Inkjet Head Voltage Pulse Width for Stable Spacer Bead Ejection
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Solution Overview
Problem
Conventional methods for arranging spacers in liquid crystal display apparatuses, such as spraying, result in uneven distribution and potential damage to active elements like TFTs, while inkjet recording methods face jetting errors and instability due to the use of larger spacer beads, leading to reduced display integrity and productivity.
Innovation Solution
An inkjet recording apparatus with a head featuring nozzles, pressure chambers, and electromechanical transducers that apply voltage pulses to jet ink containing spacer beads, with a first pulse width set to twice the acoustic resonance period of the pressure wave, ensuring stable and accurate placement of spacers on substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional spray method is used to arrange spacers, then the process is simple and fast, but the spacer distribution becomes uneven and display integrity is reduced
Solution Approach 1:
The patent replaces the conventional mechanical spray method with an inkjet recording method that uses controlled droplet ejection. The inkjet head precisely deposits spacer-containing ink at predetermined positions, eliminating the uneven distribution problem of spray methods while maintaining high productivity through automated positioning and multi-nozzle simultaneous operation.
Solution Approach 2:
The patent changes the delivery mechanism parameter from aerosol spray to controlled inkjet droplet ejection. By adjusting inkjet parameters such as droplet size, ejection frequency, and positioning accuracy, the system achieves both high precision spacer placement and maintained productivity, resolving the contradiction between speed and uniformity.
2Productivity
If spray method is used, then productivity is maintained, but TFT damage occurs when spacers lie at projecting TFT portions
Solution Approach 1:
The inkjet recording method performs preliminary positioning of spacers at predetermined positions before substrate assembly. The control unit calculates optimal spacer positions that avoid projecting TFT portions, and the inkjet head pre-deposits spacer-containing ink at these safe positions, preventing TFT damage while maintaining productivity through automated position planning.
Solution Approach 2:
The system incorporates feedback through the control unit that monitors substrate geometry and TFT positions. Based on this information, the control unit adjusts spacer placement positions in real-time to avoid projecting TFT portions, eliminating the harmful effect of spacer-induced TFT breakage while maintaining efficient spacer arrangement.
3Manufacturing precision
If inkjet method is used to place spacers precisely, then position accuracy is improved, but jetting errors increase due to large spacer bead size
Solution Approach 1:
The patent changes the physical state parameter of spacers from large coagulated beads to fine dispersed particles within ink. By controlling particle size distribution and dispersion quality in the ink formulation, the system enables stable inkjet ejection while maintaining precise spacer placement accuracy, resolving the contradiction between precision and jetting reliability.
Solution Approach 2:
The patent introduces ink as an intermediary medium to carry spacer particles. The ink acts as a carrier that disperses spacer particles uniformly and enables controlled ejection through the inkjet head. This intermediary solution allows precise spacer placement while the ink's fluid properties ensure stable jetting, even with spacer particles present.
4Quantity of substance
If large spacer beads are used for inkjetting, then spacer function is maintained, but mist and satellite droplets increase causing vibration
Solution Approach 1:
The patent changes the concentration and size distribution parameters of spacer particles in the ink. By optimizing these parameters to use fine, uniformly dispersed particles rather than large beads, the system maintains the necessary spacer quantity and function while reducing mist and satellite droplet formation, thereby stabilizing ink droplet composition during ejection.
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 approach enhances the stability and accuracy of inkjetting spacer beads, improving the position accuracy and reducing errors, thereby maintaining display integrity and increasing productivity by ensuring precise placement and reduced damage to active elements.
Implementation Method 1
an plurality of electromechanical transducers which change a capacity of each of the pressure chambers by supplying a voltage pulse to each of the electromechanical transducers
Implementation Method 2
when a half of an acoustic resonance period of a pressure wave in the pressure chambers is assumed as AL, a width of the first pulse is twice of the AL or more
Data Source
AI summary
An inkjet recording apparatus has a head which includes, a plurality of nozzles each of which jets ink containing spacer beads dispersed therein on a substrate; a plurality of pressure chambers each of which communicates with each of the nozzles; and an plurality of electromechanical transducers which change a capacity of each of the pressure chambers by applying a voltage pulse, wherein the ink is jetted from each of the nozzles by applying to each of the electromechanical transducers the voltage pulse which includes a first pulse for increasing the capacity of the pressure chamber and then decreasing the capacity after a lapse of a predetermined time, wherein, when a half of an acoustic resonance period of a pressure wave in the pressure chambers is assumed as AL, a width of the first pulse is twice of the AL or more.