Optical waveguides – Having particular optical characteristic modifying chemical... – Of waveguide core
Patent
1992-04-15
1993-10-12
Gonzalez, Frank
Optical waveguides
Having particular optical characteristic modifying chemical...
Of waveguide core
385124, 385145, 359652, 359653, 359654, 264 15, G02B 618
Patent
active
052533239
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
This invention relates to a method of manufacturing a multimode optical transmission medium made of synthetic resin, which transmission medium has the optional distribution of refractive index varying continuously in a fixed direction. More particularly, the invention relates to a method of manufacturing a multimode optical transmission medium having the distribution of refractive index varying continuously in a fixed direction, such as optical lenses and optical fibers, in which the polymerization is caused to proceed utilizing the effect of diffusion or exclusion of a monomer in the gel formed at the polymerization initiating terminal.
Background Art
As the modes of optical transmission with optical transmission media such as lenses and fibers, there are two types of single mode type and multimode type.
Among multimode type ones, the graded index type optical transmission media having the distribution of refractive index varying continuously in a fixed direction, are widely used as bar lenses having the function of convex lens, those having the function of concave lenses and broad band optical transmission fibers. Among them, the optical transmission media made of transparent synthetic resins are more widely used in recent years because they have several advantages in view of lightness in weight, economy, easy handling, high impact resistance and flexibility as compared with those made of quartz.
Concerning the method of producing optical transmission media of refractive index distribution type which are made of synthetic resins in specific reaction vessels, there are proposed the following methods in the conventional art.
In Japanese Patent Publication No. 52-5857 (U.S. Pat. No. 3,955,015), a monomer to form a polymer of a different refractive index is subjected to diffusional transfer into a specific transparent solid substance in a polymerization process having a previously formed three-dimensional network structure. After that, the whole polymerization reaction is stopped to obtain an optical transmission medium of refractive index distribution type.
In this method, however, it is necessary that the transparent solid substance is previously made into three-dimensional network structure using a multifunctional radical polymerizable monomer, in order to maintain the configuration of the transparent solid substance. For this reason, it must previously be made separately, which costs much labor. In addition, the obtained polymer of three-dimensional network structure is not good in thermoplasticity and it is not suitable for drawing and other post-forming processes. In other words, the plastics-made optical transmission fibers should have stiffness and tensile strength as fiber materials in the drawing step of manufacturing process. However, the optical transmission medium prepared through the above process has inherently three-dimensional network structure, so that it is not suitable for drawing.
In Japanese Patent Publication No. 54-30301 and Japanese Laid-Open Patent Publication No. 61-130904 are proposed methods for producing optical transmission media having refractive index gradients paying attention to the difference between the monomer reactivity ratios: r.sub.1 and r.sub.2 of two kinds of monomers.
In the above methods utilizing the difference between the monomer reactivity ratios of monomers, it is desirable that the difference between the radical copolymerization reactivity ratios of r.sub.1 and r.sub.2 is large, as a result, the formation of homopolymer occurs at first and macromolecules of homopolymer are formed with causing phase separation, which sometimes makes the obtained optical transmission medium clouded to reduce the optical transmission efficiency.
When too large monomer reactivity ratios are selected, one of monomers must be the one having a low rate of polymerization such as vinyl benzoate and vinyl o-chlorobenzoate used in the example of Japanese Patent Publication No. 54-30301, and vinyl phenylacetate used in the example of Japanese Laid-Open
REFERENCES:
patent: 3955015 (1976-05-01), Ohtsuka et al.
patent: 3999834 (1976-12-01), Ohtomo et al.
patent: 4842783 (1989-06-01), Blaylock
patent: 5037615 (1991-08-01), Kane
Koike Yasuhiro
Nihei Eisuke
Gonzalez Frank
Koike Yasuhiro
Nippon Petrochemicals Company Limited
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