Liquid Crystal Display Vertical Alignment Adhesion
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Solution Overview
Problem
Conventional liquid crystal display devices employing polymer dispersed liquid crystals (PDLC) or polymer network liquid crystals (PNLC) face challenges in maintaining high vertical alignment properties and adhesion between the liquid crystal layer and alignment film, especially under harsh environmental conditions, which affects their transparency and scattering performance.
Innovation Solution
A liquid crystal display device is developed with a liquid crystal layer formed by curing a composition containing a specific polymerizable compound and a liquid crystal alignment film treated with a polymer having a side chain structure, enhancing vertical alignment and adhesion, and using specific compounds and structures to maintain optical properties and adhesion under high temperature and humidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the polymer network is densified to increase adhesion to the liquid crystal alignment film, then adhesion is improved, but the vertical alignment property of the liquid crystal is impaired and optical properties deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters of the polymerizable compound by introducing specific groups (carboxyl, hydroxyl, or amine groups) that can form hydrogen bonds. This parameter change allows the polymer network to achieve both high adhesion and maintain vertical alignment properties, resolving the contradiction between adhesion strength and alignment reliability.
Solution Approach 2:
The patent creates a composite system where the polymer network incorporates functional groups capable of hydrogen bonding with the liquid crystal alignment film. This composite approach combines the structural integrity of the polymer network with the adhesive functionality of hydrogen-bonding groups, achieving both strong adhesion and maintained vertical alignment.
2Reliability
If a highly hydrophobic liquid crystal alignment film is used to achieve vertical alignment, then vertical alignment property is improved, but adhesion between liquid crystal layer and alignment film is reduced
Solution Approach 1:
The patent applies local quality by endowing specific regions of the polymer network (those interfacing with the alignment film) with hydrogen-bonding capability through functional groups. This localized functional differentiation allows the polymer network to maintain hydrophobic character for vertical alignment while creating localized adhesive zones for strong bonding.
Solution Approach 2:
The patent introduces hydrogen-bonding functional groups as intermediary elements between the hydrophobic polymer network and the hydrophobic alignment film. These functional groups act as mediators that can interact with both components, enabling strong adhesion without compromising the vertical alignment function.
3Strength
If polymerizable compound is introduced in large amount to increase adhesion, then adhesion is improved, but vertical alignment property is impaired and optical properties are lowered
Solution Approach 1:
The patent changes the quality parameter of the polymerizable compound from simple hydrophobic character to include hydrogen-bonding functionality. This qualitative change allows achieving high adhesion with smaller amounts of polymerizable compound, thereby maintaining the optical properties and vertical alignment without excessive polymerization that would impair performance.
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 device achieves improved transparency without voltage and scattering with voltage, while maintaining high adhesion and optical properties over time, even in harsh environments.
Implementation Method 1
a liquid crystal composition containing a liquid crystal and a polymerizable compound which undergoes polymerization by ultraviolet rays
Implementation Method 2
a liquid crystal alignment film to vertically align a liquid crystal
Implementation Method 3
the transmission state and the scattering state of the liquid crystal are controlled by application of a voltage
Data Source
AI summary
A liquid crystal display device having excellent liquid crystal vertical alignment properties, good transparency when a voltage is applied and good scattering properties when no voltage is applied, and good adhesion with the liquid crystal layer. The liquid crystal display device has a liquid crystal layer formed by irradiating and curing with ultraviolet rays a liquid crystal composition containing a liquid crystal and a polymerizable compound disposed between a pair of substrates provided with electrodes, and at least one of the substrates is provided with a liquid crystal alignment film to vertically align a liquid crystal. The liquid crystal composition contains a compound represented by the formula [1], and the liquid crystal alignment film is obtained from a liquid crystal alignment treating agent containing a polymer having a side chain structure represented by the formula [2-1] or formula [2-2], and a side chain structure represented by the formula [3].