US3911579A - Cutting instruments and methods of making same - Google Patents

Abstract

The specific disclosure is directed to razor blades and methods of making the same wherein the cutting edge formed by two intersecting surfaces is sputter deposited with a refractory material which is subsequently overlaid with a sputter deposited coating of material displaying adhesion to a final lubricious coating.

Description

United States Patent 1191 Lane et al.

[ 1 Oct. 14, 1975 1 CUTTING INSTRUIVIENTS AND METHODS OF MAKING SAME [75] Inventors: George C. Lane, Danbury; Phyllis M. Curtis, Simsbury; Arthur E. Michael, Middletown, all of Conn.

[73] Assignee: Warner-Lambert Company, Morris Plains, NJ.

[22] Filed: Apr. 18, 1973 [21] Appl. No.: 352,374

Related US. Application Data [63] Continuation of Ser. No. 144,509, May 18, 1971.

Charschan et a1. 204/298 3,402,468 9/ 1968 Kiss et a1. 30/346.53 3,419,414 12/1968 Marks 117/70 3,480,483 11/1969 Wilkinson..... 117/71 X 3,518,110 6/1970 Fischben 117/93.4 3,632,494 1/1972 Herte et al..... 204/192 3,774,703 11/1973 Sanderson 117/75 FOREIGN PATENTS OR APPLICATIONS 1,193,067 5/1970 United Kingdom 76/ 104 Primary ExaminerLeonidas Vlachos Attorney, Agent, or Firm-Albert H. Graddis; Frank S. Chow [57] ABSTRACT The specific disclosure is directed to razor blades and methods of making the same wherein the cutting edge formed by two intersecting surfaces is sputter deposited with a refractory material which is subsequently overlaid with a sputter deposited coating of material [56] References Cited displaying adhesion to a final lubricious coating.

UNITED STATES PATENTS 2,408,790 10/1946 Mack 76/104 66 Claims, 9 Drawing Figures 3 L 1 2 l l f fflzzzfnmv (EN/N i M mini/rm DEM-SHIV? OffOS/l'lfl/V US. Patent Oct. 14, 1975 Sheet 2 of4 3,911,579

US. Patent Oct.14,1975 Sheet30f4 3,911,579

U.S. Patent Oct. 14, 1975 Sheet 4 of4 3,911,579

CUTTING INSTRUMENTS AND METHODS OF MAKING SAME CROSS-REFERENCE TO A RELATED APPLICATION This application is a continuation of U.S. Pat. application Ser. No. 144,509, filed May 18, 1971.

BACKGROUND OF THE INVENTION The present invention generally relates to a method for making razor blades and is more particularly directed to a method for producing a razor blade having a cutting edge displaying certain advantages characteristics associated with refractory materials.

The razor blade industry has long sought to produce a product having an extremely sharp cutting-edge possessing both long life and concomitantly corrosion resistance. The achievement of these desires has been associated with the producing of a blade made in some fashion from a refractory material. Particular attention has been directed to sapphire or, more broadly speaking, corundum.

Refractory materials by definition comprise various compounds characteristically having a high relative hardness, resistance to working and abrasion under conditions of high temperature, and inertness under most atmospheres and conditions. the making of a razor blade from materials such as these has obvious difficulties. If the refractory material is inherently resistant to working and abrasion, it must, therefore, be extremely difficult to perform the grinding and honing operations necessary to the production of a modern razor blade. It is further characteristic of these materials that they are resistant to bending and thusly do not conform to the strip methods of making blades which are universally in practice today and lead to the economic production of the final product.

Razor blades made from refractory materials, for instance, ceramics, have been extremely difficult to manufacture and, therefore, economically unfeasible under the conditions of todays market. U.S. Pat. No. 3,543,402, R. M. Seager, issued Dec. 1, 1970, entitled Ceramic Cutting Blade, discloses a method, and the resultant product, for making a razor blade of refractory material. The difficulties involved and the stringent requirements which must be followed are detailed in the specification of this patent and point to its unfeasibility, as previously mentioned. It must be further noted that refractory materials generally do not display the toughness associated with metals, particularly those used in cutting instruments, and their use in view of this is questionable. The orientation of the ceramic crystals and their size become extremely significant when it is realized that the radius of the final apex of most razor blades manufactured today is in the neighborhood of 300 to 500 Angstroms. The abrading or loss of even single crystals from an edge thusly constructed may be of significance to its cutting and life properties.

One of the most significant advances in the art of razor blades has been the use of lubricious coatings applied to the cutting edge. This method of achieving a reduction in the cutting forces involved (shaving comfort) has evolved over a lengthy span of time commencing as far back as the 1930s, and even earlier if one considers the use of shaving lathers in this regard, ultimately resulting in the application of lubricious polymer coatings to the razor blade edges. It may be safely said that most razor blades produced today contain a coating of polytetrafluoroethylene (PTFE), which substance has provided an extremely low coefficient of friction and an adherence to the cutting edge commensurate with the ultimate life of the edge itself, i.e., the PTFE appears to remain in operable condition for as long as the blade edge maintains a cutting edge sufficient to sever normal beard hairs. This latter point has been empirically tested and verified through the statistical analysis of data received from extremely large shaving samples.

U.S. Pat. No. 3,518,110, issued June 30, I970, lnventor: Irwin W. Fischbein, entitled Razor Blade and Method of Making Same", discloses a method for applying PTFE and like low friction polymeric materials to razor blade edges. This patent does not state the mechanism of PTFE adhesion to the blade but simply hypothesizes that a monolayer of the lubricious material in some fas ion, either mechanically or through intermolecular bonding, produces interfacial bonding forces greater than the cohesive forces internal to the coating thereby permitting a minimization of friction and further providing an elimination of asperities between the cutting surface and the material to be severed. Efforts have been made to determine a more exact hypothesis for the apparent improvement in shaving comfort, but, to date, not firm and provable conclusions have been reached. It must be emphasized, however, that the adhesion of the lubricious coating appears to be sufficient to maintain a low coefficient of friction throughout the useful wear life of the blade edge, i.e., blade usefulness is limited by edge breakdown as opposed to loss of lubricity. Experience in the use of razor blade materials other than chromium stainless steel as used in the Fischbein patent has indicated wide variance in the adhesion properties of the lubricious coating; stainless steel and pure chromium and oxides thereof provide extremely long life or adhesion of the coating. Other materials, for instance, platinum and, generally, refractory materials, show a decreased and in some instances no adhesion.

The prior art, although replete with the application of different materials to razor blades, all claimed to improve blade quality and performance in some manner, has generally failed to provide a blade reflecting the overall shaving performance and comfort found in the modern razor blade in combination with the durability of refractory materials as previously discussed. The Seager patent, in addition to the significant problems previously indicated, totally fails to disclose the performance of the claimed blade relative to modern-day products and, in fact, does not show how a final product might be achieved. It is, therefore, an object of this invention to provide a razor blade exhibiting improved qualities.

It is another object of this invention to provide an improved razor blade of a refractory material.

Another object of this invention is to provide 2 method for applying a refractory material to a ram: blade.

Another object of this invention is to provide 2 method for applying a lubricious material to a razol blade of refractory material.

Yet another object of this invention is to provide 2 method for depositing a refractory material on a sub strate.

Still another object of this invention is to provide a method for depositing corundum onto a substrate.

Still another object of this invention is to provide a method for sputter depositing coatings of material onto a razor blade.

It is yet another object of this invention to provide a method for making razor blades of refractory material in a continuous batch process.

SUMMARY OF INVENTION In accordance with this invention, a method for making a razor blade is presented. The blade is formed from a suitable material and has an edge portion which consists of two intersecting surfaces which may be honed or made by some other forming process. At least the surfaces comprising the edge as well as the ultimate apex at the intersection are sputter deposited with a refractory material and then, in order to provide adhesion of a final coating of lubricious material, the edge is coated with a second material having the desired adhesive characteristics.

The invention further provides a method of applying an adherent coating of lubricious material to a razor blade edge formed by the intersection of two surfaces of refractory material. This method involves the coating of the refractory surfaces with an overlay of material displaying adhesion to both the surfaces and the lubricious material.

Also in accordance with the invention, there is disclosed a method in which razor blades having edges formed by two intersecting surfaces are sputter etched in a first vacuum chamber. The blades are then moved through a vacuum interlock to a second chamber in which they are sputter deposited with a refractory material. After deposition of the refractory material, the blades are then moved through a second vacuum interlock to a third chamber wherein the coating of material displaying adhesion to a subsequent lubricious coating is sputter deposited on the refractory material. Subsequent to the above steps, the blades are moved through a third vacuum interlock to a fourth vacuum chamber from which they are eventually vented to the atmosphere prior to a final coating with the lubricious material.

Yet another aspect of this invention involves a cutting instrument having an elongate edge of narrow included angle formed by two intersecting surfaces of a refractory material onto which an overlay coating is placed, the overlay coating having adhesion to the final coating of a lubricious material.

The invention is also directed to a method for depositing corundum onto a substrate. This method involves disposing the substrate in an evacuated chamber having an electrode on which is mounted a target of corundum. An ionizable gas is introduced into the chamber and a plasma is estabished by imposing an RF potential between the electrode and the substrate. Particles dislodged from the target by impingement of gas ions formed in the plasma by the collision of RF excited electrons and the ionized gas are then deposited on the substrate with the needed level of energy to form the desired crystal structure and orientation.

The foregoing summary of the invention as well as other objects and advantages will be made apparent upon a study of the following drawings and the detailed description of preferred and exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram of the method and apparatus for producing a razor blade having an edge formed of refractory material.

