HK1049181B - Colorants for use in tinted contact lenses and methods for their production - Google Patents

Description

Colorants for use in tinted contact lenses and methods for making same

Technical Field

The present invention relates to colorants for use in the manufacture of tinted contact lenses. In particular, the present invention provides a one-step method for tinting contact lenses and colorants for use in the method.

Background

It is known to use tinted contact lenses to change the natural color of the iris. Typically, the colored portion of the lens is located in the center of the lens, and this location of the lens will cover one or both of the pupil or iris of the lens wearer. It is also known that during tinting of contact lenses, the entire lens may be tinted slightly, as is the case with a vision meter or probe.

The colorants used to make tinted lenses generally consist of a binding polymer and a pigment. Existing colorants require the use of a cross-linking agent to form covalent bonds between the lens material and the binding polymer to form a stable, tinted lens. The "stable, tinted lens" means that the tint does not bleed or leach from the lens or transfer from one portion of the lens to another. Furthermore, with some known methods of manufacturing contact lenses, it is necessary to manufacture the lens body prior to introducing the colorant into the lens. Other methods and colorants require multiple steps to be used alone or in combination with special circles to protect the exterior of the lens from the colorant.

Thus, known colorants and methods for making tinted lenses introduce additional time or additional materials or both during the manufacture of the conventional lenses. Accordingly, there is a need to develop a colorant and a method of manufacturing a contact lens using the colorant, by which some or all of the above disadvantages are overcome.

Disclosure of Invention

The present invention provides colorants for use in the manufacture of tinted contact lenses, and methods of tinting contact lenses using the colorants of the invention. When the colorant of the present invention is applied to a lens material that is to be bent next but is not currently bent, the binding polymer forms an interpenetrating polymer network with the lens material. The colorant is thus embedded within the lens material, resulting in a stable, tinted lens. This is advantageous because the colorant does not require the use of covalent bonds to assist in the process of incorporating the pigment of the colorant into the lens. In addition, the transfer of the colorant of the present invention from the mold surface to the lens material is in a manner that results in a finished lens having a high resolution image of the pattern printed with the colorant.

In one embodiment, the present invention provides a colorant for use in tinting contact lenses, the colorant comprising, consisting essentially of, and consisting of the following components: one or more pigments, one or more solvents, and a binding polymer, wherein the binding polymer is capable of forming an interpenetrating polymer network with the lens material. In another embodiment the invention provides a method for making a tinted contact lens comprising, consisting essentially of, and consisting of the steps of: a) applying to a molding surface of a mold a tinctorially effective amount of a colorant comprising, consisting essentially of, and consisting of the following: one or more pigments, one or more solvents, and a binding polymer; b) dispensing a lens forming amount of lens material to the mold; c) swelling said colorant in said lens material and allowing said lens material to diffuse into said colorant; and d) curing the lens material in the mold under conditions suitable for the manufacture of a tinted contact lens, wherein the binding polymer forms an interpenetrating polymer network with the lens material. In another embodiment, the invention provides a mold for making a tinted contact lens comprising, consisting essentially of, and consisting of: first and second mold halves, wherein at least one of the ceramic surfaces of the first and second mold halves comprises, consists essentially of, and consists of the following: one or more pigments, one or more solvents, and a binding polymer, wherein the binding polymer is capable of forming an interpenetrating polymer network with a lens material.

