OLED Holding Capacitor Layout for Crosstalk Reduction
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Solution Overview
Problem
Display apparatuses with small pixel pitches face challenges in providing sufficient holding capacitors for data lines, leading to vertical crosstalk due to the difficulty in forming holding capacitors within the limited pixel pitch, especially in micro displays like electronic viewfinders and head-mounted displays.
Innovation Solution
The solution involves arranging N first holding capacitors in the column direction with electrode widths smaller than the total width of N adjacent pixel circuits, allowing for reduced length and increased capacitance, along with additional transistors for capacitance dividing and simultaneous writing of gradation voltages to reduce crosstalk, and incorporating second holding capacitors with transfer gates for further capacitance enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If holding capacitors are formed within the pixel pitch to enable capacitance dividing drive, then vertical crosstalk can be reduced, but in micro displays with small pixel pitch (2.5 μm), it becomes impossible to provide sufficient holding capacitors
Solution Approach 1:
The patent moves the holding capacitor formation from the planar pixel pitch constraint into the vertical dimension by using multiple data lines extending in the column direction. Each data line has its own holding capacitor formed in the column direction, effectively utilizing the vertical space outside the pixel pitch boundary. This dimensional transition allows sufficient holding capacitor area even in micro displays with small pixel pitches.
Solution Approach 2:
The patent segments the holding capacitor function across multiple data lines rather than concentrating it within a single pixel. Each data line is assigned its own holding capacitor, and the capacitors are arranged in the column direction. This segmentation distributes the capacitance requirement across multiple locations, making it feasible to provide sufficient total capacitance without increasing the pixel pitch.
2Length of stationary object
If the electrode width of first holding capacitors is made smaller than the total width of N adjacent pixel circuits, then the length in column direction can be reduced, but it becomes difficult to ensure sufficient electrode width within one pixel circuit
Solution Approach 1:
The patent merges the holding capacitor electrodes across N adjacent pixel circuits by positioning them in the column direction. The electrodes extend vertically through multiple pixel rows, effectively combining the width contribution from N pixel circuits into a single continuous electrode structure. This merging allows the total electrode width to be sufficient while keeping the length in the column direction manageable.
Solution Approach 2:
The patent resolves the electrode width limitation by transitioning from a horizontal electrode arrangement within a single pixel to a vertical arrangement spanning multiple pixels in the column direction. This dimensional change allows the electrode to accumulate sufficient width from multiple pixel circuits while maintaining a compact footprint in the column direction.
3Reliability
If additional transistors are added for capacitance dividing drive, then voltage amplitude in data lines can be compressed, but device complexity increases
Solution Approach 1:
The patent designs the additional transistors (second and third transistors) to serve multiple functions: the second transistor controls the connection between data lines and pixel transistor gates, while the third transistor controls the connection between gates and drains. These transistors enable both the capacitance dividing drive for crosstalk reduction and the necessary voltage level shifting, making them multi-functional components that justify their addition.
Solution Approach 2:
The patent uses the additional transistors to dynamically change the electrical parameters of the data line connections. By controlling the on/off states of the second and third transistors, the system can switch between different connection configurations, enabling capacitance dividing drive to compress voltage amplitude and reduce crosstalk while maintaining control flexibility.
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 ensures sufficient capacitance while minimizing space and reducing crosstalk, enabling effective voltage shifting and gradation voltage writing, even in densely packed pixel arrays, thereby improving display performance in micro displays.
Implementation Method 1
first holding capacitors that are respectively inserted and connected midway on the plurality of data lines, and shift levels of driving voltages of the first transistors; and holding capacitors that respectively hold potentials of the plurality of data lines
Implementation Method 2
Display apparatuses using light-emitting elements such as organic light-emitting diode (OLED) elements
Data Source
AI summary
A plurality of pixel circuits provided in a display apparatus respectively include light-emitting elements OLED, first transistors that supply driving currents to the light-emitting elements, second transistors that turn on and off connection between data lines and gates of the first transistors, and third transistors. The display apparatus has first holding capacitors that are spectively inserted and connected midway on the plurality of data lines and shift levels of driving voltages of the first transistors, and holding capacitors that respectively hold potentials of the plurality of data lines. N first holding capacitors are arranged in a column direction Y, each of the first holding capacitors having an electrode width that is smaller than a width of N pixel circuits arranged adjacent to each other in a row direction X, and that is equal to or larger than a width of one pixel circuit.