U.S. patent number 3,911,579 [Application Number 05/352,374] was granted by the patent office on 1975-10-14 for cutting instruments and methods of making same.
This patent grant is currently assigned to Warner-Lambert Company. Invention is credited to Phyllis M. Curtis, George C. Lane, Arthur E. Michael.
United States Patent |
3,911,579 |
Lane , et al. |
October 14, 1975 |
Cutting instruments and methods of making same
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.
Inventors: |
Lane; George C. (Danbury,
CT), Curtis; Phyllis M. (Simsbury, CT), Michael; Arthur
E. (Middletown, CT) |
Assignee: |
Warner-Lambert Company (Morris
Plains, NJ)
|
Family
ID: |
33457866 |
Appl.
No.: |
05/352,374 |
Filed: |
April 18, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
144509 |
May 18, 1971 |
|
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|
|
Current U.S.
Class: |
30/346.54;
30/346.53; 76/DIG.8; 76/104.1; 204/192.15; 204/192.16;
204/298.25 |
Current CPC
Class: |
C23C
14/56 (20130101); B26B 21/54 (20130101); C23C
14/022 (20130101); C23C 14/345 (20130101); C23C
14/34 (20130101); Y10S 76/08 (20130101) |
Current International
Class: |
C23C
14/56 (20060101); C23C 14/02 (20060101); B26B
21/54 (20060101); B26B 21/00 (20060101); C23C
14/34 (20060101); B26B 021/54 (); B21K
011/00 () |
Field of
Search: |
;76/14R,DIG.8
;30/346.5,346.53,346.54,346.55 ;204/192
;117/69R,7C,71M,93.4R,17.2R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Vlachos; Leonidas
Attorney, Agent or Firm: Graddis; Albert H. Chow; Frank
S.
Parent Case Text
CROSS-REFERENCE TO A RELATED APPLICATION
This application is a continuation of U.S. Pat. application Ser.
No. 144,509, filed May 18, 1971.
Claims
What is claimed is:
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.sup..sup.-6 Torr and the ionizable gas is
introduced to a pressure of approximately between 5 and 8
(10).sup..sup.-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.degree..
43. The cutting instrument of claim 42 wherein the narrow included
angle is approximately 20.degree..
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.
Description
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 today's
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 1930's, 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, 1970, Inventor: 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
fasion, 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 a method for
applying a refractory material to a razor blade.
Another object of this invention is to provide a method for
applying a lubricious material to a razor blade of refractory
material.
Yet another object of this invention is to provide a method for
depositing a refractory material on a substrate.
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 of a 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.degree. and
25.degree. but may, depending upon the basic substrate or blade
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 10 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 I 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 I.
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. It must be
noted, however, that other generally classified refractory
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 II 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 approximately 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 with films
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 combination with 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.degree. 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 of the 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 20
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 II. 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 101 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.degree.. It is hypothesized, however, that even a
smaller angle may be successfully used if suitable material is
utilized. However, the 15.degree. 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 FIG. 2, the razor blade, after cleaning in conformance
with the process step 2 of FIG. 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 I 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 10.sup.-.sup.3 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.sup..sup.-6 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.sup..sup.-6 Torr, Argon is
admitted to the chamber thereby lowering the vacuum level to
between approximately 1 - 2 (10).sup..sup.-3 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).sup..sup.-3 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).sup..sup.-3 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 II
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 II 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.sup..sup.-6 Torr; Argon is
then admitted to the chamber 58 through the Argon 25 unit to a
pressure of between 5 - 7 (10).sup..sup.-3 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 20 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
between 5-8 (10).sup..sup.-3 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 25 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 the material 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 II 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 I, II and
III 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 I 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 II correlates with the
Deposition II step and as indicated normally is a chromium coating.
Although this coating is shown as having essentially the same
thickness as I and II 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 III coating is that placed on the blade during the
Deposition III 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 double-edge blades are disposed on
the substrate electrode 20 in facing relationship to electrode 56
and the target 57. The remaining parameters of this example will be
presented in outline form in accordance with the steps heretofore
presented:
Surface preparation step 10 Initial background vacuum
10.sup.-.sup.6 Torr Argon pressure 1 - 2 (10).sup.-.sup.6 Torr RF
power 400 W. Self bias voltage 1 KVDC Sputter time 5 minutes Target
57 pre-clean step Argon pressure between 5 - 7 (10).sup.-.sup.3
Torr RF power 1.4 KW Self bias voltage 2.2 KVDC Sputter Deposition
I Target 57 material Linde synthetic sapphire comprising
essentially hexagonal crystal lattice structures of AL.sub.2
O.sub.3 manufactured by the Linde Crystal Products Division of
Union Carbide Target dimensions 4" in diameter by 1/4" thick Argon
pressure between 5 - 7 (10).sup.-.sup.3 Torr RF power 1.4 KW Self
bias voltage 2.2 KVDC Sputter time approximately 7-1/2 min.
Sputtering rate approximately 30 Angstroms per min. Coating
thickness between 200 and 300 Angstrom units Sputter Deposition II
Target 57 material Pure chromium Target pre-clean step Argon
pressure between 5 - 7 (10).sup.-.sup.3 Torr RF power 1.4 KW Self
bias electrode voltage 2.2 KVDC Period 1 minute Sputter deposition
step Argon pressure between 5 - 7 (10).sup.-.sup.3 Torr Power 1 KW
Self bias DC voltage 2.2 KVDC Time 10 seconds Sputter rate
approximately 180 Angstrom units per min. Coating thickness
approximately 30 Angstrom units
Thereafter Deposition III 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 1-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 1 and 2.
The blade edge was sputter etched under the following
conditions:
RF power 200 W. Argon pressure 1 (10).sup.-.sup.3 Torr Self bias
voltage 1 KVDC Sputter etch time 5 min. Target pre-clean step
Target material quartz Argon pressure Same as Example 1 RF power
Same as Example 1 Pre-clean time Same as Example 1 Self bias
voltage Same as Example 1 Sputter Deposition I step Argon pressure
Same as Example 1 RF power Same as Example 1 Time Same as Example 1
Self bias voltage Same as Example 1 Thickness approximately 200
Angstrom units Sputter Deposition II step Target material Pure
chromium Pre-clean conditions Same as that for pre- cleaning of the
Deposition I target Sputter deposition step Argon pressure Same as
Example 1 RF power Same as Example 1 Sputter time Same as Example 1
Self bias voltage Same as Example 1 Sputter coating thickness
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 utilized 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 of a 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 applicants's process. Chambers 10,
11, 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 10 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 20 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, 11, 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 I 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 II 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
11, 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, 11 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
101, 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, 11, 12 and 24' are reduced in
vacuum level to approximately 10.sup..sup.-6 Torr. Argon is 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 of a 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.sup..sup.-6 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 just-described 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.sup..sup.-6 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 11 for the Deposition I
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.sup..sup.-6 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 39 to 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 U.S. Pat.
application Ser. No. 861,937, filed Sept. 29, 1969, 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 of a 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 18, 1971, 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 continuous batch 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, 11, 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 110 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 112 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 AL.sub.2
O.sub.3 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 application 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 chrome-nickel 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. It 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.
* * * * *