For purposes of the present invention, the term "interpenetrating polymer network" or "IPN" refers to a combination of two or more separate polymers, wherein one polymer is synthesized and/or crosslinked in the presence of another polymer. Some degree of interpenetration occurs within the network structure. Typically, the individual polymers used to form the IPN are present in the form of a network. An IPN type, particularly a semi-IPN (semi-Interpenetrating Polymer network, which term may also be referred to as a "partially-Interpenetrating Polymer network" or a "semi-Interpenetrating Polymer network"), is composed of one or more crosslinked polymers and one or more non-substantially crosslinked polymers, as described in "Interpenetrating Polymer Networks: an Overview "by Sperling, L.H.in intersection Polymer Networks, Edited by Klimpen, Sperling, and Urraki, pp3-6 (1994). For the present invention, the type of interpenetrating polymer network used is a semi-IPN. In one embodiment, the semi-IPN is formed using a crosslinked lens material and a binding polymer that is not substantially crosslinked. For purposes of the present invention, the phrase "substantially free of crosslinking" means that the uncrosslinked material has not been subjected to conventional crosslinking conditions prior to contact with the lens material. The semi-IPN may be formed in one step, or in several steps referred to as a continuous semi-IPN. One of ordinary skill in the art will recognize that the presence of a crosslinking agent, either by addition or as an impurity, can create reaction conditions that favor the formation of a continuous interpenetrating polymer network. Preferably, the interpenetrating polymer networks of the present invention are continuous-interpenetrating polymer networks.

For the purposes of the present invention, the "ceramic curve" refers to the surface of the mold used to form the lens surface.

One discovery of the present invention is that by using a binding polymer that forms an interpenetrating polymer network with the lens material, a stable, tinted lens can be manufactured without the need to form covalent bonds between the colorant and the lens material. A tint stable lens is provided by inclusion of pigment within the entanglement of the binding polymer and lens matrix polymer. The binding polymers of the present invention are comprised of homopolymers or copolymers or combinations thereof having similar solubility parameters relative to each other and the binding polymers have similar solubility parameters as the lens material. These binding polymers contain functional groups that enable the polymers of the binding polymer and the copolymer to react with each other. The functional groups must be such that the groups of one polymer or copolymer interact with the groups of another polymer or copolymer, resulting in an increase in the density of the interaction to inhibit its flowability and/or inclusion of the pigment particles. The interaction between the functional groups may be of a polar, dispersive or charge transfer complex nature. The functional group may be located on the main chain of the polymer or copolymer or on a side chain of the main chain.

For example, a monomer or mixture of monomers that produces a positively charged polymer and one or more monomers that produce a negatively charged polymer may be used together to form the binding polymer. As a more specific example, methacrylic acid ("MAA") and 2-hydroxyethyl methacrylate ("HEMA") can be used to prepare MAA/HEMA copolymers which are then blended with HEMA/3- (N, N-dimethylamino) propyl acrylamide copolymers to prepare the adhesive polymer.

For another embodiment, the binding polymer may be composed of hydrophobically modified monomers including, but not limited to, amides and esters having the formula:

CH₃(CH₂)_x-L-COCR＝CH₂

wherein L may be-NH or oxygen, x may be an integer from 2 to 24, and R may be C₁To C₆Alkyl or hydrogen and preferably methyl or hydrogen. Examples of such amides and esters include, but are not limited to, lauryl methacrylamide and hexyl methacrylate. As another example, polymers of carbamate and urea extended by aliphatic chains can be used to make the binding polymer.

Preferred binding polymers of the present invention are random block copolymers of HEMA, MAA and lauryl methacrylate ("LMA"), random block copolymers of HEMA and MAA or HEMA and LMA. In these embodiments each ingredient has a weight percentage of about 93 to about 100 weight percent HEMA, about 0 to 2 weight percent MAA, and about 0 to 5 weight percent LMA, based on the total weight of the binding polymer.

The molecular weight of the binding polymer must be such that the polymer partially dissolves in the lens material and swells therein. The lens material diffuses into the binding polymer and is polymerized and/or crosslinked. On the other hand, however, the molecular weight of the binding polymer must not be too high to affect the quality of the printed image. Preferably, the molecular weight of the binding polymer is from about 7000 to about 100000, more preferably from about 7000 to about 40000, most preferably from about 17000 to about 35000, M on the SEC analyzer corresponding to the molecular weight of the highest peak_Peak(s)(＝(M_n×M_w)^1/2)。

For the present invention, the molecular weight is measured by gel permeation chromatography with a 90 ° light scattering and refractive index detector. Two PW4000 and PW2500 columns, a methanol-water eluent at a weight ratio of 75/25 adjusted with 50mM sodium chloride, and a mixture of polyethylene glycol and polyethylene oxide molecules with molecular weights defined as from 325000 to 194 were used.