FIG. 2 is a partially cross-sectional functional schematic showing a typical sputtering chamber.

FIG. 3 is a partially cross-sectional functional schematic showing a multi-chambered continuous batch sputtering system.

FIG. 4 is an outline drawing of a typical single-edge razor blade.

FIG. 5 is a diagrammatic cross-sectional drawing of a typical single-edge razor blade showing in distorted fashion material coatings.

FIG. 6 is a cross-sectional drawing of a batch of razor blades mounted in a holder.

FIG. 7 is a plan view of a fixture for holding a continuous coil of razor blade.

FIG. 8 is a cross-sectional view of FIG. 7.

FIG. 9 is a plan view ofa fixture for holding a plurality of razor blade coils.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description is made in coordination with the drawings of this application and discloses the functional and structural features of the invention. Throughout the drawings and description, conventional symbology and nomenclature is used, and similar units appearing in the different drawings are designated by the same number. It is intended that the descriptions set forth herein be exemplary of the invention and not delimiting of its scope.

A general outline of the steps involved in the manufacturing process for products conforming to the novel features of this application are shown in FIG. 1. As obvious from the nomenclature of the drawing, this process outline is specifically involved with the fabrication of an improved razor blade. The blade is first manufactured in accordance with normal procedures well known in the art. The stainless steel or other applicable blade material is formed into strips of convenient dimension and then passed through punching, heat treating, printing, grinding, and finally honing to produce a final cutting edge formed by the intersection of two surfaces. As previously indicated, this blade fabrication step 1 is amply detailed in the prior art and well known to those skilled in the art. It would serve no useful pupose to go more deeply into the cutting edge manufacture other than to indicate that the different steps involved may be altered to achieve desired characteristics on the edge. To some degree, these achievable characteristics may affect the ultimate process but do not form any intrinsic contribution to the novel concept of the applicants.

After the final edge of the razor blade is formed, which edge is grossly depicted in FIG. 5 of this application and is shown having an included angle A which normally varies between 15 and 25 but may, depending upon the basic substrate orblade material, vary in a much wider degree, it is then passed on to a cleaning step 2. The cleaning step is utilized to remove the contaminants formed on the edge during the fabrication step. Normally these contaminants comprise cutting oils, greases, printing inks, etc., which are a necessary part of the prior process. Again, the prior art quite adequately documents the type of cleaning needed and the instruments employed to effect its attainment. In a process used by the applicants, the blade edges, while stacked in juxtaposition arrangement, are subjected to jets of trichloroethylene, which fluid is constantly cleaned through a filtration process. Employment of other devices such as ultrasonic energy, agitation, air, etc., are recognized, but, once again, the process used does not lend any novel contribution to the applicants invention.

The steps depicted in that portion of the process 3 are intimately involved with the applicants novel process. Contained in this portion of this process are the steps of surface preparation 10, Deposition I, 11, Deposition II, 12, and Deposition III, 13, which are performed sequentially after the cleaning 2. The surface preparation atomically cleans the cutting edge of the blade and prepares it for proper acceptance of subsequent depositions; it normally involves the sputter etching or glow discharge cleaning of the edge, but may be achieved by any process which adequately cleans the intersecting surfaces forming the edge by the atomic removal of blade substrate material, contaminants and adsorbed gases. The description of the invention hereinafter presented in the body of this application will describe those surface preparations believed most adaptable to the inventive method of the applicants, but it must be recognized that this preparation may vary without departing from the scope of the applicants novel contribution. Deposition 1 coats the blade edge formed by the intersecting surfaces with a refractory material by a suitable deposition process. In that refractory materials are generally of a dielectric nature and since further radio frequency sputtering has achieved desirable performance results, this first coating of refractory material is applied by an RF sputtering process. Again, however, it must be recognized that any sputtering process, whether it be alternating current of sufficiently high frequency or a modified direct current sputter process having means for dissipating the charge sheath formed about the cathode or variant forms of bias sputtering, may be utilized. The nature and apparatus of sputtering is adequately set forth in Chapter 3, pp. 3-2 through 3-35, in Handbook of Thin Film Technology" edited by Leon l. Maissel and Reinhard Glang, published by McGraw-Hill Book Company, 1970. It is significant to point out at this juncture that the nature of the deposition process is not necessarily significant to the invention as long as it achieves a satisfactorily adherent and continuous coating of the refractory material which at this time can, within the applicants knowledge, only be achieved by a sputtering or equivalent process.

The refractory material to which greatest attention is currently being directed in the application of this invention is synthetic sapphire or, as previously indicated, corundum; This material when sputtered on the edge of a razor blade clearly displays the characteristics previously set forth herein which are desirable and necessary to the production of an improved razor blade. lt

'mustbe noted, however, that other generally classified Qrefractory materials such as glass, quartz, alumina, beryllia, silicon carbide, tungsten carbide and boron nitride amongst others may be successfully used in razor blade or cutting edge applications. It must be further recognized that this invention is not necessarily limited to refractory materials but may find equal application to any material displaying desirable blade or cutting edge characteristics without having the necessary or preferred degree of adhesion to a subsequent lubricious coating. Further, it is significant to point out that in sputter depositing a preferred crystalline structure of aluminum oxide, an aluminum target may be used with a reactive oxygen containing atmosphere. With appropriate choice of operating parameters and oxygen, a desired morphology and composition may be deposited.

Deposition ll constitutes the coating of the blade edge with the material displaying the desirable adhesion to the subsequent coating of lubricious material. Rather immense statistical evidence has indicated a superior degree of performance by the use of preferably chromium or some chromium alloy coatings. This material not only adheres strongly to the lubricious coating but provides a hard and durable shaving edge. In addition to chromium, other materials, namely, platinum, aluminum, titanium and iron, amongst others, and alloys of these metals, have found application to razor blade edge coatings. As our knowledge of the mechanics of adhesion increases, it may very well develop that other materials we well as the one mentioned herein may find application within the scope of this invention. The preferred method of deposition involves the radio frequency sputter depositing of chromium onto the blade edge. Of course, DC sputter coating may be used to apply the second material to the razor blade, but it has been determined that in overall aspect the use of RF sputtering techniques seems to lend a decided improvement to the product. It is generally hypothesized that this improvement is to some degree due to the inherent cleaning and desorption of gases on the surface of the razor blade edge which takes place during the RF sputtering process. The second material must be deposited to a thickness sufficient to provide the desired degree of adhesion to the subsequent lubricious material. It has been found that this desired characteristic is achieved by applying a coating of approximately 25 Angstrom units in thickness. The performance of such a thin coating is extremely surprising in that it forms only approximately a coating of five atomic layers in thickness and further cannot be considered continuous over the entire surface of the refractory material. It is pointed out, however, that this material may be deposited to any thickness sufficient to provide the desired adhesion limited only by the requirement that the thickness not in any way detract from the sharpness of the cutting edge. It has been found that thicknesses of up to and greater than ap- 1 proximately 300 Angstroms are completely compatible with the cutting properties of the blade edge.

It is not understood why such an extremely thin coating of material produces such remarkable improvements in adhesion of the lubricious coating. It is hypothesized that the second material provides a desirable crystal or other surface morphology to which the polytetrafluoroethylene or other lubricious material may find favorable adhesion through mechanical locking of the surfaces. Although such hypothesis seems totally acceptable for thicker films, it can be reasonably questioned when considered withfilms as thin as 25 Angstroms. In this regard, it has been theorized that perhaps the thin cromium or other material coating alters the surface energies of the material in such a manner as to permit some form of energenic linking between the molecules or atoms of the polymeric coating and the overlay coating of chromium either alone or in combinationwith the first coating of refractory material. The applicants, however, do not wish to be limited to the mechanism of adhesion achieved in the practice of this invention, but rather simply use the ultimate fact of its performance within the context of their novel contribution.

Deposition III involves the final process step for coating the razor blade edge with a lubricious material. As previously set forth, this coating of lubricious material is generally considered as necessary for the proper performance of all razor blades manufactured today. The Fischbein patent, supra, adequately adequately describes methods for applying a coating of polytetrafluoroethylene, which method is wholly compatible with the novel process of the applicants. Briefly, after the Deposition II coating is applied, the blades are in stacked alignment sprayed with an aqueous or Freon based dispersion of low molecular weight polytetrafluoroethylene, the thickness of such coating being substantially greater than 2,000 Angstroms. After spraying, the blades are then subjected to a heat somewhere in the range in excess of 600 F. for a limited period of time. During this heating process, the blades are maintained in a substantially inert environment comprising nitrogen or cracked ammonia. It is, however, pointed out that certain more reactive gases may be added to the environment or ambient conditions of the blade during heating to provide certain desired characteristics such as improved adhesion of the polytetrafluoroethylene. The improvements in adhesion lent by the variations in the heating atmospheres, however, are not considered as part of the applicants invention and are generally considered negligible with respect to the improvement in adhesion provided by Deposition II. In addition to polytetrafluoroethylene, other polymeric materials have found some application to razor blade edges, although up to this time not providing the same degree of performance as polytetrafluoroethylene. These are polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene, amongst others. It is entirely conceivable that the polymers mentioned, as well as others not presently considered for use, may find future application to razor blade edges if the necessary modifications to the process to achieve desirable performance are discovered or if the polymer molecules are in some manner modified or cross-linked to alter their characteristics in an advantageous manner.

