IPS LCD Common Lines Grid Reducing Light Reflection
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Solution Overview
Problem
In active matrix type LCD devices using the In Plane Switching (IPS) mode, the common lines made of metal layers reflect ambient light, leading to glare and a decrease in aperture ratio, while existing solutions to reduce parasitic capacitance increase power consumption.
Innovation Solution
The common lines are formed in a grid-shaped pattern using a combination of a first conductor with low optical reflectivity and a second conductor made of a metal layer, with the first conductor extending in one direction and the metal layer in another, intersecting each other, to reduce reflectivity and maintain low resistance and high aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common lines are made of metal layers, then electrical resistance is reduced, but ambient light reflection increases causing glare
Solution Approach 1:
The common line is segmented into two perpendicular groups: one group made of transparent conductor extending in one direction, and another group made of metal layer extending in the orthogonal direction. This segmentation allows each material to perform its optimal function while combining benefits of both materials.
Solution Approach 2:
Different materials are assigned to different spatial orientations of the common line structure. The transparent conductor is used for lines extending in one direction to minimize reflection, while metal layers are used for lines extending in the orthogonal direction to minimize resistance, creating local optimization in each direction.
2Object-affected harmful factors
If common lines are made of transparent conductors, then ambient light reflection is reduced, but electrical resistance increases
Solution Approach 1:
The common line is segmented into two perpendicular groups: one group made of transparent conductor extending in one direction, and another group made of metal layer extending in the orthogonal direction. This segmentation allows each material to perform its optimal function while combining benefits of both materials.
Solution Approach 2:
The common line structure uses asymmetric material assignment based on direction: transparent conductors for one orientation and metal layers for the perpendicular orientation. This asymmetric design optimizes the overall performance by matching material properties to functional requirements in each direction.
3Reliability
If common lines are overlapped on video signal lines with insulating film, then electric field shielding is improved, but parasitic capacitance increases causing power consumption to rise
Solution Approach 1:
The patent changes the geometric parameters of the common line structure by forming it in a grid pattern with specific pitch relationships. The pitch of common lines is designed to be smaller than or equal to the pitch of pixel electrodes, which optimizes the balance between shielding effectiveness and parasitic capacitance minimization.
4Area of stationary object
If common lines are formed in grid pattern, then aperture ratio is improved, but manufacturing complexity increases
Solution Approach 1:
The common line structure is segmented into two separate orthogonal groups that can be formed in distinct manufacturing steps. This segmentation simplifies the manufacturing process compared to forming a single complex grid pattern, while still achieving the aperture ratio benefits of the grid structure.
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 reduces ambient light reflection, maintains low power consumption by minimizing parasitic capacitance, and enhances the aperture ratio by acting as a light shielding layer without additional light shielding layers, resulting in improved display uniformity and reduced power consumption.
Implementation Method 1
a first group and a second group are crossing each other along video signal lines and scanning signal lines, wherein the first group comprises a first conductor having lower reflectivity against optical light than metal while the second group comprises a second conductor including a metal layer
Implementation Method 2
the common line is overlapped on the video signal line with an insulating film interposed between them so as to shield the electric field of the video signal line
Implementation Method 3
because currents of charge and discharge flow through a parasitic capacitance formed between the video signal line and the common line, its power consumption is increased
Implementation Method 4
The pixel electrode is applied with a desired electric potential so as to generate the lateral electric field for driving the liquid crystal between the pixel electrode and the common electrode
Data Source
AI summary
A liquid crystal display device of IPS mode includes an array of pixels arranged in a matrix pattern by crossing a plurality of video signal lines and a plurality of scanning signal lines each other. Each of the pixels is provided with at least a switching element. A transparent insulating film is provided on both signal lines, and a plurality of pixel electrodes, common electrodes and common lines are provided on the transparent insulating film. The common lines are formed in a grid-shaped pattern such that a first group of the common lines is made of a first conductor having lower reflectivity against optical light than that of metal while a second group of the common lines is made of a second conductor including a metal layer such that said first group and said second group are crossing each other along said video signal lines and said scanning signal lines.