Cross-linked Dispersant Encapsulation for Thermal Inkjet Stability
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Solution Overview
Problem
Thermal ink jet printers experience degradation in print quality over time due to heat cycling, particularly affecting pigment-based inks which suffer from colloidal stability issues leading to nozzle fouling and blockages, resulting in unreliable and precise ink droplet ejection.
Innovation Solution
A process for preparing a dispersion involving particulate solids, a liquid medium, and a dispersant with cross-linkable groups, where the dispersant is cross-linked in the presence of the particulate solid and liquid medium to create an encapsulated particulate solid, with controlled cross-linking and metal chelating agent addition to enhance colloidal stability and long-term printer performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pigment-based inks are used in thermal ink jet printers, then light fastness and optical density are improved, but colloidal stability deteriorates leading to nozzle fouling and blockages
Solution Approach 1:
A dispersant with cross-linkable groups is introduced as an intermediary substance between the pigment particles and the liquid vehicle. The dispersant adsorbs onto pigment surfaces providing steric or electrostatic stabilization, while its cross-linkable groups form a protective network that prevents pigment aggregation and fouling during thermal cycling, thus maintaining colloidal stability without compromising light fastness
Solution Approach 2:
The ink formulation is designed as a composite system combining pigment particles, liquid vehicle, dispersant, and cross-linked polymer network. This composite structure provides both the optical properties of pigment-based inks and the colloidal stability of well-dispersed systems, preventing nozzle fouling while maintaining light fastness and optical density
2Productivity
If thermal ink jet printing operates at high frequencies, then productivity is improved, but heat cycling causes component degradation and print quality deterioration
Solution Approach 1:
The dispersant cross-linking is performed beforehand to create a pre-protective network that cushions pigment particles against the mechanical and thermal stresses of high-frequency operation. This prior cushioning prevents particle aggregation and fouling during the million-cycle lifetime of the printhead, maintaining print quality consistency despite continuous high-frequency thermal cycling
Solution Approach 2:
The cross-linking degree of the dispersant is optimized to achieve the right balance between flexibility and stability. By controlling the cross-linking parameters (0.01 to 0.5 mmoles of cross-linkable groups per g of dispersant), the ink can withstand high-frequency thermal cycling without degradation, enabling both high productivity and reliable print quality
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 resulting dispersion improves the long-term robustness and operability of thermal ink jet printers by maintaining print quality and reliability, with enhanced colloidal stability and reduced nozzle fouling, allowing for consistent high-quality inkjet printing.
Implementation Method 1
cross-linking the dispersant in the presence of the particulate solid and the liquid medium thereby preparing a dispersion of an encapsulated particulate solid
Implementation Method 2
adding a metal chelating agent to the dispersion; and after stage (iii) the stage of: (iv) removing at least some of the metal chelating agent from the dispersion
Implementation Method 3
a resin comprising a mixture of resin monomers, crosslinkers and initiators, each resin monomer, crosslinker and initiator being selected from the group
Implementation Method 4
a voltage is applied to a resistor which rapidly heats up and vaporises some of the liquid vehicle in the ink jet printing ink so forming a vapour bubble
Data Source
AI summary
A process for preparing a dispersion comprising the stages: i) providing a dispersion comprising a particulate solid, a liquid medium and a dispersant having cross-linkable groups and a weight averaged molecular weight of from 1,000 to 70,000; and ii) cross-linking the dispersant in the presence of the particulate solid and the liquid medium thereby preparing a dispersion of an encapsulated particulate solid, wherein the cross-linking is performed such that 0.01 to 0.5 mmoles of cross-linkable groups in the dispersant are cross-linked per g of dispersant; said process also comprising at any stage: iii) adding a metal chelating agent to the dispersion; and after stage iii) the stage of: iv) removing at least some of the metal chelating agent from the dispersion.