Auxiliary Electrode for Top-Emission OLED Brightness Uniformity
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Solution Overview
Problem
Top-emission-type organic EL display devices face issues with non-uniform brightness due to high resistance in transparent electrodes, leading to potential differences in upper electrode potentials, which are costly to address with existing solutions that require photolithography and suffer from conduction failures at through holes.
Innovation Solution
Formation of auxiliary electrodes above or below the upper electrode using vapor deposition or sputtering, connected via through holes in an insulation film, with a contact electrode overlapping the auxiliary electrode to ensure reliable conduction and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photolithography is used to pattern auxiliary lines below the bank, then the auxiliary line can be formed to reduce resistance, but the manufacturing cost increases
Solution Approach 1:
Instead of forming the auxiliary line below the bank as in conventional technology, this patent forms the auxiliary line above the bank. This inversion eliminates the need for photolithography patterning while still achieving low-resistance conduction, thereby reducing manufacturing cost while maintaining reliability
Solution Approach 2:
The patent extracts the auxiliary line formation from the conventional below-bank position and relocates it to above the bank. This extraction allows the auxiliary line to be formed simultaneously with the upper electrode using the same ITO material and deposition process, eliminating additional photolithography steps and reducing manufacturing cost
2Reliability
If a deep through hole is formed in the bank to connect auxiliary line and upper electrode, then electrical connection is achieved, but conduction reliability becomes difficult to ensure
Solution Approach 1:
The patent extracts the connection structure from the deep through-hole configuration and replaces it with a surface-level auxiliary line formed above the bank. This eliminates the deep through hole entirely, achieving electrical connection between the terminal and upper electrode through the auxiliary line without the conduction failures associated with deep hole structures
Solution Approach 2:
Instead of connecting the auxiliary line to the upper electrode from below through a deep hole, the patent inverts the connection approach by forming the auxiliary line above the bank and connecting it to the upper electrode at the surface level, thereby eliminating the deep through hole and improving conduction reliability
3Area of stationary object
If the distance between upper electrode and terminal portion is increased to increase light emission area, then brightness increases, but potential difference increases causing non-uniform brightness
Solution Approach 1:
The patent introduces an auxiliary line as an intermediary conductive path between the terminal portion and the upper electrode. This auxiliary line, formed with low-resistance ITO material, acts as a mediator to supply electric potential uniformly across the extended upper electrode area, enabling large light emission area while maintaining brightness uniformity
Solution Approach 2:
The auxiliary line is designed to maintain equipotential conditions across the upper electrode by providing a low-resistance electrical path. This ensures that even when the distance between terminal and upper electrode is increased to expand the light emission area, the potential difference remains minimal, preserving brightness uniformity across the display
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 the uniformity of brightness and reliability of the display device by suppressing voltage drops and preventing conduction failures at through holes, thereby improving image quality and manufacturing efficiency.
Implementation Method 1
an auxiliary electrode which is conductive with the upper electrode extends between the pixels and the pixels, the auxiliary electrode is connected with a current supply line which supplies an electric current to the upper electrode
Implementation Method 2
Formation of auxiliary electrodes above or below the upper electrode using vapor deposition or sputtering
Implementation Method 3
Formation of auxiliary electrodes above or below the upper electrode using vapor deposition or sputtering
Data Source
AI summary
A top-emission-type organic EL display device which exhibits uniform screen brightness is realized by preventing a voltage drop of an upper electrode formed of a transparent conductive film. Pixels each of which is sandwiched between an upper electrode and a lower electrode are arranged in a matrix array to form a display region. An auxiliary electrode extends in the lateral direction between the pixels and the pixels for preventing a voltage drop of the upper electrode. A current supply line which supplies an electric current to the upper electrode and the auxiliary electrodes are made conductive with each other by forming a through hole in an insulation layer. To ensure reliability of connection at the through hole, a contact electrode made of metal which overlaps with the auxiliary electrode is formed on the through hole by vapor deposition.