Black Ink Composition for Uniform High-Speed Image Formation
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Solution Overview
Problem
Existing inkjet recording technologies face challenges in achieving high-quality images with black color or intermediate tones like gray, as they often result in streak-shaped unevenness, hue unevenness, and nozzle damage due to the use of carbon black, which affects image density and rubbing resistance, especially at high speeds.
Innovation Solution
A black ink composition comprising carbon black, cyan and magenta pigments coated with water-insoluble resins, along with water-insoluble resin particles, is developed to maintain a low carbon black content while ensuring desired black density and tone accuracy, reducing nozzle damage and image unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If carbon black is used as the main black pigment to achieve black density and tone, then image density and color reproducibility are improved, but streak-shaped unevenness and hue unevenness occur especially at high-speed single-pass recording
Solution Approach 1:
The patent uses a composite ink formulation containing carbon black particles (1.0-5.0 wt%), cyan pigment (0.5-3.0 wt%), magenta pigment (0.5-3.0 wt%), and yellow pigment (0.5-3.0 wt%) together with specific resin components. This composite approach allows the ink to maintain black density from carbon black while using cyan and magenta pigments to compensate for hue variations and reduce streak-shaped unevenness, achieving both image density and uniformity
Solution Approach 2:
The patent optimizes the particle size distribution of carbon black (Dv10: 0.03-0.10 μm, Dv50: 0.20-0.50 μm, Dv90: 0.80-1.50 μm) and controls the content ratio of carbon black to total pigments at 20-70 wt%. These parameter changes improve the ejection characteristics and reduce aggregation, thereby preventing streak-shaped unevenness while maintaining black density
2Productivity
If high-speed single-pass recording is performed to increase productivity, then recording speed is improved, but unevenness in hue and streak-shaped unevenness become more significant
Solution Approach 1:
The patent adjusts the viscosity of the ink to 10-50 cP at 25°C and controls the surface tension to 20-40 mN/m. These parameter changes optimize the ejection characteristics for high-speed single-pass recording, ensuring uniform droplet formation and placement, which prevents hue unevenness and streak-shaped unevenness even at high recording speeds
Solution Approach 2:
The ink contains a composite of multiple pigments (carbon black, cyan, magenta, yellow) with specific resin components (polymer A: 1.0-5.0 wt%, polymer B: 0.5-3.0 wt%). This composite formulation ensures consistent color reproduction and reduces hue variation during high-speed single-pass recording by compensating for minor ejection variations through the combined effect of multiple pigments
3Manufacturing precision
If carbon black content is increased to improve black density, then image density is improved, but nozzle damage during maintenance increases
Solution Approach 1:
The patent optimizes the carbon black content to 1.0-5.0 wt% and controls the particle size distribution (Dv10: 0.03-0.10 μm, Dv50: 0.20-0.50 μm, Dv90: 0.80-1.50 μm). These parameter changes ensure sufficient black density while minimizing particle aggregation and nozzle clogging, thereby reducing nozzle damage during maintenance
Solution Approach 2:
The patent uses resin components (polymer A and polymer B) as intermediaries that coat and protect the carbon black particles. These resins improve the dispersion stability of carbon black and reduce direct contact between carbon black particles and the nozzle surface, thereby maintaining black density while reducing nozzle damage
4Manufacturing precision
If multiple pigments are used together with carbon black to improve tone accuracy, then color reproducibility is improved, but the complexity of ink formulation increases
Solution Approach 1:
The patent uses a composite ink formulation containing carbon black (1.0-5.0 wt%), cyan pigment (0.5-3.0 wt%), magenta pigment (0.5-3.0 wt%), and yellow pigment (0.5-3.0 wt%). The cyan and magenta pigments are used in controlled amounts to adjust the hue and improve tone accuracy of black and gray images, while the yellow pigment compensates for hue variations. This composite approach improves tone accuracy without excessive complexity by using well-established pigment combinations
Data Source
AI summary
A black ink composition includes: carbon black and a water-insoluble resin that covers at least a part of the surface of the carbon black; a cyan pigment and a water-insoluble resin that covers at least a part of the surface of the cyan pigment; a magenta pigment and a water-insoluble resin that covers at least a part of the surface of the magenta pigment; water-insoluble resin particle; and water, wherein a content ratio of the carbon black is from 1.0 to 2.0% by mass with respect to the total mass of the composition, and a total amount of pigments is from 1.8 to 3.5% by mass with respect to the total mass of the composition. The black ink composition can be used in an ink set and an image forming method.