Touch Panel Printing Layer Surface Roughness Control
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Solution Overview
Problem
Touch panels face reliability issues due to surface roughness and straightness deviations in printing layers, leading to electrode damage, reduced display area, and electrical shorts, particularly when connecting sensing and wire electrodes, which can cause delamination and air infiltration.
Innovation Solution
A touch panel with a printing layer having surface roughness between 0.4 to 0.6 μm and straightness within ±0.1 to ±10 μm, formed using a roll coating scheme, which reduces thickness and prevents pin holes, enhancing adhesive strength and minimizing step differences for improved reliability and reduced Bezel area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the printing layer is provided with a predetermined height (thickness) on the cover substrate, then the wire electrode and sensing electrode can be connected, but the sensing electrode is shorted due to the step difference resulting from the height of the printing layer
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness of the printing layer within the range of 0.4 to 0.6 μm and straightness within ±0.1 to ±10 μm. This optimization of surface parameters reduces the step difference caused by the printing layer height, preventing short circuits between electrodes while maintaining reliable electrical connections.
2Ease of manufacture
If the printing layer has high surface roughness, then the printing process is easier, but the electrode may be damaged by protrusions of the printing layer
Solution Approach 1:
The patent optimizes the surface roughness parameter to a specific range of 0.4 to 0.6 μm, which balances the ease of printing process with the protection of electrode integrity. This controlled surface roughness prevents protrusions that could damage electrodes while maintaining printability.
3Area of stationary object
If the printing layer has great deviation of straightness, then the printing coverage is improved, but the printing layer is printed to an active part, so that the active area, that is, the display area may be reduced
Solution Approach 1:
The patent controls the straightness parameter within ±0.1 to ±10 μm to minimize deviation. This precision ensures that the printing layer is accurately positioned only in the unactive area, preventing encroachment on the active display area while achieving complete coverage of the intended region.
4Reliability
If the junction part is formed through the printing process, then the wire and sensing electrode can be electrically connected, but the entire surface of the substrate is heated, so that the substrate may be deformed
Solution Approach 1:
The patent optimizes the surface roughness and straightness parameters of the printing layer, which enables reliable electrical connections through improved contact quality rather than increased heating. This parameter optimization reduces the need for excessive heating during the printing process, thereby preventing substrate deformation.
Data Source
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AI summary
Provided is a touch panel including a cover substrate including an active area and an unactive area, and a printing layer on the unactive area. The printing layer has surface roughness in a range of 0.4 µm to 0. 6 µm. The printing layer has straightness in a range of ±0.1 µm to ±10 µm.