It will be appreciated by those skilled in the art that the desired molecular weight of the adhesive polymer may be obtained by using a chain transfer agent in the preparation of the adhesive polymer, using a large amount of initiator, using living polymerization, selecting the appropriate monomer and initiator concentrations, selecting the type and amount of solvent, or a combination of the above. Preferably, the chain transfer agent is used in combination with an initiator, or more preferably, an initiator and one or more solvents to achieve the desired molecular weight. On the other hand, a small amount of very high molecular weight binding polymer may be used in combination with a large amount of solvent to maintain the desired viscosity of the binding polymer. Preferably, the viscosity of the binding polymer is from about 4000 to about 15000 centipoise at 23 ℃.

Chain transfer agents useful in preparing the adhesive polymers used in the present invention have chain transfer constant values greater than about 0.01, preferably greater than about 7, and more preferably greater than about 25000. Suitable chain transfer agents of this type are known and include, but are not limited to, aliphatic mercaptans of the formula R-SH, wherein R is C₁To C₁₂Aliphatic radical, benzyl radical, cycloaliphatic radical, or CH₃(CH₂)_x-SH (where x is 1-24), benzene, n-butyl chloride, t-butyl chloride, n-butyl bromide, 2-mercaptoethanol, 1-dodecylmercaptan, 2-chlorobutane, acetone, acetic acid, chloroform, butylamine, triethylamine, bis-n-dibutylthio and disulfide, carbon tetrachloride and carbon tetrabromide, and the like, as well as combinations thereof. Typically, about 0 to 7 weight percent chain transfer agent based on the total weight of the polymer composition is used. Preferably, dodecyl mercaptan, decane mercaptan, octane mercaptan, or a combination thereof is used as the chain transfer agent.

Any desired initiator may be used including, but not limited to, ultraviolet light initiators, visible light initiators, thermal initiators, and the like, and combinations thereof. Preferably, a thermal initiator is used, more preferably 2, 2-azobisisobutyronitrile and 2, 2-azo-2-methylbutyronitrile. The amount of initiator used is about 0.1 to 5% by weight relative to the total weight of the composition. Preferably, 2, 2-azo-2-methylbutanenitrile is used together with dodecanethiol-.

The binding polymers of the present invention may be prepared using any convenient polymerization method, including but not limited to, free radical chain polymerization, step-wise polymerization, emulsion polymerization, ionic chain polymerization, ring opening polymerization, group transfer polymerization, atom transfer polymerization, and the like. Preferably thermally initiated, free radical polymerization is used. The conditions under which the polymerization is carried out are known to the person skilled in the art.

The solvent used to prepare the binding polymer is a medium boiling point solvent having a boiling point of from about 120 ℃ to about 230 ℃. The choice of solvent used is based on the type of binding polymer to be prepared and its molecular weight. Suitable solvents include, but are not limited to, diacetone alcohol, cyclohexanone, isopropyl lactate, 3-methoxy-1-butanol, 1-ethoxy-2-propanol, and the like.

The binding polymers of the invention are adapted in terms of swelling factor in water to the lens material to which they are to be applied. The swelling factor of the binding polymer matches or substantially matches the swelling factor of the cured lens material in the fill fluid, avoiding the generation of stresses within the lens that would otherwise result in poor optical performance and lens parameter drift. In addition, the binding polymer must swell in the lens material to allow swelling of the image printed with the colorant of the present invention. Due to said swelling, the image is entrapped in said lens material without exerting any influence on the wearing comfort of the lens.

The pigments used with the binding polymer in the colorants of the present invention are those organic or inorganic pigments suitable for use in contact lenses, or combinations of such pigments. The opacity can be controlled by varying the concentration of the pigment and opacifier used, with higher concentrations producing higher opacity. Exemplary organic pigments include, but are not limited to, phthalo blue dye, phthalo green dye, carbazole violet, vatorange #1, and the like, and combinations thereof. Examples of suitable inorganic pigments include, but are not limited to, black iron oxide, brown iron oxide, yellow iron oxide, red iron oxide, titanium dioxide, and the like, and combinations thereof. In addition to these pigments, soluble and insoluble pigments may be used, including but not limited to dichlorotriazine and vinyl sulfone-based dyes. The dyes and pigments used are commercially available.