FIG. 2 presents in schematic outline form a partial cross-section of a vacuum chamber 58 associated with ancillary equipment without the chamber 58 and internal appendages within the chamber 58 necessary to the performance of the applicants method. Within the chamber there is diagrammatically presented an RF electrode 56 surrounded by a shield 56 necessary to prevent leakage of RF to its surrounding environment. On the face ofthe electrode there is located a target 57 which, depending upon the step of the process being performed, may comprise the refractory material, Deposition I; or the Deposition II'material, namely, chromium, or other material as previously mentioned. The target 57 may be cemented to the face of the electrode or preferably mounted to the electrode through screws or other fastening devices which do not extend to the front of the target thereby preventing any contamination of the target or the substrate to be sputtered by the material of which the fastening devices are made. The electrode 56 is brought by means of suitable RF insulators and couplers to the outside of the chamber for its connection to the source of energy. The second electrode 20 comprises a member which includes the blade or blades or other devices on which material from the target 57 is to be sputter deposited. An RF lead is brought from the substrate through the wall of the chamber by means of suitable RF connectors and couplers to the outside source of energy. Similarly to the electrode 56, an RF shield 20' is provided to prevent leakage of energy to the surrounding environment.

Movement of the shutter 53 is provided by a mechanical linkage 54 brought through the walls of the vacuum chamber 58 to a control unit 55. This mechanical drive train 54 which may comprise any suitable mechanical linkage, for example, driven gear systems or flexible shafts or rack and pinion or screw rod drives, is provided with the necessary driving force by the control unit 55 which may comprise any suitable AC or DC motor drive limited by microswitches within the chamber sensing the position of the shutter 53. Of course, the passage of the mechanical linkages through the vacuum chamber 58 must be adequately sealed by O Ring configurations, bellows or other suitable sealing members.

A coolant unit 26 normally comprises a pump or pressure line for forcing water or other suitable coolant through passages provided within the electrode 56. In the sputtering process significant heat is generated in the electrode 56 and generally it is found advantageous, if not always necessary, to provide some medium for heat transfer from the electrode 56 in combination with the target 57 in order to prevent burnout of the sputter electrode configuration. Of course, any other members which may during any particular process require coolant may be provided with such medium by the same coolant unit 26. During the sputtering process, it is necessary to generate an electrical plasma. This plasma is maintained by the presence of an ionizable gas. In the present invention, Argon is found most suitable and is provided to the chamber by the Argon unit 25. Suitable valving for admitting the desired amount of Argon is well known to those skilled in the art and may provide a needle valve arrangement of rather simple construction. The nitrogen vent unit 39, similar to the Argon unit 25, provides for the admission of a gas to the inside of the vacuum chamber 58. The nitrogen vent 39 serves two purposes to the apparatus shown in FIG. 2. Firstly, it permits purging of the internal space of the chamber 58 prior to commencement of the steps of the process, thereby providing a drying and cleaning action to the chamber 58. Secondly, the nitrogen vent unit 39 provides through a suitable needle valve or other arrangement for the admission of gas to the chamber 58 prior to the opening of the chamber upon completion of a process step, thereby preventing potential damage to the equipment as well as the seals, etc., associated with the equipment which may be attendant to the sudden loss of vacuum. Further, it may be extremely difficult to open various parts of the chamber 58 without a reduction in vacuum provided by the nitrogen vent 39. It is pointed out that the coolant unit 26, the Argon unit 25, and nitrogen vent unit 39 must all be adequately sealed to prevent leakage within the chamber 58 environment.

A DC meter unit 48 provides a means for measuring the bias voltage which is built up on the electrode 56 during sputtering operations. This bias voltage is normally considered a figure of merit with respect to the degree of sputtering or sputtering rate which is preferred during the coating process. The RF generator 31 provides the energy source for the radio frequency sputtering operation. Generally, in conformance with FCC Regulations, a frequency of 13.56 megacycles is used. It must be pointed out and recognized, however, that any suitable high frequency may be employed notwithstanding FCC Regulations. The matching Z unit or matching impedance unit 33 provides for proper power matching or impedance matching of the RF generator 31 and the input to the RF electrode 56. This impedance viewed looking into the electrode 56-is a complex affair determined not only by the configuration of the electrodes internal to the chamber 58 but by the operation of the plasma generated during the sputtering cycle. This matching unit 33 comprises normally various inductive and capacitive components in pi, T and series or parallel arrangements necessary to achieving certain impedance matching. A copending patent application of one of the applicants, viz., U.S. Ser. No. 680,926, filed Nov. 6, 1967, now U.S. Pat. No. 3,632,494, dated Jan. 4, 1972, shows one matching unit 33 configuration which may be employed with the device shown in FIG. 2 or with similarly arranged sputtering equipment. It must be realized, however, that the establishing of the matching unit 33 parameters is substantially an empirical process varying to some degree with the particular sputtering equipment being utilized. It is considered that the design and determination of the matching unit 33 configuration is well within that level of knowledge commensurate to those individuals ordinarily skilled in the art.

The switch S provides for altering the connections from the electrodes to the ground of the system and to the matching unit 33 for achieving the different steps of the sputtering process. This switch S may necessarily be ganged with other switches or switch in the matching unit 33 to alter the output impedance configuration to conform with the changed impedance level when the switch S is moved to its second position. In position 1, it is obvious that the RF energy is applied to the substrate electrode 20. In this circuit configuration, a plasma is formed which generates a sputtering action by attracting positive Argon ions toward the substrate electrode 20. This attraction is mainly provided by the buildup of a negative bias voltage on the electrode 20 which results essentially from a series capacitor in the line between the substrate electrode 20 and the matching unit 33. This capacitor'is normally provided within the matching unit 33. This configuration thus satisfies the requirements of the surface preparation step 10 by atomically cleaning the edge of the blades or other cutting instruments. Naturally, the rate of material removal must be carefully and closely maintained.

When switch S is placed in position 2, the substrate electrode is brought to system ground as is the chamber 58 while the RF energy is connected through the matching unit 33 to the electrode 56. When in this configuration, two desirable results may be achieved. With the shutter S3 interposed between the substrate electrode 20 and the RF electrode 56, the buildup of the plasma within the chamber 58 causes sputtering of material from the target 57. This material, however,

cannot impinge upon the substrate 20 due to the interposition of the shutter 53 thereby cleaning the target surface 57 prior to the deposition of any material onto the substrate electrode 20. Once the shutter 53 is removed by the coaction of control unit 55 drive linkage 54, continued application of RF energy brings about the sputter deposition of target material onto the substrate surface or, in this case, the cutting edges of the razor blades. As is obvious from the mechanical configuration of the sputtering apparatus, the chamber must be opened between steps of Deposition I and Deposition 11. The shortcomings presented by this necessitated opening and re-evacuating of the chamber 58 are overcome by equipment conforming essentially to that presented in FIG. 3 of this application. There is shown in FIG. 3 a continuous batch sputtering process apparatus which is uniquely adaptable to the applicants invention. Prior, however, to discussing the operation of this apparatus within the context of the applicants process, operation of the equipment as well as the steps of the applicants novel process will be considered with respect to the equipment of FIG. 2.

In considering an operational analysis of the equipment and the process involved, it may first be beneficial to consider the blade holder configuration presented in FIG. 6. FIG. 6 shows in distorted dimension a partial cross-sectioning of a typical blade stack held transversely by the blade holder. It has been found for reasons not wholly understood that in order to achieve the desired uniformity of sputter deposition coating both across the individual blades as well as throughout the entire stack of blades 101 the geometric configuration of the holder ends 102 is extremely important. The apex of the end portions 102 must lie in substantially the same plane as the apex of the blade 10] contained within the holder structure. It has been discovered that the maintenance of a maximum fall off angle from this apex is essential or, speaking in complementary terms, the included angle B of end members 102 of FIG. 6 must be held to a minimum compatible with the strength necessary to apply the compressive forces to hold the blades in proper alignment.

It has been found empirically that, using a 304 type stainless steel blade holder, this angle may be successfully limited to approximately 15. It is hypothesized, however, that even a smaller angle may be successfully used if suitable material is utilized. However, the 15 angle is found to supply satisfactory performance as well as an acceptable life during commercial deployment of the equipment. As previously indicated, the effects of the geometric configuration of the holder are not understood. However, it is recognized that any modification of electrode 20 configuration will alter the shape and potential of the plasma and thereby affect the distribution and energies of the sputtered target 57 material. The transverse sides or sidewalls of the holder are not presented in that no particular configuration seems to be needed except that the plane of these sides must fall substantially in the plane of the apex of the blades 101 and extend for some reasonable distance around the periphery of the blade 101 stack. It is significant to point out particularly with regard to the equipment of FIG. 3 wherein dual facing electrode configurations are employed that a complementary form of the blade holder shown in 102 may be provided to stack a second set of single-edge blades 101 in contraposition to that shown in FIG. 6, thereby providing for contemporaneous sputtering of both edges as the holder is disposed between oppositely facing target electrode combinations. Similarly a blade holder of substantially the same geometric configuration with the bottom planar member eliminated may be used to hold double-edge blades for simultaneous sputtering of both edges in the same dual electrode configuration.

