Cover Plate for Uniform Ink Evaporation in PolyLED Printing
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Solution Overview
Problem
Ink-jet printing processes for PolyLED displays often result in uneven height distributions of printed elements due to differences in evaporation rates between edge and center portions of the printed pattern, leading to unusable LEDs as the solvent dries at varying rates based on humidity levels.
Innovation Solution
The method involves conditioning the vicinity of the printed pattern by using a cover plate to hinder solvent vapor escape or by maintaining a solvent vapor environment around the pattern to equalize evaporation rates, ensuring a uniform drying process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ink-jet printing is performed without environmental control, then the printing process is simple and fast, but the evaporation rate varies between edge and center portions causing uneven height distribution
Solution Approach 1:
A cover plate is introduced as an intermediary component between the print head and the printed pattern. The cover plate creates a controlled microenvironment that mediates the evaporation process, ensuring uniform solvent evaporation rates across the entire printed area by reducing the temperature difference between edge and center portions.
Solution Approach 2:
The invention changes the thermal parameters of the printing environment by using a cover plate with specific thermal properties. The cover plate's material composition, thickness, and surface characteristics are optimized to control heat transfer, thereby equalizing the evaporation rate across different regions of the printed pattern.
2Manufacturing precision
If the cover plate is positioned close to the print head, then the temperature difference is reduced and evaporation is equalized, but the distance for solvent vapor escape is limited
Solution Approach 1:
The cover plate is designed with spatially varying properties to address different regional requirements. The distance between the cover plate and the printed pattern varies across the surface, with closer positioning at edge portions to enhance temperature equalization and greater distance at center portions to facilitate solvent vapor escape. This local variation optimizes both evaporation uniformity and vapor removal.
3Area of stationary object
If multiple strokes are used to print large patterns, then the entire pattern can be covered, but bands with different height distribution properties appear at the boundaries
Solution Approach 1:
The cover plate is positioned and adjusted before the printing process begins, establishing a pre-conditioned environment that ensures uniform evaporation across the entire printing area. This preliminary setup prevents the formation of boundary bands by ensuring that both edge and center portions of multi-stroke patterns experience consistent thermal and evaporative conditions from the start.
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 significantly reduces differences in height distributions, ensuring that all printed elements meet predetermined limits, making all LEDs usable.
Implementation Method 1
conditioning the vicinity of at least a portion of a printed pattern 22, in order to diminish a difference between an evaporation rate of an edge portion of the printed pattern and an evaporation rate of a centre portion of the printed pattern
Implementation Method 2
differences in the evaporation rate of the various portions of the printed pattern 22
Data Source
AI summary
A machine (1) is equipped for printing a pattern on a substrate (20). The machine (1) comprises a table (10) for supporting and moving the substrate (20), and a print head (30) for firing ink droplets towards the substrate (20). Further, the machine (1) comprises a cover plate (40) which is arranged such as to encompass the print head (30), wherein the print head (30) partly extends through a hole in the cover plate (40). During a printing process, evaporation of solvent which is part of the ink droplets starts as soon as the ink droplets land on the substrate (20). The presence of the cover plate (40) has an equalizing effect on the evaporation rate over the printed pattern. As a result, a height distribution of all printed elements of the pattern is within predetermined limits, once the elements have dried up.