Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-11-09
2002-10-29
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S075000, C351S159000
Reexamination Certificate
active
06472495
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition for producing resins. The resin produced from the composition of the present invention is advantageously used as optical materials for plastic lenses, prisms, optical fibers, substrates of information recording media and filters, particularly as a material for plastic spectacle lenses.
2. Description of the Prior Art
Plastic materials have been widely used in various optical applications, particularly in manufacturing spectacle lenses, because of their light weight, toughness and easiness of dyeing. Optical products, particularly spectacle lenses are required to have, in addition to a low specific gravity, optical properties such as a high refractive index and a large Abbe's number and physical properties such as high heat resistance and large mechanical strength. A large refractive index can decrease thickness of a lens. A large Abbe's number is important to avoid chromatic aberration of a lens. A high heat resistance and a large mechanical strength are important to facilitate fabrication and also for safety.
As high refractive index materials, thermosetting optical materials having a thiourethane structure derived from the reaction of a polythiol compound and a polyisocyanate compound have been proposed in Japanese Patent Publication No. 458489 and U.S. Pat. No. 5,294,666. Japanese Patent Application Laid-Open Nos. 1-98615 and 3-81320 and EP-A-0374258 disclose the production of lenses by polymerization of an epoxy resin or an episulfide resin with a multi-functional compound. Nevertheless, higher refractive index is still demanded. A small chromatic aberration is another important property required for optical materials. The larger the Abbe's number, the smaller the chromatic aberration. Therefore, a material having a large Abbe's number is desired. Thus, a material simultaneously satisfying high refractive index and large Abbe's number is demanded.
However, the Abbe's number tends to decrease with increase in the refractive index. Plastic materials made of known compounds have the maximum Abbe's number of about 50 to 55 when the refractive index is 1.50 to 1.55, about 40 when the refractive index is 1.60 and about 31 when the refractive index is 1.66. When tried to achieve a refractive index of 1.70 or higher, no optical material suitable for practical use was obtained because the Abbe's number was as small as 30 or less.
In addition, known thiourethane materials require to increase the molecular weight of the starting sulfur compound for achieving a high refractive index, this decreasing crosslinking density. In contrast, the content of alkyl groups should be increased to achieve a large Abbe's number, this decreasing the rigidity of molecules of the starting compounds to result in drawbacks such as poor heat resistance. Namely, there is a limit to known optical materials obtained from episulfide compounds, polythiol compounds and isocyanate compounds in achieving a high refractive index. Moreover, an increase in the refractive index decreases the Abbe's number. Therefore, known optical materials cannot achieve simultaneous satisfaction of high refractive index and large Abbe's number.
To solve the above problems, the inventors found novel sulfur-containing compounds which were capable of providing thin optical materials with small chromatic aberration (U.S. Pat. Nos. 5,807,975 and 5,945,504). The inventors further found resin compositions which improved the oxidation resistance and dyeability of optical materials obtained by curing the above sulfur-containing compounds by polymerization (U.S. Pat. No. 6,117,923 and European Patent Application EP 0 921 417). However, optical materials obtained from these compositions are still insufficient in impact resistance. A small impact resistance requires a thickness large enough to practical use. This prevents the reduction in the thickness and weight, although the high refractive index of the optical materials has enabled to reducing the thickness.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the impact resistance of a resin obtained by curing sulfur-containing compounds by polymerization.
After extensive study in view of the above object, the inventors have found that the object can be achieved by a resin obtained by curing a composition by polymerization, which composition comprises (a) 30 to 95% by weight of a compound having, in one molecule, one or more structures represented by the following formula (1):
wherein R
1
is a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms, R
2
, R
3
and R
4
are each hydrogen or a hydrocarbon group having 1 to 10 carbon atoms, Y is O, S, Se or Te, m is an integer of 1 to 5 and n is an integer of 0 to 5; (b) 1 to 40% by weight of a compound having at least one group selected from the group consisting of isocyanate group and isothiocyanate group in one molecule; and (c) 1 to 50% by weight of a compound having at least one mercapto group in one molecule.
DETAILED DESCRIPTION OF THE INVENTION
In the composition of the present invention, the amount ratio of the compound (a), compound (b) and compound (c) is not strictly limited because it depends on the refractive index and viscosity of the respective compounds and the intended physical properties of the obtained resin, and preferably 30 to 95% by weight for the compound (a), 1 to 40% by weight for the compound (b) and 1 to 50% by weight for the compound (c). The amount ratios outside the above ranges result in failure to obtain the high impact resistance which is the object of the present invention. Other drawbacks are poor heat resistance, deterioration of color tone of the cured product and failure in simultaneous satisfaction of a high refractive index and a large Abbe's number. More preferred ranges are 50 to 95% by weight for the compound (a), 1 to 25% by weight for the compound (b) and 1 to 35% by weight for the compound (c). Particularly preferred ranges are 60 to 90% by weight for the compound (a), 3 to 15% by weight for the compound (b) and 5 to 25% by weight for the compound (c). The weight percentages of the compounds (a), (b) and (c) are suitably selected from the above respective ranges so that the total of the weight percentages of the compounds (a), (b) and (c) adds up to 100% by weight.
To further improve the impact resistance of the resin obtained by curing the composition by polymerization, it is preferable that the compound (a) has at least two structures represented by the formula (1) in one molecule, the compound (b) has at least two groups selected from the group consisting of isocyanate group and isothiocyanate group in one molecule and the compound (c) has at least two mercapto groups in one molecule.
To obtain a high refractive index, in the formula (1), R
1
is preferably a hydrocarbon group having 0 to 2 carbon atoms and R
2
, R
3
and R
4
are each preferably hydrogen atom or methyl group. More preferably, R
1
is a hydrocarbon group having 0 to 1 carbon atom and R
2
, R
3
and R
4
are each hydrogen atom. It is preferable that the compound (c) has a sulfur atom in addition to the sulfur atom in the mercapto group and more preferably has a sulfide linkage.
Examples of the compound (a) are listed below while classified into the groups (A) to (E):
(A) Compounds (a) having in one molecule at least one structure represented by the formula (1) wherein n is 0;
(B) Compounds (a) having in one molecule at least one structure represented by the formula (1) wherein Y is O;
(C) Compounds (a) having in one molecule at least one structure represented by the formula (1) wherein Y is S;
(D) Compounds (a) having in one molecule at least one structure represented by the formula (1) wherein Y is Se; and
(E) Compounds (a) having in one molecule at least one structure represented by the formula (1) wherein Y is Te.
The group (A) to (E) compounds has a backbone structure derived from a chain compound, a branched compound, an ali
Horikoshi Hiroshi
Niimi Atsuki
Takeuchi Motoharu
Yoshimura Yuichi
Gorr Rachel
Mitsubishi Gas Chemical Company Inc.
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