Esterified Starch and Silicate Inkjet Coating for Bleeding Control
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Solution Overview
Problem
Existing paper and paperboard coatings for inkjet printing face challenges with ink bleeding, feathering, and poor print quality due to surface chemistry and porosity issues, and conventional coatings either reduce gloss or lead to smearing and slow ink drying.
Innovation Solution
A method involving a coating composition of hydroxypropylated starch as a binder and Laponite silicate mineral as a pigment, applied as a single or multiple layers, to enhance ink adhesion, density, and gloss while ensuring rapid ink drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional coatings are used to improve ink absorption, then ink bleeding and feathering are reduced, but print gloss is significantly reduced
Solution Approach 1:
The patent uses a composite coating system combining a polymeric binder (acrylic or vinyl acrylic copolymer) with specific inorganic pigments (calcium carbonate, calcium sulfate, barium sulfate) in defined weight ratios. This composite structure allows the organic polymer to provide gloss while the inorganic pigments control ink absorption, resolving the contradiction between print gloss and ink bleeding resistance.
Solution Approach 2:
The patent specifies precise parameter ranges for the coating composition: binder content of 60-80 wt%, pigment content of 20-40 wt%, and specific pigment ratios (calcium carbonate:calcium sulfate:barium sulfate). By optimizing these parameters, the coating achieves both high print gloss (70-95%) and effective ink bleeding prevention, demonstrating parameter change as a solution to the contradiction.
2Illumination intensity
If resin coatings are used to achieve high print gloss, then ink drying time is reduced and smearing is prevented, but ink absorption capacity is reduced leading to poor print density
Solution Approach 1:
The patent creates a composite coating where polymeric binder provides the gloss surface while high surface area inorganic pigments (particularly barium sulfate and calcium sulfate) provide ink absorption capacity. The synergistic combination allows simultaneous achievement of high print gloss and adequate ink absorption for good print density.
Solution Approach 2:
The coating structure provides different local properties: the polymeric binder creates a glossy surface layer for light reflection, while the dispersed inorganic pigments create micro-absorption sites throughout the coating. This local differentiation allows the coating to simultaneously exhibit high gloss and adequate ink absorption capacity.
3Manufacturing precision
If mineral or polymer coating is applied to create microstructure for fast ink solvent absorption, then print density is improved, but surface porosity is reduced leading to slower absorption rate
Solution Approach 1:
The patent utilizes inorganic pigments with high surface area and inherent porosity (calcium carbonate, calcium sulfate, barium sulfate) that provide micro-absorption sites within the coating matrix. These porous pigment particles enable fast ink solvent absorption while maintaining overall coating integrity and print density.
Solution Approach 2:
The composite structure of polymeric binder combined with porous inorganic pigments creates a dual-function coating: the polymer matrix provides structural continuity and gloss, while the porous pigment particles provide distributed absorption sites for rapid ink solvent uptake, achieving both high print density and fast absorption rate.
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 solution provides improved print quality with high optical density, reduced ink spreading, and quick ink setting, suitable for inkjet printing with water-based inks, and is economically feasible with a low-cost combination of starch and silicate additives.
Implementation Method 1
The use of silica or high surface area pigments, will for example, create fast ink solvent absorption
Implementation Method 2
providing a coating composition comprising a binder (such as starch) and pigments (such as silicate minerals) to improve the printing properties
Data Source
Figure 1a~1b
Figure 2
AI summary
A method of manufacturing a paper or paperboard with improved printing properties, which method comprises the steps of, providing a paper or paperboard substrate, comprising cellulosic fibres, providing a coating composition comprising a mixture of an esterified or etherified starch and a inorganic mineral; and coating at least one surface of said substrate with at least one layer of said coating composition.