Organic EL Array Drive Circuit Integration for Gray Scale Control
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Solution Overview
Problem
The cost of image forming devices increases due to the high number of thin film transistors (TFTs) required for pulse width modulation in gray scale control, leading to decreased yield and increased substrate area, which affects the stability and cost-effectiveness of gray scale representation.
Innovation Solution
An image forming device with a photosensitive body, a charging unit, an exposure unit featuring a lens group and an organic EL element array, and a drive circuit with transistor circuits that control luminance using an area gray scale method, reducing the number of TFTs and substrate area, thereby lowering costs and improving stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pulse width modulation is used for gray scale control, then gray scale representation is achieved, but the number of TFTs increases and substrate area increases
Solution Approach 1:
The patent combines the light-emitting element array and the drive circuit (including TFTs) onto a single substrate. This integration merges two previously separate components, reducing the total number of discrete parts and simplifying the overall device structure while maintaining gray scale control functionality.
Solution Approach 2:
The substrate serves multiple functions: it acts as both the mounting platform for the light-emitting element array and as the circuit board for the drive circuit. This multi-functional design eliminates the need for separate substrates for each component, thereby reducing total substrate area and component count.
2Manufacturing precision
If pulse width modulation is used for gray scale control, then gray scale representation is achieved, but substrate area increases
Solution Approach 1:
By merging the light-emitting element array and drive circuit onto one substrate, the patent eliminates the need for a separate substrate for the drive circuit. This consolidation directly reduces the total substrate area required while preserving gray scale control capabilities.
Solution Approach 2:
The patent transitions from a planar arrangement where components are distributed across multiple substrates to a vertically integrated structure where the drive circuit is formed on the same substrate as the light-emitting elements. This dimensional reorganization optimizes space utilization and reduces overall substrate area.
3Ease of manufacture
If organic EL element array is used, then cost is reduced and monolithic formation is enabled, but control of luminance per unit time becomes challenging
Solution Approach 1:
The patent integrates the drive circuit directly onto the same substrate as the organic EL element array, enabling monolithic formation of both the light-emitting elements and their control circuits. This integration maintains the cost advantages of organic EL technology while providing precise luminance control through on-substrate transistor circuits.
Solution Approach 2:
The substrate itself serves as the platform for both the organic EL elements and the drive circuit, making the substrate self-sufficient for hosting both functional elements and control logic. This self-service approach eliminates the need for external control circuits and simplifies the overall device architecture.
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 provides a low-cost, stable gray scale representation by reducing the number of TFTs and substrate area, enhancing the device's efficiency and environmental stability against environmental variations.
Implementation Method 1
an element array which is arranged to face the lens group and includes a plurality of organic EL elements arrayed in parallel with the first direction on a substrate
Implementation Method 2
a lens group having a plurality of lenses arrayed in a first direction
Data Source
AI summary
An exposure unit includes a lens group having a plurality of lenses arrayed in a first direction and an element array which is arranged to face the lens group and includes a plurality of organic EL elements arrayed in parallel with the first direction on a substrate, a drive circuit including a plurality of TFT circuits for controlling luminance per unit time of the organic EL element is arranged on the substrate, and the TFT circuit controls the luminance of the organic EL element based on a signal created by an area gray scale method.