Returning now to the novel process of the applicants and its performance within the confines and context of the sputtering equipment of FlG. 2, the razor blade, after cleaning in conformance with the process step 2 of HO. 1, and it might be noted that as soon after this step as possible, the blades are disposed either singly or in stacked arrangement as shown in FIG. 6 within the vacuum chamber 58 and rigidly attached to the substrate electrode 20, thereby forming a part of such substrate electrode 20. The target material 57 required for Deposition l is then adequately fixed to the surface of the electrode 56. Upon sealing of the vacuum chamber 58 and subsequent to its purging by nitrogen through the nitrogen vent unit 39, the chamber is evacuated by a suitable pump configuration (not shown). The pumping configuration may comprise mechanical roughing pumps for first reducing the internal pressure of the chamber 58 to the range of Torr and in addition might then include turbomolecular pumps, diffusion pumps, ion pumps or cryo-pumps together or in combination to further reduce the internal working pressure of the chamber 58 to a level of approximately 10 Torr, which, under normal circumstances, is considered compatible with RF or in fact most sputtering processes. Upon reaching the desired level of vacuum as previously indicated, approximately 10 Torr, Argon is admitted to the chamber thereby lowering the vacuum level to between approximately 1 2 (10) Torr. With the application of RF energy through the RF generator 31 and the matching unit 33 and the switch S position 1, a plasma is established between the electrodes and a negative self bias forms on the substrate electrode 20. Once the plasma has formed, the energetic collisions of the plasma electrons with the Argon gas molecules causes the formation of positive Argon ions which, as previously indicated in this application, are attracted toward the surface of the substrate electrode 20. Upon their impingement on the blade edges, the apex of which are disposed toward the electrode 56, there is a resultant dislodgement of material both blade steel as well as contaminants thereon from the blade edges. This process is continued for a predetermined period of time commensurate with operational conditions determined to some extent by the blade material utilized and the cleanliness of the blade edges after the cleaning process step 2. Typical ranges of time for the completion of this, what is known as etching or sputter etching, process varies between 3 and 10 minutes. Other typical values involved in this sputter etching step is the application of between 300 and 800 W. of RF power with approximately zero refracted power and the development of approximately a thousand volt or 1 KVDC self bias on the substrate electrode 20. Of course, during this time, the coolant unit 26 is maintaining the electrodes at a desirable temperature compatible with the material used and the allowable range of temperature within the vacuum chamber 58.

After performing this sputter etching of the blade holder razor blade combination located on the substrate electrode 20, the switch S is moved to its second position in which the RF energy is applied to the electrode 56 while the substrate electrode 20 is connected to system ground. Again, with the shutter still maintained in its interposed position between the electrodes 56, 20, the plasma is again established at an Argon or vacuum pressure of normally higher value, typically between 5 and 7 (10) Torr. The power level is raised to a higher value, typically in the range of 1.5 KW of real power, and the bias reaches a considerably higher level, typically in the range of 2 KVDC negative. In this circuit configuration, the development of a negative self bias voltage on the electrode 56 now attracts the positive Argon ions generated within the plasma toward the target 57, resulting in a sputtering of material, both target material and contamination from the surface of the target 57. This results in a pre-cleaning of the target prior to performance of the actual sputter deposition process onto the razor blades contained in the substrate electrode 20. Typically this pre-cleaning operation is continued for a short interval of approximately 1 minute. Further pre-cleaning or pre-cleaning for a longer time is not normally considered necessary when the target material is substantially pure and kept in a clean environment' With proper manipulation of the control unit 55, the shutter is then removed from between the electrodes contained in the vacuum chamber 58, thereby exposing the surface of the target 57 to the apex of the blades disposed on the substrate electrode 20. At this juncture, the material sputtered from the surface of the target 57 is allowed to impinge upon and coat the razor blade edges properly disposed toward the electrode 56. Since the essential configuration of the internal vacuum chamber circuitry is not altered or greatly altered by the removal of the shutter 53, the working parameters of the sputter deposition step remain essentially the same as that of the pre-clean step, i.e., the pressure level is maintained in a range approximately 5 7 (10)" Torr, the real RF power is approximately 1.5 KW, and the self bias negative voltage developed on the electrode 56 is approximately 2 KVDC. The period of sputter deposition is, of course, varied greatly depending upon the material forming the target 57 as well as the desired thickness of coating. Many materials display widely variant sputtering rates depending upon the structure or morphology of the target 57 as well as the work function of the material utilized. Typically depending upon the target 57 material, the sputter time may vary between 1 and 15 minutes.

The chamber 58 is vented by the nitrogen vent unit 39 by the admission of nitrogen gas to the chamber through a needle valve connection. Once the chamber is vented to approximately atmospheric pressure, the chamber 58 is then opened and the target material 57 is changed to the material which is to be used in the Deposition ll step. As previously indicated, the preferred material is a pure chromium. Normally the purity of this chromium target is maintained in excess of 99.99 percent. However, less pure targets may be utilized without detracting from the quality of performance and the results of the novel process. of the applicants. The new target material 57 is attached to the electrode 56 in the same manner as the previous refractory target material for the Deposition I step. It may well be timely to point out that a chamber 58 constructed to have more than one electrode target configuration may be constructed to perform the process outlined herein. If

dual targets were arranged and could be properly indexed, the subsequent coating applied in the Deposition [I step may be deposited without the need for opening the chamber and changing the target material. It is also noted that the substrate and shutter combination 20 and 53 respectively may be indexed to a different location and placed thereby under a different target material as opposed to indexing or changing the electrode configuration which may cause some problems or difficulties associated with the RF connections.

After changing the target material to chromium, the chamber 58 is again sealed and the steps preparatory to sputter deposition are repeated with the exception of the surface preparation 10 step, i.e., the sputter etching of the substrate 20 prior to sputter deposition. obviously, the surface coating applied during the sputter Deposition I step need not be sputter etched prior to a subsequent deposition in that the material laid down on the surface is substantially pure and free of contamination. Briefly, the chamber 58 is purged by dry nitrogen supplied to the chamber 58 by the nitrogen vent unit 39; the pump unit 58' then evacuates the chamber to a level of approximately 10 Torr; Argon is then admitted to the chamber 58 through the Argon 25 unit to a pressure of between 7 (10) Torr and, of course, the coolant unit 26 continues to supply a cooling fluid through the appropriate RF electrodes. With switch S in position 2, RF energy is applied to the electrode 56 with the shutter 53 disposed between the substrate and the electrode. The power levels are adjusted to approximately 1.4 KW and the self bias voltage developed is approximately 2 KVDC. Using these operative parameters, the new target 57 is pre-cleaned for a period of approximately 1 minute.

After completion of the pre-clean step, the target 57 is exposed to the substrate 20 by removal of the shutter 53 through operation of the shutter control unit 55. With the vacuum level in a range betweenS-S (10) Torr, the substrate 20 is then sputter deposited with the target 57 chromium material for approximately 1 minute. Under these controlling conditions, a coating of chromium approximately Angstrom units in thickness is applied to the substrate 20 principally falling upon or impinging upon the cutting edges of the blades contained integrally within the substrate electrode 20. As heretofore indicated, this period of sputtering may be prolonged for a greater time if a thicker coating of chromium material is desired to the extent that such thickness dimension is compatible with the desired cutting edge sharpness of the blade which is determined through various test equipment well known to those ordinarily skilled in the razor blade art. One well established test for the determination of sharpness is the cutting of nylon fibers disposed on a moving belt at a certain angle to the razor blade cutting edge. A measurement of the cutting forces involved in this test provides acceptable data to a determination and correlation of edge sharpness. Normally, or at least under most circumstances, the final radius of curvature of the cutting edge of a razor blade is approximately in the 400 Angstrom range. This radius provides a relative indication of the allowable total thickness of thematerial provided by the combination of the sputter Deposition I step and the sputter Deposition II step. Certainly, greater than a total thickness in the range of 500 Angstrom units may not be acceptable.

After completion of the Deposition ll step, the chamber 58 is again vented through the nitrogen vent unit 39 and opened to the atmosphere for removal of the blades. The blades are then spray coated or otherwise coated with the appropriate lubricious material, normally polytetrafluoroethylene, and subjected to the thermal process necessary to provide a final adherent coating. This thermal process mainly involves the evolving from the dispersion of the volatile mediums necessary to the application of the PTFE constituents. The temperature of the heating process in addition to boiling off or evaporating the volatile medium raises the PTFE dispersed particles to approximately their fusion temperature so that in essence the PTFE is sintered to the surface forming an approximately continuous coating over the ultimate apex of the razor blade edge and the facets or intersecting surfaces forming such apex.

FIG. 5 demonstrates in typical cross-section a razor blade of distorted dimension and form showing the final product having thereon the material coatings applied during Deposition l, ll and Ill steps. The blade is of the single-edge type having a height from base to ultimate apex or cutting edge of H. The cutting edge is shown as formed by two intersecting surfaces having an included angle A therebetween. In accordance with products actually sold and used today, these intersecting surfaces actually comprise a number of facets having different included angles, only the final facets having the same angle A as depicted for the intersecting surfaces of FIG. 5. Normally, all the facets and to some extent the body of the blade 101 is covered with the various coatings comprising the novel process of this application. However, it is not necessary for performance that these coatings do extend beyond the facets of the blade.

