Antireflection Coating Scratch Resistance Gradient
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Solution Overview
Problem
Timepiece crystals with antireflection coatings formed by alternately laminating SiO2 and Si3N4 layers suffer from poor scratch resistance due to unknown effects of varying hardness films, leading to inadequate optical simulations without considering thickness ratios.
Innovation Solution
A transparent member with an antireflection coating having a silicon nitride content of 34-50 vol% within 150 nm from the surface, combined with a stain-resistant fluorinated organosilicon coating, achieves high scratch resistance and low reflectivity, using sputtering for enhanced adhesion and hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If SiO2 and Si3N4 layers are alternately laminated to form an antireflection coating, then antireflection function is improved, but scratch resistance deteriorates
Solution Approach 1:
The invention changes the parameter of silicon nitride content from a binary alternating layer structure to a continuous gradient distribution, specifically maintaining 34-50 vol% Si3N4 within 150 nm from the surface. This parameter transformation allows the coating to achieve both low reflectivity (antireflection function) and high surface hardness (scratch resistance) simultaneously, resolving the contradiction between optical performance and mechanical durability
Solution Approach 2:
The invention applies local quality by creating a non-uniform distribution of silicon nitride concentration across the coating depth. The region within 150 nm from the surface contains 34-50 vol% Si3N4 to provide scratch resistance, while deeper regions have different compositions to maintain antireflection properties. This spatial variation in material composition allows different functional requirements to be satisfied at different locations within the coating
2Ease of manufacture
If the thickness ratio of SiO2 and Si3N4 layers is not optimized, then manufacturing is simplified, but optical performance deteriorates
Solution Approach 1:
The invention establishes a specific parameter range (34-50 vol% silicon nitride content within 150 nm depth) that guarantees both manufacturing feasibility and optimal optical performance. This quantified parameter specification transforms the manufacturing process from trial-and-error thickness adjustment to a controlled deposition process with clear acceptance criteria, simultaneously improving ease of manufacture and optical performance
3Strength
If hardness is increased at depths greater than 150 nm, then surface hardness is improved, but scratch resistance shows little improvement
Solution Approach 1:
The invention recognizes that scratch resistance is primarily determined by the mechanical properties within the top 150 nm of the coating. By concentrating the silicon nitride content (34-50 vol%) specifically within this depth range, the coating achieves maximum scratch resistance where it is most needed, while avoiding unnecessary complexity in deeper regions where hardness adjustments have minimal impact on scratch performance
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 a transparent member with improved scratch resistance, surface hardness, and antireflection properties, suitable for timepieces and other applications, while maintaining optical clarity and chemical resistance.
Implementation Method 1
a method of manufacturing a transparent member, including a sputtering step of forming the high index of refraction layer and low index of refraction layer rendering the antireflection coating by sputtering
Implementation Method 2
an antireflection coating that has a high index of refraction layer made of silicon nitride and a low index of refraction layer made of silicon oxide alternately laminated on at least a part of a surface of the substrate
Data Source
Figure 1~2
AI summary
A transparent member has a transparent substrate, and an antireflection coating that has a high index of refraction layer made of silicon nitride and a low index of refraction layer made of silicon oxide alternately laminated on at least a part of a surface of the substrate. The content of silicon nitride in the region to a depth of 150 nm from the outside surface of the antireflection coating is 30 - 50 vol%.