Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-03-16
2001-03-13
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06201061
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an optical material such as a plastic lens, a prism, an optical fiber, a substrate of information recording materials and a filter, and more particularly, to a process for producing a plastic lens of glasses having excellent color tone and transparency.
2. Description of the Related Arts
Plastic materials have widely been used as various optical materials, particularly as lenses of their glasses, because of light weight, toughness and easiness of tinting. The properties required for optical materials, as particularly for lenses of glasses, are a low specific gravity and optical properties such as a large refractive index and a large Abbe number. It is also required that optical materials are colorless and transparent and show no change in color tone after use for a long time. A large refractive index is important to decrease the thickness of a lens. A large Abbe number is important to decrease the chromatic aberration of a lens and to decrease fatigue of eyes.
As conventional materials having a large refractive index, thermosetting optical materials having a thiourethane structure which are obtained by the reaction of a polythiol compound and a polyisocyanate compound have been proposed (Japanese Patent Publication Heisei 4(1992)-58489 and Japanese Patent Application Laid-Open No. Heisei 5(1993)-148340). Technology to obtain a lens by copolymerization of an epoxy resin or an epithio resin with a multi-functional compound have also been proposed in the specifications of Japanese Patent Application Laid-Open No. Heisei 1(1989)-98615, Japanese Patent Application Laid-Open No. Heisei 3(1991)-81320 and International Publication No. WO8910575. However, in accordance with the above technologies, a molecular design for an increase in the refractivity index causes a decrease in the Abbe number and it is difficult to obtain a balance between a sufficiently high refractivity index and a large Abbe number.
To overcome the above problem, the present inventors discovered compounds containing sulfur which have a novel structure containing an epithio structure or an epithioalkylthio structure and optical materials obtained by curing the compounds by polymerization.
However, the above optical materials tend to show change in color to a yellowish or greenish color when the materials are left standing for a long time and improvement in light resistance has been desired.
As the result of studies on the coloration, it was found that the problem can be overcome by addition of an ultraviolet light absorbent.
However, the addition of an ultraviolet light absorbent gave rise to a new problem in that the optical materials are colored after being prepared and are also clouded. In other words, the optical material having an epithio structure or an epithioalkylthio structure shows more marked coloring and clouding than those of conventional optical materials when an ultraviolet light absorbent is added. Therefore, it has been strongly desired that the above problems are overcome.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome the problems that resins which are obtained by curing a compound having an epithio structure or an epithioalkylthio structure by polymerization and show an excellent balance between the refractivity index and the Abbe number tend to show change in color after use for a long time and that a resin prepared by addition of an ultraviolet light to solve this problem is colored after being prepared (initial coloration), shows clouding of the material and cannot be used as an optical material, and in particular, as a lens.
The above problems can be solved by a process for producing a resin used for optical materials which process comprises, by polymerization in the presence of a catalyst, curing a composition comprising an ultraviolet light absorbent and an epithio compound having, in one molecule thereof, one or more structures represented by the following general formula (1):
wherein R
1
represents a hydrocarbon group having 1 to 10 carbon atoms, R
2
, R
3
and R
4
each represents hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, Y represents S or O and n represents 0 or 1;
wherein amounts of the ultraviolet light absorbent and the catalyst, each expressed as parts by weight per 100 parts by weight of the total amount of the epithio compound, the ultraviolet light absorbent and the catalyst, satisfy both of the following relations (a) and (b):
0.001≦ultraviolet light absorbent≦1.000 (a)
0.001≦catalyst≦5.000 (b)
DESCRIPTION OF THE PREFERRED EMBODIMENTS
To obtain a high refractivity index, a large Abbe number and an excellent balance between these properties which are the object of the present invention, it is preferable that R
1
in formula (1) represents a methylene group or an ethylene group and R
2
, R
3
and R
4
each represents a hydrogen atom or a methyl group. It is more preferable that R
1
represents a methylene group and R
2
, R
3
and R
4
each represents a hydrogen atom. The content of S is preferably 90% or more in average, more preferably 95% or more in average and most preferably substantially 100% of the total number of S and O constituting the three-membered ring. n preferably represents 1. Y may represent either S or O. It is preferable that the content of S is 50% or more in average, more preferably 90% or more in average and most preferably substantially 100% of the total number of S and O.
In the present invention, any compound having one or more structures represented by formula (1) in one molecule thereof can be used. The average number of the structure represented by formula (1) is preferably 1.3 or more and more preferably 2 or more in one molecule of the compound. Examples of the compound having one or more structures represented by general formula (1) in one molecule include the following compounds (A), (B) and (C):
(A) Organic compounds having one or more epithio groups
(B) Organic compounds having one or more epithioalkyloxy groups
(C) Organic compounds having one or more epithioalkylthio groups
Organic compounds (A), (B), and (C) have a chain backbone structure, an alicyclic backbone structure, an aromatic backbone structure or a heterocyclic backbone structure having nitrogen atom, oxygen atom or sulfur atom. The organic compounds may have a combination of epithio groups, epithioalkyloxy groups and epithioalkylthio groups in one molecule. The organic compound may also have sulfide linkages, ether linkages, sulfone linkages, ketone linkages, ester linkages, amide linkages or urethane linkages.
Preferable examples of the organic compound having one or more epithio groups of compound (A) include compounds obtained by replacing one or more epoxy groups in compounds having epoxy groups (not glycidyl groups) with epithio groups. Specific examples of the above compound include:
organic compounds having a chain aliphatic backbone structure such as 1,1-bis(epithioethyl)methane, 1-(epithioethyl)-1-(&bgr;-epithiopropyl)-methane, 1,1-bis(&bgr;-epithiopropyl)methane, 1-(epithioethyl)-1-(&bgr;-epithiopropyl)-ethane, 1,2-bis(&bgr;-epithiopropyl)ethane, 1-(epithioethyl)-3-(&bgr;-epithiopropyl)butane, 1,3-bis(&bgr;-epithiopropyl)propane, 1-(epithioethyl)-4-(&bgr;-epithiopropyl)pentane, 1,4-bis(&bgr;-epithiopropyl)butane, 1-(epithio-ethyl)-5-(&bgr;-epithiopropyl) hexane, 1-(epithioethyl)-2-(&ggr;-epithiobutylthio)-ethane, 1-(epithioethyl)-2-[2-(&ggr;-epithiobutylthio)ethylthio]ethane, tetrakis-(&bgr;-epithiopropyl)methane, 1,1,1-tris(&bgr;-epithiopropyl)propane, 1,3-bis(&bgr;-epithiopropyl)-1-(&bgr;-epithiopropyl)-2-thiapropane and 1,5-bis(&bgr;-epithiopropyl)-2,4-bis(&bgr;-epithiopropyl)-3-thiapentane;
compounds having an alicyclic backbone structure such as 1,2:3,4-diepithiocyclohexane, 1,2:4,5-diepthiocyclohexane, 4-epithioethyl-1,2-epithiocyclohexane, 1,3- and 1,4-bis(epithioethyl)cyclohexanes, 1,3- and 1,4-bis(&bgr;-epithiopropyl)cyclohexanes, bis[4-(epithioethyl)c
Amagai Akikazu
Mizuno Katsuyuki
Takeuchi Motoharu
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Michl Paul R.
Mitsubishi Gas Chemical Company Inc.
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