Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-11-22
2004-03-16
Lambkin, Deborah C (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C351S159000
Reexamination Certificate
active
06706894
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority under 35 U.S.C. § 119 of Japanese Application No. 2001-362377, filed Nov. 28, 2001, the disclosure of which is expressly incorporated by reference herein in its entirety.
DESCRIPTION
1. Field of the Invention
The present invention relates to thiol compounds, to a method for producing the same, and to an optical product made with the same. The invention generally relates to thiol compounds that may give optical materials having a high refractive index and a high Abbe's number and having excellent heat resistance and transparency. The invention also relates to a method for producing the same and to an optical product made with the same.
2. Background of the Invention
Plastics are used for various optical applications these days, for example, for lenses and others, as being lightweight, difficult to break, and easily colored when compared with glass. Optical plastic materials include poly(diethylene glycol bisallylcarbonate) (CR-39) and poly(methyl methacrylate). These plastics, however, have a refractive index of 1.50 or less. Therefore, for example, when they are used as lens materials, the lenses produced need to be thicker for increased power, and they lose the advantage of being lightweight. In particular, powerful concave lenses are thick at their periphery, and are therefore unfavorable as causing birefringence and chromatic aberration. For spectacles, such thick lenses are often not aesthetic. To obtain thin lenses, materials with higher refractive index may be used. In general, the Abbe's number of glass and plastics decreases with the increase in their refractive index, and, as a result, their chromatic aberration increases. Accordingly, plastic materials having a high refractive index and a high Abbe's number are desired.
Plastic materials proposed as having such properties include, for example, (1) polyurethanes obtained through addition-polymerization of a polythiol having bromine in the molecule and a polyisocyanate (Japanese Patent Laid-Open No. 164615/1983); and (2) polythiourethanes obtained through addition-polymerization of a polythiol and a polyisocyanate (Japanese Patent Publication No. 58489/1992 and Japanese Patent Laid-Open 148340/1993). For the starting material, polythiol for the polythiourethanes of above (2), may be branched polythiols having an increased sulfur content (Japanese Patent Laid-Open Nos. 270859/1990 and 148340/1993), and polythiols into which is introduced a dithiane structure for increasing their sulfur content (Japanese Patent Publication No. 5323/1994 and Japanese Patent Laid-Open No. 118390/1995). Other plastic materials proposed as having such properties include (3) polymers of an alkyl sulfide having a polymerization-functional group, episulfide (Japanese Patent Laid-Open Nos. 71580/1997 and 110979/1997). However, though their refractive index is increased a little, the polyurethanes of (1) above still have a low Abbe's number and have some other drawbacks in that their lightfastness is poor, their specific gravity is high and therefore, they are not lightweight. The polythiourethanes (2), those for which the starting polythiol used has a high sulfur content, have an increased refractive index of from about 1.60 to 1.68, but their Abbe's number is lower than that of optical inorganic glass having a refractive index on the same level. Therefore, they still have a problem in that their Abbe's number must be increased more. On the other hand, one example of the alkyl sulfide polymers (3) having an Abbe's number of 36 has an increased refractive index of 1.70. The lenses obtained by using this polymer can be extremely thin and lightweight. However, plastic materials having increased Abbe's number and the refractive index are still desired.
SUMMARY OF THE INVENTION
The present invention has been made to address the problems noted above. The present invention provides thiol compounds that may give optical materials having a high refractive index and a high Abbe's number and having excellent heat resistance and transparency. The present invention also provides a method for producing the same and provides an optical product made with the same.
The present inventors have determined that thiol compounds with mercaptomethyl or mercaptoethyl groups bonded to a 1,3,5-trithiane ring are useful in solving the above-noted problems, and that the compounds may be efficiently produced in a specific method.
Specifically, the invention provides a thiol compound represented by the general formula (1):
wherein n is 1 or 2.
The invention also provides a method for producing the thiol compound represented by the general formula (1) via an intermediate, i.e., 1,3,5-trithiane having a methylene or vinyl group at the 2,4,6-positions thereof, wherein the groups at the 2-, 4-, and 6-positions may be identical or different.
DESCRIPTION OF THE INVENTION
The particulars shown herein are by way of example and for purposes of illustrative discussion of the various embodiments of the present invention only. In this regard, no attempt is made to show details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
Unless otherwise stated, a reference to a compound or component, includes the compound or component by itself, as well as in combination with other compounds or components, such as mixtures of compounds.
The thiol compounds of the invention may be represented by the general formula (1) mentioned below, from which it is seen that the compound has three mercaptoalkyl groups bonded to the trithiane ring thereof, wherein the mercaptoalkyl groups in a given compound may be identical or different.
wherein n is 1 or 2.
The trithiane ring of the thiol compound represented by the general formula (1) has a high sulfur content, in which the atomic refraction is high and which therefore significantly increases the refractive index of the polymers obtained by using the thiol compounds of the invention. In addition, the polymerization-functional, terminal thiol groups in the thiol compound contribute toward introducing sulfur atoms into the main chain of the polymers of the compound, and therefore, the refractive index of the polymers obtained by using the thiol compounds of the invention is further increased. In general, the Abbe's number of amorphous materials is apt to decrease with the increase in the refractive index thereof. One problem with polymers having high sulfur content is that the electron resonance of sulfur is remarkable, therefore often significantly reducing the Abbe's number. However, the thiol compounds of the invention are free from this problem. Another cause of the increase in the refractive index is the decrease in the molar volume thereof. This is often seen in polymers having a high crosslinking density and a strong intermolecular force. The thiol compounds of the invention have three polymerization-functional groups, and the refractive index of its polymers is increased especially by the former effect. In the general formula (1), the increase in the number
n
lowers the sulfur content and the crosslinking density, therefore giving polymers having a reduced refractive index. Accordingly,
n
is generally 1 or 2. In addition, since the glass transition temperature (Tg) of the polymers obtained by using the thiol compounds of the invention lowers with the increase in
n
in the general formula (1),
n
is generally 1 or 2 in order to obtain polymers having good heat resistance.
For example, the thiol compound represented by the general formula (1) of the invention includes 2,4,6-tris(mercaptomethyl)-1,3,5-trithiane and 2,4,6-tris(mercaptoethyl)-1,3,5-trithiane.
A method for producing a thiol compound represented by the general formula (1) may comprise forming a 1,3,5-trithiane having methylene or vinyl groups at the 2,4,6-positions thereof, and r
Okubo Tsuyoshi
Takamatsu Ken
Finnegan Henderson Farabow Garrett & Dunner LLP
Hoya Corporation
Lambkin Deborah C
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