EP0582676B1

EP0582676B1 - Improvements in or relating to razor blades

Info

Publication number: EP0582676B1
Application number: EP92913377A
Authority: EP
Inventors: Manohar S. Grewel; Chong-Ping P. Chou; Steve S. Hahn; John Madeira
Original assignee: Gillette Co LLC
Current assignee: Gillette Co LLC
Priority date: 1991-04-26
Filing date: 1992-04-22
Publication date: 2000-03-22
Anticipated expiration: 2012-04-22
Also published as: ATE190892T1; MY107736A; TW221976B; CA2102222A1; CA2102222C; CZ288085B6; WO1992019425A3; RU2108234C1; CN1068058A; EG19582A; HUT69255A; EP0582676A1; AU2184292A; TR26981A; AU666659B2; KR100241239B1; CZ227593A3; CN1039527C; WO1992019425A2; ES2143473T3

Abstract

The razor blade comprises a substrate on which is formed a wedge shaped sharpened edge. The wedge has an an included angle of less than thirty degrees and a tip radius of less than 1200 angstroms. An interlayer of material, chosen from the group of molybdenum, nickel, niobium, silicon, silicon carbide, tantalum, vanadium and their alloys, is deposited on the wedge in a thickness less than 500 angstroms. A layer of diamond or diamond like carbon is deposited on the interlayer. This final layer has a thickness of at least 1200 angstroms on the wedge flanks to a tip radius of 40 microns.

