Force Sensor Between Display and Touch Overlay for Portable Devices

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Solution Overview

Problem

Existing touch-sensitive displays in portable electronic devices face challenges in accurately distinguishing between inadvertent touches and intentional selections, leading to potential deformation of the display and unwanted image distortion due to limited tactile feedback.

Innovation Solution

Incorporating a force sensor, such as pressure-sensitive adhesive or ink, between the display and the touch-sensitive overlay, which extends around the periphery to provide a seal and detect applied forces, allowing for differentiation between touches and selections by measuring resistance changes and providing tactile feedback when a threshold force is exceeded.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If a touch-sensitive overlay is used on portable electronic devices, then the device becomes more compact and portable, but the display is vulnerable to deformation and image distortion from applied forces

Engineering Contradiction:
Improvedevice portabilityVSAvoiddisplay integrity
Core Design Contradiction:
Weight of moving objectVSStability of the object's composition

Solution Approach 1:

A force sensor is positioned between the display and touch-sensitive overlay to detect applied forces before they cause deformation. The sensor measures force magnitude and provides feedback to control the overlay's response, preventing excessive force from deforming the display while maintaining the compact portable design.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

2Device complexity

If traditional touch-sensitive displays are used, then the device structure remains simple, but the ability to distinguish between inadvertent touches and intentional selections is limited

Engineering Contradiction:
Improvedisplay structureVSAvoidtouch detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

A force sensor is introduced as an intermediary component between the display and touch-sensitive overlay. This sensor detects the magnitude of applied forces and transmits this information to the control system, enabling differentiation between light inadvertent touches and intentional selections with sufficient force, thereby improving measurement precision without significantly increasing structural complexity.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The force sensor provides real-time feedback on the magnitude of applied forces to the control system. Based on this feedback, the system can determine whether a touch was intentional (sufficient force) or inadvertent (insufficient force), and accordingly control the display response to provide accurate touch detection and tactile feedback.

Inventive Principle:
Principle #23Feedback

3Device complexity

If no force sensing mechanism is implemented, then the device structure remains simple, but tactile feedback is insufficient for user interaction

Engineering Contradiction:
Improvesensor systemVSAvoiduser feedback
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The force sensor measures the magnitude of applied forces and provides feedback to the control system, which then activates tactile feedback mechanisms (such as vibration motors or piezoelectric actuators) to provide users with tactile confirmation of their input. This feedback loop significantly improves ease of operation by providing intuitive tactile response to user interactions.

Inventive Principle:
Principle #23Feedback

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 differentiates between inadvertent touches and intentional selections, reducing display deformation and enhancing user experience through improved tactile feedback, while maintaining the display's integrity and image quality.

Implementation Method 1

The force sensor may be a pressure sensitive adhesive and may include a pressure-sensitive material disposed between substrate layers and adhered to the overlay and the display

Methodology Applied
Scientific EffectPressure-sensitive adhesive: Adhesive

Implementation Method 2

The pressure-sensitive material may be a pressure-sensitive ink

Methodology Applied
Scientific EffectPressure-sensitive ink: Pressure-sensitive Paint

Implementation Method 3

a piezo actuator disposed between the touch screen display and a base of the portable electronic device for applying a force to the touch screen display

Methodology Applied
Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentEP2224313B1Touch-sensitive display including a force-sensor and portable electronic device including same
Publication Date: 2012.12.05 BLACKBERRY LTD
  • EP2224313B1 patent drawingFigure 1
  • EP2224313B1 patent drawingFigure 2
  • EP2224313B1 patent drawingFigure 3A~3C

AI summary

A touch screen display includes a display, a touch-sensitive overlay disposed on the display, and a controller operably coupled to the overlay. At least one force sensor is disposed between the display and the overlay and is arranged and constructed to determine a value of an applied force to the overlay.