Inkjet Recording Medium with Hydrophilic Salt Coating
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Solution Overview
Problem
Current inkjet printing technologies face challenges when using aqueous inks on glossy or semi-glossy coated papers, resulting in issues like coalescence, intercolor bleed, and reduced optical density due to the water-resistant coatings designed for offset lithography, which are not suitable for inkjet printing.
Innovation Solution
A topmost layer comprising 30-70 wt % of aqueous soluble salts of multivalent metal cations and at least 0.05 g/m2 of a cross-linked hydrophilic polymer binder is applied to the substrate, enabling improved inkjet printing performance by maintaining ink on the surface and enhancing optical density and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a water-resistant coating is applied to the substrate to maintain surface characteristics for offset lithography, then the surface smoothness and gloss are improved, but the ink penetration is reduced causing coalescence and poor image quality
Solution Approach 1:
The invention applies a localized hydrophilic coating layer (0.1-10 g/m2) specifically on the surface where inkjet printing occurs, while maintaining the original water-resistant coating properties elsewhere. This localized modification creates a micro-environment that promotes ink penetration without compromising the overall surface smoothness and gloss required for offset lithography compatibility.
Solution Approach 2:
The hydrophilic coating acts as an intermediary layer between the water-resistant substrate and the aqueous inkjet ink. This intermediate layer facilitates controlled water absorption and ink penetration, mediating the conflict between the water-resistant substrate properties and the water-based ink requirements, thereby preventing coalescence while maintaining surface quality.
2Manufacturing precision
If the coating is made highly porous to allow ink penetration, then the optical density is improved, but the surface gloss and smoothness are reduced
Solution Approach 1:
Rather than making the entire coating highly porous, the invention applies a thin hydrophilic layer (0.1-10 g/m2) locally at the ink reception zone. This localized approach provides sufficient porosity for ink penetration and optical density improvement without significantly affecting the overall surface gloss and smoothness characteristics required for offset lithography compatibility.
3Productivity
If aqueous inkjet inks are printed on water-resistant coated paper, then the printing speed can be increased, but the ink dries too slowly causing coalescence and intercolor bleed
Solution Approach 1:
The hydrophilic coating serves as an intermediary that accelerates water evaporation from the inkjet ink by providing a controlled pathway for moisture removal. This intermediate layer enables faster drying at high printing speeds while preventing coalescence and intercolor bleed, thus improving both productivity and reliability simultaneously.
Solution Approach 2:
The invention changes the surface energy and hydrophilicity parameters of the coating by applying a hydrophilic layer. This parameter modification creates a surface that promotes rapid water evaporation and ink fixation, enabling high-speed printing without the drying problems that would otherwise occur on water-resistant surfaces.
4Manufacturing precision
If a thick coating is applied to absorb ink, then the optical density is improved, but the basis weight increases making the paper unsuitable for mailing and distribution
Solution Approach 1:
The invention achieves high optical density by changing the hydrophilicity parameter of a thin coating layer (0.1-10 g/m2) rather than increasing coating thickness. This parameter modification allows the thin layer to effectively absorb and retain ink, providing high optical density while keeping the basis weight low enough for mailing and distribution requirements.
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 allows for high-speed inkjet printing with high optical density, reduced mottle, and improved durability on various substrates, including glossy and matte coated offset papers, while maintaining the surface characteristics and reducing issues like coalescence and intercolor bleed.
Implementation Method 1
a cross-linked hydrophilic polymer binder... maintaining ink on the surface
Implementation Method 2
cross-linked hydrophilic polymer binder... improving inkjet printing performance
Implementation Method 3
topmost layer comprises from 30-70 wt % of one or more aqueous soluble salts of multivalent metal cations and at least 0.05 g/m2 of a cross-linked hydrophilic polymer binder
Implementation Method 4
the inks have a tendency to sit on the surface of the coating, rather than penetrate into the coating and/or underlying paper substrate
Data Source
AI summary
An inkjet receiving medium including a substrate and having a topmost layer coated thereon at solid content of from 0.1 to 25 g/m2, wherein the topmost layer comprises from 30-70 wt % of one or more aqueous soluble salts of multivalent metal cations and at least 0.05 g/m2 of a cross-linked hydrophilic polymer binder. Improved optical density, reduced mottle and improved wet abrasion resistance are provided when the receiver is printed with an aqueous pigment-based ink. In further embodiments, the topmost layer may further comprise a latex dispersion for improved image durability.