Biaxially Oriented Polyester Film Hydrolysis Resistance
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Solution Overview
Problem
Conventional polyester films used for protecting the back surface of solar cells suffer from hydrolysis and adhesion issues under high-temperature and high-humidity conditions, leading to degradation in mechanical properties and adhesion to sealing resins like EVA, which increases the cost and reduces the lifespan of solar cells.
Innovation Solution
A biaxially oriented polyester film with a phosphorus content of 0 to 170 ppm and a terminal carboxylic acid content of not more than 26 equivalents/t, combined with a coating layer of polyurethane having a polycarbonate or polyether skeleton and a crosslinking agent, is used to enhance hydrolysis resistance and adhesion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a polyester film is used as a protective member for solar cells, then it provides light weight and good flexibility compared to glass, but it suffers from hydrolysis under high-temperature and high-humidity conditions leading to deterioration of mechanical properties
Solution Approach 1:
The patent changes the chemical parameters of the polyester film by controlling the terminal carboxylic acid content to 26 equivalents/t or less and adding phosphorus in amounts of 0.01-200 ppm. These parameter changes enhance the hydrolysis resistance of the polyester film while maintaining its light weight and flexibility properties
Solution Approach 2:
The patent creates a composite structure by forming a coating layer containing polyurethane and phosphorus on the polyester film base. This composite material combines the advantages of polyester (light weight, flexibility) with the hydrolysis resistance provided by the phosphorus-containing coating layer
2Strength
If an easy-bonding layer is provided on the polyester film to improve adhesion to EVA, then adhesion property is enhanced, but the easy-bonding layer deteriorates over time under high-temperature and high-humidity conditions
Solution Approach 1:
The patent forms a composite coating layer containing both polyurethane (which provides easy-bonding capability for adhesion to EVA) and phosphorus (which provides hydrolysis resistance). This composite structure ensures that the adhesion layer itself is resistant to deterioration under high-temperature and high-humidity conditions, thereby extending its service life while maintaining good adhesion strength
Solution Approach 2:
The patent modifies the chemical composition of the coating layer by controlling the phosphorus content and terminal carboxylic acid content, which enhances the stability and durability of the easy-bonding layer over time under severe environmental conditions
3Ease of manufacture
If conventional polyester films are used for solar cell protection, then initial cost is reduced, but adhesion property to sealing resins deteriorates under high-temperature and high-humidity conditions
Solution Approach 1:
The patent modifies the chemical parameters of conventional polyester films by controlling terminal carboxylic acid content and adding phosphorus, which enhances adhesion to sealing resins like EVA without requiring expensive alternative materials, thereby maintaining cost-effectiveness while improving adhesion performance
Solution Approach 2:
The patent creates a cost-effective composite coating layer using polyurethane and phosphorus that provides improved adhesion to sealing resins under high-temperature and high-humidity conditions, avoiding the need to use more expensive protective materials
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 excellent hydrolysis resistance and maintains adhesion properties over long periods, even under severe environmental conditions, making it suitable for solar cell protection and other applications like touch panels and liquid crystal displays without the need for specific materials, thus reducing costs.
Implementation Method 1
there tends to occur such a problem that the polyester films suffer from hydrolysis at an ester bond moiety in a molecular chain thereof, so that mechanical properties of the film itself tend to be deteriorated with time
Implementation Method 2
The polyester films are used as the protective member for protecting a back surface of solar cells by thermally bonding to the above sheet of EVA, etc.
Data Source
AI summary
The present invention provides a polyester film which is excellent in hydrolysis resistance of a base film, is hardly deteriorated in adhesion property to various members or top-coating agents, and can suitably used, for example, as a film for a protective member for protecting a back surface of solar cells. The present invention relates to a biaxially oriented polyester film in the form of a laminated film comprising a biaxially oriented polyester base film having a phosphorus element content of 0 to 170 ppm and a terminal carboxylic acid content of not more than 26 equivalents/t, and a coating layer formed on at least one surface of the biaxially oriented polyester base film which comprises a polyurethane having a polycarbonate skeleton or a polyether skeleton and a crosslinking agent, wherein the laminated film has a haze value of not more than 10%.