LC Display Optical Element with Retardation Layer for Luminance
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Solution Overview
Problem
Conventional liquid crystal display devices, particularly head-mounted displays, suffer from insufficient luminance and contrast ratio in the front direction due to inefficient use of light from the backlight, leading to suboptimal performance for applications requiring high front-directional brightness and contrast.
Innovation Solution
A liquid crystal display device configuration featuring a liquid crystal panel, a polarizing plate louver with a retardation layer sandwiched between reflection polarizers, where the retardation layer's slow axis is angled relative to the polarizer's reflection axis, and an absorption polarizer is strategically placed to enhance front-directional luminance and contrast by recycling oblique light through multiple reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional liquid crystal display device configuration is used, then device complexity is reduced, but front-directional luminance and contrast ratio are insufficient
Solution Approach 1:
The optical element is segmented into multiple functional layers: a polarizing plate louver with first and second polarizing plates, a retardation layer with specific slow axis orientation, and a black matrix. This segmentation allows each layer to perform a specific function (polarization, phase retardation, light absorption) that collectively improves front-directional luminance and contrast ratio while maintaining manageable device complexity.
Solution Approach 2:
The retardation layer is positioned specifically between the first and second polarizing plates with its slow axis oriented at a specific angle (e.g., 45 degrees) relative to the polarizing axes. This localized placement and orientation optimization ensures that oblique light undergoes appropriate phase retardation to achieve elliptical polarization, thereby enhancing front-directional luminance without requiring complex modifications throughout the entire device.
2Illumination intensity
If polarizing plate louver with retardation layer is added, then front-directional contrast ratio is improved, but device complexity increases
Solution Approach 1:
The patent merges the polarizing plate louver function with the retardation layer into a single integrated optical element. The first polarizing plate, retardation layer, and second polarizing plate are combined in one assembly that simultaneously performs polarization, phase retardation, and light recycling functions. This merging reduces the number of separate components needed while achieving the desired contrast ratio improvement.
Solution Approach 2:
The optical element with the polarizing plate louver and retardation layer serves multiple functions: it polarizes light, retards the phase of oblique light to create elliptical polarization, and recycles oblique light through multiple reflections. This multi-functionality allows a single optical element to address multiple performance requirements (luminance, contrast ratio, light efficiency) without proportionally increasing device complexity.
3Loss of energy
If oblique light recycling is implemented, then light flux efficiency is improved, but device complexity increases
Solution Approach 1:
The polarizing plate louver with retardation layer enables continuous recycling of oblique light through multiple reflections between the first and second polarizing plates. Instead of allowing oblique light to be lost after a single pass, the configuration maintains continuous useful action by repeatedly reflecting and redirecting oblique light back toward the liquid crystal panel, thereby improving light flux efficiency without requiring complex external light management systems.
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 significantly enhances front-directional luminance and contrast ratio by effectively recycling oblique light, improving the display's performance for head-mounted applications without reducing total light flux, thus meeting the requirements for high-brightness and high-contrast displays.
Implementation Method 1
a retardation layer (22) having a slow axis which forms an angle of 30° or more and 60° or less with respect to a reflection axis of the first reflection polarizer (21)
Implementation Method 2
a first reflection polarizer (21), a second reflection polarizer (23) in this order from a viewing surface side
Data Source
AI summary
Provided is a liquid crystal display device having high luminance and high CR in a front direction and especially useful as a head-mounted liquid crystal display device, for example. The liquid crystal display device includes: a liquid crystal panel; an optical element; and a backlight, arranged in this order from a viewing surface side. The optical element includes a first polarizer, a retardation layer, and a second polarizer. The first polarizer, the retardation layer, and the second polarizer are arranged in this order from the viewing surface side. The first polarizer and the second polarizer are reflection polarizers. A reflection axis of the first polarizer and a reflection axis of the second polarizer are parallel to each other. In oblique directions at azimuths of 0°, 45°, and 90° at a polar angle of 60°, a polarization state of light incident on the first polarizer is elliptical polarization.