Oxide Semiconductor Pixel Electrode Overlap for Voltage Stability
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Solution Overview
Problem
Display devices using amorphous silicon or polysilicon transistors face challenges in achieving multi-gray scale display due to voltage fluctuations caused by off-state current, which affect the accuracy and quality of grayscale representation.
Innovation Solution
A display device incorporating a transistor with an oxide semiconductor that has an off-state current of 100 aA/μm or less, where the pixel electrode overlaps with source and gate signal lines, reducing voltage fluctuations and parasitic capacitance to enable high-quality multi-gray scale display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transistor with amorphous silicon or polysilicon is used, then the device can be manufactured with conventional processes, but voltage fluctuation occurs due to off-state current which prevents multi-gray scale display
Solution Approach 1:
The patent changes the material parameter of the transistor from amorphous silicon or polysilicon to oxide semiconductor, which fundamentally alters the off-state current characteristic from 10^-13 A to 10^-18 A or lower. This parameter change enables voltage stability sufficient for multi-gray scale display while maintaining compatibility with conventional manufacturing processes through sputtering and other standard techniques.
2Measurement precision
If the number of gray scales is increased to 1024, then display quality improves, but voltage fluctuation of 16.6 mV corresponds to approximately 4 gray scales making the effect of off-state current不可忽略
Solution Approach 1:
By changing the transistor material to oxide semiconductor, the off-state current is reduced to 10^-18 A or lower, which suppresses voltage fluctuation to levels that do not affect grayscale precision. This enables 1024 gray scales to be displayed with high quality without significant voltage drop.
3Object-affected harmful factors
If the pixel electrode overlaps with source signal lines to reduce parasitic capacitance, then crosstalk is suppressed, but the overlapped area must be precisely controlled to maintain symmetry
Solution Approach 1:
The patent intentionally introduces asymmetry by adding dummy electrodes to one of the source signal lines to compensate for unequal overlapping areas. This asymmetric compensation approach achieves symmetry in total capacitance, suppressing crosstalk while being tolerant to manufacturing variations in the main pixel electrode overlapping.
4Reliability
If the off-state current is reduced to enable multi-gray scale display, then voltage fluctuation decreases, but the transistor material becomes more difficult to manufacture with conventional processes
Solution Approach 1:
The patent changes the material parameter to oxide semiconductor which can be manufactured using conventional sputtering processes and other standard semiconductor fabrication techniques. This parameter change achieves ultra-low off-state current (10^-18 A or lower) while maintaining ease of manufacture through established industrial processes.
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
The solution effectively reduces voltage fluctuations, allowing for precise grayscale representation and suppressing crosstalk, thereby enhancing the display quality and capability to handle increased gray scale levels without significant voltage drop.
Implementation Method 1
A display device includes a plurality of source signal lines, a plurality of gate signal lines which is provided so as to intersect with the source signal lines, and a pixel electrode to which a signal voltage of the source signal line is applied through a transistor including an oxide semiconductor
Implementation Method 2
in the pixel electrode which is provided between a pair of the adjacent source signal lines, edge portions thereof overlap with edge portions of the source signal lines and an overlapped area with one of the source signal lines is substantially equal to an overlapped area with the other source signal line
Data Source
AI summary
To provide a display device which can realize multi-gray scale display by reducing voltage fluctuation of a pixel, a display device includes a plurality of source signal lines, a plurality of gate signal lines which is provided so as to intersect with the source signal lines, and a pixel electrode to which a signal voltage of the source signal line is applied through a transistor including an oxide semiconductor, which is provided near an intersection portion of the source signal line and the gate signal line; in which in the pixel electrode which is provided between a pair of the adjacent source signal lines, edge portions thereof overlap with edge portions of the source signal lines and an overlapped area with one of the source signal lines is substantially equal to an overlapped area with the other source signal line.