Liquid Crystal Display Device Impurity Barrier
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Solution Overview
Problem
Liquid crystal display devices face issues with decreased voltage holding ratio (VHR) and increased ion density, leading to display defects such as white streaks, alignment unevenness, and image sticking, due to impurities in the color filter layer affecting the liquid crystal layer.
Innovation Solution
A liquid crystal display device is designed with a specific liquid crystal composition and color filter using particular dyes and pigments, including diketopyrrolopyrrole pigment and phthalocyanine-based dyes, to prevent these defects by optimizing the interaction between the liquid crystal layer and the color filter layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional color filter layer is used, then the device structure is simple and manufacturing is easy, but impurities from the color filter layer cause display defects such as white streaks, alignment unevenness, and image sticking
Solution Approach 1:
An alignment film is introduced as an intermediary layer between the color filter layer and the liquid crystal layer. This alignment film acts as a barrier that prevents impurities from the color filter layer from directly contacting and affecting the liquid crystal layer, thereby eliminating display defects while maintaining the simplicity of the conventional color filter structure
Solution Approach 2:
The harmful impurities are extracted or isolated from the liquid crystal layer by the alignment film, which selectively allows the alignment function to pass through while blocking the impurity contamination path from the color filter layer
2Reliability
If the transparent electrode thickness is increased to improve electrical conductivity, then electrical conductivity is improved, but the thickness remains limited to 0.5 μm or less which restricts further optimization
Solution Approach 1:
The transparent electrode is constructed as a composite structure combining multiple materials (such as ITO, IZO, or other transparent conductive oxides) with different properties. This composite approach allows optimization of electrical conductivity through material selection and composition ratios while maintaining the thickness within the required 0.5 μm or less constraint
3Reliability
If the alignment film thickness is kept at 0.1 μm or less for proper alignment function, then alignment performance is maintained, but impurities can more easily penetrate through the thin film to affect the liquid crystal layer
Solution Approach 1:
The thickness parameter of the alignment film is optimized to be 0.1 μm or less to maintain proper alignment function, while simultaneously changing the material composition parameter to include impurity-blocking components that provide enhanced barrier properties despite the thin thickness, thus achieving both alignment performance and impurity protection
Data Source
Figure 1~2
AI summary
The present invention relates to a liquid crystal display device including a particular liquid crystal composition and a color filter that uses a particular dye and/or pigment. The present invention provides a liquid crystal display device in which a decrease in the voltage holding ratio (VHR) of a liquid crystal layer and an increase in the ion density (ID) are prevented and problems of display defects such as white streaks, alignment unevenness, and image sticking are overcome. In the liquid crystal display device of the present invention, a decrease in the voltage holding ratio (VHR) of a liquid crystal layer and an increase in the ion density (ID) are prevented and display defects such as image sticking are suppressed. Therefore, the liquid crystal display device is useful for active matrix liquid crystal display apparatuses that use a VA mode or a PSVA mode and can be applied to liquid crystal display apparatuses of liquid crystal televisions, monitors, cellular phones, smart phones, and the like.