Prism Sheet Apex Angle Optimization for LCD Backlight Brightness
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Solution Overview
Problem
Conventional backlight units for liquid crystal display devices suffer from insufficient brightness due to non-uniform light emission from optical waveguides, which is not adequately addressed by increasing the refractive index of prism sheets without considering the characteristics of light emission.
Innovation Solution
The proposed solution involves a prism sheet with a refractive index and apex angle relationship (y=107.86x−140.43, where −4≦M≦4) optimized for the optical waveguide's light emission characteristics, combined with a diffusing sheet and additional prism sheets to ensure uniform light distribution and reduce moiré interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the refractive index of the prism sheet is increased, then the light refraction angle increases and brightness improves, but the light emission uniformity deteriorates because the optical waveguide emits light mainly in a specific direction
Solution Approach 1:
The patent applies parameter changes by establishing a specific mathematical relationship between the refractive index x of the prism sheet and the apex angle y of the prism (y=107.86x-140.43+M, where -4≦M≦4). This coordinated adjustment of optical parameters ensures that as the refractive index increases to improve brightness, the apex angle is simultaneously optimized to maintain uniform light emission, resolving the technical contradiction between brightness enhancement and emission uniformity.
2Stability of the object's composition
If a diffusing sheet is added to diffuse light, then uniform brightness is achieved, but the device complexity increases
Solution Approach 1:
The patent merges the light diffusing function into the existing optical waveguide structure by forming a diffusing sheet as an integrated component. This consolidation achieves uniform brightness distribution while avoiding the complexity of adding separate diffusing components, as the diffusing function is combined with the waveguide's light emission structure.
3Use of energy by moving object
If a second prism sheet is added to refract light components, then light utilization efficiency improves, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the second prism sheet to perform multiple optical functions simultaneously. Besides refracting light components toward the liquid crystal panel, it also works in conjunction with the first prism sheet and diffusing sheet to maintain uniform brightness and prevent moiré patterns. This multi-functional design improves light usage efficiency without proportionally increasing device complexity.
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 configuration enhances the brightness and usage efficiency of light in the backlight unit, achieving high brightness and uniform illumination for liquid crystal display devices while minimizing moiré occurrences.
Implementation Method 1
The prism sheet refracts the incident light to change the traveling direction of light
Implementation Method 2
Light incident on the optical waveguide from the light source travels in the optical waveguide while repeatedly reflecting from an emission surface and a reflective surface of the optical waveguide
Data Source
AI summary
An illuminating device includes a light source, an optical waveguide that emits light from the light source through an emission surface thereof, and a prism sheet that is provided on the emission surface side of the optical waveguide. In the illuminating device, the following relationship is established between a refractive index x of the prism sheet and an apex angle y of a prism: y=107.86x−140.43+M (−4≦M≦4).