White Inkjet Ink Viscosity Control via Alumina-Coated TiO2
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Solution Overview
Problem
Actinic radiation-curable inkjet white inks containing titanium dioxide as a pigment face issues with increased viscosity during discharge, leading to discharge failure and clogging of recording heads, and excessive glossiness when used for top coating or primer coating, due to sodium ion interactions with gelling agents and waxes, resulting in poor esthetic performance and image quality.
Innovation Solution
An actinic radiation-curable inkjet white ink formulation with titanium dioxide surface-coated with alumina, containing a comb-shaped block copolymer with a tertiary amine group as a dispersant, and a combination of aliphatic ketone and fatty acid ester as wax, with controlled sodium ion content below 200 ppm, to prevent viscosity increase and ensure stable gelation and pinning, thereby reducing glossiness differences and clogging risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If titanium dioxide is used as a pigment in actinic radiation-curable inkjet white ink, then the ink can achieve desired whiteness and blocking power, but the viscosity increases during discharge causing discharge failure and clogging of recording heads
Solution Approach 1:
The patent introduces a dispersant with a specific chemical structure (polymer containing amine groups and hydroxyl groups) as an intermediary between titanium dioxide pigment particles and the ink vehicle. This dispersant adsorbs onto the pigment surface, providing steric and electrostatic stabilization that prevents aggregation during heating and discharge, thereby maintaining low viscosity and preventing clogging while preserving the pigment's optical properties
Solution Approach 2:
The patent optimizes multiple parameters including the dispersant molecular weight (1,000-10,000), amine group content (0.1-5 mmol/g), hydroxyl group content (0.1-5 mmol/g), and dispersant concentration in ink (1-10 mass%). These parameter optimizations ensure the dispersant provides sufficient stabilization at discharge temperatures while maintaining appropriate ink viscosity and flow characteristics
2Stability of the object's composition
If sodium ion content is high in titanium dioxide surface-coated with alumina, then the pigment can be easily dispersed, but the gelation of ink is interrupted causing excessive glossiness and poor esthetic performance
Solution Approach 1:
The patent precisely controls the sodium ion content parameter, specifying it should be 1-100 ppm (optimally 10-50 ppm) in the ink formulation. This parameter control prevents excessive interaction between sodium ions and gelling agents that would interrupt gelation, thereby maintaining appropriate glossiness while preserving pigment dispersibility through the dispersant
Solution Approach 2:
The dispersant acts as an intermediary that provides steric and electrostatic stabilization of pigment particles, reducing the reliance on sodium ion effects for dispersibility. This allows the sodium ion content to be kept low for proper gelation while maintaining good dispersibility through the dispersant's molecular structure and adsorption properties
3Ease of operation
If dispersant adsorption is weak at high temperature, then the ink can be easily discharged, but the pigment detaches from the dispersant causing reagglomeration and viscosity increase
Solution Approach 1:
The patent employs a dispersant with a composite molecular structure containing both amine groups (for electrostatic interaction with pigment surface) and hydroxyl groups (for hydrogen bonding and steric stabilization). This composite structure provides multi-mode adsorption that maintains strong pigment-dispersant interaction at discharge temperatures, preventing detachment and reagglomeration while allowing easy discharge
Solution Approach 2:
The patent optimizes the dispersant's molecular weight (1,000-10,000) and functional group content to achieve optimal thermal stability of adsorption. The molecular weight and functional group density are tuned to provide sufficient adsorption strength at discharge temperatures (80-100°C) while maintaining appropriate ink viscosity and flow characteristics for easy discharge
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 maintains ink viscosity and prevents clogging, ensuring stable discharge and image quality with glossiness comparable to other colors, while reducing the formation of metal salts that could cause head clogging, thus enhancing the esthetic performance and operational reliability of the inkjet printing process.
Implementation Method 1
the ink is cured by irradiation with actinic radiation to form an image
Implementation Method 2
the wax or the gelling agent enables sol-gel phase transition through a temperature change, and thus the ink undergoes gelation when being attached onto a recording medium
Data Source
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AI summary
Through the active-light-ray-curable inkjet white ink and method for manufacturing the same according to the present invention, the ink including a pigment, a dispersing agent, a wax, a photopolymerizable compound, and a photopolymerization initiator, and being capable of a sol-gel phase transition by a temperature change, the pigment including titanium dioxide surface-coated with alumina, the content of the titanium dioxide being 10% by mass to 15% by mass of the total mass of the ink, the ink including sodium ions in a mass ratio of 200 ppm or lower with respect to the pigment, and the dispersing agent including a comb-shaped block copolymer having a tertiary amine group, even when titanium dioxide is used as the pigment, the viscosity of the ink can be restrained from increasing, luster equivalent to that of another color is obtained, and clogging of a recording head for ink discharge is reduced in an active-light-ray-curable inkjet ink capable of a sol-gel phase transition by a temperature change.