Silicone hydrogel lenses with relatively-long thermal stability

A method for producing silicone hydrogel contact lenses, comprising the steps of:

• (A) providing a mold for making a soft contact lens, wherein the mold has a first mold half with a first molding surface defining the anterior surface of a contact lens and a second mold half with a second molding surface defining the posterior surface of the contact lens, wherein said first and second mold halves are configured to receive each other such that a cavity is formed between said first and second molding surfaces;
• (B) introducing a lens formulation into the cavity, wherein the lens formulation comprises
• (1) a hydrophilic (meth)acrylamide-type monomer,
• (2) a siloxane vinylic monomer of formula (I) or (II) (preferably of formula (I))
• in which R′ is hydrogen or methyl, R″, R11 and R12 independent of one another are C1-C6 alkyl (preferably methyl), r1 and r2 independent of each other are integer of 0 or 1, m1 is an integer of 3 to 10 (preferably 3 to 8, more preferably 3 to 5), R9 and R10 independent of each other are a substituted or unsubstituted C1-C10alkylene divalent group, X1 is a linkage of
• in which R″ is as defined above and R12″ and R12′ independent of each other are C1-C6 alkyl (preferably methyl),
• (3) a linear polysiloxane crosslinker which has two terminal (meth)acrylamido or methacryloxy groups and is free of any ester bond without a tertiary carbon atom adjacent to the carbonyl group of the ester bond, any urethane bond or any urea bond in the backbone of the polysiloxane crosslinker between the two terminal (meth)acrylamido or methacryloxy groups, and
• (4) from about 0.05% to about 1.5% by weight of a photoinitator, wherein the lens formulation is characterized by having an ability to be cured by a UV light having an UV-intensity of about 4.1 mW/cm2 within about 100 seconds;
• and
• (C) irradiating (preferably under a spatial limitation of actinic radiation) the lens formulation in the mold for a time period of about 100 seconds or less (preferably about 75 seconds or less, more preferably about 50 seconds or less, even more preferably about 30 seconds or less), so as to crosslink the lens formulation to form the silicone hydrogel contact lens,
• wherein the relatively-long thermal stability of the produced contact lens is characterized by having an autoclave-induced change in elastic modulus,
• 
• EM
• 19
• 
• A
• 
• 
• C
• _
• -
• EM
• 1
• 
• A
• 
• 
• C
• _
• EM
• 1
• 
• A
• 
• 
• C
• _
• 
• ,
• of about 10% or less (preferably about 7.5% or less, more preferably about 5% or less), wherein EM1AC is the averaged after-one-autoclave elastic modulus of the soft contact lens and is obtained by averaging the elastic modulus of 15 soft contact lenses measured after being autoclaved one sole time for 30 minutes at 121° C. in a phosphate buffered saline at a pH of 7.20±0.05 and EM19AC is the averaged after-19-autoclaves elastic modulus of the soft contact lens and is obtained by averaging the elastic modulus of 15 soft contact lenses measured after being stored and autoclaved 19 times each for 30 minutes at 121° C. in a phosphate buffered saline at a pH of 7.20±0.05.