WO2007073022A1

WO2007073022A1 - Method for manufacturing photochromic plastic lens

Info

Publication number: WO2007073022A1
Application number: PCT/KR2006/001907
Authority: WO
Inventors: Sang Min Lee
Original assignee: COVIS OPTIC Co Ltd
Current assignee: COVIS OPTIC Co Ltd
Priority date: 2005-12-21
Filing date: 2006-05-22
Publication date: 2007-06-28
Anticipated expiration: 2008-06-21
Also published as: KR100568409B1

Abstract

Disclosed herein is a method for manufacturing photochromic plastic lens. More specifically, disclosed herein is a method for manufacturing photochromic plastic lens that improves the surface hardness of lens without deterioration in photochromic properties and reduction in production efficiency, thereby ensuring stability in hard-coating and multi-coating and enabling production of a non-frame glass. The method of the present invention is based on an optimal selection of the kind and mixing ratio of a photopolymerization initiator, and precise control of thermal polymerization. The photochromic plastic lens manufactured by the method has a surface hardness comparable to general lenses, thereby enabling stable formation of hard-coating and multi- coating, and being suitable for production of a non-frame glass, which could not be realized in the art.

Description

METHOD FOR MANUFACTURING PHOTOCHROMIC

PLASTIC LENS

Technical Field

[1] The present invention relates to a method for manufacturing photochromic plastic lens. More specifically, the present invention relates to a method for manufacturing photochromic plastic lens that enhances a surface hardness of the lens without deterioration in photochromic properties and reduction in production efficiency, thereby ensuring stability in hard-coating and multi-coating and enabling production of a non- frame glass.

[2]

Background Art

[3] Photochromism is defined as a light- induced reversible change of color, e.g., change of colorless-transparence into a specific color upon exposure to ultraviolet (UV) radiation. The materials inducing this phenomenon are known as "photochromies". The photochromies are used to produce a photochromic lens. The photochromic lens is transparent or light in color indoors where there is no sun light (UV radiation), but becomes as dark as sunglasses upon exposure to UV radiation. Thereafter, indoors where there is no UV radiation, the photochromic lens exhibits an original color, i.e., transparent or light color. Such photochromic lens is valuable for people wearing glasses even indoors for visual correction. Accordingly, the photochromic lens enables visual correction and function of a sunglass.

[4] Photochromic plastic lenses are generally produced by adding slightly a photochromic compound to a monomer and polymerizing the mixture. The photochromic compound may be selected from spiropyran, spiroxazine, fulguide, chromene, diazo compound and diarylethene. The polymer must secure a predetermined space therein to enable the photochromic compound to easily exhibit its functionality. For this reason, photochromic plastic lenses disadvantageously have weak physical properties (e.g., hardness), as compared to general lenses for visual correction. Meanwhile, general plastic lenses are subjected to hard-coating to enhance surface hardness, thereby ensuring prevention of the occurrence of scratches or scars. Recently, general plastic lenses are subjected to multi-coating, i.e., alternative deposition of a low-refractive dielectric and a high-refractive dielectric, to reduce surface reflection of lens. However, photochromic plastic lenses are considerably unstable in hard-coating due to low surface hardness, have practical limitation in multi-coating and are unsuitable for use in production of a non-frame glass. There have been attempts to improve the surface hardness of photochromic plastic lenses during production. In this case, however, improvement in surface hardness disadvantageously leads to considerable reduction in production efficiency or life time of photochromic property, thus making it difficult to put to practical use.

[5] There have been reported cases associated with photochromic plastic lenses. For example, Korean Patent Laid-open No. 2004-0094928 discloses a polymeric composition comprising a polycycloalkane-based difunctional monomer and a photochromic compound, and an optical product using the polymeric composition. Korean Patent Laid-open No. 2002-0090995 discloses a photochromic composition comprising an aromatic radical monomer, a photochromic compound (e.g., spirobenzopyran) having an absorption wave equal to or greater than 250 nm, and a photopolymerization initiator. Korean Patent Laid-open No. 2005-0026650 discloses a photochromic lens. The photochromic lens comprises a radical monomer, spirobenzopyran as a photochromic compound, various colorants and a photopolymerization initiator. Accordingly, the photochromic lens undergoes color change from light color (e.g., yellow, red and blue) to deep color (e.g., black, gray and deep blue) upon exposure to light radiation. However, low surface hardness of the photochromic lens and thus unstable coating have remained unsolved in the art.

