Anti reflection coating with a composite middle layer

Claim 2

An anti-reflection optical glass including glass having sequentially coated thereon a plurality of layers, each layer having a thickness expressed as a fraction of a predetermined wavelength (λ) consisting essentially of: (a) a medium refractive index layer selected from the group consisting of CeF 3 and Al 2 O 3 having a thickness of about 1/4 λ; (b) four sequential high refractive index layers, each of said layers selected from the group consisting of TiO 2 , CeO 2 and ZrO 2 ; (c) three thin layers of MgF 2 having a thickness of about 10 to about 100A, each of said thin layers interposed between said high refractive index layers (b) and spaced apart from each other at a distance of 1/8 λ, the plurality of layers (b) and (c) being about 1/2 λ in overall thickness; and (d) a low refractive index layer of MgF 2 having a thickness of 1/4 λ on top of the plurality of layers (b) and (c).

Claim 3

The optical glass of claim 1 wherein each thin layer (c) has a thickness of about 50A.

Claim 4

The optical glass of claim 1 wherein each of said high refractive index layers (b) is ZrO 2 .

Claim 5

A process for preparing an anti-reflection optical glass having sequentially coated thereon a plurality of coating layers, each layer having a thickness expressed as a fraction of a predetermined wave length (λ), said process including the successive steps of: (i) applying to an optical glass a coating about 1/4 λ in thickness of a medium refractive index layer selected from the group consisting of CeF 3 and Al 2 O 3 ; (ii) applying to the thus-coated layer of step (i) a coating of a high refractive index layer selected from the group consisting of TiO 2 , CeO 2 and ZrO 2 ; (iii) applying to the thus-coated layer of step (ii) a thin layer of MgF 2 having a thickness of between about 10 and 100A; (iv) repeating steps (ii) and (iii) until four of said layers (ii) and three of said layers (iii) are deposited, provided that: the thin layers of MgF 2 are interposed between the high refractive index layers and spaced apart from each other at a distance of about 1/8 λ; the plurality of layers thus formed is about 1/2 λ in overall thickness; (v) applying to the thus applied top layer of step (iv) a coating of about 1/4 λ in thickness of low refractive index MgF 2 .

Claim 6

A process for preparing an anti-reflection optical glass having sequentially coated thereon a plurality of coating layers, each layer having a thickness expressed as a fraction of a predetermined wave length (λ), said process including the successive steps of: (i) applying to an optical glass a coating about 1/4 λ in thickness of a medium refractive index layer selected from the group consisting of CeF 3 and Al 2 O 3 ; (ii) applying to the thus-coated layer of step (i) a coating of a high refractive index layer selected from the group consisting of TiO 2 , CeO 2 and ZrO 2 ; (iii) applying to the thus-coated layer of step (ii) a thin layer of MgF 2 having a thickness of between about 10 and 100A; (iv) repeating steps (ii) and (iii) until four of said layers (ii) and three of said layers (iii) are deposited, provided that: the thin layers of MgF 2 are interposed between the high refractive index layers and spaced apart from each other at a distance of about 1/8 λ; the plurality of layers thus formed is about 1/2 λ in overall thickness; (v) applying to the thus applied top layer of step (iv) a coating of about 1/4 λ in thickness of low refractive index MgF 2 .

Claim 7

The process of claim 4 wherein each thin layer of MgF 2 applied in steps (iii) and (iv) has a thickness of about 50A.

Claim 8

The process of claim 4 wherein said high refractive index material of step (ii) is ZrO 2 .