Dynamic Elastic Modulus Adhesive Layer for Bendable Display
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Solution Overview
Problem
Existing cover substrates for electronic devices, particularly those made of plastic, face challenges such as low moisture and oxidation resistibility, low surface hardness, increased weight, reduced optical transparency, reduced scratch resistance, reduced puncture resistance, and reduced thermal durability.
Innovation Solution
The development of dynamic adhesive layers with a specific dynamic elastic modulus that allows for desired impact resistance and energy dissipation during impact events while maintaining the bendability of articles. These adhesive layers have a first elastic modulus in the range of 10 kPa to 1000 kPa at low stress frequencies and a second elastic modulus of 500 MPa or more at high stress frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a plastic cover substrate is used to achieve flexibility and bendability, then the device weight is reduced and bendability is improved, but moisture and oxidation resistibility, surface hardness, scratch resistance, puncture resistance, and thermal durability are reduced
Solution Approach 1:
The patent uses a composite structure combining glass (for protection and hardness) with plastic adhesive layers (for flexibility and bendability). The glass cover substrate provides moisture and oxidation resistibility, surface hardness, and scratch resistance, while the plastic adhesive layers maintain bendability and reduce weight. This composite approach resolves the contradiction by assigning different materials to different functional requirements.
Solution Approach 2:
The patent applies different material properties to different parts of the cover substrate assembly. The glass cover substrate provides rigidity and protection where needed, while the plastic adhesive layers provide flexibility and bendability in specific regions. This local differentiation allows the structure to achieve both protection and flexibility simultaneously.
2Strength
If a glass cover substrate is used to improve surface hardness and scratch resistance, then protection is enhanced, but bendability and flexibility are reduced
Solution Approach 1:
The patent employs thin plastic adhesive layers (flexible films) to bond the glass cover substrate to the display assembly. These thin flexible layers allow the rigid glass to be bent without breaking, as the flexible adhesive absorbs the mechanical stress during bending while maintaining the glass's surface hardness and scratch resistance.
Solution Approach 2:
The patent creates a composite structure where rigid glass is combined with flexible plastic adhesive layers. The glass provides surface hardness and scratch resistance, while the plastic adhesive layers provide flexibility and bendability, resolving the contradiction between protection and flexibility.
3Strength
If a rigid adhesive layer is used to provide impact resistance, then protection during impact is improved, but bendability and ease of bending are reduced
Solution Approach 1:
The patent uses adhesive layers with dynamic elastic modulus that changes based on stress frequency. At low stress frequencies (bending), the adhesive layer is soft and flexible, allowing easy bending. At high stress frequencies (impact), the adhesive layer becomes stiff and provides impact resistance. This dynamic property resolution allows the adhesive to provide both flexibility and protection.
Solution Approach 2:
The patent specifies adhesive layers with specific elastic modulus ranges (10 kPa to 1000 kPa at low frequencies, 500 MPa or more at high frequencies). This parameter change based on stress frequency allows the adhesive to provide appropriate mechanical properties for different conditions, resolving the contradiction between impact resistance and bendability.
4Ease of operation
If a plastic cover substrate is used to achieve flexibility, then bendability is improved, but optical transparency, scratch resistance, and thermal durability are reduced
Solution Approach 1:
The patent uses glass for the cover substrate to maintain high optical transparency and scratch resistance, while using plastic adhesive layers to provide flexibility and bendability. The glass layer ensures good optical properties, while the plastic adhesive layers provide the necessary flexibility without significantly affecting overall optical transparency.
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 dynamic adhesive layers effectively enhance the impact resistance of articles without compromising their bendability or significantly increasing the bend force, thereby improving the mechanical reliability of flexible and bendable electronic devices.
Implementation Method 1
adhesive layer having a dynamic elastic modulus including a first elastic modulus in the range of 10 kPa to 1000 kPa measured at a stress frequency in the range of 0 Hertz to 5 Hertz
Implementation Method 2
a second elastic modulus of 500 MPa or more measured at a stress frequency in the range of 10 Hertz to 1000 Hertz
Data Source
AI summary
Articles including a substrate, a cover glass layer disposed over a top surface of the substrate, and an adhesive layer having a dynamic elastic modulus disposed between a bottom surface of the cover glass layer and the top surface of the substrate. The cover glass layer may have a thickness in the range of 1 micron to 200 microns. The dynamic elastic modulus of the adhesive layer may include a first elastic modulus in the range of 10 kPa to 1000 kPa measured at a stress frequency in the range of 0 Hertz to 5 Hertz and a temperature of 23 degrees C., and a second elastic modulus of 500 MPa or more measured at a stress frequency in the range of 10 Hertz to 1000 Hertz and a temperature of 23 degrees C. The adhesive layer may be optically transparent. The articles may be bendable electronic display devices or bendable electronic display device modules.