Coating or wetting the pigment particles with the binding polymer enables better dispersion of the pigment particles in the bulk of the binding polymer. The coating can be obtained by covering the surface of the pigment using electrostatic force, diffusion force or hydrogen bonding force. Preferably, the pigment is dispersed into the interior of the binding polymer using a strong shear force. The pigment is added to the binding polymer by dispensing the polymer and pigment into a suitable mixer, such as a roller mixer, and continuing the mixing operation until a homogeneous mixture is obtained, typically for a period of up to about 30 minutes. The mixture is then fed to a high shear mill, such as an Eiger mill, to disperse the pigment into the binding polymer. The milling operation is repeated as necessary to achieve thorough dispersion. Typically, the milling operation is carried out until the pigment size is about 0.2 to about 3 microns. The milling operation may be carried out using any suitable commercially available equipment including, but not limited to, high shear or ball milling equipment.

The colorants of the present invention, in addition to comprising pigments and binding polymers, also comprise one or more solvents that aid in coating the colorant on a surface. Another discovery of the present invention is that to ensure that the colorant does not diffuse or flow over the surface to which it is applied, the colorant preferably has a surface tension of less than about 27 mN/m. The surface tension is obtained by treating the surface to which the colorant is to be applied, such as a mold surface. Surface treatment may be carried out by methods known in the art, such as, but not limited to, plasma and corona treatment. On the other hand, it is preferable to obtain a desired surface tension by selecting a solvent used in the colorant.

The solvent used in the colorant of the present invention is thus a solvent capable of increasing or decreasing the viscosity of the colorant and facilitating control of the surface tension. Suitable solvents include, but are not limited to, cyclopentanone, 4-methyl-2-pentanone, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, propyl lactate, and the like, and combinations thereof. Preferably, 1-ethoxy-2-propanol and propyl lactate are used.

In a preferred embodiment, at least three different solvents are used in the colorant of the present invention. The first two of these solvents are medium boiling point solvents and are used in the preparation of the binding polymer. While these solvents may be removed from the binding polymer after it is formed, it is preferred that they remain in the binding polymer. Preferably the two solvents are 1-ethoxy-2-propanol and propyl lactate. Another low boiling point solvent (meaning that the solvent has a boiling point of about 75 c to about 120 c) is used to reduce the viscosity of the colorant as desired. Suitable low boiling solvents include, but are not limited to, 2-propanol, 1-methoxy-2-propanol, 1-propanol, and the like, and combinations thereof. Preferably 1-propanol is used.

The specific amount of solvent used depends on a variety of factors. For example, the amount of solvent used in the polymer formation process depends on the desired molecular weight of the binding polymer and the constituent components used in the binding polymer, such as monomers and copolymers. The amount of low boiling solvent used depends on the desired viscosity and surface tension of the colorant. In addition, if the colorant is applied to a mold and cured with the lens material, the amount of solvent used will depend on the lens and mold materials used, and whether the mold material has undergone any surface treatment to increase its wettability. The determination of the exact amount of solvent used is known to those of ordinary skill in the art. Generally, the total weight of solvent used will be from 40 to 75% by weight of the solvent to be used

One of ordinary skill in the art will recognize that each pigment used has a critical pigment volume for the solvent selected. The critical Pigment volume can be determined by any known method, generally this volume is established above the efficiency of solvent and binding polymer to suspend the Pigment particles, as disclosed in pattern, sample c, Paint Flow and Pigment Dispersion, 2d ed., pp126-300 (1993).

