Polarizers are pasted on the upper and lower glass substrates injected with liquid crystals. The ones pasted on the upper substrate are called detection photons, and the ones pasted on the lower substrate are called polarized photons. The optical axes of the upper and lower polarizers are orthogonal.
Polarizers only allow light vibrating in a certain direction to pass through. Now, the voltage applied to the liquid crystal is 0V, and the liquid crystal molecules in the liquid crystal cell are aligned along the rubbing channels of the alignment film of the upper glass substrate and the rubbing channel of the alignment film of the lower glass substrate at the interface respectively. Therefore, the liquid crystal molecules on the upper and lower glass substrate surfaces on the LCD display screen are arranged in a 90° twisted state.
Due to this state, when the light emitted by the backlight passes through the polarizer below, only the light vibrating in one direction can pass. Then according to the arrangement method of the liquid crystal molecules in the liquid crystal screen, it is twisted and reaches the upper polarizer.
Here, the irradiated light is twisted 90° along the alignment of the liquid crystal molecules on the LCD display screen, and passes in parallel in the direction of the upper polarizer. At this time, the state of passing light is defined as "white".
On the LCD display liquid crystal screen, when a voltage is applied, the arrangement of the liquid crystal molecules in the liquid crystal screen will change. If the axial direction of the upper and lower polarizers is 90°, only one direction of light can pass through the LCD display liquid crystal screen, depending on whether there is an external voltage, whether it passes or not determines "white" or "black", so that the LCD display an image is displayed on the screen.
Of course, the intermediate color between "white" and "black" is determined by the intermediate point of the applied voltage. When the axial direction of the upper and lower polarizers is 90°, when no voltage is applied, the irradiated light can pass through, which is "white" at this time, and when a voltage is applied, the irradiated light is blocked, and it is "black" at this time. This type of liquid crystal is known as a normally white LCD display. SFT mode is similar to TN mode.
There is a layer of color filter substrate (CF substrate) on the outside of the LCD display liquid crystal screen, and the light passing through the array substrate will be colored when it passes through the CF substrate. In fact, one pixel of the LCD display screen is divided into RGB 3 primary colors (red, green, blue), and each pixel is colored by the corresponding RGB color film. In a color display, pixels are divided into red (R), green (G) and blue (B). The three colors are called pixels, and each pigment R, G, and B is called a sub-pixel. This LCD color display is an additive mixing method, using color filters to mix RGB light to obtain various colors.
