Display Planarization Layers Balancing Light Extraction and Adhesion
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Solution Overview
Problem
Existing organic light emitting display devices face challenges in improving light extraction efficiency, particularly in bottom emission types, due to total reflection of light within the device, and issues with adhesiveness and processability of low refractive planarization layers using fluorine resin and siloxane-acrylic fluorine resin, leading to poor adhesiveness, light absorption, and degradation of luminous efficiency.
Innovation Solution
A display device with a first planarization layer having a low refractive index of 1.50 or lower and a second planarization layer with a higher refractive index, using an acrylic binder and (meth)acrylic acid-benzyl (meth)acrylic acid copolymer, to form a micro lens array structure without fluorine compounds, enhancing adhesiveness and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If fluorine resin is used to form a low refractive planarization layer, then the refractive index is reduced, but adhesiveness with upper and lower layers deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the planarization layer by replacing fluorine resin with siloxane-acrylic fluorine resin, adjusting the refractive index while improving adhesiveness through the siloxane component's bonding characteristics
Solution Approach 2:
The patent uses a composite material system (siloxane-acrylic fluorine resin) that combines the low refractive index property of fluorine-containing compounds with the adhesive properties of siloxane and acrylic components, achieving both optical and mechanical performance requirements
2Illumination intensity
If siloxane-acrylic fluorine resin is used to form a low refractive planarization layer, then the refractive index is reduced, but light absorption increases during photolithography process
Solution Approach 1:
The patent optimizes the chemical composition parameters of the resin to reduce light absorption during photolithography while maintaining the low refractive index, achieving better processability without sacrificing optical performance
3Illumination intensity
If low refractive planarization layer is formed with existing materials, then the refractive index is reduced, but roughness increases during exposure, development, and baking steps
Solution Approach 1:
The patent modifies the resin composition and processing parameters to control surface roughness during fabrication steps while maintaining the low refractive index, achieving both optical quality and manufacturing precision
4Illumination intensity
If fluorine component is used in low refractive planarization layer, then the refractive index is reduced, but transmittance decreases in short wavelength range due to yellowing after high temperature reliability test
Solution Approach 1:
The patent changes the chemical composition by reducing or eliminating fluorine components while using alternative low refractive index materials that do not yellow under high temperature conditions, maintaining both optical performance and thermal stability
Solution Approach 2:
The patent replaces fluorine-containing materials with alternative materials that may have different operational lifetimes but provide superior long-term stability and reliability under high temperature conditions
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 improves light extraction efficiency, reduces optical distortions, and ensures excellent reliability and processability by forming a micro lens structure with improved adhesiveness and thermal stability, minimizing light loss and maintaining high transmittance.
Implementation Method 1
a refractive index of the first planarization layer is lower than that of the second planarization layer
Implementation Method 2
some of light is captured in the organic light emitting display device due to the total reflection of the substrate
Implementation Method 3
a structure in which a high refractive planarization layer is formed in a position adjacent to an anode having a higher refractive index and a low refractive planarization layer is formed in a position adjacent to a substrate has been proposed
Data Source
AI summary
A display device including a substrate; a thin film transistor disposed on the substrate; a planarization layer disposed on the thin film transistor; a light emitting diode disposed on the planarization layer; and an encapsulation layer disposed so as to cover the plurality of light emitting diodes, and in which the planarization layer includes a first planarization layer which is disposed so as to cover the thin film transistor and a second planarization layer which is disposed so as to cover at least a part of the first planarization layer and a refractive index of the first planarization layer is lower than that of the second planarization layer, and the first planarization layer includes an acrylic binder and (meth)acrylic acid-benzyl (meth)acrylic acid copolymer.