Density Correction System Using Dual Inkjet Heads
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Solution Overview
Problem
Inkjet recording apparatuses face challenges in reducing droplet amount variation across nozzles, leading to density variations in printed materials, particularly in applications like color filters for liquid crystal displays, due to differences in nozzle shape accuracy and piezoelectric material characteristics, which necessitate costly and complex drive circuits for each nozzle.
Innovation Solution
A density correction system comprising two inkjet heads with different droplet volumes per nozzle, where a control unit adjusts the number of drops from each head to achieve consistent droplet amounts per pixel, utilizing a multi-drop driving system to minimize variation and optimize image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a drive waveform is changed for each nozzle to reduce droplet amount variation, then droplet amount consistency is improved, but device complexity and cost increase due to requiring a separate drive circuit for each nozzle
Solution Approach 1:
The patent divides the inkjet head into multiple inkjet heads with different nozzle groups, where each nozzle group has nozzles with similar characteristics. By segmenting the nozzles into groups and using a common drive waveform for each group rather than individual waveforms for each nozzle, the system reduces droplet variation while lowering drive circuit complexity.
Solution Approach 2:
The patent applies local quality by creating different nozzle groups with locally optimized characteristics. Each nozzle group is designed with nozzles that have similar droplet ejection characteristics, allowing a single drive waveform to effectively control droplet consistency within that local group, thereby achieving good droplet consistency without requiring individual drive circuits for each nozzle.
2Manufacturing precision
If individual drive circuits are provided for each nozzle to achieve precise droplet control, then droplet amount accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent implements universality by designing the inkjet heads so that multiple nozzles within a group share a common drive waveform. This multi-functional approach allows a single drive circuit to control multiple nozzles effectively, reducing the number of required drive circuits while maintaining acceptable droplet amount accuracy through the localized similarity of nozzle characteristics.
Solution Approach 2:
The patent changes the parameter of droplet volume by creating nozzle groups with different average droplet volumes. By adjusting the physical parameters of the nozzles (such as nozzle diameter or shape) within groups and using different drive waveforms for different groups, the system achieves precise overall droplet control without requiring individual drive circuits for each nozzle, thereby reducing manufacturing cost.
3Manufacturing precision
If multiple inkjet heads with different droplet volumes are used to correct density variation, then droplet amount consistency is improved, but device complexity increases due to requiring multiple heads and coordinated control
Solution Approach 1:
The patent merges multiple inkjet heads with different nozzle groups into a single integrated system. By combining heads that have different average droplet volumes and coordinating their operation through a control unit that adjusts the number of drops from each head, the system achieves improved droplet consistency while managing overall system complexity through unified control.
Solution Approach 2:
The patent implements feedback control by using a control unit that monitors and adjusts the number of drops ejected from each inkjet head based on the different droplet volumes of the nozzle groups. This feedback mechanism allows the system to compensate for variations in droplet volume by dynamically adjusting drop counts, achieving consistent overall droplet amounts while managing system complexity through intelligent control.
Data Source
AI summary
A density correction system includes a conveyance unit that conveys a recording medium, a first ink ejection unit that ejects ink in a multi-drop driving system to the recording medium based on image data, a second ink ejection unit that ejects ink in the multi-drop driving system to the recording medium based on the image data and in which a volume per one drop is smaller than that of the first ink ejection unit, and a control unit that corrects number of drops from the first ink ejection unit and number of drops from the second ink ejection unit, which constitute a droplet amount for one pixel on the recording medium subjected to image formation.