JPH0432017B2 - - Google Patents

Description

[Detailed description of the invention]

[Purpose of the Invention] (Field of Industrial Application) The present invention is used for color correction filter glass of color VTR cameras, etc., and is a near-red glass that efficiently transmits the visible range of 400 to 600 nm and has good absorption characteristics at 700 nm. Regarding outer cut filter glass. (Prior Art) Conventionally, in the image pickup tube used in a color VTR camera, the photosensitive element has a spectral sensitivity ranging from the visible region to the near-infrared region around 1000 nm, as shown by curve C in Figure 2. There is. Therefore, since good color reproducibility cannot be obtained as is, it is necessary to correct the visibility to normal visibility (curve D) using a filter that absorbs the infrared region.
This filter uses filter glass made by adding CuO to phosphate glass so that it selectively absorbs near-infrared wavelengths. This filter glass contains a large amount of P ₂ O ₅ and CuO as an essential component.
It exhibits a blue-green color by forming Cu ²⁺ ions coordinated with a large amount of oxygen ions in an oxidizing molten atmosphere, and has near-infrared cut characteristics as shown in curve B in Figure 1. It is something. However, when the content of CuO is increased in the above-mentioned filter glass to promote the near-infrared cutting effect, the spectral transmittance in the wavelength range of 400 to 500 nm generally decreases, showing a tendency to green.
Sharp cut characteristics deteriorate in the wavelength range of ~700 nm. Furthermore, the basic glass, phosphate glass, has insufficient weather resistance and causes weathering on the polished surface of the glass, making it difficult to use over a long period of time. (Problems to be Solved by the Invention) Conventional filter glasses cannot effectively improve near-infrared cut characteristics simply by increasing the content of CuO components, and also have poor chemical durability. There's a problem. The present invention was made in consideration of the above circumstances, and
Efficiently transmits the wavelength range of 400 to 600nm, and transmits 700nm
An object of the present invention is to provide a near-infrared cut filter glass that has good absorption characteristics and excellent chemical durability. [Structure of the invention] (Means and effects for solving the problems ₎ In order to achieve the above object, the present invention
The basic glass composition is adjusted by adding ₂ components and SnO2. i.e. in weight percentage
_{P2O5 65-85} %, _{Al2O3 3-17} %, _SiO2 0.1-12%,
_SnO2 0.1 _~ 3%, _SiO2 + _SnO2 0.3~13%, _B2O30
~10%, _Li2O + _Na2O + _K2O0 ~15%, MgO+
ZnO+CaO2~15%, BaO+SrO0~10%, _ZrO2
It is a near-infrared cut filter glass having a composition of +TiO ₂ +La ₂ O ₃ +Y ₂ O0 to 10% and CuO 1 to 8%. The reason why the glass composition of the present invention is limited to the above range will be explained. P ₂ O ₅ is the main component that makes up the glass network.
If it is less than 65%, the transmittance at 400nm will decrease,
If it exceeds 85%, chemical durability deteriorates. A ₂ O ₃ is an essential component for improving the chemical durability of glass, but if it is less than 3%, no effect will be obtained, and if it exceeds 17%, the transmittance in the ultraviolet region will decrease and devitrification will occur. becomes more likely to occur. _SiO2 and
Although SnO ₂ has the effect of improving chemical durability,
SiO ₂ 12%, SnO ₂ 3%, if the total amount exceeds 13%
Cu ions inhibit infrared sharp cutting properties and cause devitrification. B ₂ O ₃ is an effective component for improving chemical durability and stabilizing glass, but if it exceeds 10%, the transmittance in the visible range decreases.
Li ₂ O, Na ₂ O, K ₂ O contribute to stabilizing the glass,
It provides good transmittance in the 500-600 nm wavelength range and improves near-infrared cut characteristics, but if it exceeds 15%, chemical durability decreases, the viscosity of the glass decreases, and the rate of devitrification increases. MgO, ZnO, CaO are 1 type or 2 types
If the total amount of the CuO component is less than 2%, the moldability will deteriorate, and if it exceeds 15%, the infrared sharp cutting properties due to the CuO component will be inhibited. BaO and SrO act on Cu ions to sharply cut the wavelength range of 600 to 700 nm, but if their total amount exceeds 10%, devitrification occurs in the glass. ZrO ₂ , TiO ₂ , La ₂ O ₃ , and Y ₂ O ₃ are components that improve chemical durability without affecting near-infrared sharp cuts, but the total amount of one or two of them is 10%. If it exceeds this value, the glass has devitrification. CuO is added as a coloring agent and is an essential component for near-infrared sharp cutting, but if it is less than 1%, the effect cannot be obtained, and if it exceeds 8%, the transmittance in the entire visible range decreases. Filters made of phosphate glass undergo weathering in high-humidity environments, and their transmittance characteristics decrease due to surface scattering of light, but the glass of the present invention
By adding the SnO ₂ component, weathering was reduced and the decrease in transmittance characteristics could be reduced. (Example) The cooling implementation of the present invention is shown in the following table. In the table, the glass composition is shown in weight percentage, and the water resistance is shown in classification according to the method for measuring chemical durability of optical glass as specified by the Japan Optical Glass Industry Association.

【table】

〔Effect of the invention〕

As described above, the glass of the present invention is a near-infrared cut filter glass made by adding CuO to phosphate glass, and contains up to 13% of SiO ₂ and SnO ₂ in total, which has been considered a drawback in the past. It has the advantage of improving chemical durability, efficiently transmitting visible light in the range of 400 to 600 nm, and improving absorption characteristics at 700 nm.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the spectral transmittance characteristics of the glass of the present invention and the conventional glass, and FIG. 2 is a curve diagram showing the spectral sensitivity characteristics of the photosensitive element of the image pickup tube. A... Glass of the present invention (Example No. 8), B... Conventional glass (Comparative Example No. 14)

Claims (1)

[Claims] 1 In weight percentage, P ₂ O ₅ 65-85%, Al ₂ O ₃ 3-17
%, SiO ₂ 0.1-12%, SnO ₂ 0.1-3%, SiO ₂ +
_SnO2 0.3-13%, _{B2O3 0-10} %, _Li2O + _Na2O +
_K2O0 ~15%, MgO+ZnO+CaO2~15%, BaO
+SrO0~10% _{, ZrO2} + _TiO2 + _La2O3 + _{Y2O30 ~}
Near-infrared cut filter glass having a composition of 10% CuO and 1 to 8% CuO.