Bank Inclination Angle Control for OLED Film Thickness Uniformity
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Solution Overview
Problem
Maintaining a uniform film thickness of the organic light emitting layer across the entire panel of a display device is challenging, particularly in the peripheral region, due to the difficulty in precisely forming convexities on the inner surface of the banks to control the pinning location of the ink during the manufacturing process.
Innovation Solution
The display device incorporates banks with varying inclination angles, where the first bank has a larger inclination angle than the second bank, causing the pinning location of the ink to be higher on the first bank, resulting in a thinner film thickness, which helps to maintain uniformity of the organic light emitting layer even when a vapor stream is produced during drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If convexities are formed on the inner surface of the bank to control pinning location, then film thickness uniformity is improved, but manufacturing precision and device complexity deteriorate
Solution Approach 1:
The invention applies different inclination angles to different regions of the bank structure. Specifically, the bank has a first inclination angle in the region facing the peripheral light emitting cell and a second inclination angle in other regions, allowing localized control of ink pinning behavior to achieve uniform film thickness without complex convexity formation
Solution Approach 2:
The invention introduces asymmetric inclination angles in the bank structure, where the angle varies depending on the position relative to the light emitting cell. This asymmetric design enables different pinning locations at different banks, compensating for the vapor stream effect and achieving uniform film thickness without requiring symmetric convexity formation
2Manufacturing precision
If convexities are formed on the inner surface of the bank, then film thickness uniformity is improved, but ease of manufacture deteriorates
Solution Approach 1:
The invention changes the geometric parameters of the bank structure by varying the inclination angles at different positions. This parameter variation (first inclination angle vs. second inclination angle) controls the ink pinning location and film thickness distribution, providing a manufacturable alternative to forming convexities
3Illumination intensity
If uniform film thickness is maintained across the entire panel, then luminance uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The invention applies local quality by configuring banks at peripheral regions with specific inclination angles different from those at central regions. This localized structural differentiation ensures uniform film thickness and luminance across the entire panel, including peripheral areas, without requiring complex overall manufacturing 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 ensures a uniform film shape and even luminance across the peripheral light emitting cells by offsetting the increase in film thickness at the first bank, thereby achieving consistent organic light emitting layer thickness and luminance throughout the panel.
Implementation Method 1
progress has been made in the research and development of display devices that use the phenomenon of electroluminescence occurring in organic material. When the display device is driven, light is produced when holes and electrons recombine within the organic light emitting layer
Implementation Method 2
The organic light emitting layer is formed by dripping ink that includes organic light emitting material into each region partitioned by the banks and drying the ink
Data Source
AI summary
A display device includes an array of light emitting cells. Each of the light emitting cells includes a first electrode, a second electrode, and an organic light emitting layer located between the first electrode and the second electrode. Banks are above the first electrode that partition the organic light emitting layer to define each of the light emitting cells. The light emitting cells include a peripheral light emitting cell that is located in a peripheral region of the array. The banks include first and second banks that each border the peripheral light emitting cell. The first bank is closer to a periphery of the array than the second bank. An inclination angle of an innermost sidewall of the first bank that is adjacent the peripheral light emitting cell is greater than an inclination angle of an outermost sidewall of the second bank that is adjacent the peripheral light emitting cell.