A Liquid Crystal Display or an LCD is a commonly used visual display technology found in TVs, computer monitors, and smartphones. This technology uses a rectangle-shaped display surface that is evenly lit, making it easy to view the content on the screen. The rectangle is divided into smaller rectangular subdivisions, known as pixels, which work together to display the content on the screen.
Each pixel is made up of even smaller subdivisions known as subpixels, which are created by dimming the light inside the pixel and passing it through various color filters. These subpixels are used to create a small area in a portion of a solid color. However, the density of these subpixels is so high that our eyes cannot differentiate between individual subpixels.
This blending effect produces an incredible range of vivid and rich colors on the screen. There are millions of different colors that can be created due to the way that the subpixels blend. As a result, the images and videos displayed on LCDs are incredibly lifelike and realistic. Due to this reason alone, LCDs are the preferred choice for many professional and personal applications nowadays.
Working Principle of Liquid Crystal Displays
LCDs follow two different types of working principles. These include:
Field Effect Type
Liquid crystals are used in the construction of both dynamic scattering and field effect types of LCDs. The main difference between the two is that in field effect LCDs, two thin polarizing optical fibers are placed inside each glass sheet. The liquid crystals in these LCDs are of different scattering types operating in a dynamic scattering cell. Nematic material is used in field effect LCDs, which twists unenergized light passing through the cell.
This type of material consists of liquid crystals in which molecules are arranged parallel to each other but not in a well-defined plane. Light appears bright when it passes through the nematic material and optical filters. However, when the cell is energized, no light twisting occurs, and the cell appears dull.
Dynamic Scattering
When light passes through the liquid in the potential carrier, the molecular alignment of the liquid crystal display is disturbed. The liquid appears transparent when the molecules are inactive. However, when they become active, their turbulence causes light to scatter in all directions, making the cell appear bright. This phenomenon is called dynamic scattering.
Different Components Found Inside LCDs
- Microelectronics
A liquid crystal display (LCD) consists of several layers, each serving a unique purpose. While the most important layer is the screen, beneath it lies the critical layer responsible for signal processing. These micro-electronics transmit and receive video signals, enabling the LCD to bring images and videos to life with exceptional clarity.
Essentially, an LCD’s signal processing unit, typically containing a flex circuit, is split into two main functions – the video signal receiver and the panel driver. The video signal receiver is responsible for receiving the signals from the input source and processing them to ensure they are in a format the panel driver can understand. This panel driver usually consists of a flex circuit board with important electrical components.
On the other hand, the panel driver is responsible for taking the processed signals and translating them into images on the screen. This integration of micro-electronics, typically soldered on a flex circuit board, in LCDs makes them a great option for various applications, including televisions, computer monitors, and even mobile devices.
- Power Supply
An LCD cannot function with the standard 120 volts found in most homes. Therefore, a power converter becomes necessary for its operation. The power converter works by converting the main voltage into an intermediate DC voltage ranging from 12 to 24V. Once the voltage is converted, the power flow is divided into two, powering the backlight and microelectronics on a flex circuit board.
However, it is important to note that the 5V required for the display’s flex circuit board and electronics is further divided into two, supplying the LVDS receiver and bias driver. This intricate process ensures that the Liquid Crystal Display functions efficiently and effectively, providing high-quality display output.
- The Backlight
An LCD requires a white backlight that emits light to all red, green, and blue subpixels. The two commonly used sources of white light are LEDs and CCFLs. CCFLs use mercury to produce fluorescent light, while LEDs do not, making them more environmentally friendly.
However, LEDs and CCFLs are point or line light sources, whereas the light must be spread over a larger surface area. Therefore, LCDs use reflecting and diffusing layers. Diffusers help to spread the light beams evenly to illuminate the required area.
The diffused light then passes through a series of irregularly spaced bumps, proceeding to the LCD panel or bouncing back. On the other hand, the reflecting layer guides the wasted diffused light back to the LCD panel, increasing efficiency.
- The Panel
LCDs use a polarizing filter that only allows light through that is angled to a certain degree. The display panel consists of two polarizing filters attached to a glass sheet, with liquid crystals in between that can bend light.
The process of how LCDs function is quite interesting. When light from the backlight hits the first polarizing filter, it passes through the liquid crystals, where it is bent before passing through the second polarizing filter. This process allows for a clear and sharp image to be displayed on the screen.
One of the main advantages of LCDs is their ability to provide voltage control of the light traveling through the panel. This means that the amount of voltage used determines how much light is bent, allowing for a wide range of brightness levels to be achieved. This feature makes LCDs an ideal choice for various indoor and outdoor applications.
Conclusion
The advancements in LCD technology have been remarkable and constantly evolving. The underlying principles of how liquid crystals work and produce various materials have remained the same. However, the innovative methods of controlling and displaying these materials have become more sophisticated. And every flexible PCB manufacturer knows this.
As a leading flexible PCB manufacturer in the industry, we also understand the importance of staying on top of these technological advancements and how they can impact our industry. We’re excited to see what the future holds for LCD technology and how it will continue to transform the tech landscape.