Liquid Crystal Display Light-Shielding and Spacer Arrangement
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Solution Overview
Problem
The aperture ratio of liquid crystal display devices equipped with oxide semiconductor TFTs is limited due to light irradiation-induced deterioration of TFT characteristics, particularly the threshold voltage shift, which is exacerbated by the black matrix regions overlapping the TFTs, hindering further improvements in display performance.
Innovation Solution
The liquid crystal display device incorporates a specific arrangement of columnar spacers and light-shielding layers, where the second TFT light-shielding portion has a larger area and is provided every n rows, overlapping only the channel region of the TFTs in certain pixel columns, while the first TFT light-shielding portion is smaller and does not overlap with columnar spacers, optimizing the aperture ratio without compromising TFT reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light-shielding portions are added to protect oxide semiconductor TFTs from light irradiation, then TFT reliability is improved, but aperture ratio deteriorates
Solution Approach 1:
The patent applies different light-shielding strategies to different pixel columns: blue pixel columns receive protection from light irradiation through light-shielding portions, while red and green pixel columns do not require such protection. This localized approach protects vulnerable TFTs without unnecessarily reducing aperture ratio in other pixel types, thereby resolving the contradiction between reliability improvement and aperture ratio maintenance.
2Area of stationary object
If the area of light-shielding portions is reduced to improve aperture ratio, then aperture ratio is improved, but TFT characteristics deteriorate due to light irradiation
Solution Approach 1:
The invention selectively applies light-shielding portions only where necessary (blue pixel columns with oxide semiconductor TFTs) while leaving other areas (red and green pixel columns) without light-shielding portions. This targeted approach minimizes the total light-shielding area to preserve aperture ratio while still protecting vulnerable TFTs from light-induced characteristic deterioration.
3Reliability
If uniform light-shielding is applied to all pixel columns, then TFT protection is improved, but aperture ratio and display uniformity deteriorate
Solution Approach 1:
The patent implements non-uniform light-shielding by providing light-shielding portions only in blue pixel columns while omitting them from red and green pixel columns. This selective approach prevents chromaticity deviation and maintains display uniformity across different color regions, while still providing necessary protection to oxide semiconductor TFTs in blue pixels where it is most critical.
Solution Approach 2:
The invention introduces asymmetry in the light-shielding layer configuration by differentiating between blue pixel columns (with light-shielding portions) and red/green pixel columns (without light-shielding portions). This asymmetric design optimizes both TFT protection and display uniformity by matching the light-shielding strategy to the specific requirements of each pixel type rather than applying a uniform approach.
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 arrangement enhances the aperture ratio of liquid crystal display devices while suppressing chromaticity deviation, ensuring reliable TFT performance even with typical backlights, and allows for uniform aperture ratios across different pixel types.
Implementation Method 1
the light-shielding layer includes a first TFT light-shielding portion that shields at least the channel region of the TFT from light
Data Source
AI summary
A first substrate (10) of a liquid crystal display device (100) includes a TFT (2) that includes an oxide semiconductor layer (2a). A second substrate (20) includes a color filter layer (22) and a light-shielding layer (21). The light-shielding layer has a first TFT light-shielding portion (21t1) for each row in at least a blue pixel column, and a second TFT light-shielding portion (21t2) every n rows (n represents an integer of 2 or more) in a pixel column in which at least one type of color filter other than blue color filters is provided, the second TFT light-shielding portion having a larger area than the first TFT light-shielding portion. A columnar spacer (40) is arranged so as not to overlap the first TFT light-shielding portion but to overlap the second TFT light-shielding portion.