What's the solution for LCD screen black spots?

With the rapid advancement of technology, commercial LCD displays are increasingly prevalent in everyday use. This widespread adoption inevitably brings forth various issues, such as unresponsive touch functionality, screen flickering, or the appearance of black spots on the display. Today's blog post delves into the causes of black spots on these devices and provides practical solutions. We hope this information proves helpful to you.

Simply put, each pixel on an LCD screen consists of three sub-pixels: red, green, and blue. By controlling the deflection of liquid crystal molecules in each sub-pixel, the backlight transmits light at varying intensities, thereby blending different colors 'Dead pixels'primarily fall into three categories, each with distinct causes:

Dead pixels primarily fall into three categories, each with distinct causes:

1. Dark Pixel / Dead Pixel

Phenomenon: A permanently black dot on the screen. Regardless of what is displayed, this pixel does not light up.

Causes:

Manufacturing defects (main cause): During screen production and assembly, microscopic dust particles or impurities may fall into the TFT (Thin-Film Transistor)

array or color filter. These can block liquid crystal flow or cause a short/open circuit in the TFT controlling that pixel.

Note: Some devices do not feature tempered glass, allowing users to clean the LCD panel directly. However, devices with tempered glass have a gap between the

glass and the LCD panel. Outdoor digital signage despite dust protection, dust particles may still accumulate. Dust carries weight, and when the tempered glass

is tapped vertically, dust adhering to the glass surface will fall to the bottom of the screen due to gravity, forming dark spots. Therefore, regular screen

cleaning is necessary during use.

Physical damage: Pressure, impact, or squeezing can rupture liquid crystal cells or damage TFT circuits. For example, closing a laptop with an object on the keyboard

or sitting on a phone in your pocket with keys may lead to such damage.

Aging: Although less common, long-term use may cause the tiny transistor controlling a pixel to fail due to wear and aging.

2. Bright Pixel / Stuck-On Pixel

Phenomenon: A permanently white or single-color dot (red, green, or blue) that remains lit.

Causes:

Manufacturing defects: Similar to dark pixels, microscopic particles or a TFT transistor stuck in the “on” state (Stuck On) can prevent liquid crystals from shutting

off properly,causing the backlight to always pass through.

Signal issues: A malfunction in the circuitry controlling the pixel may continuously send incorrect signals, keeping the pixel permanently on.

3. Stuck Pixel

Phenomenon: The pixel displays abnormal colors, often leaning toward a specific color, or behaves incorrectly under different colors. It does not remain fully black

or white but responds sluggishly to color changes.

Causes:

Liquid crystal material issues: Contamination or inconsistency in the liquid crystal within the pixel may prevent it from responding correctly to electrical signals.

Weak TFT: The transistor driving the pixel may be underperforming, providing insufficient voltage for the liquid crystal molecules to fully align as intended.

How should I resolve this?

Check for external dirt or debris

First, unplug the power supply. Use a clean microfiber cloth with a small amount of screen cleaner to gently wipe the black spot area. Sometimes what looks like a 'black spot' may just be surface dirt.

Check for hardware damage

Play a solid color background (such as pure white or pure blue) on the digital signage.If the black spot remains fixed in position and size, it is likely a “dead pixel,” often caused by pixel aging over time.If the black spot looks blurry around the edges or appears to spread, it may indicate liquid crystal leakage due to panel

damage—commonly from impact during transportation. In such cases, the LCD panel typically needs replacement. (Note: All panels undergo aging tests before

shipment, so this issue usually arises from transport-related damage.)

Contact us if unsure

If you’re still unable to determine the cause, feel free to contact us. Our professional technical team can diagnose the issue and recommend the most suitable solution.