Vertical Alignment Film Polymerization for LCD Drop Mark Suppression
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Solution Overview
Problem
Liquid crystal display devices face issues with drop marks and ghosting during production, which affect their performance and quality, particularly in large-screen applications, where conventional methods fail to maintain optimal properties like dielectric anisotropy, viscosity, and response speed.
Innovation Solution
A liquid crystal display device is developed using a specific liquid crystal composition combined with a technique where a polymerizable compound in the vertical alignment film is polymerized by applying an active energy ray while applying a voltage between electrodes, ensuring uniform pretilt angles without foreign contamination, thus reducing drop marks and ghosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reactive monomer is added to a liquid crystal composition for polymer sustained alignment, then uniform pretilt angles and improved transmittance are achieved, but ghosting and display failure occur due to foreign matter contamination
Solution Approach 1:
The invention extracts the polymerizable compound from the liquid crystal composition and places it only in the vertical alignment film. This separation eliminates the foreign matter contamination problem caused by reactive monomers in the liquid crystal composition while maintaining the polymer sustained alignment effect for uniform pretilt angles and improved transmittance.
Solution Approach 2:
The vertical alignment film acts as an intermediary carrier for the polymerizable compound. By incorporating the polymerizable compound into the alignment film rather than the liquid crystal composition, the invention provides a controlled environment that enables polymerization without contamination, thus achieving uniform pretilt angles without ghosting or display failure.
2Ease of manufacture
If conventional alignment film materials are used, then easy manufacture is achieved, but drop marks occur during production
Solution Approach 1:
The invention changes the chemical parameter of the alignment film by incorporating a polymerizable compound that can undergo photopolymerization. This parameter change enables the formation of a crosslinked polymer structure that prevents liquid crystal composition adhesion during production, thereby eliminating drop marks while maintaining ease of manufacture through conventional alignment film application processes.
3Adaptability or versatility
If liquid crystal molecules are remote from projecting structures, then viewing angle characteristics are improved, but response speed decreases
Solution Approach 1:
The invention enables the liquid crystal molecules to self-align uniformly through the polymer sustained alignment effect created by the polymerizable compound in the vertical alignment film. This self-service mechanism provides uniform pretilt angles throughout the cell without requiring projecting structures, allowing molecules remote from any structures to maintain both improved viewing angle characteristics and fast response speed.
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 suppresses drop marks and ghosting, maintaining high response speed and optimal properties, making it suitable for large-screen liquid crystal TVs and monitors.
Implementation Method 1
a polymerizable liquid crystal that exhibits reactivity when irradiated with ultraviolet light is used instead of conventional alignment film materials such as polyimide
Implementation Method 2
a one-drop-fill (ODF)-type production method has become the mainstream technology for producing large panels
Data Source
AI summary
Provided are a liquid crystal display device that suppresses occurrence of drop marks during production without degrading various properties, such as dielectric anisotropy, viscosity, nematic phase upper limit temperature, rotational viscosity (γ1), and ghosting property, and a method for producing the liquid crystal display device.A liquid crystal display device 10 of the present invention includes a liquid crystal composition layer 13 sandwiched between a first substrate 11 and a second substrate 12 and vertical alignment films 16 and 17 formed of a cured product of a polymerizable liquid crystal compound. The liquid crystal composition constituting the liquid crystal composition layer 13 contains compounds represented by general formulae (I) and (II).