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US4046545A Expired / Lapsed US ⏱️ 0.0 years remaining

Method for making molded glass articles having bulk homogeneity and optical quality surface

Assignee: Corning Glass Works
•
Filing: 1976-05-25
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Granted: 1977-09-06
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Expires: 1996-05-25
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Abstract

Abstract An optical glass article having a desired surface figure and demonstrating maximum theoretical light transmission can be prepared by forming a base anhydrous glass of defined compositional ranges, hydrating the glass, partially dehydrating the glass at a temperature above the softening point and, using an inert gas, at a pressure above the vapor pressure of water contained therein, and then molding a preformed blank of the glass against a die having a desired optical quality surface figure, the molding being under conditions sufficient to transfer the surface figure of the die to the glass. The base glass comprises, in mole percent, about 70 to 82% SiO 2 , 10 to 17% Na 2 O and/or K 2 O, and 5 to 15% of an oxide or oxides selected from ZnO and PbO. The water content of the partially dehydrated glass ranges from about 3 to 8 wt. percent and the molded glass has a substantially uniform refractive index throughout its bulk. Homogeneous distribution of the water throughout the glass bulk appears to be assured by limiting the total water content to a range at which the diffusion coefficient of the water species (H 2 O, H + , and OH - ) exhibits the greatest dependence on the total water concentration (i.e. the range at which the coefficient is a quasi-step function).

Inventors

  • 👤 Leon M. Sanford
  • 👤 Che-Kuang Wu

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-23 04:39
CPC Classifications
C; C03; C03C; C03C3/00; C03C3/04; C03C3/076; C03C3/102; C03C3/105; C03C23/00; C03C3/078; C03C3/108; Y; Y10; Y10S; Y10S501/00; Y10S501/90

Claims Analysis

Total Claims: 9
Claim 1
Independent Claim 224 words
A method of preparing an optical glass article comprising the steps of A. preparing a base anhydrous glass comprising in mole percent, on an oxide basis, 70 to 82% SiO 2 , 10 to 17% Na 2 O and/or K 2 O, and 5 to 15% of an oxide or oxides selected from ZnO and PbO; B. hydrating the base glass; C. partially dehydrating the glass to a water content ranging from about 3 to 8 weight percent at a temperature above the softening point of the glass and, using an inert gas, at a total pressure above the vapor pressure of the water within the glass; and D. preforming a sample of the glass of step (C) and then molding the preformed sample of the partially dehydrated glass against a die having a desired optical quality surface figure under conditions sufficient to impart to a surface of the glass the surface figure of the die, the molding being done under conditions sufficient to maintain the water content in the glass, to assure that at least one portion of the glass is capable of transmitting an amount of light about equal to the maximum amount theoretically possible, and to maintain or result in an optical quality surface on that portion of the glass surface to which the surface figure of the die is transferred.
Claim 2
Independent Claim 224 words
A method of preparing an optical glass article comprising the steps of A. preparing a base anhydrous glass comprising in mole percent, on an oxide basis, 70 to 82% SiO 2 , 10 to 17% Na 2 O and/or K 2 O, and 5 to 15% of an oxide or oxides selected from ZnO and PbO; B. hydrating the base glass; C. partially dehydrating the glass to a water content ranging from about 3 to 8 weight percent at a temperature above the softening point of the glass and, using an inert gas, at a total pressure above the vapor pressure of the water within the glass; and D. preforming a sample of the glass of step (C) and then molding the preformed sample of the partially dehydrated glass against a die having a desired optical quality surface figure under conditions sufficient to impart to a surface of the glass the surface figure of the die, the molding being done under conditions sufficient to maintain the water content in the glass, to assure that at least one portion of the glass is capable of transmitting an amount of light about equal to the maximum amount theoretically possible, and to maintain or result in an optical quality surface on that portion of the glass surface to which the surface figure of the die is transferred.
Claim 3
Dependent Claim 11 words
The method of claim 1 wherein the inert gas is nitrogen.
Claim 4
Dependent Claim 42 words
The method of claim 1 wherein the optical quality surface of the molding portion of the die is such that over a distance of at least 0.1 inch, on an arithmetic average basis, the Roughness Height is less than about 3.0 microinches.
Claim 5
Dependent Claim 14 words
The method of claim 3 wherein the Roughness Height is less than 1.6 microinches.
Claim 6
Dependent Claim 23 words
The method of claim 1 wherein the base glass includes up to 5 mole percent Al 2 O 3 and/or ZrO 2 .
Claim 7
Dependent Claim 28 words
The method of claim 1 wherein the base glass includes up to 3 mole percent of a member selected from B 2 O 3 , BaO, and MgO.
Claim 8
Dependent Claim 47 words
The method of claim 1 wherein after the partial dehydration of step (C), the total water content of the glass consists of silanol groups and molecular water in such a proportion that the ratio of silanol groups to molecular water is equal to or greater than 1.0.
Claim 9
Dependent Claim 30 words
The method of claim 1 wherein after step (C) and prior to step (D), the glass is ground and polished to obtain an optical quality surface, and approximate surface figure.

References Cited (Backward Citations)

US3653864A Cited
US3868170A Cited
US3963503A Cited
US3844755A Cited
US3912481A Cited
US3899314A Cited
US3940277A Cited
US3915720A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1980-09-05 1981-03-07 1981-09-06 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1984-09-05 1985-03-07 1985-09-06 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1988-09-05 1989-03-07 1989-09-06 $7700.00 Window Closed / Lapsed

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