Flexible Device Substrate With Nickel-Plated Glass Adhesion
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Solution Overview
Problem
Existing substrates for flexible devices, such as those used in organic EL lighting and solar cells, face issues with moisture barrier properties, adhesion, bending resistance, and surface defects like seeding and cissing, particularly when using stainless steel sheets and bismuth-based glass layers.
Innovation Solution
A substrate is developed with a nickel plating layer on a stainless steel sheet, followed by an oxide film and a bismuth-based glass layer, where the bismuth concentration at 10 nm from the interface is controlled to prevent bubble formation and enhance adhesion, ensuring a dense moisture barrier and improved bending resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stainless steel sheet is used for the metal sheet, then antirust property is improved, but adhesion between the substrate and glass layer deteriorates due to formation of passivation film
Solution Approach 1:
A nickel plating layer is introduced as an intermediary between the stainless steel sheet and the bismuth-based glass layer. The nickel plating layer has dual functionality: it provides corrosion protection like stainless steel while simultaneously enabling strong adhesion to the glass layer through metal diffusion and reaction layer formation, thus resolving the adhesion problem caused by the passivation film on stainless steel.
Solution Approach 2:
The substrate employs a composite structure consisting of stainless steel sheet + nickel plating layer + bismuth-based glass layer. This multi-material composite leverages the antirust property of stainless steel, the adhesion-promoting capability of nickel, and the insulation and smoothness of glass, achieving simultaneous improvement in multiple properties that cannot be obtained by a single material.
2Ease of manufacture
If glass layer is formed directly on stainless steel sheet, then manufacturing process is simplified, but adhesion is insufficient causing glass layer to peel off during bending
Solution Approach 1:
The nickel plating layer serves as a mediator that enables reliable adhesion between the glass layer and stainless steel substrate. Without this intermediary layer, direct formation of glass on stainless steel would indeed be simpler, but the resulting structure would lack sufficient adhesion and bending resistance. The nickel layer adds a necessary intermediate step that ensures structural integrity.
3Strength
If bismuth concentration at interface is increased to improve adhesion, then adhesion is enhanced, but bubble formation and surface defects increase
Solution Approach 1:
The invention optimizes the bismuth concentration parameter at the interface between the glass layer and nickel plating layer, specifying it should be not more than 20 atomic%. This parameter control ensures sufficient adhesion through metal diffusion while preventing excessive bubble formation and surface defects that would occur with higher bismuth concentrations, thus achieving a balance between adhesion and surface quality.
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 substrate achieves excellent antirust properties, moisture barrier, insulation, and surface smoothness, with enhanced adhesion and bending resistance, suitable for flexible devices like organic EL lighting and solar cells.
Implementation Method 1
the adhesion between the metal sheet and the glass layer is developed usually since the metal diffuses from the metal sheet into the glass layer and reacts with the glass component to form a reaction layer
Implementation Method 2
an oxide film having a roughened surface is formed on the surface of the nickel plating layer
Implementation Method 3
the bismuth-based glass has excellent moisture barrier property and excellent adhesion to the metal sheet, the substrate has excellent insulation and flatness
Data Source
Figure 1~2
AI summary
The present invention provides a substrate for flexible device. The substrate includes a stainless steel sheet, a nickel plating layer formed on a surface of the stainless steel sheet, and a glass layer of electrical insulating bismuth-based glass formed in the form of layer on a surface of the nickel plating layer. The substrate is excellent in antirust property, moisture barrier property and adhesion of the glass layer, and also excellent in bending resistance and surface smoothness of the glass layer.