Polyurethane Inkjet Ink Formulation for Image Quality and Ejection Stability
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Solution Overview
Problem
Conventional pigment inks containing polyurethane polymers fail to achieve optimal ink ejection stability, image quality, and image fastness, with issues such as low acid value leading to poor ejection stability, excessive rigidity causing image deflection, and insufficient optical density due to the absence of urea bonds.
Innovation Solution
A polyurethane inkjet ink formulation with a polyurethane polymer composed of units derived from a polyisocyanate, a polyether polyol, and a diol with an acid group, where the polyether polyol constitutes 80% or more of the units, and the urethane to urea bond ratio is 85.0/15.0 or more, achieving a balanced acid value of 40-140 mgKOH/g and reduced urea bonds to minimize image deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a polyurethane polymer with low acid value (20-30 mgKOH/g) is used to improve image quality, then image quality is improved, but ink ejection stability deteriorates
Solution Approach 1:
The patent changes the acid value parameter of the polyurethane polymer from the conventional low range (20-30 mgKOH/g) to a higher range (40-140 mgKOH/g) by adjusting the type and amount of polyol components, specifically using polyols with hydroxyl values of 10-50 mgKOH/g. This parameter change simultaneously improves both image quality and ink ejection stability.
2Strength
If a polyurethane polymer containing 10% or more of compounds with three or more hydroxy groups is used to improve image fastness, then image fastness is improved, but the polymer becomes excessively rigid causing poor image fastness
Solution Approach 1:
The patent changes the compositional parameters by limiting compounds with three or more hydroxy groups to less than 10% by mole and instead using polyols with specific hydroxyl values (10-50 mgKOH/g). This parameter adjustment achieves the desired balance between image fastness and polymer flexibility.
3Illumination intensity
If a polyurethane polymer with urea bonds is used to improve optical density, then optical density is improved, but face wetting occurs causing image deflection
Solution Approach 1:
The patent changes the chemical composition parameters by carefully selecting polyol components with specific hydroxyl values and molecular weights, and by controlling the ratio of urethane to urea bonds. This achieves high optical density while minimizing face wetting and image deflection.
Solution Approach 2:
The patent creates a composite polyurethane polymer system combining multiple polyol components (including polyether polyols and polyester polyols) with specific properties to achieve a balanced formulation that provides both high optical density and reduced face wetting.
4Reliability
If conventional polyurethane polymers are used to improve ink reliability, then ink reliability is improved, but image quality and image fastness do not sufficiently satisfy requirements
Solution Approach 1:
The patent changes multiple parameters of the polyurethane polymer simultaneously: acid value (40-140 mgKOH/g), hydroxyl value of polyol (10-50 mgKOH/g), molecular weight of polyether polyol (450-4000), and urethane to urea bond ratio (85.0/15.0 or more). This multi-parameter optimization achieves high ink reliability along with superior image quality and fastness.
Data Source
AI summary
To provide an ink jet ink that produces an image having high optical density, scratch resistance, and highlighter resistance, has excellent ink ejection stability, and can reduce image deflection caused by face wetting. The ink jet ink contains a polyurethane polymer and a self-dispersing pigment. The polyurethane polymer has units derived from a polyisocyanate, a polyol having no acid group, and a diol having an acid group. The molar ratio of the percentage of the urethane bond in the polyurethane polymer to the percentage of the urea bond in the polyurethane polymer is 85.0/15.0 or more and 100.0/0 or less.