The working principle of TN (Twisted Nematic) LCDs is fundamentally based on the orientation of liquid crystal molecules and their response to an applied electric field. Here’s an overview of how this technology functions:

Arrangement of Liquid Crystal Molecules

In a TN liquid crystal display, the liquid crystal molecules are naturally arranged in a helical, or twisted, structure. This configuration causes the polarization direction of light passing through the liquid crystal layer to twist as it moves along the depth of the layer. When no external electric field is applied, this twisted arrangement remains intact, a state referred to as the “twisted” state.

Effect of Electric Field

When an electric field is applied to the TN liquid crystal layer, it influences the orientation of the liquid crystal molecules. Specifically, the electric field exerts a force that reorients the molecules, gradually unwinding the twisted structure. As the field strengthens, the molecules align more closely with the direction of the electric field, thereby reducing the degree of twist in the liquid crystal layer. This altered arrangement is known as the “untwisted” state.

Display Effect

The essence of the TN LCD’s display mechanism lies in the ability to manipulate light transmission by varying the electric field across the liquid crystal layer. By applying different voltages to various parts of the liquid crystal layer, the degree of twist—and consequently, the polarization of light—can be controlled with precision. This modulation of light enables the display of images or text. When the light passes through additional layers like polarizers and color filters, these controlled variations in light transmission create the visible output on the screen.

Transmission of Light

The transmission of light through the liquid crystal layer is directly affected by these molecular arrangements. In the “twisted” state, the helical structure of the liquid crystal molecules causes the polarization direction of the light to rotate as it passes through the layer. This rotation is crucial for controlling the light’s passage through the subsequent layers of the display. Conversely, in the “untwisted” state, the alignment of the molecules causes less rotation of the light’s polarization, altering how light is transmitted.

The simplicity and efficiency of the TN LCD’s working principle make it a widely used technology in various display applications. Its ability to swiftly change the orientation of liquid crystal molecules in response to an electric field allows for fast response times and low power consumption, making it a popular choice for a wide range of devices, from simple digital watches to complex industrial monitors.

Fast Response Speed

TN liquid crystal has a very fast response speed, which makes it very useful in applications that require high-speed refresh, such as computer monitors, gaming monitors, etc.

Low Cost

Due to the relatively simple manufacturing process, TN liquid crystal is usually low in cost, which makes it widely used in cost-sensitive markets that require mass production, such as consumer electronics, low-end computer monitors, etc.

Narrow Viewing Angle

TN liquid crystal has a relatively narrow viewing angle, which means that the display effect will change when viewed at different angles. This limits its application in some professional fields, such as image editing, medical imaging, and other occasions that require high color accuracy and viewing angle.