Touch Panel Nanowire Electrode Direct Patterning
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Solution Overview
Problem
Conventional touch panels using metal oxide thin films face issues with flexibility and visible pattern boundaries, and the fabrication process of nanowire-containing touch electrodes is hindered by etchant corrosion of metal leads and the trade-off between electrode protection and contact impedance due to the overcoat thickness.
Innovation Solution
A direct patterning method for touch panels involving a substrate with a metal nanowire layer, a pre-cured film layer, and a negative-type photosensitive layer, where the nanowire layer is patterned and removed in specific regions to form a touch sensing electrode connected to a peripheral circuit, with the bonding pad exposed for low-impedance electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an overcoat is coated on nanowires to protect the electrode, then the durability of the electrode is improved, but the contact impedance between the bonding pad and exterior circuit board increases
Solution Approach 1:
The patent applies different thicknesses of the overcoat layer to different regions: a first thickness in the display area for protection, and a second (smaller) thickness in the peripheral area for low impedance. This local differentiation resolves the contradiction by providing protection where needed while minimizing impedance where electrical contact is critical.
Solution Approach 2:
The overcoat layer is segmented into at least two distinct regions with different thicknesses: a first region (display area) with greater thickness for durability, and a second region (peripheral area) with lesser thickness for low contact impedance. This segmentation allows simultaneous optimization of both protection and electrical performance.
2Ease of manufacture
If etchant solution is used to pattern and etch nanowire material, then the touch sensing electrodes are fabricated, but the metal leads in the peripheral area are corroded
Solution Approach 1:
The patent segments the nanowire layer into a first region (display area) where nanowires are retained for electrode formation, and a second region (peripheral area) where nanowires are completely removed to expose metal leads. This segmentation allows etchant to be applied uniformly while only removing nanowires from the peripheral area, preventing lead corrosion in critical regions.
Solution Approach 2:
The patent extracts (completely removes) the nanowire material from the peripheral area where metal leads are located, before applying the etchant. This extraction prevents the etchant from coming into contact with and corroding the metal leads, while still allowing the etching process to fabricate electrodes in the display area.
3Strength
If the thickness of the remaining overcoat is increased to increase protection, then the electrode protection is improved, but the contact impedance becomes too high causing signal loss
Solution Approach 1:
The patent implements local quality by specifying different overcoat thicknesses for different functional regions: thicker overcoat (first thickness) in the display area for maximum protection, and thinner overcoat (second thickness) in the peripheral area for optimal electrical contact. This resolves the contradiction by making the overcoat thickness location-dependent.
Solution Approach 2:
The overcoat layer is divided into at least two segments with different thickness characteristics: a first segment over the display area with greater thickness for durability, and a second segment over the peripheral area with lesser thickness for low impedance. This segmentation enables simultaneous achievement of protection and low signal loss.
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 method enhances the durability of touch sensing electrodes, reduces contact impedance, and eliminates the need for etching solutions, thereby improving the electrical performance and reliability of touch panels.
Implementation Method 1
performing a photolithography step that includes exposing the negative-type photosensitive layer to define a removal region and a reserved region, and removing the negative-type photosensitive layer, the pre-cured film layer, and the metal nanowire layer in the removal region by using of a developer
Data Source
AI summary
A touch panel includes a substrate having a display area and a peripheral area. A peripheral circuit is disposed in the peripheral area. The peripheral circuit comprises at least one bonding pad made of a metal layer. A plurality of touch sensing electrodes is disposed in the display area. The plurality of touch sensing electrodes is made of a metal nanowire layer, a film layer disposed on the metal nanowire layer, and a negative-type photosensitive layer disposed on the film layer. The plurality of touch sensing electrodes is electrically connected to the peripheral circuit.