Phosphor Sheet Diffusion for Backlight Chromaticity Stability
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Solution Overview
Problem
In liquid crystal displays, the use of a phosphor sheet separated from blue-color light-emitting diodes and brought close to the liquid crystal panel leads to fluctuations in white-color chromaticity due to view angles and partial drive patterns of light sources, affecting display quality.
Innovation Solution
Incorporating a light diffusion means on the surface of the phosphor portion, specifically on both the light-incident and light-emitting surfaces, to stabilize chromaticity fluctuations, which can be achieved through a two-layer or three-layer structure of light diffusion layers and a phosphor layer, allowing for individual control of emission luminance across segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a phosphor sheet is separated from blue-color light-emitting diodes and brought close to the liquid crystal panel, then the thickness and weight of the backlight can be reduced, but chromaticity fluctuation occurs due to view angle and incident angle
Solution Approach 1:
A light diffusion means is introduced as an intermediary component between the blue-color light-emitting diodes and the phosphor sheet. This diffusion means scatters the blue light before it reaches the phosphor, ensuring uniform illumination across the phosphor sheet regardless of viewing angle or incident angle, thereby maintaining chromaticity stability while allowing the phosphor sheet to be positioned close to the liquid crystal panel
Solution Approach 2:
The patent modifies the optical parameters of the system by introducing a light diffusion means that changes the direction distribution of blue light. This parameter change in light propagation ensures that the phosphor sheet receives uniform excitation from all directions, preventing chromaticity shifts that would otherwise occur when the phosphor sheet is positioned close to the display panel
2Device complexity
If the phosphor sheet is positioned close to the liquid crystal panel, then the backlight structure can be simplified, but chromaticity fluctuation due to partial drive patterns occurs
Solution Approach 1:
The light diffusion means serves as a mediator that decouples the positioning of the phosphor sheet from the light sources. By diffusing the blue light before it reaches the phosphor, it ensures uniform chromaticity output even when the phosphor sheet is closely positioned to the liquid crystal panel and when only certain light source segments are activated
Solution Approach 2:
The light diffusion means creates local uniformity in the blue light distribution across different regions of the phosphor sheet. This ensures that even when only certain segments of light sources are driven, each local region of the phosphor sheet receives appropriate diffuse illumination, maintaining overall chromaticity stability
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
This solution effectively suppresses chromaticity fluctuations due to view angles and incident angles, enhancing display quality by maintaining consistent white-color output across varying viewing conditions and partial drive patterns.
Implementation Method 1
a phosphor portion constituted of a phosphor that obtains white light from light from the light source
Implementation Method 2
a light diffusion means provided in correspondence with a surface of the phosphor portion... suppresses a chromaticity fluctuation due to a view angle and an incident angle
Data Source
AI summary
[Object] To provide an illumination apparatus capable of suppressing a chromaticity fluctuation due to a view angle and an incident angle.[Solving Means] In an illumination apparatus for a display apparatus that includes a blue-color light-emitting diode (10) as a light source and a phosphor sheet (21) including a phosphor that obtains white light by converting a color of blue light from the blue-color light-emitting diode (10), diffusion plates (22, 23) are respectively provided opposed to a light-emitting-side surface and a light-incident-side surface of the phosphor sheet (21). The diffusion plate (22) opposed to the light-emitting-side surface of the phosphor sheet (21) suppresses a fluctuation of white-color chromaticity due to a view angle, and the diffusion plate (23) opposed to the light-incident-side surface of the phosphor sheet (21) suppresses a fluctuation of white-color chromaticity due to an incident angle.