Optical Adhesive Composition Refractive Index Control

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Solution Overview

Problem

There is a need for an optical pressure-sensitive adhesive with a high refractive index, high transmission, and high UV stability, as existing adhesives often fail to meet these requirements, particularly for bonding optical components like films and glasses.

Innovation Solution

A pressure-sensitive adhesive composition comprising acid anhydride-modified vinyl aromatic block copolymers, metal chelates, and adhesive resins, which achieves a refractive index suitable for optical components, ensuring high light transmission and low haze, while maintaining stability and compatibility with electrical conductive substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional pressure-sensitive adhesives (acrylic PSAs, silicone compounds) are used, then they provide basic bonding function, but they have low refractive index (below 1.46) which causes high reflection and reduces light transmission

Engineering Contradiction:

Improvelight transmissionVSAvoidrefractive index match

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the PSA by incorporating aromatic comonomers (styrene, alpha-methylstyrene, p-methylstyrene) in specific proportions (0-60% by weight) to adjust the refractive index from conventional values below 1.46 to the target range of 1.47-1.65, achieving better optical matching with substrates

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite PSA formulation combining multiple components: acrylic polymer base, aromatic comonomers for refractive index enhancement, functional monomers (carboxylic acid, hydroxyl, amine groups) for adhesion promotion, and optional additives. This composite approach achieves both high refractive index (1.47-1.65) and excellent bonding performance simultaneously

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If fluorinated acrylate monomers are used to achieve low refractive index (below 1.40), then light transmission is improved through anti-reflective properties, but the refractive index becomes too low (well below 1.46) for optimal optical component bonding

Engineering Contradiction:

Improveanti-reflective transmissionVSAvoidrefractive index control

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

Instead of using fluorinated monomers to reduce refractive index (conventional approach), the patent inverts the strategy by using aromatic comonomers (styrene, alpha-methylstyrene, p-methylstyrene) to increase the refractive index from conventional values to the optimal range of 1.47-1.65, achieving better optical matching with high-index substrates

Inventive Principle:

Principle #13The other way round (Inversion)

3Illumination intensity

If high refractive index is achieved through aromatic comonomers, then light transmission increases and reflection decreases, but UV stability and color stability may be compromised

Engineering Contradiction:

Improvelight transmissionVSAvoidUV stability

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The patent optimizes the proportion of aromatic comonomers (styrene, alpha-methylstyrene, p-methylstyrene) within specific ranges (0-60% by weight) to achieve the desired refractive index (1.47-1.65) while controlling UV absorption and color stability. This parameter optimization balances optical performance with long-term durability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces functional monomers containing carboxylic acid groups, hydroxyl groups, or amine groups as intermediaries that provide UV resistance and color stability while working synergistically with aromatic comonomers to maintain both high refractive index (1.47-1.65) and excellent UV durability

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of operation

If pressure-sensitive adhesive tapes are used for bonding optical components, then bonding speed and ease of operation are improved, but achieving optimal optical properties (high transmission, low haze) with appropriate refractive index is difficult

Engineering Contradiction:

Improvebonding speedVSAvoidoptical property control

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent formulates a composite PSA with precisely controlled composition: acrylic polymer base, aromatic comonomers (styrene, alpha-methylstyrene, p-methylstyrene) for refractive index (1.47-1.65), functional monomers for adhesion, and optional additives. This composite formulation achieves both ease of application as a PSA tape and precise optical properties including high light transmission and low haze

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes multiple parameters simultaneously: refractive index (1.47-1.65) through aromatic comonomer content, adhesive strength through functional monomer selection, and optical clarity through controlled formulation. This multi-parameter optimization enables the PSA to meet both application ease and optical precision requirements

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2281023B1Pressure-sensitive adhesive mass

Publication Date: 2014.04.23 TESA SE

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AI summary

The present invention relates to the use of an adhesive mass at least containing an acid-anhydride-modified vinyl aromatic block copolymer, a metal chelate, and an adhesive resin for bonding optical components, particularly optical films, wherein the adhesive mass has a transmittance greater than 86% and a haze less than 5%.