Contact lenses and contact lens formulations with reduced rippling

Abstract

This invention provides a polysiloxane hydrogel contact lens formulation comprising a difunctional siloxane, a hydrophilic N-vinylamine monomer, and at least 0.10% (wt / wt) triphenylphosphine (TPP); and the use of the polysiloxane hydrogel contact lens formed by polymerizing the polysiloxane hydrogel contact lens formulation and the use of TPP in improving the surface properties of contact lenses prepared from formulations containing a difunctional siloxane and a hydrophilic N-vinylamine monomer.

Description

Contact lenses and contact lens formulations with reduced ripples The present invention relates to a polymerizable formulation for manufacturing contact lenses, comprising triphenylphosphine, and contact lenses incorporating a polymer matrix formed from the polymerizable formulation. In particular, the present invention relates to a polymerizable formulation which has been found to impart advantageous properties (such as reduced surface ripples) to hydrogel contact lenses. Silicone hydrogel contact lenses have been developed which have advantageous lens properties such as high water content, low contact angle and high oxygen permeability (Dk). However, when certain polymerizable compositions are cast into silicone hydrogel contact lenses, surface ripples can be observed, especially when casting silicone hydrogel contact lenses in a polypropylene (PP) mold. It has been found that surface ripples are particularly severe when casting contact lenses from a polymerizable composition having a relatively high proportion of high molecular weight silicone components. There is still a need to reduce the surface ripples of silicone hydrogel contact lenses while maintaining advantageous lens properties. In a first aspect, the present invention provides a silicone hydrogel contact lens formulation comprising: a. at least 40% (wt / wt) of a polymerizable silicone component, wherein at least 50% (wt / wt) of the polymerizable silicone content is a difunctional silicone having a molecular weight of at least 5,000 Daltons, especially at least 8,000 Daltons; b. at least 30% (wt / wt) of a hydrophilic N-vinylamide monomer; and c. at least 0.10% (wt / wt) of triphenylphosphine (TPP). In addition, the silicone hydrogel contact lens formulations of the present invention typically contain other polymerizable monomers, oligomers and / or prepolymers, one or more crosslinking agents and one or more polymerization initiators. It has been found that by including at least 0.10% (wt / wt) TPP in a contact lens formulation comprising: (a.) at least 40% (wt / wt) of a polymerizable silicone component, wherein at least 50% (wt / wt) of the polymerizable silicone content is a difunctional silicone having a relatively high molecular weight, i.e., at least 5,000 Daltons, especially at least 8,000 Daltons, and (b.) at least 30% (wt / wt) of a hydrophilic N-vinylamide monomer, the resulting formulation is resistant to surface ripples, but the formulation maintains advantageous lens properties such as high water content, low contact angle and high oxygen permeability (Dk). In a second aspect, the present invention provides a polysiloxane hydrogel contact lens formed by polymerizing the formulation of the first aspect of the present invention. Accordingly, the polymeric lens material of the polysiloxane hydrogel contact lens of the second aspect of the present invention comprises a polymeric product obtained by polymerizing a formulation comprising: a. at least 40% (wt / wt) of a polymerizable siloxane component, wherein at least 50% (wt / wt) of the polymerizable siloxane content is a difunctional siloxane having a molecular weight of at least 5,000 Daltons, particularly at least 8,000 Daltons; b. at least 30% (wt / wt) of a hydrophilic N-vinylamide monomer; and c. at least 0.10% (wt / wt) of triphenylphosphine (TPP). In a third aspect, the present invention provides the use of TPP in modifying the surface properties of a contact lens prepared from a formulation comprising: a. at least 40% (wt / wt) of a polymerizable siloxane component, wherein at least 50% (wt / wt) of the polymerizable siloxane content is a difunctional siloxane having a molecular weight of at least 5,000 Daltons, particularly at least 8,000 Daltons; and b. at least 30% (wt / wt) of a hydrophilic N-vinylamide monomer. Advantageously, TPP is used in an amount of at least 0.10% (wt / wt) based on the total weight of the formulation in the third aspect of the present invention. Advantageously, in each of the first, second and third aspects of the present invention, at least 20% (wt / wt) of the polymerizable siloxane content is a monofunctional siloxane having a molecular weight of less than 3,000 Daltons. It has been found that the formulation of the present invention reduces the amount of surface ripples present on cast-molded contact lenses compared to lenses cast from other identical polymerizable formulations lacking TPP. The reduction in surface ripples is particularly evident in polysiloxane hydrogel contact lenses cast-molded in a polypropylene (PP) mold. It has been found that adding TPP to the polymerizable formulation for forming the lens does not detrimentally affect the properties of the resulting cast-molded lens, such as water content, contact angle and oxygen permeability (Dk), compared to those cast from polymerizable formulations lacking TPP. When referring to the following detailed description of the embodiments of the present invention, the present invention will be more fully understood and other advantages will become apparent. The present invention will be described in detail with particular reference to the formulation of the first aspect of the present invention (hereinafter referred to as "the formulation of the present invention"). However, it should be understood that since the contact lenses of the second aspect of the present invention (hereinafter referred to as "the contact lenses of the present invention") can be obtained by polymerizing the formulation of the first aspect of the present invention, and thus, the components of the formulation of the first aspect of the present invention will be present in the polymer lens material of the contact lenses of the second aspect of the present invention in a polymerized form. Similarly, it has been found that contact lenses that particularly benefit from the use of TPP according to the third aspect of the present invention for improving surface properties are those that have the characteristics described herein for the lenses of the second aspect of the present