Light Transmissive Member Antireflection and Antistatic Layer Design

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Solution Overview

Problem

Light transmissive members with antireflection layers are prone to electrification, leading to adhesion of foreign substances and reduced visibility and appearance issues.

Innovation Solution

A light transmissive member with an antistatic layer comprising a transparent electrically conductive film layer and a refractive index layer stack, including silicon nitride and silicon oxide, is formed on one surface, while an antireflection layer with alternating high and low refractive index layers is formed on the other surface, enhancing visibility and scratch resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If an antireflection layer is formed on the light transmissive member to enhance visibility, then visibility is improved, but the light transmissive member becomes easily electrified causing foreign substances to adhere to the surface

Engineering Contradiction:
ImprovevisibilityVSAvoidelectrification
Core Design Contradiction:
Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The invention divides the functional layers into two separate locations: an antireflection layer on one surface to improve visibility, and an antistatic layer on the opposite surface to prevent electrification. This segmentation allows each surface to independently perform its specific function without interfering with the other, resolving the contradiction between visibility enhancement and electrification prevention.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention applies different functional properties to different surfaces of the light transmissive member. One surface has antireflection properties (low refractive index) optimized for visibility, while the opposite surface has antistatic properties (electrically conductive) optimized for preventing electrification. This local differentiation of quality allows each surface to address its specific requirement without compromising the other.

Inventive Principle:
Principle #3Local quality

2Strength

If silicon oxide is deposited on the outermost layer to provide high hardness and scratch resistance, then scratch resistance is improved, but the layer becomes more prone to electrification

Engineering Contradiction:
Improvescratch resistanceVSAvoidelectrification
Core Design Contradiction:
StrengthVSObject-generated harmful factors

Solution Approach 1:

The invention separates the scratch resistance function from the antistatic function by placing them on opposite surfaces. The silicon oxide layer providing hardness and scratch resistance is on one surface, while the electrically conductive antistatic layer is on the opposite surface, eliminating the electrification problem caused by the silicon oxide coating.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention introduces an electrically conductive layer as an intermediary on the outermost surface to counteract the electrification tendency of the silicon oxide layer. This conductive layer acts as a mediator that dissipates static electricity while allowing the silicon oxide layer beneath to maintain its scratch resistance properties.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Illumination intensity

If multiple layers with different refractive indices are stacked to form the antireflection layer, then antireflection performance is improved, but the device complexity increases

Engineering Contradiction:
Improveantireflection performanceVSAvoidlayer structure complexity
Core Design Contradiction:
Illumination intensityVSDevice complexity

Solution Approach 1:

The invention segments the optical functions from the electrical functions, placing the multilayer antireflection structure on one surface and the simpler single-layer or thin-film antistatic layer on the opposite surface. This segmentation allows the complex antireflection stacking to be confined to one area while keeping the overall device structure manageable and the other surface relatively simple.

Inventive Principle:
Principle #1Segmentation

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 effectively prevents electrification, reduces adhesion of foreign substances, and improves visibility and scratch resistance, while maintaining high antireflection and antifouling properties.

Implementation Method 1

forming the antistatic layer including the transparent electrically conductive film layer on the other surface of the substrate, electrification of the light transmissive member can be prevented

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

an antireflection layer formed on one surface of the substrate... consisting of thin-film layers having a high refractive index alternating with thin-film layers having a low refractive index

Methodology Applied
Scientific EffectRefraction: Refraction

Implementation Method 3

the visibility is enhanced by the antireflection layer formed on one surface of the substrate

Methodology Applied
Scientific EffectOptical interference: Interference

Implementation Method 4

the layer composed of silicon nitride has an extremely high hardness and the layer composed of silicon oxide has a relatively high hardness, and therefore, the scratch resistance of the antireflection layer can be improved

Methodology Applied
Scientific EffectHardness:

Implementation Method 5

the deposition thereof is easily performed using general-purpose equipment

Methodology Applied
Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentEP3196678B1Light transmissive member, timepiece, and light transmissive member production method
Publication Date: 2024.05.01 SEIKO EPSON CORP
  • EP3196678B1 patent drawingFigure 1
  • EP3196678B1 patent drawingFigure 2
  • EP3196678B1 patent drawingFigure 3

AI summary

A light transmissive member includes a substrate having a light transmission property, wherein on one surface of the substrate, an antireflection layer in which a low-refractive index layer composed mainly of silicon oxide (SiO2) and a high-refractive index layer composed mainly of silicon nitride (SiN) are alternately stacked is formed, and on the other surface of the substrate, an antistatic layer including at least a transparent electrically conductive film layer is formed.