Urethane Optical Member Dimer Incorporation

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Solution Overview

Problem

Urethane optical members with high refractive indices face challenges in achieving transparency due to the formation of dimers from MDI and TDI, which lead to turbidity and fog, making it difficult to simultaneously achieve high refractive index and transparency.

Innovation Solution

Incorporating MDI or TDI dimers into the structure of urethane optical members through reaction with a polythiol compound, ensuring they are bonded covalently to prevent deposition and enhance transparency and refractive index.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the amount of MDI and TDI is increased to achieve a high refractive index exceeding 1.65, then the refractive index is improved, but the optical member develops turbidity and fog due to dimer deposition, worsening transparency

Engineering Contradiction:

Improverefractive indexVSAvoidtransparency

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of MDI/TDI dimers (which cause turbidity when deposited) into a beneficial component by incorporating them into the polymer chain structure through reaction with polythiol compounds. The dimers are transformed from unwanted byproducts into intentional structural elements that contribute to the high refractive index without causing transparency issues.

Inventive Principle:

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

Solution Approach 2:

The patent changes the chemical state and distribution parameters of the dimer compounds. Instead of allowing dimers to exist as separate deposited phases, the invention modifies the polymerization process to incorporate dimers into the polymer chain at controlled concentrations (0.05-5% by mass), transforming them from harmful deposits into beneficial structural components within the urethane polymer matrix.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the amount of MDI and TDI is reduced to improve transparency, then transparency is improved, but the refractive index cannot achieve the desired high level

Engineering Contradiction:

ImprovetransparencyVSAvoidrefractive index

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The patent utilizes the previously harmful dimer compounds as beneficial building blocks. By intentionally incorporating MDI/TDI dimers into the polymer chain through controlled reaction with polythiol compounds, the invention achieves high refractive index (exceeding 1.65) without the transparency deterioration that would normally result from dimer presence, thus converting the harmful factor into a beneficial one.

Inventive Principle:

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

3Illumination intensity

If MDI and TDI are used as raw materials to achieve high refractive index, then the refractive index is improved, but dimers are formed with the lapse of time due to high reactivity, causing turbidity and fog

Engineering Contradiction:

Improverefractive indexVSAvoidcomposition stability

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by incorporating the dimer formation step into the controlled polymerization process itself. Rather than allowing dimers to form later and cause degradation, the invention deliberately includes dimer formation as part of the synthesis process, reacting dimers with polythiol compounds during polymerization to create stable urethane linkages within the polymer chain before the dimers can cause harmful deposition.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the time-dependent harmful dimer formation (which causes turbidity) into a beneficial process by incorporating dimers into the polymer chain structure during controlled polymerization. The high reactivity of MDI/TDI that normally leads to unwanted dimer deposition is instead harnessed to create stable urethane bonds with polythiol compounds, making the dimer formation beneficial rather than harmful.

Inventive Principle:

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

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 method results in urethane optical members with excellent transparency and high refractive index, suitable for applications like plastic lenses, by effectively managing dimer content and reactivity.

Implementation Method 1

polymerizing a monomer composition containing (i) 4,4' -diphenylmethane diisocyanate and a 4,4' -diphenylmethane diisocyanate dimer and/or (ii) tolylene diisocyanate and a tolylene diisocyanate dimer, and a polythiol compound, the 4,4'-diphenylmethane diisocyanate dimer and/or the tolylene diisocyanate dimer being reacted with the polythiol compound

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentEP2746823B1Urethane-based optical component and manufacturing process therefor

Publication Date: 2016.05.04 HOYA CORPORATION

AI summary

The present invention relates to a urethane optical member containing at least one kind of structures represented by the following formulae (1) and (2) in a structure constituting the optical member, and a method for producing the same.