Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~g~
43-13505iCGC 950/lt2
Tinted contact lenses and a method for their preparation
This invention relates to tinted contact lenses and to a method for
their preparation.
In particular, the invention concerns contact lenses comprising poly-
meric lens materials in which reactive dyestuffs have been covalently
bonded to monomer Imits of the polymer backbone. The invention is of
particular interes~ in the area of so-called hydrophilic or "soft"
contact lenses, commonly referred to as hydrogel lenses.
Many of the known methods for tinting or coloring plastic materials
are unsuitable for prac~ical coloring of contact lenses, in particular
of hydrophilic contact lenses. For example, those methods whereby a
coloring agent is dispersed in a plastic by dissolving or dispersing a
dye or pigment in a monomer precursor or in the polymer matrix cannot
be used to obtain satisfacto~ywater-absorbable materials. This is
because water induces a migration of the coloring agent within ~he
plastic material and a leaching oP the colorant outside of it. This
migration, moreover) can be accelerated during heat steriliæation treat-
ments as commonly used with hydrophilic lenses, since the heating pro-
cess in most cases expands the polymer matrix. Therefore, the most
common method for preparation of hard contact lenses, in which the lens
blanks are tinted or colored, would no~ be feasible for the preparation
of soft lenses.
-- 2 ~
One alternative approach for coloring plastic materials is the use of
printing, transfer or coating methods. According to this process, a
coloring agent is caused to adhere to the surface of the plastic. This
method is also unsuitable for coloring water-absorbable plastics, such
as are used for the preparation of hydrophilic contact lenses. If a
plastic material colored by this method is allowed to swell in water, the
applied layer of coloring agent does not swell as much as the plastic
itself. Consequently, the coloring agent will become dissociated from
the surface of the plastic. In any event, a simple transfer coloring
method does not obviate the problem of leaching and will always be
limited by the degree of physical adhesion of coloring agent to the
surface.
A number of methods have been disclosed in the literature whereby all or
a portion of a soft contact lens is painted or printed using an imple-
ment such as a brush. For example, in Contact Lens Forum, volume 3,
March 1978, pp. 13-17, a method is disclosed in which the surface of a
lens is colored by a chemical printing process. This method, however, is
not entirely satisfactory, as it is noted that the color tends to fade
after several autoclavings.
The use of water-soluble dyes is also unsatisfactory for the preparation
of, in particular, soft contact lenses. Water-soluble dyes will leach
during repeated thermal sterilization treatments. Moreover, water-
soluble dyes in long term contact with the eye might permenently stain
the ocular tissue. Thus, the method disclosed in the American Journal
of Optometry and Physiological 0ptics, Volume 54, pp. 160-164 (1977),
"Methods of Tinting Soflens ~ Contact Lenses," would not provide a
solution to the problem of preparation of practical tinted soft contact
lenses.
In addition to the problems engendered by the use of hydrophilic
plastic materia] for the prepara~ion of these lenses, there is an addi-
tion complication introduced by the dimensions of the lens itself.
.. ..
17~
Conv~ntional hard contact lenses, generally prepared from formulations
using as principal co-monomer methyl methacrylate, are in general fitted
with a diameter which is less than the diameter of the cornea of the eye.
