OLED Printhead Pixel Layout for Higher Light Output and Resolution
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Solution Overview
Problem
Existing optical writing devices using organic light emitting diodes (OLEDs) face challenges with insufficient light emission and unclear positional relationships between light emitting elements and pixel drive circuits, leading to issues like shading and image streaks due to positional deviations.
Innovation Solution
A light emitting device with a specific arrangement of light emitting elements and pixel drive circuits in M columns and N rows, where the array pitches between adjacent elements and circuits are differently set to minimize positional deviations and improve light utilization efficiency, allowing for higher resolution and reduced device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light emitting elements are arranged to increase light emission amount, then the light emission amount is sufficient, but the device size increases and positional deviations cause image streaks
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional stacked arrangement where light emitting elements are positioned at different heights (Z-axis) relative to the substrate. This vertical stacking allows multiple light emitting elements to emit light toward the same photosensitive member position without increasing the horizontal device footprint, thereby increasing light emission amount while maintaining compact device size.
Solution Approach 2:
The patent implements a nested structure where light emitting elements are integrated within or adjacent to the pixel drive circuit layers. The light emitting elements in upper layers are positioned to overlap with or adjacent to circuit structures in lower layers, creating a compact nested arrangement that maximizes light emission density without proportionally increasing device volume.
2Ease of manufacture
If light emitting elements and pixel drive circuits are arranged with same array pitch, then manufacturing is simplified, but positional deviations cause shading and image streaks
Solution Approach 1:
The patent implements different array pitches for different functional regions: light emitting elements use one array pitch optimized for light emission uniformity, while pixel drive circuits use a different array pitch optimized for circuit performance. This local differentiation allows each region to be optimized independently, and the vertical stacking compensates for the pitch mismatch to maintain overall positional accuracy.
Solution Approach 2:
By introducing vertical stacking, the patent decouples the horizontal positional relationship between light emitting elements and pixel drive circuits. The Z-axis separation allows different horizontal array pitches without causing direct positional misalignment issues, as the vertical offset compensates for horizontal pitch differences.
3Area of stationary object
If device size is reduced for miniaturization, then cost is reduced, but light emission amount becomes insufficient
Solution Approach 1:
The patent utilizes the vertical dimension to pack multiple light emitting elements within a compact horizontal footprint. By stacking light emitting elements at different Z-heights, the system achieves high light emission output from a small device area, effectively decoupling light emission amount from device size.
Solution Approach 2:
The patent employs a composite integrated structure combining light emitting elements, pixel drive circuits, and current control circuits in a multi-layer stacked configuration. This composite architecture allows multiple functions to be integrated in a compact volume, achieving both miniaturization and sufficient light emission capability.
4Measurement precision
If multiple circuits are integrated for high density, then resolution is improved, but device complexity increases
Solution Approach 1:
The patent resolves circuit integration complexity by stacking circuits in the vertical dimension rather than spreading them horizontally. This 3D integration allows multiple pixel drive circuits and current control circuits to be arranged in layers, achieving high circuit density and high image resolution without proportionally increasing the horizontal device footprint or interconnect complexity.
Solution Approach 2:
The patent implements nested circuit architecture where current control circuits are integrated within or adjacent to pixel drive circuit layers. This nesting allows shared use of substrate real estate and reduces the number of discrete circuit blocks, thereby reducing overall device complexity while maintaining high integration density for high resolution.
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 proposed arrangement enhances light emission efficiency, reduces device size, and suppresses image streaks, achieving higher resolution and cost-effectiveness by optimizing the positional relationship between light emitting elements and pixel drive circuits.
Implementation Method 1
An optical writing device (an organic light emitting diode print head, OLED-PH) has been proposed that uses an organic light emitting diode (OLED) serving as a light emitting source
Data Source
AI summary
A light emitting device includes a plurality of light emitting elements arranged on a main surface of a substrate in M columns and N rows (M and N are integers of one or more), and a plurality of pixel drive circuits arranged in M columns and N rows and configured to drive a corresponding light emitting element among the plurality of light emitting elements. The N rows and M columns extend in a first and second directions, respectively. A first array pitch of a first light emitting element and a second light emitting element adjacent to each other in the first direction parallel to the N rows among the plurality of light emitting elements is different from a second array pitch of a first pixel drive circuit and a second pixel drive circuit adjacent to each other in the first direction among the plurality of pixel drive circuits.