Image-Forming Apparatus With OLED Emission-Absorption Matching

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Solution Overview

Problem

Existing image-forming apparatuses using organic light-emitting elements with optical resonator structures suffer from light absorption by the organic layer, reducing the efficiency of light transfer to the photosensitive member.

Innovation Solution

The image-forming apparatus is designed with an organic light-emitting element configuration where the maximum emission peak wavelength aligns closer to the photosensitive member's maximum absorption wavelength, minimizing light absorption by the organic compound layers and enhancing energy transfer through the Foerster mechanism, utilizing a reflective and light extraction electrode configuration with controlled optical path lengths and layer thicknesses to optimize light emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If an optical resonator structure is used in the organic light-emitting element to increase emission intensity at a specific wavelength, then the emission intensity is improved, but light is absorbed by the organic layer multiple times during reflection between electrodes, reducing the efficiency of light transfer to the photosensitive member

Engineering Contradiction:

Improveemission intensityVSAvoidlight absorption loss

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent inverts the conventional bottom emission configuration by adopting a top emission configuration, where the organic light-emitting element emits light upward through a reflective electrode rather than downward through a transparent substrate. This inversion eliminates the multiple reflections through the organic layer, preventing self-absorption while maintaining high emission intensity through the optical resonator effect between the reflective electrode and the substrate.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces a microlens array as an intermediary component positioned between the organic light-emitting element and the photosensitive member. The microlens array focuses and directs the emitted light, improving light extraction efficiency and ensuring that maximum light reaches the photosensitive member without being absorbed by intermediate layers.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the organic light-emitting element uses a bottom emission configuration with transparent substrate to emit light toward the photosensitive member, then the structure is simplified, but light absorption by the organic layer during multiple reflections reduces image formation efficiency

Engineering Contradiction:

Improvestructure complexityVSAvoidimage formation efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

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

This configuration increases the efficiency of image formation by maximizing light absorption by the photosensitive member, thereby improving the overall image quality and efficiency of the image-forming process.

Implementation Method 1

an organic light-emitting element on a first surface of a substrate; and a photosensitive member configured to receive light from the organic light-emitting element

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

a maximum emission peak wavelength in an emission spectrum of the organic light-emitting element is closer to a wavelength of a maximum absorption value in a visible light region of an optical absorption spectrum of the photosensitive member

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 3

light emitted from an organic light-emitting element with an optical resonator structure is reflected between electrodes of the organic light-emitting element

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 4

enhancing energy transfer through the Foerster mechanism

Methodology Applied

Scientific EffectEnergy transfer through Foerster mechanism: Fluorescence

Data Source

PatentEP4625059A1Image-forming apparatus

Publication Date: 2025.10.01 CANON KK

Figure 1A~1C
Figure 2A~2C
Figure 3

AI summary

An image-forming apparatus (40) includes a light source including an organic light-emitting element (26) on a first surface of a substrate (11); and a photosensitive member (27) configured to receive light from the organic light-emitting element, wherein the organic light-emitting element includes a first electrode (21), a first organic compound layer, a light-emitting layer, a second organic compound layer, and a second electrode (23) in this order from the first surface, and a maximum emission peak wavelength in an emission spectrum (1) of the organic light-emitting element is closer to a wavelength of a maximum absorption value in a visible light region of an optical absorption spectrum (2) of the photosensitive member than a longest peak wavelength in an optical absorption spectrum (3, 5) of the first organic compound layer or a longest peak wavelength in an optical absorption spectrum (4, 6, 7) of the second organic compound layer.