It is therefore possible to use a lens which is colored over its entire
extent. In contrast, soft contact lenses are most commonly fitted with
a diameter larger than that of the cornea. Because of this feature9 a
uniformly-colored soft contact lens would appear quite prominently
against the white sclera of the eye. In order to prepare a neutral
appearing contact lens, it would therefore be necessary to have a
colored central area and a clear outer perimeterO
As noted in U.S. Patent 4,252,421, the preparation of such lenses
leads to difficulties in fabrication. Ihese must be no bleeding of
color from the central portion into the outer, clear portion. Colored
area and clear area should, moreover, be concentric and easily aligned
during the preparation. Finally, it is essential that there be no
leaching of color either into the tear fluid or into the sterilization
solutionO
U.S. Patent 4,252,521 disc]oses a method for preparation of soft contact
lenses containing a tinted central core and an outer lens element which
is usually clear. The colored central core is formed from a tinted
button, which in turn is polymerized from a monomer mixture which
includes a dye as co-monomer. Thus, the water-insoluble dye or dyes are
part of the backbone of the polymer. Alternatively, a water-insoluble
dye may be added to the co-monomer mixture and this combination poly-
merized, whereby the dye is entrained in the polymer matrix. Due to the
insolubility of the dye9 it will not bleed or leach from the poly-
merized button. Two methods are also disclosed for fabricating the
contact lens. The first method involves polymerizing the tinted button,
placing the tinted button in a mold and pouring a hydrogel co-monomer
mixture arounclthe tinted button and polymerizing this mixture. An
alternative method for forming the lens is to polymerize the clear
outer button initially and then to form a centrally-positioned aperture
-- 4 --
through the button. The co-monomer mixture including the dye is then
placed within the aperture and polymerized.
This method sufers from a number of substantial drawbacks. With respect
to the method in which a water-insoluble dye is merely entrained in the
polymer matrix,the difficulties enumerated above will be present. In
contrast to the uniform composition ofa conventional hydrophilic contact
lens, the lenses produced according to U.S. Patent 4,252,421 are a
combination of hard lens and soft or hydrogel lens materials. Moreover,
the preparation of these lenses requires a number of separate fabrication
and polymerization steps. In addition, lenses of this type must be spe-
cially prepared for each prescription~Therefore, a substantial inventory
must be carried by the dispenser of contact lenses in order to cover the
range of prescriptions and colors normally desired. Finally, the use of
combination hard~soft lenses would generally lead to a wrinkling or
crimping of the edge upon hydration,causing discomfort to the wearer.
U.S. Patent 4,157~892 discloses a method for coloring water-absorbable
plastic which comprises four steps. The first step is manufacture of
a coupler monomer or coupler polymer. ~ polymerization radical is
introduced into a coupler agent to obtain a polymerizable coupler mono-
mer~ Erom ~hich a coupler polymer may be manufactured. Either of the
couplers obtained in the first step is then copolymerized or poly-
merized with a wa~er-absorbable plastic in the form of a monomer or
a polymer in the presence of a polymerization initiator ~o produce a
water-absorbable plastic capable of developing color. The material
thus prepared is formed into a intermediate product having the same
dimensions as those of the desired final product, such as a water-
absorbable contact lens. Finally, the intermediate product is colored
by immersion of the lens in an aqueous solution of a diazonium double
salt which acts as a developer. The immersion is continued for a length
of time required to cause the swelling of the intermediate product,
thereby allowing the diazo-component to penetrate into the plastic.
Then5 the solution is controlled to optimum pH value for causing a
, .
7~
-- 5 --
coupling reaction to take place and to allow the azoic dye to devolop
its color on the final product. The production of partially-colored
intermediate produc~s is possiblethrOugh the application of ultraviolet
radiation to those portions of the plastic which are not to be colored,
whereby the diazo-components on those portions are broken down.
This method again has the disadvantage of being procedurally quite
complicated. The procedure for preparation of the material in which
the color is latter to be developed must be carried out in a series of
discrete steps, and care mus~ be taken that is no premature development
of the azoic dye in the lens material. Moreover, the azoic dye precursor
is dispersed throughout the lens material, which could lead to diffe-
rences in color intensity dependent upon the thickness of the lens
ma~erial. In order to provide colored lenses for a wide variety of
prescriptions, it would again be necessary for the dispenser to keep
a large inventory. In addition, it is clear that this method is only
suitable for use with specially-prepared lens material, including a
coupler. ~herefore, it would not be feasible to use the method taught
in U.S. Patent 4,157,892 wi~h conventional hydrophilic lens materials
currently in use. Finally, the use of couplers of the type described in
this reference would be likely to lead to polymeric materials of infe-
rior quallty, compared to materials now in use for this purpose.
