Absorbent Overlayer Heat Treatment for Uniform Functional Coatings
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Solution Overview
Problem
Existing methods for heat treating functional layers on large substrates, such as glass sheets, suffer from treatment inhomogeneities due to variations in power intensity and substrate conveying, leading to defects like optical transmission variations and lineages, especially when using infrared radiation or flash lamps.
Innovation Solution
A process involving the deposition of a functional layer on a substrate followed by an absorbent layer that absorbs at least 80% of the radiation during heat treatment, with the absorbent layer being in contact with air, characterized by an absorption/transmission ratio greater than 8, typically comprising carbon particles, ensuring homogeneous energy distribution and reducing sensitivity to treatment inhomogeneities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If infrared laser radiation or flash lamps are used for heat treatment, then the functional layer can be heated quickly without significantly heating the substrate, but treatment inhomogeneities occur due to power variations and conveying irregularities
Solution Approach 1:
An absorbent layer is introduced as an intermediary between the radiation source and the functional layer. This layer absorbs the radiation uniformly and redistributes it as heat, ensuring homogeneous treatment of the functional layer while preventing direct exposure to radiation variations. The absorbent layer acts as a buffer that decouples the radiation input from the functional layer heating, eliminating the direct impact of power variations and conveying irregularities.
2Manufacturing precision
If the absorbent layer absorbs most radiation, then treatment homogeneity is improved, but the functional layer receives less direct radiation energy
Solution Approach 1:
The absorbent layer serves as a thermal intermediary that converts radiation energy to heat energy uniformly. While it absorbs most of the incident radiation, it subsequently transfers this energy as conductive and convective heat to the functional layer, ensuring uniform energy distribution. The key is that the absorbent layer transforms the energy form (radiation to heat) and redistributes it uniformly, maintaining total energy transfer while improving spatial distribution.
3Productivity
If longer laser lines are used to process wide substrates at high speed, then productivity increases, but it becomes difficult to ensure stable power over the entire line
Solution Approach 1:
The absorbent layer acts as a power-stabilizing intermediary that receives radiation across the entire laser line length and redistributes it uniformly. Even if different segments of the long laser line have power variations, the absorbent layer homogenizes the energy distribution across its surface, ensuring that the functional layer receives uniform heat treatment regardless of the underlying power instabilities in the laser source.
4Device complexity
If variations in conveying speed or substrate position occur, then treatment homogeneity deteriorates, but reducing conveying precision requirements would lower system complexity
Solution Approach 1:
The absorbent layer serves as a buffer that decouples the treatment process from conveying variations. Since the absorbent layer uniformly distributes radiation across its entire surface area, minor variations in substrate position or conveying speed do not directly translate to treatment inhomogeneities in the functional layer. The absorbent layer's uniform heat distribution property effectively filters out the impact of conveying system imperfections.
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 process achieves homogeneous heat treatment by absorbing most radiation in the absorbent layer, minimizing defects and reducing the need for precise optical and conveying systems, thereby lowering investment and maintenance costs.
Implementation Method 1
the absorbent layer absorbs at least 80% of the radiation used during the heat treatment and transmits less than 10% thereof
Implementation Method 2
The absorbent layer absorbs most of the energy of the radiation and returns it by diffusion to the rest of the coating
Data Source
AI summary
A process for obtaining a material including a substrate coated on one of its sides with a coating including a functional layer, includes depositing the functional layer on the substrate, then depositing an absorbent layer on top of the functional layer, then performing a heat treatment by radiation, the radiation having at least one treatment wavelength between 200 and 2500 nm, the absorbent layer being in contact with air during the heat treatment, wherein the ab sorb ent layer ab sorbs at least 80% of the radiation used during the heat treatment and transmits less than 10% thereof.