Ink Set Hue Angles Resolve Rainbow Effects
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Solution Overview
Problem
Existing ink sets for color ink jet printing face issues with granularity, false contours, and rainbow effects, particularly in skin tones, due to interference between cyan and yellow ink dots, leading to unsatisfactory gloss and color reproducibility.
Innovation Solution
An ink set comprising specific yellow, magenta, cyan, red, orange, and blue inks with defined hue angles and pigments, including C.I. Pigment Yellow 74, C.I. Pigment Blue 15:4, and γ-type C.I. Pigment Violet 19, along with a polyorganosiloxane surfactant, to control granularity, false contours, and rainbow effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If C ink pigment solids concentration is reduced to 3 wt % or less, then gloss is improved, but rainbow effect intensifies due to reddish interfering color
Solution Approach 1:
An orange ink is introduced as an intermediary color to mediate between the cyan and yellow inks. The orange ink absorbs the interfering red light that would otherwise create rainbow effects, while its optical properties allow it to blend smoothly with adjacent ink dots. This intermediary color layer prevents the direct interaction between cyan and yellow dots that causes rainbow effects, even at low pigment concentrations required for high gloss.
2Quantity of substance
If C ink and Y ink dots are superimposed for color reproduction, then color gamut is expanded, but false contours and green cast occur in skin tones
Solution Approach 1:
The orange ink is strategically placed in specific local regions where cyan and yellow dots would otherwise superimpose, particularly in skin tone areas. By locally introducing orange ink dots between cyan and yellow dots, the patent prevents the formation of green cast and false contours in critical regions while maintaining overall color gamut. This localized intervention allows color expansion without the harmful side effects in skin tones.
3Illumination intensity
If pigment solids concentration is increased to improve gloss, then color saturation improves, but granularity deteriorates
Solution Approach 1:
The patent uses a composite ink formulation combining multiple pigment types with different particle sizes and optical properties. The orange ink contains pigments specifically selected to provide high gloss at low concentrations, while the overall ink set combines this with cyan and yellow inks that have optimized particle distributions. This composite approach allows achieving high gloss through the synergistic effect of multiple materials rather than increasing pigment concentration in a single ink, thereby avoiding granularity issues.
Data Source
AI summary
An ink set including at least three colors of inks of yellow ink with a hue angle ∠H°, as defined in CIELAB color space on a recording medium, in the range of about 80° to about 110°, magenta ink with a hue angle ∠H° in the range of about 330° to about 360°, and cyan ink with a hue angle ∠H° in the range of about 230° to about 260°, and the following ink (A) and ink (B): ink (A): ink with a hue angle ∠H° in the range of about 0° to about 80°; and ink (B): ink with a hue angle ∠H° in the range of about 0° to about 80° (where the ink (A) has higher saturation and lower brightness than the magenta ink, and the ink (B) has higher saturation and higher brightness than the magenta ink and higher saturation and lower brightness than the yellow ink, and the hue angle (∠H°) is determined as hue angle ∠H°=tan−1(b*/a*)+180 (when a*<0) or ∠H°=tan−1(b*/a*)+360 (when a*>0), a* and b* representing the perceived chromaticity index as defined in CIELAB color space).