Sub-Pixel Hold Capacitor Layout for Mura-Resistant Displays
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Solution Overview
Problem
Unintended capacitance variations in sub-pixels of the same color lead to mura on the display screen, deteriorating visibility and display quality.
Innovation Solution
A display device design with specific capacitance configurations, including a first and second DC line, and storage capacitors, to equalize the sum of hold capacitances across sub-pixels of the same color, ensuring uniform capacitance distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional capacitance configuration is used in sub-pixels, then device complexity is reduced, but capacitance uniformity deteriorates causing mura on display screen
Solution Approach 1:
The hold capacitor is divided into two separate capacitors: a first hold capacitor connected to the first DC line and a second hold capacitor connected to the second DC line. This segmentation allows independent control and optimization of capacitance values for different sub-pixel types, ensuring that the sum of hold capacitances is equal across all sub-pixels of the same color while accommodating different electrical characteristics of different sub-pixel configurations.
Solution Approach 2:
Different sub-pixel types (e.g., red, green, blue sub-pixels) are assigned different individual capacitance values based on their specific electrical characteristics and color requirements. The first hold capacitor and second hold capacitor provide localized capacitance compensation tailored to each sub-pixel type, ensuring uniform display quality across the screen while allowing local optimization for each color channel.
2Reliability
If hold capacitance is not equalized across sub-pixels of the same color, then device complexity is reduced, but display quality deteriorates due to mura occurrence
Solution Approach 1:
The patent ensures that the sum of hold capacitances (first hold capacitor + second hold capacitor) is equalized across all sub-pixels of the same color. This equipotentiality approach compensates for differences in individual capacitor values by balancing the total capacitance, thereby eliminating potential differences in electrical characteristics that cause mura effects and ensuring uniform display quality across the screen.
Solution Approach 2:
The patent optimizes the individual capacitance values of the first and second hold capacitors based on the specific electrical characteristics of different sub-pixel types. By adjusting these parameters (capacitance values) while maintaining the constraint that their sum is equal across sub-pixels of the same color, the patent achieves reliable display quality while accommodating variations in sub-pixel configurations.
Data Source
AI summary
A display device includes: pixels each including sub-pixels; and a first and second DC lines. Each of the sub-pixels includes: a light emitting element; and a sub-pixel circuit connected to the light emitting element and the first and second DC lines. The sub-pixel circuit includes: a first transistor, where a gate electrode of the first transistor is connected to a first node and one electrode of the first transistor is connected to a second node; a storage capacitor connected between the first node and the second node; a first hold capacitor forming a first hold capacitance between the second node and the first DC line; and a second hold capacitor forming a second hold capacitance between the second node and the second DC line. In sub-pixels which provide light of a same color, a sum of the first capacitance is equal to a sum of the second hold capacitance.