Retroreflective Sheeting Low Elastic Modulus Layer
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Solution Overview
Problem
Existing retroreflective article manufacturing methods, such as cast and cure processing, result in high shrinkage of cube corner elements leading to optical imperfections and reduced retroreflectivity due to uncontrolled angle changes during curing, which affects the efficiency of light redirection.
Innovation Solution
Incorporating a low elastic modulus polymeric layer between the body layer and truncated cube corner elements, with the polymeric layer having an elastic modulus less than 1750 MPa, to absorb and dissipate stress forces during processing, thereby maintaining cube corner element fidelity and enhancing retroreflective brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cast and cure manufacturing method is used, then production efficiency is improved, but cube corner elements exhibit high shrinkage and optical imperfections
Solution Approach 1:
The patent changes the material parameter of the body layer from high elastic modulus to low elastic modulus material. This parameter change allows the body layer to better accommodate the cube corner elements during curing, reducing shrinkage and maintaining geometric precision while still enabling cast and cure manufacturing processes.
Solution Approach 2:
The patent creates a composite structure where a low elastic modulus body layer is combined with cube corner elements. This composite material approach allows the body layer to provide mechanical support and stress distribution, reducing shrinkage-induced deformations while maintaining the optical functionality of the cube corner elements.
2Stability of the object's composition
If low elastic modulus body layer is used, then dimensional stability during flexing is improved, but cast and cure processing becomes difficult without carrier
Solution Approach 1:
The patent modifies the elastic modulus parameter of the body layer material to be low (less than 1750 MPa), which provides dimensional stability during flexing. This material parameter change enables the body layer to flex without permanent deformation while maintaining cube corner element integrity.
Solution Approach 2:
The low elastic modulus body layer acts as an intermediary between the cube corner elements and the external environment. It provides mechanical support and stress distribution, enabling the cube corner elements to maintain their geometry during both processing and use without requiring additional carriers.
3Strength
If high elastic modulus body layer is used, then structural strength is improved, but retroreflective brightness decreases due to stress forces
Solution Approach 1:
The patent changes the elastic modulus parameter of the body layer from high to low values. This parameter change reduces the body layer's stiffness, allowing it to better accommodate thermal and mechanical stresses during curing and use, thereby maintaining cube corner element geometry and maximizing retroreflective brightness.
Solution Approach 2:
The patent converts what would normally be a weakness (low elastic modulus implying lower strength) into a benefit. The low elastic modulus body layer's ability to flex and accommodate stress is transformed into an advantage that protects cube corner element geometry, ultimately improving retroreflective performance by preventing optical imperfections.
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 inclusion of a low elastic modulus polymeric layer allows for the formation of retroreflective articles with increased brightness and improved dimensional stability, maintaining high retroreflective efficiency even under stress conditions.
Implementation Method 1
the polymeric layer having an elastic modulus that is less than 1750 MPa, to absorb and dissipate stress forces during processing
Implementation Method 2
Cube corner reflecting elements include generally trihedral structures that have three approximately mutually perpendicular lateral faces meeting in a single corner—a cube corner. In use, the retroreflector is arranged with the front surface disposed generally toward the anticipated location of intended observers and the light source. Light incident on the front surface enters the sheet and passes through the body of the sheet to be reflected by each of the three faces of the elements, so as to exit the front surface in a direction substantially parallel to the light source.
Data Source
AI summary
The present application generally relates to retroreflective articles and methods of making retroreflective articles. Some embodiments include a body layer having an elastic modulus of equal to or greater than 1750 MPa, a plurality of truncated cube corner elements, and a polymeric layer between the body layer and the cube corner elements, the polymeric layer having an elastic modulus of less than 1750 MPa.