UV Cured Ink Bonding via Partial Photopolymerization
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Solution Overview
Problem
Inkjet printers using UV curable ink face challenges in achieving strong bonding between colored-ink and overprint layers, leading to reduced glossiness and uneven surfaces due to incomplete curing and repulsion between inks during overprinting.
Innovation Solution
An inkjet printer system with multiple UV-light irradiating units that partially cures the colored-ink layer with weak UV light, followed by forming an overprint layer, and then fully curing both layers with strong UV light, reducing contact angles and preventing hard strip formation to achieve better bonding and surface flattening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the colored ink is completely cured before overprinting, then the colored-ink layer is stable and ready for the next step, but the overprint ink repels the cured colored ink, causing poor bonding strength and beading
Solution Approach 1:
The patent applies partial curing by irradiating the colored-ink layer with UV light at a controlled dose that achieves sufficient stability without complete curing. This partial state allows the overprint ink to bond effectively while maintaining adequate stability of the underlying layer, resolving the contradiction between stability and bonding strength.
Solution Approach 2:
The patent changes the curing parameter (UV irradiation dose) to an intermediate value that neither fully cures nor leaves the ink completely uncured. By controlling the irradiation amount to be less than that required for complete curing, the system achieves optimal bonding conditions while maintaining sufficient layer stability.
2Reliability
If UV light is strongly irradiated to cure the ink completely, then the ink layer is fully cured and stable, but the surface becomes uneven with hard strip formation and lacks glossiness
Solution Approach 1:
The patent optimizes the UV irradiation parameter to a specific range that achieves sufficient curing without excessive energy input. By controlling the irradiation amount to be less than that for complete curing, the system prevents hard strip formation and surface unevenness while maintaining adequate curing for image stability.
Solution Approach 2:
The patent applies partial curing action with controlled UV irradiation that stops before complete curing occurs. This prevents the harmful effects of over-curing (hard strip formation, surface unevenness) while achieving sufficient curing for practical purposes, thereby maintaining surface flatness and glossiness.
3Reliability
If UV light is strongly irradiated to cure the ink, then the ink is fully cured, but light is diffusely reflected and the surface lacks glossiness
Solution Approach 1:
The patent adjusts the UV irradiation parameter to an optimized intermediate value that provides sufficient curing for image stability while maintaining surface smoothness. This controlled partial curing prevents the diffuse reflection caused by over-curing, thereby preserving surface glossiness.
Solution Approach 2:
The patent applies partial curing that stops before complete curing occurs, preventing the surface roughening and light scattering associated with full curing. This maintains the surface smoothness required for glossiness while achieving adequate curing for practical application.
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 method enhances bonding between ink layers, suppresses light scattering, and increases the glossiness of printed images, resulting in improved image quality and surface flatness.
Implementation Method 1
An inkjet printer that uses a UV curable ink... a first UV-light irradiating unit that irradiates on a colored-ink layer formed of the dots of the colored ink a weak UV light so as not to cure the colored-ink layer completely... a third UV-light irradiating unit that irradiates on the colored-ink layer and the overprint layer a strong UV light sufficient for curing the colored-ink layer and the overprint layer
Data Source
AI summary
To provide a printing method that enhances bonding between a colored-ink layer and an overprint layer, flatten a surface of the overprint layer, and make it possible to print glossy images or decorative colors when performing overprinting on a colored ink print using an inkjet printer.The printing method includes sequentially performing: Step (1) of forming a UV curable colored-ink layer on a surface of a recording medium; Step (2) of irradiating the colored-ink layer with a weak UV light; Step (3) of forming an overprint layer on the colored-ink layer; Step (4) of flattening the surface of the overprint layer after allowing a predetermined time to elapse; Step (5) of irradiating the colored-ink layer and the overprint layer with a weak UV light; and Step (6) of irradiating the colored-ink layer and the overprint layer with a strong UV light to cure the colored-ink layer and the overprint layer.