Description

This invention relates to razor blades and to processes of forming razor blades with sharp and durable cutting edges.
A razor blade typically is formed of suitable substrate material such as metal or ceramic and an edge is formed with wedge-shape configuration with an ultimate edge or tip that has a radius of less than about 1,000 angstroms, the wedge shaped surfaces having an included angle of less than 30°. As shaving action is severe and blade edge damage frequently results and to enhance shavability, the use of one or more layers of supplemental coating material has been proposed for shave facilitation, and/or to increase the hardness and/or corrosion resistance of the shaving edge. A number of such coating materials have been proposed, Such as polymeric materials and metals, as well as other materials including diamond and diamond-like carbon (DLC) material. Each such layer or layers of supplemental material must have adhesion compatibility so that each layer remains firmly adhered to the substrate throughout the useful life of the razor blade, and desirably provide characteristics such as improved shavability, improved hardness and/or corrosion resistance while not adversely affecting the geometry and cutting effectiveness of the shaving edge. It has been proposed to provide the cutting edges of razor blades with improved mechanical properties by applying to the sharpened edge of the substrate a coating of diamond or diamond-like carbon (DLC) material. Such materials may be characterized as having substantial sp³ carbon bonding; a mass density greater than 1.5 grams/cm³; and a Raman peak at about 1331 cm¹ (diamond) or about 1552 cm¹ (DLC). However, such proposals have not been satisfactory due to the tendency of the diamond or diamond-like coating to have poor adhesion to and to peel off from the wedge-shaped edge of the substrate.
U.S. Patent 3,761,374 discloses a process for depositing a strengthening layer of metal or alloy material such as chromium or chrome-platinum upon a sharpened edge of a razor blade.
German Patent 3,047,888 discloses coating a tool or razor blade surface with a carbon layer having a diamond-like structure and with an interlayer of silicon or silicon dioxide,
It has now been found that an interlayer of molybdenum provides an excellent adhesion of the diamond or diamond-like carbon to the wedge-shaped edge of the substrate, but it has been found that under certain accelerated corrosion testing conditions such as immersion in hot distilled water at 80°C. for 16 hours, a diamond-like carbon coating can delaminate from a molybdenum interlayer and the steel blade substrate by what appears to be an electrochemical reaction.
The invention resides in a process of forming a razor blade which comprises providing a substrate, forming a wedge-shaped sharpened edge on the substrate having an included angle of less than 30 degrees, depositing an interlayer on the substrate, and depositing a layer of diamond or diamond-like carbon material on the interlayer so that the interlayer is between and in contact with the layer of diamond or diamond-like carbon material on the one side and with the substrate including its sharpened edge on the other side, characterized in that the substrate has a tip radius of less than twelve hundred angstroms and the interlayer consists of niobium.
The invention also resides in a razor blade which is the direct end product of the aforesaid process, comprising a substrate having a wedge-shaped edge with an included angle of less than 30 degrees, an interlayer on the substrate and a layer of diamond or diamond-like carbon material on the interlayer so that the interlayer is between and in contact with the layer of diamond or diamond-like carbon material on one side and with the substrate including its sharpened edge on the other, characterized in that the substrate has a tip radius of less than twelve hundred angstroms and the interlayer consists of niobium. The invention further resides in a shaving unit including one or more of such blades.
The blade exhibits excellent shaving properties and long shaving life.
Preferred embodiments are defined by the dependent claims.
The interlayer and the diamond or DLC layer may be deposited by various techniques such as plasma decomposition of hydrocarbon gases, sputter deposition using ions from either a plasma or an ion gun to bombard a target, directly using a beam of carbon ions, and ion bean assisted deposition (IBAD) process using either E-Beam or sputtering sources.
In a particular process, the substrate is mechanically abraded in a sequence of honing steps to form the sharpened edge; layers of niobium and diamond or diamond-like carbon material are successively deposited by sputtering; the niobium interlayer having a thickness of less than about five hundred angstroms, and the diamond or DLC coating on the niobium coated cutting edge having a thickness of at least about twelve hundred angstroms; the layer of diamond having a Raman peak at about 1331 cm^-1 and the layer of diamond-like carbon (DLC) material having a Raman peak at about 1550 cm^-1; substantial sp3 carbon bonding; and a mass density greater than 1.5 grams/cm³; and an adherent polymer coating is applied on the diamond or DLC coated cutting edge.
The shaving unit comprising a razor blade according to the invention may be of the disposable cartridge type adapted for coupling to and uncoupling from a razor handle or may be integral with a handle so that the complete razor is discarded as a unit when the blade or blades become dull. The front and rear skin engaging surfaces cooperate with the blade edge (or edges) to define the shaving geometry. Particularly preferred shaving units are of the types shown in U.S. Patent 3,876,563 and in U.S. Patent 4,586,255.
Other features and advantages of the invention will be seen as the following description of particular embodiments progresses, in conjunction with the drawings, in which:
Fig. 1 is a perspective view of a shaving unit comprising a razor blade in accordance with the invention;
Fig. 2 is a perspective view of another shaving unit comprising a razor blade in accordance with the invention;
Fig. 3 is a diagrammatic view illustrating one example of razor blade edge geometry in accordance with the invention;
Fig. 4 is a diagrammatic view of apparatus for use in the process in accordance with the invention; and
Figs. 5 and 6 are Raman spectra of DLC material deposited with the apparatus of Fig. 4.

