Liquid Crystal Display Ion Trapping via Third Electrode
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Solution Overview
Problem
Liquid crystal display devices face the issue of ion aggregation in the frame area leading to black stains at the display periphery due to the narrowing frame width, which reduces the effective display area and affects image quality.
Innovation Solution
A liquid crystal display device design featuring a third electrode outside the display area with a concave portion in an organic insulation film, impressed with a voltage lower than the common voltage, to trap and retain positive ions aggregating in the frame area, preventing them from moving back into the display area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the frame width is minimized to maximize display area, then the display area is increased, but ions aggregate in the frame area and move back to the display periphery causing black stains
Solution Approach 1:
A third electrode is introduced as an intermediary element between the display area and the frame area. This electrode is configured to generate an electric field that acts as a barrier, preventing ions aggregated in the frame area from moving back into the display area, thereby eliminating black stains while maintaining minimal frame width
Solution Approach 2:
The organic insulation film is selectively removed only in the frame area where the third electrode is formed, creating a localized structural difference. This local modification allows the third electrode to directly contact the liquid crystal in the frame area, enabling effective ion trapping without affecting the display area structure
2Ease of manufacture
If the third electrode is formed without removing organic insulation film, then manufacturing is simpler, but ions cannot be effectively trapped and black stains occur
Solution Approach 1:
The organic insulation film is selectively removed only in the frame area where the third electrode is formed, creating a localized structural difference. This local modification allows the third electrode to directly contact the liquid crystal in the frame area, enabling effective ion trapping without affecting the display area 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
Effectively prevents the formation of black stains at the display periphery by trapping positive ions outside the display area, thereby maintaining image quality and maximizing the usable display space.
Implementation Method 1
A third electrode is formed outside the display area of the TFT substrate. A concave portion is formed in an organic insulation film on the liquid crystal side of the third electrode.
Implementation Method 2
The display device forms an image suitably controlling the light transmittance of liquid crystal molecules per pixel
Implementation Method 3
Ions move in a particular direction inside a display area of the device and are liable to be localized near the display area periphery
Data Source
AI summary
A liquid crystal display device is configured to prevent the appearance on its display of a black stain stemming from a drop in volume resistivity of liquid crystal caused by ions therein. The device includes a thin-film transistor (TFT) substrate and a counter substrate bonded together along the periphery thereof by a seal material. The TFT substrate and the counter substrate have liquid crystal sandwiched therebetween and include a display region. A third electrode is formed outside the display region of the TFT substrate. A concave portion is formed in an organic insulation film on the liquid crystal side of the third electrode.