It is therefore a goal of the present invention to avoid the problems
associated with the prior art methods. In particular, it is an object
of the instant invention to provide a method of tinting or coloring
contact lenses which can be carried out without the need for complica-
ted proceduresand specialized equipment. It is an additional object of
the instant invention to provide a method of coloring lenses e~hich can
be kept in inventory in an untinted state, or which are already
available on the market and/or have been prescribed to the patient.
Further objects of the invention include the development of a method
for preparing a contact lens which appears completely natural as worn
7~
-- 6 --
on the eye, i e., lenses having a central colored portion covering the
cornea and clear edges over the part of the lens covering the sclera.
It is additionally an object of the invention to provide contact lenses
which will retain the color over long periods of time and repeated
chemical and/or heat sterili7ation treatments. It is a further object of
the invention to prepare contact lenses in a wide range of colors and
color combinations through mechanically simple procedures.
One object of the inven~ion is a contact lens at least a portion of it
is colored, comprising a copolymeric hydrogel material containing
hydroxyl, amino, amido or mercapto groups to which at least one reactive
dyestuff, capable of forming an ether group with cellulose, is cova-
lently bonded exterrial to the polymer backbone through ether, thioether,
amlno or amldo groups.
A wide variety of polymers are suitable for use in the preparation of
the novel lenses. The only requirement is that the monomers contaîn
at least one of the functional groups capable of reacting with a reac-
tive dyestuff, either before or after polymerization of the monomers
to form the polymer.
The composition of the lens material itself can vary within wide limits,
the only requiremen-t being the presence in the monomer mixture of at
least one component which will provide the polymer with the required
exoskeletal functional groups. Particularly suitable as monomers for
this purpose are hydroxyalkyl esters of polymerizable unsaturated
acids. Among such esters, hydroxyethyl methacrylete (HEMA) has been
used quite extensively; lenses prepared from such materials are
disclosed, for example, in U.S. Patents 2,976,576 and Re 27,401.
In general, however, any polymeric material suitable for use in the
preparation of a contact lens can also be used for the preparation of
the inventive tinted lenses, with the proviso that at least one of the
monomeric components which forms the material contains the exoskeletal
- 7 --
functional group which can react with the reactive dyestuff molecule.
Therefore, the instant invention can be employed with a wide variety of
known polymeric lens materials. This allows for the possibility of
preparing tinted contact lenses according to the invention from the
wide range of materials already available, as well as novel contact lens
materials yet to be developed or marketed.
In addition to hydroxyalkyl esters of unsaturated acids, the following
monomeric materials may serve as typical examples of co-monomers which
can he used in conjunction with monomers providing the required functio-
nal groups: acrylic and methacrylic acids, alkyl and cycloalkyl acryla-
tes and methacrylates; N-(l,l-dimethyl-3-oxobutyl) acrylamide; and hete-
rocyclic N-vinyl compounds containing a carbonyl functionally adjacent
to the nitrogen in the ring, in particular N-vinyl lactams such as
N-vinyl pyrrolidone. Moreover, one or more cross-linking agents may
be used, as known in the art, in order to provide a polymeric material
of optimal properties. Examples of such cross-linking agents include
trim2thylolpropane trimethacrylate, ethylene glycol dimethacrylate
(RDMA) and diethylene glycol bis-allyl carbonate.
Useful reactive dyes according to the instant invention are commonly
referred to as "reactive dyes forming ether linkages" inasmuch as the
reactive group or groups in this known class of dyes react with
cellulose to form an ether linkage, as opposed to, for example, an
ester linkage. Such reactive dyes forming ether linkages are generally
described in FIBRE-REACTIVE DYES Chapter VI, by W.F. Beech, SAF
International Inc., New ~ork (1970).
This class of reactive dyes are believed to react with hydroxyl, amino,amido or mercapto groups present in the hydrogel polymer network of
contact lens materials primarily by nucleophilic addition to form a
covalent bond therewith.
-- 8 --
A wide variety of commercially available dyes, reactive via nucleophilic
substitution, are suitable for use in the preparation of the inventive
contact lenses. In addition, virtually any desired shade or tint can be
achieved through the use of a particular reactive dye or combination of
reactive dyes.
