Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Polymerizing – cross-linking – or curing
Reexamination Certificate
1999-04-23
2001-10-30
Berman, Susan W. (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Polymerizing, cross-linking, or curing
C522S018000, C522S039000, C522S042000, C522S044000, C522S046000, C522S060000, C522S064000, C522S181000, C522S182000, C526S281000, C526S286000, C526S289000, C526S309000, C526S313000, C351S159000, C359S642000, C359S652000, C385S144000
Reexamination Certificate
active
06309585
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to curable casting resin compositions that may be used in the formation of a variety of materials, including, but not limited to, lenses, camera optics, prisms and video disks.
BACKGROUND OF THE INVENTION
Ophthalmic lenses produced in industry must meet certain requirements for their intended use. For example, as mandated by the U.S. Food and Drug Administration (FDA), ophthalmic lenses should have sufficient impact resistance in addition to having acceptable optical properties. The performance and quality of lenses has been improved with the addition of scratch resistant coatings, anti-reflective (AR) coatings, UV protection and lens materials with high refractive index and high Abbe value. Further, lens cosmetics have also been improved by aspheric and progressive lens designs.
Many efforts in fonnulating UV curable casting resin compositions have been made to produce thinner lenses having a high refractive index. By increasing the refractive index of the lens materials, the edge thickness of minus-prescripted lenses and center thickness of plus-prescripted lenses is reduced. Reducing edge and center thicknesses of lenses provides functional advantages such as lighter weight and better cosmetics. Representative examples of UV curable casting resin formulations for forming lenses are described below.
U.S. Pat. No. 4,306,780 discloses high index lens formulations comprising three types of materials: (a) 3-70% of one or more of ethoxylated bisphenol A di(meth)acrylates, (b) 30-97% of high index reactive diluents, and (c) 0-67% of low index methacrylate(s). Based on the information provided in the patent disclosure, low impact resistance and inferior thermomechanical properties are expected from the high refractive index lenses made from these formulations because of the large amount of reactive diluent used in the formulations.
U.S. Pat. Nos. 5,442,022 and 5,545,828 disclose lens formulations comprising (a) at least 50% of a monomer ormixture of monomers having formula (A), (b) 0-50% of one or more mono- or poly-functional vinyl or (meth)acrylate comonomers, and (c) 0.5 to 15% of allyl alcohols or their derivatives. Lenses produced from a homopolymer of formula (A) have a refractive index greater than or equal to 1.55; however, these lenses have an inferior physical/cosmetic property in that they are very yellow in color. Further, although incorporating components (b) and (c) into the lens formulations reduces the yellowness of the resulting lens, lens formulations comprising components (a), (b) and (c) produce lenses having an undesired lower refractive index. Also, the typical time for thermally curing these lens formulations is more than 20 hours. A curing time of this length drastically reduces lens manufacturing efficiency. The formula disclosed in U.S. Pat. Nos. 5,442,022 and 5,545,828 may be represented by: Formula A
wherein R
1
, and R
2
are H or C
1
-C
6
alkyl; X is O, S, SO
2
, CO
2
, CH
2
, CH═CH or C(CH
3
)
2
; and m+n is 0-10.
U.S. Pat. No. 5,373,033 discloses casting resin formulations with (a) 5-60% of polyoxyalkylene glycol di(meth)acrylates, (b) 10-60% of bisphenol-based monomers having the general formula (B) and a second high index component to adjust the refractive index, and (c) 2.5-20% of urethane (meth)acrylates. The impact resistance for these formulations was not reported; however, the impact resistance is expected to be improved due to the introduction of urethane (meth)acrylates into the formulation. The reported refractive index of the cured sample is no more than 1.55. The formula disclosed in U.S. Patent No. 5,373,033 may be represented by:
wherein R
1
is H, CH
3
or CH
2
CH
3
; R
2
is H, CH
3
or CH
2
CH
3
; R
3
is H, CH
3
or OH; R
4
is H, CH
3
or CH
2
CH
3
; X is a halogen (preferably Cl, Br or I) or hydrogen; and n is 0-8.
