Photopolymerizable Monomer with Naphthalene Rings for LCD Image Sticking
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Solution Overview
Problem
Liquid crystal display devices using monomers with naphthalene or biphenyl groups in PSA technology often experience image sticking due to unreacted polymerizable functional groups, which are slowly polymerized by backlight photoirradiation, altering the tilt angle of the polymer film and causing display issues.
Innovation Solution
The use of photopolymerizable monomers with two or more aromatic rings, including at least one naphthalene ring, where the bond between the naphthalene ring and another aromatic ring has a rotational degree of freedom, enhances the polymerization reaction rate, reducing the likelihood of unreacted functional groups and increasing crosslink density, thus minimizing image sticking and improving response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If monomers with naphthalene or biphenyl groups are used in PSA technology, then polymerization reactivity is enhanced, but image sticking occurs due to unreacted polymerizable functional groups being slowly polymerized by backlight photoirradiation
Solution Approach 1:
The patent changes the chemical structure parameters of the monomer by introducing a specific core structure (naphthalene or biphenyl group) with two or more aromatic rings and polymerizable functional groups. This structural parameter change enhances the polymerization reaction rate while the specific molecular design ensures complete reaction, preventing image sticking caused by unreacted groups
Solution Approach 2:
The patent uses composite monomer structures combining aromatic ring systems (naphthalene or biphenyl) with polymerizable functional groups. This composite molecular design creates a photopolymerizable monomer that achieves both high reaction rate and complete polymerization, eliminating the harmful effect of image sticking
2Illumination intensity
If wider spacing between bank-like protrusions or slits is used, then light transmittance is improved, but response time increases due to longer transfer time for liquid crystal tilt direction
Solution Approach 1:
The patent applies preliminary action by forming a photopolymer film on the alignment film before the liquid crystal molecules need to respond to voltage changes. This pre-formed polymer film provides immediate alignment control, eliminating the delay in tilt direction transfer that would otherwise occur with wider spacing between alignment structures
Solution Approach 2:
The patent replaces the mechanical alignment structures (bank-like protrusions or slits) with a photopolymer film formed through photoirradiation. This substitution allows for continuous coverage without mechanical structures, enabling both high light transmittance and fast response by eliminating the physical barriers that would slow molecular reorientation
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 approach results in a liquid crystal display device with accelerated response speed and reduced image sticking, as the photopolymer film formed has high crosslink density and is less prone to deformation, maintaining alignment control and enhancing display quality.
Implementation Method 1
a photopolymer film on the alignment film, the photopolymer film comprises polymers constituted by a photopolymerizable monomer
Implementation Method 2
a bond between the naphthalene ring and another aromatic ring has a rotational degree of freedom
Data Source
AI summary
The present invention provides a liquid crystal display device producing less image sticking. The liquid crystal display device of the present invention comprises: a pair of substrates; and a liquid crystal layer between the substrates, wherein at least one of the substrates comprises an alignment film and a photopolymer film on the alignment film, the photopolymer film comprises polymers constituted by a photopolymerizable monomer, the photopolymerizable monomer includes two or more polymerizable functional groups, the polymerizable functional groups are bonded to each other through two or more aromatic rings, the aromatic rings include at least one naphthalene ring, and a bond between the naphthalene ring and another aromatic ring has a rotational degree of freedom.