invention and / or those obtained by polymerizing a formulation having the characteristics described herein for the formulation of the first aspect of the present invention. Therefore, the components of the formulation of the first aspect of the present invention will be present in the polymer lens material of the contact lenses in which TPP is used according to the third aspect of the present invention in a polymerized form. The characteristics of the formulation or lens or its components mentioned herein, or the characteristics of using TPP (depending on the context), can be combined with any combination of the previously described or subsequently described characteristics, unless a particular combination of characteristics is mutually exclusive, or if the context otherwise indicates. In addition, as used in this specification, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" include plural referents (e.g., at least one or more). Thus, for example, reference to "contact lenses" includes a single lens and two or more of the same or different lenses. It has been found that including at least 40% (wt / wt) of siloxane in the formulation of the present invention, at least 50% of which is a high molecular weight difunctional siloxane of at least 5,000 Daltons, especially 8,000 Daltons, and 30% (wt / wt) of an N-vinyl amide hydrophilic monomer can provide contact lenses with advantageously high water content, high surface wettability and high oxygen permeability (Dk). It has been found that optionally including additional non-siloxane hydrophobic monomers, especially hydroxybutyl methacrylate and / or isobornyl methacrylate, can enhance the mechanical strength of the resulting lenses. The present invention is based on the further discovery that when at least 0.10% (wt / wt) of TPP is included in the polymerizable formulation for producing contact lenses, contact lenses and their respective formulations that are both resistant to surface ripples and have advantageous lens properties can be provided. It has been found that other comparable formulations without TPP can exhibit surface ripples. Surface ripples are an undesirable property of contact lenses because surface ripples can cause discomfort to the wearer. In addition, surface ripples can reduce the optical properties of contact lenses. Therefore, formulations with little or no surface ripples are advantageous. It has been found that those having a high viscosity, such as higher than 250 mm at 25 °C 2 The viscosity of / s, for example, is higher than 300 mm at 25 °C 2 Contact lenses formed from formulations having a viscosity of / s are particularly prone to surface ripples. Similarly, it has been found that contact lenses formed from formulations comprising a high proportion of high molecular weight silicone components, such as those in which at least 40% (wt / wt) is a polymerizable silicone component (wherein at least 50% (wt / wt) of the polymerizable silicone content is a difunctional silicone having a molecular weight of at least 5,000 Daltons, especially at least 8,000 Daltons), are particularly prone to surface ripples. It has been found that the inclusion of a large amount of high molecular weight silicone (e.g., greater than 20% by weight based on the weight of the polymerizable formulation of a silicone having a viscosity of 300 mm at 25 °C 2 / s or greater) can result in an overall formulation having a relatively high viscosity at 25 °C, such as 250 mm 2 / s or greater. It has been found that the inclusion of TPP in such formulations is effective in preventing or reducing surface ripples. The polymerizable components of the formulations of the present invention are generally incorporated into the contact lenses of the present invention. The amounts of components or constituents present in the formulations referred to herein in weight percentages (i.e., % (wt / wt)) are based on the amounts of all formulation components, excluding diluents and / or solvents that are not incorporated into the polymeric lens material of the finished contact lens. Thus, for example, in a formulation prepared by mixing 0.5 parts of TPP, 40 parts of a silicone component, 30 parts of a hydrophilic N-vinyl amide monomer, 4.5 parts of other active ingredients (such as polymerization initiators, colorants, oxygen scavengers, etc.) and 25 parts of an organic solvent and / or water (total 100 parts), the amount of TPP is 0.67% (wt / wt). As used herein, the "constituents" of a formulation generally refer to all components of a particular type. For example, if a formulation contains 20% (wt / wt) of a first silicone monomer and 25% of a second silicone monomer and no other silicones, the formulation can be described as containing 45% (wt / wt) of a silicone component. The polymerizable formulations of the present invention include triphenylphosphine (TPP; CAS No.: 603-35-0). TPP is a common organophosphorus compound used in the synthesis of organic and organometallic compounds and an intermediate in the preparation of pharmaceuticals, phosphonium salts and other phosphorus compounds. TPP The silicone hydrogel contact lens formulation of the present invention comprises at least 0.10% (wt / wt) TPP. The TPP can be present in the polymerizable formulation in an amount of at least 0.15% (wt / wt), such as at least 0.20%, especially at least 0.25%. For example, the TPP can be present in the polymerizable formulation in an amount of from about 0.15% (wt / wt) to about 2.0% (wt / wt), such as from 0.20% (wt / wt) to 1.0% (wt / wt), and is usually present in an amount of from about 0.25% (wt / wt) to about 1.0% (wt / wt). The contact lens formulation of the present invention is a silicone hydrogel contact lens formulation, which comprises: a. at least 40% (wt / wt) of a polymerizable silicone component, wherein at least 50% (wt / wt) of the polymerizable silicone content is a difunctional silicone having a molecular weight of at least 5,000 Daltons, especially at least 8,000 Daltons; and b. at least 30% (wt / wt) of a hydrophilic N-vinylamide monomer; and c. at least 0.10% (wt / wt) of TPP, for example, from about 0.20% (wt / wt) to about 2% (wt / wt) of TPP. "Silicone hydrogel" refers to a cross-linked polymer material having a three-dimensional polymer network (i.e., a polymer matrix), which is insoluble in water but contains at least 10% by weight of water in its polymer matrix when fully hydrated. "Silicone hydrogel" is obtained by polymerization of a polymerizable composition comprising at least one silicone-containing component (usually at least one silicone-containing monomer or at least one silicone-containing prepolymer