Inkjet Head Nozzle Voltage Control for LCD Panel Yield
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Solution Overview
Problem
Inkjet printing apparatuses face challenges in achieving uniform ink droplet discharge from nozzles due to varying nozzle characteristics, requiring lengthy feedback loops and multiple-order printing to adjust voltages, which results in non-uniform color values on LCD panels.
Innovation Solution
An ink discharge device with a measurement unit and control unit that adjusts voltages applied to nozzles based on target values, using both fixed and dynamic target values to ensure uniform ink discharge, minimizing overall color value dispersion and neighboring pixel differences, thereby optimizing inkjet head performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedback of substantially printed color values is used to control applied voltage, then uniform ink discharge can be achieved, but the process takes a relatively long time
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for each nozzle based on their individual characteristics before actual printing. The control unit stores the relationship between nozzle characteristics and required voltage corrections, allowing the system to apply pre-determined corrections without waiting for feedback from each printing cycle, thus significantly reducing the DPN process time while maintaining uniform ink discharge
Solution Approach 2:
The patent replaces the traditional feedback-based mechanical control system with a data-driven control system. Instead of relying on physical feedback loops that measure printed color values and adjust voltages iteratively, the system uses pre-acquired nozzle characteristic data and stored correction tables to determine optimal voltages directly, substituting computational processing for iterative physical adjustment
2Manufacturing precision
If multiple-order printing is performed to calculate voltages for noise components, then uniform color values can be obtained, but the process takes a relatively long time
Solution Approach 1:
The patent extracts and separates the noise component analysis from the main printing process. By acquiring nozzle characteristics through preliminary measurements and storing correction values separately, the system removes the need for multiple-order printing to handle noise components. The extraction of characteristic data allows the system to address noise and variations without requiring iterative re-printing, thereby improving productivity while maintaining color uniformity
Solution Approach 2:
The system performs preliminary characterization of each nozzle's response to different voltages and stores this data for future reference. This preliminary action captures noise components and variations in nozzle behavior, allowing the control unit to compensate for these factors in advance without requiring multiple printing passes, thus improving both precision and productivity
3Ease of operation
If equal voltage is applied to all nozzles, then the control process is simple, but the nozzles do not discharge equal amounts of ink droplets
Solution Approach 1:
The patent applies local quality by assigning different voltage values to different nozzles based on their individual characteristics. The control unit stores characteristic data for each nozzle and selects specific voltage levels from stored tables that correspond to each nozzle's performance profile. This localized approach ensures that each nozzle operates at its optimal voltage setting, achieving uniform ink droplet discharge across all nozzles while maintaining operational simplicity through automated control
Solution Approach 2:
The system changes the voltage parameter individually for each nozzle based on pre-acquired characteristic data. By storing multiple voltage levels and their corresponding performance outcomes for each nozzle, the control unit can select the appropriate voltage parameter that compensates for manufacturing variations, ensuring uniform ink discharge without requiring complex real-time adjustments
Data Source
AI summary
Example embodiments are directed to an ink discharge device that discharges uniform amounts of ink droplets from an inkjet head, and a control method thereof. Voltages applied to plural nozzles of the ink-head are changed based on different characteristics of the respective nozzles to discharge uniform amounts of ink droplets from the nozzles. Voltage increments are calculated using a fixed target color value so as to set color value dispersion and voltage increments are calculated using different target color values according to the nozzles so as to satisfy color value differences between the neighboring pixels and thus time required for a DPN process is shortened, and excessive changes of the applied voltages are prevented and thus a preparatory period required to mass-produce an LCD panel is shortened and yield of the LCD panel is increased.