In addition to solvents, plasticizers may be, and preferably are, added to the colorant to reduce cracking during drying of the colorant and the optical mold parts, which can improve the final quality of the image made using the colorant and improve the dispersion and swelling of the colorant through the lens material. The type and amount of plasticizer used will depend on the molecular weight of the binding polymer used and on the shelf life stability desired for the colorant to be placed in the mold where it is stored prior to use. Plasticizers used include, but are not limited to, glycerol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, or the like, and combinations thereof. Preferably glycerol is used. The amount of plasticizer used is generally from 0 to about 10% by weight relative to the weight of the colorant.

Control of the opacity of the colorant can be achieved by varying the pigment concentration and pigment particle size used. In another aspect, a sunscreen may be used. Suitable opacifiers are commercially available, for example titanium dioxide or zinc oxide.

In the preferred colorant mixture of the present invention, about 0.2 to about 25 weight percent pigment, about 30 to 45 weight percent binding polymer, about 40 to 70 weight percent solvent, about 0 to 25 weight percent titanium dioxide, and about 0.2 to 7 weight percent plasticizer are used. The weight percentages are based on the total weight of the colorant mixture.

The binding polymer may incorporate from about 0.2 to about 25 weight percent of an organic pigment and from about 0.2 to about 50 weight percent of an inorganic pigment, based on the weight of the colorant. However, a high pigment concentration may give a very black hue. It is therefore preferred to use about 0.2 to about 7 weight percent organic pigment and about 0 to 20 weight percent inorganic pigment. The ratio of the combination of the two pigments depends on the intended color, shade and hue.

One of ordinary skill in the art will recognize that additives may be included in the stain compositions of the present invention in addition to the constituent ingredients discussed above. Suitable additives include, but are not limited to, additives to aid flow and leveling, additives to prevent foam formation, additives for rheology modification, and the like, and combinations thereof.

The colorants of the present invention are embedded in the lens material during the curing of the lens material. Thus, the colorant may be embedded relatively closely in front of or behind the lens being formed, depending on the mold surface to which the colorant is applied. In addition, one or more layers of colorant may be applied in any order. In another embodiment, a transparent binding polymer layer may be used in combination with a colorant. For example, in the method of the present invention, a clear binding polymer layer may be applied to the mold surface of the on-mold type prior to application of the colorant. The transparent binding polymer may be the same or different than the binding polymer used for the colorant layer. If the transparent binding polymer is different from the binding polymer, the transparent binding polymer must be compatible with the binding polymer and lens material in terms of swelling factor and swelling capacity, and the transparent binding polymer must be capable of swelling into the lens material.

The present invention can be used to provide tinted hard or soft contact lenses made from any known lens material, or material suitable for making such lenses. Preferably, the lenses of the invention are soft contact lenses having a water content of from about 0% to about 90%. More preferably, the lenses are made from monomers containing hydroxyl groups, carboxyl groups, or both, or from silicone-containing polymers such as siloxanes, hydrogels, silicone hydrogels, and combinations thereof. The material used to make the lenses of the invention may be made in the following manner: mixtures of macromers, monomers, and combinations thereof are reacted with additives, such as polymerization initiators. Suitable materials include, but are not limited to, silicone hydrogels prepared from silicone macromers and hydrophilic monomers. Examples of such silicone macromers include, but are not limited to, polydimethylsiloxanes methacrylated with pendant hydrophilic groups, disclosed in U.S. patents US 4259467, 4260725 and 4261875; polydimethylsiloxane monomers having polymerizable functional groups disclosed in U.S. Pat. No. 4136250 (refer to patent publication nos., the same below), 4153641, 4189546, 4182822, 4343927, 4254248, 4355147, 4276402, 4327203, 4341889, 4486577, 4605712, 4543398, 4661575, 4703097, 4837289, 4954586, 4954587, 5346946, 5358995, 5387632, 5451617, 5486579, 5962548, 5981615, 5981675, and 6039913; and combinations thereof. Silicone hydrogels can also be prepared using polysiloxane macromers combined with hydrophilic monomers as disclosed in U.S. patents 5010141, 5057578, 5314960, 5371147 and 5336797; or macromers comprising polydimethylsiloxane blocks and polyether blocks, as described in U.S. Pat. Nos. 4871785 and 5034461. All of these cited patents are incorporated herein by reference in their entirety.

