Retroreflective Sheeting Halftone Ink Pattern Reflectivity
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Solution Overview
Problem
Retroreflective sheeting used in road signs experiences reduced reflectivity due to light absorption and scattering caused by printed ink layers, necessitating a clear topcoat or overlaminate film to mitigate these issues, which increases manufacturing time and cost without fully restoring reflectivity.
Innovation Solution
A halftone pattern of light-transmissive ink is applied to the retroreflective sheeting, with discrete ink areas covering between 60% and 90% of the surface, creating a single background color and incorporating light-transmissive openings that minimize absorption and scattering, thereby eliminating the need for a clear topcoat or film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a layer of light-transmissive colored ink is printed over the flat front side of the sheeting to display background colors, then the sheeting can display printed information and background colors, but the overall reflectivity of the sheeting is compromised due to light absorption and surface roughness scattering
Solution Approach 1:
The ink layer is segmented into a halftone pattern consisting of discrete ink areas (dots) separated by light-transmissive openings. This segmentation allows incident light to pass through the openings without absorption or scattering, while the discrete ink areas provide the desired background color appearance. The pattern covers 60-90% of the surface area, balancing color coverage with light transmission to maintain high retroreflectivity.
2Illumination intensity
If a clear topcoat or overlaminate film is applied over the printed top surface to reduce scattering and increase retroreflectivity, then the retroreflectivity of the sheeting is improved, but the manufacturing time and cost increase
Solution Approach 1:
The harmful clear topcoat layer is extracted/removed from the manufacturing process. The halftone printed pattern itself provides the light-transmissive openings that eliminate the need for a separate clear topcoat or overlaminate film. The discrete ink areas create the appearance of a single background color while the openings between them allow light to pass through without absorption or scattering, achieving high retroreflectivity without additional manufacturing steps.
3Illumination intensity
If a clear topcoat or overlaminate film is applied over the printed top surface to reduce scattering, then the retroreflectivity of the sheeting is improved, but the manufacturing cost increases
Solution Approach 1:
The clear topcoat layer is extracted/removed from the manufacturing process. The halftone printed pattern with discrete ink areas and light-transmissive openings inherently provides the light transmission properties that would otherwise require a clear topcoat. This eliminates the additional material cost and processing steps associated with applying a separate clear film layer.
4Illumination intensity
If discrete areas of ink are deposited in a halftone pattern covering 60-90% of the surface, then the appearance of a single background color is achieved while maintaining high light transmission, but the ink coverage is reduced compared to full printing
Solution Approach 1:
The ink is applied with local quality variation through a halftone pattern where discrete ink areas are strategically positioned to cover 60-90% of the surface. Each local area has different ink coverage, but the overall effect creates the appearance of a uniform background color. The light-transmissive openings between discrete ink areas ensure high light transmission while the sufficient ink coverage (60-90%) maintains the desired color appearance.
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 approach enhances the reflectivity of the sheeting, meeting or exceeding regulatory specifications for daytime and nighttime visibility without the additional layers, thus simplifying the manufacturing process and reducing costs.
Implementation Method 1
a retroreflective film having a planar surface on a front side and a plurality of retroreflective elements (3) on a back side
Implementation Method 2
an ink layer (22) deposited on said planar surface in a half-tone pattern that includes a pattern of light-transmissive openings (26) between discrete areas (24) (or 'dots') of deposited ink that receives incident light and transmits retroreflected light without absorption or scattering from said ink
Data Source
Figure 1A~2
Figure 3A~4D
Figure 5~6
AI summary
A printed retroreflective film has a planar surface on a front side and a plurality of retroreflective elements on a back side. A halftone printed ink layer is deposited on the planar surface formed from uniformly spaced, discrete dots of deposited ink. The areas between the dots provide light-transmissive openings that receive incident light and transmit retroreflected light. The aggregate area of the dots forming the half-tone pattern preferably covers between about 60% and 90% of the area of the half-tone pattern. The use of such a halftone pattern of ink increases the reflectivity of the printed retroreflective sheeting by reducing the amount of light absorbed by the ink, and by reducing the amount of light scattered by the layer of ink. The use of such a halftone pattern of ink further obviates the need for an anti-light scattering topcoat or film over the front surface of the retroreflective sheet.