Circular Touch Sensor Electrode Arrangement for Smartwatch Sensitivity
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Solution Overview
Problem
Touch sensors in small-sized mobile devices, such as smartwatches, face challenges in maintaining sensitivity due to the design constraints of their shape, leading to a compromise in the size of the sensing area and internal lines, which affects their performance.
Innovation Solution
The design of touch sensors with a closed shape sensing area and strategically arranged first and second touch electrodes, including sub-touch electrodes, that are connected to common signal lines and coupling pads, reduces the number of internal lines and increases the sensing area, thereby enhancing touch-sensing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the touch sensor is designed to conform to a circular shape for smartwatches, then the device compatibility and aesthetic appearance are improved, but the sensing area is reduced and internal lines become more complex, leading to decreased touch-sensing sensitivity
Solution Approach 1:
The touch sensor is divided into multiple sections (first section, second section, third section, fourth section) arranged in a circular pattern. Each section contains corresponding touch electrodes that are segmented and distributed around the circumference. This segmentation allows the sensor to maintain circular shape compatibility while improving touch detection capability through distributed electrode arrangement.
Solution Approach 2:
The patent transitions from traditional linear or rectangular electrode arrangements to a circular/dimensional arrangement. Touch electrodes are positioned at different angular positions around the circular sensing area, creating a radial distribution pattern. This dimensional change optimizes the sensing area utilization and maintains sensitivity across the curved surface of smartwatch displays.
2Reliability
If more internal lines are added to the touch sensor, then the electrode connections and signal routing are improved, but the sensing area is reduced and manufacturing complexity increases
Solution Approach 1:
Multiple touch electrodes in corresponding sections are electrically connected and merged into unified electrode groups. The first touch electrodes in different sections are connected to form a continuous sensing element, reducing the need for separate internal lines for each electrode while maintaining comprehensive coverage and reliable signal transmission.
Solution Approach 2:
The internal lines are designed to serve multiple functions: they connect touch electrodes across different sections, provide signal routing for both touch detection and display control, and maintain electrical continuity throughout the circular arrangement. This multi-functionality reduces the total number of internal lines needed while ensuring reliable connections.
3Area of stationary object
If the sensing area is reduced to accommodate internal lines, then the device size is minimized, but the touch-sensing sensitivity is degraded
Solution Approach 1:
Different regions of the circular touch sensor have optimized local characteristics. The touch electrodes are strategically positioned in specific angular sections with varying densities and configurations tailored to local sensing requirements. This local optimization ensures high sensitivity in critical areas while maintaining overall compact device dimensions.
Solution Approach 2:
The touch sensor utilizes a circular curved geometry instead of flat rectangular design. This curvature allows for optimized electrode placement along the circular path, maximizing the sensing area utilization. The curved arrangement naturally distributes internal lines more efficiently around the perimeter, reducing their encroachment on the central sensing area while maintaining device compactness.
Data Source
AI summary
A touch sensor for a display device includes: a sensing area having a closed shape and including a plurality of sections, and a non-sensing area at least partially surrounding the sensing area; first touch electrodes disposed in the sensing area; and second touch electrodes disposed in the sensing area. The first touch electrodes include first groups of first sub-touch electrodes, and first sub-touch electrodes of at least some of the first groups are spaced at a first substantially equal distance from a center of the closed shape. The second touch electrodes include second groups of second sub-touch electrodes, and second sub-touch electrodes of at least some of the second groups are spaced at a second substantially equal distance from the center of the closed shape.