An LCD (liquid crystal display) is a type of flat panel display commonly used in digital devices such as TVs, computer monitors, mobile phones, and tablet computers. The LCD technology creates a visual image by modulating the light passing through a sophisticated liquid crystal material. The process is achieved by the application of an electric field that alters the alignment of the liquid crystal molecules, thus allowing or blocking the light's passage.

To understand how the LCD display works, let us break down the process into four key components: the light source, the polarizers, the liquid crystal layer, and the color filter.

1. The light source

First, the LCD needs a light source, usually a small fluorescent lamp or LED strip, to illuminate the panel from behind. The light is directed toward the rear of the monitor by a reflective layer and a diffuser that spreads the light evenly across the screen.

2. The polarizers

A polarizer is a film that only allows light waves to pass in a specific direction. The polarizers in an LCD display are placed on the top and bottom of the screen, perpendicular to each other and at a 90-degree angle. The first polarizer is located on the bottom surface of the LCD, removing all light waves that are not oscillating in the horizontal direction.

3. The liquid crystal layer

The key component of an LCD display is the liquid crystal layer, a substance composed of long, thin molecules arranged in regular rows. In an LCD display, the liquid crystal layer is situated between two thin glass sheets. The molecules in the liquid crystal layer have a natural tendency to align themselves along a specific axis.

4. The color filter

The color filter is the final component of an LCD display. It is responsible for creating the colored pixels that make up the image on the screen. The color filter is composed of red, green, and blue (RGB) sub-pixels, which are arranged in groups to form each pixel.

 

Now let us examine how the LCD display works together. When the electric current is applied, it reorients the crystals in the liquid crystal layer. By adjusting the voltage that passes through the individual crystal cells, the screen can be made to appear either dark or light. When the crystals are aligned with the polarizer on the top of the screen, they allow the light to pass through the panel, and the pixel appears lit. When the crystals are perpendicular to the polarizer, they block the light, and that pixel appears dark.

 

The liquid crystal changes color according to the voltage applied to it. By applying different voltages to each of the RGB subpixels, the liquid crystal layer can create different colors. The colors are produced by a process called additive color mixing, in which each subpixel produces its own color of light. For example, when the blue subpixel is illuminated while red and green are blocked, the liquid crystal layer appears blue. Similarly, when all three colors are illuminated, the pixel appears white.

 

One of the key benefits of LCD displays is that only the pixels that need to be illuminated are lit, which saves energy compared to backlighting an entire screen. LCD displays also tend to produce sharper images than other display types because the liquid crystal layer can switch between light and dark quickly and precisely.

 

In conclusion, an LCD display works by modulating the light that passes through a liquid crystal layer. The liquid crystal layer's molecules are realigned by applying voltage, allowing the light to be blocked or to pass through the polarizers. The color filter creates RGB sub-pixels that the liquid crystal layer can illuminate to create the desired color. The result is a high-quality display that provides a vivid image seen on modern digital devices.