Description of Particular Embodiments

With reference to Fig. 1, shaving unit 10 includes structure for attachment to a razor handle, and a platform member 12 molded of high-impact polystyrene that includes structure defining forward, transversely-extending skin engaging surface 14. Mounted on platform member 12 are leading blade 16 having sharpened edge 18 and following blade 20 having sharpened edge 22. Cap member 24 of molded high-impact polystyrene has structure defining skin-engaging surface 26 that is disposed rearwardly of blade edge 22, and affixed to cap member 24 is shaving aid composite 28.
The shaving unit 30 shown in Fig. 2 is of the type shown in Jacobson U.S. Patent 4,586,255 and includes molded body 32 with front portion 34 and rear portion 36. Resiliently secured in body 32 are guard member 38, leading blade unit 40 and trailing blade unit 42. Each blade unit 40, 42 includes a blade member 44 that has a sharpened edge 46. A shaving aid composite 48 is frictionally secured in a recess in rear portion 36.
A diagrammatic view of the edge region of the blades 16, 20 and 44 is shown in Fig. 3. The blade includes stainless steel body portion 50 with a wedge-shaped sharpened edge formed in a sequence of edge forming honing operations that forms a tip portion 52 that has a radius typically less than 500 angstroms with facets 54 and 56 that diverge at an angle of about 13°. Deposited on tip 52 and facets 54, 56 is interlayer 58 of niobium that has a thickness of about 300 angstroms. Deposited on niobium interlayer 58 is outer layer 60 of diamond-like carbon (DLC) that has a thickness of about 2,000 angstroms, with facets 62, 64 that have lengths of about one-quarter micrometer each and define an included angle of about 80°, facets 62, 64 merging with main facet surfaces 66, 68 that are disposed at an included angle of about 13° and an aspect ratio (the ratio of the distance (a) from DLC tip 70 to stainless steel tip 52 and the width (b) of the DLC coating 60 at tip 52) of about 1.7. Deposited on layer 60 is an adherent telomer layer 72 that has a substantial as deposited thickness but is reduced to monolayer thickness during initial shaving.
Apparatus for processing blades of the type shown in Fig. 3 is diagrammatically illustrated in Fig. 4. That apparatus includes a DC planar magnetron sputtering system manufactured by Vac Tec Systems of Boulder, Colorado that has stainless steel chamber 74 with wall structure 80, door 82 and base structure 84 in which is formed port 86 coupled to a suitable vacuum system (not shown). Mounted in chamber 74 is carousel support 88 with upstanding support member 90 on which is disposed a stack of razor blades 92 with their sharpened edges 94 in alignment and facing outwardly from support 90. Also disposed in chamber 74 are support structure 76 for target member 96 of niobium (99.99% pure) and support structure 78 for target member 98 of graphite (99.999% pure). Targets 96 and 98 are vertically disposed plates, each about twelve centimeters wide and about thirty-seven centimeters long. Support structures 76, 78 and 88 are electrically isolated from chamber 74 and electrical connections are provided to connect blade stack 92 to RF power supply 100 through switch 102 and to DC power supply 104 through switch 106; and targets 96 and 98 are connected through switches 108, 110, respectively, to DC magnetron power supply 112. Shutter structures 114 and 116 are disposed adjacent targets 96, 98, respectively, for movement between an open position and a position obscuring its adjacent target.
Carousel 88 supports the blade stack 92 with the blade edges 94 spaced about seven centimeters from the opposed target plate 96, 98 and is rotatable about a vertical axis between a first position in which blade stack 92 is in opposed alignment with niobium target 96 (Fig. 4) and a second position in which blade stack 92 is in opposed alignment with graphite target 98.
In a particular processing sequence, a stack of blades 92 (five centimeters high) is secured on support 90; chamber 74 is evacuated; the targets 96, 98 are cleaned by DC sputtering for five minutes; switch 102 is then closed and the blades 92 are RF cleaned in an argon environment for five minutes at a pressure of ten millitorr, an argon flow of 200 sccm and a power of 1.5 kilowatts; the argon flow is then reduced to 150 sccm at a pressure of 2.0 millitorr in chamber 74; switch 106 is closed to apply a DC bias of -25 volts on blades 92; switch 108 is closed to commence sputtering at one kilowatt power and shutter 114 in front of niobium target 96 is opened for thirty seconds to deposit a niobium layer 58 of about 300 angstroms thickness on the blade edges 94. Shutter 114 is then closed, switches 106 and 108 are opened, and carousel 88 is rotated 90° to juxtapose the blade edges of blade stack 92 with graphite target 98. Pressure in chamber 74 is maintained at two millitorr with an argon flow of 150 sccm; switch 110 is closed to sputter graphite target 98 at 750 watts; switch 102 is closed to apply a 13.56 MHz RF bias of eight hundred watts (-420 volts DC self bias voltage) on blades 92, and concurrently shutter 116 is opened for twenty minutes to deposit a DLC layer 60 of about two thousand angstroms thickness on niobium layer 58. The DLC coating 60 had a radius at tip 70 of about 350 Angstroms that is defined by facets 62, 64 that have an included angle of about 80°, and an aspect ratio of about 1.9:1. As illustrated in Fig. 5, Raman spectroscopy of the coating material 60 deposited in this process shows a broad Raman peak 118 extending between about 1350 and 1530 cm^-1 wave numbers, a spectrum typical of DLC structure.
A coating 72 of polytetrafluoroethylene telomer is then applied to the DLC-coated edges of the blades. The process involves heating the blades in a neutral atmosphere of argon and providing on the cutting edges of the blades an adherent and friction-reducing polymer coating of solid PTFE. Coatings 58 and 60 were firmly adherent to the blade body 50, provided low wet wool felt cutter force (the lowest of the first five cuts with wet wool felt (L5) being about 0.45 kilogram), and withstood repeated applications of wool felt cutter forces indicating that the DLC coating 60 is substantially unaffected by exposure to the severe conditions of this felt cutter test and remains firmly adhered to the blade body 50, even after immersion in 80°C. distilled water for sixteen hours. Resulting blade elements 44 were assembled in cartridge units 30 of the type shown in Fig. 2 and shaved with excellent shaving results.