Thus~ dyes containing an activated double bond which is able to add to
the func~ional group external to the polymer backbone can be used
according to the invention. For example, exosketetal bond activated by
a bridge member such as an -S02-, -SO- or -CO- group are particularly
suitable for use according to the invention. Similarly, dyes with
Eunctional groups which can undergo addition reactions with exoskeletal
double bonds of the polymer may be employed.
Among the types of reactive dyes suitable for use according to the
invention, the following general classes may be mentioned: reactive
dyes containing vinyl sulfone precursors, such as ~-sulfatoethyl-
sulfonyl, ~ sulfatoethylsu]fonamido, ~-hydroxyethylsulfonyl and
~-hydroxyethylsulfonamido substituents, as well as suitable derivatives
thereaf, dyes containing acryloylamino, ~-chloropropionylamino, and
~-sulfatopropionylamino and related reactive groups; dyes containg
~-phenylsulfonylpropionylamino groups, dyes containing ~-sulfato- or
~-chloroethylsulfamoyl groups; chloroacetyl dyes; ~-bromoacryloyl dye-
stuffs; and a wide variety of other reactive dyes which have been
developed for use in the dyeing of natural and synthetic fibers, ;n
particular of cellulose and wool and function by nucleophilic addition.
Although there are many examples in the art of the use of reactive
dyestuffs with clothfiber materials, the application of these dyes to
the preparation of tinted contact lenses has not been disclosed until
this time.
Some typical examples of commercially available dyes suitable for use
according to the invention are: Dye-SO~-CH2-CH2-0-S03Na ~Remazol),
Dye-S02NHCH2CH20S03Na (Levafix), Dye-NH-OC-CH2CH2S02C6H5 (Solidazol),
* Trademark
~3 9~7~D~
9 _
Dye-NH-OC-CH-C112Br (Lanasol), Dye-NH-OC-C=CH2 , Dye-NHCH20H (Calcobond).
Br Br
Similarly, within the scope of the invention is the use of dyestuffs
containing more than one reactive group capable of forming ~ covalent
bond by nucleophilic addition with hydroxyl, amino, amido or mercapto
groups present in the hydrogel polymer network of contact lens
materials.
Preferred reactive dyestuffs capable of forming a covalent bond with the
hydroxyl, amino, amido or mercapto groups present in the contact lens
hydrogel material are those having the general formulae
D - R - C = CH (I)
or
D R - CH - CH2 (II)
X Y
wherein
D is the radical of an organic dyestuff radical;
R is a divalent organic electron attracting group capable
of causing electron withrawl of the C carbon atoms in the -C=CH2- or
CH-CH2- groups of formulae I and II, thus activating the same;
X is hydrogen or halo; and
Y is a leaving group; or mixtures thereof.
The radical D may advantageously be the radical of an azo, phthalo-
cyanine, azomethine, nitro or anthraquinone dye.
The reactive dydstuffs of formula II will eliminate in the reac
tion media HY thus forming intermediates of formula I, which react then
by nucleophilic addition.
* Trademark
j, ~
- 10 --
The divalent group -R- is advantageously bonded directly to an aromaticnuclear carbon of D, or is bonded thereto via an aliphatic group such
as an alkylene group, e.g., a lower alkylene group. Most preferably,
-R- is directly bonded to a nuclear carbon atom of D.
Suitable divalent R groups include ~CO-, -S02-, ~SO~g -NHCO-, -NHS02-,
-S02NH- and the like. Most preferablyg -R- is -S02 J -S02N~ CO- or
-NHCO~.
When X is halo~ it is most preferably chloro or bromo.
Suitable leaving groups Y include -Cl, -Br~ -OH, di-lower alkylamino,
-OCH2 ~ ~- Cl , -S02-phenyl, -OS03- Z where Z is a cation,
-OS03Rl of -OS02Rl where Rl in each case is alkyl, arylg aralkyl or
alkaryl.
