Colored Polyimide Substrate Edge Curling Prevention
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Solution Overview
Problem
The curling phenomenon at the edge of substrates in OLED displays due to stress generated during the separation of the glass support substrate from the flexible polyimide substrate, particularly where the sacrificial layer is not deposited, leading to separation failures and damage.
Innovation Solution
A display device design utilizing a flexible substrate with a first transparent polyimide substrate region for the display unit and a second colored polyimide substrate region, where the colored polyimide substrate has a higher glass transition temperature and lower thermal expansion coefficient, surrounding the display unit to prevent curling and facilitate easy separation without the sacrificial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent polyimide substrate is used for the display unit, then light transmission is improved, but edge curling occurs due to high thermal expansion coefficient
Solution Approach 1:
The substrate is divided into two distinct regions: a first substrate region made of transparent polyimide for the display unit requiring light transmission, and a second substrate region made of colored polyimide with different thermal properties for the edge area. This segmentation allows each region to have optimized properties for its specific function, preventing edge curling while maintaining display performance.
Solution Approach 2:
Different regions of the substrate are given different material properties: the central display area uses transparent polyimide with high light transmission, while the edge area uses colored polyimide with lower thermal expansion coefficient. This local differentiation of material properties solves the curling problem at edges without compromising the optical performance of the display unit.
2Ease of manufacture
If sacrificial layer is not deposited in gripper area, then manufacturing process is simplified, but separation fails in that area
Solution Approach 1:
The colored polyimide substrate region is prepared in advance in the gripper area where the sacrificial layer is not deposited. This preliminary preparation of the substrate structure ensures that separation can occur successfully in areas without sacrificial layer, eliminating the need for complex process adjustments while maintaining reliable separation throughout.
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
Prevents curling of the substrate edge by using a colored polyimide substrate with a higher glass transition temperature and lower thermal expansion coefficient, ensuring successful separation and reducing substrate damage during the manufacturing process.
Implementation Method 1
A glass transition temperature of the transparent polyimide is equal to or lower than 350° C., and a glass transition temperature of the colored polyimide is equal to or higher than 380° C.
Implementation Method 2
The polyimide substrate is transparent enough to transmit light and has a small phase difference and a high thermal expansion coefficient. Thus, an edge of the polyimide substrate may be curled.
Data Source
AI summary
A display device for preventing a curling phenomenon of an edge of a substrate and solving a problem caused by separation of the substrate is disclosed. The display device includes a flexible substrate including a first substrate region overlapping a display unit and a second substrate region except the first substrate region, and a thin film transistor and an organic light emitting diode disposed on the display unit of the first substrate region. The first substrate region is formed of transparent polyimide, and the second substrate region is formed of colored polyimide.