Mother Substrate Compensating Unit for OLED Sheet Testing
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Solution Overview
Problem
The existing methods for testing organic light emitting displays on a mother substrate suffer from brightness variation and inefficient testing due to unaccounted threshold voltage variations in driving transistors, leading to incorrect test results and non-uniform aging during sheet unit tests.
Innovation Solution
A mother substrate design with a compensating unit that subtracts threshold voltage from sheet unit test signals before transmission to the panels, using transistors and capacitors to ensure uniform voltage distribution across the panels, thereby preventing brightness variation and improving the accuracy of sheet unit tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sheet unit testing is performed without compensating for threshold voltage variations, then testing efficiency is improved by testing multiple panels simultaneously, but brightness variation occurs and measurement precision deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the test signal voltage level to compensate for threshold voltage variations in driving transistors. The compensating unit calculates the threshold voltage of each driving transistor and modifies the test signal parameters accordingly, ensuring that the gate-source voltage remains consistent across different panels despite manufacturing variations. This resolves the contradiction by maintaining measurement precision while preserving the high productivity of sheet unit testing.
2Measurement precision
If panel unit testing is performed on each separated panel, then measurement precision is maintained, but productivity deteriorates due to separate testing of each panel
Solution Approach 1:
The patent merges multiple panel testing operations into a single sheet unit test by providing a shared compensating unit that serves all panels simultaneously. The compensating unit receives a single test signal and distributes compensated signals to multiple panels through wiring lines, combining the precision of individual panel testing with the efficiency of batch processing. This eliminates the need for separate testing of each panel while maintaining test accuracy.
3Measurement precision
If a compensating unit is added to subtract threshold voltage from test signals, then brightness variation is reduced and measurement precision is improved, but device complexity increases
Solution Approach 1:
The compensating unit is designed with multi-functionality to reduce overall device complexity. It serves multiple purposes: calculating threshold voltages of driving transistors, generating compensated test signals, and distributing these signals to multiple panels simultaneously. By consolidating these functions into a single unit that serves the entire sheet, the patent minimizes the number of additional components required while achieving precise compensation across all panels.
Data Source
AI summary
A mother substrate including a plurality of organic light emitting display panels that include pixel circuits having a simple structure, is designed so that a sheet unit test may be performed while preventing or reducing brightness variation during sheet unit test, and a sheet unit test method for the mother substrate. The mother substrate also includes first and second wiring line groups and a compensating unit. The compensating unit is coupled to a coupling line for coupling a wiring line from among the first and second wiring line groups for transmitting a sheet unit test signal to the panels. The compensating unit is also for subtracting a voltage corresponding to a threshold voltage of a driving transistor included in a pixel of the panels from the sheet unit test signal before transmitting the sheet unit test signal to the panels.