Conductive Film Electrode Pattern Design for Capacitance Uniformity
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Solution Overview
Problem
Electrostatic capacitive touch panel sensors with random electrode patterns face challenges in maintaining in-plane stability and sensitivity due to variations in electrostatic capacitance, particularly when the electrodes intersect at shallow angles, leading to localized large capacitance areas and reduced responsiveness.
Innovation Solution
A conductive film with a substrate and overlapping electrode patterns formed from thin metal wires, where the electrodes are arranged to cross each other with specific parameters (Ca ≤ 1.0 for 90% of overlapping portions and Cb ≤ 0.5 for 90% of vicinity region overlaps) to ensure uniform capacitance and reduce moire interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If random electrode patterns are used to reduce moire interference, then moire occurrence is reduced, but in-plane stability of sensor sensitivity deteriorates due to variations in electrostatic capacitance
Solution Approach 1:
The patent applies local quality by making the electrode patterns asymmetric in their randomization characteristics. Specifically, the first electrode pattern has a different random pattern configuration than the second electrode pattern, creating local variations that suppress moire while maintaining overall capacitance uniformity. This is achieved by controlling the statistical properties of the random patterns rather than using completely random arrangements.
Solution Approach 2:
The patent changes the parameters of the random patterns by specifying constraints on the overlapping areas and capacitance values. By controlling the parameter Ca (overlapping area parameter) to be 1.0 or less and Cb (vicinity region overlapping parameter) to be 0.5 or less for 90% of overlapping portions, the patent achieves both moire reduction and capacitance uniformity through parameter optimization.
2Object-affected harmful factors
If electrode patterns cross at shallow angles to reduce moire, then moire occurrence is reduced, but localized large capacitance areas increase reducing responsiveness
Solution Approach 1:
The patent applies local quality by allowing different regions of the electrode patterns to have different crossing characteristics. The random patterns ensure that shallow angle crossings are distributed uniformly rather than concentrated in specific areas, creating local variations that prevent localized large capacitance areas while still reducing moire overall.
Solution Approach 2:
The patent uses feedback by establishing statistical constraints (Ca ≤ 1.0 and Cb ≤ 0.5 for 90% of overlapping portions) that guide the pattern design. These constraints act as feedback criteria to ensure that the random patterns achieve both moire reduction and responsiveness uniformity by controlling the distribution of overlapping areas.
3Stability of the object's composition
If regular electrode patterns are used to maintain uniform capacitance, then in-plane stability is improved, but moire interference increases
Solution Approach 1:
The patent applies asymmetry by using different random patterns for the first and second electrodes instead of identical regular patterns. This asymmetric randomization breaks the periodicity that causes moire interference while the controlled statistical properties maintain capacitance uniformity. The asymmetry in pattern configuration is key to eliminating moire without sacrificing stability.
Solution Approach 2:
The patent changes from fixed regular pattern parameters to controlled random pattern parameters. By specifying that 90% of overlapping portions must satisfy Ca ≤ 1.0 and Cb ≤ 0.5, the patent transforms the design approach from deterministic to probabilistic, achieving both moire reduction and capacitance uniformity through parameter control rather than fixed geometry.
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 solution achieves excellent responsiveness and maintains in-plane stability comparable to regular patterns while minimizing moire occurrence, enhancing the overall performance of the touch panel sensor.
Implementation Method 1
the electrostatic capacitive type touch panel sensor reads out changes in electrostatic capacitance by the presence or absence of a finger or the like
Data Source
AI summary
The conductive film is configured such that in a case in which a parameter Ca of a first-overlapped-portion in which a thin metal wire constituting a first-electrode and a thin metal wire constituting a second-electrode are superimposed in plan view is represented by Equation (1) of Ca=(A−wa*wb)/d, while setting an area of the first-overlapped-portion to A (μm2), line widths of the respective thin metal wires constituting the first-electrode and the second-electrode to wa and wb (μm), and a distance between the first-electrode and the second-electrode in a thickness direction of a substrate to d (μm), in a 5 mm×5 mm quadrangular region that is set to include a crossing region in which the first-electrode and the second-electrode cross each other in a conductive region, the parameter Ca of 90% or more of the first-overlapped-portions included in the region is 1.0 or less.