The first coating applied to the blade designated as l conforms to the material applied or deposited during the Deposition I step. This sputter deposited coating is normally the refractory material previously mentioned or as also indicated some other material which may have desirable blade characteristics but which does not have the ultimate adherence to PTFE coating. The thickness of this coating as it wraps about the ultimate edge of the blade is usually chosen to be between 200 and 300 Angstroms, appreciating, however, that this thickness may be radically changed if different blade edge characteristics are desired, such as increased or decreased blade sharpness. The coating designated as ll correlates with the Deposition ll step and as indicated normally is a chromium coating. Although this coating is shown as having essentially the same thickness as l and Il coatings, it is noted that this thickness is normally in the range of 25 Anstrom units which, on a relative scale, would be impossible to show within the drawing of FIG. 5. Thus, for demonstration purposes, the same thickness coating is shown. The lll coating is that placed on the blade during the Deposition lll step. As indicated, normally this coating is applied by a spray with subsequent heating for formation of a substantially continuous and uniform coating. However, as indicated in copending Application Ser. No. 680,794, filed Nov. 6, 1967, now U.S. Pat. No. 3,635,811, dated Jan. 18, 1972, this final lubricious coating may also be applied by a sputtering process which may be performed in the same chamber 58 and with the same equipment as shown in FIG. 2. Of course, if such final lubricious coating is to be sputtered, the target material 57 as well as the operating parameters of the chamber must be significantly modified. Since this final lubricious coating III is of greatly increased thickness in the range of 2,000 Angstrom units and considerably higher, its thickness as shown in FIG. 5 is greatly distorted in order to show the coating without having to scale the razor blade and coatings I and II to relative dimensions not capable of demonstrating the points of most interest with respect to the conformation of the final product. FIG. 4 shows a plan view of blade 101 indicating that the coatings extend substantially continuously throughout the entire expanse of the final facets of the razor blade edge.

To better demonstrate the applicability of the novel process presented herein and to provide a clearer understanding of both the equipment and the various steps employed, the following examples are presented:

EXAMPLE 1 Standard double-edge stainless steel razor blades of approximately 0.004 inch thickness were cleaned in accordance with the cleaning step 2 and mounted within a vacuum chamber substantially conforming to that depicted in FIG. 2, and this example and the following examples will be discussed in the context of the equipment as shown in FIG. 2. A single edge of the doubleedge blades are disposed on the substrate electrode in facing relationship to electrode 56 and the target 57.

Sputter Deposition I Target 57 material Target dimensions A rgon pressure Linde synthetic sapphire comprising essentially hexagonal crystal lattice structures of AL O manufactured by the Linde Crystal Products Division of Union Carbide 4" in diameter by V4" thick between 5 7 n0)- Torr RF power 1.4 KW Self bias voltage 2.2 KVDC Sputter time approximately 7-56 min.

Sputtering rate Coating thickness Sputter Deposition ll Target 57 material Target pre-clean step Argon pressure approximately 30 Angstroms per min. between 200 and 300 Angstrom units Pure chromium between 5 7 l0) Torr RF power 1.4 KW Self bias electrode voltage 2.2 KVDC 60 Period l minute Sputter deposition step Argon pressure between 5 7 10) Torr Power 1 KW Self bias DC voltage 2.2 KVDC Time l0 seconds Sputter rate Coating thickness approximately Angstrom units per min. approximately 30 Angstrom units Thereafter Deposition Ill step was performed and a coating of PTFE was applied to the blade surface. Standard tests showed the blade to display a low coefficient friction and an increased wear life.

EXAMPLE 2 The conditions of Example 1 were repeated in Example 2 with the exception of the sputter etch time, which was reduced from a 5-minute interval to a l-minute interval. Identical results were obtained with regard to performance of the ultimate product after application of the final lubricious coating of PTFE.

EXAMPLE 3 The equipment was set up in the same manner as Examples l and 2. The blade edge was sputter etched under the following conditions:

RF power 200 W. Argon pressure 1 (l0)' Torr Self bias voltage l KVDC Sputter etch time 5 min. Target pre-clean step Target material quartz Argon pressure RF power Pre-clean time Self bias voltage Sputter Deposition I step Argon pressure Same as Example Same as Example Same as Example Same as Example Same as Example I RF power Same as Example I Time Same as Example 1 Self bias voltage Same as Example 1 Thickness approximately 200 Angstrom units Sputter Deposition II step Target material Pre-clean conditions Same as Example I Same as Example I Same as Example 1 Same as Example 1 approximately 30 Angstrom units The blade of this example performed in a similar manner'to that produced under Examples 1 and 2 and similarly displayed improved friction and life characteristics. Note: Throughout Examples 1 3, a Bendix 6 inches diffusion pump system with a liquid nitrogen baffle was used to produce the desired vacuum levels, and throughout the three examples the distance from the target to the blades was approximately 2 inches.

As clearly demonstrated by the foregoing disclosure, razor blades displaying improved shaving characteristics may be produced by the outlined methods and the indicated examples. Processes performed in conformance with the foregoing teaching will produce blades meeting and, in some instances, greatly exceeding the qualities of razor blades presently used by the public. Although the equipment shown in FIG. 2 may be ,uti-

lized in production facilities, particularly if modified to contain more than one target and/or more than single blade holding fixtures with commensurate indexing equipment, this type of equipment is not best suited to the high production needs of a large blade manufacturing concern. When considering that in excess of two to three million blades a day must pass through and be subjected to the process outlined in FIG. 1, it can be appreciated that any equipment design intended to enhance the speed of the process and therefore the ultimate output of finished blades is of considerable value and importance. In this regard, it is noteworthy to point out that the addition of certain reactive gases, for example, oxygen, to the sputtering chamber during the refractory sputter deposition steps will under proper conditions greatly increase the sputtering rate and thereby reduce the total sputtering time needed. Any reduction of this nature in the time required for the total process performance when involved in the production of literally millions of blades is of significant import to the overall cost of production of the product. FIG. 3 shows equipment peculiarly suitable to the manufacture of razor blades in accordance with the novel process of the applicants. This equipment permits the continuous sequential batch processing ofa large quantity of blades while maintaining extreme limits of cleanliness for the targets and the chambers utilized and further limiting the need for continuous pump-down of the sputter deposition chambers prior to entry of the product into the chamber and subsequent to exit of the product from the chamber.

FIG. 3 shows an exemplary embodiment of an equipment configuration primarily designed for the continuous batch processing of razor blades in conformance with the applicantss process. Chambers 10, ll, 12 and 24' constitute the vacuum chambers necessary for completion of the process. These chambers are joined by vacuum interlocks 21, 22 and 23 between chambers 10, 11 and 12 and 24 respectively. Entrance vacuum and exit vacuum interlocks 21 and 24 are provided for entry of the blades into vacuum chamber and exit of the blades from vacuum chamber 24' respectively. Associated with each chamber is a vacuum system designated as Pump A 27, Pump B 28, Pump C 29, and Pump D 30, which pumps must be capable of producing vacuum levels commensurate with the performance of the process, which levels were previously outlined in the foregoing disclosure and Examples 1 3. The blade substrate is shown as moving sequentially through the chambers until its final exit from chamber 24 through the vacuum interlock 24. It is important to note that in a continuous batch system, there is always present in any given chamber a batch of blades mounted on the substrate electrode 20 and only at the beginning and end of any continuous production run are any of the chambers without such blade batch.

Chamber 10 shows within its structure two electrodes 42, 42' surrounded by RF shielding 45, 45 respectively. The two electrodes 42, 42' are provided for the continuous preparation of both edges of double-edge blades or of single-edge'blades mounted back-to-back on the substrate holder 20. This contemporaneous treatment of two edges greatly minimizes the time necessary for completion of the process. Vacuum chamber 10 comprises the station in which the sputter etching of the razor blade edges is performed, thereby confining the release of contaminants and the removal of blade edge material to a single chamber thusly preventing any effect of such contamination on the deposition steps of the process. The substrate electrode 20 is shown as connected to the matching impedance unit 33 and is surrounded by an RF shield 49. Vacuum chamber 11 similarly contains two RF electrodes 43, 43' surrounded by their respective shields 46, 46. The substrate holder 20 is tied to the chamber 11 wall by means of line 51, which chamber 11 is brought to system ground as are all the chambers of the system, namely, chambers 10, ll, 12 and 24. In the instance of chamber 11 both RF electrodes 43, 43' are brought to the matching unit 33 to provide for their RF power exitation. This is contrary to chamber 10 where the two electrodes 42,42 are brought to the chamber walls by line 50 and 50' respectively, which walls are, as previously indicated, brought to system ground. Targets 40, 40 are shown as fixed to the RF electrodes 43 and 43' respectively in the same manner as the target 57 was attached to the RF electrode 56 in FIG. 2. This chamber 11 is used for the performance of the Deposition l coating and thusly the targets comprise the refractory material or other material to be first applied to the blade edge in order to obtain certain desirable blade characteristics. Proceeding to chamber 12 there is shown a similar equipment arrangement as chamber 11. Mounted in the chamber are RF electrodes 44, 44 with their respective RF shields 47, 47'. Affixed to the face of each electrode are targets 41, 41 comprising the material to be applied in the Deposition ll step, i.e., the chromium material or other material displaying the necessary adherence to both the PTFE final lubricious coating and the prior coating applied during the Deposition I step. The substrate electrode 20 is brought to the chamber wall by means of line 52 while RF power is sent to the electrodes -by means of connections 37 and 38. in all instances, proper RF connectors and the necessary seals to maintain vacuum are employed to bring lines and connections in and out of the vacuum chambers. Finally we proceed to chamber 24' which is devoid of internal electrode structure as it is only used for an equipment removal purpose. The use of a separate removal vacuum chamber 24 provides for a maintenance of cleanliness in both vacuum chambers ll, 12 as well as a minimization of vacuum pump-down time. The vacuum interlock members 21, 21, 22, 23, 24 essentially comprise sliding valve doors which permit passage of the blade holding members to proceed into and through the sequential chambers until their ultimate exit through the last chamber 24'. It is further important to note at this time that an additional chamber may be inserted between chambers 12 and 24' for sputtering of the lubricious coating if such process step is to be employed, but it is pointed out that the means of application of the lubricious coating is not an essential part of the novel contribution of this invention but rather simply constitutes the process step necessary to the conformation of the ultimate product.

