Display Device Luminance Measurement Threshold Voltage Stabilization
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Solution Overview
Problem
The reliability of luminance measurement in display devices with drive transistors, such as organic EL displays, is compromised by the light-emitting state immediately before measurement and the timing of measurement, leading to inconsistent data due to threshold voltage shifts in drive transistors.
Innovation Solution
A method involving placing the display device in a light-emitting state, then a non-light-emitting state for a predetermined period to allow current and threshold voltage recovery, followed by re-measuring luminance to minimize the effects of previous light-emitting states and timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If luminance measurement is performed immediately after the light-emitting state, then measurement timing is efficient, but measurement reliability deteriorates due to threshold voltage shifts
Solution Approach 1:
The patent applies preliminary action by performing a recovery operation (placing the display device in a non-light-emitting state for a predetermined period) before the luminance measurement. This recovery period allows the drive transistor's threshold voltage to stabilize, ensuring that the subsequent measurement is not affected by previous light-emitting states. The predetermined period is set based on the time required for the threshold voltage to return to its initial value, thereby eliminating measurement errors caused by residual effects from prior operation.
2Productivity
If the display device remains in the light-emitting state continuously, then productivity is maintained, but measurement accuracy deteriorates due to light-emitting state effects
Solution Approach 1:
The patent implements periodic action by introducing a structured cycle of light-emitting state followed by a non-light-emitting recovery state before measurement. This periodic switching ensures that the drive transistor has sufficient time to reset its threshold voltage, eliminating the cumulative effects of continuous operation. The cycle is designed with a predetermined recovery period that is optimized to balance measurement accuracy with overall measurement throughput, allowing reliable measurements to be taken at regular intervals without requiring prolonged continuous operation.
Data Source
AI summary
A method for manufacturing a display device including a light-emitting pixel and a drive transistor that drives the light-emitting pixel using current, includes: (a) placing the display device in a light-emitting state; (b) placing the display device in a no-light-emitting state after (a); (c) leaving the display device in the non-light-emitting state for a predetermined period; (d) placing the display device in the light-emitting state again after (c); and (e) start measuring luminance of the display device at a start of (d).