Water-Based Ballpoint Ink Composition for Skip-Free High-Angle Writing

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Solution Overview

Problem

Existing ink compositions for water-based ballpoint pens using colored resin particles containing pigments suffer from skipped strokes and writing defects when writing at high angles or under high loads due to the pigment interposing between the ball and the ball socket, hindering the ball's rotation.

Innovation Solution

Incorporating urethane-based colored resin particles with a specific average particle size of 0.3 to 2 μm and a naphthalenesulfonic acid-formaldehyde condensate, along with a pigment such as carbon black, to enhance the ink composition's stability and prevent pigment shedding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If colored resin particles containing pigment are used as ink composition, then the ink is easy to disperse and stable when different colors are mixed, but the pigment interposes between the ball and ball socket hindering ball rotation and causing skipped strokes

Engineering Contradiction:
Improveink stabilityVSAvoidwriting continuity
Core Design Contradiction:
Stability of the object's compositionVSReliability

Solution Approach 1:

The patent changes the particle size parameter of the colored resin particles to a specific range of 0.3 to 2 μm. This parameter change allows the particles to be small enough to avoid interposing between the ball and ball socket while maintaining their stability and dispersion properties, thus resolving the contradiction between ink stability and writing continuity.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses composite colored resin particles that combine pigment with specific resin materials. This composite structure allows the pigment to be contained within a matrix that prevents it from interfering with ball rotation while maintaining color stability and dispersion characteristics.

Inventive Principle:
Principle #40Composite materials

2Stability of the object's composition

If colored resin particles containing pigment are used, then excellent dispersion and color stability are achieved, but writing defects occur at high writing angles or under high load

Engineering Contradiction:
Improvecolor stabilityVSAvoidwriting smoothness
Core Design Contradiction:
Stability of the object's compositionVSEase of operation

Solution Approach 1:

By precisely controlling the particle size parameter within 0.3 to 2 μm, the patent ensures that the colored resin particles do not create interference at high writing angles or under high load conditions, while maintaining color stability and ease of dispersion.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS12577418B2Ink composition for water-based ballpoint pens
Publication Date: 2026.03.17 MITSUBISHI PENCIL CO LTD

AI summary

An ink composition for a water-based ballpoint pen in which, even in a case of an ink composition for a water-based ballpoint pen using a colored resin particle containing a pigment, the phenomenon of skipped strokes does not occur and writing defects are less likely to occur when writing at a high writing angle or under a high load. An example of the ink composition for a water-based ballpoint pen according to the present embodiment includes an ink composition for a water-based ballpoint pen that contains at least a urethane-based colored resin particle containing a pigment and having an average particle size of 0.3 to 2 μm and a naphthalenesulfonic acid-formaldehyde condensate.