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New Film Formation Method with High Efficiency and Low Environmental ImpactMist Deposition Method
In the field of electronics, applications of films as well as silicon and glass substrates are being considered.
Nikon is conducting research on the “Roll to Roll” process, which has high probability and low environmental impact.
The mist deposition method is a technique through which the coating solution is turned into a mist and deposited onto the substrate at low temperatures.
Therefore, film formation is possible.
What is the mist deposition method?
Solution atomizing
01
The mist was produced from some nanoparticle aqueous dispersion which include coating liquid.
Mist transport
02
Transfer of mist to the film formation target by placing it on an airflow.
Mist attachment
03
The misted solution covers a large specific surface area and evaporates after attaching to the film formation object.
Thin film formation
04
Thin films can be formed without heating.
Feature comparison
Mist deposition is classified as wet deposition.
Since the film is deposited at atmospheric pressure, it has a lower environmental impact and higher productivity than dry film deposition using a vacuum. Also, "aqueous solution" which is difficult to use in general wet film formation, is applicable. Since there is no need to heat the substrate during film formation, it is also possible to use a film with a low melting point.
It is possible to form a film on a three-dimensional substrate, which is difficult when using dry film formation.
SEM image
Without nanoparticle film
With nanoparticle film
Equipment（ prototype ）
Mist Coating System for R&D "MisCo"
We have experimented a film deposition equipment for R&D which is small enough to use on a table.
This equipment consists of a mist generating unit that is easy to maintain and a nozzle that can be customized. Special utilities are not required and can be installed in small spaces.
Mist-generating unit
The mist generator consists of parts that are easy to clean and replace. Suitable for film formation experiments in R&D environments where a variety of materials are considered.
Customizable film deposition chamber
The material and nozzle shape of the film formation chamber can be easily customized.It is also possible to make small changes according to the solution to be used and the object to be formed.
“Roll to Roll” is being developed for long and large flexible devices.
A3 width compatible mist coating nozzle
To support large-scale production, we have developed a nozzle that can uniformly supply mist to an A3 width area.
Uncoated PET film
By continuously supplying mist to the film substrate being transported, film formation over a large area is possible.
Materials and Film Formation Examples
We are researching various materials to create functional thin films with mist coating system.
Transparent conductive material
ITO nanoparticles (NPs)
Although the shape of this ITO has many protrusions on its surface, it maintains high crystallinity.
TEM image
Electron Diffraction
The cubic ITO NPs were sedimented on the bottom of the vessel. By contrast, the ITO NPs with protrusions remained homogeneously dispersed in water, similar to the as-prepared dispersions.
Aqueous dispersion
Immediately after fabrication
After two weeks
Reprinted with permission from Ryoko Suzuki, Yasutaka Nishi, Masaki Matsubara , Atsushi Muramatsu and Kiyoshi Kanie Single-Crystalline Protrusion-Rich Indium Tin Oxide Nanoparticles with Colloidal Stability in Water for Use in Sustainable Coatings ACS Appl. Nano Mater.2020, 3, 4870-4879. Copyright 2020 American Chemical Society.
Transparent conductive films
ITO nanoparticles (NPs)
The transparent conductive films deposited by the mist coating system were flatter and denser than those deposited by other deposition methods.
This was also shown to be effective in achieving high conductivity and lower resistivity than other methods.
In particular, the effect is remarkable when the firing temperature is low, so application to film substrates can be expected.
AFM images
Resistivity of the ITO films
The ITO NPs are highly dispersible and do not cause local agglomeration when the mist evaporates on the substrate.
As a result, a film with high transmittance and high electrical conductivity is obtained through the dense packing of particles.
Surface SEM image
Cross-sectional STEM image
Because it does not contain dispersants, the removal process via high-temperature annealing, which was previously required, is no longer necessary.
This makes it possible to fabricate ITO thin films on low melting point film substrates.
ITO thin films on PET substrates showed extremely high transmittance in the visible light region.
Transmittance of ITO thin films
Even after 10,000 bending tests, cracks did not appear, allowing for the production of a film with high resistance to bending.
Exterior of the bending test equipment
Surface SEM images before and after 10,000 tests
Anti-reflection film
Silica coating agent
Silica coating agent was deposited on the optical substrate, and transmittance improvement was confirmed.
Substrate appearance
Transmittance
Antibacterial film
Cu-doped TiO2 (CTO) Nanoparticles
Using CTO NPs as raw material, we developed a transparent film that exhibits antibacterial activity in both light and dark conditions.
Nanoparticles
Transmittance
※Collaboration with Tohoku University
Heat insulating film
Ga-doped ZnO (GZO) Nanoparticles
Reprinted with permission from Yasutaka Nishi, Yuki Kasai, Ryoko Suzuki, Masaki Matsubara, Atsushi Muramatsu and Kiyoshi Kanie Gallium-Doped Zinc Oxide Nanoparticle Thin Films as Transparent Electrode Materials with High Conductivity ACS Appl. Nano Mater.2020, 3, 4870-4879. Copyright 2020 American Chemical Society.
Analysis
We are analyzing the dispersion state of particles during the deposition process.
In collaboration with Tohoku University, we are engaged in cutting-edge analysis of Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) at the Aichi Synchrotron Radiation Center.
The dispersion state of NPs in mist and the process of thin film formation are measured using a uniquely developed observation cell.
Mist supply unit
Observation cell
Substrate in the cell
Aichi Synchrotron Radiation Center
Mist coating technique applicable to various fields
Nikon provides comprehensive solutions for mist deposition.
Contact Us
We will respond to inquiries and consultation requests regarding mist deposition and mist coating system for R&D.
Please feel free to contact us.
