Liquid Crystal Alignment Film Epoxy Value Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid crystal alignment films suffer from inferior rubbing resistance and poor pretilt angle stability, leading to image sticking issues due to unreacted epoxy compounds after post-bake.
Innovation Solution
A liquid crystal alignment agent comprising a polymer obtained from a reaction between a tetracarboxylic dianhydride compound and a diamine compound, combined with an epoxy compound and an organic solvent, is coated on a substrate, heated, and then extracted to form a hard coating film with a specific epoxy value ratio to prevent image sticking and enhance voltage holding ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy compounds are added to the alignment agent to improve rubbing resistance, then the resistance of alignment films is improved, but unreacted epoxy compounds remain after post-bake causing image sticking problems
Solution Approach 1:
The patent changes the chemical parameters of the epoxy compound by selecting specific types (glycidyl ether, glycidyl amine, or glycidyl ester groups) and controlling the epoxy value within a precise range (0.01-0.5 mmol/g) after post-bake treatment. This parameter optimization ensures sufficient rubbing resistance while preventing image sticking by controlling the reactivity and residual content of epoxy groups.
Solution Approach 2:
The alignment agent uses a composite formulation combining polyimide or polyamic acid base materials with specifically selected epoxy compounds. This composite approach integrates the alignment properties of polyimide with the enhanced rubbing resistance of epoxy groups, while the controlled epoxy value prevents harmful side effects.
2Stability of the object's composition
If more epoxy compound is added to improve pretilt angle stability, then pretilt angle stability is improved, but the voltage holding ratio deteriorates due to excessive unreacted epoxy compounds
Solution Approach 1:
The patent precisely controls the epoxy value parameter (0.01-0.5 mmol/g) after post-bake treatment to optimize the balance between pretilt angle stability and voltage holding ratio. This quantitative parameter control ensures that sufficient epoxy groups remain for stability while preventing excessive accumulation that would harm voltage holding 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 solution effectively prevents image sticking and improves the voltage holding ratio of the liquid crystal alignment film, ensuring superior stability and performance.
Implementation Method 1
heated for 15 minutes at 220° C. to form a hard coating film
Implementation Method 2
The hard coating film is extracted for 72 hours using acetone at 60° C. to obtain an extract
Data Source
AI summary
The present invention provides a liquid crystal alignment agent and a liquid crystal alignment film formed therefrom, as well as a liquid crystal display element provided with the liquid crystal alignment film. More specifically, the present invention provides a liquid crystal alignment agent and liquid crystal alignment film formed therefrom, as well as a liquid crystal display element provided with the liquid crystal alignment film without image sticking problems and having superior voltage holding ratio. The liquid crystal alignment agent includes: a polymer (A) obtained from a reaction between tetracarboxylic dianhydride compound and diamine compounds, an epoxy compound (B), and an organic solvent (C). Wherein the liquid crystal alignment agent is coated on a glass substrate, and heated for 15 minutes at 220° C. to forth a hard coating film. The hard coating film is extracted for 72 hours by using acetone at 60° C. to obtain an extract, an epoxy value on the extract is designated O, and based on 100 parts by weight of the solid content of the liquid crystal alignment agent, the parts by weight of the epoxy compound (B) is designated W, the O and W conform to the following equation:[O÷W×103]≦0.55.