[6]

Disclosure of Invention

Technical Problem

[7] In an attempt to solve the problems of the prior arts, it is one object of the present invention to provide a method for manufacturing a photochromic plastic lens that can still retain original photochromic properties (e.g., life time and rate), secure production efficiency and improve a surface hardness.

[8] It is another object of the present invention to provide a method for manufacturing a functional photochromic plastic lens that can enhance a surface hardness, thereby ensuring stability not only in hard-coating, but also in multi-coating for reduction in reflection of lens.

[9] As a result of repeated eager examinations and studies, the inventors have found that the above objects can be accomplished by optical selection and mixing ratio of an optimal photopolymerization initiator, and precise control in thermal polymerization (thermal curing). The present invention has been completed based on the findings.

[10]

Technical Solution

[11] In accordance with an aspect of the present invention, there is provided a method for manufacturing photochromic plastic lens, the method comprising the steps of: [12] mixing 10 to 30% by weight of dimethylol tricyclodecane diacrylate or methacrylate; and 70 to 90% by weight of a monomer selected from diacrylate, dimethacrylate, and a copolymer of acrylate and dimethacrylate, with 0.001 to 10% by weight of a photochromic compound selected from spiropyran, spiroxazine, fulguide, fulgimide, chromene and diazo compound;

[13] adding 0.5 to 1% and 0.02 to 0.06% by weight of radical polymerization initiators represented by Formulas 1 and 2 below:

[14]

CH₃ CH₃

(CHa)₂CH-CH₂-C-N = N-C-CH₂CH(CHs)₂ 1 I

CN CN

(1) [15]

CHa CHs CHs CH₃

CH3O - C-CH2-C - N = N- C-CH₂C -OCH₃ CH₃ CN CN CH₃

(2)

[16] based on the total weight of the mixture, to the mixture, respectively;

[17] injecting the mixture into a mold;

[18] subjecting the mixture to first polymerization under the conditions of elevating from

25⁰C to 30+2⁰C over 200-300 min, elevating to 36+2⁰C over 200-300 min, maintaining

36+2⁰C for 450-500 min, elevating to 45+3⁰C over 200-300 min, maintaining 45+3⁰C for 200-300 min, elevating to 70+5⁰C over 100-150 min, elevating to 90+5⁰C over

100-150 min, maintaining 90+5⁰C for 50-70 min and lowering to 60+5⁰C over 20-40 min, thereby molding a lens;

[19] separating the lens from the mold, followed by washing; and

[20] subjecting the mixture to second polymerization under the conditions of elevating from room temperature to 95+5⁰C over 50-70 min, maintaining 95+5⁰C for 20-40 min and allowing to be cooled. [21]

Best Mode for Carrying Out the Invention [22] The above and other objects, features and other advantages of the present invention will be described and more clearly understood from the following detailed description. [23] The present invention relates to a method for manufacturing a photochromic plastic lens that improves a surface hardness of the lens without deterioration in photochromic properties and reduction in production efficiency, thereby ensuring stable hard-coating and multi-coating, and enabling production of a non-frame glass. Hereinafter, the method according to the present invention will be described in detail at each step.

[24]

[25] Mixing

[26] 70 to 90% by weight of a monomer selected from diacrylate, dimethacrylate, and a copolymer of aery late and dimethacrylate, and 10 to 30% by weight of dimethylol tri- cyclodecane diacrylate or methacrylate is mixed with 0.001 to 10% by weight of a photochromic compound selected from spiropyran, spiroxazine, fulguide, fulgimide, chromene and diazo compound. To the mixture is added 0.5 to 1% and 0.02 to 0.06% by weight of radical polymerization initiators represented by Formulas 1 and 2 below:

[27]

CH₃ CHs

(CHa)₂CH-CH₂-C-N = N-C-CH₂CH(CHs)₂ ! I

CN CN

(1) [28]

CHs CH₃ CH₃ CH₃

CH3O - C-CH2-C - N = N- C-CH₂C -OCH₃ CHa CN CN CH₃

(2)

[29] based on the total weight of the mixture.

