Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-11-30
2002-03-05
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S418000, C525S430000, C528S423000, C428S423100
Reexamination Certificate
active
06353059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to polyadducts produced from nonlinear-optically active copolymers and polymerizable nonlinear-optically active monomers, i.e., for electrooptical and photonic components.
Electrooptical and photonic components are important elements in nonlinear optics and in optical information technology. They are planar waveguide structures whose function can be altered by an electrical voltage. They comprise modulators, Mach-Zehnder modulators, tunable and switchable directional couplers, wavelength filters, including tunable wavelength filters, and polarization-modifying waveguide components. Their construction is described, for example, by R. C. Alferness in T. Tamir “Guided-Wave Optoelectronics”, Springer-Verlag Berlin, Heidelberg 1988, pages 145 to 210, and in K. J. Ebeling “Integrierte Optoelektronik”, 1st edition, Springer-Verlag Berlin, Heidelberg 1989, pages 152 to 162.
Components of this kind can be produced using highly anisotropic inorganic crystals which have a high 2nd-order susceptibility.
In the past, organic materials and polymers having high 2nd-order susceptibilities have also been developed. They feature considerable advantages in terms of their preparation and their use in electrooptical and photonic components. Polymers having nonlinear-optical (NLO) properties are known from the literature; in this context see, for example: S. R. Marder, J. E. Sohn, G. D. Stucky “Materials for Nonlinear Optics”, ACS Symposium Series, Vol. 455 (1991), pages 128 to 156, R. A. Norwood et al. in L. A. Hornak “Polymers for Lightwave and Integrated Optics”, Marcel Dekker, Inc., New York 1992, pages 287 to 320, and G. J. Ashwell, D. Bloor “Organic Materials for Nonlinear Optics”, Royal Society of Chemistry, Cambridge 1993, pages 139 to 155 and 332 to 343.
An overview of current problems in the development of materials having pronounced NLO properties was recently published by T. J. Marks and M. A. Ratner in Angew. Chem. 107 (1995), pages 167 to 187. In addition to the requirements that have to be set for nonlinear-optical chromophores, reference is also made to the problems in developing polymeric matrices for the embedding or binding of chromophores, and their orientation-stable alignment.
In order for such polymers, which are provided with covalently bonded or dissolved NLO chromophores, become nonlinear-optically active and have a high 2nd-order susceptibility, the chromophores must be oriented in an electrical field (in this respect, see: J. D. Swalen et al. in J. Messier, F. Kajzar, P. Prasad “Organic Molecules for Nonlinear Optics and Photonics”, Kluwer Academic Publishers 1991, pages 433 to 445). This normally takes place in the region of the glass transition temperature, where the mobility of the chain segments of the polymers allows orientation of the NLO chromophores. The orientation obtained in the field is then frozen in by cooling. The 2nd-order susceptibility &khgr;
(2)
that is achievable here is proportional to the spatial density of the hyperpolarizability &bgr;, to the ground-state dipole moment &mgr;
o
of the chromophores, to the electrical poling field, and to parameters which describe the distribution of orientation following the poling process (in this respect, see: K. D. Singer et al. in P. N. Prasad, D. R. Ulrich “Nonlinear Optical and Electroactive Polymers”, Plenum Press, New York 1988, pages 189 to 204).
Great interest attaches to compounds combining high dipole moment with high values of &bgr;. Consequently, investigation has focused in particular on those chromophores which consist of conjugated &pgr; electron systems that carry an electron donor at one end and an electron acceptor at the other end and are covalently bonded to a polymer: for example, to polymethyl methacrylate (U.S. Pat. No. 4,915,491), polyurethane (EP-A 0 350 112), or polysiloxane (U.S. Pat. No. 4,796,976).
One particular problem of said polymer materials having NLO properties is the relaxation of the oriented chromophore units and thus the loss of NLO activity. At present, this relaxation is still preventing the production of electrooptical components with long-term stability that are deployable technically.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide nonlinear-optically active copolymers and polyadducts produced from them by means of which post-orientation relaxation of the nonlinear-optically active units in the NLO polymers is prevented or at least retarded. Moreover, the nonlinear-optically active polymers should exhibit low optical losses. The aim of the present invention is in particular to provide NLO polymers with which relaxation of the chromophores is prevented up to temperatures of above 100° C. and which comprise those nonlinear-optical units which ensure thermal stability at temperatures of more than 200° C. In addition to this, the NLO polymers should allow extremely wide variation of the optical properties of the electrooptical and photonic components.
In order to achieve this object the present invention provides nonlinear-optically active copolymers of the general formula 1
in which R
1
, R
2
, R
3
, X
1
, X
2
, X
3
, Y
1
, Y
2
, Y
3
, Z, l, m and n are as defined below. These are, therefore, nonlinear-optical, glycidyl-functional copolymers which in accordance with the invention can be reacted by crosslinking with a carboxyl-functional polyester having an appropriate degree of polymerization, to give the polyadducts that are likewise of the present invention.
The use of polyadducts based on glycidyl-functional nonlinear-optically active copolymers is known per se. DE-A 196 39 381 proposes a material for which a polymer comprising a nonlinear-optical group and glycidyl groups is crosslinked by coreaction with cyanates or prepolymers in order to achieve a stable orientation of the chromophore units. However, it has been found that the resulting material possesses only a low film-forming tendency, and low thermal stability under poling conditions.
Surprisingly, it has been possible to eliminate these is disadvantages by virtue of the nonlinear-optically active copolymers of the general formula 1 of the present invention and, respectively, by the polyadducts obtained from them by crosslinking with a carboxyl-functional polyester.
The nonlinear-optical polyadducts of the present invention are prepared by crosslinking a nonlinear-optically active copolymer of the general formula 1 having a proportion from 5 to 95 mol % of glycidyl groups, preferably from 20 to 80 mol %, and having a proportion of from 5 to 95 mol %, preferably from 20 to 80 mol %, of simple linear or branched and also cyclic esters, preferably of the cyclohexyl series, with at least one carboxyl-functional polyester. Advantageously, there are from 0.1 to 5 gram equivalents of the polyester component, based on the number of carboxyl groups employed, preferably from 0.4 to 2.7 gram equivalents, per gram equivalent of glycidyl groups of the NLO copolymer. As a result of the coreaction of the glycidyl groups of the NLO copolymer and the polyester component, tightly crosslinked polymer layers are produced in the polymer film.
In the production of the electrooptical or photonic components, the above-mentioned orientation and crosslinking take place on a support, where the crosslinked polyadduct forms the functional layer which is arranged between two buffer layers. With advantage, one or both buffer layers of the electrooptical or photonic components according to the invention can also consist, like the functional layer, of an appropriate crosslinked NLO polymer. It is known that in that case the refractive index of the buffer layers is somewhat lower than that of the functional layer. The required difference in refractive index (from the light-guiding functional layer or from its waveguide structure) is established by means of an appropriate composition of the copolymers with and without nonlinear-optical units.
The nonlinear-optically active, glycidyl-functional copolymers are preferably compounds
Fricke Christian
Hartmann Horst
Kanitz Andreas
Kuhne Karsten
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Truong Duc
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