FR2577240A1 - Process for depositing a coating on the cutting edge of a razor blade - Google Patents

Abstract

Process for depositing a coating of high hardness on the cutting edge of thin blades, especially of razor blades. This process is performed in a vacuum chamber. The deposition takes place directly by thermal sublimation of a silicon compound SiO or by an ionic process starting with a silicon cathode with the reactive carrier gas on the cutting edges of the blades, the said blades to be covered being connected together electrically to form the anode at the internal temperature of the deposition chamber or at a temperature included between the ambient temperature of the said deposition chamber and 150 DEG C. The process for coating the cutting edges of blades permits a long cutting life of the said cutting edges which is superior to the cutting edges of conventional blades.

Description

 The present invention relates to a process for depositing a coating of high hardness, in particular of silicon monoxide (SiO) on the edge of thin blades, of cutting tools such as cutters and in particular of razor blades.

 Methods are already known for depositing a coating on the edge of a razor blade, for example, according to Patent No. 73,20840.

 However, these are different conventional processes, using the thermal decomposition of metal compounds, for example, carbonyl metals such as tungsten hexacarbonyl, molybdenum hexacarbonyl, or alternatively by metal alcoholates such as butoxide aluminum. These methods also relate to mixed coatings obtained from the abovementioned compounds and polytetrafluoroethylene (PTFE).

 These conventional processes also use chemical reactions starting from oxides, carbides, borides, nitrides.

 These processes are relatively complex and require several parameters.

 The methods according to patent No. 73 20840 also use a carrier gas according to the examples, which can be: either reactive or inert with the vaporized compound, while maintaining the cutting edge of the blade (according to the example) at a temperature at which the thermal decomposition of the vaporized compound takes place or the reaction between this compound and the carrier gas.

 It is noted that all the examples of patent No. 73 20840 state the use only of razor blades made of stainless steel.

 The applicant has discovered, according to the invention, a material which, in the form of a film on the edge of the blade, improves in good proportions, the cutting time thereof.

 The desired coating is obtained by thermal sublimation of a silicon oxide (SiO) which comes into contact with the edge of the blade. However, the deposition can also be obtained by ionic method, such as ion bombardment by silicon cathode.

 The process is obtained in a deposition chamber at reduced pressure.

 Before being treated by these methods, the blades are cleaned with great care by degreasing, by tempering in trichlorethylene, then installed in the deposition chamber by assemblies easily determinable from the prior art.

 Additional cleaning is carried out in the deposition chamber by ionization of metered residual dry air (effluvage), at reduced pressure. A needle screw allows the addition of dry air at the desired pressure, which causes said cleaning by ion bombardment on the blade edges, said blades forming one of the electrodes.

 The current and vacuum voltage conditions required to create and maintain the effluvation are determinable from the previous state of the technique.

 Then, when the pressure in the deposition chamber is sufficiently low, the silicon monoxide is heated in a crucible at the sublimation temperature of said compound, for a certain time by optical visualization materialized by a curve.

 In addition, a coating thickness meter (quartz) located inside the deposition chamber can, at any time, give the measurement of said coating thickness.

 The coating thus obtained by the process according to the invention allows a longer shaving period, no doubt due to its hardness and its adhesion, and it can improve the corrosion resistance of carbon steel blades.

 The present invention is illustrated by the following example, without however limiting the scope of this invention.

 Example on 50 slides.

25 stainless steel razor blades,
25 razor blades made of carbon steel, suitably sharpened, are degreased in a bath of trichlorethylene boiling for 15 min. They can undergo other easily determinable cleanings from the prior art.

 The blades are stacked on a metal support, itself adapted on a tray fixed on a rotating axis with variable speed depending on the case.

 This plate has a central bore which allows the visualization of an optical transmission materialized by a trace of curve and by the intermediary of a perfectly cleaned glass plate which becomes more or less opaque according to the deposit, and on which one can measure the coating thickness and refractive index.

 A cleaning of the blades by effluvage at reduced pressure (in the gain of 1.10-2-2 min of Hg) perfectly maintained by a nozzle of dry air regulated by a micrometric needle screw, causes an ion bombardment on the blade edges .

 This cleaning is recommended before obtaining the vacuum sought to deposit the coating and which may be between 1 * 10 5 and 6.10 6 min of Hg.

 The crucible containing the silicon monoxide is fixed between 2 electrodes and heated to the sublimation temperature of SiO (1200 C) which is thus deposited on the cutting edge of the blades.

The interest of this invention is
Cutting time of the blade edge significantly improved by a relatively simple and fast process.

 All razor blades can be treated in this way, regardless of their composition, carbon steel or stainless steel.

 Heating of the blades during coating is not necessary, however, a temperature up to, for example, the ambient temperature of the deposition chamber at 1500C by radiation, can increase the adhesion and the resistance of said deposition.

 Reduced steaming time: 30 s at a pressure of 1.10 2 min of Hg, at a voltage of 3,500 volts and a current of 140 mA.

 No carrier gas during thermal sublimation of SiO (des 10 5 6.10 mm Hg).

 Duration of sublimation of SiO: from O to 3 min.

Thickness of the deposit: from O to 3000 A
The thickness and refractive index of the coating can be measured precisely with an ellipsometer on the glass plate used for optical transmission.

By sublimation, the refractive index (n) of
SiO = 1.85.

 By sublimation, the refractive index of SiO in our example is equal to 1.88.

 It is also possible to deposit by ion bombardment, by silicon cathode with a reactive carrier gas, such as oxygen or a metered mixture of argon and oxygen, the blades thus treated forming the anode.

 The process is carried out in a manner known per se.

Claims (8)

 1) Process for forming a coating of high hardness on the edge of a blade, characterized in that it comprises bringing the edge of the blade to be covered into contact with silicon monoxide (SiO).  2) Method according to claim 1 characterized in that a hard coating is formed with said compound which is sublimated thermally.  3) Method according to claim 2 characterized in that the silicon monoxide is heated in a crucible to the sublimation temperature of said monoxide.  4) Method according to any one of claims 1 and 3 characterized in that the coating is formed in a deposition chamber directly without carrier gas.  5) Method according to claim 4 characterized in that the coating is formed at a pressure below atmospheric pressure.  6) Method according to any one of the preceding claims characterized in that the coating is formed at a temperature between room temperature and 1500C  7) A method according to claim 1 characterized in that the coating is formed in a deposition chamber at reduced pressure with reactive carrier gas such as oxygen, or mixture of metered gas such as argon and oxygen, by ion bombardment using a silicon cathode, the blades to be covered being electrically connected, together to form the anode.  8) Blade cutting edge coated with silicon monoxide, according to the method, according to any one of claims 1 to 7.