Transflective LCD Overcoat Layer Tapered Thickness Design
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Solution Overview
Problem
Transflective liquid crystal devices face decreased reflectance and worsened reflection characteristics due to the placement of color filters on the same substrate as reflecting films, affecting the quality of reflective displays.
Innovation Solution
Separating the reflecting layer and color layer on different substrates, with a conductive film, scattering layer, overcoat layer, and pixel electrode configuration on one substrate, and a color layer on the counter substrate, to prevent reflectance reduction and enhance reflection contrast, while maintaining a high aperture ratio and preventing longitudinal crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If color filters and reflecting films are provided on the same substrate, then the device structure is simplified and easier to manufacture, but the reflectance decreases and reflection characteristics worsen
Solution Approach 1:
The patent divides the device into two separate substrates: one substrate contains the reflecting film while the other substrate contains the color filter. This segmentation allows each substrate to be optimized for its specific function without the negative interference of the other component, thereby maintaining high reflectance while simplifying the overall manufacturing process.
Solution Approach 2:
The color filter is extracted from the same substrate as the reflecting film and placed on a separate substrate. This extraction eliminates the harmful refractive index influence of the color filter on the reflecting film, preventing reflectance decrease while maintaining ease of manufacture through modular assembly.
2Device complexity
If color filters are provided on the same substrate as reflecting films, then the device complexity is reduced, but the reflection contrast deteriorates
Solution Approach 1:
By segmenting the device into two separate substrates with distinct functions (one for reflecting film, another for color filter), the patent maintains relatively simple device complexity while achieving high reflection contrast. The modular design allows independent optimization of each substrate for its specific function.
Solution Approach 2:
Extracting the color filter from the reflecting film substrate eliminates the refractive index interference that causes poor reflection contrast. The separated architecture allows each component to perform its function optimally without compromising the other, thereby improving reflection contrast while keeping device complexity manageable.
3Reliability
If reflecting layer and color layer are separated on different substrates, then reflection characteristics improve, but the device structure becomes more complex
Solution Approach 1:
The patent employs segmentation by using two separate substrates, each optimized for its specific function. This segmentation improves reflection characteristics by eliminating interference between components while managing device complexity through modular architecture that simplifies alignment and assembly processes.
Solution Approach 2:
By taking out the color filter from the reflecting film substrate and placing it on a separate substrate, the patent achieves superior reflection characteristics. The extraction is implemented in a way that manages complexity through standardized interfaces and alignment features between the two substrates.
4Reliability
If contact holes are provided to connect pixel electrode and switching element, then electrical connection is established, but the aperture ratio decreases
Solution Approach 1:
The patent eliminates the need for contact holes by using a tapered overcoat layer that gradually thins toward the edge portion. This extraction of the contact hole structure allows the pixel electrode to be directly connected to the conductive film through the tapered region, maintaining electrical connection while maximizing the aperture ratio.
Solution Approach 2:
The overcoat layer's thickness parameter is changed to be non-uniform, gradually reducing from the center toward the edge portion. This parameter change allows the layer to serve dual functions: providing adequate coverage and insulation in the bulk while enabling direct electrical connection at the edge without requiring discrete contact holes, thus maintaining high aperture ratio.
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 improves reflection characteristics, maintains high-quality display images in both transmissive and reflective modes, and optimizes the liquid crystal layer thickness for enhanced display performance.
Implementation Method 1
a scattering layer that covers a part of the conductive film and the switching element
Implementation Method 2
a reflecting layer provided on a part of the scattering layer
Data Source
AI summary
A liquid crystal device includes a device substrate having a switching element, a counter substrate having a color layer, and a liquid crystal layer provided between the device substrate and the counter substrate. The device substrate includes a conductive film connected to the switching element, a scattering layer that covers a part of the conductive film and the switching element, a reflecting layer provided on a part of the scattering layer, an overcoat layer that covers a part of the conductive film, the scattering layer, and the reflecting layer, and a pixel electrode provided on the overcoat layer. The pixel electrode is connected to a contact portion of the conductive film that is not covered with the scattering layer and the overcoat layer.