Commentary

How to design high-bright LCDs for challenging applications

Designing high bright LCDs involves a meticulous balance of backlighting technology, optical design, power management, thermal considerations, color calibration and environmental durability.

Image: DCL Technologies Inc.

March 25, 2024 by Andrew Blum — President, DCL Technologies

High bright LCDs have revolutionized the way we interact with displays, providing exceptional brightness and clarity even in challenging lighting conditions. From outdoor digital signage and kiosks to automotive displays, the demand for high brightness LCDs continues to grow across various applications.

Let's explore the best practices for designing and manufacturing high bright LCDs, focusing on key factors that contribute to their exceptional performance, usability and longevity.

Although commonly done, it's not enough to simply increase measurable brightness. A well-designed solution considers temperature, effects of direct sunlight exposure and the possible need for vandal resistance.

Let's explore the key elements that should go into any LCD solution that will be used in an outdoor environment.

1. Backlighting technology

The backlighting system plays a crucial role in achieving high brightness levels in LCD displays. There are several backlighting technologies available, the current and most common uses LEDs (light emitting diodes) in various configurations as a light source behind a TFT LCD cell.

Edge LED backlighting is widely used due to its energy efficiency, long lifespan and ability to generate high brightness levels.

For some displays, a grid of LEDs can be used (direct backlighting). Advanced local dimming techniques can enhance contrast and overall picture quality, ensuring accurate color representation and deep blacks.

Further, "binning," the process of sorting LEDs by certain characteristics, such as color, voltage and brightness, can ensure consistent electrical and optical performance features.

2. Optimal optical design

Efficient light management is essential for high bright LCDs. Optical films, such as diffusers, prisms and polarizers, are strategically positioned to control light distribution, minimize reflections and improve viewing angles. Micro-lens arrays can enhance light extraction and improve overall luminance uniformity. Additionally, anti-glare and anti-reflective coatings are employed to reduce ambient light interference and enhance readability in bright environments.

The objective is to achieve the maximum light output through the LCD cell at the lowest power consumption with the least amount of self-generated heat from the backlight.

3. IR and UV blocking

High bright LCDs exposed to direct sunlight can suffer the effects of ultra-violet damage and increased surface and internal temperature rise due to infrared heat.

Regular glass blocks much of certain UV rays. However, a significant portion of other types of UV exposure can decay polarizers, bonding adhesives and other materials leading to poor optical performance. A well designed solution for such applications uses UV resistant materials wherever possible.

IR filtering can reduce the "solar load" on a display solution by as much as 50% with respect to air temperature. While proper thermal management techniques should be used in the final product design, direct sunlight IR exposure can lead to heat related LCD damage fast if not properly protected.

4. Thermal management

With higher brightness levels comes an increase in heat generation. Effective thermal management is crucial to maintaining display performance, preventing overheating and extending the lifespan of the LCD.

Final chassis designs that include integrated heat sinks, thermally conductive materials and optimized airflow designs can efficiently dissipate heat and ensure stable operation under demanding conditions.

5. Enhanced power management

High bright LCDs require robust power management systems to support increased luminance without compromising power efficiency. Advanced power management circuits and algorithms can dynamically adjust the backlight intensity based on ambient lighting conditions, optimizing power consumption while maintaining optimal brightness levels. This ensures longer battery life for portable devices and reduced energy consumption for stationary applications.

6. Robust outdoor readability: bonding

Of course, high bright LCDs often find application in outdoor environments where sunlight readability is critical. A full optical bond, which involves laminating the LCD panel with a protective cover glass or touch panel, can significantly reduce reflections and increase contrast, enhancing visibility even in direct sunlight. A lens or touch panel lens with anti-glare coatings and/or circular polarizers further improves outdoor readability by reducing glare and enhancing viewing angles.

7. Durability and environmental considerations

High bright LCDs should be designed to withstand harsh environmental conditions. Employing robust materials, such as properly sized (thickness) ruggedized glass, and ensuring proper sealing against moisture and dust ingress are essential for outdoor and industrial applications. Additionally, adherence to industry standards, such as IP (ingress protection) and IK (impact protection) ratings and MIL-STD (military standard) specifications can guarantee durability and reliability in demanding environments.

Designing high bright LCDs involves a meticulous balance of backlighting technology, optical design, power management, thermal considerations, color calibration and environmental durability. By adhering to these best practices, LCD displays that offer exceptional brightness, clarity and readability across a wide range of outdoor applications are possible, improving user experiences and enabling visual content to shine even in the most challenging lighting conditions.

About Andrew Blum

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