TFT LCD Basic Knowledge


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What is TFT Display?

 

Brief History of TFT LCDs

1957 – John Wallmark of RCA filed a patent for a thin film MOSFET.

1992 – Paul K. Weimer of RCA leveraged Wallmark’s patent and developed thin-film transistor technology (TFT).

1968 – Bernard Lechner of RCA implemented TFT technology in the liquid-crystal display (LCD) for the first time

1971 – Lechner, F. J. Marlowe, E. O. Nester, and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs.

1973 – T. Peter Brody, J. A. Asars, and G. D. Dixon at Westinghouse Research Laboratories developed a CdSe (cadmium selenide) TFT,

1974 – Brody and Fang-Chen Luo demonstrated the first flat active-matrix liquid-crystal display (AM LCD) using CdSe TFTs,

1975 – Brody coined the term “active matrix LCDs”,

2020 – TFT LCD display technology dominants the display market now. Within the last 20 years, it has wiped out the market of CRT (cathode-ray tube) and Plasma. The only challenges are OLED (organic light-emitting diode)and Micro LED (Maybe, still in lab).

How Do TFT Displays Work

TFT LCD Display (Thin-Film-Transistor Liquid Crystal Display) technology has a sandwich-like structure with liquid crystal material filled between two glass plates. Two polarizer filters, color filters (RGB, red/green/blue)and two alignment layers determine exactly the amount of light is allowed to pass and which colors are created. Each pixel in an active matrix is paired with a transistor that includes capacitor which gives each sub-pixel the ability to retain its charge, instead of requiring an electrical charge sent each time it needed to be changed.  The TFT layer controls light flow a color filter displays the color and a top layer houses your visible screen.

See Fig. 1 for TFT LCD structure

Utilizing an electrical charge that causes the liquid crystal material to change their molecular structure allowing various wavelengths of backlight to “pass-through”. The active matrix of the TFT display is in constant flux and changes or refreshes rapidly depending upon the incoming signal from the control device.

The pixels of TFT displays are determined by the underlying density (resolution) of the color matrix and TFT layout. The more pixels the higher detail is available. Available screen size, power consumption, resolution, interface (how to connect) define the TFT displays.

The pixels of TFT displays are determined by the underlying density (resolution) of the color matrix and TFT layout. The more pixels the higher detail is available. Available screen size, power consumption, resolution, interface (how to connect) define the TFT displays.

The TFT screen itself can’t emit light like OLED display, it has to be used with a back-light of white bright light to generate the picture. Newer panels utilize LED backlight (light emitting diodes) to generate their light and therefore utilize less power and require less depth by design.

TFT display modules include the TFT display screen, LED backlight, and driving circuitry.

TFT Benefits and Uses

TFT LCDs offer several advantages over other types of displays (CRT, Plasma). It is light, thin, and energy efficient which made mobile phones, laptops, hang-on wall LCD TV, flat computer monitors and other handhold devices possible. TFT LCDs are also relatively inexpensive which makes it dominant in display world.

When we say type of lcd, we mean two kinds of LCDs: Active TFT color display and Monochrome passive display.  Before TFT display was invented, the world used passive matrix lcd for many years. passive matrix lcd can only used for monochrome displays like calculators, watches (not iWatch), thermostats (not Nest), utility meters etc. Thanks for TFT LCD, the world is more colorful.

Fig. 2 Active TFT Color Display

Fig. 3 Monochrome Passive LCD Display

New TFT Technologies

TFT LCD technology used to have viewing angle and slow response time issues. Thanks for new TFT LCD screen technology, IPS display (in-plane switching) used, we don’t see these kinds of issues in the market. For future development, the TFT LCDs are getting bigger (146 inches by Samsung at CES’19), high resolution (8K 7680 × 4320 pixels), high-speed good for gaming, wide viewing angles good enough for 170 degrees, high contrast ratio good enough for most demanding aviation computer monitors, high image quality fitting most critical medical surgery monitors, combining with PCAP (capacitive touch screen).

Learn More About TFT Displays?

If you want to learn more about TFT display technology, please visit Orient Display’s TFT Knowledge Center or view our TFT products.

Check out our Youtube training video here!