or at least one cross-linkable silicone-containing prepolymer). The polymerizable contact lens formulation of the first aspect of the present invention is suitable for forming a silicone hydrogel contact lens. The polymerizable formulations suitable for preparing the silicone hydrogel contact lens body are well known in the art. In addition to TPP, the polymerizable silicone component and the hydrophilic N-vinylamide monomer, the silicone hydrogel contact lens formulation of the first aspect of the present invention may comprise other components suitable for forming the contact lens body. These polymerizable formulations usually comprise a cross-linking agent and a polymerization initiator. These polymerizable formulations may comprise additional polymerizable monomers, oligomers and / or prepolymers. Typically, silicone hydrogel contact lenses are formed by a free radical propagation reaction involving the polymerization of terminal ethylenically unsaturated groups (also referred to herein as "polymerizable groups"). Exemplary polymerizable groups include (meth)acrylic groups, (meth)acrylamides, allyl, vinyl, and styryl groups. As used herein, a "vinyl-containing monomer" is any non-silicone monomer having a single polymerizable carbon-carbon double bond (i.e., a vinyl group) present in its molecular structure, wherein the carbon-carbon double bond of the vinyl group is attached to an sp3 hybridized carbon atom. The reactivity of vinyl under free radical polymerization is less than that of the carbon-carbon double bond present in acrylate or methacrylate polymerizable groups. The term "(meth)acrylamide" refers to methacrylamide and / or acrylamide. The term "(meth)acrylate" refers to methacrylate and / or acrylate. The term "terminal (meth)acrylic group" refers to one (meth)acrylic group at one of the two ends of the main chain / backbone of an organic compound. An "N-vinyl amide monomer" is an amide compound having a vinyl CH=CH2 directly attached to the nitrogen atom of the amide group. A "monomer" is a molecule having one or more polymerizable groups that can react with the same or different other monomers to form larger polymer or copolymer chains or three-dimensional matrices during a polymerization process. A monomer having two or more polymerizable groups may be referred to as a "crosslinking agent", as further described below. The term "monomer" encompasses macromonomers and polymerizable oligomers, i.e., polymerizable molecules containing one or more chains of repeating units, such as polymerizable polysiloxanes; thus there is no size constraint (i.e., maximum molecular weight) on the monomer unless otherwise indicated. The term "polymer" refers to a material formed by the polymerization and / or crosslinking of one or more monomers. As used in this application, unless otherwise specifically noted, the "molecular weight" of a polymeric material (including components containing multiple silicone units) refers to the absolute number average molecular weight (in daltons), e.g., measured by GPC using polystyrene standards or by 1 1H NMR end group analysis. An "oligomer" is a compound composed of 2 to 10 repeating units that can be actually or conceptually derived from monomers. A prepolymer is a partially polymerized polymer containing multiple monomer units, usually more than 10, which has been reacted to an intermediate molecular mass state that retains the ability to continue reacting to fully cure into a higher molecular mass polymeric material. In addition to N-vinyl amide-containing monomers, the silicone hydrogel contact lens formulations of the present invention may include other hydrophilic monomers and may also include hydrophobic monomers. As used herein, "hydrophilic monomer" refers to a polysiloxane-free monomer in which at least 50 grams of the monomer are completely soluble in 1 liter of water at 20 °C (i.e., approximately 5% soluble in water), as visually determined using the standard shaking flask method. The polysiloxane hydrogel contact lens formulation comprises an amount of at least 30% (wt / wt), such as an amount of at least 35% (wt / wt), especially an amount of at least 37% (wt / wt) of one or more hydrophilic N-vinylamide-containing monomers. The formulation may additionally comprise other hydrophilic monomers, such as hydrophilic vinyl ether-containing monomers. The total amount of hydrophilic monomers in the formulation of the first aspect of the invention is generally not more than 55% (wt / wt), such as not more than 50% (wt / wt). In some examples, the hydrophilic N-vinylamide-containing monomer may be selected from N-vinyl-N-methylacetamide (VMA), or N-vinylpyrrolidone (NVP), or N-vinylformamide, or N-vinylacetamide, or N-vinyl-N-ethylacetamide, or N-vinylisopropylamide, or N-vinylcaprolactam, or N-vinyl-N-ethylformamide, or any combination thereof. In some examples, the hydrophilic vinylamide-containing monomer consists of VMA or NVP, or a combination of VMA and NVP. The vinyl ether-containing monomers may be selected from 1,4-butanediol vinyl ether (BVE), or ethylene glycol vinyl ether (EGVE), or diethylene glycol vinyl ether (DEGVE), or 1,4-cyclohexanedimethanol vinyl ether (CHDMVE), or poly(ethylene glycol) vinyl ether having 4 to 10 ethylene glycol units, or poly(ethylene glycol) vinyl ether having more than 10 ethylene glycol units, or any combination thereof. In some examples, the vinyl ether-containing monomer may be a poly(ethylene glycol) vinyl ether having at least 1, 2 or 3 ethylene glycol units and up to 4, 6, 8 or 10 ethylene glycol units. In addition to the hydrophilic N-vinylamide-containing monomers and hydrophilic vinyl ether-containing monomers, one or more vinyl-containing monomers may be included in the polymerizable formulations of the invention described herein. For example, in addition to the N-vinylamide-containing monomers and vinyl ether-containing monomers, vinyl monomers having vinyl ester or allyl ester polymerizable groups may be included in the formulations of the invention. The hydrophilic monomer may be a hydrophilic monomer containing (meth)acrylate or (meth)acrylamide groups, examples of which include 2-hydroxyethyl methacrylate (HEMA), 4-hydroxybutyl acrylate, glycerol methacrylate, 2-hydroxyethyl methacrylamide, ethoxyethyl methacrylamide (EOEMA), polyethylene glycol monomethacrylate, methacrylic acid (MA) and acrylic acid. The formulation of the first aspect of the present invention comprises at least 30% (wt / wt), especially at least 35% (wt / wt), of at least one N-vinyl amide hydrophilic monomer. The formulation of the first aspect of the present invention generally