U.S. patent application number 11/903172 was filed with the patent office on 2008-01-17 for novel biocompatible inks, preparation, and uses thereof.
Invention is credited to John Christopher Phelan, Michael Hugh Quinn.
Application Number | 20080012164 11/903172 |
Document ID | / |
Family ID | 32230411 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080012164 |
Kind Code |
A1 |
Phelan; John Christopher ;
et al. |
January 17, 2008 |
Novel biocompatible inks, preparation, and uses thereof
Abstract
An aqueous ink comprising containing a colorant and a
radiation-curable oligomer or polymer containing H-active groups
bonded to the oligomer or polymer backbone, some or all of whose
hydrogen atoms have been substituted by radicals of a
N-hydroxyalkyl (meth)acrylamide. Methods for printing the inventive
inks upon medical devices, such as contact lenses, are also
disclosed.
Inventors: |
Phelan; John Christopher;
(Gurnee, IL) ; Quinn; Michael Hugh; (Valparaiso,
IN) |
Correspondence
Address: |
CIBA VISION CORPORATION;PATENT DEPARTMENT
11460 JOHNS CREEK PARKWAY
DULUTH
GA
30097-1556
US
|
Family ID: |
32230411 |
Appl. No.: |
11/903172 |
Filed: |
September 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10676764 |
Oct 1, 2003 |
7288578 |
|
|
11903172 |
Sep 20, 2007 |
|
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60423230 |
Nov 1, 2002 |
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Current U.S.
Class: |
264/2.7 ;
427/2.1 |
Current CPC
Class: |
C09D 11/101 20130101;
C09D 11/36 20130101; G02B 1/043 20130101 |
Class at
Publication: |
264/002.7 ;
427/002.1 |
International
Class: |
B29D 11/00 20060101
B29D011/00; B05D 3/00 20060101 B05D003/00 |
Claims
1-8. (canceled)
9. A method for printing on a biomedical device, comprising the
steps of: (a) providing a medical device constructed of a polymer;
(b) applying a color coat to at least a portion of a surface of the
biomedical device, wherein said color coat comprises comprising
water, at least one colorant including pigment particles, and a
(meth)acrylamidoalkyl derivative of a oligomer or polymer
containing a plurality of H-active groups; and (c) exposing the
color coat to actinic radiation sufficient to crosslink said
(meth)acrylamidoalkyl derivative.
10. A method as claimed in claim 9, wherein said H-active groups
are selected from the group consisting of --NH.sub.2 groups and
--OH groups.
11. A method as claimed in claim 9, wherein the
(meth)acrylamidoalkyl derivative is obtained by substituting at
least one hydrogen atom in H-active groups of the oligomer or
polymer with radicals of a compound selected from the group
consisting of N-2-hydroxylethyl acrylamide, N-2-hydroxyethyl
methacrylamide, N-methylol acrylamide, and N-methylol
methacrylamide.
12. A method as claimed in claim 9, wherein said polymer is the
(meth)acrylamidoalkyl derivative of a polymer selected from the
group consisting of polysaccharides, polysaccharide derivatives,
poly(vinyl alcohol), poly(ethylene glycol), poly(propylene oxide),
PEG-block-PPO, poly(acrylamide), and copolymers thereof.
13. A method as claimed in claim 12, wherein said polymer is the
(meth)acrylamidoalkyl derivative of a polymer selected from the
group consisting of dextran, hydroxypropylcellulose,
hydroxyethylcellulose, and polysaccharides comprising glucose
monosaccharide units.
14. A method as claimed in claim 9, wherein said polymer is a
N-methylol acrylamido derivative of dextran.
15. A method as claimed in claim 9, wherein said color coat further
comprises a crosslinkable, water-soluble acrylate-modified
poly(vinyl alcohol).
16. A method for making a colored contact lens comprising the
steps: (a) coating at least a portion of at least one lens-forming
surface of a lens mold with an ink comprising water, at least one
colorant including pigment particles, and a (meth)acrylamidoalkyl
derivative of a oligomer or polymer containing a plurality of
H-active groups; and (b) adding a lens forming composition to the
lens mold while maintaining the ink in position; and (c) curing the
lens-forming composition to form a colored lens.
17. A method as claimed in claim 16, wherein said H-active groups
are selected from the group consisting of --NH.sub.2 groups and
--OH groups.
