Coating method for strengthening vitreous and vitrocrystalline bodies

Claim 2

A process as defined in claim 2 wherein the thickness of the coating is no greater than 1 mm.

Claim 3

A process as defined in claim 3 wherein the thickness of the coating is between 1 and 150 microns.

Claim 4

A process as defined in claim 1 wherein the coating is of a vitreous material.

Claim 5

A process as defined in claim 1 wherein the chemical modification of the coating involves the chemical combination of one ingredient in the coating with at least one ingredient of a substance brought into contact with the coating during said step of effecting such modification.

Claim 6

A process as defined in claim 6 wherein the chemical modification involves the oxidation of a metal or metal compound forming one ingredient of the coating.

Claim 7

A process as defined in claim 7 wherein the oxidation is carried out by Contacting the coating with an oxidizing agent.

Claim 8

A process as defined in claim 7 wherein the oxidation is carried out by contacting the coating with molten potassium nitrate.

Claim 9

A process as defined in claim 6 wherein the coating contains a metal and the chemical modification involves the chemical combination of such metal with an oxidizing element whose ions have a greater radius than that of oxygen ions.

Claim 10

A process as defined in claim 6 wherein one ingredient of the coating is a metallic element having an invariable valency.

Claim 11

A process as defined in claim 6 wherein the coating consists of a single metallic element.

Claim 12

A process as defined in claim 1 wherein said step of effecting such modification is carried out by bringing the coating into communication with an ion exchange medium and producing an ion exchange between alkali metal ions in the coating and different alkali metal ions in the medium.

Claim 13

A process as defined in claim 13 wherein the modification involves replacement of alkali metal ions in the coating by ions derived from the medium and which confer on the coating a lower coefficient of thermal expansion, the heated condition being at a temperature above the strain point of the glass constituting the coating.

Claim 14

A process as defined in claim 13 wherein the coating is of glass, said step of maintaining the coating in such heated condition is carried out so as to maintain the coating at a temperature below the annealing point of the glass constituting the coating, and the ion exchange involves the replacement of ions in the coating by larger ions derived from the medium.

Claim 15

A process as defined in claim 13 wherein the coating is applied so as to cover only one or more margins of the layer and the entire layer is subjected to such chemical modification.

Claim 16

A process as defined in claim 1 wherein the layer is constituted by a soda-lime glass disc having a diameter of 12 cm. and a thickness of 1.5 mm., the coating is a titanium film having a thickness of 60 m Mu , said step of maintaining the coating in such heated condition is carried out by maintaining the coated disc at a temperature of 550* C., and said step of effecting such modification is carried out by maintaining the coating in contact with ozone for 4 hours.

Claim 17

A process as defined in claim 1 wherein the layer constitutes a beaker made of soda-lime glass, the coating is a film of SnO having a thickness of 100 m Mu and deposited on the internal and external lateral surfaces of the beaker, said step of maintaining the coating in such heated condition is carried out by maintaining the coated beaker at a temperature of 500* C., and said step of effecting such modification is carried out by placing the coating in contact with molten potassium nitrate for 3 hours.

Claim 18

A process as defined in claim 1 wherein the layer is a partially devitrified glass having the following composition, by weight: Li2O 15% Al2O3 10% SiO2 50% CaO 10% B2O3 8% TiO2 7% the coating is constituted by a mixture of germanium and sodium in the weight proportion of 80:20 and has a thickness of 2 Mu , and said steps of maintaining the coating in such heated condition and effecting such modification are carried out by maintaining the coated glass in contact with hydrogen sulfide gasses at a temperature of 90* C., and then maintaining the sheet at a temperature of 250* C. for 1 hour.

Claim 19

A process as defined in claim 1 wherein the layer is constituted by a sheet of soda-lime glass, the coating is constituted by a mixture of Ge, Cd and Na having a thickness of 3 Mu , which coating is preliminarily sulfurized, and said steps of maintaining the coating in such heated condition and effecting such modification are carried out by immersing the coated sheet in a bath composed of a mixture of Kcl and AlCl3 in a molecular proportion of 70:30 and at a temperature of 270* C. for 3

Claim 20

A process as defined in claim 1 wherein the layer is constituted by a sheet of partially devitrified glass having the following composition, by weight: Li2O 15% Al2O3 10% SiO2 50% CaO 10% B2O3 8% TiO2 7%, the coating is constituted by an enamel having the following ingredients in the following molecular proportions: SiO2 40 B2O3 10 PbO 25 PbF2 5 NaF 10 ZrO2 3 CdO 7, the coating additionally containing 2 percent, by weight, of very fine zinc powder and being deposited on the sheet to a thickness of 0.3 mm., and said steps of maintaining the coating in such heated condition and effecting such modification are carried out by exposing the coated sheet to a stream of dry hydrogen selenide gas at a temperature of 400* C. for 2 hours.

Claim 21

A layer of vitreous or vitrocrystalline material which has been physically strengthened by being subjected to the process as defined in claim 1.

Claim 22

A process according to claim 1 wherein the chemical modification comprises introduction of ions into the coating and is effected while said coating is in the solid state.

Claim 23

A process according to claim 1 wherein the chemical modification is oxidation of at least one component of the coating.

Claim 24

A process according to claim 25 wherein the one component of the composition is a metal element selected from the group consisting of tin, titanium, silicon, vanadium, lead, manganese, aluminum, zirconium, thorium, bismuth and nickel.

Claim 25

A process according to claim 25 wherein the one component of the composition is a compound selected from the group consisting of SiO, TiO, SnO and PbO.

Claim 26

A vitreous or vitrocrystalline layer, at least marginal surface zones of which are coated with a solid coating having chemically impressed compressive stresses therein, the zones being symmetrically disposed at respectively opposite sides of the layer''s median surface.

Claim 27

A process according to claim 1 for physically strengthening a layer of vitreous or vitrocrystalline material comprising the steps of: I. covering at least surface zones of the layer, which are symmetrically disposed at respectively opposite sides of the layer''s median surface, with a solid chemically temperable coating having exchangeable ions in its composition and wherein compressive stresses are produced by a. chemically tempering the coating while it is in solid state and in a heated condition by exchanging the exchangeable ions for others of a different size followed by b. cooling the thus chemically modified coating; II. maintaining the coating in such heated condition and exchanging the exchangeable ions for others of a different size; and III. subsequently cooling the resulting chemically modified coating.

Claim 28

A process according to claim 1 for physically strengthening a layer of vitreous or vitrocrystalline material comprising the steps of: I. covering at least surface zones of the layer, which are symmetrically disposed at respectively opposite sides of the layer''s median surface, with a solid coating having in its composition at least one oxidizable ingredient and wherein compressive stresses are produced by a. chemical modification thereof while the coating is in solid state and in a heated condition by oxidizing the oxidizable ingredient followed by b. cooling the thus chemically modified coating; II. maintaining the coating in such Heated condition and effecting the chemical modification; and III. subsequently cooling the resulting chemically modified coating.