Fiber Brush Tip Structure for Stable Ultra-Fine Cosmetic Lines

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Solution Overview

Problem

Existing cosmetic implements struggle to draw extremely thin lines corresponding to lower eyelashes or eyebrows with minimal change in line width in response to varying application loads.

Innovation Solution

A cosmetic implement with a brush tip having a total volume of 10 to 40 mm³, a density of 0.03 to 0.10 mg/mm³ excluding the flange portion, and a flange portion volume of 10 to 25% of the total, optimized for fiber composition and shape, ensuring consistent line width and appropriate liquid supply.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the brush tip volume is reduced to draw extremely thin lines, then line thinness is improved, but line width stability deteriorates due to sensitivity to application load variations

Engineering Contradiction:
Improveline thicknessVSAvoidline width stability
Core Design Contradiction:
Length of moving objectVSReliability

Solution Approach 1:

The patent optimizes specific parameters of the brush tip including fiber diameter (0.03-0.08mm), brush tip volume (15-30mm³), and fiber bundle dimensions to achieve a balance that enables thin line drawing while maintaining stability against application load variations

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The brush tip employs fibers with specifically engineered local properties including diameter, length (10-20mm), and material composition (synthetic resin with solvent resistance) to create regions optimized for both thin line application and load tolerance

Inventive Principle:
Principle #3Local quality

2Length of moving object

If the brush tip is made smaller for thin line application, then line fineness is improved, but liquid supply capacity deteriorates

Engineering Contradiction:
Improveline finenessVSAvoidliquid supply capacity
Core Design Contradiction:
Length of moving objectVSQuantity of substance

Solution Approach 1:

The patent specifies optimal parameter ranges including brush tip volume (15-30mm³), fiber diameter (0.03-0.08mm), and fiber length (10-20mm) to achieve sufficient liquid capacity while maintaining fine line application capability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The brush tip uses composite fiber structures combining synthetic resin materials with specific physical properties to optimize both liquid absorption capacity and fine line delivery in a compact form

Inventive Principle:
Principle #40Composite materials

3Quantity of substance

If fibers with larger diameter are used to improve liquid storage, then liquid supply capacity is improved, but line thinness deteriorates

Engineering Contradiction:
Improveliquid storage capacityVSAvoidline thinness
Core Design Contradiction:
Quantity of substanceVSLength of moving object

Solution Approach 1:

The patent identifies optimal fiber diameter range (0.03-0.08mm) that provides sufficient liquid storage capacity in the fiber bundle while maintaining the ability to deposit extremely thin lines, balancing both requirements through precise parameter control

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

The implement achieves extremely thin lines with minimal line width variation and controlled liquid consumption, preventing huskiness or bleeding, suitable for lower eyelashes and eyebrows.

Implementation Method 1

the base portion of a bundle of fibers made of thermoplastic resin is bundled into a cylindrical shape and heated, thereby forming a heated and melted flange portion at the base portion

Methodology Applied
Scientific EffectHeating and melting: Melting

Data Source

PatentEP4706448A1Cosmetic implement
Publication Date: 2026.03.11 MITSUBISHI PENCIL CO LTD
  • EP4706448A1 patent drawingFigure 1(A)~1(B)
  • EP4706448A1 patent drawingFigure 2~3
  • EP4706448A1 patent drawingFigure 4(A)~4(C)

AI summary

The present invention provides a cosmetic implement that is provided with a brush head which makes it possible to draw very fine lines corresponding to lower eyelashes, for example, and in which the degree of change in line width with respect to the application load (pressing amount) applied to the brush head is small. Provided is a cosmetic implement that comprises a brush head 21 in which resin fibers are bundled at one end of a shaft cylinder 1, and which is configured such that a liquid cosmetic stored inside the shaft cylinder can be supplied to the brush head, wherein: the brush head has an application part for the liquid cosmetic formed at the tip end side thereof by a fiber bundle, and has a flange part 21 for holding the fibers formed at the base end side thereof; the volume of the entire brush head is 10-40 mm3; the density of the brush head excluding the flange part, which is expressed as [weight W mg of brush head excluding flange part/volume V mm3 of brush head excluding flange part] is 0.03-0.10; and the volume of the flange part is set to be 10-25% of the volume V of the brush head excluding the flange part.