Transparent Label with Refractive Index Matched Adhesive
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Solution Overview
Problem
Current labeling technologies face challenges in achieving high-speed labeling while maintaining a clear, visually appealing, and cost-effective solution for attaching labels to items, particularly in applications like glass bottles, where label thickness and adhesive properties impact the visibility and durability of the label.
Innovation Solution
A label comprising a semi-crystalline polyethylene terephthalate film face layer with a tensile modulus of at least 4000 MPa and a transparent polymeric adhesive layer, optimized for thickness and refractive index to ensure dimensional stability, high gloss, and minimal visibility, allowing for high-speed labeling and improved visual appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a paper label is used for high-speed labeling, then labeling productivity is improved, but the visual appearance and clarity are compromised
Solution Approach 1:
The patent changes the material parameter from paper to semi-crystalline polymeric film (such as PET), which maintains the high-speed labeling capability while providing superior optical properties including transparency, gloss, and clarity that paper cannot achieve
Solution Approach 2:
The label is constructed as a composite structure with a semi-crystalline polymeric film face layer and a transparent polymeric adhesive layer, combining the dimensional stability and printability of the film with the bonding properties of the adhesive to achieve both high-speed application and visual appeal
2Strength
If the adhesive layer thickness is increased to improve adhesion, then bonding strength is improved, but the label becomes more visible and less aesthetically pleasing
Solution Approach 1:
The patent optimizes the adhesive layer thickness to a specific range (8-25 μm) and selects transparent polymeric adhesive materials with refractive indices closely matched to the face layer (80%-98.5%), making the adhesive layer optically invisible while maintaining sufficient bonding strength for durable attachment
Solution Approach 2:
The adhesive layer is designed with differentiated properties: it is thick enough to provide adequate adhesion strength but thin enough and transparent enough to remain visually invisible, creating a local optimization where functional and aesthetic requirements are simultaneously satisfied
3Illumination intensity
If the face layer thickness is reduced to improve visual appearance, then label visibility is reduced, but the mechanical strength and dimensional stability deteriorate
Solution Approach 1:
The patent specifies a face layer thickness range of 10-50 μm and requires a tensile modulus of at least 4000 MPa in the machine direction, ensuring that even at minimal thickness the label maintains sufficient mechanical strength and dimensional stability for high-speed labeling applications while maximizing transparency
Solution Approach 2:
The patent requires the refractive index of the uppermost adhesive sub-layer to be in the range of 80% to 98.5% of the refractive index of the semi-crystalline polyethylene terephthalate film, minimizing optical contrast and making the label edges less visible, thereby enhancing the overall visual 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
The solution enables high-speed labeling with reduced material costs, improved visual appearance by minimizing label thickness and visibility, and enhanced durability, while reducing air bubbles and scattering, thus improving the overall labeling process efficiency and product aesthetics.
Implementation Method 1
the face layer is a semi-crystalline polyethylene terephthalate film having a tensile modulus higher than or equal to 4000 MPa in the machine direction (MD)
Implementation Method 2
the adhesive layer consists of one or more adhesive sub-layers, a lowermost adhesive sub-layer of said adhesive sub-layers comprises transparent polymeric adhesive
Data Source
Figure 1a~2b
Figure 3a~3c
Figure 4a~4b
AI summary
An adhesive label (100) comprises: - a face layer (10), and - an adhesive layer (20), wherein the face layer (10) comprises a semi-crystalline polymeric film, the adhesive layer (20) consists of one or more adhesive sub-layers (21,22), a lowermost adhesive sub-layer (22) of said adhesive sub-layers comprises transparent polymeric adhesive, the thickness (d10) of the face layer (10) is in the range of 10 µm to 50 µm, the thickness (d20) of the adhesive layer (20) is in the range of 8 µm to 25 µm, the thickness (d20) of the adhesive layer (20) is smaller than 95% of the thickness (d10) of the face layer (10), an uppermost sub-layer (21) of said adhesive sub-layers is in contact with the face layer (10), and the refractive index (n2) of the uppermost adhesive sub-layer (21) is in the range of 80% to 98.5% of the refractive index (n1) of the semi-crystalline polymeric film.