Indium Tin Oxide Coating with Tin Oxide Interlayer for Adhesion
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Solution Overview
Problem
Existing transparent electrically conductive oxide coatings, such as indium tin oxide, face challenges in achieving a balance between low sheet resistance, high visible transmission, and neutral color properties while maintaining durability and adhesion to other overcoat films like silicon nitride or silicon dioxide.
Innovation Solution
A multiple-pane insulating glazing unit with a coating comprising both an indium tin oxide film and a tin oxide film, where the tin oxide film is located over the indium tin oxide film, achieving a sheet resistance of less than 20 ohms/square and visible transmission of greater than 75%, along with a low U-value and specific color coordinates, using a combination of film thicknesses and materials like silicon nitride and silver-based low-emissivity coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an indium tin oxide film is used as a transparent electrically conductive coating, then electrical conductivity is improved, but adhesion to overcoat films and durability are worsened
Solution Approach 1:
A tin oxide intermediate layer is introduced between the indium tin oxide film and the overcoat films (silicon nitride or silicon dioxide). This intermediate layer serves as a mediator that improves adhesion between the TCO film and the overcoat, while also providing a composition gradient that enhances durability. The tin oxide layer contains tin that can bond with both the indium tin oxide below and the silicon-based overcoats above, resolving the adhesion problem.
Solution Approach 2:
The coating structure is designed as a composite system comprising multiple layers: indium tin oxide film, tin oxide intermediate layer, and overcoat films. This composite structure combines the electrical conductivity of ITO with the adhesion and durability properties of the tin oxide and silicon-based overcoats, achieving a balance between electrical performance and mechanical reliability.
2Reliability
If the thickness of the indium tin oxide film is increased to reduce sheet resistance, then electrical conductivity is improved, but visible transmission is worsened
Solution Approach 1:
The coating is segmented into multiple functional layers with different thicknesses and compositions: a thinner indium tin oxide layer for conductivity, a tin oxide intermediate layer, and overcoat layers. This segmentation allows each layer to be optimized for its specific function, preventing the need for a single thick layer that would block light while trying to achieve low sheet resistance.
Solution Approach 2:
The invention changes the compositional parameters of the coating by introducing tin oxide and varying the indium-to-tin ratio in the ITO film. By adjusting these composition parameters rather than simply increasing thickness, the coating achieves low sheet resistance while maintaining high visible transmission through optimized material properties rather than increased quantity.
3Duration of action of stationary object
If the composition of the overcoat film is made different from the TCO film, then durability is improved, but adhesion to the TCO film is worsened
Solution Approach 1:
The tin oxide intermediate layer acts as a compositional bridge between the indium tin oxide TCO film and the silicon-based overcoat films. This intermediate layer provides a gradual composition transition, containing elements that can bond with both the ITO (through tin) and the silicon overcoats, thereby maintaining strong adhesion while allowing the overcoat to have a different composition for durability.
Solution Approach 2:
Different layers are assigned different local compositions optimized for their specific functions: the ITO layer for conductivity, the tin oxide intermediate layer for adhesion, and the silicon-based overcoat for durability and protection. This local quality differentiation allows each layer to excel at its specific role while maintaining interlayer bonding through the intermediate tin oxide layer.
Data Source
AI summary
The invention provides transparent conductive coatings based on indium tin oxide. The coating has an oxide overcoat, such as an alloy oxide overcoat. In some embodiments, the coating further includes one or more overcoat films comprising silicon nitride, silicon oxynitride, silicon dioxide, or titanium dioxide.