Polyimide Window Film with ALD Inorganic Layer for Flexible Displays
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Solution Overview
Problem
Window cover films for flexible displays face issues with yellowing, durability, weather resistance, and moisture sensitivity under high-temperature and high-humidity conditions, particularly due to the lifting or peeling of hard coating layers and the degradation of mechanical properties over time.
Innovation Solution
A window cover film with a laminated structure comprising a polyimide-based film, an inorganic thin film layer, and a hard coating layer, where the inorganic thin film layer is formed using atomic layer deposition (ALD) to enhance adhesion, moisture barrier properties, and solvent resistance, and is applied on at least one surface of the polyimide-based film to prevent peeling and curling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is formed on a plastic film to improve mechanical properties and prevent scratches, then scratch resistance is improved, but lifting or peeling off occurs under high-temperature and high-humidity conditions due to moisture
Solution Approach 1:
An inorganic thin film layer is introduced as an intermediary between the plastic film and the hard coating layer. This intermediate layer acts as a moisture barrier that prevents water molecules from penetrating to the interface between the hard coating and the plastic film, thereby eliminating the cause of peeling while preserving the scratch resistance provided by the hard coating layer.
Solution Approach 2:
The window cover film is constructed as a composite structure consisting of multiple layers: a plastic film base layer, an inorganic thin film intermediate layer, and a hard coating layer. This composite structure combines the flexibility of the plastic film with the protective properties of the hard coating, while the inorganic layer provides moisture barrier functionality to ensure long-term adhesion stability.
2Reliability
If sunscreen or ultraviolet absorber is added into the film in large amount to block ultraviolet rays, then light resistance is improved, but transmittance and mechanical physical properties are deteriorated
Solution Approach 1:
The ultraviolet protection function is extracted from the bulk plastic film material and relocated to a separate inorganic thin film layer. This allows the main plastic film to maintain its optical transmittance and mechanical properties without UV absorbers, while the inorganic layer provides the necessary ultraviolet blocking capability through its inherent optical properties.
Solution Approach 2:
The inorganic thin film layer serves as an intermediary that blocks ultraviolet rays before they can reach and degrade the plastic film. This intermediate barrier protects the plastic film from UV damage without requiring the addition of UV absorbers that would compromise transmittance and mechanical properties.
3Duration of action of stationary object
If the window cover film is used for long time, then durability is tested, but yellowing occurs and physical properties deteriorate due to aging
Solution Approach 1:
The inorganic thin film layer, which has superior chemical stability and UV resistance compared to organic materials, is used to protect the plastic film from degradation. The inorganic layer absorbs the harmful effects of ultraviolet radiation and environmental exposure, converting potential damage into a protective effect that extends the service life of the entire window cover film structure.
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 window cover film with excellent light resistance, durability, and weather resistance, maintaining optical and mechanical properties even under prolonged exposure to UV and high-humidity conditions, with improved solvent resistance and coatability, and flexibility to prevent microcracks and deformation.
Implementation Method 1
a light transmittance measured at 388 nm is 50% or less
Implementation Method 2
an inorganic thin film layer and a hard coating layer which are formed on at least one surface of the polyimide-based film
Implementation Method 3
has a minimized moisture content even under high-temperature and high-humidity conditions so that an occurrence of peeling off and curling of the hard coating layer is improved
Data Source
AI summary
Provided are a window cover film and a display panel including the same. More specifically, a window cover film includes a polyimide-based film, and an inorganic thin film layer and a hard coating layer formed on at least one surface of the polyimide-based film. A light transmittance measured at 388 nm is 50% or less and a total light transmittance measured at 400 to 700 nm is 87% or more, is provided.