Pixel Defining Layer Composition for Flexible OLED Light Blocking

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Solution Overview

Problem

Existing organic light emitting display devices face challenges in achieving high optical density and plastic hardness while maintaining flexibility due to the limitations of polarizing films and colored light blocking layers, which can lead to issues like cracks and dark spots.

Innovation Solution

A method for preparing a pixel defining layer using a photosensitive composition that includes a specific formulation of colorants, binder resins, and processing steps to achieve an optical density of 0.8/μm to 1.5/μm, plastic hardness of 350 N/mm² to 470 N/mm², and modulus of 5,200 Mpa to 6,800 Mpa, enabling improved visibility and impact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the content of organic pigment is increased to increase plastic hardness, then plastic hardness is improved, but residues are generated and dark spots appear on the panel

Engineering Contradiction:

Improveplastic hardnessVSAvoidresidues and dark spots

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by precisely controlling the organic pigment content within 17-35 wt% and optimizing post-baking parameters (temperature: 250-270°C, time: 60-120 minutes) to achieve the desired plastic hardness while preventing residue formation. This quantitative parameter optimization resolves the contradiction between hardness improvement and dark spot prevention.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining organic pigments with binder resins (acryl-based and/or cardo-based) in specific ratios to create a photosensitive composition that achieves both high plastic hardness and complete curing without residues. The composite formulation ensures uniform distribution and complete polymerization, eliminating dark spots while maintaining hardness.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If the optical density is increased to improve visibility, then visibility is improved, but the formulation complexity increases

Engineering Contradiction:

Improveoptical densityVSAvoidformulation complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent achieves high optical density (0.8/μm to 1.5/μm) by optimizing the concentration of light-absorbing components within the 17-35 wt% organic pigment range and controlling film thickness and post-baking parameters, rather than using complex multi-component formulations. This parameter optimization approach achieves the desired optical performance with a relatively simple formulation.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If a polarizing film is used to block reflected light, then light blocking performance is improved, but flexibility is lost

Engineering Contradiction:

Improvelight blocking performanceVSAvoidflexibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical polarizing film structure with a chemically formulated photosensitive composition containing organic pigments and binder resins that can be applied as a thin flexible layer. This compositional substitution maintains light blocking functionality while enabling flexibility and bendability required for flexible displays.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances visibility and impact resistance by increasing optical density and plastic hardness, allowing for flexible and reliable organic light emitting displays without cracks, even under external impacts.

Implementation Method 1

a method for preparing a pixel defining layer which includes the steps of application and coating; pre-baking; exposure to light; developing; and post-baking of a photosensitive composition

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

the photosensitive composition includes a binder resin, a reactive unsaturated compound, and a photoinitiator

Methodology Applied

Scientific EffectCrosslinking: Chemical Bonding

Data Source

PatentUS12593571B2Method for preparing pixel define layer

Publication Date: 2026.03.31 DUK SAN NEOLUX

AI summary

The pixel separation layer used in OLED displays has a plastic hardness of 500 N/mm2 or more and a modulus of 7,000 Mpa or more; however, since the pixel separation layer requires a polarizing plate, it has a physical disadvantage in that it is not bendable and heavy. In contrast, the pixel separation layer enables the implementation of a flexible display and reduces the thickness and weight of the display. Additionally, visibility increases through blocking and absorption of external reflected light, and the plastic hardness and modulus are improved to the levels of the conventional pixel separation layer, and thus there is an advantage in that it is possible to implement a display without cracks even from external impacts. Consequently, a coloring pattern is implemented with a high optical density on an electrode substrate to improve impact resistance, display reliability, and lifetime of a display as well as vivid colors.