Metal Mesh Touch Sensor Low Birefringence Substrate UV Cut
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Solution Overview
Problem
Conventional touch screen technologies face challenges in maintaining optimal performance, particularly in larger devices, due to limitations in materials like ITO and PET, which result in degraded optical quality, increased brittleness, and UV-induced yellowing, leading to compromised input and output functionalities.
Innovation Solution
A touch-sensitive display using a low birefringence substrate with UV stabilizers and a metal mesh on both surfaces, which enhances optical properties by reducing haze and transmittance while preventing UV-induced degradation, ensuring durability and improved performance in various lighting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PET is used as the touch sensor substrate, then the substrate provides structural support and flexibility, but the high birefringence degrades optical quality and causes colorations across the display field of view
Solution Approach 1:
The patent changes the optical parameters of the substrate by switching from PET to a low-birefringence material such as cyclic olefin copolymer (COC) or cyclic olefin polymer (COP). This material substitution maintains the structural support function while eliminating the harmful optical effects including rainbow-like colorations and high haze, thereby resolving the contradiction between structural integrity and optical quality.
Solution Approach 2:
The patent employs composite material structures where the low-birefringence substrate is combined with UV stabilizers and metal mesh layers. This composite approach provides both the structural benefits of the substrate and the optical benefits of the UV protection and conductive properties, while maintaining low birefringence to preserve display quality.
2Strength
If PET is used as the touch sensor substrate, then the substrate provides flexibility and durability, but UV radiation causes permanent discoloration and yellowing of the PET material
Solution Approach 1:
The patent converts the harmful effect of UV radiation into a beneficial outcome by incorporating UV stabilizers into the low-birefringence substrate. These stabilizers absorb or block UV radiation, preventing the yellowing and discoloration that would otherwise occur, while maintaining the flexibility and durability of the substrate material.
Solution Approach 2:
The patent changes the chemical composition parameters of the substrate by incorporating UV stabilizers into the low-birefringence material matrix. This modification maintains the mechanical properties (flexibility and durability) while adding UV resistance, thereby preventing discoloration and yellowing under sunlight exposure.
3Reliability
If ITO is used for the conductive layer in larger devices, then the layer provides transparency and conductivity, but thicker ITO is needed for suitable conductance which results in poor optical quality
Solution Approach 1:
The patent changes the material composition by replacing ITO with a metal mesh structure. This substitution allows the conductive layer to achieve suitable conductance through the mesh geometry rather than thickness, maintaining both electrical performance and optical quality without the trade-off inherent in ITO-based solutions.
Solution Approach 2:
The patent employs a composite structure combining metal mesh with low-birefringence substrate and UV stabilizers. This composite approach provides both the conductive functionality of the metal mesh and the optical clarity of the low-birefringence substrate, resolving the contradiction between conductance and optical quality that plagues ITO-based systems.
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 solution extends the lifespan of the touch sensor, improves both touch-based input and optical output functionalities, especially in larger displays, by maintaining low haze, high transmittance, and preventing color changes, thus providing enhanced user experience across different ambient conditions.
Implementation Method 1
conventional touch sensors typically utilize materials such as polyethylene terephthalate (PET) for a touch-sensor substrate. PET is known to exhibit unsuitably high birefringence that degrades the optical quality of the touch sensor
Implementation Method 2
exposure to ultraviolet (UV) radiation may accelerate failure conditions through UV degradation (e.g., increased brittleness) of the materials used for various components of the electronic device
Data Source
AI summary
A touch-sensitive display for an electronic device may include a touch sensor comprising a low birefringence substrate, ultraviolet (UV) stabilizers, and a metal mesh disposed on at least a portion of the low birefringence substrate. The low birefringence characteristic of the touch sensor substrate causes the touch sensor to exhibit low haze, high transmittance, and substantially no color, which provides improved optical properties over conventional touch sensor substrate materials used with metal mesh film. In some embodiments, the retardation value of the touch sensor substrate may be no greater than about 15 nanometers (nm). Additionally, the UV stabilizers prevent the substrate from yellowing and becoming brittle from exposure to UV radiation.