comprises no more than 55% (wt / wt) of the N-vinyl amide hydrophilic monomer, such as less than 50% (wt / wt) of the N-vinyl amide hydrophilic monomer. The formulation of the first aspect of the present invention may comprise 35 to 55%, especially 37 to 50%, of the N-vinyl amide hydrophilic monomer. The formulation of the first aspect of the present invention may comprise 30 to 55%, such as 35 to 50%, especially 37 to 50%, of N-methyl N-vinyl acetamide. In the case where more than one hydrophilic monomer is included in the formulation of the present invention, advantageously, at least 70 wt% or 80 wt% of these hydrophilic monomers have a solubility of ≥20% in water. In a specific example, 100% of the hydrophilic vinyl-containing monomers in the polymerizable formulation have a solubility of ≥10% in water. The hydrophilic vinyl-containing monomers generally have a molecular weight of about 75 to about 500, and more generally about 75 to 250. The formulation of the present invention may optionally comprise a hydrophobic monomer lacking a siloxane group. The term "hydrophobic monomer" as used herein refers to a monomer lacking a siloxane group and having less than 5% solubility in water at 20 °C, as determined using the standard shaking flask method. The hydrophobic monomer may be a hydrophobic monomer containing a (meth)acrylate group. As used herein, "hydrophobic acrylate-containing monomer" refers to any non-siloxane monomer having a single polymerizable acrylate group (e.g., methyl methacrylate, acrylamide, etc.). In a specific example, the hydrophobic acrylate-containing monomer has a polymerizable methacrylate group. Many suitable acrylate-containing monomers are known in the art. Exemplary hydrophobic acrylate-containing monomers include methyl acrylate, isopropyl acrylate, cyclohexyl acrylate, methyl methacrylate (MMA), butyl acrylate, tert-butyl methacrylate (tBMA), perfluorohexylethylthio carbonylaminoethyl methacrylate, isobornyl methacrylate (IBM), trifluoroethyl methacrylate, hexafluoroisopropyl methacrylate, hexafluorobutyl methacrylate, 2-hydroxybutyl methacrylate (HOB), 2-hydroxypropyl methacrylate (HPMA), and ethylene glycol methyl ether methacrylate (EGMA). Advantageous non-siloxane hydrophobic monomers include hydroxybutyl methacrylate, isobornyl methacrylate, or a combination of hydroxybutyl methacrylate and isobornyl methacrylate. The polysiloxane hydrogel contact lens formulation may comprise an acrylate-containing hydrophobic monomer to further enhance the mechanical strength and / or hardness of the lens, or to impart other desired properties. The hydrophobic monomers lacking siloxane groups are not limited to (meth)acrylate group-containing monomers and may include vinyl or other ethylenically unsaturated reactive groups. Other examples of hydrophobic monomers include vinyl acetate, vinyl propionate, vinyl butyrate, styrene, chloroprene, vinyl chloride, vinylidene chloride, acrylonitrile, and methacrylonitrile. The polymerizable formulation may comprise from about 2% to about 20% (wt / wt), such as from 4% to 16% (wt / wt), especially from 6% to 12% (wt / wt) of a non-siloxane hydrophobic monomer component. 2 to 20% (wt / wt) (especially 5 to 15% (wt / wt)) of the formulation may be hydroxybutyl methacrylate, isobornyl methacrylate, or a combination of hydroxybutyl methacrylate and isobornyl methacrylate. "Siloxane monomer" as used herein refers to a monomer having at least one siloxane group. The siloxane monomer may comprise terminal acrylate or methacrylate groups. (Meth)acrylate-containing siloxane monomers useful in the inventive formulations described herein are well known in the art. Such siloxane monomers may include monofunctional (meth)acrylate-containing siloxanes, difunctional (meth)acrylate-containing siloxanes, or combinations comprising monofunctional and difunctional (meth)acrylate-containing siloxane monomers. In instances where the (meth)acrylate-containing siloxane monomers consist of one or more monofunctional (meth)acrylate-containing siloxane monomers (i.e., they do not contain any polyfunctional (meth)acrylate-containing siloxane monomers), the polymerizable formulation will typically further comprise a (meth)acrylate-containing crosslinker further described below. In one particular example, the (meth)acrylate-containing siloxane monomer has one or more polymerizable methacrylate groups. Various non-limiting examples of suitable acrylate-containing siloxane monomers include 3-[tris(trimethylsiloxy)silyl]propyl methacrylate ("TRIS"), 3-methacryloyloxy-2-hydroxypropoxy)propylbis(trimethylsiloxy)methylsilane ("SiGMA"), methyl 2-(methacryloyloxy)propylbis(trimethylsiloxy)silicate ("SiGEMA"), and monomethacryloyloxypropyl-functional polydimethylsiloxanes such as MCR-M07 and MCS-M11, all available from Gelest (Morrisville, PA, USA). The inventive polysiloxane hydrogel contact lens formulation comprises at least 40% (wt / wt) by amount, such as at least 42% (wt / wt) by amount, especially at least 45% (wt / wt) by amount of a polymerizable siloxane component. The polymerizable siloxane component generally accounts for no more than 60% (wt / wt) of the formulation, for example, no more than 55% (wt / wt) of the formulation. The polysiloxane hydrogel contact lens formulation may comprise at least one monofunctional siloxane monomer having, for example, a molecular weight of less than 3000 Daltons. At least 10% (wt / wt) of the siloxane content may be a monofunctional siloxane having a molecular weight of less than 3000 Daltons. At least 20% (wt / wt) of the siloxane content is monofunctional and has a molecular weight of less than 3000 Daltons. The formulation may comprise between 10 wt% and 30 wt% of a monofunctional siloxane monomer, for example, between 10 wt% and 30 wt% of a monofunctional siloxane monomer having a molecular weight of less than 3000 Daltons. These monofunctional siloxanes generally have a molecular weight of at least 200 Daltons. In one example, the monofunctional siloxane monomer may comprise a (meth)acrylate-containing siloxane monomer represented by formula (I), (I) wherein m is an integer from 3 to 10, n is an integer from 0 to 10, R 1 is an alkyl group having 1 to 4 carbon atoms, R 2 is hydrogen or methyl, and R 3 is hydrogen or methyl. In another specific example, the acrylate-containing siloxane monomer is represented by formula I, wherein R 1 is butyl, R 2 is hydrogen, R 3 is methyl, m is 4, and n is 1. A method for preparing the siloxane monomer represented by formula (I) is described in U.S. Publication No. 2009 / 0299022, which is incorporated herein by reference. In another example, the