Five-Color Ink Set for Corrugated Cardboard Color Reproducibility
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Solution Overview
Problem
Conventional inkjet methods for forming multi-color images on corrugated cardboard struggle with color reproducibility for the 18 colors defined by Japanese Corrugated Fiberboard Industry Standards (JCS) due to the impracticality of using 18 separate inkjet heads and the impairment of on-demand printability in small quantities.
Innovation Solution
An inkjet ink set comprising five colors - cyan, magenta, yellow, black, and an α ink, with specific hue angles, chroma saturation, and lightness values that satisfy certain formulas in the CIE 1976 L*a*b* color space, allowing for excellent color reproducibility of the 18 colors, and an image forming method using these inks with a treatment liquid containing an acidic compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 18 separate inkjet heads are used to reproduce the 18 colors defined by JCS, then color reproducibility is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent merges the function of 18 separate inkjet heads into a single inkjet head by developing a five-color ink set (CMYK plus α ink) that can reproduce all 18 JCS colors through controlled combination and layering of the five base inks on corrugated cardboard substrate
Solution Approach 2:
The patent changes the color parameters of the five base inks (hue angle, chroma saturation, lightness) to specific ranges that enable the reproduction of the full spectrum of 18 JCS colors. The α ink with hue angle of 33° to 62° and specific chroma saturation and lightness values is key to expanding the color gamut while maintaining reproducibility
2Device complexity
If inkjet heads are switched to reduce the number of heads, then device complexity is reduced, but on-demand printability and productivity are significantly impaired
Solution Approach 1:
The single inkjet head is designed to be universal by accommodating all five ink types (cyan, magenta, yellow, black, and α ink) simultaneously, enabling the system to print any combination of the 18 JCS colors in a single pass without head switching, thus maintaining on-demand printability while reducing device complexity
3Device complexity
If conventional CMYK inks are used, then device complexity is kept simple, but color reproducibility of the 18 JCS colors is insufficient
Solution Approach 1:
The patent creates a composite ink system by combining five specifically formulated inks (CMYK plus α ink) with defined color parameters. This composite ink set expands the color gamut beyond conventional CMYK while maintaining compatibility with standard inkjet printing systems, achieving superior reproduction of the 18 JCS colors
Data Source
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AI summary
Provided are an inkjet ink set for corrugated cardboard, the inkjet ink set including inks of five colors, including a cyan ink, a magenta ink, a yellow ink, a black ink, and an α ink, in which in a case where images having a halftone dot area ratio of 100% are formed on a corrugated cardboard base material using the five color inks each separately, the hue angle h, the chroma saturation C*, and the lightness L* of the formed images in the CIE 1976 L*a*b* color space satisfy the relations of the following Formula 1 to the following Formula 3; and an image forming method. In Formula 1, hM, hα, and hY represent the respective hue angles h of the inks. In Formula 2, C*M, C*α, and C*Y represent the respective chroma saturations C* of the inks. In Formula 3, L*M and L*α represent the respective lightness L* of the inks. hM<hα<hY C*M<C*α<C*Y L*M<L*α