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How LCD (liquid crystal display) works

Beijing HTDisplay Electronics Co., Ltd.

2024-07-26

The working principle of LCD (liquid crystal display) is based on the directional arrangement of liquid crystal molecules under the action of an electric field to control the transmission and blocking of light to achieve image display.The following is the basic working principle of LCD screen

LCD screen

Beijing HTDisplay Electronics Co., Ltd.——LCD screen

Basic structure: The LCD screen is composed of two parallel glass substrates, with the middle layer filled with liquid crystal material.Each liquid crystal pixel unit consists of a pair of transparent electrodes, and the liquid crystal molecules between the electrodes can control the transmission of light.
Liquid crystal molecular arrangement: LCD screens use two main types of liquid crystal molecular arrangement: nematic (TN) and vertical alignment (VA).Liquid crystal molecules exhibit a specific arrangement in the absence of an electric field.

- TN liquid crystal: The molecules in TN liquid crystal are arranged in a spiral shape without the action of an electric field.When an electric field is applied to an LCD screen, the electric field changes the alignment direction of the liquid crystal molecules, causing light to rotate as it passes through the liquid crystal.

- VA liquid crystal: The molecules in VA liquid crystal are aligned vertically without the action of an electric field.When an electric field is applied to an LCD screen, it tilts the molecules horizontally, thereby regulating the transmission of light.

Transmission and blocking of light: Each pixel unit of the LCD screen has a control electrode that can apply an electric field.When an electric field is applied to the pixel unit, the arrangement of the liquid crystal molecules changes, changing the transmission and blocking of light.

- Transparent state: When an electric field is applied, the arrangement of liquid crystal molecules changes so that light rotates to a minimum when passing through the liquid crystal layer.At this time, the light can pass through the liquid crystal layer and be displayed through components such as color filters.

- Blocking state: When the electric field is not applied, the liquid crystal molecules maintain their original arrangement, causing the light to rotate when passing through the liquid crystal layer and cannot be displayed through components such as color filters.

Backlight: LCD screens usually require a backlight to provide light source.The backlight is located on the back of the LCD screen and illuminates the screen through transparent pixels that pass through the liquid crystal layer.

Control signal: The control circuit of the LCD screen controls the application of electric field to each pixel unit according to the input signal, thereby controlling the arrangement state of the liquid crystal molecules and realizing the display of the image.

Through the above working principle, the LCD screen can change the arrangement of liquid crystal molecules according to the control of the electric field, thereby controlling the transmission and blocking of light to form an image display.The backlight provides the light source so that the displayed image can be seen by the observer.

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