Advantageously where Rl is alkyl, it is alkyl of 1 to 6 carbon atoms,
preferably alkyl of 1 to 4 carbons, including for example, methyl,
ethyl, isopropyl, butyl and the like. Where Rl is aryl, it is preferably
phenyl or naphthyl. Where Rl is aralkyl, it is preferably lower alkyl
substituted phenyl, such as tolyl or xylyl, and where Rl is alkaryl, it
is preEerably lower alkylenephenyl, such as benzyl or phenethyl.
The reactive dyes of the class known as those forming ether linkages
especially suitable for tinting hydrogel contact lens materials are those
reactive dyes which form a covalent bond with the hydroxyl, amino,
amido, or mercapto groups present in a hydrogel polymer network in an
aqueous medium having p~ of 9 or greater and a temperature of up to
40C. Such reactive dyes, especially those of formula (I) or (II), are
capable of dyeing hydrogel contact lenses without any significant de-
gradation or deformation of the hydrogel substrate, due to the mild
reaction conditions.
The invention provides novel tinted lenses with exceptional color fast-ness and color uniformity. According to the requirements in a particular
instance, the dyestuff can be applied to both surfaces of a lens or to
one surface only. In addition~ the lens may be colored only in a particu-
lar portion. Thus, it is possible without difficulty to prepare lenses
with, e.g., colored central portions and clear edges, or with an annu-
lar colored portion corresponding to the iris. The method can also be
used, for example, for the application of identifiying indicia on
lenses, such as to indicate the concave or convex surface of a flexible
lens.
Although tinting or coloring is effected by cvntacting one or both sur-faces of the lens with an aqueous solution of the dyPstuff, interior
parts of the lens will also be tinted or colored to some extent due to
the diffusion of the dyestuff during the reaction time.
In general, the formation of a covalent bond between the lens material
and the reactive dyestuff is effected by a simple contacting of the
dyestuff formulatlon, such as a mildly basic a~ueous solution, with the
lens material until reaction is complete. In a case where both surface
of a lens are to be dyed, the lens is contacted on both surfaces with
a formulation of the reactive dyestuff. The shade of color is con-
trolled by the time of contacting with the dye formulation, as well
as the reactivity of the eye with the surface of the lens. When it is
desired to apply the dye to one surface only, or to a specific portion
of the surface, the prepared lens may be placed on a fixture or in a
mold, and the reactive dyestuff formulation applied only to a
specific portion or portions of the lens surface. In view of the compli-
cated methods generally employed in the art, this simple mechanical
procedure for tinting contact lenses is an enormous advance over the
known methods~
Moreover, where desired, deep, fast dyeings can be easily obtained,
e.g. such that the lens has a light transmission of 90 % or less in the
- 12 -
desired visible color range~ and substantially devoid of opacity, over
the colored portion of the lens.
After the reaction of the lens material with the reactive dyestuff is
effected, unreacted dyestuff may be removed using any suitable solvent.
The choice of solvent for extract;on or rinsing is, of course, dependent
upon the solubility of the particular dyestuff. For the majority of
dyestuffs in current use, lower alcohols such as methanol are suitable
solvents. After the cleaning process, the tinted lens is freed of traces
of the solvent, for example by boiling in distilled water.
For economic reasons, it is preferable to treat the already polymerized
material with the dyestuff preparation. However, it would also be
possible to treat a monomer such as HEMA with reac~ive dyestuff prior
to polymerization, and subsequently to polymerize the reactive dyestuff
- monomer units.
Because of the formation of a covalent bond between the polymeric mate-
rial forming the contact lens and the reactive dyestuff, the lenses of
the invention show a remarkable color fastness to all types of sterili-
zation treatments commonly used for contact lenses,such as chemical,
enzymatic and heat sterilizations. Moreover, since the co]oring material
is applied directly to the surface or surfaces of the lens, the shade
is independentof lens thickness. This is in marked contrast to lenses
prepared from plastic buttons in which pigment is entrained in the
polymer matrix, since, in this case~ the intensity of the shade is
directly dependent upon the thickness of the lens. This is true, for
example, with the contact lenses prepared according to U.S. Patent
4.157.~72.