Suitable materials may also be prepared from oxygen-permeable and ion-permeable components, as described in U.S. patents 5760100, 5776999, 5789461, 5965631 and 5958440. Hydrophilic monomers may be combined with such copolymers, including 2-hydroxyethyl methacrylate ("HEMA"), 2-hydroxyethyl acrylate, N-dimethylacrylamide ("DMA"), N-vinylpyrrolidone, 2-vinyl-4, 4-dimethyl-2-oxazolin-5-one (2-vinyl-4, 4-dimethyl-2-oxazolin-5-one), methacrylic acid, and 2-hydroxyethyl methacrylamide. Additional siloxane monomers, such as tris (trimethylsiloxy) silylpropyl methacrylate or siloxane monomers, can be incorporated as disclosed in U.S. patents 5998498, 3808178, 4139513, 5070215, 5710302, 5714557, and 5908906. The material composition may also include various toughening agents, UV blockers (blocks), and wetting agents. They may be prepared with diluents such as primary, secondary or tertiary alcohols, as disclosed in US 6020445. All cited patents are incorporated herein by reference in their entirety.

Materials for making contact lenses are known and commercially available. Preferably, the material used is a HEMA-based hydrogel, more preferably etafilcon a, the adhesive polymer being formed from: linear random block copolymers of MAA, HEMA, and lauryl methacrylate ("LMA"); linear random block copolymers of MAA and HEMA; random block copolymers of HEMA and LMA; or a homopolymer of HEMA. Etafilcon a, disclosed in U.S. patent nos. 4680336 and 4495313, which are incorporated herein by reference in their entirety, typically consists of 100 parts by weight ("pbw") of HEMA, about 1.5 to about 2.5pbw MAA, about 0.3 to about 1.3pbw ethylene glycol dimethacrylate, about 0.05 to about 1.5pbw 1, 1, 1-trihydroxypropane trimethacrylate, and about 0.017 to about 0.024pbw visible tint (visible tint). Preferably etafilcon A is used with linear random block copolymers of MAA, HEMA and LMA in a ratio of 0.47 MAA: 100 HEMA: 4.14LMA, or with linear block copolymers of HEMA and MAA in a ratio of 99.9HEMA and 0.1MAA to 99.5HEMA and 0.5 MAA.

A tinctorially effective amount of colorant is used in an amount sufficient to produce a target level of tint to the manufactured lens. Typically, about 0.5mg to about 4.0mg of colorant is used per pair of lenses.

The colorants used in the lenses of the invention are applied to the lens surface by any convenient method. In a preferred method of the invention, a thermoplastic optical mold is used, made of any suitable material including, but not limited to, polypropylene or polystyrene resin. A tinctorially effective amount of a colorant is applied to the desired portion of the ceramic curve of the mold. The coating can be carried out in any convenient manner. Preferably, the coating is performed by means of embossing.

A lens forming amount of lens material is dispensed into the mold. The "lens forming amount" refers to the amount of material necessary to produce a lens of the desired size and thickness. Typically, about 10 to about 40mg of lens material is used. The colorant is swollen in the lens material. Preferably, the swelling is carried out under conditions suitable to swell the colorant to 1 to 4 times its dry thickness. Typically, this swelling is achieved at a temperature of about 40 to 68 ℃ for a time of about 1 to about 30 minutes.

The mold containing the lens material and colorant is then placed under conditions suitable to form a tinted lens. The exact conditions will depend on the composition of the colorant and the lens material selected, as can be determined by one skilled in the art. Once curing is complete, the lens is removed from the mold and placed in a buffered saline solution to be equilibrated.

A preferred method of making a colored lens is by an embossing process as shown below. A metal plate, preferably made of steel or more preferably stainless steel, is covered with a photoresist that becomes insoluble in water once cured. A pattern of colorant is selected or designed and then reduced to the desired size using any of a number of techniques, such as photographic techniques, placed onto the metal plate, and the photoresist cured. The conditions for performing the pattern etching are known to those skilled in the art.

