Ink Formulation Using Composite Pigments for Optical Density and Bleeding Control
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Solution Overview
Problem
Existing ink jet recording technologies fail to simultaneously achieve high optical density, bleeding resistance, and white blur resistance across various recording media, particularly on media with high ink permeability, and suffer from reliability issues like pigment sticking to the recording head.
Innovation Solution
An ink formulation using a combination of phosphonic acid-type self-dispersible pigment and another self-dispersible pigment with a different functional group, where the second pigment has a faster solid-liquid separation rate to enhance optical density and prevent bleeding and white blur, while maintaining sticking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphonic acid-type self-dispersible pigment is used to increase optical density, then optical density is improved, but white blur occurs on recording media with low calcium content
Solution Approach 1:
The patent uses a composite pigment system combining phosphonic acid-type self-dispersible pigment (0.1-5 mass%) with other types of self-dispersible pigments (5-20 mass%). This composite approach allows the phosphonic acid-type pigment to provide high optical density through calcium ion coordination, while the other pigments compensate for white blur by providing alternative dispersion mechanisms that do not depend on calcium content in the recording medium.
Solution Approach 2:
The patent optimizes the introduced amount of functional groups on pigment particles, specifically controlling the ratio of phosphonic acid groups to other functional groups. By adjusting these parameter ranges (phosphonic acid-type pigment: 0.1-5 mass%, other self-dispersible pigments: 5-20 mass%), the system achieves high optical density while preventing white blur through balanced interaction with recording medium components.
2Illumination intensity
If self-dispersible pigment is used to improve image characteristics, then optical density is improved, but pigment sticks to the recording head
Solution Approach 1:
The patent carefully controls the introduced amount of functional groups on pigment particles within specific ranges. By optimizing the density and type of functional groups (phosphonic acid groups combined with other anionic groups), the pigment maintains sufficient reactivity for high optical density while preventing excessive adhesion to the recording head, thus improving sticking resistance.
Solution Approach 2:
The patent creates pigments with non-uniform functional group distribution on particle surfaces, combining different functional groups (phosphonic acid groups and other anionic groups) in specific ratios. This local quality variation allows different regions of the pigment to exhibit different properties: high reactivity for optical density enhancement in the image area, while reduced sticking tendency in the ejection path.
3Illumination intensity
If ink formulation is optimized for high optical density, then optical density is improved, but bleeding resistance decreases on high permeability media
Solution Approach 1:
The patent employs a composite ink formulation containing multiple types of self-dispersible pigments with different functional group characteristics. The phosphonic acid-type pigment (0.1-5 mass%) provides high optical density through strong coordination with calcium ions, while the additional self-dispersible pigments (5-20 mass%) with different functional groups enhance bleeding resistance by interacting with other components in the recording medium, creating a balanced system that addresses both optical density and bleeding control.
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 achieves excellent optical density, bleeding resistance, and white blur resistance on high permeability media and maintains reliable performance with the recording head, ensuring stable image quality and reduced pigment sticking.
Implementation Method 1
self-dispersible pigment to a particle of which a functional group showing high reactivity to calcium is bonded
Implementation Method 2
the second pigment has a faster solid-liquid separation rate to enhance optical density
Data Source
AI summary
The present invention provides an ink that can achieve image characteristics for recording an image having excellent optical density, bleeding resistance, and white blur resistance and also can achieve reliability that provides excellent sticking resistance to a recording head. The ink is one for ink jet containing a first pigment and second pigment. The first pigment is a self-dispersible pigment to a surface of a particle of which a first functional group containing a phosphonic acid group is bonded. The second pigment is a self-dispersible pigment to a surface of a particle of which a second functional group not containing a phosphonic acid group but containing an anionic group other than the phosphonic acid group, and further containing another atomic group is bonded. The introduced amount of the functional group of the second pigment is 0.25 mmol/g or more.