Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
1999-09-03
2001-08-07
Beck, Shrive P. (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C427S248100, C427S255500, C427S255700, C427S294000, C427S350000, C427S336000, C427S337000, C427S402000
Reexamination Certificate
active
06270840
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to plane-parallel flakes and, more particularly, to an apparatus and method for producing plane-parallel flakes.
BACKGROUND OF THE INVENTION
In the past few years there has been an increased interest in using plane-parallel flakes as pigments in paints and printing inks, as a catalyst material, as a starting product for magnetic and electric screens, and as a starting material for conductive lacquers. In contrast with the classical pigments produced in accordance with a grinding process and having a more or less spherical shape, plane-parallel flakes are characterized by an improved brilliance and by the fact that their quantity required in a paint as a pigment is substantially smaller. Thus, for example, aluminum flakes produced in accordance with a physical vapor deposition (PVD) process typically have a thickness of 30-500 nm; their superficial dimensions ranging between 5 and 50 microns. Even 3-4 layers of such aluminum flakes produce an optically opaque layer at quantities of no more than 0.3 to 0.4 g/m
2
.
Plane-parallel flakes have heretofore been produced, in accordance with the prior art, through a costly, intermittent three-stage process. The high costs of this process and the low production quantities do not allow for use in mass-produced articles such as in metallic paintcoats or printer's inks.
One example for production according to an intermittent. multi-stage process is the production of optically variable pigment flakes used to enhanced safety against forgery oil banknotes such as disclosed in EP 227423. Similar products and processes are disclosed in U.S. Pat. No. 5,278,590.
A process disclosed in U.S. Pat. No. 4,434,010 does not involve use of separating agents. Vapor deposition is instead performed directly onto a plastic film which is subsequently comminuted and dissolved completely in a suitable solvent. As a result, the vapor deposition layer dissociated into particles remains as a suspension.
In all of the above-represented cases, large amounts of solvents are required for washing out the product. These must either be reprocessed or disposed of.
In summary, it may therefore be noted with respect to the prior art that in all of the known PVD processes for producing plane-parallel flakes, with the exception of U.S. Pat. No. 4,434,010, the following stages are passed through:
(1) application of a separating lacquer on a polyester film substrate by printing and drying, with this process being performed on classical rotary gravure printing machines for coiled material in an atmosphere under explosion protection conditions;
(2) sequential vapor deposition of the layers under high vacuum, partly through several reciprocating passages of the film substrate in the vacuum unit, and removal of the vapor coated roll; and
(3) removing the composite product by dissolving the separating lacquer in a solvent (acetone, ethyl acetate), and filtering out the product from the solvent, for which purpose scraping and brushing means are used in a solvent bath through which the web of film passes, with the product subsequently being filtered out and proceeding towards further processing.
The use of inorganic separating agents vapor deposited in a vacuum is described, for different applications, by Rosenfeld in U.S. Pat. No. 5,156,720. In this process, as well, a film substrate preferably comprised of polyester film is used, with this film substrate being usable only once owing to the high strain caused by the process. As one square meter of aluminum flakes having a thickness of 30 nm and a mass of 0.091 g is produced from one square meter of film having a, weight of 16.8 g by using a separating agent in a quantity of approx. 6 g/m
2
in manufacture, the yield by weight is merely 1/272 of used film and separating lacquer. This method is therefore uneconomical. Ratios are somewhat more favorable when using a vapor deposited separating agent with approx. 0.1 g/m
2
, however the ratio still is only 1/180. In each case, this is an intermittent process which must be carried out consecutively on 2 or 3 different machines. The production costs are correspondingly high and hitherto thwarted a wider use of the product. Particular vapor deposition or sputtering materials may not even be applied on a film substrate as their thermal resistance is too low.
A vacuum coating machine for the production of oxide layers, which are preferably made of silicon monoxide, on temperature-sensitive plastic films, such as polyethylene and polypropylene, is disclosed in DE 4221800 A1. The purpose of this machine is to increase the barrier properties of the base film for oxygen, water vapor, and aroma substances. The characteristics of web path, evaporation zone, and array of thermal treatment steps allow for the production of oxide layers which are substantially free of micro cracks. This machine allows for the continuous removal of excess condensate, which allows the coating process to operate without the need to shield the rims of the film against, coatings. However, the removal is accomplished by spalling when the belt passes over a deflection roller, or by scraping or brushing the excess condensate.
A system of a closed loop belt to remove waste metal coatings which deposit right and left of a traveling web, or in areas near a melting process under vacuum, is disclosed in French Patent No. 1,507,784. During a melting process under vacuum, splashes and deposits from metal vapor take place. This system allows for the removal of those deposits before a certain build-up thickness has been reached. However, this system is largely inapplicable to the production of plane-parallel flakes.
In view of the foregoing, it would be desirable to provide a technique for producing plane-parallel flakes which overcomes the above-described inadequacies and shortcomings. More particularly, it would be desirable to provide a technique for producing plane-parallel flakes in an efficient and cost effective manner.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an apparatus and method for producing plane-parallel flakes wherein production costs are reduced, a longer service life and a higher product output of any apparatus used are ensured, and increased safety requirements are taken into account.
The above-stated primary object, as well as other objects, features, and advantages, of the present invention will become readily apparent to those of ordinary skill in the art from the following detailed description which is to be read in conjunction with the appended drawings. While the present invention is described below with reference to preferred embodiment(s), it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could, be of significant utility.
SUMMARY OF THE INVENTION
According to the present invention, an apparatus and method for producing plane-parallel flakes is provided. In a preferred embodiment, the present invention apparatus is realized as a belt-type vapor deposition apparatus comprising a vapor deposition chamber having first and second evaporation means for applying a separating agent layer and at least one additional layer on an endless substrate. The belt-type vapor deposition apparatus also comprises a stripping chamber wherein the separating agent layer and the at least one additional layer are stripped from the substrate with the aid of stripping means in such a manner that the separating agent layer is present in a dissolved state, and the at least one additional layer is present in the form of plane-parallel flakes. The pressure in the stripping chamber is higher than in the vapor deposition chamber and lower than atmospheric pressure. As a result, production costs of plan
Barr Michael
Beck Shrive P.
Gerstman George H.
Shaw Seyfarth
Weinert Vakuum Verfahrenstechnik GmbH
LandOfFree
Apparatus and method for producing plane-parallel flakes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for producing plane-parallel flakes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for producing plane-parallel flakes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484201