The lenses produced using these high index materials represented above by formulae (A) and (B) may have one or more of the shortcomings mentioned above. For instance, the high index materials of formulae (A) and (B) are mixed with at least 2 other types of materials to adjust index, viscosity and impact resistance in order to obtain lenses with reasonable overall properties. However, the impact resistance and themomechanical properties of these lenses are expected to be inferior. Further improvement is needed to formulate high index casting resins capable of producing much higher quality lenses by developing new high index materials.
Steps have also been taken to impart UV protection in lenses produced from the aforementioned formulations. These steps are typically accomplished by dipping the cured lenses in a UV tinting bath in separate steps. However, the UV tinting process tends to introduce yellowness into the lens and increases the cost of lenses.
Thus, there is a need to formulate a low viscosity casting resin formulation that is curable in a short amount of time and produces lenses having a high refractive index and excellent impact resistance. In particular, there is a need for high impact resistance in lenses having a center thickness of 1 mm. That way, true thin and light high refractive index lenses having the required impact resistance can be produced. Further, there is a need for lenses having at least 99% inherent UVA protection up to 380 nm. Having inherent UV protection eliminates additional UV tinting process steps and the resulting yellowness in the lens. Lastly, a casting resin composition of low viscosity enables easier processing in the mold-filling stage and prevents flow lines and bubbles in the cured lenses.
SUMMARY OF THE INVENTION
The present invention is generally directed to a low viscosity casting resin composition that can be cured under radiation to produce high refractive index lenses with excellent impact resistance and inherent UV protection, even on lenses with 1 mm center thickness. By mixing ethoxylated bisphenol A di(meth)acrylates of varying degrees of ethoxylation, compositions can be obtained with an enhanced balance of impact resistance and refractive index. Moreover, the present invention is directed to a curable casting resin composition having a UV absorber therein to provide more than 99% inherent UVA protection.
In one aspect, the present invention is directed to a high refractive index composition comprising:
a core resin mixture comprising
(i) an ethoxylated bisphenol A di(meth)acrylate having the formula (I):
wherein n and n′ independently are 0-30, R
1
-R
4
independently represent H or C-C
6
alkyl, X is O, S, SO
2
, CO
2
, CH
2
, CH═CH, C(CH
3
)
2
or a single bond, and y
1
-y
8
, independently represent H, OH, halogen, mercaptan or C
1-C
4
alkyl,
(ii) an ethoxylated bisphenol A di(meth)acrylate having the formula (11):
wherein m and m independently are 1-30, R
1
-R
4
independently represent H or C
1
-C
6
alkyl, X is O, S, SO
2
, CO
2
, CH
2
, CH═CH, C(CH
3
)
2
or a single bond, and y
1
-y
8
independently represent H, OH, halogen, mercaptan or C
1
-C
4
alkyl, and
(iii) a reactive diluent;
the mixture having greater than 70 parts by weight of the composition of the combined components (i) and (ii), and less than 30 parts by weight of the composition of component (iii), based on the total parts by weight of the core resin equaling 100, and n and n′ being less than m and m′ so as to provide a refractive index of greater than 1.53 and a high impact resistance after curing the composition.
In another aspect, the composition of the present invention comprises
(a) a core resin comprising
(i) greater than 70 parts by weight of the composition of an ethoxylated bisphenol A di(meth)acrylate or a mixture of ethoxylated bisphenol A di(meth)acrylates having the formula (I):
wherein n and n′ independently are 0-30, R
1
-R
4
independently represent H or C
1
-C
6
alkyl, X is O, SO SO
2
, CO
2
, CH
2
, CH═CH, C(CH
3
)
2
or a single bond, and y
1
-y
8
independently represent H, OH, halogen, mercaptan or C
1
-C
4
alkyl,
(ii) less than 30 parts by weight of the compositi
Berman Susan W.
Needle & Rosenberg P.C.
Rodenstock North America, Inc.
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