NO135203B - - Google Patents

Description

The present invention relates to razor blades with a coating of a metal or a metal alloy on at least one egg, and an outer coating of a polymer.

It has previously been proposed to coat at least one surface of a razor blade with various materials to improve its shaving properties. In DOS 1,817,427 there is e.g. described the use of carbides, borides, oxides or nitrides of various metals as coating material for razor blades. It is also proposed to coat at least one egg surface of a razor blade with a polymer that provides reduced friction during shaving. British Patent No. 1,050,243 describes the use of a silicone and an organic lubricant, and U.S. Pat. patent no. 3,402,468 describes razor blades that are coated with polytetrafluoroethylene on a chrome-plated coating.

It has further been proposed to improve the adhesion between metal surfaces and perhalogen polymers by first applying an organic nitrogen base mixture to the metal sheet, which is described in U.S. Pat. patent no. 2,918,387..

Although coated razor blades belonging to the state of the art have improved shaving properties compared to corresponding uncoated blades, there is a great need for further improvement of the shaving properties, e.g. when it comes to close shaving without scratching the skin.

The purpose of the present invention is to arrive at razor blades that have better shaving properties than previously known. In contrast to the previously known blades, razor blades according to the invention have three overlapping coatings. The use of three coatings improves the shaving properties compared to the previously known blades, as the effect of the first coating of a metal or an alloy is quite unexpectedly achieved with the blade despite the overlying coatings and the outer polymeric coating. One would expect that the coating between the polymer coating and the metal or alloy coating would cover the effect of the metal or alloy coating. However, it has been shown that all three coatings play a role in producing the good shaving properties of blades according to the invention.

The invention is characterized by the features set out in the claims and will be described in more detail below.

The reason why the invention results in an improvement is currently not fully understood. However, without limiting the scope of the invention, I believe. one that as a general rule when it comes to materials that can be used for. the non-polymeric coatings, it is preferable to use for the first coating a material that will act so that it strengthens the edge and reduces damage that occurs to the edge during shaving, as well as acting to reduce corrosion. Examples of materials that can be used for this first coating are chromium, platinum and other noble metals, including tridium, osmium, palladium, rhodium and ruthenium, titanium, zircon, vanadium, niobium, tantalum, molybdenum, cobalt, nickel, manganese, and tungsten as well as alloys of any of these.

For the same reason as mentioned above, it is believed that the second coating should preferably be chosen for its wear-resistant and corrosion-protective properties so that it provides a surface that is less susceptible to increased wear during shaving than the first coating. Alternatively or in addition, the second coating can be selected so that it provides a better substrate for attaching the subsequently applied polymer coating and/or to facilitate the crystallization of the polymer coating during deposition in a way that results in an improved polymer coating. Examples of materials that can be used for the second coating are carbides, borides, oxides, nitrides, silicides and fluorides, all of which are examples of typical so-called "low-melting" materials, either alone or in admixture, (e.g. carbon nitrides), of the following elements: chromium, silicon, tungsten, molybdenum, cobalt, aluminium, manganese, vanadium, niobium, tantalum, titanium, zircon, hafnium, rhenium and the rare earths.

Preferably, the second coating is then given a coating

of a polymer that improves the blade's shaving properties and can

e.g. comprise a fluorocarbon polymer, e.g. polytetrafluoroethylene, or a copolymer of thio-carbonyl fluoride and tetrafluoroethylene.

In a preferred embodiment of the invention, the blade is thus first given a chromium coating on the edge, then a coating of chromium nitride is laid over the first coating, and finally a polymer coating is laid on the nitride coating. Other typical second coatings can be molybdenum nitride and vanadium nitride.

One method of providing a double-coated stainless steel razor blade of the type just described is to first form a chromium coating by bombarding chromium onto the previously clean electroplated steel egg at a pressure of between 1/10 micron mercury in an ambient atmosphere of an inert gas, such as argon, or helium, using a commercially available ion plasma bombardment apparatus. The chrome coating can e.g. have a thickness between 50 to 450 Angstroms, but preferably no more than 200 Angstroms. The bombardment process is then repeated with an ambient atmosphere of nitrogen at a pressure of e.g. 1 to 4 x 10 — 3 mm of mercury to form a chromium nitride coating.

Preferably, the blades are exposed to an oxide-forming atmosphere after the first coating has been formed so that the surface area of the original coating is oxidized. One way to achieve this is to allow controlled air to leak into the bombarding apparatus between the two coating stages.

The nitride coating can have a thickness of e.g. from 50 to 450 Angstroms, but preferably not more than 150 Angstroms, and a preferred range for the thickness of the two coatings together is from 100 to 500 Angstroms or even up to 750 Angstroms.

The term "nitride" is intended to encompass coatings over a range from a small amount of nitrogen in solid solution with chromium, up to any of the chromium nitride compounds C^N, Cr^2 and CrN/or any combination thereof. The composition range can extend e.g. from 0.01 atomic percent nitrogen to 55 atomic percent nitrogen.

The reaction between chromium or any other metal used and nitrogen or another gas during the bombardment process may take place on the surface of the steel, or when the metallic particles are bombarded through the ionized nitrogen plasma, or after the metal is deposited on the sheet

the surface.

The gas composition can vary greatly depending on the material being bombarded and the bombardment conditions. E.g. thus, nitrogen or another gas can be diluted with an inert gas, such as argon, from 5% by volume of the gas in argon to 100% by volume of nitrogen or another gas. For nitrogen formation, one can e.g. use a gas with a high nitrogen content, such as pressure distilled ammonia and/or air diluted with an inert gas.

The bombardment may be direct current or radio frequency bombardment, and in the latter case the bombardment may be directed from a chromium nitride or other metallic compound target in an inert atmosphere.

As an alternative to bombardment, the coatings can be produced using chemical vapor deposition or reactive evaporation. It is to be understood that the terms "metallic compound" and "silicone compounds" as used herein include not only compounds of a metal or silicone, but also the distribution or dispersion of such compounds in a metallic matrix.

Claims (2)

1. Razor blade with at least one egg surface coated with a metal or an alloy and an outer coating of polymer, characterized by an intermediate coating of at least one refractory carbide, boride, oxide, nitride, silicide or fluoride of chromium, silicon, tungsten, molybdenum, cobalt , aluminium, manganese, vanadium, niobium, tantalum, titanium, zirconium, hafnium, rhenium or rare earths between the coating of metal or alloy and the polymer coating. 2. Razor blade as stated in claim 1, characterized in that the intermediate coating has a thickness of between 50 and 450 Angstroms, preferably no more than 150 Angstroms, and that the total thickness of the intermediate coating and the coating of metal or alloy is from 100 to 500 Angstroms.