Cast-molding process for producing contact lenses

1. A process for producing contact lenses, comprising the steps of:

(A) obtaining a lens-forming composition comprising at least one lens-forming material, at least one photoinitiator, and at least one thiol-containing polymer in an amount for reducing the curing time of the lens-forming composition by at least 20%, compared to a control composition,

wherein the lens-forming material comprises a water-soluble prepolymer which is a crosslinkable polyvinyl alcohol prepolymer comprising repeating units of vinyl alcohol of

 repeating units of formula (I), and

in which:

R 1 is hydrogen or C 1 -C 6 alkyl,

R 2 is an ethylenically unsaturated group of

 in which q1 and q2 independently of each another are zero or one, and R 5 and R 6 independently of each another are a C 2 -C 8 alkylene divalent radical, R 7 is C 2 -C 8 alkenyl,

R 3 can be hydrogen or a C 1 -C 6 alkyl group, and

R 4 is a C 1 -C 6 alkylene divalent radical,

wherein the lens-forming composition comprises a thiol-containing polyvinyl alcohol which comprises at least about 50% by mole of repeating units of vinyl alcohol; and repeating units of formula (1)

in which: R o and R 3 independent of each other are hydrogen or a C 1 -C 6 alkyl group, R 4 is a C 2 -C 6 alkylene divalent radical, R a is hydrogen or methyl, and Rb is hydrogen, C 1 -C 3 alkyl, acetyl, or C 2 -C 4 alkanoylamino which optionally has a carboxyl group;

(B) introducing the lens-forming composition into a mold, 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 for receiving the lens-forming composition is formed between said first and second molding surfaces; and

(C) irradiating, with a UV or visible light, the lens-forming composition in the mold for a time period of about 15 seconds or less, so as to crosslink and/or polymerize said at least one lens-forming material to form the contact lens.

2. The process of claim 1 , wherein the crosslinkable polyvinyl alcohol prepolymer further comprises UV-absorbing repeating units, each of which is a repeating unit of formula (II)

in which:

R 8 is a monovalent radical of any one of formula (III)-(VII)

in which:

q1 is zero or 1-4;

R o is H, CH 3 or C 2 H 5 ;

R 9 , R 10 and R 17 independent of one other are H, CH 3 , CCl 3 , CF 3 , Cl, Br, NR′R″ in which R′ and R″ independent of each other are H or C 1 -C 4 alkyl, OH, or OCH 3 ;

R 11 and R 12 independent of each other are H or a first hydrophilic group which is *—CH 2 —(OC 2 H 4 ) n1 —OCH 3 , *—CH 2 —(OC 2 H 4 ) n1 —OH,

 provided that at least one of R 11 and R 12 is the first hydrophilic group;

n1 is an integer of 2 to 20;

R 13 is H, *—COOH, *—CONH—C 2 H 4 —(OC 2 H 4 ) n1 —OCH 3 , or *—CONH—C 2 H 4 —(OC 2 H 4 ) n1 —OH;

one of R 14 and R 15 is H or a second hydrophilic group which is *—CH 2 —(OC 2 H 4 ) n1 —OCH 3 , *—CH 2 —(OC 2 H 4 ) n1 —OH,

 while the other of R 14 and R 15 is

R 16 independent of each other are H, CH 3 , CCl 3 , CF 3 , Cl, Br, NR 1 ′R 1 ″ in which R 1 ′ and R 1 ″ independent of each other are H or C 1 -C 4 alkyl, OH, OCH 3 , SO 3 H, or SO 3 − Na + ;

R 18 is SO 3 Na,

R 19 is H, SO 3 Na,

R 20 is CH 3 , C 2 H 5 ,

R 21 is methyl or ethyl;

L1 is a linkage of

L2 is a linkage of *—CH 2 —*, *—C 2 H 4 —*, *—C 3 H 6 —*, *—C 3 H 6 —S—C 2 H 4 —*, *—C 3 H 6 —S—C 3 H 6 —*, or

L3 is a linkage of *—CH 2 —* or

X1 is O or NR o .

3. The process of claim 1 , wherein the photoinitiator is a visible-light photoinitiator which initiates free radical crosslinking and/or polymerizing reaction upon irradiation with a visible light having a wavelength greater than 380 nm and less than 500 nm and the step of irradiating is performed by using the visible light having a wavelength greater than 380 nm and less than 500 nm.

4. The process of claim 1 , wherein the lens-forming composition is a water-based lens-forming composition.

5. The process of claim 1 , wherein the step of irradiating is performed under a spatial limitation of radiation, wherein the mold is a reusable mold comprising a mask which is fixed, constructed or arranged in, at or on the mold half having the radiation-permeable molding surface, wherein the mask is radiation-impermeable or at least of poor radiation-permeability compared with the radiation-permeable molding surface, wherein the mask extends inwardly right up to the mold cavity and surrounds the mold cavity so as to screen all areas behind the mask with the exception of the mold cavity.

6. The process of claim 2 , wherein the step of irradiating is performed under a spatial limitation of radiation, wherein the mold is a reusable mold comprising a mask which is fixed, constructed or arranged in, at or on the mold half having the radiation-permeable molding surface, wherein the mask is radiation-impermeable or at least of poor radiation-permeability compared with the radiation-permeable molding surface, wherein the mask extends inwardly right up to the mold cavity and surrounds the mold cavity so as to screen all areas behind the mask with the exception of the mold cavity.

7. The process of claim 3 , wherein the step of irradiating is performed under a spatial limitation of radiation, wherein the mold is a reusable mold comprising a mask which is fixed, constructed or arranged in, at or on the mold half having the radiation-permeable molding surface, wherein the mask is radiation-impermeable or at least of poor radiation-permeability compared with the radiation-permeable molding surface, wherein the mask extends inwardly right up to the mold cavity and surrounds the mold cavity so as to screen all areas behind the mask with the exception of the mold cavity.