Top-Emission Light Source Layout for Efficient Photoconductor Exposure
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Solution Overview
Problem
Existing bottom emission light emitting devices in electrophotographic image forming apparatuses have limited light emission efficiency due to the optical path being constrained by the TFT circuit, requiring increased light production to achieve desired image quality.
Innovation Solution
The image forming apparatus employs a top emission light emitting device with a silicon substrate, a two-dimensional array of electrodes, and a lens array to guide light efficiently onto the photoconductor surface, utilizing a drive circuit to control electrode voltages based on image data, enhancing light transmission and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bottom emission light emitting device is used, then the device structure is simplified, but the light emission efficiency is reduced due to optical path limitations
Solution Approach 1:
The patent inverts the conventional bottom emission configuration by adopting a top emission structure where light exits from the top surface of the organic EL device rather than from the bottom. This allows light to pass through the transparent electrode and upper electrode without being blocked by the TFT circuit, thereby improving light emission efficiency while maintaining structural simplicity.
2Illumination intensity
If the amount of light produced is increased to compensate for bottom emission limitations, then image quality improves, but the light emitting device requires more power and generates more heat
Solution Approach 1:
The patent changes the emission direction parameter of the organic EL device from bottom emission to top emission. This parameter change allows the light to pass through the transparent electrode with minimal absorption, improving light output efficiency without requiring proportional increases in power consumption or heat generation.
3Loss of energy
If a top emission light emitting device is used, then light transmission efficiency is improved, but the electrode structure becomes more complex
Solution Approach 1:
The transparent electrode serves multiple functions: it acts as both an electrode for applying voltage to the organic EL device and as an optical window to transmit light to the photoconductor. This multi-functionality improves light transmission efficiency without adding separate components that would increase structural complexity.
Solution Approach 2:
The transparent electrode acts as an intermediary element that simultaneously performs electrical conduction and optical transmission functions. By using this intermediary material with dual properties, the patent achieves efficient light transmission without requiring additional structural elements.
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 improves light utilization efficiency, allowing for higher image quality and reduced component count while maintaining a compact and cost-effective design.
Implementation Method 1
a light emitting layer formed in a layer on the second electrode layer and configured to produce light when a voltage is applied
Implementation Method 2
a lens array configured to guide light emitted from the light emitting device to a photoconductor surface
Implementation Method 3
a photoconductor configured to be driven to rotate about a rotational axis
Data Source
AI summary
A second electrode is laminated on a light emitting layer on an opposite side across the light emitting layer from a first electrode laminated on a silicon substrate. The second electrode is capable of transmitting light. A photoconductor drum is exposed to light by using light transmitted through the second electrode.