Prismatic Sheet Angular Displacement for LCD Luminance
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Solution Overview
Problem
Liquid crystal display devices with prismatic light guides and sheets suffer from interference fringes on the display screen and decreased luminance due to the perpendicular orientation of prisms in the prismatic sheet and light guide, which affects light polarization and emission efficiency.
Innovation Solution
A liquid crystal display device design where the prismatic sheet's prisms are angled counterclockwise by 4° to 8° relative to the light guide's prisms, and the polarization axis of the prismatic sheet is set between 0° and 20° relative to the polarizer plate's axis, preventing interference fringes and maintaining luminance by optimizing light emission and polarization alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the prismatic sheet is disposed such that the prisms are perpendicular to the prisms of the light guide, then the light emission efficiency is improved, but interference fringes occur on the display screen
Solution Approach 1:
The patent applies asymmetry by setting the prisms of the prismatic sheet at an angle different from perpendicular (specifically 4° to 8° counterclockwise displacement) relative to the prisms of the light guide. This asymmetric angular relationship disrupts the regular interference pattern that causes fringes while maintaining effective light extraction and emission efficiency.
2Productivity
If the prismatic sheet is disposed such that the prisms are perpendicular to the prisms of the light guide, then the light extraction is optimized, but the polarization alignment with the polarizer plate deteriorates
Solution Approach 1:
The patent changes the angular parameter of the prismatic sheet orientation from the conventional perpendicular (90°) to a specific range (4° to 8° counterclockwise displacement). This parameter modification simultaneously optimizes both light extraction efficiency and polarization alignment with the polarizer plate, resolving the contradiction between these two requirements.
3Illumination intensity
If the angle between the polarization axis of the prismatic sheet and the polarizer plate is set to maximize luminance, then the display brightness is improved, but interference fringes may occur
Solution Approach 1:
The patent uses asymmetric angular positioning (4° to 8° counterclockwise displacement) of the prismatic sheet relative to the light guide prisms. This asymmetric configuration breaks the symmetry that causes interference fringes while maintaining optimal polarization alignment between the prismatic sheet and polarizer plate, thus preserving high display luminance without fringes.
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 effectively prevents interference fringes on the display screen while maintaining or enhancing luminance by adjusting the angular relationships between the prismatic sheet, light guide, and polarizer axes, thereby improving light utilization and display quality.
Implementation Method 1
the prismatic sheet has prisms which extend in a direction that is displaced counterclockwise by a first predetermined angle (between 4° and 8°) from a direction that is perpendicular to a direction of extension of the prisms of the light guide
Implementation Method 2
the prismatic sheet polarizes light that is emitted from the light guide
Data Source
AI summary
A liquid crystal display device includes an area light source unit which is opposed to one of polarizer. The area light source unit includes a light guide having a light incidence surface opposed to a cold cathode tube, a light emission surface which emits light that is incident on the light incidence surface, and an opposed surface which is opposed to the light emission surface, and a prismatic sheet disposed between the polarizer plate and the light guide. The light guide has prisms on at least the opposed surface. The prismatic sheet has prisms which extend in a direction that is displaced counterclockwise by a first predetermined angle from a direction that is perpendicular to a direction of extension of the prisms. An angle between a polarization axis of the polarizer plate and a polarization axis of the prismatic sheet is set at a second predetermined angle.