Touch Panel Insulating Layer Surface Roughness Control
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Solution Overview
Problem
Existing touch panels face issues with wire electrode reliability due to step differences and high surface roughness of printing layers, leading to cracking and degradation of electrodes.
Innovation Solution
An insulating layer with average surface roughness between 0.2 μm to 0.4 μm is applied on the printing layer to reduce surface roughness and prevent electrode failure, while also reducing the inclination angles of step differences between layers, thereby enhancing the adhesive strength and reliability of the wire electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the wire electrode is directly formed on the printing layer, then the manufacturing process is simplified, but the wire electrode may be cracked or damaged due to high surface roughness and step differences
Solution Approach 1:
An insulating layer is introduced as an intermediary between the printing layer and the wire electrode. This insulating layer has a surface roughness of 0.2 μm to 0.4 μm, which is lower than the printing layer, providing a smoother surface for the wire electrode while maintaining electrical insulation. This resolves the contradiction by enabling direct formation on printing layer (ease of manufacture) while preventing cracking and damage (improving reliability).
Solution Approach 2:
The surface roughness parameter of the insulating layer is specifically controlled to be 0.2 μm to 0.4 μm, which is lower than the printing layer's surface roughness. This parameter change creates an optimal surface for wire electrode formation, reducing stress concentration and preventing cracks while maintaining the simplified manufacturing process.
2Adaptability or versatility
If multiple printing layers are formed to achieve design requirements, then the design flexibility is improved, but step differences are created that can crack the wire electrode
Solution Approach 1:
The insulating layer serves as a mediator that covers the step differences created by multiple printing layers. By providing a continuous, smoother surface across the step differences, it prevents stress concentration and crack formation in the wire electrode, thereby maintaining both design flexibility and wire electrode integrity.
Solution Approach 2:
The insulating layer is selectively applied in regions where step differences exist between printing layers. It provides localized smoothing and stress distribution exactly where needed, allowing multiple printing layers to maintain their design flexibility while preventing wire electrode cracking at the critical interfaces.
3Stability of the object's composition
If the surface roughness of the printing layer is high to maintain material properties, then the material characteristics are preserved, but the wire electrode adhesion and reliability are degraded
Solution Approach 1:
The insulating layer acts as an intermediary that decouples the material characteristics of the printing layer from the adhesion requirements of the wire electrode. The printing layer can maintain its inherent high surface roughness and material properties, while the insulating layer provides the smoother surface needed for reliable wire electrode adhesion and positioning.
Solution Approach 2:
The surface roughness parameter is changed from the printing layer's high roughness to the insulating layer's controlled roughness of 0.2 μm to 0.4 μm. This parameter transformation allows the underlying printing layer to maintain its material stability while the insulating layer surface provides the precision needed for wire electrode formation and adhesion.
Data Source
AI summary
A touch panel includes a cover substrate having an active area and an unactive area. A printing layer is provided on the unactive area while forming a step difference from the cover substrate. An insulating layer is provided on the printing layer, and the insulating layer has average surface roughness in a range of 0.2 μm to 0.4 μm.