After patterning, the plate is then washed with an aqueous solution and the resulting image is etched into the plate to a suitable depth, e.g., about 20 microns. The colorant is then deposited onto the pattern to fill the depressions with colorant. A silicon wafer of suitable geometry and varying hardness (typically about 1 to about 10shore a durometer units) is pressed against the image on the plate to remove the colorant, which is then dried slightly to evaporate the solvent. The wafer is then pressed against the ceramic curve of an optical mold and the colorant is dried. The molds are degassed for up to 12 hours to remove excess solvent and oxygen before the molds are filled with a lens forming amount of lens material. The mold assembly is then assembled using an auxiliary mold half and, after the printed image is allowed to swell, the mold assembly is placed under conditions suitable to cure the lens material used.

Detailed Description

The invention will become more apparent from the following non-limiting examples.

Examples

EXAMPLE 1 Synthesis of an adhesive Polymer

To a 5L glass container was added 2.65 wt% dodecyl mercaptan, 1.56 wt% lauryl methacrylate, 0.18 wt% MAA, 37.69 wt% 2-HEMA, and 42.35 wt% isopropyl lactate, and 10.59 wt% 1-ethoxy-2-propanol as a solvent. The mixture was premixed for about 10 minutes using a magnetic stirrer and then transferred to a 5L stainless steel reactor having a built-in heating mantle and equipped with a mechanical stirrer, nitrogen inlet, reflux condenser and a temperature sensor. The mixture was heated for about 25 minutes to a temperature of about 63 ℃ at which point 3.0 wt% 2, 2-azo 2-methylbutyronitrile and residual isopropyl lactate were added. Nitrogen was fed to the reactor to create a nitrogen blanket for use in the remainder of the polymerization process.

After about 17-19 hours, 1.96% by weight glycerol was added to the reaction mixture, and the resulting mixture was then stirred for about 30 minutes. Next, stirring and nitrogen supply were interrupted and the reaction mixture was cooled to room temperature.

Example 2 Synthesis of binding Polymer

To a 5L glass container was added 0.69 wt% decyl mercaptan, 0.16 wt% MAA, 33.55 wt% 2-HEMA, and 51.1 wt% isopropyl lactate, and 12.8 wt% 1-ethoxy-2-propanol as solvents. The mixture was premixed for about 10 minutes using a magnetic stirrer and then transferred to a 5L stainless steel reactor with an internal heating mantle and equipped with mechanical stirrer, nitrogen inlet, reflux condenser and a temperature sensor. The mixture was heated for about 25 minutes to a temperature of about 68 ℃ at which point 0.20% by weight of 2, 2-azo-2-methylbutyronitrile was added with residual isopropyl lactate. Nitrogen was fed to the reactor to create a nitrogen blanket for use in the remainder of the polymerization process.

After about 17-19 hours, 1.56% by weight glycerol was added to the reaction mixture, and the resulting mixture was then stirred for about 30 minutes. The reaction mixture was heated at 80 ℃ for an additional 23 hours to decompose the residual thermal initiator. Next, stirring and nitrogen supply were interrupted and the reaction mixture was cooled to room temperature.

Example 3

A binding polymer similar to or the same as example 1 was used to make the colorant compositions shown in the table below.

	Colorant 1	Colorant 2	Colorant 3	Colorant 4	Colorant 5	Colorant 6
							Phthalo blue dye	2	0	0	2	0	0
Ferrite black	0	10	0	3	5	0
							Ferrite yellow	0	0	3	15	5	0
Ferrite brown	0	0	8	0	5	0
							Ferrite red	0	0	2	0	0	0
TiO2	0	5	5	5	5	0
							Total pigments	0	15	18	25	20	0
Adhesive polymer	41.49	35.63	34.28	31.12	33.37	42.39
							Propyl lactate	38.96	33.46	32.19	29.22	3134	39.81
1-ethoxy-2-propanol	9.74	8.37	8.05	7.31	7.84	9.95
							1-propanol	6	6	6	6	6	6
Glycerol	1.96	1.96	1.96	1.96	1.96	1.96

