Gradient Chromium-Boron Coating for Razor Blade Adhesion
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Solution Overview
Problem
Razor blades face issues with adhesion between dissimilar materials, leading to inadequate durability, particularly between stainless steel and hard thin layers, and the conventional deposition methods require larger chambers and longer times, with multilayer coatings prone to fracture at interlayer boundaries.
Innovation Solution
A razor blade with a hard coating layer composed of chromium and boron, where the atomic ratio varies in the thickness direction, and a polymer coating, formed using physical vapor deposition with a single sputter target, enhancing adhesion and durability by suppressing initial fracture at interlayer boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sputter targets are arranged around the razor blade under different voltage and bias conditions to deposit dissimilar materials, then adhesion between dissimilar materials is improved, but the deposition chamber size increases and deposition time is extended
Solution Approach 1:
The patent combines multiple sputter targets into a single composite sputter target that contains both chromium and boron materials. This single target is rotated during deposition to deposit both materials simultaneously, eliminating the need for multiple separate targets and reducing chamber complexity while maintaining adhesion between dissimilar materials
Solution Approach 2:
The single composite sputter target serves multiple functions by containing both chromium and boron materials and depositing them in sequence through rotation. This multi-functional target replaces what would traditionally require multiple specialized targets, reducing system complexity while achieving the same adhesion improvement
2Manufacturing precision
If a multilayer coating is made on the metallic substrate with clear interlayer boundaries, then manufacturing precision is improved, but the probability of destruction starting from the boundary increases
Solution Approach 1:
The patent applies local quality by creating a gradient in material composition within the hard coating layer. The chromium to boron atomic ratio varies through the thickness of the layer, with chromium-rich regions providing adhesion and boron-rich regions providing hardness. This gradual transition eliminates sharp interlayer boundaries that would otherwise be prone to destruction
Solution Approach 2:
The patent changes the compositional parameter (atomic ratio of chromium to boron) continuously through the thickness of the hard coating layer. By controlling the rotation speed and deposition conditions, the material composition transitions gradually from chromium-rich at the substrate interface to boron-rich at the outer surface, eliminating abrupt boundaries and improving reliability
3Strength
If a hard thin layer is deposited to increase strength and durability of the razor blade edge, then hardness is improved, but adhesion between the hard thin layer and substrate or polymer coating deteriorates
Solution Approach 1:
The hard coating layer has non-uniform composition with chromium-rich regions near the substrate for adhesion and boron-rich regions near the polymer coating for compatibility. This local variation in material properties ensures both strong adhesion to the substrate and good bonding to the polymer coating while maintaining overall hardness
Solution Approach 2:
The patent creates a composite hard coating layer that combines chromium and boron in a controlled gradient structure. This composite material approach allows the layer to exhibit multiple properties: adhesion to substrate (from chromium), adhesion to polymer coating (from boron), and overall hardness (from the composite structure), resolving the adhesion-hardness contradiction
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 provides improved durability and wear resistance, maintaining shaving performance and reducing skin irritation, with a single-layer coating that effectively combines strength, hardness, and adhesion, outperforming multilayer coatings in tests.
Implementation Method 1
forming a hard coating layer by performing a physical vapor deposition (PVD) on the heat-treated blade substrate at which the blade edge is formed
Implementation Method 2
forming a hard coating layer composed of chromium and boron, where the atomic ratio varies in the thickness direction, and a polymer coating, formed using physical vapor deposition with a single sputter target
Data Source
AI summary
The present disclosure provides a razor blade coating by a physical vapor deposition method through performing a deposition with a single composite target composed of dissimilar materials with their area ratio defined to be varied in the single composite target in the direction of transferring the razor blade subject to the deposition, thereby forming a single layer in which the composition ratio of the dissimilar materials gradually changes in the thickness direction of the coating layer to improve the durability of the razor blade coating layer