TFT LCD Panel Structure Process, TFT-LCD Industrial LCD Panel
News 2025-11-13
A TFT LCD panel is not a simple piece of glass, but a complex “sandwich” structure made up of multiple layers of precision materials and components. Each layer has a specific function, and they work together to present the rich images we see.
I. Components of a TFT Industrial LCD Panel
- Polarizer
These are the outermost and innermost layers of the panel, located on either side of the glass substrate. A polarizer is a special optical film that allows only light with a specific vibration direction to pass through. The polarization directions of the two polarizers are perpendicular, controlling the rotation of liquid crystal molecules to determine whether light can pass through, thus controlling the brightness of the pixels.
- Glass Substrates
The panel consists of two glass substrates.
Upper Glass Substrate: Typically the carrier of the color filter and black matrix.
Lower Glass Substrate: The carrier of the TFT (Thin Film Transistor) array and pixel electrodes.
The distance between these two glass substrates is precisely controlled at the micrometer level.
- Color Filter and Black Matrix
This layer is located inside the upper glass substrate.
Color Filter: Composed of tiny red (R), green (G), and blue (B) units, each unit corresponding to a pixel. When light passes through the liquid crystal layer and then through the color filter, it is filtered into the corresponding color.
Black Matrix: Composed of opaque black material, located between the color filters, it separates different pixels, preventing light leakage and color crosstalk, thereby improving image contrast and clarity.
- TFT Thin Film Transistor Array
This is the core of the TFT LCD screen. Located on the lower glass substrate, it consists of densely packed thin film transistors, with each pixel corresponding to an independent TFT switch. These tiny switches precisely control the voltage flowing to each pixel, ensuring that each pixel can be independently and stably controlled.
- Liquid Crystal Layer
This is the central layer of the panel, sandwiched between two glass substrates. It is composed of liquid crystal molecules. These molecules are randomly arranged in the absence of an electric field, but rotate in a specific direction after a voltage is applied. It is this characteristic that allows them to act like a “light valve,” precisely controlling the amount of light passing through each pixel.
- Other Auxiliary Layers
In addition to the core structure described above, the panel contains several auxiliary layers, such as:
Alignment film: Used to ensure that liquid crystal molecules align in a specific direction when no voltage is applied.
Spacer: Evenly distributed between the two glass substrates to ensure that the distance between them (i.e., cell thickness) remains consistent.
Sealant: Used to seal the two glass substrates, preventing liquid crystal molecules from leaking out.
II. Key Processes and Details of TFT LCD Panels
- TFT Array Process
Each pixel consists of a thin-film transistor (TFT) and a storage capacitor.
TFTs generally use amorphous silicon (aSi) or low-temperature polycrystalline silicon (LTPS) technology.
aSi TFT: Mature process, low cost, widely used in industrial displays and most consumer displays.
LTPS TFT: High electron mobility, supports high resolution and high refresh rates, commonly found in mobile phones and high-end displays.
The emerging oxide TFT (IGZO) has the potential for lower leakage current and higher resolution, and is already used in some high-end automotive and medical displays.
- Liquid Crystal Layer Modes
TFT panels are not a single structure; they are also divided into several modes based on the arrangement of liquid crystal molecules:
TN (Twisted Nematic): Commonly used in the past, fast response but poor viewing angle.
IPS (InPlane Switching): Liquid crystal molecules rotate horizontally, wide viewing angle, accurate color, currently the mainstream for industrial and automotive displays.
VA (Vertical Alignment): Liquid crystal molecules are vertically aligned, resulting in high contrast; commonly found in televisions.
- Polarizing Films and Optical Films
Polarizing films not only control light transmission but also determine the screen’s contrast ratio.
Industrial/automotive screens commonly use anti-glare (AG) films, anti-reflective (AR) films, and anti-fingerprint (AF) coatings to ensure clear visibility even in sunlight.
Some high-brightness screens also add a brightness enhancement film (BEF) to increase front brightness.
- Backlight Module Design
Direct-lit backlight: LEDs are distributed behind the screen, providing high brightness; suitable for large sizes and outdoor applications.