monofunctional siloxane monomer may comprise a (meth)acrylate-containing siloxane monomer represented by formula (II), (II) wherein n is an integer of about 10 to 25, especially 10 to 20. The siloxane monomer of formula II and other suitable monomers are described in U.S. Patent No. 6,867,245 and U.S. Patent No. 6,310,169, both of which are incorporated herein by reference. Examples of commercially available monofunctional silicone monomers include 2-methyl-2-[3-(9-butyl-1,1,3,3,5,5,7,7,9,9-decamethylpentasiloxan-1-yl)propoxy]ethyl acrylate X-22-1622 / KF-1622 (available from Shin-Etsu Chemical Co., Ltd., Tokyo, Japan) (CAS No. 1052075-57-6), poly(dimethyl)siloxane FMM capped with methacryloxypropyl (Shin-Etsu Silicones, America, Akron, Ohio, USA) (CAS No. 697234-76-7), and 3-methacryloxy-2-hydroxypropyloxypropylbis(trimethylsiloxy)methylsilane SiGMA. The polysiloxane hydrogel contact lens formulation comprises at least one difunctional siloxane having a molecular weight of at least 5,000 Daltons, such as at least 6,500 Daltons, especially at least 8,000 Daltons. The difunctional siloxanes may comprise or consist of difunctional (meth)acrylate-containing siloxane monomers, especially difunctional (meth)acrylate-containing siloxanes having a molecular weight of at least 5,000 Daltons, such as at least 6,500 Daltons, especially at least 8,000 Daltons. The difunctional siloxanes generally have a molecular weight of less than 25,000 Daltons, such as a molecular weight of less than 20,000 Daltons, especially a molecular weight of less than 15,000 Daltons. It has been found that including siloxanes with higher molecular weights can result in formulations with unacceptably high viscosities. The polysiloxane hydrogel contact lens formulation may comprise at least one difunctional siloxane having a molecular weight of 5,000 to 25,000 Daltons, such as at least one difunctional siloxane having a molecular weight of 6,500 to 20,000 Daltons, especially at least one difunctional siloxane having a molecular weight of at least 8,000 to 15,000 Daltons. At least 50% (wt / wt) of the siloxane content is a difunctional siloxane having a molecular weight of at least 5,000 Daltons, especially a difunctional (meth)acrylate-containing siloxane. At least 50% (wt / wt) of the siloxane content may be a difunctional siloxane having a molecular weight of at least 6,500 Daltons, especially a difunctional (meth)acrylate-containing siloxane. Advantageously, at least 50% (wt / wt) of the siloxane content is a difunctional siloxane having a molecular weight of at least 8,000 Daltons, especially a difunctional (meth)acrylate-containing siloxane. The formulation may comprise from 20% (wt / wt) to 45% (wt / wt) of difunctional siloxane, such as from 20% (wt / wt) to 40% (wt / wt) of difunctional siloxane, especially difunctional (meth)acrylate-containing siloxane. The formulation may comprise from 20% (wt / wt) to 45% (wt / wt) of difunctional siloxane having a molecular weight of at least 5,000 Daltons, especially difunctional (meth)acrylate-containing siloxane, such as from 20% (wt / wt) to 40% (wt / wt) of difunctional siloxane having a molecular weight of at least 5,000 Daltons, especially difunctional (meth)acrylate-containing siloxane.The formulation may comprise a difunctional siloxane having a molecular weight of at least 8,000 Daltons between 15% (wt / wt) and 45% (wt / wt), in particular a difunctional (meth)acrylate-containing siloxane, for example a difunctional siloxane having a molecular weight of at least 8,000 Daltons between 20% (wt / wt) and 45% (wt / wt) or between 20% (wt / wt) and 40% (wt / wt), in particular a difunctional (meth)acrylate-containing siloxane. It has been found that the incorporation of TPP is particularly advantageous in formulations containing a high amount of high molecular weight siloxanes, such as formulations containing at least 20% (wt / wt), in particular at least 25% (wt / wt) of a siloxane having a molecular weight of at least 5,000 Daltons, in particular at least 8,000 Daltons. In one example, the difunctional siloxane monomer may comprise a (meth)acrylate-containing siloxane monomer represented by formula (III), (III) wherein R 1 is selected from hydrogen or methyl; R 2 is selected from hydrogen or C 1-4 hydrocarbyl; m represents an integer from 0 to 10; n represents an integer from 4 up to about 15, 25 or 100; a and b represent integers of 1 or more; a + b equals 20 to 500; b / (a + b) equals 0.01 to 0.22; and the configuration of the siloxane units comprises a random configuration. For example, the difunctional siloxane monomer M5A is represented by formula (III), wherein R1 is methyl, R2 is methyl, m is 0, n is about 7, a is about 75, and b is about 10. M5A has a molecular weight between 8,000 Daltons and 11,000 Daltons. Other suitable difunctional siloxane monomers are represented by formula (IV): (IV) wherein R 3 is selected from hydrogen or methyl, m represents an integer from 0 to 10, and n represents an integer from 1 to 500. In a particular example, the difunctional siloxane monomer is a methacryloxypropyl-terminated polydimethylsiloxane having an Mw of 4500 to 5500 represented by formula (IV (wherein R 3 is methyl, m is 0, and n is an integer from 40 to 60), available from Gelest (Morrisville, PA, USA) and designated by the manufacturer as "DMS-R18". Other suitable methacryloxypropyl-terminated polydimethylsiloxanes include DMS-R22 and DMS-R31, also available from Gelest. Yet another suitable difunctional siloxane monomer is represented by formula (V), (V) wherein n is an integer of about 100 to 150, m and p are each an integer of about 5 to 10, and h is an integer of about 2 to 8. The method for preparing the compound of formula (V) is described in U.S. Patent No. 6,867,245, which is incorporated herein by reference. An example of a suitable siloxane monomer represented by formula (V) is (α-ω)-bis(methacryloyloxyethyliminocarboxyethoxy-propyl)-poly(dimethylsiloxane)-poly(trifluoropropylmethylsiloxane)-poly(copoly-methoxy-poly(ethylene glycol)propylmethylsiloxane) (M3U), wherein n is 121, m is 7.6, h is 4.4, and the molecular weight is from 12,000 to 20,000 daltons, typically about 12,800 daltons. Additional (meth)acrylate-containing siloxane monomers useful in the inventive formulations described herein are known in the art (see, for example, U.S. Patent No. 7,572,841, U.S. Patent Application Publication No. 2006 / 0063852, and U.S. Patent No. 5,998,498, each of which is incorporated herein by reference). In one example, the siloxane monomers can comprise a combination of monofunctional (meth)acrylate-containing siloxane monomers