Liquid Crystal Display Color Filter Slope Parameter Control
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Solution Overview
Problem
Liquid crystal display devices face issues with display defects such as white streaks, variations in alignment, and image sticking due to impurities in the liquid crystal layer, primarily caused by organic pigments in the color filter layer, which affect the voltage holding ratio and ion density.
Innovation Solution
A liquid crystal display device incorporating a specific liquid crystal composition and a color filter with a particular slope parameter, as determined by ultra-small angle X-ray scattering analysis, to control the aggregation of organic pigments and minimize impurity migration, thereby preventing decreases in voltage holding ratio and increases in ion density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the color filter layer is made thin to reduce impurity migration, then the electrical conductivity is improved, but the color filtering performance deteriorates
Solution Approach 1:
A resin layer is introduced as an intermediary barrier between the color filter layer and the liquid crystal layer. This resin layer prevents impurity migration from the color filter to the liquid crystal while maintaining electrical conductivity through the transparent electrode. The resin layer acts as a protective mediator that blocks the harmful impurity transport path without compromising the overall device performance.
Solution Approach 2:
The patent specifies particular parameters for the resin layer including thickness (50-200 nm), refractive index (1.4-1.6), and chemical composition (containing fluorine atoms). By controlling these parameters, the resin layer effectively blocks impurity migration while maintaining optical transparency and electrical conductivity properties of the display device.
2Reliability
If the transparent electrode is made thick to enhance electrical conductivity, then the electrical properties are improved, but the separation between color filter and liquid crystal layers is reduced
Solution Approach 1:
The resin layer serves as an intermediary barrier that compensates for the reduced separation distance caused by thicker transparent electrodes. It provides an additional protective layer that prevents impurity migration from reaching the liquid crystal, thereby maintaining device reliability even when the transparent electrode thickness is increased for better conductivity.
Solution Approach 2:
The patent employs a composite structure combining the transparent electrode material (such as ITO) with a resin layer having specific chemical composition (containing fluorine atoms). This composite structure leverages the electrical conductivity of the transparent electrode while the resin component provides impurity blocking functionality, achieving both electrical performance and reliability.
3Ease of manufacture
If conventional pigment purification methods are used, then the manufacturing process is simple, but display defects such as white streaks and image sticking occur
Solution Approach 1:
The resin layer acts as a protective intermediary that prevents impurities from conventional pigments from migrating to the liquid crystal layer. This allows the use of pigments with standard purification levels while still achieving high display quality, thereby maintaining ease of manufacture without sacrificing reliability.
Solution Approach 2:
Instead of requiring extremely pure pigments that would complicate manufacturing, the patent converts the potential harm of impurity migration into a benefit by using the resin layer as a barrier. The impurities remain in the color filter layer where they cannot harm the liquid crystal, effectively converting the manufacturing simplicity into a viable solution for preventing display defects.
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
The solution effectively prevents display defects like white streaks and image sticking by maintaining a stable voltage holding ratio and low ion density, ensuring improved display performance.
Implementation Method 1
a particular slope parameter which indicates a degree of aggregation of an organic pigment in a color filter, is 2 or less
Data Source
AI summary
There is provided a liquid crystal display device that includes a liquid crystal composition and a color filter having a particular slope parameter that indicates the degree of aggregation of an organic pigment. The liquid crystal display device prevents a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in a liquid crystal layer and resolves the problems of display defects, such as white streaks, variations in alignment, and image sticking. The liquid crystal display device prevents a decrease in the voltage holding ratio (VHR) and an increase in the ion density (ID) in a liquid crystal layer and suppressing display defects such as image sticking. Therefore, the liquid crystal display device is useful for active matrix driving liquid crystal display devices with an IPS mode or an FFS mode and can be applied to liquid crystal display devices.