White Ink Composition for Digital Offset Printing
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Solution Overview
Problem
Existing white inks for digital offset printing lack sufficient tack and tack stability, leading to inadequate coverage and transfer issues on substrates, particularly on metallic substrates and those requiring white background labels or special effects.
Innovation Solution
A white ink composition comprising a mixture of white pigment particles with specific size ranges, a dispersant, a curable monomer or oligomer, and a photo-initiator, which enhances tack and tack stability, ensuring predictable ink cohesion and transfer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If white ink contains titanium dioxide pigment, then the ink provides white color and hiding power, but the tack and tack stability are insufficient
Solution Approach 1:
The patent uses a composite pigment system combining titanium dioxide with zinc oxide and/or barium sulfate. This composite approach maintains the white color and hiding power of TiO2 while incorporating materials with different surface properties that improve tack and tack stability. The synergistic combination resolves the contradiction by achieving both functional requirements (coverage) and performance stability without requiring complex additional formulations.
Solution Approach 2:
The patent modifies the particle size distribution parameters of the pigment particles, specifying that at least 40% of particles fall within particular size ranges. This parameter change optimizes the balance between hiding power (requiring sufficient particle size) and tack stability (influenced by surface area and particle morphology). By controlling these physical parameters, the ink achieves both coverage and stability without formulation complexity.
2Reliability
If the ink viscosity is increased to improve cohesion, then ink transfer is improved, but the ink becomes difficult to meter and apply uniformly
Solution Approach 1:
The patent optimizes the viscosity parameter of the ink composition by selecting specific polymer carriers and their molecular weights. The formulation achieves sufficient cohesion for reliable transfer while maintaining viscosity within the operational range required for uniform metering and application by the inking subsystem. This parameter optimization resolves the contradiction between cohesion and ease of operation.
3Reliability
If the white ink coverage is increased to improve hiding power, then substrate coverage is improved, but the ink transfer efficiency decreases
Solution Approach 1:
The composite pigment system (TiO2 with zinc oxide and/or barium sulfate) provides enhanced hiding power and coverage while maintaining optimal transfer characteristics. The different materials in the composite have different optical and surface properties that work synergistically to achieve both high coverage and efficient transfer, resolving the contradiction between coverage and transfer efficiency.
Solution Approach 2:
The patent optimizes particle size distribution parameters to achieve the desired balance. By controlling that at least 40% of particles fall within specific size ranges, the formulation achieves sufficient hiding power for complete substrate coverage while maintaining particle characteristics that facilitate efficient transfer from the imaging member to the substrate, thus resolving the contradiction between coverage and transfer efficiency.
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 ink composition achieves improved tack and tack stability, resulting in enhanced coverage and transfer efficiency on various substrates, meeting the requirements of digital offset printing systems and providing consistent opacity and hiding power.
Implementation Method 1
at least one component selected from a curable monomer or a curable oligomer, and a photo-initiator
Data Source
AI summary
The present disclosure is directed to a white ink composition for use in digital offset printing, including a first white colorant including a first plurality of white pigment particles, wherein an average diameter of at least about 40% of the first plurality of white pigment particles is in a range of about 250 nanometers to about 350 nanometers, a second white colorant including a second plurality of white pigment particles, wherein an average diameter of at least about 40% of the second plurality of white pigment particles is in a range of about 350 nanometers to about 550 nanometers, at least one dispersant, at least one component selected from a curable monomer or a curable oligomer, and a photo-initiator. Also provided is a method of digital offset printing using the white ink composition of the present disclosure.