Liquid Crystal Display Light Guide Plate Polarized Light Directivity
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Solution Overview
Problem
Liquid crystal display apparatuses using surface light source devices face issues with insufficient brightness and mechanical strength due to flaws in the light guide plate, particularly when the prism sheet is integrated with a polarizing plate, leading to reduced illuminance and front brightness.
Innovation Solution
A liquid crystal display apparatus design featuring a surface light source device with a light guide plate that outputs polarized light with maximum intensity at a predetermined angle, combined with a second polarizing plate including an absorptive polarizer and columnar unit prisms, and a polarized light selective reflection sheet to enhance light utilization efficiency and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the prism sheet is integrated with the polarizing plate, then the mechanical strength is improved and flaws in the light guide plate are prevented, but the accumulated illuminance and front brightness become insufficient
Solution Approach 1:
The patent integrates the polarizing plate and prism sheet into a single combined structure. The polarizing plate has a prism portion formed on its light guide plate-facing surface, eliminating the need for a separate prism sheet. This merging prevents relative movement and rubbing between separate components, thereby preventing flaws in the light guide plate while maintaining mechanical strength.
Solution Approach 2:
The patent optimizes the refractive index of the prism portion to be higher than that of the polarizing plate (specifically, np > nx of the polarizing plate). This parameter change in refractive index enables effective total reflection of s-polarized light at the prism surfaces, significantly improving front brightness and accumulated illuminance while maintaining the integrated structure's mechanical strength.
2Device complexity
If the prism sheet is integrated with the polarizing plate, then the device complexity is reduced, but the light utilization efficiency becomes insufficient
Solution Approach 1:
By combining the polarizing plate and prism sheet into one integrated component, the patent reduces the number of separate optical elements and assembly steps. This simplification lowers device complexity while the optimized prism design ensures efficient light management.
Solution Approach 2:
The patent carefully controls the refractive index parameters of the prism portion to maximize light utilization. By setting np > nx of the polarizing plate and optimizing the prism geometry, the structure achieves high efficiency in reflecting s-polarized light while minimizing losses, thereby improving overall light utilization efficiency despite the simplified structure.
3Illumination intensity
If more light sources or higher output is used to improve brightness, then the front brightness is improved, but the power consumption increases
Solution Approach 1:
The patent optimizes the refractive index of the prism portion (np > nx of polarizing plate) and the prism geometry to maximize the reflection efficiency of s-polarized light. This parameter optimization increases front brightness and accumulated illuminance without requiring additional light sources or higher power consumption, thereby improving brightness efficiency.
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 solution results in a brighter image display with improved light utilization efficiency and reduced power consumption, while preventing flaws in the light guide plate and enhancing mechanical strength, thereby increasing the number of light sources or their output can be reduced.
Implementation Method 1
light emitted from a light source enters a light guide plate, and propagates through an inside of the light guide plate while repeating a total reflection on a light output surface (liquid crystal cell-side surface) of the light guide plate and a back surface thereof
Implementation Method 2
the prism portion including a plurality of columnar unit prisms arrayed so as to protrude on the light guide plate side
Data Source
AI summary
A liquid crystal display apparatus comprises: a liquid crystal display panel including a liquid crystal cell between a first polarizing plate and a second polarizing plate; and a surface light source device having a light source unit and a light guide plate. In a polarized light output from the light guide plate, when the normal direction of a light output surface is defined to be at a polar angle of 90°, and the light guiding direction of the light guide plate is defined to be a direction of an azimuth angle of 0°-180°, a ratio La/Lt of integrated intensity La of output light in ranges where the polar angle is 50° to 80° and the azimuth angle is 135° to 225°, 0° to 45°, and 315° to 360° to integrated intensity Lt of total output light is 0.3 or more.