18. A method as claimed in claim 16, wherein the
(meth)acrylamidoalkyl derivative is obtained by substituting at
least one hydrogen atom in H-active groups of the oligomer or
polymer with radicals of a compound selected from the group
consisting of N-2-hydroxylethyl acrylamide, N-2-hydroxyethyl
methacrylamide, N-methylol acrylamide, and N-methylol
methacrylamide.
19. A method as claimed in claim 16, wherein said polymer is the
(meth)acrylamidoalkyl derivative of a polymer selected from the
group consisting of polysaccharides, polysaccharide derivatives,
poly(vinyl alcohol), poly(ethylene glycol), poly(propylene oxide),
PEG-block-PPO, poly(acrylamide), and copolymers thereof.
20. A method as claimed in claim 19, wherein said polymer is the
(meth)acrylamidoalkyl derivative of a polymer selected from the
group consisting of dextran, hydroxypropylcellulose,
hydroxyethylcellulose, and polysaccharides comprising glucose
monosaccharide units.
21. A method as claimed in claim 16, wherein said polymer is a
N-methylol acrylamido derivative of dextran.
22. A method as claimed in claim 16, wherein said color coat
further comprises a crosslinkable, water-soluble acrylate-modified
poly(vinyl alcohol).
23-25. (canceled)
Description
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 (e) of U.S. provisional application No. 60/423,230 filed
Nov. 1, 2002, and is incorporated by reference in it's
entirety.
[0002] The present invention relates to ink for creating images
upon biomedical devices, particularly, contact lenses. Furthermore,
the present invention is related to a method for making a colored
contact lens.
BACKGROUND OF THE INVENTION
[0003] Methods have been disclosed to make printing inks suitable
for printing either contact lenses or the molds that are then used
to make contact lenses. For example, U.S. Pat. No. 4,668,240 to
Loshaek discloses colored contact lenses produced by providing a
contact lens constructed of polymer and coating at least a portion
of the lens with coloring substance, a binding polymer having
functional groups, and an additional compound having at least one
of --NCO or epoxy.
[0004] U.S. Pat. No. 4,857,072 to Narducy, et al. discloses a
method for making colored hydrophilic contact lenses. At least a
portion of the surface of the lens is coated with a color coat
comprising at least one pigment, binding polymer having functional
groups, and an additional compound having at least two groups per
molecule of --NCO.
[0005] U.S. Pat. No. 5,272,010 to Quinn discloses a method for
preparation of colored contact lenses similar to that of those
above except that an isocyanate compound is not required. Instead,
adhesion promoters such as hexamethoxymethylmelamine are used.
[0006] However, all the above methods involve complex chemistry and
result in a lens that requires extraction following the printing
operation to remove unwanted residual compounds from the ink. If
not extracted, such compounds would, at a minimum, cause irritation
and discomfort when in contact with bodily tissue. The extraction
process can be expensive and time-consuming and carries all the
disadvantages of an additional step in any manufacturing
process.
[0007] U.S. Pat. No. 6,162,844 to Lally, et al. teaches introducing
at least one polymeric dye and polyvinyl alcohol into a mold, and
crosslinking or polymerizing to form a lens. Likewise, U.S. Pat.
No. 6,149,842 to Lally, et al. teaches the making of a tinted lens
by mixing a metal phthalocyanine dye or pigment with polyvinyl
alcohol, which is then dispensed into a lens mold and crosslinked
or polymerized to entrap the dye or pigment within the polymeric
network of the lens. However, while neither method requires
extraction after printing, both result in a lens with dye or
pigment dispersed throughout the lens, not an image printed on the
surface or within the lens.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides for biocompatible ink useful
for printing upon biomedical moldings. Such inks comprise water, at
least one colorant, and a (meth)acrylamidoalkyl derivative of a
polymer containing a plurality of H-active groups.
[0009] A second embodiment of the present invention provides a
method for making a colored polymer substrate, preferably a medical
device, most preferably a hydrophilic contact lens, comprising the
steps of: [0010] (a) providing a contact lens constructed of a
polymer; [0011] (b) coating at least a portion of a surface of the
lens with a color coat comprising water, at least one colorant, and
a (meth)acrylamidoalkyl derivative of a polymer containing a
plurality of H-active groups; and [0012] (c) exposing the color
coat to actinic radiation sufficient to crosslink said
(meth)acrylamidoalkyl derivative.
