Ferroelectric Polymer Haptic Actuator for Display Transparency
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Solution Overview
Problem
Conventional haptic devices in touch-sensitive display devices face challenges in providing immediate and accurate feedback due to their large size, difficulty in modulating vibration frequency, and issues with light transmittance, leading to suboptimal user experience and image quality.
Innovation Solution
A touch-sensitive device utilizing a ferroelectric polymer as the first electroactive layer and an electroactive polymer as the second electroactive layer, with transparent electrodes, to enhance vibration levels and light transmittance, allowing for stronger haptic feedback and reduced driving voltage while minimizing image quality deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a vibratory motor such as ERM or LRA is used to increase vibration intensity, then the vibration level is improved, but the device size increases and response time significantly increases
Solution Approach 1:
The patent replaces conventional mechanical vibratory motors (ERM, LRA) with piezoelectric actuators that convert electrical energy directly to mechanical vibration. This substitution eliminates the need for massive rotating or reciprocating mechanical components, achieving high vibration intensity with a compact device structure and faster response time.
Solution Approach 2:
The patent changes the operating parameters by using piezoelectric materials that respond to high-frequency electrical signals (20-200 kHz), enabling the generation of intense vibrations without requiring large mechanical masses. The piezoelectric effect allows direct conversion of electrical energy to mechanical displacement at high frequencies.
2Device complexity
If conventional haptic devices are positioned on the back of the display panel, then the device structure is simplified, but the touch feedback immediacy and accuracy deteriorate
Solution Approach 1:
Instead of placing the haptic device on the back of the display panel as conventionally done, the patent inverts the positioning by placing the piezoelectric actuator on the front surface of the display panel, directly at the user's touch location. This inversion enables immediate and accurate tactile feedback while maintaining a simplified device structure.
3Speed
If electroactive ceramics (EAC) are used for haptic devices, then the response time is improved, but the durability against external impact deteriorates and the device becomes fragile
Solution Approach 1:
The patent uses piezoelectric polymers such as PVDF (polyvinylidene fluoride) and P(VDF-TrFE) (copolymer of vinylidene fluoride and trifluoroethylene) as composite materials that combine fast response characteristics with high durability and flexibility. These polymer materials resist external impacts better than brittle ceramics while maintaining quick response times.
4Force
If opaque materials such as shape memory alloy (SMA) or electroactive ceramics (EAC) are used for haptic devices, then the haptic feedback is improved, but the light transmittance deteriorates and image quality is compromised
Solution Approach 1:
The patent employs transparent or translucent piezoelectric polymer materials that allow light to pass through while still providing effective haptic feedback. The materials maintain optical transparency in the visible spectrum, ensuring that display image quality is not compromised by the presence of the haptic actuator on the front surface.
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 higher vibration levels with lower driving voltage and improved light transmittance, enabling direct and effective haptic feedback to users without compromising display image quality.
Implementation Method 1
The vibrators comprise a piezoelectric base film, which is a piezoelectric resin, for example, polyvinylidene fluoride (PVDF)
Implementation Method 2
The material of the photorefractive polymer material layer is preferably made of a polymer, which exhibits change in terms of size and form when it is excited by an electric field
Data Source
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AI summary
Provided are a touch sensitive device and a display device including the same. The touch sensitive device includes: a first electroactive layer formed of a ferroelectric polymer; a plurality of electrodes disposed on at least one surface of the first electroactive layer; and a second electroactive layer in contact with the plurality of electrodes and the first electroactive layer and formed of an electroactive polymer. A coating layer having a low refractive index and formed of an electroactive polymer is formed on the first electroactive layer formed of a ferroelectric polymer having a low light transmittance, and, thus, a vibration level and a light transmittance of the touch sensitive device can be improved simultaneously.