Coating processes – Frictional application
Patent
1985-11-04
1988-05-03
Beck, Shrive P.
Coating processes
Frictional application
427180, 427194, 118249, B05D 102
Patent
active
047419180
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for depositing thin films of coating material onto a substrate, and to substrates having thin film coatings thereon.
Thin films have an enormously varying range of industrial applciations. For example, thin films of gold, silver and chromium are used for decorative purposes, thin films of aluminium and nickel-boron have been used for corrosion protection, and thin films of magnesium fluoride, aluminium oxide and silicon oxide have all been used as non-reflective coatings for optical lenses.
Kirk-Othmer's "Encyclopaedia of Chemical Technology", 3rd Edition (1980) Vol. 10, pages 247 to 283 describes the following types of process for depositing thin films:
The present invention provides a method of depositing films which falls into none of the above-mentioned categories. The method has application to a vast range of substrates and coating materials, and produces a type of thin film which is believed to be unique.
The present invention is based on the unexpected discovery that thin films of unprecedented characteristics can be made merely by rubbing small particles of a coating material (such as copper) with sufficient force across the surface of a substrate (such as a sheet of glass). Our investigations have shown that the bond obtained between the copper coating and the glass substrate in the above-mentioned example was not merely the result of mechanical keying between the copper and microscopic rugosities on the surface of the substrate, but is a quite different kind of bond which is only achieved at or beyond certain critical rates of energy input. This was demonstrated by an experiment in which copper particles were rubbed across the surface of glass by means of a rotating buffing wheel, while gradually increasing the force with which the wheel was pressed against the glass. Measurement of the frictional force acting on the glass, (i.e. the force acting on the glass in a direction tangential to the circumference of the wheel) gave a most unexpected result. It was found that the frictional force increased gradually, and generally in proportion to the load on the glass, until a critical load was reached. At this point the frictional force increased very markedly upon only slight increase in the applied load. It was only at and beyond this point that copper was deposited on the glass. Had the bond between the copper coating and the substrate been merely the result of mechanical keying, it might have been expected that the extent of coating would have increased gradually with the applied load.
It is therefore believed that the copper coating described above is totally unrelated in character to the type of coating which may be formed by drawing a relatively soft material across a microscopically or macroscopically rough surface, so that fragments of the soft material are mechanically held in fissures or on microscopic protuberances in or on the coated surface. Examples of such mechanically keyed coatings are those obtained when waxes are applied to wood, graphite or paper, and when copper is applied to iron or steel as described in U.S. Pat. No. 826,628.
The exact nature of the copper/glass bond obtained in the experiments described above is imperfectly understood. However, it is thought that the critical conditions of roller pressure and peripheral speed represent the conditions necessary to remove contaminants from the surface of the substrate, and to present fresh copper particles to the decontaminated surface before recontamination can occur. In the extremely short period of time for which the surface remains uncontaminated, the surface molecules are thought to be in some way activated, and highly receptive to any molecule with which they might come into contact.
A possible alternative mechanism is that under the very high energy conditions which obtain at interface between the particle of coating material and the substrate, an intimate molecular mixture or complex is formed between the coating material and the material of the substrate, analogous to a metallic alloy,
REFERENCES:
patent: 461667 (1891-10-01), Chatfield
patent: 3041140 (1962-06-01), Alexander
patent: 3075279 (1963-01-01), Haltner et al.
patent: 3669705 (1972-06-01), Morrison
patent: 4159352 (1979-06-01), Martin
patent: 4161250 (1979-07-01), Pierce
patent: 4390562 (1983-06-01), Yanagisawa
patent: 4391854 (1983-07-01), Kanda et al.
patent: 4485757 (1984-12-01), Ebner
Nagy de Nagybaczon Erno
Paterson Alan C.
Beck Shrive P.
Tribohesion Limited
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