[0013] A further aspect of the invention, a method for making a
colored contact lens is provided. The method comprises the steps:
[0014] (a) coating at least a portion of at least one lens-forming
surface of a lens mold with an ink comprising water, at least one
colorant, and a (meth)acrylamidoalkyl derivative of a polymer
containing a plurality of H-active groups; and [0015] (b) adding a
lens forming composition to the lens mold while maintaining the ink
in position; and [0016] (c) curing the lens-forming composition to
form a colored lens.
[0017] Yet another embodiment of the present invention provides a
biocompatible ink for printing a contact lens comprising water, at
least one colorant, a crosslinkable, water-soluble poly(vinyl
alcohol), and a (meth)acrylamidoalkyl derivative of a polymer
containing a plurality of H-active groups
[0018] The present invention provides the foregoing and other
features, and the advantages of the invention will become further
apparent from the following detailed description of the presently
preferred embodiments, read in conjunction with the accompanying
figures. The detailed description is merely illustrative of the
invention and does not limit the scope of the invention, which is
defined by the appended claims and equivalents thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In this specification, "(meth)acryl-" means "acryl-" and/or
"methacryl-". For example, (meth)acrylamidoalkyl means
acrylamidoalkyl and/or methacrylamidoalkyl, and (meth)acrylamide
means acrylamide and/or methacrylamide.
[0020] "Colorant" includes both dyes and opaque coloring agents,
either alone or in combination.
[0021] "Dye" means a substance that is soluble in a solvent and is
used to impart color. Dyes are typically translucent and absorb,
but do not scatter light. Dyes can cover both optical (covering the
pupil) and non-optical regions (not covering the pupil) of contact
lens. Nearly any dye can be used in the present invention, as long
as it is compatible with the processes described herein, including
fluorescent dyes, phosphorescent dyes, pearlescent dyes, and
conventional dyes.
[0022] "Opaque coloring agent" includes both pigments and
particles.
[0023] "Pigment" in the context of opaque coloring agents refers to
a variety of organic or inorganic insoluble pigments known in the
art, such as titanium dioxide, red iron oxide, yellow iron oxide,
Pigment Blue 15 (phthalocyanine blue (Cl 74160)), Pigment Green 7
(phthalocyanine green (Cl 74260)), Pigment Blue 36 (cobalt blue (Cl
77343)), or chromium sesquioxide. Some pigments may exhibit
fluorescence or phosphorescence. The skilled artisan will recognize
that any of a variety of pigments may be used.
[0024] "Particle" in the context of opaque coloring agents refers
to a variety of colored particles, as they are known in the art,
such as India ink. This term also includes structures that while
not colored, give the appearance of color by, for example,
diffraction or scattering (for example) of light by the particle.
Some particles may exhibit fluorescence or phosphorescence.
[0025] "Ophthalmically compatible," as used herein, refers to a
material or surface of a material which may be in intimate contact
with the ocular environment for an extended period of time without
significantly damaging the ocular environment and without
significant user discomfort. Thus, an ophthalmically compatible
contact lens will not produce significant corneal swelling, will
adequately move on the eye with blinking to promote adequate tear
exchange, will not have substantial amounts of lipid adsorption,
and will not cause substantial wearer discomfort during the
prescribed period of wear. The lenses of the present invention are
preferably ophthalmically compatible.
[0026] "Ocular environment," as used herein, refers to ocular
fluids (e. g., tear fluid) and ocular tissue (e.g., the cornea)
which may come into intimate contact with a contact lens used for
vision correction, drug delivery, wound healing, eye color
modification, or other ophthalmic applications.
[0027] "Pattern" refers to a predetermined image to be printed onto
the contact lenses. The pattern may either be fanciful or realistic
in appearance. The pattern is preferably designed in accordance
with U.S. Pat. Nos. 5,160,463 to Evans et al. and 5,414,477 to
Jahnke).
[0028] A "medical device" refers to a device having surfaces that
contact tissue, blood, or other bodily fluids of patients in the
course of their operation. Exemplary medical devices include, among
others: (1) prostheses implanted in a human or animal body; (2)
devices for temporary use within the body for purposes of e.g.,
monitoring or repair; and (3) ophthalmic lenses.
