Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-02-03
2002-04-30
Turner, Archene (Department: 1774)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C359S359000, C359S586000, C428S212000, C428S216000, C428S426000, C428S432000, C428S697000, C428S699000, C428S701000, C428S702000
Reexamination Certificate
active
06379803
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a low reflection glass article, particularly a low reflection glass article endowed with function preventing reflection of visible light obtained by coating an optical thin film on the surface of a transparent glass substrate and a method for producing the same, and an optical filter and plasma display using the above-described low reflection glass article.
BACKGROUND ART
A reflection preventing system employing an optical thin film is used for reducing the surface reflectivity and thereby enhancing the optical properties of optical parts such as a camera and glasses, or display parts of OA electronic apparatuses such as a display panel, a display, a filter for a display and the like. These reflection preventing films are required to have a low reflectivity property and high transmission property, to enhance visibility or to further enhance the original optical properties.
The reduction in reflectivity owing to an optical thin film is caused by a light interference effect. Regarding an optical multi-layer film composed of three layers, there is known, for example, a low reflection glass article obtained by laminating a first layer having a middle refractive index (1.71) and an optical film thickness of one-fourth wave length, a second layer having a high refractive index (2.43) and an optical film thickness of half wave length, and a third layer having a high refractive index (1.39) and an optical film thickness of one-fourth wave length in this order on a transparent glass substrate (refractive index: 1.52) (for example, H. K. Pulker, “Coatings on Glass”, P. 402 to 403, Amsterdam, Elsevier, 1984), and it is known that by such constitution, wave length range of which the refractive index is near zero can be enlarged and simultaneously reflection color can-be improved.
On the other hand, a plasma display panel has been recently put into practical use as a large-scale screen wall television, and development for general consumption thereof is intensive. It is known that an optical filter which has a multi-layer reflection preventing film layer for preventing reflection of a light from the outer environment and an electromagnetic wave shielding layer and corrects emitted color from PDP is placed at the front surface of this PDP. For example, there is known an optical filter which is prepared by adhering a reflection preventing film (obtained by laminating a plurality of films composed of materials having different refractive indexes, and by conducting vapor deposition on a plastic film substrate) using a transparent pressure-sensitive adhesive on one surface of a colored transparent substrate (a plate made of an acrylic resin or a polycarbonate resin which is colored to prevent violet-like appearance of emitted color tone which should be naturally blue by dispersing into the plate a pigment which absorbs excess red components emitted by PDP) and adhering (1) a film shielding an electromagnetic wave and line spectrum in near-infrared range (for example, a film obtained by sputtering a silver-inorganic oxide fine particle on the surface of a PET film) and (2) an interference fringe preventing film (for example, a film obtained by forming slight indentations and protrusions on the outer surface of a transparent film so as to prevent close fitting thereof to PDP even when it is contacted with PDP) in this order using a transparent pressure-sensitive adhesive on the other surface of the transparent substrate; the optical filter being an invention described in Japanese Laid-Open Patent Publication No. 306366 of 1997 which has been laid-open after the priority date of the current invention.
However, in the above-described optical thin film system reducing refractivity by using light interference action, facilities are in large scale since the thin films are formed by using vacuum equipment.
On the other hand, the above-described optical filter used for PDP has a problem in that production cost is high since a pigment is mixed in a resin plate, and further, a reflection preventing film is adhered on the surface.
The present invention has been accomplished for solving such problems in conventional technologies, and an object thereof is to provide a low reflection glass article coated with an optical multi-layer film which can reduce reflectivity in visible light wide range without requiring large-scale facilities.
Further, an object of the present invention is to solve the above-described problems of conventional technologies, to provide a glass article coated with a reflection preventing colored film which has excellent ability for preventing reflection of visible light, in addition, can freely control the tone of transmitted light, and has high visible light transmission, and to provide an optical filter for PDP using the same.
DISCLOSURE OF THE INVENTION
The present invention is a low reflection glass article which is prepared by laminating a first layer which has a middle refractive index (n
1
) from 1.60 to 1.95 and has a film thickness of (60 to 130 nm)
1
, a second layer which has a high refractive index (n
2
) which is in a range from 1.91 to 2.60 and higher than the refractive index of said first layer by at least 0.20 and has a film thickness of (140 to 230 nm)
2
, and a third layer which has a low refractive index (n
3
) which is in a range from 1.35 to 1.59 and lower than the refractive index of said first layer by at least 0.20 and has a film thickness of (110 to 150 nm)
3
in this order on a transparent glass substrate having a refractive index from 1.47 to 1.53.
Further, the present invention provides a low reflection glass article, wherein said second layer contains at least one metal oxide selected from a group consisting of titanium oxide, cerium oxide, bismuth oxide, zirconium oxide, niobium oxide and tantalum oxide in an amount of 70 mol % or more in total, said third layer contains a silicon oxide in an amount from 50 to 100 mol % and said metal oxides in an amount from 0 to 10 mol % in total, and said first layer contains a silicon oxide in an amount from 15 to 80 mol % and said metal oxides in an amount from 20 to 70 mol % in total.
The present invention will be described in detail below. In the present invention, when the refractive indices (defined as a value when light having a wave length of 550 nm is used unless otherwise stated, hereinafter the same) of the first layer (middle refractive index layer), the second layer (high refractive index layer), and the third layer (low refractive index layer) laminated on the transparent glass substrate having a refractive index from 1.47 to 1.53 are expressed by n
1
, n
2
and n
3
, respectively, the refractive index (n
1
) of the first layer (middle refractive index layer) is in a range from 1.60 to 1.95, the refractive index (n
2
) of the second layer (high refractive index layer) is in a range from 1.91 to 2.60 and higher than the refractive index of said first layer by at least 0.20, and the refractive index (n
3
) of the third layer (low refractive index layer) is in a range from 1.35 to 1.59 and lower than the refractive index of said first layer by at least 0.20.
It is preferable that these refractive indices are selected so that the relation represented by the following formula (1) is satisfied, namely, the value of right side is in a range from 95 to 110% of the value of left side in the formula (1). In other words, it is preferable that the refractive index (n
1
) of the first layer (middle refractive index layer), the refractive index (n
2
) of the second layer (high refractive index layer) and the refractive index (n
3
) of the third layer (low refractive index layer) satisfy the following formula (2).
n
2
×n
3
=n
1
2
(1)
0.95
×n
2
×n
3
≦n
1
2
≦1.10
×n
2
×n
3
(2)
Further, for reducing the refractive index in visible light range, the first layer has an optical film thickness from 60 to 120 nm, namely has a film thickness of (60 to 120 nm)
1
, the second layer has an optical film thickness
Nakamura Koichiro
Tsujino Toshifumi
Yokoi Koji
Conlin David G.
Dike, Bronstein, Roberts, and Cushman, IP Group of Edwards & Ang
Hazzard Lisa Swiszcz
Nippon Sheet Glass Co. Ltd.
Turner Archene
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