PLASTIC LENS WITH HIGH REFRACTIVE INDEX

Abstract: Plastic lens comprising a copolymer of diethylene glycol bisallyl carbonate, benzyl methacrylate, and diallyl isophthalate, which has a refractive index of a least 1.54, forms no clouding and no cords, and shows good physical and chemical properties as lens for spectacles.

Description: Description A high refractive plastic lens Technical Field This invention relates to a plastic lens with a high refractive index, and more particularly to a plastic spectacle lens whose refractive index (no) is at least 1.54. Background Art There have been plastic lenses produced by the cast polymerization of a monomer such as diethyleneglycolbisallylcarbonate (hereinafter referred to CR-39) or methylmethacrylate. These plastic lenses are superior in terms of the lightness, safety and dyeability, but are inferior in terms of the refractive index, to ordinary lenses of inorganic glass such as crown glass; the refractive index of the former is about 1.50, and the latter is about 1.523, so that the plastic lenses must be thicker than the inorganic glass lenses in the center and edge thereof. Therefore, developing a plastic lens with a high refractive index has been desired. There has been known heretofore a method for increasing refractive index in which a comonomer for increasing the refractive index is copolymerized with a monomer such as CR-39. But, such a comonomer must be the one capable of yielding the copolymer having not only a high refractive index, but also excellent physical and chemical properties, and good workability. But, such comonomer has not been discovered yet. For instance the copolymer of CR-39 and diallylisophthalate disclosed in Japanese Patent Disclosure No. 7787/1978, or a copolymer of CR-39 and benzylmethacrylate disclosed in Japanese Patent Disclosure No. 41965/1979 is known as a copolymer for plastic spectacle lens. However, the both copolymers are not endowed with all the good properties. The former copolymer can have a refractive index changed in the range of from 1.50 to 1.57, but increasing the refractive index causes decrease of the workability, and increasing the content of diallylisophthalate causes a considerable decrease of the superficial hardness, impact resistance, and dyeability. The latter copolymer also can have a refractive index changed in the range of from 1.50 to 1.57, but becomes to have a superficial hardness extremely lower than that of CR-39 homopolymer and becomes to have a surface on which glass coating by vacuum evaporation can not be conducted. And using an increased amount of benzylmethacrylate causes blur on the copolymer which is unfavorable for spectacle lens the official gazette of Japanese Patent Disclosure No. 41965/1979 discloses that the addition of a cross-linking agent in an amount up to 20 wt.% to the system of CR-39benzylmethacrylate enables the resulting polymer to improve the scratch resistance. However, the addition surely improve the scratch resistance, but simultaneously tends to give some blur or striac to the lens thereof even in the amount which is not sufficient to give a high refractive index. We have now found that a terpolymer consisting of CR-39, benzylmethacrylate and diallylisophthalate in an special composition range can give a plastic lens having a refractive index higher than 1.54, no blur and no striae and excellent physical and chemical properties which are suitable for spectacle lenses. The object of this invention is to provide a plastic lens having a refractive index of at least 1.54 and excellent physical and chemical properties and no blur and striae. Disclosure of Invention This invention relates to a higher refractive plastic lens comprised of a cross-linked terpolymer comprising CR-39, benzylmethacrylate, and diallylisophthalate, and having a refractive index of at least 1.54. Best Mode of Carrying Out the Invention In this invention, CR-39 is preferably used in an amount ranging from 5 to 40 wt.%, benzylmethacrylate is preferably used in an amount ranging from 5 to 40 wt.%, and diallylisophthalate is preferably used in an amount ranging from 90 to 20 wt.. Using CR-39 in an amount of above 40 wt.% enables the terpolymer to improve the physical and chemical properties such as scratch resistance, impact resistance, solvent resistance, weatherability, etc., but is liable to give the lens of the terpolymer a refractive index of below 1.54, blur and striae, which are unfavorable for spectacle lens. Using CR-39 in an amount of below S wt.t is liable to give the terpolymer bad physical and chemical properties, and bad workability, which are unfavorable in the practical use. Using benzylmethacrylate in an amount of above 40 wt.% is liable to give the terpolymer blur and striae and very bad workability. Using diallylisophthalate in an amount of above 90 wt.% is liable to give the terpolymer bad physical and chemical properties and bad workability, which are unfavorable. The high refractive plastic lens of this invention can be produced by a method comprising pouring a mixed solution consisting of CR-39, benzylmethacrylate, diallylisophthalate, and a polymerization initiator into a mold made of two plates of glass mold and a plastic gasket, and heating or irradiating with ultraviolet ray the one to cure it. The high refractive plastic lens of this invention differs from prior plastic lenses having only a higher refractive index in terms of having no blur and no striae, better workability, better optical, chemical and physical properties, so that they are preferable as spectacle lens. This invention will be more clearly understood with reference to the following examples, in which parts are weight parts. Example 1 A mixed solution consisting of 30 parts of CR-39, 10 parts of benzylmethacrylate, 60 parts of diallyl- isophthalate, and 3 parts of diisopropylperoxycarbonate was poured into a mold made of two plates of glass mold and a plastic gasket, and the resulting one was heated to raise gradually the temperature from 40"C to 900C in 24 hours to make a lens. The lens obtained was taken out of the mold, and then was heated at 1200C for one hour. The lens had 1.549 of refractive index, 90 % of transmittance, and no blur and no striae which are unfavorable for spectacle lens, and had the properties such as superficial hardness, dyeability, etc. which are as good as those of homopolymer of CR-39. Example 2 - 8, Comparative Example 1 - 4 The lenses were made in the same manner as in Example 1, except that compositions in Table 1 were used. The result is shown in Table 1. Table 1 EMI6.1 <tb> <SEP> Composition <SEP> (parts) <SEP> Refr. <SEP> % <SEP> Trans <tb> <SEP> CR-39 <SEP> BzMA <SEP> DAIP <SEP> Ind. <SEP> mittance <SEP> blur <SEP> striae <tb> Ex. <SEP> 1 <SEP> 30 <SEP> 10 <SEP> 60 <SEP> 1.549 <SEP> 91 <SEP> none <SEP> none <tb> <SEP> 2 <SEP> 30 <SEP> 20 <SEP> 50 <SEP> 1.549 <SEP> 91 <tb> <SEP> 3 <SEP> 30 <SEP> 30 <SEP> 40 <SEP> 1.548 <SEP> 91 <tb> <SEP> 4 <SEP> 35 <SEP> 15 <SEP> 50 <SEP> 1.546 <SEP> 91 <tb> <SEP> 5 <SEP> 5 <SEP> 40 <SEP> 10 <SEP> # <SEP> 50 <SEP> 1.542 <SEP> 91 <tb> <SEP> 6 <SEP> 20 <SEP> 20 <SEP> 60 <SEP> 1.556 <SEP> 90 <SEP> " <SEP> It <SEP> <tb> <SEP> 7 <SEP> 20 <SEP> 30 <SEP> 50 <SEP> 1.554 <SEP> 90 <tb> <SEP> 8 <SEP> 20 <SEP> 10 <SEP> 70 <SEP> 1.557 <SEP> 90 <tb> C.Ex.l <SEP> 70 <SEP> O <SEP> t <SEP> 30 <SEP> 1.522 <SEP> 92 <SEP> " <SEP> exist <tb> <SEP> 2 <SEP> 30 <SEP> 0 <SEP> # <SEP> 70 <SEP> 1.551 <SEP> 90 <tb> <SEP> 3 <SEP> 60 <SEP> 30 <SEP> 10 <SEP> 1.524 <SEP> 92 <SEP> exist <SEP> " <SEP> <tb> <SEP> II <SEP> <tb> <SEP> @@@ <tb> Note 1 BzMA: benzylmethacrylate DAIP: diallylisophthalate Note 2 Refractive Index: measured by Abbe's refractometer of Atago Co., Ltd. % Transmittance: measured with spectrophotometer of Hitachi Co., Ltd. Blur: measured with eyes Striae: measured with a strainmeter

Claims: Claims 1. A plastic lens having a high refractive index of at least 1.54 prepared from the terpolymer comprising diethylene glycolbisallylcarbonate,.benzylmethacrylate, and diallylisophthalate. 2. A plastic lens as is claimed in Claim 1, wherein diethyleneglycolbisallylcarbonate is in an amount ranging from 5 to 40 wt.%, benzylmethacrylate is in an amount ranging from 5 to 40 wt.%, and diallylisophthalate is in an amount ranging from 90 to 20 wt..

Inventors: KOMIYA, SIGEO, SUGIMURA, MITSUO, TARUMI, NIRO
Applicants: HOYA LENS CORPORATION
Application year: 1982
Main classification: G02B1
IPC codes: C08F218, G02C7, C08F18, G02B1, C08F20