Multilayer Polyester Film Optical Density
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Solution Overview
Problem
Current films with high optical density and low transparency, suitable for greenhouse blinds and display applications, face challenges in achieving the required thickness, flexibility, UV resistance, and cost-effective production while maintaining high whiteness and optical density, especially when thickness is below 80 μm.
Innovation Solution
A three-layer biaxially oriented polyester film with a carbon-black-filled outer layer and two TiO2-containing layers, where the outer layers are 4-15 μm thick, the base layer is thicker than the outer layers combined, and the film includes a high percentage of TiO2 and carbon black, ensuring optical density >3.5 and whiteness >90%, while being produced on conventional polyester film plants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the film thickness is reduced to improve flexibility, then flexibility is improved, but achieving high optical density and whiteness becomes more difficult
Solution Approach 1:
The film is divided into multiple functional layers: a base layer providing mechanical strength and UV resistance, a white intermediate layer providing whiteness and light reflection, and a carbon-black outer layer providing optical density. This segmentation allows each layer to optimize its function independently, achieving high optical density and whiteness in thin films.
Solution Approach 2:
The invention uses composite material structure combining different polymers (PET, PEN, PVDC) with functional pigments (TiO2, carbon black) in specific layers. The composite structure enables simultaneous achievement of flexibility, high optical density (>3.5), and high whiteness (>90%) in films with total thickness ≤60 μm.
2Length of stationary object
If the film thickness is reduced to minimize display thickness, then display thickness is reduced, but UV resistance and mechanical strength deteriorate
Solution Approach 1:
UV resistance is concentrated in the base layer which contains 3-15% carbon black and specific UV stabilizers (HALS, benzotriazole derivatives), while the total film thickness is kept thin (≤60 μm). This local concentration of UV protection functionality achieves both thinness and UV resistance.
Solution Approach 2:
The base layer uses composite material with carbon black (3-15%) and polyester polymers (PET/PEN) providing inherent UV absorption, supplemented by UV stabilizers. This composite structure provides adequate UV resistance in thin films.
3Illumination intensity
If the TiO2 content is increased to improve whiteness, then whiteness is improved, but production cost and processing difficulty increase
Solution Approach 1:
TiO2 (10-40%) is concentrated in the white intermediate layer which is only 5-20 μm thick, rather than distributing it throughout the entire film. This localized concentration achieves high whiteness (>90%) while reducing total TiO2 usage and associated costs.
Solution Approach 2:
The white intermediate layer is segmented as a distinct functional layer between the base layer and carbon-black outer layer. This segmentation allows optimal TiO2 concentration (10-40%) in just this layer, achieving high whiteness without excessive cost or processing difficulty.
4Manufacturing precision
If the carbon-black content is increased to improve optical density, then optical density is improved, but flame retardancy and UV resistance may be compromised
Solution Approach 1:
Carbon black is concentrated in the outer layer (3-15% in white layer, up to 50% in carbon-black outer layer) where it provides optical density, while the base layer contains UV stabilizers and flame retardants. This local quality distribution optimizes each function without compromise.
Solution Approach 2:
The invention uses composite material strategy: carbon-black/polymer composites in outer layers for optical density, and polyester/carbon black/composite stabilizer systems in base layer for flame retardancy and UV resistance. The multi-composite structure achieves all requirements simultaneously.
5Ease of manufacture
If conventional extrusion equipment is used to reduce production cost, then production cost is reduced, but achieving high optical density in thin films below 80 μm becomes difficult
Solution Approach 1:
The film structure is segmented into layers with different functions, allowing conventional extrusion equipment to produce each layer at appropriate thickness. The white intermediate layer (5-20 μm) and carbon-black outer layer (10-30 μm) can be extruded using standard equipment, achieving high optical density in thin films.
Solution Approach 2:
The invention changes the parameter distribution: concentrates functional pigments (TiO2 in white layer, carbon black in outer layer) in specific layers rather than uniform distribution. This parameter change enables high optical density in thin films using conventional extrusion equipment.
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 film achieves the desired optical density and whiteness with improved flexibility and cost-effectiveness, suitable for greenhouse blinds and display applications, while maintaining reliability and UV resistance, even at thicknesses below 60 μm.
Implementation Method 1
the film has to have a certain UV resistance in order to be suitable for long-term use... the film has low flammability... the film is also intended to be capable of cost-effective production... High whiteness in reflected light or, respectively, high lightness in reflected light is also important
Implementation Method 2
a carbon-black-containing external layer... optical density OD>3.5 or, respectively, very low transparency
Implementation Method 3
the film also has to have a certain UV resistance in order to be suitable for long-term use
Data Source
AI summary
The invention relates to an at least three-layer, biaxially oriented polyester film with a carbon-black-filled outer layer and with two TiO2-containing layers, where a TiO2-containing layer is also an outer layer and wherethe thickness of the outer layers is from 4 to 15 μm,the thickness of the base layer is ≧the total of the thicknesses of the outer layers,the white outer layer includes at least 15% by weight of TiO2,the base layer includes at least 4% by weight of TiO2,the carbon-black-containing outer layer includes from 3 to 15% by weight of carbon black, andthe SV value of the film is at least 600,where all % by weight data are based on the weight of the respective layer, and also to a process for the production of this type of film and to the use of the film in particular in blinds, including roller blinds, Venetian blinds, or projection screens, or in displays.