Salt-Forming Dye Ink Composition for Ballpoint Pen
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Solution Overview
Problem
Conventional oil-based ink compositions for ball-point pens face issues with ink stability over time, poor light resistance, and writing feel, particularly due to the instability of nigrosine-based dyes and the reactivity of surfactants with dyes leading to precipitate formation and increased viscosity.
Innovation Solution
An oil-based ink composition incorporating salt-forming dyes such as dodecyl diphenyl oxide disulfonic acid and xanthene-based basic dyes, combined with a pigment like basic carbon black, and a polyvinyl butyral resin, along with an aromatic amine, to enhance stability, light resistance, and writing feel, while maintaining a suitable viscosity and pH range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nigrosine-based dye is used as coloring agent, then high concentration and low cost are achieved, but ink stability over time deteriorates due to poor solubility in organic solvent
Solution Approach 1:
The patent changes the chemical parameters of the dye system by selecting specific salt-forming dyes (triarylmethane-based, xanthene-based, or azomethine-based basic dyes) with defined solubility characteristics in organic solvents. This parameter change resolves the contradiction by achieving both high concentration (1-10 mass%) and long-term stability without precipitation.
2Ease of operation
If surfactant is incorporated as lubricant to improve feeling of writing, then writing smoothness is enhanced, but reaction with dye occurs and precipitate is generated
Solution Approach 1:
The patent extracts and eliminates the surfactant component from the ink composition, resolving the contradiction by achieving writing smoothness through alternative means (ball material selection, tip design, or natural lubrication from ink additives) without introducing substances that react with the dye to form precipitates.
3Ease of operation
If viscosity of ink is decreased to improve feeling of writing, then writing smoothness is enhanced, but lubrication state changes from fluid lubrication to boundary lubrication and wear increases
Solution Approach 1:
The patent optimizes the viscosity parameter to a specific range (100-5000 mPa·s at 20°C) that maintains fluid lubrication conditions. This parameter change ensures both improved writing smoothness and preserved wear resistance by keeping the lubrication regime in the fluid or mixed lubrication zone rather than transitioning to boundary lubrication.
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 composition provides a stable, deep-colored written trace with improved light resistance and writing feel, reducing wear and maintaining lubricity even under high writing pressure, thus addressing the limitations of previous ink formulations.
Implementation Method 1
the composition further comprises a salt-forming dye of an acid dye and an aromatic ring amine
Implementation Method 2
a polyvinyl butyral resin in which a hydroxyl group in a molecule is 20 to 40 mol%
Implementation Method 3
comprising at least a dye, a pigment, and an organic solvent
Data Source
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AI summary
[Problem to be Solved] Provided are: an oil-based ink composition for a ball-point pen having a favorable feeling of writing, the favorable deepness of a written trace, favorable light resistance, favorable ink stability over time, and favorable pigment dispersibility; and an oil-based ball-point pen refill using the oil-based ink composition. [Solution] An oil-based ink composition for a ball-point pen comprising at least a dye, a pigment, and an organic solvent, wherein the dye is at least one salt-forming dye selected from the group consisting of salt-forming dyes of alkylbenzene sulfonic acids and xanthene-based basic dyes, salt-forming dyes of alkylbenzene sulfonic acids and triarylmethane-based basic dyes, and salt-forming dyes of alkylbenzene sulfonic acids and azomethine-based basic dyes.