Polyimide Cover Substrate with Silicon Oxide Layer for Flexible Touch Displays
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Solution Overview
Problem
The demand for a flexible, lightweight, and portable cover substrate with high hardness and optical transmittance for handheld devices is increasing, as conventional glass substrates are inadequate for flexible displays, and existing solutions do not provide sufficient scratch resistance and conductivity for touch integration.
Innovation Solution
A polyimide cover substrate with a support film, conductive coating layer, hard coating layer, adhesive layer, and silicon oxide layer, where the silicon oxide layer is formed between the hard coating and adhesive layers, ensuring a thickness of 50-200 micrometers, high transmittance, and surface hardness, while enabling conductivity for touch functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional glass cover substrate is used, then high hardness and scratch resistance are achieved, but flexibility and portability are compromised
Solution Approach 1:
The patent replaces the conventional rigid glass cover substrate with a flexible polyimide film-based cover substrate. The polyimide film serves as the base layer providing flexibility, while multiple coating layers (conductive coating, hard coating, silicon oxide layer) are formed on its surfaces to impart conductivity, scratch resistance, and optical properties. This flexible film structure enables the cover substrate to be bent and adapted to flexible display devices while maintaining protective functions.
Solution Approach 2:
The cover substrate is constructed as a composite structure consisting of a polyimide film base layer combined with multiple functional coating layers. These include a conductive coating layer (e.g., ITO, silver nanowires, graphene), a hard coating layer (e.g., silicon oxide, silicon nitride), and additional protective layers. Each layer contributes specific properties, and their combination achieves the desired balance of flexibility, conductivity, hardness, and optical transmittance that cannot be obtained with a single material.
2Ease of manufacture
If the cover substrate thickness is increased to a predetermined level or more, then existing manufacturing processes can be adopted without design changes, but flexibility and portability are reduced
Solution Approach 1:
The patent employs a thin-film structure where the polyimide film and multiple coating layers are deposited to achieve the required functional properties at reduced thickness. The flexible nature of the thin polyimide film allows it to maintain flexibility even when the total thickness is sufficient for manufacturing process compatibility, unlike rigid glass substrates that require greater thickness for structural integrity.
Solution Approach 2:
The patent optimizes the thickness parameters of each layer (polyimide film, conductive coating, hard coating, silicon oxide layer) to achieve a balance between flexibility and manufacturability. By controlling the thickness of each individual layer and their combined total, the substrate maintains flexibility for portable devices while meeting the minimum thickness requirements for existing manufacturing processes.
3Adaptability or versatility
If a conductive coating is added to enable touch functionality, then touch integration is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the cover substrate and touch sensor functions into a single integrated structure. The conductive coating layer (such as ITO, silver nanowires, or graphene) is formed directly on the polyimide film surface, serving simultaneously as part of the cover substrate structure and as the transparent electrode for touch sensing. This integration eliminates the need for separate touch sensor layers or additional manufacturing steps, reducing overall device complexity despite adding touch functionality.
Solution Approach 2:
The polyimide film-based cover substrate serves multiple functions simultaneously: it provides the structural base layer, mechanical flexibility, support for conductive and protective coatings, and enables touch sensing through the integrated conductive coating. The single substrate structure performs what would traditionally require multiple separate components, simplifying the overall device architecture.
4Strength
If multiple coating layers are formed on the polyimide film, then scratch resistance and conductivity are improved, but manufacturing complexity and process steps increase
Solution Approach 1:
The patent segments the protective and functional properties into distinct coating layers: a conductive coating layer for touch functionality, a hard coating layer for scratch resistance, and a silicon oxide layer for additional protection and optical properties. Each layer is optimized for its specific function, allowing independent selection of materials and deposition parameters, which simplifies the overall manufacturing approach despite the multiple layers.
Solution Approach 2:
The multi-layer structure uses composite materials where each layer (polyimide film, conductive coating, hard coating, silicon oxide layer) contributes specific properties. This composite approach allows the manufacturing process to target each layer's specific requirements independently, making the complex multi-functional substrate manufacturable through standardized coating and deposition techniques.
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 polyimide cover substrate achieves superior optical properties, conductivity, and scratch resistance, making it suitable for flexible electronic devices without compromising on thickness or handling difficulties.
Implementation Method 1
The silicon oxide layer may be formed on at least one surface of the polyimide film by a physical vapor deposition method
Implementation Method 2
The silicon oxide layer may be formed on at least one surface of the polyimide film by a chemical vapor deposition method
Implementation Method 3
the conductive coating layer is formed on at least one surface of the support film
Implementation Method 4
a conductive coating layer formed on at least one surface of the support film
Implementation Method 5
an adhesive layer formed between the first base layer and the second base layer
Data Source
Figure 1
AI summary
Disclosed is a polyimide cover substrate, which has a thickness of a predetermined level or more to implement processes, and can prevent generation of usual scratches in a flexible electronic device and can protect a substructure, and also has conductivity to thus provide a touch-integrated transparent polyimide cover substrate which enables screen touch.