[0029] An "ophthalmic lens," as used herein, refers to a contact
lens (hard or soft), or an intraocular lens. In certain aspects of
the present invention, a lens need not act as an optical lens, such
as a contact lens that is used for vanity purposes as opposed to
purposes relating to the correction, improvement, or alteration of
a user's eyesight.
[0030] The biocompatible prepolymers within the inks of this
invention are radiation-curable oligomers and polymers containing
H-active groups bonded to the oligomer or polymer backbone, some or
all of whose H atoms have been substituted by radicals of a
N-hydroxyalkyl (meth)acrylamide. The H-active groups are --OH,
and/or --NH-- groups, with --OH being preferred. The H-active
groups may be attached to the polymer in a variety of ways. For
example, the H-active groups can be attached directly (as in PVA)
or indirectly (as in poly(acrylamide)) to the polymer backbone.
Acrylamide or dimethylacrylamide (DMA) can be copolymerized with
the N-hydroxyalkyl (meth)acrylamide and the pendant H-active group
from the N-hydroxyalkyl (meth)acrylamide will be present in the
resultant copolymers. The resultant copolymers can then be
functionalized with a N-hydroxyalkyl (meth)acrylamide. In addition
the N-hydroxyalkyl (meth)acrylamide can be directly attached to
poly(acrylamide) copolymers through condensation reactions of
poly(acrylamide) amide groups with NHMA. Likewise, among
polysaccharides, the --OH group can be attached directly to the
sugar ring (as in dextran), or, as in hydroxypropylcellulose, the
hydroxyl group of interest can be indirectly attached to the
polymer backbone.
[0031] The water-soluble polymers that may be modified in
accordance with this invention include polysaccharides or
polysaccharide derivatives and synthetic polymers. The term
"polysaccharide or polysaccharide derivative" is used
conventionally herein and refers generally to polysaccharides
(i.e., polymers comprised of monosaccharide units linked together
by glycosidic bonds) or chemical modifications of polysaccharides
which polysaccharides or chemical modifications thereof are soluble
in one or more aqueous liquids. By the term "water soluble," it is
meant that the polymer is capable of being admixed with water under
appropriate temperature and pH conditions such that the resulting
mixture appears as a homogeneous liquid under visual inspection
with no magnification. Thus, water-soluble polymers may form true
solutions in water, colloidal dispersions in water, or emulsions in
water. Alternatively, the prepolymer can be a material that is a
liquid under ambient physiological conditions. Preferably, the
polymer can form a true solution in water.
[0032] Particularly suitable polymers are polysaccharides that
contain one or more of the following monosaccharide units:
arabinose, fructose, galactose, galactopyranosyl, galacturonic
acid, guluronic acid, glucuronic acid, glucose, glucoside,
N-acetylglucosamine, mannuronic acid, mannose, pyranosyl sulfate,
rhamnose, or xylose. Polysaccharides containing the foregoing units
include cyclodextrins, starch, hyaluronic acid, deacetylated
hyaluronic acid, chitosan, trehalose, cellobiose, maltotriose,
maltohexaose, chitohexaose, agarose, chitin 50, amylose, glucans,
heparin, xylan, pectin, galactan, glycosaminoglycans, dextran,
aminated dextran, cellulose, hydroxyalkylcelluloses,
carboxyalkylcelluloses, fucoidan, chondroitin sulfate, sulfate
polysaccharides, mucopolysaccharides, gelatin, zein, collagen,
alginic acid, agar, carrageean, guar gum, gum arabic, gum ghatti,
gum karaya, gum konjak, gum tamarind, gum tara, gum tragacanth,
locust bean gum, pectins, and xanthan gum. Polysaccharides that are
either anionic or cationic include the natural polysaccharides
alginic acid, carrageenan, chitosan (partially deacetylated
chitin), gum arabic, gum ghatti, gum karaya, gum tragacanth,
pectins, and xanthan gum.
[0033] The preferred polysaccharides are dextran,
hydroxypropylcellulose, hydroxyethylcellulose, and those comprising
glucose monosaccharide units. Dextran is the most preferred
polysaccharide.
[0034] The solubility of the aforementioned polysaccharides and
derivatives thereof is dependent upon a variety of factors
including crystalinity, the average degree of polymerization and,
in the case of polysaccharide derivatives, the particular
substituent and the degree of substitution, i.e., the number of
substituent groups per anhydroglucose unit of the polysaccharide
molecule. In general, the relative solubility of the polysaccharide
in an aqueous liquid increases as the molecular weight decreases.
