Protective film, reflective member, and method for producing protective film
A protective film placed on an upper part of a metal film for protecting the metal film placed on a glass substrate. The protective film includes a silica film. The silica film has an extinction coefficient “k” less than or equal to 1×10 −4 , a refractive index “n” greater than or equal to 1.466 at a wavelength of 632 nm, and a carbon content less than or equal to 3 atomic %.
1. A protective film, comprising:
a silica film having a thickness of 1500 Å or less,
wherein the silica film has an extinction coefficient “k” less than or equal to 1×10 −4 at a wavelength of 632 nm, a refractive index “n” greater than or equal to 1.466 at a wavelength of 632 nm and a carbon content less than or equal to 3 atomic %.
2. A method for producing the protective film of claim 1 provided on an upper part of a metal film placed on a glass substrate, the method comprising:
depositing a metal reflective film on an upper part of the glass substrate; and
depositing the silica film on an upper part of the metal reflective film;
wherein the depositing the silica film is performed by a plasma CVD method in a condition in which a pressure is less than or equal to 2 Pa.
3. The method as claimed in claim 2 ,
wherein the depositing the metal reflective film is performed by a sputtering method.
4. The method as claimed in claim 3 ,
wherein the depositing the metal reflective film and the depositing the silica film are performed by an inline method.
5. The method as claimed in claim 2 , wherein the metal reflective film comprises a silver or a silver alloy.
6. The method as claimed in claim 2 , further comprising:
forming a film that has a refractive index higher than the silica film on an upper part of the silica film.
7. The method as claimed in claim 6 ,
wherein the film having a refractive index higher than the silica film is a silicon nitride film.
8. The protective film as claimed in claim 1 , wherein the silica film has a thickness ranging from 50 to 1500 Å.
9. A reflective member, comprising:
a glass substrate;
a metal reflective film; and
a protective film,
wherein the protective film comprises a silica film having a thickness of 1500 Å or less,
wherein the silica film has an extinction coefficient “k” less than or equal to 1×10 −4 at a wavelength of 632 nm, a refractive index “n” greater than or equal to 1.466 at a wavelength of 632 nm and a carbon content less than or equal to 3 atomic %.
10. The reflective member as claimed in claim 9 ,
wherein the metal reflective film comprises silver or a silver alloy.
11. The reflective member as claimed in claim 9 , further comprising:
a single film provided between the glass substrate and the metal reflective film, and
wherein the single film is selected from the group consisting of a metal nitride, a metal oxide, and a metal oxynitride.
12. The reflective member as claimed in claim 9 ,
wherein a film having a refractive index higher than the silica film is provided on a side of the silica film that is opposite from the metal reflective film.
13. The reflective member as claimed in claim 12 ,
wherein the film having a refractive index higher than the silica film is a silicon nitride film.
14. The reflective member as claimed in claim 9 ,
wherein the glass substrate comprises a glass having a sodium oxide content of equal to or less than 4% by mass.
15. A low-E glass comprising:
the reflective member as claimed in claim 9 .
16. A secondary mirror of a solar energy generating system comprising:
the reflective member as claimed in claim 9 .
17. The reflective member as claimed in claim 9 , wherein on an upper part of the glass substrate, the metal reflective film and the protective film are arranged in this order.
18. The reflective member as claimed in claim 9 , wherein the silica film has a thickness ranging from 50 to 1500 Å.