Siliceous Bonding of Optical Bodies with Protective Oxide Layers

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Solution Overview

Problem

Silicate bonding processes for optical components often result in defects like bubbles, opacifications, and discolorations due to the alkaline solution attacking oxide coatings, leading to reduced optical quality and mechanical strength.

Innovation Solution

Applying a transparent oxide protective layer with a refractive index higher than silicon dioxide, such as aluminum oxide, to prevent the alkaline bonding solution from degrading the coated surfaces, which enhances the bond strength and optical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If alkaline silicate bonding solution is applied to oxide-coated optical components, then bonding occurs, but the alkaline solution attacks and degrades the oxide coatings causing defects

Engineering Contradiction:

Improvebond strengthVSAvoidcoating degradation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

A silicon oxide protective layer is applied as an intermediary between the oxide coating and the alkaline bonding solution. This protective layer acts as a barrier that prevents the alkaline solution from attacking and degrading the underlying oxide coating, while still allowing the bonding process to occur at the interface between the protective layer and the bonding solution.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The silicon oxide protective layer is applied in advance before the silicate bonding process. This preliminary protective coating prevents the harmful interaction between the alkaline bonding solution and the oxide coating during subsequent bonding operations, eliminating defects before they can form.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If oxide coatings are present on optical components, then optical properties are enhanced, but bonding defects occur during silicate bonding

Engineering Contradiction:

Improveoptical qualityVSAvoidbond zone defect freedom

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The silicon oxide protective layer serves as a mediator that allows both the oxide coating and bonding solution to coexist without harmful interaction. It preserves the optical properties provided by the oxide coating while preventing bonding defects in the bond zone.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective silicon oxide layer is applied specifically to the bonding surfaces where it is needed to prevent alkaline attack, while leaving other areas of the optical component unchanged. This localized application maintains optical quality without affecting overall component performance.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If vapor deposition is used to apply oxide coatings, then coating is achieved, but coating porosity increases making it more susceptible to alkaline attack

Engineering Contradiction:

Improvecoating applicationVSAvoidalkaline solution penetration

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The silicon oxide protective layer acts as an intermediary barrier that covers the porous vapor-deposited oxide coating. This protective layer prevents the alkaline bonding solution from penetrating into the porous structure and attacking the underlying coating, regardless of the coating's porosity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 oxide protective layer significantly reduces defects, improves optical transmission, mechanical strength, and long-term resistance, especially for components with Si, Ti, Hf, Nb, or Ta ions, while allowing silicate bonding to occur without compromising the coating.

Implementation Method 1

Applying a transparent oxide protective layer with a refractive index higher than silicon dioxide, such as aluminum oxide, to prevent the alkaline bonding solution from degrading the coated surfaces

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

connecting ('bonding,' 'joining') especially coated, but also solid optical bodies made of inorganic materials such as glass bodies, especially of optical glasses and optical elements by means of aqueous, silicate solutions

Methodology Applied

Scientific EffectSilicate bonding: Chemical Bonding

Data Source

PatentUS9233873B2Method for the siliceous bonding of coated and uncoated optical bodies

Publication Date: 2016.01.12 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

The present invention pertains to a process for the silicate bonding of joined surfaces, facing one another, of two components by means of an aqueous, alkaline, silicon-cation-containing joining solution for the purpose of producing an optical element, characterized in that one or both of said joined surfaces (1; 2b; 10) are covered with a layer of an oxide (3), which has a higher refractive index than SiO2 and is selected from among oxides of the third and fourth main group elements, of the second and third group of the transition elements as well as zirconium and from among mixed oxides of the said elements, whereupon the joining solution is applied to at least one of the surfaces to be joined and the surfaces are bonded to one another. The present invention also teaches the use of oxide layer (3) as a topmost layer of a component to be joined by means of an alkaline, silicate-containing solution for preventing or reducing opacifications and/or defects as a result of a chemical attack on the layer lying under it by the said alkaline solution.