Cationic Coating Formulation for Inkjet Printing on Recycled Paper
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Solution Overview
Problem
Existing digital printing technologies face challenges in achieving high image quality on substrates with lower brightness, such as brownish recycled paper or paperboard, due to poor ink absorption, pigment and dye fixation, and the need for additional primer application, which increases costs and reduces margins.
Innovation Solution
A cationic coating formulation comprising anionic ultrafine ground calcium carbonate, non-ionic polyvinyl alcohol, water-soluble salt of a divalent metal ion, dispersing agent, and cationic polymer, with specific pore size distribution and charge interactions, to enhance ink absorption, fixation, and surface brightness without requiring a separate primer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a primer is applied to improve ink absorption and fixation, then image quality improves, but production costs increase and process complexity increases
Solution Approach 1:
The patent combines the primer coating and top coating into a single integrated coating layer applied in one step. The coating formulation contains both primer-like components (for ink absorption and fixation) and top coat components (for surface properties), merging two separate functional layers into one unified layer that eliminates the need for sequential application while maintaining image quality.
Solution Approach 2:
The single coating layer performs multiple functions simultaneously: it provides ink absorption, pigment fixation, surface brightness, and smudge resistance. The coating formulation is designed as a universal composition that delivers all these functions in one application, replacing the need for separate primer and top coat applications.
2Manufacturing precision
If a primer is applied to improve ink absorption and fixation, then image quality improves, but production costs increase
Solution Approach 1:
The patent combines the primer coating and top coating into a single integrated coating layer applied in one step. The coating formulation contains both primer-like components (for ink absorption and fixation) and top coat components (for surface properties), merging two separate functional layers into one unified layer that eliminates the need for sequential application while maintaining image quality.
3Quantity of substance
If conventional coating formulations are used on lower brightness substrates, then production costs are reduced, but image quality deteriorates due to poor ink absorption and bleeding
Solution Approach 1:
The patent modifies the chemical and physical parameters of the coating formulation to enhance performance on lower brightness substrates. The formulation includes specific polymers with controlled molecular weights, charged particles for electrostatic ink attraction, and binders optimized for adhesion to darker substrates. These parameter changes enable the coating to provide sufficient contrast and ink fixation even when applied to substrates with lower brightness, eliminating the need to use only high-brightness substrates.
4Productivity
If rapid drying is achieved to prevent smearing, then productivity improves, but ink absorption may be insufficient leading to poor image quality
Solution Approach 1:
The patent incorporates porous structures within the coating layer that facilitate rapid capillary absorption of liquid ink. The porous network allows ink to be quickly drawn into the coating matrix, enabling fast drying times that prevent smearing. Simultaneously, the porous structure provides sufficient pathways for complete ink absorption, ensuring that pigments are fully taken up by the coating and fixed properly, thereby maintaining high image quality.
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 formulation improves inkjet print quality by increasing brightness, reducing bleeding, and enhancing optical print density on lower brightness substrates, eliminating the need for additional primer application and reducing production costs.
Implementation Method 1
A cationic coating formulation consists of: water, at least one anionic ultrafine ground calcium carbonate, at least one non-ionic polyvinyl alcohol, at least one water-soluble salt of a divalent metal ion, at least one dispersing agent, and at least one cationic polymer
Implementation Method 2
at least one anionic ultrafine ground calcium carbonate, when in the form of a compacted bed, has a monomodal pore size distribution, a volume defined pore size polydispersity expressed as full width at half maximum (FWHM) from 40 to 80 nm, and a volume defined median pore diameter from 30 to 80 nm
Data Source
AI summary
The present invention relates to a cationic coating formulation, which contains beside water a specific anionic ultrafine ground calcium carbonate, a non-ionic polyvinyl alcohol, a water-soluble salt of a divalent metal ion, a dispersing agent and a cationic polymer. Said coating formulation according to the present invention can be used for manufacturing a digital print medium, preferably an inkjet print medium.