The radio frequency energy again comprises a 13.56 megacycle supply and provides the energy necessary for the electrodes 43, 43', 47, 47' and for substrate electrode 20 in chamber 10. Lines 34-38 are previously indicated supply the RF power to the previously mentioned electrodes and the substrate electrode 20. The switching unit 32 serves to interrupt the RF power supplied by the radio frequency generator 31 when desired and to further either apply RF energy to the various lines or to interrupt it when the particular step of the process so requires. To briefly describe the function of the switching unit, it is pointed out that during the sputter etching step performed in vacuum chamber 10 RF energy is applied to line 34. When the sequential deposition steps are performed in chambers 11 and 12, then the same RF power is applied to the appropriate lines 34-38. The matching impedance unit 33 constitutes separate impedance matching units for each of the electrodes involved in the process. No doubt this unit might comprise one single. matching unit with various lines or taps brought to the lines 34-38 but, however, it is found most economical and simpler of construction to provide a separate impedance matching unit within the confines of the unit 33 to individually match each of the electrodes during the process step involved.

The DC meter unit 48 is used to monitor the self bias voltage developed during the radio frequency sputtering process on each of the lines 34-38. As heretofore indicated in the specification, each of the electrodes associated with the numbered RF power lines will develop a self bias voltage depending upon the level of power applied and other operating parameters of the system. In addition to the external units now mentioned necessary to the batch process system of FIG. 3, there is also provided for similar purposes as previously outlined with respect to the equipment of FIG. 2 a nitrogen vent unit suitable to purging the chambers and for raising the vacuum level prior to opening of the chambers after evacuation. Argon unit 25 is further provided to supply the ionizable gas to each of the chambers involved in the sputtering process, namely, chambers 10, ll and 12, and. finally a coolant unit 26 passes either water or some other cooling fluid such as ethylene glycol to'properly cool the RF electrodes and other members which may be subject to heat problems during the performance of the steps necessary to producing the desired coatings on the razor blade edge.

Briefly to consider the equipment of FIG. 3 in an operational sequence a stack of razor blades held in a fixture similar to that shown in FIG. 6 only deploying blades in opposite directions so that both edges of the blades, in the case of double-edge blades, or complementarily facing blades in the case of single-edge blades 10], are exposed to the sputtering or sputter etching electrodes. The first batch of blades is introduced to the chamber 10 through the vacuum interlock or slide valve 21. Once within this chamber the entire system of chambers 10, ll, 12 and 24' are reduced in vacuum level to approximately 10' Torr. Argon is y then admitted to vacuum chamber 10 by means of the Argon unit 25 which, with the application of RF energy to line 34, results in the formation ofa plasma and sputtering of material and contaminants from the exposed edges of the razor blades takes place. Upon completion of this sputter etching operation, vacuum chamber 10 is again pumped down to its 10 Torr level and the vacuum interlock valve 21 is opened to allow for passage of the razor blades by means of suitable carriers through to vacuum chamber 11. Similar to the justdescribed sequence of operation for the sputtering etching of the blades in chamber 10, Argon by means of Argon unit 25 is admitted to the vacuum chamber 11 with the application of RF energy to the lines 35, 36. Again, a plasma results. However, in this instance, since the electrodes 43, 43' and their targets 40 and 40 respectively are now brought to the RF power, the sputtering takes place from the target onto the blade edges. Since the electrodes to which RF energy is applied take on the negative self biasing voltage, the positive ions created in the plasma by collisions with the energetic electrons are attracted toward the targets 40, 40, thereby causing the removal of material from their surfaces and their resultant energetic deposition upon the intersecting surfaces forming the blade edges. Once again the chamber 11 is evacuated to the 10" Torr range and the associated vacuum interlock valve 22 is opened for passage of the blades through to the chamber 12.

The same steps are performed in chamber II for the Deposition 1 process are repeated in chamber 12 for the Deposition II process, thereby resulting in a blade having two coatings placed over its ultimate edge and the facets or surfaces forming such ultimate edge. Subsequent to this last sputter deposition step, chamber 12 is evacuated to the 10 Torr level and the blades are passed through vacuum interlock valve 23 to the last chamber 24. It should be pointed out at this time that each of the valves 21, 21 22, 23 close after passage of the blades through to the next chamber. With the blades in vacuum chamber 24' this chamber is vented by means of the nitrogen vent unit 39to atmospheric level and vacuum interlock valve 24 is opened for removal of the blades from the system. As previously pointed out, as blades are removed from one chamber to the next, new blades are being introduced from the chamber going before, thus constituting a continuous batch sequential processing system. The operating parameters, i.e., vacuum, time, power, self bias voltage, are substantially the same as those indicated in Examples 1-3 and the description going before such examples, the difference being that each step in the operation is performed in a separate chamber rather than a single chamber requiring frequent opening and closing of the system with resultant susceptibility to contamination. Operation of equipment such as this is well known to those individuals ordinarily skilled in the art once the essential operating parameters and conditions are brought to their attention. It is pointed out that US. Pat. application Ser. No. 861,937, filed Sept. 29, I969, adequately describes and discloses a system appropriate to the carrying out of the continuous batch process herein disclosed. It would be only necessary to alter the target materials and operating parameters to conform to those novel aspects of the applicant's invention.

In considering both the continuous batch process of FIG. 3 and the single batch operating equipment and procedure demonstrated in FIG. 2, it is important to indicate its applicability to band razor blades, which comprise continuous strips of predetermined length commensurate with a certain number of shaving edges normally provided on discreetly dimensioned razor blades. In use, such continuous strips are indexed a certain length substantially equaling a single-edge length ofa discreet dimensioned razor blade. When depositing coatings, or, more precisely, sputter depositing coatings, on such edges a long continuous length of band razor blade is utilized, often comprising lengths constituting miles or substantial portions of miles in length. A copending application Ser. No. 144,510, filed May l8, 197 l describes a single target electrode configuration capable of sputter depositing coatings on a band razor steel blade. However, due to the limited dimensions of the target, the band blade must be rotated under the target during the sputtering process, thusly seriously hampering the efficiency and output of the process. While the equipment of FIG. 2 would still require rotation of the band razor under the target 57 in order to obtain a reasonably uniform and continuous sputter deposit coating due principally to the limitations on dimensions of such chambers, the continuousbatch system of FIG. 3 is capable of much more efficient operation with respect to this type of razor blade.

FIGS. 7, 8 and 9 show an exemplary fixture capable of holding continuous strips of band blade during the sputtering process. Due to the large target configurations which may be employed in the chambers 10, ll, 12 of the continuous batch system, it is possible to place a complete spiral of band razor steel in facing relationship to the sputtering targets, thereby obviating the need for rotation of the blade edge transversely across the face of the target during the sputtering process or operation. It has been found to be most advantageous to place in the fixture shown in FIGS. 7, 8 and 9 more than a single spiral of band razors and to place them in oppositely facing directions so as to take advantage of the dual electrode configuration of FIG. 3. Thusly, it is possible to greatly increase the efficiency and improve the uniformity of the sputtering process on band razor blades in that a total of four stationary spirals may be coated at one time as opposed to a single spiral being rotated beneath a target as previously or heretofore utilized. The fixture for holding the band razor strip constituting two nests into which the strip is placed in spiral configuration, which nests are then clamped together in oppositely facing directions by means of a ring clamp. It has been found that the nesting of the blades exposing no more than 0.005 of an inch over the upper surface of the nest holder 1 10 is essential to providing a uniform coating on the surfaces forming the blade edge. It has also been determined that while of less criticality than the exposure of the edge of the upper surface 110, the dimensions of the inner hub indicated by diameter D1 and the outer hub indicated by diameter D2 are of significance. Generally it is preferred that the diametrical distance from the outside of the periphery formed by diameter D2 to the outermost edge of the blade spiral should most appropriately be between one and two inches and that the inner hub be approximately between 5 and 9 inches in diameter. Of course, these dimensions may be altered depending upon the amount of blade steel desired to be contained in the blade spiral and the dimensions of the sputtering chambers. The nests 110 in combination with the band clamp 111 are in turn captured within a second fixture 1 12 for actual placement within the continuous batch system. The holder 112 is then carried by appropriate motion drives through the various chambers for application of the desired coatings.

Referring to Example 1 heretofore set forth, it has been found that the material sputtered upon the substrate surface in the Deposition I step comprises a crystalline structure of hexagonal lattice form having a preferred orientation. It has also been found through the application of microprobe analysis, i.e., the examination of emitted X-rays upon subjection of the material to an electron beam, that the material constitutes in its elemental forms pure A1 0 within the precision limits of the microprobe equipment. Relating these two factors as to the morphology of the coating and the purity of the constituents, the material sputtered from the target 57 onto the substrate apparently constitutes the same synthetic sapphire of which the target is composed. Thus, in addition to disclosing a novel method for the application of refractory materials to razor blades or, more generally, cutting edges and the subsequent preparation of such surfaces for the lubricious material, there is further presented in accordance with the invention a novel process for applying a coating of corundum or synthetic sapphire to the surface of a substrate. While not fully understanding the mechanism of this material transfer by means of sputter deposition, it is presumed that the energies of the atomic size particles or molecules removed from the surface of the target 57 are within the range necessary to bring about the desired crystalline formation on the surface of the substrate. Thus, there is completely transferred to the substrate the characteristics of the refractory target material commensurate with a thin film formed of such material. Thus, this wholly unexpected result of the described blade manufacturing process finds ready appli cation for other purposes. It would now seem possible to transfer sapphire or other material through sputter deposition means from a target to a substrate, which substrate may comprise any equipment on which such refractory coatings would be suitable either for wear, dielectric or other suitable and appropriate reasons.

