Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Utility Patent
1998-06-02
2001-01-02
Szekely, Peter A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C427S488000, C427S491000, C523S105000, C523S108000, C351S159000, C524S548000
Utility Patent
active
06169127
ABSTRACT:
The present invention relates to coated articles wherein the coating comprises a polymer having desirable characteristics regarding adherence to the substrate, durability, wettability, biocompatibility and permeability. More particularly, the present invention relates to an article, such as a biomedical material or article, especially a contact lens, including an extended-wear contact lens which is at least partially coated with a polymer obtainable by after-glow plasma-induced polymerization of a polymerizable unsaturated compound, preferably a polymerizable vinyl or isopropenyl compound under specific plasma conditions. The invention further relates to a method for the production of articles coated with a polymer of said features.
The provision of a coating on a substrate may generally be desirable for a variety of reasons including protection of the substrate and provision of desirable surface characteristics which the substrate material does not exhibit to the required degree. In the case of biomedical devices, such as ophthalmic devices, e.g. contact lenses it is desirable to have surfaces which are readily wettable by an aqueous liquid such as tear fluid and are capable to retain an aqueous fluid layer which is beneficial for the comfort of the wearer. The sliding motion of the contact lens is facilitated by the presence of a continuous layer of tear fluid on the contact lens, a layer which lubricates the tissue/lens interface. Additionally, the adhesiveness towards proteins, lipids, minerals, cell debris and other spoilations or microorganisms, the permeability and stability characteristics of the surface of the contact lens having a coating thereon are of great importance. The permeability of the lens material for gases, water and ions which are required especially in the case of extended wear contact lenses, preferably must not be impaired by the coating which is provided in order to impart hydrophilicity to the surface, and the coating should exhibit thermal, oxidative and hydrolytic stability as well as resistance to formation of deposits from tear components and delamination caused by mechanical stress.
A variety of different types of processes for preparing polymeric coatings on a substrate have been disclosed in the prior art. Coatings can be prepared on the surface of a substrate by any of the classical polymerization methods including bulk polymerization, deposition of polymerizing material from the vapour phase and coating of the substrate surface with a layer of a polymerizable monomer and polymerizing said monomer on the surface of the substrate. Representative for the prior art disclosing preparation of coatings on substrates using classical “wet” chemistry EP-A-632 329 should be mentioned, which describes functionalized photoinitiators which may be bound to an inorganic or organic substrate. One embodiment of said disclosure relates to a contact lens which comprises a thin outer polymer layer on the layer of the photoinitiator which is obtainable by applying a thin coating of photopolymerizable ethylenically unsaturated substances on the surface of the substrate carrying photoinitiator groups and polymerization of the layer of ethylenically unsaturated substances by irradiation.
With these methods using classical “wet” chemistry, however, it is not always possible to obtain the desired coating characteristics, for example resistance to delamination, stability and permeability characteristics which are necessary for the surface of biomedical devices including contact lenses.
A method for preparing polymeric coatings, especially thin coatings on a variety of substrates which is substantially different from the wet chemical methods is the polymerization of polymerizable unsaturated or saturated compounds under the effect of a plasma generated by electric discharge. Plasma-induced polymerization is a physical method of modifying surfaces by depositing a polymer on the surface in a way which is basically dry and without direct contact of the substrate with a solution of the material to be coated. The term “plasma” denotes an ionized gas, e.g. created by electric glow discharge which may be composed of electrons, ions of either polarity, gas atoms and molecules in the ground or any higher state of any form of excitation, as well as of photons. It is often called “low temperature plasma”. For a review of plasma polymerization and its uses reference is made to R. Hartmann “Plasmapolymerisation: Grundlagen, Technik und Anwendung, Jahrb. Oberfl{umlaut over (a)}chentechnik (1993) 49, pp. 283-296, Battelle-Inst. e.V. Frankfurt/Main Germany; H. Yasuda, “Glow Discharge Polymerization”, Journal of Polymer Science: Macromolecular Reviews, vol. 16 (1981), pp. 199-293; H. Yasuda, “Plasma Polymerization”, Academic Press, Inc. (1985); Frank Jansen, “Plasma Deposition Processes”, in “Plasma Deposited Thin Films”, ed. by T. Mort and F. Jansen, CRC Press Boca Raton (19); O. Auciello et al. (ed.) “Plasma-Surface Interactions and Processing of Materials” publ. by Kluwer Academic Publishers in NATO ASI Series; Series E: Applied Sciences, vol. 176 (1990), pp. 377-399; and N. Dilsiz and G. Akovali “Plasma Polymerization of Selected Organic Compounds”, Polymer, vol. 37 (1996) pp. 333-341.
For plasma polymerization to produce a coating on a substrate which may also be called “plasma grafting”, “plasma deposition” or “plasma coating” a suitable organic monomer or a mixture of monomers having polymerizable unsaturated groups is introduced into the plasma zone of the reactor where it is fragmented and/or activated forming further excited species in addition to the complex mixture of the activated plasma gases. The excited species and fragments of the monomer recombine upon contact with the substrate in an undefined way to a largely undefined structure which contains a complex variety of different groups and chemical bonds forming a highly crosslinked polymer deposit on the substrate. If O
2
, N
2
or oxygen or nitrogen containing molecules are present, either within the plasma reactor during the plasma coating process, or on exposure of the plasma coated substrate to oxygen or air subsequent to the plasma process the polymeric deposit will include a variety of polar groups.
In this technique, which is called in the following “in-glow” plasma polymerization the substrate may be located within the plasma zone or alternatively outside (below) the plasma zone and the monomer(s) as well as the plasma gas stream (e.g. H
2
, He, Ar) are introduced into the plasma zone. With respect to the preparation of coatings on contact lenses using in-glow plasma polymerization U.S. Pat. No. 4,312,575 discloses a soft corneal contact lens comprising a soft, highly oxygen-permeable polymeric lens having formed on the surface thereof an ultrathin optically clear, impermeable barrier coating which is tightly cross-linked and comprises the reaction product resulting from an electrical glow discharge polymerization process. JP-A-62/031803 discloses plasma polymerization of a mixture of oxygen and a saturated hydrocarbon to form a thin film on the surface of optical parts, e.g. contact lenses. U.S. Pat. No. 4,783,374 discloses an ophthalmic lens having an abrasion resistant transparent coating which comprises a plasma assisted chemical vapor-deposition deposited alkene-silane plasma reaction product of a silane, an alkene and an oxygen source. JP-A-60/163901 discloses the plasma polymerization of mixtures of unsaturated hydrocarbons and oxygen to form thin hydrophilic films on contact lenses. Plasma deposition of an ultra thin layer of a polymer of acetylene-H
2
O—N
2
onto poly(methylmeth-acrylate) contact lenses is disclosed by H. Yasuda et al. in J. Biomed. Mater. Res. (1975), pp. 629-643. EP-A-152 256 discloses an optical product having a thin film on its surface which is obtained by subjecting a mixed gas of oxygen and a hydrocarbon compound having a double bond to plasma polymerization. U.S. Pat. No. 5,260,093, U.S. Pat. No. 5,326,584, WO-A-94/11118 and U.S. Pat. No. 5,080,924 disclose a method of permanent
Chabrecek Peter
Hopken Jens
Lohmann Dieter
Gorman Jr. Robert J.
Meece R. Scott
Novartis AG
Szekely Peter A.
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