Wavelength Conversion Sheet Primer Composition for Humidity-Resistant Adhesion

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Solution Overview

Problem

The existing wavelength conversion sheets experience peeling between the phosphor layer and the primer layer under high-temperature and high-humidity conditions, leading to oxygen and water vapor invasion and degradation of the phosphor layer.

Innovation Solution

A wavelength conversion sheet with a phosphor layer and a film comprising a base material layer and a primer layer, where the primer layer contains an element X (sulfur or phosphorus) with a specific concentration ratio (C PR /C QD ≤ 0.10) and a coefficient of variation of 0.60 or more, ensuring excellent adhesion even after long-term exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a phosphor layer is laminated on a primer layer to improve adhesion, then close adhesion is enhanced, but peeling occurs under high-temperature and high-humidity conditions

Engineering Contradiction:
Improveadhesion strengthVSAvoidstability under humidity
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the primer layer by controlling the content of specific elements (such as oxygen, carbon, hydrogen ratios) to optimize adhesion performance. This parameter optimization prevents peeling under high-temperature and high-humidity conditions while maintaining strong adhesion between the phosphor layer and primer layer.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite primer layer structure with specific elemental composition that combines multiple chemical components in optimized ratios. This composite material approach enhances both adhesion strength and resistance to humidity-induced peeling by synergistically combining the properties of different elemental components.

Inventive Principle:
Principle #40Composite materials

2Reliability

If a barrier film is added to prevent water vapor invasion, then phosphor layer protection is improved, but device complexity increases

Engineering Contradiction:
Improveprotection from degradationVSAvoidstructure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the primer layer multi-functional by optimizing its chemical composition to simultaneously provide adhesion enhancement and water vapor barrier properties. This eliminates the need for a separate barrier film, maintaining phosphor layer protection while avoiding increased device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the functions of the primer layer and barrier film into a single integrated primer layer structure. By combining adhesion and barrier functions in one layer with optimized elemental composition, the patent reduces structural complexity while maintaining reliable phosphor layer protection.

Inventive Principle:
Principle #5Merging (Combining)

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 solution provides a wavelength conversion sheet with enhanced adhesion between the phosphor and primer layers, preventing degradation and maintaining performance under harsh environmental conditions.

Implementation Method 1

The quantum dot can be adjusted over the entire visible region of the emission wavelength by the quantum confinement effect (quantum size effect), in which an electron or an exciton is confined in a nanometer-sized small crystal. The quantum dot can generate strong fluorescence in a narrow wavelength band

Methodology Applied
Scientific EffectQuantum confinement effect:

Implementation Method 2

a phosphor layer obtained by dispersing a nanometer-sized phosphor fine particle of a semiconductor in a resin layer

Methodology Applied
Scientific EffectPhosphorescence: Phosphorescence

Data Source

PatentEP4703778A1Wavelength conversion sheet, backlight, and liquid crystal display device
Publication Date: 2026.03.04 DAI NIPPON PRINTING CO LTD
  • EP4703778A1 patent drawingFigure 1~2
  • EP4703778A1 patent drawingFigure 3
  • EP4703778A1 patent drawing

AI summary

Provided is a wavelength conversion sheet having excellent close adhesion between a phosphor layer and a primer layer even after a long-term environment test. A wavelength conversion sheet, including: a phosphor layer including a phosphor; and a film for a wavelength conversion sheet provided on at least one surface side of the phosphor layer, wherein the film for a wavelength conversion sheet includes at least a base material layer and a primer layer laminated thereon, and the primer is in contact with the phosphor layer, the phosphor layer and the primer layer include an element X, and CPR/CQD satisfies 0.10 or less, where CQD (atomic%) is an average value of proportions of the element X in the phosphor layer within a region from an interface between the primer layer and the phosphor layer to 400 nm in a thickness direction of the phosphor layer, obtained by X-ray photoelectron spectroscopy, and where CPR (atomic%) is a proportion of the element X in the primer layer at any depth within a region between 20 nm or more and 40 nm or less from the interface in a thickness direction of the primer layer, obtained by X-ray photoelectron spectroscopy.