It is apparent that the blade material may be composed of material such as carbon steel, chromium steel, tungsten steel, molybdenum steel or chrome-nickel steel. Further, it is obvious that the blade material may be an alloy containing material selected from the group consisting of stainless steel, carbon steel, chromium steel, tungsten steel, molybdenum steel, and chromenickel steel.

In summary, the disclosure of this application has set forth a novel process for the production of razor blades, or more generally speaking cutting edges,.having wholly unanticipated and unpredictable qualities. [t is emphasized that the teachings of this disclosure are intended to be illustrative and exemplary of the invention and not to be delimiting of its scope. Thus, it is intended that those variations and modifications of the novel process and products produced thereby which would become obvivous to one ordinarily skilled in the art are to be considered within the scope and ambit of the applicants invention.

What is claimed is:

l. A method of making a razor blade comprising the steps of:

forming a blade from a suitable material, the blade having an elongate edge comprising two intersecting surfaces;

sputter depositing on the edge a first coating of refractory material;

coating the edge with a second material displaying adhesion to a subsequent coating of lubricious material and to the refractory material; and then coating the edge with the lubricious material.

2. The method of claim 1 wherein the first coating is RF sputter deposited and the second material is sputter deposited.

3. The method of claim 2 wherein the refractory material is corundum.

4. The method of claim 2 wherein the refractory material is selected from the group consisting of glass, corundum, quartz, alumina, beryllia, silicon carbide, boron nitride, and tungsten carbide.

5. The method of claim 4 wherein the refractory material comprises alloys and mixtures of materials selected from the group.

6. The method of claim 2 wherein the refractory material is synthetic sapphire.

7. The method of claim 1 wherein the total thickness of the deposited refractory material and the second material is limited to that necessary to maintain a desired degree of edge sharpness.

8. The method of claim 7 wherein the total thickness is approximately 500 Angstrom units.

9. The method of claim 7 wherein the thickness of the refractory material is approximately 300 Angstrom units and the thickness of the second material is approximately 25 Angstrom units.

10. The method of claim 2 wherein the RF sputter depositing comprises the steps of:

disposing the blade in an evacuated chamber having an electrode on which is mounted a target of refractory material;

introducing into the chamber an ionizable gas and establishing a plasma by imposing an RF potential between the electrode and the blade;

depositing on the edge particles dislodged from the target by impingement of gas ions formed in the plasma upon collision of RF excited electrons and the ionizable gas molecules.

11. The method of claim 10 wherein the chamber is evacuated to approximately l Torr and the ionizable gas is introduced to a pressure of approximately between and s '10 Torr.

12. The method of claim 11 wherein the refractory material is synthetic sapphire, the ionizable gas is Argon and the blade is positioned approximately 2 inches from the target, the edge apex being disposed substantially in a plane parallel to the target and the refractory material is deposited at a rate of approximately 30 Angstroms per minute for a period between approximately 5 and minutes.

13. The method of claim 12 wherein the frequency is 13.56 MC and wherein the blade is sputter etched prior to deposition of the refractory material and a shutter is interposed between the target and the blade during the step of sputter etching.

14. The method of claim 13 wherein capacitor means is serially connected between the blade and the RF potential and the shutter is connected to ground during sputter etching and wherein when the shutter is removed, the RF potential is connected to the electrode and the blade is connected to ground for sputter deposition.

15. The method of claim 14 wherein the target is precleaned prior to sputter etching and wherein during pre-cleaning the shutter is interposed, the RF potential connected to the electrode and the shutter is connected to ground.

16. The method of claim 15 wherein the following parameters are maintained during pre-cleaning, sputter etching and sputter deposition, respectively:

Power approximately 400 W.

1.4 KW and L4 KW; approximately I KVDC 2.2 KVDC and 2.2 KVDC and approximately 5 min.,

l min. and between 5 and 10 min.

Self bias electrode voltage Time 19. The method of claim 18 wherein the second material is deposited to a thickness of approximately 25 Angstrom units and the second material is a metal containing material.

20. The method of claim 19 wherein the second ma terial is selected from the group consisting of chromium, platinum, aluminum, titanium and iron.

21. The method of claim 19 wherein the second material comprises mixtures and alloys of metals selected from the group consisting of chromium, platinum, aluminum, titanium and iron.

22. The method of claim 19 wherein the second material is chromium.

23. The method of claim 19 wherein the lubricious material is a polymer material.

24. The method of claim 23 wherein the polymer is selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

25. The method of claim 23 wherein the lubricious material comprises copolymers and telomers of polymers selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

26. The method of claim 23 wherein the polymer is polytetrafluoroethylene.

27. The method of claim 6 wherein the lubricious material is sputter deposited onto the edge.

28. The method of claim 27 wherein the lubricious material is deposited to a thickness of at least 1,000 Angstrom units.

29. The method of claim 17 wherein the edge is sputter etched in a first vacuum chamber, the blade is moved through a vacuum interlock to a second vacuum chamber in which the edge is sputter deposited with the refractory material, the blade is then moved through a second vacuum interlock to a third vacuum chamber in which the edge is sputter deposited with the second material, and finally the blade is moved through a third vacuum interlock to a fourth vacuum chamber which is then vented to the atmosphere to permit blade removal for subsequent coating with the lubricious material.

30. The method of claim 29 wherein blades are continuously sequentially passes through the chambers.

31. The method of claim 1 wherein the refractory material comprises an aluminum oxide compound formed on the elongate edge when material sputtered from an aluminum target combines with oxygen present in the environment.

32. The method of claim 10 wherein the sputtering rate is increased by the presence of a reactive gas.

33. A cutting instrument comprising: an elongate edge of narrow included angle formed by two intersecting surfaces of a refractory material,

an overlay coating of material over the edge for providing adhesion to the refractory material and a lubricious material, and

a final coating of the lubricious material.

34. The cutting instrument of claim 33 wherein the refractory material and the coating are sputter deposited on the edge.

35. The cutting instrument of claim 33 wherein the refractory material is synthetic sapphire.

36. The cutting instrument of claim 34 wherein the refractory material is selected from the group consisting of corundum, alumina, glass, quartz, beryllia, silicon carbide, tungsten carbide and boron nitride.

37. The cutting instrument of claim 35 wherein the refractory material is RF sputter deposited on the edge.

38. The cutting instrument of claim 37 wherein the overlay coating is RF sputter deposited.

39. The cutting instrument of claim 38 wherein the lubricious material is RF sputter deposited.

40. The cutting instrument of claim 37 wherein the total thickness of the refractory material and the overlay coating does not exceed approximately 500 Angstrom units.

41. The cutting instrument of claim 40 wherein the thickness of the refractory material is approximately 300 Angstrom units and the thickness of the overlay coating is approximately 25 Angstrom units..

42. The cutting instrument of claim 41 wherein the intersecting surfaces are honed surfaces and the narrow included angle is less than approximately 30.

43. The cutting instrument of claim 42 wherein the narrow included angle is approximately 44. The cutting instrument of claim 43 wherein the cutting instrument material is stainless steel.

45. The cutting instrument of claim 43 wherein the cutting instrument material is selected from the group consisting of stainless steel, carbon steel, chromium steel, tungsten steel, molybdenum steel, and chromenickel steel.

46. The cutting instrument of claim 43 wherein the cutting instrument material is an alloy containing material selected from the group consisting of stainless steel, carbon steel, chromium steel, tungsten steel, molybdenum steel, and chrome-nickel steel.

47. A method for applying a lubricious material to a cutting instrument having an edge formed by two intersecting surfaces of a refractory material having limited adhesion to the lubricious material comprising the steps of:

sputter depositing on the edge an overlay coating displaying adhesion to the lubricious material; and then coating the edge with the lubricious material.

48. The method of claim 47 wherein both the refractory material and the overlay coating material are sputtered on the edge and the refractory material is synthetic sapphire.

49. The method of claim 48 wherein both the refractory material and the overlay material are RF sputtered on the edge.

50. The method of claim 49 wherein the refractory material is selected from the group consisting of glass, quartz, corundum, alumina, beryllia, silicon carbide, tungsten carbide and boron nitride.

51. The method of claim 49 wherein the refractory material is an aluminum oxide compound formed by sputter depositing aluminum in an oxygen atmosphere.

52. The method of claim 49 wherein the lubricious material is selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

53. The method of claim 52 wherein the lubricious material is sputter deposited on the overlay coating.

54. The method of claim 49 wherein the overlay coating is a metal containing material.

55. The method of claim 54 wherein the metal is selected from the group consisting of chromium, platinum, titanium, aluminum and iron.

56. The method of claim 54 wherein the overlay coating is an alloy containing metal selected from the group consisting of chromium, platinum, titanium, aluminum and iron.

57. The method of claim 54 wherein the overlay coating material is chromium.

58. The method of claim 54 wherein the overlay coating thickness is approximately 25 Angstrom units and the total thickness of boththe refractory material and the overlay coating is limited to that necessary to maintain a desired degree of edge sharpness.