[30] The main monomer constituting an optical resin of the present invention may be a monomer selected from diacrylate, dimethacrylate and a copolymer of acrylate and dimethacrylate, which are well-known in the art. It has been reported that the diacrylate monomer enables the photochromic compound to easily exhibit its functionality.

[31] Dimethylol tricyclodecane diacrylate or methacrylate is copolymerized with the main monomer to form a copolymer. PCT Publication No. WO 96/0038486 discloses dimethylol tricyclodecane diacrylate and methacrylate. Polycycloalkane within the molecule has a bulky stereo- structure and thus secures a sufficient space within the copolymer, thereby enabling the photochromic compound to easily exhibit its functionality. In addition, polycycloalkane hinders oxygen from accessing the photochromic compound, owing to its steric hindrance effect, thereby obtaining an increase in life time of the photochromic compound. [32] The contents of the main monomer and dimethylol tricyclodecane diacrylate

(methacrylate) are preferably about 70 to 90% by weight and about 10 to 30% by weight, respectively. If the content of dimethylol tricyclodecane diacrylate (methacrylate) is lower than 10%, the photochromic property of the compound may decrease. Meanwhile, if the content of dimethylol tricyclodecane diacrylate (methacrylate) is higher than 30%, the hardness of a polymerized resin may decrease, thereby causing considerable deterioration in moldability and workability. Alternatively, the monomer may be selected from any well-known monomers in the art.

[33] The addition of 0.001 to 10 wt% of the photochromic compound to the monomer enables the polymerized resin to have photochromicity. The photochromic compound may be selected from spiropyran, spiroxazine, fulguide, fulgimide, chromene and diazo compound.

[34] After mixing the photochromic compound with the monomer, 0.5 to 1% and 0.02 to

0.06% by weight of redial polymerization initiators represented by Formulas 1 and 2 above are added to the mixture, respectively, based on the total weight of the mixture. The kind and content of redial polymerization initiators have a great effect on the hardness of polymerized resin. As can be confirmed from Examples below, replacement by other redial polymerization initiators or addition of the initiators in the content out of the range defined above leads to greater deterioration in the hardness and coating stability of final products (lenses). This is the reason that non- polymerization causes unstability in molding of lens and unreactants inhibits coating of lens. More preferably, redial polymerization initiators represented by Formulas 1 and 2 are added in a content of 0.7% and 0.04% by weight, based on the total weight of the mixture, respectively.

[35]

[36] First polymerization

[37] A mold acting as a die is assembled for lens production. A mold and B mold having a predetermined diopter (D.P.) are assembled with a tape or gasket while an emptied space within each mold is maintained. The mixtureis injected into the resulting mold, followed by first polymerizing under the following conditions, thereby molding a lens. Generally, the polymerization is also called as "thermal curing reaction".

[38] Conditions: increase in reaction temperature from 25⁰C to 30+2⁰C over 200-300 min -> increase in reaction temperature to 36+2⁰C over 200-300 min -> maintenance in reaction temperature of 36+2⁰C for 450-500 min -> increase in reaction temperature to 45+3⁰C over 200-300 min -> maintenance in reaction temperature of 45+3⁰C for 200-300 min -> increase in reaction temperature to 70+5⁰C over 100-150 min -> increase in reaction temperature to 90+5⁰C over 100-150 min -> maintenance in reaction temperature of 90+5⁰C for 50-70 min -> decrease in reaction temperature to 60+5⁰C over 20-40 min

[39] After the first polymerization, the molded lens is separated from the mold. At this time, the separation is preferably carried out while the temperature of 60+5⁰C was maintained.

