Aqueous Topcoat for Thermal Dye Image Receiver
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Solution Overview
Problem
Current thermal dye transfer systems face challenges in achieving high gloss prints while avoiding surface roughness and dye instability, particularly due to the use of organic solvent-coated overcoats and hollow particle layers, which lead to sticking issues and reduced print quality.
Innovation Solution
The development of an image receiving element with a non-crosslinked extruded image receiving layer and an aqueous-coated topcoat, where the topcoat has a glass transition temperature close to that of the image receiving layer, and a dry thickness ratio that allows for efficient dye transfer without jamming in printers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an organic solvent-coated overcoat is used to protect the dye image receiving layer, then the layer structure is simplified, but sticking occurs during thermal dye transfer and dye instability increases
Solution Approach 1:
The patent removes the organic solvent-coated overcoat layer entirely and replaces it with an aqueous-coated topcoat containing polymer particles. This extraction eliminates the sticking and dye instability problems associated with organic solvents while maintaining the protective function through the aqueous-based alternative.
Solution Approach 2:
The patent changes the coating basis from organic solvent to aqueous solution. This parameter change in the coating medium eliminates the harmful effects of organic solvents (sticking and dye migration) while achieving the same protective function through water-based polymer particles with controlled glass transition temperature.
2Manufacturing precision
If a hollow particle layer is used to provide compliance between support and dye receiving layer, then close contact is improved, but surface roughness increases and surface gloss is reduced
Solution Approach 1:
The patent removes the hollow particle layer from the structure and instead provides compliance through an extruded compliant layer made of thermoplastic elastomer. This extraction eliminates the surface roughness and gloss reduction caused by hollow particles while maintaining the necessary compliance and heat insulation functions.
Solution Approach 2:
The patent applies different material properties to different layers: the extruded compliant layer provides compliance and heat insulation, while the aqueous-coated topcoat provides a smooth, glossy surface. This local differentiation of material functions achieves both contact uniformity and surface quality without compromise.
3Manufacturing precision
If hollow particles are coated from aqueous solutions, then compliance is provided, but a powerful drying stage is required and productivity is reduced
Solution Approach 1:
The patent removes the hollow particle coating process entirely and replaces it with extrusion of a thermoplastic elastomer compliant layer. This extraction eliminates the need for aqueous coating and subsequent powerful drying stages, thereby significantly improving productivity while maintaining compliance functionality.
Solution Approach 2:
The patent replaces the wet coating and drying process (thermal-evaporation-based) with a mechanical extrusion process. This substitution eliminates the lengthy drying stage required for aqueous coatings while achieving the same compliance layer formation through controlled extrusion and cooling.
4Strength
If the topcoat polymer has a glass transition temperature significantly different from the image receiving layer, then adhesion is improved, but dye migration increases and stability decreases
Solution Approach 1:
The patent optimizes the glass transition temperature parameter of the topcoat polymer to be within ±20°C of the image receiving layer's Tg. This parameter matching prevents excessive dye migration while maintaining adequate adhesion, resolving the contradiction between strong bonding and dye stability.
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 solution enables the production of high gloss and matte prints with improved dye stability and reduced surface roughness, while simplifying the layer composition and avoiding the use of antistatic layers, thus enhancing print quality and manufacturing efficiency.
Implementation Method 1
the topcoat is an aqueous-coated layer and has a polymer that has a Tg that is within a range of plus or minus 20° C. of the Tg of the extruded image receiving layer
Implementation Method 2
U.S. Pat. No. 4,775,657 (Harrison et al.) describes the use of organic solvent-coated overcoats in thermal dye transfer elements, which overcoats containing polycondensation polymers having a glass transition temperature that is at least 40° C. less than the Tg of the organic solvent-coated dye image receiving layer. This difference in Tg tends to cause sticking of the element during thermal dye transfer.
Data Source
AI summary
An image receiving element has an extruded compliant layer, an extruded image receiving layer, and a topcoat immediately adjacent the extruded image receiving layer. The extruded image receiving layer is non-crosslinked and has a glass transition temperature (Tg) of from about 40° C. to about 80° C. whereas the topcoat is an aqueous-coated layer and has a Tg that is within a range of plus or minus 10° C. of the Tg of the extruded image receiving layer. The dry thickness ratio of the topcoat to the extruded image receiving layer is from 1:2 to 1:20.