Additionally, a polysaccharide derivative having a low degree of
substitution may only be soluble in alkaline aqueous liquid,
whereas a polysaccharide derivative having a higher degree of
substitution may be soluble in water as well as an alkaline aqueous
liquid. The particular substituent and the degree of substitution
which imparts the desired solubility to the polysaccharide
derivatives are well known in the art and reference is made thereto
for the purposes of this invention.
[0035] Synthetic polymers containing a plurality of pendent
hydroxyl groups are also suitable for use in the present invention.
Suitable synthetic hydroxy containing polymers include poly(vinyl
alcohol), poly(ethylene glycol), poly(propylene oxide), and
PEG-block-PPO, PEG-block-PPO-block-PEG and PPO-block-PEG-block-PPO.
Polymers having a plurality of pendent hydroxyl groups can be
formed by the polymerization of vinyl esters. The pendent ester
groups, when hydrolyzed, form polymers containing pendent hydroxyl
groups. A preferred class of polymers having a plurality of pendent
hydroxyl groups are based upon hydrolyzed vinyl acetate polymers
wherein vinyl acetate is polymerized as a homopolymer or in
conjunction with other monomers to form copolymers and are known as
poly(vinyl alcohol) or vinyl alcohol copolymers. Polymerization or
copolymerizaiton of 2-hydroxyethylmethacrylate (HEMA),
glcyerolmethacrylate will yield hydroxy containing polymers or
copolymers.
[0036] Polyvinyl alcohols that can be derivatized in accordance
with the invention preferably have a molecular weight of at least
10,000. As an upper limit the polyvinyl alcohols may have a
molecular weight of up to 1,000,000. Preferably, the polyvinyl
alcohols have a molecular weight of up to 300,000, especially up to
approximately 100,000 and especially preferably up to approximately
50,000.
[0037] Amide containing polymers, such as poly(acrylamide) and
poly(acrylamide), copolymers can also be converted to radiation
curable prepolymers by the present invention.
[0038] The preferred polymer is dextran, which is commercially
available in a wide variety of molecular weights. Preferably, the
dextran has a molecular weight of at least 5,000 Daltons. As an
upper limit the dextran may have a molecular weight of up to
1,000,000. Preferably, the dextran has a molecular weight of 5,000
to 500,000, especially from 10,000 to 100,000, and especially
preferably up to approximately 50,000.
[0039] The functionalizing compound contains a hydroxyl group, an
amine group, and a radical-polymerizable acrylic group.
Specifically preferred are N-hydroxyalkyl (meth)acrylamides of the
general structure: ##STR1## wherein R.sub.1 is methyl or --H;
R.sub.2 is --[(CH.sub.2).sub.x--O--].sub.y--H, where x is 1,2, or 3
and y is 1-5. The preferred R.sub.1 is --H. Within R.sub.2, x is
preferably 1, and y is preferably 1 or 2; most preferably, both x
any y are 1.
[0040] The preferred N-hydroxyalkyl (meth)acrylamides include, for
example, N-2-hydroxylethyl acrylamide, N-2-hydroxyethyl
methacrylamide, N-methylol acrylamide, and N-methylol
methacrylamide. N-methylol acrylamide is the most preferred
functionalizing compound.
[0041] Starting with a water-soluble polymer as described above,
such materials are modified by reaction with a N-hydroxyalkyl
(meth)acrylamide to impart a functionality capable of covalent
crosslinking by free radical polymerization. Such free radical
polymerization may be initiated by light or other forms of energy
using appropriate initiators. Polysaccharides are generally
insoluble in organic solvents, thus limiting the ability to modify
these materials. One aspect of the present invention involves the
modification of these materials by reaction with a N-hydroxyalkyl
(meth)acrylamide in a substantially aqueous solution.
[0042] To prepare the modified polymer, the concentration of the
water-soluble polymer is generally as high as possible to maximize
productivity. It is usually above 20% and preferably above 40%. For
example, for cellulosic derivatives the concentration is at least
10% by weight and usually at least 20% by weight. For dextrans the
concentration is generally at least 20% by weight and preferably
between 40 and 60% by weight. The maximum concentration is
generally below 80%, usually below 60%, and is dependent upon the
viscosity of the resultant dispersion or solution.
