LCD Aligning Member Parallel to Data Lines
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Solution Overview
Problem
Conventional liquid crystal displays (LCDs) face issues with luminance discontinuity and stitch defects due to inaccuracies in the step-and-repeat exposure process, leading to parasitic capacitance differences between signal lines and pixel electrodes, which affect the viewing angle and contrast ratio.
Innovation Solution
A thin film transistor array panel design that includes a first and second signal line, a thin film transistor, and a pixel electrode connected to the transistor, with an aligning member extending parallel to the second signal line and closer to the pixel electrode, along with a common electrode and a liquid crystal layer, which determines the tilt directions of liquid crystal molecules for improved viewing angles and contrast ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the step-and-repeat exposure process is used for large active areas, then the exposure can be completed in divisional shots, but the shots are not aligned accurately causing luminance discontinuity and stitch defects
Solution Approach 1:
The exposure process is divided into multiple shots that are sequentially written across the large active area. Each shot is exposed independently and then the mask is stepped to the next position. This segmentation allows large areas to be exposed with standard-sized masks while maintaining acceptable alignment through careful positioning between shots.
Solution Approach 2:
Overlapping regions are designed into the exposure pattern where adjacent shots overlap by a certain margin. This preliminary overlapping structure ensures that even if alignment is not perfect, the overlapping regions provide a buffer zone that reduces the visibility of stitch defects and luminance discontinuities at boundaries.
2Adaptability or versatility
If cutouts and protrusions are used to determine LC molecule tilt directions, then the reference viewing angle is widened, but the device complexity increases
Solution Approach 1:
The pixel electrode is divided into multiple regions with different local structures. Cutouts are created in specific areas while protrusions are formed in other areas, each serving to control LC molecule tilt directions in their respective local regions. This local differentiation allows multiple tilt directions to be achieved within a single pixel, widening the reference viewing angle while keeping the overall structure manageable.
3Illumination intensity
If a normally black mode is employed to obtain high contrast ratio, then the contrast ratio is improved, but the lateral visibility decreases causing the displayed image to look brighter and whiter at the sides
Solution Approach 1:
The alignment structure introduces asymmetric control over LC molecule orientations. By creating specific asymmetric patterns of cutouts and protrusions, or by using asymmetric alignment layers, the LC molecules are induced to tilt in preferred directions that compensate for the viewing angle limitations of normally black mode. This asymmetric molecular arrangement helps maintain contrast ratio while improving lateral visibility.
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 design enhances the uniformity of parasitic capacitance and reduces stitch defects, thereby improving the viewing angle and contrast ratio of LCDs, maintaining high contrast and luminance consistency across the display.
Implementation Method 1
an aligning member extending substantially parallel to the second signal line and having an edge closer to the pixel electrode than the second signal line
Implementation Method 2
applying voltages to the field-generating electrodes to generate an electric field in the LC layer, which determines orientations of LC molecules in the LC layer to adjust polarization of incident light
Data Source
AI summary
A liquid crystal display is provided, which includes: a substrate; a field-generating electrode formed on the substrate; and a slope member formed on the substrate and having an inclination angle smaller than about 45 degrees.