How to Prevent LCD Backlight Leakage

      LCD backlight leakage primarily occurs when light from the backlight source (usually LED) isn't fully contained by the panel or light-guiding structure, allowing it to escape from the edges or non-display areas. To prevent or reduce light leakage, comprehensive control is required across multiple stages, including design, production, material selection, and maintenance. Specific measures are as follows:

A. Design and Process Optimization

1. Backlight Unit Structural Design

· Light Guide Plate (LGP) Optimization: The LGP is a core component of the backlight. Its edges should be designed with "microstructures" (such as beveled edges or gradient dots) to prevent direct light from hitting the edges. This should also improve the uniformity of the LGP (reducing localized bright spots). This can be achieved by optimizing dot distribution (laser engraving or printing).

· Light-Block Reinforcement: Add a black light-blocking adhesive strip (such as PI tape or EPDM foam) between the LGP and the panel (LCD/OLET). This covers the gap between the LGP edge and the panel, blocking light leakage paths. The light-blocking adhesive should adhere tightly to the panel to prevent warping.

Backlight unit and panel lamination accuracy: A full lamination process using precision jigs or optical bonding adhesive (OCA) ensures a uniform gap (typically ≤0.1mm) between the backlight unit and the panel (color filter layer), minimizing light leakage caused by excessive gaps.

2. LED lamp layout and driver

LED quantity and pitch control: The number and pitch of LEDs in the LED light strip (e.g., fine-pitch LED backlights) are optimally designed based on the screen size to avoid uneven brightness ("hot spots") caused by too few LEDs or excessive spacing, which indirectly exacerbates light leakage.

Driver circuit optimization: Local dimming technology is employed to independently drive LEDs in different zones, dynamically adjusting brightness and reducing light leakage at the edges due to overly bright backlights (especially suitable for high-end TVs and monitors).

B. Material Selection and Quality Control

1. Core Material Performance

· Light Guide Plate Material: Select PMMA (polymethyl methacrylate) or PC (polycarbonate) with high transmittance (≥92%) and low haze (≤0.5%) to reduce light absorption and uneven scattering.

· Diffuser and Brightness Enhancement Film: Diffusers must have high uniformity (controllable diffusion angle) to prevent localized light concentration. Brightness Enhancement Film (BEF) must have an optimized prism structure to improve light utilization and reduce unused light leakage from the edges.

· Shading Material: Shading tape must have a high light blocking rate (≥99%), be temperature-resistant (-40°C to 85°C), and resist aging (anti-yellowing) to prevent light leakage due to failure after long-term use.

2. Production Process Quality Control

· Light Guide Plate Edge Treatment: After cutting, the light guide plate must undergo polishing or edge sealing (such as coating with UV adhesive) to eliminate burrs and micro-cracks and prevent light leakage from micro-slits at the edges.

· Assembly Process Precision: During backlight unit assembly, a visual alignment system (such as a CCD camera) ensures that the positional deviation of the light guide plate, diffuser, and brightness enhancement film is ≤0.05mm to prevent interlayer misalignment and light leakage.

· Full Lamination: The panel and backlight unit are fully bonded using OCA optical adhesive (rather than frame adhesive), eliminating air gaps (where differences in air refractive index can cause light scattering) and improving overall sealing.

C. Usage and Maintenance Recommendations

1. Environmental Control

· Avoid prolonged exposure to high temperatures (>50°C) or high humidity (>85% RH). Material expansion due to heat and cold, or moisture, may cause separation of the bonding layer, leading to light leakage.

· Keep away from strong magnetic fields or static electricity to prevent abnormalities in the LED driver circuit (such as current fluctuations) from causing localized overbrightness of the backlight.

2. Physical Protection

· Protect the screen from pressure, collisions, or scratches. External forces may cause deformation or displacement of the light guide plate and light-shielding adhesive strips, compromising the sealing structure. During the production and assembly process, be careful not to let the motherboard components touch the LCD screen. Doing so may cause light leakage.

· When cleaning the screen, use a soft, dust-free cloth and a neutral detergent, and avoid applying pressure to the edges (especially on curved screens or narrow bezels).

3. Regular Inspection

· If light leakage gradually increases (e.g., spreading from the edges to the center), this may indicate aging of the backlight module (LED degradation, adhesive failure) or structural looseness. Contact the manufacturer for repair immediately.

     Completely eliminating LCD light leakage is difficult (especially against a pure black background, where slight light leakage may occur at the edges). However, through optimized design (such as high-precision shading structures and zoned light control), the use of high-quality materials (such as low-defect light guide plates and high-light-shielding adhesive strips), and rigorous production processes (such as full lamination and precision assembly), light leakage can be significantly reduced. Shenzhen Hongjia Technology has 12 years of industry experience, specializing in the research and development, production and sales of 1.14-inch to 12.1-inch LCD screens and matching touch screens. It has rich experience in dealing with backlight leakage and can meet the demanding requirements of our customers. We can also accept customization. Customers are welcome to email us for consultation.