Organic Light Emitting Display Pixel Planarization Thickness Variation
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Solution Overview
Problem
In organic light emitting display devices, uneven ink drying times across pixels lead to non-uniform thin film thicknesses, resulting in deteriorated light emission characteristics and display quality due to different ink discharge times.
Innovation Solution
The implementation of a planarization pattern with varying thicknesses and depths for main pixel blocks, ensuring equal or similar drying rates across pixels by adjusting the surface areas of ink discharge, thereby achieving uniform organic layer thickness and improved light emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ink is discharged onto respective pixels at different times using inkjet printing method, then productivity is improved, but manufacturing precision deteriorates due to non-uniform thin film thickness
Solution Approach 1:
The pixel defining layer is designed with different opening depths for different pixel groups. Specifically, pixels discharged at earlier times have deeper openings while pixels discharged at later times have shallower openings. This local variation in opening depth compensates for the different drying times, ensuring uniform thin film thickness across all pixels despite sequential ink discharge.
Solution Approach 2:
The invention changes the geometric parameter of the pixel defining layer openings based on the discharge time of each pixel group. By adjusting the depth parameter of openings corresponding to different discharge sequences, the system maintains consistent drying conditions and achieves uniform film thickness while preserving the benefits of sequential inkjet printing.
2Device complexity
If sequential ink discharge is performed across pixels, then device complexity is reduced, but manufacturing precision deteriorates due to different drying times
Solution Approach 1:
The pixel defining layer incorporates locally adapted opening depths tailored to each pixel group's discharge time. This local customization of the opening depth parameter ensures that each pixel group experiences optimal drying conditions, resulting in uniform organic layer thickness and consistent light emission characteristics across the entire display device.
3Device complexity
If uniform opening depth is used in pixel defining layer, then device complexity is reduced, but manufacturing precision deteriorates due to non-uniform drying rates
Solution Approach 1:
The pixel defining layer is designed with spatially varying opening depths that correspond to the discharge sequence of pixels. This local differentiation in opening depth creates uniform drying rates across all pixels, ensuring consistent organic layer thickness and light emission uniformity while maintaining a relatively simple overall device structure.
Solution Approach 2:
The invention modifies the depth parameter of the pixel defining layer openings based on the discharge timing of each pixel group. This parameter adjustment compensates for temporal variations in drying rates, achieving uniform film formation without significantly complicating the device architecture.
Data Source
AI summary
Provided is a light emitting display device.The emitting display device comprises: a substrate including a plurality of pixels which are arranged in a first direction and a second direction that crosses the first direction, the plurality of pixels comprising a first main pixel block and a second main pixel block; a planarization pattern arranged on the substrate; a first electrode on the planarization pattern for each of the plurality of pixels; a pixel defining layer partitioning the respective pixels on the substrate and having an opening for exposing the first electrode; an organic layer on the first electrode; and a second electrode on the organic layer, wherein a thickness of the planarization pattern of the pixel in the second main pixel block is larger than a thickness of the planarization pattern of the pixel in the first main pixel block.