OLED Pixel Definition via Photolithography Mask Removal
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Solution Overview
Problem
Current OLED manufacturing techniques face challenges in achieving high pixel density due to limitations in mask-based processes, making it difficult to produce pixel densities higher than 800 ppi.
Innovation Solution
The use of photolithography to form light emitting units directly on a substrate without a mask, allowing for precise pixel definition and increased pixel density through the use of photo-sensitive materials and metal-containing layers with transitional or alkali metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mask-based coating process is used to form light emitting units, then manufacturing process is simple, but pixel density is limited to below 800 ppi
Solution Approach 1:
The patent removes the mask component from the manufacturing process entirely. Instead of using a physical mask to define pixels, the invention uses photolithography to directly pattern the light emitting material on the substrate, extracting the masking step and replacing it with a photo-sensitive material-based approach that enables higher pixel density without mask fabrication limitations
Solution Approach 2:
The patent replaces the mechanical mask-based coating system with a photolithography system. The mechanical constraint of mask critical dimensions is substituted by optical patterning using photo-sensitive materials, where pixel definition is achieved through light exposure and chemical development rather than physical mask contact, enabling sub-100 micron feature sizes
2Productivity
If photolithography process is used to form light emitting units directly on substrate, then pixel density can exceed 800 ppi, but manufacturing process complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated layers. The electron transportation layer and metal-containing layer are merged into a single composite layer that performs both electron transport and provides the necessary metal elements for light emission, reducing the total number of deposition steps while achieving high pixel density through photolithography
Solution Approach 2:
The metal-containing layer serves multiple functions simultaneously: it acts as an electron transportation medium, provides metal atoms for electroluminescence, and functions as part of the photolithography pattern definition. This multi-functionality reduces process complexity by eliminating separate layers for each function
3Reliability
If thickness of first electron transportation layer is varied between different light emitting units, then display performance is enhanced, but manufacturing uniformity becomes difficult
Solution Approach 1:
The patent implements local quality by varying the thickness of the first electron transportation layer at different locations on the substrate. Different light emitting units have different layer thicknesses optimized for their specific color emission requirements (e.g., thicker layers for red, thinner for blue), with each local region having tailored properties to achieve optimal display performance across the entire panel
4Reliability
If second meeting point is spaced apart from first meeting point, then light emitting unit structure is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-defining the meeting point positions through photolithography pattern design before material deposition. The photo-sensitive material is patterned with predetermined features that establish the first and second meeting points at optimized spacings, ensuring proper layer alignment and structural integrity without requiring high-precision positioning during subsequent deposition steps
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 enables the production of high pixel density OLEDs, potentially exceeding 1200 ppi, by allowing for precise control over the thickness and arrangement of light emitting units and their metal-containing layers, enhancing the aspect ratio and overall display performance.
Implementation Method 1
The light emitting units are formed by a photo sensitive material. The photo sensitive material is directly disposed on a substrate without through a mask. The pixel definition is realized by a photolithography process.
Implementation Method 2
Each of the first and second light emitting units includes a first electrode and an organic emissive layer over the first electrode; and a first electron transportation layer over the organic emissive layer, at least one of the first electron transportation layer and the metal-containing layer includes transitional metal or alkali metal.
Data Source
AI summary
A light emitting device includes a substrate and a light emitting unit over the substrate. The light emitting unit includes a first electrode, an organic emissive layer over the first electrode, a first electron transportation layer over the organic emissive layer, and a metal-containing layer over the first transportation layer. An end of the first electron transportation layer meets the organic emissive layer and the metal-containing layer at a first meeting point, the organic emissive layer has an end which is close to the first meeting point meets the metal-containing layer at a second meeting point, the second meeting point is spaced apart from the first meeting point and away from the first electron transportation layer. Further, at least one of the first electron transportation layer and the metal-containing layer includes transitional metal or alkali metal.