Laminated Polyester Film Adhesion and Optical Clarity
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Solution Overview
Problem
Conventional polyester films with hard coat layers face issues of poor adhesion and interference fringes due to refractive index differences, limiting their versatility and durability, especially in high-temperature, high-humidity environments, and requiring modifications that can compromise functionality.
Innovation Solution
A laminated polyester film with a lamination layer containing a polyester resin, specifically designed with polyesters A and B having different glass transition temperatures, sulfonic acid, and multivalent carboxylic acid components, and a melamine or oxazoline crosslinking agent, achieving a wetting tension of 35-45 mN/m and optimized adhesion to various hard coat layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thin hard coat layer is used to maintain UV absorptivity, then ultraviolet protection is improved, but adhesive strength deteriorates
Solution Approach 1:
The patent introduces a lamination layer as an intermediary between the polyester base film and the hard coat layer. This lamination layer has optimized surface properties (wetting tension of 35-45 mN/m) that enable strong adhesion to the hard coat layer, allowing the hard coat layer to remain thin for UV protection while maintaining adequate adhesive strength through the mediating lamination layer.
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers: polyester base film, lamination layer with specific polyester resin composition, and hard coat layer. The lamination layer contains polyesters with specific glass transition temperatures and functional groups that provide both adhesion and surface properties, enabling the thin hard coat layer to maintain both UV protection and adhesive strength.
2Strength
If a lamination layer is formed to improve adhesion, then adhesive strength is improved, but interference fringes occur due to refractive index difference
Solution Approach 1:
The patent carefully controls the refractive index of the lamination layer by selecting specific polyester resins with appropriate molecular structures and compositions. By adjusting parameters such as glass transition temperature, functional group content, and resin composition ratios, the lamination layer achieves both strong adhesion (wetting tension 35-45 mN/m) and refractive index matching to minimize interference fringes.
3Strength
If conventional lamination layers are used to achieve adhesion, then initial adhesion is improved, but moisture resistant adhesion deteriorates in high-temperature high-humidity environments
Solution Approach 1:
The patent specifies polyesters with glass transition temperatures of 40-90°C in the lamination layer, which provides optimal balance between initial adhesion and moisture resistance. The functional groups (sulfonic acid and multivalent carboxylic acid) in these polyesters create crosslinking structures that maintain adhesive strength under high-temperature high-humidity conditions while preserving good initial adhesion.
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 provides durable and versatile adhesion to hard coat layers, suppressing interference fringes and maintaining high adhesive strength in diverse environmental conditions, suitable for applications like touch panels and in-mold decoration.
Implementation Method 1
the surface of the lamination layer (layer C) having a wetting tension of 35 to 45 mN/m
Implementation Method 2
the lamination layer (layer C) contains polyesters (A) with glass transition temperatures (Tg) of 110 to 140° C. and polyesters (B) with glass transition temperatures (Tg) of 40 to 90° C.
Implementation Method 3
at least either polyesters (A) or polyesters (B) contain both a monomer having a sulfonic acid component and a monomer having a multivalent, i.e., tri- or higher-valent, carboxylic acid component
Implementation Method 4
interference fringes are suppressed to ensure good appearance
Data Source
AI summary
A layered polyester film includes a substrate polyester film with at least one surface laminated with a lamination layer including a polyester resin as a primary component, the surface of the lamination layer having a wetting tension of 35-45 mN/m and the polyester resin contained in the lamination layer meeting (a) to (c): (a) the lamination layer contains polyesters (A) having a glass transition temperature (Tg) of 110-140° C. and polyesters (B) having a glass transition temperature (Tg) of 40-90° C., (b) at least either polyesters (A) or polyesters (B) contains both a monomer having a sulfonic acid component and a monomer having a tri or higher-valent, carboxylic acid component, and (c) the mixing ratio between polyesters (A) and polyesters (B) is 10/90 to 60/40.