What is TFT LCD?
TFT LCD is a type of "liquid crystal display " that uses "thin film transistor " technology to enhance performance It can be said that the vast majority of LCD screens we see in our daily lives are TFT LCDs
What is TFT LCD?
Let's explain in detail what TFT LCD is.
This is a very common technical term in the field of electronics, and we can break it down to understand it:
LCD: Liquid Crystal Display
TFT: Thin Film Transistor
So, TFT LCD is a type of "liquid crystal display" that uses "thin film transistor" technology to enhance performance. It can be said that the vast majority of LCD screens we see in our daily lives are TFT LCDs, which have become the mainstream of LCD technology.
1. Core principle: How does LCD display?
To understand TFT, one must first understand the basic working principle of LCD.
Liquid crystal: This is a substance between liquid and crystal, which can flow like a liquid and has directionality like a crystal. The key feature is that its arrangement direction will change with the variation of the applied electric field.
Light control: LCD itself does not emit light, it requires backlight (usually LED) to provide light source. The liquid crystal is sandwiched between two parallel glass substrates (referred to as "substrates") to form a "liquid crystal cell".
Polarizing plate: On the outer side of two glass substrates, there are polarizing plates with polarization directions perpendicular to each other. Under normal circumstances, light cannot pass through these two perpendicular polarizing plates.
Electricity changes arrangement: When no voltage is applied, liquid crystal molecules undergo specific twisting, which can guide light to rotate 90 degrees, allowing light to pass through two layers of polarizing film smoothly and display a "bright" state. When a voltage is applied, the liquid crystal molecules will align neatly and no longer twist the light, and the light cannot pass through the second polarizer, displaying a "dark" state.
Colorization: By adding red, green, and blue filters in front of each pixel and controlling their brightness ratio, various colors can be mixed.
2. Key upgrade: What is the function of TFT (thin film transistor)?
In early simple LCDs (such as calculator and electronic watch screens), all pixels were "passively" controlled, with slow response, color differences, and ghosting, and could only perform simple displays. The introduction of TFT technology has solved the core "control" problem.
What is TFT?
TFT is actually a tiny switching transistor. It is made by thin film technology on a glass substrate, and each sub-pixel (one of red, green, and blue) corresponds to a TFT switch.
How does TFT work? ——Active Matrix Control
You can imagine each TFT as a 'micro water valve' serving its corresponding sub-pixel.
When a sub-pixel needs to display a specific brightness, the driving circuit will send a voltage signal (representing water volume) through the "source line", and at the same time send an open signal to the TFT of this sub-pixel through the "gate line" (opening valve).
After the TFT is turned on, the voltage signal will be charged into a tiny storage capacitor (like a reservoir), and then applied to the liquid crystal, causing it to produce corresponding deflection.
When the TFT is turned off (valve closed), the storage capacitor can maintain this voltage for one refresh cycle, stabilizing the liquid crystal state until the next refresh.
3.The main advantages and disadvantages of TFT LCD
Advantages:
High image quality: Fast response speed, greatly reducing ghosting phenomenon.
High contrast&vibrant colors: Each pixel is independently and precisely controlled, capable of displaying deeper black and richer colors.
Relatively low cost: mature technology, complete industrial chain, and advantages in production costs in large-scale fields.
Long lifespan: The technology is stable, and the lifespan is mainly affected by the backlight module.
Disadvantages:
Viewing angle: Traditional TFT LCDs (such as TN panels) have poor viewing angles, resulting in color distortion and decreased contrast when viewed from the side. However, the later development of IPS technology greatly improved this problem.
Response time: Although much faster than passive LCD, there is still a delay in pixel switching compared to newer OLED technology, especially when displaying high-speed dynamic images.
Contrast: Due to the presence of a backlight layer, it is not possible to completely block the backlight when displaying black, resulting in a less pure black color that appears as "gray black".
Power consumption: The backlight needs to be always on, even if a black image is displayed, it still consumes power, so the power consumption is usually higher than OLED screens that can individually turn off pixels.
Flexibility: The structure is hard and cannot be bent or folded.
4. Common types (TFT LCD panel technology)
TFT LCDs are mainly divided into several types based on the arrangement of liquid crystal molecules and driving methods:
TN: Lowest cost, fast response time, but worst color and viewing angle.
VA: High contrast, better color and viewing angle than TN, but slower response time.
IPS: Currently the most mainstream high-end technology, with excellent viewing angle and color accuracy, but relatively high power consumption and "light leakage" phenomenon.
summary
Simply put, TFT LCD is a traditional LCD screen that is equipped with a "micro intelligent switch" (TFT) for each pixel, enabling fast, precise, and stable control of each pixel, ultimately resulting in bright colors, clear images, and fast response display effects.
For over twenty years, it has been the absolute dominant display technology for devices such as televisions, computer monitors, laptops, tablets, and smartphones, until it has been replaced by more advanced OLED technology in certain fields in recent years.
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