and difunctional (meth)acrylate-containing siloxane monomers. In this example, the monofunctional (meth)acrylate-containing siloxane monomer has a molecular weight of less than 3,000, 2,000, or 1,000 daltons, and the difunctional acrylate-containing siloxane monomer has a molecular weight of at least 5,000, 6,500, or 8,000 daltons. In a particular example, the monofunctional (meth)acrylate-containing siloxane monomer has a molecular weight of about 250 to about 1000 daltons, and the difunctional acrylate-containing siloxane monomer has a molecular weight of about 5,000 to about 16,000 daltons. In another particular example, the monofunctional (meth)acrylate-containing siloxane monomer has a molecular weight of about 500 to about 1000 daltons, and the difunctional (meth)acrylate-containing siloxane monomer has a molecular weight of about 5,000 to about 12,000 daltons. The silicone hydrogel contact lens formulations of the present invention generally include one or more polymerization initiators, that is, the formulations may include an initiator, or may contain an initiator component including two or more polymerization initiators or a combination of a polymerization initiator, a synergist, and an activator. The term "initiator" refers to a chemical that initiates a crosslinking / polymerization reaction. The initiator is typically a free radical initiator that forms free radicals that initiate a polymerization reaction in which free radicals propagate. Polymerization initiators that may be included in the formulations of the present invention include, for example, azo compounds, or organic peroxides, or both. The initiator may be a photoinitiator that is activated upon exposure to actinic radiation such as UV light, or a thermal initiator that is activated upon exposure to heat. Initiators that may be present in the polymerizable formulations include, for example, benzoin ethyl ether, or benzyl dimethyl ketal, or α,α - diethoxyacetophenone, or 2,4,6 - trimethylbenzoyl diphenylphosphine oxide, or benzoin peroxide, or tert - butyl peroxide, or azobisisobutyronitrile, or azobis - dimethylvaleronitrile, or any combination thereof. UV photoinitiators may include, for example, phosphine oxides such as diphenyl(2,4,6 - trimethylbenzoyl)phosphine oxide, or benzoin methyl ether, or 1 - hydroxycyclohexyl phenyl ketone, or Darocur (available from BASF, Florham Park, N.J., USA), or Irgacur (also available from BASF), or any combination thereof. Advantageously, the polymerization initiator is a thermal initiator. Examples of suitable thermal initiators include 2,2′ - azobis - 2 - methylpropionitrile, abbreviated as "AIBN" (VAZO - 64, available from E.I. DuPont de Nemours & Co., Wilmington, Del., USA), 2,2′ - azobis(2,4 - dimethylvaleronitrile) (VAZO - 52), and 1,1′ - azobis(cyanocyclohexane) (VAZO - 88, also available from E.I. DuPont). The polymerization initiator or initiator component may be present in the silicone hydrogel contact lens formulations of the present invention in an amount of from about 0.1% (wt / wt) to about 1.5% (wt / wt), or from about 0.2% (wt / wt) to about 1.0% (wt / wt), especially from about 0.2 to about 0.8% (wt / wt). The formulations of the first aspect of the present invention are optionally thermally cured formulations containing at least one thermal initiator. Thermal curing or photochemical curing methods are well known to those skilled in the art. The polysiloxane hydrogel contact lens formulation may further comprise a crosslinking agent. The crosslinking agent may react with functional groups on two or more polymer chains to bridge one polymer to another. As used herein, a "crosslinking agent" is any compound having a molecular weight of less than about 2000 Daltons, typically less than 700 Daltons, and having two or more polymerizable groups. As used herein, an "acrylate-containing crosslinking agent" has at least two polymerizable acrylate groups and no other types of polymerizable groups. A "vinyl-containing crosslinking agent" has at least two polymerizable vinyl groups and no other types of polymerizable groups. These vinyl-containing crosslinking agents and these acrylate-containing crosslinking agents generally may have a molecular weight of less than 1500, 1000, 500, or 250 Daltons. Examples of vinyl-containing crosslinking agents that can be used in the inventive formulations disclosed herein include, but are not limited to, divinyl ether, or divinyl sulfone, or triallyl isocyanurate (TAIC), and any combination thereof. Exemplary divinyl ethers include diethylene glycol divinyl ether, or triethylene glycol divinyl, or 1,4-butanediol divinyl ether, or 1,4-cyclohexanedimethanol divinyl ether, or any combination thereof. Generally, the vinyl-containing crosslinking agent may have two or three polymerizable vinyl groups. When present, the total amount of the vinyl-containing crosslinking agent in the polysiloxane hydrogel contact lens formulation is generally from about 0.02, 0.04, or 0.06 mole % up to about 0.10, 0.15, or 0.20 mole %. Examples of acrylate-containing crosslinking agents that can be used in the inventive formulations disclosed herein include, but are not limited to, lower carbon number alkylene glycol di(meth)acrylates, poly(lower carbon number alkylene) glycol di(meth)acrylates, lower carbon number alkylene di(meth)acrylates, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, bisphenol A di(meth)acrylate, methylenebis(meth)acrylamide, and 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane. In certain instances, the acrylate-containing crosslinking agent is a non-siloxane crosslinking agent. When present, the total amount of the acrylate-containing crosslinking agent in the inventive formulation is generally from about 0.20, 0.25, 0.30, or 0.35 mole % up to about 0.50, 0.60, 0.70, 0.80, or 1.0 mole %. For the avoidance of doubt, monofunctional polymerizable compounds having a molecular weight greater than 2000 Daltons are not considered crosslinking agents. Thus, difunctional siloxanes having a molecular weight greater than 2000 Daltons as described herein are not considered crosslinking agents. The inventive formulation may optionally further comprise a chain transfer agent. Chain transfer is a polymerization reaction in which the activity of a growing polymer chain is transferred to another molecule, reducing the average molecular weight of the final polymer. Examples of chain transfer agents include, for example, thiol compounds, halo-carbon compounds, or C3-C5 hydrocarbons such as allyloxyethanol. In addition to the polymerizable components, the formulations of the present invention may include