Coating apparatus – Immersion or work-confined pool type – With tank structure – liquid supply – control – and/or...
Patent
1991-02-21
1993-09-21
Sluby, P. C.
Coating apparatus
Immersion or work-confined pool type
With tank structure, liquid supply, control, and/or...
118402, 118425, 427402, 4274343, 428339, 4284111, B05C 300, B05C 1902, B05D 136, B32B 904
Patent
active
052464989
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process and to an apparatus for producing thin layers of at least one amphiphilic compound on a carrier. In the process according to the invention, boundary layers are produced at the interface between a fluid and a polar liquid, and compressed by flow. The compressed boundary layers are transferred to a solid carrier by the method indicated by Langmuir-Blodgett.
It is known that insoluble layers, spread on liquid surfaces, of amphiphilic molecules can be mechanically compressed by means of so-called push barriers in such a way that, depending on the type of molecule and the compressional state of the surface film when a solid carrier is moved through, the film can be transferred onto this carrier. In particular, the multiple coating thus possible is known as the so-called Langmuir-Blodgett technique and is of great current interest for various applications.
In this method, the compounds are in most cases dissolved in volatile organic solvents. The solution is distributed ("spread") on the surface of the polar liquid (almost always water) and the solvent is then evaporated. The states of high compression required for the transfer of a layer can be produced by movement of a barrier only in the case of insoluble molecules. The Langmuir-Blodgett technique is therefore restricted to compounds which are insoluble in the liquid phase.
To carry out the layer transfer continuously is extremely involved since, in this case, the preceding spreading must also take place continuously. A continuous Langmuir-Blodgett technique with the aid of a mechanical "roller method" has been described by A. Barraud et al. 1983 (Thin Solid Films 99, 221).
Layers of amphiphilic molecules which are soluble in the liquid phase cannot be transferred in the usual mechanical compression in the Langmuir trough, because they "evade" into the subphase as a result of desorption.
It was therefore the object to provide a process, by means of which even those amphiphilic molecules which are soluble in the subphase can be compressed on the surface and transferred. It was a further object to indicate a process, in which both soluble and insoluble amphiphilic molecules can be concentrated continuously on the surface of the subphase and compressed, so that transfer is possible.
The process according to the invention achieves this object. It relates to the production of a thin layer of at least one amphiphilic compound on a carrier, an at least partially oriented layer of molecules of an amphiphilic compound being produced by compression and, if appropriate (for insoluble compounds), prior spreading at the interface between a fluid and a polar liquid, and a solid carrier being moved through the layer so that the layer is transferred thereto. This process comprises generating, in an approximately horizontally located channel, a directional flow of the polar liquid which contains amphiphilic molecules in solution or as insoluble molecules in a spread form on the surface, damming the flow at a barrier arranged in the channel at the fluid/polar liquid interface, selecting the flow velocity and, if appropriate, the concentration of the amphiphilic molecules in such a way that a layer of amphiphilic molecules is continuously formed by compression in front of the barrier at the fluid/polar liquid phase boundary, and moving the carrier through this compression zone. The transfer of the layer itself can be carried out in the process according to the invention in the manner known per se according to the discontinuous technique indicated by Langmuir-Blodgett. Many layers on top of each other can be produced by repeated immersion and pulling-out of the carrier which is to be coated. In most cases, double layers are here transferred (immersion and emergence) However, continuous transfer is also possible. For example, a polyester wire or a polyester film can be immersed at uniform speed into the polar liquid at a position where a rigid boundary layer is not yet present, deflected by rollers and pulled out again from the liquid at the pos
REFERENCES:
patent: 4599969 (1986-07-01), Barraud et al.
patent: 4783348 (1988-11-01), Albrecht et al.
patent: 4978574 (1990-12-01), Mino
patent: 5021268 (1991-06-01), Khanarian et al.
A. Barraud et al., Thin Solid Films, 1983, 99, pp. 221-225.
R. Ollenik, W. Nitsch, Bunsenges. Phys. Chem., 1981, 85, pp. 901-904.
Kurthen Christoph
Nitsch Walter
Hoechst Aktiengesellschaft
Sluby P. C.
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