Direct Backlight Unit with Circular Polarization Film
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Solution Overview
Problem
Existing direct backlight units for LCDs face challenges in achieving high luminance due to low light utilization efficiency, with previous configurations either resulting in insufficient luminance improvement or degradation due to increased stray light from repeated reflections and reduced film thickness.
Innovation Solution
A direct backlight unit is designed with a rear-side reflective plate, a perforated reflective plate having fine holes with a depolarization degree of 60% or less on the emission surface, and a circular polarization reflection film, which enhances light reuse and reduces stray light by maintaining the state of polarized light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a diffusion plate is used to randomize the polarization plane of reflected light, then light can be reused through reflection, but the quantity of reflected light that can be reused is small and stray light is increased
Solution Approach 1:
The patent changes the polarization state parameter from linear to circular polarization by introducing a circular polarization reflection film. This allows reflected light to be reused multiple times without randomizing the polarization plane, thereby improving light utilization efficiency while reducing stray light generation
Solution Approach 2:
The circular polarization reflection film enables continuous reuse of reflected light by maintaining a consistent polarization state throughout multiple reflections. Unlike linear polarization that gets randomized by diffusion plates, circular polarization allows the light to continue being reflected and reused without degradation, extending the useful action of the light
2Stability of the object's composition
If a semi-transmissive semi-reflective film is provided between the light source and diffusion plate, then uniform light distribution is realized, but luminance is degraded due to increased stray light from repeated reflections
Solution Approach 1:
The patent changes the polarization characteristic of the reflection film to maintain circular polarization with a depolarization degree of 60% or less. This parameter change allows the film to provide uniform light distribution through controlled reflection while preventing the stray light generation that would occur with repeated reflections of linearly polarized light
Solution Approach 2:
The perforated reflective plate introduces local variation in light transmission through its fine hole structure, allowing different regions to have different light transmission characteristics. This creates uniform overall light distribution while the circular polarization film maintains high luminance by preventing stray light from repeated reflections
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 configuration effectively improves luminance by efficiently reusing reflected light while minimizing stray light, resulting in a higher light utilization efficiency and enhanced display performance.
Implementation Method 1
a circular polarization reflection film which is disposed on the emission-side surface of perforated reflective plate
Implementation Method 2
both the light source-side surface and the emission-side surface are reflection surfaces
Data Source
AI summary
A direct backlight unit includes: a rear-side reflective plate; a light source which is disposed on a reflection surface side of the rear-side reflective plate; a perforated reflective plate which is disposed to face the rear-side reflective plate through the light source and has a plurality of fine holes, which penetrate from a light source-side surface to an emission-side surface facing the light source-side surface and transmit light, and in which both the light source-side surface and the emission-side surface are reflection surfaces and a depolarization degree of the emission-side surface is 60% or less; and a circular polarization reflection film which is disposed on the emission-side surface side of the perforated reflective plate.