Hybrid Touch Sensor Layout for Portable Devices
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Solution Overview
Problem
In portable electronic devices, such as smartphones and tablets, the capacitive touch sensor can inadvertently detect the user's holding hand or finger, leading to erroneous operations due to its sensitivity, which affects the device's operability.
Innovation Solution
A combination of capacitive and pressure-sensitive touch sensors is used, where the capacitive sensor is placed in the central area of the display surface and the pressure-sensitive sensor is placed in the edge area, with the edge area potentially having a curved surface and an antireflection film to reduce external light reflectance, thereby minimizing unintended touches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a capacitive touch sensor is used across the entire display surface, then quick operability is obtained, but erroneous operations occur due to unintended detection of the holding hand
Solution Approach 1:
The display surface is divided into a main area (central portion) and a side area (edge portion). A capacitive touch sensor is disposed in the main area to enable quick operability, while a pressure-sensitive touch sensor is disposed in the side area to prevent erroneous operations from unintended contact with the holding hand. This segmentation allows each sensor type to perform its optimal function in the appropriate zone.
Solution Approach 2:
Different sensor types are assigned to different regions of the display surface based on their respective strengths. The capacitive sensor in the main area provides fast response for intentional touches, while the pressure-sensitive sensor in the side area provides reliable detection only for deliberate presses, filtering out accidental contact from the holding hand.
2Ease of manufacture
If the side area has a flat surface, then manufacturing is simple, but external light reflection reduces visibility
Solution Approach 1:
The side area of the display surface is formed with a curved surface shape instead of a flat surface. This curvature reduces external light reflection, improving display visibility. The curved shape also provides an ergonomic benefit, making the device easier to hold and operate with one hand.
3Illumination intensity
If the side area is made curved to reduce light reflection, then visibility is improved, but manufacturing complexity increases
Solution Approach 1:
The curved surface shape is integrated into the display panel structure itself, combining the optical function (reducing light reflection) with the structural form. This merging approach achieves the visibility improvement without adding separate components or complex assembly steps, thereby limiting the increase in manufacturing complexity.
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
This configuration reduces the likelihood of erroneous operations by distinguishing between intended and unintended touches, enhancing the device's operability and visibility while being easy to hold and use.
Implementation Method 1
a capacitive contact sensor is disposed in a main area of the display surface
Implementation Method 2
a pressure-sensitive contact sensor is disposed in a side area of the display surface
Implementation Method 3
an antireflection film to make an external light reflectance lower than that in the main area may be disposed in the side area
Data Source
AI summary
An erroneous operation is made less likely to occur in a portable electronic device including a touch panel. The portable electronic device has a plate-like external shape. An organic EL display panel that displays an image on a display surface is disposed on one surface of the external shape. A touch sensor is disposed on the display surface and detects contact of an object with the display surface. As the touch sensor, a capacitive contact sensor is disposed in a main area of the display surface that is set to include a central portion, and a resistive contact sensor is disposed in a side area of the display surface that includes at least a portion of an edge of the display surface and is set exclusively of the main area.