Four-Black Ink Set for Reducing Graininess and Bronzing

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Solution Overview

Problem

Existing ink sets with multiple black inks of varying carbon black concentrations struggle to reduce graininess and eliminate bronzing, especially in bright gradation regions, leading to undesirable color shifts and metallic luster effects.

Innovation Solution

An ink set comprising four black ink compositions with specific carbon black and resin emulsion ratios, including a first ink with less than 0.3% carbon black, a second with 0.3-0.6%, a third with 0.6-1.5%, and a fourth with 1.5-10%, along with a pH-adjusted resin component and surfactants, to optimize ink distribution and image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If an ink set with multiple black inks of different carbon black concentrations is used, then the color reproducibility of the darkest gradation region is improved, but graininess and bronzing occur in bright gradation regions

Engineering Contradiction:

Improvecolor reproducibilityVSAvoidgraininess and bronzing

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the black ink into four distinct compositions with progressively increasing carbon black concentrations (0.01-0.3%, 0.3-0.6%, 0.6-1.5%, and 1.5-10%). Each ink composition is assigned to specific gradation regions, allowing precise control over different brightness levels while maintaining uniform resin emulsion content across all compositions to prevent graininess and bronzing in bright regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different black ink compositions are applied to different local regions of the image based on brightness requirements. Bright gradation regions use inks with lower carbon black concentration (first and second compositions), while dark gradation regions use inks with higher carbon black concentration (third and fourth compositions). This local differentiation optimizes image quality for each region without causing graininess or bronzing in bright areas.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If a high concentration of ink is used in bright gradation regions to adjust ink generation amount, then coverage is improved, but graininess and bronzing are generated

Engineering Contradiction:

Improveink generation amountVSAvoidgraininess and bronzing

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent changes the carbon black concentration parameter across different ink compositions while maintaining consistent resin emulsion content. By adjusting only the carbon black concentration and not the resin content, the ink provides adequate coverage in bright regions without causing graininess or bronzing, as the resin emulsion forms a uniform matrix that prevents crystallization and metallic luster effects.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9783691B2Ink set and recording method

Publication Date: 2017.10.10 SEIKO EPSON CORP

AI summary

An ink set includes a first black ink which includes water, less than 0.3 mass % of carbon black, and a resin, in which a solid content in the ink is 20 times or more a content of the carbon black; a second black ink which includes water, 0.3 mass % or more and less than 0.6 mass % of carbon black, and a resin, in which a solid content in the ink is 10 times or more a content of the carbon black; a third black ink which includes water, 0.6 mass % or more and less than 1.5 mass % of carbon black, and a resin, in which a solid content in the ink is twice or more a content of the carbon black; and a fourth black ink which includes water, 1.5 mass % to 10 mass % of carbon black, and a resin.