Moreover, since the inventive method allows for the introduction of
the coloring material at any time during the preparation of the
colored lenses, it is possible to tint lenses after filling a particu-
lar prescription with conventional clear lenses. Thus, it is not
~ .,,
- 13 -
necessary to keep a large inventory of precolored lenses, a substantial
drawback of many of the known methods for preparing tinted lenses.
After fitting conventional clear lenses, the color could be introduced
as a final step before despensing to the patient. Alternatively,
previously prescribed lenses could be subsequently custom-tinted accor-
ding to the desires of the wearer. Since the range of polymeric
materials suitable for use according to the invention is sufficiently
broad to embrace virtually all lens materials in current use, the inven-
tive method is of an almost universal applicability.
Another advantage of the inventive method is the extreme reduction in
cost of preparation of the inventive contact le,lses, relative to known
methods for preparation of lenses containing at least a central portion
which has been colored. Suitable reactive dyes are readily available,
and the ease of application of these dyes to the lens materials makes
unnecessary the use of complicated polymeri~ation procedures or equipment.
Tests on the o~ygen premeability of lenses treated according to the
invention have sho~n that there is virtually no change in oxygen preme-
ability after tretament, as can be seen from the following table:
Clear Lenses Tinted Lens (Blue)
Oxygen Concentration *(PL) Transmittance Oxygen Conc. (PL)
P= 6.10) (at max. = 587nm) (P= 6.10)
1. 1.68 - 68.3 % 1.71
2. 1.47 23.0 % 1.50
3. 1.56 9.3 % 1.51
4. 1.66 0.0 % 1.60
* Tested under same technique as reported by M.F. ~efojo, F.~. ~lolly
and F.L. Leong, Contd. Intraocular Lens Med. J., 3(4) (1977) 27.
- 14 -
An additional advantage of the invent;ve lenses is the fact thaL most
of the dyestuffs employed for tinting tend to absorb ultraviolet radia-
tion, particularly of the wavelengths shown to be harmful to the eye,
for example in Optical Management, "Ultraviolet Radiation and the
Ocular Media, "January 1981, pp. 21-33. In particular, it has been re-
ported that ultraviolet radiation may be directly linked to the develop-
ment of cataracts.
The invention may be better understood through the following examples:
Example 1: Totally Blue on Both Sides of Tinted Lens
A stock solution, stable for at least 5 weeks, i5 prepared by dissolving
0.1 g of a dyestuff of the formula
HO NH
I 1 2
HO S-O-C H S~o -N=N-! -N=N-- -S-C2H~-O-SO H
NaO3S ~ S03Na
in 10 ml of O.OOlM HCl solution. A clear HEMA lens is soaked in l.OM
sodium carbonate solution. The sodium carbonate soaked lens is then
placed into 0.11 ml of the stock solution. 4 ml of 1.0~ sodium carbonate
solution is then added, and the lens allowed to remain in the solution
for 53 minutes. The tinted lens is then neutralized with a buffered
saline solution (pH = 7.0). Then the tinted lens is extracted, with
methanol as a solvent, in a solvent extraction apparatus, until there
are no dye molecules leaching out. This may be readily determined, for
example, by spectrophotometer. After the extraction process, the
tinted lens is boiled in distilled water for one hour to get rid of
any trace of methanol Then the tinted lens is stored in a saline
butter solution.
The transmittance of the tinted lens at wavelength 600 nm is 68 %.
- ]5 -
Example 2: Totally Aquamarine on Both Sides of Tinted Lens
A stock solution, stable for at least 3 weeks, is prepared ~y dissolving
0.1 g of a dyestuEf of the formula
(S02NH-n\ /-~S02cH2cH2-o-s03H~
CuPhc (S02NH2)0_
(S03H)~_3
in 10 ml of O.OOlM HCl sol-ltion. The lens which has been soaked in 1.0
sodium carbonate for 10 minutes, is placed into 1 ml of the stock solu-
tion. Thus 4 ml of l.OM sodium carbonate solution is added, and the lens
soaked for the desired time. The procedures of washing, extracting and
rinsing of the lenses are the same as in Example 1.
