Plastic lens material and process for preparing the same

Details Plastic lens material and process for preparing the same Plastic lens material and process for preparing the same

1998-12-08

2000-04-25

Gorr, Rachel

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

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

528 79, 528 73, 523106, 526301, 351159, C08G 1867

Patent

active

060545038

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND ART

Plastic materials have begun being widely used as recent materials for optical lenses from the viewpoints of lightweight property, processability, stability, dyeability, high-volume production capability, reducibility in cost, etc.
Among various properties required 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 obtained, the use of such a lens permits reduction in the weight of a lens system, which occupies an important position in optical instruments, for example, microscopes, cameras and telescopes, and spectacle lenses.
Even in plastic lens materials, therefore, there is a tendency to attempt making their specific gravity further lower so as to stress predominance over materials for inorganic glass lenses.
For example, a diethylene glycol bisallyl carbonate resin designated "CR-39" is known as a plastic material for spectacle lenses spreading widest at present. However, the specific gravity of this resin is as comparatively high as 1.31 (in terms of a value measured at 20.degree. C.; the same shall apply to the following).
Besides, plastic lens materials containing halogen atoms or sulfur atoms have recently been known as materials for high-refractive index lenses. However, such plastic lens materials also have a specific gravity as comparatively high as about 1.3 to 1.4.
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 plastic lens materials having a comparatively low specific gravity. However, these thermoplastic resins do not have sufficient optical properties required from the viewpoint of practical use.
On the other hand, copolymers having a 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, "NIKON LIGHT DELUXE II" and the like have been put to practical use as plastic lens materials having a triazine ring structure. The specific gravity of the plastic lens material is as comparatively low as 1.17. However, this plastic lens material cannot be yet said to be satisfactory for more reducing the weight of plastic lenses.


DISCLOSURE OF THE INVENTION

The present invention has been made on the basis of the foregoing circumstances and has as its object the provision of a plastic lens material having both excellent optical and mechanical properties and moreover having a low specific gravity.
Another object of the present invention is to provide a process for producing a plastic lens material having various excellent properties and a low specific gravity.
The present inventors have carried out an extensive investigation with a view toward achieving the above objects. As a result, it has been found that when a reaction product obtained by subjecting a polyhydric alcohol, which is obtained by subjecting a dimer and/or a trimer of a specific higher unsaturated fatty acid to a reducing treatment, and an isocyanate compound having a radical-polymerizable unsaturated bond in its molecule to a urethanation reaction is radical-polymerized together with a monomer copolymerizable with the reaction product, a copolymer suitable for use as a lens material having a low specific gravity, excellent transparency and a high refractive index is obtained. The present invention has been led to completion on the basis of such a finding.
Namely, a plastic lens material according to the present invention comprises a copolymer obtained by polymerizing a monomer mixture comprising 20 to 80 mass % of a reaction product (hereinafter may also referred to as "radical-polymerizable urethane compound") obtained by subjecting the following component [A] and the following component [B] to a urethanation reaction in proportions that a ratio (b/a) of the number (b) of moles of an isocyanate group containe

REFERENCES:
patent: 5416880 (1995-05-01), Edwards et al.
patent: 5880171 (1999-03-01), Lim et al.

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