected.

In conclusion, it is obvious that the LCDs have totally revolutionized the display industry, making creation of high quality and portable devices possible. While the advancement of LCDs continues, it is anticipated that new inventions of display technology will bloom in the industry, and brighten our world with color and creativity.

Reference List:

1. Castellano, Joseph A. 2005. Liquid Gold : The Story Of Liquid Crystal Displays and the Creation of an Industry. River Edge, NJ, USA: World Scientific Publishing Company, Incorporated.

2. Frank R. Libsch. 2003. ‘Thin-Film Transistors in Active-Matrix Liquid Crystal

Displays (AMLCDs)’ in Kagan C. R. and Andry P. (Eds.) THIN-FILM TRANSISTORS

New York, USA: Marcel Dekker. p 209-300.

3. Tannas, L.E., Glenn, W.E., Doane, J.W. 1995. Flat-Panel Display Technologies - Japan, Russia, Ukraine, and Belarus. New York: William Andrew Publishing/Noyes

4. Crawford, W. 2002. ‘This is in: does LCD finally replace CRT?’ Online Journal 26(3): 82-83.

5. Jurichich, S. 2002. Technology and cost modeling of hydrogenated amorphous silicon and low-temperature poly-silicon thin film transistor liquid crystal display manufacturing. Standford, USA: UMI.

6. Nomura Research Institute, Ltd. Asian Economies Research Units. 2002. Asian Economic Outlook 2002-2003 3rd Quarter Report [online]. Available:

http://www.nri.co.jp/english/news/2002/020619/020619.pdf [accessed 3rd March 2006].

7. Centre for Display Research. The Hong Kong University of Science and Technology. Available: http://www.ee.ust.hk/~cdr/frmain.htm [accessed 3rd March 2006].

8. [Anonymous]. 2006 12th September. More than 70% Hong Kong people owns one digital camera [online] [translation]. Sing Tao Daily. Available: http://hk.news.yahoo.com/060911/60/1sv4e.html [accessed 3rd March 2006].