Optical Element with Anisotropic Phase Layers for Display Contrast
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Solution Overview
Problem
Existing optical elements fail to effectively reduce oblique light at azimuths in top and bottom directions in liquid crystal display devices, leading to decreased contrast ratios and increased stray light, particularly due to side lobe light generated by prism sheets.
Innovation Solution
An optical element comprising a first polarizer, a laminate of n first phase difference layers, and a second polarizer, where the phase difference layers have anisotropic molecules with varying tilt angles on the viewing and back surfaces, and slow axes oriented to reduce oblique light transmission, combined with a backlight and prism sheet configuration that aligns polarizer axes with prism sheet ridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a prism sheet is used to focus light from the backlight to the front, then the front contrast ratio is increased, but the oblique contrast ratio during black display decreases due to side lobe light generation
Solution Approach 1:
The patent introduces a polarizing plate as an intermediary component between the backlight and the liquid crystal panel. This polarizing plate selectively transmits or blocks light based on its polarization state, thereby reducing the side lobe light generated by the prism sheet without significantly affecting the front luminance. The polarizing plate acts as a mediator that filters harmful oblique light while preserving the useful front light transmission.
Solution Approach 2:
The patent applies different properties to different regions of light transmission. By orienting the polarization axis of the polarizing plate perpendicular to the ridge lines of the prism sheet, the system achieves local optimization: front light (small polar angle) passes through effectively, while oblique light (large polar angle, side lobe light) is blocked. This directional selectivity resolves the contradiction between maintaining front contrast and reducing oblique light.
2Object-affected harmful factors
If the absorption axis of the polarizing plate is perpendicular to the ridge lines of the prism sheet, then oblique light is reduced, but the front luminance may be affected
Solution Approach 1:
The patent applies partial action by using a polarizing plate that only affects specific polarization components of light. Rather than blocking all oblique light indiscriminately, the plate selectively blocks only the polarization components that contribute to side lobe light while allowing other components to pass. This partial filtering approach reduces oblique light transmission without excessively compromising front luminance.
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
Significantly reduces oblique light transmission at azimuths in top and bottom directions, enhancing the anti-glare and anti-reflection effects, thereby improving the contrast ratio and reducing stray light in liquid crystal display devices.
Implementation Method 1
the phase difference layer is a laminate of n first phase difference layers and m second phase difference layers... each of the n first phase difference layers contains first anisotropic molecules... each of the m second phase difference layers contains second anisotropic molecules... the slow axes of the n first phase difference layers and the slow axes of the m second phase difference layers are anti-parallel to each other
Implementation Method 2
each of the n first phase difference layers contains first anisotropic molecules, in each of the n first phase difference layers, a tilt angle of the first anisotropic molecules on a viewing surface side differs from a tilt angle of the first anisotropic molecules on a back surface side
Implementation Method 3
an optical element including, sequentially from a viewing surface side toward a back surface side: a first polarizer... and a second polarizer, wherein the phase difference layer is a laminate of n first phase difference layers and m second phase difference layers... 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 a phase difference layer. The phase difference layer is a laminate of n first phase difference layers and m second phase difference layers. The n first phase difference layers each contain first anisotropic molecules with tilt angles different between a viewing surface side and a back surface side. The m second phase difference layers each contain second anisotropic molecules with tilt angles different between a viewing surface side and a back surface side. Slow axes of the n first phase difference layers are in a same orientation. Slow axes of the m second phase difference layers are in a same orientation. The slow axes of the n first phase difference layers and the slow axes of the m second phase difference layers are anti-parallel to each other and are parallel to or perpendicular to the transmission axis of the first polarizer.