Charge Transfer Layer Crack Suppression in Display Devices
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Solution Overview
Problem
Existing display devices with charge transfer layers in light-emitting regions are prone to uncontrolled cracks due to inherent stress from film shrinkage, leading to deterioration in display quality.
Innovation Solution
A display device design featuring a substrate with a light-emitting element comprising a charge transfer layer formed as a continuous film over both light-emitting and non-light-emitting regions, with a protruding portion in the non-light-emitting region having a thinner film thickness than the light-emitting region, to mitigate crack occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a charge transfer layer with uniform film thickness is provided over the entire display region, then the manufacturing process is simplified, but cracks occur in the light-emitting region due to inherent stress from film shrinkage
Solution Approach 1:
The charge transfer layer is designed with non-uniform film thickness, where the film thickness in the light-emitting region is made thinner than in the non-light-emitting region. This local differentiation allows the light-emitting region to have reduced inherent stress and suppressed cracks, while the thicker portions in non-light-emitting regions provide structural stability. The protruding portion structure further emphasizes this local quality variation to control stress distribution.
2Reliability
If a charge transfer layer with thinner film thickness in the light-emitting region is provided, then crack occurrence is suppressed, but the film becomes more susceptible to shrinkage stress during formation
Solution Approach 1:
The protruding portion is formed in the non-light-emitting region before forming the charge transfer layer. This preliminary structural preparation creates a template that guides the subsequent charge transfer layer formation, ensuring that the thinner film portion is deposited precisely where needed (on the protruding portion) while the thicker film is formed in non-light-emitting regions. This prevents premature crack formation while maintaining the stress-reducing thin film structure in the light-emitting region.
3Ease of manufacture
If the charge transfer layer is formed as a continuous film over the entire display region, then manufacturing is simplified, but uncontrolled cracks occur based on unintended triggers
Solution Approach 1:
The film thickness parameter is varied across different regions of the charge transfer layer. By making the film thickness smaller in the light-emitting region and larger in the non-light-emitting region, the inherent stress during film formation is differentially controlled. This parameter change allows the continuous film to be formed without uncontrolled cracks, as the stress distribution is optimized through the thickness variation, turning a harmful effect into a beneficial control mechanism.
Data Source
AI summary
A display device includes a substrate, on the substrate, a light-emitting element including a first electrode, a second electrode, and a light-emitting layer and a charge transfer layer between the first electrode and the second electrode, in which the display device includes a light-emitting region of the light-emitting element and a non-light-emitting region that is a peripheral portion of the light-emitting region, a protruding portion is provided in a layer lower than the charge transfer layer in part of the non-light-emitting region, and the charge transfer layer is formed as a continuous film in a display region including the light-emitting region and the non-light-emitting region on the substrate, and includes a thin film portion, on the protruding portion, being thinner than a portion in the light-emitting region and a portion in the non-light-emitting region other than the protruding portion.