Materials for Deep and Vivid Color Dyeing - 1.Intensification of Color by Coating the Surface with Substance of Low Refractive Index

Sep 21, 2026

Shinji Yamaguchi, from Kuraray Co., Ltd., Department of Fiber Research and Development, addresses the demand for deep and vivid color in dyed fabrics and explains how polyester’s relatively low stainability has been improved through black intensification techniques. The work analyzes factors affecting fiber coloring, then details two mechanisms: reducing surface reflection by coating fibers with low refractive-index substances, and enhancing both intensity and brightness via controlled roughness inspired by the moth-eye optical principle. Numerous patent-linked examples support the approaches, including coating methods, emulsions, and industrial processing considerations.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages20

Reading Time50 min

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1.Intensification of Color by Coating the Surface with Substance of Low Refractive Index

2.Intensification and Brightening of Color by Rough Surface of Fiber

Yamaguchi,S. Materials for deep and vivid colordyeing.5 p. Sen i Gakkaishi 40,4-5:204-6 (1984)。Filed: TRANSLATION NO.4432SENGSEN6AS MATERIALS FOR DEEP AND VIVID COLOR DYEING Shinji Yamaguchi Department of Fiber Research &Development,Kurashiki Plant,Kuraray Co.,Ltd. Demand for deep and vivid color in dyed fabric exists whether the fiber isnatural or synthetic.Polyester fibers have been a focus of attention in recenttimes,the effort being to improve its relative deficiency in stainability.Thetechnology of intensification of black color has been at the center of the endeavor,since blackness in formal wear is a clear index of the stainability of the material. # 1.Intensification of Color by Coating the Surface with Substance of Low Refractive Index Factors associated with fiber coloring include refractive index of fiber,fiber morphology(shape of cross section,crimp),and fiber surface.Stated simply,the color of an object(excluding materials which are intrinsically luminescent)is determined byreflection,transmission,and absorption of light,although lightreflected at the surface does not contribute to the degree of coloration of coloredsubstance.Color is intensified when surface reflection is diminished and the amountsof transmitted and absorbed light are increased.Polyester fiber,among garment fibers,has the highest refractive index.By coating its surface with material of low refrac-tive index,deep black dyeing has been attained¹.Studies on coating of fiber sur-face with low refracting resin havelong been practiced on cotton²)and polyester³.Examples include application of silicone on the surface of fiber product(JapanesePatent Disclosure 48-13695 [Teijin])and formation of thin polymer film of lowerrefractive index than the base fiber by plasma polymerization or discharge grafting(Japanese Patent Disclosure 53-1ll192 [Toray]).The latter requires costly specialapparatus and could hardly be considered for practical processing.In the former,in which a padding of silicone simply as aqueous suspension or organic solution isapplied,stability and uniformity of the application have been sources of problems. There have been a number of recent proposals,including one which employsagents of refractive index of under 1.45,e.g.,fluorinated compound,silicon resin,and acrylic ester in emulsion or solution to impregnate at high temperature orspray-coat followed by heating(Japanese Patent Disclosure 55-26232[Toray]),andothers in which electrolyzable substance is added to an emulsion of low refractivepolymer to allow uniform adsorption(Japanese Patent Disclosures 56-112580,112581,112588 [Teijin]).Various low refracting substances have also been devised,such asaqueous suspension containing silica particles(Japanese Patent Disclosure 56-112583[Nikka Chem.]),polyurethane or its mixture with low refractive polymer for surfacecoating to improve durability in dry cleaning(Japanese Patent Disclosure 56-73175[Toray]),auto-emulsifying polyurethane(Japanese Patent Disclosure 56-29681[Kao Digitized by the Internet Archivein 2019 https://archive.org/details/materialsfordeep00yama Soap]),low refracting polymer containing inert inorganic fine particles(JapanesePatent Disclosure 57-66184 [Toray]),polyurethane-urea polyamine heat setting resincoating(Japanese Patent Disclosure 58-60082 [Toray]),and fluorinated polymerhaving blocked polyfluoroalkyl group(Japanese Patent Disclosure 57-176275[AsahiGlass]). # 2.Intensification and Brightening of Color by Rough Surface of Fiber Conferring elevations and depressions on fiber surface increased light scatter-ing and reduced color brightness⁴.It was therefore not expected that this treat-ment would lead to color intensification.The arrangement which occurs in nature,however,utilizes optical behavior with unexpected ingenuity.The so-called "motheye"principle pertains to the surface of the eye of moth flying at dusk,the sur-face being provided with elevations and depressions of 0.2 um pitch⁵) whic

FAQs

What determines the coloration of a non-luminescent dyed material according to the document?

It is determined by reflection, transmission, and absorption of light, with color intensified when surface reflection is diminished and transmitted and absorbed light increase.

Why is polyester highlighted for deep black dyeing?

The document states that polyester fiber has the highest refractive index among garment fibers, making it a key focus for improving blackness and stainability.

How does the moth-eye principle relate to color intensification in dyed fibers?

By creating elevations and depressions on a surface at a scale comparable to light wavelengths, surface reflection is reduced; refining the roughness to the appropriate range increases both color intensity and brightness.

Sep 21, 2026

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