non-polymerizable components conventionally used in contact lens formulations. Additional components may also be included, such as organic solvent diluents. Non-limiting examples of such and other components that may be included in the polymerizable formulations are provided in US 2007 / 0296914. The formulations of the present invention may include no more than 2% (wt / wt) of non-polymerizable components other than TPP, especially no more than 1% (wt / wt) of non-polymerizable components other than TPP. Specifically, the formulations of the present invention may include no more than 2% (wt / wt) of organic solvent diluents, especially no more than 1% (wt / wt) of organic solvent diluents. Advantageous formulations of the present invention include a silicone component present in an amount of at least 40% (wt / wt), wherein at least 50% of the silicone content is a difunctional silicone having a molecular weight of at least 5,000 Daltons; and an N-vinylamide monomer component present in an amount of at least 30% (wt / wt). The contact lenses of the second aspect of the present invention advantageously comprise a polymeric lens material derived from the advantageous polymerizable formulation of the first aspect of the present invention comprising the above monomers and silicone component. The improved formulations in the third aspect of the present invention are advantageously those described above for the formulations of the other aspects of the present invention. For example, the improved formulations in the third aspect of the present invention may include any or all of the above silicone component, hydrophilic N-vinylamide monomers, optional other hydrophilic monomers, optional other hydrophobic monomers, optional crosslinking agents, optional chain transfer agents, and optional free radical initiators. In addition, for example, the improved formulations in the third aspect of the present invention include the silicone component, hydrophilic N-vinylamide monomers, optional other hydrophilic monomers, and optional other hydrophobic monomers in the amounts described above for the formulations of the present invention. Examples The following examples illustrate certain aspects and advantages of the present invention, which should be understood as not being limited thereto. Base formulations Preparing a base polymerizable polysiloxane hydrogel contact lens Formulation 1, which contains: ● 11% by weight of hydrophobic monomers (composed of 8.29% by weight of hydroxybutyl methacrylate and 2.49% by weight of isobornyl methacrylate), ● 42% by weight of hydrophilic N-vinylamide monomers (composed of 10.48% by weight N-vinyl N-methylacetamide and 31.44% by weight Composed of N-vinylpyrrolidone, ● 45 wt% polymerizable silicone (monomers with different ratios - as shown in Table 1), ● 2 wt% of other agents, including a thermal initiator (azobisisobutyronitrile (AIBN)) and a crosslinking agent (triallyl isocyanate). Preparation of a substrate polymerizable polysiloxane hydrogel contact lens Formulation 2, which contains: ● 9 wt% hydrophobic monomer (composed of 9.94% hydroxybutyl methacrylate and 2.09% isobornyl methacrylate), ● 39 wt% hydrophilic N-vinylamide monomer ( N-vinyl N-methylacetamide), ● 49 wt% polymerizable silicone, a high molecular weight difunctional silicone in a 62:38 ratio (30.23 wt% M5A, Mn 8,000 to 11,000): low molecular weight monofunctional silicone (18.04 wt% FMM and 0.49 wt% KF-1622 Mn < 2,000), ● 3 wt% of other agents, including a thermal initiator (azobisisobutyronitrile (AIBN)) and a crosslinking agent (triallyl isocyanate). Evaluation of surface ripples Using the following scale, visually evaluate the ripple severity based on a zonometer or the SAG optimec image of the lens and rate it from 0 to 5: ● 0 - No visible ripples. ● 1 - Very tiny, faint ripples. ● 2 - Tiny ripples. ● 3 - Medium ripples. ● 4 - Severe ripples. ● 5 - Very severe, long and deep ripples. In the absence of TPP Surface ripples The following examples illustrate the severity of the surface ripples that occur in a PP mold for the formulation and how this can be alleviated by including TPP. A polymerizable mixture was used to study the severity of surface ripples. The polymerizable mixture combined base formulation 1, where the silicone content was fixed at 46 parts by weight and different silicone ratios between M5A:KF-1622 and M5A:FMM. TPP was not included in these polymerizable mixtures and no further changes were made to the monomer formulation. All formulations were cast in the same PP mold. The results are summarized in Table 1 below. The table shows that the ripple severity increases with increasing loading of M5A, with mixture 6 (containing 75:25 M5A:FMM) showing the most severe surface ripples. Table 1. Severe ripples were also observed in lenses manufactured from mixture 7 (containing 81:19 M3U:FMM). In comparison, Stenfilcon A lenses (containing approximately 35% (wt / wt) of a silicone content containing 75:25 KF-1622:M5A) and fanfilcon A lenses (containing approximately 39% (wt / wt) of a silicone content containing 68:32 KF-1622:M5A), manufactured using the same process in a PP mold, did not show ripples (0). TPP Effect on surface ripples Adding TPP to the monomer formulation enabled the manufacture of contact lenses without surface ripples. As the TPP loading increased, a decrease in the degree of ripples was observed. Adding TPP to the substrate Formulation 2 (with an overall silicone content of 54 parts by weight, consisting of a formulation of 62:38 difunctional:monofunctional siloxanes) is shown in Table 2 below. Table 2. The table shows that the severity of the ripples decreased as the TPP loading increased. When TPP was not included (mixture 9), the ripples were at their most pronounced. When 0.404% TPP was included (mixture 13), the ripples were alleviated to such an extent that they could no longer be visually observed. Certain illustrative examples are disclosed herein. It should be understood that these examples are presented by way of example and not by way of limitation. Although the foregoing detailed description is presented, it is intended to be construed to cover all modifications, alternatives, and equivalents of such examples as may fall within the spirit and scope of the invention as defined by additional disclosure. The entire contents of all references cited in this invention are incorporated herein by reference to the extent that they are not inconsistent with this invention. Those skilled in the art will appreciate other embodiments of the invention from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims and their equivalents.