Note: all values in the tables are in weight percent

Example 4

To the binding polymer of example 1 was added 0.5 wt% of a phthalo blue dye blue pigment and ground to form a blue colorant. A sample of the colorant is then imprinted onto the front curve mold of the contact lens, and the printing mold is degassed under vacuum for about 8 hours to remove the volatile solvent from the colorant. A reactive monomer mixture comprising 100 parts by weight ("pbw") of HEMA, about 2pbw MAA, about 0.8pbw ethylene glycol dimethacrylate, about 0.1pbw 1, 1, 1-trimethylolpropane trimethacrylate, about 1pbw Norbloc ® 7966 and about 1.3pbw Irgacure (photoinitiator, available from Ciba) was dosed into the printing die. A contact lens base curve mold (base curve mold) is deposited over the filled front curve mold and the two mold halves are pressed together. Held under the extrusion conditions for about 2 minutes to allow the reactive monomer mixture to disperse into and around the colorant layer, resulting in swelling of the colorant layer. After a two minute residence time, the mold assembly was exposed to visible light (wavelength of about 420nm) for about 5 minutes, wherein the reactive monomer mixture was polymerized and crosslinked into and around the binding polymer of the colorant layer to form the partially-interpenetrating polymer network. The mold halves are separated and the tinted lens is removed for further processing steps. Thus, embodiments of the present invention show that tinted contact lenses may be formed from an adhesive polymer that is not substantially cross-linked and a base lens material that is cross-linked when dispersed into the interior and around the adhesive polymer. Advantageously, the pigment mixed into the binding polymer is immobilized in the resulting contact lens without the need for functionalization or additional binding steps.

Claims (10)

1. A method for manufacturing a tinted contact lens comprising the steps of: a) applying a tinctorially effective amount of a colorant to the contoured ceramic surface of the mold, the colorant comprising: one or more pigments, one or more solvents and a binding polymer having a molecular weight of 7,000 to 100,000; b) dispensing a lens forming amount of lens material into the mold; c) swelling a colorant in the lens material; and d) curing said lens material in said mold to produce a tinted contact lens wherein said binding polymer forms an interpenetrating polymer network with said lens material and the binding polymer comprises a copolymer of methacrylic acid, 2-hydroxyethyl methacrylate and lauryl methacrylate, a copolymer of methacrylic acid and 2-hydroxyethyl methacrylate or a homopolymer of 2-hydroxyethyl methacrylate.

2. The method of claim 1, wherein the one or more solvents comprise two medium boiling point solvents and one low boiling point solvent.

3. The process of claim 2, wherein the two mid-boiling solvents comprise 1-ethoxy-2-propanol and isopropyl lactate.

4. The method of claim 1, wherein the pigment is coated or wetted with the binding polymer.

5. A mold for making a tinted contact lens, the mold comprising first and second mold halves, wherein at least one ceramic curve of the first and second mold halves comprises: one or more pigments, one or more solvents, and a binding polymer having a molecular weight of 7,000 to 100,000, wherein the binding polymer is capable of forming an interpenetrating polymer network with a lens material and the binding polymer comprises a copolymer of methacrylic acid, 2-hydroxyethyl methacrylate and lauryl methacrylate, a copolymer of methacrylic acid and 2-hydroxyethyl methacrylate or a homopolymer of 2-hydroxyethyl methacrylate.

6. The mold of claim 5 wherein the interpenetrating polymer network formed between said binding polymer and said lens material is a partial-interpenetrating polymer network.

7. The mold of claim 5 wherein the interpenetrating polymer network formed between said binding polymer and said lens material is a continuous-interpenetrating polymer network.

8. The mold defined in any one of claims 5-7, wherein the one or more solvents comprise two medium boiling point solvents and one low boiling point solvent.

9. The mold defined in claim 8, wherein the two mid-boiling solvents comprise 1-ethoxy-2-propanol and isopropyl lactate.

10. A lens made by the method of claim 3 and the mold of claim 9.