US 3743551 A
Description (OCR text may contain errors)
United States Patent 3,743,551 RAZOR BLADES AND METHODS OF MANUFACTURE THEREOF Michael D. Sanderson, Egham, England, assignor to Wilkinson Sword Limited, London, England No Drawing. Filed Apr. 14, 1971, Ser. No. 140,186 Claims priority, application Great Britain, Apr. 17, 1970, 18,409/ 70 Int. Cl. B26b 21 /54 US. Cl. 148-63 12 Claims ABSTRACT OF THE DISCLOSURE On a razor blade having at least one cutting edge there is provided a first coating of chromium, whose surface region may be oxidised, upon which is superposed a second coating of chromium nitride. A coating of a polymer which improves the shaving properties of the blade may be provided on the chromium nitride coating.
This invention relates to razor blades and to methods of manufacture thereof.
It is known to provide a coating of chromium on the cutting edge of a razor blade and to coat the chromium with polytetrafluoroethylene.
According to the present invention there is provided a razor blade wherein at least a cutting edge has an upper coating of chromium nitride superposed on a lower coating of chromium.
Preferably the surface region of the lower coating is chromium oxide.
The invention also provides the method of manufacturing a razor blade wherein at least a cutting edge is coated with chromium and the chromium coating is thereafter provided with a coating of chromium nitride.
Preferably the upper coating is provided with a coating of a polymer which improves the shaving properties of the blade and may, for example comprise a fluorocarbon polymer, for example polytetrafiuoroethylene or a copolymer of thiocarbonyl fluoride and tetrafluoroethylene.
Thus, in a preferred form of the invention the blade is first provided with a chromium coating on the cutting edge, thereafter a chromium nitride coating is superposed on the first coating and, finally, a polymer coating is provided on the nitride coating.
One method of providing a stainless steel razor blade with a double coating in accordance with the present invention is, tfilSt, to form a chromium coating by sputtering chromium onto the previously cleaned cutting edges from electroplated targets at a pressure of between A of a micron and 10 microns of mercury in a residual atmosphere of inert gas such as argon or helium using commercially available ion-plasma sputtering apparatus. The chromium coating may, for example, be of a thickness between 50 and 450 angstroms but preferably not greater than 200 angstroms. Thereafter the sputtering process is repeated with a residual atmosphere of nitrogen at a pressure of, for example, 1 to 4X10 millimetres of mercury, to form a chromium nitride coating.
Preferably, the blades are exposed to an oxide-forming atmosphere after formation of the initial coating so that the surface region of the initial coating is oxidised. One way of achieving this is by allowing a controlled air leak into the sputtering apparatus between the two coating stages.
3,743,551 Patented July 3, 1973 p CC I The nitride coating may have a thickness of, for example, from 50 to 450 angstroms but preferably not greater than 150 angstroms and a preferred range for the thickness of the two coatings together is from to 500 angstroms or even up to 750 angstroms.
The term nitride is intended to embrace coatings over the range from a small amount of nitrogen in solid solution with chromium up to any of the chromium nitride compounds, Cr N, Cr N and ON, or any combination thereof. Thus for example the composition range may extend from 0.01 atomic percent nitrogen to 55 atomic percent nitrogen.
The reaction between chromium and nitrogen in the sputtering process may take place on the surface of the target, or as the metallic particles are being sputtered through the ionised nitrogen plasma or after the metal has been deposited on the blade surface.
The gas composition can vary widely depending upon the sputtering conditions. Thus, for example, the nitrogen may be diluted with an inert gas, such as argon, from 5 volume percent of the gas in argon to 100 volume percent of the nitrogen or other gas. Alternatively a gas with a large nitrogen content such as cracked ammonia and/ or air diluted by an inert gas may be used.
The sputtering may be direct current or radio frequency sputtering and in the latter case sputtering may be direct from a chromium nitride target in an inert atmosphere.
As an alternative to sputtering the coatings may be produced by chemical vapour deposition or by reactive evaporation.
1. A razor blade wherein at least a cutting edge has an upper coating of chromium nitride superposed on a lower coating of chromium.
2. A razor blade according to claim 1, wherein the surface region of said lower coating is chromium oxide.
3. A razor blade according to claim 1, wherein each coating has a thickness of between 50 and 450 angstroms.
4. A razor blade according to claim 1, wherein said lower coating has a thickness of between 70 and 200 angstroms.
5. A razor blade according to claim 1, wherein said upper coating has a thickness of between 50 and angstroms.
6. A razor blade according to claim 1, wherein a coating of a shaving facilitating polymer is provided on said upper coating.
7. A razor blade according to claim 1, wherein a coating of a fluorocarbon polymer is provided on said upper coating.
8. A razor blade according to claim 1, wherein a coating of polytetrafluoroethylene is provided on said upper coating.
9. A razor blade according to claim 1, wherein a coating of a copolymer of thio-carbonyl fluoride and tetrafluoro'e'thylene is provided on said upper coating.
10. The method of manufacturing a razor blade wherein at least a cutting edge is coated with chromium and the chromium coating is thereafter provided with a coating of chromium nitride.
11. The method according to claim 10, wherein at least the surface region of the initial chromium coating is oxidised.
12. The method according to claim 10, wherein each 6618472 3/1967 Netherlands 30346.53
coating is applied by ion-plasma sputtering. 1,200,165 7/ 1970 Great Britain 148--16.6
References Cited OTHER REFERENCES UNITED STATES PATENTS 5 Chem. Abstracts, vol. 67: 35237t (1967).
3,480,483 11/1969 Wilkinson 1486.3 1 94 025 1 1934 Frost 14 1 RALPH KENDALL, Prlmary Examlner FOREIGN PATENTS 1,193,067 5/1970 Great Britain 30 346 54 10 30-346.54; 29-195, 196.6; 14816.6; 204-192; 117
1,065,724 4/1967 Great Britain 30346.54 71 M