Near-Infrared Absorbing Adhesive Layer With Low Haze Stability

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Solution Overview

Problem

Existing near-infrared absorbing films suffer from insufficient near-infrared absorption properties, oxidative fading of near-infrared absorbers due to exposure to air, and issues with adhesive compositions that become cloudy or gel quickly, leading to reduced productivity and high haze values.

Innovation Solution

An adhesive layer containing composite tungsten oxide fine particles with specific lattice constants, a dispersant, a metal coupling agent with an amino group, and a crosslinking agent, which are stabilized by a surface coating, ensuring high near-infrared absorption and low haze while maintaining stability and productivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If near-infrared absorbing films are used to shield solar energy and reduce cooling load, then near-infrared absorption ability is improved, but the absorbers undergo oxidative fading due to exposure to air, reducing reliability

Engineering Contradiction:
Improvenear-infrared absorption stabilityVSAvoidoxidative fading
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses composite tungsten oxide fine particles (MxWyOz) as the near-infrared absorbing material, combining tungsten oxide with metal elements (Ca, Sr, Ba, Pb, or Bi) to create a composite structure that maintains stable near-infrared absorption properties without oxidative fading, resolving the reliability issue

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent creates a protective environment by incorporating the near-infrared absorbing particles into an adhesive layer that shields them from direct exposure to air, effectively creating an inert environment that prevents oxidative fading while maintaining absorption stability

Inventive Principle:
Principle #39Inert atmosphere (Inert environment)

2Productivity

If adhesive compositions are used to form adhesive layers with near-infrared absorbing particles, then near-infrared absorption is achieved, but the compositions become cloudy or gel quickly, reducing productivity

Engineering Contradiction:
Improveadhesive layer formation efficiencyVSAvoidadhesive composition stability
Core Design Contradiction:
ProductivityVSStability of the object's composition

Solution Approach 1:

The patent specifies precise parameter ranges for the adhesive composition including particle size (0.1-10 μm), metal content ratios (0.01<x/y≤1, 2.0<z/y≤3.0), and adhesive composition ratios, which control the chemical and physical properties to prevent clouding and gelation while maintaining composition stability during application

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses a coupling agent as an intermediary substance between the near-infrared absorbing particles and the adhesive resin, improving compatibility and dispersion stability, which prevents the composition from becoming cloudy or gelling quickly, thereby maintaining productivity

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If inorganic particles are used as near-infrared absorbers, then absorption ability is improved, but haze value increases, reducing transparency

Engineering Contradiction:
Improvenear-infrared absorption abilityVSAvoidvisible light transmittance
Core Design Contradiction:
ReliabilityVSIllumination intensity

Solution Approach 1:

The patent optimizes the local properties of the inorganic particles by controlling their size distribution (0.1-10 μm), shape, and refractive index, creating particles with specific local characteristics that absorb near-infrared light while minimizing visible light scattering, thus maintaining transparency

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the physical parameters of the inorganic particles including size, shape, and refractive index to optimize the balance between near-infrared absorption and visible light transmission, reducing haze value while maintaining absorption ability

Inventive Principle:
Principle #35Parameter changes

4Reliability

If ATO and ITO particles are used as heat ray absorbing particles, then near-infrared absorption is attempted, but absorption properties are insufficient

Engineering Contradiction:
Improvenear-infrared absorption propertiesVSAvoidabsorption efficiency
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent replaces单一的 ATO and ITO particles with composite tungsten oxide particles (MxWyOz) that combine tungsten oxide with metal elements, creating a composite material with superior near-infrared absorption properties and higher absorption efficiency

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent changes the chemical composition parameters by using tungsten oxide with specific metal additives and controlling the oxidation state (z/y ratio), which fundamentally improves the near-infrared absorption mechanism and efficiency compared to ATO and ITO

Inventive Principle:
Principle #35Parameter changes

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 adhesive layer effectively absorbs near-infrared light, maintains transparency in the visible light region, and exhibits improved stability, reducing haze and production issues, thus enhancing productivity and cost-effectiveness.

Implementation Method 1

an adhesive layer containing composite tungsten oxide fine particles... which effectively absorbs near-infrared light

Methodology Applied
Scientific EffectNear-infrared absorption: Absorption (EM radiation)

Implementation Method 2

a near-infrared absorbing layer capable of shielding a part of a solar energy that enters cars or buildings and reducing a cooling load

Methodology Applied
Scientific EffectPhotothermal conversion:

Implementation Method 3

a metal coupling agent with an amino group... stabilized by a surface coating

Methodology Applied
Scientific EffectSurface complexation: Adsorption

Implementation Method 4

a metal coupling agent having an amino group

Methodology Applied
Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 5

a crosslinking agent... ensuring high near-infrared absorption and low haze while maintaining stability

Methodology Applied
Scientific EffectCrosslinking: Chemical Bonding

Implementation Method 6

stabilized by a surface coating, ensuring high near-infrared absorption and low haze

Methodology Applied
Scientific EffectSurface coating: Coatings

Data Source

PatentEP3715429B1Adhesive layer
Publication Date: 2026.01.21 SUMITOMO METAL MINING CO LTD
  • EP3715429B1 patent drawingFigure 1
  • EP3715429B1 patent drawingFigure 2
  • EP3715429B1 patent drawingFigure 3

AI summary

There are provided an adhesive composition, an adhesive layer, that transmit light in a visible light region and has an ability to absorb light in a near-infrared region, has a low haze value, and is excellent in stability, and a near-infrared absorbing film, a laminated structure, a laminated body using the above adhesive composition and adhesive layer, and are provided an adhesive layer, a near-infrared absorbing film, a laminated structure, a laminated body, and an adhesive composition containing composite tungsten oxide fine particles, a dispersant, a metal coupling agent having an amino group, an adhesive, and a crosslinking agent, wherein the composite tungsten oxide fine particles include a hexagonal crystal structure, and the composite tungsten oxide fine particles have lattice constant values such as 7.3850 Å or more and 7.4186 Å or less on the a-axis, and 7.5600 Å or more and 7.6240 Å or less on the c-axis, and the composite tungsten oxide fine particles having an average particle size of 100 nm or less.