Method of coating a transparent synthetic polymer substrate with glass boron oxide-silicon dioxide

Claim 2

A method according to claim 1 wherein the B2O3 content of the glass is adjusted so that said glass coating resulting therefrom has a coefficient of expansion which is closer to that of the substrate than is the coefficient of expansion of SiO2.

Claim 3

A method according to claim 3 wherein the vapor deposition is effected in a high vacuum of less than 5 X 10 4 torr.

Claim 4

A method according to claim 3 wherein the direction of impingement of the vapor stream of the molten glass onto the surface of the thermoplastic substrate is approximately 90*.

Claim 5

A method according to claim 5 wherein said direction is 90* .

Claim 6

A method according to claim 1, said glass containing between 10 and 70 percent boron oxide.

Claim 7

A method according to claim 7, said glass containing between 30 and 50 percent boron oxide.

Claim 8

A method according to claim 1, said glass consisting of B2O3, and less than 5 percent by weight of Na2O.

Claim 9

A method according to claim 1, said glass containing between 10 and 70 percent boron oxide, said vacuum for degassing being between 5 X 10 4 torr to 8 X 10 5 torr the B2O3 content of the glass being adjusted so that said glass coating has a coefficient of expansion which is closer to that of the substrate than is the coefficient of expansion of Si02, the vapor depositing being effected in a vacuum of less than 5 X 10 4 torr.

Claim 10

A method according to claim 10, the vapor deposition being effected in a vacuum from 2 X 10 4 to 10 5 torr.

Claim 11

A method according to claim 10, said glass containing 40 percent boron oxide and being prepared from a mixture of 50 percent of B2O3 of a grain size distribution between 20 and 30 Mu and 50 percent SiO2 of about the same grain size by melting at 1,550* C. under a vacuum for degassing increased from 5 X 10 4 10 torr to 8 X 10 5 torr, the molten mixture being held at 1, 550* C. for 10 minutes and then cooled to glass; the substrate being polycarbonate having a coefficient of expansion of 6.5 X 10 5 per * C.; the vapor depositing being done using an electron beam at a pressure as low as 5 X 10 5 torr to provide a coating thickness of 3 Mu ; the coated substrate being allowed to remain under vacuum for some five minutes following the deposition of the coating.