Display Spacer Height Design for Uniformity and Defect Reduction
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Solution Overview
Problem
Existing display devices face issues with spacer height uniformity, leading to increased number of spacers and foreign substance defects during the spacer forming process.
Innovation Solution
The display device design includes a spacer with a height greater than the pixel defining layer, improving height uniformity and reducing the number of spacers, while using a method that involves patterning organic layers with photomasks to expose the electrode and spacer, enhancing the effective area ratio and preventing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the number of spacers is increased to improve height uniformity, then the height uniformity of the spacer is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention divides the spacer structure into two distinct functional parts: a first spacer with a first height and a second spacer with a second height greater than the first height. This segmentation allows different regions to serve different purposes - the first spacer provides baseline support while the second spacer ensures height uniformity in critical areas, thereby resolving the contradiction between needing uniform height and avoiding excessive complexity
Solution Approach 2:
The invention applies local quality by making the second spacer taller than the first spacer in specific regions where height uniformity is critical. The pixel defining layer is configured to expose portions of both spacers, with the second spacer's top surface positioned at a higher level. This localized height differentiation ensures uniformity where needed without increasing the overall number of spacer components throughout the entire device
2Area of stationary object
If the spacer height is increased to reduce the number of spacers, then the effective area ratio is improved, but the height uniformity and precision are compromised
Solution Approach 1:
The spacer is segmented into two height levels rather than using a single uniform height. The first spacer provides coverage over a larger area while the second spacer, being taller, ensures the critical height uniformity requirement is met. This segmentation allows the structure to achieve both a larger effective area ratio and maintained height uniformity simultaneously
Solution Approach 2:
The invention transitions from a single-dimension spacer height approach to a two-dimension height approach by implementing spacers with different heights (first height and second height). This dimensional change allows the structure to optimize both area coverage and height uniformity by utilizing vertical variation to achieve horizontal uniformity in the exposed regions
3Productivity
If the spacer forming process is simplified to reduce manufacturing steps, then the productivity is improved, but foreign substance defects increase
Solution Approach 1:
The pixel defining layer is configured in advance to expose specific portions of the first and second spacers before the light emitting layer is formed. This preliminary configuration ensures that when the light emitting layer is subsequently deposited, it can be precisely positioned over the electrode through the exposed spacer regions. By establishing this exposure pattern beforehand, the process avoids the need for complex real-time alignment procedures that could introduce foreign substances, thereby maintaining both productivity and reliability
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 enhances spacer uniformity, reduces the number of spacers, and minimizes foreign substance defects, thereby improving yield and reliability of the display device.
Implementation Method 1
patterning the first organic layer using a first photomask
Data Source
AI summary
A display device includes a substrate, a pixel defining layer defining a first opening, a light emitting element including a first electrode exposed to outside the pixel defining layer by the first opening and a light emitting layer in the first opening and facing the first electrode, and a spacer spaced apart from the pixel defining layer along the substrate. The pixel defining layer and the spacer each includes a top surface which is furthest from the substrate and a height of the top surface from the substrate, and the height of the top surface of the spacer is greater than the height of the top surface of the pixel defining layer.