Si Semiconductor Layer Suppresses DC Afterimage in COA LCD
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Solution Overview
Problem
Conventional liquid crystal display devices with a color filter on the TFT substrate face issues of reduced screen brightness and color shift due to insufficient photoconductivity and wavelength-dependent resistance in the alignment film, leading to DC afterimage and color shifting, especially when the color filter is formed on the side of the backlight.
Innovation Solution
Incorporating a Si semiconductor layer between the pixel electrode and the interlayer insulation film or alignment film on the TFT substrate, which reduces the resistance and allows electric charges to escape independently of the photoconductive effect, preventing color shift and afterimage without altering pixel size or color filter thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a color filter is formed on the TFT substrate (COA system), then manufacturing cost is reduced and screen fineness is improved, but the alignment film receives insufficient light intensity from the backlight causing DC afterimage phenomenon
Solution Approach 1:
A light guide layer is introduced as an intermediary component between the backlight and the alignment film. This light guide layer diffuses and redirects light to increase the intensity of light reaching the alignment film, thereby enabling sufficient photoconductivity to prevent DC afterimage while maintaining the COA configuration
Solution Approach 2:
The optical parameters of the light guide layer are optimized to control light distribution. By adjusting the light guide layer's thickness, refractive index, and scattering properties, the light intensity reaching the alignment film is enhanced without altering the basic COA structure
2Manufacturing precision
If the color filter is formed on the TFT substrate, then positioning accuracy is improved, but the alignment film's photoconductivity is insufficient leading to charge accumulation
Solution Approach 1:
The light guide layer serves as a mediator that compensates for the reduced light intensity caused by the COA configuration, ensuring the alignment film receives adequate light for photoconductivity while maintaining the positioning advantages of COA
3Reliability
If a photoconductive alignment film is used to reduce resistance during operation, then DC afterimage is suppressed, but wavelength-dependent resistance causes color shift in the displayed image
Solution Approach 1:
The spectral distribution of light reaching the alignment film is modified by the light guide layer, which diffuses and redistributes wavelengths more uniformly. This reduces the wavelength-dependent photoconductivity effect that causes color shift while maintaining sufficient overall light intensity for afterimage suppression
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 effectively suppresses DC afterimage and color shift, improving screen brightness and fineness by allowing electric charges to escape early, regardless of backlight intensity, without relying on the photoconductive effect of the alignment film.
Implementation Method 1
Incorporating a Si semiconductor layer between the pixel electrode and the interlayer insulation film or alignment film on the TFT substrate, which reduces the resistance
Implementation Method 2
The electric resistance of the alignment film during operation can be reduced by using a photoconductive material for the alignment film
Data Source
AI summary
In a liquid crystal display device including: TFT substrate; color filter; counter electrode; interlayer insulation film; pixel electrode; alignment film; liquid crystal layer; counter substrate; and Si semiconductor layer. The color filter, counter electrode, interlayer insulation film, pixel electrode, and alignment film being formed on the side where the TFT substrate is provided, the counter substrate being disposed in facing relation to the TFT substrate with the liquid crystal layer put between the counter substrate and TFT substrate, the Si semiconductor layer is formed between the pixel electrode and interlayer insulation film. Even when light from a backlight is absorbed by the color filter and sufficient light cannot reach the alignment film, electric charges accumulated on the alignment film can escape to the pixel electrode in an early stage by the Si semiconductor layer formed under the alignment film, thereby capable of erasing the afterimage in an early stage.