Capacitance Touch Sensor Retardation Control
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Solution Overview
Problem
Conventional capacitance type touch panels suffer from recognition of transparent conductive parts due to differences in light transmittance and brightness, leading to erroneous inputs and decreased display screen brightness, especially when using dummy electrodes to address these issues.
Innovation Solution
A capacitance type touch sensor is developed with a resin sheet and transparent conductive parts where the difference in retardation values is suppressed by controlling the thickness, stress relaxation, and material properties, such as using a photoelastic coefficient of not greater than 30×10−8 cm2/N, and incorporating a polarizing plate to reduce reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy electrodes are arranged to reduce transparency differences, then transparency uniformity is improved, but light transmittance decreases and display screen brightness decreases
Solution Approach 1:
The patent changes the physical parameters of the transparent conductive parts by controlling their thickness to be 3 μm or less, and adjusting the ratio of non-presence region width to presence region width to be 0.05 or more. These parameter changes allow the transparent conductive parts to have sufficient conductivity while minimizing their visual impact and maintaining high light transmittance, thus improving transparency uniformity without sacrificing display brightness
Solution Approach 2:
The patent applies local quality by creating regions with different properties: the transparent conductive parts have optimized thickness and distribution patterns that provide necessary electrical conductivity in specific areas while maintaining optical transparency in other areas. This localized optimization allows different parts of the touch sensor to serve different functions (conduction vs. transparency) simultaneously
2Manufacturing precision
If the gap between adjacent transparent electrodes is narrowed to improve transparency uniformity, then transparency uniformity is improved, but erroneous input increases
Solution Approach 1:
The patent optimizes the gap dimensions by controlling the width of non-presence regions to be 3 μm or more, which is sufficient to prevent erroneous input between adjacent keys while keeping the gap narrow enough to maintain transparency uniformity. This precise parameter control resolves the contradiction between the two requirements
3Illumination intensity
If transparent conductive parts are made thinner to maintain light transmittance, then display screen brightness is maintained, but conductivity decreases
Solution Approach 1:
The patent achieves the right balance by setting the thickness of transparent conductive parts to 3 μm or less while optimizing other parameters such as the width ratio of non-presence to presence regions (0.05 or more). This combination of parameter changes maintains adequate conductivity for touch detection while preserving high light transmittance for display brightness
Solution Approach 2:
The patent uses composite structures combining transparent conductive parts with insulating resin sheets and polarizing plates. This composite approach allows the system to achieve both electrical conductivity (through the transparent conductive parts) and optical transparency (through the composite structure's overall design), resolving the contradiction between conductivity and brightness
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 effectively suppresses the recognition of transparent conductive parts, maintaining display screen brightness and improving appearance by reducing retardation differences and stress in the resin sheet, thus enhancing the touch sensor's performance.
Implementation Method 1
incorporating a polarizing plate to reduce reflection
Implementation Method 2
using a photoelastic coefficient of not greater than 30×10−8 cm2/N, and incorporating a polarizing plate to reduce reflection
Data Source
AI summary
A capacitance-type touch sensor and a display device equipped with this sensor are provided in which the detection of the transparent conductive portions can be suppressed without employing a technique using a dummy electrode. The capacitance-type touch sensor of the present invention includes a resin sheet and a plurality of transparent conductive portions formed in parallel on the resin sheet. In this capacitance-type touch sensor, the difference between the maximum and minimum retardation values of a resin sheet equipped with transparent conductive portions is 3 nm or less.