Plastic lens

Details Plastic lens Plastic lens

2002-03-06

2004-08-24

Boykin, Terressa (Department: 1711)

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

Synthetic resins

Treating polymer containing material or treating a solid...

C528S196000, C528S198000, C528S50200C

Reexamination Certificate

active

06780965

ABSTRACT:

DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a plastic lens and a copolycarbonate resin to be used therefor. More specifically, it relates to a plastic lens and a copolycarbonate resin having transparency, heat resistance and impact resistance at high levels, having a well balance between a refractive index and an Abbe's number and having a low birefringence. The copolycarbonate resin of the present invention is excellent in the above optical properties and physical properties, so that it can be applied not only to various plastic lenses but also other optical molded articles, and since it is also excellent in flowability, it is suitable for easily molding and processing these molded articles.
2. Prior Art
A polycarbonate resin (to be sometimes referred to as “PC” hereinafter) is a polymer formed by bonding bisphenols with carbonate ester, and above all, a polycarbonate resin obtained from 2,2-bis(4-hydroxyphenyl)propane (so-called bisphenol A) is excellent in transparency and heat resistance and has properties excellent in mechanical properties such as impact resistance, so that it is used in many fields. In the optical fields of various lenses and optical disks, it attracts attention to its properties such as impact resistance, transparency and low water absorption, and it holds an important position as a material for optical use.
In the field of lenses in particular, PC that is a thermoplastic resin is of great interest thanks to excellent productivity and processibility, and demands thereof are increasing as a substitute for thermosetting resins typified by CR-39 (diethylene glycol bisallyl carbonate) that has been a mainstream material for plastic lenses.
However, a polycarbonate resin obtained by reacting bisphenol A with phosgene or a carbonate precursor substance such as diphenyl carbonate has a high refractive index of 1.585 but has a low Abbe's number of 30, so that it is liable to suffer a chromatic aberration problem and has a defect that it has a poor balance between the refractive index and the Abbe's number. Further, it has a defect that it has a large photoelasticity constant whereby molded article therefrom comes to have a large birefringence.
For overcoming the above defects of the polycarbonate resin, there have been proposed some copolycarbonate resins formed from bisphenols and aliphatic diols (JP-A-1-66234, JP-A-10-120777, JP-A-11-228683, JP-A-11-349676 and JP-A-2000-63506). These techniques involve problems that polycarbonate resins have a low refractive index and a low Abbe's number, that polycarbonate resins have a large photoelasticity constant and therefore come to have a large birefringence, that the moldability, heat resistance, etc., thereof are insufficient for obtaining satisfactory molded articles and that polycarbonate resins are colored.
PROBLEMS TO BE SOLVED BY THE INVENTION
It is a first object of the present invention to provide a plastic lens, particularly, a spectacle lens, which is excellent in transparency, heat resistance and impact resistance.
It is a second object of the present invention to provide a plastic lens, particularly, a spectacle lens, which has a good balance between refractive index and an Abbe's number and has a refractive index and an Abbe's number at good levels, and which has a low photoelasticity constant.
It is a third object of the present invention to provide an optical molded article having the above physical properties and optical properties.
It is another object of the present invention to provide a copolycarbonate resin that is suitable for producing the above plastic lens and the above optical molded article and has excellent flowability.
It is still another object of the present invention to provide means that permits production of a copolycarbonate resin having the above various excellent properties at a relatively low cost by selecting industrially advantageous raw materials and polymerization method(s).
MEANS TO SOLVE THE PROBLEMS
For overcoming the above problems, the present inventors have made studies in various ways and as a result have found that a lens formed of a copolycarbonate resin obtained from a dihydroxy compound component containing constant amounts of cyclohexanedimethanol and a specific bisphenol achieves the above objects of the present invention, and the present invention has been accordingly reached.
That is, according to the present invention, there is provided a plastic lens formed of a copolycarbonate resin comprising a structural unit (I) of the following general formula (I),
and a structural unit (II) of the following formula (II),
the structural unit (I) having a molar amount percentage of 15 to 85% on the basis of the total amount of the structural units (I) and (II).
In the above structural unit (II), each of R
1
and R
2
is independently a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, each of q and r is independently an integer of 0 to 4, W is a group represented by
wherein each of R
3
and R
4
are the same as, or different from, each other and each is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, each of R
5
and R
6
is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, p is an integer of 4 to 7, and each of R
7
and R
8
is independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms.
The plastic lens of the present invention is not only excellent in transparency, impact resistance and heat resistance but also has a good balance between a refractive index and an Abbe's number, and it also has a low photoelasticity constant, so that it is particularly suitable as a spectacle lens. Moreover, it has high surface hardcoating properties and high impact resistance, so that there is provided a spectacle lens that has a small thickness but has high practical utility.
As far as the present inventors have searched for literatures, there are some literatures on copolycarbonate resins obtained by polymerizing cyclohexanedimethanol (CHDM) as a dihydroxy component together with bisphenol. Such literatures will be briefly described below.
(1) U.S. Pat. No. 4,501,875 (JP-A-59-74121)
This literature describes a copolycarbonate resin that is improved in processability by reacting dihdyric phenol and bishaloformate of aliphatic (or alicyclic) glycol with phosgene. Specifically, it is only described that a polycarbonate obtained by copolymerization of 4 mol % of bischloroformate of CHDM and bisphenol A is improved in flowability (melt flow) as compared with a polycarbonate obtained from bisphenol A alone, and that the thus-obtained polycarbonate shows a impact resistance value, a loaded flexure temperature and ductility nearly equivalent to those of the polycarbonate obtained from bisphenol A alone.
(2) JP-A-63-92642
This literature describes that a copolycarbonate obtained by ester exchange of bisphenol A and 2 to 4 mol %, based thereon, of CHDM with diphenyl carbonate is used as an optical disk substrate.
(3) JP-A-8-302005
This literature describes that a copolycarbonate is obtained by polymerization of bisphenol A and CHDM (4 mol %) with diphenyl carbonate according to an ester exchange reaction, that a large amount of the diphenyl carbonate is used in this case so that a polymer whose hydroxy terminal group content is extremely decreased can be obtained, and that the above polymer is improved in hydrolysis resistance.
(4) European Polymer Journal, Vol. 12, pp 279-282 (1976)
This literature describes that a copolycarbonate is obtained by uniform-solution polymerization of bisphenol A and CHDM with phosgene in a methylene chloride solvent in the presence of pyridine as an acid binder and th

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