OLED Light-Emitting Layer Structure to Prevent Coffee Ring Nonuniformity

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Solution Overview

Problem

Existing display devices face challenges in controlling the film thickness of the light-emitting layer, leading to non-uniformity and deterioration in light emission performance due to the coffee ring phenomenon during solvent evaporation in the dripping technique.

Innovation Solution

A display device with a light-emitting element layer comprising a function layer sandwiched by holding layers made of photosensitive materials and conductive nanoparticles, allowing precise control of the light-emitting layer thickness through a dripping technique.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the light-emitting layer is formed by dripping droplets into the interior of the bank and drying them, then the light-emitting layer can be formed, but the film thickness cannot be easily controlled and thickness non-uniformity occurs due to the coffee ring phenomenon

Engineering Contradiction:

Improveease of forming light-emitting layerVSAvoidfilm thickness control precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by forming the holding layer structure (including bank and cap) before dripping the light-emitting layer material. The holding layer is pre-formed with specific thickness and structural characteristics that constrain the droplet formation process, ensuring uniform film thickness from the beginning of the material deposition rather than attempting to correct non-uniformity after formation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The holding layer acts as an intermediary between the bank structure and the light-emitting layer material. It provides a controlled interface that mediates the droplet deposition process, preventing direct contact between the droplets and the bank walls that would cause the coffee ring phenomenon, while still allowing for effective material deposition and uniform film formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If droplets are dripped into the interior of the bank, then the light-emitting layer can be formed, but position control of droplets requires high precision to avoid performance deterioration

Engineering Contradiction:

Improveease of forming light-emitting layerVSAvoiddroplet position control precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating a holding layer with spatially varying properties - specifically, the holding layer has different thickness characteristics at different locations within the bank. This local structural variation guides the droplet material to distribute uniformly across the intended area, with the holding layer's local thickness profile compensating for position variations and ensuring consistent film formation without requiring extreme droplet placement precision.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the light-emitting layer is formed by evaporating solvent from dripped droplets, then the light-emitting layer can be formed, but the coffee ring phenomenon occurs causing thickness non-uniformity

Engineering Contradiction:

Improveease of forming light-emitting layerVSAvoidfilm thickness uniformity

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary anti-action by designing the holding layer structure in advance to counteract the coffee ring phenomenon. The holding layer's specific thickness and structural characteristics create conditions that prevent solvent evaporation-induced material redistribution toward the droplet edges. By pre-configuring the holding layer to provide uniform capillary action and evaporation conditions across the droplet area, the harmful coffee ring effect is prevented rather than corrected after it occurs.

Inventive Principle:

Principle #9Preliminary anti-action

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 ensures uniform light-emitting layer thickness, preventing performance deterioration and enhancing light emission quality.

Implementation Method 1

each including a photosensitive material and a conductive nanoparticle

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

droplets including a constituent material of the light-emitting layer and a predetermined solvent are dripped into the interior of the bank, and the droplets are further dried (the solvent is evaporated) to form the light-emitting layer

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS12520655B2Display device and method for producing display device

Publication Date: 2026.01.06 SHARP KK

AI summary

A display device is a display device provided with a display region including a plurality of pixels and a frame region surrounding the display region, and includes: a thin film transistor layer; and a light-emitting element layer including a plurality of light-emitting elements, each including a first electrode, a function layer, and a second electrode, and each having a different luminescent color, wherein the function layer includes a light-emitting layer, and a pair of holding layers sandwiching the light-emitting layer and each including a photosensitive material and a conductive nanoparticle.