Relief Image Edge Rounding via Partial Photopolymer Curing
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Solution Overview
Problem
Existing methods for producing relief images using liquid photopolymerizable resins often result in sharp edges, which are undesirable in applications such as signage and bronze casting where rounded or smooth edges are preferred.
Innovation Solution
A method involving the placement of an image film and coverfilm on an exposure glass, followed by casting a photopolymer resin and laminating a flexible polyester sheet, with controlled exposure to actinic radiation to under-cure the resin, resulting in a relief image with rounded edges by limiting the penetration of the imagewise exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the photopolymer resin is fully cured by exposing to actinic radiation, then the relief image structure is strong and well-defined, but sharp edges are formed at the junction of top surface and sidewall which are undesirable for signage and casting applications
Solution Approach 1:
The patent applies different exposure conditions to different regions of the photopolymer resin layer. The bottom region (near the substrate) receives full exposure to ensure strong adhesion and structural strength, while the top region receives reduced exposure to prevent sharp edge formation. This local differentiation of exposure quality resolves the contradiction between structural strength and edge smoothness.
Solution Approach 2:
The patent uses partial curing by controlling the exposure parameters (intensity, time, distance) to cure only a portion of the photopolymer resin layer thickness. By using less than full exposure action, the top surface and sidewall junction avoids the sharp edges that would result from complete curing, while still maintaining adequate structural strength through the partially cured region.
2Reliability
If the exposure parameters are increased to ensure complete curing, then the relief image is fully cross-linked and durable, but the edges become sharp and angular rather than rounded
Solution Approach 1:
Different regions of the photopolymer layer are subjected to different effective exposure levels. The lower region maintains high cross-linking for durability, while the upper region has reduced cross-linking to produce rounded edges. This spatial variation in curing quality achieves both reliability and aesthetic shape requirements.
Solution Approach 2:
The exposure parameters are deliberately set below the level required for complete curing of the entire layer thickness. This partial action approach ensures that the relief image has sufficient durability through adequate cross-linking in critical regions, while avoiding over-curing that would create sharp edges.
3Length of moving object
If the photopolymer resin layer thickness is increased to achieve desired relief height, then the relief image prominence is improved, but the edges become sharper and more angular
Solution Approach 1:
When thicker photopolymer layers are used to achieve greater relief heights, the patent maintains rounded edges by ensuring that the exposure parameters create a gradient where the top portions of the relief features receive reduced effective exposure. This local quality control at the edges prevents sharpness even as overall height increases.
Solution Approach 2:
For thicker resin layers, the exposure parameters are adjusted to provide partial curing through the increased thickness. The exposure intensity or duration is controlled so that while the full thickness is not completely cured (maintaining rounded edges), sufficient curing occurs to maintain structural integrity and achieve the desired relief prominence.
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
The method produces relief images with rounded/smooth edges, preventing sharp edges at the top surface and sidewall junction, suitable for applications requiring smooth edges, such as signage and bronze casting.
Implementation Method 1
Photopolymerizable and/or photocurable and/or radiation curable resins can be selectively cross-linked and cured to create relief images
Implementation Method 2
a liquid photopolymerizable resin is released from a resin reservoir and is cast onto the cover film
Implementation Method 3
The image-bearing transparency and coverfilm are secured by vacuum to the platen so that air is displaced and bubbles are not created in the liquid photopolymerizable layer
Implementation Method 4
The liquid photopolymerizable resin is then exposed to actinic radiation to crosslink and cure the photopolymerizable resin and produce the relief image printing plate or other relief image product
Data Source
Figure 1~2
AI summary
A method of producing a relief image or mold from a liquid photopolymer resin, said method comprising the steps of: a) placing an image film onto an exposure glass; b) placing a cover film over the image film and drawing a vacuum c) placing substrate material on a bottom glass d) casting a liquid photopolymer resin layer onto the substrate material; d) laminating a flexible polyester sheet onto a backside of the liquid photopolymer resin layer as the liquid photopolymer resin layer is being cast onto the substrate material; and e) exposing the liquid photopolymer resin layer through the image film to selectively crosslink and cure the photopolymerizable resin layer and form a cured relief image, wherein said depth of the cured relief image is less than the height of the cast liquid photopolymerizable resin.