[40]

[41] Washing

[42] After the separation from the mold, the lens is subjected to general washing. During the washing, residues and foreign materials remaining on the surface of the lens are removed. The washing is required for stabilization of the lens surface and coating film upon a subsequent coating by removal of the foreign materials inhibiting an adherence of the coating film. The washing is preferably conducted using a plurality of washing baths. That is, washing with a cleaner is carried out in some baths, and washing with hot water or distilled water is carried out in the remaining baths. It is most preferable to use a washer including twelve to fourteen washing baths. 40 to 60% by weight of a cleaner is used in 1-2 washing baths, 20 to 40% by weight of a cleaner is used in 3-4 washing baths. Hot water is used in 5-8 washing baths and distilled water is used in 9-12 washing baths. The cleaner may be selected from any cleaners containing an anionic surfactant commonly used in the art. The cleaner containing both anionic and nonionic surfactants is preferably used. The cleaner used herein was Neozol-LC 600 (available from Neopharm. Co., Ltd. Korea).

[43]

[44] Second polymerization

[45] After the washing, the lens is subjected to second-polymerization (thermal curing reaction) under the following conditions to manufacture a photochromic plastic lens.

[46] Conditions: increase in reaction temperature from room temperature to 95+5°C over

50-70 min -> maintenance in reaction temperature of 95+5°C for 20-40 min -> allowance to be cooled

[47] The manufactured thus photochromic plastic lens is subjected to quality inspection.

If necessary, a series of subsequent coating processes may be conducted to ensure the functionality of lens.

[48]

[49] Hard-coating

[50] The manufactured photochromic plastic lens is subjected to hard-coating. The hard- coating is carried out by dipping the lens in a hard solution. That is, the lens is dipped in the hard solution, i.e., a coating liquid containing a silicon resin, thereby forming a silicon resin film with a high hardness on the surface thereof. Common hard-coating processes associated with a glass lens may be applied to the hard-coating of the present invention. The hard solution used herein was 8H (available fromLG Chem. Ltd.). [51]

[52] Multi-coating

[53] The hard-coated lens is subjected to multi-coating, i.e., formation of multi thin films by alternative deposition of a low-refractive dielectric and a high-refractive dielectric, thereby reducing surface reflection. SiO may be used as the low-refractive dielectric. ZrO , TiO , ITO, Y O , ZnS and La O may be used as the high-refractive dielectric.

2 2 2 3 2 3

The deposition is conducted under a reduced pressure of about 1 x 10 to about 5 x 10-

Torr using a vapor-deposition chamber for deposition of glass lens. Common multi- coating processes associated with a glass lens may be applied to the multi-coating of the present invention. Three to nine thin films are formed on the both sides of the lens, i.e., concave and convex sides thereof, respectively. For example, multi-coating is carried out by sequentiallydepositing multi-layers of SiO ,ZrO SiO ,ZrO andSiO on each of theboth sides thereof.

[54]

Mode for the Invention

[55] The present invention will be better understood from the preferred following examples. These examples are not to be construed as limiting the scope of the invention. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[56]

[57] EXAMPLES

[58] EXAMPLE 1

[59] (1) Mixing

[60] 20 g of Dimethylol tricyclodecane diacrylate(DCP-A, available from KYOEISHA), and 1 g of spiropyran (Reversacol Sea Green , available from JAMES ROBINSON) as a photochromic compound were added to 79 g of diacrylate of propyleneoxide modified bisphenol A (BP-4PA, available from KYOEISHA), followed by mixing. 0.7 g and 0.04 g of radical polymerization initiators represented by Formulas 1 (V-65 , WAKO) and 2 (V-70 , WAKO) below were simultaneously added to the mixture, respectively, followed by mixing.

[61]

[62] (2) First polymerization

[63] The resulting mixture is inserted into a mold, followed by thermal curing under the following conditions:

[64] Conditions: increase in reaction temperature from 25⁰C to 3O⁰C over 240 min -> increase in reaction temperature to 36⁰C over 240 min -> maintenance in reaction temperature of 36⁰C for 480 min -> increase in reaction temperature to 45⁰C over 240 min -> maintenance in reaction temperature of 45⁰C for 240 min -> increase in reaction temperature to 7O⁰C over 120 min -> increase in reaction temperature to 9O⁰C over 120 min -> maintenance in reaction temperature of 9O⁰C for 60 min -> decrease in reaction temperature to 6O⁰C over 30 min

[65] The resulting lens is separated from the mold while the temperature of 6O⁰C is maintained.

