What Is TFT-LCD?The TFT-LCD (Thin Film Transistor Liquid Crystal Display) is the non-emissive display device that acquires the visual effect using the characterization of the liquid crystal, which is inserted between a lower glass plate (film transistor is formed on it) and an upper glass plate (color filter is formed on it).
With its low (electrical) power consumption and portability, the TFT-LCD is the next-generation display device that is a highly value-added and technology-integrated product.
The liquid crystal is the material that possess the liquid (characteristics of liquid like fluidity) and solid (characteristics of the solid like the long-range order) state at the same time. Liquid crystal molecules have the unique structure of a bar shape. Because the liquid crystal materials are rod-like molecules, it has an anisotropic characteristic that changes its characteristic value (reflection, dielectric constant, transmission and viscosity) according to the horizontal and vertical direction of the molecule axis. It is the most important characteristic for visual display.
- Optical Anisortropy
The liquid crystal shows the birefringence due to the optical anisotropy that the light vibrating to the axis direction of the liquid crystal molecules is different from that vibrating to the vertical axis direction. The optical anisotropy of the liquid crystal plays a role in changing the status of polarized light that is passing through or vibration direction of it.
- Dielectric Anisortropy
Characteristic of the dielectric anisotropy is that the light vibrating to the axis direction of the liquid crystal molecules is different from that vibrating in the vertical axis direction. Because of this characteristic, the liquid crystal reacts differently according to the strength of the voltage input to the liquid crystal layer. The amount of transmitting light is controlled by the optical anisotropy. The "P (Positive)" type liquid crystal is that dielectric constant of the axis direction is stronger than that of the vertical axis direction. The "N (Negative)" type liquid crystal is that the dielectric constant of the axis direction is weaker than that of the vertical axis direction. Generally, the "P" type liquid crystals are used.
- Elastic Constant of the Liquid Crystal
The elastic constant is the value that measures the status of the molecular array due to external force. It shows the strength of force that returned to the original state after responding to the voltage.