The manufacturing process of FPD

28 Mar.,2024

 

As mentioned above, there are various types of FPDs. Still, this section will explain the mechanisms of liquid crystal displays (LCDs) and organic EL displays, which are often used in electronic products.

How does a liquid crystal display (LCD) work?

LCDs are arranged from back to front in the following order: backlight, a glass substrate, polarizer, liquid crystal layer, color filter, and glass substrate. During display, the backlight is always on, and the image is created by adjusting how much of the backlight passes through which part of the color filter.

At this time, the liquid crystal layer is responsible for adjusting the amount of light transmission. The mechanism by which the liquid crystal layer adjusts the transmission of light is the same as for monochrome liquid crystals and utilizes the principle of the polarizer. In their natural state, liquid crystal molecules have the property of lining up in a loosely regular manner, but when they come into contact with a plate with fine grooves (alignment film), they are regularly aligned alo in a regular manner along the grooves.

When light is shone on a liquid crystal in this state, only light with a wavelength in a certain direction is transmitted. On the other hand, when a voltage is applied to a liquid crystal, the molecules are aligned perpendicular to the alignment film, allowing light to pass through regardless of the direction of the wavelength.

The light emitted from the backlight passes through the polarizer, and only light with a wavelength in a certain direction reaches the liquid crystal layer. The grooves of the alignment film are oriented orthogonally to the grooves of the polarizer, so when no voltage is applied, the light from the backlight is blocked and does not appear on the surface.

However, the portion of the liquid crystal layer where voltage is applied allows light to pass through, so light passing through the color filter is recognized as an image. Thus, in a liquid crystal display (LCD), electricity is applied to the liquid crystal layer to let light through or block it, and to adjust the amount of light that passes through.

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