[66]

[67] (3) Washing

[68] The resulting lens was washed in a washer including twelve washing baths. Neo zol-

LC 600 (available from Neopharm. Co., Ltd. Korea) as a cleaner was introduced into 1-2 baths and 3-4 baths in a content of 54% and 34% by weight, respectively. Hot water was filled with 5-8 baths. Distilled water was filled with 9-12 baths. The resulting lens was sufficiently washed through twelve washing baths.

[69]

[70] (4) Second polymerization

[71] After the washing, the lens is subjected to second-polymerization (thermal curing reaction) under the following conditions, thereby manufacturing a photochromic plastic lens.

[72] Conditions: increase in reaction temperature from room temperature to 95⁰C over

60 min -> maintenance in reaction temperature of 95⁰C for 30 min -> allowance to be cooled

[73]

[74] (5) Hard-coating

[75] The manufactured photochromic plastic lens is dipped in a hard solution (8H™, available from LG Chem. Ltd., Korea) to form a silicon hard-film having a thickness of 2 D.

[76]

[77] Example 2

[78] SiO and ZrO were alternatively deposited under vacuum on the hard-coated lens obtained in Example 1. The deposition is conducted under a reduced pressure of about 2 x 10 Torr using a vapor-deposition chamber for deposition of a glass lens. Five coating thin films were deposited oneach oftheconcave and convex sides of lens, in the order SiO ->ZrO ->SiO ->ZrO ->SiO The deposited structure is observed using a scanning electron microscope (SEM). As a result, it could be confirmed that the structure of the lens was stable comparable to that of general lenses for visual correction. [80] Comparative Example 1

[81] (1) Mixing

[82] A mixture was prepared in the same manner as in Example 1, except that 0.1 g of

V-60™ (WAKO) as a radical polymerization initiator was used exclusively.

[83]

[84] (2) First polymerization

[85] The resulting mixture is subjected to first polymerization under the following conditions:

[86] Conditions: maintenance in reaction temperature to 25⁰C for 60 min -> increase in reaction temperature to 3O⁰C over 60 min -> increase in reaction temperature to 4O⁰C over 120 min -> increase in reaction temperature to 5O⁰C over 60 min -> increase in reaction temperature to 6O⁰C over 90 min -> increase in reaction temperature to 7O⁰C over 120 min -> increase in reaction temperature to 8O⁰C over 60 min -> increase in reaction temperature to 95⁰C over 60 min -> maintenance in reaction temperature of 95⁰C for 30 min -> decrease in reaction temperature to 7O⁰C over 30 min

[87] The temperature was dropped to 6O⁰C. The resulting lens is separated from the mold under the temperature of 6O⁰C.

[88]

[89] (3) Washing

[90] A lens was washed in the same manner as in Example 1, except that hot water and distilled water only were used without using any cleaner.

[91]

[92] (4) Second polymerization

[93] Second polymerization was conducted in the same manner as in Example 1.

[94] It could be confirmed that product defects occurred in the overall lens.

[95]

[96] Comparative Example 2

[97] (1) Mixing

[98] A mixture was prepared in the same manner as in Example 1, except that 0.1 g of

V-70 (WAKO) as a radical polymerization initiator was used exclusively.

[99]

[100] (2) First polymerization

[101] The resulting mixture is subjected to first polymerization under the following conditions:

[102] Conditions: maintenance in reaction temperature to 25⁰C for 60 min -> increase in reaction temperature to 3O⁰C over 60 min -> increase in reaction temperature to 4O⁰C over 120 min -> increase in reaction temperature to 5O⁰C over 60 min -> increase in reaction temperature to 6O⁰C over 90 min -> increase in reaction temperature to 7O⁰C over 120 min -> increase in reaction temperature to 8O⁰C over 60 min -> increase in reaction temperature to 95⁰C over 60 min -> maintenance in reaction temperature of 95⁰C for 30 min -> decrease in reaction temperature to 7O⁰C over 30 min

[103] The temperature was dropped to 6O⁰C. The resulting lens is separated from the mold under the temperature of 6O⁰C.

[104]

[105] (3) Washing

[106] A lens was washed in the same manner as in Example 1, except that hot water and distilled water only were used without using any cleaner.

