High strength ophthalmic lens

• US 4,042,405 A
• Filed: 03/18/1976
• Issued: 08/16/1977
• Est. Priority Date: 03/18/1976
• Status: Expired due to Term

• Current Assignee: Cabot Safety Intermediate Corporation et al
• Original Assignee: American Optical Corporation
• Inventors: Krohn, David A., Deeg, Emil W., Graf, Robert E.
• Primary Examiner(s): Douglas, Winston A.
• Assistant Examiner(s): Bell, Mark
• Application Number:
  US05/668,174
• Time in Patent Office: 516 Days
• Field of Search: 106/472, 106/52, 65/30 E, 351/166
• US Class Current: 428/410
• CPC Class Codes: C03C 21/00 Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
• CPC Class Codes: C03C 3/097 containing phosphorus, niobium or tantalum
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

An ophthalmic glass lens having a compressively-stressed surface zone after ion exchanging which is at least 120 microns in depth, formed from an alkali metal oxide silicate glass comprising by weight about 4 to about 15 percent sodium oxide and about 3 to about 15 percent potassium oxide. There is a compressively-stressed surface layer having a strength of at least 25,000 psi. The total amount of sodium, potassium and other alkali metal oxides is up to about 20 percent. The total amount of zinc oxide, lanthanum oxide, magnesium oxide, and calcium oxide is about 8 to 15 percent, and there is about 3 to about 15 percent phosphorus pentoxide. An ion exchange process takes place at a temperature either above or below the strain point of conventional ophthalmic crown glass to produce satisfactory physical properties in the ophthalmic glass lens.

Claims

1. A chemically-strengthened ophthalmic glass lens made from a phospho-silicate glass having the following chemical analysis:

space="preserve" listing-type="tabular">______________________________________ Ingredient Percent by Weight ______________________________________ sodium oxide about 4 to about 15 potassium oxide about 3 to about 15 Other Alkali Metal Oxides;

lithium oxide up to about 5 rubidium oxide up to about 5 cesium oxide up to about 5 lanthanum oxide up to about 15 aluminum oxide up to about 5 zirconium oxide up to about 5 zinc oxide up to about 15 calcium oxide up to about 10 titanium oxide up to about 5 magnesium oxide up to about 4 boron oxide up to about 2 phosphorus pentoxide about 3 to about 15 Total Na.sub.2 O + K.sub.2 O and other alkali metal oxides about 12 to about 20 Total ZnO + La.sub.2 O.sub.3 + CaO + MgO about 8 to about 15 Total MgO + Al.sub.2 O.sub.3 about 0.2 to about 5 Fining Agents (antimony oxide, cerium oxide, arsenic oxide and mixtures thereof) up to about 2 silica balance ______________________________________

said lens characterized by an index of refraction in the range of about 1.50 to 1.52 having a minimum depth of penetration of potassium ions of 120 microns and a compressively-stressed surface layer having a strength of at least 25,000 psi.

2. A chemically-strengthened ophthalmic glass lens according to claim 1 made from a glass containing the following chemical analysis:

space="preserve" listing-type="tabular">______________________________________ Ingredient Percent by Weight ______________________________________ sodium oxide about 7 to about 10 potassium oxide about 7 to about 11 zinc oxide up to about 15 aluminum oxide about 0.2 to about 4 phosphorus pentoxide about 3 to about 15 lanthanum oxide up to about 15 Calcium oxide up to about 10 titanium oxide up to about 5 magnesium oxide up to about 4 Total ZnO + CaO + about 8 to about 15 La.sub.2 O.sub.3 + MgO Fining Agents (antimony oxide, cerium oxide, arsenic oxide and mixtures thereof) up to about 2 silica balance ______________________________________

3. The lens of claim 1 wherein said glass comprises by weight 8.8 percent sodium oxide, 9.9 percent potassium oxide, 3.3 percent magnesium oxide, 2.5 percent aluminum oxide, 10.9 percent zinc oxide, and about 3 to about 15 percent phosphorus pentoxide.