Liquid Coating Apparatus Circulation System for Particle Dispersion
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Solution Overview
Problem
Conventional methods for dispensing spacer particles in liquid crystal displays face issues with uneven distribution, sedimentation, and aggregation, leading to unstable and imprecise ejection, which can damage active elements like TFTs and affect display quality.
Innovation Solution
A liquid coating apparatus with a circulation flow channel system, including a common liquid chamber, sub-tank, and flow channels, uses piezo elements to maintain even dispersion of spacer particles through ultrasonic vibrations and shear stress, preventing aggregation and ensuring stable ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inkjet apparatus ejects solvent including large sized spacer particles, then the spacer particles can be arranged at accurate locations with high productivity, but the spacer particles tend to sediment and aggregate, causing unstable ejection and malfunction
Solution Approach 1:
The patent applies ultrasonic vibration to the solvent in the tank to prevent sedimentation and aggregation of spacer particles. The vibration keeps particles uniformly dispersed in the solvent, ensuring stable ejection characteristics while maintaining high productivity through inkjet apparatus operation.
2Stability of the object's composition
If the spacer particles are evenly dispersed in the solvent, then the ejection characteristics remain stable, but the sedimentation rate is very high causing particles to settle in the tank and aggregate near nozzles
Solution Approach 1:
Ultrasonic vibration is applied to the solvent to counteract gravitational sedimentation. The vibration energy prevents particles from settling and aggregating, maintaining uniform dispersion over time and ensuring consistent ejection performance without particle accumulation in the tank or near nozzles.
3Stability of the object's composition
If a mixing device with motor driven screw is provided in the tank, then the spacer particles can be evenly dispersed in the liquid crystals, but the device complexity increases
Solution Approach 1:
The patent replaces the complex motor-driven screw mixing device with ultrasonic vibration. This substitution achieves the same dispersion effect with a simpler system, eliminating the need for mechanical mixing components while maintaining uniform particle distribution in the solvent.
Solution Approach 2:
The patent changes the physical state of the solvent by applying ultrasonic vibration, transforming it from a static liquid to a vibrated state that naturally prevents particle sedimentation. This parameter change achieves dispersion without requiring complex mechanical mixing devices.
4Stability of the object's composition
If the pressuring chamber is vibrated by piezo element, then the spacer particles can be evenly dispersed, but the ejection precision may be affected by vibration during coating operation
Solution Approach 1:
The patent separates the vibration function into two distinct locations: ultrasonic vibration is applied to the tank containing the solvent, while the piezo element in the pressuring chamber is used only for ejection. This segmentation prevents vibration interference during ejection while maintaining particle dispersion through tank vibration.
Solution Approach 2:
The patent applies periodic ultrasonic vibration to the tank during standby periods when the inkjet apparatus is not ejecting. This periodic action maintains particle dispersion without interfering with the precise ejection process, as vibration is applied only when coating operation is suspended.
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 apparatus effectively prevents spacer particle sedimentation and aggregation, ensuring stable and precise ejection, reducing the risk of damaging active elements and maintaining display quality.
Implementation Method 1
a piezo element which is provided for each pressuring chamber to change the volume of the pressuring chamber
Implementation Method 2
a device which circulates the liquid in a circulation flow channel which includes the common liquid chamber, the first flow channel, the sub-tank and the second flow channel
Data Source
AI summary
A liquid coating apparatus, including; a head which has plural nozzles which eject liquid in which plural particles are dispersed, plural pressuring chambers each communicates to each nozzle, a piezo element which is provided on the pressuring chamber to change a volume of the pressuring chamber, and a common liquid chamber which communicates to each of the plural pressuring chambers; a sub-tank which stores the liquid and has an acceleration device to accelerate the plural particles to disperse in the liquid; a first flow channel which connects the common liquid chamber with the sub-tank; a second flow channel which connects the common liquid chamber with the sub-tank; and a circulation device which circulates the liquid through a circulation flow channel which includes the common liquid chamber, the first flow channel, the sub-tank and the second flow channel.