59. The method of claim 58 wherein the refractory material coating is approximately 300 Angstrom units in thickness.

60. The method of claim 32 wherein said reactive gas is oxygen.

61. The cutting instrument of claim 33 wherein the cutting instrument is a razor blade.

62. The cutting instrument of claim 35 wherein the cutting instrument is a razor blade.

63. The cutting instrument of claim 36 wherein the cutting instrument is a razor blade.

64. The cutting instrument of claim 37 wherein the cutting instrument is a razor blade.

65. The cutting instrument of claim 38 wherein the cutting instrument is a razor blade.

66. The cutting instrument of claim 40 wherein the cutting instrument is a razor blade.

Claims (66)

1. A method of making a razor blade comprising the steps of: forming a blade from a suitable material, the blade having an elongate edge comprising two intersecting surfaces; sputter depositing on the edge a first coating of refractory material; coating the edge with a second material displaying adhesion to a subsequent coating of lubricious material and to the refractory material; and then coating the edge with the lubricious material.

2. The method of claim 1 wherein the first coating is RF sputter deposited and the second material is sputter deposited.

3. The method of claim 2 wherein the refractory material is corundum.

4. The method of claim 2 wherein the refractory material is selected from the group consisting of glass, corundum, quartz, alumina, beryllia, silicon carbide, boron nitride, and tungsten carbide.

5. The method of claim 4 wherein the refractory material comprises alloys and mixtures of materials selected from the group.

6. The method of claim 2 wherein the refractory material is synthetic sapphire.

7. The method of claim 1 wherein the total thickness of the deposited refractory material and the second material is limited to that necessary to maintain a desired degree of edge sharpness.

8. The method of claim 7 wherein the total thickness is approximately 500 Angstrom units.

9. The method of claim 7 wherein the thickness of the refractory material is approximately 300 Angstrom units and the thickness of the second material is approximately 25 Angstrom units.

10. The method of claim 2 wherein the RF sputter depositing comprises the steps of: disposing the blade in an evacuated chamber having an electrode on which is mounted a target of refractory material; introducing into the chamber an ionizable gas and establishing a plasma by imposing an RF potential between the electrode and the blade; depositing on the edge particles dislodged from the target by impingement of gas ions formed in the plasma upon collision of RF excited electrons and the ionizable gas molecules.

11. The method of claim 10 wherein the chamber is evacuated to approximately 10 6 Torr and the ionizable gas is introduced to a pressure of approximately between 5 and 8 (10) 3 Torr.

12. The method of claim 11 wherein the refractory material is synthetic sapphire, the ionizable gas is Argon and the blade is positioned approximately 2 inches from the target, the edge apex being diSposed substantially in a plane parallel to the target and the refractory material is deposited at a rate of approximately 30 Angstroms per minute for a period between approximately 5 and 10 minutes.

13. The method of claim 12 wherein the frequency is 13.56 MC and wherein the blade is sputter etched prior to deposition of the refractory material and a shutter is interposed between the target and the blade during the step of sputter etching.

14. The method of claim 13 wherein capacitor means is serially connected between the blade and the RF potential and the shutter is connected to ground during sputter etching and wherein when the shutter is removed, the RF potential is connected to the electrode and the blade is connected to ground for sputter deposition.

15. The method of claim 14 wherein the target is pre-cleaned prior to sputter etching and wherein during pre-cleaning the shutter is interposed, the RF potential connected to the electrode and the shutter is connected to ground.

16. The method of claim 15 wherein the following parameters are maintained during pre-cleaning, sputter etching and sputter deposition, respectively:

17. The method of claim 10 wherein the second material is RF sputtered in accordance with the steps of claim 10.

18. The method of claim 17 wherein the second material is deposited to a thickness sufficient to provide adhesion of the subsequent lubricious material.

19. The method of claim 18 wherein the second material is deposited to a thickness of approximately 25 Angstrom units and the second material is a metal containing material.

20. The method of claim 19 wherein the second material is selected from the group consisting of chromium, platinum, aluminum, titanium and iron.

21. The method of claim 19 wherein the second material comprises mixtures and alloys of metals selected from the group consisting of chromium, platinum, aluminum, titanium and iron.

22. The method of claim 19 wherein the second material is chromium.

23. The method of claim 19 wherein the lubricious material is a polymer material.

24. The method of claim 23 wherein the polymer is selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

25. The method of claim 23 wherein the lubricious material comprises copolymers and telomers of polymers selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

26. The method of claim 23 wherein the polymer is polytetrafluoroethylene.

27. The method of claim 6 wherein the lubricious material is sputter deposited onto the edge.

28. The method of claim 27 wherein the lubricious material is deposited to a thickness of at least 1,000 Angstrom units.

29. The method of claim 17 wherein the edge is sputter etched in a first vacuum chamber, the blade is moved through a vacuum interlock to a second vacuum chamber in which the edge is sputter deposited with the refractory material, the blade is then moved through a second vacuum interlock to a third vacuum chamber in which the edge is sputter deposited with the second material, and finally the blade is moved through a third vacuum interlock to a fourth vacuum chamber which is then vented to the atmosphere to permit blade removal for subsequent coating with the lubricious material.

30. The method of claim 29 wherein blades are continuously sequentially passes through the chambers.

31. The method of claim 1 wherein the refractory material comprises an aluminum oxide compound formed on the elongate edge when material sputtered from an aluminum target combines with oxygen present in The environment.

32. The method of claim 10 wherein the sputtering rate is increased by the presence of a reactive gas.

33. A cutting instrument comprising: an elongate edge of narrow included angle formed by two intersecting surfaces of a refractory material, an overlay coating of material over the edge for providing adhesion to the refractory material and a lubricious material, and a final coating of the lubricious material.

34. The cutting instrument of claim 33 wherein the refractory material and the coating are sputter deposited on the edge.

35. The cutting instrument of claim 33 wherein the refractory material is synthetic sapphire.

36. The cutting instrument of claim 34 wherein the refractory material is selected from the group consisting of corundum, alumina, glass, quartz, beryllia, silicon carbide, tungsten carbide and boron nitride.

37. The cutting instrument of claim 35 wherein the refractory material is RF sputter deposited on the edge.

38. The cutting instrument of claim 37 wherein the overlay coating is RF sputter deposited.

39. The cutting instrument of claim 38 wherein the lubricious material is RF sputter deposited.

40. The cutting instrument of claim 37 wherein the total thickness of the refractory material and the overlay coating does not exceed approximately 500 Angstrom units.

41. The cutting instrument of claim 40 wherein the thickness of the refractory material is approximately 300 Angstrom units and the thickness of the overlay coating is approximately 25 Angstrom units.

42. The cutting instrument of claim 41 wherein the intersecting surfaces are honed surfaces and the narrow included angle is less than approximately 30*.

43. The cutting instrument of claim 42 wherein the narrow included angle is approximately 20*.

44. The cutting instrument of claim 43 wherein the cutting instrument material is stainless steel.

45. The cutting instrument of claim 43 wherein the cutting instrument material is selected from the group consisting of stainless steel, carbon steel, chromium steel, tungsten steel, molybdenum steel, and chrome-nickel steel.

46. The cutting instrument of claim 43 wherein the cutting instrument material is an alloy containing material selected from the group consisting of stainless steel, carbon steel, chromium steel, tungsten steel, molybdenum steel, and chrome-nickel steel.

47. A method for applying a lubricious material to a cutting instrument having an edge formed by two intersecting surfaces of a refractory material having limited adhesion to the lubricious material comprising the steps of: sputter depositing on the edge an overlay coating displaying adhesion to the lubricious material; and then coating the edge with the lubricious material.

48. The method of claim 47 wherein both the refractory material and the overlay coating material are sputtered on the edge and the refractory material is synthetic sapphire.

49. The method of claim 48 wherein both the refractory material and the overlay material are RF sputtered on the edge.

50. The method of claim 49 wherein the refractory material is selected from the group consisting of glass, quartz, corundum, alumina, beryllia, silicon carbide, tungsten carbide and boron nitride.

51. The method of claim 49 wherein the refractory material is an aluminum oxide compound formed by sputter depositing aluminum in an oxygen atmosphere.

52. The method of claim 49 wherein the lubricious material is selected from the group consisting of polytetrafluoroethylene, polypropylene, polyhexafluoropropylene, polychlorotrifluoroethylene and polyethylene.

53. The method of claim 52 wherein the lubricious material is sputter deposited on the overlay coating.

54. The method of claim 49 wherein the overlay coating is a metal containing material.

55. The method of claim 54 wherein the metal is selected from the group consisting of chromium, platinum, titanium, aluminum anD iron.

56. The method of claim 54 wherein the overlay coating is an alloy containing metal selected from the group consisting of chromium, platinum, titanium, aluminum and iron.

57. The method of claim 54 wherein the overlay coating material is chromium.

58. The method of claim 54 wherein the overlay coating thickness is approximately 25 Angstrom units and the total thickness of both the refractory material and the overlay coating is limited to that necessary to maintain a desired degree of edge sharpness.

59. The method of claim 58 wherein the refractory material coating is approximately 300 Angstrom units in thickness.

60. The method of claim 32 wherein said reactive gas is oxygen.

61. The cutting instrument of claim 33 wherein the cutting instrument is a razor blade.

62. The cutting instrument of claim 35 wherein the cutting instrument is a razor blade.

63. The cutting instrument of claim 36 wherein the cutting instrument is a razor blade.

64. The cutting instrument of claim 37 wherein the cutting instrument is a razor blade.

65. The cutting instrument of claim 38 wherein the cutting instrument is a razor blade.

66. The cutting instrument of claim 40 wherein the cutting instrument is a razor blade.

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