OLED Light-Emitting Device Group Segmentation for Wiring Resistance
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Solution Overview
Problem
In organic light-emitting diode (OLED) print heads, light quantity unevenness among multiple OLEDs occurs due to wiring resistance, affecting image quality and increasing circuit and chip size with existing solutions.
Innovation Solution
A light-emitting device configuration with multiple groups of transistors and OLEDs, where a light-emitting element from a second group is arranged between those of the first group, and a current mirror circuit with reference voltage and constant current source to control current flow, reducing the impact of wiring fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a common power source line is used to supply current to multiple OLEDs, then wiring resistance causes variation in light emission quantity among OLEDs, but adding adjustment circuits increases circuit scale and chip size
Solution Approach 1:
The patent segments the light-emitting element array into multiple groups (first group, second group, etc.), each controlled by independent control transistors (first group control transistor, second group control transistor). This segmentation allows independent current control for each group, compensating for wiring resistance variations without requiring complex adjustment circuits for each individual element.
Solution Approach 2:
The patent applies local quality control by introducing group-specific control transistors that adjust current distribution locally within each group. The control transistors are positioned at different locations to account for local wiring resistance variations, enabling targeted compensation without global circuit complexity.
2Manufacturing precision
If control circuits are added to each light-emitting element to correct light quantity differences, then light quantity unevenness is suppressed, but chip size increases
Solution Approach 1:
Instead of controlling each light-emitting element individually, the patent segments elements into groups and controls each group with a dedicated control transistor. This reduces the number of control elements from N (for N elements) to sqrt(N) or log(N) groups, significantly reducing chip area while maintaining uniformity.
Solution Approach 2:
The patent merges multiple light-emitting elements into groups that share common control transistors and power source lines. By combining elements into manageable groups, the circuit scale is reduced while still achieving sufficient light quantity uniformity through group-level control.
3Reliability
If more contact points are arranged on power source lines to supply reference potential, then fluctuation in light quantity is suppressed, but circuit complexity increases
Solution Approach 1:
The patent places control transistors at specific locations along the power source lines to locally adjust current distribution. This local control approach suppresses light quantity fluctuation caused by wiring resistance without requiring multiple contact points throughout the entire line, thereby limiting circuit complexity.
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 configuration minimizes light quantity unevenness and image quality degradation by equalizing current flow through groups, reducing visibility of density unevenness in images without increasing circuit complexity.
Implementation Method 1
The OLED is a light-emitting element of a current driving type
Implementation Method 2
transistors arranged corresponding to the plurality of light-emitting elements, respectively and configured to supply current to the plurality of light-emitting elements
Data Source
AI summary
A plurality of groups are arranged in a light emitting device. Each of the groups includes a plurality of light-emitting elements, a plurality of transistors arranged corresponding to the plurality of light-emitting elements and configured to supply current to the plurality of light-emitting elements, and a group control transistor configured to control current flowing through the plurality of transistors. The plurality of groups have a first group and a second group. The first group has a plurality of light-emitting elements. The second group has a plurality of light-emitting elements. A light-emitting element of the second group is arranged between one light-emitting element of the first group and the other light-emitting element of the first group.