Liquid Crystal Module Azimuth Luminance Compensation
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Solution Overview
Problem
Liquid crystal modules with prism sheets face challenges in maintaining consistent peak luminance when the polar angle is large, leading to variations in luminance depending on the azimuth angle during black display, which affects durability and manufacturing cost.
Innovation Solution
The liquid crystal module design includes a liquid crystal panel with an in-cell retardation layer and an out-cell retardation layer, where the in-cell retardation layer is a positive A plate and the out-cell retardation layer is an A plate with principal refractive indexes satisfying specific relationships, and a backlight with a prism sheet configuration where the first ridge line of the prism sheet is aligned parallel to the maximum transmittance azimuth of the liquid crystal panel during black display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional prism sheet configuration is used, then the backlight can be simplified, but peak luminance varies depending on azimuth angle during black display when polar angle is large
Solution Approach 1:
The patent introduces asymmetric prism groove configurations where the first and second prism sheets have different groove directions (first groove direction and second groove direction that are not parallel). This asymmetric arrangement creates different light extraction characteristics for different azimuth angles, allowing compensation of luminance variations. The asymmetric structure enables the backlight to maintain more uniform peak luminance across different viewing directions during black display.
Solution Approach 2:
The patent applies different prism sheet configurations to different regions of the backlight. The first prism sheet has prisms with first groove directions while the second prism sheet has prisms with second groove directions, creating locally optimized light extraction for different azimuth ranges. This local differentiation allows specific regions to compensate for luminance variations in their respective viewing angle ranges.
2Manufacturing precision
If negative A plates are used to compensate for luminance variations, then peak luminance consistency improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive negative A plates with inexpensive prism sheets that have specific groove configurations. Instead of using costly retardation films with negative A plate properties, the invention uses simple plastic or resin prism sheets with carefully designed groove patterns to achieve the same luminance compensation effect. This substitution significantly reduces manufacturing cost while maintaining peak luminance consistency.
Solution Approach 2:
The patent substitutes the optical-mechanical system of negative A plates (requiring precise retardation control) with a geometric-optical system using prism groove configurations. The light extraction is controlled through the shape and orientation of prism grooves rather than through material retardation properties, simplifying manufacturing and reducing cost while achieving the same functional outcome.
3Productivity
If prism grooves are arranged orthogonal to each other in two prism sheets, then light extraction is improved, but azimuth angle dependence of luminance increases
Solution Approach 1:
The patent optimizes the groove direction parameters of the two prism sheets. Instead of using completely orthogonal (90 degrees) groove directions, the invention specifies that the first groove direction and second groove direction should be at a predetermined angle relationship that balances light extraction efficiency with luminance uniformity. This parameter optimization prevents excessive azimuth angle dependence while maintaining good light extraction.
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 compensates for transmittance and luminance variations, reducing peak luminance fluctuations and enhancing durability and manufacturing cost-effectiveness without requiring negative A plates.
Implementation Method 1
apply a voltage to the liquid crystal composition to change an alignment of liquid crystal molecules, thereby controlling an amount of light transmitted through the liquid crystal module
Implementation Method 2
the in-cell retardation layer is a positive A plate and the out-cell retardation layer is an A plate with principal refractive indexes satisfying specific relationships
Implementation Method 3
a prism sheet having a plurality of prisms
Implementation Method 4
prism sheet provided with an uneven portion including a first ridge line, and a second prism sheet provided on the back side from the first prism sheet and provided with an uneven portion including a second ridge line orthogonal to the first ridge line
Data Source
AI summary
Provided is a liquid crystal module being excellent in durability and manufacturing cost and exhibiting reduced variations in peak luminance that are caused depending on an azimuth angle during black display when the polar angle is large. The liquid crystal module includes: a liquid crystal panel including a first polarizer, a first substrate, a liquid crystal layer, an in-cell retardation layer (λ/4 plate of nx>ny=nz), a second substrate, an out-cell retardation layer (λ/4 plate of nx>ny≥nz), and a second polarizer, from a back side toward an observation side; and a backlight. The backlight includes a first prism sheet including a first ridge line, and a second prism sheet provided on a back side from the first prism sheet and including a second ridge line orthogonal to the first ridge line. The first ridge line is parallel to an azimuth at which the liquid crystal panel has a maximized transmittance in an oblique direction during black display.