Aqueous Writing Ink Composition for Durable Low-Viscosity Marking

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Solution Overview

Problem

Existing aqueous ink compositions for writing utensils face challenges in achieving a high degree of compatibility between durability and writing performance after long-term storage, while also considering environmental impact, as increasing resin content for durability leads to increased viscosity and environmental concerns.

Innovation Solution

Incorporating water-insoluble cellulose and an evaporation inhibitor into the ink composition, with a vapor pressure of less than 12.3 kPa, and using an acetylene-based surfactant to maintain low viscosity and improve writing performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the blending amount of fixing resin is increased to improve durability, then the durability (water resistance, alcohol resistance) is improved, but the liquid viscosity is increased which restricts ink design

Engineering Contradiction:
ImprovedurabilityVSAvoidviscosity
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention extracts and removes the fixing resin component from the ink composition entirely, replacing it with water-insoluble cellulose particles that provide durability without increasing viscosity. This extraction of the problematic substance while maintaining the desired function directly resolves the contradiction between durability and viscosity.

Inventive Principle:
Principle #2Taking out (Extraction)

2Reliability

If blending compositions using resin with low solubility parameter and non-polar solvent is performed to enhance durability further, then the durability is improved, but the environmental load increases making it unfavorable

Engineering Contradiction:
ImprovedurabilityVSAvoidenvironmental load
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the fundamental parameters of the ink composition by switching from organic solvents and resins to an aqueous system with water-insoluble cellulose. This parameter change eliminates the need for non-polar solvents and low solubility parameter resins, thereby reducing environmental load while maintaining durability through the unique properties of water-insoluble cellulose particles.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If cellulose nanofibers and biomass nanofibers are used to improve drawing quality and storage stability, then the drawing quality and storage stability are improved, but adverse effects on weather resistance, viscosity change after long-term storage, and writing performance occur

Engineering Contradiction:
Improvedrawing qualityVSAvoidweather resistance
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The invention uses water-insoluble cellulose particles that remain stable and do not degrade over time, unlike nanofibers that can cause viscosity changes and performance degradation during storage. The water-insoluble cellulose provides consistent weather resistance and writing performance throughout the product lifecycle without the adverse effects of nanofiber degradation.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

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 composition achieves excellent durability and writing performance, including water and alcohol resistance, with reduced environmental burden, by using water-insoluble cellulose and an evaporation inhibitor, and an acetylene-based surfactant to maintain ink fluidity and prevent blurring.

Implementation Method 1

containing at least a water-insoluble cellulose

Methodology Applied
Scientific EffectHydrophobicity: Hydrophobe

Implementation Method 2

having a vapor pressure of ink at 50°C of less than 12.3 kPa

Methodology Applied
Scientific EffectVapor pressure reduction: Vapour Pressure

Implementation Method 3

the aqueous ink composition for a writing utensil further contains an acetylene-based surfactant

Methodology Applied
Scientific EffectSurfactant action: Surfactant

Data Source

PatentEP4711424A1Aqueous ink composition for writing utensils, and writing utensil obtained using same
Publication Date: 2026.03.18 MITSUBISHI PENCIL CO LTD
  • EP4711424A1 patent drawingFigure 1(a)~1(c)
  • EP4711424A1 patent drawingFigure 2(a)~2(d)
  • EP4711424A1 patent drawingFigure 3(a)~3(b)

AI summary

Provided are an aqueous ink composition for a writing utensil and a writing utensil using the same suitable for a marking pen, a marker pen, and the like, which can highly achieve and maintain compatibility in both durability (water resistance, polyalcohol) and good writing performance even after long-term storage without using a fixing resin and is also excellent to the recent environmental action (less environmental burden). The aqueous ink composition for a writing utensil of the present invention contains at least a water-insoluble cellulose and an evaporation inhibitor, in which a vapor pressure of ink at 50°C is less than 12.3 kPa. A writing utensil of the present invention is characterized by being loaded with the aqueous ink composition for a writing utensil having the configuration described above.