Process for making multifocal photochromic ophthalmic lens

Claim 2

A process for manufacturing a photochromic multifocal ophthalmic lens comprising a major lens portion composed of a photochromic glass and at least one lens segment fused to the major lens portion composed of a glass having a higher index of refraction than the major lens portion, comprising the steps of: a. providing a major lens portion composed of a silver halide-containing glass consisting essentially, in weight percent on the oxide basis, of about 48-57% SiO 2 , 6-10% Al 2 O 3 , 15-22% B 2 O 3 , 0.8-2% Na 2 O, 2.4-3.1% Li 2 O, 0-4% K 2 O, 3.2-7.2% Na 2 O + Li 2 O + K 2 O, 4.5-5.3% PbO, 3-9% BaO, 0-7.2% ZrO 2 , 0.10-0.6% Ag, 0.01-0.10% CuO, 0.15-1.2% Cl, 0-1.0% Br, 0-0.1% I, and 0-1.2% F, which lens portion is potentially photochromic; b. subjecting the potentially photochromic major lens portion to a nucleating heat treatment at a temperature in the range of about 510°-550° C. for a time in the range of about 10-50 minutes to initiate the growth of silver halide crystals therein, said time being insufficient to render the major lens portion photochromic but to provide a nucleated major lens portion; c. combining the nucleated major lens portion with at least one lens segment composed of a glass having a higher index of refraction than the major lens portion;

Claim 3

d. subjecting the nucleated major lens portion and lens segment to a fusion heat treatment comprising exposure to a temperature in the range of about 635°-670° C. for a time in the range of about 15-45 minutes, to develop the photochromic properties of the nucleated major lens portion and to fuse the lens segment thereto; and e. cooling the fused major lens portion and lens segment.

Claim 4

d. subjecting the nucleated major lens portion and lens segment to a fusion heat treatment comprising exposure to a temperature in the range of about 635°-670° C. for a time in the range of about 15-45 minutes, to develop the photochromic properties of the nucleated major lens portion and to fuse the lens segment thereto; and e. cooling the fused major lens portion and lens segment.

Claim 5

A process according to claim 1 wherein the nucleated major lens portion and lens segment are subjected to a fusion heat treatment comprising exposure to a temperature in the range of about 640°-660° C. for a time in the range of about 20-30 minutes.

Claim 6

A process according to claim 2 wherein the fused major lens portion and lens segment are cooled at a cooling rate in the range of about 2°-10° C./minute over the range from about 525°-200° C.

Claim 7

A process according to claim 1 wherein the major lens portion additionally contains at least one glass coloring agent selected in the indicated proportion from the group consisting of 0-0.5% CoO, 0-1.0% NiO, 0-1.0% Cr 2 O 3 and 0-5.0% total of oxides selected from the group consisting of Er 2 O 3 , Pr 2 O 3 , Ho 2 O 3 and Nd 2 O 3 .

Claim 8

A process for manufacturing a photochromic multifocal ophthalmic lens comprising a major lens portion composed of a photochromic glass and at least one lens segment fused to the major lens portion composed of a glass having a higher index of refraction than the major lens portion, comprising the steps of: a. providing a major lens portion composed of a silver halide-containing glass which is potentially photochromic, said glass consisting essentially, in weight percent on the oxide basis, of about 48-57% SiO 2 , 6-10% Al 2 O 3 , 15-22% B 2 O 3 , 0.8-2% Na 2 O, 2.4-3.1% Li 2 O, 0-4% K 2 O, 3.2-7.2% Na 2 O + Ki 2 O + K 2 O, 4.5-5.3% PbO, 3-9% BaO, 0-7.2% ZrO 2 , 0.10-0.6% Ag, 0.01-0.10% CuO, 0.15-1.2% Cl, 0-1.0% Br, 0-0.1% I and 0-1.2% F; b. subjecting the potentially photochromic major lens portion to a nucleating heat treatment above the annealing point of the glass for a time sufficient to initiate the growth of silver halide crystals therein, but insufficient to render the glass photochromic, to provide a nucleated major lens portion; c. combining the nucleated major lens portion with at least one lens segment composed of a glass having a higher index of refraction than the major lens portion; d. subjecting the nucleated major lens portion and lens segment to a fusion heat treatment at a temperature near the softening point of at least one of the glasses for a time sufficient to develop photochromic properties in the nucleated major lens portion and fuse the lens segment thereto; and e. cooling the fused major lens portion and lens segment.

Claim 9

A process for manufacturing a photochromic multifocal ophthalmic lens comprising a major lens portion composed of a photochromic glass and at least one lens segment fused to the major lens portion composed of a glass having a higher index of refraction than the major lens portion, comprising the steps of: a. providing a major lens portion composed of a silver halide-containing glass which is potentially photochromic, said glass consisting essentially, in weight percent on the oxide basis, of about 48-57% SiO 2 , 6-10% Al 2 O 3 , 15-22% B 2 O 3 , 0.8-2% Na 2 O, 2.4-3.1% Li 2 O, 0-4% K 2 O, 3.2-7.2% Na 2 O + Ki 2 O + K 2 O, 4.5-5.3% PbO, 3-9% BaO, 0-7.2% ZrO 2 , 0.10-0.6% Ag, 0.01-0.10% CuO, 0.15-1.2% Cl, 0-1.0% Br, 0-0.1% I and 0-1.2% F; b. subjecting the potentially photochromic major lens portion to a nucleating heat treatment above the annealing point of the glass for a time sufficient to initiate the growth of silver halide crystals therein, but insufficient to render the glass photochromic, to provide a nucleated major lens portion; c. combining the nucleated major lens portion with at least one lens segment composed of a glass having a higher index of refraction than the major lens portion; d. subjecting the nucleated major lens portion and lens segment to a fusion heat treatment at a temperature near the softening point of at least one of the glasses for a time sufficient to develop photochromic properties in the nucleated major lens portion and fuse the lens segment thereto; and e. cooling the fused major lens portion and lens segment.