OLED Display Substrate Planarization for Inkjet Uniformity
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Solution Overview
Problem
Inkjet printing technology for OLED manufacturing results in uneven film layers due to fluidity issues, leading to poor brightness uniformity in top emission type OLED devices, as the amount of ink material varies across different portions of the pixel defining layer, causing thickness inconsistencies in the organic functional layer.
Innovation Solution
A display substrate structure with a first and second pixel defining layer, a planarization pattern, and an organic functional layer, where the planarization pattern is flush with the surface of the first pixel defining layer, and the second container portion penetrates through the second pixel defining layer, ensuring uniform thickness and flatness of the organic functional layer, and a method involving patterning and inkjet printing processes to form these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inkjet printing technology is used to form the organic functional layer, then the manufacturing process is simple and cost-effective, but the film layer becomes uneven due to fluidity issues, resulting in poor brightness uniformity
Solution Approach 1:
The patent applies preliminary action by forming a planarization pattern before depositing the organic functional layer. This planarization pattern pre-compensates for the uneven substrate surface, ensuring that when the inkjet printing process deposits the organic material, the final thickness is uniform across the pixel defining layer despite the underlying irregularities.
Solution Approach 2:
The patent implements local quality by creating a planarization pattern with varying thickness in different regions. The planarization pattern has greater thickness in areas where the substrate is lower and lesser thickness where the substrate is higher, providing locally-adapted compensation that ensures uniform organic functional layer deposition across the entire pixel area.
2Device complexity
If the organic functional layer is deposited directly on the pixel defining layer, then the process is simplified, but the film thickness becomes inconsistent, leading to non-uniform light emission
Solution Approach 1:
The planarization pattern is formed in advance as a preliminary structural element that prepares the surface for subsequent organic functional layer deposition. This preliminary structure ensures that the organic layer achieves uniform thickness without requiring complex deposition process control.
Solution Approach 2:
The planarization pattern acts as an intermediary layer between the pixel defining layer and the organic functional layer. It mediates the interface between the uneven substrate and the sensitive organic material, providing a controlled foundation that ensures uniform light emission while maintaining relative structural simplicity.
3Productivity
If inkjet printing is used with fluid ink material, then the process is simple and scalable, but the ink distributes unevenly across the pixel defining layer, causing thickness variations
Solution Approach 1:
The planarization pattern is prepared beforehand to create a uniform receiving surface for the inkjet printing process. This preliminary surface preparation allows the fluid ink material to distribute evenly during the scalable printing process, maintaining both productivity and precision.
Solution Approach 2:
The planarization pattern modifies the surface topology parameters of the substrate, changing the local height and slope characteristics. This parameter modification creates optimal conditions for uniform ink spreading and deposition, enabling consistent thickness control even with fluid ink materials in a scalable manufacturing process.
Data Source
AI summary
A display substrate includes a substrate; a first pixel defining layer on the substrate, wherein the first pixel defining layer has a first container portion therein; a planarization pattern filled in the first container portion, wherein a surface of the planarization pattern distal to the substrate is flush with a surface of the first pixel defining layer distal to the substrate; a second pixel defining layer on a side of the planarization pattern distal to the substrate, wherein a second container portion is in the second pixel defining layer and penetrates through the second pixel defining layer along a stacking direction of the first pixel defining layer and the substrate, and an orthographic projection of the second container portion on the substrate falls within an orthographic projection of the first container portion on the substrate; and an organic functional layer in the second container portion.