Optical Film with Parallel Diffraction Layers for LCD Light Leakage
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Solution Overview
Problem
Liquid crystal displays (LCDs) suffer from color washout and uneven image quality at wide viewing angles due to light leakage, which affects contrast and color presentation.
Innovation Solution
An optical film with a first diffraction layer and a second diffraction layer, both with parallel gratings, and a cover layer, optimized with specific refractive indices and microstructure dimensions, is used to reduce light leakage and enhance image uniformity at wide viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional liquid crystal display is used, then the display can show images in front view, but light leakage occurs at wide viewing angles causing color washout and uneven image quality
Solution Approach 1:
The optical film is divided into multiple diffraction layers (first diffraction layer, second diffraction layer) with different grating structures. Each layer segments the light control function, with the first layer having gratings of one pitch and the second layer having gratings of a different pitch, working together to control light leakage at wide viewing angles while maintaining front view brightness
Solution Approach 2:
Different regions of the optical film have different diffraction grating configurations. The first diffraction layer and second diffraction layer have locally optimized grating pitches and orientations tailored to control light leakage in specific viewing angle directions, providing localized light control quality rather than uniform treatment across all viewing angles
2Reliability
If the liquid crystal panel is switched to dark state to shade light, then black color can be displayed, but light leakage still occurs at wide viewing angles affecting contrast
Solution Approach 1:
The patent converts the harmful light leakage effect into a beneficial control mechanism by using diffraction gratings to redirect leakage light. The diffraction layers take the light that would normally leak at wide viewing angles and redirect it back toward the front view direction or absorb it, transforming the harmful leakage into a useful light control function that enhances dark state performance
Solution Approach 2:
The optical film with diffraction layers acts as an intermediary between the liquid crystal panel and the viewer. This intermediate layer controls and modifies the light path, preventing direct light leakage from reaching the viewer at wide viewing angles while allowing the dark state function of the LCD to work effectively
3Ease of manufacture
If diffraction layers with different grating pitches are used, then light leakage at wide viewing angles is reduced, but the device structure becomes more complex
Solution Approach 1:
Multiple diffraction layers with different grating characteristics are merged into a single integrated optical film structure. The first diffraction layer and second diffraction layer are combined in one film, with their respective grating patterns working synergistically to control light leakage across different viewing angles, achieving complex light control functionality through integration rather than separate components
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 optical film effectively reduces light leakage and improves image uniformity and quality at various viewing angles, as demonstrated by reduced maximum brightness in the dark-state and improved Gamma Distortion Index and P-value measurements.
Implementation Method 1
a first diffraction layer with a upper surface and a lower surface, including a plurality of first diffraction gratings arranged in the same direction on the upper surface thereof; a second diffraction layer with a plurality of second diffraction gratings arranged in the same direction gap-filled in and on the first diffraction gratings
Implementation Method 2
a cover layer formed on the second diffraction gratings of the second diffraction layer to fill and planarize the second diffraction gratings of the second diffraction layer
Data Source
AI summary
An optical film includes a first diffraction layer, a second diffraction layer, and a cover layer. The first diffraction layer includes a plurality of first diffraction gratings arranged in a direction on a surface thereof. The second diffraction layer is filled in the gap of the first diffraction gratings of the first diffraction layer and forms a plurality of second diffraction gratings arranged in a direction on the first diffraction layer, wherein the directions of the first diffraction gratings and the second diffraction gratings are parallel to each other. The cover layer fills and planarizes the second diffraction gratings of the second diffraction layer. The optical film can reduce the light leakage defect of a conventional liquid crystal display in a wide viewing angle and make the liquid crystal display have a uniform dark-state image and color image quality.