Capacitive Input Device Curved Surface Moisture Resistance
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Solution Overview
Problem
Conventional capacitive input devices with curved surfaces face limitations due to the use of indium tin oxide (ITO) films, which require vacuum deposition, restricting their shape to simple two-dimensional designs and suffering from reduced detection precision due to moisture absorption by conductive polymers, leading to persistent lowered performance in humid environments.
Innovation Solution
A capacitive input device with a conductive layer of conductive macromolecules, such as PEDOT:PSS, formed on the film base opposite to the external body, allowing easy moisture release and preventing absorption by the film base and external body, thus maintaining detection precision even in humid conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the circuit pattern layer is interposed between the film base and the supporting body, then detection precision can be improved through multi-layer structure, but moisture absorption by the conductive polymer leads to increased resistance and persistent loss of detection precision in humid environments
Solution Approach 1:
The patent inverts the conventional layer arrangement by placing the conductive polymer layer on the outer surface of the film base rather than between the film base and supporting body. This inversion allows moisture to be released from the outer surface, preventing the moisture trapping problem that occurs when the conductive layer is sandwiched between other layers.
Solution Approach 2:
The patent extracts the conductive polymer layer from the intermediate position between the film base and supporting body and relocates it to the outer surface of the film base. This extraction removes the layer from the moisture-trapping configuration, allowing moisture to escape freely from the outer surface while maintaining the multi-layer detection structure.
2Adaptability or versatility
If a three-dimensionally formed film base is used to accommodate curved surfaces, then the device can be applied to curved product portions, but the use of conductive polymer requires vacuum deposition processes that limit manufacturing flexibility
Solution Approach 1:
The patent replaces the mechanical vacuum deposition process with a chemical coating method using conductive polymer. Instead of requiring vacuum deposition equipment to form the conductive layer, the polymer can be applied through solution coating, spray coating, or other liquid-phase methods, significantly simplifying the manufacturing process for three-dimensionally formed film bases.
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 capacitive input device quickly recovers from lowered detection precision by easily releasing absorbed moisture, maintaining resistance values and ensuring consistent performance in varying environmental conditions, while also being more resistant to bending and humidity.
Implementation Method 1
capacitive input device that detects a slight change in capacitance at a portion that a user has lightly touched with a fingertip
Implementation Method 2
the property of the conductive polymer (conductive macromolecules) used in the conventional examples is that when the layer of the conductive polymer absorbs moisture, the resistance of the layer is increased
Data Source
AI summary
A capacitive input device having a curved surface shape includes: an external body molded with a synthetic resin, the external body having an external curved surface facing a user; a film base, which is integrally provided so as to conform to the internal curved surface of the external body; a conductive layer made of conductive macromolecules, the conductive layer being formed on an opposite surface of the film base, the opposite surface being opposite to a bonded surface, of the film base, that is bonded to the external body; and wiring layers that are electrically connected to the conductive layer.