In-Plane Switching LCD Aperture Ratio and Parasitic Capacitance
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Solution Overview
Problem
In-plane switching liquid crystal display devices face challenges in achieving high light transmittance and aperture ratio due to parasitic capacitance and damage to data lines, particularly in horizontal electric field type LCDs, which also have lower aperture ratios and are prone to parasitic capacitance issues.
Innovation Solution
The solution involves minimizing the marginal area between data lines and pixel electrodes by shielding data lines with a common electrode and reducing parasitic capacitance using a low dielectric additional insulating layer, such as photoacryl, and protecting copper data lines with a protective metal layer like molybdenum, titanium, or chromium to enhance light transmittance and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a horizontal electric field type LCD structure is used to achieve wider view angle, then view angle is improved, but aperture ratio deteriorates
Solution Approach 1:
The patent transitions from conventional planar electrode arrangements to a three-dimensional stacked structure where pixel electrodes and common electrodes are positioned at different vertical levels. This dimensional change allows the electrodes to overlap in the vertical direction while maintaining horizontal separation, effectively increasing the aperture ratio without compromising the wide view angle characteristics of IPS mode.
Solution Approach 2:
The patent divides the electrode structure into multiple segments: pixel electrodes on the lower substrate, spacers for vertical separation, and common electrodes on the upper substrate. This segmentation allows independent optimization of each electrode's function and position, enabling the overlapping configuration that increases aperture ratio while maintaining IPS mode operation.
2Device complexity
If data line and common electrode are placed close to each other to reduce manufacturing complexity, then device complexity is reduced, but parasitic capacitance increases
Solution Approach 1:
The patent introduces an insulating layer as an intermediary substance between the data line and the common electrode. This insulating layer acts as a mediator that allows the data line and common electrode to be positioned close together for manufacturing simplicity while preventing direct electrical interaction, thereby reducing parasitic capacitance.
Solution Approach 2:
The patent extracts the electrical isolation function from the physical distance requirement. Instead of relying solely on large spacing between data lines and common electrodes, the design extracts the isolation function into a dedicated insulating layer material, allowing closer positioning while maintaining electrical independence.
3Object-generated harmful factors
If additional insulating layer with low dielectric property is inserted to reduce parasitic capacitance, then parasitic capacitance is reduced, but data line material may be damaged
Solution Approach 1:
The patent applies a protective metal layer beforehand on the data line surface before depositing the additional insulating layer. This protective layer serves as a cushioning barrier that prevents direct contact between the insulating layer materials and the copper data line, preventing potential damage while allowing the insulating layer to provide parasitic capacitance reduction.
Solution Approach 2:
The patent creates a composite structure with multiple layers: copper data line core, protective metal layer coating, and additional insulating layer. This composite material approach combines the electrical conductivity of copper with the protective properties of the metal layer and the electrical isolation properties of the insulating layer, achieving both parasitic capacitance reduction and data line protection.
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 approach results in a high light transmittance in-plane switching liquid crystal display device with improved aperture ratio, reduced parasitic capacitance, and extended service life by preventing data line damage, enabling larger and higher definition display panels with simplified manufacturing processes.
Implementation Method 1
inserting an additional insulating layer having the low dielectric property between the data line and the common electrode
Implementation Method 2
shielding the data line with the common electrode to enhance the aperture ratio
Implementation Method 3
the data line material is prevented from being damaged by the additional insulating layer having a low dielectric material
Data Source
AI summary
The present disclosure relates to a high light transmittance in-plan switching liquid crystal display device and a method for manufacturing the same. The liquid crystal display device includes: a substrate; a gate line disposed in horizontal direction on the substrate; a gate insulating layer covering the gate line; a data line disposed in vertical direction on the gate insulating layer; an additional insulating layer on the data line having same size and shape with the data line; a passivation layer covering the additional insulating layer; and a common electrode overlapping with the data line on the passivation layer. According to the present disclosure, the failure due to the parasitic capacitance and the load for driving the display panel are reduced and it is possible to make large and high definition display panel.