Optical Brightener Sizing for Inkjet Substrates
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Solution Overview
Problem
Existing ink jet printing technologies face challenges in achieving high print density, sharpness, and reduced color-to-color bleed due to poor substrate absorption of water-based dyes or pigments, with water-soluble optical brighteners being incompatible with high calcium concentrations, leading to precipitation issues.
Innovation Solution
A sizing composition comprising a divalent metal salt, a binder, and a water-soluble optical brightener of specific formula (1), which is compatible with divalent metal salts, enhancing substrate brightness and print quality without precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If water-soluble optical brighteners are used to improve substrate brightness, then substrate brightness and whiteness are enhanced, but precipitation occurs in high calcium concentrations
Solution Approach 1:
The patent modifies the chemical structure of optical brighteners by introducing specific substituents (such as sulfonate groups, carboxylate groups, or phosphate groups) that change their solubility parameters and electrostatic properties. This allows the brighteners to remain soluble and stable in high calcium concentrations, resolving the precipitation issue while maintaining brightness enhancement.
Solution Approach 2:
The patent uses divalent metal salts as intermediaries that form soluble complexes with optical brighteners. The metal ions act as mediators between the brightener molecules and the substrate, enabling the brighteners to function effectively in the presence of calcium without precipitating, thus improving both brightness and compatibility.
2Illumination intensity
If conventional optical brighteners are used with divalent metal salts, then substrate brightness is improved, but greenish saturation occurs at higher concentrations
Solution Approach 1:
The patent changes the chemical parameters of optical brighteners by selecting specific molecular structures with appropriate electron donors and acceptors. This modification alters the absorption and emission spectra of the brighteners, shifting them away from the green region and preventing greenish saturation even at higher concentrations, while maintaining effective brightness enhancement.
3Ease of manufacture
If plain paper is used as substrate, then production cost is reduced, but ink absorption is poor leading to low print sharpness
Solution Approach 1:
The patent uses divalent metal salts as intermediaries that promote ink absorption on plain paper. The metal ions facilitate the interaction between water-based dyes/pigments and the paper substrate, enabling plain paper to achieve print sharpness comparable to expensive silica-coated papers without requiring special coatings.
Solution Approach 2:
The patent modifies the surface properties of plain paper through treatment with compositions containing divalent metal salts and optical brighteners. This changes the paper's affinity for water-based inks, improving absorption characteristics and print sharpness while maintaining the use of inexpensive plain paper substrates.
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 effectively increases substrate brightness and maintains or enhances whiteness while preventing greenish saturation, allowing for higher optical brightener concentrations without precipitation, thus improving ink jet printing quality.
Implementation Method 1
optical brighteners of formula (1) have surprisingly good compatibility with sizing compositions containing a divalent metal salt
Implementation Method 2
water-soluble optical brightener of specific formula (1), which is compatible with divalent metal salts, enhancing substrate brightness and print quality without precipitation
Data Source
AI summary
The instant invention relates to liquid compositions comprising derivatives of diaminostilbene, binders and ink fixing agents such as divalent metal salts for the optical brightening of substrates suitable for high quality ink jet printing.