The Principle of Liquid Crystal Display- Professional Custom LCD display of Sinocrystal

The principle of most LCD liquid crystal displays

At the most basic level, most (not all) liquid crystal displays change the polarization state of light passing through the layer of liquid crystal material. The competition between the boundary conditions and the applied electric field controls the geometry of the layer. Generally, for this type of liquid crystal display, nematic liquid crystals are applied to the front and rear substrates together with special coatings. The coating is used to create boundary conditions and apply the required electric field. On the outside of the LCD unit, an optical film (including a polarizer) is attached. They convert light polarization changes into light and dark contrasts. The display structure is assembled in such a way that the zero external field produces an extreme brightness state, and the complete external field produces another extreme brightness state. The middle field creates the middle brightness level.

The most common material used to impose boundary conditions is called polyimide. The solution (or precursor) of polyimide is deposited on the substrate and cured. The type of polyimide and the type of liquid crystal determine the angle of the liquid crystal molecules at the contact point between the polyimide and the liquid crystal. If the materials are "similar," the liquid crystal molecules are flat. If they are different (like oil and water), the liquid crystal molecules will stand upright. "Molecular engineering" is used to achieve the ideal application angle, which is different for different types of displays. In order to determine the direction of orientation, the polyimide surface is rubbed or brushed in one direction. The liquid crystal molecules are aligned parallel to the rubbing direction. If the angle and the rubbing direction do not match on the two alignment surfaces, the alignment of the liquid crystal will be elastically deformed. The nematic liquid crystal molecules are expected to be parallel to each other, but if the rubbing directions on the two surfaces are orthogonal, the liquid crystal molecules are forced to twist slightly from one molecule to the other until they pass through the entire layer and the direction is rotated by 90°. Nematic liquid crystals have three main modes of deformation. Each has its own spring constant (spring constant). Depending on the molecular structure of the liquid crystal, some deformation may require more or less force. These three main deformations are called "spreading", "bending" and "twisting".