Copolymer Binder Resin for Aqueous Ink Image Density
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Solution Overview
Problem
Inkjet recording methods using pigment inks face issues with water resistance, light resistance, and image density on plain paper, leading to paper curl and increased risk of paper jam due to the permeation of ink into the paper, which affects storage stability and printing quality.
Innovation Solution
A copolymer with structural units having a biphenyl group is used as a binder resin in aqueous ink, enhancing pigment adsorption and dispersion, preventing beading, and improving image density by promoting rapid pigment agglomeration on the paper surface through π-π stacking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pigment concentration in the ink is increased to improve image density, then image density increases, but the ink becomes viscous and discharging stability degrades
Solution Approach 1:
A copolymer binder resin with specific structural units (containing aromatic rings and carboxyl groups) is introduced as an intermediary substance. This binder resin adsorbs pigment particles through π-π stacking and hydrogen bonding, forming stable pigment-binder complexes that maintain fluidity even at high pigment concentrations (10-30 wt%), thereby preserving discharging stability while achieving high image density.
Solution Approach 2:
The ink formulation uses a composite system combining pigment particles, copolymer binder resin, and aqueous solvent. The copolymer binder resin with specific molecular weight (5,000-50,000) and structural units creates a composite material that balances pigment loading capacity with ink fluidity, enabling high pigment concentration without excessive viscosity increase.
2Reliability
If water is added to the pigment ink to maintain fluidity, then ink viscosity is reduced, but the water swells the paper surface and causes curling
Solution Approach 1:
The invention changes the chemical parameters of the ink formulation by introducing a copolymer binder resin with specific functional groups (carboxyl groups with pKa 4-6) and molecular weight range. This allows achieving the desired ink viscosity and fluidity through molecular interactions rather than simply increasing water content, thereby avoiding excessive paper swelling and curling.
3Shape
If a permeating agent is added to promote water permeation into paper to prevent curling, then paper curling is reduced, but the ink becomes hydrophobic and storage stability decreases
Solution Approach 1:
The invention optimizes the pH parameter of the ink formulation (pH 5-8, preferably 6-7) to match the pKa range of the copolymer binder resin's carboxyl groups. This parameter optimization ensures adequate water permeation into paper for curl prevention while maintaining ink hydrophilicity and storage stability through balanced molecular interactions.
4Reliability
If pigment ink is used instead of hydrosoluble dye to improve water resistance and light resistance, then durability improves, but image density on plain paper decreases due to pigment permeation
Solution Approach 1:
The copolymer binder resin acts as an intermediary that adsorbs pigment particles and anchors them on the paper surface through strong molecular interactions (π-π stacking, hydrogen bonding). This prevents pigment permeation into the paper bulk while maintaining water and light resistance, thereby achieving both high durability and high image density on plain paper.
Solution Approach 2:
The invention replaces physical pigment deposition with chemical adsorption mechanisms. The copolymer binder resin provides chemical bonding sites (carboxyl groups) that form strong attachments to pigment particles, substituting weak physical adhesion with robust chemical interactions, thereby preventing pigment loss and maintaining image density.
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 copolymer improves storage stability, image density, and prevents beading by effectively adsorbing pigments, reducing paper curl, and maintaining ink viscosity, thus enhancing the overall printing quality and preventing paper jam.
Implementation Method 1
promoting rapid pigment agglomeration on the paper surface through π-π stacking
Implementation Method 2
enhancing pigment adsorption and dispersion, preventing beading
Data Source
AI summary
A copolymer includes structural units having the following formulae (1) and (2): wherein each of R1 and R2 independently represents a hydrogen atom or a methyl group; X represents a hydrogen atom or a cationic ion; and L represents a single bond or -(CH2)n-O-, the oxygen atom of which is bonded with the biphenyl; and n represents an integer of from 2 to 18.