Method for coating anti-reflection film on surface of optical material

Claim 1

A method for coating an anti-reflection film on the surface of an optical material, comprising a first step of vacuum-depositing under a first condition of vacuum-deposited a silicon oxide SiO film having a predetermined thickness on said surface of said optical material while said optical material is placed in a vacuum chamber having a first vacuum degree and kept at temperatures below 120° C. at which the quality and the shape of said material are not changed, and a second step of vacuum-depositing under a second condition of vacuum-deposition different from said first condition a silicon dioxide SiO 2 film having a predetermined thickness on said SiO film while the temperature of said optical material is kept the same as in said first step but said first vacuum degree is changed to a second vacuum degree different from said first vacuum degree.

Claim 2

A method for coating an anti-reflection film on the surface of an optical material, comprising a first step of vacuum-depositing under a first condition of vacuum-deposited a silicon oxide SiO film having a predetermined thickness on said surface of said optical material while said optical material is placed in a vacuum chamber having a first vacuum degree and kept at temperatures below 120° C. at which the quality and the shape of said material are not changed, and a second step of vacuum-depositing under a second condition of vacuum-deposition different from said first condition a silicon dioxide SiO 2 film having a predetermined thickness on said SiO film while the temperature of said optical material is kept the same as in said first step but said first vacuum degree is changed to a second vacuum degree different from said first vacuum degree.

Claim 3

A method for coating an anti-reflection film on the surface of an optical material, comprising a first step of vacuum-depositing at a speed of 50-150 nm/min. a silicon oxide SiO film having a thickness of λ/2 (wavelength λ = 500-550 nm) on said surface of said optical material while said material is placed in a vacuum chamber having vacuum degrees of 5 × 10 -5 -8 × 10 -6 Torr and kept at temperatures of 20°-120° C., and a second step of vacuum-depositing at a speed of 15-40 nm/min. a silicon dioxide SiO 2 film having a thickness of λ/4 (λ = 500-550 nm) on said SiO film with said temperatures kept the same but said vacuum degrees changed to 2 × 10 -4 -7 × 10 -5 Torr.

Claim 4

A method for coating an anti-reflection film on the surface of an optical material, comprising a first step of vacuum-depositing at a speed of 50-150 nm/min. a silicon oxide SiO film having a thickness of λ/2 (wavelength λ = 500-550 nm) on said surface of said optical material while said material is placed in a vacuum chamber having vacuum degrees of 5 × 10 -5 -8 × 10 -6 Torr and kept at temperatures of 20°-120° C., and a second step of vacuum-depositing at a speed of 15-40 nm/min. a silicon dioxide SiO 2 film having a thickness of λ/4 (λ = 500-550 nm) on said SiO film with said temperatures kept the same but said vacuum degrees changed to 2 × 10 -4 -7 × 10 -5 Torr.