Backlight Reflective Polarizer and Diffuse Film for LCD Uniformity
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Solution Overview
Problem
Large and thin LCDs face challenges with non-uniform brightness due to warping of reflective films, leading to mura defects and reduced luminance, which existing backlighting technologies struggle to address effectively.
Innovation Solution
A backlight system incorporating a reflective polarizer and an extended light source with a diffuse reflective film assembly, including a specularly reflective film and an optically diffusive film, which enhances light reflection and transmission efficiency, and an optically diffusive film with fibers dispersed in a material, bonded at discrete locations to improve light distribution and reduce mura defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective film is used in large and thin LCDs, then luminance can be improved, but the film warps causing mura defects and non-uniform brightness
Solution Approach 1:
The reflective film is segmented into multiple discrete bonding locations rather than being continuously bonded, creating isolated bonding zones that prevent warping while maintaining light reflection functionality
Solution Approach 2:
The bonding is applied locally at specific discrete locations rather than uniformly across the entire film, allowing different regions to have different properties (bonded vs. unbonded) to prevent warping
2Illumination intensity
If light management films are added to enhance light efficiency, then luminance improves, but device complexity increases
Solution Approach 1:
Multiple light management functions (diffusion, reflection, polarization) are merged into a single integrated reflective polarizer film, reducing the total number of separate films while maintaining or improving light efficiency
Solution Approach 2:
The reflective polarizer performs multiple functions simultaneously: it polarizes light, reflects polarized light back through the LCD, and provides structural support, replacing what would traditionally require multiple separate films
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved luminance and reduced mura defects by increasing the fraction of light reaching the liquid crystal panel, resulting in brighter and more uniform images across larger and thinner LCDs.
Implementation Method 1
the reflective polarizer reflects at least 60% of the incident light having a first polarization state and transmits at least 60% of the incident light having an orthogonal second polarization state
Implementation Method 2
the reflective polarizer reflects at least 60% of the incident light having a first polarization state
Implementation Method 3
The optically diffusive film is bonded to the specularly reflective film at a plurality of discrete spaced apart bonded locations
Implementation Method 4
the reflective film specularly reflects at least 80% of the incident light for each of the first and second polarization states
Data Source
AI summary
A backlight for providing illumination to a liquid crystal panel includes a reflective polarizer and an extended light source. The extended light source includes a diffuse reflective film assembly and an emission surface disposed between the reflective polarizer and the diffuse reflective film assembly. The extended light source is configured to emit light through the emission surface toward the reflective polarizer. The diffuse reflective film assembly includes a specularly reflective film and an optically diffusive film disposed between the emission surface and the specularly reflective film. The optically diffusive film is bonded to the specularly reflective film at a plurality of discrete spaced apart bonded locations with a total bonding area of less than about 20%.