Optical Film Birefringence Stability via Cyclohexane Ester Structure

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Solution Overview

Problem

Optical films with optically-anisotropic layers face durability issues due to changes in birefringence index when exposed to high temperatures and humidity, particularly with the use of certain polymerizable liquid crystal compounds and initiators.

Innovation Solution

The use of a specific combination of a polymerizable liquid crystal compound with a cyclohexane ring and a polymerizable compound having a cyclohexane ring, along with an oxime-type polymerization initiator, to form an optical film with an optically-anisotropic layer that maintains stability through reduced moisture permeability and hydrolysis resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polymerizable liquid crystal compounds and polymerization initiators are used to form optically-anisotropic layers, then the optical film can be manufactured with standard materials, but the birefringence index changes when exposed to high temperature and high humidity, reducing durability

Engineering Contradiction:

ImprovedurabilityVSAvoidbirefringence index stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical parameters of the polymerizable liquid crystal compound by introducing a specific molecular structure with a cyclohexane ring and ester groups. This structural parameter change makes the compound resistant to hydrolysis, thereby maintaining birefringence index stability under high temperature and humidity conditions while improving overall durability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite system by combining the specifically structured polymerizable liquid crystal compound with a polymerization initiator. This composite material approach ensures that the resulting optically-anisotropic layer has both the desired optical properties and enhanced durability against environmental degradation

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If the optically-anisotropic layer is exposed to high temperature and high humidity, then the optical film can operate in various environmental conditions, but the polymerizable liquid crystal compound undergoes hydrolysis, causing deterioration of optical properties

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidhydrolysis damage

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potential harm of ester groups (which are typically susceptible to hydrolysis) into a beneficial feature by strategically placing them in a stable molecular configuration. The ester-containing cyclohexane ring structure resists hydrolysis under high temperature and humidity, allowing the optical film to maintain its optical properties in harsh environmental conditions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If standard polymerization conditions are used, then the manufacturing process is simple and fast, but the resulting optically-anisotropic layer lacks resistance to environmental degradation

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidenvironmental resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent incorporates the hydrolysis-resistant molecular structure into the polymerizable liquid crystal compound before the polymerization process. This preliminary structural design ensures that the resulting optically-anisotropic layer inherently resists environmental degradation from the outset, eliminating the need for additional protective treatments while maintaining manufacturing efficiency

Inventive Principle:

Principle #10Preliminary action

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 optical film exhibits enhanced durability and resistance to environmental changes, maintaining optical properties and extending the lifespan of the optically-anisotropic layer.

Implementation Method 1

a layer obtained by polymerizing a polymerizable liquid crystal composition containing a polymerizable compound represented by Formula (I), a liquid crystal compound represented by Formula (II), and a polymerization initiator

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentUS10782567B2Optical film, polarizing plate, image display device, polymerizable compound, and method for manufacturing 1,4-cyclohexanedicarboxylic acid monoaryl ester

Publication Date: 2020.09.22 FUJIFILM CORP

AI summary

An object of the present invention is to provide an optical film having an optically-anisotropic layer having excellent durability, a polarizing plate and an image display device in which the optical film is used, a polymerizable compound used in the optical film, and a method for manufacturing a 1,4-cyclohexanedicarboxylic acid monoaryl ester. The optical film of the present invention is an optical film having at least an optically-anisotropic layer, in which the optically-anisotropic layer is a layer obtained by polymerizing a polymerizable liquid crystal composition containing a polymerizable compound which has a specific structure, a liquid crystal compound which has a specific structure, and a polymerization initiator.