Multi-Core Pen Ink Composition for Smear-Free Thermochromic Erasing

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Solution Overview

Problem

Thermochromic handwriting made on a trial basis with a multi-core writing implement often smears when erased with a friction member, due to adsorption or trailing of non-thermochromic ink colorant, making it difficult to use both types of ink proximally.

Innovation Solution

A multi-core writing implement with a retractable mechanism that houses both thermochromic and non-thermochromic writing bodies, featuring an oil-based non-thermochromic ink composition with specific pigments and a friction member, allowing selective use and erasure of thermochromic ink without smearing the non-thermochromic ink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a multi-core writing implement contains both thermochromic and non-thermochromic writing bodies, then the user can enjoy both thermochromic and non-thermochromic handwriting with a single implement, but the non-thermochromic colorant smears when the thermochromic handwriting is erased with a friction member

Engineering Contradiction:

Improvecapability to produce both thermochromic and non-thermochromic handwritingVSAvoidsmearing of non-thermochromic handwriting during erasure of thermochromic handwriting

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the non-thermochromic ink to an oil-based formulation containing specific pigments and resin components. This parameter change makes the non-thermochromic ink resistant to smearing during friction-based erasure of thermochromic handwriting, while maintaining normal writing functionality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The non-thermochromic ink is formulated as a composite material containing pigment, oil-based vehicle, and specific resin components. This composite structure provides both the coloring function and the smear-resistant property during friction contact, solving the contradiction between versatility and harmful smearing effects.

Inventive Principle:

Principle #40Composite materials

2Reliability

If thermochromic handwriting is erased with a friction member, then the thermochromic ink decolors, but the non-thermochromic colorant is adsorbed onto the friction member or trails on the writing surface

Engineering Contradiction:

Improveerasure function of friction member on thermochromic handwritingVSAvoidadsorption and trailing of non-thermochromic colorant

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the physical and chemical parameters of the non-thermochromic ink formulation, specifically using oil-based ink with high pigment content (50% or more by mass) and specific resin components. These parameter changes prevent the colorant from being adsorbed by the friction member or trailing during the erasure process, while maintaining reliable thermochromic erasure functionality.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If non-thermochromic ink composition uses conventional dye-based formulation, then the writing function is achieved, but the colorant smears and adsorbs onto the friction member during thermochromic erasure

Engineering Contradiction:

Improvewriting functionVSAvoidsmearing and adsorption during friction contact

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The invention fundamentally changes the parameter of the colorant type from conventional dye-based formulation to pigment-based oil-based ink formulation. This parameter change maintains ease of writing operation while eliminating the smearing and adsorption problems that occur during friction-based erasure of thermochromic handwriting.

Inventive Principle:

Principle #35Parameter changes

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

Enables proximal use of thermochromic and non-thermochromic handwriting without smearing, suitable for official documents, with the non-thermochromic ink remaining intact even after erasing the thermochromic ink.

Implementation Method 1

a reversibly thermochromic ink composition

Methodology Applied

Scientific EffectThermochromism: Thermochromism

Implementation Method 2

a friction member is provided at the other end in the lengthwise direction of the shaft cylinder

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS20260061771A1Multi-core writing implement

Publication Date: 2026.03.05 PILOT PEN CO LTD

AI summary

A multi-core writing implement includes a shaft cylinder, a retractable mechanism, and a friction member. Inside the shaft cylinder, a plurality of writing bodies is stored. The retractable mechanism selectively protrudes and retracts one of the writing bodies through a front-end opening provided at one end in a lengthwise direction of the shaft cylinder. The friction member is provided at the other end in the lengthwise direction of the shaft cylinder. The writing bodies includes at least one thermochromic writing body in which a reversibly thermochromic ink composition is stored, and at least one non-thermochromic writing body in which a non-thermochromic ink composition is stored. The non-thermochromic ink composition is an oil-based ink composition including a pigment.