What are LCDs or Liquid Crystal Displays?

 LIQUID-CRYSTAL DISPLAYS

A liquid crystal is a material that will flow like a liquid but whose molecular structure has some properties normally associated with solids.

In the electronic industry, the smectic and nematic types of liquid crystals have been used in thin lightweight display devices such as digital cameras, watches and calculators.

Working of LCDs

A thin film of a liquid crystal is placed between two sheets of glass, one is coated with a thin layer of tin oxide. when no current passes through the conductive coating, the molecules are uniformly oriented so that the light can pass through the cell. When an electric current is applied, the molecular alignment changes and the cell appears dark. Thus, a number or a letter is displayed in black against a silvery background.

Now, as LCD requires a very small amount of current, the small electronic devices can run for long times(years) within the help of small cells or batteries.

SEVEN Segment digit display

A digit on an LCD display may have the segment appearance as shown above. The black area is actually a clear conducting surface connected to the terminals below for external control. Two similar masks are placed on opposite sides of a sealed thick layer of liquid-crystal material. 

For example, If the number 6 were required, terminals 1,6,7,5,4 and 3 would be energized, and only those regions would be frosted while the other areas would remain clear as shown in the figure.

Further, the complete display is made up of two polarizers that transmit light in perpendicular directions, a mirrored surface and a layer of liquid crystal material between two glass plates are placed. In the absence of the applied voltage, the liquid crystal molecules in all the segments are precisely aligned so that the entire panel appears silvery because light passes through both the polarizers and finally, gets reflected from the mirror. However, when voltage is applied to the segment of a display, the precise alignment of liquid crystal molecules is lost. As a result, the light from the first polarizer fails to get rotated through the required angle of 90° to align with the second polarizer. The second polarizer thus blocks the passage of light. Since no get reflected from the mirror, the panel appears dark.

Frequently Asked Questions – FAQs LCDs or Liquid Crystal Displays

Q: What is a liquid-crystal display (LCD)?

A: A liquid-crystal display is a flat-panel display technology that uses liquid crystals to produce images.

Q: How does an LCD work?

A: An LCD works by using liquid crystals to control the polarization of light passing through them, producing an image on the screen with varying colors and brightness levels.

Q: What are the advantages of LCD displays?

A: The advantages of LCD displays include their thin and lightweight design, low power consumption, and ability to produce sharp and clear images.

Q: What are the disadvantages of LCD displays?

A: The disadvantages of LCD displays include their limited viewing angles, lower color accuracy compared to other display technologies, and potential for backlight bleeding.

Q: Can LCD displays produce their own light?

A: Traditional LCD displays require a separate light source, such as a backlight, to provide illumination for the liquid crystals. However, some newer types of LCD displays, such as OLED displays, do use light-emitting diodes (LEDs) to produce light.

Q: What is backlight bleeding?

A: Backlight bleeding is a phenomenon in which light from the backlight of an LCD display leaks through the edges of the screen, causing uneven brightness and a loss of contrast.

Let me know if you have more questions or if there is a specific topic that you would like to know more about.