Clay Membrane on PET Substrate for Solar Cell Back Sheet
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional back sheets for solar cell modules lack comprehensive performance in water vapor barrier, gas barrier, flexibility, heat resistance, and weather resistance, making them unsuitable for long-term outdoor use and requiring improved materials with enhanced mechanical strength and durability.
Innovation Solution
A laminated film with a clay membrane coated on a polyethylene terephthalate (PET) resin film substrate, where the clay membrane is formed with a thermoplastic or thermosetting resin additive, and a water resistance imparting heat treatment is applied to achieve high water vapor barrier and gas barrier properties, flexibility, and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single resin film (e.g., PET) is used as back sheet, then cost and mechanical strength are improved, but water vapor barrier properties deteriorate (transmission rate 14.4 g/m2·day)
Solution Approach 1:
The patent applies composite materials by combining PET resin film with a clay membrane layer to create a laminated structure. The clay membrane contains organomodified clay particles dispersed in a binder resin, forming a composite material that provides both mechanical strength from the PET substrate and superior water vapor barrier properties from the clay layer, reducing transmission rate to less than 3 g/m2·day
2Temperature
If inorganic sheets or metal sheets are used as gas barrier materials, then heat resistance is improved, but flexibility and ease of handling deteriorate
Solution Approach 1:
The patent uses a flexible clay membrane as a thin film coating on the PET substrate. This clay membrane provides heat resistance through the inorganic clay particles while maintaining flexibility because it is applied as a thin, conformal coating that can bend with the substrate, unlike rigid inorganic sheets or metal sheets
Solution Approach 2:
The composite structure of organic binder resin and inorganic clay particles creates a material that combines the thermal stability of inorganic materials with the flexibility of organic polymers, allowing the back sheet to withstand high temperatures while remaining flexible for handling and installation
3Reliability
If conventional clay membranes are used, then water vapor barrier properties are improved, but ease of handling and continuous production capability deteriorate
Solution Approach 1:
The patent segments the water vapor barrier function into a separate clay membrane layer that is applied onto the PET substrate. This modular approach allows the clay membrane to be optimized for barrier properties while the PET substrate provides mechanical strength and handling ease, and the laminated structure enables continuous roll-to-roll production
Solution Approach 2:
The patent modifies the clay properties by using organomodified clay with controlled particle size distribution and aspect ratio. These parameter changes optimize the clay's dispersibility in the binder resin and its packing density in the membrane, achieving superior barrier properties while maintaining processability for continuous production
4Productivity
If thin-film solar cells are used to reduce cost, then efficiency is improved, but weather resistance and flexibility requirements become more stringent
Solution Approach 1:
The patent uses a composite laminated structure combining PET and clay membrane that provides enhanced weather resistance through the clay layer's superior water vapor and gas barrier properties. This protects the thin-film solar cells from moisture and oxygen degradation, improving long-term durability while maintaining the cost efficiency of thin-film technology
Solution Approach 2:
The flexible clay membrane coating provides weather protection for thin-film solar cells without adding significant weight or rigidity. The thin film structure conforms to the flexible substrate, maintaining the flexibility needed for thin-film applications while providing robust protection against environmental degradation
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 a film with an oxygen gas transmission coefficient of less than 4.0×10−15 cm2s−1 cmHg−1, volume resistivity of 10 MΩ or more, and a water vapor transmission rate of less than 3 g/m2·day, ensuring excellent weather resistance and durability suitable for solar cell back sheets and other electronic device applications.
Implementation Method 1
a clay membrane which is formed of a clay and an additive consisting of a thermoplastic or thermosetting resin... has a water vapor transmission rate of less than 3 g/m2·day... and an oxygen gas transmission coefficient of less than 4.0×10−15 cm2s−1 cmHg−1
Implementation Method 2
after applying and drying, a water resistance imparting heat treatment is provided
Implementation Method 3
the clay membrane is formed of a clay and an additive consisting of a thermoplastic or thermosetting resin
Implementation Method 4
applying a clay paste prepared from a clay, an additive consisting of a thermoplastic or thermosetting resin and a dispersion medium as a solvent on a resin film having a flat surface, drying the same, removing the dispersion medium
Data Source
AI summary
The present invention provides a film for a back sheet of a solar cell exhibiting excellent water vapor barrier properties, water resistance and gas barrier properties, has flexibility and mechanical strength and has excellent heat stability, and a method for producing the film.The present invention is a water vapor barrier film comprising a clay membrane coated on a PET substrate, wherein the clay membrane is formed of clay and an additive; the weight ratio of the clay relative to the total sold is 60 to 90% by weight in the clay membrane; the production process thereof comprises a water resistance imparting heat treatment at 100 to 200° C. after the coating and drying; the film has a water vapor transmission rate of less than 3 g/m2·day; the additive in the modified clay is a polyimide; and at least 90% by mole of exchangeable ions is lithium ion, and a method for producing the water vapor barrier film.The above film exhibits water vapor barrier properties and is useful as a back sheet for a solar cell and the like.