Water-Based Ink Overprinting for Sharp Black Text and Low Graininess
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Solution Overview
Problem
Ink-jet recording methods face challenges in producing high-quality black images with gradations of medium to high lightness, as existing methods using three primary colors result in unnatural images, increased ink volume, and poor drying properties due to graininess and blurring.
Innovation Solution
A water-based ink combination using two color inks with specific hue angle relationships (120°≦|α−β|≦240°) is overprinted to form a black image, reducing graininess and improving drying properties while maintaining high optical density for text and lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If black image is formed by overprinting three primary colors (yellow, magenta, cyan), then optical density is improved, but image quality deteriorates due to graininess and unnatural appearance
Solution Approach 1:
The patent segments the black ink formation process into two distinct components: a first black ink providing base optical density and a second black ink providing grain reduction. This segmentation allows each ink to be optimized for its specific function, resolving the contradiction between achieving high optical density and maintaining image quality.
Solution Approach 2:
The patent uses a composite approach by combining two different black inks with distinct properties. The first black ink (with lower graininess) and second black ink (with higher optical density) work together as a composite system, where each component contributes its strengths to achieve both high optical density and reduced graininess simultaneously.
2Manufacturing precision
If black image is formed only with black ink, then sharp text and lines are achieved, but gradation capability deteriorates in medium to high lightness areas
Solution Approach 1:
The patent segments the black ink system into two functional inks: the first black ink optimized for sharpness and gradation (with lower graininess), and the second black ink optimized for optical density. This allows the system to achieve both sharp text/lines and good gradation capability across different lightness ranges.
Solution Approach 2:
The patent applies local quality by assigning different properties to different black inks based on their specific functions. The first black ink has properties suited for gradation and sharpness (lower graininess), while the second black ink has properties suited for optical density. This localized optimization resolves the contradiction between sharpness and gradation capability.
3Illumination intensity
If volume of ink droplets is increased to form black image, then optical density is improved, but drying property deteriorates due to ink absorption failure
Solution Approach 1:
The patent segments the ink volume distribution by using two different black inks with different graininess characteristics. The first black ink (lower graininess) can be applied with appropriate volume for good drying, while the second black ink (higher optical density) supplements the optical density without proportionally increasing total ink volume, thus maintaining drying properties.
Solution Approach 2:
The composite black ink system allows optimization of the overall ink formulation. By combining inks with different properties, the system achieves high optical density without requiring a proportional increase in total ink volume, thereby preventing ink absorption failure and maintaining good drying properties.
Data Source
AI summary
A water-based ink for ink-jet recording and an ink-jet recording method allow the formation of sharp text and lines in high density black, and the formation of a high quality gradation image in which the graininess is reduced in a black image of a medium lightness to a high lightness (e.g., an achromatic image in dark gray to light gray) in ink-jet recording. The water-based ink combination for ink-jet recording comprises a black ink, and a color ink (A) and a color ink (B) that satisfy a color relationship of the following expression (I):about 120°≦|α−β|≦about 240° (I)wherein α is the hue angle of the color ink (A) and β is the hue angle of the color ink (B).