Edge-lit backlight: LEDs are located at the edge of the screen, combined with a light guide plate; thinner, suitable for small sizes and slim products.
In industrial and automotive applications, high-brightness LEDs + aluminum substrates for heat conduction are often used to improve stability and lifespan.
III. Comparison of Expanded Application Scenarios
- Consumer Electronics
Mobile phones, tablets, and laptops commonly use
IPS/AMOLED displays, prioritizing color accuracy and refresh rates.
Mid-to-low-end devices still primarily use TFT-LCDs, offering high cost-performance.
- Industrial Displays Emphasize
Wide temperature range (30℃ ~ 85℃), high brightness (≥1000cd/m²), and long lifespan.
Typical applications: industrial control terminals, medical monitors, smart grids, and military equipment.
- Automotive and Motorcycle Instrument Panels Focus on
Waterproof and dustproof, anti-glare, and sunlight visibility.
High-end models already use IPS + full lamination technology to ensure stable display even under vibration.
IV. Common Questions about TFT LCD Panel Structure
Q1: Why does a TFT LCD screen need backlighting?
A1: Liquid crystal molecules themselves do not emit light; they can only regulate light transmittance. A TFT screen requires a backlight module (LED/light guide plate/diffuser) to provide a light source, and the liquid crystal layer then controls the light to form an image.
Q2: What is the function of the polarizer in a TFT LCD screen?
A2: The polarizer is a key component of LCD displays; it determines whether light can pass through. Liquid crystal molecules change their polarization direction under the influence of an electric field, and in conjunction with the upper and lower polarizers, they switch between “bright” and “dark” states, thus displaying an image.
Q3: What are the differences between IPS and TN panel structures?
A3: TN (Twisted Nematic): Liquid crystal molecules rotate vertically, resulting in a fast response but narrow viewing angle.
IPS (In-Plane Switching): Liquid crystal molecules rotate in parallel, resulting in a wide viewing angle and accurate color, making it the mainstream for industrial and automotive displays.
Different structures → Different directions of liquid crystal molecule rotation → Significant differences in display effects.
Q4: If a TFT screen yellows or dims, which layer is aging?
A4: Common causes include: ① LED backlight decay; ② Polarizing film yellowing due to UV exposure; ③ Discoloration of the light guide plate or diffuser; ④ Degradation of liquid crystal molecule performance. Different aging areas can lead to color shift or decreased brightness.
Q5: What are the structural differences between industrial and consumer TFT LCD screens?
A5: Industrial screens feature enhanced wide-temperature liquid crystal formulations, UV-resistant polarizers, waterproof and dustproof structures, and backlight heat dissipation designs to ensure long-term use in harsh environments; while consumer screens prioritize thinness and color performance.
Q6: Is a color filter essential for a TFT screen?
A6: Yes. A color filter decomposes white light into red, green, and blue sub-pixels, which combine with different transmittance to form a full-color image. Without a filter, a TFT screen can only display black and white grayscale.
Q7: Why is “full lamination technology” frequently emphasized in automotive and outdoor screens?
A7: Full lamination technology involves filling a transparent adhesive layer between the LCD panel and the cover glass to prevent air gaps, reduce reflection and haze, improve visibility under sunlight, and enhance shock resistance.
The panel structure of a TFT LCD screen is a multi-layered system, encompassing TFT arrays, liquid crystal layers, color filters, polarizers, and backlight modules. Each layer determines image quality, brightness, viewing angle, and lifespan. With advancements in technology, it is developing towards higher resolution, wider color gamut, lower power consumption, and wider temperature adaptability, remaining mainstream in industrial, medical, and automotive applications.
Hangzhou LEEHON Technology Co., Ltd., as a provider of LCD driver solutions specializing in the industrial field, has established deep partnerships with many leading global LCD panel manufacturers, including BOE, TIANMA, IVO, AUO, Innolux, and Kyocera, professionally supplying multi-brand, full-series industrial-grade LCD displays and customized solutions.