[0043] Application of heat and/or the addition of a condensation
catalyst such as ammonium chloride, or organic acids, such as
acetic acid, benzoic acid, or tartaric acid catalyze the
functionalization of the starting polymer. Accordingly, the
reaction solution preferably comprises a water-soluble condensation
catalyst. For the reaction of the starting polymer with a
N-hydroxyalkyl (meth)acrylamide, the catalyst is preferably an acid
(often an acid generating) catalyst, such as ammonium chloride. The
concentration of an acid catalyst in the aqueous phase is generally
sufficient to generate a pH of less than 6 and preferably less than
5. For example, the concentration of ammonium chloride is generally
at least 0.1% by weight, generally at least 0.5% by weight, and
preferably at least 2% by weight.
[0044] One of skill in the art will recognize that the degree of
substitution or loading of the photo-curable groups onto polymer
substrates can be controlled through the concentration and the
amount of the N-hydroxyalkyl acrylamide in a reaction solution. The
degree of substitution can also be controlled through the reaction
temperature, reaction time, and amount of catalyst (e.g. ammonium
chloride) used.
[0045] Because the N-hydroxyalkyl acrylamide contains an
unsaturated group, a polymerization inhibitor should be included in
the aqueous solution to prevent premature polymerization of the
solution. Because the reaction is carried out in an aqueous
solution a water-soluble polymerization inhibitor can be dissolved
or dispersed throughout the solution to prevent polymerization and
cross-linking reactions during the condensation reaction. These
reactions are undesirable since the product is heterogeneous,
difficult to isolate, insoluble, and possibly commercially
unsatisfactory for the purposes contemplated herein.
[0046] The polymerization inhibitor preferably comprises
monomethylether hydroquinone (MEHQ) in an amount of at least 1 ppm,
preferably more than 50 ppm, often at least 500 ppm, and sometimes
greater than 2,000 ppm. Other conventional inhibitors which are
compatible with the functionalization reaction may be used in
effective amounts. For example, other effective polymerization
inhibitors are hydroquinone, paramethoxyphenol, phenylthiazine,
copper salts, and methylene blue. If copper (II) is used, it is
used in an amount of at least 1 ppm, preferably 5 or 10 ppm, often
at least 100 ppm, and sometimes 2,000 ppm or more. The inhibitor
may be removed, if necessary, in a subsequent step but may often be
left in the product. Copper (II) ions or other metal ions may be
removed by contacting an aqueous solution of the product with an
ion exchange resin. Alternatively, one could bubble oxygen or air
or other mixtures containing oxygen into the reaction mixture to
prevent premature polymerization. Oxygen is easily removed from the
reaction mixture by known methods.
[0047] By way of the above-described process a water-soluble
photo-crosslinkable N-hydroxyalkyl (meth)acrylamide functionalized
polymer can be obtained. Due to their inherent biocompatibility,
physical properties, and optical clarity, the preferred polymers
are dextran and polyvinyl alcohol. Dextran is preferably reacted
with a N-hydroxyalkyl (meth)acrylamide in the presence of heat
and/or ammonium chloride to yield a compound of the following
general structure: ##STR2## wherein R.sub.1 is methyl or --H; and
R.sub.3 is --(CH.sub.2).sub.a-- or
--[(CH.sub.2).sub.a--O--].sub.b--, where a is 1,2, or 3 and b is
1-5. The preferred R.sub.1 is --H. R.sub.3 is preferably
--(CH.sub.2).sub.a-, with a being 1. If R.sub.3 is
--[(CH.sub.2).sub.a--O--].sub.b-, both b and a are preferably
1.
[0048] The preferred prepolymer of the present invention is an
acrylamidomethyl derivative of dextran. As discussed and
exemplified in more detail below, by way of example, the conversion
of dextran to a photo-curable prepolymer through reaction with
N-hydroxymethyl acrylamide results in a compound of the general
structure: ##STR3##
[0049] The functionalized polymers of the present invention can be
used as an ink binder. In this aspect of the invention, an ink
comprises water, a functionalized polymer, and a colorant. Such
inks are useful in printing biomedical moldings, preferably contact
lens. For cosmetic purposes, contact lenses having one or more
colorants dispersed in the lens or printed on the lens are in high
demand. These colored contact lenses enhance the natural beauty of
the eye, or provide unique patterns on the iris of the wearer, or
provide non cosmetic patterns or marks, such as rotation marks,
inversion marks, product/brand codes, lot numbers, "DEMO" lenses,
and the like, which are of benefits to wearers, eye-care
practitioners and manufacturers.
