How TFT LCD panel works and what's inside it
How does LCD work? What is the function of the vertical & horizontal polarizer, TFT substrate, color filter, and backlight?
The Full form of LCD should be known to most people, but for those curious, the answer is Liquid Crystal Display (LCD).
This display panel, widely used worldwide, is called just LCD, but its full name remains hidden; its full name is TFT LCD (Thin Film Transistor Liquid Crystal Display).
Liquid Crystal Display (LCD): In addition to LCD, Several Types of display panels are used in various electronic devices capable of displaying images, such as LCD Monitors, LCD TVs, Laptop screens, Mobile Phones, etc.
LCD panels are widely used in all these devices, keeping in mind the purchasing power of the people. So, we first try to learn the working method of liquid crystal display.
 |
TFT LCD Panels Internal Structure |
To understand how an LCD works, it is imperative to have a clear understanding of the internal structure of the Liquid Crystal Display.
Typically, a liquid crystal display is less than two millimeters thick. Surprisingly, this thin glass display has six distinct functional layers inside. So first, you need to know the names of these six Substrates-
(Match the six layers below with the diagram above)
• 1. LED Backlight (Light Source)
• 2. Vertical Polarizer (Vertical Polarizing Filter).
• 3. Thin Film Transistor substrate (TFT matrix).
• 4. Liquid crystals substrate.
• 5. RGB color filter.
• 6. Horizontal Polarizer (Horizontal Polarizing Filter).
• 7. Glass cover.
From the above list, we are familiar with the names of the arranged substrates of the LCD panel. Now, we will patiently try to understand the function of each substrate or how a liquid crystal display works.
Internal structure of LCD panel and its analysis
1. Backlight
What is the function of the backlight on an LCD?
The Backlight is the Light source of the Liquide Crystal Display Panel. This Backlight is the only light source for the images that appear on LCD TVs, Laptop displays, monitors, and mobile phone displays.
In the latest technology, the LCD Panels' light source is LED backlights placed separately at the bottom of the screen. In thin displays, LED strips are placed on the edges of light-conducting glass. Also, old-model displays used high-voltage fluorescent tubes as the light source.
We understand that the backlight is placed below the LCD panel. Now, we will know about the internal structure of the LCD panel above the Backlight.
2. Vertical Polarizer
What does a vertical polarizer do in an LCD?
What is a Polarizer? A polarizer is not an electronic component. Polarizers are made of PVA (Polyvinyl Alcohol), a polarizing film sheet or Polarizing Filter for LCD panels.
As the light from the Backlight passes through the LCD panel, it encounters a polarizing filter. This filter only allows light waves to pass through, oscillating in a specific direction. This helps ensure the light is polarized before interacting with the liquid crystals.
A vertical polarizer in an LCD (Liquid Crystal Display) panel controls the orientation of light passing through the display. It's one of the polarizing filters used in conjunction with others in the display structure.
In an LCD, light passes through multiple layers, including polarizers and liquid crystal molecules, to produce the images you see. The vertical polarizer allows light waves oscillating vertically to pass through while blocking those oscillating horizontally. This controlled passage of light helps manipulate the orientation of liquid crystal molecules within the display, thus preventing the amount and color of light that ultimately reaches your eyes, creating the images and hues you see on the screen.
3. TFT (Thin Film Transistors) Substrate
What is TFT and its function in LCD?
The TFT (Thin Film Transistor) substrate is crucial in LCD technology. It serves as the foundation or base layer for the thin film transistors that control the individual pixels on the display. The TFT substrate is typically made of glass and is coated with thin films of semiconductor materials, such as amorphous silicon.
The primary function of the TFT substrate is to enable precise and rapid control of each pixel on the LCD screen. Each pixel consists of a liquid crystal element sandwiched between two layers of glass. The TFTs on the substrate act as switches that control the voltage applied to the liquid crystal, determining its optical state (either allowing light to pass through or blocking it).
By using thin film transistors, the TFT substrate allows for more accurate and faster manipulation of individual pixels than traditional passive matrix displays. This results in improved image quality, shorter response times, and better overall performance in modern LCD screens, making them suitable for various applications such as computer monitors, televisions, and mobile devices.
4. Liquid Crystals Substrate:
What is the function of liquid crystal in LCD?
LCD panels contain a liquid crystal substrate and other layers. This layer consists of billions of liquid crystal cells based on the resolution of the screen, and each cell has two electrodes, the positive terminal AVDD and the negative terminal VCOM voltage supply, to activate the cells.
Liquid crystals are unique materials that move their molecules from vertical to horizontal when energized and de-energized, and the degree to which they move depends on the amount of AVDD, VCOM, and signal voltage.
Liquid crystals in a Liquid Crystal Display panel serve a crucial role in controlling the passage of light. These crystals have properties that allow them to change their orientation when an electric current is applied. The liquid crystals align in specific ways, allowing light to pass through or block it. This manipulation of light by the liquid crystals creates the images and colors we see on the screen. Essentially, the liquid crystals act as shutters, modulating the passage of light to form the display's visual output.
5. Color filter / Pixel structure:
What is the function of color filters in TFT LCD?
The LCD panel is divided into a grid of tiny pixels. Each pixel comprises three sub-pixels: red, green, and blue. These sub-pixels are the building blocks for displaying colors on the screen.
The color filter in an LCD (Liquid Crystal Display) serves the crucial function of producing the colors you see on the screen. It's placed over the pixels and subpixels of the display and works by selectively filtering the white light generated by the Backlight. Each pixel on the screen comprises three subpixels, typically red, green, and blue (RGB), and the color filter determines which subpixels allow specific wavelengths of light to pass through. By controlling the light passing through these subpixels, the color filter helps create the full spectrum of colors visible on the display.
The RGB filter is essential for accurate color reproduction and ensuring the display can represent a diverse and vibrant array of colors. It suits tasks like image and video viewing, graphic design, and other color-sensitive applications.
Horizontal Polarizing Filter:
What is the function of a horizontal polarizer in an LCD?
The Horizontal polarizer, placed after the liquid crystal layer, is oriented horizontally. It only allows light waves that are horizontally aligned to pass through.
The liquid crystal layer twists the light waves based on the electrical signal applied to create the desired image. When an electric current is applied to a pixel, it adjusts the orientation of the liquid crystals in that pixel. This twisting effect changes the polarization of the light passing through that pixel, allowing it to pass through the horizontal polarizer and become visible.
The LCD creates the images and colors you see on the screen by selectively controlling which pixels allow light to pass through. The combination of these polarizers and the manipulation of the liquid crystals form the basis of how LCDs function to display images.
How Does Liquid Crystal Display Work? You can patiently watch the video below to understand it better.
No comments: