Description of the Prior Art Plastic lenses are more lightweight, less breakable and more easily dyeable as compared with inorganic lenses, and for this reason, they have been widely used in the fields of optical instruments.

Among the resins used for plastic lens materials, diethylene glycol bis (allylcarbonate) has been characterized by lightweight of lens, since its specific gravity (1.32) is lower than that of inorganic glass lens (2.54).

However, this plastic lens has the disadvantage such as an increase in the center thickness and the edge thickness as compared with inorganic lenses, because the refractive index of the lens prepared using this resin (nD20=1. 50) is lower than that of an inorganic glass lens (nD20=1. 52).

Among the resins used for plastic lens materials having high refractive indices, polycarbonate (n2°D=1. 58) and polystyrene (nD20=1. 60) are limited in narrow

range of optical use, because they have the physical properties of low polishing processability, low scratch resistance caused by low surface hardness, and low resistance for organic solvent.

Resins suggested for plastic lens materials with a high refractive index are (1) diacrylate or dimethacrylate derived from bisphenol A [JP 116,301/83], (2) diacrylate or dimethacrylate derived from halogenated bisphenol A [JP 10,491/82], (3) halogenated styrene monomer and multifunctional methacrylate compound [JP 104,101/82,28,118/82, and 28.116/82], and (4) diallyl phthalate monomer [JP 212,401/82 and 15,513/83]. However, the material (1) is hard to form a crosslinked three-dimensional network of which a refractive index is 1.60 or higher, and also the material (2), (3), and (4) have the tendency of discoloring during casting polymerization, and are not satisfactory in weathering property and optical transmittance of visible light.

Therefore, it is necessary to develop a new resin for an optical use, which overcomes the disadvantages mentioned above, and also has a high refractive index and a high abbe number.

The object of the present invention is to provide the resin composition, which solves the cited problems and can prepare an optical lens with the properties of a high refractive index, a high Abbe number, high transparency, optical homogeneity and lightweight, and an optical lens formed thereof.

DISCLOSURE OF THE INVENTION The present invention provides an optical resin composition comprising (A) 10-75 parts by weight of (meth) acrylate compound having bisphenol A structure

represented as the formula 1, (B) 1-70 parts by weight of aliphatic polythiol compound represented as the formula 2, (C) 1-40 parts by weight of (meth) acrylate compound having sulfur bond represented as the formula 3, and (D) 1-45 parts by weight of (meth) acrylate compound having aliphatic or alicyclic group represented as the formula 4.

<Formula 1>

wherein Rl and R2 are H or CH3 ; each of m and n is an integer between 0 and 4; m+n is 0 to 8 ; Y is H or OH.

<Formula 2>

wherein R is S or C; R3 and R4 are CH2SH, CH2CH2SH, COOCH2SH, or COOCH2CH2SH ; where R is C, R5 and R6 are CH2SH, and where R is S, R5 and R6 do not exist.

<Formula 3>

wherein X is alicyclic or aromatic group; Y is H or CH3.

<Formula 4> wherein X is aliphatic or alicyclic group; Y is H or CH3.

Preferably, the composition of the present invention comprises 20-70 parts by weight of component (A), 1-20 parts by weight of component (B), 1-20 parts by weight of component (C), and 1~15 parts by weight of component (D).

Also, the present invention provides the optical lens with a high refractive index, a high Abbe's number, and the excellent properties of transparency, optical homogeneity and lightweight by polymerization and curing the above composition.

The components of the optical resin composition of the present invention are as follows in detail: (A) (Meth) acrylate compound having bisphenol A structure represented as the formula 1 The component (A) has a high refractive index, a low viscosity, and at least 2 functional groups. Due to these 2 more functional groups, the component (A) can

be added radically.

Radical addition means the thiol-additional reaction to the unsaturated bond of polyene compound or (meth) acrylate compound, or the additional reaction among the said unsaturated bonds.

Preferably, the component (A) can be BPA-2A (Ethyleneoxide (2mol) added Diacrylate of Bisphenol A Diglycidyl ether), BPA-4EA (Diacrylate of ethyleneoxide modified bisphenol A), BPA-4PA (Diacrylate of propyleneoxide modified bisphenol A), BPA-2EM (Dimethacrylate of ethyleneoxide modified bisphenol A) etc.

The amount of the component (A) is 10-75 parts by weight in the total resin composition, preferably 20-70 parts by weight.

(B) aliphatic polythiol compound represented as the formula 2 The component (B) is preferably thiol compound having at least 2 functional groups and can be added radically to the above component (A).

Preferably, the component (B) can be DMDS (Dimercapto Dimethylsulfide), BMEE (Bis (2-mercaptoethyl) ether) etc.

The amount of the component (B) is 1-70 parts by weight in the total resin composition, preferably 1-20 parts by weight.

(C) (Meth) acrylate compound having sulfur bond represented as the formula 3.

The component (C) can be radically copolymerized with the component (A).

Preferably, the component (C) can be PTEA (Phenylthioethyl acrylate), HTEMA (Hexylthioethyl methacrylate), PTEEA (Phenylthioethyl ethacrylate) etc.

The amount of the component (C) is 1-40 parts by weight in the total resin composition, preferably 1-20 parts by weight.

(D) (Meth) acrylate compound having aliphatic or alicyclic group represented as the formula 4 The component (D) can be radically copolymerized with the component (A), (B) or (C).

Preferably, the component (D) can be DTDDA (Dimethylol tricyclo decane diacrylate), HAPMA (2-Hydroxy-3-acryloyloxy propylmethacrylate), TMGDA (poly tetramethylene glycol diacrylate) etc.

The amount of the component (D) is 1-45 parts by weight in the total resin composition, preferably 1-15 parts by weight.

Diluents such as divinylbenzene, diisopropenylbenzene, styrene, nucleophilic substituted styrene, monofunctional (meth) acrylate, etc., can be added to the resin composition of the present invention in order to control a viscosity and a refractive index of the resin composition.

More specifically, the diluents can be o-divinylbenzene, m-divinylbenzene, p-divinylbenzene, m-diisopropenylbenzene, p-diisopropenylbenzene, styrene, methylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isoprophyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acylate, phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidylallylether, etc., and more preferably, divinylbenzene and styrene.

If necessary, various additives such as uv absorbents, antioxidants, anti- yellowing agents, dyes, fragrant, chain transfer agents and mold releasing agents can be added to the resin composition of the present invention in order to achieve desired physical properties or functions, as long as it does not adversely affect the effects of this invention.

An optical lens with a high refractive index and a high Abbe's number can be prepared by polymerizing and curing the resin composition of the present invention, wherein the refractive index (nD20) should be higher than at least 1. 59.

If necessary, the optical lens may be annealed after the curing. Also, physical or chemical treatment such as surface-polishing, antistatic treatment, hard coating, non-reflection coating and dyeing treatment can be performed in order to prevent reflection and to improve hardness and appearance of the optical lens.

The optical lens of the present invention is prepared by casting polymerization using a known radical polymerization.

Specifically, a catalyst such as a radical-polymerization initiator and a photo-polymerization initiator or the like is added to the resin composition of the present invention and mixed, the mixture is filtered, and sufficiently defoamed under a reduced pressure and then is injected into a mold to initiate a radical polymerization.

A mold may consist of, for example, two plates of template using a polyester adhesive tape or a gasket. The template may be a combination of glass-glass, glass- plastic, glass-metal plate or the like.

Preferably, a catalyst for the polymerization reaction in preparing the optical lens of the present invention, that is, a radical-polymerization initiator, can be known peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, lauroyl peroxide, acetyl peroxide, di-t-butyl peroxide, 1, 1-di-t-butylperoxy-3, 3, 5-trimethylcyclohexane, t-butylperoxy pivalate, t-butylperoxy 2-ethylhexanoate, t-butylperoxy benzoate, bis (4-t-butylcyclohexyl) peroxy dicarbonate, diisopropylperoxy dicarbonate and t- butylperoxy isopropyl carbonate; and azo compounds such as azobisisobutyronitrile or a mixture of these compounds.

The amount of the catalyst is 0.001 to 5 parts by weight, preferably 0.01 to 3 parts by weight.

The above-mentioned amounts of the components can be determined according to the temperature and time for polymerization, the kind of a radical- polymerization initiator used, and the size of a cured product and the like.

After the resin composition of the present invention is put into a mold, the optical lens of the present invention is prepared by polymerization and curing the said resin composition at 25-110 C, for 15-30 hours.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Hereinafter, preferred embodiments of the present invention are described in order to facilitate understanding of the present invention.

Example 1 At room temperature, 47g of bisphenol A diacrylate, 15g of hexylthioethylmethacrylate, 5g of 2-hydroxy-3-acryloyloxypropylmethacrylate, 12g of bis (2-mercaptoethyl) ether, 5g of styrene, 16g of divinylbenzene were mixed homogeneously, and 0.3g of t-butylperoxyisopropylcarbonate was added to this mixture. The mixture was injected into two plates of glass template, polymerized and cured at 35-1 IOC for 19 hours. At the end of curing reaction, the cured product was removed from the mold after cooling down to 40°C. A plastic lens was obtained by annealing the cured product at 90~110 C, for 1-2 hours to remove residual stress.

Examples 2-5 Each plastic lens was prepared according to the amount of the component shown as Table 1. The same procedure as described in Example 1 was conducted.

Comparative Example 40g of bisphenol A diacrylate, 21g of ethylene oxide added bisphenol A methacrylate, 8g of phenylthioethylmethacrylate, 3g of dimethyloltricyclodecane diacrylate, lOg of styrene, 18g of vinyltoluene were mixed homogeneously and then plastic lens was obtained through the same casting polymerization procedure as described in Example 1.

Experimental example : The measurement of physical properties Physical properties of lenses in Examples 1-5 and Comparative Example were evaluated as described below.

(1) Transparency: this was visually observed, and one without color, turbidity and distortion was rated to"good".

(2) Refractive index and Abbe's number: these were determined with a Pulfrich refractometer provided that a refractive index of a prepolymer was determined with an Abbe refractometer.

(3) Impact resistance: a lens with a center thickness of 1.5-1.6 mm was subject to a dropping-ball test using a 28.5 g of steel ball at height of 150 cm, and was rated to"O"if passed or"X"if not passed.

(4) Thermal resistance: a lens was investigated with TMA in penetration mode, and the lens with a heat distortion temperature of below 80° C and above 80° C was rated to"X"and"O", respectively.

(5) Tintability: a resin/lens was dyed together with a diethyleneglycol bisallylcarbonate resin as a control in a dyeing bath, and was rated to"O"if dyed equal to or more than the control, or"X"if less than the control.

(6) Weathering: the optical lens was placed in a weathering apparatus equipped with sunshine carbon-arc lamps, and the test was conducted for 200 hours.

The color of the test specimen was compared with virgin optical lens, and rated"0" if there was no difference or"X"if the tested lens became yellow.

The measured physical properties of this lens are shown in Table 1.

<Table 1> Component Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example A BPA-2A 55 58 40 BPA-4EA 50 BPA-4PA 47 BPA-2EM 55 21 B DMDS 8 10 9 BMEE 12 10 C PTEA 7 10 HTEMA 15 8 PTEEA 12 8 D DTDDA 3 3 3 HAPMA 5 5 TMGDA 3 SM 5 7 7 5 10 10 DVB 16 20 15 10 15 VT 5 18 Physical Refractive 1.591 1.595 1.593 1.589 1.595 1.588 PropertiesIndex mD20 Abbe 38.0 34.5 35.0 35.5 35.0 33.5 Number (vs20)- Density 1. 14 1. 15 1. 15 1. 16 1.14 1.27 (S/cm) Impact 0 0 0 0 0 X Resistance Weathering X 0 0 X 0 X Tintability 0 0 0 0 0 X Thermal X 0 X 0 X X Resistance

* BPA-2A: Ethyleneoxide (2mol) added Diacrylate of Bisphenol A Diglycidyl ether * BPA-4EA: Diacrylate of ethyleneoxide modified bisphenol A * BPA-4PA: Diacrylate of propyleneoxide modified bisphenol A * BPA-2EM: Dimethacrylate of ethyleneoxide modified bisphenol A * DMDS : Dimercapto Dimethylsulfide * BMEE : Bis (2-mercaptoethyl) ether * PTEA: Phenylthioethyl acrylate * HTEMA : Hexylthioethyl methacrylate * PTEEA: Phenylthioethyl ethacrylate * DTDDA: Dimethylol tricyclo decane diacrylate * HAPMA : 2-Hydroxy-3-acryloyloxy propylmethacrylate * TMGDA : poly tetramethylene glycol diacrylate * SM: Styrene Monomer * DVB: Divinyl Benzene * VT: Vinyl Toluene As represented in Table 1, an optical lens of the present invention prepared

by the procedures as described in Example 1-5 has not only a high refractive index and a high Abbe number, but also excellent properties in impact resistance, weathering, tintability, and thermal resistance.

The density of the cured product of the present invention is 1. 14-1. 16, and is lower as compared with those of CR-39 (1. 32) and dimetharylphthalate (1. 22).

Therefore, the cured product of the present invention is proper to prepare an optical lens having lighter weight than the existing commercial products.

INDUSTRIAL APPLICABILITY This invention can provide a resin composition and an optical lens having a high refractive index, a high Abbe's number, an excellent transparency, an optical homogeneity, and lightweight by polymerization and curing of the resin composition.