White Pixel Transistor Channel Width for Display Luminance Matching
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Solution Overview
Problem
Display apparatuses with unit pixels composed of red, green, and blue pixels often suffer from color irregularity due to differences in luminance when producing white light, as the white light from mixing these colors can have varying luminance compared to the white light emitted by a white pixel, leading to inconsistent image display.
Innovation Solution
Incorporating a white pixel with a second thin film transistor and pixel electrode, where the channel area of the second thin film transistor has a larger electric resistance and a different current flow direction than the first thin film transistor, allowing the white pixel to output a second white light with the same gray scale and luminance as the mixed white light from the color pixels, by reducing the on-current of the second thin film transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If white light is produced by mixing light from red, green, and blue pixels, then the display can achieve white light output, but the luminance of the mixed white light differs from the white light produced by a white pixel, causing color irregularity
Solution Approach 1:
The patent adjusts the channel width of the thin film transistor in the white pixel to control the current magnitude. By changing the transistor parameter (channel width), the white pixel's light output is regulated to match the luminance of the mixed white light from color pixels, resolving the luminance inconsistency issue.
2Device complexity
If the white pixel uses the same current magnitude as color pixels, then the transistor design is simplified, but the luminance of white light from the white pixel becomes inconsistent with mixed white light from color pixels
Solution Approach 1:
The patent applies different design parameters to different pixel types within the same display. The white pixel's transistor has a different channel width specifically tailored to its function, while color pixels use standard transistor designs. This localized differentiation allows each pixel type to optimize its performance for its specific purpose.
3Illumination intensity
If the channel area of the second thin film transistor has larger electric resistance, then the white pixel can output white light with matching luminance to mixed white light, but the current control becomes more challenging
Solution Approach 1:
Instead of adjusting current control complexity, the patent changes the physical parameter of the transistor (channel width) to inherently control the current magnitude. This parameter change simplifies the overall design by built-in current regulation through geometry rather than complex control circuits.
Data Source
AI summary
A display apparatus includes a first substrate and a second substrate opposite to the first substrate. The first substrate includes a plurality of color pixels and a white pixel that outputs a second white light having a same gray scale as a first white light formed by mixing light outputted from the plurality of color pixel. The white pixel is activated by a second current that is lower than a first current that activates the color pixels.