Claims

A process of forming a razor blade which comprises providing a substrate (50), forming a wedge-shaped sharpened edge (52) on the substrate having an included angle of less than 30 degrees, depositing an interlayer (58) on the substrate, and depositing a layer (60) of diamond or diamond-like carbon material on the interlayer so that the interlayer is between and in contact with the layer of diamond or diamond-like carbon material on the one side and with the substrate including its sharpened edge on the other side, characterized in that the substrate has a tip radius of less then twelve hundred angstroms and the interlayer (58) consists of niobium.
A process according to claim 1, characterized by the fact that the interlayer (58) on the sharpened edge (52) has a thickness of less than about five hundred angstroms, and the diamond or diamond-like carbon layer (60) on the interlayer-coated sharpened edge has a thickness of at least twelve hundred angstroms from the sharpened edge of the substrate to a distance of forty micrometers from said edge.
A process according to claim 1 or 2, characterized by the fact that the substrate (50) is of metal and the diamond or diamond-like carbon layer (60) is at least twice as hard as said metal substrate.
A process according to any one of the preceding claims, characterized by the fact that the diamond or diamond-like carbon layer (60) is deposited in an argon atmosphere in an evacuated chamber (74) in which graphite and niobium targets (96,98) are located; the niobium target (96) is energized, and an interlayer (58) of niobium is deposited on the blade edge by sputtering, and the graphite target (98) is then energized to deposit a layer (60) of the diamond or diamond-like carbon material on the niobium layer while an RF bias is applied to the substrate (50).
A process according to any one of the preceding claims, characterized by the fact that the layer (60) of diamond or diamond-like carbon material has a radius at its ultimate tip of less than about four hundred angstroms.
A process according to any one of the preceding claims, characterized by the fact that the diamond or diamond-like carbon material layer (60) on the blade edge (52) has a thickness of about two thousand angstroms.
A process according to any one of the preceding claims, characterized by the further step of applying an adherent polymer coating (72) on the diamond or diamond-like carbon material coated sharpened edge (52).
A razor blade obtained as the direct end product of the process of any one of claims 1-7, comprising a substrate having a wedge-shaped edge with an included angle of less than 30 degrees, an interlayer on the substrate and a layer of diamond or diamond-like carbon material on the interlayer so that the interlayer is between and in contact with the layer of diamond or diamond-like carbon material on one side and with the substrate including its sharpened edge on the other, characterized in that the substrate has a tip radius of less than twelve hundred angstroms and the interlayer consists of niobium.
A razor blade according to claim 8, characterized by the fact that the layer (60) of diamond or diamond-like carbon material has a Raman peak at about 1331 cm^-1 (diamond) or about 1552 cm^-1 (DLC), an aspect ratio of less than about 3:1; substantial sp³ carbon bonding; and a mass density greater than 1.5 grams/cm³.
A shaving unit characterized by the fact that it includes one or more razor blades according to claim 8 or 9.