Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
2001-03-01
2003-09-02
Chen, Bret (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S489000, C427S509000, C427S515000, C427S535000, C427S162000, C204S192120, C204S192260
Reexamination Certificate
active
06613393
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for applying multiple-ply wear protection layers having optical properties onto surfaces.
BACKGROUND INFORMATION
It is conventional to apply layers onto substrates using various techniques, for example laser polymerization, reactive sputtering, or electroplating. U.S. Pat. No. 4,830,873 describes an application of thin transparent layers onto the surface of optical elements by plasma polymerization of silicon initial compounds. The polysiloxane layers thereby created are very hard and transparent. U.S. Pat. No. 4,619,865 describes a method for applying wear protection layers, in particular multiple-ply protective layers, by way of magnetron sputtering. Each layer has a different hardness or abrasion resistance. Different layer properties can also be combined with one another in these multiple-ply layers; for example, one layer acts as a diffusion barrier for water vapor, the second layer is extremely hard, and the third layer can, for example, be electrically insulating.
The problem of imparting sufficient wear resistance to substrates other than steel, ceramic, or glass—especially plastics—has not, however, hitherto been satisfactorily solved. For example, if plastics are to be mechanically loaded, it is thus necessary, for example, to equip molded plastic parts with wear protection coatings. For this purpose, it is known that in addition to the application of a scratchproof protective varnish layer. It is also possible to apply, for example, wear-resistant polysiloxane layers by plasma polymerization. Often, however, because of the substrate used for example, polycarbonate, it is necessary to make the wear protection layer UV-resistant by way of suitable additives, so that the uppermost plastic layer does not break down when exposed to outdoor weathering and thus degrade the adhesion of the wear protection layer. To prevent this, a UV absorber, for example, is dissolved in the varnish. This is intended, after the varnish has cured, to protect the substrate from the effect of light. Varnishes are not wear-resistant on a long-term basis.
SUMMARY OF THE INVENTION
An object of the present invention is to develop a method of combining incorporated or multiple-ply layers that possess optical properties, in particular UV properties such as resistance to and absorption or reflection of UV radiation, with high wear resistance on substrates, in particular substrates that can degrade upon weathering, for example, plastic components.
The present invention provides a method for applying protective layers having optical properties, for example, having good UV protective functions, onto surfaces by way of at least two different deposition steps. One step comprises a plasma-enhanced Chemical Vapor Deposition (“CVD”) method, and the at least one other step compromises a material deposition using the Physical Vapor Deposition (“PVD”) technique. Combining these methods in one vacuum vessel greatly decreases capital costs. Coating times can be further reduced by operating the two deposition processes simultaneously, which can result in an additional cost decrease. Deposition of the wear protection layer can be performed by plasma polymerization. Plasma polymerization is a coating method in which an evaporable chemical compound, for example, an aliphatic-aromatic or olefinic hydrocarbon compound, preferably methane, ethane, ethylene, or acetylene, is used. It is preferable to use a silicon-organic compound including the elements silicon, carbon, and hydrogen, or with additional nitrogen and/or oxygen, may include tetramethylsilane (TMS), hexamethyldisilane (HMDS), hexamethyldisilazane (HMDS(N)), tetraorthosilicate (TEOS), dimethyldiethoxysilane (DMDEOS), methyltrimethoxysilane (MTMOS), tetramethyldisiloxane (TMDS(O)), divinyltetramethyldisiloxane (VSI2), and very particularly advantageously hexamethyldisiloxane (HMDS(O)). These “monomers”—many of which cannot be polymerized by conventional chemical methods—can have further evaporable additives mixed into them, for example metalorganic compounds such as tetraethyl orthotitanate (TEOT), tetraisopropyl orthotitanate (TIPOT), or tetrakis(dimethylamino)titanium.
In another embodiment of the present invention, halogenated additives such as tetrafluoromethane, chloroform, or freons can be used. The monomer/additive mixture is then exposed in the vessel to an electric field that can be capable of igniting a plasma of the vapor. The vapor molecules are thereby activated and fragmented into ions and radicals. These highly reactive fragments condense onto the substrate surface and combine into a new, very dense monomer network. In order to prevent the electrodes necessary for the electric field from becoming insulated with insulating layers, which can occur, for example, when silicon-containing vapors are used, it is recommended to power the plasma with electrical high-frequency fields in a frequency range between 50 kHz and 2.45 GHz, preferably between 400 kHz and 2.45 GHz. Because of the higher deposition rate, it is particularly advantageous to use radio-frequency (13.56 MHz) or microwave radiation (2.45 GHz). Microwave plasmas can be operated in pulsed or unpulsed fashion, with or without magnetic field enhancement (ECR). The pulse frequencies can be between a few Hz and 10 kHz, preferably in the range between 50 Hz and 2 kHz; the pulse-to-interpulse ratio can be set without restriction.
In another embodiment of the present invention, in the case of a microwave plasma the chemical structure and stoichiometry of the deposited layer can be more freely adjusted by physically separating the plasma from the deposition region, since fragmentation of the monomer molecules proceeds more gently and more controllably.
In another embodiment of the present invention, this can be achieved by “remote placement,” in which a noble gas and/or a non-coating gas, which can be called the “reactive gas”, e.g., oxygen, nitrogen, hydrogen, ammonia, laughing gas, halogen, is activated and fragmented in the source and/or in the vicinity of the source, and passes by way of a correspondingly guided gas flow toward the substrate. At that point the activated reactive gas encounters the monomer gas, causing the monomer gas to be activated and fragmented. This embodiment of the present invention provides better control of thermal loads, e.g., in the case of microwave-absorbing materials such as plastics, since the source and the point of highest plasma density is located farther away from the substrate.
In a further embodiment of the present invention, deposited polymer networks can be additionally densified by substrate heating and/or ion bombardment. Since additional heating can have limitations in the case of temperature-sensitive substances, e.g., plastic materials, ion bombardment is useful because densification, rearrangement of bonds in the network in the direction of maximum bond saturation of the atoms participating in the network, can be combined with a comparatively small heat input. A further embodiment of the present invention provides using a bias voltage on the substrate by way of an electrode mounted behind the substrate. This allows pulling ions directly onto the substrate. Both pulsed and unpulsed bias voltages can be used in this context. In the case of pulsing, frequencies between 5 kHz and 27 MHz are usable, in particular between 10 kHz and 13.56 MHz. Bias voltages can be used in addition to the PECVD process, i.e., microwave plasma polymerization. In another embodiment of the present invention, bias voltages can also be utilized as the only source for Plasma Enhanced Chemical Vapor Deposition (“PECVD”) deposition of the wear protection layer. High-frequency bias voltages have proven particularly effective in this context, in particular those with frequencies in the range of 50 kHz to 800 kHz or 13.56 MHz.
Particular optical properties, in particular UV protection, can be implemented in three ways: first, by way of a package of thin layers having different refractive indices that are capable of re
Rauschnabel Johannes
Voigt Johannes
Chen Bret
Robert & Bosch GmbH
LandOfFree
Method for applying a wear protection layer system having... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for applying a wear protection layer system having..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for applying a wear protection layer system having... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3024821