OLED Planarization Layer Segmentation for Surface Flatness
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Solution Overview
Problem
The challenge in organic light-emitting display devices is to maintain a thin planarization layer while minimizing surface unevenness, which can degrade display quality due to the structural shapes of thin-film transistors and wirings, leading to uneven anode, organic light-emitting, and cathode layers.
Innovation Solution
A method involving a substrate with thin-film transistors, a planarization layer comprising a first and second planarization portion, where the first planarization portion defines openings and the second planarization portion is formed within these openings, using materials like polyacrylates resin and epoxy resin, and the second planarization portion is formed using an inkjet transfer method to ensure a smooth surface for uniform electrode and organic light-emitting layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the planarization layer is made thin to reduce device thickness, then the device becomes thinner, but the surface unevenness increases due to underlying TFT and wiring structures
Solution Approach 1:
The planarization layer is divided into a first planarization layer and a second planarization layer. The first planarization layer provides initial planarization, while the second planarization layer specifically addresses surface unevenness in pixel regions. This segmentation allows each layer to have optimized thickness and function, achieving overall surface flatness while maintaining thin device profile.
Solution Approach 2:
The second planarization layer is selectively formed only in pixel regions where uniform surface flatness is critical for OLED performance. This local application of planarization material ensures high manufacturing precision in critical areas without unnecessarily increasing device thickness across the entire substrate.
2Length of stationary object
If the planarization layer is made thin to reduce device thickness, then the device becomes thinner, but the display quality deteriorates due to uneven electrode and organic light-emitting layer formation
Solution Approach 1:
By dividing the planarization function into two layers, the first layer provides structural support and initial planarization, while the second layer ensures the critical surface flatness needed for uniform electrode and organic light-emitting layer formation. This segmentation maintains display quality without compromising device thinness.
Solution Approach 2:
The first planarization layer is formed first to provide a preliminary planar surface, upon which the second planarization layer is then formed to achieve final surface precision. This preliminary action creates a stable foundation that enables the second layer to effectively ensure display quality.
3Length of stationary object
If a single planarization layer is used to maintain device thinness, then device thickness is reduced, but the surface unevenness from TFT and wiring structures cannot be adequately compensated
Solution Approach 1:
The planarization function is segmented into two distinct layers with different thicknesses and functions. The first layer compensates for major unevenness from TFT and wiring structures, while the second layer provides fine-tuned surface uniformity in pixel regions. This segmentation enables adequate surface compensation while maintaining overall device thinness.
Solution Approach 2:
The solution transitions from a single-layer planarization approach to a multi-layer approach, adding a vertical dimension to the planarization structure. This dimensional change allows for differentiated planarization functions at different depth levels, achieving both surface uniformity and device thinness.
Data Source
AI summary
A method of manufacturing an organic light-emitting display device includes providing a substrate which comprises thin-film transistors (TFTs), and forming a planarization layer over the substrate. The planarization layer comprises a first planarization portion and a plurality of second planarization portions. The method further includes forming a plurality of first electrodes over the planarization layer, forming an organic light-emitting layer over each of the first electrodes, and forming a second electrode over the organic light-emitting layer. The forming of the planarization layer includes forming the first planarization portion which defines a plurality of first openings and forming one of the second planarization portions in each of the first openings.