Liquid Ejection Head Drive Signal Uniformity
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Solution Overview
Problem
Existing methods for setting up drive signals in liquid ejection heads struggle to ensure uniform ejection rates across nozzles with varying frequencies and patterns, leading to uneven liquid distribution and quality issues in thin film production, such as striped density unevenness in color filters.
Innovation Solution
A method that calculates the ejection rate for each nozzle using a moving average, classifies nozzles into groups based on these rates, determines proper drive signal conditions for each group, and selects the most suitable condition for each nozzle to ensure uniform ejection, even when nozzles are used with different frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive signal is used for all nozzles, then the control system is simple, but the ejection rate varies among nozzles causing non-uniform liquid distribution
Solution Approach 1:
The patent applies local quality by setting different drive signal conditions for different nozzles based on their individual ejection characteristics. Each nozzle is classified into groups according to its ejection rate, and specific drive signal parameters (voltage, pulse width, frequency) are assigned to each group to compensate for variations, thereby achieving uniform ejection across all nozzles while maintaining manageable control complexity.
Solution Approach 2:
The patent utilizes parameter changes by adjusting drive signal parameters (voltage level, pulse width, frequency) for different nozzle groups. By measuring and comparing ejection rates, the system modifies these parameters systematically to compensate for manufacturing variations and frequency-of-use differences, transforming a uniform drive signal approach into a differentiated parameter strategy that achieves precision.
2Manufacturing precision
If drive signals are set up independently for each nozzle, then ejection uniformity is improved, but the hardware configuration and control requirements become excessive
Solution Approach 1:
The patent applies merging by combining multiple nozzles with similar ejection characteristics into the same group, which shares a common drive signal condition. This grouping strategy reduces the number of independent control channels needed, as nozzles within each group are controlled collectively rather than individually, thereby simplifying hardware configuration while still achieving precision through group-level differentiation.
Solution Approach 2:
The patent implements universality by creating a multi-functional drive signal system where a single drive signal condition can serve multiple nozzles (a group of nozzles). This approach allows the control system to handle diverse nozzle characteristics through a unified grouping and classification framework, reducing the overall complexity of the control architecture while maintaining the ability to address each nozzle's specific needs.
3Adaptability or versatility
If nozzles are used with different frequencies for different substrate patterns, then adaptability is improved, but variation in ejection rate occurs due to nozzle wear and usage differences
Solution Approach 1:
The patent applies preliminary action by measuring and classifying nozzle ejection characteristics before actual production use. The system performs initial ejection rate measurements for each nozzle, groups them by characteristics, and assigns appropriate drive signal conditions in advance. This preparatory classification and setup ensures that even when nozzles are used with different frequencies for various substrate patterns, their ejection rates remain consistent because the drive signals are pre-configured to compensate for individual variations and usage differences.
Data Source
AI summary
A method for setting up a condition for a drive signal in a liquid ejection head that includes a plurality of linearly-arranged nozzles and driving elements provided for each of the nozzles, includes: calculating an ejection rate for each nozzle relating to a supply of the drive signal under a predetermined condition by using a moving average; classifying the plurality of nozzles into a plurality of groups based on the ejection rate calculated by using the moving average of each nozzle; calculating a proper condition for the drive signal corresponding to each group based on a statistical value of the ejection rate relating to the group; and selecting one proper condition among proper conditions corresponding to the groups so as to set the selected proper condition for each nozzle.