Claims

1. A polysiloxane hydrogel contact lens formulation comprising: a. at least 40% (wt / wt) of a polymerizable siloxane component, wherein at least 50% (wt / wt) of the polymerizable siloxane content is a difunctional siloxane having a molecular weight of at least 5,000 Daltons; b. at least 30% (wt / wt) of a hydrophilic N-vinylamine monomer; and c. at least 0.10% (wt / wt) of triphenylphosphine (TPP).

2. The formulation of claim 1, comprising 35 to 50% (wt / wt) of N-methyl-N-vinylacetamide monomer.

3. The formulation of claim 1 or 2 contains at least 37% (wt / wt) of N-vinylaminoamine monomer.

4. The formulation of claim 1 or 2, wherein the polymerizable siloxane component is present in an amount of at least 45% (wt / wt).

5. The formulation of claim 1 or 2, wherein at least 50% (wt / wt) of the polymerizable siloxane content is a difunctional siloxane having a molecular weight of at least 8,000 Daltons.

6. The formulation of claim 1 or 2, comprising 20 to 40% (wt / wt) of a difunctional siloxane containing (meth)acrylate having a molecular weight of at least 8,000 Daltons.

7. The formulation of claim 1 or 2, wherein 20 to 50% (wt / wt) of the polymerizable siloxane content is a monofunctional siloxane having a molecular weight of less than 3,000 Daltons.

8. The formulation of claim 1 or 2, comprising 10 to 30% (wt / wt) of a monofunctional siloxane containing (meth)acrylate with a molecular weight of less than 3,000 Daltons.

9. The formulation of claim 1 further comprises: d. a non-siloxane hydrophobic monomer.

10. The formulation of claim 9, wherein the nonsiloxane hydrophobic monomer is a hydrophobic methacrylate monomer.

11. The formulation of claim 9, wherein the non-siloxane hydrophobic monomer comprises hydroxybutyl methacrylate, isoborneol methacrylate, or a combination of hydroxybutyl methacrylate and isoborneol methacrylate, or is composed of the like.

12. A formulation of any one of claims 9 to 11, wherein at least 5% (wt / wt) of the formulation is a non-siloxane hydrophobic monomer.

13. The formulations of claim 1 or 2 contain 0.2% to 2.0% (wt / wt) of TPP.

14. The formulation of claim 1, comprising: a1. a difunctional siloxane containing (meth)acrylate having a molecular weight of at least 8,000 Daltons, in an amount of 20 to 40% (wt / wt); a2. a monofunctional siloxane containing (meth)acrylate having a molecular weight of less than 3,000 Daltons, in an amount of 10 to 30% (wt / wt); b. N-methyl-N-vinylacetamide, in an amount of 37 to 50% (wt / wt); c. at least 0.2% (wt / wt) TPP; and d. at least 5% (wt / wt) hydroxybutyl methacrylate, isoborneol methacrylate, or a combination of hydroxybutyl methacrylate and isoborneol methacrylate.

15. A formulation of any one of claims 1, 2 and 14, wherein the polymerizable siloxane component comprises a difunctional siloxane monomer containing (meth)acrylate represented by formula (III), wherein (III) R1 is selected from hydrogen or methyl; R2 is selected from hydrogen or C1-4 hydrocarbon; m represents an integer from 0 to 10; n represents an integer from 4 to about 100; a and b represent integers of 1 or greater; a+b equals 20 to 500; b / (a+b) equals 0.01 to 0.22; and the configuration of the siloxane unit includes a random configuration.

16. A formulation of any one of claims 1, 2 and 14, wherein the polymerizable silica component comprises a monofunctional methacrylate-containing silica monomer represented by formula (II), where n is an integer from about 10 to 15.

17. A hydrogel obtained by polymerizing a formulation as claimed in any one of claims 1 to 16.

18. A polysiloxane hydrogel contact lens obtained by polymerizing a formulation as claimed in any one of claims 1 to 16.

19. Use of a TPP in improving the surface properties of contact lenses prepared from a self-formulated compound, the compound comprising: a. at least 40% (wt / wt) of a polymerizable siloxane component, wherein at least 50% (wt / wt) of the polymerizable siloxane content is a difunctional siloxane having a molecular weight of at least 5,000 Daltons, and wherein at least 20% (wt / wt) of the polymerizable siloxane content is a monofunctional siloxane having a molecular weight of less than 3,000 Daltons; and b. at least 30% (wt / wt) of a hydrophilic N-vinyl amide monomer.

20. As used in claim 19, wherein the compound is further as defined in any one of claims 2 to 16.