Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1999-07-01
2001-03-06
Cameron, Erma (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S404000, C427S414000
Reexamination Certificate
active
06197387
ABSTRACT:
The invention relates to the production of thin metal layers and structures on substrate supports having a planar or three-dimensional structure, as are required, for example, for depicting writing or drawings. The method avoids printing techniques.
The field of application of the invention described is the production of finely structured elements on decorative films or other thin or thick materials which may be flexible or rigid at room temperature. Such materials provided with thin metal layers are customarily used as packaging material or for other decorative purposes, as advertising materials, in optical signal and information processing or in semiconductors technology and microelectronics as conductor plates and IC chip material or for recircuiting, e.g. on semiconductor substrates.
PRIOR ART, DISADVANTAGES OF THE PRIOR ART
Known methods and processes for producing such metallic structures on the materials mentioned can be classified roughly into two basic types. The classification into direct and indirect methods employed here is based on the first electrically conductive layer which is structured or applied in structured form on a substrate having a significantly lower conductivity. The known methods work either directly and subtractively (e.g. laser-induced ablation), directly and additively (chemical deposition from the gas phase—CVD, including laser-induced) or indirectly using a complicated combination of different process steps from the range of microlitho-graphic structuring methods (e.g. etching processes in the aqueous or gas phase). These methods are widely used in semiconductor technology.
Those techniques which utilize only a few process steps start out from a closed metal layer or a closed metal film on the respective substrate. These can be, for example, layers obtained by lamination in the case of thick layers (>5 &mgr;m) or layers produced by chemical and physical gas-phase deposition methods or combinations thereof in the case of thin layers. The latter methods typically require vacuum conditions and high voltages or chemically aggressive gases and reagents.
Starting from a closed metal covering as is always produced, the areas which are required and are therefore to be retained (structural elements) are covered with a protective layer and the part corresponding to the negative of the desired image is removed by etching. (Cf.: Menz, W.; Bley, P. (1993) Mikrosystem-technik für Ingenieure, Weinheim, New York, Basel, Cambridge: VCH). Relatively coarse structures can be obtained by simple cutting or stamping from a metal foil and adhesively bonded to the appropriate surface.
Likewise, again starting from a closed metallic layer, the negative image can be masked with opaque lacquer or paint or a masking layer can be applied by lamination, overprinting, adhesive bonding or in another way, leaving the image elements clearly exposed as shiny metallic areas. The latter technique restricts the usability of the patterns and structures produced solely for decoration and packaging purposes.
The industrially usable production of complex metallic structures in the micron and submicron range by means of a direct lamination or sputtering process is not known. However, highly resolved, planar and also three-dimensional metallic structures can be produced on various materials by means of laser-induced chemical deposition (laser-assisted deposition—LAD, synonymously chemical vapor deposition—CVD).
However, these methods are, as mentioned above, tied to particular pressure or atmospheric conditions and can be used only for the manufacture of small batches down to a batch size of 1.
It is also possible to use combined methods. These are either printing methods, for example screen printing techniques, in which an auxiliary-containing metal paste is applied to the material and is then fixed to the substrate surface by remelting at elevated temperature (from about 200 to above 800 degrees Celsius). The resolution (smallest structure width) of such processes and thus the quality of the images obtained is limited. The relatively high temperature required for the remelting step for pastes for producing durable metallizations restricts the range of materials which can be utilized here to appropriately stable materials such as ceramics and glasses.
Printing and reproduction techniques using printing plates have, in the form of the LIGA technique, successfully found a place in the range of microstructuring methods (Becker, E. W. et al., Microelectronic Engineering 4: 35-56 (1986)). Here they are part of a complex sequence of individual steps. Due to the plate materials employed, their maximum lateral resolution is likewise restricted to structure widths in the &mgr;m range.
A method employing printing from plates has been described by Hockberger's research group for finely structured biomolecule deposition on glass surfaces for the purpose of redirecting cell growth (Soekarno, A. et al., Neuroimage, 1, 129-144 (1994); Lom, B. et al., J. Neuroscience Methods, 50, 385-397 (1993)). A microlitho-graphically produced plate enables chemical surface modifications having a lateral resolution in the &mgr;m range to be carried out.
Pritchard et al. (Angew. Chemie, 107, 84-86 (1995)) achieved protein strip widths of 1.5 &mgr;m on an SiO
2
surface using a mask-aided photochemical activation process.
The deposition of inorganic molecules and their ordered arrangement in crystalline form is a principle which has already been used in biology by “primitive” microorganisms. Higher life forms employ the same principle to provide themselves with a protective shell, a supporting skeleton or even teeth. The use of these principles for industrial applications is being stimulated by, inter alia, Mann et al., (Science 261, 1286-1292 (1993)). These authors likewise present a method of enriching ferritin monolayers with iron oxide. However, the known methods have hitherto not led to crystallization of metals at localized deposition sites determined by proteins.
Metallization of supramolecular lipid structures is also known. It was found to be possible to metallize the surfaces of helical super-structures (Schnur, J. M., Science 262, 1669-1676 (1993)).
It is an object of the present invention to provide a method in which, to produce laterally very finely structurable, metallic layers on any materials having a flat or three-dimensional surface, the necessary metallic, previously reduced or reducible material can be applied in a targeted way with very high accuracy to the site of deposition. This method should preferably do without the use of environmentally harmful components.
This object is achieved by applying a layer consisting of or comprising proteins to the substrate to be coated, wherein under illumination (action of light) in an appropriate environment the protein or proteins of the layer build up (form) a vectorial gradient of a physical or chemical property between two compartments formed by the layer and the change in the physical or chemical property effected in this way in one of the two compartments results in metal ions being reduced to metal or being accessible to a future reduction, after which the substrate provided with the protein-containing layer is illuminated at those places where the metal is to be deposited (positive illumination), or said change in the property results in a metal deposit already present being removed (etched away) at the illuminated areas of the layer (negative illumination).
The subclaims relate to preferred embodiments of the invention.
The proteins used according to the invention are ones which can act as a “pump” for the formation of a gradient of a physical or chemical property directed counter to the equilibrium which is normally established. The “property” can be of a physical nature, e.g. an electron gradient, but it is preferably of a chemical nature. Examples of chemical gradients are pH or ion (cation or anion) gradients. The proteins can be natural proteins, proteins derived from natural proteins (e.g. gene-modified or chemically modified proteins)
Fiedler Stefan
Meyer Heinrich
Oesterhelt Dieter
Reichl Herbert
Scheel Wolfgang
Cameron Erma
Foley & Lardner
Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung
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