Organic EL Bank Layer Photolithography Heat Loosening
Solution Overview
Problem
The manufacturing of organic EL display panels faces issues with heat-caused loosening of photoresist during the formation of bank layers, leading to slope portions with small inclination angles, which result in a lower aperture ratio and unevenness in functional layer thickness and shape.
Innovation Solution
A method involving photolithography to form bank layers with photoresist, where masked exposure followed by supplementary exposure and baking minimizes heat-caused loosening, ensuring greater inclination angles and improved wettability without excessive UV radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photoresist is baked after masked exposure and developing to provide solvent resistance and enhance liquid repellency, then the bank layer gains resistance against organic solvents and increased liquid repellency, but heat-caused loosening occurs leading to slope portions with small inclination angles
Solution Approach 1:
The patent applies a liquid repellent coating to the substrate before forming the photoresist bank layer. This preliminary action ensures that the substrate surface is pre-treated to prevent ink outflow, reducing the need for excessive baking of the photoresist and thereby minimizing heat-caused loosening while still achieving the desired liquid repellency and solvent resistance.
2Reliability
If photoresist is baked to enhance liquid repellency through component movement to the surface, then liquid repellency increases, but heat-caused loosening occurs resulting in smaller aperture areas
Solution Approach 1:
The liquid repellent coating is applied to the substrate before photoresist formation, pre-establishing the liquid repellency needed. This reduces the dependence on photoresist baking for liquid repellency, thereby minimizing heat exposure and preventing the reduction of aperture area that would otherwise occur due to heat-caused loosening.
3Shape
If slope portions with small inclination angles are formed due to heat-caused loosening, then the aperture ratio decreases, but this results in lower luminous efficiency and color representation
Solution Approach 1:
By pre-applying the liquid repellent coating to the substrate, the patent reduces the need for extensive photoresist baking. This maintains the aperture ratio by preventing heat-caused loosening and slope formation, thereby preserving the display performance including luminous efficiency and color representation.
4Device complexity
If conventional photolithography is used without supplementary exposure, then the process is simpler, but heat-caused loosening occurs during baking leading to poor manufacturing precision
Solution Approach 1:
The liquid repellent coating is applied to the substrate before photoresist formation. This preliminary treatment reduces the sensitivity of the photoresist to heat-caused loosening during baking, thereby improving manufacturing precision of the bank layer shape without requiring complex supplementary exposure processes.
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
This approach suppresses heat-caused loosening, enhances the aperture ratio, and reduces the risk of uneven functional layer formation, maintaining desirable wettability and preventing ink flow issues.
Implementation Method 1
baking of developed photoresist is performed to provide a bank layer with resistance against organic solvents
Implementation Method 2
the baking, when performed in the forming of a bank layer containing a liquid repellent component, causes movement of the liquid repellent component to the bank layer surface, and thus increases the liquid repellency of the bank layer surface
Data Source
AI summary
An organic EL display panel manufacturing method including: preparing a substrate; forming at least first electrodes on the substrate; forming, by performing photolithography on the substrate having the first electrodes, a bank layer made of a photoresist and having apertures corresponding one-to-one with the first electrodes; forming a functional layer in each of the apertures by applying an ink containing a functional material to the aperture and drying the applied ink; and forming at least a second electrode on the functional layer. The forming of the bank layer includes: applying the photoresist to the substrate having the first electrodes; forming apertures corresponding one-to-one with the first electrodes in the photoresist by performing exposure using a mask and then developing the photoresist; after forming the apertures, performing exposure of the photoresist having the apertures; after performing the exposure of the photoresist having the apertures, baking the photoresist.