Carboxy-Polymer Ink Composition for Stable Inkjet Dot Formation
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Solution Overview
Problem
Existing inkjet recording methods face challenges in achieving high-quality ink images with sufficient jetting stability and graininess, particularly when using a two-liquid system where ink droplets coalesce on the recording medium, leading to uneven density and poor graininess, and require adjustments for different types of recording media.
Innovation Solution
An ink composition comprising water, a pigment, and a water-soluble polymer with a carboxy group, satisfying the expression 230 mgKOH/g≤Σ(a×b)≤750 mgKOH/g, applied on a recording medium treated with a pretreatment liquid containing aggregating agents, enhances jetting stability and graininess by promoting pigment aggregation and viscosity increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface tension of the colored ink is reduced to suppress landing interference, then the permeation rate of ink droplets is improved, but the jetting stability becomes insufficient
Solution Approach 1:
The solution divides the inkjet recording system into two separate liquid components: a colored ink and a pretreatment liquid. The colored ink maintains its original surface tension for stable jetting, while the pretreatment liquid applied to the recording medium suppresses landing interference through aggregating agents. This segmentation allows each component to optimize its properties independently.
Solution Approach 2:
The pretreatment liquid is applied to the recording medium before the colored ink is jetted. This preliminary action prepares the recording medium surface with aggregating agents that will suppress droplet coalescence when the colored ink lands, without requiring modification of the colored ink's surface tension properties.
2Manufacturing precision
If the permeation rate of ink droplets is adjusted for different recording media, then the landing interference is suppressed, but the surface tension must be adjusted for each type of recording medium
Solution Approach 1:
The pretreatment liquid serves as a universal solution that can be applied to various types of recording media. The aggregating agents in the pretreatment liquid adapt to different recording medium surfaces, providing landing interference suppression without requiring customization of the colored ink's surface tension for each medium type.
3Reliability
If a pretreatment liquid is applied to suppress spread of ink droplets, then the jetting stability is improved, but the graininess is insufficient
Solution Approach 1:
The pretreatment liquid contains aggregating agents that change the surface properties of the recording medium. When the colored ink lands on the pretreated surface, the aggregating agents promote pigment aggregation through chemical or physical interactions, enhancing graininess while the pretreatment liquid simultaneously suppresses droplet spread for improved jetting stability.
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 solution provides ink images with excellent jetting stability and good graininess by suppressing droplet coalescence and adjusting pigment aggregation, ensuring uniform dot formation and improved image quality.
Implementation Method 1
a water-soluble polymer having a carboxy group... pretreatment liquid including at least one aggregating agent selected from the group consisting of acids, cationic polymers, and polyvalent metal salts
Implementation Method 2
pretreatment liquid including at least one aggregating agent selected from the group consisting of acids, cationic polymers, and polyvalent metal salts... promotes pigment aggregation
Implementation Method 3
pretreatment liquid including at least one aggregating agent selected from the group consisting of acids, cationic polymers, and polyvalent metal salts... promotes pigment aggregation
Data Source
AI summary
Provided is an ink composition for inkjet recording containing water, a pigment, and a water-soluble polymer having a carboxy group, in which the water-soluble polymer satisfies the following expression (1), and the ink composition for inkjet recording is used for recording an ink image on a recording medium to which a pretreatment liquid including at least one aggregating agent selected from the group consisting of acids, cationic polymers, and polyvalent metal salts is applied:230 mgKOH/g≤Σ(a×b)≤750 mgKOH/g (1)a means an acid value of the water-soluble polymer, in terms of mgKOH/g, and b means a content of the water-soluble polymer with respect to a total amount of the ink composition, in terms of % by mass.