[0050] Presently, methods of printing inks onto contact lens molds
involve cliche ink transfer printing. A typical example of this
printing follows. An image is etched into metal to form a cliche.
The cliche is placed in a printer. Once in the printer, the cliche
is inked by either an open inkwell doctoring system or by a closed
ink cup sliding across the image. Then, a silicone pad picks up the
inked image from the cliche and transfers the image to the contact
lens. The silicone pads are made of a material comprising silicone
that can vary in elasticity. The properties of the silicone
material permit the inks to stick to the pad temporarily and fully
release from the pad when it contacts the contact lens mold. A
number of inks are known in the art for cliche ink transfer
printing of color images on a contact lens. Examples of such inks
include those disclosed in U.S. Pat. Nos. 4,668,240; 4,857,072;
5,272,010; and 5,414,477; and copending and commonly assigned
Application Ser. No. 60/______ filed Sep. 3, 2002, all incorporated
herein by reference.
[0051] Recently, however, methods of printing contact lenses have
been developed that employ ink-jetting as a method of placing a
color pattern upon the surface of the lens. Such methods require
inks of much lower viscosity than currently available inks. For
example, while the viscosity of inks used in pad-printing
techniques is typically between 200 and 500 cps, the viscosity
required for ink-jet printing is below 50, and preferably lower
than 30 cps.
[0052] Solutions having low viscosity tend to be "runny" when
dispensed, and can allow different colors to merge and blend,
resulting in an image with a more natural appearance. Such blending
can be enhanced using a variety of methods, including sonication or
vibration at appropriate duration and frequency to promote
appropriate blending. Solutions having too low a viscosity can
result in images that are too "runny" and thus have potentially,
undesirable characteristics, such as pooling of ink in a pattern or
spreading of ink to an unintended location. The skilled artisan
will recognize that the size of the ink droplet as applied to the
lens and the surface tension thereof will also influence the
behavior of the ink when printed on a lens or a mold. Thus,
depending on these factors, the viscosity of the ink may vary from
the numbers given above and still function within the scope of this
invention.
[0053] Solutions having too high a viscosity may not be easily
dispensed using a variety of printing structures, such as inkjets
and thus may not be appropriate for the present invention.
Furthermore, solutions having high viscosity can tend to "bead" on
a surface and not blend with the surrounding environment, including
surrounding droplets or beads of ink. Under these circumstances,
the ink may form unnatural appearing images.
[0054] Copending U.S. Application Ser. No. 60/348,257, filed Nov.
7, 2001, incorporated herein by reference and commonly assigned
with the present application, discloses a colored ink to be printed
upon a medical device by ink-jetting methods. Consistent with the
teachings of that application, every ink disclosed therein has a
viscosity significantly lower than 50 centipoise. Because nelfilcon
A is a rather viscous solution, water must be added to the ink to
obtain the desired viscosity. However, at higher levels of
colorant, the reduced concentration of nelfilcon may be inadequate
to bind the ink to the contact lens.
[0055] While the viscosity lowering effects of the addition of an
acrylamidomethyl derivative of dextran to nelfilcon is especially
suited for inks employed in ink-jet printing, such binders can also
be useful in pad-printing applications. At high levels of colorant
(.apprxeq.8% PCN), up to 47% nelfilcon was unable to hold the ink
together and properly bind to the contact lens. It is suspected
that the polymer density of such inks was too low to hold the high
PCN levels. However, the addition of nelfilcon up to 71% by weight
resulted in ink much more viscous than is preferred, even for pad
printing. Accordingly, the addition of an acrylamidomethyl
derivative of dextran to the nelfilcon ink having high colorant
levels is expected to result in an ink with low enough viscosity to
be pad printed, but yet still have sufficient stability when
printed on a contact lens.
[0056] It has been found that the addition of an acrylamidomethyl
derivative of the present invention to a functionalized poly (vinyl
alcohol) in both major and minor amounts may expand the range at
which concentrations of the various components may be employed. One
particularly preferred functionalized poly(vinyl alcohol) is an
acrylate-modified PVA known generically as nelfilcon A. Nelfilcon A
can be prepared substantially as described in U.S. Pat. No.
