Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
1999-01-20
2001-05-01
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S047000, C501S048000, C501S073000, C501S079000, C501S904000
Reexamination Certificate
active
06225244
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a glass for a near infrared absorption filter, a near infrared absorption filter formed of the glass, and a solid-state image sensing device to which the filter is applied. More specifically, it relates to a glass for a near infrared absorption filter, which has spectral characteristics that it efficiently transmits light in a wavelength region of from ultraviolet region to 600 nm and selectively absorbs light in a near infrared region of a wavelength of larger than about 600 nm and which is suitable particularly for use for the color correction of a color VTR camera, a near infrared absorption filter which uses the above glass and is suitable for the above use, a solid-state image sensing device to which the filter is applied.
2. Explanation of Related Technology
As a solid-state image sensing device, conventionally, a color VTR camera mainly uses CCD (charge coupled device) or MOS (metal oxide semi-conductor). Generally, the solid-state image sensing device has a spectral sensitivity to light having a wavelength of approximately from ultraviolet region to 1,000 nm, and the sensitivity extends to a near infrared region, so that it is required to correct the above sensitivity so as to meet the luminous efficacy of human eyes. When natural light comes into the image sensing device, a formed image comes to be reddish and no good color reproduction is attained. In general practice, therefore, light which comes into the image sensing device is corrected with a filter which absorbs light in the near infrared region.
As a glass for use as the above near infrared absorption filter, a variety of glasses obtained by incorporating CuO as a coloring component into a phosphate glass have been developed and are practically used.
For example, there have been disclosed (1) a colored glass containing, by % by weight, 60 to 90% of P
2
O
5
, 7.5 to 20% of Al
2
O
3
, 0 to 15% of a total of B
2
O
3
and SiO
2
, 1 to 25% of a total of BaO, MgO, CaO and SrO, 0 to 15% of a total of Y
2
O
3
, La
2
O
3
, ZrO
2
, Ta
2
O
5
and TiO
2
, 0 to 10% of PbO and 0.4 to 15% CuO (JP-A-62-128943), (2) a phosphate glass containing, by % by weight, 60 to 80% of P
2
O
5
, 3 to 11% of Al
2
O
3
, 3 to 9.5% of BaO, 3 to 20% of a total of MgO, CaO, BaO and SrO, 1 to 5.5% of Li
2
O, 1 to 10% of a total of LiO
2
, Na
2
O and K
2
O, 0 to 5% of a total of SiO
2
and B
2
O
3
, 0 to 5% of ZrO
2
, TiO
2
, Y
2
O
3
and La
2
O
3
and 0.2 to 10% of CuO (JP-A-4-104918) and (3) a phosphate glass containing, by % by weight, 35 to 50% of P
2
O
5
, 0 to 5% of Li
2
O, 0 to 12% of Na
2
O, 0 to 20% of K
2
O, 0 to 20% of Cs
2
O, 1.5 to 20% of R
2
O (in which R is an alkali metal), 0 to 48% of ZnO, 0 to 7% of MgO, 0 to 7% of CaO, 0 to 7% of SrO, 0 to 12% of BaO, 0 to 15% of R′O (in which R′ is an alkaline earth metal) and 0.2 to 12% of CuO (JP-A-9-100136).
Since, however, the above glasses (1) and (2) contain a relatively large amount of P
2
O
5
, a glass component may be eluted when they are used for a long period of time, and it is therefore difficult to use them for a long period of time. Further, when a relatively large amount of Al
2
O
3
is incorporated for improving climate resistance, the melting temperature thereof increases, and as a result, Cu
2+
is reduced and Cu
+
having an absorption in an ultraviolet region decreases the transmittance to light at and around 400 nm. There is therefore a defect that such a glass is undesirable as a sensitivity correction filter for CCD.
In the above glass (3), the content of P
2
O
5
is decreased so as to be relatively smaller than that in a conventional phosphate glass, a relatively larger amount of ZnO is incorporated, and an alkaline earth metal oxide and an alkali metal oxide are added as required, whereby the climate resistance and the high transmittance to light in ultraviolet to visible light regions, which cannot be obtained with a conventional phosphate glass, can be obtained.
However, the above glass is not necessarily fully satisfactory although it is relatively fine concerning its alkali resistance.
When a glass has excellent alkali resistance, it is advantageous in that it is free from latent damage even when it is washed with an alkaline detergent highly capable of washing after the glass is polished.
SUMMARY OF THE INVENTION
Under the circumstances, it is a first object of the present invention to provide a glass for a near infrared absorption filter, which is durable in use for a long period of time, has high climate resistance and a high transmittance to light in ultraviolet to visible light regions and has excellent alkali resistance.
It is a second object of the present invention to provide a near infrared absorption filter formed of the above glass, which is suitable for a solid-state image sensing device using a photoelectric conversion element.
It is a third object of the present invention to provide a solid-state image sensing device to which the above infrared absorption filter is applied.
For achieving the above objects, the present inventors have made diligent studies for developing a glass for a near infrared absorption filter, which has the above excellent performances, and as a result it has been found that a specific composition of a phosphate-based near infrared absorption glass containing copper oxide can give a glass (1) which has high chemical durability, (2) which has a high transmittance to light having a wavelength of from ultraviolet region to 600 nm, which transmittance is useful for a near infrared absorption filter, (3) which selectively absorbs light in a wavelength region greater than 600 nm, (4) which is excellent in climate resistance and alkali resistance, and (5) which has a low thermal expansion coefficient (average linear expansion coefficient) as an index for processability. On the basis of the above findings, the present invention has been completed.
That is, (1) according to the present invention, there is provided a glass for a near infrared absorption filter, which comprises, by cationic %, 35 to 54% of P, 20 to 47% of Zn, 0 to 8% of R which represents a total of Li, Na, K and Cs which are monovalent metal elements, 0 to 17% of M which represents a total of Mg, Ca, Ba, Sr and Pb which are divalent metal elements, the total of R and M being 1 to 22%, 0.1 to 7% of As, 0.2 to 9% of Cu and 0 to 6% of Al (the above glass for a near infrared absorption filter will be referred to as “glass I” hereinafter).
(2) According to the present invention, further, there is provided a glass for a near infrared absorption filter, which comprises, by % by weight, 35 to 50% of phosphorus oxide, 25 to 46% of zinc oxide, 0 to less than 1.5% of an oxide I which represents a total of lithium oxide, sodium oxide, potassium oxide and cesium oxide, 0 to 24% of an oxide II which represents a total of magnesium oxide, calcium oxide, barium oxide, strontium oxide and lead oxide, the total of the oxide I and the oxide II being 0.5 to 25%, 0.05 to 5% of arsenic oxide, 0.2 to 5% of copper oxide and 0 to 5% of aluminum oxide, the total amount of the above components being at least 80% based on the total glass components (the above glass for a near infrared absorption filter will be referred to as “glass II” hereinafter).
(3) According to the present invention, further, there is provided a glass for a near infrared absorption filter, which comprises P, Zn, As and Cu as cationic components, and which has a transmittance of at least 80.0% to light having a wavelength of 400 nm at a thickness at which it has a transmittance of 10.0% to light having a wavelength of 700 nm (the above glass for a near infrared absorption filter will be referred to as “glass III” hereinafter).
(4) According to the present invention, further, there is provided a near infrared absorption filter formed of the above glass I, II or III.
(5) According to the present invention, further, there is provided a solid-state image sensing device to which the above near infrared absorption filter is appl
Group Karl
Hoya Corporation
Nixon & Vanderhye
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