[107]

[108] (4) Second polymerization

[109] Second polymerization was conducted in the same manner as in Example 1. It could be confirmed that the overall polymerization was incomplete and 20% product defect was occurred.

[HO]

[111] (5) Hard-coating

[112] Hard-coating was conducted in the same manner as in Example 1.

[113]

[114] Comparative Example 3

[115] (1) Mixing

[116] A mixturewas prepared in the same manner as in Example 1, except that 0.5 g of V-

40™ (WAKO) and 0.05 g of V-70™ (WAKO) as radical polymerization initiators were simultaneously added, respectively.

[117]

[118] (2) First polymerization

[119] The resulting mixture is subjected to first polymerization under the following conditions:

[120] Conditions: maintenance in reaction temperature to 25⁰C over 30 min -> increase in reaction temperature to 3O⁰C over 30 min -> increase in reaction temperature to 4O⁰C over 60 min -> increase in reaction temperature to 5O⁰C over 60 min -> increase in reaction temperature to 6O⁰C over 60 min -> increase in reaction temperature to 7O⁰C over 280 min -> increase in reaction temperature to 8O⁰C over 240 min -> increase in reaction temperature to 9O⁰C over 60 min -> maintenance in reaction temperature of 9O⁰C for 90 min -> decrease in reaction temperature to 7O⁰C over 30 min

[121] The temperature was dropped to 6O⁰C. The resulting lens is separated from the mold under the temperature of 6O⁰C.

[122] [123] (3) Washing

[124] A lens was washed in the same manner as in Example 1, except that hot water and distilled water only were used without using any cleaner. [125]

[126] (4) Second polymerization

[127] Second polymerization was conducted in the same manner as in Example 1. It could be confirmed that the overall polymerization was incomplete and about 34 to 48% product defects occurred at each diopter. [128]

[129] (5) Hard-coating

[130] Hard-coating was conducted in the same manner as in Example 1.

[131]

[132] Comparative Example 4

[133] (1) Mixing

[134] A mixture was prepared in the same manner as in Example 1, except that 0.4 g of

V-65™ (WAKO) and 0.05 g of V-70™ (WAKO) as radical polymerization initiators were simultaneously added, respectively. [135]

[136] (2) First polymerization

[137] The resulting mixture is subjected to first polymerization under the following conditions: [138] Conditions: increase in reaction temperature from 2O⁰C to 25⁰C over 60 min -> increase in reaction temperature to 4O⁰C over 120 min -> increase in reaction temperature to 5O⁰C over 240 min -> increase in reaction temperature to 6O⁰C over 240 min -> increase in reaction temperature to 7O⁰C over 60 min -> increase in reaction temperature to 9O⁰C over 60 min -> maintenance in reaction temperature of 9O⁰C for

90 min -> decrease in reaction temperature to 65⁰C over 30 min -> decrease in reaction temperature to 6O⁰C over 30 min [139] The resulting lens is separated from the mold while the temperature of 6O⁰C is maintained. [140]

[141] (3) Washing

[142] Washing was conducted in the same manner as in Example 1.

[143]

[144] (4) Second polymerization

[145] Second polymerization was conducted in the same manner as in Example 1.

[146] [147] (5) Hard-coating [148] Hard-coating was conducted in the same manner as in Example 1.

[149]

[150] It could be confirmed from quality inspection, the final products with "A" grade of

69%, "B" grade of 12% and defects of 19% were manufactured.

[151]

[152] Experiment Example 1 : Surface Hardness Test

[153] Each of the photochromic plastic lenses (prior to hard-coating) manufactured in

Example 1 and Comparative Examples 1 to 4 was tested for surface hardness. The test was carried out by drop ball test (DBT). After dropping a ball of 27 g at a height of 1.2 M ten times, damage to the lens was evaluated. The lens manufactured in Example 1 was not damaged at all and maintained its original state. On the other hand, each of the lenses manufactured in Comparative Examples 1 to 3 got damaged (about 30 to 50%). The lens manufactured in Comparative Example 4 was slightly cracked.