5,508,317 to Muller, incorporated herein by reference.
[0057] Accordingly, the functionalized polymers of the present
invention can be used in conjunction with nelfilcon as an ink
binder. In this aspect of the invention, an ink comprises water, a
functionalized polymer, nelfilcon, and a colorant. The substitution
in part of the functionalized polymer according the present
invention for nelfilcon will result in lower viscosity than the
nelfilcon alone. The preferred functionalized polymer is an
acrylamidomethyl derivative of dextran.
[0058] The proper concentration of an acrylamidomethyl derivative
of the present invention, nelfilcon, the colorant, and water to
achieve the preferred ink viscosity can be determined, for example,
by a design of experiment by modeling the design as a quadratic
D-optimal mixture design. This can be done, for example, with a
commercial software program, such as Design Expert (v. 6.0.0, from
Stat-Ease of Minneapolis, Minn.).
[0059] When employing a functionalized polymer of the present
invention as an ink binder, either alone or in conjunction with
another binder, for printing contact lenses, it is not important
that the functionalized polymer be optically transparent unless the
ink is to be printed over the pupil area of the contact lens.
[0060] Lenses colored by this invention can be formed from any
known polymerizable hydrophilic or hydrophobic material suitable
for ophthalmic uses. Lens forming materials that are suitable in
the fabrication of contact lenses are illustrated by numerous
issued US patents and familiar to those skilled in the art.
Preferred materials are hydrophilic and absorb substantial amounts
of water to form hydrogels. While the selection of a lens material
is largely determined upon the final modality of use of the final
contact lens, the presently preferred lens material is nelfilcon.
Nelfilcon contact lenses are available commercially from CIBA
Vision of Duluth, Ga.
[0061] Producing the lens by polymerization, crosslinking, and/or
shaping is well known in the art and is not presently considered a
critical part of this invention. Any of the well-known techniques
of cast molding and spin casting may be employed.
[0062] If the ink is printed onto a formed polymeric lens, the lens
is subjected to conditions that cause the ink to adhere to the
lens, thereby entrapping the colorant within the ink in a manner
that forms a colored contact lens. The coated lens, for example,
may be exposed to actinic radiation, such as, for example, UV
light, or by ionizing radiation, such as, for example, gamma
radiation, electron radiation or X radiation. Crosslinking can
usually be carried out in a very short time, for example in less
than five minutes, preferably in less than one minute. One of
ordinary skill in the art can easily ascertain the type, time, and
energy of the radiation required to crosslink the polymer within
the ink.
[0063] When the color coat is applied to the lens mold, rather than
to the lens itself, the color coat is applied to a surface of the
mold and the mold is then charged with the lens forming monomer
while maintaining the color coat in the iris portion and
configuring the resin about the color coat. The lens monomer is
then polymerized using any of the well-known polymerization
techniques. Alternatively, if the lens forming composition is a
polymer (such as poly(vinyl) alcohol) the composition is then
cross-linked according to well-known techniques. In this manner the
color coat becomes integral with the body of the lens when the
molded lens is removed from the mold. The resulting lens is
essentially smooth and continuous on the surface containing the
color coat.
[0064] If the lens is intended to be natural in appearance, the
pattern applied to the lens preferably contains voids. Typically
the voids comprise about 5 to about 80% of the pattern's area. On
the other hand, it is preferred that the pattern occupy from 50% to
all of the area of the lens in the iris region thereof (or that
portion of the mold corresponding to the iris region of the lens).
If the colorant is opaque, then only the portion of the lens
corresponding to the iris is usually printed, leaving the pupil
section clear. For lenses that are larger in diameter than the
iris, the portion of the lens extending beyond the iris may be left
unprinted.
[0065] It is to be understood that the foregoing description and
specific embodiments are merely illustrative of the best mode of
the invention and the principles thereof, and that various
modifications and additions may be made to the apparatus by those
skilled in the art, without departing from the spirit and scope of
this invention, which is therefore understood to be limited only by
the scope of the appended claims. Furthermore, any headings of
various portions of the description of the preferred embodiment are
for convenience only and are not meant to limit the scope of the
invention in any way.
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