Acrylic Copolymer Film for Liquid Crystal Alignment and Overcoat
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Solution Overview
Problem
Existing liquid crystal alignment layers for color filters have low transparency, poor solvent resistance, and insufficient heat resistance, making them unsuitable for use as both alignment layers and overcoats in display devices.
Innovation Solution
A composition for forming a thermoset film with photo alignment properties, comprising an acrylic copolymer with both photodimerizing and thermal cross-linking moieties, along with a cross-linking agent, acid or thermal acid generator, and sensitizer, which can be dissolved in glycol or ketone solvents, enabling high transparency, solvent resistance, and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid crystal alignment layer is formed using conventional materials (polyimide or acrylic resin with photodimerizing moiety), then alignment properties are achieved, but transparency, solvent resistance, and heat resistance are insufficient
Solution Approach 1:
The patent merges the functions of liquid crystal alignment layer and color filter overcoat into a single integrated layer. The acrylic resin composition is designed to simultaneously provide alignment properties (through photodimerizing moieties), overcoat functionality (through high transparency and solvent resistance), and heat resistance (through cross-linking agents and curable groups), eliminating the need for separate layers and resolving the contradiction between achieving alignment properties and maintaining other required properties.
Solution Approach 2:
The patent uses a composite material system consisting of acrylic resin with photodimerizing moieties, cross-linking agents, and curable groups. This composite approach allows the material to exhibit multiple functions simultaneously: the acrylic resin provides transparency and solubility, the photodimerizing moieties provide alignment properties upon UV irradiation, and the cross-linking agents provide heat resistance and solvent resistance after curing, thereby resolving the contradiction between achieving alignment properties and maintaining other required properties.
2Object-affected harmful factors
If acrylic resin is used for color filter overcoat to ensure high transparency, then transparency is improved, but alignment properties are insufficient even with rubbing or polarized UV exposure
Solution Approach 1:
The patent changes the chemical parameters of the acrylic resin by introducing photodimerizing moieties (such as cinnamoyl or chalcone groups) and curable groups into the polymer structure. These parameter changes enable the material to undergo photodimerization upon UV irradiation, thereby achieving alignment properties while maintaining the high transparency characteristic of acrylic resin. This resolves the contradiction between transparency and alignment properties.
3Reliability
If polyimide is used for liquid crystal alignment layer to achieve sufficient alignment properties, then alignment properties are improved, but transparency and solubility in glycol/ester/ketone solvents are poor
Solution Approach 1:
The patent applies local quality by introducing photodimerizing moieties specifically at the molecular level within the acrylic resin structure. These localized photodimerizing groups (cinnamoyl or chalcone) are embedded in the acrylic polymer chains, enabling alignment functionality only where needed (upon UV irradiation) while the bulk acrylic resin maintains its inherent transparency and solubility in glycol/ester/ketone solvents. This resolves the contradiction between alignment properties and transparency/solubility.
4Object-affected harmful factors
If conventional acrylic resin overcoat is used, then high transparency is achieved, but heat resistance and solvent resistance are insufficient after thermal or photo curing
Solution Approach 1:
The patent incorporates cross-linking agents and curable groups into the acrylic resin composition in advance, before the coating and curing processes. These preliminary incorporated components are designed to react and form cross-linked networks during subsequent thermal or photo curing, thereby pre-establishing the structural framework needed for heat resistance and solvent resistance while maintaining the transparency characteristics of the acrylic resin. This resolves the contradiction between transparency and heat/solvent resistance.
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 composition forms a cured film with excellent liquid crystal alignment performance, high transparency, and improved heat and solvent resistance, suitable for use as both a liquid crystal alignment layer and overcoat, reducing production costs and process complexity.
Implementation Method 1
an acrylic resin including a side chain having a photodimerizing moiety such as a cinnamoyl group and a chalcone group is subjected to the polarized UV exposure to exhibit sufficient liquid crystal alignment properties
Implementation Method 2
an acrylic copolymer having a photodimerizing moiety and a thermal cross-linking moiety
Data Source
AI summary
A material from which a cured film exhibiting high solvent resistance, liquid crystal-alignment performance, heat resistance and high transparency can be formed. A composition for forming a thermoset film having photo alignment properties, including: a component (A) that is an acrylic copolymer having a photodimerizing moiety and a thermal cross-linking moiety; and a component (B) that is a cross-linking agent.