Optical waveguides – Having particular optical characteristic modifying chemical... – Of waveguide core
Patent
1991-12-12
1992-12-29
Schofer, Joseph L.
Optical waveguides
Having particular optical characteristic modifying chemical...
Of waveguide core
385145, 526245, G02B 602
Patent
active
051757907
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to amorphous polymers which contain units of 2,3-difluoroacrylic acid esters and have a high glass transition temperature and a high transparency.
BACKGROUND OF THE INVENTION
The copolymerization of methyl 2,3-difluoroacrylate with .alpha.,.beta.,.beta.-trifluorostyrene is known (q.v. Tevlina A.S. et al., VINITI 127-81 (1981)). The properties of the copolymers formed were not published.
A transparent molding compound containing monomer groups derived from 2,3-difluoroacrylic acid of fluorinated, chlorinated or brominated polycyclic alcohols has also been disclosed (q.v. DE 3707923). Nothing is known of the properties of these compounds.
Transparent thermoplastic molding compounds which are derived from (meth)acrylates of cyclic alcohols are disclosed in EP-A 282,019. The refractive indices of these polymers are about 1.43, frequently even above 1.52.
Furthermore, an optical material is known which consists of polymeric 2-fluoroacrylic acid esters of, in particular, aliphatic alcohols, it being possible for said esters to contain deuterium atoms both in the alcohol component and in the .beta.-position of the 2-fluoroacrylic acid component (q.v. EP 128517). These polymers have refractive indices of between 1.45 and 1.60 and glass transition temperatures of between 100 and 200.degree. C. and are used as the core material for optical fibers (beam waveguides).
The preparation and properties of polymers of fluoroalkyl 2-fluoroacrylates are also known (q.v. EP 128516). The polymers are prepared by free radical-initiated bulk, solution or suspension polymerization of the monomers in the presence of a chain transfer agent at a temperature of between 0.degree. and 100.degree. C. They have refractive indices of between 1.36 and 1.44 and softening points of between 80.degree. and 140.degree. C.
These polymers still contain two hydrogen atoms in the acid component and perhaps further hydrogen atoms in the alcohol component, thereby impairing the transparency of the polymers in the visible and near infrared regions of the electromagnetic spectrum.
Moreover, it has already been proposed to use beam waveguides of poly(2-fluoroacrylic acid esters) in the core and either poly(2,3-difluoroacrylic acid esters) or copolymers of TFE, perfluoroalkyl vinyl ethers and .omega.-alkoxycarbonyl (perfluoroalkyl vinyl ethers) in the sheath of a beam waveguide.
OBJECTS AND SUMMARY OF THE INVENTION
The object of the invention was to provide a polymer which had a high transparency in the wavelength region of visible light and at the same time a high glass transition temperature, and which could be processed to form beam waveguides for long transmission distances and high continuous use temperatures.
The invention relates to a transparent thermoplastic molding compound consisting of 10 to 100% by weight of units derived from one or more esters of formula I: ##STR1## wherein X is a hydrogen atom or a deuterium atom and -C.sub.10 aryl group, it being possible for all or some of the hydrogen atoms in R to be replaced with fluorine, chlorine, bromine or deuterium atoms, and 90 to 0% by weight of units derived from other copolymerizable vinyl compounds.
The invention further relates to the preparation of the molding compounds and to their use for the manufacture of optical objects, especially beam waveguides.
In formula I, X is a hydrogen atom or a deuterium atom and R is a linear or branched C.sub.1 -C.sub.10 alkyl group or a C.sub.6 -C.sub.10 aryl group, preferably a phenyl or benzyl group, it being possible for all or some of the hydrogen atoms in R to be replaced with fluorine, chlorine or bromine atoms.
The acid component of the esters preferably consists of 2,3-difluoroacrylic acid or 3-deutero-2,3-difluoroacrylic acid, especially 3-deutero-2,3-difluoroacrylic acid.
The alcohol component is preferably methanol or a fluorinated or chlorinated linear or branched alcohols or an aromatic alcohol having 2 to 10 carbon atoms. Especially preferred alcohol components are methanol, fluorinated and
REFERENCES:
patent: 4863236 (1989-09-01), Herbrechtsmeier
patent: 5081165 (1992-01-01), Inukai et al.
Groh Werner
Herbrechtsmeier Peter
Heumuller Rudolf
Theis Jurgen
Wieners Gerhard
Hoechst Aktiengesellschaft
Sarofim N.
Schofer Joseph L.
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