UV Inkjet Yellow Ink Wrinkle Suppression via Direct Strong Curing
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Solution Overview
Problem
Ink jet printing apparatuses using UV ink face issues with wrinkles formation, particularly with yellow ink, due to uneven curing and shrinkage, especially when using specific polymerizable compounds and pigments like C. I. Pigment Yellow 150, 155, and 180, which leads to image quality degradation.
Innovation Solution
A printing apparatus configuration where the yellow ink head is positioned downstream of other color ink heads, allowing for main curing without pre-curing, ensuring ultraviolet light reaches the inner portion of yellow ink dots, and a stronger irradiation energy is used for main curing to prevent wrinkles, while avoiding pre-curing light exposure to yellow ink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-curing with weak ultraviolet light is applied to yellow UV ink, then wetting and spreading are controlled and bleeding is suppressed, but wrinkles are generated due to uneven curing and shrinkage
Solution Approach 1:
The patent extracts the pre-curing step for yellow ink from the standard two-stage curing process. By removing the pre-curing light source for yellow ink, the system avoids the harmful effect of weak UV light causing surface curing while leaving the inner portion uncured, which subsequently leads to wrinkles during main curing.
Solution Approach 2:
The patent inverts the conventional approach by applying strong UV light directly to yellow ink without pre-curing. Instead of using weak light first and then strong light (which causes wrinkles), the system applies strong light immediately, ensuring uniform curing from the start and preventing the shrinkage that causes wrinkles.
2Reliability
If strong ultraviolet light is used for main curing of yellow ink after pre-curing, then complete curing is achieved, but wrinkles are generated due to curing shrinkage of the inner portion
Solution Approach 1:
The patent removes the pre-curing step for yellow ink entirely. By extracting this intermediate step, the system eliminates the problem where the surface is cured but the inner portion remains uncured, which then causes wrinkles when the inner portion cures during the main curing stage.
Solution Approach 2:
The patent applies strong UV light directly to yellow ink from the beginning, performing the complete curing action in one step rather than in two stages. This preliminary strong irradiation ensures that the entire yellow ink layer cures uniformly without creating the differential curing state that leads to wrinkles.
3Reliability
If yellow ink is positioned upstream and pre-cured, then other colors can be printed on top without bleeding, but ultraviolet light does not reach the inner portion of yellow ink dots
Solution Approach 1:
The patent changes the irradiation energy parameter from weak (in pre-curing) to strong (in main curing) applied directly to yellow ink. By using strong UV light from the start, the system ensures sufficient light penetration to the inner portion of yellow ink dots, achieving both complete curing and prevention of bleeding without the need for a separate pre-curing step.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses wrinkles in yellow ink, enhancing image quality by ensuring uniform curing and preventing surface shrinkage issues, thus improving the overall print quality.
Implementation Method 1
UV ink which is cured by the irradiation of light (for example, ultraviolet light (UV), visible light, or the like)
Data Source
Figure 1
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Figure 3A~3C
AI summary
There is provided a printing apparatus including: a transport unit which transports a medium (S) in a transport direction, a first head (41M, 41C, 41K), a first light source (81M, 81C, 81K) which is provided further to the downstream side in the transport direction than the first head (41M, 41C, 41K), a second head (41Y) which is provided further to the downstream side in the transport direction than the first head (41M, 41C, 41K) and the first light source (81M, 81C, 81K), and a second light source (91) which is provided further to the downstream side in the transport direction than the second head (41Y) and which irradiates light with a stronger irradiation energy than the irradiation energy of the first light source (81M, 81C, 81K), in which the first head (41M, 41C, 41K) ejects ink of one color of any among magenta ink, cyan ink, and black ink onto a medium (S), and the second head (41Y) ejects yellow ink onto the medium (S).