Flexible Light-Emitting Device Transfer Process
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Solution Overview
Problem
Flexible substrates used in light-emitting devices are prone to deformation, making it challenging to achieve precise and selective formation of light-emitting layers and color filters, which is necessary for full color display with high resolution.
Innovation Solution
The solution involves forming an element formation layer comprising a thin film transistor (TFT), color filter, and pixel electrode on a glass substrate, and then transferring this layer to a plastic substrate, where a white-emissive light-emitting element is formed. This structure allows for the display of full color images with high resolution while maintaining flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a flexible substrate is used to enable curvature and weight reduction, then the device becomes lightweight and can be curved, but the substrate deforms and twists making precise formation of light-emitting layers and color filters difficult
Solution Approach 1:
The manufacturing process is divided into two distinct phases: first, forming the element formation layer (including color filters and light-emitting elements) on a rigid glass substrate where high precision is achievable; second, transferring this pre-formed layer to a flexible plastic substrate. This segmentation allows each phase to be optimized independently - precision during formation on glass, then flexibility during transfer to plastic.
Solution Approach 2:
A glass substrate serves as an intermediary carrier during the formation process. The element formation layer is created on the rigid glass substrate which provides the necessary mechanical stability for precise patterning, then the entire assembly is transferred to the flexible plastic substrate. The glass substrate acts as a temporary mediator that enables precision manufacturing without compromising the final flexible device.
2Shape
If a flexible substrate is used to achieve curvature, then the display can be bent, but deformation and twisting occur that prevent full color display with high resolution
Solution Approach 1:
The process separates the formation of the element formation layer from the final flexible substrate. The layer is formed on a rigid substrate first, then transferred to the flexible substrate. This ensures that high-resolution patterning and color filter formation occur when the substrate is rigid, while the final flexible substrate only needs to maintain the transferred layer's integrity during bending.
Solution Approach 2:
The element formation layer is prepared in advance on a rigid glass substrate under controlled conditions that ensure high resolution and proper color filter alignment. This preliminary formation is completed before transfer to the flexible substrate, so that the critical precision work is done when the substrate can provide the necessary mechanical stability.
3Reliability
If protective insulating films are added to protect from contaminants, then reliability improves, but device complexity increases
Solution Approach 1:
Protective insulating films are introduced as intermediary layers between the color filter and the light-emitting element. These films serve as barriers that prevent harmful gases and contaminants from reaching sensitive components. The protective films are positioned strategically to block contaminants from the color filter while maintaining the overall device structure and electrical functionality.
Data Source
AI summary
A lightweight flexible light-emitting device which is able to possess a curved display portion and display a full color image with high resolution and the manufacturing process thereof are disclosed. The light-emitting device comprises: a plastic substrate; an insulating layer with an adhesive interposed therebetween; a thin film transistor over the insulating layer; a protective insulating film over the thin film transistor, a color filter over the protective insulating film; and a white-emissive light-emitting element formed over and being in contact with the thin film transistor.