Flexible Display Adhesive Modulus Gradient for Foldability
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Solution Overview
Problem
Flexible display apparatuses face challenges in maintaining reliability and durability, especially under high temperature and humidity conditions, due to poor foldability and bubble generation issues caused by adhesive films with similar moduli, which affect the connection between the display unit, optical film, and window film.
Innovation Solution
The use of a flexible display apparatus structure with a first adhesive film having a lower modulus and a second adhesive film with a higher modulus, where the second adhesive film is specifically designed to have a higher modulus than the first at −20° C. to 25° C., ensuring excellent preservation and restoration, and the first adhesive film provides good reliability and durability at high temperature and humidity without bubble generation or cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive films with similar moduli are used to adhere the display unit, optical film, and window film, then the manufacturing process is simple, but the foldability and reliability deteriorate under high temperature and humidity conditions
Solution Approach 1:
The patent applies local quality by differentiating the modulus of adhesive films at different locations in the stack. The first adhesive film (between display unit and optical film) has a lower modulus of 0.1 to 1 GPa, while the second adhesive film (between optical film and window film) has a higher modulus of 1 to 3 GPa. This localized differentiation optimizes foldability and prevents bubble generation at specific interfaces under high temperature and humidity conditions.
Solution Approach 2:
The patent changes the physical parameter of modulus for different adhesive films to resolve the contradiction. By specifying that the first adhesive film has a lower modulus (0.1-1 GPa) and the second adhesive film has a higher modulus (1-3 GPa), the system achieves both manufacturing simplicity and improved reliability/foldability under extreme environmental conditions.
2Device complexity
If adhesive films with similar moduli are used to connect the layers, then the device structure is simple, but bubble generation and cracking occur under high temperature and humidity
Solution Approach 1:
The patent implements local quality by assigning different modulus values to different adhesive film positions. The first adhesive film (lower modulus: 0.1-1 GPa) is placed between the display unit and optical film to prevent cracking, while the second adhesive film (higher modulus: 1-3 GPa) is placed between the optical film and window film to prevent bubble generation. This localized property differentiation eliminates harmful effects without increasing overall device complexity.
Solution Approach 2:
The patent uses composite material principles by combining adhesive films with different modulus characteristics in a layered configuration. This composite approach creates a system where each adhesive film layer contributes different mechanical properties, preventing both bubble generation and cracking under high temperature and humidity while maintaining structural integrity.
3Reliability
If the second adhesive film has a higher modulus than the first at −20° C. to 25° C., then the foldability is improved, but the adhesive film design becomes more complex
Solution Approach 1:
The patent applies parameter changes by specifying precise modulus ranges for each adhesive film (first: 0.1-1 GPa, second: 1-3 GPa) at specific temperature conditions (−20°C to 25°C). This quantitative parameter differentiation improves foldability while keeping the design manageable through clear numerical specifications rather than complex qualitative descriptions.
Solution Approach 2:
The patent uses local quality by differentiating the modulus parameter at specific locations and temperature ranges. The first adhesive film is designed with lower modulus (0.1-1 GPa) and the second with higher modulus (1-3 GPa) specifically at −20°C to 25°C, creating localized optimization that improves foldability without requiring complex overall design changes.
Data Source
AI summary
A flexible display apparatus includes a display unit, a first adhesive film on the display unit, an optical film on the first adhesive film, a second adhesive film on the optical film, and a window film on the second adhesive film, and the second adhesive film has a higher modulus than the first adhesive film at −20° C. to 25° C.