[154]

[155] Experiment Example 2: Hard-coating Film Adherence Test

[156] (1) Each of the hard-coated photochromic plastic lenses manufactured in Example 1 and Comparative Examples 2 to 4 was tested for hard-coating film adherence. The test was carried out by crosscut tape test as follows. The coating film was subjected to cutting in the form of lattice on the surface thereof using a knife. Then, a tape (available fromNichiban Co., LTD.) was attached to the film surface and quickly peeled off. The test was independently repeated ten times. The hard-coating film manufactured in Example 1 was not detached at all from the photochromic plastic lenses during the overall test. On the other hand, 3-4 grids of the films manufactured in Comparative Examples 2 and 3 were detached during the overall test. 1-2 grids of the films manufactured in Comparative Example 4 were detached two times during the test.

[157] (2) A large spoonful of salt was added to 500 mL of water, followed by heating.

Then, the lens was precipitated in boiling water for 3 min. The overall test of (1) was repeated once. One grid of the film manufactured in Example 1 was scarred once during the overall test (ten times). On the other hand, 60 to 80% grids of the films manufactured in Comparative Examples 2 and 3 were detached during the overall test. 2-3 grids of the film manufactured in Comparative Example 4 were detached three times during the test.

[158]

Industrial Applicability

[159] As apparent from the above description, the method of the present invention enables considerable improvement in a surface hardness of the lens without deterioration in photochromic properties (e.g., life time and rate) and reduction in production efficiency. Accordingly, photochromic plastic lens manufactured by the method has a surface hardness, comparable to general lenses, thereby enabling functional coating such as hard-coating and multi-coating, and being suitable for production of a non- frame glass, which could not be realized in the art. As a result, the photochromic plastic lens contributes to practical use of photochromic lens, which has had practical limitation due to its low hardness in spite of its many advantages.

Claims

Claims [1] A method for manufacturing photochromic plastic lens, the method comprising the steps of: mixing 10 to 30% by weight of dimethylol tricyclodecane diacrylate or methacrylate; and 70 to 90% by weight of a monomer selected from diacrylate, dimethacrylate and a copolymer of acrylate and dimethacrylate, with 0.001 to 10% by weight of a photochromic compound selected from spiropyran, spiroxazine, fulguide, fulgimide, chromene and diazo compound; adding 0.5 to 1% and 0.02 to 0.06% by weight of radical polymerization initiators represented by Formulas 1 and 2 below: CH3 CH3 (CHa)2CH-CH2-C-N = N-C-CH2CH(CHs)2 CN CN

(1)

CHa CH₃ CH₃ CHs

I l I l

CH3O - C-CH2-C - N = N- C -CH₂C - OCHa

CHs CN CN CHs

(2) based on the total weight of the mixture, to the mixture, respectively; injecting the mixture into a mold; subjecting the mixture to first polymerization under the conditions of elevating from 25⁰C to 30+2⁰C over 200-300 min, elevating to 36+2⁰C over 200-300 min, maintaining 36+2⁰C for 450-500 min, elevating to 45+3⁰C over 200-300 min, maintaining 45+3⁰C for 200-300 min, elevating to 70+5⁰C over 100-150 min, elevating to 90+5⁰C over 100-150 min, maintaining 90+5⁰C for 50-70 min and lowering to 60+5⁰C over 20-40 min, thereby molding a lens; separating the lens from the mold, followed by washing; and subjecting the mixture to second polymerization under the conditions of elevating from room temperature to 95+5⁰C over 50-70 min, maintaining 95+5⁰C for 20-40 min and allowing to be cooled.

[2] The method according to claim 1, wherein the radical polymerization initiators are added in a content of 0.7% and 0.04% by weight, respectively, based on the total weight of the mixture.

[3] The method according to claim 1 or 2, further comprising the step of dipping the lens in a hard solution and forming a hard film, thereby hard-coating the lens. [4] The method according to claim 3, further comprising the step of, after the hard- coating, alternatively depositing a low-refractive dielectric of SiO and a high- refractive dielectric selected from ZrO , TiO , ITO, Y O , ZnS and La O on the

2 2 2 3 2 3 lens and forming three to nine multi-thin films on each of the both sides of the lens, thereby multi-coating the lens.