The transmittance of the tinted lenses at wavelength 670nm are 80 %
and 70 % for two and four hour soakings, respectively.
Example 3: Totally Brown on Both Sides of Tinted Lens
Three stock solutions are req~ired for this process, all of which are
stable for at least six weeks.
A) 0.0512 g of a dyestuff of the formula
1l ~- OH
H-S03-0-C2H4-1S~ ~N=N\ ~ / 3
O I ,
NaO S/ ~./ \.
in 5 ml of O.OOlM HCl solution.
B) 0.0574g of a dyestuff of the formula
O OCH3 OH ._.
H-03S-O-C2H4-S-~ 7-N=N-.
o T=- I=
CH3 CH3
7~
- 16 -
in 5 ml of O.OOlM HCl solution
C) 0.0291 g of a dyestuff of the formula
H-O S-O-C H -S-~ -N=~ =N--~ ~-Il-C H O SO H
O i i1 i P
in 5 ml of O.OOlM HCl solution.
The lens, which has been soaked in l.OM sodium carbonate solution for
10 minutes, is placed into 0.18 ml of A, 0.12 ml of B and 0.2 ml of C
stock solutions. 1 ml of l.OM sodium carbonate solution is then added
and for one hour allowed to stand. The transmittance of the tinted
lens at wavelengths 400, 490 and 605nm are 45 %, 51 % and 60 % respecti-
vely.
Example 4: Totally Green on Both Sides of Tinted lens
The lens, which has been soaked in l.OM sodium carbonate for 10 minutes,
is placed into 0.18 ml of solution C and 0.12 ml of solution B prepared
according to Example 3. Then 1 ml of l.OM sodium carbonate solution is
added~ and the lens allowed to soak in the solution for 30 minutes. The
transmittance of the tinted lens at wavelengths 580 and 385nm are 64 %
and 58 %, respectively.
~xample 5: Edge Clear/One Side Tinted Lens
The tinting procedures are the same as for the Examples 1-4. The only
difference is that the clear lens sits in a fixture. A suitable dye
solution is then put into a mold, rather than immersing the lens in the
dye solution. The area to be colored only is then brought into contact
with the dye solution. The final steps of the procedure are the same
as in Example 1.
- 17 -
Preparation of a fixture suitable for preparing the specific type 3f
partially-tinted lens desired is a mechanically simple task. One type
of fixture found useful for preparing clear-edge lenses may be described
as follows:
The fixture has three interlocking pieces. The bottom piece is a dome
upon which the lens is positioned. The curved surface of the dome has a
diameter corresponding to that of the lens to be tinted. The top piece
acts as a reservoir for the dye solution and has an elastic gasket. This
gasket forms a seal on the surface of the lens at the edge of the area
to be tinted. The third piece is a housing for the reservoir/gasket
assembly. The entire fixture is then inserted in a clamp to hold the
aSsembly firmly in place during the dyeing process.
The lens, which has been soaking in l.OM sodium carbonate for 10 minutes~
is placed in position on the dome. The reservoir portion of the fixture
is pcsitioned and clamped. The reservoir is filled with the desired
concentration of dye and sodium carbonate solution. The solution is
allowed to remain in contact with the lens until the desired shade is
obtained. The reservoir is purged with water until all traces of the
dye solution have been removed. The lens is then removed from the
fixture.
Similarly good results may be obtained using, for example, dyestuffs ofthe following structures:
/So3Na
11 11
O ~H-~ ~.
=0
S02CH2C1120S03H
18 -
Cu ~ ~HCOCH3
~ - a~ -N~
~02C2H40S03H NaO3S ~S03Na
OCH3IOH ~--9~
~ SO Na
3 O C2H4S2 \ /~_N=N_-~
OCH3 CH3
OIH
HO S--c2H4s2--\ /~-N=N j rl t 3
N O S/ ~
Many o these dyes are readily available on the market, and dyes of this
type have been known in the art for many years. These examples should
be viewed as illustrative only, without in any way limiting the scope
of:the instant invention.
