Anti-reflection film

Details Anti-reflection film Anti-reflection film

1999-04-01

2001-06-19

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Composite

Of quartz or glass

C428S446000, C428S480000, C428S500000, C428S689000, C428S697000, C428S698000

Reexamination Certificate

active

06248448

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an anti-reflection film as an optical film deposited on a supporting layer and configured for having anti-reflection properties and for preventing leakage of electro-magnetic waves or accumulation of static charges.
DESCRIPTION OF RELATED ART
Up to now, an anti-reflection film has been extensively used in the field of optical or opto-electrical application where it is desired or necessary to decrease the reflection from an optical boundary between, for example, air and glass. Examples of such application include a camera lens, a platen for a copying machine, a cover glass for equipment, a panel for a cathode ray tube and other display devices.
Among optical thin-film coatings, employed in a variety of application fields, there are a sole coating layer of a film composed of magnesium fluoride, a dual-layer coating which minimizes the refractive index in a wavelength range, and a multi-layer broad-range coating producing a low refractive index over a broader wavelength range, such as a visible range.
The dual-layer coating is now explained.
A dual-layer anti-reflection film, as disclosed in U.S. Pat. No. 4,422,721 (anti-reflection film A), is made up of at least one layer of a low refractive index material, such as magnesium fluoride, a thin transparent layer of an electrically conductive high refractive index material, such as indium tin oxide (ITO), cadmium stannate or tin antimony oxide. This dual-layer anti-reflection film is made up of the layer of low refractive index material and the thin transparent layer of the electrically conductive high refractive index material, deposited in this order on the surface of an optical substrate. The layer of the electrically conductive material has an optical thickness of 1.0 to 30.0 nm, while the layer of the low refractive index material has a film thickness correlated with the thickness of the layer of the electrically conductive material for prohibited deterioration of the layer of the electrically conductive material.
The dual-layer anti-reflection film A, made up of a film of low refractive index material and a high refractive index material, provides a directly electrically connectable electrically conductive anti-reflection film which may be used with advantage for a CRT or copying machine.
A dual-layer anti-reflection film, disclosed in U.S. Pat. No. 4,732,454 (anti-reflection film B), is made up of a transparent substrate of a synthetic material, a hard scratch-proof first layer deposited on the substrate, a second layer of an electrically conductive material, intimately affixed to the first layer and formed by vacuum deposition or sputtering by high frequency discharge at a temperature lower than 150° C. in the presence of oxygen atoms and a third layer formed of a material having a lower refractive index than that of the second layer and intimately affixed to the second layer. The second layer is comprised of ITO as its ingredient.
The anti-reflection film B can propagate light and can be coated on a protective layer of a synthetic material so as to serve as an anti-reflection film suitable as a filter with respect to electromagnetic waves emanating from the CRT filter.
The above anti-reflection film A leaves much to be desired in that it is lower in electrical conductivity and in reflection inhibiting ratio over a wide frequency range.
Similarly to the anti-reflection film A, the above anti-reflection film B leaves much to be desired in that it is lower in reflection inhibiting ratio over a wide frequency range.
If the anti-reflection film low in electrical conductivity is attached to a panel for CRT, it has only little effect in preventing static charges or inhibiting an output of electro-magnetic waves from being outputted from a CRT panel.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an anti-reflection film having high electrical conductivity and high reflection inhibiting ratio in a broad frequency range.
An anti-reflection film according to the present invention has two mutually neighboring layers which are deposited directly or via a hard coating layer on a supporting layer. One of the layers that is closer to a substrate layer is formed of an electrically conductive material capable of absorbing light, while the remaining second layer is formed of a material having a refractive index not higher than 2.0. If the first layer has the refractive index and the extinction coefficient for a shorter wavelength &lgr;
v
of n
v
and k
v
, respectively, and the refractive index and the extinction coefficient for a longer wavelength &lgr;
r
of n
r
and k
r
, respectively, n
v
is larger than n
r
and k
v
is smaller than k
r
(n
v
>n
r
and k
v
<k
r
).
If the first layer is generated in the presence of oxygen with an oxygen partial pressure of not more than 50%, the amount of generation of oxides may be reduced for reducing deterioration in electrical conductivity.
According to the present invention, there is provided an anti-reflection film having high electrical conductivity and high anti-reflection effect over a wide frequency range despite its simplified structure, thus prohibiting static charges or electro-magnetic waves from being outputted from an optical substrate on which is affixed the anti-reflection film.


REFERENCES:
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patent: 4422721 (1983-12-01), Hahn et al.
patent: 4732454 (1988-03-01), Saito et al.
patent: 4870322 (1989-09-01), Matsudaira et al.
patent: 5091244 (1992-02-01), Biornard
patent: 5190807 (1993-03-01), Kimock et al.
patent: 5298312 (1994-03-01), Oyama et al.
patent: 5318830 (1994-06-01), Takamatsu et al.
patent: 5407733 (1995-04-01), Bjornard et al.
patent: 5464683 (1995-11-01), Rudigier et al.

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