Ink Set Hue Angle Control for Lightfastness
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Solution Overview
Problem
Ink-jet images suffer from deteriorating long-term storage stability due to exposure to sunlight and illuminating lamps, with existing evaluation methods relying on color difference (ΔE) and optical density difference (ΔOD) failing to accurately reflect human perception of hue changes in yellow, magenta, and cyan colors.
Innovation Solution
An ink set for ink-jet recording is developed, comprising yellow, magenta, and cyan inks with controlled hue angle changes (Δh) to improve lightfastness, where the yellow ink contains C.I. Direct Yellow 132, magenta ink includes specific magenta dyes, and cyan ink contains copper phthalocyanine-based dyes, all within specific weight percentages, to minimize hue angle changes on glossy paper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color difference (ΔE) or optical density difference (ΔOD) is used to evaluate long-term storage stability, then measurement can be performed objectively, but the evaluation does not correspond to human eye perception of hue changes
Solution Approach 1:
The patent changes the evaluation parameter from ΔE or ΔOD to hue angle change (Δh). This parameter transformation allows the evaluation to directly reflect human eye sensitivity to hue changes while maintaining objective measurability through colorimetric systems.
2Ease of manufacture
If conventional dyes are used in ink formulations, then inkjet printing can be performed with standard materials, but lightfastness and hue stability deteriorate under sunlight and illuminating lamps
Solution Approach 1:
The patent employs composite dye formulations combining multiple dyes with complementary properties: C.I. Direct Yellow 132 for yellow ink, specific magenta dyes (including copper phthalocyanine complexes) for magenta ink, and copper phthalocyanine-based dyes for cyan ink. This composite approach achieves superior lightfastness and hue stability while maintaining manufacturability.
Solution Approach 2:
The patent optimizes the chemical structure and composition of dyes at the molecular level to achieve specific local properties: high lightfastness, excellent hue stability, and appropriate color strength. Each dye is selected or synthesized with specific functional groups and molecular structures that provide these localized quality improvements.
3Measurement precision
If optical density (OD value) measurements are performed on medium colors, then quantitative color data can be obtained, but the values do not faithfully reflect the color density of the medium color itself
Solution Approach 1:
The patent transforms the measurement parameter from optical density (OD) to hue angle (h) in the L*a*b* colorimetric system. This parameter change allows direct evaluation of hue stability that corresponds to human perception, avoiding the decomposition issue inherent in OD measurements of medium colors.
Data Source
AI summary
An ink set for ink-jet recording is provided defined by an evaluation indicator approximately corresponding to an evaluation sensed by human eyes without relying on a color difference (ΔE) or an optical density difference (ΔOD) at the time of evaluating a long-term storage stability of the ink set for ink-jet recording. In the ink set for ink-jet recording which contains a yellow ink, a magenta ink and a cyan ink, values of hue angle change (Δh), between before and after lightfastness tests, of print regions corresponding to respective inks formed on glossy paper by using the yellow ink, the magenta ink and the cyan ink are not more than about 3° for the yellow ink, not more than about 2° for the magenta ink, and not more than about 6° for the cyan ink.