Color Filter Refractive Index Grading for Brighter Display Panels
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Solution Overview
Problem
The issue of lower brightness in OLEDs and LCDs is caused by the large refractive index difference between Indium Tin Oxide (ITO) and the glass substrate, leading to total reflection and light loss.
Innovation Solution
A liquid crystal display panel design with a color film structure comprising transparent conductive oxide film layers and color filter units, where the refractive indices of color filter films gradually increase from the base substrate to the transparent conductive oxide film, reducing total reflection and enhancing light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ITO film is used as transparent conductive oxide layer, then electrical conductivity is improved, but light transmission is worsened due to total reflection at the ITO-glass interface
Solution Approach 1:
The patent introduces an intermediary layer (prism layer or microlens array layer) between the ITO layer and the color filter layer. This intermediary acts as a mediator that redirects oblique incident light to normal incidence, preventing total reflection at the ITO-glass interface while maintaining the electrical conductivity function of the ITO layer.
Solution Approach 2:
The patent changes the optical parameters (refractive index, light incident angle) by introducing the prism layer or microlens array layer. This layer modifies the light path and incident angle parameters, transforming oblique light into normal light to eliminate total reflection and improve light transmission efficiency.
2Ease of manufacture
If conventional single-layer color filter structure is used, then manufacturing simplicity is maintained, but light extraction efficiency is insufficient due to refractive index mismatch
Solution Approach 1:
The patent segments the color filter layer into multiple sub-layers (red sub-layer, green sub-layer, blue sub-layer) with different refractive indices. This segmentation allows each sub-layer to optimize light extraction for its specific wavelength range while collectively improving overall light extraction efficiency without significantly complicating the manufacturing process.
Solution Approach 2:
The patent employs a composite color filter structure where multiple materials with different refractive indices are combined in a layered configuration. This composite structure optimizes optical performance by matching refractive indices across layers, reducing total internal reflection, and improving light extraction efficiency while maintaining manufacturability.
3Device complexity
If ITO layer is placed directly on glass substrate, then device structure is simplified, but display brightness is reduced due to light loss from total reflection
Solution Approach 1:
The patent introduces an intermediary optical layer (prism layer or microlens array layer) between the ITO layer and the color filter layer. This intermediary component, while adding structural complexity, significantly improves display brightness by redirecting light paths and eliminating total reflection losses at the ITO-glass interface.
Solution Approach 2:
The patent introduces new structural dimensions by adding prism layers with specific geometric shapes or microlens arrays with three-dimensional lens structures. These dimensional additions create new light paths and redirect oblique light to normal incidence, improving brightness output despite increased structural complexity.
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 design increases display brightness by minimizing light loss due to refractive index mismatch, resulting in improved luminance and color purity.
Implementation Method 1
there is a relatively large refractive index difference between the ITO film and a glass substrate with the refractive index of 1.5. When incident light is irradiated to the glass substrate after passing the ITO film, part of the incident light will be subjected to total reflection
Implementation Method 2
one layer of the color filter films of the blue color filter unit adjacent to the base substrate has a refractive index larger than that of the base substrate, and one layer of the color filter films of the blue color filter unit adjacent to the transparent conductive oxide film layer has a refractive index less than that of the transparent conductive oxide film layer, wherein refractive indices of the color filter films of the blue color filter unit gradually increase in a direction from the base substrate towards the transparent conductive oxide film layer
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 2c~2d
AI summary
A display substrate, a display panel and a display device are disclosed. The display substrate includes: a base substrate (1), and a color film structure (2) and a transparent conductive oxide film layer (3) subsequently laminated on the base substrate (1). The color film structure (2) includes a plurality of color filter units arranged in a matrix and having different colors; at least one color of the color filter units in the color film structure (2) includes at least two layers of laminated color filter films, refractive indices of the color filter films gradually increase in a direction from the base substrate (1) towards the transparent conductive oxide film layer (3), and one layer of the color filter films adjacent to the base substrate (1) has refractive index larger than that of the base substrate (1), one layer of the color filter films adjacent to the transparent conductive oxide film layer (3) has refractive index less than that of the transparent conductive oxide film layer (3). The display substrate reduces the loss of light transmitted in the display panel, and thus the display brightness of the display device is increased.