Trapezoidal Cut Portions in Touch Sensor Substrates
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Solution Overview
Problem
Conventional touch sensors face cracking issues during the outline blanking process due to stress concentration at the interface portion of the transparent film substrate, leading to potential damage and defects.
Innovation Solution
A touch sensor design featuring a transparent film substrate with trapezoidal-shaped cut portions in the upper and lower protective films, which widens from the opening end toward the inward portion, and reinforcement layers at the cut ends, to distribute stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional rectangular cut portions are used in the protective films, then the manufacturing process is simple, but stress concentrates at the interface portion during outline blanking causing cracking
Solution Approach 1:
The patent applies asymmetry by changing the cut portion shape from a symmetric rectangular form to an asymmetric tapered shape with different widths at the opening end and inward portion. This asymmetric geometry redistributes the stress field during outline blanking, preventing stress concentration at the interface portion and thereby eliminating cracking while maintaining manufacturing simplicity.
Solution Approach 2:
The patent changes the geometric parameters of the cut portion, specifically the width dimension varying along the depth from the opening end to the inward portion. By making the width at the opening end smaller than the width at the inward portion, the stress distribution is optimized to prevent cracking at the interface portion during the blanking process.
2Device complexity
If the cut portion width is uniform, then the structure is simple, but stress concentration occurs at the interface portion during pressurizing
Solution Approach 1:
The patent introduces asymmetry in the cut portion width along its depth, making the width at the opening end smaller than the width at the inward portion. This asymmetric configuration creates a gradual stress transition zone that prevents stress concentration at the interface portion, thereby enhancing the strength of the transparent film substrate without significantly increasing structural complexity.
3Ease of manufacture
If rectangular cut portions are used, then manufacturing is straightforward, but cracking occurs toward the transparent film substrate from both ends of the opening end
Solution Approach 1:
The patent modifies the width parameter of the cut portion along its depth direction, creating a tapered shape where the width increases from the opening end toward the inward portion. This parameter change ensures that stress is distributed more favorably during outline blanking, preventing crack initiation and propagation from the opening ends while maintaining ease of manufacturing through standard cutting processes.
Data Source
AI summary
A touch sensor, including a transparent film substrate; a front electrode formed on one surface of the transparent film substrate; a front terminal formed on the surface of the transparent film substrate where the front electrode is formed, the front terminal being connected to the front electrode; a back electrode formed on the other surface of the transparent film substrate; and a back terminal formed on the surface of the transparent film substrate where the back electrode is formed, the back terminal being not overlapping with the front terminal in a plan view and being connected to the back electrode.