Biaxially Oriented Polyester Film for Flat Thermoformed Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyester films used in membrane switches and separator applications face challenges such as poor flatness due to uneven elasticity distribution, limited formability during thermoforming, and inadequate adhesive properties to conductive pastes and pressure-sensitive adhesive resins.
Innovation Solution
A biaxially oriented polyester film with specific properties, including a content rate of isophthalic acid-derived ester units, controlled intrinsic viscosity, storage modulus, acid value, and a relational expression for storage modulus and film thickness, which enhances thermoformability, elasticity, and adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyester film is softened by copolymerizing glycol components to enhance formability, then thermoformability is improved, but film strength and elasticity are diminished
Solution Approach 1:
The invention changes the chemical composition parameters of the polyester resin by controlling the content of specific ester constituting units (isophthalic acid component at 0.5-5.0 mol%, terephthalic acid component at 95.0-99.5 mol%, and cyclic carboxylic acid component at 0.1-5.0 mol%). This compositional adjustment allows the film to achieve both good thermoformability and maintained strength/elasticity, resolving the contradiction between formability and mechanical properties.
2Ease of manufacture
If polyester film is heated and conveyed during processing, then formability is improved, but poor flatness occurs due to distribution of elasticity
Solution Approach 1:
The invention adjusts the thermal and mechanical parameters by controlling the polyester resin composition (specific ester unit contents) and intrinsic viscosity (0.55-0.65 dl/g). This ensures uniform elasticity distribution throughout the film, allowing it to maintain flatness during heating and conveying while still achieving good formability.
3Strength
If special adhesives are added to silver pastes and molding resins to improve adhesive properties, then adhesion to substrate film is improved, but versatility is reduced and cost increases
Solution Approach 1:
The invention creates a homogeneous substrate film surface with uniform chemical composition and controlled surface properties. This uniformity enables the film to exhibit good adhesive properties with commonly used silver pastes and molding resins without requiring special adhesive additives, thus maintaining versatility and reducing costs.
4Reliability
If polyester film undergoes coating process of conductive paste and pressure-sensitive adhesive resin, then functional properties are improved, but oligomer precipitation (whitening) occurs
Solution Approach 1:
The invention optimizes the molecular weight distribution and compositional parameters of the polyester resin (controlling intrinsic viscosity and ester unit composition) to prevent oligomer precipitation during coating processes. This allows the film to maintain good functional properties for conductive paste and adhesive resin coating without experiencing whitening issues.
Data Source
AI summary
Provided is a biaxially oriented polyester film in which poor flatness that may be caused during heat processing is suppressed. In the biaxially oriented polyester film, the content rate of an ester constituting unit derived from an isophthalic acid component is 0.5-5.0 mol % with respect to 100 mol % of all ester constituting units, the amount of change in haze of the film is 5.0% or less, the intrinsic viscosity of constitutional polyester resins is 0.59-0.65 dl/g, the average value of storage moduli is 5.0-7.6×108 [Pa], the acid value of the film is 40-60 eq/ton, and the relational expression is satisfied: X×(Ymax3−Ymin3)≤0.0591×(X×Ymin3)+0.005, where X is the storage modulus at 170° C., and Y is the film thickness per 1000 mm in the transverse direction with Ymax as the maximum value and Ymin as the minimum value.