Optical Element Phase Difference Layer Oblique Light Reduction
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in reducing oblique light at azimuths in top and bottom directions due to side lobe light generated by prism sheets, which decreases the contrast ratio, especially when the optical element's effectiveness is insufficient in these directions.
Innovation Solution
An optical element comprising a first polarizer, a negative C plate, and a phase difference layer with anisotropic molecules, where the tilt angles of the molecules on both sides of the phase difference layer are the same and greater than 0°, and the slow axis is parallel or perpendicular to the transmission axis of the first polarizer, combined with a second polarizer, effectively reduces oblique light at azimuths in top and bottom directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a prism sheet is used to focus light from the light source to the front, then the front contrast ratio is increased, but oblique CR decreases due to side lobe light generation
Solution Approach 1:
The patent converts the harmful side lobe light generated by the prism sheet into a beneficial effect by using a phase difference layer with specific optical characteristics. The phase difference layer is designed to have a retardation value and slow axis orientation that causes it to selectively transmit or block oblique light, thereby converting the previously harmful side lobe light into a controlled optical element that improves oblique contrast ratio while maintaining front contrast ratio enhancement
Solution Approach 2:
The phase difference layer acts as an intermediary between the prism sheet and the viewer. It receives the light including side lobe light from the prism sheet and processes it through its specific optical properties (retardation value, slow axis orientation) to selectively transmit or block oblique light components, thereby mediating the optical path and improving oblique contrast ratio without compromising the front contrast ratio enhancement provided by the prism sheet
2Ease of manufacture
If the optical element uses a conventional phase difference film structure, then manufacturing is simpler, but the effectiveness in reducing oblique light at top and bottom azimuths is insufficient
Solution Approach 1:
The patent applies parameter changes by specifying precise values for the phase difference layer's optical characteristics: the retardation value is set to a specific range (e.g., 100-300 nm) and the slow axis orientation is set to specific angles (e.g., 0° or 90° relative to the ridge lines). These parameter specifications ensure that the phase difference layer effectively reduces oblique light at top and bottom azimuths while maintaining compatibility with conventional manufacturing processes
Solution Approach 2:
The patent applies local quality by designing the phase difference layer with specific optical properties targeted at particular directions (top and bottom azimuths). The slow axis orientation and retardation value are specifically optimized to address oblique light at these directions, providing localized optical control where needed most, rather than attempting to solve all viewing angle problems uniformly
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 the contrast ratio by effectively reducing oblique light at azimuths in top and bottom directions, providing a wider region of low transmittance and improving the anti-glare and anti-reflection effects against external light.
Implementation Method 1
the phase difference layer introduces an in-plane phase difference of from 110 nm to 240 nm
Implementation Method 2
the phase difference layer contains anisotropic molecules... a tilt angle of the anisotropic molecules on a viewing surface side in the phase difference layer and a tilt angle of the anisotropic molecules on a back surface side in the phase difference layer
Implementation Method 3
a first polarizer; a negative C plate; a phase difference layer; and a second polarizer, wherein a transmission axis of the first polarizer is parallel to a transmission axis of the second polarizer
Data Source
AI summary
Provided is an optical element including, sequentially from a viewing surface side toward a back surface side: a first polarizer; a negative C plate; a phase difference layer; and a second polarizer. A transmission axis of the first polarizer is parallel to a transmission axis of the second polarizer. The phase difference layer contains anisotropic molecules. In the phase difference layer, a tilt angle of the anisotropic molecules on a viewing surface side in the phase difference layer and a tilt angle of the anisotropic molecules on a back surface side in the phase difference layer are the same as each other and greater than 0°. A slow axis of the phase difference layer, in a case of lying in a tilt direction of the anisotropic molecules, is parallel to or perpendicular to the transmission axis of the first polarizer.