Touch Sensing Structure Optical Path Length Yellowing Compensation
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Solution Overview
Problem
Existing flexible touch screens using plastic substrates tend to yellow during the high-temperature fabrication process, leading to decreased color performance due to the yellowing phenomenon, which is not effectively addressed by current touch panel technologies.
Innovation Solution
A touch sensing structure comprising a plastic substrate, a buffer layer, a patterned transparent electrode layer, an insulation unit, and a passivation layer, where the total optical path length of the electrode and passivation layers is optimized between 1000 nm to 2500 nm to minimize interference peaks in the visible light range, reducing the b* value in the CIE L*a*b* color space and preventing yellow bias in the touch screen's color performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a plastic substrate is used to make the touch panel flexible, then the flexibility and adaptability of the touch screen is improved, but the substrate is liable to be yellowed under high temperature of the fabrication process, resulting in yellowing phenomenon and decreased color performance
Solution Approach 1:
The patent applies preliminary anti-action by designing the buffer layer and passivation layer with specific optical properties before the yellowing can occur. The buffer layer (first refractive index) and passivation layer (second refractive index) are configured to produce optical interference that counteracts the yellowing effect, preventing the harmful visual impact before it manifests in the final product.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the optical path lengths of the buffer layer and passivation layer. By adjusting the thickness and refractive index parameters within specific ranges, the optical interference pattern is optimized to cancel out yellow wavelengths, transforming the optical parameters to achieve color correction.
2Object-affected harmful factors
If the touch panel uses a glass substrate, then the color performance is maintained, but the flexibility is reduced and the volume cannot be reduced
Solution Approach 1:
The patent introduces intermediary layers (buffer layer and passivation layer) between the plastic substrate and the electrode structure. These intermediary layers serve as mediators that optically compensate for the yellowing tendency of the plastic substrate, allowing the system to achieve both flexibility and acceptable color performance without using glass.
Solution Approach 2:
The patent creates a composite structure combining multiple materials with different optical properties. The buffer layer material and passivation layer material are selected and configured to work together with the plastic substrate, forming a composite system where the optical interference effects of the composite layers compensate for the substrate's yellowing characteristic.
3Ease of manufacture
If the optical path length of the electrode layer and passivation layer is not optimized, then the fabrication process is simpler, but the yellowing phenomenon occurs and color performance decreases
Solution Approach 1:
The patent specifies parameter ranges for the optical path lengths (buffer layer: 50-200 nm, passivation layer: 50-300 nm) that achieve yellowing compensation. By defining these parameter ranges, the invention provides a manufacturable solution where standard fabrication processes can be used while achieving the desired optical compensation effect within the specified parameter windows.
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 optimized optical path length reduces the yellowing effect, maintaining the color performance of flexible touch screens even when fabricated at high temperatures, ensuring the touch sensing structure does not significantly influence the image displayed on a display panel.
Implementation Method 1
Twice a total optical path length of the electrode layer and the passivation layer along a direction substantially parallel to a normal direction of the plastic substrate ranges from 1000 nm to 2500 nm
Data Source
AI summary
A touch sensing structure including a plastic substrate, a buffer layer, an electrode layer, an insulation unit, and a passivation layer is provided. The buffer layer is disposed on the plastic substrate, and the electrode layer includes a first patterned transparent electrode layer and a second patterned transparent electrode layer. The first patterned transparent electrode layer is disposed on the buffer layer, and the second patterned transparent electrode layer is disposed on the buffer layer. The insulation unit insulates the first patterned transparent electrode layer and the second patterned transparent electrode layer, and the passivation layer is disposed on the electrode layer. Twice a total optical path length of the electrode layer and the passivation layer along a direction substantially parallel to a normal direction of the plastic substrate ranges from 1000 nm to 2500 nm.