Composite adhesive for optical and opto-electronic applications

Details Composite adhesive for optical and opto-electronic applications Composite adhesive for optical and opto-electronic applications

1997-10-03

1999-06-08

Cain, Edward J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

524492, 524493, C08K 300

Patent

active

059105224

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a composite adhesive for optical and opto-electronic applications, for example for connecting individual components such as optical fibres or for constructing (integrated) optical chips (IO-chips) for the production of optical fibre-chip couplings etc.
2. Description of the Background
Various UV or thermally curing transparent organic adhesives are presently employed in opto-electronics for connecting components of different materials, e.g., SiO.sub.2 optical fibres and IO-chips made of glass, silicon, lithium niobate or semi-conductors, and for constructing optical components from these materials.
In doing so, utmost precision in adjusting the parts to be connected is required (.+-.0,1 .mu.m) so that e.g., in fibre-chip-couplings the lightwave guides in the fibre and in the chip come into exact contact and light transmission losses are minimized thereby. An additional requirement is that the glued joint must remain stable in the temperature range of from -45.degree. C. to +85.degree. C. (or +135.degree. C., respectively) and does not undergo maladjustment within said range.
Conventional adhesives do not meet said requirements satisfactorily. They often tear at temperatures below -40.degree. C. and due to the relatively high coefficient of thermal expansion of the organic adhesive the glued joint is subject to an excessively high maladjustment or may be destroyed at elevated temperatures.
It is known from the prior art that, e.g., the curing behaviour (shrinkage) of transparent adhesive may be improved by mixing finely ground (particle size in the .mu.m range), already cured adhesive into the uncured adhesive. This, however, inevitably leads to an increase in the viscosity of the adhesive so that the amount of solids that can be added is limited to a few %, depending on the application.
Furthermore, no qualitative change in the properties of the cured composite adhesive (e.g. an increase of the thermal stability or a decrease of the coefficient of thermal expansion) can be achieved in this manner. When using inorganic powder having particle sizes in the .mu.m or sub-.mu.m range the transparency decreases due to light scattering. With certain limitations this also applies to agglomerated powders of nanoscale primary particles (e.g. aerosils).


SUMMARY OF THE INVENTION

Object of the present invention is to provide composite adhesives for optical and opto-electronic applications which are operable in the temperature range of at least from -45.degree. C. to +85.degree. C. (and even better to 135.degree. C.), result in low optical scattering and attenuation and afford sufficient adhesive strength for application. Furthermore said adhesives should have a viscosity which is advantageous for handling purposes.
A further object is the provision of optical and opto-electronic elements made by means of said composite adhesives.
Object of the present invention are composite adhesives for optical and opto-electronic applications which are characterized in that they contain polymerizable monomer suitable for use as adhesive; particles; and


DETAILED DESCRIPTION OF THE INVENTION

Tt has surprisingly been found that if nanoscale particles are incorporated in organic or organic-inorganic, respectively, polymer adhesives in agglomerate-free condition not only the optical transparency can be maintained, but also a so far not observed steep qualitative increase in the mechanical and thermo-mechanical properties can be generated, which increase leads to a strong improvement in the use properties of the adhesive.
The important factor for said improvement is that said nanoscale particles are integrated into the adhesive not as agglomerated powders but in the form of stabilized, (substantially) agglomerate-free suspensions and that said agglomerate-free condition is maintained (optionally by an appropriate surface modification of said particles) even after the excess solvent has been stripped off the adhesive. This is effected, e.g., by matching th

REFERENCES:
patent: 5307438 (1994-04-01), Bilkadi et al.

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