Razor Blade Substrate Thickness Profile and Coating
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Solution Overview
Problem
Existing razor blades require high cutting forces, leading to discomfort during shaving due to inadequate balance between edge strength and sharpness.
Innovation Solution
A razor blade with a substrate having specific thickness ratios and a cross-sectional shape defined by the equation w=ad^n, where 'w' is the thickness in micrometers from the blade tip, 'a' is between 0.50 to 0.62, and 'n' is between 0.76 to 0.80, combined with a niobium or chromium interlayer, a DLC hard coating, and a polytetrafluoroethylene outer layer, to reduce cutting force and enhance edge strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the razor blade edge is made thinner to improve sharpness, then the cutting force is reduced, but the edge strength decreases leading to premature failure
Solution Approach 1:
The patent applies composite materials by combining a metal substrate with multiple coating layers including hard coatings (diamond, amorphous diamond, DLC, nitrides, carbides, oxides, or ceramics) and friction-reducing outer layers (PTFE). This composite structure allows the edge to be made thinner for reduced cutting force while the hard coatings provide the necessary edge strength and durability to prevent premature failure.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the thickness of the substrate and various coating layers, as well as the tip radius (500 to 1500 Angstroms) and thickness profile at different distances from the blade tip. These parameter optimizations enable the blade to achieve both sharpness (lower cutting force) and sufficient edge strength through optimized geometric and material properties.
2Strength
If hard coatings are applied to improve edge strength, then the edge durability is enhanced, but the friction increases reducing shaving comfort
Solution Approach 1:
The patent segments the coating structure into distinct functional layers: hard coatings (nitrides, carbides, oxides, or ceramics) applied directly to the substrate for edge strength, followed by an intermediate layer, and finally an outer friction-reducing layer (PTFE or similar polymer). This segmentation allows each layer to perform its specific function independently, resolving the contradiction between edge strength and friction reduction.
Solution Approach 2:
The patent applies local quality by giving different regions of the blade different material properties - the cutting edge region has hard coatings for strength, while the outer surface has low-friction polymer coating for comfort. This spatial differentiation of material properties allows the blade to simultaneously achieve edge durability and reduced friction during shaving.
3Force
If the substrate thickness is reduced to achieve sharper edge, then the cutting performance is improved, but the overall blade strength and durability decrease
Solution Approach 1:
The patent uses composite materials to compensate for reduced substrate thickness. By applying hard coatings (diamond, amorphous diamond, DLC, nitrides, carbides, oxides) and friction-reducing outer layers (PTFE), the blade maintains edge strength and overall durability even with a thinner substrate, thereby achieving both sharp cutting performance and reliable operation.
Solution Approach 2:
The patent employs parameter changes by optimizing the thickness profile of the substrate and coating layers at specific distances from the blade tip, as well as controlling the tip radius. These precise parameter adjustments allow the blade to achieve optimal sharpness while maintaining sufficient structural integrity and durability through balanced geometric and material design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a razor blade with improved sharpness and reduced cutting force, providing a more comfortable shaving experience by balancing edge strength and sharpness, as evidenced by cutting force measurements below 40 milliNewtons.
Implementation Method 1
Interlayers of niobium, chromium, or titanium containing materials can aid in improving the binding between the substrate, typically stainless steel, and hard carbon coatings, such as DLC
Implementation Method 2
Polytetrafluoroethylene (PTFE) outer layer can be used to provide friction reduction
Implementation Method 3
The substrate may include a nitride region disposed at or beneath a surface of the substrate which may be formed by plasma nitriding
Data Source
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AI summary
A razor blade having a substrate with a cutting edge being defined by a sharpened tip. The substrate has thicknesses of 1.60-1.75micrometers and 9.25-10.00micrometers measured at a distance of four and forty micrometers from the blade tip, respectively. A ratio of the thickness measured at four micrometers to the thickness measured at forty micrometers is between 0.165-0.185. The substrate thickness is about 2.70-3.00micrometers at eight micrometers from the blade tip, about 4.44-5.00micrometers at sixteen micrometers from the blade tip with a thickness ratio measured at four micrometers and eight micrometers between 0.56-0.62, and a thickness ratio measured at four micrometers and sixteen micrometers between 0.32-0.40. The blade edge shape is defined by equation w=adn where "a" is between 0.50-0.62 and "n" is between 0.76-0.80. An included angle of less than 7° is measured at a distance of forty micrometers or greater from the blade tip. A nitrided substrate may also be provided.