Cutlery – Blades – Razor blade
Reexamination Certificate
1999-11-03
2001-09-18
Watts, Douglas D. (Department: 3724)
Cutlery
Blades
Razor blade
C076S104100, C076SDIG001
Reexamination Certificate
active
06289593
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved razors and razor blades and to processes for producing razor blades or similar cutting tools with sharp and durable cutting edges, and in particular to amorphous diamond coating of blades using a filtered cathodic arc plasma source. The invention has particular utility for forming a very hard and rigid coating of high aspect ratio on very thin cutting edges of razor blades.
BACKGROUND OF THE INVENTION
A razor blade typically is formed of suitable substrate material such as metal or ceramic, and an edge is formed with wedge-shape configuration with an ultimate edge or tip that has a radius of less than about 1,000 angstroms, the wedge shaped surfaces having an included angle of less than 30°. As shaving action is severe and blade edge damage frequently results and to enhance shavability, the use of one or more layers of supplemental coating material has been proposed for shave facilitation, and/or to increase the hardness and/or corrosion resistance of the shaving edge.
A number of such coating materials have been proposed, such as polymeric materials and metals, as well as other materials including diamond-like carbon (DLC) material. Each such layer or layers of supplemental material must have adhesion compatibility so that each layer remains firmly adhered to the substrate throughout the useful life of the razor blade, and desirably provide characteristics such as improved shavability, improved hardness and/or corrosion resistance while not adversely affecting the geometry and cutting effectiveness of the shaving edge.
U.S. Pat. No. 5,032,243 of Bache et al. describes blade substrate materials sharpened by ion bombardment from ion sources having the axes of their beams directed at the edges of the razor blades. U.S. Pat. Nos. 5,232,568 of Parent et al. and 5,295,305 of Hahn et al. show blades which have an interlayer interposed between the substrate and the diamond-like coating, wherein the interlayer is deposited on the substrate and then the diamond-like coating is deposited on the interlayer.
The prior solutions are not entirely successful, and it would be desirable simply to use mechanical honing processes to form the sharpened substrate (rather than the ion beam formation shown in Bache et al.) followed by a direct deposition of amorphous diamond coating on the substrate (without the intervening step of depositing an interlayer). It would be desirable, therefore, to be able to start with a thin blade substrate produced by mechanical honing and to impart both rigidity and hardness to the substrate by depositing an amorphous diamond coating directly on the substrate.
SUMMARY OF THE INVENTION
According to this invention, the cutting edges of razor blades are provided with improved mechanical properties by applying to the sharpened edge of the substrate a coating of an amorphous diamond material. Such materials may be characterized as having at least 40 percent sp3 carbon bonding, a hardness of at least 45 gigapascals and a modulus of at least 400 gigapascals. In addition, such materials are not corroded by hot aqueous solutions and compounds commonly used in shaving. Materials having these characteristics will be denoted as amorphous diamond in the further course of this disclosure. In contrast to the amorphous diamond material of this invention, traditional diamond-like carbon coatings (DLC) produced by such traditional methods as sputtering do not exhibit such high hardnesses. Unlike the amorphous diamond of this disclosure, DLC coatings typically have hardnesses not exceeding 30 gigapascals.
The extreme hardness and rigidity of the applied amorphous diamond coating can provide strength to a very thin razor blade edge. U.S. Pat. No. 4,720,918 of Curry et al. describes edges of this type, and they are included here as examples and need not be considered limiting. A very thin blade edge can provide increased shaving comfort, but is practical only if the edge is strong enough to withstand shaving. A thin edge, including but not limited to those described in U.S. Pat. No. 4,720,918, strengthened by 400 to 2000 angstroms of amorphous diamond will comprise a finished edge which is significantly thinner than edges presently used for shaving, coupled with sufficient strength to withstand shaving, this due to the extraordinary strength of the amorphous diamond coating.
Further contributing to a thin edge is the large aspect ratio attainable by the particular cathodic arc deposition process used in this invention for manufacture of amorphous diamond coatings. The “aspect ratio” is explained in greater detail with reference to
FIG. 3
in the discussion which follows, but may be understood for purposes of this summary as being the ratio of (a) to (b) where (a) is a first distance from the tip of the coating to the tip of the substrate, and (b) is a second distance from a surface of the coating to the tip of the substrate.
The aspect ratio provides a useful measure of the effect of a coating on the underlying blade edge geometry of the substrate—the larger or higher the aspect ratio of the coating, the “sharper” is the coated blade compared to a blade coated at a lower aspect ratio. As a further consequence of the extraordinary strength of the amorphous diamond coatings of this invention, application of such a coating to a razor blade of normal cross-section will be expected to provide longer shaving life.
In accordance with one aspect of the invention, there is provided a wedge-shaped edge and a layer of amorphous diamond on the tip and flanks of the wedge-shaped edge, preferably with a thickness of at least 400 angstroms, which defines a tip radius of less than about 500 angstroms and an aspect ratio of 2:1 to 4:1. The blade exhibits excellent shaving properties and long life.
In preferred embodiments, the razor blade substrate is steel, the amorphous diamond coating is at least four times as hard as the steel substrate; the wedge-shaped edge is formed by a sequence of mechanical abrading steps; and the layer of amorphous diamond is formed of carbon ions provided from a graphite target used as a filtered cathodic arc source.
In accordance with another aspect of the invention, there is provided a process for forming a razor blade that includes the steps of providing a substrate; forming on an edge of the substrate a wedge-shaped sharpened edge that has an included angle of less than 30° and a tip radius (i.e. the estimated radius of the largest circle that may be positioned within the ultimate tip of the edge when such ultimate tip is viewed under a scanning electron microscope at magnifications of at least 25,000) preferably of less than 1,200 angstroms; and depositing, by filtered cathodic arc evaporation, a layer of amorphous diamond on the sharpened edge to provide a radius at the ultimate tip of the amorphous diamond layer of less than about 1000 angstroms. The amorphous diamond layer may be deposited by several techniques, all having in common the energetic deposition of carbon as a highly ionized species. While methods of cathodic arc, anodic arc, plasma decomposition of hydrocarbon gases, sputtering with post-ionization by inductively coupled rf, laser ablation, laser absorptive wave deposition (LAWD) and direct ion beam deposition might be used for this purpose, the preferred embodiment of this invention uses a filtered cathodic arc.
In a particular process, the substrate is mechanically abraded in a sequence of honing steps to form the sharpened edge; a layer of amorphous diamond is deposited by filtered cathodic arc, the amorphous diamond coating on the cutting edge having a thickness of at least 400 angstroms, the layer of amorphous diamond having at least 40 percent sp3 carbon bonding, a hardness of at least 45 gigapascals; and an adherent polymer coating may be applied on the amorphous diamond coated cutting edge.
In accordance with another aspect of the invention, there is provided a shaving unit that comprises blade support structure that has external surfaces for engaging user skin ahead and rearwardly of th
Decker Thomas G.
Lundie Gregory P.
Pappas David L.
Parent C. Robert
Welty Richard P.
Chrisman Bynum & Johnso
Folsom Thomas C.
Watts Douglas D.
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