Plastic lens and production process thereof

Details Plastic lens and production process thereof Plastic lens and production process thereof

1996-10-16

1998-07-07

Michl, Paul R.

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

Synthetic resins

Processes of preparing a desired or intentional composition...

526322, 5263231, C08F 2020

Patent

active

057770000

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a plastic lens made of a synthetic resin and a production process thereof, and more particularly to a lightweight plastic lens formed of a crosslinked polymer and a production process thereof.


BACKGROUND ART

A variety of inorganic glass lenses have heretofore been used as optical lenses. In recent years, plastic lenses have begun being used widely other than the inorganic glass lenses owing to their good lightweight property, processability, safety, dyeability, high-volume production capability and reducibility in cost.
Among various required properties of materials for optical lenses, it is extremely important for them to have a low specific gravity. More specifically, if an optical lens formed of a material low in specific gravity is realized, the use of such a lens permits reduction in the weight of a lens system, which occupies a significant part in optical instruments, for example, microscopes, cameras, telescopes, etc., and spectacle lenses.
Even in the research and development of materials for plastic lenses, therefore, there is a tendency to attempt making their specific gravity still lower so as to stress predominance over materials for inorganic glass lenses.
For example, there has been known a diethylene glycol bisallyl carbonate resin designated "CR-39" as a plastic material for spectacle lenses, which has spread widest at present. However, the specific gravity of this resin is as comparatively high as 1.31 (as measured at 20.degree. C.; the same shall apply to the following).
Besides, materials for plastic lenses, which contain halogen or sulfur atoms, have recently been known as materials for high-refractive index lenses. Such a material for plastic lenses however has a specific gravity as comparatively high as 1.3-1.4 or so.
Further, thermoplastic resins such as polystyrene (specific gravity: 1.02), polymethyl methacrylate (specific gravity: 1.20) and polycarbonate (specific gravity: 1.19) have been known as materials for plastic lenses having comparatively low specific gravities. However, the polystyrene resin is low in hardness and lacking in solvent resistance, the polymethyl methacrylate resin is low in refractive index, and the polycarbonate resin is also low in hardness and lacking in impact resistance. Therefore, such materials cannot be said to have sufficient performance in use.
On the other hand, copolymers having crosslinked structure have been introduced as plastic lens materials excellent in various performance characteristics such as heat resistance, solvent resistance and mechanical strength. For example, a plastic lens material, "NIKON LIGHT DELUXE II" (trade name), which has triazine ring structure, or the like has been put to practical use. This plastic lens material has a specific gravity as comparatively low as 1.17. However, such a specific gravity is not said to be sufficient for more reducing the weight of plastic lenses.
In the conventional materials for plastic lenses, particularly, the copolymers having crosslinked structure, as described above, it is not said that the reduction in specific gravity has been fully achieved. There has thus been a strong demand for development of an optical material combining a high density of crosslinking with an extremely low specific gravity.


DISCLOSURE OF INVENTION

The present invention has been completed in view of the foregoing circumstances and has as its object the provision of a plastic lens formed of a crosslinked polymer being high in density of crosslinking and having excellent physical properties that the specific gravity is low, and moreover possessing good optical properties, as well as a production process thereof.
The plastic lens according to the present invention is characterized in that it is formed of a crosslinked polymer obtained by polymerizing or copolymerizing a monomer composition comprising as essential component the following component (A) and/or the following component (B), and optionally a component (C) composed of at least one monomer copolymerizabl

REFERENCES:
patent: 4513349 (1985-04-01), Olson
patent: 4515931 (1985-05-01), Olson

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